An aldose reductase intragenic polymorphism associated with diabetic retinopathy

Aldose Reductase: An Emerging Target for Development of Interventions for Diabetic Cardiovascular Complications

Diabetes is a leading cause of cardiovascular morbidity and mortality. Despite numerous treatments for cardiovascular disease (CVD), for patients with diabetes, these therapies provide less benefit for protection from CVD. These considerations spur the concept that diabetes-specific, disease-modifying therapies are essential to identify especially as the diabetes epidemic continues to expand. In this context, high levels of blood glucose stimulate the flux via aldose reductase (AR) pathway leading to metabolic and signaling changes in cells of the cardiovascular system. In animal models flux via AR in hearts is increased by diabetes and ischemia and its inhibition protects diabetic and non-diabetic hearts from ischemia-reperfusion injury. In mouse models of diabetic atherosclerosis, human AR expression accelerates progression and impairs regression of atherosclerotic plaques. Genetic studies have revealed that single nucleotide polymorphisms (SNPs) of the ALD2 (human AR gene) is associated with diabetic complications, including cardiorenal complications. This Review presents current knowledge regarding the roles for AR in the causes and consequences of diabetic cardiovascular disease and the status of AR inhibitors in clinical trials. Studies from both human subjects and animal models are presented to highlight the breadth of evidence linking AR to the cardiovascular consequences of diabetes.

Meta-analysis of the association between aldose reductase gene (CA)n microsatellite variants and risk of diabetic retinopathy

Diabetic retinopathy (DR) is one of the most severe microvascular complications of diabetes mellitus (DM). The (CA)n microsatellite variation of the aldose reductase (ALR) gene has been indicated to be associated with DR in previous studies; however, the results were inconclusive. To provide a more precise evaluation of the association between the (CA)n variations of ALR and the risk for DR, a meta-analysis was performed in the present study. Relevant articles were retrieved from the PubMed, Embase, Chinese National Knowledge Infrastructure and Cochrane Library databases. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were used to evaluate the strength of the associations. The present meta-analysis included 17 studies comprising 1,575 DM patients with retinopathy and 1,741 DM patients without retinopathy. The results indicated that the Z-2 allele was a risk factor for DR in Asian (OR=1.82, 95% CI: 1.16-2.86, P=0.009) and Caucasian (OR=2.08, 95% CI: 1.14-3.79, P=0.02) populations, as well as in type 1 diabetes (T1D; OR=3.42, 95% CI: 1.46-8.04, P=0.005) and type 2 diabetes (T2D; OR=1.66, 95% CI: 1.05-2.63, P=0.03). Furthermore, the Z+2 allele was determined to be a protective factor for DR in Caucasian individuals (OR=0.50, 95% CI: 0.34-0.73, P=0.0004) and those with T1D (OR=0.39, 95% CI: 0.27-0.57, P<0.00001). Z+4 was also identified to be a protective factor, reducing the risk of DR in patients with T1D (OR=0.74, 95% CI: 0.57-0.96, P=0.02). Z-4 was revealed to be a risk factor for DR in Asian populations (OR=1.57, 95% CI: 1.22-2.03, P=0.0005) and in individuals with T1D (OR=1.62, 95% CI: 1.27-2.08, P=0.0001). However, no association was detected between the Z, Z+6 and Z-6 alleles and the risk of DR (P>0.05). In conclusion, the present results revealed the following: Z+2 may serve as a protective factor for DR in Caucasian individuals and those with T1D; Z+4 may be a protective factor for DR in patients with T2D; Z-2 may represent a risk factor for DR in all subgroups analyzed; and Z-4 may be a risk factor for DR in Asian populations and patients with T2D.

Asthma and allergic rhinitis associate with the rs2229542 variant that induces a p.Lys90Glu mutation and compromises AKR1B1 protein levels

Asthma and rhinitis are two of the main clinical manifestations of allergy, in which increased reactive oxygen or electrophilic species can play a pathogenic role. Aldose reductase (AKR1B1) is involved in aldehyde detoxification and redox balance. Recent evidence from animal models points to a role of AKR1B1 in asthma and rhinitis, but its involvement in human allergy has not been addressed. Here, the putative association of allergic rhinitis and asthma with AKR1B1 variants has been explored by analysis of single-strand variants on the AKR1B1 gene sequence in 526 healthy subjects and 515 patients with allergic rhinitis, 366 of whom also had asthma. We found that the rs2229542 variant, introducing the p.Lys90Glu mutation, was significantly more frequent in allergic patients than in healthy subjects. Additionally, in cells transfected with expression vectors carrying the wild-type or the p.Lys90Glu variant of AKR1B1, the mutant consistently attained lower protein levels than the wild-type and showed a compromised thermal stability. Taken together, our results show that the rs2229542 variant associates with asthma and rhinitis, and hampers AKR1B1 protein levels and stability. This unveils a connection between the genetic variability of aldose reductase and allergic processes.

Identification of potential quinoxalinone-based aldose reductase inhibitors by 3D-QSAR, molecular docking and molecular dynamics

The 3D-QSAR model of aldose reductase (ARIs) inhibitors is built to gain insights into the key structural factors affecting the inhibitory activity. Based on the model, six new potential ARIs were designed.

ALDOSE REDUCTASE: New Insights for an Old Enzyme

In the past years aldose reductase (AKR1B1; AR) is thought to be involved in the pathogenesis of secondary diabetic complications such as retinopathy, neuropathy, nephropathy and cataractogenesis. Subsequently, a number of AR inhibitors have been developed and tested for diabetic complications. Although, these inhibitors have found to be safe for human use, they have not been successful at the clinical studies because of limited efficacy. Recently, the potential physiological role of AR has been reassessed from a different point of view. Diverse groups suggested that AR besides reducing glucose, also efficiently reduces oxidative stress-generated lipid peroxidation-derived aldehydes and their glutathione conjugates. Since lipid aldehydes alter cellular signals by regulating the activation of transcription factors such as NF-kB and AP1, inhibition of AR could inhibit such events. Indeed, a wide array of recent experimental evidence indicates that the inhibition of AR prevents oxidative stress-induced activation of NF-kB and AP1 signals that lead to cell death or growth. Further, AR inhibitors have been shown to prevent inflammatory complications such as sepsis, asthma, colon cancer and uveitis in rodent animal models. The new experimental in-vitro and in-vivo data has provided a basis for investigating the clinical efficacy of AR inhibitors in preventing other inflammatory complications than diabetes. This review describes how the recent studies have identified novel plethoric physiological and pathophysiological significance of AR in mediating inflammatory complications, and how the discovery of such new insights for this old enzyme could have considerable importance in envisioning potential new therapeutic strategies for the prevention or treatment of inflammatory diseases.

Aldose reductase and cardiovascular diseases, creating human-like diabetic complications in an experimental model

Hyperglycemia and reduced insulin actions affect many biological processes. One theory is that aberrant metabolism of glucose via several pathways including the polyol pathway causes cellular toxicity. Aldose reductase (AR) is a multifunctional enzyme that reduces aldehydes. Under diabetic conditions AR converts glucose into sorbitol, which is then converted to fructose. This article reviews the biology and pathobiology of AR actions. AR expression varies considerably among species. In humans and rats, the higher level of AR expression is associated with toxicity. Flux via AR is increased by ischemia and its inhibition during ischemia reperfusion reduces injury. However, similar pharmacological effects are not observed in mice unless they express a human AR transgene. This is because mice have much lower levels of AR expression, probably insufficient to generate toxic byproducts. Human AR expression in LDL receptor knockout mice exacerbates vascular disease, but only under diabetic conditions. In contrast, a recent report suggests that genetic ablation of AR increased atherosclerosis and increased hydroxynonenal in arteries. It was hypothesized that AR knockout prevented reduction of toxic aldehydes. Like many in vivo effects found in genetically manipulated animals, interpretation requires the reproduction of human-like physiology. For AR, this will require tissue specific expression of AR in sites and at levels that approximate those in humans.

Genetic susceptibility of diabetic retinopathy

Diabetes continues to be a major source of -morbidity and mortality among working-age adults nationally and internationally. The microvascular complications of diabetes, including diabetic retinopathy, account for a major proportion of disease-associated morbidity and likely contribute to macrovascular complications. Although glycemic control contributes to -susceptibility for diabetic complications, some people with strict control develop these complications, whereas -others with poor control remain complication free. This suggests a genetic contribution to disease development. Although many genes and proteins of vascular growth have been studied in association with diabetic retinopathy, no definitive major predisposing genes or functional consequences of genetic variants have been identified for microvascular complications of the disease. In this article, we review the studies done on candidate genes.

Association between sorbitol dehydrogenase gene polymorphisms and type 2 diabetic retinopathy

Diabetic retinopathy (DR) may affect 98% of diabetic patients, but its aetiology is poorly understood. Besides glycaemic exposure, genetic factors likely contribute to the onset of DR. The polyol pathway, including aldose reductase and sorbitol dehydrogenase (SDH), can be activated under hyperglycaemic conditions. In our work we searched for an association between the C-1214G and G-888C polymorphisms of the SDH gene promoter and the occurrence and progression of type 2 DR. Two hundred and fifteen unrelated individuals with type 2 diabetes mellitus (T2DM) were divided into three groups: without DR, with non-proliferative diabetic retinopathy (NPDR) and with proliferative diabetic retinopathy (PDR). Genotypes of the C-1214G (rs2055858) and G-888C (rs3759890) polymorphisms of the SDH gene were determined with DNA from the peripheral blood lymphocytes of patients by restriction fragment length polymorphism and allele-specific PCR, respectively. The genotype distributions were contrasted by the chi(2) test and the significance of the polymorphism was assessed by multiple logistic regression producing odds ratios (ORs) and 95% confidence intervals (CIs). We found an association (OR 1.73, 95% CI 1.06-2.83) between NPDR and the G allele of the G-888C polymorphism. There was no association between NPDR and the other polymorphisms of the SDH gene. No differences were found in the distributions of these polymorphisms between patients with PDR and those with NPDR. A weak association (OR 2.0, 95% CI 1.29-3.07) was found between DR and the G allele of the G-888C polymorphism. Analysis of the combined genotypes (haplotypes) of both polymorphisms revealed associations between the C/G-C/G genotype and NPDR (OR 2.95, 95% CI 1.07-8.13) as well as DR in general (OR 2.91, 95% CI 1.15-7.36). The G-888C polymorphism of the SDH gene may be associated with the onset of DR rather than with its progression, and its effect may be strengthened by the interaction with the C-1214G polymorphism, but this association is rather weak and requires further study.

Identifying children at particular risk of long-term diabetes complications

Formerly a 'taboo' subject, long-term complications are now being increasingly discussed with the family by the health-care team. Identifying potential predictors and establishing early intervention can change the course of these complications in the young patient with diabetes. Although the most recognized risk factor is glycaemic exposure, the development of diabetes complications is likely to result from an interaction between genetic and environmental factors. Other major environmental risk factors are hypertension, smoking, higher body mass index and lipid disorders. This article will concentrate on specific paediatric aspects, including the impact of puberty; endothelial dysfunction and genetic susceptibility. Endothelial function assessed by flow-mediated dilatation is a non-invasive method that has been suitable for use in children and adolescents. In type 1 diabetes mellitus children, endothelium dysfunction has been documented among patients with short diabetes duration and has been correlated to folate status, triglyceride and low-density lipoprotein cholesterol levels. Studies in the paediatric population have also revealed an association of diabetes complications with genetic variants in the renin-angiotensin system, polyol pathway, lipid oxidation and folate metabolism. Currently, achieving the best glycaemic control remains the gold standard for prevention of long-term diabetes complications in the clinical context. However, recent identification of genetic markers and development of research tools that predict long-term complications might have a potential role as instruments in assessing the effectiveness of intervention in the early course of the disease.

A genome-wide linkage scan for diabetic retinopathy susceptibility genes in Mexican Americans with type 2 diabetes from Starr County, Texas

We conducted a genome-wide linkage scan for genes contributing to retinopathy risk using 794 diabetes case subjects from 393 Mexican-American families from Starr County, Texas, having at least two diabetic siblings. The sample included 567 retinopathy case subjects comprising 282 affected sibling pairs. Retinopathy was classified as none, early nonproliferative, moderate-to-severe nonproliferative, or proliferative. Using 360 polymorphic markers (average spacing 9.4 cM), we conducted nonparametric linkage analysis followed by ordered-subset analysis (OSA) ranking families by average age of diabetes diagnosis. For any retinopathy, the highest LOD scores including all families were on chromosomes 3 (2.41 at 117 cM) and 12 (2.47 at 15.5). OSA logarithm of odds (LOD) scores >2 for any retinopathy occurred on chromosomes 12 (4.47 at 13.2 cM), 15 (3.65 at 100.6), and 20 (2.67 at 54.1). Scores >2 for either moderate-to-severe nonproliferative or proliferative retinopathy occurred on chromosomes 5 (2.53 at 11.2 cM), 6 (2.28 at 30.6), and 19 (2.21 at 100.6). Thus, unconditional linkage analysis revealed suggestive evidence of linkage with retinopathy on two chromosomes, whereas OSA revealed strong evidence of linkage on two chromosomes, and suggestive evidence on four. Candidate genes were identified in most implicated regions.

Decline in neurophysiological function after 7 years in an adolescent diabetic cohort and the role of aldose reductase gene polymorphisms

OBJECTIVE

This 7-year longitudinal study examines the potential impact of aldose reductase gene (AKR1B1) polymorphisms on the decline of nerve function in an adolescent diabetic cohort.

RESEARCH DESIGN AND METHODS

Patients with type 1 diabetes (n = 262) were assessed with three cardiovascular autonomic tests (heart rate variation during deep breathing, Valsalva maneuver, and during standing from a lying position) and pupillometry (resting pupil diameter, constriction velocity, and reflex amplitude), thermal, and vibration thresholds on the foot. Genotyping was performed for promoters (C-106T and C-12G), (CA)(n) dinucleotide repeats, and intragenic BamH1 polymorphism.

RESULTS

Median time between first and last assessment was 7.0 years (interquartile range 5.1-11.1), with a median of five assessments (four to seven) per individual. At first assessment, median age was 12.7 years (11.7-13.9), median duration was 5.3 years (3.4-8.0), and median HbA(1c) was 8.5% (7.8-9.3). All tests declined over time except for two cardiovascular autonomic tests and vibration discrimination. Faster decline in maximum constriction velocity was found to associate with the Z-2 allele (P = 0.045), Z-2/Z-2 (P = 0.026). Slower decline in hot thermal threshold discrimination associated with Z+2 (P = 0.044), Z+2/Z+2 (P < 0.0005), Z+2/T (P = 0.038), and bb (P = 0.0001).

CONCLUSIONS

Most autonomic and quantitative sensory nerve testings declined over time. AKR1B1 polymorphisms were strongly associated with the rate of decline of these complications.

The association of aldose reductase gene (AKR1B1) polymorphisms with diabetic neuropathy in adolescents

AIMS

Variants in the aldose reductase gene (AKR1B1) have been implicated in the development of diabetic retinopathy and nephropathy, with the most convincing data identifying a (CA)(n) repeat microsatellite allele (Z-2), which has a functional role in gene expression. In this study the association between polymorphisms in the AKR1B1 gene and diabetic neuropathy was investigated.

METHODS

The pupillary response to light was used as the major outcome in this study along with abnormal hot thermal threshold. Three hundred and sixty-three adolescents underwent genotyping of the AKR1B1 gene. The microsatellite (CA)(n) repeat was sequenced and two single nucleotide polymorphisms, -106C-->T and -12C-->G, were investigated by restriction fragment length polymorphism.

RESULTS

Seventy-six percent of participants had pupillary abnormalities (45% with two, 15% with three abnormalities). Presence of the Z-2/Z-2 genotype increased the risk nearly three-fold for pupillary abnormalities [odds ratio (OR) 3.02, 95% confidence interval (CI) 1.14, 7.98). The susceptibility genotypes (Z-2/Z-2 with -106C/-106C, Z-2/Z with -106C/-106C or Z/Z with -106C/-106C) were associated with resting pupil diameter abnormalities when compared with the protective genotypes (Z+2/Z+2 or -106T/-106T) (OR 2.83, 95% CI 1.25, 6.41). The combination of Z+2/-106T reduced the risk of abnormal heat discrimination (OR 0.48, 95% CI 0.23, 0.99).

CONCLUSIONS

In this study we have shown that Z-2/Z-2 genotype is significantly associated with the development of pupillary abnormality, an early indicator of diabetic autonomic neuropathy, in adolescent Australian patients with Type 1 diabetes.

Relation between polymorphisms G1704T and G82S of rage gene and diabetic retinopathy in Japanese type 2 diabetic patients

OBJECTIVE

To clarify whether polymorphisms G1704T and G82S of the rage gene were related to diabetic retinopathy, we performed a case-control study in Japanese type 2 diabetic patients.

PATIENTS AND METHODS

Two hundred and sixty-eight patients with type 2 diabetes were examined for polymorphisms G1704T and G82S of the RAGE gene. The genotypes of G1704T and G82S of the RAGE gene were determined with a fluorescent allele-specific DNA primer assay system. Diabetic retinopathy (DR) was diagnosed in a masked manner by independent ophthalmologists using fundus photographs and was classified as non-diabetic retinopathy (NDR), non-proliferative retinopathy (NPDR), and proliferative retinopathy (PDR).

RESULTS

The T allele frequency of G1704T and S allele frequency of G82S in patients with DR did not significantly differ from those without retinopathy. There were no differences among the genotypes of G1704T and G82S of the RAGE gene regarding age, duration of diabetes, BMI, HbA(1c), blood pressure, and lipids levels.

CONCLUSION

These data suggest that polymorphisms G1704T and G82S of the RAGE gene are not related to DR in Japanese type 2 diabetic patients.

Familial aggregation of severity of diabetic retinopathy in Mexican Americans from Starr County, Texas

OBJECTIVE

Diabetic retinopathy is a major cause of blindness. To determine whether retinopathy itself or only its severity aggregates in families, we examined the occurrence and severity of diabetic retinopathy in Mexican-American siblings with type 2 diabetes.

RESEARCH DESIGN AND METHODS

Using stereoscopic fundus photography of seven standard fields, we measured retinopathy in 656 type 2 diabetic patients from 282 Mexican-American families from Starr County, Texas. Retinopathy severity was scored using the Early Treatment of Diabetic Retinopathy Study system and classified as no retinopathy, early nonproliferative diabetic retinopathy (NPDR-E), moderate-to-severe nonproliferative diabetic retinopathy (NPDR-S), or proliferative diabetic retinopathy (PDR).

RESULTS

Of 249 siblings of randomly selected probands with retinopathy, 169 (67.9%) had retinopathy, compared with 95 of 125 siblings of unaffected probands (76.0%; P = 0.11). Proband retinopathy class was associated (P = 0.03) with sibling retinopathy class, with significant odds ratios (ORs) for NPDR-E versus no retinopathy (OR 0.57 [95% CI 0.35-0.93]) and PDR versus NPDR-E (2.02 [1.13-3.63]); the contrast of NPDR-S versus NPDR-E approached significance (1.78 [0.99-3.20]). With the more severe classes (PDR and NPDR-S) combined in one group and the less severe ones (none and NPDR-E) in another, more severe proband retinopathy was associated with more severe sibling retinopathy (1.72 [1.03-2.88]).

CONCLUSIONS

More severe diabetic retinopathy showed evidence of familial aggregation, but the occurrence of diabetic retinopathy per se did not. The factors involved in the onset of diabetic retinopathy may differ from those involved in its progression to more severe forms.

Génétique des complications du diabète : rétinopathie

Multiple clinical and physiopathological studies as well as genetic analysis, suggest that diabetic retinopathy (DR) is a consequent of interactions between environmental factors, especially hyperglycaemia, and several genetic factors. The genes of aldose reductase (AR), inducible nitric oxide synthase (NOS2A), endothelial nitric oxide synthase (NOS3), vascular endothelial growth factor (VEGF), pigmented epithelium-derived factor (PEDF), protein kinase C-beta (PKC-beta) and receptor for advanced glycation end products (RAGE) implicated in the pathogenesis of DR. The only genetic marker associated with risk of DR in several studies is a microsatellite (A-C)n at 5'end of AR. The synergistic combination of conventional approaches (e.g. candidate gene association studies) with new emerging technologies (e.g. biochips) will be a key factor in the elucidation of the genetic aspects of DR.

Polyol pathway and diabetic peripheral neuropathy

This chapter critically examines the concept of the polyol pathway and how it relates to the pathogenesis of diabetic peripheral neuropathy. The two enzymes of the polyol pathway, aldose reductase and sorbitol dehydrogenase, are reviewed. The structure, biochemistry, physiological role, tissue distribution, and localization in peripheral nerve of each enzyme are summarized, along with current informaiton about the location and structure of their genes, their alleles, and the possible links of each enzyme and its alleles to diabetic neuropathy. Inhibitors of pathway enzyme and results obtained to date with pathway inhibitors in experimental models and human neuropathy trials are updated and discussed. Experimental and clinical data are analyzed in the context of a newly developed metabolic odel of the in vivo relationship between nerve sorbitol concentration and metabolic flux through aldose reuctase. Overall, the data will be interpreted as supporting the hypothesis that metabolic flux through the polyol pathway, rather than nerve concentration of sorbitol, is the predominant polyol pathway-linked pathogeneic factor in diabetic preipheral nerve. Finally, key questions and future directions for bsic and clinical research in this area are considered. It is concluded that robust inhibition of metabolic flux through the polyol pathway in peripheral nerve will likely result in substantial clinical benefit in treating and preventing the currently intractable condition of diabetic peripheral neuropathy. To accomplish this, it is imperative to develop and test a new generation of "super-potent" polyol pathway inhibitors.

Polymorphism R25P in the gene encoding transforming growth factor-beta (TGF-beta1) is a newly identified risk factor for proliferative diabetic retinopathy

Associations of the genetic polymorphisms in the promoter region and the signal peptide sequence of the transforming growth factor-beta (TGF-beta1) gene with proliferative diabetic retinopathy (PDR) in patients with non-insulin-dependent diabetes mellitus (NIDDM) were studied. A total of 245 Caucasian subjects comprised the two groups: NIDDM patients with PDR (n = 73) and NIDDM patients without PDR (n = 172). Allele frequencies of common TGF-beta1 polymorphisms (at positions -988C/A, -800G/A, -509C/T, +869T/C (L10P), and +915G/C (R25P)) were determined by PCR-based methodology. All polymorphisms were in strong linkage disequilibrium (P < 10(-2)). Significantly higher frequencies of both the L allele and the R allele of the signal sequence polymorphisms in PDR subjects were found (after a correction for multiple comparisons, P(corr) < 10(-2) and P(corr) < 10(-4), respectively). Calculated odds ratios (ORs) for the LL and RR genotypes were 2.89 (95% confidence interval (CI), 1.6-5.1) and 19.73 (95% CI, 2.6-146.8), respectively. No significant differences between groups were found for the -800G/A and -509C/T polymorphisms. The -988A allele was not represented in our sample. Multiple logistic regression identified age, diabetes duration, and R25P polymorphism as significant predictors (P = 0.002, P = 0.000003, and P = 0.007, respectively). The frequencies of genotype combinations of the -800G/A, -509C/T, L10P, and R25P TGF-beta(1) polymorphisms were significantly different between the PDR and non-PDR groups (chi(2) = 37.83, df = 20, P < 10(-2)). The frequency of haplotype consisting of majority alleles was found significantly associated with PDR (P < 0.03). The presented data indicate that the R25P polymorphisms in the TGF-beta1 gene could be regarded as a strong genetic risk factor for PDR.

Analysis of the association between diabetic nephropathy and polymorphisms in the aldose reductase gene in Type 1 and Type 2 diabetes mellitus

AIMS

To investigate the association between polymorphisms of the aldose reductase gene and diabetic nephropathy in both Type 1 and Type 2 diabetes mellitus, and to carry out a meta-analysis of published results.

METHODS

We have investigated the role of two aldose reductase polymorphisms in four independent cohorts of cases and controls (two each with Type 1 and Type 2 diabetes) drawn from two ethnic populations, including 471 patients with nephropathy and 494 control diabetic patients without nephropathy. A C/T transition at position -106, and a (CA)n microsatellite marker 2.1 kb from the start site of the aldose reductase gene were genotyped in nephropathic patients and non-nephropathic controls from each cohort.

RESULTS

Carriage of the -106 T allele was significantly associated with diabetic nephropathy in three of the four study groups. The Mantel-Haenszel combined odds ratio was 2.22 (95% CI 1.69, 2.94), P = 1.05 x 10(-8). We found no evidence for association of the microsatellite marker with nephropathy, despite moderate levels of disequilibrium between the two markers. Meta-analysis of published data yielded no evidence for association of the microsatellite marker with diabetic nephropathy in Type 2 diabetes, but varying degrees of association with diabetic nephropathy in Type 1 diabetes.

CONCLUSIONS

Meta-analyses provide more convincing evidence of a role for the ALR2-106 marker than for the microsatellite marker in diabetic nephropathy (DN). More studies are now required to confirm these results and to establish whether the ALR2-106 polymorphism has a functional role in DN.

Retinopathy in juvenile diabetes: a 10-year (1990-2000) review

Diabetic retinopathy (DR) is the most frequent complication of diabetes and a leading cause of impaired vision in the Western world. There is general agreement that early diagnosis and treatment of DR can slow its progression and help to prevent blindness. However, as a result of its asymptomatic nature and its etiopathogenesis, which is still unclear due to its multifactorial complexity, DR-related blindness has a growing social impact in industrialized countries. Therefore, in order to gain a better understanding of this serious disease, the author performed an updated 10-year review of risk factors and management of DR in type 1 diabetes.

Association of retinopathy with a microsatellite at 5' end of the aldose reductase gene in Chinese patients with late-onset Type 2 diabetes

Recent experimental data suggest that a microsatellite polymorphism at 5' end of the aldose reductase gene may be associated with the development of diabetic retinopathy. In the present study, we examined the allele distribution of the polymorphism in 384 Hong Kong Chinese patients who had late-onset (age at diagnosis > or =35 years) Type 2 diabetes, but no clinical evidence of cataract. Approximately 17% of them (n = 64) had retinopathy. The patients with retinopathy were older (52 +/- 11 years vs. 60 +/- 9 years, p < 0.01) and had a higher HbA1c (8.9 +/- 2.2% vs. 7.7 +/- 2.0%, p < 0.01 with adjustment for age) than those without the complication. Amongst all of the patients, we detected 10 microsatellite alleles and found that allele Z-4 was overpresented in those with retinopathy (9% vs. 4%, p < 0.05). There were no significant differences in allelic distributions of the major alleles Z + 2, Z, and Z-2, which accounted for more than 80% of the overall frequency, between the two groups of patients. Using multiple logistic regression analysis (R2 = 0.17, p < 0.01), we found that age (p < 0.01) and HbA1c (p < 0.05) were associated with retinopathy. In conclusion, our data suggest that the occurrence of diabetic retinopathy in the Chinese population may be influenced by clinical and metabolic factors. The aldose reductase gene may be implicated, but is not likely to play a major role.