Demonstration of Pepsin Activity in Circulating Immune Complexes Isolated from Diabetic Patients

Pepsin activity was demonstrated in circulating immune complexes, isolated from sera of 90 diabetic patients, which included 30 type 1, 60 type 2 diabetic patients and 40 control subjects, by the polyethylene glycol method. Pepsin activity was estimated by the proteolytic assay, using acidified haemoglobin as substrate. The mean polyethylene glycol indices in type 1 and type 2 diabetic patients were 21.9±3.6 and 24.9±5.3 respectively, when compared to controls which was 9.2±1.4. The mean pepsin activity is such complexes was found to be 772.5±222.2 units/ml/24hrs in type 1, 741.2±71.2 units/ml/24 hrs in type 2 and 593.3+59.0 units/ml/24 hrs in control subjects, respectively. The specificity of the pepsin assay was checked using pepstatin, a specific inhibitor of pepsin. Inhibition of pepsin activity was observed in a dose dependent manner by increasing the concentration of the inhibitor. Significance of this observation in clinical association with circulating immune complex is discussed.