Glucose transporter (GLUT1) allele (XbaI-) associated with nephropathy in non-insulin-dependent diabetes mellitus

Interaction between a diabetes-related methylation site (TXNIP cg19693031) and variant (GLUT1 rs841853) on fasting blood glucose levels among non-diabetics

Background

Type 2 diabetes mellitus (T2DM) is caused by a combination of environmental, genetic, and epigenetic factors including, fasting blood glucose (FBG), genetic variant rs841853, and cg19693031 methylation. We evaluated the interaction between rs841853 and cg19693031 on the FBG levels of non-diabetic Taiwanese adults.

Methods

We used Taiwan Biobank (TWB) data collected between 2008 and 2016. The TWB data source contains information on basic demographics, personal lifestyles, medical history, methylation, and genotype. The study participants included 1300 people with DNA methylation data. The association of cg19693031 methylation (stratified into quartiles) with rs841853 and FBG was determined using multiple linear regression analysis. The beta-coefficients (β) and p-values were estimated.

Results

The mean ± standard deviation (SD) of FBG in rs841853-CC individuals (92.07 ± 7.78) did not differ significantly from that in the CA + AA individuals (91.62 ± 7.14). However, the cg19693031 methylation levels were significantly different in the two groups (0.7716 ± 0.05 in CC individuals and 0.7631 ± 0.05 in CA + AA individuals (p = 0.002). The cg19693031 methylation levels according to quartiles were β < 0.738592 (< Q1), 0.738592 ≤ 0.769992 (Q1–Q2), 0.769992 ≤ 0.800918 (Q2–Q3), and β ≥ 0.800918 (≥ Q3). FBG increased with decreasing cg19693031 methylation levels in a dose–response manner (p_trend = 0.005). The β-coefficient was − 0.0236 (p = 0.965) for Q2–Q3, 1.0317 (p = 0.058) for Q1–Q2, and 1.3336 (p = 0.019 for < Q1 compared to the reference quartile (≥ Q3). The genetic variant rs841853 was not significantly associated with FBG. However, its interaction with cg19693031 methylation was significant (p-value = 0.036). Based on stratification by rs841853 genotypes, only the CC group retained the inverse and dose–response association between FBG and cg19693031 methylation. The β (p-value) was 0.8082 (0.255) for Q2–Q3, 1.6930 (0.022) for Q1–Q2, and 2.2190 (0.004) for < Q1 compared to the reference quartile (≥ Q3). The p_trend was 0.002.

Conclusion

Summarily, methylation at cg19693031 was inversely associated with fasting blood glucose in a dose-dependent manner. The inverse association was more prominent in rs841853-CC individuals, suggesting that rs841853 could modulate the association between cg19693031 methylation and FBG. Our results suggest that genetic variants may be involved in epigenetic mechanisms associated with FBG, a hallmark of diabetes. Therefore, integrating genetic and epigenetic data may provide more insight into the early-onset of diabetes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03269-y.

Genetic associated complications of type 2 Diabetes Mellitus: a review

According to the International Diabetes Federation, the number of adults (age of 20-79) being diagnosed with Diabetes Mellitus (DM) have increased from 285 million in year 2009 to 463 million in year 2019 which comprises of 95% Type 2 DM patient (T2DM). Research have claimed that genetic predisposition could be one of the factors causing T2DM complications. In addition, T2DMcomplications cause an incremental risk to mortality. Therefore, this article aims to discuss some complications of T2DM in and their genetic association. The complications that are discussed in this article are diabetic nephropathy, diabetes induced cardiovascular disease, diabetic neuropathy, Diabetic Foot Ulcer (DFU) and Alzheimer's disease. According to the information obtained, genes associated with diabetic nephropathy (DN) are gene GABRR1 and ELMO1 that cause injury to glomerular. Replication of genes FRMD3, CARS and MYO16/IRS2 shown to have link with DN. The increase of gene THBS2, NGAL, PIP, TRAF6 polymorphism, ICAM-1 encoded for rs5498 polymorphism and C667T increase susceptibility towards DN in T2DM patient. Genes associated with cardiovascular diseases are Adiponectin gene (ACRP30) and Apolipoprotein E (APOE) polymorphism gene with ξ2 allele. Haptoglobin (Hp) 1-1 genotype and Mitochondria Superoxide Dismutase 2 (SOD2) plays a role in cardiovascular events. As for genes related to diabetic neuropathy, Janus Kinase (JAK), mutation of SCN9A and TRPA1 gene and destruction of miRNA contribute to pathogenesis of diabetic neuropathy among T2DM patients. Expression of cytokine IL-6, IL-10, miR-146a are found to cause diabetic neuropathy. Besides, A1a16Va1 gene polymorphism, an oxidative stress influence was found as one of the gene factors. Diabetic retinopathy (DR) is believed to have association with Monocyte Chemoattractant Protein-1 (MCP-1) and Insulin-like Growth Factor 1 (IGF1). Over-expression of gene ENPP1, IL-6 pro-inflammatory cytokine, ARHGAP22's protein rs3844492 polymorphism and TLR4 heterozygous genotype are contributing to significant pathophysiological process causing DR, while research found increases level of UCP1 gene protects retina cells from oxidative stress. Diabetic Foot Ulcer (DFU) is manifested by slowing in reepithelialisation of keratinocyte, persistence wound inflammation and healing impairment. Reepithelialisation disturbance was caused by E2F3 gene, reduction of Tacl gene encoded substance P causing persistence inflammation while expression of MMp-9 polymorphism contributes to healing impairment. A decrease in HIF-1a gene expression leads to increased risk of pathogenesis, while downregulation of TLR2 increases severity of wound in DFU patients. SNPs alleles has been shown to have significant association between the genetic dispositions of T2DM and Alzheimer's disease (AD). The progression of AD can be due to the change in DNA methylation of CLOCK gene, followed with worsening of AD by APOE4 gene due to dyslipidaemia condition in T2DM patients. Insulin resistance is also a factor that contributes to pathogenesis of AD.

SNPs in PRKCA-HIF1A-GLUT1 are associated with diabetic kidney disease in a Chinese Han population with type 2 diabetes

OBJECTIVE

To explore the relationship between SNPs in PRKCA-HIF1A-GLUT1 and diabetic kidney disease in Chinese Han people.

MATERIALS AND METHODS

A total of 2552 participants from Shanghai Diabetes Institute Inpatient Database of Shanghai Jiao Tong University Affiliated Sixth People's Hospital were involved in the stage 1 cross-sectional population. A total of 6015 subjects from the Hong Kong Diabetes Register were included for validation. Genotyping of participants was conducted by the MassARRAY Compact Analyzer (Agena Bioscience). The data were analysed by plink, SAS, Haploview.

RESULTS

We identified variants associated with diabetic kidney disease in stage 1. Rs1681851 (P = .0105, OR = 1.331) in GLUT1 as well as rs2301108 (P = .0085, OR = 1.289) and rs79865957 (P = .0204, OR = 1.263) in HIF1A were significantly associated with diabetic kidney disease. Regarding DKD-related traits, rs1681851 was associated with plasma creatinine levels (P = .0169, β = 4.822) and eGFR (P = .0457, β = -6.956). Moreover, the results showed the interactions between PRKCA-GLUT1 in the occurrence of DKD. We further sought validation of the 17 SNPs in a prospective cohort and found that rs900836 and rs844501 were associated with the percentage change in eGFR slope. We performed a meta-analysis of case-control analysis data from the Hong Kong samples together with the stage 1 data from Shanghai. Rs9894851 showed significant correlation with the serum creatinine level as well as eGFR and no SNP showed association with DKD after meta-analysis.

CONCLUSIONS

Our results suggest potential association between SNPs in PRKCA-HIF1A-GLUT1 and diabetic kidney disease in Chinese Han people.

Associations between the HaeIII Single Nucleotide Polymorphism in the SLC2A1 Gene and Diabetic Nephropathy in Korean Patients with Type 2 Diabetes Mellitus

BACKGROUND

Diabetic nephropathy (DN) is the most serious microvascular complication of diabetes mellitus and is one of the leading causes of end stage renal failure. In previous studies, the contribution of genetic susceptibility to DN showed inconsistent results. In this study, we investigated the association between the solute carrier family 2 facilitated glucose transporter member 1 (SLC2A1) HaeIII polymorphism and DN in Korean patients with type 2 diabetes mellitus (T2DM) according to disease duration.

METHODS

A total of 846 patients with T2DM (mean age, 61.3 ± 12.3 years; mean duration of T2DM, 10.3 ± 7.9 years; 55.3% men) who visited the Chungbuk National University Hospital were investigated. The HaeIII polymorphism of the SLC2A1 gene was determined by the real time polymerase chain reaction method. Genotyping results were presented as GG, AG, or AA. A subgroup analysis was performed according to duration of T2DM (≤ 10 years, > 10 years).

RESULTS

The AG + AA genotype showed a significantly higher risk of DN compared with the GG genotype in patients with a type 2 DM duration less than 10 years (12.4% vs. 4.2%; P < 0.001). No significant differences were observed in terms of other diabetic complications, including retinopathy, peripheral neuropathy, cardiovascular disease, cerebrovascular disease or peripheral artery disease, according to the genotypes of the SLC2A1 HaeIII polymorphism.

CONCLUSION

The SLC2A1 HaeIII polymorphism was associated with DN in Korean patients with T2DM, particularly in the group with a relatively short disease duration.

Ion channels and transporters in diabetic kidney disease

Type 1 and 2 diabetes mellitus are major medical epidemics affecting millions of patients worldwide. Diabetes mellitus is the leading cause of diabetic kidney disease (DKD), which is the most common cause of end-stage renal disease (ESRD). DKD is associated with significant changes in renal hemodynamics and electrolyte transport. Alterations in renal ion transport triggered by pathophysiological conditions in diabetes can exacerbate hypertension, accelerate renal injury, and are integral to the development of DKD. Renal ion transporters and electrolyte homeostasis play a fundamental role in functional changes and injury to the kidney during DKD. With the large number of ion transporters involved in DKD, understanding the roles of individual transporters as well as the complex cascades through which they interact is essential in the development of effective treatments for patients suffering from this disease. This chapter aims to gather current knowledge of the major renal ion transporters with altered expression and activity under diabetic conditions, and provide a comprehensive overview of their interactions and collective functions in DKD.

The contribution of genetic variants of SLC2A1 gene in T2DM and T2DM-nephropathy: association study and meta-analysis

An association study was conducted to investigate the relation between 14 variants of glucose transporter 1 gene (SLC2A1) and the risk of type 2 diabetes (T2DM) leading to nephropathy. We also performed a meta-analysis of 11 studies investigating association between diabetic nephropathy (DN) and SLC2A1 variants. The cohort included 197 cases (T2DM with nephropathy), 155 diseased controls (T2DM without nephropathy) and 246 healthy controls. The association of variants with disease progression was tested using generalized odds ratio (ORG). The risk of type 2 diabetes leading to nephropathy was estimated by the OR of additive and co-dominant models. The mode of inheritance was assessed using the degree of dominance index (h-index). We synthesized results of 11 studies examining association between 5 SLC2A1 variants and DN. ORG was used to assess the association between variants and DN using random effects models. Significant results were derived for co-dominant model of rs12407920 [OR = 2.01 (1.17-3.45)], rs841847 [OR = 1.73 (1.17-2.56)] and rs841853 [OR = 1.74 (1.18-2.55)] and for additive model of rs3729548 [OR = 0.52 (0.29-0.90)]. The mode of inheritance for rs12407920, rs841847 and rs841853 was 'dominance of each minor allele' and for rs3729548 'non-dominance'. Frequency of one haplotype (C-G-G-A-T-C-C-T-G-T-C-C-A-G) differed significantly between cases and healthy controls [p = .014]. Regarding meta-analysis, rs841853 contributed to an increased risk of DN [(ORG = 1.43 (1.09-1.88); ORG = 1.58 (1.01-2.48)] between diseased controls versus cases and healthy controls versus cases, respectively. Further studies confirm the association of rs12407920, rs841847, rs841853, as well as rs3729548 and the risk of T2DM leading to nephropathy.

Human genetics of diabetic retinopathy

There is evidence demonstrating that genetic factors contribute to the risk of diabetic retinopathy (DR). Genetics variants, structural variants (copy number variation, CNV) and epigenetic changes play important roles in the development of DR. Genetic linkage and association studies have uncovered a number of genetic loci and common genetic variants susceptibility to DR. CNV and interactions of gene by environment have also been detected by association analysis. Apart from nucleus genome, mitochondrial DNA plays critical roles in regulation of development of DR. Epigenetic studies have indicated epigenetic changes in chromatin affecting gene transcription in response to environmental stimuli, which provided a large body of evidence of regulating development of diabetes mellitus. Identification of genetic variants and epigenetic changes contributed to risk or protection of DR will benefit uncovering the complex mechanism underlying DR. This review focused on the current knowledge of the genetic and epigenetic basis of DR.

Identified single-nucleotide polymorphisms and haplotypes at 16q22.1 increase diabetic nephropathy risk in Han Chinese population

Background

Diabetic nephropathy (DN) has become one of the most common causes of end-stage renal disease (ESRD) in many countries, such as 44.5% in Taiwan. Previous studies have shown that there is a genetic component to ESRD. Studies attempting to determine which genetic variants are related to DN in Han Chinese are limited. A case–control study was conducted to identify DN susceptibility variants in Han Chinese patients with type 2 diabetes.

Results

We included 574 unrelated type 2 diabetes patients (217 DN cases and 357 controls), who were genotyped using Illumina HumanHap550-Duo BeadChip. In single-SNP association tests, the SNPs rs11647932, rs11645214, and rs6499323 located at 16q22.1 under the additive-effect disease model were significantly associated with an approximately 2-fold increased risk of DN. In haplotype association tests, identified haplotypes located in the chromosome 16q22.1 region (containing ST3GAL2, COG4, SF3B3, and IL34 genes) raised DN risk. The strongest association was found with haplotype rs2288491-rs4985534-rs11645214 (C-C-G) (adjusted odds ratio [AOR] 1.93, 95% confidence interval [CI] 1.83-2.03, p = 6.25 × 10⁻⁷), followed by haplotype rs8052125-rs2288491-rs4985534-rs11645214 (G-C-C-G) (AOR 1.92, 95% CI 1.82-2.02, p = 6.56 × 10⁻⁷), and haplotype rs2303792-rs8052125-rs2288491-rs4985534-rs11645214 (A-G-C-C-G) (AOR 1.91, 95% CI 1.81-2.01, p = 1.15 × 10⁻⁶).

Conclusions

Our results demonstrate that the novel SNPs and haplotypes located at the 16q22.1 region may involve in the biological pathways of DN in Han Chinese patients with type 2 diabetes. This study can provide new insights into the etiology of DN.

Electronic supplementary material

The online version of this article (doi:10.1186/s12863-014-0113-8) contains supplementary material, which is available to authorized users.

Genetics of diabetic retinopathy

Multiple studies have shown that genetic factors may play an important role in determining an individual's risk for the development of diabetic retinopathy (DR) and progression to proliferative DR. However, consistent and definitive genetic associations with DR across broad populations have been not been established. Numerous genes have been studied for their association with DR and the results of these investigations have most specifically pointed to three specific genes that are likely involved in DR development and progression. The gene coding for vascular endothelial growth factor, aldose reductase, and the receptor for advanced glycation end products have been extensively evaluated, and specific polymorphisms of these genes have been suggested to potentially increase the risk of DR development. In this paper, we have reviewed the published literature on the genetics of DR and the potential implications for DR development and progression.

Association between glucose transporter 1 rs841853 polymorphism and type 2 diabetes mellitus risk may be population specific (1rs8418532)

BACKGROUND

So far, studies on the association between the glucose transporter 1 (GLUT1) rs841853 polymorphism and type 2 diabetes mellitus (T2DM) risk have generated considerable controversy. The present study was performed to clarify the association of this genetic variation with T2DM.

METHODS

A comprehensive literature search of electronic databases was conducted to obtain articles focused on the relationship between the GLUT1 rs841853 polymorphism and T2DM, followed by a systemic meta-analysis.

RESULTS

Fourteen articles and 19 individual studies were included for analysis. Main analyses revealed extreme heterogeneity and random effect pooled odds ratios (OR) were weakly significant in allele contrast (OR 1.28; 95% confidence interval [CI] 1.01, 1.63; P=0.04) and dominant model (OR 1.52; 95% CI 1.19, 1.94; P=0.0008) for T allele. Subgroup analyses for Caucasians showed marginal positive results in the dominant model. However, analyses for Asians yielded an obvious relationship to T2DM risk in all genetic models. Interestingly, T allele even seemed to be a protective factor against the development of T2DM in Blacks in allele contrast. Sensitivity analyses did not alter materially for most comparisons and no publication bias was found in this meta-analysis.

CONCLUSIONS

The results of the present meta-analysis provide evidence that the GLUT1 rs841853 polymorphism may confer increased susceptibility to T2DM in Asians. However, there is no currently available strong evidence supporting the association between this genetic variation and T2DM in Caucasians, Blacks, or the overall population.

Gene polymorphisms are associated with posttransplantation diabetes mellitus among Taiwanese renal transplant recipients

BACKGROUND

Genetic variations may affect posttransplantation metabolic syndrome and diabetes mellitus (PTDM), which is associated with greater morbidity and progressive impairment of both patient and graft survivals. The aim of this study was to evaluate several candidate gene polymorphisms for their association with the risk of developing PTDM.

METHODS

In April 1999, we enrolled 278 renal transplant participants, including 251 subjects free of diabetes and 27 with PTDM. We studied several candidate gene polymorphisms associated with diabetes: 4G/5G polymorphism of plasminogen activator inhibitor 1 (PAI-1) at -675; C/T polymorphism of interleukin-1beta (IL-1β) at -511; G/C polymorphism of IL-6 at 174; polymorphic XbaI of Glucose transporter 1 (GLUT1); and C/T polymorphism of methylenetetrahydrofolate redutase (MTHFR) at 677.

RESULTS

The PTDM group had an older mean age (47.6 ± 9.8 years), greater predominance of men (77.8%), higher number of chronic diseases (CDN ≥2, 96.3%), and more patients using tacrolimus-based immunosuppression (44.4%; P < .05). Using model A, a simple logistic regression, we observed that patients with the IL-6 G/G genotype experienced a lower risk of developing PTDM (odds ratio [OR], 0.08; 95% confidence interval [CI] 0.01-0.86), and multiple logistic regression models B and C, after adjusting for different variables, confirmed this observation (model B: OR, 0.05; 95% CI, 0.00-0.66). The IL-6 G/G genotype showed a borderline effect in model C (OR, 0.02; 95% CI, 0.00-1.16). There were no significant differences between the 2 groups in genotype variations of PAI-1, IL-1β, GLUT-1, and MTHFR.

CONCLUSIONS

The G/G genotype of IL-6 may play an important role to lower the risk for PTDM development.

Relationship between five GLUT1 gene single nucleotide polymorphisms and diabetic nephropathy: a systematic review and meta-analysis

So far, case-control studies on the association between glucose transporter 1 (GLUT1) gene single nucleotide polymorphisms (SNPs) and diabetic nephropathy (DN) have generated considerable controversy. To clarify the linkage of GLUT1 SNPs on the risk of DN, a systematic review and meta-analysis was performed. A comprehensive literature search of electronic databases was conducted to obtain relative studies. Nine case-control studies were included. Significant differences were found between XbaI SNP (rs841853) and increased risk of DN in all genetic models. Subgroup analyses for Caucasians population and DN from both type 1 and type 2 diabetes also revealed positive results. For Enh2-1 SNP (rs841847), Enh2-2 SNP (rs841848) and HaeIII SNP (rs1385129), obvious linkages were demonstrated in recessive model. However, analysis for the association between HpyCH4V SNP (rs710218) and the susceptibility of DN showed no significance. Likewise, negative outcome was also found in the assessment for the influence of XbaI or Enh2-2 SNP on the pathogenesis progress of DN. The evidence currently available shows that XbaI, Enh2 and HaeIII SNPs, but not HpyCH4V SNP, in GLUT1 gene may be genetic susceptibility to DN. However, data does not support the association between either XbaI or Enh2-2 SNP and the severity of DN.

Genetic variation of glucose transporter-1 (GLUT1) and albuminuria in 10,278 European Americans and African Americans: a case-control study in the Atherosclerosis Risk in Communities (ARIC) study

Background

Evidence suggests glucose transporter-1(GLUT1) genetic variation affects diabetic nephropathy and albuminuria. Our aim was to evaluate associations with albuminuria of six GLUT1 single nucleotide polymorphisms(SNPs), particularly XbaI and the previously associated Enhancer-2(Enh2) SNP.

Methods

A two-stage case-control study was nested in a prospective cohort study of 2156 African Americans and 8122 European Americans with urinary albumin-to-creatinine ratio(ACR). Cases comprised albuminuria(N = 825; ≥ 30 μg/mg) and macroalbuminuria(N = 173; ≥ 300 μg/mg). ACR < 30 μg/mg classified controls(n = 9453). Logistic regression and odds ratios(OR) assessed associations. The evaluation phase(stage 1, n = 2938) tested associations of albuminuria(n = 305) with six GLUT1 SNPs: rs841839, rs3768043, rs2297977, Enh2(rs841847) XbaI(rs841853), and rs841858. Enh2 was examined separately in the replication phase(stage 2, n = 7340) and the total combined sample (n = 10,278), with all analyses stratified by race and type 2 diabetes.

Results

In European Americans, after adjusting for diabetes and other GLUT1 SNPs in stage 1, Enh2 risk genotype(TT) was more common in albuminuric cases(OR = 3.37, P = 0.090) whereas XbaI (OR = 0.94, p = 0.931) and remaining SNPs were not. In stage 1, the Enh2 association with albuminuria was significant among diabetic European Americans(OR = 2.36, P = 0.025). In African Americans, Enh2 homozygosity was rare(0.3%); XbaI was common(18.0% AA) and not associated with albuminuria. In stage 2(n = 7,340), Enh2 risk genotype had increased but non-significant OR among diabetic European Americans(OR = 1.66, P = 0.192) and not non-diabetics(OR = 0.99, p = 0.953), not replicating stage 1. Combining stages 1 and 2, Enh2 was associated with albuminuria(OR 2.14 [1.20-3.80], P = 0.009) and macroalbuminuria(OR 2.69, [1.02-7.09], P = 0.045) in diabetic European Americans. The Enh2 association with macroalbuminuria among non-diabetic European Americans with fasting insulin(OR = 1.84, P = 0.210) was stronger at the highest insulin quartile(OR = 4.08, P = 0.040).

Conclusions

As demonstrated with type 1 diabetic nephropathy, the GLUT1 Enh2 risk genotype, instead of XbaI, may be associated with type 2 diabetic albuminuria among European Americans, though an association is not conclusive. The association among diabetic European Americans found in stage 1 was not replicated in stage 2; however, this risk association was evident after combining all diabetic European Americans from both stages. Additionally, our results suggest this association may extend to non-diabetics with high insulin concentrations. Rarity of the Enh2 risk genotype among African Americans precludes any definitive conclusions, although data suggest a risk-enhancing role.

Mitochondrial and nuclear gene mutations in the type 2 diabetes patients of Coimbatore population

Involvement of mitochondrial and nuclear gene mutations in the development of type 2 diabetes (T2D) has been established well in various populations around the world. Previously, we have found the mitochondrial A>G transition at nucleotide position 3243 and 8296 in the T2D patients of Coimbatore population. This study is aimed to screen for the presence of various mitochondrial and nuclear DNA mutations in the T2D patients of Coimbatore to identify most prevalent mutation. This helps in identifying the susceptible individuals based on their clinical phenotype in future. Blood samples were collected from 150 unrelated late-onset T2D patients and 100 age-matched unrelated control samples according to World Health Organization criteria. Genotyping for the selected genes was done by polymerase chain reaction-single strand confirmation polymorphism, direct sequencing, and polymerase chain reaction-restriction fragment length polymorphism. The mitochondrial T>C transition at 8356 and nuclear-encoded GLUT1 gene mutation were found in the selected T2D patients. The T8356C mutation was found in two patients (1.3%), and the clinical characteristics were found to be similar in both the patients whereas GLUT1 gene mutation was found in seven patients. Four out of seven patients showed homozygous (-) genotype and three patients showed heterozygous (±) genotype for the mutant allele XbaI. Among these three patients, one patient was found to have elevated level of urea and creatinine with the history of kidney dysfunction and chronic T2D. Our results suggest that the T8356C and GLUT1 gene mutations may have an important role in developing late-onset T2D in Coimbatore population. Particularly, individuals with GLUT1 gene may develop kidney dysfunction at their later age.

The association of 18F-deoxyglucose (FDG) uptake of PET with polymorphisms in the glucose transporter gene (SLC2A1) and hypoxia-related genes (HIF1A, VEGFA, APEX1) in non-small cell lung cancer. SLC2A1 polymorphisms and FDG-PET in NSCLC patients

BACKGROUND

Positron emission tomography imaging of lung cancers with 2-[fluorine-18]-fluoro-2-deoxy-D-glucose is a non-invasive diagnostic, and prognostic tool that measures tumor metabolism. We have analyzed the effect of solute carrier family 2 (facilitated glucose transporter), member 1 polymorphisms on 2-[fluorine-18]-fluoro-2-deoxy-D-glucose-uptake with a combination of polymorphisms of hypoxia-inducible factor 1 alpha, apurinic/apyimidinic endonuclease, and vascular endothelial growth factor A in a hypoxia-related pathway.

METHODS

We investigated the association between solute carrier family 2 (facilitated glucose transporter), member 1 -2841A>T, hypoxia-inducible factor 1 alpha Pro582Ser, Ala588Thr, apurinic/apyimidinic endonuclease Asp148Glu, or vascular endothelial growth factor A +936C>T and 2-[fluorine-18]-fluoro-2-deoxy-D-glucose-uptake among 154 patients with non-small-cell lung cancer.

RESULTS

The solute carrier family 2 (facilitated glucose transporter), member 1 -2841A>T polymorphism was significantly associated with 2-[fluorine-18]-fluoro-2-deoxy-D-glucose-uptake in combination with the apurinic/apyimidinic endonuclease Asp148Glu (T>G) polymorphism in the squamous cell type of non-small-cell lung cancer. The solute carrier family 2 (facilitated glucose transporter), member 1 TT genotype had a higher maximum standardized uptake values than the AA + AT genotype when the apurinic/apyimidinic endonuclease genotype was TT (mean maximum standardized uptake values, 12.47 +/- 1.33 versus 8.46 +/- 2.90, respectively; P = 0.028). The mean maximum standardized uptake values were not statistically different with respect to vascular endothelial growth factor A and hypoxia-inducible factor 1 alpha polymorphisms.

CONCLUSION

A glucose transporter gene polymorphism was shown to be statistically associated with glucose-uptake when the apurinic/apyimidinic endonuclease genotype is TT in patients with the squamous cell type of non-small-cell lung cancer. Our findings suggest that a newly developed tracer for positron emission tomography could be affected by genetic polymorphisms.

Frequency distribution of XbaIG > T and HaeIIIT > C GLUT1 polymorphisms among different Brazilian ethnic groups

GLUT is the major glucose transporter in mammalian cells. Single nucleotide polymorphisms (SNP) at GLUT1 promoter and regulatory regions have been associated to the risk of developing nephropathy in different type 1 and type 2 diabetic populations. It has been demonstrated that differences in allelic and genotypic frequencies of GLUT1 gene (SLC2A1) polymorphisms occur among different populations. Therefore, ethnic differences in distribution of GLUT1 gene polymorphisms may be an important factor in determining gene-disease association. In this study, we investigated the XbaIG > T and HaeIIIT > C polymorphisms in six different Brazilian populations: 102 individuals from Salvador population (Northern Brazil), 56 European descendants from Joinville (South Brazil), 85 Indians from Tiryió tribe (North Brazil) and 127 samples from Southern Brazil: 44 from European descendants, 42 from African descendants and 41 from Japanese descendants. Genotype frequencies from both sites did not differ significantly from those expected under the Hardy-Weinberg equilibrium. We verified that the allele frequencies of both polymorphisms were heterogeneous in these six Brazilian ethnic groups.

Polymorphisms at GLUT1 gene are not associated with the development of TSP/HAM in Brazilian HTLV-1 infected individuals and the discovery of a new polymorphism at GLUT1 gene

The development of HTLV-1 associated clinical manifestations, such as TSP/HAM and ATLL, occur in 2-4% of the infected population and it is still unclear why this infection remains asymptomatic in most infected carriers. Recently, it has been demonstrated that HTLV uses the Glucose transporter type 1 (GLUT1) to infect T-CD4(+) lymphocytes and that single nucleotide polymorphisms (SNP) in the GLUT1 gene are associated with diabetic nephropathy in patients with diabetes mellitus in different populations. These polymorphisms could contribute to a higher GLUT1 protein expression on cellular membrane, facilitating the entry of HTLV and its transmission cell by cell. This could result in a higher provirus load and consequently in the development of TSP/HAM. To evaluate the role of GLUT1 gene polymorphisms in the development of TSP/HAM in HTLV-1 infected individuals, the g.22999G > T, g.15339T > C and c.-2841A > T sites were analyzed by PCR/RFLP or sequencing in 244 infected individuals and 102 normal controls. The proviral load of the HTLV-1 infected patients was also analyzed using Real Time Quantitative PCR. Genotypic and allelic frequencies of the three sites did not differ significantly between controls and HTLV-1 infected individuals. There was no difference in genotypic and allelic distributions among patients as to the presence or absence of HTLV-1 associated clinic manifestations. As regards the quantification of the provirus load, we observed a significant reduction in the asymptomatic individuals compared with the oligosymptomatic and TSP/HAM individuals. These results suggest that g.22999G > T, g.15339T > C, and c.-2841A > T SNP do not contribute to HTLV-1 infection nor to the genetic susceptibility of TSP/HAM in Brazilian HTLV-1 infected individuals.

Risk genotypes and haplotypes of the GLUT1 gene for type 2 diabetic nephropathy in the Tunisian population

OBJECTIVE

Diabetic nephropathy (DN) is a long-term complication of both type 1 and type 2 diabetes. Genetic studies on DN have been of little help so far, since several genetic association studies have shown conflicting results. Here we report the findings of a case-control study on five SNPs in the glucose transporter 1 (GLUT1) gene. The study investigated the association of five GLUT1 genotypes and haplotypes with DN.

RESEARCH DESIGN AND METHODS

All subjects, 126 DN (cases) and 273 type 2 diabetes (controls), were genotyped using the polymerase chain reaction restriction fragment length polymorphism.

RESULTS

The TT and the AA genotypes of the Haell and Enh2 SNP1, increased the risk of DN. The study also identified CGT as the highest risk haplotype (4.4-fold) followed by CAT with an increased risk of DN of 2.6-fold.

CONCLUSIONS

The GLUT1 gene confers susceptibility to DN in type 2 diabetes patients in the Tunisian population.

The GLUT-1 XbaI gene polymorphism is associated with vascular calcifications in nondiabetic uremic patients

BACKGROUND

Glucose transporters mediate the facilitative uptake of glucose into cells, with GLUT-1 being the predominant isoform in vascular smooth muscle cell (VSMC). Clones of human cells overexpressing the GLUT-1 transporter showed a high increase in intracellular glucose concentrations, mimicking the diabetic milieu. It is possible that high intracellular glucose together with uremic factors may play an important role in vascular calcification by transforming VSMC into osteoblast-like cells. The XbaI polymorphism in the GLUT-1 gene has been linked to variations in GLUT-1 expression, with consequent changes in intracellular glucose concentration.

METHODS

To assess the association between the GLUT-1 XbaI gene polymorphism and the presence of VC in nondiabetic uremic patients, a total of 105 nondiabetic patients on hemodialysis were studied. VC were evaluated by conventional simple X-ray. Mean values of serum calcium, phosphorous, cholesterol, triglycerides, HbA1c, PTH and insulin were measured. Height, weight, BMI and waist circumference were also determined. The GLUT-1 XbaI polymorphism in the second intron of the gene was ascertained by means of the polymerase chain reaction and restriction fragment length polymorphism analysis on DNA isolated from peripheral blood DNA. In the absence of an XbaI site, a fragment of 305 bp was seen (so-called x allele), whereas fragments of 232 and 73 bp were generated if the XbaI site was present (X allele).

RESULTS

Genotype distribution in all patients was similar to the Caucasian population. However, when the patients were grouped according to the presence or absence of VC, there were marked differences in the frequency of the GLUT1 genotypes: the xx GLUT-1 genotype was more prevalent in the group with VC (30.7 vs. 4.5%, p = 0.001). Stepwise logistic regression demonstrated that the xx GLUT-1 genotype was independently associated with the presence of VC after adjusting for other variables such as age, calcium x phosphrus product, BMI and time on dialysis (OR 7.68; 95% CI 1.28-45.7).

CONCLUSIONS

GLUT-1 XbaI gene polymorphism is associated with vascular calcifications in nondiabetic uremic patients.

Relationship of angiotensin-converting enzyme gene polymorphism with nephropathy associated with Type 2 diabetes mellitus in Asian Indians

OBJECTIVE

Diabetic nephropathy (DN) has become the leading cause of end-stage renal disease, but the pathogenesis of this condition is not exactly understood. Several studies from different parts of the world have examined angiotensin-converting enzyme (ACE) gene polymorphism as a candidate for DN. Two studies yielding controversial results have been reported from India. To rule out this discrepancy, we carried out a hospital-based study on a cohort from our population to determine whether ACE gene polymorphism is associated with DN.

RESEARCH DESIGN AND METHODS

ACE gene polymorphism was analyzed by polymerase chain reaction in 460 individuals consisting of 174 cases of DN, 175 cases of Type 2 diabetes mellitus (DM), and 111 controls. The DN cases included in the study were Type 2 DM cases with serum creatinine >1.5 mg/dl and serum albumin >30 mg/dl in a 24-h urine sample.

RESULTS

ACE insertion/deletion genotyping analysis showed DD genotype in 22.75% of DN cases, 15.42% of Type 2 DM cases, and 21.62% of controls. Chi-square test between the DN group and the control group did not show a significant difference in D allele. However, the difference was significant at P<.05 between the DN group and the DM group. The odds ratio was 2.0953 (95% confidence interval=1.35-3.2522), indicating a significant association of DD genotype and D allele with DN.

CONCLUSION

Our data enable us to conclude that Asian Indians with D allele and Type 2 DM are at greater risk for developing DN.

Glucose transporter polymorphisms are associated with clear-cell renal carcinoma

Clear-cell renal cell carcinoma (CCRCC) is identified by abundant glycogen-rich cytoplasm, due to the aberrant influx and storage of glucose. The objective was to investigate the frequency of polymorphisms of the facilitative glucose transporter (GLUT1). GLUT1 is a downstream target of Hypoxia-inducible factor (HIF-1alpha), a mediator of hypoxia-controlled angiogenesis. In this study, we examine the allelic frequency of polymorphisms in the promoter and the second intron of the GLUT1 gene. Genomic DNA was extracted from normal tissue of 92 patients undergoing nephrectomy for CCRCC, and 99 normal cord blood DNA samples were used to provide control frequencies. The regions of DNA encompassing the polymorphisms were amplified and digested with appropriate endonuclases. The products were separated and viewed by gel electrophoresis. There was a highly significant decrease in the A-2841 genotype (P=0.0004) in the promoter region of those patients with CCRCC compared to the control population. There was also a significant decrease in the T+22999 allele in the intron 2 of those patents with CCRCC (P=0.004) compared to the same control population. This study suggests that GLUT1 is one of a number of genes that may increase susceptibility to developing CCRCC.

Is non-insulin dependent glucose uptake a therapeutic alternative? Part 2: Do such mechanisms fulfil the required combination of power and tolerability?

The worldwide burden of diabetes, the unavoidable worsening which is observed in long-term clinical trials despite treatment and the close link between glycaemia and microangiopathy appeal for much stronger treatment strategies. This, in turn, either requires polypharmacy (with new risks) or new, more powerful drugs to be invented. The first part of this review dealt with a thorough analysis of pros and cons for some selected pathways which could potentially increase glucose uptake without necessitating insulin. The choice of such targets for developing completely new drugs, however, requires a favourable background from existing tentatives with either drugs or cell biology approaches. Moreover, because vascular complications are what must ultimately be avoided when treating diabetic patients, we must be sure that increasing glucose uptake in a fashion which is no more controlled by normal physiology is compatible with the physiology of vascular cells (long-term tolerance). The aspect of drug side-effects must therefore be considered systematically. For reasons which are individually developed, it appears that each of the potential pathways analyzed either lacks sufficient power and/or is likely to induce side effects which are not acceptable for long-term application. The fact that GLUT-1 transporters are ubiquitously distributed even extends this cardinal question to the general principle of increasing glucose uptake. In conclusion a precise evaluation suggests that, although non-insulin dependent glucose uptake represents (3/4) of whole body glucose transport, it is difficult to consider such mechanisms able to generate a new treatment fulfilling the unavoidable request of combined efficacy and tolerability.

Glucose transporters in diabetic nephropathy

Changes in glucose transporter expression in glomerular cells occur early in diabetes. These changes, especially the GLUT1 increase in mesangial cells, appear to play a pathogenic role in the development of ECM expansion and perhaps other features of diabetic nephropathy. In addition, it appears that at least some diabetic patients may be predisposed to nephropathy because of polymorphisms in their GLUT1 genes. GLUT1 overexpression leads to increased glucose metabolic flux which in turn triggers the polyol pathway and activation of PKC alpha and B1. Activation of these PKC isoforms can lead directly to AP-1 induced increases in fibronectin expression and ECM accumulation. Other, more novel effects of GLUT1 on cellular hypertrophy and injury could also promote changes of diabetic nephropathy. Strategies to prevent GLUT1 overexpression could ameliorate or prevent the progression of diabetic nephropathy.

A novel polymorphism in the 5' flanking region of the glucose transporter (GLUT1) gene is strongly associated with diabetic nephropathy in patients with Type 1 diabetes mellitus

Glucose transporter 1 (GLUT1) activity has been implicated in renal hypertrophy and extracellular matrix formation in mesangial cells. Recent studies have suggested that polymorphisms in the GLUT1 gene are associated with susceptibility to diabetic nephropathy (DN) in patients with diabetes mellitus. In this study, a novel polymorphism (A-2841T) in the 5' flanking region of GLUT1 was examined in 288 patients with Type 1 diabetes mellitus (T1DM) and 101 normal controls. The polymorphisms were amplified and the fragment digested with the enzyme HpyCH4V. There was a highly significant increase in the frequency of the TT-2841 genotype in patients with nephropathy (n=131) compared with those with either no microvascular complications after a 20-year duration of diabetes (uncomplicated; n=72; 54.5% vs. 2.7%, chi=79.4, P<.000001). There was no difference between the uncomplicated group and those who only had retinopathy (n=50; 2.7% vs. 4.0%, respectively). The frequency in recently diagnosed patients was 17.1% and only 2.0% in normal controls. In contrast, the AA genotype was found in 13.6% of the nephropaths, 76.3% of uncomplicated, 48.0% of retinopaths, and 65% of normal controls. These results confirm previous reports of an association between the GLUT1 gene and susceptibility to DN but not retinopathy. The localisation of this polymorphism suggests that it may be involved in the expression of the gene.

Association between the GLUT1 gene polymorphism and the risk of diabetic nephropathy: a meta-analysis

The association between diabetic nephropathy (DN) and the XbalphaI polymorphism in the GLUT1 gene has been investigated in several case-control studies. These studies rendered contradictory results: the allele XbalphaI(-) was shown either to be a risk factor or neutral, or even protective for the development of the disease. To shed some light on these inconclusive findings, a meta-analysis of all available studies relating the XbalphaI polymorphism to the risk of developing DN was conducted. Five out of six identified studies included Caucasian populations, and only one involved samples from an Asian population. Overall, the meta-analysis suggested large heterogeneity between studies (P<0.01, I2=68%) and lack of association between allele XbalphaI(-) and the risk of developing DN relative to allele XbalphaI(+): random effects odds ratio (OR)=1.26 [95% CI (0.93, 1.69)]. Excluding one study with the controls not in Hardy-Weinberg equilibrium, the sensitivity analysis revealed that heterogeneity (P=0.28, I2=21%) could be explained, and then, there is an overall association: fixed effects OR=1.34 [95% CI (1.13, 1.60)]. Then, significant ORs were also found on analysis of subgroups: for the Caucasian population, fixed effects OR=1.29 [95% CI (1.08, 1.56)] and for the type 2 diabetic patients fixed effects OR=1.69 [95% CI (1.09, 2.63)]. In type 1 diabetes, there is a moderate heterogeneity (P=0.19, I2=41%) with fixed effects OR=1.29 [95% CI (1.06, 1.56)] and random effects OR=1.32 [95% CI (1.01, 1.71)]. There is a source of bias in the selected studies: large studies failed to show association while small studies claimed an association. Although there is evidence of association between GLUT1 and DN, the above findings reinforce the need for further and more rigorous association studies.

Examination of Hardy-Weinberg equilibrium in papers of Kidney International: an underused tool

BACKGROUND

Population-genetic studies investigating genetic polymorphisms of Mendelian inheritance should always test whether the measured genotype frequencies deviate from the expected one. For this purpose Hardy-Weinberg (HW) criteria are generally used. If genotype distribution of control population misses HW equilibrium, the results should be treated cautiously because the observed genotype distribution in control population does not represent genotype distribution in the overall population. If HW criteria are not fulfilled in the investigated population, this may be further evidence for the correlation between genotype and investigated condition.

METHODS

Between September, 1998, and September, 2003, we tested papers published in Kidney International if HW criteria were ordinarily and correctly checked in studies investigating genetic polymorphisms. Seventy-five genotype distributions of the selected 39 articles were reanalyzed.

RESULTS

HW calculation was reportedly performed in 25 papers (64%). The observed genotype distribution deviated significantly from the expected one in three control, and in 16 patient populations and in three populations of association studies of 15 papers overall; however, this fact was not mentioned in 12 papers.

CONCLUSION

Although the deviation of genotype distribution from the expected one is important information, HW calculations are not performed routinely for each investigated subject groups in these papers investigating genetic polymorphisms.

Cellular basis of diabetic nephropathy: III. In vitro GLUT1 mRNA expression and risk of diabetic nephropathy in type 1 diabetic patients

AIMS/HYPOTHESIS

Altered glucose transporter expression has been implicated in the pathogenesis of diabetic nephropathy. There is increasing evidence that genetic factors convey risk of, or protection from, diabetic nephropathy and that the behaviour of cultured skin fibroblasts from type 1 diabetic patients may reflect these genetic influences. This study aimed to compare GLUT1 mRNA expression levels in skin fibroblasts from type 1 diabetic patients with either rapid ("fast-track", n=25) or slow ("slow-track", n=25) development of diabetic nephropathy and from non-diabetic normal control subjects (controls, n=25).

METHODS

Skin fibroblasts were cultured in Dulbecco's Modified Eagle's Medium with 25 mmol/l glucose for 36 h. Total RNA was isolated, and GLUT1 mRNA levels were estimated by microarray analysis and RT-PCR.

RESULTS

Levels of GLUT1 mRNA expression in skin fibroblasts from "slow-track" patients were greater than those from "fast-track" patients (p=0.02), as initially detected by microarray. GLUT1 mRNA expression levels were confirmed by RT-PCR to be higher in skin fibroblasts from "slow-track" patients (4.59+/-2.04) than in those from "fast-track" patients (3.34+/-1.2, p=0.02), and were also higher than in skin fibroblasts from control subjects (3.52+/-1.66, p=0.03). There was no statistically significant difference between levels of expression in the "fast-track" patients and the control subjects.

CONCLUSIONS/INTERPRETATION

This finding is consistent with the presence of cellular protection factors against diabetic nephropathy in the "slow-track" patients. These factors could be associated with the regulation of the GLUT1 pathway and may be genetically determined.

Microsatellite DNA polymorphism of human adrenomedullin gene in type 2 diabetic patients with renal failure

BACKGROUND

Adrenomedullin (AM) is a hypotensive peptide widely produced in the cardiovascular organs and tissues such as the heart, kidney, and the vascular cells. We have previously cloned and sequenced the genomic DNA encoding human AM gene, and determined that the gene is located in the short arm of chromosome 11. The 3'-end of the gene is flanked by the microsatellite marker of cytosine adenine (CA) repeats. In this study, we investigated the association between DNA variations in AM gene and the predisposition to develop nephropathy in type 2 diabetes mellitus.

METHODS

Genomic DNA was obtained from the peripheral leukocytes of 233 normal healthy subjects (NH), 139 type 2 diabetic patients on hemodialysis (DM-HD), 106 control patients with type 2 diabetes without nephropathy (DM-C) and 318 hemodialysis patients due to chronic glomerulonephritis (CGN-HD). The genomic DNA was subject to polymerase chain reaction (PCR) using a fluorescence-labeled primer, and the number of CA repeats were determined by polyacrylamide gel electrophoresis (PAGE).

RESULTS

In our Japanese subjects, there existed four types of alleles with different CA-repeat number; 11, 13, 14, and 19. The frequencies of these alleles were 11: 27.7%, 13: 32.8%, 14: 35.6%, and 19: 3.9% in NH. These allele frequencies were not significantly different in DM-C and CGN-HD. However, DM-HD showed significantly different distribution of allele frequency from other groups (chi 2 = 18.9, P = 0.026). Namely, the frequency of 19-repeat allele in DM-HD was higher (9.0%) than NH, DM-C, and CGN-HD (P = 0.005, 0.041, and 0.004, respectively).

CONCLUSION

The microsatellite DNA polymorphism of AM gene may be associated with the genetic predisposition to develop nephropathy in Japanese patients with type 2 diabetes mellitus.

Molecular genetics of microvascular disease in diabetic retinopathy

Diabetic retinopathy is a sight-threatening complication of the retinal microvasculature. While important environmental factors have been clearly identified as influencing its development, increasing evidence suggests that diabetic retinopathy has a genetic component. A variety of studies have explored associations between candidate genes and frequency and severity of retinopathy. Overall, this review has found that the majority of candidate genes studied exhibit weak or no association with retinopathy status, and where associations have been detected these results have not been replicated in multiple populations. This may reflect inaccurate case definition, small subject numbers and possibly inadequate markers for genetic studies.

Impact of renal denervation on renal content of GLUT1, albuminuria and urinary TGF-beta1 in streptozotocin-induced diabetic rats

In long-term diabetes mellitus, the progression of nephropathy has been related to the occurrence of autonomic neuropathy. This study was designed to evaluate the effects of bilateral denervation of the kidneys of streptozotocin-diabetic rats, an experimental model that presents diabetic nephropathy with increased abundance of cortical GLUT1 in the kidney and increased urinary excretion of albumin and transforming growth factor-beta1 (TGF-beta1). Twenty-four-hour urinary TGF-beta1 (ELISA), urinary albumin (electroimmunoassay) and GLUT1 protein levels (Western blotting) in the renal cortex and medulla were evaluated in diabetic (n=13) and control (n=13) rats 45 days after streptozotocin injection, submitted or not to surgical renal denervation. Evaluations were performed 15 days after the surgery. The effects of renal denervation were confirmed by intra-renal decrease of norepinephrine levels. Mean arterial pressure did not differ between diabetic and control rats, whether they underwent renal denervation or not. Renal denervation increased cortical (6905+/-287, 3506+/-193, 4144+/-246 and 5204+/-516 AU in renal-denervated controls, controls, renal-denervated diabetics and diabetics, respectively) and medullar GLUT1 protein in control rats, but reverted the cortical GLUT1 protein rise determined by diabetes. Although kidney denervation in diabetic rats induced a decrease in cortical GLUT1 abundance toward normal levels, these levels did not reach those of normal animals. However, renal denervation did not determine any changes in urinary albumin and urinary TGF-beta1 in both diabetic (127.3+/-12 microg/24 h and 111.8+/-24 ng mg(-1) creatinine, respectively) and control rats (45.9+/-3 microg/24 h and 13.4+/-4 ng mg(-1) creatinine, respectively). In conclusion, early-phase renal denervation in streptozotocin-diabetic rats produces a normalisation of previously elevated cortical GLUT1 protein content, but is not enough for reverting the increased urinary TGF-beta1 and albuminuria of diabetes.

Minor effect of GLUT1 polymorphisms on susceptibility to diabetic nephropathy in type 1 diabetes

Elevation of intracellular glucose in mesangial cells as mediated by GLUT1 may be important in initiating cellular mechanisms that cause diabetic nephropathy. To determine whether DNA sequence differences in GLUT1 confer susceptibility to this complication, single-nucleotide polymorphisms (SNPs) in this gene were examined using a large case-control study. SNPs examined included the known XbaI (intron 2) and HaeIII SNPs (exon 2). Four novel SNPs located in three putative enhancers were also investigated. Homozygosity for the XbaI(-) allele was associated with diabetic nephropathy (odds ratio 1.83 [95% CI 1.01-3.33]). Furthermore, homozygosity for the A allele for a novel SNP (enhancer-2 SNP 1) located in a putative insulin-responsive enhancer-2 was associated with diabetic nephropathy (2.38 [1.16-4.90]). Patients who were homozygous for risk alleles at both XbaI SNP and enhancer-2 SNP 1 [i.e., homozygosity for XbaI(-)/A haplotype] also had an increased risk of diabetic nephropathy (2.40 [1.13-5.07]). Because enhancer-2 SNP 1 may directly control GLUT1 expression, the strong linkage disequilibrium between the two SNPs likely accounts for XbaI SNP being associated with diabetic nephropathy. In conclusion, our study confirms that SNPs at the GLUT1 locus are associated with susceptibility to diabetic nephropathy in type 1 diabetes. Although these SNPs confer a considerable personal risk for diabetic nephropathy, they account for a limited proportion of cases among type 1 diabetic patients.

Diabetic microvascular complications are not associated with two polymorphisms in the GLUT-1 and PC-1 genes regulating glucose metabolism in Caucasian type 1 diabetic patients

BACKGROUND

An XbaI polymorphism in the gene encoding the glucose transporter, GLUT-1, is associated with development of diabetic nephropathy in Chinese type 2 diabetic patients. In addition, an amino acid variant (K121Q) in the gene encoding the glycoprotein plasma cell differentiating antigen (PC-1), a specific inhibitor of insulin receptor signalling, has been reported to predict a faster progression of nephropathy in Italian and British type 1 diabetic patients.

METHODS

The XbaI and K121Q polymorphisms were determined by PCR-RFLP in Danish type 1 diabetic patients with nephropathy (122 men/77 women, age 40.9+/-9.6 years, diabetes duration 27+/-8 years) and type 1 diabetic patients with persistent normoalbuminuria (118 men/74 women, age 42.7+/-10.2 years, diabetes duration 26+/-9 years). Proliferative retinopathy was present in 156 patients (40%), while 67 patients (17%) had no diabetic retinopathy.

RESULTS

There were no differences in the frequency of GLUT-1 XbaI genotypes between type 1 diabetic patients with diabetic nephropathy and type 1 diabetic patients with normoalbuminuria: 72 (41%)/87 (50%)/16 (9%) vs 94 (49%)/74 (39%)/24 (13%) had GLUT-1 XbaI +/+, +/- or -/- genotype respectively (NS). The frequency of PC-1 KK, KQ and QQ genotypes were 141 (71%)/52 (26%)/6 (3%) vs 138 (73%)/45 (24%)/7 (4%) in patients respectively with and without nephropathy (NS). Neither were associations between the investigated polymorphisms and simplex or proliferative retinopathy revealed.

CONCLUSIONS

Neither the PC-1 K121Q nor the GLUT-1 XbaI polymorphism contribute to the genetic susceptibility of diabetic microvascular complications in Danish type 1 diabetic patients.

Aldose reductase expression is induced by hyperglycemia in diabetic nephropathy

BACKGROUND

Despite good metabolic control, many patients with type 1 diabetes still develop nephropathy, implicating a role for genetic factors. Recent studies examining the regulatory region of the aldose reductase (ALR2) gene, the rate-limiting enzyme of the polyol pathway, support its role as a candidate gene for nephropathy. Here we report the quantitation of ALR2, together with sorbitol dehydrogenase mRNA in the peripheral blood mononuclear cells (PBMCs) of type 1 diabetic patients with (N = 29) and without nephropathy (N = 11) following stimulation with high levels of D-glucose.

METHODS

PBMCs from patients and normal controls were cultured for five days with phytohemagglutinin in either normoglycemia (11 mmol/L D-glucose) or supplemented with 10 mmol/L D-glucose (moderate hyperglyemia) or 20 mmol/L D-glucose (hyperglycemia). The RNA was extracted and analyzed by ribonuclease protection assay.

RESULTS

ALR2 mRNA levels were significantly elevated with increasing D-glucose concentration (normal to hyperglycemic) in those patients with nephropathy (P < 0.0001). In marked contrast, in those without nephropathy and in the normal healthy controls, there was no change in mRNA expression. Furthermore, those patients with nephropathy and the Z-2/X susceptibility genotype had the greatest increase in ALR2 mRNA compared with those with low-risk genotypes (P < 0.007).

CONCLUSION

These results show that patients with nephropathy exhibit marked disturbances in the expression of the enzyme components of the polyol pathway. Ultimately this leads to tissue damage and ischemia.

Polymorphisms of the glucose transporter (GLUT1) gene are associated with diabetic nephropathy

BACKGROUND

Diabetic nephropathy (DN) is a major cause of morbidity and mortality in patients with type 1 diabetes mellitus. Recent studies suggest that genetic factors, including polymorphisms in the flanking region of the aldose reductase gene (5'ALR2), play an important role in the pathogenesis of nephropathy. Glucose transporter (GLUT1) activity has been implicated in renal hypertrophy and extracellular matrix formation in mesangial cells. The aim was to investigate the frequency of a polymorphism within the GLUT1 gene in 186 Caucasoid patients with type 1 diabetes and 104 normal controls.

METHODS

Amplimers flanking the Xba-I polymorphic site in the second intron were employed to amplify DNA from subjects. The amplified DNA was restricted with endonuclease Xba-I, separated by gel electrophoresis, and visualized. In the absence of an Xba-I site, a fragment of 1.1 kilobase was seen, whereas fragments of 0.9 and 0.2 were generated if the Xba-I site was present.

RESULTS

There was a highly significant increase in the frequency of the 1.1 allele in those patients with nephropathy (N = 70) compared with those with no proteinuria or retinopathy after 20 years of diabetes (uncomplicated N = 44, 61.4 vs. 40.9%, respectively, P < 0.001). The 1.1/1.1 genotype was also significantly increased in the nephropathy group compared with the uncomplicated group of patients (37.1 vs. 13.6%, respectively, P < 0.01). The frequency of the 1.1/1.1 genotype was similar in 30 patients with retinopathy but not nephropathy when compared with the uncomplicated group of patients (13.6 vs. 16.7%). Furthermore, only 8 out of 49 patients with DN had the Z+2 5'ALR2 DN "protective" allele and the 0.9 GLUT1 allele in contrast to 21 out of 39 uncomplicated patients (P < 0.0002).

CONCLUSION

These results suggest that the GLUT1 gene together with the aldose reductase gene are associated with susceptibility to DN in patients with type 1 diabetes.

Role of GLUT1 gene in susceptibility to diabetic nephropathy in type 2 diabetes

BACKGROUND

The XbaI polymorphism in the glucose transporter GLUT1 gene has been implicated in the development of diabetic nephropathy in Chinese type 2 diabetes patients.

METHODS

To examine whether the XbaI polymorphism is involved in the development of diabetic nephropathy in Caucasian type 2 diabetes patients, a large case control study was performed. The study group of 444 patients with type 2 diabetes consisted of three subgroups: 162 patients with normoalbuminuria (only patients with duration of type 2 diabetes of at least 10 years after diagnosis); 150 with microalbuminuria; and 132 subjects with persistent proteinuria or chronic renal failure (CRF). The polymerase chain reaction (PCR)-based genotyping of the XbaI polymorphism was performed in each subject.

RESULTS

The genotype distribution in the subgroups showed an increased frequency of the (+/+) genotype in patients with microalbuminuria (41%; OR 1.40, 95% CI, 0.89 to 2.24) and proteinuria/CRF (47%; OR 1.82, 95% CI, 1.13 to 2.93, P = 0.013) when compared with normoalbuminuria (33%). No difference in the genotype distribution was observed between type 2 diabetes patients and healthy controls.

CONCLUSIONS

The results of this study in Caucasian patients with type 2 diabetes indicate that the XbaI(-) allele in the GLUT1 gene protects against the development of diabetic nephropathy. Our results are in contrast to the case control study in Chinese patients with type 2 diabetes in which the presence of the XbaI(-) allele appeared to have a strong association with the development of diabetic nephropathy.

GLUT1 and TGF-beta: the link between hyperglycaemia and diabetic nephropathy

Recent experimental work implicates transforming growth factor-beta (TGF-beta) as an aetiologic mediator of diabetic nephropathy and the ubiquitous glucose transporter GLUT1 as an important permissive factor for the tissue injury caused by hyperglycaemia. High ambient glucose increases GLUT1 expression and glucose transport activity when compared with physiologic glucose concentrations. Treatment of rat mesangial cells with TGF-beta up-regulates GLUT1 mRNA and protein levels and significantly increases glucose uptake. Addition of neutralizing anti-TGF-beta antibody prevents the stimulatory effects of high glucose on GLUT1 expression. Cultured rat mesangial cells transduced with the human GLUT1 gene and thus overexpressing the GLUT1 protein show marked increase in glucose uptake and the synthesis of extracellular matrix molecules, even when grown in normal ambient glucose concentrations. Thus, TGF-beta and GLUT1, two proteins that are up-regulated in glomerular mesangial cells in a hyperglycaemic milieu, can influence the expression of one another. It is therefore fair to conclude that, with successful interruption of the TGF-beta-GLUT1 axis, the beneficial effects of strict glucose control on the development of diabetic nephropathy could likely be augmented.