On the Role of Illness Duration and Nutrient Restriction in Cholestatic Alterations that Occur During Critical Illness

Skeletal Muscle Myokine Expression in Critical Illness, Association With Outcome and Impact of Therapeutic Interventions

Context

Muscle expresses and secretes several myokines that bring about benefits in distant organs.

Objective

We investigated the impact of critical illness on muscular expression of irisin, kynurenine aminotransferases, and amylase; association with clinical outcome; and impact of interventions that attenuate muscle wasting/weakness.

Methods

We studied critically ill patients who participated in 2 randomized controlled trials (EPaNIC/NESCI) and documented time profiles in critically ill mice. Included in the study were 174 intensive care unit (ICU) patients (day 8 ± 1) vs 19 matched controls, and 60 mice subjected to surgery/sepsis vs 60 pair-fed healthy mice. Interventions studied included 7-day neuromuscular electrical stimulation (NMES), and withholding parenteral nutrition (PN) in the first ICU week (late PN) vs early PN. The main outcome measures were FNDC5 (irisin- precursor), KYAT1, KYAT3, and amylase mRNA expression in skeletal muscle.

Results

Critically ill patients showed 34% to 80% lower mRNA expression of FNDC5, KYAT1, and amylases than controls (P < .0001). Critically ill mice showed time-dependent reductions in all mRNAs compared with healthy mice (P ≤ .04). The lower FNDC5 expression in patients was independently associated with a higher ICU mortality (P = .015) and ICU-acquired weakness (P = .012), whereas the lower amylase expression in ICU survivors was independently associated with a longer ICU stay (P = .0060). Lower amylase expression was independently associated with a lower risk of death (P = .048), and lower KYAT1 expression with a lower risk of weakness (P = .022). NMES increased FNDC5 expression compared with unstimulated muscle (P = .016), and late PN patients had a higher KYAT1 expression than early PN patients (P = .022).

Conclusion

Expression of the studied myokines was affected by critical illness and associated with clinical outcomes, with limited effects of interventions that attenuate muscle wasting or weakness.

The hypothalamus-pituitary-adrenal axis in sepsis- and hyperinflammation-induced critical illness: Gaps in current knowledge and future translational research directions

The classical model of the vital increase in systemic glucocorticoid availability in response to sepsis- and hyperinflammation-induced critical illness is one of an activated hypothalamus-pituitary-adrenocortical axis. However, research performed in the last decade has challenged this rather simple model and has unveiled a more complex, time-dependent set of responses. ACTH-driven cortisol production is only briefly increased, rapidly followed by orchestrated peripheral adaptations that maintain increased cortisol availability for target tissues without continued need for increased cortisol production and by changes at the target tissues that guide and titrate cortisol action matched to tissue-specific needs. One can speculate that these acute changes are adaptive and that treatment with stress-doses of hydrocortisone may negatively interfere with these adaptive changes. These insights also suggest that prolonged critically ill patients, treated in the ICU for several weeks, may develop central adrenal insufficiency, although it remains unclear how to best diagnose and treat this condition.

Efficacy and safety of ketone ester infusion to prevent muscle weakness in a mouse model of sepsis-induced critical illness

In septic mice, 3-hydroxybutyrate-sodium-salt has shown to partially prevent sepsis-induced muscle weakness. Although effective, the excessive sodium load was toxic. We here investigated whether ketone ester 3-hydroxybutyl-3-hydroxybutanoate (3HHB) was a safer alternative. In a mouse model of abdominal sepsis, the effects of increasing bolus doses of 3HHB enantiomers on mortality, morbidity and muscle force were investigated (n = 376). Next, plasma 3HB^- clearance after bolus d-3HHB was investigated (n = 27). Subsequently, in septic mice, the effect on mortality and muscle force of a continuous d,l-3HHB infusion was investigated (n = 72). In septic mice, as compared with placebo, muscle force was increased at 20 mmol/kg/day l-3HHB and at 40 mmol/kg/day d- and d,l-3HHB. However, severity of illness and mortality was increased by doubling the effective bolus doses. Bolus 3HHB caused a higher 3HB⁻ plasma peak and slower clearance with sepsis. Unlike bolus injections, continuous infusion of d,l-3HHB did not increase severity of illness or mortality, while remaining effective in improving muscle force. Treatment of septic mice with the ketone ester 3HHB partly prevented muscle weakness. Toxicity of 3HHB administered as bolus was completely avoided by continuous infusion of the same dose. Whether continuous infusion of ketone esters represents a promising intervention to also prevent ICU-acquired weakness in human patients should be investigated.

Critical Illness-induced Corticosteroid Insufficiency: What It Is Not and What It Could Be

Critical illnesses are hallmarked by increased systemic cortisol availability, a vital part of the stress response. Acute stress may trigger a life-threatening adrenal crisis when a disease of the hypothalamic-pituitary-adrenal (HPA) axis is present and not adequately treated with stress doses of hydrocortisone. Stress doses of hydrocortisone are also used to reduce high vasopressor need in patients suffering from septic shock, in the absence of adrenal insufficiency. Research performed over the last 10 years focusing on the HPA axis during critical illness has led to the insight that neither of these conditions can be labeled "critical illness-induced corticosteroid insufficiency" or CIRCI. Instead, these data suggested using the term CIRCI for a condition that may develop in prolonged critically ill patients. Indeed, when patients remain dependent on vital organ support for weeks, they are at risk of acquiring central adrenal insufficiency. The sustained increase in systemic glucocorticoid availability, mainly brought about by suppressed circulating cortisol-binding proteins and suppressed hepatic/renal cortisol metabolism, exerts negative feedback inhibition at the hypothalamus/pituitary, while high levels of other glucocorticoid receptor ligands, such as bile acids, and drugs, such as opioids, may further suppress adrenocorticotropic hormone (ACTH) secretion. The adrenal cortex, depleted from ACTH-mediated trophic signaling for weeks, may become structurally and functionally impaired, resulting in insufficient cortisol production. Such a central HPA axis suppression may be maladaptive by contributing to lingering vasopressor need and encephalopathy, hence preventing recovery. Here, we review this concept of CIRCI and we advise on how to recognize and treat this poorly understood condition.

Pathophysiology of sepsis‐induced cholestasis: A review

Sepsis is a critical condition resulting from the excessive activation of the inflammatory/immune system in response to an infection, with high mortality if treatment is not administered promptly. One of the many possible complications of sepsis is liver dysfunction with consequent cholestasis. The aim of this paper is to review the main mechanisms involved in the development of cholestasis in sepsis. Cholestasis in a septic patient must raise the suspicion that it is the consequence of the septic condition and limit the laborious attempts of finding a hepatic or biliary disease. Prompt antibiotic administration when sepsis is suspected is essential and may improve liver enzymes. Cholestasis is a syndrome with a variety of etiologies, among which sepsis is frequently overlooked, despite a number of studies and case reports in the literature demonstrating not only the association between sepsis and cholestasis but also the role of cholestasis as a prognostic factor for sepsis‐induced death.

Identification of the toxic threshold of 3-hydroxybutyrate-sodium supplementation in septic mice

BACKGROUND

In septic mice, supplementing parenteral nutrition with 150 mg/day 3-hydroxybutyrate-sodium-salt (3HB-Na) has previously shown to prevent muscle weakness without obvious toxicity. The main objective of this study was to identify the toxic threshold of 3HB-Na supplementation in septic mice, prior to translation of this promising intervention to human use.

METHODS

In a centrally-catheterized, antibiotic-treated, fluid-resuscitated, parenterally fed mouse model of prolonged sepsis, we compared with placebo the effects of stepwise escalating doses starting from 150 mg/day 3HB-Na on illness severity and mortality (n = 103). For 5-day survivors, also the impact on ex-vivo-measured muscle force, blood electrolytes, and markers of vital organ inflammation/damage was documented.

RESULTS

By doubling the reference dose of 150 mg/day to 300 mg/day 3HB-Na, illness severity scores doubled (p = 0.004) and mortality increased from 30.4 to 87.5 % (p = 0.002). De-escalating this dose to 225 mg still increased mortality (p ≤ 0.03) and reducing the dose to 180 mg/day still increased illness severity (p ≤ 0.04). Doses of 180 mg/day and higher caused more pronounced metabolic alkalosis and hypernatremia (p ≤ 0.04) and increased markers of kidney damage (p ≤ 0.05). Doses of 225 mg/day 3HB-Na and higher caused dehydration of brain and lungs (p ≤ 0.05) and increased markers of hippocampal neuronal damage and inflammation (p ≤ 0.02). Among survivors, 150 mg/day and 180 mg/day increased muscle force compared with placebo (p ≤ 0.05) up to healthy control levels (p ≥ 0.3).

CONCLUSIONS

This study indicates that 150 mg/day 3HB-Na supplementation prevented sepsis-induced muscle weakness in mice. However, this dose appeared maximally effective though close to the toxic threshold, possibly in part explained by excessive Na+ intake with 3HB-Na. Although lower doses were not tested and thus might still hold therapeutic potential, the current results point towards a low toxic threshold for the clinical use of ketone salts in human critically ill patients. Whether 3HB-esters are equally effective and less toxic should be investigated.

Induction of blood-circulating bile acids supports recovery from myelosuppressive chemotherapy

Chemotherapeutic agents can reduce bone marrow (BM) activity, causing myelosuppression, a common life-threatening complication of cancer treatment. It is challenging to predict the patients in whom prolonged myelosuppression will occur, resulting in a delay or discontinuation of the treatment protocol. An early indicator of recovery from myelosuppression would thus be highly beneficial in clinical settings. In this study, bile acids (BAs) were highly increased in the systemic circulation as a natural response during recovery from myelosuppression, supporting regeneration of BM cells. BA levels in the blood of pediatric cancer patients and mice treated with chemotherapeutic agents were increased, in synchrony with early proliferation of BM cells and recovery from myelosuppression. In a mouse model of altered BA composition, Cyp8b1 knockout mice, a subset of mice recovered poorly after chemotherapy. The poor recovery correlated with low levels and changes in composition of BAs in the liver and systemic circulation. Conversely, BA supplementation in chemotherapy-treated wild-type mice resulted in significantly improved recovery. The results suggest that part of the mechanism by which BAs support recovery is the suppression of endoplasmic reticulum stress pathways in expanding and recovering hematopoietic cells. The findings propose a novel role of BAs as early markers of recovery and active components of the recovery process after chemotherapy.

The role of pro-opiomelanocortin in the ACTH-cortisol dissociation of sepsis

Background

Sepsis is typically hallmarked by high plasma (free) cortisol and suppressed cortisol breakdown, while plasma adrenocorticotropic hormone (ACTH) is not increased, referred to as ‘ACTH–cortisol dissociation.’ We hypothesized that sepsis acutely activates the hypothalamus to generate, via corticotropin-releasing hormone (CRH) and vasopressin (AVP), ACTH-induced hypercortisolemia. Thereafter, via increased availability of free cortisol, of which breakdown is reduced, feedback inhibition at the pituitary level interferes with normal processing of pro-opiomelanocortin (POMC) into ACTH, explaining the ACTH–cortisol dissociation. We further hypothesized that, in this constellation, POMC leaches into the circulation and can contribute to adrenocortical steroidogenesis.

Methods

In two human studies of acute (ICU admission to day 7, N = 71) and prolonged (from ICU day 7 until recovery; N = 65) sepsis-induced critical illness, POMC plasma concentrations were quantified in relation to plasma ACTH and cortisol. In a mouse study of acute (1 day), subacute (3 and 5 days) and prolonged (7 days) fluid-resuscitated, antibiotic-treated sepsis (N = 123), we further documented alterations in hypothalamic CRH and AVP, plasma and pituitary POMC and its glucocorticoid-receptor-regulated processing into ACTH, as well as adrenal cortex integrity and steroidogenesis markers.

Results

The two human studies revealed several-fold elevated plasma concentrations of the ACTH precursor POMC from the acute to the prolonged phase of sepsis and upon recovery (all p < 0.0001), coinciding with the known ACTH–cortisol dissociation. Elevated plasma POMC and ACTH–corticosterone dissociation were confirmed in the mouse model. In mice, sepsis acutely increased hypothalamic mRNA of CRH (p = 0.04) and AVP (p = 0.03) which subsequently normalized. From 3 days onward, pituitary expression of CRH receptor and AVP receptor was increased. From acute throughout prolonged sepsis, pituitary POMC mRNA was always elevated (all p < 0.05). In contrast, markers of POMC processing into ACTH and of ACTH secretion, negatively regulated by glucocorticoid receptor ligand binding, were suppressed at all time points (all p ≤ 0.05). Distorted adrenocortical structure (p < 0.05) and lipid depletion (p < 0.05) were present, while most markers of adrenocortical steroidogenic activity were increased at all time points (all p < 0.05).

Conclusion

Together, these findings suggest that increased circulating POMC, through CRH/AVP-driven POMC expression and impaired processing into ACTH, could represent a new piece in the puzzling ACTH–cortisol dissociation.

[Effects of cholestasis and hypoxic hepatitis on prognosis of ICU patients: a retrospective study based on MIMIC Ⅲ database]

OBJECTIVE

Abnormalities of liver-related indices are common in ICU patients, but the effects of cholestasis and hypoxic hepatitis in critically ill patients remains unclarified. The purpose of this study was to investigate the effects of cholestasis and hypoxic liver dysfunction on the prognosis of ICU patients.

METHODS

A retrospective study was conducted based on the data of patients admitted to the ICU for the first time between 2001 and 2011 archived in the MIMIC-Ⅲ database. The patients were divided into cholestasis, hypoxic hepatitis and control groups, and their 28-day case fatality rate as the primary outcome was compared among the groups.

RESULTS

A total of 5852 ICU patients were included in the analysis. The incidence of cholestasis and hypoxic liver dysfunction was 31.9% (1869/5852) and 17.9% (1046/5852), respectively. There was no significant difference in 28-day case fatality rate between cholestasis group and the control group. Compared with the control group, the patients with hypoxic hepatitis had a significantly higher 28-day case fatality rate (46% vs 35%, P &lt; 0.01), a higher hospital case fatality rate (40% vs 31%, P &lt; 0.01), and a higher ICU case fatality rate (35.7% vs 22.2%, P &lt; 0.01). Logistic regression analysis showed that lactic acid (LAC), aspartate transaminase (AST), and international standard ratio (INR) were independent risk factors for 28-day case fatality rate.

CONCLUSIONS

The incidence of cholestatic liver dysfunction is higher than that of hypoxic hepatitis, but it does not increase the 28-day case fatality rate of the ICU patients, suggesting that cholestatic liver dysfunction may be the early adaptation of the liver to critical diseases.

Diarrhea and elevation of plasma markers of cholestasis are common and often occur concomitantly in critically ill patients

PURPOSE

We aimed to describe epidemiology of diarrhea and cholestasis in critically ill patients and explore associations between these two conditions.

MATERIAL AND METHODS

We performed a retrospective study including all consecutive patients who stayed in the ICU for at least 3 days and in whom plasma measurements of liver enzymes/cholestasis parameters were performed. Diarrhea was defined as 3 or more loose or liquid stools per day and cholestasis as increase of alkaline phosphatase (ALP) and gamma glutamyl transpeptidase (GGT) 1.5 times above the upper limit of normality.

RESULTS

Diarrhea was observed in 26.1% and cholestasis in 27.9% of study patients, about one third of the cases in both diarrhea and cholestasis occurred beyond the first week of patient's ICU stay. Cholestasis occurred in 45.6% of patients with diarrhea vs 28.0% of patients without diarrhea (p < 0.001). In 94 patients (13.1%) both diarrhea and cholestasis occurred, cholestasis was more commonly (2/3 of cases) documented before manifestation of diarrhea.

CONCLUSIONS

Cholestasis is more common in patients with diarrhea and vice versa. Diarrhea and cholestasis both occur in approximately one quarter of ICU patients, with significant proportion manifesting beyond the first week in the ICU.

Prevalence and Prognostic Value of Abnormal Liver Test Results in Critically Ill Children and the Impact of Delaying Parenteral Nutrition

OBJECTIVES

In the Early versus Late Parenteral Nutrition in the Pediatric ICU randomized controlled trial, delaying parenteral nutrition to beyond day 7 (late parenteral nutrition) was clinically superior to supplemental parenteral nutrition initiated within 24 hours (early parenteral nutrition), but resulted in a higher rise in bilirubin. We aimed to document prevalence and prognostic value of abnormal liver tests in the PICU and the impact hereon of withholding early parenteral nutrition.

DESIGN

Preplanned secondary analysis of the Early versus Late Parenteral Nutrition in the Pediatric ICU randomized controlled trial. Total bilirubin, alanine aminotransferase, aspartate aminotransferase, gamma-glutamyl transpeptidase, alkaline phosphatase plasma concentrations were measured systematically in PICU. Liver test analyses were adjusted for baseline characteristics including severity of illness.

SETTING

Three PICUs in Belgium, the Netherlands, and Canada.

PATIENTS

As neonatal jaundice was considered a confounder, only the 1,231 of the 1,440 Early versus Late Parenteral Nutrition in the Pediatric ICU-patients 28 days to 17 years old were included.

INTERVENTIONS

Late parenteral nutrition as compared with early parenteral nutrition.

MEASUREMENTS AND MAIN RESULTS

During the first seven PICU days, the prevalence of cholestasis (> 2 mg/dL [34.2 μmol/L] bilirubin) ranged between 3.8% and 4.9% and of hypoxic hepatitis (≥ 20-fold upper limit of normality for alanine aminotransferase and aspartate aminotransferase) between 0.8% and 2.2%, both unaffected by the use of parenteral nutrition. Throughout the first week in PICU plasma bilirubin concentrations were higher in late parenteral nutrition patients (p < 0.05), but became comparable to early parenteral nutrition patients as soon as parenteral nutrition was started on day 8. Plasma concentrations of gamma-glutamyl transpeptidase, alkaline phosphatase, alanine aminotransferase, and aspartate aminotransferase were unaffected by parenteral nutrition. High day 1 plasma concentrations of gamma-glutamyl transpeptidase, alanine aminotransferase, and aspartate aminotransferase (p ≤ 0.01), but not alkaline phosphatase, were independent risk factors for PICU mortality. Day 1 plasma bilirubin concentrations displayed a U-shaped association with PICU mortality, with higher mortality associated with bilirubin less than 0.20 mg/dL and greater than 0.76 mg/dL (< 3.42 μmol/L and > 13 μmol/L) (p ≤ 0.01).

CONCLUSIONS

Overt cholestasis and hypoxic hepatitis were rare and unrelated to the nutritional strategy. However, withholding parenteral nutrition up to 1 week in PICU increased plasma bilirubin. A mild elevation of bilirubin on the first PICU day was associated with lower risk of death and may reflect a stress response, rather than true cholestasis.

Disease-Associated Changes in Drug Transporters May Impact the Pharmacokinetics and/or Toxicity of Drugs: A White Paper From the International Transporter Consortium

Drug transporters are critically important for the absorption, distribution, metabolism, and excretion (ADME) of many drugs and endogenous compounds. Therefore, disruption of these pathways by inhibition, induction, genetic polymorphisms, or disease can have profound effects on overall physiology, drug pharmacokinetics, drug efficacy, and toxicity. This white paper provides a review of changes in transporter function associated with acute and chronic disease states, describes regulatory pathways affecting transporter expression, and identifies opportunities to advance the field.

The Hepatic Glucocorticoid Receptor Is Crucial for Cortisol Homeostasis and Sepsis Survival in Humans and Male Mice

Sepsis is hallmarked by hypercortisolemia, a stress response essential for survival. This elevation in plasma cortisol is partially brought about by suppressed hepatic cortisol breakdown. We demonstrate that a controlled downregulation of the hepatic glucocorticoid receptor (hepatic GR) is crucial. In a mouse model of fluid-resuscitated, antibiotic-treated abdominal sepsis and in human intensive care unit patients, sepsis reduced hepatic GR expression and signaling but increased (free) plasma cortisol/corticosterone, explained by suppressed cortisol/corticosterone-binding proteins and A-ring reductases. However, further experimental inhibition of hepatic GR with short hairpin RNA (shRNA) in septic mice increased mortality fivefold. Acutely, this further hepatic GR suppression prevented the rise in total corticosterone but further reduced binding proteins, resulting in elevated free corticosterone. After 3 days of shRNA-GR inhibition in sepsis, both total and free corticosterone levels were elevated, now explained by an additional reduction in A-ring reductase expression. Hepatic GR inhibition blunted the hyperglycemic stress response without causing hypoglycemia but also markedly increased circulating and hepatic inflammation markers and caused liver destruction, the severity of which explained increased mortality. In human sepsis, glucocorticoid treatment further suppressed hepatic GR expression, which could directly predispose to worse outcomes. In conclusion, sepsis partially suppressed hepatic GR expression, which appeared crucial to upregulate free cortisol/corticosterone availability. However, further sustained hepatic GR suppression evoked lethal excessive liver and systemic inflammation, independent of systemic cortisol/corticosterone availability.