Obesity-related systemic oxidative stress promotes acute exacerbation of asthma
Systemic oxidative stress in obese patients with asthma is associated with acute exacerbation and is therefore an important risk factor for poor asthma control, according to a recent study.
In a cohort of 16 asthmatic patients with obesity (mean age 58 years; mean body mass index [BMI], 28.4 kg/m2) and 33 asthmatic patients with normal weight (mean age 52 years; mean BMI, 22.1 kg/m2), the frequency of severe acute exacerbations of asthma was significantly higher in the obese group than in the nonobese group (0 vs 2 per year; p=0.038). [Allergol Int 2017;doi:10.1016/j.alit.2017.06.002]
Asthmatic patients with obesity also had markedly higher serum leptin (27.3 vs 16.9 ng/mL; p=0.007) and malondialdehyde (MDA) levels (3.3 vs 2.8 μM; p=0.034).
All patients were receiving Global Initiative for Asthma therapy step 4 or 5 and had been on regular medication for at least 12 months prior to enrolment, with severe acute exacerbations defined as use of systemic corticosteroids for at least 3 days or a hospitalization/unscheduled visit due to asthma, requiring systemic corticosteroids. Serum leptin and MDA levels were measured using ELISA and thiobarbituric acid reactive substances assay kit.
On nonparametric Spearman analysis, BMI was significantly correlated with the frequency of severe acute exacerbations (p=0.006), serum leptin (p=0.001) and serum MDA (p=0.023). Exacerbation frequency particularly had a positive association with serum MDA in the obese group (p=0.030) and with poor lung function levels in the nonobese group (forced vital capacity, p=0.023; forced expiratory volume in 1 sec, p=0.015; peak expiratory flow, p=0.016). No significant correlations were observed between the frequency of severe acute exacerbations and serum leptin in either patient group.
“These results suggest that systemic oxidative stress in obese asthmatic patients is a stronger facilitator of acute exacerbations than a decline in pulmonary function,” the investigators said.
“Elevated systemic oxidative stress in obesity is known to induce more severe airway inflammation and resistance to steroid therapy. This condition potentially causes poor asthma control, even in patients with good pulmonary function, resulting in frequent severe acute exacerbations,” they explained. [Metab Syndr Relat Disord 2015;13:423–444; Antioxid Redox Signal 2005;7:144–152]
Furthermore, the lack of association observed between leptin and exacerbation frequency (p=0.190) or MDA (p=0.934) in the obese group indicates that “that oxidative stress … does not originate from elevated serum leptin but likely … from various mechanisms related to obesity,” they added.
Despite the absence of data on the association between asthma control statuses or the frequency of exacerbations and obesity-related oxidative stress, the findings show that obesity-related systemic oxidative stress have close association with acute exacerbation of asthma in obese patients.
“Decreasing oxidative stress and/or argumentation of antioxidants may be beneficial for the management of obesity-related severe asthma,” the investigators said.