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Dietary linoleic acid, antioxidants, and flight training influence the activity of oxidative enzymes in European Starlings (Sturnus vulgaris)


Multiple studies have demonstrated that diet (e.g., fatty acid composition, antioxidants) and exercise training affect the metabolic performance of songbirds during aerobic activity, although the physiological mechanisms that cause such an effect remain unclear. We tested the hypothesis that elevated proportions of dietary linoleic acid (18:2n6) and amounts of dietary anthocyanins (a hydrophilic antioxidant class) influence the activity and protein expression of oxidative enzymes in flight and leg muscle of European Starlings (Sturnus vulgaris N = 96), a subset of which were flown over 15 days in a wind tunnel. Carnitine palmitoyl transferase (CPT) and citrate synthase (CS) activity displayed 18:2n6-dependent relationships with soluble protein concentration. Lactate dehydrogenase (LDH) was similarly related to protein concentration although also dependent on both dietary anthocyanins and flight training. 3-Hydroxyacyl CoA Dehydrogenase (HOAD) activity increased throughout the experiment in flight muscle, whereas this relationship was dependent on dietary anthocyanins in the leg muscle. Soluble protein concentration also increased throughout the experiment in the flight muscle, but was unrelated to date in the leg muscle, instead being influenced by both dietary anthocyanins and flight training. Training also produced additive increases in CPT and leg muscle HOAD activity. FAT/CD36 expression was related to both dietary 18:2n6 and training and changed over the course of the experiment. These results demonstrate a notable influence of our diet manipulations and flight training on the activity of these key oxidative enzymes, and particularly CPT and CS. Such influence suggests a plausible mechanism linking diet quality and metabolic performance in songbirds.

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We would like to thank Morag Dick for providing us with the enzyme activity protocols used in this study, as well as valuable advice on how to successfully run them. We would also like to thank Chris Guglielmo, Andrew Gould, Mikaela Rebuli, and all of the staff at AFAR for providing us unrestricted access to the AFAR facility, for helping us think critically about the experiment, and for their support throughout. We are especially thankful for the efforts of Luke Douglas and Keara Bohannon, our undergraduate research assistants, who made the project both possible and much more enjoyable. We thank Artemis International for their kind donation of the elderberry powder used in this study. Finally, we thank Todd at Hyland Dairy Farms Ltd. for graciously allowing us to catch and remove the starlings used in this experiment on his property.


This research was funded by Grant Number IOS-1354187 from the National Science Foundation.

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SRM and BJP conceived of and designed the experiment. WAC and KJD refined the methodology and conducted the experiment. WAC analyzed the data and primarily wrote the manuscript; all other authors provided editorial advice to the manuscript.

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Correspondence to Wales A. Carter.

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The authors declare that they have no conflicts of interest.

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Communicated by P. Withers.

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Carter, W.A., DeMoranville, K.J., Pierce, B.J. et al. Dietary linoleic acid, antioxidants, and flight training influence the activity of oxidative enzymes in European Starlings (Sturnus vulgaris). J Comp Physiol B 191, 357–370 (2021).

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  • Linoleic acid
  • Enzyme activity
  • Citrate synthase
  • Carnitine palmitoyl transferase
  • Songbirds