Common variants in <Emphasis Type="Italic">CNDP1</Emphasis> and <Emphasis Type="Italic">CNDP2</Emphasis>, and risk of nephropathy in type 2 diabetes

Aims/hypothesis  

Several genome-wide linkage studies have shown an association between diabetic nephropathy and a locus on chromosome 18q harbouring two carnosinase genes, CNDP1 and CNDP2. Carnosinase degrades carnosine (β-alanyl-l-histidine), which has been ascribed a renal protective effect as a scavenger of reactive oxygen species. We investigated the putative associations of genetic variants in CNDP1 and CNDP2 with diabetic nephropathy (defined either as micro- or macroalbuminuria) and estimated GFR in type 2 diabetic patients from Sweden.     

Genetic association analyses of non-synonymous single nucleotide polymorphisms in diabetic nephropathy

Aims/hypothesis  Diabetic nephropathy, characterised by persistent proteinuria, hypertension and progressive kidney failure, affects a subset of susceptible individuals with diabetes. It is also a leading cause of end-stage renal disease (ESRD). Non-synonymous (ns) single nucleotide polymorphisms (SNPs) have been reported to contribute to genetic susceptibility in both monogenic disorders and common complex diseases. The objective of this study was to investigate whether nsSNPs are involved in susceptibility to diabetic nephropathy using a case-control design. Methods  White type 1 diabetic patients with (cases) and without (controls) nephropathy from eight centres in the UK and Ireland were genotyped for a selected subset of nsSNPs using Illumina’s GoldenGate BeadArray assay. A χ ² test for trend, stratified by centre, was used to assess differences in genotype distribution between cases and controls. Genomic control was used to adjust for possible inflation of test statistics, and the False Discovery Rate method was used to account for multiple testing. Results  We assessed 1,111 nsSNPs for association with diabetic nephropathy in 1,711 individuals with type 1 diabetes (894 cases, 817 controls). A number of SNPs demonstrated a significant difference in genotype distribution between groups before but not after correction for multiple testing. Furthermore, neither subgroup analysis (diabetic nephropathy with ESRD or diabetic nephropathy without ESRD) nor stratification by duration of diabetes revealed any significant differences between groups. Conclusions/interpretation  The nsSNPs investigated in this study do not appear to contribute significantly to the development of diabetic nephropathy in patients with type 1 diabetes. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorised users.     

Investigation of Adducin 2 (beta) DNA polymorphisms in genetic predisposition to diabetic nephropathy in Type 1 diabetes

Aims Adducin 2 (beta) (ADD2) is a biological and positional candidate gene proposed to confer genetic risk for diabetic nephropathy. This study aimed to comprehensively investigate all common and putatively functional polymorphisms in the genomic region encompassing this gene. Methods Tag single nucleotide polymorphisms (n = 23) derived from phase II of the International HapMap Project and in silico functional variants (n = 2) were genotyped in 1467 White individuals from the British Isles (cases, n = 718; control subjects, n = 749) by a combination of Sequenom iPLEX and TaqMan technologies. Results χ² analysis of genotype and allele frequencies in cases vs. control subjects revealed weak evidence for association of one variant at the 5% level of significance (rs10164951, P = 0.02). Adjusting for multiple testing in the present case–control collection negated this association. Conclusions We selected an appropriate subset of variants suitable for genetic investigations of the ADD2 gene and report the first investigation of polymorphisms in ADD2 with diabetic nephropathy. Our results suggest that common polymorphisms and putatively functional variants in the ADD2 gene do not strongly influence genetic susceptibility to diabetic nephropathy in this White population with Type 1 diabetes.     

Carnosinase,diabetes mellitus and the potential relevance of carnosinase deficiency

Carnosinase (CN1) is a dipeptidase, encoded by the CNDP1 gene, that degrades histidine-containing dipeptides, such as carnosine, anserine and homocarnosine. Loss of CN1 function (also called carnosinase deficiency or aminoacyl-histidine dipeptidase deficiency) has been reported in a small number of patients with highly elevated blood carnosine concentrations, denoted carnosinaemia; it is unclear whether the variety of clinical symptoms in these individuals is causally related to carnosinase deficiency. Reduced CN1 function should increase serum carnosine concentrations but the genetic basis of carnosinaemia has not been formally confirmed to be due to CNDP1 mutations. A CNDP1 polymorphism associated with low CN1 activity correlates with significantly reduced risk for diabetic nephropathy, especially in women with type 2 diabetes, and may slow progression of chronic kidney disease in children with glomerulonephritis. Studies in rodents demonstrate antiproteinuric and vasculoprotective effects of carnosine, the precise molecular mechanisms, however, are still incompletely understood. Thus, carnosinemia due to CN1 deficiency may be a non-disease; in contrast, carnosine may potentially protect against long-term sequelae of reactive metabolites accumulating, e.g. in diabetes and chronic renal failure.     

PAI—1基因4G／5G多态性与2型糖尿病合并肾病的相关性研究

目的探讨血浆纤溶酶原激活物抑制物-1(PAI-1)基因启动子区4G/5G多态性与中国北方汉族人2型糖尿病合并肾病的相关性.方法运用等位基因特异性引物PCR扩增技术,检测病程超过10年的2型糖尿病患者(1 43例)和健康人(85例)的PAI-1基因4G/5G多态位点的基因型,用发色底物法测血浆PAI-1活性.结果 (1)糖尿病肾病组血浆PAI-1活性明显高于糖尿病非肾病组(P＜0.05).(2)4G/4G基因型者PAI-1活性明显高于4G/5G和5G/5G者(P＜0.005).(3)糖尿病肾病组PAI-1 4G/4G基因型频率(39%)和4G等位基因频率(60.5%)高于糖尿病非肾病组(33%和56.5%),但无统计学意义(P＞0.05).结论 PAI-1活性升高是糖尿病肾病的独立危险因素,PAI-1基因启动子区4G/5G多态性与PAI-1活性密切相关,4G/4G基因型可能是易发糖尿病肾病的遗传标记.     

Investigation of DNA polymorphisms in SMAD genes for genetic predisposition to diabetic nephropathy in patients with type 1 diabetes mellitus

Aims/hypothesis  SMAD proteins are involved in multiple signalling pathways and are key modulators of gene expression. We hypothesised that genetic variation in selected SMAD genes contributes to susceptibility to diabetic nephropathy. Methods  We selected 13 haplotype tag (ht) single nucleotide polymorphisms (SNPs) from 67 variants identified by resequencing the SMAD2 and SMAD3 genes. For SMAD1, SMAD4 and SMAD5 genes, genotype data were downloaded for 217 SNPs from Phase II of the International HapMap project. Of these, 85 SNPs met our inclusion criteria, resulting in the selection of 13 tag SNPs for further investigation. A case–control approach was employed, using 267 nephropathic patients and 442 controls with type 1 diabetes from Ireland. Two further populations (totalling 1,407 patients, 2,238 controls) were genotyped to validate initial findings. Genotyping was conducted using iPLEX, TaqMan and gel electrophoresis. Results  The distribution of genotypes was in Hardy–Weinberg equilibrium. Analysis by the χ ² test of genotype and allele frequencies in patients versus controls in the Irish population (n = 709) revealed evidence for the association of one allele at 5% level of significance (rs10515478, p _uncorrected = 0.006; p _corrected = 0.04). This finding represents a relatively small difference in allele frequency of 6.4% in the patient group compared with 10.7% in the control group; this difference was not supported in subsequent investigations using DNA from European individuals with similar phenotypic characteristics. Conclusions/interpretation  We selected an appropriate subset of variants for the investigation of common genetic risk factors and assessed SMAD1 to SMAD5 genes for association with diabetic nephropathy. We conclude that common polymorphisms in these genes do not strongly influence genetic susceptibility to diabetic nephropathy in white individuals with type 1 diabetes mellitus. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorised users.     

Association of the rs3758391 polymorphism in the SIRT1 gene with diabetic nephropathy and decreased estimated glomerular filtration rate (GFR) in a population from southwest Iran

Introduction

Type 2 diabetes mellitus (T2DM) is a polygenic metabolic disorder. SIRT1 has an essential role in the insulin-signaling pathway and energy homeostasis. SIRT1 exerts protective effects in the kidney cells.

Objectives

We aimed to investigate whether the rs3758391 variant was associated with diabetic nephropathy, measures of kidney function, and BMI in a population with and without diabetes in southwest Iran.

Methods

The study comprised 132 patients with type 2 diabetes mellitus (T2DM) (with and without nephropathy). They were compared with 66 normal subjects. The subjects were genotyped for the rs3758391 polymorphism by the PCR–RFLP method. Fasting blood glucose, HbA1c, urea, creatinine, and urinary albumin were measured using a biochemistry analyzer. Serum cystatin C levels were measured by ELISA.

Results

The genotype distribution and allele frequencies were significantly different between the entirely diabetic group and the healthy subjects (p value < 0.05). For T2DM, the odds ratios (ORs) for the TT genotype and the T allele carrier were 5.7 (95% confidence interval (CI) 2.2–14.9, p < 0.001) and 4.01 (95% CI 2.1–7.5, p < 0.001), respectively. For diabetic nephropathy, the ORs for the TT genotype and the T allele carrier were 3.96 (95% CI 1.5–10.0, p = 0.003) and 3.0 (95% CI 1.4–6.4, p = 0.003), respectively. For decreased eGFR below 60 mL/min/1.73m², the OR for TT was 2.9 (95% CI 1.1–7.5, p = 0.02).

Conclusion

Our results confirm that the risk allele of the rs3758391 SNP in the SIRT1 gene is strongly associated with T2DM and diabetic nephropathy. The TT genotype is also associated with decreased eGFR.

     

The −374 T/A polymorphism in the gene encoding RAGE is associated with diabetic nephropathy and retinopathy in type 1 diabetic patients

Aims/hypothesis The receptor for AGE (RAGE) is considered to be mainly an intracellular signal-transducer or pro-inflammatory peptide of possible importance for inflammation and autoimmune diseases. Our aim was to study whether the −374 T/A polymorphism in the gene encoding RAGE (AGER) is associated with diabetes type and presence of diabetic complications.Methods The AGER −374 T/A polymorphism was genotyped in 867 type 1 diabetic patients, 2,467 type 2 diabetic patients and 205 non-diabetic control subjects of Scandinavian origin.Results AGER polymorphism was related to different HLA-DQB1 genotypes and the presence of diabetic complications. Type 1 diabetic patients had a higher frequency of the AGER −374 A/A or T/A genotypes than type 2 diabetic patients (51.1 vs 44.9%, p=0.002) and control subjects (51.1 vs 47.6%, p=0.0006). The RAGE −374 T/A polymorphism was associated with HLA-DQB1 genotypes; patients with HLA risk genotypes had a higher frequency of the A/A or T/A genotypes than patients with other HLA-DQB1 genotypes (60.3 vs 40.3%, p<0.000001). In type 1 diabetic patients, the frequency of the A/A or T/A genotypes was higher in patients with diabetic nephropathy than without (61.1 vs 46.8%, p=0.006) and with sight-threatening retinopathy than without (56.1 vs 47.6%, p=0.03). In type 2 diabetic patients with HbA_1c values below the median, the T/T genotype was more frequent in patients with diabetic nephropathy than without (54.3 vs 38.2%, p=0.02).Conclusions/interpretation Our results show an association between the AGER −374 T/A polymorphism and type 1 diabetes. This association was HLA-DQB1-dependent. The polymorphism was associated with diabetic nephropathy in both type 1 and type 2 diabetes, in an HbA_1c-dependent manner in the latter group, and also with sight-threatening retinopathy in type 1 diabetic patients.Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible to authorised users.     

Association analysis of podocyte slit diaphragm genes as candidates for diabetic nephropathy

Aims/hypothesis The slit diaphragm is an adhesion and signalling protein complex linking the interdigitating podocyte foot processes in the kidney glomerulus, and mutations in slit diaphragm-associated genes result in severe proteinuria. Here we report a genetic association analysis of four slit diaphragm genes, LRRC7, KIRREL, NPHS2 and ACTN4, in a Finnish diabetic nephropathy cohort. Materials and methods A total of 40 single nucleotide polymorphisms (SNPs) were genotyped in 1103 patients with type 1 diabetes. The patients were classified according to their renal status, and the genotype data were analysed in a cross-sectional case–control setting. To confirm positive associations, four SNPs were genotyped in 1,025 additional patients with type 1 diabetes. Results No associations with diabetic nephropathy were observed for any of the analysed SNPs. The SNPs were not associated with the time from the onset of diabetes to the diagnosis of nephropathy or with glomerular filtration rate or AER as quantitative variables. In a sex-specific sub-analysis, the variants rs979972 and rs749701 in the first intron of ACTN4 were nominally associated with diabetic nephropathy in females, with odds ratios of 1.81 (95% CI 1.18–2.79, p = 0.007) and 1.93 (95% CI 1.26–2.96, p = 0.003) respectively. Conclusions/interpretation Our study has not found any evidence that common variants in LRRC7, KIRREL, NPHS2 and ACTN4 contribute to susceptibility to diabetic nephropathy in Finnish patients with type 1 diabetes. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorised users.     

FTO gene variants are strongly associated with type 2 diabetes in South Asian Indians

Aims and hypothesis  Variants of the FTO (fat mass and obesity associated) gene are associated with obesity and type 2 diabetes in white Europeans, but these associations are not consistent in Asians. A recent study in Asian Indian Sikhs showed an association with type 2 diabetes that did not seem to be mediated through BMI. We studied the association of FTO variants with type 2 diabetes and measures of obesity in South Asian Indians in Pune. Methods  We genotyped, by sequencing, two single nucleotide polymorphisms, rs9939609 and rs7191344, in the FTO gene in 1,453 type 2 diabetes patients and 1,361 controls from Pune, Western India and a further 961 population-based individuals from Mysore, South India. Results  We observed a strong association of the minor allele A at rs9939609 with type 2 diabetes (OR per allele 1.26; 95% CI 1.13–1.40; p = 3 × 10⁻⁵). The variant was also associated with BMI but this association appeared to be weaker (0.06 SDs; 95% CI 0.01–0.10) than the previously reported effect in Europeans (0.10 SDs; 95% CI 0.09–0.12; heterogeneity p = 0.06). Unlike in the Europeans, the association with type 2 diabetes remained significant after adjusting for BMI (OR per allele for type 2 diabetes 1.21; 95% CI 1.06–1.37; p = 4.0 × 10⁻³), and also for waist circumference and other anthropometric variables. Conclusions  Our study replicates the strong association of FTO variants with type 2 diabetes and similar to the study in North Indians Sikhs, shows that this association may not be entirely mediated through BMI. This could imply underlying differences between Indians and Europeans in the mechanisms linking body size with type 2 diabetes. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorised users. C. S. Janipalli, S. Bhaskar, S. R. Kulkarni and R. M. Freathy contributed equally to this study.     

A polymorphism in the gene encoding carnosinase (CNDP1) as a predictor of mortality and progression from nephropathy to end-stage renal disease in type 1 diabetes mellitus

Aims/hypothesis

Homozygosity for a five leucine repeat (5L–5L) in the carnosinase gene (CNDP1) has been found to be cross-sectionally associated with a low frequency of diabetic nephropathy (DN), mainly in type 2 diabetes. We prospectively investigated in patients with type 1 diabetes whether: (1) 5L–5L is associated with mortality; (2) there is an interaction of 5L–5L with DN or sex for prediction of mortality; and (3) 5L–5L is associated with progression to end-stage renal disease (ESRD).

Methods

In this prospective study in white European patients with type 1 diabetes, individuals with DN were defined by persistent albuminuria ≥300 mg/24 h. Controls without nephropathy were defined by persistent (>15 years) normoalbuminuria <30 mg/24 h. Leucine repeats were assessed with a fluorescent DNA analysis system. Onset of ESRD was defined by need to start chronic dialysis or kidney transplantation.

Results

The study involved 916 patients with DN and 1,170 controls. During follow-up for 8.8 years, 107 patients (14%) with 5L–5L died compared with 182 patients (13.8%) with other genotypes (p?=?0.99). There was no significant interaction of 5L–5L with DN for prediction of mortality (p?=?0.57), but a trend towards interaction with sex (p?=?0.08). In patients with DN, HR for ESRD in 5L–5L vs other genotypes was not constant over time, with increased risk for 5L–5L beyond 8 years of follow-up (p?=?0.03).

Conclusions/interpretation

CNDP1 polymorphism was not associated with mortality, and nor was there an interaction of this polymorphism with DN for prediction of mortality in patients with type 1 diabetes. CNDP1 polymorphism predicts progression to ESRD in patients with DN, but only late after baseline measurements.     

纤溶酶原激活物抑制剂活性及其4G/5G基因多态性与急性冠状动脉综合征发病的关系

目的了解急性冠状动脉综合征患者血浆纤溶酶原激活物抑制剂1活性变化及其启动子4G/5G基因多态性特点,以探讨血浆纤溶酶原激活物抑制剂1及其基因多态性在急性冠状动脉综合征发病过程中的作用。方法对106例急性冠状动脉综合征患者9、8例稳定型冠心病患者和60例对照者用聚丙烯酰胺凝胶电泳寡核苷酸杂交分析法测定白细胞启动子4G/5G多态性位点的基因型,用酶联免疫吸附法测定血浆纤溶酶原激活物抑制剂1活性。结果急性冠状动脉综合征组血浆纤溶酶原激活物抑制剂1活性(18.0±2.9 kAU/L)较稳定型冠心病组(16.8±2.7 kAU/L)和对照组(16.2±2.8 kAU/L)增高(P<0.01和P<0.005);急性冠状动脉综合征组中4G/4G纯合子个体(49.1%)较稳定型冠心病组(28.6%)和对照组(26.7%)频率高(P<0.05);4G/4G纯合子个体的血浆纤溶酶原激活物抑制剂1活性最高,5G/5G个体最少(P<0.05)。结论血浆纤溶酶原激活物抑制剂1活性与启动子4G/5G基因型有关;血浆纤溶酶原激活物抑制剂1活性增高是急性冠状动脉综合征发病的危险因素之一。     

Increased end-stage diabetic nephropathy in Indo-Asian immigrants living in the Netherlands

Aims/hypothesis: We aimed to investigate the risk of end-stage diabetic nephropathy due to Type II (non-insulin-dependent) diabetes mellitus in Indo-Asian immigrants from Surinam. Methods: A demographically based case-control study was carried out in Surinamese Indo-Asian immigrants and Dutch Caucasian subjects. All patients with end-stage diabetic nephropathy who had started dialysis between 1990 and 1998 were identified through a national registry of all patients entering a renal replacement program in the Netherlands. The general population of native Dutch and Surinamese Indo-Asians were considered the control subjects. Results: Among Indo-Asian immigrants, the age adjusted relative risk of end-stage diabetic nephropathy was 38 (95 % CI 16 to 91) compared with the native Dutch population. The duration of diabetes until the start of dialysis treatment was similar in both ethnic groups, about 17 years. Conclusion/interpretation: The Indo-Asian subjects had a nearly 40-fold increase in the risk for end-stage diabetic nephropathy due to Type II diabetes, compared with the native Dutch population. This was higher than expected on the basis of the eightfold higher prevalence of diabetes in the Indo-Asian population. The similar duration of diabetes until the start of dialysis treatment in both ethnic groups supports the hypothesis of a higher incidence of diabetic nephropathy in the Indo-Asian diabetic population. Early and frequent screening for diabetes and microalbuminuria is recommended in Indo-Asian subjects. [Diabetologia (2002) 45: 337–341] Received: 6 August 2001 and in revised form: 14 November 2001     

The relationship between angiotensin-converting enzyme insertion/deletion polymorphism and proliferative retinopathy in type 2 diabetes

A total of 136 type 2 diabetic patients with nonproliferative and 94 patients with proliferative diabetic retinopathy (PDR) without nephropathy were studied. The DD genotype of the angiotensin-converting enzyme polymorphism was more common in the PDR group (P < 0.001). In multivariate regression, the association remained significant (OR = 3.516).     

Association of a genetic polymorphism in ectonucleotide pyrophosphatase/phosphodiesterase 1 with hepatitis C virus infection and hepatitis C virus core antigen levels in subjects in a hyperendemic area of Japan

Background  The clinical course of chronic hepatitis C virus (HCV) infection is strongly associated with insulin resistance and obesity. The K121Q polymorphism in the ectonucleotide pyrophosphatase/phosphodiesterase (ENPP)-1 gene and the rs7566605 genotype located near insulin-induced gene 2 have been shown to be associated with insulin resistance and obesity. This study examined whether the K121Q polymorphism in ENPP1 or the rs7566605 genotype is associated with the clinical course of HCV infection. Methods  The relationships between the clinical characteristics of 469 anti-HCV antibody-seropositive subjects (353 were positive for HCV core antigen or RNA, whereas 116 were negative for HCV RNA) and the polymorphisms were analyzed. Results  No significant differences in body mass index, plasma glucose level, serum insulin level, and other biochemical markers were observed between subgroups of subjects with different genotypes at the K121Q polymorphism or rs7566605. The frequency of the homozygous wild-type genotype at K121Q in HCV carriers, however, was significantly higher than that in subjects who were negative for HCV RNA (84.5% vs. 75.9%; P < 0.05). Moreover, in HCV carriers, HCV core antigen levels in subjects homozygous for the wild-type genotype at K121Q were significantly higher than in heterozygous carriers of K121Q (5358 fmol/l vs. 4002 fmol/l; P = 0.04). In contrast, the rs7566605 genotype was not associated with hepatitis C viremia or with the HCV core antigen level. Conclusions  The K121Q variant of ENPP1 may be associated with hepatitis C viremia and core antigen levels in HCV carriers.     

PAI-1基因启动子区4G/5G基因多态和Enos第4内含子a/b基因多态与糖尿病肾病的相关性研究

为探讨 PAI- 1基因启动子区 4 G/ 5 G基因多态性、一氧化氮合酶 (e NOS)第 4内含子 2 7bp插入 /缺失 (a/b)多态性与糖尿病肾病 (DN)的相关性 ,采用发色底物法测定 PAI- 1活性 ;等位基因特异性引物 PCR扩增技术测定 PAI- 1基因 4 G/ 5 G多态性 ;聚合酶链反应测定 e NOS基因第 4内含子 2 7bp的 a/ b多态性。结果显示 ,Hb A1c、SBP、TC、e NOS基因第 4内含子 a/ b多态均属 DN的独立危险因素。早期糖尿病肾病组 (DN+组 ) a等位基因及 ab基因型频率显著高于糖尿病非肾病组 (DN-组 ) (P<0 .0 5 )。DN+组血浆 PAI- 1活性明显高于 DN-组 (P<0 .0 5 ) ;4 G纯合子组 PAI- 1活性明显高于 4 G/ 5 G杂合子及 5 G纯合子组 (P<0 .0 0 5 )。2型糖尿病患者中 ,4 G纯合子和a/ b杂合子携带者 DN的相对风险明显增加 (P<0 .0 5 ) ,4 G杂合子携带者 DN的相对风险增加不明显 (P>0 .0 5 )。当 a/ b杂合子和 4 G纯合子基因多态并存时 DN的发病风险明显增加。认为 PAI- 1基因启动子区 4 G/ 5 G基因多态、e NOS基因第 4内含子 a/ b多态与 DN的发生、发展有关。两种基因多态同时存在时 ,DN的发病风险明显增加     

Microarray analysis of multiple candidate genes and associated plasma proteins for nephropathy secondary to type 2 diabetes among Chinese individuals

Aims/hypothesis  Evolving research suggests that common and rare alleles jointly constitute the genetic landscape of complex disease. We studied the association between 43 pathway-related candidate genes with ‘intermediate phenotype’ (i.e. corresponding plasma protein) and diabetic nephropathy in a customised microarray of 1,536 SNPs. Methods  In this case–control study of type 2 diabetic Chinese individuals with and without diabetic nephropathy, cases (n = 545) were defined on the basis of a spot urinary albumin/creatinine ratio (ACR) > 113 mg/mmol; the value for controls (n = 503) was ACR < 3.3 mg/mmol. Genotyping was performed using Illumina GoldenGate assay. Results  No single nucleotide polymorphism (SNP) remained significant in single locus analysis after correction for multiple testing. Therefore, we explored the best ∼1% SNPs. Of these 13 SNPs, four clustered to a 5′ end NADPH oxidase homologue 4 (NOX4) haplotype (GGCC frequency = 0.776) with estimated OR for diabetic nephropathy of 2.05 (95% CI 1.04–4.06) (heterozygous) and 2.48 (1.27–4.83) (homozygous) (p = 0.0055). The haplotype was correlated with plasma Cu/Zn superoxide dismutase (SOD) concentration, suggesting increased oxidative burden. Endothelin-1 SNP (rs1476046G>A, frequency = 0.252) was correlated with plasma C-terminal pro-endothelin-1 concentrations with an estimated OR for diabetic nephropathy of (heterozygous) 1.26 (0.96–1.66) and (homozygous) 1.87 (1.13–3.12) (p = 0.0072). Nitric oxide synthase 1 (NOS1) 5′ haplotype (TGTC frequency = 0.38) also revealed a suggestive association with diabetic nephropathy: heterozygous 1.26 (0.95–1.67), homozygous 1.57 (1.04–2.35) (p = 0.0073). A rare NADPH oxidase homologue 1 (NOX1)-coding non-synonymous SNP (Arg315His, frequency = 0.006) was found exclusively among cases. Conclusions/interpretation  Our preliminary observations suggest that common haplotypes from NOX4 and endothelin-1 SNP correlated with plasma Cu/Zn SOD and C-terminal pro-endothelin-1 concentrations, respectively, and might have conferred diabetic nephropathy susceptibility. Common NOS1 and rare NOX1 variants also revealed a suggestive association with diabetic nephropathy. Future studies to validate our observation are needed. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorised users.     

Role of MKK3–p38 MAPK signalling in the development of type 2 diabetes and renal injury in obese db/db mice

Aims/hypothesis  Obesity and diabetes are associated with increased intracellular p38 mitogen-activated protein kinase (MAPK) signalling, which may promote tissue inflammation and injury. Activation of p38 MAPK can be induced by either of the immediate upstream kinases, MAP kinase kinase (MKK)3 or MKK6, and recent evidence suggests that MKK3 has non-redundant roles in the pathology attributed to p38 MAPK activation. Therefore, this study examined whether MKK3 signalling influences the development of obesity, type 2 diabetes and diabetic nephropathy. Methods  Wild-type and Mkk3 (also known as Map2k3) gene-deficient db/db mice were assessed for the development of obesity, type 2 diabetes and renal injury from 8 to 32 weeks of age. Results   Mkk3 ^+/+ db/db and Mkk3 ^−/− db/db mice developed comparable obesity and were similar in terms of incidence and severity of type 2 diabetes. At 32 weeks, diabetic Mkk3 ^+/+ db/db mice had increased kidney levels of phospho-p38 and MKK3 protein. In comparison, kidney levels of phospho-p38 in diabetic Mkk3 ^−/− db/db mice remained normal, despite a fourfold compensatory increase in MKK6 protein levels. The reduced levels of p38 MAPK signalling in the diabetic kidneys of Mkk3 ^−/− db/db mice was associated with protection against the following: declining renal function, increasing albuminuria, renal hypertrophy, podocyte loss, mesangial cell activation and glomerular fibrosis. Diabetic Mkk3 ^−/− db/db mice were also significantly protected from tubular injury and interstitial fibrosis, which was associated with reduced Ccl2 mRNA expression and interstitial macrophage accumulation. Conclusions/interpretation  MKK3–p38 MAPK signalling is not required for the development of obesity or type 2 diabetes, but plays a distinct pathogenic role in the progression of diabetic nephropathy in db/db mice.