Patent Application
20110064773
The present invention relates to new pharmaceutical compositions comprising a thyroid hormone and their therapeutic use.
Thyroid hormones have been known for a long time. The thyroid hormone family consists in T4 hormone and the derived iodothyronines resulting from successive monodeiodinations of T4. The pathways of the deiodination cascade of T4 have been described by Hulbert A. J. (Biol. Rev., 2000). T4 gives T3 via an outer ring 5′-deiodination or rT3 via an inner ring 5′-deiodination. T3 results in 3,5-T2 via an outer ring 5′-deiodination or 3,3′-T2 via an inner ring 5′-deiodination. rT3 results in 3,3′-T2 via an outer ring 5′-deiodination or 3′,5′-T2 via an inner ring 5′-deiodination. 3-T1 is obtained via an inner ring 5′-deiodination from 3,5-T2 or via an outer ring 5′-deiodination from 3,3′-T2. 3′-T1 is obtained via an inner ring 5′-deiodination from 3,3′-T2 or via an outer ring 5′-deiodination from 3′,5′-T2.
For information, table 1 indicates the formula of several members of the thyroid hormone family.
The known effects of thyroid hormones, particularly of the T3 hormone, result mainly from the binding to two nuclear receptors of the thyroid hormones, TRα-1 and TRβ-1 belonging to the family of nuclear receptors TR-α and TR-β, which are supposed to have different effects. These receptors are thought to be highly specific towards T3, particularly relating to the number of iodine and the spatial arrangement (Bolger et al., J. Biol. Chem., 1980; Koerner et al., J. Biol. Chem., 1975; Dietrich et al., J. Med. Chem., 1977). Since the discovery of the thyroid nuclear receptors, most of scientists have focused on the effects of transcriptional changes of thyroid hormones.
T3 hormone binds very efficiently to the nuclear receptors, whereas the T4 hormone binds less efficiently. The hormones derived from T4 and T3 do not bind to the nuclear receptors (Koerner et al., J. Biol. Chem., 1975; Lazar, Endocrine Rev., 1993; Hulbert, Bio. Rev., 2000; Oppenheimer, Biochimie, 1999; Yen, Physiol. Rev., 2001).
The use of T3 hormone for treating obesity is well known by the man skilled in the art. However, its use has been highly limited because of serious side effects of T3 hormone, particularly cardiac side effects. The treatment of hypothyroidism lies on T3, which can be used directly or produced in vivo by the transformation of its very little active precursor, the T4 hormone (Yen, Physiol. Rev., 2001). T3 is known as the real active thyroid hormone.
The effects induced by thyroid hormones, such as T3, via the nuclear receptor pathway are physiologically important effects observed at very low concentrations. These effects are often deleterious when T3 is administered to subjects that do not suffer from hypothyroidism.
These effects can be considered as “hyperthyroidic effects” linked to the nuclear receptor pathway.
The international application WO2005/009433 and the corresponding scientific paper (Lanni et al., The FASEB Journal, 2005) have disclosed an effect of the 3,5-T2 on energetic metabolism. More particularly, normal rats receiving a high-fat diet and treated with a daily peritoneal injection of 3,5-T2 gained less weight and had less fat deposit than untreated rats. The 3,5-T2 hormone was thus proposed for the treatment of obesity and related pathologies.
The rT3 hormone is generally considered as an inactive hormone and was thought to represent the inactivation pathway of thyroid hormones (Yen, Physiol. Rev., 2001). Thus, increased rT3 plasmatic concentrations are often found in low T3 syndrome. Recently, cerebral effects of rT3 have been disclosed in the establishment and structuring of astrocytes (Farwell et al. Endocrinology, 2006).
In prior art, it has never been disclosed that thyroid hormones may have effects on insulin and glycemia.
Diabetes is a chronic disease characterized by a hyperglycemia.
Type 1 diabetes results from the destruction of the pancreatic 13 cells secreting insulin. Treatment of type 1 diabetes particularly consists in the administration of insulin.
Type 2 diabetes is more frequent than type 1 diabetes in the population and is generally associated to obesity. Type 2 diabetes is characterized by two interdependent abnormalities: an insulin-resistance and a reduced production of insulin by response to glycemia.
Treatments of type 2 diabetes particularly consist in using an agonist drug of insulin or an agonist of insulin secretion by the beta cells, in reducing the glycemia and the weight of the diabetic patients.
Obesity is one of the major public health concerns in developed countries as well as in developing countries. The mechanisms involved in obesity are not really understood. Factors involved in obesity are particularly alimentation (fat and sweet diets) and environment conditions (physical activity, social environment, food availability).
More efficient and more appropriate treatments (particularly in term of side effects, comfort of patients such as frequency of use and administering route) are needed against chronic diseases such as diabetes, obesity and dyslipidemia.
One aim of the present invention is to provide new pharmaceutical compositions comprising a thyroid hormone as active substance.
Another aim of the invention is to provide new pharmaceutical compositions for the treatment of metabolic disorders that do not induce hyperthyroidism.
Another aim of the invention is to provide a new therapeutic class of drugs for the treatment of diabetes.
Another aim of the invention is to provide a combination product for a simultaneous, separate or sequential use intended for the treatment of diabetes.
The present invention relates to a pharmaceutical composition comprising, as active substance, at least one hormone chosen among:
Contrary to the teaching of the prior art presenting rT3 as inactive, the Inventors have found that the rT3 hormone can be used as a drug, as well as its derived hormones.
Furthermore, contrary to the effects of other thyroid hormones such as T3, the effects of the hormones according to the invention seem not to involve the nuclear receptor pathway since rT3 is know to have a very little affinity to TH receptors.
The rT3 hormone and the rT3 derived hormones are the physiological forms of thyroid hormones that are inactive for the treatment of hypothyroidism or as hyperthyroidism inducer. Contrary to 3,5-T2, these hormones can not be obtained via T3, which is the active thyroid hormone.
According to the Inventors, rT3, a rT3 derived hormone or a rT3 precursor are shown for the first time to have an energetic activity and to have an effect on glycemia and on insulin sensitivity as well as plasma concentrations.
The Inventors propose that the use of rT3 and its derived hormone is the physiological way to obtain beneficial metabolic effects without inducing hyperthyroidism.
Furthermore, the Inventors propose that rT3 has beneficial effect only on the glycemia of diabetic subjects and has no hypoglycemic effect on non diabetic subjects (see Examples section).
According to the present invention, the term “3′,5′,3-triiodothyronine” refers to reverse T3 or rT3.
By the expression “rT3 derived hormone”, one means any compound that has at least one iodine susceptible to be obtained from rT3, particularly by removing one or several iodines, via natural occurring and/or artificial ways.
By “natural occurring way”, it is particularly meant that the rT3 derived hormone is obtained via enzymes such as the iodothyronine deiodinases that remove one or several iodines from rT3. Several biological reactions may be needed to obtain the desired derived hormone.
By the expression “via an artificial way”, it is particularly meant that the rT3 derived hormone is obtained via chemical synthesis, biochemical synthesis or recombinant technology.
The preferred rT3 derived hormones are diiodothyronines and iodothyronines. The preferred rT3 derived hormones are 3′,3-diiodothyronine, 3′,5′-diiodothyronine, 5′,3-diiodothyronine, 3′-iodothyronine, 5′-iodothyronine or 3-iodothyronine.
By the expression “a precursor of rT3”, one means any compound susceptible to give rT3. The precursor of rT3 may be a natural hormone, a synthesis or recombinant hormone, or a modified hormone.
By the expression “natural hormone”, one means a hormone found in a living being, such as an animal or a human being, and which is purified and isolated from said living being.
By the expression “synthesis or recombinant hormone”, one means a hormone obtained by chemical or biochemical synthesis or recombinant technology.
By the expression “modified hormone”, one means a hormone which is chemically modified to add functional groups. Said functional groups may modify the activity of said hormone or protect said hormone from degradation.
In an advantageous embodiment of the invention, the precursor of rT3 is the T4 hormone, also called “thyroxine”.
The rT3 precursor is preferentially used in association with a molecule susceptible to promote the formation of rT3. The use of the precursor of rT3 and said molecule can be simultaneous, separate or sequential.
Particularly, when the T4 hormone is used as rT3 precursor, said molecule susceptible to promote the formation of rT3 is:
The present invention particularly relates to a pharmaceutical composition as defined above, wherein said active substance is rT3.
The present invention particularly relates to a pharmaceutical composition as defined above, in a suitable form for the release of about 0.01 μg/kg/day to about 250 μg/kg/day, particularly about 0.01 μg/kg/day to about 25 μg/kg/day, particularly about 0.1 μg/kg/day to about 15 μg/kg/day of active substance, more particularly about 0.1 μg/kg/day to about 5 μg/kg/day of active substance, most particularly about 0.1 μg/kg/day to 1 μg/kg/day of active substance.
The dosage of active substance particularly depends on the administration route, which is easily determined by the man skilled in the art.
The present invention further relates to pharmaceutical composition as defined above, comprising by dosage unit about 5 μg to about 1.5 g of active substance, particularly about 75 mg to about 750 mg of active substance, to be released in a lapse of time corresponding to the above-mentioned values of the ranges in μg/kg/day or mg/kg/day for a 70 kg human.
As an example, for the treatment of a 70 kg human, the dosage will be:
By the expression “dosage unit”, one means the quantity of active substance comprised in one drug unit.
Depending on the administration route and on the formulation of the pharmaceutical composition, the active substance comprised in the dosage unit can be released quickly or continuously over a period of time. The pharmaceutical composition can also be a slow-release drug.
Pharmaceutical compositions of the invention may be administered in a partial dose or a dose one or more times during a 24 hour period. Fractional, double or other multiple doses may be taken simultaneously or at different times during a 24 hour period.
In an advantageous embodiment, the pharmaceutical composition of the invention is administered in a unique dose, which allows a continuous release for a period of time of at least 24 h, preferably at least one week, more preferably at least one month, most preferably at least two months, in particular three months.
The present invention also relates to the use of at least one hormone chosen among:
In an advantageous embodiment, the present invention relates to the use as defined above, for the preparation of a drug intended for the treatment of type 1 and type 2 diabetes, hyperglycemia, insulin resistance, beta pancreatic cell insufficiency, or related pathologies.
The Inventors have shown for the first time that rT3, a rT3 derived hormone or a rT3 precursor are capable of reducing glycemia and insulin plasmatic concentrations.
Hyperglycemia is characterized by fasting glucose concentrations higher that 1.1 g/l (or 110 mg/dl or 5.5 mmol/l), particularly higher than 1.20 g/L. The use of rT3, a rT3 derived hormone or a rT3 precursor allows reducing glycemia to normal concentrations.
By the expression “normal concentrations of glucose”, one means glucose plasmatic concentration comprised from 4.4 mmol/l to 5.5 mmol/l, “abnormal” blood glucose is defined by fasting plasma glucose >5.55 mmol/l and diabetes by fasting plasma glucose >6.1 mmol/l (Meggs et al., Diabetes, 2003).
Glycemia is assessed by classical blood tests using the glucose oxidase method as reference (Yeni-Komshian et al., Diabetes Care, 2000, p 171-175; Chew et al., MJA, 2006, p 445-449; Wallace et al., Diabetes Care, 2004, p 1487-1495).
The use of rT3, a rT3 derived hormone or a rT3 precursor also improves insulin resistance.
Insulin resistance is characterized by insulin plasmatic concentrations higher than 8 mU/l or 60 pmol/l (Wallace et al., Diabetes Care, 2004, p 1487-1495).
Insulin resistance is the condition in which normal amounts of insulin are inadequate to produce a normal response from fat, muscle and liver cells, i.e. a resistance to the physiological action of insulin.
It is defined as the lowest quartile of measures of insulin sensitivity (e.g. insulin stimulated glucose uptake during euglycaemic clamp) or highest quartile of fasting insulin or homeostasis model assessment (HOMA) insulin resistance index in the population studied (Alberti et al. “Definition, diagnosis and classification of diabetes mellitus and its complications. Part 1: Diagnosis and classification of diabetes mellitus, provisional report of a WHO consultation”, Diabetic Med, 1998, p 539-553; Wallace et al., Diabetes Care, 2004, p 1487-1495).
The use of the above-mentioned active substances allows reducing insulin plasmatic concentrations to normal concentrations, increasing the sensitivity to insulin and improving the metabolism of glucose and lipids.
By the expression “normal concentrations of insulin”, one means insulin plasmatic concentration comprised from 5 to 8 mU/l (36 to 60 μmol/l).
Insulin concentration is assessed by classical blood tests (RIA assay with human antibody; Yeni-Komshian et al., Diabetes Care, 2000, p 171-175; Chew et al., MJA, 2006, p 445-449; Wallace et al., Diabetes Care, 2004, p 1487-1495).
Sensitivity to insulin can be assessed by the HOMA (Homeostasis Model Assessment) method (Wallace et al., Diabetes Care, 2004, p 1487-1495, see
Surprisingly, the use of the above-mentioned active substances seems to improve pancreatic β cells survival, and thus the regeneration of said insulin secreting cells.
The regeneration of said cells is evaluated through the measurement of insulin concentration (RIA assay with human antibody; Yeni-Komshian et al., Diabetes Care, 2000, p 171-175; Chew et al., MJA, 2006, p 445-449; Wallace et al., Diabetes Care, 2004, p 1487-1495).
Results obtained on ZDF rats show that treatment with rT3 induced decreasing glucose concentration and increasing plasmatic insulin concentration.
In Goto-Kakizaki (GK) rats, a genetic model of type 2 diabetes, there is a restriction of the β cell mass as early as fetal age, which is maintained in the adult animal. The restriction of the β cell mass can be considered as a crucial event in the sequence leading to overt diabetes in this model. In the GK model, the regeneration of β cells occurs with a lower efficiency as compared to non-diabetic Wistar rats. This defect in the GK rats is both the result of genetic predisposition contributing to an altered β cells neogenesis potential and environment factors, such as chronic hyperglycemia, leading to a reduced β cell proliferative capacity specific to the adult animals. These results are described in Movassat et al., Diabetologia, 1997, p 916-925 and in Plachot et al., Histochem Cell Biol., 2001, p 131-139, the entire contents of which are incorporated herein by reference.
Assuming that a chronic hyperglycemia induced a destruction of pancreatic β cells and thus a decreased secretion of insulin, restored normal insulin concentrations could mean that the β cells are regenerated.
The β cells functional mass can be correlated to the level of insulin secretion through the HOMA method. On animal models, the man skilled in the art can envision the direct evaluation of pancreas mass.
According to another embodiment, the present invention relates to the use as defined above, for the preparation of a drug intended for the treatment of pathologies wherein the cholesterol and/or triglyceride plasmatic concentrations are higher than the normal concentrations, or dyslipidemia, or pathologies related to overweight or related to an excess of fat deposit.
A cholesterol concentration higher than the normal concentrations means a plasmatic concentration higher than 2.5 g/l.
A triglyceride concentration higher than the normal concentrations means a plasmatic concentration higher than 2 g/l.
Dyslipidemia is characterized by a triglyceride concentration higher than 1.7 mmol/l and/or a HDL-cholesterol level lower than 1 mmol/l (men) or 1.3 mmol/l (women) (Chew, MJA, 2006, p 445-449, see table entitled “Clinical definitions of the metabolic syndrome”).
An excess of fat deposit is characterized by a body mass index: (weight, kg/height2, m2) higher than 25 kg/m2 and obesity is characterized by a body mass index higher than 30 kg/m2.
The invention further relates to the use as define above, for the preparation of a drug intended for the treatment of pathologies chosen among diabetes, particularly type 1 or 2 diabetes, beta pancreatic cell insufficiency, obesity, overweight or related pathologies, hypercholesterolemia, hypertriglyceridemia, dyslipidemia, alcoholic and non alcoholic hepatic steatosis, atherosclerosis, hepatopathies associated to a dysmetabolism, cholecystopathies, deposit of subcutaneous fat, particularly cellulite or vasomotor rhinitis.
In an advantageous embodiment, the invention related to the uses as defined above, wherein said hormone is rT3.
The present invention particularly relates to a pharmaceutical composition as defined above, wherein said pharmaceutically acceptable vehicle refers to pharmaceutically acceptable solid or liquid, diluting or encapsulating, filling or carrying agents, which are usually employed in pharmaceutical industry for making pharmaceutical compositions.
The present invention relates to a pharmaceutical composition as defined above, suitable for an administration via an oral, intravenous, intramuscular, subcutaneous, transcutaneous, nasal, intraperitoneal, sublingual, or rectal route.
In the oral route, drugs are administered orally, particularly under the shape of tablets, coated tablets, pills, syrup or elixirs, dragees, troches, lozenges, aqueous or oily suspensions, liquid solutions, dispersible powders or granules, emulsions, hard or soft capsules.
In the intravenous route or systemic route, the drug can be administered in the bloodstream by a single injection or via a continuous infusion, eventually via a pump.
In the cutaneous route, drugs are applied to the skin. The formulation may be an ointment, a cream, a lotion, a solution, a powder or a gel.
In the subcutaneous route, the drug can be injected directly into fatty tissue just beneath the skin or the drug can be included in capsules that are inserted under the skin.
In the transcutaneous route, the drug passes through the skin to the bloodstream without injection. Particularly, the drug is comprised in a patch applied on the skin. Concerning patches formulation, the drug can be mixed with a chemical, such as alcohol, to enhance skin penetration.
The dosage forms include immediate release, extended release, pulse release, variable release, controlled release, timed release, sustained release, delayed release, long acting, and combinations thereof.
The dosage forms include, without limitation, tablets, multi-layer tablets, bi-layer tablets, chewable tablets, quick dissolve tablets, effervescent tablets, syrup, suspensions, emulsions, capsules, soft gelatin capsules, hard gelatin capsules, lozenges, chewable lozenges, beads, powders, granules, particles, microparticles, dispersible granules, cachets, creams, topicals, patches, implants, injectables (including subcutaneous, intramuscular, intravenous, and intradermal), infusions.
In an advantageous embodiment of the invention, the pharmaceutical composition is suitable for a transcutaneous, particularly by means of patches.
In an advantageous embodiment, the administration of the pharmaceutical composition avoids partially that the drug passes through liver, which is susceptible of an important degradation of the hormones.
In another advantageous embodiment of the invention, the pharmaceutical composition is suitable for a subcutaneous administration, particularly by means of a capsule injected beneath the skin.
The present invention also relates to a pharmaceutical composition as defined above, wherein said pharmaceutically acceptable vehicle allows a continuous, preferably constant, release, of said active substance, the active substance being chosen among:
The continuous, preferably constant, release of the active substance allows obtaining:
By the expression “continuous release”, one means a continuous release of the drug over at least 24 hours, preferably at least one month, most preferably at least two months, in particular three months. Also, a continuous release in the invention can correspond to a discontinuous release. Indeed one release can be separated by a short time interval from another release, such that the concentration of drug remains substantially constant in blood, or at a sufficient efficient amount in blood, between two releases. This short time interval is for example comprised from 10 s to 3 hours, preferably from 1 minute to 2 hours, more preferably from 5 minutes to 1 hour.
By the expression “constant release”, one means a continuous release of the drug over at least 24 hours, preferably at least one month, most preferably at least two months, in particular three months, the quantity of released drug/time unit being essentially constant.
A continuous and constant release is for example achieved by using patches or capsules injected under the skin. Also, an electric syringe, or an electric pump, continuously releasing the hormone, and placed under the skin, can also be used. The syringe or pump can also be placed in the peritoneal cavity.
Also, the continuous and constant release can be provided by controlled-release (CR) formulation of the drug.
Controlled release formulations allow a slow release of a drug over time, such that the concentration of the drug remains substantially constant in blood, or at a sufficiently efficient amount in blood.
Controlled release drugs are for instance formulated such that the active ingredient is embedded in a matrix of insoluble substance (e.g. some acrylics, chitin, PEG (polyethylen glycol) . . . ), or of a slowly degradable substance. To be liberated, the drug has to find its way out through the holes in the matrix. In some controlled released formulations, the matrix swells up to form a gel, and the drug has to dissolve in matrix to be diffused in the outer surface of the matrix.
In another embodiment, rT3, the rT3 derived hormone and the rT3 precursor of the invention are used in a simultaneous, separate or sequential combination with another thyroid hormone, such as 3,5-T2 or 3′,5-T2.
The present invention also relates to a product comprising:
The present invention also relates to nutraceutics or food compositions comprising at least one hormone chosen among:
The present invention also relates to a method for improving meat quality, in particular pork meat quality, by controlling the ratio between the weight of adipose tissues and lean tissues, in particular by:
by the administration of nutraceutics or food compositions comprising at least one hormone chosen among:
In the following figures, asterisk or star (*) represents either significant results with a p-value<0.05, or a specific indicated p-value.
High dose of hormones correspond to 25 μg/100 g of body weight (BW), low doses correspond to 2.5 μg/100 g of body weight and ultra low doses correspond to 0.25 μg/100 g of body weight.
Growth rate of Wistar rats treated with a high dosage of rT3 or 3,3′-T2 (25 μg/100 g of body weight (BW))
Food intake of Wistar rats treated with a high dosage of rT3 or 3,3′-T2 (25 μg/100 g BW)
Energy expenditure of Wistar rats treated with a high dosage rT3 or 3,3′-T2 (25 μg/100 g BW)
The horizontal black line indicates a period where the rats are in the dark.
Respiratory quotient (RQ) of Wistar rats treated with a high dosage of rT3 or 3,3′-T2 (25 μg/100 g BW).
The horizontal black line indicates a period where the rats are in the dark.
Weight and relative weight of adipose tissues, skeletal muscles and brown adipose tissue of Wistar rats treated with a high dosage of rT3 (250 μg/kg BW).
The results of the rats treated with thyroid hormones are shown in white and the results of those treated with placebo in black.
The asterisk corresponds to a p-value <0.01.
Weight and relative weight of adipose tissues, skeletal muscles and brown adipose tissue of Wistar rats treated with a high dosage of 3,3′-T2 (250 μg/kg BW).
The results of the rats treated with thyroid hormones are shown in white and the results of those treated with placebo in black.
The asterisk corresponds to a p-value <0.01.
Rate of liver mitochondrial oxygen consumption (JO2 in nmol of O2/min/mg of protein) of animals treated with a 250 μg/kg BW/day of rT3 or 3,3′-T2.
Measurements were performed using mitochondria (1.0 mg of mitochondrial protein/ml) incubated with various substrates:
GM: glutamate/malate (5 mM/2.5 mM)
SR: succinate/rotenone (5 mM/5 μM),
GMS: glutamate/malate/succinate (5 mM/2.5 mM/5 mM),
Palm: palmitoyl carnitine (55 μM),
Octa: octanoyl carnitine (100 μM),
TMPD/ascorbate (0.5 mM/0.5 mM) and
TMPD/ascorbate/DNP (0.5 mM/0.5 mM/75 μM) OK JO2 was recorded in the presence of the substrate and following the addition of 1 mM ADP (adenosine diphosphate) (state 3).
The oligomycin was added to the mitochondrial suspension to determine the non-phosphorylating respiratory rate (state 4).
Oxygen consumption of rats treated with thyroid hormones is shown in white, and oxygen consumption of those treated with placebo in black.
The asterisk corresponds to a p-value <0.01.
Rate of muscle mitochondrial oxygen consumption (JO2 in nmol of O2/min/mg of protein) of Wistar rats treated with 250 μg/kg BW/day of rT3 or 3,3′-T2.
All measurements were performed using mitochondria (0.2 mg of mitochondrial protein/ml) incubated with various substrates:
GM: glutamate/malate (5 mM/2.5 mM)
SR: succinate/rotenone (5 mM/5 μM),
GMS: glutamate/malate/succinate (5 mM/2.5 mM/5 mM),
Palm: palmitoyl carnitine (55 μM), and
Octa: octanoyl carnitine (100 μM).
JO2 was recorded in the presence of the substrate and following the addition of 1 mM ADP (state 3).
The oligomycin was added to the mitochondrial suspension to determine the non-phosphorylating respiratory rate (state 4).
Oxygen consumption of rats treated with thyroid hormones is shown in white, and oxygen consumption of those treated with placebo in black.
The asterisk corresponds to a p-value <0.01.
Rate of liver mitochondrial oxygen consumption (JO2 in nmol of O2/min/mg of protein) of Wistar rats treated with a low dosage of rT3 (25 μg/kg BW/day).
Oxygen consumption of rats treated with thyroid hormones is shown in white, and oxygen consumption of those treated with placebo in black.
All measurements were performed using mitochondria (1.0 mg of mitochondrial protein/ml) incubated with various substrates:
GM: glutamate/malate (5 mM/2.5 mM),
SR: succinate/rotenone (5 mM/5 μM),
GMS: glutamate/malate/succinate (5 mM/2.5 mM/5 mM),
Palm: palmitoyl carnitine (55 μM),
Octa: octanoyl carnitine (100 μM),
TMPD/ascorbate (0.5 mM/0.5 mM) and
TMPD/AsC/DNP: TMPD/ascorbate/DNP (0.5 mM/0.5 mM/75 μM)
The asterisk corresponds to a p-value <0.01.
Plasma concentrations of glucose, triglycerides, cholesterol, FFA (Free Fatty Acid) and HDL (Heavy Density Lipoprotein) in Wistar rats treated with 250 μg/kg BW/day of rT3 or 3,3′-T2.
These measurements were done on venous blood of the rats the day of the sacrifice.
The results of the rats treated with rT3 are shown in white, the results of those treated with 3,3′-T2 in grey and the results of those treated with placebo in black. The asterisk corresponds to a p-value<0.01.
Mass of Wistar rats at day 0 and day 8 after a treatment with a high dosage of rT3 (25 μg/100 g BW). The results of the rats treated with thyroid hormones are shown in white and the results of those treated with placebo in black.
Weight of adipose tissues of Wistar rats treated with a high dosage of rT3 (25 μg/100 g BW) after 8 days of treatment. The results of the rats treated with thyroid hormones are shown in white and the results of those treated with placebo in black.
Weight of brown adipose tissue of Wistar rats treated with a high dosage of rT3 (25 μg/100 g BW) after 8 days of treatment. The results of the rats treated with thyroid hormones are shown in white and the results of those treated with placebo in black.
Weight of skeletal muscles of Wistar rats treated with a high dosage of rT3 (25 μg/100 g BW) after 8 days of treatment. The results of the rats treated with thyroid hormones are shown in white and the results of those treated with placebo in black.
Energy expenditure of Wistar rats treated with a high dosage of rT3 (25 μg/100 g BW)
Blood rT3 dosage. The rT3 concentration is measured for 24 hours in Wistar rats treated with a high dosage of rT3 by intra-peritoneal injection (IP, square), oral ingestion (per os, triangle) or subcutaneous injection (sc, star). Basal rT3 level is measured in animal treated with placebo (lozenge).
Blood glucose concentration of ZDF rats at day 0, and after 8, 16 and 21 days of treatment with a low dose of rT3 (2.5 μg/100 g BW). Glucose concentration of animals treated with placebo is represented in black and glucose concentration of animals treated with low dose of rT3 is represented in white. Star (*) represents significant differences.
Blood insulin concentration of ZDF rats at day 0, and after 8, 16 and 21 days of treatment with a low dose of rT3 (2.5 μg/100 g BW). Insulin concentration of animals treated with placebo is represented in black and insulin concentration of animals treated with a low dose of rT3 is represented in white. Star (*) represents significant differences.
Pancreas mass in grams of ZDF rats treated with a low dose of rT3 (2.5 μg/100 g BW) (White) or treated with placebo (Black) after X days.
Photography of ZDF rats treated for 21 days with placebo (left) or with a low dose of rT3 (right).
Body weight (g) of ZDF rats at day 0, and after 8, 16 and 21 days of treatment with a low dose of rT3 (2.5 μg/100 g BW). Mass of ZDF rats treated with rT3 is represented by white squares and mass of ZDF rats treated with placebo is represented by black lozenges.
Food intake (g/days) of ZDF rats at day 0, and after 8, 16 and 21 days of treatment with a low dose of rT3 (2.5 μg/100 g BW). Food intake of ZDF rats treated with rT3 is represented by white squares and food intake of ZDF rats treated with placebo is represented by black lozenges.
Energy expenditure of ZDF rats treated with a low dosage rT3 (2.5 μg/100 g BW)
The energy expenditure of the rats treated with thyroid hormones is shown on the curve with white squares and the energy expenditure of those treated with placebo is represented with black lozenges.
Respiratory quotient (RQ) of ZDF rats treated with a low dosage of rT3 (2.5 μg/100 g BW). The respiratory quotient of the rats treated with thyroid hormones is shown on the curve with white squares and the respiratory quotient of those treated with placebo is represented with black lozenges.
Weight of adipose tissues of ZDF rats treated with a low dosage of rT3 (2.5 μg/100 g BW). The results of the rats treated with thyroid hormones are shown in white and the results of those treated with placebo in black.
Weight of brown adipose tissue of ZDF rats treated with a low dosage of rT3 (2.5 μg/100 g BW). The results of the rats treated with thyroid hormones are shown in white and the results of those treated with placebo in black.
Weight of skeletal muscles of ZDF rats treated with a low dosage of rT3 (2.5 μg/100 g BW). The results of the rats treated with thyroid hormones are shown in white and the results of those treated with placebo in black.
Plasma concentrations FFA (Free Fatty Acid) in ZDF rats treated with 2.5 μg/100 g BW of rT3. These measurements were done on venous blood of the rats the day of the sacrifice. The results of the rats treated with rT3 are shown in white and the results of those treated with placebo in black. Star (*) represents significant differences.
Plasma concentrations triglycerides in ZDF rats treated with 2.5 μg/100 g BW of rT3. These measurements were done on venous blood of the rats the day of the sacrifice. The results of the rats treated with rT3 are shown in white and the results of those treated with placebo in black.
Plasma concentrations cholesterol in ZDF rats treated with 2.5 μg/100 g BW of rT3. These measurements were done on venous blood of the rats the day of the sacrifice. The results of the rats treated with rT3 are shown in white and the results of those treated with placebo in black. Star (*) represents significant differences.
Plasma concentrations HDL (Heavy Density Lipoprotein) in ZDF rats treated with 2.5 μg/100 g BW of rT3. These measurements were done on venous blood of the rats the day of the sacrifice. The results of the rats treated with rT3 are shown in white and the results of those treated with placebo in black.
Area under the curve of the glucose concentration 3 h after OGTT in n0STZ rats treated with 2.5 μg/100 g BW of rT3. Rats were fed with 2 g/kg of glucose. The results of the rats treated with rT3 are shown in grey and the results of those treated with placebo in black.
Area under the curve of the insulin concentration 3 h after OGTT (Oral Glucose tolerance test) in n0STZ rats treated with 2.5 μg/100 g BW of rT3. Rats were fed with 2 g/kg of glucose. The results of the rats treated with rT3 are shown in grey and the results of those treated with placebo in black.
Kinetic of glucose concentration in plasma in n0STZ rats treated with 2.5 μg/100 g BW of rT3. Rats were fed with 2 g/kg of glucose. The results of the rats treated with rT3 are shown with white triangles and the results of those treated with placebo with black lozenges.
Kinetic of Insulin concentration in plasma in n0STZ rats treated with 2.5 μg/100 g BW of rT3. Rats were fed with 2 g/kg of glucose. The results of the rats treated with rT3 are shown with white triangles and the results of those treated with placebo with black lozenges.
Pancreas mass in n0STZ rats treated with 2.5 μg/100 g BW of rT3. The results of the rats treated with rT3 are shown in grey and the results of those treated with placebo in black. Star (*) represents significant differences.
Area under the curve of the glucose concentration 3 h after OGTT in GK rats treated with 2.5 μg/100 g BW of rT3. Rats were fed with 2 g/kg of glucose. The results of the rats treated with rT3 are shown in grey and the results of those treated with placebo in black.
Area under the curve of the insulin concentration 3 h after OGTT (Oral Glucose tolerance test) in GK rats treated with 2.5 μg/100 g BW of rT3. Rats were fed with 2 g/kg of glucose. The results of the rats treated with rT3 are shown in grey and the results of those treated with placebo in black.
Kinetic of glucose concentration in plasma in GK rats treated with 2.5 μg/100 g BW of rT3.
Rats were fed with 2 g/kg of glucose. The results of the rats treated with rT3 are shown with white triangles and the results of those treated with placebo with black lozenges.
Kinetic of Insulin concentration in plasma in GK rats treated with 2.5 μg/100 g BW of rT3. Rats were fed with 2 g/kg of glucose. The results of the rats treated with rT3 are shown with white triangles and the results of those treated with placebo with black lozenges.
Pancreas mass in GK rats treated with 2.5 μg/100 g BW of rT3. The results of the rats treated with rT3 are shown in grey and the results of those treated with placebo in black.
Area under the curve of the glucose concentration 3 h after OGTT in Wistar rats treated with 2.5 μg/100 g BW of rT3. Rats were fed with 2 g/kg of glucose. The results of the rats treated with rT3 are shown in grey and the results of those treated with placebo in black.
Area under the curve of the insulin concentration 3 h after OGTT (Oral Glucose tolerance test) in Wistar rats treated with 2.5 μg/100 g BW of rT3. Rats were fed with 2 g/kg of glucose. The results of the rats treated with rT3 are shown in grey and the results of those treated with placebo in black.
Kinetic of glucose concentration in plasma in Wistar rats treated with 2.5 μg/100 g BW of rT3.
Rats were fed with 2 g/kg of glucose. The results of the rats treated with rT3 are shown with white triangles and the results of those treated with placebo with black lozenges.
Kinetic of Insulin concentration in plasma in Wistar rats treated with 2.5 μg/100 g BW of rT3. Rats were fed with 2 g/kg of glucose. The results of the rats treated with rT3 are shown with white triangles and the results of those treated with placebo with black lozenges.
Pancreas mass in Wistar rats treated with 2.5 μg/100 g BW of rT3. The results of the rats treated with rT3 are shown in grey and the results of those treated with placebo in black.
Growth rate of Wistar rats treated with a high dosage (25 μg/100 g of body weight (BW)) or a low dosage (2.5 Mg/100 g BW) of rT3. The weight of the rats treated with a high dosage is shown on the curve with white squares, with low dosage with white triangle and the weight of those treated with placebo is represented with black lozenges.
Food intake Wistar rats treated with a high dosage (25 μg/100 g of body weight (BW)) or a low dosage (2.5 Mg/100 g BW) of rT3. The Food intake of the rats treated with a high dosage is shown on the curve with white squares, with a low dosage with white triangle and the Food intake of those treated with placebo is represented with black lozenges.
Growth rate of Wistar rats treated with an ultra low dosage (0.25 μg/100 g BW) of rT3. The weight of the rats treated with an ultra low dosage is shown on the curve with white squares and the weight of those treated with placebo is represented with black lozenges.
Energy expenditure of Wistar rats treated with a high dosage of rT3 (25 μg/100 g BW), or a low dosage (2.5 μg/100 g BW) of rT3. The energy expenditure of the rats treated with high dosage of thyroid hormones is shown on the curve with white squares, the energy expenditure of the rats treated with low dosage of thyroid hormones is shown on the curve with white triangles and the energy expenditure of those treated with placebo is represented with black lozenges.
Energy expenditure of Wistar rats treated with a ultra low dosage (0.25 μg/100 g BW) of rT3. The energy expenditure of the rats treated with high dosage of thyroid hormones is shown on the curve with white squares and the energy expenditure of those treated with placebo is represented with black lozenges.
Respiratory quotient (RQ) of Wistar rats treated with a high dosage of rT3 (25 μg/100 g BW), or a low dosage (2.5 μg/100 g BW) of rT3. The respiratory quotient of the rats treated with high dosage of thyroid hormones is shown on the curve with white squares, the respiratory quotient of the rats treated with low dosage of thyroid hormones is shown on the curve with white triangles and the respiratory quotient of those treated with placebo is represented with black lozenges.
Respiratory quotient of Wistar rats treated with a ultra low dosage (0.25 μg/100 g BW) of rT3. The respiratory quotient of the rats treated with high dosage of thyroid hormones is shown on the curve with white squares and the respiratory quotient of those treated with placebo is represented with black lozenges.
Weight of adipose tissues of Wistar rats treated with a high dosage of rT3 (25 μg/100 g BW), or a low dosage (2.5 μg/100 g BW) of rT3. The results of the rats treated with high dose of thyroid hormones are shown in white, the results of the rats treated with low dose of thyroid hormones are shown in grey and the results of those treated with placebo in black.
Weight of muscle tissue of Wistar rats treated with a high dosage of rT3 (25 μg/100 g BW), or a low dosage (2.5 μg/100 g BW) of rT3. The results of the rats treated with high dose of thyroid hormones are shown in white, the results of the rats treated with low dose of thyroid hormones are shown in grey and the results of those treated with placebo in black.
Weight of brown adipose tissue of Wistar rats treated with a high dosage of rT3 (25 μg/100 g BW), or a low dosage (2.5 μg/100 g BW) of rT3. The results of the rats treated with high dose of thyroid hormones are shown in white, the results of the rats treated with low dose of thyroid hormones are shown in grey and the results of those treated with placebo in black.
Rate of mitochondrial oxygen consumption (JO2 in nmol of O2/min/mg of protein) of Wistar rats treated with a high dosage of rT3 (25 μg/100 g BW), or a low dosage (2.5 μg/100 g BW) of rT3. Oxygen consumption of rats treated with thyroid hormones at high dose is shown in white, at low dose is shown in grey and oxygen consumption of those treated with placebo in black. All measurements were performed using mitochondria (1.0 mg of mitochondrial protein/ml) incubated with various substrates:
GM: glutamate/malate (5 mM/2.5 mM),
SR: succinate/rotenone (5 mM/5 μM),
GMS: glutamate/malate/succinate (5 mM/2.5 mM/5 mM),
Palm: palmitoyl carnitine (55 μM),
Octa: octanoyl carnitine (100 μM),
TMPD/ascorbate (0.5 mM/0.5 mM) and
TMPD/AsC/DNP: TMPD/ascorbate/DNP (0.5 mM/0.5 mM/75 μM)
The asterisk corresponds to a p-value <0.01.
Activity of the GPdH enzyme. Activity of the mitochondrial glycerol 3 phosphate dehydrogenase was assessed in mitochondria from liver extracted from placebo (black) 25 μg/A, 100 g rT3 (white) or 2.5 μg/100 g (grey).
Plasma concentrations triglycerides, cholesterol, FFA (Free Fatty Acid) and HDL (Heavy Density Lipoprotein) in Wistar rats treated with a high dosage of rT3 (25 μg/100 g BW), or a low dosage (2.5 μg/100 g BW) of rT3. These measurements were done on venous blood of the rats the day of the sacrifice (i.e. after 21 days of treatment).
The results of the rats treated with high rT3 are shown in white, with low rT3 are shown in grey and those treated with placebo in black.
The asterisk corresponds to a p-value<0.01.
Body weight of Wistar rats treated with a low dosage (2.5 μg/100 g BW) of rT3. Results from rats treated with subcutaneous pellet are shown in white, results from rats treated with subcutaneous pump are shown in light grey, results from rats treated with intra-peritoneal pump are shown in grey and results from those treated with placebo are shown in black.
Fat mass of different adipose tissues (retroperitoneal, epididymal, mesenteric and subcutaneous fat) of Wistar rats treated with a low dosage (2.5 μg/100 g BW) of rT3. Results from rats treated with subcutaneous pellet are shown in white, results from rats treated with subcutaneous pump are shown in light grey, results from rats treated with intra-peritoneal pump are shown in grey and results from those treated with placebo are shown in black.
Brown adipose tissue mass of Wistar rats treated with a low dosage (2.5 μg/100 g BW) of rT3. Results from rats treated with subcutaneous pellet are shown in white, results from rats treated with subcutaneous pump are shown in light grey, results from rats treated with intra-peritoneal pump are shown in grey and results from those treated with placebo are shown in black.
mGPdH activity of Wistar rats treated with a low dosage (2.5 μg/100 g BW) of rT3. Results from rats treated with subcutaneous pellet are shown in white, results from rats treated with subcutaneous pump are shown in light grey, results from rats treated with intra-peritoneal pump are shown in grey and results from those treated with placebo are shown in black.
EE of Wistar rats treated with a low dosage (2.5 μg/100 g BW) of rT3. Results from rats treated with subcutaneous pellet are shown in white, results from rats treated with subcutaneous pump are shown in light grey, results from rats treated with intra-peritoneal pump are shown in grey and results from those treated with placebo are shown in black.
RQ of Wistar rats treated with a low dosage (2.5 μg/100 g BW) of rT3. Results from rats treated with subcutaneous pellet are shown in white, results from rats treated with subcutaneous pump are shown in light grey, results from rats treated with intra-peritoneal pump are shown in grey and results from those treated with placebo are shown in black.
Body weight of Wistar rats treated with a low dosage (2.5 μg/100 g BW) of rT3 and treated or not with PTU (Propylthiouracil)) and IOP (iopanoïc acid). Results from rats treated with PTU-IOP are shown in white triangles, results from rats treated with PTU-IOP and rT3 are shown in white squares and results from those treated with placebo are shown in black squares.
Food intake of Wistar rats treated with a low dosage (2.5 μg/100 g BW) of rT3 and treated or not with PTU (Propylthiouracil)) and IOP (iopanoïc acid). Results from rats treated with PTU-IOP are shown in white triangles, results from rats treated with PTU-IOP and rT3 are shown in white squares and results from those treated with placebo are shown in black squares.
Energy expenditure of Wistar rats treated with a low dosage (2.5 μg/100 g BW) of rT3 and treated or not with PTU (Propylthiouracil)) and IOP (iopanoïc acid). Results from rats treated with PTU-IOP are shown in white triangles, results from rats treated with PTU-IOP and rT3 are shown in white squares and results from those treated with placebo are shown in black squares.
Respiratory quotient of Wistar rats treated with a low dosage (2.5 μg/100 g BW) of rT3 and treated or not with PTU (Propylthiouracil)) and IOP (iopanoïc acid). Results from rats treated with PTU-IOP are shown in white triangles, results from rats treated with PTU-IOP and rT3 are shown in white squares and results from those treated with placebo are shown in black squares.
Rate of mitochondrial oxygen consumption (JO2 in nmol of O2/min/mg of protein) of Wistar rats treated with a high dosage of rT3 (25 μg/100 g BW), and treated or not with PTU (Propylthiouracil) and IOP (iopanoïc acid). Oxygen consumption of rats treated with PTU+IOP is shown in grey, treated with PTU+IOP and rT3 is shown in white and oxygen consumption of those treated with placebo in black. All measurements were performed using mitochondria (1.0 mg of mitochondrial protein/ml) incubated with various substrates:
GM: glutamate/malate (5 mM/2.5 mM),
SR: succinate/rotenone (5 mM/5 μM),
GMS: glutamate/malate/succinate (5 mM/2.5 mM/5 mM),
Palm: palmitoyl carnitine (55 μM),
Octa: octanoyl carnitine (100 μM),
TMPD/ascorbate (0.5 mM/0.5 mM) and
TMPD/AsC/DNP: TMPD/ascorbate/DNP (0.5 mM/0.5 mM/75 μM)
JO2 was recorded in the presence of the substrate and following the addition of 1 mM ADP (state 3).
mGPdH activity of Wistar rats treated with a low dosage (2.5 μg/100 g BW) of rT3 and treated or not with PTU (Propylthiouracil) and IOP (iopanoïc acid). Activity of rats treated with PTU+IOP is shown in grey, treated with PTU+IOP and rT3 is shown in white and activity of those treated with placebo in black.
Brown adipose tissue mass of Wistar rats treated with a low dosage (2.5 μg/100 g BW) of rT3 and treated or not with PTU (Propylthiouracil) and IOP (iopanoïc acid). Mass of brown adipose tissue of rats treated with PTU+IOP is shown in grey, treated with PTU+IOP and rT3 is shown in white and mass of brown adipose tissue of those treated with placebo in black.
Plasma concentration of T4 hormone of Wistar rats treated with a low dosage (2.5 μg/100 g BW) of rT3 and treated or not with PTU (Propylthiouracil) and IOP (iopanoïc acid). T4 concentration of rats treated with PTU+IOP is shown in dark grey, treated with PTU+IOP and rT3 is shown in white and T4 of those treated with placebo in grey.
Area under the curve of the glucose concentration 3 h after OGTT in Wistar rats after 8 weeks of feeding with a high-fat high-sucrose diet and treated with 2.5 μg/100 g BW of rT3. Rats were fed with 2 g/kg of glucose. The results of the rats treated with rT3 are shown in grey and the results of those treated with placebo in black.
Area under the curve of the insulin concentration 3 h after OGTT (Oral Glucose tolerance test) in Wistar rats after 8 weeks of feeding with a high-fat high sucrose diet and treated with 2.5 μg/100 g BW of rT3. Rats were fed with 2 g/kg of glucose. The results of the rats treated with rT3 are shown in grey and the results of those treated with placebo in black.
Kinetic of glucose concentration in plasma in Wistar rats after 8 weeks of feeding with a high-fat high sucrose diet and rats treated with 2.5 μg/100 g BW of rT3. Rats were fed with 2 g/kg of glucose. The results of the rats treated with rT3 are shown with white triangles and the results of those treated with placebo with black lozenges.
Kinetic of Insulin concentration in plasma in Wistar rats after 8 weeks of feeding with a high-fat high sucrose diet and rats treated with 2.5 μg/100 g BW of rT3. Rats were fed with 2 g/kg of glucose. The results of the rats treated with rT3 are shown with white triangles and the results of those treated with placebo with black lozenges.
Hepatic lipogenesis during day and night in Wistar rats treated with 2.5 μg/100 g BW of rT3. The results of the rats treated with rT3 are shown in grey and the results of those treated with placebo in black.
Animal Handling
Adult male rat bred in the animal room facilities of Laboratory of Fundamental and Applied Bioenergetics (Wistar strain) or purchased from Charles-River Laboratories, Domaine des oncins, L'ARBRESLE France [(genetically obese normoglycemic (Zucker or Fa/Fa) or diabetic (ZDF)] were caged individually in stainless steel hanging cages and maintained in a 22° C., 50±10% relative humidity and 12 h:12 h light:dark environment. All animals were fed ad libitum with a standard rat chow (Safe A04, Villemoisson, France) and tap water. Body mass and food intake were recorded twice/thrice a week and fresh food was provided at the same time to ensure minimal disturbance to the animals' food behavior.
Pellet Implant
Eight-week old rats (300 g±10 g) were anesthetized by simultaneous intraperitoneal injection of diazepam 4 mg/kg and ketamine 100 mg/kg. In order to maintain body temperature during the surgery (10 min), animals were placed on a warm blanket. After interscapular shaving, a small incision of 0.5 cm of the skin allows the subcutaneous implantation of a small pellet (containing rT3 or 3′,3-T2) with a 10-gauge precision trochar. The pellets, manufactured by Innovative Research of America (Sarasota, Fla., USA) are constituted of a biodegradable matrix that effectively and continuously release the active product in the animal.
3,3′,5 triiodo-thyronine (reverseT3) or 3-3′ diiodothyronine (3-3′ T2) were used at different doses (5, 0.5, or 0.1 mg/pellet) were implanted in order to provide a continuous and constant drug delivery over 60 days (which represents 25 μg, 2.5 μg or 0.5 μg/day/100 g BW).
Indirect Calorimetry
Energy expenditure as well as the nature of substrate oxidized (carbohydrates or lipids) were investigated by indirect calorimetry. This principle is based on the determinations of CO2 release (VCO2) and O2 consumption (VO2) by each animal. It assumes that O2 is entirely involved in substrate oxidation in the respiratory chain (leading to water production) while CO2 release is related to substrate decarboxylation (in the Krebs' cycle). These measurements allow assessing energy expenditure (EE) and respiratory quotient (VO2/VCO2, RQ). EE represent the absolute energy dissipation during rest and activity. RQ is a relative measurement indicating the ratio of carbohydrate versus lipid involved in oxidative pathway. A ratio of 1.0 indicates exclusive carbohydrate oxidation while a ratio of 0.7 indicates exclusive lipid oxidation. Each value between these two extreme values indicates the relative proportion of each substrate (of note protein oxidation was not evaluated). As an example, RQ approaches 0.7 during fasting, indicating lipid oxidation, conversely after feeding RQ increases close to 1 indicating carbohydrate oxidation resulting from food intake and blood insulin rise. Likewise, animals fed high-carbohydrate diets have higher RQs than those fed high-fat diets.
The indirect calorimetry system (Panlab, Barcelona, Spain) consists of cages, pumps, flow controllers, valves, and analyzers. It is computer-controlled in order to sequentially measure O2 and CO2 concentrations as well as air flow in four separate cages allowing four simultaneous determinations. Rats are isolated in one of the four metabolic chambers, and room air is used as a reference to monitor ambient O2 and CO2 concentrations periodically.
At predefined intervals, the computer sends a signal to store differential CO2 and O2 concentrations, flow rate, allowing computing VCO2, VO2, RQ, and EE (Weir equation) with data acquisition hardware (Metabolism, Panlab, Barcelona, Spain).
Body Composition, Blood and Tissue Sampling
At the end of the experimental period, animals were sacrificed by decapitation, in order to avoid the well-known effects of general anesthetics on mitochondrial metabolism. Blood samples were immediately collected and plasma was frozen for subsequent determination of serum metabolites and hormones. Liver, muscles and fat depots were quickly excised and weighed. Liver median lobe was rapidly freeze-clamped. Muscles (plantaris, soleus and gastrocnemius) were frozen in isopentane precooled in liquid nitrogen. Mesenteric fat consisted of adipose tissue surrounding the gastro-intestinal tract from the gastro-oesophageal sphincter to the end of the rectum with special care taken in distinguishing and removing the pancreas. Retroperitoneal fat pad was taken as the distinct depot behind each kidney along the lumbar muscles. Epididymal fat consisted of adipose tissue on top of the epididymis. For subcutaneous depot measurement, a rectangular piece of skin was taken on the right side of each animal from the median line of the abdomen between the spine and the right hip to the first rib. Interscapular brown adipose tissue was removed and dissected free from adjacent muscles and white adipose tissue. The heart ventricles, the right kidney and the spleen were also excised, weighed and frozen.
Mitochondrial Isolation
The major part of the liver and the red part of each quadriceps were rinsed, and chopped into isolation medium (250 mM sucrose, 20 mM Tris-HCl and 1 mM EGTA-Tris, pH 7.4). Nuclei and cell debris were removed by centrifugation at 800 g for 10 min. Mitochondria were then isolated from the supernatant by spinning twice at 8,000 g for 10 minutes. The mitochondrial pellet was resuspended in 0.5 ml of isolation buffer and kept on ice. Mitochondrial protein was measured by the bicinchoninic acid method (Pierce, Rockford, Ill.). The final mitochondrial suspensions were maintained on ice and were used for measurements of oxygen consumption rate.
Mitochondrial Oxygen Consumption
The rate of mitochondrial oxygen consumption (JO2) was measured at 30° C. in an incubation chamber with a Clark-type O2 electrode filled with 2 ml of incubation medium (125 mM KCl, 10 mM Pi-Tris, 20 mM Tris-HCl, 0.1 mM EGTA, pH 7.2). All measurements were performed using mitochondria (1.0 or 0.2 mg mitochondrial protein/ml for liver and skeletal muscle) incubated either with various substrates: glutamate/malate (5 mM/2.5 mM) and succinate (5 mM), alone or in combination, palmitoyl carnitine (55 μM) and octanoyl carnitine (100 μM). For each substrate, JO2 was recorded in the presence of the substrate alone (State 2) and following the addition of 1 mM ADP (state 3). Oligomycin (1.25 μg/mg protein) was added to the mitochondrial suspension to determine the non-phosphorylating respiratory rate (state 4). The incubation medium was constantly stirred with a built-in electromagnetic stirrer and bar flea. The efficiency of the mitochondrial oxidative phosphorylation was assessed by the state 3/state 4 ratio which measures the degree of control imposed on oxidation by phosphorylation (respiratory control ratio, RCR).
Oxidative Phosphorylation Efficiency
ATP/0 ratios with 5 mM glutamate/2.5 mM malate/5 mM succinate or octanoyl-carnitine (100 μM) as respiratory substrates were determined from the ATP synthesis rate (JATP) versus respiratory rate JO2 with an ADP regenerating system based on hexokinase (EC 2.7.1.1) plus glucose. JATP and JO2 were measured as described above in a medium containing 125 mM KCl, 1 mM EGTA, 5 mM Tris-Pi, 20 mM Tris-HCl, 0.1% fat free BSA (pH 7.2). JATP was determined from glucose 6-phosphate formation in presence of 20 mM glucose, 1 mM MgCl2, and 125 μM ATP. JO2 and JATP were modulated by addition of increasing concentrations of hexokinase (Nogueira et al, J Bioenerg Biomemb., 34: 55-66, 2002).
Enzymatic Activities
Measurement of the specific activity of the respiratory-chain complex I, II and IV was performed spectrophotometrically. A total of 8-10 μg of mitochondrial proteins were required to determine the activity of complex I and II, and 4 μg were used for complex IV. Enzyme activity was expressed as nmoles of reduced or oxidized substrate per min and per mg of mitochondrial protein.
Measurement of complex I (rotenone-sensitive NADH-ubiquinone oxidoreductase, EC 1.6.99.3): The assay was performed using decylubiquinone (100 μM) as electron acceptor and NADH (200 μM) as a donor, in a 10 mM KH2PO4/K2HPO4 buffer (pH 7.5) containing BSA (3.75 mg/ml), and in the presence of KCN (2 mM) and antimycin A (7.5 μM). The oxidation of NADH was then measured at 340 nm before and after the addition of rotenone (4 μM), allowing the calculation of the rotenone-sensitive specific activity of complex I.
Measurement of complex II (succinate-ubiquinone reductase, EC 1.3.99.1): Succinate-ubiquinone oxidoreductase activity was quantified by measuring the decrease in UV absorbance due to the reduction of DCPIP (100 μM) at 600 nm. The measurement was performed in a medium containing 50 mM KH2PO4/K2HPO4 (pH 7.5) in the presence of decylubiquinone (100 μM), rotenone (2 μM) and KCN (2 mM).
Measurement of complex IV (cytochrome c oxidase, EC 1.9.3.1): The assay was performed by measuring cytochrome c (100 μM) oxidation at 550 nm in a 50 mM KH2PO4/K2HPO4 buffer (pH 7.0).
Citrate synthase activity was determined by measuring the UV absorbance at 412 nm due to the formation of the ion mercaptide in the presence of oxaloacetate dinitrothiobenzoïque acid and acetyl-CoA in a 150 mM Tris buffer pH 8 (Garait et al, Free Rad Biol Med, 2005).
Mitochondrial glycerol 3-phosphate dehydrogenase (mGPdH) activity was measured on the supernatant of isolated mitochondria after three cycles of freezing-thawing. Forty μg of mitochondria were incubated in a KH2PO4/K2HPO4 buffer (50 mM, pH 7.5) containing 9.3 μM of antimycin A, 5 μM of rotenone and decylubiquinone (50 μM). The reduction of 50 μM dichloro-indophenol (DCIP) by mGPDH was measured spectrophotometrically at 600 nm at 37° C. and enzymatic activity was expressed as μmol·min−1·mg prot−1.
Cytochromes
Cytochromes content of the mitochondrial respiratory chain was measured in parallel experiments by comparing the spectra of fully oxidized (potassium ferricyanide) versus fully reduced (few crystals of sodium dithionite) cytochromes. Knowing the contributions in absorbance of each cytochrome to the major maxima and minima of each of the other cytochromes, a set of 4 simultaneous equations with 4 unknowns can be derived and concentration of each cytochrome can be calculated (Williams, Arch Biochem Biophys.; 107: 537-43, 1964).
Hepatocytes Isolation
Wistar rats fasted for 20-24 h were anesthetized with sodium pentobarbital (10 mg/100 g body wt i.p.), and the hepatocytes were isolated according to the method of Berry and Friend (J. Cell. Biol. 43: 506-520, 1969) as modified by Groen et al. (Eur. J. Biochem. 122: 87-93, 1982). Briefly, the portal vein was cannulated, and a 2-min anterograde perfusion with Ca2+-free Krebs-Ringer bicarbonate buffer (25 ml/min; 37° C., pH=7.4, continuously gassed with 95% O2-5% CO2) was performed to remove blood from the liver. A 10-min retrograde perfusion (25 ml/min) through the posterior vena cava was started with the same perfusion medium. Subsequently, a recirculating perfusion was performed (20 min at 40 ml/min) with 100 ml Krebs-Ringer medium supplemented with 0.25 mg/ml collagenase (type IV, Sigma, St. Louis, Mo.). The liver was then cut and shaken in the perfusion medium for 2 min under constant gassing (95% O2-5% CO2). Finally, the cell suspension was filtered through nylon gauze (pore size, 120 μm), washed twice with Krebs-Ringer bicarbonate buffer containing 1.6 mM Ca2+, and then washed for a third time with the same buffer supplemented with 1% BSA.
Perifusion of Hepatocytes
Liver cells were perifused according to the method of van der Meer and Tager (FEBS Lett. 67: 36-40, 1976) modified by Groen et al. (Eur. J. Biochem. 122: 87-93, 1982). Hepatocytes (225-250 mg dry mass) were placed in 15-ml perifusion chambers at 37° C. and were perifused (5 ml/min) with a continuously gassed (95% O2-5% CO2) Krebs-Ringer bicarbonate solution (pH=7.4) containing 0.2% BSA. The experiments were carried out in duplicate in two perifusion chambers placed in parallel. At the chamber outlet, perifusate O2 content was monitored with Clark electrodes (Yellow Springs Instruments, Yellow Springs, Ohio) to assess O2 uptake of the hepatocyte suspension. After 40 min, when O2 uptake had reached a steady state, hepatocytes were perifused with increasing amount of glycerol (0.15, 0.30, 0.60, 1.2, 2.4, 4.8, and 9.6 mM), in the presence or not of 0.4 mM octanoate. At the end of each steady state of 20 min, perifusate and cells samples were collected at 2-min intervals for subsequent determination of glucose, lactate, pyruvate, acetoacetate, and β-hydroxybutyrate concentrations. Samples were stored at 4° C. and analyzed within 12 h after the end of the experiment. In addition, 300 μl of the cell suspension were sampled from the chamber for intra- and extracellular fractionation. For this purpose, mitochondrial and cytosolic spaces were separated with the digitonin fractionation method described by Zuurendonk and Tager (Biochim. Biophys. Acta 333: 393-399, 1974). Briefly, the cell suspension was placed in a 2.2-ml Eppendorf tube in an isotonic medium containing 2 mM of digitonin (Merck, Lyon, France) at 4° C. After 15 s, the tube was centrifuged for 15 s at 10,000 g to precipitate mitochondria through the underlying 800-μl layer of silicon oil (Rhodorsil 640 V 100, Rhône-Poulenc) into 250 μl HClO4 (10% mass/vol)+25 mM EDTA. The supernatant (700 μl) was immediately removed, deproteinized with HClO4 (5% mass/vol), and neutralized. The intracellular content was then neutralized and kept at −20° C. for determination of intracellular metabolites (DHAP and G3P, spectrophotometry) and adenine nucleotides content (HPLC).
Western Blot Analysis
For mGPdH quantification, polyacrylamide gel electrophoresis and immunoblotting were performed as previously described (23). Briefly, lysed hepatocytes were mixed with 200 μl of buffer containing 40 mM Tris(hydroxymethyl)aminomethane pH 6.8, 1% SDS, 6% glycerol, and 1% b-mercaptoethanol. This mixture was then heated at 100° C. for 10 min, and subjected to one-dimensional sodium dodecyl sulfate (SDS)-PAGE with a 5% stacking and 12.5% resolving gels for 12 hours. After electrophoretic separation, proteins were transferred at a constant voltage to PVDF membranes. After protein transfer, the membranes were blocked for 2 h, then incubated 2 h with a monoclonal antibody specific for mGPDH (generous gift from Dr. J. Weitzel) and then exposed to the secondary antibody (goat anti-mouse immunoglobulin G conjugated to horseradish peroxidase, Bio-Rad at a 1:10000 dilution). mGPDH were visualized by the enhanced chemiluminescence detection method (RPN 2106, Amersham). Scanning with a densitometer performed quantification of bands from blots and the data were expressed numerically as integrated optical density arbitrary units.
RNA Purification and Reverse Transcription-Coupled PCR
Total RNA were extracted from tissue using Tripure RNA Isolation reagent (Roche Diagnostics). Concentration and purity were verified by measuring optimal density at 260 and 280 nm. Their integrity was checked by 1% agarose gel electrophoresis (Eurobio). mRNA concentrations were measured by semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) using β actin as reference. Primer sequences are shown in table 1. For each target mRNA, a RT was performed from 0.1 μg of total RNA with 100 U of M-MLV Reverse Transcriptase (Promega), 5 μL of M-MLV RT 5× buffer, 20 U of RNasin Ribonuclease Inhibitor, 12 picomoles of deoxynucleoside triphosphate and 15 picomoles of the specific antisense primer, in a final volume of 25 μL. The reaction consisted in 5 min at 70° C. (RNA and antisense primer), then 60 min at 42° C. (all mix) followed by 15 min at 70° C. After chilling, 5 μL were used for PCR reaction. The 5 μL of RT medium were added to 45 μL of PCR mix (5 μL 10×REDTaq PCR buffer) containing 6 picomoles of MgCl2, 8 picomoles of deoxynucleoside triphosphate, 2.5 U of REDTad DNA polymerase (Sigma), 15 picomoles of corresponding antisense primers and 22.5 picomoles of sense primers. The PCR conditions were: 2 min at 94° C. followed by 28 cycles, 35 cycles or 18 cycles for UCP3, UCP2 and β actin respectively (1 cycle=1 min at 94° C., 1 min at 60° C., 1 min at 72° C.). PCR was ended by 10 min at 72° C. Products were analysed on 2% agarose gel prestained with ethidium bromide. For quantitation of relative bands intensities, pictures were taken with a Camera DC120 (Kodak) and the ratio of each target to β actine was determined for each sample with Kodak Digital Science 1D 2.0 (Kodak Scientific Imaging System).
As shown in
This indicates a very powerful prevention of normal weight gain in these young adult animals.
As shown in
Hence the decrease in body weight in both groups of treated animals was associated with an increased food intake.
The energy expenditure (EE) of rats was assessed by indirect calorimetry (see material and method section) and values were analyzed over a period of 24 hours (=1440 minutes). All groups of animals, treated with placebo (
This very important result indicates that the metabolic expenses are largely increased by the two treatments both during the nocturnal and the diurnal periods.
The respiratory quotient (RQ) is defined as the ratio between released carbon dioxide to consumed oxygen: VCO2/VO2. It is largely accepted that this ratio indicate the origin of oxidized substrates (carbohydrate versus lipids). This value is equal to 1 if carbohydrates represent the exclusive source of energy and 0.7 were lipids represent the unique energetic substrate.
As already shown the EE, RQ also varies between day and night (
The change in body composition of rats treated with rT3 or placebo are presented both as absolute values (g) or as percentage of total body mass since the two groups of animals did not exhibit the same mass after three weeks (see
Retroperitoneal, mesenteric and subcutaneous fat masses were significantly lower (p<0.01) in rT3 group as compared to placebo, epididymal mass being not different (
These results clearly indicate that the decrease in body mass after rT3 treatment is purely due to a loss of fat mass, the lean body mass being not affected.
Similar results are obtained with 3,3′-T2 (
The effect of both treatments (rT3 or 3,3′-T2) on the efficacy of the coupling between oxidation and phosphorylation at the level of liver mitochondrial respiratory chain were evaluated (
Very interestingly completely different results were obtained with muscle mitochondria. Indeed both rT3 and 3,3′-T2 failed to substantially affect both non-phosphorylating (state 4,
Hence this indicated that although both rT3 and 3,3′-T2 exhibit a powerful effect on liver mitochondria leading to the a decreased oxidative phosphorylation efficiency and to an increased maximal respiratory capacity, almost no effect was found on muscle mitochondrial despite the fact that the drug was administered to every tissue (subcutaneous progressive release from the pellet).
In conclusion, the dramatic effect observed in the body mass is completely explained by the decreased fat mass, while the lean body mass (muscle mass) seems not affected. This effect, which is observed despite increased food consumption, is due to an increased energy expenditure, which was substantiated by indirect calorimetry measurement. Since the normal diet of these animals is rather poor in lipid content (4-5%) the increase fat oxidation is achieved at the expense of the fat storage as shown by the strong decrease in fat mass and also probably by a de novo lipogenesis, an expensive pathway, which might explain the higher RQ observed in the fed period. The data concerning the overall increase in energy metabolism (indirect calorimetry) are in very good agreement with the data obtained in liver isolated mitochondria indicating the probably occurrence of energy wasting process at the level of the respiratory chain and ATP synthesis associated with a significant higher maximal respiratory capacity. Most interestingly none of these effects was observed in muscle mitochondria indicating that the wasting process affects more the liver than the muscle mass and concerns lipid oxidation.
Hence in total both rT3 and 3,3′-T2 enhance lipid oxidation and energy expenditure leading to a marked decrease in the mass of adipose tissue only.
The Material and Methods are those described in Example 1.
Animals
Wistar rats were used in these studies.
Administrations
Wistar rats were treated with rT3 hormone by a daily intraperitoneal injection (IP) (25 μg/100 g BW), a daily sub-cutaneous injection (SC) (25 μg/100 g BW), or a per os administration included in the rat food (25 μg/100 g BW). The continuous and constant administration was performed by using a pellet (25 μg/100 g BW).
In order to compare the effect of rT3 administration in the rat weight, Wistar rats were treated for 8 days by a pellet diffusing a continuous and constant dose of rT3 (25 μg/100 g BW/day), or daily treated by intra-peritoneal or sub-cutaneous injection of rT3 (25 μg/100 g BW by injection) or by oral administration (25 μg/100 g BW by ingestion).
As shown in
To confirm these data, the individual weight of adipose tissues was measured in the animals treated with the four different rT3 administrations. As previously observed for the global mass, only animals treated with continuous and constant rT3 administration have a significant white fatty tissue mass reduction (
To confirm the effect on the metabolism of the treated animals, the EE was estimated by indirect calorimetry over a period of 24 hours. The
Therefore, all these data demonstrate that only a continuous and constant administration of rT3 is able, after 8 days of treatment, to significantly reduce the body mass of animals, by only affecting the white fat tissues, by inducing an increase of the fatty acid metabolism.
In order to understand why the discontinuous treated failed to give results, the circulating rT3 was measured in animals, for 24 hours, after the injection. The graph in
The Material and Methods are those described in Example 1.
Animals
Rats were genetically obese normoglycemic (Zucker or Fa/Fa), 10-11 week-old diabetic rats (ZDF), genetic non-overweight diabetic (type 2 diabetes) rats (Goto-Kakizaki (GK) model), non-overweight diabetic (type 2 diabetes) rats n0STZ model or normal Wistar rats submitted to an 8-week high-fat high sucrose diet (a model of nutritional induction of insulin resistance).
Blood Sampling
The day of the study, after a fasted period overnight (18 h), blood samplings will be taken in awaked rats from the tail vein.
Blood Parameters
The following biochemical parameters were analyzed: glycemia, insulinemia, HbAlc, TG and Cholesterol.
Thyroid Stimulating Hormone (TSH) and thyroxine (T4) were measured by radioimmunoassay with rat standards (RPA 554 Amersham bioscience, RIA FT4-immunotech, for TSH and T4 respectively).
Insulin levels were determined with commercial kits (Linco Research).
Glucose and 3-hydroxybutyrate (3-HB) were measured enzymatically and non esterified fatty acid (NEFA) by colorimetric assay (Wako Chemicals).
Triglycerides and cholesterol were measured by classical routine automate apparatus.
ZDF diabetic rats are a good model for studying the anti-diabetic treatments, since these animals develop a major hyperglycaemia during their life due to the combination of moderate obesity and pancreas degeneracy. To date, treatments are ineffective when the hyperglycaemia is established.
Then ZDF rats were treated with low doses of rT3 for 21 days (2.5 μg/100 g BW/day) and the glycaemia, insulinaemia were measured after 8, 16 and 21 days.
Surprisingly, the insulin level in rats treated with rT3 is associated with an increased of the pancreas mass (
These data indicate that rT3 can reverse the installed diabetic disease of ZDF rats, probably by a mechanism involving the β-pancreas cell self renewing. By this way ZDF rats recover their ability to regulate the glycaemia.
ZDF are also fatty animals with hypertriglyceridemia. So the effect of the rT3 treatment was also evaluated.
Indeed, as shown in
Interestingly, even if the global mass of rT3-treated animals is decreased, the white adipose tissue of the ZDF rats seems not to be affected by the rT3 treatment as shown in
Also, muscular mass is not affected by the rT3 treatment (
To better understand the lipid metabolism, lipid profiles of free fatty acid (FFA,
In rats treated with rT3, FFA are significantly enhanced (
In conclusion, a low dose of rT3 administered in ZDF rats has a double effect:
N0STZ rats are diabetic non obese with moderate insulin-resistance, and have received an injection of streptozotocine just after the birth, said product killing pancreatic cells.
The glucose resistance of these animals was tested by an oral glucose tolerance test (OGTT) Animals were fed with 2 g/kg BW of glucose and the Glucose concentration and Insulin concentration in blood were measured.
In rats treated with low dose of rT3 (2.5 g/100 g BW), 3 hours after the OGGT, the area under the curve (AUC) of the glucose concentration is significantly reduced compared to rats treated with placebo (
To confirm these results, kinetic curves of the OGTT were performed for 20 min. The glucose concentration (
In
Therefore, a rT3 treatment is able to correct the glucose regulation dysfunction. The increase of the insulin level observed in OGTT is associated with an increase of the pancreas mass of rT3 treated animals (
Then, rT3 treatment regulates the pancreas proliferation.
GK rats are diabetic non obese with moderate insulin-resistance, and have lower pancreatic cells than control rats. The pancreatic cells are also less efficient in the insulin secretion.
The glucose resistance of these animals was tested by an oral glucose tolerance test (OGTT) Animals were fed with 2 g/kg BW of glucose and the Glucose concentration and Insulin concentration in blood were measured.
In rats treated with low dose of rT3 (2.5 g/100 g BW), 3 hours after the OGGT, the area under the curve (AUC) of the glucose concentration is significantly reduced compared to rats treated with placebo (
To confirm these results, kinetic curves of the OGTT were performed for 20 min. The glucose concentration (
In
Therefore, rT3 treatment is able to correct the glucose regulation dysfunction. The increase of the insulin level observed in OGTT is associated with an increase of the pancreas mass of rT3 treated animals (
Then, rT3 treatment regulates the pancreas proliferation.
Wistar rats are non-diabetic, non-obese without insulin-resistance, however like in humans, they tend to get slightly obese and insulin resistant with age. However this is supposed to be “physiological”.
The glucose resistance of these animals was tested by an oral glucose tolerance test (OGTT). Animals were fed with 2 g/kg BW of glucose and the Glucose concentration and Insulin concentration in blood were measured.
In rats treated with low dose of rT3 (2.5 g/100 g BW), 3 hours after the OGGT, the area under the curve (AUC) of the glucose concentration is slightly reduced, however not significantly when compared to rats treated with placebo (
The Material and Methods are those described in the previous examples.
Wistar rats were treated with high dose (25 μg/100 g BW), with low dose (2.5 μg/100 g BW) or with ultra low dose (0.25 μg/100 g BW) of rT3.
After 20 days of treatments, ultra low doses of rT3 and high doses of rT3 give similar results.
With respect to the previous data concerning the metabolic influence of rT3, the energy expenditure of Wistar rats treated with high, low and ultra low doses of rT3 was evaluated.
As shown in
Concerning the RQ, animals treated with high and low doses of rT3 have an increase in their RQ compared to the placebo (
Therefore, although the metabolic involvement of high, low and ultra low doses of rT3 are different, all the doses of the thyroid hormone have a significant effect on the body mass of treated animal.
As a consequence, a dosage comprised from 0.25 μg/100 g BW to 25 μg/100 g BW can be used for the treatment of obesity.
Then, the different dosages of rT3 do not affect the muscle tissues mass (
Similarly the enzymatic activity of mitochondrial glycerol-3-phosphate dehydrogenase was significantly increased with both treatments in a dose-dependent manner.
Concerning the lipid profile of Wistar rats treated with high or low doses of rT3, a high dosage stimulates the liberation of FFA (
For Glycerol (
All these data demonstrate that high, low and ultra low dosages of rT3 are suitable for the reduction of the body weight.
The effect of continuous sub-cutaneous release (sc pellet) was shown to be significantly superior to oral or intraperitonally discontinuous administration of the same dose. However the role of the administration site was further investigated by comparing continuous administration of rT3 by osmotic pump implanted either subcutaneously or intraperitonally with the reference treatment administered by sub-cutaneous pellets. Wistar rats were treated for 21 days with placebo, sub-cutaneous pellet or sub-cutaneous or intraperitoneal osmotic pumps. rT3 was administered continuously (2.5 μg/100 g).
Wistar rats were treated by a continuous and constant administration of low doses of rT3 by 3 different methods of administration:
The results of these three administrations were analyzed after 21 days.
All the methods give similar results, i.e. an increase of the metabolic activity, associated with the mass reduction.
Therefore all the tested method of administration of a continuous and constant dose of rT3 give satisfying results to be used in the treatment of the obesity. These results indicate that the rate of administration was more important for the efficacy that the site of injection (sc versus ip).
All the previous examples have demonstrated the effect of rT3 administration for the therapy of obesity, dyslipidemia and diabetes.
In order to understand the mode of action of the treatments, Wistar rats were treated with pharmacological products that inhibit the synthesis and deiodination of thyroid hormones PTU and IOP.
Animals (Wistar) were submitted to a treatment by propyl-thiouracile (PTU in the drinking water) and iopanoic acid (IOP one sc-injection weekly) inducing a complete inhibition of all deiodinases (types I, II and III). Such treatment is responsible for the induction of a severe hypothyroid state. In addition this treatment impairs the peripheral metabolism of all thyroid hormones by deiodination. Some rats were also submitted to a sub-cutaneous administration of rT3 (2.5 μg/100 g). Three groups were constituted: controls, PTU+IOP and PTU+IOP+rT3 and duration of the experiment was 3 weeks.
Then, since PTU and IOP inhibit the endogenous synthesis of thyroid hormones, the data suggest that the rT3 used in the treatment acts without the intervention of the metabolism of the administered hormone (rT3) nor of other endogenous hormones. To confirm these hypotheses, the T4 concentration was assayed in rats treated or not with PTU+IOP. As shown in
Concerning the brown adipose tissue, PTU+IOP treatment enhances the mass of the energetic adipose tissue, but this mass is also enhanced when rats are treated with rT3.
In conclusion, all these data demonstrate that rT3 administration has an effect on body mass and metabolic activity of treated animals without intervention of the endogenous thyroid hormones and without further deiodination of rT3.
A clinically relevant situation of a nutritionally-induced insulin resistance is known as a high fat high sucrose diet (HF). Therefore, the effects of rT3 on glucose and insulin response to an OGTT test were investigated. Wistar rats were fed a diet containing 45.5% fat (38% lard and 7.5% soy oil) and 34% carbohydrate (25% as sucrose) for 8 weeks. OGTT was performed as described above.
These results confirm the effect of a treatment with rT3 for increasing insulin sensitivity in a situation where the resistance of insulin is due to an inappropriate diet.
Taken together, the effects of rT3 show an increased energy expenditure associated to a decrease in body mass no major change in food intake and a decrease in blood glucose and triglyceride levels while free fatty acid are increased. This indicates that fatty acid oxidation is increased (as it is found in isolated mitochondria). However, global assessments of glucose versus fatty acid oxidation via the tool of indirect calorimetry are not univocal since RQ is sometimes increased and sometimes decreased. One hypothesis is that low fat content of rodent chow, in some situations, fatty acids must be first synthesized from carbohydrate, before being oxidized. Indeed this might be especially relevant when fatty acid oxidation is strongly activated, for instance with high dose of rT3.
To confirm this point, the rate of endogenous triglyceride synthesis by using stable isotopes has been assessed.
These results confirm that rT3 could be responsible for a simultaneous activation of both lipolysis, lipid oxidation and lipogenesis, resulting in a futile cycling, which may explain the considerable increase in basal energy expenditure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 07290635.7 | May 2007 | FR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2008/056076 | 5/16/2008 | WO | 00 | 10/22/2010 |
