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Abstract
Dyslipidemia is a potent cardiovascular (CV) risk factor in the general population. Elevated low-density lipoprotein cholesterol (LDL-C) and/or low high-density lipoprotein (HDL-C) are well-established CV risk factors, but more precise determinants of risk include increased apoprotein B (ApoB), lipoprotein(a) [Lp(a)], intermediate and very low-density lipoprotein (IDL-C, VLDL-C; “remnant particles”), and small dense LDL particles. Lipoprotein metabolism is altered in association with declining glomerular filtration rate such that patients with non dialysis-dependent chronic kidney disease (CKD) have lower levels of HDL-C, higher triglyceride, ApoB, remnant IDL-C, remnant VLDL-C, and Lp(a), and a greater proportion of oxidized LDL-C. Similar abnormalities are prevalent in hemodialysis (HD) patients, who often manifest proatherogenic changes in LDL-C in the absence of increased levels. Patients treated with peritoneal dialysis (PD) have a similar but more severe dyslipidemia compared to HD patients due to stimulation of hepatic lipoprotein synthesis by glucose absorption from dialysate, increased insulin levels, and selective protein loss in the dialysate analogous to the nephrotic syndrome. In the dialysis-dependent CKD population, total cholesterol is directly associated with increased mortality after controlling for the presence of malnutrition–inflammation.Treatment with statins reduces CV mortality in the general population by approximately one third, irrespective of baseline LDL-C or prior CV events. Statins have similar, if not greater, efficacy in altering the lipid profile in patients with dialysis-dependent CKD (HD and PD) compared to those with normal renal function, and are well tolerated in CKD patients at moderate doses (≤ 20 mg/day atorvastatin or simvastatin). Statins reduce C-reactive protein as well as lipid moieties such as ApoB, remnants IDL and VLDL-C, and oxidized and small dense LDL-C fraction. Large observational studies demonstrate that statin treatment is independently associated with a 30% – 50% mortality reduction in patients with dialysis-dependent CKD (similar between HD- and PD-treated patients). One recent randomized controlled trial evaluated the ability of statin treatment to reduce mortality in type II diabetics treated with HD (“4D”); the primary end point of death from cardiac cause, myocardial infarction, and stroke was not significantly reduced. However, results of this trial may not apply to other end-stage renal disease populations. Two ongoing randomized controlled trials (SHARP and AURORA) are underway evaluating the effect of statins on CV events and death in patients with CKD (including patients treated with HD and PD). Recruitment to future trials should be given a high priority by nephrologists and, until more data are available, consideration should be given to following published guidelines for the treatment of dyslipidemia in CKD. Additional consideration could be given to treating all dialysis patients felt to be at risk of CV disease (irrespective of cholesterol level), given the safety and potential efficacy of statins. This is especially relevant in patients treated with PD, given their more atherogenic lipid profile and the lack of randomized controlled trials in this population.
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Affiliation(s)
- Sabin Shurraw
- Division of Nephrology University of Alberta, Canada
| | - Marcello Tonelli
- Division of Nephrology University of Alberta, Canada
- Division of Critical Care Medicine, University of Alberta, Canada
- Institute of Health Economics, Edmonton, Alberta, Canada
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Nam GE, Han K, Kim DH, Park YG, Yoon YJ, Kim YE, Lee S, Lee S, Roh YK. Relationship between dyslipidemia and albuminuria in prediabetic adults: the Korea National Health and Nutrition Examination Survey 2011-2012. Endocrine 2015; 48:557-65. [PMID: 25205446 DOI: 10.1007/s12020-014-0411-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Accepted: 08/27/2014] [Indexed: 11/30/2022]
Abstract
UNLABELLED This study aimed to estimate the relationship between various lipid abnormalities and albuminuria in Korean prediabetic adults. Data obtained from the Korea National Health and Nutrition Examination Survey (KNHANES) 2011-2012 were analyzed. The study consisted of 4,811 subjects in the normal glucose group and 3,872 in the prediabetic group. Prediabetes was defined by the fasting plasma glucose or hemoglobin A1c level. Albuminuria was defined as a urine albumin to creatinine ratio (UACR) ≥30 mg/g. Various parameters of dyslipidemia were assessed. No differences were observed in the prevalence of lipid abnormalities in prediabetic men with different values of UACR. Prediabetic women with increased urinary albumin excretion showed a significantly higher prevalence of lipid abnormalities. The proportion of mixed dyslipidemia was significantly higher in prediabetic women with albuminuria. Higher levels of total cholesterol, triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), non-high-density lipoprotein cholesterol (non-HDL-C), and TC to HDL-C ratio, TG to HDL-C ratio, and LDL-C to HDL-C ratio were significantly associated with increased risk of albuminuria in prediabetic women. CONCLUSIONS Several lipid abnormalities were significantly associated with the increased risk of albuminuria in prediabetic women. Hence, screening for lipid abnormalities may be helpful for identification of risk for albuminuria in prediabetic subjects.
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Affiliation(s)
- Ga Eun Nam
- Department of Family Medicine, Korea University Ansan Hospital, Korea University College of Medicine, Ansan-Si, Republic of Korea
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Inhibition of endothelial lipase activity by sphingomyelin in the lipoproteins. Lipids 2014; 49:987-96. [PMID: 25167836 DOI: 10.1007/s11745-014-3944-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Accepted: 08/14/2014] [Indexed: 10/24/2022]
Abstract
Endothelial lipase (EL) is a major determinant of plasma HDL concentration, its activity being inversely proportional to HDL levels. Although it is known that it preferentially acts on HDL compared to LDL and VLDL, the basis for this specificity is not known. Here we tested the hypothesis that sphingomyelin, a major phospholipid in lipoproteins is a physiological inhibitor of EL, and that the preference of the enzyme for HDL may be due to low sphingomyelin/phosphatidylcholine (PtdCho) ratio in HDL, compared to other lipoproteins. Using recombinant human EL, we showed that sphingomyelin inhibits the hydrolysis of PtdCho in the liposomes in a concentration-dependent manner. While the enzyme showed lower hydrolysis of LDL PtdCho, compared to HDL PtdCho, this difference disappeared after the degradation of lipoprotein sphingomyelin by bacterial sphingomyelinase. Analysis of molecular species of PtdCho hydrolyzed by EL in the lipoproteins showed that the enzyme preferentially hydrolyzed PtdCho containing polyunsaturated fatty acids (PUFA) such as 22:6, 20:5, 20:4 at the sn-2 position, generating the corresponding PUFA-lyso PtdCho. This specificity for PUFA-PtdCho species was not observed after depletion of sphingomyelin by sphingomyelinase. These results show that sphingomyelin not only plays a role in regulating EL activity, but also influences its specificity towards PtdCho species.
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Krikken JA, Waanders F, Dallinga-Thie GM, Dikkeschei LD, Vogt L, Navis GJ, Dullaart RPF. Antiproteinuric therapy decreases LDL-cholesterol as well as HDL-cholesterol in non-diabetic proteinuric patients: relationships with cholesteryl ester transfer protein mass and adiponectin. Expert Opin Ther Targets 2009; 13:497-504. [DOI: 10.1517/14728220902905865] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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de Boer IH, Astor BC, Kramer H, Palmas W, Rudser K, Seliger SL, Shlipak MG, Siscovick DS, Tsai MY, Kestenbaum B. Mild elevations of urine albumin excretion are associated with atherogenic lipoprotein abnormalities in the Multi-Ethnic Study of Atherosclerosis (MESA). Atherosclerosis 2007; 197:407-14. [PMID: 17681346 PMCID: PMC2288670 DOI: 10.1016/j.atherosclerosis.2007.06.018] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2007] [Revised: 04/10/2007] [Accepted: 06/21/2007] [Indexed: 11/28/2022]
Abstract
OBJECTIVE Elevated urine albumin excretion is an established risk factor for cardiovascular disease. Increased cardiovascular risk may be partly mediated by abnormalities in lipoprotein metabolism. We examined cross-sectional associations of urine albumin-creatinine ratio (ACR) with standard lipid measurements and with lipoprotein particle concentrations measured by nuclear magnetic resonance (NMR) in the Multi-Ethnic Study of Atherosclerosis. METHODS AND RESULTS Among 5633 participants who were not using lipid-lowering medications, greater ACR was associated with greater triglyceride concentration and lesser high density lipoprotein cholesterol concentration (women only), but not with low density lipoprotein (LDL) cholesterol calculated using conventional methods. In contrast, unadjusted mean small LDL particle concentrations measured by NMR were 770, 827 and 935 nmol/L for women (p<0.001) and 996, 1030 and 1040 nmol/L for men (p=0.037) among participants with normal, high normal and elevated ACR. Adjusting for age, race/ethnicity, diabetes, impaired fasting glucose, hypertension, smoking, medications, body mass index and serum creatinine, each two-fold greater ACR was associated with an increase in small LDL particle concentration of 27 nmol/L for women (p<0.001) and 14 nmol/L for men (p=0.008). Greater ACR was also associated with greater intermediate density lipoprotein particle concentration and smaller mean LDL particle size. CONCLUSIONS Mild elevations of urine ACR are associated with atherogenic lipoprotein abnormalities that are not directly observed with a standard lipid panel.
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Affiliation(s)
- Ian H de Boer
- Division of Nephrology, University of Washington, Seattle, WA 98195, USA.
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Zhang C, Yao M, Wang X, Zhuang Y, Xia Z, Yang Y, Li Y, Liu X, Li K, Wang J. Effect of hypoalbuminemia on the increased serum cholesteryl ester transfer protein concentration in children with idiopathic nephrotic syndrome. Clin Biochem 2007; 40:869-75. [PMID: 17555738 DOI: 10.1016/j.clinbiochem.2007.04.016] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2006] [Revised: 04/02/2007] [Accepted: 04/09/2007] [Indexed: 11/21/2022]
Abstract
OBJECTIVES To examine the alteration of cholesteryl ester transfer protein (CETP) mass with the regression of albumin level in childhood nephrotic syndrome (NS) in order to clarify the effect of albumin on CETP in NS. DESIGN AND METHODS Serum concentrations of CETP, kidney parameters and lipid traits were determined in 110 children with idiopathic NS and 150 control subjects. Of the NS patients, 69 children with an active phase formed group 1, and 41 in remission formed group 2. RESULTS Group 1 presented severe hypoalbuminemia and hyperlipidemia, while group 2 exhibited marked recovery in both serum albumin level and lipid/lipoprotein profile. CETP concentration was significantly higher in group 1 (7.36+/-2.43 mg/L, compared with controls 3.38+/-1.83 mg/L, P<0.0001), and declined to within normal range in group 2 (2.91+/-1.77 mg/L). CETP concentration had a strong inverse correlation with serum albumin level (r=-0.688, P<0.0001) in NS patients. Furthermore, when multiple linear regression analysis was performed, in which albumin, proteinuria, lipid traits, and prednisone dose were treated as independent variables, albumin was the only variable showing a significant correlation with CETP in the NS patients (R(2)=0.587, beta=-0.475, P<0.0001). CONCLUSIONS The results demonstrate that the decreased serum albumin level might be a main determinant of the increased CETP concentration in pediatric NS.
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Affiliation(s)
- Chunni Zhang
- Department of Biochemistry, Jinling Hospital, Clinical School of Medicine, Nanjing University, 210002, Nanjing, PR China
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Subbaiah PV, Horvath P, Achar SB. Regulation of the activity and fatty acid specificity of lecithin-cholesterol acyltransferase by sphingomyelin and its metabolites, ceramide and ceramide phosphate. Biochemistry 2006; 45:5029-38. [PMID: 16605271 PMCID: PMC1451158 DOI: 10.1021/bi0600704] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Sphingomyelin (SM), the second most abundant phospholipid in plasma lipoproteins, was previously shown to be a physiological inhibitor of the lecithin-cholesterol acyltransferase (LCAT) reaction. In this study, we investigated the effects of its metabolites, ceramide and ceramide phosphate, on the activity and fatty acid specificity of LCAT in vitro. Treatment of SM-containing substrate with SMase C, which hydrolyzes SM to ceramide, abolished the inhibitory effect of SM, whereas treatment with SMase D, which hydrolyzes it to ceramide phosphate, increased the level of inhibition. Although incorporation of ceramide into the substrate in the absence of SM activated the LCAT reaction only modestly, its co-incorporation with SM neutralized the inhibitory effect of SM. Ceramide phosphate, on the other hand, inhibited the LCAT reaction more strongly than SM. The effects of the sphingolipids on the phospholipase A and cholesterol esterification reactions of the enzyme were similar, indicating that they regulate the binding of phosphatidylcholine (PC) to the active site, rather than the esterification step. Incorporation of ceramide into the substrate stimulated the synthesis of unsaturated cholesteryl esters at the expense of saturated esters. However, these effects on fatty acid specificity disappeared when the PC substrates were incorporated into an inert diether PC matrix, suggesting that ceramide increases the availability of polyunsaturated PCs to the enzyme by altering the macromolecular structure of the substrate particle. Since the plasma ceramide levels are increased during inflammation, these results indicate that the activity and fatty acid specificity of LCAT may be altered during the inflammatory response.
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Affiliation(s)
- Papasani V Subbaiah
- Department of Medicine, University of Illinois, Chicago, Illinois 60612, USA.
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Prescott WA, Streetman DAD, Streetman DS. The Potential Role of HMG-CoA Reductase Inhibitors in Pediatric Nephrotic Syndrome. Ann Pharmacother 2004; 38:2105-14. [PMID: 15507504 DOI: 10.1345/aph.1d587] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
OBJECTIVE To evaluate the safety and efficacy of the hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) as a potential treatment option for the dyslipidemia associated with childhood nephrotic syndrome. DATA SOURCES Searches of MEDLINE (1966–April 2004), Cochrane Library, International Pharmaceutical Abstracts (1977–April 2004), and an extensive manual review of journals were performed using the key search terms nephrotic syndrome, familial hypercholesterolemia, dyslipidemia, and HMG-CoA reductase inhibitor. STUDY SELECTION AND DATA EXTRACTION Two prospective uncontrolled studies evaluating the safety and efficacy of statin therapy in pediatric nephrotic syndrome were included. DATA SYNTHESIS While an extensive amount of data is available in adult nephrotic syndrome in which statin therapy decreases total plasma cholesterol 22–39%, low-density lipoprotein cholesterol (LDL-C) 27–47%, and total plasma triglycerides 13–38%, only 2 small uncontrolled studies have been conducted evaluating the utility of these agents in pediatric nephrotic syndrome. These studies indicate that statins are capable of safely reducing total cholesterol up to 42%, LDL-C up to 46%, and triglyceride levels up to 44%. CONCLUSIONS Lowering cholesterol levels during childhood may reduce the risk for atherosclerotic changes and may thus be of benefit in certain patients with nephrotic syndrome. Statins have demonstrated short-term safety and efficacy in the pediatric nephrotic syndrome population. Implementing pharmacologic therapy with statins in children with nephrotic syndrome must be done with care until controlled studies are conducted in this population.
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Affiliation(s)
- William A Prescott
- College of Pharmacy, Department of Pharmacy Services, University of Michigan Health System, 1500 E. Medical Center, Ann Arbor, MI 48109-0008, USA
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Le Goff W, Guerin M, Chapman MJ. Pharmacological modulation of cholesteryl ester transfer protein, a new therapeutic target in atherogenic dyslipidemia. Pharmacol Ther 2004; 101:17-38. [PMID: 14729390 DOI: 10.1016/j.pharmthera.2003.10.001] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
In mediating the transfer of cholesteryl esters (CE) from antiatherogenic high density lipoprotein (HDL) to proatherogenic apolipoprotein (apo)-B-containing lipoprotein particles (including very low density lipoprotein [VLDL], VLDL remnants, intermediate density lipoprotein [IDL], and low density lipoprotein [LDL]), the CE transfer protein (CETP) plays a critical role not only in the reverse cholesterol transport (RCT) pathway but also in the intravascular remodeling and recycling of HDL particles. Dyslipidemic states associated with premature atherosclerotic disease and high cardiovascular risk are characterized by a disequilibrium due to an excess of circulating concentrations of atherogenic lipoproteins relative to those of atheroprotective HDL, thereby favoring arterial cholesterol deposition and enhanced atherogenesis. In such states, CETP activity is elevated and contributes significantly to the cholesterol burden in atherogenic apoB-containing lipoproteins. In reducing the numbers of acceptor particles for HDL-derived CE, both statins (VLDL, VLDL remnants, IDL, and LDL) and fibrates (primarily VLDL and VLDL remnants) act to attenuate potentially proatherogenic CETP activity in dyslipidemic states; simultaneously, CE are preferentially retained in HDL and thereby contribute to elevation in HDL-cholesterol content. Mutations in the CETP gene associated with CETP deficiency are characterized by high HDL-cholesterol levels (>60 mg/dL) and reduced cardiovascular risk. Such findings are consistent with studies of pharmacologically mediated inhibition of CETP in the rabbit, which argue strongly in favor of CETP inhibition as a valid therapeutic approach to delay atherogenesis. Consequently, new organic inhibitors of CETP are under development and present a potent tool for elevation of HDL in dyslipidemias involving low HDL levels and premature coronary artery disease, such as the dyslipidemia of type II diabetes and the metabolic syndrome. The results of clinical trials to evaluate the impact of CETP inhibition on premature atherosclerosis are eagerly awaited.
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Affiliation(s)
- Wilfried Le Goff
- Institut National de la Santé et de la Recherche Médicale (INSERM) Unité 551, "Dyslipoproteinemia and Atherosclerosis: Genetics, Metabolism and Therapy", Hôpital de la Pitié, 83 boulevard de l'Hôpital, 75651 Cedex 13, Paris, France
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Vaziri ND, Liang K. Up-regulation of acyl-coenzyme A:cholesterol acyltransferase (ACAT) in nephrotic syndrome. Kidney Int 2002; 61:1769-75. [PMID: 11967026 DOI: 10.1046/j.1523-1755.2002.00319.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
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.
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Affiliation(s)
- Nosratola D Vaziri
- Division of Nephrology and Hypertension, Department of Medicine, University of California, Irvine, Irvine, California, USA.
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Süllentrop F, Moka D, Neubauer S, Haupt G, Engelmann U, Hahn J, Schicha H. 31P NMR spectroscopy of blood plasma: determination and quantification of phospholipid classes in patients with renal cell carcinoma. NMR IN BIOMEDICINE 2002; 15:60-68. [PMID: 11840554 DOI: 10.1002/nbm.758] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Advanced renal cell carcinoma (RCC) has a poor prognosis and is characterized by an unpredictable clinical course. The aim of this study was to assess the systemic phospholipid distribution as a possible marker of tumor stage and tumor spread beyond the kidney. To this end, the effect of renal cell carcinoma (RCC) on phospholipid concentrations in blood plasma using 31P NMR spectroscopy was studied in: (a) 29 patients with RCC prior to nephrectomy; (b) 19 healthy volunteers; (c) three patients with other renal tumors (renal metastases of bronchial carcinoma and of renal pelvic carcinoma, and a benign renal tumor). Furthermore, the phospholipid concentrations of eight patients of group (a) were determined 6 months after nephrectomy, when they were in remission. We found considerable deviations in the concentrations of the lysophosphatidylcholines (LPC1, LPC2) in both male and female patients with RCC compared to healthy volunteers (male--LPC1 0.217+/-0.062 vs 0.297+/-0.049 mmol/l, LPC2 0.036+/-0.014 vs 0.068+/-0.024 mmol/l; female--LPC1 0.195+/-0.071 vs 0.296+/-0.044 mmol/l, LPC2 0.037+/-0.027 vs 0.044+/-0.014 mmol/l). In addition, female patients with RCC showed lower concentrations of phosphatidylcholines (PC; 1.409+/-0.268 vs 1.947+/-0.259 mmol/l). The low phospholipid concentrations normalized for patients in remission. Phospholipid concentrations were found to depend on tumor stage and metastatic spread. The deviations in phospholipid concentrations (LPC1, LPC2, PC) observed may be attributable to systemic effects caused by the tumor as well as changes in enzyme activities.
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Affiliation(s)
- F Süllentrop
- Institute of Inorganic Chemistry, University of Cologne, Cologne, Germany
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Vaziri ND, Liang K, Parks JS. Acquired lecithin-cholesterol acyltransferase deficiency in nephrotic syndrome. Am J Physiol Renal Physiol 2001; 280:F823-8. [PMID: 11292624 DOI: 10.1152/ajprenal.2001.280.5.f823] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Lecithin-cholesterol acetyltransferase (LCAT) is involved in the synthesis of plasma cholesteryl esters and is pivotal in the maturation of plasma high-density lipoprotein (HDL) and conversion of HDL3 to HDL2. In nephrotic syndrome (NS), the ratio of HDL2 to HDL3 is low even though the total concentration of HDL is generally normal. We hypothesize that the reduced HDL2/HDL3 ratio in NS is due to urinary losses of LCAT, leading to plasma LCAT deficiency. To test this hypothesis, Sprague-Dawley rats were randomized to NS (given 130 mg puromycin aminonucleoside on day 1 and 60 mg ip on day 14) or control groups and were studied on day 30. To dissect the effect of proteinuria from hypoalbuminemia, a group of Nagase rats with inherited hypoalbuminemia was included. Hepatic LCAT and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA abundance and plasma and urine LCAT activity were measured. The NS group showed a fourfold rise in serum cholesterol and triglycerides, a fivefold rise in free cholesterol, and a fourfold fall in the HDL-to-total cholesterol ratio. Despite severe hypoalbuminemia, the Nagase rats showed only a mild elevation of serum cholesterol and triglycerides with a normal serum free cholesterol and HDL-to-total cholesterol ratio. The NS group exhibited a normal hepatic LCAT-to-GAPDH mRNA ratio, a marked reduction in plasma LCAT activity, and a significant increase in urinary LCAT excretion. LCAT/GAPDH mRNA and plasma and urine LCAT were normal in Nagase rats. Thus NS led to heavy urinary losses and reduced plasma concentration of LCAT, despite normal hepatic LCAT mRNA abundance. However, hypoalbuminemia, per se, without proteinuria as seen in the Nagase rats had no effect on plasma LCAT or the HDL-to-total cholesterol ratio. Therefore, proteinuria, not hypoalbuminemia, causes LCAT deficiency and a depressed HDL-to-total cholesterol ratio in NS.
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Affiliation(s)
- N D Vaziri
- Division of Nephrology, Department of Medicine, University of California-Irvine, Irvine, CA 92697, USA
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Liu M, Clair RWS, Subbaiah PV. Impaired function of lecithin:cholesterol acyltransferase in atherosclerosis-susceptible White Carneau pigeons: possible effects on metabolism of oxidized phospholipids. J Lipid Res 1998. [DOI: 10.1016/s0022-2275(20)33886-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Braschi S, Masson D, Rostoker G, Florentin E, Athias A, Martin C, Jacotot B, Gambert P, Lallemant C, Lagrost L. Role of lipoprotein-bound NEFAs in enhancing the specific activity of plasma CETP in the nephrotic syndrome. Arterioscler Thromb Vasc Biol 1997; 17:2559-67. [PMID: 9409228 DOI: 10.1161/01.atv.17.11.2559] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Plasma cholesteryl ester transfer protein (CETP) activity, evaluated by the transfer of radiolabeled cholesteryl esters from a tracer dose of tritiated HDL to the plasma apolipoprotein B-containing lipoproteins, was significantly higher in patients with untreated idiopathic nephrotic syndrome (n = 15) than in normolipidemic control subjects (n = 22) (81.5 +/- 8.4 versus 43.1 +/- 3.1 micrograms CE.mL-1.h-1, respectively; P < .001). The increased CETP activity in nephrotic plasma was explained by a significant rise in both the CETP mass concentration (3.2 +/- 0.2 versus 2.1 +/- 0.1 mg/L; P < .001), and the specific CETP activity, calculated as the ratio of CETP activity to CETP mass (25.3 +/- 1.7 versus 20.4 +/- 1.6 micrograms CE.mg-1.h-1; P < .05). Elevated CETP activity in nephrotic patients was shown to be associated with a significant decrease in the mean size of LDL (24.4 +/- 0.5 versus 26.3 +/- 0.5 nm; P < .0001) as well as in the relative abundance of HDL2a (29.6 +/- 1.6% versus 34.8 +/- 1.1%; P < .05). The nephrotic syndrome was characterized by a significant increase in the relative proportion of lipoprotein-bound nonesterified fatty acids (NEFAs) (35.4 +/- 7.7% versus 7.6 +/- 3.0% of total; P < .01), leading to a significant increase in the electronegative charge of LDL (-4.3 +/- 0.1 versus -3.9 +/- 0.1 mV; P < .05) and HDL (-11.5 +/- 0.1 versus -11.1 +/- 0.2 mV; P < .05). Compared with native, non-supplemented plasma, removal of lipoprotein-bound NEFAs by addition of fatty acid-poor albumin to total plasma from nephrotic patients or control subjects significantly decreased CETP activity and specific CETP activity. Specific CETP activity no longer differed between nephrotic and control groups after albumin supplementation (19.7 +/- 1.5 versus 17.7 +/- 1.5 micrograms CE.mg-1.h-1; NS). It is concluded that, in addition to elevated CETP mass concentration, lipoprotein-bound NEFAs, by increasing the negative electrostatic charge of nephrotic lipoproteins, can facilitate the CETP-mediated neutral-lipid transfer reaction in total plasma from nephrotic patients.
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Affiliation(s)
- S Braschi
- Service de Médecine V, Hôpital Henri Mondor, Créteil, France
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Subbaiah PV, Liu M, Witt TR. Impaired cholesterol esterification in the plasma in patients with breast cancer. Lipids 1997; 32:157-62. [PMID: 9075205 DOI: 10.1007/s11745-997-0020-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
An important factor which determines the movement of cholesterol in and out of the cells is the free cholesterol (FC)/esterified cholesterol (EC) ratio in the plasma. Although this ratio has been shown to be increased in several types of malignancies in humans as well as experimental animals, it is not known whether such an abnormality is found in breast cancer patients. Furthermore, the reasons for such an increase in cancer patients are unknown. We studied the plasma lipid composition and the activity of lecithin-cholesterol acyltransferase (LCAT), the enzyme responsible for the formation of most of EC in human plasma, in 12 women with breast cancer and 9 age-matched control women. The plasma EC concentration was found to be significantly decreased in cancer patients, whereas the FC concentration was unchanged, leading to increased FC/EC ratios (P < 0.05). The concentration of phosphatidylcholine, the acyl donor in the LCAT reaction, was decreased significantly, whereas all other phospholipids were unaffected. The cholesterol-esterifying activity of LCAT was significantly lower in cancer patients, whether assayed with endogenous substrates (P < 0.05), or with an exogenous substrate (P < 0.01). However, another function of the enzyme, namely the lysolecithin acyltransferase activity, was increased (P < 0.02), indicating that the enzyme concentration in plasma may not be decreased. These results show that the increase in the FC/EC ratio in cancer patients is due to an impaired esterification of cholesterol by plasma LCAT, probably due to an alteration in the composition of substrate lipoproteins, or the presence of an inhibitory factor.
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Affiliation(s)
- P V Subbaiah
- Department of Internal Medicine, Rush Medical College, Chicago, Illinois 60612, USA
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Braschi S, Lagrost L, Florentin E, Martin C, Athias A, Gambert P, Krempf M, Lallemant C, Jacotot B. Increased cholesteryl ester transfer activity in plasma from analbuminemic patients. Arterioscler Thromb Vasc Biol 1996; 16:441-9. [PMID: 8630671 DOI: 10.1161/01.atv.16.3.441] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Hypercholesterolemia associated with analbuminemia, an inherited disease manifesting low plasma albumin concentration, is characterized by enhanced LDL cholesterol levels and reduced HDL cholesterol levels. In addition, compared with normal counterparts, the esterified cholesterol:triglyceride ratio tends to be higher in analbuminemic apoB-containing lipoproteins and lower in analbuminemic HDL. The aim of the present study was to investigate the mechanism that may account for the association of a hypoalbuminemic state with alterations in the concentration and composition of plasma lipoprotein fractions. To this end, endogenous cholesterol esterification activity, phospholipid transfer activity, and cholesteryl ester transfer activity were measured in total plasma from three analbuminemic patients and five control subjects. Whereas endogenous cholesterol esterification and phospholipid transfer rates were not significantly affected in analbuminemia, the transfer of radiolabeled cholesteryl esters from HDL toward apoB-containing lipoproteins was constantly higher in analbuminemic plasmas than in normal control plasma (473.6+/-107.3% x h(-1) x mL(-1) versus 227.5+/-84.0% x h(-1) x mL(-1), respectively; P=.036). The rise in cholesteryl ester transfer protein (CETP) activity in analbuminemic plasma was due to a significant increase in the transfer of radiolabeled cholesteryl esters toward LDL but not toward the triglyceride-rich lipoproteins. The CETP mass was higher in analbuminemic patients than in control subjects, but the difference did not reach the significance level (5.18+/-0.82 mg/L versus 3.13+/-1.19 mg/L respectively; P=.07). Since abnormally elevated nonesterified fatty acid (NEFA) levels were shown to be associated with analbuminemic lipoproteins, mostly LDL, the direct role of lipoprotein-bound NEFA in enhancing CETP activity was suspected. In support of this view, supplementation of total plasmas with fatty acid-poor albumin was shown to reduce CETP activity to a significantly greater extent in analbuminemic plasmas than in normal control plasma. It is concluded that hyperlipidemia associated with the hypoalbuminemic state can relate, at least in part, to the combined effect of CETP and NEFA in promoting the transfer of cholesteryl esters from the antiatherogenic HDL toward the proatherogenic apoB-containing lipoproteins.
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Affiliation(s)
- S Braschi
- Service de Médecine V, Hôpital Henri Mondor, Créteil, France
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Murata Y, Maeda E, Yoshino G, Kasuga M. Cloning of rabbit LCAT cDNA: increase in LCAT mRNA abundance in the liver of cholesterol-fed rabbits. J Lipid Res 1996. [DOI: 10.1016/s0022-2275(20)39144-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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18
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Specificity of lecithin:cholesterol acyltransferase and atherogenic risk: comparative studies on the plasma composition and in vitro synthesis of cholesteryl esters in 14 vertebrate species. J Lipid Res 1995. [DOI: 10.1016/s0022-2275(20)41500-7] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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