The relationship of serum triglycerides, serum HDL, and obesity to the risk of wheezing in 85,555 adults

Association of blood lipid profiles and asthma: A bidirectional two-sample Mendelian randomization study

BACKGROUND

Observational studies and meta-analyses have indicated associations between blood lipid profiles and asthma. However, the causal association is unknown. Therefore, this study investigated the causal relationship between blood lipid profiles and asthma using bidirectional Mendelian randomization analysis.

METHODS AND MATERIALS

Our analyses were performed using individual data from the Taiwan Biobank and summary statistics from the Asian Genetic Epidemiology Network (AGEN). The causal estimates between all genetic variants, exposures of interest and asthma were calculated using an inverse-variance weighted method based on Taiwan Biobank data from 24,853 participants (mean age, 48.8 years; 49.8% women). Sensitivity analyses, including the weighted median, MR Egger regression, MR-PRESSO, mode-based estimate, contamination mixture methods, and leave-one-out analysis, were applied to validate the results and detect pleiotropy.

RESULTS

In the inverse-variance weighted (IVW) analyses, we found evidence of a significant causal effect of an increased level of low-density lipoprotein cholesterol on asthma risk (βIVW = 1.338, p = 0.001). A genetically decreased level of high-density lipoprotein cholesterol was also associated with asthma risk (βIVW = -0.338, p = 0.01). We also found that an increased level of total cholesterol was associated with an increased risk of asthma (βIVW = 1.343, p = 0.001). Several sensitivity analyses generated consistent findings. We did not find evidence to support the causality between asthma and blood lipid profiles in either direction.

CONCLUSION

Our results supported the causal relationship between higher levels of LDL cholesterol and total cholesterol and lower levels of HDL cholesterol with an increased risk of asthma.

Association between serum lipid and all-cause mortality in asthmatic populations: a cohort study

BACKGROUND

Presently, the majority of investigations primarily evaluate the association between lipid profiles and asthma. However, few investigations explore the connection between lipids and mortality related to the disease. This study aims to explore the association of serum lipids with all-cause mortality within asthmatic adults.

METHODS

The investigation included 3233 eligible patients with asthma from the NHANES (2011-2018). The potential associations were explored using three Cox proportional hazards models, restricted cubic splines (RCS), threshold effect models, and CoxBoost models. In addition, subgroup analyses were conducted to investigate these associations within distinct populations.

RESULTS

After controlling all covariables, the Cox proportional hazards model proved a 17% decrease in the probability of death for each increased unit of low-density lipoprotein-cholesterol (LDL-C) (mmol/L). Yet, there was no association seen between blood high-density lipoprotein cholesterol (HDL-C), total cholesterol, or triglyceride and all-cause mortality in asthmatics. The application of RCS and threshold effect models verified an inverse and linear association of LDL-C with all-cause mortality. According to the results from the CoxBoost model, LDL-C exhibited the most substantial impact on the follow-up status of asthmatics among the serum lipids.

CONCLUSION

Our investigation concluded that in American asthmatic populations, LDL-C levels were inversely and linearly correlated with mortality. However, no independent relationship was found between triglycerides, total cholesterol, or HDL-C and mortality.

Are higher levels of lipid profile parameters associated with increased chances of uncontrolled asthma among adults?

BACKGROUND

Studies on the relationship between asthma and various parameters of fasting lipid profile have reported conflicting results. In this study, we intend to explore this association between asthma and its level of control with fasting serum lipid profile further.

METHODS

In our observational prospective cohort study, we studied 107 known asthmatic patients presenting in large tertiary care centre of North India. Fasting serum samples for lipid profile reports of all patients were collected. Patients were divided into controlled and uncontrolled asthma groups on the basis of clinical symptoms and spirometric findings. We evaluated the statistical difference and significance for various lipid profile parameters in between two groups using an independent t-test.

RESULTS

On comparing the fasting lipid profile of 38 patients with uncontrolled asthma and 69 patients with controlled asthma, we found that serum levels of low-density lipoprotein (LDL) and ratio of total cholesterol to high-density lipoprotein (TC: HDL) were significantly higher among patients with uncontrolled asthma. On statistical analysis, their P values were 0.03 and 0.047, respectively.

CONCLUSION

Serum levels of LDL and ratio of TC: HDL were higher in patients with uncontrolled asthma.

Assessment of Behavioral Risk Factors in Chronic Obstructive Airway Diseases of the Lung Associated with Metabolic Syndrome

BACKGROUND

Diet and lifestyle play important roles in preventing and improving chronic diseases, and evaluating behavioral risk factors in these pathologies allows for efficient management.

METHODS

A clinical study by screening biochemical parameters and pulmonary function was carried out to evaluate behavioral risk factors in obstructive pulmonary disease associated with metabolic syndrome.

RESULTS

Of the total of 70 patients included in the clinical study, 46 were men and 24 were women (χ2 = 3.9, p = 0.168). Forty-eight patients presented at least three met risk criteria associated with the metabolic syndrome (19 women and 29 men). Regarding the assessment of lung function, only 7 of the patients presented normal spirometry values (χ2 = 75.28, p < 0.001), and the other 63 patients presented with ventilatory dysfunction; most (over 80%) declared that they were smokers or had smoked in the past (χ2 = 5.185, p = 0.075). In terms of body weight, 45 of the patients are overweight or obese, most of them declaring that they do not consume enough vegetable products, they consume large amounts of foods of animal origin (meat, milk, eggs) but also super processed foods (food products type of junk food), do not hydrate properly, and are predominantly sedentary people (54 of the patients do no physical activity at all; χ2 = 2.12, p = 0.713).

CONCLUSION

From the statistical processing of the data, it is noted that insufficient hydration, low consumption of vegetables, increased consumption of hyper-caloric food products rich in additives, sedentary lifestyle, and smoking are the main disruptive behavioral factors that worsen the health status in lung disease associated with the metabolic syndrome. An important conclusion emerging from the study is that the imbalances that aggravate obstructive lung diseases are generated by unhealthy food and an unbalanced lifestyle.

Risk of asthma and/or wheezing in obese individuals with or without metabolic syndrome: From the Korea National Health and Nutrition Examination Survey data

Introduction: Obesity increases the risk of asthma; however, whether metabolic syndrome (MS), with obesity being one of its five components, is also associated with increased asthma risk remains unclear. Objective: To investigate the association between the risk of asthma and obesity, MS, and each component of MS. Methods: We performed a cross-sectional study of 41,480 Korean adults by using data from the 2007-2016 Korean National Health and Nutrition Examination Survey. Asthma was defined as a history of physician-diagnosed asthma or wheezing sound within the past 12 months. Results: The adjusted odds ratio (OR) for asthma was significantly increased in participants with obesity (OR 1.30 [95% confidence interval {CI}, 1.27-1.33]; p < 0.0001) and MS (OR 1.23 [95% CI, 1.20-1.25]; p < 0.0001). Obesity and MS showed an additive effect (OR 1.38 [95% CI, 1.34-1.41]; p < 0.001), followed by obesity(+)MS(-) (OR 1.28 [95% CI, 1.25-1.31]; p < 0.001) and obesity(-)MS(+) (OR 1.14 [95% CI, 1.10-1.18]; p < 0.001). Among each metabolic component, only abdominal obesity (OR 1.28 [95% CI, 1.24-1.32]; p < 0.001) and hypertension (OR 1.16 [95% CI, 1.12-1.20]; p < 0.001) significantly increased the risk of asthma. Unlike the female patients (OR 1.39 [95% CI, 1.35-1.43]; p < 0.001), having MS showed a lower risk of asthma in the male patients (OR 0.79 [95% CI, 0.75-0.82]; p < 0.001). Conclusion: The risk of asthma was highest when both obesity and MS were present, followed by obesity alone and MS alone. Abdominal obesity and hypertension were associated with an increased asthma risk, and there was a sex difference that MS lowered the risk of asthma in Korean male patients.

Differences in the lipid metabolism profile and clinical characteristics between eosinophilic and non-eosinophilic acute exacerbation of chronic obstructive pulmonary disease

Objective: In this study, we aimed to investigate the differences in serum lipid metabolite profiles and their relationship with clinical characteristics between patients with eosinophilic and non-eosinophilic AECOPD. Methods: A total of 71 AECOPD patients were enrolled. Eosinophilic AECOPD was defined as blood EOS% ≥ 2% (n = 23), while non-eosinophilic AECOPD, as blood EOS< 2% (n = 48). Clinical data were collected, and serum lipid metabolism profiles were detected by liquid chromatography-mass spectrometry (LC-MS). The XCMS software package was used to pre-process the raw data, and then, lipid metabolite identification was achieved through a spectral match using LipidBlast library. Differences in lipid profiles and clinical features between eosinophilic and non-eosinophilic groups were analyzed by generalized linear regression. The least absolute shrinkage and selection operator (LASSO) was applied to screen the most characteristic lipid markers for the eosinophilic phenotype. Results: Eosinophilic AECOPD patients had less hypercapnic respiratory failures, less ICU admissions, a shorter length of stay in the hospital, and a lower fibrinogen level. In the lipid metabolism profiles, 32 significantly different lipid metabolites were screened through a t-test adjusted by using FDR (FDR-adjusted p < 0.05 and VIP> 1). Nine differential lipid metabolites were found to be associated with the three clinical features, namely, hypercapnia respiratory failure, ICU admission, and fibrinogen in further integration analysis. The species of triacylglycerol (TAG), phosphatidylcholine (PC), lysophosphatidylcholine (LPC), and diacylglyceryl trimethylhomoserine (DGTS) were high in these eosinophilic AECOPD. The LASSO was applied, and three lipid metabolites were retained, namely, LPC (16:0), TAG (17:0/17:2/17:2), and LPC (20:2). The logistic regression model was fitted using these three markers, and the area under the ROC curve of the model was 0.834 (95% CI: 0.740-0.929). Conclusion: Patients with eosinophilic AECOPD had a unique lipid metabolism status. Species of TAGs and LPCs were significantly increased in this phenotype and were associated with better clinical outcomes.

High density lipoprotein-cholesterol is inversely associated with blood eosinophil counts among asthmatic adults in the USA: NHANES 2011-2018

Background

A growing number of research strongly suggest that metabolic syndrome and dyslipidemia contribute to the establishment of a pro-inflammatory state in asthma, according to accumulating data. However, the majority of recent research has focused on the association between lipids and asthma in children and adolescents, with contradictory findings. Consequently, we analyzed the relationship between serum lipid and blood eosinophil counts using data from the NHANES in the USA.

Methods

After screening the individuals from the 2011 to 2018 NHANES survey, a total of 2,544 out of 39156 participants were eligible for our study. The potential association was discussed using the linear regression model, XGBoost algorithm model, generalized additive model, and two-piecewise linear regression model. In addition, we ran stratified analysis to identify specific demographics.

Results

After adjusting for covariates, the result indicated that blood eosinophil counts decreased by 45.68 (-68.56, -22.79)/uL for each additional unit of HDL-C (mmol/L). But serum LDL-C, total cholesterol or triglyceride was not correlated with blood eosinophil counts. Furthermore, we used machine learning of the XGBoost model to determine LDL-C, age, BMI, triglyceride, and HDL-C were the five most critical variables in the blood eosinophil counts. The generalized additive model and two-piecewise linear regression model were used to further identify linear relationship between the serum HDL-C and blood eosinophil counts.

Conclusions

Our study elucidated a negative and linear correlation between serum HDL-C and blood eosinophil counts among American asthmatic adults, suggesting that serum HDL-C levels might be associated with the immunological condition of asthmatic adults. There was no correlation between serum LDL-C, total cholesterol, or triglyceride levels and blood eosinophil counts.

A new perspective on cholesterol in pediatric health: association of vitamin D metabolism, respiratory diseases, and mental health problems

Cholesterol, the main structural molecule of cell membranes, is involved in essential functions of the human body. Dyslipidemia is an established risk factor for cardiovascular diseases (CVDs) that is observed even in childhood. To reduce the risk of CVDs in children, several clinical guidelines have been published for the management of pediatric dyslipidemia. However, pediatric dyslipidemia is also associated with several health problems other than CVDs. This article reviews the current data on dyslipidemia-related pediatric health issues. There is strong evidence that low serum vitamin D levels, asthma, and mental health problems may be associated with dyslipidemia in the pediatric population regardless of body mass index. This review also highlights the need for further large-scale population-based studies in the Korean pediatric population to establish effective strategies for promoting children's health.

Association of Dyslipidemia and Respiratory Resistance Assessed by the Forced Oscillation Technique in Asthmatic Children

PURPOSE

This study aimed to evaluate the associations between dyslipidemia and pulmonary function parameters assessed by spirometry and the forced oscillation technique in asthmatic children.

METHODS

Asthmatic children (5-18 years old) had fasting serum lipid profiles including low-density lipoprotein cholesterol (LDL-C), total cholesterol (TC), triglyceride (TG), and high-density lipoprotein cholesterol (HDL-C) concentrations, and C-reactive protein (CRP) measured. Pulmonary function tests were assessed by spirometry and the forced oscillation technique (FOT).

RESULTS

One hundred forty-one asthmatic children were enrolled with a mean (SD) age of 11.82 (3.38) years. Eighty-eight (62.4%) children were boys, 64 (45.4%) had dyslipidemia, and 20 (14.2%) were obese. Among the children with dyslipidemia, a high LDL-C concentration (65.6%) was the most common form of dyslipidemia, followed by high TC (57.8%), high TG (35.9%), and low HDL-C concentrations (15.6%). Multivariable analysis showed significant associations between HDL-C concentrations and respiratory resistance at 5 Hz (R₅) and respiratory resistance at 20 Hz (R₂₀), and TC concentrations were modestly associated with reactance at 5 Hz (X₅), the frequency of resonance (Fres), and the area of reactance (ALX). Asthmatic children who had high LDL-C concentrations had a significantly higher expiratory phase R₅, whole breath R₂₀, and expiratory phase R₂₀ than those in children with normal LDL-C concentrations.

CONCLUSION

This study suggests an association of blood cholesterol, especially HDL-C and LDL-C, and respiratory resistance measured by the FOT, irrespective of the obesity status. An intervention for improving LDL-C and HDL-C concentrations may be beneficial on lung function parameters in asthmatic children.

CLINICAL TRIAL REGISTRATION

TCTR20200305005; date of registration: 03-04-2020 (retrospectively registered).

Asthma and Three Colinear Comorbidities: Obesity, OSA, and GERD

Asthma is a complex disease with heterogeneous phenotypes and endotypes that are incompletely understood. Obesity, obstructive sleep apnea, and gastroesophageal reflux disease co-occur in patients with asthma at higher rates than in those without asthma. Although these diseases share risk factors, there are some data suggesting that these comorbidities have shared inflammatory pathways, drive the development of asthma, or worsen asthma control. This review discusses the epidemiology, pathophysiology, management recommendations, and key knowledge gaps of these common comorbidities.

Additive Effect of Obesity and Dyslipidemia on Wheezing in Korean Adults: A Nationwide Representative Survey Study

Besides obesity, there are limited studies regarding the relationship between the individual components of metabolic syndrome and wheezing. It is largely unknown whether the co-existence of other metabolic syndrome components has additive effects on wheezing in the adult population. The association between the individual components of metabolic syndrome and current wheezing was evaluated in adults using data from the Korea National Health and Nutrition Examination Survey from 2008 to 2012. Subjects with metabolic syndrome more frequently had wheezing during the past 12 months (current wheezing) (adjusted odds ratio [aOR] = 1.56; 95% confidence interval [CI] = 1.37–1.77) and wheezing during exercise in the past 12 months (aOR = 1.59; 95% CI = 1.37–1.84). Of the individual metabolic syndrome components, central obesity (aOR = 1.48; 95% CI = 1.31–1.66) and low high-density lipoprotein (HDL) cholesterol (aOR = 1.18; 95% CI = 1.05–1.34) were significantly associated with current wheezing. There were no significant associations between the other components of metabolic syndrome (high triglyceride level, blood pressure, and fasting plasma glucose level) and the presence of current wheezing. In addition, the association was much higher when both central obesity and low HDL cholesterol were present together compared to when either of the conditions was present alone (aOR = 1.67; 95% CI = 1.44–1.94). There is a significant association between metabolic syndrome and current wheezing in Korean adults. Of the components of metabolic syndrome, low HDL cholesterol and central obesity are independently and additively associated with the increased rate of current wheezing.

Association of Triglyceride-Glucose Index and Lung Health: A Population-based Study

BACKGROUND

Metabolic syndrome and insulin resistance are associated with worsened outcomes of chronic lung disease. The triglyceride-glucose index (TyG), a measure of metabolic dysfunction, is associated with metabolic syndrome and insulin resistance, but its relationship to lung health is unknown.

RESEARCH QUESTION

What is the relationship of TyG to respiratory symptoms, chronic lung disease, and lung function?

STUDY DESIGN AND METHODS

This study analyzed data from the National Health and Nutrition Examination Survey from 1999 to 2012. Participants included fasting adults age ≥ 40 years (N = 6,893) with lung function measurements in a subset (n = 3,383). Associations of TyG with respiratory symptoms (cough, phlegm production, wheeze, and exertional dyspnea), chronic lung disease (diagnosed asthma, chronic bronchitis, and emphysema), and lung function (FEV₁, FVC, and obstructive or restrictive spirometry pattern) were evaluated, adjusting for sociodemographic variables, comorbidities, and smoking. TyG was compared vs insulin resistance, represented by the homeostatic model assessment of insulin resistance (HOMA-IR), and vs the metabolic syndrome.

RESULTS

TyG was moderately correlated with HOMA-IR (Spearman ρ = 0.51) and had good discrimination for metabolic syndrome (area under the receiver-operating characteristic curve, 0.80). A one-unit increase in TyG was associated with higher odds of cough (adjusted OR [aOR], 1.28; 95% CI, 1.06-1.54), phlegm production (aOR, 1.20; 95% CI, 1.01-1.43), wheeze (aOR, 1.18; 95% CI, 1.03-1.35), exertional dyspnea (aOR, 1.21; 95% CI, 1.07-1.38), and a diagnosis of chronic bronchitis (aOR, 1.21; 95% CI, 1.02-1.43). TyG was associated with higher relative risk of a restrictive spirometry pattern (adjusted relative risk ratio, 1.45; 95% CI, 1.11-1.90). Many associations were maintained with additional adjustment for HOMA-IR or metabolic syndrome.

INTERPRETATION

TyG was associated with respiratory symptoms, chronic bronchitis, and a restrictive spirometry pattern. Associations were not fully explained by insulin resistance or metabolic syndrome. TyG is a satisfactory measure of metabolic dysfunction with relevance to pulmonary outcomes. Prospective study to define TyG as a biomarker for impaired lung health is warranted.

The Gut/Lung Microbiome Axis in Obesity, Asthma, and Bariatric Surgery: A Literature Review

Mounting evidence suggests that obesity, parameters of metabolic syndrome, and asthma are significantly associated. Interestingly, these conditions are also associated with microbiome dysbiosis, notably in the airway microbiome for patients with asthma and in the gut microbiome for patients with obesity and/or metabolic syndrome. Considering that improvements in asthma control, lung function, and airway hyperresponsiveness are often reported after bariatric surgery, this review investigated the potential role of bacterial gut and airway microbiome changes after bariatric surgery in ameliorating asthma symptoms. Rapid and persistent gut microbiota alterations were reported following surgery, some of which can be sustained for years. The gut microbiome is thought to modulate airway cellular responses via short-chain fatty acids and inflammatory mediators, such that increased propionate and butyrate levels following surgery may aid in reducing asthma symptoms. In addition, increased prevalence of Akkermansia muciniphila after Roux-en-Y gastric bypass and sleeve gastrectomy may confer protection against airway hyperreactivity and inflammation. Metabolic syndrome parameters also improved following bariatric surgery, and whether weight-loss-independent metabolic changes affect airway processes and asthma pathobiology merits further research. Fulfilling knowledge gaps outlined in this review could facilitate the development of new therapeutic options for patients with obesity and asthma.

Dyslipidemia among allergic rhinitis patients: Frequency and risk factors

Background

Although cumulative data strongly suggest an association between dyslipidemia and allergic disorders, especially asthma, evidence regarding allergic rhinitis (AR) is lacking. We aimed to assess frequency and associated risk factors of dyslipidemia among patients with AR.

Methods

The current study is a cross-sectional study that recruited 150 AR patients by systematic randomization. Blood samples for serum lipid profile, total immunoglobulin E (IgE) and serum interleukin-17A (IL-17A) were withdrawn from all patients.

Results

Dyslipidemia was prevalent in 84 AR patients (56%). Higher levels of total IgE, IL17-A, and sensitization to hay dust and mixed mites significantly increased the risk of dyslipidemia among AR patients by 1.004, 1.062, 4.057 and 3.652 respectively (P < 0.05).

Conclusion

High serum total IgE level, high serum IL-17A level, and sensitization to hay dust and mixed mites are independent risk factors for dyslipidemia among AR patients.

High-Density Lipoprotein (HDL) in Allergy and Skin Diseases: Focus on Immunomodulating Functions

From an evolutionary perspective, lipoproteins are not only lipid transporters, but they also have important functions in many aspects of immunity. High-density lipoprotein (HDL) particles are the most abundant lipoproteins and the most heterogeneous in terms of their composition, structure, and biological functions. Despite strong evidence that HDL potently influences the activity of several immune cells, the role of HDL in allergies and skin diseases is poorly understood. Alterations in HDL-cholesterol levels have been observed in allergic asthma, allergic rhinitis, atopic dermatitis (eczema), psoriasis, urticaria, and angioedema. HDL-associated apolipoprotein (apo) A-I, apoA-IV, and apoC-III, and lyso-phosphatidylcholines potently suppress immune cell effector responses. Interestingly, recent studies provided evidence that allergies and skin diseases significantly affect HDL composition, metabolism, and function, which, in turn, could have a significant impact on disease progression, but may also affect the risk of cardiovascular disease and infections. Interestingly, not only a loss in function, but also, sometimes, a gain in function of certain HDL properties is observed. The objective of this review article is to summarize the newly identified changes in the metabolism, composition, and function of HDL in allergies and skin diseases. We aim to highlight the possible pathophysiological consequences with a focus on HDL-mediated immunomodulatory activities.

Glycated Hemoglobin A1c, Lung Function, and Hospitalizations Among Adults with Asthma

BACKGROUND

Insulin resistance and metabolic dysfunction have been associated with asthma risk and asthma severity.

OBJECTIVE

To examine the association between glycated hemoglobin A_1c (HbA_1c), asthma-related hospitalizations, and lung function measures among adults in the United Kingdom.

METHODS

A cross-sectional study was conducted of 47,606 adults aged 40 to 69 years who participated in the UK Biobank and had asthma but no diagnosis of diabetes mellitus. HbA_1c level was analyzed as a continuous measure and also categorized as normal (<42 mmol/mol) or as consistent with prediabetes/diabetes (≥42 mmol/mol). An asthma-related hospitalization was defined as ever having had a hospitalization with an International Classification of Diseases, Ninth/Tenth Revision, Clinical Modification code of a main diagnosis compatible with asthma (International Classification of Diseases, Ninth Revision, Clinical Modification code 493.x or International Classification of Diseases, Tenth Revision, Clinical Modification codes J45.x and J46.x). Logistic or linear regression was used for the multivariable analysis of asthma hospitalizations and lung function measures (FEV₁, forced vital capacity [FVC], and FEV₁/FVC). All models were adjusted for age, sex, ethnic background, body mass index, average annual household income, current smoking status, pack-years of smoking, fasting time, and C-reactive protein level.

RESULTS

Both HbA_1c level (odds ratio, 1.03; 95% CI, 1.01-1.04) and an HbA_1c level in the prediabetes/diabetes range (odds ratio, 1.68; 95% CI, 1.18-2.41) were associated with 1 or more asthma hospitalizations. Moreover, both HbA_1c level and an HbA_1c level in the prediabetes/diabetes range were significantly and inversely associated with FEV₁ and FVC.

CONCLUSIONS

HbA_1c is linked to asthma-related hospitalizations and small decrements in FEV₁ and FVC among British adults with asthma but no diagnosis of diabetes mellitus.

No Associations Between Serum Lipid Levels or HOMA-IR and Asthma in Children and Adolescents: A NHANES Analysis

OBJECTIVE

Studies have reported inconsistent results on the associations between lipids and insulin resistance (IR) and asthma. The purpose of this study was to examine the associations between abnormal serum lipid levels and homeostatic model assessment-IR (HOMA-IR) and the presence of current asthma in children and adolescents.

METHODS

The United States National Health and Nutrition Examination Survey database from 1999 to 2012 was randomly searched for children (aged 3-11 years) and adolescents (aged 12-19 years) with and without asthma and with complete demographic and clinical data of interest. Logistic regression analyses were performed to examine associations between abnormal serum lipids, glucose and HOMA-IR and the current presence of asthma.

RESULTS

The data of 11,662 children (3 to 11 years of age) and 12,179 adolescents (12 to 19 years of age) were included in the analysis. The study group included 3,703 participants with asthma and 20,138 participants without asthma. The prevalence of self-reported current asthma was higher among participants aged between 3-11 years (52.9%) than among those aged between 12-19 years (50.7%). Multivariate analyses, after adjusting for sex, race, income-to-poverty ratio, low birth weight, prenatal maternal smoking, tobacco exposure, C-reactive protein level and body mass index Z-score, revealed no associations between elevated fasting plasma glucose, reduced high-density lipoprotein cholesterol, elevated low-density lipoprotein cholesterol, total cholesterol, triglycerides and HOMA-IR and the presence of current asthma in children or adolescents.

CONCLUSION

In this cross-sectional study, no association was found between abnormal serum lipids or HOMA-IR and the presence of current asthma in children or adolescents.

Lipid profiles in adolescents with and without asthma: Korea National Health and nutrition examination survey data

Background

Metabolic syndrome and dyslipidemia contribute to the development of a pro-inflammatory state in asthma. However, studies investigating the association between asthma and dyslipidemia have reported conflicting results. This study aimed to uncover the relationship between asthma and lipid profiles in adolescents using a national health and nutrition survey.

Methods

This cross-sectional study analyzed the 2010–2012 Korea National Health and Nutrition Examination Survey data and included 2841 subjects aged 11–18 years with fasting blood sample data. Serum total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C) levels were analyzed. We compared asthma prevalence between high-risk and low-risk lipid groups.

Results

There were 123 adolescents with asthma and 2718 without asthma (controls). The TC/HDL-C ratio, LDL-C/HDL-C ratio, and non-HDL-C levels were significantly higher in the asthma group than in the non-asthma group (P < 0.05). The high-risk groups displayed significantly higher asthma prevalence with higher TC, TG, LDL-C, and non-HDL-C levels and TG/HDL-C ratio than the low-risk groups (P < 0.05). After adjusting for potential confounding factors, the high-risk groups were associated with asthma according to their higher TC levels (adjusted odds ratio, 1.69; 95% confidence interval, 1.012–2.822) and TG/HDL-C ratios (adjusted odds ratio, 1.665; 95% confidence interval, 1.006–2.756).

Conclusions

Asthma prevalence was greater in adolescents with a high TC level and TG/HDL-C ratio. In addition to the standard lipid profile, elevated TG/HDL-C ratio can be used as a useful additional lipid measure to evaluate interactions between dyslipidemia and asthma.

Pediatric metabolic outcome comparisons based on a spectrum of obesity and asthmatic symptoms

RATIONALE

Asthma and obesity are 2 of the most prevalent public health issues for children in the U.S. Trajectories of both have roughly paralleled one another over the past several decades causing many to explore their connection to one another and to other associated health issues such as diabetes and dyslipidemia. Earlier models have commonly designated obesity as the central hub of these associations; however, more recent models have argued connections between pediatric asthma and other obesity-related metabolic conditions regardless of children's obesity risk.

OBJECTIVES

To examine the relationships between asthma, obesity, and abnormal metabolic indices.

METHODS

We conducted a cross-sectional study of 179 children ages 7 to 12 years recruited from a rural, Appalachian region. Our model controlled for children's smoke exposure, body mass index percentile, and gender to examine the association between children's asthma (based on pulmonary function tests, medical history, medications, and parent report of severity), lipids (fasting lipid profile), and measures of altered glucose metabolism (glycosylated hemoglobin and homeostatic model assessment 2-insulin resistance).

RESULTS

Our findings revealed a statistically significant model for low density lipids, high density lipids, log triglyceride, and homeostatic model assessment 2-insulin resistance; however, Asthma had a significant effect for the mean triglycerides. We also found an asthma-obesity interaction effect on children's glycosylated hemoglobin with asthmatic obese children revealing significantly higher glycosylated hemoglobin values than non-asthmatic obese children.

CONCLUSIONS

Our findings support a connection between asthma and children's glycosylated hemoglobin values; however, this association remains entwined with obesity factors.

Association between lipid profile and the prevalence of asthma: a meta-analysis and systemic review

OBJECTIVE

To explore the association of asthma with serum levels of high-density lipoprotein (HDL), low-density lipoprotein (LDL), total cholesterol, and triglyceride.

METHODS

PubMed, Cochrane, and Embase databases were systematically searched through November 2015 using the following search terms: dyslipidemia, HDL, LDL, triglyceride, cholesterol, and asthma. Eligible studies included randomized controlled trials (RCTs), retrospective, cohort, and cross-sectional studies. Sensitivity analysis and publication bias were performed.

RESULTS

Twenty studies were included in the analysis, with a total 32,604 patients (3,458 in the asthma group and 29,146 in the control group). The pooled analysis found that the mean difference between groups was significantly higher in the asthma group for levels of LDL (6.026 mg/dL, 95% CI = 2.696-9.356, p < .001) and total cholesterol (8.161 mg/dL, 95% CI = 3.006-13.316, p = .002) compared with the control group. No association was observed between asthma and control groups for levels of HDL (mean difference = -0.728, 95% CI = -3.146-1.691, p = .555) or triglycerides (mean difference = 1.436, 95% CI = -2.768-5.640, p = .503).

CONCLUSIONS

Levels of LDL and total cholesterol were higher in patients with asthma than non-asthmatic patients.

The Alteration of Irisin-Brain-Derived Neurotrophic Factor Axis Parallels Severity of Distress Disorder in Bronchial Asthma Patients

Distress disorder (a collective term for generalized anxiety disorder and major depressive disorder) is a well-known co-morbidity of bronchial asthma. The irisin-brain-derived neurotrophic factor (BDNF) axis is a pathway that influences several neurobehavioral mechanisms involved in the pathogenesis of distress disorder. Thus, the aim of the present study was to quantify the serum irisin and BDNF concentrations in order to investigate the possible link between the irisin/BDNF axis and distress disorder in an asthma patient cohort. Data of 167 therapy-controlled asthma patients were analyzed. Demographic, anthropometric, and anamnestic data were collected, routine laboratory parameters supplemented with serum irisin and BDNF levels were determined, pulmonary function test was performed using whole-body plethysmography, and quality of life was quantified by means of the St. George's Respiratory Questionnaire (SGRQ). Correlation analysis as well as simple and multiple linear regression were used to assess the relationship between the irisin level and the Impacts score of SGRQ, which latter is indicative of the presence and severity of distress disorder. We have found a significant, positive linear relationship between the Impacts score and the reciprocal of irisin level. This association was stronger in patients whose BDNF level was higher, and it was weaker (and statistically non-significant) in patients whose BDNF level was lower. Our results indicate that higher serum irisin level together with higher serum BDNF level are associated with milder (or no) distress disorder. This finding suggests that alteration of the irisin/BDNF axis influences the presence and severity of distress disorder in asthma patients.

Association between Allergies and Hypercholesterolemia: A Systematic Review

BACKGROUND

There is controversy in the literature regarding the potential relationship between atopic predisposition (AP) and serum cholesterol levels. To this purpose, we reviewed human studies that investigated this possible link.

METHODS

Following PRISMA guidelines, a literature search of PubMed and Science Direct for peer-reviewed journal articles in English from January 2003, with updates through to August 2016, was conducted. Relevant publications were reviewed that included pediatric and adult populations. Information on the study design, sample, intervention, comparators, outcome, time frame, and risk of bias were abstracted for each article.

RESULTS

Of 601 reviewed reports, 18 were included in this systematic review. Fifteen studies assessed the relationship between AP and serum cholesterol levels. Due to the lack both of observational and cross-sectional studies from the literature search at this time (only 8 studies also analyzed confounding factors) there is a high possibility of confounding variables (familial and genetic predisposition, age, gender, BMI, comorbidity, and medication status) that could not be ruled out.

CONCLUSION

Existing studies are heterogeneous, making it difficult to draw broad conclusions. Future studies and more detailed analyses, considering confounding variables and including a larger and homogeneous population, are needed to strengthen the argument for a link between lipid metabolism and atopy.

Association of systemic inflammation, adiposity, and metabolic dysregulation with asthma burden among Hispanic adults

RATIONALE

Obesity-related asthma is associated with higher disease burden than normal-weight asthma among Hispanics. Adiposity, metabolic dysregulation, and inflammation are all implicated in pathogenesis of obesity-related asthma, but their independent contributions are poorly understood.

OBJECTIVE

To examine the independent contributions of body fat distribution, metabolic abnormalities and inflammation on asthma symptoms and pulmonary function among Hispanics.

METHODS

Participants of the Hispanic Community Health Study/Study of Latinos with doctor-diagnosed asthma who completed an asthma symptom questionnaire and performed a valid spirometry were included in the analysis (n = 1126). Multivariate analysis was used to examine the independent association of general adiposity (assessed using body mass index), truncal adiposity (assessed by waist circumference), metabolic dysregulation (presence of insulin resistance and low HDL) and inflammation (high-sensitivity C-Reactive Protein≥3 mg/L) with reported asthma symptoms or pulmonary function measures (FEV₁, and FVC) while adjusting for demographic and clinical covariates.

RESULTS

Of the 1126 participants, 334 (29.5%) were overweight, and 648 (57.8%) were obese. FEV₁ and FVC were lower in obese compared to normal-weight asthmatics. In analyses controlling for metabolic and adiposity factors, high hs-CRP (>7 mg/L) was associated with more symptoms (prevalence-ratio 1.27 (95%CI 1.05, 1.54), and lower FVC (β -138 ml (95%CI -27 ml, -249 ml)) and FEV₁ (β -155 ml (95% CI -38 ml, -272 ml). Low HDL was also associated with lower FVC (β -111 ml (-22 ml, -201 ml) and FEV₁ (β -100 ml (-12 ml, -188 ml)). Results were similar in men and women.

CONCLUSIONS

Our findings suggest that hs-CRP and low HDL, rather than general and truncal adiposity, are associated with asthma burden among overweight and obese Hispanic adults.

IL-17 protein levels in both induced sputum and plasma are increased in stable but not acute asthma individuals with obesity

BACKGROUND

Obesity worsens asthma control partly through enhanced airway neutrophilia, altered lung mechanics and comorbidities, including obstructive sleep apnea syndrome, gastroesophageal reflux disease and depression. Although controversial, obesity may also cause poorer outcomes in acute asthma. IL-17 is associated with neutrophilic inflammation, steroid resistance and severe asthma, but its importance in the association between asthma and obesity is unknown.

OBJECTIVE

To investigate the role of IL-17 in obese asthma in both acute and stable settings.

METHODS

Both stable (n = 177) and acute (n = 78) asthmatics were recruited and categorized into lean (n = 77 and 39 respectively), overweight (n = 41 and 17 respectively) and obese (n = 59 and 22 respectively) groups and compared for clinical characteristics, including sputum and plasma IL-17 protein concentrations, sputum cellularity, spirometry and comorbidities. Correlations of IL-17 expression with other measures were explored.

RESULTS

In stable subjects, airway neutrophilia and IL-17 concentrations were most prominent in the obese, and correlated positively with each other. Significant increase in plasma IL-17 levels was also noted and associated with elevated depressive symptoms in obesity. In acute asthma, IL-17 expression, like most other clinical measures, was similar among lean, overweight and obese groups, but was higher in acute versus stable asthma subjects, with sputum IL-17 correlating positively with sputum neutrophils and negatively with FEV₁ and plasma IL-17 showing a positive connection to airway eosinophilia during exacerbation.

CONCLUSIONS

IL-17 contributes to worse disease control in obese asthma through enhancing airway neutrophilia and depression, and may implicate in asthma exacerbations. Effects of adiposity on acute asthma remain uncertain.

Cholesterol-sensing liver X receptors stimulate Th2-driven allergic eosinophilic asthma in mice

INTRODUCTION

Liver X receptors (LXRs) are nuclear receptors that function as cholesterol sensors and regulate cholesterol homeostasis. High cholesterol has been recognized as a risk factor in asthma; however, the mechanism of this linkage is not known.

METHODS

To explore the importance of cholesterol homeostasis for asthma, we investigated the contribution of LXR activity in an ovalbumin- and a house dust mite-driven eosinophilic asthma mouse model.

RESULTS

In both models, airway inflammation, airway hyper-reactivity, and goblet cell hyperplasia were reduced in mice deficient for both LXRα and LXRβ isoforms (LXRα(-/-)β(-/-)) as compared to wild-type mice. Inversely, treatment with the LXR agonist GW3965 showed increased eosinophilic airway inflammation. LXR activity contributed to airway inflammation through promotion of type 2 cytokine production as LXRα(-/-)β(-/-) mice showed strongly reduced protein levels of IL-5 and IL-13 in the lungs as well as reduced expression of these cytokines by CD4(+) lung cells and lung-draining lymph node cells. In line herewith, LXR activation resulted in increased type 2 cytokine production by the lung-draining lymph node cells.

CONCLUSIONS

In conclusion, our study demonstrates that the cholesterol regulator LXR acts as a positive regulator of eosinophilic asthma in mice, contributing to airway inflammation through regulation of type 2 cytokine production.

The lipid profile in obese asthmatic children compared to non-obese asthmatic children

BACKGROUND

A relationship between asthma and obesity has been documented in children and adolescents. An alternate day calorie restriction diet has been reported to improve asthma symptoms by decreasing levels of serum cholesterol and triglycerides, reducing markers of oxidative stress and increasing levels of the antioxidant uric acid. Therefore, to investigate the lipid profile in asthmatic children may be important in asthma control treatment.

MATERIALS AND METHODS

One hundred and sixty newly diagnosed persistent asthmatic children were selected to participate in the study. They were divided into four groups based on their body mass index (BMI): Group I normal weight (BMI=20-24.9kg/m(2), n=30); Group II under-weight (BMI<20kg/m(2), n=30); Group III overweight (BMI=25-30kg/m(2), n=25); and Group IV obese (BMI>30kg/m(2), n=25). Fasting blood sugar, fasting insulin, and HbA1c were measured to exclude the possibility of pre-diabetes. Lipid profile measurements included total cholesterol, high-density lipoprotein (HDL), low-density lipoprotein (LDL), apo-A1, apo-B and triglycerides.

RESULTS

There were no significant differences in the levels of apo-A1, apo-B, triglycerides, cholesterol and LDL in all four groups. Only the level of HDL was higher in GIV>GIII>GII>GI (75.84±13.95, 68.56±15.28, 64.17±13.93, 63.17±14.34mg/dl, respectively). There were no cases of pre-diabetes in any of the four groups.

CONCLUSION

Hypercholesterolaemia and hypertriglyceridaemia were not found in any of the persistent asthmatic children, and thus they are not high risk factors for asthma. Similarly, there were no differences in apo-A1 and apo-B between any of the BMI groups. No differences were found in LDL levels, however HDL levels were increased in all four groups, indicating that allergic sensitisation may have occurred. Controlling body weight and restricting calorie intake may be as important as appropriate pharmacological management in controlling asthma.

Adipokines, asymmetrical dimethylarginine, and pulmonary function in adolescents with asthma and obesity

OBJECTIVE

This study was to investigate whether the metabolic abnormalities of adipokines and asymmetrical dimethylarginine (ADMA) associate with pulmonary function deficits in adolescents with obesity and asthma.

METHODS

This study enrolled 28 obese adolescents with asthma, 46 obese adolescents without asthma, 58 normal-weight adolescents with asthma, and 63 healthy control subjects. Serum levels of leptin, high-molecule-weight (HMW) adiponectin, retinol binding protein 4 (RBP4), asymmetrical dimethylarginine (ADMA), and pulmonary function were qualified.

RESULTS

The obese subjects had higher levels of leptin and ADMA but lower levels of HMW adiponectin than the normal-weight subjects with or without asthma. The subjects with asthma had higher levels of RBP4 than those without asthma. The obese adolescents with asthma had lowest forced expiratory lung volume in the first second (FEV₁)/forced vital capacity (FVC) ratio among the four study groups. In all the study subjects and in the subjects with asthma alone, the FEV₁/FVC ratio associated negatively with leptin, however, such association was rendered non-significant when adjusted for BMI. The pulmonary function deficits associated inversely with BMI percentile in the subjects with asthma. However, the decreased FEV₁/FVC ratio was not correlated with HMW adiponectin, RBP4 or ADMA.

CONCLUSIONS

Our present study confirmed obstructive pattern of pulmonary function characterized by the reduced FEV₁/FVC ratio in the obese adolescents with asthma. These pulmonary deficits were associated inversely with the increased BMI percentile.

Pediatric Obesity-Related Asthma: The Role of Metabolic Dysregulation

The burden of obesity-related asthma among children, particularly among ethnic minorities, necessitates an improved understanding of the underlying disease mechanisms. Although obesity is an independent risk factor for asthma, not all obese children develop asthma. Several recent studies have elucidated mechanisms, including the role of diet, sedentary lifestyle, mechanical fat load, and adiposity-mediated inflammation that may underlie the obese asthma pathophysiology. Here, we review these recent studies and emerging scientific evidence that suggest metabolic dysregulation may play a role in pediatric obesity-related asthma. We also review the genetic and epigenetic factors that may underlie susceptibility to metabolic dysregulation and associated pulmonary morbidity among children. Lastly, we identify knowledge gaps that need further exploration to better define pathways that will allow development of primary preventive strategies for obesity-related asthma in children.

Regulation of Adaptive Immunity in Health and Disease by Cholesterol Metabolism

Four decades ago, it was observed that stimulation of T cells induces rapid changes in cellular cholesterol that are required before proliferation can commence. Investigators returning to this phenomenon have finally revealed its molecular underpinnings. Cholesterol trafficking and its dysregulation are now also recognized to strongly influence dendritic cell function, T cell polarization, and antibody responses. In this review, the state of the literature is reviewed on how cholesterol and its trafficking regulate the cells of the adaptive immune response and in vivo disease phenotypes of dysregulated adaptive immunity, including allergy, asthma, and autoimmune disease. Emerging evidence supporting a potential role for statins and other lipid-targeted therapies in the treatment of these diseases is presented. Just as vascular biologists have embraced immunity in the pathogenesis and treatment of atherosclerosis, so should basic and clinical immunologists in allergy, pulmonology, and other disciplines seek to encompass a basic understanding of lipid science.

The contribution of twin studies to the understanding of the aetiology of asthma and atopic diseases

The prevalence of asthma and other atopic diseases has increased markedly during the past decades and the reasons for this are not fully understood. Asthma is still increasing in many parts of the world, notably in developing countries, and this emphasizes the importance of continuing research aimed at studying the aetiological factors of the disease and the causes of its increase in prevalence. Twin studies enable investigations into the genetic and environmental causes of individual variation in multifactorial diseases such as asthma. Thorough insight into these causes is important as this will ultimately guide the development of preventive strategies and targeted therapies. This review explores the contribution of twin studies to the understanding of the aetiology of asthma and atopic diseases.

Serum apolipoprotein A-I and large high-density lipoprotein particles are positively correlated with FEV1 in atopic asthma

RATIONALE

Although lipids, apolipoproteins, and lipoprotein particles are important modulators of inflammation, varying relationships exist between these parameters and asthma.

OBJECTIVES

To determine whether serum lipids and apolipoproteins correlate with the severity of airflow obstruction in subjects with atopy and asthma.

METHODS

Serum samples were obtained from 154 atopic and nonatopic subjects without asthma, and 159 subjects with atopy and asthma. Serum lipid and lipoprotein levels were quantified using standard diagnostic assays and nuclear magnetic resonance (NMR) spectroscopy. Airflow obstruction was assessed by FEV1% predicted.

MEASUREMENTS AND MAIN RESULTS

Serum lipid levels correlated with FEV1 only in the subjects with atopy and asthma. Serum levels of high-density lipoprotein (HDL) cholesterol and apolipoprotein A-I (apoA-I) were positively correlated with FEV1 in subjects with atopy and asthma, whereas a negative correlation existed between FEV1 and serum levels of triglycerides, low-density lipoprotein (LDL) cholesterol, apolipoprotein B (apoB), and the apoB/apoA-I ratio. NMR spectroscopy identified a positive correlation between FEV1 and HDLNMR particle size, as well as the concentrations of large HDLNMR particles and total IDLNMR (intermediate-density lipoprotein) particles in subjects with atopy and asthma. In contrast, LDLNMR particle size and concentrations of LDLNMR and VLDLNMR (very-low-density lipoprotein) particles were negatively correlated with FEV1 in subjects with atopy and asthma.

CONCLUSIONS

In subjects with atopy and asthma, serum levels of apoA-I and large HDLNMR particles are positively correlated with FEV1, whereas serum triglycerides, LDL cholesterol, and apoB are associated with more severe airflow obstruction. These results may facilitate future studies to assess whether apoA-I and large HDLNMR particles can reduce airflow obstruction and disease severity in asthma.

Asthma and metabolic syndrome: Current knowledge and future perspectives

Asthma and obesity are epidemiologically linked; however, similar relationships are also observed with other markers of the metabolic syndrome, such as insulin resistance and dyslipidemia, which cannot be accounted for by increased body mass alone. Obesity appears to be a predisposing factor for the asthma onset, both in adults and in children. In addition, obesity could make asthma more difficult to control and to treat. Although obesity may predispose to increased Th2 inflammation or tendency to atopy, other mechanisms need to be considered, such as those mediated by hyperglycaemia, hyperinsulinemia and dyslipidemia in the context of metabolic syndrome. The mechanisms underlying the association between asthma and metabolic syndrome are yet to be determined. In the past, these two conditions were believed to occur in the same individual without any pathogenetic link. However, the improvement in asthma symptoms following weight reduction indicates a causal relationship. The interplay between these two diseases is probably due to a bidirectional interaction. The purpose of this review is to describe the current knowledge about the possible link between metabolic syndrome and asthma, and explore potential application for future studies and strategic approaches.

Inflammation, metabolic dysregulation, and pulmonary function among obese urban adolescents with asthma

RATIONALE

Insulin resistance and low high-density lipoprotein (HDL) are associated with pulmonary morbidity, including asthma, but the underlying mechanisms are not well elucidated.

OBJECTIVES

To investigate whether systemic inflammation underlies the association of metabolic abnormalities with pulmonary function among urban adolescents.

METHODS

Th-cell responses and monocyte subsets, and their association with serum homeostatic model assessment of insulin resistance (HOMA-IR) and HDL, and pulmonary function were quantified in 168 adolescents, including 42 obese subjects with asthma, 42 normal-weight subjects with asthma, 40 obese subjects without asthma, and 44 healthy control subjects. Th-cell responses (Th1 [CD4(+)IFNγ(+)] and Th2 [CD4(+)IL4(+)] cells) to stimulation with phytohemagglutinin, leptin, and dust mite, and classical (CD14(+)CD16(-)), resident (CD14(+)CD16(+)), and patrolling (CD14dimCD16(+)) monocytes, and their C-C chemokine receptor type-2 (CCR2) expression were quantified by flow cytometry.

MEASUREMENTS AND MAIN RESULTS

Th1/Th2 ratio to all three stimuli was higher in obese subjects with asthma than normal-weight subjects with asthma and directly correlated with HOMA-IR. Classical monocytes inversely associated with Th1/Th2 ratio to phytohemagglutinin (r = -0.43; P = 0.01) and directly with Asthma Control Test score (β = 1.09; P = 0.04), while patrolling monocytes correlated with Composite Asthma Severity Index score (β = 1.11; P = 0.04) only among obese subjects with asthma. HDL was inversely associated with patrolling monocytes and directly associated with CCR2 expression on resident monocytes. CCR2 expression on patrolling monocytes predicted residual volume (RV), RV/TLC ratio, and FRC, after adjusting for HDL, but not after adjusting for body mass index. Association of Th1/Th2 ratio with RV, FRC, and inspiratory capacity was attenuated after adjusting for HOMA-IR.

CONCLUSIONS

Th1 polarization and monocyte activation among obese subjects with asthma correlates with metabolic abnormalities. Association of monocyte activation with pulmonary function is mediated by body mass index, whereas that of Th1 polarization is mediated by insulin resistance.

Association of pulmonary function with adiposity and metabolic abnormalities in urban minority adolescents

RATIONALE

Childhood obesity is a known risk factor for pulmonary diseases, likely due to obesity-mediated alteration of pulmonary function. Inflammation and mechanical fat load are two proposed causative mechanisms for altered pulmonary function among obese children; however, the association of metabolic abnormalities with pulmonary function among children is poorly understood.

OBJECTIVES

We investigated the independent association of truncal and general adiposity and metabolic abnormalities with pulmonary function in a sample of urban minority adolescents.

METHODS

Spirometry and lung volume indices were compared between adolescents with general (body mass index [BMI] > 95th percentile) or truncal adiposity (waist circumference > 90th percentile) and normal-weight (BMI < 85th percentile or waist circumference ≤ 90th percentile) and between those with metabolic abnormalities (homeostatic model assessment of insulin resistance [HOMA-IR] in the top quartile or high-density lipoprotein [HDL] < 40 mg/dl) and those with a normal metabolic profile.

MEASUREMENTS AND MAIN RESULTS

Obese adolescents had lower lung volumes, including residual volume (RV), RV/TLC ratio, expiratory reserve volume (ERV), and FRC, and higher inspiratory capacity (IC) than normal-weight adolescents, but did not differ in measures of lower airway obstruction, FEV1/FVC ratio, and mid-expiratory flow rate. Adolescents with high HOMA-IR had lower FEV1/FVC ratio, RV, RV/TLC ratio, ERV, and FRC and higher IC, whereas those with low HDL had lower FEV1/FVC and RV/TLC ratios. After adjusting for adiposity, HOMA-IR remained a predictor of ERV (β = -1.4; P = 0.02) and FEV1/FVC ratio (β = -0.5; P = 0.03), and HDL remained a predictor of FEV1/FVC ratio (β = 0.1; P = 0.01). General adiposity was a predictor of FRC (β = -0.5; P < 0.001), IC (β = 0.3; P < 0.001), RV (β = -0.8; P < 0.0001), and RV/TLC ratio (β = -0.2; P < 0.0001), and truncal adiposity was a predictor of RV (β = -20.3; P = 0.03) and FRC (β = -13.8; P = 0.004). Thus, adiposity and metabolic abnormalities were independent predictors of ERV, but only metabolic abnormalities independently predicted FEV1/FVC ratio. Although general adiposity predicted RV and RV/TLC ratio, truncal adiposity was predictive of RV and FRC, conferring additional risk above general adiposity.

CONCLUSIONS

These results suggest that metabolic abnormalities and adiposity are independently associated with pulmonary function deficits among urban adolescents. Metabolic assessment of obese adolescents may identify those at risk of developing obesity-associated pulmonary morbidity.

Asthma: the role of low high-density-lipoprotein cholesterol in childhood and adolescence

BACKGROUND

Several studies have examined the relationship of asthma with serum dyslipidemia and reported positive, negative or no association. Most studies were limited by their cross-sectional design and the wide age range of the participants. In a cohort of children in Cyprus, we explored the association of asthma with serum high-density-lipoprotein cholesterol (HDL-C) at age 16-18 years (follow-up) independently of and in relation to HDL-C at age 11-12 years (baseline).

METHODS

In a case-control design, we recruited active asthmatics (AA; n = 68), current wheezers only (CWO; n = 123) and non-asthmatic controls (n = 660). Logistic regression models were used to evaluate associations of asthma with follow-up serum HDL-C and the role of baseline HDL-C.

RESULTS

At follow-up, mean HDL-C levels in AA and CWO patients were significantly lower than in the controls (47.9 and 49.7 vs. 53.4 mg/dl; p = 0.001 and p = 0.011). We observed significant associations of AA patients with low HDL-C (<15th percentile; OR 2.32, 95% CI 1.16-4.47) that remained significant after further adjustment for baseline HDL-C (OR 2.14, 95% CI 1.06-4.14). Stratification by baseline HDL-C indicated that the association was significant only in those with high baseline HDL-C (OR 2.40, 95% CI 1.03-5.20). Stratification by IgE sensitization showed that the association was pronounced only in subjects who were sensitized (OR 3.41, 95% CI 1.12-9.88).

CONCLUSIONS

Adolescent asthma is associated with low serum HDL-C independent of previous HDL-C levels in childhood. The association appears pronounced in those with a drop in HDL-C levels between childhood and adolescence and in those who have IgE sensitization.

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.