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Mikael Knip

Publications and source records attributed to Mikael Knip.

At least 55 records · Page 3Linked to original sources
PubMed2004

Distinct idiotypes of insulin autoantibody in autoimmune polyendocrine syndrome type 2 and childhood onset type 1 diabetes.

Insulin autoantibodies (IAA) are present in type 1 diabetes (T1D) and other autoimmune diseases. The differences in the IAA epitopes in various clinical diseases have not been evaluated. We used phage display to select phagotopes specific to IAA from a newly diagnosed T1D child (designated FPP) and from an adult-onset T1D subject with autoimmune polyendocrine syndrome type 2 (APS-II). The phagotopes randomly selected were tested as antiidiotope reagents to displace human radiolabeled insulin in the microfiltration radiobinding assay using IAA(+) sera from T1D subjects and insulin antibody (IA(+)) sera from insulin-treated type 2 diabetes subjects. The DNA of the phagotopes selected from the FPP and APS sera revealed consensus amino acid sequences of GRG and LGKRS, respectively. Phagotope FPP-10 displaced insulin binding in 90% of IAA(+) subjects but not in the IA(+) or the APS subject. Phagotope APS-4 was able to displace insulin binding from the APS subject but not in the IAA(+) or IA(+) subjects. We have demonstrated antiidiotope reagents able to distinguish childhood-onset T1D-associated IAA(+) from adult-onset T1D (APS-II-associated IAA(+)) that are different from their specificity for human insulin and from its antiidiotope amino acid sequence.

Adult↗
PubMed2004

Geographical variation in risk HLA-DQB1 genotypes for type 1 diabetes and signs of beta-cell autoimmunity in a high-incidence country.

OBJECTIVE: To assess possible differences in the frequency of HLA-DQB1 risk genotypes and the emergence of signs of beta-cell autoimmunity among three geographical regions in Finland. RESEARCH DESIGN AND METHODS: The series comprised 4,642 children with increased HLA-DQB1-defined genetic risk of type 1 diabetes from the Diabetes Prediction and Prevention (DIPP) study: 1,793 (38.6%) born in Turku, 1,646 (35.5%) in Oulu, and 1,203 (25.9%) in Tampere. These children were examined frequently for the emergence of signs of beta-cell autoimmunity, for the primary screening of which islet cell antibodies (ICA) were used. If the child developed ICA, all samples were also analyzed for insulin autoantibodies (IAA), GAD65 antibodies (GADA), and antibodies to the IA-2 molecule (IA-2A). RESULTS: The high- and moderate-risk genotypes were unevenly distributed among the three areas (P<0.001); the high-risk genotype was less frequent in the Oulu region (20.4%) than in the Turku (28.4%; P<0.001) or Tampere regions (27.2%; P<0.001). This genotype was associated with an increased frequency of ICA seroconversion relative to the moderate risk genotypes (hazard ratio 1.89, 95% CI 1.36-2.62). Seroconversions to ICA positivity occurred less commonly in Tampere than in Turku (0.47, 0.28-0.75), whereas the seroconversion rate in Oulu did not differ from that in Turku (0.72, 0.51-1.03). The Tampere-Turku difference persisted after adjustment for risk genotypes, sex, and time of birth (before January 1998 versus later). Seroconversion for at least one additional autoantibody was also less frequent in Tampere than in Turku (0.39, 0.16-0.82). CONCLUSIONS: These data show that in Finland, the country with the highest incidence of type 1 diabetes in the world, both the frequency of the high-risk HLA-DQB1 genotype and the risk of seroconversion to autoantibody positivity show geographical variation. The difference in seroconversion rate could not be explained by the difference in HLA-DQB1-defined disease susceptibility, implying that the impact of environmental triggers of diabetes-associated autoimmunity may differ between the three regions studied.

Autoantibodies↗
PubMed2003

Insulin autoantibody isotypes during the prediabetic process in young children with increased genetic risk of type 1 diabetes.

This work aimed to assess the maturation of the humoral immune response to insulin in preclinical type 1 diabetes by observing the emergence of various isotypes of insulin autoantibodies (IAA) in children with HLA-DQB1-conferred disease susceptibility. The series was derived from the Finnish Type 1 Diabetes Prediction and Prevention Study and comprised 15 IAA-positive children who presented with type 1 diabetes during prospective observation (progressors) and 30 children who remained nondiabetic (nonprogressors). An isotype-specific radiobinding assay was used to determine isotype-specific IAA (IgG1-4 and IgA) from samples obtained with an interval of 3-12 mo. The progressors had IAA of subclass IgG3 in their first IAA-positive sample more often than did the nonprogressors (13 of 15 versus 12 of 30; p = 0.003). Nine progressors had a dominant IgG1-IAA response initially, and six had a dominant IgG3-IAA response. The corresponding distribution among the nonprogressors was that 20 had a dominant IgG1-IAA response, none had an IgG3-IAA response, and three had a dominant response other than IgG1- or IgG3-IAA (chi(2)(df = 2) = 12.02; p = 0.002). The progressors had higher integrated levels (area under the curve) of IgG1-IAA (p = 0.05) and IgG3-IAA (p = 0.002). Nine progressors had a dominant integrated IgG1-IAA response and six had a dominant IgG3-IAA response over the observation period, whereas 22 nonprogressors had a dominant IgG1-IAA response, six had a dominant IgG2-IAA response, and one an IgG3-IAA response (chi(2)(df = 2) = 11.23; p = 0.004). Genetically susceptible young children who progress rapidly to clinical type 1 diabetes are characterized by strong IgG1 and IgG3 responses to insulin, whereas a weak or absent IgG3 response is associated with relative protection from disease.

Autoantibodies↗
PubMed2003

Prevalence of Celiac disease among children in Finland.

BACKGROUND: Wheat, rye, and barley proteins induce celiac disease, an autoimmune type of gastrointestinal disorder, in genetically susceptible persons. Because the disease may be underdiagnosed, we estimated the prevalence of the disease and tested the hypothesis that assays for serum autoantibodies can be used to detect untreated celiac disease and that positive findings correlate with specific HLA haplotypes. METHODS: Serum samples were collected from 3654 students (age range, 7 to 16 years) in 1994 and screened in 2001 for endomysial and tissue transglutaminase antibodies. HLA typing was also performed on stored blood samples. All antibody-positive subjects were asked to undergo small-bowel biopsy in 2001. RESULTS: Of the 3654 subjects, 56 (1.5 percent) had positive antibody tests, as determined in 2001. Results of the two antibody tests were highly concordant. As of 1994, none of the subjects had received a clinical diagnosis of celiac disease, but 10 who had positive tests for both antibodies in serum obtained in 1994 received the diagnosis between 1994 and 2001. Of the 36 other subjects with positive antibody assays who agreed to undergo biopsy in 2001, 27 had evidence of celiac disease on biopsy. Thus, the estimated biopsy-proved prevalence was 1 case in 99 children. All but two of the antibody-positive subjects had either the HLA-DQ2 or the HLA-DQ8 haplotype. The prevalence of the combination of antibody positivity and an HLA haplotype associated with celiac disease was 1 in 67. CONCLUSIONS: The presence of serum tissue transglutaminase and endomysial autoantibodies is predictive of small-bowel abnormalities indicative of celiac disease. There is a good correlation between autoantibody positivity and specific HLA haplotypes. We estimate that the prevalence of celiac disease among Finnish schoolchildren is at least 1 case in 99 children.

Adolescent↗
PubMed2003

Enterovirus infections are associated with the induction of beta-cell autoimmunity in a prospective birth cohort study.

Enterovirus infections have been associated with the manifestation of clinical type 1 diabetes in a number of reports, and recent prospective studies have suggested that enterovirus infections may initiate the autoimmune process, leading to the disease. In the present study, we analyzed the role of enterovirus infections in a Finnish birth cohort study, Diabetes Prediction and Prevention (DIPP), in which all newborn infants are screened for diabetes-associated HLA-DQB1 alleles, and those with an increased genetic risk are invited for prospective follow-up. Enterovirus infections were diagnosed by serology and reverse transcriptase-polymerase chain reaction (RT-PCR) from serum samples taken from birth every 3-6 months. Case children included 41 infants who became positive for diabetes-associated autoantibodies during the observation. Control children comprised altogether 196 infants who remained autoantibody negative and were matched for the time of birth, sex, and HLA-DQB1 alleles. Enterovirus infections were more frequent in case children than in control children (P = 0.004), and the average enterovirus antibody levels were also higher in the case children (P = 0.003). Enterovirus infections were particularly frequent during the 6-month period preceding the first detection of autoantibodies: 51% of the case children compared with 28% of the control children had an infection in that time interval (P = 0.003). There was no difference in the frequency of adenovirus infections between the groups (P = 0.9). The present results imply that enterovirus infections are associated with the appearance of beta-cell autoantibodies. A possible causal relationship is supported by the clustering of infections to the time when autoantibodies appeared.

Adenoviridae Infections↗
PubMed2003

Gonadal morphology and sex hormones in male and female Wistar rats after long-term lamotrigine treatment.

Drug-induced disturbances in reproductive hormones and gonadal morphology have been observed both in patients with epilepsy and in non-epileptic animals. Less is known about the influence of newer antiepileptic drugs including lamotrigine on reproduction. Lamotrigine is now increasingly used both in epilepsy and psychiatric disorders. Sixty-five Wistar rats were fed by gastric tube either 5 mg kg(-1) lamotrigine solution (males=15, females=20) or 0 (vehicle control, males=15, females=15) twice daily for 90 days. In males, no significant differences were found in body or testicular weight. Testicular atrophy was observed in one control animal and in two of the rats receiving lamotrigine. No morphological changes were seen in the other organs investigated (liver, kidney, pancreas, brain, lymphatic tissue, heart). None of the animals showed over-expression of p53. No significant differences were observed between the control rats and the male rats receiving lamotrigine regarding testosterone, FSH and LH. In females, no changes in ovarian morphology or alterations in other tissues were observed. Serum testosterone, FSH, LH, insulin and progesterone remained unchanged in the lamotrigine treated animals, while serum estrogen was significantly reduced.

Animals↗
PubMed2003

Nutritional risk predictors of beta cell autoimmunity and type 1 diabetes at a young age.

Type 1 diabetes is an immune-mediated disease characterized by a preclinical prodrome during which beta cell autoimmunity proceeds at a variable rate. Large geographic differences and a conspicuous increase in incidence, especially among young children since the 1950s, and the relatively low concordance in identical twins are factors that favor a critical role of environmental factors in the etiology of this disease. Only approximately 5% or fewer subjects with HLA-conferred genetic susceptibility to type 1 diabetes actually develop the clinical disease. Breastfeeding, nicotinamide, zinc, and vitamins C, D, and E have been reported as possibly protecting against type 1 diabetes, whereas N-nitroso compounds, cow milk, increased linear growth, and obesity may increase the risk. Thus far, only the significance of infant feeding, cow milk, and vitamin D have been studied in both case-control and cohort settings. The major shortcoming of most studies done so far is that only single dietary exposures have been assessed at single time points. Putative nutritional and other confounding factors have received little attention as have the limitations of the dietary methods used. There is little firm evidence of the significance of nutritional factors in the etiology of type 1 diabetes. The availability of good markers of preclinical type 1 diabetes and of genetic risk have decreased the sample sizes needed and made longitudinal cohort studies of the assessment of children's diets feasible.

Animals↗
PubMed2003

Increased frequency of islet cell antibodies in unaffected brothers of children with type 1 diabetes.

AIM: To assess the relation between islet cell antibody (ICA) positivity and demographic characteristics in an extensive series of first-degree relatives of children with type 1 diabetes (T1D). METHODS: Family members of children diagnosed with T1D before the age of 16 years and attending one of 27 participating paediatric units in Finland taking care of children with diabetes were invited to volunteer for an ICA screening program aimed at identifying individuals eligible for inclusion in the European Nicotinamide Diabetes Intervention Trial (ENDIT). The final series comprised 2,522 first-degree relatives (1,107 males) with a mean age of 20.4 (range 0.1-51.9) years, out of whom 390 were fathers, 622 mothers, 717 brothers, and 793 sisters of affected cases. RESULTS: Two hundred and four family members (8.1%) tested positive for ICA with levels ranging from 3 to 564 (median 18) Juvenile Diabetes Foundation (JDF) units. One hundred and five relatives (4.2%) had an ICA level of 18 JDF units or more. Males had detectable ICA more often than females (9.6 vs. 6.9%; p = 0.02). Antibody-positive family members under the age of 20 years had higher ICA levels than the older ones [median 18 (range 3-514) JDF units vs. 10 (range 3-564) JDF units; p = 0.008]. Among the adult relatives (>or=20 years of age) antibody-positive females had higher ICA levels than the males [median 10 (range 5-564) JDF units vs. 9 (range 3-130) JDF units; p = 0.04]. Siblings had an increased frequency of high-titre ICA (>or=18 JDF units) when compared to the parents (4.8 vs. 3.2%; p = 0.05). Among siblings, we found a higher frequency of ICA positivity in brothers than in sisters (10.8 vs. 6.9%; p = 0.01), and this was also true for high-titre ICA (6.0 vs. 3.8 %; p = 0.04). Geographically, the highest ICA prevalence was seen among relatives living in the middle of Finland (10.4 vs. 7.2% in the other parts of Finland; p = 0.01). CONCLUSIONS: These results imply that male gender and young age favour positive ICA reactivity among family members of children with T1D. Siblings test positive for high ICA titres (>or=18 JDF units) more frequently than parents. Accordingly, judged from demographic characteristics, the yield of ICA screening in first-degree relatives would be maximized by targeting young brothers of affected cases.

Adolescent↗
PubMed2003

Time-resolved fluorometric assay for detection of autoantibodies to glutamic acid decarboxylase (GAD65).

BACKGROUND: Type 1 diabetes mellitus results from destruction of the pancreatic insulin-producing beta cells by a chronic autoimmune process. Methods are needed for the detection of circulating autoantibodies to glutamic acid decarboxylase (GAD65), a major marker of this process. METHODS: Streptavidin-coated microtiter plates were incubated with biotinylated GAD65, and after incubation with serum samples from patients with type 1 diabetes mellitus and control individuals, europium-labeled GAD65 was added. After washing steps, the delayed fluorescence was measured in duplicate in a fluorometer. Samples collected from 100 patients with newly diagnosed type 1 diabetes mellitus and 100 healthy controls were measured by the new assay and by a radiobinding assay. RESULTS: The detection limit of the new assay was 1.49 WHO units/mL, the calibration curve was linear to 4140 WHO units/mL, and no hook effect was observed up to 41,400 WHO units/mL. The intraassay CV was 2.1-6.3% over the calibration range. For patient serum samples, the intraassay, interassay, and total CVs were 5.4-7.0%, 9.8-13%, and 12-14%, respectively. Compared with conventional radioimmunologic methods, the analytical range was broader and the analysis time required to perform the measurements was shorter. At a cutoff with 99% specificity, the new assay and the radiobinding assay were positive in 71 and 67 patients, respectively. CONCLUSIONS: The new assay provides a rapid and sensitive nonradioactive method applicable for large-scale screening for beta-cell autoimmunity. It has a broad linear analytical range, is easy to perform and automate, and has sensitivity and specificity comparable to those for the conventional radioisotope assay.

Adolescent↗
PubMed2003

Detection of autoantibodies to protein tyrosine phosphatase-like protein IA-2 with a novel time-resolved fluorimetric assay.

BACKGROUND: Circulating autoantibodies to pancreatic glutamic acid decarboxylase (GAD65; the 65-kDa isoform of glutamic acid decarboxylase), protein tyrosine phosphatase-like protein IA-2, and insulin can be used as predictive markers of type 1 diabetes. We developed a novel assay for the detection of IA-2 autoantibodies (IA-2As) in serum based on time-resolved fluorimetry, hypothesizing that this kind of assay could provide several advantages over methods described to date, including radiobinding assays (RBAs) and ELISAs. METHODS: The intracellular part of IA-2 (IA-2ic) was biotinylated and bound to streptavidin-coated 96-well plates by simultaneous incubation with serum samples and glutathione S-transferase (GST)-IA-2ic fusion protein. GST-IA-2ic captured by autoantibodies in the serum was detected with europium-labeled anti-GST antibody, and the signal was measured in a time-resolved fluorimeter. A serum sample panel from 100 patients with newly diagnosed type 1 diabetes and 100 unaffected controls was analyzed with the new assay and a conventional RBA. RESULTS: Among the 100 serum samples from patients with type 1 diabetes, the time-resolved fluorimetric assay identified 74 IA-2A-containing sera, whereas the RBA detected 80 IA-2A-positive samples. Five of the six samples positive in the RBA but not detected by the time-resolved fluorimetric assay were only weakly positive in the RBA. The performance time of the time-resolved fluorimetric assay was 2.5 h compared with 10-12 h required by the RBA. CONCLUSIONS: The time-resolved fluorimetric assay provides a simple, nonradioactive analysis method for the detection of IA-2As with a specificity and a sensitivity comparable to the RBA method. This assay allows substantial reduction in performance time compared with the conventional RBA.

Adolescent↗
PubMed2003

Vitamin D receptor polymorphisms: no association with type 1 diabetes in the Finnish population.

OBJECTIVE: The effect of polymorphisms of the vitamin D receptor (VDR) gene on susceptibility to type 1 diabetes has recently been investigated extensively. Several findings on positive disease associations have been observed and, in addition, a protective effect of vitamin D supplementation has been reported. DESIGN: We studied the effect of three vitamin D receptor gene polymorphisms (VDRA, VDRB, VDRF) on susceptibility to type 1 diabetes in a large case-control series (more than 2000 controls and about 1000 patients) from the Finnish population. METHODS: A combination of case-control and affected-family based approaches was used. Subjects were genotyped for VDRA (ApaI), VDRB (BsmI) and VDRF (FokI) single nucleotide polymorphisms using a minisequencing reaction. RESULTS: A few borderline significant associations were observed with both approaches used. In the case-control association analyses we found significant differences between cases and controls in frequencies of VDRB (P=0.024, all subjects and P=0.016, HLA DQB1*0302-positive subjects) and VDRF (P=0.0063, Turku cohort). In the total family set a decreased (39.3%) transmission of the VDRA-VDRB-VDRF haplotype 1-1-2 and an increased (60.3%) transmission of haplotype 2-1-2 to sons was seen (P=0.0059 and P=0.024 respectively). Transmission of the haplotype 2-2-1 to daughters was decreased (37.6%, P=0.022). Interestingly, we also observed significant differences in allele frequencies of the polymorphisms studied between populations from three different regions in Finland. CONCLUSIONS: All these differences disappeared after correction for multiple testing. We conclude that the single nucleotide polymorphisms analysed are unlikely to be associated with type 1 diabetes in the Finnish population.

Adolescent↗
PubMed2003

Androgen receptor gene exon 1 CAG repeat polymorphism in Finnish patients with childhood-onset type 1 diabetes.

OBJECTIVE: Animal models suggest that androgen receptor gene polymorphisms might affect disease predisposition in human immune-mediated diabetes. The aim of this study was to investigate the effect of the human androgen receptor gene exon 1 CAG repeat polymorphisms on type 1 diabetes (T1D) susceptibility. DESIGN AND METHODS: A combined strategy of case-control and family-based approaches was used. Affected sibling pair families (n=120), nuclear families (n=645) and cohorts of sporadic cases (n=208) and controls (n=1381) were genotyped for androgen receptor gene exon 1 CAG repeat polymorphism. An automated fluorescence-based DNA fragment-sizing method was used. RESULTS: The distribution of CAG repeat alleles did not differ significantly between patients and controls. However, short repeat alleles (7-14) were more prevalent among cases in girls compared with controls (8.77% vs 5.91%; P=0.03). Long repeat alleles (19-28) were less frequent among HLA DR3-positive diseased boys than in DR3-positive control boys (32.6% vs 40.6%; P=0.011). The differences were not significant after adjustment for multiple comparisons. Transmission of CAG repeat alleles was not different from expected in the total material. However, transmissions to girls deviated from the expected value significantly (extended transmission disequilibrium test (ETDT) 37.82; P=0.0016). A decreased transmission of the alleles with 13, 20 and 26 repeats to girls was observed (T%0, P=0.046; T%25.5, P=0.0003, T%0, P=0.025). CONCLUSION: The results do not support a common role for the androgen receptor gene exon 1 CAG repeat in T1D susceptibility; however, an effect of a disease variant in linkage disequilibrium could be detected.

Adolescent↗
PubMed2003

A simulation model for estimating direct costs of type 1 diabetes prevention.

BACKGROUND: The ongoing Type 1 Diabetes Prediction and Prevention Project in Finland (DIPP) is based on screening of genetic type 1 diabetes mellitus susceptibility, subsequent autoantibody follow-up and experimental preventive treatment with nasal insulin. OBJECTIVE: To analyse direct costs of type 1 diabetes prevention therapy with nasal insulin as it is now being studied in the DIPP project, and as it might be used as a part of routine healthcare in Finland. DATA AND METHODS: For the purposes of cost analysis, two different diabetes prevention models were constructed. The research-oriented model followed accurately the DIPP protocol and the practice-oriented model was based on the estimates of a panel of experts on how the prevention would be conducted as a part of the routine healthcare in Finland. To take into account the uncertainty and variability attached to the use of resources, a Monte Carlo simulation model was utilised. The costs of the two models comprising 500 iterations each were simulated using the Monte Carlo model. STUDY PERSPECTIVE: This study was performed from the healthcare provider's viewpoint. RESULTS: The total direct costs per person of the research-oriented model were 2102 and 1676 euros (EUR) in the first and second year and those of the practice-oriented model EUR827 and EUR675, respectively (EUR1 approximately dollars US1.1; 2002 values). Subsequently, the costs rose only as a result of the increased use of insulin as the children grew older. After the 15th year, when the age structure of the population in the study had stabilised, the annual direct costs per person were EUR1798 (research-oriented model) and EUR797 (practice-oriented model). CONCLUSIONS: The costs of prevention with nasal insulin are low when compared with estimates of the annual healthcare costs of type 1 diabetes. This study suggests, with some critical assumptions (in particular, that nasal insulin is effective in the prevention of type I diabetes), that a 2 to 3-year delay in the disease onset may make prevention according to the practice-oriented model cost saving.

Administration, Intranasal↗