Molecular Characterization of the Fecal Microbiota in Patients with Nonalcoholic Steatohepatitis – A Longitudinal Study

Background

The human gut microbiota has profound influence on host metabolism and immunity. This study characterized the fecal microbiota in patients with nonalcoholic steatohepatitis (NASH). The relationship between microbiota changes and changes in hepatic steatosis was also studied.

Methods

Fecal microbiota of histology-proven NASH patients and healthy controls was analyzed by 16S ribosomal RNA pyrosequencing. NASH patients were from a previously reported randomized trial on probiotic treatment. Proton-magnetic resonance spectroscopy was performed to monitor changes in intrahepatic triglyceride content (IHTG).

Results

A total of 420,344 16S sequences with acceptable quality were obtained from 16 NASH patients and 22 controls. NASH patients had lower fecal abundance of Faecalibacterium and Anaerosporobacter but higher abundance of Parabacteroides and Allisonella. Partial least-square discriminant analysis yielded a model of 10 genera that discriminated NASH patients from controls. At month 6, 6 of 7 patients in the probiotic group and 4 of 9 patients in the usual care group had improvement in IHTG (P = 0.15). Improvement in IHTG was associated with a reduction in the abundance of Firmicutes (R² = 0.4820, P = 0.0028) and increase in Bacteroidetes (R² = 0.4366, P = 0.0053). This was accompanied by corresponding changes at the class, order and genus levels. In contrast, bacterial biodiversity did not differ between NASH patients and controls, and did not change with probiotic treatment.

Conclusions

NASH patients have fecal dysbiosis, and changes in microbiota correlate with improvement in hepatic steatosis. Further studies are required to investigate the mechanism underlying the interaction between gut microbes and the liver.     

Polymorphisms in the mTOR Gene and Risk of Sporadic Prostate Cancer in an Eastern Chinese Population

Background

The mTOR gene regulates cell growth by controlling mRNA translation, ribosome biogenesis, autophagy, and metabolism. Abnormally increased expression of mTOR was associated with carcinogenesis, and its functional single nucleotide polymorphisms (SNPs) may regulate the expression of mTOR and thus contribute to cancer risk.

Methodology/Principal Findings

In a hospital-based case-control study of 1004 prostate cancer (PCa) cases and 1051 cancer-free controls, we genotyped six potentially functional SNPs of mTOR (rs2536 T>C, rs1883965 G>A, rs1034528 G>C, rs17036508 T>C, rs3806317 A>G, and rs2295080 T>G) and assessed their associations with risk of PCa by using logistic regression analysis.

Conclusions/Significances

In the single-locus analysis, we found a significantly increased risk of PCa associated with mTOR rs2536 CT/CC and rs1034528 CG/CC genotypes [adjusted OR = 1.42 (1.13–1.78), P = 0.003 and 1.29 (1.07–1.55), P = 0.007), respectively], compared with their common homozygous genotypes, whereas mTOR rs2295080 GT/GG genotypes were associated with a decreased risk of PCa [adjusted OR = 0.76 (0.64–0.92), P = 0.003], compared with wild-type TT genotypes. In the combined analysis of the six SNPs, we found that individuals carrying two or more adverse genotypes had an increased risk of PCa [adjusted OR = 1.24 (1.04–1.47), P = 0.016], compared with individuals carrying less than two adverse genotypes. In the multiple dimension reduction analysis, body mass index (BMI) was the best one-factor model with the highest CVC (100%) and the lowest prediction error (42.7%) among all seven factors. The model including an interaction among BMI, rs17036508, and rs2536 was the best three-factor model with the highest CVC (100%) and the lowest prediction error of 41.9%. These findings suggested that mTOR SNPs may contribute to the risk of PCa in Eastern Chinese men, but the effect was weak and needs further validation by larger population-based studies.     

TSA促进转基因猪体细胞核移植胚胎发育和外源基因表达

不完全的表观遗传重编程是造成转基因克隆动物效率低下的主要原因,组蛋白修饰作为表观遗传修饰的一个重要部分,可以直接影响克隆胚胎的发育和外源基因的表达情况。TSA(Trichostatin A)作为一种组蛋白去乙酰化抑制剂,可以改变组蛋白的乙酰化水平,促进表观遗传重编程,提高克隆动物的效率。同时TSA能改变染色质结构,使转录因子易于与DNA序列结合,促进外源基因的表达。文章确定了TSA处理转基因猪成纤维细胞和核移植胚胎的最佳条件,分别为250 nmol/L、24 h和40 nmol/L、24 h,通过进一步正交实验发现,TSA同时处理供体细胞和克隆胚胎可以显著的促进核移植胚胎的体外发育。此外,无论TSA处理转基因猪成纤维细胞或核移植胚胎,都可以提高外源基因的表达水平。     

Correlative proteomics identify the key roles of stress tolerance strategies in Acinetobacter baumannii in response to polymyxin and human macrophages

The opportunistic pathogen Acinetobacter baumannii possesses stress tolerance strategies against host innate immunity and antibiotic killing. However, how the host-pathogen-antibiotic interaction affects the overall molecular regulation of bacterial pathogenesis and host response remains unexplored. Here, we simultaneously investigate proteomic changes in A. baumannii and macrophages following infection in the absence or presence of the polymyxins. We discover that macrophages and polymyxins exhibit complementary effects to disarm several stress tolerance and survival strategies in A. baumannii, including oxidative stress resistance, copper tolerance, bacterial iron acquisition and stringent response regulation systems. Using the spoT mutant strains, we demonstrate that bacterial cells with defects in stringent response exhibit enhanced susceptibility to polymyxin killing and reduced survival in infected mice, compared to the wild-type strain. Together, our findings highlight that better understanding of host-pathogen-antibiotic interplay is critical for optimization of antibiotic use in patients and the discovery of new antimicrobial strategy to tackle multidrug-resistant bacterial infections.     

豌豆蚜翅分化相关miRNA及其预测靶基因对蜕皮激素的应答及miR-92a-1-p5靶基因的验证

[目的]蜕皮激素对孤雌蚜翅两型性分化具有重要调控作用.在前期研究中我们发现5个微小RNA(microRNA,miRNA)在豌豆蚜Acyrthosiphon pisum翅两型性分化中也发挥关键作用,但蜕皮激素是否与miRNA互作参与蚜虫翅型分化未知.本研究旨在探索蜕皮激素对5个miRNA及其预测靶基因表达的影响,揭示蜕皮...     

曲古抑菌素A对克隆猪端粒长度的影响

端粒是染色体末端结构, 在细胞分裂时随着DNA复制而缩短, 体细胞核移植能不同程度地延长端粒长度, 但有些克隆动物端粒的长度在体细胞核移植过程中不能有效恢复, 因而这些克隆动物就会表现出早衰现象。文章发现克隆东北民猪以及eGFP、Mx和PGC1α转基因克隆猪的端粒长度与核供体成体成纤维细胞相比显著缩短(P<0.05), 表明体细胞核移植的重编程过程没能延长细胞的“寿命”。曲古抑菌素A(Trichostatin A, TSA)是一种去乙酰化酶抑制剂, 有研究表明其能提高某些物种的体细胞核重编程效率。为了使端粒长度有效恢复, 文章利用40 nmol/L TSA处理1细胞期猪克隆胚胎24 h, 结果发现, 与对照组相比, TSA处理能显著地提高克隆胚胎体外发育的囊胚率(16.35% vs. 2 7.09%, 21.60% vs. 34.90%, P<0.05), 而且囊胚期端粒长度也得到显著延长(P<0.05)。克隆胚胎移植受体后得到了TSA处理组与非处理组的克隆猪, 虽然TSA处理并没有提高克隆效率(1.3% vs. 1.7%, TSA vs. control), 但端粒长度与对照组和供体细胞相比均显著延长(P<0.05)。猪体细胞核移植不能有效恢复端粒长度, 但是TSA处理能有效延长克隆猪端粒长度。     

Pioglitazone and dexamethasone induce adipogenesis in D1 bone marrow stromal cell line, but not through the peroxisome proliferator-activated receptor-gamma pathway

Osteoblasts and adipocytes share a common progenitor in bone marrow. Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) plays a critical role in adipogenesis. Using a mouse pluripotent mesenchymal cell, D1, as a model, several reports have demonstrated that dexamethasone, a glucocorticoid, can induce adipogenesis. We first examined whether adipogenesis induction in D1 cells is initiated by activation of PPAR-gamma. The results revealed that pioglitazone induces adipogenesis in D1 cells in a dose-dependent manner and decreases alkaline phosphatase activity in D1 cells. Interestingly, this adipogenesis was not blocked by bisphenol A diglycidyl ether, a PPAR-gamma antagonist. A PPAR-gamma-mediated reporter gene assay showed no response to pioglitazone. We then asked whether dexamethasone-induced adipogenesis can be repressed by mifepristone (RU486), an antagonist of glucocorticoid receptor. The results disclosed that mifepristone cannot counteract dexamethasone-induced adipogenesis, and mifepristone itself induced adipogenesis in D1 cells. Moreover, glucocorticoid receptor-mediated reporter gene assay was not responsive to dexamethasone or mifepristone. We concluded that the adipogenesis induced by pioglitazone and dexamethasone in D1 cells may not occur via a PPAR-gamma and glucocorticoid receptor pathway. Finally, we analyzed the gene expression profile of D1 by cDNA microarray after treatment with dexamethasone. We found that the expression of several adipogenesis-related genes is highly provoked by this agent.     

Latency-associated peptide identifies a novel CD4+CD25+ regulatory T cell subset with TGFbeta-mediated function and enhanced suppression of experimental autoimmune encephalomyelitis

CD4(+)CD25(+) regulatory T cells (Tregs) are essential for maintaining self-tolerance and immune homeostasis. Here we characterize a novel subset of CD4(+)CD25(+) Tregs that express latency-associated peptide (LAP) on their cell surface (CD4(+)CD25(+)LAP(+) cells). CD4(+)CD25(+)LAP(+) cells express elevated levels of Foxp3 and Treg-associated molecules (CTLA4, glucocorticoid-induced TNFR-related gene), secrete TGFbeta, and express both cell surface TGFbeta and surface receptors for TGFbeta. In vitro, the suppressive function of CD4(+)CD25(+)LAP(+) cells is both cell contact and soluble factor dependent; this contrasts with CD4(+)CD25(+)LAP(-) cells, which are mainly cell contact dependent. In a model of experimental autoimmune encephalomyelitis, CD4(+)CD25(+)LAP(+) cells exhibit more potent suppressive activity than CD4(+)CD25(+)LAP(-) cells, and the suppression is TGFbeta dependent. We further show that CD4(+)CD25(+)LAP(+) cells suppress myelin oligodendrocyte glycoprotein-specific immune responses by inducing Foxp3 and by inhibiting IL-17 production. Our findings demonstrate that CD4(+)CD25(+) Tregs are a heterogeneous population and that the CD4(+)CD25(+) subset that expresses LAP functions in a TGFbeta-dependent manner and has greater in vivo suppressive properties. Our work helps elucidate the ambiguity concerning the role of TGFbeta in CD4(+)CD25(+) Treg-mediated suppression and indicates that LAP is an authentic marker able to identify a TGFbeta-expressing CD4(+)CD25(+) Treg subset.