Alveolar macrophage activation and an emphysema-like phenotype in adiponectin-deficient mice

The association between adipokines and pulmonary diseases: a mendelian randomization study

BACKGROUND

The role of adipokines in the development of lung diseases is significant, yet their specific relationship with different lung diseases remains unclear.

METHODS

In our research, we analyzed genetic variations associated with adipokines and various lung conditions such as interstitial lung disease, chronic obstructive pulmonary disease, asthma, lung cancer, sleep apnea, pneumonia, and tuberculosis, using data from public genome-wide studies. We employed Mendelian randomization techniques, including inverse variance weighting, weighted median, and MR-Egger regression methods, and conducted sensitivity checks to validate our findings.

RESULTS

A study using the FinnGen database, which included 198,955 participants, identified 13 SNPs associated with adiponectin. Notably, adiponectin was found to significantly reduce the risk of interstitial lung disease and idiopathic pulmonary fibrosis. However, little evidence was found to establish a direct cause-effect relationship between the six adipokines and several other lung conditions, including sarcoidosis, asthma, chronic obstructive pulmonary disease, lung cancer, tuberculosis, pneumonia, and sleep apnea syndrome.

CONCLUSION

This study reveals a reverse link between adiponectin levels and the likelihood of interstitial lung disease, including idiopathic pulmonary fibrosis.

Isthmin-1 attenuates allergic Asthma by stimulating adiponectin expression and alveolar macrophage efferocytosis in mice

BACKGROUND

Allergic asthma is a common respiratory disease that significantly impacts human health. Through in silico analysis of human lung RNASeq, we found that asthmatic lungs display lower levels of Isthmin-1 (ISM1) expression than healthy lungs. ISM1 is an endogenous anti-inflammatory protein that is highly expressed in mouse lungs and bronchial epithelial cells, playing a crucial role in maintaining lung homeostasis. However, how ISM1 influences asthma remains unclear. This study aims to investigate the potential involvement of ISM1 in allergic airway inflammation and uncover the underlying mechanisms.

METHODS

We investigated the pivotal role of ISM1 in airway inflammation using an ISM1 knockout mouse line (ISM1-/-) and challenged them with house dust mite (HDM) extract to induce allergic-like airway/lung inflammation. To examine the impact of ISM1 deficiency, we analyzed the infiltration of immune cells into the lungs and cytokine levels in bronchoalveolar lavage fluid (BALF) using flow cytometry and multiplex ELISA, respectively. Furthermore, we examined the therapeutic potential of ISM1 by administering recombinant ISM1 (rISM1) via the intratracheal route to rescue the effects of ISM1 reduction in HDM-challenged mice. RNA-Seq, western blot, and fluorescence microscopy techniques were subsequently used to elucidate the underlying mechanisms.

RESULTS

ISM1-/- mice showed a pronounced worsening of allergic airway inflammation and hyperresponsiveness upon HDM challenge. The heightened inflammation in ISM1-/- mice correlated with enhanced lung cell necroptosis, as indicated by higher pMLKL expression. Intratracheal delivery of rISM1 significantly reduced the number of eosinophils in BALF and goblet cell hyperplasia. Mechanistically, ISM1 stimulates adiponectin secretion by type 2 alveolar epithelial cells partially through the GRP78 receptor and enhances adiponectin-facilitated apoptotic cell clearance via alveolar macrophage efferocytosis. Reduced adiponectin expression under ISM1 deficiency also contributed to intensified necroptosis, prolonged inflammation, and heightened severity of airway hyperresponsiveness.

CONCLUSIONS

This study revealed for the first time that ISM1 functions to restrain airway hyperresponsiveness to HDM-triggered allergic-like airway/lung inflammation in mice, consistent with its persistent downregulation in human asthma. Direct administration of rISM1 into the airway alleviates airway inflammation and promotes immune cell clearance, likely by stimulating airway adiponectin production. These findings suggest that ISM1 has therapeutic potential for allergic asthma.

Linking Adiposity to Interstitial Lung Disease: The Role of the Dysfunctional Adipocyte and Inflammation

Adipose tissue has functions beyond its principal functions in energy storage, including endocrine and immune functions. When faced with a surplus of energy, the functions of adipose tissue expand by mechanisms that can be both adaptive and detrimental. These detrimental adipose tissue functions can alter normal hormonal signaling and promote local and systemic inflammation with wide-ranging consequences. Although the mechanisms by which adipose tissue triggers metabolic dysfunction and local inflammation have been well described, little is known about the relationship between adiposity and the pathogenesis of chronic lung conditions, such as interstitial lung disease (ILD). In this review, we detail the conditions and mechanisms by which adipose tissue becomes dysfunctional and relate this dysfunction to inflammatory changes observed in various forms of ILD. Finally, we review the existing basic and clinical science literature linking adiposity to ILD, highlighting the need for additional research on the mechanisms of adipocyte-mediated inflammation in ILD and its clinical implications.

Regulation of lung inflammation by adiponectin

Adiponectin is an insulin sensitizing hormone that also plays a role in the regulation of inflammation. Although adiponectin can exert pro-inflammatory effects, more studies have reported anti-inflammatory effects, even in non-adipose tissues such as the lung. Obesity is considered an inflammatory disease, is a risk factor for lung diseases, and is associated with decreased levels of plasma adiponectin. The results of recent studies have suggested that adiponectin exerts anti-inflammatory activity in chronic obstructive pulmonary disease, asthma and invasive fungal infection. The signaling receptors of adiponectin, AdipoR1 and AdipoR2, are expressed by epithelial cells, endothelial cells, and immune cells in the lung. In this mini-review, we discuss the anti-inflammatory mechanisms of adiponectin in lung cells and tissues.

Herbal medicine for the treatment of obesity-associated asthma: a comprehensive review

Obesity is fast growing as a global pandemic and is associated with numerous comorbidities like cardiovascular disease, hypertension, diabetes, gastroesophageal reflux disease, sleep disorders, nephropathy, neuropathy, as well as asthma. Studies stated that obese asthmatic subjects suffer from an increased risk of asthma, and encounter severe symptoms due to a number of pathophysiology. It is very vital to understand the copious relationship between obesity and asthma, however, a clear and pinpoint pathogenesis underlying the association between obesity and asthma is scarce. There is a plethora of obesity-asthma etiologies reported viz., increased circulating pro-inflammatory adipokines like leptin, resistin, and decreased anti-inflammatory adipokines like adiponectin, depletion of ROS controller Nrf2/HO-1 axis, nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3 (NLRP3) associated macrophage polarization, hypertrophy of WAT, activation of Notch signaling pathway, and dysregulated melanocortin pathway reported, however, there is a very limited number of reports that interrelates these pathophysiologies. Due to the underlying complex pathophysiologies exaggerated by obese conditions, obese asthmatics respond poorly to anti-asthmatic drugs. The poor response towards anti-asthmatic drugs may be due to the anti-asthmatics approach only that ignores the anti-obesity target. So, aiming only at the conventional anti-asthmatic targets in obese-asthmatics may prove to be futile until and unless treatment is directed towards ameliorating obesity pathogenesis for a holistic approach towards amelioration of obesity-associated asthma. Herbal medicines for obesity as well as obesity-associated comorbidities are fast becoming safer and more effective alternatives to conventional drugs due to their multitargeted approach with fewer adverse effects. Although, herbal medicines are widely used for obesity-associated comorbidities, however, a limited number of herbal medicines have been scientifically validated and reported against obesity-associated asthma. Notable among them are quercetin, curcumin, geraniol, resveratrol, β-Caryophyllene, celastrol, tomatidine to name a few. In view of this, there is a dire need for a comprehensive review that may summarize the role of bioactive phytoconstituents from different sources like plants, marine as well as essential oils in terms of their therapeutic mechanisms. So, this review aims to critically discuss the therapeutic role of herbal medicine in the form of bioactive phytoconstituents against obesity-associated asthma available in the scientific literature to date.

Maternal BMI and allergy in children until 3 years of age (JECS)

Background

Maternal prepregnancy body mass index (BMI) may influence allergic diseases in the children who are the product of those pregnancies.

Objective

The purpose of our study was to investigate the association between mothers' prepregnancy BMI and the risk of physician-diagnosed asthma, food allergy (FA), and atopic dermatitis (AD) in their children during the first 3 years of life.

Methods

Data on mothers' prepregnancy BMI and physician-diagnosed asthma, FA, and AD in their children until the age of 3 years were obtained from the Japan Environment and Children's Study, a nationwide birth cohort study that has recruited 103,099 pregnant women between 2011 and 2014. Logistic regression analysis was used to analyze the results.

Results

We analyzed 67,204 mother-child pairs with available information on physician-diagnosed allergic diseases. The risk of asthma was significantly higher in children born to overweight mothers (adjusted OR [aOR] =1.17 [95% CI = 1.07-1.28]) and obese mothers (aOR = 1.28 [95% CI = 1.08-1.50]), whereas the risk of FA, cow's milk allergy, and egg allergy decreased significantly in children born to overweight mothers (aOR = 0.84 [95% CI = 0.76-0.92]; aOR = 0.78 [95% CI = 0.64-0.93]; and aOR = 0.83 [95% CI = 0.74-0.94]) and obese mothers (aOR = 0.81 [95% CI = 0.67-0.97]; aOR = 0.58 [95% CI = 0.36-0.87]; and aOR = 0.73 [95% CI = 0.56-0.93]) compared with in children born to normal weight mothers, respectively. Associations between AD and maternal BMI were not detected.

Conclusion

Our study showed that an increase in mothers' prepregnancy BMI was associated with an increase in asthma prevalence and a decrease in FA prevalence in their children. Further studies are needed to reveal the mechanisms associated with maternal BMI and pediatric allergic diseases.

Adiponectin ameliorates hyperoxia-induced lung endothelial dysfunction and promotes angiogenesis in neonatal mice

BACKGROUND

Bronchopulmonary dysplasia (BPD) is a common respiratory disease of preterm infants. Lower circulatory/intrapulmonary levels of the adipokine, adiponectin (APN), occur in premature and small-for-gestational-age infants and at saccular/alveolar stages of lung development in the newborn rat. However, the role of low intrapulmonary APN during hyperoxia exposure in developing lungs is unknown.

METHODS

We test the hypothesis that treatment of hyperoxia-exposed newborn mice with recombinant APN protein attenuates the BPD phenotype characterized by inflammation, impaired alveolarization, and dysregulated vascularization. We used developmentally appropriate in vitro and in vivo BPD modeling systems as well as human lung tissue.

RESULTS

We observed reduced levels of intrapulmonary APN in experimental BPD mice and human BPD lungs. APN-deficient (APN^-/-) newborn mice exposed to moderate (60% O₂) hyperoxia showed a worse BPD pulmonary phenotype (inflammation, enhanced endothelial dysfunction, impaired pulmonary vasculature, and alveolar simplification) as compared to wild-type (WT) mice. Treatment of hyperoxia-exposed newborn WT mice with recombinant APN protein attenuated the BPD phenotype (diminished inflammation, decreased pulmonary vascular injury, and improved pulmonary alveolarization) and improved pulmonary function tests.

CONCLUSIONS

Low intrapulmonary APN is associated with disruption of lung development during hyperoxia exposure, while recombinant APN protein attenuates the BPD pulmonary phenotype.

IMPACT

Intrapulmonary APN levels were significantly decreased in lungs of experimental BPD mice and human BPD lung tissue at various stages of BPD development. Correlative data from human lung samples with decreased APN levels were associated with increased lung adhesion markers (intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and E-selectin). Decreased APN levels were associated with endothelial dysfunction and moderate BPD phenotype in APN-deficient, as compared to WT, experimental BPD mice. WT experimental BPD mice treated with recombinant APN protein had an improved pulmonary structural and functional phenotype. Exogenous APN may be considered as a potential therapeutic agent to prevent BPD.

Roles of estrogens, estrogen-like compounds, and endocrine disruptors in adipocytes

Women are subject to constitutional changes after menopause, which increases conditions and diseases prone to cardiovascular risks such as obesity and diabetes mellitus. Both estrogens and androgens influence the individual's metabolic mechanism, which controls the fat distribution and the hypothalamic organization of the regulatory centers of hunger and satiety. While androgens tend to accumulate fat in the splanchnic and the visceral region with an increase in cardiovascular risk, estrogens generate more subcutaneous and extremity distribution of adipose tissue. The absence of estrogen during menopause seems to be the main factor that gives rise to the greater predisposition of women to suffer cardiovascular alterations. However, the mechanisms by which estrogens regulate the energy condition of people are not recognized. Estrogens have several mechanisms of action, which mainly include the modification of specific receptors that belong to the steroid receptor superfamily. The alpha estrogen receptors (ERα) and the beta receptors (ERβ) have a fundamental role in the metabolic control of the individual, with a very characteristic corporal distribution that exerts an influence on the metabolism of lipids and glucose. Despite the significant amount of knowledge in this field, many of the regulatory mechanisms exerted by estrogens and ER continue to be clarified. This review will discuss the role of estrogens and their receptors on the central regulation of caloric expenditure and the influence they exert on the differentiation and function of adipocytes. Furthermore, chemical substances with a hormonal activity that cause endocrine disruption with affectation on estrogen receptors will be considered. Finally, the different medical therapies for the vasomotor manifestations of menopause and their role in reducing obesity, diabetes, and cardiovascular risk will be analyzed.

High-fat Western diet consumption exacerbates silica-induced pulmonary inflammation and fibrosis

Consumption of a high-fat Western diet (HFWD) contributes to obesity, disrupted adipose endocrine function, and development of metabolic dysfunction (MetDys). Impaired lung function, pulmonary hypertension, and asthma are all associated with MetDys. Over 35% of adults in the U.S. have MetDys, yet interactions between MetDys and hazardous occupational inhalation exposures are largely unknown. Occupational silica-inhalation leads to chronic lung inflammation, progressive fibrosis, and significant respiratory morbidity and mortality. In this study, we aim to determine the potential of HFWD-consumption to alter silica-induced inflammatory responses in the lung. Six-wk old male F344 rats fed a high fat Western diet (HFWD; 45 kcal % fat, sucrose 22.2% by weight) to induce MetDys, or standard rat chow (STD, controls) for 16 wk were subsequently exposed to silica (6 h/d, 5 d/wk, 39 d; Min-U-Sil 5®, 15 mg/m³) or filtered air; animals remained on their assigned diet for the study duration. Indices of lung inflammation and histopathologic assessment of lung tissue were quantified at 0, 4, and 8 wk after cessation of exposure. Combined HFWD+silica exposure increased bronchoalveolar lavage (BAL) total cells, leukocytes, and BAL lactate dehydrogenase compared to STD+silica exposure controls at all timepoints. HFWD+silica exposure increased BAL proinflammatory cytokines at 4 and 8 wk compared to STD+silica exposure. At 8 wk, histopathological analysis confirmed that alveolitis, epithelial cell hypertrophy and hyperplasia, lipoproteinosis, fibrosis, bronchoalveolar lymphoid hyperplasia and granulomas were exacerbated in the HFWD+silica-exposed group compared to STD+silica-exposed controls. Our results suggest an increased susceptibility to silica-induced lung disease caused by HFWD consumption.

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HFWD exacerbates silica (SIL)-induced lung injury at 8 wk post-exposure.

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HFWD+SIL increases BAL cells and LDH compared to STD+SIL.

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HFWD+SIL increases BAL proinflammatory cytokines compared to STD+SIL.

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Histopathology confirms exacerbated lung injury HFWD+silica treatment.

Adiponectin Inhibits the Production of TNF-α, IL-6 and Chemokines by Human Lung Macrophages

Background: Obesity is associated with an elevated risk of severe respiratory infections and inflammatory lung diseases. The objectives were to investigate 1) the production of adiponectin by human lung explants, 2) the expression of the adiponectin receptors AdipoR1 and AdipoR2 by human lung macrophages (LMs), and 3) the impact of recombinant human adiponectin and a small-molecule APN receptor agonist (AdipoRon) on LMs activation. Material and methods: Human parenchyma explants and LMs were isolated from patients operated for carcinoma. The LMs were cultured with recombinant adiponectin or AdipoRon and stimulated with lipopolysaccharide (10 ng ml^-1), poly (I:C) (10 µg ml^-1) or interleukin (IL)-4 (10 ng ml^-1) for 24 h. Cytokines or adiponectin, released by explants or LMs, were measured using ELISAs. The mRNA levels of AdipoR1 and AdipoR2 were determined using real-time quantitative PCR. AdipoRs expression was also assessed with confocal microscopy. Results: Adiponectin was released by lung explants at a level negatively correlated with the donor's body mass index. AdipoR1 and AdipoR2 were both expressed in LMs. Adiponectin (3-30 µg ml^-1) and AdipoRon (25-50 μM) markedly inhibited the LPS- and poly (I:C)-induced release of Tumor Necrosis Factor-α, IL-6 and chemokines (CCL3, CCL4, CCL5, CXCL1, CXCL8, CXCL10) and the IL-4-induced release of chemokines (CCL13, CCL17, CCL22) in a concentration-dependent manner. Recombinant adiponectin produced in mammalian cells (lacking low molecular weight isoforms) had no effects on LMs. Conclusion and implications: The low-molecular-weight isoforms of adiponectin and AdipoRon have an anti-inflammatory activity in the lung environment. Targeting adiponectin receptors may constitute a new means of controlling airways inflammation.

Adiponectin and Asthma: Knowns, Unknowns and Controversies

Adiponectin is an adipokine associated with the healthy obese phenotype. Adiponectin increases insulin sensitivity and has cardio and vascular protection actions. Studies related to adiponectin, a modulator of the innate and acquired immunity response, have suggested a role of this molecule in asthma. Studies based on various asthma animal models and on the key cells involved in the allergic response have provided important insights about this relation. Some of them indicated protection and others reversed the balance towards negative effects. Many of them described the cellular pathways activated by adiponectin, which are potentially beneficial for asthma prevention or for reduction in the risk of exacerbations. However, conclusive proofs about their efficiency still need to be provided. In this article, we will, briefly, present the general actions of adiponectin and the epidemiological studies supporting the relation with asthma. The main focus of the current review is on the mechanisms of adiponectin and the impact on the pathobiology of asthma. From this perspective, we will provide arguments for and against the positive influence of this molecule in asthma, also indicating the controversies and sketching out the potential directions of research to complete the picture.

Does fetal leptin and adiponectin influence children's lung function and risk of wheeze?

Adipocytokines, which are secreted during fetal development by both mothers and fetuses, may influence fetal lung development, but little human data are available. We used data from the HOME Study to investigate the associations of cord blood adipocytokine concentrations with children's lung forced expiratory volume (FEV1; N = 160) and their risk of wheeze (N = 281). We measured umbilical cord serum adipocytokine concentrations using enzyme-linked immunosorbent assays and FEV1 using a portable spirometer at ages 4 and 5 to calculate the percent predicted FEV1 (%FEV1). Parents completed standardized questionnaires of their child's wheeze symptoms every 6 months from birth to age 5, then again at ages 6 and 8. We used multivariable linear mixed models and modified Poisson regression with generalized estimating equations to estimate associations of adipocytokine concentrations (log2-transformed) with children's %FEV1 and the risk of wheeze, respectively, adjusting for sociodemographic, perinatal, and child factors. Cord serum leptin was not associated with children's %FEV1. Higher cord serum adiponectin concentrations were associated with higher %FEV1 in girls (β = 3.1, 95% confidence interval [CI]: 0.6, 5.6), but not in boys (β = -1.3, 95% CI: -5.9, 3.3) (sex × adiponectin p-value = 0.05). Higher leptin was associated with lower risk of wheeze in girls (RR = 0.74, 95% CI: 0.66, 0.84), but not boys (RR = 0.87, 95% CI: 0.69, 1.11) (sex × leptin p-value = 0.01). In contrast, higher adiponectin concentrations were associated with lower risk of wheeze (RR = 0.84, 95% CI: 0.73, 0.96) in both boys and girls. These data suggest that fetal adipocytokines may impact lung development and function in early childhood. Future studies are needed to confirm these findings and explore the mechanisms underlying these associations.

Obesity: A critical risk factor in the COVID-19 pandemic

Obesity is an emerging independent risk factor for susceptibility to and severity of coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Previous viral pandemics have shown that obesity, particularly severe obesity (BMI > 40 kg/m2 ), is associated with increased risk of hospitalization, critical care admission and fatalities. In this narrative review, we examine emerging evidence of the influence of obesity on COVID-19, the challenges to clinical management from pulmonary, endocrine and immune dysfunctions in individuals with obesity and identify potential areas for further research. We recommend that people with severe obesity be deemed a vulnerable group for COVID-19; clinical trials of pharmacotherapeutics, immunotherapies and vaccination should prioritize inclusion of people with obesity.

Adiponectin antagonises LPS-regulated secretion of inflammatory factors in airway epithelial cells, and its expression is regulated by many factors

Many studies have shown that adiponectin is closely related to chronic obstructive pulmonary disease (COPD), but the specific role of adiponectin in COPD is still not well understood. Adiponectin and IL-6 expression in patients with acute exacerbation of COPD (AECOPD) was detected by ELISA. Human bronchial epithelial cells (HBECs) were stimulated with TNF-α, IL-6, apoptotic cells or LPS. Then, the expression of adiponectin was detected by qRT-PCR and western blotting, and pro- and anti-inflammatory factors were detected by ELISA. Adiponectin expression in AECOPD patients increased after treatment. TNF-α and apoptotic cells promoted adiponectin expression in HBECs in a dose-dependent manner, and apoptotic cells significantly promoted adiponectin secretion. IL-6 also promoted adiponectin expression, but it inhibited adiponectin expression at high doses and with long treatment times. LPS inhibited adiponectin expression, but when HBECs were pretreated with anti-TNF-α and then treated with LPS, the expression and secretion of adiponectin increased significantly with increasing anti-TNF-α concentrations. Adiponectin stimulated the secretion of pro-inflammatory factors in HBECs, but this effect was not concentration dependent. Adiponectin promoted the secretion of anti-inflammatory factors in a dose-dependent manner. Although LPS also stimulated HBECs to secrete pro-inflammatory and anti-inflammatory factors, adiponectin inhibited LPS-induced pro-inflammatory factor secretion and enhanced anti-inflammatory factor secretion. Many factors regulate the expression and secretion of adiponectin, and adiponectin regulates the balance of the inflammatory response and inhibits further expansion of inflammation. SIGNIFICANCE OF THE STUDY: Many studies have shown that adiponectin is closely related to chronic obstructive pulmonary disease (COPD), but the specific role of adiponectin in COPD is still not well understood. Adiponectin expression in AECOPD patients increased after treatment. TNF-α, IL-6 and apoptotic cells promoted adiponectin expression in HBECs. Adiponectin stimulated the secretion of pro-inflammatory factors in HBECs, but this effect was not concentration dependent. Adiponectin promoted the secretion of anti-inflammatory factors in a dose-dependent manner. Adiponectin inhibited LPS-induced pro-inflammatory factor secretion and enhanced anti-inflammatory factor secretion. Therefore, many factors regulate the expression and secretion of adiponectin, and adiponectin regulates the balance of the inflammatory response and inhibits further expansion of inflammation.

Recombinant adiponectin protects the newborn rat lung from lipopolysaccharide-induced inflammatory injury

Preterm infants are at high risk for developing bronchopulmonary dysplasia and pulmonary hypertension from inflammatory lung injury. In adult models, adiponectin (APN)—an adipocyte‐derived hormone—protects the lung from inflammatory injury and pulmonary vascular remodeling. Cord blood APN levels in premature infants born < 26 weeks gestation are 5% of the level in infants born at term. We previously reported the expression profile of APN and its receptors in neonatal rat lung homogenates during the first 3 weeks of postnatal development. Here, we characterize the expression profile of APN and its receptors in specific lung cells and the effects of exogenous recombinant APN (rAPN) on lipopolysaccharide‐(LPS)‐induced cytokine and chemokine production in total lung homogenates and specific lung cells. In vitro, rAPN added to primary cultures of pulmonary artery smooth muscle cells attenuated the expression of LPS‐induced pro‐inflammatory cytokines while increasing the expression of anti‐inflammatory cytokines. In vivo, intraperitoneal rAPN (2 mg/kg), given 4 hr prior to intrapharyngeal administration of LPS (5 mg/kg) to newborn rats at postnatal day 4, significantly reduced gene and protein expression of the pro‐inflammatory cytokine IL‐1ß and reduced protein expression of the chemokines monocyte chemoattractant protein (MCP‐1) and macrophage inflammatory protein‐1 alpha (MIP‐1α) in the lung. LPS‐induced histopathological changes in the lung were also decreased. Moreover, rAPN given 20 hr after intrapharyngeal LPS had a similar effect on lung inflammation. These findings suggest a role for APN in protecting the lung from inflammation during early stages of lung development.

Anti-inflammatory effects of adiponectin in cigarette smoke-activated alveolar macrophage through the COX-2/PGE2 and TLRs signaling pathway

OBJECTIVES

Airway macrophages represents a central site for the mechanisms involved in the complex interactions between environmental triggers and airway inflammation. Based on anti-inflammatory activity of adiponectin, we hypothesize that adiponectin inhibits the proinflammatory cytokines production and the activation of alveolar macrophages expose to cigarette smoke.

MATERIALS AND METHODS

To examine the effects of adiponectin on alveolar macrophages, we used the cigarette smoke-induced the alveolar inflammation model in C57BL/6 mice and the macrophages activation model in vitro, both in the presence or absence of adiponectin, to assess the accumulation of inflammatory cells and the concentration of inflammatory cytokines and chemokines in the bronchoalveolar lavage (BAL), and the proinflammatory cytokines production and M1/2 phenotype in alveolar macrophages.

RESULTS

Our results showed that adiponectin improves cigarette smoke-induced airway inflammation in vivo and decreases proinflammatory cytokine production and alveolar macrophages polarization in vitro. Moreover, our study further demonstrates that anti-inflammatory activity of adiponectin depends on the suppression of the proinflammatory cytokine production through TLR2/4 signaling and the inhibition of macrophage polarization vit COX-2/PGE2 signaling.

CONCLUSIONS

Our study suggests that the anti-inflammatory activity of adiponectin might contribute to its therapeutic potential in airway inflammation, such as COPD.

Adiponectin, a unique adipocyte-derived factor beyond hormones

Visceral fat accumulation has a marked impact on atherosclerotic cardiovascular diseases and metabolic syndrome clustering diabetes, dyslipidemia, and hypertension. Adiponectin, an adipocyte-derived circulating protein, is a representative adipocytokine and uniquely possesses two major properties: 1) its circulating concentration is approximately 3-6 orders of magnitude greater than ordinary hormones and cytokines; 2) its concentration inversely correlates with body fat mass despite its adipocyte-specific production. Low serum levels of adiponectin correlate with cardiometabolic diseases. Extensive experimental evidence has demonstrated that adiponectin possesses multiple properties, such as anti-atherosclerotic, anti-diabetic, and anti-inflammatory activities. It has been shown to play a central role against the development of metabolic syndrome and its complications. However, even approximately 25 years after its discovery, the properties of adiponectin, including how and why it exerts multiple beneficial effects on various tissues and/or organs, remain unclear. Furthermore, the mechanisms responsible for the very high circulating concentrations of adiponectin in the bloodstream have not been elucidated. Several adiponectin-binding partners, such as AdipoR1/2, have been identified, but do not fully explain the multi-functional and beneficial properties of adiponectin. Recent advances in adiponectin research may resolve these issues. Adiponectin binds to and covers cell surfaces with T-cadherin, a unique glycosylphosphatidylinositol (GPI)-anchored cadherin. The adiponectin/T-cadherin complex enhances exosomal production and release, excreting cell-toxic products from cells, particularly in the vasculature. In this review, we discuss adiponectin and the role of the adiponectin/T-cadherin system in the maintenance of whole body homeostasis and cardiovascular protection.

BMI is associated with FEV1 decline in chronic obstructive pulmonary disease: a meta-analysis of clinical trials

Background

There is considerable heterogeneity in the rate of lung function decline in chronic obstructive pulmonary disease (COPD), the determinants of which are largely unknown. Observational studies in COPD indicate that low body mass index (BMI) is associated with worse outcomes, and overweight/obesity has a protective effect – the so-called “obesity paradox”. We aimed to determine the relationship between BMI and the rate of FEV₁ decline in data from published clinical trials in COPD.

Methods

We performed a systematic review of the literature, and identified 5 randomized controlled trials reporting the association between BMI and FEV₁ decline. Four of these were included in the meta-analyses. We analyzed BMI in 4 categories: BMI-I (< 18.5 or <  20 kg/m²), BMI-II (18.5 or 20 to < 25 kg/m²), BMI-III (25 to < 29 or < 30 kg/m²) and BMI-IV (≥29 or ≥ 30 kg/m²). We then performed a meta-regression of all the estimates against the BMI category.

Results

The estimated rate of FEV₁ decline decreased with increasing BMI. Meta-regression of the estimates showed that BMI was significantly associated with the rate of FEV₁ decline (linear trend p = 1.21 × 10^− 5).

Conclusions

These novel findings support the obesity paradox in COPD: compared to normal BMI, low BMI is a risk factor for accelerated lung function decline, whilst high BMI has a protective effect. The relationship may be due to common but as-of-yet unknown causative factors; further investigation into which may reveal novel endotypes or targets for therapeutic intervention.

Adiponectin Expression Is Modulated by Long-Term Physical Activity in Adult Patients Affected by Cystic Fibrosis

Cystic fibrosis (CF) is a genetic disease characterized by progressive decline of lung function and chronic airway inflammation. Adipose tissue, through adiponectin and leptin, exerts several effects on energy metabolism and inflammatory processes. This study evaluated the levels of adiponectin and leptin in adult healthy subjects, in patients with CF and their correlation with long-term physical activity. CF patients were divided into two groups (sedentary versus active) based on their regular physical activity over 3 years. Anthropometric and serum biochemical profiles of CF patients and controls were evaluated and compared. Total serum adiponectin and leptin levels were measured by ELISA; adiponectin oligomeric profiles were analysed by western blot. Adiponectin levels were significantly higher while leptin levels were lower in patients with CF than in healthy controls. Furthermore, adiponectin was significantly lower in active compared to sedentary CF (p = 0.047), while leptin was slightly increased in active compared to sedentary CF. In addition, C-reactive protein levels were significantly lower in active than in sedentary CF patients (p = 0.048). Interestingly, only in the active group adiponectin levels were inversely correlated with forced expiratory volume (FEV) 1% decrease/year and FEV1% decrease. Moreover, adiponectin levels negatively correlated with lipid profiles. Our findings indicated that regular, long-term physical activity in CF improves respiratory function, metabolism, and inflammation status. These improvements in patients' conditions are associated with immunometabolic processes involving adiponectin, leptin, and C-reactive protein. Therefore, we propose that both adipokines may be a useful biomarker in the evaluation of metabolic and inflammatory status in patients with CF.

The Metabolic Cytokine Adiponectin Inhibits Inflammatory Lung Pathology in Invasive Aspergillosis

Systemic immunity and metabolism are coregulated by soluble factors, including the insulin-regulating adipose tissue cytokine adiponectin. How these factors impact detrimental inflammatory responses during fungal infection remains unknown. In this study, we observed that mortality, fungal burden, and tissue histopathology were increased in adiponectin-deficient mice in a neutropenic model of invasive aspergillosis. Lung RNA sequencing, quantitative RT-PCR, and subsequent pathway analysis demonstrated activation of inflammatory cytokine pathways with upstream regulation by IL-1 and TNF in adiponectin-deficient mice with decreased/inhibited anti-inflammatory genes/pathways, suggesting broad cytokine-mediated pathology along with ineffective fungal clearance. Quantitative RT-PCR analysis confirmed increased transcription of IL-1a, IL-6, IL-12b, IL-17A/F, and TNF in adiponectin-deficient mice at early time points postinfection, with a specific increase in intracellular TNF in alveolar macrophages. Although eosinophil recruitment and activation were increased in adiponectin-deficient mice, mortality was delayed, but not decreased, in mice deficient in both adiponectin and eosinophils. Interestingly, neutrophil depletion was required for increased inflammation in adiponectin-deficient mice in response to swollen/fixed conidia, suggesting that immune suppression enhances detrimental inflammation, whereas invasive fungal growth is dispensable. Our results suggest that adiponectin inhibits excessive lung inflammation in invasive aspergillosis. Our study has therefore identified the adiponectin pathway as a potential source for novel therapeutics in immune-compromised patients with detrimental immunity to invasive fungal infection.

[Chronic obstructive pulmonary disease concurrent with metabolic syndrome: Pathophysiological and clinical features]

Chronic obstructive pulmonary disease (COPD) still remains a serious public health problem, which is a common cause of disability and death in the able-bodied population. Furthermore, the number of patients with metabolic syndrome (MS) is steadily increasing worldwide. Recently, there is also an increase in the number of patients with COPD concurrent with MS, which is a mutually confounding risk factor for concomitant cardiovascular disease and adversely affects prognosis in these patients. Systemic subclinical inflammation is a common link between COPD and the components of MS. Systemic inflammation in patients with comorbidity is complemented by an inflammatory process in the abdominal visceral adipose tissue that serves as a source of proinflammatory adipokines (leptin, resistin, and tumor necrosis factor-α). Patients with COPD in the presence of MS components have in general higher ventilation needs, more obvious clinical manifestations of bronchopulmonary diseases, and more frequent COPD exacerbations and frequently require higher doses of inhaled glucocorticosteroids. As compared with normal-weight patients with COPD, obese patients with this condition have more limited physical activity and much more exercise intolerance. There are currently no practical recommendations for the management of patients with comorbidity; patients with COPD concurrent with MS need an individual therapeutic approach. It is important to elaborate a package of preventive measures to improve quality of life in patients, to reduce the incidence of systemic complications, and to achieve symptomatic improvements. Thus, to develop and implement practical guidelines for physicians and patients are an urgent issue.

Auto-measure emphysematous parameters and pathophysiological gene expression profiles in experimental mouse models of acute and chronic obstructive pulmonary diseases

Pulmonary emphysema, inflammation and senescence-like phenotype are pathophysiological characteristics of chronic obstructive pulmonary disease (COPD). Recently, a murine model of COPD has been established by inducing airway-specific overexpression of epithelial Na⁺ channel β subunit (βENaC-Tg mice). However, little is known about the histological and biochemical differences between βENaC-Tg mice and an existing acute emphysematous mouse model (elastase-induced model). Here, we first utilized whole lung image-based quantification method for histological analysis to determine auto-measure parameters, including alveolar area, alveolar perimeter, (major axis + minor axis)/2 and Feret diameter. Even though the extent of emphysema was similar in both models, the coefficient of variation (CV) of all histological parameters was smaller in βENaC-Tg mice, indicating that βENaC-Tg mice show homogeneous emphysema as compared with elastase-induced acute model. Expression analysis of lung tissue RNAs further revealed that elastase-induced model exhibits transient changes of inflammation markers (Kc, Il-6, Lcn2) and senescence-related markers (Sirt1, p21) at emphysema-initiation stage (1 day), which does not last until emphysema-manifestation stage (3 weeks); while the up-regulation is stable at emphysema-manifestation stage in βENaC-Tg mice (14-week old). Thus, these studies demonstrate that βENaC-Tg mice exhibit diffuse-type emphysema with stable expression of inflammatory and senescence-like markers.

Adiponectin Attenuates the Inflammation in Atopic Dermatitis-Like Reconstructed Human Epidermis

Background

Atopic dermatitis (AD) is a chronic disorder, with a vicious cycle of repetitive inflammation and deterioration of the epidermal barrier function. Adiponectin, an adipokine, has anti-inflammatory effects on various metabolic and inflammatory disorders. Recently, its level was found to be reduced in serum and tissue samples from AD patients.

Objective

We aimed to investigate the effects of adiponectin on epidermal inflammation and barrier structures in AD skin.

Methods

A three-dimensional in vitro epidermal equivalent model mimicking AD was obtained by adding an inflammatory substance cocktail to normal human epidermal equivalents (HEEs). The expression of epidermal differentiation markers, primary inflammatory mediators, and lipid biosynthetic enzymes was compared between adiponectintreated AD-HEEs, untreated control AD-HEEs, and normal HEEs.

Results

Adiponectin co-treatment 1) inhibited the increase in mRNA expression of major inflammatory mediators (carbonic anhydrase II, neuron-specific NEL-like protein 2, thymic stromal lymphopoietin, interleukin-8, tumor necrosis factor-alpha, and human beta-defensin-2) from keratinocytes in AD-inflammatory HEEs, 2) enhanced the expression of lipid biosynthetic enzymes (fatty acid synthase, HMG CoA reductase, and serine-palmitoyl transferase), and 3) promoted the expression of differentiation factors, especially filaggrin. We also found that the expression of adiponectin receptor-1 and -2 decreased in the epidermis of chronic AD lesion.

Conclusion

Activation of the adiponectin pathway is expected to enhance epidermal differentiation and barrier function as well as attenuate inflammatory response to AD as a therapeutic approach.

The Impact of Aging on Adipose Function and Adipokine Synthesis

During the last 40 years, there has been a world-wide increase in both the prevalence of obesity and an increase in the number of persons over the age of 60 due to a decline in deaths from infectious disease and the nutrition transition in low and middle income nations. While the increase in the elderly population indicates improvements in global public health, this population may experience a diminished quality of life due to the negative impacts of obesity on age-associated inflammation. Aging alters adipose tissue composition and function resulting in insulin resistance and ectopic lipid storage. A reduction in brown adipose tissue activity, declining sex hormones levels, and abdominal adipose tissue expansion occur with advancing years through the redistribution of lipids from the subcutaneous to the visceral fat compartment. These changes in adipose tissue function and distribution influence the secretion of adipose tissue derived hormones, or adipokines, that promote a chronic state of low-grade systemic inflammation. Ultimately, obesity accelerates aging by enhancing inflammation and increasing the risk of age-associated diseases. The focus of this review is the impact of aging on adipose tissue distribution and function and how these effects influence the elaboration of pro and anti-inflammatory adipokines.

Association of Adiponectin with Lung Function Impairment and Disease Severity in Chronic Obstructive Pulmonary Disease

Context:

Chronic obstructive pulmonary disease (COPD) is not only restricted to the pulmonary inflammation and airway obstruction but is also associated with comorbidities, which affect the therapeutic intervention and the quality of life and survival. Markers that can predict the systemic inflammation and a decline in the pulmonary function are of scientific interest. Adiponectin (APN) appears to be one such biomarker and can be used as a potential indicator of severity and response to treatment in patients of COPD.

Aims:

The study aims to find out the role of APN as a marker of inflammation in the pathogenesis of COPD and explore its relationship with the severity of the disease.

Settings and Design:

This was a cross-sectional study.

Subjects and Methods:

The study group consisted of 60 patients of COPD, which included 30 males admitted with acute exacerbation of COPD (AECOPD) and 30 males with stable COPD. The study group was compared with 30 healthy, age-matched males. APN was estimated by commercially available ELISA kits. Pulmonary function tests were performed on all cases and controls using standardized protocols on SPIROLAB III.

Statistical Analysis Used:

Statistical analysis was performed using Student's t-test and Pearson's correlation coefficient.

Results:

The levels of APN were found to be significantly higher in patients with COPD as compared to the controls and the levels increased with the severity of the disease were 16.10 ± 4.97 ng/ml and 11.43 ± 4.22 ng/ml, respectively, in AECOPD and COPD. A significant positive correlation was found between the levels of APN and interleukin (IL)-8 in patients of COPD, while the levels correlated negatively with percentage of forced expiratory volume in 1 s (FEV1%).

Conclusions:

The results reveal that APN is associated with the inflammatory process of COPD as suggested by its significant inverse relationship with FEV1% and positive correlation with a marker of inflammation such as IL-8. It can thus be used as a biomarker for disease severity and progression in patients of COPD, therefore aiding in risk stratification and therapeutic intervention.

The impact of BMI on non-malignant respiratory symptoms and lung function in arsenic exposed adults of Northern Chile

BACKGROUND

Elevated body mass index (BMI) and arsenic are both associated with cancer and with non-malignant lung disease. Using a unique exposure situation in Northern Chile with data on lifetime arsenic exposure, we previously identified the first evidence of an interaction between arsenic and BMI for the development of lung cancer.

OBJECTIVES

We examined whether there was an interaction between arsenic and BMI for the development of non-malignant lung disease.

METHODS

Data on lifetime arsenic exposure, respiratory symptoms, spirometry, BMI, and smoking were collected from 751 participants from cities in Northern Chile with varying levels of arsenic water concentrations. Spirometry values and respiratory symptoms were compared across subjects in different categories of arsenic exposure and BMI.

RESULTS

Adults with both a BMI above the 90th percentile (>33.9kg/m²) and arsenic water concentrations ≥11µg/L exhibited high odds ratios (ORs) for cough (OR = 10.7, 95% confidence interval (CI): 3.03, 50.1), shortness of breath (OR = 14.2, 95% CI: 4.79, 52.4), wheeze (OR = 14.4, 95% CI: 4.80, 53.7), and the combined presence of any respiratory symptom (OR = 9.82, 95% CI: 4.22, 24.5). In subjects with lower BMIs, respiratory symptom ORs for arsenic water concentrations ≥11µg/L were markedly lower. In never-smokers, reductions in forced vital capacity associated with arsenic increased as BMI increased. Analysis of the FEV₁/FVC ratio in never-smokers significantly increased as BMI and arsenic concentrations increased. Similar trends were not observed for FEV₁ alone or in ever-smokers.

CONCLUSIONS

This study provides preliminary evidence that BMI may increase the risk for arsenic-related non-malignant respiratory disease.

Plasma Leptin and Reduced FEV1 and FVC in Chronic Spinal Cord Injury

BACKGROUND

Adipose tissue produces leptin, which is pro-inflammatory, and adiponectin, which has anti-inflammatory properties. Participants with chronic spinal cord injury (SCI) have increased body fat and are at increased risk for respiratory illness.

OBJECTIVE

To assess the associations between leptin and adiponectin with pulmonary function in a chronic SCI cohort.

DESIGN

Cross-sectional study.

SETTING

Veterans Affairs Medical Center.

PARTICIPANTS

A total of 285 participants (237 men and 48 women) with chronic SCI with mean (standard deviation) injury duration 17.8 (13.2) years from the VA Boston and the community participating in an epidemiologic study assessing factors associated with respiratory health.

METHODS

Participants (24.6% cervical American Spinal Injury Association Impairment Scale (AIS) level A, B, and C; 33.6% other AIS A, B, and C; 41.8% AIS D) provided a blood sample, completed a respiratory health questionnaire, and underwent spirometry. Linear regression methods were used to assess cross-sectional associations between plasma leptin and adiponectin with spirometric measures of pulmonary function adjusted for age, race, gender, and height. Level and severity of SCI, mobility mode, body mass index, smoking, chronic obstructive pulmonary disease, asthma, chest injury history, laboratory batch, and other potential confounders were also considered.

MAIN OUTCOME MEASUREMENTS

forced expiratory volume in 1 second (FEV₁), forced vital capacity (FVC), and FEV₁/FVC.

RESULTS

There was a statistically significant inverse relationship between plasma leptin assessed in quartiles or as a continuous covariate with FEV₁ and FVC. In fully adjusted models, each interquartile range (16,214 pg/mL) increase in leptin was associated with a significant decrease in FEV₁ (-93.1 mL; 95% confidence interval = -166.2, -20.0) and decrease in FVC (-130.7 mL; 95% confidence interval = -219.4, -42.0). There were no significant associations between leptin and FEV₁/FVC or between plasma adiponectin with FEV₁, FVC, or FEV₁/FVC.

CONCLUSION

Plasma leptin in individuals with chronic SCI is inversely associated with FEV₁ and FVC, independently of SCI level and severity and other covariates. This finding suggests that plasma leptin may contribute to reduced pulmonary function in chronic SCI.

LEVEL OF EVIDENCE

II.

Beyond BMI: Obesity and Lung Disease

The worldwide prevalence of obesity has increased rapidly in the last 3 decades, and this increase has led to important changes in the pathogenesis and clinical presentation of many common diseases. This review article examines the relationship between obesity and lung disease, highlighting some of the major findings that have advanced our understanding of the mechanisms contributing to this relationship. Changes in pulmonary function related to fat mass are important, but obesity is much more than simply a state of mass loading, and BMI is only a very indirect measure of metabolic health. The obese state is associated with changes in the gut microbiome, cellular metabolism, lipid handling, immune function, insulin resistance, and circulating factors produced by adipose tissue. Together, these factors can fundamentally alter the pathogenesis and pathophysiology of lung health and disease.

Airway and serum adipokines after allergen and diesel exposure in a controlled human crossover study of atopic adults

Adipokines are mediators released from adipose tissue. These proteins are regarded as active elements of systemic and pulmonary inflammation, whose dysregulation can alter an individual's risk of developing allergic lung diseases. Despite this knowledge, adipokine responses to inhaled stimuli are poorly understood. We sought to measure serum and lung adiponectin, leptin, and resistin in an atopic adult study population following exposure to allergen and diesel exhaust (DE). Two types of lung samples including bronchoalveolar lavage (BAL) and bronchial wash (BW), and a time course of serum samples, were collected from the 18 subjects who participated in the randomized, double-blinded controlled human study. The two crossover exposure triads in this study were inhaled DE and filtered air each followed by instilled allergen or saline. Serum and lung adipokine responses to these exposures were quantified using enzyme-linked immunosorbent assay. Allergen significantly increased adiponectin and leptin in BAL, and adiponectin in the BW 48 hours after exposure. Serum leptin and resistin responses were not differentially affected by exposure, but varied over time. Coexposure with DE and allergen revealed significant correlations between the adiponectin/leptin ratio and FEV₁ changes and airway responsiveness measures. Changes in lung and serum adipokines in response to allergen exposure were identified in the context of a controlled exposure study. Coexposure identified a potentially protective role of adiponectin in the lung. This response was not observed in those with baseline airway hyper-responsiveness, or after allergen exposure alone. The clinical relevance of this potentially adaptive adipokine pattern warrants further study.

Comparison of Serum Adiponectin in Smoke-induced Pulmonary Emphysema Rats Fed Different Diets

BACKGROUND

Smoking and body mass index (BMI) are the key risk factors for chronic obstructive pulmonary disease (COPD). Adiponectin with both anti-inflammatory and pro-inflammatory properties is a vital modulator of inflammatory processes, which is expressed in epithelial cells in the airway in COPD-emphysema. The aim of this study was to examine the effects of adiponectin on tobacco smoke-induced emphysema in rats, which were fed different diets.

METHODS

Seventy-six adult (6-8 weeks old) male Sprague-Dawley rats (average weight 220 ± 20 g) were exposed to smoke or smoke-free room atmosphere and fed different diets (regular, high-fat, or low-fat diets) for 6 months. The rats were randomly divided into six groups. They are nonsmoke-exposed regular diet (n = 10), nonsmoke-exposed high-fat diet (n = 14), nonsmoke-exposed low-fat diet (n = 14), smoke-exposed regular diet (n = 10), smoke-exposed high-fat diet (n = 14), and smoke-exposed low-fat diet groups (n = 14). A full 2 3 factorial design was used to evaluate the effect of independent variables on smoke exposure and different rearing methods. Serum adiponectin and inflammatory cytokines were measured by the enzyme-linked immunosorbent assay (ELISA).

RESULTS

Serum adiponectin levels in rats fed low-fat and regular diets exposed to smoke exposure were remarkably higher than that of rats exposed to room air while serum adiponectin levels of fat-rich diet rats exposed to tobacco smoke were lower than that of rats exposed to room air. Compared with regular diet or low-fat diet group, serum adiponectin levels in high-fat diet rats exposed to tobacco smoke were lower (t = 6.932, 11.026; all P < 0.001). BMI was inversely correlated with serum adiponectin levels (r = -0.751, P = 0.012). Serum interleukin 6 (IL-6), tumor necrosis factor-α (TNF-α), and 4-hydroxy 2-nonenal (HNE) levels in rats exposed to low-fat or fat-rich diets were remarkably higher than that of rats exposed to normal diets (IL-6, t = 4.196, 3.480; P < 0.01, P = 0.001; TNF-α, t = 4.286, 3.521; P < 0.01, P = 0.001; 4-HNE, t = 4.298, 4.316; all P < 0.001). In nonhigh-fat diet rats exposed to tobacco smoke, serum adiponectin levels correlated positively with serum IL-6, TNF-α, and 4-HNE, bronchoalveolar lavage cell count, and mean linear intercept. In contrast, in high-fat diet rats, serum adiponectin levels correlated inversely with these parameters.

CONCLUSIONS

In smoke-induced emphysema and fat-rich diet rat model, serum adiponectin level was decreased, and the anti-inflammatory effect was attenuated. By contrast, nonhigh-fat diet elevated serum adiponectin and enhanced the role of pro-inflammatory.

The burden of obesity in asthma and COPD: Role of adiponectin

The influence of obesity on development, severity and prognosis of both asthma and COPD is attracting growing interest. The impact of obesity on the respiratory system ranges from structural modifications (decline of total lung capacity) to humoral alterations. Adipose tissue strongly contributes to the establishment of an inflammatory state being an important source of adipokines. Amongst adipokines, adiponectin is an important component of organ cross talk with adipose tissue exerting protective effects on a variety of pathophysiological processes. Adiponectin is secreted in serum where it abundantly circulates as complexes of different molecular weight. Adiponectin properties are mediated by specific receptors that are widely expressed with AdipoR1, AdipoR2, and T-cadherin being present on epithelial and endothelial pulmonary cells indicating a functional role on lung physiology. In COPD, mild to moderate obesity has been shown to have protective effects on patient's survival, while a higher mortality rate has been observed in patients with low BMI. A specific cluster of obese patients has been identified; in this group, asthma features are particularly severe and difficult to treat. Better understanding of the molecular mechanisms at the base of cross talk among different tissues and organs will lead to identification of new targets for both diagnosis and treatment of asthma and COPD.

Different forms of adiponectin reduce the apoptotic and damaging effect of cigarette smoke extract on human bronchial epithelial cells

Chronic obstructive pulmonary disease (COPD) is a common respiratory disease, in which adiponectin may serve an important role. The present study investigated the role of adiponectin in the apoptotic and damaging effect of cigarette smoke extract (CSE) on human bronchial epithelial cells (16HBECs). An MTT assay showed that CSE significantly inhibited the proliferation of 16HBECs (F=1808.88, P<0.01). The 16HBECs were treated with different concentrations of high molecular weight (HMW) adiponectin and globular domain (gAd) adiponectin and it was observed that HMW and gAd dose-dependently inhibited the expression of tumor necrosis factor (TNF)-α and interleukin (IL)-8, and the generation of 4-hydroxy-nonenal and reactive oxygen species (ROS) in 16HBECs, thereby blocking the upregulating effect of CSE on these factors. However, the inhibitory effect of gAd on TNF-α and IL-8 expression was stronger compared with that of HMW, but the suppressing effect of HMW on ROS production was superior compared with that of gAd. Further testing of apoptosis indicated that CSE and HMW promoted the apoptosis of 16HBECs. However, such effects of HMW declined with an increase in concentration. In contrast, gAd showed an inhibitory effect on apoptosis and inhibited the occurrence of CSE-induced apoptosis in a dose-dependent manner. Therefore, the present study demonstrated that different forms of adiponectin may have different mechanisms of action, suggesting that further exploration of their effects may open a new avenue for the treatment of COPD.

AdipoR-increased intracellular ROS promotes cPLA2 and COX-2 expressions via activation of PKC and p300 in adiponectin-stimulated human alveolar type II cells

Adiponectin, an adipokine, accumulated in lung system via T-cadherin after allergens/ozone challenge. However, the roles of adiponectin on lung pathologies were controversial. Here we reported that adiponectin stimulated expression of inflammatory proteins, cytosolic phospholipase A2 (cPLA2), cyclooxygenase-2 (COX-2), and production of reactive oxygen species (ROS) in human alveolar type II A549 cells. AdipoR1/2 involved in adiponectin-activated NADPH oxidase and mitochondria, which further promoted intracellular ROS accumulation. Protein kinase C (PKC) may involve an adiponectin-activated NADPH oxidase. Similarly, p300 phosphorylation and histone H4 acetylation occurred in adiponectin-challenged A549 cells. Moreover, adiponectin-upregulated cPLA2 and COX-2 expression was significantly abrogated by ROS scavenger (N-acetylcysteine) or the inhibitors of NADPH oxidase (apocynin), mitochondrial complex I (rotenone), PKC (Ro31-8220, Gö-6976, and rottlerin), and p300 (garcinol). Briefly, we reported that adiponectin stimulated cPLA2 and COX-2 expression via AdipoR1/2-dependent activation of PKC/NADPH oxidase/mitochondria resulting in ROS accumulation, p300 phosphorylation, and histone H4 acetylation. These results suggested that adiponectin promoted lung inflammation, resulting in exacerbation of pulmonary diseases via upregulating cPLA2 and COX-2 expression together with intracellular ROS production. Understanding the adiponectin signaling pathways on regulating cPLA2 and COX-2 may help develop therapeutic strategies on pulmonary diseases.

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.

Non-Invasive Ventilation (NIV) and Homeostatic Model Assessment (HOMA) Index in Stable Chronic Obstructive Pulmonary Disease (COPD) Patients with Chronic Hypercapnic Respiratory Failure: A Pilot Study

The effects of Non-invasive Ventilation (NIV) on Insulin Resistance (IR) in stable Chronic Obstructive Pulmonary Disease (COPD) patients have not been fully explored. The aim of this study was to assess the effects of NIV on IR and adiponectin levels during one year application of NIV in stable COPD patients with Chronic Hypercapnic Respiratory Failure. Twenty-five (25) stable COPD patients with Chronic Hypercapnic Respiratory Failure and with no self-reported comorbidities completed the study. NIV was administered in the spontaneous/timed mode via a full face mask using a bi-level positive airway pressure system. Spirometry, blood pressure, arterial blood gases, dyspnea, daytime sleepiness, serum fasting glucose and insulin levels were assessed. IR was assessed with the calculation of the Homeostatic Model Assessment (HOMA) index. Adiponectin was measured with radioimmunoassay. Study participants were re-evaluated on the first, third, sixth, ninth and twelfth month after the initial evaluation. There was a significant improvement in FEV1 values from the first month (34.1 ± 11.6% vs 37 ± 12.3%, p = 0.05). There was a significant decrease in IR by the ninth month of NIV use (3.4 ± 2.3 vs 2.2 ± 1.4, p < 0.0001), while adiponectin levels significantly improved from the first month of NIV use. Stepwise regression analysis revealed that baseline HOMA index was associated with paCO2 (β = 0.07 ± 0.02, p = 0.001), while baseline adiponectin levels were associated with FVC (β = 0.05 ± 0.02, p = 0.035) and the concentration of serum bicarbonate (HCO3-) (-β = 0.18 ± 0.06, p = 0.002). Insulin sensitivity and glucose metabolism as well as adiponectin levels improved along with the improvements in respiratory failure.

Association of plasma adipokines with chronic obstructive pulmonary disease severity and progression

RATIONALE

Two adipokines, leptin and adiponectin, regulate metabolic and inflammatory systems reciprocally. The role of adiponectin in chronic obstructive pulmonary disease (COPD) has been studied. However, there are few data evaluating the relationship of plasma leptin with COPD severity or progression.

OBJECTIVES

The objective of this study was to evaluate the relationship of leptin, adiponectin, and the leptin/adiponectin ratio with COPD severity and progression according to COPD phenotypes.

METHODS

Plasma leptin and adiponectin levels were measured in 196 subjects with COPD selected from the Korean Obstructive Lung Disease cohort. Using a linear regression model and mixed linear regression, we determined the relationship of plasma leptin and adiponectin levels and the leptin/adiponectin ratio to COPD severity and progression over 3 years.

MEASUREMENTS AND MAIN RESULTS

The concentration of adiponectin in plasma positively correlated with percent emphysema on initial computed tomography (CT) (adjusted P = 0.022), whereas plasma leptin concentrations and the leptin/adiponectin ratio exhibited a significant inverse correlation with initial FEV1 (adjusted P = 0.013 for leptin and adjusted P = 0.041 for leptin/adiponectin ratio). Increased plasma leptin and leptin/adiponectin ratio were significantly associated with change in percent emphysema over 3 years (adjusted P = 0.037 for leptin and adjusted P = 0.029 for leptin/adiponectin ratio), whereas none of the adipokines demonstrated an association with FEV1 decline over the 3-year period.

CONCLUSIONS

Plasma adiponectin and leptin vary according to COPD phenotypes. Plasma leptin and the leptin/adiponectin ratio, but not adiponectin, were significantly associated with changes in CT-assessed emphysema, suggesting a potential role as a biomarker in emphysema progression in patients with COPD.

Low Plasma Levels of Adiponectin Do Not Explain Acute Respiratory Distress Syndrome Risk: a Prospective Cohort Study of Patients with Severe Sepsis

BACKGROUND

Obesity is associated with the development of acute respiratory distress syndrome (ARDS) in at-risk patients. Low plasma levels of adiponectin, a circulating hormone-like molecule, have been implicated as a possible mechanism for this association. The objective of this study was to determine the association of plasma adiponectin level at ICU admission with ARDS and 30-day mortality in patients with severe sepsis and septic shock.

METHODS

This is a prospective cohort study of patients admitted to the medical ICU at the Hospital of the University of Pennsylvania. Plasma adiponectin was measured at the time of ICU admission. ARDS was defined by Berlin criteria. Multivariable logistic regression was used to determine the association of plasma adiponectin with the development of ARDS and mortality at 30 days.

RESULTS

The study included 164 patients. The incidence of ARDS within 5 days of admission was 45%. The median initial plasma adiponectin level was 7.62 mcg/ml (IQR: 3.87, 14.90) in those without ARDS compared to 8.93 mcg/ml (IQR: 4.60, 18.85) in those developing ARDS. The adjusted odds ratio for ARDS associated with each 5 mcg increase in adiponectin was 1.12 (95% CI 1.01, 1.25), p-value 0.025). A total of 82 patients (51%) of the cohort died within 30 days of ICU admission. There was a statistically significant association between adiponectin and mortality in the unadjusted model (OR 1.11, 95% CI 1.00, 1.23, p-value 0.04) that was no longer significant after adjusting for potential confounders.

CONCLUSIONS

In this study, low levels of adiponectin were not associated with an increased risk of ARDS in patients with severe sepsis and septic shock. This argues against low levels of adiponectin as a mechanism explaining the association of obesity with ARDS. At present, it is unclear whether circulating adiponectin is involved in the pathogenesis of ARDS or simply represents an epiphenomenon of other unknown functions of adipose tissue or metabolic alterations in sepsis.

Mitochondrial iron chelation ameliorates cigarette smoke-induced bronchitis and emphysema in mice

Chronic obstructive pulmonary disease (COPD) is linked to both cigarette smoking and genetic determinants. We have previously identified iron-responsive element-binding protein 2 (IRP2) as an important COPD susceptibility gene and have shown that IRP2 protein is increased in the lungs of individuals with COPD. Here we demonstrate that mice deficient in Irp2 were protected from cigarette smoke (CS)-induced experimental COPD. By integrating RNA immunoprecipitation followed by sequencing (RIP-seq), RNA sequencing (RNA-seq), and gene expression and functional enrichment clustering analysis, we identified Irp2 as a regulator of mitochondrial function in the lungs of mice. Irp2 increased mitochondrial iron loading and levels of cytochrome c oxidase (COX), which led to mitochondrial dysfunction and subsequent experimental COPD. Frataxin-deficient mice, which had higher mitochondrial iron loading, showed impaired airway mucociliary clearance (MCC) and higher pulmonary inflammation at baseline, whereas mice deficient in the synthesis of cytochrome c oxidase, which have reduced COX, were protected from CS-induced pulmonary inflammation and impairment of MCC. Mice treated with a mitochondrial iron chelator or mice fed a low-iron diet were protected from CS-induced COPD. Mitochondrial iron chelation also alleviated CS-induced impairment of MCC, CS-induced pulmonary inflammation and CS-associated lung injury in mice with established COPD, suggesting a critical functional role and potential therapeutic intervention for the mitochondrial-iron axis in COPD.

Role of adiponectin in sphingosine-1-phosphate induced airway hyperresponsiveness and inflammation

Epidemiological data suggest that obesity represent an important risk factor for asthma, but the link between excess fat and airway hyperresponsiveness (AHR) and inflammation is not fully understood. Recently, a key role in physiopathologic conditions of lungs has been given to adiponectin (Acrp30). Acrp30 is one of the most expressed adipokines produced and secreted by adipose tissue, showing an intriguing relationship with metabolism of sphingolipids. Sphingosine-1-phosphate (S1P) has been proposed as an important inflammatory mediator implicated in the pathogenesis of airway inflammation and asthma. In the present study we analyze the effects of recombinant Acrp30 administration in an experimental model of S1P-induced AHR and inflammation. The results show that S1P is able to reduce endogenous Acrp30 serum levels and that recombinant Acrp30 treatment significantly reduce S1P-induced AHR and inflammation. Moreover, we observed a reduction of Adiponectin receptors (AdipoR1, AdipoR2 and T-cadherin) expression in S1P treated mice. Treatment with recombinant Acrp30 was able to restore Acrp30 serum levels and adiponectin receptors expression. These results could indicate the ability of S1P to modulate the Acrp30 action, by modulating not only the serum levels of the protein, but also its receptors. Taken together, these data suggest that adiponectin could represent a possible biomarker in obesity-associated asthma.

Lower leptin/adiponectin ratio and risk of rapid lung function decline in chronic obstructive pulmonary disease

RATIONALE

The rate of annual change in FEV1 is highly variable among patients with chronic obstructive pulmonary disease (COPD). Reliable blood biomarkers are needed to predict prognosis.

OBJECTIVES

To explore plasma biomarkers associated with an annual change in FEV1 in patients with COPD.

METHODS

Plasma samples of 261 subjects, all Japanese, with COPD from the 5-year Hokkaido COPD cohort study were analyzed as a hypothesis-generating cohort, and the results were validated using data of 226 subjects with and 268 subjects without airflow limitation, mainly white, from the 4-year COPD Quantification by Computed Tomography, Biomarkers, and Quality of Life (CBQ) study conducted in Denmark. The plasma samples were measured using Human CardiovascularMAP (Myriad RBM, Austin, TX), which could analyze 50 biomarkers potentially linked with inflammatory, metabolic, and tissue remodeling pathways, and single ELISAs were used to confirm the results.

MEASUREMENTS AND MAIN RESULTS

Higher plasma adiponectin levels and a lower leptin/adiponectin ratio at enrollment were significantly associated with an annual decline in FEV1 even after controlling for age, sex, height, and body mass index in the Hokkaido COPD cohort study (P = 0.003, P = 0.004, respectively). A lower plasma leptin/adiponectin ratio was also significantly associated with an annual decline in FEV1 in subjects with airflow limitation in the CBQ study (P = 0.014), the patients of which had largely different clinical characteristics compared with the Hokkaido COPD cohort study. There were no significant associations between lung function decline and adipokine levels in subjects without airflow limitation.

CONCLUSIONS

A lower leptin/adiponectin ratio was associated with lung function decline in patients with COPD in two independent Japanese and Western cohort studies of populations of different ethnicity. Measure of systemic adipokines may provide utility in predicting patients with COPD at higher risk of lung function decline.

Role of anti-inflammatory adipokines in obesity-related diseases

Obesity results in many health complications. Accumulating evidence indicates that the obese state is characterized by chronic low-grade inflammation, thereby leading to the initiation and progression of obesity-related disorders such as type 2 diabetes, hypertension, cardiovascular disease, and atherosclerosis. Fat tissue releases numerous bioactive molecules, called adipokines, which affect whole-body homeostasis. Most adipokines are proinflammatory, whereas a small number of anti-inflammatory adipokines including adiponectin exert beneficial actions on obese complications. The dysregulated production of adipokines seen in obesity is linked to the pathogenesis of various disease processes. In this review we focus on the role of the anti-inflammatory adipokines that are of current interest in the setting of obesity-linked metabolic and cardiovascular diseases.

Association between plasma adiponectin levels and decline in forced expiratory volume in 1 s in a general Japanese population: the Takahata study

BACKGROUND

Adiponectin is an anti-inflammatory and cardio-protective cytokine. However, several studies have demonstrated that plasma adiponectin levels were inversely associated with pulmonary function in patients with chronic obstructive pulmonary disease, suggesting a proinflammatory or pulmonary-destructive role. It is still unclear whether adiponectin is a potent biomarker predicting declines in pulmonary function. The aim of this study was to investigate the association between adiponectin and pulmonary function among Japanese individuals who participated in an annual health check-up.

METHODS

Spirometry and blood sampling, including measurements of plasma adiponectin, were performed for 3,253 subjects aged 40 years or older who participated in a community-based annual health check-up in Takahata, Japan from 2004 to 2006. In 2011, spirometry was re-performed, and the data from 872 subjects (405 men and 467 women) were available for a longitudinal analysis.

RESULTS

Plasma adiponectin levels were found to be significantly associated with age, body mass index (BMI), and alanine aminotransferase (ALT), triglycerides (TG), and high-density lipoprotein-cholesterol (HDL-c) levels among both men and women in the study population. Plasma adiponectin levels were found to be associated with lifetime cigarette consumption (Brinkman index, BI) in men only. Plasma adiponectin levels were inversely correlated with forced expiratory volume in 1 s (FEV1) per forced vital capacity in both men and women. In addition, the annual change in FEV1 was inversely associated with plasma adiponectin levels in both genders. A multiple linear regression analysis revealed that this association was independent of other confounding factors such as age, BMI, BI, ALT, TG, and HDL-c.

CONCLUSIONS

The results of the present study suggest that adiponectin levels are predictive of declines in FEV1 in the general population.

Scleroderma-related lung disease: are adipokines involved pathogenically?

Scleroderma is a systemic autoimmune disease of unknown etiology whose characteristic features include endothelial cell dysfunction, fibroblast proliferation, and immune dysregulation. Although almost any organ can be pathologically involved in scleroderma, lung complications including interstitial lung disease (ILD) and pulmonary arterial hypertension (PAH) are the leading cause of death in patients with this condition. Currently, the molecular mechanisms leading to development of scleroderma-related lung disease are poorly understood; however, the systemic nature of this condition has led many to implicate circulating factors in the pathogenesis of some of its organ impairment. In this article we focus on a new class of circulating factors derived from adipose-tissue called adipokines, which are known to be altered in scleroderma. Recently, the adipokines adiponectin and leptin have been found to regulate biological activity in endothelial, fibroblast, and immune cell types in lung and in many other tissues. The pleiotropic nature of these circulating factors and their functional activity on many cell types implicated in the pathogenesis of ILD and PAH suggest these hormones may be mechanistically involved in the onset and/or progression of scleroderma-related lung diseases.

Obesity, inflammation, and lung injury (OILI): the good

Obesity becomes pandemic, predisposing these individuals to great risk for lung injury. In this review, we focused on the anti-inflammatories and addressed the following aspects: adipocytokines and obesity, inflammation and other mechanisms, adipocytokines and lung injury in obesity bridged by inflammation, and potential therapeutic targets. To sum up, the majority of evidence supported that adiponectin, omentin, and secreted frizzled-related protein 5 (SFRP5) were reduced significantly in obesity, which is associated with increased inflammation, indicated by increase of TNFα and IL-6, through activation of toll-like receptor (TLR4) and nuclear factor light chain κB (NF-κB) signaling pathways. Administration of these adipocytokines promotes weight loss and reduces inflammation. Zinc-α2-glycoprotein (ZAG), vaspin, IL-10, interleukin-1 receptor antagonist (IL-1RA), transforming growth factor β (TGF-β1), and growth differentiation factor 15 (GDF15) are also regarded as anti-inflammatories. There were controversial reports. Furthermore, there is a huge lack of studies for obesity related lung injury. The effects of adiponectin on lung transplantation, asthma, chronic obstructive pulmonary diseases (COPD), and pneumonia were anti-inflammatory and protective in lung injury. Administration of IL-10 agonist reduces mortality of acute lung injury in rabbits with acute necrotizing pancreatitis, possibly through inhibiting proinflammation and strengthening host immunity. Very limited information is available for other adipocytokines.

Recipient-related clinical risk factors for primary graft dysfunction after lung transplantation: a systematic review and meta-analysis

Background

Primary graft dysfunction (PGD) is the main cause of early morbidity and mortality after lung transplantation. Previous studies have yielded conflicting results for PGD risk factors. Herein, we carried out a systematic review and meta-analysis of published literature to identify recipient-related clinical risk factors associated with PGD development.

Method

A systematic search of electronic databases (PubMed, Embase, Web of Science, Cochrane CENTRAL, and Scopus) for studies published from 1970 to 2013 was performed. Cohort, case-control, or cross-sectional studies that examined recipient-related risk factors of PGD were included. The odds ratios (ORs) or mean differences (MDs) were calculated using random-effects models

Result

Thirteen studies involving 10042 recipients met final inclusion criteria. From the pooled analyses, female gender (OR 1.38, 95% CI 1.09 to 1.75), African American (OR 1.82, 95%CI 1.36 to 2.45), idiopathic pulmonary fibrosis (IPF) (OR 1.78, 95% CI 1.49 to 2.13), sarcoidosis (OR 4.25, 95% CI 1.09 to 16.52), primary pulmonary hypertension (PPH) (OR 3.73, 95%CI 2.16 to 6.46), elevated BMI (BMI≥25 kg/m²) (OR 1.83, 95% CI 1.26 to 2.64), and use of cardiopulmonary bypass (CPB) (OR 2.29, 95%CI 1.43 to 3.65) were significantly associated with increased risk of PGD. Age, cystic fibrosis, secondary pulmonary hypertension (SPH), intra-operative inhaled nitric oxide (NO), or lung transplant type (single or bilateral) were not significantly associated with PGD development (all P>0.05). Moreover, a nearly 4 fold increased risk of short-term mortality was observed in patients with PGD (OR 3.95, 95% CI 2.80 to 5.57).

Conclusions

Our analysis identified several recipient related risk factors for development of PGD. The identification of higher-risk recipients and further research into the underlying mechanisms may lead to selective therapies aimed at reducing this reperfusion injury.