Dietary fatty acids modulate liver mitochondrial cardiolipin content and its fatty acid composition in rats with non alcoholic fatty liver disease

No data are reported on changes in mitochondrial membrane phospholipids in non-alcoholic fatty liver disease. We determined the content of mitochondrial membrane phospholipids from rats with non alcoholic liver steatosis, with a particular attention for cardiolipin (CL) content and its fatty acid composition, and their relation with the activity of the mitochondrial respiratory chain complexes. Different dietary fatty acid patterns leading to steatosis were explored. With high-fat diet, moderate macrosteatosis was observed and the liver mitochondrial phospholipid class distribution and CL fatty acids composition were modified. Indeed, both CL content and its C18:2n-6 content were increased with liver steatosis. Moreover, mitochondrial ATP synthase activity was positively correlated to the total CL content in liver phospholipid and to CL C18:2n-6 content while other complexes activity were negatively correlated to total CL content and/or CL C18:2n-6 content of liver mitochondria. The lard-rich diet increased liver CL synthase gene expression while the fish oil-rich diet increased the (n-3) polyunsaturated fatty acids content in CL. Thus, the diet may be a significant determinant of both the phospholipid class content and the fatty acid composition of liver mitochondrial membrane, and the activities of some of the respiratory chain complex enzymes may be influenced by dietary lipid amount in particular via modification of the CL content and fatty acid composition in phospholipid.     

Serum acid sphingomyelinase is upregulated in chronic hepatitis C infection and non alcoholic fatty liver disease

Sphingolipids constitute bioactive molecules with functional implications in homeostasis and pathogenesis of various diseases. However, the role of sphingolipids as possible disease biomarkers in chronic liver disease remains largely unexplored. In the present study we used mass spectrometry and spectrofluorometry methods in order to quantify various sphingolipid metabolites and also assess the activity of an important corresponding regulating enzyme in the serum of 72 healthy volunteers as compared to 69 patients with non-alcoholic fatty liver disease and 69 patients with chronic hepatitis C virus infection. Our results reveal a significant upregulation of acid sphingomyelinase in the serum of patients with chronic liver disease as compared to healthy individuals (p < 0.001). Especially in chronic hepatitis C infection acid sphingomyelinase activity correlated significantly with markers of hepatic injury (r = 0.312, p = 0.009) and showed a high discriminative power. Accumulation of various (dihydro-) ceramide species was identified in the serum of patients with non-alcoholic fatty liver disease (p < 0.001) and correlated significantly to cholesterol (r = 0.448, p < 0.001) but showed a significant accumulation in patients with normal cholesterol values as well (p < 0.001). Sphingosine, a further bioactive metabolite, was also upregulated in chronic liver disease (p < 0.001). However, no significant correlation to markers of hepatic injury was identified. Conclusion: Chronic hepatitis C virus infection and non-alcoholic fatty liver disease induce a significant upregulation of serum acid sphingomyelinase which appears as a novel biomarker in chronic hepatopathies. Further studies are required to elucidate the potential of the sphingolipid signaling pathway as putative therapeutic target in chronic liver disease.     

Recent advances in alcoholic liver disease. IV. Dysregulated cytokine metabolism in alcoholic liver disease

Alcoholic liver disease (ALD) remains a leading cause of death from liver disease in the United States for which there is no FDA-approved therapy. Abnormal cytokine metabolism is a major feature of ALD. Elevated serum concentration levels of TNF-alpha and TNF-alpha-inducible cytokines/chemokines, such as IL-6, -8, and -18, have been reported in patients with alcoholic hepatitis and/or cirrhosis, and levels correlated with markers of the acute phase response, liver function, and clinical outcome. Studies in animal models support an etiologic role for cytokines in the liver injury of ALD. Cytokines, such as transforming growth factor-beta, play a critical role in the fibrosis of ALD. Multiple new strategies are under investigation to modulate cytokine metabolism as a form of therapy for ALD.     

Evidence-based efficacy of Kampo formulas in a model of non alcoholic fatty liver

Data on the efficacy of herbal compounds are often burdened by the lack of appropriate controls or a limited statistical power. Treatments to prevent the progression of non alcoholic fatty liver disease (NAFLD) to steatohepatitis (NASH) remain unsatisfactory. A total of 56 rabbits were arrayed into 7 groups fed with standard rabbit chow (SRC), SRC with 1% cholesterol, or each of the five experimental treatments (Kampo formulas 1% keishibukuryogan [KBG], 1% orengedokuto [OGT], and 1% shosaikoto [SST]; vitamin E [VE]; or pioglitazone [PG]) in a 1% cholesterol SRC. We analyzed changes after 12 weeks in plasma and liver lipid profiles, glucose metabolism, adipocytokines, oxidative stress, and liver fibrosis. Data demonstrated that all five treatments were associated with significant amelioration of lipid profiles, oxidative stress, and liver fibrosis compared to no supplementation. KBG was superior to VE and PG in the reduction of liver total cholesterol (P < 0.01) and lipid peroxidase levels (P < 0.05), urinary 8-hydroxy-2'-deoxyguanosine (P < 0.05), hepatic alpha-smooth muscle actin positive areas (P < 0.01) and activated stellate cells (P < 0.01). In conclusion, there was a statistically significant benefit of Kampo formulas (KBG in particular) on a dietary model of NAFLD/NASH. Future studies need to be directed at the mechanisms in the treatment of NASH.     

双歧杆菌三联活菌肠溶胶囊对高脂饮食所致大鼠非酒精性脂肪肝的疗效及机制探讨

目的 观察微生态制剂贝飞达(双歧杆菌三联活菌肠溶胶囊)治疗高脂饮食所致大鼠非酒精性脂肪肝的疗效并探讨其可能的作用机制.方法 雄性SD大鼠32只,适应性饲养1周后,随机分为3组,正常组:12只给予普通饲料喂养;模型组:12只,贝飞达治疗组:8只,均给予高脂饲料喂养;于喂养12周末正常组及模型组各处死4只,经肝组织HE染色确定造模成功后,贝飞达治疗组给予贝飞达[0.113 g/(kg·d)]灌胃,于16周末全部处死.检测大鼠血清AST、ALT、TC、TG、LDL、HDL、血清内毒素水平,观察其肝组织学变化.结果 模型组于高脂饲料喂养12周末出现脂肪肝,与正常组比较,模型组大鼠血清AST、ALT、TG、TC、LDL、HDL及血清内毒素水平均明显升高(P＜0.01).贝飞达治疗组大鼠各项指标较模型组均有显著改善,肝脏脂肪变性程度减轻.结论 微生态制剂贝飞达可能通过改善肠道菌群紊乱,减轻内毒素血症,从而调节肝脏脂质代谢紊乱,对非酒精性单纯性脂肪肝起到治疗作用.     

Roles of necroptosis in alcoholic liver disease and hepatic pathogenesis

Chronic alcohol consumption can cause alcoholic liver disease (ALD), leading to morbidity and mortality worldwide. Complex disease progression of ALD varies from alcoholic fatty liver to alcoholic steatohepatitis, eventually contributing to fibrosis and cirrhosis. Accumulating evidence revealed that necroptosis, a way of programmed cell death different from apoptosis and traditional necrosis, is involved in the underlying pathogenic molecular mechanism of ALD. Receptor‐interacting protein kinase 1 (RIPK1), RIPK3 and mixed‐lineage kinase domain‐like pseudokinase have been implicated as key mediators to execute necroptosis. Also, necroptosis has gained increasing attention due to its potential association with primary pathological hallmarks of ALD, including oxidative stress, hepatic steatosis and inflammation. This review summarizes the recent progress on the roles and mechanisms of necroptosis and focuses on the crosstalk between necroptosis and the other pathogenesis of ALD, providing a theoretical basis for targeting necroptosis as a novel treatment for ALD.

Necroptosis has been implicated as a novel type of programmed cell death, which is mediated by RIPK1, RIPK3 and MLKL. When caspases are inhibited, RIPK1 interacts with RIPK3 to form a complex called ‘necrosome’ and initiates necroptosis. The activation of RIPK1 and RIPK3 is modulated by post‐translational modifications, including ubiquitination and phosphorylation, which is essential to control necroptosis     

Recent insights into hepatic lipid metabolism in non-alcoholic fatty liver disease (NAFLD)

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in Western countries and is considered the hepatic manifestation of metabolic syndrome. The hallmark of NAFLD is hepatic neutral lipid accumulation, mainly triacylglycerol, in the absence of significant ethanol consumption, viral infection or other specific etiologies. Hepatic lipid accumulation results from an imbalance between lipid availability (from circulating lipid uptake or de novo lipogenesis) and lipid disposal (via free fatty acid oxidation or triglyceride-rich lipoprotein secretion) and eventually triggers lipoperoxidative stress and hepatic injury. Each of these steps is altered in NAFLD, although to a different extent. Regulation of these pathways is complex and involves nuclear receptors, membrane transport proteins and cellular enzymes. We will review available data on different steps of hepatic lipid metabolism in NAFLD and recent advances in understanding molecular mechanisms underlying hepatic fat accumulation in these subjects.     

Mesenteric adipose tissue B lymphocytes promote local and hepatic inflammation in non‐alcoholic fatty liver disease mice

Mesenteric adipose tissue (MAT) inflammation is associated with non‐alcoholic fatty liver disease (NAFLD), and immune cells play pivotal roles in the inflammation of adipose tissue. Here, we investigated the roles of MAT B lymphocytes in NAFLD. Mice fed with high‐fat diet (HFD) and normal diet (ND) were killed in time gradients (4, 8 and 12 weeks). Compared with ND‐fed mice, intra‐hepatic CD45⁺CD19⁺ B lymphocytes increased after 4 weeks (P < 0.01) of HFD feeding, and lasted until the 12th week, infiltrated earlier than CD45⁺CD3⁺ T lymphocytes and CD45⁺F4/80⁺ macrophages. The mRNA expression of tumour necrosis factor (TNF)‐α, interleukin (IL)‐6 and monocyte chemotactic protein (MCP)‐1 decreased in MAT of B^null HFD‐fed mice compared to that in wild‐type HFD‐fed mice, along with lesser macrophages. Mesenteric adipose tissue B cells from HFD‐fed mice promoted macrophage differentiation to type‐Ι macrophages and expression of pro‐inflammatory cytokines in vitro. Macrophages pre‐treated with MAT B cells from HFD‐fed mice showed elevated mRNA expression of IL‐6 and TNF‐α and declined IL‐10 levels in adipocytes compared to ND MAT B cell pre‐treated macrophages. Besides, internal near‐infrared scanning and external transwell assay showed that HFD MAT B cells migrated to the liver more than ND MAT B cells. High‐fat diet MAT B cells induced higher MCP‐1 and lower IL‐10 expression in primary hepatocytes compared to ND MAT B cells in co‐culture experiment. These data indicate that B lymphocytes infiltrate early in MAT during the development of NAFLD, which may not only promote MAT inflammation by regulating macrophages but also migrate to the liver and induce hepatocytes inflammation.     

Hepatic glutathione content in patients with alcoholic and non alcoholic liver diseases

Reduced and oxidized hepatic glutathione was evaluated during alcoholic and non alcoholic liver injury. We studied 35 chronic alcoholics, 20 patients with non alcoholic liver diseases, 15 control subjects. Hepatic glutathione was measured in liver biopsies and correlated with histology and laboratory tests. Alcoholic and non alcoholic patients exhibited a significant decrease of hepatic glutathione compared to control subjects (controls: 4.14 +/- 0.1 mumol/g liver; alcoholics: 2.55 +/- 0.1, p less than 0.001; non alcoholics 2.77 +/- 0.1, p less than 0.001). Oxidized glutathione was significantly higher in the two groups of patients compared to controls (controls: 4.4 +/- 0.2% of total; alcoholics 8.2 +/- 0.3, p less than 0.001; non alcoholics: 8.5 +/- 0.8, p less than 0.001). The decreased hepatic glutathione levels in patients with alcoholic and non alcoholic liver diseases may represent a contributing factor of liver injury and may enhance the risk of toxicity in these patients.     

Mechanism of hepatic insulin resistance in non-alcoholic fatty liver disease

Short term high fat feeding in rats results specifically in hepatic fat accumulation and provides a model of non-alcoholic fatty liver disease in which to study the mechanism of hepatic insulin resistance. Short term fat feeding (FF) caused a approximately 3-fold increase in liver triglyceride and total fatty acyl-CoA content without any significant increase in visceral or skeletal muscle fat content. Suppression of endogenous glucose production (EGP) by insulin was diminished in the FF group, despite normal basal EGP and insulin-stimulated peripheral glucose disposal. Hepatic insulin resistance could be attributed to impaired insulin-stimulated IRS-1 and IRS-2 tyrosine phosphorylation. These changes were associated with activation of PKC-epsilon and JNK1. Ultimately, hepatic fat accumulation decreased insulin activation of glycogen synthase and increased gluconeogenesis. Treatment of the FF group with low dose 2,4-dinitrophenol to increase energy expenditure abrogated the development of fatty liver, hepatic insulin resistance, activation of PKC-epsilon and JNK1, and defects in insulin signaling. In conclusion, these data support the hypothesis hepatic steatosis leads to hepatic insulin resistance by stimulating gluconeogenesis and activating PKC-epsilon and JNK1, which may interfere with tyrosine phosphorylation of IRS-1 and IRS-2 and impair the ability of insulin to activate glycogen synthase.     

Increased hepatic synthesis and dysregulation of cholesterol metabolism is associated with the severity of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is associated with increased cardiovascular and liver-related mortality. NAFLD is characterized by both triglyceride and free cholesterol (FC) accumulation without a corresponding increment in cholesterol esters. The aim of this study was to evaluate the expression of cholesterol metabolic genes in NAFLD and relate these to disease phenotype. NAFLD was associated with increased SREBP-2 maturation, HMG CoA reductase (HMGCR) expression and decreased phosphorylation of HMGCR. Cholesterol synthesis was increased as measured by the circulating desmosterol:cholesterol ratio. miR-34a, a microRNA increased in NAFLD, inhibited sirtuin-1 with downstream dephosphorylation of AMP kinase and HMGCR. Cholesterol ester hydrolase was increased while ACAT-2 remained unchanged. LDL receptor expression was significantly decreased and similar in NAFLD subjects on or off statins. HMGCR expression was correlated with FC, histologic severity of NAFLD and LDL-cholesterol. These data demonstrate dysregulated cholesterol metabolism in NAFLD which may contribute to disease severity and cardiovascular risks.     

Resveratrol alleviates alcoholic fatty liver in mice

Alcoholic fatty liver is associated with inhibition of sirtuin 1 (SIRT1) and AMP-activated kinase (AMPK), two critical signaling molecules regulating the pathways of hepatic lipid metabolism in animals. Resveratrol, a dietary polyphenol, has been identified as a potent activator for both SIRT1 and AMPK. In the present study, we have carried out in vivo animal experiments that test the ability of resveratrol to reverse the inhibitory effects of chronic ethanol feeding on hepatic SIRT1-AMPK signaling system and to prevent the development of alcoholic liver steatosis. Resveratrol treatment increased SIRT1 expression levels and stimulated AMPK activity in livers of ethanol-fed mice. The resveratrol-mediated increase in activities of SIRT1 and AMPK was associated with suppression of sterol regulatory element binding protein 1 (SREBP-1) and activation of peroxisome proliferator-activated receptor gamma coactivator alpha (PGC-1alpha). In parallel, in ethanol-fed mice, resveratrol administration markedly increased circulating adiponectin levels and enhanced mRNA expression of hepatic adiponectin receptors (AdipoR1/R2). In conclusion, resveratrol treatment led to reduced lipid synthesis and increased rates of fatty acid oxidation and prevented alcoholic liver steatosis. The protective action of resveratrol is in whole or in part mediated through the upregulation of a SIRT1-AMPK signaling system in the livers of ethanol-fed mice. Our study suggests that resveratrol may serve as a promising agent for preventing or treating human alcoholic fatty liver disease.     

非肥胖者发生非酒精性脂肪肝的预测指标

目的：探讨能够预测非肥胖者是否发生非酒精性脂肪肝（Nonalcohohc fatty liver disease,NAFLD）的临床指标。方法：从广州社区人群中选取体重指数〈25且年龄、性别相匹配的NAFLD和非NAFLD个体分别为38和82例,测量其身高、体重、腰围、臀围及空腹血糖、甘油三脂、胆固醇、低密度脂蛋白、高密度脂蛋白、HBsAg和空腹胰岛素,计算体重指数、腰臀比、腰围身高比和HOMA胰岛素抵抗指数。先采用t检验和x^2检验对上述临床指标进行分析,对两组间存在显著差异者进行Logisde回归以发现独立的预测指标,再针对各预测指标进行受试者工作特征（reciever operating charactefistic,ROC）曲线分析判断各指标的预测准确度,并确定最佳的预测截断值。结果：NAFLD和非NAFLD的体重、腰围、臀围、体重指数、腰臀比、腰围身高比及空腹血糖、甘油三脂、低密度脂蛋白、胰岛素、HOMA胰岛素抵抗指数均有显著差异,但仅腰围、低密度脂蛋白和HOMA胰岛素抵抗指数进入Logistic回归方程,且其ROC曲线下面积均大于0．5（分别是0．821,0．665和0、722）。以腰围的预测准确度最高,且在80．5cm处敏感性和特异性之和最大。结论：腰围是预测非肥胖者是否发生NAFLD的合适指标,80．5cm为其最佳预测截断值。     

Involvement and mechanism of DGAT2 upregulation in the pathogenesis of alcoholic fatty liver disease

The mechanisms involved in the development of alcoholic liver disease (ALD) are not well established. We investigated the involvement of acyl-CoA: diacylglycerol acyltransferase 2 (DGAT2) upregulation in mediating hepatic fat accumulation induced by chronic alcohol consumption. Chronic alcohol feeding caused fatty liver and increased hepatic DGAT2 gene and protein expression, concomitant with a significant suppression of hepatic MAPK/ERK kinase/extracellular regulated kinase 1/2 (MEK/ERK1/2) activation. In vitro studies demonstrated that specific inhibitors of the MEK/ERK1/2 pathway increased DGAT2 gene expression and triglyceride (TG) contents in HepG2 cells, whereas epidermal growth factor, a strong ERK1/2 activator, had the opposite effect. Moreover, chronic alcohol feeding decreased hepatic S-adenosylmethionine (SAM): S-adenosylhomocysteine (SAH) ratio, an indicator of disrupted transmethylation reactions. Mechanistic investigations revealed that N-acetyl-S-farnesyl-l-cysteine, a potent inhibitor of isoprenylcysteine carboxyl methyltransferase, suppressed ERK1/2 activation, followed by an enhanced DGAT2 expression and an elevated TG content in HepG2 cells. Lastly, we demonstrated that the beneficial effects of betaine supplementation in ALD were associated with improved SAM/SAH ratio, alleviated ERK1/2 inhibition, and attenuated DGAT2 upregulation. In conclusion, our data suggest that upregulation of DGAT2 plays an important role in the pathogenesis of ALD, and that abnormal methionine metabolism contributes, at least partially, to DGAT2 upregulation via suppression of MEK/ERK1/2 activation.