Detection of tissue origin of a 43 kDa diabetogenic protein from alloxan-induced diabetic rats

BACKGROUND Earlier, we had found high levels of circulating immune complexes (CICs) in the serum of type 2 diabetes mellitus patients along with a novel 43 kDa protein. METHODS Different tissues of alloxan-induced, diabetic, male albino rats (200-250 g in body weight) were collected for the present study. Tissue proteins were isolated and separated by 10% SDS-polyacrylamide gel electrophoresis (SDS-PAGE). A primary cell culture of polymorphonuclear neutrophils (PMNs) was used to evaluate the effects of the diabetogenic protein. Cell proliferative index, oxidant/antioxidant status, and ion-transporting ability were chosen as study parameters. RESULTS SDS-PAGE of different tissues shows that the diabetic liver alone was the only tissue that contained the 43 kDa protein band compared to the normal liver. In vitro effects of the new liver protein on PMNs include significantly decreased cell proliferative activity, increased free radical levels, and decreased levels of antioxidant enzymes as well as ionic transporters. The new liver protein also exhibited protease activity when compared with standard trypsin. CONCLUSIONS This study concluded that a novel 43 kDa protein obtained from the livers of alloxan-induced diabetic rats shows protease activity as well as antiproliferative activity. Also, this protein may act as a diabetogenic factor as it elicited a significantly gross elevation in the oxidant status level as well as in the levels of lysosomal enzymes and a decrease in the levels of antioxidative enzymes and ionic transporters of PMNs.