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The hitherto identified hallmarks of the autoimmune aspects in Type 1 diabetes are reviewed. Their implication in the disclosure of the pre-clinical phase of the disease is put forward. The possible delineation of this pre-diabetic phase can lead to an early immunotherapeutic approach. The effect of immunomodulation by agents such as azathioprine, cyclosporin A and nicotinamide in newly diagnosed diabetes and the use of some of these drugs in clinical trials on pre-diabetic individuals are discussed.

The hitherto identified hallmarks of the autoimmune aspects in Type 1 diabetes are reviewed. Their implication in the disclosure of the pre-clinical phase of the disease is put forward. The possible delineation of this pre-diabetic phase can lead to an early immunotherapeutic approach. The effect of immunomodulation by agents such as azathioprine, cyclosporin A and nicotinamide in newly diagnosed diabetes and the use of some of these drugs in clinical trials on pre-diabetic individuals are discussed.

Two cases of hepatic artery aneurysm are reported. The first presented as obstructive jaundice, the second as an upper gastrointestinal bleeding. The diagnosis was made by performing ultrasound, CT-scan and angiography. In both cases surgery was the treatment. However, in some cases, interventional angiography with embolisation of the affected vessel offers an alternative treatment.

Extracellular Ca2+, at concentrations exceeding 10 mmol/l, causes a dose-related stimulation of insulin release. The dynamics of Ca2+-induced insulin release are characterized by a quick onset, a progressive build-up and a later return towards basal secretory rate. The release of insulin evoked by Ca2+ is inhibited in the presence of either Mg2+ (10 mmol/l) or the organic Ca2+-antagonist verapamil (81 μmol/l), both of which are known to inhibit Ca2+ entry in the B-cell. Glucose and theophylline, which are thought to affect the net uptake or intracellular distribution of Ca2+ in the B-cell, both enhance Ca2+-induced insulin release. As little as 2.7 mmol/l glucose is sufficient to augment Ca2+-induced insulin secretion. Exposure of the pancreas to somatostatin significantly retards the secretory response to Ca2+. Cytochalasin B potentiates the insulin release evoked by Ca2+ (12 mmol/l) and lowers the threshold concentration of Ca2+ required to stimulate secretion. These data suggest that high extracellular Ca2+ concentrations may sufficiently increase the amount of Ca2+ accumulated in the B-cell to eventually trigger insulin release. Agents known to cause a remodelling of Ca2+ fluxes across membrane systems in the B-cell interfere with Ca2+-induced insulin release, a process also dependent on the integrity of the cytochalasin B-sensitive microfilamentous effector system.

1. In isolated pancreatic islets, pyruvate causes a shift to the left of the sigmoidal curve relating the rate of insulin release to the ambient glucose concentration. The magnitude of this effect is related to the concentration of pyruvate (5–90 mM) and, at a 30 mM concentration, is equivalent to that evoked by 2 mM-glucose. Pyruvate also enhances insulin release in the presence of fructose, leucine and 4-methyl-2-oxopentanoate. 2. In the presence of glucose 8 mM), the secretory response to pyruvate is an immediate process, displaying a biphasic pattern. 3. The insulinotropic action of pyruvate coincides with an inhibition of 45Ca efflux and a stimulation of 45Ca net uptake. The relationship between 45Ca uptake and insulin release displays its usual pattern in the presence of pyruvate. 4. Exogenous pyruvate rapidly accumulates in the islets in amounts close to those derived from the metabolism of glucose. The oxidation of [2-14C]pyruvate represents 64% of the rate of [1-14C]pyruvate decarboxylation and, at a 30 mM concentration, is comparable with that of 8 mM-[U-14C]glucose. 5. When corrected for the conversion of pyruvate into lactate, the oxidation of 30 mM-pyruvate corresponds to a net generation of about 314 pmol of reducing equivalents/120 min per islet. 6. Pyruvate does not affect the rate of glycolysis, but inhibits the oxidation of glucose. Glucose does not affect pyruvate oxidation. 7. Pyruvate (30 mM) does not affect the concentration of ATP, ADP and AMP in the islet cells. 8. Pyruvate (30 mM) increases the concentration of reduced nicotinamide nucleotides in the presence but not in the absence of glucose. A close correlation is seen between the concentration of reduced nicotinamide nucleotides and the net uptake of 45Ca. Menadione inhibits the effect of pyruvate on insulin release, without altering its rate of oxidation. 9. Pyruvate, like glucose, modestly stimulates lipogenesis. 10. Pyruvate, in contrast with glucose, markedly inhibits the oxidation of endogenous nutrients. The latter effect accounts for the apparent discrepancy between the rate of pyruvate oxidation and the magnitude of its insulinotropic action. 11. Dichloroacetate fails to affect glucose oxidation and glucose-stimulated insulin release. 12. It is concluded that the effect of pyruvate to stimulate insulin release depends on its ability to increase the concentration of reduced nicotinamide nucleotides in the islet cells.

D-erythrose (5.0 to 20.0 mM) stimulates insulin release. This insulinotropic action of erythrose displays several features in common with that of glucose. First, erythrose (20 mM) causes a shift to the left of the sigmoidal curve relating the secretory rate to the glucose eoncentration, but fails to enhance the maximal response to glucose. Second, the secretory response to erythrose occurs as an early peak followed by a phase of sustained release. Third, erythrose increases the output of lactate from the islets. Last, erythrose inhibits the efflux of 45calcium and favours its accumulation in isolated islets. It is suggested that, whether in response to glucose or erythrose, an increase in glycolytic flux may represent the key process involved in the identification of the secretagogue, a subsequent remodeling of calcium fluxes being apparently responsible for the activation of the insulin-releasing system.

A duodenal somatostatinoma is described in a patient suffering from a tumoral obstruction of the bile duct. The diagnosis was based upon histologic and immunocytochemical characterization of tumoral fragments and later confirmed by immunochemical analysis of liver metastases. Basal peripheral somatostatin immunoreactivity levels were normal until liver failure developed. A hypersomatostatinemia was induced by combined injection of calcium and pentagastrin, which was not the case in normal volunteers or in patients with disseminated pancreatic adenocarcinoma. This test was also positive in a case of generalized pancreatic somatostatinoma 4 yr after streptozotocin treatment. It was concluded that the calcium-pentagastrin test might be useful in the diagnosis of somatostatinomas.

In order to document the participation of microtubules in the dynamics of insulin release, the secretory response of the isolated perfused rat pancreas was measured after various times of exposure to vincristine (2.10−5M). After a short exposure time (25 min), both phases of glucose-induced insulin release were increased. After longer pretreatment (60 min), this facilitating effect disappeared and a slight, insignificant reduction of both phases of the secretory response to glucose was observed. A still longer exposure time (120 min) provoked a more marked and significant inhibition of the early and late phases of insulin release. The same enhancing effect after short pretreatment with vincristine was noticed when gliclazide was used as the insulinotropic agent. The ultrastructural studies indicated a progressive disappearance of microtubules concomitantly with an increase in number and size of vincristine-induced paracrystalline deposits. These findings suggest that microtubules indeed participate in the dynamics of insulin release, a reduction of both phases of insulin secretion being caused by an extended disruption of the microtubular apparatus, whereas a more limited disturbance of the microtubular system appears to be associated with facilitated insulin release in response to either glucose or sulfonylurea.

1. Menadione (2-methyl-1,4-naphthoquinone) inhibits insulin release evoked in the rat endocrine pancreas by glucose or glyceraldehyde, but fails to affect the secretory response to Ca2+, Ba2+, theophylline or gliclazide. The inhibitory effect of menadione upon glucose-induced insulin release is a dose-related, rapid and reversible phenomenon, menadione and glucose acting apparently as competitive antagonists. Menadione affects both the early and late phase of the secretory response to glucose. Menadione also antagonizes in a dose-related fashion the ability of glucose to reduce 86Rb efflux, to provoke 86Rb accumulation, to cause biphasic changes in 45 Ca efflux and to stimulate 45 Ca net uptake in pancreatic islets. 2. It is concluded that menadione impairs the insulinotropic action of glucose and other nutrients by impeding the remodelling of cationic fluxes normally provoked by these secretagogues in islet cells. Menadione, however, does not affect the capacity of divalent cations to activate the effector system which controls the release of secretory granules. Menadione may therefore represent a valuable tool to elucidate the mechanism by which glucose normally modifies the movement of cations in the pancreatic B-cell.

Recent experimental contributions concerning the nature of the glucoreceptor mechanism in the B-cell are reviewed. The relative aptitude of different hexoses (glucose, mannose, fructose, galactose) to affect various parameters of islet function (insulin biosynthesis, calcium uptake, insulin release, ability to support the insulinotropic action of theophylline) does not support the view that a receptor molecule can be activated by unmetabolized sugars. The specific inhibition by mannoheptulose and other metabolic inhibitors of the stimulant action of glucose upon these various parameters rather indicates that the glucoreceptor mechanism for both insulin biosynthesis and release is dependent on a pathway of glucose metabolism in the B-cell. The accumulation of calcium in the cytosol of the B-cell represents a selective requirement for the releasing process, and apparently does not affect the glucoreceptor mechanism. The influence of alkali cations (Na+, K+, Li+, Tris) upon the various parameters of insular function suggests that the glucoreceptor mechanism for both insulin biosynthesis and release involves a sodium-sensitive step of glucose handling by the B-cell. Agents known to act upon the B-cell microtubular-microfilamentous system modify the secretory responsiveness to glucose, probably by altering the sensitivity of microtubules and microfilaments to cytosolic calcium. ©1973 by the American Society of Zoologists.

A sufficient influx of Ca’+ into the pancreatic B-cell is known to usually play a permissive role in the maintenance of the insulin secretory process [ 1 ] . This inward movement of Ca2’ across the B-cell membrane is thought to be mediated by a finite number of carriers, the relationship between the rate of Ca2+entry and extracellular Ca2’concentration being described by the Michaelis-Menten equation [2]. In the B-cell, this native ionophore system is further characterized by competition between Ca2+, Mg”, Co” and Ba2’ [3-51 and by its sensitivity to organic Ca2?antagonists, such as verapamil and D600 [6,7]. The data presented in this report suggest that the native Ca2’carrier system of the pancreatic B-cell also behaves in a mannner analogous to A23 187, an antibiotic ionophore from streptomyces [S] that is known to promote insulin release [9-l 31 .

L-glutamine dramatically augments insulin release evoked by L-leucine. The dynamics, specificity and environmental modifications of the insulin secretory response to the combination of L-glutamine and L-leucine were investigated. L-glutamine alone failed to stimulate proinsulin biosynthesis or insulin release in rat pancreatic islets, but augmented synthesis and secretion evoked by L-leucine. In relation to the secretory response, L-glutamine could be replaced by L-asparagine but not L-glutamate; L-leucine could be replaced by L-norvaline or L-isoleucine but not by L-valine, L-norleucine, glycine, L-serine, L-lysine, L-phenylalanine or L-arginine. The secretory response to L-leucine was rapid and biphasic whereas the enhancing action of L-glutamine upon insulin release was progressive. The release of insulin evoked by the combination of L-leucine and L-glutamine was inhibited by antimycin A, menadione, ammonium ions, verapamil, adrenaline, and by the absence of extracellular Ca2+. It was increased at high carbon dioxide tension, and by glucose, theophylline and cytochalasin B. It is concluded that the enhancing action of L-glutamine upon insulin release evoked by certain amino acids represents a phenomenon dependent on the integrity of oxidative metabolism and involving essentially the same sequence of metabolic, ionic and motile events as that characterizing the process of glucose-induced insulin release.

NH4+ caused a dose-related, rapid, and reversible inhibition of glucose-stimulated insulin release by isolated rat islets. It also inhibited glyceraldehyde-, Ba2+-, and sulfonylurea-stimulated insulun secretion. NH4+ failed to affect glucose utilization and oxidation, glucose-stimulated proinsulin biosynthesis, the concentration of ATP, AD, and AMP, and the intracellular pH. NH4+ also failed to affect the ability of theophylline and cytochalasin B to augment glucose-induced insulin release. However, in the presence and absence of glucose, accumulation of NH4+ in islet cells was associated with a fall in the concentration of NADH and HADPH and a concomitant alteration of 86Rb+ and 45Ca2+ (or 133Ba2+) handling. These findings suggest that reduced pyridine nucleotides, generated by the metabolism of endogenous of exogenous nutrients, may modulate ionophoretic processes in the islet cells and by doing so, affect the net uptake of Ca2+ and subsequent release of insulin.

D600 (2 to 20 muM; alpha-isopropyl-alpha [(N-methyl-N-homoveratril)-gamma-aminopropyl]-3,4,5-trimethoxyphenyl-acetonitril) caused a dose-related, rapid and reversible inhibition of glucose-induced insulin release. It also suppressed the insulinotropic action of a sulphonylurea but failed to affect the enhancing action of theophylline upon glucose-induced release. The inhibitory effect of D600 was enhanced at low extracellular Ca2+ concentration. D600 reduced both basal and glucose-stimulated 45calcium net uptake, whilst failing to affect the efflux of 45calcium from perifused islets. The recognition of glucose by the B-cell was also unaffected by D600 as judged by the effect of the sugar upon both 45calcium efflux and net uptake in the isolated islets. These findings are compatible with the hypothesis that the primary mode of action of D600 is to inhibit Ca2+ entry in the B-cell.

In order to assess the participation of the microfilamentous cell web in the multiphasic response of the pancreatic beta cell, the effect of cytochalasin B upon both glucose- and sulfonylurea-induced insulin release was investigated in the perfused isolated pancreas. Cytochalasin B failed to affect the basal rate of insulin release, but enhanced the initial and later phases of insulin secretion in response to either glucose or gliclazide. In addition, cytochalasin B lowered the threshold concentration for the stimulant action of glucose upon insulin release. Ultrastructural studies supported the concept of a specific interaction of cytochalasin B with the microfilamentous cell web of the beta cell. It is concluded that the integrity of such a structure is equally important for both the initial and later secretory responses of the beta cell to various insulinotropic agents.

A standardized method has been developed for the assay of cell surface antibodies in IgM- and IgG-fractions from human serum. Suspensions of adult rat islet beta cells, islet non-beta cells, and anterior pituitary cels were used as antigen source and a cell sorter as analyser of the immunoglobulin binding to individual cells. Assay conditions were selected wherein no surface antibodies were detected in 33 control subjects younger than 20 years. In 30% of type 1 (insulin-dependent) diabetic patients, surface antibodies were measured with rat anterior pituitary cells as well as with rat isle beta cells. Binding to pituitary cells occured with IgM- and IgG-fractions and correlated positively with IgG binding to islet beta cells. At onset of the disease, the prevalence of IgM-rat anterior pituitary cell surface antibodies was higher than that of IgG-rat anterior pituitary cell surface antibodies. Cell surface antibodies were also detected in first-degree relatives of type 1 diabetic patients, but corresponded primarily to IgM-rat anterior pituitary cell surfaca antibodies. It is concluded that the development of type 1 diabetes in subjects younger than 20 years is associated with the generation of both IgM and IgG cell surface antibodies. The IgM surface antibodies may result from stimulated production of polyreactive natural autoantibodies and could precede the switch to the formation of monoreactive IgG autoantibodies. The assay of IgM cell surface antibodies can be useful in studies on the sequence of immune events in diabetes and other autoimmune disease.

A standardized cell surface antibody assay was used to measure binding of circulating human immunoglobulins to rat or piglet splenocytes. In 100-fold diluted serum fractions, lymphocyte surface antibodies were detected in 30% of type 1 (insulin-dependent) diabetic patients under 20 years of age but in none of 33 control subjects. Binding occurred with T and B lymphocytes, appeared unrelated to Fc receptors or protein glycosylation and was not attributable to insulin or albumin antibodies. At clinical onset of the disease, the lymphocyte surface antibodies belonged primarily to the IgM-class. Their presence was positively correlated to that of IgM-pituitary cell surface antibodies and their absorption by anterior pituitary cells occurred as well as by splenocytes. Lymphocyte surface antibodies remained present during the first years of insulin, treatment. They were also detected in first degree relatives of lymphocyte surface antibody-positivie patients. It is unlikely that IgM-lymphocyte surface antibodies mark the destructive process in the pancreatic B cell population. They may, instead, express a stat of immune reactivity which precedes the formation of IgG-autantibodies and therefore be associated with an event in the development of diseases such as type 1 (insulin-dependent) diabetes.

Islet cell surface antibodies (ICSA) have been detected in insulin-dependent diabetes (IDD). Current techniques for the detection of ICSA often suffer from a lack of standardization and from a poorly defined specificity. We have developed a standardized method to quantify binding of circulating IgM and IgG fractions with the surface of purified rat pancreatic B cells; parallel experiments on islet non-B cells serve as control for islet cell specificity. Using this procedure no abnormalities were detected in the binding of circulating IgM from 30 recent onset IDD to islet B or non-B cells, comparison being made with 30 healthy age-matched controls. On the other hand, the IgG fraction from IDD patients was found to bind selectively to islet B cells (p 0.01) while no binding was observed with IgG from the normal controls. It is concluded that the developed procedure allows the recognition, quantification and specification of autoimmune reactions against surface components of islet cells.