Studies investigating the distinct effects of estradiol deficiency and aging on the redox system of skeletal muscle as it relates to strength and power

Abstract

Aging results in a loss of skeletal muscle strength. This decline is further augmented by low levels of ovarian hormones in females, such as experienced following menopause. Power is arguably more critical to muscle function than is maximal strength, yet the impact of and mechanisms whereby aging and hormones impact muscle power are largely unknown. The studies of this dissertation utilize mouse models to investigate the impact of aging and removal of ovarian hormones on skeletal muscle maximal power and submaximal strength. The results of these studies are the first to convincingly demonstrate that ovarian hormones provide similar input to skeletal muscle function during adulthood and aging in females. This work lends further evidence for a critical transition in skeletal muscle function between 24 and 28 months of age in mice. Additionally, these dissertation studies reveal impacts of both aging and ovarian hormones on redox balance (oxidative stress levels and antioxidant system response) in skeletal muscle. Oxidative damage to contractile proteins of skeletal muscle increases with aging, and removal of ovarian hormones has a similar effect. It is speculated the increase in damage is a result of the decline in protein expression of key antioxidants, such as superoxide dismutase and glutathione peroxidase, that occurs with aging and when ovarian hormones are absent. Taken together, the results of this dissertation are suggestive of an important role of ovarian hormones in maintaining redox balance in skeletal muscle, particularly during aging in females. Further studies investigating methods to mitigate age-related changes are warranted.