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

Abstract

Background & aims: Plasma 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.

Methods: Four 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.

Results: Plasma 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.

Conclusions: Plasma BA concentrations are elevated only in those NASH patients exhibiting pronounced IR.

Lay summary: Non-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.

Keywords: ABOS, Biological Atlas of Severe Obesity; ADA, American Diabetes Association; BA, bile acids; Bile acids; C4, 7alpha-hydroxy-4-cholesten-3-one; CA, cholic acid; CDCA, chenodeoxycholic acid; DCA, deoxycholic acid; Diabetes; FPG, fasting plasma glycaemia; FXR, farnesoid-X-receptor; GCA, glycocholic acid; GCDCA, glycochenodeoxycholic acid; GDCA, glycodeoxycholic acid; GHCA, glycohyocholic acid; GHDCA, glycohyodeoxycholic acid; GLCA, glycolithocholic acid; GUDCA, glycoursodeoxycholic acid; HCA, hyocholic acid; HDCA, hyodeoxycholic acid; HOMA2, homeostatic model assessment 2; HbA1c, glycated haemoglobin; IR, insulin resistance; Insulin resistance; LCA, lithocholic acid; MAFLD, metabolic associated fatty liver disease; NAFL, non-alcoholic fatty liver; NAFLD; NAFLD, non-alcoholic fatty liver disease; NASH; NASH, non-alcoholic steatohepatitis; OGTT, oral glucose tolerance test; Obesity; T2D, type 2 diabetes; TCA, taurocholic acid; TCDCA, taurochenodeoxycholic acid; TDCA, taurodeoxycholic acid; THCA, taurohyocholic acid; THDCA, taurohyodeoxycholic acid; TLCA, taurolithocholic acid; TUDCA, tauroursodeoxycholic acid; Translational study; UDCA, ursodeoxycholic acid.

Graphical abstract

Fig. 1

Plasma BA concentrations are higher in NASH vs. No-NASH irrespective of T2D status in the ABOS study cohort (n = 219). (A) Plasma total (free + conjugated) BA and C4 concentrations (log-scale, nmol/L) according to NASH status (grey, No-NASH; purple, NASH). (B) Plasma total (free + conjugated) BA and C4 concentrations (log-scale, nmol/L) according to T2D status (left, No-T2D; right, T2D) and NASH status (grey, No-NASH; purple, NASH). Data are expressed as mean and SEM (standard error of mean). p values from the non-parametric Mann-Whitney U test. To compare No-NASH and NASH groups: ∗p <0.05, ∗∗p <0.01, ∗∗∗p <0.001. To compare No-T2D and T2D groups: ^$p <0.05. ABOS, Biological Atlas of Severe Obesity; BAs, bile acids; C4, 7alpha-hydroxy-4-cholesten-3-one; CA, cholic acid; CDCA, chenodeoxycholic acid; DCA, deoxycholic acid; HCA, hyocholic acid; HDCA, hyodeoxycholic acid; LCA, lithocholic acid; NASH, non-alcoholic steatohepatitis; T2D, type 2 diabetes; UDCA, ursodeoxycholic acid.

Fig. 2

Plasma BA concentrations are mainly associated with NASH and not with glucose homeostasis parameters in patients of the ABOS study cohort. Unadjusted Spearman correlations between plasma BA concentrations and BMI, glucose homeostasis parameters and NASH parameters in the ABOS study cohort (n = 219). Colours and area of circles reflect the Spearman rho values (red for positive, blue for inverse correlations). Only rho values with significant p value (p <0.05) were represented. BA species, ratios and total values were determined according to Table S1. ABOS, Biological Atlas of Severe Obesity; BA, bile acid; C4, 7alpha-hydroxy-4-cholesten-3-one; CA, cholic acid; CDCA, chenodeoxycholic acid; DCA, deoxycholic acid; GCA, glycocholic acid; GCDCA, glycochenodeoxycholic acid; GDCA, glycodeoxycholic acid; GHCA, glycohyocholic acid; GHDCA, glycohyodeoxycholic acid; GLCA, glycolithocholic acid; GUDCA, glycoursodeoxycholic acid; HCA, hyocholic acid; HDCA, hyodeoxycholic acid; HOMA, Homeostatic Model Assessment; LCA, lithocholic acid; NASH, non-alcoholic steatohepatitis; OGTT, oral glucose tolerance test; T2D, type 2 diabetes; TCA, taurocholic acid; TCDCA, taurochenodeoxycholic acid; TDCA, taurodeoxycholic acid; THCA, taurohyocholic acid; THDCA, taurohyodeoxycholic acid; TLCA, taurolithocholic acid; TUDCA, tauroursodeoxycholic acid; UDCA, ursodeoxycholic acid.

Fig. 3

Identification of specific BA discriminating NASH independently of type 2 diabetes (T2D) in the ABOS study cohort (n = 219). (A) Variable importance plot of the Random Forest analysis. The variables are ordered top-to-bottom as most-to-least important in classifying between No-NASH and NASH groups. (B–G) Plasma BA concentrations (log-scale, nmol/L) according to T2D status (B, D, F) and NASH status (C, E, G). Data are expressed as median and IQR. p values were from the non-parametric Mann-Whitney U test. ABOS, Biological Atlas of Severe Obesity; BA, bile acids; CA, cholic acid; CDCA, chenodeoxycholic acid; DCA, deoxycholic acid; GCA, glycocholic acid; GCDCA, glycochenodeoxycholic acid; GUDCA, glycoursodeoxycholic acid; HCA, hyocholic acid; NASH, non-alcoholic steatohepatitis; T2D, type 2 diabetes; TCA, taurocholic acid; THCA, taurohyocholic acid; UCDA, ursodeoxycholic acid.

Fig. 4

Insulin sensitivity modulates the NASH-associated increase in plasma BA in the combined cohort (n = 239). (A) Plasma total CA concentrations (nmol/L) according to HOMA2S (%). (B) Plasma total CA concentrations (nmol/L) according to HOMA2B (%). White circles represent the No-NASH and black circles the NASH patients. Dashed lines: regression curves for No-NASH patients; solid lines: regression curves for NASH patients. Rho coefficients and p values were obtained using the Spearman Rank test. BA, bile acids; CA, cholic acid; HOMA, homeostatic model assessment; NASH, non-alcoholic steatohepatitis.

Fig. 5

The impact of NASH on plasma BA concentrations depends on the degree of IR. In patients with mild IR, NASH does not affect plasma BA which are driven by metabolic homeostasis. In contrast, in patients with severe IR, NASH is associated with increased plasma BA. BA, bile acid; IR, insulin resistance; NASH, non-alcoholic steatohepatitis.