Prevalence of residual B cell function and its metabolic consequences in Type 1 (insulin-dependent) diabetes.

Abstract

Several reports suggest that most patients have surviving B cells at the onset of Type 1 (insulin-dependent) diabetes. After starting insulin therapy, most have a transient improvement in B cell function which peaks between 2 and 6 months after diagnosis. Thereafter B cell function declines. However, even after 2 years most patients still display some residual B cell function. During the following 10–15 years, the prevalence of residual B cell function decreases to about 15% and stays at this level. At present it is unknown why patients with Type 1 diabetes have different degrees of B cell function after several years of disease. Age at onset is of importance for the first 10–15 years of disease. Patients with late onset have a higher prevalence of retained B cell function than patients with early onset. Both at the onset of disease and after the initial remission period, an improvement in glycaemic control results in improved B cell function but the effect is transient. The occurrence of islet cell antibodies, islet cell surface antibodies and the many abnormal cellular immunological parameters found in Type 1 patients have not been correlated to the degree of B cell function. The metabolic importance of even minimal endogenous insulin secretion on intermediate metabolism has been clearly demonstrated during insulin withdrawal. During hypoglycaemia, patients with B cell function have a greater glucagon and pancreatic polypeptide response than patients without. The nadir and recovery of blood glucose do not differ, but rates of lipolysis and ketogenesis are exaggerated in those without B cell function. Residual B cell function is clearly linked to clinical remission but seems to have little effect on metabolic control in daily life after years of diabetes. Only patients with considerable B cell function have markedly better metabolic control than patients without B cell function, but those with residual B cell function need a smaller daily dose of insulin to obtain the same degree of control. Whether residual B cell function protects against or delays the development of late complications is not clear.