Chymotrypsin-reactive antibodies in insulin-dependent diabetes mellitus

In a previous study (Frazieret al., 1990), it was demonstrated that two patients with type 1 (insulin-dependent) diabetes mellitus had antibodies in their serum which reacted with four 29 kDa pancreas-specific proteins on two-dimensional immunoblots. This paper reports on the purification and identification of these pancreatic proteins. The protein with the pI closest to pH7 was purified through the use of ammonium sulfate fractionation and ion-exchange chromatography. Gel filtration chromatography established that the protein's molecular weight was closer to 25 kDa. Amino acid composition and sequence analyses demonstrated homology between the protein and chymotrypsin. It is suggested that an abnormal regulation of chymotrypsin activity might be related to antibodies formed in some diabetic patients.     

Zinc kinetics in insulin-dependent diabetes mellitus patients

Zinc has an important role in the control of carbohydrate metabolism, and diabetic patients are at risk for zinc deficiency. However, there are conflicting data concerning nutritional zinc status. In order to investigate this topic, 10 normal and 10 insulin-dependent diabetic patients were studied following venous zinc tolerance test. Our results found no evidence of zinc deficiency or of changes on the kinetic parameters of zinc in patients with insulin-dependent diabetes mellitus following a venous zinc tolerance test.     

Influence of maternal insulin-dependent diabetes mellitus on neonatal morbidity.

OBJECTIVE: To compare the neonatal morbidity rates (corrected for gestational age at delivery and method of delivery) among infants of women with insulin-dependent diabetes mellitus and those of women without diabetes. DESIGN: Historical cohort analysis. SETTING: Tertiary care centre. PATIENTS: All liveborn infants of women with insulin-dependent diabetes mellitus (IDM group) born between Jan. 1, 1980, and Dec. 31, 1989, each matched for gestational age at delivery, method of delivery and year of birth with two newborns of women without diabetes (control group). MAIN OUTCOME MEASURES: Neonatal respiratory distress, jaundice, hypoglycemia, polycythemia, hypocalcemia, intraventricular hemorrhage, seizure and macrosomia. RESULTS: There were 230 infants in the IDM group and 460 in the control group. Compared with the control group the IDM group had significantly higher incidence rates of glucose infusion (odds ratio [OR] 5.38), birth weight above the 90th percentile (OR 4.15) and neonatal jaundice (OR 1.94). No significant difference was found in the incidence rate of respiratory distress, polycythemia or hypocalcemia. The maternal serum hemoglobin A (HbA) level was not significantly related to birth weight, and neither the serum HbA level nor the presence of macrosomia was predictive of neonatal morbidity. Nearly 25% of the infants in the IDM group were born before 37 weeks'' gestation; 48.2% of these were delivered early because of maternal hypertension. CONCLUSIONS: Neonatal morbidity in infants of women with diabetes is determined more by gestational age at delivery than by the maternal diabetes. Within the limits obtained in this study the degree of control of the diabetes does not seem to affect neonatal morbidity.     

HLA DR antigens and susceptibility to insulin-dependent diabetes mellitus.

Two novel analytic methods to evaluate the roles of the HLA alleles of the human major histocompatibility complex in disease predisposition have been formulated and applied to insulin-dependent diabetes mellitus (IDDM). The HLA-DR antigens, as they are presently defined, are shown not to directly predispose individuals to IDDM. This result does not discount the possibility that subdivision of the DR antigens will yield the predisposing agents. In Caucasian populations, after consideration of the predisposing effect of the antigens DR3 and DR4, the protective effect of DR2 in predisposition is demonstrated. Additionally, DR1 and possibly DRw8 exhibit a higher than expected frequency in patients.     

Insulin clearance during hypoglycemia in patients with insulin-dependent diabetes mellitus.

Eight male patients with insulin-dependent diabetes mellitus (IDDM) without residual beta-cell function were studied on two occasions in random order. In one experiment hypoglycemia was induced by a constant rate iv infusion of insulin (0.034 U/kg/h) during 150 minutes. At the other occasion an identical infusion of insulin was given, but this time euglycemia was maintained by a variable iv infusion of glucose. Plasma levels of free insulin were almost identical during the two experiments indicating that insulin clearance is not influenced by hypoglycemia in patients with IDDM.     

Pituitary responsiveness to thyrotropin releasing hormone in insulin-dependent diabetes mellitus.

The pituitary responses to the intravenous administration of 200 mg of Thyrotropin Releasing Hormone were investigated in 14 poorly controlled insulin dependent diabetic males and in nine matched controls. The mean TSH and prolactin responses in the two groups were similar although both tended to be lower in the diabetics. There was a small FSH rise in 11 of the 23 subjects.     

Prolactin response to TRH in insulin-dependent diabetes mellitus

17 obese women were examined, 8 of which were diabetic and 9 affected only by essential obesity. These patients, all of whom had become obese during adult life and 8 control subjects were tested for IRI, GH and PRL levels in basal conditions and after infusion of TRH. In the obese and diabetic women fasting GH values were normal while IRI levels were higher than those of the control subjects. In all cases neither IRI nor GH variations during TRH stimulation test. There was no difference in the plasma levels of PRL between the 3 groups when examined in basal conditions. After TRH the hormone increased considerably in all the subjects. In the obese and diabetic obese women the incremental area did not present different values from those observed in the control subjects. In conclusion in insulin-independent diabetes, as in essential obesity, the pharmacological stimulus did not show any evident alteration of the specific hypofisary receptorial system that regulates the secretion of PRL and GH.     

Cellular mechanisms involved in experimental insulin-dependent diabetes mellitus

Many tissue-specific autoimmune diseases are mediated by the induction of autoantigen-specific T cells. These cells are believed to cause tissue damage through the production of cytokines, through direct lysis of cells expressing self-antigens, or through the induction of inflammatory responses. The escape from self-tolerance or anergy is a prerequisite for initiation of an autoimmune process. INS-HA (insulin-hemagglutinin) transgenic mice express the HA of A PR8 34 influenza virus in the pancreatic beta-cells under the rat insulin promotor. TCR-HA (T cell receptor-hemagglutinin) transgenic mice express the TCR specific for the immunodominant epitope HA110-120 from the same virus. Double transgenic (dTg) mice expressing both genes represent an excellent model for understanding the mechanism leading to autoimmune diabetes independently of susceptibility genes. In order to gain information on the breaking down of neonatal self-tolerance we studied the occurrence of insulin dependent diabetes mellitus (IDDM) after birth. Our results showed that newborn mice develop fulminant IDDM characterized by occurrence of insulitis as early as 3 days after birth, followed by hyperglycemia by 7 days, and significant hypoinsulinemia by 28 days. Such "double transgenic" mice expressing wild-type or targeted IL-4R alpha genes were examined for the onset of IDDM. Eight of eleven mice homozygous for the wild-type IL-4R alpha were hyperglycemic by 8 weeks of age, whereas only 1 of 16 mice homozygous for the targeted allele were hyperglycemic at this time. Most IL-4R alpha -/- mice remained normoglycemic to 36 weeks of age. Although only 10% of double transgenic mice homozygous for wild-type IL-4R alpha allele survived to 30 weeks, 80% of mice homozygous for the targeted allele did so. Even as late as 270 days of age, mice homozygous for the targeted allele had no insulitis or only peri-insulitis. Heterozygous mice displayed an intermediate frequency of diabetes. The IL-4R alpha chain acts as the high affinity binding chain and the principal signaling chain for IL-4; it also acts as the signaling chain for IL-13, but in this case the IL-13R alpha 1 chain conveys the bulk of the cytokine specificity. Thus, IL-4R alpha knock-out mice are unresponsive to both IL-4 and IL-13. The finding that the lack of IL-4R alpha chain protects TCR-HA, INS-HA double transgenic mice against diabetes, and death implies that either IL-4 or IL-13 plays a role in the progression of this disease. These studies demonstrate that TCR-HA, INS-HA double transgenic mice may provide a useful model to evaluate new strategies for the prevention of diabetes.     

A combined segregation and linkage analysis of insulin-dependent diabetes mellitus.

In an effort to clarify the mode of inheritance of insulin-dependent diabetes mellitus (IDDM), a total of 230 nuclear families with pointers were analyzed using the computer program COMBIN. Each family was ascertained without deliberate selection for multiplex families, and most families were completely typed for HLA-B, HLA-DR, and properdin factor B (Bf). There were 186 families with normal parents, 44 families with one affected parent, and no families with two affected parents. The computer program COMBIN evaluates evidence for a major locus of disease susceptibility, linkage of the major locus to a known genetic marker locus, linkage disequilibrium between the marker haplotypes and disease susceptibility, pleiotropic effects, and presence of an unlinked modifier. The parameters of COMBIN are T, Q, and D, representing the displacement, gene frequency of the IDDM allele, and dominance, respectively, of the major locus--and TM, QM, and DM being the analogous parameters of the modifier. In addition, the recombination fraction, theta, between the IDDM locus and HLA as well as the coupling frequencies are estimated. Finally, COMBIN simultaneously performs segregation and linkage analysis, with the optimal model being adjusted by the fit to the haplotype sharing distribution of IDDM. The results of these analyses indicated that the best-fitting genetic model of diabetic susceptibility appears to be a single major locus with near recessivity on a scale of standardized genetic liability, with gene frequency of the IDDM susceptibility allele of approximately 14%. In addition, the recombination fraction between the major locus and HLA is zero in all models; that is, for the B-BF-DR haplotype, the IDDM locus is tightly linked, probably (according to data from previous studies) to HLA-DR. Information determined by magnitude of coupling frequencies indicated that there is significant positive linkage disequilibrium with the haplotypes B8-BfS-DR4 and B15-BfS-DR4, significant negative linkage disequilibrium with B7-BfS-DR2, and intermediate disequilibrium for B8-BfS-DR3, B18-BfF1-DR3, and B40-BfS-DR4. Significant evidence in favor of an unlinked (to HLA) modifier (either single major locus or polygenes) could not be demonstrated. In conclusion, genetic susceptibility to IDDM appears to be most consistent with a single major locus with near recessivity that is tightly linked to HLA.     

Anti-thyroid autoantibodies in children with insulin-dependent diabetes mellitus

The study was aimed at the assessment of frequency of occurrence of thyroid antimicrosomal and antithyreoglobuln autoantibodies in children with insulin-dependent diabetes and healthy control children. The occurrence of thyroid autoantibodies was analyzed with respect to the age and sex of children and the duration of the disease. The studied group was composed of 199 children of age between 2 and 17 years with insulin-dependent diabetes. Control group included 100 healthy children. Thyroid autoantibodies were determined by using a solid phase radioimmunoassay. Antimicrosomal antibodies were detected in 35% of diabetic children, but only in 1% of healthy children. Neither in diabetic nor in control children the occurrence of antithyreoglobulin antibodies was significant. The frequency of occurrence of antimicrosomal antibodies was not related to age of children or the duration of diabetes. The occurrence of these antibodies was significantly more frequent in girls (in 70% of cases) than in boys (30% of cases).     

Plasmapheresis in the initial treatment of insulin-dependent diabetes mellitus in children.

Several factors indicate that autoimmune mechanisms may play a part in the aetiology of insulin-dependent diabetes mellitus. At the onset of the disease in 10 children (aged 11-16 years) plasmapheresis was performed four times over one to two weeks. Seventeen age-matched children with the same clinical features served as controls. The C-peptide concentrations at onset were the same in the two groups, but after one month the children treated with plasmapheresis had significantly higher values. This difference became even more pronounced after three, nine, and 18 months, both during fasting and at the maximum response to a standardised meal. The study group also had a significantly more stable metabolism, longer partial remission, and no higher insulin requirement. Of the 10 treated children islet-cell cytoplasmic antibodies were present in seven before plasmapheresis and in nine during treatment. The antibodies remained detectable in five and six out of nine patients at one and six months respectively after plasmapheresis. Although the mechanisms are obscure, plasmapheresis performed at the onset of insulin-dependent diabetes mellitus may help to preserve beta-cell function.     

Genetic markers and insulin-dependent diabetes mellitus (IDDM) in Sardinia.

The distributions of some genetic markers in 106 Sardinian individuals with insulin-dependent diabetes mellitus (IDDM) and in a control sample of 186 nondiabetic Sardinians were studied. A strong association of IDDM with some phenotypes of ACP, PGM1, C3 and GC genetic markers was found. In the IDDM patients there is a significant increase of ACP B, ACP B-C, PGM1 1S-1F and GC 1S-2 phenotypes. Particularly the individuals with the ACP B, PGM1 1S-1F and GC 1S-2 phenotypes show the highest values of the relative risk (RR) and the attributable risk (AR) and seem to be more susceptible to IDDM disease.     

Erythrocyte membrane acetylcholinesterase in type 1 (insulin-dependent) diabetes mellitus.

1. The erythrocyte membrane acetylcholinesterase activity is significantly (P less than 0.001) decreased in insulin-dependent diabetes mellitus. 2. The activity is negatively correlated (r = -0.97) with the fasting blood glucose level. 3. Insulin treatment restores the activity to normal. 4. The Km of the enzyme for acetylthiocholine iodide was unchanged; however, the Vmax. was decreased, suggesting a decrease in the number of active enzyme molecules in diabetes.     

Modifications in platelet membrane transport functions in insulin-dependent diabetes mellitus and in gestational diabetes.

The pathogenesis of plasma membrane alterations present in diabetes mellitus is unclear. To add new insights to the question, platelet membrane properties were evaluated in 16 women presenting impaired glucose tolerance at the 28-29th week of gestation (GDM) and in 8 women with insulin-dependent diabetes mellitus (IDDM). 15 healthy pregnant women (HPW) and 21 healthy non-pregnant (HNPW) women were the control group for GDM and IDDM, respectively. Pregnancy (HPW vs. HNPW) provoked an increase in Ca(2+)-ATPase activity and a decrease in membrane fluidity; in contrast, Na+/K(+)-ATPase, intracellular free Ca2+ concentrations, membrane cholesterol and phospholipid content did not vary. Both GDM and IDDM showed lower Na+/K(+)-ATPase activity and higher Ca2+ concentration, compared to HPW and HNPW, respectively, whereas Ca(2+)-ATPase activity was higher only in IDDM; furthermore, membrane fluidity was lower in GDM and higher in IDDM. Finally, GDM showed higher membrane cholesterol content. Both GDM and IDDM showed a very good metabolic control so that variations reported cannot be due to hyperglycemia; it is tempting to suggest that membrane variations are present before the clinical metabolic alteration. Furthermore, both GDM and IDDM were on insulin therapy, therefore: (i) insulin may be the pathogenetic factor of higher intracellular free Ca2+ concentrations and lower Na+/K(+)-ATPase activity since they both varied accordingly in GDM and IDDM, but not of (ii) changes in Ca(2+)-ATPase, membrane fluidity and cholesterol content which did not vary accordingly in GDM and IDDM.