Understanding the heart-brain axis response in COVID-19 patients: A suggestive perspective for therapeutic development.

In-depth characterization of heart-brain communication in critically ill patients with severe acute respiratory failure is attracting significant interest in the COronaVIrus Disease 19 (COVID-19) pandemic era during intensive care unit (ICU) stay and after ICU or hospital discharge. Emerging research has provided new insights into pathogenic role of the deregulation of the heart-brain axis (HBA), a bidirectional flow of information, in leading to severe multiorgan disease syndrome (MODS) in patients with confirmed infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Noteworthy, HBA dysfunction may worsen the outcome of the COVID-19 patients. In this review, we discuss the critical role HBA plays in both promoting and limiting MODS in COVID-19. We also highlight the role of HBA as new target for novel therapeutic strategies in COVID-19 in order to open new translational frontiers of care. This is a translational perspective from the Italian Society of Cardiovascular Researches.

Visnagin attenuates acute pancreatitis via Nrf2/NFκB pathway and abrogates associated multiple organ dysfunction.

Acute pancreatitis (AP) is an exocrine dysfunction of the pancreas where oxidative stress and inflammatory cytokines play a key role in induction and progression of the disease. Studies have demonstrated that antioxidant phytochemicals have been effective in improving pancreatitis condition, but there are no clinically approved drugs till date. Our study aims to assess the preventive activity of visnagin, a novel phytochemical isolated from Ammi visnaga against cerulein induced AP. Male Swiss albino mice were divided into six groups (n = 6, each group) comprising of normal control, cerulein control, seven day pre-treatment with visnagin at three dose levels; visnagin low dose (10 mg/kg), visnagin mid dose (30 mg/kg), visnagin high dose (60 mg/kg) and visnagin control (60 mg/kg). AP was induced by six injections of cerulein (50 µg/kg, i.p.) on the 7th day and the animals were sacrificed after 6 h of last cerulein dose. Various markers of pancreatic function, oxidative stress and inflammation were assessed. Visnagin was found to be effective in reducing plasma amylase and lipase levels, reduced cerulein induced oxidative stress. Visnagin dose dependently decreased the expression of IL-1ß, IL-6, TNF-α and IL-17. It attenuated the levels of nuclear p65-NFκB. Visnagin improved the antioxidant defence by improving Nrf2 expression and halted pancreatic inflammation by suppressing NFκB and nitrotyrosine expression in the acinar cells. Further, it attenuated the expression of markers of multiple organ dysfunction syndrome and reduced inflammatory cytokines in lungs and intestine. Cumulatively, these findings indicate that visnagin has substantial potential to prevent cerulein induced AP.

Administration of nicotinamide riboside prevents oxidative stress and organ injury in sepsis.

AIMS: Sepsis-caused multiple organ failure remains the major cause of morbidity and mortality in intensive care units. Nicotinamide riboside (NR) is a precursor of nicotinamide adenine dinucleotide (NAD+), which is important in regulating oxidative stress. This study investigated whether administration of NR prevented oxidative stress and organ injury in sepsis. METHODS: Mouse sepsis models were induced by injection of lipopolysaccharides (LPS) or feces-injection-in-peritoneum. NR was given before sepsis onset. Cultured macrophages and endothelial cells were incubated with various agents. RESULTS: Administration of NR elevated the NAD+ levels, and elicited a reduction of oxidative stress, inflammation and caspase-3 activity in lung and heart tissues, which correlated with attenuation of pulmonary microvascular permeability and myocardial dysfunction, leading to less mortality in sepsis models. These protective effects of NR were associated with decreased levels of plasma high mobility group box-1 (HMGB1) in septic mice. Consistently, pre-treatment of macrophages with NR increased NAD+ content and reduced HMGB1 release upon LPS stimulation. NR also prevented reactive oxygen species (ROS) production and apoptosis in endothelial cells induced by a conditioned-medium collected from LPS-treated macrophages. Furthermore, inhibition of SIRT1 by EX527 offset the negative effects of NR on HMGB1 release in macrophages, and ROS and apoptosis in endothelial cells. CONCLUSIONS: Administration of NR prevents lung and heart injury, and improves the survival in sepsis, likely by inhibiting HMGB1 release and oxidative stress via the NAD+/SIRT1 signaling. Given NR has been used as a health supplement, it may be a useful agent to prevent organ injury in sepsis.

Mitochondria-meditated pathways of organ failure upon inflammation.

Liver failure induced by systemic inflammatory response (SIRS) is often associated with mitochondrial dysfunction but the mechanism linking SIRS and mitochondria-mediated liver failure is still a matter of discussion. Current hypotheses suggest that causative events could be a drop in ATP synthesis, opening of mitochondrial permeability transition pore, specific changes in mitochondrial morphology, impaired Ca2+ uptake, generation of mitochondrial reactive oxygen species (mtROS), turnover of mitochondria and imbalance in electron supply to the respiratory chain. The aim of this review is to critically analyze existing hypotheses, in order to highlight the most promising research lines helping to prevent liver failure induced by SIRS. Evaluation of the literature shows that there is no consistent support that impaired Ca++ metabolism, electron transport chain function and ultrastructure of mitochondria substantially contribute to liver failure. Moreover, our analysis suggests that the drop in ATP levels has protective rather than a deleterious character. Recent data suggest that the most critical mitochondrial event occurring upon SIRS is the release of mtROS in cytoplasm, which can activate two specific intracellular signaling cascades. The first is the mtROS-mediated activation of NADPH-oxidase in liver macrophages and endothelial cells; the second is the acceleration of the expression of inflammatory genes in hepatocytes. The signaling action of mtROS is strictly controlled in mitochondria at three points, (i) at the site of ROS generation at complex I, (ii) the site of mtROS release in cytoplasm via permeability transition pore, and (iii) interaction with specific kinases in cytoplasm. The systems controlling mtROS-signaling include pro- and anti-inflammatory mediators, nitric oxide, Ca2+ and NADPH-oxidase. Analysis of the literature suggests that further research should be focused on the impact of mtROS on organ failure induced by inflammation and simultaneously providing a new theoretical basis for a targeted therapy of overwhelmed inflammatory response.

13-Ethylberberine reduces HMGB1 release through AMPK activation in LPS-activated RAW264.7 cells and protects endotoxemic mice from organ damage.

High mobility group box 1 (HMGB1), a highly conserved non-histone DNA-binding protein, plays an important role in the pathogenesis of sepsis. Previously, the authors reported 13-ethylberberine (13-EBR) has anti-inflammatory and antibacterial effects. However, the effect of 13-EBR on HMGB1 release was not investigated. In the present study, it was hypothesized 13-EBR might reduce HMGB1 release by activating AMPK under septic conditions. The results obtained showed 13-EBR significantly reduced HMGB1 release from LPS-activated RAW264.7 cells, and that this reduction was reversed by silencing p38, or AMPK, or by co-treating cells with p38 MAPKinase inhibitor. 13-EBR increased the phosphorylations of p38 and AMPK, and the phosphorylation of p38 by 13-EBR was inhibited by AMPK-siRNA, indicating AMPK acted upstream of p38. In the lung tissues of LPS-treated mice, 13-EBR administration significantly increased p-AMPK but reduced inducible nitric oxide synthase (iNOS) protein levels. Hematoxylin and eosin staining revealed 13-EBR significantly reduced LPS-induced lung and liver damage. In addition, 13-EBR inhibited NF-kB in LPS-activated RAW264.7 cells, and in LPS-treated mice, 13-EBR administration significantly increased survival. Furthermore, co-administration of 13-EBR plus LPS prevented LPS-induced aortic rings hypocontractile response to phenylephrine in vitro. Taken together, these results indicate 13-EBR might offer a means of treating sepsis through AMPK activation.

Oxidative stress in sepsis: Pathophysiological implications justifying antioxidant co-therapy.

Sepsis is one of the main causes of death among critically ill patients. Sepsis pathogenesis includes infection by gram-negative and gram-positive bacteria, fungi, or both; exacerbated inflammatory response; hypotension, with potential to cause vasodilatory shock; and lesser delivery of oxygen to tissues due to impairment of oxygen utilization by cells. The participation of reactive species and/or free radicals such as nitric oxide (NO), peroxynitrite (ONOO-), superoxide (O2-), hydrogen peroxide (H2O2), and hydroxyl radical (OH) has been reported to underlie these effects. Mitochondrial dysfunction is related to loss of inner membrane potential and inhibition of the mitochondrial electron transfer chain and FoF1-adenosine triphosphate-synthase, resulting in cellular energetic failure. In addition, overproduction of NO due to inducible nitric oxide synthase (iNOS) activity has been associated with harmful effects such as general vasodilatation and hypo-responsiveness to therapeutic vasoconstrictor agents. Considering that iNOS expression is regulated by nuclear factor-κB, which may be activated by ROS, antioxidants could inhibit the overexpression of iNOS in sepsis. In line with this, several antioxidants such as vitamins C and E, polyphenols, melatonin, ß-glucan, N-acetylcysteine, mitochondrion-targeted antioxidants (MitoQ, MitoE, and peptides associated with dimethyltyrosine), selenium salts, and organoselenium compounds were effective in ameliorating oxidative stress in animal models of sepsis and in a number of clinical trials with septic patients.

Dietary interventions designed to protect the perinatal brain from hypoxic-ischemic encephalopathy--Creatine prophylaxis and the need for multi-organ protection.

Birth asphyxia or hypoxia arises from impaired placental gas exchange during labor and remains one of the leading causes of neonatal morbidity and mortality worldwide. It is a condition that can strike in pregnancies that have been uneventful until these final moments, and leads to fundamental loss of cellular energy reserves in the newborn. The cascade of metabolic changes that occurs in the brain at birth as a result of hypoxia can lead to significant damage that evolves over several hours and days, the severity of which can be ameliorated with therapeutic cerebral hypothermia. However, this treatment is only applied to a subset of newborns that meet strict inclusion criteria and is usually administered only in facilities with a high level of medical surveillance. Hence, a number of neuropharmacological interventions have been suggested as adjunct therapies to improve the efficacy of hypothermia, which alone improves survival of the post-hypoxic infant but does not altogether prevent adverse neurological outcomes. In this review we discuss the prospect of using creatine as a dietary supplement during pregnancy and nutritional intervention that can significantly decrease the risk of brain damage in the event of severe oxygen deprivation at birth. Because brain damage can also arise secondarily to compromise of other fetal organs (e.g., heart, diaphragm, kidney), and that compromise of mitochondrial function under hypoxic conditions may be a common mechanism leading to damage of these tissues, we present data suggesting that dietary creatine supplementation during pregnancy may be an effective prophylaxis that can protect the fetus from the multi-organ consequences of severe hypoxia at birth.

ANGIOGENESIS INHIBITOR ENDOSTATIN PROTECTS MICE WITH SEPSIS FROM MULTIPLE ORGAN DYSFUNCTION SYNDROME.

Endostatin is an endogenous inhibitor of vascular endothelium. It can inhibit endothelial cell migration, proliferation, and vascular angiogenesis and is mainly used for anticancer therapy. We have previously found that endostatin is an important node protein in the pathogenesis of sepsis. However, its impacts on sepsis have not yet been reported. We established a septic mouse model using cecal ligation and puncture (CLP) and gave the mice either endostatin or placebo (saline). The effects of endostatin on serum enzyme, Evans blue leakage, lung wet-to-dry weight ratio, and cytokine (tumor necrosis factor α, interleukin 1ß [IL-1ß], and IL-6) production were assessed. Survival rates were observed for up to 3 days. In addition, we examined the effects of endostatin on serum vascular endothelial growth factor A (VEGF-A), VEGF-C, and pathological changes and scores of lung tissues as well as the phosphorylation of JNK, p38, and ERKl/2 proteins in lung tissues of mice with sepsis. We found that endostatin can increase the survival of septic mice in a time- and dose-dependent manner probably by reducing multiorgan dysfunctions shown by serum indicators, morphologic changes, Evans blue leakage, wet-to-dry weight ratio, and inflammation of lung tissues. In addition, endostatin could reduce serum tumor necrosis factor α, IL-1ß, IL-6, and VEGF-C levels in septic mice as well as inhibit phosphorylation of p38 and ERK1/2 in lung tissues of septic mice. This is the first study demonstrating the protective effect of endostatin on sepsis and its possible underlying mechanisms from the aspects of inhibiting inflammatory responses, blocking VEGF receptor, attenuating VEGF-C expression, and reducing vascular permeability. Overall, the study revealed the potential protect role for endostatin in the treatment of sepsis.

Vitamin C treatment attenuates hemorrhagic shock related multi-organ injuries through the induction of heme oxygenase-1.

BACKGROUND: Vitamin C (VitC) has recently been shown to exert beneficial effects, including protecting organ function and inhibiting inflammation, in various critical care conditions, but the specific mechanism remains unclear. Induction of heme oxygenase (HO)-1, a heat shock protein, has been shown to prevent organ injuries in hemorrhagic shock (HS) but the relationship between VitC and HO-1 are still ill-defined so far. Here we conducted a systemic in vivo study to investigate if VitC promoted HO-1 expression in multiple organs, and then tested if the HO-1 induction property of VitC was related to its organ protection and anti-inflammatory effect. METHODS: Firstly, to determine the HO-1 induction property of VitC, the HO-1 level were measured in tissues including kidney, liver and lung of the normal and HS model of Sprague-Dawley (SD) rats after VitC treatment (100 mg/kg body weight). Secondly, to testify if VitC prevented HS related organ injuries via inducing HO-1, the HS model of rats were separately pre- and post-treated with VitC, and some of them also received Zinc protoporphyrin (Znpp), a specific HO-1 inhibitor. The HO-1 activity in tissues was tested; the organ injuries (as judged by histological changes in tissues and the biochemical indicators level in serum) and inflammatory response in tissues (as judged by the level of pro-inflammatory cytokines Tumor necrosis factor-α and Interleukin-6 ) were analyzed. RESULTS: The HO-1 mRNA and protein level in kidney, liver, and lung were highly induced by VitC treatement under normal and HS conditions. The HO-1 activity in tissues was enhanced by both VitC pre- and post-treatment, which was shown to improve the organ injuries and inhibit the inflammatory response in the HS model of rats. Of note, the beneficial effects of VitC were abolished after HO-1 activity was blocked by Znpp. CONCLUSIONS: VitC led to a profound induction of HO-1 in multiple organs including the kidney, liver and lung, and this property might be responsible for the organ protection and inflammation inhibitory effects of both pre- and post-treatment with VitC in HS.

Effect of N-acetylcysteine treatment on oxidative stress and inflammation after severe burn.

Oxidative stress and inflammation generate edema in burns. The aim of our study was to assess effect of N-acetylcysteine (NAC) on oxidative stress, inflammation, fluid requirement, multiple organ dysfunction (MOD) score and vasoactive drug requirement. In this study 15 patients were on standard therapy, whereas for other 15 patients NAC was supplemented. Blood samples were taken on admission and on the next five consecutive mornings. Levels of malondialdehyde, protein sulfhydril (PSH) groups, reduced gluthation (GSH), activity of myeloperoxidase, catalase and superoxide dismutase enzymes and induced free radical generating capacity were measured as well as concentrations of TNF-α, IL-6, IL-8, and IL-10. MOD score, use of vasopressor agents and fluid utilisation were recorded daily. NAC treatment increased GSH level on days 4-5 (p<0.05) and PSH level on days 2-6 (p<0.05) compared to controls. Plasma IL-6 was lower on days 4-5 (p<0.05), IL-8 on days 4-6 (p<0.05) and IL-10 on days 4-6 (p<0.05) in NAC group. NAC group received less catecholamines than controls (p<0.01) from day 4 without significant differences in MOD score. NAC treatment is associated with a diminished oxidative stress reflected in preserved antioxidant levels, lower inflammation mirrored in lower interleukin levels and less vasopressor requirement.

Hyperbaric oxygen therapy reduces the toll-like receptor signaling pathway in multiple organ failures.

PURPOSE: Zymosan-induced generalized inflammation is the only experimental model that reproduces characteristics of human multiple organ dysfunction syndrome (MODS). Toll-like receptors (TLRs) are key components in innate immune responses and their signaling pathway is known to activate target genes such as nuclear factor-κB (NF-κB) and cytokines that are involved in inflammation and immune responses. We previously reported that hyperbaric oxygen (HBO) therapy is effective in the treatment of severe zymosan-induced inflammation in MODS. The aim of this study was to investigate the effect of HBO exposure on TLR2 and TLR4 signal transduction and organ dysfunction during MODS induced by zymosan in the rat. METHODS: Male Wistar rats were randomized into four groups and treated as follows: (1) saline solution (control); (2) zymosan; (3) HBO 4 and 11 h after zymosan injection; (4) HBO 4 and 11 h after saline solution injection. Zymosan-induced damage of the lungs, liver, and small intestine was evaluated using histology and biochemistry. The activation of the TLR signaling pathway was measured with Western blot, reverse transcriptase polymerase chain reaction analysis (RT-PCR), and immunohistochemistry. RESULTS: Zymosan induced a severe inflammatory response characterized by the activation of the TLR signaling pathway and by an organ dysfunction. HBO exposure significantly reduced the development of lung, liver, and intestine injury in our experimental model. It also significantly reduced the zymosan-induced expression of TLR2 and TLR4, NF-κB activation, and cytokine production. CONCLUSIONS: Taken together, these results suggest that, by interfering with the TLR pathway, HBO treatment may exert a protective effect against tissue injury caused by zymosan-induced generalized inflammation.

Effects of trace element supplementation on the inflammatory response in a rabbit model of major trauma.

Patients with a severe trauma exhibit a strong oxidative stress, an intense inflammatory response, and long-lasting hypermetabolism, all of which are proportional to the severity of injury. In this study, we investigated the impact of trace element (TE) supplementation on the inflammatory response in an animal model of major trauma. New Zealand White rabbits were randomly assigned as a control group (n=5) and an experimental group (n=70) that, after receiving a major trauma, was subdivided into Trauma-Control (n=35) and Trauma-TE (n=35) groups. Systemic inflammatory response syndrome (SIRS) was observed in 40 out of 70 rabbits with a trauma, with a higher incidence in the Trauma-Control group (88.6%; 31/35) than the Trauma-TE group (28.6%; 10/35) (p<0.01). The mortality rate was significantly different between the Trauma-Control and the Trauma-TE groups; (34% vs. 8%; p<0.01). There were significant post-trauma alterations in the levels of (1) serum and spleen zinc (Zn), copper (Cu), selenium (Se), and manganese (Mn), (2) serum AST and ALT, (3) serum interleukin-6/10, and (4) nuclear factor kappa binding (NF-kappaB) activity and the expression. TE supplementation: (1) improved blood urea nitrogen (BUN), and creatinine (Cr) levels, (2) stabilized IL-6/10 production, (3) decreased NF-kappaB p(65) production. Appropriate TE supplementation can improve the TE status, mitigate SIRS, and reduce the mortality due to multiple organ dysfunction syndromes (MODS)/multiple organ failure (MOF) after major trauma.

Investigation of the alterations in cellular electrophysiology underlying ventricular arrhythmia in dogs with the multiple organ dysfunction syndrome.

BACKGROUND: Multiple organ dysfunction syndrome (MODS)-specific cellular electrophysiological changes have so far not been reported and it seemed unlikely that they were related to arrhythmogenesis. METHODS AND RESULTS: Twelve dogs, weight 12 +/- 2 kg, were divided into a control group (n = 6) and an MODS group (n = 6). MODS lasting for 72 h was induced by the 'two-hit' method in 6 dogs. Ventricular myocytes were enzymatically isolated. Early afterdepolarizations (EADs), action potential duration (APD) and L-type calcium currents (ICa,L) were assessed. Sinus arrhythmias in all MODS dogs (100%; 6 of 6) and premature ventricular beats in 4 MODS dogs (66%; 4 of 6) were recorded, while no arrhythmias were found in the control animals. The prolongation of the APD was associated with a decreased ICa,L, and frequently provoked EADs were the typical electrophysiological alterations in the myocytes of MODS dogs. The action potential prolongation was shortened, the ICa,L blocked and EAD suppressed by using verapamil (100 micromol/l) in the myocytes of MODS dogs (66%; 4 of 6). CONCLUSION: The changes in cellular electrophysiology within 72 h in the heart of MODS dogs are APD prolongation, markedly decreased ICa,L as well as frequently provoked EAD, the most common types of arrhythmia being sinus arrhythmia and premature ventricular beats. This study suggests that verapamil appears to be an effective agent in reversing alterations in cellular electrophysiology at the early stage of MODS.

[Chaotic dynamic process of multiple organs dysfunction syndrome and the regulatory function of shenqin liquid on it].

OBJECTIVE: To explore the chaotic dynamic process of multiple organs dysfunction syndrome (MODS) and the regulatory effect of Shenqin Liquid (SQL), a Chinese herbal liquid preparation with the action of purging and qi-tonifying. METHODS: Eighty SD rats were divided into 4 groups, and were given suspension of zymosan A and paraffine (1 mL/kg) by peritoneal injection except for those in the blank control group to set up the multiple organs dysfunction syndrome (MODS) model. Low and high doses SQL were administered twice at the doses of 30 and 60 g/kg of SQL respectively at an interval of 8 h per day before modeling. Serum concentration of tumor necrosis factor alpha (TNF-alpha) and nitric oxide (NO) in MODS model animals were tested diachronically, eg. 12, 6 h before modeling, during modeling, 6 and 12 h after modeling, and then the mathematic models were built up with compartment analysis. Lyapunov exponents (LE) of the mathematic models were calculated to evaluate their chaotic characteristics of movement and the degree of chaos was ascertained with the correlation dimension (CD). RESULTS: The serum levels of TNF-alpha and NO were significantly higher than those in the bland control group at modeling, 6, and 12 h after modeling (P <0.01), while those in the low and high doses of SQL were significantly lower than the model group (P <0.01). Moreover, the level of NO in the high dose of SQL was significantly lower than that in the low dose group (P <0. 01). CD of TNF-alpha movement in the blank control group was 0.803 with the LE less than zero; those in the model group was 1. 966 and > 0 respectively; in the low dose and high dose SQL treated groups, CD was 0.517 and 0.653 respectively and LE >0. CD of NO movement in the blank control group was 0.670 and with LE < 0; in the model group, 1.242 with LE > 0; in the low dose SQL group, 0.574 and in the high dose SQL group 0.850, and LE <0 in the two groups. CONCLUSION: Under the normal physiologic condition, TNF-alpha and NO moved steadily without chaotic properties; while under the pathologic condition of MODS, they manifest relatively complicated chaotic properties. SQL can intervene the movement of TNF-alpha and NO, decrease the complexity of their chaotic movement, and make them return back to a stable state.

Substrate utilization in sepsis and multiple organ failure.

Sepsis and multiple organ failure are characterized by an excessive release of inflammatory mediators and a marked stimulation of stress hormones. These in turn have profound effects on energy and substrate metabolism: energy expenditure is generally increased, and increased lipolysis and fat oxidation are observed. Net protein breakdown occurs and leads to accelerated wasting. Most of these effects can be produced in healthy humans by administration of bacterial endotoxin or by tumor necrosis factor-alpha. Hyperlactatemia is a hallmark of sepsis and critical illness, and its severity is related to mortality. An increased lactate production, possibly secondary to activation of Na-K adenosine 5'-triphosphatase and to muscle mitochondrial dysfunction, is involved. Lactate production by immune cells and wound tissue may also play a role. Long-chain, n-3 polyunsaturated fatty acids have anti-inflammatory effects that may be beneficial in sepsis. They also decrease the stimulation of stress hormones induced by bacterial endotoxin, possibly through an effect exerted at the level of the central nervous sytem. Their use in patients with sepsis does not lead to adverse metabolic effects.

Exogenous glutamine: the clinical evidence.

We know that critically ill patients suffering from undernutrition with a limited nutritional reserve have a poorer outcome. Furthermore, having a low body mass index has been shown to be an independent predictor of excess mortality in multiple organ failure. Therefore, nutritional support has gained increasing interest in critical illness with the hope of preventing or attenuating the effects of malnutrition. A negative nitrogen balance is the characteristic metabolic feature in critical illness, with the major protein loss derived from skeletal muscle. In particular, glutamine concentrations are rapidly reduced in plasma and muscle. Over the last 20 yrs or so, increasing evidence is emerging to support the use of glutamine supplementation in critical illness. Clinical trials have found a mortality and morbidity advantage with glutamine supplementation. The advantage appears to be greater the more glutamine is given and greater again when given parenterally. Various modes of action have been postulated. Glutamine seems to have an effect on the immune system, antioxidant status, glucose metabolism, and heat shock protein response. However, the benefit of exogenous glutamine on morbidity and mortality is not universally accepted. This review critically appraises the current clinical evidence regarding glutamine supplementation in critical illness.

Exogenous glutamine--compensating a shortage?

There is still insufficient knowledge about in vivo glutamine metabolism and the regulation of glutamine homeostasis, particularly during metabolic stress. A shortage of glutamine is associated with a poor outcome, whereas for septic patients in the intensive care unit an increased availability of glutamine can prevent mortality and morbidity. Cellular defense mechanisms depend on normal glutamine availability to respond adequately to challenges presented. In clinical practice, treatment of plasma glutamine depletion improves outcome for the critically ill patient. An increased metabolic need for glutamine must be met with an increased consumption of glutamine. Ordinary food is not a sufficient supply of glutamine for the patient with multiple organ failure in the intensive care unit, but that is also true for several other nutrients. It is, therefore, debatable whether an exogenous supply of glutamine should be regarded as a pharmacologic treatment or whether this just represents physiology in stressed states. If a glutamine shortage requires substitution, supplementation to the normal concentration is compensation of a shortage, and the effect is physiological.

Use of exogenous arginine in multiple organ dysfunction syndrome and sepsis.

Given the multiple biological, metabolic, and pharmacologic effects of supplemental arginine, much effort has been devoted to defining its role in numerous clinical conditions. Herein, we review the multiple pathways of arginine metabolism with its various enzyme systems; the effect of arginine on nutrition, healing, and immune system; and its clinical use. Sepsis has been postulated to be an arginine-deficient state and/or a syndrome with elevated levels of nitric oxide. So-called immunonutritional formulations containing various nutritional components have been used most often, yet the effects often are attributed to arginine alone. Such conclusions led to guidelines recommending against the use of arginine-supplemented diets in critically ill patients. While caution in the face of a lack of evidence for benefit in sepsis is commended, well-defined studies examining arginine monotherapy in the context of full nutritional support should be carried out so as to define the possible clinical uses of arginine in critically ill and septic patients.

Glutamine kinetics during intravenous glutamine supplementation in ICU patients on continuous renal replacement therapy.

OBJECTIVE: To investigate glutamine kinetics during continuous renal replacement therapy (CRRT) in multiple organ failure (MOF) patients with and without exogenous intravenous glutamine supplementation. DESIGN AND PATIENTS: In a pragmatic clinical study 12 patients without urine production receiving CRRT were prospectively randomized in a cross-over design to receive glutamine intravenously for 20 h before placebo or placebo before glutamine on two consecutive days. Alanyl-glutamine or placebo (saline) was infused. MEASUREMENTS: Plasma glutamine concentration was measured in artery, femoral vein, and filtration fluid. Blood flow across the leg was measured and the efflux of glutamine calculated. The rate of appearance of glutamine was calculated from the plasma decay curve of glutamine concentration on the day of treatment. RESULTS: Glutamine supplementation increased plasma concentrations from 570+/-252 to 831+/-367 micromol l(-1). Glutamine losses into the filtration fluids were similar during treatment and control days: 25+/-13 vs. 24+/-11 mmol 24 h(-1), corresponding to 3.6+/-1.9 and 3.5+/-1.6 g 24 h(-1), respectively. Net glutamine balance across the leg was also similar on treatment and control days: 150+/-138 and 188+/-205 nmol min(-1) 100 ml(-1), respectively. The rate of appearance of glutamine was 54+/-17 g 24 h(-1). CONCLUSION: The loss of glutamine into the ultrafiltrate during CRRT in MOF patients suggests a greater need for exogenous glutamine than in patients without renal failure. The leg efflux and the filtration losses of glutamine were not affected in response to intravenous glutamine supplementation.

Protective effect of Hypericum perforatum in zymosan-induced multiple organ dysfunction syndrome: relationship to its inhibitory effect on nitric oxide production and its peroxynitrite scavenging activity.

Hypericum perforatum is a medicinal plant species containing many polyphenolic compounds, namely flavonoids and phenolic acids. Since polyphenolic compounds have high antioxidant potential, we have investigated the effects of H. perforatum extract on the development of multiple organ dysfunction syndrome caused by zymosan (500 mg/kg, administered i.p. as a suspension in saline) in mice. Organ failure and systemic inflammation in rats was assessed 18 h after administration of zymosan and/or H. perforatum extract and monitored for 12 days (for loss of body weight and mortality). Treatment of mice with H. perforatum extract (30 mg/kg i.p., 1 and 6h after zymosan) attenuated the peritoneal exudation and the migration of polymorphonuclear cells caused by zymosan, pulmonary, intestinal and pancreatic injury, and renal dysfunction as well as the increase in myeloperoxidase in the lung and intestine. Immunohistochemical analysis for inducible nitric oxide synthase (iNOS), nitrotyrosine, and poly(ADP-ribose) (PAR) revealed positive staining in lung and intestine tissues obtained from zymosan-injected mice. The degree of staining for nitrotyrosine, iNOS, and PAR was markedly reduced in tissue sections obtained from zymosan-treated mice, which received H. perforatum extract. In conclusion, this study provides evidence, for the first time, that H. perforatum extract attenuates the degree of zymosan-induced multiple organ dysfunction syndrome in mice.