AMP-activated protein kinase (AMPK) contributes to the anti-obesity effects and adipose tissue browning of alpha-lipoic acid in ovariectomized rats

Abstract

BackgroundBilateral ovariectomy is an experimental model used to analyze the conditions of menopause and develop strategies for alleviation of the deleterious effects during estrogen deficiency. Brown and beige adipocytes exert thermogenesis capacities and are promising therapeutic strategy for obesity. This study aims to investigate the adipose tissue browning potentials of antioxidant α-lipoic acid (ALA) and underlying mechanisms involved in ovariectomized (Ovx) rats.Methods:Eight weeks old female Wistar rats were randomly divided into Sham or Ovx groups. The Ovx rats were subjected to bilateral ovariectomy and administered with ALA 200 or ALA 300 mg/kg/day (gavage) for 8 weeks. Results:Ovx group significantly increased boy weight (BW) and fat pad mass as compared to Sham group, while ALA supplementation reversed these changes. Lipid profiles including serum triglycerides (TG), total (TC) and low-density lipoprotein cholesterol (LDL-C) levels were significantly elevated in the Ovx group, whereas the ALA treatment showed a significant decrease in these levels. Furthermore, high density lipoprotein cholesterol (HDL-C) and myokine irisin secretion were increased by ALA as well. Morphology results showed ALA treatment reduced Ovx-induced adipocyte hypertrophy and enhanced UCP1 expression by immunohistochemical staining in inguinal WAT. Protein expression of brown fat-specific markers UCP1, PRDM16 and CIDEA was markedly reduced in Ovx rats, whereas ALA treatment reversed these changes. ALA significantly increased liver kinase B1 (LKB1) and phosphorylation of AMP-activated protein kinase (AMPK) and the downstream acetyl-CoA carboxylase (ACC) that were decreased by Ovx, suggesting the browning effects were mediated by AMPK signaling. Conclusions:ALA ameliorates obesity caused by hormone deprivation in menopause via conversion of white to beige adipocytes concomitant with the activation of AMPK signaling.