The non-invasive (13)C-methionine breath test detects hepatic mitochondrial dysfunction as a marker of disease activity in non-alcoholic steatohepatitis

Abstract

Introduction: Mitochondrial dysfunction plays a central role in the general pathogenesis of non-alcoholic fatty liver disease (NAFLD), increasing the risk of developing steatosis and subsequent hepatocellular inflammation. We aimed to assess hepatic mitochondrial function by a non-invasive (13)C-methionine breath test (MeBT) in patients with histologically proven NAFLD.

Methods: 118 NAFLD-patients and 18 healthy controls were examined by MeBT. Liver biopsy specimens were evaluated according to the NASH scoring system.

Results: Higher grades of NASH activity and fibrosis were independently associated with a significant decrease in cumulative (13)C-exhalation (expressed as cPDR(%)). cPDR (1.5h) was markedly declined in patients with NASH and NASH cirrhosis compared to patients with simple steatosis or borderline diagnosis (cPDR1.5h: 3.24 ± 1.12% and 1.32 ± 0.94% vs. 6.36 ± 0.56% and 4.80 ± 0.88% respectively; p<0.001). (13)C-exhalation further declined in the presence of advanced fibrosis which was correlated with NASH activity (r = 0.36). The area under the ROC curve (AUROC) for NASH diagnosis was estimated to be 0.87 in the total cohort and 0.83 in patients with no or mild fibrosis (F0-1).

Conclusion: The (13)C-methionine breath test indicates mitochondrial dysfunction in non-alcoholic fatty liver disease and predicts higher stages of disease activity. It may, therefore, be a valuable diagnostic addition for longitudinal monitoring of hepatic (mitochondrial) function in non-alcoholic fatty liver disease.

Figure 1

Cumulative ¹³C-exhalation after 1.5 h test time (cPDR1.5h) in118 patients with non-alcoholic fatty liver disease (NAFL) according to different histological stages (simple steatosis, borderline diagnosis, definite NASH, and NASH cirrhosis) and 18 lean controls. p < 0.001 for definite NASH and NASH cirrhosis vs. lean controls, simple steatosis and borderline diagnosis by Kruskal-Wallis ANO VA and Dunn's post hoc tests.

Figure 2

Cumulative ¹³C-exhalation after 1.5 h test time (cPDR_1.5h) in 99 patients with borderline diagnosis or definite NASH stratified for the presence of advanced (F2-3) fibrosis and 7 patients with complete cirrhotic conversion. p < 0.001 for F0-1 vs. F2-3 in each group and for F0-1 vs. cirrhosis; p < 0.05 for F0-1 with borderline diagnosis vs. F0-1 with definite NASH p = n.s. for F2-3 vs. cirrhosis by Kruskal-Wallis ANOVA and Dunn's post hoc tests.

Figure 3

ROC curves for ¹³C-methionine breath test outcome parameter cumulative percentage recovery after 90 min test time (cPDR_1.5h) in patients with non-alcoholic fatty liver (NAFL). A: for differentiation of non-NASH (steatosis and borderline-diagnosis) from NASH in the total cohort (solid line) and a subgroup of patients (n = 92) with mild (F0-1) fibrosis (dashed line). B: for differentiation of non-significant (F0-1) from advanced (F2-3) fibrosis in 99 patients with borderline diagnosis or definite NASH.