Oliver Weingärtner

Vascular Effects of Diet Supplementation With Plant Sterols

OBJECTIVES The purpose of this study was to evaluate vascular effects of diet supplementation with plant sterol esters (PSE). BACKGROUND Plant sterol esters are used as food supplements to reduce cholesterol levels. Their effects on endothelial function, stroke, or atherogenesis are not known. METHODS In mice, plasma sterol concentrations were correlated with endothelial function, cerebral lesion size, and atherosclerosis. Plasma and tissue sterol concentrations were measured by gas-liquid chromatography-mass spectrometry in 82 consecutive patients with aortic stenosis. RESULTS Compared with those fed with normal chow (NC), wild-type mice fed with NC supplemented with 2% PSE showed increased plant sterol but equal cholesterol plasma concentrations. The PSE supplementation impaired endothelium-dependent vasorelaxation and increased cerebral lesion size after middle cerebral artery occlusion. To test the effects of cholesterol-lowering by PSE, apolipoprotein E (ApoE)-/- mice were randomized to Western-type diet (WTD) with the addition of PSE or ezetimibe (EZE). Compared with WTD, both interventions reduced plaque sizes; however, WTD + PSE showed larger plaques compared with WTD + EZE (20.4 +/- 2.1% vs. 10.0 +/- 1.5%). Plant sterol plasma concentration strongly correlated with increased atherosclerotic lesion formation (r = 0.50). Furthermore, we examined plasma and aortic valve concentrations of plant sterol in 82 consecutive patients with aortic stenosis. Patients eating PSE-supplemented margarine (n = 10) showed increased plasma concentrations and 5-fold higher sterol concentrations in aortic valve tissue. CONCLUSIONS Food supplementation with PSE impairs endothelial function, aggravates ischemic brain injury, effects atherogenesis in mice, and leads to increased tissue sterol concentrations in humans. Therefore, prospective studies are warranted that evaluate not only effects on cholesterol reduction, but also on clinical endpoints.

Controversial role of plant sterol esters in the management of hypercholesterolaemia

Hypercholesterolaemia is a risk factor of cardiovascular diseases and is therefore a major target for primary and secondary prevention.1,2 Maintaining a healthy diet and lifestyle reduces cardiovascular risk.3 ‘Functional foods’ supplemented with phytosterols are advertised for the management of hypercholesterolaemia and have become a widely used non-prescription approach to lower plasma cholesterol levels. It is estimated that in 2005 worldwide 3 billion US-dollars were spent on various functional foods that have regulator-approved health claims for the management of elevated cholesterol levels.4 In September 2000, the US Food and Drug Administration (FDA) issued an interim final rule allowing a health claim for reducing the risk of coronary heart disease for foods that contain phytosterols and are low in saturated fat and cholesterol.5 In fact, this was only the 12th time the FDA has authorized a health claim. The National Cholesterol Education Program Expert Panel (NCEP ATP III) recommends since 2001 phytosterol enriched functional foods as part of an optimal dietetic prevention strategy in primary and secondary prevention of cardiovascular diseases.6 The American Heart Association (AHA) has followed and sees phytosterols ‘as a therapeutic option … for individuals with elevated cholesterol levels’.3 Since then other well-esteemed societies such as the Spanish Cardiology Society ,7 the Association of Clinical and Public Health Nutritionists in Finland ,8 and the National Heart Foundation in Australia ,9 to name only a few, have identified phytosterols as an important additional dietary option in the management of hypercholesterolaemia. However, recently released guidelines are more critical of food supplementation with phytosterols and draw attention to significant safety issues.10,11 ‘Phytosterols’ are natural constituents of plants and are part of the broad group of isoprenoides. In plant cells, they contribute to the regulation of the fluidity and permeability of …

Dietary intake of plant sterols stably increases plant sterol levels in the murine brain

Plant sterols such as sitosterol and campesterol are frequently administered as cholesterol-lowering supplements in food. Recently, it has been shown in mice that, in contrast to the structurally related cholesterol, circulating plant sterols can enter the brain. We questioned whether the accumulation of plant sterols in murine brain is reversible. After being fed a plant sterol ester-enriched diet for 6 weeks, C57BL/6NCrl mice displayed significantly increased concentrations of plant sterols in serum, liver, and brain by 2- to 3-fold. Blocking intestinal sterol uptake for the next 6 months while feeding the mice with a plant stanol ester-enriched diet resulted in strongly decreased plant sterol levels in serum and liver, without affecting brain plant sterol levels. Relative to plasma concentrations, brain levels of campesterol were higher than sitosterol, suggesting that campesterol traverses the blood-brain barrier more efficiently. In vitro experiments with brain endothelial cell cultures showed that campesterol crossed the blood-brain barrier more efficiently than sitosterol. We conclude that, over a 6-month period, plant sterol accumulation in murine brain is virtually irreversible.

Plant Sterols the Better Cholesterol in Alzheimer's Disease? A Mechanistical Study

Amyloid-β (Aβ), major constituent of senile plaques in Alzheimers disease (AD), is generated by proteolytic processing of the amyloid precursor protein (APP) by β- and γ-secretase. Several lipids, especially cholesterol, are associated with AD. Phytosterols are naturally occurring cholesterol plant equivalents, recently been shown to cross the blood–brain-barrier accumulating in brain. Here, we investigated the effect of the most nutritional prevalent phytosterols and cholesterol on APP processing. In general, phytosterols are less amyloidogenic than cholesterol. However, only one phytosterol, stigmasterol, reduced Aβ generation by (1) directly decreasing β-secretase activity, (2) reducing expression of all γ-secretase components, (3) reducing cholesterol and presenilin distribution in lipid rafts implicated in amyloidogenic APP cleavage, and by (4) decreasing BACE1 internalization to endosomal compartments, involved in APP β-secretase cleavage. Mice fed with stigmasterol-enriched diets confirmed protective effects in vivo, suggesting that dietary intake of phytosterol blends mainly containing stigmasterol might be beneficial in preventing AD.

Relationship between cholesterol synthesis and intestinal absorption is associated with cardiovascular risk.

Hypercholesterolemia is a major risk factor for cardiovascular disease. The HMG-CoA-reductase inhibitors, statins, reduce plasma cholesterol and, as a consequence, decrease cardiovascular morbidity and mortality. Data from a subgroup analysis of the 4-S Study, however, indicate that patients with high cholesterol absorption may not benefit from statin treatment. Furthermore, there is accumulating evidence that lower hepatic synthesis and higher intestinal absorption markers are associated with increased cardiovascular risk. Therefore, prospective clinical trials are needed to evaluate whether subjects with altered cholesterol homeostasis may benefit from treatment strategies that reduce cholesterol absorption in addition to statin treatment.

The relationships of markers of cholesterol homeostasis with carotid intima-media thickness.

Background The relationship of cholesterol homeostasis and carotid intima-media thickness (cIMT) is unknown. To address this, we assessed markers of cholesterol homeostasis (serum plant sterols and cholesterol precursor concentrations as surrogate measures of cholesterol absorption and synthesis, respectively) and cIMT in a middle-aged, statin-naive population. Methods In this prospective study of primary prevention cIMT was measured by ultrasound in 583 hospital employees aged 25–60 years without prevalent cardiovascular disease or lipid-modifying medication. The serum concentrations of plant sterols (as markers of cholesterol absorption) were measured by gas-liquid chromatography. Lathosterol serum concentrations were quantitated to assess hepatic cholesterol synthesis. Results cIMT correlated positively with serum cholesterol (r = 0.22, P<0.0005) and lathosterol-to-cholesterol (r = 0.18, P<0.001). In contrast, plant sterols, as markers of cholesterol absorption, showed a weak negative correlation to cIMT measurements (r = −0.18; P<0.001 for campesterol-to-cholesterol). Stratifying subjects by serum sterol levels, we found that cIMT increased continuously over quintiles of serum cholesterol (P<0.0005) and was positively associated to serum lathosterol-to-cholesterol levels (P = 0.007), on the other hand, plant sterol levels showed a weak negative association to cIMT (P<0.001 for campesterol-to-cholesterol). Conclusions In this population without prevalent cardiovascular diseases or lipid-modifying medication, markers of increased endogenous cholesterol synthesis correlated positively with cIMT, while markers of cholesterol absorption showed a weakly negative correlation. These data suggest that not only total serum cholesterol levels but also differences in cholesterol homeostasis are associated with cIMT.

Markers of enhanced cholesterol absorption are a strong predictor for cardiovascular diseases in patients without diabetes mellitus.

OBJECTIVE Hypercholesterolemia is a major risk factor for cardiovascular disease (CVD), and diabetes mellitus and statin treatment affect cholesterol metabolism. The aim of the present study was to evaluate markers of cholesterol metabolism and determine their relationship with CVD in patients without diabetes mellitus who were not receiving statin treatment. METHODS In addition to conventional CVD risk factors, plasma levels of campesterol and sitosterol (indicators of cholesterol absorption) and lathosterol (an indicator of cholesterol synthesis) were determined in 835 consecutive patients referred for coronary angiography. Coronary artery disease was evaluated by coronary angiograms, carotid atherosclerosis and peripheral vascular disease were assessed by Doppler ultrasound, and cerebrovascular accidents and transient ischemic attacks were identified by medical history. RESULTS After excluding patients with known diabetes mellitus and those receiving statin treatment, 177 patients were included in the analysis. Compared to patients without CVDs (n=111), patients with concomitant CVDs (n=66) had a reduced lathosterol-to-cholesterol ratio (1.25±0.61 vs. 1.38±0.63, P<0.05) and an increased campesterol-to-cholesterol ratio (1.81±1.04 vs. 1.50±0.69, P<0.05), indicating that enhanced absorption and reduced synthesis of cholesterol is associated with CVD development. Logistic regression analysis including all established cardiovascular risk factors (age, sex, total cholesterol, arterial hypertension, body mass index and smoking) revealed that campesterol and the campesterol-to-cholesterol ratio were significant predictors of concomitant CVD in this patient population. CONCLUSION In patients without diabetes mellitus, markers of enhanced cholesterol absorption were a strong predictor for concomitant CVD.

Differential effects on inhibition of cholesterol absorption by plant stanol and plant sterol esters in apoE−/− mice

Aims ‘Functional foods’ supplemented with plant sterol esters (PSE) and plant stanol esters (PSA) are therapeutic options for the management of hypercholesterolaemia. However, their effects on blood monocytes, endothelial function, atherogenesis, and sterol tissue concentrations are poorly understood. Methods and results Male apoE−/− mice (n= 30) were randomized to three different diets for 6 weeks (n= 10 per group): high-cholesterol (1.25%) western-type diet (WTD), WTD + 2% PSE, and WTD + 2% PSA. Both supplements reduced serum cholesterol. WTD + PSE resulted in increased plant sterol serum concentrations and increased inflammatory Ly-6C(high) monocyte numbers. WTD + PSA increased plant stanol serum concentrations and Ly-6C-monocyte numbers, but decreased vascular superoxide release, lipid hydroperoxides, and inflammatory cytokines in aortic tissue, in plasma, and in circulating monocytes. Despite reduced serum cholesterol concentrations, both supplements impaired endothelial vasodilation compared with WTD. WTD + PSA reduced the development of atherosclerotic lesions compared with WTD alone (12.7 ± 3.7 vs. 28.3 ± 3.5%), and WTD + PSE was less effective (17.5 ± 3.7%). WTD + PSE and WTD + PSA reduced the cholesterol content in the liver, but not in the brain. However, WTD + PSE and WTD + PSA increased plant sterol and plant stanol concentrations in the liver as well as in the brain. Conclusion PSE and PSA supplementation reduced serum cholesterol, but increased plant sterol and plant stanol concentrations. Elevated levels of PSE and PSA were associated with endothelial dysfunction and increased central nervous system depositions. Atherosclerotic lesion retardation was more pronounced in WTD + PSA, coinciding with higher regenerative monocyte numbers, decreased oxidative stress, and decreased inflammatory cytokines compared with WTD + PSE.

Alterations in cholesterol homeostasis are associated with coronary heart disease in patients with aortic stenosis.

ObjectiveHypercholesterolemia is a risk factor for aortic stenosis (AS) and for coronary artery disease (CAD). Serum cholesterol concentrations are determined by intestinal cholesterol absorption and endogenous cholesterol synthesis. Vascular effects of differences in cholesterol metabolism in patients with AS are so far unknown. Therefore, the aim of this study was to investigate differences in cholesterol metabolism in relation to vascular diseases in this subset of patients. MethodsIn addition to identifying conventional coronary risk factors, we determined plant sterols (indicators of cholesterol absorption) and lathosterol (indicator of cholesterol synthesis) levels in 40 consecutive men and women with AS. Coronary angiograms before the aortic valve replacement determined the extent of CAD. ResultsPatients with a positive history of cardiovascular disease exhibited an increased campesterol-to-lathosterol ratio in plasma (P<0.005) and in aortic valve cusps (P<0.05). The plasma campesterol-to-lathosterol ratio increased with CAD severity (zero, single, two, three-vessel disease; P<0.05). Coronary vessel score strongly correlated with the campesterol-to-lathosterol ratio in plasma (r = 0.52; P<0.001) and in aortic valve cusps (r = 0.33; P<0.03). Logistic regression analysis revealed that the ratio of campesterol-to-lathosterol was the sole predictor of CAD among coronary risk factors tested (P<0.01). ConclusionEnhanced absorption and reduced synthesis of cholesterol is related to a positive family history of cardiovascular diseases and the development of concomitant CAD in patients with AS.

Vascular effects of oxysterols and oxyphytosterols in apoE −/− mice

OBJECTIVES The aim of our study was to investigate vascular effects of oxysterols and oxyphytosterols on reactive oxygen species (ROS), endothelial progenitor cells, endothelial function and atherogenesis. METHODS Male apoE-/-mice were treated with cholesterol, sitosterol, 7-ß-OH-cholesterol, 7-ß-OH-sitosterol, or cyclodextrin by daily intraperitoneal application. The respective concentrations in the plasma and in the arterial wall were determined by gas chromatography-flame ionization or mass spectrometry. ROS production was assessed by electron-spin resonance spectroscopy in the aorta, endothelial function of aortic rings and atherosclerosis in the aortic sinus was quantitated after 4 weeks. RESULTS Compared to vehicle, there was no difference in plasma cholesterol levels and arterial wall concentrations after i.p. application of cholesterol. 7-ß-OH-cholesterol concentrations were increased in the plasma (33.7±31.5 vs. 574.57.2±244.92 ng/ml) but not in the arterial wall (60.1±60.1 vs. 59.3±18.2 ng/mg). Sitosterol (3.39±0.96 vs. 8.16±4.11 mg/dL; 0.08±0.04 vs. 0.16±0.07 μg/mg, respectively) and 7-ß-OH-sitosterol concentrations (405.1±151.8 vs. 7497±3223 ng/ml; 0.24±0.13 vs. 16.82±11.58 ng/mg, respectively) increased in the plasma and in the aorta. The i.p-application of the non-oxidized cholesterol or sitosterol did not induce an increase of plasma oxysterols or oxyphytosterols concentrations. Oxidative stress in the aorta was increased in 7-ß-OH-sitosterol treated mice, but not in mice treated with cholesterol, sitosterol, or 7-ß-OH-cholesterol. Moreover, cholesterol, sitosterol, 7-ß-OH-cholesterol, and 7-ß-OH-sitosterol did not affect endothelial-dependent vasodilation, or early atherosclerosis. CONCLUSION Increased oxyphytosterol concentrations in plasma and arterial wall were associated with increased ROS production in aortic tissue, but did not affect endothelial progenitor cells, endothelial function, or early atherosclerosis.