Leptin potentiates IFN-gamma-induced expression of nitric oxide synthase and cyclo-oxygenase-2 in murine macrophage J774A.1

Leptin levels in childhood tuberculosis and its correlation with body mass index, IFN-γ, and TNF-α in an Indonesian population

BACKGROUND

Leptin plays a key role in the regulation of energy and inflammation in tuberculosis (TB). However, its correlation in children with TB remains unclear. Therefore, this study aimed to evaluate the correlations between body mass index, IFN-γ, TNF-α, and leptin levels in children with TB.

METHODS

This was a cross-sectional study of children aged 2-14 years with TB. Sputum examination, chest radiography, and tuberculin skin test findings and clinical symptoms were considered for TB diagnosis. Data on body weight; height; mid-upper arm circumference (MUAC); body mass index (BMI); food intake; and IFN-γ, TNF-α, and leptin levels were collected and analyzed.

RESULTS

Of the 64 diagnosed TB subjects, 2 subjects had positive bacteriological results. The median age was 6 (2-14) years, body weight was 17.7 (9.45-55) kg, height was 114 ± 21.46 cm, and Z score BMI was -0.85 ± 1.14 kg/m2. Malnourished was observed in 17.2% of the subjects. The median calorie intake was 1448.5 (676-4674) kcal, carbohydrate intake was 182.5 (63-558) g, protein intake was 57.9 (15.8-191.0) g, and fat intake was 81.6 (23.6-594.1) g. The median leptin level was 1.2 (0.2-59) ng/mL, IFN-γ was 2.5 (0.9-161) pg/mL, and TNF-α was 13.0 (5.7-356) pg/mL. Correlations were observed between leptin and MUAC (r = 0.251, p = 0.02), Z score (r = 0.453, p = 0.00), and IFN-γ (r = 0.295, p = 0.018).

CONCLUSION

There were positive correlations between BMI and leptin levels, whereas IFN-γ and MUAC showed weak correlations.

Myosteatosis as a prognostic factor of Mycobacterium avium complex pulmonary disease

Quantitative body composition affects the prognosis of patients with Mycobacterium avium complex pulmonary disease (MAC-PD). However, whether the qualitative body composition obtained indirectly through computed tomography (CT) affects their prognosis is debatable. We retrospectively analyzed patients with MAC-PD who underwent non-contrast CT at MAC-PD diagnosis. The cross-sectional area of the erector spinae muscle (ESM area), the Hounsfield unit of the erector spinae muscle (ESM HU), and the cross-sectional area of subcutaneous fat (SQF area) were measured at the level of the first lumbar vertebra. Myosteatosis were defined below the median value of ESM HU for each sex. Of 377 patients, 45 (11.9%) died during the follow-up. Patients who died were older and had a lower ratio of females (33.3%). In body compositions, SQF area and ESM HU were lower in the patients who died. In multivariable analysis, a low ESM HU was associated with increased mortality (ESM HU adjusted hazard ratio [aHR] 0.95, 95% confidence interval [CI] 0.93-0.97) through body composition. SQF area revealed protective effects in MAC-PD patients with body mass index ≥ 18.5 kg/m2 (aHR 0.98, 95% CI 0.95-1.00). In conclusion, the decrease in ESM HU, which indirectly reflects myosteatosis, is associated with mortality in patients with MAC-PD.

Leptin/obR signaling exacerbates obesity-related neutrophilic airway inflammation through inflammatory M1 macrophages

BACKGROUND

Obesity-related asthma is a kind of nonallergic asthma with excessive neutrophil infiltration in the airways. However, the underlying mechanisms have been poorly elucidated. Among the adipokines related to obesity, leptin is related to the inflammatory response. However, little is understood about how leptin acts on the leptin receptor (obR) in neutrophilic airway inflammation in obesity-associated asthma. We explored the inflammatory effects of leptin/obR signaling in an obesity-related neutrophilic airway inflammation mouse model.

METHODS

We established a neutrophilic airway inflammation mouse model using lipopolysaccharide (LPS)/ovalbumin (OVA) sensitization and OVA challenge (LPS + OVA/OVA) in lean, obese, or db/db (obR deficiency) female mice. Histopathological, bronchoalveolar lavage fluid (BALF) inflammatory cell, and lung inflammatory cytokine analyses were used to analyze airway inflammation severity. Western blotting, flow cytometry, reverse transcription-polymerase chain reaction (RT-PCR), and enzyme-linked immunosorbent assay (ELISA) were used to evaluate the underlying mechanisms. In vitro bone marrow-derived macrophage (BMDM) and bone marrow-derived neutrophil experiments were performed.

RESULTS

We found that the serum leptin level was higher in obese than in lean female mice. Compared to LPS/OVA + OVA-treated lean female mice, LPS/OVA + OVA-treated obese female mice had higher peribronchial inflammation levels, neutrophil counts, Th1/Th17-related inflammatory cytokine levels, M1 macrophage polarization levels, and long isoform obR activation, which could be decreased by the obR blockade (Allo-Aca) or obR deficiency, suggesting a critical role of leptin/obR signaling in the pathogenesis of obesity-related neutrophilic airway inflammation in female mice. In in vitro experiments, leptin synergized with LPS/IFN-γ to promote the phosphorylation of the long isoform obR and JNK/STAT3/AKT signaling pathway members to increase M1 macrophage polarization, which was reversed by Allo-Aca. Moreover, leptin/obR-mediated M1 macrophage activity significantly elevated CXCL2 production and neutrophil recruitment by regulating the JNK/STAT3/AKT pathways. In clinical studies, obese patients with asthma had higher serum leptin levels and M1 macrophage polarization levels in induced sputum than non-obese patients with asthma. Serum leptin levels were positively correlated with M1 macrophage polarization levels in patients with asthma.

CONCLUSIONS

Our results demonstrate leptin/obR signaling plays an important role in the pathogenesis of obesity-related neutrophilic airway inflammation in females by promoting M1 macrophage polarization.

Regulation of cardiovascular health and disease by visceral adipose tissue-derived metabolic hormones

Visceral adipose tissue (VAT) is a metabolic organ known to regulate fat mass, and glucose and nutrient homeostasis. VAT is an active endocrine gland that synthesizes and secretes numerous bioactive mediators called 'adipocytokines/adipokines' into systemic circulation. These adipocytokines act on organs of metabolic importance like the liver and skeletal muscle. Multiple preclinical and in vitro studies showed strong evidence of the roles of adipocytokines in the regulation of metabolic disorders like diabetes, obesity and insulin resistance. Adipocytokines, such as adiponectin and omentin, are anti-inflammatory and have been shown to prevent atherogenesis by increasing nitric oxide (NO) production by the endothelium, suppressing endothelium-derived inflammation and decreasing foam cell formation. By inhibiting differentiation of vascular smooth muscle cells (VSMC) into osteoblasts, adiponectin and omentin prevent vascular calcification. On the other hand, adipocytokines like leptin and resistin induce inflammation and endothelial dysfunction that leads to vasoconstriction. By promoting VSMC migration and proliferation, extracellular matrix degradation and inflammatory polarization of macrophages, leptin and resistin increase the risk of atherosclerotic plaque vulnerability and rupture. Additionally, the plasma concentrations of these adipocytokines alter in ageing, rendering older humans vulnerable to cardiovascular disease. The disturbances in the normal physiological concentrations of these adipocytokines secreted by VAT under pathological conditions impede the normal functions of various organs and affect cardiovascular health. These adipokines could be used for both diagnostic and therapeutic purposes in cardiovascular disease.

Inhibition of nitric oxide synthase or cystathionine gamma-lyase abolishes leptin-induced fever in male rats

Leptin is an adipokine that regulates energy balance and immune function. Peripheral leptin administration elicits prostaglandin E₂-dependent fever in rats. The gasotransmitters nitric oxide (NO) and hydrogen sulfide (H₂S) are also involved in lipopolysaccharide (LPS)-induced fever response. However, there is no data in the literature indicating if these gasotransmitters have a role in leptin-induced fever response. Here, we investigate the inhibition of NO and H₂S enzymes neuronal nitric oxide synthase (nNOS), inducible nitric oxide synthase (iNOS), and cystathionine γ-lyase (CSE) in leptin-induced fever response, respectively. Selective nNOS inhibitor 7-nitroindazole (7-NI), selective iNOS inhibitor aminoguanidine (AG), and CSE inhibitor dl-propargylglycine (PAG) were administered intraperitoneally (ip). Body temperature (Tb), food intake, and body mass were recorded in fasted male rats. Leptin (0.5 mg/kg ip) induced a significant increase in Tb, whereas AG (50 mg/kg ip), 7-NI (10 mg/kg ip), or PAG (50 mg/kg ip) caused no changes in Tb. AG, 7-NI, or PAG abolished leptin increase in Tb. Our results highlight the potential involvement of iNOS, nNOS, and CSE in leptin-induced febrile response without affecting anorexic response to leptin in fasted male rats 24 h after leptin injection. Interestingly, all the inhibitors alone had the same anorexic effect induced by leptin. These findings have implications for understanding the role of NO and H₂S in leptin-induced febrile response.

Obesity and Risk for Lymphoma: Possible Role of Leptin

Obesity, which is considered a pandemic due to its high prevalence, is a risk factor for many types of cancers, including lymphoma, through a variety of mechanisms by promoting an inflammatory state. Specifically, over the last few decades, obesity has been suggested not only to increase the risk of lymphoma but also to be associated with poor clinical outcomes and worse responses to different treatments for those diseases. Within the extensive range of proinflammatory mediators that adipose tissue releases, leptin has been demonstrated to be a key adipokine due to its pleotropic effects in many physiological systems and diseases. In this sense, different studies have analyzed leptin levels and leptin/leptin receptor expressions as a probable bridge between obesity and lymphomas. Since both obesity and lymphomas are prevalent pathophysiological conditions worldwide and their incidences have increased over the last few years, here we review the possible role of leptin as a promising proinflammatory mediator promoting lymphomas.

Acid external and internal environment exchange the Oreochromis niloticus tissue immune gene expression compared to the mouse macrophage polarization model

The water environment plays an important role in animal physiology. In this study, we sought to evaluate the effect of the acid environment on the Oreochromis niloticus (Nile tilapia) internal microenvironment immune response compare to the mouse macrophage model (J77A.1). The acid environment treated mouse macrophage J774A.1 model have shown that acidic treatment is able to polarize macrophages into M2-like macrophages via an increase in Ym1, Tgm2, Arg1, Fizz1, and IL-10 expression. Metabolic analysis of mouse macrophages (J774A.1) at pH 2 vs. pH 7 and pH 4 vs. pH 7 have been shown to promote the expression of intracellular acetylcholine, choline, prochlorperazine, L-leucine, and bisphenol A,2-amino-3-methylimidazo[4,5-f] quinolone metabolites in the M2-like macrophage. Immune gene expression of the O. niloticus spleen and liver treated at pH 2, 4, and 7 was shown to reduce TNF-α, IL-1 β, IL-8, and IL-12 expression compared to pH 7 treatment. Immune gene was induced in O. niloticus following culture at pH 5, 6, and 7 fresh water environment. Taken together, we found that the acid internal environment polarizes tissues into an M2 macrophage developmental microenvironment. However, if the external environment is acid, tissues are exposed to an M1 macrophage developmental microenvironment.

Disseminated cutaneous Mycobacterium haemophilum infection in a patient on infliximab for rheumatoid arthritis

Mycobacterium haemophilum is a rarely encountered pathogen that is difficult to identify given its unique growth requirements. It is most often seen in adult patients who are immunosuppressed due to advanced HIV or haematological malignancy. Our case highlights a typical presentation of an atypical pathogen in a patient with rheumatoid arthritis receiving anti-tumour necrosis factor therapy. This case represents an important patient population in whom this previously rare infection is increasingly common.

Inflammation in Metabolic Cardiomyopathy

Overlapping pandemics of lifestyle-related diseases pose a substantial threat to cardiovascular health. Apart from coronary artery disease, metabolic disturbances linked to obesity, insulin resistance and diabetes directly compromise myocardial structure and function through independent and shared mechanisms heavily involving inflammatory signals. Accumulating evidence indicates that metabolic dysregulation causes systemic inflammation, which in turn aggravates cardiovascular disease. Indeed, elevated systemic levels of pro-inflammatory cytokines and metabolic substrates induce an inflammatory state in different cardiac cells and lead to subcellular alterations thereby promoting maladaptive myocardial remodeling. At the cellular level, inflammation-induced oxidative stress, mitochondrial dysfunction, impaired calcium handling, and lipotoxicity contribute to cardiomyocyte hypertrophy and dysfunction, extracellular matrix accumulation and microvascular disease. In cardiometabolic patients, myocardial inflammation is maintained by innate immune cell activation mediated by pattern recognition receptors such as Toll-like receptor 4 (TLR4) and downstream activation of the NLRP3 inflammasome and NF-κB-dependent pathways. Chronic low-grade inflammation progressively alters metabolic processes in the heart, leading to a metabolic cardiomyopathy (MC) phenotype and eventually to heart failure with preserved ejection fraction (HFpEF). In accordance with preclinical data, observational studies consistently showed increased inflammatory markers and cardiometabolic features in patients with HFpEF. Future treatment approaches of MC may target inflammatory mediators as they are closely intertwined with cardiac nutrient metabolism. Here, we review current evidence on inflammatory processes involved in the development of MC and provide an overview of nutrient and cytokine-driven pro-inflammatory effects stratified by cell type.

Trajectory of leptin and leptin receptor in vertebrates: Structure, function and their regulation

The present review provides a comparative insight into structure, function and control of leptin system in fishes, herptiles, birds and mammals. In general, leptin acts as an anorexigenic hormone since its administration results in decrease of food intake in vertebrates. Nonetheless, functional paradox arises in fishes from contradictory observations on level of leptin during fasting and re-feeding. In addition, leptin is shown to modulate metabolic functions in fishes, reptiles, birds and mammals. Leptin also regulates reproductive and immune functions though more studies are warranted in non-mammalian vertebrates. The expression of leptin and its receptor is influenced by numerous factors including sex steroids, stress and stress-induced catecholamines and glucocorticoids though their effect in non-mammalian vertebrates is hard to be generalized due to limited studies.

TSP-1 (Thrombospondin-1) Deficiency Protects ApoE-/- Mice Against Leptin-Induced Atherosclerosis

OBJECTIVE

Hyperleptinemia, hallmark of obesity, is a putative pathophysiologic trigger for atherosclerosis. We previously reported a stimulatory effect of leptin on TSP-1 (thrombospondin-1) expression, a proatherogenic matricellular protein implicated in atherogenesis. However, a causal role of TSP-1 in leptin-driven atherosclerosis remains unknown. Approach and Results: Seventeen-weeks-old ApoE-/- and TSP-1-/-/ApoE-/- double knockout mice, on normocholesterolemic diet, were treated with or without murine recombinant leptin (5 µg/g bwt, IP) once daily for 3 weeks. Using aortic root morphometry and en face lesion assay, we found that TSP-1 deletion abrogated leptin-stimulated lipid-filled lesion burden, plaque area, and collagen accumulation in aortic roots of ApoE-/- mice, shown via Oil red O, hematoxylin and eosin, and Masson trichrome staining, respectively. Immunofluorescence microscopy of aortic roots showed that TSP-1 deficiency blocked leptin-induced inflammatory and smooth muscle cell abundance as well as cellular proliferation in ApoE-/- mice. Moreover, these effects were concomitant to changes in VLDL (very low-density lipoprotein)-triglyceride and HDL (high-density lipoprotein)-cholesterol levels. Immunoblotting further revealed reduced vimentin and pCREB (phospho-cyclic AMP response element-binding protein) accompanied with augmented smooth muscle-myosin heavy chain expression in aortic vessels of leptin-treated double knockout versus leptin-treated ApoE-/-; also confirmed in aortic smooth muscle cells from the mice genotypes, incubated ± leptin in vitro. Finally, TSP-1 deletion impeded plaque burden in leptin-treated ApoE-/- on western diet, independent of plasma lipid alterations.

CONCLUSIONS

The present study provides evidence for a protective effect of TSP-1 deletion on leptin-stimulated atherogenesis. Our findings suggest a regulatory role of TSP-1 on leptin-induced vascular smooth muscle cell phenotypic transition and inflammatory lesion invasion. Collectively, these results underscore TSP-1 as a potential target of leptin-induced vasculopathy.

Adipose Tissue Immunomodulation: A Novel Therapeutic Approach in Cardiovascular and Metabolic Diseases

Adipose tissue is a critical regulator of systemic metabolism and bodily homeostasis as it secretes a myriad of adipokines, including inflammatory and anti-inflammatory cytokines. As the main storage pool of lipids, subcutaneous and visceral adipose tissues undergo marked hypertrophy and hyperplasia in response to nutritional excess leading to hypoxia, adipokine dysregulation, and subsequent low-grade inflammation that is characterized by increased infiltration and activation of innate and adaptive immune cells. The specific localization, physiology, susceptibility to inflammation and the heterogeneity of the inflammatory cell population of each adipose depot are unique and thus dictate the possible complications of adipose tissue chronic inflammation. Several lines of evidence link visceral and particularly perivascular, pericardial, and perirenal adipose tissue inflammation to the development of metabolic syndrome, insulin resistance, type 2 diabetes and cardiovascular diseases. In addition to the implication of the immune system in the regulation of adipose tissue function, adipose tissue immune components are pivotal in detrimental or otherwise favorable adipose tissue remodeling and thermogenesis. Adipose tissue resident and infiltrating immune cells undergo metabolic and morphological adaptation based on the systemic energy status and thus a better comprehension of the metabolic regulation of immune cells in adipose tissues is pivotal to address complications of chronic adipose tissue inflammation. In this review, we discuss the role of adipose innate and adaptive immune cells across various physiological and pathophysiological states that pertain to the development or progression of cardiovascular diseases associated with metabolic disorders. Understanding such mechanisms allows for the exploitation of the adipose tissue-immune system crosstalk, exploring how the adipose immune system might be targeted as a strategy to treat cardiovascular derangements associated with metabolic dysfunctions.

Positive and negative cooperativity of TNF and Interferon-γ in regulating synovial fibroblast function and B cell survival in fibroblast/B cell co-cultures

Synovial fibroblasts (SF) were reported to produce B cell activating factor (BAFF) in response to stimulation with interferon-γ (IFN-γ) or tumor necrosis factor (TNF). However, the influence of these pro-inflammatory cytokines on other receptors/ligands of the TNF superfamily or associated cytokine receptors in SF has not been investigated yet. Here we show the differential regulation of BAFF (CD257), Fn14 (CD266), TACI (CD267), BAFF-R (CD268), BCMA (CD269), CD40 ligand (CD40L, CD154), IFN-γR (CD119), Leptin receptor (ObR, CD295), VCAM-1 (CD106) and membrane TGF-β in isolated SF and the impact of IFN-γ/TNF co-incubation on proliferation, IL-6 and IL-8 production. In addition, the impact of differentially stimulated SF on B cell survival in co-cultures was assessed. Surface cytokines and cytokine receptors were detected by flow cytometry. Soluble cytokine receptors and cytokines were quantified by ELISA. Proliferation was assessed by cell titer blue. Murine B cell survival in fibroblast/ B cell co-cultures was determined by annexin V/propidium iodide staining and flow cytometry. IFN-γ together with TNF synergistically and significantly increased the cell surface levels of BAFF, Fn14, TACI, BAFF-R, BCMA, CD40L, ObR and IFN-γR in rheumatoid arthritis SF after 72 h incubation. Soluble BAFF was only induced by IFN-γ and inhibited by TNF. Addition of TWEAK had no influence on proliferation or IL-8 production but decreased TNF-induced IL-6 production, whereas APRIL, BAFF and leptin did not modulate TNF or TNF/IFN-γ-induced proliferation or cytokine production. Proliferation was increased by TNF and further enhanced by the addition of IFN-γ. In co-culture experiments, SF stimulated with TNF/IFN but not TNF or IFN-γ alone increased shedding of VCAM-1 and expression of membrane TGFβ, which was associated with reduced survival of murine B cells. IFN-γ and TNF regulate the expression of TNF family member cytokines and associated receptors. Ligation of IFN-γR and Fn14 under pro-inflammatory conditions modulated IL-6/IL-8 production and proliferation. In B cell/SF co-cultures, the combination of TNF/IFN reduced B cell survival possibly via enhanced VCAM-1 shedding and/or increased TGF-β production. IFN-γ is necessary for the observed effects on B cell survival and SF cytokine production and emphasizes its anti-inflammatory role in rheumatoid arthritis.

Leptin in Tumor Microenvironment

Leptin is a hormone that plays a major role as mediator of long-term regulation of energy balance, suppressing food intake, and stimulating weight loss. More recently, important physiological roles other than controlling appetite and energy expenditure have been suggested for leptin, including neuroendocrine, reparative, reproductive, and immune functions. These emerging peripheral roles let hypothesize that leptin can modulate also cancer progression. Indeed, many studies have demonstrated that elevated chronic serum concentrations of leptin, frequently seen in obese subjects, represent a stimulatory signal for tumor growth. Current knowledge indicates that also different non-tumoral cells resident in tumor microenvironment may respond to leptin creating a favorable soil for cancer cells. In addition, leptin is produced also within the tumor microenvironment creating the possibility for paracrine and autocrine action. In this review, we describe the main mechanisms that regulate peripheral leptin availability and how leptin can shape tumor microenvironment.

Functional Relationship between Leptin and Nitric Oxide in Metabolism

Leptin, the product of the ob gene, was originally described as a satiety factor, playing a crucial role in the control of body weight. Nevertheless, the wide distribution of leptin receptors in peripheral tissues supports that leptin exerts pleiotropic biological effects, consisting of the modulation of numerous processes including thermogenesis, reproduction, angiogenesis, hematopoiesis, osteogenesis, neuroendocrine, and immune functions as well as arterial pressure control. Nitric oxide (NO) is a free radical synthesized from L-arginine by the action of the NO synthase (NOS) enzyme. Three NOS isoforms have been identified: the neuronal NOS (nNOS) and endothelial NOS (eNOS) constitutive isoforms, and the inducible NOS (iNOS). NO mediates multiple biological effects in a variety of physiological systems such as energy balance, blood pressure, reproduction, immune response, or reproduction. Leptin and NO on their own participate in multiple common physiological processes, with a functional relationship between both factors having been identified. The present review describes the functional relationship between leptin and NO in different physiological processes.

The Role of Adipose Tissue in the Pathogenesis and Therapeutic Outcomes of Inflammatory Bowel Disease

Though historically regarded as an inert energy store, adipose tissue is a complex endocrine organ, which is increasingly implicated in the pathogenesis of inflammatory bowel disease (IBD). Accumulating evidence points to visceral adipose tissue and specifically to its mesenteric component, or “creeping fat” as impacting on the disease course through its immunomodulatory properties. On the one hand, mesenteric fat acts as a physical barrier to inflammation and is involved in controlling host immune response to translocation of gut bacteria. On the other hand, however, there exists a strong link between visceral fat and complicated course of the disease with unfavorable therapeutic outcomes. Furthermore, “creeping fat” appears to play different roles in different IBD phenotypes, with the greatest pathogenetic contribution probably to an ileal form of Crohn’s disease. In this review, we summarize and discuss the existing literature on the subject and identify high-priority areas for future research. It may be that a better understanding of the role of mesenteric fat in IBD will determine new therapeutic targets and translate into improved clinical outcomes.

Leptin Functions in Infectious Diseases

Leptin, a pleiotropic protein has long been recognized to play an important role in the regulation of energy homeostasis, metabolism, neuroendocrine function, and other physiological functions through its effects on the central nervous system (CNS) and peripheral tissues. Leptin is secreted by adipose tissue and encoded by the obese (ob) gene. Leptin acts as a central mediator which regulates immunity as well as nutrition. Importantly, leptin can modulate both innate and adaptive immune responses. Leptin deficiency/resistance is associated with dysregulation of cytokine production, increased susceptibility toward infectious diseases, autoimmune disorders, malnutrition and inflammatory responses. Malnutrition induces a state of immunodeficiency and an inclination to death from communicable diseases. Infectious diseases are the disease of poor who invariably suffer from malnutrition that could result from reduced serum leptin levels. Thus, leptin has been placed at the center of many interrelated functions in various pathogenic conditions, such as bacterial, viruses and parasitic infections. We review herein, the recent advances on the role of leptin in malnutrition in pathogenesis of infectious diseases with a particular emphasis on parasitic diseases such as Leishmaniasis, Trypanosomiasis, Amoebiasis, and Malaria.

Kobophenol A Isolated from Roots of Caragana sinica (Buc'hoz) Rehder Exhibits Anti-inflammatory Activity by Regulating NF-κB Nuclear Translocation in J774A.1 Cells

Kobophenol A (KPA) is a biologically active natural compound isolated from the roots of Caragana sinica (Buc'hoz) Rehder (C. sinica). However, the anti-inflammatory effects of KPA have not been reported. This study aims to find out whether KPA isolated from roots of C. sinica can act as a potential substance on inflammation and analyze the molecular mechanism using the lipopolysaccharide (LPS)-stimulated J774 A.1 macrophage cell line. We showed that KPA treatment significantly suppressed the production of nitric oxide (NO) by inhibiting inducible nitric oxide synthase (iNOS) expression in a dose-dependent manner without cytotoxicity. In the KPA also inhibited pro-inflammatory cytokine gene expression and production, such as interleukin-1β (IL-1β) and interleukin-6 (IL-6) in LPS-stimulated J774 A.1 cells. As continuing study on the mechanisms involved, we confirmed that these effects of KPA were related to the inhibition of nuclear factor-κB (NF-κB) pathway including the suppression of IκB kinase α/β (IKKα/β) phosphorylation and translocation of NF-κB into the nucleus. Taken together, the present study is the first to demonstrate that KPA isolated from C. sinica suppresses the expression of inflammatory mediators and cytokines by inhibiting NF-κB nuclear translocation in LPS-stimulated J774 A.1 macrophages. KPA may be a potential candidate for the treatment of inflammatory diseases in the future.

Chronic hyper-leptinemia induces insulin signaling disruption in adipocytes: Implications of NOS2

Leptin, following its discovery, has developed a formidable interest in the scientific community to delineate its contribution towards overall metabolic homeostasis. Contradictory reports have been published on leptin administration effects on whole body insulin sensitivity. Following late reports, we surveyed human serum leptin levels along with other metabolic parameters including BMI and HOMA-IR. We found a positive correlation between leptin levels and insulin resistance parameters. Considering the presence of the long form of leptin receptor on adipocytes, we explored the effects of chronic physiological hyper-leptinemic exposure on adipocyte insulin sensitivity. Chronic leptin (50ng/ml) treatment in 3T3-L1 adipocytes decreased insulin-induced phosphorylation of nodal insulin signaling proteins along with reduced glucose uptake. Metabolic flux studies indicated mitochondrial dysfunction and reduced oxygen consumption rate. Leptin treatment also increased both cellular and mitochondrial superoxide levels concomitant to increased expression of nitric oxide synthase-2 (NOS2). Further, pharmacological depletion of NOS2 reversed leptin mediated effects on insulin signaling. In-vivo implantation of leptin osmotic pumps in C57BL/6 mice also decreased insulin responsiveness. Interestingly, these effects were lacking in NOS2 knockout strain. In conclusion, our studies put forward a potential link between leptin and adipocyte insulin responsiveness in an NOS2 dependent manner.

Serum and exhaled breath condensate leptin levels in asthmatic and obesity children: a pilot study

BACKGROUND

Recent studies have highlighted the possible involvement of leptin in inflammation. The leptin receptor is also expressed by alveolar macrophages, T lymphocytes and bronchial epitelial cells, suggesting a possible role in the cascade of airway inflammation.

OBJECTIVES

The aim of the study was to evaluate the levels of leptin in exhaled breath condensate (EBC) from asthmatic, normal- and overweight children, in relationship with airway inflammation.

METHODS

15 asthmatic non-obese children, 15 healthy non-asthmatic non-obese children, 11 obese children with asthma (OA) and 20 obese children without asthma (ONA) were enrolled. Body impedance of body weight, EBC collection, FeNO, spirometry and a blood sampling for serum leptin were assessed.

RESULTS

Leptin EBC levels were significantly higher (3.9 ng ml^-1 ± 1.3) in overweight children than those obese with asthma (3.6 ng ml^-1 ± 1.6; p = 0.97), non-owerweight asthmatics (2.2 ng ml^-1 ± 1.2; p < 0.0001) and in healthy children (0.9 ng ml^-1 ± 0.6; p < 0.001). Leptin EBC levels in asthmatic children were significantly higher than in healthy children (p = 0.05). Leptin serum levels were significantly higher in the overweight children compared with the asthmatics (12.7 ng ml^-1 ± 13.2; p < 0.001) and the healthy group (11.1 ng ml^-1 ± 11.2; p < 0.001). We observed a significant correlation between EBC-leptin levels and the serum-leptin levels (p = 0.001). No correlations were found between EBC-leptin levels, FeNO and lung function.

CONCLUSIONS

This study shows that leptin is measurable in EBC in children and that EBC-leptin levels are significantly higher in the obese subjects and in asthmatic ones compared with healthy subjects. Leptin may therefore represent a non-invasive marker of non-specific airway inflammation in children.

Immunomodulatory effects of anesthetics in obese patients

Anesthesia and surgery have an impact on inflammatory responses, which influences perioperative homeostasis. Inhalational and intravenous anesthesia can alter immune-system homeostasis through multiple processes that include activation of immune cells (such as monocytes, neutrophils, and specific tissue macrophages) with release of pro- or anti-inflammatory interleukins, upregulation of cell adhesion molecules, and overproduction of oxidative radicals. The response depends on the timing of anesthesia, anesthetic agents used, and mechanisms involved in the development of inflammation or immunosuppression. Obese patients are at increased risk for chronic diseases and may have the metabolic syndrome, which features insulin resistance and chronic low-grade inflammation. Evidence has shown that obesity has adverse impacts on surgical outcome, and that immune cells play an important role in this process. Understanding the effects of anesthetics on immune-system cells in obese patients is important to support proper selection of anesthetic agents, which may affect postoperative outcomes. This review article aims to integrate current knowledge regarding the effects of commonly used anesthetic agents on the lungs and immune response with the underlying immunology of obesity. Additionally, it identifies knowledge gaps for future research to guide optimal selection of anesthetic agents for obese patients from an immunomodulatory standpoint.

Obesity-associated digestive cancers: A review of mechanisms and interventions

The prevalence of obesity has steadily increased over the past few decades. Previous studies suggest that obesity is an oncogenic factor and that over 20% of all cancers are obesity-related. Among such cancers, digestive system malignancies (including esophageal adenocarcinomas, colorectal cancers, and cancers of the gastric cardia, liver, and pancreas) are reported most frequently. While the 5-year survival rates of cancers of the breast and prostate are 90%, that rate is only 45% for digestive cancers. In this review, the mechanisms of obesity-associated digestive cancers are discussed, with an emphasis on obesity-related gene mutations, insulin and insulin-like growth factor signaling pathways, chronic inflammation, and altered adipokine levels. Evidence that these factors often function interdependently rather than independently in carcinogenesis is presented. Recommended interventions that may reduce the burden of obesity-associated digestive cancers, such as participation in physical activity, diet modulation, and calorie restriction, are also described.

Treatment of obese asthma in a mouse model by simvastatin is associated with improving dyslipidemia and decreasing leptin level

Obesity can cause or worsen asthma. Compared with common asthma, obese asthma is difficult to control. Statins are effective serum cholesterol-lowering agents in clinical practice, and they also have anti-inflammatory properties, which in theory are potentially beneficial in asthma. Many studies have shown that simvastatin has good therapeutic effect in animal models of asthma. However, the therapeutic effect and action mechanism of simvastatin for obese asthma remain unclear. Leptin, a satiety hormone, is in positive correlation with total body fat mass and may also play a significant role in the pathogenesis of asthma. In this study, we use the method of high-fat diet and ovalbumin (OVA) sensitization and challenge to establish the mouse model of obesity and asthma, and find that obese asthmatic mice has higher levels of glucose, lipid and leptin in serum, and neutrophil percentage in bronchoalveolar lavage fluid (BALF), and more severe airway inflammation and structural changes in lung tissues than non-obese asthmatic mice, and respond poorly to dexamethasone treatment, which indicates that obese asthma might belong to steroid-resistant (SR) asthma. Simvastatin treatment reduces the levels of glucose, lipid, leptin and neutrophil percentage, and improves airway inflammation and remodeling, which can be as a potential therapeutic target used in the treatment of obese asthma in humans. Correlation analysis shows that there is positive correlation between neutrophil percentage and serum leptin/cholesterol level, which indicates that the therapeutic efficacy of simvastatin on obese asthma might be associated with improving dyslipidemia and decreasing leptin level.

Leptin-Induced JAK/STAT Signaling and Cancer Growth

Growth factor and cytokine signaling can influence the development of several cancer types. One of the key players in the development of cancer is the Janus kinas (JAK) signal transducer of activators of transcription (STAT) signaling pathway. The majority of growth factors and cytokine interactions with their membrane-bound receptors trigger JAK-STAT activation. The influential relationship between obesity and cancer is a fact. However, there is a complex sequence of events contributing to the regulation of this mechanism to promote tumor growth, yet to be fully elucidated. The JAK-STAT pathway is influenced by obesity-associated changes that have been shown to impact cancer growth and progression. This intricate process is highly regulated by a vast array of adipokines and cytokines that exert their pleiotropic effects on cancer cells to enhance metastasis to distant target sites. Leptin is a cytokine, or more precise, an adipokine secreted mainly by adipose tissue that requires JAK-STAT activation to exert its biological functions. Leptin is the central regulator of energy balance and appetite. Leptin binding to its receptor OB-R in turn activates JAK-STAT, which induces proliferation, angiogenesis, and anti-apoptotic events in normal cells and malignant cells expressing the receptor. Leptin also induces crosstalk with Notch and IL-1 (NILCO), which involves other angiogenic factors promoting tumor growth. Therefore, the existence of multiple novel classes of therapeutics that target the JAK/STAT pathway has significant clinical implications. Then, the identification of the signaling networks and factors that regulate the obesity-cancer link to which potential pharmacologic interventions can be implemented to inhibit tumor growth and metastasis. In this review, we will discuss the specific relationship between leptin-JAK-STAT signaling and cancer.

Leptin augments recruitment of IRF-1 and CREB to thrombospondin-1 gene promoter in vascular smooth muscle cells in vitro

We previously reported that high pathophysiological concentrations of leptin, the adipocyte-secreted peptide, upregulate the expression of a potent proatherogenic matricellular protein, thrombospondin-1 (TSP-1), in vascular smooth muscle cells. Moreover, this regulation was found to occur at the level of transcription; however, the underlying molecular mechanisms remain unknown. The goal of the present study was to investigate the specific transcriptional mechanisms that mediate upregulation of TSP-1 expression by leptin. Primary human aortic smooth muscle cell cultures were transiently transfected with different TSP-1 gene (THBS1) promoter-linked luciferase reporter constructs, and luciferase activity in response to leptin (100 ng/ml) was assessed. We identified a long THBS1 promoter (-1270/+750) fragment with specific leptin response elements that are required for increased TSP-1 transcription by leptin. Promoter analyses, protein/DNA array and gel shift assays demonstrated activation and association of transcription factors, interferon regulatory factor-1 (IRF-1) and cAMP response element-binding protein (CREB), to the distal fragment of the THBS1 promoter in response to leptin. Supershift, chromatin immunoprecipitation, and coimmunoprecipitation assays revealed formation of a single complex between IRF-1 and CREB in response to leptin; importantly, recruitment of this complex to the THBS1 promoter mediated leptin-induced TSP-1 transcription. Finally, binding sequence decoy oligomer and site-directed mutagenesis revealed that regulatory elements for both IRF-1 (-1019 to -1016) and CREB (-1198 to -1195), specific to the distal THBS1 promoter, were required for leptin-induced TSP-1 transcription. Taken together, these findings demonstrate that leptin promotes a cooperative association between IRF-1 and CREB on the THBS1 promoter driving TSP-1 transcription in vascular smooth muscle cells.

The role of adipokines in chronic inflammation

Adipose tissue has traditionally been defined as connective tissue that stores excess calories in the form of triacylglycerol. However, the physiologic functions attributed to adipose tissue are expanding, and it is now well established that adipose tissue is an endocrine gland. Among the endocrine factors elaborated by adipose tissue are the adipokines; hormones, similar in structure to cytokines, produced by adipose tissue in response to changes in adipocyte triacylglycerol storage and local and systemic inflammation. They inform the host regarding long-term energy storage and have a profound influence on reproductive function, blood pressure regulation, energy homeostasis, the immune response, and many other physiologic processes. The adipokines possess pro- and anti-inflammatory properties and play a critical role in integrating systemic metabolism with immune function. In calorie restriction and starvation, proinflammatory adipokines decline and anti-inflammatory adipokines increase, which informs the host of energy deficits and contributes to the suppression of immune function. In individuals with normal metabolic status, there is a balance of pro- and anti-inflammatory adipokines. This balance shifts to favor proinflammatory mediators as adipose tissue expands during the development of obesity. As a consequence, the proinflammatory status of adipose tissue contributes to a chronic low-grade state of inflammation and metabolic disorders associated with obesity. These disturbances are associated with an increased risk of metabolic disease, type 2 diabetes, cardiovascular disease, and many other pathological conditions. This review focuses on the impact of energy homeostasis on the adipokines in immune function.

Serum Leptin Levels in Patients with Allergic Rhinitis

OBJECTIVE: To investigate the serum leptin levels in patients with allergic rhinitis during the symptomatic period.

STUDY DESIGN AND SETTING: A randomized, prospective study was performed on 26 adult patients with allergic rhinitis and 20 control subjects with similar age, sex and body mass index in a tertiary otolaryngology center.

RESULTS: Leptin levels were 28.8 ± 14.1 ng/mL in the patients with allergic rhinitis, and 20.8 ± 13.5 ng/mL in the control group respectively. The difference between the groups was statistically significant (p = 0.04).

CONCLUSION: Serum leptin levels were found to be significantly higher in patients with allergic rhinitis in symptomatic period.

SIGNIFICANCE: Apart from its primary role in the regulation of body weight and energy expenditure, leptin may have a role in the inflammatory process of the allergic rhinitis.

Differential Role of Leptin as an Immunomodulator in Controlling Visceral Leishmaniasis in Normal and Leptin-Deficient Mice

Visceral leishmaniasis (VL) is caused by the protozoan parasite Leishmania donovani. There are no vaccines and available drugs against leishmaniasis are toxic. Immunomodulators that specifically boost the anti-microbial activities of the immune cells could alleviate several of these limitations. Therefore, finding novel immunomodulators for VL therapy is a pressing need. This study is aimed to evaluate the immunomodulatory role of leptin, an adipocyte-derived hormone capable of regulating the immune response, in L. donovani-infected mice. We observed that recombinant leptin treatment reduced splenic parasite burden compared with non-treated infected normal mice. Decrease in parasite burden correlated with an induction of innate immune response in antigen-presenting cells that showed an increase in nitric oxide, enhanced pro-inflammatory cytokine (interferon gamma [IFNγ], interleukin12 [IL]12, and IL1β) response in the splenocytes, indicating host-protecting Th1 response mediated by leptin. Moreover, in infected normal mice, leptin treatment induced IFNγ production from both CD4⁺ and CD8⁺ T cells, compared with non-treated infected mice. Alternatively, leptin-deficient (Ob/Ob) mice had higher splenic and liver parasite burden compared with the infected normal mice. However, leptin treatment failed to reduce the splenic parasite burden and improve a host-protective cytokine response in these mice. In addition, in contrast to dendritic cells (DCs) from a normal mouse, Ob/Ob mouse–derived DCs showed a defect in the induction of innate immune response on Leishmania infection that could not be reversed by leptin treatment. Therefore, our findings reveal that leptin has a differential immunomodulatory effect in controlling VL in normal and Ob/Ob mice.

Menopause, obesity and inflammation: interactive risk factors for Alzheimer's disease

Alzheimer’s disease (AD) is a multifactorial neurodegenerative disorder, the development of which is regulated by several environmental and genetic risk factors. Two factors theorized to contribute to the initiation and/or progression of AD pathogenesis are age-related increases in inflammation and obesity. These factors may be particularly problematic in women. The onset of menopause in mid-life elevates the vulnerability of women to AD, an increased risk that is likely associated with the depletion of estrogens. Menopause is also linked with an abundance of additional changes, including increased central adiposity and inflammation. Here, we review the current literature to explore the interactions between obesity, inflammation, menopause and AD.

Leptin activation of mTOR pathway in intestinal epithelial cell triggers lipid droplet formation, cytokine production and increased cell proliferation

Accumulating evidence suggests that obesity and enhanced inflammatory reactions are predisposing conditions for developing colon cancer. Obesity is associated with high levels of circulating leptin. Leptin is an adipocytokine that is secreted by adipose tissue and modulates immune response and inflammation. Lipid droplets (LD) are organelles involved in lipid metabolism and production of inflammatory mediators, and increased numbers of LD were observed in human colon cancer. Leptin induces the formation of LD in macrophages in a PI3K/mTOR pathway-dependent manner. Moreover, the mTOR is a serine/threonine kinase that plays a key role in cellular growth and is frequently altered in tumors. We therefore investigated the role of leptin in the modulation of mTOR pathway and regulation of lipid metabolism and inflammatory phenotype in intestinal epithelial cells (IEC-6 cells). We show that leptin promotes a dose- and time-dependent enhancement of LD formation. The biogenesis of LD was accompanied by enhanced CXCL1/CINC-1, CCL2/MCP-1 and TGF-β production and increased COX-2 expression in these cells. We demonstrated that leptin-induced increased phosphorylation of STAT3 and AKT and a dose and time-dependent mTORC activation with enhanced phosphorilation of the downstream protein P70S6K protein. Pre-treatment with rapamycin significantly inhibited leptin effects in LD formation, COX-2 and TGF-β production in IEC-6 cells. Moreover, leptin was able to stimulate the proliferation of epithelial cells on a mTOR-dependent manner. We conclude that leptin regulates lipid metabolism, cytokine production and proliferation of intestinal cells through a mechanism largely dependent on activation of the mTOR pathway, thus suggesting that leptin-induced mTOR activation may contribute to the obesity-related enhanced susceptibility to colon carcinoma.

Establishment and characterization of DB-1: a leptin receptor-deficient murine macrophage cell line

Metabolic and immune mediators activate many of the same signal transduction pathways. Therefore, molecules that regulate metabolism often affect immune responses. Leptin is an adipokine that exemplifies this interplay. Leptin is the body's major nutritional status sensor, but it also plays a key role in immune system regulation. To provide an in vitro tool to investigate the link between leptin and innate immunity, we immortalized and characterized a leptin receptor-deficient macrophage cell line, DB-1. The cell line was created using bone marrow cells from leptin receptor-deficient mice. Bone marrow cells were differentiated into macrophages by culturing them with recombinant mouse macrophage colony stimulating factor, and passaged when confluent for 6 months. The cells spontaneously immortalized at approximately passage 20. Cells were cloned twice by limiting dilution cloning prior to characterization. The macrophage cell line is diploid and grows at a linear rate for 4-5 days before reaching the growth plateau. The cells are MAC-2 and F4/80 positive and have phagocytic activity similar to primary macrophages from wild-type and leptin receptor-deficient mice. DB-1 cells were responsive to stimulation with interferon-γ as measured by increase in Nos2 transcript levels. In addition, DB-1 macrophages are not responsive to the chemotactic signaling of adipocyte conditioned media nor leptin when compared to primary WT macrophages. We believe that DB-1 cells provide a dependable tool to study the role of leptin or the leptin receptor in obesity-associated inflammation and immune system dysregulation.

Risk of mycobacterial infections associated with rheumatoid arthritis in Ontario, Canada

OBJECTIVE

Patients with rheumatoid arthritis (RA) are at increased risk of TB. Little is known about the risk of nontuberculous mycobacteria (NTM) disease in these patients. We sought to ascertain the rate of NTM infection and TB in all residents of Ontario, Canada, with and without RA.

METHODS

In a cohort study, all Ontarians aged ≥ 15 years in January 2001 were followed until December 2010. Individuals with RA were identified using a validated algorithm to search hospitalization and physician billing claims. We linked Public Health Ontario Laboratory data to identify all cases of laboratory-confirmed TB and NTM disease. Analysis was performed using Cox proportional hazards regression.

RESULTS

We identified 113,558 Ontarians with RA and 9,760,075 Ontarians without RA. Relative to the non-RA group, adjusted hazard ratios (HRs) and 95% CIs for TB (1.92, [1.50-2.47]) and NTM disease (2.07, [1.84-2.32]) demonstrated increased risks in the RA group. Among those with RA, per 100,000 person-years, NTM disease (HR, 41.6; 95% CI, 37.1-46.5) was more common than TB (HR, 8.5; 95% CI, 6.5-10.8). After full adjustment, people with RA who developed NTM disease were 1.81 times as likely to die than uninfected people with RA.

CONCLUSIONS

Mycobacterial infections are more common in Ontarians with RA, with NTM disease more likely than TB. NTM disease is associated with an increased risk of death in patients with RA. Given the rising rates of NTM disease worldwide, determining whether this risk is due to the use of immunosuppressive medications vs RA itself is an important objective for future research.

A serum component mediates food restriction-induced growth attenuation

Proper nutrition in terms of calories and essential food components is required to maximize longitudinal growth in children. Our previous study showed that prepubertal male rats subjected to 10 days of 40% food restriction (RES) exhibited a dramatic reduction in weight and epiphyseal growth plate height, as well as changes in gene expression and microRNAs (miRNAs) in the epiphyseal growth plate. These findings reversed rapidly after renewal of the regular food supply (catch-up [CU]). To further elucidate the mechanisms underlying the nutrition-growth association, serum collected from the RES and CU rats and control rats fed ad libitum (AL) was added to the culture medium of the chondrocyte cell line ATDC5 (instead of fetal calf serum). Serum from the RES group induced a reduction in cell viability (25%, P < .05) concomitant with an increase in cell differentiation compared with that for the AL group serum. The most interesting observation, in our opinion, was the significant reduction in the expression of specific miRNAs, including the chondro-specific miR-140. These effects were not observed for serum from refed (CU) rats. Serum levels of IGF-I, leptin, and fibroblast growth factor 21 were reduced by food restriction. The addition of IGF-I and leptin to the culture increased cell viability, whereas fibroblast growth factor 21 reduced it, suggesting the involvement of IGF-I, leptin, and possibly other still unidentified serum factors in chondrocyte cell growth. In conclusion, specific miRNAs respond to nutritional cues, and these effects are mediated by serum-borne factors. These results may promote the development of superior interventions for children with malnutrition and growth abnormalities.

Effects of weight loss and pharmacotherapy on inflammatory markers of cardiovascular disease

Obesity is currently an epidemic, and the prevalence of cardiovascular risk factors is increasing dramatically as a result. Visceral adiposity is correlated with a proinflammatory and prothrombotic state that is believed to promote atherosclerosis and acute coronary syndromes. This article will review clinical trials on the effects of weight loss and pharmacotherapy on obesity associated inflammatory and thrombotic markers linked with cardiovascular disease.

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.

The effects of obesity on skeletal muscle regeneration

Obesity and metabolic disorders such as type 2 diabetes mellitus are accompanied by increased lipid deposition in adipose and non-adipose tissues including liver, pancreas, heart and skeletal muscle. Recent publications report impaired regenerative capacity of skeletal muscle following injury in obese mice. Although muscle regeneration has not been thoroughly studied in obese and type 2 diabetic humans and mechanisms leading to decreased muscle regeneration in obesity remain elusive, the initial findings point to the possibility that muscle satellite cell function is compromised under conditions of lipid overload. Elevated toxic lipid metabolites and increased pro-inflammatory cytokines as well as insulin and leptin resistance that occur in obese animals may contribute to decreased regenerative capacity of skeletal muscle. In addition, obesity-associated alterations in the metabolic state of skeletal muscle fibers and satellite cells may directly impair the potential for satellite cell-mediated repair. Here we discuss recent studies that expand our understanding of how obesity negatively impacts skeletal muscle maintenance and regeneration.

Melatonin inhibits visfatin-induced inducible nitric oxide synthase expression and nitric oxide production in macrophages

Aberrant expression of inducible nitric oxide synthase (iNOS) in macrophages, which has been reported to be suppressed by melatonin, has an important contribution in the development of pathological inflammation. Visfatin, an adipokine, regulates the expression of various inflammatory factors, leading to inflammation; however, the influence of visfatin on iNOS-driven processes in macrophages is unclear. Here, we report the assessment of the role of visfatin in the regulation of iNOS gene expression in macrophages. Our data show that the levels of iNOS protein in peritoneal macrophages as well as nitric oxide (NO) in blood plasma were significantly lower after lipopolysaccharide treatment in visfatin(+/-) mice than those in the WT mice. In addition, visfatin increases iNOS mRNA and protein levels in RAW 264.7 cells, along with increasing production of NO. The enhancement of iNOS expression was prevented by treating the cells with inhibitors of the Janus kinase 2/signal transducers and activators of transcription 3 (JAK2/STAT3), nuclear factor (NF)-κB, extracellular signal-regulated kinase 1/2, and c-Jun N-terminal kinase pathways. Our results also show that visfatin-induced iNOS expression and NO production were significantly inhibited by melatonin, an effect that was closely associated with a reduction in phosphorylated JAK2/STAT3 levels and with the inhibition of p65 translocation into nucleus. In conclusion, our data show, for the first time, that melatonin suppresses visfatin-induced iNOS upregulation in macrophages by inhibiting the STAT3 and NF-κB pathways. Moreover, our data suggest that melatonin could be therapeutically useful for attenuating the development of visfatin-iNOS axis-associated diseases.

Ghrelin-leptin network influences serum chitinase 3-like protein 1 (YKL-40) levels in obese prepubertal children

OBJECTIVE

This study aimed to investigate any possible interactions between hormonal regulators of weight gain and markers of subclinical inflammation in childhood obesity. Forty-one obese prepubertal children and 41 age- and gender-matched lean controls were included. Children were classified as obese or non-obese according to international age- and gender-specific body mass index (BMI) cutoff points defined by the International Obesity Task Force to define childhood obesity. Anthropometric measurements, serum insulin, chitinase 3-like protein (YKL-40), ghrelin and leptin levels as well as plasma glucose in the fasting state were determined.

RESULTS

Obese children as compared with controls had higher YKL-40 (50.7±15.2 vs 41.0±10.5 ng/ml, p=0.003), higher leptin (33.8±16.0 vs 9.7±7.5 ng/ml, p<0.001) and lower ghrelin serum levels (871.4±368.0 vs 1417.6±387.3 pg/ml, p<0.001). The obese children with ghrelin levels above median (43.8±10.2 ng/ml) as compared to those with ghrelin below median (57.2±16.6 ng/ml) presented lower serum YKL-40 levels (p=0.009), indicating more severe inflammation with lower levels of ghrelin. By contrast, although the obese children with leptin levels above median (49.7±16.3 ng/ml) presented lower serum YKL-40 levels as compared to those with leptin levels below median (51.6±14.6 ng/ml), this difference did not reach the level of statistical significance (p=0.726). Moreover, serum YKL-40 levels were significantly correlated with ghrelin (r=-0.359, p=0.014) but not with leptin levels (r=0.169, p=0.261). A significant negative correlation between ghrelin and leptin levels was also found (r=-0.276, p=0.041). These findings remained unchanged for obese, when analyses were done separately, whereas the significance of correlations was lost for non-obese subjects.

CONCLUSIONS

Ghrelin-leptin network had an impact on serum YKL-40 levels in obese prepubertal children; upregulation of YKL-40 secretion seems to be a consequence of reduced ghrelin rather than elevated leptin concentrations.

Eicosanoids and adipokines in breast cancer: from molecular mechanisms to clinical considerations

Chronic inflammation is one of the foremost risk factors for different types of malignancies, including breast cancer. Additional risk factors of this pathology in postmenopausal women are weight gain, obesity, estrogen secretion, and an imbalance in the production of adipokines, such as leptin and adiponectin. Various signaling products of transcription factor, nuclear factor-kappaB, in particular inflammatory eicosanoids, reactive oxygen species (ROS), and cytokines, are thought to be involved in chronic inflammation-induced cancer. Together, these key components have an influence on inflammatory reactions in malignant tissue damage when their levels are deregulated endogenously. Prostaglandins (PGs) are well recognized in inflammation and cancer, and they are solely biosynthesized through cyclooxygenases (COXs) from arachidonic acid. Concurrently, ROS give rise to bioactive isoprostanes from arachidonic acid precursors that are also involved in acute and chronic inflammation, but their specific characteristics in breast cancer are less demonstrated. Higher aromatase activity, a cytochrome P-450 enzyme, is intimately connected to tumor growth in the breast through estrogen synthesis, and is interrelated to COXs that catalyze the formation of both inflammatory and anti-inflammatory PGs such as PGE(2), PGF(2α), PGD(2), and PGJ(2) synchronously under the influence of specific mediators and downstream enzymes. Some of the latter compounds upsurge the intracellular cyclic adenosine monophosphate concentration and appear to be associated with estrogen synthesis. This review discusses the role of COX- and ROS-catalyzed eicosanoids and adipokines in breast cancer, and therefore ranges from their molecular mechanisms to clinical aspects to understand the impact of inflammation.

Patients with nontuberculous mycobacterial lung disease exhibit unique body and immune phenotypes

RATIONALE

Among patients with nontuberculous mycobacterial lung disease is a subset of previously healthy women with a slender body morphotype, often with scoliosis and/or pectus excavatum. We hypothesize that unidentified factors predispose these individuals to pulmonary nontuberculous mycobacterial disease.

OBJECTIVES

To compare body morphotype, serum adipokine levels, and whole-blood cytokine responses of patients with pulmonary nontuberculous mycobacteria (pNTM) with contemporary control subjects who are well matched demographically.

METHODS

We enrolled 103 patients with pNTM and 101 uninfected control subjects of similar demographics. Body mass index and body fat were quantified. All patients with pNTM and a subset of control subjects were evaluated for scoliosis and pectus excavatum. Serum leptin and adiponectin were measured. Specific cytokines important to host-defense against mycobacteria were measured in whole blood before and after stimulation.

MEASUREMENTS AND MAIN RESULTS

Patients with pNTM and control subjects were well matched for age, gender, and race. Patients with pNTM had significantly lower body mass index and body fat and were significantly taller than control subjects. Scoliosis and pectus excavatum were significantly more prevalent in patients with pNTM. The normal relationships between the adipokines and body fat were lost in the patients with pNTM, a novel finding. IFN-γ and IL-10 levels were significantly suppressed in stimulated whole blood of patients with pNTM.

CONCLUSIONS

This is the first study to comprehensively compare body morphotype, adipokines, and cytokine responses between patients with NTM lung disease and demographically matched controls. Our findings suggest a novel, predisposing immunophenotype that should be mechanistically defined.

Leptin, adiponectin, and ghrelin levels in female patients with asthma during stable and exacerbation periods

OBJECTIVE

The mechanisms underlying the relationship between obesity and asthma have not been fully established. Data in the literature suggest that adipose tissue-derived hormones may be implicated. However, no definite conclusions regarding the role of leptin and adiponectin with asthma are available. No studies have examined the role of ghrelin in asthma.

METHODS

We assessed the circulating concentrations of leptin, adiponectin, and ghrelin in 32 postmenopausal stable asthma patients, 37 female asthmatics during exacerbations and 8 weeks later, and 22 controls. We examined the relationship between the three peptides and indexes of pulmonary function, airway inflammation, and atopy.

RESULTS

Stable asthma patients exhibited higher leptin and lower ghrelin concentrations compared with controls. Patients with severe asthma had higher leptin and lower adiponectin levels versus patients with mild to moderate asthma. Both leptin concentrations and leptin/adiponectin ratio served as markers for discriminating asthma patients from controls on the one hand, and severe from mild to moderate asthmatics on the other. Leptin levels were inversely correlated with both FEV(1)/FVC and FEF(25-75) in patients with mild to moderate asthma. Atopic asthma patients had higher leptin concentrations than nonatopic asthma patients. There was a positive correlation between serum leptin and total IgE levels in atopic asthmatics. Finally, serum leptin levels and leptin/adiponectin ratio were significantly increased during asthma exacerbations, while adiponectin and ghrelin levels were significantly decreased.

CONCLUSION

Our findings suggest that leptin, adiponectin, and ghrelin may play a significant role in the pathogenesis of asthma during both stable state and asthma exacerbation, independent of obesity.

Effects of enriched environment on COX-2, leptin and eicosanoids in a mouse model of breast cancer

Cyclooxygenase-2 (COX-2) and adipokines have been implicated in breast cancer. This study investigated a possible link between COX-2 and adipokines in the development of mammary tumors. A model of environmental enrichment (EE), known to reduce tumor growth was used for a syngeneic murine model of mammary carcinoma. 3-week-old, female C57BL/6 mice were housed in standard environment (SE) or EE cages for 9 weeks and transplanted orthotopically with syngeneic EO771 adenocarcinoma cells into the right inguinal mammary fat pad. EE housing influenced mammary gland development with a decrease in COX-2 expressing cells and enhanced side-branching and advanced development of alveolar structures of the mammary gland. Tumor volume and weight were decreased in EE housed mice and were associated with a reduction in COX-2 and Ki67 levels, and an increase in caspase-3 levels. In tumors of SE mice, high COX-2 expression correlated with enhanced leptin detection. Non-tumor-bearing EE mice showed a significant increase in adiponectin levels but no change in those of leptin, F(2)-isoprostanes, PGF(2α), IL-6, TNF-α, PAI-1, and MCP-1 levels. Both tumor-bearing groups (SE and EE housing) had increased resistin, IL-6, TNF-α, PAI-1 and MCP-1 levels irrespective of the different housing environment demonstrating higher inflammatory response due to the presence of the tumor. This study demonstrates that EE housing influenced normal mammary gland development and inhibited mammary tumor growth resulting in a marked decrease in intratumoral COX-2 activity and an increase in the plasma ratio of adiponectin/leptin levels.

Adverse neuro-immune-endocrine interactions in patients with active tuberculosis

The nervous, endocrine and immune systems play a crucial role in maintaining homeostasis and interact with each other for a successful defensive strategy against injurious agents. However, the situation is different in long-term diseases with marked inflammation, in which defensive mechanisms become altered. In the case of tuberculosis (TB), this is highlighted by several facts: an imbalance of plasma immune and endocrine mediators, that results in an adverse environment for mounting an adequate response against mycobacteria and controlling inflammation; the demonstration that dehidroepiandrosterone (DHEA) secretion by a human adrenal cell line can be inhibited by culture supernatants from Mycobacterium tuberculosis-stimulated peripheral blood mononuclear cells - PBMC - of TB patients, with this effect being partly reverted when neutralizing transforming growth factor-β in such supernantants; the in vitro effects of adrenal steroids on the specific immune response of PBMC from TB patients, that is a cortisol inhibition of mycobacterial antigen-driven lymphoproliferation and interferon-γ production as well as a suppression of TGF-β production in DHEA-treated PBMC; and lastly the demonstration that immune and endocrine compounds participating in the regulation of energy sources and immune activity correlated with the consumption state of TB patients. Collectively, immune-endocrine disturbances of TB patients are involved in critical components of disease pathology with implications in the impaired clinical status and unfavorable disease outcome. This article is part of a Special Issue entitled 'Neuroinflammation in neurodegeneration and neurodysfunction'.

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.

Upregulation of thrombospondin-1 expression by leptin in vascular smooth muscle cells via JAK2- and MAPK-dependent pathways

Hyperleptinemia, characteristic of diabetes and a hallmark feature of human obesity, contributes to the increased risk of atherosclerotic complications. However, molecular mechanisms mediating leptin-induced atherogenesis and gene expression in vascular cells remain incompletely understood. Accumulating evidence documents a critical role of a potent antiangiogenic and proatherogenic matricellular protein, thrombospondin-1 (TSP-1), in atherosclerosis. Although previous studies reported elevated TSP-1 levels in both diabetic and obese patients and rodent models, there is no direct information on TSP-1 expression in vascular cells in response to leptin. In the present study, we show that leptin upregulates TSP-1 expression in cultured human aortic smooth muscle cells (HASMC) in vitro, and this increase occurs at the level of transcription, revealed by mRNA stability and TSP-1 promoter-reporter assays. Utilizing specific pharmacological inhibitors and siRNA approaches, we demonstrate that upregulation of TSP-1 expression by leptin is mediated by JAK2/ERK/JNK-dependent mechanisms. Furthermore, we report that while ERK and JNK are required for both the constitutive and leptin-induced expression of TSP-1, JAK-2 appears to be specifically involved in leptin-mediated TSP-1 upregulation. Finally, we found that increased HASMC migration and proliferation in response to leptin is significantly inhibited by a TSP-1 blocking antibody, thereby revealing the physiological significance of leptin-TSP-1 crosstalk. Taken together, these findings demonstrate, for the first time, that leptin has a direct regulatory effect on TSP-1 expression in HASMCs, underscoring a novel role of TSP-1 in hyperleptinemia-induced atherosclerotic complications.

Differential effects of energy balance on experimentally-induced colitis

AIM: To characterize the influence of diet-induced changes in body fat on colitis severity in SMAD3-/- mice.

METHODS: SMAD3-/- mice (6-8 wk of age) were randomly assigned to receive a calorie restricted (30% of control; CR), control (CON), or high fat (HF) diet for 20 wk and were gavaged with sterile broth or with Helicobacter hepaticus (H. hepaticus) to induce colitis. Four weeks after infection, mice were sacrificed and the cecum and colons were processed for histological evaluation.

RESULTS: Dietary treatment significantly influenced body composition prior to infection (P < 0.05), with CR mice having less (14% ± 2%) and HF-fed mice more body fat (32% ± 7%) compared to controls (22% ± 4%). Differences in body composition were associated with alterations in plasma levels of leptin (HF > CON > CR) and adiponectin (CON > HF ≥ CR) (P < 0.05). There were no significant differences in colitis scores between CON and HF-fed mice 4 wk post-infection. Consistent with this, differences in proliferation and inflammation markers (COX-2, iNOS), and infiltrating cell types (CD3⁺ T lymphocytes, macrophages) were not observed. Unexpectedly, only 40% of CR mice survived infection with H. hepaticus, with mortality observed as early as 1 wk following induction of colitis.

CONCLUSION: Increased adiposity does not influence colitis severity in SMAD3-/- mice. Importantly, caloric restriction negatively impacts survival following pathogen challenge, potentially due to an impaired immune response.

A multifaceted analysis of immune-endocrine-metabolic alterations in patients with pulmonary tuberculosis

Our study investigated the circulating levels of factors involved in immune-inflammatory-endocrine-metabolic responses in patients with tuberculosis with the aim of uncovering a relation between certain immune and hormonal patterns, their clinical status and in vitro immune response. The concentration of leptin, adiponectin, IL-6, IL-1β, ghrelin, C-reactive protein (CRP), cortisol and dehydroepiandrosterone (DHEA), and the in vitro immune response (lymphoproliferation and IFN-γ production) was evaluated in 53 patients with active untreated tuberculosis, 27 household contacts and 25 healthy controls, without significant age- or sex-related differences. Patients had a lower body mass index (BMI), reduced levels of leptin and DHEA, and increased concentrations of CRP, IL-6, cortisol, IL-1β and nearly significant adiponectin values than household contacts and controls. Within tuberculosis patients the BMI and leptin levels were positively correlated and decreased with increasing disease severity, whereas higher concentrations of IL-6, CRP, IL-1β, cortisol, and ghrelin were seen in cases with moderate to severe tuberculosis. Household contacts had lower DHEA and higher IL-6 levels than controls. Group classification by means of discriminant analysis and the k-nearest neighbor method showed that tuberculosis patients were clearly different from the other groups, having higher levels of CRP and lower DHEA concentration and BMI. Furthermore, plasma leptin levels were positively associated with the basal in vitro IFN-γ production and the ConA-driven proliferation of cells from tuberculosis patients. Present alterations in the communication between the neuro-endocrine and immune systems in tuberculosis may contribute to disease worsening.