Non-esterified fatty acids promote expression and secretion of angiopoietin-like protein 4 in calf hepatocytes cultured in vitro.

An elevated plasma non-esterified fatty acids (NEFA) concentration is an important indicator of negative energy balance, which is often associated with metabolic diseases such as fatty liver and ketosis. Angiopoietin-like protein 4 (ANGPTL4) is a hepatokine that plays important roles in the regulation of lipid metabolism. However, the direct effects of high concentrations of NEFA on ANGPTL4 expression and secretion in hepatocytes from cows are not entirely clear. The objective of this study was to investigate the effects of different NEFA concentrations on ANGPTL4 expression and secretion in calf hepatocytes cultured in vitro. NEFA was added to the culture solution at final concentrations of 0.6, 1.2, 1.8, and 2.4 mmol/L. After 24 h of continuous culture, ANGPTL4 mRNA and protein expression levels in the hepatocytes were determined by real-time polymerase chain reaction and western blot, respectively. ANGPTL4 secretion in the supernatant was determined by enzyme-linked immunosorbent assay. The results showed similar levels of ANGPTL4 expression and secretion following treatment with 0.6 and 1.2 mmol/L NEFA, which were higher than those observed for the controls (P < 0.05). ANGPTL4 expression and secretion were also similar at 1.8 and 2.4 mmol/L NEFA and significantly higher than those observed for controls (P < 0.01). These data suggest that high concentrations of NEFA significantly promote ANGPTL4 expression and secretion in bovine hepatocytes. In particular, this promotion occurs in a dose-dependent manner and may be involved in the pathological processes of energy metabolism disorders of dairy cows in the peripartum period.