Metabolic Engineering of Escherichia coli for Production of 2,5-Dimethylpyrazine.

2,5-Dimethylpyrazine (2,5-DMP) is a high-value-added alkylpyrazine compound with important applications in both the food and pharmaceutical fields. In response to the increasing consumer preference for natural products over chemically synthesized ones, efforts have been made to develop efficient microbial cell factories for the production of 2,5-DMP. However, the previously reported recombinant strains have exhibited low yields and relied on expensive antibiotics and inducers. In this study, we employed metabolic engineering strategies to develop an Escherichia coli strain capable of producing 2,5-DMP at high levels without the need for inducers or antibiotics. Initially, the biosynthesis pathway of 2,5-DMP was constructed that realized 2,5-DMP production from glucose. Subsequently, efforts focused on enhancing 2,5-DMP production by improving the availability of the cofactor NAD+ and precursor l-threonine. Additionally, the supply and conversion of l-threonine were balanced by optimizing the copy number of the key gene tdh on the chromosome and by modifying the l-threonine transport system. The final engineering strain D19 produced 3.1 g/L of 2,5-DMP, which is the highest titer for fermentative production of 2,5-DMP using glucose as the carbon source up to date. The strategies used in this study lay a good foundation for the production of 2,5-DMP on a large scale.

Light irradiation changes the regulation pattern of BtCrgA on carotenogenesis in Blakeslea trispora.

CrgA has been shown to be a negative regulator of carotenogenesis in some filamentous fungi, while light irradiation is an inducible environmental factor for carotenoid biosynthesis. To clarify the relationship between CrgA and light-inducible carotenogenesis in Blakeslea trispora, the cis-acting elements of the btcrgA promoter region were investigated, followed by the analyses of correlation between the expression of btcrgA and carotenoid structural genes under different irradiation conditions. A variety of cis-acting elements associated with light response was observed in the promoter region of btcrgA, and transcription of btcrgA and carotenoid structural genes under different irradiation conditions was induced by white light with a clear correlation. Then, RNA interference and overexpression of btcrgA were performed to investigate their effects on carotenogenesis at different levels under irradiation and darkness. The analyses of transcription and enzyme activities of carotenoid structural gene, and accumulation of carotenoids among btcrgA-interfered, btcrgA-overexpressed, and wild-type strains under irradiation and darkness indicate that btcrgA negatively regulates the synthesis of carotenoid in darkness, while promotes the carotenogenesis under irradiation regardless of reduced or overexpression of btcrgA .

Role of MUC1 rs4072037 polymorphism in gastric cancer: a meta-analysis.

Background and objective: To further determine the association between mucin 1 (MUC1) rs4072037 polymorphism and gastric cancer risk on the basis of previously published studies. Methodology: PubMed and Embase were used to search all the available publications. The relative risk of the correlation was shown as odds ratio (OR) with 95% confidence interval (95% CI) under all the genetic comparisons. Subgroup analyses based on ethnicity, study design and HWE were also executed to detect effects of specific factors on the risk of gastric cancer. Results: MUC1 rs4072037 polymorphism was observed to reduce the risk of gastric cancer under the five genetic comparisons [(GG versus AA: OR (95% CI)=0.72 (0.61, 0.84); GG + GA versus AA: OR (95% CI)=0.82 (0.76, 0.88); GG versus AA + GA: OR (95% CI)=0.83 (0.71, 0.96); G versus A: OR (95% CI)=0.78 (0.72, 0.84); GA versus AA: OR (95% CI)=0.80 (0.74, 0.87)]. This decreased risk of gastric cancer was also detected in subgroup analyses based on ancestry (Asian and Caucasian), study design (population-based and hospital-based) and HWE (P HWE>0.05). Conclusions: MUC1 rs4072037 polymorphism may have an important role in gastric cancer, and this protective effect may vary among different ethnic populations and control subjects.

miR-378 suppresses the proliferation, migration and invasion of colon cancer cells by inhibiting SDAD1.

BACKGROUND: MicroRNAs (miRNAs) play important roles in the growth and metastasis of colon cancer. It is known that one set of miRNAs are dysregulated in colon cancer cells, but the mechanism of their role in cancer development is still largely unknown. Our study focuses on the role of miR-378 in colon cancer cells. METHODS: Human colon cancer tissues and adjacent non-tumor tissues were collected from patients diagnosed in pathological examinations. In addition, human colon cancer cell lines LoVo, CaCo2, SW1116, SW480 and HCT-116, and a normal colonic mucosa cell line NCM460 were included. Quantitative RT-PCR was used to detect the miR-378 level in the clinical tissues and cell lines. In SW480 and HCT-116, miR-378 was artificially overexpressed or suppressed. Cell viability and proliferation were measured using MTT and colony formation assays, and apoptosis was detected via annexin V-PI staining and flow cytometry analysis. The transwell technique was applied to detect the migration and invasion of the colon cancer cells, and their epithelial-mesenchymal transition (EMT) was evaluated by detecting EMT-associated markers using Western blotting. Bioinformatics methods were used to predict the potential targets of miR-378, and luciferase reporter assays were performed to conform the direct binding between miR-378 and its target mRNA. The activity of the Wnt/ß-catenin pathway was evaluated by detecting the key factors through Western blotting. RESULTS: We found that miR-378 expression was low in colon cancer tissues and cell lines. Overexpression of miR-378 not only inhibits the proliferation of colon cancer cells in vitro by inducing apoptosis, but also inhibits migration and invasion by inhibiting the EMT of colon cancer cells. SDAD1 is a direct target gene of miR-378, and knockdown of SDAD1 suppresses the proliferation, migration and invasion of colon cancer cells. We also confirmed that miR-378 alleviated the malignant phenotypes of colon cancer cells by inhibiting the Wnt/ß-catenin pathway. CONCLUSION: miR-378 inhibits the proliferation, migration and invasion of colon cancer cells by targeting SDAD1, defining miR-378 as a potential target for the diagnosis and treatment of colon cancer.

[Efficacy of antioxidants in treatment of nonalcoholic fatty liver: a systematic review].

OBJECTIVE: To evaluate the efficacy of antioxidants in the treatment of non-alcoholic fatty liver. METHODS: The Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE or PUBMED (1978-2011), EMBASE (1978-2011), ISI, OVID Database (1978-2011), CNKI Net and WANFANG database (1978-2011) were searched for relevant randomized controlled trials, with also manual search of the bibliographies of the retrieved articles. The data were synthesized to assess the histological response of the patients (hepatic steatosis, inflammation and fibrosis) and hepatic biochemical changes after the treatments (alanine aminotransferase responses). RESULTS: Fourteen trials involving 1284 patients were included in the Meta-analysis. The quality of the trials was inconsistent. The data were extracted for meta-analysis or descriptive analysis, which did not yield sufficient evidence that antioxidants could improve hepatic steatosis, inflammation, fibrosis or alanine aminotransferase responses. CONCLUSIONS: The current data do not support a positive therapeutic effect of antioxidants on nonalcoholic fatty liver, and antioxidants are therefore not recommended in the clinical treatment of the condition.