Phosphate Metabolism

―Understanding Intestinal Phosphate Transport―

Abstract

Dysregulation of phosphorus metabolism is associated with not only growth retardation but also the development of chronic diseases, including chronic kidney disease and abnormal bone metabolism, as well as the progression of aging in multiple organs. The kidney is the major organ mediating phosphate metabolism in the body, regulating urinary phosphate excretion in response to changes in the dietary phosphorus level and blood phosphorus concentration. In this way, phosphorus homeostasis and balance are efficiently maintained. Phosphate control is important in patients who have chronic kidney disease, as hyperphosphatemia is a risk factor that can affect their condition. Treatment of hyperphosphatemia includes restriction of dietary phosphorus intake, phosphorus removal by dialysis, and inhibition of phosphate absorption by administration of an oral phosphate binder. Intestinal phosphate absorption is hypothesized to involve passive transport via the paracellular pathway and the transcellular pathway via the sodium (Na⁺)-dependent Pi transporter. The paracellular phosphate absorption pathway is the predominant pathway, whereas the transcellular phosphate absorption pathway plays a role in conditions where the body's phosphorus requirement is increased, such as during growth and phosphorus deficiency. Understanding the intestinal phosphate absorption pathway and its regulation may lead to more effective control of hyperphosphatemia.