CPT1A and hyperinsulinism: Mechanistically, insulin resistance at both hepatic and systemic levels, along with hyperinsulinemia, acts to increase the expression of genes for lipogenic enzymes such as acetyl-CoA carboxylase 1 (ACC1) and fatty acid synthase (FAS) [5], [6] and to decrease the expression of genes for fatty acid oxidation including carnitine palmitoyltransferase 1a (CPT1a) [7].