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J Mol Cell Cardiol. 2015 Apr 11. pii: S0022-2828(15)00107-8. doi: 10.1016/j.yjmcc.2015.03.016. [Epub ahead of print]

Increased LDL electronegativity in chronic kidney disease disrupts calcium homeostasis resulting in cardiac dysfunction.

Abstract

Chronic kidney disease (CKD), an independent risk factor for cardiovascular disease, is associated with abnormal lipoprotein metabolism. We examined whether electronegative low-density lipoprotein (LDL) is mechanistically linked to cardiac dysfunction in patients with early CKD. We compared echocardiographic parameters between patients with stage 2 CKD (n=88) and normal controls (n=89) and found that impaired relaxation was more common in CKD patients. Reduction in estimated glomerular filtration rate was an independent predictor of left ventricular relaxation dysfunction. We then examined cardiac function in a rat model of early CKD induced by unilateral nephrectomy (UNx) by analyzing pressure-volume loop data. The time constant of isovolumic pressure decay was longer and the maximal velocity of pressure fall was slower in UNx rats than in controls. When we investigated the mechanisms underlying relaxation dysfunction, we found that LDL from CKD patients and UNx rats was more electronegative than LDL from their respective controls and that LDL from UNx rats induced intracellular calcium overload in H9c2 cardiomyocytes in vitro. Furthermore, chronic administration of electronegative LDL, which signals through lectin-like oxidized LDL receptor-1 (LOX-1), induced relaxation dysfunction in wild-type but not LOX-1-/- mice. In in vitro and in vivo experiments, impaired cardiac relaxation was associated with increased calcium transient resulting from nitric oxide (NO)-dependent nitrosylation of SERCA2a due to increases in inducible NO synthase expression and endothelial NO synthase uncoupling. In conclusion, LDL becomes more electronegative in early CKD. This change disrupts SERCA2a-regulated calcium homeostasis, which may be the mechanism underlying cardiorenal syndrome.

Copyright © 2015. Published by Elsevier Ltd.

KEYWORDS:

SERCA2a; cardiorenal syndrome; lipoproteins; unilateral nephrectomy

 

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Fig. 1. 

Relaxation dysfunction in UNx rats. A, Representative echocardiograms showing a longer mitral deceleration time in an UNx rat than in a sham rat. B, Representative P–V loops at different preloads showing no significant differences in either the end-systolic P–V relationship (ESPVR) or the diastolic P–V relationship (EDPVR) between UNx and sham rats. C, Comparison of the mean slopes of the ESPVR and the EDPVR in UNx and sham rats. D, Comparison of the mean end-systolic volume (Ves), end-diastolic volume (Ved), end-systolic pressure (Pes), and end-diastolic pressure (Ped) in UNx and sham rats. E, Comparison of the maximal velocity of pressure rise (+ dP/dt) and fall (− dP/dt) and the maximal volume rise (+ dV/dt) and fall (− dV/dt) in UNx and sham rats. F, Comparison of the mean arterial elastance (Ea) and isovolumic relaxation constant (tau) in UNx and sham rats. For the quantitative analyses, n = 10 per group.*P < 0.05 vs. sham rats.

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