Jean-Claude Sodoyez

Evidence for an Insulin-Induced Inhibition of Insulin Release by Isolated Islets of Langerhans∗

Summary Isolated islets of Langerhans were incubated in a medium containing different concentrations of glucose with or without different concentrations of insulin. The results suggest that insulin inhibits further insulin release and that the insulin level at which this feedback mechanism operates is determined by the intensity of the insulinogenic stimulus.

Abnormal circulating pancreatic enzyme activities in more than twenty-five percent of recent-onset insulin-dependent diabetic patients: Association of hyperlipasemia with high-titer islet cell antibodies.

Pancreatic amylase and lipase activities were measured in sera of 307 Caucasian insulin-dependent diabetes mellitus patients (IDDM) at clinical onset, 303 nondiabetic siblings of registered patients, and 207 control subjects under age 40 years. In all subject groups lipasemia and pancreatic (but not salivary) amylasemia increased with age and were significantly correlated. Using age-dependent reference ranges, reduced pancreatic enzyme levels were measured in 18% of patients, 6% of siblings, and only 2% of control subjects (p < 0.001). Increased lipase levels were noted in 10% of patients and in only 3% of siblings and 2% of control subjects (p, < 0.001). Using both univariate and multivariate statistical analysis, elevated lipase activities at clinical onset were associated with higher titers of autoantibodies against islet cell cytoplasmic antigens and glucagon, but not against insulin or the 65-kDa isoform of glutamic acid decarboxylase (GAD65-Ab), or with markers of genetic predispovsition or metabolic dysregulation. These findings indicate the presence of modest, but statistically significant, variations in circulating pancreatic enzyme levels in 28% of IDDM patients at clinical onset (p < 0.001 vs. 5% in control subjects). Increased lipase levels may express a form or a stage of the disease with exocrine cell damage; their association with higher titers of islet cell and glucagon autoantibodies is not yet explained. Lower lipase and isoamylase levels are thought to result from the reduced acinar cell function in the vicinity of insulin-depleted islets. It must be tested whether pancreatic enzyme activities in serum can also be altered during the preclinical stage and can thus be considered as an additional marker for the disease process in the pancreas.

Effects of Gestational Age, Birth and Feeding on the Insulinogenic Response to Glucose and Tolbutamide by Fetal and Newborn Rat Pancreas

Perinatal maturation of the pancreatic beta cells was studied in the rat. Insulin synthesis proceeded rapidly be tween the twentieth gestational day and the third postnatal day. The insulin concentration in the pancreas and the amount of insulin available per gram of body weight reached a maximum sixty hours after birth and then decreased slowly toward the values observed in the adult rat. The pancreatic beta cells became responsive to glucose and to tolbutamide during the twenty-third day after fertilization, This phenomenon seemed to be related to the gestational age and not to act of birth or to feeding, although feeding appeared to increase the insulinogenic response to glucose.

Superiority of Radiobinding Assay Over ELISA for Detection of IAAs in Newly Diagnosed Type I Diabetic Children

Objective Liquid- or solid-phase assays have been used for insulin autoantibody (IAA) determination, and the method of IAA measurement has not been standardized. Research Design and Methods IAAs were determined by radiobinding assay (RBA) and enzyme-linked immunosorbent assay (ELISA) in two large age-matched groups of nondiabetic and newly diagnosed insulin-dependent (type I) diabetic children. Results Positivity for IAA by RBA (≥ to nondiabetic mean + 3SD) was 2 of 178 (1.1%) and 55 of 173 (32%) in nondiabetic and diabetic children, respectively. Prevalence of IAA by RBA was significantly higher in the youngest age-group (63% between 0-4 yr). Positivity for IAA by ELISA was 1 of 178 (0.6%) and 8 of 169 (4.7%) in nondiabetic and diabetic children, respectively. Concordance rates between both assays were 0 of 3 (0%) in control subjects and 5 of 58 (8.6%) in diabetic children. Conclusions We conclude that RBA is more appropriate than ELISA for IAA detection at the onset of the disease. In addition, because available data suggest that IAAs detected by RBA only are high-affinity antibodies, it is tempting to speculate that IAAs reflect a mature immune reaction against endogenous insulin.

Reduction in the Activity of the Pancreatic Islets Induced in Normal Rodents by Prolonged Treatment with Derivatives of Sulfonylurea

Normal Syrian hamsters were given daily intraperitoneal injections of tolbutamide sodium or 0.9 per cent NaCl solution. Normal albino rats were fed a control or a glyburide (HB-419) containing diet. After seven weeks of treatment, the animals were killed, the pancreatic islets were isolated by collagenase digestion and their diameter and secretory activity in vitro were measured. In other animals, the total pancreatic acid-alcohol extractable insulin was measured. In control animals, there was a linear relationship · between body weight on the one hand and pancreatic insulin content on the other. In animals previously treated with tolbutamide, at the dose of 63 mg./kg., the relationships between these two variables were altered: a slight increase in body weight was accompanied by a decrease in pancreatic insulin content. The islets of animals treated with either drug released less insulin in vitro than those of control animals; the degree of B cell depression was related to the dose of tolbutamide which the animals had received. All drug-induced abnormalities disappeared approximately one week after the cessation of treatment. The possible significance of these observations to human therapy is discussed.

Detection of autoantibodies against islet amyloid polypeptide in human serum. Lack of association with Type 1 (insulin-dependent) diabetes mellitus, or with conditions favouring amyloid deposition in islets

SummaryA radiobinding assay for the detection of autoantibodies against islet amyloid polypeptide was developed, analytically validated, and -in parallel with a similar assay for the detection of autoantibodies against insulin — applied to sera from recent-onset Type 1 (insulin-dependent) diabetic patients and from age- and sex-matched control subjects. There was no difference in islet amyloid polypeptide autoantibody titres between patient groups and matched control subjects, nor within subject groups according to age. At onset of Type 1 diabetes, elevated islet amyloid polypeptide-autoantibody levels (> 97th percentile of control subjects) were only detected in 1 of 30 patients aged 0–19 years and in 2 of 35 patients aged 20–39 years. By contrast, insulin autoantibodies were frequently demonstrated, in particular at onset of diabetes under age 20 (0–19 years: 18 of 30 patients; 20–39 years: 10 of 35 patients; p < 0.01 vs matched control subjects). Islet amyloid polypeptide autoantibodies were not detectable in 3 insulinoma patients nor in 37 patients (aged 33–70 years) with Type 2 diabetes (vs 1 of 40 in matched control subjects). In positive serum, adsorption onto protein A-Sepharose removed islet amyloid polypeptide binding activity, hereby confirming its antibody nature. In conclusion, Type 1 diabetes is associated with an age-dependent autoantibody reaction against insulin but not against islet amyloid polypeptide. Conditions associated with amyloid deposition in islets (Type 2 diabetes, insulinoma and ageing) do not favour the formation of autoantibodies against islet amyloid polypeptide.

Function of the pancreatic B-cells in hamsters bearing a transplantable islet cell tumor

Abstract Hyperinsulinism produced in the Syrian hamster by a transplantable islet cell tumor caused a decrease in the amount of insulin extractable from the pancreas and in the amount of insulin released by the B-cell in vivo as well as in vitro. A comparable pancreatic suppression was obtained by daily injections of Lente insulin ( 1.5 U 100 Gm. ), but not by daily injections of phlorizin ( 20 mg. 100 Gm. ). These results suggest that insulin itself plays a mamor role in the islet cells inhibition of tumor-bearing animals.

Polymorphism of insulin antibodies in six patients with insulin-immune hypoglycaemic syndrome

Insulin antibodies in six patients with immune hypoglycaemic syndrome were studied. The antibodies displayed a higher affinity for bovine insulin in two patients, were specific for human insulin in one patient and non‐species specific in the other three patients. The predominant IgG subclass of the insulin antibodies was IgG4 in two patients, IgG3 in two and IgG 1 in two. In one of these, the other three subclasses were also detectable. Insulin autoantibodies of four patients were homogeneous with regard to light chains (k), and those of the other two contained both k and γ light chains. Analysis of insulin immune complex size by fast protein liquid chromatography was possible in three patients and demonstrated immune complexes with elution profile close to that of IgG, although not exactly superimposable to the one obtained with a mouse monoclonal insulin antibody. In two patients, avidity was too low to permit chromatography of the immune complexes, and, moreover, in these two cases insulin antibodies were of the IgG3 isotype and spontaneously formed aggregates independently of insulin binding. We conclude that insulin antibodies of the insulin immune syndrome are polymorphic but different from those generated by insulin therapy.

In Vivo Demonstration of Insulin-Receptor Defect With 123I-Labeled Insulin and Scintigraphic Scanning in Severe Insulin Resistance

Objective Insulin-receptor function in humans is usually studied in vitro on readily available cells, e.g., erythrocytes and fibroblasts. Although these cells are not metabolically important targets for insulin action, information derived from them are often taken as representative of other tissues. The aim of this study was to investigate insulin receptors in vitro on erythrocytes and in vivo on one of the main insulin-target organs, the liver. Research Design and Methods A 16-yr-old girl affected by severe insulin resistance was identified. Insulin receptor binding was measured on the erythrocytes of the patient and of 6 nondiabetic volunteers. The biodistribution of 123I-labeled insulin was studied in vivo by scintigraphic scanning in the insulin-resistant patient and in 10 nondiabetic volunteers. Results Erythrocytes of this patient displayed a markedly reduced [125I]insulin binding. In vivo 123I-insulin biodistribution was characterized by lack of hormone uptake by the liver (4 vs. 21% of the injected dose in control subjects) contrasting with intense accumulation of radioactivity in the kidneys. Conclusions Our studies show that defects of insulin binding can be directly demonstrated in vivo on liver receptors with a noninvasive technique with low radiotoxicity.

Glycerol-insulin raises circulating insulin antibodies in type I diabetic patients treated with permanently implanted devices

The instability of insulin in the reservoirs of implantable insulin delivery devices has been a major obstacle in implementing this form of therapy. To overcome the problem of precipitation, a glycerol-insulin preparation has been used in large-scale long-term clinical trials. The aim of this study was to evaluate the stability of the glycerol-insulin solution and its effects on circulating insulin antibodies in eight type I diabetic patients who were implanted with an Infusaid pump (Infusaid Corporation, Norwood, MA) and followed for 1 year or more. Total insulin requirement did not change throughout the observation period. Plasma free insulin was higher during treatment with glycerol-insulin than with the standard insulin treatment (P less than .02). Insulin antibodies increased in all patients (P less than .05). High-performance liquid HPLC analysis of insulin samples from the pump reservoirs showed the generation of insulin modification products at a daily rate of 1.84%, reaching 40% to 50% of the total reservoir content 3 weeks after refilling; among these products, high molecular weight species accounted for about 15%. It is concluded that glycerol-insulin is not an adequate insulin preparation for use in implanted devices. Insulin deteriorated in the pump reservoirs, and insulin antibody concentration increased in the treated patients. It is believed that this antibody production is favored by circulating insulin fragments and polymers of insulin generated inside the pump reservoirs.