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.

Human SA gene Pst1 polymorphism and chronic renal failure: results of the family-based study

BACKGROUND

Because of the heterogeneous aetiology of kidney diseases, interactions between multiple genetic and environmental factors are thought to be involved in the process of progression to end-stage renal disease (ESRD). Raised blood pressure remains a well-established, independent risk factor for a more rapid decline of renal function in various kidney diseases. The aim of the study was to investigate the role of the human SA gene Pst1 polymorphism in the development and/or progression of chronic renal failure (CRF).

METHODS

This polymorphism was genotyped in a group of 247 family trios (offspring affected with end-stage renal disease, and both parents): 120 with primary chronic glomerulonephritis, 80 with interstitial nephritis, and 47 with diabetic nephropathy. Transmission/disequilibrium test (TDT) was used to evaluate allele transmission from heterozygous parents to affected offspring.

RESULTS

SA gene Pst1 allele transmission did not differ from random proportion of 50:50, with no significant variation in the slope of reciprocal serum creatinine over time between patients with SA Pst1 A1A1, A1A2, and A2A2 genotypes. In addition, no impact of this marker on the rate of progression of CRF in the course of diabetes mellitus, interstitial nephritis, and chronic glomerular nephritis was shown.

CONCLUSION

Results of the study suggest no major role of SA gene polymorphism in promoting renal damage. However, the limited numbers of patients having both parents alive included in the analysis might have resulted in insufficient power to detect a minor impact of this polymorphism, especially if such effect is confined to a certain aetiology of CRF.

Angiotensinogen M235T and chymase gene CMA/B polymorphisms are not associated with nephropathy in type II diabetes

BACKGROUND

Several studies have suggested that the same genetic factors may be involved in the predisposition to both essential hypertension and diabetic nephropathy, but the molecular mechanism underlying this predisposition still remains unclear. In particular, the role of genes involved in blood-pressure regulation and angiotensin II action is still controversial. This study examines a possible association between angiotensinogen M235T and chymase gene CMA/B polymorphisms with the presence of nephropathy in type II diabetic Caucasians.

METHODS

For the purposes of the study, 323 microalbuminuric and 127 overt proteinuric cases, together with 243 normoalbuminuric controls with long-duration diabetes were selected from a group of 941 type II diabetic patients with established renal status.

RESULTS

No differences in the genotype distributions or allele frequencies of the examined polymorphisms between the study groups were observed. The study groups were also stratified by gender, diabetes duration, level of glycaemic control, body mass index, hypertension, and retinopathy status, but still no distortion in the distributions of genotypes of any of the examined polymorphisms in any of the strata was shown.

CONCLUSIONS

Our study provided evidence against an association between angiotensinogen M235T or chymase gene CMA/B polymorphisms and the presence of incipient or overt nephropathy in Caucasian patients with type II diabetes.

[The role of angiotensin I converting enzyme (ACE) Pst 1 polymorphism in the development of chronic renal failure]

Chronic renal failure (CRF) is a complex phenotype, which results from the underlying kidney disease and superimposing environmental and genetic factors. The aim of the study was to evaluate the role of angiotensin converting enzyme gene Pst 1 polymorphism in the development and/or progression of CRF. 247 family trios (patients with CRF and both parents): 120 with primary chronic glomerulonephritis, 80 with interstitial nephritis and 47 with diabetic nephropathy were examined, and transmission/disequilibrium test (TDT) was used to evaluate allele transmission from heterozygous parents to affected off-spring. No significant deviation from random transmission of the examined ACE gene Pst 1 alleles was observed, as well as no impact of this marker on the rate of progression of chronic renal failure.

Angiotensin I-converting enzyme gene insertion/deletion and angiotensinogen M235T polymorphisms: risk of chronic renal failure. End-Stage Renal Disease Study Group

BACKGROUND

Chronic renal failure (CRF) is a complex phenotype that results from an underlying kidney disease and superimposing environmental and genetic factors. The aim of our study was to evaluate the role of polymorphisms in the genes encoding for components of the renin-angiotensin system (RAS) in the development and/or progression of CRF.

METHODS

Two hundred forty-seven family trios (patients with CRF and both parents; 120 with primary chronic glomerulonephritis, 80 with interstitial nephritis, and 47 with type 1 diabetes with nephropathy) were examined, and transmission/disequilibrium test (TDT) was used to evaluate allele transmission from heterozygous parents to affected offspring.

RESULTS

The D allele of the angiotensin I-converting enzyme (ACE) gene insertion/deletion polymorphism was transmitted significantly more frequently than expected for no association among all examined trios and in the subgroup of patients with interstitial nephritis. The angiotensinogen 235T allele was transmitted significantly more frequently to patients with CRF than expected for no association, but the effect was seen only in patients with interstitial nephritis. The presence of the DD or ID genotype was associated with a faster rate of decline of renal function, which was not observed for the angiotensinogen M235T polymorphism. For chymase gene and angiotensin II receptor type 1 gene, allele transmission did not deviate significantly from a random proportion of 50:50%.

CONCLUSIONS

The results of this study suggest that ACE gene insertion/deletion and angiotensinogen M235T polymorphisms contribute to the increased risk for the development of CRF, but the magnitude of the effect within subsets of patients with specific etiologies of CRF must be evaluated further.

[Primary prevention of essential hypertension among doctors and medical students]

Doctors' and medical students' attitude to the primary prevention of hypertension is important, as this community is responsible for medical education. The level of acceptance for some antihypertensive strategies was assessed in 180 doctors and 300 medical students (263 women and 217 men). The study consisted of reading and filling the anonymous questionnaires. The necessity of primary prevention of hypertension in absolutely essential in medical education.

G-Protein beta(3) subunit C825T variant, nephropathy and hypertension in patients with type 2 (Non-insulin-dependent) diabetes mellitus

BACKGROUND

There is substantial evidence that hereditary factors contribute to the predisposition to diabetic nephropathy. On the other hand, it has been suggested that genetics of diabetic nephropathy and hypertension may overlap. Recently, a C to T substitution (C825T) in the gene encoding for the guanine-nucleotide-binding protein beta(3) subunit (GNB3) was identified, and this molecular variant was found to be associated with enhanced activation of G proteins and increased risk of the development of hypertension. The aim of the study was to test whether GNB3 C825T polymorphism contributes to the development of incipient or overt nephropathy or hypertension in type 2 diabetic patients.

METHODS

GNB3 genotype was determined in 130 type 2 diabetic patients with overt proteinuria or chronic renal failure, 155 diabetic patients with microalbuminuria and 163 control subjects with normoalbuminuria and known type 2 diabetes duration of at least 10 years.

RESULTS

No differences in GNB3 genotype distributions or allele frequencies between the study groups were found. Also, no differences between normotensive and hypertensive patients were demonstrated.

CONCLUSION

The study provided evidence against the major impact of the GNB3 C825T polymorphism on the increased risk of the development of nephropathy or hypertension in type 2 diabetic patients.

[Polymorphism of the chymase gene and development of retinopathy in type 2 diabetic patients]

Diabetic retinopathy is one of the major causes of blindness in developed countries. Among the factors involved in development of retinopathy genetic factors related to the generation of angiotensin II are mentioned. Recently was described that tissue chymase enzyme is the alternative trait for angiotensin II formulation. The aim of the study was assessment of association of CMA/B hCC polymorphism of chymase gene with the development and progression of diabetic retinopathy. The study was conduced in 587 type 2 diabetic patients with diabetes duration longer than 10 years. Mean age 62.8 +/- 8.58, mean duration 16.7 +/- 5.66, HbA1c 8.23 +/- 1.71, BMI 29.1 +/- 4.91. Ophthalmological examination was performed to determine the presence of retinopathy. Next polymorphism CMA/B hCC chymase gene by PCR method was assessed. Gene distribution was estimated by chi-square test. In the whole examined group no significant changes of gene distribution was found. However, in female group without retinopathy the tendency to lower incidence of GG genotype was observed (p = 0.06). When assessed the female group without retinopathy despite 15 years duration of diabetes frequency decrease of GG genotype was significant (p = 0.04). According to the results we conclude that CMA/B hCC chymase gene polymorphism is associated with the presence of diabetic retinopathy. Association is expressed by decreased frequency of GG genotype in female group without retinopathy.

[The evaluation of hypertensive patients' adherence to the pharmacological treatment of hypertension]

Evaluation of patients' compliance is very important considering possible influence on the effectiveness of antihypertensive treatment. The adherence to the rules of pharmacological therapy was assessed by anonymous questionnaires. 414 patients with hypertension participated in the study. Non-compliance is one of the commonest therapeutic problems. Forgetting is the most frequent reason of irregular administration of medicine.

[Evaluation of complement component C4 concentration and immunoglobulins IgA, IgG, and IgM in serum of patients with primary essential hypertension]

The aim of the study was to determine serum concentration of complement component C4 and IgA, IgG, IgM immunoglobulins in hypertensive patients and healthy controls as well as to assess the interrelationships regarding some immunological and clinical data in the study group. The study group consisted of 81 hypertensive patients (with secondary forms of hypertension excluded), 44 females and 37 males (mean age 51.2 +/- 14.5 years). The control group comprised 34 healthy volunteers, 19 females and 15 males (mean age 47.5 +/- 15.3 years). C4, IgA, IgG, IgM serum concentrations were evaluated with turbidymetry. C4 serum concentration was significantly higher in hypertensive patients when compared to the controls. No significant differences in IgA, IgG, IgM serum concentrations existed between the groups. The duration of hypertension correlated positively with C4 serum concentration. Elevated C4 serum concentration may be one of the markers of immunological disturbances existing in hypertensive patients. IgA, IgG, IgM immunoglobulins do not seem to be directly associated with essential hypertension.

[Diagnosis of diabetic autonomic neuropathy in young patients with diabetes mellitus type 1]

Autonomic neuropathy, particularly cardiovascular autonomic neuropathy (CAN) is one of the complications of the diabetes mellitus both types. It leads to life comfort's declination but may also be the direct cause of death in diabetes mellitus patients. It seems that degree of metabolic control and duration of the disease is connected with prevalence and severity of CAN. The aim of our study was to assess cardiac autonomic function in young subjects suffered from insulin-dependent diabetes mellitus (IDDM) with relatively short duration time of the disease. We subdivided 25 (m-12, f-13) IDDM patients aged from 18 to 30 years: mean--26 +/- 38 years, with duration time of the disease up to 10 years, normotensive and without nephropathy and retinopathy. We created 25 healthy volunteers control group with similar age and sex. In all selected subjects full Ewing's battery tests were performed as well as the spectral analysis of power heart rate variability (HRV) was assessed with Finapress device (Ohmeda 2300) and automatically computed with special software. HRV in total spectrum power TP from 0.001-0.5 Hz, high frequency (HF) band from 0.15-0.3 Hz, low frequency (LF) band from 0.03-0.15 Hz and LF/HF ratio were examined both in supine and tilt. All assessed spectral values were significantly lower in IDDM patients then these in controls whereas LF/HF were respectively higher. Valsalva tests and deep breathing HR response tests were significantly differed among groups but within normal limits. We concluded that when spectral analyse was performed, in young IDDM patients with short duration time of the disease, impairment of cardiac autonomic function was observed.

Angiotensin II type 1 receptor gene A1166C polymorphism is associated with the increased risk of pregnancy-induced hypertension

OBJECTIVE

The aim of our study was to evaluate the relation of parental history of hypertension to the development of PIH, and to assess the potential role of plausible candidate loci in the susceptibility to PIH.

STUDY DESIGN

Five polymorphisms: ACE gene I/D and Pst1 RFLP polymorphism, AGT gene M235T polymorphism, AGTR1 gene A1166C polymorphism, and chymase gene CMA/B polymorphism were studied in 126 women suffering from PIH in comparison with 150 healthy pregnant women. Genotyping was performed using methods based on polymerase chain reaction.

RESULTS

Among the PIH patients, positive parental history of hypertension (hypertension in both parents, in mother alone or in father alone) was significantly more frequent than in healthy pregnant women. Having a hypertensive father or mother statistically significantly increased the risk of PIH (odds ratio 4.34, 95% CI, 1.86-10.13, and 2.33, 95% CI, 1.29-4.12 respectively). CC genotype was significantly more frequent in women with PIH as compared with healthy controls and the C allele frequency was also significantly higher among the cases compared to controls. Having a CC genotype increased the risk of development of PIH 2.74 times (95% CI, 1.08-6.97). We observed no significant differences in genotype distributions or the allele frequencies of other examined polymorphisms.

CONCLUSION

On the basis of the results of our study, we may suggest that AGTR1 gene A1166C polymorphism may predispose women to the development of PIH. It seems that ACE gene I/D and Pst1 RFLP polymorphism, AGT gene M235T polymorphism, and finally chymase gene CMA/B polymorphism do not play any significant role in the pathogenesis of PIH in Caucasian women.

[Some aspects of non-pharmacologic treatment of hypertension]

Non-pharmacological methods of intervention are often used as individual or complementary forms of antihypertensive therapy. The aim of the study was to assess the level of compliance and acceptance of some life-style modifications in patients with hypertension. 432 hypertensive patients participated in the study. The study consisted of filling in anonymous questionnaires, taking blood pressure, height and weight measurements. Different approaches of nonpharmacological treatment of hypertension are accepted in differing degree. Life-style modifications and blood pressure self-monitoring should be an integral part of antihypertensive-treatment-programme.

[The effect of hemodialysis on the virgin CD45RA+, CD45RO- and memory CD45RO+, CD45RA- lymphocyte count in patients with chronic renal failure]

The hallmark of immunological memory is a quick and effective response to a repeated antigen exposure. Virgin lymphocytes, with their surface receptors CD45RA+, CD45RO- are produced in primary lymphatic organs, then migrating to secondary lymphatic structures. Memory lymphocytes CD45RO+, CD45RA- produced in these organs migrate to non-lymphatic organs--a possible location of inflammatory process, thus enabling the immunological system to eliminate effectively the same antigen, when repeatedly present. The aim of the study was 1) to test the influence of hemodialysis on the number of virgin lymphocytes and/or memory lymphocytes; 2) whether such impact (if any) depends on the type of dialysis membrane used (cuprophan or polysulphon), 3) if the effect is different in patients with or without diabetes. Overall number of virgin T helper lymphocytes CD45RA+CD4+ was significantly lower in patients with end-stage renal disease, while the number of total CD45RO+, CD45RA- memory lymphocytes was significantly greater among patients with diabetic nephropathy, compared to normal control subjects. After 15 minutes of hemodialysis, number of virgin lymphocytes CD45RA+, CD45RO- (p < 0.001, p < 0.01) and their subclasses, as well as memory lymphocytes CD45RO+, CD45RA- were significantly decreased. After 15 minutes of hemodialysis with polysulphon membrane, the decrease in T virgin cytotoxic, B virgin CD45RA+CD4-, T memory cytotoxic as well as B memory CD45RO+CD4- lymphocytes was significantly lower, when compared with cuprophan membrane (p < 0.02). Among patients treated with cuprophan hemodialysis, the decrease of T helper memory CD45RO+CD4+ lymphocytes was significantly lower in patients with diabetic nephropathy, than in non-diabetic patients.

CONCLUSIONS

In all patients with end-stage renal disease, the impact of hemodialysis on the number of memory lymphocytes CD45RO+, CD45RA-, as well as virgin lymphocytes CD45RA+, CD45RO- was shown, but the effect was less profound during hemodialysis with polysulphon membrane, compared to cuprophan. The presence of diabetic nephropathy effects the hemodialysis-induced changes in the number of T memory helper CD45RO+ CD45RO+CD4+ lymphocytes, with no impact on other subclasses of the examined cells.

Polymorphisms in the genes encoding for human kinin receptors and the risk of end-stage renal failure: results of transmission/disequilibrium test. The End-Stage Renal Disease Study Group

There is evidence that environmental factors and genetic predisposition affect the development of end-stage renal disease (ESRD). The role of kinin peptides in renal pathology has been also suggested, and a nephroprotective effect of kinins, mediated by B1 and B2 kinin receptors, has been postulated. Recently, two novel sequence differences in the B1R gene were identified, and the C allele of the G-->C substitution at position -699 in the promoter region of the B1R gene was found to be less frequent among patients with ESRD compared with healthy control subjects. In this study, the association between B1R and B2R polymorphisms and ESRD was examined using a family-based study design: transmission/disequilibrium test. B1R gene G-->C substitution at position -699 in the promoter region and B2R gene C-->T transition at position 181 in exon 2 were genotyped in 247 family trios: offspring affected with ESRD and both parents. The less common alleles of both polymorphisms (B1R C allele and B2R T allele) were transmitted from heterozygous parents to offspring affected with ESRD less frequently than expected (37 and 36%, respectively; P < 0.05). In conclusion, results obtained in this study support a hypothesis of the protective role of bradykinin receptor gene polymorphisms in the development of ESRD.

[The influence of the Wysowa Spa treatment on heart function]

The authors performed the study of the influence of spa treatment in Wysowa Health Resort on heart function in 294 subjects during their 24-day stay in sanatorium within three groups of patients: 28 with diabetes mellitus, 63 with arterial hypertension and a control group. Hemodynamic parameters were recorded by non-invasive impedance cardiography twice: in the first three days of spa treatment and again in the last three days of a 24-day stay. The following hemodynamic parameters were evaluated: SBP, DBP, MAP, CI, SVRI, IC, ACI, LCWI, EF, SI, EDI, TFC, HR. Relation of hemodynamic parameter changes on other measurable features was described in each group by correlation analysis. A small value of Pearson r coefficient proves a small relation among the examined variables. Both in the control group and in diabetic patients and also in patients with arterial hypertension, a spa treatment in Wysowa Health Resort does not show a significant influence to the examined hemodynamic parameters measured by impedance cardiography.

Reduced insulin-mediated glucose uptake by euglycemic clamp in offspring of patients with type 2 diabetes

Family studies point to an important genetic element in the genesis of type 2 diabetes. A variety of metabolic abnormalities have been documented in offspring of patients with type 2 diabetes. It has not been shown, however, at what age reduced insulin sensitivity is demonstrable using the sensitive the euglycemic clamp technique. To address this issue we screened 425 consecutive type 2 diabetic patients and examined all available (n = 48) normotensive, normoglycemic, non-smoking offspring (mean age 31.4+/-0.9 years) and compared them to 22 healthy offspring of non-diabetic parents (controls). The two groups were of similar age and BMI. Measurements in offspring and controls included baseline IRI, tissue glucose uptake (TGU, using euglycemic hyperinsulinemic clamp technique), and 24 hour ambulatory blood pressure (ABP). TGU was significantly (p < 0.001) lower in offspring of diabetic parents (338.8+/-19.9 (mol/kg/min) when compared to controls (516.6+/-22.2 micromol/kg/min). 24 h systolic ABP was significantly higher (p < 0.02) in propositi compared to controls (121.2+/-2.2 mm Hg and 113.8+/-1.7 mm Hg, respectively). No difference in triglycerides concentration was found. A borderline negative correlation was observed, however, between triglyceride levels and TGU (R = -0.48, p < 0.001). TGU was not related to the presence or absence of diabetic nephropathy in the parents. We conclude: Insulin resistance and various facets of the metabolic syndrome are demonstrable even at age 30 years in young non-obese, normotensive offspring of patients with type 2 diabetes. These disturbances are not related to the presence of microvascular complications in parents.

[Insulin resistance in offspring of type 2 diabetic patients]

Diabetes mellitus is the disease with heterogeneous aetiology. Among the causes of hyperglycaemia the insulin resistance with it's genetical background is mentioned. The aim of the study was the assessment of insulin resistance in healthy offspring of type 2 diabetic patients as well as assessment whether the coexistence of nephropathy in parents has an impact on insulin resistance in offspring. 56 subjects with positive familial history of diabetes type 2 divided into 2 groups were admitted. Subgroup A1 30 subjects (mean age 33.0 +/- 8.5 years) consisted of those who had familial history of diabetes without nephropathy and subgroup A2 26 subjects (mean age 33.0 +/- 6.5 years) with familial history of diabetic nephropathy. Control group consisted of 30 healthy volunteers without familial history. Euglycemic hyperinsulinemic clamp test was performed in all subjects studied. Tissue glucose uptake (TGU) was significantly lower while fasting insulinemia In0 was significantly higher in A1 and A2 groups when compared to controls (respectively TGU 5.6 +/- 2.2, 6.3 +/- 2.5 and 9.5 +/- 2.2 mg/kg/min p < 0.005, In0 19.4 +/- 8.3, 20.8 +/- 8.9 and 11.4 +/- 6.0 p < 0.001). No differences in TGU and In0 when compared A1 vs. A2 group were found. In-depth analysis did not show any differences in relation on whether diabetes was inherited from father's or mother's side. It was also shown that BMI did not interfere on insulin resistance in patients with positive familial history of diabetes. We conclude that insulin resistance has the genetical background and that insulin resistance and nephropathy are inherited separately.

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.