Previous data has demonstrated that aging impedes the ability of skeletal muscle to adapt to repetitive stretch-shortening cycle (SSC) exercise. Our lab has hypothesized that oxidative stress may impair the resolution capacity of the inflammatory process and participate in the observed mal-adaptation in aged-skeletal muscle.
PURPOSE: To determine if two different dietary antioxidant regimens improve the ability of aged skeletal muscle to adapt to chronic-S SC exercise training.
METHODS: Nine Fischer 344 x Brown Norway rats (30 months) were randomly assigned to a Vitamin C (2% by weight) & E (30,000 I. U.) supplemented group (N = 4) or Curcumin group (1% by weight) (N = 5). Dorsiflexor muscles of the left limb in all animals were exposed 3 times per week for 4.5 weeks to a protocol of 80 maximal SSCs per exposure in vivo (14 total exposures). Twenty four hours following the final exposure rats were weighed, anesthetized and exsanguinated. The left (exercised) and right (non-exercised) tibialis anterior muscles were excised, weighed, sectioned, quick-frozen, and stored at −80°C. Transverse sections (12 μm) were cut, mounted on pre-coated microscope slides, and stained using a routine procedure with H&E. Stereological methods, consisting of point and intercept counts from tissue sections (evaluated on a Leica DMLB microscope at 40x magnification), were used to quantify the degree of inflammation, myofiber degeneration and modifications to the interstitial space in muscle from each group.
RESULTS: Stereological analyses from Vitamin C & E or Curcumin supplementation revealed that there were no changes in the volume density of normal myofibers or the presence of degenerative myofibers or cellular infiltrates resulting from repetitive-SSC exercise. However, there was a significant increase in the volume density of non-cellular interstitium, indicative of edema, in the exercised limb of the Curcumin-treated animals compared to the non-exercised limb (p<0.05); no such change was evident in the Vitamin C & E supplemented group. In contrast, a recent study from our lab that employed the same experimental protocol to unsupplemented young and aged animals demonstrated a significant increase in the volume density of cellular interstitium in aged-skeletal muscle only; this was indicative of latent inflammation.
CONCLUSIONS: Antioxidant supplementation appears to maintain (possibly even augment) the adaptive profile in aged-skeletal muscle exposed to repetitive-SSC exercise. This seems to be accomplished by buffering oxidative stress and allowing for an internal-cellular environment capable of resolving the inflammatory process.