Hypercholesterolemic Human Subjects Research Articles

FCG RECEPTOR IIA GENOTYPE, AFFECTING BINDING OF C-REACTIVE PROTEIN TO PHAGOZYTES IN VITRO, IS ASSOCIATED WITH ENDOTHELIAL FUNCTION IN VIVO: 1D.05

Objective: Experimental studies suggest C-reactive protein (CRP) directly promotes atherosclerosis, but supporting evidence in humans is scarce. Recently, a gene polymorphism substituting arginine (R) for histidine (H) at position 131 has been described within the Fcγ receptor IIa (FcγRIIa), increasing CRP-binding and subsequent calcium signaling of phagocytes. We hypothesized this would affect endothelial function in vivo. Design and Methods: Genomic DNA was extracted and allele-specific PCR reactions were used to determine the presence or absence of the H and/or R alleles in 36 hypercholesterolemic subjects, previously included in a trial on endothelial effects of antihyperlipidemic treatment. Forearm blood flow (FBF) responses to intraarterial infusion of acetylcholine (ACH, 12 and 48 μg/min), for endothelium-dependent vasodilation (EDV), and to nitroprusside (NP, 3.2 and 12.8 μg/min), for endothelium-independent vasodilation (EIV), were assessed by plethysmography. Results: Compared to homozygous carriers of the H allele (n = 12), EDV was significantly attenuated in carriers of the R allele (H/R and R/R genotypes combined, n = 24) (% increase of FBF to 12 and 48 μg/min ACH: 419 ± 316 and 614 ± 387 versus 219 ± 161 and 508 ± 378, p = 0.05 by 2-way ANOVA). In contrast, EIV was not affected by genotype (% increase to 3.2 and 12.8 μg/min NP: 241 ± 135 and 404 ± 228 versus 242 ± 131 and 568 ± 349, n.s.). Conclusions: The arginine for histidine substitution at position 131 of the FcγRIIa receptor is associated with impaired EDV in hypercholesterolemic human subjects. These data suggest that the increased CRP-binding of phagocytes previously observed in carriers of the R allele in vitro translates into a clinically relevant impairment of endothelial function in vivo.

Antihypercholesterolemic effect of Chinese black tea extract in human subjects with borderline hypercholesterolemia

A water-soluble extract of a traditional Chinese black tea (Pu-Ehr) has been shown to precipitate mixed bile salt micelles in foods. In addition, long-term ingestion of this black tea extract (BTE) significantly reduces blood cholesterol levels in rats. We investigated the effects of BTE tablets (a formula designed to enhance compliance) as a dietary supplement in a 3-month double-blind randomized group comparison study in borderline hypercholesterolemic human subjects (n = 47). All subjects ingested BTE tablets (333 mg) or placebo 3 times daily before meals for 3 months. In the BTE-treated group, the initial mean blood total (6.14 +/- 0.14 mol/L) and low-density lipoprotein (LDL) cholesterol (4.32 +/- 0.14 mol/L) levels decreased with time and were significantly (P < .01) lower (total cholesterol, 5.62 +/- 0.11; LDL cholesterol, 3.81 +/- 0.13 mol/L) after 3 months of ingestion. Furthermore, the mean body weights (P < .05) and triacylglycerol levels (P < .01) were also significantly reduced after 3 months of BTE intake compared with the baseline levels. Significant improvements in the mean LDL cholesterol, body weight, and triacylglycerol values were not accompanied with undesirable changes in other biochemical parameters measured in the subjects. None of the subjects complained of any adverse effects (eg, abdominal distension). The results indicate that BTE intake elicited a significant antihypercholesterolemic effect and might be useful for improving blood cholesterol levels in subjects at risk for heart disease or obesity.

Hydroxypropylmethylcellulose significantly lowers blood cholesterol in mildly hypercholesterolemic human subjects

To determine the cholesterol-lowering efficacy of hydroxypropylmethylcellulose (HPMC) in mildly hypercholesterolemic humans. Trial one: entry mean (range) total serum cholesterol values of eight female and four male subjects were 6.48 (5.57-7.51) mmol l(-1) (250 (215-290) mg dl(-1)) and 6.60 (5.57-7.64) mmol l(-1) (255 (215-295) mg dl(-1)), respectively. Trial two: corresponding values for 20 women and 20 men were 5.96 (5.43-6.48) mmol l(-1) 230 (210-250) mg dl(-1)) and 6.05 (5.46-6.63) mmol l(-1) 233 (211-256) mg dl(-1)), respectively. Trial one: HPMC decreased (P< or =0.05) total and LDL-cholesterol 9.3 and 15.3% (medium), 16.9 and 23.5% (high) and 13.8 and 19.4% (ultra-high), respectively, over placebo. Trial two: total and LDL-cholesterol decreased (P< or =0.05) throughout the 8 weeks, with mean (weeks 4-8) reductions of 7 and 8% at 5 g day(-1), and 12 and 15% at 15 g day(-1), respectively, over placebo. Adverse effects were minimal. Trial one: medium, high and ultra-high viscosity HPMC at 15 g day(-1) for 1 week each;1-week wash-out between treatments. Trial two: ultra-high viscosity HPMC at 5 or 15 g day(-1) for 8 weeks. HPMC soluble fiber, especially high-viscosity grades, significantly lowers cholesterol at well-tolerated doses, showing promise as a treatment of hypercholesterolemia.

Genetics and molecular biology: macrophage ACAT depletion – mechanisms of atherogenesis

Genetics and molecular biology: macrophage ACAT depletion – mechanisms of atherogenesis

Dose-dependent suppression of serum cholesterol by tocotrienol-rich fraction (TRF 25) of rice bran in hypercholesterolemic humans

Tocotrienols are effective in lowering serum total and LDL-cholesterol levels by inhibiting the hepatic enzymic activity of β-hydroxy-β-methylglutaryl coenzymeA (HMG-CoA) reductase through the post-transcriptional mechanism. α-Tocopherol, however, has an opposite effect (induces) on this enzyme activity. Since tocotrienols are also converted to tocopherols in vivo, it is necessary not to exceed a certain dose, as this would be counter-productive. The present study demonstrates the effects of various doses of a tocotrienol-rich fraction (TRF 25) of stabilized and heated rice bran in hypercholesterolemic human subjects on serum lipid parameters. Ninety (18/group) hypercholesterolemic human subjects participated in this study, which comprised three phases of 35 days each. The subjects were initially placed on the American Heart Association (AHA) Step-1 diet and the effects noted. They were then administered 25, 50, 100, and 200 mg/day of TRF 25 while on the restricted (AHA) diet. The results show that a dose of 100 mg/day of TRF 25 produce maximum decreases of 20, 25, 14 ( P<0.05) and 12%, respectively, in serum total cholesterol, LDL-cholesterol, apolipoprotein B and triglycerides compared with the baseline values, suggesting that a dose of 100 mg/day TRF 25 plus AHA Step-1 diet may be the optimal dose for controlling the risk of coronary heart disease in hypercholesterolemic human subjects.

Beneficial effects of a novel IH636 grape seed proanthocyanidin extract and a niacin-bound chromium in a hamster atherosclerosis model.

Atherosclerosis is a disease of the arteries in which fatty plaques develop on the inner arterial wall, which eventually obstructs blood flow. Identified risk factors for atherosclerosis include genetics, diet, lifestyle, smoking, circulating lipid and cholesterol levels, and molecular and circulating signals of chronic vascular inflammation. The link between flavonoids and atherosclerosis is based partly on the evidence that some flavonoids possess antioxidant properties and have been shown to be potent inhibitors of LDL oxidation in vitro. Hypercholesterolemia, a significant cardiovascular risk factor is prevalent in the American population. Grape seed proanthocyanidin extracts are known to exhibit a broad spectrum of chemopreventive and cardioprotective properties against oxidative stress. A recent study has shown that a combination of IH636 grape seed proanthocyanidin extract (GSPE) and a niacin-bound chromium (NBC) can decrease total cholesterol, LDL and oxidized LDL levels in hypercholesterolemic human subjects. In this study, we assessed the efficacy of GSPE supplementation in hamsters, singly and in combination with NBC, since these animals have a similar lipid profile to hypercholesterolemic humans when fed a hypercholesterolemic diet of 0.2% cholesterol and 10% coconut oil (HCD). After 10 weeks of feeding HCD, these animals developed foam cells, which is a biomarker of early stages of atherosclerosis. Atherosclerosis (% of aorta covered with foam cells) was reduced by approximately 50% and 63% following supplementation of these animals with 50 mg/kg and 100 mg/kg of GSPE, respectively, in conjunction with a HCD, while approximately 32% reduction was observed following supplementation of GSPE plus NBC. A range of 7-9 animals was used in each study group. GSPE alone and in combination with NBC exerted a pronounced effect on the cholesterol, and triglyceride levels, as well as oxidative lipid damage as demonstrated by the formation of thiobarbituric acid reactive substances (TBARS). This data demonstrates that GSPE and NBC may provide significant health benefits by dramatically ameliorating the incidence of atherosclerosis as demonstrated by reducing the formation of foam cells.

Novel tocotrienols of rice bran modulate cardiovascular disease risk parameters of hypercholesterolemic humans

Tocotrienols inhibit cholesterol synthesis by post-transcriptionally suppressing β-hydroxy-β-methylglutaryl-coenzyme A reductase activity. A double blind, 12-week study was performed to investigate the effect of a novel tocotrienol-rich fraction (TRF 25; obtained by molecular distillation from specially processed rice bran oil) on cardiovascular disease risk factors of hypercholesterolemic human subjects (serum total cholesterol >5.69 mmol/L). After acclimation to an alcohol-free regimen (baseline) participants were assigned to the National Cholesterol Education Program (NCEP) Step-1 diet (saturated fat <19%, total fat <30% of total calories and cholesterol <7.76 mmol/L). The participants were evaluated after 4 weeks of exposure to the NCEP Step-1 diet; one group of 21 participants was continued on the NCEP Step-1 diet for 4 weeks receiving an additional 1.2 gm corn oil (placebo group) and a second group of 20 received 200 mg TRF 25 dissolved in 1.0 gm corn oil (TRF 25 group). Serum total cholesterol and LDL-cholesterol levels of all the participants, stable during the baseline phase of the study, decreased 5% and 8%, respectively, during the 4-week NCEP Step-1 diet. Placebo continuing on the NCEP Step-1 diet for an additional 4 weeks experienced additional but modest decreases in serum total cholesterol (2%) and LDL-cholesterol (3%), yielding significant ( P < 0.05) decreases when compared with the baseline values. These responses confirm the cholesterol-lowering action of a low fat, low cholesterol diet. Participants receiving TRF 25 had 12% and 16% reductions ( P < 0.05) in total cholesterol and LDL-cholesterol levels during the 4-week experimental phase; during the two phases (NCEP Step-1 diet plus treatment) the serum total cholesterol and LDL-cholesterol levels of these participants were decreased ( P < 0.05) by 17% and 24%, respectively. TRF 25-mediated decreases in Apo B, Lp(a), platelet factor 4 and thromboxane B 2 (15%, 17%, 14%, and 31%, respectively) were significant ( P < 0.05). There was no change in the levels of HDL-cholesterol and apolipoprotein A-I by this treatment. The treatments also resulted in remarkable increases in the levels of LDL-bound antioxidants, especially tocotrienols, which have substantially greater antioxidant activity than vitamin E.

Wheat bread supplemented with depolymerized guar gum reduces the plasma cholesterol concentration in hypercholesterolemic human subjects

Recent human studies have shown that the physiologic effects of guar gum are not diminished by partial depolymerization of its galactomannan fraction. We evaluated the effect of depolymerized guar galactomannan on fasting plasma cholesterol and triacylglycerol concentrations in healthy volunteers with moderately raised plasma cholesterol concentrations (range: 5.2-8.0 mmol/L). This study was designed as a randomized, double-blind crossover of two 3-wk feeding periods separated by a 4-wk washout period. Control and guar wheat breads were prepared by a commercial bread-making process. Subjects (n = 11) were asked to replace their normal bread with that provided, receiving control bread for one 3-wk period and guar bread for the other period, without altering their baseline diet. Subjects recorded their intake of foods for 6 consecutive days on three occasions during the study. Fasting venous blood samples (10 mL) were taken from subjects on two consecutive mornings at the start and end of each feeding period. No significant changes in body weight or dietary intake were recorded in the control and guar bread periods. There was a significant reduction (10%) in total plasma cholesterol concentration after the guar treatment (P < 0.001), mainly because of a reduction in the low-density-lipoprotein-cholesterol fraction. No changes in plasma high-density-lipoprotein-cholesterol or triacylglycerol concentrations were seen. The cholesterol-lowering effect of partially depolymerized guar gum appears to be of a magnitude similar to that of high-molecular-weight guar gum used in earlier studies.

Lovastatin decreases plasma and platelet cholesterol levels and normalizes elevated platelet fluidity and aggregation in hypercholesterolemic patients

The lipid composition of whole platelets and the fluidity of platelet membranes, as well as the sensitivity of the cell to aggregation, were studied in type IIA hypercholesterolemic human subjects before and after treatment with lovastatin. Fourteen patients with primary hypercholesterolemia having initial cholesterol levels of 383 ± 52 mg/dL (mean ± standard deviation) were studied and compared with 21 control subjects having cholesterol levels of 187 ± 32 mg/dL. Lovastatin was administered orally at a starting dose of 40 mg daily. The dose was increased to 80 mg daily for eight patients who did not achieve the target cholesterol level of 200 mg/dL at 6 weeks. Serum cholesterol level was decreased by 37% following 20 weeks' administration of the drug. The fluidity of platelet membranes expressed in terms of the fluorescence anisotropy parameter was determined using the probe 1,6-diphenyl-1,3,5-hexatriene (DPH). When compared with platelets obtained from normocholesterolemic controls, platelets from hypercholesterolemic patients had a higher molar ratio of cholesterol to phospholipids ([ C/ PL] 0.86 ± 0.15 v 0.57 ± 0.06 for controls) and of phosphatidylcholine to sphingomyelin ([ PC/ SM] 2.64 ± 0.87 v 2.00 ± 0.15 for controls), enhanced fluidity (anisotropy parameter at 37°C of 0.892 ± 0.066 v 0.977 ± 0.065 for controls), and a greater tendency to aggregate (aggregation of 84.2% ± 6.3% v 78.5% ± 7.6% for controls). Lovastatin administration for 20 weeks to hypercholesterolemic patients markedly normalized platelet lipid composition ( C/ PL, 0.58 ± 0.13; PC/ SM, 1.84 ± 0.60), membrane fluidity (anisotropy parameter, 0.980 ± 0.033), and aggregation (aggregation, 75.9% ± 10.0%), suggesting that lovastatin treatment may attenuate the involvement of platelets in the pathogenesis of atherosclerosis.

Long-Term Wheat Germ Intake Beneficially Affects Plasma Lipids and Lipoproteins in Hypercholesterolemic Human Subjects

In previous short-term studies in rats and humans, the ingestion of raw wheat germ lowered plasma triglycerides and cholesterol. Thus, the present study was designed to investigate the possible long-term effects of wheat germ intake. Diet supplementation with raw wheat germ or partially defatted wheat germ was tested in two separate groups of 10 and 9 free-living human subjects, respectively. They all exhibited hypercholesterolemia (6.14–9.67 mmol/L cholesterol) and 11 had hypertriglyceridemia. None was diabetic. Fasting blood samples were taken at the beginning of the study, after 4 wk of 20 g/d wheat germ intake, after 14 additional weeks of 30 g/d wheat germ intake and after 12 wk without any supplementation. Dietary records were kept for seven and three consecutive days, before and during the wheat germ intake periods, respectively. Raw wheat germ intake significantly decreased plasma cholesterol (-8.7%) and tended to reduce VLDL cholesterol (-19.6%) after 4 wk. After 14 additional weeks, plasma cholesterol (-7.2%) and LDL cholesterol (-15.4%) remained lower and plasma triglycerides (-11.3%) tended to be lower. The apo B:apo A1 ratio significantly decreased after both periods. Partially defatted wheat germ transiently decreased plasma triglycerides and cholesterol after a 4-wk intake. The present data indicate that wheat germ reduces cholesterolemia in the long term and could play a beneficial role in the dietary management of type IIa and IIb hyperlipidemia.

Lowering of serum cholesterol in hypercholesterolemic humans by tocotrienols (palmvitee)

A double-blind, crossover, 8-wk study was conducted to compare effects of the tocotrienol-enriched fraction of palm oil (200 mg palmvitee capsules/day) with those of 300 mg corn oil/d on serum lipids of hypercholesterolemic human subjects (serum cholesterol 6.21-8.02 mmol/L). Concentrations of serum total cholesterol (-15%), LDL cholesterol (-8%), Apo B (-10%), thromboxane (-25%), platelet factor 4 (-16%), and glucose (-12%) decreased significantly only in the 15 subjects given palmvitee during the initial 4 wk. The crossover confirmed these actions of palmvitee. There was a carry over effect of palmvitee. Serum cholesterol concentrations of seven hypercholesterolemic subjects (greater than 7.84 mmol/L) decreased 31% during a 4-wk period in which they were given 200 mg gamma-tocotrienol/d. This indicates that gamma-tocotrienol may be the most potent cholesterol inhibitor in palmvitee capsules. The results of this pilot study are very encouraging.

Short-term effects of substituting protein for carbohydrate in the diets of moderately hypercholesterolemic human subjects

The short-term effects of plasma lipoprotein lipids of substituting meat and dairy protein for carbohydrate in the diets of 10 free-living moderately hypercholesterolemic human subjects (four men, six women) were studied under closely supervised dietary control during the consumption of constant, low intakes of fat and cholesterol and the maintenance of stable body weight as well as constant fiber consumption. Subjects were randomly allocated to either the high or low protein diets (mean, 23% v 11% of energy as protein, 24% as fat, and 53% v 65% as carbohydrate) and then switched to the other diet for another 4 to 5 weeks. Mean fasting plasma high-density lipoprotein cholesterol (HDL-C) was significantly higher by 12% ± 4% (0.97 ± 0.08 v 0.89 ± 0.08 mmol/L, P < .01), whereas mean total cholesterol (TC) was lower by 6.5% ± 1.3% (5.7 ± 0.3 v 6.1 ± 0.3 mmol/L, P < .001), mean low-density lipoprotein-cholesterol (LDL-C) lower by 6.4% ± 2.0% (4.5 ± 0.2 v 4.8 ± 0.2 mmol/L, P < .02), mean total triglycerides (TG) lower by 23% ± 5% (1.7 ± 0.1 v 2.4 ± 0.3 mmol/L, P < .02), and mean very-low-density lipoprotein triglycerides (VLDL-TG) lower by 31% ± 9% (0.96 ± 0.15 v 1.48 ± 0.26 mmol/L, P < .05) on the high versus low protein diet. Mean values of LDL-C were significantly lower during weeks 3 to 5 of the high protien diet than during either weeks 1 to 5 or weeks 1 to 2 of the high protein diet (4.3 ± 0.3, 4.5 ± 0.2, and 4.7 ± 0.3 mmol/L, respectively, P < .05) and 11% ± 3% lower than on low protein diet, P < .005. The ratio of plasma LDL-C to HDL-C was consistently lower by 17% ± 3% during the high versus low protein diet (4.9 ± 0.5 v 5.8 ± 0.5, P < .001). Lowering plasma TC and LDL-C and total TG and VLDL-TG and increasing HDL-C by chronic isocaloric substitution of dietary protein for carbohydrate may enhance the cardiovascular risk reduction obtained by restriction of dietary fat and cholesterol.

Effect of nicotinic acid on catabolism and synthesis of cholesterol in man

Sterol balance studies carried out in five hypercholesterolemic human subjects before and during the first 9–14 days on nicotinic acid treatment showed that the nicotinic acid-induced fall in serum cholesterol level was associated with a significant increase in the fecal excretion of neutral steroids of endogenous origin. The output of fecal bile acids and of dietary unabsorbed cholesterol appeared to rise less consistently. The increment of fecal steroid excretion was higher in three and lower in two subjects than the respective decrement of serum cholesterol. Since, in addition, the slope of the serum cholesterol specific activity-time curve decreased or remained unchanged during the nicotinic acid-induced decrease of serum cholesterol it was suggested that the enhanced cholesterol catabolism was associated with increased mobilization of tissue cholesterol and possibly also with reduced cholesterol synthesis.