Fenofibrate induces HDL-associated PAF-AH but attenuates enzyme activity associated with apoB-containing lipoproteins
2003; Elsevier BV; Volume: 44; Issue: 5 Linguagem: Inglês
10.1194/jlr.m200452-jlr200
ISSN1539-7262
AutoresVasilis Tsimihodimos, Anna I. Kakafika, Afroditi P. Tambaki, Eleni Bairaktari, M. John Chapman, Moses Elisaf, Alexandros D. Tselepis,
Tópico(s)Hibiscus Plant Research Studies
ResumoHuman plasma platelet-activating factor acetylhydrolase (PAF-AH) is an enzyme associated mainly with the apolipoprotein B (apoB)-containing lipoproteins and primarily with LDL. A small proportion of enzymatic activity is also associated with HDL. Plasma paraoxonase 1 (PON1) is an esterase exclusively associated with HDL. The effect of fenofibrate on PAF-AH and PON1 activities in patients with dyslipidemias of Types IIA, IIB, and IV were studied. Fenofibrate reduced plasma PAF-AH activity in all patient groups. In Type IIA patients, this reduction was mainly due to a fall in enzyme activity associated with the dense LDL subspecies, whereas in Type IIB and Type IV patients, it was due to the decrease in PAF-AH activity associated with both the VLDL+IDL and dense LDL subspecies. Drug therapy in Type IIB and Type IV patients significantly increased the HDL-associated PAF-AH activity due to the increase in enzyme activity associated with the HDL-3c subfraction. Fenofibrate did not affect serum PON1 activities toward paraoxon and phenylacetate in either patient group.The fenofibrate-induced elevation of HDL-associated PAF-AH activity in dyslipidemic patients of Type IIB and Type IV, as well as the reduction in enzyme activity associated with atherogenic apoB-containing lipoproteins in all patient groups, may represent a new and important antiatherogenic effect of this potent lipid-modulating agent. Human plasma platelet-activating factor acetylhydrolase (PAF-AH) is an enzyme associated mainly with the apolipoprotein B (apoB)-containing lipoproteins and primarily with LDL. A small proportion of enzymatic activity is also associated with HDL. Plasma paraoxonase 1 (PON1) is an esterase exclusively associated with HDL. The effect of fenofibrate on PAF-AH and PON1 activities in patients with dyslipidemias of Types IIA, IIB, and IV were studied. Fenofibrate reduced plasma PAF-AH activity in all patient groups. In Type IIA patients, this reduction was mainly due to a fall in enzyme activity associated with the dense LDL subspecies, whereas in Type IIB and Type IV patients, it was due to the decrease in PAF-AH activity associated with both the VLDL+IDL and dense LDL subspecies. Drug therapy in Type IIB and Type IV patients significantly increased the HDL-associated PAF-AH activity due to the increase in enzyme activity associated with the HDL-3c subfraction. Fenofibrate did not affect serum PON1 activities toward paraoxon and phenylacetate in either patient group. The fenofibrate-induced elevation of HDL-associated PAF-AH activity in dyslipidemic patients of Type IIB and Type IV, as well as the reduction in enzyme activity associated with atherogenic apoB-containing lipoproteins in all patient groups, may represent a new and important antiatherogenic effect of this potent lipid-modulating agent. Platelet-activating factor (PAF) is a potent proinflammatory lipid mediator that is implicated in atherogenesis (1Evangelou A.M. Platelet-activating factor (PAF): implications for coronary heart and vascular diseases.Prostaglandins Leukot. Essent. Fatty Acids. 1994; 50: 1-28Google Scholar). In plasma, PAF is hydrolyzed and inactivated by PAF-acetylhydrolase (PAF-AH) (EC 3.1.1.47), an enzyme associated mainly with the apolipoprotein B (apoB)-containing lipoproteins and primarily with LDL (2Tselepis A.D. Chapman M.J. Inflammation, bioactive lipids and atherosclerosis: potential roles of a lipoprotein-associated phospholipase A2, platelet activating factor-acetylhydrolase.Atherosclerosis. 2002; 3: 57-68Google Scholar). A small proportion of circulating enzyme activity is also associated with HDL (2Tselepis A.D. Chapman M.J. Inflammation, bioactive lipids and atherosclerosis: potential roles of a lipoprotein-associated phospholipase A2, platelet activating factor-acetylhydrolase.Atherosclerosis. 2002; 3: 57-68Google Scholar, 3McCall M.R. LaBelle M. Forte T.M. Krauss R.M. Takanami Y. Tribble D.L. Dissociable and nondissociable forms of platelet-activating factor acetylhydrolase in human plasma LDL: implications for LDL oxidative susceptibility.Biochim. Biophys. Acta. 1999; 1437: 23-36Google Scholar). PAF-AH exhibits a α/β hydrolase conformation (4Tjoelker L.W. Eberhardt C. Unger J. Trong H.L. Zimmerman G.A. McIntyre T.M. Stafforini D.M. Prescott S.M. Gray P.W. Plasma platelet-activating factor acetylhydrolase is a secreted phospholipase A2 with a catalytic triad.J. Biol. Chem. 1995; 270: 25481-25487Google Scholar) and has broad substrate specificity toward lipid esters containing short acyl chains (5Min J.H. Wilder C. Aoki J. Arai H. Inoue K. Paul L. Gelb M.H. Platelet-activating factor acetylhydrolases: Broad substrate specificity and lipoprotein binding does not modulate the catalytic properties of the plasma enzyme.Biochemistry. 2001; 40: 4539-4549Google Scholar). Thus, PAF-AH can hydrolyze short-chain diacylglycerols, triacylglycerols, and acetylated alkanols, but also displays phospholipase A1 and A2 activities, as well as transacetylase activity (5Min J.H. Wilder C. Aoki J. Arai H. Inoue K. Paul L. Gelb M.H. Platelet-activating factor acetylhydrolases: Broad substrate specificity and lipoprotein binding does not modulate the catalytic properties of the plasma enzyme.Biochemistry. 2001; 40: 4539-4549Google Scholar, 6Tsoukatos D.C. Liapikos T.A. Tselepis A.D. Chapman M.J. Ninio E. Platelet-activating factor acetylhydrolase and transacetylase activities in human plasma low-density lipoprotein.Biochem. J. 2001; 357: 457-464Google Scholar). Among them, the Ca2+-independent phospholipase A2 activity of PAF-AH has been principally studied, and thus this enzyme has been denoted as lipoprotein-associated phospholipase A2 (7MacPhee C.H. Moores K.E. Boyd H.F. Dhanak D. Ife R.J. Leach C.A. Leake D.S. Milliner K.J. Patterson R.A. Suckling K.E. Tew D.G. Hickey D.M. Lipoprotein-associated phospholipase A2, platelet-activating factor acetylhydrolase, generates two bioactive products during the oxidation of low-density lipoprotein: use of a novel inhibitor.Biochem. J. 1999; 338: 479-487Google Scholar). Indeed, PAF-AH has marked preference for phospholipids with short-chain moieties at the sn-2 position and, with the exception of PAF, can hydrolyze proinflammatory and proatherogenic oxidized phospholipids produced by peroxidation of phosphatidylcholines containing an sn-2 polyunsaturated fatty acyl residue (8Stremler K.E. Stafforini D.M. Prescott S.M. McIntyre T.M. Human plasma platelet-activating factor acetylhydrolase. Oxidatively fragmented phospholipids as substrates.J. Biol. Chem. 1991; 266: 11095-11103Google Scholar). The role of PAF-AH in atherosclerotic disease is controversial. Data from the West of Scotland Coronary Prevention Study (Scotland, 1989–1995) trial suggest that plasma levels of PAF-AH mass, which mainly reflects the LDL-associated enzyme, represent an independent risk factor for coronary artery disease (9Packard C.J. O'Reilly D.S. Caslake M.J. McMahon A.D. Ford I. Cooney J. Macphee C.H. Suckling K.E. Krishna M. Wilkinson F.E. Rumley A. Lowe G.D. Lipoprotein-associated phospholipase A2 as an independent predictor of coronary heart disease. West of Scotland and Coronary Prevention Study Group.N. Engl. J. Med. 2000; 343: 1148-1155Google Scholar). In contrast, recent findings in the Women's Health Study (US, 1992 to present) suggest that plasma PAF-AH is not a strong predictor of cardiovascular risk in apparently healthy middle-aged women over a mean follow-up of 3 years (10Blake G.J. Dada N. Fox J.C. Manson J.E. Ridker P.M. A prospective evaluation of lipoprotein-associated phospholipase A(2) levels and the risk of future cardiovascular events in women.J. Am. Coll. Cardiol. 2001; 38: 1302-1306Google Scholar). Nonetheless, loss of plasma PAF-AH activity due to a G994→T mutation in the PAF-AH gene may constitute a genetic determinant of atherosclerotic disease in the Japanese population (11Yamada Y. Ichihara S. Fujimura T. Yokota M. Identification of the G994→T missense in exon 9 of the plasma platelet-activating factor acetylhydrolase gene as an independent risk factor for coronary artery disease in Japanese men.Metabolism. 1998; 47: 177-181Google Scholar). Despite conflicting observations concerning the potential relevance of total plasma- and LDL-associated PAF-AH to atherosclerotic disease, several lines of evidence suggest that HDL-associated PAF-AH activity, although present at low levels, may contribute to the antiatherogenic effects of this lipoprotein (12Mertens A. Holvoet P. Oxidized LDL and HDL: antagonists in atherothrombosis.FASEB J. 2001; 15: 2073-2084Google Scholar). Thus, adenoviral transfer of human plasma PAF-AH gene in apoE−/− mice significantly reduced macrophage adhesion and homing (13Theilmeier G. De Geest B. Van Veldhoven P.P. Stengel D. Michiels C. Lox M. Landeloos M. Chapman M.J. Ninio E. Collen D. Himpens B. Holvoet P. HDL-associated PAF-AH reduces endothelial adhesiveness in apoE−/− mice.FASEB J. 2000; 14: 2032-2039Google Scholar), and inhibited injury-induced neointima formation and spontaneous atherosclerosis (14Quarck R. De Geest B. Stengel D. Mertens A. Lox M. Theilmeier G. Michiels C. Raes M. Bult H. Collen D. Van Veldhoven P. Ninio E. Holvoet P. Adenovirus-mediated gene transfer of human platelet-activating factor-acetylhydrolase prevents injury-induced neointima formation and reduces spontaneous atherosclerosis in apolipoprotein E-deficient mice.Circulation. 2001; 103: 2495-2500Google Scholar). A contributory role in the HDL-associated PAF-AH activity may be played by paraoxonase 1 (PON1), an enzyme that is present in plasma exclusively associated with this lipoprotein (15Mackness M.I. Mackness B. Durrington P.N. Connely P.W. Hegele R.A. Paraoxonase: biochemistry, genetics and relationship to plasma lipoproteins.Curr. Opin. Lipidol. 1996; 7: 69-76Google Scholar). Indeed, PON1 exhibits PAF-AH-like catalytic activity in addition to its paraoxon and phenyl acetate hydrolytic activities (16Rodrigo L. Mackness B. Durrington P.N. Hernandez A. Mackness M.I. Hydrolysis of platelet-activating factor by human serum paraoxonase.Biochem. J. 2001; 354: 1-7Google Scholar). We recently demonstrated that patients with primary hypercholesterolemia exhibit an alteration in the relative distribution of PAF-AH between LDL and HDL particles, resulting in a decrease in the ratio of HDL-PAF-AH to plasma-PAF-AH [or to LDL-cholesterol (LDL-C)] levels, which is proportional to the severity of the hypercholesterolemia (17Tsimihodimos V. Karabina S.A. Tambaki A.P. Bairaktari E. Miltiadous G. Goudevenos J.A. Cariolou M.A. Chapman M.J. Tselepis A.D. Elisaf M. Altered distribution of platelet activating factor-acetylhydrolase activity between LDL and HDL as a function of the severity of hypercholesterolemia.J. Lipid Res. 2002; 43: 256-263Google Scholar). Furthermore, atorvastatin therapy partially restored such an altered PAF-AH distribution by reducing both plasma LDL-C levels and LDL-associated PAF-AH activity, although this statin did not affect plasma levels of HDL-C or HDL-associated PAF-AH activity (18Tsimihodimos V. Karabina S.A. Tambaki A.P. Bairaktari E. Goudevenos J.A. Chapman M.J. Elisaf M. Tselepis A.D. Atorvastatin preferentially reduces LDL-associated platelet activating factor acetylhydrolase activity in dyslipidemias of type IIA and IIB.Arterioscler. Thromb. Vasc. Biol. 2002; 22: 306-311Google Scholar). Considered together, the above findings support the convention that HDL-associated PAF-AH may play an antiatherogenic role. It remains indeterminate, however, as to whether drugs that modify plasma levels of HDL could influence PAF-AH activity associated with this lipoprotein. Fibrates are a family of hypolipidemic drugs that may reduce plasma LDL-C levels but equally induce elevation in HDL-C levels (19Fruchart J.C. Staels B. Duriez P. PPARs, metabolic disease and atherosclerosis.Pharmacol. Res. 2001; 44: 345-352Google Scholar). We therefore undertook the present study to investigate the effect of a potent fibrate, fenofibrate, on HDL-associated PAF-AH relative to its effects on enzyme activity associated with apoB-containing lipoproteins in atherogenic dyslipidemias of Types IIA, IIB, and IV. This question is of special interest as this fibrate induces a shift in LDL particle profile from small, dense LDL to large, buoyant particles; indeed, PAF-AH is primarily associated with dense LDL particles in plasma (20Tselepis A.D. Dentan C. Karabina S.A. Chapman M.J. Ninio E. PAF-degrading acetylhydrolase is preferentially associated with dense LDL and VHDL-1 in human plasma. Catalytic characteristics and relation to the monocyte-derived enzyme.Arterioscler. Thromb. Vasc. Biol. 1995; 15: 1764-1773Google Scholar). Unrelated hyperlipidemic patients (n = 71) attending the Outpatient Lipid Clinic of the University Hospital of Ioannina participated in the study. Secondary causes of dyslipidemia (hypothyroidism, diabetes mellitus, liver or renal diseases, alcoholism, etc.) were excluded by personal history, physical examination, and appropriate laboratory tests. None of the study participants was obese (BMI > 30 kg/m2), hypertensive (blood pressure > 140/90 mmHg on repeated measurements), or was taking medications known to interfere with lipid metabolism. No patient had any clinical or ECG evidence of cardiovascular disease. After the initial screening, patients gave informed consent and were advised to follow the National Cholesterol Education Program Step 1 diet for 3 months. At the end of this period, a complete laboratory baseline analysis was performed. According to their lipid levels, patients were divided into the following groups: 1) primary hypercholesterolemia (Type IIA dyslipidemia), consisting of 18 patients (mean age 54.2 ± 10.8 years, BMI 25.8 ± 3.9 kg/m2, seven active smokers, eight males), exhibiting plasma LDL-C levels >160 mg/dl. 2) Combined hyperlipidemia (Type IIB dyslipidemia), consisting of 23 patients (mean age 51.5 ± 11.4 years, BMI 26.6 ± 4.5 kg/m2, 10 active smokers, 14 males), exhibiting plasma LDL-C levels >160 mg/dl and triglyceride levels >200 mg/dl. 3) Primary hypertriglyceridemia (Type IV dyslipidemia), consisting of 30 patients (mean age 51.1 ± 11.7 years, BMI 28.1 ± 4.4 kg/m2, 12 active smokers, 13 males), exhibiting plasma triglyceride levels >200 mg/dl, and LDL-C levels <160 mg/dl. Patients with familial hypercholesterolemia were excluded by appropriate genetic analysis (17Tsimihodimos V. Karabina S.A. Tambaki A.P. Bairaktari E. Miltiadous G. Goudevenos J.A. Cariolou M.A. Chapman M.J. Tselepis A.D. Elisaf M. Altered distribution of platelet activating factor-acetylhydrolase activity between LDL and HDL as a function of the severity of hypercholesterolemia.J. Lipid Res. 2002; 43: 256-263Google Scholar). No difference in the above biological and clinical characteristics was observed among patient groups. Micronized fenofibrate (200 mg at bedtime) was initiated in all patients; after 3 months of active treatment, a second blood analysis was performed. Compliance with treatment and diet was assessed as described previously (18Tsimihodimos V. Karabina S.A. Tambaki A.P. Bairaktari E. Goudevenos J.A. Chapman M.J. Elisaf M. Tselepis A.D. Atorvastatin preferentially reduces LDL-associated platelet activating factor acetylhydrolase activity in dyslipidemias of type IIA and IIB.Arterioscler. Thromb. Vasc. Biol. 2002; 22: 306-311Google Scholar). Ninety-eight age- and sex-matched apparently healthy normolipidemic subjects were selected from individuals receiving a medical check-up at our hospital and served as controls. The study was approved by the Ethics Committee of the University Hospital of Ioannina. Lipoproteins were fractionated by isopycnic density gradient ultracentrifugation as previously described (20Tselepis A.D. Dentan C. Karabina S.A. Chapman M.J. Ninio E. PAF-degrading acetylhydrolase is preferentially associated with dense LDL and VHDL-1 in human plasma. Catalytic characteristics and relation to the monocyte-derived enzyme.Arterioscler. Thromb. Vasc. Biol. 1995; 15: 1764-1773Google Scholar). Total plasma and the HDL-containing supernatant, after treatment of plasma with magnesium chloride/dextran sulfate (to precipitate all apoB-containing lipoproteins), were separately subjected to ultracentrifugation. After ultracentrifugation, 30 fractions of 0.4 ml each were collected and analyzed for their protein content. When plasma was used, equal volumes of gradient fractions 1 to 12 were pooled to constitute the following apoB-containing subfractions: fractions 1 and 2 (VLDL+IDL; d < 1.019 g/ml); 3 and 4 (LDL-1; d = 1.019–1.023 g/ml); 5 and 6 (LDL-2; d = 1.023–1.029 g/ml); 7 and 8 (LDL-3; d = 1.029–1.039 g/ml); 9 and 10 (LDL-4; d = 1.039–1.050 g/ml); 11 and 12 (LDL-5; d = 1.050–1.063 g/ml). When the HDL-containing supernatant was used, equal volumes of gradient fractions 13 to 23 were pooled to constitute the following apoA-I-containing subfractions: fractions 13 to 15 (HDL-2b; d = 1.063–1.091 g/ml); 16 and 17 (HDL-2a; d = 1.091–1.100 g/ml); 18 and 19 (HDL-3a; d = 1.100–1.133 g/ml); 20 and 21 (HDL-3b; d = 1.133–1.156 g/ml); 22 and 23 (HDL-3c; d = 1.156–1.179 g/ml) (21Tselepis A.D. Karabina S.A. Stengel D. Piedagnel R. Chapman M.J. Ninio E. N-linked glycosylation of macrophage-derived PAF-AH is a major determinant of enzyme association with plasma HDL.J. Lipid Res. 2001; 42: 1645-1654Google Scholar). It must be noted that PON1 activities were also determined in HDL subfractions. In these experiments, serum was used instead of plasma. Peripheral blood monocytes from patients (before the initiation of therapy with fenofibrate) as well as from healthy volunteers were isolated and cultured as previously described (21Tselepis A.D. Karabina S.A. Stengel D. Piedagnel R. Chapman M.J. Ninio E. N-linked glycosylation of macrophage-derived PAF-AH is a major determinant of enzyme association with plasma HDL.J. Lipid Res. 2001; 42: 1645-1654Google Scholar). After 6 days of culture, the cells were treated either with fenofibrate or with fenofibric acid (dissolved in DMSO) at final concentrations ranging from 10 μM to 300 μM. Treatments were performed for 24 h and 48 h in RPMI medium containing 10% human serum in which endogenous PAF-AH was completely and irreversibly inactivated by preincubation with 1 mM Pefabloc for 30 min. After treatment, PAF-AH activity was determined in supernatants and cell lysates prepared as previously described (18Tsimihodimos V. Karabina S.A. Tambaki A.P. Bairaktari E. Goudevenos J.A. Chapman M.J. Elisaf M. Tselepis A.D. Atorvastatin preferentially reduces LDL-associated platelet activating factor acetylhydrolase activity in dyslipidemias of type IIA and IIB.Arterioscler. Thromb. Vasc. Biol. 2002; 22: 306-311Google Scholar). PAF-AH activity in plasma, lipoprotein subfractions, cell lysates, and supernatants was measured by the trichloroacetic acid precipitation procedure using [3H]PAF (100 mM final concentration) as a substrate, whereas PON1 activities in serum and lipoprotein subfractions were determined using paraoxon and phenyl acetate as substrates (18Tsimihodimos V. Karabina S.A. Tambaki A.P. Bairaktari E. Goudevenos J.A. Chapman M.J. Elisaf M. Tselepis A.D. Atorvastatin preferentially reduces LDL-associated platelet activating factor acetylhydrolase activity in dyslipidemias of type IIA and IIB.Arterioscler. Thromb. Vasc. Biol. 2002; 22: 306-311Google Scholar). Serum total cholesterol, triglycerides, HDL-C, apoB, apoA-I, and apoE were determined as previously described (18Tsimihodimos V. Karabina S.A. Tambaki A.P. Bairaktari E. Goudevenos J.A. Chapman M.J. Elisaf M. Tselepis A.D. Atorvastatin preferentially reduces LDL-associated platelet activating factor acetylhydrolase activity in dyslipidemias of type IIA and IIB.Arterioscler. Thromb. Vasc. Biol. 2002; 22: 306-311Google Scholar). Serum LDL-C was calculated using the Friedewald formula (provided that triglyceride levels were lower than 350 mg/dl. In 15 patients with high triglyceride values, LDL-C was not determined). The total cholesterol, triglyceride, and phospholipid content in each HDL subfraction were measured enzymatically using the Bio-Merieux kit (20Tselepis A.D. Dentan C. Karabina S.A. Chapman M.J. Ninio E. PAF-degrading acetylhydrolase is preferentially associated with dense LDL and VHDL-1 in human plasma. Catalytic characteristics and relation to the monocyte-derived enzyme.Arterioscler. Thromb. Vasc. Biol. 1995; 15: 1764-1773Google Scholar), whereas the protein content of the lipoprotein subfractions was measured by the BCA method (Pierce). The lipoprotein mass of each subfraction was calculated as the sum of the mass of the individual lipid and protein components (20Tselepis A.D. Dentan C. Karabina S.A. Chapman M.J. Ninio E. PAF-degrading acetylhydrolase is preferentially associated with dense LDL and VHDL-1 in human plasma. Catalytic characteristics and relation to the monocyte-derived enzyme.Arterioscler. Thromb. Vasc. Biol. 1995; 15: 1764-1773Google Scholar). Data were expressed as mean ± SD. Statistical analysis was performed using paired Student's t-test for comparisons between baseline and posttreatment values, while one-way ANOVA followed by the LSD test was used for comparisons between individual groups. Correlations between PAF-AH activity and lipid parameters were estimated using linear regression analysis. Fenofibrate significantly decreased serum total cholesterol and triglyceride levels as well as serum apoE levels in all patient groups (Table 1). A significant reduction in serum apoB levels in all groups was also observed, whereas LDL-C levels were reduced in Type IIA and IIB patients, but not in Type IV patients; this finding suggests that the decrease in serum total cholesterol levels in Type IV patients was mainly due to reduction in VLDL-C levels. Most importantly, fenofibrate induced significant elevation in both serum HDL-C and apoA-I levels in Type IIB and IV dyslipidemic patients, but not in the Type IIA patient group (Table 1).TABLE 1Effect of fenofibrate on plasma lipid and lipoprotein levels in Type IIA, Type IIB, and Type IV dyslipidemiasType IIA (n = 18)Type IIB (n = 23)Type IV (n = 30)BeforeAfterChangePBeforeAfterChangePBeforeAfterChangeP%%%Cholesterol271.4 ± 32.6217.8 ± 36.3−19.40.000296.3 ± 31.9237.7 ± 34.5−19.40.000237.1 ± 38.8219.6 ± 36.7−6.7<0.01Triglycerides151.1 ± 34.6116.1 ± 41.1−22.80.000318.3 ± 92.7177.5 ± 70.6−43.60.000395.8 ± 179.3219.7 ± 104.7−41.70.000LDL-cholesterol193.7 ± 31.8149.9 ± 34.3−22.20.000193.5 ± 27.8157.4 ± 32.3−18.10.000127.8 ± 28.5136.3 ± 34.6+7.9NSHDL-cholesterol47.5 ± 12.846.6 ± 11.7−5.0NS39.2 ± 5.444.8 ± 8.2+14.6<0.00132.5 ± 5.338.8 ± 10.6+22.1<0.01ApoB139.6 ± 27.0107 ± 21.7−22.40.000156.3 ± 20.0126.6 ± 23.2−19.00.000127.1 ± 19.3117 ± 26.9−8.1<0.05ApoAI142.3 ± 26.2137.2 ± 19.3−1.7NS144.5 ± 18.0159.4 ± 24.2+10.4<0.005127.3 ± 20.7139.3 ± 21.6+11.8<0.05ApoE4.0 ± 0.93.3 ± 0.9−15.9<0.056.1 ± 2.63.8 ± 1.0−31.50.0006.4 ± 2.64.6 ± 1.6−24.20.000Values represent the mean ± SD and are expressed as mg/dl. Paired Student's t-test was used for comparisons between baseline and posttreatment values. A P value < 0.05 was considered significant. Open table in a new tab Values represent the mean ± SD and are expressed as mg/dl. Paired Student's t-test was used for comparisons between baseline and posttreatment values. A P value < 0.05 was considered significant. Total plasma PAF-AH activity at baseline was higher in all patient groups as compared with controls. Furthermore, baseline values of enzyme activity in dyslipidemic Type IIB patients were significantly higher compared either to those in Type IIA or to Type IV patients (Table 2). HDL-associated PAF-AH activity (HDL-PAF-AH) in dyslipidemic Type IIB and Type IV patients was significantly lower compared either to normolipidemic controls or to Type IIA patients. Furthermore, Type IV patients exhibited significantly lower HDL-PAF-AH activity as compared with Type IIB patients (Table 2). In all patient groups, HDL-PAF-AH activity was negatively correlated to plasma triglyceride levels (r = −0.29, P < 0.02). It is important to note that the ratio of HDL-PAF-AH to LDL-C levels before treatment was significantly lower in all patient groups compared with controls, whereas no difference in this ratio was observed among the patient groups (Table 2).TABLE 2Effect of fenofibrate on plasma platelet activating factor acetylhydrolase and plasma paraoxonase 1 activities in Type IIA, Type IIB, and Type IV dyslipidemiasControlsType IIAType IIBType IVBeforeAfterBeforeAfterBeforeAfterPlasma PAF-AH activity, (nmol/ml/min)48.8 ± 13.363.63 ± 23.8dP < 0.001 compared with controls.45.9 ± 12.52bP < 0.001 compared with baseline values.78.1 ± 19.5dP < 0.001 compared with controls.,eP < 0.05 compared with Type IIA at the same time (baseline or posttreatment).56.7 ± 18.4bP < 0.001 compared with baseline values.,cP < 0.05 compared with controls.,eP < 0.05 compared with Type IIA at the same time (baseline or posttreatment).66.13 ± 25.16dP < 0.001 compared with controls.,gP < 0.05 compared with Type IIB (baseline or posttreatment).51.36 ± 21.5bP < 0.001 compared with baseline values.HDL-PAF-AH activity, (nmol/ml/min)3.3 ± 1.33.22 ± 0.893.13 ± 0.922.37 ± 0.79dP < 0.001 compared with controls.,eP < 0.05 compared with Type IIA at the same time (baseline or posttreatment).2.71 ± 0.76aP < 0.05 compared with baseline values.,cP < 0.05 compared with controls.1.78 ± 0.43dP < 0.001 compared with controls.,fP < 0.001 compared with Type IIA at the same time (baseline or posttreatment).,gP < 0.05 compared with Type IIB (baseline or posttreatment).2.48 ± 0.7bP < 0.001 compared with baseline values.,dP < 0.001 compared with controls.Ratio HDL PAF-AH/ LDL-C (nmol/mg/min)2.6 ± 1.51.4 ± 0.6cP < 0.05 compared with controls.2.1 ± 0.8aP < 0.05 compared with baseline values.,cP < 0.05 compared with controls.1.2 ± 0.4cP < 0.05 compared with controls.1.8 ± 0.8bP < 0.001 compared with baseline values.,cP < 0.05 compared with controls.1.4 ± 0.5dP < 0.001 compared with controls.2.0 ± 0.7bP < 0.001 compared with baseline values.,cP < 0.05 compared with controls.PON1 activity (paraoxon) (U/l)75.1 ± 45.748.6 ± 28.453 ± 32.870.8 ± 40.669.2 ± 41.367.4 ± 58.974 ± 68.3PON1 activity (phenylacetate) (U/ml)63.2 ± 20.672.3 ± 41.961.7 ± 3156.6 ± 22.758.2 ± 22.871.3 ± 3674.3 ± 38PAF-AH, platelet-activating factor-acetylhydrolase; PON1, paraoxonase 1. Values represent the mean ± SD. Paired Student's t-test was used for comparisons between baseline and posttreatment values while one-way ANOVA followed by LSD test was used for comparisons between individual groups. A P value < 0.05 was considered to be significant.a P < 0.05 compared with baseline values.b P < 0.001 compared with baseline values.c P < 0.05 compared with controls.d P < 0.001 compared with controls.e P < 0.05 compared with Type IIA at the same time (baseline or posttreatment).f P < 0.001 compared with Type IIA at the same time (baseline or posttreatment).g P < 0.05 compared with Type IIB (baseline or posttreatment). Open table in a new tab PAF-AH, platelet-activating factor-acetylhydrolase; PON1, paraoxonase 1. Values represent the mean ± SD. Paired Student's t-test was used for comparisons between baseline and posttreatment values while one-way ANOVA followed by LSD test was used for comparisons between individual groups. A P value < 0.05 was considered to be significant. Fenofibrate treatment led to a reduction in total plasma PAF-AH activity in all patient groups. Enzyme activity in Type IIA and Type IV patients was decreased by 28% and 22%, respectively, to reach control values. A decrease (27%) in enzyme activity was also observed in Type IIB patients, although it remained significantly elevated as compared with controls, even after fenofibrate therapy (Table 2). The reduction in plasma PAF-AH activity in Type IIA and Type IIB patients, but not in Type IV patients, was positively correlated with a reduction in LDL-C levels (r = 0.45, P < 0.005 for Type IIA and r = 0.53, P < 0.01 for Type IIB). In contrast, the reduction in enzyme activity in Type IV patients was positively correlated with reduction in plasma apoE levels (r = 0.45, P < 0.05). Importantly, fenofibrate treatment significantly increased HDL-PAF-AH in Type IIB and Type IV patients, although posttreatment values remained lower than levels in controls. By contrast, no change was observed in HDL-PAF-AH in Type IIA patients after fenofibrate administration (Table 2). Furthermore, the ratio of HDL-PAF-AH to LDL-C levels significantly increased in all patient groups after fenofibrate treatment (50% in Type IIA and Type IIB, and 43% in Type IV), although it still remained lower as compared with the control group (Table 2). No difference was observed in baseline values of serum PON1 activity toward paraoxon in any of the groups studied. Equally, no difference was found in PON1 activity toward phenyl acetate between Type IIA or Type IV dyslipidemic patients and controls, whereas Type IIB patients exhibited lower enzyme activity compared with controls (although it did not reach statistical significance). Fenofibrate therapy did not affect enzyme activity in any patient group (Table 2). To further investigate the effect of fenofibrate on the PAF-AH activity associated with apoB- and apoA-I-containing plasma lipoprotein subspecies, we fractionated plasma lipoproteins before and after fenofibrate therapy. To study the effect of fenofibrate on enzyme activity associated with apoB-lipoprotein subspecies, total plasma was subjected to ultracentrifugation. As previously reported, a proportion of LDL-bound PAF-AH dissociates and is redistributed to HDL during ultracentrifugation of total plasma (3McCall M.R. LaBelle M. Forte T.M. Krauss R.M. Takanami Y. Tribble D.L. Di
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