Type 2 Diabetes (T2D) significantly increases the risk of a cardiovascular event, with acute myocardial infarction (AMI) the leading cause of mortality in these patients. The impact of T2D on the myocardial molecular mechanisms is however, poorly understood. Previous studies have demonstrated the essential role of protein phosphorylation to the outcomes following AMI. The current study uses large-scale phosphoproteomics to offer insight into the global impact of T2D on the heart and aims to elucidate the altered signalling cascades mediated by phosphorylation in response to AMI in the T2D setting.

Rats were fed a CHOW (12% fat) or high fat (HF) (42% fat) diet for 8 weeks, with T2D induced in 50% of the animals after 4 weeks utilising a low dose of Streptozocin (STZ; 35mg/kg) a pancreatic β-cell toxin. At the cessation of the feeding protocol, hearts were excised and subject to Langendorff perfusion to produce either non-ischemic time control (NITC) or ischemia / reperfusion (I/R) injury (30I/30R). Peptides were labelled with iTRAQ prior to enrichment of phosphopeptides utilising the TiSH method for analysis by tandem MS.

HF T2D hearts showed a significant decrease in functional recovery post-I/R (6.91 ± 2.42% versus 32.68 ± 4.98% in CH controls). This study identified 16,845 and 11,803 unique phosphosites, originating from 3,586 and 2,786 unique proteins from hearts subjected to NITC and I/R respectively. Using z-score cutoff >+1 or <-1, we observed 9,086 phosphosites significantly regulated following NITC and 6,432 phosphosites regulated by I/R. These regulated phosphosites were mapped to functional pathways utilising Kyoto Encyclopedia of Genes and Genomes (KEGG), identifying components of vital regulatory pathways such as the PI3K/Akt signalling cascade. By elucidating potential mechanisms behind the severely reduced capacity of the T2D heart to recover from AMI, improved outcomes and novel therapeutic targets are possible for these patients.