Abstract
Cocoa flavanols and fish oil omega-3 fatty acids are two bio-active nutrients that may improve muscle microvascular function, insulin sensitivity and mitochondrial function in older adults. We assessed changes in gene expression of these pathways in muscle from two nutritional intervention studies in older healthy volunteers: (i) 6-weeks daily fish oil supplementation in older females (3.4 g/d; age: 64.4 ± 0.8 y, BMI: 26.2 ± 0.7 kg/m2), and (ii) 7-day daily cocoa flavanol supplementation in older males (1050 mg/d; age: 70.1 ± 0.9 y, BMI: 25.7 ± 0.6 kg/m2). There was a main effect of 6-weeks fish oil supplementation on angiogenesis gene expression, with no overall changes in mitochondrial or insulin signaling genes. 7-day cocoa supplementation elicited changes in extracellular matrix (ECM) related genes. Thus, the effects of fish oil supplementation on vascular remodeling in skeletal muscle, and ECM remodeling with cocoa supplementation have emerged as areas for future study.
Highlights
Impaired skeletal muscle microvascular function, mitochondrial abundance/activity and insulin sensitivity are key features of ageing in humans, whereby age-related declines in muscle microvascular blood flow may contribute to impaired uptake of insulin/amino acids in response to feeding (Phillips et al, 2012)
In order to explore the temporal nature of these changes, muscle biopsies that were collected after 2-weeks of fish oil supplementation were analyzed, there were no overall effects on either mitochondrial or insulin signaling associated genes in this time-frame, there was an increase in mechanistic target of rapamycin (MTOR) expression (6.0 ± 1.9-fold; P < 0.05 vs. baseline; Fig. 1)
Insulin signaling and insulin-like growth factor (IGF)-1 signaling pathways in the skeletal muscle of older males after 7-days of cocoa flavanol supplementation showed no overall difference in mitochondrial or insulin/IGF-1-related gene expression compared to a no supplementation control group, NRF1 expression was significantly lower (0.55 ± 0.05-fold; P < 0.05 vs. non-cocoa; Fig. 2)
Summary
Impaired skeletal muscle microvascular function, mitochondrial abundance/activity and insulin sensitivity are key features of ageing in humans, whereby age-related declines in muscle microvascular blood flow may contribute to impaired uptake of insulin/amino acids in response to feeding (Phillips et al, 2012). In healthy young male humans, dietary fish oil supplementation for 4-weeks resulted in increased resting femoral arterial blood flow (Pearson, Johnson, & Robins, 2014). Chronic fish oil supplementation has been demonstrated to increase whole-body endogenous glucose production (Kamolrat, Gray, & Carole Thivierge, 2013), and administration to mice fed a high-fat diet resulted in attenuation of insulin resistance through improvements in mitochondrial function (Martins et al, 2018). Long-term omega-3 PUFA treatment resulted in increased muscle mass and function (Smith et al, 2015), while the anabolic response to insulin and amino acid infusion was found to be enhanced with omega-3 PUFA administration in healthy young and middle-aged human volunteers (Smith et al, 2011)
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