Antarctic fish tissues preferentially catabolize monoenoic fatty acids

Tissues of Antarctic marine fishes are very high in lipids, predominantly triacylglycerols (TAG). In addition to conferring static lift to these swimbladderless fishes, these rich lipid stores long have been considered as an important caloric resource to the animals. We have performed in vitro measurements of the rates of oxidation of 14 C‐labeled carbohydrates and fatty acids by oxidative skeletal muscle and heart ventricle of an Antarctic teleost, Gobionotothen gibberifrons to assess the relative importance of these substrates to aerobic energy metabolism. Capacities for regeneration of ATP calculated from oxidation rates of these fuels clearly indicate that fatty acids are more effective substrates of energy metabolism than either glucose or lactate with both tissues. Substrate competition experiments conducted between the saturated fatty acid palmitate (16:0) and the monoenoic unsaturate oleate (18:1) comparing the oxidation rate of radiolabeled fatty acid in the presence and absence of unlabeled competitor demonstrate a clear preference of both tissue types for catabolism of the monounsaturated substrate. Measurements of maximal activity of the putative flux‐generating enzyme of mitochondrial β‐oxidation, carnitine palmitoyltransferase (CPT), with a variety of fatty acyl CoA esters also show significant preference for a monoenoic fatty acyl CoA, palmitoleoyl CoA (16:1). The general pattern of results suggests that monounsaturated fatty compounds are the most readily utilized substrates for energy metabolism by oxidation muscle tissues of this Antarctic species.