Abnormal Bile Acid Synthesis Research Articles

Mechanism of action of bile acid metabolism in regulating cholestatic liver disease and the research and development of drugs

Bile acids are the end products of cholesterol metabolism and are classified as primary bile acids and secondary bile acids. They can promote nutrition absorption and regulate immune response, glucose/lipid/energy metabolism, and microbiota homeostasis by acting on bile acid nuclear receptors and membrane receptors. Cholestatic liver disease (CLD) is a type of liver disease caused by abnormalities of the hepatobiliary system due to cholestasis, with the initial manifestations of hepatocyte and/or bile duct injury, which further leads to abnormal bile acid synthesis, secretion, and excretion. In-depth studies have gradually revealed the role and mechanism of bile acids in CLD, and drugs targeting the action sites of bile acids are under research and development. This article elaborates on the role and mechanism of bile acid metabolism in CLDand summarizes the research and development of drugs for CLD treatment based on bile acid metabolism, so as to provide a reference for future research on the prevention and treatment of CLD.

Inflammation Drives MicroRNAs to Limit Hepatocyte Bile Acid Transport in Murine Biliary Atresia

BackgroundBiliary atresia (BA) is an inflammatory pediatric cholangiopathy with only surgical means for treatment. Many contributors to bile acid synthesis and transport have previously been reported to be downregulated in patients with BA; yet, the driving factors of the abnormal bile acid synthesis and transport in regard to BA have not been previously studied. Materials and methodsWild type or Ig-α-/- mice were injected with salt solution (control) or rotavirus on day of life 0, and analyses were performed on day of life 14. The mRNA levels of bile acid transporters/nuclear receptors and liver microRNAs (miRNAs) were compared between groups. A mouse hepatocyte cell line was used to examine the effects of innate cytokines on miRNA levels and bile acid transporter/nuclear receptor expression and miRNAs on bile acid transporter/nuclear receptor expression. ResultsBA mice had significantly increased mRNA expression of innate cytokines and miRNAs known to bind bile acid transporters/nuclear receptors (miRNAs -22-5p, -34a-5p, and -222-3p) and decreased mRNA expression of bile acid transporters and nuclear receptors. In vitro, TNF-α and IL-1β decreased BSEP and CYP7A1 while increasing miRNA-34a-5p and miRNA 222-3p. LXR, SHP, CYP7A1, NTCP, and MRP2 were decreased by miRNA-34a-5p, whereas miRNA-222-3p decreased NTCP and MRP4. TNF-α and IL-1β increased expression of miRNAs 34a-5p and 222-3p and these miRNAs then decrease expression of multiple bile acid transporters and nuclear receptors. ConclusionsLoss of bile acid transporters increases hepatotoxicity via bile acid retention. Therapeutic agents that increase bile acid transport or nuclear receptor functioning should be investigated in BA.

Profiling of carboxyl-containing metabolites in smokers and non-smokers by stable isotope labeling combined with LC-MS/MS

Profiling of carboxyl-containing metabolites in smokers and non-smokers provides insight into the smoking-related biological events and causal relationships between exposure and adverse events. However, more comprehensive analysis of carboxyl-containing metabolites in bio-matrices with high sensitivity and accuracy is challenging. In this work, stable isotope labeling in combination with liquid chromatography-tandem mass spectrometry was used for untargeted profiling and relative quantification of carboxyl-containing metabolites in plasma of smokers and non-smokers. A pair of isotope labeling reagents, N, N-dimethylethylenediamine (DMED) and d4-DMED was used to label carboxyl-containing metabolites. Since the isotope labeled dimethylamino moieties of DMED and d4-DMED are easily fragmented and lost as characteristic neutral fragments of 45 and 49 Da, respectively, double neutral loss scans can be used to profiling of carboxyl-containing metabolites. Subsequently, based on the ion pair parameters obtained from double neutral loss scans, relative quantification method was developed. As a result, 269 carboxyl-containing metabolite candidates were discovered, and 88 metabolite candidates were found to have significant alterations between smokers and non-smokers. 7Z, 10Z-hexadecadienoic acid, myristic acid and 3β-hydroxy-5-cholestenoic acid with significant differences confirmed by standard comparison are linked to smoking related inflammation, abnormal bile acid synthesis and cholesterol metabolism.

MALDI Mass Spectral Imaging of Bile Acids Observed as Deprotonated Molecules and Proton-Bound Dimers from Mouse Liver Sections

Bile acids (BAs) play two vital roles in living organisms, as they are involved in (1) the secretion of cholesterol from liver, and (2) the lipid digestion/absorption in the intestine. Abnormal bile acid synthesis or secretion can lead to severe liver disorders. Even though there is extensive literature on the mass spectrometric determination of BAs in biofluids and tissue homogenates, there are no reports on the spatial distribution in the biliary network of the liver. Here, we demonstrate the application of high mass resolution/mass accuracy matrix-assisted laser desorption/ionization (MALDI)-Fourier-transform ion cyclotron resonance (FTICR) to MS imaging (MSI) of BAs at high spatial resolutions (pixel size, 25 μm). The results show chemical heterogeneity of the mouse liver sections with a number of branching biliary and blood ducts. In addition to ion signals from deprotonation of the BA molecules, MALDI-MSI generated several further intense signals at larger m/z for the BAs. These signals were spatially co-localized with the deprotonated molecules and easily misinterpreted as additional products of BA biotransformations. In-depth analysis of accurate mass shifts and additional electrospray ionization and MALDI-FTICR experiments, however, confirmed them as proton-bound dimers. Interestingly, dimers of bile acids, but also unusual mixed dimers of different taurine-conjugated bile acids and free taurine, were identified. Since formation of these complexes will negatively influence signal intensities of the desired [M – H]- ions and significantly complicate mass spectral interpretations, two simple broadband techniques were proposed for non-selective dissociation of dimers that lead to increased signals for the deprotonated BAs.Graphical ᅟ

Conjugated Hyperbilirubinemia in Children

A variety of anatomic, infectious, autoimmune, and metabolic diseases can lead to conjugated hyperbilirubinemia, both in the newborn period and later in childhood. The pediatric practitioner is most likely to encounter conjugated hyperbilirubinemia in the neonatal period.It is crucial to maintain a high degree of suspicion for cholestasis in the persistently jaundiced newborn. The goal is recognition of conjugated hyperbilirubinemia between 2 and 4 weeks after birth, allowing for the prompt identification and management of infants who have biliary atresia, which remains the most common cause of neonatal cholestasis.

Enlarged cauda equina nerve roots in Cerebrotendinous Xanthomatosis

CXT is a rare inherited autosomal recessive lipid storage disease due to the impaired metabolic pathway of cholesterol secondary to a deficiency in 27- sterol hydroxylase, an enzyme in the synthesis of chenodeoxycholic acid (CDCA), a primary bile acid. Abnormal bile acid synthesis leads to elevated plasma Cholestanol (a derivative of cholesterol) accumulation, especially in the lens, central nervous system (CNS) and tendons.

Clinical relevance and neurophysiological correlates of spasticity in cerebrotendinous xanthomatosis

Cerebrotendinous xanthomatosis (CTX) is a rare neurometabolic disease due to defective activity of sterol 27-hydroxylase, with plasma and tissue cholestanol storage. Clinical phenotype is characterized by both systemic manifestations and neurological signs. Therapy with chenodeoxycholic acid (CDCA) suppresses abnormal bile acid synthesis. The purpose of the study was to assess the frequency and clinical relevance of spasticity in the CTX phenotype and to study the usefulness of transcranial magnetic stimulation (TMS) in detecting corticospinal tract damage and monitoring the effects of replacement therapy. Twenty-four CTX patients underwent clinical evaluation including general disability scores, pyramidal and cerebellar function scales, assessment of serum cholestanol and TMS. Nine patients who started CDCA therapy at baseline received clinical and neurophysiological follow up. All patients showed signs of pyramidal damage which were relevant for clinical disability in 18 out of 24 cases (75%), resulting in spastic paraparesis. TMS revealed corticospinal alterations even in subjects with mild clinical signs of corticospinal tract involvement. After CDCA treatment, serum cholestanol decreased to normal concentrations in all patients. Clinical picture was unchanged in seven out of nine cases; in two others pyramidal signs disappeared. A reduction in abnormal neurophysiological parameters was found. Spastic paraparesis is the most frequent and relevant neurological feature in CTX patients. Replacement treatment with CDCA can prevent the progression of pyramidal damage, especially if started early in the course of the disease. TMS represents a sensitive indicator of corticospinal tract dysfunction and subclinical improvements in pyramidal function after CDCA therapy.

CEREBROTENDINOUS XANTHOMATOSIS

Cerebrotendinous xanthomatosis is a rare familial lipid storage that is caused by a defect in bile acid synthesis. As a result, large amounts of cholestanol, the 5a-dihydro derivative of cholesterol, accumulate in virtually every tissue, with extra large deposits in the nervous system, xanthomas, and bile. Clinically, progressive neurologic dysfunction, tendon xanthomas, cataracts, and atherosclerosis are commonly found. Because chenodeoxycholic acid, a primary bile acid, is almost devoid from the bile, replacement therapy (750 mg per day) suppresses abnormal bile acid synthesis, reduces elevated cholestanol synthesis and plasma concentrations, and improves neurologic function in this disease.

Hydrophilic 7β-hydroxy bile acids, lovastatin, and cholestyramine are ineffective in the treatment of cerebrotendinous xanthomatosis

We compared the effect of treatments with hydrophilic bile acids (ursodeoxycholic and ursocholic acids), cholestyramine, and lovastatin versus chenodeoxycholic acid in 4 patients with cerebrotendinous xanthomatosis (CTX). Bile acids and bile alcohols in plasma, bile, and urine before and after treatment were quantitated by gas-liquid chromatography. Untreated, all patients showed abnormal biliary bile acid composition: cholic acid (72.7%) and chenodeoxycholic acid (6.2%), and polyhydroxylated C 27-bile alcohols (10.0%), and elevated plasma cholestanol levels. Treatment with hydrophobic chenodeoxycholic acid inhibited abnormal bile acid synthesis (virtual disappearance of C 27-bile alcohols from plasma, bile, and urine and marked reduction of plasma cholestanol levels). Hydrophilic ursodeoxycholic and ursocholic acids did not inhibit abnormal bile acid synthesis, while cholestyramine increased abnormal bile acid synthesis (continued increased formation of polyhydroxylated C 27-bile alcohols and further elevation of plasma cholestanol levels). Lovastatin did not affect abnormal bile acid synthesis or reduce plasma cholestanol levels. The results demonstrate that impaired side-chain oxidation in bile acid synthesis due to mutations of Cyp27 results in increased formation of polyhydroxylated C 27-bile alcohols and cholestanol in CTX. Hydrophobic chenodeoxycholic acid, but not cholestyramine, lovastatin, or hydrophilic 7β-hydroxy acids, inhibited the abnormal synthetic pathway. The role of chenodeoxycholic acid in downregulating abnormal bile acid synthesis in CTX is emphasized.

Comparative effects of lovastatin and chenodeoxycholic acid on plasma cholestanol levels and abnormal bile acid metabolism in cerebrotendinous xanthomatosis

We investigated the effect of the hepatic hydroxymethyl glutaryl coenzyme A (HMG-CoA) reductase inhibitor lovastatin and the primary bile acid chenodeoxycholic acid (CDCA) on plasma sterol and bile alcohol concentrations and the excretion of bile alcohols in urine in a 38-year-old homozygote with cerebrotendinous xanthomatosis (CTX). Untreated, plasma cholesterol concentrations were less than normal (171 ± 5 v 185 ± 3 mg/dL, P < .05) while plasma cholestanol levels were more than 20 times higher than the control mean (2.26 ± 0.17 v 0.1 ± 0.1 mg/dL, P < .0001). Plasma and urinary bile alcohol concentrations were markedly increased (12.6 ± 0.6 and 154 μg/mL, respectively, v trace amounts in controls), with the ratio of 5β-cholestane-3α,7α,12α, 25-tetrol to 5β-cholestane,3α,7α,12α,23 (22 and 24),25-pentols being 1.6 in plasma and reversed to 0.15 in urine. Treatment with lovastatin (40 mg/d) reduced plasma cholesterol concentrations 13%, but failed to decrease plasma cholestanol or bile alcohol levels. Abundant amounts of bile alcohols continued to be excreted in urine. In contrast, CDCA (750 mg/d) inhibited abnormal bile acid synthesis, as evidenced by a 17-fold decrease in total bile alcohol levels in plasma and a 29-fold decrease in urine and the virtual elimination of cholic acid and deoxycholic acid from the bile. Plasma cholestanol concentrations also decreased 85%, but cholesterol levels increased 14%. The combination of CDCA with lovastatin did not improve plasma cholestanol or bile alcohol concentrations compared with CDCA treatment alone. These results demonstrate that suppression of abnormal bile acid synthesis with CDCA corrects the two principal biochemical abnormalities in CTX—it diminishes elevated plasma cholestanol concentrations and virtually eliminates bile alcohols from plasma and urine. In contrast, competitively inhibiting HMG-CoA reductase with lovastatin did not correct abnormal bile acid synthesis or reduce elevated plasma cholestanol levels. Thus, the most effective treatment for CTX remains CDCA alone; the combination with lovastatin produced no additional biochemical benefit.

Cerebrotendinous Xanthomatosis

Cerebrotendinous xanthomatosis is a rare familial lipid storage that is caused by a defect in bile acid synthesis. As a result, large amounts of cholestanol, the 5a-dihydro derivative of cholesterol, accumulate in virtually every tissue, with extra large deposits in the nervous system, xanthomas, and bile. Clinically, progressive neurologic dysfunction, tendon xanthomas, cataracts, and atherosclerosis are commonly found. Because chenodeoxycholic acid, a primary bile acid, is almost devoid from the bile, replacement therapy (750 mg per day) suppresses abnormal bile acid synthesis, reduces elevated cholestanol synthesis and plasma concentrations, and improves neurologic function in this disease.

Increased plasma bile alcohol glucuronides in patients with cerebrotendinous xanthomatosis: effect of chenodeoxycholic acid

Large quantities of C27 bile alcohols hydroxylated at C-25 are excreted in the bile and urine of patients with cerebrotendinous xanthomatosis, a lipid storage disease that results from defective bile acid synthesis. The presence of both biliary and urinary bile alcohols reflects impaired bile acid synthesis. After treatment of samples with beta-glucuronidase, plasma bile alcohols were quantitated by gas-liquid chromatography-mass spectrometry. 5 beta-Cholestane-3 alpha,7 alpha,12 alpha,25-tetrol (334 micrograms/dl) was found to be the major bile alcohol, followed by 5 beta-cholestane-3 alpha,7 alpha,12 alpha,23R,25-pentol (65 micrograms/dl), and 5 beta-cholestane-3 alpha,7 alpha,12 alpha,24(R and S),25-pentols (62.5 micrograms/dl and 64.5 micrograms/dl, respectively) in the plasma of these patients. When compared to biliary and urinary bile alcohol excretions, the plasma pattern resembled bile where 5 beta-cholestane-3 alpha,7 alpha,12 alpha,25-tetrol glucuronide predominated. In contrast, urinary bile alcohols were composed chiefly of 5 beta-cholestanepentol glucuronides with only small amounts of 5 beta-cholestane-3 alpha,7 alpha,12 alpha,25-tetrol glucuronide. Treatment with chenodeoxycholic acid, which suppresses abnormal bile acid synthesis in these patients, reduced plasma bile alcohol concentrations dramatically. These results show that large quantities of bile alcohol glucuronides, particularly 5 beta-cholestane-3 alpha,7 alpha,12 alpha,25-tetrolglucuronide, circulate in plasma of patients with cerebrotendinous xanthomatosis. The plasma bile alcohols closely resemble biliary bile alcohols which indicates their hepatic origin. The large quantities of polyhydroxylated bile alcohols in the urine may suggest their formation, at least in part, from 5 beta-cholestane-3 alpha,7 alpha,12 alpha,25-tetrol by renal hydroxylating mechanisms.(ABSTRACT TRUNCATED AT 250 WORDS)

Bile acids and plasma high density lipoproteins: biliary lipid metabolism in fish eye disease

Cholesterol in plasma high density lipoproteins (HDL) has been proposed to serve as preferential precursor for bile acid biosynthesis in the liver. Furthermore, a negative relationship between plasma levels of HDL cholesterol and biliary saturation with cholesterol has been reported in healthy females. We have performed metabolic studies on a female patient with fish eye disease, a familial condition where plasma HDL levels are reduced by 90% and the concentration of plasma triglycerides is moderately increased. Both the total production of bile acids and the net steroid 'balance' (reflecting total body cholesterol synthesis) were within the range seen in normolipidaemic as well as in hypertriglyceridaemic females. Also the biliary lipid composition and cholesterol saturation of bile were normal. A qualitative abnormality in the bile acid pattern was observed, however, in that the ratio between the synthesis of cholic acid and chenodeoxycholic acid was reduced. It is concluded that a low HDL cholesterol level is not necessarily associated with quantitative abnormalities of biliary lipid metabolism. The abnormal bile acid synthesis ratio may reflect changes in the hepatic precursor pools of cholesterol as the consequence of HDL deficiency, however.

Long-term treatment of cerebrotendinous xanthomatosis with chenodeoxycholic acid.

We studied the effect of chenodeoxycholic acid in 17 patients with cerebrotendinous xanthomatosis. Before treatment, all subjects were symptomatic, with Achilles tendon xanthomas (in 15 of 17), cataracts (in 12 of 17), dementia (in 13 of 17), pyramidal-tract signs (in all 17), cerebellar dysfunction (in 13 of 17), mild peripheral neuropathy (in 7 of 17), electroencephalographic abnormalities (in 10 of 13), and abnormal cerebral computerized axial tomographic scans (in 10 of 12). After at least one year of chenodeoxycholic acid treatment (750 mg per day), dementia cleared in 10 subjects, and pyramidal and cerebellar signs disappeared in 5 and improved in another 8. Peripheral neuropathy was no longer detected in six. The electroencephalogram became normal in five and showed fewer abnormalities in another three subjects. Cerebral computerized axial tomographic scans improved in seven patients; the changes included the disappearance of a cerebellar xanthoma in one case. Concomitantly, mean plasma cholestanol levels declined threefold, and abnormal bile acid synthesis was suppressed. We conclude that long-term therapy with chenodeoxycholic acid may correct the biochemical abnormalities and arrest and possibly reverse the progression of cerebrotendinous xanthomatosis.