Nutrients Turned into Toxins: Microbiota Modulation of Nutrient Properties in Chronic Kidney Disease.

In chronic kidney disease (CKD), accumulation of uremic toxins is associated with an increased risk of death. Some uremic toxins are ingested with the diet, such as phosphate and star fruit-derived caramboxin. Others result from nutrient processing by gut microbiota, yielding precursors of uremic toxins or uremic toxins themselves. These nutrients include l-carnitine, choline/phosphatidylcholine, tryptophan and tyrosine, which are also sold over-the-counter as nutritional supplements. Physicians and patients alike should be aware that, in CKD patients, the use of these supplements may lead to potentially toxic effects. Unfortunately, most patients with CKD are not aware of their condition. Some of the dietary components may modify the gut microbiota, increasing the number of bacteria that process them to yield uremic toxins, such as trimethylamine N-Oxide (TMAO), p-cresyl sulfate, indoxyl sulfate and indole-3 acetic acid. Circulating levels of nutrient-derived uremic toxins are associated to increased risk of death and cardiovascular disease and there is evidence that this association may be causal. Future developments may include maneuvers to modify gut processing or absorption of these nutrients or derivatives to improve CKD patient outcomes.

Use of sevelamer in chronic kidney disease: beyond phosphorus control.

Sevelamer is a non-calcium phosphate binder used in advanced chronic kidney disease (CKD) and in dialysis for hyperphosphataemia control. Several experimental, observational studies and clinical trials have shown that sevelamer has pleiotropic effects, beyond hyperphosphataemia control, including actions on inflammation, oxidative stress, lipid profile and atherogenesis, vascular calcification, endothelial dysfunction and the reduction of several uremic toxins. This is the biological basis for its global effect on cardiovascular morbidity and mortality in patients with chronic kidney disease. This review focuses on these pleiotropic actions of sevelamer and their impact on cardiovascular health, with the experience published after more than ten years of clinical expertise.

Uso del sevelamer en la enfermedad renal crónica. Más allá del control del fósforo / Using sevelamer in chronic kidney disease. Beyond phosphorus control

El sevelamer es un captor no cálcico de fósforo que se utiliza en la ERC avanzada y en diálisis para el control de la hiperfosforemia. Varios estudios experimentales, observacionales y ensayos clínicos han mostrado que el sevelamer tiene efectos pleiotrópicos, más allá del control de la hiperfosforemia, incluyendo acciones sobre la inflamación, el estrés oxidativo, el perfil lipídico y la aterogénesis, la calcificación vascular, la disfunción endotelial y la disminución de diversas toxinas urémicas, todo lo cual sería la base biológica de su efecto global sobre la morbilidad y la mortalidad cardiovascular en pacientes con enfermedad renal crónica. En esta revisión, se hace énfasis en estas acciones pleiotrópicas del sevelamer y su impacto en la salud cardiovascular, con la experiencia publicada después de más de 10 años de experiencia clínica (AU)

Sevelamer is a calcium-free phosphate binder used in advanced chronic kidney disease (CKD) and in dialysis to control hyperphosphatemia. Several experimental and observational studies and clinical trials have shown that sevelamer has pleiotropic effects that go beyond controlling hyperphosphatemia; these pleiotropic effects include acting on inflammation, oxidative stress, lipid profile and atherogenesis, vascular calcification, endothelial dysfunction and decreasing various uremic toxins. All of these represent the biological basis for the global effect of sevelamer on cardiovascular morbidity and mortality in patients with CKD. In this review, we emphasis these pleiotropic actions of sevelamer and their impact on cardiovascular health, with the experience published after more than 10 years of clinical experience (AU)

Correction of hypocalcemia allows optimal recruitment of FGF-23-dependent phosphaturic mechanisms in acute hyperphosphatemia post-phosphate enema.

Both parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF23) are phosphaturic hormones. These hormones should increase in response to phosphate excess. However, they also regulate serum calcium; PTH increases serum calcium concentration and FGF23 suppresses renal production of calcitriol, favoring hypocalcemia. We report the case of an 83-year-old woman with hyperphosphatemia and hypocalcemia resulting from phosphate-containing enemas. PTH and calcitriol increased in response to hypocalcemia, and FGF23 increased in response to hyperphosphatemia. Unexpectedly, peak FGF23 did not coincide with peak serum phosphate. Rather, peak FG23 was observed only after severe hypocalcemia was partially corrected with exogenous calcium administration, even though serum phosphate had been already decreasing for 32 h. Correction of severe hypocalcemia was thus associated with peak FGF23 values and with a precipitous decrease in PTH. Peak FGF23 was followed by an accelerated decrease in serum phosphate and significant phosphaturia. This clinical report is consistent with experimental data in rats showing a blunted FGF23 response to high phosphate in the presence of severe hypocalcemia. Thus, complementary experimental and clinical data suggest that partial correction of severe hypocalcemia is required for optimal FGF23-mediated phosphaturia, which takes place despite correction of PTH levels. We believe this the first human report suggesting blunting of the FGF23 response to high phosphate by severe hypocalcemia.