Sepsis-induced hypocholesterolemia is linked to low cardiomyocyte membrane cholesterol and impaired catecholamine responsiveness

Abstract

Sepsis-induced cardiomyopathy (SIM) is characterized by myocardial dysfunction, diminished catecholamine responsiveness and worse outcomes. Hypocholesterolemia is also a well-recognized prognosticator of poor outcomes in sepsis. In vitro physiology/pharmacology studies indicate that low cholesterol levels within the cardiomyocyte membrane regulate ß-adrenergic receptor activity. We therefore hypothesized that cardiomyocyte membrane cholesterol levels are reduced in sepsis and this contributes to SIM. Cardiovascular biomarkers and plasma lipid profiles measured sequentially (6, 24 and 72 h) in a fluid-resuscitated rat model of fecal peritonitis were compared against those measured in 27 septic patients on Days 1–3 of ICU admission. In separate studies, rat hearts were excised at the same time points for measurement of cardiomyocyte membrane cholesterol and downstream adrenergic signaling. In a final study, the impact of a 15-hour infusion of cholesterol, either given as HDL-cholesterol or liposomal cholesterol, commencing at 6 h post-sepsis induction, on dobutamine responsiveness and cardiomyocyte membrane cholesterol levels was assessed. The magnitude of fall in stroke volume, rise in heart rate, plasma troponin and BNP, and fall in plasma HDL-cholesterol on ICU Day 1 in septic patients and at 6 h in the rat model all prognosticated for poor outcomes. In parallel, cardiomyocyte membrane cholesterol fell in the rats, more so in poor prognosis animals, with a blunted inotropic response to dobutamine, indicative of SIM. Cholesterol administration restored cardiomyocyte membrane cholesterol, dobutamine responsiveness and adrenergic signaling. In a long-term rat model of sepsis, that parallels changes seen in septic patients, cardiomyocyte membrane cholesterol fell with associated decreases in catecholamine responsiveness. These features could be restored by cholesterol infusion, suggesting potential utility as a therapeutic.