Growth hormone does not affect non‐insulin‐mediated glucose uptake in sheep

Abstract

SUMMARYFour adult Merino sheep were used in the experiment, which was divided into four parts. For the 5 days before parts 1 and 3 saline was injected and for the 5 days before parts 2 and 4 growth hormone (GH; 4 mg day-1 subcutaneously) was injected. In parts 1 and 2 a primed continuous infusion of [6,6-2H2]glucose and either saline or GH, respectively, were infused for 5 h. The first 3 h was the control period. From 3 to 5 h insulin (0-5 mU kg-' min-) was infused. Coincident with the insulin infusion, normal glucose was also infused at a variable rate, dependent on the rapidly determined plasma glucose concentration, in order to keep the plasma glucose concentration constant. Parts 3 and 4 of the experiment were the same as parts 1 and 2, respectively, except for the following: the glucose isotope and saline or GH were infused for 7 h, from 3 to 7 h somatostatin (SRIF; 0 417 jug kg-1 min-') was infused, and from 5 to 7 h insulin was infused. Measurements of glucose turnover were made in the last 40 min of the control, insulinonly, SRIF-only and insulin-plus-SRIF infusion periods. Plasma insulin levels were reduced to below the level of detection by the SRIF infusion; under such conditions whole body glucose uptake should be entirely non-insulin mediated (NIMGU). Expressing glucose uptake as glucose metabolic clearance rate revealed that GH had no effect on NIMGU but significantly reduced the level of insulin-mediated glucose uptake (IMGU). Thus a reduction in the rate of NIMGU is probably not part of the mechanism by which GH repartitions glucose to sites of growth and milk production, whilst the present study confirms the antagonistic effect of GH on IMGU.

Effect of glucose‐dependent insulinotropic polypeptide on whole‐body glucose utilization in sheep

“…1). As for a previous experiment in sheep (Rose et al 1997a), and unlike our experiments in dairy cows (Rose, Obara, Itoh, Hashimoto & Takahashi, 1997b;Rose, Itoh, Matsumoto, Takahashi & Obara, 1998), the SS infusion did not cause a decrease in the concentration of glucose so that an exogenous infusion of glucose was not necessary.…”

“…The GIP kit contained porcine GIP as the standard, and thus GIP concentrations presented are the porcine equivalents of ovine GIP. The measurement of the enrichment of [6,6-2H2]glucose in plasma was done as described by Rose, Obara, Itoh, Hashimoto & Takahashi (1997a).…”

“…The glucose infusion rate required to maintain euglycaemia during the insulin infusion (which is an overall measure of the effect of insulin on glucose turnover) was calculated at 10 min intervals and expressed as mg kg-' min-'. Whole-body rates of glucose appearance (Ra) and disappearance (Rd) and the glucose metabolic clearance rate (MCR) were calculated using non-steady-state kinetics, as described previously (Rose et al 1997a).…”

Glucose-mediated glucose disposal in insulin-resistant normoglycemic relatives of type 2 diabetic patients.

“…This FFA suppression occurred despite the known lipolytic effect of GH administration (38) seen with higher doses of GH over prolonged time frames (38). Furthermore, it has been shown in sheep that GH does not affect non-insulin-mediated glucose uptake (39).…”

Propionate supplementation did not increase whole body glucose turnover in growing lambs fed rye grass

“…In ruminants, their use is recent and not very frequent because of the high cost of stable isotopes and analytical equipment. Only a few studies dealing with glucose turnover in ruminants have been conducted using stable isotopes ( [30][31][32] with [U-13 C]-glucose, [33][34][35][36] …”