Fibroblast growth factor 21 in chronic kidney disease.

Fibroblast growth factor 21 (FGF21) is a member of the endocrine FGF family that acts as a metabolic regulator of both glucose and lipid metabolism. Similar to fibroblast growth factor 23 (FGF23), serum FGF21 levels rise progressively with the loss of renal function, reaching 20 times normal values in end-stage renal disease. In patients with chronic kidney disease (CKD), higher serum FGF21 levels correlate with poorer metabolic profile, higher inflammatory markers, more comorbidities, and higher mortality. The high serum FGF21 levels are above and beyond what can be explained by the loss of FGF21 renal clearance, suggesting increased production and/or impaired non-renal clearance. In diabetic nephropathy, serum FGF21 levels correlate with the severity of albuminuria and faster loss of glomerular filtrate rate and can potentially be a biomarker of poor prognostic. The observational and associative human data contrast sharply with in vitro and in vivo preclinical experimental data, which is more in line with a protective role of FGF21 in chronic nephropathies. We here review the physiology of FGF21, and the literature regarding its behavior in CKD with particular focus on diabetic nephropathy. Finally, we speculate on the role of FGF21 in CKD.

Hyperuricemia, Acute and Chronic Kidney Disease, Hypertension, and Cardiovascular Disease: Report of a Scientific Workshop Organized by the National Kidney Foundation.

Urate is a cause of gout, kidney stones, and acute kidney injury from tumor lysis syndrome, but its relationship to kidney disease, cardiovascular disease, and diabetes remains controversial. A scientific workshop organized by the National Kidney Foundation was held in September 2016 to review current evidence. Cell culture studies and animal models suggest that elevated serum urate concentrations can contribute to kidney disease, hypertension, and metabolic syndrome. Epidemiologic evidence also supports elevated serum urate concentrations as a risk factor for the development of kidney disease, hypertension, and diabetes, but differences in methodologies and inpacts on serum urate concentrations by even subtle changes in kidney function render conclusions uncertain. Mendelian randomization studies generally do not support a causal role of serum urate in kidney disease, hypertension, or diabetes, although interpretation is complicated by nonhomogeneous populations, a failure to consider environmental interactions, and a lack of understanding of how the genetic polymorphisms affect biological mechanisms related to urate. Although several small clinical trials suggest benefits of urate-lowering therapies on kidney function, blood pressure, and insulin resistance, others have been negative, with many trials having design limitations and insufficient power. Thus, whether uric acid has a causal role in kidney and cardiovascular diseases requires further study.