Serum α1-protease inhibitor in diabetes mellitus: reduced concentration and impaired activity
We investigated possible alterations in serum α1-protease inhibitor (α1-PI) concentration and activity from insulin-dependent diabetic subjects (IDDs) and in vitro in serum samples containing high glucose concentrations. The in vivo measurements were compared to others taken from normal reference subjects and the in vitro measurements were performed in serum samples containing 0, 10, 20, and 40 mmol/l of glucose. The diabetics had a significantly lower mean α1-PI concentration in their serum than did the reference subjects (1.74±0.1 g/l vs. 2.1±0.1 g/l, P<0.05), as well as a lower total α1-PI inhibitory activity (201±0.7 vs. 246.9±13.5 U/l, P<0.02). Addition of glucose to the serum samples in the in vitro study significantly reduced the mean α1-PI concentrations (P<0.01 in the case of 10 mmol/l glucose, and P<0.001 in the cases of 20 and 40 mmol/l). Added glucose also significantly reduced the mean serum α1-PI activity as determined by the percentage of elastase inhibition in 1, 2 and 3 μl of reference serum (P<0.02 in the case of 10 mmol/l glucose, P<0.01 in 20 mmol/l, and P<0.001 in 40 mmol/l). Hyperglycaemia thus impaired serum α1-PI concentration and activity both in vivo and in vitro. While the underlying mechanisms and clinical implications of these observations are unknown, the abnormally low α1-PI activity in diabetics may worsen the severity and contribute to the chronicity of their infections.