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PH Riihimaa, M Knip, A Ruokonen and P Tapanainen

OBJECTIVE: To evaluate the interaction between serum free insulin, insulin-like binding protein (IGFBP)-1 and leptin concentrations during puberty in insulin-dependent diabetes mellitus (IDDM). DESIGN: Adolescent patients with IDDM (n=101, age >9 years, duration >2 years) from the Outpatient Clinic of the Department of Pediatrics at Oulu University Hospital, and non-diabetic controls, were recruited to the study. Free insulin, IGFBP-1, leptin and insulin antibody concentrations were measured from a fasting serum sample. RESULTS: Free insulin concentrations were lower in the patients than in the controls (4.3+/-2.3 mU/l compared with 6.5+/-3.1 mU/l, P<0.001), and there was an inverse correlation between free insulin and fasting blood glucose in the boys with diabetes (r=-0.53, P<0.001), whereas a positive correlation was observed between free insulin and leptin concentrations in the girls with diabetes (r=0.30, P=0.020). The IGFBP-1 concentrations were greater in the patients than in the controls (16.5+/-10.6 microg/l compared with 4.0+/-3.3, P<0.001), and they correlated significantly with blood glucose (r=0.63, P<0.001) and free insulin (r=-0.35, P<0.001). No significant difference was observed in the leptin concentrations between the patients and controls overall, despite greater total body fat in the girls with diabetes compared with the control girls. CONCLUSIONS: Adolescents with IDDM are characterised by morning hypoinsulinaemia and high circulating IGFBP-1 concentrations, which may contribute to insulin resistance and impaired metabolic control during puberty. The mechanism behind the increased total body fat in the postpubertal female patients remains to be determined.

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F. Koivusalo, J. Leppäluoto, M. Knip and H. Rajaniemi

Abstract.

Isolated rat pancreatic islet extracts were submitted to reverse phase high pressure chromatography (HPLC) and assayed for thyrotrophin releasing factor (TRF), glucagon and insulin in radioimmunoassays (RIA). Our anti-TRF serum was prepared by immunizing rabbits with TRF conjugated to bovine thyroglobulin (bTG) by bisdiazobenzidine. Anti-glucagon and anti-insulin sera were from a commercial source (Novo, Denmark). The concentrations of TRF, glucagon and insulin were 0.05 ± 0.02, 0.06 ± 0.02 and 1.0 ± 0.2 pmol/islet, respectively.

Formalin-fixed pancreatic sections were stained for TRF, glucagon and insulin by peroxidase, antiperoxidase (PAP) complex method. When the adjacent sections were stained for glucagon or insulin, it was observed that TRF and glucagon-specific peroxidase reactions were confined to the marginal islet cells, but insulin reactions to the central cells. The TRF-specific peroxidase reaction was clearly reduced when the anti-TRF serum was adsorbed with TRF-TG-Sepharose, whereas it was unchanged when the antiserum was pre-incubated with synthetic TRF.

The present HPLC results suggest that the islets contain TRF. Immunocytochemical studies show that the TRF-immunoreactive material, either synthesized or bound, is localized in the marginal islet cells.

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SG Hartling, M Knip, ME Roder, B Dinesen, HK Akerblom and C Binder

OBJECTIVE: To follow proinsulin immunoreactive material (PIM) in healthy siblings from the time of diagnosis of insulin-dependent diabetes mellitus (IDDM) in the proband, for at least 2 years. DESIGN AND METHODS: The study comprised 148 siblings representing 112 families. The siblings were recruited from the nationwide 'Childhood Diabetes in Finland' study and tested for immunological markers. If a sibling was found positive for islet cell antibodies (ICA) or insulin autoantibodies (IAA), PIM sampling was extended beyond 2 years. RESULTS: Of the 148 siblings, 12 developed IDDM 3-53 months after the diagnosis in the proband. Eleven of these siblings exhibited initially normal PIM concentrations. In nine siblings, samples were available both more than 6 months and during the last 6 months before the diagnosis of IDDM; PIM concentrations increased in seven, remained unchanged in one, and decreased in one in the period up to the diagnosis of IDDM (P < 0.05). Median PIM concentration did not change significantly during the examination period of 2 years in the 136 siblings who did not contract IDDM. Constantly increased PIM concentrations were found in 12 of the 136 siblings who did not develop IDDM. These 12 siblings were all ICA negative. CONCLUSION: In healthy siblings of IDDM patients exhibiting an initially low PIM concentration, an abrupt increase in PIM seems to precede the clinical manifestation of IDDM within 0-6 months. However, there were too few patients available to close follow-up to allow calculation of any predictive value of this increase. Persistently increased PIM concentrations were present in some healthy siblings who did not develop IDDM. The reason for that finding remains unclear, but it could be associated with previous B cell damage.

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PENTTI LAUTALA, MIKAEL KNIP, HANS K. AKERBLOM, KAUKO KOUVALAINEN and JULIO M. MARTIN

Abstract

Pathogenesis and etiology of the various clinical features of the Prader-Willi syndrome (PWS) are not completely understood. There is evidence suggesting a hypothalamic abnormality leading to hypogonadism in this syndrome. To test the possible hypothalamic involvement in the pathogenesis of obesity in these patients we studied the sera of 5 patients with PWS for insulin-releasing activity of possible hypothalamic origin. In addition 4 patients with a PWS-like syndrome and 6 obese patients with signs of central nervous system damage were studied. All five patients with PWS showed significant insulin-releasing activity in their sera. Of the four patients with PWS-like symptoms three showed similar activity while three of the obese patients with central nervous system damage had this activity in their sera. Serum insulin-releasing activity has been shown earlier to be associated with childhood obesity and it could play a role in the pathogenesis of obesity in PWS.

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H Turpeinen, R Hermann, S Vaara, AP Laine, O Simell, M Knip, R Veijola and J Ilonen

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.

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Z Gombos, R Hermann, R Veijola, M Knip, O Simell, P Pollanen and J Ilonen

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.

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P Tapanainen, M Knip, L Risteli, L Kemppainen, ML Kaar and J Risteli

To evaluate the role of collagen metabolites in the prediction of the response to GH treatment we measured the serum concentrations of the C-terminal propeptide of type I procollagen (PICP) and the N-terminal propeptide of type III procollagen (PIIINP) with specific RIAs in 35 short children (16 boys) before and after 5 days, 5 weeks and 3 months of GH therapy. The mean age of the children was 10.3 years (range 1.9-16.4 years) and the bone age ranged from 1.2 to 12.5 years (mean 7.6 years). The initial mean relative height (RH) was -3.6 SDS (range -6.6 to -2.4 S.D.). Nineteen children were found to have GH deficiency (GHD; peak GH responses in two pharmacological tests < 10 micrograms/l), while the remaining 16 were considered to have undefined short stature (USS). The children were treated with recombinant human GH (0.1 U/kg given subcutaneously at bedtime 6-7 times/week). The increases in RHI over the first 6 and 12 months of therapy were used as response measures. There was already a significant increase (P < 0.001) in both the serum PICP and PIIINP levels at 5 days, and the concentrations continued to rise up to 3 months, PICP levels rising less than the PIIINP levels. In the whole group the RHI over 6 months correlated most strongly with the absolute PICP concentrations at 3 months (rS = 0.59; P < 0.05), while the absolute PIIINP concentrations at 3 months showed the strongest relation to the one year RHI (rS = 0.69; P < 0.001). In the GHD group the 6 month RHI was most strongly related to the absolute PICP concentration at 3 months (rS = 0.59; P < 0.05). In the USS group the absolute PICP concentrations at 3 months correlated most strongly with the one year RHI (rS = 0.82; P < 0.01). Significant correlations were also observed between the absolute PIIINP levels at 3 months and the 6 month RHI (rS = 0.60; P < 0.05) and 12 month RHI (rS = 0.76; P < 0.01) in this group. These results show that GH therapy results in an unequivocal increase in circulating concentrations of PICP and PIIINP. The serum PICP and PIIINP concentrations may be of value in the prediction of the long-term response to GH therapy.

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T Lopponen, AL Saukkonen, W Serlo, P Tapanainen, A Ruokonen, P Lanning and M Knip

OBJECTIVE: Children with shunted hydrocephalus experience slow linear growth in prepuberty, accelerated pubertal maturation and a reduced final height. A substantial proportion of these patients have a poor growth hormone (GH) response to stimulation and reduced pituitary volume. The basic mechanisms behind these phenomena are still unknown, but one can hypothesize that an unphysiological intracranial pressure (ICP) may be involved. This study was undertaken to investigate the effect of increased ICP on pituitary function. DESIGN: Twenty-one children (nine males) aged 4 months to 15 years were evaluated for pituitary function before and after their first shunting operation. METHODS: A clinical examination was performed, bone age was determined and a combined pituitary stimulation test was performed to evaluate GH, luteinizing hormone, follicle-stimulating hormone, cortisol, thyrotropin and prolactin secretion. RESULTS: GH concentrations were significantly higher 10 and 15 min before the operation (P=0.04 and P=0.03 respectively) than after it. The basal levels of insulin-like growth factor-I (IGF-I) tended to be higher before the operation than afterwards and those of its binding protein-3 (IGFBP-3) were significantly so (P<0.01). CONCLUSIONS: The higher GH response to GH releasing hormone and circulating IGFBP-3 levels in children with hydrocephalus before compared with after their first shunting operation raise the possibility that the reduced GH secretion and retarded linear growth observed in children with shunted hydrocephalus may be a consequence of decreased ICP and/or the lack of physiological pressure variations.