Not Aging but Calorie Restriction Strongly Affects Protein Oxidation in Heart and Brain Mitochondria

Aging is an inevitable consequence for all organisms. According to the mitochondrial free radical theory of aging (MFRTA), reactive oxygen species (ROS), which are predominantly generated in mitochondria, are assumed to play a key role. Calorie restriction (CR) delays aging by improving mitochondrial function; however, the molecular mechanisms underlying the effects of ROS and CR on mitochondria remain poorly understood. Oxidative protein modifications in mitochondrial proteins from the heart and cerebrum of young (6.5 months) and old (27 months) rats were quantified and the effects of short-term and lifelong CR interventions were investigated. Mass spectrometry was leveraged to achieve an unbiased and comprehensive analysis of various types of oxidative postranslational modifications (oxPTMs). Contrary to the MFRTA, aging did not cause significant increases in mitochondrial protein oxidation in the heart and cerebrum. CR markedly diminished the overall level of oxPTMs in the heart, particularly in transmembrane proteins. Similarly, the level of oxidative modification of transmembrane proteins in cerebrum was reduced by CR, whereas it perplexingly increased in mitochondrial proteins. The absolute level of oxidized mitochondrial protein was always higher in the heart than in the cerebrum under all conditions. Carbonylation, a prevalent marker of protein oxidation and aging, increased in the heart with age and was notably reduced by CR. However, this trend was not consistent in cerebrum or for some other types of oxPTMs. Therefore, protein oxidation in the heart and cerebrum exhibits distinct responses to chronological aging and dietary interventions, with the latter exerting a stronger influence.