title: Decline in insulin action with age in endurance-trained humans.
abstract: We tested the hypothesis that regular endurance exercise prevents the age-related decline in insulin action typically observed in healthy, sedentary adults. An index of whole body insulin sensitivity (ISI), obtained from minimal model analysis of insulin and glucose concentrations during a frequently sampled intravenous glucose tolerance test, was determined in 126 healthy adults: 25 young [27 +/- 1 (SE) yr; 13 men/12 women] and 43 older (59 +/- 1 yr; 20/13) sedentary and 25 young (29 +/- 1 yr; 12/13) and 33 older (60 +/- 1 yr; 20/13) endurance trained. ISI values were lower in the older vs. young adults in both sedentary (-53%; 3.9 +/- 0.3 vs. 7.0 +/- 0.7 x10(-4) x min(-1) x microU(-1) x ml(-1); P < 0.01) and endurance-trained (-36%; 7.9 +/- 0.6 vs. 12.4 +/- 1.0 x 10(-4) min(-1) x microU(-1) x ml(-1); P < 0.01) groups, but the value was 72-102% higher in the trained subjects at either age (P < 0.01). In subgroup analysis of sedentary and endurance-trained adults with similar body fat levels (n = 62), the age-related reduction in ISI persisted only in the endurance-trained subjects (12.9 +/- 1.9 vs. 8.7 +/- 1.2 x 10(-4) x min(-1) x microU(-1) x ml(-1); P < 0.01). The results of the present study suggest that habitual endurance exercise does not prevent the age-associated decline insulin action. Moreover, the age-related reduction in ISI in endurance-trained adults appears to be independent of adiposity.
authors.affiliation: Department of Kinesiology and Applied Physiology, University of Colorado, Boulder 80309, USA.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Clevenger
authors.forename: Pamela
authors.initials: P
authors.lastname: Parker Jones
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Tanaka
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Seals
authors.forename: Christopher A
authors.initials: CA
authors.lastname: DeSouza
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism*; D001823:Body Composition; D005260:Female; D005947:Glucose / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D007333:Insulin Resistance / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D010807:Physical Endurance / Q000502:physiology*; D010809:Physical Fitness / Q000502:physiology
chemical_list: D007328:Insulin; D005947:Glucose