Effects of supplemental chromium and isolation stress on tissue responsiveness and sensitivity to insulin in sheep

The hyperinsulinemic euglycemic clamp approach was used to study the effect s of supplemental chromium (Cr) and isolation stress on tissue responsivene ss and sensitivity to insulin in sheep. The sheep (n = 4) were housed toget her in individual cages in an animal room and were fed a basal diet with ei ther 0 or 0.5 mg of Cr/kg from Cr yeast. Therefore, the sheep consumed 14 a nd 24 mu g of Cr/kg BW/day for the Control and +Cr diets, respectively. Blo od metabolites and endocrine hormone responses were measured over the 2 h p eriod of isolation stress. Plasma cortisol and lactate concentrations, howe ver, increased (p < 0.01) transiently in response to isolation stress regar dless of Cr supplementation. The hyperinsulinemic euglycemic clamp was carr ied out 1 week before and 2 h after the initiation of isolation stress for both dietary treatments. Insulin was infused over four sequential 2 h perio ds at rates from 0.64 to 10 mU kg(-1) min(-1) with concomitant glucose infu sion, to maintain preinfusion blood glucose concentrations. Plasma insulin concentrations and glucose infusion rates increased (p < 0.001) with insuli n infusion rates. The maximal glucose infusion rate and the plasma insulin concentration at the half-maximal glucose infusion rate did not change with either Cr supplementation or isolation stress. These results suggest that in sheep supplemental Cr and isolation stress have a limited influence on t issue responsiveness and sensitivity to insulin. Chromium supplementation d id not influence blood metabolite and endocrine hormone responses to isolat ion stress. (C) 1999 Elsevier Science B.V. All rights reserved.