Abstract
Humans and mammalian species are unable to synthesize significant amounts of polyunsaturated fatty acids (PUFA), which therefore must be introduced with the diet. In birds, lipogenesis takes place primarily in the liver, whereas adipose tissue serves as the storage site for triacylglycerols (TG, composed by 80–85% esterified fatty acids). However, both the nature (unsaturation level, n-3, or n-6 series) and the allocation (such as constituents of complexed lipids) of PUFA are very important to evaluate their function in lipid metabolism. The objective of the present investigation was to study the liver lipid metabolism, with particular attention to non-esterified fatty acids (NEFA), TG, phospholipids (PL), FADS2 gene expression, and Δ6-desaturase activity of three chicken genotypes, Leghorn (Leg), Ross 308 (Ross), and their crossbreed (LxR), by LC/MS analysis. The concentration of single fatty acids in muscle was quantified by GC-FID. The results showed that the Ross has a lipid metabolism related mainly to storage and structural roles, exhibiting higher levels of TG, phosphatidylethanolamine (PE) and phosphatidylcholine (PC) that are largely unsaturated. Meanwhile Leg showed a relevant amount of n-3 NEFA characterized by a higher phosphatidylserine (PS) unsaturation level, FADS2 gene expression and enzyme activity. The LxR seem to have a moderate trend: n-6 and n-3 NEFA showed intermediate values compared with that of the Ross and Leg and the TG trend was similar to that of the Ross, while PE and PC were largely unsaturated (mainly 6 and 7 UNS most of the metabolic energy for storage fatty acids in their tissues (TG) whereas, the Leg birds were characterized by different lipid metabolism showing in their liver a higher content of n-3 NEFA and higher unsaturation level in PS. Furthers details are needed to better attribute the lipid energy to the different metabolic portion.
Highlights
Humans and mammalian species are unable to synthesize significant amounts of polyunsaturated fatty acids (PUFA), which must be introduced with the diet
The n-3 “free PUFA” (NEFA), TG and PL may originate from four different sources: i) de novo lipogenesis, ii) cytoplasmic triacylglycerol stores, iii) FA derived from TG or PL of lipoprotein remnants directly taken up by the liver, and iv) plasma NEFA released by adipose tissue[27]
The results confirmed that FG strain, such as the Ross 308 genotype, showed a lipid metabolism connected with storage and structural roles as demonstrated by TG, PE and PC profiles
Summary
Humans and mammalian species are unable to synthesize significant amounts of polyunsaturated fatty acids (PUFA), which must be introduced with the diet. Lipogenesis takes place primarily in the liver, whereas adipose tissue serves as the storage site for triacylglycerols (TG, composed by 80–85% esterified fatty acids) Both the nature (unsaturation level, n-3, or n-6 series) and the allocation (such as constituents of complexed lipids) of PUFA are very important to evaluate their function in lipid metabolism. The LxR seem to have a moderate trend: n-6 and n-3 NEFA showed intermediate values compared with that of the Ross and Leg and the TG trend was similar to that of the Ross, while PE and PC were largely unsaturated (mainly 6 and 7 UNS most of the metabolic energy for storage fatty acids in their tissues (TG) whereas, the Leg birds were characterized by different lipid metabolism showing in their liver a higher content of n-3 NEFA and higher unsaturation level in PS. The PUFA may be ingested as precursors: α-linolenic acid (ALA, C18:3n-3) for the n-3 series and linoleic acid (LA, C18:2n-6) for the n-6 series, which are essential fatty acids, or as derivatives (long chain PUFA, LC PUFA), with more than 20 carbon atoms
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