Background: Nonalcoholic fatty liver disease (NAFLD) increases risk for obesity-related insulin resistance and type 2 diabetes. Recent studies have demonstrated that stimulating pyruvate dehydrogenase (PDH) , the rate-limiting enzyme in glucose oxidation, can reverse obesity-induced NAFLD. Moreover, our lab has observed that treatment with the antianginal drug, ranolazine, augments hepatic PDH activity, leading to a reversal of obesity-induced glucose intolerance and NAFLD in mice. Our aim herein was to determine whether ranolazine's ability to mitigate obesity-induced NAFLD and hyperglycemia requires increases in hepatic PDH activity.
Methods: We generated liver-specific PDH deficient (PDHLiver-/-) mice by crossing floxed Pdha1 mice with albumin-Cre (Alb-Cre) mice. PDHLiver-/- and Alb-Cre mice were placed on a high-fat diet for 12-weeks to induce obesity, whereas their lean controls were fed a low-fat diet. Mice were randomized to treatment with either vehicle control or ranolazine (50 mg/kg) once daily via oral gavage for 5-weeks, following which we assessed glucose homeostasis and hepatic steatosis.
Results:Lean PDHLiver-/- mice exhibited no overt phenotypic differences (e.g. adiposity, glucose tolerance) from their Alb-Cre littermates, though a mild but nonsignificant worsening of pyruvate tolerance was observed. Similar findings were observed in obese PDHLiver-/- mice compared to their Alb-Cre littermates. Of interest, ranolazine treatment produced mild improvements in glucose tolerance in obese Alb-Cre mice, but not in obese PDHLiver-/- mice. However, this improvement in ranolazine treated Alb-Cre mice appears to be independent of decreases in hepatic triacylglycerol content.
Conclusions: Although hepatic PDH activity appears to contribute to the glucose-lowering actions of ranolazine, this appears to be dissociated from its actions on hepatic steatosis, and impaired hepatic PDH activity per se is not sufficient to produce an NAFLD phenotype.
C. T. Saed: None. S. Tabatabaei dakhili: None. A. A. Greenwell: None. J. S. F. Chan: None. K. Yang: None. K. Gopal: None. F. Eaton: None. J. R. Ussher: None.