Modulation of lipid metabolism with the overexpression of NPC1L1 in mouse liver.

Niemann-Pick C1-like 1 protein (NPC1L1), a transporter crucial in intestinal cholesterol absorption, is expressed in human liver but not in murine liver. To elucidate the role of hepatic NPC1L1 on lipid metabolism, we overexpressed NPC1L1 in murine liver utilizing adenovirus-mediated gene transfer. C57BL/6 mice, fed on normal chow with or without ezetimibe, were injected with NPC1L1 adenovirus (L1-mice) or control virus (Null-mice), and lipid analyses were performed five days after the injection. The plasma cholesterol levels increased in L1-mice, and FPLC analyses revealed increased cholesterol contents in large HDL lipoprotein fractions. These fractions, which showed α-mobility on agarose electrophoresis, were rich in apoE and free cholesterol. These lipoprotein changes were partially inhibited by ezetimibe treatment and were not observed in apoE-deficient mice. In addition, plasma and VLDL triglyceride (TG) levels decreased in L1-mice. The expression of microsomal triglyceride transfer protein (MTP) was markedly decreased in L1-mice, accompanied by the reduced protein levels of forkhead box protein O1 (FoxO1). These changes were not observed in mice with increased hepatic de novo cholesterol synthesis. These data demonstrate that cholesterol absorbed through NPC1L1 plays a distinct role in cellular and plasma lipid metabolism, such as the appearance of apoE-rich lipoproteins and the diminished VLDL-TG secretion.

The effect of low-dose pravastatin in metabolic syndrome for primary prevention of cardiovascular disease in Japan: a post hoc analysis of the MEGA study.

The Management of Elevated Cholesterol in the Primary Prevention Group of Adult Japanese (MEGA) Study demonstrated the beneficial effect of low-dose pravastatin treatment (10-20 mg/d) on cardiovascular disease (CVD) in Japanese patients with mild-to-moderate hypercholesterolemia. However, it is not known whether mild lipid modification is effective even for patients at high risk. In this study, we evaluated low-dose pravastatin treatment in patients with metabolic syndrome in the MEGA Study. Metabolic syndrome (MetSyn) was defined according to the modified US National Cholesterol Education Program criteria. There were 72 coronary heart disease (CHD) events and 130 CVD events in 2636 patients with MetSyn, and 70 CHD events and 125 CVD events in 5196 patients without MetSyn (hazard ratios 1.85 and 1.90, respectively). No significant risk reduction in CHD was found in the diet plus pravastatin group compared with the diet group patients with MetSyn (hazard ratio .78, P = .29). On the other hand, there was a significant 36% CVD risk reduction (P = .01) in the diet plus pravastatin group compared with the diet group patients with MetSyn, with a small number needed to treat (45). These results indicate that low-dose pravastatin provides a substantial beneficial effect for the prevention of CVD in Japanese patients with MetSyn without known CVD, a population at proportionally high risk in primary prevention.

Determination of immuno-reactive rabbit apolipoprotein B-48 in serum by ELISA.

Apolipoprotein B-48 (apoB-48) is produced by the small intestine, is associated with chylomicrons, and appears to be a suitable marker for clinical studies of postprandial dynamics of lipoproteins. It is also associated with cardiovascular risk factors. We have developed an assay system to quantify immuno-reactive apoB-48 in rabbit serum or plasma. A microtiter-plate was coated with monoclonal antibody raised against human apoB-48 C-terminal specific decapeptide that has high homology to the rabbit C-terminal sequence. Appropriate ELISA standard curves were obtained using apoB-48 extracted from rabbit serum by immuno-affinity chromatography. No cross-reactivity was found with apoB-100 in western blot analyses. Intra- and inter-assay CVs were less than 3%. Recovery of rabbit apoB-48 spiked in serum was within 93.4-105%. ApoB-48 levels in healthy controls rabbits fed a normal diet were within the range of 0.903-1.09 microg/ml (mean +/- SD: 1.03 +/- 0.084 microg/ml). In healthy animals, the blood apoB-48 level was markedly increased by a high fat diet and in the postprandial state in parallel with serum triglyceride. Ezetimibe, cholesterol absorption inhibitor, given orally to rabbits fed on a high fat diet blocked further increase of blood levels of apoB-48 and triglyceride. This method for measuring apoB-48 using the monoclonal antibody is simple, reliable, and suitable for routine analyses.

Distribution of dolichol in the serum and relationships between serum dolichol levels and various laboratory test values.

We examined the correlations between serum dolichol levels and laboratory test parameters in patients affected by disease, as well as the distribution of dolichol in sera from patients with hyperbetalipoproteinemia and hyperalphalipoproteinemia. Serum dolichol was evaluated by a reverse-phase HPLC method. After centrifugation, the serum dolichol found in healthy controls was mainly associated with medium-sized particles of the high-density lipoprotein (HDL) fraction. For patients with hyperbetalipoproteinemia, serum dolichol was also associated with the medium HDL fractions. However, for hyperalphalipoproteinemia patients the levels of large HDL and serum dolichol were increased, and serum dolichol was mainly associated with the large HDL fraction. On laboratory tests of components, the dolichol level was not correlated with the values for markers of the liver and biliary system, with the values of renal function markers, with creatine kinase activity, amylase activity or uric acid concentration, but was correlated with total cholesterol, HDL-cholesterol and apoA-I concentrations, and with lactate dehydrogenase (LDH) activity. These results suggest that serum dolichol exclusively localized in HDL, and in subpopulation, that in normocholesterolemia or hyperbeta-cholesterolemia is associated with HDL(3), which is small sized and high density HDL, however, that in hyperalphacholesterolemia is associated with HDL(2), which is large sized and lower density HDL.

Detection of apolipoproteins B-48 and B-100 carrying particles in lipoprotein fractions extracted from human aortic atherosclerotic plaques in sudden cardiac death cases.

BACKGROUND: ApoB-48 is a major apolipoprotein secreted by the small intestine and is the main constitutive apolipoprotein in chylomicrons (CM). In the past, presence of apoB-48 in human aortic atherosclerotic plaques has not been detected. METHODS: A newly developed apoB-48 ELISA together with an HPLC fractionation technique, were applied to investigate the presence of apoB-48 (CM) in aortic atherosclerotic plaques. The atherosclerotic plaques were obtained from aortae of sudden cardiac death cases. Total cholesterol, triglycerides (TG), apoB-100 and apoB-48 were measured in the aortic plaques extracts. RESULTS: HPLC analysis of plaques extracts monitored by cholesterol revealed mainly particle sizes of CM and very low density lipoproteins (VLDL) in the d>1.006 fractions. The plaques extracts were monitored by apoB-48 and apoB-100 ELISA. There were no TG peaks in any lipoprotein fraction extracted from the plaques except as free glycerol. ApoB-100 was detected in VLDL particles and in LDL sizes. In contrast, apoB-48 was detected in particles of CM, VLDL and LDL sizes. Further, in postmortem plasma, apo B-48 was detected in particles sizes of HDL or smaller and the Western blot analysis could not show any 250 kDa molecular weight (MW) protein in the plaque extracts, but smaller and broader MW staining were observed at 20-150 kDa. CONCLUSION: Hitherto there has been lack of an appropriate assay to measure apoB-48 in plaques. Our investigations show that apoB-48 is present in atherosclerotic plaques with denatured or degraded structure. This is the first report describing presence of apoB-48 in human atherosclerotic plaques.

Determination of apolipoprotein B-48 in serum by a sandwich ELISA.

BACKGROUND: Apolipoprotein B-48 (apoB-48) is produced by the small intestine, as a part of chylomicrons (CMs), and appears to be a suitable marker for clinical studies of postprandial lipoproteins and related cardiovascular risk factors. We have developed an assay for routine analysis to quantify apoB-48 in serum or plasma. METHODS: A microtiter plate was coated with monoclonal antibody (4C8) raised against apoB-48 C-terminal specific decapeptide. Serum samples were diluted 100-fold with 0.05 mol/l Tris-HCl buffer (with or without 0.1% Triton X-100). Appropriate calibration curves were obtained in the ELISA by using apoB-48 recombinant antigen. RESULTS: No cross-reactivity (<0.001%) was found with apoB-100, as verified by ELISA and Western blot analyses. Intra- and inter-assay CVs were 4.8% and 5.4%, respectively. Recovery of added recombinant apoB-48 in serum was within 94-105%. The assay linearity was intact >5-fold dilution of serum by dilution buffer. ApoB-48 levels in healthy controls (n=18) at fasting were within the range of 2.69-6.56 microg/ml (mean+/-S.D.: 4.60+/-1.54 microg/ml). In healthy subjects, serum apoB-48 concentrations markedly increased in the postprandial state, in parallel with serum triglycerides. CONCLUSION: This method for measuring apoB-48 using the monoclonal antibody 4C8 is simple, reliable and suitable for routine analyses.

Clinical efficacy and safety of rosuvastatin in Japanese patients with heterozygous familial hypercholesterolemia.

Rosuvastatin is a new statin that has been shown to produce substantial dose-dependent reductions in low-density lipoprotein cholesterol (LDL-C) in Western and Japanese hypercholesterolemic patients. Rosuvastatin efficacy and safety were assessed in an open-label, dose-titration trial of 37 Japanese patients with heterozygous familial hypercholesterolemia. After an 8-week dietary lead-in period, patients received rosuvastatin on the following schedule: 10 mg/day during weeks 0-6; 20 mg/day during weeks 6-12, and 40 mg/day for weeks 12-18. Mean percentage reductions from baseline in LDL-C (49.2-56.7%), total cholesterol (39.4-45.4%), and non-high-density lipoprotein cholesterol (non-HDL-C) (46.7-54.3%) were highly significant at each dose (p < 0.0001). Similar significant reductions in triglycerides (18.2-25.0%; p < 0.006) and increases in HDL-C (9.6-13.6%; p < 0.005) were observed. Rosuvastatin was well tolerated. Two patients withdrew from the study because of adverse events unrelated to the study treatment. No patients had clinically significant elevations in liver transaminases. Two patients exhibited a single increase in creatine kinase (one unrelated to study treatment, the other possibly related) with no muscle symptoms. Rosuvastatin produced significant beneficial changes in all lipid parameters in Japanese patients with heterozygous familial hypercholesterolemia and was well tolerated.

Pravastatin at 10 mg/day does not decrease plasma levels of either amyloid-beta (Abeta) 40 or Abeta 42 in humans.

It has been assumed that statins work as a preventative drug for Alzheimer's disease (AD). Although some epidemiological observations raise doubts to the effectiveness of statins for AD, many in vitro and clinical studies insist on the effectiveness of statins decreasing amyloid-beta (Abeta) levels in medium or blood. To explore the effect of pravastatin on Abeta production, we followed the longitudinal plasma levels of both Abeta 40 and Abeta 42 during the allocation of pravastatin in 46 patients with hyperlipidemia. We found no correlation between plasma cholesterol levels or the decreasing values of total cholesterol and those of Abeta 40 or Abeta 42. Patients having Apolipoprotein E4 (ApoE4) had higher low-density lipoprotein levels and lower Abeta 40 levels in plasma, suggesting ApoE4 seems to influence plasma Abeta levels via cholesterol metabolism.

Isoform-dependent cholesterol efflux from macrophages by apolipoprotein E is modulated by cell surface proteoglycans.

OBJECTIVE: Apolipoprotein E (apoE) mediates cellular cholesterol efflux and plays a crucial role in the inhibition of atherogenesis. We investigated whether there is an isoform-specific difference in its function for cholesterol efflux from cholesterol-loaded RAW264.7 cells, a murine macrophage cell line that lacks endogenous apoE expression. METHODS AND RESULTS: When human apoE was expressed in RAW264.7 cells, apoE2 reduced cellular total cholesterol (TC) and esterified cholesterol (EC) levels significantly, whereas apoE3 and apoE4 had no effect. However, treatment of cells with 4-methylumbelliferyl-7-beta-D-xyloside (beta-DX) resulted in all 3 isoforms' reducing cellular TC and EC contents significantly. We also investigated the effect of exogenously derived apoE on cholesterol efflux by utilizing the medium harvested from HeLa cells expressing apoE. ApoE2 and E3 reduced both cellular TC and EC contents significantly, whereas apoE4 did not. However, treatment of the cells with beta-DX resulted in all 3 exogenously derived apoE isoforms' reducing TC and EC contents significantly. The binding ability of apoE to heparan sulfate proteoglycans examined by heparinase I treatment revealed less binding ability of apoE2 compared with that of apoE3 or apoE4. CONCLUSIONS: The present study clarified the differential cellular cholesterol-modulating effect of apoE isoforms in macrophages, which would be due to the difference in their binding to proteoglycans.

Intracellular fatty acid downregulates ob gene expression in 3T3-L1 adipocytes.

The effect of intracellular free fatty acid (FFA) accumulation on ob gene expression in adipocytes was examined. In fully differentiated 3T3-L1 adipocytes, triacsin C, a specific acyl CoA synthetase inhibitor with a K(i) of 8.97 microM, inhibited ob gene expression by 20% at 5 x 10(-5)M. At this concentration, triacsin C induced accumulation of intracellular FFA. Treatment with both chylomicron and triacsin C reduced ob gene expression more than treatment with triacsin C alone. Treatment with 2-bromopalmitate, a poorly metabolizable palmitate analog, reduced ob gene expression by 50% at 10(-4)M, but palmitate at the same concentration had no effect. This is the first demonstration that the ob gene is downregulated by intracellular FFA accumulation, thereby raising the possibility that ob product is regulated in response to lipolysis.