Cholesteryl ester transfer protein gene polymorphism is a determinant of HDL cholesterol and of the lipoprotein response to a lipid-lowering diet in type 1 diabetes

The TaqIB cholesteryl ester transfer protein (CETP) gene polymorphism (B1B2) is a determinant of HDL cholesterol in nondiabetic populations. Remarkably, this gene effect appears to be modified by environmental factors. We evaluated the effect of this polymorphism on HDL cholesterol levels and on the lipoprotein response to a linoleic acid-enriched, low-cholesterol diet in patients with type 1 diabetes. In 44 consecutive type 1 diabetic patients (35 men), CETP polymorphism, apolipoprotein (apo) E genotype, serum lipoproteins, serum CETP activity (measured with an exogenous substrate assay, n = 30), clinical variables, and a diet history were documented. The 1-year response to diet was assessed in 14 type 1 diabetic patients, including 6 B1B1 and 6 B1B2 individuals. HDL cholesterol was higher in 10 B2B2 than in 14 B1B1 homozygotes (1.63 +/- 0.38 vs. 1.24 +/- 0.23 mmol/l, P < 0.01). HDL cholesterol, adjusted for triglycerides and smoking, was 0.19 mmol/l higher for each B2 allele present. CETP activity levels were not significantly different between CETP genotypes. Multiple regression analysis showed that VLDL + LDL cholesterol was associated with dietary polyunsaturated:saturated fatty acids ratio (P < 0.02) and total fat intake (P < 0.05) in the B1B1 homozygotes only and tended to be related to the presence of the apo E4 allele (P < 0.10). In response to diet, VLDL + LDL cholesterol fell (P < 0.05) and HDL cholesterol remained unchanged in 6 B1B1 homozygotes. In contrast, VLDL + LDL cholesterol was unaltered and HDL cholesterol decreased (P < 0.05) in 6 B1B2 heterozygotes (P < 0.05 for difference in change in VLDL + LDL/HDL cholesterol ratio). This difference in response was unrelated to the apo E genotype. Thus, the TaqIB CETP gene polymorphism is a strong determinant of HDL cholesterol in type 1 diabetes. This gene effect is unlikely to be explained by a major influence on the serum level of CETP activity, as an indirect measure of CETP mass. Our preliminary data suggest that this polymorphism may be a marker of the lipoprotein response to dietary intervention.     

Lovastatin decreases de novo cholesterol synthesis and LDL Apo B-100 production rates in combined-hyperlipidemic males

The effect of lovastatin, an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity, on the kinetics of de novo cholesterol synthesis and apolipoprotein (apo) B in very-low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), and low-density lipoprotein (LDL) was investigated in five male patients with combined hyperlipidemia. Subjects were counseled to follow a Step 2 diet and were treated with lovastatin and placebo in randomly assigned order for 6-week periods. At the end of each experimental period, subjects were given deuterium oxide orally and de novo cholesterol synthesis was assessed from deuterium incorporation into cholesterol and expressed as fractional synthesis rate (C-FSR) and production rate (C-PR). Simultaneously, the kinetics of VLDL, IDL, and LDL apo B-100 were studied in the fed state using a primed-constant infusion of deuterated leucine to measure fractional catabolic rates (FCR) and production rates (PR). Drug treatment resulted in significant decreases in total cholesterol (-29%), VLDL cholesterol (-40%), LDL cholesterol (-27%), and apo B (-16%) levels and increases in HDL cholesterol (+13%) and apolipoprotein (apo) A-I (+11%) levels. Associated with these plasma lipoprotein responses was a significant reduction in both de novo C-FSR (-40%; P = .04) and C-PR (-42%; P = .03). Treatment with lovastain in these patients had no significant effect on the FCR of apoB-100 in VLDL, IDL, or LDL, but resulted in a significant decrease in the PR of apoB-100 in IDL and LDL. Comparing the kinetic data of these patients with those of 10 normolipidemic control subjects indicates that lovastatin treatment normalized apoB-100 IDL and LDL PR. The results of these studies suggest that the declines in plasma lipid levels observed after treatment of combined hyperlipidemic patients with lovastatin are attributable to reductions in the C-FSR and C-PR of de novo cholesterol synthesis and the PR of apoB-100 containing lipoproteins. The decline in de novo cholesterol synthesis, rather than an increase in direct uptake of VLDL and IDL, may have contributed to the decline in the PR observed.     

Potencies of lipoproteins in fasting and postprandial plasma to accept additional cholesterol molecules released from cell membranes

To investigate the role of various lipoproteins in plasma to promote cholesterol efflux from cell membranes, potencies of lipoproteins in normolipidemic fasting and postprandial (PP) plasmas to accept additional cholesterol molecules from cell membranes were determined. We used red blood cells (RBCs) and lipoproteins in fresh blood as donors and acceptors of cell membrane cholesterol, respectively. When fresh fasting plasma (n=24) containing active lecithin:cholesterol acyltransferase (LCAT) and cholesteryl ester transfer proteins (CETP) was incubated with a 3-fold excess of autologous RBCs at 37 degrees C for 18 hours, plasma cholesterol levels increased by 19.6% (38.5+/-14.2 mg/dL) owing to an exclusive increase in the CE level. Very low density lipoprotein (VLDL), low density lipoprotein (LDL), and high density lipoprotein (HDL) fractions retained 48.1%, 26.3%, and 25.6% of the net cholesterol mass increase in fasting plasma, resulting in 91%, 8%, and 21% increases in their cholesterol contents, respectively. The PP plasma was 1.3-fold more potent than fasting plasma in promoting cholesterol efflux from RBCs by associating excess cholesterol with chylomicrons, resulting in a 356% increase in the cholesterol content of chylomicrons. These increases in lipoprotein cholesterol content indicate that chylomicrons were about 3.9x, 44x, and 17x more potent than fasting VLDL, LDL, and HDL, respectively, in accepting additional cholesterol molecules released from RBCs. The capacity of PP plasma to promote cholesterol efflux from RBCs was significantly correlated with plasma cholesterol levels (r=0.60, P<0.005), triglycerides (r=0.68, P<0.001), chylomicrons (r=0.90, P<0.001), VLDL (r=0.65, P<0.001), and LDL (r=0.47, P<0.025) but not with the levels of HDL (r= -0.34, P<0.20). In fasting plasma containing a low level of VLDL and HDL, isolated chylomicrons supplemented to the plasma were approximately 9x more potent than HDL in boosting the capacity of plasma to promote cholesterol efflux from RBCs. This study indicates that chylomicrons in PP plasma are the most potent ultimate acceptors of cholesterol released from cell membranes and that a low HDL level is not a factor that limits the ability of PP plasma to promote cholesterol efflux from cell membranes. Our data obtained from an in-vitro system suggest that PP chylomicrons may play a major role in promoting reverse cholesterol transport in vivo, since the transfer of cholesterol from cell membranes to chylomicrons will lead to the rapid removal of this cholesterol by the liver. HDL in vivo may promote reverse cholesterol transport by enhancing the rapid removal of chylomicrons from the circulation, since the rate of clearance of chylomicrons is positively correlated with the HDL level in plasma.     

A low temperature flotation method to rapidly isolate lipoproteins from plasma

To minimize oxidative modification, a low temperature, sequential flotation method was developed to isolate plasma lipoproteins in 18 h using a benchtop ultracentrifuge. The protein distributions were characterized using agarose and SDS-polyacrylamide gel electrophoresis, and an SDS-Lowry protein assay. The lipid distributions were assessed using a gas chromatography-mass spectrometric assay for cholesterol and an enzymatic assay for triglycerides. To validate the rapid flotation method, lipoproteins were also isolated from the same plasma samples using a modified Havel et al. flotation method (J. Clin. Invest. 34: 1345-1353, 1955). The same lipoproteins and apolipoproteins were present in fractions of comparable density, and the summed recoveries of protein, cholesterol, and triglyceride were also identical for the Havel et al. and rapid flotation procedures. Likewise, the amount of cholesterol and triglyceride in corresponding very low, intermediate, and low density lipoprotein (VLDL/IDL and LDL) fractions was the same for the two flotation procedures. The triglyceride and cholesterol levels in high density lipoprotein (HDL) isolated by rapid flotations, however, were 9-12% higher than in the HDL as isolated by Havel et al. Because a 9-12% increase in the HDL fraction reflects only 1-4% of the total triglyceride and cholesterol in plasma, we conclude that, while maintained at 4 degrees C, lipoproteins were quantitatively isolated from human plasma in 1 day.     

Increases in dietary cholesterol and fat raise levels of apoprotein E-containing lipoproteins in the plasma of man

Previous studies from this laboratory have determined that diets containing the usual amounts of fat to which are added 750-1500 mg/day cholesterol elevate the plasma cholesterol concentration by variable amounts, depending upon the ratio of polyunsaturated to saturated fatty acids (P/S ratio) of the diet. Diets with P/S ratios of 0.25-0.4 are accompanied by elevations of low density lipoprotein (LDL) cholesterol, whereas diets with a P/S ratio of 2.5 produce no significant changes in cholesterol levels. On the low P/S ratio diets, the structure, composition, and interaction with cultured fibroblasts of LDL are not significantly changed. Plasma high density lipoprotein (HDL) cholesterol levels remain constant, but HDL2 increase relative to HDL3. In the present study, not only dietary cholesterol but also total dietary fat was altered. Six normal young men were fed a basal diet consisting of 18% protein, 51% carbohydrate, and 30% fat, containing 250 mg/day cholesterol. After 2 weeks, an experimental diet consisting of 18% protein, 42% carbohydrate, and 39% fat, containing 1760 mg/day cholesterol, was fed for 4 weeks. The P/S ratios of both diets were about 0.4. Plasma samples were taken twice during each dietary period from 12- to 14-h-fasted subjects and analyzed for their contents of lipoprotein lipids. Plasma levels of LDL and HDL cholesterol increased by 30 and 13 mg/dl, respectively; total and very low density lipoprotein (VLDL) triglyceride concentrations were unaltered. The plasma concentrations of apoproteins (apo) B, E. and A-I, but not A-II, were elevated. Plasma samples also were studied by zonal ultracentrifugation, gel permeation column chromatography, and Pevikon electrophoresis. Although on zonal ultracentrifugation the total concentrations of LDL were increased, the flotation properties and chemical compositions of LDL were not changed. By contrast, HDL2 and HDL3L concentrations increased, and HDL2 became enriched with cholesteryl esters. On gel permeation chromatography, with the subjects on the basal diet, plasma cholesterol eluted in two peaks, corresponding to LDL and HDL. The sizes of the peaks increased on the experimental diet. ApoE eluted in two peaks: one at the leading edge of LDL (corresponding to VLDL or IDL) and the other in the area between LDL and HDL, corresponding to HDLC. On the experimental diet, the apoE peak between LDL and HDL increased. On Pevikon electrophoresis apoE migrated between the LDL and HDL bands. This apoE peak was increased on the experimental diet. These findings suggest that increasing the concentrations of both dietary cholesterol and total fat can increase the levels of plasma LDL, HDL2, and HDLC in fasting normal subjects. Thus, the concentrations of some putatively atherogenic as well as antiatherogenic lipoproteins increased in plasma, and the apparent paradox between the epidemiological and metabolic behaviors of some lipoproteins remains. Clearly, more work is needed to resolve the roles of various lipoproteins in plasma in atherosclerosis.     

Hyperbetalipoproteinemia with small low-density lipoprotein, a characteristic disorder of lipoprotein in essential hypertension

The purpose of the present study was to elucidate the characteristic lipoprotein disorder in essential hypertension. Twenty-six patients with essential hypertension (HT) but without diabetes mellitus or obesity and 24 healthy subjects (control) were recruited into this study. Lipoproteins of HT and controls were separated by ultracentrifugation to very-low-density lipoprotein (VLDL), intermediate density lipoprotein (IDL), low-density liproprotein (LDL), and (HDL) fractions. Cholesterol and triglycerides were determined with enzyme assay, and apoB were determined by highly sensitive latex agglutination (Kyowa-hakko Co. LD). There was no difference in age (mean +/- SE; HT, 63 +/- 2 versus control, 60 +/- 2 years) or body-mass index (22.7 +/- 0.4 versus 21.7 +/- 0.5 kg/m2) between HT and controls. Blood pressure in HT and controls was 158 +/- 2/87 +/- 12 mm Hg and 123 +/- 3/72 +/- 2 mm Hg, respectively. Cholesterol did not change significantly in plasma (192.1 +/- 7.0 versus 176.4 +/- 4.2 mg/dL), VLDL (15.2 +/- 2.4 versus 11.8 +/- 1.7 mg/dL), IDL (14.8 +/- 2.4 versus 10.7 +/- 1.6 mg/dL), LDL (93.7 +/- 4.6 versus 83.1 +/- 3.9 mg/dL), nor in HDL (51.9 +/- 2.7 versus 58.1 +/- 3.2 mg/dL). Triglycerides (TG) increased in plasma (120.0 +/- 10.0 versus 87.5 +/- 9.3 mg/dL, p < 0.05), although TG did not change in all subfractions. ApoB increased in plasma (105.5 +/- 5.1 versus 85.6 +/- 3.6 mg/dL, p < 0.01), IDL (9.0 +/- 1.3 versus 5.4 +/- 0.6 mg/dL, p < 0.05), and LDL (76.3 +/- 4.3 versus 59.4 +/- 3.7 mg/dL, p < 0.01) in HT compared with controls. The ratio of cholesterol to apoB in LDL decreased (1.27 +/- 0.06 versus 1.48 +/- 0.08, p < 0.05). In essential HT, number of apoB containing lipoproteins (IDL, LDL) increased. Low ratio of cholesterol to apoB was noted in LDL, indicating the presence of small, dense LDL. As cholesterol in LDL was normal, hyperbetalipoproteinemia is also a characteristic disorder of essential HT.     

Evidence for nonesterified fatty acids as modulators of neutral lipid transfers in normolipidemic human plasma

The relations between the level of plasma nonesterified fatty acid (NEFA) and both the mass concentration and activity of the cholesteryl ester transfer protein (CETP) were studied in fasted normolipidemic subjects. Plasma NEFA correlated positively with both CETP mass concentration (r = .50; P < .01) and the transfer of cholesteryl ester from HDL toward plasma VLDL+LDL (CETHDL-->VLDL+LDL activity) (r = .46; P < .05) but not with the transfer of cholesteryl ester from LDL toward plasma HDL (CETLDL-->HDL activity) (r = .05; NS). The high binding capacity of albumin for NEFA was used to investigate whether lipoprotein-bound NEFAs were implicated in the modulation of the cholesteryl ester transfer reaction. As compared with nonsupplemented controls, the addition of an excess of fatty acid-free albumin (8 g/L) to total normolipidemic plasmas reduced CETHDL-->VLDL+LDL activity (18.3 +/- 5.5% versus 9.8 +/- 3.1%; P < .0001) but not CETLDL-->HDL activity (22.3 +/- 4.5% versus 23.3 +/- 5.1%; NS). Moreover, CETHDL-->VLD+LDL and CETLDL-->HDL activities correlated negatively when measured in native plasma (r = -.45; P < .05) but positively when measured in albumin-supplemented plasma (r = .40; P < .05). In long-term incubation experiments, lipoprotein-bound NEFA increased the net mass transfer of cholesteryl esters from HDL toward VLDL+LDL but reduced the net mass transfer of triglycerides in the opposite direction, from VLDL+LDL toward HDL. Taken together, data of the present study brought strong and concordant arguments in favor of a dual effect of plasma NEFA in modulating both the mass and the activity of CETP in vivo.     

Apolipoprotein E polymorphism influences lipid phenotypic expression, but not the low density lipoprotein subfraction distribution in familial combined hyperlipidemia

The impact of apo E polymorphism on interindividual variation in plasma lipid, lipoprotein concentrations, and LDL subfraction profiles was studied in 201 well-defined patients (88 men and 103 women) with familial combined hyperlipidemia (FCH). When corrected for the concomitant influences of age, gender and obesity, the allelic variation in the apo E gene was shown to explain a statistically significant portion of the variability in lipid and (apo)lipoprotein concentrations. Carriers of the apo epsilon 2 allele exhibited a substantially higher plasma triglyceride concentration and a lower low density lipoprotein (LDL) cholesterol level, while subjects with the apo epsilon 4 allele had significant higher total plasma cholesterol and LDL cholesterol levels. In line with this observation, our FCH population was characterized by an over-representation of the apo E4 allele as compared with a Dutch standard population (chi 2 = 55.2, P < 0.0001). The contribution of apo E polymorphism to trait variability was different between sexes for plasma triglyceride, VLDL cholesterol, VLDL triglycerides, and high density lipoprotein (HDL) cholesterol levels. Apo E polymorphism had no impact on chemical composition of VLDL; for LDL particles the apo epsilon 2 allele was associated with a lower cholesterol to protein (C/P) ratio, whereas the opposite was true for the apo epsilon 4 allele. Despite the demonstrated impact of apo E polymorphism on plasma lipids and LDL chemical composition, in all phenotypic groups a dense LDL subfraction profile predominated. Thus, apo E polymorphism contributes to the lipid phenotypic expression in FCH, whereas further evidence was obtained that a dense LDL subfraction profile is an integral feature of FCH.     

Effects of two different fibric acid derivatives on lipoproteins, cholesteryl ester transfer, fibrinogen, plasminogen activator inhibitor and paraoxonase activity in type IIb hyperlipoproteinaemia

We have investigated the effects of two fibric acid derivatives, bezafibrate mono (400 mg daily) and gemfibrozil (600 mg b.d.), in 29 patients with type IIb hyperlipoproteinaemia. All patients received placebo and each drug for 8 weeks in randomised order in a double-blind, cross-over study designed to evaluate any different effects of the drugs on serum lipoproteins, cholesteryl ester transfer protein (CETP), cholesteryl ester transfer activity (CETA), plasma fibrinogen, plasminogen activator inhibitor-I (PAI-1) or paraoxonase. Serum cholesterol decreased (P < 0.05) with gemfibrozil, but the effect of bezafibrate on serum cholesterol did not achieve statistical significance (placebo 8.34 +/- 1.05 (mean +/- S.D.), gemfibrozil 7.70 +/- 1.23 and bezafibrate 7.8 +/- 1.37 mmol/l). Both drugs decreased the serum triglyceride concentration (both P < 0.001) (placebo 4.39 (3.13-5.75) (median (interquartile range)), bezafibrate 2.26 (1.89-3.89) and gemfibrozil 2.00 (1.30-3.30) mmol/l) and very low density lipoprotein (VLDL) cholesterol (both P < 0.001) (placebo 1.18 (0.74-2.30), bezafibrate 0.59 (0.34-0.85) and gemfibrozil 0.48 (0.34-0.68) mmol/l). Discontinuous gradient ultracentrifugation (DGU) revealed that Sf 60-400 (large VLDL) decreased by more than 50% and Sf 20-60 (small VLDL) by more than 30% with each of the drugs (both P < 0.001), neither of which affected the composition of these lipoproteins. Gemfibrozil decreased the concentration of Sf 12-20 lipoprotein (intermediate density lipoprotein; IDL) by 23% (P < 0.01), whereas the effect of bezafibrate on this lipoprotein did not achieve statistical significance. Neither drug altered the concentration of apolipoprotein B or of total Sf 0-12 lipoproteins (low density lipoprotein, (LDL)). Both, however, significantly increased the quantity of free cholesterol in Sf 0-12 lipoproteins (P < 0.05). Overall the concentration of triglycerides decreased significantly in all lipoproteins isolated by DGU (Sf 0-12, Sf 12-20, Sf 20-60, Sf 60-400) on gemfibrozil treatment, but only in Sf 20-60 and Sf 60-400 on bezafibrate (all P < 0.05). Both drugs also increased serum high density lipoprotein (HDL) cholesterol (placebo 1.15 +/- 0.29, bezafibrate 1.27 +/- 0.38 (P < 0.01) and gemfibrozil 1.26 +/- 0.49 (P < 0.05) mmol/l) and HDL3 cholesterol concentration (placebo 0.59 +/- 0.12, bezafibrate 0.72 +/- 0.23 (P < 0.001) and gemfibrozil 0.70 +/- 0.24 (P < 0.01) mmol/l). Serum apolipoprotein A1 (apo A1) was increased (P < 0.05) by bezafibrate compared to gemfibrozil (placebo 103 +/- 26, bezafibrate 111 +/- 28 and gemfibrozil 102 +/- 25 mg/dl) and CETA from HDL to VLDL and LDL was decreased (P < 0.05) by bezafibrate compared to placebo, but the apparent decrease with gemfibrozil did not achieve statistical significance (placebo 39.6 +/- 17.7, bezafibrate 32.3 +/- 14.7 and gemfibrozil 33.8 +/- 15.0 nmol/ml/h). Neither drug affected the circulating concentration of CETP. Plasma fibrinogen was increased (P < 0.05) by gemfibrozil (placebo 4.16 (3.38-4.71) and gemfibrozil 4.65 (4.05-5.77) g/l) and was significantly lower (P < 0.001) on bezafibrate (3.60 (3.18-4.54) g/l) than on gemfibrozil treatment. There was a significant (P < 0.05) increase in PAI-1 activity with bezafibrate and a similar trend with gemfibrozil (placebo 41.2 (25.6-64.5), bezafibrate 50.5 (35.1-73.9) and gemfibrozil 48.5 (31.5-5.4 U/l). Neither fibrate influenced plasma concentrations of PAI-1 nor were the activities of lecithin:cholesterol acyl transferase or paraoxonase affected. The major difference in the action of the two drugs on lipoprotein metabolism was the greater effect of gemfibrozil in decreasing the overall serum concentration of Sf 12-20 lipoproteins and the triglycerides in Sf 12-20 and 0-12 lipoproteins. Bezafibrate, however, increased serum apo A1 concentration and significantly decreased CETA. The two drugs also had different effects on the plasma fibrinogen levels, which increased with gemfibrozil and tended to decrea     

alpha-Tocopherol concentrations in plasma but not in lipoproteins fluctuate during the menstrual cycle in healthy premenopausal women

Because premenopausal women experience cyclic fluctuations of plasma carotenoids and their lipoprotein carriers, it was hypothesized that plasma alpha-tocopherol (A-T) fluctuates by phase of the menstrual cycle. Twelve free-living women, with a confirmed ovulatory cycle, were given a controlled diet for two consecutive menstrual cycles. Blood was drawn during the menses, early follicular, late follicular and luteal phases to simultaneously measure serum hormones, plasma lipoproteins and A-T concentrations, and A-T distribution in the lipoprotein fractions. Plasma A-T concentrations were significantly lower during menses than during the luteal phase by approximately 12% in each controlled diet cycle (P < 0.001). Adjustment for serum cholesterol and triglyceride concentrations did not alter these findings. The distributions of A-T in lipoprotein cholesterol fractions were not significantly different by menstrual phase. From 61 to 62% of A-T was concentrated in the LDL fraction, with another 9-14% in HDL2, 17-22% in HDL3 and the remaining 6-8% in VLDL+ IDL. There were no significant differences in lipoprotein cholesterol fractions by menstrual phase, except for a significant increase (P = 0.03) in HDL2 cholesterol from the early follicular to the late follicular phase. Spearman rank correlations from data during the second controlled diet month showed A-T in HDL2 in the late follicular phase was positively correlated with HDL cholesterol in the early follicular (r = 0.88), late follicular (r = 0.86) and luteal phases (r = 0.86) and with luteal apolipoprotein (ApoA-1) level (r = 0.90), and luteal HDL2 cholesterol (r = 0.83). A-T in HDL3 in the early follicular phase was negatively correlated with HDL2 cholesterol (r = -0.96) and ApoA-1 (r = -0.85), whereas luteal A-T in HDL3 was correlated with luteal HDL3 cholesterol (r = -0.79). Late follicular A-T in VLDL was positively correlated with early follicular HDL3 cholesterol and late follicular HDL3 cholesterol (r = 0.83). Fluctuations of A-T concentrations by phase of the menstrual cycle should be taken into consideration in future research concerning premenopausal women and the risk of chronic disease.     

Reduced cholesteryl ester transfer in plasma of patients with lipoprotein lipase deficiency

The net mass transfer of cholesteryl ester (CE) from high density lipoprotein (HDL) to the apolipoprotein (apo) B-containing lipoproteins, very low density lipoprotein (VLDL) and low density lipoprotein (LDL) in plasma (cholesteryl ester transfer (CET)) from three patients lacking lipoprotein lipase (LpL) activity was significantly lower (P < 0.001) than in plasma from fasting control subjects with comparable triglyceride levels. Chylomicrons isolated from LpL-deficient fasting plasma showed the same low level of CET activity as observed in the intact plasma when combined with HDL and cholesteryl ester transfer protein (CETP)-containing d 1.063 g/ml bottom fractions from control subjects. Preincubation of chylomicrons and large triglyceride-rich lipoproteins (Sf > 400) from LpL-deficient plasma with milk LpL, however, stimulated the capacity to engage in CET 4- to 5-fold to the same level as chylomicrons and VLDL from control subjects after a fat load. Consistent with these measurements of CET activity in plasma, chylomicrons obtained from the LpL-deficient subjects after a 14-h fast had higher TG/CE ratios than chylomicrons from controls 3 h after ingesting a fat load (LpL-deficient 26.3 +/- 9.0 vs. controls 6.9 +/- 2.1; mean +/- SD). The mass of CETP did not differ in LpL-deficient and control subjects (LpL-deficient 1.03 +/- 0.22 micrograms/ml vs. controls 1.58 +/- 0.58 micrograms/ml). These studies are consistent with earlier in vitro studies showing that the actions of lipoprotein lipase and its lipolytic products are essential, for maximal cholesteryl ester transfer protein activity.     

Fenofibrate reduces plasma cholesteryl ester transfer from HDL to VLDL and normalizes the atherogenic, dense LDL profile in combined hyperlipidemia

The effect of fenofibrate on plasma cholesteryl ester transfer protein (CETP) activity in relation to the quantitative and qualitative features of apoB- and apoA-I-containing lipoprotein subspecies was investigated in nine patients presenting with combined hyperlipidemia. Fenofibrate (200 mg/d for 8 weeks) induced significant reductions in plasma cholesterol (-16%; P < .01), triglyceride (-44%; P < .007), VLDL cholesterol (-52%; P = .01), LDL cholesterol (-14%; P < .001), and apoB (-15%; P < .009) levels and increased HDL cholesterol (19%; P = .0001) and apoA-I (12%; P = .003) levels. An exogenous cholesteryl ester transfer (CET) assay revealed a marked decrease (-26%; P < .002) in total plasma CETP-dependent CET activity after fenofibrate treatment. Concomitant with the pronounced reduction in VLDL levels (37%; P < .005), the rate of CET from HDL to VLDL was significantly reduced by 38% (P = .0001), whereas no modification in the rate of cholesteryl ester exchange between HDL and LDL occurred after fenofibrate therapy. Combined hyperlipidemia is characterized by an asymmetrical LDL profile in which small, dense LDL subspecies (LDL-4 and LDL-5, d = 1.039 to 1.063 g/mL) predominate. Fenofibrate quantitatively normalized the atherogenic LDL profile by reducing levels of dense LDL subspecies (-21%) and by inducing an elevation (26%; P < .05) in LDL subspecies of intermediate density (LDL-3, d = 1.029 to 1.039 g/mL), which possess optimal binding affinity for the cellular LDL receptor. However, no marked qualitative modifications in the chemical composition or size of LDL particles were observed after drug treatment. Interestingly, the HDL cholesterol concentration was increased by fenofibrate therapy, whereas no significant change was detected in total plasma HDL mass. In contrast, the HDL subspecies pattern was modified as the result of an increase in the total mass (11.7%) of HDL2a, HDL3a, and HDL3b (d = 1.091 to 1.156 g/mL) at the expense of reductions in the total mass (-23%) of HDL2b (d = 1.063 to 1.091 g/mL) and HDL3c (d = 1.156 to 1.179 g/mL). Such changes are consistent with a drug-induced reduction in CETP activity. In conclusion, the overall mechanism involved in the fenofibrate-induced modulation of the atherogenic dense LDL profile in combined hyperlipidemia primarily involves reduction in CET from HDL to VLDL together with normalization of the intravascular transformation of VLDL precursors to receptor-active LDLs of intermediate density.     

Influence of plasma cholesteryl ester transfer activity on the LDL and HDL distribution profiles in normolipidemic subjects

The relations of cholesteryl ester transfer protein (CETP) activity to the distribution of low density lipoproteins (LDLs) and high density lipoproteins (HDLs) were investigated in fasting plasma samples from 27 normolipidemic subjects. LDL and HDL subfractions were separated by electrophoresis on 20-160 g/L and 40-300 g/L polyacrylamide gradient gels, respectively. Subjects were subdivided into two groups according to their LDL pattern. Monodisperse patterns were characterized by the presence of a single LDL band, whereas polydisperse patterns were characterized by the presence of several LDL bands of different sizes. To investigate the influence of lipid transfers on LDL patterns, total plasma was incubated at 37 degrees C in the absence of lecithin:cholesterol acyltransferase (LCAT) activity. The incubation induced a progressive transformation of polydisperse patterns into monodisperse patterns. Under the same conditions, initially monodisperse patterns remained unchanged. Measurements of the rate of radiolabeled cholesteryl esters transferred from HDL3s to very low density lipoproteins (VLDLs) and LDLs revealed that subjects with a monodisperse LDL pattern presented a significantly higher plasma CETP activity than subjects with a polydisperse LDL pattern (301 +/- 85%/hr per milliliter versus 216 +/- 47%/hr per milliliter, respectively; p < 0.02). In addition, when total plasma was incubated for 24 hours at 37 degrees C in the absence of LCAT activity, the relative mass of cholesteryl esters transferred from HDLs to apolipoprotein B-containing lipoproteins was greater in plasma with monodisperse LDL than in plasma with polydisperse LDL (0.23 +/- 0.06 versus 0.17 +/- 0.06, respectively; p < 0.02). These results indicated that in normolipidemic plasma, CETP could play an important role in determining the size distribution of LDL particles. The analysis of lipoprotein cholesterol distribution in the two groups of subjects sustained this hypothesis. Indeed, HDL cholesterol levels, the HDL:VLDL+LDL cholesterol ratio, and the esterified cholesterol:triglyceride ratio in HDL were significantly lower in plasma with the monodisperse LDL pattern than in plasma with the polydisperse LDL pattern (p < 0.01, p < 0.01, and p < 0.02, respectively). Plasma LCAT activity did not differ in the two groups. Plasma CETP activity correlated positively with the level of HDL3b (r = 0.542, p < 0.01) in the entire study population. Whereas plasma LCAT activity correlated negatively with the level of HDL2b (r = -0.455, p < 0.05) and positively with the levels of HDL2a (r = 0.475, p < 0.05) and HDL3a (r = 0.485, p < 0.05), no significant relation was observed with the level of HDL3b.(ABSTRACT TRUNCATED AT 400 WORDS)     

Serum lipid levels in children and teenagers from Concepción, Chile

BACKGROUND: There is a relationship between serum lipid levels in children with those of adults. Preventive measures to reduce serum lipid levels should start in childhood. AIM: To study serum lipid levels in a representative sample of children and teenagers from Concepción, Chile. SUBJECTS AND METHODS: Serum total, HDL cholesterol and triglycerides were measured in 1,286 males and 816 females from 5 to 18 years old in the city of Concepción. RESULTS: Mean total cholesterol levels were 159 +/- 30 and 162 +/- 31 mg/dl in males and females respectively. The figures for HDL cholesterol were 46 +/- 11 and 47 +/- 11 mg/dl, for LDL cholesterol were 94 +/- 27 and 96 +/- 29 mg/dl and for triglycerides were 80 +/- 35 and 87 +/- 38 mg/dl. Nine percent of males and 12% of females had a total cholesterol over 200 mg/dl. Likewise 10% of males and 11% of females had a LDL cholesterol over 130 mg/dl. CONCLUSIONS: These numbers will help to plan and perform interventions in children, in order to prevent cardiovascular diseases.     

Initial clinical experience with the Ahmed Glaucoma Valve implant in pediatric patients

There is evidence that a low-density lipoprotein (LDL) subfraction profile of increased concentrations of small, dense LDL particles is less common among trained than among sedentary normocholesterolemic men, but it is still uncertain whether there is a similar association in hypercholesterolemia also. Therefore, we determined the lipid and apolipoprotein concentration and composition of six LDL subfractions (density gradient ultracentrifugation) in 20 physically fit, regularly exercising (>three times per week) hypercholesterolemic men and 20 sedentary hypercholesterolemic controls. Trained (maximal oxygen consumption [VO2max], 57.3 +/- 7.4 mL/kg/min) and sedentary (VO2max, 37.5 +/- 8.8 mL/kg/min) individuals (aged 35 +/- 11 years; body mass index [BMI], 23.9 +/- 2.7 kg/m2) were matched for LDL apolipoprotein (apo) B levels (108 +/- 23 and 112 +/- 36 mg/dL, respectively). Trained subjects had significantly lower serum triglyceride (P < .05) and very-low-density lipoprotein (VLDL) cholesterol levels (P < .05) and higher high-density lipoprotein 2 (HDL2) cholesterol levels (P < .01) than sedentary controls. LDL particle distribution showed that trained individuals had significantly less small, dense LDL (d = 1.040 to 1.063 g/mL) and more large LDL (d = 1.019 to 1.037 g/mL) subfraction particles than sedentary controls, despite equal total LDL particle number. Analysis of LDL composition showed that LDL particles of hypercholesterolemic trained men had a higher free cholesterol content than LDL of untrained hypercholesterolemic men. Small, dense LDL in hypercholesterolemic trained men were richer in phospholipids than those in sedentary controls. These data demonstrate the significant influence of aerobic fitness on lipoprotein subfraction concentration and composition, thereby emphasizing the role of exercise in the treatment and risk reduction of hypercholesterolemia.     

Neutral lipid mass transfer among lipoproteins in plasma from normolipidemic subjects is not an equimolar heteroexchange

To further characterize the cholesteryl ester transfer protein (CETP)-mediated distribution of neutral lipids that occurs among lipoproteins in plasma, the net mass transfer of core lipids between donor and acceptor lipoproteins in intact plasma was measured in ten healthy normolipidemic subjects. The rate of loss of cholesteryl ester (CE) from high density lipoprotein-3 (HDL3) (19.5 +/- 8.8 nmol/ml per h) was linear and increased significantly (P < 0.01) during the 6-h incubation. Approximately 50% of the CE transferred from HDL3 (118.7 +/- 54.3 nmol/ml) went to very low density lipoprotein (VLDL); the remainder was distributed to low density lipoprotein (LDL) (approximately 30%) and HDL2 (approximately 20%). The rate of loss of triglyceride (TG) from VLDL (14.5 +/- 6.6 nmol/ml per h) to the HDL subfractions and LDL also was linear and increased significantly with time (P < 0.01). About 50% of the TG mass lost from VLDL (85.2 +/- 38.4 nmol/ml) was transferred to LDL and the remainder was recovered in HDL2 (approximately 10%) and HDL3 (approximately 40%). As the number of nmoles of CE lost from HDL3 was almost three times greater than the nmoles of TG it acquired, these findings indicate that the exchange of core lipids in plasma that result from the interaction between CETP-VLDL-HDL3 is not equimolar. Even in the absence of VLDL, HDL3 continued to donate CE to LDL and HDL2 to almost the same degree as in intact plasma (plasma minus VLDL: 17.5 +/- 5.9 nmol/ml per h vs. intact plasma: 20.2 +/- 7.5 nmol/ml per h) without accepting any TG. Our findings demonstrate that independent pathways exist for the transfer of CE and TG among the plasma lipoproteins and, contrary to what is generally believed, a heteroexchange of TG for CE during cholesteryl ester transfer is not obligatory.     

Synaptic proteins of the temporal associative area of the neocortex of cats (field Ep) with normal and reduced cognitive capacities

Genetically hypercholesterolaemic RICO rats (male, 6 weeks old) were randomly distributed into 6 experimental groups. The zero-time basal group A was sacrificed at the start of the experiment while the other groups were fed for 6 weeks and then sacrificed. Group B was fed a stock diet. Control group C was fed a high-sucrose (45%) diet with 0.5% added cholesterol. In the diet of group D, only the magnesium (Mg) content was reduced from the level of group C (883 ppm) to 200 ppm. The diet of group E was the same as that of group D with the addition of 12 ppm of fluoride (F) and the diet of group G was the same as that of group E, but with its Mg content elevated from 200 ppm to 300 ppm. Analysis of aortic blood samples, taken before sacrifice, indicated significant increases in total serum cholesterol (p < 0.01), very low density lipoprotein (VLDL) (p < 0.001) and low density lipoprotein (LDL), (p < 0.001) cholesterol, and a trend to lower high density lipoprotein (HDL) cholesterol in group C, as compared to group B. Significantly lower total (p < 0.05), VLDL (p < 0.01) and LDL (p < 0.01) triglycerides were observed in group C when compared to group B. The LDL phospholipids were significantly higher in group C (p < 0.001) than in group B. When cholesterol levels in groups D, E and G were compared with group C, the VLDL cholesterol in group E and the LDL cholesterol in group G were slightly but significantly (p < 0.05) reduced, while total cholesterol and the other subfractions were unaltered. The LDL triglycerides of groups E and G were significantly smaller still than the already small fraction in group C. The VLDL triglyceride in group E was significantly lower than that of group C (35% reduction, p < 0.001), D and G (p < 0.05). Phospholipids were slightly but significantly reduced in the VLDL fraction of group E and in the LDL fraction of group G (p < 0.05 and 0.01, respectively), as compared to those of group C.     

The use of an interactive computer program for the education of parents of asthmatic children

OBJECTIVES: To evaluate the effect of a single evening meal (gorging) on plasma lipids and lipoproteins in normal individuals observing the Ramadan Fast. During the Ramadan month, Muslims refrain from food and liquids during the day and eat a large meal after sundown. DESIGN: Sequential measurement of plasma lipids and lipoproteins in Muslims observing the Ramadan Fast and non-fasting individuals. SETTING: The study was conducted in the Bedouin town of Rahat, in the northern Negev area of Israel. SUBJECTS: Twenty-two healthy subjects who fasted during Ramadan and 16 non-fasting laboratory workers, were studied before Ramadan, at week 1, 2 and 4 of the Ramadan month, and again four weeks after the end of Ramadan. RESULTS: Plasma high-density lipoprotein cholesterol (HDL) rose significantly (P < 0.001) at the week 4 measurement, returning to basal levels 4 weeks after the end of Ramadan. Total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL), very-low density lipoprotein cholesterol (VLDL), and lipoprotein (a) [Lp(a)] did not change significantly. CONCLUSIONS: Plasma HDL increased by 23% after four weeks of gorging. The dietary change did not affect the composition of other lipoproteins, such as LDL, VLDL or Lp(a), other plasma biochemical parameters, or BMI. Prolonged gorging, well tolerated by all individuals, is a very effective non-pharmacological method to increase plasma HDL-cholesterol.     

Phosphorylation and cytotoxicity of therapeutic nucleoside analogues: a comparison of alpha and gamma herpesvirus thymidine kinase suicide genes

The effect of a triphasic oral contraceptive containing ethinyl estradiol and gestodene (EE/GSD) on various lipid and lipoprotein parameters was compared with that of a monophasic formulation containing 35 micrograms ethinyl estradiol and 250 micrograms norgestimate (EE/NGM). Blood samples were collected from 46 women on days 2, 11, and 21 of the preceding control cycle and of the third, sixth, and twelfth treatment cycles. There was no significant difference between formulations with regard to the influence on any measured parameter. As compared with controls, a significant increase was observed in the plasma levels of total triglycerides (24-78%), total phospholipids (7-20%), very low density lipoprotein (VLDL) triglycerides (61-76%), VLDL-phospholipids (14-60%), low density lipoprotein (LDL) triglycerides (8-35%), LDL-phospholipids (28-30%), high density lipoprotein (HDL) cholesterol (8-16%), HDL 3-cholesterol (11-20%), HDL-triglycerides (17-66%), HDL-phospholipids, HDL 3-phospholipids (7-11%), apolipoprotein (apo) A-I (5-20%) and apo A-II (10-40%) during treatment with both formulations. In contrast, the LDL-cholesterol levels were significantly decreased. These changes in lipid metabolism appear to reflect a predominance of the effect of the estrogen component. The results indicate that both low dose oral contraceptives containing different progestins and different amounts of EE do not exert a deleterious effect on lipoprotein metabolism, as high HDL-cholesterol and low LDL-cholesterol levels are known as low risk factors of cardiovascular disease. In contrast to endogenous hypertriglyceridemia, an EE-induced rise in triglyceride levels does not appear to increase cardiovascular risk if LDL is not increased.     

Effect of psyllium in hypercholesterolemia at two monounsaturated fatty acid intakes

We performed two studies to determine whether the lipid-lowering effect of viscous soluble fiber was modified by monounsaturated fatty acid (MUFA). First, psyllium (1.4 g/MJ) was compared with wheat bran (control) in 1-mo metabolic diets by using a randomized crossover design (n = 32 hyperlipidemic subjects). The background diet contained approximately 6% of energy as MUFA (20% of total fat). The second study (n = 27 hyperlipidemic subjects) was similar to the first but the background diet contained approximately 12% MUFA (29% of total fat) because of the addition of canola oil. At both fat intakes, psyllium resulted in significant reductions in total, low-density-lipoprotein (LDL), and high-density-lipoprotein (HDL) cholesterol compared with the wheat bran control. For the psyllium diet at 6% compared with 12% MUFA, the decreases in LDL cholesterol were 12.3 +/- 1.5% (P < 0.001) and 15.3 +/- 2.4% (P < 0.001), respectively. With the higher-MUFA diet triacylglycerol fell significantly over the control phase (16.6 +/- 5.5%, P = 0.006) and the ratio of LDL to HDL cholesterol fell significantly over the psyllium phase (7.3 +/- 2.8%, P = 0.015). Psyllium and MUFA intakes were negatively related to the percentage change in the ratio of LDL to HDL cholesterol (r = -0.34, P = 0.019 and r = -0.44, P = 0.002, respectively). Chenodeoxycholate synthesis rate increased (30 +/- 13%, P = 0.038) with the psyllium diet in the 12 subjects in whom this was assessed. We conclude that psyllium lowered LDL- and HDL-cholesterol concentrations similarly at both MUFA intakes. However, there may be some advantage in combining soluble fiber and MUFA to reduce the ratio of LDL to HDL cholesterol.