Weight Loss and Vitamin D Improve Hyporesponsiveness to Corticosteroids in Obese Asthma.

BACKGROUND AND OBJECTIVES: Obesity negatively impacts on the response of asthma patients to inhaled corticosteroids. The mechanisms underlying this impact are unknown. Objective: To demonstrate that the poor response to inhaled corticosteroids in obese asthma patients is associated with impaired anti-inflammatory activity of corticosteroids and vitamin D deficiency, both of which are improved by weight loss. METHODS: The study population comprised 23 obese asthma patients (OA) (18 females; median (IQR) age 56 [51-59] years), 14 nonobese asthma patients (NOA) (11 females; 53 [43-60] years), 15 obese patients (OP) (13 females; 47 [45-60] years), and 19 healthy controls (HC) (14 females; 43 [34-56] years). Ten OA and 11 OP were evaluated at baseline (V1) and 6 months after bariatric surgery (V2). Corticosteroid response was measured using dexamethasone-induced inhibition of peripheral blood mononuclear cell (PBMC) proliferation. Lung function and serum levels of leptin, adiponectin, and vitamin D were measured at V1 and V2. RESULTS: We found a reduced response to dexamethasone in PBMCs of OP and OA with respect to NOA and HC; this inversely correlated with the adiponectin/leptin ratio and vitamin D levels. Bariatric surgery improved corticosteroid responses in OP and OA and normalized the adiponectin/leptin ratio and vitamin D levels. Exposure of PBMCs to vitamin D potentiated the antiproliferative effects of corticosteroids. Dexamethasone and vitamin D induced similar MKP1 expression in OP and OA. CONCLUSION: The efficacy of weight loss to improve symptoms and lung function in OA may be due, at least in part, to the recovered anti-inflammatory effects of corticosteroids. Vitamin D deficiency may contribute to corticosteroid hyporesponsiveness in OA.