Selective seasonal fatty acid accumulation and mobilization in the wild raccoon dog (Nyctereutes procyonoides).

Previous studies on laboratory rodents, rabbits and humans have demonstrated that fatty acid (FA) mobilization from white adipose tissue (WAT) is selective and its efficiency is related to FA structure. Selective FA mobilization was also documented in a carnivore, the farmed raccoon dog (Nyctereutes procyonoides), fasted for 8 weeks. The present study explored whether similar selectivity of FA mobilization was manifested in wild mammals experiencing seasonal food scarcity and abundance. Fractional mobilization from and incorporation into WAT of a wide spectrum of FA were studied by gas-liquid chromatography from the subcutaneous WAT of free-ranging raccoon dogs with the same individuals sampled in consecutive seasons. The wintertime FA mobilization was selective and mostly confirmed the patterns of FA release in captivity. Mobilization correlated inversely with the FA chain length but increased with unsaturation and when the first double bond was located closer to the methyl end. 18-20 C n-3 polyunsaturated FA (PUFA) and 14-17 C monounsaturated FA (MUFA) were preferentially mobilized while 19-24 C saturated FA and MUFA were preserved during wintering. The summertime FA incorporation correlated inversely with the chain length and increased with unsaturation and in MUFA and PUFA with double bonds closer to the methyl end. The principles of selective FA mobilization were valid in wild mammals. FA incorporation was also selective and reversed the wintertime losses of the preferably mobilized FA.