From immunobiology to β-cell biology: the changing perspective on type 1 diabetes

Abstract

Type 1 Diabetes (T1D) is characterized by the immune mediated destruction of β cells. Clinical studies have focused on drug therapies to modulate autoimmunity, yet none of these interventions has resulted in durable preservation of β-cell function. These findings raise the possibility that initiating or propagating events outside of the immune system should be considered in future efforts to prevent or reverse T1D. An emerging concept suggests that defects inherent to the β cell may trigger autoimmunity. A study by Engin et al. in type 1 diabetic NOD mice suggests that excessive β-cell endoplasmic reticulum stress arising from environmental insults results in abnormal protein synthesis, folding, and/or processing. Administration of the chemical protein folding chaperone TUDCA resulted in recovery of β-cell endoplasmic reticulum function and a diminished incidence of diabetes in NOD mice. We propose here that these data and others support a model whereby an inadequate or defective β-cell endoplasmic reticulum response results in the release of β-cell antigens and neoantigens that initiate autoimmunity. Pharmacologic therapies that either mitigate these early β-cell stressors or enhance the ability of β cells to cope with such stressors may prove to be effective in the prevention or treatment of T1D.

Keywords: ATF6; ER stress; Etiology; Immunology/autoimmunity/immune mechanisms; Islet cell biology/physiology; Pharmacologic agents; autoimmunity; sXBP1; type 1 diabetes; unfolded protein response; β cell.

Figure 1. The β cell-centric model of T1D pathogenesis. The model proposes that sustained systemic inflammation arising from environmental factors (e.g., viral infections, gut microbiome, diet) leads to development of ER stress in β cells. Irremediable ER stress, as a result of failed compensatory responses by ATF6 and sXBP1, leads to the dysfunction and death of β cells. The subsequent release of β-cell antigens and endogenous neoantigens triggers secondary autoimmunity. A vicious cycle then ensues, leading to destruction of β-cell mass and development of T1D. The figure shows the potential stages in pathogenesis where intervention with TUDCA might allow for ER stress remediation.