GDF15 and chronic kidney disease: In the study of two independent, well characterized CKD cohorts from Clinical Phenotyping and Resource Biobank (C-PROBE) study (224 participants, mean age 58) and the Seattle Kidney Study (SKS) (297 participants, mean age 62), Nair et al. (2017) tested whether kidney tissue expression of GDF15 mRNA correlates with circulating levels of GDF15 and the association between circulating GDF15 and kidney function.