Enhanced responsiveness to insulin in sheep exposed to cold

Abstract

The effects of cold exposure on tissue sensitivity and responsiveness to insulin were determined by the euglycemic insulin clamp technique. Insulin was infused at rates of 0.2, 0.5, 1.0, 6.0, and 30.0 mU x kg-1 x min-1 into five adult sheep in a warm environment and after cold exposure (0 degree C) from 7 to 23 days. Cold exposure increased basal plasma glucose concentration and basal glucose irreversible loss. Glucose metabolic clearance rate (MCR) was significantly increased by cold exposure at all rates of insulin infusion, with increases ranging from 44 to 72%. The insulin concentration causing half-maximal stimulation of glucose MCR was unchanged by environment (warm, 42 microU/ml; cold, 36 microU/ml). Combined alpha + beta-adrenergic blockade did not affect the increased response to insulin during cold exposure. Endogenous (hepatic) glucose production was inhibited by insulin to a similar extent in the two environments and was less sensitive to insulin than was glucose utilization or MCR. The results suggest that cold exposure increases the responsiveness to insulin of a postreceptor event in peripheral tissues.

Effect of supplemental calcium propionate on insulin action to blood glucose metabolism in adult sheep

“…The inconsistency of effects of supplemental propionate on blood glucose metabolism may be involved in the dose, duration or method of propionate supplementation, the stage of animals, or feeding managements. Although basal blood GTR was within the ranges of blood GTR as determined by the isotope dilution methods using stable and radio isotopes, blood GTR for the Prop diet seemed to be near the upper margin [12,18,28,29]. Because blood GTR is influenced by the type of diet, energy intake and physiological status [28][29][30], these factors may be related.…”

“…The hyperinsulinemic euglycemic clamp procedure was applied to determine blood glucose metabolism in response to insulin infusion [12,15]. Insulin (64 and 400 U·L -1 of saline solution for two lower and two higher infusion rates, respectively; Actrapid monocomponent porcine insulin, Novo Industri, Denmark) was infused over four sequential 2-h periods at rates of 0.64, 1.6, 4.0 and 10 mU·kg -1 BW per min by another peristaltic pump through the same jugular catheter during the last 8 h of [U- 13 C]glucose infusion.…”

“…Blood GTR was calculated according to the equation of Tserng and Kalhan [16] and the equation of nonsteady states by Steele [19] before and after the initiation of the glucose clamp procedure, respectively. The glucose distribution volume and the pool fraction were assumed to be 179 mL·kg -1 BW and 0.65 as described by Weekes et al [12] and Brockman [20], respectively. The EGPR was calculated from GTR minus GIR.…”

“…A glucose clamp procedure has been used to determine whole body tissue 10 H. Sano, T. Fujita responsiveness and sensitivity to insulin [11]. Weekes et al [12] applied the glucose clamp procedure combining an isotope dilution method of H]glucose to determine whole body glucose turnover rate (GTR) and endogenous glucose production rate (EGPR) in addition to tissue responsiveness and sensitivity to insulin in sheep in vivo. It was hypothesized that the propionate supplementation enhances tissue responsiveness and sensitivity to insulin, thus modifying the production of ruminants.…”

Responses of plasma glucose metabolism to exogenous insulin infusion in sheep-fed forage herb plantain and exposed to heat

“…V is the distribution volume of glucose and p the pool fraction. The distribution volume was assumed to be 179 ml/kg BW (Weekes et al, 1983) and the pool fraction was assumed 0.65 (Brockman, 1979).…”