NEW HEPATIC FAT ACTIVATES PPARA TO MAINTAIN GLUCOSE LIPID CHOLESTEROL HOMEO

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. De novo lipogenesis is an energy-expensive process whose role in adult mammals is poorly understood. We generated mice with liver-specific inactivation of fatty-acid synthase (FAS), a key lipogenic enzyme. On a zero-fat diet, FASKOL (FAS knockout in liver) mice developed hypoglycemia and fatty liver, which were reversed with dietary fat. These phenotypes were also observed after prolonged fasting, similarly to fasted PPARa-deficiency mice. Hypoglycemia, fatty liver, and defects in expression of PPARa target genes in FASKOL mice were corrected with a PPARa agonist. On either zero-fat or chow diet, FASKOL mice had low serum and hepatic cholesterol levels with elevated SREBP-2, decreased HMG-CoA reductase expression, and decreased cholesterol biosynthesis; these were also corrected with a PPARa agonist. These results suggest that products of the FAS reaction regulate glucose, lipid, and cholesterol metabolism by serving as endogenous activators of distinct physiological pools of PPARa in adult li