Heat shock protein studies in type 1 and type 2 diabetes and human islet cell culture

Abstract

Heat shock proteins (HSP) play an important role in auto-immunity and infection. Glutamic acid decarboxylase (GAD) the prime antigen in Type 1 diabetes has similar amino acid sequences to HSP65. An ELISA was developed using a plant-derived HSP65 antibody. HSP65 antibody was present in the serum of all normal subjects (median 1.64 AU, IQ range 1.49-1.74). Lower levels were found in established Type 1 diabetes (1.41 AU, 1.32-1.61, p < 0.001) and Type 2 diabetes (1.45 AU, 1.35-1.59, p < 0.006). In Type 1 HSP antibody levels fell with age (p = 0.007) and with duration (p = 0.008) and women with Type 1 had lower levels than men (p = 0.009). Human islet cell culture subjected to heat shock revealed an approximate four fold increase in heat shock protein antigen in the surrounding medium. The release of HSP antigen from stressed islet cells together with the finding of HSP antibody in the serum of all subjects suggest that HSP65 should not be completely discarded as having a possible role in the development of Type 1 diabetes. Low levels of HSP antibody in patients with established diabetes is probably a manifestation of impaired immunity induced by the diabetic state.