Molecular genetics in 1991 arrhythmia probands and 2782 relatives in Norway: Results from 17 years of genetic testing in a national laboratory.

The aim of this study was to explore the prevalence of likely pathogenic or pathogenic variants and assess the diagnostic yield from genetic testing for cardiac arrhythmias in Norway since 2003. Data from 1991 probands and 2782 relatives were retrospectively collected from the laboratory information management system at Unit for Cardiac and Cardiovascular Genetics, Oslo University hospital. Of 1991 probands, 57.4% were females, age at genetic testing was 33.1 (±22.7) years, and 32.5% were under the age of 18. A likely pathogenic or pathogenic variant (including 14 novel) was detected in 15.4% in total. Of the 2782 relatives, 53.7% were females, age at genetic testing was 35.6 (±22.5) years, 27.3% were under the age of 18, and 45.3% carried the family variant. Probands and relatives combined, 1/3356 persons in the Norwegian population were heterozygous for an arrhythmia-causing variant. The founder variant p.Q530X (NM_000218.2: c.1588C>T) in KCNQ1 accounted for 34% of all variants in Norway. In conclusion, genetic testing provided a genetic basis of the arrhythmia in 15.4% of the probands. Familial cascade screening identified four times as many variant-positive relatives, allowing early detection and prompt stratification of arrhythmic risk of those variant carriers.

Flavonoids regulate LDLR through different mechanisms tied to their specific structures.

Flavonoids, polyphenolic compounds found in plant-based diets, are associated with reduced risk of cardiovascular disease and longevity. These components are reported to reduce plasma levels of low-density lipoprotein (LDL) through an upregulation of the LDL receptor (LDLR), but the mechanism is still largely unknown. In this study, we have systematically screened the effect of 12 flavonoids from six different flavonoid subclasses on the effect on LDLR. This paper provides an in-depth analysis on how these flavonoids affect LDLR regulation and functionality. We found that most but not all of the tested flavonoids increased LDLR mRNA levels. Surprisingly, this increase was attributed to different regulatory mechanisms, such as enhanced LDLR promoter activity, LDLR mRNA stabilization, or LDLR protein stabilization, of which specific effectual parts of the flavonoid molecular structure could be assigned. These types of comparative analysis of various flavonoids enhance clarity and deepen the understanding of how the different structures of flavonoids affect LDLR regulation. Our data offer useful insights that may guide future research in developing therapeutic approaches for cardiovascular health.

Functional characterization of missense variants affecting the extracellular domains of ABCA1 using a fluorescence-based assay.

Excess cholesterol originating from nonhepatic tissues is transported within HDL particles to the liver for metabolism and excretion. Cholesterol efflux is initiated by lipid-free or lipid-poor apolipoprotein A1 interacting with the transmembrane protein ABCA1, a key player in cholesterol homeostasis. Defective ABCA1 results in reduced serum levels of HDL cholesterol, deposition of cholesterol in arteries, and an increased risk of early onset CVD. Over 300 genetic variants in ABCA1 have been reported, many of which are associated with reduced HDL cholesterol levels. Only a few of these have been functionally characterized. In this study, we have analyzed 51 previously unclassified missense variants affecting the extracellular domains of ABCA1 using a sensitive, easy, and low-cost fluorescence-based assay. Among these, only 12 variants showed a distinct loss-of-function phenotype, asserting their direct association with severe HDL disorders. These findings emphasize the crucial role of functional characterization of genetic variants in pathogenicity assessment and precision medicine. The functional rescue of ABCA1 loss-of-function variants through proteasomal inhibition or by the use of the chemical chaperone 4-phenylbutyric acid was genotype specific. Genotype-specific responses were also observed for the ability of apolipoprotein A1 to stabilize the different ABCA1 variants. In view of personalized medicine, this could potentially form the basis for novel therapeutic strategies.

Molecular genetic testing and measurement of levels of GPIHBP1 autoantibodies in patients with severe hypertriglyceridemia: The importance of identifying the underlying cause of hypertriglyceridemia.

BACKGROUND: Severe hypertriglyceridemia can be caused by pathogenic variants in genes encoding proteins involved in the metabolism of triglyceride-rich lipoproteins. A key protein in this respect is lipoprotein lipase (LPL) which hydrolyzes triglycerides in these lipoproteins. Another important protein is glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1 (GPIHBP1) which transports LPL to the luminal side of the endothelial cells. OBJECTIVE: Our objective was to identify a genetic cause of hypertriglyceridemia in 459 consecutive unrelated subjects with levels of serum triglycerides ≥20 mmol/l. These patients had been referred for molecular genetic testing from 1998 to 2021. In addition, we wanted to study whether GPIHBP1 autoantibodies also were a cause of hypertriglyceridemia. METHODS: Molecular genetic analyses of the genes encoding LPL, GPIHBP1, apolipoprotein C2, lipase maturation factor 1 and apolipoprotein A5 as well as apolipoprotein E genotyping, were performed in all 459 patients. Serum was obtained from 132 of the patients for measurement of GPIHBP1 autoantibodies approximately nine years after molecular genetic testing was performed. RESULTS: A monogenic cause was found in four of the 459 (0.9%) patients, and nine (2.0%) patients had dyslipoproteinemia due to homozygosity for apolipoprotein E2. One of the 132 (0.8%) patients had GPIHBP1 autoantibody syndrome. CONCLUSION: Only 0.9% of the patients had monogenic hypertriglyceridemia, and only 0.8% had GPIHBP1 autoantibody syndrome. The latter figure is most likely an underestimate because serum samples were obtained approximately nine years after hypertriglyceridemia was first identified. There is a need to implement measurement of GPIHBP1 autoantibodies in clinical medicine to secure that proper therapeutic actions are taken.

Variants in the CETP gene affect levels of HDL cholesterol by reducing the amount, and not the specific lipid transfer activity, of secreted CETP.

BACKGROUND: Cholesteryl ester transfer protein (CETP) transfers cholesteryl esters in plasma from high density lipoprotein (HDL) to very low density lipoprotein and low density lipoprotein. Loss-of-function variants in the CETP gene cause elevated levels of HDL cholesterol. In this study, we have determined the functional consequences of 24 missense variants in the CETP gene. The 24 missense variants studied were the ones reported in the Human Gene Mutation Database and in the literature to affect HDL cholesterol levels, as well as two novel variants identified at the Unit for Cardiac and Cardiovascular Genetics, Oslo University Hospital in subjects with hyperalphalipoproteinemia. METHODS: HEK293 cells were transiently transfected with mutant CETP plasmids. The amounts of CETP protein in lysates and media were determined by Western blot analysis, and the lipid transfer activities of the CETP variants were determined by a fluorescence-based assay. RESULTS: Four of the CETP variants were not secreted. Five of the variants were secreted less than 15% compared to the WT-CETP, while the other 15 variants were secreted in varying amounts. There was a linear relationship between the levels of secreted protein and the lipid transfer activities (r = 0.96, p<0.001). Thus, the secreted variants had similar specific lipid transfer activities. CONCLUSION: The effect of the 24 missense variants in the CETP gene on the lipid transfer activity was mediated predominantly by their impact on the secretion of the CETP protein. The four variants that prevented CETP secretion cause autosomal dominant hyperalphalipoproteinemia. The five variants that markedly reduced secretion of the respective variants cause mild hyperalphalipoproteinemia. The majority of the remaining 15 variants had minor effects on the secretion of CETP, and are considered neutral genetic variants.

Missense mutation Q384K in the APOB gene affecting the large lipid transfer module of apoB reduces the secretion of apoB-100 in the liver without reducing the secretion of apoB-48 in the intestine.

BACKGROUND: Molecular genetic testing of patients with hypobetalipoproteinemia may identify a genetic cause that can form the basis for starting proper therapy. Identifying a genetic cause may also provide novel data on the structure-function relationship of the mutant protein. OBJECTIVE: To identify a genetic cause of hypobetalipoproteinemia in a patient with levels of low density lipoprotein cholesterol at the detection limit of 0.1 mmol/l. METHODS: DNA sequencing of the translated exons with flanking intron sequences of the genes adenosine triphosphate-binding cassette transporter 1, angiopoietin-like protein 3, apolipoprotein B, apolipoprotein A1, lecithin-cholesterol acyltransferase, microsomal triglyceride transfer protein and proprotein convertase subtilisin/kexin type 9. RESULTS: The patient was homozygous for mutation Q384K (c.1150C>A) in the apolipoprotein B gene, and this mutation segregated with hypobetalipoproteinemia in the family. Residue Gln384 is located in the large lipid transfer module of apoB that has been suggested to be important for lipidation of apolipoprotein B through interaction with microsomal triglyceride transfer protein. Based on measurements of serum levels of triglycerides and apolipoprotein B-48 after an oral fat load, we conclude that the patient was able to synthesize apolipoprotein B-48 in the intestine in a seemingly normal fashion. CONCLUSION: Our data indicate that mutation Q384K severely reduces the secretion of apolipoprotein B-100 in the liver without reducing the secretion of apolipoprotein B-48 in the intestine. Possible mechanisms for the different effects of this and other missense mutations affecting the large lipid transfer module on the two forms of apoB are discussed.

The risk of various types of cardiovascular diseases in mutation positive familial hypercholesterolemia; a review.

Familial hypercholesterolemia (FH) is a common, inherited disease characterized by high levels of low-density lipoprotein Cholesterol (LDL-C) from birth. Any diseases associated with increased LDL-C levels including atherosclerotic cardiovascular diseases (ASCVDs) would be expected to be overrepresented among FH patients. There are several clinical scoring systems aiming to diagnose FH, however; most individuals who meet the clinical criteria for a FH diagnosis do not have a mutation causing FH. In this review, we aim to summarize the literature on the risk for the various forms of ASCVD in subjects with a proven FH-mutation (FH+). We searched for studies on FH+ and cardiovascular diseases and also included our and other groups published papers on FH + on a wide range of cardiovascular and other diseases of the heart and vessels. FH + patients are at a markedly increased risk of a broad range of ASCVD. Acute myocardial infarction (AMI) is the most common in absolute numbers, but also aortic valve stenosis is by far associated with the highest excess risk. Per thousand patients, we observed 3.6 incident AMI per year compared to 1.9 incident aortic valve stenosis, however, standardized incidence ratio (SIR) for incident AMI was 2.3 compared to 7.9 for incident aortic valve stenosis. Further, occurrence of ischemic stroke seems not to be associated with increased risk in FH+. Clinicians should be aware of the excess risk of almost all kind of ASCVD in FH+, and the neutral risk of stroke need to be studied further in FH + patients.

Risk of stroke in genetically verified familial hypercholesterolemia: A prospective matched cohort study.

BACKGROUND AND AIMS: Individuals with familial hypercholesterolemia (FH), causing severely elevated LDL-C, are expected to have a higher risk of ischemic stroke. The risk of hemorrhagic stroke and impact of statin use are, however, not known. We aimed to investigate the risk of incident total, ischemic and hemorrhagic stroke in individuals with FH compared to controls, and to explore the association between cumulative statin use and risk of total stroke in FH. METHODS: This prospective cohort study consists of 4186 individuals with genetically verified FH and 82 180 age and sex matched controls followed from 2008 to 2018 for incident stroke. Daily defined doses (DDD) described cumulative statin exposure: 0-5000 DDD ("low"), 5000-10,000 DDD ("intermediate"), and >10 000 DDD ("high"). Results were presented as hazard ratio (95% CI) derived from Cox proportional hazards models. RESULTS: Individuals with FH did not have a higher risk of total stroke (1.16 (0.95-1.43) nor ischemic stroke (1.11 (0.88-1.38). Excess risk of hemorrhagic stroke was observed (1.63 (1.07, 2.48) but attenuated after adjusting for antithrombotic medication (1.25 (0.81, 1.93). Among individuals with FH, there was no association between statin use and total stroke for intermediate vs. low DDD [0.69 (0.32, 1.48)] or for high vs. low DDD [0.83 (0.41, 1.67)]. CONCLUSIONS: No significant excess risk of incident total and ischemic stroke in FH, and no difference in total stroke risk among the FH population with low, intermediate, and high statin exposure were observed. The observed relationship between FH and hemorrhagic stroke was no longer significant after adjusting for use of anti-thrombotic medication.

Cascade screening for familial hypercholesterolemia should be organized at a national level.

PURPOSE OF REVIEW: Patients with familial hypercholesterolemia (FH) have a markedly increased risk of premature cardiovascular disease. However, there are effective lipid-lowering therapies available to reduce the risk of cardiovascular disease. This makes it important to diagnose these patients. The most cost-effective strategy to diagnose patients with FH is to perform cascade screening. However, cascade screening as part of ordinary healthcare has not been very successful. Thus, there is a need to implement more efficient cascade screening strategies. RECENT FINDINGS: Cascade screening for FH should be organized at a national level and should be run by dedicated health personnel such as genetic counsellors. As part of a national organization a national registry of patients with FH needs to be established. Moreover, for cascade screening to be effective, diagnosis of FH must be based on identifying the underlying mutation. There should preferably only be one genetics centre in each country for diagnosing FH, and this genetics centre should be an integrated part of the national cascade screening program. SUMMARY: Cascade screening for FH is very effective and should be organized at a national level. Even a modest national cascade screening program can result in a large number of patients being identified.

Molecular genetics in 4408 cardiomyopathy probands and 3008 relatives in Norway: 17 years of genetic testing in a national laboratory.

AIMS: To describe results from genetic testing for cardiomyopathies in a national laboratory for genetic testing in Norway since 2003. METHODS AND RESULTS: Retrospective data collection from the laboratory information management system at Unit for Cardiac and Cardiovascular Genetics, Oslo University hospital. Data from 4408 probands and 3008 relatives were available. Three probands had two variants, nine had incidental findings of variants not related to their cardiomyopathy diagnosis. Of the remaining 4396 probands, 65.1% were males, age at genetic testing was 50.9 (±18.1) years and 6.1% were under the age of 18. A likely pathogenic or pathogenic variant (216 different variants including 67 novel) was detected in 574 probands, corresponding to a hit-rate of genetic testing of 13.1% in total, 11.9% in hypertrophic, 14.1% in dilated, and 14.9% in arrhythmogenic right ventricular cardiomyopathy. Of the 3008 relatives, 47.6 % were males, age at genetic testing was 39.3 (±20.5) years, 17.9% were under the age of 18, and 43.2% were positive for the variant found in their family. Probands and relatives combined, 1/2809 persons in Norway were found to be heterozygous for a cardiomyopathy variant. Next Generation Sequencing provided more findings in dilated cardiomyopathy, especially in TTN accounting for 44.2% of all variants. Otherwise, the majority of variants were found in the classical sarcomeric and desmosomal genes. CONCLUSION: Genetic testing provided a genetic basis of the cardiomyopathy in 13.1% of probands, and subsequent family testing identified almost three times as many variant-positive relatives which could be offered preventive follow-up.

Association of Familial Hypercholesterolemia and Statin Use With Risk of Dementia in Norway.

Importance: Hypercholesterolemia, which is a cardiovascular risk factor, may also be associated with dementia risk. The benefit of statin treatment on dementia risk is controversial. Objective: To determine whether individuals with familial hypercholesterolemia (FH), who have been exposed to lifelong hypercholesterolemia, have an excess risk of dementia and whether statin use is associated with dementia risk. Design, Setting, and Participants: This was a prospective cohort study performed from 2008 to 2018 in Norway. Statistical analysis was performed from January 2021 to February 2022. This study included individuals with genetically verified FH and age-matched and sex-matched controls obtained from the general Norwegian population. Exposures: Dementia was defined according to International Statistical Classification of Diseases and Related Health Problems, Tenth Revision codes F00-03 and G30. Main Outcomes and Measures: Incident cases of total dementia, vascular dementia, Alzheimer disease-dementia in Alzheimer disease, and data on lipid-lowering medication were obtained from the Norwegian Patient Registry, Cause of Death Registry, and the Norwegian Prescription Database. Hazard ratios (HRs) for risk of dementia for individuals with FH vs matched controls were calculated using Cox regression. The cumulative sum of defined daily doses (DDDs) of statins prescribed during study follow-up was calculated for individuals with FH and was analyzed as a time-varying covariate with 3 levels: 1 to 4999 DDDs, 5000 to 10 000 DDDs, and more than 10 000 DDDs. Results: Among the 3520 individuals with FH (1863 women [52.9%]; mean [SD] age at the start of follow-up, 51.8 [11.5] years) and the 69 713 controls (36 958 women [53.0%]; mean [SD] age at the start of follow-up, 51.7 [11.5] years), 62 patients with FH (39 women [62.9%]) and 1294 controls (801 women [61.9%]) had developed dementia over the course of 10 years of follow-up. Most dementia cases occurred among individuals aged 70 years and older (39 patients with FH [62.9%] and 870 patients [67.2%] in the control group). We found no excess risk of dementia in patients with FH vs matched controls (HR for total dementia, 0.9; 95% CI, 0.7-1.2). There was no association between cumulative DDDs of statins and total dementia in patients with FH with HRs of 1.2 (95% CI, 0.4-3.8) for cumulative DDDs of 5000 to 10 000 and 1.9 (95% CI, 0.7-5.0) for cumulative DDDs greater than 10 000. Conclusions and Relevance: These findings suggest that individuals with FH have no excess risk of dementia compared with age-matched and sex-matched controls and that there is no association between use of statins and risk of dementia in patients with FH.

The importance of cascade genetic screening for diagnosing autosomal dominant hypercholesterolemia: Results from twenty years of a national screening program in Norway.

BACKGROUND: The most cost-effective strategy to diagnose patients with autosomal dominant hypercholesterolemia (ADH) is to perform cascade genetic screening. OBJECTIVE: To present the cascade genetic screening program for ADH in Norway. METHODS: A national cascade genetic screening program for ADH in Norway has been operating at Unit for Cardiac and Cardiovascular Genetics, Oslo University Hospital for twenty years. This program has been run by just one genetic counsellor. We now present the main findings of this cascade genetic screening program. RESULTS: After genetic counselling, 8182 at-risk relatives have consented to genetic testing for the mutation that causes ADH in the family. Of these, 3076 (37.6%) relatives have tested positive. Among mutation-positive relatives 31.3% were on lipid-lowering therapy at the time of genetic testing. However, only 9.8% of these relatives had a value for low density lipoprotein (LDL) cholesterol below 2.5 mmol/l (97 mg/dl). At follow-up six months after genetic testing, reductions in the levels of total serum cholesterol and LDL cholesterol of 12% and 17%, respectively were observed. A total of 8811 ADH heterozygotes have been diagnosed in Norway. Thus, the number of patients diagnosed by this modest cascade genetic screening program constitutes 35% of all Norwegian ADH patients provided with a molecular genetic diagnosis. CONCLUSION: Cascade genetic screening for ADH is very effective and should be organized at a national level. Even a modest cascade genetic screening program with small resources, can result in a large number of patients being identified.

Molecular genetic testing for autosomal dominant hypercholesterolemia in 29,449 Norwegian index patients and 14,230 relatives during the years 1993-2020.

BACKGROUND AND AIMS: In this study, we present the status regarding molecular genetic testing for mutations in the genes encoding the low density lipoprotein receptor (LDLR), apolipoprotein B (APOB) and proprotein convertase subtilisin/kexin type 9 (PCSK9) as causes of autosomal dominant hypercholesterolemia (ADH) in Norway. METHODS: We have extracted data from the laboratory information management system at Unit for Cardiac and Cardiovascular Genetics, Oslo University Hospital for the period 1993-2020. This laboratory is the sole laboratory performing molecular genetic testing for ADH in Norway. RESULTS: A total of 29,449 unrelated hypercholesterolemic patients have been screened for mutations in the LDLR gene, in the APOB gene and in the PCSK9 gene. Of these, 2818 (9.6%) were heterozygotes and 11 were homozygotes or compound heterozygotes. Most of the 264 different mutations identified were found in the LDLR gene. Only two and three mutations were found in the APOB gene or in the PCSK9 gene, respectively. Several founder mutations were identified. After testing of 14,230 family members, a total of 8811 heterozygous patients have been identified. Of these, 94.0% had a mutation in the LDLR gene, 5.4% had a mutation in the APOB gene and 0.6% had a mutation in the PCSK9 gene. CONCLUSIONS: A large proportion of Norwegian ADH patients have been provided with a molecular genetic diagnosis. Norway is probably only second to the Netherlands in this respect. A molecular genetic diagnosis may form the basis for starting proper preventive measures and for identifying affected family members by cascade genetic screening.

2.5-fold increased risk of recurrent acute myocardial infarction with familial hypercholesterolemia.

BACKGROUND AND AIMS: A first-time acute myocardial infarction (AMI) is a severe diagnosis that leads to initiation or intensification of lipid-lowering medication to prevent recurrent events. Individuals with familial hypercholesterolemia (FH) already use high-intensity lipid-lowering medication at the time of an incident AMI due to their diagnosis. Hence, we hypothesized that compared with matched non-FH controls, individuals with genetically verified FH have increased mortality and risk of recurrent AMI after their first event. METHODS: The study population comprised 4871 persons with genetically verified FH, and 96,251 age and sex matched controls randomly selected from the Norwegian population. Data were obtained from the Cardiovascular Disease in Norway Project, the Norwegian Patient Registry and the Norwegian Cause of Death Registry. Incidence of AMI, all-cause mortality and recurrent AMI after incident AMI were analyzed for the period 2001-2017. Incidence and mortality were compared using hazard ratios (HR) from Cox regression. Risk of recurrent AMI was compared using sub-hazard ratios (SHR) from competing risk regression with death as a competing event. RESULTS: We identified 232 individuals with FH and 2118 controls with an incident AMI [HR 2.10 (95% CI 1.83-2.41)]. Among survivors ≥29 days after the incident AMI, both mortality [HR = 1.45 (95% CI: 1.07-1.95)] and recurrent AMI [SHR = 2.53 (95% CI: 1.88-3.41)] were significantly increased among individuals with FH compared with non-FH controls. CONCLUSIONS: Individuals with FH have increased mortality and increased risk of recurrent AMI after the first AMI event compared with controls. These findings call for intensive follow-up of individuals with FH following an AMI.

Prevalence of genetically verified familial hypercholesterolemia among young (<45 years) Norwegian patients hospitalized with acute myocardial infarction.

BACKGROUND: Patients with familial hypercholesterolemia (FH) have an increased risk of premature myocardial infarction (MI). OBJECTIVES: The objective of the study is to investigate the prevalence of FH among young patients hospitalized with acute MI. METHODS: Data were collected from medical charts of all patients aged <45 years admitted with acute MI to the Department of Cardiology, Oslo University Hospital Ullevål, in the period 2012 to 2016. Patients who had not already been genetically tested for FH were contacted and offered genetic testing if the pretreatment or the statin-adjusted low-density lipoprotein cholesterol level was >4.0 mmol/L (155 mg/dL). RESULTS: Of 9332 patients admitted with acute MI, 357 were aged <45 years. Sixteen patients were deceased, and 13 patients did not have MI on an atherosclerotic basis. Of the remaining 328 patients eligible for investigation, 130 had the pretreatment or statin-adjusted low-density lipoprotein cholesterol level >4.0 mmol/L (155 mg/dL). Of these, data from 52 patients genetically tested for FH were available. Eleven patients had genetically verified FH constituting 3.4% of the total eligible population (n = 328), 8.5% of those with indications for genetic testing (n = 130), and 21.2% of those actually tested (n = 52). A Dutch Lipid Clinic Network score for clinical FH diagnosis of "definite FH" identified only 5 of the 11 patients with positive genetic test (45%). Including a score of "probable FH" identified all patients with FH but also 17 of the 41 patients (41%) with a negative genetic test. CONCLUSION: The prevalence of FH in young patients with acute MI was higher than in the general population. Routine evaluation of FH diagnosis among these patients could identify more patients with FH, thereby increasing the possibility of initiating early and adequate treatment also among affected relatives.

Lysosomal acid lipase does not have a propeptide and should not be considered being a proprotein.

Lysosomal acid lipase (LAL) plays an important role in lipid metabolism by performing hydrolysis of triglycerides and cholesteryl esters in the lysosome. Based upon characteristics of LAL purified from human liver, it has been proposed that LAL is a proprotein with a 55 residue propeptide that may be essential for proper folding, intracellular transport, or enzymatic function. However, the biological significance of such a propeptide has not been fully elucidated. In this study, we have performed a series of studies in cultured HepG2 and HeLa cells to determine the role of the putative propeptide. However, by Western blot analysis and subcellular fractionation, we have not been able to identify a cleaved LAL lacking the N-terminal 55 residues. Moreover, mutating residues surrounding the putative cleavage site at Lys76 ↓ in order to disrupt a proteinase recognition sequence, did not affect LAL activity. Furthermore, forcing cleavage at Lys76 ↓ by introducing the optimal furin cleavage site RRRR↓EL between residues 76 and 77, did not affect LAL activity. These data, in addition to bioinformatics analyses, indicate that LAL is not a proprotein. Thus, it is possible that the previously reported cleavage at Lys76 ↓ could have resulted from exposure to proteolytic enzymes during the multistep purification procedure.

Bone morphogenetic protein 1 cleaves the linker region between ligand-binding repeats 4 and 5 of the LDL receptor and makes the LDL receptor non-functional.

The cell-surface low-density lipoprotein receptor (LDLR) internalizes low-density lipoprotein (LDL) by receptor-mediated endocytosis and plays a key role in the regulation of plasma cholesterol levels. The ligand-binding domain of the LDLR contains seven ligand-binding repeats of approximately 40 residues each. Between ligand-binding repeats 4 and 5, there is a 10-residue linker region that is subject to enzymatic cleavage. The cleaved LDLR is unable to bind LDL. In this study, we have screened a series of enzyme inhibitors in order to identify the enzyme that cleaves the linker region. These studies have identified bone morphogenetic protein 1 (BMP1) as being the cleavage enzyme. This conclusion is based upon the use of the specific BMP1 inhibitor UK 383367, silencing of the BMP1 gene by the use of siRNA or CRISPR/Cas9 technology and overexpression of wild-type BMP1 or the loss-of-function mutant E214A-BMP1. We have also shown that the propeptide of BMP1 has to be cleaved at RSRR120↓ by furin-like proprotein convertases for BMP1 to have an activity towards the LDLR. Targeting BMP1 could represent a novel strategy to increase the number of functioning LDLRs in order to lower plasma LDL cholesterol levels. However, a concern by using BMP1 inhibitors as cholesterol-lowering drugs could be the risk of side effects based on the important role of BMP1 in collagen assembly.

Lower risk of smoking-related cancer in individuals with familial hypercholesterolemia compared with controls: a prospective matched cohort study.

According to guidelines, individuals with familial hypercholesterolemia (FH) shall receive lifestyle intervention and intensive lipid-lowering treatment from early in life to reduce the risk of coronary heart disease. Our aim was to study if treatment of FH also could affect risk of lifestyle-related cancer. We presented cumulative incidence of total cancer and lifestyle-related cancer sites in individuals with genetically verified FH (n = 5531) compared with age and sex matched controls (n = 108354). Individuals with FH had 20% lower risk of smoking-related cancer compared with the control population [HR 0.80 (95% CI, 0.65-0.98)], in particular men with FH at 40-69 years at age of diagnosis with HR 0.69 (95% CI, 0.49-0.97). The FH population and controls had similar rates of total cancer [HR 0.97 (95% CI, 0.86-1.09)], cancer related to poor diet [HR 0.82 (95% CI, 0.59-1.15)], cancer related to physical inactivity [HR 0.93 (95% CI, 0.73-1.18)], alcohol-related cancer [HR 0.98 (95% CI, 0.80-1.22)] and cancer related to obesity [HR 1.03 (95% CI, 0.89-1.21)]. In summary, we found reduced risk of smoking-related cancer in individuals with FH, most likely due to a lower prevalence of smoking. Implications of these findings can be increased motivation and thus compliance to treatment of hypercholesterolemia.