Distribución de polimorfismos del gen del antígeno-4 del linfocito T citotóxico en población chilena con diabetes mellitus tipo 1 / Distribution of cytotoxic T lymphocyte antigen-4 gene polymorphisms in Chilean population with type 1 diabetes mellitus

Background: Cytotoxic T lymphocyte antigen-4 (CTLA-4) molecule is an important regulator of T cell activation involved in the down-regulation of immune response. Their polymorphisms +49 A/G and CT60 have been suggested to confer susceptibility to autoimmune endocrine disorders. The aim of this study was to determine the association of CTLA-4 gene polymorphisms with T1D in the Chilean population. We also wanted to study if the combined haplotypes of +49 A/G and CT60 had an impact on risk for T1D. Methods: To evaluate the impact of allelic variants CT60 and +49 A/G SNPs were studied in a Chilean population, including 248 T1D patients and 160 controls. Genotypes of both polymorphisms of CTLA-4 gene were determinate by PCR-restriction fragment polymorphism (PCRRFLP).Results: No statistical differences were observed when comparing patients with diabetes and controls for both CTLA-4 genotypes. However, the haplotype analysis between CT60 and +49 A/G showed an interesting combination of risk conformed by G*G combination with an OR of 1.648 [1.19- 2.28], (p = 0.002). Conclusions: The G*G haplotype could be a risk marker in patients with T1D in Chilean population.

Frecuencia del polimorfismo PD-1.3 del gen del receptor de muerte celular programada 1 (PD-1) y su asociación con diabetes tipo 1 / Frequency of polymorphism PD-1.3 of programmed cell death 1 (PD-1) and their association with type 1 diabetes

Background: The programmed cell death 1 (PDCD-1) immune-receptor is a key element in the negative regulation of peripheral tolerance in T cells. The gene has several polymorphisms and can be associated with susceptibility to autoimmune diseases. Aim: To analyze the frequency and distribution of PD-1.3 polymorphism of PDCD-1 gene and explore its possible contribution as a susceptibility gene for type 1 diabetes (T1D). Patients and Methods: We analyzed 248 cases with T1D with recent diagnosis and 160 control children under 15 years of Santiago. Genetic polymorphism in PD-1 gene variant for PD-1.3 (rs 11568821) was analyzed by polymerase chain reaction and restriction fragment length polymorphism. Comparison of genotype, allele frequency and consistency with respect to Hardy-Weinberg were analyzed using X2 tests and Fisher exact test. Results: There was a very low frequency of the genotype A/A, both in T1D patients and in controls (< 2 percent). The A/G genotype was more common in diabetic patients than in controls (41.6 and 18.8 percent respectively, p < 0.04). G/G genotype was more common in controls than in patients (79.4 and 56.8 percent respectively, p < 0.02). T1D patients carrying genotype G/G had a higher frequency of anti-GAD65 and anti-A-2 antibodies (81 and 67 percent respectively). Conclusions: The distribution of PD-1.3 genotype frequencies are similar to that reported elsewhere. Possibly, this genetic variant (rs 11568821) does not have an important marker role in Chilean T1D patients.

Expresión disminuida de caspasa 3 asociada al polimorfismo del gen del antígeno-4 asociado a linfocito T-citotóxico (CTLA4) en pacientes chilenos con diabetes tipo 1 / Decreased caspase 3 expression and cytotoxic T lymphocyte antigen-4 polymorphism in Chilean patients with type 1 diabetes

Background: Several polymorphisms of the CTLA4 gene have been associated with autoimmune diseases. The activation of induced cell death is the major event and caspase 3 represents the main protein for the apoptotic machinery, especially in lymphocytes. Aim: To correlate CTLA4 polymorphisms with caspase 3 expression in peripheral blood mononuclear cells (PBMC) simulating in vitro the glucose effect. Material and Methods: CTLA4 polymorphisms were determined by restriction fragment length polymorphisms (RFLPs). PBMC from 21 patients with type 1 diabetes aged 8.5 ± 4.3 years and 21 healthy subjects aged 18.3 ± 1.8 years, were stimulated under normal (5 mM) and toxic (14 mM) glucose conditions to assess its effect on the expression and activity of caspase 3. Relative abundance of caspase 3 mRNA was measured by semi quantitative RT-PCR and its activity, by a colorimetric assay. Results: When stimulated with 14mM glucose, PBMC of G allele carriers with type 1 diabetes had significantly lower relative mRNA abundance of caspase 3 (median value = 0.12, range 0.01-0.70 AU) compared with non-carriers (median value = 0.81, range 0.06-1.09 AU). When the incubation was carried out with the lower glucose concentration, a similar profile of caspase 3 activity was observed in diabetic patients carrying G allele (median value = 0.57, range 0.13-1.20 AU) as compared with non-carriers (median value = 0.89, range 0.14-5.50 AU). No significant changes after stimulating with glucose, were observed in PBMCs of the control group. Conclusions: PBMC of recently diagnosed patients with T1D, carrying the G allele in + 49A/G polymorphisms of CTLA4, have a decreased expression and activity of caspase 3.

Frecuencia de polimorfismo C1858T del gen PTPN22 y marcadores de autoinmunidad en pacientes chilenos con diabetes tipo 1 y enfermedad celíaca / C1858T polymorphism of protein tyrosine phosphatase, non-receptor type 22 (PTPN22) gene in diabetic and celiac patients

Background: A genetic polymorphism called C1858T of protein tyrosine phosphatase, non-receptor type 22 (PTPN22) gene has been associated with autoimmune diseases Aim: To describe the association between two autoimmune diseases, namely type 1 diabetes (T1D) and celiac disease (CD)and tyrosine phosphatase gene polymorphisms (variant C1858T of PTPN22). Subjects and Methods: C1858T single-nucleotide polymorphism within the PTPN22 gene was genotyped in 209 patients with T1D, 43 celiac patients and 100 healthy controls. Results: CC gene frequency was 0.906 and 0.790 in CD patients and controls respectively ( p < 0.01). All analyzed groups had a low frequency of the TT genotype. Compared with the other study groups, patients with T1D had a low frequency of CC genotype (0.636). Also, in these patients, there was a non-significant association between CC genotype and islet cell IA-2 auto antibodies (p < 0.065). Among CD patients, CC genotype was significantly associated with anti-transglutaminase or anti endomysial antibodies (p < 0.03). Conclusions: These results confirm the association of the genetic variant C1858T of PTPN22 with CD. In contrast to published data, this association was not found in T1D patients.