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- Title
Exercise Training with and without Weight Loss: Effects on Hepatic and Peripheral Insulin Sensitivity.
- Authors
Coker, Robert H.; Williams, Rick H.; Kortebein, Patrick M.; Evans, William J.
- Abstract
Our objective was to determine the influence of exercise training (with and without weight loss) on hepatic and peripheral insulin resistance in obese adults. Following medical exams, 16 older (56±2 years), obese (BMI=31±1 kg/m²) individuals were randomized to: exercise training with caloric compensation (EX), exercise training without caloric compensation (EWL) or a control group (CN). Utilizing a training paradigm to ensure a matched caloric expenditure (2500 kcal/week at 50% of VO[sub 2peak]) in EX and EWL, subjects also completed a dietary feeding study that included a 4 week weight maintenance period, a 12 week intervention period, a 2 week gradual re-feeding period, and 4 week weight stabilization period. Immediately following the weight maintenance and weight stabilization periods designed to ensure caloric balance, pre-and post-testing procedures were completed. In order to specifically examine hepatic and peripheral insulin sensitivity, an octreotide (60 ng⋅kg[sup -1]⋅min[sup -1]), glucagon (0.65 ng⋅kg[sup -1]⋅.min[sup -1]), multi-stage insulin (0.25 and 1.0 mU⋅kg[sup -1]⋅ min[sup -1]) infusion (MSI) was performed. During the MSI, euglycemia was maintained by a variable rate infusion of 20% dextrose spiked with [6,6 ²H[sub 2]]glucose. Endogenous glucose production (glucose R[sub a]) was measured at baseline and during the MSI using a primed, multi-stage infusion [0.22 (first stage) and 0.44 (second stage) µmol⋅kg[sup -1]⋅min[sup -1]] of [6,6²H[sub 2]]glucose. Hepatic insulin action (HIA) was calculated as the % of glucose R[sub a] suppressed by mild hyperinsulinemia (ie., elicited by the 0.25 mU⋅kg[sup -1]⋅min[sup -1] insulin infusion) relative to the peripheral insulin concentration. Insulin-stimulated glucose disposal (ISGD) was calculated by subtracting glucose R[sub a] from 20% dextrose infusion rate required to maintain euglycemia during the second stage of the MSI. Body weight remained stable in EX (+0.2±0.1 kg), decreased significantly in EWL (-6.4±0.4 kg), and increased in CN (+2.3±1.0 kg). While EX was associated with a positive trend in HIA (+4.3%), EWL resulted in a significant improvement in HIA (7.8%). Similarly, EX promoted a modest increase in ISGD (+1.1±0.4 mg⋅kgFFM[sup -1]⋅min[sup -1]), and EWL facilitated a greater than twofold improvement in ISGD (+2.5±-0.4 mg⋅kgFFM[sup -1]⋅min[sup -1]) compared to EX. HIA and ISGD declined in CN. EWL resulted in superior improvements in HIA and ISGD compared to EX. These results suggest that exercise training designed to promote weight loss may provide a synergistic benefit in the treatment of insulin resistance in obese individuals.
- Publication
Diabetes, 2007, Vol 56, pA38
- ISSN
0012-1797
- Publication type
Academic Journal