Sestrin2 Mediates Metformin Rescued the Age-Related Cardiac Dysfunctions of Cardiorenal Syndrome Type 3

Abstract

Acute kidney injury (AKI) leads to acute cardiac injury and dysfunction in cardiorenal syndrome Type 3 (CRS3) through oxidative stress (OS). The stress-inducible Sestrin2 (Sesn2) protein reduces reactive oxygen species (ROS) accumulation and activates AMP-dependent protein kinase (AMPK) to regulate cellular metabolism and energetics during OS. Sesn2 levels and its protective effects decline in the aged heart. Antidiabetic drug metformin upregulates Sesn2 levels in response to ischemia-reperfusion (IR) stress. However, the role of metformin in CRS3 remains unknown. This study seeks to explore how the age-related decrease in cardiac Sesn2 levels contributes to cardiac intolerance to AKI-induced insults, and how metformin ameliorates CRS3 through Sesn2. Young (3-5 months) and aged (21-23 months) C57BL/6J wild-type mice along with cardiomyocyte-specific knockout (cSesn2^-/-) and their wild type of littermate (Sesn2^f/f) C57BL/6J mice were subjected to AKI for 15 min followed by 24 h of reperfusion. Cardiac and mitochondrial functions were evaluated through echocardiograms and seahorse mitochondria respirational analysis. Renal and cardiac tissue was collected for histological analysis and immunoblotting. The results indicate that metformin could significantly rescue AKI-induced cardiac dysfunction and injury via Sesn2 through an improvement in systolic and diastolic function, fibrotic and cellular damage, and mitochondrial function in young, Sesn2^f/f, and especially aged mice. Metformin significantly increased Sesn2 expression under AKI stress in the aged left-ventricular tissue. Thus, this study suggests that Sesn2 mediates the cardioprotective effects of metformin during post-AKI.

Keywords: Sestrin2; acute kidney injury; aging; cardiorenal syndrome 3; metformin.

Figure 1

Experimental design. Male and female young and aged C57BL/6J wild-type mice along with cSesn2^−/− and Sesn2^f/f C57BL/6J mice underwent a laparotomy and the clamping of the renal artery and vein for 15 min, followed by 24 h of reperfusion. Echocardiograms were performed, and tissues were collected for immunoblotting, histopathological, AKI induction, and mitochondrial respiration analyses.

Figure 2

Effects of AKI surgery and metformin on renal structure and function. (A) Plasma creatinine concentration (PCr); means ± SEM; n = 4–8 per group. (B,D) Representative H&E staining and statistical analysis; means ± SEM; n = 5 per group. (C) Immunoblotting of Sesn2 with isolated cardiomyocytes from Sesn2^f/f or cSesn2^−/− mouse hearts.

Figure 3

Evaluation of cardiac function through echocardiograms. (A) Diastolic function (E/A) and systolic function (LVEF and LVFS) of aged and young mice. (B) Diastolic and systolic functions of Sesn2^f/f and cSesn2^−/− mice. Means ± SEM; n = 7 per group.

Figure 4

Western blot representative images and statistical analysis. Sesn2 expression in young vs. aged hearts in sham and AKI conditions. Analysis represented as mean ± SEM; n = 4–5 per group.

Figure 5

Effects of AKI and metformin on the development of cardiac cellular and fibrotic damage. (A) Representative Masson’s trichrome staining and percent collagen volume fraction (CVF). Means ± SEM; n = 6 per group. (B) Representative hematoxylin and eosin staining.

Figure 6

Oxygen consumption rate (OCR) of isolated cardiomyocytes from Seahorse X96 mitochondrial stress test. Mitochondrial stress test profile including Basal and Maximum Respiration of (A) young vs. aged mice and (B) cSesn2^−/− vs. Sesn2^f/f mice. Means ± SEM; n = 8–15 per group.