after 1, 2, and 3 weeks, respectively.ZO also reduced serum phosphorus by 18%, 14.2%, and 25.1% (similar to the rats' data) after 1, 2, and 3 weeks, respectively.Free fecal phosphorus concentration (was not assessed in the rats' studies) is remarkably reduced (70-80%) by ZO over this 3-week period.ZO is expected to increase rather than decrease fecal phosphorus excretion and our findings indicate that phosphate binding by ZO is so strong that it is not available to be measured by our assay.Importantly, the fecal samples were processed using 5M HCL digestion following published methods, and all samples were similarly acidified to a pH <1.ZO releases hydroxide when it binds phosphate, which can potentially lead to metabolic alkalosis if significantly absorbed systemically.Serum bicarbonate and urine pH are similar in ZO-treated and Control mice, reflecting no or minimal absorption of the released hydroxide.Importantly, ZO has no significant toxic effects on gastrointestinal and renal tissues in preliminary studies. Conclusion:We conclude that ZO decreases serum and urinary phosphorus levels in mice fed a high oxalate diet as observed in rats fed a normal chow, which is remarkable given the potential competition from the high dietary oxalate in binding to ZO. ZO reduces serum and urinary phosphorus levels likely via effective gut phosphate binding as reflected by the remarkably reduced free fecal phosphorus concentration.This study was done as part of another study using a high oxalate diet to assess if ZO can bind oxalate in the gut and it is important to show that ZO is capable of effectively binding phosphate in the gut at higher dietary phosphate intake to mimic the situations of many CKD and ESRD patients who are not compliant with dietary phosphate restrictions, which will be done in future studies.Showing that ZO effectively inhibits gut phosphate absorption in the setting of a liberalized phosphate diet, leading to reduced serum phosphorus concentration, will have remarkable nutritional benefits to CKD and ESKD patients.I have potential conflict of interest to disclose.
Pineda et al. (Wed,) studied this question.