Branched chain fatty acid content of edible portions of northeastern U.S. freshwater fish

Abstract

IntroductionBranched chain fatty acids (BCFA) are major components of skin/membranes across various mammals and bacterial genera. BCFA are bioactive and alter gut microbiota. Intake of BCFA, mainly from dairy/beef was estimated at 500 mg per day in US. Our goal was to investigate BCFA levels in common freshwater fish species.MethodsWe captured over 20 fish species from several lakes and streams in New York and Pennsylvania. We dissected larger fish and sampled muscle tissue from dorsal and caudal fins as well as the belly and the skin. Smaller fish were entirely grinded before processing. All samples were extracted, saponified and methylated. BCFA profiles were analyzed using gas chromatography mass spectrometry.ResultsBCFA content varied across species and ranged from 0.6–2.7%, w/w of total fatty acids in fish muscle samples, with an overall mean of 1.2%. Some low trophic level fishes, such as killifish, rainbow smelt, and juvenile pumpkinseed, had over 2% BCFA while some common game fish species white perch, yellow perch, smallmouth bass, and walleye had about 1% BCFA, w/w or less of total fatty acids. A few low trophic level fishes such as fantail darter in the same perch family as yellow perch and walleye had low BCFA levels, suggesting influences related to phylogenetic structure. Skin contained between 1.2–3.2% BCFA, w/w of total fatty acids. Across all species sampled, skin samples had higher BCFA levels compared to muscle samples. The overall fatty acid profile, including BCFA was similar across muscles from different parts of a fish. The major BCFA in fish are iso‐15:0, anteiso‐15:0, iso‐16:0, iso‐17:0 and anteiso‐17:0. Trace amounts of iso‐13:0, anteiso‐13:0, iso‐14:0, iso‐18:0, anteiso‐19:0 and iso‐20:0 were also detected.ConclusionMany low‐trophic‐level fishes had BCFA levels comparable with dairy products and their skin samples showed higher BCFA content than muscle.Support or Funding InformationNIH R01 AT007003