Inhibition of stearoyl-CoA desaturase1 activates AMPK and exhibits beneficial lipid metabolic effects in vitro

Stearoyl-CoA desaturase1 (SCD1) whole body deficiency protects mice from diet-induced obesity. However the specific mechanism of how SCD1 deficiency protects mice from obesity is not clear yet. To understand the tissue-specific role of SCD1 in energy homeostasis, we investigated the responses of adipocytes, hepatocytes and myotubes to SCD1 inhibition. 3T3-L1 adipocytes treated with a SCD1 inhibitor had decreased expression of lipogenic genes including fatty acid synthase (FAS), acetyl-CoA carboxylase (ACC), and sterol-regulatory element binding protein 1c (SREBP1c) while the expression of fatty acid oxidative genes including carnitine palmitoyltransferase 1 (CPT1), uncoupling protein 2 (UCP2), and peroxisome proliferator-activated receptor gamma coactivator 1-α (PGC1-α) remained unaltered. In mouse primary hepatocytes, treatment with the inhibitor reduced the expression of FAS, ACC, and SREBP1c but increased the expression of fatty acid oxidative genes including acyl-CoA oxidase (AOX), CPT1, and PGC1-α. In addition, inhibitor-treated C2C12 myotubes showed decrease in ACC and FAS expression and increase in expression of CPT1, AOX and PGC1-α. AMP-activated protein kinase (AMPK) is known to regulate cellular metabolism in response to available energy and AMPK activation is associated with enhancement of fatty acid oxidation and suppression of lipogenesis. In all tested cell models, AMPK phosphorylation was increased significantly when SCD1 was inhibited. Taken together, our results indicate that inhibition of SCD1 activity has beneficial lipid metabolic effects of decreased lipogenesis and/or increased fatty acid oxidation, which is at least in part due to an increase of AMPK activation.