Low serum high-density lipoprotein cholesterol in childhood is associated with adolescent asthma

Exploring the causal relationship between asthma in the metabolic syndrome: a Mendelian randomization study

BACKGROUND

Previous observational studies have indicated a potential association between metabolic syndrome (MetS) and asthma, though the causal nature of this connection is still uncertain. Our study used Mendelian randomization (MR) to examine the causal relationship between metabolic syndrome (MetS) and its components with asthma.

METHODS

This study utilized single nucleotide polymorphisms (SNPs) related to MetS and its components, sourced from publicly available genome-wide association studies (GWAS) data, in combination with asthma data from the FinnGen database. Statistical analyses were conducted using the inverse variance weighted method (IVW), MR-Egger, and weighted median method. The robustness of the findings was confirmed through various sensitivity analyses.

RESULTS

The IVW analysis indicated that MetS was associated with an increased risk of asthma (OR = 1.0781, 95% CI = 1.0255-1.1333, p = 0.0032). Among the components of MetS, waist circumference (WC) showed a strong association with asthma (OR = 1.4777, 95% CI = 1.3412-1.6281, p = 2.8707 × 10-15). Conversely, high-density lipoprotein cholesterol (HDL-C) was found to be inversely related to the risk of asthma (OR = 0.9186, 95% CI = 0.8669-0.9734, p = 0.0041).

CONCLUSION

The findings of this study support that MetS and its specific components, particularly abdominal obesity, are linked to a higher risk of asthma, while HDL-C might offer protective effects against asthma. These findings provide a foundation both for further research and possible therapeutic interventions.

Repurposing lipid-lowering drugs on asthma and lung function: evidence from a genetic association analysis

OBJECTIVE

To explore the correlation between asthma risk and genetic variants affecting the expression or function of lipid-lowering drug targets.

METHODS

We conducted Mendelian randomization (MR) analyses using variants in several genes associated with lipid-lowering medication targets: HMGCR (statin target), PCSK9 (alirocumab target), NPC1L1 (ezetimibe target), APOB (mipomersen target), ANGPTL3 (evinacumab target), PPARA (fenofibrate target), and APOC3 (volanesorsen target), as well as LDLR and LPL. Our objective was to investigate the relationship between lipid-lowering drugs and asthma through MR. Finally, we assessed the efficacy and stability of the MR analysis using the MR Egger and inverse variance weighted (IVW) methods.

RESULTS

The elevated triglyceride (TG) levels associated with the APOC3, and LPL targets were found to increase asthma risk. Conversely, higher LDL-C levels driven by LDLR were found to decrease asthma risk. Additionally, LDL-C levels (driven by APOB, NPC1L1 and HMGCR targets) and TG levels (driven by the LPL target) were associated with improved lung function (FEV1/FVC). LDL-C levels driven by PCSK9 were associated with decreased lung function (FEV1/FVC).

CONCLUSION

In conclusion, our findings suggest a likely causal relationship between asthma and lipid-lowering drugs. Moreover, there is compelling evidence indicating that lipid-lowering therapies could play a crucial role in the future management of asthma.

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.

Dyslipidemia Is Associated With Worse Asthma Clinical Outcomes: A Prospective Cohort Study

BACKGROUND

Dyslipidemia has been widely documented to be associated with cardiovascular disease, and recent studies have found an association with asthma prevalence. However, longitudinal studies investigating the relationships between dyslipidemia, asthma phenotypes, and future asthma exacerbations (AEs) are lacking.

OBJECTIVE

To investigate the relationships between dyslipidemia, asthma phenotypes, and AEs.

METHODS

This study used an observational cohort study design with a 12-month follow-up. All subjects underwent serum lipid measurement, and they were then classified into 2 groups: the normal-lipidemia group and the dyslipidemia group. Demographic and clinical information and details regarding pulmonary function and asthma phenotypes at baseline were collected. All patients were followed up regularly to assess AEs. Associations of dyslipidemia with airway obstruction and asthma phenotypes were assessed at baseline, whereas dyslipidemia and AEs were assessed longitudinally.

RESULTS

A total of 477 patients with asthma were consecutively enrolled in this study. At baseline, the dyslipidemia group (n = 218) had a higher proportion of uncontrolled asthma, defined by the 6-item Asthma Control Questionnaire score (≥1.5). Furthermore, dyslipidemia was associated with severe asthma, nonallergic asthma, asthma with fixed airflow limitation, and older adult asthma phenotypes at baseline. In addition, dyslipidemia was associated with increased frequencies of severe AEs and moderate to severe AEs during the 12-month follow-up. In sensitivity analyses, after excluding the patients who were receiving statins, results did not differ significantly from those of the main analysis.

CONCLUSIONS

We identified the clinical relevance of dyslipidemia, which is associated with specific asthma phenotypes and increased AEs, independent of other components of metabolic syndrome. These findings highlight the importance of considering dyslipidemia as an "extrapulmonary trait" in asthma management.

Lipid Nutrition in Asthma

Asthma is a heterogeneous pulmonary disease that has constantly increased in prevalence over the past several decades. Primary symptoms include airway constriction, airway hyperresponsiveness, and airway remodeling with additional symptoms such as shortness of breath, wheezing, and difficulty breathing. Allergic asthma involves chronic inflammation of the lungs, and the rise in its yearly diagnosis is potentially associated with the increased global consumption of foods similar to the western diet. Thus, there is growing interest into the link between diet and asthma symptoms, with mounting evidence for an important modulatory role for dietary lipids. Lipids can act as biological mediators in both a proinflammatory and proresolution capacity. Fatty acids play key roles in signaling and in the production of mediators in the allergic and inflammatory pathways. The western diet leads to a disproportionate ω-6:ω-3 ratio, with drastically increased ω-6 levels. To counteract this, consumption of fish and fish oil and the use of dietary oils with anti-inflammatory properties such as olive and sesame oil can increase ω-3 and decrease ω-6 levels. Increasing vitamin intake, lowering LDL cholesterol levels, and limiting consumption of oxidized lipids can help reduce the risk of asthma and the exacerbation of asthmatic symptoms. These dietary changes can be achieved by increasing intake of fruits, vegetables, nuts, oily fish, seeds, animal-related foods (eggs, liver), cheeses, grains, oats, and seeds, and decreasing consumption of fried foods (especially fried in reused oils), fast foods, and heavily processed foods.

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.

Novel Insights From Human Studies on the Role of High-Density Lipoprotein in Mortality and Noncardiovascular Disease

The vast majority of research about HDL (high-density lipoprotein) has for decades revolved around the possible role of HDL in atherosclerosis and its therapeutic potential within cardiovascular disease prevention; however, failures with therapies aimed at increasing HDL cholesterol has left questions as to what the role and function of HDL in human health and disease is. Recent observational studies have further shown that extreme high HDL cholesterol is associated with high mortality leading to speculations that HDL could in some instances be harmful. In addition, evidence from observational, and to a lesser extent genetic studies has emerged indicating that HDL might be associated with the development of other major noncardiovascular diseases, such as infectious disease, autoimmune disease, cancer, type 2 diabetes, kidney disease, and lung disease. In this review, we discuss (1) the association between extreme high HDL cholesterol and mortality and (2) the emerging human evidence linking HDL to several major diseases outside the realm of cardiovascular disease.

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.

Exposure to PM2.5 affects blood lipid levels in asthmatic rats through notch signaling pathway

BACKGROUND

Epidemiological studies have confirmed atmospheric PM_2.5 could affect asthma, and dyslipidemia may be related to pathogenesis of asthma. Recent studies show Notch ligands had lipid combination domains which are responsible for regulating lipid levels. However, the effect of PM_2.5 on asthmatic rats' lipid levels and the role of Notch signaling pathway is unclear.

METHODS

Rats were treat with ovalbumin (OVA) to establish asthma models. Notch signaling pathway inhibitor (DAPT) was injected intraperitoneally. Asthmatic and healthy rats were exposed to different concentrations of PM_2.5. Lung tissues were collected and the expression of Hes1 protein was detected by Western Blot. Blood samples were collected to detect the serum lipid levels.

RESULTS

Hes1 expression levels in healthy and asthma pathway inhibition groups were lower than those in control groups. Compared with control group, rats exposed to PM_2.5 in middle and high dose, the levels of TG and TC were decreased. Similar results were observed after exposure to the same concentration of PM_2.5 in asthmatic rats. Rats, which were exposed to PM_2.5 after being established the asthma model successfully, could exhibit more significant dyslipidemia than those with direct exposure. After Notch signaling pathway inhibited, TC and LDL in asthma pathway inhibition group were lower than those in healthy group.

CONCLUSIONS

PM_2.5 can affect the lipid levels of asthmatic rats through the Notch signaling pathway.

EAACI position paper: Influence of dietary fatty acids on asthma, food allergy, and atopic dermatitis

The prevalence of allergic diseases such as allergic rhinitis, asthma, food allergy, and atopic dermatitis has increased dramatically during the last decades, which is associated with altered environmental exposures and lifestyle practices. The purpose of this review was to highlight the potential role for dietary fatty acids, in the prevention and management of these disorders. In addition to their nutritive value, fatty acids have important immunoregulatory effects. Fatty acid-associated biological mechanisms, human epidemiology, and intervention studies are summarized in this review. The influence of genetics and the microbiome on fatty acid metabolism is also discussed. Despite critical gaps in our current knowledge, it is increasingly apparent that dietary intake of fatty acids may influence the development of inflammatory and tolerogenic immune responses. However, the lack of standardized formats (ie, food versus supplement) and standardized doses, and frequently a lack of prestudy serum fatty acid level assessments in clinical studies significantly limit our ability to compare allergy outcomes across studies and to provide clear recommendations at this time. Future studies must address these limitations and individualized medical approaches should consider the inclusion of specific dietary factors for the prevention and management of asthma, food allergy, and atopic dermatitis.

Semantic integration of clinical laboratory tests from electronic health records for deep phenotyping and biomarker discovery

Electronic Health Record (EHR) systems typically define laboratory test results using the Laboratory Observation Identifier Names and Codes (LOINC) and can transmit them using Fast Healthcare Interoperability Resource (FHIR) standards. LOINC has not yet been semantically integrated with computational resources for phenotype analysis. Here, we provide a method for mapping LOINC-encoded laboratory test results transmitted in FHIR standards to Human Phenotype Ontology (HPO) terms. We annotated the medical implications of 2923 commonly used laboratory tests with HPO terms. Using these annotations, our software assesses laboratory test results and converts each result into an HPO term. We validated our approach with EHR data from 15,681 patients with respiratory complaints and identified known biomarkers for asthma. Finally, we provide a freely available SMART on FHIR application that can be used within EHR systems. Our approach allows readily available laboratory tests in EHR to be reused for deep phenotyping and exploits the hierarchical structure of HPO to integrate distinct tests that have comparable medical interpretations for association studies.

Serum lipoproteins are not associated with the severity of asthma

BACKGROUND

Asthma is a chronic inflammatory disorder of the bronchi with a complicated and largely unknown pathogenesis. In this context, an emerging role is attributed to the apolipoproteins which serve as structural components of plasma lipoproteins. Low density lipoproteins (LDL) may be involved in the inflammatory pathways of the asthmatic airways; in particular, small dense LDL (sdLDL) particles were associated with increased oxidative susceptibility compared to medium and large sized LDL. In our previous study, we found a positive correlation between forced expiratory volume 1 s (FEV₁) % predicted and larger LDL particles (LDL-1), and an inverse correlation between FEV₁% predicted and sdLDL (LDL-3) in mild, untreated asthmatics. Although LDL appear to be important modulators of inflammation, data on their clinical implications are still lacking.

OBJECTIVE

The aim of the study is to investigate whether LDL subclasses correlate with the severity of asthma, assuming that the atherogenic and most pro-inflammatory LDL contribute to ignite and perpetuate the airway inflammatory processes.

METHODS

The study was conducted in one visit, and included clinical and lung functional assessments, as well as measurements of serum concentrations of the LDL subclasses. Non-denaturing, linear polyacrylamide gel electrophoresis was used to separate and measure LDL subclasses, with the LipoPrint^© System (Quantimetrix Corporation, Redondo Beach, CA, USA). LDL subclasses were distributed as seven bands (LDL-1 to LDL-7), LDL-1 and -2 being defined as large LDL (least pro-inflammatory), and LDL-3 to 7 defined as sdLDL (most pro-inflammatory).

RESULTS

70 asthmatics under inhaled treatment (M/F: 35/35) were enrolled; 10 healthy subjects (M/F: 3/7) served as controls. In the asthmatic group, FEV₁% predicted was 81 ± 22% (mean ± SD), vital capacity (VC) % predicted was 97 ± 18%, and FEV₁/FVC was 0.68 ± 0.1. The mean asthma control test (ACT) score was 18 ± 5. LDL-1 were significantly lower in asthmatics as compared to controls (18 ± 4% vs. 22 ± 4%, p = 0.008). On the contrary, LDL-2 (12 ± 4% vs. 12 ± 5%) and LDL-3 (3 ± 3% vs. 2 ± 2%) were not statistically different between the two groups; smaller subclasses were undetectable. To comply with the design of the study, subjects were classified according to their degree of severity into the 5 Global Initiative for Asthma (GINA) steps: Step 1 (M/F: 4/3, 44 ± 12 yrs), Step 2 (M/F: 1/2, 37 ± 11 yrs), Step 3 (M/F: 12/7, 47 ± 12 yrs), Step 4 (M/F: 8/15, 54 ± 12 yrs), and Step 5 (M/F: 7/9, 56 ± 9 yrs). None of the LDL subclasses showed significant differences between classes of severity: LDL-1 were 16.1 ± 5.6% in Step 1, 18 ± 2.8% in Step 2, 16.7 ± 3.7% in Step 3, 18 ± 3.3% in Step 4, and 19.5 ± 3.2% in Step 5 (p = NS); LDL2 were 14 ± 3.6%, 15 ± 3.4%, 12.4 ± 5.3%, 12.7 ± 4.4% and 11.3 ± 4.2%, respectively (p = NS); LDL3 were 5 ± 5.2%, 4.4 ± 2.6%, 3.3 ± 3.6%, 3.2 ± 2.6% and 2.4 ± 1.8%, p = NS. Finally, no relationship was detected between LDL subclasses and lung function parameters as well as the ACT scores.

CONCLUSIONS

The current findings confirm a role of LDL as a potential biomarker in the diagnostic process for asthma, and suggest that LDL cannot be used as marker of severity of the disease.

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.

Association of Serum Lipids and Obstructive Lung Disease in Hispanic/Latino Adults of Diverse Backgrounds

Rationale

Substantial variation in the prevalences of obstructive lung disease exist between Hispanic/Latino heritage groups. Experimental studies have posited biological mechanisms linking serum lipids and lipid-lowering medications with obstructive lung disease. The aim of this study is to examine the associations of serum lipid levels with the prevalences of asthma and chronic obstructive pulmonary disease in the Hispanic Community Health Study/Study of Latinos and how these associations vary by Hispanic/Latino heritage group.

Methods

The Hispanic Community Health Study/Study of Latinos is a population-based probability sample of 16,415 self-identified Hispanic/Latino persons aged 18–74 years recruited between 2008 and 2011 from randomly selected households in four US field centers. The baseline clinical examination included comprehensive biological testing (fasting serum lipid levels), behavioral and socio-demographic assessments, medication inventory including inhalers, and respiratory data including questionnaires for asthma and standardized spirometry with post-bronchodilator measures for identification of obstructive lung disease.

Measurements and main results

Hispanic/Latinos with current asthma had lower age- and statin-use-adjusted mean serum total cholesterol, low-density lipoprotein cholesterol, and triglyceride levels than their non-asthmatic counterparts. In analysis adjusted for age plus gender, ethnicity, cigarette smoking, alcohol intake, body mass index, lipid/cholesterol-lowering medications, age at immigration, health insurance status, and use of oral corticosteroids, increasing serum levels of total cholesterol and low-density lipoprotein cholesterol were associated with lower odds of current asthma in the estimated population. Unlike asthma, Hispanic/Latinos with chronic obstructive pulmonary disease had lower mean high-density lipoprotein than their non- chronic obstructive pulmonary disease counterparts. In the fully adjusted analysis no significant associations were found between lipid levels and prevalent chronic obstructive pulmonary disease.

Conclusions

We showed a modest inverse relationship between serum lipid levels and current asthma. These results highlight some important differences in Hispanics/Latinos and certain serum lipids may be factors or markers of obstructive lung disease.

Meta-analysis of the association between asthma and serum levels of high-density lipoprotein cholesterol and low-density lipoprotein cholesterol

BACKGROUND

The reported associations of blood lipid profiles with asthma are ambiguous.

OBJECTIVE

To explore the association between asthma and the serum levels of high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C).

METHODS

A systematic search was performed in the PubMed, MEDLINE, Cochrane Library, and Chinese Biomedical Literature databases. Ten studies were identified. We divided these studies into 2 subgroups according to age: children (<18 years old) and adults (≥18 years old).

RESULTS

In children, the asthma group had lower HDL-C levels (weighted mean difference, -3.44; 95% confidence interval [CI], -5.83 to -1.04; P = .005) compared with the nonasthma group, whereas the serum levels of LDL-C in these 2 groups were not statistically different. In contrary, in adults, the asthma group had higher LDL-C levels (weighted mean difference, 8.95; 95% confidence interval, 3.55-14.35; P = .001) compared with the nonasthma group, whereas the HDL-C levels were not statistically different.

CONCLUSION

There is a significant association between asthma and the serum levels of HDL-C and LDL-C. Moreover, this association differs in children and adults.

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.

Interaction between allergic asthma and atherosclerosis

Prior studies have established an essential role of mast cells in allergic asthma and atherosclerosis. Mast cell deficiency or inactivation protects mice from allergen-induced airway hyper-responsiveness and diet-induced atherosclerosis, suggesting that mast cells share pathologic activities in both diseases. Allergic asthma and atherosclerosis are inflammatory diseases that contain similar sets of elevated numbers of inflammatory cells in addition to mast cells in the airway and arterial wall, such as macrophages, monocytes, T cells, eosinophils, and smooth muscle cells. Emerging evidence from experimental models and human studies points to a potential interaction between the 2 seemingly unrelated diseases. Patients or mice with allergic asthma have a high risk of developing atherosclerosis or vice versa, despite the fact that asthma is a T-helper (Th)2-oriented disease, whereas Th1 immunity promotes atherosclerosis. In addition to the preferred Th1/Th2 responses that may differentiate the 2 diseases, mast cells and many other inflammatory cells also contribute to their pathogenesis by more than just T cell immunity. Here, we summarize the different roles of airway and arterial wall inflammatory cells and vascular cells in asthma and atherosclerosis and propose an interaction between the 2 diseases, although limited investigations are available to delineate the molecular and cellular mechanisms by which 1 disease increases the risk of the other. Results from mouse allergic asthma and atherosclerosis models and from human population studies lead to the hypothesis that patients with atherosclerosis may benefit from antiasthmatic medications or that the therapeutic regimens targeting atherosclerosis may also alleviate allergic asthma.

Shared genetic variants between serum levels of high-density lipoprotein cholesterol and wheezing in a cohort of children from Cyprus

Background

In a cohort of children in Cyprus, we recently reported low levels of high density lipoprotein cholesterol (HDL-C) to be associated with asthma. We examined whether genetic polymorphisms that were previously linked individually to asthma, obesity, or HDL-C are associated with both asthma and HDL-C levels in the Cyprus cohort.

Methods

We assessed genotypes frequencies in current-wheezers (n = 190) and non-asthmatic controls (n = 671) and HDL-C levels across several genotypes. Binary logistic regression models were used to assess the effect of genotypes on wheezing risk and examined whether this effect is carried out through changes of HDL–C.

Results

Of the 16 polymorphisms tested, two polymorphisms TNFa rs3093664 and PRKCA rs9892651 presented significant differences in genotype distribution among current-wheezers and controls. Higher HDL-C levels were noted in carriers of genotype GG of polymorphism TNFa rs3093664 that was protective for wheezing Vs AG and AA genotypes (65.3 Vs 51.8 and 53.3 mg/dl, p-value < 0.001 and p-value for trend = 0.028). In polymorphism PRKCA rs9892651, HDL-C levels were lower in carriers of CC and TC genotypes that were more frequent in current-wheezers Vs TT genotype (52.2 and 52.7 Vs 55.2 mg/dl, p-value = 0.042 and p-value for trend = 0.02). The association of TNFa rs3093664 with wheezing is partly mediated by its effect on HDL-C whereas association of PRKCA rs9892651 with wheezing appeared to be independent of HDL-C.

Conclusions

We found evidence that two SNPs located in different genetic loci, are associated with both wheezing and HDL-C levels, although more studies in other populations are needed to confirm our results.

Electronic supplementary material

The online version of this article (doi:10.1186/s13052-016-0276-1) contains supplementary material, which is available to authorized users.

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.

Association of vitamin D receptor gene polymorphisms and vitamin D levels with asthma and atopy in Cypriot adolescents: a case-control study

Background

Polymorphisms in the vitamin D receptor (VDR) gene have been studied in immune-related disorders either as independent contributors or in combination with vitamin D concentration. Vitamin D and VDR have been independently linked to asthma susceptibility. We investigated whether VDR variants were associated independently or in relation to vitamin D levels with asthma in Cypriot adolescents.

Methods

We studied 190 current wheezers, 69 of which were categorized as active asthmatics and 671 healthy controls. We determined three VDR genotypes (BsmI, TaqI, ApaI) and measured serum 25(OH)D levels. Logistic regression and stratified analyses by the presence of hypovitaminosis D (≤20 ng/ml) were used to evaluate the association of the VDR variants with asthma.

Results

The distribution of TaqI genotypes was significantly different between controls and current wheezers (p = 0.030) or active asthmatics (p = 0.014). The tt genotype was over-represented in wheezers (19.2 %) and asthmatics (21.3 %) compared to respective controls (12.9 %). No difference was observed between controls, current wheezers and active asthmatics in the genotypic distribution of BsmI and ApaI polymorphic sites. After stratification by the presence of hypovitaminosis D, a significant association was detected between tt genotype of TaqI polymorphism with wheezing (OR: 1.97, 95 % CI: 1.12, 3.46) and asthma (OR: 2.37, 95CI%: 1.02, 5.52) only in those with normal vitamin D levels (>20 ng/ml) but not in subjects with low vitamin D.

Conclusions

The minor TaqI genotype of VDR is associated with asthma in Cypriot adolescents. This polymorphism may contribute to asthma susceptibility primarily under conditions of normal vitamin D levels (>20 ng/ml).

Electronic supplementary material

The online version of this article (doi:10.1186/s40248-015-0025-0) contains supplementary material, which is available to authorized users.

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.

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.

Cholesterol selectively regulates IL-5 induced mitogen activated protein kinase signaling in human eosinophils

Eosinophils function contributes to human allergic and autoimmune diseases, many of which currently lack curative treatment. Development of more effective treatments for eosinophil-related diseases requires expanded understanding of eosinophil signaling and biology. Cell signaling requires integration of extracellular signals with intracellular responses, and is organized in part by cholesterol rich membrane microdomains (CRMMs), commonly referred to as lipid rafts. Formation of these organizational membrane domains is in turn dependent upon the amount of available cholesterol, which can fluctuate widely with a variety of disease states. We tested the hypothesis that manipulating membrane cholesterol content in primary human peripheral blood eosinophils (PBEos) would selectively alter signaling pathways that depend upon membrane-anchored signaling proteins localized within CRMMs (e.g., mitogen activated protein kinase [MAPK] pathway), while not affecting pathways that signal through soluble proteins, like the Janus Kinase/Signal Transducer and Activator of Transcription [JAK/STAT] pathway. Cholesterol levels were increased or decreased utilizing cholesterol-chelating methyl-β-cyclodextrin (MβCD), which can either extract membrane cholesterol or add exogenous membrane cholesterol depending on whether MβCD is preloaded with cholesterol. Human PBEos were pretreated with MβCD (cholesterol removal) or MβCD+Cholesterol (MβCD+Chol; cholesterol delivery); subsequent IL-5-stimulated signaling and physiological endpoints were assessed. MβCD reduced membrane cholesterol in PBEos, and attenuated an IL-5-stimulated p38 and extracellular-regulated kinase 1/2 phosphorylation (p-p38, p-ERK1/2), and an IL-5-dependent increase in interleukin-1β (IL-1β) mRNA levels. In contrast, MβCD+Chol treatment elevated PBEos membrane cholesterol levels and basal p-p38, but did not alter IL-5-stimulated phosphorylation of ERK1/2, STAT5, or STAT3. Furthermore, MβCD+Chol pretreatment attenuated an IL-5-induced increase in cell survival at 48 hours, measured as total cellular metabolism. The reduction in cell survival following cholesterol addition despite unaltered STAT phosphorylation contradicts the current dogma in which JAK/STAT activation is sufficient to promote eosinophil survival, and suggests an additional, unidentified mechanism critically regulates IL-5-mediated human PBEos survival.

Prevalence of asthma and respiratory symptoms in 15-17 year-old Greek-Cypriots by proximity of their community of residence to power plants: Cyprus 2006-07

OBJECTIVES

Numerous studies have reported adverse effects of traffic pollution on respiratory health. Exposure to power plants emissions has not been as comprehensively studied. The prevalence of asthma and respiratory symptoms was investigated among 15-17 year-olds in communities in the vicinity of power plants in Cyprus in relation to the rest of the island.

STUDY DESIGN

Cross-sectional study

METHODS

Based on responses of 5817 participants to the ISAAC questionnaire, study outcomes were: active asthma (i.e. report of asthma and current symptoms), inactive asthma and respiratory symptoms without a diagnosis. Associations in terms of the distance of the participants' community to any of the three power plants were investigated in logistic models before and after adjusting for known confounders.

RESULTS

At 7.4% (95% CI: 4.5, 11.3), the prevalence of active asthma in communities at 5 km of power plants appeared elevated but reduced to national levels of 5% at longer distances. Adjusted odds ratio for active asthma was 1.83 (95% CI: 1.04, 3.24) in the 5 km zone compared to 30 km away. No clear pattern was observed for inactive asthma while the odds ratio of respiratory symptoms in the absence of diagnosis was 0.76 (95% CI: 0.58, 1.01) in the affected communities.

CONCLUSIONS

Higher prevalence of active asthma was observed in the vicinity of power plants, with no evidence of a distance-response relationship. With less than 5% of this age-group residing in close proximity to power plants, this corresponds to a small fraction of active asthma attributable to power plant emissions.

Increased IL-4 mRNA expression and poly-aromatic hydrocarbon concentrations from children with asthma

Background

Asthma is the most common chronic childhood disease. Imbalance of cytokines released from T helper cells and environmental factors, such as exposure to poly-aromatic hydrocarbon (PAH), play pivotal roles in the pathogenesis of asthma. The aim of this study was to compare the mRNA expression patterns of Interleukin (IL)-4, interferon (IFN)-γ and Acyl Co A long chain 3 (ACSL3) in peripheral blood leukocytes of children with and without asthma. To correlate the obtained mRNA data with serum IL-4, IFN-γ and PAH levels. Further, to determine the effect of in vivo exposure to PAH on mRNA expression of IL-4, IFN-γ and ACSL3 genes in a rat model.

Methods

A total of 170 children below 16 years (85 pediatric asthma patients and 85 matched healthy controls) were randomly selected from the Riyadh Cohort, Saudi Arabia. Gene expression analysis was performed using qRTPCR. Serum IL-4, IFN-γ and PAH were measured using LINCOplex (human multiplex immunoassay kit) and HPLC respectively.

Results

IL-4 mRNA expression was significantly increased (P < 0.05) in children with asthma compared to healthy control group whereas no differences were observed for either IFN-γ or ACSL3 mRNA. Similarly, serum IL- 4 and PAHs concentration was significantly higher as well in children with asthma in whom IFN-γ was also significantly lower. Results obtained in rats showed that exposure to the benzopyrene prototype PAH resulted in a 2.6 fold (P < 0.001) increased IL-4 mRNA expression in blood.

Conclusion

Peripheral blood IL-4 mRNA levels, serum concentration of this cytokine are elevated in children with asthma. Also, elevated levels of PAH were observed in children with asthma. Additionally, PAH administration in rodents resulted in an increased IL-4 mRNA which is supposed to partly mediate the inflammatory response noted in asthma.

Association of vitamin D with adiposity measures and other determinants in a cross-sectional study of Cypriot adolescents

OBJECTIVE

To assess vitamin D status among Cypriot adolescents and investigate potential determinants including BMI and body fat percentage (BF%).

DESIGN

Participants had cross-sectional assessments of serum vitamin D, physical activity, dietary vitamin D intake and sun exposure. Linear and logistic regression models were used to explore the associations of vitamin D with potential predictors.

SETTING

Hospitals, Cyprus, November 2007-May 2008.

SUBJECTS

Adolescents (n 671) aged 16-18 years.

RESULTS

Mean serum vitamin D was 22·90 (sd 6·41) ng/ml. Only one in ten children had sufficient levels of vitamin D (≥30 ng/ml), while the prevalence of vitamin D deficiency (12-20 ng/ml) and severe deficiency (<12 ng/ml) was 31·7 % and 4·0 %, respectively. Lower vitamin D was associated with winter and spring season, female gender, reduced sun exposure in winter and darker skin. Participants with highest BMI and BF% when compared with a middle reference group had increased adjusted odds of vitamin D insufficiency (OR = 3·00; 95 % CI 1·21, 7·45 and OR = 5·02; 95 % CI 1·80, 13·97, respectively). A similar pattern, although not as strong, was shown for vitamin D deficiency with BF% (OR = 1·81; 95 % CI 1·04, 3·16) and BMI (OR = 1·51; 95 % CI 0·85, 2·67). Participants in the lowest BMI and BF% groups also displayed compromised vitamin D status, suggesting a U-shaped association.

CONCLUSIONS

Vitamin D deficiency in adolescence is very prevalent in sunny Cyprus, particularly among females, those with darker skin and those with reduced sun exposure in winter. Furthermore, vitamin D status appears to have a U-shaped association with adiposity measures.

Links between allergy and cardiovascular or hemostatic system

In addition to a well-known immunologic background of atherosclerosis and influences of inflammation on arterial and venous thrombosis, there is growing evidence for the presence of links between allergy and vascular or thrombotic disorders. In this interpretative review, five pretty well-documented areas of such overlap are described and discussed, including: (1) links between atherosclerosis and immunoglobulin E or atopy, (2) mutual effects of blood lipids and allergy, (3) influence of atopy and related disorders on venous thromboembolism, (4) the role of platelets in allergic diseases, and (5) the functions of protein C system in atopic disorders.

Serum low density lipoprotein subclasses in asthma

BACKGROUND

The levels of serum low-density lipoproteins (LDL) have been implicated in the inflammatory cascade in a murine model of asthma. Recent findings suggest that LDL may modulate the inflammatory state of the asthmatic airways in humans.

OBJECTIVE

We explored whether LDL subclasses are associated with the occurrence and severity of asthma.

METHODS

24 asthmatics (M/F: 11/13) and 24 healthy individuals, with normal BMI and absence of metabolic syndrome, matched for age and gender. Serum concentrations of LDL subclasses were distributed as seven bands (LDL-1 and -2 defined as large, least pro-inflammatory LDL, and LDL-3 to -7 defined as small, most pro-inflammatory LDL), using the LipoPrint(©) System (Quantimetrix Corporation, Redondo Beach, CA, USA).

RESULTS

LDL-1 was similar in the two groups (56 ± 16% vs. 53 ± 11, p = NS), while LDL-2 was significantly lower in asthmatics as compared to controls (35 ± 8% vs. 43 ± 10%, p = 0.0074). LDL-3 levels were two-fold higher in the asthmatics, but the difference did not reach the statistical significance (8 ± 7.3% vs. 4 ± 3%, p = NS). Smaller subclasses LDL-4 to LDL-7 were undetectable in controls. In asthmatics, LDL-1 was positively associated with VC% predicted (r = +0.572, p = 0.0035) and FEV1% predicted (r = +0.492, p = 0.0146). LDL-3 was inversely correlated with both VC% predicted (r = -0.535, p = 0.0071) and FEV1% predicted (r = -0.465, p = 0.0222).

CONCLUSIONS

The findings of this pilot study suggest a role of LDL in asthma, and advocate for larger studies to confirm the association between asthma and dyslipidemia.

Arterial inflammation in bronchial asthma

BACKGROUND

Bronchial asthma is a chronic inflammatory condition associated with increased cardiovascular (CV) events. Here, we assess arterial inflammation, using 18F-fluorodeoxyglucose positron emission tomography/computed tomography imaging (FDG-PET/CT), in patients with bronchial asthma and low to intermediate Framingham risk scores (FRS).

METHODS

A total of 102 patients underwent FDG-PET/CT imaging for clinical indications. Thirty-four patients (mean age 54.9 ± 16.1) with mild asthma and no known atherosclerotic disease were compared to 2 non-asthmatic groups. The first control group (n = 34) were matched by age, gender, and FRS. The second control group (n = 34) had clinical atherosclerosis and were matched by gender. Thereafter, arterial FDG uptake on PET images was determined, while blinded to patient identifiers.

RESULTS

Target-to-background-ratio (TBR) in the aorta was higher in asthmatics vs non-asthmatic FRS-matched controls (1.96 ± 0.26 vs 1.76 ± 0.20; P < .001). The aortic TBR remained elevated in asthmatics vs non-asthmatic controls after adjusting traditional CV risk factors (P < .001). An inverse correlation was observed between FDG uptake and lung function, FEV1 (P = .02) and peak flow (P = .03).

CONCLUSIONS

Bronchial asthma is associated with increased arterial inflammation beyond that estimated by current risk stratification tools. Further studies are required to evaluate whether attenuation of systemic inflammation will decrease CV events.

Associations between airway hyperresponsiveness, obesity and lipoproteins in a longitudinal cohort

BACKGROUND

Epidemiological data have linked obesity with an increased risk of asthma, but the mechanisms responsible for this relationship remain unknown. One possible mechanism, which has received little attention, could be the effect of cholesterol metabolism on airway smooth muscle function. The present study investigated the association between airway hyperresponsiveness (AHR) to methacholine and body mass index (BMI) and plasma lipoproteins [low-density lipoprotein (LDL), high-density lipoprotein (HDL) and total cholesterol].

METHODS

Associations between AHR, BMI and plasma lipoproteins were assessed in a population-based cohort at ages 14 and 20 years.

RESULTS

In unadjusted analyses, higher LDL cholesterol levels at age 14 were associated with AHR at age 20 in both sexes (P < 0.05). HDL, LDL/HDL ratio and total cholesterol were not associated with AHR. In multiple regression analyses adjusted for sex, lung function, smoking and asthma, only higher levels of BMI at age 14 or 20 years were significantly associated with increased AHR at age 20 years, while neither LDL, HDL and LDL/HDL ratio nor total cholesterol were significantly associated with AHR.

CONCLUSION

We confirmed that in teenagers there is a strong association between BMI and AHR to methacholine. This association seems to be independent of the plasma lipoprotein levels at that age.