Effect of acute muscle contusion injury, with and without dietary fish oil, on adult and aged male rats: contractile and biochemical responses.

AIM: Contusion injury in aging muscle has not been studied in detail, but older adults are at risk for such injuries due to increased risk of falls. As falls in older populations are unlikely to be eliminated, interventions to minimize the negative impact of falls, including contusion injury should be pursued. Dietary fish oil (FO) is a common often supplement in older adults, which is associated with factors that might reduce or worsen the negative impact of contusion. METHODS: Here, we investigate whether 8 weeks of FO can blunt the impact of contusion injury in adult (n = 14) and aged (n = 12) rats. We assessed contractility and several biochemical markers in adult and aged gastrocnemius muscles 48 h post-contusion injury, using the uninjured muscles as controls. RESULTS: Injury reduced force production ~40% (P < 0.001), sarcoplasmic reticulum calcium release by ~20% (P = 0.003) and significantly increased several markers of muscle damage (i.e., protein carbonyls, Grp78 abundance (P = 0.022, 0.006, respectively)), and these injury-related changes were not affected by aging. The effects of FO were limited. A main effect (P = 0.018) for FO to increase the myogenic factor Myf5 was observed. In addition FO reduced the injury-associated decline in the mitophagy factor DRP1 (P = 0.027). CONCLUSION: Although age-related differences in certain protein markers differed, aged muscles exhibited no greater acute functional deficits following injury. Similarly, while FO did not reduce functional deficits, it did not worsen them. However, changes in Myf5 and DRP1 with dietary FO suggest the potential to improve recovery from contusion injury, which should be investigated in future studies.