Effects of docosahexaenoic acid on vascular pathology and reactivity in hypertension

Pharmacological modulation of vascular ageing: A review from VascAgeNet

Vascular ageing, characterized by structural and functional changes in blood vessels of which arterial stiffness and endothelial dysfunction are key components, is associated with increased risk of cardiovascular and other age-related diseases. As the global population continues to age, understanding the underlying mechanisms and developing effective therapeutic interventions to mitigate vascular ageing becomes crucial for improving cardiovascular health outcomes. Therefore, this review provides an overview of the current knowledge on pharmacological modulation of vascular ageing, highlighting key strategies and promising therapeutic targets. Several molecular pathways have been identified as central players in vascular ageing, including oxidative stress and inflammation, the renin-angiotensin-aldosterone system, cellular senescence, macroautophagy, extracellular matrix remodelling, calcification, and gasotransmitter-related signalling. Pharmacological and dietary interventions targeting these pathways have shown potential in ameliorating age-related vascular changes. Nevertheless, the development and application of drugs targeting vascular ageing is complicated by various inherent challenges and limitations, such as certain preclinical methodological considerations, interactions with exercise training and sex/gender-related differences, which should be taken into account. Overall, pharmacological modulation of endothelial dysfunction and arterial stiffness as hallmarks of vascular ageing, holds great promise for improving cardiovascular health in the ageing population. Nonetheless, further research is needed to fully elucidate the underlying mechanisms and optimize the efficacy and safety of these interventions for clinical translation.

Antihypertensive Potential of Tartaric Acid and Exploration of Underlying Mechanistic Pathways

Tartaric acid is capable of balancing blood pressure. It is the main constituent of antihypertensive agents (grapes and wine) and has not been scientifically explored as an antihypertensive remedy. This study aimed to investigate the antihypertensive effect of a low-dose tartaric acid in vivo and explore underlying mechanisms in vitro. Intravenous administration of tartaric acid at the dose of 50 µg/kg caused a % fall in mean arterial pressure (MAP) in normotensive and hypertensive rats [51.5 ± 1.7 and 63.5 ± 2.9% mmHg]. This hypotensive effect was partially inhibited by atropine (1 mg/kg) and _L-NAME (100 µg/kg) pretreatment. In hypertensive rats, oral administration of tartaric acid (.1, .5, 1, 5, and 10 mg/kg) for 2 weeks resulted in 65 ± 7.3 mmHg MAP at 10 mg/kg. This antihypertensive effect was comparable to the orally administered verapamil (10 mg/kg) for 2 weeks which caused a decrease in MAP 60.4 ± 3.8 mmHg. Tartaric acid relaxed phenylephrine (PE) and High K⁺-induced contractions with EC₅₀ values of .157 (.043-.2) and 1.93 (.07-2) µg/mL in vitro. This endothelium-dependent relaxation was inhibited with atropine (1 µM) and _L-NAME (10 µM) pretreatment. Tartaric acid also suppressed phenylephrine contractions in Ca⁺² free/EGTA medium and on voltage-dependent calcium channels, causing the concentration–response curves toward right. Tartaric acid induced negative inotropic and chronotropic effects with EC₅₀ values of .26 (.14-.4) and .60 (.2-.8) in rat atria. It showed its effect by complete blockade against atropine and partially in propranolol pretreatment. These findings provide scientific basis to low-dose tartaric acid as an antihypertensive and vasodilatory remedy through muscarinic receptor-linked nitric oxide (NO) pathway and Ca⁺² channel antagonist.

Effect of omega-3 polyunsaturated fatty acids in modulation of vascular tone under physiological and pathological conditions

Omega-3 polyunsaturated fatty acids (n-3 PUFAs), including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are mainly found in marine fish oils and commercially available fish oil supplements. Several studies have documented that n-3 PUFAs can reduce the risk of cardiovascular diseases through anti-inflammatory, anti-thrombotic, and anti-atherosclerotic properties. Notably, regulation of vascular tone is one of the most important bases of cardiovascular health and especially for maintaining blood pressure within optimal physiological ranges. Recent clinical and animal studies indicate an association between n-3 PUFAs and vascular functions. In this regard, many clinical trials and basic experimental studies have been conducted so far to investigate the influence of n-3 PUFAs on vascular tone. In this review, we have summarized the results obtained from both clinical and basic studies that evaluated the effect of n-3 PUFAs under physiological and pathological conditions. Moreover, we also focus on verifying the underlying basic molecular mechanism of n-3 PUFAs on the vascular system.

Dietary Docosahexaenoic Acid Reduces Oscillatory Wall Shear Stress, Atherosclerosis, and Hypertension, Most Likely Mediated via an IL-1-Mediated Mechanism

BACKGROUND

Hypertension is a complex condition and a common cardiovascular risk factor. Dietary docosahexaenoic acid (DHA) modulates atherosclerosis and hypertension, possibly via an inflammatory mechanism. IL-1 (interleukin 1) has an established role in atherosclerosis and inflammation, although whether IL-1 inhibition modulates blood pressure is unclear.

METHODS AND RESULTS

Male apoE-/- (apolipoprotein E-null) mice were fed either a high fat diet or a high fat diet plus DHA (300 mg/kg per day) for 12 weeks. Blood pressure and cardiac function were assessed, and effects of DHA on wall shear stress and atherosclerosis were determined. DHA supplementation improved left ventricular function, reduced wall shear stress and oscillatory shear at ostia in the descending aorta, and significantly lowered blood pressure compared with controls (119.5±7 versus 159.7±3 mm Hg, P<0.001, n=4 per group). Analysis of atheroma following DHA feeding in mice demonstrated a 4-fold reduction in lesion burden in distal aortas and in brachiocephalic arteries (P<0.001, n=12 per group). In addition, DHA treatment selectively decreased plaque endothelial IL-1β (P<0.01).

CONCLUSIONS

Our findings revealed that raised blood pressure can be reduced by inhibiting IL-1 indirectly by administration of DHA in the diet through a mechanism that involves a reduction in wall shear stress and local expression of the proinflammatory cytokine IL-1β.

Lecithin derived from ω-3 PUFA fortified eggs decreases blood pressure in spontaneously hypertensive rats

Hypertension is the most common risk factor for stroke, coronary heart disease and heart failure, which are the leading causes of death worldwide. Dietary patterns and supplements intakes are becoming important factors in the hypertension. The aim of this study was to estimate the effects of new generation egg yolk phospholipids rich in lecithin (SL) esterified with omega-3 and omega-6 fatty acids on blood pressure in hypertensive rats (SHR). Here we have reported that lecithin (SL) derived from egg yolk lowers blood pressure in pathology of hypertension. The SHR rats treated with SL had significantly lower blood pressure than control group (157/104 vs. 178/121 mmHg; P < 0.05) and down-regulated mesenteric artery over-response to norepinephrine and potassium chloride, giving similar arterial response as for normotensive Wistar Kyoto rats (WKY). Hypertensive rats treated by SL demonstrated significantly lower serum level of inflammatory factors. This work also indicates that SL treatment lowers heart rate and reduces the serum level of oxidative stress marker - nitrotyrosine - by 30–34% in both hypertensive and normotensive animals. Phospholipids with lecithin derived from PUFA fortified eggs may be a valuable dietary supplement in prophylaxis of hypertension and in patients with hypertension, however, this requires further studies on humans.

Docosahexaenoic Acid Supplemented Diet Influences the Orchidectomy-Induced Vascular Dysfunction in Rat Mesenteric Arteries

Over the past few decades, the cardiovascular benefits of a high dietary intake of long-chain polyunsaturated fatty acids (PUFAs), like docosahexaenoic acid (DHA), have been extensively studied. However, many of the molecular mechanisms and effects exerted by PUFAs have yet to be well explained. The lack of sex hormones alters vascular tone, and we have described that a DHA-supplemented diet to orchidectomized rats improve vascular function of the aorta. Based on these data and since the mesenteric artery importantly controls the systemic vascular resistance, the objective of this study was to analyze the effect of a DHA-supplemented diet on the mesenteric vascular function from orchidectomized rats. For this purpose mesenteric artery segments obtained from control, orchidectomized or orchidectomized plus DHA-supplemented diet were utilized to analyze: (1) the release of prostanoids, (2) formation of NO and ROS, (3) the vasodilator response to acetylcholine (ACh), as well as the involvement of prostanoids and NO in this response, and (4) the vasoconstrictor response to electrical field stimulation (EFS), analyzing also the effect of exogenous noradrenaline (NA), and the NO donor, sodium nitroprusside (SNP). The results demonstrate beneficial effects of DHA on the vascular function in orchidectomized rats, which include a decrease in the prostanoids release and superoxide formation that were previously augmented by orchidectomy. Additionally, there was an increase in endothelial NO formation and the response to ACh, in which NO involvement and the participation of vasodilator prostanoids were increased. DHA also reversed the decrease in EFS-induced response caused by orchidectomy. All of these findings suggest beneficial effects of DHA on vascular function by reversing the neurogenic response and the endothelial dysfunction caused by orchidectomy.

Serum Phospholipid Docosahexaenoic Acid Is Inversely Associated with Arterial Stiffness in Metabolically Healthy Men

We hypothesized that lower proportion of serum phospholipid docosahexaenoic acid (DHA) is inversely associated with increased cardiovascular risk and vascular function in metabolically healthy men. To elucidate it, we first compared serum phospholipid free fatty acid (FA) compositions and cardiovascular risk parameters between healthy men (n = 499) and male patients with coronary artery disease (CAD, n = 111) (30-69 years) without metabolic syndrome, and then further-analyzed the association of serum phospholipid DHA composition with arterial stiffness expressed by brachial-ankle pulse wave velocity (ba-PWV) in metabolically healthy men. Basic parameters, lipid profiles, fasting glycemic status, adiponectin, high sensitivity C-reactive protein (hs-CRP) and LDL particle size, and serum phospholipid FA compositions were significantly different between the two subject groups. Serum phospholipid DHA was highly correlated with most of long-chain FAs. Metabolically healthy men were subdivided into tertile groups according to serum phospholipid DHA proportion: lower (< 2.061%), middle (2.061%-3.235%) and higher (> 3.235%). Fasting glucose, insulin resistance, hs-CRP and ba-PWVs were significantly higher and adiponectin and LDL particle size were significantly lower in the lower-DHA group than the higher-DHA group after adjusted for confounding factors. In metabolically healthy men, multiple stepwise regression analysis revealed that serum phospholipid DHA mainly contributed to arterial stiffness (β'-coefficients = -0.127, p = 0.006) together with age, systolic blood pressure, triglyceride (r = 0.548, p = 0.023). Lower proportion of serum phospholipid DHA was associated with increased cardiovascular risk and arterial stiffness in metabolically healthy men. It suggests that maintaining higher proportion of serum phospholipid DHA may be beneficial for reducing cardiovascular risk including arterial stiffness in metabolically healthy men.

Dietary Calanus oil antagonizes angiotensin II-induced hypertension and tissue wasting in diet-induced obese mice

BACKGROUND

We have recently shown that Calanus oil, which is extracted from the marine copepod Calanus finmarchicus, reduces fat deposition, suppresses adipose tissue inflammation and improves insulin sensitivity in high fat-fed rodents. This study expands upon our previous observations by examining whether dietary supplementation with Calanus oil could antagonize angiotensin II (Ang II)-induced hypertension and ventricular remodeling in mice given a high fat diet (HFD).

METHODS

C57BL/6J mice were initially subjected to 8 weeks of HFD with or without 2% (w/w) Calanus oil. Thereafter, animals within each group were randomized for the administration of either Ang II (1µg/kg/min) or saline for another two weeks, while still on the same dietary regimen.

RESULTS

Ang II caused a marked decline in body and organ weights in mice receiving non-supplemented HFD, a response which was clearly attenuated in mice receiving Calanus oil supplementation. Furthermore, Ang II-induced elevation in blood pressure was also attenuated in the Calanus oil-supplemented group. As expected, infusion of Ang II produced hypertrophy and up-regulation of marker genes (mRNA level) of both hypertrophy and fibrosis in cardiac muscle, but this response was unaffected by dietary Calanus oil. Fibrosis and inflammation were up-regulated also in the aorta following Ang II infusion. However, the inflammatory response was blocked by Calanus oil supplementation. A final, and unexpected, finding was that dietary intake of Calanus oil caused a robust increase in the level of O-GlcNAcylation in cardiac tissue.

CONCLUSION

These results suggest that dietary intake of oil from the marine copepod Calanus finmarchicus could be a beneficial addition to conventional hypertension treatment. The compound attenuates inflammation and the severe metabolic stress caused by Ang II infusion. Although the present study suggests that the anti-hypertensive effect of the oil (or its n-3 PUFAs constituents) is related to its anti-inflammatory action in the vessel wall, other mechanisms such as interaction with intracellular calcium mechanisms or a direct antagonistic effect on Ang II receptors should be examined.

Effect of Dietary Docosahexaenoic Acid Supplementation on the Participation of Vasodilator Factors in Aorta from Orchidectomized Rats

Benefits of n-3 polyunsaturated fatty acids (PUFAs) against cardiovascular diseases have been reported. Vascular tone regulation is largely mediated by endothelial factors whose release is modulated by sex hormones. Since the incidence of cardiovascular pathologies has been correlated with decreased levels of sex hormones, the aim of this study was to analyze whether a diet supplemented with the specific PUFA docosahexaenoic acid (DHA) could prevent vascular changes induced by an impaired gonadal function. For this purpose, control and orchidectomized rats were fed with a standard diet supplemented with 5% (w/w) sunflower oil or with 3% (w/w) sunflower oil plus 2% (w/w) DHA. The lipid profile, the blood pressure, the production of prostanoids and nitric oxide (NO), and the redox status of biological samples from control and orchidectomized rats, fed control or DHA-supplemented diet, were analyzed. The vasodilator response and the contribution of NO, prostanoids and hyperpolarizing mechanisms were also studied. The results showed that orchidectomy negatively affected the lipid profile, increased the production of prostanoids and reactive oxygen species (ROS), and decreased NO production and the antioxidant capacity, as well as the participation of hyperpolarizing mechanisms in the vasodilator responses. The DHA-supplemented diet of the orchidectomized rats decreased the release of prostanoids and ROS, while increasing NO production and the antioxidant capacity, and it also improved the lipid profile. Additionally, it restored the participation of hyperpolarizing mechanisms by activating potassium. Since the modifications induced by the DHA-supplemented diet were observed in the orchidectomized, but not in the healthy group, DHA seems to exert cardioprotective effects in physiopathological situations in which vascular dysfunction exists.

Omega-3 Polyunsaturated Fatty Acids: Structural and Functional Effects on the Vascular Wall

Omega-3 polyunsaturated fatty acids (n-3 PUFA) consumption is associated with reduced cardiovascular disease risk. Increasing evidence demonstrating a beneficial effect of n-3 PUFA on arterial wall properties is progressively emerging. We reviewed the recent available evidence for the cardiovascular effects of n-3 PUFA focusing on structural and functional properties of the vascular wall. In experimental studies and clinical trials n-3 PUFA have shown the ability to improve arterial hemodynamics by reducing arterial stiffness, thus explaining some of its cardioprotective properties. Recent studies suggest beneficial effects of n-3 PUFA on endothelial activation, which are likely to improve vascular function. Several molecular, cellular, and physiological pathways influenced by n-3 PUFA can affect arterial wall properties and therefore interfere with the atherosclerotic process. Although the relative weight of different physiological and molecular mechanisms and the dose-response on arterial wall properties have yet to be determined, n-3 PUFA have the potential to beneficially impact arterial wall remodeling and cardiovascular outcomes by targeting arterial wall stiffening and endothelial dysfunction.

Effect of docosahexaenoic acid monoacylglyceride on systemic hypertension and cardiovascular dysfunction

ω-3 Fatty acid supplementation has been associated with lower blood pressure. Cardiovascular diseases are also known to be linked directly to an increase in ω-6 and a reduction in ω-3 fatty acid levels in blood circulation and tissues. To determine the effect of docosahexaenoic acid monoglycerides (MAG-DHA) on blood pressure, lipid profiles, and vascular remodeling in rats fed a high-fat/high-carbohydrate (HFHC) diet. Studies were performed in male rats subjected to 8 wk of HFHC diet supplemented or not with 3 g/day MAG-DHA. After 8 wk of daily MAG-DHA treatment, rats in the HFHC + MAG-DHA group had lower arterial blood pressure and heart rate compared with the HFHC group. Moreover, MAG-DHA prevented the increase aortic wall thickness, whereas lipid analysis of aortic tissues revealed an increase in DHA/AA ratio correlated with the production of resolvin D2 and D3 metabolites. Histological analysis revealed that MAG-DHA prevented the development of LVH in the HFHC group. Serum lipid profile analysis further showed a decrease in total cholesterol (TC) and LDL, including very low-density lipoprotein (VLDL) and triglyceride (TG) levels, together with an increase in HDL levels after 8 wk of MAG-DHA treatment compared with the HFHC group. Furthermore, daily MAG-DHA treatment resulted in reduced proinflammatory marker levels such as CRP, IL-6, TNFα, and IL-1β. Altogether, these findings revealed that per os administration of MAG-DHA prevents HFHC-diet induced hypertension and LVH in rats.

Unsaturated fatty acids supplementation reduces blood lead level in rats

Some dietary factors could inhibit lead toxicity. The aim of this study was to evaluate the effect of dietary compounds rich in unsaturated fatty acids (FA) on blood lead level, lipid metabolism, and vascular reactivity in rats. Serum metallothionein and organs' lead level were evaluated with the aim of assessing the possible mechanism of unsaturated FA impact on blood lead level. For three months, male Wistar rats that were receiving drinking water with (100 ppm Pb) or without lead acetate were supplemented per os daily with virgin olive oil or linseed oil (0.2 mL/kg b.w.) or egg derived lecithin fraction: “super lecithin” (50 g/kg b.w.). Mesenteric artery was stimulated ex vivo by norepinephrine (NE) administered at six different doses. Lecithin supplementation slightly reduced pressor responses of artery to NE. Lead administered to rats attenuated the beneficial effect of unsaturated FA on lipid metabolism and vascular reactivity to adrenergic stimulation. On the other hand, the super lecithin and linseed oil that were characterized by low omega-6 to omega-3 ratio (about 1) reduced the blood lead concentration. This effect was observed in lead poisoned rats (p < 0.0001) and also in rats nonpoisoned with lead (p < 0.05).

The effect of dietary omega-3 polyunsaturated fatty acids on plasma lipids and lipoproteins of C57BL/6 mice is age and sex specific

There is clear evidence of the effects of sex and age on the prevalence of cardiovascular disease. We investigated the interactions of dietary omega (n)-3 polyunsaturated fatty acids (PUFA), sex, and age on plasma lipids and lipoproteins in the offspring of C57BL/6 mice exposed to high, medium, or low n-3 PUFA at weaning and 16 weeks postweaning. There was an increase in plasma triglycerides from weaning to 16 weeks in male and female offspring; however, the high n-3 PUFA group showed a reduction in triglycerides in both sexes at 16 weeks. High n-3 PUFA caused an increase in plasma LDL-cholesterol from weaning to 16 weeks in male offspring; however, the LDL particle size was significantly larger in the high n-3 PUFA group. Plasma from male mice showed higher cholesterol efflux compared to females; high n-3 PUFA increased cholesterol efflux. Thus the effects of n-3 PUFA are age and sex dependent.

An omega-3 epoxide of docosahexaenoic acid lowers blood pressure in angiotensin-II-dependent hypertension

Mediators of antihypertensive actions of docosahexaenoic acid (DHA) are largely unknown. The omega-3 epoxide of DHA, 19, 20-EDP (epoxy docosapentaenoic acid), is metabolized by soluble epoxide hydrolase (sEH), which also metabolizes the anti-inflammatory and antihypertensive arachidonic acid epoxides, epoxyeicosatrienoic acids (EETs). Based in part on plasma levels of EDPs after a DHA-rich diet, we hypothesized that 19, 20-EDP contributes to the antihypertensive actions of DHA in angiotensin-II (Ang-II)-dependent hypertension. Treatment individually with 19, 20-EDP and a potent sEH inhibitor TPPU (1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea) significantly lowered blood pressure (BP) as compared with Ang-II-infused animals. The largest reduction in BP was obtained with the combination of 19, 20-EDP and TPPU, which was more efficacious than the combination of 14, 15-EET and TPPU. Oxylipin profiling revealed that 19, 20-EDP and 14, 15-EET infusion affected not only most metabolites of the P450 pathway but also renal levels of prostaglandin-E2. Our findings suggest that 19, 20-EDP is a mediator of the antihypertensive effects of DHA in Ang-II-dependent hypertension. It seems that 19, 20-EDP requires metabolic stabilization with a sEH inhibitor to be most effective in lowering BP, although both TPPU and 19, 20-EDP are so effective on their own that demonstrating additive or synergistic interactions is difficult.

Anti-inflammatory effects of ω-3 polyunsaturated fatty acids and soluble epoxide hydrolase inhibitors in angiotensin-II-dependent hypertension

The mechanisms underlying the anti-inflammatory and antihypertensive effects of long-chain ω-3 polyunsaturated fatty acids (ω-3 PUFAs) are still unclear. The epoxides of an ω-6 fatty acid, arachidonic acid epoxyeicosatrienoic acids also exhibit antihypertensive and anti-inflammatory effects. Thus, we hypothesized that the major ω-3 PUFAs, including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), may lower the blood pressure and attenuate renal markers of inflammation through their epoxide metabolites. Here, we supplemented mice with an ω-3 rich diet for 3 weeks in a murine model of angiotensin-II-dependent hypertension. Also, because EPA and DHA epoxides are metabolized by soluble epoxide hydrolase (sEH), we tested the combination of an sEH inhibitor and the ω-3 rich diet. Our results show that ω-3 rich diet in combination with the sEH inhibitor lowered Ang-II, increased the blood pressure, further increased the renal levels of EPA and DHA epoxides, reduced renal markers of inflammation (ie, prostaglandins and MCP-1), downregulated an epithelial sodium channel, and upregulated angiotensin-converting enzyme-2 message and significantly modulated cyclooxygenase and lipoxygenase metabolic pathways. Overall, our findings suggest that epoxides of the ω-3 PUFAs contribute to lowering systolic blood pressure and attenuating inflammation in part by reduced prostaglandins and MCP-1 and by upregulation of angiotensin-converting enzyme-2 in angiotensin-II-dependent hypertension.

Eicosapentaenoic acid/docosahexaenoic acid 1:1 ratio improves histological alterations in obese rats with metabolic syndrome

Background

Marine polyunsaturated fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been associated with improvement in the Metabolic Syndrome (MS). The aim of this study is to evaluate how three fish-oil diets with different eicosapentaenoic acid/docosahexaenoic acid ratios (EPA/DHA ratio) affect the histology of liver, kidney, adipose tissue and aorta in a preliminary morphological study. This work uses an animal model of metabolic syndrome in comparison with healthy animals in order to provide information about the best EPA:DHA ratio to prevent or to improve metabolic syndrome symptoms.

Methods

35 Wistar rats, as a control, and 35 spontaneously hypertensive obese rats (SHROB) were fed for 13 weeks with 3 different suplemmentation of fish oil containing EPA and DHA ratios (1:1, 2:1 and 1:2, respectively). All samples were stained with haematoxylin/eosin stain, except aorta samples, which were stained also with Verhoeff and van Gieson’s stain. A histological study was carried out to evaluate changes. These changes were statistically analyzed using SPSS IBM 19 software. The quantitative data were expressed by mean ± SD and were compared among groups and treatments using ANOVA with post-hoc tests for parametric data and the U-Mann–Whitney for non-parametric data. Qualitative data were expressed in frequencies, and compared with contingency tables using χ² statistics.

Results

EPA:DHA 1:1 treatment tended to improve the density and the wrinkling of elastic layers in SHROB rats. Only Wistar rats fed with EPA:DHA 1:1 treatment did not show mast cells in adipose tissue and has less kidney atrophy. In both strains EPA:DHA 1:1 treatment improved inflammation related parameters in liver and kidney.

Conclusions

EPA:DHA 1:1 treatment was the most beneficial treatment since improved many histological parameters in both groups of rats.

Omega-3 fatty acids and blood pressure

Epidemiological and clinical studies suggest that consumption of omega (ω-3) polyunsaturated fatty acids (PUFA) contributes to the reduction of cardiovascular mortality through different mechanisms including modulation of cellular metabolic functions, gene expression and beneficial effects on lipid profile or blood pressure. The aim of the study is to review the effects of ω-3 PUFA supplemented as fish oil or blue fish in blood pressure. The analysis of different studies suggests that high doses ω-3 PUFA ( ≥ 3 g/day) produces a small but significant decrease in blood pressure, especially systolic blood pressure, in older and hypertensive subjects; however, the evidence is not consistent among different studies. ω-3 polyunsaturated fatty acids consumption might have a place in the control of patients with mild hypertension before starting drug treatment and of those who prefer changes of lifestyles like diet.

Serum long-chain n-3 polyunsaturated fatty acids, methylmercury and blood pressure in an older population

Fish or fish oil consumption has been associated with lower blood pressure. Fish may also contain methylmercury, which has been associated with cardiovascular diseases and higher blood pressure. Our aim was to study the associations of serum long-chain n-3 polyunsaturated fatty acids (PUFA) eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA), mainly reflecting fish or fish oil intake, and hair mercury concentration with blood pressure. Data were available for 848 men and 909 women from the Kuopio Ischaemic Heart Disease Risk Factor Study, aged 53-73 years. We excluded participants with ischemic heart disease, stroke, diabetes or hypertension treatment, leaving 396 men and 372 women. Log-transformed values were used to study the associations. The mean serum concentrations were 1.63% (s.d. 0.91) for EPA, 0.77% (s.d. 0.16) for DPA and 2.73% (s.d. 0.90) for DHA of all serum fatty acids. Multivariate-adjusted serum EPA+DPA+DHA was associated with lower systolic blood pressure (β = -4.50, 95% confidence interval (CI) -8.02 - -0.99) and pulse pressure (β = -4.41, 95% CI -6.95 - -1.87), but not with diastolic blood pressure (β = -0.45, 95% CI -2.31-1.52). The associations were similar with EPA, DPA and DHA evaluated individually. The mean hair mercury concentration was 1.42 μg g(-1) (s.d. 1.54). Hair mercury was not associated with blood pressure and it did not modify the association between PUFA and blood pressure. These results suggest that higher serum long-chain n-3 PUFA concentration has a modest inverse association with blood pressure in older men and women.

The differential effects of EPA and DHA on cardiovascular risk factors

Compelling evidence exists for the cardioprotective benefits resulting from consumption of fatty acids from fish oils, EPA (20:5n-3) and DHA (22:6n-3). EPA and DHA alter membrane fluidity, interact with transcription factors such as PPAR and sterol regulatory element binding protein, and are substrates for enzymes including cyclooxygenase, lipoxygenase and cytochrome P450. As a result, fish oils may improve cardiovascular health by altering lipid metabolism, inducing haemodynamic changes, decreasing arrhythmias, modulating platelet function, improving endothelial function and inhibiting inflammatory pathways. The independent effects of EPA and DHA are poorly understood. While both EPA and DHA decrease TAG levels, only DHA appears to increase HDL and LDL particle size. Evidence to date suggests that DHA is more efficient in decreasing blood pressure, heart rate and platelet aggregation compared to EPA. Fish oil consumption appears to improve arterial compliance and endothelial function; it is not yet clear as to whether differences exist between EPA and DHA in their vascular effects. In contrast, the beneficial effect of fish oils on inflammation and insulin sensitivity observed in vitro and in animal studies has not been confirmed in human subjects. Further investigation to clarify the relative effects of consuming EPA and DHA at a range of doses would enable elaboration of current understanding regarding cardioprotective effects of consuming oily fish and algal sources of long chain n-3 PUFA, and provide clearer evidence for the clinical therapeutic potential of consuming either EPA or DHA-rich oils.

Omega 3 polyunsaturated fatty acids supplementation and blood pressure levels in hypertriglyceridemic patients with untreated normal-high blood pressure and with or without metabolic syndrome: a retrospective study

Recent evidence suggests that at least a part of the polyunsaturated fatty acids (PUFAs) heart protective effect is mediated by a relatively small but significant decrease in blood pressure level. We retrospectively evaluated the long-term effect of a PUFA supplementation on the blood pressure level of 111 hypertriglyceridemic subjects with untreated normal-high blood pressure that were prescribed a 2 grams PUFA supplementation in order to improve their plasma lipid pattern. After 12 months of treatment, systolic blood pressure (SBP) meanly decreased by 2.7 +/- 2.5 mmHg (p = 0.001) and diastolic blood pressure (DBP) by 1.3 +/- 3.3 mmHg (p < 0.001), while basal heart rate decreased by 4.0 +/- 4.4 bpm (p < 0.001). Both SBP and DBP reduction were significantly related to the baseline SBP (p < 0.001) and DBP (p < 0.001), respectively. Diastolic blood pressure change was also inversely related to the patient's age (p = 0.004). No significant difference was perceived in the metabolic syndrome subgroup. In our retrospective study, highly purified omega-3 PUFA long-term supplementation is associated with a significant reduction in SBP, DBP, Pulse pressure (PP), and basal heart rate in hypertriglyceridemic patients with normal-high blood pressure. No significant difference was perceived in the metabolic syndrome subgroup. The main determinants of the PUFA anti-hypertensive effect appear to be the basal blood pressure level and age.

Effects of dietary fish oil and trans fat on rat aorta histopathology and cardiovascular risk markers

Fish oil and shortening have been suggested to have opposite effects on cardiovascular disease (CVD). This study investigated the effect of shortening and fish oil on CVD risk factors and aorta histopathology, and the association between risk factors and aorta histopathology. Male Wister rats (n=30) were fed an AIN-93G diet containing 20% fat in the form of fish oil, shortening, or soybean oil for 4 weeks. Total cholesterol (TC), triacylglyceride (TG), and C-reactive protein levels were significantly (P<0.001) lower in the fish oil than in soybean oil and shortening groups. HDL-cholesterol concentrations were significantly different (P<0.001) between groups. In addition, LDL-cholesterol levels were significantly (P<0.001) lower in the fish oil and shortening groups than in the soybean oil group. Insulin and glucose concentrations did not differ among groups. Effect of dietary fat on tissue fatty acid composition significantly differed in abdominal fat and brain compared with RBC, heart, kidney and liver. The aortic wall was significantly (P=0.02) thinner in the fish oil group than in the soybean oil and shortening groups. The aortic wall thickness was positively correlated with TG and TC, but negatively with EPA + DHA levels of all tissues. These results suggested that fish oil had protective effects on aorta histopathology by hypolipidemic action in this rat model.

Anti-hypertensive nutraceuticals and functional foods

Epidemiological studies have demonstrated that elevated blood pressure is one of the major risk factors for stroke and coronary heart disease (CHD). A close association between blood pressure and the incidence of cardiovascular diseases is well established if systolic/diastolic blood pressure is above 140/90 mmHg. In recent years, nutraceuticals and functional foods have attracted considerable interest as potential alternative therapies for treatment of hypertension, especially for prehypertensive patients, whose blood pressure is marginally or mildly high but not high enough to warrant the prescription of blood pressure-lowering medications. This review summarizes the findings of recent studies on the chemistry, production, application, efficacy, and mechanisms of popular blood pressure-lowering nutraceuticals and functional foods including the Dietary Approaches to Stop Hypertension (DASH) diet plan, L-arginine, chlorogenic acid, fermented milk, garlic, onion, tea, soybean, ginger, hawthorn, and fish oil.

A systemic review of the roles of n-3 fatty acids in health and disease

Attention to the role of n-3 long-chain fatty acids in human health and disease has been continuously increased during recent decades. Many clinical and epidemiologic studies have shown positive roles for n-3 fatty acids in infant development; cancer; cardiovascular diseases; and more recently, in various mental illnesses, including depression, attention-deficit hyperactivity disorder, and dementia. These fatty acids are known to have pleiotropic effects, including effects against inflammation, platelet aggregation, hypertension, and hyperlipidemia. These beneficial effects may be mediated through several distinct mechanisms, including alterations in cell membrane composition and function, gene expression, or eicosanoid production. A number of authorities have recently recommended increases in intakes of n-3 fatty acids by the general population. To comply with this recommendation a variety of food products, most notably eggs, yogurt, milk, and spreads have been enriched with these fatty acids. Ongoing research will further determine the tissue distribution, biological effects, cost-effectiveness, and consumer acceptability of such enriched products. Furthermore, additional controlled clinical trials are needed to document whether long-term consumption or supplementation with eicosapentaenoic acid/docosahexaenoic acid or the plant-derived counterpart (alpha-linolenic acid) results in better quality of life.

Effects of docosahexaenoic acid on large-conductance Ca2+-activated K+ channels and voltage-dependent K+ channels in rat coronary artery smooth muscle cells

AIM

To investigate the effects of docosahexaenoic acid (DHA) on large-conductance Ca(2+)-activated K(+)(BK(Ca)) channels and voltage-dependent K(+) (K(V)) channels in rat coronary artery smooth muscle cells (CASMCs).

METHODS

Rat CASMCs were isolated by an enzyme digestion method. BK(Ca) and K(V) currents in individual CASMCs were recorded by the patch-clamp technique in a whole-cell configuration at room temperature. Effects of DHA on BK(Ca) and K(V) channels were observed when it was applied at 10, 20, 30, 40, 50, 60, 70, and 80 micromol/L.

RESULTS

When DHA concentrations were greater than 10 micromol/L, BK(Ca) currents increased in a dose-dependent manner. At a testing potential of +80 mV, 6.1%+/-0.3%, 76.5%+/-3.8%, 120.6%+/-5.5%, 248.0%+/-12.3%, 348.7%+/-17.3%, 374.2%+/-18.7%, 432.2%+/-21.6%, and 443.1%+/-22.1% of BK(Ca) currents were increased at the above concentrations, respectively. The half-effective concentration (EC(50)) of DHA on BK(Ca) currents was 37.53+/-1.65 micromol/L. When DHA concentrations were greater than 20 micromol/L, K(V) currents were gradually blocked by increasing concentrations of DHA. At a testing potential of +50 mV, 0.40%+/-0.02%, 1.37%+/-0.06%, 11.80%+/-0.59%, 26.50%+/-1.75%, 56.50%+/-2.89%, 73.30%+/-3.66%, 79.70%+/-3.94%, and 78.1%+/-3.91% of K(V) currents were blocked at the different concentrations listed above, respectively. The EC(50) of DHA on K(V) currents was 44.20+/-0.63 micromol/L.

CONCLUSION

DHA can activate BK(Ca) channels and block K(V) channels in rat CASMCs, and the EC(50) of DHA for BK(Ca) channels is lower than that for K(V) channels; these findings indicate that the vasorelaxation effects of DHA on vascular smooth muscle cells are mainly due to its activation of BK(Ca) channels.

Omega-3 Fatty acids and neural development to 2 years of age: do we know enough for dietary recommendations?

The omega (omega)-3 fatty acids are essential nutrients, explained by the absence of a Delta-15 desaturase in mammalian cells. The omega-3 fatty acids are found in the diet as alpha-linolenic acid (18:3omega-3) and eicosapentaenoic acid (20:5omega-3), as well as docosahexaenoic acid (DHA), with different functions of each of the omega-3 fatty acids in different cells. One essential role of the omega-3 fatty acids is fulfilled by the 22 carbon DHA (22:6omega-3). Depletion of DHA from brain and retina interferes with normal neurogenesis and neurological function, and visual signaling pathways. Observation and intervention studies with pregnant and lactating women, and with infants fed some formulas show that dietary DHA is associated with higher scores on tests of visual and neural development in infants and children. The estimated average requirement and variability in requirement among individuals both of which are needed to set dietary recommended intakes (DRIs) for the different omega-3 fatty acids are unknown. However, because omega-3 fatty acids are essential, adequate intakes to minimize risk of poor neural development and function can be justified, but dose-response data to provide a safe upper limit with different omega-6 fatty acid intakes are needed. Dietary recommendations do affect the food supply and supplements and are used in labeling, all impacting population health. When scientific information is incomplete, consideration must be given to the implications of recommendations that focus on individual nutrients, rather than dietary patterns such as breast-feeding and consuming fish that promote health and minimize disease risk.

Effects of n-3 fatty acids and acute exercise on endothelium-dependent vasorelaxation in healthy rat aorta

The purpose of this study was to determine whether n-3 PUFA result in an effect on endothelial function that is in addition to that of acute exercise. For 4 weeks, male Sprague–Dawley rats were subjected to a diet based on n-3 PUFA or a standard diet. In each diet group, ten rats were submitted to an acute treadmill exercise while the remaining ten acted as sedentary controls. The running speed was progressively increased until the animals were exhausted. Endothelial function was then assessed by measuring isometric tension in rings of the thoracic aorta. In vessels precontracted with 0·1 μm-phenylephrine, responses to acetylcholine (ACh) were significantly improved following acute exercise in all diet groups. When PUFA supplementation was compared to the standard diet no significant difference was found in response to ACh, either at rest or after an acute exercise. Pretreatment of rings with Nω-nitro-l-arginine methyl esther (50 μm) inhibited the ACh-mediated vasorelaxation in all groups. Response to 10 μm-nifedipine, an L-type Ca2+ channel antagonist, was similarly enhanced after acute exercise in both standard and PUFA diets. Furthermore, response to 0·01 μm-nifedipine was significantly higher after acute exercise only in the PUFA diet. In conclusion, in our ‘healthy’ rat model with ‘normal’ baseline endothelial function, acute exercise improves response to ACh while PUFA supplementation alone or in combination with acute exercise has no effect on endothelium-dependent vasorelaxation. However, PUFA may potentiate the acute exercise effect on smooth muscle cell relaxation via L-type Ca2+ channel modifications.

n-3 Fatty acids and cardiovascular disease: mechanisms underlying beneficial effects

Dietary n-3 fatty acids, particularly eicosapentaenoic acid and docosahexaenoic acid, are important nutrients through the life cycle. Evidence from observational, clinical, animal, and in vitro studies indicates a beneficial role of n-3 fatty acids in the prevention and management of cardiovascular disease. Although the precise mechanisms are still unclear, clinical and preclinical studies indicate that the cardioprotective effects of n-3 fatty acids may be attributed to a number of distinct biological effects on lipid and lipoprotein metabolism, blood pressure, platelet function, arterial cholesterol delivery, vascular function, and inflammatory responses.

Antihypertensive effect and safety of dietary alpha-linolenic acid in subjects with high-normal blood pressure and mild hypertension

We investigated the antihypertensive effect and safety of alpha-linolenic acid (ALA) in human subjects. In Experiment 1, subjects with high-normal blood pressure and mild hypertension ingested bread containing 14 g of common blended oil (control oil) or ALA-enriched oil for 12 weeks. The test oil contained 2.6g/14 g of ALA. The subjects ingested strictly controlled meals during the study period. Systolic blood pressure was significantly lower in the ALA group than in the control group after ingestion of the test diet for 4, 8 and 12 weeks. Diastolic blood pressure was significantly lower in the ALA group than in the control group after ingestion of the test diet for 12 weeks. In Experiment 2, we evaluated the safety of high intake of ALA (7.8 g/d), particularly its effects on oxidation in the body and blood coagulation. Normotensive, high-normotensive and mildly hypertensive subjects ate bread that contained 42 g of the control oil or the test oil for 4 weeks. No significant difference was noted in the lipid peroxide level, high-sensitive C-reactive protein level, plasma prothrombin time or activated partial thromboplastin time between the two groups. No abnormal changes were noted after test diet ingestion on blood test or urinalysis, and no adverse event considered to have been induced by the test oil was observed in Experiment 1 and 2. These results suggest that ALA have an antihypertensive effect with no adverse effect in subjects with high-normal blood pressure and mild hypertension.

Fish oil supplementation improves large arterial elasticity in overweight hypertensive patients

OBJECTIVES

To observe the effect of fish oil supplementation on arterial elasticity and blood pressure (BP) in overweight hypertensive patients.

SUBJECTS AND METHODS

This was a double-blind, randomized and placebo-controlled clinical study, in which 52 overweight hypertensive patients from a community were selected and randomly allocated to two groups (26 in the fish oil group (3 g day(-1), fish oil capsules) and 26 in the placebo group (only capsules). All the subjects were follow-up for 8 weeks. The arterial elasticity was determined by CVProfilor DO-2020 and expressed as elasticity indexes (C(1)-large artery and C(2)-small artery). During the follow-up, totally nine cases were dropped out (three cases from the fish oil group and six cases from the placebo group).

RESULTS

After 8 weeks follow-up, the large artery elasticity in the fish oil group, compared with its baseline, was significantly improved (C(1): 15.5+/-1.5 vs 12.8+/-3.7 ml mm Hg(-1) x 10), whereas no effects were found in the placebo group (C(1): 13.0+/-3.4 vs 13.4+/-3.8 ml mm Hg(-1) x 10), P=0.027, RM-ANOVA across the two groups. The small artery elasticity (C(2)), BP and pulse pressure were not found any changes, either in the fish oil group or in the placebo group. At same time, the serum soluble vascular cell adhesion molecule-1(sVCAM-1) and leptin levels, the lipid profile and insulin sensitivity index (ISI) as well, did not show significant differences between two groups.

CONCLUSIONS

Fish oil supplementation certainly would improve large arterial elasticity but no effect on BP in overweight hypertensive patients. Further study is needed to confirm the benefits of fish oil supplementation on age-related increases in arterial stiffness.

n-3 Fatty acids, hypertension and risk of cognitive decline among older adults in the Atherosclerosis Risk in Communities (ARIC) study

OBJECTIVE

Recent research indicates that n-3 fatty acids can inhibit cognitive decline, perhaps differentially by hypertensive status.

DESIGN

We tested these hypotheses in a prospective cohort study (the Atherosclerosis Risk in Communities). Dietary assessment using a food-frequency questionnaire and plasma fatty acid exposure by gas chromatography were completed in 1987-1989 (visit 1), while cognitive assessment with three screening tools--the Delayed Word Recall Test, the Digit Symbol Substitution Test of the Wechsler Adult Intelligence Scale-Revised and the Word Fluency Test (WFT)--was completed in 1990-1992 (visit 2) and 1996-1998 (visit 4). Regression calibration and simulation extrapolation were used to control for measurement error in dietary exposures.

SETTING

Four US communities--Forsyth County (North Carolina), Jackson (Mississippi), suburbs of Minneapolis (Minnesota) and Washington County (Maryland).

SUBJECTS

Men and women aged 50-65 years at visit 1 with complete dietary data (n = 7814); white men and women in same age group in the Minnesota field centre with complete plasma fatty acid data (n = 2251).

RESULTS

Findings indicated that an increase of one standard deviation in dietary long-chain n-3 fatty acids (% of energy intake) and balancing long-chain n-3/n-6 decreased the risk of 6-year cognitive decline in verbal fluency with an odds ratio (95% confidence interval) of 0.79 (0.66-0.95) and 0.81 (0.68-0.96), respectively, among hypertensives. An interaction with hypertensive status was found for dietary long-chain n-3 fatty acids (g day-1) and WFT decline (likelihood ratio test, P = 0.06). This exposure in plasma cholesteryl esters was also protective against WFT decline, particularly among hypertensives (OR = 0.51, P < 0.05).

CONCLUSION

One implication from our study is that diets rich in fatty acids of marine origin should be considered for middle-aged hypertensive subjects. To this end, randomised clinical trials are needed.

Adult cardiorenal benefits from postnatal fish oil supplement in rat offspring of low-protein pregnancies

We investigated the effect of fish oil (FO) treatment on cardiorenal structure of adult offspring from low-protein pregnancies. Three month old offspring were assigned to eight groups (four male groups and four female groups, n=8 each) (NP=normal-protein diet, LP=low-protein diet): NP, LP, NP plus FO, and LP plus FO. Left ventricle and kidney were analyzed with light microscopy and stereology. The both sexes of LP offspring showed 30% lower birth weights than the respective NP offspring and high blood pressure (BP) levels in adulthood which was efficiently reduced by FO treatment. In the heart, FO treated the cardiomyocyte hypertrophy, the vascularization impairment, and decreased the cardiomyocyte loss usually observed in adult LP offspring. In the kidney, FO treated, in the male, the imbalance of the cortex-to-medulla ratio observed in both sexes of LP offspring, and reduced the glomeruli loss in the LP offspring. The positive correlation between the number of cardiomyocyte nuclei later in life and the body mass (BM) at birth was significant only in both sexes of LP offspring and this correlation disappeared in LP plus fish oil offspring. The positive correlation between the number of glomeruli later in life and the BM at birth was significant in NP male offspring and in both sexes of LP offspring. In conclusion, FO supplement, which is a rich source of n-3 fatty acids (DHA and EPA), has beneficial effects on BP control and cardiac and renal adverse remodeling usually seen in offspring of the LP pregnancies.

Renal cortex remodeling in streptozotocin-induced diabetic spontaneously hypertensive rats treated with olive oil, palm oil and fish oil from Menhaden

We studied the effects of edible oils intake on the renal cortical structure of streptozotocin-induced diabetic (Db) and non-diabetic spontaneously hypertensive rats (SHR). Male SHR divided into 5 groups were studied during 6 weeks: one non-diabetic SHR group and four diabetic SHR groups (three groups received by gavage olive, palm or fish oil). Kidneys were analyzed by light microscopy and stereology. Oils intake did not change the plasma glucose levels. The blood pressure (BP) was lower in SHR-Db than in SHR, but SHR-Db-fish oil showed the lowest BP. Creatinine clearance was different between diabetic SHR and non-diabetic SHR, but not between treated SHR-Db and untreated SHR-Db. The renal cortex showed scars surrounding obsolete glomeruli with inflammatory infiltrate mainly in untreated SHR-Db. The olive oil, palm oil and mainly fish oil intake retard the usual loss of glomeruli and attenuate the renal cortex adverse remodeling of Db and non-Db SHR.

Omega-3 polyunsaturated fatty acids: Their potential role in blood pressure prevention and management

Omega-3 polyunsaturated fatty acids (PUFAs) from fish and fish oils appear to protect against coronary heart disease: their dietary intake is in fact inversely associated to cardiovascular disease morbidity/mortality in population studies. Recent evidence suggests that at least part of their heart protective effect is mediated by a relatively small but significant decrease in blood pressure level. In fact, omega-3 PUFAs exhibit wide-ranging biological actions that include regulating both vasomotor tone and renal sodium excretion, partly competing with omega-6 PUFAs for common metabolic enzymes and thereby decreasing the production of vasocostrincting rather than vasodilating and anti-inflammatory eicosanoids. PUFAs also reduce angiotensin-converting enzyme (ACE) activity, angiotensin II formation, TGF-beta expression, enhance eNO generation and activate the parasympathetic nervous system. The final result is improved vasodilation and arterial compliance of both small and large arteries. Preliminary clinical trials involving dyslipidemic patients, diabetics and elderly subjects, as well as normotensive and hypertensive subjects confirm this working hypothesis. Future research will clarify if PUFA supplementation could improve the antihypertensive action of specific blood pressure lowering drug classes and of statins.

Fish oils--adjuvant therapy in chronic heart failure?

Despite advances in medical management and device therapy, chronic heart failure (CHF) remains a condition of high mortality and poor quality of life. Patients with CHF endure frequent admissions to hospital, with exacerbations of breathlessness or recurrent acute myocardial infarction and have a high incidence of sudden death. A high intake of marine polyunsaturated fatty acids (PUFAs) is associated with lower cardiovascular mortality in the general population, and diabetics, and can reduce cardiovascular deaths post-infarction. Many of the effects of PUFAs could be of benefit in CHF patients. They can improve endothelial function, reduce vascular tone, reduce platelet aggregability, improve myocardial relaxation, stabilize myocardial cells by prolonging the refractory period, and lead to increased appetite and weight gain. They also have potentially important immune-modulating effects, reducing cytokine production and release and altering prostaglandin metabolism. In this review article we discuss the potential benefits of PUFA supplementation in CHF patients using data from clinical trials and in vitro experiments.

Omega-3 fatty acids: role in cardiovascular health and disease

Dietary omega-3 polyunsaturated fatty acids, eicosapentaenoic and docosahexaenoic acids, play an important role in cardiovascular health and disease. Clinical trials provide substantial evidence to support current dietary recommendations for omega-3 fatty acids in cardiovascular disease management. The cardioprotective benefits of omega-3 fatty acids may be attributed to multiple physiological effects on lipids, blood pressure, vascular function, cardiac rhythms, platelet function, and inflammatory responses. The metabolism of omega-3 fatty acids, physiological effects, and clinical considerations with current dietary recommendations and sources of omega-3 fatty acids are presented.

Long-term intake of edible oils benefits blood pressure and myocardial structure in spontaneously hypertensive rat (SHR) and streptozotocin diabetic SHR

The beneficial effects of edible oils long-term supplementation in blood pressure (BP) and cardiac structure were investigated in spontaneously hypertensive rat (SHR) and streptozotocin diabetic (Db) SHR (45 mg/rat i.p.). Twenty-five 12-week old male SHR were divided into four SHR-Db groups and one SHR group, SHR-Db groups each receiving, respectively, olive oil, palm oil and fish oil, and another SHR-Db group with placebo by gavage on a daily basis for 6 weeks. Myocardial structures were analyzed through light microscopy and stereology. In SHR-Db, the BP and the myocardium were significantly altered by oil supplementation. The BP, the interstitial fibrosis and cardiomyocyte size showed a significant decrease in treated SHR-Db than in SHR or untreated SHR-Db. The myocardial microvasculature and number of cardiomyocytes were higher in all treated groups, especially in fish oil group. Long-term edible oil supplementation showed beneficial effects decreasing BP levels and offsetting adverse myocardial remodeling in diabetic SHR.

Effect of omega-3 fatty acid-containing phospholipids on blood catecholamine concentrations in healthy volunteers: a randomized, placebo-controlled, double-blind trial

OBJECTIVE

We previously reported that administration of fish oil rich in docosahexaenoic acid (DHA) increased the plasma ratio of epinephrine to norepinephrine (NE) at rest in young adults who were under chronic stress and that this effect was achieved mainly through depression of NE. However, not many reports have documented the effects of eicosapentaenoic acid (EPA) and DHA on blood catecholamine levels in healthy humans. Therefore, we performed another intervention study to test their effect on catecholamines with healthy subjects under no chronic stress.

METHODS

Twenty-one healthy young adults (15 men and 6 women) were randomly assigned to an omega-3 group (n = 9) or a control group (n = 12) in a double-blind manner. Twenty capsules of shellfish-derived lipids containing 762 mg of EPA plus DHA per day were administered to the omega-3 group for 2 mo. The controls took the same amount of placebo capsules. Fasting blood samples after a 30-min rest with a catheter in a forearm vein were obtained at the start and the end of the study for catecholamine measurements.

RESULTS

EPA but not DHA concentrations in red blood cells significantly increased in the omega-3 group compared with the control group (P < 0.001). Plasma NE concentrations were significantly decreased in the omega-3 group (from 1.49 +/- 0.39 nmol/L to 1.05 +/- 0.14 nmol/L) compared with the control group (from 1.12 +/- 0.24 nmol/L to 1.39 +/- 0.32 nmol/L) with analysis of covariance (P < 0.001). The differences remained significant (P = 0.01) even after deletion of three subjects in the omega-3 group who had the highest baseline NE values and one in the control group who had the lowest baseline NE value to nullify a significant baseline differences in NE between groups.

CONCLUSION

This study demonstrated that EPA plus DHA supplementation lowered plasma NE concentrations in normal volunteers even at the small dose of 762 mg of EPA plus DHA per day. This effect of EPA plus DHA to lower plasma NE concentrations may be important to understand some of the effects of fish oils on diseases.

The inhibitory effect of dibutyryl cyclic AMP on docosahexaenoic acid-induced apoptosis in HL-60 cells through activation of the phosphatidylinositol-3 kinase pathway

OBJECTIVE

Docosahexaenoic acid (DHA) is known as a chemopreventive substance for cancers. Previously we reported that DHA induces apoptosis in HL-60 cells. The aim of this study was to clarify the role of phosphatidylinositol 3-kinase (PI3-kinase)/Akt signaling during DHA-induced apoptosis in HL-60 cells.

METHODS

The inhibitory effects of dibutyryl cAMP (db-cAMP) or LY294002 (a specific inhibitor of the PI3-kinase/Akt pathway) on DHA-induced apoptosis in HL-60 cells were evaluated by the appearance of apoptosis, and from the activities of caspases (3 and 8), the phospholylation of Akt, and cleavage of Bid using DNA indexes, emzymatic measurement of fragmented substrates, and Western blotting, respectively.

RESULTS

The pre-incubation of db-cAMP reduced the activation of caspasses (3 and 8) during the occurrence of DHA-induced apoptosis in HL-60. However, the inhibition of PI3-kinase/Akt signaling by LY294002 resulted in recovery of the caspases' activities, appearance of apoptotic cells, and cleavage of the Bid molecule when LY294002 was co-treated with db-cAMP before the occurrence of DHA-induced apoptosis in HL-60. It was also confirmed that LY294002 strongly inhibited phospholylation of Akt during db-cAMP induced-reduction of DHA-induced apoptosis in HL-60.

CONCLUSION

We demonstrated that DHA-induced apoptosis was sensitive to the modulation of PI3-kinase activity by treatment with db-cAMP or LY294002. These results may provide new insights into the mechanisms of the anti-cancer activity of DHA.

Effect of docosahexaenoic acid on lipoprotein subclasses in hyperlipidemic children (the EARLY study)

To test the hypothesis that a dietary omega-3 fatty acid, docosahexaenoic acid, improves the lipoprotein subclass profile of children who have hyperlipidemia, we conducted a randomized, double-blind, placebo-controlled study. Children who had hyperlipidemia (n = 20) were stabilized on a low-fat diet for 6 weeks and then randomized to receive 1.2 g/day of docosahexaenoic acid for 6 weeks or placebo. Supplementation with docosahexaenoic acid significantly increased low-density lipoprotein subclass 1 and high-density lipoprotein subclass 2 (large and buoyant; less atherogenic particles) by 91% and 14%, respectively, compared with the placebo phase. Low-density lipoprotein subclass 3 (small and dense; more atherogenic particles) decreased by 48%.