Ghrelin reduces hepatic mitochondrial fatty acid β oxidation

Ghrelin is a 28-amino-acid peptide secreted during starvation by gastric cells. Ghrelin physiologically induces food intake and seems to alter lipid and glucid metabolism in several tissues such as adipose tissue and liver. Liver has a key position in lipid metabolism as it allows the metabolic orientation of fatty acids between oxidation and esterification. We investigated the effects of peripheral ghrelin administration on 2 crucial parameters of fatty acid oxidation: the levocarnitine (L-carnitine)-dependent entry of the fatty acids in the mitochondria and the mitochondrial fatty acid oxidation. Ghrelin was either given to rats prior to the hepatocyte preparation and culture or used to treat hepatocytes prepared from control animals. Direct incubation of ghrelin to raw hepatocytes did not induce any change in the studied parameters. In hepatocytes prepared from 3 nmol ghrelin-treated rats, a 44% reduction of the mitochondrial fatty acid oxidation while no alteration of the L-carnitine-related parameters were observed. These results suggested (a) that ghrelin has no direct effect on liver, and (b) that when administrated to a whole organism, ghrelin may alter the lipid metabolism and the energy balance through a marked decrease in liver fatty acid oxidation.