丁酸在非酒精性脂肪性肝病发生发展中的作用

非酒精性脂肪性肝病(NAFLD)特征为非酒精性因素所致的肝脂肪变性,其发病机制、疾病演变过程以及治疗和预防都逐渐受到广泛重视。目前关于肠道微生态与肥胖、糖尿病、心血管疾病等代谢性疾病关系的研究越来越多。近来也有许多研究发现肠道菌群代谢产物丁酸与NAFLD有着密切的关系,通过多种机制影响NAFLD的发生发展,如减轻炎症反应、抑制胰岛素抵抗以及减弱肝线粒体氧化应激等,研究丁酸与NAFLD疾病发病的关系有望为NAFLD的防治开辟新的途径。     

Current pharmacological therapies for nonalcoholic fatty liver disease/nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease(NAFLD)/nonalcoholic steatohepatitis(NASH) is considered to be a hepatic manifestation of metabolic syndrome, and its incidence is rapidly increasing worldwide. It is currently the most common chronic liver disease. NASH can progress to liver cirrhosis and hepatocellular carcinoma, and may result in liver-related death. Currently, the principal treatment for NAFLD/NASH is lifestyle modification by diet and exercise. However, pharmacological therapy is indispensable because obese patients with NAFLD often have difficulty maintaining improved lifestyles. The pathogenesis of NAFLD/NASH has not been completely elucidated. However, insulin resistance, inflammatory cytokines, and oxidative stress are thought to be important in the development and/or progression of the disease. Currently, insulin sensitizers(thiazolidinediones) and antioxidants(vitamin E) seem to be the most promising therapeutic agents for NAFLD/NASH, and lipid-lowering drugs, pentoxifylline, angiotensin receptor blockers, and n-3 polyunsaturated fatty acids also have promise. However, there is a lack of consensus regarding the most effective and appropriate pharmacotherapy for NAFLD/NASH. Animal experiments suggest that herbal medicines and natural products may be promising therapeutic agents for NAFLD/NASH, but their efficacy and safety are yet to be investigated in human studies. In this paper, we review the existing and potential pharmacological therapies for NAFLD/NASH.     

Probiotics as a complementary therapeutic approach in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease(NAFLD) is currently recognized as one of the most common causes of chronic liver disease. It involves a spectrum of conditionsthat include pure steatosis without inflammation, steatohepatitis, fibrosis and cirrhosis. The key factor in the pathophysiology of NAFLD is insulin resistance that determines lipid accumulation in the hepatocytes and, thus, oxidative stress, which is followed by inflammatory response. However, NAFLD pathogenesis is still largely unknown and has been extensively investigated. Although life style modification with the aim of losing weight has been advocated to treat this disorder, its effectiveness is limited; additionally, there is no specific pharmacologic treatment until nowadays. Recent evidence suggests that the gut microbiota may play a role in the development of insulin resistance, hepatic steatosis, necroinflammation and fibrosis. Differences in gut microbiota between NAFLD patients and lean individuals as well as presence of small intestinal bacterial overgrowth in NAFLD subjects have been demonstrated. Furthermore, some data indicate that the immunoregulatory effects of probiotics may be beneficial in NAFLD treatment as they modulate the intestinal microbiota; improve epithelial barrier function and strengthen the intestinal wall decreasing its permeability; reduce bacterial translocation and endotoxemia; improve intestinal inflammation; and reduce oxidative and inflammatory liver damage. In this article, we review the clinical trials on the use of probiotics in the treatment of NAFLD and discuss the effects of these agents and their efficacy as an emerging therapeutic resource to treat NAFLD patients.     

Insulin resistance in development and progression of nonalcoholic fatty liver disease

Although insulin resistance(IR)is strongly associated with nonalcoholic fatty liver disease(NAFLD),the association of IR and NAFLD is not universal and correlation between IR and severity of NAFLD is still controversial.In this review,we summarize recent evidence that partially dissociates insulin resistance from NAFLD.It has also been reported that single-nucleotide polymorphisms in the diacylglycerol acyltransferase gene,rather than IR,account for the variability in liver fat content.Polymorphisms of the patatin-like phospholipase 3 gene have also been reported to be associated with NAFLD without metabolic syndrome,which suggests that genetic conditions that promote the development of fatty changes in the liver may occur independently of IR.Moreover,environmental factors such as nutrition and physical activity as well as small intestinal bacterial overgrowth have been linked to the pathogenesis of NAFLD,although some of the data are conflicting.Therefore,findings from both genetically engineered animal models and humans with genetic conditions,as well as recent studies that have explored the role of environmental factors,have confirmed the view that NAFLD is a polygenic disease process caused by both genetic and environmental factors.Therefore,IR is not the sole predictor of the pathogenesis of NAFLD.     

肠道菌群与非酒精性脂肪性肝病研究进展

非酒精性脂肪性肝病(nonalcoholic fatty liver disease,NAFLD)发病率不断升高,对其发生、发展及防治研究变得极为迫切。近年来肠道菌群被认为是机体一个重要的"特殊器官",参与机体代谢及相关疾病的发生、发展,与NAFLD关系密切。本文就肠道菌群与NAFLD的关系研究进行综述。     

An integrated view of liver injury and disease progression in nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is rapidly becoming the most common cause of chronic liver disease globally. NAFLD represents a host of pathophysiologic mechanisms that culminate in the accumulation of fat, in a predominantly macrovesicular pattern, in the liver along with varying degrees of inflammation, hepatocellular injury, apoptosis and fibrosis. The most common mechanism for the development of NAFLD is insulin resistance. Insulin resistance is commonly associated with obesity, although it can develop in individuals who do not have obesity. A consequence of insulin resistance is increased peripheral lipolysis and increased delivery of free fatty acids to the liver. The concept of lipotoxicity emerged as the mechanisms by which fatty acids produce cell injury, promote apoptosis and activate inflammatory pathways were elucidated. While much work has been done mainly in cell culture models, the free fatty acid concentration in the liver is not significantly changed in NAFLD. Recently, the focus has shifted to alterations in other lipid metabolic pathways that appear to play an important role in the genesis of nonalcoholic steatohepatitis, the aggressive form of NAFLD. The innate immune system and the intestinal microbiota have been implicated in the development of NAFLD. These mechanisms are reviewed in this article.     

Mediterranean diet and nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease(NAFLD) is emerging as the most common chronic liver disease, and is characterized by a wide spectrum of fat-liver disorders that can result in severe liver disease and cirrhosis. Inflammation and oxidative stress are the major risk factors involved in the pathogenesis of NAFLD. Currently, there is no consensus concerning the pharmacological treatment of NAFLD. However, lifestyle interventions based on exercise and a balanced diet for quality and quantity, are considered the cornerstone of NAFLD management. Mediterranean diet(MD), rich in polyunsaturated fats, polyphenols, vitamins and carotenoids, with their anti-inflammatory and antioxidant effects, has been suggested to be effective in preventing cardiovascular risk factors. In adults, MD has also been demonstrated to be efficacious in reducing the risk of metabolic syndrome. However, few studies are available on the effects of the MD in both adult and pediatric subjects with NAFLD. Thus, the aims of the present narrative review are to analyze the current clinical evidence on the impact of MD in patients with NAFLD, and to summarize the main mechanisms of action of MD components on this condition.     

非酒精性脂肪性肝病对肠道炎症及通透性的影响

目的通过高脂饮食建立非酒精性脂肪性肝病(NAFLD)大鼠模型,观察NAFLD大鼠是否也同时伴随存在肠道炎症,并探讨NAFLD对肠道通透性的影响。方法 24只雄性大鼠以1∶1比例随机接受标准饲料和高脂饲料喂食18周,分别建立对照组和NAFLD大鼠模型。通过大鼠肝脏病理切片HE染色和油红O染色验证模型的成立,根据大鼠结肠病理切片HE染色观察是否存在肠道炎症进行进一步分组分析。使用酶联免疫吸附测定血浆二胺氧化酶、D-乳酸水平和内毒素水平,检测肠道通透性改变情况。结果与对照组相比,12只NAFLD大鼠肝脏均呈大泡和小泡性脂肪变以及气球样变,其中发现有7只大鼠的肠道存在轻度炎症细胞浸润,组织学符合肠道炎症改变;NAFLD组中另5只大鼠未见组织学上肠道炎症改变;而在对照组中未见任何肠道炎症改变。与对照组相比,NAFLD大鼠血浆中二胺氧化酶和D-乳酸水平显著升高(P0.05)。其中,NAFLD伴肠道炎症组大鼠的D-乳酸水平较NAFLD不伴肠道炎症组显著升高(P0.05)。NAFLD伴肠道炎症组大鼠血浆中LBP水平明显高于对照组和NAFLD不伴肠道炎症组(均P0.05)。结论 NAFLD可增加肠道炎症发生的风险,NAFLD导致肠道炎症时肠道通透性显著增加。     

Melatonin ameliorates nonalcoholic fatty liver induced by high-fat diet in rats

Nonalcoholic fatty liver disease (NAFLD) is an increasingly recognized condition that may progress to end-stage liver disease, which ranges from simple steatosis to steatohepatitis, advanced fibrosis, and cirrhosis. Oxidative stress and lipid peroxidation are key pathophysiological mechanisms in NAFLD. We investigate the preventive effects of intraperitoneal administration of melatonin (2.5, 5, 10 mg/kg, daily, respectively) in NAFLD rats induced by high-fat diets for 12 wk. Liver damage was evaluated by serological analysis, serum and hepatic lipid assay as well as hematoxylin-eosin staining in liver sections. Oxidative stress and lipid peroxidation were assessed by measuring malondialdehyde (MDA) levels and superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities in liver. The results showed that high-fat diet induced oxidative stress with extensive liver steatosis in rats. Melatonin (5 or 10 mg/kg) was effective in reducing hepatic steatosis and inflammation with lowering serum alanine aminotransferase, aspartate aminotransferase, and levels liver total cholesterol and triglycerides in high-fat diet rats. Moreover, melatonin (2.5, 5, 10 mg/kg) increased SOD and GSH-Px activities and the 10 mg/kg dose of melatonin reduced MDA levels in liver. This study shows that melatonin exerts protective effects against fatty liver in rats induced by high-fat diet possibly through its antioxidant actions.     

Probiotics and antibodies to TNF inhibit inflammatory activity and improve nonalcoholic fatty liver disease

Ob/ob mice, a model for nonalcoholic fatty liver disease (NAFLD), develop intestinal bacterial overgrowth and overexpress tumor necrosis factor alpha (TNF-alpha). In animal models for alcoholic fatty liver disease (AFLD), decontaminating the intestine or inhibiting TNF-alpha improves AFLD. Because AFLD and NAFLD may have a similar pathogenesis, treatment with a probiotic (to modify the intestinal flora) or anti-TNF antibodies (to inhibit TNF-alpha activity) may improve NAFLD in ob/ob mice. To evaluate this hypothesis, 48 ob/ob mice were given either a high-fat diet alone (ob/ob controls) or the same diet + VSL#3 probiotic or anti-TNF antibodies for 4 weeks. Twelve lean littermates fed a high-fat diet served as controls. Treatment with VSL#3 or anti-TNF antibodies improved liver histology, reduced hepatic total fatty acid content, and decreased serum alanine aminotransferase (ALT) levels. These benefits were associated with decreased hepatic expression of TNF-alpha messenger RNA (mRNA) in mice treated with anti-TNF antibodies but not in mice treated with VSL#3. Nevertheless, both treatments reduced activity of Jun N-terminal kinase (JNK), a TNF-regulated kinase that promotes insulin resistance, and decreased the DNA binding activity of nuclear factor kappaB (NF-kappaB), the target of IKKbeta, another TNF-regulated enzyme that causes insulin resistance. Consistent with treatment-related improvements in hepatic insulin resistance, fatty acid beta-oxidation and uncoupling protein (UCP)-2 expression decreased after treatment with VSL#3 or anti-TNF antibodies. In conclusion, these results support the concept that intestinal bacteria induce endogenous signals that play a pathogenic role in hepatic insulin resistance and NAFLD and suggest novel therapies for these common conditions.     

Screening and interventions to prevent nonalcoholic fatty liver disease/nonalcoholic steatohepatitis-associated hepatocellular carcinoma

Liver cancer is the sixth most commonly diagnosed cancer worldwide, with hepatocellular carcinoma (HCC) comprising most cases. Besides hepatitis B and C viral infections, heavy alcohol use, and nonalcoholic steatohepatitis (NASH)-associated advanced fibrosis/cirrhosis, several other risk factors for HCC have been identified (i.e. old age, obesity, insulin resistance, type 2 diabetes). These might in fact partially explain the occurrence of HCC in non-cirrhotic patients without viral infection. HCC surveillance through effective screening programs is still an unmet need for many nonalcoholic fatty liver disease (NAFLD) patients, and identification of pre-cirrhotic individuals who progress to HCC represents a substantial challenge in clinical practice at the moment. Patients with NASH-cirrhosis should undergo systematic HCC surveillance, while this might be considered in patients with advanced fibrosis based on individual risk assessment. In this context, interventions that potentially prevent NAFLD/ NASH-associated HCC are needed. This paper provided an overview of evidence related to lifestyle changes (i.e. weight loss, physical exercise, adherence to healthy dietary patterns, intake of certain dietary components, etc.) and pharmacological interventions that might play a protective role by targeting the underlying causative factors and pathogenetic mechanisms. However, well-designed prospective studies specifically dedicated to NAFLD/NASH patients are still needed to clarify the relationship with HCC risk.     

Obesity,fatty liver disease and intestinal microbiota

Nonalcoholic fatty liver disease(NAFLD) is a chronic liver disorder that is increasing in prevalence with the worldwide epidemic of obesity. NAFLD is the hepatic manifestation of the metabolic syndrome. The term NAFLD describes a spectrum of liver pathology ranges from simple steatosis to steatosis with inflammation nonalcoholic steatohepatitis and even cirrhosis. Metabolic syndrome and NAFLD also predict hepatocellular carcinoma. Many genetic and environmental factors have been suggested to contribute to the development of obesity and NAFLD, but the exact mechanisms are not known. Intestinal ecosystem contains trillions of microorganisms including bacteria, Archaea, yeasts and viruses. Several studies support the relationship between the intestinal microbial changes and obesity and also its complications, including insulin resistance and NAFLD. Given that the gut and liver are connected by the portal venous system, it makes the liver more vulnerable to translocation of bacteria, bacterial products, endotoxins or secreted cytokines. Altered intestinal microbiota(dysbiosis) may stimulate hepatic fat deposition through several mechanisms: regulation of gut permeability, increasing low-grade inflammation, modulation of dietary choline metabolism, regulation of bile acid metabolism and producing endogenous ethanol. Regulation of intestinal microbial ecosystem by diet modifications or by using probiotics and prebiotics as a treatment for obesity and its complications might be the issue of further investigations.     

胡桃苷对非酒精性脂肪性肝小鼠中肝脂质代谢紊乱、肝损伤以及小肠完整性的改善作用

背景现有研究对胡桃苷在非酒精性脂肪性肝病(nonalcoholicfattyliverdisease,NAFLD)中的治疗作用尚未得到充分关注.目的本研究通过高脂饮食(high fatty diet, HFD)小鼠模型评估了胡桃苷在NAFLD中的治疗效果.方法C57B L/6小鼠分为标准饮食组、H F D组、胡桃苷低、中和高剂量治疗组.给药方案结束后,采集小鼠血样和组织(肝和小肠)进行生化及组织学测定.结果胡桃苷抑制了HFD诱导的肝组织形态学改变和肝脂质沉积,并降低了血清中谷草转氨酶、谷丙转氨酶和胆固醇含量以及葡萄糖、血清胰岛素水平和胰岛素抵抗稳态模型值.胡桃苷显著改善了HFD引起的代谢损伤,增加了肝脏过氧化物酶体增殖体激活受体及其下游调节基因成纤维细胞生长因子21的m RNA水平,并且提高了乙酰辅酶A羧化酶的磷酸化水平和肉碱-棕榈酰基转移酶的m RNA水平.此外,胡桃苷还减少了肝脏炎症,恢复了肠道屏障的完整性和功能(FITC-dextran通透性下降和小肠组织紧密连接蛋白1表达增加).结论胡桃苷可恢复NAFLD引起的脂肪变性、减少肝脏炎症、恢复葡萄糖稳态和改善肠道完整性.     

Noncoding RNAs as additional mediators of epigenetic regulation in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) has emerged as the most common cause of chronic liver disorder worldwide. It represents a spectrum that includes a continuum of different clinical entities ranging from simple steatosis to nonalcoholic steatohepatitis, which can evolve to cirrhosis and in some cases to hepatocellular carcinoma, ultimately leading to liver failure. The pathogenesis of NAFLD and the mechanisms underlying its progression to more pathological stages are not completely understood. Besides genetic factors, evidence indicates that epigenetic mechanisms occurring in response to environmental stimuli also contribute to the disease risk. Noncoding RNAs (ncRNAs), including microRNAs, long noncoding RNAs, and circular RNAs, are one of the epigenetic factors that play key regulatory roles in the development of NAFLD. As the field of ncRNAs is rapidly evolving, the present review aims to explore the current state of knowledge on the roles of these RNA species in the pathogenesis of NAFLD, highlight relevant mechanisms by which some ncRNAs can modulate regulatory networks implicated in NAFLD, and discuss key challenges and future directions facing current research in the hopes of developing ncRNAs as next-generation non-invasive diagnostics and therapies in NAFLD and subsequent progression to hepatocellular carcinoma.     

饮食对非酒精性脂肪性肝病肠道微生物菌型相关菌群的影响

非酒精性脂肪性肝病(NAFLD)是一种典型的慢性肝病,与肠道微生态的失调密切相关。饮食因素可能是影响肠道细菌组成和功能的最重要的驱动因素。基于肠道微生物菌型的概念,总结了饮食对NAFLD肠道微生物菌型相关菌群的影响,包含厚壁菌门/拟杆菌门的比值、拟杆菌属、普雷沃菌属、瘤胃球菌属、变形菌门、放线菌门及其他菌。指出改善饮食进而调节肠道菌群是防治NAFLD的重要策略之一,具有良好的前景,但尚需进一步的机制和临床研究。     

饮食干预对非酒精性脂肪性肝病肠道菌群的影响

非酒精性脂肪性肝病(NAFLD)的发生与遗传和环境密切相关,肠道菌群在其发生和发展中发挥了重要作用,调节肠道菌群已成为干预NAFLD的重要靶点之一.无论是饮食总量还是结构都会对肠道菌群产生直接且长期的影响.通过低脂饮食、增加饮食中不饱和脂肪酸或者增加难以吸收的多糖等方式调整饮食结构,可以有效调节肠道菌群并治疗NAFLD,但高蛋白饮食的作用还存在争议.     

Dietary approach in the treatment of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease(NAFLD) has been identified as one of the most prevalent chronic liver disease in adults and children populations. NAFLD is usually associated with the metabolic syndrome(MS), which is chiefly related to insulin resistance and its consequences. Insulin resistance has a crucial role in the pathogenesis of hepatic steatosis and potentially nonalcoholic steatohepatitis(NASH). Because of the contemporary epidemics of MS and obesity, the burden of NAFLD is also expected to rise. Unhealthy diets, such as the so-called western diet, are enriched in fructose, trans-fatty acids and saturated fat and seem to be associated with the development of NAFLD. In human studies, certain dietary sugars, particularly fructose, are used as a substrate for lipogenesis leading to hepatic fatty infiltration, inflammation, and possibly fibrosis. Other investigations have shown that fat consumption especially cholesterol and trans/saturated fatty acids are also steatogenic and seem to increase visceral adiposity. The identification of specific dietary components that favor the development of NASH could be important for the management of this disorder. This review focuses on the effects of different dietary approaches to prevent and treat NAFLD emphasizing the macronutrients and energy composition.     

非酒精性脂肪性肝病与动脉粥样硬化之间关系的研究进展

非酒精性脂肪性肝病( NAFLD)常与肥胖、糖尿病、高血脂、高血压以及代谢综合征合并存在,认为是代谢综合征的肝脏表现。NAFLD的患病率约20％～30％,在2型糖尿病人群中NAFLD患病率更高。NAFLD与心血管疾病(CVD)关系密切,NAFLD患者的主要死亡原因是CVD。NAFLD和动脉粥样硬化(AS)关系密切,其机制可能涉及氧化应激、炎症反应、脂代谢紊乱、脂肪激素水平的变化和胰岛素抵抗等方面。本文就NAFLD和AS间的关系以及可能机制进行综述。     

The role of nutrients in the development, progression, and treatment of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of liver disease in adults and children and is currently the third most common indication for liver transplantation in North America. Its pathogenesis is thought to be secondary to multiple "hits" derived from the dietary components, adipose tissue, immune system, and intestinal microbiota. Lack of physical activity may contribute as well. Nutrients may exert their effect directly or through alteration of the intestinal microbiota. Research focusing on specific dietary components predisposing to NAFLD has shown conflicting results. Total energy intake, and macronutrients, has been linked to the development of NAFLD. Fructose not only contributes to hepatic steatosis but may trigger inflammatory signals as well. Polyunsaturated fatty acids are thought to exert anti-inflammatory effects. The role of vitamins as well as minerals in this field is actively being investigated. In this review, we discuss the evidence-linking macronutrients (such as carbohydrates and fat in general and fructose, fiber, short chain fatty acids, polyunsaturated fatty, and choline specifically) and micronutrients (such as vitamin E and C and minerals) with the development and treatment of NAFLD. We also discuss the literature on physical activity and NAFLD.