The treatment of asthma in obesity

TRP channels associated with macrophages as targets for the treatment of obese asthma

Globally, obesity and asthma pose significant health challenges, with obesity being a key factor influencing asthma. Despite this, effective treatments for obese asthma, a distinct phenotype, remain elusive. Since the discovery of transient receptor potential (TRP) channels in 1969, their value as therapeutic targets for various diseases has been acknowledged. TRP channels, present in adipose tissue cells, influence fat cell heat production and the secretion of adipokines and cytokines, which are closely associated with asthma and obesity. This paper aims to investigate the mechanisms by which obesity exacerbates asthma-related inflammation and suggests that targeting TRP channels in adipose tissue could potentially suppress obese asthma and offer novel insights into its treatment.

Management of the pediatric patient with asthma and obesity

Asthma and obesity are 2 of the most significant chronic diseases of childhood. Both are major public health problems that have been increasing in prevalence. Obesity increases the risk of developing asthma in children, and in children with asthma, obesity increases asthma severity and morbidity. The nature of this relationship is complex and not fully understood, but some pediatric patients with "obesity-related asthma" may represent a phenotype that differs from the more classical, atopic pediatric asthma. In this review, we investigate and discuss some of the currently available literature regarding treatment for asthma complicated by obesity in the pediatric population. We cover the importance of healthy lifestyle modifications, management of obesity-related comorbidities, and the potential role of nutritional supplementation or modification. We then review recent literature, mostly in adults, investigating the potential role of obesity or diabetes medications in the management of patients with asthma who have obesity. Finally, we discuss some of the necessary next steps before these potential new treatments can be considered as part of the standard clinical management of asthma.

Pediatric obesity and severe asthma: Targeting pathways driving inflammation

Asthma affects more than 300 million people of all ages worldwide, including about 10-15% of school-aged children, and its prevalence is increasing. Severe asthma (SA) is a particular and rare phenotype requiring treatment with high-dose inhaled corticosteroids plus a second controller and/or systemic glucocorticoid courses to achieve symptom control or remaining "uncontrolled" despite this therapy. In SA, other diagnoses have been excluded, and potential exacerbating factors have been addressed. Notably, obese asthmatics are at higher risk of developing SA. Obesity is both a major risk factor and a disease modifier of asthma in children and adults: two main "obese asthma" phenotypes have been described in childhood with high or low levels of Type 2 inflammation biomarkers, respectively, the former characterized by early onset and eosinophilic inflammation and the latter by neutrophilic inflammation and late-onset. Nevertheless, the interplay between obesity and asthma is far more complex and includes obese tissue-driven inflammatory pathways, mechanical factors, comorbidities, and poor response to corticosteroids. This review outlines the most recent findings on SA in obese children, particularly focusing on inflammatory pathways, which are becoming of pivotal importance in order to identify selective targets for specific treatments, such as biological agents.

Therapeutic ketosis decreases methacholine hyperresponsiveness in mouse models of inherent obese asthma

Obese asthmatics tend to have severe, poorly controlled disease and exhibit methacholine hyperresponsiveness manifesting in proximal airway narrowing and distal lung tissue collapsibility. Substantial weight loss in obese asthmatics or in mouse models of the condition decreases methacholine hyperresponsiveness. Ketone bodies are rapidly elevated during weight loss, coinciding with or preceding relief from asthma-related comorbidities. As ketone bodies may exert numerous potentially therapeutic effects, augmenting their systemic concentrations is being targeted for the treatment of several conditions. Circulating ketone body levels can be increased by feeding a ketogenic diet or by providing a ketone ester dietary supplement, which we hypothesized would exert protective effects in mouse models of inherent obese asthma. Weight loss induced by feeding a low-fat diet to mice previously fed a high-fat diet was preceded by increased urine and blood levels of the ketone body β-hydroxybutyrate (BHB). Feeding a ketogenic diet for 3 wk to high-fat diet-fed obese mice or genetically obese db/db mice increased BHB concentrations and decreased methacholine hyperresponsiveness without substantially decreasing body weight. Acute ketone ester administration decreased methacholine responsiveness of normal mice, and dietary ketone ester supplementation of high-fat diet-fed mice decreased methacholine hyperresponsiveness. Ketone ester supplementation also transiently induced an "antiobesogenic" gut microbiome with a decreased Fermicutes/Bacteroidetes ratio. Dietary interventions to increase systemic BHB concentrations could provide symptom relief for obese asthmatics without the need for the substantial weight loss required of patients to elicit benefits to their asthma through bariatric surgery or other diet or lifestyle alterations.

Pediatric Obesity-Related Asthma: The Role of Nutrition and Nutrients in Prevention and Treatment

Childhood obesity rates have dramatically risen in numerous countries worldwide. Obesity is likely a factor in increased asthma risk, which is already one of the most widespread chronic respiratory pathologies. The pathogenic mechanism of asthma risk has still not yet been fully elucidated. Moreover, the role of obesity-related inflammation and pulmonary overreaction to environmental triggers, which ultimately result in asthma-like symptoms, and the importance of dietary characteristics is well recognized. Diet is an important adjustable element in the asthma development. Food-specific composition of the diet, in particular fat, sugar, and low-quality nutrients, is likely to promote the chronic inflammatory state seen in asthmatic patients with obesity. An unbalanced diet or supplementation as a way to control asthma more efficiently has been described. A personalized dietary intervention may improve respiratory symptoms and signs and therapeutic response. In this narrative review, we presented and discussed more recent literature on asthma associated with obesity among children, focusing on the risk of asthma among children with obesity, asthma as a result of obesity focusing on the role of adipose tissue as a mediator of systemic and local airway inflammation implicated in asthma regulation, and the impact of nutrition and nutrients in the development and treatment of asthma. Appropriate early nutritional intervention could possibly be critical in preventing and managing asthma associated with obesity among children.

BMI but not central obesity predisposes to airway closure during bronchoconstriction

BACKGROUND AND OBJECTIVE

Obesity produces restrictive effects on lung function. We previously reported that obese patients with asthma exhibit a propensity towards small airway closure during methacholine challenge which improved with weight loss. We hypothesized that increased abdominal adiposity, a key contributor to the restrictive effects of obesity on the lung, mediates this response. This study investigates the effect of body mass index (BMI) versus waist circumference (WC) on spirometric lung function, sensitivity to airway narrowing and closure, and airway closure during bronchoconstriction in patients with asthma.

METHODS

Participants underwent spirometry and methacholine challenge. Sensitivity to airway closure and narrowing was assessed from the dose-response slopes of the forced vital capacity (FVC) and the ratio of forced expiratory volume in 1 s (FEV₁ ) to FVC, respectively. Airway closure during bronchoconstriction (closing index) was computed as the percent reduction in FVC divided by the percent reduction in FEV₁ at maximal bronchoconstriction.

RESULTS

A total of 116 asthmatic patients (56 obese) underwent methacholine challenge. Spirometric lung function was inversely related to WC (P < 0.05), rather than BMI. Closing index increased significantly during bronchoconstriction in obese patients and was related to increasing BMI (P = 0.01), but not to WC. Sensitivity to airway closure and narrowing was not associated with BMI or WC.

CONCLUSION

Although WC is associated with restrictive effects on baseline lung function, increased BMI, rather than WC, predisposes to airway closure during bronchoconstriction. These findings suggest that obesity predisposes to airway closure during bronchoconstriction through mechanisms other than simple mass loading.

The effect of obesity on lung function

INTRODUCTION

There is a major epidemic of obesity, and many obese patients suffer with respiratory symptoms and disease. The overall impact of obesity on lung function is multifactorial, related to mechanical and inflammatory aspects of obesity. Areas covered: Obesity causes substantial changes to the mechanics of the lungs and chest wall, and these mechanical changes cause asthma and asthma-like symptoms such as dyspnea, wheeze, and airway hyperresponsiveness. Excess adiposity is also associated with increased production of inflammatory cytokines and immune cells that may also lead to disease. This article reviews the literature addressing the relationship between obesity and lung function, and studies addressing how the mechanical and inflammatory effects of obesity might lead to changes in lung mechanics and pulmonary function in obese adults and children. Expert commentary: Obesity has significant effects on respiratory function, which contribute significantly to the burden of respiratory disease. These mechanical effects are not readily quantified with conventional pulmonary function testing and measurement of body mass index. Changes in mediators produced by adipose tissue likely also contribute to altered lung function, though as of yet this is poorly understood.

Factors reducing omalizumab response in severe asthma

BACKGROUND

Despite adding Omalizumab to conventional therapy, several severe asthmatics still show poor disease control. We investigated the factors that may affect a reduced Omalizumab response in a large population of severe asthmatics.

METHODS

340 patients were retrospectively evaluated. FEV₁%, FVC%, Asthma Control Test (ACT), fractional exhaled nitric oxide (FENO), possible step-downs/step-ups of concomitant therapies, exacerbations, disease control levels, ICS doses and SABA use, observed at the end of treatment, were considered as a response to Omalizumab.

RESULTS

Age was an independent risk factor for a reduced response concerning FEV₁%, FVC%, ACT and for a lower asthma control. Obesity (vs normal weight) was a determinant condition for exacerbations (OR:3.114[1.509-6.424], p = 0.002), for a disease partial/no control (OR:2.665[1.064-6.680], p = 0.036), for excessive SABA use (OR:4.448[1.837-10.768], p = 0.002) and for an unchanged/increased level of concomitant asthma medications. Furthermore, obesity also reduced the response in FEV₁ (β = -6.981,p = 0.04), FVC (β = -11.689,p = 0.014) and ACT (β = -2.585, p = 0.027) and was associated with a higher FENO level (β = 49.045,p = 0.040). Having at least one comorbidity was a risk factor for exacerbations (OR:1.383[1.128-1.697], p = 0.008) and for an ACT <20 (OR:2.410[1.071-3.690], p = 0.008). Specifically, chronic heart disease was associated with both a lower ACT and FVC% whereas gastroesophageal reflux with a partial/no asthma control. Nasal polyps were a predisposing factor leading both to exacerbations and to the use of higher inhaled corticosteroids doses. Moreover, smoking habits, pollen or dog/cat dander co-sensitizations may negatively influence Omalizumab response.

CONCLUSION

Age, obesity, comorbidities, smoking habits, nasal polyps, allergic poly-sensitization might reduce Omalizumab effectiveness independently to other asthma-influencing factors.

Effect of obesity on sinonasal disease in asthma

OBJECTIVE

Sinonasal disease can contribute to poor asthma control. There are reports that link obesity with an increased prevalence of sinonasal disease, but no studies evaluating the severity of sinonasal disease in obese asthmatics, and how this impacts asthma control. The purpose of the current study was to determine if obesity is associated with increased severity of sinonasal disease, and/or affects response to nasal corticosteroid treatment in asthma.

METHODS

This study included 236 adults participating in a 24-week randomized, double-masked, placebo-controlled study of nasal mometasone for the treatment of poorly controlled asthma. Sinonasal disease severity was assessed using validated questionnaires, and compared in participants of differing BMIs. Eosinophilic inflammation was assessed using markers in nasal lavage, serum and exhaled nitric oxide. Response to treatment was compared in different BMI groups.

RESULTS

Obesity had no effect on the severity of sinonasal disease symptoms in asthmatics (Sino-Nasal Outcome Test 22 (SNOT 22) score [mean ± SD] 35.4 ± 18.5, 40.2 ± 22.8, and 39.1 ± 21.7, p = 0.43, in lean, overweight and obese participants), nor on nasal, bronchial or systemic markers of allergic inflammation. Nasal steroids had some limited effects on symptoms, lung function and inflammatory markers in lean participants, but no detectable effect was found in obese patients.

CONCLUSIONS

Obesity does not affect severity of sinonasal disease in patients with asthma; the association of sinonasal disease symptoms with increased asthma severity and markers of Type 2 inflammation are consistent across all BMI groups. The response of obese patients to nasal corticosteroids requires further study.

[How to consider triggers and comorbid conditions in severe asthma in adults]

Triggers and precipitating factors as well as comorbid conditions are associated with asthma and severe asthma. They interfere with the potential to control the disease and represent an additional burden for the patients. Allergen exposure is well known to induce loss of control and exacerbations. Comorbid conditions belong to various fields of medicines including cardiovascular diseases, osteoporosis, obesity and sleep apneas and GERD. They should be diagnosed and treated for themselves according to the best state of the art. Their precise role et their contribution to severe asthma pathophysiology is largely unknown and longitudinal cohort studies are needed to better understand and treat the patients with severe asthma.

Weight Loss Decreases Inherent and Allergic Methacholine Hyperresponsiveness in Mouse Models of Diet-Induced Obese Asthma

Obese asthma presents with inherent hyperresponsiveness to methacholine or augmented allergen-driven allergic asthma, with an even greater magnitude of methacholine hyperresponsiveness. These physiologic parameters and accompanying obese asthma symptoms can be reduced by successful weight loss, yet the underlying mechanisms remain incompletely understood. We implemented mouse models of diet-induced obesity, dietary and surgical weight loss, and environmental allergen exposure to examine the mechanisms and mediators of inherent and allergic obese asthma. We report that the methacholine hyperresponsiveness in these models of inherent obese asthma and obese allergic asthma manifests in distinct anatomical compartments but that both are amenable to interventions that induce substantial weight loss. The inherent obese asthma phenotype, with characteristic increases in distal airspace tissue resistance and tissue elastance, is associated with elevated proinflammatory cytokines that are reduced with dietary weight loss. Surprisingly, bariatric surgery-induced weight loss further elevates these cytokines while reducing methacholine responsiveness to levels similar to those in lean mice or in formerly obese mice rendered lean through dietary intervention. In contrast, the obese allergic asthma phenotype, with characteristic increases in central airway resistance, is not associated with increased adaptive immune responses, yet diet-induced weight loss reduces methacholine hyperresponsiveness without altering immunological variables. Diet-induced weight loss is effective in models of both inherent and allergic obese asthma, and our examination of the fecal microbiome revealed that the obesogenic Firmicutes/Bacteroidetes ratio was normalized after diet-induced weight loss. Our results suggest that structural, immunological, and microbiological factors contribute to the manifold presentations of obese asthma.

Obesity-related asthma in adults

Obesity as a risk factor for asthma has been identified in previous studies. Additionally, a disproportionate number of patients with severe or difficult-to-control asthma are obese. Patients with obesity-related asthma tend to have worse asthma control and quality of life disproportionate to their pulmonary function tests, are less responsive to corticosteroid therapy, and are more likely to have obesity-related comorbidities such as obstructive sleep apnea and gastroesophageal disease that complicate asthma treatment. With the increasing prevalence of obesity, the prevalence of asthma is anticipated to grow proportionally. Addressing weight loss and encouraging activity is essential in the management of obesity-related asthma. This article briefly overviews the epidemiology, unique distinguishing features, potential mechanisms, and approach to management of patients with obesity-related asthma in adults.

Patient stratification and the unmet need in asthma

Asthma is often described as an inflammatory disease of the lungs and in most patients symptomatic treatment with bronchodilators or inhaled corticosteroids is sufficient to control disease. Unfortunately there are a proportion of patients who fail to achieve control despite treatment with the best current treatment. These severe asthma patients have been considered a homogeneous group of patients that represent the unmet therapeutic need in asthma. Many novel therapies have been tested in unselected asthma patients and the effects have often been disappointing, particularly for the highly specific monoclonal antibody-based drugs such as anti-IL-13 and anti-IL-5. More recently, it has become clear that asthma is a syndrome with many different disease drivers. Clinical trials of anti-IL-13 and anti-IL-5 have focused on biomarker-defined patient groups and these trials have driven the clinical progression of these drugs. Work on asthma phenotyping indicates that there is a group of asthma patients where T helper cell type 2 (Th2) cytokines and inflammation predominate and these type 2 high (T2-high) patients can be defined by biomarkers and response to therapies targeting this type of immunity, including anti-IL-5 and anti-IL-13. However, there is still a subset of T2-low patients that do not respond to these new therapies. This T2-low group will represent the new unmet medical need now that the T2-high-targeting therapies have made it to the market. This review will examine the current thinking on patient stratification in asthma and the identification of the T2-high subset. It will also look at the T2-low patients and examine what may be the drivers of disease in these patients.

A pilot randomized controlled trial of pioglitazone for the treatment of poorly controlled asthma in obesity

BACKGROUND

Obese asthmatics tend to have poorly controlled asthma, and resistance to standard asthma controller medications. The purpose of this study was to determine the efficacy of pioglitazone, an anti-diabetic medication which can alter circulating adipokines and have direct effects on asthmatic inflammation, in the treatment of asthma in obesity.

METHODS

A two-center, 12-week, randomized, placebo-controlled, double-blinded trial. Treatments were randomly assigned with concealment of allocation. The primary outcome was difference in change in airway reactivity between participants assigned to pioglitazone versus placebo at 12 weeks.

RESULTS

Twenty-three participants were randomized to treatment, 19 completed the study. Median airway reactivity, measured by PC20 to methacholine was 1.99 (IQR 3.08) and 1.60 (5.91) mg/ml in placebo and pioglitazone group at baseline, and 2.37 (15.22) and 5.08 (7.42) mg/ml after 12 weeks, p = 0.38. There was no difference in exhaled nitric oxide, asthma control or lung function between treatment groups over the 12 week trial. Participants assigned to pioglitazone gained a significant amount more weight than those assigned to placebo (pioglitazone group mean weight 113.6, CI 94.5-132.7 kg at randomization and 115.9, CI 96.9-135.1 at 12 weeks; placebo mean weight 127.5, CI 108.4 - 146.6 kg at randomization and 124.5, CI 105.4 - 143.6 kg at 12 weeks; p = 0.04).

CONCLUSIONS

This pilot study suggests limited efficacy for pioglitazone in the treatment of poorly controlled asthma in obesity, and also the potential for harm, given the weight gain in those assigned to active treatment, and the association between increased weight and worse outcomes in asthma.

TRIAL REGISTRATION

Clinicaltrials.gov (NCT00634036).

Immunological characteristics and management considerations in obese patients with asthma

Obesity is associated with severe, poorly controlled asthma that does not respond as well to therapy as asthma in leaner asthmatics. Important insights gained from animal models of obesity and asthma suggests that different forms of obesity may lead to different manifestations of airway disease: obesity is associated with both innate increased airway reactivity and altered responses to aeroallergen and pollutant challenges. In humans, at least two broad groups of obese asthmatics have been recognized: one that is likely unique to obesity and another that is likely lean allergic asthma much complicated by obesity. This article will discuss what we have learned about the immunological and pathophysiological basis of asthma in obesity from animal and human studies, and how this might guide therapy.

Body mass index change and atopic diseases are not always associated in children and adolescents

BACKGROUND

Several studies have suggested an association between the increasing prevalence of allergic diseases and dietary factors.

OBJECTIVE

To prospectively explore the association between changes in body mass index (BMI) and symptoms of asthma, rhinitis, rhinoconjunctivitis, and atopic dermatitis to find out whether an increase in BMI increases the risk of developing atopic diseases in adolescence.

METHODS

Comprehensive questionnaires and anthropometric measurements were applied in a random subsample of the International Study of Asthma and Allergies in Childhood phase II (1995-1996, 9 to 11 years of age) in Germany. Of these participants, 1,794 could be followed up in 2002 to 2003 in the Study on Occupational Allergy Risks (16 to 18 years of age). The associations between changes of BMI from baseline to follow-up and incident and persistent respiratory diseases and atopic dermatitis were assessed.

RESULTS

In logistic regression analyses, weight change in either direction was not statistically significantly associated with the incidence or persistence of any of the diseases of interest except for rhinitis. An increase in BMI was linked to an increased risk of incident rhinitis (odds ratio 1.9, 95% confidence interval 1.2-2.9).

CONCLUSION

These results indicate a nonsignificant trend between increased body weight and risk of atopic diseases. Aside from limitations owing to a small subgroup of obese participants and questionnaire-based asthma diagnosis, reasons might be related to an interaction between BMI and hormonal influences, age, and duration and severity of overweight. The results underline that BMI does not necessarily play a decisive role in the course of atopic diseases in all populations.

The nonallergic asthma of obesity. A matter of distal lung compliance

RATIONALE

The pathogenesis of asthma in obesity is poorly understood, but may be related to breathing at low lung volumes.

OBJECTIVES

To determine if lung function in obese patients with asthma and control subjects would respond differently to weight loss.

METHODS

Lung function was evaluated by conventional clinical tests and by impulse oscillometry in female late-onset, nonallergic patients with asthma and control subjects before, and 12 months after, bariatric surgery.

MEASUREMENTS AND MAIN RESULTS

Patients with asthma (n = 10) had significantly lower FEV1 (79.8 ± 10.6 vs. 95.5 ± 7.0%) and FVC (82.4 ± 13.2 vs. 93.7 ± 8.9%) compared with control subjects (n = 13). There were no significant differences in FRC or TLC at baseline. Twelve months after surgery, control subjects had significant increases in FEV1 (95.5 ± 7.0 to 100.7 ± 5.9), FVC (93.6 ± 8.9 to 98.6 ± 8.3%), FRC (45.4 ± 18.5 to 62.1 ± 15.3%), and TLC (84.8 ± 15.0 to 103.1 ± 15.3%), whereas patients with asthma had improvement only in FEV1 (79.8 ± 10.6 to 87.2 ± 11.5). Control subjects and patients with asthma had a significantly different change in respiratory system resistance with weight loss: control subjects exhibited a uniform decrease in respiratory system resistance at all frequencies, whereas patients with asthma exhibited a decrease in frequency dependence of resistance. Fits of a mathematical model of lung mechanics to these impedance spectra suggest that the lung periphery was more collapsed by obesity in patients with asthma compared with control subjects.

CONCLUSIONS

Weight loss decompresses the lung in both obese control subjects and patients with asthma, but the more pronounced effects of weight loss on lung elastance suggest that the distal lung is inherently more collapsible in people with asthma.

Prescribing optimal nutrition and physical activity as "first-line" interventions for best practice management of chronic low-grade inflammation associated with osteoarthritis: evidence synthesis

Low-grade inflammation and oxidative stress underlie chronic osteoarthritis. Although best-practice guidelines for osteoarthritis emphasize self-management including weight control and exercise, the role of lifestyle behavior change to address chronic low-grade inflammation has not been a focus of first-line management. This paper synthesizes the literature that supports the idea in which the Western diet and inactivity are proinflammatory, whereas a plant-based diet and activity are anti-inflammatory, and that low-grade inflammation and oxidative stress underlying osteoarthritis often coexist with lifestyle-related risk factors and conditions. We provide evidence-informed recommendations on how lifestyle behavior change can be integrated into "first-line" osteoarthritis management through teamwork and targeted evidence-based interventions. Healthy living can be exploited to reduce inflammation, oxidative stress, and related pain and disability and improve patients' overall health. This approach aligns with evidence-based best practice and holds the promise of eliminating or reducing chronic low-grade inflammation, attenuating disease progression, reducing weight, maximizing health by minimizing a patient's risk or manifestations of other lifestyle-related conditions hallmarked by chronic low-grade inflammation, and reducing the need for medications and surgery. This approach provides an informed cost effective basis for prevention, potential reversal, and management of signs and symptoms of chronic osteoarthritis and has implications for research paradigms in osteoarthritis.