Docosahexaenoic Acid Attenuates Cardiovascular Risk Factors via a Decline in Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9) Plasma Levels

Effect of chia seeds or concentrated fish oil on cardiometabolic risk markers in subjects with hypertriglyceridaemia: a parallel clinical trial

BACKGROUND

The beneficial effects of n-3 polyunsaturated fatty acids (PUFA) in reducing high blood triglyceride (TG) levels have been well demonstrated. This study aimed to investigate the effect of chia seeds on blood TG and its associated cardiometabolic factors in hypertriglyceridaemic individuals.

METHODS

This three-group randomised controlled trial compared the effects of a low-calorie diet (n = 22), a low-calorie diet with chia seeds (30 g/day, n = 22) or a low-calorie diet with concentrated fish oil (1.8 g/day of n-3 long-chain PUFAs, n = 22) in patients with hypertriglyceridaemia. Anthropometrics, fasting blood lipids, proprotein convertase subtilisin/kexin type 9, insulin, adiponectin, leptin and interleukin-6 levels were measured.

RESULTS

After 8 weeks, the mean reduction in weight exhibited by the three groups was not statistically different (2.0, 2.7 and 2.8 kg, respectively, for the control, fish oil and chia seed groups). The plasma TG decreased in both the chia seed and fish oil groups in comparison to the control group (p = 0.001). However, no significant difference was observed between the chia seed and fish oil groups (change from baseline mean: 145.2 and 136.7 mg/dL for the chia seed and fish oil groups, respectively). The consumption of chia seeds was associated with a reduction in diastolic blood pressure (change from baseline mean: 8.4 mmHg) compared to the other two groups. No significant alterations were observed in the other blood biochemical factors between the three groups.

CONCLUSIONS

In people with moderate hypertriglyceridaemia, a low-calorie diet with 30 g of chia seeds compared to fish oil supplements containing 1.8 g of long-chain PUFAs has a similar effect on reducing plasma TG levels, whereas it has a higher blood pressure-lowering effect.

Meta-GWAS on PCSK9 concentrations reveals associations of novel loci outside the PCSK9 locus in White populations

BACKGROUND AND AIMS

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a key regulator of lipid homeostasis. A few earlier genome-wide association studies (GWAS) investigated genetic variants associated with circulating PCSK9 concentrations. However, uncertainty remains about some of the genetic loci discovered beyond the PCSK9 locus. By conducting the largest PCSK9 meta-analysis of GWAS (meta-GWAS) so far, we aimed to identify novel loci and validate the previously reported loci that regulate PCSK9 concentrations.

METHODS

We performed GWAS for PCSK9 concentrations in two large cohorts (GCKD (n = 4,963) and KORA F3 (n = 2,895)). These were meta-analyzed with previously published data encompassing together 20,579 individuals. We further conducted a second meta-analysis in statin-naïve individuals (n = 15,390). A genetic risk score (GRS) was constructed on PCSK9-increasing SNPs and assessed its impact on the risk for coronary artery disease (CAD) in 394,943 statin-naïve participants (17,077 with events) of the UK Biobank by performing CAD-free survival analysis.

RESULTS

Nine loci were genome-wide significantly associated with PCSK9 concentrations. These included the previously described PCSK9, APOB, KCNA1/KCNA5, and TM6SF2/SUGP1 loci. All imputed SNPs in the PCSK9 locus account for ∼15% of variance of PCSK9 concentrations. We further identified FADS2 as a novel locus that was also found in statin-naïve participants. All imputed SNPs within the FADS2 locus explain ∼1.2% of variance of PCSK9 concentrations. Additionally, four further loci (a region on chromosome 5, SDK1, SPATA16 and HPR) were genome-wide significant in either the main model or the statin-naïve subset. The linear increase in a PCSK9 genetic risk score was associated with 1.41-fold (95%CI 1.16-1.72, p < 0.001) higher risk for incident CAD.

CONCLUSIONS

We identified five novel loci (FADS2, SPATA16, SDK1, HPR and a region on chromosome 5) for PCSK9 concentrations that would require further research. Additionally, we confirm the genome-wide significant loci that were previously detected.

Molecular and cellular biology of PCSK9: impact on glucose homeostasis

Proprotein convertase substilisin/kexin 9 (PCSK9) inhibitors (PCSK9i) revolutionised the lipid-lowering therapy. However, a risk of type 2 diabetes mellitus (T2DM) is evoked under PCSK9i therapy. In this review, we summarise the current knowledge on the link of PCSK9 with T2DM. A significant correlation was found between PCSK9 and insulin, homeostasis model assessment (HOMA) of insulin resistance and glycated haemoglobin. PCSK9 is also involved in inflammation. PCSK9 loss-of-function variants increased T2DM risk by altering insulin secretion. Local pancreatic low PCSK9 regulates β-cell LDLR expression which in turn promotes intracellular cholesterol accumulation and hampers insulin secretion. Nevertheless, the association of PCSK9 loss-of-function variants and T2DM is inconsistent. InsLeu and R46L polymorphisms were associated with T2DM, low HOMA for β-cell function and impaired fasting glucose, while the C679X polymorphism was associated with low fasting glucose in Black South African people. Hence, we assume that the impact of these variants on glucose homeostasis may vary depending on the genetic background of the studied populations and the type of effect caused by those genetic variants on the PCSK9 protein. Accordingly, these factors should be considered when choosing a genetic variant of PCSK9 to assess the impact of long-term use of PCSK9i on glucose homeostasis.

PCSK9: A Key Target for the Treatment of Cardiovascular Disease (CVD)

Proprotein convertase subtilisin/kexin type 9 (PCSK9), as a vital modulator of low-density lipoprotein cholesterol (LDL-C) , is raised in hepatocytes and released into plasma where it binds to LDL receptors (LDLR), leading to their cleavage. PCSK9 adheres to the epidermal growth factor-like repeat A (EGF-A) domain of the LDLR which is confirmed by crystallography. LDLR expression is adjusted at the transcriptional level through sterol regulatory element binding protein 2 (SREBP-2) and at the post translational stages, specifically through PCSK9, and the inducible degrader of the LDLR PCSK9 inhibition is an appealing new method for reducing the concentration of LDL-C. In this review the role of PCSK9 in lipid homeostasis was elucidated, the effect of PCSK9 on atherosclerosis was highlighted, and contemporary therapeutic techniques that focused on PCSK9 were summarized. Several restoration methods to inhibit PCSK9 have been proposed which concentrate on both extracellular and intracellular PCSK9, and they include blockage of PCSK9 production by using gene silencing agents and blockage of it's binding to LDLR through antibodies and inhibition of PCSK9 autocatalytic processes by tiny molecule inhibitors.

How lipids may affect risk for suicidal behavior

Suicide and nonfatal suicidal behaviors are major causes of mortality and morbidity worldwide. Variability in rates of suicide and suicidal behaviors within and between countries has been attributed to population and individual risk factors, including economic status and cultural differences, both of which can have suicide risk effects mediated through a variety of factors, of which perhaps the least understood is the role of diet. We therefore review the scientific literature concerning two major dietary lipid classes, cholesterol and polyunsaturated fatty acids (PUFAs), that have been associated with higher risk of suicide attempts and suicide. We consider potential mechanistic intermediates including serotonin transporters and receptors, toll-like receptors (TLRs), nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB), and peroxisome proliferator activated receptors (PPARs). Based on this review, we describe a theoretical model linking cholesterol and PUFA status to suicide risk, taking into account the effects of cholesterol-lowering interventions on PUFA balance, membrane lipid microdomains (rafts) as a nexus of interaction between cholesterol and omega-3 PUFAs, and downstream effects on serotonergic neurotransmission and specific inflammatory pathways.

High-Dose DHA Has More Profound Effects on LDL-Related Features Than High-Dose EPA: The ComparED Study

CONTEXT

Supplementation with high-dose docosahexaenoic acid (DHA) increases serum low-density lipoprotein (LDL) cholesterol (LDL-C) concentrations more than high-dose eicosapentaenoic acid (EPA). The mechanisms underlying this difference are unknown.

OBJECTIVE

To examine the phenotypic change in LDL and mechanisms responsible for the differential LDL-C response to EPA and DHA supplementation in men and women at risk of cardiovascular disease.

DESIGN, SETTING, PARTICIPANTS, AND INTERVENTION

In a double-blind, controlled, crossover study, 48 men and 106 women with abdominal obesity and subclinical inflammation were randomized to a sequence of three treatment phases: phase 1, 2.7 g/d of EPA; phase 2, 2.7 g/d of DHA; and phase 3, 3 g/d of corn oil. All supplements were provided as three 1-g capsules for a total of 3 g/d. The 10-week treatment phases were separated by a 9-week washout period.

MAIN OUTCOME MEASURE

In vivo kinetics of apolipoprotein (apo)B100-containing lipoproteins were assessed using primed-constant infusion of deuterated leucine at the end of each treatment in a subset of participants (n = 19).

RESULTS

Compared with EPA, DHA increased LDL-C concentrations (+3.3%; P = 0.038) and mean LDL particle size (+0.7 Å; P < 0.001) and reduced the proportion of small LDL (-3.2%; P < 0.01). Both EPA and DHA decreased proprotein convertase subtilisin/kexin type 9 concentrations similarly (-18.2% vs -25.0%; P < 0.0001 vs control). Compared with EPA, DHA supplementation increased both the LDL apoB100 fractional catabolic rate (+11.4%; P = 0.008) and the production rate (+9.4%; P = 0.03).

CONCLUSIONS

The results of the present study have shown that supplementation with high-dose DHA increases LDL turnover and contributes to larger LDL particles compared with EPA.

Docosahexaenoic acid and disulfiram act in concert to kill cancer cells: a mutual enhancement of their anticancer actions

We previously reported a synergistic anticancer action of clioquinol and docosahexaenoic acid (DHA) in human cancer cells. However, clioquinol has been banned from the clinic due to its neurotoxicity. This study identified disulfiram (DSF) as a substitute compound to clioquinol, acting in concert with DHA to more effectively kill cancer cells and suppress tumor growth. Treatment with DSF and DHA induced greater apoptotic cell death and suppression of tumor growth in vitro and in vivo, as compared to DSF and DHA used alone. Mechanistic studies demonstrated that DSF enhances DHA-induced cellular oxidative stress as evidenced by up-regulation of Nrf2-mediated heme oxygenase 1 (HO-1) gene transcription. On the other hand, DHA was found to enhance DSF-induced suppression of mammosphere formation and stem cell frequency in a selected cancer model system, indicating that alterations to cancer cell stemness are involved in the combinatory anticancer action of DSF and DHA. Thus, DHA and DSF, both clinically approved drugs, act in concert to more effectively kill cancer cells. This combinatory action involves an enhancement of cellular oxidative stress and suppression of cancer cell stemness.

Omega-3 fatty acids eicosapentaenoic acid and docosahexaenoic acid and their mechanisms of action on apolipoprotein B-containing lipoproteins in humans: a review

Background

Epidemiological and genetic studies suggest that elevated triglyceride (TG)-rich lipoprotein levels in the circulation increase the risk of cardiovascular disease. Prescription formulations of omega-3 fatty acids (OM3FAs), mainly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), reduce plasma TG levels and are approved for the treatment of patients with severe hypertriglyceridemia. Many preclinical studies have investigated the TG-lowering mechanisms of action of OM3FAs, but less is known from clinical studies.

Methods

We conducted a review, using systematic methodology, of studies in humans assessing the mechanisms of action of EPA and DHA on apolipoprotein B-containing lipoproteins, including TG-rich lipoproteins and low-density lipoproteins (LDLs). A systematic search of PubMed retrieved 55 articles, of which 30 were used in the review; 35 additional arrticles were also included.

Results

In humans, dietary DHA is retroconverted to EPA, while production of DHA from EPA is not observed. Dietary DHA is preferentially esterified into TGs, while EPA is more evenly esterified into TGs, cholesterol esters and phospholipids. The preferential esterification of DHA into TGs likely explains the higher turnover of DHA than EPA in plasma. The main effects of both EPA and DHA are decreased fasting and postprandial serum TG levels, through reduction of hepatic very-low-density lipoprotein (VLDL)-TG production. The exact mechanism for reduced VLDL production is not clear but does not include retention of lipids in the liver; rather, increased hepatic fatty acid oxidation is likely. The postprandial reduction in TG levels is caused by increased lipoprotein lipase activity and reduced serum VLDL-TG concentrations, resulting in enhanced chylomicron clearance. Overall, no clear differences between the effects of EPA and DHA on TG levels, or on turnover of TG-rich lipoproteins, have been observed. Effects on LDL are complex and may be influenced by genetics, such as APOE genotype.

Conclusions

EPA and DHA diminish fasting circulating TG levels via reduced production of VLDL. The mechanism of reduced VLDL production does not involve hepatic retention of lipids. Lowered postprandial TG levels are also explained by increased chylomicron clearance. Little is known about the specific cellular and biochemical mechanisms underlying the TG-lowering effects of EPA and DHA in humans.

Regulation of PCSK9 by nutraceuticals

PCSK9 (proprotein convertase subtilisin kexin type 9) is a liver secretory enzyme that regulates plasma low-density lipoprotein (LDL) cholesterol (LDL-C) levels through modulation of LDL receptor (LDLR) density on the surface of hepatocytes. Inhibition of PCSK9 using monoclonal antibodies can efficiently lower plasma LDL-C, non-high-density lipoprotein cholesterol and lipoprotein (a). PCSK9 inhibition is also an effective adjunct to statin therapy; however, the cost-effectiveness of currently available PCSK9 inhibitors is under question. Nutraceuticals offer a safe and cost-effective option for PCSK9 inhibition. Several nutraceuticals have been reported to modulate PCSK9 levels and exert LDL-lowering activity. Mechanistically, those nutraceuticals that inhibit PCSK9 through a SREBP (sterol-responsive element binding protein)-independent pathway can be more effective in lowering plasma LDL-C levels compared with those inhibiting PCSK9 through the SREBP pathway. The present review aims to collect available data on the nutraceuticals with PCSK9-inhibitory effect and the underlying mechanisms.

PCSK9 variant, long-chain n-3 PUFAs, and risk of nonfatal myocardial infarction in Costa Rican Hispanics

Background: Previous studies have indicated that the cardioprotective effects of long-chain (LC) n-3 (ω-3) polyunsaturated fatty acids (PUFAs) may vary across various ethnic populations. Emerging evidence has suggested that the gene-environment interaction may partly explain such variations. Proprotein convertase subtilisin/kexin type 9 (PCSK9) was shown to have a mutually regulating relation with LC n-3 PUFAs and also to reduce the risk of cardiovascular diseases (CVDs). Therefore, we hypothesized that certain PCSK9 genetic variants may modify the association between LC n-3 PUFA intake and CVD risk.Objective: We determined whether a PCSK9 variant (rs11206510), which has been identified for early onset myocardial infarction (MI), modified the association of LC n-3 PUFAs with nonfatal MI risk in Costa Rican Hispanics.Design: We analyzed cross-sectional data from 1932 case subjects with a first nonfatal MI and 2055 population-based control subjects who were living in Costa Rica to examine potential gene-environment interactions. Two-sided P values <0.05 were considered significant.Results: We observed a significant interaction between the PCSK9 rs11206510 genotype and LC n-3 PUFA intake on nonfatal MI risk (P-interaction = 0.012). The OR of nonfatal MI was 0.84 (95% CI: 0.72, 0.98) per 0.1% increase in total energy intake from LC n-3 PUFAs in protective-allele (C-allele) carriers, whereas the corresponding OR (95% CI) in non-C-allele carriers was 1.02 (95% CI: 0.95, 1.10). Similar results were observed when we examined the association between docosahexaenoic acid, which is one type of LC n-3 PUFA, and nonfatal MI risk (P-interaction = 0.003).Conclusion: LC n-3 PUFA intake is associated with a lower risk of nonfatal MI in C-allele carriers of PCSK9 rs11206510 (n = 799) but not in non-C-allele carriers (n = 3188).

Nutritional and Lipid Modulation of PCSK9: Effects on Cardiometabolic Risk Factors

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a serine protease involved in the regulation of LDL receptor (LDLR) expression and apolipoprotein B lipoprotein cholesterol metabolism. Hepatic PCSK9 protein expression, activity, and secretion have been shown to affect cholesterol homeostasis. An upregulation of hepatic PSCK9 protein leads to increased LDLR degradation, resulting in decreased uptake of apoB lipoproteins and a consequent increase in the plasma concentration of these lipoproteins, including LDL and chylomicron remnants. Hence, PCSK9 has become a novel target for lipid-lowering therapies. The aim of this review is to outline current findings on the metabolic and dietary regulation of PCSK9 and effects on cholesterol, apoB lipoprotein metabolism, and cardiovascular disease (CVD) risk. PCSK9 gene and protein expression have been shown to be regulated by metabolic status and the diurnal pattern. In the fasting state, plasma PCSK9 is reduced via modulation of the nuclear transcriptional factors, including sterol regulatory element-binding protein (SREBP) 1c, SREBP2, and hepatocyte nuclear factor 1α. Plasma PCSK9 concentrations are also known to be positively associated with plasma insulin and homeostasis model assessment of insulin resistance, and appear to be regulated by SREBP1c independently of glucose status. Plasma PCSK9 concentrations are stable in response to high-fat or high-protein diets in healthy individuals; however, this response may differ in altered metabolic conditions. Dietary n-3 polyunsaturated fatty acids have been shown to reduce plasma PCSK9 concentration and hepatic PCSK9 mRNA expression, consistent with their lipid-lowering effects, whereas dietary fructose appears to upregulate PCSK9 mRNA expression and plasma PCSK9 concentrations. Further studies are needed to elucidate the mechanisms of how dietary components regulate PCSK9 and effects on cholesterol and apoB lipoprotein metabolism, as well as to delineate the clinical impact of diet on PCSK9 in terms of CVD risk.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) and metabolic syndrome: insights on insulin resistance, inflammation, and atherogenic dyslipidemia

Low-density lipoprotein (LDL) cholesterol plays a pivotal role in the pathogenesis of atherosclerotic cardiovascular disease (CVD). The discovery that proprotein convertase subtilisin/kexin type 9 (PCSK9) represents a key regulator pathway for hepatic LDL receptor (LDLR) degradation sheds light on new uncovered issues regarding LDL-C homeostasis. Indeed, as confirmed by phase II and III clinical trials with monoclonal antibodies, targeting PCSK9 represents the newest and most promising pharmacological tool for the treatment of hypercholesterolemia and related CVD. However, clinical, genetic, and experimental evidence indicates that PCSK9 may be either a cause or an effect in the context of metabolic syndrome (MetS), a condition comprising a cluster of risk factors including insulin resistance, obesity, hypertension, and atherogenic dyslipidemia. The latter is characterized by a triad of hypertriglyceridemia, low plasma concentrations of high-density lipoproteins, and qualitative changes in LDLs. PCSK9 levels seem to correlate with many of these lipid parameters as well as with the insulin sensitivity indices, although the molecular mechanisms behind this association are still unknown or not completely elucidated. Nevertheless, this area of research represents an important starting point for a better understanding of the physiological role of PCSK9, also considering the recent approval of new therapies involving anti-PCSK9. Thus, in the present review, we will discuss the current knowledge on the role of PCSK9 in the context of MetS, alteration of lipids, glucose homeostasis, and inflammation.

Effects of MAT9001 containing eicosapentaenoic acid and docosapentaenoic acid, compared to eicosapentaenoic acid ethyl esters, on triglycerides, lipoprotein cholesterol, and related variables

BACKGROUND

Long-chain omega-3 fatty acid concentrate pharmaceuticals are used in the United States for treatment of severe hypertriglyceridemia (≥500 mg/dL) and are under investigation as adjuncts to statins for lowering cardiovascular risk in patients with high triglycerides (TGs; 200-499 mg/dL).

OBJECTIVE

To evaluate MAT9001, an investigational prescription-only omega-3 fatty acid agent containing predominantly eicosapentaenoic acid (EPA) and docosapentaenoic acid, in 42 men and women with fasting TG 200 to 400 mg/dL.

METHODS

In this open-label, crossover trial, subjects received MAT9001 and EPA ethyl esters (EPA-EE) in random order. They were housed in a clinical research unit for 2 14-day treatment periods, separated by a ≥35-day washout. Lipoprotein lipids, apolipoproteins (Apos) and proprotein convertase subtilisin kexin type 9 levels were measured before and at the end of each treatment period.

RESULTS

MAT9001, compared with EPA-EE, resulted in significantly (P < .05) larger reductions from pretreatment levels for TG (-33.2% vs -10.5%), total cholesterol (-9.0% vs -6.2%), non-high-density lipoprotein cholesterol (-8.8% vs -4.6%), very low-density lipoprotein cholesterol (-32.5% vs -8.1%), Apo C3 (-25.5% vs -5.0%), and proprotein convertase subtilisin kexin type 9 (-12.3% vs +8.8%). MAT9001 also produced a significantly (P = .003) larger reduction in Apo A1 (-15.3% vs -10.2%), but responses for high-density lipoprotein cholesterol (-11.3% vs -11.1%), low-density lipoprotein cholesterol (-2.4% vs -4.3%), and Apo B (-3.8% vs -0.7%), respectively, were not significantly different relative to EPA-EE.

CONCLUSIONS

MAT9001 produced significantly larger reductions than EPA-EE in several lipoprotein-related variables that would be expected to favorably alter cardiovascular disease risk in men and women with hypertriglyceridemia.