Diabetes, Vol 48, Issue 9 1677-1685, Copyright © 1999 by American Diabetes Association
Onset of type 1 diabetes: a dynamical instability
B Freiesleben De Blasio, P Bak, F Pociot, AE Karlsen and J Nerup
Niels Bohr Institute, Copenhagen, Denmark.
Type 1 diabetes is a disease characterized by progressive loss of beta-cell
function due to an autoimmune reaction affecting the islets of Langerhans.
It is now generally accepted that cytokines are implicated in the
pathogenesis of autoimmune diseases. Animal studies have shown that
interleukin-1beta, tumor necrosis factor-alpha, and interferon-gamma affect
type 1 diabetes development profoundly. It has been suggested that
beta-cells are destroyed by cytokine-induced free radical formation before
cytotoxic T-helper (Th)-lymphocytes and/or autoantibody-mediated cytolysis.
This hypothesis is known as the "Copenhagen model." We introduce a
mathematical model encompassing the various processes within this
framework. The model is expressed in rate equations describing the changes
in numbers of beta-cells, macrophages, and Th-lymphocytes. Being concerned
with the earliest events, we explore the conditions necessary to maintain
self-sustained beta-cell elimination based on the feedback between immune
cells and insulin-producing cells. The motivation for this type of analysis
becomes clear when we consider the multifactorial and complicated nature of
the disease. Indeed, recent research has provided detailed information
about the different factors that contribute to the development of the
disease, stressing the importance of incorporating these findings into a
more general picture. A mathematical formalism allows for a more
comprehensive description of the biological problem and can reveal
nonintuitive properties of the dynamics. Despite the rather complicated
structure of the equations, our main conclusion is simple: onset of type 1
diabetes is due to a collective, dynamical instability, rather than being
caused by a single etiological factor.