Mitochondrial dysfunction as a mechanistic biomarker in patients with non-alcoholic fatty liver disease (NAFLD)

Background: Dysfunctional metabolism lies at the centre of the pathogenesis for Non-Alcoholic Fatty Liver Disease (NAFLD) and involves mitochondrial dysfunction, lipid dysmetabolism and oxidative stress. This study, for the first time, explores real-time energy changes in peripheral blood and corresponding metabolite changes, to investigate whether mitochondria-related immunometabolic biomarkers can predict progression in NAFLD. Methods: Thirty subjects divided into 3 groups were assessed: NAFLD with biopsy-proven mild fibrosis (n = 10), severe fibrosis (n = 10) and healthy controls (HC, n = 10). Mitochondrial functional analysis was performed in a Seahorse XFp analyzer in live peripheral blood mononuclear cells (PBMCs). Global metabolomics quantified a broad range of human plasma metabolites. Mitochondrial carbamoyl phosphate synthase 1(CPS-1), Ornithine transcarbamoylase (OTC), Fibroblast growth factor-21 (FGF-21) and a range of cytokines in plasma were measured by ELISA. Results: NAFLD patients with severe fibrosis demonstrated reduced maximal respiration (106 +/- 25 versus 242 +/- 62, p < 0.05) and reserve capacity (56 +/- 16 versus 184 +/- 42, p = 0.006) compared to mild/moderate fibrosis. Comparing mild/ moderate vs severe liver fibrosis in patients with NAFLD, 14 out of 493 quantified metabolites were significantly changed (p < 0.05). Most of the amino acids modulated were the urea cycle (UC) components which included citrulline/ornithine ratio, arginine and glutamate. Plasma levels of CPS-1 and FGF-21 were significantly higher mild versus severe fibrosis in NAFLD patients. This novel panel generated an area under the ROC of 0.95, sensitivity of 100% and specificity 80% and p = 0.0007 (F1-F2 versus F3-F4). Conclusion: Progression in NAFLD is associated with mitochondrial dysfunction and changes in metabolites associated with the urea cycle. We demonstrate a unique panel of mitochondrial-based, signatures which differentiate between stages of NAFLD. Lay summary: Mitochondrial dysfunction in peripheral cells along with alterations in metabolites of urea cycle act as a sensor of hepatocyte mitochondrial damage. These changes can be measured in blood and together represent a unique panel of biomarkers for progression of fibrosis in NAFLD.

Automated summary

This study demonstrates for the first time the association of NAFLD progression with mitochondrial dysfunction and changes in metabolites related to the urea cycle. A unique panel of mitochondrial-based signatures was identified to differentiate between stages of NAFLD progression.