Abstract
Hyperphosphatemia results from an imbalance in phosphate (Pi) homeostasis. In patients with and without reduced kidney function, hyperphosphatemia is associated with cardiovascular complications. The current mainstays in the management of hyperphosphatemia are oral Pi binder and dietary Pi restriction. Although these options are employed in patients with chronic kidney disease (CKD), they seem inadequate to correct elevated plasma Pi levels. In addition, a paradoxical increase in expression of intestinal Pi transporter and uptake may occur. Recently, studies in rodents targeting the renal Na+/Pi cotransporter 2a (Npt2a), responsible for ∼70% of Pi reabsorption, have been proposed as a potential treatment option. Two compounds (PF-06869206 and BAY-767) have been developed which are selective for Npt2a. These Npt2a inhibitors significantly increased urinary Pi excretion consequently lowering plasma Pi and PTH levels. Additionally, increases in urinary excretions of Na+, Cl− and Ca2+ have been observed. Some of these results are also seen in models of reduced kidney function. Responses of FGF23, a phosphaturic hormone that has been linked to the development of left ventricular hypertrophy in CKD, are ambiguous. In this review, we discuss the recent advances on the role of Npt2a inhibition on Pi homeostasis as well as other pleiotropic effects observed with Npt2a inhibition.
Highlights
Plasma phosphate (Pi) is tightly controlled in the range from 0.9 to 1.45 mmol L−1 in healthy adults [1], and requires a concerted interplay between intestinal uptake, storage/release from bone, and renal excretion
Hyperphosphatemia is a common consequence of deranged Pi homeostasis and is classified as plasma Pi levels >1.45 mmol L−1 [1,2]
Plasma fibroblast growth factor 23 (FGF23) starts to increase in the early stages of chronic kidney disease (CKD) which is followed by an increase in parathyroid hormone (PTH)
Summary
The current mainstays in the management of hyperphosphatemia are oral Pi binder and dietary Pi restriction. These options are employed in patients with chronic kidney disease (CKD), they seem inadequate to correct elevated plasma Pi levels. Two compounds (PF-06869206 and BAY-767) have been developed which are selective for Npt2a. These Npt2a inhibitors significantly increased urinary Pi excretion lowering plasma Pi and PTH levels. Increases in urinary excretions of Na+, Cl− and Ca2+ have been observed. Some of these results are seen in models of reduced kidney function.
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