Abstract Body (Do not enter title and authors here): Background: Dox cardiomyopathy remains a clinically significant problem. Alternate-day fasting has been shown to exacerbate Dox cardiomyopathy and cachexia. We sought to identify common disease mechanisms by comparing proteomics in mice vs. humans with Dox cardiomyopathy.

Methods: Chow-fed C57BL/6 male mice (n=50) were treated with Dox (5 mg/kg intraperitoneal x 3 doses). One day after the last dose, mice were randomized to ad-lib feeding or ADF (24 hours of fasting followed by 24 hours of refeeding) for two weeks, followed by echocardiography, and body composition analysis. For aptamer-based human proteomics, we utilized banked blood from patients with Dox cardiomyopathy (n=47) and other cardiomyopathy (n=2167) from the Penn Heart Failure Study. For 2 group comparisons in mice and humans, we used Student’s t-test and false-discovery rate adjusted for covariates, respectively. For 3-group analyses, one-way ANOVA with Sidak’s correction for multiple comparisons was utilized.

Results: Alternate-day fasting (ADF) decreased left ventricular (LV) ejection fraction (p=0.047, 95% CI of difference: -5.61 to -0.04) and LV mass (p=0.012, 95% CI of difference: -10.10 to -1.39) and increased end-diastolic volume/body weight (p=0.035, 9.5% relative reduction) in mice treated with Dox. Dox+ADF also increased adiposity (p=0.005, 95% CI of difference: 6.266 to 29.52) and brown adipose mass (p<0.001, 95% CI: 1.231 to 3.206). Aptamer-based plasma proteomics showed that Dox+ADF upregulated SLIT2, which was the most significant and pronounced protein identifying human Dox cardiomyopathy (vs other cardiomyopathies, p<0.0001, 95% CI of difference: 20307 to 25447). Furthermore, Dox+ADF stimulated SLIT2 and its target UCP1 in inguinal adipose tissue, while UCP1 knockout attenuates Dox cardiotoxicity. Further studies showed that SLIT2 was both necessary and sufficient for Dox cardiotoxicity.

Conclusion: These findings suggest that adipose-cardiac crosstalk mediated by SLIT2 is a novel mechanism of Dox cardiomyopathy.