Abstract
Insulin resistance increases and muscle oxidative capacity decreases during aging, but lifestyle changes-especially physical activity-may reverse these trends. Here we report the effect of a 16-week aerobic exercise program (n = 65) or control activity (n = 37) performed by men and women aged 21-87 years on insulin sensitivity and muscle mitochondria. Insulin sensitivity, measured by intravenous glucose tolerance test, decreased with age (r = -0.32) and was related to abdominal fat content (r = -0.65). Exercise increased peak oxygen uptake (VO(2peak); 10%), activity of muscle mitochondrial enzymes (citrate synthase and cytochrome c oxidase, 45-76%) and mRNA levels of mitochondrial genes (COX4, ND4, both 66%) and genes involved in mitochondrial biogenesis (PGC-1alpha, 55%; NRF-1, 15%; TFAM, 85%). Exercise also increased muscle GLUT4 mRNA and protein (30-52%) and reduced abdominal fat (5%) and plasma triglycerides (25%). None of these changes were affected by age. In contrast, insulin sensitivity improved in younger people but not in middle-aged or older groups. Thus, the muscle mitochondrial response to 4 months of aerobic exercise training was similar in all age-groups, although the older people did not have an improvement in insulin sensitivity.
Publication types
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Clinical Trial
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Randomized Controlled Trial
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Adult
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Aged
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Aged, 80 and over
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Aging / physiology*
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Blood Glucose
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Body Composition
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Citrate (si)-Synthase / genetics
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DNA-Binding Proteins / genetics
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Diabetes Mellitus, Type 2 / physiopathology
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Diabetes Mellitus, Type 2 / prevention & control
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Exercise / physiology*
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Female
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Gene Expression
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Glucose Intolerance / physiopathology
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Glucose Intolerance / prevention & control*
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Glucose Transporter Type 4
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Humans
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Insulin / blood
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Insulin Resistance / physiology*
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Lipids / blood
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Male
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Middle Aged
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Mitochondria / enzymology
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Mitochondrial Proteins*
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Monosaccharide Transport Proteins / genetics
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Muscle Proteins*
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Muscle, Skeletal / metabolism*
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NF-E2-Related Factor 1
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Nuclear Proteins / genetics
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Nuclear Respiratory Factor 1
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Nuclear Respiratory Factors
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Oxidation-Reduction
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Prostaglandin-Endoperoxide Synthases / genetics
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Trans-Activators / genetics
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Transcription Factors / genetics
Substances
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Blood Glucose
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DNA-Binding Proteins
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Glucose Transporter Type 4
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Insulin
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Lipids
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Mitochondrial Proteins
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Monosaccharide Transport Proteins
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Muscle Proteins
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NF-E2-Related Factor 1
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NRF1 protein, human
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Nuclear Proteins
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Nuclear Respiratory Factor 1
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Nuclear Respiratory Factors
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SLC2A4 protein, human
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TFAM protein, human
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Trans-Activators
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Transcription Factors
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mitochondrial transcription factor A
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peroxisome-proliferator-activated receptor-gamma coactivator-1
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Prostaglandin-Endoperoxide Synthases
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Citrate (si)-Synthase