Normal oxidative stress and enhanced lipoprotein resistance to in vitro oxidation in hypertriglyceridemia: effects of bezafibrate therapy.

Although there is evidence that hyperlipidemia and predominance of small dense low density lipoproteins (LDLs) are associated with increased oxidative stress, the oxidation status in patients with hypertriglyceridemia (HTG) has not been studied in detail. Therefore, we studied urinary levels of F(2)-isoprostanes (8-isoprostaglandin F(2alpha) and 2,3-dinor-5,6-dihydro-8-isoprostaglandin F(2alpha)) and susceptibility of very low density lipoproteins (VLDLs) and LDLs to oxidation ex vivo in 18 patients with endogenous HTG and 20 matched control subjects. In addition, the effects of 6 weeks of bezafibrate therapy were assessed in a double-blind, placebo-controlled, crossover trial. Urinary levels of F(2)-isoprostanes were similar in the HTG and normolipidemic group. Bezafibrate caused an increase in 8-isoprostaglandin F(2alpha) (762+/-313 versus 552+/-245 ng/24 h for bezafibrate and placebo therapy, respectively; P=0.03), whereas 2,3-dinor-5, 6-dihydro-8-isoprostaglandin F(2alpha) levels tended to be increased (1714+/-761 versus 1475+/-606 ng/24 h for bezafibrate and placebo therapy, respectively; P=0.11). VLDLs and LDLs were more resistant to copper-induced oxidation in patients with HTG than in control subjects. Bezafibrate reversed the oxidation resistance to the normal range. In conclusion, these results indicate the following: (1) HTG is associated with normal in vivo oxidative stress and enhanced ex vivo resistance of lipoproteins to oxidation. (2) Bezafibrate reduces the resistance of lipoproteins to copper-induced oxidation and enhances oxidative stress in HTG patients.

Consumption of French-press coffee raises cholesteryl ester transfer protein activity levels before LDL cholesterol in normolipidaemic subjects.

OBJECTIVES: To determine the long-term effects of unfiltered coffee consumption on the activity levels of cholesteryl ester transfer protein (CETP), phospholipid transfer protein (PLTP) and lecithin:cholesterol acyltransferase (LCAT) and to assess a possible role of CETP activity levels in the rise in serum LDL cholesterol. SUBJECTS AND DESIGN: Forty-six healthy normolipidaemic subjects consumed 0.9 L of either French-press or filtered coffee for 24 weeks. Fasting blood samples were obtained after 0, 2, 12 and 24 weeks of intervention and after and 12 weeks of follow-up. MAIN OUTCOME MEASURES: Serum activity levels of CETP, PLTP and LCAT. RESULTS: Relative to baseline, French-press coffee significantly increased average CETP activity by 12% after 2 weeks, by 18% after 12 weeks, and by 9% after 24 weeks. PLTP activity was significantly increased by 10% after 12 and 24 weeks. LCAT activity was significantly decreased by 6% after 12 weeks and by 7% after 24 weeks. The increase in CETP clearly preceded the increase in LDL cholesterol, but not the increase in total triglycerides. However, consumption of French-press coffee caused a persistent rise in CETP activity, whereas the rise in serum triglycerides was transient. CONCLUSIONS: Consumption of cafestol and kahweol cause a long-term increase in CETP as well as PLTP activity; the increase in CETP activity may contribute to the rise in LDL cholesterol.

No effect of consumption of green and black tea on plasma lipid and antioxidant levels and on LDL oxidation in smokers.

Intake of flavonoids is associated with a reduced cardiovascular risk. Oxidation of LDL is a major step in atherogenesis, and antioxidants may protect LDL from oxidation. Because tea is an important source of flavonoids, which are strong antioxidants, we have assessed in a randomized, placebo-controlled study the effect of consumption of black and green tea and of intake of isolated green tea polyphenols on LDL oxidation ex vivo and on plasma levels of antioxidants and lipids. Healthy male and female smokers (aged 34+/-12 years, 13 to 16 per group) consumed during a 4-week period 6 cups (900 mL) of black or green tea or water per day, or they received as a supplement 3.6 grams of green tea polyphenols per day (equivalent to the consumption of 18 cups of green tea per day). Consumption of black or green tea had no effect on plasma cholesterol and triglycerides, HDL and LDL cholesterol, plasma vitamins C and E, beta-carotene, and uric acid. No differences were found in parameters of LDL oxidation. Intake of green tea polyphenols decreased plasma vitamin E significantly in that group compared with the control group (-11% P=.016) but had no effect on LDL oxidation ex vivo. We conclude that consumption of black or green tea (6 cups per day) has no effect on plasma lipids and no sparing effect on plasma antioxidant vitamins and that intake of a high dose of isolated green tea polyphenols decreases plasma vitamin E. Although tea polyphenols had a potent antioxidant activity on LDL oxidation in vitro, no effect was found on LDL oxidation ex vivo after consumption of green or black tea or intake of a green tea polyphenol isolate.

Seasonal variation in low density lipoprotein oxidation and antioxidant status.

Accumulating evidence indicates that oxidative modification of low-density lipoproteins is atherogenic and that antioxidants may play a role in protection of LDL against oxidation. Several studies have reported a seasonal fluctuation in antioxidant levels, but to date nothing is known about seasonal fluctuations in parameters of oxidizability. We collected blood from 10 volunteers at four different periods over one year (February, May, September and December), and measured the amount of plasma lipids, plasma antioxidants, lipid and fatty acid composition of the LDL particle, LDL antioxidant content, LDL particle size and oxidation parameters (lag time and propagation rate). No seasonal fluctuation for lag time and propagation rate of copper ion-induced LDL oxidation was found. Small seasonal fluctuations were observed for some determinants of LDL oxidation, e.g. plasma and LDL vitamin E and LDL particle size, and for plasma lipids, plasma and LDL lutein and LDL beta-carotene. Fatty acid composition of LDL did not change during the year. The main determinant of oxidation susceptibility was the fatty acid composition of LDL. We conclude that LDL oxidation parameters do not change over the year.

Effect of 17 beta-estradiol on plasma lipids and LDL oxidation in postmenopausal women with type II diabetes mellitus.

In type II diabetes mellitus the altered hormonal state after menopause may represent an additional cardiovascular risk factor. Estrogen replacement therapy (ERT) is associated with a decreased cardiovascular risk, at least in nondiabetic postmenopausal women. We studied the effect of ERT on plasma lipids and lipoproteins and on LDL oxidation in 40 postmenopausal women with type II diabetes but with minimal vascular complications in a randomized placebo-controlled trial. Twenty patients were treated orally with 2 mg/d micronized 17 beta-estradiol and 20 patients with placebo for 6 weeks. Plasma total cholesterol (-6%, P = .04), LDL cholesterol (-16%, P = .0001), and apoB (-11%, P = .001) levels decreased and HDL cholesterol (20%, P = .0001) and apoA-I (14%, P = .0001) levels increased after ERT compared with placebo. Glycated hemoglobin (HbA1c) decreased significantly after ERT (-3%, P = .03), the cholesterol content of the LDL particles decreased (-5%, P = .006), triglyceride content increased (16%, P = .01), and LDL particle size did not change significantly. ERT had no effect on parameters of LDL oxidation. We conclude that plasma levels of HDL cholesterol, apoA-I, LDL cholesterol, apoB, and glycated hemoglobin are improved in postmenopausal women with type II diabetes mellitus after treatment with 17 beta-estradiol, indicative of a better metabolic control, and that ERT has no effect on LDL oxidizability.

The effect of medrogestone on plasma lipids and lipoproteins in postmenopausal women using conjugated estrogens: an open randomized comparative study.

OBJECTIVE: To test the hypothesis that the progestogen medrogestone has no effect on changes in lipoprotein metabolism evoked by continuous estrogen replacement therapy, paying special attention to high-density lipoproteins (HDL). DESIGN: Open multicenter randomized comparative trial. PATIENTS: Postmenopausal hysterectomized women aged 49 to 64 years. INTERVENTION: Continuous oral treatment with 0.625 mg daily of conjugated estrogens (CE) alone (n = 55) or CE plus 5 mg of the progestogen medrogestone orally during the last 12 days of each 28-day cycle (n = 59). MAIN OUTCOME MEASURES: At baseline and at cycles 3, 6, and 13 we measured the plasma levels of apolipoprotein (Apo) A1, cholesterol in total HDL and in its subfractions HDL2 and HDL3, using density gradient ultracentrifugation. RESULTS: High-density lipoprotein cholesterol increased from baseline at all assessments in both treatment groups, being significantly greater in the CE group (+15% at cycle 13) than in the CE and medrogestone group (+8%). However, HDL2-cholesterol increased in both treatment groups, but with no significant difference between the two groups. High-density lipoprotein 3 cholesterol increased only in the CE group (+7% at cycle 13); there was no significant change in HDL3-cholesterol in the CE and medrogestone group. Low-density lipoprotein (LDL) cholesterol decreased from baseline at all assessments in both treatment groups (-6% and -9%, respectively, at cycle 13). The change in very low-density (VLDL) lipoprotein cholesterol was not significant in either of the two groups. Medrogestone had no significant effects on the estrogen-induced increases in apo A-1 and triglycerides nor on the decreases in ApoB and LDL-cholesterol. Neither hormone significantly affected VLDL-cholesterol or Lp(a) levels. CONCLUSION: Medrogestone did not eliminate the increase in plasma HDL levels evoked by CE.

Supplementation with low doses of vitamin E protects LDL from lipid peroxidation in men and women.

There is accumulating evidence that oxidative modification of LDL is an important step in the process of atherogenesis and that antioxidants may protect LDL from oxidation. We and others have previously shown that ingestion of pharmacological doses of the antioxidant D,L-alpha-tocopherol (vitamin E), far above the recommended daily intake (ie, 12 to 15 IU/d for adults), increases the oxidation resistance of LDL. In this study, we ascertained the minimal supplementary dose of vitamin E necessary to protect LDL against oxidation in vitro. Twenty healthy volunteers (10 men and 10 women, aged 21 to 31 years) ingested consecutively 25, 50, 100, 200, 400, and 800 IU/d, D,L-alpha-tocopherol acetate during six 2-week periods. No changes were observed in LDL triglyceride content, fatty acid composition of LDL, or LDL size during the intervention. Concentrations of alpha-tocopherol in plasma and LDL were both 1.2 times the baseline values after the first period (25 IU/d) and 2.6 and 2.2 times, respectively, after the last period (800 IU/d). There was a linear increase in LDL alpha-tocopherol levels up to an intake of 800 IU/d (r = .79, P < .0001) and a good correlation between alpha-tocopherol in plasma and LDL (r = .66, P < .0001). Simultaneously, the resistance of LDL to oxidation was elevated dose-dependently (+28% after the last period) and differed significantly from the baseline resistance time even after ingestion of only 25 IU/d.(ABSTRACT TRUNCATED AT 250 WORDS)

No effect of beta-carotene supplementation on plasma lipoproteins in healthy smokers.

A high intake of beta-carotene has been associated with a decreased risk for cardiovascular disease. To evaluate whether beta-carotene intake may exert a protective effect through an impact on lipoprotein metabolism, we conducted a randomized, double-blind trial in healthy, male cigarette smokers. Total cholesterol, high-density-lipoprotein (HDL) cholesterol, apolipoprotein A-I (apo) A-I, apo B-100, and lipoprotein(a) were measured before and after 14 wk of treatment with beta-carotene (20 mg/d, n = 25) or placebo (n = 25). The beta-carotene and placebo groups were comparable with respect to all initial characteristics, but initial apo B-100 was significantly higher in the beta-carotene group (1.23 vs 1.44 g/L). During the intervention, plasma concentrations of beta-carotene increased 15-fold in the treatment group. Mean concentrations of total and HDL cholesterol, lipoprotein(a), apo A-I, and apo B-100 did not change significantly in either group. We conclude that a 20 mg beta-carotene supplement/d does not influence plasma lipoproteins in healthy male smokers.

Supplementation with vitamin E but not beta-carotene in vivo protects low density lipoprotein from lipid peroxidation in vitro. Effect of cigarette smoking.

Several lines of evidence suggest that oxidatively modified low density lipoprotein (LDL) is atherogenic and that antioxidants may protect LDL against oxidation. In addition, cigarette smoking is known to induce oxidant stress. We have examined the effect of ingestion of the antioxidants D,L-alpha-tocopherol (vitamin E) and beta-carotene and of smoking on the resistance of LDL against copper-mediated oxidation. Six healthy nonsmoking volunteers ingested 1,000 IU/day D,L-alpha-tocopherol acetate for 7 days. After vitamin E ingestion concentrations of alpha-tocopherol in plasma and LDL increased 3.0- and 2.4-fold, respectively. Simultaneously, the oxidation resistance of LDL was elevated significantly (+41%), and the rate of oxidation was decreased significantly (-19%). The increase in alpha-tocopherol content of LDL and the increase in resistance time were highly correlated (rs = 0.89, p = 0.014). Eight weeks after termination of the vitamin E intake, alpha-tocopherol concentrations in plasma and LDL and oxidation resistance of LDL had returned to baseline values. In smokers (n = 46), plasma levels of vitamin C (-26%) and concentrations of beta-carotene (-44%, -43%) and total carotenoids (-23%, -29%) in plasma and LDL, respectively, were significantly lower compared with nonsmokers (n = 23). No differences were found in alpha-tocopherol content of LDL and the susceptibility of LDL to lipid peroxidation in both groups. Supplementation of a group of smokers in a 14-week randomized, double-blind, placebo-controlled intervention trial with beta-carotene resulted in a 16.6- and 5.0-fold increase of LDL beta-carotene and total carotenoid content, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Liver parenchymal cells differ from the fat-storing cells in their lipid composition.

The neutral lipid and phospholipid compositions of purified sinusoidal (fat-storing, endothelial and Kupffer) cells, parenchymal cells and liver homogenates were determined by thin layer chromatography. In addition, the retinoid content of the same purified cell populations was determined by high performance liquid chromatography. From each cell type, both a lipid droplet fraction and a pellet fraction (containing the majority of the remaining cell organelles) were prepared by differential centrifugation. Electron microscopic analysis showed that lipid droplets isolated from fat-storing cells were larger (up to 8 microns) than those isolated from parenchymal cells (up to 2.5 microns). Moreover, the parenchymal lipid droplets seemed to be surrounded by a membranous structure, while the fat-storing lipid droplets seemed not to be. Both fat-storing and parenchymal cells contained high concentrations of neutral lipids, 57.9 micrograms and 71.0 micrograms/10(6) cells, respectively, while endothelial and Kupffer cells contained only 8.6 micrograms and 13.8 micrograms/10(6) cells of neutral lipids, respectively. Sixty-five percent of fat-storing cell lipid droplet fractions comprised esters of retinol and cholesterol. This combined ester fraction contained mainly retinyl esters. In addition, considerable quantities (20%) of triglycerides were present. Parenchymal cell lipid droplet fractions comprised triglycerides (62%) and cholesteryl esters (up to 30%). The pellet fractions prepared from all four cell types consisted mainly of cholesterol (41-67%) and free fatty acids (20-28%). The phospholipid content was much higher in parenchymal cells than in the sinusoidal liver cell types. The relative proportions of the four major phospholipid classes were comparable in all liver cell types analyzed.(ABSTRACT TRUNCATED AT 250 WORDS)

Association of cholesterol concentrations in low-density lipoprotein, high-density lipoprotein, and high-density lipoprotein subfractions, and of apolipoproteins AI and AII, with coronary stenosis and left ventricular function.

We examined the association of cholesterol levels in serum lipoprotein fractions, as well as of serum apolipoprotein-AI (apo-AI) and apo-AII levels, with coronary artery stenosis (CAS) and left ventricle function in a group of 43 patients with angina pectoris (33 men and 10 women) subjected to angiography. Cholesterol level in VLDL, LDL, HDL2, and HDL3 fractions was determined after separation of these fractions by density gradient ultracentrifugation. HDL-cholesterol is the sum of cholesterol in HDL2 and HDL3. Cineangiography yielded scores for CAS and for left ventricle ejection fraction (LVEF). On univariate regression CAS was correlated weakly with LDL-cholesterol (positive) and with HDL3-cholesterol and HDL-cholesterol (negative), and more strongly with LDL-cholesterol/HDL-cholesterol (positive), but not with HDL2-cholesterol. LVEF was correlated positively with HDL3-cholesterol, HDL-cholesterol, apo-AI, and apo-AII. Of other "risk factors," none was correlated with CAS, and a history of previous myocardial infarction (PMI) was the only one significantly correlated with LVEF. CAS itself was also correlated negatively with LVEF. In multiple regression analysis with two or three independent variables, the relation of HDL(3)-cholesterol with CAS remained significant when other risk factors were taken into account. LVEF remained related positively with HDL(3)-cholesterol, apo-AI, or apo-AII, when either of them was tested in combination with other risk factors; of these only PMI made a significant independent contribution. Conclusions for this patient group (with low HDL-cholesterol): HDL3-cholesterol, and not HDL2-cholesterol, is informative for CAS; HDL(3)-cholesterol, apo-AI, or apo-AII, as well as CAS and PMI, are associated with LVEF.(ABSTRACT TRUNCATED AT 250 WORDS)