title: Diet-induced weight loss is associated with an improvement in beta-cell function in older men.
abstract: Although weight loss in older subjects has been shown to improve insulin sensitivity, it is unclear what effect this lifestyle intervention has on beta-cell function. To determine whether diet-induced weight loss can improve beta-cell function in older subjects, we studied 19 healthy male subjects (age, 65.4 +/- 0.9 yr; body mass index, 30.9 +/- 0.6 kg/m2; mean +/- SEM) before and after a 3-month 1200-kcal/d diet. The insulin sensitivity index (SI) was quantified using Bergman's minimal model. The acute insulin response to glucose (AIRg) and the maximal glucose-potentiated insulin response (AIRmax) were determined and then adjusted for SI (SI x AIRg and SI x AIRmax), thus providing measures of beta-cell function. Subjects demonstrated significant weight loss (95.6 +/- 2.4 to 86.1 +/- 2.5 kg; P < 0.001). Both fasting plasma glucose [97.3 +/- 1.6 to 95.1 +/- 1.3 mg/dl (5.4 +/- 0.09 to 5.3 +/- 0.07 mM); P = 0.05] and insulin [18.5 +/- 1.3 to 12.2 +/- 1.0 microU/ml (110.9 +/- 7.7 to 73.5 +/- 5.9 pM); P < 0.001] levels decreased. With weight loss, SI increased [1.59 +/- 0.24 to 2.49 +/- 0.32 x 10(-4) min(-1)/(microU/ml) (2.65 +/- 0.4 to 4.15 +/- 0.5 x 10(-5) min(-1)/pM); P < 0.001], whereas both AIRg [63.4 +/- 13.4 to 51.0 +/- 10.7 microU/ml (380 +/- 80 to 306 +/- 64 pM); P < 0.05] and AIRmax [314 +/- 31.4 to 259.9 +/- 33.4 microU/ml (1886 +/- 188 to 1560 +/- 200 pM); P < 0.05] decreased. Overall beta-cell function improved (SI x AIRg, 9.63 +/- 2.28 to 12.78 +/- 2.58 x 10(-3) min(-1), P < 0.05; and SI x AIRmax, 51.01 +/- 9.2 to 72.69 +/- 13.4 x 10(-3) min(-1), P < 0.05). Thus, the weight loss-associated improvements in both insulin sensitivity and beta-cell function may explain the beneficial effects of a lifestyle intervention on delaying the development of diabetes in older subjects.
authors.affiliation: Department of Medicine, Veterans Affairs Puget Sound Health Care System and Harborview Medical Center, University of Washington, Seattle, Washington 98108, USA. kutzschn@u.washington.edu
authors.forename: Kristina M
authors.initials: KM
authors.lastname: Utzschneider
authors.forename: Darcy B
authors.initials: DB
authors.lastname: Carr
authors.forename: Suzanne M
authors.initials: SM
authors.lastname: Barsness
authors.forename: Steven E
authors.initials: SE
authors.lastname: Kahn
authors.forename: Robert S
authors.initials: RS
authors.lastname: Schwartz
mesh_terms: D000367:Age Factors; D000368:Aged; D001120:Arginine / Q000008:administration & dosage; D001786:Blood Glucose; D001823:Body Composition; D003924:Diabetes Mellitus, Type 2 / Q000517:prevention & control*; D004038:Diet, Reducing; D006801:Humans; D007328:Insulin / Q000097:blood / Q000378:metabolism; D007333:Insulin Resistance; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D008019:Life Style; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000178:diet therapy* / Q000503:physiopathology; D015431:Weight Loss / Q000502:physiology*
chemical_list: D001786:Blood Glucose; D007328:Insulin; D001120:Arginine