Age-related changes in skeletal muscle composition: A pilot nuclear magnetic resonance spectroscopy study in mice

The composition of skeletal muscle was investigated in the quadriceps and gastrocnemius muscle of 13-month-old (n = 15) and 23-month-old (n = 19) mice by means of high-resolution nuclear magnetic resonance (NMR) spectroscopy. Muscle specimens were dissected out, frozen in liquid nitrogen and extracted in chloroform/methanol, and proton NMR spectra of the resulting aqueous and organic fractions were obtained at 600 MHz. Several metabolites were unambiguously identified and quantified. Multivariate ANOVA (factor: age, muscle, age × muscle) showed a significant main effect of age (P = 0.031) on the amount of muscle metabolites, suggesting that the aging process affects the composition of skeletal muscle. Univariate tests showed significant differences for lactate, acetate, taurine, and uridine in 13- and 23-month-old mice. A trend for the effect of muscle (quadriceps vs. gastrocnemius; P = 0.128) was also found. No significant muscle x age interaction was present. When the same data were used in principal component analysis, the first two principal components separated muscles (quadriceps and gastrocnemius) and ages (13- and 23-month-old), explaining 66.7% of total variance. The results of this pilot study show that high-resolution NMR spectroscopy is able to detect age-associated changes in skeletal muscle metabolites, thereby paving the way to future detailed metabolomics investigation in sarcopenia of aging.