Low Frequencies of Autoimmunity-Associated PTPN22 Polymorphisms in MODY Patients, Including Those Transiently Expressing Islet Cell Autoantibodies.

BACKGROUND: The protein tyrosine phosphatase nonreceptor type 22 (PTPN22) gene encodes lymphoid tyrosine phosphatase (LYP), which is expressed primarily in lymphoid tissues. The functional but geographically highly variable PTPN22 single-nucleotide polymorphisms (SNPs), particularly c.1858C>T, contribute to the onset and progression of autoimmunity-associated diseases and facilitate the expression of disease-associated autoantibodies. In Central Europe, 17-25% of patients with monogenic diabetes (maturity-onset diabetes of the young, MODY) transiently express islet cell autoantibodies. METHODS: We addressed the links between the functional and geographically variable PTPN22 SNPs with MODY manifestation and the expression of islet cell autoantibodies in 276 MODY patients who originated from four regions (the Czech Republic, Israel, Japan and Brazil). RESULTS: The frequency of PTPN22 polymorphisms in the MODY patients was similar to those in geographically matched healthy populations, with the exception of c.788G>A, the minor allele frequency of which was significantly elevated in the Czech hepatocyte nuclear factor 1-α (HNF1A) MODY patients [odds ratio (OR) 4.8, 95% confidence interval (CI) 2.2-10.7] and the Brazilian MODY patients (OR 8.4, 95% CI 1.8-39.1). A barely significant increase in the c.788G>A minor allele was also detected in the islet cell autoantibody-positive Czech MODY patients. However, c.788A behaves as a loss-of-function mutant in T cells, and thus protects against autoimmunity. CONCLUSIONS: MODY patients (including islet cell autoantibody-positive cases) do not display any increase in autoimmunity-associated PTPN22 alleles. The absence of autoimmunity-associated PTPN22 alleles was also demonstrated in latent autoimmune diabetes in adults, which suggests that the slow kinetics of the onset of autoantibodies is subject to a regulation that is different from that experienced in type 1 diabetes and other autoimmune disorders.

Evaluation of risk for atherosclerosis in Alagille syndrome and progressive familial intrahepatic cholestasis: two congenital cholestatic diseases with different lipoprotein metabolisms.

OBJECTIVES: To evaluate the risk for atherosclerosis in Alagille syndrome (AGS) and progressive familial intrahepatic cholestasis (PFIC) on the basis of lipoprotein metabolism and by ultrasonography. STUDY DESIGN: Five patients with AGS and 5 with PFIC, ages 3 to 4 years, were enrolled. Intimal-medial thickness and wall stiffness of the common carotid artery were examined by ultrasonography. Serum levels of lipids and lipoproteins were determined. Further, the chemical composition of LDL and its ability to transform macrophages into foam cells were determined. RESULTS: Intimal-medial thickness and wall stiffness were increased in patients with PFIC but not in patients with AGS. Total cholesterol, LDL cholesterol, HDL cholesterol, and lipoprotein X were remarkably increased in patients with AGS, whereas in patients with PFIC, an increase in triglyceride and a decrease in HDL cholesterol were the prominent findings. However, despite the normal LDL cholesterol level, oxidized LDL level was strikingly high in patients with PFIC. LDLs from patients with PFIC had high TG contents and exhibited high abilities to transform macrophages into foam cells. CONCLUSIONS: These findings suggest that patients with PFIC are at high risk for cardiovascular disorders involving atherosclerosis.

Nitric oxide synthesis in ornithine transcarbamylase deficiency: possible involvement of low no synthesis in clinical manifestations of urea cycle defect.

Nitric oxide (NO) levels in plasma and urine were determined in 5 girls with ornithine transcarbamylase deficiency (OTCD) of late-onset type, who often developed migraine-like headache or vomiting. The patients were found to have low NO synthesis, suggesting that the low NO synthesis contributes to the clinical manifestations of urea cycle defect.