Identification of a novel 43-kDa protein in serum-circulating immune complex of type 2 diabetic patients

Abstract

^BACKGROUND: High levels of circulating immune complexes (CICs) in the serum have been reported in both, type 1 and type 2 diabetes. METHODOLOGY: Fasting blood samples of type 1 and type 2 diabetes mellitus (DM) subjects and normal controls of both sexes were collected (age 30-45 years) for the study. CICs were isolated by employing polyethylene glycol precipitation technique and subsequent separation of its proteins by SDS-PAGE. A neutrophil model was employed for evaluating the in-vitro effect of CIC protein (CICP). Cell proliferative index, oxidant/ antioxidant status and ion transporting ability were chosen for the study. RESULTS: A signifi cant elevated level of CIC was shown in both types of diabetes. Postexamination of CICs on SDS-PAGE demonstrated that a new protein moiety was expressed only in type 2 DM with a molecular weight of 43 kDa. In-vitro action of 43-kDa protein on polymorphonuclear neutrophils (PMN) showed signifi cantly decreased cell proliferative activity, increased free radical levels and decreased antioxidant enzyme activity and decreased ionic transporters. The 43-kDa protein also exhibited protease activity when compared with trypsin. CONCLUSIONS: This study concluded that a 43-kDa protein present in CIC in type 2 DM demonstrated a protease activity as well as antimitogenecity. Furthermore, this protein may act as a diabetogenic factor, since it elicited a gross elevation in the level of oxidant status and depression in ionic transport in PMN when preincubated with it.