FNDC5 and Renal insufficiency: Liu found that circulating irisin was significantly decreased in 179 T2DM patients with renal insufficiency (eGFR < 60 ml/min/1.73 m2) compared to 186 T2DM patients with normal renal function (eGFR ≥ 60 ml/min/1.73 m2); and the reduction in irisin was most pronounced in stage 5 CKD patients [19].