Lightning Talk & Poster 27th Annual Lorne Proteomics Symposium 2022

Acute treatment with antioxidant N-propionylglycine improves contractile function and minimises the extent of cysteine redox post-translational modifications in the diabetic heart as identified by quantitative mass spectrometry (#21)

Alexander W Rookyard 1 2 , Desmond K Li 2 3 , Stuart J Cordwell 1 2 4 5 , Melanie Y White 2 4 , Molly K Talbot 6
  1. School of Life and Environmental Sciences, University of Sydney, Camperdown, NSW, Australia
  2. Charles Perkins Centre, University of Sydney, Camperdown, NSW, Australia
  3. Heart Research Institute , Sydney , NSW, Australia
  4. Discipline of Pathology, School of Medical Sciences, University of Sydney, Camperdown, NSW, Australia
  5. Sydney Mass Spectrometry , University of Sydney, Camperdown, NSW, Australia
  6. School of Medical Science, University of Sydney, Camperdown, NSW, Australia

The pathophysiology of metabolic syndrome (MetS) involves obesity, hyperglycaemia, insulin resistance and hyperlipidaemia, each of which has the potential to promote a myriad of complications, the most prevalent being type 2 diabetes (T2D) and cardiovascular disease (CVD). A common underlying feature of these mechanisms is the supraphysiological production of reactive oxygen and nitrogen species, unable to be sequestered by endogenous protective mechanisms including glutathione, superoxide dismutases, thioreductases and peroxiredoxins. As a major target of oxidative damage, cysteine is at risk of modification in redox altered environments, including MetS, T2D and CVD. We therefore examined the extent of the cysteine oxidative modifications in the T2D heart to define the extent of cellular targets of redox damage. Using a rat model that combines the effects of caloric excess from high-fat diet and pancreatic β-cell injury induced by low-dose streptozotocin, this study investigated the extent of myocardial redox modifications in the presence and absence of an acute therapeutic dose of antioxidant N-propionylglycine (MPG). The contractile dysfunction observed as a depressed rate pressure product in the T2D cohort was minimised with 1mM MPG treatment. We next examined the redox modified cardiac proteome by thiol-disulfide exchange and differential alkylation, with quantitation by isobaric tagging and identification of reversibly oxidised cysteine residues using liquid chromatography-tandem mass spectrometry (MS/MS). This approach identified that the mitochondria in general and more specifically the TCA cycle are at risk of redox modifications in the T2D setting. Changes in the levels of redox modified TCA enzymes were identified with metabolomics showing concurrent changes in TCA intermediates including malate dehydrogenase and malate respectively, that were somewhat reversed through the addition of MPG. Metabolomics also demonstrated that MPG treatment restored the cellular levels of glutathione, an endogenous antioxidant. This study has identified that the mitochondria are at the greatest risk of redox damage and that acute treatment with MPG lessened the extent of oxidative damage that arises in the diabetic heart.