The Role of Wheat-Gluten in Polycystic Kidney Disease

常染色体显性多囊肾病（ADPKD）是由PKD 1或PKD 2基因突变引起的。疾病的严重程度是高度可变的，即使在具有相同PKD基因突变的家庭中也是如此。这种差异部分归因于环境因素。其中，高蛋白饮食是公认的ADPKD进展加速因素之一。蛋白质成分也是影响囊肿生长速度的关键因素。例如，与酪蛋白（动物性蛋白质）饮食相比，大豆蛋白减缓了啮齿动物PKD模型中的肾囊肿。我们的临床前数据显示，与酪蛋白饮食相比，小麦面筋（WG）饮食减少了肾脏巨噬细胞（M β）的数量，Ccl 2（但不是Csf 1或Ccl 5）的表达，并减缓了Pkd 1基因敲除小鼠的囊肿生长速度。因此，基于动物的蛋白质负荷可能通过增强促囊生成Ccl 2途径而具有促囊生成作用。先前的研究表明，Pkd 1的缺失增加了肾小管中的Ccl 2，促进了MMP 3的募集，促进了肾囊肿的生长，并且这些作用在Ccl 2-Pkd 1双敲除小鼠中减弱。我们发现，动物蛋白负荷损害肾脏线粒体功能的Pkd 1基因敲除小鼠。当这些小鼠喂食富含酪蛋白中丰富的前3种氨基酸的WG饮食时，与喂食等热量WG饮食的对应小鼠相比，肾脏M细胞和囊肿生长的数量增加。这表明酪蛋白饮食中的特定AA促进囊肿生长。此外，用赖氨酸（与WG饮食相比，酪蛋白中最丰富的AA）而不是天冬氨酸（在酪蛋白中第二丰富）或谷氨酸（在WG中最丰富）处理，抑制线粒体功能的标志物，损害葡萄糖代谢，增加Pkd 1小鼠肾细胞中的线粒体生成标志物磷酸烯醇丙酮酸（Pepck 1）和增加肾小管损伤。口服赖氨酸补充（1周）在Pkd 1基因敲除小鼠增加肾囊肿的生长和Pepck 1的水平相比，给予生理盐水。这些数据与肾脏通过线粒体在AA代谢中发挥的主要作用完全一致，线粒体是一种因PKD突变而功能受损的细胞器。我们的总体假设是，动物蛋白质饮食中丰富的特定AA（s）加剧线粒体功能障碍，增加趋化因子表达，M β募集，并加速囊肿形成。Aim 1将测试高酪蛋白饮食损害线粒体功能，激活趋化因子Ccl 2表达，增加肾脏Mcl 2积累，促进囊肿生长的假设;在Pkd 1敲除小鼠中删除Ccl 2具有相反的效果。Aim 2将检验以下假设：与植物性饮食相比，动物性蛋白质饮食中丰富的特定AA（赖氨酸）会导致线粒体功能障碍、免疫反应增强和囊肿生长加速。这项拨款提案的临床意义在于，PKD患者可以从植物性蛋白饮食中受益，最近植物性肉类的发展使膳食蛋白质修饰成为一种可行的干预措施，这种干预措施是安全的，可以对需要长期治疗的ADPKD患者产生直接影响。

Autosomal dominant polycystic kidney disease (ADPKD), is caused by mutations in PKD1 or PKD2 genes. Disease severity is highly variable, even among families with the same PKD gene mutation. This variability has been attributed, in part, to environmental factors. Among them, a high protein diet is one of the most recognized ADPKD progression-accelerating factor. Protein composition is also a key element that can affect the rate of cyst growth. For example, soy protein compared to casein (animal-based protein) diet slows kidney cyst in rodent PKD models. Our preclinical data shows that wheat gluten (WG) diet compared to casein protein diet decreased the number of kidney macrophages (MФ), expression of Ccl2 (but not Csf1 or Ccl5) and slowed the rate of cyst growth in Pkd1-knockout mice. Therefore, animal-based protein load may have cystogenesis-promoting effects through augmentation of the cystogenesis-promoting Ccl2 pathway. Previous studies show that loss of Pkd1 increases Ccl2 in the renal tubules facilitating the recruitment of MФ, promoting kidney cyst growth and that these effects were attenuated in Ccl2-Pkd1 double knockout mice. We found that animal protein load impairs kidney mitochondrial function in Pkd1-knockout mice. When these mice were fed a WG diet enriched with top 3 amino acids abundant in casein compared to WG diet, there was increased number of kidney MФ and cyst growth compared to counterparts fed an isocaloric WG diet. This suggest that specific AAs in the casein diet promotes cyst growth. Furthermore, treatment with lysine (most abundant AA in casein compared to WG diet), but not aspartate (second abundant in casein) or glutamate (most abundant in WG), suppressed markers of mitochondrial function, impaired glucose metabolism, increased gluconeogenesis marker phosphoenolpyruvate (Pepck1) and increased tubular injury in Pkd1 mouse kidney cells. Oral lysine supplementation (1wk) in Pkd1 knockout mouse increased kidney cyst growth and levels of Pepck1 compared to counterparts given a saline. These data are well aligned with a major role kidneys play in AA metabolism through the mitochondria, an organelle that is functionally impaired by PKD mutations. Our overarching hypothesis is that specific AA(s) abundant in an animal protein-based diet exacerbate mitochondrial dysfunction, increase chemokine expression, MФ recruitment, and accelerate cystogenesis. Aim1 will test the hypothesis that high casein-protein diet impairs mitochondrial function, activates chemokine Ccl2 expression, increases kidney MФ accumulation, and promotes cyst growth; and deletion of Ccl2 in Pkd1-knockout mice have opposite effects. Aim2 will test the hypothesis that specific AA (lysine) abundant in an animal-based protein diet compared to a plant-based diet, leads to mitochondrial dysfunction, increased immune response and accelerated cyst growth. The clinical significance of this grant proposal is that patients with PKD could benefit from a plant-based protein diet and recent plant-based meat development has made dietary protein modification a feasible intervention that is safe and can have immediate impact for patients with ADPKD that require long-term treatment.