SPP1 and diabetic kidney disease: One of six FDA-approved urinary safety biomarkers included in the safety composite biomarker panel. Its purpose is to complement traditional measures and assist in identifying kidney tubular injury during phase 1 trials conducted with healthy volunteers.Increased mRNA and protein levels of OPN have been seen after kidney injuryOPN expression is increased in the kidneys, blood, and urine of patients with CKD, particularly in those with diabetic kidney disease and glomerulonephritis.