Modulation of the hepatic malonyl-CoA-carnitine palmitoyltransferase 1A partnership creates a metabolic switch allowing oxidation of de novo fatty acids

Liver mitochondrial beta-oxidation of LCFAs (long-chain fatty acids) is tightly regulated through inhibition of CPT1A (carnitine palmitoyltransferase 1A) by malonyl-CoA, all intermediate of lipogenesis stimulated by glucose and insulin. Moreover, CPT1A sensitivity to malonyl-CoA inhibition varies markedly depending on the physiopathological state of the animal. In the present study, we asked whether an increase in CPTI A activity solely or in association with a decreased malonyl-CoA sensitivity could, even in the presence of high glucose and insulin concenterations, maintain a Sustained LCFA beta-oxidationand/or protect from triacylglycerol (triglyceride) accumulation in hepatocytes. We have shown that adenovirus-mediated expression of rat CPT1wt (witd-type CPT1A) and malonyl-CoA-insensitive CPT1wt (CPT1AM593S mutant) in cultured fed rat hepatocytes counteracted the inhibition of oleate beta-oxidation induced by 20 mM glucose/10 nM insulin. Interestingly, the glucose/insulin cellular triacylglycerol accumulation was prevented, both in the presence and absence of exogenous oleate. This resulted from the generation of a metabolic switch allowing beta-oxidation of de novo synthesized LCFAs. Which Occurred without alteration in glucose oxidation and glycogen synthesis. Moreover, CPT1mt expression was more effective than CPT1wt overexpression to counteract glucose/insulin effects, demonstrating that control of CPT1A activity by malonyl-CoA is an essential driving force for hepatic LCFA metabolic Fate. In conclusion, the present Study highlights that CPT1A is a prime target to increase hepatic LCFA beta-oxidation and that acting directly on the degree of its malonyl-CoA sensitivity may be a relevant strategy to prevent and/or correct hepatic steatosis.