Patent Application
20180246128
The present invention relates to methods for the diagnosis or prognosis of conditions caused by defects in cholesterol biosynthesis, such as Smith-Lemli-Opitz syndrome (SLOS), in particular to early diagnostic methods including in utero methods. An additional aspect of the invention relates to therapeutic uses of certain compounds.
Oxysterols are usually thought of as oxidised forms of cholesterol. However, they can also be formed from cholesterol precursors and the resulting products can have biological activity. 7-Dehydrocholesterol (7-DHC) is an immediate precursor of cholesterol; it is converted to cholesterol by the enzyme 7-dehydrocholesterol reductase (DHCR7). Mutations in DHCR7 leading to reduced enzyme activity result in accumulation of 7-DHC and the disease Smith-Lemli-Opitz syndrome (SLOS). SLOS may present as a malformation syndrome with a distinctive cognitive phenotype. Whether the disease is a consequence of reduced cholesterol synthesis or accumulation of 7-DHC or its metabolites is unknown. Furthermore, little is Known of how 7-DHC is metabolised other than it can be isomerised to 8-DHC.
Bile acids are a large family of steroids possessing a carboxyl group on the side-chain. They are largely synthesised in the liver, but also extrahepatically and there is compelling evidence for their biosynthesis in the brain. Bile acids are synthesised predominantly via two pathways. The dominating pathway in man is the neutral or normal pathway which starts with 7α-hydroxylation of cholesterol by the hepatic cytochrome P450 (CYP) 7A1 enzyme. The second pathway, known as the acidic pathway, starts with 25R(26)-hydroxylation of cholesterol by CYP27A1 to give (25R)26-hydroxycholesterol either in the liver or extrahepatically.
The systematic numbering system according to IUPAC rules is used herein with respect to the (25R)26-hydroxylation of cholesterol. However, much of the literature describes the resulting product as 27-hydroxycholesterol.
Other minor pathways begin with 25-hydroxylation of cholesterol by cholesterol 25-hydroxylase (CH25H) in activated macrophages or with 24S-hydroxylation of cholesterol by cholesterol 245-hydroxylase (CYP46A1) in brain. Many of the subsequent enzymes converting hydroxycholesterols to bile acids are operative in multiple pathways allowing metabolite crossing between pathways.
The major bile acids in man are cholic acid, chenodeoxycholic acid, ursodeoxycholic, deoxycholic acid and lithocholic acid. The latter two are derived from the former two by 7α-dehyroxylation. They are secreted in bile as glycine or taurine conjugates, or in the case of lithocholic acid as a 3-sulphate. Bile acids function in the intestine to aid absorption of lipids, and are recycled to the liver via the enterohepatic system. As well as functioning as detergents in the intestine bile acids are also signalling molecules, regulating their own synthesis via interaction with the farnasoid X receptor, while intermediates in their biosynthetic pathways from cholesterol are ligands to nuclear receptors e.g. liver X receptors (LXRs), pregnane X receptor (PXR), vitamin D receptor (VDR), constitutive androstane receptor (CAR) and to G-protein coupled receptors (GPCRs) e.g. EBI2 and TGR5.
Interestingly, there is increasing evidence for an involvement of bile acid biosynthesis pathways in the nervous system. Almost all of the acidic pathway intermediates from cholesterol to bile acids can be found in brain or cerebrospinal fluid (CSF), and many of these intermediates can cross the blood brain barrier providing traffic in and out of the CNS. Cholic acid has been identified in brain and shown to act as a ligand to LXRs regulating the neurogenesis of red nucleus neurons, while the C27 bile acid 3β,7α-dihydroxycholest-5-en-(25R)26-oic acid (3β,7α-diHCA) has been shown to regulate the survival of motor neurons, again through interaction with LXRs.
It is now accepted that bile acid biosynthesis not only provides detergent molecules essential in the intestine, but also numerous signalling molecules important in a diverse array of biological processes. Unsurprisingly, deficiency in enzymes of the bile acid biosynthesis pathways lead to disease [Setchell JPGN 2006], however, as a consequence of the redundancy provided by multiple pathways, often not to a total elimination of bile acid formation e.g. cerebrotendinous xanthomatosis (CTX) where there is a deficiency of CYP27A1 but cholic acid formation is maintained [Bjorkhem BBRC 2010].
Likewise defects in cholesterol biosynthesis result in clinical disorders [Shackleton Steroids 2012], however, it is unknown if there is sufficient metabolic redundancy for cholesterol to be bypassed and bile acid biosynthesis still maintained by yet another metabolic pathway.
The applicants have found that bile acids can be biosynthesised from 7-dehydrocholesterol (7-DHC), an immediate precursor of cholesterol, in patients with conditions caused by defective cholesterol biosynthesis such as the disorder Smith-Lemli-Opitz syndrome (SLOS), where the enzyme 7-dehydrocholesterol reductase (DCHCR7) is deficient and 7-DHC is abundant in tissues and plasma.
The SLOS phenotype is very broad; severely affected cases often die in utero or soon after birth, whereas mild cases show only minor physical abnormalities, together with learning and behavioural problems. Limb abnormalities are common in SLOS, and in addition to physical malformations SLOS patients have impaired cognitive function although normal intelligence is also possible. Dietary cholesterol supplementation and treatment with statins is standard. Although the primary enzymatic defect in SLOS is well defined, its pathophysiology is not, and it is unlikely that one mechanism explains the myriad of symptoms.
The applicants have found a range of compounds which appear to be associated with SLOS or which are found at elevated levels in SLOS patients. Some of these compounds are indicative of the presence of a new biosynthetic pathway associated with conditions such as SLOS. This leads to the provision of novel methods of diagnosis or prognosis of these conditions. Furthermore, certain intermediates in the pathway are ligands to Smoothened, an oncoprotein activated during Hedgehog signalling required for embryonic patterning and regeneration of postembryonic tissue. Accordingly, the compounds may be formulated as a pharmaceutical preparation comprising a pharmaceutically acceptable excipient. Compounds of the invention and/or preparations comprising them may be administered to a patient to treat conditions involving unwanted cell proliferation, e.g., cancer and/or tumors (such as medulloblastoma, basal cell carcinoma, etc.), non-malignant hyperproliferative disorders, etc. The compounds can also be used to regulate the growth and differentiation of normal tissues. In certain embodiments, such compounds or preparations are administered systemically and/or locally, e.g., topically.
According to the present invention there is provided a method for diagnosing or monitoring the progress of a condition caused by defective cholesterol biosynthesis, said method comprising detecting in a biological sample, levels of deltα-5 bile acid conjugated with 2-(acetylamine)-2-deoxy-D-glucose (GlcNAc) of formula (I)
or a derivative thereof or a precursor, or of any one of compounds of formulae (II)-(VII), or (XX)-(XXlll) or a derivative or a precursor thereof;
which are higher than those found in a sample from a subject not suffering from said condition.
According to a second embodiment, the invention relates to a method of modulating Smoothened (Smo) receptor activity comprising administering to a patient in need thereof an amount of Compound VI or Compound XXI, or pharmaceutically acceptable salt thereof.
According to a third embodiment, the invention relates to a method of treating cancer comprising administering to a patient in need thereof an amount of Compound VI or Compound XXI, or pharmaceutically acceptable salt thereof.
According to a fourth embodiment, the invention relates to the use of Compound VI or Compound XXI, or pharmaceutically acceptable salt thereof, in a method of treating cancer.
The applicants have found that the compound of formula (I) is a product in a novel biosynthetic pathway (as shown in
Precursors of the compound of formula (I) in the biosynthetic pathway are compounds of formulae (II)-(VII) and (XX)-(XXIII) as defined above together with compounds of formulae (VIII) and (IX)
Although it has previously been reported that compounds of formulae (VIII) and (IX) above, were present in elevated levels in SLOS patients, it had not previously been understood that they were part of the pathway of
Compounds of formula (II)-(VII), and (XX)-(XXIII)and in particular compounds of formula (II)-(VI) and (XX) are much better diagnostic markers than compounds of formula (VIII) or (IX) as they are present at low or trace amounts in healthy individuals, and so elevation as a result of a condition such as SLOS, is more easily determined.
A further precursor of formula (XII) in the pathway
is found only in low levels which are difficult to measure accurately, making it less useful as a diagnostic moiety.
Suitably, precursors of formulae (II)-(VII), and (XX)-(XXIII) are detected at elevated levels in blood, serum, plasma or CSF samples from a subject to provide a diagnosis of SLOS in said subject, or to monitor the progress of the disease in subjects known to be suffering from SLOS.
It has been found however that compounds of formula (I) and derivatives thereof are markers that may be found additionally in urine. Urinary markers are preferred for diagnostic purposes as sample retrieval is easy and less invasive for the subject. In addition, however, a urinary marker may be used in pre-natal diagnosis. The presence of elevated levels of the compound of formula (I) or derivatives thereof in a maternal urine sample would be indicative of the presence of a condition such as SLOS in the foetus.
Thus, in a particular embodiment, the invention provides a method for diagnosing SLOS which comprises detecting levels of the compound of formula (I) or a derivative thereof, in a urine sample from a subject suspected of or suffering from SLOS or from a urine sample from an expectant mother and comparing these with the levels found in healthy subject.
Suitable derivatives of Compounds of formula (I) include compounds of formula (X) and (XI)
wherein R is a hydroxyl, glycine (—NHCH2CO2H) or taurine (—NHCH2CH2SO3H) group.
In particular in the compound of formula (X), R is a glycine or taurine group, and in the compound of formula (XI), R is a hydroxyl group.
Compounds of formula (I) as well as compounds of formula (X) and (XI) have previously been detected in the urine of a patient suffering from Niemann Pick disease, an inherited lipid trafficking disorder, (G. Alvelius et al. (2001) The Journal of Lipid Research, 42, 1571-1577, October 2001; The Journal of Lipid Research, 42, 1571-1577) but they have not previously been associated with conditions caused by defective cholesterol biosynthesis such as SLOS. Niemann Pick disease is quite a distinct ailment, presenting different symptoms from those present in, for example, SLOS and thus is unlikely to be confused in patients. However, confirmatory tests for SLOS, for example for detecting a second compound which acts as a diagnostic marker for conditions such as SLOS as described below may be carried out in addition to the method of the invention in order to confirm a diagnosis of a condition caused by defective cholesterol biosynthesis, such as SLOS.
As used herein, the expression ‘elevated level’ refers to levels of a compound which is higher, in particular at least 1.5 times, for example at least double, the level of the compound found in a sample taken from healthy subjects, who are not suffering from the condition such as SLOS (See Table 1 hereinafter). These levels may be determined empirically or by comparison with a previously determined standard level. Typically, these compounds are found at low levels in samples taken from healthy individuals, for example at levels of 1 ng/ml or less. Thus, levels of compounds of formula II, IV, VI and VII excess of 5 ng/ml, or in excess of 10, 20 or 30 ng/ml in a sample may be indicative of the presence of the condition.
In a particular embodiment, the method of the invention further comprises detecting a further compound or diagnostic marker which is characteristic of a condition caused by defective cholesterol biosynthesis such as SLOS. Such tests would provide further reassurance of the veracity of the result. In addition to the compounds described above, the applicants explored patterns of other oxysterols found in plasma of patients with SLOS exploiting Girard derivatisation and LC-MS via a technology designated ‘enzyme assisted derivatisation for sterol analysis’ or EADSA.
They have additionally identified, for the first time, the 8-DHC metabolites 24-hydroxy-8-DHC (24—OH—8-DHC), 25—OH—8-DHC and 26—OH—8-DHC as well as elevated levels of the known 7-DHC metabolites 4—OH—7-DHC, 7-oxocholesterol (Compound (VIII) above), 7α, 8α-epoxycholesterol and 3β,5α-dihydroxycholest-7-en-6-one.
Certain of these compounds may also provide means of diagnosis of conditions such as SLOS, in particular as a confirmatory test, to provide a clear differentiation of distinction from this and Niemann Pick disorder, and this forms a further aspect of the invention.
In particular, in a particular embodiment, the method of the invention further provides the detection of elevated levels of 8-dehydocholesterol (8-DHC) of formula (XIII)
or a metabolite thereof, selected from 24-hydroxy-8-DHC (24—OH—8-DHC) of formula (XIV), 25—OH—8-DHC of formula (XV) and 26—OH—8-DHC of formula (XVI),
and in particular, compounds of formula (XIV) and (XV) above.
Alternatively or additionally, the further step may comprise the detection of levels of 7-DHC of formula (IX) above or 7-DHC metabolites such as 4—OH—7-DHC of formula (XVII), 7-oxocholesterol (Compound VIII), 7α, 8α-epoxycholesterol (XVIII) and 3β,5α-dihydroxycholest-7-en-6-one (Compound XIX) which are higher than those found in a sample from a subject not suffering from said condition
Detection of the compounds of formula (I)-(XXIII) may be carried out using conventional methods, in particular using liquid chromatography combined with mass spectrometry, particularly following derivatisation such as Girard derivatisation with reagents such are Girard P to facilitate detection of specific forms. These compounds may be identified and quantified using methods known in the art.
Bile acid biosynthesis normally starts from cholesterol, however, CYP7A1 can also use 7-DHC as a substrate giving 7-oxocholesterol (VIII) which can be reduced by HSD11B1 to 7β-hydroxycholesterol (VII) opening a new route to bile acid biosynthesis (
Further evidence for this pathway was provided by the presumptive identification of 3β,7β,24-trihydroxycholest-5-en-26-oic acid (Compound III), a necessary intermediate as the CoA thioester in peroxisomal side-chain shortening of 3β,7β-dihydroxycholest-5-en-26-oic acid (IV) to 3β,7β-dihydroxychol-5-en-24-oic acid (II), A second branch to the pathway is defined by the identification of elevated amounts of 3β,26-Dihydroxycholest-5-en-7-one (26-Hydroxy-7-oxocholesterol) (Compound XX) and 3β-Hydroxy-7-oxochol-5-en-24-oic acid (Compound XXI) in the plasma of SLOS patients, and also the identification of elevated amounts of 3β-hydroxy-7-oxocholest-5-en-26-oic acid (VI) in plasma of patients with a high 7-DHC to cholesterol ratio, which can also presumably act as a substrate for HSD11B1. A third branch to the pathway proceeds through 3β,25-dihydroxycholest-5-en-7-one (Compound XXII), 7β,25-dihydroxycholesterol (Compound XXIII) and 3β,7β,25-trihydroxycholest-5-en-26-oic acid (Compound V), although it is not known whether CYP27A1 is responsible for the oxidation of the terminal carbon to the carboxylic acid and how the resulting triol undergoes side-chain shortening. The 7β-hydroxy group in bile acids is known to become conjugated with (N-Acetylglucosamine) GIcNAC, leading to the excretion of GlcNAc conjugates in urine. Screening for bile acids in urine of SLOS patients revealed elevated levels of 3β,7β-dihydroxychol-5-en-24-oic acid conjugated with GlcNAC (elevated by a factor of 10) and in some cases doubly (GIcNAc sulphate double conjugate elevated by a factor of 20) or triply conjugated with sulphuric acid, glycine (GIcNAc, sulphate, glycine triple conjugate elevated by a factor of 10) or taurine (X-XI).
Hedgehog (Hh) signalling is required for embryonic patterning and regeneration of postembryonic tissue and aberrant Hh signalling has been linked to SLOS [Cooper Nat Genetics 2003, Myers Dev Cell 2013]. In fact, many developmental malformations attributed to SLOS occur in tissues where Hh signalling is required for development [Koide Dev 2006]. DHCR7, the defective enzyme in SLOS, has been implicated to function as a positive regulator of Hh signalling, and the cause of some of the developmental abnormalities seen in SLOS have been attributed to cholesterol deficiency interfering with normal Hh signalling [Cooper Nat Gen 2003, Blassberg HMG 2016]. Alternatively, Koide et al [Dev 2006] have suggested that DHCR7 functions as a negative regulator of Hh signalling and its inhibitory effect is at the level, or downstream, of the oncoprotein Smoothened (Smo). Both of these proposals can be accommodated by the model suggested by Myers et al where oxysterols and cholesterol bind to and modulate Smo at different structural regions [Dev Cell 2013]. Smo is a seven-transmembrane protein with extended extracellular and cytoplasmic termini. Hh pathway activation is initiated by binding of cholesterol-modified Hh protein to its receptor Patched 1 (Ptch1) which releases inhibition of Smo and triggers transcription of Hh target genes via Gli transcription factors [Lum Science 2004, Rohatgi Science 2007]. Myers et al have shown that an extracellular cysteine-rich domain (CRD) is the site for oxysterol binding to Smo and suggested that oxysterols may stabilise an active Smo conformation induced by loss of Ptchl mediated repression [Dev Cell 346]. 205-Hydroxycholesterol (20S-HC) has been shown to activate Smo in vitro [Corcoran PNAS 2006, Nachtergaele Nat Chem Bio 2012] but its presence in vivo is under debate [Lin JSBMB 2003, Roberg-Larsen JCA 2012]. Two other oxysterols identified herein, 25H,7O—C (XXII) and 26H,7O—C (XX), are also activators of Smo [Myers Dev Cell 346]. 26H,7O—C (XX) has been previously identified in extracts of retinal pigment epithelial cells, and have been shown to be generated from 7-OC (VIII) by CYP27A1 [Heo JLR 2011] (
According to a further aspect, the invention provides a method of modulating Smoothened (Smo) receptor activity comprising administering to a patient in need thereof an amount of Compound VI or Compound XXI, or pharmaceutically acceptable salt thereof.
According to a further aspect, the invention provides a method of modulating (preferably inhibiting) Hedgehog signalling (Hh) comprising administering to a patient in need thereof an amount of Compound VI or Compound XXI, or pharmaceutically acceptable salt thereof.
According to a further aspect, the invention provides a method of treating cancer comprising administering to a patient in need thereof an amount of Compound VI, or pharmaceutically acceptable salt thereof. Preferably, the cancer is selected from the group consisting of an adenocarcinoma of the pancreas, prostate, breast, stomach, esophagus or biliary tract; a medulloblastoma or glioma; a small-cell lung cancer; a basal cell carcinoma; a rhabdomyosarcoma; a urothelial carcinoma; a squamous cell carcinoma of the oral cavity; and a hepatocellular carcinoma.
According to a further aspect, the invention provides a method of treating a wound comprising administering to a patient in need thereof an amount of Compound VI, or pharmaceutically acceptable salt thereof.
According to a further aspect, the invention provides a composition comprising a pharmaceutically acceptable carrier, excipient or diluent and Compound VI, or pharmaceutically acceptable salt thereof.
The invention will now be particularly described by way of example with reference to the accompanying diagrammatic drawings in which:
Extraction of Sterols and Oxysterols (II-IX, XIII-XXIII) from Plasma
The applicants investigated the possibility that patients suffering from SLOS may use 7-DHC as a starting point for bile acid biosynthesis rather than cholesterol. Liquid chromatography (LC)—mass spectrometry (MS) was used to determine the nature of bile acid intermediates found in plasma from patients suffering from SLOS as well as from healthy individuals as controls. Specifically compounds (II)-(IX), and (XX) to (XXIII) were identified by a process involving Girard P derivatisation and LC-MS as described by Crick P J et al., J. Olin Chem. 2015 February; 61(2):400-11. Compounds (I) and (X)-(XI) were identified in urine by an LC-MS process as described by Griffiths W J, et al. Mass Spectrometry Handbook, Ed Mike S Lee, 2012 John Wiley & Sons, 2012 p.297-337 and elucidated further below.
Plasma (100 μL) was added dropwise to a solution of absolute ethanol (1.05 mL) containing 24R/S-[25,26,26,26,27,27,27-2H7]hydroxycholesterol ([2H7]24—OHC) and 22R-[25,26,26,26,27,27,27-2H7]hydroxycholest-4-en-3-one ([2H7]22R—OHCO]) (20 ng of each in 1.05 mL of absolute ethanol) in an ultrasonic bath. After 5 min the solution was diluted to 70% ethanol by addition of 0.35 mL of water, ultrasonicated for a further 5 min and centrifuged at 14,000×g at 4° C. for 30 min. The supernatant was loaded onto a 200 mg Certified Sep-Pak C18 cartridge (pre-conditioned with 4 mL of absolute ethanol followed by 6 mL 70% ethanol) and allowed to flow at ˜0.25 mL/min. The flow-through was combined with a column wash of 70% ethanol (5.5 mL) to give SPE1-Fr1 containing the oxysterols. A second fraction (SPE1-Fr2) was collected by eluting with a further 4 mL of 70% ethanol before elution 5 of cholesterol, 7-dehydrocholesterol and similarly hydrophobic sterols using 2 mL of absolute ethanol (SPE1-Fr3). Each fraction was divided into two portions (A) and (B) and concentrated under reduced pressure using a vacuum concentrator (ScanLaf, Denmark).
Charge Tagging of Sterols and Oxysterols from Plasma
The sterol and oxysterol fractions (A) from above were re-constituted in 100 μL of propan-2-ol then treated with KH2PO4 buffer (1 mL 50mM, pH 7) containing 3 μL of cholesterol oxidase (2 mg/mL in H2O, 44 units/mg protein). The reaction mixture was incubated at 37 ° C. for 1 hr then quenched with 2.0 mL of methanol. Glacial acetic acid (150 μL) was added followed by Girard P (GP) reagent (190 mg bromide salt or 150 mg chloride salt, 0.80 mmol). The mixture was vortexed then incubated at room temperature overnight in the dark. To remove excess reagent from the reaction mixture a recycling method was used. A 200 mg Certified Sep-Pak C18 cartridge was preconditioned with methanol (6 mL), 10% methanol (6 mL) and finally 70% methanol (4 mL). The derivatization mixture from above (3.25 mL in -70% organic) was applied to the column and allowed to flow through at -0.25 mL,/min. The column was washed with 70% methanol (1 mL) followed by 35% methanol (1 mL) and the combined eluent diluted with water (4 mL) to give a solution in 9 mL of 35% methanol. This solution was applied to the column, collected, and combined with a column wash of 17.5% methanol (1 mL). Water (9 mL) was added to give a solution in 19 mL of 17.5% methanol which was again applied to the column. The flow-through was discarded and the column washed with 10% methanol (6 mL). Derivatized sterols/oxysterols were then eluted from the column with methanol (3×1 mL, SPE2-Fr1, Fr2, Fr3) followed by absolute ethanol (1 mL, SPE2-Fr4). Cholesterol and 7-dehydrocholesterol were found to be almost exclusively present in SPE2-Fr3 while oxysterols elute in SPE2-Fr1 and Fr2. The fractions (B) were treated in an identical fashion to the (A) fractions but in the absence of cholesterol oxidase. This allows differentiation of sterols oxidised to contain an oxo group from those naturally possessing one. In later studies the 200 mg Certified Sep-Pak C18 cartridge has been replaced by an Oasis HLB 60-mg column [Crick An Bio Chem 2015].
LC-MS(MSn) on 5 the LTQ-Orbitrap
To analyse GP-tagged oxysterols, SPE2-Fr1 and -Fr2 were combined and diluted to give a final solution of 60% methanol. For each experiment, 20 μL was injected onto the LC column and MS, MS2 and MS3 spectra recorded as described below. For the analysis of the more non-polar sterols SPE2-FR1, -Fr2 and -Fr3 were combined prior to dilution to 60% methanol.
LC was performed on a Ultimate 3000 HPLC system (Dionex, Surrey, UK) using a Hypersil GOLD revered phase column (1.9 pm particle size, 50×2.1 mm, Thermo Fisher). Mobile phase A consisted of 33.3% methanol, 16.7% acetonitrile and 0.1% formic acid. Mobile phase B consisted of 63.3% methanol, 31.7% acetonitrile and 0.1% formic acid. The chromatographic run started at 20% B for 1 min before increasing the proportion of B to 80% over 7 minutes and maintaining this for a further 5 min. The proportion of B was returned to 20% over 6 s and re-equilibration was for 3 min, 54 s to give a total run time of 17 min. The flow rate was 200 μL/min and the eluent was directed to the atmospheric pressure ionization (API) source of an LTQ-Orbitrap. The Orbitrap was calibrated externally before each analytical session and the mass accuracy was better than 5 ppm.
The method consisted of a Fourier Transform (FT)-MS scan in the Orbitrap at 30,000 resolution (full width at half-maximum height; FWHM), simultaneous to which sequential MS2 or MS3 scans were carried out in the linear ion trap (LIT) with normalised collision energies of for MS2 and for MS3 (instrument settings).
Elevated levels of the 7-DHC metabolites, 7-oxocholesterol (Compound VIII), 7β-hydroxycholesterol (Compound VII), 3β, 7β-dihydroxycholest-5-en-26-oic (Compound IV) and 3β, 7β-dihydroxychol-5-en-24-oic (Compound II) acids in SLOS plasma were detected (
In patient samples where the 7-DHC to cholesterol ratio is high, 3β-hydroxy-7-oxocholest-5-en-26-oic acid (Compound VI) was also observed. Low levels of metabolites with retention time and fragmentation patterns consistent with 3β, 7β, 24-trihydroxycholest-5-en-26-oic (Compound III) and 3β, 7β,25-trihydroxycholest-5-en-26-oic structures (Compound V) were also presumptively identified in these patient samples by comparison to the 7α-epimers which were available as authentic standards.
Sterols with a 3β, 7β-dihydroxy-5-ene function are not substrates for HSD3B7, the oxidoreductase required to initiate A/B ring transformation to the 3α-hydroxy-5α-hydrogen configuration found in primary bile acids [Russell ARB 2003], so the 3β, 7β-dihydroxy-5-ene structure is maintained in the products of this bile acid biosynthesis pathway.
Extraction and Analysis of Bile Acids (I, X, XI) from Urine
Sterols possessing a 7β-hydroxy group are known to be conjugated with N-acetylglucosamine (GlcNAc) and excreted in urine, and so the applicants investigated the urine of SLOS patients for GlcNAc conjugated bile acids using LC-MS methods.
Working solutions of [2,2,4,4-2H4]cholic acid (20 ng/μL), [2,2,4,4-2H4]glycochenodeoxycholic acid (20 ng/μL) and [2,2,4,4-2H4]taurochenodeoxycholic (20 ng/μL) were prepared in absolute ethanol. 2 μL (40 ng) of each working solution was added to 994 μL of water in a 2 mL Eppendorf tube.
Urine (100 μL, pH 6-7) was added drop-wise to the 1 mL of water containing deuterated standards (above). After 10 min ultrasonication the solution was centrifuged at 14,000 rpm, 4° C. for 30 min and the supernatant 5 retained. An Oasis HLB (60 mg, Waters) column was washed with absolute ethanol (4 mL), methanol (4 mL) and conditioned with water (4 mL). The supernatant from above was loaded onto the column and allowed to flow at 0.25 mL/min. After a 3 mL wash with water bile acids were eluted in 4×1 mL of methanol. The first two 1 mL fractions were combined, diluted to 60% methanol and analysed by LC-MS(MS)n in an identical fashion to derivatised oxysterols as described in Example 1 with the exception that bile acid urine analysis was performed in the negative ion mode.
It was found that, in urine from SLOS patients, there was elevated levels of 3β, 7β-dihydroxychol-5-en-24-oic conjugated with GlcNAc (compound of formula (I)) presumably at position 7β, and also the double conjugate as the 3-sulphate (
Identification of Additional Sterols and Oxysterols in Plasma
Historical residual clinical plasma samples from SLOS patientswere analysed along with samples from newly diagnosed patients and a range of healthy controls.
Sterols and oxysterols were analysed by LC-ESI-MSn using a chargetagging approach (enzyme-assisted derivatisation for sterolanalysis, EADSA) as described in Example 1 above. In brief, nonpolar sterols including cholesterol, 7-DHC and 8-DHC were separated from more-polar oxysterols by reversed-phase solid phase extraction (RP-SPE). The separated fractions were individually treated with cholesterol oxidase to convert 3β-hydroxy-5-ene and 3β-hydroxy-5,7(or 8)-diene to their 3-oxo-4-ene and 3-oxo-4,7(or 8)-diene equivalents, then derivatised with Girard P (GP) reagent to add a charged quaternary nitrogen group to the analytes which greatly improve their LC-ESI-MS and MSn response. When fragmented by MS2 GP-tagged analytes give an intense 5 [M-Py]' ion, corresponding to the loss of the pyridine (Py) ring, which can be fragmented further by MS3 to give a structurally informative pattern. Some sterols and oxysterols naturally contain an oxo group and can be differentiated from those oxidised to contain one by omitting the cholesterol oxidase enzyme from the sample work-up procedure.
Representative results from these studies are illustrated in
Hedgehog Signalling Assays Using Quantitative RT-PCR
NIH-3T3 cells were grown to confluency in Dulbecco's Modified Eagle's Medium (DMEM) containing 10% Fetal Bovine Serum (FBS, Optima Grade, Atlanta Biologicals). Confluent cells were exchanged into 0.5% FBS DMEM for 24 hours to allow ciliogenesis prior to treatment with sterols in DMEM containing 0.5% FBS for ˜16 hours. SHH protein carrying a C-terminal hexa-histidine tag was expressed in bacteria and purified as described previously [Bishop Nat Struct Mol Biol 2009]. The mRNA levels of Gli1, a direct Hh target gene commonly used as a metric for signalling strength, were measured using the Power SYBR Green Cells-To-CT kit (Thermo Fisher Scientific). The primers used are Gli1 (forward primer: 5′-ccaagccaactttatgtcaggg-3′ and reverse primer: 5′-agcccgcttctttgttaatttga-3′), Gapdh (forward primer: 5′-agtggcaaagtggagatt-3′ and reverse primer: 5′-gtggagtcatactggaaca-3′). Transcript levels relative to Gapdh were calculated using the Δelta-Ct method. Each qRT-PCR experiment, which was repeated twice, included two biological replicates, each with two technical replicates.
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| Number | Date | Country | Kind |
|---|---|---|---|
| 1515573.2 | Sep 2015 | GB | national |
| 1516441.1 | Sep 2015 | GB | national |
| 1608459.2 | May 2016 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2016/052710 | 9/2/2016 | WO | 00 |
