Fig. 6.

Neuromuscular changes with age and chronic brain IGF-1 overexpression. a, b Chronic overexpression of brain IGF-1 profoundly attenuated the age-related decline in exercise performance in male HET3 mice (n = 11 Young Control males, n = 13 Old Control males, n = 13 Old bIGF-1 males) and tended to improve grip strength (P = 0.09, n = 11 Young Control males, n = 12 Old Control males, n = 13 Old bIGF-1 males). c, d In contrast, there was an age-related decline but no such benefit was noted for endurance or strength in Old bIGF-1 females (n = 12 Young Control females, n = 11 Old Control females, n = 11 Old bIGF-1 females). e–g Complex I activity (n = 8 Young Control males, n = 8 Old Control males, n = 8 Old bIGF-1 males) and VDAC protein expression in muscle of male mice showed no difference between groups (n = 7 Young Control males, n = 8 Old Control males, n = 8 Old bIGF-1 males), while citrate synthase levels were increased with age and restored to young control levels in old bIGF-1 mice. h–j In female muscle, citrate synthase showed no significant differences between groups, while Complex I activity was significantly decreased with age (n = 8 Young Control females, n = 9 Old Control females, n = 8 Old bIGF-1 females) and VDAC protein expression was significantly increased in bIGF-1 females, compared to age-matched controls (n = 8 Young Control females, n = 9 Old Control females, n = 6 Old bIGF-1 females). Bars represent mean ± SE. ns = not significant. Different letters denote a significant difference between groups, P ≤ 0.05