Polymorphisms of the UCP2 gene are associated with proliferative diabetic retinopathy in patients with diabetes mellitus.

BACKGROUND AND OBJECTIVE: Uncoupling protein 2 (UCP2) plays a role in controlling reactive oxygen species (ROS) production by mitochondria. As ROS overproduction is related to diabetic retinopathy (DR), UCP2 gene polymorphisms might be involved in the development of this complication. We investigated whether the -866G/A (rs659366), Ala55Val (rs660339) and 45 bp insertion/deletion (Ins/Del) polymorphisms in the UCP2 gene might be associated with proliferative DR (PDR). DESIGN AND METHODS: In this case-control study, we analysed 501 type 2 diabetic patients (242 patients with PDR and 259 subjects without any degree of DR) and 196 type 1 diabetic patients (85 cases with PDR and 111 without DR). Haplotypes constructed from the combination of the three UCP2 polymorphisms were inferred using a Bayesian statistical method. RESULTS: In the type 2 diabetic group, multivariate analyses confirmed that the haplotype [A Val Ins] was an independent risk factor for PDR when present in one [adjusted odds ratio (aOR) = 2.12; P = 0.006], at least one (aOR = 2.75; P = 0.00001), or two copies (aOR = 5.30; P = 0.00001), suggesting an additive model of inheritance. Nevertheless, in type 1 diabetic patients, the association of this haplotype with PDR was confirmed only when it was present in at least one (aOR = 2.68; P = 0.014) or two copies (aOR = 6.02; P = 0.005). CONCLUSIONS: The haplotype [A Val Ins] seems to be an important risk factor associated with PDR in both type 2 and 1 diabetic groups.

The rs225017 polymorphism in the 3'UTR of the human DIO2 gene is associated with increased insulin resistance.

The Thr92Ala (rs225014) polymorphism in the type 2 deiodinase (DIO2) gene has been associated with insulin resistance (IR) and decreased enzyme activity in human tissues but kinetic studies failed to detect changes in the mutant enzyme, suggesting that this variant might be a marker of abnormal DIO2 expression. Thus, we aimed to investigate whether other DIO2 polymorphisms, individually or in combination with the Thr92Ala, may contribute to IR. The entire coding-region of DIO2 gene was sequenced in 12 patients with type 2 diabetes mellitus (T2DM). Potentially informative variants were evaluated in 1077 T2DM patients and 516 nondiabetic subjects. IR was evaluated using the homeostasis model assessment (HOMA-IR) index. DIO2 gene sequencing revealed no new mutation but 5 previously described single nucleotide polymorphisms (SNPs). We observed that all T2DM patients displaying high HOMA-IR index (n = 6) were homozygous for the rs225017 (T/A) polymorphism. Further analysis showed that the median fasting plasma insulin and HOMA-IR of T2DM patients carrying the T/T genotype were higher than in patients carrying the A allele (P = 0.013 and P = 0.002, respectively). These associations were magnified in the presence of the Ala92Ala genotype of the Thr92Ala polymorphism. Moreover, the rs225017 and the Thr92Ala polymorphisms were in partial linkage disequilibrium (|D'| = 0.811; r2 = 0.365). In conclusion, the rs225017 polymorphism is associated with greater IR in T2DM and it seems to interact with the Thr92Ala polymorphism in the modulation of IR.

Type 2 deiodinase Thr92Ala polymorphism is associated with disrupted placental activity but not with dysglycemia or adverse gestational outcomes: a genetic association study.

OBJECTIVE: To study whether the D2 Thr92Ala polymorphism-a genetic marker that is associated with reduced thyroid type 2 deiodinase (D2) activity, increased insulin resistance, and risk for type 2 diabetes-is associated with disrupted placental D2 activity and with glycemic control and gestational outcomes. DESIGN: Cross-sectional study. SETTING: Tertiary hospital in Brazil. PATIENT(S): Consecutive singleton-pregnancy patients, 18-45 years old. INTERVENTION(S): Clinical examination and genotyping of the D2 Thr92Ala polymorphism, with placental samples collected and assayed for D2 mRNA and activity. MAIN OUTCOME MEASURE(S): Glucose homeostasis and gestational outcomes. RESULT(S): A total of 294 patients were included in the study. The clinical and laboratory characteristics were similar among the D2 genotypes. No differences were observed in D2 placental mRNA levels, but D2 activity was decreased in patients with the Ala92Ala genotype (0.35 ± 0.15 vs. 1.96 ± 1.02 fmol/mg/min.). Newborn serum thyroid-stimulating hormone levels (TSHneo) did not differ according to maternal D2 Thr92Ala genotype. Also, maternal glucose control, insulin resistance evaluated by the homeostasis model assessment (HOMA-IR), and gestational outcomes did not differ across D2 genotypes. CONCLUSION(S): The D2 Ala92Ala genotype is associated with reduced placental D2 activity but is not associated with dysglycemia, increased insulin resistance, or worse gestational outcomes.

Genetic changes in severe haemophilia A: new contribution to the aetiology of a complex disease.

Haemophilia A is an X-linked bleeding disorder caused by reduced or absent clotting factor VIII (FVIII) activity, determined by heterogeneous mutations in the F8 gene. Identification of these pathogenic mutations is important for genetic counseling and the assessment of clinical manifestations. Although more than 700 mutations of the F8 gene have been reported as responsible for severe haemophilia (FVIII: C<1%), the corresponding data is currently insufficient for southern Brazilian populations, and world reviews concerning these changes are scarce. Thirty-six unrelated severe haemophilia A patients who showed negative results for introns 22 and 1 inversions were studied for gross exon deletions and mutations there and in adjacent regions. Missense mutations were examined using molecular structural methods. The presence of FVIII inhibitors was also investigated. The results were compared with the information available from respectively 2878 and 1952 patients from all over the world. Twenty-nine different genetic changes were found, 16 of them novel. Seventeen of the carriers developed FVIII inhibitors, and molecular analysis suggested that Asp542Gly and Ser109Pro may interfere with calcium binding, whereas Leu2297Arg clearly affects the molecule's electrostatic surface. The main aetiological factor in the severe form of haemophilia seems to be missense mutations. Of all genetic changes occurring in these patients, large deletions are the most important in inhibitors formation.

Additive effect of RET polymorphisms on sporadic medullary thyroid carcinoma susceptibility and tumor aggressiveness.

OBJECTIVE: RET single nucleotide polymorphisms (SNPs) have been implicated in the pathogenesis and progression of medullary thyroid carcinoma (MTC). Here, we investigated the influence of multiple RET variants (G691S, L769L, S836S, and S904S) on the risk of MTC and tumor behavior. DESIGN AND METHODS: One hundred and seven MTC patients and 308 cancer-unaffected control individuals were included. SNPs were analyzed using Custom TaqMan Genotyping Assays. Haplotypes based on the combination of allelic variants were inferred using a Bayesian statistical method. RESULTS: The minor allele frequencies in MTC patients were as follows: L769L: 28.0%, S836S: 8.9%, and G691S/S904S: 22.2%. The RET L769L and S836S SNPs were associated with increased risk of MTC (odds ratio (OR)=1.95, 95% CI: 1.2-3.1, P=0.005 and OR=2.29, 95% CI: 1.2-4.5, P=0.017 respectively). The adjusted OR for individuals harboring haplotypes with three or more polymorphic alleles was 3.79 (95% CI: 1.5-9.5; P=0.004), indicating an additive effect of these variants on the risk for MTC. Among MTC patients, no significant associations were observed between RET variants and age of diagnosis or tumor size but serum calcitonin levels increased according to the number of risk alleles (P=0.003). Remarkably, patients carrying haplotypes with three or four risk alleles had increased risk for lymph node and distant metastases at diagnosis (OR=5.84, 95% CI: 1.1-31.2, P=0.039). Further analysis using Kaplan-Meier model demonstrated that metastatic disease occurred earlier in individuals harboring multiple risk alleles. CONCLUSION: Our results demonstrated an additive effect of RET polymorphic alleles on the estimated risk of developing aggressive MTC.

D2 Thr92Ala and PPARγ2 Pro12Ala polymorphisms interact in the modulation of insulin resistance in type 2 diabetic patients.

Type 2 deiodinase (D2) converts T4 into its active metabolite T3, an essential step in thyroid metabolism. A Thr92Ala polymorphism in the gene encoding D2 has been inconsistently associated with insulin resistance (IR). Recently, it was reported that the D2 Thr92Ala (rs225014) and the peroxisome proliferator-activated receptor (PPAR) γ2 Pro12Ala (rs1801282) polymorphisms interact in the modulation of metabolic syndrome in nondiabetic subjects. Here, we investigated the effect of both polymorphisms, isolated or in combination, on IR in patients with type 2 diabetes mellitus (DM2). The D2 Thr92Ala and PPARγ2 Pro12Ala polymorphisms were genotyped in 721 DM2 patients. IR was evaluated using the homeostasis model assessment-IR (HOMA(IR)) index in a subgroup of 246 DM2 subjects. The frequencies of D2 Ala92 and PPARγ2 Ala12 variants were 0.390 and 0.074, respectively. Patients carrying D2 Ala/Ala genotype had a higher fasting plasma insulin and HOMA(IR) index as compared to patients carrying Thr/Ala or Thr/Thr genotypes (P = 0.022 and P = 0.001, respectively). A significant synergistic effect was observed between D2 Thr92Ala and PPARγ2 Pro12Ala polymorphisms on HOMA(IR) index, with carriers of both D2 Ala/Ala genotype and PPARγ2 Ala12 allele showing the highest HOMA(IR) values, after adjusting for age, gender, BMI, and use of medication for DM2 (P = 0.010). In conclusion, DM2 patients harboring both D2 Ala/Ala genotype and PPARγ2 Ala12 allele seem to present more severe IR than those with other D2/PPARγ2 genotype combinations. These findings suggest that these polymorphisms interact in the IR modulation, which may constitute a potential therapeutic target.

Isolation, characterization, and transcriptional analysis of the chitinase chi2 Gene (DQ011663) from the biocontrol fungus Metarhizium anisopliae var. anisopliae.

Metarhizium anisopliae infects arthropods via a combination of specialized structures and cuticle degradation. Hydrolytic enzymes are accepted as key factors for the host penetration step and include chitinases. The characterization of the chi2 chitinase gene from M. anisopliae var. anisopliae is reported. The chi2 gene is interrupted by two short introns and is 1,542-bp long, coding a predicted protein of 419 amino acids with a stretch of 19 amino acid residues displaying characteristics of signal peptide. The predicted chitinase molecular mass is 44 kDa with a mature protein of 42 kDa and a theoretical pI of 4.8. The comparison of the CHI2 predicted protein to fungal orthologues revealed similarity to the glycohydrolase family 18 and a phylogenetic analysis was conducted. The chi2 gene is up-regulated by chitin as a carbon source and in conditions of fungus autolysis, and is down-regulated by glucose. This regulation is consistent with the presence of putative CreA/Crel/Crr1 carbon catabolic repressor binding domains on the regulatory sequence.