Up-regulation of acyl-coenzyme A:cholesterol acyltransferase (ACAT) in nephrotic syndrome

BACKGROUND: We have previously demonstrated that hypercholesterolemia in rats with puromycin-induced nephrotic syndrome (NS) is associated with up-regulation of hepatic 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase and relative down-regulation of cholesterol 7alpha-hydroxylase (Ch-7alpha), which represent the rate-limiting steps in cholesterol biosynthesis and catabolism. Expression of HMG-CoA reductase is inhibited and Ch-7alpha is augmented by intracellular free cholesterol, which is avidly esterified by acyl-CoA:cholesterol acyltransferase (ACAT). Therefore, we hypothesized that NS may result in up-regulation of hepatic ACAT. METHODS: Hepatic tissue ACAT mRNA (Northern blot), protein (Western blot) and enzymatic activity were determined in rats with puromycin-induced NS, placebo-treated control rats and Nagase hypoalbuminemic (NAG) rats. RESULTS: The NS group exhibited heavy proteinuria, hypoalbuminemia, normal creatinine clearance, severe hypercholesterolemia and hypertriglyceridemia. Despite severe hypoalbuminemia, NAG rats with inherited hypoalbuminemia exhibited only a mild elevation of plasma cholesterol and triglycerides. Severe hypercholesterolemia in the NS group was coupled with depressed liver tissue free cholesterol concentration and marked increases in hepatic ACAT mRNA, protein and enzymatic activity. In contrast, ACAT mRNA and protein contents of the liver were normal and ACAT activity was mildly elevated in the NAG group. CONCLUSIONS: NS results in marked up-regulation of hepatic ACAT, which is primarily due to proteinuria and not hypoalbuminemia, since the latter alone, as seen in NAG rats, does not significantly impact ACAT expression. Elevated ACAT in NS can contribute to dysregulation of cholesterol biosynthesis and catabolism by limiting the normal cholesterol signaling involved in regulation of these processes.     

Hepatic HDL receptor, SR-B1 and Apo A-I expression in chronic renal failure.

BACKGROUND: Chronic renal failure (CRF) is associated with hypertriglyceridaemia and depressed plasma high-density lipoprotein (HDL)-cholesterol and apolipoprotein A-I (Apo A-I) concentrations. Uraemic hypertriglyceridaemia is due, in part, to lipoprotein lipase and hepatic lipase deficiencies, which are causally linked to excess parathormone (PTH). This study was designed to test the hypothesis that depressed plasma concentration and abnormal composition of HDL in CRF may be due to dysregulation of hepatic expression of Apo A-I and/or the newly discovered HDL receptor. METHODS: Hepatic Apo A-I and HDL receptor mRNA abundance (Northern blot), and HDL receptor protein mass (Western blot) were determined in CRF rats (5/6 nephrectomy), parathyroidectomized CRF rats (CRF-PTx) and sham-operated controls. RESULTS: The CRF group exhibited normal hepatic HDL receptor mRNA and HDL receptor protein abundance coupled with reduced hepatic Apo A-I mRNA. Hepatic Apo A-I mRNA, HDL receptor mRNA and protein abundance were not affected by PTx. CONCLUSIONS: CRF results in the down-regulation of hepatic Apo A-I gene expression, which accounts for the known reduction in plasma Apo A-I concentration. However, CRF does not affect HDL receptor mRNA or protein expression in this model. Neither Apo A-I nor HDL receptor expression were modified by PTx in CRF rats.     

Down-regulation of hepatic lecithin:cholesterol acyltransferase gene expression in chronic renal failure

BACKGROUND: Chronic renal failure (CRF) is associated with premature arteriosclerosis, impaired high-density lipoprotein (HDL) maturation, increased pre-beta HDL (a lipid-poor HDL species), reduced HDL/total cholesterol ratio, hypertriglyceridemia, and depressed lipolytic activity. The latter has been, in part, attributed to elevated pre-beta HDL, which is a potent inhibitor of lipoprotein lipase (LPL). Accumulation of cholesterol in the arterial wall is a critical step in atherogenesis, and HDL-mediated cholesterol removal from peripheral tissues mitigates atherosclerosis. Lecithin:cholesterol acyltransferase (LCAT) is essential for maturation of HDL and cholesterol removal by HDL from peripheral tissues. Earlier studies have revealed depressed plasma LCAT enzymatic activity in patients with CRF. This study was conducted to determine whether impaired LCAT activity can be confirmed in CRF animals and if so whether it is due to down-regulation of hepatic LCAT expression. METHODS: Hepatic tissue LCAT mRNA and plasma LCAT enzymatic activity were measured in male Sprague-Dawley rats six weeks after excisional 5/6 nephrectomy or sham operation. RESULTS: Compared with the controls, the CRF group exhibited a significant reduction of hepatic tissue LCAT mRNA abundance. The reduction in hepatic LCAT mRNA was accompanied by a marked reduction of plasma LCAT activity and elevation of serum-free cholesterol in the CRF animals. LCAT activity correlated positively with the HDL/total cholesterol ratio and inversely with free cholesterol and triglyceride concentrations. CONCLUSIONS: CRF leads to a marked down-regulation of hepatic LCAT mRNA expression and plasma LCAT activity. This abnormality can impair HDL-mediated cholesterol uptake from the vascular tissue and contribute to cardiovascular disease. In addition, LCAT deficiency can, in part, account for elevated serum-free cholesterol, reduced HDL/total cholesterol, and elevated pre-beta HDL in CRF. The latter can, in turn, depress lipolytic activity and hinder triglyceride-rich lipoprotein clearance in CRF.     

Defective calcium signalling in uraemic platelets and its amelioration with long-term erythropoietin therapy.

BACKGROUND: Chronic renal failure (CRF) is associated with prolonged bleeding time and impaired platelet adhesion and aggregation. Erythropoietin (Epo) administration improves platelet adhesion/aggregation and ameliorates prolongation of bleeding time in CRF. However, the mechanisms of improved platelet function after Epo therapy have not been fully elucidated. The present study examined the hypothesis that the improved uraemic platelet function after Epo therapy is, in part, due to correction of the platelet calcium signalling. METHODS: Rats were randomized into four groups after 5/6 nephrectomies to produce CRF. The Epo-treated CRF group received Epo, 150 U/kg, twice weekly for 6 weeks to prevent anaemia; the felodipine and Epo-treated CRF group received Epo but was kept normotensive by felodipine treatment; the placebo-treated CRF group received placebo injections and became anaemic; and the iron-deficient CRF group received Epo but was kept anaemic by dietary iron-deficiency. A group of sham-operated rats was included as normal control. Basal and thrombin-stimulated platelet cytosolic calcium ([Ca(2+)](i)) were determined using a Ca(2+)-sensitive dye (fura-2). RESULTS: Platelets from placebo-treated CRF group exhibited a profound attenuation of thrombin-stimulated surge in [Ca(2+)](i), which is the final pathway of platelet activation. Long-term Epo administration led to a normalization of the thrombin-induced rise in platelet [Ca(2+)](i) in the CRF animals, independent of either haematocrit or blood pressure values. Further studies revealed that improved Ca(2+) signalling with Epo is associated with increased Ca(2+) uptake and expanded Ca(2+) stores in the platelets. CONCLUSIONS: The defective Ca(2+) signalling in uraemic animals and its improvement with chronic Epo therapy provides the biochemical basis of the previously reported platelet dysfunction and prolonged bleeding time in uraemic patients and animals, and their amelioration with chronic Epo therapy.     

肾皮质大部分切除与肾缺血再灌注损伤对大鼠肾干、祖细胞的影响及其对肾损伤预后的意义

目的 比较肾皮质大部分切除与肾缺血再灌注损伤对大鼠肾干、祖细胞的影响,探讨肾干、祖细胞在肾脏损伤修复中的意义及急性肾衰竭（AFR）和慢性肾衰竭（CRF）预后不同的可能机制。 方法 肾动脉结扎再灌注和5/6肾皮质切除术（假手术为对照）分别制作SD大鼠ARF和CRF模型,定期监测血肌酐、尿素氮及24 h尿蛋白量。于设定时间采集肾脏标本,HE染色检查病理改变,免疫荧光检测肾鲍曼囊区CD24、CD133及肾小球podocin表达;RT-PCR检测大鼠肾皮质区podocin mRNA表达和肾组织转化生长因子β1（TGF-β1）、Notch2、肝细胞生长因子（HGF）、成骨蛋白7（BMP7）和Pax-2 mRNA表达。分析5/6肾皮质切除术后Pax-2 mRNA表达量与podocin mRNA表达量及肾小球硬化指数（GSI）的相关性。 结果 两种模型大鼠分别出现急、慢性肾衰竭的典型肾脏病理及功能变化。CRF组随时间延长肾小球硬化指数逐渐升高,于术后第14、30、60、90天分别为（2.34±0.28）%、（25.12±5.67）%、（89.42±12.28）%和（171.23±32.28）%。与假手术组比较,ARF组不同时间点大鼠鲍曼囊区CD24+CD133+表达细胞分布无显著变化,而CRF组大鼠鲍曼囊区CD24+CD133+表达细胞逐渐减弱;ARF组肾小球podocin表达有短暂减少后迅速恢复,而CRF组肾小球podocin表达则进行性减少。与假手术组相比,ARF组HGF、BMP7 mRNA表达升高（P ＜ 0.05）,而CRF组TGF-β1、Notch2 mRNA表达升高（P ＜ 0.05）,Pax-2和podocin mRNA表达均进行性减少（P ＜ 0.05）。后两者呈正相关（r = 0.872）,且均与GSI呈负相关（r = -0.906、-0.872,均P ＜ 0.05）。 结论 肾脏缺血再灌注损伤对大鼠肾干、祖细胞无明显损伤,足细胞修复迅速,肾脏结构及功能完全恢复。肾皮质大部分切除引起大鼠肾干、祖细胞所处环境中生长抑制因子水平上调,促生长因子降低,导致肾干、祖细胞逐渐减损,足细胞修复缺陷,肾小球硬化及肾功能进行性衰竭。两种肾损伤对肾脏干、祖细胞的不同影响及由此产生肾脏再生修复功能的差异可能是其预后不同的主要机制。     

HMG-CoA reductase, cholesterol 7alpha-hydroxylase, LDL receptor, SR-B1, and ACAT in diet-induced syndrome X

BACKGROUND: Long-term consumption of Western diets can lead to acquired syndrome X, which presents with obesity, insulin resistance, hypertension, hyperlipidemia, and risk of atherosclerotic cardiovascular disease. While plasma lipid abnormalities in syndrome X have been well characterized, their molecular basis remains unclear. This study explored potential mechanisms of hypercholesterolemia in diet-induced syndrome X. METHODS: Female Fischer rats were fed a high-fat, refined-carbohydrate (sucrose) diet (HFS) or standard rat chow (low-fat, complex carbohydrate, LFCC) for 20 months. Plasma lipids and hepatic tissue mRNA, protein, and/or activities of the key enzymes and receptors involved in cholesterol metabolism were determined. RESULTS: The HFS group exhibited hypertension, hyperlipidemia, insulin resistance, obesity, significant down-regulation of hepatic cholesterol 7alpha-hydroxylase (the rate-limiting step in cholesterol catabolism) and low-density lipoprotein (LDL) receptor (LDL-R, the primary pathway of LDL clearance). In contrast, hepatic tissue acyl-coenzyme A:cholesterol acyltransferase (ACAT-2, the primary enzyme involved in intracellular esterification of cholesterol) and scavenger-receptor class B, type 1 (SR-B1 or HDL receptor) were up-regulated. While 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase mRNA expression was increased, its protein abundance and activity were unchanged, and HMG-CoA reductase-to-cholesterol 7alpha-hydroxylase ratio was increased in HFS-fed animals. CONCLUSION: Hypercholesterolemia in diet-induced syndrome X is associated with depressed cholesterol 7alpha-hydroxylase, diminished LDL-R, elevated ACAT, and increased HMG-CoA reductase-to-cholesterol 7alpha-hydroxylase ratio. These findings point to impaired hepatic catabolism and uptake of cholesterol and inappropriate cholesterol production capacity as the underlying causes of hypercholesterolemia in rats with diet-induced syndrome X.     

红细胞生成素对慢性肾衰竭大鼠肾小球内皮细胞功能的影响

目的 探讨红细胞生成素（EPO）对慢性肾衰竭（CRF）大鼠肾小球内皮细胞功能的影响。 方法 采用分阶段5/6肾切除术制备大鼠慢性肾衰竭动物模型。实验动物按数字随机法分为4组：假手术组（对照组）、慢性肾衰竭组（模型组）及EPO干预的两个剂量组（小剂量组EPO用量30 U/kg,大剂量组EPO用量50 U/kg）。慢性肾衰竭大鼠皮下注射EPO 6周后处死。检测各组大鼠血肌酐（Scr）、血尿素氮（BUN）、尿蛋白、血红蛋白（Hb）和血压的变化,并观察肾组织病理改变。免疫组化法检测肾小球CD34、CD31表达;RT-PCR检测肾组织内皮素1（ET-1）、内皮细胞一氧化氮合酶（eNOS）和血管内皮细胞生长因子（VEGF） mRNA的表达。 结果 与模型组比较,EPO治疗能显著增加大鼠肾小球CD34、CD31的表达（均P < 0.05）;下调肾组织ET-1 mRNA的表达（P < 0.05）;上调肾组织eNOS和 VEGF mRNA的表达（均P < 0.05）。此外,EPO治疗还能使大鼠Scr、BUN、尿蛋白和血压水平显著降低（均P < 0.05）,Hb水平显著增高（P < 0.05）,肾组织病理损害明显减轻。 结论 EPO能减轻慢性肾衰竭大鼠肾脏的病理损害,改善肾功能。这种作用可能与其促进肾小球内皮细胞的修复和改善内皮功能有关。     

Downregulation of intestinal cytochrome p450 in chronic renal failure

Chronic renal failure (CRF) is associated with a decrease in intestinal drug metabolism. The mechanisms remain poorly understood, but one hypothesis involves a reduction in cytochrome P450 levels. This study aimed to investigate the effects of CRF on intestinal cytochrome P450. Two groups of rats were defined, i.e., rats with CRF (induced by 5/6 nephrectomy) and control pair-fed rats. Total cytochrome P450 levels and protein and mRNA expression of cytochrome P450 isoforms, as well as in vitro N-demethylation of erythromycin (a probe for CYP3A activity) and 7-ethoxyresorufin o-deethylase activity (a probe for CYP1A), were assessed in intestinal microsomes. Body weights were similar in the two groups. Creatinine clearance was reduced by 77% (P < 0.001) in CRF rats, compared with control pair-fed animals. Total intestinal cytochrome P450 activity was reduced by 32% (P < 0.001) in CRF rats. CYP1A1 and CYP3A2 protein expression was considerably reduced (>40%, P < 0.001) in rats with CRF. CYP2B1, CYP2C6, and CYP2C11 levels were the same in the two groups. RT-PCR assays revealed marked downregulation of CYP1A1 and CYP3A2 gene expression in CRF rats (P < 0.001). Although intestinal cytochrome P450 levels were reduced in CRF, induction by dexamethasone was present. N-Demethylation of erythromycin and 7-ethoxyresorufin o-deethylase activity were decreased by 25% (P < 0.05) in CRF rats, compared with control rats. In conclusion, CRF in rats is associated with decreases in intestinal cytochrome P450 activity (mainly CYP1A1 and CYP3A2) secondary to reduced gene expression.     

慢性肾功能衰竭对大鼠红细胞生成素受体基因表达的影响

目的研究５／６肾切除引起大鼠慢性肾功能衰竭并出现贫血时骨髓细胞红细胞生成素（ＥＰＯ）受体基因表达的变化。方法用二步法切除５／６肾组织诱发大鼠肾功能衰竭并出现贫血，另以盐酸苯肼导致的急性贫血大鼠和正常大鼠为对照。用ＲＴＰＣＲ检测３组大鼠骨髓有核细胞ＥＰＯ受体ｍＲＮＡ表达，并经灰度扫描，与共扩增的β肌动蛋白基因相比，再用ＳｏｕｔｈｅｒｎＢｌｏｔｉｎｇ证实特异性。结果５／６肾切除后５周大鼠出现明显的肾功能衰竭和贫血。正常大鼠、急性贫血大鼠和肾性贫血大鼠骨髓有核细胞ＥＰＯ受体ｍＲＮＡ表达量分别为０２６±００６、０５１±０２４、０１５±００６，急性贫血大鼠ＥＰＯ受体ｍＲＮＡ表达量高于正常大鼠（Ｐ＜００５），而肾性贫血大鼠明显低于正常大鼠（Ｐ＜００１）。结论大鼠在出现慢性肾功能衰竭并出现贫血时，骨髓有核细胞ＥＰＯ受体ｍＲＮＡ表达明显减少，这可能在慢性肾功能衰竭并发贫血过程中起着一定作用。     

Erythropoietin delivery by genetically engineered bone marrow stromal cells for correction of anemia in mice with chronic renal failure

The goal of this research was to develop a strategy to couple stem cell and gene therapy for in vivo delivery of erythropoietin (Epo) for treatment of anemia of ESRD. It was shown previously that autologous bone marrow stromal cells (MSCs) can be genetically engineered to secrete pharmacologic amounts of Epo in normal mice. Therefore, whether anemia in mice with mild to moderate chronic renal failure (CRF) can be improved with Epo gene-modified MSCs (Epo+MSCs) within a subcutaneous implant was examined. A cohort of C57BL/6 mice were rendered anemic by right kidney electrocoagulation and left nephrectomy. In these CRF mice, the hematocrit (Hct) dropped from a prenephrectomy baseline of approximately 55% to 40% after induction of renal failure. MSCs from C57BL/6 donor mice were genetically engineered to secrete murine Epo at a rate of 3 to 4 units of Epo/10(6) cells per 24 h, embedded in a collagen-based matrix, and implanted subcutaneously in anemic CRF mice. It was observed that Hct increased after administration of Epo+MSCs, according to cell dose. Implants of 3 million Epo+MSCs per mouse had no effect on Hct, whereas 10 million led to a supraphysiologic effect. The Hct of CRF mice that received 4.5 or 7.5 million Epo+MSCs rose to a peak 54+/-4.0 or 63+/-5.5%, respectively, at 3 wk after implantation and remained above 48 or 54% for >19 wk. Moreover, mice that had CRF and received Epo+MSCs showed significantly greater swimming exercise capacity. In conclusion, these results demonstrate that subcutaneous implantation of Epo-secreting genetically engineered MSCs can correct anemia that occurs in a murine model of CRF.     

Sulfate homeostasis, NaSi-1 cotransporter, and SAT-1 exchanger expression in chronic renal failure in rats

BACKGROUND: It is known that hypersulfatemia, like hyperphosphatemia, occurs in chronic renal failure (CRF). The aim of this study was to assess the effects of CRF on sulfate homeostasis and on sodium sulfate cotransport (NaSi-1) and sulfate/oxalate-bicarbonate exchanger (Sat-1) expression in the kidney. In addition, sulfate homeostasis was compared with phosphate homeostasis. METHODS: Experimental studies were performed in adult male rats at three and six weeks after 80% subtotal nephrectomy (Nx) or sham-operation (S) (N = 9 per group). Transporter protein and mRNA expressions were measured by Western blot and RNase protection assay (RPA), respectively. Results were quantitated by densitometric scanning (Western) and electronic autoradiography (RPA), and were expressed in densitometric units (DUs; Western) and cpm (RPA). RESULTS: Creatinine clearance was lower in Nx-3 compared with S-3 rats (0.23 vs. 0.51 mL/min/100 g body weight, P < 0.001) and was further impaired in Nx-6 rats (0.15 vs. 0.48, P < 0.001). Sulfatemia was significantly higher in Nx-3 rats (1.08 vs. 0.84 mmol/L, P < 0.05) and further increased in Nx-6 rats (1.42 vs. 0.90 mmol/L, P < 0.01). Fractional sulfate excretion (FESO4) was increased by twofold in Nx-3 and Nx-6 rats compared with corresponding S rats. Phosphatemia did not differ between Nx-3 rats and controls, but was increased in Nx-6 rats (P < 0.01). Total amounts of both NaSi-1 and Sat-1 proteins were significantly decreased in both Nx-3 and Nx-6 rats when compared with controls. However, NaSi-1 protein and mRNA densities did not significantly change in Nx-3 rats, but were significantly increased in Nx-6 rats when compared with controls (4.8 vs. 3.7 DU/microg protein, P < 0.05, and 7.1 vs. 2.8 cpm/microg RNA, P < 0.01, respectively, for protein and mRNA). In contrast to NaSi-1, Sat-1 protein density was significantly decreased both in Nx-3 (2.9 vs. 3.6 DU/microg protein, P < 0.05) and Nx-6 rats (2.4 vs. 3.4 DU/microg protein, P < 0.05), and Sat-1 mRNA density significantly decreased in Nx-6 rats (10.7 vs. 14.7 cpm/microg RNA, P < 0.05). Na-PO4 cotransporter (NaPi-2) protein total abundance and density were decreased at three and six weeks in Nx rats. CONCLUSIONS: These results demonstrate that both NaSi-1 and Sat-1 total protein abundances are decreased in CRF, which may contribute to the increase in fractional sulfate excretion. Strikingly, NaSi-1 density was not decreased in CRF three weeks after Nx, and furthermore, increased six weeks after Nx, in contrast to NaPi-2 density, which was decreased at both times. The significance of this difference remains to be determined, but may explain why hypersulfatemia occurs earlier than hyperphosphatemia in CRF.     

血管内皮生长因子基因转染骨髓间充质干细胞对慢性肾衰竭大鼠肾脏的修复作用

目的探讨血管内皮生长因子（vascularendothelialgrowthfactor,VEGF）基因转染骨髓间充质干细胞（mesenchymalstemcelis,MSC）对慢性肾衰竭（chronicrenalfailure,CRF）大鼠肾脏的修复作用。方法体外分离、培养大鼠MSC,Ad—VEGF转染MSC。SD大鼠随机分为假手术组（对照组）、慢性肾衰竭模型组（肾衰组）、慢性肾衰竭大鼠MSC移植组（MsC组）、慢性。肾衰竭竭大鼠AdVEGF注射组（VEGF组）和慢性肾衰竭大鼠Ad—VEGF转染的MSC移植组（转染组）。采用分阶段5／6肾切除术制备大鼠CRF动物模型。对照组与肾衰组于切除右肾之前从该侧肾动脉注射不含血清的DMEM培养液,其他3组分别给予MSC、Ad—VEGF和VEGF基因转染的MSC。8周后检测各组大鼠血肌酐（SCr）、血尿素氮（BUN）和24h尿蛋白,观察各组大鼠残肾组织病理形态,并用免疫印迹和RT—PCR方法检测各组大鼠残肾组织VEGFmRNA和蛋白的表达。结果MSC组和转染组SCr、BUN和尿蛋白均较。肾衰组降低（P〈0．05）;与MSC组比较,转染组SCr、BUN和尿蛋白降低更明显（P〈0．05）。肾衰组残肾组织VEGFmRNA和蛋白的表达较对照组显著减少（P〈0．05）,MSC组和转染组残肾组织VEGFmRNA和蛋白的表达明显增加（与肾衰组比较,均P〈0．05）,转染组残肾组织VEGFmRNA和蛋白的表达增加更明显（与M9C组比较,P〈0．05）。结论VEGF基因转染的MSC移植对CRF大鼠的肾脏有修复作用,这可能与VEGF在肾组织中高表达有关。     

HMG-CoA reductase,cholesterol 7alpha-hydroxylase,LCAT, ACAT,LDL receptor,and SRB-1 in hereditary analbuminemia

BACKGROUND: Hereditary analbuminemia is associated with hypercholesterolemia, which has been shown to be primarily caused by increased extrahepatic production of cholesterol. Nagase rats with hereditary analbuminemia (NAR) have been used as a model to dissect the effect of primary hypoalbuminemia from that caused by proteinuria in nephrotic syndrome. The present study was undertaken to explore the effect of hereditary analbuminemia on protein expression of the key factors involved in cholesterol metabolism. METHODS: Hepatic tissue protein abundance of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, cholesterol 7alpha-hydroxylase (a rate-limiting enzyme in cholesterol catabolism), low density lipoprotein (LDL) receptor, high density lipoprotein (HDL) receptor (SRB-1), acyl-coA cholesterol acyltransferase-2 (ACAT-2), and plasma concentration of lecithin cholesterol acyltransferase (LCAT), as well as HMG-CoA reductase, ACAT, and LCAT activities were determined in fasting male NAR and Sprague-Dawley control rats. RESULTS: The NAR group exhibited significant up-regulation of HMG-CoA reductase protein abundance but normal HMG-CoA reductase enzymatic activity. This was coupled with a significant up-regulation of cholesterol 7alpha-hydroxylase and a mild up-regulation of ACAT protein abundance and activity. However, hepatic LDL receptor and HDL receptor and plasma LCAT protein concentration and activity were normal in NAR. CONCLUSION: Hypercholesterolemia in NAR is associated with elevated hepatic HMG-CoA reductase protein abundance, but normal HMG-CoA reductase activity. These findings point to post-translational regulation of this enzyme and favor an extrahepatic origin of hypercholesterolemia in NAR. The observed up-regulation of cholesterol 7alpha-hydroxylase represents a compensatory response to the associated hypercholesterolemia. Unlike nephrotic syndrome, which causes severe LDL receptor, HDL receptor, and LCAT deficiencies, hereditary analbuminemia does not affect these proteins.     

酰基辅酶A胆固醇酰基转移酶抑制剂对人系膜细胞细胞内脂质稳态的影响

目的 研究酰基辅酶A胆固醇酰基转移酶抑制剂（ACATI，58-035）对脂质负荷人系膜细胞系（HMCL）细胞内脂质稳态的影响。 方法 油红O染色观察细胞内脂滴变化。偶氮四唑盐（MTT）法了解细胞增殖。高效液相色谱法（HPLC）测定细胞内游离胆固醇(FC)和胆固醇酯（CE）。Western印迹法检测ACATI对HMCL ACAT1和腺苷三磷酸结合盒转运体A1(ABCA1)的蛋白表达。荧光实时定量PCR检测ACATI对HMCL ACAT1、ABCA1和低密度脂蛋白（LDL）受体的影响。瞬时转染检测ACATI对HMCL ACAT1 p1启动子的影响。 结果 100 mg/L LDL明显增加HMCL内脂滴和CE含量。10 mg/L ACATI 58-035没有细胞毒性，且能显著抑制LDL导致的脂滴形成和CE含量增加(相对对照比值，分别是1.91±0.36和1.07±0.30,P < 0.01)。100 mg/L LDL主要在蛋白水平增加ACAT1表达（为对照1.27倍），在10 mg/L ACATI 58-035共同作用时，ACAT1蛋白表达进一步增加（为对照1.77倍）；100 mg/L LDL明显上调HMCL ABCA1 mRNA表达[为对照（2.97±0.39）倍，P < 0.01]，明显下调LDL受体mRNA表达[为对照（0.08±0.02）倍, P < 0.01]，在10 mg/L ACATI 58-035共同作用时，HMCL ABCA1的蛋白和mRNA表达进一步上调[为对照（4.41±1.27）倍，与LDL作用组比较，P < 0.05]，LDL受体mRNA表达进一步下调[为对照（0.04±0.005）倍，与LDL作用组比较，P < 0.01]。 结论 脂质负荷HMCL在一定剂量ACATI作用下，细胞内CE含量明显减少，FC并没有明显增加，这与HMCL上调ABCA1蛋白和mRNA表达、下调LDL受体mRNA表达有关。脂质负荷主要引起HMCL ACAT1蛋白表达增加。     

红细胞生成素对慢性肾衰竭大鼠外周血内皮祖细胞的影响

目的 探讨红细胞生成素（EPO）对慢性肾衰竭大鼠外周血内皮祖细胞（EPC）数量和功能的影响。 方法 采用分阶段5/6肾切除制备大鼠慢性肾衰竭模型。实验动物按数字随机表法分为4组（均n = 7）：假手术组、慢性肾衰竭组（模型组）、30 U/kg EPO干预组（小剂量组）和50 U/kg EPO干预组（大剂量组）。大鼠皮下注射EPO 6周后,取其外周血分离培养EPC,并检测EPC数量及其增殖、黏附和形成血管结构的能力。 结果 与假手术组比较,慢性肾衰竭大鼠外周血EPC数量及其增殖、黏附与形成血管结构的能力均显著下降（均P < 0.05）。应用EPO治疗能显著增加慢性肾衰竭大鼠外周血EPC数量（P < 0.05）,改善外周血EPC增殖、黏附及形成血管结构的能力（均P < 0.05）,并且呈剂量依赖性。 结论 EPO可改善慢性肾衰竭大鼠外周血EPC的数量和功能。     

Down-regulation of hepatic high-density lipoprotein receptor, SR-B1, in nephrotic syndrome.

BACKGROUND: Nephrotic syndrome (NS) is a prototype of acquired hypercholesterolemia. Hepatic synthesis and removal of cholesterol play major roles in the regulation of plasma concentration of this sterol. Low-density lipoprotein (LDL) and high-density lipoprotein (HDL) particles are the primary vehicles for cholesterol transport to the liver. We have recently demonstrated that NS results in acquired hepatic LDL receptor deficiency in rats. This study was undertaken to determine the effect of NS on hepatic expression of the newly discovered, long-sought HDL receptor. METHODS: Hepatic HDL receptor and apolipoprotein A-I (apo A-I) expressions were studied in rats with puromycin-induced NS. The results were compared with those obtained in placebo-treated, normal controls. RESULTS: The NS group exhibited a marked reduction in hepatic tissue HDL receptor protein abundance when compared with the control group. In contrast, hepatic HDL receptor mRNA abundance in the NS group was similar to that of the control group. As expected, the NS group showed a marked increase in hepatic apo A-I mRNA abundance. CONCLUSIONS: The study explored the effect of experimental NS on hepatic HDL receptor expression, and the results revealed a marked down-regulation of HDL receptor in rats with NS. In contrast, hepatic expression of Apo A-I, the principal protein constituent of HDL, was markedly increased in NS rats. The HDL receptor deficiency shown here can potentially limit the efficiency of HDL as the primary vehicle for reverse cholesterol transport in NS.     

Beneficial influence of recombinant human erythropoietin therapy on the rate of progression of chronic renal failure in predialysis patients.

BACKGROUND: Partial correction of anaemia with recombinant human erythropoietin (rHuEpo) has been shown to markedly improve the general condition and quality of life of predialysis patients, but the effects of rHuEpo therapy on blood pressure and the rate of progression of chronic renal failure (CRF) are still disputed. In particular, no study evaluated the time duration until the start of maintenance dialysis in treated patients, compared to untreated predialysis patients. METHODS: We retrospectively evaluated the rate of decline of creatinine clearance (Delta Ccr) and the duration of the predialysis period in 20 patients with advanced CRF treated with rHuEpo (Epo+ group), and in 43 patients with a similar degree of CRF but with less marked, asymptomatic anaemia, not requiring rHuEpo therapy (Epo- group). All patients were submitted to identical clinical and laboratory surveillance. All received similar oral supplementation with B(6), B(9), and B(12) vitamins and oral iron supplementation. Maintenance dose of subcutaneous epoetin was 54.3+/-16.5 U/kg/week (median dose 3300 U/week). RESULTS: Initial and final haemoglobin (Hb) levels were 8.8+/-0.7 and 11.3+/-0.9 g/dl in the Epo+ group, vs 10.9+/-1.2 and 9.5+/-0.9 g/dl in the Epo- group. In the Epo+ group, Delta Ccr declined from 0.36+/-0.16 during the preceding 24 months to 0.26+/-0.15 ml/min/ 1.73 m(2)/month after the start of rHuEpo therapy (P<0.05). No significant variation was observed in the Epo- group. Time duration until the start of dialysis was 16.2+/-11.9 in the Epo+ group, compared to 10.6+/-6.1 months in the Epo- group (P<0.01). Slowing of progression was observed in 10 Epo+ patients, whereas no significant variation in Delta Ccr occurred in the other 10. There was no difference in previous Delta Ccr rate, nor in Hb or blood pressure levels while on rHuEpo therapy between the two subgroups. CONCLUSIONS: Our study affords conclusive evidence that rHuEpo therapy did not result in accelerated progression of CRF in any treated predialysis patients, nor deleterious increase in blood pressure, but instead resulted in significant slowing of progression and substantial retardation of maintenance dialysis. Such encouraging results remain to be validated in a large prospective, randomized study.     

肾衰养真胶囊对5/6肾切除慢性肾衰竭营养不良大鼠下丘脑神经肽Y mRNA表达的影响

目的：观察肾衰养真胶囊对5/6肾切除慢性肾衰竭（CRF）营养不良大鼠的改善作用和探讨其作用机制。方法：5/6肾切除同时予4%酪蛋白饮食制作CRF营养不良大鼠模型,观察其营养不良发生时间,符合CRF营养不良模型的随机分为正常组、模型组、肾衰养真胶囊组和开同组。药物干预4周后检测尿素氮、肌酐、白蛋白、血红蛋白、24h尿蛋白,动态观察摄食量及体重变化,灌胃4周后检测血浆神经肽Y（NPY）和下丘脑NPY mRNA表达水平。结果：CRF大鼠在术后10周末出现营养不良,与模型组比较,肾衰养真胶囊组大鼠摄食量、体重显著增高,白蛋白和血红蛋白显著升高,肾功能改善,肾衰养真胶囊可上调下丘脑NPY mRNA表达,降低血浆NPY水平。结论：肾衰养真胶囊可改善CRF营养不良其机制可能是通过上调下丘脑NPY mRNA表达及降低血浆NPY从而促进CRF营养不良大鼠摄食,增加体重。