Mechanisms of tubular atrophy

描述（由申请人提供）：美国有超过2600万人患有慢性肾脏疾病，最常见的是糖尿病肾小球损伤。然而，进展到终末期与近端小管消失（小管萎缩）更紧密地结合，这是由细胞凋亡引起的。在之前的资助期间，我们确定了非酯化脂肪酸（NEFA）代谢产物长链酰基辅酶A（LC-CoA）的细胞内蓄积通过抑制NHE 1 Na+/H+交换依赖性细胞存活的机制刺激肾小管萎缩。过量的LC-CoA以细胞质脂滴的形式储存，以保护细胞免受脂毒性的影响，尽管这种NEFA缓冲能力在近端小管中是有限的。多种因素共同导致NEFA在糖尿病肾病中蓄积，但最显著的是与NEFA结合的滤过白蛋白的重吸收。 我们推测，脂肪酸转运蛋白-2（FATP-2）的管腔内NEFA摄取导致近端小管脂凋亡，这有助于肾小管萎缩和糖尿病肾病的进展。（1）为了确定FATP 2是否是管腔近端小管NEFA摄取的主要转运蛋白，将在来自FATP 2缺陷小鼠的分离的灌注近端小管中测量荧光标记的NEFA摄取，并在用针对FATP 2的shRNA处理的培养的近端小管细胞中测定细胞凋亡;（2）为了确定糖尿病肾病中FATP 2介导的NEFA内化的病理生理学相关性，将在易患糖尿病肾病的eNOS-/-db/db小鼠中体内测定13 C标记的NEFA摄取，并将测量胰岛素对近端小管细胞中FATP 2依赖性NEFA摄取的影响;（3）将采用遗传和药理学工具来测试近端小管NEFA摄取是否调节eNOS-/-db/db小鼠中的糖尿病肾病进展。在完成这些实验后，我们希望FATP 2将成为治疗糖尿病肾病的药物靶点。

DESCRIPTION (provided by applicant): Over 26 million people in the U.S. have chronic kidney diseases, most commonly from diabetic glomerular injury. However, progression to end stage is more tightly coupled to proximal tubule disappearance (tubular atrophy), which is caused by apoptosis. In the previous funding period we determined that intracellular accumulation of a non-esterified fatty acid (NEFA) metabolite, long-chain acyl-coenzyme A (LC-CoA), stimulates tubular atrophy by a mechanism that involves inhibition of NHE1 Na+/H+ exchanger-dependent cell survival. Excess LC-CoAs are stored as cytoplasmic lipid droplets to shield cells from lipotoxicity, though this NEFA buffering capacity is limited in the proximal tubule. Multiple factors converge to cause NEFA accumulation in diabetic nephropathy, but most notably reabsorption of filtered albumin bound to NEFA. We hypothesize that luminal NEFA uptake by fatty acid transporter-2 (FATP2) causes proximal tubule lipoapoptosis, which contributes to tubular atrophy and progression of diabetic nephropathy. The hypothesis will be pursued with the following specific aims: (1) To determine whether FATP2 is the major transporter for luminal proximal tubule NEFA uptake, fluorescently labeled NEFA uptake will be measured in isolated perfused proximal tubules from FATP2-deficient mice, and apoptosis will be assayed in cultured proximal tubule cells treated with shRNAs directed against FATP2; (2) To determine the pathophysiological relevance of FATP2- mediated NEFA internalization in diabetic nephropathy 13C-labeled NEFA uptake will be assayed in vivo in eNOS-/-db/db mice prone to diabetic nephropathy, and the effects of insulin on FATP2-dependent NEFA uptake in proximal tubule cells will be measured; (3) Genetic and pharmacologic tools will be employed to test whether proximal tubule NEFA uptake regulates diabetic nephropathy progression in eNOS-/-db/db mice. Upon completion of these experiments we are hopeful that FATP2 will emerge as a druggable target for the treatment of diabetic nephropathy.