title: S(G), S(I), and EGP of exercise-trained middle-aged men estimated by a two-compartment labeled minimal model.
abstract: To examine the effects of physical training on glucose effectiveness (S(G)), insulin sensitivity (S(I)), and endogenous glucose production (EGP) in middle-aged men, stable-labeled frequently sampled intravenous glucose tolerance tests (FSIGTT) were performed on 11 exercise-trained middle-aged men and 12 age-matched sedentary men. The time course of EGP during the FSIGTT was estimated by nonparametric stochastic deconvolution. Glucose uptake-specific indexes of glucose effectiveness (S(2*)(G) x 10(2): 0.81 +/- 0.08 vs. 0.60 +/- 0.05 dl. min(-1). kg(-1), P < 0.05) and insulin sensitivity [S(2*)(I) x 10(4): 24.59 +/- 2.98 vs. 11.89 +/- 2.36 dl. min(-1). (microU/ml)(-1). kg(-1), P < 0.01], which were analyzed using the two-compartment minimal model, were significantly greater in the trained group than in the sedentary group. Plasma clearance rate (PCR) of glucose was consistently greater in the trained men than in sedentary men throughout FSIGTT. Compared with sedentary controls, EGP of trained middle-aged men was higher before glucose load. The EGP of the two groups was similarly suppressed by approximately 70% within 10 min, followed by an additional suppression after insulin infusion. EGP returned to basal level at approximately 60 min in the trained men and at 100 min in the controls, followed by its overshoot, which was significantly greater in the trained men than in the controls. In addition, basal EGP was positively correlated with S(2*)(G) . The higher basal EGP and greater EGP overshoot in trained middle-aged men appear to compensate for the increased insulin-independent (S(2*)(G)) and -dependent (S(2*)(I)) glucose uptake to maintain glucose homeostasis.
authors.affiliation: Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya 464-8601, 814-0180 Japan.
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Nishida
authors.forename: Kumpei
authors.initials: K
authors.lastname: Tokuyama
authors.forename: Shoichiro
authors.initials: S
authors.lastname: Nagasaka
authors.forename: Yasuki
authors.initials: Y
authors.lastname: Higaki
authors.forename: Kanta
authors.initials: K
authors.lastname: Fujimi
authors.forename: Akira
authors.initials: A
authors.lastname: Kiyonaga
authors.forename: Munehiro
authors.initials: M
authors.lastname: Shindo
authors.forename: Ikuyo
authors.initials: I
authors.lastname: Kusaka
authors.forename: Tomoatsu
authors.initials: T
authors.lastname: Nakamura
authors.forename: San-E
authors.initials: SE
authors.lastname: Ishikawa
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Saito
authors.forename: Orie
authors.initials: O
authors.lastname: Nakamura
authors.forename: Yuzo
authors.initials: Y
authors.lastname: Sato
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Tanaka
mesh_terms: D000328:Adult; D003903:Deuterium; D015444:Exercise / Q000502:physiology*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005947:Glucose / Q000096:biosynthesis* / Q000493:pharmacokinetics*; D005951:Glucose Tolerance Test; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D007333:Insulin Resistance / Q000502:physiology; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D010809:Physical Fitness / Q000502:physiology
chemical_list: D005230:Fatty Acids, Nonesterified; D003903:Deuterium; D005947:Glucose