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See detailRelationship between ZnT8Ab, the SLC30A8 gene and disease progression in children with newly diagnosed type 1 diabetes
Nielsen, L. B.; Vaziri-Sani, F.; Pörksen, S. et al

in Autoimmunity (2011), 44(8), 616-623

Autoantibodies against the newly established autoantigen in type 1 diabetes, zinc transporter 8, ZnT8, are presented as two types, ZnT8RAb and ZnT8WAb. The rs13266634 variant of the SLC30A8 gene has ... [more ▼]

Autoantibodies against the newly established autoantigen in type 1 diabetes, zinc transporter 8, ZnT8, are presented as two types, ZnT8RAb and ZnT8WAb. The rs13266634 variant of the SLC30A8 gene has recently been found to determine the type of ZnT8Ab. The aim of this study was to explore the impact of this genetic variant and the ZnT8Ab on the residual beta-cell function during disease progression the first year after disease diagnosis in children with newly diagnosed type 1 diabetes. This cohort consists of 257 children aged < 16 years, all patients were newly diagnosed with type 1 diabetes. A Boost-test was carried out at 1, 6, and 12 months to characterize the residual beta-cell function. Carriers of the CC and CT genotype groups of the rs13266634 SNP of the SLC30A8 gene had higher stimulated C-peptide levels the first year after onset compared with those of the TT genotype group (29%, p = 0.034). CC genotype carriers were highly associated with the presence of ZnT8RAb subtype during disease progression (compared with TT, p < 0.0001). On the other hand, the TT genotype was associated with the presence of ZnT8WAb subtype during disease progression (compared with CC, p < 0.0001).The C allele of the SLC30A8 gene is associated with preserved beta-cell function in type 1 diabetes patients. The genetic determination of the rs13266634 variant on the ZnT8Ab specificity is sustained the first 12 months after the diagnosis of type 1 diabetes in a pediatric cohort. © 2011 Informa UK, Ltd. [less ▲]

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See detailThe PTPN22 C1858T gene variant is associated with proinsulin in new-onset type 1 diabetes
Nielsen, L.B.; Pörksen, S.; Andersen, M.L. et al

in BMC Medical Genetics (2011), 12(41),

BACKGROUND: The protein tyrosine phosphatase nonreceptor type 2 (PTPN22) has been established as a type 1 diabetes susceptibility gene. A recent study found the C1858T variant of this gene to be ... [more ▼]

BACKGROUND: The protein tyrosine phosphatase nonreceptor type 2 (PTPN22) has been established as a type 1 diabetes susceptibility gene. A recent study found the C1858T variant of this gene to be associated with lower residual fasting C-peptide levels and poorer glycemic control in patients with type 1 diabetes. We investigated the association of the C1858T variant with residual beta-cell function (as assessed by stimulated C-peptide, proinsulin and insulin dose-adjusted HbA1c), glycemic control, daily insulin requirements, diabetic ketoacidosis (DKA) and diabetes-related autoantibodies (IA-2A, GADA, ICA, ZnT8Ab) in children during the first year after diagnosis of type 1 diabetes. METHODS: The C1858T variant was genotyped in an international cohort of children (n = 257 patients) with newly diagnosed type 1 diabetes during 12 months after onset. We investigated the association of this variant with liquid-meal stimulated beta-cell function (proinsulin and C-peptide) and antibody status 1, 6 and 12 months after onset. In addition HbA1c and daily insulin requirements were determined 1, 3, 6, 9 and 12 months after diagnosis. DKA was defined at disease onset. RESULTS: A repeated measurement model of all time points showed the stimulated proinsulin level is significantly higher (22%, p = 0.03) for the T allele carriers the first year after onset. We also found a significant positive association between proinsulin and IA levels (est.: 1.12, p = 0.002), which did not influence the association between PTPN22 and proinsulin (est.: 1.28, p = 0.03). CONCLUSIONS: The T allele of the C1858T variant is positively associated with proinsulin levels during the first 12 months in newly diagnosed type 1 diabetes children. [less ▲]

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See detailDisease progression and search for monogenic diabetes among children with new onset type 1 diabetes negative for ICA, GAD- and IA-2 Antibodies
Pörksen, S.; Laborie, L. B.; Nielsen, L. et al

in BMC Endocrine Disorders (2010), 10

Background: To investigate disease progression the first 12 months after diagnosis in children with type 1 diabetes negative (AAB negative) for pancreatic autoantibodies [islet cell autoantibodies(ICA ... [more ▼]

Background: To investigate disease progression the first 12 months after diagnosis in children with type 1 diabetes negative (AAB negative) for pancreatic autoantibodies [islet cell autoantibodies(ICA), glutamic acid decarboxylase antibodies (GADA) and insulinoma-associated antigen-2 antibodies (IA-2A)]. Furthermore the study aimed at determining whether mutations in KCNJ11, ABCC8, HNF1A, HNF4A or INS are common in AAB negative diabetes.Materials and methods: In 261 newly diagnosed children with type 1 diabetes, we measured residual β-cell function, ICA, GADA, and IA-2A at 1, 6 and 12 months after diagnosis. The genes KCNJ11, ABCC8, HNF1A, HNF4A and INS were sequenced in subjects AAB negative at diagnosis. We expressed recombinant K-ATP channels in Xenopus oocytes to analyse the functional effects of an ABCC8 mutation.Results: Twenty-four patients (9.1%) tested AAB negative after one month. Patients, who were AAB-negative throughout the 12-month period, had higher residual β-cell function (P = 0.002), lower blood glucose (P = 0.004), received less insulin (P = 0.05) and had lower HbA1c(P = 0.02) 12 months after diagnosis. One patient had a heterozygous mutation leading to the substitution of arginine at residue 1530 of SUR1 (ABCC8) by cysteine. Functional analyses of recombinant K-ATP channels showed that R1530C markedly reduced the sensitivity of the K-ATP channel to inhibition by MgATP. Morover, the channel was highly sensitive to sulphonylureas. However, there was no effect of sulfonylurea treatment after four weeks on 1.0-1.2 mg/kg/24 h glibenclamide.Conclusion: GAD, IA-2A, and ICA negative children with new onset type 1 diabetes have slower disease progression as assessed by residual beta-cell function and improved glycemic control 12 months after diagnosis. One out of 24 had a mutation in ABCC8, suggesting that screening of ABCC8 should be considered in patients with AAB negative type 1 diabetes. © 2010 Pörksen et al; licensee BioMed Central Ltd. [less ▲]

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See detailCo-localisation of the Kir6.2/SUR1 channel complex with glucagon-like peptide-1 and glucose-dependent insulinotrophic polypeptide expression in human ileal cells and implications for glycaemic control in new onset type 1 diabetes
Nielsen, L. B.; Ploug, K. B.; Swift, P. et al

in European Journal of Endocrinology (2007), 156(6), 663-671

Objective: The ATP-dependent K+-channel (KATP) is critical for glucose sensing and normal glucagon and insulin secretion from pancreatic endocrine α- and β-cells. Gastrointestinal endocrine L- and K-cells ... [more ▼]

Objective: The ATP-dependent K+-channel (KATP) is critical for glucose sensing and normal glucagon and insulin secretion from pancreatic endocrine α- and β-cells. Gastrointestinal endocrine L- and K-cells are also glucose-sensing cells secreting glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotrophic polypeptide (GIP) respectively. The aims of this study were to 1) investigate the expression and co-localisation of the KATP channel subunits, Kir6.2 and SUR1, in human L- and K-cells and 2) investigate if a common hyperactive variant of the Kir6.2 subunit, Glu2Lys, exerts a functional impact on glucose-sensing tissues in vivo that may affect the overall glycaemic control in children with new-onset type 1 diabetes. Design and methods: Western blot and immunohistochemical analyses were performed for expression and co-localisation studies. Meal-stimulated C-peptide test was carried out in 257 children at 1, 6 and 12 months after diagnosis. Genotyping for the Glu23Lys variant was by PCR-restriction fragment length polymorphism. Results: Kir6.2 and SUR1 co-localise with GLP-1 in L-cells and with GIP in K-cells in human ileum tissue. Children with type 1 diabetes carrying the hyperactive Glu23Lys variant had higher HbA1c at diagnosis (coefficient= 0.61%, P= 0.02) and 1 month after initial insulin therapy (coefficient= 0.30%, P=0.05), but later disappeared. However, when adjusting HbA1c for the given dose of exogenous insulin, the dose-adjusted HbA1c remained higher throughout the 12 month study period (coefficient= 0.42%, P=0.03). Conclusions: Kir6.2 and SUR1 co-localise in the gastrointestinal endocrine L- and K-cells. The hyperactive Glu2Lys variant of the KATP channel subunit Kir6.2 may cause defective glucose sensing in several tissues and impaired glycaemic control in children with type 1 diabetes. © 2007 Society of the European Journal of Endocrinology. [less ▲]

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