Rationale: Inhaled human insulin (INH; Exubera [human insulin (recombinant DNA origin) Inhalation Powder]) causes small changes in pulmonary function and increases in insulin antibodies compared with subcutaneous (SC) insulin.
Objectives: To investigate the relationship between changes in pulmonary function and insulin antibodies and acute effects of INH on lung function.
Methods: In a 24-wk multicenter study, 226 patients with type 1 diabetes were randomized to receive daily premeal INH or SC insulin for 12 wk (comparative phase), followed by SC insulin for 12 wk (washout phase).
Measurements: Spirometry tests were conducted and insulin antibody levels were measured throughout the study. Acute insulin-induced changes in lung function were calculated as the difference between FEV1 before, and 10 and 60 min after, insulin.
Main results: There was a temporal dissociation between pulmonary function changes and insulin antibody generation. Small treatment group differences in changes in FEV1 from baseline, favoring SC insulin, were fully manifest by 2 wk of INH therapy, did not increase during the remainder of the comparative phase, and resolved within 2 wk of INH discontinuation. By contrast, insulin antibody levels remained low for the first 2 wk with INH, increased during Weeks 2 to 12, and gradually declined during washout. There was no evidence of acute insulin-induced alterations in lung function 10 and 60 min postinhalation.
Conclusion: The small lung function changes observed with INH therapy are not mediated by the humoral immune response, or associated with acute decrements in lung function immediately after insulin inhalation.