The control of hepatic glycogen metabolism in an in vitro model of sepsis

Prognostic Factors and Outcomes in Patients With Septic Shock After Allogeneic Hematopoietic Stem Cell Transplantation

Septic shock remains a potentially life-threatening complication among allogeneic hematopoietic stem cell transplant (allo-HSCT) recipients. There is a paucity of information on the clinical characteristics, outcome and prognostic factors of septic shock patients after allo-HSCT. We aimed to describe the clinical characteristics of septic shock after allo-HSCT and its associated health outcomes and to evaluate the role of patient demographics, transplantation-related laboratory and clinical variables associated with the short-term mortality of septic shock after allo-HSCT. We retrospectively studied 242 septic shock patients from 6105 consecutive patients allografted between 2007 and 2021. We assessed 29 risk factors as candidate predictors and used multivariable logistic regression to establish clinical model. The primary outcome was 28-day mortality. The median age of the subjects was 34 (IQR 24 to 45) years. A total of 148 patients (61.2%) had positive blood cultures. Gram-negative bacilli accounted for 61.5% of the positive isolates, gram-positive cocci accounted for 12.2%, and fungi accounted for 6.1%. Coinfections were found in 30 (20.3%) patients. Escherichia coli was the dominant isolated pathogen (31.1%), followed by Pseudomonas spp. (12.8%) and Klebsiella pneumoniae (10.1%). With a median follow-up of 34 (IQR: 2 to 528) days, a total of 142 (58.7%) patients died, of whom 118 (48.8%) died within the first 28 days after septic shock diagnosis, 131 (54.1%) died within 90 days, and 141 (58.3%) died within 1 year. A large majority of deaths (83.1% [118/142]) occurred within 28 days of septic shock diagnosis. Finally, 6 independent predictive variables of 28-day mortality were identified by multivariable logistic regression: time of septic shock, albumin, bilirubin, PaO2/FiO2, lactate, and sepsis-induced coagulopathy. Patients with late onset shock had higher 28-day mortality rates (64.6% versus 25.5%, P < .001) and more ICU admission (32.6% versus 7.1%, P < .001) than those with early onset shock. We highlight the poor survival outcomes in patients who develop septic shock, emphasizing the need for increasing awareness regarding septic shock after allo-HSCT. The information from the current study may help to assist clinicians in identifying high-risk patients.

Regulation of systemic metabolism by tissue-resident immune cell circuits

Recent studies have demonstrated that tissue homeostasis and metabolic function are dependent on distinct tissue-resident immune cells that form functional cell circuits with structural cells. Within these cell circuits, immune cells integrate cues from dietary contents and commensal microbes in addition to endocrine and neuronal signals present in the tissue microenvironment to regulate structural cell metabolism. These tissue-resident immune circuits can become dysregulated during inflammation and dietary overnutrition, contributing to metabolic diseases. Here, we review the evidence describing key cellular networks within and between the liver, gastrointestinal tract, and adipose tissue that control systemic metabolism and how these cell circuits become dysregulated during certain metabolic diseases. We also identify open questions in the field that have the potential to enhance our understanding of metabolic health and disease.

Gluconeogenesis is reduced from alanine, lactate and pyruvate, but maintained from glycerol, in liver perfusion of rats with early and late sepsis

Sepsis induces several metabolic abnormalities, including hypoglycaemia in the most advanced stage of the disease, a risk factor for complications and death. Although hypoglycaemia can be caused by inhibition of hepatic gluconeogenesis, decreased and increased gluconeogenesis were reported in sepsis. Furthermore, gluconeogenesis from glycerol was not yet evaluated in this disease. The main purpose of this study was to investigate the gluconeogenesis from alanine, lactate, pyruvate and glycerol in rats with early (8 hours) and late (18 hours) sepsis. Parameters related to the characterization of sepsis were also evaluated. Sepsis was induced by cecal ligation and puncture and gluconeogenesis was assessed in liver perfusion. Rats with early and late sepsis showed increased lactataemia, depletion of liver glycogen and peripheral insulin resistance, characterizing the establishment of sepsis. Rats with early and late sepsis showed decreased gluconeogenesis from alanine, lactate and pyruvate. Interestingly, gluconeogenesis from glycerol, a precursor that enters in the pathway at a later step, subsequent to the entry of alanine, lactate and pyruvate, was maintained in rats with early and late sepsis. In conclusion, gluconeogenesis is decreased from alanine, lactate and pyruvate, but maintained from glycerol, in liver perfusion of rats with early and late sepsis. SIGNIFICANCE OF THE STUDY: The maintenance of gluconeogenesis from glycerol, but not from alanine, lactate and pyruvate, together with the liver glycogen depletion, points the glycerol as an important precursor for the maintenance of glycaemic homeostasis in sepsis. The findings open the possibility of further investigation on the administration of glycerol in the treatment of hypoglycaemia associated with more advanced sepsis.

Biomarker-assisted identification of sepsis-related acute liver impairment: a frequent and deadly condition in critically ill patients

Background The prognostic impact of mild/moderate liver impairment among critically ill patients is not known. We aimed to determine whether acute liver impairment, as measured by several biomarkers, (i) is frequent, (ii) influences prognosis and (iii) to determine whether such an effect is specific for infected critically ill patients. Methods A biomarker and clinical cohort study based on a randomized controlled trial. All-cause mortality was the primary endpoint. Biomarkers hyaluronic acid (HA), bilirubin, albumin, alkaline phosphatase and the international normalized ratio (INR) were determined. Multivariable statistics were applied to estimate risk increase according to liver biomarker increase at baseline and the model was adjusted for age, APACHE II, severe sepsis/septic shock vs. milder infection, chronic alcohol abuse Charlson's co-morbidity index, cancer disease, surgical or medical patient, body mass index, sex, estimated glomerular filtration rate, mechanical ventilation and the other biomarkers. Time-to-event graphs were used. The patients were critically ill patients (n = 1096) from nine mixed medical/surgical intensive care units without known hepatobiliary disease. Results HA levels differed between infected patients (median 210.8 ng/mL [IQR: 93.2-556.6]) vs. the non-infected (median 56.8 ng/mL [IQR: 31.9-116.8], p < 0.001). Serum HA quartiles 2, 3 and 4 were independent predictors of 90-day all-cause mortality for the entire population (infected and non-infected). However, the signal was driven by the infected patients (positive interaction test, no signal in non-infected patients). Among infected patients, HA quartiles corresponded directly to the 90-day risk of dying: 1st quartile: 57/192 = 29.7%, 2nd quartile: 84/194 = 43.3%, 3rd quartile: 90/193 = 46.6%, 4th quartile: 101/192 = 52.3 %, p for trend: <0.0001. This finding was confirmed in adjusted analyses: hazard ratio vs. 1st quartile: 2nd quartile: 1.3 [0.9-1.8], p = 0.14, 3rd quartile: 1.5 [1.1-2.2], p = 0.02, 4th quartile: 1.9 [1.3-2.6], p < 0.0001). High bilirubin was also an independent predictor of mortality. Conclusions Among infected critically ill patients, subtle liver impairment, (elevated HA and bilirubin), was associated with a progressive and highly increased risk of death for the patient; this was robust to adjustment for other predictors of mortality. HA can identify patients at high risk.

Whey Acidic Protein/Four-Disulfide Core Domain 21 Regulate Sepsis Pathogenesis in a Mouse Model and a Macrophage Cell Line via the Stat3/Toll-Like Receptor 4 (TLR4) Signaling Pathway

Background

Whey acidic protein/four-disulfide core domain 21 (Wfdc21), also known as Lnc-DC, it has been reported to be correlated with immune response. However, the role of Wfdc21 in the pathogenesis of sepsis is still unknown. In the present study, we aimed to investigate the role of Wfdc21 in the pathogenesis of sepsis.

Material/Methods

The cecal ligation and puncture (CLP)-induced sepsis model was established in Balb/c mice. Animals were euthanized 4, 8, 16, or 24 h after CLP. The glycogen distribution in the kidney and liver was checked by Periodic acid-Schiff (PAS) staining. Changes in the serum interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) concentrations were monitored with ELISA, and Wdfc21 expression was determined by qPCR. Mouse macrophage-like RAW264.7 cells were treated with different doses of lipopolysaccharide (LPS) from Escherichia coli to mimic sepsis in vitro. Western blot analysis was performed to confirm whether LPS-induced in vitro sepsis was correlated with the involvement of the Stat3/TLR4 signaling pathway. In addition, RAW 264.7 cells were infected with lentiviruses containing Wfdc21 shRNA to further confirm the role of Wfdc21 in the pathogenesis of sepsis.

Results

We found that Wfdc21 level was elevated in the CLP-induced animal model and LPS-treated RAW264.7 cells. Furthermore, the downregulation of Wfdc21 modulated the concentration of pro-inflammatory factors in LPS-treated macrophages, such as IL-1β and TNF-α, in LPS-treated macrophages. This regulatory effect was mediated through the Stat3/TLR4 signaling pathway, since Wfdc21 can regulate p-Stat3 and TLR4 levels in LPS-treated macrophages.

Conclusions

Wfdc21 plays a critical role in the pathogenesis of sepsis and may provide a therapeutic target for sepsis treatment.

Hypoxic Signaling and Cholesterol Lipotoxicity in Fatty Liver Disease Progression

Cholesterol is the only lipid whose absorption in the gastrointestinal tract is limited by gate-keeping transporters and efflux mechanisms, preventing its rapid absorption and accumulation in the liver and blood vessels. In this review, I explored the current data regarding cholesterol accumulation in liver cells and key mechanisms in cholesterol-induced fatty liver disease associated with the activation of deleterious hypoxic and nitric oxide signal transduction pathways. Although nonalcoholic fatty liver disease (NAFLD) affects both obese and nonobese individuals, the mechanism of NAFLD progression in lean individuals with healthy metabolism is puzzling. Lean NAFLD individuals exhibit normal metabolic responses, implying that liver damage is not associated with impaired metabolism per se and that direct lipotoxic effects are crucial for disease progression. Several redox and oxidant signaling pathways involving cholesterol are at play in fatty liver disease development. These include impairment of the mitochondrial and lysosomal function by cholesterol loading of the inner-cell membranes; formation of cholesterol crystals and hepatocyte degradation; and crown-like structures surrounding degrading hepatocytes, activating Kupffer cells, and evoking inflammation. The current review focuses on the induction of liver inflammation, fibrosis, and steatosis by free cholesterol via the hypoxia-inducible factor 1α (HIF-1α), a main oxygen-sensing transcription factor involved in all stages of NAFLD. Cholesterol loading in hepatocytes can result in chronic HIF-1α activity because of the decreased oxygen availability and excessive production of nitric oxide and mitochondrial reactive oxygen species.

Survival, bacterial clearance and thrombocytopenia are improved in polymicrobial sepsis by targeting nuclear transport shuttles

The rising tide of sepsis, a leading cause of death in the US and globally, is not adequately controlled by current antimicrobial therapies and supportive measures, thereby requiring new adjunctive treatments. Severe microvascular injury and multiple organ failure in sepsis are attributed to a "genomic storm" resulting from changes in microbial and host genomes encoding virulence factors and endogenous inflammatory mediators, respectively. This storm is mediated by stress-responsive transcription factors that are ferried to the nucleus by nuclear transport shuttles importins/karyopherins. We studied the impact of simultaneously targeting two of these shuttles, importin alpha 5 (Imp α5) and importin beta 1 (Imp β1), with a cell-penetrating Nuclear Transport Modifier (NTM) in a mouse model of polymicrobial sepsis. NTM reduced nuclear import of stress-responsive transcription factors nuclear factor kappa B, signal transducer and activator of transcription 1 alpha, and activator protein 1 in liver, which was also protected from sepsis-associated metabolic changes. Strikingly, NTM without antimicrobial therapy improved bacterial clearance in blood, spleen, and lungs, wherein a 700-fold reduction in bacterial burden was achieved while production of proinflammatory cytokines and chemokines in blood plasma was suppressed. Furthermore, NTM significantly improved thrombocytopenia, a prominent sign of microvascular injury in sepsis, inhibited neutrophil infiltration in the liver, decreased L-selectin, and normalized plasma levels of E-selectin and P-selectin, indicating reduced microvascular injury. Importantly, NTM combined with antimicrobial therapy extended the median time to death from 42 to 83 hours and increased survival from 30% to 55% (p = 0.022) as compared to antimicrobial therapy alone. This study documents the fundamental role of nuclear signaling mediated by Imp α5 and Imp β1 in the mechanism of polymicrobial sepsis and highlights the potential for targeting nuclear transport as an adjunctive therapy in sepsis management.

New diagnostic possibilities in systemic neonatal infections: metabolomics

Systemic neonatal infection is a serious complication in preterm and term infants and is defined as a complex clinical syndrome caused by bacteria, fungi and virus. Sepsis remains among the leading causes of death in both developed and underdeveloped countries above all in the neonatal period. Earlier diagnosis may offer the ability to initiate treatment to prevent adverse outcomes. There have been many studies on various diagnostic haematological markers like acute phase reactants, C-reactive protein, procalcitonin, interleukins and presepsin. However, there is still no single test that satisfies the criteria as being the ideal marker for the early diagnosis of neonatal sepsis. In this regard, metabolomic analysis seems to be a promising method for determining metabolic variations correlated with systemic neonatal infections.

A novel antihypoglycemic role of inducible nitric oxide synthase in liver inflammatory response induced by dietary cholesterol and endotoxemia

AIMS

The current study aim was to elucidate the antihypoglycemic role and mechanism of inducible nitric oxide synthase (iNOS) under inflammatory stress.

METHODS

Liver inflammatory stress was induced in wild-type (WT) and iNOS-knockout (iNOS(-/-)) mice by lipopolysaccharide (LPS) (5 mg/kg) with and without the background of nonalcoholic steatohepatitis (NASH)-Induced by high cholesterol diet (HCD, 6 weeks).

RESULTS

HCD led to steatohepatitis in WT and iNOS(-/-) mice. LPS administration caused marked liver inflammatory damage only in cholesterol-fed mice, which was further exacerbated in the absence of iNOS. Glucose homeostasis was significantly impaired and included fatal hypoglycemia and inhibition of glycogen decomposition. In iNOS(-/-) hypoxia-inducible factor-1 (HIF1), signaling was impaired compared to control WT. Using hydrodynamic gene transfer method HIF1α was expressed in the livers of iNOS(-/-) mice, and significantly ameliorated cholesterol and LPS-induced liver damage. WT mice overexpressing HIF1α exhibited higher blood glucose levels and lower glycogen contents after LPS injection. Conversely, induction of HIF1α was not effective in preventing LPS-induced glucose lowering effect in iNOS(-/-) mice. The critical role of NO signaling in hepatocytes glucose output mediated by HIF1 pathway was also confirmed in vitro. Results also demonstrated increased oxidative stress and reduced heme oxygenase-1 mRNA in the livers of iNOS(-/-) mice. Furthermore, the amounts of plasma tumor necrosis factor-α (TNFα) and intrahepatic TNFα mRNA were significantly elevated in the absence of iNOS.

INNOVATION AND CONCLUSION

These data highlight the essential role of iNOS in the glycemic response to LPS in NASH conditions and argues for the beneficial effects of iNOS.

Differential involvement of the suprachiasmatic nucleus in lipopolysaccharide-induced plasma glucose and corticosterone responses

The hypothalamic suprachiasmatic nucleus (SCN) is an essential component of the circadian timing system, and an important determinant of neuroendocrine and metabolic regulation. Recent data indicate a modulatory role for the immune system on the circadian timing system. The authors investigated how the circadian timing system affects the hypothalamo-pituitary-adrenal (HPA) axis and glucose regulatory responses evoked by an immune challenge induced by lipopolysaccharide (LPS). LPS-induced increases in corticosterone were minimal during the trough of the daily corticosterone rhythm; in contrast, LPS effects on glucose, glucagon, and insulin did not vary across time-of-day. Complete ablation of the SCN resulted in increased corticosterone responses but did not affect LPS-induced hyperglycemia. The paraventricular nucleus (PVN) of the hypothalamus is an important neuroendocrine and autonomic output pathway for hypothalamic information, as well as one of the main target areas of the SCN. Silencing the neuronal activity in the PVN did not affect the LPS-induced corticosterone surge and only slightly delayed the LPS-induced plasma glucose and glucagon responses. Finally, surgical interruption of the neuronal connection between hypothalamus and liver did not affect the corticosterone response but slightly delayed the LPS-induced glucose response. Together, these data support the previously proposed circadian modulation of LPS-induced neuroendocrine responses, but they are at variance with the suggested major role for the hypothalamic pacemaker on the autonomic output of the hypothalamus, as reflected by the effects of LPS on glucose homeostasis. The latter effects are more likely due to direct interactions of LPS with peripheral tissues, such as the liver.

General review on in vitro hepatocyte models and their applications

In vitro hepatocyte models represent very useful systems in both fundamental research and various application areas. Primary hepatocytes appear as the closest model for the liver in vivo. However, they are phenotypically unstable, have a limited life span and in addition, exhibit large interdonor variability when of human origin. Hepatoma cell lines appear as an alternative but only the HepaRG cell line exhibits various functions, including major cytochrome P450 activities, at levels close to those found in primary hepatocytes. In vitro hepatocyte models have brought a substantial contribution to the understanding of the biochemistry, physiology, and cell biology of the normal and diseased liver and in various application domains such as xenobiotic metabolism and toxicity, virology, parasitology, and more generally cell therapies. In the future, new well-differentiated hepatocyte cell lines derived from tumors or from either embryonic or adult stem cells might be expected and although hepatocytes will continue to be used in various fields, these in vitro liver models should allow marked advances, especially in cell-based therapies and predictive and mechanistic hepatotoxicity of new drugs and other chemicals. All models will benefit from new developments in throughput screening based on cell chips coupled with high-content imaging and in toxicogenomics technologies.

Immune-metabolic balance in stressed rats during Candida albicans infection

We evaluated the host metabolic response to chronic varied stress during infection with the fungus Candida albicans. We used four groups of female Wistar rats: normal uninfected and unstressed, stressed, C. albicans infected and infected, and stressed. Infected rats reacted with rapid metabolic adjustments, evident as anorexia and body weight loss, partly mediated by glucocorticoids and TNF-alpha. Higher circulating levels of IL-6 and glucose (p < 0.05) revealed the progress and catabolic effect of the inflammatory response. Infected and stressed rats instead showed anorexia associated with infection and weight loss as the result of reduced food intake. This group exhibited a prompt reduction in circulating leptin on day 3 (p < 0.05), reduction in glucose levels and depletion of hepatic glycogen depots. We also evaluated the contribution of TNF-alpha, glucocorticoids, and food deprivation to liver damage. Lipid peroxidation in liver detected in the infected and infected-stressed groups was exacerbated by the glucocorticoid receptor antagonist RU 486, suggesting the modulatory activity of glucocorticoids, while hepatic fat accumulation and glycogen depletion decreased with anti-TNF-alpha treatment. Food deprivation exacerbated liver injury while the response to stress contributed to greater fungal colonization. Our findings emphasize the impact of metabolic alterations on tissue damage when the host immune activity is modulated by stress mediators.

Bench-to-bedside review: Glucose and stress conditions in the intensive care unit

The physiological response to blood glucose elevation is the pancreatic release of insulin, which blocks hepatic glucose production and release, and stimulates glucose uptake and storage in insulin-dependent tissues. When this first regulatory level is overwhelmed (that is, by exogenous glucose supplementation), persistent hyperglycaemia occurs with intricate consequences related to the glucose acting as a metabolic substrate and as an intracellular mediator. It is thus very important to unravel the glucose metabolic pathways that come into play during stress as well as the consequences of these on cellular functions. During acute injuries, activation of serial hormonal and humoral responses inducing hyperglycaemia is called the 'stress response'. Central activation of the nervous system and of the neuroendocrine axes is involved, releasing hormones that in most cases act to worsen the hyperglycaemia. These hormones in turn induce profound modifications of the inflammatory response, such as cytokine and mediator profiles. The hallmarks of stress-induced hyperglycaemia include 'insulin resistance' associated with an increase in hepatic glucose output and insufficient release of insulin with regard to glycaemia. Although both acute and chronic hyperglycaemia may induce deleterious effects on cells and organs, the initial acute endogenous hyperglycaemia appears to be adaptive. This acute hyperglycaemia participates in the maintenance of an adequate inflammatory response and consequently should not be treated aggressively. Hyperglycaemia induced by an exogenous glucose supply may, in turn, amplify the inflammatory response such that it becomes a disproportionate response. Since chronic exposure to glucose metabolites, as encountered in diabetes, induces adverse effects, the proper roles of these metabolites during acute conditions need further elucidation.

Liver metabolomic changes identify biochemical pathways in hemorrhagic shock

BACKGROUND

Despite ongoing advances in treatment, thousands of patients still die annually from complications due to hemorrhagic shock, a condition causing dramatic physiologic and metabolic changes as cells switch to anaerobic metabolism in response to oxygen deprivation. As the shift from aerobic to anaerobic metabolism occurs in the peripheral tissues during shock, the liver must increase production of endogenous glucose as well as process excess lactate produced in the periphery. This places the liver at the center of metabolic regulation in the body during hemorrhagic shock. Therefore, we hypothesized that liver tissue from pigs during an in vivo model of hemorrhagic shock (n = 6) would reflect resultant metabolic changes.

MATERIALS AND METHODS

The in vivo model of shock consisted of 45 min of shock followed by 8 h of hypotensive resuscitation (80 mmHg) and subsequent normotensive resuscitation (90 mmHg) ending 48 h after the shock period. Control groups of pigs (n = 3) (1) shock with no resuscitation, and (2) only anesthesia and instrumentation, also were included. Metabolic changes within the liver after shock and during resuscitation were investigated using both proton ((1)H) and phosphorous ((31)P) nuclear magnetic resonance (NMR) spectroscopy.

RESULTS

Concentrations of glycerylphosphorylcholine (GPC) and glycerylphosphorylethanolamine (GPE) were significantly lower at 8 h after shock, with recovery to baseline by 23 and 48 h after shock. Uridine diphosphate-glucose (UDP-glucose), and phosphoenolpyruvate (PEP) were elevated 23 h after shock.

CONCLUSIONS

These results indicate that (1)H and (31)P NMR spectroscopy can be used to identify differences in liver metabolites in an in vivo model of hemorrhagic shock, indicating that metabolomic analysis can be used to elucidate biochemical events occurring during this complex disease process.