Effects of Lanthanum Carbonate on Whole-Body Calcium Balance, Vascular Function, and Mineral Metabolites in Adults With CKD 3b-4 and Normophosphatemia

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Background: We previously showed long-term treatment with the phosphate binder lanthanum carbonate (LC) may reduce whole-body phosphorus (P) balance in adults with CKD 3b-4 and normophosphatemia (ASN ‘21 PO-0543). Long-term effects of LC on total body calcium (Ca) balance, vascular function, and mineral metabolites are unknown. We determined Ca balance in normophosphatemic adults with CKD 3b-4 after a 12w RCT of LC v. placebo, and relationships of Ca and P balance with vascular function and mineral metabolites. Methods: A subset of 15 subjects with CKD 3b-4 were randomized to receive 12w of LC or placebo investigating effects of phosphate lowering on vascular function, assessed by brachial artery flow-mediated dilation (FMD), (NCT02209636) volunteered to participate in this ancillary aim. At the end of 12w, subjects consumed a control diet (1000 mg/d phosphorus and 800 mg/d calcium) for 9d and continued their randomized treatment (n=7 LC, n=8 placebo). Fasting AM blood samples and stool and urine were collected during a 48h inpatient balance study on day 8-9 of the controlled diet. Ca balance (mg/d) was determined by values averaged over the 48h period: dietary Ca intake - urine Ca - fecal Ca. We used T-tests to compare means, correlation coefficients to examine relationships between P and Ca balance with FMD, and fixed effects models to examine mineral metabolites change within groups. Results: Subjects were 65±7y with eGFR 33±6 mL/min/1.73m2. We excluded 1 LC subject from balance results due to insufficient stool. 24h urine Ca was similar with LC and placebo (46±28 v. 40±32 mg, p=0.73). Fecal Ca was higher with LC compared with placebo (737±446 v. 317±138 mg, p=0.03), and whole-body Ca balance was lower with LC compared with placebo (-46±410 v. 410 ± 131 mg, p=0.01). Neither P nor Ca balance correlated with FMD in either group (all p>0.05). FGF-23 decreased over the study with LC (p=0.03), but 25D, 1,25D, and PTH did not change. Conclusions: Long-term treatment with LC may reduce whole-body Ca balance in adults with CKD 3b-4 and normophosphatemia, but neither P nor Ca balance correlated with FMD. FGF23 decreased with LC, which coincided with negative Ca balance and a trend towards negative P balance. Funding: Veterans Affairs Support

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