Leptin and leptin receptor polymorphisms are associated with poor outcome (death) in patients with non-appendicular secondary peritonitis

Leptin and leptin receptor expression as biomarkers for breast cancer: a retrospective study

BACKGROUND

Effective screening and treatment have reduced the number of women dying from breast cancer (BC). However, the long-term sequelae of BC treatment and psychosocial factors seriously affect the life quality of BC patients and survivors. Therefore, the discovery and application of targeted biomarkers to improve the functional outcome and life quality of BC patients is necessary.

AIMS

To explore the impact of leptin (LEP)/ leptin receptor (LEPR) expression on occurrence and survival of BC.

METHODS

Totally 132 primary BC and 66 non-BC patients who underwent surgery in department of breast surgery in Shanxi Cancer Hospital from January to October in 2009 were enrolled in this retrospective study. LEP and LEPR were examined in BC tissues, benign breast tissues, para-carcinoma tissues using immunohistochemical staining. Kaplan-Meier curve was generated to test survival time.

RESULTS

The high level expression of LEP and LEPR in BC tissues were significantly higher than that in benign breast tissues and in para-carcinoma tissues (all P < 0.05). The LEP expression in patients with lymph node metastases was significantly higher than that in patients without lymph nodes metastases (P = 0.002). LEPR expression was correlated with higher Ki-67 rate (P = 0.002). LEP and LEPR both had no impact on survival (all P > 0.05).

CONCLUSIONS

High LEP/LEPR expression were risk factors for occurrence of BC, but without impact on survival.

Leptin Receptor q223r Polymorphism Influences Clostridioides difficile Infection-Induced Neutrophil CXCR2 Expression in an Interleukin-1β Dependent Manner

Neutrophils are key first-responders in the innate immune response to C. difficile infection (CDI) and play a central role in disease pathogenesis. Studies have clearly shown that tissue neutrophil numbers need to be tightly regulated for optimal CDI outcomes: while excessive colonic neutrophilia is associated with severe CDI, neutrophil depletion also results in worse outcomes. However, the biological mechanisms that control CDI-induced neutrophilia remain poorly defined. C-X-C chemokine receptor 2 (CXCR2) is a chemotactic receptor that is critical in neutrophil mobilization from bone marrow to blood and tissue sites. We have previously reported that a single nucleotide polymorphism (SNP) in leptin receptor (LEPR), present in up to 50% of people, influenced CDI-induced neutrophil CXCR2 expression and tissue neutrophilia. Homozygosity for mutant LEPR (i.e. RR genotype) was associated with higher CXCR2 expression and more tissue neutrophils. Here, we investigated the biological mechanisms that regulate neutrophil CXCR2 expression after CDI, and the influence of host genetics on this process. Our data reveal that: a) CXCR2 plays a key role in CDI-induced neutrophil extravasation from blood to colonic tissue; b) plasma from C. difficile-infected mice upregulated CXCR2 on bone marrow neutrophils; c) plasma from C. difficile-infected RR mice induced a higher magnitude of CXCR2 upregulation and had more IL-1β; and d) IL-1β neutralization reduced CXCR2 expression on bone marrow and blood neutrophils and their subsequent accrual to colonic tissue. In sum, our data indicate that IL-1β is a key molecular mediator that communicates between gastro-intestinal tract (i.e. site of CDI) and bone marrow (i.e. primary neutrophil reservoir) and regulates the intensity of CDI-induced tissue neutrophilia by modulating CXCR2 expression. Further, our studies highlight the importance of host genetics in affecting these innate immune responses and provide novel insights into the mechanisms by which a common SNP influences CDI-induced neutrophilia.

Molecular dynamic (MD) studies on Gln233Arg (rs1137101) polymorphism of leptin receptor gene and associated variations in the anthropometric and metabolic profiles of Saudi women

The Gln233Arg (A>G; rs1137101) polymorphism of the leptin receptor gene (LEPR) has been investigated extensively and is reported to be associated with different metabolic states. In this investigation, we aimed to study the frequency of Gln233Arg genotypes and alleles in a group of Saudi women stratified by their body mass index (BMI), to correlate the LEPR genotypes with variations in anthropometric, lipid and hormonal parameters and to investigate conformational and structural variations in the mutant LEPR using molecular dynamic (MD) investigations. The study group included 122 Saudi women (normal weight = 60; obese = 62) attending the clinics for a routine checkup. Anthropometric data: height, weight, waist and hip circumference were recorded and fasting serum sample was used to estimate glucose, lipids, ghrelin, leptin and insulin. BMI, W/H ratio, and HOMA-IR values were calculated. Whole blood sample was used to extract DNA; exon 6 of the LEPR gene was amplified by PCR and sequencing was conducted on an ABI 3100 Avant Genetic Analyser. Molecular Dynamic Simulation studies were carried out using different softwares. The results showed the presence of all three genotypes of Gln233Arg in Saudi women, but the frequencies were significantly different when compared to reports from some populations. No differences were seen in the genotype and allele frequencies between the normal weight and obese women. Stratification by the genotypes showed significantly higher BMI, waist and hip circumference, leptin, insulin, fasting glucose and HOMA-IR and lower ghrelin levels in obese women carrying the GG genotype. Even in the normal weight group, individuals with GG genotype had higher BMI, waist and hip circumference and significantly lower ghrelin levels. The MD studies showed a significant effect of the Gln/Arg substitution on the conformation, flexibility, root-mean-square fluctuation (RMSF), radius of gyration (Rg) values, solvent-accessible surface area (SASA) and number of inter- and intra-molecular H-bonds. The results suggest that the structural changes brought about by the mutation, influence the signaling pathways by some unknown mechanism, which may be contributing to the abnormalities seen in the individuals carrying the G allele of rs1137101.

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.

Emergence of Leptin in Infection and Immunity: Scope and Challenges in Vaccines Formulation

Deficiency of leptin (ob/ob) and/or desensitization of leptin signaling (db/db) and elevated expression of suppressor of cytokine signaling-3 (SOCS3) reported in obesity are also reported in a variety of pathologies including hypertriglyceridemia, insulin resistance, and malnutrition as the risk factors in host defense system. Viral infections cause the elevated SOCS3 expression, which inhibits leptin signaling. It results in immunosuppression by T-regulatory cells (Tregs). The host immunity becomes incompetent to manage pathogens' attack and invasion, which results in the accelerated infections and diminished vaccine-specific antibody response. Leptin was successfully used as mucosal vaccine adjuvant against Rhodococcus equi. Leptin induced the antibody response to Helicobacter pylori vaccination in mice. An integral leptin signaling in mucosal gut epithelial cells offered resistance against Clostridium difficile and Entameoba histolytica infections. We present in this review, the intervention of leptin in lethal diseases caused by microbial infections and propose the possible scope and challenges of leptin as an adjuvant tool in the development of effective vaccines.

Leptin receptor q223r polymorphism influences neutrophil mobilization after Clostridium difficile infection

Clostridium difficile is the leading cause of nosocomial infections in the United States. Clinical disease outcomes after C. difficile infection (CDI) are dependent on intensity of host inflammatory responses. Specifically, peak peripheral white blood cell (WBC) count >20 × 10⁹ l^-1 is an indicator of adverse outcomes in CDI patients, and is associated with higher 30-day mortality. We show that homozygosity for a common single nucleotide polymorphism (Q to R mutation in leptin receptor that is present in up to 50% of people), significantly increases the risk of having peak peripheral WBC count >20 × 10⁹ l^-1 (odds ratio=5.41; P=0.0023) in CDI patients. In a murine model of CDI, we demonstrate that mice homozygous for the same single nucleotide polymorphism (RR mice) have more blood and tissue leukocytes (specifically neutrophils), exaggerated tissue inflammation, and higher mortality as compared with control mice, despite similar pathogen burden. Further, we show that neutrophilia in RR mice is mediated by gut microbiota-directed expression of CXC chemokine receptor 2 (CXCR2), which promotes the release of neutrophils from bone marrow reservoir. Overall these studies provide novel mechanistic insights into the role of human genetic polymorphisms and gut microbiota in regulating the fundamental biological process of CDI-induced neutrophilia.

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.

Smoking Functions as a Negative Regulator of IGF1 and Impairs Adipokine Network in Patients with Rheumatoid Arthritis

Objectives. Smoking is pathogenic for rheumatoid arthritis (RA) being tightly connected to the genetic and serological risk factors for this disease. This study aims to understand connections between cigarette smoking and serum levels of IGF1 and adipokines in RA. Methods. Serum levels of IGF1 and adipokines leptin, adiponectin, resistin, and visfatin were measured in two independent cohorts of RA patients from Gothenburg (n = 350) and Leiden (n = 193). An association of these parameters with smoking was tested in a direct comparison and proved by bivariate correlation analysis. The obtained associations were further tested in multivariate regression models where the confounders (age, gender, disease duration, and BMI) were controlled. Results. The smokers had significantly lower serum levels of IGF1, adiponectin, and leptin compared to never smokers. In regression analysis, smoking and low leptin, but not adiponectin, were associated and predicted low IGF1. Additionally, high disease activity and high BMI increased the probability of low leptin. Conclusions. The study indicates cigarette smoking as an important cause of a relative IGF1 and leptin deficiency in RA patients. This novel association between smoking and hypoleptinemia may be of importance for long-term prognosis of RA and for prediction of comorbidities.

Leptin Regulation of Immune Responses

Leptin is a regulatory hormone with multiple roles in the immune system. We favor the concept that leptin signaling 'licenses' various immune cells to engage in immune responses and/or to differentiate. Leptin is an inflammatory molecule that is capable of activating both adaptive and innate immunity. It can also 'enhance' immune functions, including inflammatory cytokine production in macrophages, granulocyte chemotaxis, and increased Th17 proliferation. Leptin can also 'inhibit' cells; CD4(+) T cells are inhibited from differentiating into regulatory T cells in the presence of elevated leptin, while NK cells can exhibit impaired cytotoxicity under the same circumstances. Consequently, understanding the effect of leptin signaling is important to appreciate various aspects of immune dysregulation observed in malnutrition, obesity, and autoimmunity.

Role of obesity and adipose tissue-derived cytokine leptin during Clostridium difficile infection

Obesity is among the most pressing health concerns in the world since it is increasingly common even in the developing world, and is clearly associated with increased risk for chronic debilitating diseases and death. Furthermore, obesity can influence the pathogenesis of infectious diseases by affecting the balance of pathogen clearance and pathological inflammation. The mechanisms that result in enhanced inflammation in obese individuals are poorly understood. Clostridium difficile is a major cause of nosocomial infections worldwide. Recent studies have shown that obesity is associated with increased risk of C. difficile infections. In this review, we will discuss our current knowledge of the role of obesity in determining risk of C. difficile infections, and focus on the role of the adipose tissue-derived cytokine leptin in C. difficile infections.

Leptin receptor mutation results in defective neutrophil recruitment to the colon during Entamoeba histolytica infection

Amebiasis is an enteric infection caused by Entamoeba histolytica, with symptoms ranging in severity from asymptomatic colonization to dysentery. Humans with the Q223R leptin receptor mutation have increased susceptibility to amebiasis, but the mechanism has been unclear. Using a mouse model expressing the mutation, we tested the impact of the Q223R mutation on the innate immune response to E. histolytica infection. The 223R mutation resulted in delayed clearance of amebae from the cecum, as had been previously observed. We found that neutrophil influx to the site of the infection was reduced 12 h after infection in 223R mice. Depletion of neutrophils with anti-Ly6G monoclonal antibody increased susceptibility of wild-type mice to infection, supporting the importance of neutrophils in innate defense. Leptin expression was increased in the cecum by E. histolytica infection, suggesting that leptin could serve as a homing signal for neutrophils to the gut. Interestingly, neutrophils from mice with the 223R mutation had diminished chemotaxis toward leptin. This impaired chemotaxis likely explained the reduced gut infiltration of neutrophils. The newly recognized effect of the leptin receptor Q223R mutation on neutrophil chemotaxis and the impact of this mutation on multiple infectious diseases suggest a broader impact of this mutation on susceptibility to disease.

The Q223R leptin receptor mutation results in increased susceptibility of children and adults to E. histolytica, one of the leading causes of diarrhea morbidity and mortality in children of the developing world. Here we show that the mutation results in reduced neutrophil infiltration to the site of infection. This decreased infiltration is likely due to the mutation’s impact on neutrophil chemotaxis toward leptin, an inflammatory agent upregulated in the cecum after infection. The significance of this work thus extends beyond understanding E. histolytica susceptibility by also providing insight into the potential impact of leptin on neutrophil function in other states of altered leptin signaling, which include both malnutrition and obesity.

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.

Kinetics of leptin binding to the Q223R leptin receptor

Studies in human populations and mouse models of disease have linked the common leptin receptor Q223R mutation to obesity, multiple forms of cancer, adverse drug reactions, and susceptibility to enteric and respiratory infections. Contradictory results cast doubt on the phenotypic consequences of this variant. We set out to determine whether the Q223R substitution affects leptin binding kinetics using surface plasmon resonance (SPR), a technique that allows sensitive real-time monitoring of protein-protein interactions. We measured the binding and dissociation rate constants for leptin to the extracellular domain of WT and Q223R murine leptin receptors expressed as Fc-fusion proteins and found that the mutant receptor does not significantly differ in kinetics of leptin binding from the WT leptin receptor. (WT: k_a 1.76×10⁶±0.193×10⁶ M⁻¹ s⁻¹, k_d 1.21×10⁻⁴±0.707×10⁻⁴ s⁻¹, K_D 6.47×10⁻¹¹±3.30×10⁻¹¹ M; Q223R: k_a 1.75×10⁶±0.0245×10⁶ M⁻¹ s⁻¹, k_d 1.47×10⁻⁴±0.0505×10⁻⁴ s⁻¹, K_D 8.43×10⁻¹¹±0.407×10⁻¹¹ M). Our results support earlier findings that differences in affinity and kinetics of leptin binding are unlikely to explain mechanistically the phenotypes that have been linked to this common genetic variant. Future studies will seek to elucidate the mechanism by which this mutation influences susceptibility to metabolic, infectious, and malignant pathologies.

Role of leptin-mediated colonic inflammation in defense against Clostridium difficile colitis

The role of leptin in the mucosal immune response to Clostridium difficile colitis, a leading cause of nosocomial infection, was studied in humans and in a murine model. Previously, a mutation in the receptor for leptin (LEPR) was shown to be associated with susceptibility to infectious colitis and liver abscess due to Entamoeba histolytica as well as to bacterial peritonitis. Here we discovered that European Americans homozygous for the same LEPR Q223R mutation (rs1137101), known to result in decreased STAT3 signaling, were at increased risk of C. difficile infection (odds ratio, 3.03; P = 0.015). The mechanism of increased susceptibility was studied in a murine model. Mice lacking a functional leptin receptor (db/db) had decreased clearance of C. difficile from the gut lumen and diminished inflammation. Mutation of tyrosine 1138 in the intracellular domain of LepRb that mediates signaling through the STAT3/SOCS3 pathway also resulted in decreased mucosal chemokine and cell recruitment. Collectively, these data support a protective mucosal immune function for leptin in C. difficile colitis partially mediated by a leptin-STAT3 inflammatory pathway that is defective in the LEPR Q223R mutation. Identification of the role of leptin in protection from C. difficile offers the potential for host-directed therapy and demonstrates a connection between metabolism and immunity.

Association of serum adiponectin, leptin, and resistin concentrations with the severity of liver dysfunction and the disease complications in alcoholic liver disease

Background and aims. There is growing evidence that white adipose tissue is an important contributor in the pathogenesis of alcoholic liver disease (ALD). We investigated serum concentrations of total adiponectin (Acrp30), leptin, and resistin in patients with chronic alcohol abuse and different grades of liver dysfunction, as well as ALD complications. Materials and Methods. One hundred forty-seven consecutive inpatients with ALD were prospectively recruited. The evaluation of plasma adipokine levels was performed using immunoenzymatic ELISA tests. Multivariable logistic regression was applied in order to select independent predictors of advanced liver dysfunction and the disease complications. Results. Acrp30 and resistin levels were significantly higher in patients with ALD than in controls. Lower leptin levels in females with ALD compared to controls, but no significant differences in leptin concentrations in males, were found. High serum Acrp30 level revealed an independent association with advanced liver dysfunction, as well as the development of ALD complications, that is, ascites and hepatic encephalopathy. Conclusion. Gender-related differences in serum leptin concentrations may influence the ALD course, different in females compared with males. Serum Acrp30 level may serve as a potential prognostic indicator for patients with ALD.