Suppression of Organismal Death Pathway in the Heart Tissues of Diabetic Mice by NP‐ 6A4, A Peptide Agonist of the Angiotensin II Receptor AT2R

Abstract

BackgroundDiabetes accelerates cardiac dysfunction and aging. Angiotensin II type 2 receptor AT2R is a member of the anti‐inflammatory arm of the renin‐angiotensin‐aldosterone (RAAS) system. NP‐6A4 is an AT2R peptide agonist with the FDA orphan drug designation for pediatric cardiomyopathy. To test the hypothesis that NP‐6A4‐AT2R signaling is cardioprotective in chronic diabetes, we investigated the changes in cardiac proteome of 63‐week old diabetic mice after a 55‐week treatment with NP‐6A4.Methods and ResultsAll studies were conducted in accordance with the FASEB Statement of Principles for the use of Animals in Research and Education. Diabetes was induced in 8‐week old male c57Bl6 mice via intraperitoneal delivery of streptozotocin (STZ: 50mg/kg/day: 5 days; n=11). Fasting insulin levels were decreased in the STZ‐treated mice (~0.2±0.03 ng/mL versus ~0.94±0.08ng/mL in control mice; p<0.05), but fasting glucose was increased (313±29mg/dL p<0.05). STZ‐treated mice also showed a reduction in body weight by ~10–14% compared to control mice (p<0.05). NP‐6A4 treatment (5mg/kg/day; n=5) of STZ‐treated mice did not change these metabolic parameters. Whole proteome analysis of the cardiac tissues of these 63‐week old mice identified a total of 2760 protein groups in 15 samples with the following criteria: >=2 unique peptides per protein, peptide spectrum FDR <1%. For quantification, a threshold minimum of 4 spectral counts (average of each group of replicates) was used. This resulted in a quantified proteome of 1,569 proteins. NP‐6A4 treated mice hearts exhibited 109 significant differences (p<0.01) compared to vehicle treated diabetic mice hearts with 100 proteins showing increased and 9 proteins showing decreased abundance. Analysis of these data using Ingenuity Pathway Analysis (IPA) showed that 32 of deferentially expressed proteins in diabetic mouse heart induced a pathway designated ‘suppression of organismal death’ (Z score −4.706). Comparing NP‐6A4‐treated mice hearts to healthy mice hearts resulted in 311 significant differences (p<0.01), with 253 proteins increased and 58 proteins decreased. Moreover, 82 of these differentially expressed proteins in the NP‐6A4‐treated mice hearts, compared to healthy control mice hearts, also induced the pathway ‘suppression of organismal death’ (Z score‐3.415).ConclusionA 55‐week treatment with NP‐6A4 induced a cardioprotective pathway in diabetic mouse heart that has the potential to suppress organismal death when compared to age‐matched healthy mice or vehicle treated diabetic mice. This observation suggests that continuous treatment with NP‐6A4 in chronic diseases such as diabetes has the potential to confer cardiac protection and prevent organ failure.Support or Funding InformationThis work was supported by NIH NHLBI 1R01HL118376‐01 (LP), and NIH NHLBI 1R01HL138988‐01A1 (LP) and a small grant from Novopyxis Inc. (LP).