Low-density Lipoprotein Cholesterol Metabolism Research Articles

Combined hyperlipidemia is genetically similar to isolated hypertriglyceridemia

Combined hyperlipidemia (CHL) is a common disorder defined by concurrently elevated low-density lipoprotein cholesterol (LDL-C) and triglyceride (TG) levels. Despite decades of study, the genetic basis of CHL remains unclear. To characterize the genetic profiles of patients with CHL and compare them to those in patients with isolated hypercholesterolemia and isolated hypertriglyceridemia (HTG). DNA from 259, 379 and 124 patients with CHL, isolated hypercholesterolemia and isolated HTG, respectively, underwent targeted sequencing. We assessed: 1) rare variants disrupting canonical LDL-C or TG metabolism genes; and 2) two polygenic scores-for elevated LDL-C and TG-calculated using common trait-associated single-nucleotide polymorphisms (SNPs). Genetic profiles were compared against 1000 Genomes Project controls. Both CHL and isolated HTG patients had significantly increased odds of a high polygenic score for TG: 2.50 (95% confidence interval [CI] 1.61-3.88; P<0.001) and 3.72 (95% CI 2.24-6.19; P<0.001), respectively. CHL patients had neither a significant accumulation of rare variants for LDL-C or TG, nor a high polygenic score for LDL-C. In contrast, patients with isolated hypercholesterolemia had a 3.03-fold increased odds (95% CI 2.22-4.13; P<0.001) of carrying rare variants associated with familial hypercholesterolemia, while patients with isolated HTG had a 2.78-fold increased odds (95% CI 1.27-6.10; P=0.0136) of carrying rare variants associated with severe HTG. CHL is genetically similar to isolated HTG, a known polygenic trait. Both cohorts had a significant accumulation of common TG-raising variants. Elevated LDL-C levels in CHL are not associated with common or rare LDL-C-related genetic variants.

SUN-574 A1AT: Novel Inhibitor of Active PCSK9

Heart disease is the principal cause of death and disability for both men and women in the US, accounting for 40% of all annual deaths. African American populations are disproportionately burdened with metabolic diseases, due in part to cholesterol metabolism deficiencies. Elevated low density lipoprotein (LDL) cholesterol levels and inflammation promote atherogenic conditions which lead to heart disease. Proprotein convertase subtilisin/kexin-9 (PCSK9) is a biomarker which enhances athrogenic progression by controlling the number of LDL receptor molecules expressed at the plasma membrane. PCSK9 indirectly regulates LDL-cholesterol levels. Previous reports show some patients do not respond well to general anti-cholesterolemic treatments. We believe this is due to altered PCSK9 activity, which is currently not being evaluated. We have developed a novel assay to detect active PCSK9. A1AT is a SERPIN family member whose primary objective is inhibition of proteases. Specific levels of A1AT are required to maintain metabolic homeostasis. Based on this, we hypothesized that a specific ratio between A1AT serum levels and PCSK9 activity levels would eliminate statin intolerance/resistance, regulating LDL-cholesterol metabolism congruently. Using this novel active PCSK9 detection assay, we provide evidence that A1AT interacts with PCSK9 in the medium of C3A hepatic-like cells, preventing the formation of PCSK9/LDL receptor complexes in vitro. There was an approximate 20% inhibition in PCSK9-LDL receptor complex formation when liver cells were treated with recombinant A1AT (rA1AT). A dose dependent response analysis proved 200ng/ml of rA1AT had an 46% reduction in PCSK9 activity. We determined PCSK9 activty and A1AT levels correlate with key diabetic factors in humans, suggesting that A1AT could effect diabetes progression.

Familial hypercholesterolemia: Detect, treat, and ask about family.

Familial hypercholesterolemia is an autosomal dominant disorder that affects the metabolism of low-density lipo-protein cholesterol (LDL-C) through mutations in the gene for LDL receptor (LDLR), and less commonly in those for apolipoprotein B (APOB), proprotein convertase subtili-sin-kexin type 9 (PCSK9), and others. Patients with these mutations have elevated plasma levels of LDL-C and, as a result, an increased risk of atherosclerotic cardiovascular disease beginning in childhood, leading to significant risk of illness and death.

Impaired adult hippocampal neurogenesis in a mouse model of familial hypercholesterolemia: A role for the LDL receptor and cholesterol metabolism in adult neural precursor cells

ObjectiveIn familial hypercholesterolemia (FH), mutations in the low-density lipoprotein (LDL) receptor (LDLr) gene result in increased plasma LDL cholesterol. Clinical and preclinical studies have revealed an association between FH and hippocampus-related memory and mood impairment. We here asked whether hippocampal pathology in FH might be a consequence of compromised adult hippocampal neurogenesis. MethodsWe evaluated hippocampus-dependent behavior and neurogenesis in adult C57BL/6JRj and LDLr−/− mice. We investigated the effects of elevated cholesterol and the function of LDLr in neural precursor cells (NPC) isolated from adult C57BL/6JRj mice in vitro. ResultsBehavioral tests revealed that adult LDLr−/− mice showed reduced performance in a dentate gyrus (DG)-dependent metric change task. This phenotype was accompanied by a reduction in cell proliferation and adult neurogenesis in the DG of LDLr−/− mice, suggesting a potential direct impact of LDLr mutation on NPC. Exposure of NPC to LDL as well as LDLr gene knockdown reduced proliferation and disrupted transcriptional activity of genes involved in endogenous cholesterol synthesis and metabolism. The LDL treatment also induced an increase in intracellular lipid storage. Functional analysis of differentially expressed genes revealed parallel modulation of distinct regulatory networks upon LDL treatment and LDLr knockdown. ConclusionsTogether, these results suggest that high LDL levels and a loss of LDLr function, which are characteristic to individuals with FH, might contribute to a disease-related impairment in adult hippocampal neurogenesis and, consequently, cognitive functions.

Effect of Physical Activity on Plasma PCSK9 in Subjects With High Risk for Type 2 Diabetes.

BackgroundProprotein convertase subtilisin/kexin type 9 (PCSK9) is a liver serine protease regulating LDL cholesterol metabolism. PCSK9 binds to LDL receptors and guides them to lysosomes for degradation, thus increasing the amount of circulating LDL cholesterol. The aim of the study was to investigate associations between physical activity and plasma PCSK9 in subjects with high risk for type 2 diabetes (T2D).MethodsSixty-eight subjects from both genders with a high risk for T2D were included to a randomized controlled trial with a 3-month physical activity intervention. Physical activity intensities and frequencies were monitored throughout the intervention using a hip worn portable accelerometer. The plasma was collected before and after intervention for analysis of PCSK9 and cardiovascular biomarkers.ResultsPlasma PCSK9 did not relate to physical activity although number of steps were 46% higher in the intervention group than in the control group (p < 0.029). Total cholesterol was positively correlated with plasma PCSK9 (R = 0.320, p = 0.008), while maximal oxygen uptake was negatively associated (R = -0.252, p = 0.044). After the physical activity intervention PCSK9 levels were even stronger inversely associated with maximal oxygen uptake (R = -0.410, p = 0.0008) and positively correlated with HDL cholesterol (R = 0.264, p = 0.030). Interestingly, plasma PCSK9 levels were higher in the beginning than at the end of the study.ConclusionThe low physical activity that our subjects with high risk for T2D could perform did not influence plasma PCSK9 levels. Intervention with higher physical activities might be more effective in influencing PCSK9 levels.

Study on Regulation of Low Density Lipoprotein Cholesterol Metabolism using PCSK9 Gene Silencing: A computational Approach.

Combating and preventing abnormality in lipid metabolism becomes a pivotal criterion for research. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a circulating protein; it promotes the degradation of low-density lipoprotein receptors (LDL-R) and hence increases LDL-C levels. Silencing the gene PCSK9 at post-transcriptional level with the help of small interfering Ribo nucleic acid (siRNA) gives a new insight and a novel therapeutic way to regulate LDL-C metabolism. Designing and selecting an efficient siRNA for silencing PCSK9 at post transcriptional level through computational approach. We have designed three siRNAs to silence each mRNA of PCSK9 through computational analysis using software Invivogen. Their minimum free energy of hybridization along with their secondary structure was obtained using bioinformatics tool BIBISERV2-RNAHYBRID. Further factors like GC content, structural linearity and h-b index of mRNA-siRNA complex was calculated to assess their knockdown efficiency. The minimum free energy of hybridization of the three designed siRNA1, siRNA2 and siRNA3 for target mRNA is as follows -27.1kcal/mol, -25.7kcal/mol and - 28.8 kcal/mol. siRNA1 having the least minimum free energy of hybridization i.e. -27.1 kcal/mol are predicted to be the most efficient towards the PCSK9 gene silencing.

Vaccines Targeting PCSK9: A Promising Alternative to Passive Immunization with Monoclonal Antibodies in the Management of Hyperlipidaemia?

Hypercholesterolaemia is frequently observed in patients with cardiovascular diseases (CVD) and is associated with increased mortality. Statin treatment has been the standard of care for reducing low-density lipoprotein cholesterol (LDL-C) to improve cardiovascular outcomes. However, statins have limited effects in some patients and may be discontinued due to adverse effects resulting in LDL-C above target levels. The proprotein convertase subtilisin kexin type 9 (PCSK9) is a pivotal regulator in the LDL-C metabolism by degrading the LDL-C receptor on hepatocytes. Inhibition of PCSK9 by monoclonal antibodies (mAb) significantly lowers LDL-C levels and is considered to reduce the likelihood of adverse cardiac events. However, such treatment regimens are not cost-effective, and require frequent administrations at high doses that may be associated with side effects and poor drug adherence. Furthermore, it has been shown that these PCSK9 medicines may trigger the formation of antidrug antibodies followed by a significant attenuation of the LDL-C-lowering effect. Active vaccination inducing high-affinity antibodies against PCSK9 with less frequent administration intervals may be a novel promising therapeutic approach to overcome the drawback of passive immunization with PCSK9 mAb. However there is a paucity of available clinical safety and efficacy data. This article discusses challenges in the development of PCSK9 vaccines and their potential therapeutic benefits by reviewing clinical studies that evaluated the safety and efficacy of PCSK9 mAb.

Thyroid stimulating hormone exhibits the impact on LDLR/LDL-c via up-regulating hepatic PCSK9 expression

ContextThyroid stimulating hormone (TSH) has received increasing attention as being closely associated with increased low-density lipoprotein cholesterol (LDL-c) level and higher atherosclerotic risks. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is known for increasing circulating LDL-c level by inducing LDL receptor degradation. However, whether TSH influences hepatic PCSK9 expression and LDL-c metabolism remains unclear. MethodsFirst, the correlation between TSH and lipid profiles were investigated in euthyroid population and in subclinical hypothyroidism patients. Then, an in vitro study was conducted to validate the effects of TSH on hepatic PCSK9 expression in HepG2 cells. ResultsSerum TSH concentrations positively correlated with LDL-c levels in euthyroid subjects. Subclinical hypothyroidism patients with higher serum TSH levels showed significantly increased serum PCSK9 levels than the matched euthyroid participants (151.29 (89.51–293.03) vs. 84.70 (34.98–141.72) ng/ml, P<0.001), along with increased LDL-c concentrations. In HepG2 cells, LDLR expression on the plasma membrane was decreased, and PCSK9 mRNA and protein levels were synchronously upregulated after recombinant human TSH (rhTSH) treatment, while the effects could be blocked by TSH receptor blocking antibody K1-70. Sterol regulatory element binding protein (SREBP) 1c and SREBP2 mRNA expressions were enhanced after rhTSH treatment, and specific siRNAs significantly inhibited the effects of rhTSH. Furthermore, there was a noticeable induction of PCSK9 expression by rhTSH even though HMGCR gene expression was silenced. ConclusionWe conclude a regulating role of TSH on hepatic PCSK9 expression, which further contributing to a higher LDL-c level.

Glycaemic control influences the relationship between plasma PCSK9 and LDL cholesterol in type 1 diabetes.

Pro-protein convertase subtilisin/kexin type 9 (PCSK9) is a critical regulator of LDL cholesterol metabolism. Little is known, however, about the regulation of PCSK9 in patients with type 1 diabetes (T1D). In the present study, we aimed to determine the relationship between circulating PCSK9 and metabolic variables in T1D. Plasma PCSK9 levels were measured in 195 people with T1D (mean age 38.8 years, mean diabetes duration 17.2 years, mean glycated haemoglobin [HbA1c] 8.3%), who were free of any lipid-lowering agent. Plasma PCSK9 was positively correlated with LDL cholesterol (P = .0007), triglycerides (P = .004), apolipoprotein B (P = .005), HbA1c (P = .003), systolic (P = .003) and diastolic (P = .001) blood pressure and body mass index (0.02). In multivariate analysis, PCSK9 concentration was independently associated with HbA1c (P = .02) and LDL cholesterol (P = .03). After classifying patients according to HbA1c tertile, the correlation between PCSK9 and LDL cholesterol was only observed in the highest tertile (P = .0006; Rho = 0.43), whereas no correlation was found in the lowest and intermediate tertiles. This study suggests that good glycaemic control abolishes the positive relationship between PCSK9 and LDL cholesterol in patients with T1D; however, the underlying molecular mechanisms remain to be established.

Fetal gender and gestational age differentially affect PCSK9 levels in intrauterine growth restriction.

BackgroundMaternal and fetal Low Density Lipoprotein-Cholesterol (LDL-C) concentrations are compromised in intrauterine growth restriction (IUGR). Generally, LDL-C catabolism is under control of PCSK9 by binding to the LDL-receptor leading to its degradation. Hence, we hypothesized a role for PCSK9 in the modulation of lipid metabolism and placental transport in IUGR.Methods172 women, 70 IUGR and 102 controls were included in the study. Maternal and fetal serum PCSK9 levels and lipid profiles including LDL-C were measured. Placental LDL-receptor and PCSK9 expressions were estimated by tissue microarray immunohistochemistry, and analyzed by two blinded observers using an immunoreactivity score. Non-parametric tests and multivariate regression analyses were used for statistical estimations.ResultsPCSK9 levels in the maternal and fetal compartment independently predicted LDL-C levels (maternal compartment: adjusted R 2 = 0.2526; coefficient b i = 0.0938, standard error sbi =0.0217, rpartial = 0.4420, t-value = 4.323, p < 0.0001; fetal compartment: adjusted R 2 = 0.2929; b i = 0.1156, sbi =0.020, rpartial = 0.5494, t-value = 5.81, p < 0.0001). We did not find significant differences in maternal PCSK9 concentrations between IUGR and controls. However, we found lower fetal serum PCSK9 concentrations in IUGR than in controls (IUGR median 137.1 ng/mL (95% CI 94.8-160.0) vs. controls 176.8 (154.6-202.5), p = 0.0005). When subgrouping according to early onset, late onset IUGR, and fetal gender differences remained consistent only for male neonates born before 34 weeks of gestation. In the placenta we found no correlation between PCSK9 and LDL-receptor expression patterns. However, the LDL-receptor was significantly upregulated in IUGR when compared to controls (p = 0.0063).ConclusionsOur results suggest that PCSK9 play a role in impaired fetal growth by controlling fetal LDL-C metabolism, which seems to be dependent on gestational age and fetal gender. This underlines the need to identify subgroups of IUGR that may benefit from individualized and gender-specific pharmacotherapy in future studies.

Obstructive sleep apnea is associated with visit-to-visit variability in low-density lipoprotein-cholesterol in patients with coronary artery disease.

Visit-to-visit variability in low-density lipoprotein-cholesterol (LDL-C) was found to be a novel predictor of adverse cardiac events. Obstructive sleep apnea (OSA), an emerging cardiovascular risk factor, is characterized by sympathetic activation and increased oxidative stress which are regulators of LDL-C metabolism. We hypothesized that OSA was associated with LDL-C variability. We prospectively recruited 190 patients with coronary artery disease for an overnight sleep study. Statin was prescribed upon discharge for 186 patients. Serum LDL-C levels were measured at clinic every 3 to 6months. Severity of OSA (on the basis of apnea-hypopnea index (AHI)) was correlated with visit-to-visit LDL-C variability (on the basis of variation independent of mean (VIM)) in outpatient clinic. The mean AHI was 21.9 ± 18.9. Using an AHI cut-off of 5-14.9, 15-29.9, and ≥30, the prevalence of mild, moderate, and severe OSA was 26.3, 18.9, and 27.4%, respectively. After 53.2 ± 25.3months, LDL-C was recorded over 8.1 ± 4.2 measurements. VIM positively correlated with AHI (Pearson's r = 0.183, p = 0.016), but not body mass index, baseline and mean follow-up LDL-C levels, and number of LDL-C measurements. In multiple linear regression analysis, AHI remained an independent predictor of VIM after adjusting for diabetes mellitus and hyperlipidemia. A 10-unit rise in AHI led to a 3.8% increase in VIM (95% CI 0.1 to 7.4%; p = 0.044). This is the first study to show the independent correlation between OSA severity and visit-to-visit LDL-C variability. Our finding contributes to the understanding of the vasculopathic effects of OSA.

Disadvantages of Current LDL-cholesterol Lowering and the Role of PCSK9 Inhibitors.

LDL cholesterol (LDL-C) is a strong independent cardiovascular (CV) risk factor that can be easily influenced. Today, statins are the therapy of choice for the achievement of target LDL-C values. Although controlled clinical trials have demonstrated their effectiveness and safety, in practice we are often met with statin intolerance as well as a failure to achieve target LDL-C values in a significant portion of the patients despite maximal doses. In patients with high and very high CV risk, other antilipemic pharmacotherapy is often also insufficient. PCSK9 inhibitors (PCSK9-I) are new revolutionary drugs with a potent effect on LDL-C. The rapid development of PCSK9-I began in 2003 with the discovery of a PCSK9 gene mutation in patients with familial hypercholesterolemia. The product of this gene, proprotein convertase subtilisin/kexin type 9 (PCSK9), has an important role in the expression of LDL receptors and cholesterol metabolism. Animal models demonstrated that inactivation of the PCSK9 gene lowers LDL-C with regression of atherosclerotic changes in the aorta. Heterozygotes and homozygotes with the inactivation mutation of PCSK9 have lower LDL-C values and lower incidence of atherosclerosis. Among the various groups of PCSK9-I, monoclonal antibodies saw strong development (alirocumab, evolocumab, bococizumab). Phase 3 clinical trials on familial and primary hypercholesterolemia with statin intolerance or resistance have demonstrated a strong positive effect of alirocumab and evolocumab on LDL-C values (a reduction of 60%), with high safety and good tolerability. The OSLER study on evolocumab also demonstrated positive effects on CV outcomes. Multiple clinical trials on PCSK9-I are currently monitoring their effect on CV morbidity and mortality. Positive results from these studies would confirm the great potential of PCSK9-I for better prevention and treatment of CV diseases.

PCSK9-Inhibitoren – Durchbruch bei der LDL-Cholesterin-Senkung?

The proprotein convertase subtilisin / kexin type 9 (PCSK9) plays an important role in LDL cholesterol (LDL-C) metabolism. Subjects harboring loss-of-function mutations in the gene encoding for PCSK9 display markedly reduced LDL-C plasma levels. PCSK9 is secreted by the liver, binds to the LDL receptor and, following endocytosis, induces lysosomal degradation of the receptor together with the bound LDL-C. Current PCSK9 inhibitors are monoclonal antibodies that specifically absorb PCSK9. Subsequently, instead of being degraded the receptor can dissociate from LDL-C and recycle, consecutively resulting in an increased hepatocyte LDL receptor density and higher LDL-C clearance. In clinical trials, the PCSK9 inhibitors alirocumab and evolocumab induced reductions in LDL-C of up to 70 % in statin-treated as well as statin-naïve patients. So far, serious side effects (requiring cessation of drug treatment) occurred only in rare cases. Since this new class of lipid lowering drugs promises a high potential benefit, they have been approved by the EMA even before completion of the studies addressing clinically relevant endpoints like cardiovascular events and mortality. Therefore, the expected publication of these study results in 2017 may allow a better assessment of the efficacy and safety of PCSK9 inhibitors.

Association between plasma PCSK9 levels and 10-year progression of carotid atherosclerosis beyond LDL-C: A cohort study

BackgroundTo evaluate the association of plasma proprotein convertase subtilisin/kexin type 9 (PCSK9) levels with the progression of carotid atherosclerosis and identify additional PCSK9-lipoprotein-atherosclerosis pathway beyond low-density lipoprotein cholesterol (LDL-C). MethodsAmong 643 participants (aged from 45 to 74years) free of cardiovascular disease at baseline, carotid ultrasound examinations were performed in 2002 (baseline) and 2012 (follow-up). None of the participants were taking lipid-lowering drugs or had detectable carotid plaques at baseline. Carotid plaque formation and total plaque area (TPA) were used to reflect 10-year progression of atherosclerosis. ResultsBaseline plasma PCSK9 levels have a wide variation, ranged from 64.60–532.20ng/mL (median: 192.57ng/mL). PCSK9 levels were significantly associated with new plaque formation after adjusting for LDL-C levels and other risk factors (relative risk for per quartile increase=1.09, 95% confidence interval: 1.03–1.15). PCSK9 levels were also linearly associated with TPA after multivariate adjustment including LDL-C (P=0.008). Among participants with the lowest or second tertile of LDL-C, PCSK9 quartiles were linearly associated with TPA (P=0.021), but the association lost significance after additional adjustment for very low-density lipoprotein cholesterol (VLDL-C) tertiles (P=0.072). Further stepwise linear regression (entry, 0.05; removal, 0.05) indicated that VLDL-C tertiles could be entered into the model but PCSK9 quartiles could not. ConclusionsPlasma PCSK9 levels are associated with 10-year progression of atherosclerosis. The LDL-independent association of PCSK9 levels may through its ability to regulate VLDL-C levels. Further research is needed to systematically investigate the role of PCSK9 for the pathogenesis of atherosclerosis, beyond LDL-C metabolism.

OBSTRUCTIVE SLEEP APNEA IS ASSOCIATED WITH VISIT-TO-VISIT VARIABILITY IN LOW DENSITY LIPOPROTEIN-CHOLESTEROL IN PATIENTS WITH CORONARY ARTERY DISEASE

Purpose Visit-to-visit variability in low-density lipoprotein-cholesterol (LDL-C) was found to be a novel predictor of adverse cardiac events. Obstructive sleep apnea (OSA), an emerging cardiovascular risk factor, is characterized by sympathetic activation and increased oxidative stress which are regulators of LDL-C metabolism. We hypothesized that OSA was associated with LDL-C variability.

Genetic insights into statin-associated diabetes risk.

Meta-analyses of major statin trials have suggested that statin therapy modestly increases the risk of developing diabetes. However, the quality of the data on which these findings are based is not without weaknesses and it has also been unclear whether this effect, if true, is an on-target or off-target effect of statins. In a major Mendelian randomization study of variants in the HMGCR gene, which encodes the protein through which statins exert their effect, two polymorphisms associated with lower LDL-cholesterol were also associated with higher weight, higher waist circumference, higher glucose and higher diabetes risk. These findings correspond with findings from the statin trials. In addition, new observational studies using a genetic risk score for LDL-cholesterol suggest that other pathways linked to LDL-cholesterol metabolism may also affect diabetes risk. Genetic studies indicate that the observed effect of statins on diabetes risk in trials is highly likely to be a true on-target effect. Although other recent studies have suggested that genetically determined lower LDL-cholesterol may be linked to diabetes risk, further data from both genetic studies and clinical trials of other LDL-cholesterol lowering agents are needed to confirm or refute this.

MiRNA regulation of LDL-cholesterol metabolism

In the past decade, microRNAs (miRNAs) have emerged as key regulators of circulating levels of lipoproteins. Specifically, recent work has uncovered the role of miRNAs in controlling the levels of atherogenic low-density lipoprotein LDL (LDL)-cholesterol by post-transcriptionally regulating genes involved in very low-density lipoprotein (VLDL) secretion, cholesterol biosynthesis, and hepatic LDL receptor (LDLR) expression. Interestingly, several of these miRNAs are located in genomic loci associated with abnormal levels of circulating lipids in humans. These findings reinforce the interest of targeting this subset of non-coding RNAs as potential therapeutic avenues for regulating plasma cholesterol and triglyceride (TAG) levels. In this review, we will discuss how these new miRNAs represent potential pre-disposition factors for cardiovascular disease (CVD), and putative therapeutic targets in patients with cardiometabolic disorders. This article is part of a Special Issue entitled: MicroRNAs and lipid/energy metabolism and related diseases edited by Carlos Fernández-Hernando and Yajaira Suárez.

Increased Aortic Valve Calcification in Familial Hypercholesterolemia: Prevalence, Extent, and Associated Risk Factors

BackgroundFamilial hypercholesterolemia is typically caused by LDL receptor (LDLR) mutations that result in elevated levels of LDL cholesterol (LDL-C). In homozygous FH, the prevalence of aortic valve calcification (AoVC) reaches 100% and is often symptomatic. ObjectivesThe objective of this study was to investigate the prevalence, extent, and risk-modifiers of AoVC in heterozygous FH (he-FH) that are presently unknown. MethodsAsymptomatic patients with he-FH and 131 non-familial hypercholesterolemia controls underwent CT computed tomography calcium scoring. AoVC was defined as the presence of calcium at the aortic valve leaflets. The extent of AoVC was expressed in Agatston units, as the AoVC-score. We compared the prevalence and extent of AoVC between cases and controls. In addition, we investigated risk modifiers of AoVC, including the presence of LDLR mutations without residual function (LDLR-negative mutations), maximum untreated LDL-cholesterol (maxLDL), LDL-C, blood pressure, and coronary artery calcification (CAC). ResultsWe included 145 asymptomatic patients with he-FH (93 men; mean age 52 ± 8 years) and 131 non-familial hypercholesterolemia controls. The prevalence (%) and AoVC-score (median, IQR) were higher in he-FH patients than in controls: 41%, 51 (9–117); and 21%, 21 (3–49) (p < 0.001 and p = 0.007). Age, untreated maxLDL, CAC, and diastolic blood pressure were independently associated with AoVC. LDLR-negative mutational he-FH was the strongest predictor of the AoVC-score (OR: 4.81; 95% CI: 2.22 to 10.40; p = <0.001). ConclusionsCompared to controls, he-FH is associated with a high prevalence and a large extent of subclinical AoVC, especially in patients with LDLR-negative mutations, highlighting the critical role of LDL-C metabolism in AoVC etiology.

Abstract 19109: Low PCSK9 and LDL Cholesterol and Risk of Dementia, Parkinson’s Disease, and Epilepsy - A Mendelian Randomization Study

Introduction: Low levels of low-density-lipoprotein cholesterol(LDL-C) due to statin use has been associated with reduced cognitive function. We aimed to assess whether low LDL-C due to genetic variation in the 3-hydroxy-3-methylglutaryl-CoA reductase(HMGCR; rs17238484) and proprotein convertase subtilisin kexin 9(PCSK9; rs11591147, rs148195424, rs562556, rs505151) genes, involved in LDL-C biosynthesis and metabolism, respectively, is associated with risk of Alzheimer’s dementia, vascular dementia, all dementia, Parkinson’s disease, and epilepsy in a general population off and on lipid lowering medication. Methods: We examined associations of plasma LDL-C with observational risk of disease; genetic variants with plasma LDL-C levels; and genetic variants and risk of disease as an indication of causality using a Mendelian randomization design in 92,068 participants off and 11,519 participants on lipid lowering medication from the Copenhagen General Population Study and the Copenhagen City Heart Study. Results: In observational analysis, risk of epilepsy was 98%(95% confidence interval: 32%-297%) higher in participants with an LDL-C &lt;1.5mmol/L versus ≥3.0mmol/L. Low LDL-C was not associated with risk of Alzheimer’s dementia, vascular dementia, all dementia, and Parkinson’s disease. In causal genetic analyses, PCSK9 and HMGCR variants associated with 7.8% and 2.9% lower LDL-C. Genotypes were not associated with risk of Alzheimer’s dementia, vascular dementia, all dementia, Parkinson’s disease, or epilepsy. Conclusions: Using 103,587 individuals from the general population, we found that observationally low LDL-C level was associated with increased risk of epilepsy. Low LDL-C due to PCSK9 and HMGCR variants was not associated with Alzheimer’s dementia, vascular dementia, all dementia, Parkinson’s disease or epilepsy, and results does not support a causal role of low LDL-C in these diseases.

New CETP inhibitor K-312 reduces PCSK9 expression: a potential effect on LDL cholesterol metabolism.

Despite significant reduction of cardiovascular events by statin treatment, substantial residual risk persists, driving emerging needs for the development of new therapies. We identified a novel cholesteryl ester transfer protein (CETP) inhibitor, K-312, that raises HDL and lowers LDL cholesterol levels in animals. K-312 also suppresses hepatocyte expression of proprotein convertase subtilisin/kexin 9 (PCSK9), a molecule that increases LDL cholesterol. We explored the underlying mechanism for the reduction of PCSK9 expression by K-312. K-312 inhibited in vitro human plasma CETP activity (IC50; 0.06 μM). Administration of K-312 to cholesterol-fed New Zealand White rabbits for 18 wk raised HDL cholesterol, decreased LDL cholesterol, and attenuated aortic atherosclerosis. Our search for additional beneficial characteristics of this compound revealed that K-312 decreases PCSK9 expression in human primary hepatocytes and in the human hepatoma cell line HepG2. siRNA silencing of CETP in HepG2 did not compromise the suppression of PCSK9 by K-312, suggesting a mechanism independent of CETP. In HepG2 cells, K-312 treatment decreased the active forms of sterol regulatory element-binding proteins (SREBP-1 and -2) that regulate promoter activity of PCSK9. Chromatin immunoprecipitation assays demonstrated that K-312 decreased the occupancy of SREBP-1 and SREBP-2 on the sterol regulatory element of the PCSK9 promoter. PCSK9 protein levels decreased by K-312 treatment in the circulating blood of cholesterol-fed rabbits, as determined by two independent mass spectrometry approaches, including the recently developed, highly sensitive parallel reaction monitoring method. New CETP inhibitor K-312 decreases LDL cholesterol and PCSK9 levels, serving as a new therapy for dyslipidemia and cardiovascular disease.