Lipoprotein(a) levels and carotid intima-media thickness in children: A 20-year follow-up study.

Elevated lipoprotein(a) [Lp(a)] is independently associated with cardiovascular disease (CVD). In a recent long-term follow-up study involving children with familial hypercholesterolemia, Lp(a) levels contributed significantly to early atherosclerosis, as measured by carotid intima-media thickness (cIMT). To determine if this holds true for children without FH, we conducted a 20-year follow-up study, examining 88 unaffected siblings (mean age: 12.9 years) of children with FH. No significant association was found between Lp(a) and cIMT during follow-up (ß-adjusted [95% CI] = 0.0001 [-0.008 to 0.008] mm per 50 nmol/L increase Lp(a), p = 0.97). In conclusion, our findings suggest that elevated levels of Lp(a) do not play a significant role in arterial wall thickening among children without FH during the 20-year follow-up period. This leads us to consider the possibility that cIMT may not be a suitable marker for detecting potential subtle changes in the arterial wall mediated by Lp(a) in the young, general population. However, it could also be that elevated Lp(a) is only a significant risk factor for atherosclerosis in the presence of other risk factors such as FH.

Thyroid Hormone Mimetics: the Past, Current Status and Future Challenges.

The association between thyroid hormone status and plasma levels of low-density lipoprotein cholesterol has raised the awareness for the development of thyroid hormone mimetics as lipid-lowering agents. The discovery of the two main types of thyroid hormone receptors (α and ß) as well as the development of novel combinatorial chemistry providing organ specificity has drastically improved the selectivity of these compounds. In the past decades, several thyroid hormone mimetics have been investigated with the purpose of lowering low-density lipoprotein cholesterol levels. However, until now, none of the thyromimetics reached the stage of completing a phase III clinical trial without deleterious side effects. Here, we review the currently available literature on thyromimetics investigated for the treatment of dyslipidemia, their rise, their downfall and the challenges for the development of novel agents.

Loss of function in heparan sulfate elongation genes EXT1 and EXT 2 results in improved nitric oxide bioavailability and endothelial function.

BACKGROUND: Heparanase is the major enzyme involved in degradation of endothelial heparan sulfates, which is associated with impaired endothelial nitric oxide synthesis. However, the effect of heparan sulfate chain length in relation to endothelial function and nitric oxide availability has never been investigated. We studied the effect of heterozygous mutations in heparan sulfate elongation genes EXT1 and EXT2 on endothelial function in vitro as well as in vivo. METHODS AND RESULT: Flow-mediated dilation, a marker of nitric oxide bioavailability, was studied in Ext1(+/-) and Ext2(+/-) mice versus controls (n=7 per group), as well as in human subjects with heterozygous loss of function mutations in EXT1 and EXT2 (n=13 hereditary multiple exostoses and n=13 controls). Endothelial function was measured in microvascular endothelial cells under laminar flow with or without siRNA targeting EXT1 or EXT2. Endothelial glycocalyx and maximal arteriolar dilatation were significantly altered in Ext1(+/-) and Ext2(+/-) mice compared to wild-type littermates (glycocalyx: wild-type 0.67±0.1 µm, Ext1(+/-) 0.28±0.1 µm and Ext2(+/-) 0.25±0.1 µm, P<0.01, maximal arteriolar dilation during reperfusion: wild-type 11.3±1.0%), Ext1(+/-) 15.2±1.4% and Ext2(+/-) 13.8±1.6% P<0.05). In humans, brachial artery flow-mediated dilation was significantly increased in hereditary multiple exostoses patients (hereditary multiple exostoses 8.1±0.8% versus control 5.6±0.7%, P<0.05). In line, silencing of microvascular endothelial cell EXT1 and EXT2 under flow led to significant upregulation of endothelial nitric oxide synthesis and phospho-endothelial nitric oxide synthesis protein expression. CONCLUSIONS: Our data implicate that heparan sulfate elongation genes EXT1 and EXT2 are involved in maintaining endothelial homeostasis, presumably via increased nitric oxide bioavailability.

The pharmacokinetics and pharmacokinetic/pharmacodynamic relationships of evacetrapib administered as monotherapy or in combination with statins.

Evacetrapib is a novel cholesteryl ester transfer protein (CETP) inhibitor currently being evaluated in a late-stage cardiovascular outcome trial. Using population-based models, we analyzed evacetrapib concentration data along with high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) data from a 12-week study in dyslipidemic patients treated with evacetrapib alone or in combination with atorvastatin, simvastatin, or rosuvastatin. Evacetrapib pharmacokinetics were characterized using a two-compartment model with first-order absorption. Evacetrapib exposure increased in a less than dose-proportional manner, similar to other CETP inhibitors. No patient factors had a clinically relevant impact on evacetrapib pharmacokinetics. The relationships between evacetrapib exposure and HDL-C and LDL-C were characterized using Emax models. The theoretical maximal mean HDL-C increase and LDL-C decrease relative to baseline were 177 and 44.1%, respectively. HDL-C change from baseline was found to be negatively correlated with baseline HDL-C. A pharmacologically independent LDL-C reduction was found when evacetrapib was coadministered with statins.CPT Pharmacometrics Syst. Pharmacol. (2014) 3, e94; doi:10.1038/psp.2013.70; published online 22 January 2014.

Two novel mutations in apolipoprotein C3 underlie atheroprotective lipid profiles in families.

Apolipoprotein C3 (APOC3) mutations carriers typically display high plasma high-density lipoprotein cholesterol (HDL-C) and low triglycerides (TGs). We set out to investigate the prevalence and clinical consequences of APOC3 mutations in individuals with hyperalphalipoproteinemia. Two novel mutations (c.-13-2A>G and c.55+1G>A) and one known mutation (c.127G>A;p.Ala43Thr) were found. Lipid profiles and apoCIII isoform distributions were measured. c.55+1G>A mutation carriers displayed higher HDL-C percentiles (35.6 ± 35.8 vs 99.0 ± 0, p = 0.002) and lower TGs (0.51 (0.37-0.61) vs 1.42 (1.12-1.81) mmol/l, p = 0.007) and apoCIII levels (4.24 ± 1.57 vs 7.33 ± 3.61 mg/dl, p = 0.18). c.-13-2A>G mutation carriers did not display significantly different HDL-C levels (84.0 ± 30.0 vs 63.7 ± 45.7, p = 0.50), a trend towards lower TGs [0.71 (0.54 to 0.78) vs 0.85 (0.85 to -) mmol/l, p = 0.06] and significantly lower apoCIII levels (3.09 ± 1.08 vs 11.45 ± 1.06 mg/dl, p = 0.003). p.Ala43Thr mutation carriers displayed a trend towards higher HDL-C percentiles (91.2 ± 31.8 vs 41.0 ± 29.7 mmol/l, p = 0.06) and significantly lower TGs [0.58 (0.36-0.63) vs 0.95 (0.71-1.20) mmol/l, p = 0.02] and apoCIII levels (4.92 ± 2.33 vs 6.60 ± 1.60, p = 0.25). Heterozygosity for APOC3 mutations results in high HDL-C and low TGs and apoCIII levels. This favourable lipid profile in patients with genetically low apoCIII levels holds promise for current studies investigating the potential of apoCIII inhibition as a novel therapeutic in cardiovascular disease prevention.

Plasma levels of PCSK9 and phenotypic variability in familial hypercholesterolemia.

The extent of hypercholesterolemia varies considerably in patients with familial hypercholesterolemia (FH). We hypothesized that the variability of the FH phenotype might be partly explained by variation in proprotein convertase subtilisin kexin type 9 (PCSK9) activity. Individuals between 18 and 53 years of age who had been tested for a pathogenic LDLR or APOB mutation were eligible. Mutation carriers with a LDL-C level below the 75(th) percentile (called "FH low") were selected, as well as those with LDL-C above the 90(th) percentile (called "FH high"). Relatives who tested negative for the mutation were the "controls." PCSK9 plasma levels were assessed in 267 individuals who did not receive cholesterol-lowering treatment at the time of the study. Mean PCSK9 plasma levels (95% CI) were lower in the FH-low group compared with the FH-high group [152 (137-167) ng/ml vs. 186 (165-207) ng/ml, P = 0.010] and the control group [177 (164-190) ng/ml, P = 0.013]. Mean PCSK9 levels did not statistically differ between the FH-high and control groups (P = 0.50). Plasma PCSK9 levels are positively associated with LDL-C levels in FH patients and might contribute to the phenotypic severity in this disorder. Therefore, the results of pharmaceutical inhibition of PCSK9 in FH patients are eagerly awaited.

Mutations in LPL, APOC2, APOA5, GPIHBP1 and LMF1 in patients with severe hypertriglyceridaemia.

OBJECTIVES: The severe forms of hypertriglyceridaemia (HTG) are caused by mutations in genes that lead to the loss of function of lipoprotein lipase (LPL). In most patients with severe HTG (TG > 10 mmol L(-1) ), it is a challenge to define the underlying cause. We investigated the molecular basis of severe HTG in patients referred to the Lipid Clinic at the Academic Medical Center Amsterdam. METHODS: The coding regions of LPL, APOC2, APOA5 and two novel genes, lipase maturation factor 1 (LMF1) and GPI-anchored high-density lipoprotein (HDL)-binding protein 1 (GPIHBP1), were sequenced in 86 patients with type 1 and type 5 HTG and 327 controls. RESULTS: In 46 patients (54%), rare DNA sequence variants were identified, comprising variants in LPL (n = 19), APOC2 (n = 1), APOA5 (n = 2), GPIHBP1 (n = 3) and LMF1 (n = 8). In 22 patients (26%), only common variants in LPL (p.Asp36Asn, p.Asn318Ser and p.Ser474Ter) and APOA5 (p.Ser19Trp) could be identified, whereas no mutations were found in 18 patients (21%). In vitro validation revealed that the mutations in LMF1 were not associated with compromised LPL function. Consistent with this, five of the eight LMF1 variants were also found in controls and therefore cannot account for the observed phenotype. CONCLUSIONS: The prevalence of mutations in LPL was 34% and mostly restricted to patients with type 1 HTG. Mutations in GPIHBP1 (n = 3), APOC2 (n = 1) and APOA5 (n = 2) were rare but the associated clinical phenotype was severe. Routine sequencing of candidate genes in severe HTG has improved our understanding of the molecular basis of this phenotype associated with acute pancreatitis and may help to guide future individualized therapeutic strategies.

Extreme xanthomatosis in patients with both familial hypercholesterolemia and cerebrotendinous xanthomatosis.

Two unrelated individuals were referred to Lipid Clinics in The Netherlands and Chile with extreme xanthomatosis and hypercholesterolemia. Both were diagnosed with heterozygous familial hypercholesterolemia (heFH) after molecular genetic analysis of the low-density lipoprotein (LDL) receptor gene. Since heFH by itself could not account for the massive xanthomas, the presence of an additional hereditary lipid or lipoprotein disorder was suspected. Further genetic analysis revealed homozygozity for mutations in the sterol 27-hydroxylase gene, confirming the diagnosis of cerebrotendinous xanthomatosis (CTX). Markedly, the typical neurological manifestations of CTX were absent, suggestive of a protective role of LDL-receptor deficiency against the severe neurological consequences of CTX.

Differential effect of the rs4149056 variant in SLCO1B1 on myopathy associated with simvastatin and atorvastatin.

Statins reduce cardiovascular morbidity and mortality in appropriately selected patients. However, statin-associated myopathy is a significant risk associated with these agents. Recently, variation in the SLCO1B1 gene was reported to predict simvastatin-associated myopathy. The aim of this study was to replicate association of the rs4149056 variant in SLCO1B1 with severe statin-associated myopathy in a cohort of patients using a variety of statin medications and to investigate the association with specific statin types. We identified 25 cases of severe statin-associated myopathy and 84 controls matched for age, gender, statin type and dose. The rs4149056 variant in SLCO1B1 was not significantly associated with myopathy in this group as a whole. However, when subjects were stratified by statin type, the SLCO1B1 rs4149056 genotype was significantly associated with myopathy in patients who received simvastatin, but not in patients who received atorvastatin. Our findings provide further support for a role for SLCO1B1 genotype in simvastatin-associated myopathy, and suggest that this association may be stronger for simvastatin compared with atorvastatin.

Familial hypercholesterolemia: present and future management.

Patients suffering from familial hypercholesterolemia (FH) are characterized by increased plasma levels of low-density lipoprotein cholesterol (LDL-C) levels and are at increased risk for premature cardiovascular disease (CVD). Current guidelines emphasize the need to aggressively lower LDL-C in FH patients, and statins are the cornerstone in the current regimen. However, additional therapies are eagerly awaited, especially for those patients not tolerating statin therapy or not reaching the goals for therapy. Our understanding of LDL metabolism has improved over the last years and an increasing number of potential novel targets for therapy have been recently identified. Apart from novel targets, we have also been confronted with novel modalities of treatment, such as mRNA antisense therapy. Some of these emerging therapies have proven to be effective in lowering plasma LDL-C levels and are as such expected to have beneficial effects on CVD. Hopefully, they will enrich our armamentarium against the severe dyslipidemia observed in FH patients in the not too distant future.

Reducing cardiovascular disease risk in patients with type 2 diabetes and concomitant macrovascular disease: can insulin be too much of a good thing?

Despite improvement of microvascular outcomes as a consequence of optimal glucose control in patients with type 2 diabetes, prevention of macrovascular complications is still a major challenge. Of interest, large-scale intervention studies (Action to Control Cardiovascular Risk in Diabetes, Action in Diabetes and Vascular Disease-Preterax and Diamicron Modified Release Controlled Evaluation and Veterans Affairs Diabetes Trial) comparing standard therapy versus more intensive glucose-lowering therapy failed to report beneficial impacts on macrovascular outcomes. Consequently, it is currently under debate whether the high doses of exogenous insulin that were administered in these trials to achieve strict target glucose levels could be responsible for these unexpected outcomes. Additionally, a potential role for plasma insulin levels in predicting macrovascular outcomes has emerged in patients with or without type 2 diabetes. These observations, combined with evidence from in vitro and animal experiments, suggest that insulin might have intrinsic atherogenic effects. In this review, we summarize clinical trials, population-based studies as well as data emerging from basic science experiments that point towards the hypothesis that the administration of high insulin doses might not be beneficial in patients with type 2 diabetes and established macrovascular disease.

Novel mutations in scavenger receptor BI associated with high HDL cholesterol in humans.

The scavenger receptor class B, member 1 (SR-BI), is a key cellular receptor for high-density lipoprotein (HDL) in mice, but its relevance to human physiology has not been well established. Recently a family was reported with a mutation in the gene encoding SR-BI and high HDL cholesterol (HDL-C). Here we report two additional individuals with extremely high HDL-C (greater than the 90th percentile for age and gender) with rare mutations in the gene encoding SR-BI. These mutations segregate with high HDL-C in family members of each proband and are associated with a 37% increase in plasma HDL-C in heterozygous individuals carrying them. Both mutations occur at highly conserved positions in the large extracellular loop region of SR-BI and are predicted to impair the function of the SR-BI protein. Our findings, combined with the prior report of a single mutation in the gene encoding SR-BI, further validate that mutations in SR-BI are a rare but recurring cause of elevated HDL-C in humans.

Founder mutations in the Netherlands: geographical distribution of the most prevalent mutations in the low-density lipoprotein receptor and apolipoprotein B genes.

BACKGROUND: In the Netherlands, a screening programme was set up in 1994 in order to identify all patients with familial hypercholesterolaemia (FH). After 15 years of screening, we evaluated the geographical distribution, possible founder effects and clinical phenotype of the 12 most prevalent FH gene mutations. METHODS: Patients who carried one of the 12 most prevalent mutations, index cases and those identified between 1994 and 2009 through the screening programme and whose postal code was known were included in the study. Low-density lipoprotein cholesterol (LDL-C) levels at the time of screening were retrieved. The prevalence of identified FH patients in each postal code area was calculated and visualised in different maps. RESULTS: A total of 10,889 patients were included in the study. Mean untreated LDL-C levels ranged from 4.4 to 6.4 mmol/l. For almost all mutations, a region of high prevalence could be observed. In total, 51 homozygous patients were identified in the Netherlands, of which 13 true homozygous for one of the 12 most prevalent mutations. The majority of them were living in high-prevalence areas for that specific mutation. CONCLUSIONS: Phenotypes with regard to LDL-C levels varied between the 12 most prevalent FH mutations. For most of these mutations, a founder effect was observed. Our observations can have implications with regard to the efficiency of molecular screening and physician's perception of FH and to the understanding of the prevalence and distribution of homozygous patients in the Netherlands.

Genome-wide association studies in atherosclerosis.

Cardiovascular disease remains the major cause of worldwide morbidity and mortality. Its pathophysiology is complex and multifactorial. Because the phenotype of cardiovascular disease often shows a marked heritable pattern, it is likely that genetic factors play an important role. In recent years, large genome-wide association studies have been conducted to decipher the molecular mechanisms underlying this heritable and prevalent phenotype. The emphasis of this review is on the recently identified 17 susceptibility loci for coronary artery disease. Implications of their discovery for biology and clinical medicine are discussed. A description of the landscape of human genetics in the near future in the context of next-generation sequence technologies is provided at the conclusion of this review.

Proteinuria in early childhood due to familial LCAT deficiency caused by loss of a disulfide bond in lecithin:cholesterol acyl transferase.

INTRODUCTION: Familial lecithin:cholesterol acyltransferase (LCAT) deficiency (FLD) is a rare recessive disorder of cholesterol metabolism characterized by the absence of high density lipoprotein (HDL) and the triad of corneal opacification, hemolytic anemia and glomerulopathy. PATIENTS: We here report on FLD in three siblings of a kindred of Moroccan descent with HDL deficiency. In all cases (17, 12 and 3 years of age) corneal opacification and proteinuria were observed. In the 17-year-old female proband, anemia with target cells was observed. RESULTS: Homozygosity for a mutation in LCAT resulted in the exchange of cysteine to tyrosine at position 337, disrupting the second disulfide bond in LCAT. LCAT protein and activity were undetectable in the patients' plasma and in media of COS7 cells transfected with an expression vector with mutant LCAT cDNA. Upon treatment with an ACE inhibitor and a thiazide diuretic, proteinuria in the proband decreased from 6g to 2g/24h. CONCLUSION: This is the first report that FLD can cause nephropathy at a very early age.

Long-term LDL-c lowering in heterozygous familial hypercholesterolemia normalizes carotid intima-media thickness.

OBJECTIVE: We investigated the effectiveness of statins in daily practice in reducing the arterial wall thicknesses by comparing the carotid intima-media thickness (cIMT) between statin-treated familial hypercholesterolemia (FH) patients and their unaffected spouses. METHODS: FH subjects treated with LDL-c lowering medication for at least 5 years and their unaffected spouses were included in this observational study. Clinical data and carotid intima-media thickness (cIMT) as surrogate marker for atherosclerosis were acquired. RESULTS: In total 40 FH patients, age 48.4±4.2 years, and their 40 unaffected spouses, age 47.4±3.9 years, were included. Pre-treatment total cholesterol levels of FH patients were on average 9.3±2.0 mmol/L. Treated FH patients and unaffected spouses exhibited similar LDL-c (3.8±1.5 vs. 3.5±1.1 mmol/L; p=0.25) and total cholesterol levels (5.8±1.6 vs. 5.6±1.1 mmol/L; p=0.56). Also, in a multivariate model cIMT adjusted for age and sex did not differ between affected and spouses (95% CI: -0.032 to 0.092 mm; p=0.34). CONCLUSION: Long-term statin treatment normalizes cIMT in severe FH patients and therefore it is likely that the extreme risk of cardiovascular disease in FH patients is significantly reduced by this therapy.

Increased prevalence of risk factors for cardiovascular disease in long-term survivors of acute lymphoblastic leukemia and Wilms tumor treated with radiotherapy.

BACKGROUND: Only a few studies have assessed cardiovascular risk factors (CRFs) in childhood cancer survivors. We determined the prevalence of CRFs in long-term survivors of acute lymphoblastic leukemia (ALL) and Wilms tumor. PROCEDURE: Adult survivors of ALL and Wilms tumor treated with radiotherapy and chemotherapy (RT + CT) or treated with chemotherapy alone (CT) were compared with sibling controls. CRFs (hypertension, diabetes mellitus, hypercholesterolemia, obesity, renal insufficiency) and hormonal deficiencies were assessed in each participant. Multivariate logistic regression analysis was used to evaluate the association between CRFs and treatment. RESULTS: Seventy-nine ALL, 62 Wilms tumor survivors, and 69 control subjects (mean ages 24.5, 25.9, and 26 years, respectively) were enrolled. Mean follow-up time since cancer treatment was 20.8 years. In the Wilms RT + CT group significantly more survivors had hypertension (21.6% vs. 1.4%, P < 0.001) and renal insufficiency (8.1% vs. 0%, P = 0.016) compared to controls. There were also more patients with multiple CRFs in the Wilms RT + CT group (16.2% vs. 2.9% in controls, P = 0.019). Almost 15% of ALL RT + CT survivors had growth hormone deficiency. Hypogonadism was seen in 18.9% of survivors in the Wilms RT + CT group. We observed no significant differences between CT-treated survivors of both malignancies and controls. The adjusted odds ratio for the occurrence of at least one CRF was 2.6 increased for survivors following abdominal radiotherapy. Treatment with CT alone was not associated with the occurrence of multiple CRFs. CONCLUSIONS: Long-term survivors of ALL and Wilms tumor have unfavorable CRFs due to previous RT not CT.

Cardiovascular outcomes and their relationships to lipoprotein components in patients with and without chronic kidney disease: results from the IDEAL trial.

OBJECTIVES: In Incremental Decrease in Endpoints through Aggressive Lipid-lowering (IDEAL), we compared cardiovascular outcomes in patients with and without chronic kidney disease (CKD) (estimated glomerular filtration rate <60 mL min(-1) 1.73 m(-2)) and analysed relationships between lipoprotein components (LC) and major coronary events (MCE) and other cardiovascular (CV) events. DESIGN: Exploratory analysis of CV endpoints in a randomized trial comparing high dose of atorvastatin to usual dose of simvastatin on MCE. SETTINGS: Patients with CKD were compared with the non-CKD patients. Cox regression models were used to study the relationships between on-treatment levels of LC and incident MCE. FINDINGS: Chronic kidney disease was strongly associated with cardiovascular end-points including total mortality. In patients with CKD, a significant benefit of high dose atorvastatin treatment was found for any CV events, stroke and peripheral artery disease, but not for MCE. However, all cardiovascular end-points except stroke and CV mortality were reduced in the non-CKD group. Differential changes in LC or relationships to LC could not explain the different treatment outcomes in MCE in the two groups. INTERPRETATION: Chronic kidney disease was a powerful risk factor for all cardiovascular end-points. The reason why the significant reductions achieved by high-dose statin treatment in most CV end-points in the non-CKD group were only in part matched by similar reductions in the CKD patients is not apparent. This difference did not result from differential changes in or relations to LC, but limited power may have increased the possibility of chance findings.