Department of Nephrology and Mineral Metabolism, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Mexico City, Mexico.
MD/PhD (PECEM) program, Faculty of Medicine, Universidad Nacional Autónoma de México, Mexico City, Mexico.
J Am Soc Nephrol. 2023 Jan 1;34(1):55-72. doi: 10.1681/ASN.2021121544. Epub 2022 Oct 26.
The calcium-sensing receptor (CaSR) in the distal convoluted tubule (DCT) activates the NaCl cotransporter (NCC). Glucose acts as a positive allosteric modulator of the CaSR. Under physiologic conditions, no glucose is delivered to the DCT, and fructose delivery depends on consumption. We hypothesized that glucose/fructose delivery to the DCT modulates the CaSR in a positive allosteric way, activating the WNK4-SPAK-NCC pathway and thus increasing salt retention.
We evaluated the effect of glucose/fructose arrival to the distal nephron on the CaSR-WNK4-SPAK-NCC pathway using HEK-293 cells, C57BL/6 and WNK4-knockout mice, ex vivo perfused kidneys, and healthy humans.
HEK-293 cells exposed to glucose/fructose increased SPAK phosphorylation in a WNK4- and CaSR-dependent manner. C57BL/6 mice exposed to fructose or a single dose of dapagliflozin to induce transient glycosuria showed increased activity of the WNK4-SPAK-NCC pathway. The calcilytic NPS2143 ameliorated this effect, which was not observed in WNK4-KO mice. C57BL/6 mice treated with fructose or dapagliflozin showed markedly increased natriuresis after thiazide challenge. Ex vivo rat kidney perfused with glucose above the physiologic threshold levels for proximal reabsorption showed increased NCC and SPAK phosphorylation. NPS2143 prevented this effect. In healthy volunteers, cinacalcet administration, fructose intake, or a single dose of dapagliflozin increased SPAK and NCC phosphorylation in urinary extracellular vesicles.
Glycosuria or fructosuria was associated with increased NCC, SPAK, and WNK4 phosphorylation in a CaSR-dependent manner.
远曲小管（DCT）中的钙敏感受体（CaSR）激活氯化钠共转运蛋白（NCC）。葡萄糖是 CaSR 的正变构调节剂。在生理条件下，DCT 中没有葡萄糖输送，而果糖的输送取决于消耗。我们假设葡萄糖/果糖输送到 DCT 以正变构方式调节 CaSR，激活 WNK4-SPAK-NCC 途径，从而增加盐潴留。
我们使用 HEK-293 细胞、C57BL/6 和 WNK4 敲除小鼠、离体灌注肾脏和健康人类，评估葡萄糖/果糖到达远曲肾单位对 CaSR-WNK4-SPAK-NCC 途径的影响。
暴露于葡萄糖/果糖的 HEK-293 细胞以依赖于 WNK4 和 CaSR 的方式增加 SPAK 磷酸化。暴露于果糖或单次给予达格列净以诱导短暂糖尿的 C57BL/6 小鼠显示 WNK4-SPAK-NCC 途径的活性增加。钙敏剂 NPS2143 改善了这种作用，但在 WNK4-KO 小鼠中未观察到。用果糖或达格列净治疗的 C57BL/6 小鼠在噻嗪类药物挑战后表现出明显增加的排钠量。用高于近端重吸收生理阈值水平的葡萄糖灌注离体大鼠肾脏显示 NCC 和 SPAK 磷酸化增加。NPS2143 阻止了这种作用。在健康志愿者中，西那卡塞给药、果糖摄入或单次给予达格列净增加了尿细胞外囊泡中 SPAK 和 NCC 的磷酸化。
糖尿或糖尿与 CaSR 依赖性的 NCC、SPAK 和 WNK4 磷酸化增加有关。
