Effects of hyperinsulinemia on local cerebral insulin binding and glucose utilization in normoglycemic awake rats

The present study was carried out to characterize the effects of insulin, using the euglycemic hyperinsulinemic clamp, on insulin binding and glucose utilization in specific areas of rat brain, by autoradiographic methods. Binding of [125I]Insulin was significantly higher in the hippocampus CA1, the ventromedial and lateral hypothalamus nuclei of the hyperinsulinemic rats than in control rats. Glucose utilization was slightly but not significantly decreased in the hippocampus CA1, the ventromedial and lateral hypothalamus of hyperinsulinemic rats. These data suggest that insulin, via its specific receptors, may exert its central actions by affecting glucose utilization.     

Effect of Halothane Anesthesia on Glucose Utilization and Production in Adolescents

Background: It should be possible to avoid variations in plasma glucose concentration during anesthesia by adjusting glucose infusion rate to whole-body glucose uptake. To study this hypothesis, we measured glucose utilization and production, before and during halothane anesthesia.

Methods: After an overnight fast, six adolescents between 12 and 17 yr of age were infused with tracer doses of [6,6-sup 2 H2]glucose for 2 h before undergoing anesthesia, and the infusion was continued after induction, until the beginning of surgery. Plasma glucose concentration was monitored throughout, and free fatty acids, lactate, insulin, and glucagon concentrations were measured before and during anesthesia.

Results: Despite the use of a glucose-free maintenance solution, plasma glucose concentration increased slightly but significantly 5 min after induction (5.3 plus/minus 0.4 vs. 4.5 plus/minus 0.4 mmol *symbol* 1 sup -1 , P < 0.05). This early increase corresponded to a significant increase in endogenous glucose production over basal conditions (4.1 plus/minus 0.4 vs. 3.6 plus/minus 0.2 mg *symbol* kg sup -1 *symbol* min sup -1, P < 0.05), with no concomitant change in peripheral glucose utilization. Fifteen minutes after induction, both glucose utilization and production rates decreased steadily and were 20% less than basal values by 35 min after induction (2.9 plus/minus 0.3 vs. 3.6 plus/minus 0.2 mg *symbol* kg sup -1 *symbol* min sup -1, P < 0.05). Similarly, glucose metabolic clearance rate decreased by 25% after 35 min. Despite the increase in blood glucose concentration, anesthesia resulted in a significant decrease in plasma insulin concentration.     

Clinical and electrophysiologic study of the peripheral nerve in 28 cases of mitochondrial disease]

Twenty-eight patients with mitochondrial disease were systematically investigated on clinical and electrophysiological grounds for peripheral neuropathy (PN): 25 had predominant ophthalmoplegia (including 4 with Kearns-Sayre syndrome) and 3 had predominant central nervous system involvement. There were 11 men and 17 women, mean age 43 years. Nine of the 28 patients had signs of sensory polyneuropathy involving mainly the lower limbs. These 9 patients and another asymptomatic patient had electrophysiological abnormalities: in the lower limbs, sensory potentials were absent or decreased in amplitude in all cases. In peroneal nerves, motor conduction nerve velocities were decreased in 4/10 cases. These data were consistent with an axonopathy. No correlation was found between the presence of PN and the clinical features of the mitochondrial diseases or with the respiratory chain defect (studied in 14 cases).     

Effects of counterregulatory hormones on insulin-induced glucose utilization by individual tissues in rats

The effect of counterregulatory hormones (epinephrine, norepinephrine and glucocorticoids) on insulin-induced glucose utilization in individual tissues of normal rats was investigated in vivo. This was done in normoglycaemic conditions, using the euglycaemic hyperinsulinaemic clamp combined with an injection of 2-[1-3H]-deoxyglucose. The main effect of these hormones was to reduce insulin-induced glucose utilization in skeletal muscles and particularly in the oxidative one. No changes were observed in heart diaphragm and adipose tissues. These results emphazise the role of counterregulatory hormones on glucose utilization and demonstrate that muscles are their major site of action. They support the notion that the increase in plasma concentrations of these hormones could play a role in states of insulin resistance like obesity and diabetes.