Dietary fish oil supplement induces age-specific contractile and proteomic responses in muscles of male rats

Proteomes of aging and omega-3 supplementation in rat soleus skeletal muscle

Aging is a pan-organ process with an intricate and multimodal nature. Deciphering the aging phenomenon is complex, yet recent attention is analyzing the potential benefits of non-invasive life adjustments to achieve healthy aging. Omega-3 polyunsaturated fatty acids (FA) have emerged as promising nutraceuticals for a plethora of different medical conditions. In the current study we conducted an in-depth, bottom-up, global, shotgun proteomic study (LC-MS/MS) investigating both the effects of aging on skeletal muscle and the potential alterations due to ω-3 FA. Sprague Dawley rats were fed different diets and divided into four groups (n = 5 per group): adult controls (7-8 months, ADCTL); aged controls (22 months, AGCTL); and adult (ADω3) and aged (AGω3) rats fed an ω-3 supplemented diet. Among the identified 30,000 soleus proteins, our proteomic analysis identified 149 proteins differentially expressed in aging; 207 proteins with aging, but fed ω-3 FA; and 105 and 26 proteins, respectively, when aged and adult rats were fed ω-3 FA. Aging alone (ADCTL/AGCTL) affects many processes: carbohydrate and lipid metabolisms, proteostasis, mRNA processing and sarcomeric proteins. With FA supplementation and aging (ADω3/AGω3) similar processes were affected, but increased chromatin-related protein abundances (methylation or histone deacetylation) were observed in AGω3; while proteins involved in OXPHOS and mitochondrial homeostasis, including mTOR, were more represented in ADω3 rats. Supplementation with FA had a greater effect in aged rats (AGCTL/AGω3) than in adult ones (ADCTL/ADω3). In the ADCTL/ADω3 comparison, modest changes were seen, whereas in the AGCTL/AGω3 comparisons DNA damage repair increased and protein synthesis and degradation were observed. Further, a potential link to enhancement of myogenesis is also evident. The data presented in this work suggest potential beneficial and protective effects of ω3 FA supplementation in the soleus muscle, as well as some potential molecular mechanisms of action.

Synergistic Effects of Omega-3 Fatty Acids and Physical Activity on Oxidative Stress Markers and Antioxidant Mechanisms in Aged Rats

BACKGROUND

Aging induces degenerative processes in the body, contributing to the onset of various age-associated diseases that affect the population. Inadequate dietary habits and low physical activity are major contributors to increased morbidity during aging. This study aimed to investigate the combined effects of omega-3 fatty acid supplementation and physical activity on the markers of oxidative stress and antioxidant defense mechanisms in aged male Wistar rats (23-24 months).

METHODS

The rats were randomly divided into four experimental groups: a sedentary control (placebo, no exercise), a trained (placebo and moderate-intensity graded aerobic exercise; Ex), and two trained groups supplemented with low (160 mg/kg of body weight; O1 + Ex) and high (320 mg/kg of body weight; O2 + Ex) doses of omega-3 fatty acids. The biochemical and functional parameters related to sarcopenia and the markers of oxidative stress were measured in blood and gastrocnemius muscle.

RESULTS

The results demonstrated dose-dependent, synergistic effects of omega-3 fatty acid supplementation and physical activity. The higher dose (320 mg/kg of body weight) improved plasma antioxidant capacity (TEAC, +21.01%, p < 0.01) and GPx activity (+78.05%, p < 0.05) while reducing CAT activity in erythrocytes (-19.92%, p < 0.05), likely as an adaptive stress response. Combined interventions also normalized cholesterol levels, improved the functional parameters of sarcopenia (stride length, +14.82%, p < 0.001), and enhanced antioxidant protection in aged rats.

CONCLUSIONS

These findings highlight the potential of combining omega-3 fatty acid supplementation and physical activity to counteract aging-related degenerative changes. Further research is needed to elucidate the underlying mechanisms and evaluate the long-term benefits of these strategies in aging populations.

Fish Oil Supplement Mitigates Muscle Injury In Vivo and In Vitro: A Preliminary Report

Background: Following injury, older adults exhibit slow recovery of muscle function. Age-related impairment of sarcolemmal membrane repair may contribute to myocyte death, increasing the need for myogenesis and prolonging recovery. Dietary fish oil (FO) is a common nutritional supplement that may alter plasma membrane composition to enhance the response to membrane injury. Methods: We assessed effects of an 8-week dietary intervention on muscle contractile recovery in aged (22 mo.) rats on control (n = 5) or FO (control + 33 g/kg FO (45% eicosapentaenoic acid; 10% docosahexaenoic acid); n = 5) diets 1-week after contusion injury, as well as adult (8 mo., n = 8) rats on the control diet. Results: Recovery was reduced in aged rats on the control diet vs. adults (63 vs. 80%; p = 0.042), while those on the FO diet recovered similarly to (78%) adults. To directly assess sarcolemma injury, C2C12 cells were cultured in media with and without FO (1, 10, and 100 μg/mL; 24 or 48 h) and injured with an infrared laser in medium containing FM4-64 dye as a marker of sarcolemmal injury. FO reduced the area under the FM4-64 fluorescence-time curve at all concentrations after both 24 and 48 h supplementation. Conclusions: These preliminary data suggest FO might aid recovery of muscle function following injury in older adults by enhancing membrane resealing and repair.

Potential of Fatty Acids in Treating Sarcopenia: A Systematic Review

This paper presents a systematic review of studies investigating the effects of fatty acid supplementation in potentially preventing and treating sarcopenia. PubMed, Embase, and Web of Science databases were searched using the keywords 'fatty acid' and 'sarcopenia'. Results: A total of 14 clinical and 11 pre-clinical (including cell and animal studies) studies were included. Of the 14 clinical studies, 12 used omega-3 polyunsaturated fatty acids (PUFAs) as supplements, 1 study used ALA and 1 study used CLA. Seven studies combined the use of fatty acid with resistant exercises. Fatty acids were found to have a positive effect in eight studies and they had no significant outcome in six studies. The seven studies that incorporated exercise found that fatty acids had a better impact on elderlies. Four animal studies used novel fatty acids including eicosapentaenoic acid, trans-fatty acid, and olive leaf extraction as interventions. Three animal and four cell experiment studies revealed the possible mechanisms of how fatty acids affect muscles by improving regenerative capacity, reducing oxidative stress, mitochondrial and peroxisomal dysfunctions, and attenuating cell death. Conclusion: Fatty acids have proven their value in improving sarcopenia in pre-clinical experiments. However, current clinical studies show controversial results for its role on muscle, and thus the mechanisms need to be studied further. In the future, more well-designed randomized controlled trials are required to assess the effectiveness of using fatty acids in humans.

Analysis of fatty acid composition and sensitivity to dietary n-3 PUFA intervention of mouse n-3 PUFA-enriched tissues/organs

PURPOSE

n-3 polyunsaturated fatty acids (PUFAs), docosahexaenoic acid (DHA; C22:6 n3) and eicosapentaenoic acid (EPA; C20:5 n3), are of concern for their health-promoting effects such as anti-inflammatory, but the tissue selectivity for n-3 PUFA (i.e., which tissues and organs are rich in n-3 PUFA) is still not well known. In addition, it is unclear which tissues and organs are more sensitive to n-3 PUFA intervention. These unresolved issues have greatly hindered the exploring of the health benefits of n-3 PUFA.

METHODS

Twenty-four 7-week-old male C57BL/6 J mice were assigned to the control, fish oil, DHA, and EPA groups. The last three groups were given a 4-week oral intervention of fatty acids in ethyl ester (400 mg/kg bw). The fatty acid profiles in 27 compartments were determined by gas chromatography.

RESULTS

The proportion of long-chain n-3 PUFA (the total relative percentage of EPA, DPA n3, and DHA) was analyzed. Eight tissues and organs, including the brain (cerebral cortex, hippocampus, hypothalamus) and peripheral organs (tongue, quadriceps, gastrocnemius, kidney, and heart) were determined as being n-3 PUFA-enriched tissues and organs, owing to their high n-3 PUFA levels. The highest n-3 PUFA content was observed in the tongue for the first time. Notably, the content of linoleic acid (LA; C18:2 n6c) in peripheral organs was observed to be relatively high compared with that in the brain. Interestingly, the proportions of EPA in the kidney, heart, quadriceps, gastrocnemius, and tongue increased more markedly after the EPA intervention than after the DHA or fish oil intervention. As expected, the levels of proinflammatory arachidonic acid (AA; C20:4 n6) in the kidney, quadriceps, and tongue were markedly decreased after the three dietary interventions.

CONCLUSION

Peripheral tissues and organs, including the tongue, quadriceps, gastrocnemius, kidney, and heart, besides the brain, showed obvious tissue selectivity for n-3 PUFA. In the whole body of mice, the tongue exhibits the strongest preference for n-3 PUFA, with the highest proportion of n-3 PUFA. Moreover, these peripheral tissues and organs, especially the kidney, are more sensitive to dietary EPA administration in comparison with the brain.

Omega-3 fatty acids and human skeletal muscle

PURPOSE OF REVIEW

To examine recent findings related to the influence of omega-3 (ω-3) fatty acid supplementation on skeletal muscle anabolism with a particular focus on situations of skeletal muscle disuse.

RECENT FINDINGS

Skeletal muscle disuse results in a reduction in fed and fasted rates of skeletal muscle protein synthesis leading to the loss of skeletal muscle mass. Recent evidence has suggested that supplementation with ω-3 fatty acids during a period of skeletal muscle disuse increases the ω-3 fatty acid composition of skeletal muscle membranes, heightens rates of skeletal muscle protein synthesis, and protects against skeletal muscle loss. The protective effects of ω-3 fatty acids towards skeletal muscle during disuse appear to be related to changes in mitochondrial bioenergetics suggesting crosstalk between mitochondria and the regulation of skeletal muscle protein synthesis.

SUMMARY

ω-3 fatty acid ingestion is a potential preventive therapy to combat skeletal muscle-disuse atrophy but additional, appropriately powered randomized controlled trials are now needed in a range of populations before firm conclusions can be made.