Effects of exercise training on glucose homeostasis: the HERITAGE Family Study.
ABSTRACT To determine the effect of a 20-week endurance training program in healthy, previously sedentary participants on measures derived from an intravenous glucose tolerance test (i.v.GTT).
An i.v.GTT was performed before and after a standardized training program in 316 women and 280 men (173 blacks and 423 whites). Participants exercised on cycle ergometers 3 days per week for 60 sessions. The exercise intensity was progressively increased from 55% VO2max for 30 min per session to 75% VO2max for 50 min per session.
Mean insulin sensitivity increased by 10% (P < 0.001) following the intervention, but the variability in the changes was high. Men had larger improvements than women (P = 0.02). Improvements in fasting insulin were transitory, disappearing 72 h after the last bout of exercise. There were also significant mean increases in the glucose disappearance index (3%, P = 0.02) and in glucose effectiveness (11%, P < 0.001), measures of glucose tolerance and of the capacity of glucose to mediate its own disposal, respectively. The acute insulin response to glucose, a measure of insulin secretion, increased by 7% in the quartile with the lowest baseline glucose tolerance and decreased by 14% in the quartile with the highest baseline glucose tolerance (P < 0.001). The glucose area below fasting levels during the i.v.GTT was reduced by 7% (P = 0.02).
Although the effects of structured regular exercise were highly variable, there were improvements in virtually all i.v.GTT-derived variables. In the absence of substantial weight loss, regular exercise is required for sustained improvements in glucose homeostasis.
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ABSTRACT: Objective. To document sex differences in the impact of the Mediterranean diet (MedDiet) on glucose/insulin homeostasis and to verify whether these sex-related effects were associated with changes in nonesterified fatty acids (NEFA). Methods. All foods were provided to 38 men and 32 premenopausal women (24-53 y) during 4 weeks. Variables were measured during a 180 min OGTT before and after the MedDiet. Results. A sex-by-time interaction for plasma insulin iAUC was found (men: -17.8%, P = 0.02; women: +9.4%, P = 0.63; P for sex-by-time interaction = 0.005). A sex-by-time interaction was also observed for insulin sensitivity (Cederholm index, P = 0.03), for which only men experienced improvements (men: +8.1%, P = 0.047; women: -5.9%, P = 0.94). No sex difference was observed for glucose and C-peptide responses. Trends toward a decrease in NEFA AUC (P = 0.06) and an increase in NEFA suppression rate (P = 0.06) were noted, with no sex difference. Changes in NEFA were not associated with change in insulin sensitivity. Conclusions. Results suggest that the more favorable changes in glucose/insulin homeostasis observed in men compared to women in response to the MedDiet are not explained by sex differences in NEFA response. This clinical trial is registered with clinicaltrials.gov NCT01293344.
Article: Diabetes, Sport und BewegungDiabetologie und Stoffwechsel 01/2015; 9(S 02):S196-S201. DOI:10.1055/s-0034-1385400 · 0.31 Impact Factor
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ABSTRACT: Regular exercise is associated with better mental health. This association is widely assumed to reflect causal effects of exercise. In this paper we propose that two additional mechanisms contribute to the association between exercise and mental health in the population-at-large: genetic pleiotropy and gene-by-exercise interaction. Both mechanisms assume heritability of exercise behavior and a partial overlap between the genes influencing exercise behavior and mental health. We review a number of large-scale studies in monozygotic and dizygotic twins that support these assumptions. Based on the importance of genetic factors in exercise behavior we develop a model for gene-by-exercise interaction that explains differences in voluntary exercise behavior by differential genetic sensitivity to the mental health benefits of exercise. We focus on the genetic modulation of acute mood effects of exercise and longer-term effects on self-esteem through genetic effects on exercise ability. If correct, our model calls for a change from ‘population-based’ to ‘personalized’ intervention strategies.Mental Health and Physical Activity 12/2008; 1(2):53-61. DOI:10.1016/j.mhpa.2008.09.005