Thyroid Hormone Status in Sitosterolemia Is Modified by Ezetimibe.

OBJECTIVES: To assess the association between biomarkers of thyroid status and 5α-stanols in patients with sitosterolemia treated with ezetimibe (EZE). STUDY DESIGN: Eight patients with sitosterolemia (16-56 years of age) were studied during 14 weeks off EZE therapy and 14 weeks on EZE (10 mg/day). Serum thyroid biomarkers (free triiodothyronine [FT3], free thyroxine [FT4], FT3/FT4 ratio, thyroid-stimulating hormone), 5α-stanols (sitostanol and cholestanol), and cholestanol precursors (total cholesterol and its synthesis marker lathosterol, and 7α-hydroxy-4-cholesten-3-one cholestenol) were measured at baseline and during the 14 weeks off EZE and on EZE. RESULTS: EZE increased FT3/FT4 (10% ± 4%; P = .02). EZE reduced plasma and red blood cells sitostanol (-38% ± 6% and -20% ± 4%; all P < .05) and cholestanol (-18% ± 6% and -13% ± 3%; all P < .05). The change in plasma cholestanol level on EZE inversely correlated with the change in FT3/FT4 (r = -0.86; P = .01). EZE lowered total cholesterol (P < .0001) and did not affect 7α-hydroxy-4-cholesten-3-one cholestanol. EZE increased (P < .0001) lathosterol initially, but the level was not sustained, resulting in similar levels at week 14 off EZE and on EZE. CONCLUSION: In patients with STSL, 5α-stanols levels might be associated with thyroid function. EZE reduces circulating 5α-stanols while increasing FT3/FT4, implying increased conversion of T4 to T3, thus possibly improving thyroid hormone status. TRIAL REGISTRATION: ClinicalTrials.govNCT01584206.

Effect of ezetimibe on low- and high-density lipoprotein subclasses in sitosterolemia.

BACKGROUND AND AIMS: Sitosterolemia displays high plasma total sterols [high plant sterols (PS) + normal to high total cholesterol (TC)] with normal to moderately elevated low-density lipoprotein (LDL) levels. High LDL, intermediate-density lipoprotein (IDL) and very low-density lipoprotein (VLDL) particles, low high-density lipoprotein (HDL), and increased non-HDL and the ratios of TC and triglycerides (TG) to HDL can increase the risk for atherosclerosis. Ezetimibe (EZE) can reduce plasma PS and TC levels in sitosterolemia, but its effect on lipoprotein subclasses has not been previously reported. METHODS: Sitosterolemia patients (n = 8) were taken off EZE for 14 weeks (OFF EZE) and placed on EZE (10 mg/d) for 14 weeks (ON EZE). Serum lipids were measured enzymatically and lipoprotein subclasses were assessed by polyacrylamide gel electrophoresis. RESULTS: EZE reduced (p < 0.05) total sterols (-12.5 ± 4.1%) and LDL-sterol (-22.7 ± 5.7%) and its sterol mass of large VLDL (-24.4 ± 4.5%), VLDL remnants (-21.1 ± 7.9%) and large IDL (-22.4 ± 7.2%) compared to OFF EZE. EZE did not affect large LDL subclasses or mean LDL particle size (273.8 ± 0.6 vs. 274.6 ± 0.3 Å). EZE increased HDL-sterol (25.5 ± 8.0%, p = 0.008) including intermediate (34 ± 14%, p = 0.02) and large (33 ± 16%, p = 0.06) HDL. EZE reduced non-HDL-sterol (-21.8± 5.0%), total sterols/HDL (-28.2 ± 5.5%) and TG/HDL (-27.4 ± 6.5%, all p < 0.01). CONCLUSIONS: EZE improves VLDL and HDL subfraction distribution, thereby reducing the atherogenic lipid profile, thus providing potential clinical benefit in sitosterolemia beyond TC and PS reduction.

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.

Ezetimibe reduces plant sterol accumulation and favorably increases platelet count in sitosterolemia.

OBJECTIVE: To assess if ezetimibe (EZE), a sterol-absorption inhibitor, improves platelet (PLT) count and size relative to its effect on plasma plant sterol (PS) in patients with sitosterolemia (STSL). STUDY DESIGN: Patients with STSL (5 males, 3 females, 16-56 years of age) receiving EZE intervention as part of their routine care participated in this study. EZE was discontinued for 14 weeks (off) and then resumed for another 14 weeks (on). Hematology variables along with plasma and red blood cells (RBC) PS and total cholesterol (TC) levels were measured at the end of each phase. RESULTS: EZE increased PLT count (23% ± 9%) and decreased mean PLT volume (MPV; 10% ± 3%, all P < .05). In patients off EZE, PLT counts inversely correlated (r = -0.96 and r = -0.91, all P < .01) with plasma and RBC PS to TC ratio (PS/TC), and MPV positively correlated (r = 0.91, P = .03 and r = 0.93, P = .02) with plasma and RBC PS/TC. EZE reduced plasma and RBC sitosterol (-35% ± 4% and -28% ± 3%), total PS (-37% ± 4% and -28% ± 3%, all P < .0001) levels, and PS/TC (-27% ± 4% and -28% ± 4%, P < .01). CONCLUSIONS: EZE reduces plasma and RBC PS levels, while increasing PLT count and decreasing MPV, and thereby may reduce the risk for bleeding in STSL. Plasma PS levels and ABCG5/ABCG8 genes should be analyzed in patients with unexplained hematologic abnormalities.

Non-cholesterol sterols and cholesterol metabolism in sitosterolemia.

Sitosterolemia (STSL) is a rare autosomal recessive disease, manifested by extremely elevated plant sterols (PS) in plasma and tissue, leading to xanthoma and premature atherosclerotic disease. Therapeutic approaches include limiting PS intake, interrupting enterohepatic circulation of bile acid using bile acid binding resins such as cholestyramine, and/or ileal bypass, and inhibiting intestinal sterol absorption by ezetimibe (EZE). The objective of this review is to evaluate sterol metabolism in STSL and the impact of the currently available treatments on sterol trafficking in this disease. The role of PS in initiation of xanthomas and premature atherosclerosis is also discussed. Blocking sterols absorption with EZE has revolutionized STSL patient treatment as it reduces circulating levels of non-cholesterol sterols in STSL. However, none of the available treatments including EZE have normalized plasma PS concentrations. Future studies are needed to: (i) explore where cholesterol and non-cholesterol sterols accumulate, (ii) assess to what extent these sterols in tissues can be mobilized after blocking their absorption, and (iii) define the factors governing sterol flux.

Beyond cholesterol-lowering effects of plant sterols: clinical and experimental evidence of anti-inflammatory properties.

Inflammation is a strong risk factor for cardiovascular disease. Dietary plant sterols are known to reduce plasma cholesterol levels and thereby reduce cardiovascular risk. Recent observations from animal and human studies have demonstrated anti-inflammatory effects of phytosterols. For example, several animal and human studies report reductions in the levels of proinflammatory cytokines, including C-reactive protein, after consumption of dietary plant sterols. Although the cholesterol-lowering effects of phytosterols in humans are well documented, studies on the effects of phytosterols on inflammatory markers have produced inconsistent results. This review summarizes and discusses findings from recent animal and human studies with regard to the potential anti-inflammatory effects of dietary phytosterols. Findings on the effects of plant sterols on inflammation remain limited and confounding. Future research using better-designed and well-controlled laboratory studies and clinical trials are needed to fully understand the mechanisms through which phytosterols influence inflammation. Additional well-designed placebo-controlled studies are needed to better understand how and to what extent dietary plant sterols may modify the immune system and the production of inflammatory markers.

Cholesterol-lowering effects of oat ß-glucan.

Elevated total and low-density lipoprotein (LDL) cholesterol levels are considered major risk factors for cardiovascular disease. Oat ß-glucan, a soluble dietary fiber that is found in the endosperm cell walls of oats, has generated considerable interest due to its cholesterol-lowering properties. The United States Food and Drug Administration (FDA) approved a health claim for ß-glucan soluble fiber from oats for reducing plasma cholesterol levels and risk of heart disease in 1997. Similarly, in 2004 the United Kingdom Joint Health Claims Initiative (JHCI) allowed a cholesterol-lowering health claim for oat ß-glucan. The present review aims to investigate if results from more recent studies are consistent with the original conclusions reached by the FDA and JHCI. Results of this analysis show that studies conducted during the past 13 years support the suggestion that intake of oat ß-glucan at daily doses of at least 3 g may reduce plasma total and low-density lipoprotein (LDL) cholesterol levels by 5-10% in normocholesterolemic or hypercholesterolemic subjects. Studies described herein have shown that, on average, oat consumption is associated with 5% and 7% reductions in total and LDL cholesterol levels, respectively. Significant scientific agreement continues to support a relationship between oat ß-glucan and blood cholesterol levels, with newer data being consistent with earlier conclusions made by the FDA and JHCI.

Pro-atherogenic effects of probucol in apo E-KO mice may be mediated through alterations in immune system: Parallel alterations in gene expression in the aorta and liver.

OBJECTIVE: To establish underlying molecular mechanisms of pro-atherogenic effects of probucol in apo E-KO mice. METHODS: Affymetrix Gene Chip System, GenMAPP/MAPPFinder software and real-time PCR techniques were used to identify alterations in gene expression and biological pathways in the liver and aorta of both male apo E-KO and male wild-type mice treated with or without probucol (1%, w/w) for 18 weeks. Plasma levels of lipids, cytokines, liver function test, and the extent of atherosclerosis and liver histology were examined. RESULTS AND CONCLUSIONS: Probucol treatment paradoxically reduced plasma cholesterol levels, increased plasma cytokine levels and atherogenesis in apo E-KO mice. Three hundred and sixty genes/transcripts and 110 biological processes were significantly differentially expressed in the liver of probucol-treated apo E-KO mice. The response to biotic stimulus, immune response and inflammatory response were the most prominent processes expressed in the liver. The expression of 60 of these genes involved in immune response including inflammatory responses, antigen presentation, humoral immune response, immune cell activation, innate immune response, and regulation of immune response was over-expressed. Many of these genes were also over-expressed in the aorta of probucol-treated apo E-KO mice. Such effects of probucol were not observed in the liver and aorta of wild-type mice. A significant interaction between apo E deficiency and probucol treatment was observed. Histological examinations showed a significant infiltration of inflammatory cells in the liver of probucol-treated apo E-KO mice, but not in C57BL/6 mice. These findings suggest that probucol-induced atherogenesis may be mediated through a pro-inflammatory state.

A systemic review of the roles of n-3 fatty acids in health and disease.

Attention to the role of n-3 long-chain fatty acids in human health and disease has been continuously increased during recent decades. Many clinical and epidemiologic studies have shown positive roles for n-3 fatty acids in infant development; cancer; cardiovascular diseases; and more recently, in various mental illnesses, including depression, attention-deficit hyperactivity disorder, and dementia. These fatty acids are known to have pleiotropic effects, including effects against inflammation, platelet aggregation, hypertension, and hyperlipidemia. These beneficial effects may be mediated through several distinct mechanisms, including alterations in cell membrane composition and function, gene expression, or eicosanoid production. A number of authorities have recently recommended increases in intakes of n-3 fatty acids by the general population. To comply with this recommendation a variety of food products, most notably eggs, yogurt, milk, and spreads have been enriched with these fatty acids. Ongoing research will further determine the tissue distribution, biological effects, cost-effectiveness, and consumer acceptability of such enriched products. Furthermore, additional controlled clinical trials are needed to document whether long-term consumption or supplementation with eicosapentaenoic acid/docosahexaenoic acid or the plant-derived counterpart (alpha-linolenic acid) results in better quality of life.

Effects of long-term consumption of a high-fructose diet on conventional cardiovascular risk factors in Sprague-Dawley rats.

We investigated the effects of a high-fructose (HF) diet on cardiovascular risks in Sprague-Dawley rats. Twelve rats were randomly assigned to standard chow or HF diet for 20 weeks. Systolic blood pressure and circulating insulin, total cholesterol, and triacylglycerol levels were significantly higher in the HF group. Aortic sections appeared normal, but liver sections from the HF group showed lipid accretion, mild inflammation, and bile pigmentation. Liver samples from the HF group showed significantly higher total lipid levels and changes in fatty acid profile. Levels of 16:0, cis-9-18:2, cis-11-20:1, cis-13-20:1, cis-11-20:2 and 24:0 were significantly raised in the phospholipid fraction. Lower levels of cis-11-18:1, cis-9-18:2, and cis-11-20:1 and increased levels of 16:1, cis-9-18:1, and cis-13-20:1 were found in the non-esterified fatty acid fraction. HF-feeding resulted in significant reductions in plasma levels of certain inflammatory biomarkers. HF intake over time may negatively impact cardiovascular health and liver function in rats.

The role of Tissue Doppler imaging in the noninvasive detection of chronic rejection after heterotopic cardiac transplantation in rats.

BACKGROUND: Chronic rejection is a risk factor for the development of cardiac allograft vasculopathy (CAV) in heart transplant recipients. A useful animal model to study the role of immunosuppressive strategies in the prevention of chronic rejection involves heterotopic abdominal cardiac transplantation in rats. The detection of rejection and concurrent CAV traditionally involves subjective serial palpation of the graft from a scale of 0 to 4, with 4 indicating vigorous beats. Recent advances in murine echocardiography, in particular Tissue Doppler imaging (TDI), may allow for objective in vivo monitoring of chronic rejection in this transplant model. OBJECTIVE: The objective of this study was to compare the diagnostic accuracy of murine echocardiography as compared to the abdominal palpation heart score for the noninvasive detection of chronic cardiac graft rejection. METHODS: In an animal model of heterotopic cardiac transplantation, 18 male Fischer and Lewis rats were used as donors and recipients, respectively. Abdominal palpation and murine transthoracic echocardiography were performed to assess in vivo function of the transplanted heart. Left ventricular (LV) structure and function and TDI indices, including endocardial velocity (Vendo) and strain rate (SR), were evaluated in the ectopic heart. Graft tissues were processed for histological examination and graded for chronic rejection. RESULTS: Abdominal palpation scores were obtained in all 18 rats; score 1 (n = 5); score 2 (n = 4); score 3 (n = 6); and score 4 (n = 3). The mean LV ejection fraction was significantly (P <0.01) lower in score 3 and 4 grafts as compared to score 1 grafts. There was no correlation between the abdominal palpation score and LV systolic function. There was a significant relationship between decreasing Vendo or SR values and increasing grades of rejection (r = 0.65, P <0.05 and r = 0.75, P < 0.05, respectively). CONCLUSION: TDI of the transplanted heart in rats is feasible, reproducible, and more sensitive than palpation for the detection of chronic rejection.

A comparison of the effects of fish oil and flaxseed oil on cardiac allograft chronic rejection in rats.

Both fish and flaxseed oils are major sources of different n-3 fatty acids. Beneficial effects of fish oil on posttransplantation complications have been reported. The current study aimed to compare the effects of flaxseed and fish oils in a rat cardiac allograft model. Male Fischer and Lewis rats were used as donors and recipients, respectively, to generate a heterotopic cardiac allograft model. Animals were randomly assigned into three groups and fed a diet supplemented with 1) 5% (wt/wt) safflower oil (control, n = 7), 2) 5% (wt/wt) flaxseed oil (n = 8), or 3) 2% (wt/wt) fish oil (n = 7), and an intraperitoneal injection of cyclosporine A (CsA; 1.5 mg.kg(-1).day(-1)) over 12 wk. Body weight, blood pressure, plasma levels of lipids, CsA, select cytokines, as well as graft function and chronic rejection features were assessed. Body weight and blood CsA levels were similar among the groups. Relative to controls, both treated groups had lower systolic and diastolic blood pressure and plasma levels of macrophage chemotactic protein-1. Treatment with fish oil significantly (P < 0.05) lowered plasma levels of triglycerides, total cholesterol, and LDL-cholesterol. HDL-cholesterol concentrations were significantly higher (P < 0.05) in the flaxseed oil-treated group compared with the other two groups. Both flaxseed oil and fish oil may provide similar biochemical, hemodynamic, and inflammatory benefits after heart transplantation; however, neither of the oils was able to statistically significantly impact chronic rejection or histological evidence of apparent cyclosporine-induced nephrotoxicity in this model.