Plasma Bile Acid Concentrations Research Articles

Reversal of insulin resistance in people with obesity by lifestyle-induced weight loss does not impact the proportion of circulating 12α-hydroxylated bile acids.

Bile acids (BAs) are implicated in the pathogenesis of several metabolic syndrome-related diseases, including insulin resistance (IR) and type 2 diabetes (T2D). It has been reported that IR and T2D are associated with an increased ratio of 12α/non-12α-hydroxylated BAs in the circulating BA pool. It is, however, unknown whether the improvement of insulin sensitivity inversely affects BA composition in humans. Therefore, we assessed whether lifestyle-induced weight loss induces changes in BA metabolism in people with obesity, with or without T2D, and if these changes are associated with metabolic parameters. Individual BAs and C4 were quantified by ultra-high-performance liquid chromatography-tandem mass spectrometry in plasma samples collected from two cohorts of people with obesity (OB) and with T2D and obesity (T2D), before and after a lifestyle intervention. Lifestyle-induced weight loss improved glycaemic control in both cohorts, with plasma BA concentrations not affected by the lifestyle interventions. The ratio of 12α/non-12α-hydroxylated BAs remained unchanged in OB (p = .178) and even slightly increased upon intervention in T2D (p = .0147). Plasma C4 levels were unaffected in OB participants (p = .20) but significantly reduced in T2D after intervention (p = .0003). There were no significant correlations between the ratio of 12α/non-12α-hydroxylated BAs and glucose, insulin, or homeostatic model assessment-IR, nor in plasma triglycerides, low-density lipoprotein cholesterol, lipoprotein (a) in the T2D cohort. Lifestyle-induced weight loss did improve glycaemic control but did not affect BA concentrations. Improvements in insulin sensitivity were not associated with changes in BA parameters in people with obesity, with or without T2D.

Postprandial effects following a semielemental critical-care diet lead to changes in uric acid, bile acids, and glucose in the central bearded dragon (Pogona vitticeps).

To assess the prandial effects of a semielemental diet on plasma uric acid, bile acid, and glucose concentrations in the central bearded dragon (Pogona vitticeps). 13 healthy adult male bearded dragons. Following a 72-hour fasting period, blood was collected to measure preprandial uric acid, bile acid, and glucose concentrations. The animals were then gavage fed 1.2% body weight of an omnivore critical-care diet containing 20% protein, 9.5% fat, 2.5% fiber, and 2.39 kcal/mL. Blood was collected for repeat concentrations at 4 and 24 hours. Median (IQR) uric acid concentration (mg/dL) increased from 3.8 preprandial (2.8 to 4.3) to 4.7 4 hours postprandial (4 to 7; P = .0001). Median (IQR) bile acid concentration (mg/dL) increased from 1.8 preprandial (1 to 3.4) to 9.5 24 hours postprandial (5.6 to 10.4; P = .004). Median (IQR) glucose concentration (mg/dL) was 209 at time 0 (193 to 216), 287 at 4 hours (258 to 312), and 393 at 24 hours (361 to 464). Significant increases were seen between pre- and 4-hours-postprandial (P < .0001), pre- and 24-hours-postprandial (P < .0001), and 4-hours- and 24-hours-postprandial (P < .0001) glucose concentrations. Results suggest that postprandial status and diet composition should be considered during the interpretation of some biochemical analytes in the bearded dragon.

Targeted LC-MS/MS profiling of bile acids reveals primary/secondary bile acid ratio as a novel biomarker for necrotizing enterocolitis.

Bile acids (BAs) are involved in the development of necrotizing enterocolitis (NEC), which mainly occurs in preterm infants. We aim to identify the change of BAs in preterm infants and validate its potential value in the detection of NEC. Targeted liquid chromatography-tandem mass spectrometry (LC-MS/MS) was performed to measure the plasma BAs in healthy preterm infants and patients with NEC. By analyzing the level of BAs in healthy preterm infants, we found that the plasma concentrations of BAs were related to sex, gestational/postnatal age, birth weight, mode of birth, and feeding type after birth. The plasma levels of TCA, GCA, TCDCA, GCDCA, primary BAs, and total BAs and the primary/secondary BA ratio were decreased, while DCA, UDCA, and secondary BAs were increased in NEC. The primary/secondary BA ratio (cutoff point 62.9) can effectively differentiate NEC from healthy preterm infants, with an AUC of 0.9, a sensitivity of 94.5%, and a specificity of 78.1%. Combining the ratio with high-risk factors of NEC can better distinguish between NEC and control, with an AUC of 0.95. Importantly, significantly lower levels of primary/secondary BA ratio were found in infants with surgical NEC than in nonsurgical NEC cases. The cutoff point of 28.7 identified surgical NEC from nonsurgical NEC with sensitivity and specificity of 76.9% and 100%. Thus, our study identified that the primary/secondary BA ratio in the plasma can differentiate NEC from healthy preterm infants and effectively differentiate the surgical NEC from nonsurgical NEC. Therefore, LC-MS/MS was expected to be a novel measurement platform used to distinguish infants who are most in need of close monitoring or early surgical intervention.

CYP2D6 Activity Is Correlated with Changes in Plasma Concentrations of Taurocholic Acid during Pregnancy and Postpartum in CYP2D6 Extensive Metabolizers.

Cytochrome P450 2D6 (CYP2D6) is involved in the metabolism of >20% of marketed drugs. CYP2D6 expression and activity exhibit high interindividual variability and is induced during pregnancy. The farnesoid X receptor (FXR) is a transcriptional regulator of CYP2D6 that is activated by bile acids. In pregnancy, elevated plasma bile acid concentrations are associated with maternal and fetal risks. However, modest changes in bile acid concentrations may occur during healthy pregnancy, thereby altering FXR signaling. A previous study demonstrated that hepatic tissue concentrations of bile acids positively correlated with the hepatic mRNA expression of CYP2D6. This study sought to characterize the plasma bile acid metabolome in healthy women (n = 47) during midpregnancy (25-28 weeks gestation) and ≥3 months postpartum and to determine if plasma bile acids correlate with CYP2D6 activity. It is hypothesized that during pregnancy, plasma bile acids would favor less hydrophobic bile acids (cholic acid vs. chenodeoxycholic acid) and that plasma concentrations of cholic acid and its conjugates would positively correlate with the urinary ratio of dextrorphan/dextromethorphan. At 25-28 weeks gestation, taurine-conjugated bile acids comprised 23% of the quantified serum bile acids compared with 7% ≥3 months postpartum. Taurocholic acid positively associated with the urinary ratio of dextrorphan/dextromethorphan, a biomarker of CYP2D6 activity. Collectively, these results confirm that the bile acid plasma metabolome differs between pregnancy and postpartum and provide evidence that taurocholic acid may impact CYP2D6 activity during pregnancy. SIGNIFICANCE STATEMENT: Bile acid homeostasis is altered in pregnancy, and plasma concentrations of taurocholic acid positively correlate with CYP2D6 activity. Differences between plasma and/or tissue concentrations of farnesoid X receptor ligands such as bile acids may contribute to the high interindividual variability in CYP2D6 expression and activity.

Multidrug Resistance-Associated Protein 2 Deficiency Aggravates Estrogen-Induced Impairment of Bile Acid Metabolomics in Rats.

Multidrug resistance-associated protein 2 (Mrp2) mediates biliary secretion of anionic endobiotics and xenobiotics. Genetic alteration of Mrp2 leads to conjugated hyperbilirubinemia and predisposes to the development of intrahepatic cholestasis of pregnancy (ICP), characterized by increased plasma bile acids (BAs) due to mechanisms that are incompletely understood. Therefore, this study aimed to characterize BA metabolomics during experimental Mrp2 deficiency and ICP. ICP was modeled by ethinylestradiol (EE) administration to Mrp2-deficient (TR) rats and their wild-type (WT) controls. Spectra of BAs were analyzed in plasma, bile, and stool using an advanced liquid chromatography–mass spectrometry (LC–MS) method. Changes in BA-related genes and proteins were analyzed in the liver and intestine. Vehicle-administered TR rats demonstrated higher plasma BA concentrations consistent with reduced BA biliary secretion and increased BA efflux from hepatocytes to blood via upregulated multidrug resistance-associated protein 3 (Mrp3) and multidrug resistance-associated protein 4 (Mrp4) transporters. TR rats also showed a decrease in intestinal BA reabsorption due to reduced ileal sodium/bile acid cotransporter (Asbt) expression. Analysis of regulatory mechanisms indicated that activation of the hepatic constitutive androstane receptor (CAR)-Nuclear factor erythroid 2-related factor 2 (Nrf2) pathway by accumulating bilirubin may be responsible for changes in BA metabolomics in TR rats. Ethinylestradiol administration to TR rats further increased plasma BA concentrations as a result of reduced BA uptake and increased efflux via reduced Slco1a1 and upregulated Mrp4 transporters. These results demonstrate that Mrp2-deficient organism is more sensitive to estrogen-induced cholestasis. Inherited deficiency in Mrp2 is associated with activation of Mrp3 and Mrp4 proteins, which is further accentuated by increased estrogen. Bile acid monitoring is therefore highly desirable in pregnant women with conjugated hyperbilirubinemia for early detection of intrahepatic cholestasis.

Metformin impairs bile acid homeostasis in ethinylestradiol-induced cholestasis in mice

Metformin, an oral antidiabetic drug, recently demonstrated a reducing effect on bile acids (BA) plasma concentrations in one patient with intrahepatic cholestasis of pregnancy (ICP) by unknown mechanism. Therefore, the aim of the present study was to examine the effect of metformin on BA homeostasis and related molecular pathways in the liver and intestine using a mouse model of ICP. The cholestasis was induced in female C57BL/6 mice by repeated administration of ethinylestradiol (10 mg/kg BW s.c.) and/or metformin (150 mg/kg BW orally) over 5 consecutive days with subsequent bile collection and molecular analysis of samples. We demonstrated that metformin significantly increased the rate of bile secretion in control mice. This increase was BA dependent and was produced both by increased liver BA synthesis via induced cholesterol 7α-hydroxylase (Cyp7a1) and by increased BA reabsorption in the ileum via induction of the apical sodium-dependent BA transporter (Asbt). In contrast, metformin further worsened ethinylestradiol-induced impairment of bile secretion. This reduction was also BA dependent and corresponded with significant downregulation of Bsep, and Ntcp, major excretory and uptake transporters for BA in hepatocytes, respectively. The plasma concentrations of BA were consequently significantly increased in the metformin-treated mice. Altogether, our data indicate positive stimulation of bile secretion by metformin in the intact liver, but this drug also induces serious impairment of BA biliary secretion, with a marked increase in plasma concentrations in estrogen-induced cholestasis. Our results imply that metformin should be used with caution in situations with hormone-dependent cholestasis, such as ICP.

NASH-related increases in plasma bile acid levels depend on insulin resistance

Background & AimsPlasma bile acids (BAs) have been extensively studied as pathophysiological actors in non-alcoholic steatohepatitis (NASH). However, results from clinical studies are often complicated by the association of NASH with type 2 diabetes (T2D), obesity, and insulin resistance (IR). Here, we sought to dissect the relationship between NASH, T2D, and plasma BA levels in a large patient cohort.MethodsFour groups of patients from the Biological Atlas of Severe Obesity (ABOS) cohort (Clinical Trials number NCT01129297) were included based on the presence or absence of histologically evaluated NASH with or without coincident T2D. Patients were matched for BMI, homeostatic model assessment 2 (HOMA2)-assessed IR, glycated haemoglobin, age, and gender. To study the effect of IR and BMI on the association of plasma BA and NASH, patients from the HEPADIP study were included. In both cohorts, fasting plasma BA concentrations were measured.ResultsPlasma BA concentrations were higher in NASH compared with No-NASH patients both in T2D and NoT2D patients from the ABOS cohort. As we previously reported that plasma BA levels were unaltered in NASH patients of the HEPADIP cohort, we assessed the impact of BMI and IR on the association of NASH and BA on the combined BA datasets. Our results revealed that NASH-associated increases in plasma total cholic acid (CA) concentrations depend on the degree of HOMA2-assessed systemic IR, but not on β-cell function nor on BMI.ConclusionsPlasma BA concentrations are elevated only in those NASH patients exhibiting pronounced IR.Lay summaryNon-alcoholic steatohepatitis (NASH) is a progressive liver disease that frequently occurs in patients with obesity and type 2 diabetes. Reliable markers for the diagnosis of NASH are needed. Plasma bile acids have been proposed as NASH biomarkers. Herein, we found that plasma bile acids are only elevated in patients with NASH when significant insulin resistance is present, limiting their utility as NASH markers.

Analysis of bile acid profile in plasma to differentiate cholangiocarcinoma from benign biliary diseases and healthy controls

Bile acids (BAs) are currently considered as causative agents for Cholangiocarcinoma (CCA). However, the profile of circulating BAs in CCA have not been well characterized. The aim of this study was to describe the alterations of BAs metabolism in patients with CCA compared to benign biliary diseases (BBD) and healthy controls (HC), and to discover the specific BAs as biomarkers for CCA diagnosis. The concentrations of 15 BAs in plasma were measured in a total of 329 subjects, including patients with BBD, CCA, gallbladder cancer (GC), hepatocellular carcinoma (HCC), and healthy subjects, using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Binary logistic regression analysis was used to build a diagnostic model for CCA. An imbalance in the ratio of conjugated to unconjugated BAs was observed in CCA patients compared to BBD and HC groups, with higher conjugated BAs and lower unconjugated BAs. A panel of 2 BA metabolites consisting of CDCA and TCDCA showed high diagnostic performance for CCA versus BBD and CCA versus HC, with higher AUC, sensitivity and specificity than carbohydrate antigen 19−9 (CA 199), clinically employed CCA biomarker. Importantly, HCC and GC samples were also included to confirm specificity of the BA biomarkers for CCA diagnosis. In summary, specific changes in plasma concentrations of BAs may serve as diagnostic biomarkers for distinguishing CCA from BBD and HC, with higher performance than CA199.

Spontaneous liver disease in wild-type C57BL/6JOlaHsd mice fed semisynthetic diet.

Mouse models are frequently used to study mechanisms of human diseases. Recently, we observed a spontaneous bimodal variation in liver weight in C57BL/6JOlaHsd mice fed a semisynthetic diet. We now characterized the spontaneous variation in liver weight and its relationship with parameters of hepatic lipid and bile acid (BA) metabolism. In male C57BL/6JOlaHsd mice fed AIN-93G from birth to postnatal day (PN)70, we measured plasma BA, lipids, Very low-density lipoprotein (VLDL)-triglyceride (TG) secretion, and hepatic mRNA expression patterns. Mice were sacrificed at PN21, PN42, PN63 and PN70. Liver weight distribution was bimodal at PN70. Mice could be subdivided into two nonoverlapping groups based on liver weight: 0.6 SD 0.1 g (approximately one-third of mice, small liver; SL), and 1.0 SD 0.1 g (normal liver; NL; p<0.05). Liver histology showed a higher steatosis grade, inflammation score, more mitotic figures and more fibrosis in the SL versus the NL group. Plasma BA concentration was 14-fold higher in SL (p<0.001). VLDL-TG secretion rate was lower in SL mice, both absolutely (-66%, p<0.001) and upon correction for liver weight (-44%, p<0.001). Mice that would later have the SL-phenotype showed lower food efficiency ratios during PN21-28, suggesting the cause of the SL phenotype is present at weaning (PN21). Our data show that approximately one-third of C57BL/6JOlaHsd mice fed semisynthetic diet develop spontaneous liver disease with aberrant histology and parameters of hepatic lipid, bile acid and lipoprotein metabolism. Study designs involving this mouse strain on semisynthetic diets need to take the SL phenotype into account. Plasma lipids may serve as markers for the identification of the SL phenotype.

Effect of a Flaxseed Lignan Intervention on Circulating Bile Acids in a Placebo-Controlled Randomized, Crossover Trial.

Plant lignans and their microbial metabolites, e.g., enterolactone (ENL), may affect bile acid (BA) metabolism through interaction with hepatic receptors. We evaluated the effects of a flaxseed lignan extract (50 mg/day secoisolariciresinol diglucoside) compared to a placebo for 60 days each on plasma BA concentrations in 46 healthy men and women (20–45 years) using samples from a completed randomized, crossover intervention. Twenty BA species were measured in fasting plasma using LC-MS. ENL was measured in 24-h urines by GC-MS. We tested for (a) effects of the intervention on BA concentrations overall and stratified by ENL excretion; and (b) cross-sectional associations between plasma BA and ENL. We also explored the overlap in bacterial metabolism at the genus level and conducted in vitro anaerobic incubations of stool with lignan substrate to identify genes that are enriched in response to lignan metabolism. There were no intervention effects, overall or stratified by ENL at FDR < 0.05. In the cross-sectional analysis, irrespective of treatment, five secondary BAs were associated with ENL excretion (FDR < 0.05). In vitro analyses showed positive associations between ENL production and bacterial gene expression of the bile acid-inducible gene cluster and hydroxysteroid dehydrogenases. These data suggest overlap in community bacterial metabolism of secondary BA and ENL.

Effect of a Flaxseed Lignan Intervention on Circulating Bile Acids in a Randomized, Crossover Trial

Abstract Objectives Health benefits of high-fiber foods may be attributed, in part, to microbial metabolites of plant compounds. Lignans and their microbial metabolites, the enterolignans [enterolactone (ENL) and enterodiol (END)], reduce serum lipids through a variety of mechanisms, including regulation of bile acid (BA) synthesis. BA, released into the gut lumen in response to dietary fat, undergo microbial metabolism to secondary (2°) BA, which have been positively associated with chronic disease, e.g., liver disease and colorectal cancer. Our aims were to evaluate the effects of a flaxseed lignan supplement on circulating BA and examine associations between enterolignans and 2° BA. Methods We conducted a randomized, crossover trial of a flaxseed lignan supplement (50 mg/d secoisolariciresinol diglucoside) compared to placebo in 46 healthy men and women (20-45 y). Each period lasted 60 days, separated by a 60-day washout period. Six primary and fourteen 2° BA species were measured in fasting plasma using LC-MS. ENL and END were measured in 24-h urines by GC-MS. Low- and high-ENL excreters were defined as below and above the median 24-h ENL excretion at the end of the flaxseed lignan intervention (23.4 µmol/24 h). Linear mixed models were used to a) test the effects of the intervention on individual BA concentrations, overall and stratified by low and high ENL excreters; and b) to cross-sectionally determine the association between plasma 2o BA and ENL and END. Results There was no significant effect of the flaxseed lignan intervention compared to placebo on BA concentrations overall, or by ENL-excreter status, after FDR adjustment. In the cross-sectional analysis, irrespective of treatment, six 2° BA were statistically significantly associated with ENL (FDR &amp;lt; 0.05), with two positive associations (isolithocholic and lithocholic acids), and four inverse associations (glycoursodeoxycholic, glycohyodeoxycholic, hyodeoxycholic, and muricholic acids). Conclusions The flaxseed lignan intervention and subsequent ENL production had no effect on plasma BA concentrations. However, the strong associations between ENL excretion and certain 2° BA concentrations suggests that the gut microbial communities capable of producing ENL may also play a role in 2° BA metabolism. Funding Sources NIH.

Model-based data analysis of individual human postprandial plasma bile acid responses indicates a major role for the gallbladder and intestine.

BackgroundBile acids are multifaceted metabolic compounds that signal to cholesterol, glucose, and lipid homeostasis via receptors like the Farnesoid X Receptor (FXR) and transmembrane Takeda G protein‐coupled receptor 5 (TGR5). The postprandial increase in plasma bile acid concentrations is therefore a potential metabolic signal. However, this postprandial response has a high interindividual variability. Such variability may affect bile acid receptor activation.MethodsIn this study, we analyzed the inter‐ and intraindividual variability of fasting and postprandial bile acid concentrations during three identical meals on separate days in eight healthy lean male subjects using a statistical and mathematical approach.Main findingsThe postprandial bile acid responses exhibited large interindividual and intraindividual variability. The individual mathematical models, which represent the enterohepatic circulation of bile acids in each subject, suggest that interindividual variability results from quantitative and qualitative differences of distal active uptake, colon transit, and microbial bile acid transformation. Conversely, intraindividual variations in gallbladder kinetics can explain intraindividual differences in the postprandial responses.ConclusionsWe conclude that there is considerable inter‐ and intraindividual variation in postprandial plasma bile acid levels. The presented personalized approach is a promising tool to identify unique characteristics of underlying physiological processes and can be applied to investigate bile acid metabolism in pathophysiological conditions.

Effects of Nicotinamide Riboside on Endocrine Pancreatic Function and Incretin Hormones in Nondiabetic Men With Obesity.

Augmenting nicotinamide adenine dinucleotide (NAD+) metabolism through dietary provision of NAD+ precursor vitamins translates to improved glucose handling in rodent models of obesity and diabetes. Preclinical evidence suggests that the NAD+/SIRT1 axis may be implicated in modulating important gut-related aspects of glucose regulation. We sought to test whether NAD+ precursor supplementation with nicotinamide riboside (NR) affects β-cell function, α-cell function, and incretin hormone secretion as well as circulating bile acid levels in humans. A 12-week randomized, double-blind, placebo-controlled, parallel-group trial in 40 males with obesity and insulin resistance allocated to NR at 1000 mg twice daily (n = 20) or placebo (n = 20). Two-hour 75-g oral glucose tolerance tests were performed before and after the intervention, and plasma concentrations of glucose, insulin, C-peptide, glucagon, glucagon-like peptide 1 (GLP-1), and glucose-dependent insulinotropic polypeptide (GIP) were determined. β-Cell function indices were calculated based on glucose, insulin, and C-peptide measurements. Fasting plasma concentrations of bile acids were determined. NR supplementation during 12 weeks did not affect fasting or postglucose challenge concentrations of glucose, insulin, C-peptide, glucagon, GLP-1, or GIP, and β-cell function did not respond to the intervention. Additionally, no changes in circulating adipsin or bile acids were observed following NR supplementation. The current study does not provide evidence to support that dietary supplementation with the NAD+ precursor NR serves to impact glucose tolerance, β-cell secretory capacity, α-cell function, and incretin hormone secretion in nondiabetic males with obesity. Moreover, bile acid levels in plasma did not change in response to NR supplementation.

High soluble endoglin levels regulate cholesterol homeostasis and bile acids turnover in the liver of transgenic mice

AimsIncreased plasma soluble endoglin concentrations (sEng) are frequently detected in metabolic disorders accompanied with hypercholesterolemia in serum, but effect of sEng on the cholesterol biochemistry is unknown. Cholesterol and bile acids (BA) are important products of liver metabolism with numerous functions within the organism. Turnover of these substances requires precise regulation due to potential toxicities during their cumulation. In this study, we hypothesized that high sEng levels affect cholesterol homeostasis and BA turnover in mice liver. Main methodsNine-month-old transgenic male mice overexpressing human sEng and wild-type mice underwent plasma, bile, stool, and organ samples analysis by analytical, qRT-PCT and Western blot methods. Key findingssEng mice demonstrated decreased plasma total and LDL cholesterol concentrations due to upregulation of hepatic Sr-b1 and Ldlr receptors, increased liver cholesterol content, and increased Abcg8-mediated cholesterol efflux into bile. sEng also increased conversion of cholesterol into bile acids (BA) via upregulation of Cyp7a1 and increased Mdr1 expression. Plasma concentrations of BA were increased in sEng mice due to their enhanced reabsorption via ileum. Increased hepatic disposition of BA led to their increased biliary excretion coupled with choleretic activity. SignificanceFor the first time, we have shown that high sEng plasma levels affect cholesterol and BA homeostasis on the basis of complex liver and intestinal effects. The significance of these findings for pathophysiology of diseases associated with increased sEng concentrations remains to be elucidated in prospective studies.

Serum Bile Acid Levels Before and After Sleeve Gastrectomy and Their Correlation with Obesity-Related Comorbidities

The rising prevalence of morbid obesity is increasing the demand for bariatric surgery. The benefits observed after bariatric surgery seems to be not fully explained by surgery-induced weight loss or traditional cardiovascular risk factors regression or improvement. Some evidences suggest that bile acid (BA) levels change after bariatric surgery, thus suggesting that BA concentrations could influence some of the metabolic improvement induced by bariatric surgery. In this report, we have characterized circulating BA patterns and compared them to metabolic and vascular parameters before and after sleeve gastrectomy (SG). Seventy-nine subjects (27 males, 52 females, aged 45 ± 12years, mean BMI 45 ± 7kg/m2) SG candidates were included in the study. Before and about 12months after SG, all subjects underwent a clinical examination, blood tests (including lipid profile, plasma glucose and insulin, both used for calculating HOMA-IR, and glycated hemoglobin), ultrasound visceral fat area estimation, ultrasound flow-mediated dilation evaluation, and determination of plasma BA concentrations. Before SG, both primary and secondary BA levels were higher in insulin-resistant obese subjects than in non-insulin resistant obese, and BA were positively associated with the markers of insulin-resistance. After SG, total (conjugated and unconjugated) cholic acids significantly decreased (p 0.007), and total lithocholic acids significantly increased (p 0.017). SG-induced total cholic and chenodeoxycholic acid changes were directly associated with surgery-induced glycemia (p 0.011 and 0.033 respectively) and HOMA-IR (p 0.016 and 0.012 respectively) changes. Serum BA are associated with glucose metabolism and particularly with markers of insulin-resistance. SG modifies circulating BA pool size and composition. SG-induced BA changes are associated with insulin-resistance amelioration. In conclusion, an interplay between glucose metabolism and circulating BA exists but further studies are needed.

Impaired Hepatic Phosphatidylcholine Synthesis Leads to Cholestasis in Mice Challenged With a High-Fat Diet.

Phosphatidylethanolamine N‐methyltransferase (PEMT) is a hepatic integral membrane protein localized to the endoplasmic reticulum (ER). PEMT catalyzes approximately 30% of hepatic phosphatidylcholine (PC) biosynthesis. Pemt–/– mice fed a high‐fat diet (HFD) develop steatohepatitis. Interestingly, portions of the ER located close to the canaliculus are enriched in PEMT. Phospholipid balance and asymmetrical distribution by adenosine triphosphatase phospholipid transporting 8B1 (ATP8B1) on the canalicular membrane is required for membrane integrity and biliary processes. We hypothesized that PEMT is an important supplier of PC to the canaliculus and that PEMT activity is critical for the maintenance of canalicular membrane integrity and bile formation following HFD feeding when there is an increase in overall hepatic PC demand. Pemt+/+ and Pemt–/– mice were fed a chow diet, an HFD, or a choline‐supplemented HFD. Plasma and hepatic indices of liver function and parameters of bile formation were determined. Pemt–/– mice developed cholestasis, i.e, elevated plasma bile acid (BA) concentrations and decreased biliary secretion rates of BAs and PC, during HFD feeding. The maximal BA secretory rate was reduced more than 70% in HFD‐fed Pemt–/– mice. Hepatic ABCB11/bile salt export protein, responsible for BA secretion, was decreased in Pemt–/– mice and appeared to be retained intracellularly. Canalicular membranes of HFD‐fed Pemt–/– mice contained fewer invaginations and displayed a smaller surface area than Pemt+/+ mice. Choline supplementation (CS) prevented and reversed the development of HFD‐induced cholestasis. Conclusion: We propose that hepatic PC availability is critical for bile formation. Dietary CS might be a potential noninvasive therapy for a specific subset of patients with cholestasis.

Plasma stearoyl-CoA desaturase activity indices and bile acid concentrations after a low-fat meal: association with a genetic variant in the FTO gene.

PurposeDietary macronutrient composition, stearoyl-CoA desaturase (SCD) activity indices, and primary bile acid (BA) concentrations are among the factors that have been associated with lipid metabolism and contributed to obesity. We investigated the association between the polymorphic expression of the fat mass and obesity-associated (FTO) gene and its relationship with SCD activity indices and primary BA concentrations after a low-fat meal.Subjects and methodsBlood plasma samples were collected from 56 young (20–36 years) healthy subjects with different rs9939609 FTO genotypes. Fasting and post-meal (2 hours after a low-fat breakfast) blood samples were collected on the subsequent morning for the analysis of DNA methylation, SCD activity indices (product-to-precursor fatty acid ratios; 16:1n-7/16:0 and 18:1n-9/18:0), and chenodeoxycholic acid (CDCA) and cholic acid (CA) concentrations. Expression of lipogenic genes was investigated post-meal to assess the relationship between the CDCA and CA concentrations and mRNA levels of lipogenic genes.ResultsThe FTO AA (obesity risk) genotype group (n=18) had higher (P<0.05) post-meal SCD-16 activity index than the FTO TT (wild type) genotype group (n=26). In both the FTO TT (n=16) and AA (n=8) genotype groups, the post-meal concentrations of CDCA and CA were lower (P<0.05) compared with the fasted state. No difference in BA concentrations between the FTO TT and AA genotype groups in both meal states was observed. After adjusting for the body mass index, the highest 50% post-meal concentrations of CA were inversely (P=0.010) correlated with the level of mRNA SCD expression.ConclusionFTO AA carriers may be at a higher risk for obesity through higher SCD activity in a low-fat diet environment. This effect may be partly pronounced by very low CA concentrations.

Plasma bile acid changes in type 2 diabetes correlated with insulin secretion in two-step hyperglycemic clamp.

Bile acids (BAs) conduct crucial signals in human metabolism. Correlations between changes in plasma BA concentrations, insulin secretion defects, and progression of type 2 diabetes mellitus (T2DM) in humans have not been sufficiently investigated. This study explored the trajectories of changes in human plasma BA concentrations and their association with insulin secretion dynamics during a two-step hyperglycemic clamp. Eleven healthy subjects with normal glucose tolerance (NGT) and 33 drug-naïve T2DM subjects were enrolled in the study. The two-step hyperglycemic clamp consisted of a classic clamp as Step 1 with fasting, followed by a Step 2 clamp after ingestion of a carbohydrate meal, illustrating basal and incretin-amplified insulin responses to glucose. Plasma BA were assayed using liquid chromatography-tandem mass spectrometry. Nine T2DM subjects were followed-up, and the two-step clamp was repeated after 3 months sulfonylurea treatment. Ursodeoxycholic acid (UDCA) was lower and lithocholic acid (LCA) and taurocholic acid (TCA) were higher in T2DM compared with NGT subjects. The dynamics of plasma UDCA concentrations and the UDCA/LCA ratio was positively correlated with insulin secretion in T2DM subjects and were corrected after treatment. Moreover, fasting ratios of UDCA/LCA and unconjugated/conjugated BAs were correlated with the first phase of insulin secretion in T2DM subjects. The abnormal BA composition in T2DM subjects and its correlation with insulin secretion during the clamp suggest an interaction between BA signals and insulin secretion capacity, and the potential to use fasting plasma BA composition indices to predict and evaluate the progression and prognosis of T2DM.

Circulating bile acids in healthy adults respond differently to a dietary pattern characterized by whole grains, legumes and fruits and vegetables compared to a diet high in refined grains and added sugars: A randomized, controlled, crossover feeding study

ObjectiveThe effects of diets high in refined grains on biliary and colonic bile acids have been investigated extensively. However, the effects of diets high in whole versus refined grains on circulating bile acids, which can influence glucose homeostasis and inflammation through activation of farnesoid X receptor (FXR) and G protein-coupled bile acid receptor 1 (TGR5), have not been studied. Materials and MethodsWe conducted a secondary analysis from a randomized controlled crossover feeding trial (NCT00622661) in 80 healthy adults (40 women/40 men, age 18–45 years) from the greater Seattle Area, half of which were normal weight (BMI 18.5–25.0 kg/m2) and half overweight to obese (BMI 28.0–39.9 kg/m2). Participants consumed two four-week controlled diets in randomized order: 1) a whole grain diet (WG diet), designed to be low in glycemic load (GL), high in whole grains, legumes, and fruits and vegetables, and 2) a refined grain diet (RG diet), designed to be high GL, high in refined grains and added sugars, separated by a four-week washout period. Quantitative targeted analysis of 55 bile acid species in fasting plasma was performed using liquid chromatography tandem mass spectrometry. Concentrations of glucose, insulin, and CRP were measured in fasting serum. Linear mixed models were used to test the effects of diet on bile acid concentrations, and determine the association between plasma bile acid concentrations and HOMA-IR and CRP. Benjamini-Hochberg false discovery rate (FDR) < 0.05 was used to control for multiple testing. ResultsA total of 29 plasma bile acids were reliably detected and retained for analysis. Taurolithocholic acid (TLCA), taurocholic acid (TCA) and glycocholic acid (GCA) were statistically significantly higher after the WG compared to the RG diet (FDR < 0.05). There were no significant differences by BMI or sex. When evaluating the association of bile acids and HOMA-IR, GCA, taurochenodeoxycholic acid, ursodeoxycholic acid (UDCA), 5β‑cholanic acid‑3β,12α‑diol, 5‑cholanic acid‑3β‑ol, and glycodeoxycholic acid (GDCA) were statistically significantly positively associated with HOMA-IR individually, and as a group, total, 12α‑hydroxylated, primary and secondary bile acids were also significant (FDR < 0.05). When stratifying by BMI, chenodeoxycholic acid (CDCA), cholic acid (CA), UDCA, 5β-cholanic acid-3β, deoxycholic acid, and total, 12α-hydroxylated, primary and secondary bile acid groups were significantly positively associated with HOMA-IR among overweight to obese individuals (FDR < 0.05). When stratifying by sex, GCA, CDCA, TCA, CA, UDCA, GDCA, glycolithocholic acid (GLCA), total, primary, 12α‑hydroxylated, and glycine-conjugated bile acids were significantly associated with HOMA-IR among women, and CDCA, GDCA, and GLCA were significantly associated among men (FDR < 0.05). There were no significant associations between bile acids and CRP. ConclusionsDiets with comparable macronutrient and energy composition, but differing in carbohydrate source, affected fasting plasma bile acids differently. Specifically, a diet characterized by whole grains, legumes, and fruits and vegetables compared to a diet high in refined grains and added sugars led to modest increases in concentrations of TLCA, TCA and GCA, ligands for FXR and TGR5, which may have beneficial effects on glucose homeostasis.

Combination of lysosphingomyelin, 7-ketocholesterol and bile acid W for diagnosis of Japanese patients with Niemann Pick disease type C by MS/MS

Neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD) is characterized by conjugated hyperbilirubinemia and increased plasma bile acid concentrations. However, the underlying mechanisms remain unclear. We established a liquid chromatography tandem mass spectrometry (LC-MS/MS) method for simultaneously quantifying plasma bile acids and examined bile acid profiles in NICCD infants.We measured 15 bile acids within 15 min and found a wide linear range for individual bile acids.The within-run and run-to-run CV of all bile acids was 1.2–10.9% and 3.1–10.8%, respectively, with a mean recovery of 90.5–112.6%. Compared to infants with citrullinemia without mutations in SLC25A13 (non-NICCD), NICCD infants showed increased plasma total bile acid concentrations (mean: 201 vs. 42 μM, p < 0.001), with a distinct bile acid profile characterized by increased conjugated primary bile acid concentrations. The calculated ratios, including primary/secondary bile acid (714 vs. 235, p < 0.05) and conjugated/free bile acid (371 vs. 125, p < 0.05) ratios, were higher in NICCD infants. The area under receiver operating characteristic curve for conjugated/free bile acid ratio to identify infants with NICCD was 0.871 (95% confidence interval, 0.713–1.0).Together, our findings indicated plasma bile acid profile as a potential noninvasive diagnostic biomarker for NICCD.