Alterations in plasma transforming growth factor β in normoalbuminuric type 1 and type 2 diabetic patients

Transforming growth factor β (TGF-β) is an immunosuppressor. It plays a role in regulating cell proliferation, and deletion of its gene in transgenic mice leads to an autoimmune-like disorder. A role of this cytokine has been proposed in the pathogenesis of type 1 diabetes and probably type 2 diabetes. Previous studies had shown an elevated serum level in type 2 diabetes and a reduced serum level in type 1 diabetes; however, these studies did not address the onset of the alterations of TGF-β with regard to the duration of diabetes. In this study, we compared the levels of TGF-β in the serum of groups of patients with type 1 and type 2 diabetes mellitus divided according to the duration of their disease. Twenty-six normoalbuminuric patients with type 1 diabetes and 25 normoalbuminuric patients with type 2 diabetes were divided into three groups according to the onset of their diabetes and were compared with 27 and 15 age-matched normal subjects, respectively. We conclude that in normoalbuminuric patients serum TGF-β levels increased at the onset of type 2 diabetes and remained elevated throughout the disease; they did not change at the onset of type 1 diabetes, however, they started to decrease around 2 yr after the onset of the disease.