Exploring the implications of vitamin B12 conjugation to insulin on insulin receptor binding.

We recently reported a vitamin B(12) (B(12)) based insulin conjugate that produced significantly decreased blood glucose levels in diabetic STZ-rat models. The results of this study posed a fundamental question, namely what implications does B(12) conjugation have on insulin's interaction with the insulin receptor (IR)? To explore this question we used a combination of molecular dynamics simulations and immunoelectron microscopy, and the results are described herein. This investigation demonstrates that chemical modification of insulin by linking relatively large pendant groups does not inherently interfere with IR recognition. Furthermore, given that we have previously demonstrated a significant drop in blood glucose concentration following the oral administration of the B(12)-insulin bioconjugate used in this work, it is reasonable to conclude that the IR recognition described herein is associated with maintenance of biological activity for insulin. This outcome offers significant research scope for chemical modification of insulin with the purpose of improving oral-uptake efficiency.