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... Our hypothesis is based on research findings obtained over the last sixty years which show that glutathione deficiency seems to occur initially in type 2 diabetes due to impaired biosynthesis and/or depletion of GSH [25,26,27,28,29,30]. The hypothesis is supported by our [31,32,33,34,35] and some other [36,37,38] studies which have revealed that single nucleotide polymorphisms (SNP) at genes encoding glutathione metabolizing enzymes such as catalytic and modifier subunits of glutamate cysteine ligase, gamma-glutamyl cyclotransferase, glutathione S-transferases (mu, pi, and theta classes), gamma-glutamyltransferase-6 and glutathione peroxidase-1 substantially contribute to type 2 diabetes susceptibility. This means that glutathione metabolism represents an attractive pathway for genetic research of type 2 diabetes because these genes are directly involved in biosynthesis, catabolism, and utilization of reduced glutathione and thereby may influence disease risk. ...
... The control group included healthy volunteers who visited Kursk Blood Transfusion Station within the same time frame as well as healthy individuals recruited in our previous studies [31,40,41,42]. The criteria for inclusion of persons in the control group were: 1) age over 35 years, 2) normal blood glucose levels to the WHO criteria, 3) the absence of chronic diseases and 3) a written informed consent. ...
... However, it is still unclear whether glutathione deficiency is primary or secondary condition for type 2 diabetes. Although glutathione metabolizing enzymes have an essential role in determining cellular glutathione content, nevertheless, a very limited number of studies have been undertaken to evaluate the relationship between genetic variation at genes encoding and susceptibility to type 2 diabetes [31,32,33,34,35,36,37,38]. No studies have so far been done to investigate the contribution of polymorphisms at GSS and GGT7 genes to the development of type 2 diabetes. ...
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The present study was designed to investigate whether the genetic predisposition to type 2 diabetes (T2D) is associated with polymorphisms of genes encoding glutathione-metabolizing enzymes such as glutathione synthetase (GSS) and gamma-glutamyl transferase 7 (GGT7), and also to analyze in silico the molecular mechanisms of their involvement in disease pathogenesis. A total of 3198 unrelated Russian subjects including 1572 T2D patients and 1626 healthy subjects were enrolled. Single nucleotide polymorphisms (SNP) of the GSS and GGT7 genes were genotyped using the MALDI-TOF mass spectrometry iPLEX platform. We found for the first time that SNPs rs11546155 (OR 0.42, 95%CI 0.22-0.80, P=0.022) and rs6119534 (OR 0.73, 95%CI 0.53-0.99, P=0.0003) of the GGT7 are significantly associated with T2D regardless of sex, age, and body mass index. The association of SNP rs11546155 with diabetes risk has been replicated in a large ethnically diverse cohort (P=0.018). The GSS and GGT7 polymorphisms in diabetics correlated with the levels of plasma glutathione, hydrogen peroxide, and fasting blood glucose in a gender-specific manner. Epistatic interactions between the gene polymorphisms determining disease susceptibility have been observed with strong protective effects of genotype combinations such as GGT7 rs6119534-C/T × GSS rs1801310-A/A and GGT7 rs6119534-C/T × GSS rs13041792-G/G against disease risk (FDR<1.8×10-5). The risk alleles of GSS and GGT7 correlated with tissue-specific expression of genes located at genomic region 20q11.22 that spans numerous genes involved in the unfolded protein response pathway and regulation of proteostasis. Transcriptome-wide association analysis has shown that pancreatic expression of some of these genes such as EDEM2, MYH7B, MAP1LC3A, and CPNE1 is linked with the genetic susceptibility to type 2 diabetes. Taken together the study findings along with our previous results allowed proposing a new hypothesis for the etiology of type 2 diabetes that endogenous deficiency of glutathione is a key condition responsible for impaired folding of proinsulin and triggering unfolded protein response which ultimately leads to β-cell apoptosis, disease development, and progression.
... Our hypothesis is based on research findings obtained over the last sixty years which show that glutathione deficiency seems to occur initially in type 2 diabetes due to impaired biosynthesis and/or the depletion of GSH [25][26][27][28][29][30]. This hypothesis is supported by our [31][32][33][34][35] and some other [36][37][38] studies which have revealed that single nucleotide polymorphisms (SNPs) at genes encoding glutathione-metabolizing enzymes such as catalytic and modifier subunits of glutamate cysteine ligase, gamma-glutamyl cyclotransferase, glutathione S-transferases (mu, pi, and theta classes), gamma-glutamyltransferase-6 and glutathione peroxidase-1 substantially contribute to type 2 diabetes' susceptibility. This means that glutathione metabolism represents an attractive pathway for genetic research into type 2 diabetes because these genes are directly involved in biosynthesis, catabolism, and the utilization of reduced glutathione and thereby may influence disease risk. ...
... Criteria for the exclusion of patients in the case group were the following: (1) below 35 years of age; (2) the absence of written informed consent to participate in the study; and (3) clinical conditions such as a pronounced degree of decompensation of T2D or coma, immune-mediated or idiopathic type 1 diabetes, gestational diabetes, MODY types of diabetes, diseases of the exocrine pancreas such as pancreatitis, pancreatic trauma or pancreatectomy, pancreatic tumors, hereditary diseases affecting the pancreas, and any other endocrine disorders. The control group included healthy volunteers who visited Kursk Blood Transfusion Station within the same time frame as well as healthy individuals recruited in our previous studies [31,[40][41][42]. The criteria for the inclusion of persons in the control group were: (1) age over 35 years; (2) normal blood glucose levels according to the WHO criteria; (3) the absence of chronic diseases; and (4) written informed consent. ...
... The level of glutathione is determined by both the activity and expression of the enzymes involved in the biosynthesis of GSH. As it has been observed by the present study, our previous [31,32,34,35] and some other [36][37][38] studies, the genetic factors contribute to both the levels of glutathione and susceptibility to type 2 diabetes, and single nucleotide polymorphisms at genes encoding enzymes for glutathione metabolism such as glutamate cysteine ligase (catalytic and modifier subunits), gamma-glutamyl cyclotransferase, glutathione S-transferases (mu, pi, and theta classes), gamma-glutamyltransferase 6 and 7 are illustrative examples of that relationship. Although the contribution of each SNP of the GSS and GGT7 genes was low or moderate, the joint effects of the genetic variants on the risk of type 2 diabetes were more pronounced, as has been shown by the analysis of SNP-SNP interactions (Tables 4 and 5). ...
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The present study investigated whether type 2 diabetes (T2D) is associated with polymor-phisms of genes encoding glutathione-metabolizing enzymes such as glutathione synthetase (GSS) and gamma-glutamyl transferase 7 (GGT7). A total of 3198 unrelated Russian subjects including 1572 T2D patients and 1626 healthy subjects were enrolled. Single nucleotide polymorphisms (SNPs) of the GSS and GGT7 genes were genotyped using the MassArray-4 system. We found that the GSS and GGT7 gene polymorphisms alone and in combinations are associated with T2D risk regardless of sex, age, and body mass index, as well as correlated with plasma glutathione, hydrogen peroxide, and fasting blood glucose levels. Polymorphisms of GSS (rs13041792) and GGT7 (rs6119534 and rs11546155) genes were associated with the tissue-specific expression of genes involved in unfolded protein response and the regulation of proteostasis. Transcriptome-wide association analysis has shown that the pancreatic expression of some of these genes such as EDEM2, MYH7B, MAP1LC3A, and CPNE1 is linked to the genetic risk of T2D. A comprehensive analysis of the data allowed proposing a new hypothesis for the etiology of type 2 diabetes that endogenous glutathione deficiency might be a key condition responsible for the impaired folding of proinsulin which triggered an unfolded protein response, ultimately leading to beta-cell apoptosis and disease development.
... T2D was diagnosed on the basis of WHO criteria [2]: fasting blood glucose (FBG) level ≥ 7.0 mmol/L or random blood glucose level ≥ 11.1 mmol/L and/or glycated hemoglobin HbA1c level ≥ 6.5%. The control group included healthy volunteers who presented at the Kursk Blood Transfusion Station within the same time frame as well as healthy individuals recruited in our previous studies [23]. Subjects of the control group had normal FBG levels and 75-g oral glucose tolerance test results. ...
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Oxidative stress contributes to the pathogenesis of type 2 diabetes (T2D). This study investigated whether single nucleotide polymorphisms (SNPs) at genes encoding glutamate cysteine ligase catalytic (rs12524494, rs17883901, rs606548, rs636933, rs648595, rs761142 at GCLC) and modifer (rs2301022, rs3827715, rs7517826, rs41303970 at GCLM) subunits are associated with susceptibility to type 2 diabetes. 2096 unrelated Russian subjects were enrolled for the study. Genotyping was done with the use of the MassArray System. Plasma levels of reactive oxygen species (ROS) and glutathione in the study subjects were analyzed by fuorometric and colorimetric assays, respectively.The present study found, for the frst time, an association of SNP rs41303970 in the GCLM gene with a decreased risk of T2D (P=0.034, Q=0.17). Minor alleles such as rs12524494-G GCLC gene (P=0.026, Q=0.17) and rs3827715-C GCLM gene (P=0.03, Q=0.17) were also associated with reduced risk for T2D. Protective efects of variant alleles such as rs12524494-G at GCLC (P=0.02, Q =0.26) and rs41303970-A GCLM (P=0.013, Q =0.25) against the risk of T2D were seen solely in nonsmokers. As compared with healthy controls, diabetic patients had markedly increased levels of ROS and decreased levels of total GSH in plasma. Interestingly, fasting blood glucose level positively correlated with oxidized glutathione concentration (rs=0.208, P=0.01). Three SNPs rs17883901, rs636933, rs648595 at GCLC and one rs2301022 at GCLM were associated with decreased levels of ROS, while SNPs rs7517826, rs41303970 at GCLM were associated with increased levels of total GSH in plasma. Single nucleotide polymorphisms in genes encoding glutamate cysteine ligase subunits confer protection against type 2 diabetes and their efects are mediated through increased levels of glutathione.
... Donors of the regional blood transfusion station were invited to participate in the study as healthy individuals, and we also used material from our previous studies [21]. The criteria for inclusion of people in the control group were: age over 35 years; normal glycemic profile according to the WHO guideline, 1999-2013; the absence of severe chronic diseases and written informed consent. ...
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The aim of the study was to investigate the associations of single-nucleotide polymorphisms (SNP) rs5917471, rs5963327 and rs6610650 of the gene encoding the beta chain of cytochrome b-245 of NADPH oxidase (CYBB gene) with the redox-homeostasis parameters of blood plasma and the risk of development of type 2 diabetes mellitus (T2D). The study included 2086 unrelated individuals of Slavic origin (1022 patients with T2D and 1064 healthy volunteers). Genotyping of SNPs was performed on a MassArray Analyzer 4 genomic mass spectrometer. Due to the localization of the CYBB gene on the X chromosome, the analysis of the effect of its single nucleotide variants on the predisposition to diabetes mellitus and the parameters of the redox status of blood plasma was carried out separately in men and women by the method of linear regression analysis, adjusted for age and body mass index. In men, the association of the allele T rs5963327 (OR 1.7, 95% CI 1.06–2.75, P = 0.028) and the allele A rs6610650 (OR 1.71, 95% CI 1.05–2.78, P = 0.029) with an increased risk of T2D development was established. Genotype T/T rs5963327 (OR 1.35, 95% CI 1.05–1.73, P = 0.017) and genotype A/A rs6610650 (OR 1.34, 95% CI 1.05–1.72, P = 0.020) were also associated with the risk of T2D development in women. The T-T-A haplotype, including minor alleles of the studied rs5917471–rs5963327–rs6610650 polymorphisms, was associated with an increased risk of developing diabetes mellitus in both men (OR 1.29, 95% CI 1.04–1.58, P = 0.022) and women (OR 1.27, 95% CI 1.02–1.58, P = 0.034). Patients with T2D had a significantly higher content of hydrogen peroxide in plasma compared to the control group (P < 0.05) regardless of sex, however, the relationship between rs5963327 and rs6610650 and the increased content of oxidized glutathione GSSG was found only in women. Thus, we detected for the first time the associations of rs5963327 and rs6610650 of the CYBB gene with the development of T2D and redox status of patients. The studied polymorphic variants of the gene encoding the beta chain of cytochrome b-245 of NADPH oxidase may contribute to a shift of balance in the redox homeostasis system towards the prooxidant status, characteristic of T2D.
... В исследовании участвовали 579 пациетов с СД2 (340 женщин, 239 мужчин; средний возраст -60.2±5.3 года), получавших стационарное лечение на базе эндокринологического отделения ОБУЗ Курской городской клинической больницы скорой медицинской помощи с ноября 2015 г. по октябрь 2018 г. [2]. В контрольную группу вошли 542 прак тически здоровых человека (327 женщин, 215 муж чин; средний возраст -59.8±6.7 года), которые были сопоставимы с основной группой по полу и возрасту (p>0.05). ...
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In the study, which included 579 patients with type 2 diabetes and 542 healthy individuals, for the first time in the Russian population, an association of polymorphism rs11827381 of the IGF2BP2 gene with an increased risk of developing the disease was established. However, the association of variant rs11827381 with an increased risk of developing type 2 diabetes was observed solely in smoking patients and was not detected in non-smokers. Bioinformatics analysis revealed that transcription factors, which binding sites appear in the presence of the C allele, differ from the spectrum of transcription factors specifically associated with the reference T allele and are involved in the regulation of the biosynthesis of ketone bodies, as well as the cellular response to glucocorticoid hormones. The results indicate the trigger role of smoking in the relationship of the polymorphic variant rs11827381 of the IGF2BP2 gene with the development of type 2 diabetes.
... To date, over 100 candidate genes for T2DM have been studied in various populations worldwide (Marullo, Gaulton, & Eicher;Zhao et al., 2017). Gene coding for the synthesis of drugs metabolizing enzymes such as NAT2, CYP2R1, CYP3A4, CYP2C9, Glutathione S-transferase has shown to be linked with the susceptibility to Type 2 diabetes mellitus (Al-Shaqha, Alkharfy, Al-Daghri, & Mohammed, 2015;Alexey, 2018;Nesa, Rahman, Kabir, & Rupam, 2014;Rabiee, Marjani, Khajeniazi, & Mojerloo, 2018;Semiz et al., 2011;Wang et al., 2018;Yalin et al., 2007). N-acetyltransferase 2 is a gene that encodes an enzyme (EC 2.3.1.5) ...
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Although several environmental factors influence the onset of type 2 Diabetes Mellitus (T2DM), genetic factors contribute to an individual vulnerability to this disease. This study was aimed at studying CYP2C9*3 single nucleotide polymorphism (SNP) and NAT2 gene polymorphisms, and their correlation, if any, in the susceptibility to type 2 diabetes in Yaoundé, Cameroon. This was a case-control study involving 70 participants living in Yaoundé, Cameroon. DNA was extracted by Chelex 100 method. Polymorphisms of NAT2 gene and CYP2C9*3 SNP were assessed using Polymerase Chain Reaction – Restriction Fragment Length Polymorphism (PCR-RFLP). NAT2 gene characterization revealed the predominance of NAT2*5 alleles (35%) and slow metabolizing phenotype (72.9%). CYP2C9 gene characterization revealed the predominance of the wild-type allele (54%) and intermediate metabolizing phenotype (91%). Individuals with the “NAT2 slow metabolizer” phenotype were more likely to have T2DM while those with “intermediate metabolizer” phenotype were less likely to develop this disease (OR = 3.9740, P = 0.0009 and OR = 0.1406, P = 0.0044, respectively). CYP2C9*3 had no discernable predisposition to T2DM (OR= 0.1765, P= 0.1981). This study demonstrates that the NAT2 slow metabolizer phenotype could be associated with the development of T2DM in Yaoundé, Cameroon.
... Interestingly, in female rats the hepatic GSH/GSSG ratio can be increased by estrogen replacement therapy, suggesting that the protection of females against oxidative stress may be related by sex hormones. Moreover, the risk of Type 2 diabetes is also associated with genes encoding glutathione transferases (GST) in a sex-specific manner [7]. ...
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Glutathione is the most abundant intracellular low molecular weight thiol in cells and tissues, and plays an essential role in numerous cellular processes, including antioxidant defenses, the regulation of protein function, protein localization and stability, DNA synthesis, gene expression, cell proliferation, and cell signaling. Sexual dimorphisms in glutathione biology, metabolism and glutathione-dependent signaling have been reported for a broad range of biological processes, spanning the human lifespan from early development to aging. Sex-depended differences with regard to glutathione and its biology have also been reported for a number of human pathologies and diseases such as neurodegeneration, cardiovascular diseases and metabolic disorders. Here we review the latest literature in this field and discuss the potential impact of these sexual dimorphisms in glutathione biology on human health and diseases.
... В исследование приглашали больных СД2, получавших стационарное лечение на базе эндокринологического отделения Курской городской клинической больницы скорой медицинской помощи. В группу здоровых индивидов вошли доноры областной станции переливания крови, а также материал наших предыдущих исследований [10,11]. Всего за три года (2016-2018) в исследование включено 2086 неродственных индивидов славянского происхождения, в том числе 1022 пациента с подтвержденным диагнозом СД2 (358 мужчин и 664 женщины, средний возраст 61,57 ± 10,44 года) и 1064 условно здоровых добровольца (392 мужчины и 672 женщины, средний возраст 61,00 ± 7,82 года). ...
Article
Background. Imbalance in the system of redox homeostasis is an important link in the pathogenesis of type 2 diabetes (T2D). Gamma-glutamyl cyclotransferase is an antioxidant defense enzyme directly involved in the metabolism of glutathione, an endogenous antioxidant. The aim of the study was to examine the association of single nucleotide polymorphisms (SNP) rs38420 (GA), rs4270 (TC), rs6462210 (CT) and rs28679 (GA) in GGCT gene with the risk of developing T2D. Materials and Methods. The study included 1022 T2D patients and 1064 healthy volunteers. Genotyping of GGCT gene loci was performed using iPLEX technology on a MassArray Analyzer 4 genome time-of-flight mass spectrometer (Agena Bioscience). Results. As a result, we identified for the first time the association of SNP rs4270 in the GGCT gene with the risk of T2D in the Russian population. We have also established genetic and environmental interactions associated with predisposition to the disease: protective effect of gamma-glutamyl cyclotransferase gene was observed only in non-smokers under condition of daily consumption of fresh vegetables and fruits, whereas in persons with insufficient consumption of plant foods, as well as in all smoking patients protective effect of GGCT was not observed. In patients with T2D, the level of hydrogen peroxide and glutathione monomer was sharply increased compared to the controls. SNP rs4270 was also found to be associated with elevated levels of reduced glutathione in the plasma of type 2 diabetics. Conclusion. Thus, for the first time it was established that polymorphic locus rs4270 in the GGCT gene is associated with a predisposition to T2D, but its relationship with the disease is modulated by smoking and fresh plant foods consumption.
... Plasma samples were aliquoted and stored at −80 • C until further use. Two alternative biochemical parameters reflecting redox homeostasis such as reactive oxygen species (ROS) and oxidized glutathione (GSSG) levels were measured by Varioscan Flash microplate reader (Thermo Fisher Scientific, Waltham, MA, USA) in all plasma samples of IS patients and healthy subjects (GSSG levels were assessed in 91 patients with IS and 44 controls), as described previously [30]. ...
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The purpose of this pilot study was to explore whether polymorphisms in genes encoding the catalytic (GCLC) and modifier (GCLM) subunits of glutamate-cysteine ligase, a rate-limiting enzyme in glutathione synthesis, play a role in the development of ischemic stroke (IS) and the extent of brain damage. A total of 1288 unrelated Russians, including 600 IS patients and 688 age- and sex-matched healthy subjects, were enrolled for the study. Nine common single nucleotide polymorphisms (SNPs) of the GCLC and GCLM genes were genotyped using the MassArray-4 system. SNP rs2301022 of GCLM was strongly associated with a decreased risk of ischemic stroke regardless of sex and age (OR = 0.39, 95%CI 0.24–0.62, p < 0.0001). Two common haplotypes of GCLM possessed protective effects against ischemic stroke risk (p < 0.01), but exclusively in nonsmoker patients. Infarct size was increased by polymorphisms rs636933 and rs761142 of GCLC. The mbmdr method enabled identifying epistatic interactions of GCLC and GCLM gene polymorphisms with known IS susceptibility genes that, along with environmental risk factors, jointly contribute to the disease risk and brain infarct size. Understanding the impact of genes and environmental factors on glutathione metabolism will allow the development of effective strategies for the treatment of ischemic stroke and disease prevention.
... Donors of the regional blood transfusion station were invited to participate in the study as healthy individuals, and we also used material from our previous studies [21]. The criteria for inclusion of people in the control group were: age over 35 years; normal glycemic profile according to the WHO guideline, 1999-2013; the absence of severe chronic diseases and written informed consent. ...
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Impairments of redox homeostasis play a key role in the development of type 2 diabetes mellitus (T2D). The main endogenous source of the superoxide radical is NADPH oxidase, one of the subunits of which is the light chain of cytochrome b-245, CYBA. The aim of the study was to study the associations of cytochrome b-245 alpha chain gene polymorphisms rs7195830 (G>A), rs8854 (C>T), rs9932581 (C>T) and rs4673 (G>A) with a risk of developing T2D. The study included 1022 patients with T2D (average age 61,1 ± 7,2 years) and 1064 sex-and age-matched healthy volunteers. Genotyping of CYBA gene polymorphisms was performed using iPLEX technology on a MassArray Analyzer 4 genome time-of-flight mass spectrometer (Agena Bioscience). The CYBA gene A/A genotype (rs4673, G>A) was associated with an increased risk of developing the disease (OR 1,49, 95%CI 1,111,99, P=0,0074, recessive model). The identified association remained significant even after the adjustment for gender, age, and body mass index (ORadj 1,51, 95%CI 1,09-2,09, padj=0,014). Gender-stratified analysis revealed that the established association rs4673 was characteristic only for females (ORadj 1,60, 95% CIadj 1,04-2,46, padj= 0,032). Patients with T2D had a significantly higher level of hydrogen peroxide in blood plasma compared with the control group (p<0,05), regardless of gender, however, the relationship between the A/A genotype rs4673 with the increase in the content of Н2О2 in plasma by 0,77 mmol/L (p = 0,044) was found only in males. The T/T genotype rs9932581 was associated with an increase in glycated hemoglobin level of 2,71% (p = 0,042) in the general group of patients with T2D, as well as with an increase in the same indicator by 4,44% (p = 0,03) among females. The association of the C/T genotype rs9932581 with an increase in the proportion of HbA1c by 0,61% (p = 0,018) and with an increase in blood glucose level by 1,06 mmol/L (p = 0,029) was noted exclusively in males. The association of fasting blood glucose level was also established with genotype A/A rs7195830, in which carriers the glucose concentration was 1.17 mmol/L higher than in homozygotes for the reference allele (P = 0,022).
Article
Objectives This study sought to identify potential pharmacogenetic associations of selected enzymes and transporters with type 2 diabetes (T2D). In addition, pharmacogenomic profiles, concentrations of asymmetric dimethylarginine (ADMA) or kidney injury molecule-1 (KIM-1), and several covariates were investigated. Methods Whole blood was collected from 63 patients, with 32 individuals with T2D. A pharmacogenomic panel was used to assay genetic profiles, and biomarker ELISAs were run to determine subject concentrations of ADMA and KIM-1. Additive genetic modeling with multiple linear and logistic regressions were performed to discover potential SNPs-outcome associations using PLINK. Results Ten SNPs were found to be significant (p<0.05) depending on the inclusion or exclusion of covariates. Of these, four were found in association with the presence of T2D, rs2231142, rs1801280, rs1799929, and rs1801265 depending on covariate inclusion or exclusion. Regarding ADMA, one SNP was found to be significant without covariates, rs1048943. Five SNPs were identified in association with KIM-1 and T2D in the presence of covariates, rs12208357, rs34059508, rs1058930, rs1902023, and rs3745274. Biomarker concentrations were not significantly different in the presence of T2D. Conclusions This exploratory study found several SNPs related to T2D; further research is required to validate and understand these relationships.
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Based on an exhaustive literature analysis and own observations, I proposed a hypothesis that glutathione deficiency is exactly the most plausible explanation for serious manifestation and death in COVID-19 infected patients. The major risk factors established for severe COVID-19 infection and relative glutathione deficiency found in COVID-19 infected patients with moderate-to-severe illness have converged me to two very important conclusions: (1) oxidative stress contributes to hyper-inflammation of the lung leading to adverse disease outcomes such as acute respiratory distress syndrome, multiorgan failure and death; (2) poor antioxidant defense due to endogenous glutathione deficiency as a result of decreased biosynthesis and/or increased depletion of GSH is the most probable cause of increased oxidative damage of the lung, regardless which of the factors aging, chronic disease comorbidity, smoking or some others were responsible for this deficit. The hypothesis provides novel insights into the etiology and mechanisms responsible for serious manifestations of COVID-19 infection and justifies promising opportunities for effective treatment and prevention of the illness through glutathione recovering with N-acetylcysteine and reduced glutathione.
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OBJECTIVE: To present scientific evidence based on a systematic review of the literature (PRISMA) to systematize information on smell and taste alterations in patients diagnosed with COVID-19. METHODS: The studies were selected through combinations based on the Medical Subject Headings (MeSH). The MEDLINE (PubMed), LILACS, SciELO, and BIREME databases were used. The search encompassed articles published from January 2010 to May 2020, with no restriction of language or localization. RESULTS: A total of 665 retrieved articles had the potential for inclusion. Of these, two answered the research question, which was to verify the smell and taste alterations in patients diagnosed with COVID-19. CONCLUSION: The results found in this review demonstrated that there likely is an association between self-reported smell and taste dysfunctions and COVID-19 infection in such patients.
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BACKGROUND: This study aimed to investigate the deletion polymorphisms of the genes of the glutathione S-transferase family GSTT1 and GSTM1 in patients with Polycystic Ovarian Syndrome (PCOS), comparing them with a control population. METHODS: Blood was collected from 219 women (110 with PCOS and 109 controls) and genomic DNA was extracted. For the analysis of polymorphisms, the technique used was multiplex PCR. In the statistical analysis, the chi-square test and multiple logistic regression were used. RESULTS: There is no association between the GSTM1 null and GSTT1 null genotypes with PCOS when analyzed separately (P = 0.616 and P = 0.188). The analysis of the combined genotypes showed differences between the groups (P < 0.05), evidencing that the genotypic combination GSTT1 positive and GSTM1 negative is more frequent among patients. In the multivariate analysis, smoking was more frequent in the control group (OR = 0.22; 95% CI - 0.87-0.57; P = 0.002) while the presence of a family history of PCOS (OR = 2, 96; 95% CI - 1.54-5.68; P = 0.001) was more frequent in women with PCOS. CONCLUSIONS: In the studied sample, the deletion polymorphisms of the GSTT1 and GSTM1 genes isolated are not associated with PCOS, but in combination, they may be implicated in the etiology of the condition.
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Background: Phosphatidylethanolamine N-methyltransferase (PEMT) is the enzyme of lipid metabolism that catalyzes the conversion of phosphatidylethanolamine to phosphatidylcholine in a series of three methylation reactions. Low activity of the enzyme can increase the availability of phosphatidic acid for triacylglycerol synthesis and thus favor obesity, one of the most important risk factors for type 2 diabetes (T2D). The aim of the study: To study the relationship of the rs12449964 (C>T) in the regulatory region of the PEMT (phosphatidylethanolamine-N-methyltransferase) gene with blood plasma triglycerides, as well as the risk of obesity and T2D in population of Central Russia. Materials and methods: The study included 2060 unrelated individuals of Slavic origin, including 1024 patients with T2D and 1036 healthy volunteers. Genotyping of PEMT gene polymorphism (C>T, rs12449964) was performed by laser desorption / ionization time-of-flight mass spectrometry using the MassArray Analyzer 4 platform (Agena Bioscience). SNPStats online program was used for statistical analysis of the obtained data. Results: Linear regression analysis did not reveal an association of rs12449964 of the PEMT gene with a risk of developing T2D regardless of body mass index (P>0,05). However, the T/T genotype of the studied SNP is associated with an increased risk of obesity in patients with type 2 diabetes (OR 1.66; 95% CI 1.11-2.46; P = 0.011, adjusted for sex and age, recessive model). In addition, carriage of the T/T genotype was associated with a higher level of triacylglycerols in the blood plasma of patients with T2D, both in the presence of obesity and without it (P<0.05). According to GTEx Portal, the rs12449964T allele is associated with decreased PEMT expression in various tissues. Conclusion: The study revealed for the first time the association of rs12449964 of the PEMT gene with hypertriglyceridemia and an increased risk of obesity in patients with T2D, which may be due to the low transcriptional activity of the phosphatidylethanolamine- N-methyltransferase gene in carriers of the alternative allele of the studied SNP.
Article
Background: Increased production of reactive oxygen species (ROS) and oxidative stress are known to play a key role in the pathogenesis of type 2 diabetes (T2D); however, the relationship between genes encoding a multi-subunit ROS-generated enzyme NADPH oxidase and disease susceptibility remains unexplored. Aims: The present pilot study investigated whether single-nucleotide polymorphisms (SNP) at the RAC1 gene (Rac family small GTPase 1), a molecular switcher of NADPH oxidase, are associated with the risk of T2D, glucose metabolism and redox homeostasis. Materials & methods: DNA samples from 3206 unrelated Russian subjects (1579 T2D patients and 1627 controls) were genotyped for six common SNPs rs4724800, rs7784465, rs10951982, rs10238136, rs836478 and rs9374 of RAC1 using the MassArray-4 system. Results: SNP rs7784465 was associated with an increased risk of T2D (p = .0003), and significant differences in the RAC1 haplotypes occurred between the cases and controls (p = .005). Seventeen combinations of RAC1 genotypes showed significant associations with T2D risk (FDR <0.05). Associations of RAC1 polymorphisms with T2D were modified by environmental factors such as sedentary lifestyle, psychological stresses, a dietary deficit of fresh fruits/vegetables and increased carbohydrate intake. RAC1 polymorphisms were associated with biochemical parameters in diabetics: rs7784465 (p = .015) and rs836478 (p = .028) with increased glycated haemoglobin, rs836478 (p = .005) with increased fasting blood glucose, oxidized glutathione (p = .012) and uric acid (p = .034). Haplotype rs4724800A-rs7784465C-rs10951982G-rs10238136A-rs836478C-rs9374G was strongly associated with increased levels of hydrogen peroxide (p < .0001). Conclusion: Thus, polymorphisms in the RAC1 gene represent novel genetic markers of type 2 diabetes, and their link with glucose metabolism and disease pathogenesis is associated with the changes in redox homeostasis.
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Aim: To estimate type 2 diabetes mellitus (T2DM) prevalence in Russian adults. Methods: NATION is a national, epidemiological, cross-sectional study, conducted in Russia. In adults (aged 20-79 years), recruitment was stratified by age, sex, geographic region and settlement type to obtain a representative sample. Recruitment was in public areas with high numbers of people. T2DM was diagnosed by glycated haemoglobin A1c (HbA1c) levels (diabetes: HbA1c ≥6.5% [≥48mmol/mol]; pre-diabetes: HbA1c ≥5.7 to <6.5% [≥39 to <48mmol/mol]). Socio-demographic and anthropometric data were collected. Results: Blood samples from 26,620 subjects were available. Overall, 5.4% were diagnosed with T2DM (previously diagnosed: 2.5%; previously undiagnosed: 2.9%); 19.3% were pre-diabetic. T2DM prevalence increased with age (up to 70 years) and was higher among females than males (6.1% vs. 4.7%, p<0.001). The estimated proportion of subjects with pre-diabetes and T2DM tended to increase with increasing body mass index. T2DM prevalence was higher in rural versus urban populations (6.7% vs. 5.0%, p<0.001). Conclusion: In the Russian adult population, 19.3% had pre-diabetes, T2DM prevalence was 5.4%, and 54% of subjects with diabetes were previously undiagnosed. These results may help to develop a new T2DM predictive, preventative and management programme in Russia.
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and Aims . Diabetic neuropathy is a frequent complication of type 2 diabetes mellitus (T2DM). Genetic susceptibility and oxidative stress may play a role in the appearance of T2DM and diabetic neuropathy. We investigated the relation between polymorphism in genes related to oxidative stress such as GSTM1 , GSTT1 , and GSTP1 and the presence of T2DM and diabetic neuropathy (DN). Methods . Samples were collected from 84 patients with T2DM (42 patients with DN and 42 patients without DN) and 98 healthy controls and genotyped by using polymerase chain reaction and restriction fragment length polymorphism method. Results . GSTP1 Ile105Val polymorphism was associated with the risk of developing T2DM ( p = 0.05 ) but not with the risk of developing DN in diabetic cases. GSTM1 and GSTT1 gene polymorphisms were associated with neither the risk of developing T2DM nor the risk of DN occurrence in diabetic patients. No association was observed between the patients with T2DM and DSPN (diabetic sensorimotor peripheral neuropathy) and T2DM without DSPN regarding investigated polymorphism. Conclusion . Our data suggest that GSTP1 gene polymorphisms may contribute to the development of T2DM in Romanian population. GSTM1 , GSTT1 , and GSTP1 gene polymorphisms are not associated with susceptibility of developing diabetic neuropathy in T2DM patients.
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Type 2 diabetes mellitus results from the interaction of environmental factors with a combination of genetic variants, most of which were hitherto unknown. A systematic search for these variants was recently made possible by the development of high-density arrays that permit the genotyping of hundreds of thousands of polymorphisms. We tested 392,935 single-nucleotide polymorphisms in a French case-control cohort. Markers with the most significant difference in genotype frequencies between cases of type 2 diabetes and controls were fast-tracked for testing in a second cohort. This identified four loci containing variants that confer type 2 diabetes risk, in addition to confirming the known association with the TCF7L2 gene. These loci include a non-synonymous polymorphism in the zinc transporter SLC30A8, which is expressed exclusively in insulin-producing beta-cells, and two linkage disequilibrium blocks that contain genes potentially involved in beta-cell development or function (IDE-KIF11-HHEX and EXT2-ALX4). These associations explain a substantial portion of disease risk and constitute proof of principle for the genome-wide approach to the elucidation of complex genetic traits.
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insulin resistance, dyslipidemia, β-cell dysfunction, impaired glucose tolerance and ultimately leading to T2DM. Chronic oxidative stress, hyperglycemia and dyslipidemia are particularly dangerous for β-cells from lowest levels of antioxidant, have high oxidative energy requirements, decrease the gene expression of key β-cell genes and induce cell death. If β-cell functioning is impaired, it results in an under production of insulin, impairs glucose stimulated insulin secretion, fasting hyperglycemia and eventually the development of T2DM. Core tip: Oxidative stress is underling in the development of cardiovascular disease, type 2 diabetes mellitus (T2DM) and diabetic complications. Increased oxidative stress appears to be a deleterious factor leading to insulin resistance, dyslipidemia, β-cell dysfunction, impaired glucose tolerance and ultimately leading to T2DM. Tangvarasittichai S. Oxidative stress, insulin resistance, dyslipidemia and type 2 diabetes mellitus. World J Diabetes 2015; 6(3): 456-480 Available from:
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p38 mitogen activated protein kinases (MAPKs) play important roles in various cellular stress responses, including cell death, which is roughly categorized into apoptosis and necrosis. Although p38 signaling has been extensively studied, the molecular mechanisms of p38-mediated cell death are unclear. ASK1 is a stress-responsive MAP3K that acts as an upstream kinase of p38 and is activated by various stresses, such as oxidative stress. Here, we show that NR4A2, a member of the NR4A nuclear receptor family, acts as necrosis promoter downstream of ASK1-p38 pathway during oxidative stress. Although NR4A2 is well-known as a nuclear-localized transcription factor, we found that it is translocated into the cytosol after phosphorylated by p38. Because the phosphorylation sites mutant of NR4A2 cannot rescue the cell death promoting activity, ASK1-p38 pathway dependent phosphorylation and subsequent cytoplasmic translocation of NR4A2 may be required for oxidative stress-induced cell death. In addition, NR4A2-mediated cell death does not depend on caspases and receptor interacting protein 1 (RIP1)/RIP3 complex, suggesting that NR4A2 promotes RIP kinases-independent necrotic type of cell death. Our findings may help more precise understanding of molecular mechanisms that regulate oxidative stress-induced and p38-mediated necrosis. Copyright © 2015, The American Society for Biochemistry and Molecular Biology.
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Abstract Type 2 diabetes mellitus (T2DM) is a metabolic disorder resulting from oxidative stress (OS), the root cause of insulin resistance, β-cell dysfunction and impaired glucose tolerance. Antioxidant enzymes play key roles in cellular defense and can be used as important biomarkers for T2DM. The present study was undertaken to evaluate three genetic polymorphisms viz. SOD1+35A/C, SOD2+47C/T and GPx +599C/T in 207 T2DM cases and 210 healthy controls from North India. DNA was extracted from blood samples and genotyping was done by PCR-RFLP. Genotypic/allelic frequencies and haplotype/gene-gene interaction analysis were performed using SPSS (version 15.0) and SHEsis (v. online). Except age, all other biochemical parameters showed highly significant association in T2DM cases (P<0.001). In North-Indian population, SOD1 +35A/C variant was monomorphic. Genotype/allele frequencies of SOD2 +47C/T polymorphism and carriage rate of 'C' allele showed significant association (p<0.05, <0.001; OR 2.434). Genotype/allele frequencies of GPx1 +599C/T and carriage rate showed no association although the odds ratio of GPx1 'C' allele indicated a 1.362 times higher risk of T2DM. SOD2 'CT' and GPx1 'CC' genotypes showed maximum association with biochemical parameters. Haplotype/gene-gene interaction analysis in controls and cases showed that SOD2 +47C/T and GPx1 +599C/T were in linkage disequilibrium (D: 0.168; r(2): 0.10) and individuals with this combination had a 1.273 times higher risk [OR; CI (95%)] of developing T2DM. Thus, we conclude that it is essential to assess the combinatorial association of gene variants with T2DM in order to identify risk haplotypes in a population.
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Background: Diabetes Mellitus is a condition of increased oxidative stress and requiries antioxidants. The sum of endogenous and food derived antioxidants represents the total antioxidant activity of the system. The cooperation among different antioxidants provides greater protection against damage caused by reactive oxygen species or reactive nitrogen species, than any single compound alone. Thus the overall antioxidant capacity may provide more relevant biological information compared to that obtained by the measurement of individual components, as it considers the cumulative effect of all antioxidants present in plasma and body fluids and hence the study. Materials and methods: The study population included healthy volunteers from staff of Sree Balaji Medical College & Hospital (SBMC&H) and Type 2 Diabetic patients attending SBMC&H, Chennai, India. Malondialdehyde levels and total antioxidant status of the case and controls was assessed. Results: A significant decrease in the total antioxidant status among Diabetic patients and significant increase in their malondialdehyde levels in comparison to healthy controls was observed. Conclusion: Type 2 Diabetes Mellitus is a condition in which there is increased oxidative stress as evident by increased Malondialdehyde levels and the condition calls for utilization of antioxidants to combat the oxidants thereby resulting in decreased total antioxidants status.
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Through whole-genome sequencing of 2,630 Icelanders and imputation into 11,114 Icelandic cases and 267,140 controls followed by testing in Danish and Iranian samples, we discovered 4 previously unreported variants affecting risk of type 2 diabetes (T2D). A low-frequency (1.47%) variant in intron 1 of CCND2, rs76895963[G], reduces risk of T2D by half (odds ratio (OR) = 0.53, P = 5.0 × 10(-21)) and is correlated with increased CCND2 expression. Notably, this variant is also associated with both greater height and higher body mass index (1.17 cm per allele, P = 5.5 × 10(-12) and 0.56 kg/m(2) per allele, P = 6.5 × 10(-7), respectively). In addition, two missense variants in PAM, encoding p.Asp563Gly (frequency of 4.98%) and p.Ser539Trp (frequency of 0.65%), confer moderately higher risk of T2D (OR = 1.23, P = 3.9 × 10(-10) and OR = 1.47, P = 1.7 × 10(-5), respectively), and a rare (0.20%) frameshift variant in PDX1, encoding p.Gly218Alafs*12, associates with high risk of T2D (OR = 2.27, P = 7.3 × 10(-7)).
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The National Human Genome Research Institute (NHGRI) Catalog of Published Genome-Wide Association Studies (GWAS) Catalog provides a publicly available manually curated collection of published GWAS assaying at least 100 000 single-nucleotide polymorphisms (SNPs) and all SNP-trait associations with P <1 × 10−5. The Catalog includes 1751 curated publications of 11 912 SNPs. In addition to the SNP-trait association data, the Catalog also publishes a quarterly diagram of all SNP-trait associations mapped to the SNPs’ chromosomal locations. The Catalog can be accessed via a tabular web interface, via a dynamic visualization on the human karyotype, as a downloadable tab-delimited file and as an OWL knowledge base. This article presents a number of recent improvements to the Catalog, including novel ways for users to interact with the Catalog and changes to the curation infrastructure.
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Background: Due to the activity of GSTs in the detoxification of oxidative stress products, deletion polymorphisms of GSTM1 and GSTT1 may contribute to susceptibility to T2DM, since B-cells express very low levels of antioxidant enzymes. Recently, some studies have shown an association between GSTM1-null/GSTT1-null genotypes and an increased susceptibility to T2DM. A relationship between these polymorphisms and changes in the clinical parameters of diabetic patients has also been investigated. However, the results diverge considerably among the studies. Thus, this case-control study was designed to contribute to existing knowledge, as there are no studies on this issue performed in the Brazilian population. Methods and findings: A total of 120 patients and 147 healthy individuals were included in this study. GSTT1 and GSTM1 deletion polymorphisms were genotyped by multiplex SYBR Green Real-Time PCR. The GSTT1-null genotype conferred a 3.2-fold increased risk to T2DM relative to the present genotype. There was no association between GSTM1-null and T2DM risk. In diabetic patients, GSTT1-null conferred higher levels of triglycerides and VLDL-cholesterol, while GSTM1-null was associated with increased levels of fasting blood glucose, glycated hemoglobin and blood pressure. We emphasized a necessity for applying log-linear analysis in order to explore an interaction between these polymorphisms properly. Conclusion: These results suggest that the GSTT1 polymorphism may play an important role in the pathogenesis of T2DM in the Brazilian population. This gene could then be added to a set of genetic markers to identify individuals with an increased risk for developing T2DM and complications associated with dyslipidemia in diabetic patients. Although there was no association of GSTM1 deletion polymorphism with susceptibility to T2DM, the influence of this polymorphism on important clinical parameters related to glycemia and blood pressure levels was verified. This finding suggests that both GSTM1-null and GSTT1-null may contribute to the clinical course of T2DM patients.
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To extend understanding of the genetic architecture and molecular basis of type 2 diabetes (T2D), we conducted a meta-analysis of genetic variants on the Metabochip, including 34,840 cases and 114,981 controls, overwhelmingly of European descent. We identified ten previously unreported T2D susceptibility loci, including two showing sex-differentiated association. Genome-wide analyses of these data are consistent with a long tail of additional common variant loci explaining much of the variation in susceptibility to T2D. Exploration of the enlarged set of susceptibility loci implicates several processes, including CREBBP-related transcription, adipocytokine signaling and cell cycle regulation, in diabetes pathogenesis.
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The common approach to the multiplicity problem calls for controlling the familywise error rate (FWER). This approach, though, has faults, and we point out a few. A different approach to problems of multiple significance testing is presented. It calls for controlling the expected proportion of falsely rejected hypotheses – the false discovery rate. This error rate is equivalent to the FWER when all hypotheses are true but is smaller otherwise. Therefore, in problems where the control of the false discovery rate rather than that of the FWER is desired, there is potential for a gain in power. A simple sequential Bonferroni-type procedure is proved to control the false discovery rate for independent test statistics, and a simulation study shows that the gain in power is substantial. The use of the new procedure and the appropriateness of the criterion are illustrated with examples.
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Substantial data indicate that oxidative stress is involved in the development of diabetic retinopathy (DR). The aim of the present study was to investigate whether the genetic polymorphisms: polymorphic deletions of glutathione S-transferases M1 (GSTM1) and T1 (GSTT1) and Ile105Val of the GSTP1 are associated with DR in Slovenian patients with type 2 diabetes. In this cross sectional case-control study 604 unrelated Slovene subjects (Caucasians) with type 2 diabetes mellitus were enrolled: 284 patients with DR (cases) and the control group of 320 subjects with type 2 diabetes of more than 10 years' duration who had no clinical signs of DR. Genotypes were determined by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP). In our study, the deletion of the GSTM1 was found less frequent in cases with DR than in the controls (27.5% versus 44.4%; P < 0.001), whereas the deletion of GSTT1 was found significantly more often in cases than in the controls (49.3% versus 29.7%; P < 0.001). We did not find statistically significant differences in the genotype distribution in GSTP1 (Ile105Val) polymorphism between cases and controls (40.5% versus 46.0%). We may conclude that individuals homozygous for the deletion of GSTT1 are at an ≈ 2-fold-greater risk of DR, whereas the GSTM1 deficiency is associated with lower frequency of DR in type 2 diabetics.
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Glutathione S-transferase (GST) protects cells against oxidative stress. We evaluated the effect of genetic polymorphisms of the GST gene family on the risk of developing type-2 diabetes mellitus and on glycemic control. We also investigated the effects of smoking combined with these polymorphisms on type-2 diabetes mellitus risk. We enrolled 100 type-2 diabetes mellitus patients and 100 healthy controls matched for age, gender and origin, from the Sinai area of Egypt. Fasting serum glucose, HbA(1c) and lipid profiles were determined. Two polymorphisms were identified by multiplex PCR within the GST genes: GSTM1 and GSTT1. The proportion of the GSTT1- and GSTM1-null genotypes was significantly greater in diabetic patients when compared to controls. Patients carrying both null polymorphisms had a 3.17-fold increased risk of having type-2 diabetes mellitus compared to those with normal genotypes of these two genes (P = 0.009). Additionally, patients with the GSTT1-null genotype had higher levels of triglycerides and very low-density lipoprotein cholesterol compared to those with the GSTT1-present genotype. On the other hand, patients with the GSTM1- null genotype had significantly higher levels of HbA(1c) and significantly higher diastolic blood pressure compared to those with the GSTM1- present genotype. The interaction between these genotypes and smoking status was not significant. These results give evidence that the GSTT1- and GSTM1-null genotypes, alone or combined, are associated with increased risk of type-2 diabetes mellitus, regardless of smoking status. Only the GSTM1-null genotype had an effect on glycemic control.
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We carried out a genome-wide association study of type-2 diabetes (T2D) in individuals of South Asian ancestry. Our discovery set included 5,561 individuals with T2D (cases) and 14,458 controls drawn from studies in London, Pakistan and Singapore. We identified 20 independent SNPs associated with T2D at P < 10(-4) for testing in a replication sample of 13,170 cases and 25,398 controls, also all of South Asian ancestry. In the combined analysis, we identified common genetic variants at six loci (GRB14, ST6GAL1, VPS26A, HMG20A, AP3S2 and HNF4A) newly associated with T2D (P = 4.1 × 10(-8) to P = 1.9 × 10(-11)). SNPs at GRB14 were also associated with insulin sensitivity (P = 5.0 × 10(-4)), and SNPs at ST6GAL1 and HNF4A were also associated with pancreatic beta-cell function (P = 0.02 and P = 0.001, respectively). Our findings provide additional insight into mechanisms underlying T2D and show the potential for new discovery from genetic association studies in South Asians, a population with increased susceptibility to T2D.
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A growing body of evidence suggests that oxidative stress plays a key role in the pathogenesis of micro- and macrovascular diabetic complications. The increased oxidative stress in subjects with type 2 diabetes is a consequence of several abnormalities, including hyperglycemia, insulin resistance, hyperinsulinemia, and dyslipidemia, each of which contributes to mitochondrial superoxide overproduction in endothelial cells of large and small vessels as well as the myocardium. The unifying pathophysiological mechanism that underlies diabetic complications could be explained by increased production of reactive oxygen species (ROS) via: (1) the polyol pathway flux, (2) increased formation of advanced glycation end products (AGEs), (3) increased expression of the receptor for AGEs, (4) activation of protein kinase C isoforms, and (5) overactivity of the hexosamine pathway. Furthermore, the effects of oxidative stress in individuals with type 2 diabetes are compounded by the inactivation of two critical anti-atherosclerotic enzymes: endothelial nitric oxide synthase and prostacyclin synthase. Of interest, the results of clinical trials in patients with type 2 diabetes in whom intensive management of all the components of the metabolic syndrome (hyperglycemia, hypercholesterolemia, and essential hypertension) was attempted (with agents that exert a beneficial effect on serum glucose, serum lipid concentrations, and blood pressure, respectively) showed a decrease in adverse cardiovascular end points. The purpose of this review is (1) to examine the mechanisms that link oxidative stress to micro- and macrovascular complications in subjects with type 2 diabetes and (2) to consider the therapeutic opportunities that are presented by currently used therapeutic agents which possess antioxidant properties as well as new potential antioxidant substances.
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Diabetes mellitus is associated with an increased production of reactive oxygen species (ROS) and a reduction in antioxidant defense. The oxidative stress becomes evident as a result of accumulation of ROS in conditions of inflammation and Type 2 diabetes mellitus (T2DM). The genes involved in redox balance, which determines the susceptibility to T2DM remain unclear. In humans, the glutathione S-transferase (GST) family comprises several classes of GST isozymes, the polymorphic variants of GSTM1, T1 and P1 genes result in decreased or loss of enzyme activity. The present study evaluated the effect of genetic polymorphisms of the GST gene family on the risk of developing T2DM in the North Indian population. GSTM1, T1 and P1 polymorphisms were genotyped in 100 T2DM patients and 200 healthy controls from North India to analyze their association with T2DM susceptibility. Analysis of GSTM1 and GSTT1 gene polymorphisms was performed by multiplex polymerase chain reaction (PCR) and GSTP1 by PCR-Restriction Fragment Length Polymorphism (RFLP). Fisher's exact test and chi2 statistics using SPSS software (Version-15.0). We observed significant association of GSTM1 null (P=0.004, OR= 2.042, 95%CI= 1.254-3.325) and GSTP1 (I/V) (P=0.001, OR= 0.397, 95%CI=0.225-0.701) with T2DM and no significant association with GSTT1 (P=0.493). The combined analysis of the three genotypes GSTM1 null, T1 present and P1 (I/I) demonstrated an increase in T2DM risk (P= 0.005, OR= 2.431 95% CI=1.315-4.496). This is the first study showing the association of a combined effect of GSTM1, T1 and P1 genotypes in a representative cohort of Indian patients with T2DM. Since significant association was seen in GSTM1 null and GSTP1 (I/V) and multiple association in GSTM1 null, T1 present and P1 (I/I), these polymorphisms can be screened in the population to determine the diabetic risk.
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A surplus of food supply has evoked a worldwide increase in incidence of type 2 diabetes. This trend will have a significant impact on the life span of people living in modern societies. In contrast, reduced calorie intake has significant impact on preventing type 2 diabetes and increasing longevity. Increased production of reactive oxygen species (ROS), resulting in oxidative stress, has long been proposed as a unifying mechanism linking nutrient excess and diabetes. This review describes the updated mechanism by which oxidative stress provoked by nutrient excess contributes to the development of insulin resistance and pancreatic betacell failure. However, despite the promising results in cellular and animal models, major clinical trials have failed to demonstrate beneficial effect of antioxidants on the prevention of type 2 diabetes or the degree of glycemic control in individuals with diabetes. Emerging evidence shows that ROS also function as an insulin-signaling molecule in normal physiology and casts doubt on the potential beneficial effect of antioxidants. The gap between basic research and clinical outcomes heightens the importance for elucidating the precise molecular mechanisms by which cellular redox status affects insulin signaling.
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By combining genome-wide association data from 8,130 individuals with type 2 diabetes (T2D) and 38,987 controls of European descent and following up previously unidentified meta-analysis signals in a further 34,412 cases and 59,925 controls, we identified 12 new T2D association signals with combined P<5x10(-8). These include a second independent signal at the KCNQ1 locus; the first report, to our knowledge, of an X-chromosomal association (near DUSP9); and a further instance of overlap between loci implicated in monogenic and multifactorial forms of diabetes (at HNF1A). The identified loci affect both beta-cell function and insulin action, and, overall, T2D association signals show evidence of enrichment for genes involved in cell cycle regulation. We also show that a high proportion of T2D susceptibility loci harbor independent association signals influencing apparently unrelated complex traits.
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In humans, glutathione-dependent conjugation of halomethanes is polymorphic, with 60% of the population classed as conjugators and 40% as non-conjugators. We report the characterization of the genetic polymorphism causing the phenotypic difference. We have isolated a cDNA that encodes a human class Theta GST (GSTT1) and which shares 82% sequence identity with rat class Theta GST5-5. From PCR and Southern blot analyses, it is shown that the GSTT1 gene is absent from 38% of the population. The presence or absence of the GSTT1 gene is coincident with the conjugator (GSST1+) and non-conjugator (GSTT1-) phenotypes respectively. The GSTT1+ phenotype can catalyse the glutathione conjugation of dichloromethane, a metabolic pathway which has been shown to be mutagenic in Salmonella typhimurium mutagenicity tester strains and is believed to be responsible for carcinogenicity of dichloromethane in the mouse. In humans, the enzyme is found in the erythrocyte and this may act as a detoxification sink. Characterization of the GSTT1 polymorphism will thus enable a more accurate assessment of human health risk from synthetic halomethanes and other industrial chemicals.
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Increases in the intracellular levels of reactive oxygen species (ROS), frequently referred to as oxidative stress, represents a potentially toxic insult which if not counteracted will lead to membrane dysfunction, DNA damage and inactivation of proteins. Chronic oxidative stress has numerous pathological consequences including cancer, arthritis and neurodegenerative disease. Glutathione-associated metabolism is a major mechanism for cellular protection against agents which generate oxidative stress. It is becoming increasingly apparent that the glutathione tripeptide is central to a complex multifaceted detoxification system, where there is substantial inter-dependence between separate component members. Glutathione participates in detoxification at several different levels, and may scavenge free radicals, reduce peroxides or be conjugated with electrophilic compounds. Thus, glutathione provides the cell with multiple defences not only against ROS but also against their toxic products. This article discusses how glutathione biosynthesis, glutathione peroxidases, glutathione S-transferases and glutathione S-conjugate efflux pumps function in an integrated fashion to allow cellular adaption to oxidative stress. Co-ordination of this response is achieved, at least in part, through the antioxidant responsive element (ARE) which is found in the promoters of many of the genes that are inducible by oxidative and chemical stress. Transcriptional activation through this enhancer appears to be mediated by basic leucine zipper transcription factors such as Nrf and small Maf proteins. The nature of the intracellular sensor(s) for ROS and thiol-active chemicals which induce genes through the ARE is described. Gene activation through the ARE appears to account for the enhanced antioxidant and detoxification capacity of normal cells effected by many cancer chemopreventive agents. In certain instances it may also account for acquired resistance of tumours to cancer chemotherapeutic drugs. It is therefore clear that determining the mechanisms involved in regulation of ARE-driven gene expression has enormous medical implications.
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Glucose toxicity in pancreatic islet beta cells causes loss of insulin gene expression, content, and secretion due to loss of binding of transcription factors, most notably PDX-1 and RIPE-3b1 activator, to the promoter region of the insulin gene. Recently, RIPE-3b1 activator was cloned and identified as the mammalian homologue of avian MafA/Maf-L (MafA). This enabled us to carry out more extensive studies of the role of MafA in glucotoxicity than were hitherto possible. Northern analysis of glucotoxic HIT-T15 cells revealed normal amounts of MafA mRNA, but Western analysis demonstrated a 97 +/- 1% reduction in MafA protein (p < 0.0001). The proteasome is a likely site for MafA degradation as lactacystin, an irreversible proteasome inhibitor, caused an accumulation of MafA protein. Antioxidants have previously been shown to prevent the adverse effects of glucose toxicity on beta cell function both in vivo and in vitro. In the current study, chronic culturing of HIT-T15 cells with the antioxidant N-acetylcysteine (NAC) prevented loss of MafA protein (late passage = 18.9 +/- 10.4% of early passage, p < 0.001; late passage with NAC = 68.7 +/- 19.7% of early passage, p = not significant) and loss of DNA binding (late passage = 63.7 +/- 9% of early passage, p < 0.02; late passage with NAC = 116 +/- 10% of early passage, p = not significant). Additionally, transient transfection of PDX-1 or MafA cDNA into glucotoxic cells increased PDX-1 and MafA protein levels and individually increased insulin promoter activity (untreated = 34%, PDX-1 = 70%, MafA = 78%; percentage of activity of early passage cells), whereas the combined transfection of MafA and PDX-1 completely restored insulin promoter activity. This recovery of promoter activity following transient transfection had no effect on endogenous insulin mRNA. However, adenoviral infection of MafA and PDX-1 significantly increased endogenous insulin mRNA levels by 93% (121 +/- 9 versus 233 +/- 18 density light units; n = 5, p < 0.001). We conclude that the absence of MafA protein from beta cells via chronic oxidative stress contributes importantly to the loss of endogenous insulin gene expression as glucose toxicity develops.
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Glutathione S-transferases (GSTs) modulate oxidative stress, and variation in GST genes has been associated with cardiovascular disease risk. We prospectively determined smoking-related cardiovascular morbidity by GST genotype in a large cohort of individuals with type 2 diabetes using a population-based diabetes research database (DARTS). We performed a cohort study of 2015 individuals with type 2 diabetes. Individuals were genotyped for the Ile105Val variant of GSTP1 and the deleted variants of GSTT1 and GSTM1. Clinical characteristics, smoking status, and incidence of subsequent cardiovascular events were obtained by examining the DARTS databases. Variation in the GSTP1 and GSTM1 genes was not associated with smoking-related risk of death or cardiovascular events. There was an increase in the rate of cardiovascular events in smokers lacking the GSTT1 gene compared with smokers with the GSTT1 gene intact (hazard ratio [HR], 1.96; P=0.001). This excess of cardiovascular events was due to both strokes (HR, 2.7; P=0.008) and myocardial infarctions (HR, 1.9; P=0.006). The rate of death as a result of a cardiovascular event was even more markedly increased in the GSTT1-null smokers (HR, 2.7; P=0.001), with a 2-fold increase in myocardial infarction fatality ratio. These effects translated into an increase in overall death and a decrease in age at death. We also found that the GSTT1- genotype was associated with progression of both diabetic retinopathy and nephropathy (P=0.005 and P=0.01, respectively), although we found little evidence for an interaction with smoking. Genetic absence of the GSTT1 enzyme is an independent and powerful predictor of premature vascular morbidity and death in individuals with type 2 diabetes.
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A web-based application has been designed from a genetic epidemiology point of view to analyze association studies. Main capabilities include descriptive analysis, test for Hardy–Weinberg equilibrium and linkage disequilibrium. Analysis of association is based on linear or logistic regression according to the response variable (quantitative or binary disease status, respectively). Analysis of single SNPs: multiple inheritance models (co-dominant, dominant, recessive, over-dominant and log-additive), and analysis of interactions (gene–gene or gene–environment). Analysis of multiple SNPs: haplotype frequency estimation, analysis of association of haplotypes with the response, including analysis of interactions. Availability:http://bioinfo.iconcologia.net/SNPstats. Source code for local installation is available under GNU license. Contact:v.moreno{at}iconcologia.net Supplementary Information: Figures with a sample run are available on Bioinformatics online. A detailed online tutorial is available within the application.
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The common approach to the multiplicity problem calls for controlling the familywise error rate (FWER). This approach, though, has faults, and we point out a few. A different approach to problems of multiple significance testing is presented. It calls for controlling the expected proportion of falsely rejected hypotheses — the false discovery rate. This error rate is equivalent to the FWER when all hypotheses are true but is smaller otherwise. Therefore, in problems where the control of the false discovery rate rather than that of the FWER is desired, there is potential for a gain in power. A simple sequential Bonferronitype procedure is proved to control the false discovery rate for independent test statistics, and a simulation study shows that the gain in power is substantial. The use of the new procedure and the appropriateness of the criterion are illustrated with examples.
Article
Objective: The present study was designed to investigate whether genetic polymorphisms of the aryl hydrocarbon receptor (AHR) signaling pathway are involved in the molecular basis of essential hypertension (EH). Methods: A total of 2160 unrelated Russian individuals comprising 1341 EH patients and 819 healthy controls were recruited into the study. Seven common AHR pathway single-nucleotide polymorphisms (SNPs) such as rs2066853, rs2292596, rs2228099, rs1048943, rs762551, rs1056836, and rs1800566 were genotyped by TaqMan-based allele discrimination assays. Results: We found that SNP rs2228099 of ARNT is associated with an increased risk of EH (odds ratio=1.20 95% confidence interval: 1.01-1.44, P=0.043) in a dominant genetic model, whereas polymorphism rs762551 of CYP1A2 showed an association with a decreased risk of disease in a recessive genetic model (odds ratio=0.68, 95% confidence interval: 0.52-0.89, P=0.006). A log-likelihood ratio test enabled identification of epistatic interaction effects on EH susceptibility for all SNPs. MB-MDR analysis showed that cigarette smoking, rs1048943, rs762551, rs1056836, and rs2228099 were significant contributing factors in 19, 18, 13, 13, and 11 interaction models, respectively. The best MDR model associated with EH risk included rs1048943, rs762551, rs1056836, and cigarette smoking (cross-validation consistency 100%, prediction error 45.7%, Ppermutation<0.0001). The mRNA expression and in-silico function prediction analyses have confirmed a regulatory potential for a majority of SNPs associated with EH susceptibility. Conclusion: Our pilot study was the first to show that gene-gene and gene-environment interactions in the AHR signaling pathway represent important determinants for the development of EH, and the pathway may become an attractive target for a pharmacological intervention in hypertensive patients in the future.
Article
Objectives: The present study was designed to investigate whether the susceptibility to acute pancreatitis (AP) attributable to polymorphism rs10273639 at the PRSS1-PRSS2 locus is dependent on alcohol consumption and cigarette smoking. Methods: A total of 603 unrelated Russian individuals including 304 patients with physician-diagnosed AP and 299 sex- and age-matched healthy controls have been recruited for the study. A polymorphism rs10273639 (-408C>T) of PRSS1-PRSS2 was genotyped by TaqMan-based assay. Results: A variant allele -408T (P = 0.003) and genotypes -408CT plus TT (P = 0.002) were associated with decreased AP risk only in men. The odds ratios for AP in the CC homozygotes versus the variant genotypes were 1.95 [95% confidence interval (CI), 0.65-5.85; P = 0.23], 1.72 (95% CI, 0.93-3.20; P = 0.08), and 2.37 (95% CI, 1.09-5.13; P = 0.03) for men who consumed up to 28, 29 to 59, and more than 60 alcohol drinks a week, respectively. Cigarette smokers with the -408CC genotype had an increased risk of AP (odds ratio, 2.07; 95% CI, 1.25-3.42; P = 0.004), whereas nonsmoker carriers did not have a disease risk (odds ratio, 1.48; 95% CI, 0.58-3.82; P = 0.42). Conclusions: We confirmed a robust association of polymorphism rs10273639 at PRSS1-PRSS2 with AP in the Russian population. The present study is the first to show that relationship between the locus and disease is significantly modified by alcohol consumption and cigarette smoking.
Article
Type 2 diabetes mellitus (T2DM), by definition is a heterogeneous, multifactorial, polygenic syndrome which results from insulin receptor dysfunction. It is an outcome of oxidative stress caused by interactions of reactive metabolites (RMs) interactions with lipids, proteins and other mechanisms of human body. Production of RMs mainly superoxide (O2·−) has been found in a variety of predominating cellular enzyme systems including NAD(P)H oxidase, xanthine oxidase (XO), cyclooxygenase (COX), uncoupled endothelial nitric oxide synthase (eNOS) and myeloperoxidase (MPO). The four main RM related molecular mechanisms are: increased polyol pathway flux; increased advanced glycation end-product (AGE) formation; activation of protein kinase C (PKC) isoforms and increased hexosamine pathway flux which have been implicated in glucose-mediated vascular damage. Superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione-S-transferase (GST), nitric oxide synthase (NOS) are antioxidant enzymes involved in scavenging RMs in normal individuals. Functional polymorphisms of these antioxidant enzymes have been reported to be involved in pathogenesis of T2DM individuals. The low levels of antioxidant enzymes or their non-functionality results in excessive RMs which initiate stress related pathways thereby leading to insulin resistance and T2DM. An attempt has been made to review the role of RMs and antioxidant enzymes in oxidative stress resulting in T2DM.
Article
The American Diabetes Association (ADA) “Standards of Medical Care in Diabetes” includes the ADA’s current clinical practice recommendations and is intended to provide the components of diabetes care, general treatment goals and guidelines, and tools to evaluate quality of care. Members of the ADA Professional Practice Committee, a multidisciplinary expert committee (https://doi.org/10.2337/dc20-SPPC), are re-sponsible for updating the Standards of Care annually, or more frequently as warranted. For a detailed description of ADA standards, statements, and reports, as well as the evidence-grading system for ADA’s clinical practice recommendations, please refer to the Standards of Care Introduction (https://doi.org/10.2337/dc20-SINT). Readers who wish to comment on the Standards of Care are invited to do so at professional.diabetes.org/SOC.
Article
Background: Cigarette smoking remains the leading avoidable cause of disease burden worldwide, and observational studies have linked various smoking behaviours (active smoking, passive smoking, and smoking cessation) with risk of type 2 diabetes. We did a meta-analysis of prospective studies to investigate the associations between various smoking behaviours and diabetes risk. Methods: We systematically searched MEDLINE (up to May 3, 2015) and Embase (up to April 16, 2014) for reports of prospective studies, using search terms related to smoking, diabetes mellitus, and studies with a prospective design. We supplemented this strategy with manual searches of the reference lists of retrieved publications and relevant reviews. We included prospective studies that reported risk of type 2 diabetes by baseline smoking status. We calculated pooled relative risks (RRs) with 95% CIs using random-effects models, and did subgroup analyses by participant and study characteristics. Findings: We identified 88 eligible prospective studies with 5 898 795 participants and 295 446 incident cases of type 2 diabetes. The pooled RR of type 2 diabetes was 1·37 (95% CI 1·33-1·42) for comparing current smoking with non-smoking (84 studies with 5 853 952 participants), 1·14 (1·10-1·18) for comparing former smoking with never smoking (47 studies with 2 930 391 participants), and 1·22 (1·10-1·35) for comparing never smokers with and without exposure to passive smoke (seven studies with 156 439 participants). The associations persisted in all subgroups, and we identified a dose-response relation for current smoking and diabetes risk: compared with never smokers, the RRs were 1·21 (1·10-1·33) for light smokers, 1·34 (1·27-1·41) for moderate smokers, and 1·57 (1·47-1·66) for heavy smokers. Based on the assumption that the association between smoking and diabetes risk is causal, we estimated that 11·7% of cases of type 2 diabetes in men and 2·4% in women (ie, about 27·8 million cases in total worldwide) were attributable to active smoking. Compared with never smokers, the pooled RR from ten studies with 1 086 608 participants was 1·54 (95% CI 1·36-1·74) for new quitters (<5 years), 1·18 (1·07-1·29) for middle-term quitters (5-9 years), and 1·11 (1·02-1·20) for long-term quitters (≥10 years). Interpretation: Active and passive smoking are associated with significantly increased risks of type 2 diabetes. The risk of diabetes is increased in new quitters, but decreases substantially as the time since quitting increases. If the association between smoking and risk of type 2 diabetes is causal, public health efforts to reduce smoking could have a substantial effect on the worldwide burden of type 2 diabetes. Funding: Chinese National Thousand Talents Program for Distinguished Young Scholars, US National Institutes of Health, the Chinese National 111 Project, and the Program for Changjiang Scholars and Innovative Research Team in University from the Chinese Ministry of Education.
Article
The purpose of this study was to investigate whether a common polymorphism -463G>A (rs2333227) in the promoter of myeloperoxidase (MPO) gene, an oxidant enzyme producing hypohalogenic radicals, is associated with the risk of essential hypertension (EH) in Russian population. A total of 2,044 unrelated subjects including 1,256 EH patients and 788 normotensive controls were recruited for this study. Genotyping of the MPO gene polymorphism was done using TaqMan-based assay. A genotype -463GA was associated with decreased risk of essential hypertension (OR=0.82, 95% CI 0.68-1.00) at a borderline significance level (P=0.05). The gender-stratified analysis showed that a carriage of the -463GA and AA genotypes is associated with decreased EH risk only in females (OR = 0.74, 95% CI 0.56–0.96, P=0.02). To the best of our knowledge, this is the first study reporting a negative association between the -463G>A polymorphism of the MPO gene and essential hypertension risk. Molecular mechanisms by which myeloperoxidase gene is involved in the pathogenesis of essential hypertension are discussed.
Article
Objective: The aims of this study were to investigate the association between smoking and incident type 2 diabetes, accounting for a large number of potential confounding factors, and to explore potential effect modifiers and intermediate factors. Research design and methods: The European Prospective Investigation into Cancer and Nutrition (EPIC)-InterAct is a prospective case-cohort study within eight European countries, including 12,403 cases of incident type 2 diabetes and a random subcohort of 16,835 individuals. After exclusion of individuals with missing data, the analyses included 10,327 cases and 13,863 subcohort individuals. Smoking status was used (never, former, current), with never smokers as the reference. Country-specific Prentice-weighted Cox regression models and random-effects meta-analysis were used to estimate hazard ratios (HRs) for type 2 diabetes. Results: In men, the HRs (95% CI) of type 2 diabetes were 1.40 (1.26, 1.55) for former smokers and 1.43 (1.27, 1.61) for current smokers, independent of age, education, center, physical activity, and alcohol, coffee, and meat consumption. In women, associations were weaker, with HRs (95% CI) of 1.18 (1.07, 1.30) and 1.13 (1.03, 1.25) for former and current smokers, respectively. There was some evidence of effect modification by BMI. The association tended to be slightly stronger in normal weight men compared with those with overall adiposity. Conclusions: Former and current smoking was associated with a higher risk of incident type 2 diabetes compared with never smoking in men and women, independent of educational level, physical activity, alcohol consumption, and diet. Smoking may be regarded as a modifiable risk factor for type 2 diabetes, and smoking cessation should be encouraged for diabetes prevention.
Article
Hesperetin, a flavanone glycoside predominantly found in citrus fruits, exhibits a wide array of biological properties. In the present study hesperetin exhibited a significant cytotoxic effect in human breast carcinoma MCF-7 cells in a concentration- and time-dependent manner without affecting normal (HMEC) as well as immortalized normal mammary epithelial cells (MCF-10A). The cytotoxic effect of hesperetin was due to the induction of apoptosis as evident from the phosphatidyl-serine externalization, DNA fragmentation, caspase-7 activation, and PARP cleavage. Apoptosis was associated with caspase-9 activation, mitochondrial membrane potential loss, release of cytochrome c, and increase in Bax:Bcl-2 ratio. Pre-treatment with caspase-9 specific inhibitor (Z-LEHD-fmk) markedly attenuated apoptosis suggesting an involvement of intrinsic mitochondrial apoptotic cascade. Further, DCFDA flow-cytometric analysis revealed triggering of ROS in a time-dependent manner. Pre-treatment with ROS scavenger N-acetylcysteine (NAC) and glutathione markedly abrogated hesperetin-mediated apoptosis whereas carbonyl cyanide m-chlorophenylhydrazone (CCCP) pretreatment along with DHR123-based flow-cytometry indicated the generation of cytosolic ROS. Profiling of MAPKs revealed activation of JNK upon hesperetin treatment which was abrogated upon NAC pre-treatment. Additionally, inhibition of JNK by SP600125 significantly reversed hesperetin-mediated apoptosis. The activation of JNK was associated with the activation of ASK1. Silencing of ASK1 resulted in significant attenuation of JNK activation as well as reversed the hesperetin-mediated apoptosis suggesting that hesperetin-mediated apoptosis of MCF-7 cells involves accumulation of ROS and activation of ASK1/JNK pathway. In addition, hesperetin also induced apoptosis in triple negative breast cancer MDA-MB-231 cells via intrinsic pathway via activation of caspase -9 and -3 and increase in Bax:Bcl-2 ratio.
Article
Glutathione S-transferases (GSTs) belong to a group of multigene and multifunctional detoxification enzymes, which defend cells against a wide variety of toxic insults and oxidative stress. Oxidative stress leads to cellular dysfunction which contributes to the pathophysiology of diseases such as cancer, atherosclerosis, and diabetes mellitus. It is important to assess whether the glutathione S-Transferase (GSTT1, GSTM1 and GSTP1) genotypes are associated with type 2 diabetes mellitus as deletion polymorphisms have an impaired capability to counteract the oxidative stress which is a feature of diabetes. GSTT1, GSTM1 and GSTP1 gene polymorphisms were analysed in 321 patients and 309 healthy controls from an endogamous population from north India. An association analysis was carried out at two levels (a) individual genes and (b) their double and triple combinations. The proportion of GSTT1 and GSTM1 null genotypes was higher in diabetics compared to controls (GSTT1 30.8 vs. 21.0 %; GSTM1 49.5 vs. 27.2 %). The frequency of the null genotype at both loci was higher in diabetics (19.6 vs. 7.8 %) leading to an odds ratio of 2.90 (CI 1.76-4.78, P < 0.0001). At GSTP1locus, patients had a higher frequency of the V/V genotype (15.6 vs. 7.5 %) and significant susceptible odds ratio (2.56, CI 1.47-4.48, P < 0.001). A combination of null genotypes at GSTT1 and GSTM1 loci and V/V genotype of GSTP1 locus showed highest odds ratio (9.64, CI 1.53-60.63, P < 0.01). Overall this study highlights that GST genes may play an important role in the pathogenesis of type 2 diabetes. The risk is higher in individuals carrying more than one susceptible genotype at these loci. The potential role of GST polymorphisms as markers of susceptibility to type 2 diabetes needs further investigations in a larger number of patients and populations.
Article
Type 2 diabetes (T2DM) commonly arises from islet β cell failure and insulin resistance. Here, we examined the sensitivity of key islet-enriched transcription factors to oxidative stress, a condition associated with β cell dysfunction in both type 1 diabetes (T1DM) and T2DM. Hydrogen peroxide treatment of β cell lines induced cytoplasmic translocation of MAFA and NKX6.1. In parallel, the ability of nuclear PDX1 to bind endogenous target gene promoters was also dramatically reduced, whereas the activity of other key β cell transcriptional regulators was unaffected. MAFA levels were reduced, followed by a reduction in NKX6.1 upon development of hyperglycemia in db/db mice, a T2DM model. Transgenic expression of the glutathione peroxidase-1 antioxidant enzyme (GPX1) in db/db islet β cells restored nuclear MAFA, nuclear NKX6.1, and β cell function in vivo. Notably, the selective decrease in MAFA, NKX6.1, and PDX1 expression was found in human T2DM islets. MAFB, a MAFA-related transcription factor expressed in human β cells, was also severely compromised. We propose that MAFA, MAFB, NKX6.1, and PDX1 activity provides a gauge of islet β cell function, with loss of MAFA (and/or MAFB) representing an early indicator of β cell inactivity and the subsequent deficit of more impactful NKX6.1 (and/or PDX1) resulting in overt dysfunction associated with T2DM.
Article
Apoptosis signal-regulating kinase 1 (ASK1) is a member of the mitogen-activated protein kinase kinase kinase family. ASK1 activates c-jun N-terminal kinase (JNK) and p38 in response to various stimuli such as oxidative stress, endoplasmic reticulum stress, infection and calcium influx. Under these stress conditions, ASK1 plays important roles in intracellular signaling pathways and biological functions. Diverse proteins are known to interact with ASK1 and regulate the activity of ASK1. However, activation mechanisms of ASK1 and ASK1-binding proteins which regulate the activity of ASK1 have not been completely understood. In this review, we focus on the recent findings on ASK1 and update the regulatory mechanisms of ASK1 activity.
Article
Diabetes Mellitus is characterized by chronic hyperglycemia and associated with an increased production of reactive oxygen species (ROS). Oxidative stress is the result of accumulation of free radicals in tissues which specially affects beta cells in pancreas. Glutathione S-transferases (GSTs) are a family of antioxidant enzymes that include several classes of GSTs. These enzymes have important roles in decreasing of ROS species and act as a kind of antioxidant defense. To investigate the association between GSTs polymorphism with type 2 diabetes mellitus (T2DM), we investigated the frequency of GSTM1, T1 and P1 genotypes in patients with T2DM and controls. The genotypes of GSTT1, M1 and P1 were determined in 171 clinically documented T2DM patients and 169 normal cases (as controls) by multiplex polymerase chain reaction and PCR-RFLP. In diabetic patients, the frequency of GSTM1-null genotype was significantly (OR = 1.74; 95 % CI = 1.13-2.69, P = 0.016) higher than that in control. However, the frequency of GSTT1 (OR = 1.29; 95 % CI = 0.07-2.14, P = 0.367) and GSTP1 (OR = 0.83; 95 % CI = 0.53-1.30, P = 0.389) genotypes were not significantly different comparing both groups. Also, the frequency of both GSTT1-null and GSTM1-null genotypes in patients (19.88 %) was significantly higher compared to controls with the same genotypes (11.83 %, P = 0.022). Our results indicated that GSTM1 and GSTT1 genotypes might be involved in the pathogenesis of T2DM in south Iranian population.
Article
Manganese superoxide dismutase (MnSOD), glutathione peroxidase-1 (GPX1), and catalase (CAT) provide the primary antioxidant defense system. Impaired antioxidant defense increases oxidative stress and contributes to the development of type 2 diabetes and diabetic cardiovascular disease (CVD). We preformed a case-control study in Chinese type 2 diabetes patients, to determine if the MnSOD Val16Ala (T→C), GPX1 Pro198Leu (C→T), and CAT -262C/T (C→T) functional polymorphisms contribute to the development of type 2 diabetes or diabetic CVD. Patients with type 2 diabetes (n = 168) were divided into the non-CVD group (n = 83, >10 year since diagnosis) and CVD group (n = 85, history of ischemic CVD). Genotyping was performed using PCR-restriction fragment length polymorphism (PCR-RFLP) or PCR-based direct sequencing. The genotypic distribution in the non-CVD- and CVD-group and the clinical parameters in genotypic groups were not significantly different in the three polymorphic sites, respectively. Among eight genotypic combinations, the most common TT+CC+CC genotype (59.5%) was associated with higher triglyceride levels than the TT+CT+CC genotype, the second frequent one (14.9%; 1.77 ± 0.12 vs. 1.21 ± 0.11 mmol/l, P = 0.001), and all non-TT+CC+CC genotypes (40.5%; 1.77 ± 0.12 vs. 1.43 ± 0.12 mmol/l, P = 0.048). In the CVD group, significantly elevated triglyceride levels were also observed in patients with TT+CC+CC compared to patients with TT+CT+CC (2.00 ± 0.18 vs. 1.37 ± 0.16 mmol/l, P = 0.018) or non-TT+CC+CC genotypes (2.00 ± 0.18 vs. 1.65 ± 0.19 mmol/l, P = 0.070). The common MnSOD, GPX1, and CAT TT+CC+CC genotype may contribute to hypertriglyceridemia in Chinese patients with type 2 diabetes or diabetic CVD.
Article
Type 2 diabetes mellitus has been at the forefront of human diseases and phenotypes studied by new genetic analyses. Thanks to genome-wide association studies, we have made substantial progress in elucidating the genetic basis of type 2 diabetes. This review summarizes the concept, history, and recent discoveries produced by genome-wide association studies for type 2 diabetes and glycemic traits, with a focus on the key notions we have gleaned from these efforts. Genome-wide association findings have illustrated novel pathways, pointed toward fundamental biology, confirmed prior epidemiological observations, drawn attention to the role of β-cell dysfunction in type 2 diabetes, explained ~10% of disease heritability, tempered our expectations with regard to their use in clinical prediction, and provided possible targets for pharmacotherapy and pharmacogenetic clinical trials. We can apply these lessons to future investigation so as to improve our understanding of the genetic basis of type 2 diabetes.
Article
Since long-term exposure to oxidative stress is strongly implicated in the pathogenesis of diabetic complications, polymorphic genes of detoxifying enzymes must be involved in the development of coronary artery disease (CAD). We assessed the potential glutathione S-transferase (GST) gene-gene (GSTM1(null)-GSTT1(null)) and gene-smoking interactions on the development of CAD in patients with Type 2 diabetes. In a case-only design, we enrolled 231 patients with Type 2 diabetes (147 male, 66.1 +/- 9.7 years) referred to our institute for coronary angiography investigation. CAD was diagnosed if there was over 50% obstruction of one or more major vessels. Coronary angiography revealed significant CAD in 184 patients (80%). Male gender (p < 0.001), smoking habits (p = 0.003) and GSTT1(null) genotype (p = 0.003) were significantly correlated with the increasing extent of the coronary atherosclerosis. Case-only analysis revealed that patients with both M(null)-T(null) genotypes had the highest risk for 3-vessel CAD compared with patients who express both GST genes (odds ratio: 3.1; 95% confidence interval: 1.0-10.3, p = 0.04). A nearly threefold interaction existed between cigarette smoking and M(null)-T(null) genotypes (odds ratio: 2.9, 95% confidence interval: 1.7-7.8, p = 0.03). A significant interaction between M(null)-T(null) genotypes and smoking was also observed on the increasing number of coronary vessels that were diseased (chi(2) = 14.0; p = 0.03). These data suggest that polymorphisms in GSTM1 and GSTT1 genes are risk factors for CAD in Type 2 diabetic patients, especially among smokers. These genetic markers may permit the targeting of preventive and early intervention on high-risk patients to reduce their cardiovascular risk.
Article
Noninsulin-dependent diabetes mellitus, a major risk factor for cardiovascular disease, is prevalent in more than 12 million Americans. A voluminous amount of data demonstrates that cigarette smoking is an important cause of cancer and coronary heart disease. However, the association between cigarette smoking and the risk of diabetes is virtually unexplored, especially in women. We examined the association between smoking and the incidence of noninsulin-dependent diabetes mellitus among 114,247 female nurses who were free of diabetes, cardiovascular disease, and cancer in 1976. We collected exposure information and disease status prospectively for 12 years from biennially self-administered questionnaires. Current smokers had an increased risk of diabetes, and we observed a significant dose-response trend for higher risk among heavier smokers. During 1,277,589 person-years of follow-up, 2333 women were clinically diagnosed with diabetes. The relative risk of diabetes, adjusted for obesity and other risk factors, was 1.42 among women who smoked 25 or more cigarettes per day compared with nonsmokers. These data suggest that cigarette smoking may be an independent, modifiable risk factor for noninsulin-dependent diabetes mellitus.
Article
The objective of this review is to summarize the literature on diabetes and smoking related to epidemiological risks, efficacy and cost-effectiveness of different cessation approaches, and implications for clinical practice. Over 200 studies were reviewed, with special emphasis placed on publications within the past 10 years. Intervention studies that included patients with diabetes but did not report results separately by disease are included. Diabetes-specific studies are highlighted. There are consistent results from both cross-sectional and prospective studies showing enhanced risk for micro- and macrovascular disease, as well as premature mortality from the combination of smoking and diabetes. The general cessation literature is extensive, generally well-designed, and encouraging regarding the impact of cost-effective practical office-based interventions. In particular, system-based approaches that make smoking a routine part of office contacts and provide multiple prompts, advice, assistance, and follow-up support are effective. Although there is minimal information on the effectiveness of cessation interventions specifically for people with diabetes, there is no reason to assume that cessation intervention would be more or less effective in this population. There is a clear need to increase the frequency of smoking cessation advice and counseling for patients with diabetes given the strong and consistent data on smoking prevalence; combined risks of smoking and diabetes for morbidity, mortality, and several complications; and the proven efficacy and cost-effectiveness of cessation strategies.
Article
Although cytosolic glutathione S-transferase (GST) enzymes occupy a key position in biological detoxification processes, two of the most relevant human isoenzymes, GSTT1-1 and GSTM1-1, are genetically deleted (non-functional alleles GSTT1*0 and GSTM1*0) in a high percentage of the human population, with major ethnic differences. The structures of the GSTT and GSTM gene areas explain the underlying genetic processes. GSTT1-1 is highly conserved during evolution and plays a major role in phase-II biotransformation of a number of drugs and industrial chemicals, e.g. cytostatic drugs, hydrocarbons and halogenated hydrocarbons. GSTM1-1 is particularly relevant in the deactivation of carcinogenic intermediates of polycyclic aromatic hydrocarbons. Several lines of evidence suggest that hGSTT1-1 and/or hGSTM1-1 play a role in the deactivation of reactive oxygen species that are likely to be involved in cellular processes of inflammation, ageing and degenerative diseases. There is cumulating evidence that combinations of the GSTM1*0 state with other genetic traits affecting the metabolism of carcinogens (CYP1A1, GSTP1) may predispose the aero-digestive tract and lung, especially in smokers, to a higher risk of cancer. The GSTM1*0 status appears also associated with a modest increase in the risk of bladder cancer, consistent with a GSTM1 interaction with carcinogenic tobacco smoke constituents. Both human GST deletions, although largely counterbalanced by overlapping substrate affinities within the GST superfamily, have consequences when the organism comes into contact with distinct man-made chemicals. This appears relevant in industrial toxicology and in drug metabolism.