Effects of dietary starch and sucrose on tissue responsiveness and sensitivity to insulin in goats fed a high-concentrate diet

A glucose clamp technique was used to compare dietary starch (ST), starch plus sucrose (ST+SU) and sucrose (SU) with regard to the effect on tissue responsiveness and sensitivity to insulin in intact adult male goats. The goats were fed diets containing 1.2 times of ME and CP for maintenance requirements twice daily for 21 d. Of the energy intake, 30% was offered with ST, ST+SU or SU for the respective diets, and 70% as alfalfa hay, ground corn and ground soybean meal at the respective weight ratio of 1, 1, and 0.3 for all diets. Tissue responsiveness and sensitivity to insulin were evaluated using a hyperinsulinemic euglycemic clamp technique with four levels of insulin infusion beyond 13 h after feeding. The concentrations of plasma metabolites and insulin were also determined at 3, 6 and 13 h after feeding to evaluate the effects of different carbohydrates on metabolic states in the body. Plasma glucose concentration was higher (p = 0.01) for SU diet than for ST and ST+SU diets. Increasing SU intake decreased (p<0.01) plasma acetate concentration across the time. At 3 h but not 6 and 13 h after feeding, high lactate (p = 0.01), and non-significant high propionate (p = 0.14) and low urea nitrogen (p = 0.19) concentrations were observed in plasma on SU compared with ST and ST+SU diets. Plasma insulin concentration was not different (p = 0.44) between ST and SU fed animals. In the glucose clamp experiment, considering the effects on the maximal glucose infusion rate (tissue responsiveness to insulin, p = 0.54) and the plasma insulin concentration at half-maximal glucose infusion rate (insulin sensitivity, p = 0.54), SU was not different from ST. It is concluded that SU may not be greatly different from ST with regard to the effect on tissue responsiveness and sensitivity to insulin in adult goats when fed twice daily as part of a high-concentrate diet. The possible greater effects of SU on plasma metabolites concentrations at 3 h than at 6 and 13 h after feeding suggest that a lack of persistency of SU effects during the postfeeding period may be associated with the poor response to SU in insulin action.