Complementation and maternal effect in insulin-dependent diabetes.

The marker association segregation chi-square (MASC) method was applied to a sample of 416 Caucasians affected with insulin-dependent diabetes mellitus (IDDM), for which information on the parental and sibship status was available, as well as HLA typing. We show that the model which best explains all the observations assumes a cis or trans complementation of two tightly linked genes within the HLA region, an additional maternal effect, and other familial factors. The HLA molecule corresponding to the complementation of Arg52(+) and Asp57(-) has been recently proposed as explaining susceptibility to IDDM. However, this hypothesis does not account for the overall observations made on the HLA marker in IDDM patients and their relatives. The MASC method may also be applied to evaluate the risk for relatives of an affected individual (the "index"). For example, the risk for a sib depends not only on the parental status and on the number of HLA haplotypes he shares with the index, but also on which haplotype the index himself inherited from his mother and father.     

A maternal hypomethylation syndrome presenting as transient neonatal diabetes mellitus

The expression of imprinted genes is mediated by allele-specific epigenetic modification of genomic DNA and chromatin, including parent of origin-specific DNA methylation. Dysregulation of these genes causes a range of disorders affecting pre- and post-natal growth and neurological function. We investigated a cohort of 12 patients with transient neonatal diabetes whose disease was caused by loss of maternal methylation at the TNDM locus. We found that six of these patients showed a spectrum of methylation loss, mosaic with respect to the extent of the methylation loss, the tissues affected and the genetic loci involved. Five maternally methylated loci were affected, while one maternally methylated and two paternally methylated loci were spared. These patients had higher birth weight and were more phenotypically diverse than other TNDM patients with different aetiologies, presumably reflecting the influence of dysregulation of multiple imprinted genes. We propose the existence of a maternal hypomethylation syndrome, and therefore suggest that any patient with methylation loss at one maternally-methylated locus may also manifest methylation loss at other loci, potentially complicating or even confounding the clinical presentation.Electronic Supplementary Material Supplementary material is available to authorised users in the online version of this article at .     

Influence of maternal diabetes on lipid metabolism in neonatal rat lung

The effect of maternal diabetes on tissue constituents, lipid metabolism and glucose utilization was examined in 1-day old rat lungs. Maternal diabetes was induced by intravenous injection of streptozotocin (50 mg/kg body weight) into pregnant Long-Evans hooded rats on the 10th day of gestation resulting in a maternal serum glucose concentration which was 3-fold higher than that of controls. Neonates from diabetic mothers showed a significant decrease in body weight (14%), lung weight (32%) and lung protein concentration (30%). Glycogen, DNA and lipid content of the lungs were significantly elevated in neonates from diabetic mothers. The percent of total phospholipid made up of phosphatidylcholine was not altered, but the percentage of disaturated phosphatidylcholine was decreased (25%). The activity of the CDPcholine pathway enzymes (choline kinase, cholinephosphate cytidylyltransferase and choline phosphotransferase) also showed a marked increase in lungs of neonates from diabetic mothers. Lung slices of neonates from diabetic mothers showed depressed in vitro incorporation of [U-¹⁴C]glucose into neutral lipids and decreased oxidation to CO₂. The results of these investigations show that maternal diabetes interferes with the structural and metabolic processes by which the undifferentiated lung becomes functional at birth.     

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.     

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.     

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.     

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.     

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.     

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).