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F Pociot

Publications and source records attributed to F Pociot.

At least 19 recordsLinked to original sources
PubMed2007

Post-translational protein modifications in type 1 diabetes: a role for the repair enzyme protein-L-isoaspartate (D-aspartate) O-methyltransferase?

AIMS/HYPOTHESIS: Post-translational modifications, such as isomerisation of native proteins, may create new antigenic epitopes and play a role in the development of the autoimmune response. Protein-L-isoaspartate (D-aspartate) O-methyltransferase (PIMT), encoded by the gene PCMT1, is an enzyme that recognises and repairs isomerised Asn and Asp residues in proteins. The aim of this study was to assess the role of PIMT in the development of type 1 diabetes. MATERIALS AND METHODS: Immunohistochemical analysis of 59 normal human tissues was performed with a monoclonal PIMT antibody. CGP3466B, which induces expression of Pcmt1, was tested on MIN6 and INS1 cells, to assess its effect on Pcmt1 mRNA and PIMT levels (RT-PCR and western blot) and apoptosis. Forty-five diabetes-prone BioBreeding (BB) Ottawa Karlsburg (OK) rats were randomised to receive 0, 14 or 500 microg/kg (denoted as the control, low-dose and high-dose group, respectively) of CGP3466B from week 5 to week 20. RESULTS: A high level of PIMT protein was detected in beta cells. CGP3466B induced a two- to threefold increase in Pcmt1 mRNA levels and reduced apoptosis by 10% in MIN6 cells. No significant effect was seen on cytokine-induced apoptosis or PIMT protein levels in INS1 cells. The onset of diabetes in the BB/OK rats was significantly delayed (85.6+/-9.0 vs 84.3+/-6.8 vs 106.6+/-13.5 days, respectively; p<0.01 for high-dose vs low-dose and control groups), the severity of the disease was reduced (glucose 22.2+/-3.2 vs 16.9+/-2.6 vs 15.8+/-2.7 mmol; p<0.01 for high- and low-dose groups vs control group) and residual beta cells were more frequently identified (43% vs 71% vs 86%; p<0.05 for high-dose vs control group) in the treated animals. CONCLUSIONS/INTERPRETATION: The results support a role for post-translational modifications and PIMT in the development of type 1 diabetes in the diabetes-prone BB rat, and perhaps also in humans.

Animals↗
PubMed2006

Association of a microsatellite in FASL to type II diabetes and of the FAS-670G>A genotype to insulin resistance.

Type II diabetes is caused by a failure of the pancreatic beta-cells to compensate for insulin resistance leading to hyperglycaemia. There is evidence for an essential role of an increased beta-cell apoptosis in type II diabetes. High glucose concentrations induce IL-1beta production in human beta-cells, Fas expression and concomitant apoptosis owing to a constitutive expression of FasL. FASL and FAS map to loci linked to type II diabetes and estimates of insulin resistance, respectively. We have tested two functional promoter polymorphisms, FAS-670 G>A and FASL-844C>T as well as a microsatellite in the 3' UTR of FASL for association to type II diabetes in 549 type II diabetic patients and 525 normal-glucose-tolerant (NGT) control subjects. Furthermore, we have tested these polymorphisms for association to estimates of beta-cell function and insulin resistance in NGT subjects. We found significant association to type II diabetes for the allele distribution of the FASL microsatellite (P-value 0.02, Bonferroni corrected). The FAS-670G>A was associated with homeostasis model assessment insulin resistance index and body mass index (P-values 0.02 and 0.02). We conclude that polymorphisms of FASL and FAS associate with type II diabetes and estimates of insulin resistance in Danish white subjects.

3' Untranslated Regions↗
PubMed2006

Increased prevalence of Down's syndrome in individuals with type 1 diabetes in Denmark: A nationwide population-based study.

AIMS/HYPOTHESIS: In patients with Down's syndrome, dogma has long held that the prevalence of diabetes is increased. The aim of the present study was to determine the actual prevalence of Down's syndrome among type 1 diabetic patients. SUBJECTS, MATERIALS AND METHODS: The background population included all children born in Denmark between 1981 and 2000. Registry-validated and clinical data on type 1 diabetes and Down's syndrome diagnoses were obtained from the National Disease Register and Danish Cytogenetic Central Register, respectively. RESULTS: The prevalence of Down's syndrome in the background population was 0.09%, whereas we identified a prevalence of Down's syndrome in type 1 diabetes patients of 0.38% (95% CI 0.17-0.75), corresponding to a 4.2-fold increased prevalence compared with the background population (p = 7.3 x 10(-5)). CONCLUSIONS/INTERPRETATION: To the best of our knowledge this is the first population-based study addressing the prevalence of Down's syndrome among verified type 1 diabetes patients. A more than fourfold increased prevalence of Down's syndrome among type 1 diabetes patients supports the notion that genes on chromosome 21 may confer risk for type 1 diabetes, probably also in the general population.

Adolescent↗
PubMed2006

Linkage disequilibrium and haplotype blocks in the MHC vary in an HLA haplotype specific manner assessed mainly by DRB1*03 and DRB1*04 haplotypes.

First generation linkage disequilibrium (LD) and haplotype maps of the human major histocompatibility complex (MHC) have been generated in order to aid the unraveling of the numerous disease predisposing genes in this region by offering a first set of haplotype tagSNPs. Several parameters, like the population studied, the marker map used, the density of polymorphisms and the applied algorithm, are influencing the appearance of haplotype blocks and selection of tags. The MHC comprises a limited number of ancestral, conserved haplotypes. We address the impact of the underlying HLA haplotypes on the LD patterns, haplotype blocks and tag selection throughout the entire extended MHC (xMHC) by studying DR-DQ haplotypes, mainly those carrying DRB1*03 and DRB1*04 alleles. We observed significantly different degree and extent of LD calculated on different HLA backgrounds, as well as variation in the size and boundaries of the defined haplotype and tags selected. Our results demonstrate that the underlying ancestral HLA haplotypic architecture is yet another parameter to take into consideration when constructing LD maps of the xMHC. This may be essential for mapping of disease susceptibility genes since many diseases are associated with and map on particular HLA haplotypes.

Chromosome Mapping↗
PubMed2006

Identification and characterization of secretagogin promoter activity.

Secretagogin is a newly identified calcium-binding protein selectively expressed in neuroendocrine tissue and pancreatic beta-cells. The function of secretagogin is unknown, but it has been suggested in beta-cells to influence calcium-influx, insulin secretion and proliferation, and has been observed downregulated in diabetes-prone BB rat islets exposed to cytokines. In the present study, we identified and characterized promoter activity of a human 1498 bp sequence upstream the transcription start site. The promoter sequence showed subtle but significant regulation by glucose within the normo-physiological range. Glucose also led to changes in expression of secretagogin protein in INS-1e cells, but not in primary cells from non-diabetes-prone Wistar Furth rats. No effects of cytokines neither on promoter activity nor protein expression were observed. The promoter region was furthermore screened by direct sequencing, and 11 polymorphisms were identified. Genotyping in a large homogenous Type 1 diabetes (T1D) family collection did not reveal association with T1D.

5' Untranslated Regions↗
PubMed2006

IRS1, KCNJ11, PPARgamma2 and HNF-1alpha: do amino acid polymorphisms in these candidate genes support a shared aetiology between type 1 and type 2 diabetes?

AIMS: Type 1 diabetes mellitus (T1DM) is a chronic disorder primarily triggered by environmental and immunological factors in genetically susceptible individuals. Despite the fact that there are indications of common aetiological features of T1DM and type 2 diabetes (T2DM), variation in genes involved in insulin secretion and insulin signalling has to a large extent been ignored as potential modifiers in the pathogenesis of T1DM. Recent studies suggest, however, that proven T2DM susceptibility gene variants may be involved in the pathogenesis of T1DM. The objective of this study was to estimate the impact of four selected amino acid polymorphisms -IRS-1 Gly972Arg, Kir6.2 Glu23Lys, HNF-1alpha Ala98Val and PPARgamma2 Pro12Ala in a Danish population of T1DM families. METHODS: All variants were genotyped in 490 simplex- and multiplex-T1DM families applying polymerase chain reaction-restriction fragment length polymorphism, and results were evaluated by means of a transmission disequilibrium test (TDT) analysis. RESULTS: TDT analysis revealed that the Arg972 IRS-1, the Lys23 Kir6.2 and the Val98 HNF-1alpha variants were transmitted from heterozygous parents to affected probands at frequencies of 49.1%, 47.0% and 54.1%, respectively (p > 0.05 for all). This was similar to the rate of transmission to unaffected siblings. The transmission rate of the Ala12 PPARgamma2 variant to affected probands was 46.5% (p > 0.05) which differed significantly from the transmission to unaffected offspring (p = 0.024). A combined analysis of the present and published pertinent data of 1691 transmissions showed a significantly decreased transmission of the PPARgamma2 Ala12 allele to affected probands (p = 0.0045). CONCLUSIONS: The Pro12Ala variant of PPARgamma2 is associated with T1DM, the minor Ala allele conferring a reduced risk. This same finding has been reported in patients with T2DM.

Adolescent↗
PubMed2005

Impact of IDDM2 on disease pathogenesis and progression in children with newly diagnosed type 1 diabetes: reduced insulin antibody titres and preserved beta cell function.

AIMS/HYPOTHESIS: The insulin-dependent diabetes mellitus 2 gene (IDDM2) is a type 1 diabetes susceptibility locus contributed to by the variable number of tandem repeats (VNTR) upstream of the insulin gene (INS). We investigated the association between INS VNTR class III alleles (-23HphIA/T) and both insulin antibody presentation and residual beta cell function during the first year after diagnosis in 257 children with type 1 diabetes. MATERIALS AND METHODS: To estimate C-peptide levels and autoantibody presentation, patients underwent a meal-stimulated C-peptide test 1, 6, and 12 months after diagnosis. The insulin -23HphIA/T variant was used as a marker of class III alleles and genotyped by PCR-RFLP. RESULTS: The insulin antibody titres at 1 and 6 months were significantly lower in the class III/III and class I/III genotype groups than in the class I/I genotype group (p = 0.01). Class III alleles were also associated with residual beta cell function 12 months after diagnosis and independently of age, sex, BMI, insulin antibody titres, and HLA-risk genotype group (p = 0.03). The C-peptide level was twice as high among class III/III genotypes as in class I/I and class I/III genotypes (319 vs 131 and 166 pmol/l, p=0.01). Furthermore, the class III/III genotype had a 1.1% reduction in HbA(1)c after adjustment for insulin dose (p = 0.04). CONCLUSIONS/INTERPRETATION: These findings suggest a direct connection in vivo between INS VNTR class III alleles, a decreased humoral immune response to insulin, and preservation of beta cell function in recent-onset type 1 diabetes.

C-Peptide↗
PubMed2005

Anaesthesia-induced hyperglycaemia early in life is not predictive for development of diabetes in diabetes-prone BB rats.

Type 1 diabetes (T1D) is an autoimmune disease in genetically predisposed individuals characterised by selective destruction of the beta-cells. Development of diabetes is in the asymptomatic pre-diabetic period characterised by impaired first-phase insulin response and the first clinical symptom is elevated blood glucose (BG). It is still uncertain whether stress or incidental hyperglycaemia can be regarded as predictors for development of T1D or not, even when immunologic and genetic markers for T1D are considered. The aim of this study was to investigate if there was any relationship between elevated BG in 30-day-old anaesthetised pre-diabetic diabetes-prone Bio Breeding (BB-DP) rats and later development of diabetes. Rats anaesthetised by intraperitoneal (ip) injection for islet transplantation displayed significantly higher BG values (Delta1.27 mmol/l, p=8.27x10(-12)) compared to non-anaesthetised non-transplanted rats, indicating that ip injection and/or anaesthesia induce a higher BG level. Linear regression analysis of BG and time of onset of diabetes in transplanted and non-transplanted BB-DP rats revealed no correlation (R(2) at 0.0075 and 0.0324 and p-values at 0.56 and 0.23 respectively). We were not able to identify any association or correlation between the induced temporary hyperglycaemia in 30-day-old BB-DP rats and later development of diabetes.

Anesthesia↗
PubMed2005

Functional promoter haplotypes of the human FAS gene are associated with the phenotype of SLE characterized by thrombocytopenia.

Systemic lupus erythematosus (SLE) is an autoimmune disorder characterized by production of autoantibodies against intracellular antigens and tissue injury. Defective apoptosis of activated immune cells leads to the development of autoantibodies in SLE. FasL initiated apoptosis is central for peripheral tolerance. Fas deficiencies in humans and mice predispose toward systemic autoimmunity. SLE is conferred by many genes. The genetic effects may be concentrated by familial clustering or by stratifying of subphenotypes. We have tested polymorphisms and haplotypes in FAS and FASL for association to SLE or subphenotypes in 126 multiplex American SLE pedigrees and found association of the FAS codon214 AC(C/T) as well as the FAS-670G>A'-codon214 AC(C/T)' haplotype to thrombocytopenia in SLE. Furthermore we have functionally characterized the FAS/FASL promoter polymorphisms associated with SLE in other populations and demonstrate that the activity depends on the allelic variants as well as on the haplotype. The presence of FAS-670G, which affects STAT1 binding, leads to the highest activity. FASL-844C activity is modified by the cis acting -478A and, hence, the haplotype and not the individual variant, determines the promoter activity. We conclude that the FAS/FASL promoter haplotypes are functional and that polymorphisms in FAS may contribute to thrombocytopenia in SLE.

Black or African American↗
PubMed2005

Fine mapping of a region on chromosome 21q21.11-q22.3 showing linkage to type 1 diabetes.

BACKGROUND: Results of a Scandinavian genome scan in type 1 diabetes mellitus (T1D) have recently been reported. Among the novel, not previously reported chromosomal regions showing linkage to T1D was a region on chromosome 21. OBJECTIVE: To fine map this region on chromosome 21. METHODS AND RESULTS: The linked region was initially narrowed by linkage analysis typing microsatellite markers. Linkage was significantly increased, with a peak NPL score of 3.61 (p = 0.0002), suggesting the presence of one or several T1D linked genes in the region. The support interval for linkage of 6.3 Mb was then studied by linkage disequilibrium (LD) mapping with gene based single nucleotide polymorphisms (SNPs). Thirty two candidate genes were identified in this narrowed region, and LD mapping was carried out with SNPs in coding regions (cSNPs) of all these genes. However, none of the SNPs showed association to T1D in the complete material, whereas some evidence for association to T1D of variants of the TTC3, OLIG2, KCNE1, and CBR1 genes was observed in conditioned analyses. The disease related LD was further assessed by a haplotype based association study, in which several haplotypes showed distorted transmission to diabetic offspring, substantiating a possible T1D association of the region. CONCLUSIONS: Although a single gene variant responsible for the observed linkage could not be identified, there was evidence for several combinations of markers, and for association of markers in conditioned analyses, supporting the existence of T1D susceptibility genes in the region.

Chromosome Mapping↗
PubMed2004

Suppressor of cytokine signalling (SOCS)-3 protects beta cells against IL-1beta-mediated toxicity through inhibition of multiple nuclear factor-kappaB-regulated proapoptotic pathways.

AIMS/HYPOTHESIS: The proinflammatory cytokine IL-1beta induces apoptosis in pancreatic beta cells via pathways dependent on nuclear factor-kappaB (NF-kappaB), mitogen-activated protein kinase, and protein kinase C. We recently showed suppressor of cytokine signalling (SOCS)-3 to be a natural negative feedback regulator of IL-1beta- and IFN-gamma-mediated signalling in rat islets and beta cell lines, preventing their deleterious effects. However, the mechanisms underlying SOCS-3 inhibition of IL-1beta signalling and prevention against apoptosis remain unknown. METHODS: The effect of SOCS-3 expression on the global gene-expression profile following IL-1beta exposure was microarray-analysed using a rat beta cell line (INS-1) with inducible SOCS-3 expression. Subsequently, functional analyses were performed. RESULTS: Eighty-two known genes and several expressed sequence tags (ESTs) changed expression level 2.5-fold or more in response to IL-1beta alone. Following 6 h of IL-1beta exposure, 23 transcripts were up-regulated. Of these, several, including all eight transcripts relating to immune/inflammatory response pathways, were suppressed by SOCS-3. Following 24 h of IL-1beta exposure, secondary response genes were detected, affecting metabolism, energy generation, protein synthesis and degradation, growth arrest, and apoptosis. The majority of these changes were prevented by SOCS-3 expression. Multiple IL-1beta-induced NF-kappaB-dependent proapoptotic early response genes were inhibited by SOCS-3 expression, suggesting that SOCS-3 inhibits NF-kappaB-mediated signalling. These observations were experimentally confirmed in functional analyses. CONCLUSIONS/INTERPRETATION: This study suggests that there is an unexpected cross-talk between the SOCS/IFN and the IL-1beta pathways of signalling in pancreatic beta cells, which could lead to a novel perspective of blocking two important proapoptotic pathways in pancreatic beta cells by influencing a single signalling molecule, namely SOCS-3.

Animals↗
PubMed2004

Mutation analysis of suppressor of cytokine signalling 3, a candidate gene in Type 1 diabetes and insulin sensitivity.

AIMS/HYPOTHESIS: Beta cell loss in Type 1 and Type 2 diabetes mellitus may result from apoptosis and necrosis induced by inflammatory mediators. The suppressor of cytokine signalling (SOCS)-3 is a natural inhibitor of cytokine signalling and also influences insulin signalling. SOCS3 could therefore be a candidate gene in the development of Type 1 and Type 2 diabetes mellitus. METHODS: Mutation analysis of the SOCS3 gene was performed in 21 patients with Type 1 diabetes mellitus and in seven healthy subjects. An identified promoter variant was examined in (i) 250 families with Type 1 diabetic family members (1097 individuals); (ii) 212 glucose-tolerant first-degree relatives of Type 2 diabetic patients; and (iii) 370 population-based young, healthy subjects who were unrelated. RESULTS: Three mutations were identified in the promoter region, but none in the coding region or the 3'UTR. Two of the three mutations had allele frequencies below 1% whereas the C -920-->A substitution had a minor allele frequency of 8%. In the group of young healthy subjects the insulin sensitivity index was higher among homozygous carriers of the A-allele than among heterozygous and wild-type subjects ( p=0.027, uncorrected). The same trend was found in the group of first-degree relatives of Type 2 diabetic patients. No association or linkage was found to Type 1 diabetes mellitus. CONCLUSIONS/INTERPRETATION: Homozygosity for the A-allele of the C -920-->A promoter polymorphism of the SOCS3 gene may be associated with increased whole-body insulin sensitivity, but deserves further investigation.

Adolescent↗
PubMed2004

Changes in expression of IL-1 beta influenced proteins in transplanted islets during development of diabetes in diabetes-prone BB rats.

AIMS/HYPOTHESIS: Type 1 diabetes mellitus is a multifactorial autoimmune disease characterised by selective destruction of beta cells in the islets of Langerhans. We have previously shown that IL-1 beta modulates beta cell function, causes beta cell death and induces expression changes in 82 out of 1815 protein spots detected by two-dimensional gel electrophoresis (2-DGE) in diabetes-prone bio-breeding (BB-DP) rat islets in vitro. The aim of this study was to describe the relevance of these proteins in the development of diabetes in vivo. METHODS: Syngeneic neonatal islets ( n=200) were transplanted under the kidney capsule of 30-day-old BB-DP and control rats, removed to different time points after transplantation or at the onset of diabetes, and metabolically labelled with S(35)-methionine for 2-DGE. The 82 proteins were re-localised and followed. In addition, transplants were examined for expression of IL-1 beta mRNA by in situ hybridisation. RESULTS: All 82 proteins could be re-localised in all syngeneic transplants from BB-DP and control rats. A total of 60 of the 82 proteins were changed during development of diabetes. Of the 82 proteins, 32 were changed in expression at the onset of diabetes compared to non-diabetic BB-DP rats, and 25 of these were changed as by IL-1 beta in vitro. Highest expression of IL-1 beta mRNA was found at the onset of diabetes. CONCLUSIONS/INTERPRETATION: IL-1 beta-induced protein expression changes in islets in vitro also occur in vivo and change in a complex pattern during the development of diabetes in the BB-DP rat. No single protein seems to be responsible for the development of diabetes, but rather the cumulative numbers of changes seem to interfere with the intracellular stability of the beta cell.

Animals↗
PubMed2004

Evidence for linkage on chromosome 4p16.1 in Type 1 diabetes Danish families and complete mutation scanning of the WFS1 (Wolframin) gene.

AIMS: To investigate whether the WFS1 gene, the gene for Wolfram syndrome, is a susceptibility gene for more common forms of diabetes in the Danish population. METHODS: One hundred and fifty-two Danish Type 1 diabetes mellitus sib-pair families were genotyped for two microsatellite markers situated within 5 cM of the WFS1 gene and analysed for linkage and association using the sib-TDT. The entire coding region, the 5'UTR and 3'UTR of the WFS1 gene, were screened for mutations by direct sequencing in 29 selected Type 1 diabetes patients. Four of the identified mutations were tested for linkage and association in 255 Danish Type 1 diabetes families (including 103 simplex families). RESULTS: Evidence for linkage to Type 1 diabetes was found as the second most frequent allele of the marker D4S394 were transmitted 137 times (T = 61%) and not transmitted 88 times to affected offspring (Puc = 0.0011). Twelve mutations were found in the coding region and three mutations in the 3'UTR. No evidence for linkage and association to Type 1 diabetes was found testing four of the identified amino acid substitutions. CONCLUSIONS: Evidence of linkage to Type 1 diabetes was observed in the Danish family collection. However, no evidence of linkage and association was observed for any of the analysed polymorphisms, suggesting that other variations must be responsible for the observed evidence of linkage in the region.

Age of Onset↗
PubMed2004

Identification of a type 1 diabetes-associated CD4 promoter haplotype with high constitutive activity.

CD4 is a candidate gene in autoimmune diseases, including Type 1 diabetes mellitus (T1DM), because the CD4 receptor is crucial for appropriate antigen responses of CD4(+) T cells. We previously found linkage between a CD4-1188(TTTTC)(5-14) promoter polymorphism and T1DM. In the present study, we screened the human CD4 promoter for mutations and identified three frequent single nucleotide polymorphisms (SNPs): CD4-181C/G, CD4-521C/G and CD4-1050T/C. The SNPs are in strong linkage disequilibrium (LD) and association with the CD4-1188(TTTTC)(5-14) alleles, and we observed nine CD4 promoter haplotypes, of which four are frequent. We genotyped the SNPs in 253 Danish T1DM families (1129 individuals) and found evidence for linkage and association of a CD4 (A4(-1188)T(-1050)G(-521)C(-181)) haplotype to T1DM. In reporter studies, we show that (1) the T1DM-associated CD4 haplotype encodes high constitutive promoter activity and (2) the CD4-181G variant encodes higher stimulated promoter activity than the CD4-181C variant. This difference is in part neutralized in the frequently occurring CD4 promoter haplotypes by the more upstream genetic variants. Thus, we report functional impact of a novel CD4-181C/G SNP on stimulated CD4 promoter activity and the identification of a novel CD4 haplotype with high constitutive promoter activity that is linked and associated with T1DM.

Adolescent↗
PubMed2003

HLA associations in type 1 diabetes: DPB1 alleles may act as markers of other HLA-complex susceptibility genes.

Alleles at the HLA-DQB1, -DQA1 and -DRB1 loci are major determinants for susceptibility to develop type 1 diabetes (T1D). Increasing evidence supports that also other genes in, or near, the HLA complex contribute to the HLA-encoded risk. Alleles at the DPB1 locus have been suggested to directly influence the risk conferred by DQB1, DQA1 and DRB1 alleles, but the results are conflicting. We therefore genotyped 217 families from Norway, Denmark, Sweden and southern France to address the role of DPB1 alleles in T1D. After taking into account linkage disequilibrium (LD) with DQB1, DQA1 and DRB1 alleles, we found evidence that some DPB1 alleles are associated with modulating the risk of developing T1D. However, we show that the strong LD in the HLA complex, and the presence of extended haplotypes complicate the interpretation of the results. On DQ2-DR3 haplotypes, both allele 3 at microsatellite D6S2223 located 5.3-Mb telomeric of DPB1 and the extended DQ2-DR3-B18 haplotype display much stronger association than DPB1 alleles. When we exclude these effects, most of the apparent association of DPB1 alleles on DQ2-DR3 haplotypes disappear. Taken together, although we cannot completely rule out an effect of some DPB1 alleles, we propose that the statistically significant, albeit weak, DPB1 associations found are most likely the result of LD with another unidentified disease-susceptibility gene(s) in this region.

Alleles↗