Islet Pathology Research Articles

Transient Clinical Diabetes Mellitus in Cats: 10 Cases (1989–1991)

Medical records of 10 cats with transient clinical diabetes mellitus were reviewed. At the time diabetes was diagnosed, clinical signs included polyuria and polydipsia (10 cats), weight loss (8 cats), polyphagia (3 cats), lethargy (2 cats), and inappetence (1 cat). Mean (+/- SD) fasting blood glucose concentration was 454 +/- 121 mg/dL, mean blood glucose concentration during an 8-hour period (MBG/8 hours) was 378 +/- 72 mg/dL, and glycosuria and trace ketonuria were identified in 10 and 5 cats, respectively. Baseline serum insulin concentration was undetectable (6 cats) or within the reference range (4 cats) and serum insulin concentration did not increase after i.v. glucagon administration in any cat. Insulin-antagonistic drugs were being administered to 5 cats and concurrent disorders were identified in all cats. Management of diabetes included administration of glipizide (6 cats), insulin (3 cats), or both (1 cat), discontinuation of insulin-antagonistic drugs, and treatment of concurrent disorders. Insulin and glipizide treatment was discontinued 4-16 weeks (mean, 7 weeks) after the initial diagnosis of diabetes was confirmed. At the time treatment for diabetes was discontinued, clinical signs had resolved, mean fasting blood glucose concentration was 102 +/- 48 mg/dL, MBG/ 8 hours was 96 +/- 32 mg/dL, glycosuria and ketonuria were not identified in any cat, and concurrent disorders (except mild renal insufficiency in 1 cat) had resolved. Significant (P < .05) increases occurred in postglucagon serum insulin concentrations, insulin peak response, and total insulin secretion, compared with values obtained when clinical diabetes was diagnosed. Histologic abnormalities were identified in pancreatic islets of 5 cats in which pancreatic biopsies were obtained and included decreased number of islets (4 cats), islet amyloidosis (3 cats), and vacuolar degeneration of islet cells (3 cats). Mean beta cell density was significantly (P < .001) decreased in diabetic cats compared with control cats (1.4 +/- 0.7 versus 2.6 +/- 0.5%, respectively). Cells within islets stained positive for insulin, however, the number of insulin-staining cells per islet and the intensity of insulin staining were decreased in 5 and 2 cats, respectively. Clinical diabetes had not recurred in 1 cat after 6 years, in 4 cats lost to follow-up after 1.5, 1.5, 2.0, and 2.5 years, and in 2 cats that died 6 months and 5.5 years after clinical diabetes resolved. Clinical diabetes recurred in 3 cats after 6 months, 14 months, and 3.4 years, respectively. These findings suggest that cats with transient clinical diabetes have pancreatic islet pathology, including decreased beta cell density, and that treatment of diabetes and concurrent disorders results in improved beta cell function, reestablishment of euglycemia, and a transition from a clinical to subclinical diabetic state.

Peripheral neuropathy in transgenic diabetic mice: restoration of C-fiber function with human recombinant nerve growth factor.

Mice (Ins.Dd1) with hypoinsulinemic diabetes were created by increased expression of syngeneic major histocompatibility complex (MHC) class I protein in pancreatic beta-cells. The diabetic state was characterized in these mice by high glucose concentrations and islet pathology. To determine whether a neuropathy would develop, motor and sensory conduction velocities (CV) were determined in the sciatic nerves of 2-, 4-, and 7-month-old control and diabetic littermate male mice. Recording bipolar electrodes were placed in the plantar muscles of the hind foot of anesthetized (ketamine/xylazine) mice. Bipolar stimulating electrodes were positioned near the sciatic nerve at the sciatic notch or near the tibial nerve at the ankle. Motor CV from alpha-motor fibers and sensory CV from proprioceptive Aalpha nerves were measured and expressed as meters per second (m/s). Group data are reported as mean +/- SE and compared by analysis of variance. The CVs from nondiabetic mice (controls) were not different across the three ages and averaged 41.3 +/- 1.7 m/s for motor and 38.7 +/- 1.7 m/s for sensory. The motor CVs from diabetic mice at 2 and 4 months were similar to controls. Sensory CVs were unchanged at 2 months but were lower at 4 months (18.9 +/- 2.4 m/s). Both sensory (23.9 +/- 2.1 m/s) and motor (18.9 +/- 1.8 m/s) CVs were significantly reduced at 7 months, which is indicative of a polyneuropathy. NGF has well-known trophic effects on sympathetic and small sensory neurons. To determine whether NGF could influence this neuropathy, 6-month-old control and diabetic mice were divided into the following groups: 1) control + vehicle, 2) diabetic + vehicle, and 3) diabetic + NGF (1 mg/kg, 3x week, s.c.). After 1 month of treatment, motor and sensory CVs were determined. In some mice, the branches of the sciatic nerve were exposed and in situ recordings from the sural nerve were performed to determine compound C-fiber CV, integral, and amplitude. Sensory CV, determined via Hoffmann's reflex (H-reflex) (A-fiber), was decreased in diabetic compared with control animals as expected (P < 0.05), and NGF did not alter this parameter. Continuing diabetes reduced the amplitude (0.9 +/- 0.2 vs. 3.2 +/- 0.7 mV x 10(-2); P < 0.05) and integral (6.9 +/- 1.9 mV/ms vs. 18.8 +/- 4.4 mV/ms; P < 0.05) of the C-fiber response versus control, suggesting fiber loss. NGF treatment normalized C-fiber amplitude (2.9 +/- 0.8 mV x 10(-2)) and integral (21.2 +/- 6.5 mV/ms) in animals with established diabetes, with no effect on blood glucose. The C-fiber CV was similar in all groups, indicating that the animals had some normally conducting small fiber sensory nerves. These studies characterized a motor and sensory polyneuropathy in transgenic diabetic mice and are the first to demonstrate directly that NGF treatment can protect or restore abnormal sensory C-fiber function.

Induction of insulitis by glutamic acid decarboxylase peptide-specific and HLA-DQ8-restricted CD4(+) T cells from human DQ transgenic mice.

Insulin-dependent diabetes mellitus in humans is linked with specific HLA class II genes, e.g., HLA-DQA1*0301/ DQB1*0302 (DQ8). To investigate the roles of HLA-DQ8 molecules and glutamic acid decarboxylase (GAD) in disease development, we generated DQ8(+)/I-Abo transgenic mice expressing functional HLA-DQ8 molecules and devoid of endogenous mouse class II. DQ8(+)/I-Abo mice produced antigen-specific antibodies and formed germinal centers after immunization with GAD65 peptides. Two GAD peptide-specific (247-266 and 509-528), DQ8 restricted Th1 CD4(+) T cell lines, were generated from immunized DQ8(+)/I-Abo mice. They induced severe insulitis after adoptive transfer into transgene positive (but not negative) mice who were treated with a very low dose of streptozotocin that alone caused no apparent islet pathology. In addition to CD4, islet mRNA from these mice also showed expression of CD8, IFNgamma, TNFalpha, Fas, and Fas ligand. Our data suggest that a mild islet insult in the presence of HLA-DQ8 bearing antigen-presenting cells promotes infiltration of GAD peptide reactive T cells into the islet.

Accelerated Loss of Islet β Cells in Sucrose-Fed Goto-Kakizaki Rats, a Genetic Model of Non-Insulin-Dependent Diabetes Mellitus

The Goto-Kakizaki (GK) rat is a spontaneously diabetic animal model of non-insulin-dependent diabetes mellitus, which is characterized by progressive loss of beta cells in the pancreatic islets with fibrosis. In the present study, we examined the effects of sucrose feeding on the islet pathology in this model. Six-week-old GK rats were fed with 30% sucrose for 6 weeks to induce severe hyperglycemia, and their condition was compared with that of nontreated rats. Age-matched normal Wistar rats were also given sucrose for the same periods and used for comparison. The sucrose-treated GK rats showed elevated blood glucose levels on oral glucose tolerance tests at 60 minutes and 120 minutes, representing 123% and 127% of values in untreated GK rats, respectively. At the end of the study, the mean beta-cell volume density in GK rats was 50% less than that in untreated Wistar rats. Sucrose feeding further reduced the volume densities of beta cells to only 50% of the levels of age-matched GK rats. Apoptotic cells were found in islet beta cells only in GK rats fed sucrose (mean 0.067%). There appeared to be more islets that immunohistochemically stained strongly positive with 8-hydroxy-deoxyguanosine as a marker of oxidative damage of DNA in GK rats fed sucrose compared with those not given sucrose. GK rats not fed sucrose showed significantly lower proliferative activity of beta cells measured by 5-bromo-2'-deoxyuridine uptake and intensified expression of Bcl-2 immunoreactivities at 6 weeks of age compared with those in age-matched Wistar rats. These two indices were reduced in both GK and Wistar rats with increasing age and were not affected by sucrose feeding in either group. The present study thus indicated that sucrose feeding promoted the apoptosis of beta cells in GK rats through increased oxidative stress without altering their proliferative activity.

Transgenic expression of mouse proinsulin II prevents diabetes in nonobese diabetic mice.

IDDM in humans and in nonobese diabetic (NOD) mice is a T-cell-dependent autoimmune disease in which the beta-cells of the pancreatic islets are destroyed. Several putative beta-cell autoantigens have been identified, but insulin and its precursor, proinsulin, are the only ones that are beta-cell specific. (Pro)insulin may be a key autoantigen in IDDM. To address the role of proinsulin in the development of IDDM, we generated NOD mice transgenic for the mouse proinsulin II gene driven off a major histocompatibility complex (MHC) class II promoter to direct expression of the transgene to MHC class II bearing cells, including those in the thymus, with the aim of deleting proinsulin-reactive T-cells. The mononuclear cell infiltration of the islets (insulitis) is almost completely absent, and diabetes is prevented in these transgenic NOD mice. The mononuclear cell infiltration of the salivary glands (sialitis) and immune responses to ovalbumin (OVA) are not altered, indicating that the protective effect of the transgene is specific for islet pathology and not due to general immunosuppression. We conclude that autoimmunity to proinsulin plays a pivotal role in the development of IDDM.

Aerosol insulin induces regulatory CD8 gamma delta T cells that prevent murine insulin-dependent diabetes.

Cellular immune hyporesponsiveness can be induced by the presentation of soluble protein antigens to mucosal surfaces. Most studies of mucosa-mediated tolerance have used the oral route of antigen delivery and few have examined autoantigens in natural models of autoimmune disease. Insulin is an autoantigen in humans and nonobese diabetic (NOD) mice with insulin-dependent diabetes mellitus (IDDM). When we administered insulin aerosol to NOD mice after the onset of subclinical disease, pancreatic islet pathology and diabetes incidence were both significantly reduced. Insulin-treated mice had increased circulating antibodies to insulin, absent splenocyte proliferation to the major epitope, insulin B chain amino acids 9-23, which was associated with increased IL-4 and particularly IL-10 secretion, and reduced proliferation to glutamic acid decarboxylase, another islet autoantigen. The ability of splenocytes from insulin-treated mice to suppress the adoptive transfer of diabetes to nondiabetic mice by T cells of diabetic mice was shown to be caused by small numbers of CD8 gamma delta T cells. These findings reveal a novel mechanism for suppressing cell-mediated autoimmune disease. Induction of regulatory CD8 gamma delta T cells by aerosol insulin is a therapeutic strategy with implications for the prevention of human IDDM.

Severe Islet Amyloidosis in Congenital Generalized Lipodystrophy

Islet amyloidosis may be one mechanism for pancreatic islet beta-cell loss that is associated with the development of NIDDM. However, the question remains whether chronic overstimulation of insulin and islet amyloid polypeptide (IAPP) secretion in states of insulin resistance could lead to formation of islet amyloidosis and hence NIDDM in some patients. We studied pancreatic islet pathology in congenital generalized lipodystrophy, a genetic syndrome of extreme insulin resistance that may provide some clues. Our patient was a 24-year-old African-American woman with congenital generalized lipodystrophy. Severe acanthosis nigricans was noted in her since age 6. At ages 12 and 16, normal and impaired glucose tolerances, respectively, were noted on oral glucose tolerance tests but were accompanied by extreme fasting and post-prandial hyperinsulnemia. Overt diabetes developed at age 18 and she required approximately 180 U of insulin daily. Immediately after an accidental death at age 24, an autopsy was performed. Pancreatic histology was studied in detail using routine methods and immunohistochemical techniques. Some scarring of the pancreas as a result of previous episodes of acute pancreatitis was observed. Severe amyloidosis was noted in 89% of the islets, sparing those that were rich in pancreatic polypeptide-secreting cells. Amyloid deposits stained intensely on immunostaining with antibodies against amylin. Marked paucity of beta-cells was evident. The ratio of beta- to alpha-cells was reduced to 1:1 (normal ratio approximately 4:1). These observations suggest that chronic presence of extreme insulin resistance may induce premature and severe islet amyloidosis as well as beta-cell atrophy.

Heterogeneity of islet pathology in two infants with recent onset diabetes mellitus

The mechanisms by which the beta cells of pancreatic islets are destroyed in insulin-dependent diabetes mellitus (IDDM) are poorly understood. In this report the pancreatic histo- and immunopathology of two children, both HLA-DR 3/4, DQ 2/8 positive and who both died from cerebral oedema within a day of clinical diagnosis of IDDM, were investigated. Patient 1, a 14-month-old girl, had a 4-week history of polydipsia and polyuria. Patient 2, a 3-year-old boy, had 2 days of illness. Both patients had a similarly severe loss of insulin cells but differed markedly as to the extent of lymphocytic islet infiltration (insulitis). Apart from insulitis, marked islet macrophage infiltration was demonstrated in both patients with the HAM-56 monoclonal antibody. Neither patient showed aberrant expression of HLA class II antigens on insulin-immunoreactive cells, but allele-specific HLA-DQ8 expression was evident on endothelial cells. Glutamic acid decarboxylase immunoreactivity was detected in both insulin- and glucagon-immunoreactive cells. It is concluded that the heterogeneity of islet pathology, especially insulitis, may reflect different dynamics and extent rather than different pathomechanisms of immune destruction of islets in IDDM.

Pancreatic pathology in non-insulin dependent diabetes (NIDDM)

NIDDM is a heterogeneous disease and subgroups of NIDDM include MODY (Maturity Onset Diabetes of the Young), Malnutrition-related diabetes (MRDM) and Fibrocalculus pancreatic diabetes (FCPD). Endocrine cell population is relatively unchanged in NIDDM: B-cells are reduced by up to 30% and A-cells increased by 10%. Islet amyloid is found in 96% of subjects occupying up to 80% of the islet associated with a reduction in B-cells. Amyloid formation is unlikely to cause diabetes but progressive accumulation increases the severity of the disease. Islet amyloid is formed from the islet amyloid polypeptide (IAPP), a normal constituent of B-cells, co-secreted with insulin. The causal factors for IAPP fibrillogenesis are unknown but abnormal synthesis or overproduction could be involved: stimulation of B-cell secretion in NIDDM by obesity, hyperglycaemia or suphonylurea therapy may promote amyloidosis and further aggravate islet pathology. A mutation of the glucokinase gene in MODY leads to diminished B-cell secretion but not amyloid formation. Diabetes and mutations of mitochondrial DNA is associated with poorly developed islet structure. Exocrine pancreatic size is reduced and there is evidence of sub-clinical chronic pancreatitis in NIDDM. In MRDM and FCPD, chronic pancreatitis and exocrine necrosis is associated with reduced insulin secretion. Unlike cystic fibrosis where islet amyloid is present in diabetic individuals, amyloid is absent from subjects with FCPD. Pathological changes in the exocrine and endocrine pancreas in NIDDM results from and contributes to the pathophysiology of insulin secretion in NIDDM.

IDDM in rats induced by thymectomy and irradiation.

A diabetic syndrome closely resembling human IDDM has been induced in rats of specific pathogen-free origin by a combination of thymectomy and irradiation, with an overall incidence (10 wk postirradiation) in female rats of 34% for acute disease and 47% for islet lesions. Males were slightly more susceptible than females. Clinical features of the syndrome included hyperglycemia, insulinopenia, ketosis, and lipidemia, and corresponding islet pathology ranged from diffuse atrophy to focal atrophy and insulitis. Onset was usually acute, and the disease fatal unless early insulin therapy was initiated. Lymphocytic thyroiditis also was observed in a proportion of thymectomized and irradiated rats (49% in females) over the same period but with no apparent correlation to the occurrence of diabetes. A significant decrease in the incidence of disease was found in thymectomized and irradiated rats of conventional origin when compared with genetically identical specific pathogen-free rats, implicating a role for environmental factors in disease susceptibility. Diabetes inducement also was found to be strain related but not RT1u dependent. Both clinical signs and islet lesions were inhibited by early reconstitution of thymectomized and irradiated animals with syngeneic lymphoid cells from normal donors. Islet lesions and glucose intolerance could be transferred to syngeneic recipients by concanavalin A-activated lymphoid cells from acute diabetic donors. The close similarities between this experimental syndrome induced by immunological manipulation and the clinical condition in humans provide further evidence for an immune-mediated pathogenesis for IDDM.

MHC molecules and beta-cell destruction. Immune and nonimmune mechanisms.

Hyperexpression of major histocompatibility complex (MHC) molecules by islet cells is a prominent, early feature of islet pathology in insulin-dependent diabetes mellitus and concomitant with beta-cell failure after exposure of islets to specific cytokines or viruses. The transgenic expression of a class I MHC gene (H-2Kb) in the beta-cells of either syngeneic or allogeneic mice leads to beta-cell failure by a nonimmune mechanism. Several class II MHC transgenes, with one exception, have the same effect, but the expression of other transgenes that have products that are membrane proteins is not necessarily detrimental. Class I MHC molecules have been shown to interact directly with other membrane proteins. The inappropriate expression of MHC molecules could therefore interfere with key cellular functions. We postulate that the hyperexpression of MHC molecules in the beta-cell, e.g. in response to viruses, is a primary, nonimmune mechanism of beta-cell failure that precedes a secondary autoimmune response.

Diabetes prevention in BB rats by frequent blood withdrawal started at a young age.

The BB rat diabetic syndrome has been prevented by various immunosuppressive and reconstitution measures. We observed an effect of multiple blood samplings on diabetes incidence and examined its immunological correlates. Individual litters were divided into two groups; one was sampled and the other was sham sampled as the control group. Sixty-four diabetes-prone and 59 non-diabetes-prone rats were studied. The sampled rats had blood removed at 15 (28% of total blood volume), 30 (30%), 50 (21%), 75 (16%), and 120 days of age. The sham-sampled control rats had blood removed only at 120 days of age. The incidence of diabetes in the sampled group was markedly lower than that of their sham-sampled littermates (22 vs. 78%). This result was associated with a correction of their OX19+ (pan-T-lymphocytes) and W3/25+ (helper/inducer) T-lymphocyte-number defects. An increase in lymphocyte subsets was also seen in the non-diabetes-prone BB rats, significant for all but the OX19+ cells. Islet pathology and pancreatic insulin content were consistent with metabolic outcomes. The effect of blood withdrawal thus has implications for understanding the pathogenesis of both the diabetes syndrome and the lymphopenia of the BB rat. Furthermore, it suggests that a stimulation of lymphopoiesis by blood withdrawal (analogous to that of erythropoiesis) may be a hitherto unrecognized physiological response in normal animals.

Islet pathology and the pathogenesis of type 1 and type 2 diabetes mellitus revisited.

The present review draws attention to the diversity of islet lesions seen in human type 1 and type 2 diabetes. This heterogeneity of islet changes is best demonstrated by immunocytochemistry. In type 1 diabetes the endocrine pancreas is characterized by selective loss of B cells, which most likely results from a slowly acting autoimmune process depending on the presence of both genetic and environmental factors. The process starts years before overt diabetes develops and manifests when the B-cell volume is reduced by about 80%. In type 2 diabetes B cells are always present, regardless of the duration and severity of the disease, but lack any signs of functional activity. This reflects a secretory defect of the B cells which obviously becomes evident under the conditions of obesity, hyperinsulinism and insulin resistance. Obese but non-diabetic subjects show, in parallel to their hyperinsulinism, an increased B cell volume, suggesting that under prediabetic conditions the B cells have still the capacity to respond to increased functional demands by enhanced proliferation. In manifest diabetes the B cells have lost their proliferative potential. Whether this is due to an inherent defect or the consequence of a functional disturbance, is not clear. The development of islet amyloidosis most likely represents an associated functional abnormality of the B cell.

The pancreatic islets in diabetes

Despite the fact that heterogeneity of diabetes in man has become more and more evident in recent years, its pancreatic pathology is still represented by two distinct entities, roughly corresponding to the classic juvenile-onset and maturity-onset types of the disease. In juvenile-onset, insulin-dependent diabetes, the pancreatic islets show severe and pathognomonic changes. B cells are greatly reduced in number already at clinical onset. Contrary to classic opinion they do not always disappear in the years to follow. Insulin's, a common finding in the pancreas of recent onset juvenile diabetic subjects, is compatible with a viral infection as well as with an autoimmune reaction as the cause of B cell destruction. In the pancreas of juvenile-onset diabetic subjects the islets, which in the past have been regarded as atrophic and inactive, are actually composed of cells containing glucagon and somatostatin. There is also a profound distortion of islet organization, and many endocrine cells are scattered as single cells in the exocrine tissue. These findings may well account for the abnormal secretory behavior of the glucagon-secreting A cells in insulin-dependent juvenile-onset diabetes. In maturity-onset, noninsulin-dependent diabetes, the pancreatic pathology is extremely variable and not pathognomonic. A numeric reduction of the B cells can be demonstrated in many maturity-onset diabetic subjects, but this reduction is much more moderate than in insulin-dependent juvenile-onset diabetic subjects and does not account for the disease. The same amount of B cell reduction can be found in many elderly subjects without clinical evidence of diabetes. In many maturity-onset diabetic subjects, the cytologic characteristics of the B cells suggest a decreased responsiveness to the stimulus of hyperglycemia. Islet fibrosis and hyalinosis (amyloidosis), although common, cannot explain this secretory dysfunction. The exact site of the defect in the B cells of maturity-onset diabetic subjects remains to be defined. Further investigations are necessary to assess the role of disturbed intraislet intercellular relationships in the pathogenesis of late-onset diabetes. The dual pattern of islet pathology in diabetes in man does not preclude a more profound heterogeneity in the etiology and pathogenesis of the disease.

Pancreatic Perinuclear Inclusions in Diabetes Mellitus and Other Diseases

Unusual perinuclear inclusions in pancreatic duct cells were observed by electron microscopy in 23 diabetic pancreases, in nine pancreases with islet hyperplasia, and in 10 of 27 pancreases without islet pathology. The origin and significance of the perinuclear inclusions could not be determined, but it is suggested that they may be of viral origin or may represent a cellular response to an unknown stimulus.

Diabetes Mellitus in the Guinea Pig

Spontaneous diabetes mellitus has been documented in a colony of guinea pigs. The contagious nature of the disease has been verified, but the nature of the infectious agent is not known. Animals from the original colony or animals exposed to the colony with normal glucose tolerance tests (GTT) became diabetic, as evidenced by elevated one- and four-hour GTT values, and in most cases have significant glycosuria. The severity of pathologic changes in the pancreatic islets parallel, in general, the severity of the clinical symptoms (glycosuria and abnormal GTT). Those animals with severe glycosuria and elevated FBS as well as one- and four-hour GTT values had the most pronounced degranulation and most prominent cytoplasmic inclusions in islet B cells. The severity of scarring in the islets can be correlated with the duration of the overt diabetic state. The other clinical parameters of note were elevated serum triglycerides, normal serum but elevated aortic cholesterol, and absence of ketonemia or ketonuria. The reproductive capacity of diabetic females was compromised. While the clinical manifestations are mild or variable, the presence of significant islet pathology is reminiscent of human juvenile diabetes mellitus. These findings lend support to the concept that infectious and/or immune mechanisms could be operative in the etiology and pathogenesis of human diabetes mellitus.

Islet pathology in diabetes.

Islet pathology in diabetes.