Association of polymorphic markers of genes FTO, KCNJ11, CDKAL1, SLC30A8, and CDKN2B with type 2 diabetes mellitus in the Russian population.

BACKGROUND: The association of type 2 diabetes mellitus (T2DM) with the KCNJ11, CDKAL1, SLC30A8, CDKN2B, and FTO genes in the Russian population has not been well studied. In this study, we analysed the population frequencies of polymorphic markers of these genes. METHODS: The study included 862 patients with T2DM and 443 control subjects of Russian origin. All subjects were genotyped for 10 single nucleotide polymorphisms (SNPs) of the genes using real-time PCR (TaqMan assays). HOMA-IR and HOMA-ß were used to measure insulin resistance and ß-cell secretory function, respectively. RESULTS: The analysis of the frequency distribution of polymorphic markers for genes KCNJ11, CDKAL1, SLC30A8 and CDKN2B showed statistically significant associations with T2DM in the Russian population. The association between the FTO gene and T2DM was not statistically significant. The polymorphic markers rs5219 of the KCNJ11 gene, rs13266634 of the SLC30A8 gene, rs10811661 of the CDKN2B gene and rs9465871, rs7756992 and rs10946398 of the CDKAL1 gene showed a significant association with impaired glucose metabolism or impaired ß-cell function. CONCLUSION: In the Russian population, genes, which affect insulin synthesis and secretion in the ß-cells of the pancreas, play a central role in the development of T2DM.

The Role of Oxidative Stress in Diabetic Neuropathy: Generation of Free Radical Species in the Glycation Reaction and Gene Polymorphisms Encoding Antioxidant Enzymes to Genetic Susceptibility to Diabetic Neuropathy in Population of Type I Diabetic Patients.

Diabetic neuropathy (DN) represents the main cause of morbidity and mortality among diabetic patients. Clinical data support the conclusion that the severity of DN is related to the frequency and duration of hyperglycemic periods. The presented experimental and clinical evidences propose that changes in cellular function resulting in oxidative stress act as a leading factor in the development and progression of DN. Hyperglycemia- and dyslipidemia-driven oxidative stress is a major contributor, enhanced by advanced glycation end product (AGE) formation and polyol pathway activation. There are several polymorphous pathways that lead to oxidative stress in the peripheral nervous system in chronic hyperglycemia. This article demonstrates the origin of oxidative stress derived from glycation reactions and genetic variations within the antioxidant genes which could be implicated in the pathogenesis of DN. In the diabetic state, unchecked superoxide accumulation and resultant increases in polyol pathway activity, AGEs accumulation, protein kinase C activity, and hexosamine flux trigger a feed-forward system of progressive cellular dysfunction. In nerve, this confluence of metabolic and vascular disturbances leads to impaired neural function and loss of neurotrophic support, and over the long term, can mediate apoptosis of neurons and Schwann cells, the glial cells of the peripheral nervous system. In this article, we consider AGE-mediated reactive oxygen species (ROS) generation as a pathogenesis factor in the development of DN. It is likely that oxidative modification of proteins and other biomolecules might be the consequence of local generation of superoxide on the interaction of the residues of L-lysine (and probably other amino acids) with α-ketoaldehydes. This phenomenon of non-enzymatic superoxide generation might be an element of autocatalytic intensification of pathophysiological action of carbonyl stress. Glyoxal and methylglyoxal formed during metabolic pathway are detoxified by the glyoxalase system with reduced glutathione as co-factor. The concentration of reduced glutathione may be decreased by oxidative stress and by decreased in situ glutathione reductase activity in diabetes mellitus. Genetic variations within the antioxidant genes therefore could be implicated in the pathogenesis of DN. In this work, the supporting data about the association between the -262T > C polymorphism of the catalase (CAT) gene and DN were shown. The -262TT genotype of the CAT gene was significantly associated with higher erythrocyte catalase activity in blood of DN patients compared to the -262CC genotype (17.8 ± 2.7 × 10(4) IU/g Hb vs. 13.5 ± 3.2 × 10(4) IU/g Hb, P = 0.0022). The role of these factors in the development of diabetic complications and the prospective prevention of DN by supplementation in formulations of transglycating imidazole-containing peptide-based antioxidants (non-hydrolyzed carnosine, carcinine, n-acetylcarcinine) scavenging ROS in the glycation reaction, modifying the activity of enzymic and non-enzymic antioxidant defenses that participate in metabolic processes with ability of controlling at transcriptional levels the differential expression of several genes encoding antioxidant enzymes inherent to DN in Type I Diabetic patients, now deserve investigation.

Studying progression from glucose intolerance to type 2 diabetes in obese children.

AIM: Identification of metabolic and genetic factors capable to mediate progression from normal glucose tolerance (NGT) through impaired glucose tolerance (IGT) to type 2 diabetes (T2D) in childhood obesity. PATIENTS AND METHODS: Three groups of obese children with NGT (n=54), IGT (n=35), and T2D (n=62) were evaluated. A control group of non-obese normal children (n=210) was also studied. In obese patients, an oral glucose tolerance test (OGTT) was performed. Insulin resistance (IR) was assessed using HOMA-IR index. Insulin sensitivity (IS) was assessed according to the Matsuda formula. Genomic DNA from obese and control children was genotyped for genetic variants of PPARG, ADIPOQ, ADIPOR1, FTO, TCF7L2, and KCNJ11 using a real-time PCR strategy. The unpaired Student's t-test and Kruskal-Wallis one-way test were used to compare quantitative data in two and more groups. To assess the extent to which the various genetic variants were associated with pathology, ORs (odds ratios) and 95% CI (confidence interval) were estimated. RESULTS: In T2D children, HOMA-IR value (7.5±3.1) was significantly (P<0.001) higher than that in IGT (4.21±2.25) and NGT (4.1±2.4) subjects. The Matsuda IS index was significantly increased in normoglycemic patients compared to IGT individuals (2.8±1.75 vs. 2.33±1.2, P<0.05). The Pro12Ala polymorphism of PPARG was significantly associated with obesity (OR=1.74, 95% CI=1.19-2.55, P=0.004) and T2D in obesity (OR=2.01, 95% CI=1.24-3.26, P=0.004). CONCLUSION: IR is a major risk factor that mediates progression from NGT to clinical T2D in Russian obese children. This progression may be genetically influenced by the Pro12Ala variant of PPARG.

The rs11705701 G>A polymorphism of IGF2BP2 is associated with IGF2BP2 mRNA and protein levels in the visceral adipose tissue - a link to type 2 diabetes susceptibility.

BACKGROUND: Insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2) regulates translation of IGF2, a growth factor that plays a key role in controlling fetal growth and organogenesis including adipogenesis and pancreatic development. In Caucasians, the rs4402960 G>T polymorphism of IGF2BP2 has been shown to predispose to type 2 diabetes (T2D) in multiple populations. In this study, we tested whether rs4402960 G>T and rs11705701 G>A contribute to the development of T2D in a Russian population. METHODS: Both markers were genotyped in Russian diabetic (n = 1,470) and non-diabetic patients (n = 1,447) using a Taqman allele discrimination assay. The odds ratio (OR) for the risk of developing T2D was calculated using logistic regression assuming an additive genetic model adjusted for age, sex, HbA1c, hypertension, obesity, and body mass index (BMI). Multivariate linear regression analyses were used to test genotype-phenotype correlations, and adjusted for age, sex, hypertension, obesity, and BMI. Expression of IGF2BP2 in the visceral adipose tissue was quantified using real-time PCR. The content of IGF2BP2 protein and both its isoforms (p58 and p66) in the adipose tissue was measured using Western blot analysis. RESULTS: There was no significant association between rs4402960 and T2D. Whereas, allele A of rs11705701 was associated with higher T2D risk (OR = 1.19, p < 0.001). Diabetic and non-diabetic carriers of genotype TT (rs4402960) had significantly increased HOMA-IR (p = 0.033 and p = 0.031, respectively). Non-diabetic patients homozygous for AA (rs11705701) had higher HOMA-IR (p = 0.04), lower HOMA-ß (p = 0.012), and reduced 2-h insulin levels (p = 0.016). Non-obese individuals (diabetic and non-diabetic) homozygous for either AA (rs11705701) or TT (rs4402960) had higher levels of IGF2BP2 mRNA in the adipose tissue than other IGF2BP2 variants. Also, allele A of rs11705701 was associated with reduced amounts of the short isoform (p58) and increased levels of the long isoform (p66) of the IGF2BP2 protein in adipose tissue of non-obese diabetic and non-diabetic subjects. CONCLUSIONS: IGF2BP2 genetic variants contribute to insulin resistance in Russian T2D patients. The short protein isoform p58 of IGF2BP2 is likely to play an anti-diabetogenic role in non-obese individuals.

The carriage of the type 1 diabetes-associated R262W variant of human LNK correlates with increased proliferation of peripheral blood monocytes in diabetic patients.

OBJECTIVE: Lymphocyte adaptor protein (LNK) plays a pivotal role as a suppressor of T-cell receptor-mediated immune signaling and negative regulator of lymphopoiesis and early hematopoiesis. Recently, association between the R262W (c.784T>C) variant of the SH2B3 gene (rs3184504) encoding human LNK and type 1 diabetes (T1D) was found in several populations. In this study, we aimed to check whether this marker is associated with T1D in a Russian population. METHODS: Using a Taqman allele discrimination assay, we genotyped 1062 unrelated Russian individuals with diabetes at childhood and adolescence onset and 1020 healthy controls. T-cell proliferation assay based on the measurement of incorporation of bromo-2'-deoxyuridine incorporation into newly synthesized DNA was used to evaluate whether carriage of SH2B3 784T>C correlates with T-cell proliferation in patients' peripheral mononuclear blood cells (PMBCs) stimulated with anti-CD28 and anti-CD3 antibodies. RESULTS: The allele 784C of SH2B3 was related to a higher risk of T1D (odds ratio of 1.52, p = 1.2 × 10(-12)). A correlation between the carriage of the predisposing C/C variant of LNK and increased proliferation of T lymphocytes was shown in PMBCs of both diabetic [C/C vs. C/T vs.T/T = optical density at 450 nm (OD(450)) 6.3 ± 0.8 vs. 4.4 ± 0.7 vs. 2.7 ± 0.5, p = 0.0007] and non-diabetic (C/C vs. C/T vs.T/T = OD(450) 2.9 ± 0.6 vs. 2.2 ± 0.4 vs. 1.7 ± 0.4, p = 0.022) patients. CONCLUSIONS: The SH2B3 784T>C variant could contribute to the pathogenesis of T1D through impaired immune response that promotes activation and expansion of self-reactive lymphocytes in susceptible individuals.

Association of the CYBA, PPARGC1A, PPARG3, and PPARD gene variants with coronary artery disease and metabolic risk factors of coronary atherosclerosis in a Russian population.

Abnormalities in lipid metabolism and enhanced oxidative stress are considered as major risk factors for coronary atherosclerosis. Functional genetic variations in genes whose products are involved in lipid metabolism and antioxidant defense could therefore modulate risk of coronary artery disease (CAD). In this study, we evaluate whether the PPARGC1A Gly482Ser, PPARG3 (-681)C/G, PPARD +294T/C, and CYBA +242C/T gene variants confer the risk of CAD in a Russian population. A total of 313 CAD patients and 132 controls with no clinical sign of CAD were studied. The polymorphic markers were tested using a TaqMan assay. Allele and genotype frequencies in CAD patients and controls were compared using the Yates chi(2) test. Association of the genetic markers with metabolic risk factors of arterial atherosclerosis was studied using the analysis of variance test and then adjusted for conventional risk factors in the multiple regression analysis. For CYBA +242C/T, both the allele T and genotype T/T showed significant association with higher risk of CAD (odds ratio =1.49 and 3.89, respectively). The allele C and genotype C/C of the +294T/C marker of PPARD were associated with increased risk of CAD providing an odds ratio of 2.12 and 2.78, respectively. The risk variants of CYBA +242C/T and PPARD +294T/C markers were associated with higher low-density lipoprotein cholesterol and increased total serum cholesterol, respectively. In conclusion, the CYBA +242C/T and PPARD +294T/C variants modulate risk of CAD through their associations with atherogenic serum lipid profiles.

The PPARgamma Pro12Ala variant is associated with insulin sensitivity in Russian normoglycaemic and type 2 diabetic subjects.

The second isoform of the PPARgamma2 is specific for adipose tissue. In adipocytes, this isoform is involved in the regulation of adipogenesis and lipid storage, insulin and glucose metabolism. Pro12Ala, a missense mutation in exon 2 of PPARG, reduces transcriptional activity of PPARgamma2 and is shown to be associated with increased insulin sensitivity and protection from T2D. Previously, this polymorphism has never been assessed in a Russian population for its relationship to T2D, insulin resistance, and diabetes-related metabolic traits. In this study, we tested 588 Russian T2D patients and 597 normoglycaemic controls. Carriers of the Pro12 allele and subjects homozygous for Pro/Pro had significantly increased risk of developing T2D (OR 1.43 and 2.04, respectively). In Pro/Pro homozygotes, adjustment for potential confounding risk factors resulted in reducing the OR value from 2.04 to 1.69, but the association remained significant (p=0.046).The Pro/Pro genotype also showed association with increased levels of fasting insulin (p=0.019) in non-diabetic controls and elevated serum triglycerides (p=0.019) in T2D patients. Compared with other genotypes, non-diabetic and diabetic subjects homozygous for Pro/Pro had a significantly higher HOMA-IR score and reduced ISI value. This observation strongly supports the implication of the PPARG Pro12Ala in insulin resistance and T2D in a Russian population.

Advanced age, low left atrial appendage velocity, and factor V promoter sequence variation as predictors of left atrial thrombosis in patients with nonvalvular atrial fibrillation.

Atrial fibrillation (AF) renders individual patients at risk for development of an atrial thrombus. The aim of this study was to determine clinical and echocardiographic factors influencing the risk of left atrial thrombosis (LAT) in patients with persistent nonvalvular AF. Genetic variants encoding haemostatic factors have been also assessed for putative association with LAT. In the cross-sectional study, a total of 212 patients (132 males and 80 females) with nonvalvular persistent AF (duration range 48 h-90 days) have been selected. LAT was visualized by transesophageal echocardiography. The FGB G(-455)A, PAI-1 4G/5G, F5 C(-224)T, and F5 R506Q genetic markers were tested using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) approach. To reveal independent factors contributing to the thromboembolic risk in AF, a multivariate logistic model was applied. LA thrombi were found in 44 out of 212 subjects (21%). LAT was more frequently observed in patients at age >75 years (P < 0.001) and those who had reduced left ventricular ejection fraction <40% (LVEF; P < 0.001) and decreased left atrial appendage velocity <20 cm/s (LAAV; P < 0.001). Logistic regression analysis showed that advanced age (OR = 1.64 per decade P < 0.001), LVEF < 40% (OR = 2.12, P < 0.001), LAAV (OR = 1.56, P = 0.007), and TT genotype of F5 C(-224)T (OR = 2.42, P = 0.041) are associated with higher risk of LAT. Age >75 years, LVEF < 40%, LAAV < 20 cm/s, and Factor V C(-224)T variant independently contribute to the thromboembolic risk in AF.

A WFS1 haplotype consisting of the minor alleles of rs752854, rs10010131, and rs734312 shows a protective role against type 2 diabetes in Russian patients.

BACKGROUND: Rare variants of the WFS1 gene encoding wolframin cause Wolfram syndrome, a monogenic disease associated with diabetes insipidus, diabetes mellitus, optic atrophy, and deafness. In contrast, common variants of WFS1 showed association with type 2 diabetes (T2D) in numerous Caucasian populations. AIM: In this study, we tested whether the markers rs752854, rs10010131, and rs734312, located in the WFS1 gene, are related to the development of T2D in a Russian population. METHODS: The polymorphic markers were genotyped in Russian diabetic (n = 1,112) and non-diabetic (n = 1,097) patients using a Taqman allele discrimination assay. The correlation between the carriage of disease-associated WFS1 variants and the patients' clinical and metabolic characteristics was studied using ANOVA and ANCOVA. Adjustment for confounding variables such as gender, age, body mass index, obesity, HbA1c, and hypertension was made. RESULTS: Haplotype GAG, consisting of the minor alleles of rs752854, rs10010131, and rs734312, respectively, showed association with decreased risk of T2D (OR = 0.44, 95% CI = 0.32-0.61, p = 4.3 x 10(-7)). Compared to other WFS1 variants, non-diabetic individuals homozygous for GAG/CAG had significantly increased fasting insulin (p(adjusted) = 0.047) and homeostasis model assessment of ß-cell function (HOMA-ß) index (p(adjusted) = 0.006). Diabetic patients homozygous for GAG/GAG showed significantly elevated levels of 2-h insulin (p(adjusted) = 0.029) and HOMA-ß = 0.011. CONCLUSIONS: Disease-associated variants of WFS1 contribute to the pathogenesis of T2D through impaired insulin response to glucose stimulation and altered ß-cell function.

A splice variant of GNB3 and peripheral polyneuropathy in type 1 diabetes.

Abnormalities in G protein-mediated signal transduction could be involved in the pathogenesis of diabetic polyneuropathy (DPN). Here we test whether the GNB3 C825T variant confers susceptibility to DPN in type 1 diabetes (T1D) mellitus. The C825T marker of GNB3 was genotyped in genomic DNA from blood isolated from a total of 213 Russian T1D patients 100 of whom had DPN. Compared to carriers of the wild-type genotype C/C, diabetic subjects with genotypes T/T had significantly increased risk to develop DPN (Odds Ratio (OR) of 4.4 (p = 0.001). The adjustment for confounders (age, sex, body mass index, cigarette smoking, and level of reduced glutathione) resulted in increase of the OR value up to 4.72 (p = 8.9 x 10;{-3}). The further adjustment for hypertension abolished the association between the GNB3 C825T variant and DPN (OR = 1.95, p = 0.18). Non-complicated subjects homozygous for T/T showed decreased levels of reduced glutathione (T/T: 69 +/- 19 vs. C/T: 74 +/- 19 vs. C/C: 77 +/- 17 micromol/l, p = 0.009). Compared to other GNB3 variants, carriers of the T/T genotype had elevated systolic blood pressure (SBP) in complicated (T/T: 115.8 +/- 9.1 vs. C/T: 113.3 +/- 8.2 vs. C/C: 109.5 +/- 8.7 mm/Hg, p = 0.036) and non-complicated T1D patients (T/T: 118.1 +/- 8.4 vs. C/T: 116.9 +/- 7.9 vs. C/C: 112.1 +/- 7.2 mm/Hg, p = 0.02). However, the significance of association between the C825T polymorphism was lost after adjustment for confounding risk factors. In conclusion, the 825T allele of GNB3 is likely to accelerate the development of DPN through primary effects to SBP and hypertension in subgroups of diabetic patients with impaired neurovascular function and advanced oxidative stress.

Adiponectin and adiponectin receptor gene variants in relation to type 2 diabetes and insulin resistance-related phenotypes.

BACKGROUND: Alterations in adiponectin-mediated pathways are known to be associated with glucose intolerance, insulin resistance (IR), obesity, and type 2 diabetes (T2D) mellitus. Genetic variations in adiponectin (ADIPOQ) and adiponectin 1 and 2 receptor (ADIPOR1 and ADIPOR2) could have effects on IR-related phenotypes and T2D. Here we examine whether the polymorphic markers rs2241766 (ADIPOQ), rs22753738 (ADIPOR1), rs11061971 and rs16928751 (both in ADIPOR2) are implicated in susceptibility to T2D in a Russian population. METHODS: The polymorphic markers were genotyped in 129 T2D patients, and 117 non-diabetic controls, by polymerase chain reaction (PCR) restriction fragment length polymorphism approach. In the subjects, biochemical characteristics including serum insulin, plasma glucose and serum lipids/lipoproteins were measured and compared for correlation with the genetic variations studied. RESULTS: Allele T of rs11061971 and allele A of rs16928751 showed association with higher risk of diabetes providing odds ratios (OR) of 2.05 (p = 0.0025) and 1.88 (p = 0.018), respectively. Haplotype A-G consisting of allele A of rs11061971 and allele G of rs16928751 was associated with reduced risk of T2D (OR = 0.59, pc = 0.0224). Compared to other variants, diabetic patients double homozygous for A/A of rs16928751 and G/G of rs16928751 had decreased homeostasis model assessment-insulin resistance (pc = 0.0375) and serum triglycerides (pc = 0.0285). CONCLUSIONS: The variants of ADIPOR2 confer susceptibility to T2D and are associated with some IR-related phenotypes in the Russian study population.

Leu54Phe and Val762Ala polymorphisms in the poly(ADP-ribose)polymerase-1 gene are associated with diabetic polyneuropathy in Russian type 1 diabetic patients.

Poly(ADP-ribose) polymerase-1 (PARP-1) is an ubiquitous DNA-binding protein involved in the cellular response to various genotoxic agents. Excessive PARP-1 activation is known to lead to the depletion of intracellular NAD+ and ATP pools and hence to threat cell survival. Therefore, PARP-1 could be involved in neuronal death and contribute to the development of diabetic polyneuropathy (DPN). This study addressed the association of Leu54Phe and Val762Ala polymorphisms of PARP-1 with DPN in Russian type 1 diabetic (T1D) patients. Eighty-six T1D patients with severe DPN and 93 T1D patients with no clinical signs of DPN have been studied by a polymerase chain reaction restriction fragment length polymorphism approach. Using Fisher's exact test revealed the association of the Phe54 and Val762 variants of PARP-1 (odds ratio (OR), 1.66 and 2.88, respectively) with increased risk of DPN in T1D. These results suggest that the PARP1 gene is involved in the pathogenesis of diabetic neuropathy in a Russian population. Additionally, a logistic regression analysis revealed a significant association between the neurological variances such as vibration detection threshold (OR, 2.08), vibration and temperature perception thresholds (OR, 1.32 and 1.67, respectively), and sensory and motor nerve conduction velocities (OR, 2.34 and 2.58, respectively), with DPN.

Association of CYP2D6 and ADRB1 genes with hypotensive and antichronotropic action of betaxolol in patients with arterial hypertension.

Betaxolol is a selective antagonist of beta(1)-adrenergic receptors. Personal response to the drug widely varies and depends on its properties and individual features including innate characteristics. Our aim was to study the association between the clinical response to betaxolol in patients with essential hypertension (EH) and polymorphous markers of two genes: beta(1) adrenergic receptor gene (ADRB1) and cytochrome P450 2D6 gene (CYP2D6). Eighty-one patients with EH were selected. Mean age was 52.2 +/- 1.22 years. Betaxolol monotherapy provided effective blood pressure control (BP < 140/90 mmHg) in 68 patients, 56 of them continued treatment with initial dose. The systolic (SBP) and diastolic (DBP) blood pressure declined significantly at the end of the study. We have not found any significant association of rest and exercise BP and heart rate (HR) with polymorphous marker Arg389Gly of ADRB1 gene except the nighttime variability of DBP. But in case of the polymorphous marker Pro34Ser of CYP2D6 gene we have found significant association with response to betaxolol therapy. The rest HR declined more significantly in Ser/Pro genotype carriers (-32.6 +/- 4.77 beats/min and -18.4 +/- 2.01 beats/min, P = 0.023). These patients demonstrated more significant increase of exercise time (4.58 +/- 0.90 and 0.59 +/- 0.58 min, P = 0.045). Maximal exercise HR and DBP were also significantly lower in Ser/Pro genotype carriers in comparison with Ser/Ser genotype carriers. Decline of mean daytime SBP in 24-h ambulatory blood pressure monitoring was more significant in Pro allele carriers (-21.0 +/- 2.55 mmHg vs. -5.2 +/- 2.27 mmHg in patients with Ser/Ser genotype, P = 0.001). Betaxolol effect on HR and BP significantly depends on variability of the gene determining the drug metabolism. The carriers of Pro34 allele of CYP2D6 gene (8.6%) are more sensitive to betaxolol therapy. Because of the relatively small group sizes our data should be considered as preliminary ones. The increase of our groups and the replication in other studies will permit to estimate the contribution of genetic factors to betaxolol effect on HR and BP.

The TAF5L gene on chromosome 1q42 is associated with type 1 diabetes in Russian affected patients.

Type 1 diabetes (T1D) is a multifactorial autoimmune disease, with strong genetic component. Several susceptibility loci contribute to genetic predisposition to T1D. One of these loci have been mapped to chromosome 1q42 in UK and US joined affected family data sets but needs to be replicated in other populations. In this study, we evaluated sixteen microsatellites located on 1q42 for linkage with T1D in 97 Russian affected sibling pairs. A 2.7-cm region of suggestive linkage to T1D between markers D1S1644 and D1S225 was found by multipoint linkage analysis. The peak of linkage was shown for D1S2847 (P = 0.0005). Transmission disequilibrium test showed significant undertransmission of the 156-bp allele of D1S2847 from parents to diabetic children (28 transmissions vs. 68 nontransmissions, P = 0.043) in Russian affected families. A preferential transmission from parents to diabetic offspring was also shown for the T(-25) and T1362 alleles of the C/T(-25) and C/T1362 dimorphisms, both located at the TAF5L gene, which is situated 103 kb from D1S2847. Together with the A/C744 TAF5L SNP, these markers share common T(-25)/A744/T1362 and C(-25)/C744/T1362 haplotypes associated with higher and lower risk of diabetes (Odds Ratio = 2.15 and 0.62, respectively). Our results suggest that the TAF5L gene, encoding TAF5L-like RNA polymerase II p300/CBP associated factor (PCAF)-associated factor, could represent the susceptibility gene for T1D on chromosome 1q42 in Russian affected patients.

Lack of association between genetic markers on chromosome 16q22-Q24 and type 1 diabetes in Russian affected families.

AIM: To evaluate whether the T1D susceptibility locus on chromosome 16q contributes to the genetic susceptibility to T1D in Russian patients. METHOD: Thirteen microsatellite markers, spanning a 47-centimorgan genomic region on 16q22-q24 were evaluated for linkage to T1D in 98 Russian multiplex families. Multipoint logarithm of odds (LOD) ratio (MLS) and nonparametric LOD (NPL) values were computed for each marker, using GENEHUNTER 2.1 software. Four microsatellites (D16S422, D16S504, D16S3037, and D16S3098) and 6 biallelic markers in 2 positional candidate genes, ICSBP1 and NQO1, were additionally tested for association with T1D in 114 simplex families, using transmission disequilibrium test (TDT). RESULTS: A peak of linkage (MLS=1.35, NPL=0.91) was shown for marker D16S750, but this was not significant (P=0.18). The subsequent linkage analysis in the subset of 46 multiplex families carrying a common risk HLA-DR4 haplotype increased peak MLS and NPL values to 1.77 and 1.22, respectively, but showed no significant linkage (P=0.11) to T1D in the 16q22-q24 genomic region. TDT analysis failed to find significant association between these markers and disease, even after the conditioning for the predisposing HLA-DR4 haplotype. CONCLUSION: Our results did not support the evidence for the susceptibility locus to T1D on chromosome 16q22-24 in the Russian family data set. The lack of association could reflect genetic heterogeneity of type 1 diabetes in diverse ethnic groups.

Evaluation of IDDM8 susceptibility locus in a Russian simplex family data set.

Type 1 diabetes (T1D) susceptibility locus, IDDM8, has been accurately mapped to 200 kilobases at the terminal end of chromosome 6q27. This is within the region which harbours a cluster of three genes encoding proteasome subunit beta 1 (PMSB1), TATA-box binding protein (TBP) and a homologue of mouse programming cell death activator 2 (PDCD2). In this study, we evaluated whether these genes contribute to T1D susceptibility using the transmission disequilibrium test of the data set from 114 affected Russian simplex families. The A allele of the G/A1180 single nucleotide polymorphism (SNP) at the PDCD2 gene, which was significant in its preferential transfer from parents to diabetic children (75 transmissions vs. 47 non-transmissions, chi2=12.85, P corrected=0.0038), was found to be associated with T1D. G/A1180 dimorphism and two other SNPs, C/T771 TBP and G/T(-271) PDCD2, were shown to share three common haplotypes, two of which (A-T-G and A-T-T) have been associated with higher development risk of T1D. The third haplotype (G-T-G) was related to having a lower risk of disease. These findings suggest that the PDCD2 gene is a likely susceptibility gene for T1D within IDDM8. However, it was not possible to exclude the TBP gene from being another putative susceptibility gene in this region.

Confirmation of a susceptibility locus for diabetic nephropathy on chromosome 3q23-q24 by association study in Russian type 1 diabetic patients.

Family-based studies and segregation analyses suggest that inherited factors play a significant role in susceptibility to diabetic nephropathy (DN). Moczulski et al. [Diabetes 47 (1998) 1164-1169] found a susceptibility locus for DN in type 1 diabetes covering a 20cM region on chromosome 3q, with a peak of linkage close to the angiotensin II type 1 receptor (AT1) gene. We examined eight polymorphic markers (D3S1512, D3S1550, D3S1557, D3S1744, D3S2326, D3S3599, D3S3694, and a (CA)(n) dinucleotide repeat polymorphism in the 3' flanking region of the AT1 gene) spanning about 6.2 megabases (Mb) in the region of maximal linkage with DN on chromosome 3q23-q24. The markers were used to genotype a total of 381 Russian type 1 diabetic subjects, 195 of whom had DN and 186 had no clinical nephropathy. Four of the markers tested, D3S1512, D3S1550, D3S2326, and D3S3599, showed an association with DN in type 1 diabetes mellitus. These markers are located within a 1.0Mb interval that starts about 4.4Mb centromeric to the AT1 gene. Thus, our results suggest the existence of the DN susceptibility locus previously described by Moczulski et al. on chromosome 3q.

Asp299Gly and Thr399Ile genotypes of the TLR4 gene are associated with a reduced prevalence of diabetic neuropathy in patients with type 2 diabetes.

OBJECTIVE: To establish whether single nucleotide polymorphisms (Asp299Gly and Thr399Ile) of the toll-like receptor 4 have an association with late diabetic complications. RESEARCH DESIGN AND METHODS: The study was conducted in 246 type 1 and 530 type 2 diabetic patients. The alleles of both polymorphisms were detected using PCR and subsequent cleavage by NcoI and HinfI restriction endonucleases. RESULTS: No difference was found between type 1 and type 2 diabetic patients in the prevalence of alleles of the Asp299Gly and Thr399Ile polymorphisms. In most cases, the alleles Gly299 and Ile399 occurred in a co-segregatory manner. The prevalence of the Gly299/Ile399 haplotype was 10.6 and 12.1% in type 1 and type 2 diabetic patients, respectively (P = 0.63). No association with diabetic nephropathy or diabetic neuropathy was found in type 1 diabetic patients. In type 2 diabetic patients, however, heterozygote carriers of the Asp299Gly and Thr399Ile genotypes had a significantly reduced prevalence of diabetic neuropathy (odds ratio 0.35 [95% CI 0.19-0.61]; P = 0.0002); no association with diabetic nephropathy was found. CONCLUSIONS: Our data indicate that Asp299Gly and Thr399Ile genotypes of the TLR4 gene are associated with reduced prevalence of diabetic neuropathy in type 2, but not in type 1, diabetes. Thus different mechanisms may be involved in the pathophysiology of diabetic neuropathy in type 1 and type 2 diabetes.

Further studies of genetic susceptibility to Graves' disease in a Russian population.

BACKGROUND: Graves' disease (GD) is a polygenic autoimmune thyroid syndrome. Some of the genes implicated in its pathogenesis may encode thyroid-stimulating hormone receptor (TSHR) and estrogen receptors 1 (ESR1) and 2 (ESR2). We examined dinucleotide repeat polymorphisms in the ESR1 and ESR2 genes and D727E amino acid substitution in the TSHR gene for possible association with GD in a Russian population. MATERIAL/METHODS: The polymorphic regions of the target genes were amplified by polymerase chain reaction (PCR) on the basis of genomic DNA isolated from blood of 78 unrelated Russian patients with GD and 93 control subjects. To detect the D727E TSHR polymorphism, the PCR product was additionally digested with Eco72I restriction endonuclease. The genotype and allele frequencies in the groups studied were compared by c2 test. The odds ratios and 95% confidence intervals (CI) were calculated to assess the strength of the relationship between the polymorphisms tested and GD. RESULTS: For polymorphic dinucleotide microsatellites at ESR1 and ESR2, no significant difference was observed in allele frequencies between affected and nonaffected patients. For the D727E TSHR polymorphism, the E allele and the DE genotype were significantly more frequent (p<0.0001) in patients with GD than in control subjects. CONCLUSIONS: The D727E variant of the TSHR gene is associated with Graves' disease in a Russian population. The E727 allele and the heterozygous D727E genotype are related to higher risk of the disease. No association with GD was found for polymorphic microsatellites of the ESR1 and ESR2 gene.