We established that the mitochondria regulators Sirt1/p-Ampkα are inhibited and the main regulator of FA synthesis Srebp1c is upregulated early in asymptomatic young Pcyt2+/−, as direct consequence of Pcyt2 gene deletion, not because of liver steatosis or insulin resistance, which develops at adult age. The gene discussed is PCYT2; the disease is Hepatic steatosis.