AZGP1 and diabetic kidney disease: ZAG is present in a variety of epithelia and is secreted into many body fluids.8 It was found that urine ZAG increased specifically in patients with diabetes and it may be used as a biomarker for specific and accurate analysis of diabetic nephropathy.9 Immunohistochemical analyses have shown that ZAG is expressed mainly in the tubules of the human kidney.10