Serum alpha-1-protease inhibitor activity and pulmonary function in young insulin-dependent diabetic subjects.

Abnormalities of lung function have previously been described in patients with impaired alpha 1-protease inhibitor (alpha 1-PI) function and more recently in insulin-dependent diabetic subjects. This study was undertaken to test the hypothesis that impaired alpha 1-PI activity may be implicated in the pathogenesis of lung function abnormalities in young insulin-dependent diabetic patients. Twelve young (16.23 +/- 4.51 years), non-smoking insulin-dependent diabetic subjects and 12 reference subjects were evaluated in respect of lung mechanics, absolute serum alpha 1-PI levels and the functional ability of alpha 1-PI to inhibit elastase. Results of the ventilatory mechanics showed that the mean value for the volume-independent index of lung elasticity Kst(L) was significantly greater in the diabetic group (0.149 +/- 0.05 vs. 0.116 +/- 0.03; p less than 0.05). The absolute serum alpha 1-PI levels in the insulin-dependent diabetic subjects was significantly lower than in reference subjects (1.74 +/- 0.11 vs. 2.06 +/- 0.09 g/l; p less than 0.05). While the specific alpha 1-PI activity of the diabetic sera showed no significant difference from that of the reference sera, the total alpha 1-PI inhibitory activity in the diabetic sera was significantly lower than reference values (201.9 +/- 9.7 vs. 246.9 +/- 13.5 U/L; p less than 0.02). Although these findings indicate impairment of both ventilatory mechanics and alpha 1-PI activity in the insulin-dependent diabetic subjects, the pathogenesis of these findings and their functional implications are at present unknown.