INSULIN-DEPENDENT GLUCOSE-UTILIZATION IN INTENSIVELY MILK-FED VEAL CALVES IS MODULATED BY SUPPLEMENTAL LACTOSE IN AN AGE-DEPENDENT MANNER

Postprandial insulin resistance with excessive hyperinsulinemia, hyper glycemia and glucosuria develops with increasing age in Veal calves in tensively fed milk replacers. We tested the age dependency of insulin resistance, modulated by high lactose intake, glucose oxidation and in sulin receptor number and affinity after an overnight period without f ood. Male carves were fed a milk replacer containing 290 or 423 g lact ose and 310 and 541 g total sugar/kg from 69-195 kg body weight. At me an body weights of 95 and 170 kg, insulin-dependent glucose metabolism was studied in euglycemic-hyperinsulinemic glucose clamps (EGC), and glucose-dependent insulin responses were tested in hyperglycemic clamp s (HGC). EGC were combined with infusions of [C-13(6)]glucose to measu re glucose kinetics and glucose oxidation by determination of (CO2)-C- 13 exhalation. During EGC and HGC, insulin concentrations were similar in both groups, indicating comparable insulin secretion and metabolic clearance rates. On the basis of glucose infusion rates required to m aintain eu-or hyperglycemia in EGC and HGC, respectively, insulin-depe ndent glucose utilization was not age dependent. However, in calves re ceiving a high lactose intake, insulin-dependent glucose utilization w as enhanced in the early phases, but was reduced in the late stages of the growth trial, insulin-dependent glucose utilization behaved inver sely with atom % excess of [C-13(6)]glucose, but changed in a manner s imilar to that of the rate of glucose appearance. inhibition of endoge nous glucose output, exhalation of (CO2)-C-13 and amounts of oxidized glucose exhibited no group differences. More glucose was therefore sto red in lactose-supplemented calves. A reduced insulin receptor number in skeletal muscle in calves fed high amounts of lactose likely contri buted to low insulin-dependent glucose utilization.