Study Links Phosphate Levels to Kidney Damage Markers

Researchers at University of Tsukuba have found that the phosphate concentration in proximal tubule fluid, estimated from urine and blood tests, is associated with elevated renal tubular damage markers.

Their findings, published in the Journal of Renal Nutrition, suggest that lifestyle modifications that reduce phosphate concentration in the proximal tubule fluid may help prevent the progression of chronic kidney disease.

Phosphorus is an essential nutrient for life and, along with calcium, helps maintain bone structure. In mice, a consistent phosphorus-rich diet increases phosphate concentration in the proximal tubule fluid of the kidney. Increased phosphate excretion has been associated with tubular damage and reduced renal function. However, this association remains unclear in humans.

In the study, researchers examined the relationship between estimated proximal fluid phosphate concentrations (ePTFp) and levels of biomarkers indicating tubular damage in humans.

Blood and urine tests were conducted on 218 middle-aged and older individuals with chronic kidney disease (CKD) at stages G2 (mild) to G4 (severe). The ePTFp was estimated according to the blood and urine creatinine levels and urinary phosphate concentrations, using a specific formula. Results showed that the ePTFp tended to increase as the CKD stage advanced.

This ePTFp increase was linked to elevated serum fibroblast growth factor 23 levels, a hormone involved in phosphate excretion, and higher urinary β2-microglobulin levels, which indicate tubular damage. These findings are consistent with those of previous murine studies.

CKD affects approximately 14.5 million people in Japan. Thus, lifestyle modification that focuses on phosphorous management may help prevent CKD progression.