Beverley A. Millward

A new marker in the HLA class I region is associated with the age at onset of IDDM

SummaryThe (MHC) class II association with insulin-dependent diabetes mellitus (IDDM) is well documented. However, it is likely that genes within the MHC class III and the class I region also play a role in determining susceptibility to IDDM. In this study we have used a novel molecular probe to investigate the class I P3A and P3B loci of 179 patients with IDDM and 142 normal control subjects. A highly significant increase in the frequency of the class I P3 4.0;1.5 kilobase (kb) and 4.0;1.8;1.5 kb genotypes was found in patients compared to the control subjects (x2 46.8, 6 df, p<0.0001). The association with the P3B 1.5 kb allele was strongly associated with the age at onset of diabetes, being present in 96.2% of subjects who developed diabetes between the age of 10–20 years compared to 55.0 and 74.6% who developed diabetes before 10 years or after 20 years, respectively (x2 31.4, p<0.0001). There was no evidence for linkage disequilibrium between the DQA1 and DQB1 loci and P3B suggesting that this is an independent association. In conclusion, these results suggest that genes in both the MHC class I and II regions confer susceptibility to IDDM and are related to the age at onset of the disease.

Drinking water composition and childhood‐onset Type 1 diabetes mellitus in Devon and Cornwall, England

Aims  Previous studies have reported inconsistent results on the association between some compositions (e.g. nitrate) in domestic water and the risk of childhood‐onset Type 1 diabetes mellitus. This study aimed to examine the relationship between nitrate, zinc and magnesium in drinking water and the risk of childhood‐onset Type 1 diabetes mellitus.

The HLA-E locus is associated with age at onset and susceptibility to type 1 diabetes mellitus

Previous studies have suggested that the human leukocyte antigen (HLA) class I region may be involved in determining the age at onset and clinical severity of type 1 diabetes. We have investigated the frequency of polymorphisms of the nonclassical HLA class I gene, HLA-E, in 199 British Caucasian patients with type 1 diabetes and 82 healthy controls. A highly significant increase in the frequency of the HLA-E 0101 genotype was found in the patients compared to controls (chi(2) = 15.3, p < 0.00009). The frequency of the HLA-E 0101 genotype was increased in those patients diagnosed after 10 years of age, while the frequency of the 0101, 0103 genotype was significantly increased in those subjects diagnosed before 10 years of age (chi(2) = 26.0 p < 0.000003 and chi(2) = 13.0 p < 0.0003, respectively). No obvious interaction between the HLA-E locus and the class II DQB1*0201, 0302, and 0501 susceptibility alleles was found. This is the first report of an association between the HLA-E locus and susceptibility to an autoimmune disease.

High glucose induction of DNA-binding activity of the transcription factor NFκB in patients with diabetic nephropathy

The aim of this study was to investigate whether high glucose induces aldose reductase (AKR1B1) expression through NFkappaB, which may contribute to the pathogenesis of diabetic nephropathy. 34 Caucasoid patients with type 1 diabetes were recruited; 20 nephropaths and 14 long-term uncomplicated subjects. Peripheral blood mononuclear cells (PBMCs) were cultured under normal or high glucose (25 mmol/l of d-glucose) with or without an aldose reductase inhibitor (ARI). High glucose increased NFkappaB binding activities in the PBMCs from nephropaths compared to the uncomplicated subjects (1.77+/-0.22 vs. 1.16+/-0.04, p=0.02). ARI induced a substantially greater decrease of NFkappaB binding activities in the nephropaths compared to the uncomplicated subjects (0.58+/-0.06 vs. 0.79+/-0.06, p=0.032). AKR1B1 protein levels in the nephropaths were increased under high glucose conditions and decreased in the presence of an ARI, whilst the silencing of the NFkappaB p65 gene in vitro reduced the transcriptional activities of AKR1B1 in luciferase assays. These results show that NFkappaB induces AKR1B1expression under high glucose conditions, and the pattern of expression differs between nephropaths and the uncomplicated subjects.

Elevated activity of transcription factor nuclear factor of activated T-cells 5 (NFAT5) and diabetic nephropathy.

The expression of aldose reductase is tightly regulated by the transcription factor tonicity response element binding protein (TonEBP/NFAT5) binding to three osmotic response elements (OREs; OREA, OREB, and OREC) in the gene. The aim was to investigate the contribution of NFAT5 to the pathogenesis of diabetic nephropathy. Peripheral blood mononuclear cells (PBMCs) were isolated from the following subjects: 44 Caucasoid patients with type 1 diabetes, of whom 26 had nephropathy and 18 had no nephropathy after a diabetes duration of 20 years, and 13 normal healthy control subjects. In addition, human mesangial cells (HMCs) were isolated from the normal lobe of 10 kidneys following radical nephrectomy for renal cell carcinoma. Nuclear and cytoplasmic proteins were extracted from PBMCs and HMCs and cultured in either normal or high-glucose (31 mmol/l d-glucose) conditions for 5 days. NFAT5 binding activity was quantitated using electrophoretic mobility shift assays for each of the OREs. Western blotting was used to measure aldose reductase and sorbitol dehydrogenase protein levels. There were significant fold increases in DNA binding activities of NFAT5 to OREB (2.06 ± 0.03 vs. 1.33 ± 0.18, P = 0.033) and OREC (1.94 ± 0.21 vs. 1.39 ± 0.11, P = 0.024) in PBMCs from patients with diabetic nephropathy compared with diabetic control subjects cultured under high glucose. Aldose reductase and sorbitol dehydrogenase protein levels in the patients with diabetic nephropathy were significantly increased in PBMCs cultured in high-glucose conditions. In HMCs cultured under high glucose, there were significant increases in NFAT5 binding activities to OREA, OREB, and OREC by 1.38 ± 0.22-, 1.84 ± 0.44-, and 2.38 ± 1.15-fold, respectively. Similar results were found in HMCs exposed to high glucose (aldose reductase 1.30 ± 0.06-fold and sorbitol dehydrogenease 1.54 ± 0.24-fold increases). Finally, the silencing of the NFAT5 gene in vitro reduced the expression of the aldose reductase gene. In conclusion, these results show that aldose reductase is upregulated by the transcriptional factor NFAT5 under high-glucose conditions in both PBMCs and HMCs.

Chromosome 7q35 and susceptibility to diabetic microvascular complications

Aldose reductase (ALR2), the first enzyme of the polyol pathway, may plan an important role in the pathogenesis of diabetic microvascular complications. The gene coding for ALR2 has been localized to chromosome 7q35. Using an ALR2 probe in conjunction with the restriction endonuclease Bam-HI, we have investigated the ALR2 locus of 128 patients with type I diabetes. A significant decrease in the frequency of the 8.2 kilobase (kb) Bam-HI ALR2 genotype and 8.2 kb allele was found in patients with nephropathy (nephropaths) compared to those with retinopathy alone (retinopaths) (p < 0.05 and 0.25, respectively). We have previously shown that an RFLP of the T-cell antigen receptor constant beta-chain (TCRBC) locus, which is also localized to chromosome 7q35, is strongly associated with susceptibility to microvascular complications. The 128 patients were genotyped using the restriction endonuclease Bgl-II and a TCRBC probe. The 10/9.2-8.2 kb TCRBC-ALR2 genotype was significantly decreased in the nephropaths compared to the retinopaths (13.7% versus 43.6%, chi 2 = 10.1, p < 0.0025). The 10/9.2 and 9.2/9.2 kb TCRBC-ALR2 haplotypes were increased in the nephropaths compared to the retinopaths (32.5% versus 8.9% chi 2 = 10.9, p < 0.001). These results suggest that chromosome 7q35 harbors a gene(s) that is involved in the pathogenesis of microvascular complications. Interestingly, the gene coding for endothelial nitric oxide synthase has recently been localized to the same chromosomal region as ALR2.

The angiotensin I-converting enzyme (ACE) locus is strongly associated with age and duration of diabetes in patients with Type I diabetes

We have investigated the frequency of the angiotensin I-converting enzyme (ACE) insertion/ deletion (I/D) polymorphism in 249 patients with type I diabetes and 162 normal healthy controls. There was no significant difference in the frequency of ACE genotypes between those patients with diabetic nephropathy (n = 72) (nephropaths) compared to those with no proteinuria after 20 years duration of diabetes (n = 86) (normoalbuminurics). There was, however, a significant difference in the frequency of ACE genotypes between the short-duration and long-term normoalbuminuric group (chi = 11.5, p = 0.001). Analysis of the ACE genotypes with respect to age and duration of diabetes showed that homozygosity for the insertion (I/I) genotype was significantly decreased with longer duration of diabetes (r2 = 92.7%, p < 0.009). No association was found with age in the normal controls. In conclusion, these results suggest that the ACE locus may be associated with longevity and survival in patients with type I diabetes rather than diabetic nephropathy or microvascular disease per se.

Space–time clustering of childhood Type 1 diabetes in Devon and Cornwall, England

Aims Several studies on space–time clustering have been reported in childhood diabetes, but the findings are conflicting. The present study was undertaken to examine whether such clustering could be detected at either birth or the time of diagnosis in the far South‐west of England.

Maternal glucose levels influence birthweight and ‘catch‐up’ and ‘catch‐down’ growth in a large contemporary cohort

Aim  To explore the effects of maternal glucose on birthweight, infant and childhood growth in non‐diabetic pregnant women using routinely collected data.

The Rate of Decline of Glomerular Filtration Rate May Not Be Associated with Polymorphism of the PPARγ2 Gene in Patients with Type 1 Diabetes and Nephropathy.

The aim of the study was to investigate whether a Pro12Ala polymorphism in the peroxisome proliferator-activated receptor gamma 2 (PPARγ2) gene is associated with the progress of diabetic nephropathy in patients with type 1 diabetes. 197 Caucasian patients with type 1 diabetes and ethnically matched 151 normal healthy controls were genotyped for this polymorphism. Results showed that there were no significant differences in the frequencies of the genotypes and alleles of the polymorphism between groups. Multiple regression analysis in 77 patients demonstrated that the rate of decline in renal function in terms of glomerular filtration rate was significantly correlated to the baseline level of cholesterol (P = 0.0014), mean diastolic blood pressure during follow-up period (P = 0.019), and baseline level of HbA1c (P = 0.022) adjusting for the effect of diabetes duration and gender, but no significant association was found between the polymorphism and the progression of diabetic nephropathy in our studied population. In summary, our results show that the PPARγ2 polymorphism is unlikely to be associated with the development and progression of the diabetic nephropathy in patients with type 1 diabetes. Further studies in different populations may be warranted to confirm our findings as the sample size in our study was relatively small.