First international descriptive and interventional survey for cholesterol and non-cholesterol sterol determination by gas- and liquid-chromatography-Urgent need for harmonisation of analytical methods.

Serum concentrations of lathosterol, the plant sterols campesterol and sitosterol and the cholesterol metabolite 5α-cholestanol are widely used as surrogate markers of cholesterol synthesis and absorption, respectively. Increasing numbers of laboratories utilize a broad spectrum of well-established and recently developed methods for the determination of cholesterol and non-cholesterol sterols (NCS). In order to evaluate the quality of these measurements and to identify possible sources of analytical errors our group initiated the first international survey for cholesterol and NCS. The cholesterol and NCS survey was structured as a two-part survey which took place in the years 2013 and 2014. The first survey part was designed as descriptive, providing information about the variation of reported results from different laboratories. A set of two lyophilized pooled sera (A and B) was sent to twenty laboratories specialized in chromatographic lipid analysis. The different sterols were quantified either by gas chromatography-flame ionization detection, gas chromatography- or liquid chromatography-mass selective detection. The participants were requested to determine cholesterol and NCS concentrations in the provided samples as part of their normal laboratory routine. The second part was designed as interventional survey. Twenty-two laboratories agreed to participate and received again two different lyophilized pooled sera (C and D). In contrast to the first international survey, each participant received standard stock solutions with defined concentrations of cholesterol and NCS. The participants were requested to use diluted calibration solutions from the provided standard stock solutions for quantification of cholesterol and NCS. In both surveys, each laboratory used its own internal standard (5α-cholestane, epicoprostanol or deuterium labelled sterols). Main outcome of the survey was, that unacceptably high interlaboratory variations for cholesterol and NCS concentrations are reported, even when the individual laboratories used the same calibration material. We discuss different sources of errors and recommend all laboratories analysing cholesterol and NCS to participate in regular quality control programs.

The Simultaneous measurement of serum testosterone and 5α-dihydrotestosterone by gas chromatography-mass spectrometry (GC-MS).

BACKGROUND: Simultaneous measurement of testosterone (T) and 5α-dihydrotestosterone (DHT) is important for diagnosing androgen deficiency states and hyperandrogenism in males and females, respectively. However, immunoassays used for T and DHT determination suffer from inadequate specificity and sensitivity, while tandem mass spectrometry is expensive and demanding in use. METHODS AND RESULTS: We developed a selective gas chromatography-mass spectrometry (GC-MS) method for parallel T and DHT measurement. The assay showed a linear response up to 46.5nmol/L, intra- and interassay imprecision and inaccuracy <15% and recoveries in spiked samples >90% for both analytes. The limit of quantitation was 0.117nmol/L for T and 0.168nmol/L for DHT. Comparison with immunoassays revealed good agreement for T in males, but a bias in favour of immunoassays at low concentrations for T in females and DHT in both sexes. We established reference ranges for T and DHT and suggest interval partitioning for T according to age in men and menstrual cycle in women. Assay validation in a clinical setting suggests that measuring DHT or T/DHT ratio may help identify patients with polycystic ovary syndrome. CONCLUSION: We developed a selective, simple and inexpensive GC-MS method for parallel measurement of T and DHT with potential use in the clinical laboratory.

Determination of serum cholestane-3ß,5α,6ß-triol by gas chromatography-mass spectrometry for identification of Niemann-Pick type C (NPC) disease.

Niemann-Pick type C (NPC) is a neurological disease caused by an intracellular cholesterol accumulation. Cholesterol oxidation product cholestane-3ß,5α,6ß-triol (C-triol) serves as diagnostic biomarker for NPC, but its measurement in the routine laboratory remains difficult. We developed an isotope dilution gas chromatography-mass spectrometry (GC-MS) method permitting screening for NPC in plasma. 1440 plasma samples obtained from clinically suspicious patients were subjected to alkaline saponification. C-triol was extracted with carbon tetrachloride, transformed into the trimethylsilylethers, separated on a fused silica capillary column with a nonpolar silicone stationary phase, and analyzed by GC-MS. NPC diagnosis was confirmed by DNA sequencing. The method was linear over a concentration range of 0.03-200ng/mL with a mean recovery rate of 98.6%. The intra- and inter-day variation coefficients assessed at two concentrations were below 15%. Limits of quantification (LOQ) and detection (LOD) were 0.03ng/mL and 0.01ng/mL, respectively. Receiver operating characteristic (ROC) analysis estimated that the area under curve was 0.997 implying a significant discriminatory power to identify subjects with NPC. Nevertheless, 13 NPC patients and 29 control subjects confirmed by sequencing showed false negative or positive results, respectively. Two patients with cerebrotendinous xanthomatosis showed a 5-10-fold increase in C-triol levels. We developed a quick and sensitive GC-MS method for determination of C-triol, which may serve as a simple and inexpensive diagnostic tool aiding NPC diagnosis in a routine hospital laboratory. As C-triol elevation is not limited to NPC, the NPC diagnosis has to be confirmed by DNA sequencing.

Rapid Diagnosis of 83 Patients with Niemann Pick Type C Disease and Related Cholesterol Transport Disorders by Cholestantriol Screening.

Niemann Pick type C (NP-C) is a rare neurodegenerative disorder caused by an impairment of intracellular lipid transport. Due to the heterogeneous clinical phenotype and the lack of a reliable blood test, diagnosis and therapy are often delayed for years. In the cell, accumulating cholesterol leads to increased formation of oxysterols that can be used as a powerful screening parameter for NP-C. In a large scale study, we evaluated the oxysterol cholestane-3ß,5α,6ß-triol (c-triol) as potential biomarker for a rapid diagnosis of NP-C. Using GC/MS, c-triol has been analyzed in 1902 plasma samples of patients with the suspicion for NP-C. Diagnosis in patients with elevated oxysterols was confirmed by genetic analysis. 71 new NP-C patients (69 NP-C1 and two NP-C2) and 12 Niemann Pick type A/B patients were identified. 24 new mutations in NPC1, one new mutation in NPC2 and three new mutations in the SMPD1 gene were found. Cholestane-3ß,5α,6ß-triol was elevated in Niemann Pick type C1, type C2, type A/B and in CESD disease. No other study has ever identified so many NP-C patients, proving that c-triol is a rapid and reliable biomarker to detect patients with NP-C disease and related cholesterol transport disorders. It should replace the filipin test as the first-line diagnostic assay.

Head-To-Head Assessment of Diagnostic Performance of Testosterone Immunoassays in Patients With Polycystic Ovary Syndrome.

BACKGROUND: Determination of plasma testosterone is critical for the proper diagnosis of polycystic ovary syndrome (PCOS), but the interpretation of biochemical tests is hampered by inadequate specificity and precision of available immunoassays. We here compared the diagnostic performance of three testosterone immunoassays (Advia Centaur, Immulite 2000 XPi, Cobas e411) in PCOS patients using receiver operator characteristics curve analysis. METHODS AND RESULTS: Plasma levels of testosterone, androstendione, dehydroepiandrosterone sulfate, 17-hydroxyprogesterone, estradiol, progesterone, steroid hormone binding globulin, luteinizing hormone, and follicular stimulating hormone were determined in 188 patients with PCOS and 202 controls. Free testosterone (fT) levels and free androgen index (FAI) were calculated. Testosterone levels measured on Advia Centaur, Immulite 2000 XPi, and Cobas e411 showed clear linear relationship to each other. Testosterone measured with Advia Centaur showed discriminatory performance superior to Immulite 2000 XPi and Cobas e411. Calculation of fT or FAI improved the performance of Advia Centaur and Immulite 2000 XPi, which nevertheless performed better than Cobas e411. The performance of other parameters was inferior to that of testosterone, fT, and FAI. CONCLUSION: Present study documents striking differences between testosterone immunoassays with respect to their capacity to identify PCOS patients and favors the use of calculated parameters reflecting active testosterone in plasma.

3ß,5α,6ß-Cholestanetriol and 25-hydroxycholesterol accumulate in ATP-binding cassette transporter G1 (ABCG1)-deficiency.

OBJECTIVE: Oxysterols are oxidized derivatives of sterols that have cytotoxic effects and are potent regulators of diverse cellular functions. Efficient oxysterol removal by the sub-family G member 1 of the ATP-binding cassette transporters (ABCG1) is essential for cell survival and control of cellular processes. However, the specific role of ABCG1 in the transport of various oxysterol species has been not systematically investigated to date. Here, we examined the involvement of ABCG1 in the oxysterol metabolism by studying oxysterol tissue levels in a mouse model of Abcg1-deficiency. METHODS AND RESULTS: Analysis of lung tissue of Abcg1(-/-) mice on a standard diet revealed that 3ß,5α,6ß-cholestanetriol (CT) and 25-hydroxycholesterol (HC) accumulated at more than 100-fold higher levels in comparison to wild-type mice. 24S-HC and 27-HC levels were also elevated, but were minor constituents. A radiolabeled assay employing regulable ABCG1-expressing HeLa cell lines revealed that 25-HC export to albumin was dependent on functional ABCG1 expression and could be blocked by an excess of unlabeled 25-HC or 27-HC. In this cell line, 25-HC at low doses triggered mitochondrial membrane potential, and reactive oxygen species production, which are both indirect indicators of cellular energy expenditure. CONCLUSION: Our results suggest that 25-HC and CT are physiologic substrates for ABCG1. Excessive accumulation of these oxysterols may explain the increased rate of cell death and the inflammatory phenotype observed in Abcg1-deficient animals and cells.

Characterization of cholesterol homeostasis in telomerase-immortalized Tangier disease fibroblasts reveals marked phenotype variability.

We compared the consequences of an ABCA1 mutation that produced an apparent lack of atherosclerosis (Tangier family 1, N935S) with an ABCA1 mutation with functional ABCA1 knockout that was associated with severe atherosclerosis (Tangier family 2, Leu(548):Leu(575)-End), using primary and telomerase-immortalized fibroblasts. Telomerase-immortalized Tangier fibroblasts of family 1 (TT1) showed 30% residual cholesterol efflux capacity in response to apolipoprotein A-I, whereas telomerase-immortalized Tangier fibroblasts of family 2 (TT2) showed only 20%. However, there were a number of secondary differences that were often stronger and may help to explain the more rapid development of atherosclerosis in family 2. First, the total cellular cholesterol content increase was 2-3-fold and 3-5-fold in TT1 and TT2 cells, respectively. The corresponding increase in esterified cholesterol concentration was 10- and 40-fold, respectively. Second, 24-, 25-, and 27-hydroxycholesterol concentrations were moderately increased in TT1 cells, but were increased as much as 200-fold in TT2 cells. Third, cholesterol biosynthesis was moderately decreased in TT1 cells, but was markedly decreased in TT2 cells. Fourth, potentially atheroprotective LXR-dependent SREBP1c signaling was normal in TT1, but was rather suppressed in TT2 cells. Cultivated primary Tangier fibroblasts were characterized by premature aging in culture and were associated with less obvious biochemical differences. In summary, these results may help to understand the differential atherosclerotic susceptibility in Tangier disease and further demonstrate the usefulness of telomerase-immortalized cells in studying this cellular phenotype. The data support the contention that side chain-oxidized oxysterols are strong suppressors of cholesterol biosynthesis under specific pathological conditions in humans.

Everolimus therapy is associated with reduced lipoprotein-associated phospholipase A2 (Lp-Pla2) activity and oxidative stress in heart transplant recipients.

BACKGROUND: Several studies demonstrated decreased severity and incidence of cardiac allograft vasculopathy (CAV) in heart transplant recipients receiving immunosuppressive therapy with everolimus. However, data regarding the influence of everolimus on risk factors predisposing to CAV are hitherto limited. We here systematically evaluated cardiovascular risk factors in heart transplanted patients, who underwent conversion to everolimus or were maintained on conventional therapy with calcineurin inhibitors (CNI). METHODS: 50 Patients receiving everolimus and 91 patients receiving CNI in addition to mycophenolate mofetil and low-dosed steroids were included in the study. CAV risk factors were determined in plasma or urine using standard enzymatic or immunochemical methods. RESULTS: No significant differences were observed between both groups with regard to lipid (total, LDL- and HDL-cholesterol), metabolic (glucose, insulin), inflammatory (C-reactive protein, IL-6, myeloperoxidase) and cardiac (troponin I, NT-proBNP) risk factors. However, significantly lower activity of lipoprotein-associated phospholipase A2 (Lp-PLA2) and a negative correlation between the Lp-PLA2 activity and the everolimus concentration were observed in plasmas from everolimus-treated patients. Conversion to everolimus significantly lowered Lp-PLA2 activity in heart transplant recipients. Studies in vitro revealed reduced Lp-PLA2 expression in hepatocytes and macrophages pre-exposed to everolimus. In addition, reduced plasma markers of oxidative stress including oxidized LDL, 8-iso-prostaglandin F2α and protein carbonyls were noted in heart transplant recipients receiving everolimus therapy. CONCLUSION: Our results suggest that everolimus specifically lowers plasma activity and cellular production of Lp-PLA2 and thereby dampens oxidative stress. These effects may additionally contribute to the reduced CAV incidence observed in heart transplant recipients receiving everolimus therapy.

Effects of high-fat and low-fat diets rich in monounsaturated fatty acids on serum lipids, LDL size and indices of lipid peroxidation in healthy non-obese men and women when consumed under controlled conditions.

OBJECTIVE: To study the effects of the dietary fat content on cardiovascular disease risk factors in humans when the fatty acid composition and types of carbohydrates are kept constant. METHODS: A controlled dietary study in healthy volunteers with 2 dietary groups and a parallel design consisting of 2 dietary periods was conducted. First, participants received a 2-week wash-in diet rich in saturated fatty acids (SFA; 47% of total fatty acids) and were then randomly assigned to either a high-fat (40% of energy) or a low-fat diet (29% of energy) for 4 weeks. Both diets were isocaloric, rich in monounsaturated fatty acids (MUFA; 51% of total fatty acids) and had similar fatty acid and carbohydrate compositions. RESULTS: Compared to the wash-in diet, the high-fat and low-fat diets significantly lowered LDL-cholesterol (-0.34 and -0.41 mmol/l, respectively; P < 0.001 for time effect in RM-ANOVA), and HDL-cholesterol (-0.13 and -0.18 mmol/l, respectively; P < 0.001 for time), without any differences between the high-fat and low-fat diets (P = 0.112 and P = 0.085 for time × group interaction in RM-ANOVA, respectively). The size of the major LDL fraction, the LDL susceptibility to oxidation and the plasma concentrations of oxidized LDL (ox-LDL) were significantly reduced by both the high-fat and low-fat diet, again without significant differences between the diets. The ratio of ox-LDL/LDL-cholesterol, serum triacylglycerols and urinary F2-isoprostanes were not significantly affected by the diets. CONCLUSION: A high-fat and a low-fat diet, both rich in MUFA, had similar effects on lipid-related cardiovascular disease risk factors in metabolically healthy men and women.

Dietary intake and plasma concentrations of PUFA and LC-PUFA in breastfed and formula fed infants under real-life conditions.

BACKGROUND: The breastfed infant is usually used as standard for formula feeding, also regarding long-chain polyunsaturated fatty acids (LC-PUFA). Here, plasma fatty acid concentrations in formula fed infants and the effects of LC-PUFA supplementation were investigated under real-life conditions. METHOD: Term healthy infants being fully milk fed until the age of 4 months were categorized as breast milk "BM" (n = 73) if consuming >95% of energy from breast milk or formula (F) if consuming >95% of energy from formula subdivided into formula without (F-) (n = 15) and with LC-PUFA supplementation (F+) (n = 15). Formula as marketed was chosen by the parents. Dietary fatty acids (FA) intake was calculated from continuous dietary records from 2 months of age onwards. Total plasma FA were analyzed at the age of 4 months with docosahexaenoic acid (DHA) as primary outcome. RESULTS: Dietary ratios of the polyunsaturated fatty acids (PUFA; linoleic acid/alpha-linolenic acid) were smaller in both F groups than in the BM group. Plasma DHA as % of total FA was similar in BM and F(+) but higher in BM in absolute amounts (mg/L). Plasma DHA as % of total FA in F(-) was higher than what might be supposed on the basis of dietary intake. CONCLUSION: Infants consuming present-day LC-PUFA-supplemented formula achieved plasma LC-PUFA concentrations similar to breastfed infants. In infants consuming non-LC-PUFA-supplemented formula, the favorable PUFA pattern of the formula may have supported n-3 LC-PUFA biosynthesis.

Dietary alpha-linolenic acid, EPA, and DHA have differential effects on LDL fatty acid composition but similar effects on serum lipid profiles in normolipidemic humans.

Our aim was to study the effects of increased dietary intake of alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), or docosahexaenoic acid (DHA) on serum lipids and LDL fatty acid compositions. To this end, a controlled parallel study was conducted in 74 healthy normolipidemic men and women aged 19-43 y. Participants were randomly assigned to 1 of 3 interventions and consumed a total intake of 4.4 g/d ALA (ALA group), 2.2 g/d EPA (EPA group), and 2.3 g/d DHA (DHA group) for 6 wk. Fatty acid ethyl esters were incorporated into margarines, which replaced the participant's normal spread. The ALA, EPA, or DHA intake led to a significant enrichment of the LDL with the respective (n-3) fatty acid. In addition, LDL EPA contents in the ALA group increased by 36% (P < 0.05) with no changes in LDL DHA. The EPA intervention led to an additional enrichment with DHA (24%; P < 0.001), whereas the DHA intervention further increased the amount of EPA (249%; P < 0.001). ALA, EPA, or DHA intake did not affect fasting serum concentrations of total and LDL cholesterol, but fasting serum triacylglycerol concentrations significantly decreased in the EPA (-0.14 mmol/L) and DHA (-0.30 mmol/L) interventions and also in the ALA intervention (-0.17 mmol/L). DHA intake significantly increased serum HDL cholesterol, whereas no changes were found with ALA or EPA intake. In conclusion, the present data support the hypothesis that isolated dietary ALA, EPA, and DHA intakes lead to differential enrichment in LDL due to interconversion. Moderate amounts of ALA, EPA, and DHA are effective in improving lipid profiles of normolipidemic humans.

Effects of ezetimibe, simvastatin, atorvastatin, and ezetimibe-statin therapies on non-cholesterol sterols in patients with primary hypercholesterolemia.

BACKGROUND: Levels of cholesterol are regulated by its synthesis, absorption, and elimination. Plasma levels of phytosterols (e.g., sitosterol, campesterol) and ratios of these sterols to total cholesterol (TC) are reported to correlate with efficiency of intestinal cholesterol absorption, whereas levels of certain cholesterol precursor sterols (e.g., desmosterol, lathosterol) and their ratios to TC correlate with cholesterol biosynthesis. However, there is a paucity of published data concerning the effects of combined treatment using HMG-CoA reductase inhibitors (statins) and a cholesterol absorption inhibitor (ezetimibe) on these parameters. OBJECTIVES: To characterize the effects of ezetimibe co-administered with statins, compared with each treatment alone, on cholesterol precursor sterols and plasma phytosterol levels. METHODS: A post-hoc analysis was performed to determine the effects of treatment with ezetimibe 10 mg, simvastatin (10-80 mg), and atorvastatin (10-80 mg), alone or in combination, on these non-cholesterol sterols using plasma samples from two randomized controlled trials involving patients with primary hypercholesterolemia (low-density lipo protein [LDL-C] = 145-250 mg/dL; triglycerides < or = 350 mg/dL; N = 975) but without a recent (< or = 6-month) history of coronary heart disease (CHD) or either uncontrolled or newly diagnosed diabetes mellitus. RESULTS: Ezetimibe monotherapy significantly reduced plasma sitosterol and campesterol concentrations from baseline compared with placebo (both p < 0.001), whereas statins significantly lowered desmo sterol and lathosterol levels (p < 0.001 vs. placebo). Co-administration of ezetimibe and statins significantly decreased plasma levels of all of these sterols (p < 0.001). CONCLUSIONS: The observed effects of co-administration of ezetimibe and statins on non-cholesterol sterols are consistent with net inhibition of sterol absorption (driven by ezetimibe) in conjunction with net inhibition of cholesterol synthesis (driven by statins). The potential influence of treatment-induced changes in phytosterols on cardiovascular risk warrants further investigation in long-term, prospective, randomized controlled trials. This post-hoc study was by nature exploratory, and, because data from such analyses are not customarily adjusted for multiple comparisons, some associations may have emerged as statistically significant by chance. Future prospective randomized controlled studies may help to confirm our findings and address other research issues, such as the generalizability of our findings to patients with CHD or diabetes mellitus and possible dose:response relationships between escalating statin (or ezetimibe-statin) doses and circulating non-cholesterol levels.

Expression of ATP binding cassette-transporter ABCG1 prevents cell death by transporting cytotoxic 7beta-hydroxycholesterol.

Oxysterols result from cholesterol by enzymatic or oxidative processes. Some exert cytotoxic effects leading to necrosis or apoptosis. Detoxification of these compounds mainly occurs in the liver and requires transport from peripheral tissues towards it. Some ATP-binding cassette transporters are involved in export of cytotoxic compounds. In the current study, we investigated whether ABC transporter family member G1 (ABCG1) may be involved in oxysterol transport, since its gene expression is highly responsive to oxysterol loading. TetOff HeLa cells stably expressing ABCG1 showed decreased mass uptake of 7beta-hydroxycholesterol (7beta-HC) whereas that of other physiologically relevant oxysterols was unaffected. Application of 7beta-HC to ABCG1 expressing cells induced hyperpolarization of mitochondrial membrane potential and production of reactive oxygen species, indicating energy consumption by the ATP-binding cassette transporter when it is activated by its correct substrate. Our study points to detoxification as one of potential cellular functions of ABCG1. We assume that ABCG1 protects against 7beta-HC-induced cell death, an important role in prevention of neurodegenerative and cardiovascular disease.

Relationship between phytosterol levels and components of the metabolic syndrome in the PROCAM study.

BACKGROUND: Components of the metabolic syndrome such as hypertriglyceridemia, low high-density lipoprotein (HDL) cholesterol and obesity have been shown to be associated with increased cholesterol synthesis and reduced cholesterol absorption. In the present study, we measured the lathosterol/cholesterol ratio as an index of cholesterol synthesis and the ratios of cholestanol, campesterol and sitosterol to cholesterol as indices of cholesterol absorption, as well as components of the metabolic syndrome, in 324 men and 168 women from the PROCAM study, an epidemiological study in which raised sitosterol was previously associated with increased coronary risk. Our aim was to determine if the indices of cholesterol synthesis and absorption show a graded relationship with severity of metabolic syndrome. RESULTS: No differences were seen between men and women with regard to the relationship of either the lathosterol/cholesterol or the sitosterol/cholesterol ratios and severity of metabolic syndrome. On multiple regression analysis in men and women together, body mass index showed a positive relationship with the lathosterol/cholesterol ratio (r=0.257, P<0.001) and a negative relationship with the sitosterol/cholesterol ratio (r=-0.221, P<0.001). HDL-cholesterol showed a negative relationship with the lathosterol/cholesterol ratio (r=-0.166, P=0.001). Triglycerides showed a negative relationship with the sitosterol/cholesterol ratio (r=0.141, P=0.005). Overall, these relationships were graded across quintiles of HDL cholesterol, body mass index and triglyceride and across an index of metabolic syndrome severity (number of components present). Only the cholestanol/cholesterol ratio showed a graded relationship with estimated overall coronary risk. CONCLUSIONS: The metabolic syndrome is associated with increased cholesterol synthesis and reduced cholesterol absorption in a relationship that is graded across severity of the individual components of the syndrome and across an index of the severity of the metabolic syndrome as a whole.

Expression and functional characterization of ABCG1 splice variant ABCG1(666).

The ATP-binding cassette transporter ABCG1 mediates the transport of excess cholesterol from macrophages and other cell types to high density lipoprotein (HDL) but not to lipid-depleted apolipoprotein AI. Several splice variants which may have different functions have been identified in mammals. In the current study, we characterized the human splice variant ABCG1(666), which differs from full-length ABCG1(678) by absence of an internal segment of 12 amino acids (VKQTKRLKGLRK). Accordingly spliced ABCG1 transcripts were detected in macrophages and liver in approximately twofold higher amounts than the alternatively spliced ABCG1 form encoding full-length ABCG1. We used transient and stable expression of ABCG1(666) fusion proteins to characterize glycosylation, subcellular localization, molecular interaction and functions of this ABCG1 variant. It could be demonstrated that ABCG1(666) is located at the cell surface and has the ability to form cholesterol transport competent homodimers which affect cellular cholesterol export in a similar manner as previously characterized forms of ABCG1. Our results support that ABCG1(666) may in fact be the most prominent form of functional ABCG1 expressed in the human.

Plasma sitosterol elevations are associated with an increased incidence of coronary events in men: results of a nested case-control analysis of the Prospective Cardiovascular Münster (PROCAM) study.

BACKGROUND AND AIM: Sitosterolemia, a rare genetic disorder characterized by profoundly elevated plasma sitosterol concentrations, is associated with premature atherosclerosis in some individuals. This study was conducted to evaluate if the modest sitosterol elevations seen in the general population are also associated with the occurrence of coronary events. METHODS AND RESULTS: A nested case-control study using stored samples from male participants in the Prospective Cardiovascular Münster (PROCAM) study was performed. Each of 159 men who suffered a myocardial infarction or sudden coronary death (major coronary event) within 10 years of follow-up in PROCAM was matched with 2 controls (N = 318) by age, smoking status, and date of investigation. Analysis was performed using conditional logistic regression. Plasma sitosterol concentrations were elevated in cases compared with controls (4.94 +/- 3.44 micromol/L versus 4.27 +/- 2.38 micromol/L; P = 0.028). The upper quartile of sitosterol (>5.25 micromol/L) was associated with a 1.8-fold increase in risk (P < 0.05) compared with the lower three quartiles. Among men with an absolute coronary risk > or = 20% in 10 years as calculated using the PROCAM algorithm, high sitosterol concentrations were associated with an additional 3-fold increase in the incidence of coronary events (P = 0.032); a similar, significant relationship was observed between a high sitosterol/cholesterol ratio and coronary risk (P = 0.030). CONCLUSIONS: Elevations in sitosterol concentrations and the sitosterol/cholesterol ratio appear to be associated with an increased occurrence of major coronary events in men at high global risk of coronary heart disease. Further evaluations are warranted to confirm these preliminary findings.

Gas chromatography-mass spectrometry and molecular genetic studies in families with the Conradi-Hünermann-Happle syndrome.

The Conradi-Hünermann-Happle syndrome is an X-linked dominant disease that is due to mutations in the gene for emopamil binding protein. Emopamil binding protein is a Delta8-Delta7 sterol isomerase and plays a pivotal role in the final steps of cholesterol biosynthesis. We wanted to know to what extent this X-linked dominant enzyme defect has functional consequences at the biochemical level and whether it is possible to predict the clinical phenotype from serum sterol measurements. Therefore we performed sterol biochemical studies in 11 Conradi-Hünermann-Happle syndrome families and compared the results obtained to the clinical and molecular genetic findings. To assess disease severity a score considering bone and skin involvement and further features was used. For evaluation of the functional consequences we studied serum samples using gas chromatography-mass spectrometry analysis. For mutation screening we analyzed the emopamil binding protein gene using polymerase chain reaction, heteroduplex analysis of all exons, direct sequencing, and restriction enzyme analysis. Mutations in the emopamil binding protein gene were found in all 11 families including seven novel mutations affecting exons 2, 4, and 5. Gas chromatography-mass spectrometry analysis revealed markedly elevated levels of 8-dehydrocholesterol and of cholest-8(9)-en-3beta-ol and helped to identify somatic mosaicism in a clinically unaffected man. The extent of the metabolic alterations in the serum, however, do not allow prediction of the clinical phenotype, nor the genotype. This lack of correlation may be due to differences in X-inactivation between different tissues of the same patient and/or loss of the mutant clone by outgrowth of proficient clones after some time.