Effect of alpha linolenic acid on cardiovascular risk markers: a systematic review

Impact of Olive Oil Components on the Expression of Genes Related to Type 2 Diabetes Mellitus

Type 2 diabetes mellitus (T2DM) is a multifactorial metabolic disorder characterized by insulin resistance and beta cell dysfunction, resulting in hyperglycemia. Olive oil, a cornerstone of the Mediterranean diet, has attracted considerable attention due to its potential health benefits, including reducing the risk of developing T2DM. This literature review aims to critically examine and synthesize existing research regarding the impact of olive oil on the expression of genes relevant to T2DM. This paper also seeks to provide an immunological and genetic perspective on the signaling pathways of the main components of extra virgin olive oil. Key bioactive components of olive oil, such as oleic acid and phenolic compounds, were identified as modulators of insulin signaling. These compounds enhanced the insulin signaling pathway, improved lipid metabolism, and reduced oxidative stress by decreasing reactive oxygen species (ROS) production. Additionally, they were shown to alleviate inflammation by inhibiting the NF-κB pathway and downregulating pro-inflammatory cytokines and enzymes. Furthermore, these bioactive compounds were observed to mitigate endoplasmic reticulum (ER) stress by downregulating stress markers, thereby protecting beta cells from apoptosis and preserving their function. In summary, olive oil, particularly its bioactive constituents, has been demonstrated to enhance insulin sensitivity, protect beta cell function, and reduce inflammation and oxidative stress by modulating key genes involved in these processes. These findings underscore olive oil's therapeutic potential in managing T2DM. However, further research, including well-designed human clinical trials, is required to fully elucidate the role of olive oil in personalized nutrition strategies for the prevention and treatment of T2DM.

The associations between dietary omega-6, omega-3, and omega 6 to omega 3 ratio fatty acids and hypertension risk among adults: A prospective cohort study

BACKGROUND AND AIMS

Previous studies have yielded mixed results on the connection between dietary omega-3 and omega-6 intakes and the risk of hypertension (HTN) incidents. Therefore, we conducted a study to survey the connection between baseline dietary intake of omega-3, omega-6, and omega-6 to omega 3 (omega-6/3) fatty acids (FA) and the risk of hypertension.

METHODS

We conducted a prospective cohort study and assessed dietary intake through a 118-item food frequency questionnaire (FFQ). To determine the relationship between dietary omega-3, omega-6, and omega-6/3 ratio intake and the risk of developing hypertension, we applied Cox proportional hazards analysis to determine hazard ratios (HR) and 95 % confidence intervals (CIs).

RESULTS

After following 7359 participants who did not have hypertension at the beginning of the study for 6.4 ± 1.33 years, we identified 597 new cases of hypertension (8.11 %). Our analysis, which controlled for all confounders, did not identify any significant link among the highest versus lowest quartile of dietary omega-3 intake (HR: 0.87, 95 % CI: 0.63, 1.18; P trend: 0.34), omega-6 intake (HR: 1.04; 95 % CI: 0.81, 1.34; P trend: 0.82), and omega-6/3 ratio intakes (HR: 1.06, 95 % CI: 0.82, 1.36; P trend: 0.66) and HTN risk.

CONCLUSIONS

To sum up, our study revealed that dietary omega-3, omega-6, and omega-6/3 ratio were not associated with the hypertension risk.

The Role of Diet in the Prevention of Hypertension and Management of Blood Pressure: An Umbrella Review of Meta-Analyses of Interventional and Observational Studies

High blood pressure (BP) is a major pathological risk factor for the development of several cardiovascular diseases. Diet is a key modifier of BP, but the underlying relationships are not clearly demonstrated. This is an umbrella review of published meta-analyses to critically evaluate the wide range of dietary evidence from bioactive compounds to dietary patterns on BP and risk of hypertension. PubMed, Embase, Web of Science, and Cochrane Central Register of Controlled Trials were searched from inception until October 31, 2021, for relevant meta-analyses of randomized controlled trials or meta-analyses of observational studies. A total of 175 publications reporting 341 meta-analyses of randomized controlled trials (145 publications) and 70 meta-analyses of observational studies (30 publications) were included in the review. The methodological quality of the included publications was assessed using Assessment of Multiple Systematic Reviews 2 and the evidence quality of each selected meta-analysis was assessed using NutriGrade. This umbrella review supports recommended public health guidelines for prevention and control of hypertension. Dietary patterns including the Dietary Approaches to Stop Hypertension and the Mediterranean-type diets that further restrict sodium, and moderate alcohol intake are advised. To produce high-quality evidence and substantiate strong recommendations, future research should address areas where the low quality of evidence was observed (for example, intake of dietary fiber, fish, egg, meat, dairy products, fruit juice, and nuts) and emphasize focus on dietary factors not yet conclusively investigated.

Evaluation of Influencing Factors on Metabolism of Land-Based n-3 Poly Unsaturated Fatty Acids-The KoALA Study

This study aimed to investigate the impact of influencing factors (sex, eicosapentaenoic acid (EPA) status at baseline, linoleic acid (LA) intake, milk fat intake) on the conversion of α-linolenic acid (ALA) obtained from linseed oil into its long-chain metabolites. In addition, the effect of ALA on cardiovascular risk markers was investigated. This study used a parallel design approach by randomly assigning the 134 subjects to one of four diets (high in LA (HLA); low in LA (LLA); high in milk fat (MF); control (Western diet)) each enriched with linseed oil (10 en%, 22-27 mL ≙ 13-16 g ALA). Blood samples were taken at baseline and after 4, 8, and 12 weeks of dietary intervention. The study was fully completed by 105 subjects (57.4 ± 12.1 years; 65.7% female). Results showed that ALA (296-465%), C-20:4n3 (54-140%), and EPA (37-73%) concentrations in erythrocytes increased in all groups (p < 0.01). In contrast, docosahexaenoic acid (19-35%, p < 0.01) and n-3 index (10-21%, p < 0.05) dropped in the HLA, LLA, and control groups. An increase in C-22:5n3 was only observed in the MF (36%) and control groups (11%) (p < 0.05). In addition, an increase in LA (7-27%) was found in the HLA, LLA, and control groups, whereas C-20:3n6 (16-22%), arachidonic acid (10-16%), C-22:4n6 (12-30%), and C-22:5n6 (32-47%) decreased (p < 0.01). The conversion into EPA was higher in men than in women (69 vs. 39%, p = 0.043) and in subjects with low EPA status compared to participants with high EPA status (79 vs. 29%, p < 0.001). A high LA status attenuates the conversion rate. In line with the literature, no clear effects on blood lipids and parameters of glucose metabolism were found in relation to ALA supplementation.

Immature Persimmon (Diospyros kaki Thunb.) Ethanol Extract Ameliorates High-Fat Diet-Induced Obesity by Modulating Lipid Metabolism

In this study, immature persimmon (Diospyros kaki Thunb.) ethanol extract was administered to an obese animal model fed a high-fat diet to measure weight change, adipose tissue weight, serum lipid level, and expression level of adipose-related genes to evaluate its efficacy. Administration of D. kaki ethanol extract (DKE) (100 and 500 mg/kg/d) decreased the body weight gain, adipose tissue weight, and serum triglyceride levels in mice fed a high-fat diet. Furthermore, it improved the leptin and adiponectin levels in the blood as well as gene expression in the liver. It also inhibited the expression of sterol regulatory element-binding protein-1c, inhibiting the production of triglyceride biosynthetic enzyme fatty acid synthesis and acetyl-CoA carboxylase, and decreased the expressions of peroxisome proliferator-activated receptor γ and CCAAT/enhancer-binding proteins that induce adipocyte differentiation. Therefore, these data suggest that DKE exerts beneficial effects on high-fat diet-induced obesity by modulating lipid metabolism in mice fed a high-fat diet.

Potential health benefits of blueberry and raspberry pomace as functional food ingredients: Dietetic intervention study on healthy women volunteers

The fruit juice industry generates pomace as a valuable by-product especially rich in polyphenols, dietary fibers, vitamins, minerals, and unsaturated fatty acids. In the cookies used in this study, 30% of the gluten-free flour was replaced with dried and ground blueberry and raspberry pomace, rich source of polyphenols, dietary fibers, linoleic and alpha-linolenic acid. In order to examine whether the addition of blueberry and raspberry pomace in cookie formulation can have beneficial effects on certain blood parameters and anthropometric measurements, the designed cookies were tested in 20 healthy, normally fed female subjects, aged 30–50 years (41.35 ± 8.58 years) over four-week dietetic intervention study. Significant changes in the composition of fatty acids serum phospholipids, decrease in LDL-cholesterol level (20.16%), increase in adiponectin level (25.52%) and decrease in ALT and AST values were observed, thus indicating that inclusion of cookies containing blueberry and raspberry dried and ground pomace to usual diet might have positive effects on certain cardiovascular risk factors and liver function indicators.

Effects of Dietary α-Linolenic Acid Treatment and the Efficiency of Its Conversion to Eicosapentaenoic and Docosahexaenoic Acids in Obesity and Related Diseases

The essential fatty acid alpha-linolenic acid (ALA) is present in high amounts in oils such as flaxseed, soy, hemp, rapeseed, chia, and perilla, while stearidonic acid is abundant in echium oil. ALA is metabolized to eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) by desaturases and elongases in humans. The conversion of ALA to EPA and DHA is limited, and these long-chain n−3 polyunsaturated fatty acids (PUFAs) are mainly provided from dietary sources (fish and seafood). This review provides an overview of studies that explored the effects of dietary supplementation with ALA in obesity and related diseases. The obesity-associated changes of desaturase and elongase activities are summarized, as they could influence the metabolic conversion of ALA. Generally, supplementation with ALA or ALA-rich oils leads to an increase in EPA levels and has no effect on DHA or omega-3 index. According to the literature data, stearidonic acid could enhance conversion of ALA to long-chain n−3 PUFA in obesity. Recent studies confirm that EPA and DHA intake should be considered as a primary dietary treatment strategy for improving the omega-3 index in obesity and related diseases.

The effects of sesame, canola, and sesame-canola oils on cardiometabolic markers in patients with type 2 diabetes: a triple-blind three-way randomized crossover clinical trial

AIMS

To compare the effects of replacing regular dietary oils intake with sesame (SO), canola (CO), and sesame-canola (SCO) oils (a novel blend), on cardiometabolic markers in adults with type 2 diabetes mellitus (T2DM), in a triple-blind, three-way, randomized, crossover clinical trial.

METHODS

Participants were assigned to receive SO, CO, and SCO in three 9-week phases (4 weeks apart). Cardiometabolic makers (serum lipids, Apolipoprotein, cardiovascular risk scores, kidney markers, and blood pressure) were considered at the beginning and the end of intervention phases.

RESULTS

Ninety-two, ninety-five, and ninety-five participants completed the SO, SCO, and CO periods, respectively. After CO consumption, serum Apo A-1 concentrations were significantly higher compared with the SCO period in the whole population (p < 0.05). A considerable reduction in visceral adiposity index values was seen in the CO compared with the SO period in males (p < 0.05). Serum high-density lipoprotein concentration was also significantly higher after the SO intake compared with SCO in females (p < 0.05). The between-period analysis showed a substantial reduction in diastolic blood pressure in the SCO period compared with the CO and SO periods and lower systolic blood pressure after SCO versus CO intake in males (p < 0.05).

CONCLUSIONS

Canola oil might protect CVD through improving Apo A-1 levels in patients with T2DM (particularly in females) and visceral adiposity index in male patients. However, the blend oil might beneficially affect blood pressure in men. Future sex-specific studies might warrant the current findings.

REGISTRY OF CLINICAL TRIALS

This trial was registered in the Iranian Registry of Clinical Trials (IRCT, registration ID: IRCT2016091312571N6).

Effect of Plant-Derived n-3 Polyunsaturated Fatty Acids on Blood Lipids and Gut Microbiota: A Double-Blind Randomized Controlled Trial

Background

Several cardioprotective mechanisms attributed to n-3 polyunsaturated fatty acids (PUFAs) have been widely documented. Significant interest has recently focused on the role of human gut microbiota in metabolic disorders. However, the role of plant-derived n-3 PUFAs on blood lipid profiles is controversial and the effect on gut microbiota is still unclear.

Objectives

We aimed to perform a double-blind randomized controlled trial to test the effect of plant-derived n-3 PUFAs on the blood lipids and gut microbiota of patients with marginal hyperlipidemia.

Methods

According to the inclusion and exclusion criteria, 75 participants with marginal hyperlipidemia were randomly assigned to the intervention group (supplied with n-3 PUFA-enriched plant oil) or control group (supplied with corn oil), respectively, for a 3-month treatment. Participants and assessors were blinded to the allocation. The primary outcomes of the trial were the changes in serum lipid levels. Secondary outcomes were changes in gut microbiota and metabolites. For the primary outcomes, we conducted both an intent-to-treat (ITT) analysis and a per protocol (PP) analysis. For the secondary outcomes, we only conducted the PP analysis among the participants who provided fecal sample.

Results

Fifty-one participants completed the trial. Relative to the control group, the n-3 PUFA supplementation resulted in significant reduction in total cholesterol (TC) levels (−0.43 mmol/L, 95% CI−0.84 to−0.01 mmol/L, P < 0.05). The n-3 PUFA supplementation was also associated with significantly increased relative abundance of Bacteroidetes in phylum level (P < 0.01; false discovery rate (FDR) corrected p = 0.11), and decreased the ratio between Firmicutes and Bacteroidetes (P < 0.05; FDR corrected p = 0.16). At genus level, the intervention of plant derived n-3 PUFAs resulted in a significant decrease in relative abundance of Phascolarctobacterium (P < 0.01; FDR corrected p = 0.18) and Veillonella (P < 0.01; FDR corrected p = 0.18) after the intervention.

Conclusions

Our results demonstrated that plant-derived n-3 PUFAs beneficially affected the serum levels of TC and decreased the ratio between Firmicutes and Bacteroidetes during the 12-week intervention period, which might confer advantageous consequences for lipid metabolism and intestinal health.

Development of Fatty Acid Reference Ranges and Relationship with Lipid Biomarkers in Middle-Aged Healthy Singaporean Men and Women

Dietary fatty acids (FA) are essential for overall human health, yet individual FA reference ranges have yet to be established. Developing individual FA reference ranges can provide context to reported concentrations and whether an individual displays deficient, or excess amounts of FA. Reference ranges of sixty-seven individual FA (μmol/L) were profiled and analyzed using gas chromatography with a flame ionization detector from serum samples collected from 476 middle-aged Singaporean males (BMI:23.3 ± 2.9) and females (BMI:21.8 ± 3.6). Measures of triglycerides (TG), high-density lipoprotein (HDL), low-density lipoprotein (LDL), and total cholesterol (TC) (mmol/L) were also collected. The mean FA concentration seen in this cohort (11,458 ± 2478 was similar to that of overweight North American cohorts assessed in past studies. Ten biologically relevant FA were compared between sexes, with females exhibiting significantly higher concentrations in four FA (p < 0.05). A multiple regression model revealed the ten FA contributed significantly to nearly all lipid biomarkers (p < 0.05). A majority of participants who had FA concentrations in the ≥95th percentile also exhibited TG, HDL, LDL, and TC levels in the “high” risk classification of developing cardiovascular disease. Future studies profiling individual FA reference ranges in many unique, global cohorts are necessary to develop cut-off values of individual FA concentrations highly related to disease-risk.

Effect of alpha linolenic acid on membrane fluidity and respiration of liver mitochondria in normoglycemic and diabetic Wistar rats

The omega 3 fatty acids (ω3FA) have been recommended for the treatment of Type 2 Diabetes Mellitus (T2DM) and its complications, but there are studies questioning those beneficial effects. In this research, we supplemented the short-chain ω3FA, alpha-linolenic acid (ALA), to a model of rats with T2DM and normoglycemic controls, for 5 months. We were mainly interested in studying the effects of diabetes and ALA on the physicochemical properties of mitochondrial membranes and the consequences on mitochondrial respiration. We found that the Respiratory Control (RC) of diabetic rats was 46% lower than in control rats; in diabetic rats with ALA supplement, it was only 23.9% lower, but in control rats with ALA supplement, the RC was 29.5% higher, apparently improving. Diabetes also decreased the membrane fluidity, changed the thermotropic characteristics of membranes, and increased the proportion of saturated fatty acids. ALA supplement partially kept regulated the physicochemical properties of mitochondrial membranes in induced rats. Our data indicate that diabetes decreased the membrane fluidity through changes in the fatty acids composition that simultaneously affected the RC, which means that the mitochondrial respiration is highly dependent on the physicochemical properties of the membranes. Simultaneously, it was followed the effects of ALA on the progress of diabetes and we found also that the supplementation of ALA helped in controlling glycaemia in rats induced to T2DM; however, in control non-induced rats, the supplementation of ALA derived in characteristics of initial development of diabetes.

Effects of α-linolenic acid intake on blood lipid profiles：a systematic review and meta-analysis of randomized controlled trials

To investigate the effect of ALA intake on blood lipid profiles, including triglycerides (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), very-low-density lipoprotein (VLDL-C) and ratio of TC to HDL-C. We systematically searched randomized controlled trials of ALA intervention on PubMed, Embase, Cochrane library and related references up to March 2018. The final values were calculated as weighted mean difference (WMD) by using a random effects model. Subgroup analysis and meta-regression were used to explore the source of heterogeneity. Generalized least square was performed for dose-response analysis. Forty-seven studies with 1305 individuals in the ALA arm and 1325 individuals in the control arm were identified. Compared with control group, dietary intake of ALA significantly reduced the concentrations of TG (WMD -0.101 mmol/L; 95% CI: -0.158 to -0.044 mmol/L; P = 0.001), TC (WMD -0.140 mmol/L; 95% CI: -0.224 to -0.056 mmol/L; P = 0.001), LDL-C (WMD -0.131 mmol/L; 95% CI: -0.191 to -0.071 mmol/L; P < 0.001), VLDL-C (WMD -0.121 mmol/L; 95% CI: -0.170 to -0.073 mmol/L; P < 0.001), TC/HDL-C ratio (WMD -0.165 mmol/L; 95% CI: -0.317 to -0.013 mmol/L; P = 0.033) and LDL-C/HDL-C ratio (WMD -0.158 mmol/L; 95% CI: -0.291 to -0.025 mmol/L; P = 0.02). There is no effect of ALA intake on HDL-C (WMD 0.008 mmol/L; 95% CI: -0.018 to 0.034 mmol/L; P = 0.541). Dose-response analysis indicated that 1 g per day increment of ALA was associated with a 0.0016 mmol/L, 0.0071 mmol/L, 0.0015 and 0.0061 mmol/L reduction in TG (95% CI: -0.0029 to -0.0002 mmol/L), TC (95% CI: -0.0085 to -0.0058 mmol/L), HDL-C (95% CI: -0.0020 to -0.0011 mmol/L) and LDL-C (95% CI: -0.0073 to -0.0049 mmol/L) levels, respectively. The effects of ALA intake on TG, TC and LDL-C concentrations were more obvious among Asian participants, and also more obvious on patients with hyperlipidemia or hyperglycemia compared to healthy individuals. Dietary ALA intervention improves blood lipid profiles by decreasing levels of TG, TC, LDL and VLDL-C. Our findings add to the evidence that increasing ALA intake could potentially prevent risk of cardiovascular diseases.

Effects of eicosapentaenoic acid and docosahexaenoic acid versus α-linolenic acid supplementation on cardiometabolic risk factors: a meta-analysis of randomized controlled trials

Previous randomized controlled trials (RCTs) made direct comparisons between EPA/DHA versus ALA on improving cardiovascular risk factors and have reached inconsistent findings. The aim of this meta-analysis was to compare the effects of EPA/DHA vs. ALA supplementation on cardiometabolic disturbances. Databases including MEDLINE, Embase, PubMed and Cochrane Trials were searched until December 2019. The pooled effects (weighted mean difference, WMD) of outcomes with moderate and high heterogeneity were calculated with a random-effects model, while low heterogeneity was calculated with a fixed-effect model. Fourteen RCTs with 1137 participants who met the eligibility criteria were pooled. Compared with participants supplemented with ALA, those who received EPA/DHA supplementation experienced a greater reduction in triglycerides (TG) (WMD -0.191 mmol l-1; 95% CI -0.249, -0.133) but a greater increase in high-density lipoprotein (HDL) (WMD 0.033 mmol l-1; 95% CI 0.004, 0.062), low-density lipoprotein (LDL) (WMD 0.130 mmol l-1; 95% CI 0.006, 0.253) and total cholesterol (TC) (WMD 0.179 mmol l-1; 95% CI 0.006, 0.352). In subgroup analyses, the WMD for TG was much lower in trials with participants >40 years old (-0.246 mmol l-1; 95% CI -0.325, -0.167). When DHA and EPA were separately administered, modest increases in HDL were observed in trials that used DHA as a supplement (0.161 mmol l-1; 95% CI 0.017, 0.304), but not in trials using EPA (0.040 mmol l-1; 95% CI -0.132, 0.212). In conclusion, dietary EPA/DHA supplementation improved the TG and HDL status but increased LDL levels in comparison with ALA.

Flaxseed oil in the context of a weight loss programme ameliorates fatty liver grade in patients with non-alcoholic fatty liver disease: a randomised double-blind controlled trial

Long-chain n-3 fatty acids have been shown to regulate lipid metabolism and reduce fat accumulation in the liver. This trial investigated the effect of flaxseed oil, as a rich source of α-linolenic acid, on fatty liver and cardiometabolic risk factors in patients with non-alcoholic fatty liver disease (NAFLD). The randomised, double-blind, controlled trial was performed on sixty-eight NAFLD patients who were divided into flaxseed (n 34) and sunflower (n 34) oil groups. Patients were given a hypoenergetic diet (−2092 kJ/d) and 20 g/d of the corresponding oil for 12 weeks. Fatty liver grade, liver enzymes and cardiometabolic parameters were determined. The intention-to-treat approach was used for data analysis. Fatty liver grade significantly decreased in both groups (−0·68 in flaxseed v. −0·29 in sunflower, P = 0·002). Alanine aminotransferase and aspartate aminotransferase decreased in both groups (P < 0·01). Also, significant reduction was observed in blood glucose (P = 0·005) and fat mass (P = 0·01) in the flaxseed and muscle mass (P = 0·01) in the sunflower group. However, none of these alterations was significantly different between the groups. Weight, waist circumference and blood pressure were significantly decreased in both groups but only weight change was significantly different between the groups (P = 0·01). IL-6 did not significantly change in either group but showed a significant between-group difference (P = 0·03). Overall, the results showed that in the context of a low-energy diet and moderate physical activity, flaxseed oil may benefit NAFLD patients to improve fatty liver grade, weight and IL-6 compared with sunflower oil.

Effect of α-linolenic acid on vascular function and metabolic risk markers during the fasting and postprandial phase: A randomized placebo-controlled trial in untreated (pre-)hypertensive individuals

BACKGROUND

Only a limited number of studies have examined the vascular and postprandial effects of α-linolenic acid (ALA, C18:3n-3). Therefore, we performed a well-controlled trial focusing specifically on the effects of ALA on vascular function and metabolic risk markers during the fasting and postprandial phase in untreated (pre-)hypertensive individuals.

METHODS

In a double-blind randomized, placebo-controlled parallel study, 59 overweight and obese adults (40 men and 19 women, aged 60 ± 8 years) with a high-normal blood pressure or mild (stage I) hypertension consumed daily either 10 g of refined cold-pressed flaxseed oil, providing 4.7 g ALA (n = 29), or 10 g of high-oleic sunflower (control) oil (n = 30) for 12 weeks.

RESULTS

As compared with the high-oleic oil control, intake of flaxseed oil did not change brachial artery flow-mediated vasodilation, carotid-to-femoral pulse wave velocity, retinal microvascular calibers and plasma markers of microvascular endothelial function during the fasting and postprandial phase. Fasting plasma concentrations of free fatty acid (FFA) and TNF-α decreased by 58 μmol/L (P = 0.02) and 0.14 pg/mL (P = 0.03), respectively. No differences were found in other fasting markers of lipid and glucose metabolism, and low-grade systemic inflammation. In addition, dietary ALA did not affect postprandial changes in glucose, insulin, triacylglycerol, FFA and plasma inflammatory markers after meal intake.

CONCLUSION

A high intake of ALA, about 3-5 times the recommended daily intake, for 12 weeks decreased fasting FFA and TNF-α plasma concentrations. No effects were found on other metabolic risk markers and vascular function during the fasting and postprandial phase in untreated high-normal and stage I hypertensive individuals.

Omega-3 Fatty Acids for the Management of Hypertriglyceridemia: A Science Advisory From the American Heart Association

Hypertriglyceridemia (triglycerides 200-499 mg/dL) is relatively common in the United States, whereas more severe triglyceride elevations (very high triglycerides, ≥500 mg/dL) are far less frequently observed. Both are becoming increasingly prevalent in the United States and elsewhere, likely driven in large part by growing rates of obesity and diabetes mellitus. In a 2002 American Heart Association scientific statement, the omega-3 fatty acids (n-3 FAs) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were recommended (at a dose of 2-4 g/d) for reducing triglycerides in patients with elevated triglycerides. Since 2002, prescription agents containing EPA+DHA or EPA alone have been approved by the US Food and Drug Administration for treating very high triglycerides; these agents are also widely used for hypertriglyceridemia. The purpose of this advisory is to summarize the lipid and lipoprotein effects resulting from pharmacological doses of n-3 FAs (>3 g/d total EPA+DHA) on the basis of new scientific data and availability of n-3 FA agents. In treatment of very high triglycerides with 4 g/d, EPA+DHA agents reduce triglycerides by ≥30% with concurrent increases in low-density lipoprotein cholesterol, whereas EPA-only did not raise low-density lipoprotein cholesterol in very high triglycerides. When used to treat hypertriglyceridemia, n-3 FAs with EPA+DHA or with EPA-only appear roughly comparable for triglyceride lowering and do not increase low-density lipoprotein cholesterol when used as monotherapy or in combination with a statin. In the largest trials of 4 g/d prescription n-3 FA, non-high-density lipoprotein cholesterol and apolipoprotein B were modestly decreased, indicating reductions in total atherogenic lipoproteins. The use of n-3 FA (4 g/d) for improving atherosclerotic cardiovascular disease risk in patients with hypertriglyceridemia is supported by a 25% reduction in major adverse cardiovascular events in REDUCE-IT (Reduction of Cardiovascular Events With EPA Intervention Trial), a randomized placebo-controlled trial of EPA-only in high-risk patients treated with a statin. The results of a trial of 4 g/d prescription EPA+DHA in hypertriglyceridemia are anticipated in 2020. We conclude that prescription n-3 FAs (EPA+DHA or EPA-only) at a dose of 4 g/d (>3 g/d total EPA+DHA) are an effective and safe option for reducing triglycerides as monotherapy or as an adjunct to other lipid-lowering agents.

Effects of Dietary Fatty Acids in Pancreatic Beta Cell Metabolism, Implications in Homeostasis

Fatty acids are involved in several metabolic processes, including the development of metabolic and cardiovascular diseases. In recent years a disease that has received escalated interest is type 2 diabetes (T2D). Many contributing factors including a high-caloric diet rich in dietary saturated fats have been broadly characterized as triggers of T2D. Insulin resistance resulting from a high saturated fat diet leads to alterations in lipid cellular intake and accumulation which generate lipotoxic conditions, a key phenomenon in the metabolism of β-cells. Alternatively, unsaturated fatty acids have been described to show opposite effects in pancreatic β-cells. The purpose of this work is to perform a critical analysis of the complex role of saturated and unsaturated fatty acids in β-cell metabolism. We discuss the diverse effects main dietary fatty acids have upon pancreatic β-cell metabolism as a key factor to maintain homeostasis by focusing in the cellular and molecular mechanisms involved in the development and progression of T2D. For instance, modifications in protein homeostasis as well as the intracellular management of lipid metabolism which are associated with inflammatory pathways. These conditions initiate critical metabolic rearrangements, that in turn have repercussions on insulin β-cell metabolism. This review allows an integral and broad understanding of different functions of fatty acids inside β-cells, being important metabolites for novel therapeutic targets in T2D treatment.

Benefits of Nut Consumption on Insulin Resistance and Cardiovascular Risk Factors: Multiple Potential Mechanisms of Actions

Epidemiological and clinical studies have indicated that nut consumption could be a healthy dietary strategy to prevent and treat type 2 diabetes (T2DM) and related cardiovascular disease (CVD). The objective of this review is to examine the potential mechanisms of action of nuts addressing effects on glycemic control, weight management, energy balance, appetite, gut microbiota modification, lipid metabolism, oxidative stress, inflammation, endothelial function and blood pressure with a focus on data from both animal and human studies. The favourable effects of nuts could be explained by the unique nutrient composition and bioactive compounds in nuts. Unsaturated fatty acids (monounsaturated fatty acids and polyunsaturated fatty acids) present in nuts may play a role in glucose control and appetite suppression. Fiber and polyphenols in nuts may also have an anti-diabetic effect by altering gut microbiota. Nuts lower serum cholesterol by reduced cholesterol absorption, inhibition of HMG-CoA reductase and increased bile acid production by stimulation of 7-α hydroxylase. Arginine and magnesium improve inflammation, oxidative stress, endothelial function and blood pressure. In conclusion, nuts contain compounds that favourably influence glucose homeostasis, weight control and vascular health. Further investigations are required to identify the most important mechanisms by which nuts decrease the risk of T2DM and CVD.

Low levels of linoleic acid and α-linolenic acid and high levels of arachidonic acid in plasma phospholipids are associated with hypertension

Dietary fat is an important determinant in the development and progression of high blood pressure (BP), a major risk factor for cardiovascular diseases and mortality. The aim of the present study was to determine the association between plasma phospholipid fatty acids and hypertension in Japanese men. The plasma level of linoleic acid (LA) in the subjects with hypertension (systolic BP ≥140 mmHg and/or diastolic BP ≥90 mmHg) was identified to be significantly higher than that in the healthy controls. Following adjustment for age, body mass index, physical activity, smoking status, alcohol consumption, salt intake, and serum levels of glucose and hemoglobin A1c, higher plasma levels of LA and α-linolenic acid (ALA), and lower levels of arachidonic acid (AA) were significantly associated with a lower prevalence of hypertension. The odds ratio (OR) for the highest quartile (Q4) versus the lowest quartile (Q1) of LA was 0.17 (P=0.003), the OR for Q4 versus Q1 of ALA was 0.26 (P=0.042) and the OR for Q4 versus Q1 of AA was 2.04 (P=0.047). These results indicate that elevated levels of LA and ALA, and reduced levels of AA in the plasma prevent hypertension.

The effect of alpha-linolenic acid on glycemic control in individuals with type 2 diabetes: A systematic review and meta-analysis of randomized controlled clinical trials

BACKGROUND

Polyunsaturated fats (PUFAs) have been shown to reduce type 2 diabetes (T2DM) risk and improve insulin responsiveness in T2DM subjects, but whether the plant sources of omega-3 PUFA (alpha-linolenic acid [ALA]) have an effect on glycemic control requires further investigation.

METHODS

The parameters of interest were glycated hemoglobin (HbA1c), fasting blood glucose (FBG), fasting blood insulin (FBI), homeostatic model assessment for insulin resistance (HOMA-IR), fructosamine, and glycated albumin. A comprehensive search was conducted with MEDLINE, Embase, CINAHL, and Cochrane. Eligible studies included randomized controlled trials (RCTs) ≥1 month in duration that compared diets enriched in ALA with usual diets on glycemic parameters. For each study, the risk of bias as well as the study quality was assessed. Using the statistical software RevMan (v5.3), data were pooled using the generic inverse method with random effects model, and final results were expressed as mean differences (MD) with 95% confidence intervals (CI). Heterogeneity was assessed by the Cochran Q statistic and quantified by the I statistic.

RESULTS

A total of 8 trials (N = 212) were included in the meta-analysis. Compared to a control diet, a median dose of 4.4 g/day of ALA intake for a median duration of 3 months did not affect HbA1c (%) (MD = -.01; [95%: -.32, .31], P = .96). A median ALA dose of 5.4 g/day did not lower FBG (MD = .07; [95% CI: -.61, .76], P = .84) or FBI (MD = 7.03, [95% CI: -5.84, 19.89], P = .28). Summary effect estimates were generally compromised by considerable and unexplained heterogeneity (I ≥75%). In the subgroup analysis of continuous predictors, a reduction in HbA1c (%) and FBG (mmol/L) was significantly associated with an increased intake of ALA. Further adjustment for Publication Bias using Duval and Tweedie's trim-and-fill analysis provided an adjusted, significant MD of -.25 (95% CI: -.38, -.12; P <.001) for HbA1c (%).

CONCLUSIONS

ALA-enriched diets did not affect HbA1c, FBG, or FBI. The scarce number of existing RCTs and the presence of heterogeneity in our meta-analysis limit the ability to make firm conclusions about ALA in T2DM management. The potential for ALA to have dose-dependent effects warrants further research in this area.

Plasma α-Linolenic and Long-Chain ω-3 Fatty Acids Are Associated with a Lower Risk of Acute Myocardial Infarction in Singapore Chinese Adults

BACKGROUND

Long-chain marine omega-3 polyunsaturated fatty acids (n-3 PUFAs) are associated with a lower risk of acute myocardial infarction (AMI), but results for plant-derived α-linolenic acid (ALA; 18:3n-3) are inconsistent.

OBJECTIVE

We aimed to examine the association between plasma n-3 PUFAs and AMI risk and to explore potential mediation by cardiovascular disease risk factors.

METHODS

A nested case-control study with 744 incident AMI cases and 744 matched controls was conducted within the Singapore Chinese Health Study for participants aged 47-83 y. Conditional logistic regression was used to calculate the multivariable ORs for AMI with and without adjustment for cardiovascular disease risk factors, including blood lipids, blood pressure, C-reactive protein, serum creatinine, and glycated hemoglobin.

RESULTS

Plasma long-chain n-3 PUFAs were associated with lower AMI risk (multivariable OR: 0.62; 95% CI: 0.41, 0.94; for the highest compared with the lowest quartile; P-trend = 0.03). This association was not substantially changed after adjustment for cardiovascular disease risk factors. Dietary intakes of fish and long-chain n-3 PUFAs were similarly inversely associated with AMI risk. Plasma ALA was marginally associated with a lower risk of AMI (multivariable OR: 0.73; 95% CI: 0.51, 1.05; P-trend = 0.07) even in persons with high plasma concentrations of long-chain n-3 PUFAs. This association became significantly weaker after adjustment for blood pressure and LDL cholesterol.

CONCLUSIONS

Plasma long-chain n-3 PUFAs are associated with a lower risk of AMI in this Asian population. Plasma ALA may be marginally associated with reduced AMI risk, even in persons with high concentrations of long-chain n-3 PUFAs, and this association may be partially mediated by lower blood pressure and LDL cholesterol.

An Update on Nutrients and Blood Pressure

Adverse blood pressure (BP) is a major independent risk factor for epidemic cardiovascular diseases affecting almost one-quarter of the adult population worldwide. Dietary intake is a major determinant in the development and progression of high BP. Lifestyle modifications, including recommended dietary guidelines, are advocated by the American Society of Hypertension, the International Society of Hypertension, the Japanese Society of Hypertension, and many other organisations for treating all hypertensive people, prior to initiating drug therapy and as an adjunct to medication in persons already on drug therapy. Lifestyle modification can also reduce high BP and prevent development of hypertension. This review synthesizes results from the International Study of Macro/Micronutrients and Blood Pressure (INTERMAP), a cross-sectional epidemiological study of 4,680 men and women aged 40-59 years from Japan, the People's Republic of China, the United Kingdom, and the United States, published over the past few years on cross cultural BP differences. INTERMAP has previously reported that intakes of vegetable protein, glutamic acid, total and insoluble fibre, total polyunsaturated fatty acid and linoleic acid, total n-3 fatty acid and linolenic acid, phosphorus, calcium, magnesium, and non-heme iron were inversely related to BP. Direct associations of sugars (fructose, glucose, and sucrose) and sugar-sweetened beverages (especially combined with high sodium intake), cholesterol, glycine, alanine, and oleic acid from animal sources with BP were also reported by the INTERMAP Study.

Functional foods as potential therapeutic options for metabolic syndrome

Obesity as part of metabolic syndrome is a major lifestyle disorder throughout the world. Current drug treatments for obesity produce small and usually unsustainable decreases in body weight with the risk of major adverse effects. Surgery has been the only treatment producing successful long-term weight loss. As a different but complementary approach, lifestyle modification including the use of functional foods could produce a reliable decrease in obesity with decreased comorbidities. Functional foods may include fruits such as berries, vegetables, fibre-enriched grains and beverages such as tea and coffee. Although health improvements continue to be reported for these functional foods in rodent studies, further evidence showing the translation of these results into humans is required. Thus, the concept that these fruits and vegetables will act as functional foods in humans to reduce obesity and thereby improve health remains intuitive and possible rather than proven.

Evidence-Based Guideline of the German Nutrition Society: Fat Intake and Prevention of Selected Nutrition-Related Diseases

As nutrition-related chronic diseases have become more and more frequent, the importance of dietary prevention has also increased. Dietary fat plays a major role in human nutrition, and modification of fat and/or fatty acid intake could have a preventive potential. The aim of the guideline of the German Nutrition Society (DGE) was to systematically evaluate the evidence for the prevention of the widespread diseases obesity, type 2 diabetes mellitus, dyslipoproteinaemia, hypertension, metabolic syndrome, coronary heart disease (CHD), stroke, and cancer through the intake of fat or fatty acids. The main results can be summarized as follows: it was concluded with convincing evidence that a reduced intake of total and saturated fat as well as a larger intake of polyunsaturated fatty acids (PUFA) at the expense of saturated fatty acids (SFA) reduces the concentration of total and low-density lipoprotein cholesterol in plasma. Furthermore, there is convincing evidence that a high intake of trans fatty acids increases risk of dyslipoproteinaemia and that a high intake of long-chain polyunsaturated n-3 fatty acids reduces the triglyceride concentration in plasma. A high fat intake increases the risk of obesity with probable evidence when total energy intake is not controlled for (ad libitum diet). When energy intake is controlled for, there is probable evidence for no association between fat intake and risk of obesity. A larger intake of PUFA at the expense of SFA reduces risk of CHD with probable evidence. Furthermore, there is probable evidence that a high intake of long-chain polyunsaturated n-3 fatty acids reduces risk of hypertension and CHD. With probable evidence, a high trans fatty acid intake increases risk of CHD. The practical consequences for current dietary recommendations are described at the end of this article.

Mechanisms of enhanced insulin secretion and sensitivity with n-3 unsaturated fatty acids

The widespread acceptance that increased dietary n-3 polyunsaturated fatty acids (PUFAs), especially α-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), improve health is based on extensive studies in animals, isolated cells and humans. Visceral adiposity is part of the metabolic syndrome, together with insulin resistance, dyslipidemia, hypertension and inflammation. Alleviation of metabolic syndrome requires normalization of insulin release and responses. This review assesses our current knowledge of the mechanisms that allow n-3 PUFAs to improve insulin secretion and sensitivity. EPA has been more extensively studied than either ALA or DHA. The complex actions of EPA include increased G-protein-receptor-mediated release of glucagon-like peptide 1 (GLP-1) from enteroendocrine L-cells in the intestine, up-regulation of the apelin pathway and down-regulation of other control pathways to promote insulin secretion by the pancreatic β-cells, together with suppression of inflammatory responses to adipokines, inhibition of peroxisome proliferator-activated receptor α actions and prevention of decreased insulin-like growth factor-1 secretion to improve peripheral insulin responses. The receptors involved and the mechanisms of action probably differ for ALA and DHA, with antiobesity effects predominating for ALA and anti-inflammatory effects for DHA. Modifying both GLP-1 release and the actions of adipokines by n-3 PUFAs could lead to additive improvements in both insulin secretion and sensitivity.

Alpha-linolenic acid: an omega-3 fatty acid with neuroprotective properties-ready for use in the stroke clinic?

Alpha-linolenic acid (ALA) is plant-based essential omega-3 polyunsaturated fatty acids that must be obtained through the diet. This could explain in part why the severe deficiency in omega-3 intake pointed by numerous epidemiologic studies may increase the brain's vulnerability representing an important risk factor in the development and/or deterioration of certain cardio- and neuropathologies. The roles of ALA in neurological disorders remain unclear, especially in stroke that is a leading cause of death. We and others have identified ALA as a potential nutraceutical to protect the brain from stroke, characterized by its pleiotropic effects in neuroprotection, vasodilation of brain arteries, and neuroplasticity. This review highlights how chronic administration of ALA protects against rodent models of hypoxic-ischemic injury and exerts an anti-depressant-like activity, effects that likely involve multiple mechanisms in brain, and may be applied in stroke prevention. One major effect may be through an increase in mature brain-derived neurotrophic factor (BDNF), a widely expressed protein in brain that plays critical roles in neuronal maintenance, and learning and memory. Understanding the precise roles of ALA in neurological disorders will provide the underpinnings for the development of new therapies for patients and families who could be devastated by these disorders.

Effects of Dietary Fat Intake on HDL Metabolism

High-density lipoprotein (HDL) is a lipoprotein which has anti-atherogenic property by reversing cholesterol transport from the peripheral tissues to liver. Low HDL-cholesterol (HDL-C) as well as high low-density lipoprotein-cholesterol (LDL-C) is associated with the development of coronary heart diseases (CHD). Various epidemiological studies have suggested that the development of CHD increase in individuals with less than 40 mg/dL of HDL-C. In spite of accumulation of evidences suggesting a significant association between low HDL-C and CHD, effects of dietary factors on HDL metabolism remained largely unknown. We reviewed published articles about effects of dietary fat intake on HDL metabolism. The substitution of fatty acids (FA) for carbohydrates is beneficially associated with HDL metabolism. Monounsaturated FA intake may not affect HDL-C. Trans-FA is significantly associated with reduction of HDL-C, and is also adversely related with total cholesterol/HDL-C. Fish oils consumption, especially docosahexaenoic acid consumption, may be favorably associated with HDL metabolism. Although plant sterols and stanols may not affect HDL-C, policosanol intake is associated with a clinically significant decrease in the LDL/HDL ratio.

Vascular effects of the Mediterranean diet-part II: role of omega-3 fatty acids and olive oil polyphenols

The lower occurrence of cardiovascular disease and cancer in populations around the Mediterranean basin as detected in the 1950s was correctly attributed to the peculiar dietary habits of those populations. Essentially, until the mid-20th century, typical Mediterranean diets were rich in fruits, vegetables, legumes, whole-wheat bread, nuts, fish, and, as a common culinary trait, the routine use of extra-virgin olive oil. Nowadays, the regular adoption of such dietary patterns is still thought to result in healthful benefits. Such patterns ensure the assumption of molecules with antioxidant and anti-inflammatory actions, among which ω-3 polyunsaturated fatty acids (PUFAs), ω-9 monounsaturated fatty acids (oleic acid), and phenolic compounds. The aim of this review is to provide an update of the vasculo-protective pathways mediated by ω-3 PUFAs and polyphenols in the context of the modern Mediterranean dietary habits, including the possible cross-talk and synergy between these typical components. This review complements a parallel one focusing on the role of dietary nitrates and alimentary fats.

Interactions between prebiotics, probiotics, polyunsaturated fatty acids and polyphenols: diet or supplementation for metabolic syndrome prevention?

The metabolic syndrome can be prevented by the Mediterranean diet, characterized by fiber, omega-3 polyunsaturated fatty acids and polyphenols. However, the composition of the Mediterranean diet, which can be viewed as a natural multiple supplement, is poorly controlled, and its beneficial effects poorly predictable. The metabolic syndrome is associated with intestinal dysbiosis and the gut microbioma seems to be the main target and player in the interactions occurring between probiotics, prebiotics, omega 3 polyunsaturated fatty acids, and polyphenols. From the reviewed evidence, it is reasonable to manage growth and metabolism of gut microflora with specific prebiotics and polyphenols. Even though the healthy properties of functional foods and nutraceuticals still need to be fully elucidated, available data suggest that well-designed supplements, containing the better ratio of omega-3 polyunsaturated fatty acids and antioxidants, specific probiotic strains, and selected polyphenols and prebiotics, could be useful in metabolic syndrome prevention and treatment.

Different dietary fatty acids are associated with blood lipids in healthy South African men and women: the PURE study

BACKGROUND

Preliminary data from the baseline Prospective Urban Rural Epidemiology (PURE) study in South Africa indicated a higher prevalence of dyslipidemia than previous South African studies. The intake of specific individual dietary fatty acids may affect blood lipids differently than sub-groups of fat (i.e. polyunsaturated fatty acids). We investigated the dietary intake of different individual fatty acids and their associations with blood lipids, in relation to urbanization and gender.

METHODS

Cross-sectional data analysis within the PURE baseline study of healthy subjects (n=1950, 35-70 years) from rural and urban areas. Dietary data were collected and blood lipid analysis performed.

RESULTS

Intake of individual fatty acids was significantly higher in urban than rural dwellers. However, the intake of n-3 PUFAs was below recommendations in all groups. Total cholesterol and LDL were higher in females than in males, with no rural‒urban differences. Intake of alpha-linolenic acid (ALA) was positively associated with total cholesterol (β=0.143) and triglycerides (β=0.256) in males. The risk for having elevated LDL also increased with increased intake of ALA (OR 1.49, 95% CI 1.04, 2.14) in males. In females, arachidonic acid and eicosapentaenoic acid (EPA) were positively associated with total cholesterol and arachidonic acid was also positively associated with LDL, whereas docosahexaenoic acid was negatively associated with total cholesterol and LDL.

CONCLUSIONS

These results suggest that specific individual dietary fatty acids may affect blood lipids in males differently than in females irrespective of rural or urban dwelling. The positive association between ALA and total cholesterol and triglycerides in males is a concern, because current advice aims to improve the dietary linoleic acid to ALA ratio by increasing ALA intake.

Serum omega-3 polyunsaturated fatty acids and risk of incident type 2 diabetes in men: the Kuopio Ischemic Heart Disease Risk Factor study

OBJECTIVE The relationship between fish or omega-3 polyunsaturated fatty acids (PUFAs) and type 2 diabetes is inconclusive. Even contaminants in fish, such as mercury, may modify the effects. We investigated the associations between serum omega-3 PUFAs eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), docosahexaenoic acid (DHA), α-linolenic acid (ALA), hair mercury, and risk of incident type 2 diabetes in middle-aged and older Finnish men. RESEARCH DESIGN AND METHODS A total of 2,212 men from the prospective, population-based Kuopio Ischemic Heart Disease Risk Factor study, aged 42-60 years and free of type 2 diabetes at baseline in 1984-1989, were investigated. Serum PUFA and hair mercury were used as biomarkers for exposure. Dietary intakes were assessed with 4-day food recording. Type 2 diabetes was assessed by self-administered questionnaires and fasting and 2-h oral glucose tolerance test blood glucose measurement at re-examination rounds 4, 11, and 20 years after the baseline and by record linkage to hospital discharge registry and reimbursement register on diabetes medication expenses. Cox proportional hazards models were used to analyze associations. RESULTS During the average follow-up of 19.3 years, 422 men developed type 2 diabetes. Men in the highest versus the lowest serum EPA + DPA + DHA quartile had 33% lower multivariate-adjusted risk for type 2 diabetes (95% CI 13-49; P trend 0.01). No statistically significant associations were observed with serum or dietary ALA, dietary fish or EPA + DHA, or hair mercury. CONCLUSIONS Serum long-chain omega-3 PUFA concentration, an objective biomarker for fish intake, was associated with long-term lower risk of type 2 diabetes.

Association of dietary omega-3 fatty acids with prevalence of metabolic syndrome: the National Heart, Lung, and Blood Institute Family Heart Study

BACKGROUND & AIMS

Metabolic syndrome (MetS), characterized by abdominal obesity, atherogenic dyslipidemia, elevated blood pressure, and insulin resistance is a major public health concern in the United States. Omega-3 fatty acids have been relatively well studied in relation to many individual cardiovascular risk factors; however, their effects on MetS are not well established.

METHODS

We conducted a cross-sectional study consisting of 4941 participants from the National Heart, Lung, and Blood Institute (NHLBI) Family Heart Study to assess the relation of dietary omega-3 fatty acids with the prevalence of MetS. Omega-3 intake was assessed using a food frequency questionnaire and we used generalized estimating equations to estimate adjusted odds ratios for prevalent MetS.

RESULTS

Our study population had a mean age (SD) of 52.1 (13.9) years and 45.9% were men. The mean (SD) of dietary omega-3 fatty acids was 0.25 g/day (0.27). From the lowest to the highest quintile of dietary omega-3 fatty acids, multivariable adjusted ORs (95% CI) for MetS were 1.00 (ref), 0.90 (0.72-1.13), 1.03 (0.82-1.28), 0.94 (0.74-1.18), and 0.99 (0.77-1.25), respectively. In a secondary analysis, neither fish consumption nor dietary alpha-linolenic acid was associated with MetS.

CONCLUSIONS

Our findings do not support an association between dietary omega-3 fatty acids and MetS in a large US population.

Beneficial effects of omega-3 fatty acids on the consequences of a fructose diet are not mediated by PPAR delta or PGC1 alpha

PURPOSE

To study, in high-fructose-fed rats, the effect of a dietary enrichment in omega-3 polyunsaturated fatty acids (n-3 PUFA) on the expression of genes involved in lipid metabolism and cardiovascular function.

METHODS

Twenty-eight male "Wistar Han" rats received for 8 weeks, either a standard chow food or an isocaloric 67% fructose diet enriched or not in alpha-linolenic acid (ALA) or in docosahexaenoic (DHA) and eicosapentaenoic acids (EPA) mix (DHA/EPA). After sacrifice, blood was withdrawn for biochemical analyses; heart, periepididymal adipose tissue and liver were collected and analyzed for the expression of 22 genes by real-time PCR.

RESULTS

Fructose intake resulted in an increase in liver weight and triglyceride content, plasma triglyceride and cholesterol concentrations, although no difference in glucose and insulin. In the liver, lipogenesis was promoted as illustrated by an increase in stearoyl-CoA desaturase and fatty acid synthase (Fasn) together with a decrease in PPAR gamma, delta and PPAR gamma coactivator 1 alpha (PGC1 alpha) expression. In the heart, Fasn and PPAR delta expression were increased. The addition of ALA or DHA/EPA into the diet resulted in a protection against fructose effects except for the decreased expression of PPARs in the liver that was not counterbalanced by n-3 PUFA suggesting that n-3 PUFA and fructose act independently on the expression of PPARs and PGC1 alpha.

CONCLUSIONS

In liver, but not in heart, the fructose-enriched diet induces an early tissue-specific reduction in PPAR gamma and delta expression, which is insensitive to n-3 PUFA intake and dissociated from lipogenesis.

Sheep cheese naturally enriched in α-linolenic, conjugated linoleic and vaccenic acids improves the lipid profile and reduces anandamide in the plasma of hypercholesterolaemic subjects

Intake of dairy fat has long been considered as a risk factor for CVD. Pasture and dietary lipid supplementation have been reported to be reliable strategies in ruminant nutrition, in order to increase the content of α-linolenic acid (ALA), conjugated linoleic acid (CLA) and vaccenic acid (VA), and decrease SFA in milk fat. In the present study, we aimed at verifying whether consumption of a sheep cheese, naturally enriched in ALA, CLA and VA, would modify the plasma lipid and endocannabinoid profiles in mildly hypercholesterolaemic subjects. A total of forty-two adult volunteers (nineteen males and twenty-three females) with diagnosed mildly hypercholesterolaemia (total cholesterol 5·68-7·49 mmol/l) were randomly assigned to eat 90 g/d of a control or enriched cheese for 3 weeks, with a cross-over after 3 weeks of washout. Plasma lipids, endocannabinoids, adipokines and inflammatory markers were measured. The intake of enriched cheese significantly increased the plasma concentrations of CLA, VA, the n-3 fatty acids ALA and EPA, and more remarkably decreased that of the endocannabinoid anandamide. LDL-cholesterol decreased significantly (7%). No changes were detected in the levels of inflammatory markers; however, a significant correlation was found between the plasma levels of anandamide and leptin. The control cheese modified none of the parameters measured. The results obtained do not support the view that intake of dairy fat is detrimental to hypercholesterolaemic subjects. Indeed, they show that a naturally enriched cheese possesses beneficial properties, since it ameliorates the plasma lipid profile, and more remarkably reduces endocannabinoid biosynthesis.

Omega-3 fatty acids and incident type 2 diabetes: a systematic review and meta-analysis

The relationship between omega-3 polyunsaturated fatty acids (n-3 PUFA) from seafood sources (eicosapentaenoic acid, EPA; docosahexaenoic acid, DHA) or plant sources (alpha-linolenic acid, ALA) and risk of type 2 diabetes mellitus (DM) remains unclear. We systematically searched multiple literature databases through June 2011 to identify prospective studies examining relations of dietary n-3 PUFA, dietary fish and/or seafood, and circulating n-3 PUFA biomarkers with incidence of DM. Data were independently extracted in duplicate by 2 investigators, including multivariate-adjusted relative risk (RR) estimates and corresponding 95 % CI. Generalized least-squares trend estimation was used to assess dose-response relationships, with pooled summary estimates calculated by both fixed-effect and random-effect models. From 288 identified abstracts, 16 studies met inclusion criteria, including 18 separate cohorts comprising 540,184 individuals and 25,670 cases of incident DM. Consumption of fish and/or seafood was not significantly associated with DM (n = 13 studies; RR per 100 g/d = 1·12, 95 % CI = 0·94, 1·34); nor were consumption of EPA+DHA (n = 16 cohorts; RR per 250 mg/d = 1·04, 95 % CI = 0·97, 1·10) nor circulating levels of EPA+DHA biomarkers (n = 5 cohorts; RR per 3 % of total fatty acids = 0·94, 95 % CI = 0·75, 1·17). Both dietary ALA (n = 7 studies; RR per 0·5 g/d = 0·93, 95 % CI = 0·83, 1·04) and circulating ALA biomarker levels (n = 6 studies; RR per 0·1 % of total fatty acid = 0·90, 95 % CI = 0·80, 1·00, P = 0·06) were associated with non-significant trend towards lower risk of DM. Substantial heterogeneity (I²~80 %) was observed among studies of fish/seafood or EPA+DHA and DM; moderate heterogeneity ( < 55 %) was seen for dietary and biomarker ALA and DM. In unadjusted meta-regressions, study location (Asia vs. North America/Europe), mean BMI, and duration of follow-up each modified the association between fish/seafood and EPA+DHA consumption and DM risk (P-interaction ≤ 0·02 each). We had limited statistical power to determine the independent effect of these sources of heterogeneity due to their high collinearity. The overall pooled findings do not support either major harms or benefits of fish/seafood or EPA+DHA on development of DM, and suggest that ALA may be associated with modestly lower risk. Reasons for potential heterogeneity of effects, which could include true biologic heterogeneity, publication bias, or chance, deserve further investigation.

Erythrocyte n-3 fatty acids and metabolic syndrome in middle-aged and older Chinese

CONTEXT

Few studies examined associations of circulating n-3 fatty acid levels with metabolic syndrome (MetS) among Chinese populations who have low consumption of these fatty acids and high risk of developing MetS.

OBJECTIVE

The objective of the study was to determine associations between erythrocyte n-3 fatty acids and MetS as well as its components among middle-aged and older Chinese men and women.

DESIGN AND PARTICIPANTS

Erythrocyte levels of docosahexaenoic acid (DHA), docosapentaenoic acid, eicosapentaenoic acid, and α-linolenic acid (ALA) were measured by gas chromatography among 2754 participants aged 50-70 yr living in Beijing and Shanghai. MetS was defined using the updated National Cholesterol Education Program Adult Treatment Panel III criteria for Asian-Americans.

RESULTS

After multivariable adjustment, higher levels of DHA, but neither eicosapentaenoic acid nor docosapentaenoic acid, were associated with lower odds of MetS as well as elevated blood pressure and triglycerides. Comparing extreme quartiles of DHA, odds ratios (95% confidence interval) were 0.75 (0.55, 1.01; P for trend = 0.04) for MetS; 0.70 (0.53, 0.92; P for trend = 0.01) for elevated blood pressure; and 0.64 (0.48, 0.87; P for trend = 0.005) for elevated triglycerides. In contrast, ALA concentrations were positively associated with MetS odds (odds ratio 4.06; 95% confidence interval 2.85, 5.80; P for trend <0.001).

CONCLUSIONS

Higher concentrations of erythrocyte DHA were associated with lower odds of MetS, whereas higher concentrations of ALA were associated with increased odds among middle-aged and older Chinese. These findings warrant replication in other populations.

Effects of n-3 fatty acids on major cardiovascular events in statin users and non-users with a history of myocardial infarction

AIMS

Recent secondary prevention trials have failed to demonstrate a beneficial effect of n-3 fatty acids on cardiovascular outcomes, which may be due to the growing use of statins since the mid-1990s. The aim of the present study was to assess whether statins modify the effects of n-3 fatty acids on major adverse cardiovascular events in patients with a history of myocardial infarction (MI).

METHODS AND RESULTS

Patients who participated in the Alpha Omega Trial were divided into consistent statin users (n = 3740) and consistent statin non-users (n = 413). In these two groups of patients, the effects of an additional daily amount of 400 mg eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA), 2 g α-linolenic acid (ALA), or both on major cardiovascular events were evaluated. Multivariable Cox's proportional hazard models were used to calculate adjusted hazard rate ratios (HR(adj)). Among the statin users 495 (13%) and among the statin non-users 62 (15%) developed a major cardiovascular event. In statin users, an additional amount of n-3 fatty acids did not reduce cardiovascular events [HR(adj) 1.02; 95% confidence interval (CI): 0.80, 1.31; P = 0.88]. In statin non-users, however, only 9% of those who received EPA-DHA plus ALA experienced an event compared with 18% in the placebo group (HR(adj) 0.46; 95% CI: 0.21, 1.01; P= 0.051).

CONCLUSION

In patients with a history of MI who are not treated with statins, low-dose supplementation with n-3 fatty acids may reduce major cardiovascular events. This study suggests that statin treatment modifies the effects of n-3 fatty acids on the incidence of major cardiovascular events.

The α-linolenic acid content of flaxseed can prevent the atherogenic effects of dietary trans fat

Dietary intake of industrially hydrogenated trans fatty acids (TFA) has been associated with coronary heart disease. Dietary flaxseed can inhibit atherosclerosis induced by dietary cholesterol. The aim of this study was to determine whether supplementing the diet with flaxseed could protect against atherosclerosis induced by a diet enriched in TFA. Low-density lipoprotein receptor-deficient (LDLr−/−) mice were fed 1 of 14 experimental diets for 14 wk containing one of two fat sources [regular (pork/soy) or trans fat] at two concentrations (4 or 8%) and supplemented with or without dietary cholesterol (2%), whole ground flaxseed, or one of the components of flaxseed [α-linolenic acid (ALA), defatted fiber, or lignan]. Adding flaxseed to the diet partially mitigated the rise in circulating cholesterol levels induced by the cholesterol-enriched diet. Atherosclerosis was stimulated by TFA and/or cholesterol. Including milled flaxseed to an atherogenic diet significantly reduced atherosclerosis compared with the groups that consumed cholesterol and/or TFA. ALA was the only component within flaxseed that could inhibit the atherogenic action of cholesterol and/or TFA on its own. Dietary flaxseed protects against atherosclerotic development induced by TFA and cholesterol feeding through its content of ALA.