Bezafibrate increases prebeta 1-HDL at the expense of HDL2b in hypertriglyceridemia

Preβ1-high-density lipoprotein binds to TG-rich lipoproteins and its release is impaired in the postprandial state among patients with poorly controlled type 2 diabetes

BackgroundAlthough preβ1-high-density lipoprotein (preβ1-HDL) promotes cholesterol efflux, high fasting preβ1-high-density lipoprotein levels after breakfast are reduced in patients with poorly controlled type 2 diabetes.ObjectiveThis study investigated whether preβ1-high-density lipoprotein binds to triglyceride (TG)-rich lipoproteins (TGRLs) in the postprandial state and is released during lipolysis.MethodsWe measured preβ1-high-density lipoprotein concentrations, lecithin-cholesterol acyltransferase (LCAT) activity, and LCAT-dependent preβ1-high-density lipoprotein conversion before and after breakfast in patients with diabetes. We also performed in vitro studies using TGRLs. Preβ1-high-density lipoprotein was quantified by enzyme-linked immunosorbent assay and native two-dimensional gradient gel (N-2D-gel) electrophoresis.ResultsBefore breakfast, the diabetes group had higher preβ1-high-density lipoprotein concentrations than the healthy controls; after breakfast, levels in the two groups were similar. Neither LCAT mass nor the LCAT-dependent preβ1-high-density lipoprotein conversion rate changed after breakfast. Mixing of fasting plasma with chylomicrons or very-low-density lipoprotein (VLDL) reduced the preβ1-high-density lipoprotein level by 15% ± 4% and 45% ± 10%, respectively. N-2D-gel electrophoresis showed that preβ1-high-density lipoprotein was generated by bacteria-derived TG lipase only from postprandial VLDL of patients with type 2 diabetes.ConclusionPreβ1-high-density lipoprotein binds to TGRLs in the postprandial state and is released during lipolysis, implying that postprandial hyperlipidemia impairs reverse cholesterol transport in patients with poorly controlled type 2 diabetes.

High-Density Lipoprotein Subclasses and Their Role in the Prevention and Treatment of Cardiovascular Disease: A Narrative Review

The association between high-density lipoprotein cholesterol (HDL-C) and cardiovascular disease (CVD) is controversial. HDL-C is one content type of high-density lipoprotein (HDL). HDL consists of diverse proteins and lipids and can be classified into different subclasses based on size, shape, charge, and density, and can change dynamically in disease states. Therefore, HDL-C levels alone cannot represent HDLs' cardioprotective role. In this review, we summarized the methods for separating HDL subclasses, the studies on the association between HDL subclasses and cardiovascular risk (CVR), and the impact of lipid-modifying medications and nonpharmacological approaches (exercise training, dietary omega fatty acids, and low-density lipoprotein apheresis) on HDL subclasses. As HDL is a natural nanoplatform, recombinant HDLs (rHDLs) have been used as a delivery system in vivo by loading small interfering RNA, drugs, contrast agents, etc. Therefore, we further reviewed the HDL subclasses used in rHDLs and their advantages and disadvantages. This review would provide recommendations and guidance for future studies on HDL subclasses' cardioprotective roles.

Preβ1-high-density lipoprotein metabolism is delayed in patients with chronic kidney disease not on hemodialysis

BACKGROUND

Preβ1-high-density lipoprotein (HDL) is a lipid-poor cholesterol acceptor that is converted to lipid-rich HDL by lecithin-cholesterol acyltransferase (LCAT). In patients receiving hemodialysis, preβ1-HDL metabolism is hampered even if HDL cholesterol is normal. Hemodialysis may affect preβ1-HDL metabolism by releasing lipases from the vascular wall due to heparin.

OBJECTIVES

We investigated whether preβ1-HDL metabolism is delayed in patients with chronic kidney disease (CKD) who are not receiving hemodialysis.

METHODS

We examined 44 patients with Stage 3 or higher CKD and 22 healthy volunteers (Control group). The patients with CKD were divided into those without renal replacement therapy (CKD group, n = 22) and those undergoing continuous ambulatory peritoneal dialysis (CAPD group, n = 22). Plasma preβ1-HDL concentrations were determined by immunoassay. During incubation at 37°C, we used 5,5-dithio-bis (2-nitrobenzoic acid) (DTNB) to inhibit LCAT activity and defined the conversion halftime of preβ1-HDL (CHT_preβ1) as the time required for the difference in preβ1-HDL concentration in the presence and absence of 5,5-DTNB to reach half the baseline concentration.

RESULTS

The absolute and relative preβ1-HDL concentrations were higher, and CHT_preβ1 was longer in the CKD and CAPD groups than in the Control group. Preβ1-HDL concentration was significantly correlated with CHT_preβ1 but not with LCAT activity in patients with CKD and CAPD.

CONCLUSION

Preβ1-HDL metabolism is delayed in patients with CKD who are not on hemodialysis. This preβ1-HDL metabolic delay may progress as renal function declines.

Elevated levels of preβ1-high-density lipoprotein are associated with cholesterol ester transfer protein, the presence and severity of coronary artery disease

Background

Preβ1-high-density lipoprotein (preβ1-HDL), plays an important role in reverse cholesterol transport and exhibits potent risk for coronary artery disease (CAD). However, the association of plasma preβ1-HDL and cholesterol ester transfer protein (CETP) levels in CAD patients and the relationship of preβ1-HDL with extent of CAD are debatable.

Methods

Preβ1-HDL and CETP levels were measured by enzymed-linked immunosorbent assay (ELISAs) in 88 acute coronary syndromes (ACS), 79 stable coronary artery disease (SCAD) patients and 85 control subjects. The correlation analyses, multiple linear regression analyses and logistic regression analyses were performed, respectively.

Results

The preβ1-HDL and CETP levels in ACS patients were significantly higher than those in SCAD patients and both of them were higher than controls’. Preβ1-HDL levels were positively associated with CETP (R = 0.348, P = 0.000), the diameter of stenosis (R = 0.253, P = 0.005), the number of vessel disease (R = 0.274, P = 0.002) and Gensini score (R = 0.227, P = 0.009) in CAD patients. Stepwise multiple linear regression analyses showed that CETP was one of the determinants of preβ1-HDL levels. Logistic regression analysis revealed that elevated preβ1-HDL and CETP were potential risk factors for both ACS and SCAD.

Conclusion

The elevated preβ1-HDL levels may change with CETP concentrations in CAD patients and were related to the presence and severity of CAD.

Effects of established hypolipidemic drugs on HDL concentration, subclass distribution, and function

The knowledge of an inverse relationship between plasma high-density lipoprotein cholesterol (HDL-C) concentrations and rates of cardiovascular disease has led to the concept that increasing plasma HDL-C levels would be protective against cardiovascular events. Therapeutic interventions presently available to correct the plasma lipid profile have not been designed to specifically act on HDL, but have modest to moderate effects on plasma HDL-C concentrations. Statins, the first-line lipid-lowering drug therapy in primary and secondary cardiovascular prevention, have quite modest effects on plasma HDL-C concentrations (2-10%). Fibrates, primarily used to reduce plasma triglyceride levels, also moderately increase HDL-C levels (5-15%). Niacin is the most potent available drug in increasing HDL-C levels (up to 30%), but its use is limited by side effects, especially flushing.The present chapter reviews the effects of established hypolipidemic drugs (statins, fibrates, and niacin) on plasma HDL-C levels and HDL subclass distribution, and on HDL functions, including cholesterol efflux capacity, endothelial protection, and antioxidant properties.

FAMP, a novel apoA-I mimetic peptide, suppresses aortic plaque formation through promotion of biological HDL function in ApoE-deficient mice

BACKGROUND

Apolipoprotein (apo) A-I is a major high-density lipoprotein (HDL) protein that causes cholesterol efflux from peripheral cells through the ATP-binding cassette transporter A1 (ABCA1), thus generating HDL and reversing the macrophage foam cell phenotype. Pre-β1 HDL is the smallest subfraction of HDL, which is believed to represent newly formed HDL, and it is the most active acceptor of free cholesterol. Furthermore it has a possible protective function against cardiovascular disease (CVD). We developed a novel apoA-I mimetic peptide without phospholipids (Fukuoka University ApoA-I Mimetic Peptide, FAMP).

METHODS AND RESULTS

FAMP type 5 (FAMP5) had a high capacity for cholesterol efflux from A172 cells and mouse and human macrophages in vitro, and the efflux was mainly dependent on ABCA1 transporter. Incubation of FAMP5 with human HDL or whole plasma generated small HDL particles, and charged apoA-I-rich particles migrated as pre-β HDL on agarose gel electrophoresis. Sixteen weeks of treatment with FAMP5 significantly suppressed aortic plaque formation (scrambled FAMP, 31.3 ± 8.9% versus high-dose FAMP5, 16.2 ± 5.0%; P<0.01) and plasma C-reactive protein and monocyte chemoattractant protein-1 in apoE-deficient mice fed a high-fat diet. In addition, it significantly enhanced HDL-mediated cholesterol efflux capacity from the mice.

CONCLUSIONS

A newly developed apoA-I mimetic peptide, FAMP, has an antiatherosclerotic effect through the enhancement of the biological function of HDL. FAMP may have significant atheroprotective potential and prove to be a new therapeutic tool for CVD.

High-density lipoprotein subfractions--what the clinicians need to know

Although the inverse relationship between plasma levels of high-density lipoprotein (HDL) and cardiovascular disease has been largely demonstrated, many observations have suggested that the assessment of HDL functionality might be more informative than a simple measurement of HDL-cholesterol plasma levels. HDLs are a class of structurally and functionally heterogeneous particles; in atherosclerosis-related diseases, changes in HDL subfraction levels and functions are frequently observed. Circulating levels of large HDL particles are decreased in dyslipidaemic conditions, while levels of small dense HDL particles are increased in patients with coronary heart disease. Furthermore, specific genetic defects in proteins involved in HDL metabolism significantly impact the distribution of HDL subpopulations. Finally, many drugs used for dyslipidaemia induce changes in HDL subfractions strictly related to cardiovascular disease. Although several methods exist to evaluate HDL subclass levels, most of them are not easily applicable in clinical practice, due to the costs and high variability. However, the possibility to measure the levels of specific HDL subfractions in patients with atherosclerosis-related diseases might help to better define their cardiovascular risk.

Development of a method to measure preβHDL and αHDL apoA-I enrichment for stable isotopic studies of HDL kinetics

Our understanding of HDL metabolism would be enhanced by the measurement of the kinetics of preβHDL, the nascent form of HDL, since elevated levels have been reported in patients with coronary artery disease. Stable isotope methodology is an established technique that has enabled the determination of the kinetics (production and catabolism) of total HDL apoA-I in vivo. The development of separation procedures to obtain a preβHDL fraction, the isotopic enrichment of which could then be measured, would enable further understanding of the pathways in vivo for determining the fate of preβHDL and the formation of αHDL. A method was developed and optimised to separate and measure preβHDL and αHDL apoA-I enrichment. Agarose gel electrophoresis was first used to separate lipoprotein subclasses, and then a 4-10 % discontinuous SDS-PAGE used to isolate apoA-I. Measures of preβHDL enrichment in six healthy subjects were undertaken following an infusion of L-[1-¹³C-leucine]. After isolation of preβ and αHDL, the isotopic enrichment of apoA-I for each fraction was measured by gas chromatography-mass spectrometry. PreβHDL apoA-I enrichment was measured with a CV of 0.51 % and αHDL apoA-I with a CV of 0.34 %. The fractional catabolic rate (FCR) of preβHDL apoA-I was significantly higher than the FCR of αHDL apoA-I (p < 0.005). This methodology can be used to selectively isolate preβ and αHDL apoA-I for the measurement of apoA-I isotopic enrichment for kinetics studies of HDL subclass metabolism in a research setting.

Gender differences in the association between HDL cholesterol and the progression of diabetic kidney disease in type 2 diabetic patients

BACKGROUND

The impact of serum lipid abnormalities on the progression of diabetic kidney disease (DKD) remains conflicting. Furthermore, gender differences in the association between dyslipidaemia and outcome of DKD are largely unknown. We therefore conducted this single-centre observational cohort study to clarify gender differences in the association between serum lipid profiles and the progression of DKD.

METHODS

Seven hundred and twenty-three Japanese type 2 diabetes mellitus (T2DM) patients with normoalbuminuria or microalbuminuria, 280 women and 443 men, with a mean (± SD) age of 63 ± 11 years were studied. The endpoint was the progression to a more advanced stage of albuminuria. For statistical analyses, Cox proportional hazard model analyses were conducted.

RESULTS

During the mean follow-up period of 4.3 years, 62 of 477 patients with normoalbuminuria and 69 of 246 patients with microalbuminuria reached the endpoint. A significant interaction between high-density lipoprotein (HDL) cholesterol and gender was detected (P(interaction) = 0.04); therefore, separate analyses were conducted for men and women. Overall, in men, the univariate Cox proportional hazard model revealed that higher triglycerides and lower HDL cholesterol levels were significantly associated with higher risk of reaching the endpoint. In the multivariate Cox proportional hazard model, only HDL cholesterol levels remained as an independent predictor of the endpoint (hazard ratio 0.391, P = 0.01). In women, no serum lipid parameters were associated with the endpoint.

CONCLUSIONS

Lower HDL cholesterol levels seem to be associated with the progression of DKD in men but not in women.

Macrophage cholesterol efflux to plasma and HDL in subjects with low and high homocysteine levels: a FIELD substudy

OBJECTIVES

Increases of homocysteine (Hcy) by fenofibrate correlated inversely to changes in HDL-C and apoA-I in the FIELD study. This finding raised the question whether high Hcy may influence HDL function and counteract benefits of fenofibrate on cardiovascular outcomes. In a subset of the FIELD study we investigated whether fenofibrate therapy or high Hcy, separately or in concert, modulate: (1) ability of plasma or HDL to facilitate cholesterol efflux from THP-1 foam cells; (2) plasma potential to generate preβ-HDL; (3) plasma phospholipid transfer protein (PLTP) activity, serum PON-1 mass and activity, HDL particle size and distribution.

METHODS

We selected 33 subjects in the FIELD fenofibrate arm according to quartiles of Hcy at 5th year: 17 subjects were in the lowest (Low Hcy group) and 16 subjects were in the highest quartile (High Hcy group). In addition, 14 subjects allocated to placebo were matched by close-out Hcy levels to Low Hcy group. This design allowed us to examine the effects of both fenofibrate (comparison between placebo vs Low Hcy groups) and Hcy (comparison between close-out Low and High Hcy groups) on plasma and HDL ability to facilitate cellular cholesterol removal in the efflux assay in vitro using THP-1 foam cells.

RESULTS

Hcy levels were 13.3±0.7 μmol/L (placebo), 13.2±2 μmol/L (Low Hcy) and 27.4±6.5 μmol/L (High Hcy). Cholesterol efflux values to HDL and plasma, percentage of plasma preβ-HDL, PLTP activity, serum PON-1 mass and HDL particle size and distribution were similar in both fenofibrate groups and comparable to those of the placebo group.

CONCLUSIONS

In the present study cohort fenofibrate and high Hcy levels did not modulate HDL and plasma functions in the first step of reverse cholesterol transport, cholesterol efflux from foam cells.

High pre-beta1 HDL concentrations and low lecithin: cholesterol acyltransferase activities are strong positive risk markers for ischemic heart disease and independent of HDL-cholesterol

BACKGROUND

We hypothesized that patients with high HDL-cholesterol (HDL-C) and ischemic heart disease (IHD) may have dysfunctional HDL or unrecognized nonconventional risk factors.

METHODS

Individuals with IHD (Copenhagen University Hospital) and either high HDL-C (n = 53; women >or=735 mg/L; men >or=619 mg/L) or low HDL-C (n = 42; women <or=387 mg/L; men <or=341 mg/L) were compared with individuals without IHD (Copenhagen City Heart Study) matched by age, sex, and HDL-C concentrations (n = 110). All participants had concentrations within reference intervals for LDL-C (<1600 mg/L) and triglyceride (<1500 mg/L), and none were treated with lipid-lowering medications. Pre-beta(1) HDL and phospholipid transfer protein concentrations were measured by using commercial kits and lecithin:cholesterol acyltransferase (LCAT) activity by using a proteoliposome cholesterol esterification assay.

RESULTS

Pre-beta(1) HDL concentrations were 2-fold higher in individuals with IHD vs no IHD in both the high [63 (5.7) vs 35 (2.3) mg/L; P < 0.0001] and low HDL-C [49 (5.0) vs 27 (1.5) mg/L; P = 0.001] groups. Low LCAT activity was also associated with IHD in the high [95.2 (6.7) vs 123.0 (5.3) micromol x L(-1) x h(-1); P = 0.002] and low [93.4 (8.3) vs 113.5 (4.9) micromol x L(-1) . h(-1); P = 0.03] HDL-C groups. ROC curves for pre-beta(1) HDL in the high-HDL-C groups yielded an area under the curve of 0.71 (95% CI: 0.61-0.81) for predicting IHD, which increased to 0.92 (0.87-0.97) when LCAT was included. Similar results were obtained for low HDL-C groups. An inverse correlation between LCAT activity and pre-beta(1) HDL was observed (r(2) = 0.30; P < 0.0001) in IHD participants, which was stronger in the low HDL-C group (r(2) = 0.56; P < 0.0001).

CONCLUSIONS

IHD was associated with high pre-beta(1) HDL concentrations and low LCAT levels, yielding correct classification in more than 90% of the IHD cases for which both were measured, thus making pre-beta(1) HDL concentration and LCAT activity level potentially useful diagnostic markers for cardiovascular disease.

Plasma triglyceride levels and body mass index values are the most important determinants of prebeta-1 HDL concentrations in patients with various types of primary dyslipidemia

OBJECTIVE

Experimental studies have shown that the prebeta-1 subclass of high-density lipoprotein particles (prebeta-1 HDL) may play an important role in the reverse cholesterol transport pathway as the initial acceptors of cellular cholesterol. The aim of the present study was the direct comparison of prebeta-1 HDL values in individuals with various types of primary dyslipidemias.

METHODS

Four hundred and eighty-six unrelated individuals were included in the study. According to their lipid values study participants were subdivided into four groups: control group (n=206), type IIA dyslipidemia group (n=148), type IIB dyslipidemia group (n=49) and type IV dyslipidemia group (n=83).

RESULTS

All dyslipidemic patients displayed higher concentrations of prebeta-1 HDL compared to control individuals. However, patients with dyslipidemias characterized by an abnormal catabolism of triglyceride-rich lipoproteins (such as dyslipidemias of type IIB and IV) tend to have higher prebeta-1 HDL values compared to patients with hypercholesterolemia, and this increase is proportional to the degree of hypertriglyceridemia. In addition, patients with metabolic syndrome exhibited significantly higher levels of prebeta-1 HDL compared to individuals that do not fulfill the criteria for the diagnosis of this syndrome. Multiple regression analysis revealed that serum triglyceride concentrations and body mass index (BMI) values were the most important determinants of prebeta-1 HDL levels in our population.

CONCLUSION

All dyslipidemic patients exhibit increased prebeta-1 HDL concentrations as compared to normolipidemic individuals. Whether this increase represents a defensive mechanism against atherosclerosis or it is indicative of impaired maturation of HDL particles and thus of a defective reverse cholesterol transport mechanism remains to be established.

Effects of bezafibrate on dyslipidemia with cholestasis in children with familial intrahepatic cholestasis-1 deficiency manifesting progressive familial intrahepatic cholestasis

No appropriate pharmaceutical therapy has been established for dyslipidemia with cholestasis in progressive familial intrahepatic cholestasis (PFIC)-1. We evaluated the efficacy of bezafibrate in PFIC-1. We monitored the clinical presentation and lipoprotein metabolism of 3 patients, aged 3, 4, and 8 years, with FIC1 deficiency, manifesting PFIC-1, over 12 months of bezafibrate therapy. Pruritus was substantially alleviated in the 3 patients after initiation of bezafibrate. Cholestasis was alleviated in 2 of them. Serum high-density lipoprotein cholesterol and low-density lipoprotein cholesterol increased 1.6- to 2.0-fold and 1.1- to 1.2-fold, respectively; but the values remained low and normal, respectively. Serum lipoprotein X, which was at normal levels before treatment, was elevated to levels above the upper limit of the reference range. High serum triglyceride levels decreased by 15% to 30%, to normal levels, after treatment initiation. The activities of lipoprotein lipase and hepatic triglyceride lipase were increased, but those of high-density lipoprotein regulators remained unchanged. Liver expression of multidrug resistance protein-3, which regulates lipoprotein X synthesis, was enhanced by bezafibrate therapy. Bezafibrate treatment favorably affected pruritus, dyslipidemia, and cholestasis in PFIC-1.

Formation of prebeta1-HDL during lipolysis of triglyceride-rich lipoprotein

Prebeta1-HDL, a putative discoid-shaped high-density lipoprotein (HDL) is known to participate in the retrieval of cholesterol from peripheral tissues. In this study, to clarify potential sources of this lipoprotein, we conducted heparin injection on four Japanese volunteer men and found that serum triglyceride (TG) level decreased in parallel with the increase in serum nonesterified fatty acids and plasma lipoprotein lipase (LPL) protein mass after heparin injection. Plasma prebeta1-HDL showed considerable increases at 15 min after the heparin injection in all of the subjects. In contrast, serum HDL-C levels did not change. Gel filtration with fast protein liquid chromatography system (FPLC) study on lipoprotein profile revealed that in post-heparin plasma, low-density lipoprotein and alphaHDL fractions did not change, whereas there was a considerable decrease in very low-density lipoprotein (VLDL) fraction and an increase in prebeta1-HDL fraction when compared with those in pre-heparin plasma. We also conducted in vitro analysis on whether prebeta1-HDL was produced during VLDL lipolysis by LPL. One hundred microliters of VLDL extracted from pooled serum by ultracentrifugation was incubated with purified bovine milk LPL at 37 degrees C for 0-120 min. Prebeta1-HDL concentration increased in a dose dependent manner with increased concentration of added LPL in the reaction mixture and with increased incubation time, indicating that prebeta1-HDL was produced during lipolysis of VLDL by LPL. Taken these in vivo and in vitro analysis together, we suggest that lipolysis of VLDL particle by LPL is an important source for formation of prebeta1-HDL.

Potent and selective PPAR-alpha agonist LY518674 upregulates both ApoA-I production and catabolism in human subjects with the metabolic syndrome

OBJECTIVE

The study of PPAR-alpha activation on apoA-I production in humans has been limited to fibrates, relatively weak PPAR-alpha agonists that may have other molecular effects. We sought to determine the effect of a potent and highly specific PPAR-alpha agonist, LY518674, on apoA-I, apoA-II, and apoB-100 kinetics in humans with metabolic syndrome and low levels of HDL cholesterol (C).

METHODS AND RESULTS

Subjects were randomized to receive LY518674 (100 microg) once daily (n=13) or placebo (n=15) for 8 weeks. Subjects underwent a kinetic study using a deuterated leucine tracer to measure apolipoprotein production and fractional catabolic rates (FCR) at baseline and after treatment. LY518674 significantly reduced VLDL-C (-38%, P=0.002) and triglyceride (-23%, P=0.002) levels whereas LDL-C and HDL-C levels were unchanged. LY518674 significantly reduced VLDL apoB-100 (-12%, P=0.01) levels, attributable to an increased VLDL apoB-100 FCR with no change in VLDL apoB-100 production. IDL and LDL apoB-100 kinetics were unchanged. LY518674 significantly increased the apoA-I production rate by 31% (P<0.0001), but this was accompanied by a 33% increase in the apoA-I FCR (P=0.002), resulting in no change in plasma apoA-I. There was a 71% increase in the apoA-II production rate (P<0.0001) accompanied by a 25% increase in the FCR (P<0.0001), resulting in a significant increase in plasma apoA-II.

CONCLUSIONS

Activation of PPAR-alpha with LY518674 (100 microg) in subjects with metabolic syndrome and low HDL-C increased the VLDL apoB-100 FCR consistent with enhanced lipolysis of plasma triglyceride. Significant increases in the apoA-I and apoA-II production rates were accompanied by increased FCRs resulting in no change in HDL-C levels. These data indicate a major effect of LY518674 on the production and clearance of apoA-I and HDL despite no change in the plasma concentration. The effect of these changes on reverse cholesterol transport remains to be determined.

The effects of orlistat and fenofibrate, alone or in combination, on high-density lipoprotein subfractions and pre-beta1-HDL levels in obese patients with metabolic syndrome

OBJECTIVE

We assessed the effect of orlistat and fenofibrate, alone or in combination, on plasma high-density lipoprotein (HDL) subfractions and plasma pre-beta1-HDL levels in overweight and obese subjects with metabolic syndrome (MetS).

METHODS

Patients (n = 89) were prescribed a low-fat low-calorie diet and were randomly allocated to receive orlistat 120 mg three times daily (O group), micronized fenofibrate 200 mg/day (F group) or both (OF group) for 6 months. HDL subfractions were determined using a polyacrylamide gel tube electrophoresis method and pre-beta1-HDL levels using enzyme-linked immunoabsorbent assay.

RESULTS

We observed a significant change of high-density lipoprotein cholesterol (HDL-C) levels only in the F group (+3%, p < 0.05). Large HDL-C levels were significantly increased and small HDL-C levels were significantly reduced with O administration. In F group we observed a significant increase of small HDL-C levels. No significant change of large or small HDL-C levels was observed with combination treatment. We observed a significant increase of pre-beta1-HDL levels in all groups, which was significantly greater in OF group compared with O or F monotherapy.

CONCLUSION

OF combination increased the antiatherogenic pre-beta1-HDL levels in overweight and obese patients with MetS. Furthermore, OF combination counterbalanced the reduction of small HDL-C levels observed with orlistat monotherapy.

Effects of fenofibrate and simvastatin on HDL-related biomarkers in low-HDL patients

The objective of the present study was to compare the effects of fenofibrate versus simvastatin on various HDL-related biomarkers in dyslipidemic patients with low HDL-C, in whom it is as yet unclear whether a statin or a fibrate is the most appropriate treatment. Fifty-two patients received either fenofibrate (160 mg/day) or simvastatin (40 mg/day) for 8 weeks in a randomized, double-blind, parallel group trial. Simvastatin effectively lowered plasma LDL-C and apoB levels, but did not change plasma HDL levels and HDL-related biomarkers, except for a small, significant increase in the capacity of plasma to promote SR-BI mediated cholesterol efflux. Fenofibrate did not affect plasma LDL-C levels but lowered triglycerides, and exerted a remarkable HDL-C raising activity (+22%), with patients in the lowest range of HDL-C getting the maximal benefit. The HDL-C raise was associated with a shift of HDL from large to small particles, and from LpA-I to LpA-I:A-II, which might explain the observed increase in the plasma capacity to promote ABCA1 mediated efflux with no changes in SR-BI efflux. The distinct and complementary effects of fenofibrate and simvastatin on lipid parameters and HDL-related biomarkers suggest that a combination therapy with the two drugs in dyslipidemic patients with low HDL would be fully justified.

Functionally defective high-density lipoprotein: a new therapeutic target at the crossroads of dyslipidemia, inflammation, and atherosclerosis

High-density lipoproteins (HDL) possess key atheroprotective biological properties, including cellular cholesterol efflux capacity, and anti-oxidative and anti-inflammatory activities. Plasma HDL particles are highly heterogeneous in physicochemical properties, metabolism, and biological activity. Within the circulating HDL particle population, small, dense HDL particles display elevated cellular cholesterol efflux capacity, afford potent protection of atherogenic low-density lipoprotein against oxidative stress and attenuate inflammation. The antiatherogenic properties of HDL can, however be compromised in metabolic diseases associated with accelerated atherosclerosis. Indeed, metabolic syndrome and type 2 diabetes are characterized not only by elevated cardiovascular risk and by low HDL-cholesterol (HDL-C) levels but also by defective HDL function. Functional HDL deficiency is intimately associated with alterations in intravascular HDL metabolism and structure. Indeed, formation of HDL particles with attenuated antiatherogenic activity is mechanistically related to core lipid enrichment in triglycerides and cholesteryl ester depletion, altered apolipoprotein A-I (apoA-I) conformation, replacement of apoA-I by serum amyloid A, and covalent modification of HDL protein components by oxidation and glycation. Deficient HDL function and subnormal HDL-C levels may act synergistically to accelerate atherosclerosis in metabolic disease. Therapeutic normalization of attenuated antiatherogenic HDL function in terms of both particle number and quality of HDL particles is the target of innovative pharmacological approaches to HDL raising, including inhibition of cholesteryl ester transfer protein, enhanced lipidation of apoA-I with nicotinic acid and infusion of reconstituted HDL or apoA-I mimetics. A preferential increase in circulating concentrations of HDL particles possessing normalized antiatherogenic activity is therefore a promising therapeutic strategy for the treatment of common metabolic diseases featuring dyslipidemia, inflammation, and premature atherosclerosis.

Serum amyloid A (SAA)-induced remodeling of CSF-HDL

Inflammation is a risk factor for Alzheimer's disease. Serum amyloid A (SAA) is an acute phase protein that dissociates apolipoprotein AI (apoAI) from plasma HDL. In cerebrospinal fluid (CSF), the SAA concentration is much higher in subjects with Alzheimer's disease than in controls. CSF-HDL is rich in apoE, which plays an important role as a ligand for lipoprotein receptors in the central nervous system (CNS). To clarify whether SAA dissociates apoE from CSF-HDL, we added recombinant SAA to CSF and determined the apoE distribution in the CSF using native two-dimensional gel electrophoresis. We found that SAA dissociated apoE from CSF-HDL in a dose-dependent manner. This effect was more evident in apoE4 carriers than in apoE3 or apoE2 carriers. After a 24-h incubation at 37 degrees C, SAA continuously dissociated apoE from CSF-HDL. Amyloid beta (Abeta) fragments (1-42) were bound to large CSF-HDL but not to apoE dissociated by SAA. In conclusion, SAA dissociates apoE from CSF-HDL. We postulate that inflammation in the CNS may impair Abeta clearance due to the loss of apoE from CSF-HDL.

Alterations of high-density lipoprotein subclasses in endogenous hypertriglyceridemia

BACKGROUND

To investigate the alterations of high-density lipoprotein (HDL) subclasses in endogenous hypertriglyceridemic subjects.

METHODS

Apolipoprotein A-I contents of plasma HDL subclasses were quantitated by 2-dimensional gel electrophoresis in 236 normolipidemic subjects (including 146 males and 90 females) and 176 endogenous hypertriglyceridemic subjects (including 103 males and 73 females).

RESULTS

Apolipoprotein A-I contents of small-sized pre-beta1-HDL and HDL3a were significantly higher (P < .01 and P < .01, respectively), but those of large-sized HDL2a and HDL2b were significantly lower (P < .01 and P < .01, respectively) in hypertriglyceridemic subjects versus normolipidemic subjects. Moreover, with the elevation of triglyceride levels, small-sized pre-beta1-HDL and HDL3a increased successively; however, large-sized HDL2a and HDL2b decreased successively. Males had significantly higher apolipoprotein A-I contents of small-sized pre-beta1-HDL and HDL3b (P < .05 and P < .05, respectively), but lower contents of large-sized HDL2b (P < .01) than females in both normolipidemic and hypertriglyceridemic subjects.

CONCLUSIONS

The particle size of HDL shifted toward smaller size in hypertriglyceridemic subjects, especially in male subjects. Of note, the shift was more obvious with the elevation of triglyceride levels. The changes mentioned above indicate that HDL maturation might be abnormal and reverse cholesterol transport might be weakened.

Effects of bezafibrate on lipoprotein subclasses and inflammatory markers in patients with hypertriglyceridemia--a nuclear magnetic resonance study

BACKGROUND

Hypertriglyceridemia is often associated with elevated remnants, small dense LDL and decreased HDL-cholesterol (C). The objective of this study was to investigate the efficacy of bezafibrate on lipoprotein subfractions profile and inflammation markers in patients with hypertriglyceridemia.

METHODS

Twenty-four hypertriglyceridemic subjects took bezafibrate, 400 mg daily, for 4 weeks. Lipoprotein subclasses were measured by nuclear magnetic resonance (NMR) spectroscopy. Inflammation markers including C-reactive protein (CRP), interleukin-6 (IL-6) and monocyte chemotactic protein-1 (MCP-1) were also determined.

RESULTS

Bezafibrate lowered triglyceride (TG) by 59% and increased HDL-C by 20%. NMR analysis revealed that bezafibrate lowered large TG-rich lipoproteins and IDL by 81% and 46%, respectively. Small LDL was selectively decreased by 53% with increase in large to intermediate LDL, thus altering the LDL distribution towards the larger particles (mean diameter 19.9 to 20.7 nm, p = 0.0001). Small (HDL1) and intermediate (HDL3) HDL significantly increased by 168% and 70%, whereby resulting in a significant reduction of the mean HDL particle size from 9.0 to 8.7 nm (p = 0.026). None of inflammation makers showed significant change by bezafibrate.

CONCLUSIONS

Bezafibrate effectively ameliorates atherogenic dyslipidemia by reducing remnants and small LDL as well as by increasing HDL particles in hypertriglyceridemic subjects.

LCAT-dependent conversion rate is a determinant of plasma prebeta1-HDL concentration in healthy Japanese

BACKGROUND

Prebeta1-HDL acts as a primary acceptor of cellular cholesterol. Prebeta1-HDL is converted into alpha-migrating high-density lipoprotein (HDL) by lecithin/cholesterol acyltransferase (LCAT). We examined whether the LCAT-dependent conversion rate of prebeta1-HDL is a determinant of the plasma prebeta1-HDL concentration in healthy Japanese.

METHODS

We measured the conversion half time (CHT(prebeta1)), the time required for 50% of baseline prebeta1-HDL to be changed into alpha-migrating HDL by LCAT, in 100 healthy Japanese (47 men, 53 women, 22-88 years).

RESULTS

Prebeta1-HDL concentration, as determined by immunoassay, was significantly lower in younger women (<50 years, n=24) than in older women (>or=50 years, n=29) (16.8+/-3.3 vs. 21.7+/-8.0 mg/l apolipoprotein AI (apoAI), p<0.01). There was no significant difference in prebeta1-HDL concentration between younger (n=24) and older (n=23) men (21.2+/-6.8 vs. 22.5+/-6.6 mg/l apoAI). The mean CHT(prebeta1) for all subjects was 47.4+/-13.0 min, and was not influenced by gender or age. Prebeta1-HDL concentration was positively correlated with CHT(prebeta1) in both men and women, suggesting that high prebeta1-HDL levels may reflect delayed conversion of prebeta1-HDL.

CONCLUSION

LCAT-dependent conversion rate is a determinant of plasma prebeta1-HDL concentration in healthy Japanese. We speculate that prebeta1-HDL concentration may be used as a metabolic marker for HDL maturation.

T13M mutation of lecithin-cholesterol acyltransferase gene causes fish-eye disease

BACKGROUND

Lecithin-cholesterol acyltransferase (LCAT) esterifies free cholesterol (FC) in plasma and plays a crucial role in the maturation of prebeta1-HDL (lipid-poor HDL) into alpha-migrating HDL (spherical HDL). Natural mutations of LCAT gene cause familial LCAT deficiency (FLD) or fish-eye disease (FED). The relationship between mutations and their phenotypes gives important clues to the functions of specific regions of LCAT. We investigated the first homozygous case with a substitution of threonine to methionine at codon 13 (T13M) of LCAT gene.

METHODS

We evaluated LCAT activity, LCAT distribution among HDL subfractions and conversion of prebeta1-HDL to alpha-migrating HDL by native two-dimensional gel electrophoresis (N-2DGE).

RESULTS

The proband had corneal opacity, severe hypo-alpha-lipoproteinemia, half-normal LCAT activity and near normal cholesteryl ester/total cholesterol (TC) ratio in plasma. These features were characteristic of FED. Plasma prebeta1-HDL concentration was near normal, but not converted to alpha-migrating HDL during 37 degrees C incubation. As expected, alpha-migrating HDL (especially large particles) was markedly reduced. In the immunoblot against LCAT, the small alpha-migrating HDL from the proband had much less LCAT in this patient than in controls.

CONCLUSION

T13M mutation of LCAT gene causes FED.

Enhanced efflux of cholesterol from ABCA1-expressing macrophages to serum from type IV hypertriglyceridemic subjects

Since elevated plasma triglycerides (TGs) are an independent cardiovascular risk factor, we have compared the cholesterol efflux potential of sera from asymptomatic hypertriglyceridemic (HTG) type IIb, type IV or normolipidemic (NLP) individuals using two different cell systems. In both type IIb and IV HTG, the efflux of cholesterol from SR-BI-rich Fu5AH cells was similar to that obtained with NLP. The maintenance of efflux efficiency in spite of reduced HDL-cholesterol levels can be mainly attributed to the relative enrichment of HDL with phospholipid. In the J774 macrophage cell system, pretreatment with cAMP, which upregulates ABCA1, induced a markedly higher increase in efflux to type IV sera compared with type IIb or NLP. In addition, type IV sera exhibited two-fold higher pre-beta HDL relative concentration (percentage of total apo AI) compared with NLP. Moreover, positive correlations were established between ABCA1-mediated efflux and the serum pre-beta HDL levels or TG concentrations. Thus, the hyperTGemia is associated with a higher fraction of apo AI recovered as pre-beta HDL which appear to be partly responsible for enhanced efflux obtained upon the cAMP stimulation of J774 cells. In conclusion, we demonstrated for the first time that the ABCA1-expressing J774 cell system is responsive to the percent of apo AI present in human serum as pre-beta HDL. Our results suggest that high-plasma TG, accompanied by low HDL may not result in an impaired cholesterol efflux capacity.

LCAT-dependent conversion of prebeta1-HDL into alpha-migrating HDL is severely delayed in hemodialysis patients

Prebeta1-HDL is a minor HDL subfraction that acts as an efficient initial acceptor of cell-derived free cholesterol. During 37 degrees C incubation, plasma prebeta1-HDL decreases over time due to its conversion to alpha-migrating HDL by lecithin:cholesterol acyltransferase (LCAT). This conversion may be delayed in hemodialysis patients who have decreased LCAT activity. To clarify whether LCAT-dependent conversion of prebeta1-HDL to alpha-migrating HDL is delayed in hemodialysis patients, prebeta1-HDL concentrations were determined in 45 hemodialysis patients and 45 gender-matched control subjects before and after 37 degrees C incubation with and without the LCAT inhibitor. It was found that the baseline prebeta1-HDL concentration in hemodialysis patients was more than twice that in the controls (44.9 +/- 21.4 versus 19.8 +/- 6.7 mg/L apoAI; P < 0.001). After 2-h incubation, the LCAT-dependent decrease in prebeta1-HDL in hemodialysis patients was about one-third of that in the controls (30 +/- 27 versus 97 +/- 17% of baseline; P < 0.01). The LCAT-dependent rate of decrease in prebeta1-HDL levels (DR(prebeta1)) was the same for samples from hemodialysis patients exhibiting normal (> or =1.03 mmol/L) and low HDL-cholesterol levels (32 +/- 32 versus 28 +/- 23% of baseline; NS). DR(prebeta1) was positively correlated with LCAT activity (r = 0.617; P < 0.001). In conclusion, the LCAT-dependent conversion of prebeta1-HDL to alpha-migrating HDL is severely delayed in hemodialysis patients. The impaired catabolism of prebeta1-HDL may accelerate atherosclerosis in hemodialysis patients.

Analytical performance of a sandwich enzyme immunoassay for pre beta 1-HDL in stabilized plasma

We have established an immunoassay for pre beta 1-HDL (the initial acceptor of cellular cholesterol) using a monoclonal antibody, MAb55201. Because pre beta 1-HDL is unstable during storage, fresh plasma must be used for pre beta 1-HDL measurements. In this study, we describe a method of stabilizing pre beta 1-HDL, and evaluate the analytical performance of the immunoassay for pre beta 1-HDL. Fresh plasma was stored under various conditions with or without a pretreatment consisting of a 21-fold dilution into 50% (v/v) sucrose. Pre beta 1-HDL concentration was measured by immunoassay. In nonpretreated samples, pre beta 1-HDL decreased significantly from the baseline after 6 h at room temperature. Although pre beta 1-HDL was more stable at 0 degrees C than at room temperature, it increased from 30.2 +/- 8.5 (SE) to 56.5 +/- 5.5 mg/l apolipoprotein A-I (apoA-I) (P < 0.001) in hyperlipidemics, and from 18.4 +/- 1.2 to 37.9 +/- 3.3 mg/l apoA-I (P < 0.001) in normolipidemics after 5-day storage. After 30-day storage at -80 degrees C, pre beta 1-HDL increased from 29.0 +/- 4.0 to 38.0 +/- 5.7 mg/l apoA-I (P < 0.001) in hyperlipidemics, whereas it did not change in normolipidemics. In pretreated samples, pre beta 1-HDL concentration did not change significantly under any of the above conditions. Moreover, pre beta 1-HDL concentrations determined by immunoassay correlated with those determined by native two-dimensional gel electrophoresis (n = 24, r = 0.833, P < 0.05). An immunoassay using MAb55201 with pretreated plasma is useful for clinical measurement of pre beta 1-HDL.

Dynamics of reverse cholesterol transport: protection against atherosclerosis

This review considers the antiatherogenic function of high density lipoprotein (HDL) from the point of view of its dynamics within the sequential steps of reverse cholesterol transport (RCT). It is postulated that the efficiency of cholesterol flux through the RCT pathways is clinically more relevant than the HDL cholesterol concentration. The particular role of pre-beta(1)-HDL is reviewed drawing attention to the relationship between its concentration and the flux of cholesterol through the RCT system.