The people being asked to participate in this study have type 2 diabetes and abnormal levels of protein in their urine. This indicates that they are starting to develop diabetic kidney disease. The standard treatment for this is the use of one of two blood pressure medicines, either an ACE inhibitor or ARB. However, these medicines are not always completely effective in stopping/reversing the kidney disease. Some studies have previously suggested that another type of medicine, called sitagliptin, normal used to treat diabetes may also help prevent diabetic kidney disease from getting worse.