The effects of linseed or chia seed dietary supplementation on adipose tissue development, fatty acid composition, and lipogenic gene expression in lambs

•Linseed or chia seed-enriched diets had no effect on growth and carcass parameters of lambs.•Linseed or chia seed increased n-3 PUFA and α-linolenic acid contents in adipose tissue and muscle.•We studied the expression of ACACA, LPL, SCD, FADS1, FADS2, and ELOVL5 in adipose tissue of lambs.•Fatty acid profile may be, at least partly, mediated by the dietary regulation of lipogenic genes.•We provide evidence supporting the idea that the intramuscular fat has its own specific features.

This study examined the effects of linseed or chia seed supplementation on growth and carcass parameters, fatty acid composition, and expression of six lipogenic genes in the intramuscular (IM) and subcutaneous (SC) adipose tissues (AT) in lambs. Thirty-one male Navarra breed lambs (56.5 ± 1.6  d old) were weaned at 16.8 ± 0.3 kg live weight (LW) and assigned randomly into three dietary groups: a control group diet of barley and soybean (C); the C diet with 10.5% linseed (L) and the C diet with 10% chia seed (Chia). The lambs were collectively reared in pens (4 weeks) and slaughtered at an average LW of 26.6 ± 0.2 kg. The results indicated that supplementing lambs' diet with either linseed or chia seed, both rich in α-linolenic acid (ALA, C18:3n-3), had no effect on the growth parameters. Supplementation of either linseed or chia seed increased the ALA, C18:1t11, eicosapentaenoic acid (EPA, C20:5n-3), and total n-3 fatty acid contents (P < 0.01), and decreased the n-6/n-3 ratio in the IM- and SC-AT (P < 0.001). Supplementation of linseed increased the proportion of docosapentaenoic acid (DPA; 22:5n-3) in both the IM- and SC-AT (P < 0.01), while supplemented chia seed increased the DPA content in the IM-AT (P < 0.01). Downregulation of acetyl-CoA carboxylase 1 or alpha (ACACA), stearoyl-CoA desaturase (SCD) and fatty acid desaturase 2 (FADS2) was observed in the IM-AT in the linseed and chia seed-supplemented lambs (P < 0.05). The linseed-containing diet did not change lipoprotein lipase (LPL) or fatty acid desaturase 1 (FADS1) gene expression in the IM-AT, whereas chia seed downregulated the expression of those genes (P < 0.01). On the contrary, supplementing either linseed or chia seed had no effect on ACACA, SCD, or LPL gene expression in the SC-AT. Supplementing linseed decreased FADS1, FADS2, and fatty acid elongase 5 (ELOVL5) mRNA in the SC-AT (P < 0.01), whereas supplemented chia seed decreased ELOVL5 expression (P < 0.001). Consequently, changes in fatty acid composition caused by dietary linseed or chia seed might be, at least partly, mediated by the regulation of several genes involved in lipogenesis and the regulation seems to be tissue-specific.