Genetic and metabolic studies in diabetic neuropathy.

Forty-one diabetic patients with symptomatic diabetic neuropathy were studied together with an equal number of matched diabetic subjects without neuropathy. The acetylator status was determined and HLA-A, B, C and DR antigens were investigated. Metabolic control was assessed by measurement of glycosylated haemoglobin and by the mean of multiple random clinic blood glucose values. No significant difference was observed between the two groups in the proportion of fast and slow acetylators. The distribution of HLA frequencies was similar in subjects with and without neuropathy for both Type 1 (insulin-dependent) and Type 2 (non-insulin-dependent) diabetic patients. When compared with diabetic subjects without neuropathy, the neuropathy group had higher levels of both glycosylated haemoglobin (mean +/- SEM: 50.1 +/- 1.4 versus 57.5 +/- 1.8 mmol hydroxymethylfurfural/mol haemoglobin (10.5 +/- 0.3 versus 12.0 +/- 0.4% haemoglobin A1, p less than 0.01) mean blood glucose (9.3 +/- 0.4 versus 11.3 +/- 0.5 mmol/l, p less than 0.005). This study provides no evidence that genetic factors increase the susceptibility of diabetic patients to develop neuropathy. In contrast, the elevated glycosylated haemoglobin and blood glucose levels strengthen the association between hyperglycaemia and diabetic neuropathy.

Tracking of indium-111-oxine labelled lymphocytes in autoimmune thyroid disease.

Peripheral lymphocytes (approximately 10(8)) from 4 subjects affected by autoimmune thyroid disease (2 Hashimoto's thyroiditis, 1 primary myxoedema, 1 Graves' disease) and 4 normal subjects were labelled in vitro with 40 microCi of indium-111-oxine and, following autologous injection, the distribution of the cells in the body was investigated by gamma camera imaging. Lymphocytes in the thyroid were observed 24 h after injection in both patients with Hashimoto's thyroiditis and in the patient with primary myxoedema, but not in the patient with Graves' disease or in any of the controls. To our knowledge, this is the first report using this method to try and demonstrate lymphocytes in the thyroid gland, and supports the concept that cell-mediated immunity may be playing an important role in the pathogenesis of Hashimoto's thyroiditis and primary myxoedema.

Evidence for an association between rheumatoid arthritis and autoimmune endocrine disease.

Evidence is presented for the first time of a significantly increased prevalence of type 1 (insulin-dependent) diabetes in the close relatives of patients with rheumatoid arthritis. Thirty-nine (13%) of 295 patients with classical or definite rheumatoid arthritis had a first or second degree relative with type 1 diabetes and 38 (13%) had a close relative with autoimmune thyroid disease. These findings could be compatible with a possible common genetically determined mechanism of susceptibility to both diseases.

IgG subclass distribution in organ specific autoantibodies. The relationship to complement fixing ability.

Indirect immunofluorescence techniques employing sheep monospecific antisera to human IgG subclasses on unfixed cryostat sections have revealed the IgG subclass distribution in autoantibodies to pancreatic islets (ICA), thyroid epithelial (TMA), gastric parietal (PCA) and adrenal fasciculata (AdA) cells. Whereas antibodies were detected in all four subclasses in 21 of 27 TMA positive sera (mean IgG titre 29 +/- 5 . 2), 13 of 15 PCA (mean IgG titre 41 +/- 3 . 8) and eight of 14 AdA sera (mean IgG titre 10 +/- 3 . 1), only four of 35 ICA positive sera (mean IgG titre 45 +/- 3 . 6) reacted in all four subclasses. Approximately 50% of ICA positive sera showed a restricted polyclonal response to the 'common' pancreatic antigen and 12% of these sera reacted only with IgG2 subclass. The restriction rarely applied to co-existent thyrogastric antibodies in these sera and was independent of the ability of ICA to fix complement. Lesser subclass restrictions were observed in antibody responses to the 'common' antigen of the adrenal cortex.

The genetic susceptibility to type 1 (insulin-dependent) diabetes: analysis of the HLA-DR association.

HLA-DR and MT1, MT2, MT3 genotypes have been investigated in 123 Type 1 (insulin-dependent) diabetic subjects and their families. Ninety-eight percent of probands possessed either DR3 (relative risk = 5.0), or DR4 (relative risk = 6.8) or both antigens (relative risk = 14.3), emphasizing the strong association of the disease with these two antigens. Almost 51% of the probands were DR3, DR4 heterozygotes. The DR antigen combinations of the parents leading to DR3, DR4 heterozygous and to DR3 and DR4 homozygous offspring were analysed. There was a marked increase in DR3, DR4 heterozygosity, but no increase in homozygosity for these antigens compared with the expected frequencies. These results are compatible with the existence of two susceptibility genes operating at a locus or at loci closely linked to that of HLA-DR. There was a striking reduction of DR7 (relative risk = 0.1) and only five probands possessed DR2 (relative risk = 0.1). In each case, the other inherited allele was DR3 or DR4. Linkage disequilibrium between B7 and DR2 was much lower in the haplotypes of the probands than in the 'non-diabetic' parental haplotype. In contrast, the association of BW62 with DR4 was more pronounced in the haplotypes of the probands. There was no increase in recombination frequency in these families and no strong effect of HLA-DR on age of onset could be demonstrated. There was a significant shift towards DR identity compared with identity for the whole HLA haplotype (A, B, C and DR) in both healthy and diabetic siblings (p less than 0.025).

Etiology of Type I diabetes mellitus: heterogeneity and immunological events leading to clinical onset.

Type I diabetes is a heterogeneous disorder and the causes of pancreatic beta-cell destruction are unknown. In 1-2% of all cases, viruses (e.g. coxsackie, rubella, mumps, or beta-cell poisons) have been implicated. Twin studies suggest at most 50% of genetic predisposition. In this review we describe the autoimmune components which, in association with inheritance of HLA-haplotypes in susceptible families, allow the future selection of predisposed sibs for possible preventive therapy to retard loss of insulin secretion. The known association of the endocrine autoimmune organ-specific disorders in 10% of Type I diabetics is the extreme expression of the other main genetic ingredient in the development of insulitis in this disease, irrespective of the triggering environmental components. In this "polyendocrine" subgroup and in the "juvenile-onset" cases there is a prolonged latency period during which pancreatic autoimmunity markers are present before clinical expression of the disease.

The genetics of Type 1 (insulin-dependent) diabetes.

The major genetic susceptibility to Type 1 (insulin-dependent) diabetes is determined by genes within the HLA region located on the short arm of chromosome 6. Ninety-seven percent of Type 1 diabetic patients belonging to the Barts-Windsor family study possess either DR3 or DR4 and about 50% possess both these antigens. This excess of DR3, DR4 heterozygosity can be best explained by postulating two different susceptibility genes which react in an interactive way. No increase in DR3 or DR4 homozygosity is found, nor is there an increase in recombination frequency in these families. Linkage disequilibrium between certain B and DR antigens differs in "diabetic" compared to "non-diabetic" haplotypes. In families with two or more Type 1 diabetic children, the affected siblings are with rare exception either HLA identical or haplo-identical. The results from the prospective Barts-Windsor family study indicate that complement fixing islet cell antibodies are a good marker of on-going immune destruction in the pancreatic islets. There is also a high prevalence of antibodies reacting with certain cells in the pituitary gland in newly diagnosed cases and their unaffected first degree relatives. A possible explanation is that a common virus may be acting to produce damage in several endocrine tissues. The Barts-Windsor family study was initiated in 1978 by the late Andrew Cudworth as a prospective family study to investigate the genetic, immunological and environmental factors involved in Type 1 (insulin-dependent) diabetes. About 200 families with a Type 1 diabetic child and at least one other unaffected sibling under the age of 20 years were ascertained from a defined geographical area of approximately 1500 square km, centered around Windsor, East Berkshire, UK. These families are visited every 3 to 4 months and are regularly screened for autoantibodies, in particular islet cell antibodies, and for viral antibodies and they have all been HLA-A, B, C genotyped. A large proportion have also been genotyped for HLA-DR and for the complement factors Bf, C2 and C4, which are coded by genes within the HLA-region.

HLA-DR typing in identical twins with insulin-dependent diabetes: difference between concordant and discordant pairs.

A total of 106 pairs of identical twins, of whom 56 were concordant and 50 discordant for insulin-dependent diabetes, were typed for HLA-DR. In both the concordant and discordant groups there was a high prevalence of the antigens DR3 and DR4, a low prevalence of DR5 and DR7, and a virtual absence of DR2. The heterozygous phenotype DR3,DR4 was more prevalent in concordant than discordant pairs. This was therefore the first demonstration of a genetic difference between concordant and discordant identical twin pairs. These findings suggest that possession of both DR3 and DR4 antigens confers a greater genetic predisposition to insulin-dependent diabetes than does the possession of either antigen alone.

Monoclonal antibodies defined abnormalities of T-lymphocytes in type I (insulin-dependent) diabetes.

Peripheral T-lymphocytes subsets have been investigated in 36 patients with type I (insulin-dependent) diabetes of varying duration, 18 patients with type II (non-insulin-dependent) diabetes, and in 23 healthy subjects, using six different monoclonal antibodies. At the time of diagnosis of type I diabetes, there was evidence of an increase in cytotoxic T-lymphocytes, a decrease in suppressor T-lymphocytes, but a normal proportion of helper/inducer T-lymphocytes. In six of seven newly diagnosed cases studied, there was evidence of an increased number of activated T cells. An increase in activated T-cells was also found in 5 of 10 genetically susceptible islet cell antibody positive unaffected siblings in type I diabetic probands. In type I diabetes of long standing, the total T-cell population was decreased, largely due to a marked decrease in helper/inducer T-lymphocytes. Type II diabetic patients showed no abnormalities in T-lymphocyte subsets, making it unlikely that hyperglycemia was responsible for the changes observed. These results suggest that an imbalance of T-lymphocyte regulation is an important feature of type I diabetes and lend support for an immunologic role in its early pathogenesis.

Long term improvement in insulin response with gliclazide treatment.

Blood glucose, plasma insulin and C-peptide concentrations were measured in response to a standard meal in eight Type 2 (non-insulin dependent) diabetic patients before and after treatment with gliclazide for 33 +/- 9 months. Compared with the pre-treatment values, blood glucose levels remained significantly lower (p less than 0.00001), while plasma insulin and C-peptide concentrations remained significantly higher (p less than 0.00001 and p less than 0.001 respectively) throughout the treatment period. In contrast to previous studies, these findings demonstrate that prolonged sulphonylurea treatment produces continued enhancement of B cell secretion.

Can future type I diabetes be predicted? A study in families of affected children.

This article examines the risk of type I (insulin-dependent) diabetes in siblings of affected children, in relation to HLA genotypes. The 288 available siblings of 160 diabetic probands were grouped according to the number of HLA haplotypes in common with their probands. HLA-identical siblings (both haplotypes in common) have an approximately 100 times greater risk of developing the disease than that in the general population, and this risk is significantly higher than that in haplo-identical siblings (one haplotype in common) P = 0.008). Thus, in Northern European populations, some 30% of HLA-identical siblings are expected to be diabetic by the age of 30 yr. The risk in nonidentical siblings (neither haplotype in common) is not significantly increased. These findings carry implications for genetic counseling and research.

Diabetic retinopathy and its relation to type of diabetes: review of a retinal clinic population.

A detailed survey was performed of 100 consecutive diabetic patients with severe retinopathy referred to a retinal clinic. They were classified as having either type 1 (insulin-dependent) or type 2 (noninsulin-dependent) diabetes. There were significant associations between an initial diagnosis of maculopathy. There was a significant association between male sex and proliferative retinopathy. Referral patterns to this clinic and the medical supervision of the patients are discussed.

Histology of the islets of Langerhans following administration of human lymphocytes into athymic mice.

Lymphocytes from seven newly diagnosed insulin-dependent (Type 1) diabetics, five islet cell antibody positive unaffected children and five normal subjects were injected i.p. into athymic nude mice. A further six mice were injected with medium and six control mice received no injection. Blood was taken from the tail vein before injection for glucose determination. After 10 days blood was again obtained from the tail vein; the pancreas was removed under deep ether anaesthesia and the mice sacrificed by exsanguination. Routine histological sections of the pancreas were prepared. There was no difference between groups in respect of the initial blood glucose. However, final blood glucose levels were raised in all mice that had received an injection including medium only, the rise being statistically significant both after injection of lymphocytes from normal subjects (P less than 0.05) and from newly diagnosed diabetics (P less than 0.001). Histology did not reveal any evidence of 'insulitis' or islet cell damage although enlarged, hyperplastic islets could be found in each group of treated mice. We conclude that passive transfer of diabetes was not achieved in this animal model. Elevation of blood glucose levels and islet hyperplasia may simply reflect a non-specific 'stress' reaction.

Increased plasma renin activity in type 1 diabetes with microvascular disease.

Plasma renin activity was measured in thirty-one subjects with Type 1 diabetes and proliferative retinopathy, and in seventeen matched diabetic subjects without evidence of any complications of their disease. The two groups were comparable for age, sex, smoking habits and duration of diabetes. Systolic and diastolic blood pressures were significantly higher in the patients with retinopathy (P less than 0.025 and P-0.05 respectively) and HbA1 was greater (P less tha 0.005) than in the patients without complications. Plasma renin activity, both lying and standing, was higher in the patients with retinopathy than in the uncomplicated group (P less than 0.05 for each). There were no correlations between plasma renin activity and mean blood pressure, HbA1 or fasting blood glucose. These findings raise the possibility that the renin-angiotensin system might be implicated in the pathogenesis of diabetic microvascular.

Autoimmunity to anterior pituitary cells and the pathogenesis of insulin-dependent diabetes mellitus.

An immunofluorescence study using unfixed cryostat sections of human pituitary glands was carried out on sera from patients with type-Ia (juvenile-onset) diabetes (61 recent onset, 48 longstanding). 63 of their selected high-risk first-degree relatives and 117 patients with type-Ib ("polyendocrine") diabetes were tested for comparison. Healthy controls included 48 sera from laboratory staff and students. Pituitary-cell antibodies were found in none of the controls, in 2% of patients with longstanding diabetes, in 16.6% of patients with diabetes of recent onset, and in 36.6% of genetically predisposed relatives with islet-cell antibodies in their sera (of whom 7 became diabetic during a 3-year follow-up period, 4 of them reacting with pituitary cells for 1-3 years before the onset of diabetes). Thus pituitary antibodies tended to disappear after onset of symptoms. Many of the sera reacted with multiple anterior-pituitary cell types. These findings suggest a wider involvement of the endocrine-organ system in the pathogenesis of insulin-dependent diabetes and are in accordance with clinical observations showing excess growth in prepubertal boys at onset of diabetic symptoms and with the results of experiments on virus-induced diabetes in mice. The connection of these pituitary antibodies with autoimmune lymphocytic hypophysitis is at present unknown.

Risk factors associated with severe proliferative retinopathy in insulin-dependent diabetes mellitus.

The natural history of disease and suspected risk factors for bad prognosis were investigated in 40 subjects with insulin-dependent diabetes mellitus who had severe retinopathy and in 22 patients with a similar duration of diabetes without evidence of complications. The retinopathy group showed a marked excess of men (ratio 2:1). Examination of the data in the literature also showed a striking excess of men, 61% (P less than 0.001) in patients with insulin-dependent diabetes and severe microvascular disease. In addition, proliferative retinopathy was found to have significant associations with current poor diabetic control, hypertension, and previous treatment with once-daily insulin regimens, particularly with protamine zinc insulin.

Genetic and immunologic factors in microvascular disease in type I insulin-dependent diabetes.

A detailed study of 133 subjects with insulin-dependent (type I) diabetes with severe microvascular disease has failed to substantiate the hypothesis that HLA factors influence the predisposition to this type of complication. A significant association between proliferative retinopathy and raised levels of circulating immune complexes was found. The distribution of insulin-binding levels in serum was similar to that in patients without complications. There was no correlation between insulin binding and the presence of immune complexes and no evidence was found that these complexes contained anti-insulin, anti-nuclear, or organ-specific antibodies. The distribution of insulin-binding levels in these subjects with diabetes of long duration was similar to that observed in 270 subjects with juvenile-onset short-duration type I diabetes. When the data were combined, significant associations between HLA-B8 and low/absent insulin binding levels were observed. HLA-BW62 was not associated with either high or low insulin-binding capacity. It is concluded that HLA genetic factors, insulin-binding capacity, and autoimmunity are unrelated to the pathogenesis of microvascular disease. Raised levels of circulating immune complexes may well be secondary to widespread tissue damage in diabetes of long duration.