Author(s): BANIC, M., GALLAGHER, I.J., VAN DIJK, M., WITARD, O.C., DICK, J.R., GALLOWAY, S.D.R., RODRIGUEZ-SANCHEZ, N., Institution: UNIVERSITY OF STIRLING, Country: UNITED KINGDOM, Abstract-ID: 1323

INTRODUCTION:
The incorporation of omega-3 polyunsaturated fatty acids (n-3 PUFA) into the phospholipid membrane of human skeletal muscle cells modulates muscle protein turnover. However, differential effects of n-3 PUFA ingestion on gene expression in young and older adults are yet to be fully understood and may contribute, in part, to age-related differences in n-3 PUFA impact on skeletal muscle. We sought to determine the influence of n-3 PUFA ingestion on global gene expression profiles in skeletal muscle of young and older adults.
METHODS:
Thirteen young (23±3 y, 7 female) and eleven older (67±6 y, 7 female) adults supplemented their diet, in capsule form, with 1.26g/day n-3 PUFA (720mg EPA + 540mg DHA) over 12 wk. Muscle biopsies were obtained at baseline and after 12 wk of supplementation for analysis of n-3 PUFA phospholipid membrane composition using gas chromatography, and global gene expression using microarrays. Gene category enrichment was determined using the Molecular Signatures Hallmark gene sets and data were analysed using R. Lean and fat mass was quantified via dual-energy X-ray absorptiometry, physical activity status monitored with ActiGraph GT3X+, and handgrip strength assessed using a Takei handgrip dynamometer.
RESULTS:
The percent of n-3 PUFA relative to total fatty acids increased in muscle phospholipid membranes of young (+1.4 ± 0.2%) and older (+1.5 ± 0.5%) adults after 12 wk with no significant age-related differences (P>0.05). In young adults, n-3 PUFA ingestion downregulated two pathways related to bioenergetics (Ox Phos and ROS) and four pathways related to tissue regeneration (MYC targets, DNA repair, IFN-α, IFN-γ), while one pathway linked to tissue regeneration (Mitotic spindle) was upregulated. In older adults, three pathways related to tissue regeneration (Epithelial mesenchymal transition, Angiogenesis, IFN-γ) were upregulated, while one gene set related to bioenergetics (Ox Phos) was downregulated. Differential regulation of IFN-α, and IFN-γ gene sets was observed between age groups (upregulation in older adults, downregulation in young adults). Although physical activity increased from 39 ± 6% to 42 ± 6% of recorded time, there was no significant difference between age groups (P>0.05). No significant effect of n-3 PUFA ingestion on lean mass or strength was observed in young or older adults (P>0.05).
CONCLUSION:
To conclude, the incorporation of n-3 PUFA into skeletal muscle membranes differentially alters gene sets involved in skeletal muscle regeneration and bioenergetics in young and older adults. These effects were unrelated to changes in physical activity status, lean mass, and strength over the 12-wk supplementation period. This study highlights the potential clinical application of n-3 PUFA supplementation in remodelling skeletal muscle across the lifespan.