Protein-Truncating Variants at the Cholesteryl Ester Transfer Protein Gene and Risk for Coronary Heart Disease.

RATIONALE: Therapies that inhibit CETP (cholesteryl ester transfer protein) have failed to demonstrate a reduction in risk for coronary heart disease (CHD). Human DNA sequence variants that truncate the CETP gene may provide insight into the efficacy of CETP inhibition. OBJECTIVE: To test whether protein-truncating variants (PTVs) at the CETP gene were associated with plasma lipid levels and CHD. METHODS AND RESULTS: We sequenced the exons of the CETP gene in 58 469 participants from 12 case-control studies (18 817 CHD cases, 39 652 CHD-free controls). We defined PTV as those that lead to a premature stop, disrupt canonical splice sites, or lead to insertions/deletions that shift frame. We also genotyped 1 Japanese-specific PTV in 27561 participants from 3 case-control studies (14 286 CHD cases, 13 275 CHD-free controls). We tested association of CETP PTV carrier status with both plasma lipids and CHD. Among 58 469 participants with CETP gene-sequencing data available, average age was 51.5 years and 43% were women; 1 in 975 participants carried a PTV at the CETP gene. Compared with noncarriers, carriers of PTV at CETP had higher high-density lipoprotein cholesterol (effect size, 22.6 mg/dL; 95% confidence interval, 18-27; P<1.0×10-4), lower low-density lipoprotein cholesterol (-12.2 mg/dL; 95% confidence interval, -23 to -0.98; P=0.033), and lower triglycerides (-6.3%; 95% confidence interval, -12 to -0.22; P=0.043). CETP PTV carrier status was associated with reduced risk for CHD (summary odds ratio, 0.70; 95% confidence interval, 0.54-0.90; P=5.1×10-3). CONCLUSIONS: Compared with noncarriers, carriers of PTV at CETP displayed higher high-density lipoprotein cholesterol, lower low-density lipoprotein cholesterol, lower triglycerides, and lower risk for CHD.

Impact of clinical signs and genetic diagnosis of familial hypercholesterolaemia on the prevalence of coronary artery disease in patients with severe hypercholesterolaemia.

AIMS: The impact of positive clinical signs (xanthoma and/or family history) and positive familial hypercholesterolaemia (FH) mutation status on risk of coronary artery disease (CAD) over and above that predicted by low-density lipoprotein (LDL) cholesterol level alone has not been fully determined. We assessed whether positive clinical signs and genetic FH diagnosis affected CAD risk among subjects with significantly elevated LDL cholesterol levels (≥180 mg/dL, or ≥140 mg/dL in subjects <15 years of age). METHODS AND RESULTS: Three genes causative for FH (LDLR, APOB, and PCSK9) were sequenced in 636 patients with severe hypercholesterolaemia (mean age, 45 years; 300 males [47%], CAD diagnosis, 185 [29%]), and the presence of clinical FH signs (xanthoma and/or family history) were assessed. CAD prevalence was compared between four subject groups categorized based on these parameters. Compared with the reference group without FH mutations or clinical signs of FH, subjects with clinical signs of FH or FH mutations had three- to four-fold higher odds of developing CAD (odds ratio [OR], 4.6; 95% confidence interval [CI], 1.5-14.5; P = 0.0011 and OR, 3.4; 95% CI, 1.0-10.9; P = 0.0047, respectively), whereas those with clinical signs of FH and FH mutation(s) had >11-fold higher odds of developing CAD (OR, 11.6; 95% CI, 4.4-30.2; P = 1.1 × 10-5) after adjusting for known risk factors including LDL cholesterol. CONCLUSION: Our findings revealed an additive effect of positive clinical signs of FH and positive FH mutation status to CAD risk among patients with significantly elevated LDL cholesterol.

Lipoprotein(a) in Familial Hypercholesterolemia With Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9) Gain-of-Function Mutations.

BACKGROUND: It has been shown that serum lipoprotein(a) [Lp(a)] is elevated in familial hypercholesterolemia (FH) with mutation(s) of the LDL receptor (LDLR) gene. However, few data exist regarding Lp(a) levels in FH with gain-of-function mutations of the PCSK9 gene. METHODS AND RESULTS: We evaluated 42 mutation-determined heterozygous FH patients with aPCSK9gain-of-function mutation (FH-PCSK9, mean age 52, mean LDL-C 235 mg/dl), 198 mutation-determined heterozygous FH patients with aLDLRmutation (FH-LDLR, mean age 44, mean LDL-C 217 mg/dl), and 4,015 controls (CONTROL, mean age 56, mean LDL-C 109 mg/dl). We assessed their Lp(a), total cholesterol, triglycerides, HDL-C, LDL-C, use of statins, presence of hypertension, diabetes, chronic kidney disease, smoking, body mass index (BMI) and coronary artery disease (CAD). Multiple regression analysis showed that HDL-C, use of statins, presence of hypertension, smoking, BMI, and Lp(a) were independently associated with the presence of CAD. Under these conditions, the serum levels of Lp(a) in patients with FH were significantly higher than those of the CONTROL group regardless of their causative genes, among the groups propensity score-matched (median Lp(a) 12.6 mg/dl [IQR:9.4-33.9], 21.1 mg/dl [IQR:11.7-34.9], and 5.0 mg/dl [IQR:2.7-8.1] in the FH-LDLR, FH-PCSK9, and CONTROL groups, respectively, P=0.002 for FH-LDLR vs. CONTROL, P=0.002 for FH-PCSK9 vs. CONTROL). CONCLUSIONS: These data demonstrate that serum Lp(a) is elevated in patients with FH caused by PCSK9 gain-of-function mutations to the same level as that in FH caused by LDLR mutations.

Changes in lipoprotein lipase and endothelial lipase mass in familial hypercholesterolemia during three-drug lipid-lowering combination therapy.

BACKGROUND: This study was performed to compare the effects of three different lipid-lowering therapies (statins, ezetimibe, and colestimide) on lipoprotein lipase and endothelial lipase masses in pre-heparin plasma (pre-heparin LPL and EL mass, respectively) from patients with familial hypercholesterolemia (FH). FH is usually treated by coadministration of these three drugs. METHODS: The pre-heparin LPL and EL masses were measured in fresh frozen plasma drawn and stored at various time points during coadministration of the three drugs from patients with heterozygous FH harboring a single mutation in the LDL receptor (n = 16, mean age 63 years). The patients were randomly divided into two groups based on the timing when ezetimibe was added. RESULTS: Plasma LPL mass concentration was significantly reduced by rosuvastatin at 20 mg/day (median = 87.4 [IQR: 71.4-124.7] to 67.5 [IQR: 62.1-114.3] ng/ml, P < 0.05). In contrast, ezetimibe at 10 mg/day as well as colestimide at 3.62 g/day did not alter its level substantially (median = 67.5 [IQR: 62.1-114.3] to 70.2 [IQR: 58.3-106.2], and to 74.9 [IQR: 55.6-101.3] ng/ml, respectively) in the group starting with rosuvastatin followed by the addition of ezetimibe and colestimide. On the other hand, the magnitude in LPL mass reduction was lower in the group starting with ezetimibe at 10 mg/day before reaching the maximum dose of 20 mg/day of rosuvastatin. Plasma EL mass concentration was significantly increased by rosuvastatin at 20 mg/day (median = 278.8 [IQR: 186.7-288.7] to 297.0 [IQR: 266.2-300.2] ng/ml, P < 0.05), whereas other drugs did not significantly alter its level. CONCLUSION: The effects on changes of LPL and EL mass differed depending on the lipid-lowering therapy, which may impact the prevention of atherosclerosis differently.

Putative Pathogenic Variants of ABCG5 and ABCG8 of Sitosterolemia in Patients With Hyper-Low-Density Lipoprotein Cholesterolemia.

Objective: Sitosterolemia is a rare autosomal recessive disease caused by the deleterious variants of adenosine 5'-triphosphate (ATP)-binding cassette sub-family G member 5 (ABCG5) or ATP-binding cassette sub-family G member 8 (ABCG8). There are only few data on the pathogenicity of ABCG5 and ABCG8. This study aimed to propose a scheme for determining variant pathogenicity and to catalog the putative pathogenic variants in sitosterolemia. Methods: This study enrolled 377 consecutive Japanese patients with hyper-low-density lipoprotein cholesterolemia (mean age: 46.5±19.8 years, with 192 men) who have targeted-sequenced data on ABCG5 or ABCG8 (among 21 Mendelian lipid genes for any dyslipidemias) and serum sitosterol levels at Kanazawa University Hospital from 2016 to 2021. Serum sitosterol levels were divided by 0.79 in patients treated with ezetimibe, accounting for the average reduction with this drug. ABCG5 or ABCG8 variants were defined as putative pathogenic if associated with serum sitosterol levels ≥5 µg/mL or homozygous if associated with serum sitosterol levels ≥10 µg/mL. Results: Twenty-three ABCG5 or ABCG8 variants (16 missense, 2 nonsense, 2 frameshift, 2 deletion, and 1 splice mutation) were identified. Based on our definition, 11 putative pathogenic variants (median sitosterol level: 10.1 [6.5-17.1] µg/mL) were found in 36 individuals and 12 benign variants (median sitosterol: 3.5 [2.5-4.1] µg/mL) in 14 individuals. Conclusion: The scheme proposed for assessing the pathogenicity of genetic variations (ABCG5 and ABCG8) is useful. Using this scheme, 11 putative pathogenic, and 12 benign variants in ABCG5 or ABCG were classified.

Post-prandial remnant lipoprotein metabolism in autosomal recessive hypercholesterolaemia.

BACKGROUND: Phenotype of autosomal recessive hypercholesterolaemia (ARH), a rare lipid disorder, is known to be milder than that of homozygous familial hypercholesterolaemia (FH) with LDL receptor gene mutation. However, few data exist regarding the functional differences in ARH and FH particularly in terms of remnant-like particles' (RLP) metabolism. MATERIALS AND METHODS: Blood sampling was performed up to 6h after OFTT cream loading (50 g/body surface area) with 2-h intervals in a single ARH proband, four heterozygous FH patients with LDL receptor gene mutation and four normal controls. Plasma lipoprotein and RLP fraction were determined by HPLC system. The area under curve (AUC) of each lipoprotein including RLP fractions was evaluated. RESULTS: The AUC of TG, RLP cholesterol (RLP-C) and RLP triglyceride (RLP-TG) levels of heterozygous FH subjects was significantly higher than those of controls (466±71 mg/dL×h vs. 303±111 mg/dL×h, P<0·05; 35±7 mg/dL×h vs. 21±8 mg/dL×h, P<0·05; 124±57 mg/dL×h vs. 51±13 mg/dL×h, P<0·05, respectively). Under these conditions, those values of ARH were close to those of controls (310 mg/dL×h, 22 mg/dL×h, 23 mg/dL×h, respectively). CONCLUSION: These data demonstrate that unlike in FH, RLP clearance is preserved in ARH. The preservation of post-prandial RLP clearance may contribute to the mild phenotype of ARH compared with FH.

A teenager boy with a novel variant of Sitosterolemia presented with pancytopenia.

BACKGROUND: Sitosterolemia, also known as phytosterolemia, results from increased intestinal absorption of plant sterols and decreased intestinal and biliary excretion of sterols, resulting in increased levels of plant sterols in the plasma. The most common symptoms include xanthomas, premature atherosclerosis, hemolytic anemia and macrothrombocytopenia, however delayed diagnosis or misdiagnosis also occur. PATIENT AND METHODS: Clinical exome sequencing was performed on a 10-year-old boy whom we followed up with signs of pancytopenia accompanied by macrothrombocytopenia and stomatocytosis. In addition, the blood sterol levels of the patient and his family were studied. RESULTS: A novel homozygous c.904 + 5G > C intronic variant was detected in ABCG5 gene in index case. The mother and father were identified as carriers. The blood plant sterol levels of the patient and his family were studied, and the levels in the patient confirmed Sitosterolemia. Sitosterol levels decreased dramatically with restricted diet and ezetimibe treatment. CONCLUSION: In children, signs of Sitosterolemia may be subtle and the only symptom may be hematological. Therefore, Sitosterolemia should be kept in mind in children with stomatocytosis and macrothrombocytopenia.

[Novel therapy for atherosclerosis and inflammatory vascular disease].

How to manage residual atherosclerosis risk after the statin therapy is a major concern in cardiovascular medicine. In addition to life-style modifications, new drugs against atherosclerotic and inflammatory vascular diseases are expected. In current clinical trials, phospholipase A2 inhibitors(darapladib, varespladib), RVX-208, D-4F, CETP inhibitors (anacetrapib, dalcetrapib), succinobucol are investigated. Some has been failed, but others are still promising. On molecular target basis of PAF-AH, CETP, PON, ABC transporters of A1 and G1, SR-BI, HO-1, potential benefits and side effects are discussed.

Serum sitosterol level predicting ABCG5 or ABCG8 genetic mutations.

BACKGROUND: Currently, serum concentrations of sitosterol above 10 µg/ml are considered to be one of the major diagnostic criteria of sitosterolemia. METHODS: We retrospectively investigated consecutive 206 Japanese dyslipidemic subjects (mean age = 46 yr, male n = 94) with the assessments of serum sitosterol level and the presence of ABCG5 or ABCG8 genetic mutations in our institute since 2009-2018. We divided the subjects into 3 groups based on the number of pathogenic mutations in ABCG5 or ABCG8 genes. We compared serum lipids and serum sitosterol among those groups, and tried to validate the cutoff value discriminating patients of sitosterolemia with double mutations from others. RESULTS: We identified 8 individuals with sitosterolemia with double mutations (affected), 26 individuals with a single mutation (carrier), and 172 individuals without any mutations (wildtype control). Serum sitosterol level of patients with sitosterolemia with double mutations (affected) exhibited significantly higher than those of any other groups (45.2. vs. 7.9 µg/ml, p = 2.5 × 10-2, 45.2 vs. 3.1 µg/ml, p = 1.8 × 10-2). Under these conditions, a cutoff value of sitosterol 10 µg/ml could discriminate the patients with sitosterolemia with double mutations in ABCG5 or ABCG8 gene from no mutation carrier (wildtype control) perfectly, although 6 heterozygous mutation carries exhibited sitosterol level greater than 10 µg/ml. Receiver-operating characteristic (ROC) analysis predicting double mutation status showed that the best cut-off value was 14.81 µg/ml. CONCLUSION: We suggest a cutoff value of sitosterol 15 µg/ml that shows higher positive predictive value than 10 µg/ml.

Prevalence, self-awareness, and LDL cholesterol levels among patients highly suspected as familial hypercholesterolemia in a Japanese community.

BACKGROUNDS: The prevalence of familial hypercholesterolemia (FH) among Japanese populations is still unclear. In addition, no prior data exist regarding the self-awareness. Accordingly, we aimed to investigate the prevalence, self-awareness, and LDL-C of patients with highly suspected as FH using data obtained in a community-based medical checkups. METHODS: This study included 52,276 subjects (18,588 men, 35.6%) aged ≥40 years who underwent the Japanese specific health checkup in Kanazawa City during 2018. We assessed the self-awareness of dyslipidemia (and the age) as well as the prevalence of patients with highly suspected as FH whose naïve LDL-C levels were ≥250 â€‹mg/dl. Naïve LDL-C levels were estimated by the adjustment (LDL-C/0.7) for those on lipid-lowering medication. We divided subjects into 3 groups based on their naïve LDL cholesterol level (≥250 â€‹mg/dl, 140-249, and ≤139 â€‹mg/dl). RESULTS: We identified 262 (0.5%) individuals highly suspected as FH whose naïve LDL-C levels were ≥250 â€‹mg/dl. Most of them (234 among 262, 89%) were under lipid-lowering medication; however, the self-awareness as dyslipidemia was not quite high (200 among 262, 76%), and their mean LDL-C level under lipid-lowering medication was 203 â€‹± â€‹35 â€‹mg/dl. Interestingly, the age of acknowledgement of dyslipidemia among the patients with highly suspected as FH was significantly younger than those in other categories (58 vs. 60/62 â€‹yrs, respectively, p â€‹< â€‹0.05 for both). CONCLUSIONS: The prevalence of patients highly suspected as FH was around 1 in 200, and their self-awareness as well as control were not still good enough among Japanese general populations.

Hokuriku-plus familial hypercholesterolaemia registry study: rationale and study design.

INTRODUCTION: Familial hypercholesterolaemia (FH) is an autosomal-dominant inherited genetic disease. It carries an extremely high cardiovascular risk associated with significantly elevated low-density lipoprotein (LDL) cholesterol. The diagnostic rate of this disease in some European nations is quite high, due to the presence of multiple prospective registries. On the other hand, few data-and in particular multicentre data-exist regarding this issue among Japanese subjects. Therefore, this study intends to assemble a multicentre registry that aims to comprehensively assess cardiovascular risk among Japanese FH patients while taking into account their genetic backgrounds. METHODS AND ANALYSIS: The Hokuriku-plus FH registry is a prospective, observational, multicentre cohort study, enrolling consecutive FH patients who fulfil the clinical criteria of FH in Japan from 37 participating hospitals mostly in Hokuriku region of Japan from April 2020 to March 2024. A total of 1000 patients will be enrolled into the study, and we plan to follow-up participants over 5 years. We will collect clinical parameters, including lipids, physical findings, genetic backgrounds and clinical events covering atherosclerotic and other important events, such as malignancies. The primary endpoint of this study is new atherosclerotic cardiovascular disease (ASCVD) events. The secondary endpoints are as follows: LDL cholesterol, secondary ASCVD events and the occurrence of other diseases including hypertension, diabetes and malignancies. ETHICS AND DISSEMINATION: This study is being conducted in compliance with the Declaration of Helsinki, the Ethical Guidelines for Medical and Health Research Involving Human Subjects, and all other applicable laws and guidelines in Japan. This study protocol has been approved by the Institutional Review Board at Kanazawa University. We will disseminate the final results at international conferences and in a peer-reviewed journal. TRIAL REGISTRATION NUMBER: UMIN000038210.

Formation of prebeta1-HDL during lipolysis of triglyceride-rich lipoprotein.

Prebeta1-HDL, a putative discoid-shaped high-density lipoprotein (HDL) is known to participate in the retrieval of cholesterol from peripheral tissues. In this study, to clarify potential sources of this lipoprotein, we conducted heparin injection on four Japanese volunteer men and found that serum triglyceride (TG) level decreased in parallel with the increase in serum nonesterified fatty acids and plasma lipoprotein lipase (LPL) protein mass after heparin injection. Plasma prebeta1-HDL showed considerable increases at 15 min after the heparin injection in all of the subjects. In contrast, serum HDL-C levels did not change. Gel filtration with fast protein liquid chromatography system (FPLC) study on lipoprotein profile revealed that in post-heparin plasma, low-density lipoprotein and alphaHDL fractions did not change, whereas there was a considerable decrease in very low-density lipoprotein (VLDL) fraction and an increase in prebeta1-HDL fraction when compared with those in pre-heparin plasma. We also conducted in vitro analysis on whether prebeta1-HDL was produced during VLDL lipolysis by LPL. One hundred microliters of VLDL extracted from pooled serum by ultracentrifugation was incubated with purified bovine milk LPL at 37 degrees C for 0-120 min. Prebeta1-HDL concentration increased in a dose dependent manner with increased concentration of added LPL in the reaction mixture and with increased incubation time, indicating that prebeta1-HDL was produced during lipolysis of VLDL by LPL. Taken these in vivo and in vitro analysis together, we suggest that lipolysis of VLDL particle by LPL is an important source for formation of prebeta1-HDL.

Remnant lipoproteins and atherosclerotic cardiovascular disease.

Lipoproteins are one of the major risk factors for atherosclerotic cardiovascular disease (ASCVD), among which, low-density lipoprotein (LDL) particles have been definitively shown to be causally associated with the development of ASCVD. Additionally, the concept of remnant lipoproteins has emerged as lipoprotein metabolism has been fully investigated. The principal concept of this lipoprotein category is triglyceride-rich lipoproteins significantly increase at the postprandial state. Although there is no clear definition of remnant lipoproteins, they typically include chylomicron remnants, which are lipolyzed particles from chylomicron, as well as very low-density lipoprotein (VLDL) and intermediate-density lipoprotein (IDL) remnants that are lipolyzed particles from VLDL and IDL particles. However, the most important factor of these lipoproteins is such remnant lipoproteins seem to be causally associated with ASCVD, independent of LDL particles or LDL cholesterol. It has been challenging to assert a causal association of remnant lipoproteins and ASCVD; however, accumulated evidence from epidemiological studies, as well as recent Mendelian randomization studies from common and rare genetic variations strongly support this association. In this article, a basic explanation of lipoprotein metabolism is presented, including remnant lipoproteins and the important causal associations with ASCVD from a clinical point of view.

Clinical whole exome sequencing in severe hypertriglyceridemia.

BACKGROUND: Little data exist regarding the clinical application of whole exome sequencing (WES) for the molecular diagnosis of severe hypertriglyceridemia (HTG). METHODS: WES was performed for 28 probands exhibiting severe HTG (≥1000 mg/dl) without any transient causes. We evaluated recessive and dominant inheritance models in known monogenic HTG genes, followed by disease-network gene prioritization and copy number variation (CNV) analyses to identify causative variants and a novel genetic mechanism for severe HTG. RESULTS: We identified possible causative variants for severe HTG, including three novel variants, in nine probands (32%). In the recessive inheritance model, we identified two homozygous subjects with lipoprotein lipase (LPL) deficiency and one subject harboring compound heterozygous variants in both LPL and APOA5 genes (hyperchylomicronemia). In the dominant inheritance model, we identified probands harboring deleterious heterozygous variants in LPL, glucokinase regulatory protein, and solute carrier family 25 member 40 genes, possibly associated with this extreme HTG phenotype. However, gene prioritization and CNV analyses did not validate the novel genes associated with severe HTG. CONCLUSIONS: In 28 probands with severe HTG, we identified potential causative variants within nine genes associated with rare Mendelian dyslipidemias. Clinical WES may be feasible for such extreme cases, potentially leading to appropriate therapies.

High frequency of a retinoid X receptor gamma gene variant in familial combined hyperlipidemia that associates with atherogenic dyslipidemia.

OBJECTIVE: The genetic background of familial combined hyperlipidemia (FCHL) has not been fully clarified. Because several nuclear receptors play pivotal roles in lipid metabolism, we tested the hypothesis that genetic variants of nuclear receptors contribute to FCHL. METHODS AND RESULTS: We screened all the coding regions of the PPARalpha, PPARgamma2, PPARdelta, FXR, LXRalpha, and RXRgamma genes in 180 hyperlipidemic patients including 60 FCHL probands. Clinical characteristics of the identified variants were evaluated in other 175 patients suspected of coronary disease. We identified PPARalpha Asp140Asn and Gly395Glu, PPARgamma2 Pro12Ala, RXRgamma Gly14Ser, and FXR -1g->t variants. Only RXRgamma Ser14 was more frequent in FCHL (15%, P<0.05) than in other primary hyperlipidemia (4%) and in controls (5%). Among patients suspected of coronary disease, we identified 9 RXRgamma Ser14 carriers, who showed increased triglycerides (1.62+/-0.82 versus 1.91+/-0.42 [mean+/-SD] mmol/L, P<0.05), decreased HDL-cholesterol (1.32+/-0.41 versus 1.04+/-0.26, P<0.05), and decreased post-heparin plasma lipoprotein lipase protein levels (222+/-85 versus 149+/-38 ng/mL, P<0.01). In vitro, RXRgamma Ser14 showed significantly stronger repression of the lipoprotein lipase promoter than RXRgamma Gly14. CONCLUSION: These findings suggest that RXRgamma contributes to the genetic background of FCHL.

Sitosterolemia, Hypercholesterolemia, and Coronary Artery Disease.

Sitosterolemia is a rare inherited disease characterized by increased levels of plant sterols, such as sitosterol. The cause of this disease is ATP-binding cassette (ABC) subfamily G member 5 or member 8 (ABCG5 or ABCG8, respectively) gene mutations. Recent advances in genetics have revealed that the prevalence of subjects with deleterious mutations in ABCG5 and/or ABCG8 genes could be more than 1 in ~200,000 individuals among the general population. Furthermore, accumulated evidence, including infantile cases exhibiting progression/regression of systemic xanthomas associated with LDL cholesterol levels, have shown that the elevation of LDL cholesterol seems to be the major cause of development of atherosclerosis and not the elevation of sitosterol. Regarding therapies, LDL apheresis, as well as proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors, could be useful for sitosterolemia, in addition to ezetimibe and/or colestimide. In this study, we provide the current understanding and future perspectives of sitosterolemia, which is currently considered an extremely rare disorder but is expected to be much more prevalent in clinical settings.

Assessment of arterial stiffness in patients with familial hypercholesterolemia.

BACKGROUND: Recently, the concept of severe familial hypercholesterolemia (FH) has been proposed to identify individuals at an extremely high risk of developing coronary artery disease (CAD) among patients with FH. Although the adverse effects of arterial stiffness have been proven in the general population, insufficient data exist regarding its clinical impact in patients with FH. OBJECTIVES: This study aimed to assess the association between arterial stiffness and CAD in patients with FH. METHODS: We examined 245 patients with FH (162 males; mean age, 46 ± 17 years) and brachial-ankle pulse wave velocity (baPWV) measurements. We assessed baseline characteristics including lipid profiles, other traditional risk factors, the presence of CAD, and the baPWV. RESULTS: Multivariable logistic analysis adjusted for age, sex, hypertension, diabetes, smoking, and low-density lipoprotein cholesterol revealed that the baPWV was independently associated with CAD (odds ratio [OR]: 1.25, 95% confidence interval: 1.10-1.41; P = .000372; per 100 cm/s). Moreover, considering the baPWV with other traditional risk factors improved the risk discrimination of CAD (C-statistics 0.736 vs 0.799; P = .006067). Compared with the reference group without hypertension and low baPWV, patients with hypertension and high baPWV had a significantly higher OR for CAD (OR: 18.68, 95% confidence interval: 6.62-60.62; P = 1.7 × 10-7). CONCLUSIONS: Arterial stiffness assessed by the baPWV was significantly associated with the presence of CAD in patients with FH. Such assessments are useful in the risk stratification of CAD and are independent of hypertension in patients with FH.

Remnant-like particles and coronary artery disease in familial hypercholesterolemia.

BACKGROUND: Although remnant-like particle cholesterol (RLP-C) has been associated with coronary artery disease (CAD) in the general population, few data exist regarding this issue in patients with familial hypercholesterolemia (FH). The aim of our study was to investigate the association between RLP-C and the presence of CAD in patients with FH. METHODS: We examined 282 patients with FH (144 males, mean age, 41 ±â€¯17 years) whose RLP-C levels were measured. We assessed the baseline characteristics, including lipid levels, other conventional risk factors for cardiovascular events, the presence of CAD, and the serum RLP-C levels. RESULTS: Serum RLP-C levels significantly correlated with serum triglyceride (TG) levels (Pearson's r = 0.631, p < 0.001). We observed that a larger proportion of individuals in the higher tertiles of serum RLP-C had a larger number of diseased coronary arteries (p < 0.001 for the trend of multi-vessel disease). Logistic regression analysis, after adjusting for age, sex, hypertension, diabetes, smoking, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and lipoprotein (a) [Lp(a)], revealed that RLP-C was significantly associated with CAD [odds ratio (OR): 1.08, 95% confidence interval (CI): 1.00-1.16, p = 0.046]; however, adding serum TG levels into the logistic regression model nullified this association (OR: 1.07, 95% CI: 0.98-1.17, p = 0.141), whereas Lp(a) was independently associated with CAD (OR: 1.02, 95% CI: 1.00-1.03, p = 0.015). CONCLUSIONS: Serum RLP-C levels were significantly associated with the presence and severity of CAD in patients with FH. However, the clinical usefulness of measuring RLP-C levels beyond that of measuring TG levels should be further assessed.

Post-prandial Remnant Lipoprotein Metabolism in Sitosterolemia.

AIM: We aimed to clarify post-prandial accumulation of remnant-like particles (RLP) in patients with sitosterolemia. METHODS: Oral fat tolerance test cream (Jomo Shokuhin, Takasaki, Japan) 50 g was given per body surface area (m2); blood sampling was performed at 2 h intervals up to 6 h. Plasma lipoprotein fractions and RLP fractions were determined in four sitosterolemic subjects with double mutations in ATP-binding cassette (ABC) sub-family G member 5 or member 8 (ABCG5 or ABCG8) gene (mean age=18 yr, median low-density lipoprotein cholesterol [LDL-C]=154 mg/dL), six heterozygous carriers (mean age=31 yr, median LDL-C=105 mg/dL), and five subjects with heterozygous familial hypercholesterolemia (FH, mean age=32 yr, median LDL-C=221 mg/dL). The incremental area under curve (iAUC) of lipids, including LDL-C, apolipoprotein B-48 (apoB48), RLP cholesterol (RLP-C), and RLP triglyceride (RLP-TG) were evaluated. RESULTS: After oral fat load, there was no significant difference of the iAUC of LDL-C between sitosterolemia and heterozygous FH, whereas the iAUC of apoB48 was significantly larger in the sitosterolemic subjects compared with that of heterozygous FH (2.9 µg/mL×h vs. 1.3 µg/mL×h, p＜0.05). Under these conditions, the iAUCs of RLP-C and RLP-TG levels were significantly larger in the sitosterolemic subject compared with those of heterozygous FH (9.5 mg/dL×h vs. 5.7 mg/dL×h, p＜0.05; 149 mg/dL×h vs. 40 mg/dL×h, p＜0.05, respectively), whereas those of heterozygous carriers were comparable with those with heterozygous FH. CONCLUSIONS: Post-prandial lipoprotein metabolism in sitosterolemia appeared to be impaired, leading to their elevation in serum sterol levels. (UMIN Clinical Trials Registry number, UMIN000020330).

Molecular and functional characterization of familial chylomicronemia syndrome.

BACKGROUND AND AIMS: Familial chylomicronemia syndrome is a rare autosomal recessive disorder leading to severe hypertriglyceridemia (HTG) due to mutations in lipoprotein lipase (LPL)-associated genes. Few data exist on the clinical features of the disorder or on comprehensive genetic approaches to uncover the causative genes and mutations. METHODS: Eight patients diagnosed with familial hyperchylomicronemia with recessive inheritance were included in this study (two males and six females; median age of onset 23.0 years; mean triglyceride level 3446 mg/dl). We evaluated their clinical features, including coronary artery disease using coronary computed tomography, and performed targeted next-generation sequencing on a panel comprising 4813 genes associated with known clinical phenotypes. After standard filtering for allele frequency <1% and in silico annotation prediction, we used three types of variant filtering to identify causative mutations: homozygous mutations in known familial hyperchylomicronemia-associated genes, homozygous mutations with high damaging scores in novel genes, and deleterious mutations within 37 genes known to be associated with HTG. RESULTS: A total of 1810 variants out of the 73,389 identified with 94.3% mean coverage (×20) were rare and nonsynonymous. Among these, our schema detected four pathogenic or likely pathogenic mutations in the LPL gene (p.Ala248LeufsTer4, p.Arg270Cys, p.Ala361Thr, and p.Val227Gly), including one novel mutation and a variant of uncertain significance. Patients harboring LPL gene mutations showed no severe atherosclerotic changes in the coronary arteries, but recurrent pancreatitis with long-term exposure to HTG was observed. CONCLUSIONS: These results demonstrate that LPL gene plays a major role in extreme HTG associated with hyperchylomicronemia, although the condition may not cause severe atherosclerosis.