Within the group of 100 transplant patients, multiple linear regression using primary renal diseases as explanatory variables revealed a significant association between the diagnosis of diabetic nephropathy (n = 21) and urinary ACE2 protein by ELISA or western analyses (p,0.001 for both). In contrast, there was no significant association between urinary ACE2 levels and other primary causes of renal disease in these patients. Further studies were performed on the association between diabetes mellitus and urinary ACE2 in the transplant patients. Of the 100 transplant patients, 38 had a diagnosis of diabetes mellitus listed on their hospital chart. The majority of these patients were taking insulin (31 out of 38, 81.6%), 6 (15.8%) were taking oral hypoglycemic agents, and only 1 patient (2.6%) was on dietary therapy alone.