Protein carbonylation and heat shock proteins in human skeletal muscle: relationships to age and sarcopenia

Abstract

Aging is associated with a gradual loss of muscle mass termed sarcopenia, which has significant impact on quality-of-life. Because oxidative stress is proposed to negatively impact upon musculoskeletal aging, we investigated links between human aging and markers of oxidative stress, and relationships to muscle mass and strength in young and old nonsarcopenic and sarcopenic adults. Sixteen young and 16 old males (further subdivided into "old" and "old sarcopenic") were studied. The abundance of protein carbonyl adducts within skeletal muscle sarcoplasmic, myofibrillar, and mitochondrial protein subfractions from musculus vastus lateralis biopsies were determined using Oxyblot immunoblotting techniques. In addition, concentrations of recognized cytoprotective proteins (eg, heat shock proteins [HSP], αβ-crystallin) were also assayed. Aging was associated with increased mitochondrial (but not myofibrillar or sarcoplasmic) protein carbonyl adducts, independently of (stage-I) sarcopenia. Correlation analyses of all subjects revealed that mitochondrial protein carbonyl abundance negatively correlated with muscle strength ([1-repetition maximum], p = .02, r (2) = -.16), but not muscle mass (p = .13, r (2) = -.08). Abundance of cytoprotective proteins, including various HSPs (HSP 27 and 70), were unaffected by aging/sarcopenia. To conclude, these data reveal that mitochondrial protein carbonylation increases moderately with age, and that this increase may impact upon skeletal muscle function, but is not a hallmark of (stage-I) sarcopenia, per se.

Keywords: Carbonylation; Heat shock protein.; Mitochondria; Sarcopenia.

Figure 1.

Purity of protein subfractions. Immunoblot representing the relative purity of mitochondrial (A), myofibrillar (B), and sarcoplasmic (C) preparations.

Figure 2.

Immunochemical detection of protein carbonyls from vastus lateralis muscle of young (Y), old (O), and old sarcopenic (OS) groups: (A) sarcoplasmic fraction, (B) myofibrillar fraction, and (C) mitochondrial fraction. Data are measured in arbitrary units, measured as the ratio between the optical density (OD) obtained from the whole lane of the protein and the OD of Coomassie stain. Representative samples are shown. Values are presented as means ± SEM.

Figure 3.

Mitochondrial carbonylation. Grouped old (O) + old sarcopenic (OS) versus young (Y) protein carbonylation data from the mitochondrial fractions. Values are presented as means ± SEM; *Indicates p ≤ .05.

Figure 4.

Correlation analysis between mitochondrial protein carbonyls and muscle mass (A) and strength (B). Circles indicate young (Y) subjects, filled triangles old (O) subjects, and empty triangles represent old sarcopenic (OS) subjects.

Figure 5.

Immunochemical detection of heat shock protein (HSP) expression in muscle of young, old, and old sarcopenic subjects at rest. (A) HSPs analyzed in sarcoplasmic protein fraction and (B) HSPs from myofibrillar protein fraction. Data are measured in arbitrary units, measured as the ratio between the optical density (OD) of marker protein and the OD of pan actin. Representative samples are shown. Values are presented as means ± SEM.