Pro-opiomelanocortin and ACTH-cortisol dissociation during pediatric cardiac surgery

In critically ill adults, high plasma cortisol in face of low ACTH coincides with high pro-opiomelanocortin (POMC) levels. Glucocorticoids further lower ACTH without affecting POMC. We hypothesized that in pediatric cardiac surgery-induced critical illness, plasma POMC is elevated, plasma ACTH transiently rises intraoperatively but becomes suppressed post-operatively, and glucocorticoid administration amplifies this phenotype. From 53 patients (0-36 months), plasma was obtained pre-operatively, intraoperatively and on post-operative day 1 and 2. Plasma was also collected from 24 healthy children. In patients, POMC was supra-normal pre-operatively (p<0.0001) but no longer thereafter (p<0.05). ACTH was never high in patients. While in glucocorticoid-naive patients ACTH became suppressed by post-operative day 1 (p<0.0001), glucocorticoid-treated patients had suppressed ACTH already intraoperatively (p≤0.0001). Pre-operatively high POMC, not accompanied by increased plasma ACTH, suggests a centrally-activated HPA-axis with reduced pituitary processing of POMC into ACTH. Increasing systemic glucocorticoid availability with glucocorticoid treatment accelerated the suppression of plasma ACTH.

Abnormal DNA methylation within HPA-axis genes years after paediatric critical illness

BACKGROUND

Critically ill children suffer from impaired physical/neurocognitive development 2 years later. Glucocorticoid treatment alters DNA methylation within the hypothalamus-pituitary-adrenal (HPA) axis which may impair normal brain development, cognition and behaviour. We tested the hypothesis that paediatric-intensive-care-unit (PICU) patients, sex- and age-dependently, show long-term abnormal DNA methylation within the HPA-axis layers, possibly aggravated by glucocorticoid treatment in the PICU, which may contribute to the long-term developmental impairments.

RESULTS

In a pre-planned secondary analysis of the multicentre PEPaNIC-RCT and its 2-year follow-up, we identified differentially methylated positions and differentially methylated regions within HPA-axis genes in buccal mucosa DNA from 818 former PICU patients 2 years after PICU admission (n = 608 no glucocorticoid treatment; n = 210 glucocorticoid treatment) versus 392 healthy children and assessed interaction with sex and age, role of glucocorticoid treatment in the PICU and associations with long-term developmental impairments. Adjusting for technical variation and baseline risk factors and correcting for multiple testing (false discovery rate < 0.05), former PICU patients showed abnormal DNA methylation of 26 CpG sites (within CRHR1, POMC, MC2R, NR3C1, FKBP5, HSD11B1, SRD5A1, AKR1D1, DUSP1, TSC22D3 and TNF) and three DNA regions (within AVP, TSC22D3 and TNF) that were mostly hypomethylated. These abnormalities were sex-independent and only partially age-dependent. Abnormal methylation of three CpG sites within FKBP5 and one CpG site within SRD5A1 and AKR1D1 was partly attributable to glucocorticoid treatment during PICU stay. Finally, abnormal methylation within FKBP5 and AKR1D1 was most robustly associated with long-term impaired development.

CONCLUSIONS

Two years after critical illness in children, abnormal methylation within HPA-axis genes was present, predominantly within FKBP5 and AKR1D1, partly attributable to glucocorticoid treatment in the PICU, and explaining part of the long-term developmental impairments. These data call for caution regarding liberal glucocorticoid use in the PICU.

Assessment of aberrant DNA methylation two years after paediatric critical illness: a pre-planned secondary analysis of the international PEPaNIC trial

Critically ill children requiring intensive care suffer from impaired physical/neurocognitive development 2 y later, partially preventable by omitting early use of parenteral nutrition (early-PN) in the paediatric intensive-care-unit (PICU). Altered methylation of DNA from peripheral blood during PICU-stay provided a molecular basis hereof. Whether DNA-methylation of former PICU patients, assessed 2 y after critical illness, is different from that of healthy children remained unknown. In a pre-planned secondary analysis of the PEPaNIC-RCT (clinicaltrials.gov-NCT01536275) 2-year follow-up, we assessed buccal-mucosal DNA-methylation (Infinium-HumanMethylation-EPIC-BeadChip) of former PICU-patients (N = 406 early-PN; N = 414 late-PN) and matched healthy children (N = 392). CpG-sites differentially methylated between groups were identified with multivariable linear regression and differentially methylated DNA-regions via clustering of differentially methylated CpG-sites using kernel-estimates. Analyses were adjusted for technical variation and baseline risk factors, and corrected for multiple testing (false-discovery-rate <0.05). Differentially methylated genes were functionally annotated (KEGG-pathway database), and allocated to three classes depending on involvement in physical/neurocognitive development, critical illness and intensive medical care, or pre-PICU-admission disorders. As compared with matched healthy children, former PICU-patients showed significantly different DNA-methylation at 4047 CpG-sites (2186 genes) and 494 DNA-regions (468 genes), with most CpG-sites being hypomethylated (90.3%) and with an average absolute 2% effect-size, irrespective of timing of PN initiation. Of the differentially methylated KEGG-pathways, 41.2% were related to physical/neurocognitive development, 32.8% to critical illness and intensive medical care and 26.0% to pre-PICU-admission disorders. Two years after critical illness in children, buccal-mucosal DNA showed abnormal methylation of CpG-sites and DNA-regions located in pathways known to be important for physical/neurocognitive development.

Development of muscle weakness in a mouse model of critical illness: does fibroblast growth factor 21 play a role?

BACKGROUND

Critical illness is hallmarked by severe stress and organ damage. Fibroblast growth factor 21 (FGF21) has been shown to rise during critical illness. FGF21 is a pleiotropic hormone that mediates adaptive responses to tissue injury and repair in various chronic pathological conditions. Animal studies have suggested that the critical illness-induced rise in FGF21 may to a certain extent protect against acute lung, liver, kidney and brain injury. However, FGF21 has also been shown to mediate fasting-induced loss of muscle mass and force. Such loss of muscle mass and force is a frequent problem of critically ill patients, associated with adverse outcome. In the present study, we therefore investigated whether the critical illness-induced acute rise in FGF21 is muscle-protective or rather contributes to the pathophysiology of critical illness-induced muscle weakness.

METHODS

In a catheterised mouse model of critical illness induced by surgery and sepsis, we first assessed the effects of genetic FGF21 inactivation, and hence the inability to acutely increase FGF21, on survival, body weight, muscle wasting and weakness, and markers of muscle cellular stress and dysfunction in acute (30 h) and prolonged (5 days) critical illness. Secondly, we assessed whether any effects were mirrored by supplementing an FGF21 analogue (LY2405319) in prolonged critical illness.

RESULTS

FGF21 was not required for survival of sepsis. Genetic FGF21 inactivation aggravated the critical illness-induced body weight loss (p = 0.0003), loss of muscle force (p = 0.03) and shift to smaller myofibers. This was accompanied by a more pronounced rise in markers of endoplasmic reticulum stress in muscle, without effects on impairments in mitochondrial respiratory chain enzyme activities or autophagy activation. Supplementing critically ill mice with LY2405319 did not affect survival, muscle force or weight, or markers of muscle cellular stress/dysfunction.

CONCLUSIONS

Endogenous FGF21 is not required for sepsis survival, but may partially protect muscle force and may reduce cellular stress in muscle. Exogenous FGF21 supplementation failed to improve muscle force or cellular stress, not supporting the clinical applicability of FGF21 supplementation to protect against muscle weakness during critical illness.

Abnormal DNA methylation within genes of the steroidogenesis pathway two years after paediatric critical illness and association with stunted growth in height further in time

BACKGROUND

Former critically ill children show an epigenetic age deceleration 2 years after paediatric intensive care unit (PICU) admission as compared with normally developing healthy children, with stunted growth in height 2 years further in time as physical correlate. This was particularly pronounced in children who were 6 years or older at the time of critical illness. As this age roughly corresponds to the onset of adrenarche and further pubertal development, a relation with altered activation of endocrine pathways is plausible. We hypothesised that children who have been admitted to the PICU, sex- and age-dependently show long-term abnormal DNA methylation within genes involved in steroid hormone synthesis or steroid sulphation/desulphation, possibly aggravated by in-PICU glucocorticoid treatment, which may contribute to stunted growth in height further in time after critical illness.

RESULTS

In this preplanned secondary analysis of the multicentre PEPaNIC-RCT and its follow-up, we compared the methylation status of genes involved in the biosynthesis of steroid hormones (aldosterone, cortisol and sex hormones) and steroid sulphation/desulphation in buccal mucosa DNA (Infinium HumanMethylation EPIC BeadChip) from former PICU patients at 2-year follow-up (n = 818) and healthy children with comparable sex and age (n = 392). Adjusting for technical variation and baseline risk factors and corrected for multiple testing (false discovery rate < 0.05), former PICU patients showed abnormal DNA methylation of 23 CpG sites (within CYP11A1, POR, CYB5A, HSD17B1, HSD17B2, HSD17B3, HSD17B6, HSD17B10, HSD17B12, CYP19A1, CYP21A2, and CYP11B2) and 4 DNA regions (within HSD17B2, HSD17B8, and HSD17B10) that were mostly hypomethylated. These abnormalities were partially sex- (1 CpG site) or age-dependent (7 CpG sites) and affected by glucocorticoid treatment (3 CpG sites). Finally, multivariable linear models identified robust associations of abnormal methylation of steroidogenic genes with shorter height further in time, at 4-year follow-up.

CONCLUSIONS

Children who have been critically ill show abnormal methylation within steroidogenic genes 2 years after PICU admission, which explained part of the stunted growth in height at 4-year follow-up. The abnormalities in DNA methylation may point to a long-term disturbance in the balance between active sex steroids and mineralocorticoids/glucocorticoids after paediatric critical illness, which requires further investigation.

The association of hypoglycemia with outcome of critically ill children in relation to nutritional and blood glucose control strategies

BACKGROUND

Withholding parenteral nutrition (PN) until one week after PICU admission facilitated recovery from critical illness and protected against emotional and behavioral problems 4 years later. However, the intervention increased the risk of hypoglycemia, which may have counteracted part of the benefit. Previously, hypoglycemia occurring under tight glucose control in critically ill children receiving early PN did not associate with long-term harm. We investigated whether hypoglycemia in PICU differentially associates with outcome in the context of withholding early PN, and whether any potential association with outcome may depend on the applied glucose control protocol.

METHODS

In this secondary analysis of the multicenter PEPaNIC RCT, we studied whether hypoglycemia in PICU associated with mortality (N = 1440) and 4-years neurodevelopmental outcome (N = 674) through univariable comparison and multivariable regression analyses adjusting for potential confounders. In patients with available blood samples (N = 556), multivariable models were additionally adjusted for baseline serum NSE and S100B concentrations as biomarkers of neuronal, respectively, astrocytic damage. To study whether an association of hypoglycemia with outcome may be affected by the nutritional strategy or center-specific glucose control protocol, we further adjusted the models for the interaction between hypoglycemia and the randomized nutritional strategy, respectively, treatment center. In sensitivity analyses, we studied whether any association with outcome was different in patients with iatrogenic or spontaneous/recurrent hypoglycemia.

RESULTS

Hypoglycemia univariably associated with higher mortality in PICU, at 90 days and 4 years after randomization, but not when adjusted for risk factors. After 4 years, critically ill children with hypoglycemia scored significantly worse for certain parent/caregiver-reported executive functions (working memory, planning and organization, metacognition) than patients without hypoglycemia, also when adjusted for risk factors including baseline NSE and S100B. Further adjustment for the interaction of hypoglycemia with the randomized intervention or treatment center revealed a potential interaction, whereby tight glucose control and withholding early PN may be protective. Impaired executive functions were most pronounced in patients with spontaneous or recurrent hypoglycemia.

CONCLUSION

Critically ill children exposed to hypoglycemia in PICU were at higher risk of impaired executive functions after 4 years, especially in cases of spontaneous/recurrent hypoglycemia.

Development and validation of clinical prediction models for acute kidney injury recovery at hospital discharge in critically ill adults

PURPOSE

Acute kidney injury (AKI) recovery prediction remains challenging. The purpose of the present study is to develop and validate prediction models for AKI recovery at hospital discharge in critically ill patients with ICU-acquired AKI stage 3 (AKI-3).

METHODS

Models were developed and validated in a development cohort (n = 229) and a matched validation cohort (n = 244) from the multicenter EPaNIC database to create prediction models with the least absolute shrinkage and selection operator (Lasso) machine-learning algorithm. We evaluated the discrimination and calibration of the models and compared their performance with plasma neutrophil gelatinase-associated lipocalin (NGAL) measured on first AKI-3 day (NGAL_AKI3) and reference model that only based on age.

RESULTS

Complete recovery and complete or partial recovery occurred in 33.20% and 51.23% of the validation cohort patients respectively. The prediction model for complete recovery based on age, need for renal replacement therapy (RRT), diagnostic group (cardiac/surgical/trauma/others), and sepsis on admission had an area under the receiver operating characteristics curve (AUROC) of 0.53. The prediction model for complete or partial recovery based on age, need for RRT, platelet count, urea, and white blood cell count had an AUROC of 0.61. NGAL_AKI3 showed AUROCs of 0.55 and 0.53 respectively. In cardiac patients, the models had higher AUROCs of 0.60 and 0.71 than NGAL_AKI3's AUROCs of 0.52 and 0.54. The developed models demonstrated a better performance over the reference models (only based on age) for cardiac surgery patients, but not for patients with sepsis and for a general ICU population.

CONCLUSION

Models to predict AKI recovery upon hospital discharge in critically ill patients with AKI-3 showed poor performance in the general ICU population, similar to the biomarker NGAL. In cardiac surgery patients, discrimination was acceptable, and better than NGAL. These findings demonstrate the difficulty of predicting non-reversible AKI early.

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.

OR26-4 Glucocorticoid Receptor Expression and Signaling During Critical Illness, in Relation to the Duration of Illness and the Systemic Glucocorticoid Availability: A Prospective, Observational, Cross-Sectional Human and a Translational Mouse Study

Critically ill patients are thought to develop maladaptive glucocorticoid-resistance which convinces many clinicians to administer stress doses of glucocorticoids to overcome this state of glucocorticoid-resistance. However, supportive data arises mainly from whole blood cells. It is currently not known if the observed changes in regulators and markers of glucocorticoid signaling and activity are also present in other cell and tissue types with a role in critical illness. We quantified regulators and markers of glucocorticoid signaling and activity in several cell and tissue types in critically ill humans and animals and in healthy controls. We found that throughout critical illness, glucocorticoid activity appeared suppressed in neutrophils, but upregulated in monocytes and skeletal muscle. Also in vital tissues GRα-signaling was altered in a tissue-specific, largely time-independent manner. Increasing systemic glucocorticoid availability increased glucocorticoid activity in adipose tissue, diaphragm and lung, whereas in immune cells and other tissues regulatory pathways counteracted. These data argue against glucocorticoid-treatable generalized glucocorticoid resistance and rather point towards an adaptive response in each specific cell or tissue type to optimally guide the beneficial actions of glucocorticoids to the tissues that need it while protecting collateral undesirable effects in tissue that are harmed by elevated systemic glucocorticoid availability.

Presentation: Monday, June 13, 2022 11:45 a.m. - 12:00 p.m.

RF09 | PSAT88 Pro-opiomelanocortin (POMC), ACTH and Cortisol Responses to Pediatric Cardiac Surgery

Introduction

In critically ill adults, high plasma free cortisol in face of suppressed plasma ACTH coincides with high plasma pro-opiomelanocortin (POMC), the ACTH precursor (1). Further augmenting the systemic glucocorticoid availability with hydrocortisone treatment further lowered plasma ACTH, while plasma POMC remained unaffected (2). The dynamics of POMC in relation to ACTH and free cortisol prior to intensive care unit (ICU) admission are unknown, as well as the impact hereon of glucocorticoid treatment. Also, elevated plasma POMC concentrations have not yet been confirmed in pediatric ICU (PICU) patients. In pediatric cardiac surgery-induced critical illness, we hypothesized that plasma POMC is elevated and that plasma ACTH transiently rises per-operatively and becomes suppressed once free cortisol has risen on PICU day 1 and 2. In addition, we hypothesized that in patients receiving glucocorticoids per-operatively, plasma ACTH is further suppressed while plasma POMC is unaffected.

Methods

From 53 children aged 0-36 months, who underwent cardiac surgery and were admitted to the PICU, blood samples were taken prior to surgery (pre-operatively, available samples N=51), during surgery (per-operatively, N=47), on the following morning (PICU day 1, N=40) and the day hereafter (PICU day 2, N=24). Blood samples were also collected from 24 age- and gender-matched healthy children. To investigate the impact of synthetic glucocorticoid treatment on the endogenous plasma hormone concentrations, patients were categorized into steroid-naive (total N=38) and steroid-treated patients (total N=15). Plasma hormone concentrations were quantified with highly-specific ELISA (POMC), RIA (ACTH, cortisol, CBG) or colorimetric assays (albumin). Cross reactivity with synthetic glucocorticoids within the used cortisol RIA is minimal (&lt;0.27% for methylprednisolone, &lt;0.1% for dexamethasone). Free cortisol was estimated with the adapted Coolens’ formula.

Results

Plasma POMC was increased pre-operatively (p&lt;0.0001) but no longer thereafter (p&gt;0.05), irrespective of steroid treatment. Plasma ACTH in patients was never higher than in healthy children. While in steroid-naive patients, plasma ACTH became suppressed only by PICU day 1 (p&lt;0.0001), steroid-treated patients had already suppressed plasma ACTH per-operatively (p≤0.0001). In steroid-naive patients, plasma free cortisol was increased from per-operatively onwards (p≤0.002), while in steroid-treated patients, plasma free cortisol (endogenous) concentrations always remained comparable to those of healthy children (p&gt;0.05).

Conclusion

Pre-operatively high plasma POMC, not followed by increased ACTH, suggests a centrally-activated HPA-axis already prior to surgery and an immature pituitary processing of POMC into ACTH. Systemic glucocorticoid availability is elevated from surgery onwards, likely driven by ACTH-independent mechanisms. Further increasing systemic glucocorticoid availability exogenously with glucocorticoid administration accelerates the suppression of plasma ACTH. The long-term impact of early glucocorticoid treatment in critically ill children remains to be investigated.

References

(1) Téblick A. et al. Critical Care 2021. (2) Téblick A. et al. Endocrinology 2022.

Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m., Saturday, June 11, 2022 1:42 p.m. - 1:47 p.m.

DNA methylation alterations in muscle of critically ill patients

BACKGROUND

Intensive care unit (ICU)-acquired weakness can persist beyond ICU stay and has been associated with long-term functional impairment of ICU survivors. Recently, DNA methylation alterations were found in the blood of ICU patients, partially explaining long-term developmental impairment of critically ill children. As illness-induced aberrant DNA methylation theoretically could also be involved in long-term weakness, we investigated whether the DNA methylation signature in muscle of adult critically ill patients differs from that in muscle of healthy controls.

METHODS

Genome-wide methylation was determined (Infinium® HumanMethylationEPIC BeadChips) in DNA extracted from skeletal muscle biopsies that had been collected on Day 8 ± 1 in ICU from 172 EPaNIC-trial patients [66% male sex, median age 62.7 years, median body mass index (BMI) 25.9 kg/m² ] and 20 matched healthy controls (70% male sex, median age 58.0 years, median BMI 24.4 kg/m² ). Methylation status of individual cytosine-phosphate-guanine (CpG) sites of patients and controls was compared with F-tests, using the Benjamini-Hochberg false discovery rate to correct for multiple comparisons. Differential methylation of DNA regions was assessed with bump hunting, with 1000 permutations assessing uncertainty, expressed as family-wise error rate. Gene expression was investigated for 10 representative affected genes.

RESULTS

In DNA from ICU patients, 565 CpG sites, associated with 400 unique genes, were differentially methylated as compared with controls (average difference 3.2 ± 0.1% ranging up to 16.9%, P < 0.00005). Many of the associated genes appeared highly relevant for muscle structure and function/weakness, including genes involved in myogenesis, muscle regeneration, nerve/muscle membrane excitability, muscle denervation/re-innervation, axon guidance/myelination/degeneration/regeneration, synapse function, ion channelling with especially calcium signalling, metabolism (glucose, protein, and fat), insulin signalling, neuroendocrine hormone regulation, mitochondrial function, autophagy, apoptosis, oxidative stress, Wnt signalling, transcription regulation, muscle fat infiltration during regeneration, and fibrosis. In patients as compared with controls, we also identified two hypomethylated regions, spanning 18 and 3 CpG sites in the promoters of the HIC1 and NADK2 genes, respectively (average differences 5.8 ± 0.01% and 12.1 ± 0.04%, family-wise error rate <0.05). HIC1 and NADK2 play important roles in muscle regeneration and postsynaptic acetylcholine receptors and in mitochondrial processes, respectively. Nine of 10 investigated genes containing DNA methylation alterations were differentially expressed in patients as compared with controls (P ≤ 0.03).

CONCLUSIONS

Critically ill patients present with a different DNA methylation signature in skeletal muscle as compared with healthy controls, which in theory could provide a biological basis for long-term persistence of weakness in ICU survivors.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT00512122, registered on 31 July 2007.

Impact of duration of critical illness and level of systemic glucocorticoid availability on tissue-specific glucocorticoid receptor expression and actions: A prospective, observational, cross-sectional human and two translational mouse studies

Background

Reduced glucocorticoid-receptor (GR) expression in blood suggested that critically ill patients become glucocorticoid-resistant necessitating stress-doses of glucocorticoids. We hypothesised that critical illness evokes a tissue-specific, time-dependent expression of regulators of GR-action which adaptively guides glucocorticoid action to sites of need.

Methods

We performed a prospective, observational, cross-sectional human study and two translational mouse studies. In freshly-isolated neutrophils and monocytes and in skeletal muscle and subcutaneous adipose tissue of 137 critically ill patients and 20 healthy controls and in skeletal muscle and adipose tissue as well as in vital tissues (heart, lung, diaphragm, liver, kidney) of 88 septic and 26 healthy mice, we quantified gene expression of cortisone-reductase 11β-HSD1, glucocorticoid-receptor-isoforms GRα and GRβ, GRα-sensitivity-regulating-co-chaperone FKBP51, and GR-action-marker GILZ. Expression profiles were compared in relation to illness-duration and systemic-glucocorticoid-availability.

Findings

In patients’ neutrophils, GRα and GILZ were substantially suppressed (p≤0·05) throughout intensive care unit (ICU)-stay, while in monocytes low/normal GRα coincided with increased GILZ (p≤0·05). FKBP51 was increased transiently (neutrophils) or always (monocytes,p≤0·05). In patients’ muscle, 11β-HSD1 and GRα were low-normal (p≤0·05) and substantially suppressed in adipose tissue (p≤0·05); FKBP51 and GILZ were increased in skeletal muscle (p≤0·05) but normal in adipose tissue. GRβ was undetectable. Increasing systemic glucocorticoid availability in patients independently associated with further suppressed muscle 11β-HSD1 and GRα, further increased FKBP51 and unaltered GILZ (p≤0·05). In septic mouse heart and lung, 11β-HSD1, FKBP51 and GILZ were always high (p≤0·01). In heart, GRα was suppressed (p≤0·05), while normal or high in lung (all p≤0·05). In diaphragm, 11β-HSD1 was high/normal, GRα low/normal and FKBP51 and GILZ high (p≤0·01). In kidney, 11β-HSD1 transiently increased but decreased thereafter, GRα was normal and FKBP51 and GILZ high (p≤0·01). In liver, 11β-HSD1 was suppressed (p≤0·01), GRα normal and FKBP51 high (p≤0·01) whereas GILZ was transiently decreased but elevated thereafter (p≤0·05). Only in lung and diaphragm, treatment with hydrocortisone further increased GILZ.

Interpretation

Tissue-specific, time-independent adaptations to critical illness guided GR-action predominantly to vital tissues such as lung, while (partially) protecting against collateral harm in other cells and tissues, such as neutrophils. These findings argue against maladaptive generalised glucocorticoid-resistance necessitating glucocorticoid-treatment.

Funding

Research-Foundation-Flanders, Methusalem-Program-Flemish-Government, European-Research-Council, European-Respiratory-Society.

Obesity attenuates inflammation, protein catabolism, dyslipidaemia, and muscle weakness during sepsis, independent of leptin

BACKGROUND

Muscle weakness is a frequently occurring complication of sepsis, associated with increased morbidity and mortality. Interestingly, obesity attenuates sepsis-induced muscle wasting and weakness. As the adipokine leptin is strongly elevated in obesity and has been shown to affect muscle homeostasis in non-septic conditions, we aimed to investigate whether leptin mediates the protective effect of obesity on sepsis-induced muscle weakness.

METHODS

In a mouse model of sepsis, we investigated the effects of genetic leptin inactivation in obese mice (leptin-deficient obese mice vs. diet-induced obese mice) and of leptin supplementation in lean mice (n = 110). We assessed impact on survival, body weight and composition, markers of muscle wasting and weakness, inflammation, and lipid metabolism. In human lean and overweight/obese intensive care unit (ICU) patients, we assessed markers of protein catabolism (n = 1388) and serum leptin (n = 150).

RESULTS

Sepsis mortality was highest in leptin-deficient obese mice (53% vs. 23% in diet-induced obese mice and 37% in lean mice, P = 0.03). Irrespective of leptin, after 5 days of sepsis, lean mice lost double the amount of lean body mass than obese mice (P < 0.0005). Also, irrespective of leptin, obese mice maintained specific muscle force up to healthy levels (P = 0.3) whereas lean mice suffered from reduced specific muscle force (72% of healthy controls, P < 0.0002). As compared with lean septic mice, both obese septic groups had less muscle atrophy, liver amino acid catabolism, and inflammation with a 50% lower plasma TNFα increase (P < 0.005). Conversely, again mainly irrespective of leptin, obese mice lost double amount of fat mass than lean mice after 5 days of sepsis (P < 0.0001), showed signs of increased lipolysis and ketogenesis, and had higher plasma HDL and LDL lipoprotein concentrations (P ≤ 0.01 for all). Muscle fibre type composition was not altered during sepsis, but a higher atrophy sensitivity of type IIb fibres compared with IIa and IIx fibres was observed, independent of obesity or leptin. After 5 days of critical illness, serum leptin was higher (P < 0.0001) and the net waste of nitrogen (P = 0.006) and plasma urea-to-creatinine ratio (P < 0.0001) was lower in overweight/obese compared with lean ICU human patients.

CONCLUSIONS

Leptin did not mediate the protective effect of obesity against sepsis-induced muscle wasting and weakness in mice. Instead, obesity-independent of leptin-attenuated inflammation, protein catabolism, and dyslipidaemia, pathways that may play a role in the observed muscle protection.

C-reactive protein rise in response to macronutrient deficit early in critical illness: sign of inflammation or mediator of infection prevention and recovery

PURPOSE

Withholding parenteral nutrition (PN) early in critical illness, late-PN, has shown to prevent infections despite a higher peak C-reactive protein (CRP). We investigated whether the accentuated CRP rise was caused by a systemic inflammatory effect mediated by cytokines or arose as a consequence of the different feeding regimens, and whether it related to improved outcome with late-PN.

METHODS

This secondary analysis of the EPaNIC-RCT first investigated, with multivariable linear regression analyses, determinants of late-PN-induced CRP rise and its association with cytokine responses (IL-6, IL-10, TNF-α) in matched early-PN and late-PN patients requiring intensive care for ≥ 3 days. Secondly, with multivariable logistic regression and Cox proportional-hazard analyses, we investigated whether late-PN-induced CRP rises mediated infection prevention and enhanced recovery or reflected an adverse effect counteracting such benefits of late-PN.

RESULTS

CRP peaked on day 3, higher with late-PN [216(152-274)mg/l] (n = 946) than with early-PN [181(122-239)mg/l] (n = 946) (p < 0.0001). Independent determinants of higher CRP rise were lower carbohydrate and protein intakes (p ≤ 0.04) with late-PN, besides higher blood glucose and serum insulin concentrations (p ≤ 0.01). Late-PN did not affect cytokines. Higher CRP rises were independently associated with more infections and lower likelihood of early ICU discharge (p ≤ 0.002), and the effect size of late-PN versus early-PN on these outcomes was increased rather than reduced after adjusting for CRP rise, not confirming a mediating role.

CONCLUSIONS

The higher CRP rise with late-PN, explained by the early macronutrient deficits, did not relate to cytokine responses and thus did not reflect more systemic inflammation. Instead of mediating clinical benefit on infection or recovery, the accentuated CRP rise appeared an adverse effect reducing such late-PN benefits.

Phasing out DEHP from plastic indwelling medical devices used for intensive care: Does it reduce the long-term attention deficit of critically ill children?

BACKGROUND

Children who have been critically ill face long-term developmental impairments. Iatrogenic exposure to di(2-ethylhexyl)phthalate (DEHP), a plasticizer leaching from plastic indwelling medical devices used in the pediatric intensive care unit (PICU), has been associated with the pronounced attention deficit observed in children 4 years after critical illness. As concerns about DEHP toxicity increased, governmental authorities urged the phase out of DEHP in indwelling medical devices and replacement with alternative plasticizers. We hypothesized that exposure to DEHP decreased over the years, attenuating the pronounced long-term attention deficit of these vulnerable children.

METHODS

We compared plasma concentrations of 3 oxidative DEHP metabolites (5cx-MEPP, 5OH-MEHP, 5oxo-MEHP) on the last PICU day in 216 patients who participated in the Tight Glucose Control study (2004-2007) and 334 patients who participated in the PEPaNIC study (2012-2015) and survived PICU stay. Corresponding minimal exposures to these metabolites (plasma concentration multiplied with number of days in PICU) were also evaluated. In patients with 4-year follow-up data, we compared measures of attention (standardized reaction times and consistency). Comparisons were performed with univariable analyses and multivariable linear regression analyses adjusted for baseline risk factors.

RESULTS

In the PEPaNIC patients, last PICU day plasma concentrations of 5cx-MEPP, 5OH-MEHP, 5oxo-MEHP and their sum, and corresponding minimal exposures, were reduced to 17-69% of those in the Tight Glucose Control study (p < 0.0001). Differences remained significant after multivariable adjustment (p ≤ 0.001). PEPaNIC patients did not show better attention than patients in the Tight Glucose Control study, also not after multivariable adjustment for risk factors.

CONCLUSION

Exposure of critically ill children to DEHP in the PICU decreased over the years, but the lower exposure did not translate into improved attention 4 years later. Whether the residual exposure may still be toxic or whether the plasticizers replacing DEHP may not be safe for neurodevelopment needs further investigation.

Persisting neuroendocrine abnormalities and their association with physical impairment 5 years after critical illness

Background

Critical illness is hallmarked by neuroendocrine alterations throughout ICU stay. We investigated whether the neuroendocrine axes recover after ICU discharge and whether any residual abnormalities associate with physical functional impairments assessed 5 years after critical illness.

Methods

In this preplanned secondary analysis of the EPaNIC randomized controlled trial, we compared serum concentrations of hormones and binding proteins of the thyroid axis, the somatotropic axis and the adrenal axis in 436 adult patients who participated in the prospective 5-year clinical follow-up and who provided a blood sample with those in 50 demographically matched controls. We investigated independent associations between any long-term hormonal abnormalities and physical functional impairments (handgrip strength, 6-min walk distance, and physical health-related quality-of-life) with use of multivariable linear regression analyses.

Results

At 5-year follow-up, patients and controls had comparable serum concentrations of thyroid-stimulating hormone, thyroxine (T₄), triiodothyronine (T₃) and thyroxine-binding globulin, whereas patients had higher reverse T₃ (rT₃, p = 0.0002) and lower T₃/rT₃ (p = 0.0012) than controls. Patients had comparable concentrations of growth hormone, insulin-like growth factor-I (IGF-I) and IGF-binding protein 1 (IGFBP1), but higher IGFBP3 (p = 0.030) than controls. Total and free cortisol, cortisol-binding globulin and albumin concentrations were comparable for patients and controls. A lower T₃/rT₃ was independently associated with lower handgrip strength and shorter 6-min walk distance (p ≤ 0.036), and a higher IGFBP3 was independently associated with higher handgrip strength (p = 0.031).

Conclusions

Five years after ICU admission, most hormones and binding proteins of the thyroid, somatotropic and adrenal axes had recovered. The residual long-term abnormality within the thyroid axis was identified as risk factor for long-term physical impairment, whereas that within the somatotropic axis may be a compensatory protective response. Whether targeting of the residual abnormality in the thyroid axis may improve long-term physical outcome of the patients remains to be investigated.

Trial registration ClinicalTrials.gov: NCT00512122, registered on July 31, 2007 (https://www.clinicaltrials.gov/ct2/show/NCT00512122).

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-021-03858-1.

Altered cholesterol homeostasis in critical illness-induced muscle weakness: effect of exogenous 3-hydroxybutyrate

Background

Muscle weakness is a complication of critical illness which hampers recovery. In critically ill mice, supplementation with the ketone body 3-hydroxybutyrate has been shown to improve muscle force and to normalize illness-induced hypocholesterolemia. We hypothesized that altered cholesterol homeostasis is involved in development of critical illness-induced muscle weakness and that this pathway can be affected by 3-hydroxybutyrate.

Methods

In both human critically ill patients and septic mice, the association between circulating cholesterol concentrations and muscle weakness was assessed. In septic mice, the impact of 3-hydroxybutyrate supplementation on cholesterol homeostasis was evaluated with use of tracer technology and through analysis of markers of cholesterol metabolism and downstream pathways.

Results

Serum cholesterol concentrations were lower in weak than in non-weak critically ill patients, and in multivariable analysis adjusting for baseline risk factors, serum cholesterol was inversely correlated with weakness. In septic mice, plasma cholesterol correlated positively with muscle force. In septic mice, exogenous 3-hydroxybutyrate increased plasma cholesterol and altered cholesterol homeostasis, by normalization of plasma mevalonate and elevation of muscular, but not hepatic, expression of cholesterol synthesis genes. In septic mice, tracer technology revealed that 3-hydroxybutyrate was preferentially taken up by muscle and metabolized into cholesterol precursor mevalonate, rather than TCA metabolites. The 3-hydroxybutyrate protection against weakness was not related to ubiquinone or downstream myofiber mitochondrial function, whereas cholesterol content in myofibers was increased.

Conclusions

These findings point to a role for low cholesterol in critical illness-induced muscle weakness and to a protective mechanism-of-action for 3-hydroxybutyrate supplementation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-021-03688-1.

Early neuromuscular electrical stimulation reduces the loss of muscle mass in critically ill patients - A within subject randomized controlled trial

PURPOSE

To investigate the effect of Neuromuscular Electrical Stimulation (NMES) on muscle thickness, strength and morphological and molecular markers of the quadriceps.

MATERIALS AND METHODS

Adult critically ill patients with an expected prolonged stay received unilateral quadriceps NMES sessions for 7 consecutive days. Before and after the intervention period, quadriceps thickness was measured with ultrasound. After the intervention period, strength was assessed in cooperative patients and muscle biopsies were taken. Multivariable regression was performed to identify factors affecting muscle thickness loss.

RESULTS

Muscle thickness decreased less in the stimulated leg (-6 ± 16% versus -12 ± 15%, p = 0.014, n = 47). Strength was comparable. Opioid administration, minimal muscle contraction and more muscle thickness loss in the non-stimulated muscle were independently associated with better muscle thickness preservation. Stimulated muscles showed a shift towards larger myofibers and higher MyHC-I gene expression. NMES did not affect gene expression of other myofibrillary proteins, MuRF-1 or atrogin-1. Signs of myofiber necrosis and inflammation were comparable for both muscles.

CONCLUSIONS

NMES attenuated the loss of muscle mass, but not of strength, in critically ill patients. Preservation of muscle mass was more likely in patients receiving opioids, patients with a minimal muscle contraction during NMES and patients more prone to lose muscle mass.

TRIAL REGISTRATION

clinicaltrials.govNCT02133300.

Time course of altered DNA methylation evoked by critical illness and by early administration of parenteral nutrition in the paediatric ICU

BACKGROUND

A genome-wide study identified de novo DNA methylation alterations in leukocytes of children at paediatric intensive care unit (PICU) discharge, offering a biological basis for their impaired long-term development. Early parenteral nutrition (early-PN) in PICU, compared with omitting PN in the first week (late-PN), explained differential methylation of 23% of the affected CpG-sites. We documented the time course of altered DNA methylation in PICU and the impact hereon of early nutritional management.

RESULTS

We selected 36 early-PN and 36 late-PN matched patients, and 42 matched healthy children. We quantified DNA methylation on days 3, 5 and 7 for the 147 CpG-sites of which methylation was normal upon PICU admission in this subset and altered by critical illness at PICU discharge. Methylation in patients differed from healthy children for 64.6% of the 147 CpG-sites on day 3, for 72.8% on day 5 and for 90.5% on day 7 as revealed by ANOVA at each time point. Within-patients methylation time course analyses for each CpG-site identified different patterns based on paired t test p value and direction of change. Rapid demethylation from admission to day 3 occurred for 76.2% of the CpG-sites, of which 67.9% remained equally demethylated or partially remethylated and 32.1% further demethylated beyond day 3. From admission to day 3, 19.7% of the CpG-sites became hypermethylated, of which, beyond day 3, 34.5% remained equally hypermethylated or partially demethylated again and 65.5% further hypermethylated. For 4.1% of the CpG-sites, changes only appeared beyond day 3. Finally, for the CpG-sites affected by early-PN on the last PICU day, earlier changes in DNA methylation were compared for early-PN and late-PN patients, revealing that 38.9% were already differentially methylated by day 3, another 25.0% by day 5 and another 13.9% by day 7.

CONCLUSIONS

Critical illness- and early-PN-induced changes in DNA methylation occurred mainly within 3 days. Most abnormalities were at least partially maintained or got worse with longer time in PICU. Interventions targeting aberrant DNA methylation changes should be initiated early.

The clinical potential of GDF15 as a "ready-to-feed indicator" for critically ill adults

Background

Circulating growth-differentiation factor-15 (GDF15), a cellular stress marker, abruptly increases during critical illness, but its later time course remains unclear. GDF15 physiologically controls oral intake by driving aversive responses to nutrition. Early parenteral nutrition (PN) in ICU patients has overall been shown not beneficial. We hypothesized that low GDF15 can identify patients who benefit from early PN, tolerate enteral nutrition (EN), and resume spontaneous oral intake.

Methods

In secondary analyses of the EPaNIC-RCT on timing of PN initiation (early PN versus late PN) and the prospective observational DAS study, we documented the time course of circulating GDF15 in ICU (N = 1128) and 1 week post-ICU (N = 72), compared with healthy subjects (N = 65), and the impact hereon of randomization to early PN versus late PN in propensity score-matched groups (N = 564/group). Interaction between upon-admission GDF15 and randomization for its outcome effects was investigated (N = 4393). Finally, association between GDF15 and EN tolerance in ICU (N = 1383) and oral intake beyond ICU discharge (N = 72) was studied.

Results

GDF15 was elevated throughout ICU stay, similarly in early PN and late PN patients, and remained high beyond ICU discharge (p < 0.0001). Upon-admission GDF15 did not interact with randomization to early PN versus late PN for its outcome effects, but higher GDF15 independently related to worse outcomes (p ≤ 0.002). Lower GDF15 was only weakly related to gastrointestinal tolerance (p < 0.0001) and a steeper drop in GDF15 with more oral intake after ICU discharge (p = 0.05).

Conclusion

In critically ill patients, high GDF15 reflected poor prognosis and may contribute to aversive responses to nutrition. However, the potential of GDF15 as “ready-to-feed indicator” appears limited.

Trial registration

ClinicalTrials.gov, NCT00512122, registered 31 July 2007, https://www.clinicaltrials.gov/ct2/show/NCT00512122 (EPaNIC trial) and ISRCTN, ISRCTN 98806770, registered 11 November 2014, http://www.isrctn.com/ISRCTN98806770 (DAS trial)

Towards a fasting-mimicking diet for critically ill patients: the pilot randomized crossover ICU-FM-1 study

BACKGROUND

In two recent randomized controlled trials, withholding parenteral nutrition early in critical illness improved outcome as compared to early up-to-calculated-target nutrition, which may be explained by beneficial effects of fasting. Outside critical care, fasting-mimicking diets were found to maintain fasting-induced benefits while avoiding prolonged starvation. It is unclear whether critically ill patients can develop a fasting response after a short-term nutrient interruption. In this randomized crossover pilot study, we investigated whether 12-h nutrient interruption initiates a metabolic fasting response in prolonged critically ill patients. As a secondary objective, we studied the feasibility of monitoring autophagy in blood samples.

METHODS

In a single-center study in 70 prolonged critically ill patients, 12-h up-to-calculated-target feeding was alternated with 12-h fasting on day 8 ± 1 in ICU, in random order. Blood samples were obtained at the start of the study, at the crossover point, and at the end of the 24-h study period. Primary endpoints were a fasting-induced increase in serum bilirubin and decrease in insulin requirements to maintain normoglycemia. Secondary outcomes included serum insulin-like growth factor I (IGF-I), serum urea, plasma beta-hydroxybutyrate (BOH), and mRNA and protein markers of autophagy in whole blood and isolated white blood cells. To obtain a healthy reference, mRNA and protein markers of autophagy were assessed in whole blood and isolated white blood cells of 23 matched healthy subjects in fed and fasted conditions. Data were analyzed using repeated-measures ANOVA, Fisher's exact test, or Mann-Whitney U test, as appropriate.

RESULTS

A 12-h nutrient interruption significantly increased serum bilirubin and BOH and decreased insulin requirements and serum IGF-I (all p ≤ 0.001). Urea was not affected. BOH was already increased from 4 h fasting onwards. Autophagic markers in blood samples were largely unaffected by fasting in patients and healthy subjects.

CONCLUSIONS

A 12-h nutrient interruption initiated a metabolic fasting response in prolonged critically ill patients, which opens perspectives for the development of a fasting-mimicking diet. Blood samples may not be a good readout of autophagy at the tissue level.

TRIAL REGISTRATION

ISRCTN, ISRCTN98404761. Registered 3 May 2017.

SAT-724 Endocrine Disruption by Phthalate Exposure in the Pediatric Intensive Care Unit

Aim: Pediatric intensive care relies on plastic indwelling medical devices softened by phthalates. Phthalates leach into the circulation and concerns about toxicity were raised. Exceeding a certain threshold of di(2-ethylhexyl)phthalate (DEHP) exposure in the pediatric intensive care unit (PICU) has been associated with an attention deficit 4 years later (1). Moreover, DEHP and its metabolites have endocrine disrupting properties. Critically ill children reveal the non-thyroidal illness syndrome (2) and unexplained relatively low cortisol (3). Whether DEHP exposure in PICU has endocrine disruptive effects is unknown. We investigated whether DEHP exposure in the PICU, exceeding the previously identified “toxic” threshold for attention, is independently associated with thyroid- and HPA-axis alterations upon PICU discharge. Methods: In this preplanned secondary analysis of the PEPaNIC RCT (N=1440) (4), plasma DEHP metabolite concentrations (MEHP, 5OH-MEHP, 5cx-MEPP, 5oxo-MEHP) were quantified for all patients with a last PICU day sample (N=920). Minimal DEHP exposure was defined as the product of the total DEHP metabolite concentrations on the last PICU day and duration of PICU stay, with 0.551 µmol/L.days identified as “toxic” threshold (1). Serum TSH, total T4, total T3 and rT3 concentrations were quantified for patients with an available last day sample (N=913). For patients with a last day plasma sample and who did not receive corticosteroids (N=391), plasma ACTH, total cortisol, albumin and CBG concentrations were quantified and free cortisol calculated. Multivariable linear regression analyses, adjusted for baseline risk factors and for duration of PICU stay, assessed whether exceeding the previously determined threshold of toxic DEHP exposure was independently associated with the hormone levels on the last PICU day. Main results: Median total DEHP metabolite concentration was 0.101 (IQR 0.049 - 0.279) µmol/L on the last PICU day. Minimal DEHP exposure was 0.337 (IQR 0.161 - 0.880) µmol/l.days, and 328 patients (35.7%) exceeded the toxic threshold. Exceeding this threshold was independently associated with lower total T4 (P=0.002), total T3 (P=0.02) and total cortisol (P=0.001), and higher rT3 (P=0.01) concentrations on the last PICU day, but not with TSH, ACTH or free cortisol. Conclusion: Critically ill children had DHEP metabolites in plasma upon PICU discharge and more than a third were exposed to toxic levels. Toxic DEHP exposure was an independent contributor to the severity of the non-thyroidal illness phenotype and to lower cortisol upon PICU discharge. Future research should assess whether such endocrine-disruptive impact of DHEP exposure in the PICU plays a role in the long-term developmental legacy of critical illness in children. 1 Verstraete et al Intensive Care Med 2016 2 Jacobs et al Thyroid 2019 3 Jacobs et al Intensive Care Med 2019 4 Fivez et al N Engl J Med 2016

Effect of Intravenous 25OHD Supplementation on Bone Turnover and Inflammation in Prolonged Critically Ill Patients

Critically ill patients have low circulating 25-hydroxyvitamin D (25OHD), vitamin D binding protein (DBP), and 1,25-dihydroxyvitamin D [1,25(OH)₂D]. Low 25OHD is associated with poor outcomes, possibly explained by its effect on bone and immunity. In this prospective, randomized double-blind, placebo-controlled study, we investigated the feasibility of normalizing 25OHD in prolonged (>10 days) critically ill patients and the effects thereof on 1,25(OH)₂D, bone metabolism, and innate immunity. Twenty-four patients were included and compared with 24 matched healthy subjects. Patients were randomized to either intravenous bolus of 200 μg 25OHD followed by daily infusion of 15 μg 25OHD for 10 days, or to placebo. Parameters of vitamin D, bone and mineral metabolism, and innate immune function were measured. As safety endpoints, ICU length of stay and mortality were registered. Infusion of 25OHD resulted in a sustained increase of serum 25OHD (from median baseline 9.2 -16.1 ng/ml at day 10), which, however, remained below normal levels. There was no increase in serum 1,25(OH)₂D but a slight increase in serum 24,25(OH)₂D. Mineral homeostasis, innate immunity and clinical safety endpoints were unaffected. Thus, intravenous 25OHD administration during critical illness increased serum 25OHD concentrations, though less than expected from data in healthy subjects, which suggests illness-induced alterations in 25OHD metabolism and/or increased 25OHD distribution volume. The increased serum 25OHD concentrations were not followed by a rise in 1,25(OH)₂D nor were bone metabolism or innate immunity affected, which suggests that low 25OHD and 1,25OHD levels are part of the adaptive response to critical illness.

Dynamics and prognostic value of the hypothalamus-pituitary-adrenal axis responses to pediatric critical illness and association with corticosteroid treatment: a prospective observational study

PURPOSE

Increased systemic cortisol availability during adult critical illness is determined by reduced binding-proteins and suppressed breakdown rather than elevated ACTH. Dynamics, drivers and prognostic value of hypercortisolism during pediatric critical illness remain scarcely investigated.

METHODS

This preplanned secondary analysis of the PEPaNIC-RCT (N = 1440), after excluding 420 children treated with corticosteroids before PICU-admission, documented (a) plasma ACTH, (free)cortisol and cortisol-metabolism at PICU-admission, day-3 and last PICU-day, their prognostic value, and impact of withholding early parenteral nutrition (PN), (b) the association between corticosteroid-treatment and these hormones, and (c) the association between corticosteroid-treatment and outcome.

RESULTS

ACTH was normal upon PICU-admission and low thereafter (p ≤ 0.0004). Total and free cortisol were only elevated upon PICU-admission (p ≤ 0.0003) and thereafter became normal despite low binding-proteins (p < 0.0001) and persistently suppressed cortisol-metabolism (p ≤ 0.03). Withholding early-PN did not affect this phenotype. On PICU-day-3, high free cortisol and low ACTH independently predicted worse outcome (p ≤ 0.003). Also, corticosteroid-treatment initiated in PICU, which further suppressed ACTH (p < 0.0001), was independently associated with poor outcomes (earlier live PICU-discharge: p < 0.0001, 90-day mortality: p = 0.02).

CONCLUSION

In critically ill children, systemic cortisol availability is elevated only transiently, much lower than in adults, and not driven by elevated ACTH. Further ACTH lowering by corticosteroid-treatment indicates active feedback inhibition at pituitary level. Beyond PICU-admission-day, low ACTH and high cortisol, and corticosteroid-treatment, predicted poor outcome. This suggests that exogenously increasing cortisol availability during acute critical illness in children may be inappropriate. Future studies on corticosteroid-treatment in critically ill children should plan safety analyses, as harm may be possible.

The GH Axis in Relation to Accepting an Early Macronutrient Deficit and Outcome of Critically Ill Patients

CONTEXT

Changes in the GH axis during critical illness resemble fasting in healthy adults and contribute to hypercatabolism, which potentially affects outcome. Accepting macronutrient deficits by withholding parenteral nutrition (PN) during the first week in the intensive care unit (ICU; late PN) reduced complications and accelerated recovery as compared with early use of PN (early PN).

OBJECTIVE

To investigate how late PN affects the GH axis in relation to its clinical outcome benefits.

DESIGN

Preplanned subanalysis of the Early Parenteral Nutrition Completing Enteral Nutrition in Adult Critically Ill Patients randomized controlled trial.

PARTICIPANTS

A total of 1128 patients for time-course study, 20 patients investigated for nocturnal GH pulsatility, and 600 patients investigated for muscle weakness, with early PN and late PN patients having comparable baseline characteristics.

INTERVENTION

Withholding PN during the first ICU week (late PN) vs early PN.

MAIN OUTCOME MEASURES

Changes in serum GH, IGF-I, IGF-binding protein (IGFBP) 3, and IGFBP1 concentrations from ICU admission to day 4 or last ICU day for patients with a shorter ICU stay (d4/LD) and association in multivariable analyses with likelihood of earlier live ICU discharge, risk of new infection, and muscle weakness.

RESULTS

Late PN attenuated a rise in serum GH and IGF-I (P < 0.0001), did not affect IGFBP3, and attenuated a decrease in IGFBP1 concentrations from admission to d4/LD (P < 0.0001) as compared with early PN. Late PN decreased nonpulsatile (P = 0.005), but not pulsatile, GH secretion. Adjusting the multivariable models for the observed GH axis alterations increased the independent benefit of late PN for all outcomes. GH axis alterations induced by late PN were independently associated with adverse outcomes (P ≤ 0.03).

CONCLUSION

Accepting macronutrient deficits early during critical illness further suppressed the GH axis, which statistically attenuated its clinical outcome benefits.

OR16-4 The Growth Hormone Axis in Relation to Muscle Weakness in the ICU: Effect of Early Macronutrient Deficit

Background: The activity of the growth hormone (GH) axis is altered by critical illness. In the acute phase, GH resistance, as reflected by increased GH and decreased insulin-like growth factor-I (IGF-I), mimics fasting-induced changes in health. Although early full feeding in ICU has long been assumed to prevent muscle wasting and weakness, the EPaNIC RCT observed fewer complications and faster recovery with accepting the macronutrient deficit in the first ICU week, as compared with early full feeding, including less acquired muscle weakness [1,2]. We previously observed that accepting the early macronutrient deficit attenuated rather than aggravated the rise in GH as compared with early full feeding [3]. We have now further characterized its impact on the GH axis, in relation to the risk of acquiring muscle weakness in ICU. Methods: This was a preplanned sub-analysis of the EPaNIC RCT. For 10 matched patients per group, serum GH was quantified every 10 min between 9 PM and 6 AM, followed by deconvolution analyses to estimate GH secretion. For 564 patients per group, matched for baseline characteristics, and for all patients investigated for muscle weakness (n=600), serum IGF-I, IGF binding protein 3 (IGFBP3) and IGFBP1 were measured upon ICU admission, at day 4 (if still in ICU), and on the last ICU day (LD). Matched healthy subjects (n=65) were included as controls. Groups were compared with Wilcoxon test or repeated-measures ANOVA. Associations between changes in concentrations from baseline to day 4 or LD for patients with shorter ICU stay (d4/LD) and risk of muscle weakness were assessed with nominal logistic regression analysis, adjusted for baseline risk factors, baseline hormone concentrations and randomization. Results: Upon ICU admission, patients revealed low IGF-I and IGFBP3 and high IGFBP1 as compared with controls (p<0.001). Tolerating an early macronutrient deficit in ICU decreased basal (non-pulsatile) GH secretion (p=0.005) without affecting pulsatile GH secretion. From admission to d4/LD IGF-I and IGFBP3 increased, whereas IGFBP1 decreased (all p<0.001) in the fully fed group. Compared to full feeding, tolerating the early macronutrient deficit prevented the rise in IGF-I (p<0.001), did not affect IGFBP3 and attenuated the decrease in IGFBP1 (p<0.001). A stronger rise in GH and IGF-I from admission to d4/LD was independently associated with a lower risk of acquiring muscle weakness (OR (95%CI) per ng/ml change 0.88 (0.81-0.96) for GH, p=0.001; 0.98 (0.97-0.99) for IGF-I, p=0.002). Conclusion: Tolerating the early macronutrient deficit suppresses basal but not pulsatile GH secretion and alters IGF-I bioavailability during critical illness. These effects may counteract the protection of the intervention against the development of muscle weakness. 1. Casaer et al. N Engl J Med 2011;365:506-17 2. Hermans et al. Lancet Respir Med 2013;1:621-9 3. Van Dyck et al. ENDO 2018;SUN601

SAT-155 Temporal Activation of the Unfolded Protein Response and Concomitant Downregulation of Key Hepatic Transcription Factors in Critical Illness

Background: Critically ill patients often develop multiple organ failure accompanied by profound metabolic and endocrine alterations. The pathogenesis is incompletely understood, but the development of cellular stress, including endoplasmic reticulum (ER) stress, might play a pivotal role (1). Indeed, markers of ER stress have been observed in critical illness, both in animal models and human patients, correlating with organ dysfunction (1). ER stress normally activates the unfolded protein response (UPR). The UPR follows a distinct temporal pattern, aimed at restoring ER homeostasis in the short term, but inducing apoptosis whenever ER stress becomes too severe or prolonged. During critical illness, the temporal activation pattern in liver has only been partially studied. In addition, the potential implications for liver function and metabolism are currently unknown. Methods: We quantified the hepatic expression of crucial markers of the 3 UPR branches and of key hepatic transcription factors in a clinically relevant fluid-resuscitated mouse model of sepsis. Mice were sacrificed at 10 hrs, 30 hrs or 3 days after cecal ligation and puncture in comparison with healthy pair-fed mice (n=15 per group per time point). We quantified the same markers in postmortem liver biopsies from patients admitted to the intensive care unit with sepsis (n=64), who died after a median ICU stay of 10 days (IQR 6-20 days), in comparison with matched patients undergoing elective restorative rectal surgery (n=18). Results: In septic mice, the UPR showed a distinct temporal pattern. In the acute phase (10-30 hrs), the PERK, IRE1α and ATF6 branches were all activated (p˂0.01). In the prolonged phase (3 days), the PERK and ATF6 branches were attenuated and only the IRE1α branch remained activated (p˂0.0001). The UPR activation in the acute phase coincided with a significant downregulation of key hepatic transcription factors important for normal liver function and metabolism, including Shp, FXR, Lrh1, PXR, Hnf6 and Foxa2 (p˂0.01). Several transcription factors remained significantly downregulated in the prolonged phase. ALT as liver damage marker correlated directly with several UPR markers and inversely with several transcription factors in the acute phase, but not in the prolonged phase. In postmortem liver biopsies of patients with sepsis, we only observed an upregulation of the IRE1α branch of the UPR, consistent with the pattern in prolonged critically ill mice. Also in patients, this coincided with a repression of several key hepatic transcription factors. Conclusion: The present findings suggest that patients admitted to the intensive care unit with sepsis develop a state of chronic ER stress in the liver, which might hamper normal hepatic function at least in part through the downregulation of key transcription factors. References: 1. Thiessen SE et al. BBA-Mol Basis Dis 2017, 1863, 2534-45

OR17-1 Changes in the Hypothalamic-Pituitary-Adrenal Axis during Pediatric Critical Illness

Critical illness in adults is hallmarked by prolonged hypercortisolism and a rapid decrease in ACTH. The high cortisol is explained by reduced cortisol breakdown and a decrease in cortisol binding proteins, rather than by adrenal production. In critically ill children, the evolution of the changes in the HPA axis and underlying mechanisms remain to be studied. Also, the impact hereon of nutritional management is unknown. In the PEPaNIC RCT, accepting low macronutrient intake up to day 8 in the pediatric intensive care unit (PICU) by withholding early supplemental parenteral nutrition (PN) accelerated recovery as compared with initiating supplemental PN early. In this preplanned secondary analysis of the PEPaNIC RCT, we assessed the changes over time in the HPA axis and their prognostic value during critical illness in children and investigated the impact on these changes of withholding early PN. We quantified plasma ACTH, total cortisol, CBG and albumin and calculated free cortisol upon PICU admission, day 3 and last PICU day for 223 short-stay (<3 days) and 309 long-stay patients (≥3 days) who did not receive corticosteroids before sampling, in comparison with 64 matched healthy children. Upon admission, ACTH was elevated in short-stay patients (P=0.02) and comparable with healthy children in long-stay patients (P=0.75), whereas total and free cortisol were elevated in both groups (P<0.0001). In short-stay patients, ACTH became subnormal on the last day (P<0.0001). Also total and free cortisol decreased, but remained higher than in healthy children (P=0.003-0.005). In long-stay patients, ACTH decreased towards day 3 (P<0.0001) and remained low on the last day (P<0.0001), whereas total and free cortisol were normal on day 3 (P=0.37-0.62) and on the last day (P=0.30-0.74). CBG and albumin were low throughout PICU stay in both groups. The rapid decrease in cortisol over time in PICU likely excludes negative feedback by cortisol on pituitary ACTH secretion as cause of the decrease in ACTH. In multivariable analysis, the decrease in ACTH was also not associated with drugs commonly used in PICU, that have been suggested to affect the HPA axis in adults. High total and free cortisol upon admission were associated with 90-day mortality and prolonged length of stay in univariable analysis. This association disappeared when adjusting for baseline risk factors. Withholding early PN did not affect the changes in the HPA axis from admission to day 3 or to last day for short-stay patients. In conclusion, the time course of the changes in the HPA axis during critical illness in children differs from that in adults, with a rapid normalization of cortisol together with a decrease in ACTH over time. Further investigation of the mechanism underlying this ACTH decrease is warranted, since it might be iatrogenic or related to a possibly more immature central secretion during critical illness in children as compared with adults.

Non-Thyroidal Illness Syndrome in Critically Ill Children: Prognostic Value and Impact of Nutritional Management

INTRODUCTION

Non-thyroidal illness (NTI), which occurs with fasting and in response to illness, is characterized by thyroid hormone inactivation with low triiodothyronine (T3) and high reverse T3 (rT3), followed by suppressed thyrotropin (TSH). Withholding supplemental parenteral nutrition early in pediatric critical illness (late-PN), thus accepting low/no macronutrient intake up to day 8 in the pediatric intensive care unit (PICU), accelerated recovery compared to initiating supplemental parenteral nutrition early (early-PN). Whether NTI is harmful or beneficial in pediatric critical illness and how it is affected by a macronutrient deficit remains unclear. This study investigated the prognostic value of NTI, the impact of late-PN on NTI, and whether such impact explains or counteracts the outcome benefit of late-PN in critically ill children.

METHODS

This preplanned secondary analysis of the Early versus Late Parenteral Nutrition in the Pediatric Intensive Care Unit randomized controlled trial quantified serum TSH, total thyroxine (T4), T3, and rT3 concentrations in 982 patients upon PICU admission versus 64 matched healthy children and in 772 propensity score-matched early-PN and late-PN patients upon admission and at day 3 or last PICU day for shorter PICU stay. Associations between thyroid hormone concentrations upon admission and outcome, as well as impact of late-PN on NTI in relation with outcome, were assessed with univariable analyses and multivariable logistic regression, linear regression, or Cox proportional hazard analysis, adjusted for baseline risk factors.

RESULTS

Upon PICU admission, critically ill children revealed lower TSH, T4, T3, and T3/rT3 and higher rT3 than healthy children (p < 0.0001). A more pronounced NTI upon admission, with low T4, T3, and T3/rT3 and high rT3 was associated with higher mortality and morbidity. Late-PN further reduced T4, T3, and T3/rT3 and increased rT3 (p ≤ 0.001). Statistically, the further lowering of T4 by late-PN reduced the outcome benefit (p < 0.0001), whereas the further lowering of T3/rT3 explained part of the outcome benefit of late-PN (p ≤ 0.004). This effect was greater for infants than for older children.

CONCLUSION

In critically ill children, the peripheral inactivation of thyroid hormone, characterized by a decrease in T3/rT3, which is further accentuated by low/no macronutrient intake, appears beneficial. In contrast, the central component of NTI attributable to suppressed TSH, evidenced by the decrease in T4, seems to be a harmful response to critical illness. Whether treating the central component with TSH releasing hormone infusion in the PICU is beneficial requires further investigation.

Role of Glucagon in Catabolism and Muscle Wasting of Critical Illness and Modulation by Nutrition

RATIONALE

Critical illness is hallmarked by muscle wasting and disturbances in glucose, lipid, and amino acid homeostasis. Circulating concentrations of glucagon, a catabolic hormone that affects these metabolic pathways, are elevated during critical illness. Insight in the nutritional regulation of glucagon and its metabolic role during critical illness is lacking.

OBJECTIVES

To evaluate whether macronutrient infusion can suppress plasma glucagon during critical illness and study the role of illness-induced glucagon abundance in the disturbed glucose, lipid, and amino acid homeostasis and in muscle wasting during critical illness.

METHODS

In human and mouse studies, we infused macronutrients and manipulated glucagon availability up and down to investigate its acute and chronic metabolic role during critical illness.

MEASUREMENTS AND MAIN RESULTS

In critically ill patients, infusing glucose with insulin did not lower glucagon, whereas parenteral nutrition containing amino acids increased glucagon. In critically ill mice, infusion of amino acids increased glucagon and up-regulated markers of hepatic amino acid catabolism without affecting muscle wasting. Immunoneutralizing glucagon in critically ill mice only transiently affected glucose and lipid metabolism, did not affect muscle wasting, but drastically suppressed markers of hepatic amino acid catabolism and reversed the illness-induced hypoaminoacidemia.

CONCLUSIONS

These data suggest that elevated glucagon availability during critical illness increases hepatic amino acid catabolism, explaining the illness-induced hypoaminoacidemia, without affecting muscle wasting and without a sustained impact on blood glucose. Furthermore, amino acid infusion likely results in a further breakdown of amino acids in the liver, mediated by increased glucagon, without preventing muscle wasting. Clinical trial registered with www.clinicaltrials.gov (NCT 00512122).

The Role of Autophagy in Critical Illness-induced Liver Damage

Mitochondrial dysfunction and endoplasmic reticulum (ER) stress, which activates the unfolded protein response (UPR), mediate critical illness-induced organ failure, often affecting the liver. Autophagy is known to alleviate both and suppressed or insufficiently activated autophagy in prolonged illness has shown to associate with organ failure. Whether insufficient autophagy contributes to organ failure during critical illness by affecting these underlying mechanisms is incompletely understood. In this study, we investigated whether the inability to acutely activate hepatic autophagy during critical illness aggravates liver damage by increasing hepatic mitochondrial dysfunction and affecting the UPR. In a mouse model of critical illness, induced by surgery and sepsis, we investigated the impact of inactivating hepatic autophagy on markers of hepatic mitochondrial function, the UPR and liver damage in acute (1 day) and prolonged (3 days) critical illness. Hepatic autophagy inactivation during critical illness acutely worsened mitochondrial dysfunction and time-dependently modulated the hepatic UPR. Furthermore, autophagy inactivation aggravated markers of liver damage on both time points. In conclusion, the inability to acutely activate autophagy in liver during critical illness worsened hepatic mitochondrial damage and dysfunction, partially prohibited acute UPR activation and aggravated liver damage, indicating that autophagy is crucial in alleviating critical illness-induced organ failure.

AKIpredictor, an online prognostic calculator for acute kidney injury in adult critically ill patients: development, validation and comparison to serum neutrophil gelatinase-associated lipocalin

PURPOSE

Early diagnosis of acute kidney injury (AKI) remains a major challenge. We developed and validated AKI prediction models in adult ICU patients and made these models available via an online prognostic calculator. We compared predictive performance against serum neutrophil gelatinase-associated lipocalin (NGAL) levels at ICU admission.

METHODS

Analysis of the large multicenter EPaNIC database. Model development (n = 2123) and validation (n = 2367) were based on clinical information available (1) before and (2) upon ICU admission, (3) after 1 day in ICU and (4) including additional monitoring data from the first 24 h. The primary outcome was a comparison of the predictive performance between models and NGAL for the development of any AKI (AKI-123) and AKI stages 2 or 3 (AKI-23) during the first week of ICU stay.

RESULTS

Validation cohort prevalence was 29% for AKI-123 and 15% for AKI-23. The AKI-123 model before ICU admission included age, baseline serum creatinine, diabetes and type of admission (medical/surgical, emergency/planned) and had an AUC of 0.75 (95% CI 0.75-0.75). The AKI-23 model additionally included height and weight (AUC 0.77 (95% CI 0.77-0.77)). Performance consistently improved with progressive data availability to AUCs of 0.82 (95% CI 0.82-0.82) for AKI-123 and 0.84 (95% CI 0.83-0.84) for AKI-23 after 24 h. NGAL was less discriminant with AUCs of 0.74 (95% CI 0.74-0.74) for AKI-123 and 0.79 (95% CI 0.79-0.79) for AKI-23.

CONCLUSIONS

AKI can be predicted early with models that only use routinely collected clinical information and outperform NGAL measured at ICU admission. The AKI-123 models are available at http://akipredictor.com/ . Trial registration Clinical Trials.gov NCT00512122.

The pattern recognition molecule collectin-L1 in critically ill children

BACKGROUND

Critically ill children are prone to nosocomial infections, which may lead to adverse outcome. Low serum concentrations upon admission to the pediatric intensive care unit (PICU) of the mannan-binding lectin (MBL)-associated serine protease (MASP)-3 protein of the lectin pathway of complement activation have been associated with risk of infection and prolonged need for intensive care. We hypothesized that also a low upon-admission concentration of collectin-L1 (CL-L1), a novel member of this pathway, is independently associated with these adverse outcomes.

METHODS

We quantified the serum concentrations of CL-L1 in 81 healthy children and in 700 critically ill children upon PICU admission.

RESULTS

CL-L1 concentrations were significantly lower in the critically ill children as compared with the healthy children. However, corrected for baseline characteristics, risk factors and several lectin pathway proteins, a higher CL-L1 concentration upon PICU admission was independently associated with an increased risk of acquiring a new infection and with a prolonged time to PICU discharge. In contrast, a low MASP-3 concentration remained independently associated with these adverse outcomes.

CONCLUSION

A high serum CL-L1 concentration in critically ill children upon PICU admission is associated with an increased risk of infection and prolonged need of intensive care, and counteracts the protective effect of having a high MASP-3 concentration.

FGF21 Response to Critical Illness: Effect of Blood Glucose Control and Relation With Cellular Stress and Survival

CONTEXT

Critical illness is hallmarked by mitochondrial damage, which is attenuated by targeting normoglycemia. Mitochondrial dysfunction induces fibroblast growth factor-21 (FGF21) via the integrated stress response (ISR).

OBJECTIVE

We evaluated whether critical illness elevates serum FGF21 concentrations and whether targeting normoglycemia (80-110 mg/dL) with insulin vs tolerating hyperglycemia may lower serum FGF21 by attenuating mitochondrial dysfunction and the ISR.

SETTING/DESIGN

We quantified serum FGF21 concentrations in critically ill patients. To allow tissue analyses, including hepatic fgf21 expression in relation with mitochondrial function and ISR markers, we studied critically ill rabbits. Patients and rabbits were randomized to hyper- or normoglycemia. Patients/Other Participants: We studied 405 fed critically ill patients vs 20 matched non-critically ill control subjects as well as 26 critically ill rabbits vs 13 healthy rabbits.

INTERVENTIONS

Insulin was infused to control blood glucose.

MAIN OUTCOME MEASURES AND RESULTS

Serum FGF21 concentrations upon intensive care unit admission were 8-fold higher than in control subjects (P < .0001), decreased with time, but always remained higher in nonsurvivors than survivors (P ≤ .006). Maintaining normoglycemia lowered serum FGF21 (P = .01), statistically explaining at least part of its mortality benefit. In ill rabbits, hepatic fgf21 expression was substantially increased (P < .0001) and was tightly correlated with mitochondrial dysfunction (all R(2) ≥ 0.49; all P ≤ .0006 for complex I and V) and ISR markers on day 3 (R(2) ≥ 0.73; P ≤ .0001), all lowered by targeting normoglycemia.

CONCLUSION

Critical illness is a potent inducer of serum FGF21 and of liver fgf21 expression, possibly driven at least in part by mitochondrial damage and the ISR, which were all attenuated by targeting normoglycemia.

Impact of duration of critical illness on the adrenal glands of human intensive care patients

CONTEXT

Adrenal insufficiency is considered to be prevalent during critical illness, although the pathophysiology, diagnostic criteria, and optimal therapeutic strategy remain controversial. During critical illness, reduced cortisol breakdown contributes substantially to elevated plasma cortisol and low plasma ACTH concentrations.

OBJECTIVE

Because ACTH has a trophic impact on the adrenal cortex, we hypothesized that with a longer duration of critical illness, subnormal ACTH adrenocortical stimulation predisposes to adrenal insufficiency.

DESIGN, SETTING AND PARTICIPANTS

Adrenal glands were harvested 24 hours or sooner after death from 13 long intensive care unit (ICU)-stay patients, 27 short ICU-stay patients, and 13 controls. Prior glucocorticoid treatment was excluded. MAIN OUTCOME AND MEASURE(S): Microscopic adrenocortical zonational structure was evaluated by hematoxylin and eosin staining. The amount of adrenal cholesterol esters was determined by Oil-Red-O staining, and mRNA expression of ACTH-regulated steroidogenic enzymes was quantified.

RESULTS

The adrenocortical zonational structure was disturbed in patients as compared with controls (P < .0001), with indistinguishable adrenocortical zones present only in long ICU-stay patients (P = .003 vs. controls). Adrenal glands from long ICU-stay patients, but not those of short ICU-stay patients, contained 21% less protein (P = .03) and 9% more fluid (P = .01) than those from controls, whereas they tended to weigh less for comparable adrenal surface area. There was 78% less Oil-Red-O staining in long ICU-stay patients than in controls and in short-stay patients (P = .03), the latter similar to controls (P = .31). The mRNA expression of melanocortin 2 receptor, scavenger-receptor class B, member 1, 3-hydroxy-3-methylglutaryl-CoA reductase, steroidogenic acute regulatory protein, and cytochrome P450 cholesterol side-chain cleavage enzyme was at least 58% lower in long ICU-stay patients than in controls (all P ≤ .03) and of melanocortin 2 receptor, scavenger-receptor class B, member 1, steroidogenic acute regulatory protein, and cytochrome P450 cholesterol side-chain cleavage enzyme at least 53% lower than in short ICU-stay patients (all P ≤ .04), whereas gene expression in short ICU-stay patients was similar to controls.

CONCLUSION AND RELEVANCE

Lipid depletion and reduced ACTH-regulated gene expression in prolonged critical illness suggest that sustained lack of ACTH may contribute to the risk of adrenal insufficiency in long-stay ICU patients.

Lectin pathway of complement activation and relation with clinical complications in critically ill children

BACKGROUND

Critically ill children are susceptible to nosocomial infections, which contribute to adverse outcomes. Deficiencies in the innate immunity lectin pathway of complement activation are implicated in a child's vulnerability to infections in conditions such as cancer, but the role during critical illness remains unclear. We hypothesized that low on-admission levels of the pathway proteins are, in part, genetically determined and associated with susceptibility to infectious complications and adverse outcomes.

METHODS

We studied protein levels of mannose-binding lectin (MBL), H-ficolin and M-ficolin, three MBL-associated-serine proteases (MASPs) and MBL-associated protein (MAp44), and relation with functional genetic polymorphisms, in 130 healthy children and upon intensive care unit (ICU) admission in 700 critically ill children of a randomized study on glycemic control.

RESULTS

Levels of MASP-1, MASP-2, MASP-3, and MAp-44 were lower and the levels of M-ficolin were higher in ICU patients on admission than those in matched healthy controls. Only a low on-admission MASP-3 level was independently associated with risk of new ICU infections and prolonged ICU stay, after correcting for other risk factors. On-admission MASP-3 varied with age, illness severity, and genetic variation.

CONCLUSION

Low on-admission MASP-3 levels in critically ill children were independently associated with subsequent acquisition of infection and prolonged ICU stay. The biological explanation needs further investigation.

Increasing glucose load while maintaining normoglycemia does not evoke neuronal damage in prolonged critically ill rabbits

BACKGROUND & AIMS

Preventing severe hyperglycemia with insulin reduced the neuropathological alterations in frontal cortex during critical illness. We investigated the impact of increasing glucose load under normoglycemia on neurons and glial cells.

METHODS

Hyperinflammatory critically ill rabbits were randomized to fasting or combined parenteral nutrition containing progressively increasing amounts of glucose (low, intermediate, high) within the physiological range but with a similar amount of amino acids and lipids. In all groups, normoglycemia was maintained with insulin. On day 7, we studied the neuropathological alterations in frontal cortex neurons, astrocytes and microglia, and MnSOD as marker of oxidative stress.

RESULTS

The percentage of damaged neurons was comparable among all critically ill and healthy rabbits. Critical illness induced an overall 1.8-fold increase in astrocyte density and activation status, largely irrespective of the nutritional intake. The percentage of microglia activation in critically ill rabbits was comparable with that in healthy rabbits, irrespective of glucose load. Likewise, MnSOD expression was comparable in critically ill and healthy rabbits without any clear impact of the nutritional interventions.

CONCLUSIONS

During prolonged critical illness, increasing intravenous glucose infusion while strictly maintaining normoglycemia appeared safe for neuronal integrity and did not substantially affect glial cells in frontal cortex.

Impact of hyperglycemia on neuropathological alterations during critical illness

CONTEXT

Although preventing excessive hyperglycemia during critical illness may provide clinical neuroprotection, it remains debated whether normoglycemia is without risk for the brain.

OBJECTIVE

To address this question, we compared the neuropathological alterations in microglia, astrocytes, and neurons, with uncontrolled hyperglycemia, moderately controlled hyperglycemia, and normoglycemia during human critical illness. We further investigated the time course in an animal model.

DESIGN AND SETTING

We analyzed brain specimens from patients who died in the intensive care unit and from critically ill rabbits randomized to hyper- or normoglycemia. PATIENTS/OTHER PARTICIPANTS: We compared 10 critically ill patients randomized to normoglycemia (104 ±9 mg/dl) or moderate hyperglycemia (173 ±32 mg/dl), and five patients with uncontrolled hyperglycemia (254 ±83 mg/dl) with 16 controls (out of hospital sudden deaths). Critically ill rabbits were randomized to hyperglycemia (315 ±32 mg/dl) or normoglycemia (85 ±13 mg/dl) and studied after 3 and 7 d.

INTERVENTIONS

Insulin was infused to control blood glucose.

MAIN OUTCOME MEASURES AND RESULTS

Patients with uncontrolled hyperglycemia showed 3.7-6-fold increased microglial activation, 54-95% reduced number and activation of astrocytes, more than 9-fold increased neuronal and glial apoptosis, and a 1.5-2-fold increase in damaged neurons in hippocampus and frontal cortex (all P ≤ 0.05). Most of these abnormalities were attenuated with moderate hyperglycemia and virtually absent with normoglycemia. Frontal cortex of hyperglycemic rabbits that had been critically ill for 3 d only revealed microglial activation, followed after 7 d by astrocyte and neuronal abnormalities similar to those observed in patients, all prevented by normoglycemia.

CONCLUSIONS

Preventing hyperglycemia with insulin during critical illness reduced neuropathological abnormalities, with microglial activation being the earliest preventable event. Whether these pathological findings associate with neurological outcome remains unknown.

Early parenteral nutrition evokes a phenotype of autophagy deficiency in liver and skeletal muscle of critically ill rabbits

Muscular and hepatic abnormalities observed in artificially fed critically ill patients strikingly resemble the phenotype of autophagy-deficient mice. Autophagy is the only pathway to clear damaged organelles and large ubiquitinated proteins and aggregates. Fasting is its strongest physiological trigger. Severity of autophagy deficiency in critically ill patients correlated with the amount of infused amino acids. We hypothesized that impaired autophagy in critically ill patients could partly be evoked by early provision of parenteral nutrition enriched with amino acids in clinically used amounts. In a randomized laboratory investigation, we compared the effect of isocaloric moderate-dose iv feeding with fasting during illness on the previously studied markers of autophagy deficiency in skeletal muscle and liver. Critically ill rabbits were allocated to fasting or to iv nutrition (220 kcal/d, 921 kJ/d) supplemented with 50 kcal/d (209 kJ/d) of either glucose, amino acids, or lipids, while maintaining normoglycemia, and were compared with healthy controls. Fasted critically ill rabbits revealed weight loss and activation of autophagy. Feeding abolished these responses, with most impact of amino acid-enriched nutrition. Accumulation of p62 and ubiquitinated proteins in muscle and liver, indicative of insufficient autophagy, occurred with parenteral feeding enriched with amino acids and lipids. In liver, this was accompanied by fewer autophagosomes, fewer intact mitochondria, suppressed respiratory chain activity, and an increase in markers of liver damage. In muscle, early parenteral nutrition enriched with amino acids or lipids aggravated vacuolization of myofibers. In conclusion, early parenteral nutrition during critical illness evoked a phenotype of autophagy deficiency in liver and skeletal muscle.

Mitochondrial fusion, fission, and biogenesis in prolonged critically ill patients

CONTEXT

Critical illness induces swelling, enlargement, and dysfunction of mitochondria, which in liver, but not in muscle, is aggravated by excessive hyperglycemia. We previously demonstrated impaired autophagic clearance of damaged mitochondria in fed prolonged critically ill patients. Impaired fusion/fission-mediated repair and/or renewal through biogenesis may further accentuate mitochondrial abnormalities.

OBJECTIVE

We studied mitochondrial fusion/fission and biogenesis and how these are affected by preventing hyperglycemia with insulin during critical illness.

DESIGN AND SETTING

Patients admitted to a university hospital surgical/medical intensive-care unit participated in a randomized study.

PATIENTS

We studied adult prolonged critically ill patients vs. controls.

INTERVENTION

Tolerating hyperglycemia up to 215 mg/dl was compared with intensive insulin therapy targeting normoglycemia (80-110 mg/dl).

MAIN OUTCOME MEASURES

In liver and skeletal muscle, we quantified levels of several proteins involved in mitochondrial fusion/fission and biogenesis.

RESULTS

Key players in mitochondrial fusion/fission and biogenesis were up-regulated in postmortem liver (1.4- to 3.7-fold) and rectus abdominis (1.2- to 4.2-fold) but not in in vivo or postmortem vastus lateralis biopsies of critically ill patients. Maintaining normoglycemia with insulin attenuated the hepatic response in the mitochondrial fusion/fission process but did not affect the markers of mitochondrial biogenesis in liver or muscle.

CONCLUSIONS

Our observations suggest tissue-dependent attempts of compensatory activation of mitochondrial repair mechanisms during critical illness. Considering the previously observed persistent mitochondrial damage, this activation may be insufficient and contribute to mitochondrial dysfunction. Suppressed activation of fusion/fission when excessive hyperglycemia is prevented with insulin may reflect reduced need for diluting (less) damage during normoglycemia or, alternatively, a suppressive effect of insulin on repair.

Insufficient activation of autophagy allows cellular damage to accumulate in critically ill patients

CONTEXT

Responses to critical illness, such as excessive inflammation and hyperglycemia, may trigger detrimental chain reactions that damage cellular proteins and organelles. Such responses to illness contribute to the risk of (nonresolving) multiple organ dysfunction and adverse outcome.

OBJECTIVE

We studied autophagy as a bulk degradation pathway able to remove toxic protein aggregates and damaged organelles and how these are affected by preventing hyperglycemia with insulin during critical illness.

DESIGN AND SETTING

Patients participated in a randomized study, conducted at a university hospital surgical/medical intensive care unit.

PATIENTS

We studied adult prolonged critically ill patients vs. controls.

INTERVENTIONS

Tolerating excessive hyperglycemia was compared with intensive insulin therapy targeting normoglycemia.

MAIN OUTCOME MEASURES

We quantified (ultra)structural abnormalities and hepatic and skeletal muscle protein levels of key players in autophagy.

RESULTS

Morphologically, both liver and muscle revealed an autophagy-deficiency phenotype. Proteins involved in initiation and elongation steps of autophagy were induced 1.3- to 6.5-fold by critical illness (P ≤ 0.01), but mature autophagic vacuole formation was 62% impaired (P = 0.05) and proteins normally degraded by autophagy accumulated up to 97-fold (P ≤ 0.03). Mitophagy markers were unaltered or down-regulated (P = 0.05). Although insulin preserved hepatocytic mitochondrial integrity (P = 0.05), it further reduced the number of autophagic vacuoles by 80% (P = 0.05).

CONCLUSIONS

Insufficient autophagy in prolonged critical illness may cause inadequate removal of damaged proteins and mitochondria. Such incomplete clearance of cellular damage, inflicted by illness and aggravated by hyperglycemia, could explain lack of recovery from organ failure in prolonged critically ill patients. These data open perspectives for therapies that activate autophagy during critical illness.