Glucose and insulin responses to oral glucose in overt non-insulin-dependent diabetics with and without the islet cell antibody

Type 1 1/2 diabetes: myth or reality?

The disease process in classical Type 1 diabetes patients (IDDM) is believed to be autoimmune. In contrast, the disease process in classical Type 2 diabetes patients (NIDDM) is not autoimmune and a decreased sensitivity to insulin action is the main abnormality. The clinical distinction of Type 1 diabetes versus Type 2 diabetes is recognized to be imperfect and has limitations. There is a group of individuals (Type 1 1/2 diabetes), who present like typical NIDDM, but have some of the immunological and clinical features of IDDM. We review the current medical literature on Type 1 1/2 diabetes with special reference to its clinical characteristics, natural history and pathophysiology. Since the distinction between these two forms of diabetes may have important therapeutic implications especially with regards to the benefits of insulin therapy in patients with Type 1 1/2 diabetes and because of the need for uniformity in its diagnosis we recommend that both clinical plus biochemical criteria (the presence of ICA and/or GAD Ab, HLA typing and tests to quantify beta cell function) be used to make a diagnosis. Comparative studies in the area of cytokine production, T cell reactivity and autoantibody clustering between classic Type 1 diabetes and Type 1 1/2 diabetes patients are needed as are studies with the animal model of Type 1 1/2 diabetes, Psammomys obesus.

Five-year follow-up of islet cell antibodies in type 2 (non-insulin-dependent) diabetes mellitus

The aim was to study the frequency and appearance of cytoplasmic islet cell antibodies in relation to impairment of insulin secretory capacity and some clinical characteristics in a representative group of middle-aged (45-64 years) patients with Type 2 (non-insulin-dependent) diabetes mellitus (70 male, 63 female) at the time of diagnosis and at five-year follow-up. Non-diabetic control subjects (62 male, 82 female) were similarly examined at five-year intervals. At the baseline five out of 133 (3.8%) diabetic patients were positive for conventional and four (3.0%) for complement-fixing islet cell antibodies. Ten patients had become positive by the second screening for conventional antibodies and six for complement-fixing antibodies, but none showed negative conversion. Two non-diabetic subjects (1.5%) became antibody positive during the follow-up. Insulin treatment was started during the follow-up for four out of 15 (27%) conventional antibody positive and for one out of 121 (0.8%) antibody negative diabetic patients (p = 0.001). The sensitivity of the positive conventional and complement-fixing antibody for identifying patients who developed an impairment of insulin secretory capacity (post-glucagon C-peptide less than or equal to 0.60 nmol/l at 5-year) was 75%. The respective specificity was 90% and the positive predictive values were highest in the case of high positivity (50%). The negative predictive value of antibody positivity was close to 100%. In conclusion, islet cell antibody positivity in patients classified as Type 2 was persistent during the follow-up and predicted the future development of insulin deficiency especially in those patients with high or increasing antibody titres.

Does knowledge of islet cell antibody status help in managing diabetes presenting in middle and old age?

It has been suggested that screening all patients with diabetes diagnosed in later life for islet cell antibodies (ICA) would help predict insulin dependence. We have surveyed the case notes of 55 patients (22 male; ages 37-88 years) who were found to be ICA positive over a 9-year screening period to assess what contribution knowledge of ICA status made to their management. Forty-two patients had been put on insulin (half within 6 months of diagnosis and the rest after up to 6 years). Of the 13 patients not on insulin, six were on diet alone and seven on oral hypoglycaemic agents after a median follow-up of 3 years. In 37 of the 42 patients, insulin treatment was started for clinical rather than immunological reasons (diabetic ketoacidosis, ketonuria, weight loss and/or severe symptoms). Five patients were started on insulin because of ICA status when there was no compelling reason on clinical grounds. Knowledge that seven non-insulin-treated patients were ICA positive made doctors reluctant to discharge them from clinic. The data suggest that routine ICA estimation in this age group is unnecessary, as the decision to treat with insulin is best made on clinical grounds, and ICA estimation can lead to unwarranted insulin treatment, or anxiety in patients and doctors who are aware of a positive result.

Islet cell antibodies and insulin autoantibodies in patients treated with oral hypoglycaemic agents

Clinical and immunological features suggesting Type 1 diabetes were assessed in 202 patients treated with oral hypoglycaemic agents for presumed Type 2 diabetes. Islet cell antibodies (ICA) were detected at a level exceeding 5 JDF units in 5.9% of patients, and complement-fixing ICA were detected in 3.4%. IgG insulin autoantibodies were detected in 8.8% of insulin-naive patients, none of whom were ICA positive. ICA were detected more frequently in patients with shorter duration of diabetes (p = 0.02). Age and relative body weight were similar in ICA positive and negative groups. ICA positive patients were more likely to have lost weight (p less than 0.02) than ICA negative patients, although this may have been attributable to the differing duration of diabetes in the two groups. Other individual clinical features suggesting Type 1 diabetes were not significantly more frequent in ICA positive patients. However, a higher proportion of ICA positive than ICA negative patients had one or more features suggestive of Type 1 diabetes irrespective of the duration of diabetes. Clinical features suggesting Type 2 diabetes were present in a similar proportion of ICA positive and ICA negative patients. Fasting and glucagon stimulated C-peptide levels were similar in ICA positive and matched ICA negative patients.

Autoimmunity in insulin-dependent diabetes mellitus

Genetic susceptibility, environmental factors and immune mechanisms are implicated in the pathogenesis and etiology of insulin-dependent diabetes mellitus. The onset of the disease is associated with a major loss of beta cells, and inflammatory cells may be seen in and around the islets of Langerhans. Insulin-dependent diabetes is often associated with autoimmune endocrinopathies. Antipancreatic cell-mediated autoimmunity is found predominantly in young patients with insulin-dependent diabetes of recent onset as are antibodies reactive with cytoplasmic components or cell surface determinants of islet cells. Antibodies reactive with live islet cells may mediate complement-dependent cytotoxicity. The antigen(s) in the islet cells remain(s) to be identified and characterized. Further studies will be necessary to determine whether autoimmunity is the cause of beta-cell destruction or whether it is a consequence of damages caused by exogenous agents in susceptible persons.