Exercise Training is More Effective Than The Ability of 17‐β‐Estradiol to Reverse Glucose Intolerance in Ovariectomized (OVX) Rats

Abstract

IntroductionLoss of estrogen in females increases the risk for insulin resistance. Hormone replacement therapy (HRT) is often prescribed to treat estrogen deficiency but has several detrimental side effects. Exercise is suggested as an HRT substitute since it improves insulin sensitivity, but the efficacy of exercise vs. HRT on glucose tolerance is unknown. The purpose of this study was to compare exercise training to 17‐β‐estradiol (E2) supplementation on restoring glucose tolerance (GT) in ovariectomized (OVX) rats.Methods30 OVX and 20 SHAM rats consumed a phytoestrogen free diet, ad libitum. Glucose tolerance tests (GTT) were performed at 10 weeks. Blood samples were drawn to assess serum insulin. Rats were randomly assigned to one of five 4 week treatment groups: SHAM sedentary (sed) or exercise (ex; 60 min, 5x/wk), OVX sed, ex or E2 (28 ug/kg/day). GTTs and blood sampling were repeated at 15 weeks. Glucose uptake in soleus and EDL muscle was assessed, and basal and maximal insulin‐stimulated EDL, soleus, adipose and liver samples were frozen for analysis.ResultsOVX rats were glucose intolerant at 10 weeks relative to SHAMs. After treatment, GT in OVX ex rats was entirely recovered, but only partially in OVX E2 rats. Insulin secretion at 15 min. during the 15 week GTT was significantly higher in OVX sed vs. OVX E2 or ex groups; however maximal insulin‐stimulated glucose uptake in soleus or EDL was unaffected.ConclusionsExercise restores GT in OVX rats more effectively than E2. Whole‐body improvements are not reflected by alterations in muscle maximal insulin response. This suggests adipose or liver as primary effectors of E2 or exercise treatment in OVX rats.Supported by NSERC