Abstract
Omega‐3 polyunsaturated fatty acids (PUFAs) have unique properties purported to influence several aspects of metabolism, including energy expenditure and protein function. Supplementing with n‐3 PUFAs may increase whole‐body resting metabolic rate (RMR), by enhancing Na+/K+ ATPase (NKA) activity and reducing the efficiency of sarcoplasmic reticulum (SR) Ca2+ ATPase (SERCA) activity by inducing a Ca2+ leak‐pump cycle. The purpose of this study was to examine the effects of fish oil (FO) on RMR, substrate oxidation, and skeletal muscle SERCA and NKA pump function in healthy older individuals. Subjects (n = 16 females; n = 8 males; 65 ± 1 years) were randomly assigned into groups supplemented with either olive oil (OO) (5 g/day) or FO (5 g/day) containing 2 g/day eicosapentaenoic acid and 1 g/day docosahexaenoic acid for 12 weeks. Participants visited the laboratory for RMR and substrate oxidation measurements after an overnight fast at weeks 0 and 12. Skeletal muscle biopsies were taken during weeks 0 and 12 for analysis of NKA and SERCA function and protein content. There was a main effect of time with decrease in RMR (5%) and fat oxidation (18%) in both the supplementation groups. The kinetic parameters of SERCA and NKA maximal activity, as well as the expression of SR and NKA proteins, were not affected after OO and FO supplementation. In conclusion, these results suggest that FO supplementation is not effective in altering RMR, substrate oxidation, and skeletal muscle SERCA and NKA protein levels and activities, in healthy older men and women.
Highlights
Resting metabolic rate (RMR) is defined as the amount of energy required to maintain the body's normal metabolic activity at rest in the postabsorptive state (Cunningham, 1980)
A study from our group observed a significant increase in resting oxygen consumption (+14%) and fat oxidation (+19%) in community-dwelling sedentary females (n = 12; 60–76 years) after a 12-week period of fish oil (FO) supplementation (5 g/day), while no changes were observed in the olive oil (OO) control group (Logan & Spriet, 2015)
Data were analyzed by paired t test e f whole-body RMR and substrate oxidation in healthy older adults
Summary
Resting metabolic rate (RMR) is defined as the amount of energy required to maintain the body's normal metabolic activity at rest in the postabsorptive state (Cunningham, 1980). Previous studies examining the effects of n-3 PUFAs on skeletal muscle energy metabolism have reported increased rates of protein synthesis in older adults (Lalia et al, 2017; Smith et al, 2011), increased NKA maximal activity in rodent heart tissue membranes with high levels of docosahexaenoic acid (DHA; n-3 PUFA) (Turner, Else, & Hulbert, 2003), and decreased efficiency and increased permeability of rodent skeletal muscle SERCA with DHA supplementation (Fajardo et al, 2015) These adaptations have been proposed to lead to increases in whole-body RMR (Fajardo et al, 2015; Hulbert, 2007)
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