Glucagon-like peptide-1, glucagon and oxyntomodulin are three peptide hormones which play a significant role in diabetes, however there is a major controversy regarding their exact roles due to difficulties in measuring of these peptides because of molecular heterogeneity, low circulating concentrations and fast degradation. Because of the lack of detailed and relevant descriptions of their composition and use, the reliability of commercially available assays for these peptides is often
questionable. An in-depth investigation of the commercial assays was therefore performed. Moreover, the addition of aprotinin to plasma prior to glucagon sample analysis was investigated. Aprotinin addition has been recommended for many years to avoid peptide degradation during sampling and storage. To make sure that the analysed samples are handled correctly and that the peptides are not degraded, a study was performed to assess the effects of time, temperature, storage and re-freezing cycles. The study showed no significant changes in peptide concentrations, so aprotinin addition has been proven irrelevant for glucagon stability based on the work presented here. The study showed that degradation was not present for glucagon at room temperature. To improve measurement of hormones we additionally took part in the development and characterised of an IPLC/MS multiplex assay for measurement of the three peptides. The application of improved techniques for sample handling and analysis should help to sort out which of the studies from the
literature that have provided reliable measurements and thereby help resolve controversies regarding the metabolic roles of the peptides. The improved technology should also provide better reliability of future publications in the field.