leptin and Infections

Leptin is a critical mediator of the immune response to changes in overall nutrition. Leptin is produced by adipocytes in proportion to adipose tissue mass and is therefore increased in obesity. Despite having a well-described role in regulating systemic metabolism and appetite, leptin displays pleiotropic actions, and it is now clear that leptin has a key role in influencing immune cell function. Indeed, many immune cells have been shown to respond to leptin directly

Topics: Adipose Tissue; Autoimmune Diseases; Diabetes Mellitus, Type 2; Humans; Infections; Leptin; Obesity; Receptors, Leptin

Topics: Animals; Comorbidity; Diabetes Mellitus; Global Health; HIV Infections; Humans; Infections; Leptin; Malaria; Malnutrition; Measles; Obesity; Protein-Energy Malnutrition; Risk Factors; T-Lymphocytes; Tuberculosis

An activated inflammatory response is a common feature of end-stage renal disease (ESRD) patients and predicts outcome. Although various factors related to the dialysis procedure may contribute to inflammation in ESRD, a number of nondialysis-related factors also are of importance. Adipose tissue is a complex organ with functions far beyond the mere storage of energy and secretes a number of proinflammatory adipokines, such as leptin, resistin, tumor necrosis factor-alpha and interleukin-6, as well as one anti-inflammatory adipokine, adiponectin. It has been proposed that adipose tissue may be a significant contributor to increased systemic inflammation in nonrenal patients. In this review, we put forward the hypothesis that a reduction of renal mass will contribute to retention of proinflammatory adipokines, thus generating adipokine imbalance. Such an imbalance may, via effects on the central nervous system and the vasculature, contribute to wasting, atherosclerosis, and insulin resistance--all common features of ESRD.

Topics: Adiponectin; Adipose Tissue; Body Composition; Body Mass Index; Cardiovascular Diseases; Cytokines; Humans; Infections; Inflammation; Interleukin-6; Kidney Failure, Chronic; Leptin; Obesity; Renal Dialysis; Resistin; Risk Factors; Tumor Necrosis Factor-alpha; Wasting Syndrome

Leptin is an adipokine which conveys information on energy availability. In humans, leptin influences energy homeostasis and regulates neuroendocrine function primarily in states of energy deficiency. As a cytokine, leptin also affects thymic homeostasis and, similar to other proinflammatory cytokines, leptin promotes Th1 cell differentiation and cytokine production. We review herein recent advances on the role of leptin in the pathophysiology of immune responses.

Topics: Adipose Tissue; Animals; Autoimmunity; Energy Metabolism; Humans; Immunity, Innate; Infections; Inflammation; Leptin; Models, Immunological; Signal Transduction

Topics: Biomarkers; Chlamydia Infections; Fatty Acids, Unsaturated; Humans; Infections; Inflammation; Inflammation Mediators; Leptin; Obesity; Stress, Physiological

During an infection, a decrease in food intake together with elevated energy expenditure appears. Anorexia is one of the most common signs of illness and is often considered as an undesirable manifestation of sickness. However, compelling data demonstrate that anorexia constitutes an adaptative strategy systematically organised for pathogens elimination. Microbial products stimulate the production by immunocompetent cells of cytokines, which orchestrate the immune response. Since the administration of cytokines reduces food intake, it has been suggested that these agents play a key role in mediating anorexia during infection. This review details the mechanisms of cytokine-induced anorexia, focusing on the role of endogenously produced brain cytokines and more particularly interleukin-1 (IL-1). De novo synthesis of IL-1 occurs in the brain during peripheral infection mimicked by the administration of bacterial endotoxin lipopolysaccharide (LPS). Centrally produced IL-1 acts on its receptors to mediate anorexia as demonstrated by the use of knockout mice and specific IL-1 receptor antagonist. Functional neuroanatomy demonstrates further that LPS or IL-1 specifically activates the hypothalamic neurons that control food intake. Leptin is tightly regulated by IL-1, suggesting the involvement of this hormone in the anorexia of infection. The mechanisms by which hypothalamic arcuate nucleus neuropeptides, which are regulated by IL-1 and leptin, could mediate anorexia during infection are discussed.

Topics: Animals; Anorexia; Brain; Cytokines; Humans; Infections; Interleukin-1; Leptin; Nutrition Disorders

Protein tyrosine phosphatases (PTPs) control signal transduction pathways and have recently emerged as potential drug targets. Inhibition of individual PTPs can result in the activation of therapeutically relevant kinase cascades. This is particularly useful in cases where disease is associated with hormonal resistance, such as insensitivity to insulin or leptin. Currently, PTP1B is being investigated by a number of companies as a promising target for leptin/insulin mimetics and in the treatment of diabetes and obesity. Since all 90-100 PTPs have been identified in the human genome, the challenge now is to identify the function of these enzymes and the therapeutic indications that may exist for specific PTP inhibitors.

Topics: Capillary Permeability; Cyclin-Dependent Kinases; Diabetes Mellitus; Drug Design; Drug Evaluation, Preclinical; Genes, Tumor Suppressor; Humans; Immune System; Infections; Insulin; Leptin; Multigene Family; Neoplasm Proteins; Neoplasms; Obesity; Osteoporosis; Protein Tyrosine Phosphatase, Non-Receptor Type 1; Protein Tyrosine Phosphatases; Receptors, Antigen; Signal Transduction; src-Family Kinases

The recent cloning of the leptin (obese, ob) gene has determined fundamental insight into the understanding of the regulation of food intake, basal metabolism and reproductive function. Leptin, mainly secreted by adipocytes, belongs to the helical cytokine family and its plasma concentrations correlate with fat mass and respond to changes in energy balance. Initially, leptin was considered as an anti-obesity hormone, but experimental evidence has also shown pleiotropic effects of this molecule on hematopoiesis, angiogenesis, lymphoid organ homeostasis and T lymphocyte functions. More specifically, leptin links the pro-inflammatory T helper (Th)-1 immune response to the nutritional status and the energy balance. Indeed, decreased leptin concentrations during conditions of food deprivation lead to impaired immune capabilities. This review focuses on the potential therapeutic utilities for agents that manipulate the leptin-adipocyte axis and discusses novel strategies for an immune intervention in pathologic conditions.

Topics: Animals; Autoimmunity; Brain; CD4-Positive T-Lymphocytes; Humans; Immune System; Infections; Inflammation; Leptin; Receptors, Cell Surface; Receptors, Leptin

Leptin, the product of the ob gene, is a pleiotropic molecule that regulates food intake as well as metabolic and endocrine functions. Leptin also plays a regulatory role in immunity, inflammation, and hematopoiesis. Alterations in immune and inflammatory responses are present in leptin- or leptin-receptor-deficient animals, as well as during starvation and malnutrition, two conditions characterized by low levels of circulating leptin. Both leptin and its receptor share structural and functional similarities with the interleukin-6 family of cytokines. Leptin exerts proliferative and antiapoptotic activities in a variety of cell types, including T lymphocytes, leukemia cells, and hematopoietic progenitors. Leptin also affects cytokine production, the activation of monocytes/macrophages, wound healing, angiogenesis, and hematopoiesis. Moreover, leptin production is acutely increased during infection and inflammation. This review focuses on the role of leptin in the modulation of the innate immune response, inflammation, and hematopoiesis.

Topics: Adaptation, Physiological; Adipose Tissue; Animals; Anorexia; Apoptosis; Cachexia; Carrier Proteins; Cell Division; Cytokines; Eating; Endocrine System; Hematopoiesis; Humans; Immune System; Infections; Inflammation; Interleukin-6; Leptin; Lymphopenia; Mice; Mice, Mutant Strains; Multigene Family; Neovascularization, Physiologic; Obesity; Organ Specificity; Phagocytes; Rats; Receptors, Cell Surface; Receptors, Cytokine; Receptors, Leptin; Signal Transduction; Starvation; T-Lymphocyte Subsets

Anorexia during infection is thought to be mediated by immunoregulatory cytokines such as interleukins 1 and 6 and tumor necrosis factor. This article reviews the potential mechanisms of action by which these cytokines are thought to suppress food intake during infection and examines the proposition that blocking of cytokine activity might be one approach to improving food intake of the infected host.

Topics: Acute-Phase Reaction; Animals; Anorexia; Cholecystokinin; Cytokines; Dinoprostone; Disease Models, Animal; Eating; Fever; Gastroparesis; Humans; Infections; Inflammation Mediators; Leptin; Vagus Nerve

Resistin is an adipokine secreted by macrophages and inflammatory cells linked to insulin resistance and inflammation. Leptin is an adipokine regulator of appetite and obesity. Although circulating levels of both have been associated with atherosclerosis, few data have reported their relation to coronary events in the context of statin therapy. This study measured on-statin levels of both resistin and leptin through enzyme-linked immunosorbent assay in a nested case-control cohort (n = 176 cases with coronary death, myocardial infarction, or unstable angina pectoris observed in follow-up matched 1:1 to 176 controls) derived from the Pravastatin or Atorvastatin Evaluation and Infection Therapy-Thrombolysis in Myocardial Infarction 22 study, a randomized controlled trial of atorvastatin 80 mg/day versus pravastatin 40 mg/day in patients with a recent acute coronary syndrome. Resistin demonstrated a moderate association with high-sensitivity C-reactive protein (hsCRP; Spearman rho = 0.25, p <0.0001). On-statin resistin levels were linked to recurrent coronary events in conditional logistic regression analysis adjusted for additional risk factors including hsCRP and history of diabetes (tertile 3 vs 1 adjusted odds ratio 2.08; 95% confidence interval [CI] 1.04 to 4.19). An additive risk was noted when patients were stratified by resistin and glycated hemoglobin levels. In contrast, leptin levels were associated with obesity, diabetes, triglycerides, and hsCRP (p <0.001 for each) but demonstrated no association with recurrent coronary events (tertile 3 vs 1 adjusted odds ratio 0.72; 95% CI 0.28 to 1.83). In conclusion, on-statin resistin, but not leptin, is an independent marker of residual risk for recurrent coronary events in patients after hospitalization for an acute coronary syndrome.

Topics: Acute Coronary Syndrome; Aged; Atorvastatin; Biomarkers; Dose-Response Relationship, Drug; Double-Blind Method; Enzyme-Linked Immunosorbent Assay; Female; Follow-Up Studies; Heptanoic Acids; Hospitalization; Humans; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Infections; Leptin; Male; Middle Aged; Myocardial Infarction; Odds Ratio; Pravastatin; Pyrroles; Recurrence; Resistin; Retrospective Studies; Risk Factors; Survival Rate; Thrombolytic Therapy; United States

Peripheral inflammation induces transmigration of interleukin (IL)-1β-expressing neutrophils to the brain. We investigated the possibility that this presents a new route of immune-to-brain communication by assessing their role in sickness behaviors relevant for mood disorders. Mice treated with lipopolysaccharide (LPS) developed despair-like behavior, and administration of an anti-polymorphonuclear antibody abolished LPS-induced despair-like and asocial behaviors, which correlated with the levels of IL-1β expression in the brain. These behavioral changes were directly mediated by the energy-regulating hormone, leptin. Increasing the concentration of endogenous leptin during obesity exacerbated, whereas its neutralization using a specific antiserum attenuated sickness behaviors and importantly the neutrophil transmigrating process. Our results indicate a role for peripheral neutrophils in conveying inflammatory signals to the brain, which appears to be dependent on the energy status of the organism. This constitutes a novel mechanism of immune-to-brain communication relevant to mood disorders.

Topics: Animals; Brain; Cell Movement; Depression; Immunologic Factors; Infections; Interleukin-1beta; Leptin; Lipopolysaccharides; Male; Mice, Inbred C57BL; Neuroimmunomodulation; Neutrophils; Obesity

The effect leptin on fetal growth in healthy and infected newborns is not well known. This study is aimed at: 1) evaluating serum leptin concentration in full term and preterm, healthy and infected newborns, according to their gender, birth asphyxia, intrauterine and neonatal infections, and 2) assessing the correlation between serum leptin levels and anthropometric parameters among healthy and infected newborns.. The study involved 146 newborns: 73 full-term and 73 preterm, 86 male and 60 female, 56 healthy and 90 infected, aged from 2nd to 4th day of life. Anthropometric parameters, including: birth weight, length, head and chest circumference, and serum leptin concentration were measured in all the subjects. Intrauterine and neonatal infections were diagnosed by the standard criteria.. In this study, it was found that both healthy and infected, but full-term newborns had significantly higher mean leptin concentration than the premature ones (p<0.05). Statistically significant (p<0.05), positive correlations were found between serum leptin level and gestational age, birth weight, head and chest circumference, both in healthy, and in infected newborns.. Findings of this study suggest that the serum leptin concentration in full term newborns is higher than in the preterm ones, and in females it is higher than in males, 2) among both healthy and infected newborns, there is a positive, linear correlation between the serum leptin concentration and anthropometric parameters, 3) intrauterine and neonatal infections do not have a significant influence on serum leptin concentration. The role of leptin in fetal growth deserves further research.

Topics: Anthropometry; Birth Weight; Body Height; Factor Analysis, Statistical; Female; Gestational Age; Humans; Infant, Newborn; Infant, Newborn, Diseases; Infant, Premature; Infections; Leptin; Linear Models; Male; Pregnancy; Pregnancy Complications, Infectious; Risk Factors; Sex Factors; Term Birth

It is hypothesized that the genesis and spread of obesity is predetermined by genetic immunity to infections and subsequent interethnic genetic admixture. As in genetic immunity to infections, obesity is determined by a constitutional incongruence between relevant acting agents and their molecular targets. Because many hormones share their specific receptors with the acting molecules of infectious agents, mutant formation of a life-saving genetic resistance to infection could also create life-threatening immunity to relevant hormones. This kind of individual molecular constitution could spread in a population as a result of natural selection for genetic immunity to infections that had performed differently in ecologically distinct populations. Extraordinary diversity in the obesity course, manifestations and severity of specific affections and their sizes and focal disposition around the body, is created by the inter-ethnic mating of persons with different grades of hormone-receptor incongruence.

Topics: Gene Expression Regulation; Genetic Predisposition to Disease; Genetic Variation; Humans; Immune System; Infections; Leptin; Models, Biological; Models, Theoretical; Obesity; Selection, Genetic

Humoral mediators are potentially involved in the pathogenesis of postoperative complications following surgery. The aim of the present study is to evaluate the postoperative responses of circulating cytokines, chemokines, and stress hormones following liver resection, and their effects on postoperative infectious complications and organ dysfunction.. Perioperative plasma concentrations of interleukin (IL)-6, IL-10, IL-4, IL-8, macrophage chemoattractant protein (MCP)-1, cortisol, macrophage migration inhibitory factor (MIF), and leptin were measured by immunoassays in 128 consecutive patients undergoing liver resection.. Forty-three patients had postoperative infection and 11 had infection-related organ dysfunction. Plasma levels of all mediators except for IL-4 increased postoperatively. Postoperative levels of IL-6, IL-10, IL-8, MCP-1, cortisol, and leptin were significantly higher in patients with organ dysfunction than in those without organ dysfunction (P < 0.05). However, postoperative MIF levels were not affected by postoperative infection or organ dysfunction. Plasma levels of IL-6, IL-10, IL-8, and MCP-1 were positively correlated with operation time (P < 0.0001) or blood loss (P < 0.0001), and higher in patients with jaundiced liver (P < 0.05). In univariate logistic regression analyses, elevated IL-6, IL-10, IL-8, and MCP-1, advanced age, large volume of blood loss, long operation time, long hepatic ischemia time, and major liver resection were significantly correlated with postoperative infection (P < 0.05). In multivariate analyses, IL-6 and IL-10 were significant predisposing factors for postoperative infection (P < 0.05), and blood loss and IL-6 for organ dysfunction (P < 0.01).. These results suggest that IL-6, IL-10, IL-8, MCP-1, cortisol, and leptin are released after liver resection in response to surgical stress and correlated with postoperative infection and organ dysfunction, and that of these circulating mediators, IL-6 and IL-10, have a close relationship to the complications.

Topics: Adult; Aged; Aged, 80 and over; Biomarkers; Chemokine CCL2; Cytokines; Female; Humans; Hydrocortisone; Infections; Interleukin-10; Interleukin-4; Interleukin-6; Interleukin-8; Leptin; Linear Models; Liver Diseases; Macrophage Migration-Inhibitory Factors; Male; Middle Aged; Multiple Organ Failure; Postoperative Complications; Stress, Physiological; Treatment Outcome

The immune responses to many infections have long been known to share features with autoimmune responses. In particular, both types of response are typified by the enhanced reactivity of T helper 1 cells - with high levels of interleukin-2, interferon gamma and tumor necrosis factor alpha - and are accompanied often by organ-specific and/or systemic damage and the production of IgG. Paradoxically, the geographical distributions of incidence of infectious diseases and autoimmunity are complementary, rather than coincident. In less-developed societies, an epidemiological association between susceptibility to infection and malnutrition has been observed, whereas in affluent countries, an increased incidence of autoimmune diseases has been described. We suggest that these observations can be explained partly by taking into consideration the immune effects of the adipocyte-derived hormone leptin, which has been shown recently to act as a link between nutritional status and the immune response.

Topics: Adipose Tissue; Animals; Autoimmune Diseases; Autoimmunity; Disease Susceptibility; Female; Humans; Infections; Inflammation; Leptin; Male; Mice; Models, Immunological; Nutritional Status; Rats