Glucocorticoid treatment increases cholesterol availability during critical illness: effect on adrenal and muscle function

Background: Hypocholesterolemia hallmarks critical illness though the underlying pathophysiology is incompletely understood. As low circulating cholesterol levels could partly be due to an increased conversion to cortisol/corticosterone, we hypothesized that glucocorticoid treatment, via reduced de novo adrenal cortisol/corticosterone synthesis, might improve cholesterol availability and as such affect adrenal gland and skeletal muscle function.

Methods: In a matched set of prolonged critically ill patients (n = 324) included in the EPaNIC RCT, a secondary analysis was performed to assess the association between glucocorticoid treatment and plasma cholesterol from ICU admission to day five. Next, in a mouse model of cecal ligation and puncture-induced sepsis, septic mice were randomized to receive either hydrocortisone (1.2 mg/day) (n = 17) or placebo (n = 15) for 5 days, as compared with healthy mice (n = 18). Plasma corticosterone, cholesterol, and adrenocortical and myofiber cholesterol were quantified. Adrenal structure and steroidogenic capacity were evaluated. Muscle force and markers of atrophy, fibrosis and regeneration were quantified. In a consecutive mouse study with identical design (n = 24), whole body composition was assessed by EchoMRI to investigate impact on lean mass, fat mass, total and free water.

Results: In human patients, glucocorticoid treatment was associated with higher plasma HDL- and LDL-cholesterol from respectively ICU day two and day three, up to day five (P < 0.05). Plasma corticosterone was no longer elevated in hydrocortisone-treated septic mice compared to placebo, whereas the sepsis-induced reduction in plasma HDL- and LDL-cholesterol and in adrenocortical cholesterol was attenuated (P < 0.05), but without improving the adrenocortical ACTH-induced CORT response and with increased adrenocortical inflammation and apoptosis (P < 0.05). Total body mass was further decreased in hydrocortisone-treated septic mice (P < 0.01) compared to placebo, with no additional effect on muscle mass, force or myofiber size. The sepsis-induced rise in markers of muscle atrophy and fibrosis was unaffected by hydrocortisone treatment, whereas markers of muscle regeneration were suppressed compared to placebo (P < 0.05). An increased loss of lean body mass and total and free water was observed in hydrocortisone-treated septic mice compared to placebo (P < 0.05).

Conclusions: Glucocorticoid treatment partially attenuated critical illness-induced hypocholesterolemia, but at a cost of impaired adrenal function, suppressed muscle regeneration and exacerbated loss of body mass.