Abstract
Fetuin‐A, an inhibitor of insulin‐stimulated insulin receptor tyrosine kinase (IR‐TK) and glucose uptake, has been shown to be associated with obesity, insulin resistance, and incident diabetes. In circulation, fetuin‐A exists in both phosphorylated and dephosphorylated forms. Phosphorylation status of fetuin‐A has been shown to be critical for its IR‐TK inhibitory activity. The objective of this study was to characterize the effects of single and repeated bouts of exercise on serum total fetuin‐A and phosphofetuin‐A (Ser312) in obese individuals. 31 obese and 11 normal‐weight men underwent a single bout of treadmill walking expending 500 kcals. Insulin, glucose, HOMA, QUICKI, and glucose/insulin ratio were not altered immediately after or 24 hours following a single bout of exercise. Total fetuin‐A concentrations were significantly elevated immediately after exercise, which decreased to pre‐exercise levels in the recovery period (24 hours after the single bout of exercise). Area under the curve for serum total fetuin‐A, phosphofetuin‐A, glucose, and insulin during an oral glucose tolerance test was significantly decreased 24 hours after a single bout of exercise. Next, we investigated the influence of repeated bouts of exercise, expending 350 kcal each session, on four consecutive days. Compared to baseline, insulin and HOMA‐IR were decreased significantly on days 2, 3, and 24 hours following the last bout of exercise. Unlike total fetuin‐A, serum phosphofetuin‐A levels were decreased significantly 24 hours after the last bout of exercise. Taken together, these results suggest that the observed lowering of serum phosphofetuin‐A (Ser312) levels, 24 hours after a single or short‐term repeated bout of exercise, in obese individuals, may contribute to the improvement of insulin sensitivity.Grant Funding Source: Supported by Alabama Agricultural Experiment Station Grants Program
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