Estrogen rapidly phosphorylates AMPK, Akt, and AS160 in isolated rat soleus muscles

Abstract

Estrogen status is positively correlated with whole body insulin sensitivity, however direct effects of estrogen on skeletal muscle glucose uptake have not been demonstrated. The aim of this study was to determine if estrogen can acutely activate Akt, AMP‐activated protein kinase (AMPK), and/or Akt substrate of 160 kDa (AS160), signaling proteins that mediate glucose uptake in skeletal muscle. METHODS: Soleus or extensor digitorum longus muscles were excised from female Sprague Dawley rats and incubated in Krebs‐Ringer‐Bicarbonate buffer. After equilibrating for 50–59 min, vehicle (ethanol) or 17‐β‐estradiol (10 nM) were added for 1, 2, 5 or 10 min. Muscles were frozen and processed for immunoblot analyses. RESULTS: Estrogen time‐dependently caused a 2–4 fold increase in the phosphorylation of AMPK (Thr172), Akt (Thr308), and AS160 (PAS) in oxidative soleus muscle only, with phosphorylation seen as early as 1 min, and maximal activation evident at 5 and10 min. CONCLUSION: In rat muscle, acute estrogen treatment rapidly activates key signaling proteins involved in glucose transport, suggesting a novel non‐genomic role of estrogen in the regulation of muscle glucose metabolism. Interestingly, these effects are specific to oxidative muscles such as soleus, perhaps reflecting muscle group differences in estrogen receptor expression.