Meeting Abstract
Muscle fatty acid (FA) composition changes in response to diet and physiological condition, which in turn affects whole-animal performance (e.g. aerobic endurance, metabolic rate, post-exercise recovery) in a wide range of taxa. The pace of compositional changes of FAs, however, remains largely unknown and limits our ability to infer their ecological consequences. We estimated the turnover rates of individual FAs in neutral lipid (NL) and polar lipid (PL) fractions extracted from the flight muscle of exercised and unexercised Zebra Finches (Taeniopygia guttata). FA turnover was quantified by measuring 13C enrichment in tissues sampled over 256 days following a C4 to C3 diet shift, with the exercise treatment used to assess the effect of elevated metabolic rate on turnover. In both fractions, turnover was fastest for linoleic acid (LA, 18:2n6) and palmitic acid (PA, 16:0) with mean retention times (τ) of, respectively, 6.6 and 9.5 days in NLs and 4.1 and 5.1 days in PLs. Arachidonic acid (ARA, 20:4n6) and docosahexaenoic acid DHA, (22:6n3) were only found in PLs and had much slower turnover (τ=26.0 days and τ=41.4 days, respectively), while stearic acid (SA, 18:0) and oleic acid (OA, 18:1n9) had more intermediate turnover in both fractions. All pairs of FAs were significantly different from one another (P < 0.05) except for LA and PA in both fractions, PA and SA in NLs, and PA and OA in PLs. Exercise increased the turnover of LA (τexercised = 3.7, T56 = -2.245, P = 0.029) and PA (τexercised = 3.8, T59 = -2.314, P = 0.024) in PLs. These results demonstrate both rapid turnover of key FAs and provide evidence that multiple mechanisms drive FA turnover, including oxidative damage and the consumption of molecules during normal function.
