Nonalcoholic fatty liver disease (NAFLD) represents a broad spectrum of histological abnormalities with clinical presentations ranging from hepatic steatosis to nonalcoholic steatohepatitis (NASH). ...Some NAFLD patients may progress to cirrhosis and ultimately hepatocellular carcinoma (HCC). Hepatic steatosis, the hallmark of NAFLD, is defined by the accumulation of triglycerides (TGs) in more than 5% of the hepatocytes. NASH is characterized by inflammation along with variable degrees of fibrosis in addition to steatosis. NAFLD has been considered to be the hepatic manifestation of metabolic syndrome (MS), as it is frequently associated with MS conditions such as insulin resistance (IR) and obesity. Hepatic steatosis mainly results from disrupted homeostasis of lipid metabolism in the setting of IR. Although the mechanism underlying the progression from steatosis to NASH is still not fully elucidated, mounting evidence has suggested oxidative stress (OS) to be a key driving force. Elevated OS has been well documented in NAFLD patients. OS can cause direct damages to lipid, protein, and DNA molecules and trigger the inflammatory and fibrogenesis signaling pathways, which promotes the progression from steatosis to NASH. OS may also have various effects on antioxidant defense mechanisms. Overproduced reactive oxygen species (ROS) may directly deplete antioxidant molecules such as glutathione (GSH) and inhibit the activities of antioxidant enzymes such as superoxide dismutase (SOD). ROS may also induce the expression of antioxidant genes to counteract the OS effects. The aim of this review is to discuss oxidative stress and antioxidant mechanisms in NAFLD.
Nonalcoholic steatohepatitis (NASH) is a serious liver disease associated with obesity. Characterized by metabolic syndrome, hepatic steatosis, and liver inflammation, NASH is believed to be under ...the influence of the gut microflora. Here, the composition of gut bacterial communities of NASH, obese, and healthy children was determined by 16S ribosomal RNA pyrosequencing. In addition, peripheral blood ethanol was analyzed to monitor endogenous ethanol production of patients and healthy controls. UniFrac‐based principle coordinates analysis indicated that most of the microbiome samples clustered by disease status. Each group was associated with a unique pattern of enterotypes. Differences were abundant at phylum, family, and genus levels between healthy subjects and obese patients (with or without NASH), and relatively fewer differences were observed between obese and the NASH microbiomes. Among those taxa with greater than 1% representation in any of the disease groups, Proteobacteria, Enterobacteriaceae, and Escherichia were the only phylum, family and genus types exhibiting significant difference between obese and NASH microbiomes. Similar blood‐ethanol concentrations were observed between healthy subjects and obese non‐NASH patients, but NASH patients exhibited significantly elevated blood ethanol levels. Conclusions: The increased abundance of alcohol‐producing bacteria in NASH microbiomes, elevated blood‐ethanol concentration in NASH patients, and the well‐established role of alcohol metabolism in oxidative stress and, consequently, liver inflammation suggest a role for alcohol‐producing microbiota in the pathogenesis of NASH. We postulate that the distinct composition of the gut microbiome among NASH, obese, and healthy controls could offer a target for intervention or a marker for disease. (HEPATOLOGY 2013)
New Reactivity of the Uranyl(VI) Ion Baker, Robert J.
Chemistry : a European journal,
December 14, 2012, Letnik:
18, Številka:
51
Journal Article
Recenzirano
The chemistry of the uranyl ion (UO22+) has evolved remarkably over the past few years, with unexpected reactivity observed that challenge our understanding of this ion, and of actinides in general. ...This review highlights some recent advances in the field, focussing on the organometallic chemistry of the uranyl moiety, which is not well developed in comparison to lower oxidation states of uranium. The use of uranyl as a catalyst is highlighted and the newly developed supramolecular chemistry is described. The uranyl oxygen atoms have been considered as inert, but recent work has shown that is not necessarily the case and is discussed herein. Finally, reduction to the UO2+ ion will be discussed.
The unusual reactivity of the uranyl ion, UO22+, reported during the past few years is highlighted. Organometallic and catalytic chemistry is reviewed and the use of uranyl in supramolecular assemblies emphasized. Oxygen functionalization and reduction to the pentavalent state is discussed.
A number of studies have associated obesity with altered gut microbiota, although results are discordant regarding compositional changes in the gut microbiota of obese animals. Herein we used a ...meta-analysis to obtain an unbiased evaluation of structural and functional changes of the gut microbiota in diet-induced obese rodents. The raw sequencing data of nine studies generated from high-fat diet (HFD)-induced obese rodent models were processed with QIIME to obtain gut microbiota compositions. Biological functions were predicted and annotated with KEGG pathways with PICRUSt. No significant difference was observed for alpha diversity and Bacteroidetes-to-Firmicutes ratio between obese and lean rodents. Bacteroidia, Clostridia, Bacilli, and Erysipelotrichi were dominant classes, but gut microbiota compositions varied among studies. Meta-analysis of the nine microbiome data sets identified 15 differential taxa and 57 differential pathways between obese and lean rodents. In obese rodents, increased abundance was observed for Dorea, Oscillospira, and Ruminococcus, known for fermenting polysaccharide into short chain fatty acids (SCFAs). Decreased Turicibacter and increased Lactococcus are consistent with elevated inflammation in the obese status. Differential functional pathways of the gut microbiome in obese rodents included enriched pyruvate metabolism, butanoate metabolism, propanoate metabolism, pentose phosphate pathway, fatty acid biosynthesis, and glycerolipid metabolism pathways. These pathways converge in the function of carbohydrate metabolism, SCFA metabolism, and biosynthesis of lipid. HFD-induced obesity results in structural and functional dysbiosis of gut microbiota. The altered gut microbiome may contribute to obesity development by promoting insulin resistance and systemic inflammation.
Pathogenesis of nonalcoholic steatohepatitis Liu, Wensheng; Baker, Robert D.; Bhatia, Tavleen ...
Cellular and molecular life sciences : CMLS,
05/2016, Letnik:
73, Številka:
10
Journal Article
Recenzirano
Nonalcoholic steatohepatitis (NASH) is a severe form of nonalcoholic fatty liver disease and a risk factor for cirrhosis and hepatocellular carcinoma. The pathological features of NASH include ...steatosis, hepatocyte injury, inflammation, and various degrees of fibrosis. Steatosis reflects disordered lipid metabolism. Insulin resistance and excessive fatty acid influx to the liver are two important contributing factors. Steatosis is also likely associated with lipotoxicity and cellular stresses such as oxidative stress and endoplasmic reticulum stress, which result in hepatocyte injury. Inflammation and fibrosis are frequently triggered by various signals such as proinflammatory cytokines and chemokines, released by injuried hepatocytes and activated Kupffer cells. Although much progress has been made, the pathogenesis of NASH is not fully elucidated. The purpose of this review is to discuss the current understanding of NASH pathogenesis, mainly focusing on factors contributing to steatosis, hepatocyte injury, inflammation, and fibrosis.
Bile acids are regulators of lipid and glucose metabolism, and modulate inflammation in the liver and other tissues. Primary bile acids such as cholic acid and chenodeoxycholic acid (CDCA) are ...produced in the liver, and converted into secondary bile acids such as deoxycholic acid (DCA) and lithocholic acid by gut microbiota. Here we investigated the possible roles of bile acids in non-alcoholic fatty liver disease (NAFLD) pathogenesis and the impact of the gut microbiome on bile acid signalling in NAFLD.
Serum bile acid levels and fibroblast growth factor 19 (FGF19), liver gene expression profiles and gut microbiome compositions were determined in patients with NAFLD, high-fat diet-fed rats and their controls.
Serum concentrations of primary and secondary bile acids were increased in patients with NAFLD. In per cent, the farnesoid X receptor (FXR) antagonistic DCA was increased, while the agonistic CDCA was decreased in NAFLD. Increased mRNA expression for cytochrome P450 7A1, Na
-taurocholate cotransporting polypeptide and paraoxonase 1, no change in mRNA expression for small heterodimer partner and bile salt export pump, and reduced serum FGF19 were evidence of impaired FXR and fibroblast growth factor receptor 4 (FGFR4)-mediated signalling in NAFLD. Taurine and glycine metabolising bacteria were increased in the gut of patients with NAFLD, reflecting increased secondary bile acid production. Similar changes in liver gene expression and the gut microbiome were observed in high-fat diet-fed rats.
The serum bile acid profile, the hepatic gene expression pattern and the gut microbiome composition consistently support an elevated bile acid production in NAFLD. The increased proportion of FXR antagonistic bile acid explains, at least in part, the suppression of hepatic FXR-mediated and FGFR4-mediated signalling. Our study suggests that future NAFLD intervention may target the components of FXR signalling, including the bile acid converting gut microbiome.
We review recent findings and hypotheses on the roles of gut microbiome in the pathogenesis of nonalcoholic fatty liver diseases (NAFLD). Microbial metabolites and cell components contribute to the ...development of hepatic steatosis and inflammation, key components of nonalcoholic steatohepatitis (NASH), the severe form of NAFLD. Altered gut microbiome can independently cause obesity, the most important risk factor for NAFLD. This capability is attributed to short-chain fatty acids (SCFAs), major gut microbial fermentation products. SCFAs account for a large portion of caloric intake of the host, and they enhance intestinal absorption by activating GLP-2 signaling. However, elevated SCFAs may be an adaptive measure to suppress colitis, which could be a higher priority than imbalanced calorie intake. The microbiome of NASH patients features an elevated capacity for alcohol production. The pathomechanisms for alcoholic steatohepatitis may apply to NASH. NAFLD/NASH is associated with elevated Gram-negative microbiome and endotoxemia. However, many NASH patients exhibited normal serum endotoxin indicating that endotoxemia is not required for the pathogenesis of NASH. These observations suggest that microbial intervention may benefit NAFLD/NASH patients. However, very limited effects were observed using traditional probiotic species. Novel probiotic therapy based on NAFLD/NASH specific microbial composition represents a promising future direction.
Non-alcoholic steatohepatitis (NASH) is a serious form of non-alcoholic fatty liver disease (NAFLD), associated with obesity and insulin resistance. Previous studies suggested that intestinal ...bacteria produced more alcohol in obese mice than lean animals.
To investigate whether alcohol is involved in the pathogenesis of NASH, the expression of inflammation, fibrosis and alcohol metabolism related genes in the liver tissues of NASH patients and normal controls (NCs) were examined by microarray (NASH, n = 7; NC, n = 4) and quantitative real-time PCR (NASH, n = 6; NC, n = 6). Genes related to liver inflammation and fibrosis were found to be elevated in NASH livers compared to normal livers. The most striking finding is the increased gene transcription of alcohol dehydrogenase (ADH) genes, genes for catalase and cytochrome P450 2E1, and aldehyde dehydrogenase genes. Immunoblot analysis confirmed the increased expression of ADH1 and ADH4 in NASH livers (NASH, n = 9; NC, n = 4).
The augmented activity of all the available genes of the pathways for alcohol catabolism suggest that 1) alcohol concentration was elevated in the circulation of NASH patients; 2) there was a high priority for the NASH livers to scavenge alcohol from the circulation. Our data is the first human evidence that suggests alcohol may contribute to the development of NAFLD.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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