Genetics Epigenetics And Genomics
Both asthma and obesity have a considerable hereditary component, and thus investigators have studied whether there are genetic variants that may represent a link. Yet to date these studies have been somewhat inauspicious. Candidate gene studies have reported a few genes associated with asthma and BMI, such as PRKCA, LEP, and ADRB3.134136 The largest pediatric genome-wide association study to date, which included over 23,000 children and adults, reported gene DENND1B, although the main single nucleotide polymorphism did not replicate in the independent cohorts.137
Other approaches have yielded more encouraging results. In a gene-by-environment analysis, Wang et al found seven SNPs in 17q21 were associated with BMI only among subjects with asthma in two independent cohorts.138 In a small pilot study in 32 children, Rastogi et al described differential epigenome-wide DNA methylation patterns in children according to their obesity and asthma status.139 In a CD4+ T-cell transcriptome analysis, they also reported Th1-related pathways that are differentially expressed in obese vs non-obese asthmatic children.140 And a study in mice and humans by Ahangari and colleagues found that expression of gene CHI3L1 can be induced by a high-fat diet, and that its product may contribute to both truncal obesity and asthma symptoms.141 Thus, while obese asthma may not be directly determined by genetic polymorphisms, it may be influenced by epigenetic or transcriptomic regulation.
How Does Obesity Affect Breathing
Obesity impacts different functional systems in the body and affects the respiratory system to a huge extent too. According to doctors, obesity has a link with respiratory function and causes problems in breathing for the patient.
The condition of having problems in breathing because of an obese body is termed OHS or Obesity Hypoventilation Syndrome. The Obesity Hypoventilation Syndrome results in obese people having poor breathing patterns, which leads to a lack of oxygen in an obese persons blood.
The condition of OHS instead increases the carbon dioxide levels in the blood. Why OHS happens is not yet fully clear, but research suggests that obesity and fat deposition often lead to the loss of neural control over breathing patterns which causes a drop in oxygen. Moreover, the deposition of fat in the chest wall stops people from breathing properly, at it becomes increasingly difficult to draw in a breath against the diaphragm.
Moreover, obesity increases the cholesterol level of the blood and reduces the oxygen capacity of the blood. This causes labored breathing patterns in a child. In a way, obesity propagates the cycle of inactivity and poor health that affects respiratory functions gravely.
Clinical Characteristics Of Obese Asthma In Children
Asthma may on occasion predispose to obesity,31 obesity may confound its diagnosis,32,33 or both may simply co-occur. However, the majority of observational and experimental evidence points towards an obese asthma phenotype, in which obesity modifies asthma.34,35
Obese children tend to have increased asthma severity,3638 poorer disease control,39 and lower quality of life.40 Many obese children with asthma tend to have Th1-skewed responses, particularly in response to inflammatory stimuli, with at least part of these responses mediated by systemic inflammation, insulin resistance, and/or alterations in lipid metabolism.4143 These children and adolescents also tend to have a decreased response to asthma medications. Using data from the Childhood Asthma Management Program , we described that overweight and obese children with asthma had a reduced response to inhaled corticosteroids , leading to increased prednisone courses and moderate-to-severe exacerbations.44 More recently, McGarry et al reported that obese black and Latino adolescents were 24% more likely to be bronchodilator unresponsive than their non-obese peers.45 Moreover, among children hospitalized for asthma, obesity is associated with longer length of stay and with higher risk of mechanical ventilation.37 Obese children with asthma may also be more susceptible to having increased symptoms with exposure to indoor pollutants.46
You May Like: Is Asthma A Restrictive Lung Disease
Evaluation Of Contractile And Relaxant Reactivity
Evaluation of contractile reactivity to ovalbumin in rat tracheaSchultzDale reaction
The tracheal rings were stimulated with 100 µg/mL OVA, and the contraction amplitude was compared between the Ctrl, Ob, Asth, Ob+Asth and Ob+Asth+Dexa,.
Assessment of tracheal contractile reactivity to KCl and CCh in rat trachea
Two cumulative concentrationresponse curves were induced for the eletromechanical agent KCl or CCh, a pharmacomechanical agent. Contractile reactivity was evaluated on the basis of the maximum effect and concentration of a substance that produced 50% of its maximal effect of the contractile agent, calculated from the concentrationresponse curves obtained, calculated by nonlinear regression.
Assessment of tracheal relaxant reactivity to nifedipine, isoprenaline and aminophylline in rat trachea precontracted with CCh
A contraction with 105 M CCh was induced, and the tonic component was added in cumulative concentrations to nifedipine, a calcium channel blocker, isoprenaline, a -adrenoceptor agonist receptor or aminophylline, a nonselective phosphodiesterase inhibitor, until they reached their Emax. Relaxant reactivity was expressed as the reverse percentage of the initial contraction force elicited by CCh and evaluated on the basis of EC50 and Emax, calculated from concentrationresponse curves, by nonlinear regression.
Lifestyle Weight Loss Interventions
Studies published on the effects of various life-style weight loss on asthma control find significant improvements in asthma control and spirometric lung function with sufficient weight loss .53,144152 Interventions vary from liquid diet replacement, to a more graduated dietary education approach. In adults, it appears that weight loss of at least 5% is required to produce a significant improvement in asthma control.150 This is typically associated with improvements in peak flow, spirometric lung function, and ERV. Studies which have produced the most weight loss appear to be associated with the most significant improvements in asthma control. Effects on AHR have been variable, with some studies151but not all145 reporting significant improvements in airway reactivity we speculate the reasons for these contrasting findings may be related to the different phenotypes of obese asthmatics. Few studies have reported the effects on markers of airway inflammation. One recent study compared dietary intervention versus exercise plus dietary intervention and found improvements in exhaled nitric oxide with exercise plus dietary intervention 152 but it is not clear if it this was related to exercise or the weight loss. Scott et al reported a decrease in airway neutrophilic inflammation in proportion to gynoid fat loss in women .53
Don’t Miss: Can You Use An Epipen For Asthma
Overweight Obese Kids Have Higher Asthma Risk
By Lisa Rapaport, Reuters Health
4 Min Read
– Children and teens who are overweight or obese may be more likely to develop asthma, a U.S. study suggests.
While obesity has long been linked to asthma in adults, research to date has offered conflicting evidence about whether this also holds true for young people, researchers note in Pediatrics.
The current study followed more than 500,000 kids, ages two to 17, for an average of four years. Overall, about eight percent had been diagnosed with asthma.
Compared to kids at healthy weight, overweight children were 17 percent more likely to have an asthma diagnosis and obese youth were 26 percent more likely to have an asthma diagnosis, the study found. This was based on a diagnosis or asthma drug prescription but not on breathing test results.
When researchers looked at the connection between asthma and obesity based on so-called spirometry tests that show how easily people can breathe air out of their lungs, the link was stronger. Obesity was associated with a 29 percent higher risk of asthma based on this stricter diagnostic criteria, the study found.
The study wasnt a controlled experiment designed to prove whether or how being overweight or obese might directly cause asthma, but the results offer some of the most compelling evidence to date suggesting that there is indeed a connection, said lead study author Dr. Jason Lang of Duke University School of Medicine in Durham, North Carolina.
How Do Hives Occur
Hives occur when you are exposed to an allergen. An allergen is something you are allergic too. Common allergens that trigger asthma are dust mites, animal dander, pollen, mold spores, cockroach urine, and certain foods. These may also trigger hives, along with latex, bees, other insects, and plants.1-3
Allergens contain proteins. In those of us with an allergic predisposition, our immune systems respond to proteins on these antigens. This induces an immune response that causes the release of chemicals, such as histamine.2
These chemicals cause tiny capillaries close to the surface of your skin to seep some of their fluid. This causes inflammation, which is what causes the hives. This produces a rash that is red and itchy.3 A similar response to inhaled allergens is what causes the asthma response.
They may also be caused by other situations, such as bacterial infections, sunlight, water on the skin, and exercise.3
Don’t Miss: Can Asthma Develop At Any Age
What Are The Best Method To Manage
Before treatment of asthma, it is necessary to prevent and manage asthma triggers in children. The same thing goes for obesity in children too. The first thing that you can do to prevent obesity in children is to ensure a balanced diet and good activity levels, so that fat deposition does not occur in the childs body. Even in obese children, the intake of proper diet and exercise can reduce fat and improve breathing too.
For the management of asthma too, the parents need to create an action plan. While medications are subjective to the kids response to them, parents can make lifestyle changes around the kids for better management of asthma. A challenge to asthma management is to get a proper diagnosis.
While asthma tests can be run on a child older than 5, the diagnosis of asthma in younger kids is based on observation of symptoms. The best approach to managing asthma in young kids is to figure out the frequency of asthma attacks and their triggers and focus on reducing these triggers. The doctor has to complement this with effective short-acting drugs that do not have any side effects for the child but work properly. Another step to managing both asthma and obesity is to maintain normal activity levels.
Causes & Consequences Of An Obese Child With Asthma
There are various medical studies that show that obesity and asthma in children are highly linked and can result from each other. Since obesity is a trigger for a slew of health problems, asthma can well be a consequence of it too. The prevalence of asthma has increased exponentially in the present population of children, and obesity is to blame.
According to studies, obesity not only triggers severe symptoms of asthma in children but also makes it difficult for doctors to treat the symptoms of asthma. For example, obese children suffer more serious symptoms of asthma that lead to a fivefold increase in the risk of hospitalization. Obese asthmatic children are less responsive to asthma therapy and procedures, which increases their vulnerability to serious harm because of asthma.
Obese children have a risk of developing more severe inflammations of the airways due to weak lungs and breathing capacity. The increased level of inflammation surely leads to early triggering of asthma and worsening of asthma symptoms. In obese asthmatic children, the quality of life is already very low, where they lack a proper level of nourishment and activity. All these factors lead to the onset of more severe symptoms of asthma.
Obesity affects blood volume and lung volume negatively, which causes a deterioration of breathing and causes asthma. As a consequence of asthma, children experience more wheezing and coughing in day-to-day life.
Also Check: How Do Doctors Test For Asthma
Lose Weight To Improve Asthma Symptoms
Theres evidence to show that if you lose excess weight there are benefits for your asthma.
And just eating healthily, and being a bit more active, has health benefits overall too.
Youll notice asthma symptoms improving
That means you could feel less breathless, less wheezy, and be coughing less. And feel more able to get on with things you want to do in life.
Youll also lower your risk of an asthma attack and needing to go to hospital because of your asthma.
Your asthma should be easier to control
You should see more benefits from your preventer medicine, keeping the inflammation down in your airways and not reacting to your triggers so much.
You may not need to use your reliever inhaler so often to deal with symptoms like coughing, wheezing and a tight chest.
You can talk about any improvements youve noticed at your annual asthma review, says Dr Andy.
And your GP or asthma nurse can update your action plan if the dose of your medicines can be changed and see if your peak flow has improved.
You could see other health benefits too
Losing weight brings with it lots of benefits for your general health too, including lower risk of other long-term conditions like diabetes and heart disease.
It can help you exercise more easily, which in turn helps you keep the weight down, and get fitter.
Losing some weight also means youre less at risk of other conditions like acid reflux and sleep apnoea, that can make asthma worse, says Dr Andy.
Weight Reduction Strategies In Asthma: Lifestyle And Surgical Interventions
Further recent studies have evaluated the impact of weight loss strategies on obesity-associated asthma, and in particular the effects of bariatric surgery . Surgical techniques, such as Roux-en-Y gastric bypass and sleeve gastrectomy, are associated with reduction in both systemic and airway pro-inflammatory markers, improvement in lung function, asthma control and quality of life scores , and a reduction in treatment burden . Some evidence suggests that asthma remission may also result, but this needs to be confirmed . Whilst these studies have limitations including small sample size and open-label design, the available evidence is that bariatric surgery may lead to improvements in outcomes in obese asthma, many of which may be sustained in the mid-to-long term. In contrast, another study by Forno et al. showed a lack of improvement, following bariatric surgery in obesity-associated asthma with concomitant metabolic disease . This implies that this phenotype of obese asthma is particularly difficult to treat, and that weight loss alone may not be effective in these patients a multifaceted, individualised, and targeted approach may be necessary.
Table 4 Summary of surgical and non-surgical intervention trials
Also Check: Why Is Asthma Worse In Evening
How Does Weight Affect Asthma
Peopleespecially adult womenwho are obese are more likely to develop asthma.2,3 Children and adults who are very overweight are more likely to have persistent asthma and more severe asthma.3 Typical asthma control medications do not work as well in people who are obese.2,5
Some symptoms of obesity overlap with asthma symptoms, making diagnosis difficult. Obesity is linked with lower fitness and feeling breathless. People who are obese are more likely to have GERD , which can cause coughing and chest tightness that is confused with asthma. Obesity is also a risk factor for sleep apnea, which can be difficult to distinguish from asthma.2,3
Inflammatory Links Between Asthma And Obesity
Asthma and obesity share some of the mechanisms responsible for their underlying inflammatory process. This finding raises the possibility that additive or synergistic effects between both inflammatory processes may account, for instance, for the reported association of severe asthma with obesity. The increased production of some pro-inflammatory cytokines by the adipose tissue in obese asthmatics could have clinical and lung function consequences for these patients. Various observations appear to support this possibility.
3.3.1. Cells and Cytokines
Several studies have evaluated the cell dominant pattern of airway inflammation in asthma patients with and without associated obesity. Data from these studies support that obesity is associated with a neutrophil dominant rather than eosinophil dominant inflammatory pattern in the airway lumen . The abundant neutrophil concentration is associated with the presence of greater levels of IL-17A, a cytokine involved in neutrophil recruitment to the airways . Data from animal models also support a link between IL-17A and obese asthma. Obese mice typically exhibit innate AHR, but this AHR is not observed when the animals are IL-17A deficient . In the lungs of obese mice, increased IL-17A, producing CCR6+ ILC3, was found associated with AHR and neutrophilic inflammation . Obese mice with a deletion of the TNF- receptor were protected against innate AHR and presented reduced levels of IL-17 in comparison with controls .
Read Also: Can You Be A Commercial Pilot With Asthma
Effects Of Weight Loss On Asthma And Inflammation
Weight loss obtained thanks to dietetic treatments has a beneficial effect on asthma control, and reduces the use rescue medication, asthma exacerbations, hospitalizations, as well as improving the quality of life and lung function tests . However, when assessed, there were no significant changes in markers of inflammation including: FeNO, induced sputum cellularity, leptin, C-reactive protein, eotaxin, and TGF- . Combining diet with exercise is more effective on asthma control than taking these measures alone . Inflammatory leptin and IL-6 plasma levels were significantly reduced after the combined interventions . Percentage sputum eosinophil was significantly reduced in subjects who completed the diet-exercise intervention. In contrast, a significant reduction in sputum percentage neutrophils was found in females but not in males . A significant reduction in plasma levels of IL-4, IL-6, TNF-, and leptin, associated with increased levels of 25-hydroxy vitamin D D), IL-10, and adiponectin has also been reported with the combined therapy .
Weight loss between 5% and 10% seems sufficient to significantly improve asthma control both with diet alone and combining dietetic and exercise therapy .
With respect to markers of allergic inflammation, no changes in submucosal cell counts of eosinophils, neutrophils, B cells, macrophages, CD4+ T cells, or CD8+ T cells were found with weight loss bariatric surgery. In contrasts, mast cells decreased significantly in the same patients .
Obesity Atopy And Airway Inflammation In Humans
With regard to airway inflammation, Todd et al studied induced sputum from 727 adults and found that BMI was not significantly associated with increased inflammation in the airways in individuals with or without asthma. McLachlan et al found that while exhaled nitric oxide levels were raised in those with asthma, there was no significant relationship between either BMI or percentage body fat and exhaled nitric oxide levels. Interestingly, in this study the investigators found that the risk of airflow obstruction and asthma were related to obesity in women but not in men, which could not be explained by differences in airway markers of inflammation.
Don’t Miss: How Do I Get An Asthma Inhaler