SPP1 and Renal insufficiency: In addition, there was a negative correlation found between OPN, but not N-half OPN, and eGFR in T2DM patients (r = -0.258; P < 0.001; Figure 1A), as well as stepwise increases in mean OPN concentrations in patients with deteriorating renal function (237 ± 72, 268 ± 120, and 338 ± 203 ng/mL in T2DM patients with normal, mild, moderate renal insufficiency, respectively; P < 0.001; Figure 1B).