Oxidized Fat Reduces Milk Triacylglycerol Concentrations by Inhibiting Gene Expression of Lipoprotein Lipase and Fatty Acid Transporters in the Mammary Gland of Rats

Abstract

Feeding oxidized fats to lactating rats causes a strong reduction of triacylglycerol concentration in the milk. The reason for this, however, has not yet been elucidated. Pregnant Sprague-Dawley rats were assigned to 2 groups of 11 rats each and fed diets containing either fresh fat (FF group) or an oxidized fat (OF group) from d 1 to d 20 of lactation. Concentrations of triacylglycerols and long-chain fatty acids in the milk and weight gain of suckling pups were lower in the OF group than in the FF group (P < 0.05). Concentrations of medium-chain fatty acids in the milk and messenger RNA (mRNA) abundance of lipogenic enzymes in the mammary gland did not differ between the 2 groups of rats. However, the OF group had a lower concentration of triacylglycerols and nonesterified fatty acids (NEFA) in plasma and lower mRNA concentrations of lipoprotein lipase and fatty acid transporters in the mammary gland than the FF group (P < 0.05). Moreover, the OF group had higher mRNA concentrations of hepatic lipase, fatty acid transporters, and several genes involved in fatty acid oxidation in the liver than the FF group (P < 0.05). The present findings suggest that a dietary oxidized fat lowers the concentration of triacylglycerols in the milk by a reduced uptake of fatty acids from triacylglycerol rich-lipoproteins and NEFA into the mammary gland. The study, moreover, indicates that an oxidized fat impairs normal metabolic adaptations during lactation, which promote the utilization of metabolic substrates by the mammary gland for the synthesis of milk.

Association of a polymorphism in the 3' untranslated region of the &lt;i&gt;OLR1&lt;/i&gt; gene with milk fat and protein in dairy cows

“…There may be an association of this kind in bovine mammary gland also. Ringseis et al (2007) reported the effect of oxidized fat on reducing milk triacylglycerol concentrations by inhibiting gene expression of lipoprotein lipase and fatty acid transporters in the mammary gland of rats. As an oxidized fat, Ox-LDL may induce a decrease in milk fat in the same way in bovine mammary gland.…”

Effect ofABCG2,PPARGC1A,OLR1 andSCD1 gene polymorphism on estimated breeding values for functional and production traits in Polish Holstein-Friesian bulls

“…Ringseis et al (2007) reported recently that oxidized fat inhibits the expression of lipoprotein lipase and fatty acid trans- porter genes, which in turn leads to a reduced uptake of fatty acids into mammary glands. As a result, the concentration of triacylglycerols in milk is reduced.…”

“…Internalization of oxLDL leads to a sequence of events that may result in endothelial dysfunction and atherosclerosis (Dunn et al 2008). Oxidized lipids were also found to impair glucose metabolism and to influence lipid metabolism in the liver and mammary glands (Ringseis et al 2007;Liao et al 2008). OLR1, as a protein important for oxLDL metabolism, may contribute to these effects.…”

Downregulation of peroxisome proliferator-activated receptor α and its coactivators in liver and skeletal muscle mediates the metabolic adaptations during lactation in mice

“…We have recently observed that activation of hepatic Ppara in the lactating rat by feeding a dietary oxidized fat, a potent activator of hepatic Ppara (Chao et al 2001, Sü lzle et al 2004, Ringseis et al 2007b, leads to an increased uptake of fatty acids into the liver and an enhanced b-oxidation in the liver, whereas uptake of fatty acids into the mammary gland by fatty acid transporters and Lpl was decreased, which, in turn, led to a dramatically reduced milk TAG content and reduced weight gains of litters during suckling (Ringseis et al 2007a). Similar observations regarding an impairment of lactation-induced energy-sparing mechanisms by the administration of Ppara activators during lactation have been reported from others .…”