Temporal changes in muscle glutathione in ICU patients

T cells and their immunometabolism: A novel way to understanding sepsis immunopathogenesis and future therapeutics

Sepsis has always been considered as a big challenge for pharmaceutical companies in terms of discovering and designing new therapeutics. The pathogenesis of sepsis involves aberrant activation of innate immune cells (i.e. macrophages, neutrophils etc.) at early stages. However, a stage of immunosuppression is also observed during sepsis even in the patients who have recovered from it. This stage of immunosuppression is observed due to the loss of conventional (i.e. CD4⁺, CD8⁺) T cells, Th17 cells and an upregulation of regulatory T cells (Tregs). This process also impacts metabolic processes controlling immune cell metabolism called immunometabolism. The present review is focused on the T cell-mediated immune response, their immunometabolism and targeting T cell immunometabolism during sepsis as future therapeutic approach. The first part of the manuscripts describes an impact of sepsis on conventional T cells, Th17 cells and Tregs along with their impact on sepsis. The subsequent section further describes the immunometabolism of these cells (CD4⁺, CD8⁺, Th17, and Tregs) under normal conditions and during sepsis-induced immunosuppression. The article ends with the therapeutic targeting of T cell immunometabolism (both conventional T cells and Tregs) during sepsis as a future immunomodulatory approach for its management.

Whole blood glutathione status and ICU morbidity in critically ill children

BACKGROUND

A high reduced glutathione ratio is associated with high mortality in adult ICU patients. Whole blood glutathione status in critically ill children is less well characterized. In this study, whole blood glutathione status in pediatric intensive care (PICU) patients was determined and the relation between the redox status of whole blood glutathione and morbidity was investigated.

METHODS

A prospective consecutive cohort of critically ill children (n = 146) admitted to the PICU of a tertiary university hospital, and a reference group of healthy children (n = 60) and healthy adults (n = 10) were included in the study. The concentrations of total and reduced whole blood were determined at admission and patient characteristics were recorded.

RESULTS

A high fraction of reduced glutathione in the glutathione redox status was associated with longer dependency of mechanical ventilation and length of stay in the PICU (P = 0.02 and P = 0.03 respectively). In patients with a prolonged stay in the PICU (> 5 days), a more reduced state of glutathione was seen in patients who had more than two organ failures as compared to patients with one or two failing organs (P < 0.01 and P < 0.05), respectively. A positive correlation was also seen between numbers of organ failures and redox status of glutathione (r  = 0.45, P < 0.001).

CONCLUSION

A high reduced glutathione ratio was associated with longer PICU stay, duration of mechanical ventilation, and multiple organ failure.

Plasma glutamine deficiency is associated with multiple organ failure in critically ill children

A low plasma glutamine concentration (<420 µmol/L) is an independent risk factor for mortality in critically ill adult patients. Glutamine metabolism in children is less well characterized. However, pediatric ICU (PICU) mortality is low and, therefore, mortality is difficult to use as an endpoint. Here we evaluated if plasma glutamine concentration at admission to the PICU, relates to the development of multiple organ failure, using pediatric logistic organ dysfunction score (PELOD)-score. In this observational study, consecutive critically ill children (n = 149) admitted to the PICU of a tertiary university hospital as well as a reference group of healthy children (n = 60) were included. Plasma glutamine concentration and the PELOD were determined at admission for all patients and at day 5 for those patients still in the PICU. Plasma glutamine concentration at admission was low in the PICU patients as compared to controls (p = 0.00002) and patients with a low plasma glutamine concentration had more organ failure as compared to patients with higher plasma glutamine concentration (p = 0.0001). Plasma glutamine concentration normalized in patients staying >5 days in the PICU. Plasma glutamine depletion was present in 40 % of patients at PICU admission and it was associated with the development of multiple organ failure. Furthermore, the majority of the critically ill children normalized their plasma glutamine concentration within 5 days, which is different from adult ICU patients. The study suggests that an initial plasma glutamine deficiency is associated with multiple organ failure in critically ill children.

Oxidative status in ICU patients with septic shock

The aim of this pilot study was to investigate variability of oxidative stress during sepsis evolution. ICU patients with the diagnosis of septic shock were included. Thiobarbituric-acid reactive substances, total antioxidant capacity, protein carbonyls in plasma, reduced, oxidized glutathione and catalase activity in erythrocyte lysate were assessed in the 1st, 3rd, 5th and 8th day after sepsis appearance. A total of 17 patients were divided in two groups: survivors (n=7) and non-survivors (n=10). APACHE II was 11.5 ± 5.4 and 19.9 ± 4.97 in survivors and non-survivors respectively (p=0.005), while mean age and SOFA score at sepsis diagnosis, were similar between the two groups. GSH levels, catalase activity and protein carbonyls presented significant different course in time between survivors and non-survivors (p<0.05). Catalase activity was significantly higher in survivors (238.8 ± 51.5) than non-survivors (166.4 ± 40.2; p=0.005), while protein carbonyls levels were significantly lower in survivors (0.32 ± 0.09) than non-survivors (0.48 ± 0.16; p=0.036) on the 1st day. Yet, non-survivors exhibited a declining course in GSH levels during time, while GSH levels were maintained in survivors. Conclusively, a longstanding antioxidant deficiency in non-surviving patients was noted. This phenomenon was clearly prominent in patients' erythrocytes.

[Intensive care unit-acquired weakness in the critically ill : critical illness polyneuropathy and critical illness myopathy]

Intensive care unit-acquired weakness (ICUAW) is a severe complication in critically ill patients which has been increasingly recognized over the last two decades. By definition ICUAW is caused by distinct neuromuscular disorders, namely critical illness polyneuropathy (CIP) and critical illness myopathy (CIM). Both CIP and CIM can affect limb and respiratory muscles and thus complicate weaning from a ventilator, increase the length of stay in the intensive care unit and delay mobilization and physical rehabilitation. It is controversially discussed whether CIP and CIM are distinct entities or whether they just represent different organ manifestations with common pathomechanisms. These basic pathomechanisms, however, are complex and still not completely understood but metabolic, inflammatory and bioenergetic alterations seem to play a crucial role. In this respect several risk factors have recently been revealed: in addition to the administration of glucocorticoids and non-depolarizing muscle relaxants, sepsis and multi-organ failure per se as well as elevated levels of blood glucose and muscular immobilization have been shown to have a profound impact on the occurrence of CIP and CIM. For the diagnosis, careful physical and neurological examinations, electrophysiological testing and in rare cases nerve and muscle biopsies are recommended. Nevertheless, it appears to be difficult to clearly distinguish between CIM and CIP in a clinical setting. At present no specific therapy for these neuromuscular disorders has been established but recent data suggest that in addition to avoidance of risk factors early active mobilization of critically ill patients may be beneficial.

Circulating and muscle glutathione turnover in human endotoxaemia

Patients with septic shock have high plasma glutathione concentrations, whereas intracellular concentrations in erythrocytes and muscle are low. In the present study, we investigated the temporal pattern of glutathione status and glutathione kinetics in healthy volunteers during the initial phase of sepsis using a human endotoxin model. The present study was a descriptive pilot study in healthy male volunteers (n=8) before and after an endotoxin challenge. The glutathione status was determined in plasma and whole blood at baseline and hourly for 4 h after intravenous endotoxin injection and in skeletal muscle at baseline and at 2 and 4 h after endotoxin injection. In plasma, the concentration of total glutathione decreased 24% (P<0.05) at 3 h after endotoxin injection and 32% (P<0.001) at 4 h. In whole blood and skeletal muscle, the concentrations of both GSH and total glutathione as well as the redox status remained unaltered during the initial 4 h after the endotoxin challenge. The FSR (fractional synthesis rate) of glutathione in whole blood was 38+/-20%/day before and 59+/-22%/day 4 h after the endotoxin challenge (P=0.088) and in skeletal muscle this was 41+/-25 and 46+/-18%/day (P=0.68) respectively. During the initial phase of sepsis, as represented by an intravenous endotoxin challenge to healthy volunteers, plasma concentrations of total glutathione decreased, whereas glutathione status and synthesis rate in skeletal muscle and whole blood remained unaltered. However, due to the variation in the synthesis measurements, larger studies are needed to confirm these findings.

The effect of intravenous alanyl-glutamine supplementation on plasma glutathione levels in intensive care unit trauma patients receiving enteral nutrition: the results of a randomized controlled trial

BACKGROUND

We sought to investigate the effect of IV alanyl-glutamine supplementation on plasma glutathione levels in severely traumatized patients receiving enteral nutrition.

METHODS

Forty adult patients with severe trauma according to the Injury Severity Score >20 were enrolled in this randomized, controlled study. The patients were assigned to two groups: Group G received 0.5 g x kg(-1) x d(-1) of alanyl-glutamine dipeptide supplementation IV, and Group C received a control solution without alanyl-glutamine for 7 days. Blood samples were taken for analysis of glutathione before the initiation of supplementation and on the 3rd, 7th, and 10th days of feeding.

RESULTS

Total plasma glutathione levels significantly increased in Group G when compared with Group C on Days 7 and 10 (1.34 +/- 0.20 microM vs 1.13 +/- 0.14 microM, and 1.38 +/- 0.19 microM vs 1.12 +/- 0.16 microM) (P < 0.001).

CONCLUSIONS

This study demonstrates that IV alanyl-glutamine supplementation for 7 days increases total plasma glutathione levels in critically ill trauma patients receiving standard enteral nutrition.

Selenium and thyroid hormone axis in critical ill states: an overview of conflicting view points

In critical ill states the plasma selenium levels are low and inversely correlated with the severity and outcome of the disease. The plasma selenium levels indicate the amount of circulating selenoproteins and selenoenzymes. These are important for the maintenance of the redox system, modulating the immune system and also for thyroid hormone metabolism. Not only all three deiodinases (D1-3) are selenoenzymes, but within the thyroid gland there are several other selenoenzymes, which are important for the maintenance of normal thyroid function. In critical ill states also triodothyronine (T3) is low and reverse T3 elevated, and also TSH and thyroxin (T4) are low, correlating like low plasma selenium with the severity of the disease. Subsequently, several intervention trials had been performed to evaluate whether an adjuvant selenium supplementation might attenuate the course of the disease and improve outcome. The selenium supplementation improved outcome and even reduced mortality in some but not all prospective randomized trials. A few prospective randomized intervention trials with selenium supplementation had also been performed to evaluate the hypothesis, whether low selenium is the cause of low-T3-syndrome, however, with conflicting results and no clear evidence that low D1 activity is due to the selenium deficiency in critical illness. Because D1 catalyses the conversion of T4 to T3 and also the clearance of reverse T3, low D1 activity would sufficiently explain low plasma T3 and elevated reverse T3. It had been, however, clearly shown that cytokines are responsible for the inhibition of D1 activity, but D2 and D3 are even higher during acute inflammation in critically ill patients. One of the most important effects of selenium on the immune system seems to be the reduction of cytokine release and therefore an indirect connection between low selenium and low D1 activity has to be postulated and not a lower D1 activity due to lower availability of selenium for the D1 expression.

Dysregulation of mitochondrial dynamics and the muscle transcriptome in ICU patients suffering from sepsis induced multiple organ failure

Background

Septic patients treated in the intensive care unit (ICU) often develop multiple organ failure including persistent skeletal muscle dysfunction which results in the patient's protracted recovery process. We have demonstrated that muscle mitochondrial enzyme activities are impaired in septic ICU patients impairing cellular energy balance, which will interfere with muscle function and metabolism. Here we use detailed phenotyping and genomics to elucidate mechanisms leading to these impairments and the molecular consequences.

Methodology/Principal Findings

Utilising biopsy material from seventeen patients and ten age-matched controls we demonstrate that neither mitochondrial in vivo protein synthesis nor expression of mitochondrial genes are compromised. Indeed, there was partial activation of the mitochondrial biogenesis pathway involving NRF2α/GABP and its target genes TFAM, TFB1M and TFB2M yet clearly this failed to maintain mitochondrial function. We therefore utilised transcript profiling and pathway analysis of ICU patient skeletal muscle to generate insight into the molecular defects driving loss of muscle function and metabolic homeostasis. Gene ontology analysis of Affymetrix analysis demonstrated substantial loss of muscle specific genes, a global oxidative stress response related to most probably cytokine signalling, altered insulin related signalling and a substantial overlap between patients and muscle wasting/inflammatory animal models. MicroRNA 21 processing appeared defective suggesting that post-transcriptional protein synthesis regulation is altered by disruption of tissue microRNA expression. Finally, we were able to demonstrate that the phenotype of skeletal muscle in ICU patients is not merely one of inactivity, it appears to be an actively remodelling tissue, influenced by several mediators, all of which may be open to manipulation with the aim to improve clinical outcome.

Conclusions/Significance

This first combined protein and transcriptome based analysis of human skeletal muscle obtained from septic patients demonstrated that losses of mitochondria and muscle mass are accompanied by sustained protein synthesis (anabolic process) while dysregulation of transcription programmes appears to fail to compensate for increased damage and proteolysis. Our analysis identified both validated and novel clinically tractable targets to manipulate these failing processes and pursuit of these could lead to new potential treatments.

Cellular energetic metabolism in sepsis: the need for a systems approach

Sepsis is a complex pathophysiological disorder arising from a systemic inflammatory response to infection. Patients are clinically classified according to the presence of signs of inflammation alone, multiple organ failure (MOF), or organ failure plus hypotension (septic shock). The organ damage that occurs in MOF is not a direct effect of the pathogen itself, but rather of the dysregulated inflammatory response of the patient. Although mechanisms underlying MOF are not completely understood, a disruption in cellular energetic metabolism is increasingly implicated. In this review, we describe how various factors affecting cellular ATP supply and demand appear to be altered in sepsis, and how these vary through the timecourse. We will emphasise the need for an integrated systems approach to determine the relative importance of these factors in both the failure and recovery of different organs. A modular framework is proposed that can be used to assess the control hierarchy of cellular energetics in this complex pathophysiological condition.

Practicalities of selenium supplementation in critically ill patients

PURPOSE OF REVIEW

To review the reason for and clinical effects of selenium supplementation in critically ill patients.

RECENT FINDINGS

Selenium-dependent enzymes and selenoprotein P regulate immune and endothelial cell function. Obviously not the anorganic compounds of selenium but the activity of selenium-dependent enzymes is the most important factor modulating the immune system and the clinical outcome of patients. Despite low selenium levels in severely ill patients and low glutathione peroxidase activity associated with the extent of multiorgan dysfunction, only a few trials have investigated the effect of selenium supplementation on clinical outcome. A metaanalysis did not reveal a statistically significant survival rate with selenium supplementation, but suggested a dose-dependent trend. The recently completed multicentre trial on high-dose selenium supplementation in septic patients also did not reveal a significant overall reduction in mortality.

SUMMARY

The available evidence suggests that selenoproteins play an important role in the immunomodulation of critically ill patients and a sodium selenite supplementation upregulates these selenoenzymes. The intervention trials with sodium selenite performed to date are small and therefore only a tendency in reduction of morbidity and mortality could be demonstrated. Larger trials are necessary to show the supposed benefits and risks of selenite supplementation in critically ill patients.

Endothelial oxidative stress induced by serum from patients with severe trauma hemorrhage

OBJECTIVE

Shock induces oxidative stress by ischemia-reperfusion phenomenon. Endothelial cells are involved in the inflammatory response and oxidative stress responsible for microcirculation impairment and organ failure. We examined the potential of serum from patients to induce in vitro reactive oxygen species production by cultured human umbilical vein endothelial cells (HUVECs).

PATIENTS

Three groups were compared: hemorrhagic shock trauma patients, isolated brain injured patients, and healthy volunteers.

METHODS

In the hemorrhagic shock group we sought a correlation between reactive oxygen species production and severity of shock. Serum was separated and perfused in an in vitro model of perfused HUVECs. Ex vivo reactive oxygen species production was assessed by fluorescence microscopy using dichlorodihydrofluorescein, an intracellular dye oxidized by H2O2. Results are expressed in proportional change from baseline and normalized by protidemia to control for variation related to hemodilution.

RESULTS

Reactive oxygen species production by endothelial cells exposed to serum from hemorrhagic shock patients (46.2+/-24.9%) was significantly greater than in those with brain injury (3.9+/-35.1%) and in healthy volunteers (-6.8+/-5.8%). In the hemorrhagic shock group dichlorodihydrofluorescein fluorescence was strongly correlated positively to Simplified Acute Physiology Score II and lactatemia and negatively to [HCO3-].

CONCLUSIONS

Serum from trauma patients with hemorrhagic shock induces reactive oxygen species formation in naive endothelial cells which is correlated to shock severity.

Temporal changes in whole-blood and plasma glutathione in ICU patients with multiple organ failure

OBJECTIVE

This study investigated the temporal changes in whole-blood and plasma glutathione in ICU patients with multiple organ failure.

DESIGN AND SETTING

Prospective and descriptive pilot study performed in an ICU with eight beds at a university hospital.

PATIENTS

Critically ill patients (n=11) with multiple organ failure and ICU stay of at least 6 days were consecutively included. Patients with chronic obstructive pulmonary disease (n=21) and healthy volunteers (n=10) were used as reference groups.

MEASUREMENTS AND RESULTS

Whole-blood and plasma glutathione were measured every 72 h. Total glutathione and the reduced fraction were determined in whole blood. The oxidized fraction and the redox status were calculated from these values. In plasma only the total concentration was determined. Patients were studied for 6-15 days. Nutrition was supplied according to routines supplying basal needs including glutamine. Both total and reduced glutathione was found to be depleted in whole blood compared to the reference groups. Redox status indicated continuing oxidative stress. Plasma glutathione showed higher values in total concentrations than the reference groups.

CONCLUSIONS

This study demonstrates that glutathione remains depleted in whole blood. This contrasts to what has previously been shown in skeletal muscle where a restitution of glutathione concentration is seen.

Skeletal muscle glutamate metabolism in health and disease: state of the art

PURPOSE OF REVIEW

Glutamate is an amino acid of interest because it participates in many metabolic pathways. However, there is evidence that skeletal muscle glutamate metabolism is disturbed in disease. This review presents current knowledge regarding the metabolic function and regulation of glutamate in skeletal muscle under physiological and pathophysiological circumstances. Furthermore, several options for modulating muscle glutamate concentration in order to improve glutamate metabolism are discussed.

RECENT FINDINGS

The high correlation between muscle glutamate concentration and muscle glutathione concentration suggests that glutamate plays a determining role in the glutathione synthesis pathway. During exercise, glutamate plays a central role in energy provision because it participates in the tricarboxylic acid and the purine nucleotide cycles. However, a consistent finding in several diseases is reduced skeletal muscle glutamate. Remarkably, only few studies focused on modulation of muscle glutamate status either by exercise or by nutritional supplementation. There are several options for modulating glutamate metabolism, but the specific effects of the individual options require further elucidation. Nutritional supplementation of glutamate or its precursors glutamine, (ornithine) alpha-ketoglutarate, or the branched chain amino acids can influence muscle glutamate status.

SUMMARY

Specific intervention studies must be conducted to investigate the effect of supplementation on skeletal muscle glutamate turnover and its related metabolic and functional consequences in healthy individuals and in patients with acute or chronic disease.

Effects on skeletal muscle of intravenous glutamine supplementation to ICU patients

OBJECTIVE

To evaluate the effect of four doses of intravenous glutamine supplementation on skeletal muscle metabolism.

DESIGN

A prospective, blinded, randomized study.

SETTING

The general Intensive Care Unit (ICU) of a university hospital.

PATIENTS

ICU patients with multiple organ failure (n=40), who were expected to stay in the unit for more than five days.

INTERVENTION

Patients received 0, 0.28, 0.57 or 0.86 g of glutamine per kg bodyweight per day intravenously for five days as part of an isocaloric, isonitrogenous and isovolumetric diet.

RESULTS

Plasma glutamine concentration responded to glutamine supplementation with normalization of plasma levels in a dose-dependent way, while free muscle glutamine concentration, as well as muscle protein synthesis and muscle protein content, did not change significantly.

CONCLUSION

Intravenous glutamine supplementation to ICU patients for a period of five days resulted in normalization of plasma glutamine concentrations in a dose-dependent way whereas muscle glutamine concentrations were unaffected.