title: Quantitative evaluation of the effect of low-intensity exercise on insulin secretion in man.
abstract: We studied insulin secretion rates (ISR) during low-intensity exercise (40% peak aerobic capacity [VO2]) in 12 normal subjects to assess the contribution of altered insulin secretion to the reduction in peripheral insulin concentrations associated with exercise. ISR were calculated by a previously validated method of two-compartment analysis of peripheral C-peptide concentrations using individual parameters derived following a bolus injection of biosynthetic human C-peptide. In addition, the effect of low-intensity exercise on kinetic parameters of C-peptide was evaluated. The results showed that low-intensity exercise did not significantly affect C-peptide kinetics. Peripheral insulin concentrations and ISR decreased to a similar degree throughout exercise. There was a mean maximum decrease in serum insulin concentrations from 42 +/- 5.4 pmol/L basally to 24 +/- 2.6 pmol/L, constituting a 51% +/- 5.9% decrease (P < .001), and ISR decreased from 85.7 +/- 11.9 pmol/min to a nadir of 45.6 +/- 10.6 pmol/min (P < .001), a 48% +/- 8.4% decline. Plasma glucose and glucagon concentrations did not change significantly either during or after exercise, although there was a matched twofold increase in glucose utilization and disposal rates. We suggest that the reduction in peripheral insulin concentrations during exercise is due to reduced insulin secretion.
authors.affiliation: Department of Medicine, University of Chicago Pritzker School of Medicine, IL.
authors.forename: N S
authors.initials: NS
authors.lastname: Levitt
authors.forename: L
authors.initials: L
authors.lastname: Hirsch
authors.forename: A H
authors.initials: AH
authors.lastname: Rubenstein
authors.forename: K S
authors.initials: KS
authors.lastname: Polonsky
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000032:analysis; D002096:C-Peptide / Q000378:metabolism; D015444:Exercise; D005260:Female; D005934:Glucagon / Q000097:blood; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D008297:Male; D008657:Metabolic Clearance Rate
chemical_list: D001786:Blood Glucose; D002096:C-Peptide; D007328:Insulin; D005934:Glucagon