Circulating obestatin is lowered by food intake, but factors involved in obestatin regulation remain unclear. The aim of this study was to determine whether intravenous glucose or insulin infusion lowers obestatin. Rats were infused over 3 h with either A. saline (controls); B. dextrose to steady state blood glucose ~16.7 mM, or C. insulin 7.5 mU/kg.min, plus dextrose as needed to clamp to euglycemic basal concentrations. During 3 h of infusion, group B had significantly greater (P<0.01) glucose, 18.75±1.27 mM, than groups A (6.10±0.33 mM) or C (6.19±0.18 mM). Groups B and C had hyperinsulinemia at the end of the 3 h infusion (1.02±0.03 ng/ml, 1.07±0.02 ng/ml) compared with saline-infused (0.38±0.01 ng/ml, P<0.01). Obestatin concentrations were significantly reduced (P<0.01) in both hyperinsulinemic groups and (B=0.95±0.06 ng/ml; C=0.87±0.04 ng/ml) versus controls (1.56±0.13 ng/ml). These data suggest that insulin can decrease the plasma obestatin levels.
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