Triglycerides

Angiopoietin-like Proteins and Lipoprotein Lipase: The Waltz Partners That Govern Triglyceride-Rich Lipoprotein Metabolism? Impact on Atherogenesis, Dietary Interventions, and Emerging Therapies

Over 50% of patients who take statins are still at risk of developing atherosclerotic cardiovascular disease (ASCVD) and do not achieve their goal LDL-C levels. This residual risk is largely dependent on triglyceride-rich lipoproteins (TRL) and their remnants. In essence, remnant cholesterol-rich chylomicron (CM) and very-low-density lipoprotein (VLDL) particles play a role in atherogenesis. These remnants increase when lipoprotein lipase (LPL) activity is inhibited. ApoCIII has been thoroughly studied as a chief inhibitor and therapeutic options to curb its effect are available. On top of apoCIII regulation of LPL activity, there is a more precise control of LPL in various tissues, which makes it easier to physiologically divide the TRL burden according to the body's requirements. In general, oxidative tissues such as skeletal and cardiac muscle preferentially take up lipids during fasting. Conversely, LPL activity in adipocytes increases significantly after feeding, while its activity in oxidative tissues decreases concurrently. This perspective addresses the recent improvements in our understanding of circadian LPL regulations and their therapeutic implications. Three major tissue-specific lipolysis regulators have been identified: ANGPTL3, ANGPTL4, and ANGPTL8. Briefly, during the postprandial phase, liver ANGPTL8 acts on ANGPTL3 (which is released continuously from the liver) to inhibit LPL in the heart and muscle through an endocrine mechanism. On the other hand, when fasting, ANGPTL4, which is released by adipocytes, inhibits lipoprotein lipase in adipose tissue in a paracrine manner. ANGPTL3 inhibitors may play a therapeutic role in the treatment of hypertriglyceridemia. Several approaches are under development. We look forward to future studies to clarify (a) the nature of hormonal and nutritional factors that determine ANGPTL3, 4, and 8 activities, along with what long-term impacts may be expected if their regulation is impaired pharmacologically; (b) the understanding of the quantitative hierarchy and interaction of the regulatory actions of apoCIII, apoAV, and ANGPTL on LPL activity; (c) strategies for the safe and proper treatment of postprandial lipemia; and (d) the effect of fructose restriction on ANGPTL3, ANGPTL4, and ANGPTL8.

The chylomicron saga: time to focus on postprandial metabolism

Since statins have had such tremendous therapeutic success over the last three decades, the field of atherosclerosis has become somewhat LDL-centric, dismissing the relevance of triglycerides (TG), particularly chylomicrons, in atherogenesis. Nonetheless, 50% of patients who take statins are at risk of developing atherosclerotic cardiovascular disease (ASCVD) and are unable to achieve their goal LDL-C levels. This residual risk is mediated, in part by triglyceride rich lipoproteins (TRL) and their remnants. Following his seminal investigation on the subject, Zilversmit proposed that atherosclerosis is a postprandial event in 1979 (1-4). In essence, the concept suggests that remnant cholesterol-rich chylomicron (CM) and very-low density lipoprotein (VLDL) particles play a role in atherogenesis. Given the foregoing, this narrative review addresses the most recent improvements in our understanding of postprandial dyslipidemia. The primary metabolic pathways of chylomicrons are discussed, emphasizing the critical physiological role of lipoprotein lipase and apoCIII, the importance of these particles' fluxes in the postprandial period, their catabolic rate, the complexities of testing postprandial metabolism, and the role of angiopoietin-like proteins in the partition of CM during the fed cycle. The narrative is rounded out by the dysregulation of postprandial lipid metabolism in insulin resistance states and consequent CVD risk, the clinical evaluation of postprandial dyslipidemia, current research limits, and potential future study directions.

High residual cardiovascular risk after lipid-lowering: prime time for Predictive, Preventive, Personalized, Participatory, and Psycho-cognitive medicine

As time has come to translate trial results into individualized medical diagnosis and therapy, we analyzed how to minimize residual risk of cardiovascular disease (CVD) by reviewing papers on "residual cardiovascular disease risk". During this review process we found 989 papers that started off with residual CVD risk after initiating statin therapy, continued with papers on residual CVD risk after initiating therapy to increase high-density lipoprotein-cholesterol (HDL-C), followed by papers on residual CVD risk after initiating therapy to decrease triglyceride (TG) levels. Later on, papers dealing with elevated levels of lipoprotein remnants and lipoprotein(a) [Lp(a)] reported new risk factors of residual CVD risk. And as new risk factors are being discovered and new therapies are being tested, residual CVD risk will be reduced further. As we move from CVD risk reduction to improvement of patient management, a paradigm shift from a reductionistic approach towards a holistic approach is required. To that purpose, a personalized treatment dependent on the individual's CVD risk factors including lipid profile abnormalities should be configured, along the line of P5 medicine for each individual patient, i.e., with Predictive, Preventive, Personalized, Participatory, and Psycho-cognitive approaches.

Sugar and Dyslipidemia: A Double-Hit, Perfect Storm

The availability of sugar has expanded over the past 50 years, due to improved industrial processes and corn subsidies, particularly in the form of sweetened beverages. This correlates with a surge in the prevalence of cardiometabolic disorders, which has brought this issue back into the spotlight for public health. In this narrative review, we focus on the role of fructose in the genesis of cardiometabolic dyslipidemia (an increase in serum triglyceride-rich lipoproteins (TRL): VLDL, chylomicrons (CM), and their remnants) bringing together the most recent data on humans, which demonstrates the crucial interaction between glucose and fructose, increasing the synthesis while decreasing the catabolism of these particles in a synergistic downward spiral. After reviewing TRL metabolism, we discuss the fundamental principles governing the metabolism of fructose in the intestine and liver and the effects of dysregulated fructolysis, in conjunction with the activation of carbohydrate-responsive element-binding protein (ChREBP) by glucose and the resulting crosstalk. The first byproduct of fructose catabolism, fructose-1-P, is highlighted for its function as a signaling molecule that promotes fat synthesis. We emphasize the role of fructose/glucose interaction in the liver, which enhances de novo lipogenesis, triglyceride (TG) synthesis, and VLDL production. In addition, we draw attention to current research that demonstrates how fructose affects the activity of lipoprotein lipase by increasing the concentration of inhibitors such as apolipoprotein CIII (apoCIII) and angiopoietin-like protein 3 (ANGPTL3), which reduce the catabolism of VLDL and chylomicrons and cause the building up of their atherogenic remnants. The end outcome is a dual, synergistic, and harmful action that encourages atherogenesis. Thus, considering the growing concerns regarding the connection between sugar consumption and cardiometabolic disease, current research strongly supports the actions of public health organizations aimed at reducing sugar intake, including dietary guidance addressing "safe" limits for sugar consumption.

Lipid profiling in maternal and fetal circulations in preeclampsia and fetal growth restriction-a prospective case control observational study

Background

While many risk factors for preeclampsia, such as increased body mass index, advanced maternal age, chronic hypertension, diabetes, are now established in clinical practice, maternal lipid profile has not been included in the risk assessment for preeclampsia. We aim to characterize the serum levels of Total Cholesterol (TC), High density lipoprotein (HDL), Low density lipoprotein (LDL), Triglycerides (TG), Apolipoprotein A1, Apolipoprotein B and their ratios TC/HDL and ApoB/ApoA1 in the maternal and fetal circulations of normal pregnancy, preeclampsia (PE), fetal growth restriction (FGR) and PE + FGR.

Methods

A prospective cross-sectional case control study was conducted measuring maternal and fetal lipid levels by enzymatic analysis and immune-turbidimetric enzymatic assays. FGR was defined by elevated umbilical artery Doppler resistance in association with estimated fetal weight < 10%. Kruskal Wallis non-parametric analysis of variance was used to test for homogeneity across the clinical groups for each of the variables, Mann-Whitney tests for pairwise comparisons and Spearman rank correlation were used to quantify gestational age-related changes.

Results

(1) TG levels were elevated in maternal PE and cord blood PE + FGR groups compared to normal pregnancies. (2) A statistically significant elevation of fetal ApoB levels was observed in PE, FGR and PE + FGR compared to normal pregnancies. Apolipoprotein levels A1 and B were not different between maternal groups. (3) TC, HDL, LDL and TC/HDL levels did not show any significant gestational variation or between clinical groups in the maternal or fetal circulation.

Conclusions

Elevation in maternal TG levels may have a role in the pathogenesis of PE. The implications of elevated maternal and fetal TG levels and elevated fetal Apolipoprotein B levels deserves further exploration of their role in long term cardiovascular risk in the mother as well as the offspring.

Biomarkers and Gene Polymorphisms in Members of Long- and Short-lived Families: A Longevity Study

Background

The influence of biomarkers in human lifespan has been investigated but with no clear results yet.

Materials and methods

Lipids, Uric Acid (UA), Adiponectin (ADIPOQ), Insulin-like Growth Factor (IGF-1), cholesteryl ester transfer protein (CETP) and angiotensin-converting enzyme (ACE) proteins, as well as CETP, ADIPOQ, insulin-like growth factor binding protein-3 (IGFBP3) and ACE-gene polymorphisms were evaluated in 149 Greek individuals. The Long-Lived Families (LON) (n=84) comprised of 3 generations: long-lived aged ≥90 years (P), offspring (FL1) and their grandchildren (FL2), while the Short-Lived Families (EAD) (n=65) where both parents died <75 years, comprised of 2 generations: middle-aged (FD1) and children (FD2).

Results

Serum CETP and IGF-1 levels were lower, whereas AdipoQ concentrations were higher in P compared with FL1 and FL2 members (CETP: p = 0.03 for both comparisons; IGF-1 p < 0.001 for both comparisons and ADIPOQ: p = 0.001 and p = 0.004, respectively). Furthermore, serum triglycerides, UA and glucose concentrations were higher in FD1 compared with FD2 subjects (p=0.001, 0.02 and ≤0.001, respectively). In FD2 and FL2, CETP levels were lower in individuals with B2B2 compared with B1B1 genotype (p=0.007). Additionally, ACE concentrations were higher in individuals with DD compared with II genotype in both Families (p=0.001). After adjustment for age and gender, CETP levels were lower in P and FL2 individuals with B2B2 compared with the B1B1 genotype (p=0.004 and 0.007, respectively).

Conclusion

Increase serum TGs, UA and GL concentrations were higher in the middle-aged individuals compared with their children in families independently of their lifespan. The serum adiponectin concentration was the highest in the oldest old individuals implying beneficial influence on lifespan. Independently of family's lifespan history, the youngest individuals with CETPB2B2 genotype, compared with individuals with CETPB1B1 genotypes, had lower serum CETP concentrations. The knowledge of the unfavourable gene(s)influencing human lifespan may be helpful in encouraging individuals to follow healthier lifestyle habits and better control their high-risk biomarkers.

Dyslipidaemia in the elderly: to treat or not to treat?

INTRODUCTION

The elderly population (i.e. aged ≥ 65 years) is increasing worldwide. Ageing is associated with a higher incidence and prevalence of cardiovascular disease (CVD). Areas covered: The prevalence of CVD risk factors including type 2 diabetes mellitus, hypertension and dyslipidaemia also increases with advancing age, contributing to the higher absolute CVD risk observed in the elderly. The present narrative review comments on the associations of dyslipidaemia with CVD as well as the effects of lifestyle measures and lipid-lowering drugs on lipids and CVD risk with a special focus on the elderly population. Individual treatment goals and therapeutic options according to current guidelines are also reviewed. Finally, we discuss special characteristics of the elderly that may influence the efficacy and safety of drug therapy and should be considered before selection of hypolipidaemic pharmacotherapy. Expert commentary: There may be a greater CVD benefit in older patients following drug therapy compared with younger ones. Treatment goals and therapeutic options should be individualized according to current guidelines. Specific characteristics that may influence the efficacy and safety of drug therapy in the elderly should be considered in relation to dyslipidaemia treatment.

Orange juice with a high-fat meal prolongs postprandial lipemia in apparently healthy overweight/obese women

OBJECTIVE

We investigated the postprandial response of lipid markers to a high-fat meal (HFM) with two different beverages in apparently healthy normal-weight and overweight/obese women.

SUBJECTS AND METHODS

This crossover, randomized study enrolled 36 women, of whom 21 had normal weight (body mass index [BMI] 22 ± 1.8 kg/m2) and 15 had overweight/obesity (BMI 31 ± 3.7 kg/m2). In two different test days, the participants ingested a HFM (37% of energy as saturated fat) with 500 mL of water (HFM-W) or 500 mL of orange juice (HFM-OJ). Blood samples were collected at baseline (12-hour fasting), and at 2, 3, and 5 hours postprandial. The analysis included fasting and postprandial total cholesterol, HDL-c, LDL-c, triglycerides (TG), uric acid, and complement C3. Brazilian Clinical Trials Registry (ReBEC); Primary Identification Number: RBR-2h3wjn (www.ensaiosclinicos.gov.br).

RESULTS

TG levels increased at 3 hours with HFM-OJ in normal-weight women (p = 0.01) and returned to normal levels at 5h. TG increased at 3 hours with HFM-W (p = 0.01) and HFM-OJ (p = 0.02), and remained high at 5 hours (p = 0.03) in overweight/obese women. Complement C3 remained unchanged, but showed different responses between meals (p = 0.01 for positive incremental area under the curve [piAUC] HFM-OJ vs. HFM-W, respectively).

CONCLUSIONS

In apparently healthy overweight/obese women compared with normal-weight ones, the concomitant intake of orange juice with a HFM prolonged postprandial lipemia but had no effect on postprandial complement C3 concentrations.

Cholesterol ester transfer protein polymorphism rs5882 is associated with triglyceride-lowering in response to plant sterol consumption

Recent work suggests that plant sterol (PS) consumption may lower triglyceride (TG) concentrations; however, human clinical trial evidence is inconsistent. We associated SNP r5882 in cholesteryl ester transfer protein with changes in TG concentrations following PS consumption (2 g/day for 4 weeks) in a dual-centre, single-blind, randomized, crossover trial. TG concentrations were lowered in homozygotes for the minor G-allele of rs5882 (-0.46 ± 0.13 mmol/L, p = 0.002, n = 10); there was no effect in the A-allele carriers.

Can red yeast rice and olive extract improve lipid profile and cardiovascular risk in metabolic syndrome?: A double blind, placebo controlled randomized trial

BACKGROUND

Metabolic syndrome (MetS) comprises a spectrum of clinical phenotypes in which dyslipidemia, dysglycemia and hypertension are clustered and where all share a high level of oxidative stress and an increased risk of cardiovascular disease. This study examines the effect of a nutritional supplement combining red yeast rice and olive fruit extract on the lipid profile and on oxidative stress in a population of patients with MetS.

METHODS

In a double blind placebo controlled randomized trial, 50 persons with MetS, as defined by the ATPIII criteria, received the study product or placebo for 8 weeks. The study product contained 10.82 mg of monacolins and 9,32 mg of hydroxytyrosol per capsule, and is commercialized as Cholesfytol plus. The primary outcome measure was the difference in LDL reduction between intervention and control groups. Furthermore, differences in changes of CH, HDL, ApoA1, ApoB, HbA1c and oxLDL were measured, as well as side-effects, CK elevation, changes in clinical parameters and in cardiovascular risk.

RESULTS

In the intervention group, LDL cholesterol was lowered by 24% whereas it increased by 1% in the control group (p < 0.001). Other effects observed were a change in total cholesterol (-17% in the intervention group vs +2% in the control group, p < 0.001), apolipoprotein B (-15% vs +6%, p < 0.001), and TG (-9% vs + 16%, p = 0.02). Oxidized LDL decreased by 20% vs an increase of 5% in the control group (p < 0.001). Systolic and diastolic arterial blood pressure decreased significantly by 10 mmHg (vs 0% in the control group, p = 0.001) and 7 mmHg (vs 0% in the control group, p = 0.05) respectively. One person in the intervention group, who suffered from Segawa's syndrome, dropped out because of severe muscle ache.

CONCLUSIONS

The combination of active products in this study may be an alternative approach to statins in people who do not need, or cannot or do not want to be treated with chemical statins. Side effects, effects on oxidative stress and on glucose metabolism need to be examined more thoroughly.

TRIAL REGISTRATION

Clinicaltrials.gov NCT02065180 (February 2014).

Aberrant hetero-disulfide bond formation by the hypertriglyceridemia-associated p.Gly185Cys APOA5 variant (rs2075291)

OBJECTIVE

Apolipoprotein A-V (apoA-V) is a low-abundance plasma protein that modulates triacylglycerol homeostasis. Gene transfer studies were undertaken in apoa5 (-/-) mice to define the mechanism underlying the correlation between the single-nucleotide polymorphism c.553G>T in APOA5 and hypertriglyceridemia.

APPROACH AND RESULTS

Adeno-associated virus (AAV) 2/8-mediated gene transfer of wild-type apoA-V induced a dramatic lowering of plasma triacylglycerol in apoa5 (-/-) mice, whereas AAV2/8-Gly162Cys apoA-V (corresponding to the c.553G>T single-nucleotide polymorphism: rs2075291; p.Gly185Cys when numbering includes signal sequence) had a modest effect. Characterization studies revealed that plasma levels of wild-type and G162C apoA-V in transduced mice were similar and within the physiological range. Fractionation of plasma from mice transduced with AAV2/8-G162C apoA-V indicated that, unlike wild-type apoA-V, >50% of G162C apoA-V was recovered in the lipoprotein-free fraction. Nonreducing SDS-PAGE immunoblot analysis provided evidence that G162C apoA-V present in the lipoprotein-free fraction, but not that portion associated with lipoproteins, displayed altered electrophoretic mobility consistent with disulfide-linked heterodimer formation. Immunoprecipitation followed by liquid chromatography/mass spectrometry of human plasma from subjects homozygous for wild-type APOA5 and c.553G>T APOA5 revealed that G162C apoA-V forms adducts with extraneous plasma proteins including fibronectin, kininogen-1, and others.

CONCLUSIONS

Substitution of Cys for Gly at position 162 of mature apoA-V introduces a free cysteine that forms disulfide bonds with plasma proteins such that its lipoprotein-binding and triacylglycerol-modulation functions are compromised.

Factors influencing dyslipidemia in statin-treated patients in Lebanon and Jordan: results of the Dyslipidemia International Study

BACKGROUND

Cardiovascular disease is the leading cause of death and disability worldwide. Therefore, as part of the Dyslipidemia International Study (DYSIS), we have analyzed the prevalence of lipid abnormalities and risk factors for dyslipidemia in statin-treated patients in Lebanon and Jordan.

METHODS

This cross-sectional, multicenter study enrolled 617 patients at 13 hospitals in Lebanon and Jordan. Patients were at least 45 years old and had been treated with statins for at least 3 months. Multivariate logistic regression analysis was used to determine patient characteristics contributing to dyslipidemia during statin therapy.

RESULTS

Our findings indicated that 55.9% of statin-treated patients (mean age 60.3 years, 47% female) in Lebanon and Jordan did not achieve goal levels for low-density lipoprotein cholesterol which were dependent on Systematic Coronary Risk Evaluation (SCORE) risk, and 70% of patients (76% men and 63.3% of women) were at very high cardiovascular risk. Low-density lipoprotein cholesterol goals were not achieved in 67.2% of those with very high cardiovascular risk. The most commonly prescribed statin was atorvastatin (44.6%), followed by simvastatin (27.7%), rosuvastatin (21.2%), fluvastatin (3.3%), pravastatin (3%), and lovastatin (0.2%). Approximately half of the population was treated with a statin dose potency of 4, equaling 40 mg of simvastatin. In Lebanon and Jordan, the strongest independent associations with low-density lipoprotein cholesterol not at goal were current smoking (odds ratio [OR] 1.96; 95% confidence [CI] 1.25-3.08), diabetes mellitus (OR 2.53; 95% CI 1.70-3.77), and ischemic heart disease (OR 2.26; 95% CI 1.45-3.53), while alcohol consumption was associated with reduced risk (OR 0.12; 95% CI 0.03-0.57).

CONCLUSION

We observed that many patients in Lebanon and Jordan experienced persistent dyslipidemia during statin treatment, supporting the notion that novel lipid-lowering strategies need to be developed. Also, social programs aimed at combating the extremely high rates of tobacco use and obesity in Lebanon and Jordan are critical for combating cardiovascular disease in these countries.

An overview of the new frontiers in the treatment of atherogenic dyslipidemias

Cardiovascular diseases (CVDs) are the leading cause of morbidity/mortality worldwide. Dyslipidemia is a major risk factor for premature atherosclerosis and CVD. Lowering low-density-lipoprotein cholesterol (LDL-C) levels is well established as an intervention for the reduction of CVDs. Statins are the first-line drugs for treatment of dyslipidemia, but they do not address all CVD risk. Development of novel therapies is ongoing and includes the following: (i) reduction of LDL-C concentrations using antibodies to proprotein convertase subtilisin/kexin-9, antisense oligonucleotide inhibitors of apolipoprotein B production, microsomal transfer protein (MTP) inhibitors, and acyl-coenzyme A cholesterol acyl transferase inhibitors; (ii) reduction in levels of triglyceride-rich lipoproteins with ω-3 fatty acids, MTP inhibitors, and diacylglycerol acyl transferase-1 inhibitors; and (iii) increase of high-density-lipoprotein (HDL) cholesterol levels, HDL particle numbers, and/or HDL functionality using cholesteryl ester transfer protein inhibitors, HDL-derived agents, apolipoprotein AI mimetic peptides, and microRNAs. Large prospective outcome trials of several of these emerging therapies are under way, and thrilling progress in the field of lipid management is anticipated.

Acute toxicity of nickel nanoparticles in rats after intravenous injection

This study was carried out to add scientific data in regard to the use of metallic nanoparticles in nanomedicine. The acute toxicity of nickel (Ni) nanoparticles (50 nm), intravenously injected through the dorsal penile vein of Sprague Dawley rats was evaluated in this study. Fourteen days after injection, Ni nanoparticles induced liver and spleen injury, lung inflammation, and caused cardiac toxicity. These results indicate that precautionary measures should be taken with regard to the use of Ni nanoparticles or Ni compounds in nanomedicine.

Genetics of lipid traits and relationship to coronary artery disease

Despite the critical importance of plasma lipoproteins in the development of atherosclerosis, varying degrees of evidence surround the causal associations of lipoproteins with coronary artery disease (CAD). These causal contributions can be assessed by employing genetic variants as unbiased proxies for lipid levels. A relatively large number of low-density lipoprotein cholesterol (LDL-C) variants strongly associate with CAD, confirming the causal impact of this lipoprotein on atherosclerosis. Although not as firmly established, genetic evidence supporting a causal role of triglycerides (TG) in CAD is growing. Conversely, high-density lipoprotein cholesterol (HDL-C) variants not associated with LDL-C or TG have not yet been shown to be convincingly associated with CAD, raising questions about the causality of HDL-C in atherosclerosis. Finally, genetic variants at the LPA locus associated with lipoprotein(a) [Lp(a)] are decisively linked to CAD, indicating a causal role for Lp(a). Translational investigation of CAD-associated lipid variants may identify novel regulatory pathways with therapeutic potential to alter CAD risk.

Common variants of apolipoprotein E and cholesteryl ester transport protein genes in male patients with coronary heart disease and variable body mass index

Plasma lipids are major risk factors for coronary heart disease (CHD). Cholesteryl ester transfer protein (CETP) and apolipoprotein (apo) E genes are involved in lipoprotein metabolism, thus affecting plasma lipid and lipoproteins levels. Furthermore, such polymorphisms have been associated with susceptibility to CHD and obesity. We evaluated the influence of the gene polymorphisms of CETP TaqIB (B1, B2) and I405V (V, I) and apo E (∊2,∊3,∊4) on lipid levels, according to body mass index (BMI) in Greek men with CHD. The TaqIB (B1, B2) polymorphism affected plasma low-density lipoprotein cholesterol levels in overweight men with CHD, whereas the I405V (V, I) polymorphism affected triglyceride concentrations in normal weight men. No correlation was found between BMI and apo E polymorphisms. Large prospective studies are required to investigate the relationships of CETP and apo E polymorphisms with lipids, BMI, and CHD susceptibility.

Phytosterols protect against diet-induced hypertriglyceridemia in Syrian golden hamsters

BACKGROUND

In addition to lowering LDL-C, emerging data suggests that phytosterols (PS) may reduce blood triglycerides (TG), however, the underlying mechanisms are not known.

METHODS

We examined the TG-lowering mechanisms of dietary PS in Syrian golden hamsters randomly assigned to a high fat (HF) diet or the HF diet supplemented with PS (2%) for 6 weeks (n = 12/group). An additional subset of animals (n = 12) was provided the HF diet supplemented with ezetimibe (EZ, 0.002%) as a positive control as it is a cholesterol-lowering agent with known TG-lowering properties.

RESULTS

In confirmation of diet formulation and compound delivery, both the PS and EZ treatments lowered (p < 0.05) intestinal cholesterol absorption (24 and 31%, respectively), blood non-HDL cholesterol (61 and 66%, respectively), and hepatic cholesterol (45 and 55%, respectively) compared with the HF-fed animals. Blood TG concentrations were lower (p < 0.05) in the PS (49%) and EZ (68%)-treated animals compared with the HF group. The TG-lowering response in the PS-supplemented group was associated with reduced (p < 0.05) intestinal SREBP1c mRNA (0.45 fold of HF), hepatic PPARα mRNA (0.73 fold of HF), hepatic FAS protein abundance (0.68 fold of HD), and de novo lipogenesis (44%) compared with the HF group. Similarly, lipogenesis was lower in the EZ-treated animals, albeit through a reduction in the hepatic protein abundance of ACC (0.47 fold of HF).

CONCLUSIONS

Study results suggest that dietary PS are protective against diet-induced hypertriglyceridemia, likely through multiple mechanisms that involve modulation of intestinal fatty acid metabolism and a reduction in hepatic lipogenesis.

PCSK9 and resistin at the crossroads of the atherogenic dyslipidemia

The atherogenic dyslipidemia is a pathophysiological lipid triad, composed of high triglycerides and low-density lipoprotein and low high-density lipoprotein. The dyslipidemia is highly prevalent in individuals who are obese, insulin resistant and those with Type 2 diabetes and is the major contributing factor to the high atherosclerotic cardiovascular disease risk in these subjects. The primary initiating event in atherogenic dyslipidemia development is the hepatic overproduction of very-low-density lipoprotein (VLDL). The intracellular and extracellular protein triggers of hepatic VLDL production were not known until the recent identification of the causal roles of PCSK9 and resistin. Both PCSK9 and resistin act in large part by targeting and reducing the hepatic degradation of VLDL apoB through distinctly different mechanisms. In the current review, we discuss both the individual roles and the interaction of these proteins in driving atherogenic dyslipidemia, and thus, atherosclerotic cardiovascular disease progression in humans. We further explore the important therapeutic implications of these findings.

Emerging approaches for the treatment of hypertriglyceridemia

Hypertriglyceridemia is frequent in diabetic and obese subjects, who are at increased risk for cardiovascular diseases (CVD). Increased triglycerides (TG) are a hallmark of atherogenic dyslipidemia, representing a marker of atherogenic small dense low-density lipoproteins (sdlDL). Importantly, non-fasting/postprandial TG measurements tend to be emphasized in clinical practice for the prediction of CVD, and TG-lowering agents (primarily fibrates) have a beneficial effect on atherogenic dyslipidemia, reducing TG-rich particles and ultimately lowering the production of sdlDL. The combination of omega-3 fatty acids and statins is also recommended, and widely used in clinical practice for subjects with hypertriglyceridemia. However, a consensus on the optimal clinical use of these pharmacological agents is not fully established yet, and additional large clinical studies are needed. It seems that there is a favorable association between fish consumption and mortality from CVD, but it remains to be confirmed by future trials. Finally, there are a number of novel therapies, such as those targeting microsomal transport protein and its inhibitors, which represent new promising option for treating subjects with hypertriglyceridemia.

Management of dyslipidemias in the presence of the metabolic syndrome or type 2 diabetes

In the metabolic syndrome and type 2 diabetes, excess energy intake on the background of genetic predisposition and lifestyle factors leads to the dysregulation of fatty acid metabolism and acquired insulin resistance. These initial metabolic defects are reflected to both lipoprotein and glucose metabolism and contribute to increased risk for cardiovascular disease. However, even after controlling for the traditional cardiovascular risk factors, subjects with the metabolic syndrome and type 2 diabetes remain at high residual cardiovascular risk despite of low/normal LDL-cholesterol concentration. For 2 decades, statin therapy has been the cornerstone of treatment of dyslipidemia in these disorders. In the metabolic syndrome and type 2 diabetes, only statin treatment has demonstrated consistently a significant reduction in cardiovascular and all cause mortality in clinical trials. Lately, increased incidence of diabetes especially in the high-risk populations using statins has raised the debate whether statins are indicated for primary prevention especially in the metabolic syndrome. Guidelines recommend intensified lifestyle intervention to those in high risk groups on statin therapy to reduce the residual risk. Despite of the proven efficacy on plasma lipids, fibrate, or niacin as monotherapy, or in combination with statins has failed in reducing cardiovascular mortality. This underlies the fact that improvement in dyslipidemia or other biomarkers is not equal to the reduction in cardiovascular events. However, fibrates in combination with statins seem to be beneficial to reduce CVD events in subjects with low HDL-cholesterol (< 0.9-1.1 mmol/L) and elevated triglycerides (> 2.3 mmol/L), but the data are derived from subgroup analysis of clinical trials. The position of niacin and ezetimibe and omega-3 fatty acids in treatment of dyslipidemia in the metabolic syndrome and type 2 diabetes is even less clear and remains to be established in future clinical trials.

Lipid content in hepatic and gonadal adipose tissue parallel aortic cholesterol accumulation in mice fed diets with different omega-6 PUFA to EPA plus DHA ratios

BACKGROUND & AIMS

Diets with low omega (ω)-6 polyunsaturated fatty acids (PUFA) to eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA) ratios have been shown to decrease aortic cholesterol accumulation and have been suggested to promote weight loss. The involvement of the liver and gonadal adipose tissue (GAT) in mediating these effects is not well understood. LDL receptor null mice were used to assess the effect of an atherogenic diet with different ω-6:EPA+DHA ratios on weight gain, hepatic and GAT lipid accumulation, and their relationship to atherosclerosis.

METHODS

Four groups of mice were fed a high saturated fat and cholesterol diet (HSF ω-6) alone, or with ω-6 PUFA to EPA+DHA ratios up to 1:1 for 32 weeks. Liver and GAT were collected for lipid and gene expression analysis.

RESULTS

The fatty acid profile of liver and GAT reflected the diets. All diets resulted in similar weight gains. Compared to HSF ω-6 diet, the 1:1 ratio diet resulted in lower hepatic total cholesterol (TC) content. Aortic TC was positively correlated with hepatic and GAT TC and triglyceride. These differences were accompanied by significantly lower expression of CD36, ATP-transporter cassette A1, scavenger receptor B class 1, 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR), acetyl-CoA carboxylase alpha, acyl-CoA synthetase long-chain family member 5, and stearoyl-coenzyme A desaturase 1 (SCD1) in GAT, and HMGCR, SCD1 and cytochrome P450 7A1 in liver.

CONCLUSIONS

Dietary ω-6:EPA+DHA ratios did not affect body weight, but lower ω-6:EPA+DHA ratio diets decreased liver lipid accumulation, which possibly contributed to the lower aortic cholesterol accumulation.