Inducible T-cell costimulator (ICOS) and CD28 polymorphisms possibly play a role in the pathogenesis of chronic autoreactive urticaria.

BACKGROUND: Clinical experience emphasizes the coexistence of chronic spontaneous urticaria (CSU) and autoimmune disturbances. In chromosome 2q33-34, there is a cluster of homologous genes that are considered promising candidate genes for susceptibility to autoimmune diseases. AIM: To examine the possible role of polymorphisms in the genes for CD28 and inducible T-cell costimulator (ICOS) in the background of CSU. METHODS: In total, 149 patients with CSU with positive autologous serum skin test were enrolled in the study. The healthy control (HC) group consisted of 100 healthy volunteers. In all subjects, the CD28 rs2140148 and rs3116496 and the ICOS rs6726035 polymorphisms were analysed. Disease severity was assessed by means of Urticaria Activity Score. RESULTS: We found a statistically significantly lower prevalence of the ICOS rs6726035 TT genotype among patients with CSU compared with HCs. Furthermore, the haplotype rs2140148A, rs3116496T and rs6726035C presented a possible association with CSU. We did not find any association between the examined polymorphisms and either urticaria severity or age of disease onset. CONCLUSIONS: Our results underline the role of autoimmune components in the pathogenesis of chronic autoreactive urticaria, and indicate it as a potentially genetically related disorder.

Possible contribution of chemokine receptor CCR2 and CCR5 polymorphisms in the pathogenesis of chronic spontaneous autoreactive urticaria

BACKGROUND: Autoimmune mechanisms play a role in the pathophysiology of chronic urticaria. As the genetic background of autoimmunity is well proven, the role of genetics in chronic urticaria is hypothesised. METHODS: 153 unrelated chronic spontaneous urticaria patients with a positive result of autologous serum skin test were included into the study, as were 115 healthy volunteers as control group. In all subjects we analysed CCR2 G190A and CCR5 d32 polymorphisms. RESULTS: We noticed higher prevalence of CCR2 A allele as well as lower frequency of CCR5 d32 in chronic urticaria group in comparison to control group, with borderline statistical significance. Additionally, we assumed haplotype Gd statistically significant negative chronic urticaria association with tendency to higher frequency of Aw haplotype in this group. CONCLUSIONS: The results of our study imply the role of autoimmune components in chronic urticaria pathogenesis and present chronic urticaria as possibly genetically related disorder

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CTLA-4 polymorphism in the pathogenesis of chronic spontaneous autoreactive urticaria

BACKGROUND: Autoimmune mechanisms are considered to play a significant role in chronic urticaria pathophysiology. Additionally, clinical experience emphasises the coexistence of chronic urticaria manifestation with thyroid autoimmunity. As the role of CTLA-4 polymorphism in autoimmune thyroid diseases is well proven we speculated on the possible role of this polymorphism in the background of chronic urticaria. MATERIALS AND METHODS: We included 128 chronic spontaneous autoreactive urticaria patients (87 females and 41 males) and 101 healthy volunteers (71 females and 30 males). In all examined subjects CTLA-4 A49G polymorphism was analysed. Disease severity with Urticaria Activity Score as well as age of disease onset was also studied. RESULTS: No statistically significant differences in the allele or genotype distribution between urticaria patients and controls were observed. Furthermore, we found no association between CTLA4 polymorphism and urticaria severity as well as the age of disease onset. CONCLUSIONS: Our data suggest that there is no contribution of CTLA-4 A49G polymorphism to chronic spontaneous autoreactive urticaria susceptibility. We recommend further research on other polymorphisms in chronic urticaria patients to explore in detail the potent role of the genetic background in the pathogenesis of this disorder

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CTLA-4 polymorphism in the pathogenesis of chronic spontaneous autoreactive urticaria.

BACKGROUND: Autoimmune mechanisms are considered to play a significant role in chronic urticaria pathophysiology. Additionally, clinical experience emphasises the coexistence of chronic urticaria manifestation with thyroid autoimmunity. As the role of CTLA-4 polymorphism in autoimmune thyroid diseases is well proven we speculated on the possible role of this polymorphism in the background of chronic urticaria. MATERIALS AND METHODS: We included 128 chronic spontaneous autoreactive urticaria patients (87 females and 41 males) and 101 healthy volunteers (71 females and 30 males). In all examined subjects CTLA-4 A49G polymorphism was analysed. Disease severity with Urticaria Activity Score as well as age of disease onset was also studied. RESULTS: No statistically significant differences in the allele or genotype distribution between urticaria patients and controls were observed. Furthermore, we found no association between CTLA4 polymorphism and urticaria severity as well as the age of disease onset. CONCLUSIONS: Our data suggest that there is no contribution of CTLA-4 A49G polymorphism to chronic spontaneous autoreactive urticaria susceptibility. We recommend further research on other polymorphisms in chronic urticaria patients to explore in detail the potent role of the genetic background in the pathogenesis of this disorder.

Possible contribution of chemokine receptor CCR2 and CCR5 polymorphisms in the pathogenesis of chronic spontaneous autoreactive urticaria.

BACKGROUND: Autoimmune mechanisms play a role in the pathophysiology of chronic urticaria. As the genetic background of autoimmunity is well proven, the role of genetics in chronic urticaria is hypothesised. METHODS: 153 unrelated chronic spontaneous urticaria patients with a positive result of autologous serum skin test were included into the study, as were 115 healthy volunteers as control group. In all subjects we analysed CCR2 G190A and CCR5 d32 polymorphisms. RESULTS: We noticed higher prevalence of CCR2 A allele as well as lower frequency of CCR5 d32 in chronic urticaria group in comparison to control group, with borderline statistical significance. Additionally, we assumed haplotype Gd statistically significant negative chronic urticaria association with tendency to higher frequency of Aw haplotype in this group. CONCLUSIONS: The results of our study imply the role of autoimmune components in chronic urticaria pathogenesis and present chronic urticaria as possibly genetically related disorder.

Lack of association of programmed cell death 1 gene (PDCD1) polymorphisms with susceptibility to chronic urticaria in patients with positive autologous serum skin test.

BACKGROUND: Autoimmune mechanisms play an important role in the pathophysiology of chronic urticaria (CU), and the autologous serum skin test (ASST) helps to identify patients with autoreactive CU. One of the factors involved in autoreactive mechanisms is the cell surface receptor programmed death-1 which is encoded by the programmed cell death 1 gene (PDCD1). OBJECTIVE: To investigate whether PDCD1 polymorphisms influence susceptibility to CU. METHODS: We enrolled 93 ASST-positive patients with CU and a control group consisting of 105 healthy volunteers. In all individuals, PD1.3 (7146 A/G; rs 11568821) and PD1.5 (7785 C/T; rs 2227981) polymorphisms were analyzed. RESULTS: No statistically significant differences were found between CU patients and controls for allele or genotype distribution. We also did not observe any association between PDCD1 genotypes and severity of urticaria or age of disease onset. CONCLUSIONS: PD1.3 and PD1.5 polymorphisms were not proven to be implicated in susceptibility to ASST-positive CU in the Polish population. A more comprehensive analysis of the 2q33-2q37 genomic region might reveal whether variants of 1 or more of the genes in this region are involved in susceptibility to CU.

PTPN22 polymorphism presumably plays a role in the genetic background of chronic spontaneous autoreactive urticaria.

BACKGROUND: The association of chronic urticaria (CU) with autoimmune disorders is relatively well proved. Protein tyrosine phosphatase-22 (PTPN22) is considered to be one of the strongest genetic factors for human autoimmunity. We decided to evaluate whether additional, non 1858C>T, PTPN22 variants are independent contributors to the risk of CU occurrence in the Polish population. METHODS: A total of 91 CU patients with a positive result of autologous serum skin test and 100 healthy volunteers were enrolled in the study. The Urticaria Activity Score was used in disease intensity assessment. In all subjects rs3811021, rs1310182 and rs2488457 polymorphisms were genotyped. RESULTS: We found a higher prevalence of -1123 C allele among CU patients. No differences in the allele and genotype distribution were found in the other analyzed polymorphisms. Haplotype construction of the three SNPs revealed statistically significant CU association of rs2488457C, rs1310182T and rs3811021T. CONCLUSIONS: Contrary to previous findings, the contribution of PTPN22 to disease susceptibility is suggested. We can speculate that CU is a genetically complex disease and that its occurrence needs multiple genetic and environmental risk factors.

Expression pattern of genes in peripheral blood mononuclear cells in diabetic nephropathy.

AIMS: Only one-third of Type 1 diabetes patients develop diabetic nephropathy, and a genetic predisposition is postulated. To obtain more insight into processes that lead to diabetic nephropathy, messenger RNA expression profiles of peripheral blood mononuclear cells from patients with and without diabetic nephropathy were compared. METHODS: We studied seven male patients with Type 1 diabetes and proteinuria and 12 male patients with Type 1 diabetes and normoalbuminuria after at least 20 years of diabetes duration. The expression of genes was examined using the microarray method with Human Genome U133A Arrays (Affymetrix, Santa Clara, CA, USA). We analysed the expression of all candidate genes suggested to be involved in the pathogenesis of diabetic nephropathy in previously published articles. Altogether, expression of 198 genes was analysed. RESULTS: We found that thrombospondin 1 (THBS1) and cyclooxygenase 1(COX1) genes were over-expressed in patients with diabetic nephropathy, and matrix metalloproteinase 9 (MMP9) and cyclooxygenase 2 (COX2) genes had lower expression in diabetic nephropathy. For other genes, we did not observe different expression between patients with and without diabetic nephropathy,or the expression was too low for analysis. CONCLUSIONS: The different gene expression pattern in peripheral blood mononuclear cells in patients with diabetic nephropathy might indicate an important pathway in the pathogenesis of this complication.

A genome-wide linkage scan for genes controlling variation in urinary albumin excretion in type II diabetes.

The main hallmark of diabetic nephropathy is elevation in urinary albumin excretion. We performed a genome-wide linkage scan in 63 extended families with multiple members with type II diabetes. Urinary albumin excretion, measured as the albumin-to-creatinine ratio (ACR), was determined in 426 diabetic and 431 nondiabetic relatives who were genotyped for 383 markers. The data were analyzed using variance components linkage analysis. Heritability (h2) of ACR was significant in diabetic (h2=0.23, P=0.0007), and nondiabetic (h2=0.39, P=0.0001) relatives. There was no significant difference in genetic variance of ACR between diabetic and nondiabetic relatives (P=0.16), and the genetic correlation (rG=0.64) for ACR between these two groups was not different from 1 (P=0.12). These results suggested that similar genes contribute to variation in ACR in diabetic and nondiabetic relatives. This hypothesis was supported further by the linkage results. Support for linkage to ACR was suggestive in diabetic relatives and became significant in all relatives for chromosome 22q (logarithm of odds, LOD=3.7) and chromosome 7q (LOD=3.1). When analyses were restricted to 59 Caucasian families, support for linkage in all relatives increased and became significant for 5q (LOD=3.4). In conclusion, genes on chromosomes 22q, 5q and 7q may contribute to variation in urinary albumin excretion in diabetic and nondiabetic individuals.

The Ala45Thr polymorphism of BETA2/NeuroD1 gene and susceptibility to type 1 diabetes mellitus in caucasians.

It has recently been shown that mutations in BETA2/NeuroD1 are responsible for the development of type 2 diabetes mellitus (T2DM) in Caucasians. This gene is located near the IDDM7 region and one of its amino acid polymorphisms, Ala45Thr, has been associated with type 1 diabetes (T1DM) in Japanese and Danish populations. The aim of our study is to examine Ala45Thr for its role in T1DM in Caucasians. We used both population-based case-control analysis and family-based transmission/disequilibrium testing (TDT). Genotyping was carried out by the dot-blotting method using P32. Study subjects comprised 202 type 1 diabetes cases (mean age at diagnosis: 11.1 years, mean age at examination: 36.4 years) and 139 controls with normal fasting glucose. For the TDT study, allelic transmission was evaluated in 209 case family trios. The frequency of the Ala45 allele was 70.3 % in cases and 62.9 % in controls (p=0.04), and 47.5 % of cases were Ala45 homozygotes compared to 36.0 % of controls (p=0.03). The TDT component of the study did not achieve statistical significance. However, given the high frequency of this variant even among controls, exceptionally large data sets are needed to provide adequate power for this approach. Our case-control study suggests that the Ala45 variant of BETA2/NeuroD1 may be associated with T1DM in Caucasians (or in linkage disequilibrium with a causative variant). However, this finding should be confirmed by a much larger family-based study.

Vitamin D receptor gene polymorphisms and association with type 2 diabetes mellitus in a Polish population.

Vitamin D plays an important role in insulin secretion. There is also evidence that this steroid may influence the insulin sensitivity. Thus genes involved in its metabolic pathway have been regarded as good candidates for type 2 diabetes mellitus (T2DM). One of them is vitamin D receptor gene (VDR). Its multiple polymorphisms have been examined for the association with T2DM in several populations. Those studies did not provide clear answers about the role of VDR in this disease. The aim of the study was to search for the association of FokI, ApaI, BsmI, and TaqI polymorphisms of VDR gene with T2DM in a Polish population using a case-control study design. Overall, 548 individuals were examined: 308 T2DM patients and 240 control individuals. The study groups were genotyped for VDR FokI, ApaI, BsmI, and TaqI variants using the restriction fragment length polymorphism (RFLP) method. Since variants of ApaI, BsmI, and TaqI polymorphisms were in very strong linkage disequilibrium, three loci haplotypes could be assigned to phase-unknown individuals with a high degree of confidence. Differences in allele, genotype, haplotype, and haplotype combination distribution between the groups were examined by chi2 test. The VDR allele frequencies for T2DM patients and controls were as follows: FokI-F/f - 53.4 %/46.6 % vs. 55.2 %/44.8 %, BsmI-B/b - 34.4 %/65.6 % vs. 37.5 %/62.5 %, ApaI-A/a - 47.9 %/52.1 % vs 50.9 %/49.1 %, TaqI-T/t - 67.6 %/32.4 % vs. 62.7 %/37.3 %, respectively. There was no difference between the groups in allele frequency. Similarly, distribution of genotypes, three locus BsmI/ApaI/TaqI haplotypes and their combinations were similar in the groups. In conclusion, our study did not provide evidence for the association of four examined VDR polymorphisms with T2DM in a Polish population. We postulate that to fully determine whether the sequence differences in VDR gene are susceptibility variants for T2DM, additional studies in different populations are required in a large study group.

Role of hemochromatosis C282Y and H63D mutations in HFE gene in development of type 2 diabetes and diabetic nephropathy.

OBJECTIVE: In patients with clinical hemochromatosis, the frequency of diabetes ranges from 20 to 50%, and the heterozygosity for the C282Y mutation in the HFE gene might be associated with an increased risk for diabetes. There are also some reports that suggest that iron overload might cause diabetic nephropathy. RESEARCH DESIGN AND METHODS: We performed an association study to assess the role of the C282Y and H63D mutations in the HFE gene as a risk factor for type 2 diabetes and diabetic nephropathy. Altogether, 563 patients with type 2 diabetes were included in the study. In the analyzed group, 108 patients had overt proteinuria, 154 had microalbuminuria, and 301 had normoalbuminuria. Among the patients with normoalbuminuria, only those with known diabetes duration > or = 10 years were considered normoalbuminuric (n = 162). A total of 196 unrelated healthy subjects were used as a control group. All subjects were genotyped for C282Y and H63D using the polymerase chain reaction-based protocol. RESULTS: There was an increased frequency of 282Y allele carriers among patients with type 2 diabetes versus healthy control subjects (OR 5.3, 95% CI 1.6-17.3). We observed an increased frequency of the 63D allele carriers among patients with diabetic nephropathy (1.8, 1.2-2.8). CONCLUSIONS: In conclusion, our study is the first to indicate that being a carrier of the H63D hemochromatosis mutation is a risk factor for nephropathy in type 2 diabetic patients. We also confirmed previous observations that the frequency of the 282Y mutation was higher in patients with type 2 diabetes than it was in the general population of healthy subjects.

Frequency of the hemochromatosis C282Y and H63D mutations in a Polish population of Slavic origin.

BACKGROUND: Hereditary hemochromatosis is one of the most common monogenic diseases among Caucasians. The most frequent mutation causing hemochromatosis is C282Y in the HFE gene, the highest frequency of which has been observed in populations of Celtic origin. There are no studies providing information about the frequency of the C282Y and H63D mutations in the HFE gene in populations of Slavic origin. MATERIAL AND METHODS: We collected 871 healthy unrelated subjects in Poland to assess the relevant frequencies. Each subject was genotyped for the C282Y and H63D mutations using a PCR-based protocol. RESULTS: Among the analysed subjects 6.0% were CY heterozygotes, and only one person was YY homozygote. The observed frequency of the 282Y allele was 3.1%. The frequency of the D allele of the H63D polymorphism was 16.2%. There were 13 (1.5%) compound heterozygotes for C282Y and H63D found in the analysed group. CONCLUSION: The high frequency of the Y allele in this Polish population of non-Celtic origin may indicate an early introduction of this mutation through admixture with a strong positive selection.

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.

The role of R576Q polymorphism of interleukin-4 receptor alpha gene in atopy: results of a family-based study design.

INTRODUCTION: There is strong evidence that the R576 allele of interleukin-4 receptor alpha gene (IL-4R) might predispose to atopy. To test this hypothesis, we examined the association between the R576Q polymorphism and atopy in a Polish population using the family-based study design. MATERIALS AND METHODS: 44 atopic patients (age range from 11 to 34 years) with pollen and house dust mite allergy or/and mild asthma together with both parents were studied. The R576Q polymorphism of the IL-4R gene was genotyped in each patient and both parents, respectively, using the PCR-based protocol. The results were analyzed by the transmission disequilibrium test (TDT). The total IgE serum level, allergen-specific IgE to the common aeroallergens, IL-4, and sIL-4Ralpha were assessed in each patient and both parents. RESULTS: In the TDT test the R576 and Q576 alleles were transmitted from the heterozygous parents to the affected offspring 20 and 15 times, respectively (McNemar test: p = 0.19). The results of the transmission disequilibrium test did not reach statistical significance. Thus, the R576 allele might contribute to the pathogenesis of allergic diseases in patients with high total IgE serum level (p < 0.05). A larger study group has to be studied to prove the observed linkage and association.

APOE polymorphisms and the development of diabetic nephropathy in type 1 diabetes: results of case-control and family-based studies.

The goal of this study was to examine the association between known polymorphisms in the apolipoprotein E gene (APOE) and diabetic nephropathy (DN) in type 1 diabetes. We used both a case-control comparison and a family-based study design known as the transmission/disequilibrium test (TDT). For the case-control comparison, we collected DNA from 223 subjects with clinically diagnosed DN and 196 control subjects with normoalbuminuria and long-duration type 1 diabetes (> or = 15 years). For the family-based study, we obtained DNA from both parents of 154 DN subjects and 81 control subjects. The frequency of the epsilon2 allele of exon 4 of APOE was significantly higher in DN subjects than in control subjects. The risk of DN was 3.1 times higher (95% CI 1.6-5.9) in carriers of this allele than in noncarriers. In the family study, heterozygous parents for the E2 allele preferentially transmitted epsilon2 to DN offspring (64 vs. 36%, P < 0.03). Four additional polymorphisms (i.e., -491 A/T, -219 G/T, IE1 G/C, and APOCI insertion/deletion [I/D]) that flank the APOE locus were not associated with DN in either the case-control comparison or in the family-based study. In conclusion, the results of the case-control as well as the family-based study provide evidence that the epsilon2 allele of APOE increases the risk of DN in type 1 diabetes. The molecular mechanisms underlying this risk are unclear at present.

Aldose reductase gene polymorphisms and susceptibility to diabetic nephropathy in Type 1 diabetes mellitus.

AIMS: To investigate association and linkage between DNA sequence variants in the aldose reductase (AR) gene on chromosome 7q35 and diabetic nephropathy (DN) in Type 1 diabetes mellitus. METHODS: By sequencing the promoter region and 10 exons in eight DN cases and eight controls, a frequent bi-allelic polymorphism (C-106T) was discovered. This polymorphism and the known 5'ALR2 dinucleotide repeat polymorphism were genotyped in unrelated cases with advanced nephropathy (n = 221) and unrelated controls with normoalbuminuria (n = 193). For a family based study, 166 case-trios (case and both parents) and 83 control-trios (control and both parents) were also genotyped. RESULTS: In the case-control study, carriers of the Z-2 allele of the 5'ALR2 polymorphism had a significantly higher risk of DN than non-carriers (odds ratios: 1.6 for heterozygotes and 2.1 for homozygotes, P<0.05 for each). The same was true for carriers of the T allele of the C-106T polymorphism (odds ratios: 1.6 for heterozygotes and 1.9 for homozygotes, P<0.05 for each). Moreover, the haplotype carrying both risk alleles was in excess in DN cases. In the family study, transmission of risk alleles from heterozygous parents was consistent with the case-control study, excess transmission in case-trios and deficient in control-trios. CONCLUSIONS: Association between DN and two DNA sequence variants in the promoter region of the AR gene implicates the polyol pathway in the development of kidney complications in Type 1 diabetes mellitus. Further examination of the molecular mechanisms underlying these findings may provide insight into the pathogenesis of DN.

Risk of advanced diabetic nephropathy in type 1 diabetes is associated with endothelial nitric oxide synthase gene polymorphism.

UNLABELLED: Risk of advanced diabetic nephropathy in type 1 diabetes is associated with endothelial nitric oxide synthase gene polymorphism. BACKGROUND: Polymorphisms in the endothelial nitric oxide synthase gene (eNOS) may be implicated in the development of nephropathy in patients with type 1 or insulin-dependent diabetes mellitus (IDDM). METHODS: Three groups of IDDM patients were selected to study this hypothesis: cases with advanced diabetic nephropathy (N = 78), cases with overt proteinuria but normal serum creatinine (N = 74), and controls with normoalbuminuria despite 15 years of diabetes (N = 195). Parents of 132 cases and 53 controls were also examined and were used for the transmission disequilibrium test, a family-based study design to test association. RESULTS: We examined four eNOS polymorphisms, and two were associated with diabetic nephropathy in the case-control comparisons: a T to C substitution in the promoter at position -786 and the a-deletion/b-insertion in intron 4. For the former, the risk of developing advanced nephropathy was higher for C allele homozygotes than for the other two genotypes (odds ratio 2.8, 95% CI, 1.4 to 5.6). For the latter polymorphism, it was the a-deletion carriers that had the higher risk (odds ratio 2.3, 95% CI, 1.3 to 4.0) in comparison with noncarriers. Both polymorphisms were analyzed together as haplotypes in a family-based study using the transmission disequilibrium test. The C/a-deletion haplotype was transmitted from heterozygous parents to cases with advanced diabetic nephropathy with a significantly higher frequency than expected (P = 0.004). CONCLUSION: The findings of the case-control and family-based studies demonstrate clearly that DNA sequence differences in eNOS influence the risk of advanced nephropathy in type 1 diabetes.

The role of aldose reductase gene in the susceptibility to diabetic nephropathy in Type II (non-insulin-dependent) diabetes mellitus.

The dinucleotide repeat polymorphism (5'-ALR2) in the promoter region of the aldose reductase gene on chromosome 7q35 has been implicated in the development of diabetic nephropathy in Type I (insulin-dependent) diabetes mellitus, and markers flanking the aldose reductase locus have given evidence suggestive of a linkage between diabetic nephropathy and Type II (non-insulin-dependent) diabetes mellitus in Pima Indians. To examine whether the 5'-ALR2 polymorphism in the aldose reductase gene is involved in the development of diabetic nephropathy in Caucasians with Type II diabetes, we carried out a large association study. Patients with Type II diabetes from one outpatient clinic were screened for diabetic nephropathy and divided into three groups according to the degree of this disease: 179 patients with normoalbuminuria, 225 patients with microalbuminuria and 70 patients with proteinuria. Patients with normoalbuminuria were included in the study only if they had had Type II diabetes for 10 or more years. DNA from all patients was genotyped for the 5'-ALR2 polymorphism using a previously established polymerase chain reaction protocol. The frequency of the putative risk allele Z-2 was 34.6%, 34.2% and 33.6% in the normoalbuminuria, microalbuminuria and proteinuria groups, respectively. Similarly no difference among groups was found for the frequency of the putative protective allele Z + 2. In conclusion, the results of our association study in Caucasian patients with Type II diabetes do not support the hypothesis that the 5'-ALR2 polymorphism in the aldose reductase gene contributes to susceptibility to diabetic nephropathy.