[Show abstract][Hide abstract] ABSTRACT: Objective:
Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a downregulator of the low density lipoprotein receptor. The aims of this cross-sectional cohort-study were to examine whether the PCSK9 R46L loss of function variant found in a cohort of familial hypercholesterolemia (FH) patients was associated with lower low density lipoprotein cholesterol, lower frequency of xanthomata, and cardiovascular risk.
Approach and results:
We studied FH patients attending the IRCM (Institut de Recherches Cliniques de Montréal) Lipid Clinic and whose DNA genotyping was positive for a low density lipoprotein receptor mutation. The presence of the PCSK9 loss of function R46L missense variant was determined among a cohort of 582 FH patients by genotyping. Frequency of the R46L variant was 3%. Carriers had significantly lower low density lipoprotein cholesterol (11%, P=0.002), total cholesterol (9%, P=0.007), apolipoprotein B (10%, P=0.037), and non-high density lipoprotein (12%, P<0.001) concentrations compared with noncarriers. Furthermore, R46L carriers showed a decreased average number of xanthoma per individual compared with noncarriers (0.33 and 0.76, respectively; P<0.001). Importantly, the R46L genetic variant was associated with a significant 86% lower odd of presenting a cardiovascular event (odds ratio, 0.14; 95% confidence interval, 0.032-0.63; P=0.001).
Even though the R46L variant was present in 3% of our FH population, carriers of this polymorphism showed attenuated effect of the low density lipoprotein receptor mutation on parameters, such as low density lipoprotein cholesterol, apolipoprotein B, total cholesterol, and non-high density lipoprotein. More importantly, this mutation is associated with a significant lower risk of cardiovascular disease compared with noncarriers. It is therefore likely that targeting PCSK9 in FH patients with novel anti-PCSK9 therapies will be useful in reducing cardiovascular risk in affected subjects.
Full-text · Article · Oct 2014 · Arteriosclerosis Thrombosis and Vascular Biology
[Show abstract][Hide abstract] ABSTRACT: Background
We previously reported the secretion of apoC-I, apoC-II, apoC-III, and apoE from adipose tissue in post-menopausal obese women, suggesting their potential regulation by energy balance in humans.
We examined the changes of these apolipoproteins, in relation to changes in cardiometabolic risks, following a hypocaloric-diet in overweight/obese women.
/Results: 137 post-menopausal overweight/obese women who were free of chronic disease were examined at baseline, 56 women of whom were re-evaluated following a 6-month hypocaloric diet. At baseline, there was no association between the plasma transferable apolipoproteins with any index of adiposity, insulin sensitivity, lipids or inflammation, except for apoE with peripheral fat mass (r = 0.18, p<0.05), and apoC-II and apoC-III with cholesterol (r = 0.23 and r = 0.20 respectively, p<0.05). The hypocaloric diet reduced adiposity, insulin resistance and inflammatory markers but had no significant effects on plasma transferable apolipoproteins or lipids, whose average concentrations were within normal range at baseline. The changes in total and central, but not peripheral, fat mass associated with changes of apoC-I only (r = 0.28 and r = 0.43; respectively, p< 0.05). Post-weight-loss apoC-I increased in some women (52%) yet it decreased in others, however there were no differences in cardiometabolic risk factors between the 2 groups.
Plasma apoC-I, apoC-II, apoC-III, and apoE are not associated with adiposity, insulin sensitivity or inflammation in obese but healthy post-menopausal women. Post-weight loss changes of total and central fat mass associate with changes of apoC-I.
[Show abstract][Hide abstract] ABSTRACT: PCSK9 (proprotein convertase subtilisin/kexin type 9) promotes the degradation of the LDLR (LDL receptor) in hepatocytes, leading to an increase in plasma LDL-C (LDL cholesterol). Previous animal studies have shown that insulin stimulates PCSK9 transcription and observational human studies showed a positive correlation between plasma PCSK9 concentration and fasting insulinemia.
The purpose of this study was to investigate the effects of chronic and acute hyperinsulinemia on PCSK9 in a large cohort of human subjects as well as at a cellular level.
The in vivo effect of hyperinsulinemia on plasma PCSK9 concentration was studied using euglycemic-hyperinsulinemic clamps in 82 non-diabetic post-menopausal obese patients. We studied the in vitro effects of insulin stimulation on PCSK9 mRNA as well as on protein expression and secretion in HepG2 and Huh7 cells.
Analysis of the pre and post-clamp data revealed a 15.4% (p<0.001) lowering of plasma PCSK9 concentration after acute insulin induction. In vitro studies post-insulin stimulation showed that mRNA levels of PCSK9 reduced by 25% in HepG2 cells (p<0.027) and by 59% in Huh7 cells (p<0.01). Intracellular concentration of PCSK9 were 10% lower in HepG2 cells (p<0.05) and 35% lower in Huh7 cells (p<0.05).
Our results show an inhibitory effect of acute hyperinsulinemia on PCSK9 in humans both in vitro and in vivo. This data may assist in evaluating PCSK9 levels in individuals on insulin therapy.
No preview · Article · Apr 2014 · Clinical biochemistry
[Show abstract][Hide abstract] ABSTRACT: Cardiovascular disease poses a major challenge for the 21st century, exacerbated by the pandemics of obesity, metabolic syndrome and type 2 diabetes. While best standards of care, including high-dose statins, can ameliorate the risk of vascular complications, patients remain at high risk of cardiovascular events. The Residual Risk Reduction Initiative (R3i) has previously highlighted atherogenic dyslipidaemia, defined as the imbalance between proatherogenic triglyceride-rich apolipoprotein B-containing-lipoproteins and antiatherogenic apolipoprotein A-I-lipoproteins (as in high-density lipoprotein, HDL), as an important modifiable contributor to lipid-related residual cardiovascular risk, especially in insulin-resistant conditions. As part of its mission to improve awareness and clinical management of atherogenic dyslipidaemia, the R3i has identified three key priorities for action: i) to improve recognition of atherogenic dyslipidaemia in patients at high cardiometabolic risk with or without diabetes; ii) to improve implementation and adherence to guideline-based therapies; and iii) to improve therapeutic strategies for managing atherogenic dyslipidaemia. The R3i believes that monitoring of non-HDL cholesterol provides a simple, practical tool for treatment decisions regarding the management of lipid-related residual cardiovascular risk. Addition of a fibrate, niacin (North and South America), omega-3 fatty acids or ezetimibe are all options for combination with a statin to further reduce non-HDL cholesterol, although lacking in hard evidence for cardiovascular outcome benefits. Several emerging treatments may offer promise. These include the next generation peroxisome proliferator-activated receptoralpha agonists, cholesteryl ester transfer protein inhibitors and monoclonal antibody therapy targeting proprotein convertase subtilisin/kexin type 9. However, long-term outcomes and safety data are clearly needed. In conclusion, the R3i believes that ongoing trials with these novel treatments may help to define the optimal management of atherogenic dyslipidaemia to reduce the clinical and socioeconomic burden of residual cardiovascular risk.
Full-text · Article · Jan 2014 · Cardiovascular Diabetology
[Show abstract][Hide abstract] ABSTRACT: Potatoes (Solanum tuberosum) are an important food crop worldwide and contribute key nutrients to the diet, including vitamin C, potassium, and dietary fiber. Potatoes and potato components have been shown to have favorable impacts on several measures of cardiometabolic health in animals and humans, including lowering blood pressure, improving lipid profiles, and decreasing markers of inflammation. A range of glycemic index (GI) values have been reported for potatoes, and data are sparse regarding the impact of potato consumption on the postprandial glycemic response, especially when potatoes are consumed with other foods. There is a lack of clinical trial data regarding the impact of potatoes on weight management. A small number of human cohort studies have reported beneficial associations between potato consumption as part of a healthy lifestyle and cardiometabolic health. Another small number of human population studies have included potatoes as part of a dietary pattern with other calorie-dense foods and have not reported cardiometabolic benefits. The epidemiological literature should be interpreted with caution due to lack of consistency in both defining dietary patterns that include potatoes and in control for potential confounding variables. Controlled clinical trials are needed to define the impact of potatoes on cardiometabolic health.
Full-text · Article · Jul 2013 · Annals of Medicine
[Show abstract][Hide abstract] ABSTRACT: Background:
Natural loss-of-function mutations in the proprotein convertase subtilisin/kexin type-9 gene (PCSK9) are associated with lower cholesterol and cardiovascular risk. Because a founder effect exists in French Canadians for many lipid-related genes, we sought to investigate PCSK9 mutations and associated variables in this population. We also investigated the combined effect of PCSK9 mutations and the apolipoprotein E (apoE) polymorphism on metabolic variables.
Gene sequencing and screening was carried out in 1745 healthy individuals ages 9, 13, and 16 years from a provincially representative population sample. In parallel, we measured related metabolic markers and used appropriate statistical methods.
We report herein that the carrier rates of the R46L single-nucleotide polymorphism were higher in the French Canadian population (4.8%) than previously seen in Caucasian individuals (2.4%). This is second to the most common variant, insertion of leucine, at a carrier rate of 24%, making it the most common PCSK9 loss-of-function mutation in French Canadian individuals. In R46L carriers, the contribution of the apoE genotype better explains the cholesterol phenotype than the R46L mutation alone. Patients, with both the R46L and apoE3/E2 genotype also showed a tendency toward insulin resistance as indicated by a 2-fold increase in insulin, homeostasis model assessment of insulin resistance, and leptin concentrations, compared with those without apoE3/E2.
R46L and insertion of leucine mutations were more frequent in French Canadian individuals and showed a specific geographic distribution. This might represent a gene selection to overcome clustering genes harbouring familial hypercholesterolemia and might suggest a founder effect. Subjects with the apoE3/E2 genotype and R46L have increased plasma insulin, homeostasis model assessment of insulin resistance, and leptin, an intriguing finding that warrants further investigation.
No preview · Article · Jun 2013 · The Canadian journal of cardiology
[Show abstract][Hide abstract] ABSTRACT: Variants of the secreted glycoprotein, proprotein convertase subtilisin/kexin 9 (PCSK9), associate with both hypo- and hyper-cholesterolemic phenotypes. Herein, we carried out full exonic sequencing of PCSK9 documenting the frequency of single and multiple PCSK9 variations and their effects on serum lipoprotein and PCSK9 levels in Caucasian Canadians.
The 12 exons of PCSK9 were sequenced in 207 unrelated Caucasian Canadians. Minor allele frequencies of PCSK9 variants were compared amongst LDL cholesterol (LDLC) quintiles. Serum PCSK9 levels were measured by ELISA and lipoproteins by enzymatic methods. Comparisons were made with a Caucasian family cohort (n = 51) and first generation African Canadians (n = 31).
In Caucasians, but not African Canadians, the c.61_63insCTG (denoted L10Ins) and A53V PCSK9 variations were linked and their frequency was significantly higher among Caucasian Canadians with LDLC levels in the <25th percentile. In both the unrelated and family Caucasian cohorts those carrying the L10A53V PCSK9 variant had significantly lower LDLC without reduction in plasma PCSK9. The I474V PCSK9 variant associated with significantly lower serum PCSK9 and LDLC. A novel PCSK9 variant was identified; E206K. We found that the frequency of multiple PCSK9 variations was higher in first generation African Canadians.
We showed that the L10A53V and I474V PCSK9 variants were significantly associated with lower LDLC levels in Caucasian Canadians but differed in their effect on serum PCSK9 concentrations, illuminating differences in their mechanism of inaction and indicating that that PCSK9 measurement alone may not always be a good indicator of PCSK9 function.
Full exonic sequencing of PCSK9 pointed to factors that may contribute to L10Ins PCSK9 variant loss of function in Canadians of Caucasian but not those of African descent. These included; (1) its tight linkage with the A53V variant in Caucasians and/or (2) for both the L10 and I474V, the combined (and negating) effect of multiple, differing phenotypic PCSK9 variants within individuals of African ancestry for which combinations of PCSK9 variations and their overall frequency was higher. No population studies, to our knowledge, have addressed or accessed the effect of multiple PCSK9 variants on cholesterol profiles. Our results indicate that this should be considered.
Full-text · Article · May 2013 · Lipids in Health and Disease
[Show abstract][Hide abstract] ABSTRACT: White adipose tissue (WAT) dysfunction is characterized by delayed clearance of dietary triglyceride-rich lipoproteins (TRL). We reported that apolipoprotein (apo) C-I, a transferable apolipoprotein that inhibits lipoprotein lipase activity when bound to TRL, was produced by a human adipocyte model. Thus, we aimed to determine whether increased WAT apoC-I secretion is related to delayed dietary fat clearance in humans.
After the ingestion of a (13)C-triolein-labeled high-fat meal, postmenopausal obese women with high-fasting WAT apoC-I secretion (median >0.81 μmol/L per g/4 hours, n=9) had delayed postprandial plasma clearance of (13)C-triglyceride and (13)C-nonesterified fatty acids over 6 hours compared with controls. WAT apoC-I secretion over 4 hours correlated with fasting total and non-high-density lipoprotein apoC-I but not with high-density lipoprotein apoC-I and was the primary predictor of 4-hour postprandial increases in TRL apoC-I. Correction for TRL apoC-I eliminated the association of WAT apoC-I with 6-hour area under the curve of plasma (13)C-triglyceride; correction for insulin sensitivity or inflammation did not. Finally, in addition to apoC-I, WAT secreted considerable amount of apoC-II, apoC-III, and apoE over 24 hours; however, only WAT apoC-I secretion was associated with 6-hour area under the curve of plasma (13)C-triglyceride.
Increased WAT apoC-I secretion in obese women is associated with delayed postprandial dietary fat clearance mediated by increased TRL apoC-I. Thus, we hypothesize that reducing WAT apoC-I secretion ameliorates WAT dysfunction and associated cardiometabolic risks in humans.
[Show abstract][Hide abstract] ABSTRACT: Increasingly the potential harm from high cholesterol intake, and specifically from egg yolks, is considered insignificant. We therefore assessed total plaque area (TPA) in patients attending Canadian vascular prevention clinics to determine if the atherosclerosis burden, as a marker of arterial damage, was related to egg intake. To provide perspective on the magnitude of the effect, we also analysed the effect of smoking (pack-years).
Consecutive patients attending vascular prevention clinics at University Hospital had baseline measurement of TPA by duplex ultrasound, and filled out questionnaires regarding their lifestyle and medications, including pack-years of smoking, and the number of egg yolks consumed per week times the number of years consumed (egg-yolk years).
Data were available in 1262 patients; mean (SD) age was 61.5 (14.8) years; 47% were women. Carotid plaque area increased linearly with age after age 40, but increased exponentially with pack-years of smoking and with egg-yolk years. Plaque area in patients consuming <2 eggs per week (n = 388) was 125 ± 129 mm(2), versus 132 ± 142 mm(2) in those consuming 3 or more eggs per week (n = 603); (p < 0.0001 after adjustment for age). In multiple regression, egg-yolk years remained significant after adjusting for coronary risk factors.
Our findings suggest that regular consumption of egg yolk should be avoided by persons at risk of cardiovascular disease. This hypothesis should be tested in a prospective study with more detailed information about diet, and other possible confounders such as exercise and waist circumference.
[Show abstract][Hide abstract] ABSTRACT: Proprotein convertase subtilisin/kexin-9 (PCSK9) enhances the degradation of hepatic low-density lipoprotein receptor (LDLR). Deletion of PCSK9, and loss-of-function mutants in humans result in lower levels of circulating LDL-cholesterol and a strong protection against coronary heart disease. Accordingly, the quest for PCSK9 inhibitors has major clinical implications. We have previously identified annexin A2 (AnxA2) as an endogenous binding partner and functional inhibitor of PCSK9. Herein, we studied the relevance of AnxA2 in PCSK9 inhibition and lipid metabolism in vivo. Plasma analyses of AnxA2(-/-) mice revealed: i) a ∼1.4-fold increase in LDL-cholesterol without significant changes in VLDLs or HDLs, and ii) a ∼2-fold increase in circulating PCSK9 levels. Western blotting and immunohistochemistry of AnxA2(-/-) tissues revealed that the LDLR was decreased by ∼50% in extrahepatic tissues, such as adrenals and colon. We also show that AnxA2-derived synthetic peptides block the PCSK9≡LDLR interaction in vitro, and adenoviral overexpression of AnxA2 in mouse liver increases LDLR protein levels in vivo. These results suggest that AnxA2 acts as an endogenous regulator of LDLR degradation, mostly in extrahepatic tissues. Finally, we identified an AnxA2 coding polymorphism, V98L, that correlates with lower circulating levels of PCSK9 thereby extending our results on the physiological role of AnxA2 in humans.