Metabolic role of the hepatic valine/3-hydroxyisobutyrate (3-HIB) pathway in fatty liver diseaseResearch in context
Mona Synnøve Bjune,
Laurence Lawrence-Archer,
Johnny Laupsa-Borge,
Cathrine Horn Sommersten,
Adrian McCann,
Robert Clay Glastad,
Iain George Johnston,
Matthias Kern,
Matthias Blüher,
Gunnar Mellgren,
Simon N. Dankel
Affiliations
Mona Synnøve Bjune
Mohn Nutrition Research Laboratory, Department of Clinical Science, University of Bergen, Bergen, Norway; Hormone Laboratory, Haukeland University Hospital, Bergen, Norway
Laurence Lawrence-Archer
Mohn Nutrition Research Laboratory, Department of Clinical Science, University of Bergen, Bergen, Norway; Hormone Laboratory, Haukeland University Hospital, Bergen, Norway
Johnny Laupsa-Borge
Mohn Nutrition Research Laboratory, Department of Clinical Science, University of Bergen, Bergen, Norway; Bevital AS, Bergen, Norway
Cathrine Horn Sommersten
Mohn Nutrition Research Laboratory, Department of Clinical Science, University of Bergen, Bergen, Norway; Mohn Nutrition Research Laboratory, Department of Clinical Medicine, University of Bergen, Bergen, Norway
Adrian McCann
Bevital AS, Bergen, Norway
Robert Clay Glastad
Department of Mathematics, University of Bergen, Bergen, Norway
Iain George Johnston
Department of Mathematics, University of Bergen, Bergen, Norway; Computational Biology Unit, University of Bergen, Bergen, Norway
Matthias Kern
Helmholtz Institute for Metabolic, Obesity and Vascular Research (HI-MAG) of the Helmholtz Zentrum München at the University of Leipzig and University Hospital Leipzig, Leipzig, Germany; Medical Department III—Endocrinology, Nephrology, Rheumatology, University of Leipzig Medical Center, Leipzig, Germany
Matthias Blüher
Helmholtz Institute for Metabolic, Obesity and Vascular Research (HI-MAG) of the Helmholtz Zentrum München at the University of Leipzig and University Hospital Leipzig, Leipzig, Germany; Medical Department III—Endocrinology, Nephrology, Rheumatology, University of Leipzig Medical Center, Leipzig, Germany
Gunnar Mellgren
Mohn Nutrition Research Laboratory, Department of Clinical Science, University of Bergen, Bergen, Norway; Hormone Laboratory, Haukeland University Hospital, Bergen, Norway
Simon N. Dankel
Mohn Nutrition Research Laboratory, Department of Clinical Science, University of Bergen, Bergen, Norway; Hormone Laboratory, Haukeland University Hospital, Bergen, Norway; Corresponding author. Department of Clinical Science, University of Bergen, Jonas Lies vei 91, 5021 Bergen, Norway.
Summary: Background: The valine (branched-chain amino acid) metabolite 3-hydroxyisobutyrate (3-HIB), produced by 3-Hydroxyisobutyryl-CoA Hydrolase (HIBCH), is associated with insulin resistance and type 2 diabetes, but implicated tissues and cellular mechanisms are poorly understood. We hypothesized that HIBCH and 3-HIB regulate hepatic lipid accumulation. Methods: HIBCH mRNA in human liver biopsies (“Liver cohort”) and plasma 3-HIB (“CARBFUNC” cohort) were correlated with fatty liver and metabolic markers. Human Huh7 hepatocytes were supplemented with fatty acids (FAs) to induce lipid accumulation. Following HIBCH overexpression, siRNA knockdown, inhibition of PDK4 (a marker of FA β-oxidation) or 3-HIB supplementation, we performed RNA-seq, Western blotting, targeted metabolite analyses and functional assays. Findings: We identify a regulatory feedback loop between the valine/3-HIB pathway and PDK4 that shapes hepatic FA metabolism and metabolic health and responds to 3-HIB treatment of hepatocytes. HIBCH overexpression increased 3-HIB release and FA uptake, while knockdown increased cellular respiration and decreased reactive oxygen species (ROS) associated with metabolic shifts via PDK4 upregulation. Treatment with PDK4 inhibitor lowered 3-HIB release and increased FA uptake, while increasing HIBCH mRNA. Implicating this regulatory loop in fatty liver, human cohorts show positive correlations of liver fat with hepatic HIBCH and PDK4 expression (Liver cohort) and plasma 3-HIB (CARBFUNC cohort). Hepatocyte 3-HIB supplementation lowered HIBCH expression and FA uptake and increased cellular respiration and ROS. Interpretation: These data implicate the hepatic valine/3-HIB pathway in mechanisms of fatty liver, reflected in increased plasma 3-HIB concentrations, and present possible targets for therapeutic intervention. Funding: Funding was provided by the Research Council of Norway (263124/F20), the University of Bergen, the Western Norway Health Authorities, Novo Nordisk Scandinavia AS, the Trond Mohn Foundation and the Norwegian Diabetes Association.
