Sitosterolemia—a rare disease

Phytosterols and Cardiovascular Risk Evaluated against the Background of Phytosterolemia Cases-A German Expert Panel Statement

Phytosterols (PSs) have been proposed as dietary means to lower plasma LDL-C. However, concerns are raised that PSs may exert atherogenic effects, which would offset this benefit. Phytosterolemia was thought to mimic increased plasma PSs observed after the consumption of PS-enriched foods. This expert statement examines the possibility of specific atherogenicity of PSs based on sterol metabolism, experimental, animal, and human data. Observational studies show no evidence that plasma PS concentrations would be associated with an increased risk of atherosclerosis or cardiovascular (CV) events. Since variants of the ABCG5/8 transporter affect the absorption of cholesterol and non-cholesterol sterols, Mendelian randomization studies examining the effects of ABCG5/8 polymorphisms cannot support or refute the potential atherogenic effects of PSs due to pleiotropy. In homozygous patients with phytosterolemia, total PS concentrations are ~4000% higher than under physiological conditions. The prevalence of atherosclerosis in these individuals is variable and may mainly relate to concomitant elevated LDL-C. Consuming PS-enriched foods increases PS concentrations by ~35%. Hence, PSs, on a molar basis, would need to have 20-40 times higher atherogenicity than cholesterol to offset their cholesterol reduction benefit. Based on their LDL-C lowering and absence of adverse safety signals, PSs offer a dietary approach to cholesterol management. However, their clinical benefits have not been established in long-term CV endpoint studies.

[Saturated fatty acids and cardiovascular risk : Is a revision of the recommendations on nutrition indicated?]

Die „Fetthypothese der koronaren Herzkrankheit“, derzufolge „gesättigte Fettsäuren“ („saturated fatty acids“, SFA) die LDL(„low-density lipoprotein“)-Cholesterin-Konzentration (LDL-C) steigern und folglich das Risiko für kardiovaskuläre Erkrankungen erhöhen, prägte die Ernährungsempfehlungen der letzten 60 Jahre, zunächst in den USA und später auch in Europa. Über die Jahre mehrte sich Evidenz aus Epidemiologie und kontrollierten klinischen Studien, dass der Konsum von SFA per se nicht mit einem erhöhten kardiovaskulären Risiko einhergeht bzw. die Einschränkung des Konsums von SFA keine präventive Wirkung zeigt. Die Fokussierung auf den SFA-Gehalt negiert die biologisch heterogenen und zum Teil biologisch günstigen Wirkungen unterschiedlicher SFA. Zudem wird hierbei außer Acht gelassen, dass SFA in intakten Lebensmitteln in unterschiedliche komplexe Matrizes eingebunden sind, die aus Dutzenden Nährstoffen mit unterschiedlicher Struktur und Begleitstoffen bestehen und damit jeweils unterschiedliche biologische Antworten und metabolische Effekte auslösen. Entsprechend sind solche nährstoffbasierten Empfehlungen prinzipiell wenig zielführend und zudem schlecht umsetzbar. Hinzu kommt, dass LDL‑C kein geeigneter Marker ist, um den Effekt von Lebensstilintervention wie der Ernährung oder aber der körperlichen Aktivität auf das globale kardiovaskuläre Risiko zu beurteilen.

Phytosterol accumulation results in ventricular arrhythmia, impaired cardiac function and death in mice

Heart failure (HF) and cardiac arrhythmias share overlapping pathological mechanisms that act cooperatively to accelerate disease pathogenesis. Cardiac fibrosis is associated with both pathological conditions. Our previous work identified a link between phytosterol accumulation and cardiac injury in a mouse model of phytosterolemia, a rare disorder characterized by elevated circulating phytosterols and increased cardiovascular disease risk. Here, we uncover a previously unknown pathological link between phytosterols and cardiac arrhythmias in the same animal model. Phytosterolemia resulted in inflammatory pathway induction, premature ventricular contractions (PVC) and ventricular tachycardia (VT). Blockade of phytosterol absorption either by therapeutic inhibition or by genetic inactivation of NPC1L1 prevented the induction of inflammation and arrhythmogenesis. Inhibition of phytosterol absorption reduced inflammation and cardiac fibrosis, improved cardiac function, reduced the incidence of arrhythmias and increased survival in a mouse model of phytosterolemia. Collectively, this work identified a pathological mechanism whereby elevated phytosterols result in inflammation and cardiac fibrosis leading to impaired cardiac function, arrhythmias and sudden death. These comorbidities provide insight into the underlying pathophysiological mechanism for phytosterolemia-associated risk of sudden cardiac death.

Crystal engineering of nutraceutical phytosterols: new cocrystal solid solutions

A cocrystal screening of solid solutions of three phytosterols (β-sitosterol, campesterol, stigmasterol) reveals that cocrystal solid solutions are enriched with β-sitosterol with respect to stigmasterol, a natural product with cytotoxicity concerns.

Progress and perspectives in plant sterol and plant stanol research

Current evidence indicates that foods with added plant sterols or stanols can lower serum levels of low-density lipoprotein cholesterol. This review summarizes the recent findings and deliberations of 31 experts in the field who participated in a scientific meeting in Winnipeg, Canada, on the health effects of plant sterols and stanols. Participants discussed issues including, but not limited to, the health benefits of plant sterols and stanols beyond cholesterol lowering, the role of plant sterols and stanols as adjuncts to diet and drugs, and the challenges involved in measuring plant sterols and stanols in biological samples. Variations in interindividual responses to plant sterols and stanols, as well as the personalization of lipid-lowering therapies, were addressed. Finally, the clinical aspects and treatment of sitosterolemia were reviewed. Although plant sterols and stanols continue to offer an efficacious and convenient dietary approach to cholesterol management, long-term clinical trials investigating the endpoints of cardiovascular disease are still lacking.

The emerging concept of "individualized cholesterol-lowering therapy": A change in paradigm

High LDL-cholesterol concentrations constitute a risk for atherosclerotic cardiovascular disease. By consensus, cholesterol-lowering therapy is initiated with a statin that reduces endogenous cholesterol synthesis, upregulates hepatic LDL receptor activity, increases LDL clearance and lowers LDL-cholesterol concentrations in the bloodstream. The efficacy of statin treatment is dose dependent and achieves a risk reduction of up to 50%. However, a substantial body of evidence suggests that a quarter of statin-treated patients do not respond adequately as a result of low endogenous cholesterol synthesis. In humans fractional cholesterol absorption varies from 20% to 80%. High cholesterol absorbers, which are characterized by a low-to-normal cholesterol synthesis, exhibit poor responsiveness to statin treatment. On the other hand, the cholesterol absorption inhibitor ezetimibe effectively reduces serum cholesterol levels in these patients. On this background, we suggest to "get personal" and individualize cholesterol-lowering therapies, according to the individual's status of cholesterol synthesis and absorption.

Stigmasterol accumulation causes cardiac injury and promotes mortality

Cardiovascular disease is expected to remain the leading cause of death worldwide despite the introduction of proprotein convertase subtilisin/kexin type 9 inhibitors that effectively control cholesterol. Identifying residual risk factors for cardiovascular disease remains an important step for preventing and clinically managing the disease. Here we report cardiac injury and increased mortality occurring despite a 50% reduction in plasma cholesterol in a mouse model of phytosterolemia, a disease characterized by elevated levels of dietary plant sterols in the blood. Our studies show accumulation of stigmasterol, one of phytosterol species, leads to left ventricle dysfunction, cardiac interstitial fibrosis and macrophage infiltration without atherosclerosis, and increased mortality. A pharmacological inhibitor of sterol absorption prevents cardiac fibrogenesis. We propose that the pathological mechanism linking clinical sitosterolemia to the cardiovascular outcomes primarily involves phytosterols-induced cardiac fibrosis rather than cholesterol-driven atherosclerosis. Our studies suggest stigmasterol is a potent and independent risk factor for cardiovascular disease.

Elevated Urinary Methylmalonic Acid/creatinine ratio and Serum Sterol levels in Patients with Acute Ischemic Stroke

Introduction: Sitosterolemia, defined as phytosterolemia, is a rare autosomal recessive disease characterized by elevated blood sterol levels. Our aim was to investigate serum plant sterols, methylmalonic acid, vitamin B12, oxidized-LDL and homocysteine levels in ischemic and hemorrhagic stroke patients and healthy subjects. Material and Methods: 50 healthy subjects (without a family history of coronary artery disease) and 89 patients hospitalized in the Selcuk University neurology clinic or intensive care unit with a diagnosis of stroke were included in this study. Serum plant sterols, homocysteine and methylmalonic acid, oxidized-LDL, total cholesterol, triglycerides, HDL-Cholesterol and vitamin B12 levels were analyzed by gas chromatography-mass spectrometry, liquid-chromatography tandem mass spectrometry, commercially available ELISA kit, spectrophotometry and chemiluminescence methods, respectively. Results: Urinary methylmalonic acid/creatinine ratio (p< 0.05), serum β-sitosterol levels and β-sitosterol/ cholesterol ratio were significantly higher (p <0.01) in patients compared to the control group. There was a significant positive correlation between the serum OxLDL- methylmalonic acid, serum homocysteine- urinary methylmalonic acid /creatinine ratio, serum methylmalonic acid - Urinary methylmalonic acid (p<0.05), serum homocysteine- urinary methylmalonic acid, urinary methylmalonic acid-methylmalonic acid/creatinine ratio, serum methylmalonic acid- methylmalonic acid/creatinine ratio, serum beta-sitosterol- beta-sitosterol /cholesterol, total cholesterol-HDL, total cholesterol-LDL (p <0.01) levels and negative correlation between vitamin B12- serum methylmalonic acid (p<0.05), cholesterol-stigmasterol/cholesterol, LDL- stigmasterol/cholesterol (p <0.01) levels in the patient group. Conclusion: Our findings presented that the serum sitosterol levels were significantly higher in stroke patients compared to controls.

Plant sterol enriched functional food and atherosclerosis

Hypercholesterolaemia is a major cardiovascular risk factor. A healthy diet and a healthy lifestyle reduces cardiovascular risk. 'Functional foods' supplemented with phytosterols are recommended for the management of hypercholesterolaemia and have become a widely used non-prescription approach to lower plasma cholesterol levels. Two billion euros are spent world-wide each year on various functional foods, which have regulator-approved health claims for the management of elevated cholesterol levels. While international societies, such as the European Atherosclerosis Society or the National Heart Foundation in Australia, still advise phytosterols as an additional dietary option in the management of hypercholesterolaemia, recently released guidelines such as those from the National Institute of Health and Clinical Excellence in the United Kingdom are more critical of food supplementation with phytosterols and draw attention to significant safety issues. This review challenges whether an intervention with phytosterol supplements is beneficial. We summarize the current evidence from genetic diseases, genetic association studies, clinical trial data and data from animal studies.

LINKED ARTICLES

This article is part of a themed section on Principles of Pharmacological Research of Nutraceuticals. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.11/issuetoc.

Individualized lipid-lowering therapy to further reduce residual cardiovascular risk

Hypercholesterolemia is a major risk factor for cardiovascular diseases. Serum cholesterol concentrations are regulated by enteral absorption, biliary secretion, and hepatic synthesis. Statins inhibit the rate-limiting enzyme of cholesterol synthesis, HMG-CoA-reductase, and reduce serum cholesterol concentrations as well as cardiovascular morbidity and mortality. Some studies indicate that patients with high baseline cholesterol absorption may show only a small response to statin treatment in terms of cholesterol lowering. Data from genetic association studies and from the IMPROVE-IT trial show that reducing intestinal cholesterol absorption via NCP1L1 further reduces cardiovascular risk. However, some patients do not attain LDL-cholesterol targets on combination therapy. For these patients PCSK9-antibody treatment and lipid-apheresis are options to be considered. This article reviews the current literature on this issue and suggests 'individualized lipid-lowering therapy' as an approach to optimize and personalize lipid-lowering treatment of patients with hypercholesterolemia to further reduce residual cardiovascular risk.

Plant Sterols, Stanols, and Sitosterolemia

Phytosterolemia (sitosterolemia) is a rare autosomal recessive sterol storage disease caused by mutations in either of the adenosine triphosphate (ATP) binding cassette transporter genes; (ABC) G5 or ABCG8, leading to impaired elimination of plant sterols and stanols, with their increased accumulation in the blood and tissues. Thus the disease is characterized by substantially elevated serum plant sterols and stanols, with moderate to high plasma cholesterol levels, and increased risk of premature atherosclerosis. Hematologic abnormalities including macrothrombocytopenia, stomatocytosis and hemolysis are frequently observed in sitosterolemia patients. Currently, ezetimibe, a sterol absorption inhibitor, is used as the routine treatment for sitosterolemia, with reported improvement in plant sterol levels and hemolytic parameters. This review summarizes the research related to the health impact of plant sterols and stanols on sitosterolemia.

The effect of a low-fat spread with added plant sterols on vascular function markers: results of the Investigating Vascular Function Effects of Plant Sterols (INVEST) study

BACKGROUND

Plant sterols (PSs) lower LDL cholesterol, an established risk factor for coronary artery disease (CAD). No direct evidence is available supporting a reduced risk of CAD for foods with added PSs. Endothelial dysfunction is seen as an early indicator of atherosclerotic damage.

OBJECTIVES

This study was primarily designed to investigate the effect of a low-fat spread with added PSs on brachial artery endothelial function as measured by flow-mediated dilation (FMD). Second, effects on arterial stiffness, blood pressure, serum lipids, and plasma PS concentrations were investigated. We hypothesized that PSs would not worsen FMD but would rather modestly improve FMD.

DESIGN

This study had a double-blind, randomized, placebo-controlled, parallel design. After a 4-wk run-in period, 240 hypercholesterolemic but otherwise healthy men and women consumed 20 g/d of low-fat spread without (control) or with added PSs (3 g/d) during 12 wk. Pre- and postintervention, vascular function measurements and blood sampling were performed.

RESULTS

In total, 232 participants completed the study period. For the primary endpoint FMD, 199 participants were included in the statistical analysis. PS intake did not affect FMD (+0.01 percentage points; 95% CI: -0.73, 0.75) compared with control. Measures of arterial stiffness (pulse wave velocity and augmentation index) and blood pressure were also not significantly changed compared with control. After PS intervention, LDL cholesterol significantly decreased on average by 0.26 mmol/L (95% CI: -0.40, -0.12) or 6.7% compared with control. Plasma sitosterol and campesterol concentrations significantly increased in the PS group up to on average 11.5 μmol/L and 13.9 μmol/L (expressed as geometric means), respectively.

CONCLUSIONS

The intake of a low-fat spread with added PSs neither improved nor worsened FMD or other vascular function markers in hypercholesterolemic men and women. As expected, serum LDL cholesterol decreased, whereas plasma PSs increased after PS intake. This study was registered at clinicaltrials.gov as NCT01803178.

Consumption of a dietary portfolio of cholesterol lowering foods improves blood lipids without affecting concentrations of fat soluble compounds

BACKGROUND

Consumption of a cholesterol lowering dietary portfolio including plant sterols (PS), viscous fibre, soy proteins and nuts for 6 months improves blood lipid profile. Plant sterols reduce blood cholesterol by inhibiting intestinal cholesterol absorption and concerns have been raised whether PS consumption reduces fat soluble vitamin absorption.

OBJECTIVE

The objective was to determine effects of consumption of a cholesterol lowering dietary portfolio on circulating concentrations of PS and fat soluble vitamins.

METHODS

Using a parallel design study, 351 hyperlipidemic participants from 4 centres across Canada were randomized to 1 of 3 groups. Participants followed dietary advice with control or portfolio diet. Participants on routine and intensive portfolio involved 2 and 7 clinic visits, respectively, over 6 months.

RESULTS

No changes in plasma concentrations of α and γ tocopherol, lutein, lycopene and retinol, but decreased β-carotene concentrations were observed with intensive (week 12: p = 0.045; week 24: p = 0.039) and routine (week 12: p = 0.031; week 24: p = 0.078) portfolio groups compared to control. However, cholesterol adjusted β-carotene and fat soluble compound concentrations were not different compared to control. Plasma PS concentrations were increased with intensive (campesterol:p = 0.012; β-sitosterol:p = 0.035) and routine (campesterol: p = 0.034; β-sitosterol: p = 0.080) portfolio groups compared to control. Plasma cholesterol-adjusted campesterol and β-sitosterol concentrations were negatively correlated (p < 0.001) with total and LDL-C levels.

CONCLUSION

Results demonstrate that consuming a portfolio diet reduces serum total and LDL-C levels while increasing PS values, without altering fat soluble compounds concentrations. The extent of increments of PS with the current study are not deleterious and also maintaining optimum levels of fat soluble vitamins are of paramount necessity to maintain overall metabolism and health. Results indicate portfolio diet as one of the best options for CVD risk reduction.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00438425.

LDL-cholesterol-lowering effect of plant sterols and stanols across different dose ranges: a meta-analysis of randomised controlled studies

Phytosterols (PS, comprising plant sterols and plant stanols) have been proven to lower LDL-cholesterol concentrations. The dose-response relationship for this effect has been evaluated in several meta-analyses by calculating averages for different dose ranges or by applying continuous dose-response functions. Both approaches have advantages and disadvantages. So far, the calculation of averages for different dose ranges has not been done for plant sterols and stanols separately. The objective of the present meta-analysis was to investigate the combined and separate effects of plant sterols and stanols when classified into different dose ranges. Studies were searched and selected based on predefined criteria. Relevant data were extracted. Average LDL-cholesterol effects were calculated when studies were categorised by dose, according to random-effects models while using the variance as weighing factor. This was done for plant sterols and stanols combined and separately. In total, 124 studies (201 strata) were included. Plant sterols and stanols were administered in 129 and fifty-nine strata, respectively; the remaining used a mix of both. The average PS dose was 2.1 (range 0.2-9.0) g/d. PS intakes of 0.6-3.3 g/d were found to gradually reduce LDL-cholesterol concentrations by, on average, 6-12%. When plant sterols and stanols were analysed separately, clear and comparable dose-response relationships were observed. Studies carried out with PS doses exceeding 4 g/d were not pooled, as these were scarce and scattered across a wide range of doses. In conclusion, the LDL-cholesterol-lowering effect of both plant sterols and stanols continues to increase up to intakes of approximately 3 g/d to an average effect of 12%.

Consumption of plant sterol-enriched foods and effects on plasma plant sterol concentrations--a meta-analysis of randomized controlled studies

OBJECTIVE

Intake of plant sterol (PS)-enriched foods effectively lowers plasma total- and LDL-cholesterol concentrations while increasing plasma PS concentrations. The magnitude of this increase has not been systematically assessed. This study aimed to investigate the effect of PS-enriched foods on plasma PS concentrations by performing a meta-analysis of randomized controlled studies.

METHODS

Published PS intervention studies reporting plasma PS concentrations were searched through June 2012. Studies were selected that fulfilled pre-defined in- and exclusion criteria. Data were extracted, particularly on campesterol, sitosterol, total- and LDL-cholesterol. Random-effects models were used to calculate net effects while weighing each study by the inverse of its variance. Potential sources of heterogeneity were investigated.

RESULTS

The meta-analysis included data from 41 studies (55 strata) with in total 2084 subjects. The average dose of PS from enriched foods was 1.6 g/d (range: 0.3-3.2 g/d). Plasma sitosterol and campesterol concentrations were increased by on average 2.24 μmol/L (31%) and 5.00 μmol/L (37%), respectively, compared to control. Total- and LDL-cholesterol were reduced by on average 0.36 mmol/L (5.9%) and 0.33 mmol/L (8.5%), respectively. The increase in sitosterol and campesterol was impacted by the dose of PS, the baseline PS concentration and the PS composition of the test products. In the highest PS dose category (2.0-3.2 g/d), increases in sitosterol and campesterol were on average 3.56 and 7.64 μmol/L, respectively.

CONCLUSION

Intake of PS-enriched foods increases plasma sitosterol and campesterol concentrations. However, total PS remain below 1% of total sterols circulating in the blood.

Serum lipids, plant sterols, and cholesterol kinetic responses to plant sterol supplementation in phytosterolemia heterozygotes and control individuals

BACKGROUND

Plant sterol (PS) supplementation is increasingly accepted as a dietary strategy to lower plasma cholesterol concentrations. However, information is scarce about the effect of increased PS intake in potentially vulnerable groups, such as phytosterolemia heterozygotes (HET).

OBJECTIVE

This study assessed the responsiveness of circulating PS and lipid concentrations and cholesterol kinetics (absorption and synthesis) to daily PS supplementation in HET (ABCG8 S107X mutation) compared with a healthy control cohort.

DESIGN

A double-blind, randomized, crossover, placebo-controlled study was conducted in 10 HET and 15 control subjects. The participants had a mean (±SEM) age of 34 ± 2 y and a BMI (in kg/m²) of 29.9 ± 1.1 and consumed ∼1.6 g PS or placebo capsules daily with supper for 4 wk. Cholesterol absorption and synthesis were assessed by using [¹³C]cholesterol and deuterium oxide, respectively.

RESULTS

Plasma LDL-cholesterol concentrations decreased (P = 0.006) in both groups after PS supplementation (HET: 2.73 ± 0.19 mmol/L; control: 3.11 ± 0.19 mmol/L) compared with placebo (HET: 3.12 ± 0.20 mmol/L; control: 3.50 ± 0.21 mmol/L), whereas PS concentrations (campesterol+β-sitosterol) increased (P = 0.03) in both groups after PS supplementation (HET: 39.72 ± 6.05 μmol/L; control: 24.03 ± 1.65 μmol/L) compared with placebo (HET: 27.32 ± 3.80 μmol/L; control: 21.12 ± 2.05 μmol/L). Cholesterol absorption efficiency decreased (P = 0.010) by ∼22% and ∼17% and synthesis rates increased (P = 0.040) by ∼20% and ∼24% in the HET and control groups, respectively, in response to PS consumption compared with placebo.

CONCLUSION

These data suggest that heterozygosity for the ABCG8 S107X mutation does not influence the action of dietary PS on circulating cholesterol concentrations but may affect sterol absorption.

ABCG transporters and disease

ATP-binding cassette (ABC) transporters form a large family of transmembrane proteins that facilitate the transport of specific substrates across membranes in an ATP-dependent manner. Transported substrates include lipids, lipopolysaccharides, amino acids, peptides, proteins, inorganic ions, sugars and xenobiotics. Despite this broad array of substrates, the physiological substrate of many ABC transporters has remained elusive. ABC transporters are divided into seven subfamilies, A-G, based on sequence similarity and domain organization. Here we review the role of members of the ABCG subfamily in human disease and how the identification of disease genes helped to determine physiological substrates for specific ABC transporters. We focus on the recent discovery of mutations in ABCG2 causing hyperuricemia and gout, which has led to the identification of urate as a physiological substrate for ABCG2.

Sterol profiles in plasma and erythrocyte membranes in patients with Smith-Lemli-Opitz syndrome: a six-year experience

BACKGROUND

This study reports our experience over the last six years in the diagnosis of Smith-Lemli-Opitz syndrome and other inborn errors of cholesterol biosynthesis.

METHODS

Gas chromatography/mass spectrometry was used to obtain sterol profiles in plasma and erythrocyte membranes of suspected patients.

RESULTS

Plasma sterol reference values calculated in unaffected subjects (n=276) were in agreement with those previously reported. Among patients investigated from 2005 to 2010, we report 16 patients affected by Smith-Lemli-Opitz syndrome, three of whom represent new cases and 13 of whom were follow-up patients. In this period we also identified a new case of chondrodysplasia punctata 2 X-linked. The estimated incidence obtained for Smith-Lemli-Opitz syndrome was 1:93 suspected patients (1.08%). We also studied the effect of storage on the dehydrocholesterols/cholesterol ratio in plasma and erythrocyte membranes of patients affected by Smith-Lemli-Opitz syndrome stored at -20°C for up to 22 and 20 months, respectively. A significant negative linear correlation between storage time and the dehydrocholesterols/cholesterol ratio was identified in both plasma and erythrocyte membranes. The decrease in the dehydrocholesterols/cholesterol ratio in erythrocyte membranes was at least two-fold higher than in plasma.

CONCLUSIONS

The results of this study may be helpful for diagnosis and interpretation of data in patients with findings suggestive of a cholesterol biosynthesis defect.

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.

Effects of long term plant sterol and -stanol consumption on the retinal vasculature: a randomized controlled trial in statin users

As sitosterolemic patients have an increased cardiovascular risk, there is concern that reducing serum LDL-cholesterol concentrations by plant sterols enriched functional foods might adversely affect vascular function. Whether increased concentrations of plant sterols truly affect vascular function and whether these effects are exclusive to the larger vessels remains unknown. We compared the effects of long-term plant sterol and -stanol consumption on changes in retinal vessels diameter which reflex alterations in the microcirculation. Three randomized groups were studied at baseline and after 85-weeks. Group one (N=11) consumed plant sterol enriched margarine (2.5g/day), the second (N=8) plant stanol enriched margarine (2.5g/day), and the control group (N=11) non-enriched margarine (2.5g/day). Serum cholesterol-standardized campesterol and sitosterol concentrations increased by 354.84±168.22·102μmol/mmol and 84.36±48.26·102μmol/mmol (p<0.001), respectively in the sterol group, while decreasing non-significantly in the plant stanol group. Serum LDL-cholesterol concentrations decreased significantly in both the plant sterol (-0.33±0.33mmol/L, p=0.016) and -stanol groups (-0.38±0.34mmol/L, p=0.018) compared to the increase in the controls (0.29±0.34mmol/L). The mean change in venular diameters for the plant sterol group (2.3±3.1μm), plant stanol groups (-0.8±3.4μm) and control group (-0.8±5.1μm) did not reach significance but the change in cholesterol-standardized campesterol concentrations correlated positively with the change in venular diameter independent of changes in serum LDL-cholesterol concentrations (r=0.39, N=30, p=0.033). Increased serum campesterol concentration correlated positively with increased retinal venular diameter, independent from changes in serum LDL-cholesterol concentrations. This may constitute an explanation for the suggested effects of plant sterols on vascular function. However, this novel finding needs confirmation and further study.

Plant sterols from rapeseed and tall oils: effects on lipids, fat-soluble vitamins and plant sterol concentrations

BACKGROUND AND AIMS

Data comparing the impact of different sources of plant sterols on CVD risk factors and antioxidant levels is scarce. We evaluated the effects of plant sterols from rapeseed and tall oils on serum lipids, lipoproteins, fat-soluble vitamins and plant sterol concentrations.

METHODS AND RESULTS

This was a double-blinded, randomized, crossover trial in which 59 hypercholesterolemic subjects consumed 25 g/day of margarine for 4 weeks separated by 1 week washout periods. The two experimental margarines provided 2g/day of plant sterols from rapeseed or tall oil. The control margarine had no added plant sterols. The control margarine reduced LDL cholesterol by 4.5% (95% CI 1.4, 7.6%). The tall and rapeseed sterol margarines additionally reduced LDL cholesterol by 9.0% (95% CI 5.5, 12.4%) and 8.2% (95% CI 5.2, 11.4%) and apolipoprotein B by 5.3% (95% CI 1.0, 9.6%) and 6.9% (95% CI 3.6, 10.2%), respectively. Lipid-adjusted beta-carotene concentrations were reduced by both sterol margarines (P<0.017). alpha-Tocopherol concentrations were reduced by the tall sterol compared to the rapeseed sterol margarine (P=0.001). Campesterol concentrations increased more markedly with the rapeseed sterol versus tall sterol margarine (P<0.001). The rapeseed sterol margarine increased while the tall sterol margarine decreased brassicasterol concentrations (P<0.001).

CONCLUSIONS

Plant sterols from tall and rapeseed oils reduce atherogenic lipids and lipoproteins similarly. The rapeseed sterol margarine may have more favorable effects on serum alpha-tocopherol concentrations.

Review article: effects of plant sterols and stanols beyond low-density lipoprotein cholesterol lowering

Consumption of foods and supplements enriched with plant sterols/stanols (PS) may help reduce low-density lipoprotein cholesterol (LDL-C) levels. In this review, we consider the effects of PS beyond LDL-C lowering. Plant sterols/stanols exert beneficial effects on other lipid variables, such as apolipoprotein (apo) B/apoAI ratio and, in some studies, high-density lipoprotein cholesterol (HDL-C) and triglycerides (TG). Plant sterols/stanols may also affect inflammatory markers, coagulation parameters, as well as platelet and endothelial function. Evidence also exists about a beneficial effect on oxidative stress, but this does not seem to be of greater degree than that expected from the LDL-C lowering. Many of these effects have been demonstrated in vitro and animal models. Some in vitro effects cannot be seen in vivo or in humans at usual doses. The epidemiological studies that evaluated the association of plasma PS concentration with cardiovascular disease (CVD) risk do not provide a definitive answer. Long-term randomized placebo-controlled studies are required to clarify the effects of supplementation with PS on CVD risk and progression of atherosclerosis.

Inhibition of intestinal absorption of cholesterol by surface-modified nanostructured aluminosilicate compounds

The aim of this work was to assess the ability of aqueous suspensions of surface-modified nanostructured aluminosilicate (NSAS) compounds to reduce the intestinal absorption of cholesterol in a rat model. The rats were divided into 10 treatment groups which included several NSAS compounds at various doses, ezetimibe at 10 mg/kg, stigmastanol at 50 mg/kg, and normal saline. All compounds and controls were independently administered by oral gavage and then a mixture of [(3)H]cholesterol and cold cholesterol in 10% Intralipid(R) was immediately administered orally to the animals. Systemic blood was sampled and the concentration of cholesterol in plasma was determined by means of radioactivity. Protonation of NSAS using an ion-exchange column resulted in significant inhibition of cholesterol absorption relative to the control group (31.5% and 38.6% reduction in absorption of cholesterol for 50 and 100 mg/kg doses, respectively). Other surface-ion modifications of NSAS compounds did not show significant effect on intestinal cholesterol absorption. The inhibition of cholesterol absorption by ezetimibe was superior and by stigmastanol was equal to the effect of protonated NSAS in the doses investigated in this study. In conclusion, protonated NSAS material seems to inhibit significantly the intestinal absorption of dietary cholesterol in a rat model.

Protonated nanostructured aluminosilicate (NSAS) reduces plasma cholesterol concentrations and atherosclerotic lesions in Apolipoprotein E deficient mice fed a high cholesterol and high fat diet

The aim of this work was to assess the effect of chronic administration of protonated nanostructured aluminosilicate (NSAS) on the plasma cholesterol levels and development of atherosclerotic lesions in Apolipoprotein (ApoE) deficient mice fed a high cholesterol and high fat diet. Apolipoprotein E (ApoE) deficient mice were divided into the following treatment groups: protonated NSAS 1.4% (w/w), untreated control and 2% (w/w) stigmastanol mixed with high-cholesterol/high-fat diet. Animals were treated for 12 weeks, blood samples were withdrawn every 4 weeks for determination of plasma cholesterol and triglyceride levels. At the end of the study the aortic roots were harvested for assessment of atherosclerotic lesions. NSAS at 1.4% (w/w) and stigmastanol at 2% (w/w) treatment groups showed significant decreases in plasma cholesterol concentrations at all time points relative to the control animals. The lesion sum area in 1.4% (w/w) NSAS and 2% (w/w) stigmastanol groups were significantly less from the control animals. In conclusion, in this study, the effectiveness of chronic administration of protonated NSAS material in the reduction of plasma cholesterol levels and decrease in development of atherosclerotic lesions was demonstrated in Apo-E deficient mice model.

Free and glycosylated sterol bioaccumulation in developing Cycas micronesica seeds

The bioaccumulation of free and glycosylated forms of stigmasterol and β-sitosterol were determined from Cycas micronesica K.D. Hill seeds throughout seed ontogeny. Per-seed pool of the four compounds increased linearly from 2 to 24 months, indicating no developmental period elicited a major shift in the rate of bioaccumulation. The slopes were not homogeneous, signifying a change in relative sterol profile concomitant with seed maturation. This shift was in favour of the glucosides, as their rate of accumulation exceeded that of the free sterols. Stigmasterol content exceeded that of β-sitosterol, but ontogeny did not influence the ratio of these dominant sterols. The quantity and quality of sterol exposure during consumption of foods prepared from gametophytes by humans is strongly influenced by age of harvested seeds. Results are critical for a further understanding of the link between human neurodegenerative diseases and historical consumption of foods derived from the seed gametophyte tissue.

Autophagy in atherosclerosis: a cell survival and death phenomenon with therapeutic potential

Autophagy is a reparative, life-sustaining process by which cytoplasmic components are sequestered in double-membrane vesicles and degraded on fusion with lysosomal compartments. A growing body of evidence suggests that autophagy is stimulated in advanced atherosclerotic plaques by oxidized lipids, inflammation, and metabolic stress conditions. However, despite the increasing interest in autophagy in various pathophysiological situations such as neurodegeneration, cancer, and cardiac myopathies, the process remains an underestimated and overlooked phenomenon in atherosclerosis. As a consequence, its role in plaque formation and stability is poorly understood. Most likely, autophagy safeguards plaque cells against cellular distress, in particular oxidative injury, by degrading damaged intracellular material. In this way, autophagy is antiapoptotic and contributes to cellular recovery in an adverse environment. An interesting observation is that basal autophagy can be intensified by specific drugs. Excessively stimulated autophagic activity is capable of destroying major proportions of the cytosol, leading finally to type II programmed cell death that lacks several hallmarks of apoptosis or necrosis. Because atherosclerosis is an inflammatory disorder of the arterial intima, pharmacological approaches could be developed to stabilize vulnerable, rupture-prone lesions through selective induction of macrophage autophagic death.

Efficacy of plant sterols is not influenced by dietary cholesterol intake in hypercholesterolemic individuals

Plant sterols (PSs) reduce plasma total and low-density lipoprotein cholesterol (LDL-C) levels by reducing cholesterol absorption; however, it is not known whether the level of dietary cholesterol intake has an impact on the efficacy of PSs on blood lipids. The purpose of this study was to determine the effect of high vs low dietary cholesterol levels on the lipid-lowering efficacy of free PSs. The study was a semirandomized, double-blind, crossover trial consisting of four 28-day feeding phases each separated by a 4-week washout period. Otherwise healthy hypercholesterolemic subjects (n = 22) consumed each of (a) low-cholesterol control (C(-)S(-)), (b) high-cholesterol control (C(+)S(-)), (c) 22 mg PSs per kilogram of body weight with a low-cholesterol diet (C(-)S(+)), and (d) 22 mg PSs per kilogram of body weight with a high-cholesterol diet (C(+)S(+)). Blood was drawn on the first and last 2 days of each phase to measure plasma total cholesterol, LDL-C, high-density lipoprotein cholesterol, and triacylglycerols as well as plasma campesterol and beta-sitosterol concentrations. Dietary cholesterol had no effect on PS efficacy as a cholesterol-lowering agent because no interaction was found between the 2 factors. However, dietary cholesterol and PS intake had significant independent effects on plasma total cholesterol, LDL-C, and high-density lipoprotein cholesterol levels. beta-Sitosterol levels in plasma increased (P < .0001) as a result of PS supplementation. Data from the present study indicate that, although PSs and dietary cholesterol exert independent effects on plasma cholesterol, PS efficacy is not affected by varying levels of cholesterol intake.

Baseline plasma plant sterol concentrations do not predict changes in serum lipids, C-reactive protein (CRP) and plasma plant sterols following intake of a plant sterol-enriched food

BACKGROUND/OBJECTIVES

Plant sterol (PS) consumption lowers serum cholesterol levels, while modestly increasing plasma PS concentrations. Plasma PS concentrations may reflect sterol absorption, thus individuals with high plasma plant sterol (HPS) concentrations may show greater changes in circulating cholesterol and PS than individuals with low plasma plant sterol (LPS) concentrations. The objective of this study was to examine whether HPS and LPS concentrations are related to subsequent changes in plasma PS, serum lipid and C-reactive protein (CRP) concentrations, following dietary PS intake in otherwise healthy hypercholesterolemic men.

SUBJECTS/METHODS

This single-blinded, randomized, diet-controlled study consisted of two 4-week phases, separated by a 4-week washout, where a diet with a placebo or the 2.0 g per day PS-enriched spread was consumed during the phases.

RESULTS

At baseline, men with HPS possessed higher (P<0.01) mean serum cholesterol concentration, while those with LPS had higher (P<0.05) body mass index. Following PS intake, plasma sum of campesterol plus sitosterol concentrations were elevated from 34.6+/-4.2 to 46.2+/-3.3 micromol l(-1) (mean+/-SE) and 16.5+/-0.9 to 20.8+/-1.2 micromol l(-1) after PS intake in men with HPS and LPS, respectively. Changes in plasma PS concentrations, however, were not different between individuals with either HPS or LPS baseline concentrations. Total cholesterol and low-density lipoprotein cholesterol levels were decreased (P<0.0001) by 6.3 and 7.8%, respectively, with PS consumption for all individuals. Changes in lipid parameters were not different between individuals with HPS or LPS baseline concentrations. No changes in CRP were apparent subsequent to PS intervention.

CONCLUSIONS

Baseline plasma PS concentrations are not associated or predictive of changes in serum cholesterol or plasma PS concentrations after PS intervention. Thus, individuals with HPS show similar increases in PS concentrations as individuals with LPS following PS supplementation. Plasma PS remained in the range of previously reported concentrations.

Beta-sitosterolaemia: a new nonsense mutation in the ABCG5 gene

BACKGROUND

Sitosterolaemia is a rare autosomal recessive disorder characterised by elevated plasma levels of plant sterols and cholesterol. Sitosterolaemia is caused by gene mutations in either of two ATP-binding cassette (ABC) half transporters, ABCG5 and ABCG8. The plasma sterol profile and genetic analysis of a 10-year-old girl who had tuberous xanthomas is the subject of this report.

MATERIALS AND METHODS

Genomic DNA was isolated from white blood cells from the proband, her family and a control group of healthy people. All exons of ABCG5 and ABCG8 were sequenced. Plasma cholesterol and triglycerides were measured by routine methods. All other plasma sterols were measured by Gas Chromatography coupled to Mass Spectrometry.

RESULTS

The proband was found to be homozygous for a single nucleotide mutation in exon 10 of the ABCG5 gene, consisting of a C to T transition at nucleotide 1336 of the coding sequence, which results in the premature termination of the ABCG5 protein at amino acid 446 (Arg446X). Her mother and brother were also homozygous for the same mutation and all had elevated plasma beta-sitosterol levels. The father was heterozygous and showed normal beta-sitosterol levels. This mutation was not found in healthy normolipidaemic subjects.

CONCLUSIONS

We describe a novel nonsense mutation in exon 10 of the ABCG5 gene in a 10-year-old girl showing clinical and biochemical features of sitosterolaemia. This family study broadens the spectrum of the ABCG5/ABCG8 mutations causing sitosterolaemia and helps highlight the correlations between such gene mutations, biochemical phenotype and the development of cardiovascular disease.

Adrenal insufficiency in phytosterolaemia

BACKGROUND

Phytosterolaemia (sitosterolaemia) is a rare autosomal recessive condition caused by mutations on the ABCG5 and ABCG8 gut transporter proteins. This leads to accumulation of plant-derived cholesterol-like molecules in blood and tissues.

CASE

We describe a family of Bangladesh origin, where three siblings (two males and one female) have homozygous mutations for phytosterolaemia, and exhibit short stature and adrenal failure with the female having ovarian failure.

FINDINGS

The index case (18-year-old female) and her sibling (16 years) have adrenal insufficiency with hyperpigmentation and raised levels of ACTH, at 367 and 690 ng/l respectively. The youngest child at 7 years has normal adrenal function. In addition, the index case has ovarian failure and sibling 2 has partial growth hormone deficiency.

CONCLUSION

Although short stature is a recognised phenomenon, no previous association has been made between phytosterolaemia and other endocrine abnormalities. We postulate that the elevated plant sterol levels in phytosterolaemia may interfere with endocrine hormone synthesis; in particular, we present evidence that adrenal cholesterol metabolism may be preferentially affected, accounting for the adrenal insufficiency.

Customary use of plant sterol and plant stanol enriched margarine is associated with changes in serum plant sterol and stanol concentrations in humans

The consumption of products enriched with plant sterol or stanol esters lowers serum total and LDL-cholesterol concentrations, thereby most likely reducing the risk of coronary heart disease. However, using plant sterol (not plant stanol) enriched products elevates serum plant sterol concentrations in humans. This may be unwanted because health effects of elevated serum plant sterol concentrations are still controversial. Within postlaunch monitoring of functional foods, we compared serum plant sterol and plant stanol concentrations among users of plant sterol (n = 67) or plant stanol (n = 13) enriched margarines with those of matched nonusers (n = 81) in the ongoing Dutch Doetinchem cohort study. Subjects (aged 29-67 y) were examined in 1994-1998 (before the introduction of enriched margarines) and re-examined in 1999-2003. Serum concentrations of plant sterols and stanols were measured in samples from nonfasting subjects by GLC-MS. Intake of plant sterols was 1.1 +/- 0.6 g/d and was associated with a decrease of serum total cholesterol concentration of 0.25 +/- 0.91 mmol/L (4%, P < 0.05), a change that differed (P < 0.05) from the nonsignificant increase in nonusers (+2%, 0.12 +/- 0.78 mmol/L, P = 0.16). Cholesterol-standardized serum sitosterol and campesterol increased in plant sterol users by 22% (P < 0.0001) and 103% (P < 0.0001), respectively. Cholesterol-standardized serum sitostanol and campestanol increased in plant stanol users by 197% (P = 0.02) and 196% (P = 0.01). To our knowledge, these data are the first to show changes in serum cholesterol, plant sterol, and plant stanol concentrations after (long-term) consumption of plant sterol and stanol enriched margarines in a free-living population in a nonexperimental setting. Whether the increased serum sterol concentrations result in adverse side effects needs to be investigated in future postlaunch monitoring studies.

Sitosterol-containing lipoproteins trigger free sterol-induced caspase-independent death in ACAT-competent macrophages

Sitosterolemia is a disease characterized by very high levels of sitosterol and other plant sterols and premature atherothrombotic vascular disease. One theory holds that plant sterols can directly promote atherosclerosis, but the mechanism is not known. Unesterified, or "free," cholesterol (FC) is a potent inducer of macrophage death, which causes plaque necrosis, a precursor to atherothrombosis. FC-induced macrophage death, however, requires dysfunction of the sterol esterifying enzyme acyl-coenzyme A-cholesterol acyltransferase (ACAT), which likely occurs slowly during lesion progression. In contrast, plant sterols are relatively poorly esterified by ACAT, and so they may cause macrophage death and plaque necrosis in an accelerated manner. In support of this hypothesis, we show here that macrophages incubated with sitosterol-containing lipoproteins accumulate free sterols and undergo death in the absence of an ACAT inhibitor. As with FC loading, sitosterol-induced macrophage death requires sterol trafficking to the endoplasmic reticulum, and sitosterol-enriched endoplasmic reticulum membranes show evidence of membrane protein dysfunction. However, whereas FC induces caspase-dependent apoptosis through activation of the unfolded protein response and JNK, sitosterol-induced death is caspase-independent and involves neither the unfolded protein response nor JNK. Rather, cell death shows signs of necroptosis and autophagy and is suppressed by inhibitors of both processes. These data establish two new concepts. First, a relatively subtle change in sterol structure fundamentally alters the type of death program triggered in macrophages. Understanding the basis of this alteration should provide new insights into the molecular basis of death pathway signaling. Second, sitosterol-induced macrophage death does not require ACAT dysfunction and so may occur in an accelerated fashion. Pending future in vivo studies, this concept may provide at least one mechanism for accelerated plaque necrosis and atherothrombotic disease in patients with sitosterolemia.

Pharmacogenomics and cardiovascular drugs: need for integrated biological system with phenotypes and proteomic markers

Personalized medicine is based on a better knowledge of biological variability, considering the important part due to genetics. When trying to identify involved genes and their products in differential cardiovascular drug responses, a five-step strategy is to be followed: 1) Pharmacokinetic-related genes and phenotypes (2) Pharmacodynamic targets, genes and products (3) Cardiovascular diseases and risks depending on specific or large metabolic cycles (4) Physiological variations of previously identified genes and proteins (5) Environment influences on them. After summarizing the most well-known genes involved in drug metabolism, we will take as example of drugs, the statins, considered as very important drugs from a Public-Health standpoint, but also for economical reasons. These drugs respond differently in human depending on multiple polymorphisms. We will give examples with common ApoE polymorphisms influencing the hypolipemic effects of statins. These drugs also have pleiotropic effects and decrease inflammatory markers. This illustrates the need to separate clinical diseases phenotypes in specific metabolic pathways, which could propose other classifications, of diseases and related genes. Hypertension is also a good example of clinical phenotype which should be followed after various therapeutic approaches by genes polymorphisms and proteins markers. Gene products are under clear environmental expression variations such as age, body mass index and obesity, alcohol, tobacco and dietary interventions which are the first therapeutical actions taken in cardiovascular diseases. But at each of the five steps, within a pharmacoproteomic strategy, we also need to use available information from peptides, proteins and metabolites, which usually are the gene products. A profiling approach, i.e., dealing with genomics, but now also with proteomics, is to be used. In conclusion, the profiling, as well as the large amount of data, will more than before render necessary an organized interpretation of DNA, RNA as well as proteins variations, both at individual and population level.