Leucine Supplementation Exacerbates Atrophy In Cancer Cachectic Mice

Delayed aging in various tissues has been observed for Snell dwarf mice (Pit1) yet muscular performance has not been characterized for this model. PURPOSE: The purpose of the present study was to characterize muscle mass and performance for 3 months old and 12 months old Snell dwarf mice in non-trained and resistance-type trained states. METHODS: Muscles of Snell dwarf mice and their wild-type littermates were exposed to 1 month of stretch-shortening contraction training. RESULTS: For non-trained muscles at both ages, muscles of Snell dwarf mice exhibited 70% less mass and 85% less isometric force relative to those of control mice. At young age, training 3 days per week had no effect regardless of mouse strain. With aging, 3 days per week training decreased muscle mass and isometric force by 12% and 25%, respectively, for control mice while no such decreases were observed for Snell dwarf mice. For control mice, training 2 days per week increased isometric force by 20% at young age with no training-induced decrements with aging. CONCLUSIONS: While Snell dwarf mice exhibit a trade-off between longevity and muscular performance, the Pit1 mutation counters age-related maladaptation to training. For wild-type muscle, modulation of frequency is a means for offsetting the maladaptive training response.