Current views on the etiology of insulin-dependent diabetes mellitus

Acute and chronic animal models for the evaluation of anti-diabetic agents

Diabetes mellitus is a potentially morbid condition with high prevalence worldwide thus being a major medical concern. Experimental induction of diabetes mellitus in animal models is essential for the advancement of our knowledge and understanding of the various aspects of its pathogenesis and ultimately finding new therapies and cure. Experimental diabetes mellitus is generally induced in laboratory animals by several methods that include: chemical, surgical and genetic (immunological) manipulations. Most of the experiments in diabetes are carried out in rodents, although some studies are still performed in larger animals. The present review highlights the various methods of inducing diabetes in experimental animals in order to test the newer drugs for their anti-diabetic potential.

Practical clinical value of the C-peptide response to glucagon stimulation in the choice of treatment in diabetes mellitus

In order to discriminate between insulin-dependent and non-insulin-dependent patients, serum C-peptide concentration was determined using antiserum M1230 in the fasting state and 6 min after an i.v. injection of 1 mg glucagon in 215 patients treated with insulin and 53 treated with diet and oral antidiabetics. A patient was considered well controlled without insulin when fasting blood glucose was below 8 mmol/l and when glucosuria was absent. After re-evaluation of therapy in hospital it was found that the majority of patients with a post-stimulatory serum C-peptide concentration above 0.60 pmol/ml appeared to have non-insulin-dependent diabetes mellitus. When fasting C-peptide was used, a great overlap was found between the two treatment groups. During evaluation of therapy in hospital, 6 previously insulin-treated patients could be well treated with diet and tablets and 6 diet- and tablet-treated patients required insulin. The glucagon test seems to be of value in the outpatient clinic to discriminate non-insulin-dependent from insulin-dependent patients.

Fatal Epstein-Barr virus myocarditis in a child with repetitive myocarditis

Fatal Epstein-Barr virus (EBV) myocarditis occurred in a 9-year-old female with a history of two prior discrete episodes of myocarditis, the first associated with chicken pox and the second of undetermined origin. Serologic studies during the fatal episode were characteristic of acute EBV infection, and EBV genome was detected by polymerase chain reaction (PCR) amplification of DNA extracted from autopsy heart and liver. PCRs for enteroviruses and cardiac viral culture were negative. An intense mononuclear cell infiltrate in the myocardium consisted entirely of T cells, without identifiable B cells. Human leukocyte antigen HLA-DR analysis using frozen tissue obtained postmortem revealed antigens DR4 and DR13. DR4 is associated with some autoimmune disorders, as well as idiopathic dilated cardiomyopathy. We postulate that an aberrant immune response, possibly associated with the DR4 locus, was responsible for the repetitive episodes of myocarditis in this patient.

Diabetes Mellitus: Experiencing a Chronic Illness

Diabetes is a chronic, complex disease involving numerous pathophysiological features. There is a paucity of studies relating to psychological factors. The available research is not conclusive and in addition is largely quantitative in nature. The aim of this investigation was to gain an understanding of the life-world of people with diabetes and to acquire insight into the demanding aspects of their lives. The research procedure involved interviewing subjects who suffer from diabetes. A pilot study was conducted in order to test a number of open-ended questions. On the basis of these results, a set of semi-structured questions was formulated for the main study. The main study involved interviews with 13 subjects aged between 20 and 45 years who belonged to a diabetic organization and who volunteered for the investigation. The interviews were recorded on audiotape and later transcribed. Five of the protocols obtained were analyzed according to the method outlined by Giorgi and they produced an encompassing description of the life-world of a diabetic. The themes which emerged included the appearance of the first symptoms and their effect on people with diabetes, the impact of the diagnosis, the emerging pattern of the life-world of people with diabetes and the prospects for the future. The phenomenological approach proved valuable in highlighting many aspects of diabetes. Recommendations are made which may be of benefit to people with diabetes and their families.

Islet expression of interferon-alpha precedes diabetes in both the BB rat and streptozotocin-treated mice

The mechanism(s) leading to beta cell dysfunction in type I diabetes has not been defined. We have investigated whether islet expression of IFN alpha could be a cause of the lesions that are hallmarks of type I diabetes. Streptozotocin induces the expression of interferon-alpha by pancreatic islets prior to the diabetes induced by streptozotocin. Increased IFN alpha, induced by poly I/C or expressed from a transgene will exacerbate the diabetogenic effects of streptozotocin. In another rodent model of type I diabetes (the BB rat), islet expression of IFN alpha precedes lymphocytic infiltration and diabetes. As in the streptozotocin model, in the BB rats poly I/C will induce islet expression of IFN alpha and accelerate the onset of diabetes. These results are consistent with the hypothesis that islet expression of IFN alpha participates in causing type I diabetes.

HLA-DQ beta 57 in Hispanic patients with insulin-dependent diabetes mellitus

OBJECTIVE

The purpose of our study was to investigate the distribution of HLA-DQ beta-chain amino acid residue 57 (HLA-DQ beta 57) as a genetic marker of susceptibility for insulin-dependent diabetes mellitus in the Hispanic population.

STUDY DESIGN

Fifteen patients of Puerto Rican descent with juvenile-onset insulin-dependent diabetes mellitus underwent human leukocyte antigen typing for HLA-DQ beta 57 by polymerase chain reaction amplification of the target genomic DQ sequence followed by hybridization of the polymerase chain reaction product to phosphorus 32-labeled allele-specific oligonucleotide probes. A control group of 44 Hispanic adults without diabetes who were undergoing human leukocyte antigen typing for tissue donation were concurrently typed for comparison.

RESULTS

The Hispanic insulin-dependent diabetes mellitus group showed a significant increase in homozygosity for a non-aspartate amino acid (p = 0.023) over a control group of Hispanic subjects without diabetes. A high rate of heterozygosity for aspartate (53.3%) is found in Hispanic subjects with insulin-dependent diabetes mellitus as well.

CONCLUSIONS

HLA-DQ beta 57 in the Hispanic population has a distribution distinct from HLA-DQ beta 57 in the Caucasian population. A single aspartate is not protective against insulin-dependent diabetes mellitus in Hispanic subjects.

Functional diversity in vascular endothelial cells: role in coxsackievirus tropism

Six plaque-purified virus isolates were obtained from liver and heart tissues of a DBA/2 mouse infected 7 days earlier with 10(4) PFU of coxsackievirus group B type 3. Each virus isolate was assayed in vitro for infectivity to vascular endothelial cells (VEC) of the liver, lungs, and heart. Both the percentage of VEC infected and the mean progeny PFU produced per infected VEC were determined. Virus isolates from the heart showed greater infectivity and replication in heart VEC than in VEC derived from either the liver or lungs. Similarly, virus isolated from the liver preferentially infected liver VEC. Virus receptor expression varied between VEC populations, as demonstrated by binding studies with a [35S]methionine-radiolabeled heart virus and by enzyme-linked immunoadsorption assay studies with a monoclonal antibody to the coxsackievirus group B type 3 receptor on heart tissue. Finally, the heart and liver virus isolates were injected (10(4) PFU) intraperitoneally into BALB/c mice. After 7 days, the animals were sacrificed, and the hearts, livers, and lungs were evaluated for tissue injury and virus concentrations. Viruses originally isolated from the heart preferentially infected the heart when reinjected into animals and caused severe myocarditis. Viruses originally derived from the liver most consistently reinfected the liver, although significant virus concentrations were also detected in the heart. The liver virus isolates, however, were incapable of causing myocarditis. Thus, selective tropism of viruses for particular organs in vivo corresponds to the ability of these isolates to infect VEC in vitro.

Streptozotocin interactions with pancreatic beta cells and the induction of insulin-dependent diabetes

The MSZ diabetic male mouse represents one of the most useful tools available to researchers interested in analyzing the consequences of insulin dependent diabetes in male mice. In contrast to the high mortality induced by single high doses of SZ, protracted administration of smaller SZ dosages yields a more stable diabetic condition. Moreover, in insulitis prone strains such as BKs, the model allows "synchronization" of beta cell destruction such that the inflammatory events occur on a predictable timescale. The MSZ-diabetic mouse represents a diabetic condition in which the primary etiopathologic effect is produced by an environmental toxin, and not by a genetically programmed loss of tolerance to beta cell specific antigens. In this regard, etiopathogenesis in the MSZ model is quite distinct from that underlying autoimmune type I diabetes in humans, NOD mice, and BB rats, and it is probably not appropriate to refer to pathogenesis in the MSZ model as one of "autoimmune insulitis" as has sometimes been done. The fact that insulitis in the MSZ model may not be "autoimmune," but may actually be a normal response to either tissue damage or to beta cells that have been structurally modified by a chemical, makes the model of special interest. Clearly, there is no single cause of insulin dependent diabetes, with disease induction representing a genetic susceptibility interacting with environmental triggers, such as toxins in the diet (including nitrosamines and fungal metabolites) as well as pathogenic viruses. The MSZ model will continue to be actively investigated because of insights it will afford regarding the genetic bases for susceptibility and resistance to diabetogenic environmental toxins. The model will be of further value by contributing to knowledge of the complicated interactions between pancreatic islet cells, other endocrine cells, and leukocytes in maintenance of glucose homeostasis.

The role of chemicals in the etiology of diabetes mellitus

Diabetes mellitus is a collection of diseases that culminate in defects in carbohydrate metabolism and result in inappropriate hyperglycemia. Most individuals with this disease can be categorized into 1 of 2 groups, depending upon their insulin requirements. Individuals who require insulin therapy to maintain life have been designated as having insulin-dependent diabetes mellitus (IDDM), while individuals who can live without insulin treatment have been classified as having noninsulin-dependent diabetes mellitus (NIDDM). The single most important pathological finding in IDDM is a substantial reduction in the number of insulin-secreting pancreatic beta cells. Compelling experimental and epidemiological evidence indicates that, at least in some forms of IDDM, environmental factors, such as chemical toxins, play an important role in the etiology of this disease. Chemical toxins can precipitate IDDM through a variety of mechanisms. They can poison beta cells directly and cause the destruction of a critical mass of beta cells; alternatively, they can trigger autoimmune processes directed against beta cells; or, finally, they can augment the diabetogenic properties of another agent, such as a virus, to hasten the onset of clinical manifestations. In NIDDM, impaired beta cell function appears to be the initial event observed at the onset of this syndrome. Functional defects similar to those seen in NIDDM can be produced in laboratory animals using a specific beta cell toxin. These animals develop permanent glucose intolerance and insulin resistance as a consequence of beta cell alteration. A variety of other chemicals also have been found to produce glucose intolerance; however, this condition is transient and is resolved when the chemical is removed.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunological aspects of diabetes mellitus: prospects for pharmacological modification

It is now well known that insulin-dependent diabetes is a chronic progressive autoimmune disease. The prolonged prediabetic phase of progressive beta-cell dysfunction is associated with immunological abnormalities. A prediabetic period is suggested by the appearance of islet cell antibodies, anti-insulin antibodies, and anti-insulin receptor antibodies. The existence of activated T lymphocytes and abnormal T cell subsets are also other markers. There is still no concensus about the use of the immunosuppression superimposed upon conventional insulin therapy in early diagnosed IDDM and the follow-up of the relatives of IDDM patients who share the genetic predisposition and serological markers for the risk of future onset of IDDM. Treatment in the prodromal period cannot be justified because a link between the disease and early markers such as ICA has not been established with certainty (Diabetes Research Program NIH, 1983). Many immunopharmacological manipulations were reported to be effective in animal models. However, most of them are not readily applied to human subjects. Moreover, IDDM patients are now believed to be heterogeneous, with a complex genetic background. HLA-DR, and more recently DQ, are closely related to the genetic predisposition to IDDM but those genes are not themselves diabetogenic. The contribution of autoimmunity does not appear to be uniform, and in some cases, the contribution of virus is considered more important. There is a lack of a marker for the future onset of IDDM. ICA and ICSA were found after mumps infection, but the existence of those autoantibodies and even the co-existence of HLA-DR3 do not always indicate the future trend to insulin dependency. More precise markers will be disclosed through the biochemical analysis of the target antigens on pancreatic beta-cell for islet antibodies and effector T cells. Much safer and more effective immunopharmacological treatment will be developed through animal experimentation using rat and mouse models. The recent development and interest in this field will further facilitate the attainment of the goal for the complete prevention of IDDM.

HLA type, islet cell antibodies, and glucose intolerance in cystic fibrosis

Impaired glucose tolerance, assessed by a raised glycated haemoglobin (HbA1) concentration, was found in 24 (39%) out of 61 patients with cystic fibrosis with an age range of 1-23 years. No correlation between age and HbA1 concentration was found indicating that factors other than progressive pancreatic fibrosis may be important in the aetiology. HLA typing, islet cell antibodies, and autoantibody screen were completed. Eighteen (75%) out of 24 patients with cystic fibrosis who had an impaired glucose tolerance had HLA-DR3 or HLA-DR4 antigens compared with 23 (62%) out of 37 patients with normal glucose tolerance. Islet cell antibodies were present in seven (15%) out of 46 patients with cystic fibrosis; the prevalence in a normal population is 0.5%. Five (25%) of the 20 patients with a raised HbA1 concentration were positive for islet cell antibodies compared with two (8%) out of the 26 with normal glucose tolerance. Six (86%) out of seven patients who were positive for islet cell antibodies had HLA-DR3 or HLA-DR4 antigens. There was no general autoantibody production. Islet cell antibodies may play a part in the development of glucose intolerance in some patients with cystic fibrosis by being produced in those who are genetically predisposed as part of an immune response to damaged pancreatic tissue.

Optic atrophy in Wolfram syndrome

The clinical and electrophysiologic findings in 11 cases of Wolfram syndrome are presented. These findings suggest that optic atrophy in Wolfram syndrome is not secondary to retinal pathology, but probably represents part of a generalized degeneration of neural structures. The relationship of diabetes mellitus to this process of neural degeneration remains unclear.

Insulin-dependent diabetes mellitus: pathophysiology

Diabetes mellitus is a heterogeneous disorder. About 80% of the patients with this disease are categorized as having non-insulin-dependent diabetes mellitus, a disorder resulting from varied degrees of insulin resistance and impaired insulin secretion; the causes for these abnormalities are unknown. The remaining 15 to 20% of patients have insulin-dependent diabetes mellitus, a disorder caused by the destruction of insulin-producing endocrine cells within the pancreas and currently considered to be the result of an autoimmune process. During the course of both types of diabetes mellitus, the so-called long-term complications of diabetes invariably occur to some extent in all patients. These complications include retinopathy, nephropathy, neuropathy, and premature atherosclerosis. The molecular basis for these complications is not completely understood, but recent evidence obtained from both experiments in animals and prospective clinical studies indicates that metabolic derangements associated with poor glycemic control are a major determinant of the frequency and severity of these complications. Such evidence is the rationale for current attempts to maintain near-normal glycemia in patients with diabetes mellitus.

Trypanosoma brucei rhodesiense infection in mice prevents virus-induced diabetes: possible role of interferon and immunological mechanisms

B10.BR, DBA/2, and BALB/c by J mice were infected with Trypanosoma brucei rhodesiense (Lou Tat clone 1). Subsequent infection with the D variant of encephalomyocarditis virus (EMC-D) resulted in no diabetes or encephalitis, even in the susceptible DBA/2 and BALB/c by J strains. Low levels of circulating interferon (IFN) were detected in trypanosome-infected mice at the time of EMC-D infection. All strains were severely immunosuppressed as a result of trypanosome infection, as evidenced by decreased virus-specific neutralizing antibody titers, compared to virus-infected controls. We attempted to simulate some aspects of T.b. rhodesiense infection in B10.BR mice by pretreating mice with cyclophosphamide and IFN prior to EMC-D infection. Immunosuppression by cyclophosphamide greatly enhanced the pathogenesis of EMC-D, while IFN protected against the diabetogenic effect of this virus. Our results indicate that: (i) T.b. rhodesiense infection inhibited EMC-D-induced diabetes, (ii) this inhibition was not due solely to the immunosuppression generated by the trypanosome infection, and (iii) IFN generated by the trypanosome infection could play some protective role in the inhibition of EMC-D-induced diabetes by trypanosome infection.

Virus-induced alterations in cyclic adenosine monophosphate generation in hamster islets of Langerhans

Inoculation of golden Syrian hamsters with Venezuelan encephalitis (VE) virus results in a sustained diminution in glucose-stimulated insulin release that is correctable by cyclic (c) AMP analogs and phosphodiesterase inhibitors. This suggested the importance of directly measuring cAMP content in VE-infected and control islets in response to insulin secretagogues. The basal cAMP content of VE-infected islets (0.14 +/- 0.02 pmol/micrograms islet DNA) was approximately half that of control islets (0.27 +/- 0.02 pmol/micrograms islet DNA) (P less than 0.05). In the presence of 10 microM glucagon (and 3 mM glucose), the rate of cAMP generation in VE-infected islets was only half that of control islets. With 10 mM alpha-ketoisocaproic acid, the rates of cAMP generation were indistinguishable between control and experimental groups. In response to 20 mM glucose and 3-isobutyl-1-methylxanthine (IBMX) (a phosphodiesterase inhibitor), cAMP generation in VE-infected islets was 81% (NS) of the control rate. When a more specific phosphodiesterase inhibitor, RO 20-1724, was used with 20 mM glucose, cAMP generation in the infected islets was only 44% (P less than 0.001) of the control value. Insulin secretion over the perifusion period paralleled the cAMP levels. In the presence of 10 mM alpha-ketoisocaproic acid, there was no difference in insulin secretion between VE-infected and control islets, while there was a statistically significant (P less than 0.05) difference with 10 microM glucagon or 20 mM glucose (in 1 mM RO 20-1724). These data point to a defect in the cAMP generation system of VE-infected islets, although additional factors involved in insulin secretion may also be impaired by the virus.

Persistent infection of rat insulinoma cells with Coxsackie B4 virus. Brief report

Plaque purified Coxsackie B4 virus (CB4) caused a persistent infection of rat insulinoma (RIN) cells which lasted for the 70 day observation period. Infectious virus was produced and no cytopathic effect was observed. Indirect immunofluorescence and infectious center assays demonstrated that a majority of RIN cells were infected. Defective interfering particles were not demonstrated. Despite persistent infection, insulin synthesis by RIN cells was not altered.

T lymphocyte responses to Coxsackie B4 and mumps virus. I. Influence of HLA-DR restriction elements

The proliferative T lymphocyte responses to Coxsackie B4-, mumps- and varicella-zoster viral antigens were characterized. No significant difference in responsiveness was found between healthy individuals and patients with Type 1 (insulin-dependent) diabetes mellitus. Theophyllamine and verapamil decreased antigen-stimulated proliferation, whereas indomethacin in physiologic concentrations (1 microgram/ml) slightly increased proliferation. A major part of the response seemed to be restricted by HLA-DR molecules. Furthermore, for the mumps antigen the DR3- and DR4-determinants which are associated with Type 1 diabetes, seemed to have a different regulatory function on the T lymphocyte response in that an increased frequency of low responders was found among DR3 positive individuals and an increased frequency of high responders among DR4 positives.

Role of life events and difficulties in the onset of diabetes mellitus

The role of stressful life and difficulties in the onset of insulin-dependent (Type 1) diabetes mellitus was examined in a group of 13 newly diagnosed diabetics and sibling and neighbourhood controls. Subjects aged between 17-34 years, were interviewed and information was collected over the 3 year period preceding clinical diagnosis of diabetes. Diabetics had a higher frequency of one or more severe life events prior to diagnosis i.e. 77% compared with their siblings and age/sex matched controls i.e. 39% and 15% respectively. Diabetics also had a higher percentage of 2 or more severe life events prior to diagnosis i.e. 54% compared with 8% for siblings and 8% for neighbourhood controls. The frequency of severe difficulties was also higher for diabetics--46% compared with 13% and 23% for siblings and neighbourhood controls respectively. Stressful events and difficulties may be triggering factors involved in the aetiology of insulin-dependent diabetes.

A mechanism by which primary or secondary hypothalamic involvement results in the development of insulin-dependent diabetes mellitus (IDDM)

A literature survey and hypothesis is presented in which it is concluded that an intracellular ventromedial hypothalamic (VMH) glucopenia results in a bibrachial response consisting of adenohypophysial release of growth hormone and ACTH as well as sympathetic discharge, both of which act to elevate plasma glucose and remove the VMH glucopenia. This glucopenia may occur as a result of either a deficiency of circulating insulin or alterations in the kinetic properties of the VMH cellular insulin receptor. Two mechanisms for the development of insulin dependent diabetes mellitus (IDDM) are presented: (1) a defect in VMH glucose transport and/or metabolism such that a VMH glucopenia occurs with a subsequent bibrachial response. The result of this is glucose overproduction and a chronic excess glucose stimulus will eventually cause B-cell exhaustion (primary hypothalamic involvement). (2) reduction of the B-cell population by chemical, genetic and/or viral interactions with a consequential insulopenia results in a VMH glucopenia (secondary to a reduced glucose transport into the VMH cells) and causes a bibrachial response. This VMH response may temporarily restore plasma glucose balance but a chronically enhanced counter-regulatory response to maintain this balance will eventually stress the remaining B-cell population and cause further reductions in B-cell numbers (secondary hypothalmic involvement).

Myocarditis and cardiomyopathy

With more widespread application of EMB techniques, a significant percentage of ICCM patients have been found to have lymphocytic myocarditis on biopsy. It is now appreciated that patients with myocarditis may also present with isolated abnormalities of left ventricular diastolic function, dysrhythmias, and/or complaints of chest discomfort with normal coronary angiograms. Epidemiologic and serologic data incriminate a viral etiology underlying many cases of acute myocarditis and ICCM. Although most cases of viral myocarditis appear to resolve without residual left ventricular dysfunction, a small but significant percentage of these patients progress to chronic congestive cardiomyopathy. In the absence of persistent active viral infection in these patients, myocardial damage may be mediated by both cellular and humoral immune mechanisms. The concept of virus-induced immune mediated myocardial damage forms the basis for attempts at immunosuppressive therapy. Whether immunosuppressive therapy alters the natural history of myocarditis is at present unknown and awaits demonstration by a controlled clinical trial.

Complications of mumps infection, islet-cell antibodies, and HLA

To investigate whether the development of islet-cell antibodies (ICA) in the course of mumps infection is associated with a "diabetes-like" immunogenetic condition, 45 children with mumps complications as well as 56 children with insulin-dependent diabetes mellitus (IDDM) were typed for HLA ABC and DR antigens. ICA were detected in 14 out of 35 mumps patients. In the IDDM group, significant deviations from antigen frequencies of normal controls were observed for HLA Bw39, DR2, DR3, and DR4. In contrast, in ICA positive mumps patients, the frequency of these antigens was normal, but Aw24 was significantly increased. Thus, no immunogenetic similarities of both groups of patients could be detected.

HLA-related heterogeneity in seasonal patterns of diagnosis in Type 1 (insulin-dependent) diabetes

HLA type, time of year of diagnosis, and age at diagnosis were studied in 52 new cases of Type 1 diabetes in Seattle, Washington. Diagnosis was found to be seasonal in diabetic patients positive for DR3 (p less than 0.005), with the expected marked reduction in new cases during the summer months. This seasonality was not age-related (p greater than 0.13). Cases who were DR3-negative did not show significant seasonality of diagnosis (p greater than 0.5). However, when age at diagnosis was adjusted for, a seasonal effect was found in the DR3-negative group (p less than 0.006), with older cases favouring a spring onset and younger cases favouring an autumn onset. Thus, DR3-positive cases showed a seasonal diagnosis pattern that did not depend on age, while DR3-negative cases showed an age-dependent seasonal pattern. These differences may reflect the predominance of different aetiological mechanisms in these two genetic groups.

A solution to the genetic and environmental puzzles of insulin-dependent diabetes mellitus

Studies of the segregation of heterozygous immunoglobulin allotypes in families with several cases of insulin-dependent diabetes mellitus (IDDM) show that germline heavy-chain V (variable region) genes are not major genetic determinants for IDDM, but data for IDDM and Graves' disease together suggest involvement of kappa light-chain V genes. Absence of IDDM at birth, the semi-random age of onset, and the 50% discordance of identical twins suggest that somatic mutation of germline V genes is involved in the development of the pathogenetic anti-beta-cell clones. The effect of histocompatibility and other alloantigens on the prevalence of IDDM is readily accounted for by the effect of the "holes" they induce, by natural tolerance, in the immune response repertoire; these alterations apparently affect the chance of emergence of anti-beta-cell clones by the somatic mutations and network of interclonal deletions that constantly change the fringes of the repertoire. Histocompatibility antigens can also influence repertoire development by changing the specificity of conjoint presentation of foreign antigens by macrophages. Antigenic stimulation by particular environmental microorganisms is probably essential to the repertoire development necessary for the occurrence of IDDM. Additionally, beta-cell damage by local infection may play a part by facilitating autoantigen presentation to the immune system.

Recombination within and between the human insulin and beta-globin gene loci

We detected a large number of polymorphic insulin restriction fragments in black Americans. These different size fragments were probably generated by unequal recombination on both sides of the human insulin gene. Population genetic analysis indicates that recombination occurred 33 times more frequently than expected to generate this large number of polymorphic fragments. Specific properties of the unique repeated 14- to 16-base-pair sequences 5' to the insulin gene suggest that this sequence would promote increased unequal recombination. Additional pedigree analysis showed that the recombination rate between the structural insulin and beta-globin gene loci was 14% with strong evidence for linkage. Since both insulin and beta-globin have been mapped to the short arm of human chromosome 11, this study establishes that the genetic map distance between these genes is 14.2 centimorgans.

Effects of the rodenticide Vacor on cultured rat pancreatic beta cells

Human ingestion of the rodenticide Vacor has been implicated in the onset of diabetes mellitus. We report here studies of the effects of Vacor on cultured rat pancreatic beta cells and fibroblasts to determine if this agent preferentially intoxicates insulin-producing beta cells. Cytotoxicity in beta cells was monitored both by phase contrast microscopy and the release of insulin into the culture medium. Changes in cellular protein were correlated with morphologic observations to determine fibroblast viability. Beta cells were 10-fold more sensitive to the toxic effects of Vacor than were fibroblasts. Vacor toxicity was reduced by treatment with nicotinamide but was unchanged by 3-O-methyl glucose. Both of these agents reduced the toxic effects of the known beta cell poison streptozotocin. The present studies indicate that Vacor possesses a toxic affinity for pancreatic beta cells and that its mechanism of toxicity may be similar but not identical to that of streptozotocin.

Transfusions of whole blood prevent spontaneous diabetes mellitus in the BB/W rat

Weekly transfusions of whole blood from a nondiabetic subline of BB/W rats reduced the incidence of diabetes in susceptible BB/W rats from 39 to 0 percent and the incidence of pancreatic insulitis from 64 to 6 percent. Responsiveness of lymphocytes to concanavalin A was found to be low in rats with diabetes or insulitis. Transfusion restored concanavalin A responsiveness to levels observed in control rats free of diabetes or insulitis. These data suggest that whole blood alters the course of autoimmune BB/W rat diabetes.

Hypertensive diabetic cardiomyopathy in the rat: ultrastructural features

We previously described a cohort of diabetic patients with typical congestive cardiomyopathy, in whom myocardial lesions were related to concomitant high blood pressure. To evaluate the association of diabetes mellitus and hypertension in more detail, we studied 4 groups of rats with either no disease, streptozotocin-induced diabetes mellitus, renovascular hypertension, or a combination of hypertension and diabetes. Analysis revealed significant myocardial fibrosis and degeneration in the hypertensive-diabetic group when compared to controls, without an obvious relationship to small vessel lesions. The myocardial alterations appeared similar to those observed in patients with hypertension and diabetes mellitus. Of note, although hypertensive animals had focal moderate lesions, diabetic animals had no pathological changes. To further characterize these histological changes, we performed electron microscopy on the 4 animal groups, which we are reporting in this study. Our analysis of the ultrastructural alterations confirms the previous histological observations. Diabetic animals only had increased cellular lipid, and mild, focal areas of myofibrillolysis, with no significant increases in perivascular and perisarcolemmal basal lamina. Consistent with our light microscopic finding that PAS positive material was associated with interstitial or replacement fibrosis, we noted basal lamina proliferation in the hypertensive and hypertensive-diabetic groups, particularly in areas of scarring. Pericapillary basal lamina was increased to the greatest extent in the hypertensive-diabetics. Qualitative alterations of myocardial cells and muscular blood vessels were similar in both the hypertensive and hypertensive-diabetic animals; however, there were more extensive changes in the latter group. This study provides further evidence that the combination of diabetes mellitus and hypertension produces significantly greater myocardial lesions than with either disease alone, not only at the light microscopic level, but ultrastructurally as well. Although the pathogenesis of this cardiomyopathy is unknown it may be related to abnormalities of the cardiac microcirculation. The prevalence of hypertension in the diabetic population suggests that greater attention should be paid to the combination of these 2 conditions and their effects on the heart.

Use of pancreatic beta cells in culture to identify diabetogenic N-nitroso compounds

Epidemiological observations suggest that environmental factors play a role in the pathogenesis of insulin dependent diabetes mellitus (1). Several chemicals have been identified as specific beta cell toxins (2-4). We report here studies to determine the feasibility of using monolayer cultures of pancreatic beta cells from neonatal rat to screen potential diabetogenic chemicals. Cytotoxicity was monitored both by phase microscopy and the release of insulin into the culture medium. In comparative studies, cellular protein and release of 51chromium (51Cr) were measured after addition of test compounds to cultures of fibroblasts derived from pancreatic tissue. The nitrosoamides 1 methyl-l-nitrosourea (MNU), 1,3 bis (2-choroethyl) nitrosourea (BCNU), chlorozotocin (CLZ), and the beta cell toxin, streptozotocin (SZ), were examined. CLZ and SZ were more toxic to pancreatic beta cells than to fibroblasts. In contrast, MNU and BCNU damaged both beta cells and fibroblasts at identical concentrations. These results suggest that in vitro techniques can be used to identify chemicals that selectively injure beta cells. Although SZ-induced toxicity was ameliorated with addition of nicotinamide to cultures of beta cells, nicotinamide did not prevent damage caused by CLZ. This observation indicates different mechanisms of drug-induced cytotoxicity.

Diabetes produced in mice by smoked/cured mutton

There is circumstantial evidence of a causal connection between type 1 diabetes in young Icelandic males and consumption of smoked cured mutton, containing N-nitroso compounds, by their parents at about the time of conception. This hypothesis has been examined in CD1 mice, and such processed mutton, consumed by the parents before mating and during pregnancy and by the offspring from day 19 until study 1-5 weeks later, produced diabetes in just over 16% of male progeny and 4.2% of female progeny. Light and electron-microscopic changes in the beta-cells were those of stages of cell death. The parent mice showed no features of diabetes. When both parents were fed the Icelandic cured mutton only up to the time of fertilisation, there was first a fall and then a significant rise in the plasma glucose of the male progeny after the 3rd week of age. The female progeny showed a significant fall in plasma glucose at 5-6 weeks of age. These findings suggest that an environmental factor in the aetiology of human diabetes mellitus had been identified. The mechanism seems to involve parental as well as maternal influences of germ cells.

Prevalence of severe arteriosclerosis obliterans in patients with diabetes mellitus. Relation to smoking and form of therapy

Noninvasive methods were used to determine the prevalence and severity of arteriosclerosis obliterans associated with diabetes in 674 subjects including 153 recruited as controls. A resting ankle systolic blood pressure that was less than 90% of the arm pressure indicated severe arteriosclerosis obliterans. Of the 71 subjects with severe disease, 64 (90%) had a history of smoking, which is significantly greater than the 60% overall smoking rate (p less than 0.001). In non-insulin-dependent diabetic smokers, the diet-treated subjects had 2.5 times the prevalence of severe arteriosclerosis obliterans as those treated with insulin (p = 0.01); the sulfonylurea-treated subjects had twice the prevalence of severe disease as those treated with insulin (p = 0.015).

Low-dose streptozotocin-induced autoimmune diabetes is under the genetic control of the major histocompatibility complex in mice

In mice, an experimental autoimmune diabetes can be induced by multiple injections with low doses of streptozotocin. Since different mouse strains show a varying susceptibility towards this treatment, we have examined whether the experimental autoimmune diabetes is under the genetic control of the major histocompatibility complex (H-2 complex). Mice of five congenic resistant strains, differing in their genome only at the H-2 region, were identically treated on five consecutive days with 40 mg streptozotocin/kg body weight. Genes at the H-2 complex were found to determine the susceptibility towards the diabetogenic effect of streptozotocin: mice of H-2 haplotype k (B10.BR) developed persistent and strong hyperglycaemia (blood glucose approximately 17 mmol/l), mice of strain B10.A (H-2a), C57BL/10 (H-2b) and B10.D2 (H-2d) reacted with moderate hyperglycaemia (between 11.5 and 15.5 mmol/l), whereas mice of strain B10.S (H-2s) were resistant to the diabetogenic effect of low-dose streptozotocin except for a small and transient rise of blood glucose levels. It is concluded that genes within the major histocompatibility complex affect the diabetogenic response to multiple low-dose streptozotocin treatment.

Development of insulin-dependent diabetes mellitus during the hemolytic-uremic syndrome

Three children developed hyperglycemia and ketoacidosis three, eight, and 60 days after the onset of hemolytic-uremic syndrome. During hyperglycemia, the two patients studied had dramatically low insulin concentrations. Circulating islet-cell and insulin antibodies were not detected. These studies suggest that pancreatic beta cell dysfunction may occur during hemolytic-uremic syndrome, and that the serum glucose concentration should be closely monitored during this disease.

Assigning the polymorphic human insulin gene to the short arm of chromosome 11 by chromosome sorting

We have determined the subchromosomal location of the human insulin gene by analyzing DNA isolated from sorted human metaphase chromosomes. Metaphase chromosome suspensions were sorted into fractions according to relative Hoechst fluorescence intensity by the fluorescence activated chromosome sorter. The chromosomal DNA in each fraction was characterized by restriction endonuclease analysis. Initial sorts indicated that the insulin gene-containing fragment resided in a fraction containing chromosomes 9, 10, 11, and 12. Studies of cell lines that contained chromosome translocations permitted the assignment of the insulin gene to a derivative chromosome that contains portions of the short arm of chromosome II. Simultaneous sorting of the normal homolog from this small derivative chromosome separated the two different sized insulin gene-containing restriction fragments in this individual. These data indicate that the two restriction fragments represent insulin gene polymorphism and not duplicate gene loci.

Expression of major histocompatibility antigens on pancreatic islet cells

Insulin-dependent diabetes mellitus is often accompanied by manifestations of autoimmunity and is frequently associated with certain HLA haplotypes, predominantly DR3 and DR4. Because the major histocompatibility antigens are important determinants of the immune response in various tissues, we have investigated their expression on the pancreatic islet cells. Human, mouse, or rat islets of Langerhans, as well as lymphocytes or other differentiated cells, were biosynthetically labeled with radioactive amino acids, lysed in detergent, and immunoprecipitated with several antisera specific for major histocompatibility antigenic groups. The immunoprecipitates were analyzed by NaDodSo4/polyacrylamide gel electrophoresis under reducing conditions followed by autoradiography. The major histocompatibility antigens corresponding to the H-2 K,D molecules in mice, the H1-A in rats, and the HLA-A, -B, and -C in humans were precipitated from both islet and lymphocyte lysates and were accompanied by beta 2-microglobulin. Binding of H-2 antibodies to islet cells was also confirmed by a radioligand assay using 125I-labeled protein A and by indirect immunofluorescence. Analyses in the fluorescence-activated cell sorter revealed that greater than 95% of the cells in the beta-cell-rich fraction were fluorescent, providing further evidence that the pancreatic beta cells express the major histocompatibility antigens. Monoclonal antibodies or mouse alloantisera against HLA-DR or Ia antigens did not react with labeled pancreatic islet cell proteins.

Prevention of diabetes in rats by bone marrow transplantation

Hyperglycemia, hypoinsulinemia and ketonemia often develop abruptly in previously normal young "BB" rats. The syndrome mimics human juvenile diabetes closely and is, thus, appropriate for assessing pancreatic transplantation. Transplantation of islet cells from closely histocompatible Wistar Furth (WF) donor resulted in permanent normoglycemia when immunosuppression with ALS was given. However, when islet cells from nondiabetic "BB" donors were transplanted to nonimmunosuppressed diabetic "BB" recipients, only transient normoglycemia followed. Transplantation of WF islets cells also failed in diabetic "BB" rats which were tolerant of WF antigens, again suggesting destruction of transplanted islet cells by the original disease process-possibly autoimmunity. Evidence for autoimmunity was strengthened by the finding that newly diabetic "BB" rats could be rendered normoglycemic by immunosuppression. Since genetic susceptibility to spontaneous autoimmune diabetes is unique to some members of the "BB" stock, an attempt was made to alter their vulnerability by modifying their cellular immune system. Accordingly, 50 million bone marrow cells from WF donors were inoculated into half the newborn members of "BB" litters, leaving the littermates as unmodified controls. Most bone marrow recipients were protected, only four of 37 (10.8%) ever becoming diabetic, while the incidence of diabetes in noninoculated littermates was 22 of 39 (56.4%). The ultimate goal in human diabetes, which also seems very likely to be an autoimmune disease, may not be replacement of destroyed islet cells but identification of potentially susceptible children and prevention of islet destruction by immunologic manipulation.

Localization of the human insulin gene to the distal end of the short arm of chromosome 11

The human insulin gene was mapped by hybridization in situ of 3H-labeled recombinant plasmid pHIG900 to chromosome preparations in the presence of 10% dextran sulfate. pHIG900 contains a 900-base pair insert of human genomic DNA that includes the coding region for the C peptide and intervening sequence 2. A significant percentage of hybridized cells (34%) exhibited silver grains on the distal end of the short arm (band p15) of chromosome 11. Furthermore, silver grains on this region represented 26% of all chromosomal label. These results demonstrate chromosomal localization of the human insulin gene to 11p15.

Risk factors for hyperglycemia in children with leukemia receiving L-asparaginase and prednisone

We determined retrospectively the frequency and risk of hyperglycemia in 421 children with leukemia who had received L-asparaginase and prednisone as part of their remission induction therapy. Forty-one patients (9.7%) developed this complication, 39 within one week after the first dose of L-asparaginase. Hyperglycemia resolved in all patients and in 32 before the end of the four-week induction period. Age, obesity, and Down syndrome each had a significant bearing on the frequency of hyperglycemia. Children 10 years of age or older were more likely to develop the complication than were younger children. When more than one factor was present in a child, the risk of hyperglycemia increased significantly. A family history of diabetes mellitus also appeared related to an increased risk of hyperglycemia. Childhood leukemia patients with any of the risk factors identified here should be closely monitored for glucosuria while receiving prednisone and L-asparaginase for remission induction.

Correlation of HLA types in premature coronary artery disease: an attempt to define independent genetic risk factors

This study was designed to investigate whether isolated genetic factors, controlled by genes in the HLA chromosomal region, could be indicted as independent contributing influences in the genesis of premature coronary artery disease (CAD). Nineteen patients with fixed obstructive CAD documented by coronary angiography had no coronary risk factors with respect to age; levels of serum cholesterol, fasting triglycerides, and blood glucose; blood pressure; obesity; history of diabetes mellitus or hypertension; and cigarette-smoking history. Sixteen patients had a family history of CAD. HLA typing was restricted to antigens of the A and B loci. Control subjects (n = 1,157) were normal. At the A locus, no antigens demonstrated an observed frequency significantly higher than that expected from the control population. At the B locus, BW 38 had a statistically significant greater frequency (p less than 0.01) in the study group with CAD (21 percent) than in the control population (4 percent). The association between BW 38 and premature CAD lost its statistical significance when conservatively corrected for the number of HLA antigens tested by the Bonferroni adjustment. The relative risk for CAD if a patient had antigen BW 38 was 6.2. Our data suggest a statistically significant trend between the presence of HLA BW 38 and premature CAD. Whether the HLA tissue antigens are involved directly in the pathogenesis of CAD, act as markers for immune response genes, or serve as markers of other yet undefined genetic factors needs further study.

The brain and subarachnoid space as possible sites for endocrine tissue transplantation

Immunological rejection has been the major problem limiting the successful transplantation of tissue from one animal to another. Recent technological developments, combined with the use of the central nervous system as an immunologically privileged site, suggest that it might be possible to achieve long-term survival of hormone-secreting tissues, between two gentically dissimilar animals, if these tissues are transplanted to the brain and subarachnoid space of the host. The physiological parameters that should be considered in the clinical application of a transplant of this type are discussed.

Multiple immunologic pathogeneses for inflammatory diseases of the colon

There has been no clear indication, although there have been many indirect suggestions, that inflammatory diseases of the colon are due to immune activation against antigens of the colon. It is possible that inflammatory diseases of the colon have different etiologies and pathogeneses. Such etiologic differences may require different therapeutic approaches. The following paper will give experimental evidence which indicates that there are at least three different immunologic etiologies which can produce inflammatory colonic disease. This must be taken as a minimum number of etiologies and does not preclude the possibility that non-immunologic mechanisms may also produce these diseases.

Viral diabetes mellitus in man and experimental animals

Accumulating evidence strongly suggests that viruses may play an etiologic role in some cases of diabetes mellitus. The importance of environmental factors in the pathogenesis of the disease is suggested by genetic and epidemiological observations. Group B Coxsackie viruses and mumps virus have been implicated, and the evidence suggests that several other agents also could play a role in the disease. In experimental animals, a picornavirus similar to the Coxsackie viruses exhibits specific tropism for the beta cells of the islets of Langerhans, causing a disease in mice that is similar to juvenile-onset diabetes. In these animals, genetic and metabolic factors appear to influence the severity of beta cell injury. Immunopathologic considerations also may be important. In man, histocompatibility genes are important determinants of juvenile-onset diabetes and abberations of immune responsiveness to beta cells have been demonstrated. In experimental animals, cell-mediated immunity develops subsequent to the occurrence of viral-induced lesions in the islets. Viewed in concert, the evidence supports the notion that certain "wild" viruses may possess specific tropism for beta cells and destroy them during the course of a systemic infection. Host factors clearly play a role, but their relative importance in the pathogenesis of the disease remains to be defined.