Nakamura T, Fukui M, Ebihara I, Tomino Y, Koide H
Department of Medicine, Juntendo University School of Medicine, Tokyo, Japan.
Kidney Int. 1994 Jun;45(6):1593-605. doi: 10.1038/ki.1994.210.
The present study was designed to assess whether expression of mRNA for extracellular matrix (ECM) components, metalloproteinases (MMP) and tissue inhibitor of metalloproteinases (TIMP) in glomeruli is affected by a low protein diet during the course of focal glomerulosclerosis (FGS). Puromycin aminonucleoside (PAN) was injected intraperitoneally in rats and the right kidney was removed on day 22. Nephrotic rats received successive intraperitoneal injections of PAN on days 27, 34, and 41. Control rats were subjected to a nephrectomy or a sham operation on day 22. Animals were divided into six groups. In group 1, the PAN-injected rats were fed a standard diet containing 22% protein. In group 2, the PAN-injected rats were fed a low protein diet containing 6% protein, starting on the same day as the first PAN injection. In group 3, the nephrectomized rats without PAN were fed a standard diet. In group 4, the nephrectomized rats without PAN were fed a low protein diet for the same period. In group 5, the sham operated rats were fed a standard diet. In group 6, the sham operated rats were fed a low protein diet for the same period. Rats were sacrificed on days 0, 60 or 80 after the initial PAN or saline injection. The percentage of sclerotic glomeruli in group 1 rats increased markedly with time, reaching 77% on day 80. The mRNA levels encoding for alpha 1(I), alpha 1(III), alpha 1(IV) collagen chains, laminin B1 and B2 chains, heparan sulfate proteoglycan (HSPG), MMP-2, TIMP-1 and TIMP-2 increased significantly as glomerulosclerosis progressed, whereas MMP-1 and MMP-3 mRNA levels were unchanged, and no MMP-9 mRNA was detected throughout the experiments. In group 2, the low protein diet reduced the prevalence of glomerulosclerosis and attenuated the increased mRNA expression for ECM components, MMP-2, TIMP-1 and TIMP-2 in FGS glomeruli. In groups 3 through 6, mRNA levels for ECM components decreased with age, whereas those for MMPs and TIMPs changed little throughout the experiments. Immunofluorescence studies revealed the accumulation of types I, III and IV collagens, laminin, and HSPG in the sclerotic area and low protein diet attenuated the accumulation of these proteins. These data suggest that glomerulosclerosis may result from an imbalance among ECM components, MMPs and TIMPs and that a low protein diet attenuates the otherwise increased levels of mRNA for ECM components, MMP-2, TIMP-1 and TIMP-2 in glomerulosclerosis.
本研究旨在评估在局灶性肾小球硬化（FGS）病程中，低蛋白饮食是否会影响肾小球中细胞外基质（ECM）成分、金属蛋白酶（MMP）和金属蛋白酶组织抑制剂（TIMP）的mRNA表达。给大鼠腹腔注射嘌呤霉素氨基核苷（PAN），并在第22天切除右肾。肾病大鼠在第27、34和41天连续腹腔注射PAN。对照大鼠在第22天接受肾切除术或假手术。动物分为六组。第1组中，注射PAN的大鼠喂食含22%蛋白质的标准饮食。第2组中，注射PAN的大鼠从首次注射PAN的同一天开始喂食含6%蛋白质的低蛋白饮食。第3组中，未注射PAN的肾切除大鼠喂食标准饮食。第4组中，未注射PAN的肾切除大鼠在同一时期喂食低蛋白饮食。第5组中，假手术大鼠喂食标准饮食。第6组中，假手术大鼠在同一时期喂食低蛋白饮食。在首次注射PAN或生理盐水后第0、60或80天处死大鼠。第1组大鼠硬化肾小球的百分比随时间显著增加，在第80天达到77%。随着肾小球硬化的进展，编码α1（I）、α1（III）、α1（IV）胶原链、层粘连蛋白B1和B2链、硫酸乙酰肝素蛋白聚糖（HSPG）、MMP - 2、TIMP - 1和TIMP - 2的mRNA水平显著增加，而MMP - 1和MMP - 3的mRNA水平未改变，并且在整个实验中未检测到MMP - 9的mRNA。在第2组中，低蛋白饮食降低了肾小球硬化的发生率，并减弱了FGS肾小球中ECM成分、MMP - 2、TIMP - 1和TIMP - 2的mRNA表达增加。在第3至6组中，ECM成分的mRNA水平随年龄下降，而MMP和TIMP的mRNA水平在整个实验中变化不大。免疫荧光研究显示I型、III型和IV型胶原、层粘连蛋白和HSPG在硬化区域积聚，低蛋白饮食减弱了这些蛋白质的积聚。这些数据表明肾小球硬化可能是由ECM成分、MMP和TIMP之间的失衡导致的，并且低蛋白饮食减弱了肾小球硬化中ECM成分、MMP - 2、TIMP - 1和TIMP - 2原本增加的mRNA水平。
