Effect of linseed addition on the expression of some lipid metabolism genes in the adipose tissue of young Italian Simmental and Holstein bulls.

The objective of this trial was to determine the effect of breed and long-term dietary linseed addition on composition of fatty acids and expression of some genes involved in the lipid metabolism within subcutaneous (s.c.) adipose tissue of young bulls. Italian Simmental and Holstein bulls (n=16/breed) were fed a corn silage-grass hay diet with or without 8% (DM basis) whole ground linseed. Inclusion of linseed, rich in α-linoleic acid (C18:3n-3), increased (P<0.05) the proportions of linolelaidic (C18:2n-6trans), γ-linolenic (C18:3n-6), C18:3n-3, and rumenic (cis9,trans11 conjugated linoleic acid) acids, as well as total n-3 fatty acid, total PUFA, and PUFA:SFA, but decreased (P<0.05) weight percentages of myristic (C14:0), pentadecanoic (C15:0), palmitic (C16:0), palmitelaidic (C16:1n-9trans), and margaric (C17:0) acids, along with n-6:n-3, in the s.c. fat of young bulls. Even though PUFA were similar (P≥0.23) between bull breeds, s.c. fat from Holstein bulls had greater (P<0.05) proportions of tridecylic (C13:0), myristoleic (C14:1) and palmitoleic (C16:1n-9cis) acids and a lower (P<0.05) proportion of margaric (C17:0) acid than s.c. fat from Simmental bulls. Feeding linseed decreased (P<0.05) the expression of stearoyl CoA desaturase (SCD) and the lipoprotein lipase (LPL) gene without affecting (P≥0.19) fatty acid synthase (FASN), leptin (LEP), and PPARγ2 mRNA in the s.c. fat of bulls; however, there was no effect of bull breed (P≥0.11) or interactive effect of breed and linseed (P≥0.23) on gene expression. Expression of PPARγ2 was positively correlated with SCD (r=0.454; P=0.01), LEP (r=0.500; P<0.01), and LPL (r=0.531; P<0.01) mRNA, indicating that PPARγ2 increases the expression of genes involved in lipogenesis.