Mitochondrial dysfunction and antioxidant therapy in sepsis

MKK3 mediates inflammatory response through modulation of mitochondrial function

Mitochondria are increasingly recognized as drivers of inflammatory responses. MAP kinase kinase 3 (MKK3), a dual-specificity protein kinase, is activated in inflammation and in turn activates p38 MAP kinase signaling. Here we show that MKK3 influences mitochondrial function and acts as a critical mediator of inflammation. MKK3-deficient (MKK3(-/-)) mice and bone marrow-derived macrophages (BMDMs) secreted smaller amounts of cytokines than wild type (WT) after lipopolysaccharide (LPS) exposure. There was improved mitochondrial function, as measured by basal oxygen consumption rate, mitochondrial membrane potential, and ATP production, in MKK3(-/-) BMDMs. After LPS exposure, MKK3(-/-) BMDMs did not show a significant increase in cellular reactive oxygen species production or in mitochondrial superoxide compared to WT. Activation of two important inflammatory mediators, i.e., the nuclear translocation of NF-κB and caspase-1 activity (a key component of the inflammasome), was lower in MKK3(-/-) BMDMs. p38 and JNK activation was lower in MKK3(-/-) BMDMs compared to WT after exposure to LPS. Knockdown of MKK3 by siRNA in wild-type BMDMs improved mitochondrial membrane potential, reduced LPS-induced caspase-1 activation, and attenuated cytokine secretion. Our studies establish MKK3 as a regulator of mitochondrial function and inflammatory responses to LPS and suggest that MKK3 may be a therapeutic target in inflammatory disorders such as sepsis.

ExoU-induced redox imbalance and oxidative stress in airway epithelial cells during Pseudomonas aeruginosa pneumosepsis

ExoU is a potent proinflammatory toxin produced by Pseudomonas aeruginosa, a major agent of severe lung infection and sepsis. Because inflammation is usually associated with oxidative stress, we investigated the effect of ExoU on free radical production and antioxidant defense mechanisms during the course of P. aeruginosa infection. In an experimental model of acute pneumonia, ExoU accounted for increased lipid peroxidation in mice lungs as soon as 3 h after intratracheal instillation of PA103 P. aeruginosa strain. The contribution of airway cells to the generation of a redox imbalance was assessed by in vitro tests carried out with A549 airway epithelial cells. Cultures infected with the ExoU-producing PA103 P. aeruginosa strain produced significantly increased concentrations of lipid hydroperoxides, 8-isoprostane, reactive oxygen intermediates, peroxynitrite and nitric oxide (NO), when compared to cells infected with exoU-deficient mutants. Overproduction of NO by PA103-infected cells likely resulted from overexpression of both inducible and endothelial NO synthase isoforms. PA103 infection was also associated with a significantly increased activity of superoxide dismutase (SOD) and decreased levels of reduced glutathione (GSH), a major antioxidant compound. Our findings unveil another potential mechanism of tissue damage during infection by ExoU-producing P. aeruginosa strains.

Vicious inducible nitric oxide synthase-mitochondrial reactive oxygen species cycle accelerates inflammatory response and causes liver injury in rats

AIMS

Increasing evidences suggest that, apart from activation of guanylyl cyclase, intracellular nitric oxide (NO) signaling is associated with an interaction between NO and reactive oxygen species (ROS) to modulate physiological or pathophysiological processes. The aim of this study was to understand the contribution of mitochondrial ROS (mtROS) to NO-mediated signaling in hepatocytes on inflammation.

RESULTS

In rats treated with lipopolysaccharide (LPS), mitochondria-targeted antioxidants (mtAOX) (mitoTEMPO and SkQ1) reduced inducible nitric oxide synthase (iNOS) gene expression in liver, NO levels in blood and plasma, and markers of organ damage (lactate dehydrogenase, aspartate aminotransferase, and alanine aminotransferase). In cultured hepatocytes, treated with inflammatory mediators, generated ex vivo by incubation of white blood cells with LPS, we observed an increase in NO and mtROS levels. l-NG-monomethyl arginine citrate, a NOS inhibitor, decreased both NO and mtROS levels. mtAOX reduced mtROS, cytoplasmic ROS levels, and expression of iNOS and interleukin (IL)-6. These data suggest that NO, generated by iNOS, elevates mtROS, which, in turn, diffuse into the cytoplasm and upregulate iNOS and IL-6.

INNOVATION

Here, for the first time, we show that intracellular signaling pathways mediated by NO and ROS are linked to each other via mtROS and form an iNOS-mtROS feed-forward loop which aggravates liver failure on acute inflammation.

CONCLUSION

Our results provide a mechanistic explanation of how NO and mtROS cooperate to conduct inflammatory intracellular signals. We anticipate our results to be the missing mechanistic link between acute systemic inflammation and liver failure.

Cross-talk between HPA-axis-increased glucocorticoids and mitochondrial stress determines immune responses and clinical manifestations of patients with sepsis

Various stressors activate the hypothalamo-pituitary-adrenal axis (HPA-axis) that stimulates adrenal secretion of glucocorticoids, thereby playing critical roles in the modulation of immune responses. Transcriptional regulation of nuclear genes has been well documented to underlie the mechanism of glucocorticoid-dependent modulation of cytokine production and immune reactions. Glucocorticoids also regulate inflammatory responses via non-genomic pathways in cytoplasm and mitochondria. Recent studies have revealed that glucocorticoids modulate mitochondrial calcium homeostasis and generation of reactive oxygen species (ROS). Although redox status and ROS generation in inflammatory cells have been well documented to play important roles in defense against pathogens, the roles of glucocorticoids and mitochondria in the modulation of immunological responses remain obscure. This review describes the role of stress-induced activation of the HPA-axis and glucocorticoid secretion by the adrenal gland in mitochondria-dependent signaling pathways that modulate endotoxin-induced inflammatory reactions and innate immunity.

Methylglyoxal as a new biomarker in patients with septic shock: an observational clinical study

Introduction

The role of reactive carbonyl species, such as methylglyoxal (MG), has been overlooked within the context of the sepsis syndrome. The aims of this study were to assess the impact of MG formation in different inflammatory settings and to evaluate its use for early diagnosis as well as prognosis of the sepsis syndrome.

Methods

In total, 120 patients in three groups were enrolled in this observational clinical pilot study. The three groups included patients with septic shock (n = 60), postoperative controls (n = 30), and healthy volunteers (n = 30). Plasma samples from patients with septic shock were collected at sepsis onset and after 24 hours and 4, 7, 14, and 28 days. Plasma samples from postoperative controls were collected prior to surgery, immediately following the end of the surgical procedure as well as 24 hours later and from healthy volunteers once. Plasma levels of MG were determined by high-performance liquid chromatography. Additionally, plasma levels of procalcitonin, C-reactive protein, soluble CD14 subtype, and interleukin-6 were determined.

Results

Patients with septic shock showed significantly higher plasma levels of MG at all measured times, compared with postoperative controls. MG was found to identify patients with septic shock more effectively—area under the curve (AUC): 0.993—than procalcitonin (AUC: 0.844), C-reactive protein (AUC: 0.791), soluble CD14 subtype (AUC: 0.832), and interleukin-6 (AUC: 0.898) as assessed by receiver operating characteristic (ROC) analysis. Moreover, plasma levels of MG in non-survivors were significantly higher than in survivors (sepsis onset: *P = 0.018 for 90-day survival; **P = 0.008 for 28-day survival). Plasma levels of MG proved to be an early predictor for survival in patients with septic shock (sepsis onset: ROC-AUC 0.710 for 28-day survival; ROC-AUC 0.686 for 90-day survival).

Conclusions

MG was identified as a marker for monitoring the onset, development, and remission of sepsis and was found to be more useful than routine diagnostic markers. Further studies are required to determine the extent of MG modification in sepsis and whether targeting this pathway could be therapeutically beneficial to the patient.

Trial registration

German Clinical Trials Register DRKS00000505. Registered 8 November 2010.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-014-0683-x) contains supplementary material, which is available to authorized users.

Downregulation of adenine nucleotide translocator 1 exacerbates tumor necrosis factor-α-mediated cardiac inflammatory responses

Inflammation contributes significantly to cardiac dysfunction. Although the initial phase of inflammation is essential for repair and healing, excessive proinflammatory cytokines are detrimental to the heart. We found that adenine nucleotide translocator isoform-1 (ANT1) protein levels were significantly decreased in the inflamed heart of C57BL/6 mice following cecal ligation and puncture. To understand the molecular mechanisms involved, we performed small-interfering RNA-mediated knockdown of ANT1 and studied tumor necrosis factor-α (TNFα)-induced inflammatory responses in myocardium-derived H9c2 cells and cardiomyocytes. ANT1 knockdown significantly increased swollen mitochondria and mitochondrial reactive oxygen species, concomitant with increased TNFα-induced NF-κB reporter gene activity and interleukin-6 and TNFα expression. A mitochondrial-targeted antioxidant mito-TEMPO attenuated TNFα-induced mitochondrial reactive oxygen species, NF-κB reporter gene activity, and cytokine expression in ANT1 knockdown cells. Interestingly, TNFα or lipopolysaccharide (LPS) treatment significantly decreased ANT1 protein levels, suggesting a feed-forward regulation of proinflammatory cytokine expression activated by ANT1 downregulation. These data suggest that ANT1 downregulation contributes to cardiac inflammation post-cecal ligation and puncture. Preventing ANT1 downregulation could provide a novel molecular target to temper cardiac inflammation.

Certain Diet and Lifestyle May Contribute to Islet β-cells Protection in Type-2 Diabetes via the Modulation of Cellular PI3K/AKT Pathway

PI3K/AKT pathway has been shown to play a pivotal role on islet β-cell protection, enhancing β-cell survival by stimulating cell proliferation and inhibiting cell apoptosis. Accordingly, this pathway appears to be crucial in type-2 diabetes. Understanding the regulations of this pathway may provide a better efficacy of new therapeutic approaches. In this review, we summarize advances on the involvement of the PI3K/AKT pathway in hypothetical intra-cellular signaling of islet β-cells. As recent findings may show the nutritional regulation of the survival pathway in the islet β-cells through activation of the PI3K/AKT pathway, we also review studies on the features of several diets, correlated lifestyle, and its signaling pathway involved in type-2 diabetes. The molecular mechanisms contributing to the disease are the subject of considerable investigation, as a better understanding of the pathogenesis will lead to novel therapies against a condition of the disease.

Modulating effects of pycnogenol® on oxidative stress and DNA damage induced by sepsis in rats

The aim of this study was to evaluate the protective effects of Pycnogenol® (Pyc), a complex plant extract from the bark of French maritime pine, on oxidative stress parameters (superoxide dismutase (SOD), and glutathione peroxidase (GPx) activities and total glutathione (GSH) and malondialdehyde (MDA) levels), an inflammatory cytokine (tumor necrosis factor alpha (TNF-α) level) and also DNA damage in Wistar albino rats. Rats were treated with 100 mg/kg intraperitonally Pyc following the induction of sepsis by cecal ligation and puncture. The decreases in MDA levels and increases in GSH levels, and SOD and GPx activities were observed in the livers and kidneys of Pyc-treated septic rats. Plasma TNF-α level was found to be decreased in the Pyc-treated septic rats. In the lymphocytes, kidney, and liver tissue cells of the sepsis-induced rats, Pyc treatment significantly decreased the DNA damage and oxidative base damage using standard alkaline assay and formamidopyrimidine DNA glycosylase-modified comet assay, respectively. In conclusion, Pyc treatment might have a role in the prevention of sepsis-induced oxidative damage not only by decreasing DNA damage but also increasing the antioxidant status and DNA repair capacity in rats.

Energy crisis: the role of oxidative phosphorylation in acute inflammation and sepsis

Mitochondrial dysfunction is increasingly recognized as an accomplice in most of the common human diseases including cancer, neurodegeneration, diabetes, ischemia/reperfusion injury as seen in myocardial infarction and stroke, and sepsis. Inflammatory conditions, both acute and chronic, have recently been shown to affect mitochondrial function. We here discuss the role of oxidative phosphorylation (OxPhos), focusing on acute inflammatory conditions, in particular sepsis and experimental sepsis models. We discuss mitochondrial alterations, specifically the suppression of oxidative metabolism and the role of mitochondrial reactive oxygen species in disease pathology. Several signaling pathways including metabolic, proliferative, and cytokine signaling affect mitochondrial function and appear to be important in inflammatory disease conditions. Cytochrome c oxidase (COX) and cytochrome c, the latter of which plays a central role in apoptosis in addition to mitochondrial respiration, serve as examples for the entire OxPhos system since they have been studied in more detail with respect to cell signaling. We propose a model in which inflammatory signaling leads to changes in the phosphorylation state of mitochondrial proteins, including Tyr304 phosphorylation of COX catalytic subunit I. This results in an inhibition of OxPhos, a reduction of the mitochondrial membrane potential, and consequently a lack of energy, which can cause organ failure and death as seen in septic patients.

Alterations in enterocyte mitochondrial respiratory function and enzyme activities in gastrointestinal dysfunction following brain injury

AIM: To determine the alterations in rat enterocyte mitochondrial respiratory function and enzyme activities following traumatic brain injury (TBI).

METHODS: Fifty-six male SD rats were randomly divided into seven groups (8 rats in each group): a control group (rats with sham operation) and traumatic brain injury groups at 6, 12, 24 h, days 2, 3, and 7 after operation. TBI models were induced by Feendy’s free-falling method. Mitochondrial respiratory function (respiratory control ratio and ADP/O ratio) was measured with a Clark oxygen electrode. The activities of respiratory chain complex I-IV and related enzymes were determined by spectrophotometry.

RESULTS: Compared with the control group, the mitochondrial respiratory control ratio (RCR) declined at 6 h and remained at a low level until day 7 after TBI (control, 5.42 ± 0.46; 6 h, 5.20 ± 0.18; 12 h, 4.55 ± 0.35; 24 h, 3.75 ± 0.22; 2 d, 4.12 ± 0.53; 3 d, 3.45 ± 0.41; 7 d, 5.23 ± 0.24, P < 0.01). The value of phosphate-to-oxygen (P/O) significantly decreased at 12, 24 h, day 2 and day 3, respectively (12 h, 3.30 ± 0.10; 24 h, 2.61 ± 0.21; 2 d, 2.95 ± 0.18; 3 d, 2.76 ± 0.09, P < 0.01) compared with the control group (3.46 ± 0.12). Two troughs of mitochondrial respiratory function were seen at 24 h and day 3 after TBI. The activities of mitochondrial complex I (6 h: 110 ± 10, 12 h: 115 ± 12, 24 h: 85 ± 9, day 2: 80 ± 15, day 3: 65 ± 16, P < 0.01) and complex II (6 h: 105 ± 8, 12 h: 110 ± 92, 24 h: 80 ± 10, day 2: 76 ± 8, day 3: 68 ± 12, P < 0.01) were increased at 6 h and 12 h following TBI, and then significantly decreased at 24 h, day 2 and day 3, respectively. However, there were no differences in complex I and II activities between the control and TBI groups. Furthermore, pyruvate dehydrogenase (PDH) activity was significantly decreased at 6 h and continued up to 7 d after TBI compared with the control group (6 h: 90 ± 8, 12 h: 85 ± 10, 24 h: 65 ± 12, day 2: 60 ± 9, day 3: 55 ± 6, day 7: 88 ± 11, P < 0.01). The changes in α-ketoglutaric dehydrogenase (KGDH) activity were similar to PDH, except that the decrease in KGDH activity began at 12 h after TBI (12 h: 90 ± 12, 24 h: 80 ± 9, day 2: 76 ± 15, day 3: 68 ± 7, day 7: 90 ± 13, P < 0.01). No significant change in malate dehydrogenase (MDH) activity was observed.

CONCLUSION: Rat enterocyte mitochondrial respiratory function and enzyme activities are inhibited following TBI. Mitochondrial dysfunction may play an important role in TBI-induced gastrointestinal dysfunction.

α-Lipoic acid protects mitochondrial enzymes and attenuates lipopolysaccharide-induced hypothermia in mice

Hypothermia is a key symptom of sepsis, but the mechanism(s) leading to hypothermia during sepsis is largely unknown and thus no effective therapy is available for hypothermia. Therefore, it is important to investigate the mechanism and develop effective therapeutic methods. Lipopolysaccharide (LPS)-induced hypothermia accompanied by excess nitric oxide (NO) production leads to a reduction in energy production in wild-type mice. However, mice lacking inducible nitric oxide synthase did not suffer from LPS-induced hypothermia, suggesting that hypothermia is associated with excess NO production during sepsis. This observation is supported by the treatment of wild-type mice with α-lipoic acid (LA) in that it effectively attenuates LPS-induced hypothermia with decreased NO production. We also found that LA partially restored ATP production, and activities of the mitochondrial enzymes involved in energy metabolism, which were inhibited during sepsis. These data suggest that hypothermia is related to mitochondrial dysfunction, which is probably compromised by excess NO production and that LA administration attenuates hypothermia mainly by protecting mitochondrial enzymes from NO damage.

Lipopolysaccharide stimulates p62-dependent autophagy-like aggregate clearance in hepatocytes

Impairment of autophagy has been associated with liver injury. TLR4-stimulation by LPS upregulates autophagy in hepatocytes, although the signaling pathways involved remain elusive. The objective of this study was to determine the signaling pathway leading to LPS-stimulated autophagy in hepatocytes. Cell lysates from livers of wild type (WT; C57BL/6) mice given LPS (5 mg/kg-IP) and hepatocytes from WT, TLR4ko, and MyD88ko mice treated with LPS (100 ng/mL) up to 24 h were collected. LC3II, p62/SQSTM1, Nrf2, and beclin1 levels were determined by immunoblot, immunofluorescence, and qPCR. Autophagy-like activation was measured by GFP-LC3-puncta formation and LC3II-expression. Beclin1, Nrf2, p62, MyD88, and TIRAP were knocked-down using siRNA. LC3II-expression increased in both liver and hepatocytes after LPS and was dependent on TLR4. Beclin1 expression did not increase after LPS in hepatocytes and beclin1-knockdown did not affect LC3II levels. In hepatocytes given LPS, expression of p62 increased and p62 colocalized with LC3. p62-knockdown prevented LC3II puncta formation. LPS-induced LC3II/p62-puncta also required MyD88/TIRAP signaling and localization of both Nrf2 and NF κ B transcription factors to the nucleus to upregulate p62-expression. Therefore, TLR4-activation by LPS in hepatocytes induces a p62-mediated, not beclin1-mediated, autophagy-like clearance pathway that is hepatoprotective by clearing aggregate-prone or misfolded proteins from the cytosol and preserving energy homeostasis under stress.

Sustained high serum malondialdehyde levels are associated with severity and mortality in septic patients

Introduction

There is a hyperoxidative state in sepsis. The objective of this study was to determine serum malondialdehyde (MDA) levels during the first week of follow up, whether such levels are associated with severity during the first week and whether non-surviving patients showed higher MDA levels than survivors during the first week.

Methods

We performed an observational, prospective, multicenter study in six Spanish Intensive Care Units. Serum levels of MDA were measured in 328 patients (215 survivors and 113 non-survivors) with severe sepsis at days one, four and eight of diagnosis, and in 100 healthy controls. The primary endpoint was 30-day mortality and the secondary endpoint was six -month mortality. The association between continuous variables was carried out using Spearman’s rank correlation coefficient. Cox regression analysis was applied to determine the independent contribution of serum MDA levels on the prediction of 30-day and 6-month mortality. Hazard ratio (HR) and 95% confidence intervals (CI) were calculated as measures of the clinical impact of the predictor variables.

Results

We found higher serum MDA in septic patients at day one (p < 0.001), day four (p < 0.001) and day eight (p < 0.001) of diagnosis than in healthy controls. Serum MDA was lower in surviving than non-surviving septic patients at day one (p < 0.001), day four (p < 0.001) and day eight (p < 0.001). Serum MDA levels were positively correlated with lactic acid and SOFA during the first week. Finally, serum MDA levels were associated with 30-day mortality (HR = 1.05; 95% CI = 1.02-1.09; p = 0.005) and six-month mortality (hazard ratio (HR) = 1.05; 95% CI = 1.02-1.09; p = 0.003) after controlling for lactic acid levels, acute physiology and chronic health evaluation (APACHE)-II, diabetes mellitus, bloodstream infection and chronic renal failure.

Conclusions

To our knowledge, this is the largest series providing data on the oxidative state in septic patients to date. The novel finding is that high serum MDA levels sustained throughout the first week of follow up were associated with severity and mortality in septic patients.

Bariatric surgery rapidly improves mitochondrial respiration in morbidly obese patients

BACKGROUND

Obesity and its attendant comorbidities are an emerging epidemic. Chronic metabolic inflammation (metainflammation) is thought to precipitate obesity-associated morbidities; however, its mechanistic progression is poorly understood. Moreover, although interventions such as diet, exercise, and bariatric surgery can control body weight, their effects on metainflammation are also poorly understood. Recently, metainflammation and the pathobiology of obesity have been linked to mitochondrial dysfunction. Herein we examined the effects of bariatric surgery on mitochondrial respiration as an index of resolving metainflammation in morbidly obese patients.

METHODS

This institutional review board-approved study involved morbidly obese patients (body mass index > 35 kg/m(2)) undergoing sleeve gastrectomy or Roux-en-Y gastric bypass. Mitochondrial respiration was assessed in peripheral blood monocytes and in skeletal muscle samples before surgery and at 12 weeks after surgery. Patient biometrics, homeostasis model assessment-estimated insulin resistance (HOMA-IR) score, C-reactive protein, and lipid profile were analyzed.

RESULTS

Twenty patients were enrolled and showed an average percent excess body weight loss of 30.3% weight loss at 12 weeks after surgery. Average HOMA-IR score decreased from 3.0 to 1.2 in insulin-resistant patients. C-reactive protein, an index of metainflammation, showed a modest decrease. Lipid profile remained stable. Intriguingly, mitochondrial basal and maximal respiration rates in peripheral blood monocytes increased after surgery. Basal rates of skeletal muscle mitochondrial respiration were unchanged, but the maximal respiration rate trended toward an increase after surgery.

CONCLUSIONS

Cellular and tissue mitochondrial respiration increased in a morbidly obese patient cohort after laparoscopic bariatric surgery. These changes were consistent in patients with postsurgical weight loss. Importantly, no significant changes or improvements occurred in canonical indices used to assess recovery after bariatric surgery over this short time course. Thus, increased mitochondrial respiration may represent a novel biomarker of early improvement and positive outcome after surgery in morbidly obese patients.

Correlation of the oxygen radical activity and antioxidants and severity in critically ill surgical patients - study protocol

BACKGROUND

Surgical patients who require an emergent operation commonly have severe sepsis or septic shock, followed by high morbidity and mortality rates.Despite advances in treatment however, no predictable markers are available. In severe sepsis, many pathophysiologic mechanisms are involved in progression to organ failure, and oxygen free radical and antioxidants are known to contribute to this process. Oxygen free radical and antioxidants contribute to progression of organ failure in severe sepsis. In fact, oxygen radical activity has been reported to be correlated with disease severity and prognosis in patients with severe sepsis or septic shock. Accordingly, we aim to assess the usefulness of oxygen free radical and antioxidant concentrations to predict the disease severity and mortality in a cohort of critically ill surgical patients.

METHODS/DESIGN

This is a prospective observation study including patient demographic characteristics, clinical information, blood sampling/serum oxygen radical activity, serum antioxidant activity, serum antioxidant concentrations (zinc, selenium and glutamate), disease severity scores, outcomes, lengths of stay in intensive care unit, hospital 30-day mortality.

Reduced plasmalogen concentration as a surrogate marker of oxidative stress in elderly septic patients

Severe sepsis is reportedly accompanied by oxidative stress with a depletion of antioxidant defense. We estimated plasmalogen vinyl ether bond (PVEB) levels in blood plasma of 20 elderly patients with initial severe sepsis, serving as a sensitive surrogate marker of oxidative stress, and compared them with standard markers, i.e., Acute Physiology and Chronic Health Evaluation (APACHE) II score, C-reactive protein (CRP), creatinine, white blood cell and platelet counts. Patients were included in the study and then blood samples were taken within 24h of the onset of symptoms of severe sepsis. Twenty sex- and age-matched, healthy individuals were included in the study as controls. We measured plasmalogen-derived hexadecanal dimethyl acetal (16:0 DMA) in isolated phospholipids from EDTA-plasma using gas chromatography. We found a 55% lower concentration of 16:0 DMA, corresponding to lower levels of PVEB in the patients' plasma compared to the controls (0.26±0.15 vs 0.58±0.13g/100g; p<0.001). In all patients' and non-survivors' samples the 16:0 DMA levels correlated negatively with plasma CRP values (RS=-0.48 and RS=-0.70, respectively; p<0.05), but not with APACHE II scores or other markers. The observed lower baseline content of PVEB may indicate oxidative stress contributing to the sequlae of sepsis, but did not correlate with the outcome or the severity of illness. Serial measurements are needed to validate PVEB as a marker in sepsis.

Roles for PI3K/AKT/PTEN Pathway in Cell Signaling of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is the most common form of liver pathologies and is associated with obesity and the metabolic syndrome, which represents a range of fatty liver diseases associated with an increased risk of type 2 diabetes. Molecular mechanisms underlying how to make transition from simple fatty liver to nonalcoholic steatohepatitis (NASH) are not well understood. However, accumulating evidence indicates that deregulation of the phosphatidylinositol 3-kinase (PI3K)/AKT pathway in hepatocytes is a common molecular event associated with metabolic dysfunctions including obesity, metabolic syndrome, and the NAFLD. A tumor suppressor PTEN negatively regulates the PI3K/AKT pathways through its lipid phosphatase activity. Molecular studies in the NAFLD support a key role for PTEN in hepatic insulin sensitivity and the development of steatosis, steatohepatitis, and fibrosis. We review recent studies on the features of the PTEN and the PI3K/AKT pathway and discuss the protein functions in the signaling pathways involved in the NAFLD. The molecular mechanisms contributing to the diseases are the subject of considerable investigation, as a better understanding of the pathogenesis will lead to novel therapies for a condition.