Abstract Body (Do not enter title and authors here):

Introduction: Diabetic cardiomyopathy (DCM) is associated with the development of overt heart failure driven by complex, interdependent pathophysiological mechanisms. Although a self-perpetuating cycle of oxidative stress and inflammation is implicated in the development and progression of DCM, the precise underlying causal mechanisms remain unclear, with limited, largely nonspecific treatment options.

Hypothesis: Regulating redox status in db/db mice using the MPO inhibitor and redox-modulating agent N-acetyl lysyltyrosylcysteine amide (KYC) improves heart function by shaping the immune response towards a more regulated state.

Methods: After two weeks of habituation, 8-week-old male type 2 diabetic db/db mice were randomly assigned to daily treatment with KYC (subcutaneous, 10 mg/kg/d) or vehicle (PBS) for 12 weeks. Additionally, sex-matched 8-week-old C57BL/6J mice were used as a control. After treatment, left ventricular function was assessed with echocardiography. Left ventricle morphologies were evaluated with hematoxylin and eosin staining; the myocardial fibrosis content was quantified with Masson’s trichrome staining. The absolute counts of total lymphocytes, monocytes, and neutrophils in the peripheral blood were measured, and splenic T cells were determined with flow cytometry. Cardiac oxidative stress, inflammatory, and regulatory marker expression were evaluated by qPCR.

Results: Treatment of db/db mice with KYC improved cardiac function and was associated with dampened systemic and cardiac inflammation. Histopathological studies of the hearts of db/db mice at 20 weeks of age revealed that KYC treatment decreased cardiomyocyte size and myocardial fibrosis. Importantly, splenic T cell characterization revealed that KYC treatment resulted in a significantly higher proportion of CD4+CD25+Foxp3+ (forkhead box P3) regulatory T cells (Tregs) and a lower ratio of both effector CD4 and CD8 T cells (Teffs) and Treg than the vehicle-treated diabetic mice. Cardiac transcriptomic analysis revealed that db/db mice exhibited an inflammatory profile, whereas those treated with KYC displayed regulatory and antioxidative defense pathways, including the Nrf2 pathway.

Conclusions: KYC improved cardiac function by expanding CD4+CD25+FoxP3+ T regulatory cells (Tregs) and limiting oxidative stress and inflammation in db/db mice. These results suggest that targeting oxidative stress and inflammation has therapeutic potential for delaying cardiac dysfunction.