Obesity, adipokines, and lung disease

The many faces of asthma in obesity

Obesity is a major risk factor for the development of asthma, and causes severe, uncontrolled disease that responds poorly to therapy. The obese state alters early onset allergic asthma, and leads to the development of a novel form of late onset asthma secondary to obesity. The presentation of early onset allergic asthma is altered through effects on immune function. Factors such as mechanical loading, effects of adipokines on airways, altered diet, insulin resistance and altered metabolism of nitric oxide likely all contribute to increased airway reactivity in obesity, causing late onset asthma in obesity. Obesity also alters responses to environmental factors such as ozone and particulate matter. Focused studies to understand the importance of these factors in the pathogenesis of airway disease in obesity will be essential to develop therapies to intervene in this new epidemic of airway disease.

The influence of leptin on Th1/Th2 balance in obese children with asthma

OBJECTIVE:

In individuals with asthma, obesity induces the production of leptin and is associated with disease severity. Our objective was to evaluate the levels of serum leptin and their effect on Th1/Th2 balance in obese and non-obese children with asthma, as well as to investigate the association between serum leptin levels and clinical outcomes.

METHODS:

We evaluated 50 atopic children with physician-diagnosed moderate-to-severe persistent asthma and 20 controls. The children with asthma were divided into two groups, by body mass index percentile: obese (n = 25) and non-obese (n = 25). From all subjects, we collected peripheral blood samples in order to determine the levels of leptin, IFN-γ, and IL-4. Asthma severity was assessed by an asthma symptom score, and the results were correlated with the parameters studied.

RESULTS:

Serum leptin levels were significantly higher in the obese asthma group than in the non-obese asthma group, as well as being significantly higher in the children with asthma than in the controls, whereas IFN-γ levels were significantly higher and IL-4 levels were significantly lower in the obese asthma group than in the non-obese asthma group. In addition, the obese asthma group showed higher asthma symptom scores and significantly lower FEV₁ (% of predicted) than did the non-obese asthma group. There was a significant positive correlation between leptin and IFN-γ levels only in the obese asthma group.

CONCLUSIONS:

Although leptin is involved in the pathogenesis of asthma in obese and non-obese children, its effect is more pronounced in the former. In the presence of high leptin levels, only obese children with asthma exhibited Th1 polarization, with higher IFN-γ levels and greater asthma severity.

The association of asthma, nasal allergies, and positive skin prick tests with obesity, leptin, and adiponectin

BACKGROUND

Cross-sectional and longitudinal reports show that obese adults have more asthma than non-obese adults. A proposed mechanism is via effects of adipokines (leptin and adiponectin) on the immune system.

OBJECTIVE

We wished to measure the associations of asthma and other atopic diseases with serum adipokine levels and to find whether the associations with asthma were strong enough to rule out the possibility that they are secondary to the association of fatness measures with asthma.

METHODS

The Global Asthma and Allergy Network of Excellence (GA(2) LEN) clinical follow-up survey is a clinical survey, embedded in a larger multi-centre cross-sectional postal survey, involving, with a case/control design, enrichment of the sample with subjects with asthma and chronic rhinosinusitis (CRS). We recorded serum leptin or adiponectin in 845 men and 1110 women in 15 centres and also anthropometric measures of fatness including body mass index and waist/hip ratio, current asthma, and specific skin prick and IgE sensitisation. We used inverse sampling-probability-weighted rank and regression statistics to measure population associations of disease outcomes with adipokines in males and females, adjusting for confounders (area, age, smoking history, and number of elder siblings) and also mutually adjusting associations with adipokines and fatness measures.

RESULTS

One thousand nine hundred and fifty-five subjects aged 16-77 years had information on leptin or adiponectin levels. Leptin and leptin/adiponectin ratio were positively associated with the level of asthma, especially in females (Somers' D of leptin by asthma score, 0.20; 95% CI, 0.08-0.30; P = 0.00079). These associations were attenuated after adjusting for confounders and became non-significant after additionally adjusting for fatness measures and multiple comparisons.

CONCLUSIONS AND CLINICAL RELEVANCE

Asthma levels are positively associated with serum leptin. However, we cannot rule out the possibility that this association is secondary to associations of both with fatness measures.

Exploring the origins of asthma: Lessons from twin studies

This thesis explores the contribution of twin studies, particularly those studies originating from the Danish Twin Registry, to the understanding of the aetiology of asthma. First, it is explored how twin studies have established the contribution of genetic and environmental factors to the variation in the susceptibility to asthma, and to the variation in several aspects of the clinical expression of the disease such as its age at onset, its symptomatology, its intermediate phenotypes, and its relationship with other atopic diseases. Next, it is explored how twin studies have corroborated theories explaining asthma's recent increase in prevalence, and last, how these fit with the explanations of the epidemiological trends in other common chronic diseases of modernity.

Influence of diet and obesity on COPD development and outcomes

The global increase in the prevalence and incidence of obesity has called serious attention to this issue as a major public health concern. Obesity is associated with many chronic diseases, including cardiovascular disease and diabetes, and recently the role of overweight and obesity in lung disease has received new interest. Independently of obesity, diet also plays a role as a risk factor for many chronic diseases, and evidence is accumulating to support a role for diet in the prevention and management of several lung diseases. Chronic obstructive lung disease is the third-leading cause of death globally, and both obesity and diet appear to play roles in its pathophysiology. Obesity has been associated with decreased lung-function measures in population-based studies, with increased prevalence of several lung diseases and with compromised pulmonary function. In contrast, obesity has a protective effect against mortality in severe chronic obstructive pulmonary disease (COPD). Nutrient intake and dietary patterns have also been associated with lung-function measures and the development and progression of COPD. Taken together, this suggests that a focus on obesity and diet should be part of public health campaigns to reduce the burden of lung disease, and could have important implications for clinicians in the management of their patients. Future research should also focus on elucidating these relationships in diverse populations and age-groups, and on understanding the complex interaction between behavior, environment, and genetics in the development and progression of COPD. The goal of this article is to review current evidence regarding the role that obesity and diet play in the development of COPD, and in COPD-related outcomes.

Interaction of metabolic syndrome with asthma in postmenopausal women: role of adipokines

The increasing prevalence of both asthma and obesity are major health problems. Recent studies established a possible link between obesity and asthma; however, the underlying mechanism is not clear. The aim of the study was to analyze the prevalence of metabolic syndrome in postmenopausal subjects with asthma and search the interactions between adipokines, metabolic syndrome, and asthma. A total of 45 female patients (57.5 ± 13.9 years) with asthma and 30 healthy subjects (59.6 ± 12.8 years) in postmenopausal status were enrolled in this study. For the diagnosis of metabolic syndrome, modified World Health Organization diagnostic criteria were used. Blood levels of glucose, lipid profile, HbA1c, insulin, CRP, leptin, adiponectin, tumor necrosis factor-alpha, interleukin (IL)-6, IL-8 and plasminogen activator inhibitor-1 (PAI-1) were measured. The mean body mass index was 29.6 ± 5.4 for asthma patients and 28.2 ± 5.3 for the control group. The incidence of metabolic syndrome was found as 26 % for both groups. Insulin resistance as calculated by homeostasis model assessment (HOMA-IR) and fasting insulin levels were significantly higher in asthma patients (p < 0.001 for both parameters). Leptin levels were significantly higher (p = 0.001) and adiponectin levels were lower (p = 0.029) in asthma patients compared to controls. We concluded that although incidence of obesity and metabolic syndrome was not higher in postmenopausal asthma patients than controls, there was an impairment of glucose metabolism and altered adipokine levels in asthma patients.

Body mass index, asthma and exhaled nitric oxide in U.S. adults, 2007-2010

OBJECTIVE

Increases in asthma and obesity over the past three decades have led to speculation about a causal link between the two diseases. However, investigations of the relationship between body mass index (BMI) and fractional exhaled nitric oxide (FeNO) - a marker of eosinophilic airway inflammation - have produced mixed results. The purpose of this study was to evaluate the relationship between body mass index (BMI), asthma and FeNO in a sample of U.S. adults using data from the National Health and Nutrition Examination Surveys (NHANES) for 2007-2010.

METHODS

We assessed the relationship between FeNO and BMI in subjects with and without asthma using categorical and continuous models for BMI. All models controlled for age, gender, ethnicity, household income-to-poverty ratio, atopy and current smoking.

RESULTS

Adjusted asthma prevalence was positively associated with BMI, and subjects with asthma had higher adjusted FeNO levels than subjects without asthma. However, no association between FeNO and BMI was observed in either those with (β = 0.002, p = 0.74) or without (β = 0.0014, p = 0.51) asthma after adjusting for covariates.

CONCLUSIONS

Our results suggest that in the U.S. adult population, BMI is not associated with eosinophilic airway inflammation.

Adipokines NUCB2/nesfatin-1 and visfatin as novel inflammatory factors in chronic obstructive pulmonary disease

COPD (chronic obstructive pulmonary disease) is a common lung disease characterized by airflow limitation and systemic inflammation. Recently, adipose tissue mediated inflammation has gathered increasing interest in the pathogenesis of the disease. In this study, we investigated the role of novel adipocytokines nesfatin-1 and visfatin in COPD by measuring if they are associated with the inflammatory activity, lung function, or symptoms. Plasma levels of NUCB2/nesfatin-1 and visfatin were measured together with IL-6, IL-8, TNF- α , and MMP-9, lung function, exhaled nitric oxide, and symptoms in 43 male patients with emphysematous COPD. The measurements were repeated in a subgroup of the patients after four weeks' treatment with inhaled fluticasone. Both visfatin and NUCB2/nesfatin-1 correlated positively with plasma levels of IL-6 (r = 0.341, P = 0.027 and rho = 0.401, P = 0.008, resp.) and TNF- α (r = 0.305, P = 0.052 and rho = 0.329, P = 0.033, resp.) and NUCB2/nesfatin-1 also with IL-8 (rho = 0.321, P = 0.036) in patients with COPD. Further, the plasma levels of visfatin correlated negatively with pulmonary diffusing capacity (r = -0.369, P = 0.016). Neither of the adipokines was affected by fluticasone treatment and they were not related to steroid-responsiveness. The present results introduce adipocytokines NUCB2/nesfatin-1 and visfatin as novel factors associated with systemic inflammation in COPD and suggest that visfatin may mediate impaired pulmonary diffusing capacity.

Fatty acid nitroalkenes ameliorate glucose intolerance and pulmonary hypertension in high-fat diet-induced obesity

AIMS

Obesity is a risk factor for diabetes and cardiovascular diseases, with the incidence of these disorders becoming epidemic. Pathogenic responses to obesity have been ascribed to adipose tissue (AT) dysfunction that promotes bioactive mediator secretion from visceral AT and the initiation of pro-inflammatory events that induce oxidative stress and tissue dysfunction. Current understanding supports that suppressing pro-inflammatory and oxidative events promotes improved metabolic and cardiovascular function. In this regard, electrophilic nitro-fatty acids display pleiotropic anti-inflammatory signalling actions.

METHODS AND RESULTS

It was hypothesized that high-fat diet (HFD)-induced inflammatory and metabolic responses, manifested by loss of glucose tolerance and vascular dysfunction, would be attenuated by systemic administration of nitrooctadecenoic acid (OA-NO2). Male C57BL/6j mice subjected to a HFD for 20 weeks displayed increased adiposity, fasting glucose, and insulin levels, which led to glucose intolerance and pulmonary hypertension, characterized by increased right ventricular (RV) end-systolic pressure (RVESP) and pulmonary vascular resistance (PVR). This was associated with increased lung xanthine oxidoreductase (XO) activity, macrophage infiltration, and enhanced expression of pro-inflammatory cytokines. Left ventricular (LV) end-diastolic pressure remained unaltered, indicating that the HFD produces pulmonary vascular remodelling, rather than LV dysfunction and pulmonary venous hypertension. Administration of OA-NO2 for the final 6.5 weeks of HFD improved glucose tolerance and significantly attenuated HFD-induced RVESP, PVR, RV hypertrophy, lung XO activity, oxidative stress, and pro-inflammatory pulmonary cytokine levels.

CONCLUSIONS

These observations support that the pleiotropic signalling actions of electrophilic fatty acids represent a therapeutic strategy for limiting the complex pathogenic responses instigated by obesity.

Obesity in Bulgarian patients with chronic obstructive pulmonary disease

It has been well defined that obesity is strongly linked with several respiratory symptoms and diseases, but no convincing evidence has been provided for chronic obstructive pulmonary disease (COPD). In the current study, we aim to assess the possible prevalence of obesity in patients with COPD in a cross-sectional case–control study of individuals from the region of Stara Zagora, Bulgaria, and to explore whether the body mass has some effect on the lung function of COPD patients. The study included 158 patients with COPD (Global Initiative for Chronic Obstructive Lung Disease (GOLD) II, III, and IV stages) and 123 individuals unaffected by the disease (control). A higher frequency of obesity compared to the controls (20.3%) was observed in patients with COPD (29.1%, p = 0.093), especially in those with GOLD II stage (37.7%, p = 0.009). Prevalence of obesity was highest in COPD GOLD II, followed by GOLD III and IV stages ( p = 0.068). When diabetes was considered as confounding factor, we found a significant prevalence of obesity in COPD patients than the controls with diabetes ( p = 0.031). Interestingly, there was a statistically significant moderate positive correlation between the body mass index and forced expiratory volume in one second as a percentage of predicted value in the whole patients’ group ( R = 0.295, p = 0.0002) as well as in the subgroups of GOLD II ( R = 0.257, p = 0.024) and GOLD III COPD ( R = 0.259, p = 0.031).The results of our study propose that the increased body mass, particularly obesity is frequent comorbidity to COPD, especially to less severe diseases. Moreover, the results suggest that the higher body weight may provide some protection against the impairment of lung functions in patients with stable COPD.

The serum levels of adiponectin and leptin in mustard lung patients

INTRODUCTION

Chronic obstructive pulmonary disease (COPD) due to sulfur mustard (SM), known as mustard lung, is an important late pulmonary complication of SM poisoning. Due to the possible role of systemic inflammation in mustard lung, we evaluated the serum levels of adiponectin and leptin in these patients.

MATERIALS AND METHODS

Thirty nonsmoker mustard lung patients in stable phase were enrolled into this study. Also, 30 COPD and 21 healthy participants were entered as control groups. Complete lung function tests were performed in the participants. The serum levels of adiponectin and leptin were measured in all groups.

RESULTS

There were no statistically significant differences in mean adiponectin and leptin levels among the groups (p = 0.38 and p = 0.35, respectively). There was a downward trend in leptin to adiponectin ratio from lower to higher stages of global initiative for chronic obstructive lung disease guidelines in mustard lung patients, which was not statistically significant (p = 0.8).

CONCLUSION

Our results showed that there is no difference in mean adipokine levels in stable mustard lung patients compared with control groups. There was a foot-point in the alterations of serum adipokines regarding the severity of COPD, which needs to be documented by larger sample group.

Immunometabolism in obese asthmatics: are we there yet?

Obesity is now recognised as a worldwide epidemic. The recent International Association for the Study of Obesity/International Obesity Taskforce (IASO/IOTF) analysis estimates that approximately 1.0 billion adults are currently overweight and a further 475 million are obese. Obesity has huge psychosocial impact with obese children and adolescents facing discrimination and stigmatization in many areas of their lives leading to body dissatisfaction, low self-esteem and depression. Indeed, obesity is recognised as an important risk factor for the development of several chronic diseases such as hypertension, cancer, asthma and metabolic syndrome. Chronic low grade systemic inflammation is considered as a hallmark of obesity and may possibly explain the link between obesity and chronic disease, in particular the increased incidence, prevalence and severity of asthma in obese individuals. There is now strong evidence for infiltration of immune and inflammatory cells into adipose tissue that drives systemic inflammation and subsequent end organ damage. In addition to adipocytes, the key adipose tissue resident immune cells are macrophages and mast cells. Immunometabolism, as an emerging field of investigation, explores the pivotal role of these immune cells in translating immunological changes to metabolic effects in obesity. Abundance of free fatty acids, along with other inflammatory cytokines shift the balance of metabolic homeostasis to pro-inflammatory status by influencing the development of inflammatory cell lineage, which, further exhibits distinct functional phenotypes. There is emerging evidence for macrophage activation and functional polarization of an anti-inflammatory M₂ phenotype towards a pro-inflammatory M₁ phenotype of macrophages in obese adipose tissue. Similarly, studies in both obese humans and murine models reveal the pathognomic presence of an increased number of mast cells in visceral adipose tissue. These suggest a possible contribution of mast cells to the unique metabolome of obese asthma. This review examines proposed multilevel interactions between metabolic and immune systems in obese asthmatics that underlie the negative effects of obesity and may offer significant therapeutic promise.

The association of adiponectin with computed tomography phenotypes in chronic obstructive pulmonary disease

RATIONALE

Chronic obstructive pulmonary disease (COPD) is a heterogeneous disorder associated with systemic manifestations that contribute to its morbidity and mortality. Recent work suggests that biomarker signatures in the blood may be useful in evaluating COPD phenotypes and may provide insight into the pathophysiology of systemic manifestations. Adiponectin, primarily produced by fat cells, has been implicated in the pathophysiology of emphysema.

OBJECTIVES

To investigate the association of adiponectin with clinical and radiologic COPD phenotypes.

METHODS

Adiponectin levels were determined in 633 individuals, including 432 individuals with COPD from a cohort of former or current smokers enrolled in the COPDGene study. Univariate and multiple regression analysis were used to examine the association of adiponectin with clinical and physiologic data together with quantitative high-resolution computed tomography parameters.

MEASUREMENTS AND MAIN RESULTS

Multiple regression analysis confirmed that higher plasma adiponectin levels were independently associated with emphysema, decreasing body mass index, female sex, older age, and lower percentage change in prebronchodilator/post-bronchodilator FEV1.

CONCLUSIONS

The association between plasma adiponectin and computed tomography-assessed emphysema suggests a contribution of adiponectin to the development of emphysema and highlights a role for metabolic derangements in the pathophysiology of emphysema.

Adiponectin is associated with dynamic hyperinflation and a favourable response to inhaled glucocorticoids in patients with COPD

OBJECTIVES

Adipokines are protein mediators first described as products of adipose tissue regulating energy metabolism and appetite. Recently, adipokines have also been found to modulate inflammation and smooth muscle cell responses. Therefore we investigated the association of two adipokines, adiponectin and leptin, with the degree of emphysema, pulmonary function, symptoms and glucocorticoid responsiveness in patients with COPD.

METHODS

Plasma adiponectin and leptin levels, spirometry, body plethysmography and symptoms were measured in 43 male COPD patients with smoking history ≥ 20 pack-years, post bronchodilator FEV1/FVC < 0.7 and pulmonary emphysema on HRCT. The measurements were repeated in a subgroup of patients after 4 weeks' treatment with inhaled fluticasone.

RESULTS

In patients with COPD, plasma adiponectin levels correlated positively with airway resistance (Raw) (r = 0.362, p = 0.019) and functional residual capacity (FRC) (r = 0.355, p = 0.046). Furthermore, the baseline adiponectin concentration correlated negatively with the fluticasone induced changes in St George's Respiratory questionnaire (SGRQ) symptom score (r = -0.413, p = 0.040) and in FRC % pred (r = -0.428, p = 0.003), i.e. a higher baseline plasma adiponectin level was associated with more pronounced alleviation of symptoms and dynamic hyperinflation. Plasma leptin levels were not related to the measures of lung function, symptoms or glucocorticoid responsiveness.

CONCLUSIONS

Plasma adiponectin levels were associated with peripheral airway obstruction and dynamic hyperinflation in patients with COPD. A higher adiponectin level predicted more favourable relief of symptoms and hyperinflation during glucocorticoid treatment. Adiponectin may have a role in the COPD pathogenesis; it may also be a biomarker of disease severity and treatment responses in this disease.

Loss of phosphatase and tensin homolog (PTEN) induces leptin-mediated leptin gene expression: feed-forward loop operating in the lung

Elevated levels of systemic and pulmonary leptin are associated with diseases related to lung injury and lung cancer. However, the role of leptin in lung biology and pathology, including the mechanism of leptin gene expression in the pathogenesis of lung diseases, including lung cancer, remains elusive. Here, using conditional deletion of tumor suppressor gene Pten in the lung epithelium in vivo in transgenic mice and human PTEN-null lung epithelial cells, we identify the leptin-driven feed-forward signaling loop in the lung epithelial cells. Leptin-mediated leptin/leptin-receptor gene expression likely amplifies leptin signaling that may contribute to the pathogenesis and severity of lung diseases, resulting in poor clinical outcomes. Loss of Pten in the lung epithelial cells in vivo activated adipokine signaling and induced leptin synthesis as ascertained by genome-wide mRNA profiling and pathway analysis. Leptin gene transcription was mediated by binding of transcription factors NRF-1 and CCAAT/enhancer-binding protein δ (C/EBP) to the proximal promoter regions and STAT3 to the distal promoter regions as revealed by leptin promoter-mutation, chromatin immunoprecipitation, and gain- and loss-of-function studies in lung epithelial cells. Leptin treatment induced expression of the leptin/leptin receptor in the lung epithelial cells via activation of MEK/ERK, PI3K/AKT/mammalian target of rapamycin (mTOR), and JAK2/STAT3 signaling pathways. Expression of constitutively active MEK-1, AKT, and STAT3 proteins increased expression, and treatment with MEK, PI3K, AKT, and mTOR inhibitors decreased LEP expression, indicating that leptin via MAPK/ERK1/2, PI3K/AKT/mTOR, and JAK2/STAT3 pathways, in turn, further induces its own gene expression. Thus, targeted inhibition of the leptin-mediated feed-forward loop provides a novel rationale for pharmacotherapy of disease associated with lung injury and remodeling, including lung cancer.

Sociocultural characteristics, obesity and inflammatory biomarkers in Puerto Rican toddlers born in New York City

BACKGROUND

In the USA, Puerto Rican children have a higher prevalence of asthma than other Latino ethnicities, and acculturation is one of hypothesized reasons for this difference. We examined associations between sociocultural characteristics and serum leptin, high-sensitivity C-reactive protein (hsCRP), and body mass index (BMI), and further, among hsCRP, leptin levels, BMI percentiles, and allergic sensitization in 2-year-old children.

METHODS

IgE antibodies, leptin, and hsCRP concentrations were measured in serum from Puerto Rican toddlers (n = 143) born in New York City with a maternal history of allergy and/or asthma. Demographic and home characteristics questionnaires were administered to the mother, postpartum and two years later. Children's weight and height were measured to determine BMI percentiles.

RESULTS

More girls (60%) had leptin levels above the median compared with boys (37%) (p = 0.0063). Leptin was positively correlated with BMI (r = 0.25; p = 0.0042). Children in daycare were more likely to be obese (40% vs. 24% p < 0.06). Maternal birthplace was significantly associated with children's leptin but not with hsCRP. Leptin levels were lower for children whose mothers were born on the US mainland (GM = 2.5 ng/ml, 95% CI [2.2-2.7]) compared with those whose mothers were born in Puerto Rico or another country (GM = 3.2 ng/ml, 95% CI [2.2-3.9], t-test p = 0.01). Mothers born in another country were more likely than those born in the US mainland or Puerto Rico to have obese children (60% vs. 26% p < 0.02). Leptin, hsCRP, and BMI percentile were not associated with sensitization to any of the measured inhalant allergens or total IgE.

CONCLUSION

Even at a very young age, some acculturation factors were associated with biomarkers and anthropometric measures of obesity among this Puerto Rican pediatric population. To our knowledge, this is the first study demonstrating the association of mother's birth place with child BMI and leptin as early as 24 months.

Obesity increases eosinophil activity in asthmatic children and adolescents

Background

A clear relationship between asthma and obesity has been reported, but the mechanisms remain unclear. The aim of this study was to evaluate the influence of obesity on eosinophil activity (chemotaxis and adhesion) in asthmatic children and adolescents compared with cells from healthy volunteers.

Methods

Asthmatic obese (AO), asthmatic non-obese (ANO), non-asthmatic obese (NAO) and non-asthmatic non-obese (NANO) individuals were included in the present study. The chemotaxis of eosinophils after stimulation with eotaxin (300 ng/ml), platelet-activating factor (10 μM; PAF) and RANTES (100 ng/ml) was performed using a microchemotaxis chamber. The eosinophil peroxidase activity was measured to determine the adhesion activity of eosinophils cultivated on fibronectin-coated plates. The serum leptin, adiponectin, TNF-α and IgE levels were quantified using ELISA assays.

Results

The serum IgE levels and eosinophil counts were significantly higher in asthmatic (obese and non-obese) individuals compared with non-asthmatic individuals (obese and non-obese). Spontaneous eosinophil chemotaxis was greater in the AO group compared with either the ANO or NANO groups. The activation of eosinophils using eotaxin and PAF increased eosinophil chemotaxis in the AO group. RANTES treatment increased eosinophil chemotaxis in the NAO group compared with the NANO or ANO groups. The activation of eosinophils using eotaxin significantly increased eosinophil adhesion in the AO group compared with other groups. The serum leptin and TNF-α levels were higher in obese subjects (asthmatic and non-asthmatic), whereas the levels of adiponectin did not significantly differ among these groups.

Conclusion

This study is the first to show increased eosinophilic activity (chemotaxis and adhesion) associated with high serum leptin and TNF-α levels in atopic asthmatic obese children and adolescents compared with non-obese healthy volunteers.

The association of asthma with BMI and menarche in the 1958 British Birth Cohort

BACKGROUND

Obesity and early menarche have been associated with asthma. In this report, we assess the association of asthma with BMI and with changes in BMI from childhood to early adulthood. In addition, we determine if, in girls, any observed association of asthma with menarche can be explained by BMI.

METHODS

In a large national birth cohort, the associations of asthma at age 7, 11, 16 and 33 years with BMI, and of, asthma at age 33 years with changes in BMI from age 7 to age 33 years was assessed using logistic and mixed effects models as appropriate. Associations of asthma with age of menarche in girls were similarly assessed with and without adjustment for BMI.

RESULTS

Information on asthma, BMI, onset of menarche and confounders at all assessments was available for 1968 girls and 2223 boys. Obesity was relatively uncommon (<2%) in childhood. Overweight (BMI 25+) girls had more asthma. Girls with early menarche were more likely to be overweight. At age 11 years, asthma was associated with early menarche (OR = 1.70, 95% CI 1.17-2.47, after adjustment for BMI OR = 1.60, 95% CI 1.10-2.34). Across all ages, asthma was significantly associated with BMI (OR = 1.50, 95% CI 1.18-1.90) but not with early menarche (OR = 1.24, 95% CI 0.95-1.63).

CONCLUSION

Asthma is more common in overweight girls. Early menarche is more common in overweight girls but this does not explain its association with asthma at age 11 years. Early menarche is not a risk factor for asthma at age 33 years in this cohort.

The effect of low lung volume on airway function in obesity

INTRODUCTION

Obesity is associated with reduced operating lung volume. We hypothesized that obesity induces airway dysfunction independent of reduced FRC.

METHODS

18 obese (BMI: 41.3 ± 6.8) and 17 non-obese subjects (BMI: 24.8 ± 2.3 kg/m(2)) had measurements of conductance (Grs) and reactance (Xrs) by forced oscillation technique, ventilation heterogeneity (lung clearance index (LCI), Scond, Sacin) by multiple breath nitrogen washout and closing capacity (CC) by single breath nitrogen washout.

RESULTS

Obese had higher LCI and Sacin and lower Grs and Xrs. After adjustment for FRC, Grs (r=-0.52, p=0.001), and Sacin (r=0.47, p=0.004) still correlated with BMI. Closing capacity (as % predicted TLC) was not increased but was closer to FRC in the obese (CC/FRC: 95.0 ± 21.7% vs 71.7 ± 19.2%, p<0.001). Xrs and LCI correlated with CC/FRC.

CONCLUSIONS

In obesity, there are abnormalities in airway function that are independent of reduced FRC. Airway closure is not increased but CC occurs close to FRC, affecting Xrs and LCI.

Whole-body cryostimulation as an effective method of reducing low-grade inflammation in obese men

This study was aimed to evaluate anti-inflammatory effect of the whole body cryostimulation in obese men. Fourteen subjects (BMI >30 kg m⁻²), divided into two subgroups according to cardiorespiratory fitness: higher (HCF) or lower (LCF), have been exposed to 10 sessions in a cryogenic chamber (−110 °C). Blood samples were collected before, 30 min and 24 h after the first, fifth and last cryostimulation. Coldness exposures affected blood cytokine profile; however, the response depended on subjects’ fitness capacity. Concentrations of pro-inflammatory cytokines in the LCF decreased by 19, 6.8, and 7.4 % in IL-6, resistin, and visfatin, respectively. TNFα in the LCF dropped 4.3-fold compared to baseline, while in the HCF, changes were smaller, yet significant. Anti-inflammatory cytokine IL-10 increased in both groups. No changes in adiponectin and leptin were observed in either group. Obtained results suggest that whole body cryostimulation can be a supplementary method for obese in reducing systemic inflammation.

The treatment of asthma in obesity

The world is facing an unprecedented epidemic of obesity. This epidemic has led to major changes in the epidemiology of common diseases such as asthma. Obesity is a major risk factor for new-onset asthma. This article will discuss the role of mechanical and metabolic factors, as well as obesity-related comorbidities, in both causing airway disease and also affecting response to therapy in obese asthmatics. Asthma in obese individuals probably includes a spectrum of disease with at least two distinct phenotypes: early-onset allergic disease complicated by obesity and late-onset disease developing in the setting of obesity. Both phenotypes are distinct from asthma in lean individuals. Treatment of asthma in obesity needs to consider altered response to controller therapy, and the fact that mechanical factors, metabolic inflammation and other comorbidities are probably contributing to airway disease. Future studies should focus on the development of therapies specifically tailored towards the treatment of asthma in obesity.

Review on the impact of pregnancy and obesity on influenza virus infection

A myriad of risk factors have been linked to an increase in the severity of the pandemic H1N1 2009 influenza A virus [A(H1N1)pdm09] including pregnancy and obesity where death rates can be elevated as compared to the general population. The goal of this review is to provide an overview of the influence of pregnancy and obesity on the reported cases of A(H1N1)pdm09 virus infection and of how the concurrent presence of these factors may have an exacerbating effect on infection outcome. Also, the hypothesized immunologic mechanisms that contribute to A(H1N1)pdm09 virus severity during pregnant or obese states are outlined. Identifying the mechanisms underlying the increased disease severity in these populations may result in improved therapeutic approaches and future pandemic preparedness.

The impact of body mass index on the physiology of patients with polytrauma

PURPOSE

Obesity is a growing problem in industrial nations. The aim was to test the hypothesis that overweight patients face early physiologic impairment.

METHODS

A total of 651 patients were included in this retrospective study, with an injury severity score greater than 16 and 16 years or older. The sample was subdivided into 3 groups: body mass index (BMI) less than 25 kg/m(2), BMI of 25 to 30 kg/m(2), and BMI greater than 30 kg/m(2). Physiologic scores-Murray, Goris, Marshall and Sequential Organ Failure Assessment scores-were analyzed at admission and at the day of their maximum. Analysis of variance and χ(2) tests were used, and the significance level was set at P < .05.

RESULTS

All 4 scores showed significant differences at their maxima according to the 3 BMI groups, respectively: Murray score (P < .001), Goris score (P < .05), Marshall score (P < .001), and Sequential Organ Failure Assessment score (P <.05). The injury severity score values of the 3 groups at admission were 27.6 ± 12.0, 29.6 ± 13.2, and 25.3 ± 9.2, respectively (P < .05). The overall mortality rates in the 3 groups were 15.1%, 21.0%, and 20%, respectively (P < .001).

CONCLUSIONS

Anticipating BMI-specific critical trauma problems will become mandatory for effective polytrauma treatment in industrialized nations given their increasing prevalence of obesity.

Obesity and asthma: an inflammatory disease of adipose tissue not the airway

RATIONALE

Obesity is a major risk factor for asthma; the reasons for this are poorly understood, although it is thought that inflammatory changes in adipose tissue in obesity could contribute to airway inflammation and airway reactivity in individuals who are obese.

OBJECTIVES

To determine if inflammation in adipose tissue in obesity is related to late-onset asthma, and associated with increased markers of airway inflammation and reactivity.

METHODS

We recruited a cohort of obese women with asthma and obese control women. We followed subjects with asthma for 12 months after bariatric surgery. We compared markers in adipose tissue and the airway from subjects with asthma and control subjects, and changes in subjects with asthma over time.

MEASUREMENTS AND MAIN RESULTS

Subjects with asthma had increased macrophage infiltration of visceral adipose tissue (P < 0.01), with increased expression of leptin (P < 0.01) and decreased adiponectin (p < 0.001) when controlled for body mass index. Similar trends were observed in subcutaneous adipose tissue. Airway epithelial cells expressed receptors for leptin and adiponectin, and airway reactivity was significantly related to visceral fat leptin expression (rho = -0.8; P < 0.01). Bronchoalveolar lavage cytokines and cytokine production from alveolar macrophages were similar in subjects with asthma and control subjects at baseline, and tended to increase 12 months after surgery.

CONCLUSIONS

Obesity is associated with increased markers of inflammation in serum and adipose tissue, and yet decreased airway inflammation in obese people with asthma; these patterns reverse with bariatric surgery. Leptin and other adipokines may be important mediators of airway disease in obesity through direct effects on the airway rather than by enhancing airway inflammation.

Adipokine adipsin is associated with the degree of lung fibrosis in asbestos-exposed workers

OBJECTIVES

Asbestos-exposure causes an inflammatory response driven by alveolar macrophages that can lead to pulmonary fibrosis. In addition to classical inflammatory cytokines, macrophages produce adipokines which regulate the inflammatory response. We studied if adipokines are related to the degree of parenchymal fibrosis, impaired lung function and inflammation in asbestos-exposed subjects.

METHODS

Eighty-five males with moderate to heavy occupational exposure to asbestos and unexposed controls were studied. We measured plasma levels of adipokines adiponectin, adipsin, leptin and resistin, IL-6, IL-8, erythrocyte sedimentation rate (ERS), spirometry and D(L,CO). Degree of interstitial lung fibrosis (septal thickening, subpleural lines, parenchymal bands or honeycombing) was scored in classes 0-5 according to a validated scoring system. The subjects were divided into three groups: normal parenchymal finding (fibrosis class 0), borderline changes (classes 0.5-1.5) and fibrosis (i.e. asbestosis; classes 2-5).

RESULTS

Adipsin correlated positively with parenchymal fibrosis (rho=0.412, p<0.001) and there was a linear increasing trend of mean plasma adipsin levels among the three groups of asbestos-exposed subjects (from normal parenchymal finding to borderline changes and to fibrosis) (p<0.0001). Accordingly, plasma adipsin levels correlated positively with the extent of pleural plaques (r=0.245, p=0.043), and negatively with D(L,CO) (r=-0.246, p=0.023). Also, a positive correlation was found between adipsin and inflammatory markers ESR (r=0.315, p=0.008) and IL-6 (r=0.256, p=0.018).

CONCLUSIONS

Adipsin was associated with the degree of parenchymal fibrosis, impairment of pulmonary diffusing capacity and with inflammatory activity in asbestos-exposed subjects suggesting that adipsin may have a role in the pathogenesis or as a biomarker in asbestos-induced lung disease.

Circulating levels of adiponectin, leptin, fetuin-A and retinol-binding protein in patients with tuberculosis: markers of metabolism and inflammation

BACKGROUND

Wasting is known as a prominent feature of tuberculosis (TB). To monitor the disease state, markers of metabolism and inflammation are potentially useful. We thus analyzed two major adipokines, adiponectin and leptin, and two other metabolic markers, fetuin-A and retinol-binding protein 4 (RBP4).

METHODS

The plasma levels of these markers were measured using enzyme-linked immunosorbent assays in 84 apparently healthy individuals (=no-symptom group) and 46 patients with active pulmonary TB around the time of treatment, including at the midpoint evaluation (=active-disease group) and compared them with body mass index (BMI), C-reactive protein (CRP), chest radiographs and TB-antigen specific response by interferon-γ release assay (IGRA).

RESULTS

In the no-symptom group, adiponectin and leptin showed negative and positive correlation with BMI respectively. In the active-disease group, at the time of diagnosis, leptin, fetuin-A and RBP4 levels were lower than in the no-symptom group [adjusted means 2.01 versus 4.50 ng/ml, P<0.0001; 185.58 versus 252.27 µg/ml, P<0.0001; 23.88 versus 43.79 µg/ml, P<0.0001, respectively]. High adiponectin and low leptin levels were associated with large infiltrates on chest radiographs even after adjustment for BMI and other covariates (P=0.0033 and P=0.0020). During treatment, adiponectin levels increased further and then decreased. Leptin levels remained low. Initial low levels of fetuin-A and RBP4 almost returned to the normal reference range in concert with reduced CRP.

CONCLUSIONS

Our data and recent literature suggest that low fat store and underlying inflammation may regulate these metabolic markers in TB in a different way. Decreased leptin, increased adiponectin, or this ratio may be a promising marker for severity of the disease independent of BMI. We should further investigate pathological roles of the balance between these adipokines.

Chronic cough and OSA: a new association?

Chronic cough is defined as cough lasting more than 2 months. Common causes for chronic cough in nonsmokers with normal chest radiographs and pulmonary functions include gastroesophageal reflux disease (GERD), cough-variant asthma (CVA), and upper airway cough syndrome (UACS). Current guidelines recommend diagnosing the etiology of chronic cough based upon the results of therapy for suspected GERD, CVA, and UACS. Despite following current recommendations for diagnosis and treatment, the cause for a significant proportion of chronic cough remains unexplained.Recent reports indicate the resolution of chronic cough following treatment of concomitantly diagnosed obstructive sleep apnea (OSA). Whether this represents a co-occurrence of two commonly prevalent disorders or a pathophysiologic relationship between OSA and cough remains unknown. This review offers insights into a pathophysiologic link between OSA and the commonly purported etiologies for cough, namely, GERD, UACS, and CVA. In addition, evidence for a relationship between airway inflammation that can trigger or perpetuate cough and OSA is discussed. This review explores mechanisms by which nocturnal continuous positive airway therapy resolves cough by improving underlying airway inflammation secondary to OSA and impacts upon GERD, CVA, and UACS.

Association of bone mineral density, parameters of bone turnover, and body composition in patients with chronic obstructive pulmonary disease

Patients with chronic obstructive pulmonary disease (COPD) often develop osteoporosis. Many hormones regulate bone metabolism and body composition, and some of them are affected in COPD patients vs controls. In 46 COPD patients, we measured hip neck, total hip, lumbar spine, and whole-body T-score with dual-energy X-ray absorptiometry, parameters of body composition (body mass index [BMI], fat mass index [FMI], and fat-free mass index [FFMI]), and adiponectin, leptin, parathormone, osteocalcin, calcitonin, and insulin-like growth factor I (IGF-I) serum levels and correlated them with COPD stage. Our results suggest that total hip bone mineral density (BMD) is affected by FFMI and COPD stage; lumbar spine BMD is affected by FMI and COPD stage; and whole-body BMD is affected by BMI, COPD stage, and leptin. Adiponectin, parathormone, osteocalcin, calcitonin, and IGF-I levels were not significantly correlated to BMD at any of the measured sites. Our findings are in agreement with the current literature in that a decline in lung function is correlated to a decline in BMD.

Prevalence and severity of asthma in obese adult candidates for bariatric surgery

OBJECTIVE

To determine the prevalence of asthma in a group of obese adult candidates for bariatric surgery and to evaluate the severity of asthma in this group of patients.

METHODS

This was a cross-sectional study involving 363 obese adults (body mass index > 35 kg/m²) evaluated by a pulmonologist, using clinical evaluation as a diagnostic tool for asthma. All patients underwent clinical evaluation and spirometry and were divided into two groups (asthma and control). The patients with asthma were stratified by the severity of asthma.

RESULTS

The prevalence of asthma in the obese population studied was 18.5% (95% CI: 14.5-22.4). That prevalence was 20.4% (95% CI: 16.2-24.5) and 13.7% (95% CI: 10.1-17.2) in the women and the men, respectively. Asthma symptoms in the last twelve months were present in 8.0% (95% CI: 5.2-10.7), and the initial manifestation of asthma symptoms occurred during childhood/adolescence in 17.4% (95% CI: 13.5-21.3). In the asthma group, intermittent asthma was present in 29 patients (43.3%), mild persistent asthma in 7 (10.4%), moderate asthma in 25 patients (37.3%), and severe persistent asthma in 6 (9.0%).

CONCLUSIONS

Using clinical evaluation as the diagnostic criterion, we found the prevalence of asthma to be high in this group of obese adults. Asthma was more common in females, and the initial manifestation of asthma symptoms more commonly occurred during childhood/adolescence. The severity of asthma in this group of obese adults was within the range of mean values predicted for the general population. Intermittent asthma, mild persistent asthma, and moderate persistent asthma predominated.

Reduction in the leptin concentration as a predictor of improvement in lung function in obese adolescents

OBJECTIVE

To assess the effects of weight loss on adipokines, asthma-related symptoms, exercise-induced bronchospasm (EIB) and lung function, and to evaluate the role of leptin and adiponectin levels on lung function after treatment in obese adolescents.

METHODS

84 postpubertal obese adolescents were enrolled and distributed in quartiles according to weight loss (low (<2.5 kg), low to moderate (>2.5 and <8 kg), moderate (<8 and <14 kg) and massive (<14 kg)). Body composition was measured by plethysmography, and visceral and subcutaneous fat were detected by ultrasound. Serum levels of adiponectin and leptin were analyzed. Lung function, asthma and EIB were evaluated according to the American Thoracic Society criteria. Patients were submitted to 1 year of interdisciplinary intervention consisting of physiotherapy, medical, nutritional, exercise, and psychological therapy.

RESULTS

After treatment the moderate and massive weight loss promoted an increase in adiponectin and adiponectin/leptin (A/L) ratio as well as a decrease in leptin levels and a reduction in EIB frequency and asthma-related symptoms. Furthermore, the reduction in leptin levels was a predictor factor to improvement in lung function.

CONCLUSION

Interdisciplinary therapy was able to decrease EIB and asthma-related symptoms and to improve pro/anti-inflammatory adipokines. Additionally, the leptin concentration was a predictor factor to explain changes in lung function.

Adipokines and their role in allergies

Both allergic disorders and obesity keep increasing in industrialized countries. Even though a strong association between obesity and allergy- related diseases has been reported in several studies, no published data show a scientific and firm link in-between the two conditions. In general, obesity and weight gain have been associated with an increased risk of asthma and allergic rhinitis. Asthma, allergic rhinitis and obesity have a common inflammatory pattern that could therefore justify their association. In fact, the chronic inflammation that characterizes the increase in white adipose tissue typically pushes the immune system toward a Th2 pattern. Such a polarization might, consequentially, worsen a pre-existing allergic disease or even stimulate the evolution from a sensitization to a respiratory form of allergy. Several studies have been published on the role of different adipokines on allergic diseases. We focus our review on the role of adipokines on asthma and allergic rhinitis.

Role of adipokines and hormones of obesity in childhood asthma

PURPOSE

The aim of this study was to evaluate serum levels of leptin, ghrelin, and adiponectin in obese and non-obese children with asthma and in healthy non-asthmatic children, and analyze their relationships with clinical outcomes.

METHODS

This study enrolled 40 obese and 51 non-obese children with asthma and 20 healthy children. Body mass index and serum leptin, ghrelin, and adiponectin levels were determined in all children. Asthma symptom scores and lung function test results were recorded for subjects with asthma.

RESULTS

Serum leptin levels (11.8±7.9, 5.3±6.8, and 2.1±2.4 ng/mL in the obese asthmatic, non-obese asthmatic, and control groups, respectively) and adiponectin levels (12,586.2±3,724.1; 18,089.3±6,452.3; and 20,297.5±3,680.7 ng/mL, respectively) differed significantly among the groups (P<0.001 for all). Mean ghrelin levels were 196.1±96.8 and 311.9±352.8 pg/mL in the obese and non-obese asthmatic groups, respectively, and 348.8±146.4 pg/mL in the control group (P=0.001). The asthma symptom score was significantly higher in the obese children with asthma than in the non-obese children with asthma (P<0.001). Leptin and adiponectin levels were correlated with the asthma symptom score in non-obese children with asthma (r=0.34 and r=-0.62, respectively).

CONCLUSIONS

Obesity leads to more severe asthma symptoms in children. Moreover, leptin, adiponectin, and ghrelin may play important roles in the inflammatory pathogenesis of asthma and obesity co-morbidity.

Molecular mechanisms of cancer development in obesity

The increasing incidence of obesity and its co-morbid conditions poses a great challenge to global health. In addition to cardiovascular disease and diabetes, epidemiological data demonstrate a link between obesity and multiple types of cancer. The molecular mechanisms underlying how obesity causes an increased risk of cancer are poorly understood. Obesity disrupts the dynamic role of the adipocyte in energy homeostasis, resulting in inflammation and alteration of adipokine (for example, leptin and adiponectin) signalling. Additionally, obesity causes secondary changes that are related to insulin signalling and lipid deregulation that may also foster cancer development. Understanding these molecular links may provide an avenue for preventive and therapeutic strategies to reduce cancer risk and mortality in an increasingly obese population.

Genetics of maximally attained lung function: a role for leptin?

OBJECTIVES

To estimate the heritabilities of maximally attained lung function in young adult twins, and to examine whether circulating leptin, leptin (LEP) and leptin receptor (LEPR) gene polymorphisms are associated with maximally attained lung function.

METHODS

Measures on forced expiratory volume in 1 s (FEV(1)) and forced vital capacity (FVC) were available of 578 twins recruited from the East Flanders Prospective Twin Survey (165 monozygotic (MZ) and 73 dizygotic (DZ) complete pairs and 102 single twins). Twin model fitting and (genetic) association analyses were performed.

RESULTS

Intra-pair correlations of FEV(1) and FVC did not differ significantly between MZ monochorionic and MZ dichorionic pairs. Heritability estimates of FEV(1) and FVC were 69% and 63%, respectively. The A allele of the LEP 19G>A SNP was significantly associated with a lower FEV(1) (p(Additive) = 0.01) and FVC (p(Dominant) = 0.047), while the LEPR K109R and Q223R SNPs showed no associations. Accounting for body mass index, serum leptin was negatively associated with FVC (p = 0.02) in men, but not in women.

CONCLUSIONS

More than 60% of variation in maximally attained FEV(1) and FVC is explained by genetic factors. Moreover, these results suggest that leptin may be important in the determination of maximally attainable lung function.

Respiratory complications of obesity

Obesity, well known as a cardiovascular risk factor, can also lead to significant respiratory complications. The respiratory changes associated with obesity extend from a simple change in respiratory function, with no effect on gas exchange, to the more serious condition of hypercapnic respiratory failure, characteristic of obesity hypoventilation syndrome. More recently, it has been reported that there is an increased prevalence of asthma which is probably multifactorial in origin, but in which inflammation may play an important role. Hypoventilation in the obese subject is the result of complex interactions that involve changes in the ventilatory mechanics and anomalies in breathing control. Two other conditions (COPD and sleep apnea-hypopnea syndrome [SAHS], often present in obese patients, can trigger or aggravate it. The prevalence of hypoventilation in the obese is under-estimated and the diagnosis is usually established during an exacerbation, or when the patient is studied due to suspicion of SAHS. Ventilatory management of these patients includes either CPAP or NIV. The choice of one or another will depend on the underlying clinical condition and whether or not there is another comorbidity. Both NIV and CPAP have demonstrated their effectiveness, not only in the control of gas exchange, but also in improving the quality of life and survival of these patients.

Adiposity, adipokines, and exhaled nitric oxide in healthy adults without asthma

BACKGROUND

Epidemiological studies have shown that obesity/adiposity is closely associated with asthma in terms of development, severity, and control of asthma. However, effects of obesity/adiposity on airway inflammation are not well known in subjects without asthma. We assessed whether fractional exhaled nitric oxide (FeNO), a marker of eosinophilic airway inflammation, was associated with obesity/adiposity in nonasthmatic healthy adults.

METHODS

We measured FeNO and serum levels of adipose-derived hormones and adipokines in 117 adult subjects without a previous diagnosis of asthma or current asthmatic symptoms. Associations between FeNO and measures of obesity/adiposity [body mass index (BMI), body fat mass, and body fat percentages] were examined by correlation analyses and uni- and multivariate linear regression analyses.

RESULTS

FeNO was not significantly associated with BMI, body fat mass, or body fat percentage by a multivariate linear regression model, adjusting for age, gender, chronic rhinitis, atopy, and lung function. No significant association of FeNO with serum levels of leptin, adiponectin, tumor necrosis factor (TNF)-α, or interleukin (IL)-6 was observed.

CONCLUSIONS

These findings suggest that in healthy subjects without asthma, obesity/adiposity has no significant effect on eosinophilic airway inflammation and that hormones and systemic inflammation derived from adipose tissue do not affect eosinophilic airway inflammation.

Effect of obesity on asthma phenotype is dependent upon asthma severity

BACKGROUND

We recently reported that obese and non-obese patients with asthma have similar airflow limitation and bronchodilator responsiveness, but obese patients have more symptoms overall. There is limited information on the effect of obesity on asthmatics of varying severity measured by objective physiological parameters. Understanding how obesity affects asthmatics of differing severity can provide insights into the pathogenesis of asthma in the obese and a rationale for the therapeutic approach to such patients.

METHODS

Participants with asthma from two American Lung Association--Asthma Clinical Research Center (ALA-ACRC) studies were grouped by tertiles of airflow obstruction (forced expiratory volume in one second (FEV(1)%) predicted, FEV(1)/forced vital capacity (FVC)) and methacholine reactivity (PC(20)FEV(1)). Within each tertile, we examined the independent effect of body mass index (BMI), divided into normal weight, overweight, and obese categories, on lung function, airway reactivity, and symptoms.

RESULTS

Overall, both FEV(1) and FVC decreased and symptoms worsened with increasing BMI; airway reactivity was unchanged. When stratified by the degree of airflow obstruction, higher BMI was not associated with greater airway reactivity to methacholine. Higher BMI was associated with more asthma symptoms only in the least obstructed FEV(1)/FVC tertile. When stratified by degree of airway reactivity, BMI was inversely associated with FVC in all PC(20)FEV(1) tertiles. BMI was directly associated with asthma symptoms only in those with the least airway reactivity.

CONCLUSIONS

Obesity does not influence airway reactivity in patients with asthma and it is associated with more symptoms only in those with less severe disease.

Respiratory function and the obesity paradox

PURPOSE OF REVIEW

Obese individuals have impaired respiratory function relative to their normal-weight counterparts. Despite these negative effects, obesity is paradoxically associated with better survival in individuals with chronic obstructive pulmonary disease (COPD). The purpose of this review is to describe this 'obesity paradox', to discuss the effects of obesity on respiratory function, and to speculate as to whether obesity-related alterations in respiratory mechanics can influence the natural history of COPD.

RECENT FINDINGS

Given the known negative effects of obesity on respiratory physiology, it is reasonable to predict that obese COPD patients would be more likely to experience greater dyspnea and exercise intolerance relative to COPD patients of normal weight. However, recent evidence suggests that obese COPD patients have similar or better dyspnea scores during exercise and do not have diminished exercise capacity. These observations may be attributable to the fact that obese COPD patients have reduced operating lung volumes and higher inspiratory capacity to total lung capacity ratios than their lean COPD counterparts.

SUMMARY

Obese patients with COPD do not appear to be at a disadvantage during exercise relative to lean COPD patients. Obesity may be associated with improved survival in COPD but specific mechanisms for this paradox remain to be elucidated.