Kegg Pathway: Bile acid biosynthesis

Curr Drug Targets. 2009 Nov 1; 10(11): 1184-1193
Kakizaki S, Takizawa D, Tojima H, Yamazaki Y, Mori M

Cholestasis results in the intrahepatic retention of cytotoxic Bile acid and it can thus lead to liver injury and/or liver fibrosis. Cholestatic liver damage is counteracted by a variety of intrinsic hepatoprotective mechanisms including a complex network of drug metabolizing enzymes and transporters. During the last decade, much progress has been made in dissecting the mechanisms which regulate the hepatic xeno- and endobiotic metabolism by nuclear receptors. The xenobiotic receptors CAR and PXR are two important members of the NR1I nuclear receptor family. They function as sensors of toxic byproducts derived from the endogenous metabolism and of exogenous chemicals, in order to enhance their elimination. Ligands for both receptors, including phenobarbital, have already been used to treat cholestatic liver diseases before the mechanisms of these receptors were revealed. Furthermore, Yin Zhi Huang, a traditional Chinese herbal medicine, which has been used to prevent and treat neonatal jaundice, was identified to be a CAR ligand which also accelerates bilirubin clearance. Therefore, CAR and PXR have a protective effect on cholestasis by activating both detoxification enzymes and transporters. As a result, novel compounds targeting CAR and PXR with specific effects and fewer side effects will therefore be useful for the treatment of cholestatic liver diseases. This article will review the current knowledge on xenobiotic-sensing nuclear receptors CAR and PXR, while also discussing their potential role in the treatment of cholestatic liver diseases.

J Pediatr Gastroenterol Nutr. 2009 Nov 12;
Subramaniam P, Clayton PT, Portmann BC, Mieli-Vergani G, Hadžić N

OBJECTIVE:: We studied the clinical features of children with 3beta-hydroxy-Delta-C27-steroid dehydrogenase (3beta-HSDH) deficiency presenting to King's College and Great Ormond Street hospitals between 1989 and 2005. The diagnosis was made biochemically by detection of sulphated dihydroxycholenoic acids and trihydroxycholenoic acids in urine by fast atom bombardment mass spectrometry or electrospray ionisation tandem mass spectrophotometry and a plasma Bile acid profile showing absent or low cholic and chenodeoxycholic acid levels and high concentrations of 3beta-7alpha-dihydroxy-5-cholenoic acid and 3beta-7alpha-12alpha-trihydroxy-5-cholenoic acid. RESULTS:: Eighteen children (12 male) with 3beta-HSDH deficiency were identified and diagnosed at a median age of 1.35 years (range 8 weeks-11 years). The presenting features included neonatal cholestasis (n = 11), rickets (n = 8, 1 of whom also had hypocalcaemic tetany, seizures, and normal liver biochemical markers), hepatomegaly (n = 7), pruritus (n = 3), and steatorrhoea and failure to thrive (n = 3). Ten children had low serum 25-OH vitamin D levels, of whom 8 also had low vitamin E and 6 had low vitamin A serum levels. Liver histology showed giant cell change and hepatocyte disarray in all with added features of cholestasis in 11, bridging fibrosis in 6, micronodular cirrhosis in 1, fatty change in 1, and active lobular and portal inflammation in 1. Five patients were treated with cholic acid and chenodeoxycholic acid (7 mg . kg . day of each), 7 with chenodeoxycholic acid only (7-18 mg . kg . day), and 1 with cholic acid (8 mg . kg . day) only. Repeated liver biopsies performed in 4 patients 6 months after starting replacement therapy showed improved histological changes. Three children died untreated before 5 years of age. After a median follow-up of 5.5 years (range 1-17 years) 12 out of 13 treated children have no clinical signs of liver disease or of fat-soluble vitamin deficiency. CONCLUSIONS:: 3beta-HSDH deficiency is a rare inborn error of metabolism with diverse clinical features. Early replacement treatment leads to clinical and biochemical control and prevents chronic liver and bone disease, at least in the medium term.

Steroids. 2009 Nov 11;
Iguchi Y, Kihira K, Nishimaki-Mogami T, Une M

FXR (farnesoid X receptor) is a Bile acid-activated nuclear receptor that regulates not only the biosynthesis and enterohepatic circulation of Bile acids, but also triglyceride, cholesterol and glucose metabolism. FXR-mediated signaling pathways have become promising novel drug targets for the treatment of common metabolic and hepatic diseases. With the aim of uncovering novel modulators of FXR and further elucidating the molecular basis of FXR activation, we investigated the structure-activity relationships of a variety of naturally occurring sterols structurally related to Bile acids in terms of their FXR agonist activity. Here, we report that the ability of Bile alcohols to activate FXR varied with the position and number of hydroxyl groups existing in the steroid side chain of Bile alcohols. In addition, we showed that the shortening of the steroid side chain of Bile acids as well as Bile alcohols resulted in a decline of the ability of these agents to activate FXR. Thus, we provide new insights into the structure-activity relationships of Bile acids and Bile alcohols as FXR agonists.

Anal Biochem. 2009 Nov 11;
Han KC, Kim JH, Kim KH, Kim EE, Seo JH, Yang EG

Farnesoid X receptor (FXR) serves as a receptor for chenodeoxycholic acid (CDCA) and other Bile acids, and coordinates cholesterol and lipid metabolism. Since targeting the FXR-CDCA interaction thus might provide a way to regulate lipid homeostasis, we developed an FXR binding assay based on fluorescence polarization. Employing a fluorescently-labeled CDCA-F, we showed that CDCA-F selectively bound to the ligand binding domain of FXR (FXR-LBD) among nuclear receptors. The assay was then utilized for screening inhibitors against the FXR-CDCA interaction, thereby discovering four relatively potent inhibitors. The selected inhibitors were further studied for changes in intrinsic tryptophan fluorescence of FXR-LBD to gain structural insights of the interaction. Furthermore, transactivation effects of the inhibitors on the human Bile salt excretory pump (BSEP) promoter were examined to reveal their cellular activities in the FXR-mediated pathway. Therefore, we demonstrated that the developed assay would offer an efficient primary screening tool for identifying FXR modulators.

Curr Drug Targets. 2009 Nov 1;
Kakizaki S, Takizawa D, Tojima H, Yamazaki Y, Mori M

Cholestasis results in the intrahepatic retention of cytotoxic Bile acid and it can thus lead to liver injury and/or liver fibrosis. Cholestatic liver damage is counteracted by a variety of intrinsic hepatoprotective mechanisms including a complex network of drug metabolizing enzymes and transporters. During the last decade, much progress has been made in dissecting the mechanisms which regulate the hepatic xeno- and endobiotic metabolism by nuclear receptors. The xenobiotic receptors CAR and PXR are two important members of the NR1I nuclear receptor family. They function as sensors of toxic byproducts derived from the endogenous metabolism and of exogenous chemicals, in order to enhance their elimination. Ligands for both receptors, including phenobarbital, have already been used to treat cholestatic liver diseases before the mechanisms of these receptors were revealed. Furthermore, Yin Zhi Huang, a traditional Chinese herbal medicine, which has been used to prevent and treat neonatal jaundice, was identified to be a CAR ligand which also accelerates bilirubin clearance. Therefore, CAR and PXR have a protective effect on cholestasis by activating both detoxification enzymes and transporters. As a result, novel compounds targeting CAR and PXR with specific effects and fewer side effects will therefore be useful for the treatment of cholestatic liver diseases. This article will review the current knowledge on xenobiotic-sensing nuclear receptors CAR and PXR, while also discussing their potential role in the treatment of cholestatic liver diseases.

Int J Mol Med. 2009 Dec; 24(6): 825-8
Nakamuta M, Yada R, Fujino T, Yada M, Higuchi N, Tanaka M, Miyazaki M, Kohjima M, Kato M, Yoshimoto T, Harada N, Taketomi A, Maehara Y, Koga M, Nishinakagawa T, Nakashima M, Kotoh K, Enjoji M

Recent investigations indicate that hepatitis C virus (HCV) infection is closely associated with hepatocytic lipid metabolism and induces hepatic steatosis. However, the actual lipid metabolism in HCV-infected liver has not been extensively investigated in humans. In this study, we evaluated the expression of lipid metabolism-associated genes in patients with HCV infection by real-time PCR. Sterol regulatory element-binding protein (SREBP)-2 expression was unchanged and low density lipoprotein receptor expression was markedly reduced by 90% in HCV-infected liver. The expression of apolipoprotein B100, microsomal triglyceride transfer protein and ATP-binding cassette G5 was significantly increased. Up-regulation of cholesterol synthesis-associated genes, including HMG-CoA reductase, HMG-CoA synthase, farnesyl-diphosphate synthase and squalene synthase, confirmed enhanced de novo cholesterol synthesis. The expression of cholesterol 7alpha-hydroxylase and farnesoid X receptor was enhanced, while Bile salt export pump expression was unchanged. Fatty acid synthase expression was increased which was accompanied by increased expression of liver X receptor alpha and SREBP-1c. In summary, the regulation of lipid metabolism was impaired and cholesterol and fatty acid synthesis continued to increase without negative feedback in HCV-infected liver. These changes may be beneficial for HCV replication.

Cell Metab. 2009 Nov; 10(5): 392-404
Kemper JK, Xiao Z, Ponugoti B, Miao J, Fang S, Kanamaluru D, Tsang S, Wu SY, Chiang CM, Veenstra TD

The nuclear Bile acid receptor FXR is critical for regulation of lipid and glucose metabolism. Here, we report that FXR is a target of SIRT1, a deacetylase that mediates nutritional and hormonal modulation of hepatic metabolism. Lysine 217 of FXR is the major acetylation site targeted by p300 and SIRT1. Acetylation of FXR increases its stability but inhibits heterodimerization with RXRalpha, DNA binding, and transactivation activity. Downregulation of hepatic SIRT1 increased FXR acetylation with deleterious metabolic outcomes. Surprisingly, in mouse models of metabolic disease, FXR interaction with SIRT1 and p300 was dramatically altered, FXR acetylation levels were elevated, and overexpression of SIRT1 or resveratrol treatment reduced acetylated FXR levels. Our data demonstrate that FXR acetylation is normally dynamically regulated by p300 and SIRT1 but is constitutively elevated in metabolic disease states. Small molecules that inhibit FXR acetylation by targeting SIRT1 or p300 may be promising therapeutic agents for metabolic disorders.

Gen Comp Endocrinol. 2009 Oct 24;
Li GG, Liang XF, Xie Q, Li G, Yu Y, Lai K

Leptin is an important hormone for the regulation of food intake, energy expenditure and reproduction in mammals, but information regarding its role in teleosts remains scant. In the present study, the gene structures of grass carp (Ctenopharyngodon idellus) and silver carp (Hypophthalmichthys molitrix) leptins were characterized. Recombinant grass carp leptin (rgc-LEP) was expressed in Escherichia coli and purified, and identified by mass spectrometric analysis. A strong anorexic effect on food intake was observed in grass carp on the first day after intraperitoneal (IP) injection of rgc-LEP, but not during the following days. Body weight of the leptin group (LEP group) and the pair-fed group (PF group) showed no difference throughout the experimental period. The acute and chronic effects on the expression of key genes correlating to food intake, energy expenditure, lipid metabolism and digestion were further characterized by real-time PCR. Accordingly, the mRNA levels of neuropeptide Y (NPY), Stearoyl-CoA desaturase 1 (SCD1) and lipoprotein lipase (LPL) were significantly reduced whereas the mRNA levels of uncoupling protein 2 (UCP2), Bile salt-activated lipase (BSAL) and fatty acid elongase (ELO) were significantly elevated on the first day after injection. No effect on the expression of these genes (except LPL) was observed on day 13. In contrast to the down-regulation by exogenous leptin in mammals, the mRNA level of grass carp leptin was elevated 5.76-fold on the first day after rgc-LEP treatment. Our results suggest that leptin has an acute effect on the regulation of food intake, energy expenditure and lipid metabolism in grass carp, but the effect can be rapidly counteracted through mechanisms that are currently unknown.

J Med Food. 2009 Oct; 12(5): 973-81
Park CH, Cho EJ, Yokozawa T

To reduce cardiovascular disease (CVD) by reducing circulating cholesterol concentrations, much attention has been focused on the search for dietary interventions for hypercholesterolemia. Corni Fructus is known to exhibit several biological activities. Therefore, in the present study, its protective effect on diet-induced hypercholesterolemia was studied using a rat model fed 1% cholesterol and 0.5% cholic acid. Corni Fructus extract was administered at an oral dose of 50, 100, or 200 mg/kg of body weight/day for 10 days. The administration inhibited the elevation of both systolic and diastolic blood pressure. In addition, it lowered serum total cholesterol levels with a decrease in esterified cholesterol. Moreover, the atherogenic index was decreased in a dose-dependent manner, suggesting its protective role against CVD through regulating cholesterol and lipoprotein levels. The hepatic levels of total and free cholesterol were also reduced by Corni Fructus. This implies that free cholesterol was used for catabolism or efflux. Consequently, the levels of total cholesterol and Bile acid in feces were significantly increased. Our present results also showed that the administration of Corni Fructus decreased lipid peroxidation, suggesting a protective effect against oxidative stress induced by hypercholesterolemia. Furthermore, hypercholesterolemic control rats had significantly lower expression of sterol regulatory element-binding protein (SREBP)-2 protein without any difference in SREBP-1 protein expression. On the other hand, the protein expression of SREBP-2 was significantly up-regulated by Corni Fructus. Furthermore, the protein expression of peroxisome proliferator-activated receptor alpha was elevated, indicating that Corni Fructus would activate fatty acid oxidation. In conclusion, Corni Fructus may protect against CVD by regulating blood pressure, cholesterol levels, and expression of proteins related to lipid metabolism.

J Endocrinol. 2009 Oct 16;
Dahlman-Wright K, Zhao C

The liver X receptors (LXRs) are nuclear receptors that are activated by endogenous oxysterols, oxidized derivatives of cholesterol. There are two isoforms of LXR, LXRalpha (NR1H3) and LXRneta (NR1H2). Both LXRalpha and LXRbeta regulate gene expression by binding to DNA sequences associated with target genes as heterodimers with the retinoid X receptor (RXR) isoforms. LXRs act as cholesterol sensors: when cellular oxysterols accumulate as a result of increasing concentrations of cholesterol, LXR induces the transcription of genes that protect cells from cholesterol overload. In this review, we summarize the roles of LXRs in controlling cholesterol homoeostasis, including their roles in Bile acid synthesis and metabolism/excretion, reverse cholesterol transport (RCT), cholesterol biosynthesis and uptake, and cholesterol absorption/excretion in the intestine. The overlapping and distinct roles of the LXRalpha and LXRbeta isoforms, and the potential use of LXRs as attractive targets for treatment of cardiovascular disease are also discussed.

Nutr Metab (Lond). 2009; 6: 43
Zhu M, Ji G, Jin G, Yuan Z

ABSTRACT: BACKGROUND: To investigate different responses to a high-fat/cholesterol diet and uncover their underlying genetic factors between C57BL/6J (B6) and DBA/2J (D2) inbred mice. METHODS: B6 and D2 mice were fed a high-fat/cholesterol diet for a series of time-points. Serum and Bile lipid profiles, Bile acid yields, hepatic apoptosis, gallstones and atherosclerosis formation were measured. Furthermore, a whole genome microarray was performed to screen hepatic genes expression profile. Quantitative real-time PCR, western blot and TUNEL assay were conducted to validate microarray data. RESULTS: After fed the high-fat/cholesterol diet, serum and Bile total cholesterol, serum cholesterol esters, HDL cholesterol and Non-HDL cholesterol levels were altered in B6 but not significantly changed in D2; meanwhile, biliary Bile acid was decreased in B6 but increased in D2. At the same time, hepatic apoptosis, gallstones and atherosclerotic lesions occurred in B6 but not in D2. The hepatic microarray analysis revealed distinctly different genes expression patterns between B6 and D2 mice. Their functional pathway groups included lipid metabolism, oxidative stress, immune/inflammation response and apoptosis. Quantitative real time PCR, TUNEL assay and western-blot results were consistent with microarray analysis. CONCLUSION: Different genes expression patterns between B6 and D2 mice might provide a genetic basis for their distinctive responses to a high-fat/cholesterol diet, and give us an opportunity to identify novel pharmaceutical targets in related diseases in the future.

J Mol Model. 2009 Oct 16;
Thompson CE, Fernandes CL, Norberto de Souza O, de Freitas LB, Salzano FM

The plant alcohol dehydrogenases (ADHs) have been intensively studied in the last years in terms of phylogeny and they have been widely used as a molecular marker. However, almost no information about their three-dimensional structure is available. Several studies point to functional diversification of the ADH, with evidence of its importance, in different organisms, in the ethanol, norepinephrine, dopamine, serotonin, and Bile acid metabolism. Computational results demonstrated that in plants these enzymes are submitted to a functional diversification process, which is reinforced by experimental studies indicating distinct enzymatic functions as well as recruitment of specific genes in different tissues. The main objective of this article is to establish a correlation between the functional diversification occurring in the plant alcohol dehydrogenase family and the three-dimensional structures predicted for 17 ADH belonging to Poaceae, Brassicaceae, Fabaceae, and Pinaceae botanical families. Volume, molecular weight and surface areas are not markedly different among them. Important electrostatic and pI differences were observed with the residues responsible for some of them identified, corroborating the function diversification hypothesis. These data furnish important background information for future specific structure-function and evolutionary investigations.

J Neurosci. 2009 Oct 14; 29(41): 13042-52
Takami M, Nagashima Y, Sano Y, Ishihara S, Morishima-Kawashima M, Funamoto S, Ihara Y

Amyloid beta protein (Abeta), a pathogenic molecule associated with Alzheimer's disease, is produced by gamma-secretase, which cleaves the beta-carboxyl terminal fragment (betaCTF) of beta-amyloid precursor protein in the middle of its transmembrane domain. How the cleavage proceeds within the membrane has long been enigmatic. We hypothesized previously that betaCTF is cleaved first at the membrane-cytoplasm boundary, producing two long Abetas, Abeta(48) and Abeta(49), which are processed further by releasing three residues at each step to produce Abeta(42) and Abeta(40), respectively. To test this hypothesis, we used liquid chromatography tandem mass spectrometry (LC-MS/MS) to quantify the specific tripeptides that are postulated to be released. Using CHAPSO (3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxyl-1-propanesulfonate)-reconstituted gamma-secretase system, we confirmed that Abeta(49) is converted to Abeta(43/40) by successively releasing two or three tripeptides and that Abeta(48) is converted to Abeta(42/38) by successively releasing two tripeptides or these plus an additional tetrapeptide. Most unexpectedly, LC-MS/MS quantification revealed an induction period, 3-4 min, in the generation of peptides. When extrapolated, each time line for each tripeptide appears to intercept the same point on the x-axis. According to numerical simulation based on the successive reaction kinetics, the induction period exists. These results strongly suggest that Abeta is generated through the stepwise processing of betaCTF by gamma-secretase.

J Physiol Pharmacol. 2009 Sep; 60(3): 79-84
Izzat NN, Overturf M, Weisbrodt NW, Loose DS

We examined Bile acid transport and expression of the apical sodium-dependent Bile acid transporter (ASBT) in ileal preparations to determine if alterations in Bile acid excretion contributed to a hypercholesterolemia-resistant phenotype in rabbits (CRT/mlo). Taurocholate transport was not different between normal (NR) and CRT/mlo rabbits fed regular diet. However, feeding cholesterol-enriched diet reduced taurocholate transport significantly in CRT/mlo rabbits (0.53 + or - 0.06 pmol/microg protein) compared to regular diet (0.95 + or - 0.14 pmol/microg protein), but had no effect in NR rabbits. Cholesterol-enriched diet increased ASBT mRNA in CRT/mlo (2.6 + or - 0.7 to 5.4 + or - 0.1); no significant changes occurred in NR. Some CRT/mlo rabbits carry a polymorphism in ASBT at amino acid 333 (P333L). In transfected HEK293 cells, TC transport of P333L allele was significantly lower (0.08 + or - 0.01 vs 0.13 + or - 0.01 pmol/microg protein/15 sec, P< 0.05). This allele was not found in NR rabbits. The data suggest that the phenotype of the CRT/mlo rabbit is due to changes in Bile acid transport as well as Bile acid metabolism.

Br J Nutr. 2009 Oct 13; 1-8
Méndez-González J, Süren-Castillo S, Calpe-Berdiel L, Rotllan N, Vázquez-Carrera M, Escolà-Gil JC, Blanco-Vaca F

Disodium ascorbyl phytostanol phosphate (FM-VP4) is a synthetic compound derived from sitostanol and campestanol that has proved to be efficient as a cholesterol-lowering therapy in mice and human subjects. However, the mechanism of action of FM-VP4 remains unknown. The present study tests the ability of FM-VP4 to alter intestinal and liver cholesterol homeostasis in mice. Female C57BL/6J mice were fed either a control chow or a 2 % FM-VP4-enriched diet for 4 weeks. FM-VP4 reduced the in vivo net intestinal cholesterol absorption and plasma and liver cholesterol concentrations by 2.2-, 1.5- and 1.6-fold, respectively, compared with control mice. Furthermore, FM-VP4 also showed an impact on Bile acid homeostasis. In FM-VP4 mice, liver and intestinal Bile acid content was increased by 1.3- and 2.3-fold, respectively, whereas faecal Bile acid output was 3.3-fold lower. FM-VP4 also increased the intestinal absorption of orally administered [3H]taurocholic acid to small intestine in vivo. Inhibition of intestinal cholesterol absorption by FM-VP4 was not mediated via transcriptional increases in intestine liver X receptor (LXR)-alpha, adenosine triphosphate-binding cassette transporter (ABC)-A1, ABCG5/G8 nor to decreases in intestinal Niemann-Pick C1-like 1 (NPC1L1) expression. In contrast, FM-VP4 up-regulated liver LXRalpha, ABCA1, ABCG5, scavenger receptor class BI (SR-BI) and hydroxymethylglutaryl coenzyme A reductase (HMGCoA-R) gene expression, whereas it down-regulated several farnesoid X receptor (FXR)-target genes such as cytochrome P450 family 7 subfamily A polypeptide 1 (CYP7A1) and Na+/taurocholate co-transporter polypeptide (NTCP). In conclusion, FM-VP4 reduced intestinal cholesterol absorption, plasma and liver cholesterol and affected Bile acid homeostasis by inducing Bile acid intestinal reabsorption and changed the liver expression of genes that play an essential role in cholesterol homeostasis. This is the first phytosterol or stanol that affects Bile acid metabolism and lowers plasma cholesterol levels in normocholesterolaemic mice.

J Chromatogr B Analyt Technol Biomed Life Sci. 2009 Nov 15; 877(30): 3920-5
Scherer M, Gnewuch C, Schmitz G, Liebisch G

Beside their role as lipid solubilizers, Bile acids (BAs) are increasingly appreciated as signaling factors. As ligands of G-protein coupled receptors and nuclear hormone receptors BAs control their own metabolism and act on lipid and energy metabolism. To study BA function in detail, it is necessary to use methods for their quantification covering the structural diversity of this group. Here we present a simple, sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the analysis of Bile acid profiles in human plasma/serum. Protein precipitation was performed in the presence of stable-isotope labeled internal standards. In contrast to previous LC-MS/MS methods, we used a reversed-phase C18 column with 1.8microm particles and a gradient elution at basic pH. This allows base line separation of 18 Bile acid species (free and conjugated) within 6.5min run time and a high sensitivity in negative ion mode with limits of detection below 10nmol/L. Quantification was achieved by standard addition and calibration lines were linear in the tested range up to 28micromol/L. Validation was performed according to FDA guidelines and overall imprecision was below 11% CV for all species. The developed LC-MS/MS method for Bile acid quantification is characterized by simple sample preparation, baseline separation of isobaric species, a short analysis time and provides a valuable tool for both, routine diagnostics and the evaluation of BAs as diagnostic biomarkers in large clinical studies.

J Endocrinol. 2009 Oct 9;
Li Q, Yin W, Cai M, Liu Y, Hou H, Shen Q, Zhang C, Xiao J, Hu X, Wu Q, Funaki M, Nakaya Y

Insulin resistance and dyslipidaemia are both involved into the risk factors of metabolic syndrome. Low levels of insulin-like growth factor 1 (IGF-1) are associated with insulin resistance. Elevation of low-density lipoprotein cholesterol (LDL-C) concomitant with depression of high-density lipoprotein cholesterol (HDL-C) increase the risk of obesity and type 2 diabetes mellitus (T2DM). Liver functions to secret IGF-1 and catabolize cholesterol regulated by the rate limiting enzyme of Bile acid synthesis from cholesterol 7alpha-hydroxylase (CYP7A1). NO-1886, a chemically synthesized lipoprotein lipase (LPL) activator, suppresses diet-induced insulin resistance with the improvement of HDL-C. The goal of the present study is to evaluate whether NO-1886 upregulates IGF-1 and CYP7A1 to benefit glucose and cholesterol metabolism. By using human hepatoma cell lines (HepG2 cells) as an in vitro model, we found that NO-1886 promoted IGF-1 secretion and CYP7A1 expression through the activation of signal transducer and activator of transcription 5 (STAT5). Pretreatment of cells with AG 490, the inhibitor of STAT pathway, completely abolished NO-1886-induced IGF-1 secretion and CYP7A1 expression. Studies performed in Chinese Bama minipigs pointed out an augmentation of plasma IGF-1 elicited by a single dose administration of NO-1886. Long-term supplementation with NO-1886, recovered hyperinsulinemia and low plasma levels of IGF-1, suppressed LDL-C and facilitated RCT by decreasing hepatic cholesterol accumulation through increasing CYP7A1 expression in high-fat/ high-sucrose/ high-cholesterol diet (HFSCD) minipigs. These findings indicate that NO-1886 upregulates IGF-1 secretion and CYP7A1 expression to improve insulin resistance and hepatic cholesterol accumulation, which may represent an alternative therapeutic avenue of NO-1886 on T2DM and metabolic syndrome.

Lipids. 2009 Oct 6;
Gustavsson C, Parini P, Ostojic J, Cheung L, Hu J, Zadjali F, Tahir F, Brismar K, Norstedt G, Tollet-Egnell P

The aim of this study was to compare the effects of cocoa butter and safflower oil on hepatic transcript profiles, lipid metabolism and insulin sensitivity in healthy rats. Cocoa butter-based high-fat feeding for 3 days did not affect plasma total triglyceride (TG) levels or TG-rich VLDL particles or hepatic insulin sensitivity, but changes in hepatic gene expression were induced that might lead to increased lipid synthesis, lipotoxicity, inflammation and insulin resistance if maintained. Safflower oil increased hepatic beta-oxidation, was beneficial in terms of circulating TG-rich VLDL particles, but led to reduced hepatic insulin sensitivity. The effects of safflower oil on hepatic gene expression were partly overlapping with those exerted by cocoa butter, but fewer transcripts from anabolic pathways were altered. Increased hepatic cholesterol levels and increased expression of hepatic CYP7A1 and ABCG5 mRNA, important gene products in Bile acid production and cholesterol excretion, were specific effects elicited by safflower oil only. Common effects on gene expression included increased levels of p8, DIG-1 IGFBP-1 and FGF21, and reduced levels of SCD-1 and SCD-2. This indicates that a lipid-induced program for hepatic lipid disposal and cell survival was induced by 3 days of high-fat feeding, independent on the lipid source. Based on the results, we speculate that hepatic TG infiltration leads to reduced expression of SCD-1, which might mediate either neutral, beneficial or unfavorable effects on hepatic metabolism upon high-fat feeding, depending on which fatty acids were provided by the diet.

Mol Cell Biol. 2009 Dec; 29(23): 6170-81
Miao J, Fang S, Lee J, Comstock C, Knudsen KE, Kemper JK

Bile acid homeostasis is critical in maintaining health and is primarily regulated by the nuclear receptors farnesoid X receptor (FXR) and small heterodimer partner (SHP). Bile acid-activated FXR indirectly inhibits expression of cholesterol 7alpha hydroxylase (CYP7A1), a key enzyme in conversion of cholesterol to Bile acids, by induction of SHP. We recently demonstrated that SHP inhibits CYP7A1 transcription by recruiting chromatin-modifying cofactors, including Brm-Swi/Snf. Swi/Snf complexes contain either Brm or Brg-1 ATPases, and whether these subunits have distinct functions remains unclear. We have examined the role of these subunits in regulation of Bile acid metabolism under physiological conditions by FXR and SHP. Brg-1 interacted with FXR and enhanced FXR-mediated transactivation of SHP, whereas Brm interacted with SHP and enhanced SHP-mediated repression of CYP7A1 and, interestingly, auto-repression of SHP. Chromatin immunoprecipitation and remodeling studies revealed that after treatment with FXR agonists, Brg-1 was recruited to the SHP promoter, resulting in transcriptionally active accessible chromatin, whereas Brm was recruited to both CYP7A1 and SHP promoters, resulting in inactive inaccessible chromatin. Our studies demonstrate that Brm and Brg-1 have distinct functions in the regulation of two key genes, CYP7A1 and SHP, within a single physiological pathway, feedback inhibition of Bile acid biosynthesis, by differentially targeting SHP and FXR.

Drug Metab Dispos. 2009 Oct 1;
Owen BM, Milona A, van Mil S, Clements P, Holder J, Boudjelal M, Cairns W, Parker M, White R, Williamson C

The intestinal-derived secondary Bile acid lithocholic acid (LCA) is hepatotoxic and is implicated in the pathogenesis of cholestatic diseases. LCA is an endogenous ligand of the xenobiotic nuclear receptor PXR but there is currently no consensus on the respective roles of hepatic and intestinal PXR in mediating protection against LCA in vivo. Under the conditions reported here, we show that mice lacking Pxr are resistant to LCA-mediated hepatotoxicity. This unexpected phenotype is found in association with enhanced urinary Bile acid excretion and elevated basal expression of drug metabolism enzymes and the hepatic sulfate donor synthesis enzyme Papss2, in Pxr(-/-) mice. By subsequently comparing molecular responses to dietary and intraperitoneal administration of LCA, we made two other significant observations: 1) LCA-feeding induces intestinal, but not hepatic, drug metabolising enzymes in a largely Pxr-independent manner. 2) In contrast to LCA-feeding, bypassing first-pass gut-transit by intraperitoneal administration of LCA did induce hepatic detoxification machinery and in a Pxr-dependent manner. These data reconcile important discrepancies in the reported molecular responses to this Bile acid and suggest that Pxr plays only a limited role in mediating responses to gut-derived LCA. Furthermore, the route of administration must be considered in the future planning and interpretation of experiments designed to assess hepatic responses to Bile acids, orally administered pharmaceuticals and dietary toxins.