Physiologic regulation of soluble Klotho levels by systemic acid/base status

全身酸/碱状态对可溶性 Klotho 水平的生理调节

• 批准号: 10454775
• 负责人: Richard Tyler Miller
• 金额: --
• 依托单位: VA NORTH TEXAS HEALTH CARE SYSTEM
• 依托单位国家: 美国
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-04-01 至 2024-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10454775
• 关键词: Acidosis; Acids; Adenine; Alkalies; Alkalinization; American; Animal Model; Atrophic condition of skin; Bicarbonates; Bilateral; Blood; Blood Circulation; Blood Vessels; Calcium-Sensing Receptors; Cells; Characteristics; Chemicals; Chronic; Chronic Kidney Failure; Citrates; Clinical Research; Clinical Trials; Contralateral; Cultured Cells; DASH diet; Dialysis procedure; Diet; Disease; Disease Progression; Disease model; Distal convoluted renal tubule structure; Divalent Cations; Early treatment; Effectiveness of Interventions; End stage renal failure; Endothelin; Environment; Family; GTP-Binding Protein alpha Subunits, Gs; Goals; Health; Heart Hypertrophy; Human; Human Volunteers; Hypertension; Inflammation; Injury to Kidney; Ischemia; Kidney; Kidney Diseases; Kidney Failure; Knockout Mice; Lead; Ligands; Link; Measures; Mediating; Membrane Microdomains; Metabolism; Modeling; Multiprotein Complexes; Mus; Nephrectomy; Oral; Parathyroid gland; Pathway interactions; Patients; Pattern; Phenotype; Physiological; Premature aging syndrome; Production; Proteins; Public Health; Rattus; Receptor Activation; Receptor Signaling; Regulation; Renal Tissue; Renal function; Renal tubule structure; Renin-Angiotensin-Aldosterone System; Reperfusion Therapy; Scaffolding Protein; Serum; Small Interfering RNA; Sodium Bicarbonate; Source; Specificity; Structure of renal vein; Supplementation; System; Testing; Tissues; Transplantation; Urine; Vascular Diseases; Vascular calcification; Veterans; Work; aged; alkalinity; base; calcification; coronary fibrosis; disease phenotype; endothelial dysfunction; falls; feeding; functional loss; in vivo; kidney fibrosis; knock-down; loss of function; mouse model; novel; preservation; prevent; receptor; renal calcium; response; sarcopenia

Chronic kidney disease (CKD) frequently progresses to end-stage renal disease accompanied by complications including cardiac hypertrophy, accelerated vascular disease, ectopic calcification, endothelial dysfunction, osteodystrophy, sarcopenia, skin atrophy, and renal fibrosis. Factors including hypertension, volume-overload, acidosis, chronic low-grade inflammation, disordered Ca and PO4 metabolism, elevated PTH and FGF23 levels, and reduced circulating Klotho (sKlotho) levels are associated with CKD. HCO3 supplementation or alkaline diets (eg. DASH diet) slow progression of CKD even in stages 3 and 4. The mechanism(s) by which HCO3 supplementation or alkaline diets work are unknown. The goal of these studies is to identify physiologic mechanisms that can slow or reverse the course of CKD. sKlotho is normally produced by the kidney and released into the circulation, preserves renal function, and prevents many of the systemic complications of renal failure. As renal disease progresses serum and urine sKlotho levels fall, and patients acquire characteristics resembling the premature aging phenotype of Klotho-/- mice. The kidney is the source of sKlotho as demonstrated by findings that Klotho levels are high in the renal vein, bilateral nephrectomy lowers sKlotho, and mice with kidney-specific Klotho deletion have patterns of disease that are phenotypically indistinguishable from Klotho-/- mice. Possible physiologic mechanisms by which sKlotho levels might be regulated have not been defined. We discovered that in intact mice and rats, mouse renal cortical homogenates, and cultured cells, calcium-sensing receptor (CaSR) activation increases sKlotho levels via ADAM10-mediated shedding. The ability of ligands to activate the CaSR is modified by pH with an alkaline pH environment increasing, and an acid pH environment decreasing CaSR signaling. We found that an alkali load increases CaSR signaling and sKlotho in mice and rats, and that an alkaline milieu increases Klotho shedding in mouse kidney homogenates and cultured cells in a CaSR-dependent manner, and that oral K citrate for 72 hrs increases serum and urine Klotho in human volunteers. These results define a novel physiologic mechanism for regulation of sKlotho levels by the renal CaSR and pH. We hypothesize that acidosis accelerates, and alkalinization slows the rate of loss of renal function in CKD because acidosis decreases, and alkalinity increases renal CaSR-stimulated Klotho shedding from the kidney. The hypothesis will be developed with studies in: 1) mice, CaSR-/- mice, renal homogenates, cultured cells, that will demonstrate that renal Klotho shedding is regulated by the CaSR in response to CaSR ligands and pH; 2) CKD disease models to show that alkali treatment increases sKlotho levels and reduces renal injury and cardiac hypertrophy, and 3) renal tissue and cultured cells to define the mechanisms that permit the CaSR, Klotho, and ADAM10 to interact focusing on the C8 tetraspanin family.

慢性肾脏病(CKD)常进展为终末期肾病并伴有并发症 包括心肌肥厚，加速血管疾病，异位钙化，内皮功能障碍， 骨质疏松症、骨质疏松症、皮肤萎缩和肾脏纤维化。因素包括高血压、容量超负荷、 酸中毒，慢性低度炎症，钙和磷酸代谢紊乱，甲状旁腺素和纤维生长因子23水平升高， 循环水平降低与慢性肾功能不全有关。补充HCO3或碱性 饮食(例如DASH饮食)即使在第三和第四阶段，慢性肾脏病的进展也是缓慢的。 补充剂或碱性饮食的效果尚不清楚。这些研究的目标是确定生理学 可以减缓或逆转CKD进程的机制。SKlotho通常由肾脏产生， 释放到循环中，保护肾功能，预防肾脏的许多系统性并发症 失败了。随着肾脏疾病的进展，血清和尿液sKlotho水平下降，患者获得特征 与Klotho-/-小鼠的早衰表型相似。如图所示，肾是血瘀证的来源 通过发现肾静脉中的Klotho水平较高，双侧肾切除术降低了sKlotho，而患有 肾脏特有的Klotho缺失具有与Klotho-/-无法区分的疾病模式 老鼠。调节sKlotho水平的可能生理机制尚未确定。我们 发现在完整的小鼠和大鼠、小鼠肾皮质匀浆和培养细胞中，钙敏感 受体(CaSR)激活通过ADAM10介导的脱落增加sKlotho水平。配基的能力 活化CaSR是用pH改性的，随着碱性pH环境的增加，以及酸性pH环境 减少CASR信号。我们发现，碱负荷增加了小鼠和大鼠的CaSR信号和sKlotho， 碱性环境增加了Klotho在小鼠肾匀浆和培养细胞中的脱落。 CaSR依赖方式，口服72小时柠檬酸钾可增加人血、尿Klotho 志愿者。这些结果为肾脏调节sKlotho水平提供了一种新的生理机制。 CaSR和pH。我们假设酸中毒会加速，碱化会减缓肾脏的损失率。 慢性肾脏病的功能是因为酸中毒减少，而碱度增加了肾CaSR刺激的Klotho 从肾脏脱落。这一假说将通过以下研究得到发展：1)小鼠、CaSR-/-小鼠、肾脏 匀浆，培养的细胞，将证明肾Klotho脱落是由CaSR调节的 对CaSR配体和pH的反应；2)显示碱处理增加sKlotho水平的CKD疾病模型 并减少肾脏损伤和心肌肥大，以及3)肾组织和培养细胞，以确定其机制 这使得CaSR、Klotho和ADAM10能够以C8 Tetraspanin家族为重点相互作用。