Body mass index is a stronger predictor than the metabolic syndrome for future asthma in women. The longitudinal CARDIA study

New insights into causal relationship between serum lipids, obesity, and asthma: a Mendelian randomization study

OBJECTIVE

To identify causal risk factors for asthma using a Mendelian randomization (MR) approach.

METHODS

Genetic variants associated with the exposures at the genome-wide significance level (p < 5 × 10 - 8) were obtained from corresponding genome-wide association studies. Summary-level statistical data for asthma were obtained from the UK Biobank (UKB) and the FinnGen Consortia. Univariate and multivariate MR analyses were performed to clarify causal relationships among obesity, serum lipids, and asthma. Meta-analyses were performed to combine UKB and FinnGen results using a fixed-effects model.

RESULTS

In FinnGen, the odds for asthma increased for every 1-SD increase in body mass index (BMI; odds ratio [OR] 1.292, p = 1.34 × 10-7), together with body fat percentage (BF%; OR 1.449, p = 4.90×10-3), and total cholesterol level (OR = 0.949, p = 0.027). However, higher BMI and BF% were found to increase the risk for asthma in the multivariate MR analysis. In the UKB, the BMI results were replicated. Meta-analysis revealed that high-density lipoprotein cholesterol could also increase the risk for asthma, although there were no associations with other risk factors included in this study.

CONCLUSION

This MR study found that genetically predicted higher BF% and BMI could increase the risk for asthma and corroborated some risk factors for asthma from previous MR studies. Moreover, the results suggest that higher BMI and BF% could serve as independent risk factors for asthma.

Food for thought: optimal diet in patients with asthma and chronic obstructive pulmonary disease

PURPOSE OF REVIEW

Nutritional intake plays a major role in the management of lung health. This review provides the latest perspective on how dietary choices can modulate lung function in patients with chronic obstructive pulmonary disease (COPD) and asthma.

RECENT FINDINGS

The pathophysiology of COPD and asthma is driven by oxidative stress and inflammation of the airways, which is exacerbated by modifiable risk factors such as cigarette smoking and diet. Various foods can influence patient symptoms; highly processed foods increase the production of reactive oxygen species that augment airway inflammation, whereas foods rich in antioxidants, fiber and protein combat oxidative stress and muscle wastage. Patients with COPD or asthma are at increased risk of developing metabolic comorbidities, including cachexia and obesity that complicate disease phenotypes, leading to greater symptom severity. While clinical findings suggest a role for antioxidant and macronutrient support of lung function, comprehensive translational and clinical studies are necessary to better understand the mechanisms underlying nutrient interaction and lung structure-function.

SUMMARY

Understanding the nutritional requirements that protect lung health and support weight management in COPD and asthma is imperative to providing personalized dietary recommendations and reducing patient morbidity.

Impact of metabolic and weight components on incident asthma using a real-world cohort

BACKGROUND

Obesity and metabolic dysregulation (MetD) have increasing prevalence and adversely affect asthma morbidity and therapeutic response.

OBJECTIVE

To determine the role of weight and MetD on incident asthma in adulthood.

METHODS

In a retrospective, longitudinal cohort of patients, we performed a time-to-asthma diagnosis analysis after a 3-year landmark period (t0-t3) during which weight and MetD components were evaluated. We assessed incident asthma risk with MetD components and weight.

RESULTS

In total, 90,081 patients met the inclusion criteria, with 836 cases (0.93%) of incident asthma in our primary cohort. Diabetes present at t0, but no other MetD components, was associated with increased risk of asthma (adjusted hazard ratio = 1.85, 95% CI: 1.27-2.71, P = .0002). The effect of weight on asthma risk, independent of other MetD components, identified individuals with overweight or obesity as having a 10-year attributable risk of 15.4%. Metformin was prescribed more frequently, and hemoglobin A1c levels were lower in patients with diabetes in whom asthma did not develop (P < .0001).

CONCLUSION

Weight and diabetes prevention and management represent modifiable risk factors for adult asthma development.

Prevalence of Obesity and Its Associated Comorbidities in Adults with Asthma: A Single-Center Study in Saudi Arabia

Background and Objectives: Asthma is associated with several comorbidities, one of which is obesity. The worldwide increase in obesity has been accompanied by a parallel rise in asthma prevalence, with obesity recognized as a significant risk factor for both the development and severity of asthma. Obesity is often linked to various comorbidities, which can complicate asthma management and lead to poorer clinical outcomes. This study aims to investigate the prevalence of obesity and its comorbidities in adults with asthma in a single center in Saudi Arabia, providing an overview of the associated health implications. Materials and Methods: This single-center, retrospective study aimed to assess the prevalence of obesity and other comorbidities in asthma patients. Data were collected from King Khalid University Hospital in Saudi Arabia between July 2023 and December 2023. Results: This study revealed that 72.1% of asthma patients were either obese or overweight. Female patients had significantly higher BMI values compared to males. Our study revealed that 38.21% of female asthma patients (mean age = 57 ± 13.85 years) had comorbidities compared to 24.14% of male asthma patients (mean age = 59 ± 14.02 years). Furthermore, the proportion of obese asthmatic patients with comorbidities was significantly greater than those without comorbidities. Conclusions: This study investigates obesity prevalence and associated comorbidities in adult asthmatics in a single center in Saudi Arabia. The findings reveal a 72.1% rate of obesity and overweight among asthmatic patients, with higher BMI and comorbidity prevalence in females. These results underscore the need for targeted interventions addressing obesity and comorbidities, especially in female asthmatics.

Chinese expert consensus on the diagnosis, treatment, and management of asthma in women across life

Background

The epidemiology and severity of asthma vary by sex and age. The diagnosis, treatment, and management of asthma in female patients are quite challenging. However, there is hitherto no comprehensive and standardized guidance for female patients with asthma.

Methods

Corresponding search strategies were determined based on clinical concerns regarding female asthma. Search terms included "sex hormones and lung development", "sex hormone changes and asthma", "hormones and asthma immune response", "women, asthma", "children, asthma", "puberty, asthma", "menstruation, asthma", "pregnancy, asthma", "lactation, asthma", "menopause, asthma", "obesity, asthma", and "women, refractory, severe asthma". Literature was retrieved from PubMed/Medline, Embase, Cochrane Library, China Biology Medicine disc, China National Knowledge Infrastructure, Wanfang Data with the search date of July 30, 2022 as the last day. This consensus used the Grading of Recommendations Assessment, Development, and Evaluation to evaluate the strength of recommendation and quality of evidence.

Results

We collected basic research results and clinical evidence-based medical data and reviewed the effects of sex hormones, classical genetics, and epigenetics on the clinical presentation and treatment response of female patients with asthma under different environmental effects. Based on that, we formulated this expert consensus on the management of female asthma throughout the life cycle.

Conclusions

This expert consensus on the management of asthma in women throughout the life cycle provides diagnosis, treatment, and research reference for clinical and basic medical practitioners.

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.

Association of Asthma With Patients Diagnosed With Metabolic Syndrome: A Cohort Study in a Tertiary Care Hospital

Introduction Asthma is defined as a chronic inflammatory airway disease. The prevalence of both asthma and obesity has been rising simultaneously, demonstrating a parallel trend. Obesity is a significant factor in metabolic syndrome, and numerous studies have indicated a connection between metabolic syndrome and bronchial asthma. Aims and objectives The aim of this paper is to evaluate the association of asthma with patients diagnosed with metabolic syndrome. The main objectives were to analyze the clinical profile and spirometric indices in patients with metabolic syndrome and to assess asthmatic patients among them with spirometry and clinical parameters at a tertiary care hospital in Chennai. Materials and methods This hospital-based cohort study was conducted on 73 patients attending the outpatient department who had a known case of metabolic syndrome and were evaluated for asthma through history, physical examination, and a pulmonary function test. A history of cough, expectoration, shortness of breath, wheezing, chest tightness, allergy, seasonal variation, and smoking habits was asked, and a thorough physical examination was performed. Bronchial asthma was confirmed with airflow reversibility by spirometry as per the Global Initiative for Asthma Guidelines. Metabolic and spirometry parameters were examined, such as body mass index (BMI), waist circumference, waist-hip ratio, fasting blood sugar (FBS), postprandial blood sugar, hemoglobin A1C (HbA1C), serum insulin, lipid profile, C-reactive protein (CRP), forced expiratory volume in the first second (FEV1), forced vital capacity (FVC), and FEV1/FVC pre- and post-reversibility (baseline vs. six months). Results and discussion The average BMI of all participants was 29.6511 ±2.64564. The waist-hip ratio was 0.5512 ±0.43855, which decreased during the follow-ups, demonstrating a decline in the risk of obesity in study participants. The level of HbA1C showed a drop from 6.1% to 5.9% at the first follow-up. This exhibited a further reduction at the six-month follow-up in addition to a positive reflection in insulin sensitivity, indicating successful control of diabetes among study participants. It was discovered that this was statistically significant (p<0.001). At the third and sixth months of follow-up, the FEV1/FVC ratio increased by 38% and 37%, respectively, when metabolic syndrome was under control. The results show that controlling diabetes, hypertension, obesity, and triglyceride values improved asthmatic symptoms, and this was determined to be statistically significant (p<0.001). Conclusion The results of the current study demonstrated that the regulation and maintenance of metabolic parameters such as BMI, diabetes, hyperlipidemia, and hypertension aid in improving asthma control.

Lifestyles and the risk of an asthma attack in adult asthma patients: a cross-sectional study using NHANES database

BACKGROUND

The influence of physical activity, diet and sleep on asthma has been well documented by recent studies respectively. However, few studies focus on the relationship between asthma attack and the overall lifestyle, which comprises interrelated lifestyle factors. This study aims to investigate the influence of lifestyles on the ratio of asthma attack. Data were extracted from the NHANES database (2017 to May 2020).

METHODS

A total of 834 asthmatic patients were enrolled and divided into non-asthma attack (N.=460) and asthma attack (N.=374) groups. The risk factors for asthma attacks were preliminarily identified by univariate logistic analysis, then multivariate logistic analysis was employed to select independent risk factors other than lifestyles and further determine the association between lifestyles and asthma attacks.

RESULTS

After multivariate logistic analysis, engagement of vigorous activity (Model 1 P=0.010, Model 2 P=0.016, Model 3 P=0.012), engagement of moderate activity (Model 1 P=0.006, Model 2 P=0.008, Model 3 P=0.003) and sleep disorder (Model1 P=0.001, Model 2 P<0.001, Model 3 P=0.008) were determined as independent risk factors of lifestyles for an asthma attack in the past year.

CONCLUSIONS

This research documented that, for asthmatic patients, engagement of vigorous activity, engagement of moderate activity, and sleep disorder will make an asthma attack more likely to happen.

Association between pediatric asthma and adult polycystic ovarian syndrome (PCOS): a cross-sectional analysis of the UAE healthy future Study (UAEHFS)

Introduction

Asthma and polycystic ovarian syndrome (PCOS) are linked in several possible ways. To date, there has been no study evaluating whether pediatric asthma is an independent risk factor for adult PCOS. Our study aimed to examine the association between pediatric asthma (diagnosed at 0-19 years) and adult PCOS (diagnosed at ≥20 years). We further assessed whether the aforementioned association differed in two phenotypes of adult PCOS which were diagnosed at 20-25 years (young adult PCOS), and at >25 years (older adult PCOS). We also evaluated whether the age of asthma diagnosis (0-10 vs 11-19 years) modified the association between pediatric asthma and adult PCOS.

Material and methods

This is a retrospective cross-sectional analysis using the United Arab Emirates Healthy Future Study (UAEHFS) collected from February 2016 to April 2022 involving 1334 Emirati females aged 18-49 years. We fitted a Poisson regression model to estimate the risk ratio (RR) and its 95% confidence interval (95% CI) to assess the association between pediatric asthma and adult PCOS adjusting for age, urbanicity at birth, and parental smoking at birth.

Results

After adjusting for confounding factors and comparing to non-asthmatic counterparts, we found that females with pediatric asthma had a statistically significant association with adult PCOS diagnosed at ≥20 years (RR=1.56, 95% CI: 1.02-2.41), with a stronger magnitude of the association found in the older adult PCOS phenotype diagnosed at >25 years (RR=2.06, 95% CI: 1.16-3.65). Further, we also found females reported thinner childhood body size had a two-fold to three-fold increased risk of adult PCOS diagnosed at ≥20 years in main analysis and stratified analyses by age of asthma and PCOS diagnoses (RR=2.06, 95% CI: 1.08-3.93 in main analysis; RR=2.74, 95% CI: 1.22-6.15 among those diagnosed with PCOS > 25 years; and RR=3.50, 95% CI: 1.38-8.43 among those diagnosed with asthma at 11-19 years).

Conclusions

Pediatric asthma was found to be an independent risk factor for adult PCOS. More targeted surveillance for those at risk of adult PCOS among pediatric asthmatics may prevent or delay PCOS in this at-risk group. Future studies with robust longitudinal designs aimed to elucidate the exact mechanism between pediatric asthma and PCOS are warranted.

The association between body mass index, abdominal fatness, and weight change and the risk of adult asthma: a systematic review and meta-analysis of cohort studies

Obesity has been associated with increased risk of adult asthma, however, not all studies have found a clear association between overweight and the incidence of asthma, and data on other adiposity measures have been limited. Hence, we aimed to summarize evidence on association between adiposity and adult asthma. Relevant studies were retrieved through searches conducted in PubMed, and EMBASE up to March 2021. A total of sixteen studies (63,952 cases and 1,161,169 participants) were included in the quantitative synthesis. The summary RR was 1.32 (95% CI 1.21-1.44, I² = 94.6%, p_{heterogeneity}< 0.0001, n = 13) per 5 kg/m² increase in BMI, 1.26 (95% CI 1.09-1.46, I² = 88.6%, p_{heterogeneity} < 0.0001, n = 5) per 10 cm increase in waist circumference and 1.33 (95% CI 1.22-1.44, I² = 62.3%, p_{heterogeneity}= 0.05, n = 4) per 10 kg increase in weight gain. Although the test for nonlinearity was significant for BMI (p_nonlinearity < 0.00001), weight change (p_nonlinearity = 0.002), and waist circumference (p_nonlinearity = 0.02), there was a clear dose-response relationship between higher levels of adiposity and asthma risk. The magnitude of the associations and the consistency of the results across studies and adiposity measures provide strong evidence that overweight and obesity, waist circumference and weight gain increases asthma risk. These findings support policies to curb the global epidemic of overweight and obesity.

The "Asthma-Polycystic Ovary Overlap Syndrome" and the Therapeutic Role of Myo-Inositol

Asthma is a heterogeneous inflammatory disease characterized by abnormalities in immune response. Due to the inherent complexity of the disease and the presence of comorbidities, asthma control is often difficult to obtain. In asthmatic patients, an increased prevalence of irregular menstrual cycles, infertility, obesity, and insulin resistance has been reported. Given that these conditions are also common in patients with polycystic ovary syndrome (PCOS), we propose the definition of "asthma-PCOS overlap syndrome" to indicate a medical condition which shares characteristics of both diseases. The aim of this review is to analyze the links between asthma and PCOS and evaluate the therapeutic role of myo-inositol, a natural compound currently utilized in patients with PCOS, in the management of asthma patients.

Asthma, obesity, and microbiota: A complex immunological interaction

Obesity and allergic asthma are inflammatory chronic diseases mediated by distinct immunological features, obesity presents a Th1/Th17 profile, asthma is commonly associated with Th2 response. However, when combined, they result in more severe asthma symptoms, greater frequency of exacerbation episodes, and lower therapy responsiveness. These features lead to decreased life quality, associated with higher morbidity/mortality rates.  In addition, obesity prompts specific asthma phenotypes, which can be dependent on atopic status, age, and gender. In adults, obesity is associated with neutrophilic/Th17 profile, while in children, the outcome is diverse, in some cases children with obesity present aggravation of atopy, and Th2 inflammation, and in others an association with a Th1 profile, with reduced IgE levels and eosinophilia. These alterations occur due to a complex group of factors among which the microbiome has been recently explored. Particularly, evidence shows its important role in susceptibility or resistance to asthma development, via gut-lung-axis, and demonstrates its relevance to the immune pathogenesis of the syndrome. Few studies address the relevance of the lung microbiome in shaping the immune response, locally. However, specific bacteria, like Moraxella catarrhalis, Haemophilus influenza, and Streptococcus pneumoniae, correlate with important features of the obese-asthmatic phenotype. Although maternal obesity is known to increase asthma risk in offspring, the impact on lung colonization is unknown. This review details the main key immune mechanisms involved in obesity-aggravated asthma, featuring the effect of maternal obesity in the establishment of gut and lung microbiota of the offspring, acting as potential childhood asthma inducer.

Associations Between Asthma and Polycystic Ovary Syndrome: Current Perspectives

A potential correlation between polycystic ovary syndrome (PCOS) and asthma, used to be identified as diseases originating from two independent systems, has been supported by increasing evidence. From an epidemiological perspective, mounting studies have confirmed that women suffering from PCOS exhibit increased susceptibility to asthma. Meanwhile, PCOS and asthma seem to share several mutual pathological conditions, such as metabolic disorders, hormonal fluctuation, proinflammatory state, etc. Here, we further elucidate the correlation between asthma and PCOS by focusing on the internal common pathophysiology and adverse influences on women's health. Understanding the internal connection between PCOS and asthma may shed light on developing new prevention and control strategies to fight against these conditions.

Severe asthma in Kuwait population: Phenotype-based approach

BACKGROUND

There is increasing recognition of marked phenotypic heterogeneity within severe asthma patients.

METHODS

Severe asthma patients on GINA step 4 or 5 treatment, followed up at Al-Rashed Allergy center Kuwait, were evaluated for: demographics (gender, age, age of asthma onset), comorbidities (allergic rhinitis (AR), chronic rhinosinusitis (CRS), chronic rhinosinusitis with nasal polyposis (CRSwNP), obesity), blood biomarkers (total serum Immunoglobulin E (IgE), peripheral eosinophils), and sensitization to inhalants allergens.

RESULTS

A total of 169 patients were candidates for biological treatment. Patients were divided in two groups based on level of total IgE as a "low" group with IgE<160 IU/ml (n = 55) and "high" group with IgE≥ 160 IU/ml (n = 114). Both groups were further divided in subgroups, "low" and "high", based on absolute number of eosinophils (Eos) in peripheral blood with <300 cells/μl or ≥ 300 cells/μl. Only 10% of patients were in low IgE/low Eos while majority (46%) were in the high IgE/high Eos group. Mean age of patients was 44.1 year with domination of females (n = 123). Majority of patients were obese. AR, CRS and CRSwNP were more common in group with IgE ≥160 IU/ml, while CRS and CRSwNP in group with Eos ≥300 cells/μl.

CONCLUSION

The majority of severe asthma patients in Kuwait are obese females with adult-onset asthma (>18 years of age) who were allergic with comorbid conditions including AR, CRS and CRSwNP, which correlates well with the level of Eos.

Obesity and asthma

Obesity has been well recognized as an important comorbidity in patients with asthma, representing a unique phenotype and endotype. This association indicates a close relationship between metabolic and inflammatory dysregulation. However, the detailed organ-organ, cellular, and molecular interactions are not completely resolved. Because of that, the relationship between obesity and asthma remains unclear. In this article, clinical and epidemiological studies, as well as data from experimental animal work, are being summarized to provide a state of the art update on this important topic. Much more work is needed, particularly mechanistic, to fully understand the interaction between obesity and asthma and to develop novel preventive and therapeutic strategies.

Retinol-binding protein-4 was associated with sensitization to inhalant allergens in the elderly population

BACKGROUND/AIMS

Recent evidence suggests an association between allergic sensitization and metabolic markers. However, this association has rarely been examined in the elderly. Retinol-binding protein-4 (RBP-4) is a recently identified adipokine that acts on the muscle and liver affecting insulin sensitivity. We evaluated the association between metabolic parameters and allergic sensitization in the elderly.

METHODS

We analysed the database of the Korean Longitudinal Study on Health and Aging cohort study conducted during 2005 to 2006. Atopy was identified by inhalant allergen skin prick test. Metabolic conditions were assessed using anthropometric indices and serum biomarkers such as fasting glucose, lipid, adiponectin, and RBP-4.

RESULTS

Among the 854 elderly subjects, 17.2% had atopy. Plasma RBP-4 levels were significantly higher in the atopic elderly than nonatopic elderly (p = 0.003). When RBP-4 percentiles were categorized as under three groups, the prevalence of atopy and current rhinitis increased significantly with percentiles of RBP-4 levels (p = 0.019 and p = 0.007, respectively). Log RBP-4 was associated with atopy (odds ratio [OR], 4.10; p = 0.009) and current rhinitis (OR, 2.73; p = 0.014), but not with current asthma (OR, 1.17; p = 0.824). Higher RBP-4 level in atopic elderly was also observed in current rhinitis patients. Atopy, but not current rhinitis, showed significant relationships with log RBP-4 levels in multivariate analyses adjusted for other metabolic markers including body mass index.

CONCLUSION

RBP-4 positively associated with atopy in the general elderly population irrespective of other metabolic markers.

Metabolic Syndrome and Incident Asthma in Chinese Adults: An Open Cohort Study

BACKGROUND

Although metabolic syndrome is awell-known risk factor for many non-communicable diseases, its contribution to asthma remains controversial.

OBJECTIVE

The aim of this study was to explore the associations of metabolic syndrome and its components with incident asthma in Chinese adults.

METHODS

We conducted an open cohort study of participants who were asthma-free at baseline (n=42,304) in the Shandong multi-center health check-up longitudinal study from 2004 to 2015. Participants aged ≥20 years and had regular physical examination (once ayear) more than three times during follow-up.

RESULTS

Ninety subjects (38 women and 52 men) developed incident asthma over 12 years of follow-up. Our study suggested that metabolic syndrome itself was not significantly associated with incident asthma in either women or men (P>0.050). Interestingly, we found that overweight and/or obesity was arisk factor for incident asthma among women but not men in the Cox proportional hazards model after adjusting covariates (adjusted incidence rate ratio (IRR)= 2.940, 95% confidence interval (CI): 1.467-5.894, P=0.002). The result was consistent with the Poisson regression model (hazard ratio (HR)= 2.241, 95% CI: 1.135-4.988, P=0.026). After stratifying according to overweight and/or obesity, we found that female subjects with overweight and obesity were associated with the occurrence of incident asthma (P<0.050). However, we did not find this result among men.

CONCLUSION

Metabolic syndrome was not significantly associated with incident asthma in both women and men; however, overweight and/or obesity was shown to be asignificant risk factor for incident asthma but only in women, not in men.

Metabolic Dysfunction and Asthma: Current Perspectives

The increasing knowledge of the mechanisms involved in metabolism is shifting the paradigms by which the pathophysiology of many pulmonary diseases is understood. Metabolic dysfunction is recognized in obesity-associated asthma, but other metabolic conditions have been shown to be independently related to asthma. Novel insights have also recently been brought by metabolomics in this filed. The purpose of this review is to discuss current perspectives regarding metabolic dysfunction in asthma, from obesity-related asthma to other metabolic conditions and the role of current pharmacological therapeutic strategies and lifestyle interventions. Obesity is a well-recognized risk factor for asthma across the lifespan, which is generally associated with poorer response to current available treatments, rendering a more severe, refractory disease status. Besides the epidemiological and clinical link, untargeted metabolomics studies have recently supported the obesity-associated asthma phenotype at the molecular level. Not only obesity-related, but also other aspects of metabolic dysregulation can be independently linked to asthma. These include hyperinsulinemia, dyslipidemia and hypertension, which need to be taken into account, even in the non-obese patient. Untargeted metabolomics studies have further highlighted several other metabolic pathways that can be altered in asthma, namely regarding oxidative stress and systemic inflammation, and also suggesting the importance of microbiota in asthma pathogenesis. Considering the reduced response to corticosteroids, other pharmacologic treatments have been shown to be effective regardless of body mass index. Non-pharmacologic treatments (namely weight reduction and dietary changes) may bring substantial benefit to the asthmatic patient. Taken together, this evidence points towards the need to improve our knowledge in this filed and, in particular, to address the influence of environmental factors in metabolic dysfunction and asthma development. Personalized medicine is definitely needed to optimize treatment, including a holistic view of the asthmatic patient in order to set accurate pharmacologic therapy together with dietary, physical exercise and lifestyle interventions.

Asthma and metabolic syndrome: a comprehensive systematic review and meta-analysis of observational studies

Introduction: This study aimed to perform a meta-analysis on the prevalence of metabolic syndrome (MetS) among patients with asthma and to measure the association asthma has with MetS.

Methods: The Web of Science, Medline, Scopus, Embase and Google Scholar were searched using the "Asthma", "Metabolic Syndrome", "Dysmetabolic Syndrome", "Cardiovascular Syndrome", "Insulin Resistance Syndrome", "Prevalence", "Odds Ratio", "Cross-Sectional Studies", and "Case-Control Studies" keywords. All observational studies reporting the prevalence of MetS among people with and without asthma were included in the study. In the presence of heterogeneity, random-effects models were used to pool the prevalence and odds ratios (OR), as measures of association in cross-sectional and case-control/ cohort studies, respectively.

Results: The prevalence of MetS among patients with asthma (8 studies) and the OR comparing the prevalence of MetS among patients with and without asthma (5 studies) were pooled separately. The pooled prevalence of MetS among patients with asthma was found to be 25% (95% confidence interval (CI): 13%–38%). In contrast, the overall pooled OR for MetS in patients with asthma, compared to healthy controls, was 1.34 (95% CI: 0.91–1.76), which was not statistically significant.

Conclusion: The prevalence of MetS was relatively high in patients with asthma. Furthermore, the odds of MetS was higher in patients with asthma, compared to healthy controls, although this difference was not statistically significant. More original studies among different populations are needed in order to more accurately examine the association between asthma and MetS, as well as the relationship asthma has with the individual components of MetS.

Sex, obesity, diabetes, and exposure to particulate matter among patients with severe asthma: Scientific insights from a comparative analysis of open clinical data sources during a five-day hackathon

This special communication describes activities, products, and lessons learned from a recent hackathon that was funded by the National Center for Advancing Translational Sciences via the Biomedical Data Translator program ('Translator'). Specifically, Translator team members self-organized and worked together to conceptualize and execute, over a five-day period, a multi-institutional clinical research study that aimed to examine, using open clinical data sources, relationships between sex, obesity, diabetes, and exposure to airborne fine particulate matter among patients with severe asthma. The goal was to develop a proof of concept that this new model of collaboration and data sharing could effectively produce meaningful scientific results and generate new scientific hypotheses. Three Translator Clinical Knowledge Sources, each of which provides open access (via Application Programming Interfaces) to data derived from the electronic health record systems of major academic institutions, served as the source of study data. Jupyter Python notebooks, shared in GitHub repositories, were used to call the knowledge sources and analyze and integrate the results. The results replicated established or suspected relationships between sex, obesity, diabetes, exposure to airborne fine particulate matter, and severe asthma. In addition, the results demonstrated specific differences across the three Translator Clinical Knowledge Sources, suggesting cohort- and/or environment-specific factors related to the services themselves or the catchment area from which each service derives patient data. Collectively, this special communication demonstrates the power and utility of intense, team-oriented hackathons and offers general technical, organizational, and scientific lessons learned.

The impact of bariatric surgery on asthma control differs among obese individuals with reported prior or current asthma, with or without metabolic syndrome

BACKGROUND

Both obesity and the metabolic syndrome have been independently associated with increased asthma morbidity. However, it is unclear whether metabolic syndrome limits the beneficial effects of weight loss on asthma.

OBJECTIVES

To evaluate whether bariatric weight loss is associated with improved asthma control, and whether this association varies by metabolic syndrome status.

METHODS

We determined the changes in asthma control, defined by the Asthma Control Test (ACT), before and after bariatric surgery among participants with asthma in the multi-center Longitudinal Assessment of Bariatric Surgery (LABS) study, stratifying our analysis by the presence or absence of metabolic syndrome.

RESULTS

Among 2,458 LABS participants, 555 participants had an asthma diagnosis and were included in our analysis. Of these, 78% (n = 433) met criteria for metabolic syndrome (MetSyn) at baseline. In patients without MetSyn, mean ACT increased from 20.4 at baseline to 22.1 by 12-24 months, ending at 21.3 at 60 months. In contrast, among those with MetSyn there was no significant improvement in ACT scores. The proportion of patients without MetSyn with adequate asthma control (ACT >19) increased from 58% at baseline to 78% and 82% at 12 and 60 months, respectively, whereas among those with MetSyn, it was 73.8% at baseline, 77.1% at 12 months, dropping to 47.1% at 60 months (p = 0.004 for interaction between metabolic syndrome and time). Having MetSyn also increased the likelihood of losing asthma control during follow-up (HR = 1.92, 95% confidence interval [CI] 1.24-2.97, p = 0.003).

CONCLUSIONS

Metabolic syndrome may negatively modify the effect of bariatric surgery-induced weight loss on asthma control.

Obesity, but not metabolic syndrome, as a risk factor for late-onset asthma in Japanese women

BACKGROUND

Several cross-sectional studies have suggested an association between obesity and asthma. However, few studies have investigated this relationship longitudinally, especially in middle-aged subjects. Although metabolic syndrome is a well-known risk factor for many non-communicable diseases, its contribution to asthma remains controversial.

METHODS

From 2008, specific health checkups for metabolic syndrome have been conducted throughout Japan. To seek relationships of obesity and metabolic syndrome with late-onset asthma in Japan, we analyzed data collected from health insurance claims and specific health checkups for metabolic syndrome at three large health insurance societies. Among subjects aged 40-64 years (n = 9888), multivariate logistic regression analyses were performed to investigate the relationships of obesity and metabolic syndrome in fiscal year 2012 (from April 2012 to March 2013) with the incidence of late-onset asthma in the following two years (from April 2013 to March 2015).

RESULTS

In women, BMI 25-29.9 kg/m² or ≥30 kg/m², waist circumference ≥90 cm, and waist-to-height ratio ≥0.5 were shown to be significant risk factors for asthma, with adjusted odds ratios (95% CI) of 1.92 (1.35-2.75), 2.24 (1.23-4.09), 1.89 (1.30-2.75), and 1.53 (1.15-2.03), respectively. Significance was retained even after adjustment for metabolic syndrome, and there were no significant relationships between metabolic syndrome itself and the incidence of asthma in men or women.

CONCLUSIONS

Only the obesity measures, not metabolic syndrome, were shown to be significant risk factors for the incidence of late-onset asthma but only in middle-aged Japanese women, and not in men.

Metabolic aspects of the relationship of asthma and obesity

Asthma and obesity are serious medical and social world problems, and their combined course is characterized by a decrease in the quality of life, an increase in the frequency and duration of hospitalization. The present review summarizes the current views on the mechanisms of formation of asthma phenotype combined with obesity, role of leptin and adiponectin imbalance in the development of systemic inflammation in obesity in the pathophysiology of asthma, its interrelations with metabolic syndrome. We present data that shows that syndrome is closely related not only to the debut of asthma, but also to a decrease in its control. Along with obesity, the role of other components of metabolic syndrome, in particular insulin resistance, as a predictor of asthma development is considered. Insulin resistance may be the most likely factor in the relationship between asthma and obesity, independent of other components of the metabolic syndrome. Insulin resistance associated with obesity can lead to disruption of nitric oxide synthesis. We reveal common mechanism of metabolic disorders of nitric oxide and arginine in metabolic syndrome and asthma and show that insulin resistance treatment can be therapeutically useful in patients with asthma in combination with obesity.

Diet and Metabolism in the Evolution of Asthma and Obesity

Obesity is a major risk factor for asthma. This association appears related to altered dietary composition and metabolic factors that can directly affect airway reactivity and airway inflammation. This article discusses how specific changes in the western diet and metabolic changes associated with the obese state affect inflammation and airway reactivity and reviews evidence that interventions targeting weight, dietary components, lifestyle, and metabolism might improve outcomes in asthma.

The relationship between metabolic syndrome and asthma in the elderly

The burden of asthma in the elderly is increasing, but the etiology of asthma in the elderly is not clearly understood. Recent studies have reported the epidemiological link between metabolic syndrome (MS) and asthma, but it has rarely been studied in the elderly. This study investigated the association between MS and asthma and the contribution of insulin resistance (IR) and systemic inflammation to this MS-asthma association in the elderly. Our study analyzed 4,060 elderly participants (≥65 years old) from a cross-sectional survey, the Korean National Health and Nutritional Examination Survey 2007–2012. Mediation analyses were performed to examine whether IR and systemic inflammation mediates the MS-asthma association. Participants with MS had significantly higher prevalence of asthma (adjusted odds ratio = 1.34; 95% confidence interval = 1.09–1.64), and those who had greater waist circumference and lower HDL-C were especially likely to have asthma. Participants with IR and systemic inflammation were associated with higher prevalence of asthma. Prevalence of IR and systemic inflammation were higher in participants with MS or with each MS component. The MS-asthma association was substantially mediated by IR and systemic inflammation. Our study showed a significant association between MS and asthma in the elderly. MS might affect asthma through both IR and systemic inflammation.

Baseline Features of the Severe Asthma Research Program (SARP III) Cohort: Differences with Age

BACKGROUND

The effect of age on asthma severity is poorly understood.

OBJECTIVES

The objective of this study was to compare the baseline features of severe and nonsevere asthma in the Severe Asthma Research Program (SARP) III cohort, and examine in cross section the effects of age on those features.

METHODS

SARP III is a National Institutes of Health/National Heart Lung Blood Institute multisite 3-year cohort study conducted to investigate mechanisms of severe asthma. The sample included 188 children (111 severe, 77 nonsevere) and 526 adults (313 severe, 213 nonsevere) characterized for demographic features, symptoms, health care utilization, lung function, and inflammatory markers compared by age and severity.

RESULTS

Compared with children with nonsevere asthma, children with severe asthma had more symptoms and more historical exacerbations, but no difference in body weight, post-bronchodilator lung function, or inflammatory markers. After childhood, and increasing with age, the cohort had a higher proportion of women, less allergen sensitization, and overall fewer blood eosinophils. Enrollment of participants with severe asthma was highest in middle-aged adults, who were older, more obese, with greater airflow limitation and higher blood eosinophils, but less allergen sensitization than adults with nonsevere asthma.

CONCLUSIONS

The phenotypic features of asthma differ by severity and with advancing age. With advancing age, patients with severe asthma are more obese, have greater airflow limitation, less allergen sensitization, and variable type 2 inflammation. Novel mechanisms besides type 2 inflammatory pathways may inform the severe asthma phenotype with advancing age.

Sex hormones and systemic inflammation are modulators of the obese-asthma phenotype

BACKGROUND

Both systemic inflammation and sex hormones have been proposed as potential mediators of the obese-asthma phenotype. The aim of this study was to examine the associations between sex hormones, oral contraceptive pill (OCP) use, systemic inflammation and airway inflammation in adults with asthma.

METHODS

Obese (n = 39) and nonobese (n = 42) females and obese (n = 24) and nonobese (n = 25) males with asthma were recruited. Females were further categorized as reproductive-aged (<50 years old; n = 36) or older (>50 years old; n = 45). Thirteen (36.1%) reproductive-aged females were using the OCP. Participants had induced sputum cell counts measured and blood analysed for sex hormones and inflammatory markers.

RESULTS

Obese reproductive-aged females had higher sputum %neutrophils than nonobese reproductive-aged females (45.4 ± 24.3% vs 27.5 ± 17.5%, P = 0.016); however, there was no difference in sputum neutrophils in obese compared with nonobese males (P = 0.620) or older females (P = 0.087). Multiple linear regression analysis found testosterone and OCP use to be negative predictors of sputum %neutrophils, while C-reactive protein and IL-6 were positive predictors of sputum %neutrophils. BMI and age were not significant predictors in the multivariate model. Reproductive-aged females using the OCP had significantly lower sputum %neutrophils than those not using the OCP (23.2 ± 12.6% vs 42.1 ± 23.8%, P = 0.015).

CONCLUSIONS

This study suggests that sex hormones and systemic inflammation may be mediating the obese-asthma phenotype. The observation that OCP use was associated with lower sputum %neutrophils in reproductive-aged females warrants further investigation.

Emerging Comorbidities in Adult Asthma: Risks, Clinical Associations, and Mechanisms

Asthma is a heterogeneous disease with many phenotypes, and age at disease onset is an important factor in separating the phenotypes. Most studies with asthma have been performed in patients being otherwise healthy. However, in real life, comorbid diseases are very common in adult patients. We review here the emerging comorbid conditions to asthma such as obesity, metabolic syndrome, diabetes mellitus type 2 (DM2), and cardiac and psychiatric diseases. Their role as risk factors for incident asthma and whether they affect clinical asthma are evaluated. Obesity, independently or as a part of metabolic syndrome, DM2, and depression are risk factors for incident asthma. In contrast, the effects of comorbidities on clinical asthma are less well-known and mostly studies are lacking. Cross-sectional studies in obese asthmatics suggest that they may have less well controlled asthma and worse lung function. However, no long-term clinical follow-up studies with these comorbidities and asthma were identified. These emerging comorbidities often occur in the same multimorbid adult patient and may have in common metabolic pathways and inflammatory or other alterations such as early life exposures, systemic inflammation, inflammasome, adipokines, hyperglycemia, hyperinsulinemia, lung mechanics, mitochondrial dysfunction, disturbed nitric oxide metabolism, and leukotrienes.

Hyperinsulinemia adversely affects lung structure and function

There is limited knowledge regarding the consequences of hyperinsulinemia on the lung. Given the increasing prevalence of obesity, insulin resistance, and epidemiological associations with asthma, this is a critical lacuna, more so with inhaled insulin on the horizon. Here, we demonstrate that insulin can adversely affect respiratory health. Insulin treatment (1 μg/ml) significantly (P < 0.05) increased the proliferation of primary human airway smooth muscle (ASM) cells and induced collagen release. Additionally, ASM cells showed a significant increase in calcium response and mitochondrial respiration upon insulin exposure. Mice administered intranasal insulin showed increased collagen deposition in the lungs as well as a significant increase in airway hyperresponsiveness. PI3K/Akt mediated activation of β-catenin, a positive regulator of epithelial-mesenchymal transition and fibrosis, was observed in the lungs of insulin-treated mice and lung cells. Our data suggests that hyperinsulinemia may have adverse effects on airway structure and function. Insulin-induced activation of β-catenin in lung tissue and the contractile effects on ASM cells may be causally related to the development of asthma-like phenotype.

Metabolic Syndrome and the Lung

A link between metabolic syndrome (MetS) and lung diseases has been observed in several cross-sectional and longitudinal studies. This syndrome has been identified as an independent risk factor for worsening respiratory symptoms, greater lung function impairment, pulmonary hypertension, and asthma. This review will discuss several potential mechanisms to explain these associations, including dietary factors and the effect of adiposity and fat-induced inflammation on the lungs, and the role of other comorbidities that frequently coexist with MetS, such as OSA and obesity. In contrast to the well-known association between asthma and obesity, the recognition that MetS affects the lung is relatively new. Although some controversy remains as to whether MetS is a unique disease entity, its individual components have independently been associated with changes in pulmonary function or lung disease. There is, however, uncertainty as to the relative contribution that each metabolic factor has in adversely affecting the respiratory system; also, it is unclear how much of the MetS-related lung effects occur independently of obesity. In spite of these epidemiological limitations, the proposed mechanistic pathways strongly suggest that this association is likely to be causal. Given the wide prevalence of MetS in the general population, it is imperative that we continue to further understand how this metabolic disorder impacts the lung and how to prevent its complications.

[Impact of obesity on response to therapy and pulmonary function in children with asthma]

OBJECTIVE

To investigate the effects of obesity on response to therapy and pulmonary function in children with asthma who receive inhaled corticosteroid (ICS) treatment.

METHODS

A total of 129 children with asthma were divided into two groups according to their body mass index: normal weight group (n=64) and obese group (n=65). The asthma control status and pulmonary function were compared between the two groups after one year of ICS treatment. The pulmonary function was expressed as percent forced expiratory volume in 1 second (FEV1%), percent predicted forced vital capacity (FVC%), peak expiratory flow (PEF), peak expiratory flow at 25% of vital capacity (PEF25), and peak expiratory flow at 50% of vital capacity (PEF50). The asthma control status was expressed as complete control rate, partial control rate, and uncontrolled rate. Sixty-eight healthy children were selected as the healthy control group.

RESULTS

There were significant differences in the indices of pulmonary function between the three groups before treatment (P<0.01); the healthy control group had the best values of pulmonary function, while the obese group had the worst values. After 1 year of treatment, the normal weight group showed significantly more improvements in FEV1% and FVC% than the obese group (P<0.01). However, there were no significant differences in improvements in PEF, PEF25, and PEF50 between the two groups. The complete control rate, partial control rate, and uncontrolled rate in the normal weight group were 72%, 19%, and 9%, respectively, while the rates in the obese group were 28%, 51%, and 22%, respectively; the normal weight group had a significantly better asthma control status than the obese group (P<0.01).

CONCLUSIONS

The asthmatic children with obesity have a significantly less improvement in large airway function and a poorer asthma control status after ICS treatment than those with the normal weight.

Adipokines and Cysteinyl Leukotrienes in the Pathogenesis of Asthma

Background. The prevalence of obesity has increased dramatically over the last decades, and its association with asthma is being increasingly recognized. Aims. Our hypothesis is that increased leptin and decreased adiponectin levels in obese subjects play a direct role in regulating inflammation in asthmatics. We wanted to examine the hypothesis that cysteinyl leukotrienes (cys-LT), inflammatory mediators that are regulated by adipokines, are involved in the pathogenesis of asthma. Methods. We studied a population of asthmatics and nonasthmatics, who in turn were divided into obese and nonobese categories. We examined leptin and its ratio to adiponectin, in asthmatics and nonasthmatics, with and without obesity. In addition, we measured cys-LT levels in exhaled breath condensate (EBC) and in peripheral blood monocytes (PBM) in these groups. Results. Leptin levels were increased in obese asthmatics compared to obese nonasthmatics. The leptin/adiponectin (L/A) ratio was higher in obese asthmatics compared to obese nonasthmatics. EBC cys-LT levels were elevated in asthmatics compared to nonasthmatics. Discussion. Proinflammatory adipokines, released from adipose tissue, may promote an asthma phenotype through enhanced cys-LT production that may result in more prevalent and difficult to control airway disease.

Phenotypes, Risk Factors, and Mechanisms of Adult-Onset Asthma

Asthma is a heterogeneous disease with many phenotypes, and age at disease onset is an important factor in separating the phenotypes. Genetic factors, atopy, and early respiratory tract infections are well-recognized factors predisposing to childhood-onset asthma. Adult-onset asthma is more often associated with obesity, smoking, depression, or other life-style or environmental factors, even though genetic factors and respiratory tract infections may also play a role in adult-onset disease. Adult-onset asthma is characterized by absence of atopy and is often severe requiring treatment with high dose of inhaled and/or oral steroids. Variety of risk factors and nonatopic nature of adult-onset disease suggest that variety of mechanisms is involved in the disease pathogenesis and that these mechanisms differ from the pathobiology of childhood-onset asthma with prevailing Th2 airway inflammation. Recognition of the mechanisms and mediators that drive the adult-onset disease helps to develop novel strategies for the treatment. The aim of this review was to summarize the current knowledge on the pathogenesis of adult-onset asthma and to concentrate on the mechanisms and mediators involved in establishing adult-onset asthma in response to specific risk factors. We also discuss the involvement of these mechanisms in the currently recognized phenotypes of adult-onset asthma.

Metabolic Syndrome Is Associated with Increased Oxo-Nitrative Stress and Asthma-Like Changes in Lungs

Epidemiological studies have shown an increased obesity-related risk of asthma. In support, obese mice develop airway hyperresponsiveness (AHR). However, it remains unclear whether the increased risk is a consequence of obesity, adipogenic diet, or the metabolic syndrome (MetS). Altered L-arginine and nitric oxide (NO) metabolism is a common feature between asthma and metabolic syndrome that appears independent of body mass. Increased asthma risk resulting from such metabolic changes would have important consequences in global health. Since high-sugar diets can induce MetS, without necessarily causing obesity, studies of their effect on arginine/NO metabolism and airway function could clarify this aspect. We investigated whether normal-weight mice with MetS, due to high-fructose diet, had dysfunctional arginine/NO metabolism and features of asthma. Mice were fed chow-diet, high-fat-diet, or high-fructose-diet for 18 weeks. Only the high-fat-diet group developed obesity or adiposity. Hyperinsulinemia, hyperglycaemia, and hyperlipidaemia were common to both high-fat-diet and high-fructose-diet groups and the high-fructose-diet group additionally developed hypertension. At 18 weeks, airway hyperresponsiveness (AHR) could be seen in obese high-fat-diet mice as well as non-obese high-fructose-diet mice, when compared to standard chow-diet mice. No inflammatory cell infiltrate or goblet cell metaplasia was seen in either high-fat-diet or high-fructose-diet mice. Exhaled NO was reduced in both these groups. This reduction in exhaled NO correlated with reduced arginine bioavailability in lungs. In summary, mice with normal weight but metabolic obesity show reduced arginine bioavailability, reduced NO production, and asthma-like features. Reduced NO related bronchodilation and increased oxo-nitrosative stress may contribute to the pathogenesis.

Asthma and obesity: mechanisms and clinical implications

Obesity is the most common asthma co-morbidity; it has been associated with increased risk for asthma exacerbations, worse respiratory symptoms and poor control. The exact mechanisms remain elusive and are probably multifactorial, stemming from mechanical alterations of the airways and lung parenchyma, to systemic and airway inflammatory and metabolic dysregulation that adversely influences lung function and or response to therapy. However, the fact that not every obese asthmatic is equally affected by weight gain highlights the many challenges and complexities in understanding this association. The factors that determine susceptibility may not depend on being obese alone, but rather the interactions with other phenotypical characteristics, such as age of asthma onset, gender and race to name a few. Inability to account for asthma phenotypes that are differentially affected by increasing body mass index (BMI) may contribute to the lack of consistent results across studies. This review will provide a succinct summary of obesity-related mechanisms and the clinical impact on asthma including highlights on recent progress.

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.

Data-driven asthma endotypes defined from blood biomarker and gene expression data

The diagnosis and treatment of childhood asthma is complicated by its mechanistically distinct subtypes (endotypes) driven by genetic susceptibility and modulating environmental factors. Clinical biomarkers and blood gene expression were collected from a stratified, cross-sectional study of asthmatic and non-asthmatic children from Detroit, MI. This study describes four distinct asthma endotypes identified via a purely data-driven method. Our method was specifically designed to integrate blood gene expression and clinical biomarkers in a way that provides new mechanistic insights regarding the different asthma endotypes. For example, we describe metabolic syndrome-induced systemic inflammation as an associated factor in three of the four asthma endotypes. Context provided by the clinical biomarker data was essential in interpreting gene expression patterns and identifying putative endotypes, which emphasizes the importance of integrated approaches when studying complex disease etiologies. These synthesized patterns of gene expression and clinical markers from our research may lead to development of novel serum-based biomarker panels.

Hyperinsulinemia potentiates airway responsiveness to parasympathetic nerve stimulation in obese rats

Obesity is a substantial risk factor for developing asthma, but the molecular mechanisms underlying this relationship are unclear. We tested the role of insulin in airway responsiveness to nerve stimulation using rats genetically prone or resistant to diet-induced obesity. Airway response to vagus nerve stimulation and airway M2 and M3 muscarinic receptor function were measured in obese-prone and -resistant rats with high or low circulating insulin. The effects of insulin on nerve-mediated human airway smooth muscle contraction and human M2 muscarinic receptor function were tested in vitro. Our data show that increased vagally mediated bronchoconstriction in obesity is associated with hyperinsulinemia and loss of inhibitory M2 muscarinic receptor function on parasympathetic nerves. Obesity did not induce airway inflammation or increase airway wall thickness. Smooth muscle contraction to acetylcholine was not increased, indicating that hyperresponsiveness is mediated at the level of airway nerves. Reducing serum insulin with streptozotocin protected neuronal M2 receptor function and prevented airway hyperresponsiveness to vagus nerve stimulation in obese rats. Replacing insulin restored dysfunction of neuronal M2 receptors and airway hyperresponsiveness to vagus nerve stimulation in streptozotocin-treated obese rats. Treatment with insulin caused loss of M2 receptor function, resulting in airway hyperresponsiveness to vagus nerve stimulation in obese-resistant rats, and inhibited human neuronal M2 receptor function in vitro. This study shows that it is not obesity per se but hyperinsulinemia accompanying obesity that potentiates vagally induced bronchoconstriction by inhibiting neuronal M2 muscarinic receptors and increasing acetylcholine release from airway parasympathetic nerves.

Is there a link between obesity and asthma?

Increasing epidemiological data identify a link between obesity and asthma incidence and severity. Based on experimental data, it is possible that shared inflammatory mechanisms play a role in determining this linkage. Although controversial, the role of adipokines may be central to this association and the maintenance of the asthma phenotype. While leptin and adiponectin have a causal link to experimental asthma in mice, data in humans are less conclusive. Recent studies demonstrate that adipokines can regulate the survival and function of eosinophils and that these factors can affect eosinophil trafficking from the bone marrow to the airways. In addition, efferocytosis, the clearance of dead cells, by airway macrophages or blood monocytes appears impaired in obese asthmatics and is inversely correlated with glucocorticoid responsiveness. This review examines the potential mechanisms linking obesity to asthma.