Middle-Molecule Uremic Toxins and Outcomes in Chronic Kidney Disease

In patients with chronic kidney disease (CKD), uremic toxins constitute a specific nontraditional risk factor. Research in this field started in the early 1990s, and a growing body of preclinical and epidemiological evidence suggests that elevated levels of uremic toxins are associated with poor outcomes in a CKD setting. The present review focuses on a specific class of uremic toxins (the "middle molecules"), which includes well-known candidates like beta-2 microglobulin and fibroblast growth factor 23. Here, we summarize the epidemiological evidence linking the middle-molecule uremic toxin (and especially the larger ones) with hard clinical end points. Our findings highlight the urgent need for clinical trials of interventions designed to decrease levels of these middle molecules in CKD patients.