Leptin exacerbates sepsis-mediated morbidity and mortality

Weight loss-induced adipose macrophage memory improves local Staphylococcus aureus clearance in male mice

Different stimuli can induce innate immune memory to improve pathogen defense or worsen cardiometabolic disease. However, it is less clear if the same stimuli can induce both the protective and detrimental effects of innate immune memory. We previously showed that weight loss induces innate immune memory in adipose macrophages that correlates with worsened diabetes risk after weight regain. In this study, we investigated the effect of weight loss on macrophage cytokine production and overall survival in a mouse model of infection. Male C57Bl/6J mice were put on high-fat or low-fat diets over 18 weeks to induce weight gain or weight loss. Lean mice served as controls. All mice were then infected IV with 2.5×10^6 CFU Staphylococcus aureus . Tissues were collected from 10 mice/group at day 3 and the remaining animals were followed for survival. Weight gain mice had the highest blood neutrophils and the highest bacterial burden in the kidney. However, there was no significant difference in survival. The weight loss group had the highest plasma TNF-α and a significant reduction in bacterial burden in the adipose tissue that correlated with increased adipose macrophage cytokine production. Thus, weight loss-induced adipose macrophage memory may both improve local S.aureus clearance and worsen diabetes risk upon weight regain. Collectively, these findings support the notion that innate immune memory is an evolutionarily protective mechanism that also contributes to the development of cardiometabolic diseases.

Caffeic acid methyl ester inhibits LPS‑induced inflammatory response through Nrf2 activation and NF‑κB inhibition in human umbilical vein endothelial cells

Caffeic acid (CA) derivatives have been reported to exert anti-inflammatory activities in various inflammatory conditions. However, the impact of CA methyl ester (CAME) on the inflammatory response in vascular endothelial cells has not been thoroughly elucidated. In the present study, the aim was to understand how CAME can reduce inflammation in human umbilical vein endothelial cells (HUVECs), which were challenged with lipopolysaccharide (LPS), and elucidate its mechanisms. CAME significantly attenuated LPS-induced TNF-α and IL-1β release. Furthermore, CAME inhibited cyclooxygenase 2 expression and consequent secretion of prostaglandin E2. CAME also suppressed LPS-stimulated inducible nitric oxide synthase expression. In addition, CAME significantly enhanced the expression of heme oxygenase-1 (HO-1) and nuclear factor erythroid-derived 2-related factor 2 (Nrf2) phosphorylation in the absence or presence of LPS stimulation in HUVECs. CAME also significantly suppressed LPS-induced NF-κB phosphorylation and inhibitor of κB phosphorylation and degradation. In conclusion, the present results provide clear evidence that CAME exerts its anti-inflammatory activities by increasing HO-1/Nrf2-mediated cytoprotection and inhibiting NF-κB-mediated pro-inflammatory pathways in HUVECs.

Relationship between leptin and white blood cells: a potential role in infection susceptibility and severity-the Olivetti Heart Study

A number of evidence showed an emerging role of leptin on immune system, involving inflammation, and innate and adaptive immunity. Few observational studies have evaluated the relationship between leptin and immunity, albeit with low statistical power and methodological differences. Therefore, the aim of this study was to evaluate the potential role of leptin on the immunity, expressed as white blood cells (WBC)-and its subpopulations, by comprehensive multivariate models in a sample of adult men. A cross-sectional evaluation of a general population comprised 939 subjects participating in the Olivetti Heart Study, with available leptin levels and WBC-and its subpopulations. WBC were significantly and positively associated with leptin, C-reactive protein and HOMA index (p < 0.05), but not with age and anthropometric indices (p > 0.05). The multivariate analysis confirmed the association between leptin and WBC, after accounting for main confounders (p < 0.05). Additional analysis on WBC subpopulations showed a positive and significant correlation between leptin and lymphocytes, monocytes and eosinophils (p < 0.05), but not with neutrophils and basophils (p > 0.05). After stratification by body weight, the positive and significant association between leptin and WBC-and its subpopulations-was found in excess body weight participants. The results of this study indicate a direct relationship between leptin levels and WBC-and its subpopulations-in excess body weight participants. These results support the hypothesis that leptin has modulatory functions on immunity and role in the pathophysiology of immune-related diseases, in particular in those associated with excess body weight.

Assessing organ-level immunoreactivity in a rat model of sepsis using TSPO PET imaging

There is current need for new approaches to assess/measure organ-level immunoreactivity and ensuing dysfunction in systemic inflammatory response syndrome (SIRS) and sepsis, in order to protect or recover organ function. Using a rat model of systemic sterile inflammatory shock (intravenous LPS administration), we performed PET imaging with a translocator protein (TSPO) tracer, [¹⁸F]DPA-714, as a biomarker for reactive immunoreactive changes in the brain and peripheral organs. In vivo dynamic PET/CT scans showed increased [¹⁸F]DPA-714 binding in the brain, lungs, liver and bone marrow, 4 hours after LPS injection. Post-LPS mean standard uptake values (SUV_mean) at equilibrium were significantly higher in those organs compared to baseline. Changes in spleen [¹⁸F]DPA-714 binding were variable but generally decreased after LPS. SUV_mean values in all organs, except the spleen, positively correlated with several serum cytokines/chemokines. In vitro measures of TSPO expression and immunofluorescent staining validated the imaging results. Noninvasive molecular imaging with [¹⁸F]DPA-714 PET in a rat model of systemic sterile inflammatory shock, along with in vitro measures of TSPO expression, showed brain, liver and lung inflammation, spleen monocytic efflux/lymphocytic activation and suggested increased bone marrow hematopoiesis. TSPO PET imaging can potentially be used to quantify SIRS and sepsis-associated organ-level immunoreactivity and assess the effectiveness of therapeutic and preventative approaches for associated organ failures, in vivo.

The Childhood Acute Illness and Nutrition (CHAIN) network nested case-cohort study protocol: a multi-omics approach to understanding mortality among children in sub-Saharan Africa and South Asia

Introduction: Many acutely ill children in low- and middle-income settings have a high risk of mortality both during and after hospitalisation despite guideline-based care. Understanding the biological mechanisms underpinning mortality may suggest optimal pathways to target for interventions to further reduce mortality. The Childhood Acute Illness and Nutrition (CHAIN) Network ( www.chainnnetwork.org) Nested Case-Cohort Study (CNCC) aims to investigate biological mechanisms leading to inpatient and post-discharge mortality through an integrated multi-omic approach. Methods and analysis; The CNCC comprises a subset of participants from the CHAIN cohort (1278/3101 hospitalised participants, including 350 children who died and 658 survivors, and 270/1140 well community children of similar age and household location) from nine sites in six countries across sub-Saharan Africa and South Asia. Systemic proteome, metabolome, lipidome, lipopolysaccharides, haemoglobin variants, toxins, pathogens, intestinal microbiome and biomarkers of enteropathy will be determined. Computational systems biology analysis will include machine learning and multivariate predictive modelling with stacked generalization approaches accounting for the different characteristics of each biological modality. This systems approach is anticipated to yield mechanistic insights, show interactions and behaviours of the components of biological entities, and help develop interventions to reduce mortality among acutely ill children. Ethics and dissemination. The CHAIN Network cohort and CNCC was approved by institutional review boards of all partner sites. Results will be published in open access, peer reviewed scientific journals and presented to academic and policy stakeholders. Data will be made publicly available, including uploading to recognised omics databases. Trial registration NCT03208725.

The Childhood Acute Illness and Nutrition (CHAIN) network nested case-cohort study protocol: a multi-omics approach to understanding mortality among children in sub-Saharan Africa and South Asia

Introduction: Many acutely ill children in low- and middle-income settings have a high risk of mortality both during and after hospitalisation despite guideline-based care. Understanding the biological mechanisms underpinning mortality may suggest optimal pathways to target for interventions to further reduce mortality. The Childhood Acute Illness and Nutrition (CHAIN) Network ( www.chainnnetwork.org) Nested Case-Cohort Study (CNCC) aims to investigate biological mechanisms leading to inpatient and post-discharge mortality through an integrated multi-omic approach. Methods and analysis; The CNCC comprises a subset of participants from the CHAIN cohort (1278/3101 hospitalised participants, including 350 children who died and 658 survivors, and 270/1140 well community children of similar age and household location) from nine sites in six countries across sub-Saharan Africa and South Asia. Systemic proteome, metabolome, lipidome, lipopolysaccharides, haemoglobin variants, toxins, pathogens, intestinal microbiome and biomarkers of enteropathy will be determined. Computational systems biology analysis will include machine learning and multivariate predictive modelling with stacked generalization approaches accounting for the different characteristics of each biological modality. This systems approach is anticipated to yield mechanistic insights, show interactions and behaviours of the components of biological entities, and help develop interventions to reduce mortality among acutely ill children. Ethics and dissemination. The CHAIN Network cohort and CNCC was approved by institutional review boards of all partner sites. Results will be published in open access, peer reviewed scientific journals and presented to academic and policy stakeholders. Data will be made publicly available, including uploading to recognised omics databases. Trial registration NCT03208725.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Circulating leptin, soluble leptin receptor and free leptin index in critically ill patients with sepsis: a prospective observational study

BACKGROUND

Leptin, the prototype adipokine, exerts immunomodulatory actions being implicated in inflammatory responses during sepsis. Clinical evidence regarding its role in sepsis has been contradictory, while free leptin has not been studied. Our aim was to jointly investigate circulating total leptin, its soluble receptor (sOBR), and free leptin, as well as their kinetics in critically ill patients with sepsis regarding their diagnostic and prognostic value.

METHODS

In a prospective study, serum total leptin, sOBR and free leptin index (FLI) were determined in 102 critically ill patients with sepsis within 48 hours from sepsis onset and one week after enrollment, and in 102 age and gender-matched healthy controls.

RESULTS

Upon enrollment, total leptin, sOB-R and FLI were significantly higher in septic patients compared to controls and they were positively correlated with sepsis severity scores, while they presented a significant decrease during the first week (p<0.001). The decrease in total leptin and sOB-R was significantly higher in patients with sepsis compared to septic shock and in survivors compared to nonsurvivors at 28 days (p<0.001). Higher serum total leptin was independently associated with survival at 28 days (enrollment: HR 0.86, p=0.03; one week after: HR 0.77, p<0.001). Higher kinetics of total leptin (but not FLI) was independently associated with survival after adjustment (HR: 0.48, p=0.001).

CONCLUSIONS

Higher circulating total leptin and its higher kinetics during the first week from sepsis onset independently predict 28 day survival in critically ill patients. Free leptin did not present any additional diagnostic and prognostic value in sepsis.

Sepsis and the Obesity Paradox: Size Matters in More Than One Way

OBJECTIVES

Multiple studies have demonstrated an obesity paradox such that obese ICU patients have lower mortality and better outcomes. We conducted this study to determine if the mortality benefit conferred by obesity is affected by baseline serum lactate and mean arterial pressure.

DESIGN

Retrospective analysis of prospectively collected clinical data.

SETTING

Five community-based and one academic medical center in the Omaha, NE.

PATIENTS

7,967 adults hospitalized with sepsis.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Patients were categorized by body mass index as underweight, normal weight, overweight, or obese. Multivariable logistic regression models were used to estimate the odds of in-hospital death by body mass index category; two-way interactions between body mass index and each covariate were also evaluated. Subgroup and sensitivity analyses were conducted using an ICU cohort and Acute Physiology and Chronic Health Evaluation III scores, respectively. The overall unadjusted mortality rate was 12.1% and was consistently lower in higher body mass index categories (all comparisons, p < 0.007). The adjusted mortality benefit observed in patients with higher body mass index was smaller in patients with higher lactate levels with no mortality benefit in higher body mass index categories observed at lactate greater than 5 mmol/L. By contrast, the association between lower MAP and higher mortality was constant across body mass index categories. Similar results were observed in the ICU cohort. Finally, the obesity paradox was not observed after including Acute Physiology and Chronic Health Evaluation III scores as a covariate.

CONCLUSIONS

Our retrospective analysis suggests that although patient size (i.e., body mass index) is a predictor of in-hospital death among all-comers with sepsis-providing further evidence to the obesity paradox-it adds that illness severity is critically important whether quantified as higher lactate or by Acute Physiology and Chronic Health Evaluation III score. Our results highlight that the obesity paradox is more than a simple association between body mass index and mortality and reinforces the importance of illness severity.

Serum leptin level as a diagnostic and prognostic marker in infectious diseases and sepsis: A comprehensive literature review

BACKGROUND

Infections and sepsis are common causes of morbidity and mortality, with an increasing incidence worldwide. Leptin is involved in the inflammatory process and may modulate the cytokine production, immune cell proliferation and endothelial function. There are conflicting results regarding alterations of leptin levels in infectious diseases and the outcome from sepsis.The aim of the current article is to provide an overview of the medical literature on the correlations between variations of leptin levels and infectious diseases and sepsis.

METHODS

We performed an extensive literature search in PubMed and Google Scholar databases, using keywords to identify articles related to leptin in infectious diseases and sepsis. Searches were referenced using medical subject headings that included "leptin," "adipokines," "sepsis," "infectious diseases," "leptin deficiency," "leptin resistance" or "hyperleptinemia." The language of publication, journal, or country were not included as limitation criteria.Articles or abstracts containing adequate information, such as age, sex, anthropometric indices, clinical presentation, comorbidities, and management were included in the study, whereas articles with insufficient clinical and demographic data were excluded. We assessed the quality of the studies selected.The final review of all databases was conducted on June 18, 2020.

RESULTS

We find the results from the current review to be of great importance due to the possible therapeutic role of leptin analogs in states of leptin deficiency associated with infectious diseases or sepsis.In hyperleptinemia, a therapeutic plan for obtaining leptin neutralization also needs further investigations. This could lead to the reduction of proinflammatory responses.There is a need for further studies to demonstrate the specificity and sensitivity of leptin in the early diagnosis of sepsis and the need to measure serum leptin levels in routine evaluation of the critical patient.

CONCLUSION

The multiple effects of leptin are of growing interest, but further studies are needed to elucidate the role of leptin signalling in infectious diseases and sepsis. Because very few human studies are reported, we recommend the need for further research.Better understanding of the pathophysiology of sepsis and the implication of circulating total leptin in this process could help physicians in managing this life-threatening condition.

Susceptibility and Severity of Viral Infections in Obesity: Lessons from Influenza to COVID-19. Does Leptin Play a Role?

The recent pandemic Sars-CoV2 infection and studies on previous influenza epidemic have drawn attention to the association between the obesity and infectious diseases susceptibility and worse outcome. Metabolic complications, nutritional aspects, physical inactivity, and a chronic unbalance in the hormonal and adipocytokine microenvironment are major determinants in the severity of viral infections in obesity. By these pleiotropic mechanisms obesity impairs immune surveillance and the higher leptin concentrations produced by adipose tissue and that characterize obesity substantially contribute to such immune response dysregulation. Indeed, leptin not only controls energy balance and body weight, but also plays a regulatory role in the interplay between energy metabolism and immune system. Since leptin receptor is expressed throughout the immune system, leptin may exert effects on cells of both innate and adaptive immune system. Chronic inflammatory states due to metabolic (i.e., obesity) as well as infectious diseases increase leptin concentrations and consequently lead to leptin resistance further fueling inflammation. Multiple factors, including inflammation and ER stress, contribute to leptin resistance. Thus, if leptin is recognized as one of the adipokines responsible for the low grade inflammation found in obesity, on the other hand, impairments of leptin signaling due to leptin resistance appear to blunt the immunologic effects of leptin and possibly contribute to impaired vaccine-induced immune responses. However, many aspects concerning leptin interactions with inflammation and immune system as well as the therapeutical approaches to overcome leptin resistance and reduced vaccine effectiveness in obesity remain a challenge for future research.

Pancreatic triglyceride lipase mediates lipotoxic systemic inflammation

Visceral adipose tissue plays a critical role in numerous diseases. Although imaging studies often show adipose involvement in abdominal diseases, their outcomes may vary from being a mild self-limited illness to one with systemic inflammation and organ failure. We therefore compared the pattern of visceral adipose injury during acute pancreatitis and acute diverticulitis to determine its role in organ failure. Acute pancreatitis-associated adipose tissue had ongoing lipolysis in the absence of adipocyte triglyceride lipase (ATGL). Pancreatic lipase injected into mouse visceral adipose tissue hydrolyzed adipose triglyceride and generated excess nonesterified fatty acids (NEFAs), which caused organ failure in the absence of acute pancreatitis. Pancreatic triglyceride lipase (PNLIP) increased in adipose tissue during pancreatitis and entered adipocytes by multiple mechanisms, hydrolyzing adipose triglyceride and generating excess NEFAs. During pancreatitis, obese PNLIP-knockout mice, unlike obese adipocyte-specific ATGL knockouts, had lower visceral adipose tissue lipolysis, milder inflammation, less severe organ failure, and improved survival. PNLIP-knockout mice, unlike ATGL knockouts, were protected from adipocyte-induced pancreatic acinar injury without affecting NEFA signaling or acute pancreatitis induction. Therefore, during pancreatitis, unlike diverticulitis, PNLIP leaking into visceral adipose tissue can cause excessive visceral adipose tissue lipolysis independently of adipocyte-autonomous ATGL, and thereby worsen organ failure.

The association between the route of nutrition and serum levels of adipokines in critical illness: a pilot study

Background/aim

Adipokines play an important role in the regulation of metabolism. In critical illness, they alter serum levels and are suspected to worsen clinical outcomes. But the effect of the route of nutrition on adipokines is not known. The purpose of this study was to evaluate the association between the route of nutrition and adipokine levels in critically ill patients.

Materials and methods

This prospective study was performed in an intensive care unit (ICU). Patients admitted to the ICU for least 72 h and receiving either enteral nutrition (EN) via tube feeding or parenteral nutrition (PN) were enrolled. Serum was obtained at baseline, 24 h, and 72 h for concentrations of leptin, adiponectin, resistin, glucagon–like peptide 1 (GLP–1), insulin–like growth factors 1 (IGF–1), and ghrelin.

Results

A total of 26 patients were included in the study. Thirteen patients received EN and 13 patients received PN. In the PN group, leptin level significantly increased (P = 0.037), adiponectin and ghrelin significantly decreased during follow up (P = 0.037, P = 0.008, respectively). There was no significant change between all adipokines in the EN group and resistin, IGF–1 and GLP–1 in the PN group during follow up. Resistin levels were markedly lower in the EN group at both 24 h (P = 0.015) and 72 h (P = 0.006) while GLP–1 levels were higher in the EN group at baseline, 24 h, and 72 h (P = 0.018, P = 0.005, and P = 0.003, respectively). There were no differences in leptin, adiponectin, IGF–1, and ghrelin levels over time.

Conclusion

The delivery of EN in critical illness was associated with decreased resistin levels and increased GLP–1 levels. Thus, the route of nutrition may impact the clinical outcome in critical illness due to adipokines.

3,4,5-Trihydroxycinnamic Acid Inhibits LPS-Induced Inflammatory Response by Increasing SIRT1 Expression in Human Umbilical Vein Endothelial Cells

3,4,5-Trihydroxycinnamic acid (THC) has been demonstrated to exert anti-inflammatory activities in LPS-induced RAW264.7 murine macrophage cells and in LPS-induced septic mice. However, the effect of THC on the inflammatory response in vascular endothelial cells has not been clearly examined. The goal of the present study was to elucidate the anti-inflammatory properties of THC and its underlying mechanism in LPS-challenged human umbilical vein endothelial cells (HUVECs). THC significantly suppressed LPS-induced interleukin-1β production and intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 expression and significantly decreased LPS-induced nuclear factor-κB activation by attenuating p65 phosphorylation and inhibitor of kappa B degradation. To understand the underlying mechanism of the anti-inflammatory effect of THC, the involvement of the sirtuin 1 (SIRT1) signaling pathway was examined. THC resulted in increased expression of SIRT1 in LPS-challenged HUVECs. Among the downstream molecular targets of SIRT1, the level of LPS-induced acetylated p53 was significantly decreased by THC treatment, whereas no noticeable change was observed in the levels of forkhead box O3 and peroxisome proliferator activated receptor gamma coactivator 1 alpha. In conclusion, the results clearly demonstrate that THC possesses anti-inflammatory properties by increasing SIRT1 expression and subsequent suppression of p53 activation in LPS-challenged HUVECs.

Leptin, Ghrelin, and Leptin/Ghrelin Ratio in Critically Ill Patients

The objective of this study was to evaluate leptin, ghrelin, and leptin/ghrelin ratio in critically ill patients and association of leptin/ghrelin ratio with outcomes. This is a sub-study of the PermiT trial (ISRCTN68144998). A subset of 72 patients who were expected to stay >14 days in the Intensive care unit were enrolled. Blood samples were collected on days 1, 3, 5, 7, and 14. Samples were analyzed for leptin and active ghrelin in addition to other hormones. Baseline leptin/ghrelin ratio was calculated, and patients were stratified into low and high leptin/ghrelin ratio based on the median value of 236. There was a considerable variation in baseline leptin level: Median 5.22 ng/mL (Q1, Q3: 1.26, 17.60). Ghrelin level was generally low: 10.61 pg/mL (Q1, Q3: 8.62, 25.36). Patients with high leptin/ghrelin ratio compared to patients with low leptin/ghrelin ratio were older, had higher body mass index and more likely to be diabetic. There were no differences in leptin/ghrelin ratio between patients who received permissive underfeeding and standard feeding. Multivariable logistic regression analysis showed that age and body mass index were significant independent predictors of high leptin–ghrelin ratio. Leptin–ghrelin ratio was not associated with 90-day mortality or other outcomes. Age and body mass index are predictors of high leptin/ghrelin ratio. Leptin/ghrelin ratio is not affected by permissive underfeeding and is not associated with mortality.

The Role of Adipose Tissue and Adipokines in Sepsis: Inflammatory and Metabolic Considerations, and the Obesity Paradox

PURPOSE

Sepsis has become a global health problem with rising incidence and high mortality, creating a substantial social and economic burden. Early diagnosis and treatment can improve outcome, but reliable sepsis biomarkers are lacking. This review summarizes current evidence of the pathophysiological mechanisms linking adipose tissue to sepsis and presents experimental and clinical data on adipokines and sepsis along with important insights into the obesity paradox in sepsis survival.

RECENT FINDINGS

Sepsis is characterized by significant alterations in circulating cytokines and adipokines, biologically active molecules produced by the adipose tissue, being implicated in metabolic and inflammatory processes. Although data are inconclusive regarding classic adipokines such as leptin and adiponectin, recent evidence have highlighted the striking elevation of resistin and visfatin in critical illness and sepsis as well as their association with sepsis severity and outcomes. Given that inflammatory and metabolic pathways are involved in sepsis, studying adipokines presents an attractive, innovative, and promising research field that may provide more powerful diagnostic and prognostic biomarkers as well as novel therapeutic targets, empowering the therapeutic armamentarium for sepsis management in order to improve survival.

Dynamics of Vagal Activity Due to Surgery and Subsequent Rehabilitation

Background

Vagal activity is critical for maintaining key body functions, including the stability of inflammatory control. Its weakening, such as in the aftermatch of a surgery, leaves the body vulnerable to diverse inflammatory conditions, including sepsis.

Methods

Vagal activity can be measured by the cardiorespiratory interaction known as respiratory sinus arrhythmia or high-frequency heart-rate variability (HRV). We examined the vagal dynamics before, during and after an orthopedic surgery. 39 patients had their HRV measured around the period of operation and during subsequent rehabilitation. Measurements were done during 24 h circadian cycles on ten specific days. For each patient, the circadian vagal activity was calculated from HRV data.

Results

Our results confirm the deteriorating effect of surgery on vagal activity. Patients with stronger pre-operative vagal activity suffer greater vagal withdrawal during the peri-operative phase, but benefit from stronger improvements during post-operative period, especially during the night. Rehabilitation seems not only to efficiently restore the vagal activity to pre-operative level, but in some cases to actually improve it.

Discussion

Our findings indicate that orthopedic rehabilitation has the potential to strengthen the vagal activity and hence boost inflammatory control. We conclude that providing a patient with a vagal reinforcement procedure prior to the surgery (“pre-habilitation”) might be a beneficial strategy against post-operative complications. The study also shows the clinical usefulness of quantifying the cardiorespiratory interactions.

Preventive Leptin Administration Protects Against Sepsis Through Improving Hypotension, Tachycardia, Oxidative Stress Burst, Multiple Organ Dysfunction, and Increasing Survival

Sepsis syndrome is the most important cause of mortality in critically ill patients admitted to intensive care units (ICUs). However, current therapies for its prevention and treatment are still unsatisfactory, and the mortality rate is still high. Non-septic ICU patients are vulnerable to acquire sepsis syndrome. Thus, a preventive treatment for this population is needed. During sepsis syndrome and endotoxemia, severe hypotension, tachycardia, oxidative and immune response increase, multiple organ dysfunction syndrome (MODS) and decreased survival are observed. Leptin administration protects against negative effects of sepsis syndrome and endotoxemia. Furthermore, it is has been reported that leptin elevates blood pressure mediated by sympathetic nervous system activation. However, whether leptin administration before sepsis induction mediates its protective effects during sepsis through blood pressure regulation is not known. Therefore, we investigated whether pre-treatment of leptin improves blood pressure and MODS, resulting in survival increase during endotoxemia. The results showed that leptin administration before endotoxemia induction reduced both the hypotension and tachycardia characteristically observed during endotoxemia. Notably, this protective effect was observed early and late in the course of endotoxemia. Endotoxemia-induced MODS decreased in leptin-treated rats, which was reflected in normal values for liver and kidney function, inhibition of muscle mass wasting and maintenance of glycemia. Furthermore, leptin pre-treatment decreased the oxidative stress burst in blood and blunted the increased pro-inflammatory cytokines TNF-α, IL-1β, and IL-6 observed during endotoxemia. Remarkably, according to the leptin-induced increase in survival, leptin pre-administration decreased the risk for death associated with sepsis syndrome at early and late times after endotoxemia induction. These results show a potential preventive therapy against sepsis syndrome and endotoxemia in vulnerable patients, based in the beneficial actions of leptin.

High Visceral Adipose Tissue to Subcutaneous Adipose Tissue Ratio as a Predictor of Mortality in Acute Respiratory Distress Syndrome

BACKGROUND

We aimed to further determine the relationship between the areas of visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), and the ratio of VAT to SAT (VAT/SAT) with the outcomes of acute respiratory distress syndrome (ARDS) patients.

METHODS

A retrospective study was performed on patients with ARDS in 7 intensive care units (ICU) of West China Hospital, Sichuan University.

RESULTS

A total of 169 patients were included in the analysis. Abdominal computed tomography scans of each patient within 24 hours of being admitted to the ICU were assessed by at least 2 investigators. Higher VAT/SAT was related with higher hospital mortality (22% vs. 44%, P = 0.003; adjusted odds ratio [aOR] 0.699, 95% CI 0.530-0.922 ([P = 0.011]). On the contrary, higher SAT and VAT were related to lower hospital mortality in ARDS (aOR 1.077, 95% CI 1.037-1.119 [P < 0.001]; aOR 1.017, 95% CI 1.004-1.030 [P = 0.011], respectively). Patients with higher SAT and VAT had shorter length of ICU stay (ICU LOS) (26.26 vs. 15.83 days, P = 0.031; 25.16 vs. 14.19 days, P = 0.007, respectively), while VAT/SAT was not related with ICU LOS. Moreover, we did not find any significant relationship either between VAT/SAT and mechanical ventilation-free days or between SAT and mechanical ventilation-free days.

CONCLUSIONS

This study suggests that VAT/SAT can contribute to adverse outcomes of patients with ARDS. However, higher SAT and VAT were related to better prognosis of ARDS patients.

Towards frailty biomarkers: Candidates from genes and pathways regulated in aging and age-related diseases

OBJECTIVE

Use of the frailty index to measure an accumulation of deficits has been proven a valuable method for identifying elderly people at risk for increased vulnerability, disease, injury, and mortality. However, complementary molecular frailty biomarkers or ideally biomarker panels have not yet been identified. We conducted a systematic search to identify biomarker candidates for a frailty biomarker panel.

METHODS

Gene expression databases were searched (http://genomics.senescence.info/genes including GenAge, AnAge, LongevityMap, CellAge, DrugAge, Digital Aging Atlas) to identify genes regulated in aging, longevity, and age-related diseases with a focus on secreted factors or molecules detectable in body fluids as potential frailty biomarkers. Factors broadly expressed, related to several "hallmark of aging" pathways as well as used or predicted as biomarkers in other disease settings, particularly age-related pathologies, were identified. This set of biomarkers was further expanded according to the expertise and experience of the authors. In the next step, biomarkers were assigned to six "hallmark of aging" pathways, namely (1) inflammation, (2) mitochondria and apoptosis, (3) calcium homeostasis, (4) fibrosis, (5) NMJ (neuromuscular junction) and neurons, (6) cytoskeleton and hormones, or (7) other principles and an extensive literature search was performed for each candidate to explore their potential and priority as frailty biomarkers.

RESULTS

A total of 44 markers were evaluated in the seven categories listed above, and 19 were awarded a high priority score, 22 identified as medium priority and three were low priority. In each category high and medium priority markers were identified.

CONCLUSION

Biomarker panels for frailty would be of high value and better than single markers. Based on our search we would propose a core panel of frailty biomarkers consisting of (1) CXCL10 (C-X-C motif chemokine ligand 10), IL-6 (interleukin 6), CX3CL1 (C-X3-C motif chemokine ligand 1), (2) GDF15 (growth differentiation factor 15), FNDC5 (fibronectin type III domain containing 5), vimentin (VIM), (3) regucalcin (RGN/SMP30), calreticulin, (4) PLAU (plasminogen activator, urokinase), AGT (angiotensinogen), (5) BDNF (brain derived neurotrophic factor), progranulin (PGRN), (6) α-klotho (KL), FGF23 (fibroblast growth factor 23), FGF21, leptin (LEP), (7) miRNA (micro Ribonucleic acid) panel (to be further defined), AHCY (adenosylhomocysteinase) and KRT18 (keratin 18). An expanded panel would also include (1) pentraxin (PTX3), sVCAM/ICAM (soluble vascular cell adhesion molecule 1/Intercellular adhesion molecule 1), defensin α, (2) APP (amyloid beta precursor protein), LDH (lactate dehydrogenase), (3) S100B (S100 calcium binding protein B), (4) TGFβ (transforming growth factor beta), PAI-1 (plasminogen activator inhibitor 1), TGM2 (transglutaminase 2), (5) sRAGE (soluble receptor for advanced glycosylation end products), HMGB1 (high mobility group box 1), C3/C1Q (complement factor 3/1Q), ST2 (Interleukin 1 receptor like 1), agrin (AGRN), (6) IGF-1 (insulin-like growth factor 1), resistin (RETN), adiponectin (ADIPOQ), ghrelin (GHRL), growth hormone (GH), (7) microparticle panel (to be further defined), GpnmB (glycoprotein nonmetastatic melanoma protein B) and lactoferrin (LTF). We believe that these predicted panels need to be experimentally explored in animal models and frail cohorts in order to ascertain their diagnostic, prognostic and therapeutic potential.

Adipokines in critical illness: A review of the evidence and knowledge gaps

Adipose tissue products or adipokines play a major role in chronic endocrine and metabolic disorders; however, little is known about critical conditions. In this article, the experimental and clinical evidence of alterations of adipokines, adiponectin, leptin, resistin, visfatin, asymmetric dimethylarginine (ADMA), and ghrelin in critical illness, their potential metabolic, diagnostic, and prognostic value, and the gaps in the field have been reviewed. The results showed considerable changes in the concentration of the adipokines; while the impact of adipokines on metabolic disorders such as insulin resistance and inflammation has not been well documented in critically ill patients. There is no consensus about the circulatory and functional changes of leptin and adiponectin. However, it seems that lower concentrations of adiponectin at admission with gradual consequent increase might be a useful pattern in determining better outcomes of critical illness. Some evidence has suggested the adverse effects of elevated resistin concentration, potential prognostic importance of visfatin, and therapeutic value of ghrelin. High ADMA levels and low arginine:ADMA ratio were also proposed as predictors of ICU mortality and morbidities. However, there is no consensus on these findings. Although primary data indicated the role of adipokines in critical illness, further studies are required to clarify whether the reason of these changes is pathophysiological or compensatory. The relationship of pathophysiological background, disease severity, baseline nutritional status and nutrition support during hospitalization, and variations in body fat percentage and distribution with adipokines, as well as the potential prognostic or therapeutic role of these peptides should be further investigated in critically ill 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.

Association between adipokines and critical illness outcomes

BACKGROUND

Adipose tissue is an endocrine organ that plays a critical role in immunity and metabolism by virtue of a large number of hormones and cytokines, collectively termed adipokines. Dysregulation of adipokines has been linked to the pathogenesis of multiple diseases, but some questions have arisen concerning the value of adipokines in critical illness setting. The objective of this review was to evaluate the associations between blood adipokines and critical illness outcomes.

METHODS

PubMed, CINAHL, Scopus, and the Cochrane Library databases were searched from inception through July 2016 without language restriction. Studies reporting the associations of adipokines, leptin, adiponectin, resistin, and/or visfatin with critical illness outcomes mortality, organ dysfunction, and/or inflammation were included.

RESULTS

A total of 38 articles were selected according to the inclusion/exclusion criteria of the study. Significant alterations of circulating adipokines have been reported in critically ill patients, some of which were indicative of patient outcomes. The associations of leptin and adiponectin with critical illness outcomes were not conclusive in that blood levels of both adipokines did not always correlate with the illness severity scores or risks of organ failure and mortality. By contrast, studies consistently reported striking increase of blood resistin and visfatin, independently of the critical illness etiology. More interestingly, increased levels of these adipokines were systematically associated with severe inflammation, and high incidence of organ failure and mortality.

CONCLUSIONS

There is strong evidence to indicate that increased levels of blood resistin and visfatin are associated with poor outcomes of critically ill patients, including higher inflammation, and greater risk of organ dysfunction and mortality.

LEVEL OF EVIDENCE

Systematic review, level III.

Leptin independently predicts development of sepsis and its outcome

Background

Sepsis is a life-threatening condition and obesity is related to the clinical outcome. The underlying reasons are incompletely understood, but the adipocyte derived hormones leptin and adiponectin may be involved.

Methods

Patients aged 18 years or more with documented first time sepsis events were included in a nested case-referent study if they had participated in previous health surveys. Two matched referents free of known sepsis were identified. Circulating levels of leptin and adiponectin were determined in stored plasma, and their impact on a future sepsis event and its outcome was evaluated.

Results

We identified 152 patients (62% women) with a sepsis event and a previous participation in a health survey. Eighty-three % had also blood samples from the acute event. Hyperleptinemia at health survey associated with a future sepsis event (OR 1.77, 95% CI 1.04–3.00) and with hospital death. After adjustment for BMI leptin remained associated with sepsis in men, but not in women. High levels in the acute phase associated with increased risk for in hospital death in women (OR 4.18, 95% CI 1.17–15.00), while being protective in men (OR 0.05, 95% CI 0.01–0.48). Furthermore, leptin increased more from baseline to the acute phase in men than in women. Adiponectin did not predict sepsis and did not relate to outcome.

Conclusions

Hyperleptinemia independently predicted the development of sepsis and an unfavourable outcome in men, and inertia in the acute response related to worse outcome.

Leptin induces osteoblast differentiation of human valvular interstitial cells via the Akt and ERK pathways

AIMS

Calcific aortic valve disease (CAVD) affects 2-6% of the population over 65 years, and age, gender, smoking, overweight, dyslipidemia, diabetes contribute to the development of this disease. CAVD results, in part, from the osteoblast differentiation of human valvular interstitial cells (VICs). This study aims to elucidate the effects of leptin on osteoblast phenotype of VICs and the signalling pathways involved.

METHODS

Patients who underwent aortic valve replacement for CAVD (n = 43) were included in this study. Patients with coronary artery disease (CAD) without CAVD (n = 129) were used as controls.

RESULTS

Patients with CAVD had higher serum leptin concentrations than CAD patients (p = 0.002). Leptin was found in calcific aortic valves, with higher concentrations in calcified versus non-calcified zones (p = 0.01). Chronic leptin stimulation of human VICs enhanced alkaline phosphatase (ALP) activity and ALP, BMP-2 and RUNX2 expression and decreased osteopontin expression. Moreover, inhibiting Akt or ERK during leptin stimulation lowered the expression of osteoblast markers in VIC.

CONCLUSIONS

Taken together, these findings indicate that leptin plays a critical role in CAVD development by promoting osteoblast differentiation of human aortic VICs in an Akt- and ERK-dependent manner. This study highlights the role of leptin in CAVD development, and further studies are needed to determine whether reducing circulating leptin levels or blocking leptin actions on VICs is efficient to slow CAVD progression.

Increased Ratio of Visceral to Subcutaneous Adipose Tissue in Septic Patients Is Associated With Adverse Outcome

OBJECTIVES

Visceral and subcutaneous adipose tissue may contribute differentially to the septic inflammatory response. Accordingly, we tested the hypothesis that the ratio of visceral to subcutaneous adipose tissue is associated with altered sepsis outcome.

DESIGN

A retrospective analysis from a cohort of sepsis patients admitted between 2004 and 2009.

SETTING

A mixed medical-surgical ICU at St. Paul's Hospital in Vancouver, Canada.

PATIENTS

Patients older than 16 years old who had sepsis and underwent abdominal CT scan (n = 257) for clinical reasons.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We measured the visceral adipose tissue and subcutaneous adipose tissue areas and calculated the visceral adipose tissue-to-subcutaneous adipose tissue ratio. Visceral adipose tissue/subcutaneous adipose tissue was not correlated with body mass index (r = -0.015, p = NS) and therefore provides additional unique information independent of body mass index. Sepsis patients with higher visceral adipose tissue/subcutaneous adipose tissue had greater 90-day mortality than patients with lower visceral adipose tissue/subcutaneous adipose tissue (log-rank test, linear-by linear association p < 0.005). After adjustment for significant covariates using Cox regression, increased visceral adipose tissue/subcutaneous adipose tissue quartile was significantly associated with increased 90-day mortality with hazard ratios of 2.01 (95% CI, 1.01-3.99) for the third visceral adipose tissue/subcutaneous adipose tissue quartile compared with the first quartile and 2.32 (95% CI, 1.15-4.69) for the highest visceral adipose tissue/subcutaneous adipose tissue quartile when compared with the first quartile. Increased mortality for patients with higher visceral adipose tissue/subcutaneous adipose tissue was found for both patients with body mass index less than 25 kg/m (p = 0.004) and for body mass index greater than or equal to 25 kg/m (p = 0.023). Furthermore, we found significantly greater need for mechanical ventilation, renal replacement therapy, and ICU stay in patients in the highest visceral adipose tissue/subcutaneous adipose tissue quartile. The ratio of proinflammatory (interleukin-8) to anti-inflammatory (interleukin-10) plasma cytokine levels was greater in patients with higher visceral adipose tissue/subcutaneous adipose tissue than in those with lower visceral adipose tissue/subcutaneous adipose tissue (p = 0.043).

CONCLUSIONS

Visceral obesity, defined by a high visceral adipose tissue-to-subcutaneous adipose tissue ratio, contributes to adverse outcome in sepsis patients perhaps because of a greater pro- versus anti-inflammatory response.

Short-Term High-Fat Diet Feeding Provides Hypothalamic but Not Hippocampal Protection against Acute Infection in Male Mice

Obesity is associated with increased fever and sickness behavior in response to infection. The hypothalamic-pituitary-adrenal (HPA) axis plays a key role in the reaction to immune stimuli. Bacterial infection, or bacterial lipopolysaccharide (LPS), induces the expression of peripheral cytokines that stimulate the hypothalamus and the hippocampus and activate the HPA axis. In this study, we explored whether the hypothalamic and hippocampal responses to infection are altered during the development of diet-induced obesity. Male mice were exposed to a high-fat diet (HFD) or a low-fat diet (LFD) for 15 days. They were then administered a single intraperitoneal injection of bacterial LPS or vehicle and sacrificed 24 h later. LPS increased circulating levels of insulin and leptin, but only in LFD animals. LPS induced a significant decrease in hypothalamic corticotrophin-releasing hormone and glucocorticoid receptor mRNA levels in LFD animals but exerted the opposite effect in HFD-fed mice. LPS increased the hypothalamic expression of molecules involved in the leptin signaling pathway (SOCS3 and STAT3), nuclear factor-κB pathway members, inflammatory mediators (tumor necrosis factor-α and interleukin-6) and glial proliferation markers (Emr1 and CD68) in LFD animals. These effects were dampened in HFD-fed mice. In contrast, the hippocampal responses to LPS were largely insensitive to HFD. These results suggest that HFD feeding reduced the inflammatory response induced by LPS in the hypothalamus but not in the hippocampus.

Obesity enhances sepsis-induced liver inflammation and injury in mice

OBJECTIVE

How obesity affects the response to sepsis was not completely understood. It was hypothesized that obesity alters adipose and hepatic tissue inflammation through signal transducer and activator of transcription (STAT3) activation.

METHODS

Male C57BL/6 mice at 6 weeks of age were randomized to a high-fat diet (60% kcal fat) or normal diet (16% kcal fat) for 6 to 7 weeks. Sepsis was then induced by cecal ligation and puncture, and animals were monitored for survival or sacrificed and tissue collected.

RESULTS

High-fat diet-fed mice gained more weight, had increased fat mass, and were glucose intolerant compared with normal diet-fed mice. Obesity increased hepatic neutrophil infiltration and injury after sepsis. Mice with obesity had higher plasma leptin levels compared with mice without obesity. Adipose tissue expression of adiponectin receptor 2, tumor necrosis factor-α, and peroxisome proliferator activated receptor gamma was altered during sepsis and affected by obesity, but the greatest change in adipose tissue expression was in leptin. Septic mice with obesity had lower plasma interleukin-17a, interleukin-23, and tumor necrosis factor-α levels and increased hepatic STAT3 and activator protein-1 activation compared with septic mice without obesity. Ultimately, mice with obesity had a lower probability of survival following sepsis.

CONCLUSIONS

Mice with obesity are more susceptible to sepsis and have higher mortality, in part, through activation of the STAT3 signaling pathway and through activator protein-1 activation.

The soluble leptin receptor

The adipokine leptin realizes signal transduction via four different leptin receptor (OB-R) isoforms. The amount of functionally active OB-R, however, is affected by constitutive shedding of the extracellular domain. The product of the cleavage process, the so-called soluble leptin receptor (sOB-R), is the main binding protein for leptin in human blood and modulates its bioavailability. Concentrations of sOB-R are differentially regulated in metabolic disorders, such as type 1 diabetes mellitus or obesity, and can, therefore, enhance or reduce leptin sensitivity. Lipotoxicity and apoptosis increase OB-R cleavage via ADAM10-dependent mechanisms. In contrast, although increased sOB-R concentrations seem to directly inhibit leptin effects, reduced amounts of sOB-R may reflect decreased membrane expression of OB-R. These findings, in part, explain alterations of leptin sensitivity that are associated with changes in serum sOB-R concentrations seen in metabolic disorders.

[Modifications of immunity in obesity: The impact on the risk of infection]

Incidence of obesity is constantly rising all over the world; obesity has developed into an important problem of public health. Clinical experience, supported by many clinical trials, shows that obesity constitutes a risk factor for numerous cardiovascular, metabolic, cancer and even infectious diseases. In this revue we summarize the present knowledge on immunological properties and functions of adipose tissue and their modifications in obese subjects, with a bending to a potentially deleterious chronic inflammatory state. We will discuss the negative impact of this chronic inflammation on physiological acute inflammatory reaction during infectious episodes. However, the modifications of anti-infectious immune response in obese subjects are not well known at present and need further investigations.

Leptin and maintenance of gastrointestinal function

Leptin is a protein hormone encoded by the obese (Ob) gene, exerting an important biological role in the life. Initially, leptin is believed to play a major role in regulating appetite control and energy metabolism, including adjusting the energy metabolism. However, recent data suggest that leptin also plays an important part in regulating the function of the gastrointestinal tract, immune and inflammation response, injury repair, and tumor angiogenesis. This article reviews the protective effects of leptin on the function of the gastrointestinal tract.

Leptin: From structural insights to the design of antagonists

After its discovery in 1994, it soon became clear that leptin acts as an adipocyte-derived hormone with a central role in the control of body weight and energy homeostasis. However, a growing body of evidence has revealed that leptin is a pleiotropic cytokine with activities on many peripheral cell types. Inappropriate leptin signaling can promote autoimmunity, certain cardiovascular diseases, elevated blood pressure and cancer, which makes leptin and the leptin receptor interesting targets for antagonism. Profound insights in the leptin receptor (LR) activation mechanisms are a prerequisite for the rational design of these antagonists. In this review, we focus on the molecular mechanisms underlying leptin receptor activation and signaling. We also discuss the current strategies to interfere with leptin signaling and their therapeutic potential.

Divergence of the response induced by xenogenic immunization in the sepsis survival of rats

We have previously described that boosted natural xenoantibodies in rats cross-react to bacteria by targeting carbohydrate antigens. This type of immunization is associated with reduced survival after cecal ligation and puncture (CLP). In the present study, we investigated further this phenomenon by immunizing Lewis rats with three intraperitoneal injections, every other day, of hamster blood compared to saline-injected control animals. One day after the last injection, CLP was performed to produce a low-grade sepsis. Induction of xenoantibodies was associated with a reduction in animal survival after CLP relative to controls (45% vs. 90%, p<0.01). No bacterial blood load was observed after CLP in this model either with or without xenoantibody enhancement, indicating that the augmented mortality was not mediated by a direct effect of boosted xenoantibodies over blood bacteria. Nevertheless, the xenoimmunization produced a systemic inflammatory response in all rats. Additionally, a lack of weight gain at the time of CLP was present in animals that died after the procedure, which was not observed in surviving rats and controls. The cytokine profile at the time of CLP in animals that died after the procedure was characterized by an increase in the serum level of several cytokines, particularly adipokines. In contrast, the cytokine profile at CLP of xenoimmunized rats that survived the procedure was characterized by a reduction in the level of cytokines. In conclusion, this study failed to show a direct effect of boosted xenoantibodies over blood bacterial isolates as cause for the decreased survival after CLP. However, it evidenced that non-infectious systemic inflammation may lead to a pattern of augmented cytokines, particularly adipokines, which impairs survival after subsequent CLP. Therefore, the profile of cytokines existing before the infectious insult appears more crucial than that resulting from the condition for the outcome of sepsis.

Endocrine dysfunction in sepsis: a beneficial or deleterious host response?

Sepsis is a systemic, deleterious inflammatory host response triggered by an infective agent leading to severe sepsis, septic shock and multi-organ failure. The host response to infection involves a complex, organized and coherent interaction between immune, autonomic, neuroendocrine and behavioral systems. Recent data have confirmed that disturbances of the autonomic nervous and neuroendocrine systems could contribute to sepsis-induced organ dysfunction. Through this review, we aimed to summarize the current knowledge about the endocrine dysfunction as response to sepsis, specifically addressed to vasopressin, copeptin, cortisol, insulin and leptin. We searched the following readily accessible, clinically relevant databases: PubMed, UpToDate, BioMed Central. The immune system could be regarded as a "diffuse sensory organ" that signals the presence of pathogens to the brain through different pathways, such as the vagus nerve, endothelial activation/dysfunction, cytokines and neurotoxic mediators and the circumventricular organs, especially the neurohypophysis. The hormonal profile changes substantially as a consequence of inflammatory mediators and microorganism products leading to inappropriately low levels of vasopressin, sick euthyroid syndrome, reduced adrenal responsiveness to ACTH, insulin resistance, hyperglycemia as well as hyperleptinemia. In conclusion, clinical diagnosis of this "pan-endocrine illness" is frequently challenging due to the many limiting factors. The most important benefits of endocrine markers in the management of sepsis may be reflected by their potential to be used as biomarkers in different scoring systems to estimate the severity of the disease and the risk of death.

Cytokine responses to Staphylococcus aureus bloodstream infection differ between patient cohorts that have different clinical courses of infection

Background

The clinical course of Staphylococcus aureus bloodstream infection is unpredictable and bacterial virulence, host immune response and patient characteristics are among the factors that contribute to the clinical course of infection. To investigate the relationship between cytokine response and clinical outcome, circulating cytokine levels were investigated in response to S. aureus bloodstream infection in patients with different clinical courses of infection.

Methods

A prospective study was carried out in 61 patients with S. aureus bloodstream infection and circulating levels of IL-6, GRO-γ, RANTES and leptin were assessed over the course of the infection. Levels were compared in patients with complicated courses of infection (e.g. infective endocarditis) versus uncomplicated courses of S. aureus bloodstream infection and methicillin-resistant S. aureus Vs methicillin-susceptible S. aureus infection.

Results

Significantly lower leptin levels (p < 0.05) and significantly higher IL-6 levels (p < 0.05) were detected at laboratory diagnosis in patients with complicated compared to uncomplicated S. aureus bloodstream infection. Significantly higher levels of GRO-γ were associated with MRSA infection compared to MSSA infection.

Conclusions

IL-6 may be an early inflammatory marker of complicated S. aureus bloodstream infection. Leptin may be protective against the development of a complicated S. aureus bloodstream infection.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-014-0580-6) contains supplementary material, which is available to authorized users.

Adipocyte versus pituitary leptin in the regulation of pituitary hormones: somatotropes develop normally in the absence of circulating leptin

Leptin is a cytokine produced by white fat cells, skeletal muscle, the placenta, and the pituitary gland among other tissues. Best known for its role in regulating appetite and energy expenditure, leptin is produced largely by and in proportion to white fat cells. Leptin is also important to the maintenance and function of the GH cells of the pituitary. This was shown when the deletion of leptin receptors on somatotropes caused decreased numbers of GH cells, decreased circulating GH, and adult-onset obesity. To determine the source of leptin most vital to GH cells and other pituitary cell types, we compared two different leptin knockout models with Cre-lox technology. The global Lep-null model is like the ob/ob mouse, whereby only the entire exon 3 is deleted. The selective adipocyte-Lep-null model lacks adipocyte leptin but retains pituitary leptin, allowing us to investigate the pituitary as a potential source of circulating leptin. Male and female mice lacking adipocyte leptin (Adipocyte-lep-null) did not produce any detectable circulating leptin and were infertile, suggesting that the pituitary does not contribute to serum levels. In the presence of only pituitary leptin, however, these same mutants were able to maintain somatotrope numbers and GH mRNA levels. Serum GH trended low, but values were not significant. However, hypothalamic GHRH mRNA was significantly reduced in these animals. Other serum hormone and pituitary mRNA differences were observed, some of which varied from previous results reported in ob/ob animals. Whereas pituitary leptin is capable of maintaining somatotrope numbers and GH mRNA production, the decreased hypothalamic GHRH mRNA and low (but not significant) serum GH levels indicate an important role for adipocyte leptin in the regulation of GH secretion in the mouse. Thus, normal GH secretion may require the coordinated actions of both adipocyte and pituitary leptin.

Obesity-induced hyperleptinemia improves survival and immune response in a murine model of sepsis

BACKGROUND

Obesity is a growing health problem and associated with immune dysfunction. Sepsis is defined as systemic inflammatory response syndrome that occurs during infection. Excessive inflammation combined with immune dysfunction can lead to multiorgan damage and death.

METHODS

The authors investigated the influence of a class 1 obesity (body mass index between 30 and 34.9) on immune function and outcome in sepsis and the role of leptin on the immune response. The authors used a long-term high-fat-diet feeding model (12 weeks) on C57Bl/6 mice (n = 100) and controls on standard diet (n = 140) followed by a polymicrobial sepsis induced by cecal ligation and puncture.

RESULTS

The authors show that class 1 obesity is connected to significant higher serum leptin levels (data are mean ± SEM) (5.7 ± 1.2 vs. 2.7 ± 0.2 ng/ml; n = 5; P = 0.033) and improved innate immune response followed by significant better survival rate in sepsis (71.4%, n = 10 vs. 10%, n = 14; P < 0.0001). Additional sepsis-induced increases in leptin levels stabilize body temperature and are associated with a controlled immune response in a time-dependent and protective manner. Furthermore, leptin treatment of normal-weight septic mice with relative hypoleptinemia (n = 35) also significantly stabilizes body temperature, improves cellular immune response, and reduces proinflammatory cytokine response resulting in improved survival (30%; n = 10).

CONCLUSIONS

Relative hyperleptinemia of class 1 obesity or induced by treatment is protective in sepsis. Leptin seems to play a regulatory role in the immune system in sepsis, and treatment of relative hypoleptinemia could offer a new way of an individual sepsis therapy.

Markers of endothelial cell dysfunction are increased in human omental adipose tissue from women with pre-existing maternal obesity and gestational diabetes

OBJECTIVE

To determine the effect of maternal obesity and gestational diabetes mellitus (GDM) on the expression and release of genes involved in endothelial cell dysfunction in human placenta and omental adipose tissue.

MATERIALS/METHODS

Human placenta and omental adipose tissue were obtained from non-obese and obese normal glucose tolerant (NGT) women and women with GDM at the time of Caesarean section. Quantitative RT-PCR was performed to determine the level of expression. Tissue explants were performed to determine the release of proteins of interest.

RESULTS

There was no effect of pre-existing maternal obesity or GDM on placental gene expression or secretion of members of the VEGF family members (PLGF and VEGF-A expression and secretion; sFlt-1 release; VEGFR1 and VEGFR2 mRNA expression); FGFR1 mRNA expression, FGF2 mRNA expression and secretion; endoglin mRNA expression and secretion (sEng); and the adhesion molecules ICAM-1 and VCAM-1. On the other hand, in omental adipose tissue, pre-existing maternal obesity and GDM were associated with increased gene expression of PLGF, endoglin and ICAM-1 and increased secretion of PLGF, sFlt-1, FGF2, sEng and sICAM-1. There was, however, no effect of maternal pre-existing obesity and GDM on VEGF-A, VEGFR1, VEGFR2, FGFR1 and VCAM-1 expression or secretion.

CONCLUSIONS

This study demonstrated the presence of abnormal expression and secretion of angiogenic proteins and adhesion molecules in omental adipose tissue, but not placenta, from pregnant women with GDM and pre-existing maternal obesity. Increased angiogenic and adhesion molecules released from adipose tissue may affect angiogenesis, inflammation and or lipid and glucose metabolism in both mum and her offspring.

Leptin fails to blunt the lipopolysaccharide-induced activation of the hypothalamic-pituitary-adrenal axis in rats

Obesity is a risk factor for sepsis morbidity and mortality, whereas the hypothalamic-pituitary-adrenal (HPA) axis plays a protective role in the body's defence against sepsis. Sepsis induces a profound systemic immune response and cytokines serve as excellent markers for sepsis as they act as mediators of the immune response. Evidence suggests that the adipokine leptin may play a pathogenic role in sepsis. Mouse endotoxaemic models present with elevated leptin levels and exogenously added leptin increased mortality whereas human septic patients have elevated circulating levels of the soluble leptin receptor (Ob-Re). Evidence suggests that leptin can inhibit the regulation of the HPA axis. Thus, leptin may suppress the HPA axis, impairing its protective role in sepsis. We hypothesised that leptin would attenuate the HPA axis response to sepsis. We investigated the direct effects of an i.p. injection of 2 mg/kg leptin on the HPA axis response to intraperitoneally injected 25 μg/kg lipopolysaccharide (LPS) in the male Wistar rat. We found that LPS potently activated the HPA axis, as shown by significantly increased plasma stress hormones, ACTH and corticosterone, and increased plasma interleukin 1β (IL1β) levels, 2 h after administration. Pre-treatment with leptin, 2 h before LPS administration, did not influence the HPA axis response to LPS. In turn, LPS did not affect plasma leptin levels. Our findings suggest that leptin does not influence HPA function or IL1β secretion in a rat model of LPS-induced sepsis, and thus that leptin is unlikely to be involved in the acute-phase endocrine response to bacterial infection in rats.

Bone marrow leptin signaling mediates obesity-associated adipose tissue inflammation in male mice

Obesity is characterized by an increased recruitment of proinflammatory macrophages to the adipose tissue (AT), leading to systemic inflammation and metabolic disease. The pathogenesis of this AT inflammation, however, remains to be elucidated. The circulating adipokine leptin is increased in obesity and is involved in immune cell function and activation. In the present study, we investigated the role of leptin in the induction of obesity-associated inflammation. We generated radiation chimeric C57BL/6J mice reconstituted with either leptin receptor-deficient (db/db) or wild-type (WT) bone marrow and challenged them with a high-fat diet (HFD) for 16 weeks. Mice reconstituted with db/db bone marrow (WT/db), had significantly lower body weight and adiposity compared with mice with WT bone marrow (WT/WT). Gonadal AT in WT/db mice displayed a 2-fold lower expression of the inflammatory genes Tnfa, Il6, and Ccl2. In addition, gonadal fat of WT/db mice contained significantly fewer crown-like structures compared with WT/WT mice, and most of their AT macrophages expressed macrophage galactose-type C type lectin 1 (MGL1) and were C-C chemokine receptor type 2 (CCR2)-negative, indicative of an anti-inflammatory phenotype. Moreover, WT/db mice exhibited greater insulin sensitivity compared with WT/WT mice. These data show that disrupted leptin signaling in bone marrow-derived cells attenuates the proinflammatory conditions that mediate many of the metabolic complications that characterize obesity. Our findings establish a novel mechanism involved in the regulation of obesity-associated systemic inflammation and support the hypothesis that leptin is a proinflammatory cytokine.

Aromadendrin Inhibits Lipopolysaccharide-Induced Nuclear Translocation of NF-κB and Phosphorylation of JNK in RAW 264.7 Macrophage Cells

Aromadendrin, a flavonol, has been reported to possess a variety of pharmacological activities such as anti-inflammatory, antioxidant, and anti-diabetic properties. However, the underlying mechanism by which aromadendrin exerts its biological activity has not been extensively demonstrated. The objective of this study is to elucidate the anti-inflammatory mechanism of aromadedrin in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophage cells. Aromadendrin significantly suppressed LPS-induced excessive production of pro-inflammatory mediators such as nitric oxide (NO) and PGE2. In accordance, aromadendrin attenuated LPSinduced overexpression iNOS and COX-2. In addition, aromadendrin significantly suppressed LPS-induced degradation of IκB, which sequesters NF-κB in cytoplasm, consequently inhibiting the nuclear translocation of pro-inflammatory transcription factor NF- κB. To elucidate the underlying signaling mechanism of anti-inflammatory activity of aromadendrin, MAPK signaling pathway was examined. Aromadendrin significantly attenuated LPS-induced activation of JNK, but not ERK and p38, in a concentration-dependent manner. Taken together, the present study clearly demonstrates that aromadendrin exhibits anti-inflammatory activity through the suppression of nuclear translocation of NF-κB and phosphorylation of JNK in LPS-stimulated RAW 264.7 macrophage cells.

The impact of obesity on sepsis mortality: a retrospective review

Background

Recent sepsis guidelines have focused on the early identification and risk stratification of patients on presentation. Obesity is associated with alterations in multiple inflammatory regulators similar to changes seen in sepsis, suggesting a potential interaction between the presence of obesity and the severity of illness in sepsis.

Methods

We performed a retrospective chart review of patients admitted with a primary billing diagnosis of sepsis at a single United States university hospital from 2007 to 2010. Seven hundred and ninety-two charts were identified meeting inclusion criteria. Obesity was defined as a body mass index (BMI) ≥ 30 kg/m². The data recorded included age, race, sex, vital signs, laboratory values, length of stay, comorbidities, weight, height, and survival to discharge. A modified APACHE II score was calculated to estimate disease severity. The primary outcome variable was inpatient mortality.

Results

Survivors had higher average BMI than nonsurvivors (27.6 vs. 26.3 kg/m2, p = 0.03) in unadjusted analysis. Severity of illness and comorbid conditions including cancer were similar across BMI categories. Increased incidence of diabetes mellitus type 2 was associated with increasing BMI (p < 0.01) and was associated with decreased mortality, with an odds ratio of 0.53 compared with nondiabetic patients. After adjusting for age, gender, race, severity of illness, length of stay, and comorbid conditions, the trend of decreased mortality for increased BMI was no longer statistically significant, however diabetes continued to be strongly protective (odds ratio 0.52, p = 0.03).

Conclusions

This retrospective analysis suggests obesity may be protective against mortality in septic inpatients. The protective effect of obesity may be dependent on diabetes, possibly through an unidentified hormonal intermediary. Further prospective studies are necessary to elaborate the specific mechanism of this protective effect.

Endocrine, metabolic, and morphologic alterations of adipose tissue during critical illness

OBJECTIVE

Observational studies report lower mortality in obese than in lean critically ill patients, an association referred to as the "obesity paradox." This may suggest a possible protective role for adipose tissue during severe illness.

DATA SOURCES

Relevant publications were identified based on searches in PubMed and on secondary searches of their bibliographies.

DATA SYNTHESIS

The endocrine functions of adipose tissue might play a role in the adaptation to critical illness. In the acute phase of illness, the anti-inflammatory adiponectin is reduced, whereas proinflammatory cytokine expression in adipose tissue is up-regulated. In the prolonged phase of critical illness, both adiponectin and anti-inflammatory cytokine production are increasing. Studies on the proinflammatory adipokine leptin during critical illness are inconsistent, possibly due to confounders such as gender, body mass index, and feeding. Morphologically, adipose tissue of critically ill patients reveals an increased number of newly differentiated, smaller adipocytes. Accentuated macrophage accumulation showing a phenotypic switch to M2-type suggests an adaptive response to the microenvironment of severe illness. Functionally, adipose tissue of critically ill patients develops an increased ability to store glucose and triglycerides.

CONCLUSIONS

Endocrine, metabolic, and morphologic properties of adipose tissue change during critical illness. These alterations may suggest a possible adaptive, protective role in optimizing chances of survival. More research is needed to understand the exact role of adipose tissue in lean vs. obese critically ill patients, in order to understand how illness-associated alterations contribute to the obesity paradox.

Alterations of leptin in the course of inflammation and severe sepsis

Background

The adipokine leptin regulates energy expenditure, vascular function, bone and cartilage growth as well as the immune system and systemic inflammatory response. Several activating effects towards T cells, monocytes, endothelium cells and cytokine production have been reported suggesting a protective role of leptin in the setting of an acute systemic inflammation. However, the pathophysiological role of leptin during severe sepsis is currently not elucidated in detail. This study aims to investigate leptin expression in cultured human adipocytes within an inflammatory model and in patients suffering from severe sepsis and evaluates treatment effects of drotrecogin alpha (activated) (DAA), the recombinant form of human activated protein C.

Methods

In an in-vitro inflammatory model of adipocyte cell-culture the effect of DAA on leptin mRNA expression was evaluated. Synthesis of mRNA was measured by quantitative polymerase chain reaction (qPCR). Additionally, supernatants of these adipocytes as well as serum levels of adiponectin were measured in blood of 104 severe septic patients by ELISA-method. 26 patients were treated with DAA (DAA+), 78 patients were not treated with DAA (DAA-).

Results

Stimulation of human adipocytes with TNF alpha over 6 and 24 hours resulted in a significant decrease by 46% and 59% of leptin mRNA transcripts compared to un-stimulated controls (p < 0.05). Leptin levels of supernatants of adipocyte culture decreased by 25% and 23% (p < 0.05) after incubation with TNF alpha after 6 and 24 hours. Incubation with DAA at 50 ng/ml DAA and 5 μg/ml doubled mRNA expression significantly at 24 hours (p < 0.05) but not at 6 hours. From day 1 to day 3 of sepsis, leptin levels increased in DAA+ compared to DAA- patients (p<0.10).

Conclusions

Leptin appears to be involved in the pathogenesis of a systemic inflammatory response during sepsis. Administration of DAA significantly increased leptin expression. The specific mechanism or even benefit of DAA towards leptin needs further ongoing research.

Leptin as a link between the immune system and kidney-related diseases: leading actor or just a coadjuvant?

Food intake and nutritional status modify the physiological responses of the immune system to illness and infection and regulate the development of chronic inflammatory processes, such as kidney disease. Adipose tissue secretes immune-related proteins called adipokines that have pleiotropic effects on both the immune and neuroendocrine systems, linking metabolism and immune physiology. Leptin, an adipose tissue-derived adipokine, displays a variety of immune and physiological functions, and participates in several immune responses. Here, we review the current literature on the role of leptin in kidney diseases, linking adipose tissue and the immune system with kidney-related disorders. The modulation of this adipose hormone may have a major impact on the treatment of several immune- and metabolic-related kidney diseases.

Adiponectin diminishes organ-specific microvascular endothelial cell activation associated with sepsis

Experimental sepsis was induced in male C57BL/6j, adiponectin-deficient mice (ADPNKO), and wild-type littermates by i.p. injection of 16 mg/kg lipopolysaccharide or cecal ligation and puncture. Blood and tissue samples were harvested 24 h after model induction. Circulating adiponectin is reduced in mice with endotoxemic challenge and after cecal ligation and puncture compared with healthy control mice. Quantitative reverse transcriptase-polymerase chain reaction for adiponectin reveals a pattern of response that is both model- and organ-specific. When challenged with sepsis, adiponectin deficiency results in increased expression of endothelial adhesion and coagulation molecules in the lung, liver, and kidney as quantified by reverse transcriptase-polymerase chain reaction, increased macrophage and neutrophil infiltration by immunohistochemistry, and vascular leakage in the liver and kidney. Adiponectin-deficient mice have reduced survival following cecal ligation and puncture and increased blood levels of interleukin 6, soluble vascular endothelial growth factor receptor 1, and soluble endothelial adhesion molecules E-selectin and intercellular adhesion molecule 1. Finally, ADPNKO promoted end-organ injury in the liver and kidney, whereas the lungs were not affected. These data suggest a protective role of adiponectin in diminishing microvascular organ-specific endothelial cell activation during sepsis.