A unique patient with coexisting cerebrotendinous xanthomatosis and beta-sitosterolemia

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.

The association between hypercholesterolemia and sitosterolemia, and report of a sitosterolemia kindred

BACKGROUND

Sitosterolemia is associated with increases in intestinal sterol absorption, low-density lipoprotein cholesterol (LDL-C), and cardiovascular disease risk.

OBJECTIVE

We examined the relationship between hypercholesterolemia and sitosterolemia in a large population and report a new sitosterolemia case.

METHODS

Plasma sterol concentrations were measured by gas chromatography/mass spectrometry, and LDL-C by direct assay.

RESULTS

Of 207,926 subjects tested, 4.3% had LDL-C ≥190 mg/dL. Plasma β-sitosterol concentrations ≥8.0 mg/L (99th percentile) were found in 4.3% of these subjects vs 0.72% with LDL-C <130 mg/dL. Among all subjects, 0.050% had β-sitosterol levels ≥15.0 mg/L, consistent with sitosterolemia, while among those with LDL-C ≥190 mg/dL, 0.334% had this rare disorder. A 13-year-old boy with the highest LDL-C (679 mg/dL) of all subjects had planar xanthomas and a β-sitosterol level of 53.5 mg/L (normal <3.3 mg/L). He was a compound heterozygote for 2 ABCG8 mutations (p.N409D and an intron 11+2T>A splice site mutation). On a low-cholesterol and plant-sterol diet, his LDL-C decreased to 485 mg/dL (-29%) and β-sitosterol to 44.6 mg/L (-27%). On atorvastatin 20 mg/d, his LDL-C decreased to 299 mg/dL (-38%). With added ezetimibe 10 mg/d, his LDL-C normalized to 60 mg/dL (-80% further decrease); and his β-sitosterol decreased to 14.1 mg/L (-68% further decrease).

CONCLUSIONS

Our data indicate that about 4% of subjects with LDL-C concentrations ≥190 mg/dL have plasma β-sitosterol concentrations above the 99th percentile and about 0.3% have concentrations consistent with sitosterolemia. Therefore, this diagnosis should be considered in such patients.

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.

Bilateral Achilles tendon enlargement

Cerebrotendinous xanthomatosis is a rare, autosomal-recessive, lipid-storage disease with accumulation of cholestanol in most tissues, particularly within the Achilles tendons. It has been characterized both clinically and biochemically, and recently from the molecular biological aspect as well. Juvenile cataract, childhood diarrhea, mental retardation, cerebellar ataxia, and tendon xanthomas are the most prominent features of this disease. Bilateral symmetrical firm masses of Achilles tendons may be the first symptom the patient recognizes because it can jeopardize his or her ability to walk. However, the treatment strategies for tendon tumors vary. In a recent case, we diagnosed the disease properly, according to the clinical manifestations and the radiological and laboratory examinations. The genetic mutation was characterized by analyzing sterol 27-hydroxylase from the patient's family (located on nucleotide 599) and led to a nonsense mutation. It is a unique type of mutation that has never been reported to our knowledge. Tendon lesions are characterized by the loss of muscle fibers and accumulation of lipid products. To help the patient regain the strength of the Achilles tendon and walking abilities, a large area of tendon tumor was excised, followed by reconstruction with a tibialis posterior allograft, which is the second strongest tendon in the foot and ankle. Although the use of this type of graft is uncommon, the final result was satisfactory. At the 10-month follow-up examination, the patient could walk easily without pain. This case report suggests that the surgical procedure will provide an alternative for the repair of large-area degenerative Achilles tendons.

Protein mediators of sterol transport across intestinal brush border membrane

Dysregulation of cholesterol balance contributes significantly to atherosclerotic cardiovascular disease (ASCVD), the leading cause of death in the United States. The intestine has the unique capability to act as a gatekeeper for entry of cholesterol into the body, and inhibition of intestinal cholesterol absorption is now widely regarded as an attractive non-statin therapeutic strategy for ASCVD prevention. In this chapter we discuss the current state of knowledge regarding sterol transport across the intestinal brush border membrane. The purpose of this work is to summarize substantial progress made in the last decade in regards to protein-mediated sterol trafficking, and to discuss this in the context of human disease.

The effects of sterol structure upon sterol esterification

Cholesterol is esterified in mammals by two enzymes: LCAT (lecithin cholesterol acyltransferase) in plasma and ACAT(1) and ACAT(2) (acyl-CoA cholesterol acyltransferases) in the tissues. We hypothesized that the sterol structure may have significant effects on the outcome of esterification by these enzymes. To test this hypothesis, we analyzed sterol esters in plasma and tissues in patients having non-cholesterol sterols (sitosterolemia and Smith-Lemli-Opitz syndrome). The esterification of a given sterol was defined as the sterol ester percentage of total sterols. The esterification of cholesterol in plasma by LCAT was 67% and in tissues by ACAT was 64%. Esterification of nine sterols (cholesterol, cholestanol, campesterol, stigmasterol, sitosterol, campestanol, sitostanol, 7-dehydrocholesterol and 8-dehydrocholesterol) was examined. The relative esterification (cholesterol being 1.0) of these sterols by the plasma LCAT was 1.00, 0.95, 0.89, 0.40, 0.85, 0.82 and 0.80, 0.69 and 0.82, respectively. The esterification by the tissue ACAT was 1.00, 1.29, 0.75, 0.49, 0.45, 1.21 and 0.74, respectively. The predominant fatty acid of the sterol esters was linoleic acid for LCAT and oleic acid for ACAT. We compared the esterification of two sterols differing by only one functional group (a chemical group attached to sterol nucleus) and were able to quantify the effects of individual functional groups on sterol esterification. The saturation of the A ring of cholesterol increased ester formation by ACAT by 29% and decreased the esterification by LCAT by 5.9%. Esterification by ACAT and LCAT was reduced, respectively, by 25 and 11% by the presence of an additional methyl group on the side chain of cholesterol at the C-24 position. This data supports our hypothesis that the structure of the sterol substrate has a significant effect on its esterification by ACAT or LCAT.

Genetic inactivation of NPC1L1 protects against sitosterolemia in mice lacking ABCG5/ABCG8

Mice lacking Niemann-Pick C1-Like 1 (NPC1L1) (NPC1L1(-/-)mice) exhibit a defect in intestinal absorption of cholesterol and phytosterols. However, wild-type (WT) mice do not efficiently absorb and accumulate phytosterols either. Cell-based studies show that NPC1L1 is a much weaker transporter for phytosterols than cholesterol. In this study, we examined the role of NPC1L1 in phytosterol and cholesterol trafficking in mice lacking ATP-binding cassette (ABC) transporters G5 and G8 (G5/G8(-/-) mice). G5/G8(-/-) mice develop sitosterolemia, a genetic disorder characterized by the accumulation of phytosterols in blood and tissues. We found that mice lacking ABCG5/G8 and NPC1L1 [triple knockout (TKO) mice] did not accumulate phytosterols in plasma and the liver. TKO mice, like G5/G8(-/-) mice, still had a defect in hepatobiliary cholesterol secretion, which was consistent with TKO versus NPC1L1(-/-) mice exhibiting a 52% reduction in fecal cholesterol excretion. Because fractional cholesterol absorption was reduced similarly in NPC1L1(-/-) and TKO mice, by subtracting fecal cholesterol excretion in TKO mice from NPC1L1(-/-) mice, we estimated that a 25g NPC1L1(-/-) mouse may secrete about 4 mumol of cholesterol daily via the G5/G8 pathway. In conclusion, NPC1L1 is essential for phytosterols to enter the body in mice.

Plant sterols cause macrothrombocytopenia in a mouse model of sitosterolemia

Mutations in either ABCG5 or ABCG8 cause sitosterolemia, an inborn error of metabolism characterized by high plasma plant sterol concentrations. Recently, macrothrombocytopenia was described in a number of sitosterolemia patients, linking hematological dysfunction to disturbed sterol metabolism. Here, we demonstrate that macrothrombocytopenia is an intrinsic feature of murine sitosterolemia. Abcg5-deficient (Abcg5(-/-)) mice showed a 68% reduction in platelet count, and platelets were enlarged compared with wild-type controls. Macrothrombocytopenia was not due to decreased numbers of megakaryocytes or their progenitors, but defective megakaryocyte development with deterioration of the demarcation membrane system was evident. Lethally irradiated wild-type mice transplanted with bone marrow from Abcg5(-/-) mice displayed normal platelets, whereas Abcg5(-/-) mice transplanted with wild-type bone marrow still showed macrothrombocytopenia. Treatment with the sterol absorption inhibitor ezetimibe rapidly reversed macrothrombocytopenia in Abcg5(-/-) mice concomitant with a strong decrease in plasma plant sterols. Thus, accumulation of plant sterols is responsible for development of macrothrombocytopenia in sitosterolemia, and blocking intestinal plant sterol absorption provides an effective means of treatment.

Dietary sitostanol and campestanol: Accumulation in the blood of humans with sitosterolemia and xanthomatosis and in rat tissues

Dietary sitostanol has a hypocholesterolemic effect because it decreases the absorption of cholesterol. However, its effects on the sitostanol concentrations in the blood and tissues are relatively unknown, especially in patients with sitosterolemia and xanthomatosis. These patients hyperabsorb all sterols and fail to excrete ingested sitosterol and other plant sterols as normal people do. The goal of the present study was to examine the absorbability of dietary sitostanol in humans and animals and its potential long-term effect. Two patients with sitosterolemia were fed the margarine Benecol (McNeill Nutritionals, Ft. Washington, PA), which is enriched in sitostanol and campestanol, for 7-18 wk. Their plasma cholesterol levels decreased from 180 to 167 mg/dL and 153 to 113 mg/dL, respectively. Campesterol and sitosterol also decreased. However, their plasma sitostanol levels increased from 1.6 to 10.1 mg/dL and from 2.8 to 7.9 mg/dL, respectively. Plasma campestanol also increased. After Benecol withdrawal, the decline in plasma of both sitostanol and campestanol was very sluggish. In an animal study, two groups of rats were fed high-cholesterol diets with and without sitostanol for 4 wk. As expected, plasma and liver cholesterol levels decreased 18 and 53%, respectively. The sitostanol in plasma increased fourfold, and sitostanol increased threefold in skeletal muscle and twofold in heart muscle. Campestanol also increased significantly in both plasma and tissues. Our data indicate that dietary sitostanol and campestanol are absorbed by patients with sitosterolemia and xanthomatosis and also by rats. The absorbed plant stanols were deposited in rat tissues. Once absorbed by sitosterolemic patients, the prolonged retention of sitostanol and campestanol in plasma might increase their atherogenic potential.

The pivotal role of cholesterol absorption inhibitors in the management of dyslipidemia

Elevated low-density lipoprotein (LDL)-cholesterol is associated with a significantly increased risk of coronary heart disease. Ezetimibe is the first member of a new class of selective cholesterol absorption inhibitors. It impairs the intestinal reabsorption of both dietary and hepatically excreted biliary cholesterol. Ezetimibe is an effective and safe agent for lowering LDL-C and non HDL-C. Short term clinical trials have established the role of ezetimibe monotherapy and its use in combination with statins. Furthermore, ezetimibe and statin combination therapy increased the percentage of patients who achieved their LDL-C treatment goal. Studies using surrogate markers of atherosclerosis have suggested a possible role of ezetimibe in combating atherosclerosis. Ezetimibe provides an effective therapeutic strategy for the management of homozygous familial hypercholesterolemia (HoFH) and sitosterolemia. The lack of outcomes and long term safety data is attributed to the relatively recent introduction of this medication.

Sitosterolemia

Sitosterolemia was first described 28 years ago in two sisters. They had tendonxanthomas, normal plasma cholesterol levels, and elevated plant sterol levels. The high plant sterol levels were shown to be due to the increased absorption and delayed removal of plant sterols from the body. The increased absorption of plant sterols does not affect cholesterol absorption in these patients. However, cholesterol biosynthesis pathway is downregulated and turnover rates are reduced. Bile acid binding resins and ileal bypass surgery are effective treatments for sitosterolemic patients, whereas statins are ineffective. Sitosterolemia is inherited as a recessive trait. Recent studies have shown that mutations in ABCG5 and ABCG8 genes contribute to sitosterolemia. Most likely, ABCG5 and ABCG8 proteins function as obligate heterodimers and play a role in the absorption of plant sterol or control their rate of absorption.

Sitosterolemia: a gateway to new knowledge about cholesterol metabolism

Sitosterolemia (OMIM 210250) is a rare, autosomal recessive lipid disorder initially described almost 30 years ago. The disease is characterized by elevated plasma levels of plant sterols due to increased intestinal absorption and reduced biliary secretion of neutral sterols. Patients with sitosterolemia are frequently hypercholesterolemic, and develop xanthomas and premature coronary heart disease (CHD). Hemolysis, arthralgias and arthritis are also frequently associated with the disorder. Recently, sitosterolemia has been revealed to be due to mutations in either of the two ATP-binding cassette (ABC) half-transporters. ABCG5 or ABCG8. These two genes are expressed almost exclusively in the liver and intestine, and are co-regulated by the nuclear hormone receptor, liver X receptor (LXR). Genetically modified mice, which express either high levels or no ABCG5 and ABCG8 have been developed. Analyses of these mice confirm that these two transporters play key roles in regulating the absorption of dietary and biliary sterols, and in mediating the excretion of neutral sterols from the liver to the bile. The elucidation of the gene defects responsible for sitosterolemia provides potential therapeutic targets for the treatment of hyperlipidemias in the general population.

Vegetable oils high in phytosterols make erythrocytes less deformable and shorten the life span of stroke-prone spontaneously hypertensive rats

Previous studies have shown that canola oil (CA), compared with soybean oil (SO), shortens the life span of stroke-prone spontaneously hypertensive (SHRSP) rats, a widely used model for hemorrhagic stroke. SHRSP rats are highly sensitive to dietary cholesterol manipulations because a deficiency of membrane cholesterol makes their cell membranes weak and fragile. Phytosterols, abundant in CA but not in SO, can inhibit the absorption of cholesterol and also replace a part of cholesterol in cell membranes. This study was performed to determine whether the high concentration of phytosterols in CA might account for its life-shortening effect on SHRSP rats. Male, 35-d-old SHRSP rats (n = 28/group) were fed semipurified diets containing CA, SO, CA fortified with phytosterols (canola oil + phytosterols, CA + P), SO fortified with phytosterols (soybean oil + phytosterols, SO + P), corn oil (CO), olive oil (OO) or a fat blend that mimicked the fat composition of a representative Canadian diet (Canadian fat mimic, CFM; 10 g/100 g diet). These fats provided 97, 36, 207, 201, 114, 27 and 27 mg phytosterols/100 g diet, respectively. Ten rats from each group were killed after 30-32 d for blood and tissue analyses. The remaining rats (18/group) were used for determination of life span. The life span of SHRSP rats fed the high phytosterol oils (CA, CA + P, SO + P and CO) was significantly (P<0.05) shorter than that of CFM- and SO-fed rats. At 30-32 d, the groups fed the high phytosterol oils had greater levels of phytosterols and significantly (P<0.05) higher ratios of phytosterols/cholesterol in plasma, RBC, liver and kidney, and a significantly (P<0.05) lower RBC membrane deformabilty index than the groups fed oils low in phytosterols (SO, OO and CFM). The mean survival times were correlated with RBC deformability index (r(2) = 0.91, P = 0.0033) and cholesterol concentration (r(2) = 0.94, P = 0.0016), and inversely correlated with RBC phytosterol concentration (r(2) = 0.58, P = 0.0798) and phytosterols/cholesterol (r(2) = 0.65, P = 0.0579), except in the OO group. This study suggests that the high concentration of phytosterols in CA and the addition of phytosterols to other fats make the cell membrane more rigid, which might be a factor contributing to the shortened life span of SHRSP rats.

Effects of dietary phytosterols on cholesterol metabolism and atherosclerosis: clinical and experimental evidence

Although plant sterols (phytosterols) and cholesterol have similar chemical structures, they differ markedly in their synthesis, intestinal absorption, and metabolic fate. Phytosterols inhibit intestinal cholesterol absorption, thereby lowering plasma total and low-density lipoprotein (LDL) cholesterol levels. In 16 recently published human studies that used phytosterols to reduce plasma cholesterol levels in a total of 590 subjects, phytosterol therapy was accompanied by an average 10% reduction in total cholesterol and 13% reduction in LDL cholesterol levels. Phytosterols may also affect other aspects of cholesterol metabolism that contribute to their antiatherogenic properties, and may interfere with steroid hormone synthesis. The clinical and biochemical features of hereditary sitosterolemia, as well as its treatment, are reviewed, and the effects of cholestyramine treatment in 12 sitosterolemic subjects are summarized. Finally, new ideas for future research into the role of phytosterols in health and disease are discussed.

Phytosterolaemia in three unrelated South African families

Phytosterolaemia (beta-sitosterolaemia), a rare, autosomal recessive disorder, has not hitherto been reported in Southern Africa. We report four new homozygous patients, from three unrelated families with significant beta-sitosterolaemia (6.6-11.3%), campesterolaemia (2.2-4.6%) and clearly detectable, though unquantified, levels of cholestanol. Three of the four patients had characteristic cutaneous and tendinous xanthomas within the first decade of life. The fourth patient, a 5 year old, was free of xanthomas despite persistently elevated concentrations of plant sterols in her plasma. All our patients were female bringing the male:female ratio in reported cases to 8:23. All were at or below the 50th percentile for height and weight, and presented at some stage with borderline, hypochromic anaemia associated with red cell abnormalities and thrombocytopaenia. The oldest patient showed suggestive clinical evidence of atherosclerosis affecting her aorta, ileofemoral bifurcation and possibly coronary arteries. All homozygotes responded to a diet restricted in phytosterols and the administration of cholestyramine with falls in plasma sterols of up to 68%. The recent discovery of a possible inherited defect in the synthesis of HMG CoA reductase in patients with phytosterolaemia makes this disorder a model system for studying the biological role of this enzyme in regulating the absorption and clearance of sterols other than cholesterol, and the factors governing the sterol composition of cell membranes.

Phytosterolemia in children with parenteral nutrition-associated cholestatic liver disease

BACKGROUND

Lipid emulsions used for parenteral nutrition (PN) contain phytosterols. Our hypothesis was that these phytosterols can accumulate and contribute to cholestatic liver disease and other complications of PN, e.g., thrombocytopenia (which occurs in hereditary phytosterolemia).

METHODS

Using gas chromatography-mass spectrometry, plasma concentrations of sterols were measured in 29 children aged 2 months to 9 years receiving PN and in 29 age-matched controls. The children receiving PN fell into two subgroups: 5 with severe PN-associated cholestatic liver disease (bilirubin level, > 100 mumol/L; aspartate aminotransferase [AST] level, > 200 U/L) and 24 with a bilirubin level of < 100 mumol/L and/or AST level of < 200 U/L.

RESULTS

The 5 children with severe PN-associated liver disease had plasma concentrations of phytosterols and sitostanol that were as high as those seen in patients with hereditary phytosterolemia (total phytosterols 1.3-1.8 mmol/L). All 5 had intermittent thrombocytopenia. A reduction in intake of lipid emulsion to < 50 mL.kg-1.wk-1 was associated with a decrease in plasma phytosterol concentrations and an improvement in liver function tests and platelet counts in two patients. Children with less severe PN-associated liver disease had lower plasma phytosterol concentrations than the 5 with severe disease.

CONCLUSIONS

Children receiving PN who have high plasma phytosterol concentrations also have cholestatic liver disease and thrombocytopenia; phytosterolemia might contribute to the pathogenesis of complications of PN.

Liver transplantation modifies serum cholestanol, cholesterol precursor and plant sterol levels

Proportions of cholesterol precursors (squalene, delta 8-cholestenol, desmosterol and lathosterol), plant sterols (campesterol and sitosterol) and cholestanol to cholesterol in serum were measured before and serially after liver transplantation in eight patients with primary biliary cirrhosis (PBC) and three with acute liver necrosis. The preoperative proportions of cholestanol were 12 and 3-times higher in the PBC and necrosis groups, respectively, than in a control group of 27 individuals, while those of lathosterol were low in both groups and the campesterol/sitosterol ratio in the PBC group. During the operation the proportions of cholestanol fell sharply and those of lathosterol rose especially in the PBC group. During the postoperative follow-up of 5 weeks the proportions of the non-cholesterol sterols were markedly improved especially in the necrosis group yet those of cholestanol remained high and the campesterol/sitosterol ratios low, particularly in the PBC group. The proportions of lathosterol increased gradually almost to the control limits within the postoperative 5-week period, whereas those of desmosterol decreased. The non-cholesterol sterol values were not related to acute rejections, while significant correlations of cholestanol to liver function tests was found especially at the end of the follow-up.

Increased sitosterol absorption is offset by rapid elimination to prevent accumulation in heterozygotes with sitosterolemia

Using plasma isotope-kinetic methods, we measured the absorption and turnover rates of cholesterol and sitosterol (24-ethylcholesterol) in two obligate heterozygotes (parents) and their homozygous daughter with sitosterolemia with xanthomatosis. Diets contained approximately 500 mg/day cholesterol and 100 mg/day sitosterol. In the homozygote, plasma cholesterol and apolipoprotein B concentrations were slightly higher, but sitosterol levels were 22 and 58 times higher than in her heterozygous parents. Cholesterol absorption was at the high end of the normal range in both heterozygotes (59% and 84%) and in the homozygote (62%) (value in the control subject 48%). In contrast, cholesterol synthesis was severely depressed in the homozygote (28% and 26% as great as in the heterozygotes and the control, respectively). Sitosterol absorption in the homozygote (34%) was 2.3 and 2.0 times greater than in the heterozygotes and 6.8 times greater than in the control. The sitosterol turnover rate, calculated independently by mathematical analysis of specific-activity decay curves, amounted to 15 and 24 mg/day in the heterozygotes compared with 27 mg/day in the homozygote and 7.9 +/- 2.3 mg/day in five control subjects. However, the total body sitosterol pool was 15 and 10.3 times larger in the homozygote (4,080 mg) than in her heterozygous parents because of extremely slow removal. The average sitosterol elimination constant in the heterozygotes (KA = 0.11 day-1) was 10 times that in the homozygote (KA = 0.01 day-1) but 35% less than that in the controls (KA = 0.17 day-1).(ABSTRACT TRUNCATED AT 250 WORDS)

Immunohistochemical analysis of spinal intradural xanthomatosis developed in a patient with phytosterolemia

Multiple intradural xanthomatous tumors developed in 48-year-old female with familial phytosterolemia. These tumors were restricted to the spinal denticulate ligaments. Histological and immunohistochemical findings were fundamentally similar to those of tendinous xanthomas. The major cellular component of these tumors were identified as of mono-histiocytic origin because they possessed myeloid histiocytic antigen (Mac 387), CD11c and lysozyme but not CD15. Sitosterols, campesterols and cholestanols were recovered from the extract of the tumors and the lesions were confirmed to be phytosterolemic xanthomas. Schwann cells stained with anti-S100 protein were confined to the perivascular small nerve bundles and did not show xanthomatous change. Although immunohistochemical preparation of epithelial membrane antigen and desmoplakin I+II revealed the presence of non-neoplastic meningothelial cells in the superficial portion of the tumors, they were too few to play a significant role in the development of these xanthomas.

Sluggish sitosterol turnover and hepatic failure to excrete sitosterol into bile cause expansion of body pool of sitosterol in patients with sitosterolemia and xanthomatosis

Sitosterolemia and xanthomatosis are characterized by the development of tendon and tuberous xanthomas at an early age and premature atherosclerosis despite normal plasma cholesterol concentrations. The reason(s) for the xanthoma formation and premature atherosclerosis are not clearly understood. The accumulation of sitosterol in the tissues of these patients could be due to increased uptake of low density lipoprotein (LDL) via LDL receptors because of an expanded sitosterol pool caused by sluggish turnover and decreased excretion of sitosterol into bile and feces coupled with the hyperabsorption of sitosterol. We have studied sitosterol and cholesterol turnovers, the biliary and fecal excretion of neutral and acidic steroids, and the response of plasma sterol (sitosterol and cholesterol) levels to either a sterol-free formula or low plant sterol diet in three patients. The average half-life of the first exponential (tA1/2) for sitosterol was 9.2 +/- 3.3 (mean +/- SD) days, which was more than twice that in normal humans. The second exponential (tB1/2) was 156 +/- 108 days, which was nearly 10 times longer than that for normal humans. The average cholesterol production rate in pool A was 0.87 g/day, which is about 40% of that in normal humans. Cholesterol synthesis measured by the sterol balance technique was also found to be about 70% lower than that for normal humans. In two patients fed a sterol-free formula diet, by 25 days their plasma sitosterol and cholesterol levels had decreased by 42% and 36%, respectively. However, in one patient plasma sitosterol and cholesterol concentrations remained unchanged while on the low plant sterol-mixed food diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Atherogenic risk factors in cerebrotendinous xanthomatosis

In a study of coronary artery disease in patients with cerebrotendinous xanthomatosis (CTX), we documented the presence or absence of atherogenic risk factors and performed detailed analyses of serum lipid and lipoprotein profiles. Four of the seven patients examined had coronary arterial narrowing and/or obstruction, but multiple atherogenic risk factors were not found in any of these patients. Total cholesterol (T.ch) levels and low density lipoprotein-cholesterol (LDL-ch) levels were lower, and high density lipoprotein2-cholesterol (HDL2-ch) levels were higher in CTX patients than in controls. Triglyceride and very low density lipoprotein (VLDL) levels were significantly lower in the former. Indices correlating with the risk of atherosclerosis, such as the atherogenic index, and the ratios of apolipoprotein B/apolipoprotein AI, HDL2-ch/LDL-ch, HDL2-ch/HDL3-ch, indicated that CTX serum was, in fact, 'anti-atherogenic'. However, coronary artery disease is frequently seen in patients with CTX. This discrepancy suggests the existence of a unique mechanism by which atherosclerosis is induced in patients with CTX. We discuss a mechanism of disturbed lipoprotein metabolism which might be responsible for the deposition of sterols in the tissues of patients with CTX.

Cerebrotendinous xanthomatosis: clinical and biochemical evaluation of eight patients and review of the literature

We present the clinical and laboratory findings of 8 patients with cerebrotendinous xanthomatosis. The clinical features consisted of a combination of bilateral Achilles tendon xanthomas, cataracts, low intelligence, pyramidal signs, cerebellar signs, convulsions, peripheral neuropathy, foot deformity, cardiovascular disease or atherosclerosis, EEG abnormality, and increased CSF protein. Increased cholesterol was present in the serum, CSF and red cell membrane of all 8 patients. The bile of one patient with late age onset of the disease showed an attenuated production of bile acids and bile alcohols. Three of the 7 had obstruction and/or marked narrowing of the coronary arteries. Data on 136 patients reported throughout the world are reviewed.

Spinal cord compression with paraplegia in xanthomatosis due to normocholesterolemic sitosterolemia

A 48-year-old woman with a 30-year history of tendinous xanthomatosis developed paraplegia. The magnetic resonance image revealed extramedullary tumors. The analysis of her sera and tumors revealed increased amount of plant sterols, especially sitosterol, and the diagnosis of sitosterolemia was made. This is the first reported case of a patient with sitosterolemia who had the neurological complication of spinal cord compression due to extramedullary sitosterolemic xanthomas.

Serum cholestanol and plant sterol levels in relation to cholesterol metabolism in middle-aged men

Serum cholestanol was studied in relation to fecal cholestanol excretion and cholesterol metabolism in a random middle-aged population of 61 men. The serum concentrations of cholestanol ranged from 1.6 to 10.8 mumol/L and were positively correlated with those of serum total LDL and HDL cholesterol. In terms of millimole per mole of cholesterol, these correlations disappeared; inverse associations were found with VLDL cholesterol and triglyceride levels, the P/S ratio of dietary fat, and the amount of fecal plant sterols, but not with fecal cholestanol. The serum contents of cholestanol (1) were also closely positively associated with those of serum plant sterols (campesterol and sitosterol) and fractional cholesterol absorption, (2) were inversely related to the fecal excretion of neutral sterols and cholesterol synthesis which were measured either by the sterol balance technique or serum cholesterol precursor sterols (desmosterol and lathosterol), and (3) were unrelated to bile acid synthesis. Fecal cholestanol (mean = 12.5 mg/d) was (1) clearly higher than the dietary cholestanol intake (less than 2 mg/d), (2) unrelated to serum cholestanol, and (3) positively correlated with the intestinal cholesterol (dietary plus endogenous) flux as well as fecal plant sterols, neutral sterols, and bacterial products of cholesterol. The study emphasizes that, in normal men, high serum cholestanol levels reflect high efficiency of intestinal sterol absorption and low cholesterol synthesis. Thus, the changes in the serum contents of cholestanol are parallel with those of plant sterols and opposite to those of cholesterol precursor sterols.

Usefulness of gas chromatographic profiles of plasma total lipids in diagnosis of phytosterolemia

A Cambodian male (aged 5 years and 9 months) presented with subcutaneous and tendon xanthomas in association with hypercholesterolemia. He was erroneously diagnosed as having familial hypercholesterolemia and treated with a low cholesterol diet (+/- cholestyramine) to which he did not respond. A determination of plasma total lipid profile by high-temperature gas chromatography revealed elevated plasma levels of free and esterified plant sterols along with the hypercholesterolemia. Introduction and maintenance of a diet low in cholesterol and plant sterols resulted in significant reduction in the blood concentration of these sterols, which returned to pretreatment level upon discontinuation of the low sterol regimen. The rapid identification and quantitation of the plant sterols by high-temperature gas chromatography provides a sensitive means of distinguishing phytosterolemia, which might be more common than previously suspected, from other forms of dyslipidemia, and for following the course of any treatment.

The presence of 5 alpha-sitostanol in the serum of a patient with phytosterolemia, and its biosynthesis from plant steroids in rats with bile fistula

The presence of 5 alpha-sitostanol (24-ethyl-5 alpha-cholestan-3 beta-ol) in serum of a patient with the rare genetic disease phytosterolemia was confirmed. This study aimed at clarifying the pathway(s) for the formation of 5 alpha-sitostanol, by use of rats with bile fistula. 5 alpha-Sitostanol was formed only slowly from sitosterol, but readily from 24-ethyl-4-cholesten-3-one. Some conversion was also obtained with 7 alpha-hydroxysitosterol as precursor. In view of the low rate of 7 alpha-hydroxylation of sitosterol, however, a pathway from sitosterol to 5 alpha-sitostanol involving 7 alpha-hydroxysitosterol as intermediate is probably of small physiological importance. Intestinal microorganisms are not essential for the above conversions, since the 5 alpha-sitostanol was found in bile from bile fistula rats. 5 alpha-Sitostanol was converted to water soluble metabolites (bile acids) much more slowly than was cholestanol (5 alpha-cholestan-3 beta-ol), and was accumulated serum to a much larger extent.

Cerebrotendinous xanthomatosis is treatable

Cerebrotendinous xanthomatosis is a recessively inherited disorder of bile acid metabolism. Cataracts and tendinous xanthomas begin during adolescence. Results of routine tests of plasma lipids are normal. Therapy with chenodeoxycholic acid may reduce the production of cholestanol and thus slow the course of the disease.

Sitosterol and cholesterol metabolism in a patient with coexisting phytosterolemia and cholestanolemia

Sitosterol and cholesterol metabolism were studied in a patient with coexisting phytosterolemia and cholestanolemia, and in a control subject, both on similar diets containing about 170 mg cholesterol and 135 mg phytosterols per day. The turnover of 22,23-3H-sitosterol and 4-14C-cholesterol, given intravenously, were followed for up to 372 days. The specific activity-time curves for both sterols were resolved into two exponentials and fitted into a two-pool model. The half-lives of both exponential curves for sitosterol, in the patient, were abnormally long. Equilibration of the tracer between the two pools, in the patient, occurred at about 30 days as compared to 10-15 days in the control subject. The daily turnover of sitosterol in the patient was estimated to be 10 times greater than that in the control subject. The patient's total body exchangeable pool of sitosterol was 9.6 g or about 80 times the amount found in the control. The patient's plasma phytosterol levels fell by 25% when he went on a diet containing only 10 mg phytosterols per day. During this period the specific activity of his plasma sitosterol with respect to an equilibrated dose of 3H-labeled tracer remained constant; this was compatible with the absence of endogenous synthesis. Cholesterol turnover in the patient showed prolonged half-lives for both exponential curves and reduced fractional daily loss from the fast-exchanging pool. The patient's xanthoma sterols underwent 16% and 55% exchange with plasma sitosterol and cholesterol, respectively, on day 60, indicating the presence of a third exchangeable pool.