Expressão in vivo de genes relacionados ao metabolismo lipídico em fígado bovino induzida por ácidos graxos como agonistas do PPAR-α: nutrigenômica aplicada à bovinocultura leiteira

Abstract

In vitro studies have shown that specific fatty acids added to culture media modulate the bovine peroxisome proliferator-activated receptor alpha (PPAR-α), a crucial regulator of hepatic lipid metabolism. These studies provide a potential strategy for preventing hepatic steatosis in dairy cows experiencing negative energy balance (NEB). However, there is a lack of in vivo experiments demonstrating the effective modulation of this receptor in these animals through the supplementation of vegetable oils as a source of fatty acids. Herein, we investigated the expression of five PPAR-α target genes and the receptor itself in the liver of heifers supplemented with three commercial vegetable oils: cottonseed, sunflower, and soyabean. After 15 days of supplementation, we observed an increase in the expression of the 3-hydroxy-3 methylglutaryl-CoA reductase (HMGCR) gene associated with increasing hepatic clearance of acetyl-CoA and triacylglycerol (TAG) exportation, particularly with cottonseed oil supplementation. These findings were corroborated by an increase in cholesterol concentration in the serum of animals supplemented with all three vegetable oils. Additionally, supplementation with sunflower and soyabean oils reduced the expression of the fatty acid translocase (CD36) gene, involved in the internalization of fatty acids by hepatocytes, potentially preventing excessive accumulation of liver fat. Cottonseed also reduced dry matter intake (DMI) without compromising weight gain. Importantly, the inclusion of these oils did not negatively affect the clinical biochemical parameters investigated, including those related to liver and kidney functions, as well as the serum lipid profile. Furthermore, no negative impact on the inflammatory state of the animals was observed through the analysis of ten acute-phase proteins. Finally, lipid supplementation did not induce significant modifications in the ruminal and fecal microbiomes. However, it fostered a relative increase in bacterial genera associated with ruminal biohydrogenation, which may positively influence the lipid profile of the animals’ meat and milk. Our findings provide valuable insights into the use of oils in dairy cattle nutrition, extending their conventional role of increasing energy density in feed.