Protein aggregation
leading to the formation of amyloid fibrils
has various adverse effects on human health ranging from fatigue and
numbness to organ failure and death in extreme cases. Insulin, a peptide
hormone commonly used to treat diabetes, undergoes aggregation at
the site of repeated injections in diabetic patients as well as during
its industrial production and transport. The reduced bioavailability
of insulin due to aggregation hinders the proper control of glucose
levels in diabetic patients. Thus, it is necessary to develop rational
approaches for inhibiting insulin aggregation, which in turn requires
a detailed understanding of the mechanism of fibrillation. Given the
relative simplicity of insulin and ease of access, insulin has also
served as a model system for studying amyloids. Approaches to inhibit
insulin aggregation have included the use of natural molecules, synthetic
peptides or small molecules, and bacterial chaperone machinery. This
review focuses on insulin aggregation with an emphasis on its mechanism,
the structural features of insulin fibrils, and the reported inhibitors
that act at different stages in the aggregation pathway. We discuss
molecules that can serve as leads for improved inhibitors for use
in commercial insulin formulations. We also discuss the aggregation
propensity of fast- and slow-acting insulin biosimilars, commonly
administered to diabetic patients. The development of better insulin
aggregation inhibitors and insights into their mechanism of action
will not only aid diabetic therapies, but also enhance our knowledge
of protein amyloidosis.