Deciphering the Hepatic Metabolism of Dietary Pentadecanoic Acid: The Synthesis of Odd Chain n -8 Polyunsaturated Fatty Acids

Pentadecanoic acid (PDA, C15:0) is a saturated odd chain fatty acid mainly found in dairy products. Although dietary PDA has been associated with beneficial physiological effects, its metabolic fate remains poorly characterized. This study aimed at elucidating the hepatic metabolism of dairy-derived PDA and its conversion into potential bioactive metabolites such as odd chain polyunsaturated fatty acids (PUFAs). We characterized in vitro all the potential desaturating pathways leading to odd chain unsaturated fatty acids. In rat hepatocytes, PDA was primarily elongated into heptadecanoic acid (HDA) and then Δ9-desaturated into C17:1 n-8, which was further converted into odd chain n-8 PUFAs, C19:2 and C19:3 n-8, by successive Δ6 and Δ5 desaturation. New chemically synthesized C17:1, C19:2, and C19:3 n-8 enabled the identification of downstream long-odd chain n-8 PUFAs. Overall, these results identify PDA as a dairy dietary precursor of a novel n-8 odd chain PUFA family, thus increasing the nutritional interest of dairy saturated odd chain fatty acids.