Muscle fat oxidative capacity is not impaired by age but by physical inactivity: association with insulin sensitivity. 2004

Virginie Rimbert, and Yves Boirie, and Mario Bedu, and Jean-François Hocquette, and Patrick Ritz, and Béatrice Morio
Protein and Energy Metabolism Research Unit, Auvergne University, Human Nutrition Research Centre of Auvergne, Clermont-Ferrand, France.

The study aimed at determining whether aging and/or sedentariness impairs muscle fat oxidative capacity (OXFA) and whether this was associated with increased risk to develop insulin resistance. We first examined muscle mitochondrial functions, OXFA and insulin sensitivity (ISI; evaluated during an oral glucose tolerance test) in a cross-sectional study with 32 sedentary (S) and endurance-trained (T), young (Y) and elderly (E) men (24.2+/-2.6 vs. 66.6+/-3.2 yr). As for mitochondrial functions, OXFA was higher in T than in S but similar between age groups (SY 41.8+/-11.3, TY 68.0+/-17.7, SE 40.1+/-14.1, TE 73.1+/-20.1 palmitate x min(-1) x g wet tissue(-1); activity P<0.0001, age P=NS, activity x age P=NS). Similar results were obtained with ISI (SY 6.2+/-2.2, TY 11.4+/-4.4, SE 5.9+/-1.5, TE 11.0+/-3.5, activity P<0.001, age P=NS, activity x age P=NS). Stepwise regression showed that, among body composition, VO2max and muscle biochemical characteristics, OXFA was the main predictor of ISI (r=0.60, P<0.001). We subsequently showed in eight sedentary elderly subjects (63.5+/-3.3 yr) that OXFA and insulin sensitivity (measured using insulin clamp) improved in parallel after 8 weeks of endurance training (r=0.79, P<0.01). We concluded that mitochondrial functions, OXFA and ISI, are not impaired by age but by physical inactivity and are closely correlated.

UI MeSH Term Description Entries
D007328 Insulin A 51-amino acid pancreatic hormone that plays a major role in the regulation of glucose metabolism, directly by suppressing endogenous glucose production (GLYCOGENOLYSIS; GLUCONEOGENESIS) and indirectly by suppressing GLUCAGON secretion and LIPOLYSIS. Native insulin is a globular protein comprised of a zinc-coordinated hexamer. Each insulin monomer containing two chains, A (21 residues) and B (30 residues), linked by two disulfide bonds. Insulin is used as a drug to control insulin-dependent diabetes mellitus (DIABETES MELLITUS, TYPE 1). Iletin,Insulin A Chain,Insulin B Chain,Insulin, Regular,Novolin,Sodium Insulin,Soluble Insulin,Chain, Insulin B,Insulin, Sodium,Insulin, Soluble,Regular Insulin
D007333 Insulin Resistance Diminished effectiveness of INSULIN in lowering blood sugar levels: requiring the use of 200 units or more of insulin per day to prevent HYPERGLYCEMIA or KETOSIS. Insulin Sensitivity,Resistance, Insulin,Sensitivity, Insulin
D008928 Mitochondria Semiautonomous, self-reproducing organelles that occur in the cytoplasm of all cells of most, but not all, eukaryotes. Each mitochondrion is surrounded by a double limiting membrane. The inner membrane is highly invaginated, and its projections are called cristae. Mitochondria are the sites of the reactions of oxidative phosphorylation, which result in the formation of ATP. They contain distinctive RIBOSOMES, transfer RNAs (RNA, TRANSFER); AMINO ACYL T RNA SYNTHETASES; and elongation and termination factors. Mitochondria depend upon genes within the nucleus of the cells in which they reside for many essential messenger RNAs (RNA, MESSENGER). Mitochondria are believed to have arisen from aerobic bacteria that established a symbiotic relationship with primitive protoeukaryotes. (King & Stansfield, A Dictionary of Genetics, 4th ed) Mitochondrial Contraction,Mitochondrion,Contraction, Mitochondrial,Contractions, Mitochondrial,Mitochondrial Contractions
D010084 Oxidation-Reduction A chemical reaction in which an electron is transferred from one molecule to another. The electron-donating molecule is the reducing agent or reductant; the electron-accepting molecule is the oxidizing agent or oxidant. Reducing and oxidizing agents function as conjugate reductant-oxidant pairs or redox pairs (Lehninger, Principles of Biochemistry, 1982, p471). Redox,Oxidation Reduction
D003430 Cross-Sectional Studies Studies in which the presence or absence of disease or other health-related variables are determined in each member of the study population or in a representative sample at one particular time. This contrasts with LONGITUDINAL STUDIES which are followed over a period of time. Disease Frequency Surveys,Prevalence Studies,Analysis, Cross-Sectional,Cross Sectional Analysis,Cross-Sectional Survey,Surveys, Disease Frequency,Analyses, Cross Sectional,Analyses, Cross-Sectional,Analysis, Cross Sectional,Cross Sectional Analyses,Cross Sectional Studies,Cross Sectional Survey,Cross-Sectional Analyses,Cross-Sectional Analysis,Cross-Sectional Study,Cross-Sectional Surveys,Disease Frequency Survey,Prevalence Study,Studies, Cross-Sectional,Studies, Prevalence,Study, Cross-Sectional,Study, Prevalence,Survey, Cross-Sectional,Survey, Disease Frequency,Surveys, Cross-Sectional
D005223 Fats The glyceryl esters of a fatty acid, or of a mixture of fatty acids. They are generally odorless, colorless, and tasteless if pure, but they may be flavored according to origin. Fats are insoluble in water, soluble in most organic solvents. They occur in animal and vegetable tissue and are generally obtained by boiling or by extraction under pressure. They are important in the diet (DIETARY FATS) as a source of energy. (Grant & Hackh's Chemical Dictionary, 5th ed)
D005951 Glucose Tolerance Test A test to determine the ability of an individual to maintain HOMEOSTASIS of BLOOD GLUCOSE. It includes measuring blood glucose levels in a fasting state, and at prescribed intervals before and after oral glucose intake (75 or 100 g) or intravenous infusion (0.5 g/kg). Intravenous Glucose Tolerance,Intravenous Glucose Tolerance Test,OGTT,Oral Glucose Tolerance,Oral Glucose Tolerance Test,Glucose Tolerance Tests,Glucose Tolerance, Oral
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000328 Adult A person having attained full growth or maturity. Adults are of 19 through 44 years of age. For a person between 19 and 24 years of age, YOUNG ADULT is available. Adults
D000368 Aged A person 65 years of age or older. For a person older than 79 years, AGED, 80 AND OVER is available. Elderly

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