Altered Bile Acid Metabolome in Patients with Nonalcoholic Steatohepatitis

Abstract

Background and aims: The prevalence of nonalcoholic fatty liver disease (NAFLD) and steatohepatitis (NASH) is increasing at an alarming rate. The role of bile acids in the development and progression of NAFLD to NASH and cirrhosis is poorly understood. This study aimed to quantify the bile acid metabolome in healthy subjects and patients with non-cirrhotic NASH under fasting conditions and after a standardized meal.

Methods: Liquid chromatography tandem mass spectroscopy was used to quantify 30 serum and 16 urinary bile acids from 15 healthy volunteers and 7 patients with biopsy-confirmed NASH. Bile acid concentrations were measured at two fasting and four post-prandial time points following a high-fat meal to induce gallbladder contraction and bile acid reabsorption from the intestine.

Results: Patients with NASH had significantly higher total serum bile acid concentrations than healthy subjects under fasting conditions (2.2- to 2.4-fold increase in NASH; NASH 2595-3549 µM and healthy 1171-1458 µM) and at all post-prandial time points (1.7- to 2.2-fold increase in NASH; NASH 4444-5898 µM and healthy 2634-2829 µM). These changes were driven by increased taurine- and glycine-conjugated primary and secondary bile acids. Patients with NASH exhibited greater variability in their fasting and post-prandial bile acid profile.

Conclusions: Results indicate that patients with NASH have higher fasting and post-prandial exposure to bile acids, including the more hydrophobic and cytotoxic secondary species. Increased bile acid exposure may be involved in liver injury and the pathogenesis of NAFLD and NASH.

Keywords: Bile acid metabolome; Bile acids; Enterohepatic recirculation; Nonalcoholic steatohepatitis.

Conflict of interest statement

Conflict of Interest: The authors have no conflict of interest to disclose.

Figures

Figure 1

Serum bile acid concentrations at screening and on study day by conjugation status in healthy subjects (grey, n=15) and patients with NASH (black, n=7). Total bile acid concentrations represent the molar sum of unconjugated, glycine-, taurine and sulfate-conjugated bile acids. Data are presented as mean (nM) and standard error of the mean. *p

Figure 2

Serum bile acid species at screening and on study day depicted as concentration vs. time profiles in healthy subjects (grey circles, n=15) and patients with NASH (black squares, n=7). Post-prandial exposure calculated as the area under the serum concentration-time profile from 0–120 min (AUCpp) is reported. Data are presented as mean (nM or μM×min) and standard error of the mean. *p<0.05 NASH vs. Healthy

Figure 3

Serum total unconjugated (left) and glycine and taurine-conjugated (right) LCA bile acid species in healthy subjects (grey circles, n=15) and patients with NASH (black squares, n=7). Post-prandial exposure calculated as the area under the serum concentration-time profile from 0–120 min (AUCpp) is reported. Data are presented as mean (nM or μM×min) and standard error of the mean.

Figure 4

Relative abundance of bile acids in healthy subjects (grey, n=15) and patients with NASH (black, n=7) as a percentage of total serum bile acid concentrations. Data are presented as mean (%) and standard error of the mean.

Figure 5

Urinary excretion of bile acid species in healthy subjects (grey, n=13) and patients with NASH (black, n=7). Data are presented as mean (nmoles) and standard error of the mean.

Figure 6

Scores plots of the OPLS-DA models of bile acid profiles at each sample time in patients with NASH (black diamonds) compared to healthy subjects (grey circles) under fasting conditions (screening and pre-prandial) and following a high fat meal (30, 60, 90 and 120 min post-prandial).