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.

[Genetic diseases of lipid metabolism - Focus familial hypercholesterolemia]. / Genetische Erkrankungen des Lipidstoffwechsels.

Congenital disorders of lipid metabolism are characterised by LDL-C concentrations > 190 mg/dl (4.9 mM) and/or triglycerides > 200 mg/dl (2.3 mM) in young individuals after having excluded a secondary hyperlipoproteinemia. Further characteristics of this primary hyperlipoproteinemia are elevated lipid values or premature myocardial infarctions within families or xantelasms, arcus lipoides, xanthomas and abdominal pain. This overview summarises our current knowledge of etiology and pathogenesis of primary hyperlipoproteinemia.

Computed tomography criteria for discrimination of adrenal adenomas and adrenocortical carcinomas: analysis of the German ACC registry.

OBJECTIVE: Thresholds of 2-20 hounsfield units (HU) in unenhanced computed tomography (CT) are suggested to discriminate benign adrenal tumors (BATs) from malignant adrenal tumors. However, these studies included only low numbers of adrenocortical carcinomas (ACCs). This study defines a HU threshold by inclusion of a large cohort of ACCs. DESIGN: Retrospective, blinded, comparative analysis of CT scans from 51 patients with ACCs (30 females, median age 49 years) and 25 patients with BATs (12 females, median age 64 years) diagnosed during the period of 2005-2010 was performed. METHODS: Tumor density was evaluated in unenhanced CT by two blinded investigators. RESULTS: Median tumor size was 9 cm (range 2.0-20) for ACCs vs 4 cm (2.0-7.5) for BATs (P<0.0001). In ACCs, the median unenhanced HU value was 34 (range 14-74) in comparison with 5 (-13 to 40) in BATs (P<0.0001). ROC analysis revealed a HU of 21 as threshold with the best diagnostic accuracy (sensitivity 96%, specificity 80%, and AUC 0.89). However, two ACCs that were 5 and 6 cm in size would have been missed. Setting the threshold to 13.9 allowed for 100% sensitivity, but a lower specificity of 68%. CONCLUSIONS: This first large study on ACCs confirmed that the vast majority of ACCs have unenhanced HU >21. However, to avoid misdiagnosing an ACC as benign, a threshold of 13 should be used.

New AHA and ACC guidelines on the treatment of blood cholesterol to reduce atherosclerotic cardiovascular risk.

After the publication of the new guidelines of the European Society of Cardiology and the European Atherosclerosis Society for the prevention and treatment of dyslipidemias (Eur Heart J 32:1769-1818, 2011; Eur Heart J 33:1635-1701, 2012), a group of authors has recently published on behalf of the American Heart Association and the American College of Cardiology guidelines on the treatment of blood cholesterol to reduce atherosclerotic cardiovascular risk (Circulation 2013). These new guidelines are supposed to replace the until now widely accepted, at least in the USA, recommendations of the National Cholesterol Education Program Adult Treatment Panel III from the years 2002 (Circulation 106:3143-3421, 2002) and 2004 (Circulation 110:227-39, 2004). Furthermore, they claim to be based mainly on hard evidence derived from the interpretation of results of prospective randomized controlled trials. This Joint Position Statement of the Society for the Prevention of Cardiovascular Diseases e.V. (D.A.CH), the Austrian Atherosclerosis Society and the Working Group on Lipids and Atherosclerosis (AGLA) of the Swiss Society of Cardiology concludes that the use of individualized prevention strategies based on specific indications and LDL cholesterol target concentrations, a strategy whose worth has been widely proven and accepted for more than a decade in Europe, should not be given up.

Resequencing the untranslated regions of the lipoprotein lipase (LPL) gene reveals that variants in microRNA target sequences are associated with triglyceride levels.

BACKGROUND: Rare variants in the protein coding regions of the lipoprotein lipase (LPL) gene have been shown to be important in the development of hypertriglyceridemia. OBJECTIVES: The aim of this study was to determine whether rare variants in the 3' and 5' untranslated regions (UTRs) of the LPL gene are also associated with severe hypertriglyceridemia. METHODS: The DNA sequences of the 3' and 5' UTRs of the LPL gene of 63 patients with triglycerides > 875 mg/dL (10 mmol) and 69 probands with triglycerides below the 25th percentile for age and sex were determined. The sequence at the 5' end was extended to include 2 further elements (-702 to -666 and -468 to -430) shown to be associated with the control of LPL expression. RESULTS: No statistically significant difference was found in the occurrence of rare mutations in either the 3' or the 5' UTRs between the 2 groups. Sequence analysis allowed the genotyping of 47 single nucleotide polymorphisms (SNPs) in the 3' UTR and 11 in the 5' UTR. Two groups of SNPs in the 3' UTR, based on allelic association, were statistically significantly associated with plasma triglycerides. Each of these groups contained SNPs in the target sequences for microRNAs. These findings were replicated in independently formed groups. CONCLUSION: We provide genetic evidence that microRNAs may play a role in the expression of LPL and thus plasma triglyceride levels.

Resequencing the APOE gene reveals that rare mutations are not significant contributory factors in the development of type III hyperlipidemia.

BACKGROUND: APOE (apolipoprotein E gene) 2/2 genotype and an apolipoprotein B/total cholesterol (ApoB/TC) ratio <0.15 are diagnostic for type III hyperlipidemia. We hypothesized that patients with APOE genotype 2/3 or 2/4 and an ApoB/TC ratio <0.15 may have a mutation in their epsilon 3 or 4 allele, resulting in a type III hyperlipidemia phenotype. OBJECTIVE: We tested this hypothesis. METHODS: The DNA sequence of all 4 exons and exon/intron boundaries of the APOE (plus 600 bp upstream of exon 1) of 47 patients with APOE 2/3 and 18 patients with APOE 2/4 genotype and an ApoB/TC ratio <0.15 was determined. As controls the APOE sequence of 53 APOE genotype 2/3 and 20 APOE genotype 2/4 probands with ApoB/TC ratio >0.15 was determined. The sequence analysis was extended to include 47 patients with APOE genotype 3/3, 14 with APOE genotype 3/4, and 3 with APOE genotype 4/4 and an ApoB/TC ratio <0.15. Finally, we determined the sequence of the APOE gene in 145 patients with an ApoB/TC ratio >0.15 and who had triglycerides above the 90th percentile for age and sex. RESULTS: No deleterious variants in the APOE gene were observed in patients with APOE genotype other than 2/2 and an ApoB/TC ratio <0.15. Only a single probably deleterious variant, K72E, was observed in patients with triglycerides above the 90th percentile. CONCLUSIONS: Patients with an ApoB/TC ratio <0.15 do not have an increased likelihood of mutation in the APOE gene, and rare variants in the APOE gene are not important in the development of hypertriglyceridemia.

The relative importance of common and rare genetic variants in the development of hypertriglyceridemia.

Plasma lipid levels are a complex trait with a genetic and an environmental component. There are two models for the genetic basis of complex traits: the common-disease common-variant hypothesis, in which susceptibility is due to variants occurring at relatively high frequency but low effect size; and the common-disease rare-variant hypothesis, where disease is due to multiple rare variants each occurring at low frequency but with high effect size. Genome-wide association studies have identified a number of common variants associated with plasma lipid levels. However, they account for only a proportion of the genetic variance. Resequencing studies are revealing the importance of rare variants in accounting for the missing variance. Next-generation sequencing will allow the relative importance of the two hypotheses to be assessed.

Comparison of whole body MR angiography at 1.5 and 3 Tesla in patients with hereditary hyperlipidemia.

BACKGROUND: Patients suffering from hereditary hyperlipidemia have a high risk for premature cardiovascular disease and death as a consequence of accelerated atherosclerosis. PURPOSE: To prospectively and intra-individually compare image quality and detectability of stenoses in contrast enhanced whole-body MRA (WBMRA) at 1.5 and 3 Tesla (T) in patients with hereditary hyperlipidemia. MATERIAL AND METHODS: Twenty-seven patients with hereditary hyperlipidemia received a 1.5 and 3 T gadopentetate dimeglumine contrast-enhanced WBMRA. Twenty-three defined arterial segments were analyzed regarding depiction of target vessels and image quality according to a 5-point-scale ('not evaluable' to 'excellent'). Wilcoxon matched pair test was performed for comparison. Forty-three defined arterial segments were analyzed for the degree of stenosis (0%, 1-49%, 50-99% and 100%) as well as vessel alterations such as aneurysms. Chi-square test was performed for comparison. RESULTS: 1.5 T and 3 T scans yielded WBMRA with diagnostic quality in all patients. In seven of 23 arterial segments (30.4%) image quality was rated significantly higher at 3 T, whereas there was no significant difference in the remaining 16 segments between WBMRA at 1.5 T and 3 T. All relevant stenoses (n = 5), occlusions (n = 6), and aneurysms (n = 3) were evaluated similarly at both field strengths. CONCLUSION: WBMRA can be performed at 1.5 T and 3 T with diagnostic image quality. Image quality was significantly higher at 3 T than at 1.5 T in only 30.4% of the arterial segments. In order to effectively take advantage of the higher field strength, further optimization of sequence parameters and injection protocols for WBMRA at 3 T is necessary.

Possibilities and limitations in imaging the intracranial arteries in the context of a contrast-enhanced whole-body magnetic resonance angiographic screening protocol at 1.5 versus 3 Tesla.

OBJECTIVE: Evaluation of the diagnostic detectability of the intracranial vasculature on contrast-enhanced whole-body magnetic resonance angiographic (WBMRA) scans at 1.5 versus 3 T. METHODS: Twenty-seven patients with hereditary hyperlipidemia participated. Two experienced neuroradiologists scored the image quality regarding the intracranial arteries applying a 5-point scale. Stenoses and other findings were documented. Weighted κ-statistics were calculated to assess interobserver agreement. RESULTS: Interobserver agreement was very good. Image quality scoring resulted in the following mean values: 3.0 at 1.5 T versus 3.9 at 3 T (P < 0.001). Venous contrast overlay and insufficient anatomic coverage occurred in both groups. Three stenoses were found at both field strengths. CONCLUSIONS: Assessment of the intracranial vasculature on WBMRA data is basically feasible; image quality at 3 T seems superior. Shortcomings appear because of venous contamination and insufficient volume coverage. Therefore, adding a dedicated intracranial MRA to a WBMRA protocol would substantially increase diagnostic certainty.

Genetic variation may influence obesity only under conditions of diet: analysis of three candidate genes.

Under the hypothesis of obesity as a polygenetic disease numerous genes have been associated with an obese phenotype and metabolic co-morbidities. The cannabinoid receptor 1 (CB 1) is part of an underinvestigated system that participates in appetite control. Previous publications suggest that the endocannabinoid systems interact with the better understood leptin-melanocortin axis. Neuropeptide Y (NPY) is a player in the latter. Finally resistin has been shown to influence NPY expression in the brain. In a cohort of 1721 caucasion men and women with a BMI of 25kg/m(2) or more we therefore investigated three candidate polymorphisms at baseline and following 3 months low fat caloric restriction diet by polymerase chain reaction and restriction digestion: the 1359 G/A variant of the cannabinoid receptor 1 (CB1), the L7P variation in neuropeptide Y (NPY) and the -420C>G polymorphism in resistin. Comparing groups according to genotype for each gene separately revealed significant results at baseline only for the CB1 gene. However, upon dieting significant data was found for all 3 genes. Carriers of at least one A allele in CB1 lost more weight and reduced LDL cholesterol more than wildtype patients. LL homocygotes in NPY had a greater reduction in glucose, triglycerides, and LDL cholesterol whereas in resistin carriers of the G allele had a greater reduction in weight and triglycerides. Creating two groups defined by NPY and resistin genotype, respectively, with similar BMI values resulted in significant differences concerning weight loss and metabolic improvement. In conclusion, genetic polymorphisms associated with obesity may become relevant only under the condition of a low calory diet. The presence of a certain genotype may then be beneficial for obesity treatment.

Association of the T+294C polymorphism in PPAR delta with low HDL cholesterol and coronary heart disease risk in women.

BACKGROUND: The +T294C polymorphism in PPARdelta represents a functional SNP affecting transcriptional activity of the PPARdelta gene. To address whether this polymorphism is associated with the risk for coronary heart disease and/or plasma lipid levels in women, we studied a group of 967 female patients with hyperlipidaemia in the presence (n=453) or absence (n=514) of coronary heart disease. METHODS: 967 female patients with or without coronary heart disease were genotyped using mutagenically separated polymerase chain reaction (MS-PCR). Statistical analysis was performed according to genotype with parameters of lipid metabolism as dependant variables. RESULTS: A highly significant association between the rare C allele and lower plasma HDL concentrations was found in female subjects. The effect remained significant after correcting for multiparametric testing according to Bonferoni and was seen only in subjects with a BMI below the median. Moreover, a significant association of the C-allele with coronary heart disease and BMI was obtained. Regarding the entire group, trends towards higher VLDL and LDL levels were observed. CONCLUSIONS: Our data show for the first time that the PPARdelta +T294C polymorphism is associated with lipid levels and coronary heart disease in women. However, the molecular mechanism of action remains to be elucidated.

Regulation of the human leukemia inhibitory factor gene by ETS transcription factors.

OBJECTIVES: Leukemia inhibitory factor (LIF) is a pleiotropic cytokine mainly produced by activated T lymphocytes. We previously demonstrated that human Jurkat T lymphoma cells represent a valid model of LIF gene expression. This study was designed to identify regions critical for LIF promoter activation in Jurkat cells. METHODS: Luciferase constructs under the control of different portions of the human LIF promoter were transfected into Jurkat cells, and promoter activity was determined by luminometry. Similar experiments were performed with constructs bearing mutations in the putative ETS binding regions in the LIF promoter. RT-PCR, Western blot and gelshift experiments were performed to study expression and DNA binding of ETS factors in lymphoid cells. RESULTS: With the exception of the shortest construct not including the putative ETS binding sites, all wildtype LIF promoter constructs were strongly inducible by phorbol ester/ionomycin. In contrast, the mutant constructs were significantly less inducible. Cotransfection of the wild-type constructs with ETS expression vectors resulted in significant enhancement of promoter activity. ets-1 and ets-2 mRNA and protein were shown to be expressed in Jurkat cells. Gelshift experiments revealed that proteins present in nuclear extracts from Jurkat cells specifically bind to both artificial ETS consensus sites and ETS binding sites present in the LIF promoter. CONCLUSIONS: We conclude that binding of ETS transcription factors to the ETS binding sites in the human LIF promoter is critical for its inducibility in response to T cell activators. ETS transcription factors thus play an important functional role within the endocrine-immune network.

Mutations in the human ATP-binding cassette transporters ABCG5 and ABCG8 in sitosterolemia.

Phytosterolemia or Sitosterolemia is a rare autosomal recessive disorder characterized by highly elevated plasma levels of plant sterols and cholesterol as a consequence of hyperabsorption and impaired biliary secretion of sterols. The disease is caused by mutations in two half size ATP-binding cassette transporters, ABCG5 and ABCG8. We have analyzed the genomic sequence of ABCG5 and ABCG8 in five well-characterized patients with Sitosterolemia. In the first patient we found a heterozygous mutation in exon 8 of the ABCG5 gene leading to a premature termination of the protein (Arg408Ter). This German patient is the first European showing a mutation of the ABCG5 gene. In a second patient we found a novel heterozygous mutation in exon 5 of ABCG8 (c.584T>A; Leu195Gln). Both patients were heterozygous for the identified mutation, but no mutation could be identified on the other chromosome. In three further analyzed patients we found mutations in exons 7, 9 and 11 of the ABCG8 gene, respectively, of which two result in a premature termination signal for translation products. One of these patients was compound heterozygous (Trp361Ter and Arg412Ter), the other was homozygous for Trp361Ter. The third patient was homozygous for an amino acid exchange (Gly574Arg). In conclusion this report describes one novel mutation affecting a highly conserved amino acid and two previously identified mutations in the ABCG8 gene. In addition, we identified for the first time a mutation in the ABCG5 gene of a European Sitosterolemia patient.