Prevention of diabetes by administration of GnRH antagonists

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention is directed to a method of reducing the incidence or delaying the onset of diabetes in diabetes-susceptible mammals by the administration to the mammal of an effective amount of a gonadatropin-releasing hormone (GnRH) antagonist. The administration of such an antagonist gives statistically significant reductions in diabetes incidence and/or onset.

[0003] 2. Description of the Prior Art

[0004] There are 15.7 million people (5.9% of the population) in the United States who have diabetes. An estimated 10.3 million people have been diagnosed with diabetes, while 5.4 million people are unaware that they have a disease. Each day approximately 2,200 people are diagnosed with diabetes. Diabetes is the seventh leading cause of death (sixth-leading cause of death by disease) in the United States. Diabetes is a chronic disease that has no cure. Diabetes is one of the most costly health problems in America. Health care and other costs directly related to diabetes treatment, as well as the costs of lost productivity, are believed to be $98 billion annually.

[0005] Diabetes is a disease in which the body does not produce or properly use insulin, a hormone that is needed to convert sugar, starches and other food into energy needed for daily life. The cause of diabetes is a mystery, although both genetics and environmental factors such as obesity and lack of exercise appear to play roles. There are two major types of diabetes:

[0006] Type 1. An autoimmune disease in which the body does not produce any insulin, most often occurring in children and young adults. People with Type 1 diabetes must take daily insulin injections to stay alive. Type 1 diabetes accounts for 5-10 percent of diabetes.

[0007] Type 2. A metabolic disorder resulting from the body's inability to make enough, or properly use, insulin. It is the most common form of the disease. Type 2 diabetes accounts for 90-95 percent of diabetes. Type 2 diabetes is nearing epidemic proportions, due to an increased number of older Americans, and a greater prevalence of obesity and sedentary lifestyles.

[0008] There are two forms of Type 1 diabetes. Immune-mediated diabetes mellitus results from an autoimmune process in which the body's immune system attacks and destroys the insulin producing cells of the pancreas. Since glucose cannot enter the cells, it builds up in the blood and the body's cells literally starve to death. The second, Idiopathic Type 1, refers to rare forms of the disease that have no known cause. People with Type 1 diabetes must take daily insulin injections to stay alive.

[0009] The strikingly increased incidence of certain autoimmune diseases in females compared to males is well accepted. Although there is evidence that androgens and estrogens play a role in the pathogenesis of autoimmunity, the exact roles of gonadal steroids in autoimmune diseases remain unclear. A number of studies in experimental models have shown that gonadectomy modifies the expression of autoimmune diseases, including diabetes. (Roubinian, et al., (1978) Effect of Castration and Sex Hormone Treatment on Survival, Anti-nucleic Acid Antibodies, and Glomerulonephritis in Nzb/nzw F1 Mice. J. Exp Med, 147, 1568-83; Hawkins, et al., (1993) The Effect of Neonatal Sex Hormones on the Incidence of Diabetes in Nonobese Diabetic Mice. Proc. Soc. Exper. Biol. Med, 202, 201-205; Makino, et al., (1981) The Effect of Castration on the Appearance of Diabetes in Nod Mouse. Exp Anim, 30; and Fitzpatrick, et al., (1991) Influence of Castration, along or Combined with Thyrmectomy, on the Development of Diabetes in the Non-obese Diabetic Mouse. Endocrinology, 129, 1382-1390).

[0010] However, most studies of gender differences in autoimmunity are performed in vivo, where manipulations such as gonadectomy or administration of gonadal steroids will necessarily alter feedback effects on hypothalamic and pituitary hormones, some of which are now known to be immunomodulatory. One hypothalamic hormone with imunomodulatory properties is gonadotropin-releasing hormone (GnRH). GnRH is known to possess indirect immunomodulatory properties via its regulation of gonadal steroids. GnRH has been shown to exert direct immunomodulatory effects in vitro and in vivo in gonadectomized rats. GnRH agonists can prevent the involution of the thymus gland which normally occurs with aging in the rat (Marchetti, et al., (1989) Luteinizing Hormone-releasing Hormone (Lhrh) Agonist Restoration of Age-associated Decline of Thymus Weight, Thymic Lhrh Receptors, and Thymocyte Proliferative Capacity. Endocrinology, 125, 1037-45). GnRH agonist administration has been associated with increases in B and T cell proliferative responses and in an increase in the number of T lymphocytes expressing the I1-2 receptor in rats (Morale, et al., (1991) Blockade of Central and Peripheral Luteinizing Hormone-releasing Hormone (Lhrh) Receptors in Neonatal Rats with a Potent Lhrh-antagonist Inhibits the Morphofunctional Development of the Thymus and Maturation of the Cell-mediated and Humoral Immune Responses. Endocrinology, 128, 1073-85; and Batticane, et al., (1991) Luteinizing Hormone-releasing Hormone Signaling at the Lymphocyte Involves Stimulation of Interleukin-2 Receptor Expression. Endocrinology, 129, 277-86). Moreover, spleen and thymus preparations have been shown to contain mRNA for GnRH and to produce an immunoreactive GnRH (Emanuele, et al. (1990) Rat Spleen Lymphocytes Contain an Immunoactive and Bioactive Luteinizing Hormone-releasing Hormone. Endocrinology, 126, 2482-6; and Maier, et al., (1992) Thymocytes Express a Mrna That Is Identical to Hypothalamic Luteinizing Hormone-releasing Hormone Mrna. Cell Mol Neurobiol, 12, 447-54). A recent study demonstrates that lymphocytic GnRH production increases when T-cells are activated by PHA in vitro (Azad, et al., (1993) Immunoactivation Enhances the Concentration of Luteinizing Hormone-releasing Hormone Peptide and its Gene Expression in Human Peripheral T-lymphocytes. Endocrinology, 133, 215-23). Thus, GnRH appears to exert generally stimulatory effects on the immune system.

SUMMARY OF THE INVENTION

[0011] The present invention addresses the problem of mammalian diabetes by provision of a method for reducing the incidence of the ailment and/or delaying the onset thereof in at-risk mammals having a susceptibility to diabetes. Broadly speaking, the method involves administration to such susceptibly mammals of an effective amount of a GnRH antagonist. This has been found to give statistically significant decreases in development of diabetes or delays in the onset of the disease. A GnRH antagonist is a substance which inhibits the relevant function of the endocrine system, the biosynthesis of GnRH, or the in vivo action of GnRH.

[0012] In practice, susceptible mammals such as mice, rats and humans can be treated in accordance with the invention. Generally, an effective GnRH antagonist is administered (usually by subcutaneous injection) repeatedly over time to achieve the best results. A variety of known GnRH antagonists may be employed, such as Acetyl-β-[2-Naphthyl]-D-Ala-D-p-Chloro-Phe-β-[3-Pyridyl]-D-Ala-Ser-Nε-[Nicotinoyl]-D-Lys-Leu-Nε-[Isopropyl]-Lys_Pro-D-Ala-NH2, Glu-Nal, Abarelix (PPI-149) and acyline (Garnick et al., Abarelix (PPI-14). A novel and potent GnRH antagonist, induces a rapid and profound prostate gland volume reduction (PGYR) and androgen suppression before brachytherapy (BT) or radiation thereapy (XRT), Poster Sessions, Endo ‘98, p.265. Other such antagonists are disclosed in U.S. Pat. Nos. 6,156,772, 6,156,767, 6,150,522, 6,150,522, 6,150,352, 6,147,088, 6,077,858, 6,077,847, 6,025,366, 6,017,944, 6,004,984, and 5,998,432. It is presently believed that Abarelix-Depot (a controlled release form of Albarelix) will be the GnRH antagonist of choice.

[0013] As used herein, a “diabetes-susceptible mammal” refers to a mammal having a statistically significant predisposition to contract Type 1 (autoimmune) diabetes, as compared with the normal, non-susceptible population. Such a predisposition can be ascertained using a number of genetic and/or antibody screens or tests. For example, a diabetes-susceptible human would generally exhibit at least one, and preferably two or more, of the following enumerated risk categories. A susceptible human would range in age from 0-45 years, and:

[0014]

1
. Be a sibling, offspring or a second or third degree relative (e.g., niece, nephew, aunt, uncle, cousin, grandchild) of a person who suffered from Type 1 diabetes; or

[0015]

2
. Have a titre of islet cell autoantibodies (ICA) greater than 10 Juvenile Diabetes Foundation (JDF) Units; or

[0016]

3
. Exhibit in a serum screening sample the presence of insulin autoantibodies.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]
FIG. 1 is a graph illustrating the effects of GnRH, a GnRH antagonist and a GnRH agonist on IgG levels in castrated NOD mice; and

[0018]
FIG. 2 is a graph illustrating the effect of GnRH antagonist, vehicle and GnRH agonists upon the timing and incidents of diabetes in gonadectomized male NOD mice (percentage diabetes-free mice versus time in days).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0019] The following example sets forth a series of tests using diabetes-susceptible mice where the mice were treated using a known GnRH antagonist. It is to be understood that this example is provided by way of illustration and nothing therein should be taken as a limitation upon the overall scope of the invention.

EXAMPLE

[0020] In this example, intact and gonadectomized non-obese mousen model of diabetes (NOD mouse) mice were treated with GnRH agonists and antagonists to determine the effect thereof on serum IgG levels and the incidence and onset of diabetes.

METHODS

Mice

[0021] The well-characterized NOD mice were used throughout the study. Male and female mice were purchased from the Jackson Laboratory (Bar Harbor, Me.). These mice are art-recognized animal models used in diabetes research. (Makino et al., (1980) Breeding of a Non-obese Diabetic Strain of Mice. Exp Anim, 29, 1-13; Miyazaki, A. T., et al, (1985) Predominance of T Lymphocytes in Pancreatic Islets and Spleen in Prediabetic Non-obese Diabetic (Nod) Mice: a Longitudinal Study. Clin Exp immunol, 60, 622-630)

Experimental Design

[0022] Both intact and gonadectomized mice (GDX) were used. Gonadectomies were performed to demonstrate an increase in the incidence of diabetes and also order to eliminate the variable of sex hormone production. To compare the effects of GnRH agonists and antagonists, gonadectomized animals were randomized at 14 to 18 days of age and begun immediately in one of the following main treatment groups: GnRH agonist; Antide; vehicle. One group of gonadectomized males was treated with Nal-Glu, as an additional control.

[0023] Data from mice born over a period of several weeks and randomized to treatment or control groups in several different batches were combined. Serum collection was staggered so that all mice were bled at the same 4 week intervals. Sera for antibody measurements were stored at −20° C., and all samples from each timepoint were run in the same assay in an effort to avoid interassay variability.

Gonadectomy

[0024] Males were gonadectomized via a single scrotal incision under pentobarbital anesthesia.

[0025] Sham operated males underwent pentobarbital anesthesia and a scrotal incision.

Injections

[0026] GnRH (native decapeptide) was purchased from Bachem (Bubendorf, Switzerland). GnRH antagonist Antide (Acetyl-β-[2-Naphthyl]-D-Ala-D-p-Chloro-Phe-β-[3-Pyridyl]-D-Ala-Ser-Nε-]-Lys-Nε-[Nicotinoyl]-D-Lys-Leu-Nε-[Isopropyl]-Lys-Pro-D-Ala-NH2) was supplied by Contraceptive Development Branch (NICHHD) of the National Institutes of Health and Ares-Serono (Randolph, Mass.). A second GnRH antagonist, Nal-Glu (acetyl-D2Nal1, D4ClPhe2, D3Pal3, Arg5, Dglu6(AA), DAla10) was supplied by NICHHD and was used on a subset of mice. All references to GnRH agonist refer to the native decapeptide. Animals were injected subcutaneously in the nape of the neck six times weekly, in the a.m., with 100 μg of GnRH or GnRH antagonist in 100 μl of vehicle consisting of 50% propylene glycol and 50% double distilled water.

Sera

[0027] Sera were collected from blood obtained every six weeks by retroorbital puncture after light isofluorane anesthesia.

Hormone Measurements

[0028] Serum testosterone concentrations were measured by RIA using a commercial kit (Coat-A-Count, Diagnostic Products Corporation, Los Angeles, Calif.). Serum LH and prolactin were measured by radioimmunoassay (RIA) using previously described methods. (Neill, J. D. et al. (1971) Development of a radioimmunoassay for rat prolactin and evaluation of the NIAMD rat prolactin radioimmunoassay. Endocrinology, 88, 548-55; Niswender, et al. (1968) Radioimmunoassay for Rat Luteinizing Hormone with Antiovine Lh Serum and Ovine Lh-131-i. Proc Soc Exp Biol Med, 128, 807-11.

Clinical Tests

[0029] Total immunoglobulin G concentrations were measured by single radial immunodiffusion assay using immunodiffusion plates containing monospecific antiserum for IgG (ICN Biomedicals, Inc., Costa Mesa, Calif.). Serum glucoses were checked weekly using a One Touch Fast Take meter (Lifescan, Milpitas, Calif.) Urine was tested for glucose by urinalysis reagent strips (Miles, Inc., Elkhart Ind.). Glycosuria was scored by comparison to reference standards on a scale of 0 to 4 as follows: negative=0; 30 mg/dL=1; 100 mg/dL=2; 300 mg/dL=3;>1000 mg/dL=4.

Necropsies

[0030] Necropsies were performed on representative mice. No residual ovarian or testicular tissue was found.

Statistics

[0031] Serum immunoglobulin measurements were compared by two-tailed Student's paired t-tests. Percentages of mice remaining diabetes-free was assessed by Mantel-Haenszel methodology. (Mantel, N. (1966) Evaluation of Survival Data and Two New Rank Order Statistics Arising in its Consideration. Cancer Chemother Rep, 50, 163-70)

RESULTS

Serum Immunoglobulin G Concentrations

[0032] Gonadectomy significantly increased IgG levels compared to sham gonadectomy after 8 weeks of treatment. Treatment of gonadectomized mice with GnRH agonist further increased IgG levels compared to vehicle. In gonadectomized males, Antide treatment reduced serum IgG concentrations to levels seen in sham operated mice at 8 weeks. The data are shown in FIG. 1.

Incidence Of Diabetes

[0033] In gonadectomized males, the incidence of diabetes was significantly decreased by administration of the GnRH antagonist Antide. At 60 weeks of age 0% of Antide treated mice were diabetic compared to vehicle (p=0.0025; FIG. 2).

[0034] GnRH agonist treatment significantly increased the incidence and accelerated the timing of onset of diabetes.

DISCUSSION

[0035] The of this study was to determine whether a reduction in GnRH activity was associated with an amelioration of diabetes in gonadectomized male mice susceptible to diabetes. No attempt was made to distinguish hypothalamic versus pituitary hormone effects; likewise, no attempt was made to determine the relative importance of gonadal hormones versus hypothalamic/pituitary hormones. Nevertheless, this Example confirms that GnRH and/or its pituitary products appear to modify the expression of murine diabetes, and raise the hypothesis that hormones other than gonadal steroids might contribute to the well-known gender differences in expression of autoimmunity.

[0036] In this Example, gonadectomized mice were studied in order to eliminate the actions of GnRH on gonadal steroid production as well as gonadal feedback effects on GnRH release. This allowed a more direct assessment of the role of GnRH in modulating murine diabetes. It was found that gonadectomized NOD mice treated with GnRH antagonist displayed statistically significant decreases in total IgG, and delayed onset of diabetes. GnRH agonist administration resulted in reciprocal effects.

[0037] GnRH antagonists might act on the immune system directly, by a direct effect on B or T lymphocytes, or indirectly, either by a reduction in gonadotropins or in cytokine production by immune cells. The prior art suggests that GnRH agonists may play a role in both B and T cell proliferation in vivo and in vitro (Marchetti, B., et al., (1989) Luteinizing Hormone-releasing Hormone (Lhrh) Agonist Restoration of Age-associated Decline of Thymus Weight, Thymic Lhrh Receptors, and Thymocyte Proliferative Capacity. Endocrinology, 125, 1037-45; Morale, M. C., et al., (1991) Blockade of Central and Peripheral Luteinizing Hormone-releasing Hormone (Lhrh) Receptors in Neonatal Rats with a Potent Lhrh-antagonist Inhibits the Morphofunctional Development of the Thymus and Maturation of the Cell-mediated and Humoral Immune Responses. Endocrinology, 128, 1073-85; and Batticane, N., et al., (1991) Luteinizing Hormone-releasing Hormone Signaling at the Lymphocyte Involves Stimulation of Interleukin-2 Receptor Expression. Endocrinology, 129, 277-86). For example, work demonstrating previous decreased percentages of B lymphocytes in gonadectomized lupus-prone mice treated with GnRH antagonists suggests that GnRH antagonists in some way interfere with B lymphocyte proliferation. A decrease in B lymphocyte proliferation could explain the observed reduction in serum IgG and autoantibody concentrations and in decreased immune complex-mediated renal disease.

[0038] Inhibition of prolactin release has been shown to decrease disease severity and prolong survival in murine diabetes, whereas prolactin therapy exacerbates disease. (McMurray, R., et al., (1991) Prolactin Influences Autoimmune Disease Activity in the Female B/w Mouse. J Immunol, 147, 3780-7) However, it was found that neither agonist nor antagonist treatment altered serum prolactin levels. Thus, it is believed that the observed effects were independent of prolactin.

[0039] Previous reports have documented the ability of estradiol to exacerbate murine diabetes. Although the feedback effects of estradiol on GnRH are complex, it is known that estradiol exerts positive feedback effects on GnRH production in some circumstances. Estradiol has been shown to increase GnRH release from hypothalamic cells in vitro. (Leadem, C. A. et al., (1984) Stimulation with Estrogen and Progesterone of Luteinizing Hormone (Lh)-releasing Hormone Release from Perifused Adult Female Rat Hypothalami: Correlation with the Lh Surge. Endocrinology, 114, 51-6. A rise estradiol is believed to contribute to the midcycle GnRH surge. (Roselli, C. E. et al. (1990) Regulation of Hypothalamic Luteinizing Hormone-releasing Hormone Levels by Testosterone and Estradiol in Male Rhesus Monkeys. Brain Res, 509, 343-6) An estrogen response element with positive regulatory effects has been identified on the 5′side of the GnRH gene. (Radovick, S., et al. (1991) Evidence for Direct Estrogen Regulation of the Human Gonadotropin-releasing Hormone Gene. J Clin Invest, 88, 1649-55) Based on these observations, it is possible that some of the immunostimulatory actions of estradiol may result from its positive feedback on GnRH.

[0040] Androgens have been shown to negatively regulate GnRH and gonadotropin production and release. (Finkelstein, J. S., et al. (1991) Sex Steroid Control of Gonadotropin Secretion in the Human Male. I. Effects of Testosterone Administration in Normal and Gonadotropin-releasing Hormone-deficient Men. J Clin Endocrinol Metab, 73, 609-20; Veldhuis, J. D., et al. (1992) Evidence That Androgen Negative Feedback Regulates Hypothalamic Gonadotropin-releasing Hormone Impulse Strength and the Burst-like Secretion of Biologically Active Luteinizing Hormone in Men. J Clin Endocrinol Metab, 74, 1227-35; and Kalra, P. S. et al. (1982) Discriminative Effects of Testosterone on Hypothalamic Luteinizing Hormone-releasing Hormone Levels and Luteinizing Hormone Secretion in Castrated Male Rats: Analyses of Dose and Duration Characteristics. Endocrinology, 111, 24-9). They have also been shown to exert suppressive actions in autoimmunity: androgen treatment ameliorates murine diabetes, whereas gonadectomy of males exacerbates the disease. (Hawkins, T., et al. (1993) The Effect of Neonatal Sex Hormones on the Incidence of Diabets in Nonobese Diabetic Mice. Proc. Soc. Exper. Biol. Med., 202, 201-205; Makino, S., et al. (1981) The Effect of Castration on the Appearance of Diabetes in NOD Mouse. Exp Anim, 30; Fitzpatrick, F., et al. (1991) Influence of Castration, along or Combined

Prevention of diabetes by administration of GnRH antagonists

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