Incretion of Insulin by Pancreas and Its Inactivation in Women during Long-Term Head-down Tilt Bed Rest

Abstract

An increase in insular activity in response to hyperglycemia when performing a glucose tolerance test (GTT) during normal physical activity in eight women volunteers was found to be associated with increased blood concentrations of insulin provided by an increase in secretion rate and a decrease in inactivation rate. After 81 days of stay in long-term –6° head-down tilt bed rest (bed rest), flattened glycemic curves (with low hyperglycemic lifting) observed during the GTT, what was indicated high insular activity. An increase in the insular activity was evidencing also by a smaller peak of the blood concentration of glucose from 5 min after intravenous nfusion of 20 mL of 40% glucose solution at 120 minute of the GTT. In bed rest on empty stomach no significant changes in the concentrations of insulin and C-peptide were observed. The dynamics of hormone during the GTT was showed that the appearance of flattened glycemic curves when performing GTT during bed rest was associated with more pronounced, than under the usual conditions, an increase in insulin concentration in response to hyperglycemia. An increase in the blood insulin concentration when performing GTT in bed rest was mainly provided by increased hormone secretion rate in the pancreas, but not by a decrease in its inactivation rate. If you use regular exercises for prevention of hypokinesia under conditions of bed rest, an increase in insulin concentration during GTT was mainly provided by a decrease in its inactivation rate and not by an increase in secretion rate.