Fish oil speeds muscle recovery in aging rats, suggesting potential benefits for humans

New research suggests that fish oil supplements may accelerate muscle healing in aging rats and muscle cells, potentially offering a solution for quicker recovery from age-related muscle injuries in humans.

Study: Fish Oil Supplement Mitigates Muscle Injury In Vivo and In Vitro: A Preliminary Report. Image Credit: Fototocam / Shutterstock

In a recent study published in the journal Nutrients, researchers conducted in vitro (C2C12 mouse myoblast cells) and in vivo (using aged (22-month) and adult (8-month) Sprague Dawley rats) experiments to investigate fish oil supplements’ potential muscle healing benefits. Results revealed that aging significantly prolonged recovery periods in rat model systems, with older rats demonstrating much slower recovery than their younger counterparts.

Notably, fish oil supplementation (containing 45% eicosapentaenoic acid (EPA) and 10% docosahexaenoic acid (DHA) incorporated into the diet at a concentration of 33 g/kg) was shown to help mitigate the repair-retarding impacts of aging, with 78% of older fish oil-supplemented rats demonstrating comparable muscle healing speeds as their younger counterparts. In adult rats, there was a 20–25% reduction in muscle contractility 7 days post-injury, while aged control rats showed a 30–40% reduction. The results of the in vitro murine cell line experiments confirmed these findings and suggested that fish oil may enhance membrane resealing and repair, thereby contributing to accelerated healing.

Background

Despite older adults (OAs) comparatively lower participation in physically strenuous activity, they are prone to mechanical muscle injury during their routine exercise and mobility programs or regular day-to-day activities. Muscle contusions, colloquially known as ‘bruised muscles,’ are the most common injuries accompanying collisions and falls in OAs. Characterized as pain and swelling accompanying blunt force trauma to muscle fibers and connective tissue, the condition has historically received meager geriatric attention due to the latter’s focus on fall-related fractures.

Unfortunately, even in the absence of fractures, falls, and similar impacts can result in muscle contusions that may leave OAs with weeks or even months of pain and debilitation. Recent research has elucidated the duration of muscle healing (a few to several weeks) in younger adults. Despite the shortage of similar evidence in OAs, the effects of aging mechanisms in other organ systems alongside previous rat model system experiments by the current research team suggest that healing durations are prolonged in older cohorts.

Conventional contusion treatment involves the use of non-steroidal anti-inflammatory drugs (NSAIDs), primarily for the latter’s pain-suppressing properties. Unfortunately, the muscle-healing effects of NSAIDs have never been clinically validated, with some experts suggesting that the interventions may have counterproductive effects. Dietary supplements such as fish oils (FOs) have shown significant promise in reversing age-associated effects, with notable benefits linked to their anti-inflammatory and antioxidant properties. While their utility in muscle repair remains untested, previous studies have suggested their potential to improve musculoskeletal health.

“Incomplete recovery from muscle injury is a frequently reported consequence of old age and has been observed even if the degree of acute injury is equal. Muscle cells are exposed to regular mechanical injury during contraction and thus need a robust, rapid process to maintain sarcolemmal membrane integrity and maintain cell homeostasis. Key proteins involved in this repair process include dysferlin and TRIM72/MG53, whose inhibition can increase muscle degeneration and, in turn, fibrosis, thus impairing or slowing recovery.”

About the Study

The present study evaluates the effects of FO supplements on rats, focusing on their muscle recovery. Two differentially aged cohorts of Sprague Dawley rats were employed to simultaneously assess the impacts of aging on normal muscle recovery rates and to investigate if FO supplements can mitigate these effects. The “adult” cohort comprised eight individuals between 6-8 months, while the “aged” cohort comprised ten individuals aged 20 months. Each cohort was divided to contain similar representation across the case (FO intervention) and control (normal diet) subcohorts.

Rats were raised on their respective diets for eight weeks, following which they were anesthetized (using isoflurane), and the left hindlimb was intentionally injured for further procedures. Muscle injury was induced by dropping a weight onto the medial gastrocnemius muscle (MG). Grip strength was assessed in aged rats prior to injury, and contractility was measured on days 1 and 32 (grip strength) and day 7 following injury. Additionally, immunoblotting experiments using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and fluorescence microscopy were used to unravel the differences in protein profiles between injured and uninjured muscles.

For in vitro evaluations of FO’s muscle repair mechanisms, C2C12 mouse myoblast cell lines were used (‘case’ cell lines supplemented with different concentrations of FO extract). Muscle (herein ‘membrane’) injury was achieved using a FluoView FV1000 multi-photon confocal laser-scanning microscope.

Study Findings

Baseline grip testing results revealed no differences between aged cases and controls. However, during the 8-week-long experiment, significant declines in control rat grip strength (prior to injury) were observed, versus no observed decline in case rats. Muscle contractility experiments (day 7) revealed the most rapid recovery in adult rats, with aged rats on FO-supplemented diets being nearly statistically indistinguishable from their younger counterparts. In contrast, control diet rats were observed to lag the other cohorts significantly in muscle recovery.

All three incubation dosages (1 µg/mL, 10 µg/mL, 20 µg/mL) were observed to enhance membrane repair in injured C2C12 cells. While cells incubated in 10 µg/mL of FO-supplemented medium healed faster than those incubated in 1 µg/mL, no additional benefit was observed between 20 µg/mL and 10 µg/mL, suggesting a plateau in the effect.

Conclusions

The present study highlights the muscle-healing potential of fish oil supplements, which were observed to hasten muscle recovery in both in vivo aged rat models and in vitro C2C12 cells. Study findings further confirmed age-associated declines in muscle recovery speed in rats but encouragingly observed the protective effects of FO supplements in mitigating these declines.

“These data suggest that fish oil may promote recovery from mechanical injury by enhancing membrane repair processes, involving key proteins such as dysferlin and TRIM72/MG53, though other effects of FO may be at work. Further study of these phenomena is needed to better understand the potential benefits of FO for aging muscle.”