Dose-response of n-3 polyunsaturated fatty acids on lipid profile and tolerability in mildly hypertriglyceridemic subjects

Dietary fatty acids intake and all-cause and cardiovascular mortality in patients on peritoneal dialysis

BACKGROUND & AIMS

The relationship between dietary fatty acids (FA) and clinical outcomes are relatively lacking in non-dialyzed and dialyzed chronic kidney disease (CKD) population, resulting in insufficient guide about the dietary FA intake in this population. In this study, we aimed to observe the association between the intake of total or different types of FA and all-cause and cardiovascular (CV) mortality in patients undergoing peritoneal dialysis (PD).

METHODS

This is a prospective cohort study with data retrospectively analyzed in 881 patients undergoing PD. Dietary FA intake measured by 3-day dietary records. The outcomes were defined as all-cause and CV death. Baseline FA intake and time-averaged FA intake were categorized by tertiles based on the distribution among the study population. We used univariate and multivariate Cox proportional regression models to determine the association between amounts and types of FA and all-cause and CV mortality.

RESULTS

During a median follow up of 45 months, 93 patients were still being maintained on PD, 467 had died, including 189 (40.5%) attributable to CV death. Compared to patients in the low tertile of total FA (TFA) intake at baseline group, the middle or/and high tertile groups were more likely to be male, younger, well-educated and better nutritional status (P < 0.05). At the baseline, no association was found between all-cause and CV death in either total or different types of FA after adjusting for nutritional variables. As for time-averaged analyses, the associations of TFA, saturated FA (SFA), monounsaturated FA (MUFA), ω-3 and ω-6 polyunsaturated FA (PUFA) and all-cause mortality were weakened after adjustment for laboratory and nutrients variables. However, PUFA independently reduced 5% of mortality even after adjustment for laboratory and nutrients variables [HR 0.95 (0.91, 0.99), P = 0.023], and the ratio of MUFA/PUFA was positively associated with the risk for all-cause mortality [HR 1.05 (1.01, 1.09), P = 0.008]. Furthermore, each 10% increase of the ratio of ω-6/ω-3 was only weakly associated with the risk for all-cause mortality [HR 1.02 (1.00, 1.04), P = 0.034]. As for CVD mortality, the impacts of total and each type of FA disappeared after adjustment for laboratory or nutrients variables.

CONCLUSIONS

Time-averaged PUFA intake was independently associated with a lower risk for all-cause mortality in our PD cohort, while the higher ratio of MUFA/PUFA and ω-6/ω-3 increased all-cause mortality. More observational and interventional researches are needed to determine these associations.

Role of circulating sphingolipids in lipid metabolism: Why dietary lipids matter

Sphingolipids are structural components of cell membranes and lipoproteins but also act as signaling molecules in many pathophysiological processes. Although sphingolipids comprise a small part of the plasma lipidome, some plasma sphingolipids are recognized as implicated in the development of metabolic diseases and cardiovascular diseases. Plasma sphingolipids are mostly carried out into lipoproteins and may modulate their functional properties. Lipids ingested from the diet contribute to the plasma lipid pool besides lipids produced by the liver and released from the adipose tissue. Depending on their source, quality and quantity, dietary lipids may modulate sphingolipids both in plasma and lipoproteins. A few human dietary intervention studies investigated the impact of dietary lipids on circulating sphingolipids and lipid-related cardiovascular risk markers. On the one hand, dietary saturated fatty acids, mainly palmitic acid, may increase ceramide concentrations in plasma, triglyceride-rich lipoproteins and HDL. On the other hand, milk polar lipids may decrease some molecular species of sphingomyelins and ceramides in plasma and intestine-derived chylomicrons. Altogether, different dietary fatty acids and lipid species can modulate circulating sphingolipids vehicled by postprandial lipoproteins, which should be part of future nutritional strategies for prevention of cardiovascular diseases.

Changes in lipoprotein particle subclasses, standard lipids, and apolipoproteins after supplementation with n-3 or n-6 PUFAs in abdominal obesity: A randomized double-blind crossover study

BACKGROUND & AIMS

Marine-derived omega-3 (n-3) polyunsaturated fatty acids (PUFAs), mainly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), lower circulating levels of triacylglycerols (TAGs), and the plant-derived omega-6 (n-6) PUFA linoleic acid (LA) may reduce cholesterol levels. Clinical studies on effects of these dietary or supplemental PUFAs on other blood fat fractions are few and have shown conflicting results. This study aimed to determine effects of high-dose supplemental n-3 (EPA + DHA) and n-6 (LA) PUFAs from high-quality oils on circulating lipoprotein subfractions and standard lipids (primary outcomes), as well as apolipoproteins, fatty acids, and glycemic control (secondary outcomes), in females and males with abdominal obesity.

METHODS

This was a randomized double-blind crossover study with two 7-wk intervention periods separated by a 9-wk washout phase. Females (n = 16) were supplemented with 3 g/d of EPA + DHA (TAG fish oil) or 15 g/d of LA (safflower oil), while males (n = 23) received a dose of 4 g/d of EPA + DHA or 20 g/d of LA. In fasting blood samples, we investigated lipoprotein particle subclasses by nuclear magnetic resonance spectroscopy, as well as standard lipids, apolipoproteins, fatty acid profiles, and glucose and insulin. Data were analyzed by linear mixed-effects modeling with 'subjects' as the random factor.

RESULTS

The difference between interventions in relative change scores was among the lipoprotein subfractions significant for total very-low-density lipoproteins (VLDLs) (n-3 vs. n-6: -38%∗ vs. +16%, p < 0.001; ∗: significant within-treatment change score), large VLDLs (-58%∗ vs. -0.91%, p < 0.001), small VLDLs (-57%∗ vs. +41%∗, p < 0.001), total low-density lipoproteins (LDLs) (+5.8%∗ vs. -4.3%∗, p = 0.002), large LDLs (+23%∗ vs. -2.1%, p = 0.004), total high-density lipoproteins (HDLs) (-6.0%∗ vs. +3.7%, p < 0.001), large HDLs (+11%∗ vs. -5.3%, p = 0.001), medium HDLs (-24%∗ vs. +6.2%, p = 0.030), and small HDLs (-9.9%∗ vs. +9.6%∗, p = 0.002), and among standard lipids for TAGs (-16%∗ vs. -2.6%, p = 0.014), non-esterified fatty acids (-19%∗ vs. +5.5%, p = 0.033), and total cholesterol (-0.28% vs. -4.4%∗, p = 0.042). A differential response in relative change scores was also found for apolipoprotein (apo)B (+0.40% vs. -6.0%∗, p = 0.008), apoA-II (-6.0%∗ vs. +1.5%, p = 0.001), apoC-II (-11%∗ vs. -1.7%, p = 0.025), and apoE (+3.3% vs. -3.8%, p = 0.028).

CONCLUSIONS

High-dose supplementation of high-quality oils with n-3 (EPA + DHA) or n-6 (LA) PUFAs was followed by reductions in primarily TAG- or cholesterol-related markers, respectively. The responses after both interventions point to changes in the lipoprotein-lipid-apolipoprotein profile that have been associated with reduced cardiometabolic risk, also among people with TAG or LDL-C levels within the normal range.

REGISTRATION

Registered under ClinicalTrials.gov Identifier: NCT02647333.

CLINICAL TRIAL REGISTRATION

Registered at https://clinicaltrials.gov/ct2/show/NCT02647333.

Effect of Fish Oil Supplementation on Hepatic and Visceral Fat in Overweight Men: A Randomized Controlled Trial

Being overweight increases the risk of the development of metabolic conditions such as non-alcoholic fatty liver disease (NAFLD), which is itself an independent predictor of cardiovascular disease. Omega-3 polyunsaturated fatty acid (PUFA) supplementation is recommended for prevention of chronic disease, and is thought to reduce raised liver fat, yet there have been few randomized controlled trials with accurate measurement of liver fat. We assessed the effect of 12 weeks of supplementation with omega-3 PUFA from fish oil versus placebo on quantified liver fat, liver tests, and body composition including visceral adipose tissue (VAT) in a double-blind randomized controlled trial. Fifty apparently healthy overweight men (BMI 25.0–29.9 kg/m²; waist > 94 cm) were randomly allocated to consume fish oil (total daily dose: 1728 mg marine triglycerides, of which 588 mg EPA and 412 mg DHA, combined with 200 mg antioxidant, coenzyme Q10) or placebo (olive oil capsules) daily for 12 weeks. Liver fat was assessed using proton magnetic resonance spectroscopy. All outcomes were assessed at baseline and following 6 and 12 weeks of supplementation. Baseline liver fat was 4.6 ± 0.5% (range: 0.6 to 18.2%); 16 (32%) participants met the criteria for NAFLD (>5.5% liver fat). Repeated measures ANOVA revealed no significant time or group × time effect for fish oil versus placebo for liver fat, liver enzymes, anthropometry, or body composition including VAT (p > 0.05 for all), with similar finding for sub-analysis of participants with NAFLD. Omega-3 PUFA did not appear to be an effective agent for reducing liver fat in overweight men. The factors determining the health benefits of omega-3 PUFA supplementation on an individual level need to be clarified.

Science behind the cardio-metabolic benefits of omega-3 polyunsaturated fatty acids: biochemical effects vs. clinical outcomes

Lower incidence of cardiovascular disease (CVD) in the Greenland Inuit, Northern Canada and Japan has been attributed to their consumption of seafood rich in long chain omega-3 polyunsaturated fatty acids (LCn-3PUFA). While a large majority of pre-clinical and intervention trials have demonstrated heart health benefits of LCn-3PUFA, some studies have shown no effects or even negative effects. LCn-3PUFA have been shown to favourably modulate blood lipid levels, particularly a reduction in circulating levels of triglycerides. High density lipoprotein-cholesterol (HDL-C) levels are elevated following dietary supplementation with LCn-3PUFA. Although LCn-3PUFA have been shown to increase low-density lipoprotein-cholesterol (LDL-C) levels, the increase is primarily in the large-buoyant particles that are less atherogenic than small-dense LDL particles. The anti-inflammatory effects of LCn-3PUFA have been clearly outlined with inhibition of NFkB mediated cytokine production being the main mechanism. In addition, reduction in adhesion molecules (intercellular adhesion molecule, ICAM and vascular cell adhesion molecule 1, VCAM-1) and leukotriene production have also been demonstrated following LCn-3PUFA supplementation. Anti-aggregatory effects of LCn-3PUFA have been a subject of controversy, however, recent studies showing sex-specific effects on platelet aggregation have helped resolve the effects on hyperactive platelets. Improvements in endothelium function, blood flow and blood pressure after LCn-3PUFA supplementation add to the mechanistic explanation on their cardio-protective effects. Modulation of adipose tissue secretions including pro-inflammatory mediators and adipokines by LCn-3PUFA has re-ignited interest in their cardiovascular health benefits. The aim of this narrative review is to filter out the reasons for possible disparity between cohort, mechanistic, pre-clinical and clinical studies. The focus of the article is to provide possible explanation for the observed controversies surrounding heart health benefits of LCn-3PUFA.

Eicosapentaenoic acid and docosahexaenoic acid containing supplements modulate risk factors for cardiovascular disease: a meta-analysis of randomised placebo-control human clinical trials

BACKGROUND

Over 200 clinical trials have examined the effect of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) supplements on risk factors associated with cardiovascular disease. However, an updated analysis of the evidence is lacking. The aim of the present meta-analysis was to quantify the effect of supplements containing EPA and DHA on risk factors for cardiovascular disease.

METHODS

An analysis was carried on 171 clinical trials with acceptable quality (Jadad score ≥3) that were identified from a comprehensive electronic search strategy of two databases (Pubmed and Cochrane Library). A random effect model was used to obtain an overall estimate on outcomes of interest. Heterogeneity between trial results was tested for using a standard chi-squared test.

RESULTS

Compared with control, EPA and DHA supplements produced significant reductions of triglycerides of 0.368 mmol L^-1 [95% confidence interval (CI) = -0.427 to -0.309], systolic blood pressure of 2.195 mmHg (95% CI = -3.172 to -1.217), diastolic blood pressure of 1.08 mmHg (95% CI = -1.716 to -0.444), heart rate of 1.37 bpm (95% CI = -2.41 to -0.325) and C-reactive protein of 0.343 mg L^-1 (95% CI = -0.454 to -0.232). This analysis indicates an increase in both low-density lipoprotein cholesterol (mean difference = 0.150 mmol L^-1 ; 95% CI = 0.058-0.243) and high-density lipoprotein cholesterol (mean difference = 0.039 mmol L^-1 ; 95% CI = 0.024-0.054). The triglyceride-lowering effect was dose-dependent.

CONCLUSIONS

The lipid-lowering, hypotensive, anti-arrhythmic and anti-inflammatory actions of EPA and DHA supplements were confirmed in this analysis of randomised placebo-control blinded clinical trials.

Secondary hypertriglyceridemia in children and adolescents

Secondary dyslipidemia with predominant hypertriglyceridemia may occur as a consequence of both common and rare causes. After accounting for obesity and associated insulin resistance, clinicians should carefully consider other contributing factors and conditions. Genetic background and causative factors prevail during gestation, infancy, and childhood and continue in adults. Elevations in triglyceride (TG) are associated with transfer of TG to high-density lipoprotein (HDL) and low-density lipoprotein (LDL) resulting in lipolysis, HDL degradation, and formation of atherogenic LDL particles. Defining and treating the underlying cause is the first step toward restoring the lipids and lipoproteins to normal, especially in cases with severe hypertriglyceridemia, who are at risk for acute pancreatitis. Disorders involving the liver, kidney, endocrine, and immune systems and medications need to be considered. Rare diseases such as lipodystrophy and glycogen storage disease are particularly challenging, and there have been promising new developments. Treatment depends on the severity; prevention of acute pancreatitis being a priority in severe cases and lifestyle modification being a foundation for general management followed by targeting TG and predictors of coronary artery disease such as LDL cholesterol and non-HDL cholesterol, when they exceed cutpoints.

Comprehensive profiling of plasma fatty acid concentrations in young healthy Canadian adults

Circulating fatty acids (FA) are associated with a multitude of chronic diseases. However, a major gap in establishing such relationships is the lack of accepted fatty acid reference ranges representing healthy individuals. Data on validated FA reference ranges would provide a better understanding of study baseline measures and aid in the evaluation and interpretation of pharmaceutical or dietary interventions. Reference ranges for plasma FA levels have been reported in a few small studies and on a limited number of FA. Therefore, we determined the average and percentiles of a broad set of 61 FA (C14 - C24:1) from plasma total lipids from an ethnically diverse population of healthy young Canadian males and females (Total n = 826). Plasma concentrations of some of the major FA ranged from 0.3 to 4.1 mmol/L for palmitic acid, 0.1 to 1.0 mmol/L for stearic acid, 0.03 to 3.2 mmol/L for oleic acid, 0.2 to 5.0 mmol/L for linoleic acid (LA), 12.0 to 186.9 μmol/L for α-linolenic acid, and 7.2 to 237.5 μmol/L for docosahexaenoic acid (DHA). Males had significantly higher plasma concentrations of γ-linolenic acid (GLA) and n-3 docosapentaenoic acid and lower concentrations of palmitoleic acid, LA and DHA than females. Comparison of FA concentrations between Caucasians, East Asians and South Asians revealed that South Asians had significantly lower levels of palmitoleic acid (p < 0.01) and oleic acid (p = 0.01) while East Asians had lower levels of GLA (p = 0.02) and dihomo-γ-linolenic acid (p = 0.03). Overall, these data provide a comprehensive set of quantitative values that profiles a small cohort of Canadians which highlights the utility of establishing validated FA reference ranges that may be used to understand how deficient, suboptimal, or excess amounts of a given FA may be associated with chronic disease.

Associations between Omega-3 Index increase and triacylglyceride decrease in subjects with hypertriglyceridemia in response to six month of EPA and DHA supplementation

INTRODUCTION

Ingestion of long-chain n-3 PUFA effectively decreases serum triacylglycerol (TAG) levels and increases the Omega-3 Index, defined as the % of EPA and DHA in erythrocyte fatty acids. However, it remains unclear whether there is a relationship between the Omega-3 Index increase (ΔO3I increase) and the TAG level decrease (ΔTAG). We hypothesized that TAG reduction is strongly depended on Omega-3 Index increase.

SUBJECTS AND METHODS

Secondary analyses of data from a former double-blind placebo-controlled trial in which 150 dyslipidemic statin-treated subjects were randomized to four capsules of fish oil daily either as re-esterified TAG or ethyl esters in identical doses (1.01 g EPA+0.67 g DHA) or corn oil as a placebo for a period of six month.

RESULTS

108 subjects fulfilled the criteria of the current study protocol and were included in the analyses. A weak but significant negative correlation between ΔO3I and ΔTAG was observed (r=-0.211, p<0.05). However, the relation between ΔO3I and serum ΔTAG was not linear (coefficients of determination R(2): 0.044). After sub-grouping the study population into Omega-3 Index response groups, the group with a mean ΔO3I of>4% after six months of n-3 PUFA treatment demonstrated the greatest TAG reduction.

DISCUSSION AND CONCLUSIONS

A weak association between Omega-3 Index increase and TAG level decrease was found. This may be explained by highly fluctuating TAG levels, a large inter-individual difference in response of the Omega-3 Index, a cohort of subjects with only slightly elevated TAG levels and high Omega-3 Index values at baseline, and possibly to insufficient statistical power. Since there was no strong association between Omega-3 Index increase and the TAG level decrease, we conclude that changes in serum TAG levels are not a viable substitute for the Omega-3 Index to monitor treatment with EPA and DHA.

Dietary modulators of statin efficacy in cardiovascular disease and cognition

Cardiovascular disease remains the leading cause of morbidity and mortality in the United States and other developed countries, and is fast growing in developing countries, particularly as life expectancy in all parts of the world increases. Current recommendations for the prevention of cardiovascular disease issued jointly from the American Academy of Cardiology and American Heart Association emphasize that lifestyle modification should be incorporated into any treatment plan, including those on statin drugs. However, there is a dearth of data on the interaction between diet and statins with respect to additive, complementary or antagonistic effects. This review collates the available data on the interaction of statins and dietary patterns, cognition, genetics and individual nutrients, including vitamin D, niacin, omega-3 fatty acids, fiber, phytochemicals (polyphenols and stanols) and alcohol. Of note, although the available data is summarized, the scope is limited, conflicting and disparate. In some cases it is likely there is unrecognized synergism. Virtually no data are available describing the interactions of statins with dietary components or dietary pattern in subgroups of the population, particularly those who may benefit most were positive effects identified. Hence, it is virtually impossible to draw any firm conclusions at this time. Nevertheless, this area is important because were the effects of statins and diet additive or synergistic harnessing the effect could potentially lead to the use of a lower intensity statin or dose.

Fish oil -- how does it reduce plasma triglycerides?

Long chain omega-3 fatty acids (FAs) are effective for reducing plasma triglyceride (TG) levels. At the pharmaceutical dose, 3.4g/day, they reduce plasma TG by about 25-50% after one month of treatment, resulting primarily from the decline in hepatic very low density lipoprotein (VLDL-TG) production, and secondarily from the increase in VLDL clearance. Numerous mechanisms have been shown to contribute to the TG overproduction, but a key component is an increase in the availability of FAs in the liver. The liver derives FAs from three sources: diet (delivered via chylomicron remnants), de novo lipogenesis, and circulating non-esterified FAs (NEFAs). Of these, NEFAs contribute the largest fraction to VLDL-TG production in both normotriglyceridemic subjects and hypertriglyceridemic, insulin resistant patients. Thus reducing NEFA delivery to the liver would be a likely locus of action for fish oils (FO). The key regulator of plasma NEFA is intracellular adipocyte lipolysis via hormone sensitive lipase (HSL), which increases as insulin sensitivity worsens. FO counteracts intracellular lipolysis in adipocytes by suppressing adipose tissue inflammation. In addition, FO increases extracellular lipolysis by lipoprotein lipase (LpL) in adipose, heart and skeletal muscle and enhances hepatic and skeletal muscle β-oxidation which contributes to reduced FA delivery to the liver. FO could activate transcription factors which control metabolic pathways in a tissue specific manner regulating nutrient traffic and reducing plasma TG. This article is part of a Special Issue entitled Triglyceride Metabolism and Disease.