Study on roles of anaplerotic pathways in glutamate overproduction of Corynebacterium glutamicum by metabolic flux analysis

<p>Abstract</p> <p>Background</p> <p><it>Corynebacterium glutamicum </it>has several anaplerotic pathways (anaplerosis), which are essential for the productions of amino acids, such as lysine and glutamate. It is still not clear how flux changes in anaplerotic pathways happen when glutamate production is induced by triggers, such as biotin depletion and the addition of the detergent material, Tween 40. In this study, we quantitatively analyzed which anaplerotic pathway flux most markedly changes the glutamate overproduction induced by Tween 40 addition.</p> <p>Results</p> <p>We performed a metabolic flux analysis (MFA) with [1-¹³C]- and [U-¹³C]-labeled glucose in the glutamate production phase of <it>C. glutamicum</it>, based on the analysis of the time courses of ¹³C incorporation into proteinogenic amino acids by gas chromatography-mass spectrometry (GC-MS). The flux from phosphoenolpyruvate (PEP) to oxaloacetate (Oxa) catalyzed by phosphoenolpyruvate carboxylase (PEPc) was active in the growth phase not producing glutamate, whereas that from pyruvate to Oxa catalyzed by pyruvate carboxylase (Pc) was inactive. In the glutamate overproduction phase induced by the addition of the detergent material Tween 40, the reaction catalyzed by Pc also became active in addition to the reaction catalyzed by PEPc.</p> <p>Conclusion</p> <p>It was clarified by a quantitative ¹³C MFA that the reaction catalyzed by Pc is most markedly increased, whereas other fluxes of PEPc and PEPck remain constant in the glutamate overproduction induced by Tween 40. This result is consistent with the previous results obtained in a comparative study on the glutamate productions of genetically recombinant Pc- and PEPc-overexpressing strains. The importance of a specific reaction in an anaplerotic pathway was elucidated at a metabolic level by MFA.</p

Impact of MDM2 single nucleotide polymorphism on tumor onset in head and neck squamous cell carcinoma

金沢大学附属病院耳鼻咽喉科・頭頸部外科Conclusions. The GG genotype of MDM2 SNP309 is associated with an earlier onset of head and neck squamous cell carcinoma (HNSCC) in the Japanese population. SNP309 may be a key factor in the tumorigenesis of HNSCC as well as other hereditary or sporadic tumors. Objective. This study was designed to evaluate the association between the single nucleotide polymorphism (SNP) 309 in the MDM2 gene with HNSCC. An MDM2 protein down-regulates the p53 pathway. Recently, an important SNP was discovered in the MDM2 promoter region, which could affect the tumorigenesis of HNSCC by attenuation of the p53 pathway. Patients and methods. Patients with 103 HNSCCs were genotyped using direct sequencing and real-time PCR. The relationship between the SNP309 genotypes and the clinicopathological features was statistically analyzed. Results. The number of patients genotyped to TT, TG, and GG was 29 (28%), 46 (44.7%), and 28 (27.2%), respectively. The average age at tumor onset was 65.6 years for TT, 62.9 years for TG, and 56.7 years for GG. The patients with the GG genotype had a significantly earlier tumor onset in comparison to those with the TT genotype (p=0.032). © 2008 Taylor & Francis.全文公開20090

Treatment of locally recurrent Epstein-Barr virus-associated nasopharyngeal carcinoma using the anti-viral agent cidofovir

金沢大学附属病院耳鼻咽喉科Nasopharyngeal carcinoma (NPC) is an Epstein-Barr virus (EBV) associated malignant tumor. Recently, cidofovir, an anti-viral drug which is an acyclic nucleoside analogue, has been reported to have an anti-tumor potential. Two patients with NPC, who had previously received multi-round therapy, were treated with cidofovir. Cidofovir was topically injected in and around the tumor once every 3 weeks (originally 75 mg/ml sulution, diluted to 15 mg/ml just before injection, 37.5 mg of cidofoviratatime).Tumorgrowth was suppressed for several months around the injection site in each patient. EBV-encoded RNAs in situ hybridization revealed the reduction of the tumor cell population; however, the EBER expression was still maintained in the NPC tumor cells. Although the anti-tumor mechanism remains unclear, these results suggest that cidofovir is actually an effective and safe agent for the treatment of NPC. © 2008 Wiley-Liss, Inc

Regulation of Pancreatic β Cell Mass by Cross-Interaction between CCAAT Enhancer Binding Protein β Induced by Endoplasmic Reticulum Stress and AMP-Activated Protein Kinase Activity

During the development of type 2 diabetes, endoplasmic reticulum (ER) stress leads to not only insulin resistance but also to pancreatic beta cell failure. Conversely, cell function under various stressed conditions can be restored by reducing ER stress by activating AMP-activated protein kinase (AMPK). However, the details of this mechanism are still obscure. Therefore, the current study aims to elucidate the role of AMPK activity during ER stress-associated pancreatic beta cell failure. MIN6 cells were loaded with 5-amino-1-ϐ-D-ribofuranosyl-imidazole-4-carboxamide (AICAR) and metformin to assess the relationship between AMPK activity and CCAAT enhancer binding protein ϐ (C/EBPϐ) expression levels. The effect of C/EBPϐ phosphorylation on expression levels was also investigated. Vildagliptin and metformin were administered to pancreatic beta cell-specific C/EBPϐ transgenic mice to investigate the relationship between C/EBPϐ expression levels and AMPK activity in the pancreatic islets. When pancreatic beta cells are exposed to ER stress, the accumulation of the transcription factor C/EBPϐ lowers the AMP/ATP ratio, thereby decreasing AMPK activity. In an opposite manner, incubation of MIN6 cells with AICAR or metformin activated AMPK, which suppressed C/EBPϐ expression. In addition, administration of the dipeptidyl peptidase-4 inhibitor vildagliptin and metformin to pancreatic beta cell-specific C/EBPϐ transgenic mice decreased C/EBPϐ expression levels and enhanced pancreatic beta cell mass in proportion to the recovery of AMPK activity. Enhanced C/EBPϐ expression and decreased AMPK activity act synergistically to induce ER stress-associated pancreatic beta cell failure

Novel Urinary Glycan Biomarkers Predict Cardiovascular Events in Patients With Type 2 Diabetes: A Multicenter Prospective Study With 5-Year Follow Up (U-CARE Study 2)

Background: Although various biomarkers predict cardiovascular event (CVE) in patients with diabetes, the relationship of urinary glycan profile with CVE in patients with diabetes remains unclear. Methods: Among 680 patients with type 2 diabetes, we examined the baseline urinary glycan signals binding to 45 lectins with different specificities. Primary outcome was defined as CVE including cardiovascular disease, stroke, and peripheral arterial disease. Results: During approximately a 5-year follow-up period, 62 patients reached the endpoint. Cox proportional hazards analysis revealed that urinary glycan signals binding to two lectins were significantly associated with the outcome after adjustment for known indicators of CVE and for false discovery rate, as well as increased model fitness. Hazard ratios for these lectins (+1 SD for the glycan index) were UDA (recognizing glycan: mixture of Man5 to Man9): 1.78 (95% CI: 1.24-2.55, P = 0.002) and Calsepa [High-Man (Man2-6)]: 1.56 (1.19-2.04, P = 0.001). Common glycan binding to these lectins was high-mannose type of N-glycans. Moreover, adding glycan index for UDA to a model including known confounders improved the outcome prediction [Difference of Harrel's C-index: 0.028 (95% CI: 0.001-0.055, P = 0.044), net reclassification improvement at 5-year risk increased by 0.368 (0.045-0.692, P = 0.026), and the Akaike information criterion and Bayesian information criterion decreased from 725.7 to 716.5, and 761.8 to 757.2, respectively]. Conclusion: The urinary excretion of high-mannose glycan may be a valuable biomarker for improving prediction of CVE in patients with type 2 diabetes, and provides the rationale to explore the mechanism underlying abnormal N-glycosylation occurring in patients with diabetes at higher risk of CVE

Plasma angiotensin-converting enzyme 2 (ACE2) is a marker for renal outcome of diabetic kidney disease (DKD) (U-CARE study 3)

Introduction ACE cleaves angiotensin I (Ang I) to angiotensin II (Ang II) inducing vasoconstriction via Ang II type 1 (AT1) receptor, while ACE2 cleaves Ang II to Ang (1-7) causing vasodilatation by acting on the Mas receptor. In diabetic kidney disease (DKD), it is still unclear whether plasma or urine ACE2 levels predict renal outcomes or not. Research design and methods Among 777 participants with diabetes enrolled in the Urinary biomarker for Continuous And Rapid progression of diabetic nEphropathy study, the 296 patients followed up for 9 years were investigated. Plasma and urinary ACE2 levels were measured by the ELISA. The primary end point was a composite of a decrease of estimated glomerular filtration rate (eGFR) by at least 30% from baseline or initiation of hemodialysis or peritoneal dialysis. The secondary end points were a 30% increase or a 30% decrease in albumin-to-creatinine ratio from baseline to 1 year. Results The cumulative incidence of the renal composite outcome was significantly higher in group 1 with lowest tertile of plasma ACE2 (p=0.040). Group 2 with middle and highest tertile was associated with better renal outcomes in the crude Cox regression model adjusted by age and sex (HR 0.56, 95% CI 0.31 to 0.99, p=0.047). Plasma ACE2 levels demonstrated a significant association with 30% decrease in ACR (OR 1.46, 95% CI 1.044 to 2.035, p=0.027) after adjusting for age, sex, systolic blood pressure, hemoglobin A1c, and eGFR. Conclusions Higher baseline plasma ACE2 levels in DKD were protective for development and progression of albuminuria and associated with fewer renal end points, suggesting plasma ACE2 may be used as a prognosis marker of DKD.Trial registration number UMIN000011525