Dietary Metabolites and Chronic Kidney Disease

Abstract

Dietary contents and their metabolites are closely related to chronic kidney disease (CKD) progression. Advanced glycated end products (AGEs) are a type of uremic toxin produced by glycation. AGE accumulation is not only the result of elevated glucose levels or reduced renal clearance capacity, but it also promotes CKD progression. Indoxyl sulfate, another uremic toxin derived from amino acid metabolism, accumulates as CKD progresses and induces tubulointerstitial fibrosis and glomerular sclerosis. Specific types of amino acids (d-serine) or fatty acids (palmitate) are reported to be closely associated with CKD progression. Promising therapeutic targets associated with nutrition include uremic toxin absorbents and inhibitors of AGEs or the receptor for AGEs (RAGE). Probiotics and prebiotics maintain gut flora balance and also prevent CKD progression by enhancing gut barriers and reducing uremic toxin formation. Nrf2 signaling not only ameliorates oxidative stress but also reduces elevated AGE levels. Bardoxolone methyl, an Nrf2 activator and NF-κB suppressor, has been tested as a therapeutic agent, but the phase 3 clinical trial was terminated owing to the high rate of cardiovascular events. However, a phase 2 trial has been initiated in Japan, and the preliminary analysis reveals promising results without an increase in cardiovascular events.

Keywords: ">d-amino acids; advanced glycated end products; chronic kidney disease; indoxyl sulfate; nutrients; palmitate; uremic toxins.

Figure 1

Glycative stress and chronic kidney disease (CKD). Glycative stress caused by uremic toxins, such as AGEs, derived from glycation is closely associated with CKD progression through the activation of the AGE-RAGE system. AGEs; Advanced glycated end products, RAGE; the receptor for AGEs, PTC; proximal tubular epithelial cells.

Figure 2

Pathogenic effects of indoxyl sulfate as a uremic toxin. Indoxyl sulfate induces renal tubulointerstitial (TI) fibrosis, renal proximal tubular cell (PTC) senescence, vascular endothelial dysfunction, vascular smooth muscle cell (SMC) senescence, and chronic renal hypoxia, all of which lead to CKD progression. PAI-1; plasminogen activator inhibitor-1, NF-κB; nuclear factor-kappa B, STAT3; signal transducer and activator of transcription 3, CITED2; Cbp/p300-interacting transactivator with Glu/Asp-rich carboxy-terminal domain 2, HIF-α; hypoxia-inducible factor-α, EPO; erythropoietin.