Short communication: High insulin concentrations inhibit fatty acid oxidation-related gene expression in calf hepatocytes cultured in vitro

In dairy cows, ketosis is an important disease associated with negative energy balance, which leads to low blood glucose levels and high blood nonesterified fatty acid levels. The liver is the most active organ in cows for the metabolism of nonesterified fatty acids. Insulin is an anabolic hormone that plays numerous roles in the metabolism of carbohydrates, lipids, and proteins, as well as being a potent regulator of fatty acid oxidation. In this study, using fluorescent quantitative reverse-transcription PCR, ELISA, and primary hepatocytes cultured in vitro, we examined the effect of insulin (0, 5, 10, 20, 50, and 100 nmol/L) on fatty acid oxidation by monitoring mRNA and protein expression levels of key enzymes: long-chain acyl-coenzyme A synthetase, carnitine palmitoyltransferase I, and long-chain acyl-coenzyme A dehydrogenase. The results showed that the mRNA and protein expression of long-chain acyl-coenzyme A synthetase, carnitine palmitoyltransferase I, and long-chain acyl-coenzyme A dehydrogenase was markedly decreased when the concentration of insulin in the media was increased. These findings indicate that high levels of insulin significantly inhibit the expression of genes related to fatty acid oxidation and consequently results in a decreased level of fatty acid oxidation in calf hepatocytes.