SAN ANTONIO – Interventions that address variations in inflammation type and metabolism unique to might prove useful for improving their management, Cherry Wongtrakool, MD, of Emory University, Atlanta, said in a presentation at the annual meeting of the American College of Chest Physicians.
Dr. Cherry Wongtrakool
Obese patients with asthma or COPD typically have metabolic and inflammatory profiles that differ from those of nonobese patients with the disorders. Obesity is associated with the development of asthma as well as its severity and the risk for exacerbations. Obese patients with asthma are less likely to have controlled disease or to respond to medication.
The variations in asthma related to obesity even can be traced to infancy for some. Children with rapid weight gain after birth, for example, have an increased risk for developing asthma. In the recently published Boston Birth Cohort study, more than 500 babies from urban, low income families were followed from birth until age 16. Babies with rapid weight gain at 4 months and at 24 months had an increased risk for developing asthma by age 16. Even after adjusting for multiple risk factors, the increased risk for developing asthma persisted in these obese infants.
Higher BMIs during infancy may affect lung development, which continues up to age 5-8 years, Dr. Wongtrakool said. Obesity may affect immune system development. Asthma may develop when persistent inflammation during infancy gets a second hit from genetic factors or from risk factors such as atopy or maternal smoking.
Dr. Wongtrakool noted that obese patients with asthma, unlike nonobese asthma patients, tend to have non-TH2 inflammation. Their TH1/TH2 ratio in stimulated T cells is higher and is directly associated with insulin resistance. Similar to obese patients without asthma, they have higher levels of circulating TNF-alpha, interferon-gamma inducible protein 10, and monocyte chemoattractant protein-1 (MCP-1). They are more likely to have insulin resistance, low high-density lipid levels, differences in gut microbiota, increased leptin, decreased adiponectin, increased asymmetric dimethylarginine, and decreased exhaled nitrous oxide (NO).
In broncheoalveolar lavage samples, obese asthma patients have more cells that secrete interleukin-17, Dr. Wontrakool said. TH17-associated inflammation also has an influence in asthma with obesity. A recent study of 30 obese and lean asthma patients found a difference in metabolites measured in breath samples of obese people with asthma, compared with lean people with asthma and obese people without asthma.
In terms of metabolites in their breath, obese asthma patients clustered together and differed from lean patients with asthma and obese patients without asthma.
Obese people with asthma also differ in their gut microbiota, having more firmicutes species and decreased bacteroides species. Studies in mice indicate that these species have a role in body weight and that altering gut microbiota via fecal transplant was associated with weight loss when obese mice received fecal transplants from lean mice, and vice versa.
In the Supplemental Nutrition in Asthma Control (SNAC) study, preadolescents with asthma were given a nutrition bar designed by researchers at the Children’s Hospital Oakland (Calif.) Research Institute. The children also received asthma education and exercise classes, but the intervention was not designed to reduce weight. FVC and FEV1 improved in all study participants, but those participants in the low inflammation subgroup had the most pronounced improvements in FVC and FEV1 after 2 months.
Dr. Wongtrakool called the study “intriguing,” as it indicates asthma patients with lower level inflammation appear more likely to benefit from nutritional supplementation.
In another study of 55 obese adult asthma patients, a hypocaloric diet, access to a nutritionist and psychologist, and exercise classes were associated with improved asthma control and an improved inflammatory and metabolic profile.
In a British registry of the outcomes of bariatric surgery for obesity, patients who also had asthma had a decrease in asthma prevalence in the year after surgery that persisted over 5 years.
The association of COPD with obesity has been less studied than asthma and COPD, but metabolic syndrome appears to be on the rise in these patients. In a study performed over a decade ago, 47% of COPD patients met the definition of metabolic syndrome; a more recent study found 77% of COPD patients met the standard.
Admission glucose levels also have been found to influence the severity of COPD exacerbation. With higher blood glucose levels, there was a higher risk of mortality—from 12% in those with glucose levels of less than 6.0 mmol/l to 31% among those with glucose levels exceeding 9.0 mmol/l, one study showed.
Bariatric surgery may reduce the risk of acute exacerbations of COPD in obese patients, another recent study found. In a study of 480 obese patients with COPD who underwent bariatric surgery, their 28% presurgical risk of acute exacerbations of COPD was cut in half by 12 months after surgery, and the reduction persisted at 24 months.