Abstract：
Nitrite, a highly toxic environmental contaminant, induces various physiological toxicities in aquatic animals. Herein, we investigate the in vivo effects of nitrite exposure at concentrations of 0, 0.2, 2, and 20 mg/L on glucose and lipid metabolism in zebrafish. Our results showed that exposure to nitrite induced mitochondrial oxidative stress in zebrafish liver and ZFL cells, which were evidenced by increased levels of malondialdehyde (MDA) and reactive oxygen species (ROS) as well as decreased mitochondrial membrane potential (MMP) and adenosine triphosphate (ATP). Changes in these oxidative stress markers were accompanied by alterations in the expression levels of genes involved in HIF-1α pathway (hif1α and phd), which subsequently led to the upregulation of glycolysis and gluconeogenesis-related genes (gk, pklr, pdk1, pepck, g6pca, ppp1r3cb, pgm1, gys1 and gys2), resulting in disrupted glucose metabolism. Moreover, nitrite exposure activated ERs (Endoplasmic Reticulum stress) responses through upregulating of genes (atf6, ern1 and xbp1s), leading to increased expression of lipolysis genes (pparα, cpt1aa and atgl) and decreased expression of lipid synthesis genes (srebf1, srebf2, fasn, acaca, scd, hmgcra and hmgcs1). These results were also in consistent with the observed changes in glycogen, lactate and decreased total triglyceride (TG) and total cholesterol (TC) in the liver of zebrafish. Our in vitro results showed that co-treatment with Mito-TEMPO and nitrite attenuated nitrite-induced oxidative stress and improved mitochondrial function, which were indicated by the restorations of ROS, MMP, ATP production, and glucose-related gene expression recovered. Co-treatment of TUDCA and nitrite prevented nitrite-induced ERs response and which was proved by the levels of TG and TC ameliorated as well as the expression levels of lipid metabolism-related genes. In conclusion, our study suggested that nitrite exposure disrupted hepatic glucose and lipid metabolism through mitochondrial dysfunction and ERs responses. These findings contribute to the understanding of the potential hepatotoxicity for aquatic animals in the presence of ambient nitrite.
摘要：
亚硝酸盐,一种剧毒的环境污染物，在水生动物中诱导各种生理毒性。在这里，我们研究了0、0.2、2和20mg/L浓度的亚硝酸盐暴露对斑马鱼体内糖脂代谢的影响。我们的结果表明，亚硝酸盐暴露会诱导斑马鱼肝脏和ZFL细胞的线粒体氧化应激，丙二醛（MDA）和活性氧（ROS）的水平升高以及线粒体膜电位（MMP）和三磷酸腺苷（ATP）的降低证明了这一点。这些氧化应激标志物的变化伴随着参与HIF-1α途径（hif1α和phd）的基因表达水平的改变，随后导致糖酵解和糖异生相关基因的上调(gk，pklr,pdk1,pepck,g6pca,ppp1r3cb,pgm1、gys1和gys2)，导致葡萄糖代谢中断。此外，亚硝酸盐暴露通过上调基因（atf6，ern1和xbp1s）激活内质网应激（内质网应激）反应，导致脂解基因表达增加(pparα，cpt1aa和atgl）和脂质合成基因表达降低（srebf1，srebf2，fasn，阿卡卡,scd,hmgcra和hmgcs1)。这些结果也与观察到的糖原变化一致，乳酸和降低斑马鱼肝脏中的总甘油三酯（TG）和总胆固醇（TC）。我们的体外研究结果表明，与Mito-TEMPO和亚硝酸盐共同处理可以减弱亚硝酸盐诱导的氧化应激并改善线粒体功能。ROS的修复表明，MMP,ATP生产，和葡萄糖相关的基因表达恢复。TUDCA和亚硝酸盐的共同治疗可防止亚硝酸盐诱导的ERs反应，这已通过TG和TC水平的改善以及脂质代谢相关基因的表达水平得到证明。总之,我们的研究提示亚硝酸盐暴露通过线粒体功能障碍和ERs反应破坏肝脏葡萄糖和脂质代谢.这些发现有助于了解在环境亚硝酸盐存在下水生动物的潜在肝毒性。
