Effect of Calcium Treatment on Catabolic Rates of ¹³C-Labeled Fatty Acids Bound to the α and β Positions of Triacylglycerol

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The absorption efficacies and catabolic rates of fatty acids are affected by their binding position on triacylglycerol (TAG). However, the kind of effect calcium treatment has on the catabolism of fatty acids is unclear. In this study, the catabolic rates of ¹³C-labeled palmitic acid, oleic acid, and linoleic acid bound to sn-1, 3 (α) and sn-2 (β) position of TAG in the presence of calcium were compared using isotope ratio mass spectrometry. The catabolic rates of ¹³C-labeled fatty acids were evaluated using the ratio of ¹³C to ¹²C in the carbon dioxide expired by mice. The catabolic rate of palmitic acid bound to the α position was significantly lower than that of palmitic acid bound to the β position of TAG. The rates of ¹³CO₂ formation from palmitic acid at the β position remained higher for a long time. In contrast, oleic and linoleic acids at the α position were as well catabolized as those at the β position. These results indicate that in the presence of calcium, the saturated fatty acid bound to the β position is highly catabolized, whereas that bound to the α position is not well catabolized. Saturated fatty acid at the α position is hydrolyzed by pancreatic lipase to promptly form insoluble complexes with calcium, which are excreted from the body, and thereby reducing the catabolic rate of these fatty acids.