Postprandial hemorrheology and apolipoprotein B metabolism in patients with familial hypertriglyceridemia

Pravastatin improves postprandial endothelial dysfunction and hemorheological deterioration in patients with effort angina pectoris

Postprandial hypertriglyceridemia and hyperglycemia may promote endothelial and hemorheological dysfunction. The present study investigated the effects of pravastatin on endothelial function and hemorheology in patients with stable angina pectoris (AP) before and after eating a test meal. We recruited 26 patients with stable AP who had impaired glucose tolerance and mild dyslipidemia and six healthy men as controls to assess endothelial function and hemorheological behavior. In each group, we measured forearm blood flow (FBF) during post-ischemic reactive hyperemia and obtained blood samples before and 2 h after the test meal. Pravastatin 20 mg/day was then commenced in the 26 AP patients. The above tests were repeated after 2 days and 6 months. Maximum FBF during hyperemia in the baseline fasting phase was significantly lower in the AP patients than in the controls (p < 0.05). Fasting and postprandial FBF during reactive hyperemia time-dependently improved after pravastatin treatment (p < 0.05 vs. baseline data for each phase). Pravastatin treatment for 6 months, but not for 2 days, inhibited leukocyte activation and improved hemorheological parameters. In conclusion, pravastatin treatment for 6 months improved fasting and postprandial endothelial and hemorheological dysfunction in AP patients.

Therapeutic effects of fibrates in postprandial lipemia

Hypertriglyceridemia is observed in many metabolic diseases such as the metabolic syndrome, diabetes mellitus, or mixed dyslipidemia frequently leading to premature coronary heart disease (CHD). Additionally, several studies have shown that postprandial hypertriglyceridemia is pronounced in patients with CHD, metabolic syndrome, hypertension, and other pathologic conditions. The triglyceride-rich lipoprotein remnants accumulating in the postprandial state seem to be involved in atherogenesis and in events leading to thrombosis. Since abnormal postprandial lipemia is associated with pathologic conditions, its treatment is of clinical importance.Fibrates are of significant help in managing hypertriglyceridemia. This review summarizes the effect of fibric acid derivatives on postprandial lipemia. Fibrates decrease the production of and enhance the catabolism of triglyceride-rich lipoproteins through the activation of peroxisome proliferator-activated receptor-alpha. Results of clinical studies with fibrates have confirmed their action in decreasing postprandial triglyceride levels by increasing lipoprotein lipase activity, decreasing apolipoprotein CIII production, and by increasing fatty acid oxidation in the liver.It is concluded that fibrates are effective agents in lowering the postprandial increase in remnant lipoprotein particles and retinyl palmitate. Furthermore, fibrates can also affect the postprandial lipid profile by increasing hepatic lipase levels and in some cases, by reducing cholesterol ester transfer protein activity. The main target of fibrate therapy is to improve fasting hypertriglyceridemia, which is an essential component associated with improving postprandial lipemia. Fibrates are well tolerated by patients and adverse effects have been reported rarely after their administration.

Effect of atorvastatin on lipid parameters, LDL subtype distribution, hemorrheological parameters and adhesion molecule concentrations in patients with hypertriglyceridemia

BACKGROUND AND AIM

Hypertriglyceridemia is a risk factor for atherosclerosis that is typically associated with high concentrations of adhesion molecules, impaired hemorrheology and an unfavourable low-density lipoprotein (LDL) subtype distribution. We hypothesised that some of these risk markers might be beneficially influenced by lipid-lowering therapy with atorvastatin in hypertriglyceridemic patients.

METHODS AND RESULTS

Nineteen patents with primary hypertriglyceridemia were given 10 mg of atorvastatin per day for four weeks. Their cholesterol, triglyceride, LDL and high-density lipoprotein cholesterol (HDL-C) levels, LDL subtype profile, hemorrheological parameters and E-selectin, vascular cell adhesion molecule-1 and intercellular adhesion molecule-1 concentrations were measured before and at the end of atorvastatin therapy. The levels of total and LDL cholesterol respectively decreased by 25% and 24% (both p < 0.001). Furthermore, cholesterol was reduced by 8-29% in all seven LDL subfractions (density range: 1.020-1.066 g/mL) (p < 0.05). The reduction in triglyceride concentrations was of marginal significance (9%, p = 0.1), but its degree positively correlated with the reduction of small-dense LDL (r = 0.5, p < 0.025). Plasma viscosity and blood viscosity at low shear rates were respectively reduced by 2% and 16% (both p < 0.05). The effect of the treatment on the concentrations of HDL-C, fibrinogen and adhesion molecules was not significant.

CONCLUSIONS

Atorvastatin (10 mg/day) not only reduced the plasma concentrations of atherogenic lipoproteins but also improved the LDL-subtype profile and reduced plasma and blood viscosity in patients with hypertriglyceridemia; however, it failed to significantly lower triglyceride concentrations.

Changes in fat synthesis influenced by dietary macronutrient content

DE NOVO: lipogenesis is the biological process by which C2 precursors of acetyl-CoA are synthesized into fatty acids. In human subjects consuming diets higher in fat (> 30 % energy), lipogenesis is down regulated and extremely low; typically < 10 % of the fatty acids secreted by the liver. This percentage will increase when dietary fat is reduced and replaced by carbohydrate, although the extent of carbohydrate-induced lipogenesis is dependent on the type of carbohydrate (monosaccharide v. polysaccharide) and the form in which the carbohydrate is fed (liquid meals, solid less-processed food). Clearly, massive overconsumption of carbohydrate can also increase lipogenesis. A second related phenomenon that occurs when dietary fat is reduced is hypertriacylglycerolaemia. This rise in blood triacylglycerol concentration could be due to increased de novo lipogenesis or to reduced clearance of lipid from the blood. The present paper will review the metabolic mechanisms leading to the elevations in blood triacylglycerol concentration that occur with dietary fat reduction. Studies considered will be those investigating fatty acid synthesis in subjects chronically fed low-fat high-carbohydrate diets and studies in which data were obtained in both the fasted and fed states. Also summarized will be data from subjects who had consumed diets of different carbohydrate types, as well as the most recent data from postprandial studies investigating factors that affect the magnitude of the rise in blood lipids following a meal. Given the changing availability of carbohydrate in the food supply, it will be important to understand how the balance of fat and carbohydrate in the diet influences lipogenesis, and the relative contribution of the process of de novo lipogenesis to the escalating incidence of obesity observed around the world.

Influence of atorvastatin versus simvastatin on fibrinogen and other hemorheological parameters in patients with severe hypercholesterolemia treated with regular low-density lipoprotein immunoadsorption apheresis

Low-density lipoprotein (LDL) apheresis is a treatment option in patients with coronary artery disease and elevated LDL cholesterol concentrations if maximal drug therapy fails to achieve adequate LDL cholesterol reduction. This therapy is more effective when combined with strong lipid-lowering drugs, such as atorvastatin. However, conflicting data have been published concerning the effect of atorvastatin on fibrinogen concentration. Therefore, we investigated the effect of atorvastatin compared to simvastatin on fibrinogen concentration and other hemorheological parameters in patients treated by weekly LDL apheresis. Hemorheological parameters were, studied twice in 9 patients (4 female, 5 male, 54.0+/-8.9 years) with coronary artery disease treated by weekly LDL immunoadsorption, once during concomitant simvastatin therapy (40 mg daily) and once during atorvastatin therapy (40 mg daily). Fibrinogen concentration, plasma and blood viscosity at different shear rates, parameters of red cell aggregation at stasis and shear rate 3/s, and erythrocyte filterability were determined 7 days after the last LDL apheresis after each drug had been given for a minimum for 8 weeks. Fibrinogen concentration did not show any statistically significant difference during therapy with atorvastatin (3.09+/-0.36 g/L) compared to simvastatin (3.13+/-0.77 g/L). Plasma and blood viscosity as well as erythrocyte filterability were also unchanged. The increase in red cell aggregation at stasis during atorvastatin treatment (5.82+/-1.00 U versus 4.89+/-0.48 U during simvastatin; p < 0.05) was inversely correlated with a lower high-density liprotein (HDL) cholesterol concentration (1.17+/-0.21 mmol/L versus 1.31+/-0.30 mmol/L during simvastatin; p < 0.05). LDL cholesterol showed a strong trend to lower concentrations during atorvastatin (4.14+/-0.61 mmol/L versus 4.56+/-0.66 mmol/L during simvastatin; p = 0.07), despite a reduced plasma volume treated (3,547+/-1,239 ml during atorvastatin versus 3,888+/-1,206 mL during simvastatin; p < 0.05). In conclusion, fibrinogen concentration and other hemorheological parameters were unchanged during atorvastatin compared to simvastatin therapy with the exception of a higher red cell aggregation at stasis. Therefore, with respect to hemorheology, we conclude that atorvastatin should not be withheld from hypercholesterolemic patients regularly treated with LDL immunoadsorption.

Contribution of fibrinogen and lipoproteins to plasma viscosity in hypercholesterolemia and hypertriglyceridemia: evaluation by selective depletion of low-density lipoproteins or fibrinogen

Epidemiological studies suggest that the plasma fibrinogen concentration is the main determinant of plasma viscosity (PV), but the concentration of other macromolecules (eg, immunoglobulins) and low-density lipoprotein (LDL) cholesterol and triglycerides are also correlated with PV. However, only a few data exist concerning the in vitro effects of these plasma constituents on PV. Therefore, we investigated PV before and after the specific elimination of fibrinogen and LDL in hypercholesterolemic and hypertriglyceridemic plasma. First, hypercholesterolemic samples (n = 7) were pumped simultaneously through 2 columns: a fibrinogen-depleting column containing the pentapeptide Gly-Pro-Arg-Pro-Lys (GPRPK) and a LDL-depleting column containing specific antibodies against apolipoprotein B-100. In the plasma and in each fraction from the column, the cholesterol level was measured enzymatically, fibrinogen was determined by immunonephelometry, and PV was analyzed using a low-shear rotation viscosimeter. After the fibrinogen-depleting column, the fibrinogen concentration decreased from 3.21 +/- 0.20 to 0.94 +/- 0.16 g/L (P < .005), inducing a decrease in PV from 1.27 +/- 0.02 to 1.17 +/- 0.01 mPas (milliPascal seconds) (P < .005). Despite a marked reduction of the LDL cholesterol after the LDL-depleting column (from 6.40 +/- 0.23 to 4.08 +/- 0.32 mmol/L, P < .005), PV remained unchanged. Second, hypertriglyceridemic samples (n = 7) were pumped through the fibrinogen-depleting column, which reduced the fibrinogen concentration from 4.29 +/- 0.79 to 1.62 +/- 0.69 g/L (P < .001) and PV from 1.42 +/- 0.06 to 1.03 +/- 0.05 mPas (P < .01) while the triglyceride concentration remained unchanged. Our results confirm the epidemiological correlation between the fibrinogen concentration and PV in patients with hypercholesterolemia and hypertriglyceridemia. The influence of fibrinogen on PV seems much more pronounced than the direct effect of lipoprotein concentrations. Therefore, the elevated PV in patients with hypercholesterolemia and especially with hypertriglyceridemia seems mainly due to elevated fibrinogen levels.

Effects of acipimox on haemorheology and plasma lipoproteins in patients with mixed hyperlipoproteinaemia

AIMS

Epidemiological data have shown that haemorheological disorders are associated with an increased risk of atherosclerosis. We evaluated the effect of the nicotinic acid derivative acipimox on haemorheological and lipid parameters in 18 patients with mixed hyperlipoproteinaemia using a randomized, double-blind, placebo-controlled, cross-over study protocol.

METHODS

Patients (7 women, 11 men, aged 49.3+/-3.0 years) were investigated with acipimox (dose adjusted to weight, 500 or 750 mg daily) compared with placebo treatment each for 12 weeks. Lipid parameters, whole blood viscosity, plasma viscosity, fibrinogen, and red cell aggregation at native and standardized (0.45) haematocrit as well as red cell filterability were measured at baseline, at week 12 (change of therapy), and at week 24.

RESULTS

Total cholesterol concentration (8.30+/-0.32 vs 8.72+/-0.36 mmol/l(-1)) and apolipoprotein B (198.5+/-9.9 vs 217+/-9.9 mg dl(-1)) were significantly lower (P<0.05) during acipimox therapy compared with placebo, no significant changes were observed for triglycerides and low-density lipoprotein [LDL] cholesterol. However, total high-density lipoprotein [HDL] cholesterol (1.24+/-0.05 vs 1.10+/-0.05 mmol l(-1), P<0.001) as well as HDL2 and HDL3 cholesterol (P<0.05) were significantly higher during acipimox therapy. The LDL cholesterol to HDL cholesterol ratio significantly improved during acipimox therapy (4.63+/-0.25 vs 5.49+/-0.26, P<0.001). Red cell aggregation at native and standardized haematocrit were the only haemorheological parameters which improved during acipimox therapy in comparison with placebo (shear rate 3 s(-1):10.69+/-0.40 vs 11.50+/-0.44 U, P<0.05, for native red cell aggregation; 10.40+/-0.36 vs 11.28+/-0.39 U, P<0.05, for standardized red cell aggregation).

CONCLUSIONS

We conclude, that the cardiovascular risk profile improves during acipimox therapy due to an elevation in HDL cholesterol and its subfractions as well as a decrease in red cell aggregation.

Genetics of lipoprotein disorders

The study of lipoprotein metabolism has led to major breakthroughs in the fields of cellular physiology, molecular genetics, and protein chemistry. These advances in basic science are reflected in medicine in the form of improved diagnostic methods and better therapeutic tools. Perhaps the greatest benefit is the improved ability to identify at an early stage patients who are at high risk for atherosclerosis, providing clinicians the opportunity to proceed swiftly with intensive lipid-lowering therapy for the prevention of cardiovascular complications. Recent clinical trials have shown that such an approach is not only cost-effective but saves lives while improving the quality of life. They also emphasize the important role physicians can have in prevention. More than half of patients with premature CAD have a familial form of dyslipoproteinemia. This review of the genetics of atherogenic lipoprotein disorders underscores the importance of identifying major genetic defects. It also stresses the need to take into account multifactorial etiologies and clustering of risk factors, as well as gene-gene and gene-environment interactions in assessing the atherogenic potential of a lipid transport disorder. Table 2 summarizes the key points in the diagnosis, clinical implications, and treatment of the major inherited atherogenic dyslipidemias.