The Role of Wheat-Gluten in Polycystic Kidney Disease

常染色体显性遗传性多囊肾病(ADPKD)是由PKD1或PKD2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。这种变化在一定程度上归因于环境因素。其中，高蛋白饮食是公认的ADPKD进展加速因素之一。蛋白质组成也是影响包囊生长速度的关键因素。例如，与酪蛋白(动物蛋白)饮食相比，大豆蛋白可以减缓啮齿动物PKD模型中的肾囊肿。我们的临床前数据显示，与酪蛋白蛋白饮食相比，小麦面筋蛋白(WG)饮食减少了肾巨噬细胞(MФ)的数量，降低了CCL2(但不包括CSF1或CCL5)的表达，并减缓了PKD1K基因敲除小鼠的包囊生长速度。因此，动物性蛋白负载可能通过增强促进囊性发生的CCL2途径而具有促进囊性发生的作用。以往研究表明，肾小管中CCL2的缺失促进了M-Ф的募集，促进了肾囊的生长，并且在CCL2-PKD1双基因敲除小鼠中这些作用被减弱。我们发现，动物蛋白负荷损害了PKD1基因敲除小鼠的肾脏线粒体功能。当这些小鼠喂食富含酪蛋白的前3种氨基酸的WG饲料时，与等热量的WG饲料相比，肾脏MФ的数量和囊泡生长都有所增加。这表明酪蛋白饮食中的特定AAs促进了包囊的生长。此外，赖氨酸(与WG饲料相比，酪蛋白中AA含量最高)，而不是天冬氨酸(第二丰富的酪蛋白)或谷氨酸(WG中最丰富的谷氨酸)的处理，抑制了线粒体功能的标志物，损害了葡萄糖代谢，增加了糖异生标志物磷酸烯醇式丙酮酸(Pepck 1)，并增加了PKD1小鼠肾脏细胞的肾小管损伤。与给予生理盐水的小鼠相比，口服赖氨酸(1wk)可促进PKD1基因敲除小鼠肾囊肿的生长和Pepck 1的水平。这些数据与肾脏通过线粒体在AA新陈代谢中发挥的主要作用很好地结合在一起，线粒体是一种功能受到PKD突变损害的细胞器。我们的主要假设是，动物蛋白饮食中丰富的特定AA(S)加剧了线粒体功能障碍，增加了趋化因子的表达，促进了M-Ф的募集，并加速了囊变。AIM1将验证这一假说，即高酪蛋白饮食损害线粒体功能，激活趋化因子CCL2的表达，增加肾脏MФ的积聚，促进囊泡生长；而在PKD1K基因敲除小鼠中，CCL2的缺失具有相反的作用。AIM2将验证这样一个假设，即与植物性饮食相比，动物性蛋白质饮食中丰富的特定氨基酸(赖氨酸)会导致线粒体功能障碍、免疫反应增强和加速包囊生长。这项赠款建议的临床意义是，PKD患者可以从植物性蛋白质饮食中受益，最近以植物为基础的肉类开发使饮食蛋白质修改成为一种可行的干预措施，是安全的，并可以立即对需要长期治疗的ADPKD患者产生影响。

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.