The great weight gain experiment, accelerators, and their implications for autoantibodies in diabetes

Aetiology of type 1 diabetes: Physiological growth in children affects disease progression

The prevailing view is that type 1 diabetes (T1D) develops as a consequence of a severe decline in β-cell mass resulting from T-cell-mediated autoimmunity; however, progression from islet autoantibody seroconversion to overt diabetes and finally to total loss of C-peptide production occurs in most affected individuals only slowly over many years or even decades. This slow disease progression should be viewed in relation to the total β-cell mass of only 0.2 to 1.5 g in adults without diabetes. Focal lesions of acute pancreatitis with accumulation of leukocytes, often located around the ducts, are frequently observed in people with recent-onset T1D, and most patients display extensive periductal fibrosis, the end stage of inflammation. An injurious inflammatory adverse event, occurring within the periductal area, may have negative implications for islet neogenesis, dependent on stem cells residing within or adjacent to the ductal epithelium. This could in part prevent the 30-fold increase in β-cell mass that would normally occur during the first 20 years of life. This increase occurs in order to maintain glucose metabolism during the physiological increases in insulin production that are required to balance the 20-fold increase in body weight during childhood and increased insulin resistance during puberty. Failure to expand β-cell mass during childhood would lead to clinically overt T1D and could help to explain the apparently more aggressive form of T1D occurring in growing children when compared with that observed in affected adults.

Is autoimmunity or insulin resistance the primary driver of type 1 diabetes?

Diabetes is usually classified as autoimmune or metabolic but, as difficulties have arisen with the taxonomy of diabetes, it may help to forego the conventional classification for a more inclusive model. Thus, all diabetes can be ascribed to beta cell insufficiency-hyperglycemia occurs only when the insulin supply fails to meet demand. Humans enter the world with a reserve of beta cells, which is eroded variably by apoptosis over the course of a lifetime. For most, the loss is slow and inconsequential but, for others fast enough to be critical within a lifetime. The challenge now is to define the factors that vary the tempo of beta cell loss, because tempo, not type, seems likely to determine whether diabetes occurs at all, in adulthood or in childhood. Insulin resistance is generally believed to underpin T2D, but has been a feature of insulin-dependent diabetes as well for nearly 80 years, though largely ignored until immunotherapy trials to test the autoimmunity hypothesis persistently failed to bring patient benefit. It seems possible that insulin resistance accelerates beta cell loss generally, its impact modulated by an immune response (autoimmunity) to the beta-cell stress whose intensity varies with immunogenotype. If so, the target for prevention of T1D might more logically lie with insulin sensitivity than with immunoregulation.

Increasing incidence of pediatric type 1 diabetes mellitus in Southeastern Wisconsin: relationship with body weight at diagnosis

Introduction

Several studies have confirmed the increasing rate of type 1 diabetes mellitus (T1DM) in children and the link with increasing BMI at diagnosis termed the ‘accelerator hypothesis’. Our objective was to assess whether changing incidence of type 1 diabetes in a group of children and adolescent from the Midwest United States was associated with changes in BMI.

Methods

Data from 1618 (52.1% M/47.9% F) newly-diagnosed children and adolescents (<19 years) with T1DM, admitted to Children's Hospital of Wisconsin (CHW) between January 1995 and December 2004, was analyzed in relationship to body mass index (BMI) standard deviation score (SDS).

Results

An overall, 10-year cumulative incidence of 27.92 per 100,000 (19.12 to 41.72/100,000) was observed, with an average yearly cumulative incidence of 2.39%. The increase was largest in the younger age groups, 0–4, 5–9, and 10–14 having an average yearly increase of 2.4, 2.3, and 3.0%, respectively, corresponding to a relative 10-year increase of 25.3, 33.8, and 38.0%, respectively. Age at diagnosis was inversely correlated with BMI SDS (p<0.001) and remained significant for both males and females.

Conclusions

Annual incidence of T1DM increased two-fold at CHW over the 10-year study period. The majority of the increase was observed in the youngest age groups, which also appeared to be the heaviest. This research adds to the growing literature supporting the hypothesis that excess weight gain during childhood may be a risk factor for early manifestation of T1DM.

Changing perspectives in diabetes: their impact on its classification

Type 1 and type 2 diabetes are usually regarded as distinct disorders, but the convergence of their phenotypes over recent years, the relationship of body weight to the risk of type 1 diabetes, the diminishing importance of the type 1 susceptibility genes and the finding of autoantibodies in patients with type 2 diabetes, invite a different interpretation. The possibility that type 1 and type 2 diabetes, rather than being different, are merely poles of a single spectrum, where variation in the tempo of beta cell loss determines age at onset and symptoms at presentation, has important implications. Correct classification is crucial because it directs appropriate treatment and, where available, prevention. This article argues that type 1 diabetes is currently misclassified, provides evidence that insulin resistance drives type 1 diabetes as it does type 2, and proposes how the 'accelerator hypothesis' can be tested in a randomised controlled trial, which could demonstrate, for the first time, the safe and effective prevention of type 1 diabetes.