Propionate alleviates palmitic acid-induced endoplasmic reticulum stress by enhancing autophagy in calf hepatic cells
Propionate alleviates palmitic acid-induced endoplasmic reticulum stress by enhancing autophagy in calf hepatic cells
复制标题
丙酸通过增强小牛肝细胞自噬减轻棕榈酸诱导的内质网应激
DOI：
10.3168/jds.2020-19969
复制
发表时间：
2021-07-08
影响因子：
3.5
通讯作者：
Du, Xiliang
中科院分区：
文献类型：
--
作者：
Gao, Wenwen;Fang, Zhiyuan;Du, Xiliang
能量负平衡导致奶牛产后早期血液中游离脂肪酸浓度升高是导致奶牛肝损伤的主要原因。处于严重负能量平衡的奶牛通常具有次优的饲料摄入量，这导致瘤胃丙酸盐和循环葡萄糖的生产不足。虽然通过饲料添加剂（如丙二醇）增加瘤胃丙酸盐的产生可有效帮助奶牛缓解膳食能量供应不足，但丙酸盐影响肝脏功能的机制尚不清楚。因此，本研究的目的是探讨丙酸盐是否可以保护小牛肝细胞免受棕榈酸（PA）诱导的脂毒性和潜在的机制。从5头健康小牛（1日龄，雌性，30-40 kg，禁食）中分离小牛肝细胞，在给予或不给予自噬抑制剂后，用不同浓度的PA（0，100，200或400 μ M）和丙酸盐（0，1，2或4 mM）处理。丙酸盐增强小牛肝细胞中的自噬活性，如自噬标记物LC 3-II（微管相关蛋白1轻链3-II，由MAP 1 LC 3编码）的表达升高和SQSTM 1（隔离体-1，也称为p62）的表达降低所示。相反，PA抑制自噬活性，降低细胞活力，这是改善丙酸在小牛肝细胞。此外，丙酸盐降低了PA处理的小牛肝细胞中蛋白EIF 2AK 3（激酶R/PKR，如ER激酶）和ERN 1（肌醇需要酶1 α）的磷酸化，并切割了ATF 6（激活转录因子6），表明丙酸盐对内质网（ER）应激的抑制作用。然而，氯喹或巴弗洛霉素A1对自噬活性的抑制阻碍了丙酸盐对ER应激和细胞活力的有益作用。这些结果表明，丙酸盐通过增强自噬作用减轻了PA处理的小牛肝细胞的内质网应激，提高了细胞活力，这表明自噬可能是改善奶牛过渡期肝损伤的一个有希望的靶点。
Negative energy balance-induced high blood concentrations of free fatty acids during the early postpartum period in dairy cows is a major cause of liver injury. Cows in severe negative energy balance often have suboptimal intakes of feed, which contributes to shortfalls in production of ruminal propionate and circulating glucose. Although increasing propionate production by the rumen through feed additives such as propylene glycol is effective in helping cows alleviate the shortfall in dietary energy supply, mechanisms whereby propionate affects liver function beyond gluconeogenesis are unknown. Therefore, the objective of this study was to investigate whether propionate could protect calf hepatic cells from palmitic acid (PA)-induced lipotoxicity and the underlying mechanisms. Calf hepatic cells were isolated from 5 healthy calves (1 d old, female, 30-40 kg, fasting) and treated with various concentrations of PA (0, 100, 200, or 400 mu M) and propionate (0, 1, 2, or 4 mM) after being administered with or without autophagic inhibitor. Propionate enhanced autophagic activity in calf hepatic cells, as indicated by elevated expression of autophagy markers LC3-II (microtubule-associated protein 1 light chain 3-II, encoded by MAP1LC3) and decreased expression of SQSTM1 (sequestosome-1, also called p62). Conversely, PA suppressed autophagic activity and decreased cell viability, which was improved by propionate in calf hepatic cells. In addition, propionate decreased the phosphorylation of proteins EIF2AK3 (kinase R/PKR like ER kinase) and ERN1 (inositol-requiring enzyme 1 alpha) and cleaved ATF6 (activating transcription factor 6) in PA-treated calf hepatic cells, indicating the suppression effect of propionate on endoplasmic reticulum (ER) stress. However, inhibition of autophagic activity by chloroquine or bafilomycin A1 impede the beneficial effects of propionate on ER stress and cell viability. These results demonstrated that propionate alleviates ER stress and elevates cell viability in PA-treated calf hepatic cells by enhancing autophagy, which implies that autophagy may be a promising target in improving liver injury of dairy cows during transition period.