Exercise training eliminates age-related differences in skeletal muscle insulin receptor and IRS-1 abundance in rats

Insulin resistance is common in old age, and exercise training can improve insulin sensitivity. The purpose of this study was to determine the influen ce of age (6 vs 26 months) and exercise training (10 weeks of treadmill run ning) on insulin signaling protein abundance in skeletal muscle from male F isher 344 rats. Muscle levels of insulin receptor (IR), insulin receptor su bstrate-1 (IRS-1), phosphatidylinositol 3-kinase (P13K), and Akt1, a serine -threonine kinase, were determined. IRS-1 was reduced with aging, IR and P1 3K abundance was greater in old rats, and Akt1 was unchanged. IRS-1 was inc reased by training in old but not young rats, and IR was increased by train ing in young but not old rats. P13K tended to increase and Akt1 did not cha nge with training, regardless of age. Aging does not uniformly affect insul in signaling protein abundance, and exercise differentially alters IR and I RS-1 in young and old rats, thereby eliminating age-related differences in these proteins.