Comparison of 8-hydroxy-2′-deoxyguanosine (8-OHdG) levels using mass spectrometer and urine albumin creatinine ratio as a predictor of development of diabetic nephropathy

Abstract

Background. Measurement of urinary 8-hydroxy-2′-deoxyguanosine (8-OHdG) has recently become more popular as a means of assessing oxidative stress in the human body. The aim of this study is to compare the levels of urine 8-OHdG in patients with type 2 diabetes with and without nephropathy and to evaluate its role as a biochemical marker for distinguishing these patients from healthy and patients without complications. Methods. For this purpose, 52 patients with type 2 diabetes mellitus (32 with nephropathy (DMN), 20 without nephropathy (DM)) and 20 healthy control subjects (C) were included in this study. The urine concentrations of 8-OHdG were measured by modified LC-MS/MS method and compared with the first morning voiding urine albumin/creatinine ratio (UACR) and HbA1c values of the same patients. Results. The concentrations of urine 8-OHdG in DMN and DM patients were higher than those of the control subjects (3.47?±?0.94, 2.92?±?1.73, 2.1?±?0.93 nmol/mol creatinine, respectively). But there was no statistical difference between DMN and DM (p =?0.115). There is significant correlation between urinary 8-OHdG and UACR (r =?0.501, p <?0.001). According to ROC analysis, the AUC value of HbA1c was higher than the value of the AUC of 8-OHdG (0.882 and 0.771, respectively). Conclusions. This study shows that the urine 8-OHdG levels increase in diabetic patients. However, urinary 8-OHdG is not a useful clinical marker, compared with UACR, to predict the development of diabetic nephropathy in diabetic patients.     

醛糖还原酶基因5′调控区新的点突变对基因表达调控的影响

为了进一步研究醛糖还原酶 (AR)基因 5′调控区存在的可引起蛋白质表达发生改变的遗传变异及其对糖尿病并发症的影响 ,应用PCR SSCP对中国人 2型糖尿病患者的AR基因 5′调控区进行筛选 ,在两名糖尿病患者中发现一新点突变C- 1 6 7→A ,使AR基因 5′调控区产生一个新的CCAAT盒。含点突变的两名患者尽管患病多年 ,长期处于高血糖状态 ,但无糖尿病并发症发生。而且他们的红细胞中AR活性都很低 ,处于无视网膜病变患者组的下限范围。将含野生型和点突变DNA片段分别克隆至氯霉素乙酰转移酶报告基因载体 (pCAT) ,检测CAT的活性确定野生型和突变型序列的转录活性。同时进行凝胶滞留试验以观测DNA与蛋白质的相互作用。结果显示 :含C- 1 6 7→A的启动子相对转录活性 (5 .7% )明显低于野生型(15 .7% )。凝胶滞留试验中 ,突变序列迁移速率较野生型慢。以上结果说明 ,AR基因 5′调控区C- 1 6 7→A点突变干扰了启动子区顺式作用元件与反式作用因子的结合 ,导致AR基因转录活性降低 ,使患者组织中AR活性下降 ,从而阻止或减缓 2型糖尿病视网膜病变发生发展。     

Astrocytic Gap Junctional Communication Decreases Neuronal Vulnerability to Oxidative Stress-Induced Disruption of Ca2+ Homeostasis and Cell Death

Abstract: We investigated the effect of uncoupling astrocytic gap junctions on neuronal vulnerability to oxidative injury in embryonic rat hippocampal cell cultures. Mixed cultures (neurons growing on an astrocyte monolayer) treated with 18-α-glycyrrhetinic acid (GA), an uncoupler of gap junctions, showed markedly enhanced generation of intracellular peroxides (2,7-dichlorofluorescein fluorescence), impairment of mitochondrial function [(dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction], and cell death (lactate dehydrogenase release) following exposure to oxidative insults (FeSO₄ and 4-hydroxynonenal). GA alone had little or no effect on basal levels of peroxides, mitochondrial function, or neuronal survival. Intercellular dye transfer analyses revealed extensive astrocyte-astrocyte coupling but no astrocyte-neuron or neuron-neuron coupling in the mixed cultures. Studies of pure astrocyte cultures and microscope analyses of neurons in mixed cultures showed that the increased oxidative stress and cell death in GA-treated cultures occurred only in neurons and not in astrocytes. Antioxidants (propyl gallate and glutathione) blocked the death of neurons exposed to FeSO₄/GA. Elevations of neuronal intracellular calcium levels ([Ca²⁺]_i) induced by FeSO₄ were enhanced in neurons in mixed cultures exposed to GA. Removal of extracellular Ca²⁺ and the L-type Ca²⁺ channel blocker nimodipine prevented impairment of mitochondrial function and cell death induced by FeSO₄ and GA, whereas glutamate receptor antagonists were ineffective. Finally, GA exacerbated kainate- and FeSO₄-induced injury to pyramidal neurons in organotypic hippocampal slice cultures. The data suggest that interastrocytic gap junctional communication decreases neuronal vulnerability to oxidative injury by a mechanism involving stabilization of cellular calcium homeostasis and dissipation of oxidative stress.     

The total burden of rare,non-synonymous exome genetic variants is not associated with childhood or late-life cognitive ability

Human cognitive ability shows consistent, positive associations with fitness components across the life-course. Underlying genetic variation should therefore be depleted by selection, which is not observed. Genetic variation in general cognitive ability (intelligence) could be maintained by a mutation–selection balance, with rare variants contributing to its genetic architecture. This study examines the association between the total number of rare stop-gain/loss, splice and missense exonic variants and cognitive ability in childhood and old age in the same individuals. Exome array data were obtained in the Lothian Birth Cohorts of 1921 and 1936 (combined N = 1596). General cognitive ability was assessed at age 11 years and in late life (79 and 70 years, respectively) and was modelled against the total number of stop-gain/loss, splice, and missense exonic variants, with minor allele frequency less than or equal to 0.01, using linear regression adjusted for age and sex. In both cohorts and in both the childhood and late-life models, there were no significant associations between rare variant burden in the exome and cognitive ability that survived correction for multiple testing. Contrary to our a priori hypothesis, we observed no evidence for an association between the total number of rare exonic variants and either childhood cognitive ability or late-life cognitive ability.     

认知地图的神经环路基础

空间记忆是人类认识世界和改造世界的基本认知能力,与我们的生活息息相关.无论是寻找常用的生活物件,如钥匙和手机,还是外出上班、购物和约会,都依赖我们对周围环境的记忆.截止到目前已有大量研究从不同水平探讨大脑如何表征其周围环境,但仍然有很多未解的问题.本文系统综述了基于脑成像和神经电生理技术开展的空间记忆研究进展.通过梳理以往研究中有关生物体在构建认知地图的神经结构和神经活动规律,提出了海马结构和新皮层对空间记忆的编码环路和表征机制,并在此基础上对未来研究进行了展望.     

Building protein interaction maps for Down's syndrome.

Now that the complete sequences for human chromosome 21 and the orthologous mouse genomic regions are known, reasonably complete, conserved, protein-coding gene catalogues are also available. The central issue now facing Down's syndrome researchers is the correlation of increased expression of specific, normal, chromosome 21 genes with the development of specific deficits in learning and memory. Because of the number of candidate genes involved, the number of alternative splice variants of individual genes and the number of pathways in which these genes function, a pathway analysis approach will be critical to success. Here, three examples, both gene specific and pathway related, that would benefit from pathway analysis are discussed: (1) the potential roles of eight chromosome 21 proteins in RNA processing pathways; (2) the chromosome 21 protein intersectin 1 and its domain composition, alternative splicing, protein interactions and functions; and (3) the interactions of ten chromosome 21 proteins with components of the mitogen-activated protein kinase and the calcineurin signalling pathways. A productive approach to developing gene-phenotype correlations in Down's syndrome will make use of known and predicted functions and interactions of chromosome 21 genes to predict pathways that may be perturbed by their increased levels of expression. Investigations may then be targeted in animal models to specific interactions, intermediate steps or end-points of such pathways and the downstream - perhaps amplified - consequences of gene dosage directly assessed. Once pathway perturbations have been identified, the potential for rational design of therapeutics becomes practical.     

Inherited mitochondrial variants are not a major cause of age-related hearing impairment in the European population

Mitochondrial DNA (mtDNA) mutations have been implicated in various age-related diseases. To further clarify the role of mtDNA variants in age-related hearing impairment (ARHI), we determined the DNA sequence of the entire mitochondrial genome of 400 individuals using the Affymetrix Human Mitochondrial Resequencing Array. These were the 200 worst hearing and the 200 best hearing from a collection of 947 Belgian samples. We performed association tests with individual mitochondrial variants, comparison of the mutation load, and association with European haplogroups and their interaction with environmental risk factors. We also tested the influence of rare variants on ARHI. None of these tests showed any association with ARHI.     

The <Emphasis Type="Italic">Idd6.2</Emphasis> diabetes susceptibility region controls defective expression of the <Emphasis Type="Italic">Lrmp</Emphasis> gene in nonobese diabetic (NOD) mice

The identification of genes mediating susceptibility to type 1 diabetes (T1D) remains a challenging task. Using a positional cloning approach based on the analysis of nonobese diabetic (NOD) mice congenic over the Idd6 diabetes susceptibility region, we found that the NOD allele at this locus mediates lower mRNA expression levels of the lymphoid restricted membrane protein gene (Lrmp/Jaw1). Analysis of thymic populations indicates that Lrmp is expressed mainly in immature thymocytes. The Lrmp gene encodes a type 1 transmembrane protein that localizes to the ER membrane and has homology to the inositol 1,4,5-triphosphate receptor-associated cGMP kinase substrate gene, which negatively regulates intracellular calcium levels. We hypothesize that the observed decrease in expression of the Lrmp gene in NOD mice may constitute a T1D susceptibility factor in the Idd6 region.