Expression and nutritional regulation of lipogenic genes in mammary gland and adipose tissues of lactating goats

Abstract

While the effect of long-chain fatty acids on adipose tissue (AT) lipogenic activities has been described in non-lactating ruminants (Vernon, 1977), little is known about their effects on the mammary gland and the AT in lactating animals. However, in cows in mid lactation, duodenal rapeseed oil infusion decreased the rate of fatty acid (FA) synthesis in AT and increased milk yield of long-chain FA (18[ratio ]1, 18[ratio ]2 and 18[ratio ]3) and decreased medium-chain FA (14[ratio ]0 and 16[ratio ]0), suggesting a depressive effect of fat feeding on mammary lipid synthesis de novo (Chilliard et al. 1991). On the other hand, in goat species, the addition of vegetable lipids to the diet led to an increase in the milk fat content and yield (Chilliard et al. 2003) suggesting that the possible negative effect of long-chain FA on FA synthesis in the lactating mammary gland could be more than compensated by increasing the supply of FA brought to the mammary gland for milk synthesis. Elsewhere, AT from various anatomical sites are characterized by different FA composition in goat (Bas et al. 1987) together with different patterns of lipogenic gene expression in sheep (Barber et al. 2000). These results suggest that each AT site is characterized by a specific metabolism. However, in lactating ruminants, few data are available on the extent of expression and regulation of genes coding for lipogenic enzymes in AT. Therefore, the current study was performed in three lipogenic tissues of lactating goats, namely the mammary gland, an internal AT site (perirenal AT) and an external AT site (subcutaneous AT).