Effects of fish oil on VLDL triglyceride kinetics in humans

Update on management of paediatric dyslipidaemia

PURPOSE OF REVIEW

Atherosclerosis and associated cardiovascular risk factors originate in childhood; hence, early management of dyslipidaemia is vital. However, hypercholesterolemia remains untreated or undertreated in many youths. We review current therapies, drugs under investigation and consider potential future directions for the management of paediatric dyslipidaemia to highlight the recent evidence and new therapeutic options for future use.

RECENT FINDINGS

Cardiovascular disease (CVD) risk factors in childhood, including dyslipidaemia, are associated with CVD risk and clinical CVD events in adulthood. Recent data show that initiation of statin therapy in childhood in children with familial hypercholesterolemia reduces the risk of CVD in adulthood. Several well tolerated and efficacious treatment options have become available in recent times for the management of dyslipidaemia in youth. Many new lipid-lowering drugs are under investigation to widen the available choices. Some of these drugs are now available for use in paediatrics, while some remain targets for future use.

SUMMARY

We review available treatment options for paediatric dyslipidaemia management, discuss potential limitations and propose future directions. We also acknowledge the need for continued research in paediatrics for optimal paediatric dyslipidaemia management.

Time-of-day effects of consumption of fish oil-enriched sausages on serum lipid parameters and fatty acid composition in normolipidemic adults: A randomized, double-blind, placebo-controlled, and parallel-group pilot study

OBJECTIVES

The body clock controls diurnal rhythms of nutrient digestion, absorption, and metabolism. Fish oil (FO) contains abundant ω-3 polyunsaturated fatty acids (PUFA), including docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), that are thought to lower triglyceride (TG) levels. This randomized, placebo-controlled, double-blind, parallel-group trial aimed to confirm the effects of the time of FO intake on TG in healthy Japanese adults.

METHODS

Twenty healthy Japanese adults (age, 20-60 y) were assigned to either a group that consumed sausages enriched with FO (DHA 1010 mg; EPA 240 mg) in the morning and a placebo (DHA 40 mg; EPA 15 mg) in the evening (BF-FO) or another group that consumed FO-enriched sausages in the evening and the placebo in the morning (DN-FO). Serum lipid parameters, fatty acid (FA) composition, and messenger RNA expression of lipogenic genes in circulating blood cells were evaluated in fasting blood samples before, as well as after 4 and 8 wk of FO intake.

RESULTS

Serum concentrations of TG and total saturated FA were significantly decreased in the BF-FO group, whereas those of ω-3 PUFA were significantly and identically increased in both groups. Serum concentrations of ω-6 PUFA were significantly decreased in the BF-FO but not the DN-FO group. Messenger RNA expression of the lipogenic genes ACLY, SCD, and FASN were similarly reduced in both groups.

CONCLUSIONS

These findings suggested that the timing of FO intake affects both serum FA concentrations and TG metabolism in normolipidemic humans. The mechanisms of these effects of FO on lipid metabolism require further investigation.

Identification of Phenotypic Lipidomic Signatures in Response to Long Chain n-3 Polyunsaturated Fatty Acid Supplementation in Humans

Background

Supplementation with long chain n‐3 polyunsaturated fatty acids is used to reduce total circulating triacylglycerol (TAG) concentrations. However, in about 30% of people, supplementation with long chain n‐3 polyunsaturated fatty acids does not result in decreased plasma TAG. Lipidomic analysis may provide insight into this inter‐individual variability.

Methods

Lipidomic analyses using targeted, mass spectrometry were performed on plasma samples obtained from a clinical study in which participants were supplemented with 3 g/day of long chain n‐3 in the form of fish oil capsules over a 6‐week period. TAG species and cholesteryl esters (CE) were quantified for 130 participants pre‐ and post‐supplementation. Participants were segregated into 3 potential responder phenotypes: (1) positive responder (R^pos; TAG decrease), (2) non‐responder (R^non; lacking TAG change), and (3) negative responder (R^neg; TAG increase) representing 67%, 18%, and 15% of the study participants, respectively. Separation of the 3 phenotypes was attributed to differential responses in TAG with 50 to 54 carbons with 1 to 4 desaturations. Elevated TAG with higher carbon number and desaturation were common to all phenotypes following supplementation. Using the TAG responder phenotype for grouping, decreases in total CE and specific CE occurred in the R^pos phenotype versus the R^neg phenotype with intermediate responses in the R^non phenotype. CE 20:5, containing eicosapentaenoic acid (20:5n‐3), was elevated in all phenotypes. A classifier combining lipidomic and genomic features was built to discriminate triacylglycerol response phenotypes and reached a high predictive performance with a balanced accuracy of 75%.

Conclusions

These data identify lipidomic signatures, TAG and CE, associated with long chain n‐3 response p henotypes and identify a novel phenotype based upon CE changes.

Registration

URL: https://www.ClinicalTrials.gov; Unique Identifier: NCT01343342.

Supplementing flaxseed oil for long periods improved carcass quality and breast fatty acid profile in Japanese quail

The efficient time for supplementing flaxseed oil to meat-type quail to produce n-3 fatty acid fortified meat has not been determined. This study was conducted to find out the effects of different periods of flaxseed oil supplementation in the Japanese quail diet on the subsequent growth performance, carcass characteristics, fatty acids profile of breast, and functional properties of the Japanese quail meat. Totally, 720 one-day-old Japanese quail were studied in a 35-day experiment using a completely randomized design. Substituting sunflower oil with flaxseed oil had no significant effect on weight gain and feed intake in Japanese quails. Supplementing flaxseed oil for the whole 35-day growth period significantly reduced abdominal fat proportion. Flaxseed oil addition to the quail diet just a week before slaughter resulted in a 4.97-fold increase in the n-3 fatty acid content of the breast muscle. Feeding flaxseed oil decreased the activity of delta-9-desaturase in quail's breast compared to sunflower oil. The greatest thrombogenic index observed in the breast meat from control while consumption of flaxseed oil significantly decreased the thrombogenic index. Supplementing flaxseed oil to quail's diet for 21 and 35 days before slaughter significantly increased breast malondialdehyde content. Feeding flaxseed oil for long periods had no significant impact on the breast meat pH while water holding capacity was decreased. The breast lightness was increased when the flaxseed oil was fed for longer periods. Generally, feeding flaxseed oil in the last week of the growth period improved the feed conversion ratio and the fatty acid profile of quail breast meat with the minimum deterioration effects on meat quality characteristics.

Omega-3 Fatty Acids Effects on Inflammatory Biomarkers and Lipid Profiles among Diabetic and Cardiovascular Disease Patients: A Systematic Review and Meta-Analysis

The purpose of this systematic review and meta-analysis was to investigate omega-3 fatty acids’ influence on 12 inflammatory biomarkers—LDL, HDL, total cholesterol, TG, HbA1c, Apo AI, Apo AII, Apo B, CRP, TNF-α, glucose, and fasting blood glucose among diabetic and cardiovascular disease (CVD) patients. We searched articles in six database engines, and 16 of the 696 articles reviewed met the inclusion criteria. Among these, lipid and inflammatory biomarkers investigated commonly included total cholesterol (11 studies), LDL, and TG (10 studies each). Overall, omega-3 was associated with a significant reduction in Apo AII among diabetic patients, as compared to different controls (−8.0 mg/dL 95% CI: −12.71, −3.29, p = 0.0009), triglycerides (−44.88 mg/dL 95% CI: −82.6, −7.16, p < 0.0001), HDL (−2.27 mg/dL 95% CI: −3.72, −0.83, p = 0.002), and increased fasting blood glucose (16.14 mg/dL 95% CI: 6.25, 26.04, p = 0.001). Omega-3 also was associated with increased LDL among CVD patients (2.10 mg/dL 95% CI: 1.00, 3.20, p = 0.0002). We conclude that omega-3 fatty acids may be associated with lower inflammatory biomarkers among diabetic and cardiovascular patients. Clinicians should be aware of these potential benefits; however, it is essential to recommend that patients consult with clinicians before any omega-3 intake.

Oily Fish Consumption and the Risk of Dyslipidemia in Korean Adults: A Prospective Cohort Study Based on the Health Examinees Gem (HEXA-G) Study

Despite the beneficial effects of omega-3 fatty acids from fish or fish oil on cardiovascular diseases, limited information is available regarding the effects of oily fish in the diet on the risk of dyslipidemia. This study aimed to investigate the association between oily fish consumption and the incidence of dyslipidemia among Korean adults included in the Health Examinees Gem (HEXA-G) cohort during 5 years of follow-up. In total, 20,670 participants (5710 men and 14,960 women) were included in this study. The average intake of oily fish including dark meat fish, such as mackerel, pacific saury, and Spanish mackerel, and eel, was estimated using food frequency questionnaires. Oily fish consumption was associated with a significantly lower risk of hypertriglyceridemia in both men (Relative risk (RR) comparing extreme quintiles = 0.75; 95% CI 0.60–0.95; P for trend = 0.0121) and women (RR comparing extreme quintiles = 0.81; 95% CI 0.69–0.96; P for trend = 0.0110) after adjusting for potential confounders. In conclusion, increased consumption of oily fish was significantly associated with a lower risk of hypertriglyceridemia in the general Korean population. Future randomized clinical trials or prospective studies are required to confirm these findings in the Korean or other Asian populations.

Cardiovascular, electrophysiologic, and hematologic effects of omega-3 fatty acids beyond reducing hypertriglyceridemia: as it pertains to the recently published REDUCE-IT trial

Heart disease continues to affect health outcomes globally, accounting for a quarter of all deaths in the United States. Despite the improvement in the development and implementation of guideline-directed medical therapy, the risk of adverse cardiac events remains substantially high. Historically, it has been debated whether omega-3 polyunsaturated fatty acids provide clinical benefit in cardiac disease. The recently published REDUCE-IT trial demonstrated a statistically significant absolute risk reduction of 4.8% in its primary endpoint (cardiovascular death, nonfatal myocardial infarction, nonfatal stroke, coronary revascularization, or unstable angina) with the use of icosapent ethyl, which is a highly purified eicosapentaenoic acid (EPA) ethyl ester. However, the mechanism of action of omega-3 fatty acids is not commonly discussed. Moreover, the use of EPA was not without risk, as the incidence of atrial fibrillation was increased along with a trend towards increased bleeding risk. Thus, our aim is to help explain the function of purified EPA ethyl ester, especially at the molecular level, which will ultimately lead to a better understanding of their clinically observable effects.

Effect of Nutrient and Micronutrient Intake on Chylomicron Production and Postprandial Lipemia

Postprandial lipemia, which is one of the main characteristics of the atherogenic dyslipidemia with fasting plasma hypertriglyceridemia, low high-density lipoprotein cholesterol and an increase of small and dense low-density lipoproteins is now considered a causal risk factor for atherosclerotic cardiovascular disease and all-cause mortality. Postprandial lipemia, which is mainly related to the increase in chylomicron production, is frequently elevated in individuals at high cardiovascular risk such as obese or overweight patients, type 2 diabetic patients and subjects with a metabolic syndrome who share an insulin resistant state. It is now well known that chylomicron production and thus postprandial lipemia is highly regulated by many factors such as endogenous factors: circulating factors such as hormones or free fatty acids, genetic variants, circadian rhythms, or exogenous factors: food components, dietary supplements and prescription drugs. In this review, we focused on the effect of nutrients, micronutrients and phytochemicals but also on food structure on chylomicron production and postprandial lipemia.

Disentangling the Effects of Monounsaturated Fatty Acids from Other Components of a Mediterranean Diet on Serum Metabolite Profiles: A Randomized Fully Controlled Dietary Intervention in Healthy Subjects at Risk of the Metabolic Syndrome

SCOPE

The Mediterranean (MED) diet has been associated with a decreased risk of cardiovascular diseases. It is unclear whether this health effect can be mainly contributed to high intakes of monounsaturated fatty acids (MUFA), characteristic for the MED diet, or whether other components of a MED diet also play an important role.

METHODS AND RESULTS

A randomized fully controlled parallel trial is performed to examine the effects of the consumption of a saturated fatty acid rich diet, a MUFA-rich diet, or a MED diet for 8 weeks on metabolite profiles, in 47 subjects at risk of the metabolic syndrome. A total of 162 serum metabolites are assessed before and after the intervention by using a targeted NMR platform. Fifty-two metabolites are changed during the intervention (false discovery rate [FDR] p < 0.05). Both the MUFA and MED diet decrease exactly the same fractions of LDL, including particle number, lipid, phospholipid, and free cholesterol fraction (FDR p < 0.05). The MED diet additionally decreases the larger subclasses of very-low-density lipoprotein (VLDL), related VLDL fractions, VLDL-triglycerides, and serum-triglycerides (FDR p < 0.05).

CONCLUSION

The findings clearly demonstrate that the MUFA component is responsible for reducing LDL subclasses and fractions, and therefore causes an antiatherogenic lipid profile. Interestingly, consumption of the other components in the MED diet show additional health effects.

Triglycerides: Emerging Targets in Diabetes Care? Review of Moderate Hypertriglyceridemia in Diabetes

PURPOSE OF REVIEW

Moderate hypertriglyceridemia is exceedingly common in diabetes, and there is growing evidence that it contributes to residual cardiovascular risk in statin-optimized patients. Major fibrate trials yielded inconclusive results regarding the cardiovascular benefit of lowering triglycerides, although there was a signal for improvement among patients with high triglycerides and low high-density lipoprotein (HDL)-the "diabetic dyslipidemia" phenotype. Until recently, no trials have examined a priori the impact of triglyceride lowering in patients with diabetic dyslipidemia, who are likely among the highest cardiovascular-risk patients.

RECENT FINDINGS

In the recent REDUCE IT trial, omega-3 fatty acid icosapent ethyl demonstrated efficacy in lowering cardiovascular events in patients with high triglycerides, low HDL, and statin-optimized low-density lipoprotein (LDL). The ongoing PROMINENT trial is examining the impact of pemafibrate in a similar patient population. Emerging evidence suggests that lowering triglycerides may reduce residual cardiovascular risk, especially in high-risk patients with diabetic dyslipidemia.

PPARγ Pro12Ala Polymorphism Influences the Relationship between Dietary Fat Intake, Adiposity and Lipid Profile in Patients with Type 2 Diabetes

Abstract. Background: Peroxisome proliferator-activated receptor γ (PPARγ) Pro12Ala polymorphism (rs1801282) has been associated with metabolic syndrome components in some studies. Moreover, the PPARγ gene may mediate the physiological response to dietary fat intake in a ligand-dependent manner. Methods: Metabolic syndrome components (body mass index, waist circumference, and lipid profile) were determined in 290 type 2 diabetes mellitus patients in a cross-sectional study. DNA genotyping for determining PPARγ Pro12Ala polymorphism was conducted using the polymerase chain reaction-restriction length polymorphism method. A semi-quantitative food frequency questionnaire was used to assess the participants’ dietary intakes in the previous year. Results: There were significant differences between the two genotype groups of PPARγ Pro12Ala polymorphism, Ala carriers (Pro/Ala + Ala/Ala) versus non-Ala carriers (Pro/Pro), in terms of mean body mass index (p = 0.04) and waist circumference (p = 0.02). Below the median percentage of energy from monounsaturated and polyunsaturated fatty acids, Ala carriers had a higher body mass index (p = 0.01) compared to non-Ala carriers. Furthermore, a significant interaction between this single-nucleotide polymorphism and polyunsaturated fatty acids intake on serum triglyceride levels (p = 0.01) was seen, and in higher polyunsaturated fatty acids intake (≥ median) Ala carriers had lower triglyceride levels than non-Ala carriers (p = 0.007). Conclusions: The findings of the current study support a significant association between PPARγ Pro12Ala polymorphism and metabolic syndrome components, and they suggest that this polymorphism can modulate the biological response of dietary fat intake on body mass index and triglyceride levels.

A Diabetic Patient with Abdominal Pain and Lactescent Serum

We present the case of a poorly controlled diabetic patient suffering from acute onset of abdominal pain and vomiting. A blood sample taken at the bedside revealed lactescent serum and provided an important clue to the patient's status of having severe hypertriglyceridaemia. The clinical diagnosis of hypertriglyceridaemia-induced acute pancreatitis was correctly made in the accident and emergency department. Clinical photos of the lactescent serum are shown. The incidence, risk factors and management of this particular type of acute pancreatitis are discussed.

Targeting inflammation in metabolic syndrome

The metabolic syndrome (MetS) is comprised of a cluster of closely related risk factors, including visceral adiposity, insulin resistance, hypertension, high triglyceride, and low high-density lipoprotein cholesterol; all of which increase the risk for the development of type 2 diabetes and cardiovascular disease. A chronic state of inflammation appears to be a central mechanism underlying the pathophysiology of insulin resistance and MetS. In this review, we summarize recent research which has provided insight into the mechanisms by which inflammation underlies the pathophysiology of the individual components of MetS including visceral adiposity, hyperglycemia and insulin resistance, dyslipidemia, and hypertension. On the basis of these mechanisms, we summarize therapeutic modalities to target inflammation in the MetS and its individual components. Current therapeutic modalities can modulate the individual components of MetS and have a direct anti-inflammatory effect. Lifestyle modifications including exercise, weight loss, and diets high in fruits, vegetables, fiber, whole grains, and low-fat dairy and low in saturated fat and glucose are recommended as a first line therapy. The Mediterranean and dietary approaches to stop hypertension diets are especially beneficial and have been shown to prevent development of MetS. Moreover, the Mediterranean diet has been associated with reductions in total and cardiovascular mortality. Omega-3 fatty acids and peroxisome proliferator-activated receptor α agonists lower high levels of triglyceride; their role in targeting inflammation is reviewed. Angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and aldosterone blockers comprise pharmacologic therapies for hypertension but also target other aspects of MetS including inflammation. Statin drugs target many of the underlying inflammatory pathways involved in MetS.

n-3 Polyunsaturated Fatty Acid Supplementation Has No Effect on Postprandial Triglyceride-Rich Lipoprotein Kinetics in Men with Type 2 Diabetes

Dietary n-3 polyunsaturated fatty acids (PUFAs) have been proposed to modulate plasma lipids, lipoprotein metabolism, and inflammatory state and to reduce triglyceride (TG) concentrations. The present double-blind, randomized, placebo-controlled, crossover study investigated the effects of n-3 PUFA supplementation at 3 g/d for 8 weeks on the intravascular kinetics of intestinally derived apolipoprotein (apo) B-48-containing lipoproteins in 10 men with type 2 diabetes. In vivo kinetics of the TG-rich lipoprotein (TRL) apoB-48 and VLDL apoB-100 were assessed using a primed-constant infusion of L-[5,5,5-D3] leucine for 12 hours in a fed state. Compared with the placebo, n-3 PUFA supplementation significantly reduced fasting TG concentrations by -9.7% (P = 0.05) but also significantly increased plasma levels of cholesterol (C) (+6.0%, P = 0.05), LDL-C (+12.2%, P = 0.04), and HDL-C (+8.4, P = 0.007). n-3 PUFA supplementation had no significant impact on postprandial TRL apoB-48 and VLDL apoB-100 levels or on the production or catabolic rates of these lipoproteins. These data indicate that 8-week supplementation with n-3 PUFAs in men with type 2 diabetes has no beneficial effect on TRL apoB-48 and VLDL apoB-100 levels or kinetics.

Effect of DHA-rich fish oil on PPARγ target genes related to lipid metabolism in type 2 diabetes: A randomized, double-blind, placebo-controlled clinical trial

BACKGROUND

The beneficial effects of omega-3 polyunsaturated fatty acids on lipid levels are well documented. However, the related molecular mechanisms are widely unknown. Omega-3 polyunsaturated fatty acids are natural ligand for peroxisome proliferator-activated receptor γ (PPARγ).

OBJECTIVE

The aim of this study was to evaluate the effect of docosahexaenoic acid (DHA)-rich fish oil supplementation on modulation of some PPARγ-responsive genes related to lipid metabolism.

METHODS

Patients with type 2 diabetes were randomly assigned to consume either DHA-rich fish oil (containing 2400 mg/d fish oil; DHA: 1450 mg and eicosapentaenoic acid: 400 mg) or placebo for 8 weeks. Lipid profile and glycemic control parameters as well as the gene expression of PPARγ, liver x receptor-a, ATP-binding cassette A1, and CD36 in peripheral blood mononuclear cells were measured at baseline and after 8 weeks.

RESULTS

DHA-rich fish oil supplementation resulted in decreased triglycerides (TG) level compared with placebo group, independently of the baseline value of TG (all patients (P = .003), hypertriglyceridemic subjects (P = .01), and normotriglyceridemic subjects (P = .02)). Moreover, a higher reduction in TG level was observed in hypertriglyceridemic subjects, comparing to normotriglyceridemic subjects with DHA-rich fish oil supplementation (P = .01). Other lipid parameters as well as the expression of PPARγ, liver x receptor-a, ATP-binding cassette A1, and CD36 were not affected by DHA-rich fish oil supplementation. Only in hypertriglyceridemic subjects, DHA-rich fish oil supplementation upregulated CD36 expression, compared with the placebo group (P = .01).

CONCLUSIONS

DHA-rich fish oil supplementation for 8 weeks increased CD36 expression in hypertriglyceridemic subjects, which might result to higher reduction in TG level, comparing with normotriglyceridemic subjects. However, this finding should be investigated in further studies.

Effect of cocoa butter and sunflower oil supplementation on performance, immunoglobulin, and antioxidant vitamin status of rats

This study investigated the effects of cocoa butter and sunflower oil alone and in combination on performance, some biochemical parameters, immunoglobulin, and antioxidant vitamin status in Wistar rats. Forty-eight male rats were assigned to four groups, consisting of 12 rats with 3 replicates. Control received balanced rat diet without oil, cocoa butter group received 3.5% cocoa butter, sunflower oil group received 3.5% sunflower oil, the last group received 1.75% sunflower oil + 1.75% cocoa butter supplementation in the rat diet for 8 weeks. The total feed consumption in sunflower oil group was statistically lower than in the other groups. The serum creatinine level was decreased in cocoa butter group compared to control. Triglyceride and VLDL cholesterol levels were decreased in only sunflower oil and only cocoa butter groups as compared to control. The level of Ig M was statistically lower in cocoa butter and cocoa butter + sunflower oil groups than in control and sunflower oil groups. There were no statistically important difference in vitamin concentrations among trial groups. It was concluded that the supplementation of cocoa butter in diet decreased Ig M level, while the supplementation of cocoa butter and sunflower oil alone decreased the triglyceride and VLDL cholesterol levels.

Atorvastatin plus omega-3 fatty acid ethyl ester decreases very-low-density lipoprotein triglyceride production in insulin resistant obese men

AIM

To test the effect of atorvastatin (ATV) and ATV plus ω-3 FAEEs on VLDL-TG metabolism in obese, insulin resistant men.

METHODS

We carried out a 6-week randomized, placebo-controlled study to examine the effect of ATV (40 mg/day) and ATV plus ω-3 FAEEs (4 g/day) on VLDL-TG metabolism in 36 insulin resistant obese men. VLDL-TG kinetics were determined using d5 -glycerol, gas chromatography-mass spectrometry and compartmental modelling.

RESULTS

Compared with the placebo, ATV significantly decreased VLDL-TG concentration (-40%, p < 0.001) by increasing VLDL-TG fractional catabolic rate (FCR) (+47%, p < 0.01). ATV plus ω-3 FAEEs lowered VLDL-TG concentration to a greater degree compared with placebo (-46%, p < 0.001) or ATV monotherapy (-13%, p = 0.04). This was achieved by a reduction in VLDL-TG production rate (PR) compared with placebo (-32%, p = 0.008) or ATV (-20%, p = 0.03) as well as a reciprocal increase in VLDL-TG FCR (+42%, p < 0.05) compared with placebo.

CONCLUSION

In insulin resistant, dyslipidaemic, obese men, ATV improves VLDL-TG metabolism by increasing VLDL-TG FCR. The addition of 4 g/day ω-3 FAEE to statin therapy provides further TG-lowering by lowering VLDL-TG PR.

Comparative effects of plant oils on the cerebral hemorrhage in stroke-prone spontaneously hypertensive rats

OBJECTIVES

Since oils and fats can induce metabolic syndrome, leading to cardiovascular and cerebrovascular diseases, the present study was performed to find out whether the plant oils affect the cerebral hemorrhage in stroke-prone spontaneously hypertensive (SHR-SP) rats.

METHODS

From 47 days of age, male SHR-SP rats were given drinking water containing 1% NaCl to induce hypertension, and simultaneously fed semi-purified diets containing 10% perilla oil, canola oil, or shortening. The onset time of convulsion following cerebral hemorrhage was recorded, and the areas of hemorrhage and infarction were analyzed in the stroke brains.

RESULTS

In comparison with 58-day survival of SHR-SP rats during feeding NaCl alone, perilla oil extended the survival time to 68.5 days, whereas canola oil shortened it to 45.7 days. Feeding perilla oil greatly reduced the total volume of cerebral hemorrhage from 17.27% in the control group to 4.53%, while shortening increased the lesions to 21.23%. In a microscopic analysis, perilla oil also markedly decreased the hemorrhagic and infarction lesions to 1/10 of those in control rats, in contrast to an exacerbating effect of shortening. In blood analyses, perilla oil reduced blood total cholesterol and low-density lipoproteins which were increased in SHR-SP, but canola oil further increased them and markedly lowered platelet counts.

DISCUSSION

Perilla oil delayed and attenuated cerebral hemorrhage by improving hyperlipidemia in hypertensive stroke animals, in contrast to the aggravating potential of canola oil and shortening. It is suggested that perilla oil should be the first choice oil for improving metabolic syndrome in hypertensive persons at risk of hemorrhagic stroke.

Effect of probiotic (VSL#3) and omega-3 on lipid profile, insulin sensitivity, inflammatory markers, and gut colonization in overweight adults: a randomized, controlled trial

To evaluate the effects of probiotic (VSL#3) and omega-3 fatty acid on insulin sensitivity, blood lipids, and inflammation, we conducted a clinical trial in 60 overweight (BMI > 25), healthy adults, aged 40–60 years. After initial screening the subjects were randomized into four groups with 15 per group. The four groups received, respectively, placebo, omega-3 fatty acid, probiotic VSL#3, or both omega-3 and probiotic, for 6 weeks. Blood and fecal samples were collected at baseline and after 6 weeks. The probiotic (VSL#3) supplemented group had significant reduction in total cholesterol, triglyceride, LDL, and VLDL and had increased HDL (P < 0.05) value. VSL#3 improved insulin sensitivity (P < 0.01), decreased hsCRP, and favorably affected the composition of gut microbiota. Omega-3 had significant effect on insulin sensitivity and hsCRP but had no effect on gut microbiota. Addition of omega-3 fatty acid with VSL#3 had more pronounced effect on HDL, insulin sensitivity and hsCRP. Subjects with low HDL, insulin resistance, and high hsCRP had significantly lower total lactobacilli and bifidobacteria count and higher E. coli and bacteroides count.

Long-chain omega-3 fatty acids: time to establish a dietary reference intake

The beneficial effects of consuming omega-3 polyunsaturated fatty acids (n-3 PUFAs), specifically eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), on cardiovascular health have been studied extensively. To date, there is no dietary reference intake (DRI) for EPA and DHA, although many international authorities and expert groups have issued dietary recommendations for them. Given the substantial new evidence published since the last Institute of Medicine (IOM) report on energy and macronutrients, released in 2002, there is a pressing need to establish a DRI for EPA and DHA. In order to set a DRI, however, more information is needed to define the intakes of EPA and DHA required to reduce the burden of chronic disease. Information about potential gender- or race-based differences in requirements is also needed. Given the many health benefits of EPA and DHA that have been described since the 2002 IOM report, there is now a strong justification for establishing a DRI for these fatty acids.

Nutritional properties of dietary omega-3-enriched phospholipids

Dietary fatty acids regulate several physiological functions. However, to exert their properties, they have to be present in the diet in an optimal balance. Particular attention has been focused on tissue highly polyunsaturated fatty acids (HPUFAs) n-6/n-3 ratio, influenced by the type and the esterified form of dietary fatty acids. Dietary EPA and DHA when esterified to phospholipids (PLs) are more efficiently incorporated into tissue PLs and seem to possess peculiar properties through specific mechanism(s) of action, such as the capacity to affect endocannabinoid biosynthesis at much lower doses than EPA and DHA in triglyceride form, probably because of the above mentioned higher incorporation into tissue PLs. Downregulation of the endocannabinoid system seems to mediate the positive effects exerted by omega-3-enriched PLs on several parameters of metabolic syndrome. PLs are one of the major dietary forms of EPA and DHA we are exposed to with the everyday diet; therefore, it is not surprising that it guarantees an effective EPA and DHA nutritional activity. Future studies should address whether EPA and DHA in PL form are also more effective than other formulations in ameliorating other pathological conditions where n-3 HPUFAs seem to exert beneficial activities such as cancer and psychiatric disorders.

Echium oil reduces plasma triglycerides by increasing intravascular lipolysis in apoB100-only low density lipoprotein (LDL) receptor knockout mice

Echium oil (EO), which is enriched in SDA (18:4 n-3), reduces plasma triglyceride (TG) concentrations in humans and mice. We compared mechanisms by which EO and fish oil (FO) reduce plasma TG concentrations in mildly hypertriglyceridemic male apoB100-only LDLrKO mice. Mice were fed one of three atherogenic diets containing 0.2% cholesterol and palm oil (PO; 20%), EO (10% EO + 10% PO), or FO (10% FO + 10% PO). Livers from PO- and EO-fed mice had similar TG and cholesteryl ester (CE) content, which was significantly higher than in FO-fed mice. Plasma TG secretion was reduced in FO vs. EO-fed mice. Plasma very low density lipoprotein (VLDL) particle size was ordered: PO (63 ± 4 nm) > EO (55 ± 3 nm) > FO (40 ± 2 nm). Post-heparin lipolytic activity was similar among groups, but TG hydrolysis by purified lipoprotein lipase was significantly greater for EO and FO VLDL compared to PO VLDL. Removal of VLDL tracer from plasma was marginally faster in EO vs. PO fed mice. Our results suggest that EO reduces plasma TG primarily through increased intravascular lipolysis of TG and VLDL clearance. Finally, EO may substitute for FO to reduce plasma TG concentrations, but not hepatic steatosis in this mouse model.

Omega-3 fatty acid ethyl ester supplementation decreases very-low-density lipoprotein triacylglycerol secretion in obese men

Dysregulated VLDL-TAG (very-low-density lipoprotein triacylglycerol) metabolism in obesity may account for hypertriacylglycerolaemia and increased cardiovascular disease. ω-3 FAEEs (omega-3 fatty acid ethyl esters) decrease plasma TAG and VLDL concentrations, but the mechanisms are not fully understood. In the present study, we carried out a 6-week randomized, placebo-controlled study to examine the effect of high-dose ω-3 FAEE supplementation (3.2 g/day) on the metabolism of VLDL-TAG in obese men using intravenous administration of d5-glycerol. We also explored the relationship of VLDL-TAG kinetics with the metabolism of VLDL-apo (apolipoprotein) B-100 and HDL (high-density lipoprotein)-apoA-I. VLDL-TAG isotopic enrichment was measured using gas chromatography-mass spectrometry. Kinetic parameters were derived using a multicompartmental model. Compared with placebo, ω-3 FAEE supplementation significantly lowered plasma concentrations of total (−14%, P<0.05) and VLDL-TAG (−32%, P<0.05), as well as hepatic secretion of VLDL-TAG (−32%, P<0.03). The FCR (fractional catabolic rate) of VLDL-TAG was not altered by ω-3 FAEEs. There was a significant association between the change in secretion rates of VLDL-TAG and VLDL-apoB-100 (r=0.706, P<0.05). However, the change in VLDL-TAG secretion rate was not associated with change in HDL-apoA-I FCR (r=0.139, P>0.05). Our results suggest that the TAG-lowering effect of ω-3 FAEEs is associated with the decreased VLDL-TAG secretion rate and hence lower plasma VLDL-TAG concentration in obesity. The changes in VLDL-TAG and apoB-100 kinetics are closely coupled.

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.

Current concepts in triglyceride metabolism, pathophysiology, and treatment

It is becoming more evident that age, gender, and race play a significant role in the metabolic profiles that are seen among individuals in a clinical setting. It is important to understand these variances in metabolic profiles; and with these variances in mind it is now possible to understand why a single diet might not decrease cardiovascular disease risk profiles uniformly for everyone. Much is now understood about triglyceride metabolism and its contribution to energy storage. In this review we will focus on triglycerides; their production, metabolism and influence on daily life, as well as the various methods for the treatment of hypertryglyceridemia and prevention of its sequelae.

Effects of dietary lipids and Clostridium butyricum on fat deposition and meat quality of broiler chickens

The effects of dietary lipids and Clostridium butyricum on carcass quality, fat deposition, meat quality, and fatty acid contents of breast meat in broiler chickens were investigated. One hundred sixty one-day-old broiler chicks (Arbor Acres) were divided into 4 treatment groups in a 2x2 factorial arrangement and fed 4 diets with 2 lipid sources (soybean oil or fish oil) and 2 levels of C. butyricum (0 or 5 g/kg of diets) were used. Abdominal fat was significantly reduced when chicks were fed the fish oil diet compared with the soybean oil diet (P<0.01). Fish oil diets increased drip losses of the breast and thigh muscles, thawing losses of breast muscle, and boiling losses of thigh muscle (P<0.05). Moreover, the C. butyricum diet profoundly reduced shear force of muscle (P<0.05). The supplementation of C. butyricum increased i.m. fat, the contents of C20:5n-3 (P<0.05), and total n-3 polyunsaturated fatty acids (P<0.05) in breast muscle. Additionally, there were significant interactions between lipids and C. butyricum for drip losses of breast muscle (P<0.01) and boiling losses of thigh muscle (P<0.05) and for the contents of C20:5n-3 (P<0.05) and n-3 polyunsaturated fatty acids (P<0.05) of breast muscle. The results of this study indicate that dietary inclusion of C. butyricum improves meat quality and fatty acid profiles of breast meat in male broilers, particularly interacting with a fish oil diet.

Optimization of N-methyl-N-[tert-butyldimethylsilyl]trifluoroacetamide as a derivatization agent for determining isotopic enrichment of glycerol in very-low density lipoproteins

Stable isotope kinetic studies play an important role in the study of very-low density lipoprotein (VLDL) metabolism, including basic and clinical research. Today, [1,1,2,3,3-(2)H(5)]glycerol is the most cost-effective alternative to measure glycerol and triglyceride kinetics. Recycling of glycerol from glycolysis and gluconeogenesis may lead to incompletely labelled tracer molecules. Many existing methods for the measurement of glycerol isotopic enrichment involve the production of glycerol derivatives that result in fragmentation of the glycerol molecule after ionization. It would be favourable to measure the intact tracer molecule since incompletely labelled tracer molecules may be measured as fully labelled. The number of methods available to measure the intact tracer in biological samples is limited. The aim of this project was to develop a gas chromatography/mass spectrometry (GC/MS) method for glycerol enrichment that measures the intact glycerol backbone and is suitable for electron ionization (EI), which is widely available. A previously published method for N-methyl-N-[tert-butyldimethylsilyl]trifluoroacetamide (MTBSTFA) derivatization was significantly improved; we produced a stable derivative and increased recovery 27-fold in standards. We used the optimized MTBSTFA method in VLDL-triglyceride and found that further modification was required to take matrix effects into account. We now have a robust method to measure glycerol isotopic enrichment by GC/EI-MS that can be used to rule out the known problem of tracer recycling in studies of VLDL kinetics.

Dietary supplementation of n-3 PUFA reduces weight gain and improves postprandial lipaemia and the associated inflammatory response in the obese JCR:LA-cp rat

BACKGROUND

Postprandial dyslipidaemia occurs in obesity and insulin resistance (IR), and is associated with an increased risk of developing cardiovascular disease. We have recently established that the JCR:LA-cp rodent model develops postprandial dyslipidaemia concomitant with complications of the metabolic syndrome. Dietary n-3 polyunsaturated fatty acids (n-3 PUFAs) are proposed to modulate plasma lipids, serum hormone levels, lipoprotein metabolism and the inflammatory state; however, results remain inconsistent during conditions of IR.

AIM

To assess the acute metabolic and inflammatory effects of dietary fish oil supplementation on existing postprandial dyslipidaemia in the JCR:LA-cp model.

METHODS

JCR:LA-cp rats (14 weeks of age) were fed either a control, isocaloric, lipid balanced diet (15% w/w total fat, 1.0% cholesterol, P:S ratio 0.4), a lipid balanced diet with 5% n-3 PUFA [fish oil derived eicosapentaenoic acid (EPA)/docosahexaenoic acid (DHA)] or a lipid balanced diet with 10% n-3 PUFA for 3 weeks. Fasting plasma lipid, cytokine levels, postprandial chylomicron (apoB48) metabolism and the postprandial inflammatory response [haptoglobin and lipopolysaccharide binding protein (LBP)] were assessed following a standardized 'oral fat challenge'.

RESULTS

n-3 PUFA treatment resulted in a significant improvement (i.e. decrease) in the postprandial response for triglyceride (45%) (p < 0.05), apoB48 (45%) (p < 0.03) and LBP (33%) (p < 0.05) compared to controls (measured as area under the clearance curve). In contrast, we observed a significant elevation in postprandial haptoglobin (165%) (p < 0.001) in obese rats supplemented with 10% n-3 PUFA. Treatment with 5% n-3 PUFA in the JCR:LA-cp obese animals resulted in a complementary decrease in total body weight gain (6%) (p < 0.001) and an increase (i.e. improvement) in adiponectin (33%) (p < 0.05) compared to controls, without a concomitant reduction in food intake.

CONCLUSION

Acute dietary n-3 PUFA dietary supplementation can improve fasting as well as postprandial lipid metabolism and components of the associated inflammatory response in the JCR:LA-cp rat. Further, moderate dose n-3 PUFA supplementation may reduce corresponding body weight during conditions of hypercholesterolaemia and/or modulate inflammation associated with obesity and the metabolic syndrome.

VLDL-TG kinetics: a dual isotope study for quantifying VLDL-TG pool size, production rates, and fractional oxidation in humans

Very-low-density lipoproteins (VLDLs) are large, complex particles containing both surface proteins (e.g., ApoB100) and core lipids, e.g., cholesterol and triglycerides (TG). Whereas ApoB100 kinetics have been thoroughly studied, accurate measurement of VLDL-TG kinetics have proven difficult due to either complex mathematics or laborious procedures. The present study was therefore designed to measure VLDL-TG kinetics by dual isotope ex vivo labeled VLDL-TG tracers and well-established kinetics equations (bolus injection or the primed continuous infusion). Ten healthy Caucasian men [age, 23 +/- 3 yr old (mean +/- SD); body mass index, 24.7 +/- 1.3 kg/m(2)] were included in the study. VLDL-TG rate of appearance (Ra) was measured using a dual-tracer technique ([9,10-(3)H]-labeled VLDL-TG and [1-(14)C]-labeled VLDL-TG) to allow comparison of various bolus decay curve fits with the Ra obtained by the primed continuous infusion (PCI; considered the gold standard). In addition, VLDL-TG fatty acid oxidation was measured as (14)CO(2) in exhaled breath, using the hyamine trapping technique. Following a bolus injection, tracer decay was better described by a biexponential than a monoexponential fit (r(2) = 0.99 +/- 0.01 vs. 0.97 +/- 0.04, respectively, P = 0.01). VLDL-TG Ra calculated using the PCI correlated significantly with the biexponential fit (rho = 0.62, P < 0.05), whereas this was not the case for the monoexponential fit (rho = -0.18, P = not significant). VLDL-TG Ra using the best fit of the bolus injection method (biexponential) was less than values obtained by the constant infusion technique [biexponential, 34.3 (range, 27.1-69.6) vs. PCI, 44.4 (range, 33.0-72.7), P < 0.05]. Fractional oxidation of VLDL-TG was 37.2 +/- 8.8% at 240 min corresponding to 198.8 +/- 55.9 kcal/day or 10.6 +/- 3.3% of resting energy expenditure (REE). Our data demonstrate that VLDL-TG Ra measured by a biexponential fit to a bolus decay curve correlates well with VLDL-TG Ra measured by a primed continuous infusion, and therefore that a "second" peripheral VLDL-TG compartment with rapid exchange of TG exists. VLDL-TG volume of distribution is therefore greater than previously anticipated. Finally our data supports that VLDL-TG contributes quantitatively to REE.

Therapeutic potential of n-3 polyunsaturated fatty acids in disease

PURPOSE

The potential therapeutic benefits of supplementation with n-3 polyunsaturated fatty acids (PUFAs) in various diseases are reviewed, and the antiinflammatory actions, activity, and potential drug interactions and adverse effects of n-3 PUFAs are discussed.

SUMMARY

Fish oils are an excellent source of long-chain n-3 PUFAs, such as eicosapentaenoic acid and docosahexaenoic acid. After consumption, n-3 PUFAs can be incorporated into cell membranes and reduce the amount of arachidonic acid available for the synthesis of proinflammatory eicosanoids (e.g., prostaglandins, leukotrienes). Likewise, n-3 PUFAs can also reduce the production of inflammatory cytokines, such as tumor necrosis factor alpha, interleukin-1, and interleukin-6. Considerable research has been conducted to evaluate the potential therapeutic effects of fish oils in numerous conditions, including arthritis, coronary artery disease, inflammatory bowel disease, asthma, and sepsis, all of which have inflammation as a key component of their pathology. Additional investigations into the use of supplementation with fish oils in patients with neural injury, cancer, ocular diseases, and critical illness have recently been conducted. The most commonly reported adverse effects of fish oil supplements are a fishy aftertaste and gastrointestinal upset. When recommending an n-3 PUFA, clinicians should be aware of any possible adverse effect or drug interaction that, although not necessarily clinically significant, may occur, especially for patients who may be susceptible to increased bleeding (e.g., patients taking warfarin).

CONCLUSION

The n-3 PUFAs have been shown to be efficacious in treating and preventing various diseases. The wide variation in dosages and formulations used in studies makes it difficult to recommend dosages for specific treatment goals.

Contribution of apolipoprotein E genotype and docosahexaenoic acid to the LDL-cholesterol response to fish oil

OBJECTIVES

To investigate the impact of apolipoprotein E (apoE) genotype on the response of the plasma lipoprotein profile to eicosapentaenoic acid (EPA) versus docosahexaenoic acid (DHA) intervention in humans.

METHODS AND RESULTS

38 healthy normolipidaemic males, prospectively recruited on the basis of apoE genotype (n=20 E3/E3 and n=18 E3/E4), completed a double-blind placebo-controlled cross-over trial, consisting of 3 x 4 week intervention arms of either control oil, EPA-rich oil (ERO, 3.3g EPA/day) or DHA-rich oil (DRO, 3.7g DHA/day) in random order, separated by 10 week wash-out periods. A significant genotype-independent 28% and 19% reduction in plasma triglycerides in response to ERO and DRO was observed. For total cholesterol (TC), no significant treatment effects were evident; however a significant genotype by treatment interaction emerged (P=0.045), with a differential response to ERO and DRO in E4 carriers. Although the genotype x treatment interaction for LDL-cholesterol (P=0.089) did not reach significance, within DRO treatment analysis indicated a 10% increase in LDL (P=0.029) in E4 carriers with a non-significant 4% reduction in E3/E3 individuals. A genotype-independent increase in LDL mass was observed following DRO intervention (P=0.018). Competitive uptake studies in HepG2 cells using plasma very low density lipoproteins (VLDL) from the human trial, indicated that following DRO treatment, VLDL(2) fractions obtained from E3/E4 individuals resulted in a significant 32% (P=0.002) reduction in LDL uptake relative to the control.

CONCLUSIONS

High dose DHA supplementation is associated with increases in total cholesterol in E4 carriers, which appears to be due to an increase in LDL-C and may in part negate the cardioprotective action of DHA in this population subgroup.

Improved cholesterol phenotype analysis by a model relating lipoprotein life cycle processes to particle size

Increased plasma cholesterol is a known risk factor for cardiovascular disease. Lipoprotein particles transport both cholesterol and triglycerides through the blood. It is thought that the size distribution of these particles codetermines cardiovascular disease risk. New types of measurements can determine the concentration of many lipoprotein size-classes but exactly how each small class relates to disease risk is difficult to clear up. Because relating physiological process status to disease risk seems promising, we propose investigating how lipoprotein production, lipolysis, and uptake processes depend on particle size. To do this, we introduced a novel model framework (Particle Profiler) and evaluated its feasibility. The framework was tested using existing stable isotope flux data. The model framework implementation we present here reproduced the flux data and derived lipoprotein size pattern changes that corresponded to measured changes. It also sensitively indicated changes in lipoprotein metabolism between patient groups that are biologically plausible. Finally, the model was able to reproduce the cholesterol and triglyceride phenotype of known genetic diseases like familial hypercholesterolemia and familial hyperchylomicronemia. In the future, Particle Profiler can be applied for analyzing detailed lipoprotein size profile data and deriving rates of various lipolysis and uptake processes if an independent production estimate is given.

Differential influence of different dietary fatty acids on very low-density lipoprotein secretion when delivered to hepatocytes in chylomicron remnants

The influence of dietary fats carried in chylomicron remnants on the hepatic secretion of very low-density lipoprotein (VLDL) was investigated using chylomicron remnant-like particles (CRLPs) and cultured rat hepatocytes as the experimental model. Chylomicron remnant-like particles containing triacylglycerol (TG) from palm, olive, or corn (enriched in saturated, monounsaturated, or n-6 polyunsaturated fatty acids) oil, respectively, were incubated with cultured hepatocytes for 5 hours. The medium was then removed and replaced with medium without CRLPs; and the secretion of TG, cholesterol, and apolipoprotein B48 during the following 16 hours was determined. Secretion of TG into the d less than 1.050-g/mL fraction containing VLDL was unaffected by olive CRLPs, but was significantly increased in cells exposed to palm or corn CRLPs in comparison with both olive CRLPs and control incubations without CRLPs. Secretion of apolipoprotein B48, however, was not changed by any of the CRLP types. Apolipoprotein B messenger RNA levels were decreased by olive and corn CRLPs, and 3-hydroxy-3-methylglutaryl coenzyme A reductase messenger RNA abundance was increased by palm CRLPs; but expression of other genes involved in the regulation of VLDL secretion was unaffected. These findings demonstrate that CRLPs enriched in saturated fatty acids or n-6 polyunsaturated fatty acids increase the secretion of TG in VLDL, possibly because of the secretion of larger particles, whereas those enriched in monounsaturated fatty acids have no effect. Thus, different dietary fats have differential effects on VLDL secretion directly when delivered to the liver in chylomicron remnants.

Role of lipids and fatty acids in macrosomic offspring of diabetic pregnancy

Diabetic pregnancy frequently results in macrosomia or fetal obesity. It seems that the anomalies in carbohydrate and lipid metabolism in macrosomic infants of diabetic mothers are due to maternal hyperglycemia, which leads to fetal hyperinsulinemia. We have developed a rat model of macrosomic offspring and assessed the onset of obesity in these animals. The macrosomic offspring born to diabetic mothers are prone to the development of glucose intolerance and obesity as a function of age. It seems that in utero programming during diabetic pregnancy creates a "metabolic memory" which is responsible for the development of obesity in macrosomic offspring. We have demonstrated that the metabolism of lipids, and altered anti-oxidant status and immune system are implicated in the etiopathology of obesity in these animals. We have reported beneficial effects of n-3 polyunsaturated fatty acids (PUFAs) in obese animals, born to diabetic dams.

Dietary, physiological, genetic and pathological influences on postprandial lipid metabolism

Most of diurnal time is spent in a postprandial state due to successive meal intakes during the day. As long as the meals contain enough fat, a transient increase in triacylglycerolaemia and a change in lipoprotein pattern occurs. The extent and kinetics of such postprandial changes are highly variable and are modulated by numerous factors. This review focuses on factors affecting postprandial lipoprotein metabolism and genes, their variability and their relationship with intermediate phenotypes and risk of CHD. Postprandial lipoprotein metabolism is modulated by background dietary pattern as well as meal composition (fat amount and type, carbohydrate, protein, fibre, alcohol) and several lifestyle conditions (physical activity, tobacco use), physiological factors (age, gender, menopausal status) and pathological conditions (obesity, insulin resistance, diabetes mellitus). The roles of many genes have been explored in order to establish the possible implications of their variability in lipid metabolism and CHD risk. The postprandial lipid response has been shown to be modified by polymorphisms within the genes for apo A-I, A-IV, A-V, E, B, C-I and C-III, lipoprotein lipase, hepatic lipase, fatty acid binding and transport proteins, microsomal triglyceride transfer protein and scavenger receptor class B type I. Overall, the variability in postprandial response is important and complex, and the interactions between nutrients or dietary or meal compositions and gene variants need further investigation. The extent of present knowledge and needs for future studies are discussed in light of ongoing developments in nutrigenetics.

Interaction of exercise training andn-3 fatty acid supplementation on postprandial lipemia

The effect of combining omega-3 fatty acid (n-3 FA) supplementation and exercise training treatment on postprandial lipemia (PPL) has not been studied. The purpose of this study was to examine the interaction of n-3 FA and exercise training in attenuating PPL after a high-fat meal. Previously sedentary, overweight, subjects (n = 22; 12 women, 10 men, BMI 26.6 ±0.7 kg/m2) were randomly assigned to one of two treatment groups: n-3 FA supplementation alone (FO, n = 10) or n-3 FA supplementation plus exercise training (FO+ExTr, n = 12). Both groups consumed 4 g/d n-3 FA, and one group also exercise trained for 45 min/d, 5d/week of brisk walking and (or) jogging at 60% VO2 max. Before and after 4 weeks of treatment, subjects performed a baseline PPL and a PPL following a single session of exercise (ExPPL). PPL was assessed by triglyceride (TG) area under the curve (AUC) and peak TG response (TGpeak). A two-way analysis of variance (ANOVA) with repeated measures was used to compare results from treatments for baseline and exercise trials. FO alone reduced PPL and Ex PPL, and FO+ExTr attenuated the ExPPL response measured as total AUC and TGpeak. There was no significant main effect for group or group by time interaction for baseline PPL or ExPPL. Fasting high-density lipoprotein cholesterol (HDL-C) and HDL2-C (i.e., subfraction 2) concentrations were significantly increased in the FO+ExTr group after the treatments. These results suggest that n-3 FA supplementation reduced PPL in sedentary subjects. Exercise training has no interference or additive effects with n-3 FA supplementation in attenuating PPL, but combined treatments may be additive in raising high-density lipoprotein cholesterol.

Effects of omega-3 fatty acids on serum markers of cardiovascular disease risk: A systematic review

Greater fish oil consumption has been associated with reduced CVD risk, although the mechanisms are unclear. Plant-source oil omega-3 fatty acids (ALA) have also been studied regarding their cardiovascular effect. We conducted a systematic review of randomized controlled trials that evaluated the effect of consumption of fish oil and ALA on commonly measured serum CVD risk factors, performing meta-analyses when appropriate. Combining 21 trials evaluating lipid outcomes, fish oil consumption resulted in a summary net change in triglycerides of -27 (95% CI -33, -20)mg/dL, in HDL cholesterol of +1.6 (95% CI +0.8, +2.3)mg/dL, and in LDL cholesterol of +6 (95% CI +3, +8)mg/dL. There was no effect of fish oil on total cholesterol. Across studies, higher fish oil dose and higher baseline levels were associated with greater reductions in serum triglycerides. Overall, the 27 fish oil trials evaluating Hgb A(1c) or FBS found small non-significant net increases compared to control oils. Five studies of ALA were inconsistent in their effects on lipids, Hgb A(1c) or FBS. Four studies investigating the effects of omega-3 fatty acids on hs-CRP were also inconsistent and non-significant. The evidence supports a dose-dependent beneficial effect of fish oil on serum triglycerides, particularly among people with more elevated levels. Fish oil consumption also modestly improves HDL cholesterol, increases LDL cholesterol levels, but does not appear to adversely affect glucose homeostasis. The evidence regarding the effects of omega-3 fatty acids on hs-CRP is inconclusive, as are data on ALA.

Hypercholesterolaemia alters the responses of the plasma lipid profile and inflammatory markers to supplementation of the diet with n-3 polyunsaturated fatty acids from fish oil

BACKGROUND

The influence of supplementing the diet with long-chain n-3 polyunsaturated fatty acids (PUFA) from fish oil on plasma lipids and lipid peroxides and the production of pro-inflammatory mediators in normolipidaemic and hypercholesterolaemic rats were studied.

MATERIALS AND METHODS

Rats were divided into four groups and fed one of the following diets: a control diet (containing 4% corn oil); an n-3 PUFA diet [containing 4% eicospentaenoic (EPA) + docosahexaenoic (DHA)]; a hypercholesterolaemic diet (HCH); or a HCH + n-3 PUFA diet over a 4-week period. Plasma lipids, lipid peroxides, cytokines [tumour necrosis factor (TNF)alpha, interleukin (IL)-6, interferon (IFN)gamma] and mRNA for hepatic nuclear factor-4alpha (HNF4alpha) were determined.

RESULTS

Plasma triglyceride (TG), but not cholesterol, levels were decreased by the n-3 PUFA as compared with the control diet (P < 0.001), but the addition of n-3 PUFA to the HCH diet decreased both the TG (P < 0.01) and cholesterol (P < 0.05) concentrations. Plasma lipid peroxides and expression HNF4alpha mRNA were increased by n-3 PUFA in the normolipidaemic (P < 0.05), but not in the hyperlipidaemic rats. Compared with the control diet group, plasma concentrations of TNFalpha and IL-6 were increased in the n-3 PUFA (P < 0.05) and HCH diet (P < 0.05, P < 0.01, respectively) groups, but not in animals given the HCH + n-3 PUFA diet, whereas IFNgamma levels were increased in hypercholesterolaemia (P < 0.05), but were unaffected by n-3 PUFA.

CONCLUSION

These results demonstrate that the major effect of fish oil n-3 PUFA is to lower the TG levels in both normo- and hyperlipidaemia. Furthermore, in the hypercholesterolaemic state, fish oil n-3 PUFA induces additional beneficial changes in the immune and peroxidation responses.

Why do omega-3 fatty acids lower serum triglycerides?

PURPOSE OF REVIEW

Fish oils rich in n-3 fatty acids reduce serum triglyceride levels. This well known effect has been shown to be caused by decreased very low-density lipoprotein triglyceride secretion rates in kinetic studies in humans. Animal studies have explored the biochemical mechanisms underlying this effect. Triglyceride synthesis could be reduced by n-3 fatty acids in three general ways: reduced substrate (i.e. fatty acids) availability, which could be secondary to increase in beta-oxidation, decreased free fatty acids delivery to the liver, decreased hepatic fatty acids synthesis; increased phospholipid synthesis; or decreased activity of triglyceride-synthesizing enzymes (diacylgylcerol acyltranferase or phosphatidic acid phosphohydrolase).

RECENT FINDINGS

Rarely were experimental conditions used in rat studies physiologically relevant to the human situation in which 1.2% energy as n-3 fatty acids lowers serum triglyceride levels. Nevertheless, the most consistent effect of n-3 fatty acids feeding in rats is to decrease lipogenesis. Increased beta-oxidation was frequently, but not consistently, reported with similar numbers of studies reporting increased mitochondrial compared with peroxisomal oxidation. Inhibition of triglyceride-synthesizing enzymes was only occasionally noted.

SUMMARY

As the vast majority of studies fed unphysiologically high doses of n-3 fatty acids, these findings in rats must be considered tentative, and the mechanism by which n-3 fatty acids reduce triglyceride levels in humans remains speculative.