PDF(Pubmed)
Abstract：
Fatty liver hemorrhage syndrome (FLHS) is the leading cause of noninfectious mortality in caged layers worldwide. Osteocalcin (OCN) is a protein secreted by osteoblasts, and its undercarboxylated form (ucOCN) acts as a multifunctional hormone that protects laying hens from FLHS. Lipophagy is a form of selective autophagy that breaks down lipid droplets (LDs) through lysosomes, and defective lipophagy is associated with FLHS. The aim of this study was to investigate the effects of ucOCN on the lipophagy of chicken embryonic hepatocytes and associated the function of the adiponectin (ADPN) signaling pathway. In this study, chicken embryonic hepatocytes were divided into 5 groups: control (CONT), fat emulsion (FE, 10% FE, v/v), FE with ucOCN at 1 ng/mL (FE-LOCN), 3 ng/mL (FE-MOCN), and 9 ng/mL (FE-HOCN). In addition, 4 μM AdipoRon, an adiponectin receptor agonist, was used to investigate the function of ADPN. The results showed that compared with CONT group, FE promoted the levels of phosphorylation of mammalian target of rapamycin (p-mTOR) (P < 0.05) and decreased the mRNA expression of ADNP receptors (AdipoR1 and AdipoR2). Compared with FE group, 3 and 9 ng/mL ucOCN inhibited the levels of autophagy adaptor p62 and p-mTOR (P < 0.05), increased the ratios of LC3-II/LC3-I (P < 0.05) and phosphorylated adenosine 5\'-monophosphate-activated protein kinase (p-AMPK)/AMPK (P < 0.05), as well as the levels of peroxisome proliferator-activated receptor α (PPAR-α) and ADPN (P < 0.05). In addition, ucOCN at the tested concentrations increased the colocalization of LC3 and LDs in fatty hepatocytes. Administrated 4 μM AdipoRon activated AdipoR1 and AidpoR2 mRNA expression (P < 0.05), decreased the concentrations of triglyceride (P < 0.05), without effects on cell viability (P > 0.05). AdipoRon also increased the LC3-II/LC3-I ratio (P < 0.05) and the levels of p-AMPK/AMPK and PPAR-α (P < 0.05). In conclusion, the results reveal that ucOCN regulates lipid metabolism by activating lipophagy via the ADPN-AMPK/PPARα-mTOR signaling pathway in chicken embryonic hepatocytes. The results may provide new insights for controlling FLHS in laying hens.
摘要：
脂肪肝出血综合征（FLHS）是全球笼中非感染性死亡的主要原因。骨钙蛋白（OCN）是一种由成骨细胞分泌的蛋白质，其欠羧化形式（ucOCN）充当多功能激素，可保护蛋鸡免受FLHS的侵害。脂质吞噬是一种通过溶酶体分解脂滴（LD）的选择性自噬，有缺陷的吸脂性与FLHS有关。本研究旨在探讨ucOCN对鸡胚肝细胞脂肪吞噬的影响及其与脂联素(ADPN)信号通路功能的关系。在这项研究中,鸡胚肝细胞分为5组:对照组(CONT),脂肪乳剂(FE，10%FE,v/v),FE，ucOCN为1ng/mL（FE-LOCN），3ng/mL（FE-MOCN），和9ng/mL(FE-HOCN)。此外,4μMAdipoRon,一种脂联素受体激动剂，用于研究ADPN的功能。结果表明,与CONT组相比,FE促进哺乳动物雷帕霉素靶蛋白（p-mTOR）的磷酸化水平（P<0.05），并降低ADNP受体（AdipoR1和AdipoR2）的mRNA表达。与FE组相比，3和9ng/mL的ucOCN抑制自噬接头p62和p-mTOR的水平（P<0.05），增加了LC3-II/LC3-I（P<0.05）和磷酸化腺苷5'-一磷酸活化蛋白激酶（p-AMPK）/AMPK（P<0.05），以及过氧化物酶体增殖物激活受体α(PPAR-α)和ADPN水平(P<0.05)。此外,在测试浓度下的ucOCN增加了脂肪肝细胞中LC3和LD的共定位。4μMAdipoRon激活AdipoR1和AidpoR2mRNA表达(P<0.05),降低甘油三酯浓度（P<0.05），对细胞活力无影响(P>0.05)。AdipoRon还增加了LC3-II/LC3-I比值（P<0.05）以及p-AMPK/AMPK和PPAR-α的水平（P<0.05）。总之,结果表明，ucOCN通过激活鸡胚肝细胞的ADPN-AMPK/PPARα-mTOR信号通路，从而调节脂质代谢。研究结果可能为蛋鸡FLHS的控制提供新的见解。
