Adherence to statin treatment in patients with familial hypercholesterolemia: A dynamic prediction model

BACKGROUND

Statins are the primary therapy in patient with heterozygous familial hypercholesterolemia (HeFH). Non-adherence to statin therapy is associated with increased cardiovascular risk.

OBJECTIVE

We constructed a dynamic prediction model to predict statin adherence for an individual HeFH patient for each upcoming statin prescription.

METHODS

All patients with HeFH, identified by the Dutch Familial Hypercholesterolemia screening program between 1994 and 2014, were eligible. National pharmacy records dated between 1995 and 2015 were linked. We developed a dynamic prediction model that estimates the probability of statin adherence (defined as proportion of days covered >80%) for an upcoming prescription using a mixed effect logistic regression model. Static and dynamic patient-specific predictors, as well as data on a patient's adherence to past prescriptions were included. The model with the lowest AIC (Akaike Information Criterion) value was selected.

RESULTS

We included 1094 patients for whom 21,171 times a statin was prescribed. Based on the model with the lowest AIC, age at HeFH diagnosis, history of cardiovascular event, time since HeFH diagnosis and duration of the next statin prescription contributed to an increased adherence, while adherence decreased with higher untreated LDL-C levels and higher intensity of statin therapy. The dynamic prediction model showed an area under the curve of 0.63 at HeFH diagnosis, which increased to 0.85 after six years of treatment.

CONCLUSION

This dynamic prediction model enables clinicians to identify HeFH patients at risk for non-adherence during statin treatment. These patients can be offered timely interventions to improve adherence and further reduce cardiovascular risk.

Novel PCSK9 (Proprotein Convertase Subtilisin Kexin Type 9) Variants in Patients With Familial Hypercholesterolemia From Cape Town

OBJECTIVE

Familial hypercholesterolemia (FH) is characterized by elevated low-density lipoprotein-cholesterol and markedly increased cardiovascular risk. In patients with a genetic diagnosis, low-density lipoprotein receptor (LDLR) mutations account for >90% of cases, apolipoprotein B (APOB) mutations for ≈5% of cases, while proprotein convertase subtilisin kexin type 9 (PCSK9) gain of function mutations are rare (<1% of cases). We aimed to evaluate the functional impact of several novel PCSK9 variants in a cohort of patients with FH by genetic cascade screening and in vitro functionality assays. Approach and Results: Patients with clinically diagnosed FH underwent genetic analysis of LDLR, and if negative, sequential testing of APOB and PCSK9. We analyzed cosegregation of hypercholesterolemia with novel PCSK9 variants. Gain of function status was determined by in silico analyses and validated by in vitro functionality assays. Among 1055 persons with clinical FH, we identified nonsynonymous PCSK9 variants in 27 (2.6%) patients and 7 of these carried one of the 4 previously reported gain of function variants. In the remaining 20 patients with FH, we identified 7 novel PCSK9 variants. The G516V variant (c.1547G>T) was found in 5 index patients and cascade screening identified 15 additional carriers. Low-density lipoprotein-cholesterol levels were higher in these 15 carriers compared with the 27 noncarriers (236±73 versus 124±35 mg/dL; P<0.001). In vitro studies demonstrated the pathogenicity of the G516V variant.

CONCLUSIONS

In our study, 1.14% of cases with clinical FH were clearly attributable to pathogenic variants in PCSK9. Pathogenicity is established beyond doubt for the G516V variant.

Risk Factors for Cholecystectomy After Laparoscopic Roux-En-Y Gastric Bypass

BACKGROUND

Patients who have undergone bariatric surgery are at risk for subsequent cholecystectomy. We aimed to identify risk factors for cholecystectomy after laparoscopic Roux-en-Y gastric bypass (LRYGB).

METHODS

We conducted a retrospective case-control study of patients who underwent LRYGB between 2013 and 2015. Cases underwent cholecystectomy because of biliary symptoms after LRYGB. For each case, two controls were selected without subsequent cholecystectomy. Logistic regression analyses were used to identify risk factors.

RESULTS

Between 2013 and 2015, 1780 primary LRYGBs were performed. We identified 233 (13.1%) cases who had undergone cholecystectomy after a median (IQR) of 12 (8-17) months, and 466 controls. Female gender (OR (95% CI) 1.83 (1.06-3.17)), Caucasian ethnicity (OR (95% CI) 1.82 (1.10-3.02)), higher percent total weight loss (%TWL) at 12 months (OR (95% CI) 1.06 (1.04-1.09)), and preoperative pain syndrome (OR (95% CI) 2.72 (1.43-5.18)) were significantly associated with an increased risk for cholecystectomy. Older age (OR (95% CI) 0.98 (0.96-0.99)) and preoperative statin use were associated with a reduced risk (OR (95% CI) 0.56 (0.31-1.00)). A dose-effect relationship was found between the intensity of preoperative statin and risk for cholecystectomy.

CONCLUSIONS

In our study, higher %TWL and preoperative pain syndrome were associated with an increased risk for cholecystectomy besides the traditional risk factors female gender and Caucasian ethnicity. These factors can be used to identify high-risk patients, who might benefit from preventive measures. Whether statins can protect bariatric patients from developing gallstones should be investigated prospectively.

Determining When to Add Nonstatin Therapy: A Quantitative Approach

BACKGROUND

Costs and uncertainty about the benefits of nonstatin therapies limit their use.

OBJECTIVES

The authors sought to identify patients who might benefit from the addition of a nonstatin to background statin therapy.

METHODS

We performed systematic reviews of subgroup analyses from randomized trials and observational studies with statin-treated participants to determine estimated 10-year absolute risk of atherosclerotic cardiovascular disease (ASCVD) and to define high-risk and very high-risk patients. We used the relative risk reductions for the addition of a nonstatin to lower low-density lipoprotein (LDL-C) used to determine the number needed to treat (NNT) to prevent 1 ASCVD event over 5 years for each patient group and to allow comparisons with 5-year cost analyses.

RESULTS

The 10-year ASCVD risk is at least 30% (very high risk) for statin-treated participants with clinical ASCVD and comorbidities, and 20% to 29% (high risk) for those with ASCVD without comorbidities or who have heterozygous familial hypercholesterolemia. Adding ezetimibe to reduce low-density LDL-C by 20% would provide a 5-year NNT ≤50 for very high-risk patients with LDL-C ≥130 mg/dl or for high-risk patients with LDL-C ≥190 mg/dl, and an NNT ≤30 for very high-risk patients with LDL-C ≥160 mg/dl. Adding a PCSK9 monoclonal antibody to lower LDL-C by at least 50% would provide an NNT ≤50 for very high-risk and high-risk patients with LDL-C ≥70 mg/dl, and an NNT ≤30 for very high-risk and high-risk patients with an LDL-C ≥130 mg/dl.

CONCLUSIONS

Adding ezetimibe or PCSK9 monoclonal antibodies to maximally tolerated statin therapy may be cost effective in very high-risk and high-risk patients, depending on baseline LDL-C levels.

PCSK9 inhibition: the way forward in the treatment of dyslipidemia

Barely a decade after the discovery of the gene encoding proprotein convertase subtilisin/kexin type 9 (PCSK9) and its recognition as a key player in cholesterol metabolism, PCSK9 inhibition is now considered an exciting approach in the reduction of residual risk of cardiovascular disease. The progress from PCSK9 discovery to the development of targeted treatment has been unprecedented in terms of scale and speed. The first suggestion of a link between PCSK9 and hypercholesterolemia was published in 2003; a decade later, two meta-analyses of clinical trials comparing anti-PCSK9 treatment to placebo or ezetimibe, including >10,000 hypercholesterolemic individuals, were published. Currently, three PCSK9 inhibitors are being evaluated in clinical outcome trials and the results will determine the future of these lipid-lowering therapies by establishing their clinical efficacy in terms of cardiovascular event reduction, safety, and the consequences of prolonged exposure to very low levels of LDL-cholesterol. Irrespective of their outcomes, the exceptionally rapid development of these drugs exemplifies how novel technologies, genetic validation, and rapid clinical progression provide the tools to expedite the development of new drugs.

The impact of LDLR function on fibroblast growth factor 21 levels

CONTEXT

Fibroblast growth factor 21 (FGF21) has been described to have beneficial effects on glucose and lipid metabolism, and FGF21 analogs are currently evaluated in phase 1 trials. However, the complete spectrum of effects and regulators of FGF21 is yet partly elucidated. Recent studies have shown that FGF21 plays a role in transmembrane cholesterol transport.

OBJECTIVE

We set out to examine the association between FGF21 and LDLR mediated transmembrane cholesterol transport, by comparing FGF21 levels in patients with genetically impaired LDLR function and unaffected relatives. Secondly, we explored whether the severity of the LDLR mutation was associated with FGF21 levels.

METHODS

We performed a cross-sectional study in carriers of an LDLR mutation and their unaffected relatives. Subjects were eligible if they participated in the Dutch national screening program for familial hypercholesterolemia (FH), were 18-55 years old, and were carrier of a pathogenic LDLR mutation with an untreated LDL-C level below the 75(th) or above the 90(th) percentile of the general population, or did not carry an FH mutation. The outcome measure was the level of FGF21, which was assessed using ELISA.

RESULTS

We included 224 carriers of an LDLR mutation and 148 unaffected relatives. FGF21 levels were lower in LDLR mutation carriers compared to unaffected relatives (median [interquartile range]: 96.92 [60.80-174.05] versus 136.98 [77.34-219.47] pg/mL, respectively; p = 0.08), but after adjusting for potential confounders, there was no association between LDLR mutations and FGF21 levels (p = 0.70). Neither, did we find a relationship between the severity of LDLR mutations and FGF21 levels (p = 0.51, after adjustment for potential confounders).

CONCLUSIONS

We showed that levels of FGF21 are not different in patients with and without LDLR mutations, which suggests that decreased LDLR expression does not have a negative effect on FGF21 levels. Given the potential beneficial effects of FGF21 analogs on lipids and lipoproteins in a phase 1 study, we deem this of great interest for future treatment options for FH patients.

Inheritance pattern of familial hypercholesterolemia and markers of cardiovascular risk

Studies in children and adults have resulted in conflicting evidence in the quest for the answer to the hypothesis that offspring from hypercholesterolemic mothers might have an increased cardiovascular risk. Previous studies might have suffered from limitations such as cohort size and clinical sampling bias. We therefore explored this hypothesis in large cohorts of both subjects with familial hypercholesterolemia (FH) and unaffected siblings in a wide age range. In three cohorts (cohort 1: n = 1,988, aged 0-18 years; cohort 2: n = 300, 8-30 years; cohort 3: n = 369, 18-60 years), we measured lipid and lipoproteins as well as carotid intima-media thickness (c-IMT) in offspring from FH mothers versus FH fathers. For LDL cholesterol, triglycerides (TGs), and c-IMT, we performed a pooled analysis. No significant differences could be observed in c-IMT, lipid, or lipoprotein levels from offspring of FH mothers versus FH fathers. Pooled analyses showed no significant differences for either LDL cholesterol [mean difference 0.02 (-0.06,0.11) mmol/l, P = 0.60], TGs [mean difference 0.07 (0.00,0.14) mmol/l, P = 0.08], or c-IMT [mean difference -0.00 (-0.01,0.01) mm, P = 0.86]. Our data do not support the hypothesis that cardiovascular risk markers are different between offspring from FH mothers and FH fathers.

Real-time MSE measurements for current profile control on KSTAR

To step up from current day fusion experiments to power producing fusion reactors, it is necessary to control long pulse, burning plasmas. Stability and confinement properties of tokamak fusion reactors are determined by the current or q profile. In order to control the q profile, it is necessary to measure it in real-time. A real-time motional Stark effect diagnostic is being developed at Korean Superconducting Tokamak for Advanced Research for this purpose. This paper focuses on 3 topics important for real-time measurements: minimize the use of ad hoc parameters, minimize external influences and a robust and fast analysis algorithm. Specifically, we have looked into extracting the retardance of the photo-elastic modulators from the signal itself, minimizing the influence of overlapping beam spectra by optimizing the optical filter design and a multi-channel, multiharmonic phase locking algorithm.

Follow-up of children diagnosed with familial hypercholesterolemia in a national genetic screening program

OBJECTIVE

To assess the follow-up of children diagnosed as having familial hypercholesterolemia (FH) in the nationwide DNA-based cascade screening program (the Netherlands).

STUDY DESIGN

Questionnaires covering topics such as demographics, family history, physician consultation, and treatment were sent to parents of patients with FH (age 0-18 years), 18 months after diagnosis.

RESULTS

We retrieved 207 questionnaires of patients aged 10.9 ± 4.2 years (mean ± SD) at diagnosis; 48% were boys, and the mean low-density lipoprotein cholesterol (LDL-C) level at diagnosis was 167 ± 51 mg/dL. Of these patients, 164 (79%) consulted a physician: a general practitioner (35%), lipid-clinic specialist (27%), pediatrician (21%), internist (11%), or another physician (6%). LDL-C level at diagnosis and a positive family history for cardiovascular disease were independent predictors for physician consultation. Of the patients who visited a physician, 62% reported to have received lifestyle advice, and 43 (26%) were prescribed statin treatment. Independent predictors for medication use were age, LDL-C level, and educational level of parents.

CONCLUSION

The follow-up of children with FH after diagnosis established through cascade screening is inadequate. Better education of patients, parents, and physicians, with a structured follow-up after screening, should improve control of LDL-C levels and hence cardiovascular risk in children with FH.

Discriminative Ability of LDL-Cholesterol to Identify Patients With Familial Hypercholesterolemia

Background—

Screening for familial hypercholesterolemia (FH) within affected families is often based on cutoff values for low-density lipoprotein cholesterol (LDL-C). However, the diagnostic accuracy of LDL-C levels is influenced by the magnitude of the LDL-C overlap between FH patients and unaffected relatives. The purpose of the current study was to assess to what extent this overlap is influenced by the severity of specific FH mutations.

Methods and Results—

Individuals were eligible if they underwent family screening for FH between 2003 and 2010. The entire cohort was then compared with those who were investigated for the presence of the most severe mutations (class 1). The area under the receiver operating characteristics curve and the sensitivity of the 90th percentile of LDL-C were calculated for both cohorts. We included 26 406 individuals, of whom 9169 (35%) carried an FH-causing mutation. In the entire cohort at baseline, mean LDL-C was 4.63±1.44 mmol/L for FH carriers (n=5372) and 2.96±0.96 mmol/L for unaffected relatives (n=15 148); P <0.001. The corresponding operating characteristics curve (95% CI) was 86.6% (85.9%–87.2%), and the cutoff level of LDL-C above the 90th percentile showed a sensitivity of 68.5%. The operating characteristics curve and sensitivity significantly improved when the 5933 individuals tested for class 1 mutations were assessed separately; 96.2% (95.3%–97.1%) and 91.3%, respectively.

Conclusions—

In summary, the overlap in terms of LDL-C levels between those with molecularly proven FH and unaffected relatives is to a large extent because of the high prevalence of modestly severe LDL-receptor mutations in the Netherlands.

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.

Advances in genetics show the need for extending screening strategies for autosomal dominant hypercholesterolaemia

Aims Autosomal dominant hypercholesterolaemia (ADH) is a major risk factor for coronary artery disease. This disorder is caused by mutations in the genes coding for the low-density lipoprotein receptor (LDLR), apolipoprotein B (APOB), and proprotein convertase subtilisin/kexin 9 (PCSK9). However, in 41% of the cases, we cannot find mutations in these genes. In this study, new genetic approaches were used for the identification and validation of new variants that cause ADH. Methods and results Using exome sequencing, we unexpectedly identified a novel APOB mutation, p.R3059C, in a small-sized ADH family. Since this mutation was located outside the regularly screened APOB region, we extended our routine sequencing strategy and identified another novel APOB mutation (p.K3394N) in a second family. In vitro analyses show that both mutations attenuate binding to the LDLR significantly. Despite this, both mutations were not always associated with ADH in both families, which prompted us to validate causality through using a novel genetic approach. Conclusion This study shows that advances in genetics help increasing our understanding of the causes of ADH. We identified two novel functional APOB mutations located outside the routinely analysed APOB region, suggesting that screening for mutations causing ADH should encompass the entire APOB coding sequence involved in LDL binding to help identifying and treating patients at increased cardiovascular risk.

Cardiovascular risk in relation to functionality of sequence variants in the gene coding for the low-density lipoprotein receptor: a study among 29,365 individuals tested for 64 specific low-density lipoprotein-receptor sequence variants

AIMS

A plethora of mutations in the LDL-receptor gene (LDLR) underlie the clinical phenotype of familial hypercholesterolaemia (FH). For the diagnosis of FH, it is important, however, to discriminate between pathogenic and non-pathogenic mutations. The aim of the current study was to assess whether true pathogenic mutations were indeed associated with the occurrence of coronary artery disease (CAD) when compared with non-functional variants. The latter variants should not exhibit such an association with CAD.

METHODS AND RESULTS

We assessed 29 365 individuals tested the 64 most prevalent LDLR variants. First, we determined pathogenicity for each of these sequence variants. Subsequently, a Cox-proportional hazard model was used to compare event-free survival, defined as the period from birth until the first CAD event, between carriers and non-carriers of LDLR mutations. Fifty-four sequence variants in the LDLR gene were labelled as pathogenic and 10 as non-pathogenic. The 9 912 carriers of a pathogenic LDLR mutation had a shorter event-free survival than the 18 393 relatives who did not carry that mutation; hazard ratio 3.64 [95% confidence interval (CI): 3.24-4.08; P< 0.001]. In contrast, the 355 carriers of a non-pathogenic LDLR variant had similar event-free survival as the 705 non-carrying relatives; hazard ratio 1.00 (95% CI: 0.52-1.94; P= 0.999).

CONCLUSION

These findings with respect to clinical outcomes substantiate our criteria for functionality of LDLR sequence variants. They also confirm the CAD risk associated with FH and underline that these criteria can be used to decide whether a specific sequence variant should be used in cascade screening.

Factor VIII deficiency does not protect against atherosclerosis

BACKGROUND

Hemophilia A patients have a lower cardiovascular mortality rate than the general population. Whether this protection is caused by hypocoagulability or decreased atherogenesis is unclear.

OBJECTIVES

To evaluate atherosclerosis and endothelial function in hemophilia A patients with and without obesity as well as in matched, unaffected controls.

METHODS

Fifty-one obese (body mass index [BMI] ≥ 30 kg m(-2)) and 47 non-obese (BMI ≤ 25 kg m(-2)) hemophilia A patients, and 42 obese and 50 matched non-obese male controls were included. Carotid and femoral intima–media thickness [IMT] and brachial flow-mediated dilatation (FMD) were measured as markers of atherogenesis and endothelial function.

RESULTS

The overall population age was 50 ± 13 years. Carotid IMT was increased in obese subjects (0.77 ± 0.22 mm) as compared with non-obese subjects (0.69 ± 0.16 mm) [mean difference 0.07 mm (95% confidence interval [CI] 0.02–0.13, P = 0.008)]. No differences in mean carotid and femoral IMT between obese hemophilic patients and obese controls were found (mean difference of 0.02 mm [95% CI ) 0.07–0.11, P = 0.67], and mean difference of 0.06 mm [95% CI ) 0.13–0.25, P = 0.55], respectively). Thirty-five per cent of the obese hemophilic patients and 29% of the obese controls had an atherosclerotic plaque (P = 0.49), irrespective of the severity of hemophilia. Brachial FMD was comparable between obese hemophilic patients and obese controls (4.84% ± 3.24% and 5.32% ± 2.37%, P = 0.45).

CONCLUSION

Hemophilia A patients with obesity develop atherosclerosis to a similar extent as the general male population. Detection and treatment of cardiovascular risk factors in hemophilic patients is equally necessary.

Genetic variation in APOB, PCSK9, and ANGPTL3 in carriers of pathogenic autosomal dominant hypercholesterolemic mutations with unexpected low LDL-Cl Levels

Autosomal Dominant Hypercholesterolemia (ADH) is caused by LDLR and APOB mutations. However, genetically diagnosed ADH patients do not always exhibit the expected hypercholesterolemic phenotype. Of 4,669 genetically diagnosed ADH patients, identified through the national identification screening program for ADH, 75 patients (1.6%) had LDL-cholesterol (LDL-C) levels below the 50th percentile for age and gender prior to lipid-lowering therapy. The genes encoding APOB, PCSK9, and ANGPTL3 were sequenced in these subjects to address whether monogenic dominant loss-of-function mutations underlie this paradoxical phenotype. APOB mutations, resulting in truncated APOB, were found in five (6.7%) probands, reducing LDL-C by 56%. Rare variants in PCSK9, and ANGPTL3 completely correcting the hypercholesterolemic phenotype were not found. The common variants p.N902N, c.3842+82T>A, p.D2312D, and p.E4181K in APOB, and c.1863+94A>G in PCSK9 were significantly more prevalent in our cohort compared to the general European population. Interestingly, 40% of our probands carried at least one minor allele for all four common APOB variants compared to 1.5% in the general European population. While we found a low prevalence of rare variants in our cohort, our data suggest that regions in proximity of the analyzed loci, and linked to specific common haplotypes, might harbor additional variants that correct an ADH phenotype.

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.

Assessment of Carotid Atherosclerosis in Normocholesterolemic Individuals With Proven Mutations in the Low-Density Lipoprotein Receptor or Apolipoprotein B Genes

Background—

Genetic cascade screening for heterozygous familial hypercholesterolemia (FH) revealed that 15% of individuals given this diagnosis do not exhibit elevated low-density lipoprotein cholesterol (LDL-C) levels. We assessed whether cardiovascular risk for these individuals differs from that of hypercholesterolemic FH heterozygotes and unaffected relatives.

Methods and Results—

Individuals aged 18 to 55 years were recruited within 18 months after genetic screening. Three groups were studied: subjects given a molecular diagnosis of FH and with LDL-C levels at genetic screening below the 75th percentile (FH-low), subjects with FH and an LDL-C level above the 90th percentile (FH-high), and subjects without FH (no-FH). We measured carotid intima-media thickness (IMT) by ultrasonography. Differences in carotid IMT among the groups were assessed using multivariate linear regression analyses. Mean carotid IMT of 114 subjects in the FH-low group (0.623 mm; 95% CI, 0.609 to 0.638 mm) was significantly smaller than that of 162 subjects in the FH-high group (0.664 mm; 95% CI, 0.648 to 0.679 mm; P <0.001) and did not significantly differ from the mean carotid IMT in 145 subjects in the no-FH group (0.628 mm; 95% CI, 0.613 to 0.642 mm; P =0.67).

Conclusions—

Our findings suggest that the risk of cardiovascular disease in patients with FH to a large extent is related to LDL-C levels and not to the presence of a mutation per se. Consequently, this study cautiously suggests that individuals with an FH genotype without expression of hypercholesterolemia may not require a pharmaceutical intervention that is as aggressive as the standard for subjects with FH.

Molecular Basis of Autosomal Dominant Hypercholesterolemia

Background—

Autosomal dominant hypercholesterolemia (ADH) is characterized by elevated low-density lipoprotein cholesterol levels and premature cardiovascular disease. Mutations in the genes encoding for low-density lipoprotein receptor ( LDLR ), apolipoprotein B ( APOB ), and proprotein convertase subtilisin/kexin 9 ( PCSK9 ) underlie ADH. Nevertheless, a proportion of individuals who exhibit the ADH phenotype do not carry mutations in any of these 3 genes. Estimates of the percentage of such cases among the ADH phenotype vary widely. We therefore investigated a large pediatric population with an unequivocal ADH phenotype to assess the molecular basis of hereditary hypercholesterolemia and to define the percentage of individuals with unexplained dyslipidemia.

Methods and Results—

We enrolled individuals with low-density lipoprotein cholesterol levels above the 95th percentile for age and gender and an autosomal dominant inheritance pattern of hypercholesterolemia from a large referred pediatric cohort of 1430 children. We excluded children with thyroid dysfunction, nephrotic syndrome, autoimmune disease, liver disease, primary biliary cirrhosis, and obesity (body mass index >75th percentile for age and gender), as well as children referred via a cascade screening program and those from families with a known molecular diagnosis. Of the 269 children who remained after the exclusion criteria were applied, 255 (95%) carried a functional mutation ( LDLR , 95%; APOB , 5%).

Conclusion—

In the vast majority of children with an ADH phenotype, a causative mutation can be identified, strongly suggesting that most of the large-effect genes underlying ADH are known to date.

Functionality of sequence variants in the genes coding for the low-density lipoprotein receptor and apolipoprotein B in individuals with inherited hypercholesterolemia

Patients with familial hypercholesterolemia (FH) have elevated LDL-C levels, usually above the 90th percentile (P90) for age and gender. However, large-scale genetic cascade screening for FH showed that 15% of the LDL-receptor (LDLR) or Apolipoprotein B (APOB) mutation carriers have LDL-C levels below P75. Nonpathogenicity of sequence changes may explain this phenomenon. To assess pathogenicity of a mutation we proposed three criteria: (1) mean LDL-C 4P75 in untreated mutation carriers; (2) higher mean LDL-C level in untreated carriers than in untreated noncarriers; and (3) higher percentage of medication users in carriers than in noncarriers at screening. We considered a mutation nonpathogenic when none of the three criteria were met. We applied these criteria to mutations that had been determined in more than 50 untreated adults. Segregation analysis was performed to confirm nonpathogenicity. Forty-six mutations had been tested in more than 50 untreated subjects, and three were nonpathogenic according to our criteria: one in LDLR (c.108C4A, exon 2) and two in APOB (c.13154T4C and c.13181T4C, both in exon 29). Segregation analysis also indicated nonpathogenicity. According to our criteria, three sequence variants were nonpathogenic. The criteria may help to identify nonpathogenic sequence changes in genetic cascade screening programs.

Two years after molecular diagnosis of familial hypercholesterolemia: majority on cholesterol-lowering treatment but a minority reaches treatment goal

Background

The risk of premature cardiovascular disease in patients with familial hypercholesterolemia (FH) can be profoundly reduced by cholesterol-lowering therapy, and current guidelines for FH advocate ambitious low-density lipoprotein cholesterol (LDL-C) goals. In the present study, we determined whether these goals are reflected in current clinical practice once FH has been diagnosed.

Methodology/Principal Findings

In 2008, we sent questionnaires to all subjects (aged 18–65 years) who were molecularly diagnosed with FH in the year 2006 through the screening program in the Netherlands. Of these 1062 subjects, 781 completed the questionnaire (46% males; mean age: 42±12 years; mean LDL-C at molecular diagnosis (baseline): 4.1±1.3 mmol/L). The number of persons that used cholesterol-lowering therapy increased from 397 (51%) at baseline to 636 (81%) after diagnosis. Mean treated LDL-C levels decreased significantly to 3.2±1.1 mmol/L two years after diagnosis. Only 22% achieved the LDL-C target level of ≤2.5 mmol/L.

Conclusions/Significance

The proportion of patients using cholesterol-lowering medication was significantly increased after FH diagnosis through genetic cascade screening. The attained LDL-C levels were lower than those reported in previous surveys on medication use in FH, which could reflect the effect of more stringent lipid target levels. However, only a minority of the medication users reached the LDL-C target.

Venous thrombosis is associated with hyperglycemia at diagnosis: a case-control study

BACKGROUND

Patients with (undiagnosed) diabetes mellitus, impaired glucose tolerance or stress-induced hyperglycemia may be at greater risk for venous thrombosis and present with relative hyperglycemia during the thrombotic event.

OBJECTIVES

To assess whether venous thrombosis is associated with hyperglycemia at diagnosis.

PATIENTS/METHODS

We performed a case-control study, derived from a cohort of consecutive patients referred for suspected deep vein thrombosis. Cases were patients with confirmed symptomatic venous thrombosis of the lower extremity. Controls were randomly selected in a 1 : 2 ratio from individuals in whom this diagnosis was excluded. We measured plasma glucose levels upon presentation to the hospital.

RESULTS

In total, 188 patients with thrombosis and 370 controls were studied. The glucose cut-off levels for the first to fourth quartiles were as follows: first quartile, < 5.3 mmol L(-1); second quartile, 5.3-5.7 mmol L(-1); third quartile, 5.7-6.6 mmol L(-1); and fourth quartile, >or= 6.6 mmol L(-1). When adjusted for body mass index, a known history of diabetes mellitus, age, sex, ethnicity and whether known risk factors for deep vein thrombosis were present, the odds ratios for deep vein thrombosis in the second, third and fourth quartiles of glucose levels as compared with the first quartile were 1.59 [95% confidence interval (CI) 0.89-2.85], 2.04 (95% CI 1.15-3.62) and 2.21 (95% CI 1.20-4.05), respectively; P for trend = 0.001.

CONCLUSIONS

Increased glucose levels measured at presentation were associated with venous thrombosis. Experimental evidence supports a potential causal role for hyperglycemia in this process. As this is the first report on the association between (stress) hyperglycemia and venous thrombosis, confirmation in other studies is required.

Hip surgery sequentially induces stress hyperglycaemia and activates coagulation

BACKGROUND

A frequent complication of orthopaedic procedures is venous thromboembolism (VTE ). Hyperglycaemia has been shown to activate the coagulation system and is associated with postoperative morbidity and mortality. Therefore, we hypothesised that glucose levels increase during orthopaedic surgery and are associated with an activation of the coagulation system.

METHODS

Nine adult patients undergoing elective hip replacement were included. Venous blood samples were taken before, during and after surgery. Plasma glucose levels, factor VIII clotting activity (fVIII:c), von Willebrand ristocetin cofactor activity, von Willebrand factor antigen and prothrombin fragment 1+2 were measured.

RESULTS

Immediately after induction of anaesthesia, plasma glucose levels started to increase until the second day postoperatively (peak 8.0 mmol/l). After seven weeks glucose values had returned to baseline (6.1 mmol/l), p<0.001 with ANOVA. All coagulation parameters increased during surgery, subsequent to the rise in glucose. The change in mean FVIII:c and von Willebrand ristocetin cofactor activity was significantly correlated with mean glucose values.

CONCLUSIONS

These observations indicate that total hip replacement surgery causes an increase in glucose levels that precedes the proportional rise of the measured coagulation parameters. This suggests a possible role of glucose in the activation of the coagulation system during hip surgery.