Advanced glycation end-product accumulation and associated protein modification in type II skeletal muscle with aging.

One mechanism that may influence the quality of skeletal muscle proteins, and explain the age-related decline in contractility, is protein damage. Advanced glycation end-products (AGE) in vivo are useful biomarkers of damage. In this study, comparison of extensor digitorum longus (EDL) muscles from young (8 months), old (33 months), and very old (36 months) Fischer 344 Brown Norway F1 (F344BNF1) hybrid rats shows that muscles from the very old rats have a significantly higher percentage of myofibers that immunolabel intracellularly for AGE-antibody 6D12 compared to the younger age group. The AGE-modified proteins, determined in the semimembranosus muscles from young (9 months) and old (27 months) F344 rats, identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry include creatine kinase, carbonic anhydrase III, beta-enolase, actin, and voltage-dependent anion-selective channel 1. Moreover, there is a significant increase in AGE modification of beta-enolase with age. These results identify a common subset of proteins that contain AGE and suggest that metabolic proteins are targets for glycation with aging.