The effects of exercise and green tea extract on glucose homeostasis in overweight and obese post menopausal sedentary women
Jordan, Shannon L.
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The purpose of this study was to investigate the individual and combined effects of an acute bout of exercise expending 400 Kcals at 65% of HRR or green tea supplementation on insulin sensitivity and adipokine levels in overweight to obese postmenopausal sedentary women. Green tea extract (400 mg) was administered with lunch and dinner the day prior to the OGTT and also on the morning of the OGTT. Each participant (n=8) performed all four trials (Control, Green Tea, Exercise, and Green Tea + Exercise. Each exercise session was performed the day prior to an OGTT on a treadmill. Samples were drawn at baseline, 30, 60, 90, and 120 minutes during the OGTT. No changes were found in glucose and insulin profiles or adipokines (total adiponectin, HMW adiponectin, globular adiponectin, or TNF-) between trials. Mean fasting glucose values ranged from 5.5 mmol/L to 6 mmol/L amongst the trials. Mean fasting insulin levels were between 10 – 11 U/ml amongst trials. Mean TNF- ranged from 3.55 – 5.45 pg/ml between trials. Mean total adiponectin levels varied from 4496 ng/ml to 10060 ng/ml amongst trials. Participants displayed high levels of TNF- and lower levels of adiponectin which may reflect an inflammatory state associated with menopause interfering with phosphorylation of the insulin receptor and AMP kinase resulting in interruption of both insulin dependent and insulin independent glucose uptake. This state would explain the high levels of insulin as the body secretes more insulin when glucose uptake is hindered and glucose levels remain elevated. The overweight to obese postmenopausal woman may present a unique challenge in regards to prevention of type 2 diabetes as insulin levels rise independent of adiposity as estrogen levels decline. An acute dosage of green tea as an antioxidant was not effective in improving glucose or insulin profiles or adipokine levels. The acute bout of exercise and the combination of green tea and exercise were also not effective. This population may require chronic green tea ingestions and chronic exercise training in order to see a favorable impact in glucose and insulin profiles along with adipokine profile.