Structural and Functional Characterisation of the A6-A11 Dicarba Insulin Analolgues

Author: Shee Chee Ong

Ong, Shee Chee, 2018 Structural and Functional Characterisation of the A6-A11 Dicarba Insulin Analolgues, Flinders University, College of Medicine and Public Health

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Insulin is an indispensable treatment for type 1 and late stage type 2 diabetes. While current insulin and insulin analogue treatments are effective for many patients, further improvements could provide better blood glucose control and minimise long term diabetic complications. New insulin analogue design aims to improve the pharmacokinetic and pharmacodynamic profiles and stability. In addition, concerns raised recently over some insulin analogues that have greater mitogenic potential than native insulin also calls for the design of insulin analogues that are metabolically-biased with low risk of promoting cancer growth.

Defining the physiologically relevant, active conformation of insulin is essential for the development of improved insulin mimetics. This project explored the possibility to improve insulin analogues through unconventional manipulation of the intra-chain A6–A11 disulfide bond. In collaboration with the Robinson laboratory (Prof. A. Robinson, Monash), the A6–A11 disulfide of native insulin, rapid-acting insulin lispro and long-acting insulin glargine were substituted with a rigid, non-reducible C=C (dicarba) linkage via chemical synthesis. During the synthesis, two non-interconvertible dicarba stereoisomers were generated with either a cis or trans configuration of the dicarba bond. It was discovered that the dicarba isomers exhibit completely different biological properties; cis isomer being active and trans isomer being inactive.

This study also discovered that while the cis dicarba insulins are not more stable than insulin, they are more rapid-acting, effectively lower blood glucose levels in mice and also exhibit significantly lower mitogenic potential. Importantly, through the biophysical analyses of these dicarba insulin analogues, this thesis describes the roles of A6–A11 bond that are critical for the regulation of insulin action, stability and signalling outcomes that have never been described before. These new insights into the insulin structure and function should hopefully provide a meaningful basis to the future design of improved insulin analogues.

Keywords: Insulin, dicarba, chemical synthesis, disulfide bonds, biophysical, conformation, signalling bias, structure, function

Subject: Medical Science thesis

Thesis type: Doctor of Philosophy
Completed: 2018
School: College of Medicine and Public Health
Supervisor: Prof. Briony E. Forbes