Michael S. Kappy

Maturity-Onset Diabetes of Youth in Black Americans

Twelve of 129 black patients with youth-onset diabetes were identified as having an unusual clinical course, with apparent insulin dependence at the time of presentation followed by absence of dependence months to years later. This atypical form of diabetes was found in at least two generations in 9 of the 12 families of the propositi. Fourteen of the diabetic relatives, as well as the 12 propositi, were studied. Islet-cell autoantibodies were not found in any of the patients, and thyroid microsomal auto-antibodies were found in only one. The frequencies of the insulin-dependent-diabetes-associated antigens HLA-DR3 and DR4 were not increased among the propositi, and diabetes did not cosegregate with HLA haplotypes in the informative families. Insulin secretion, as measured by C-peptide responses to a liquid mixed meal (Sustacal), was intermediate between secretion in nondiabetic controls and that in patients with classic insulin-dependent diabetes. Peripheral-blood monocytes expressed increased numbers of insulin receptors as well as decreased empty-site affinities. The atypical form of diabetes in black Americans can be distinguished from classically defined insulin-dependent diabetes and may be best classified as a form of maturity-onset diabetes of youth.

Increased Integrated Concentration of Norepinephrine, Epinephrine, Aldosterone, and Growth Hormone in Patients with Uncontrolled Juvenile Diabetes Mellitus

SUMMARY The 24-h integrated plasma concentration of glucose (IC-glucose), norepinephrine (IC-NE), epinephrine (IC-E), cortisol (IC-F), growth hormone (IC-QH), aldosterone (IC-ALDO), and plasma renin activity (IC-PRA) were measured in 11 nonobese juvenile-onset nonke-totic diabetic patients exhibiting hyperglycemie and glycosuria and 34 matched control subjects using a portable pump, drawing blood at a constant rate through a nonthrombogenic i.v. catheter. The diabetic patients had a noticeable rise of their IC-NE, IC-E, IC-GH, and IC-ALDO. There was no significant difference between the IC-F and IC-PRA of the patients and the control subjects.

Studies of Insulin Binding in Children Using Human Erythrocytes in Small Amounts of Blood

We have demonstrated specific insulin binding by the erythrocytes (RBCs) of children. Complete binding studies were done using as little as 5 ml of blood. The receptors exhibited competition-inhibition curves and nonlinear Scatchard plots similar to those reported for insulin target tissues, such as the hepatocyte and the adipocyte. Compared with those from adults, the RBCs from children had significantly greater numbers of insulin receptors per cell (P < 0.05). The total insulin bound by the RBCs from both children and adults, however, was not different over the physiologic range of insulin concentrations. Cord blood RBCs showed greater numbers of receptors per cell than did those from either children or adults; however, the affinity for insulin was similar in both groups. The total amount of insulin bound by cord blood was significantly greater than that in either children (P < 0.01) or adults (P < 0.05) over the physiologic range of insulin concentrations. The method used to measure insulin binding by erythrocytes had relatively little intra- and interassay variability, and there was little diurnal variation in binding. Storage of heparinized blood at 4°C for 24-36h had no effect on insulin binding by the RBCs. We conclude that the measurement of insulin binding by RBCs from small volumes of blood may be particularly useful in the study of infants and children with disorders of carbohydrate metabolism to elucidate the role, if any, of abnormal receptor function in their condition.

INSULIN IS A GROWTH-PROMOTING PEPTIDE IN THE RAT BRAIN

Previous work in this laboratory documented specific insulin binding (IB) in various areas of the developing rat brain (J Neurochem, Jan. 1984, in press). IB was correlated with brain growth and increments in protein content in these areas during the first 21 days of postnatal life, supporting our hypothesis that insulin stimulates brain growth directly.We recently studied the effect of insulin on protein and nucleic acid synthesis in newborn rat brain glial cells in culture to further substantiate the role of insulin as a growth factor for the brain.IB to glial cells is rapid, reversible and specific (particularly with respect to insulin-like growth factors which competed only 3% as well as insulin for binding). Insulin stimulated the incorporation of valine into glial cell protein beginning at a concentration of 0.8nM. The stimulation was dose-dependent and became significant at 3.5nM, which was well below the empty site dissociation constant for IB by glial cells. A dose-dependent stimulation of thymidine incorporation into DNA nucleo-protein was also seen, but at higher concentrations of insulin.The studies document that glial cells have specific receptors for IB. In addition, and of particular importance, glial cells in culture are target cells for insulin with respect to those metabolic processes (i.e. protein and nucleic acid synthesis) which mediate brain growth.

STUDIES OF 3β-HYDROXYSTEROID DEHYDROGENASE (3β-HSD) GENES IN INFANTS AND CHILDREN MANIFESTING PREMATURE PUBARCHE (PP) AND INCREASED ACTH STIMULATED Δ5 STEROID LEVELS. † 573

STUDIES OF 3β-HYDROXYSTEROID DEHYDROGENASE (3β-HSD) GENES IN INFANTS AND CHILDREN MANIFESTING PREMATURE PUBARCHE (PP) AND INCREASED ACTH STIMULATED Δ5 STEROID LEVELS. † 573

1217 DEVELOPING RAT BRAIN (RB) BINDS MONOIODINATED INSULIN ISOMERS SIMILAR TO OTHER EXTRAHEPATIC TARGET TISSUES

Considerable interest in the relationship between insulin and the brain has developed since Havrankova et al reported insulin and insulin receptors in RB in 1978. There is evidence that insulin may be synthesized in RB, and that the insulin/insulin receptor system in RB is functionally separate from that in the periphery. Recently, we documented that insulin stimulates protein and nucleic acid synthesis in glia from newborn RB, and established that the developing RB is a target tissue for insulin.We studied the relative binding of monoiodinated insulin isomers (826 and A14) to determine if membranes and cells from newborn RB showed relative binding characteristics which were similar to other extrahepatic insulin target tissues. RB membranes, neurons and glia bound B26 better than A14, whereas liver plasma membranes bound both equally. Competition-inhibition curves were generated using homologous 127 I-insulin isomers. Binding of B26 was greater than A14 at all concentrations. The relative maximal binding of B26 compared to A14 was 1.35.Scatchard plots of the data were curvilinear, which is characteristic of other insulin target tissues. Receptor concentrations for each isomer were similar, but affinities for B26 were greater than for A14 at all points, suggesting that the entire differences in relative binding could be accounted for by differences in receptor affinity for the two isomers. This is in agreement with the findings in other insulin target tissues.

A NOVEL DIABETES SYNDROME IN AMERICAN BLACKS (TYPE 1.5 DIABETES): INSULIN SECRETORY AND BINDING STUDIES

We have recently described an early onset (<30y/o) diabetes syndrome (1.5 diabetes) in Blacks characterized by 1) Absence of HLA DR3 and DR4 (unusual in whites (3%) vs Blacks with diabetes (26%) ) and islet cell autoantibodies, 2) insulin dependence at onset, 3) frequent noninsulin dependent course thereafter and 4) frequent autosomal dominant family history of diabetes. We studied 14 such pts (1.5 DM) for their plasma C-peptide (CP) responses to oral sustacal (4 cal/kg) and their monocyte insulin binding characteristics. Six controls (C) and 5 pts with classical IDD were also studied for CP responses. Peak stimulated CP levels for the 1.5 DM pts (0.31±0.8 pmol/ml) were less than C (0.78±0.05; p=0.004), but greater than IDD (0.05±0.02) despite their having diabetes of greater duration (4±3 years for IDD vs 11±10 years for 1.5 DM). Maximal insulin binding in the 1.5 DM pts was no different from 18 controls (8.9±3.1% vs 7.4±1.6%; p=0.10), and all 1.5 DM pts had normal insulin affinities. Insulin receptor sites were increased in pts with 1.5 DM (29.7K±24 sites/peripheral monocyte) over C (13.2K±5K; p<0.01). 1.5 DM is reminiscent of Jamacian (J) type diabetes. In summary, 1.5 DM patients had CP responses intermediate between IDD and C. In general, there were no defects in insulin binding or affinity; however there appears to be upregulation of the number of insulin receptors secondary to insulinopenia.

273 THE EFFECT OF EXOGENOUS INSULIN ON OVINE FETAL GBOWTH

Macrosomia in association with a hyperinsulinemic intrauterine environment is found in the fetus of the diabetic mother. We have studied the ovine fetus to demonstrate directly that exogenous insulin administration accelerates fetal growth. Seven mixed breed ewes with radiologically confirmed, nondiscordent twin fetuses were used. Insulin was infused at 90±50 mu/kg/day to one randomly selected fetus while the other twin was infused with saline as control. Infusion was continued for 14.9±1.5 days during which there were no differences in serum glucose, PO2, PCO2, pH or hematocrit between infused and control fetuses. Studies of insulin binding to erythrocyte receptors revealed no differences in maximum percentage binding, mean empty site binding affinity, receptor concentration or the concentration of insulin which inhibited (125I) iodoinsulin by 50%. Following infusion, analysis of fetal growth demonstrated no differences in weight, length or organ weights between control and experimental animals. No effects of insulin infusion were found on tissue water, protein, RNA, DNA or glycogen. We have demonstrated that small amounts of exogenous insulin do not alter the normal pattern or rate of ovine intrauterine growth over a 15 day infusion period. It is possible that insulin at physiologic concentrations has little role in the regulation of fetal growth.

985 INFLUENCE OF VARIOUS MATERNAL FACTORS ON FETAL OUTCOME

A 5-year retrospective study of 4,430 deliveries assessed the influence of maternal obesity, pre-pregnant weight, weight gain, age, and diabetes on fetal outcome. Male babies were heavier than females (p<.05). Thus different curves may be needed to determine the designation “LGA” in some populations. Obese mothers, mothers who gained > 30 1bs. during their pregnancy, and Class A diabetics all had heavier babies and increased numbers of LGA births compared to controls (p<.01). When obesity and diabetes were present, 66.7% of the births were LGA vs. 12.1% for controls (p<.01).The prevalence of major malformations correlated only with maternal diabetes, where there was a 4-fold increase over controls (11.3% vs. 2.7%, p<.05). Perinatal mortality was affected by maternal factors only insofar as they adversely affected birthweight or gestational age. Diabetes however, resulted in increased mortality at all birthweights and gestational ages, and gave an overall perinatal mortality rate of 143/1000 births, which was almost 4 times greater than controls (p<.01).Maternal obesity, pre-pregnant weight, weight gain and diabetes are significant determinants of birthweight and the percentage of LGA births, whereas only maternal diabetes was found to directly increase the prevalence of major malformations or the perinatal death rate.