Effects of non‐esterified fatty acids on the expression and secretion of angiopoietin‐like protein 4 and fibroblast growth factor 21 in calf hepatocytes cultured in vitro

Abstract

IntroductionNegative energy balance (NEB) is considered as the pathological basis of energy metabolic disorders, such as fatty liver and ketosis, in periparturient dairy cows. An elevated serum non‐esterified fatty acids (NEFA) concentration is one of the most important indicators of NEB. Angiopoietin‐like protein 4 (ANGPTL4) and fibroblast growth factor 21 (FGF21) have been identified as hepatokines, which involved in regulation of metabolic adaptations. In dairy cows, most circulating ANGPTL4 and FGF21 originate from the liver. However, the direct effects of NEFA on the expression and secretion of ANGPTL4 and FGF21 in bovine hepatocytes are not entirely clear. The purpose of the present study was to investigate the effects of different NEFA concentrations on the expression and secretion of these two hepatokines in calf hepatocytes cultured in vitro.MethodsBovine hepatocytes were cultured using the collagenase perfusion method. After culture for 72 h, the hepatocytes were treated with NEFA at final concentrations of 0 (control), 0.6, 1.2, 1.8 and 2.4 mmol/L. After 24 h of continuous culture, the mRNA and protein expression levels of ANGPTL4 and FGF21 in the hepatocytes were determined by real‐time PCR and Western blot, respectively. ANGPTL4 and FGF21 secretions in the supernatant were determined by enzyme‐linked immunosorbent assay (ELISA).ResultsThe 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). The expression and secretion of FGF21 at 0.6 mmol/L NEFA‐treated hepatocytes was higher than that of the control group (P<0.05). The FGF21 expression and secretion were similar at 1.2, 1.8 and 2.4 mmol/L NEFA‐treated hepatocytes and significantly higher than those observed for controls (P<0.01).ConclusionThe results of this study indicate that high concentrations of NEFA significantly increase the expression and secretion of ANGPTL4 and FGF21 in bovine hepatocytes cultured in vitro in a dose‐dependent manner. Specifically, NEFA promotes the expression and secretion of ANGPTL4 and FGF21, which may worsen fat mobilization under NEB conditions and thereby lead to the pathological processes of energy metabolism disorders in dairy cows in the peripartum period. However, further studies are needed to elucidate the underlying mechanisms.Support or Funding InformationThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.