Abstract 14470: Novel Autophagy Mechanisms of NP-6A4 Protection in Heart Disease Induced by Untreated Obesity

Abstract

Introduction & Hypothesis: Untreated obesity induces insulin resistance and heart disease affecting 42% of the US population. Autophagy, a conserved homeostatic process for cellular quality control, plays a critical role in maintaining health. Heart tissues of obese humans and rodent models show impaired autophagy. Drugs that can regulate autophagy are thus of high clinical significance. We reported recently that NP-6A4, a new peptide agonist of the cardiovascular protective angiotensin receptor AT2R, mitigated obesity-induced cardiac dysfunction and damage in rats with untreated obesity and pre-diabetes. We hypothesized that activation of autophagy by NP-6A4 is involved in NP-6A4-AT2R-induced cardioprotection in untreated obesity. Methods & Results: 7-week old female ZDF rats fed high fat diet (D12468, Research Diet) for 6 weeks were randomized to receive either NP-6A4 (10mg/kg/day), NP6A4+AT2R antagonist PD123319 (PD, 5mg/kg/day) delivered subcutaneously (N=6/group), or vehicle (N=5) for 4 weeks. Echocardiography showed that NP-6A4 reduced abnormal E/A ratio from 2.1 to 1.45 (P<0.006), and isovolumic contraction (P<0.004) and relaxation times (P<0.02), and increased myocardial radial strain (P<0.019) and radial strain rate (P<0.033). PD reversed these effects. Immunohistochemistry (IHC) and Western blot analysis revealed a significant 5.9-fold increase (p<0.0006) in LC3 puncta (Fig. A-B) and 2.2-fold increase (p<0.0008) in lipidated autophagy marker LC3-II (Fig. C) compared to vehicle controls. The autophagy activation by NP-6A4 was not seen with the co-administration of PD (Fig. A-C). Cardiac proteome analysis showed that Sec16a, an important partner of autophagy initiators ULK1/2 is increased in ZDF rat heart by NP-6A4 (2.75 fold; P<0.020), but PD suppressed this effect. Conclusions: We identified NP-6A4’s dual targeting of AT2R and novel autophagy regulation to mitigate cardiac dysfunction induced by untreated obesity in female rats