Development of an LC-MS/MS methodology to quantify hormone peptides from human islet cells

Abstract

Type 1 diabetes mellitus (T1DM) is a chronic, incurable autoimmune disease that affects millions of individuals globally and is prevalent amongst children, adolescents, and adults. As a result, there is a critical need to explore and develop improved treatment options that enhance quality of life and reduce disease burden. The current standard of treatment for T1DM is lifelong exogenous insulin therapy, which has significantly improved patient outcomes since its introduction, transforming T1DM from a terminal illness into a manageable condition. However, insulin therapy does not replicate the complex, dynamic regulatory functions of a healthy pancreas. It requires constant monitoring of blood glucose levels, provides delayed pharmacokinetic responses compared to endogenous insulin secretion, and carries the risk of hypoglycaemia. These limitations underscore the need for more physiologically responsive treatment strategies.

One such promising approach is islet cell transplantation, the only approved clinical procedure for cell therapy in T1DM, in which functional islet cells, typically sourced from a cadaveric donor, are infused into the portal vein of the liver in T1DM patients. These transplanted cells replace the function of damaged islet cells and have the potential to restore insulin and other islet peptide secretion, thereby improving glycemic control and possibly reducing or eliminating the need for exogenous insulin, at least temporarily (mostly around 1-5 years). Despite its promise, a major challenge still remains in accurately assessing the functionality of the transplanted islets and the overall success of the procedure. Quantifying circulating islet peptide concentrations offers a meaningful way to evaluate transplantation efficacy, as these peptides (particularly insulin, glucagon, somatostatin, and C-peptide) play central roles in maintaining glucose homeostasis.

This thesis presents the development and optimization of a robust LC-MS/MS method for the simultaneous and rapid (15-minute) quantification of the islet peptides insulin, glucagon, and C-peptide in both solvent standards and human plasma samples. The method was refined through systematic selection of quantifier and qualifier ions, alongside rigorous diagnostic work to identify and address system contamination. Contamination was attributed to two main sources: sample carryover from prior injections and peptide adsorption to LC-MS system surfaces.

Date of Thesis submission	2025
Original language	English
Awarding Institution	Western Sydney University
Supervisor	David Harman (Supervisor), David Mahns (Supervisor) & Anand Hardikar (Supervisor)