n-3多不饱和脂肪酸、内质网应激与非酒精性脂肪肝病的研究进展

非酒精性脂肪性肝病(nonalcoholic fatty liver disease, NAFLD)已逐渐成为一个全球性健康问题, 但其发病的具体机制不甚明朗。内质网是细胞内蛋白质加工、脂质合成和钙储存的主要场所, 内质网结构和功能的失常所致的内质网应激(endoplasmic reticulum stress, ERS)对脂代谢和细胞功能具有重要调控作用, 可能是NAFLD的发生和发展的重要机制。近来大量研究显示, 脂类中特定的脂质负荷(饱和脂肪酸、胆固醇)可能是诱导ERS导致NAFLD重要原因, 而另一方面, n-3多不饱和脂肪酸(n-3 polyunsaturated fatty acids, n-3 PUFA)的摄入量却与NAFLD患病率呈负相关。本文就脂肪酸与内质网应激及其与NAFLD的联系作一综述, 进一步探讨n-3多不饱和脂肪酸防治NAFLD的机制。     

Effect of frying oils on the postprandial endoplasmic reticulum stress in obese people

The addition of antioxidants to frying oil reduces postprandial oxidative stress and the inflammatory response. ER stress may trigger both inflammation and oxidative stress processes. We aimed to determine the biological effects of the intake of four models of frying oils on postprandial ER stress in peripheral blood mononuclear cells. Twenty obese people received four breakfasts following a randomized crossover design, consisting of muffins made with different oils (virgin olive oil (VOO), sunflower oil (SFO), and a mixture of seed oils (SFO/canola oil) with either dimethylpolysiloxane (SOD) or natural antioxidants from olives (SOP) added), which were previously subjected to 20 heating cycles. ER stress was assessed by measuring the mRNA levels of sXBP1, BiP, CRT, and CNX in peripheral blood mononuclear cells. Our study showed that the intake of the muffins made with SFO induced the postprandial increase of the mRNA levels of the ER stress‐sensor sXBP1, and the ER stress related chaperones BiP and CRT (all p‐values <0.05). The harmful effects associated with the use of SFO as frying oil, in terms of inflammatory response and postprandial oxidative stress, may be partially mediated by the induction of postprandial ER stress.     

The potential of flavonoids in the treatment of non-alcoholic fatty liver disease

The contemporary pathophysiological model of non-alcoholic fatty liver disease (NAFLD) comprises multiple parallel pathways with a dynamic cross talk that cumulate in steatosis and inflammation, and ultimately fibrosis, cirrhosis, liver failure, and hepatocellular carcinoma. So far, no pharmacological treatment has been approved. A major impediment of drugs, in general, is that they are intended to act on one single target in the pathology of a disease. However, the multitude of pathways involved in the pathogenesis of NAFLD underpins the need for treatments that address these various pathways. Interestingly, flavonoids have been found to have positive effects on lipid metabolism, insulin resistance, inflammation, and oxidative stress, the most important pathophysiological pathways in NAFLD. This puts flavonoids in the spotlight for the treatment of NAFLD and prompted us to review the existing evidence for the use of these food-derived compounds in the treatment of NAFLD.     

Research progress regarding the effect and mechanism of dietary phenolic acids for improving nonalcoholic fatty liver disease via gut microbiota

Phenolic acids (PAs), a class of small bioactive molecules widely distributed in food and mainly found as secondary plant metabolites, present significant advantages such as antioxidant activity and other health benefits. The global epidemic of nonalcoholic fatty liver disease (NAFLD) is becoming a serious public health problem. Existing studies showed that gut microbiota (GM) dysbiosis is highly associated with the occurrence and development of NAFLD. In recent years, progress has been made in the study of the relationship among PA compounds, GM, and NAFLD. PAs can regulate the composition and functions of the GM to promote human health, while GM can increase the dietary sources of PAs and improve its bioavailability. This paper discussed PAs, GM, and their interrelationship while introducing several representative dietary PA sources and examining the absorption and metabolism of PAs mediated by GM. It also summarizes the effect and mechanisms of PAs in improving and regulating NAFLD via GM and their metabolites. This helps to better evaluate the potential preventive effect of PAs on NAFLD via the regulation of GM and expands the utilization of PAs and PA-rich food resources.     

Efficacy of synbiotic supplementation in patients with nonalcoholic fatty liver disease: A systematic review and meta-analysis of clinical trials: Synbiotic supplementation and NAFLD

ABSTRACT

Objective: We systematically reviewed available randomized clinical trials (RCTs) to elucidate the overall effects of synbiotic supplementation in patients with nonalcoholic fatty liver disease (NAFLD).

Methods: PubMed, Scopus, ISI Web of science and Google Scholar were searched up to December, 2017. All RCTs using synbiotic supplements to treat NAFLD included in this systematic review and meta-analysis. Mean Difference (MD) was pooled using a random-effects model.

Results: Eleven eligible databases from seven RCTs were identified for the present meta-analysis. Our results showed that synbiotic supplementation can decrease body weight, fasting blood sugar, insulin, low density lipoprotein cholesterol, total cholesterol, triglyceride, high-sensitivity C-reactive protein, tumor necrosis factor alpha, alanine transaminase and aspartate transaminase levels among patients with NAFLD. In contrast, synbiotic did not have favorable effects on body mass index (BMI), waist circumference, homeostasis model assessment for insulin resistance (HOMA-IR), and high density lipoprotein cholesterol (HDL) levels compared with the placebo group.

Conclusion: The current study revealed that synbiotic supplementation has favorable effect on inflammatory factors, liver enzymes and some anthropometric indices, lipid profiles and glucose homeostasis parameters in patients with NAFLD.     

Effects of probiotic and prebiotic supplementation on metabolic parameters,liver aminotransferases,and systemic inflammation in nonalcoholic fatty liver disease: A randomized clinical trial

This study aimed to evaluate the clinical efficacy of probiotic and prebiotic supplementation on the metabolic parameters, liver enzymes, and inflammation in patients with nonalcoholic fatty liver disease (NAFLD). In this study, patients with NAFLD were assigned to receive either probiotic capsule + placebo of prebiotic (probiotic group), oligofructose + placebo of probiotic (prebiotic group), or placebo of probiotic + placebo of prebiotic (control group) for 12 weeks. All participants followed a weight loss diet and physical activity recommendation during intervention. Anthropometric measurements decreased in all three groups, but there was no significant difference among groups. Probiotic supplementation was able to decrease triglyceride, alanine aminotransferase (ALT), aspartate aminotransferase (AST), γ-glutamyltransferase (GGT), and alkaline phosphatase compared to control group. The serum levels of triglyceride, total and low-density lipoprotein cholesterol, ALT, AST, and GGT differed significantly in prebiotic group in comparison to the placebo. High-sensitive C-reactive protein significantly decreased within all groups; however, there was no significant difference among groups after intervention. Probiotic and prebiotic may be beneficial in improving liver enzymes and lipid profile in patients with NAFLD.     

A high-concentrate diet provokes inflammation,endoplasmic reticulum stress,and apoptosis in mammary tissue of dairy cows through the upregulation of STIM1/ORAI1

High-concentrate feeding can induce subacute ruminal acidosis, which leads to mammary tissue injury in dairy cows. Therefore, the purpose of this research was to evaluate the effect of high-concentrate feeding on STIM1 (stromal interaction molecule 1)/ORAI1 (Orai calcium release-activated calcium modulator 1)-mediated inflammation, endoplasmic reticulum stress (ERS), and apoptosis in the mammary tissue of dairy cows. A total of 12 healthy mid-lactating Holstein cows of similar weight were randomly allotted into the following 2 groups: a high-concentrate (HC) group (concentrate:forage = 6:4) and a low-concentrate (LC) group (concentrate:forage = 4:6). The trial lasted for 3 wk. After the feeding experiment, rumen fluid, lacteal vein blood, and mammary tissue samples were collected. The results showed that the HC diet significantly increased blood lipopolysaccharide levels, decreased ruminal pH, and upregulated the concentrations of Ca²⁺ and proinflammatory cytokines, including TNF-α, IL-1β, and IL-6, and the enzyme activities of caspase-3, caspase-9, PKC, and IKK. The upregulation of STIM1, ORAI1, PKCα, IKKβ, phosphorylated-IκBα, phosphorylated-p65, TNF-α, and IL-1α proteins in the HC group indicated activation of the STIM1/ORAI1-mediated inflammatory signaling pathway compared with that in the LC group. The HC diet also induced ERS by increasing the mRNA and protein abundances of GRP78, CHOP, PERK, ATF6, and IRE1α in the mammary tissue. Compared with the LC group, the mRNA expression levels and protein abundances of caspase-3, cleaved caspase-3, caspase-9, and BAX were markedly increased in the HC group. However, the mRNA and protein expression levels of Bcl-2 were significantly decreased in the HC group. Therefore, this study demonstrated that the HC diet can activate the store-operated calcium entry channel by upregulating the expression of STIM1 and ORAI1 and induce inflammation, ERS, and apoptosis in the mammary tissue of dairy cows.     

Hut1 proteins identified in Saccharomyces cerevisiae and Schizosaccharomyces pombe are functional homologues involved in the protein-folding process at the endoplasmic reticulum

The Saccharomyces cerevisiae HUT1 gene (scHUT1) and the Schizosaccharomyces pombe hut1(+) gene (sphut1(+)) encode hydrophobic proteins with approximately 30% identity to a human UDP-galactose transporter-related gene (UGTrel1) product. These proteins show a significant similarity to the nucleotide sugar transporter and are conserved in many eukaryotic species, but their physiological functions are not known. Both scHUT1 and sphut1(+) genes are non-essential for cell growth under normal conditions, and their disruptants show no defects in the modification of O- and N-linked oligosaccharides, but are sensitive to a membrane-permeable reducing agent, dithiothreitol (DTT). Consistent with this phenotype, scHUT1 has genetic interaction with ERO1, which plays an essential role in the oxidation of secretory proteins at the endoplasmic reticulum (ER). Overexpression of the MPD1 or MPD2 genes, which were isolated as multicopy suppressors of protein disulphide isomerase (PDI) depletion, could not replace the essential function of PDI in Delta hut1 S. cerevisiae cells. Our results indicate that scHut1p and spHut1p are functional homologues, and their physiological function is to maintain the optimal environment for the folding of secretory pathway proteins in the ER.     

Dietary Monascus adlay supplements facilitate suppression of cigarette smoke-induced pulmonary endoplasmic reticulum stress,autophagy, apoptosis and emphysema-related PLGF in the rat

Cigarette smoke (CS) exposure may cause oxidative stress in the lung, leading to cell death and long-term injury. Monascus adlay (MA) with antioxidant components produced by inoculating adlay (Cois lachrymal-jobi L. var. ma-yuen Stapf) with Monascus purpureus may protect lung against CS-induced lung injuries in rats. MA and lovastatin had higher antioxidant activities than either M. purpureus or adlay. CS exposure caused significant lung damage, as evidenced by higher levels of reactive oxygen species (ROS), neutrophil infiltration, dityrosine and 4-HNE, as well as lower levels of Mn-superoxide dismutase and catalase expression. Lung tissues with CS exposure had higher levels of ER stress, apoptosis, autophagy and emphysema-related placenta growth factor (PlGF) expressions. All CS-induced injuries were significantly suppressed by MA supplements. MA would be a beneficial nutritional therapy to ameliorate CS-induced lung injury via preserving antioxidant defense mechanisms, decreasing oxidative stress and inhibiting ER stress, autophagy, apoptosis and emphysema-related risk factor.     

Tolerance to thermal and reductive stress in Saccharomyces cerevisiae is amenable to regulation by phosphorylation-dephosphorylation of ubiquitin conjugating enzyme 1 (Ubc1) S97 and S115

Ubiquitin conjugating enzyme 1 (Ubc1) is a member of the E2 family of enzymes that conjugates ubiquitin to damaged proteins destined for degradation by the ubiquitin proteasomal system. It is necessary for stress tolerance and is essential for cell survival in Saccharomyces cerevisiae. Ubc1 has five serine residues that are potential substrates for phosphorylation by kinases. However, no data are available to indicate that Ubc1 function or stress tolerance in S. cerevisiae is regulated by serine phosphorylation of Ubc1. We demonstrate that Ubc1 is phosphorylated in serine residue(s). Furthermore, expression of Ubc1 mutants that are ‘constitutively phosphorylated’ or ‘dephosphorylated’ in mitogen‐activated protein (MAP) kinase serine residues (S97 and S115) affected tolerance to thermal and reductive stress in S. cerevisiae. Specifically, expression of Ubc1S97A and S115D increased thermo‐tolerance in both BY4741 and TetO₇‐UBC1ura3Δ cells. Serine phosphorylation of Ubc1 was decreased in BY4741 cells following exposure at 40 °C. Tolerance to reductive stress in the same strains correlated with the expression of Ubc1S97A. Ubc1 phosphorylation did not show significant alteration under similar conditions. Both hog1Δ and slt2Δ cells expressing Ubc1S115D and Ubc1S115A were rendered tolerant to thermal and reductive stress respectively. Ubc1 phosphorylation was higher in BY4741 cells compared to hog1Δ cells at 30 °C and was significantly reduced in BY4741 cells upon exposure at 40 °C. Taken together, the cell survival assays and Ubc1 phosphorylation status in strains and under conditions as described above suggest that tolerance to thermal and reductive stress in S. cerevisiae may be regulated by MAP kinase‐mediated phosphorylation of Ubc1S97 and S115. Copyright © 2011 John Wiley & Sons, Ltd.     

木瓜发酵液对非酒精性脂肪性肝病小鼠肝脏脂质代谢及AMPK/SIRT1通路的影响

目的:观察木瓜发酵液对高糖高脂饲料诱导的非酒精性脂肪性肝病（NAFLD）小鼠脂质代谢及AMP激活蛋白酶（AMPK）/沉默信息调节因子1（SIRT1）通路的调控机制。方法:取雄性昆明小鼠32只,随机分为4组,即正常组、模型组、木瓜发酵液高（10 m L/kg）和低剂量组（5 m L/kg）,每组8只。三周后,收集小鼠血液及组织样本。用试剂盒检测血清ALT、肝组织甘油三酯（TG）含量,分别用RT-PCR和Western Bloting检测p-AMPK和SIRT1基因的mRNA和蛋白表达水平。结果:与正常组比较,模型组小鼠病理证实肝组织脂质蓄积严重,血清ALT和肝脏TG水平明显升高（p<0.05）,肝组织SIRT1、Fox O1和p-AMPK mRNA及蛋白表达均显著降低（p<0.05）。与模型组比较,木瓜发酵液明显改善肝组织脂质蓄积,肝组织TG含量明显下降（p<0.05）,肝组织SIRT1、Fox O1 mRNA和SIRT1、p-AMPK蛋白表达均显著上调（p<0.05）,其中木瓜发酵液高剂量组较低剂量组效果好,但二者比较差异无统计学意义。结论:木瓜发酵液能够改善高糖高脂饮食诱导的NAFLD小鼠脂肪代谢紊乱,减轻肝脏脂质蓄积,其作用机制可能与肝细胞内AMPK/SIRT1通路的激活有关。      

基于Nrf2/CYP2E1通路探讨刺梨多糖对酒精性肝损伤小鼠的保护机制

目的:探讨刺梨多糖（Rosa roxburghii polysaccharide,RP）对食用酒精诱导的酒精中毒小鼠肝脏的影响及保护机制。方法:采用热水浸提法制得纯度为64％的RP。将60只健康KM雄性小鼠分为空白组、模型组、阳性组、RP低、中、高剂量组,连续给药15d,于末次给药4h后,除空白组外,其余各组一次性灌胃16 mL/kg 50％的食用酒精建立酒精性肝损伤（alcoholic liver disease,ALD）小鼠模型;解剖后记录脏器质量,测定血清中谷草转氨酶（aspartate aminotransferase,AST）、谷丙转氨酶（alanine aminotransferase,ALT）、总胆固醇（total cholesterol,TC）、甘油三酯（triglyceride,TG）含量、测定肝脏氧化应激指标含量,核因子-红细胞2相关因子2（nuclear factor erythroid2-related factor 2,Nrf2）信号通路相关蛋白表达量及细胞色素P450 2E1（cytochrome P450 2E1,CYP2E1）蛋白表达量、并进行肝脏病理和肝细胞凋亡观察。结果:与模型组相比,RP各剂量组均能降低肝脏指数、血清中转氨酶AST、ALT,血脂指标TC、TG含量、肝脏丙二醛（Malonaldehyde,MDA）含量,提高谷胱甘肽（glutathione,GSH）、超氧化物歧化酶（superoxide dismutase,SOD）含量,上调Nrf2、血红素氧合酶1(heme oxygenase-1,HO-1)、超氧化物歧化酶1（superoxide dismutase-1,SOD-1）蛋白表达量,下调CYP2E1蛋白表达量,并改善肝脏病变和肝细胞凋亡情况。结论:RP对酒精性肝损伤小鼠起到良好的护肝效果,这可能与调控Nrf2信号通路起到抗氧化作用及调节脂质代谢有关。