Lipid acquisition and tissue storage in hagfish: new insights from an ancient vertebrate
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Hagfishes are ancient vertebrates, which have the ability to tolerate nearly a year of food deprivation with energy during fasting maintained using lipid stores. While lipid transporters are evolutionarily conserved, there are relatively few studies examining mechanisms of lipid acquisition in teleosts and no reports in the primitive and evolutionarily important agnathans. We examined tissue lipid droplet distribution and used gut sac preparations to characterize uptake mechanisms of the monounsaturated fatty acid, oleic acid (OA; 18:1 cis-9), in the Pacific hagfish. OA absorption was carrier-mediated and demonstrated saturable concentration-dependent uptake with an affinity constant of 55 ± 7 µM, and a maximal rate of uptake of 1311 ± 97 pmol cm− 2 h− 1. Additionally, regulation of intestinal transport was demonstrated as feeding significantly increased uptake. To further examine post-prandial effects on fatty acid transport, hagfish were dosed with bovine insulin, which had no effect on OA intestinal acquisition, but did lower plasma glucose. Overall, this is the first evidence for intestinal fatty acid acquisition in an agnathan, which are ideal models for understanding the evolution of nutrient transport processes in vertebrates, and are particularly suited to lipid research owing to their dependence upon this energy source during prolonged periods of fasting.
KeywordsDietary lipids Fatty acid Transport Insulin Lipid droplets Agnathan
The authors would like to thank Arlene Oatway of the UAlberta Microscopy Sciences and the staff at Bamfield Marine Sciences Centre, with particular thanks to the research coordinator Dr. Eric Clelland and Janice Pierce for hagfish collection.
A.M.W was supported by a National Science and Engineering Research Council Post-Graduate Scholarship Doctoral and the Presidents Doctoral Prize of Distinction. GGG was supported by an National Science and Engineering Research Council Discovery Grant (203736). CNG is supported by a Campus Alberta Innovates Program Research Chair.
Compliance with ethical standards
The authors declare no competing interests.
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