Anxiolytic- and Antidepressant-Like Effects of Fish Oil-Enriched Diet in Brain-Derived Neurotrophic Factor Deficient Mice.

Despite significant advances in the understanding of the therapeutic activity of antidepressant drugs, treatment-resistant depression is a public health issue prompting research to identify new therapeutic strategies. Evidence strongly suggests that nutrition might exert a significant impact on the onset, the duration and the severity of major depression. Accordingly, preclinical and clinical investigations demonstrated the beneficial effects of omega-3 fatty acids in anxiety and mood disorders. Although the neurobiological substrates of its action remain poorly documented, basic research has shown that omega-3 increases brain-derived neurotrophic factor (BDNF) levels in brain regions associated with depression, as antidepressant drugs do. In contrast, low BDNF levels and hippocampal atrophy were observed in animal models of depression. In this context, the present study compared the effects of long-lasting fish oil-enriched diet, an important source of omega-3 fatty acids, between heterozygous BDNF+/- mice and their wild-type littermates. Our results demonstrated lower activation of Erk in BDNF+/- mice whereas this deficit was rescued by fish oil-enriched diet. In parallel, BDNF+/- mice displayed elevated hippocampal extracellular 5-HT levels in relation with a local decreased serotonin transporter protein level. Fish oil-enriched diet restored normal serotonergic tone by increasing the protein levels of serotonin transporter. At the cellular level, fish oil-enriched diet increased the pool of immature neurons in the dentate gyrus of BDNF+/- mice and the latter observations coincide with its ability to promote anxiolytic- and antidepressant-like response in these mutants. Collectively, our results demonstrate that the beneficial effects of long-term exposure to fish oil-enriched diet in behavioral paradigms known to recapitulate diverse abnormalities related to the depressive state specifically in mice with a partial loss of BDNF. These findings contrast with the mechanism of action of currently available antidepressant drugs for which the full manifestation of their therapeutic activity depends on the enhancement of serotoninergic and BDNF signaling. Further studies are warranted to determine whether fish oil supplementation could be used as an add-on strategy to conventional pharmacological interventions in treatment-resistant patients and relevant animal models.

Contrasting effects of arachidonic acid and docosahexaenoic acid membrane incorporation into cardiomyocytes on free cholesterol turnover.

The preservation of a constant pool of free cholesterol (FC) is critical to ensure several functions of cardiomyocytes. We investigated the impact of the membrane incorporation of arachidonic acid (C20:4 ω6, AA) or docosahexaenoic acid (C22:6 ω3, DHA) as ω6 or ω3 polyunsaturated fatty acids (PUFAs) on cholesterol homeostasis in primary cultures of neonatal rat cardiac myocytes. We measured significant alterations to the phospholipid FA profiles, which had markedly different ω6/ω3 ratios between the AA and DHA cells (13 vs. 1). The AA cells showed a 2.7-fold lower cholesterol biosynthesis than the DHA cells. Overall, the AA cells showed 2-fold lower FC masses and 2-fold higher cholesteryl ester masses than the DHA cells. The AA cells had a lower FC to phospholipid ratio and higher triglyceride levels than the DHA cells. Moreover, the AA cells showed a 40% decrease in ATP binding cassette transporter A1 (ABCA1)-mediated and a 19% decrease in ABCG1-mediated cholesterol efflux than the DHA cells. The differences in cholesterol efflux pathways induced by AA or DHA incorporation were not caused by variations in ABCs transporter expression and were reduced when ABC transporters were overexpressed by exposure to LXR/RXR agonists. These results show that AA incorporation into cardiomyocyte membranes decreased the FC turnover by markedly decreasing the endogenous cholesterol synthesis and by decreasing the ABCA1- and ABCG1-cholesterol efflux pathways, whereas DHA had the opposite effects. We propose that these observations may partially contribute to the beneficial effects on the heart of a diet containing a high ω3/ω6 PUFA ratio.

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.

Involvement of cholesterol efflux pathway in the control of cardiomyocytes cholesterol homeostasis.

Although cholesterol-rich microdomains are highly involved in the functions of cardiomyocytes, the cholesterol homeostasis is largely unknown in these cells. We developed experimental procedures to assess cholesterol synthesis, cholesterol masses and cholesterol efflux from primary cultures of cardiac myocytes obtained from 2 to 4 days old Wistar rats. We first observed that cardiomyocytes poorly internalized exogenously supplied native or modified LDL and that free cholesterol (FC) efflux to free apolipoprotein AI (apo AI) and to HDL was mediated by ATP binding cassette transporter A1 (ABCA1) and likely by ATP binding cassette transporter G1 (ABCG1), respectively, which are both upregulated by liver X receptor/retinoid X receptor (LXR/RXR) activation. We then investigated the consequences of cholesterol synthesis inhibition on cholesterol homeostasis using an HMGCoA reductase inhibitor (pravastatin, 90% effective concentration (EC90): 0.11 mM, 18 h). We observed no impact of cholesterol synthesis inhibition on the FC or cholesteryl ester (CE) masses. Consistently with no FC mass changes, pravastatin treatment had no notable impact on LDL receptors mRNA expression or on the capacity of cardiomyocytes to uptake radiolabeled LDL. Conversely, pravastatin treatment induced a significant decrease of cholesterol efflux to both apo AI and HDL whereas the passive aqueous diffusion remained unchanged. The cholesterol efflux pathway reductions induced by cholesterol synthesis inhibition were not caused by a reduction of ABC transporter expression (mRNA or protein). These results show that cardiac myocytes down-regulate active cholesterol efflux processes when endogenous cholesterol synthesis is inhibited, allowing them to preserve cholesterol homeostasis.

Deleterious impact of elaidic fatty acid on ABCA1-mediated cholesterol efflux from mouse and human macrophages.

Consumption of trans fatty acids (TFA) increase cardiovascular risk more than do saturated FA, but the mechanisms explaining their atherogenicity are still unclear. We investigated the impact of membrane incorporation of TFA on cholesterol efflux by exposing J774 mouse macrophages or human monocyte-derived macrophages (HMDM) to media enriched or not (standard medium) with industrially produced elaidic (trans-9 18:1) acid, naturally produced vaccenic (trans-11 18:1) acid (34 h, 70 µM) or palmitic acid. In J774 macrophages, elaidic and palmitic acid, but not vaccenic acid, reduced ABCA1-mediated efflux by ~23% without affecting aqueous diffusion, SR-BI or ABCG1-mediated pathways, and this effect was maintained in cholesterol-loaded cells. The impact of elaidic acid on the ABCA1 pathway was weaker in cholesterol-normal HMDM, but elaidic acid induced a strong reduction of ABCA1-mediated efflux in cholesterol-loaded cells (-36%). In J774 cells, the FA supplies had no impact on cellular free cholesterol or cholesteryl ester masses, the abundance of ABCA1 mRNA or the total and plasma membrane ABCA1 protein content. Conversely, TFA or palmitic acid incorporation induced strong modifications of the membrane FA composition with a decrease in the ratio of (cis-monounsaturated FA+polyunsaturated FA):(saturated FA+TFA), with elaidic and vaccenic acids representing each 20% and 13% of the total FA composition, respectively. Moreover, we demonstrated that cellular ATP was required for the effect of elaidic acid, suggesting that it contributes to atherogenesis by impairing ABCA1-mediated cholesterol efflux in macrophages, likely by decreasing the membrane fluidity, which could thereby reduce ATPase activity and the function of the transporter.

Impact of polyunsaturated fatty acids on oxidized low density lipoprotein-induced U937 cell apoptosis.

AIM: Dietary supplements in polyunsaturated fatty acids (PUFA), particularly omega-3, are well known for their beneficial effects in preventing cardiovascular diseases (CVD). The aim of this study was to determine the role of PUFA on the modulation of apoptosis induced by hypochlorous acidoxidized LDL (HOCl-oxLDL) in U937 cells. METHODS: We tested the effect of monocyte cell line U937 supplementation with eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), arachidonic acid (ARA) or oleic acid (OA) on the modulation of HOCl-oxLDL-induced apoptosis. RESULTS: First, we showed the incorporation of fatty acids in the cellular membrane in U937 cells. Then, we showed that both EPA and ARA exerted a pro-apoptotic effect through the intrinsic mitochondrial apoptotic pathway including the dissipation of mitochondrial membrane potential followed by cardiolipin depletion, the downstream activation of caspase-3 and the increase in DNA fragmentation. The pro-apoptotic effect of EPA or ARA was completely blocked in U937/Bcl-2 cells. CONCLUSIONS: A new mechanism of dietary supplements in PUFA with likely consequences in apoptosis could be suggested through the mitochondrial pathway in monocytes.

Metabolic imprinting, programming and epigenetics - a review of present priorities and future opportunities.

Metabolic programming and metabolic imprinting describe early life events, which impact upon on later physiological outcomes. Despite the increasing numbers of papers and studies, the distinction between metabolic programming and metabolic imprinting remains confusing. The former can be defined as a dynamic process whose effects are dependent upon a critical window(s) while the latter can be more strictly associated with imprinting at the genomic level. The clinical end points associated with these phenomena can sometimes be mechanistically explicable in terms of gene expression mediated by epigenetics. The predictivity of outcomes depends on determining if there is causality or association in the context of both early dietary exposure and future health parameters. The use of biomarkers is a key aspect of determining the predictability of later outcome, and the strengths of particular types of biomarkers need to be determined. It has become clear that several important health endpoints are impacted upon by metabolic programming/imprinting. These include the link between perinatal nutrition, nutritional epigenetics and programming at an early developmental stage and its link to a range of future health risks such as CVD and diabetes. In some cases, the evidence base remains patchy and associative, while in others, a more direct causality between early nutrition and later health is clear. In addition, it is also essential to acknowledge the communication to consumers, industry, health care providers, policy-making bodies as well as to the scientific community. In this way, both programming and, eventually, reprogramming can become effective tools to improve health through dietary intervention at specific developmental points.

Impact of android overweight or obesity and insulin resistance on basal and postprandial SR-BI and ABCA1-mediated serum cholesterol efflux capacities.

Since android overweight/obesity and insulin resistance are independent risk factors for cardiovascular disease, we investigated their impact on basal and postprandial scavenger receptor BI (SR-BI) and ATP binding cassette transporter A1 (ABCA1)-mediated serum cholesterol efflux. Twelve android overweight to obese and 9 normal weight controls women underwent body composition analysis by dual energy X-ray absorptiometry, a euglycemic hyperinsulinemic clamp, and an oral fat load with blood sampling at initial time (T0), 4h (T4) and 10h (T10) after the fat load. Serum lipids and HDL-parameters, capacities of serum to promote cholesterol efflux from SR-BI expressing Fu5AH hepatoma cells or from ABCA1-expressing J774 macrophages and to abilities of serum to induce a net removal of cholesterol from macrophage foam cells were measured at T0, T4 and T10. Sera from overweight/obese exhibited moderately decreased SR-BI-mediated cholesterol efflux capacities, in accordance with reduced HDL concentrations, but importantly increased ABCA1-mediated cholesterol efflux and increased cholesterol extraction capacities over the postprandial period, partly related to higher prebeta-HDL concentrations. In multiple regression analyses, android obesity-related parameters and HDL-PL or prebeta-HDL levels remained the only independent correlates for SR-BI or ABCA1-dependent fractional cholesterol efflux while only prebeta-HDL levels remained correlated to cholesterol extraction capacities. Our results suggest that android overweight/obesity may not result in an impaired cholesterol efflux capacity.

Effects of trimetazidine, a partial inhibitor of fatty acid oxidation, on ventricular function and survival after myocardial infarction and reperfusion in the rat.

Trimetazidine (TMZ), a partial inhibitor of fatty acid oxidation, has been effective in treating chronic angina, but its effects on the development of post-myocardial infarction (MI) left ventricular remodeling are not defined. In this study, we tested whether chronic pre-MI administration of TMZ would be beneficial during and after acute MI. Two-hundred male Wistar rats were studied in four groups: sham + TMZ diet (n = 20), sham + control diet (n = 20), MI + TMZ diet (n = 80), and MI + control diet (n = 80) splitted into one short-term and one long-term experiments. Sham surgery consisted of a thoracotomy without coronary ligation. MI was induced by coronary occlusion followed by reperfusion. Left ventricle (LV) function and remodeling were assessed by serial echocardiography throughout a 24-week post-MI period. LV remodeling was also assessed by quantitative histological analysis of post-MI scar formation at 24 weeks post-MI. During the short-term experiment, 10/80 rats died after MI, with no difference between groups (MI + control = 7/40, MI + TMZ = 3/40, P = 0.3). In the long-term experiment, the deaths occurred irregularly over the 24 weeks with no difference between groups (MI + control = 16% mortality, MI + TMZ = 17%, P = 0.8). There was no difference between groups as regard to LV ejection fraction (MI + control = 36 +/- 13%, MI + TMZ = 35 +/- 13%, P = 0.6). In this experimental model, TMZ had no effects on the post-MI occurrence of LV dysfunction or remodeling. Further investigations are warranted to assess whether the partial inhibition of fatty acid oxidation may limit the ability of the heart to respond to acute severe stress.

Per os administered refined olive oil and marine PUFA-rich oils reach the cornea: possible role on oxidative stress through caveolin-1 modulation.

BACKGROUND: Olive oil and fish oils are known to possess beneficial properties for human health. We investigated whether different oils and fatty acids alone were able to decrease oxidative stress induced on corneal cells. METHODS: In our in vivo study, rats were fed with marine oils rich in polyunsaturated fatty acids (PUFA) or refined olive oil during 28 days. At the end of the protocol, corneas were analysed for their fatty acids composition to study the incorporation of fatty acids in cell membranes. In our in vitro study, a human corneal cell line was incubated with marine oils or refined olive oil and subjected to oxidative stress (tBHP 50 muM, 1 hour). Effects on reactive oxygen species generation, mitochondria and caveolin-1 expression were studied using microcytofluorometry, flow cytometry and confocal microscopy. RESULTS: Our results indicate that dietary oils changed the fatty acids composition of corneal cell membranes. According to our results, PUFA-rich oils and refined olive oil (free of antioxidants) blocked reactive oxygen species production. Oleic acid, the major fatty acid of olive oil, also decreased oxidative stress. Moreover, oleic acid modified caveolin-1 expression. Antioxidant properties of oleic acid could be due to disruption of membrane microdomains such as caveolae. CONCLUSION: Oleic acid, a potential potent modulator of oxidative stress, could be added to PUFA-rich oils to prevent oxidative stress-linked corneal pathology.

Docosahexaenoic acid, but not eicosapentaenoic acid, lowers ambulatory blood pressure and shortens interval QT in spontaneously hypertensive rats in vivo.

This study was designed to evaluate the effects of individual dietary long-chain n-3 polyunsaturated fatty acids (LCPUFA) on hypertension and cardiac consecutive disorders in spontaneously hypertensive rats (SHR) as compared to Wistar-Kyoto rats (WKY). Rats were fed for 2 months an eicosapentaenoic (EPA)- or docosahexaenoic acid (DHA)-rich diet (240 mg/day) or an n-3 PUFA-free diet. Male SHR (n=6), implanted with cardiovascular telemetry devices, were housed in individual cages for continuous measurements of cardiovascular parameters (blood pressure (BP) and heart rate (HR)) during either activity or rest periods, ECG were recorded during the quiet period. The n-6 PUFA upstream of arachidonic acid was affected in SHR tissues. The cardiac phospholipid fatty acid profile was significantly affected by dietary DHA supply, and EPA in a very lower extent, since DHA only was incorporated in the membranes instead of n-6 PUFAs. Endothelium n-6 PUFA content increased in all SHR groups. Compared to WKY, linoleic acid content decreased in both studied tissues. Cardiac noradrenalin decreased while the adrenal catecholamine stores decreased in SHR as compared to WKY. Both n-3 PUFA supply induced a decrease of adrenal catecholamine stores. Nevertheless after 6 weeks, DHA but not EPA induced a lowering-blood pressure effect and shortened the QT interval in SHR, most probably through its tissue enrichment and a specific effect on adrenergic function. Dietary DHA supply retards blood pressure development and has cardioprotective effect. These findings, showing the cardioprotective effects of DHA in living animals, were obtained in SHR, but may relate to essential hypertension in humans.

Effects of alpha-linolenic acid vs. docosahexaenoic acid supply on the distribution of fatty acids among the rat cardiac subcellular membranes after a short- or long-term dietary exposure.

BACKGROUND: Previous work showed that the functional cardiac effect of dietary alpha-linolenic acid (ALA) in rats requires a long feeding period (6 months), although a docosahexaenoic (DHA) acid-supply affects cardiac adrenergic response after 2 months. However, the total cardiac membrane n-3 polyunsaturated fatty acid (PUFA) composition remained unchanged after 2 months. This delay could be due to a specific reorganization of the different subcellular membrane PUFA profiles. This study was designed to investigate the evolution between 2 and 6 months of diet duration of the fatty acid profile in sarcolemmal (SL), mitochondrial (MI), nuclear (NU) and sarcoplasmic reticulum (SR) membrane fractions. METHODS: Male Wistar rats were randomly assigned to 3 dietary groups (n = 10/diet/period), either n-3 PUFA-free diet (CTL), or ALA or DHA-rich diets. After 2 or 6 months, the subcellular cardiac membrane fractions were separated by differential centrifugations and sucrose gradients. Each membrane profile was analysed by gas chromatography (GC) after lipid extraction. RESULTS: As expected the n-3 PUFA-rich diets incorporated n-3 PUFA instead of n-6 PUFA in all the subcellular fractions, which also exhibited individual specificities. The diet duration increased SFA and decreased PUFA in SL, whereas NU remained constant. The SR and MI enriched in n-3 PUFA exhibited a decreased DHA level with ageing in the DHA and CTL groups. Conversely, the n-3 PUFA level remained unchanged in the ALA group, due to a significant increase in docosapentaenoic acid (DPA). N-3 PUFA rich diets lead to a better PUFA profile in all the fractions and significantly prevent the profile modifications induced by ageing. CONCLUSION: With the ALA diet the n-3 PUFA content, particularly in SR and SL kept increasing between 2 and 6 months, which may partly account for the delay to achieve the modification of adrenergic response.

Protective effects of EPA and deleterious effects of DHA on eNOS activity in Ea hy 926 cultured with lysophosphatidylcholine.

Oxidized low density lipoprotein (Ox-LDL) is a well-established risk factor in atherosclerosis and lysophosphatidylcholine (LysoPtdCho) is considered to be one of the major atherogenic component of Ox-LDL. The purpose of this work was to investigate the effects of two membrane n-3 long chain polyunsaturated fatty acids (n-3 PUFAs), EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) compared to n-6 PUFA, ARA (arachidonic acid), on the activation of endothelial NO synthase (eNOS) by histamine in Ea hy 926 endothelial cells incubated during 24 h in the presence or the absence of LysoPtdCho. DHA (50 muM) produced a ROS induction in cells and aggravated the LysoPtdCho-induced oxidative stress. It did not modify the basal eNOS activity but impaired the stimulation of eNOS induced by histamine and was unable to correct the deleterious effect of LysoPtdCho on histamine-stimulated eNOS activity or phosphorylation of Ser 1177. In contrast, EPA (90 muM) did not modify the ROS level produced in the presence or absence of LysoPtdCho or basal eNOS activity and the stimulating effect of histamine on eNOS. However, it diminished the deleterious effect of LysoPtdCho as well as on the histamine-stimulated eNOS activity on the phosphorylation on Ser 1177 of eNOS. The beneficial effect of EPA but not DHA on endothelial eNOS activity in Ea hy 926 could be also partially due to a slight decrease in membrane DHA content in EPA-treated cells. Consequently, the equilibrium between NO generated by eNOS and ROS due to oxidative stress could explain, in part, the beneficial effect of EPA on the development of cardiovascular diseases. By contrast ARA an n-6 PUFA was devoid of any effect on ROS generation or eNOS activity in the basal state or after histamine-induced stimulation. In vivo experiments should be undertaken to confirm these results.

Long-chain (n-3) polyunsaturated fatty acids prevent metabolic and vascular disorders in fructose-fed rats.

The crossover relationship between cardiometabolic risk, in terms of insulin resistance and vascular dysfunction, and the fatty acid (FA) profile of insulin-sensitive tissues as well as the dietary FA impact has almost never been explored in the same experiment. In this study, the intake of alpha-linolenic acid (ALA) alone and/or with its higher metabolites, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) were evaluated in a nonobese, hypertriglyceridemic and insulin-resistant rat model, that exhibits the 2 main characteristics of metabolic syndrome. Wistar rats were fed either a cornstarch and (n-6) PUFA-based diet (C-N6) or a 66% fructose diet over a 10-wk period. Fructose-fed rats received a diet containing ALA alone (F-ALA group) or ALA plus EPA and DHA (F-LC3 group) or no (n-3) PUFA (F-N6 group). The 10-wk high-fructose diet (F-N6) induced an insulin-resistant state, as assessed by glucose and insulin tolerance tests. Insulin resistance was linked to a specific FA pattern in insulin-sensitive tissues, which probably involved modifications of Delta9, Delta6, and Delta5-desaturases. This pathological status was related to high cardiovascular risk as assessed by increases in systolic and diastolic blood pressures and particularly by the increase of pulse pressure, an index of vascular stiffness obtained from telemetry investigations. The (n-3) experimental diets prevented changes in the FA patterns in insulin-sensitive tissues, insulin resistance, and vascular dysfunction. This beneficial effect was large with an intake of long chain (n-3) PUFA (ALA+EPA+DHA) and to a lesser extent with dietary ALA alone.

Protective effect of eicosapentaenoic acid on palmitate-induced apoptosis in neonatal cardiomyocytes.

Long chain polyunsaturated fatty acids (PUFAs) play an important role in cardioprotection. These effects have been largely attributed to membrane docosahexaenoic acid. Conversely, saturated fatty acids trigger apoptosis in cardiomyocytes, with modifications of mitochondrial properties including cardiolipin loss, cytochrome c release and caspase-3 activation. The purpose of this study was to investigate the chronic effect of eicosapentaenoic acid (EPA) on mitochondrial apoptosis induced by palmitate treatment and the associated signalling pathways. Confluent cultures of rat neonatal cardiomyocytes were treated for 2 days in media enriched with either EPA or arachidonic acid (AA) and then exposed to palmitate (0.5 mM) to induce apoptosis, in the absence of PUFA supplements. The EPA treatment resulted in significant membrane enrichment in n-3 PUFAs, especially in docosapentaenoic acid (DPA), and a large decrease in AA. Both AA and EPA treatments prevented caspase-3 activation, translocation of Bax to the mitochondria and release of cytochrome c induced by palmitate treatment. Furthermore, EPA, but not AA prevented the loss of mitochondrial cardiolipin due to apoptosis. These results suggest that EPA supplementation is able to protect cardiomyocytes against palmitate-induced apoptosis via an implication of different mitochondrial elements, possibly through its elongation to DPA, which is very efficient in cardiomyocytes.

Dietary n-3 polyunsaturated fatty acids and endothelium dysfunction induced by lysophosphatidylcholine in Syrian hamster aorta.

This study investigated the influence of an eicosapentaenoic acid (EPA)- or a docosahexaenoic acid (DHA)-supplemented diet on the deleterious effects of lysophosphatidylcholine (LPC) on endothelium-dependent vasorelaxation of Golden Syrian hamster thoracic aorta. In a second step, LPC-modulated phospholipase A(2) (PLA(2))-derived ways of relaxation were investigated. Golden Syrian hamsters were fed for 6 weeks with a control diet or an EPA- or DHA-supplemented diet. Aortic fatty acid composition was analyzed by gas chromatography. Aortic rings were incubated for 20 minutes with LPC before constructing cumulative concentration-response curves for acetylcholine (ACh; 3 nmol/L-30 micromol/L) or sodium nitroprusside (3 nmol/L-30 micromol/L). The EPA- or DHA-supplemented diet increased n-3 polyunsaturated fatty acids in aortic fatty acids content because of the increase of EPA or DHA content, respectively, and decreased arachidonic acid aortic content. Lysophosphatidylcholine (1, 10, 15, and 20 micromol/L) induced a concentration-dependent inhibition of ACh-induced relaxation of preconstricted aortic rings in the control group, but did not influence sodium nitroprusside-induced aortic relaxation. The DHA- or EPA-supplemented diet worsened LPC (20 micromol/L) inhibitory effects on ACh-induced vasorelaxation. In the control diet group, ACh-induced relaxation was abolished by the nitric oxide synthase inhibitor (l-N(G)-nitro-arginine methyl ester; 100 micromol/L), whether LPC was added or not. The ACh-induced vasorelaxation was partially inhibited by PLA(2) inhibitors methyl arachidonyl fluorophosphonate (25 micromol/L) and arachidonyl trifluoromethyl ketone (20 micromol/L) as well as by the combination of 2 Ca(2+)-dependent potassium (K(Ca)) channel inhibitors charybdotoxin (0.1 micromol/L) plus apamin (0.3 micromol/L). In the presence of LPC (20 micromol/L), ACh-induced vasorelaxation was abolished by these inhibitors. These effects were not influenced by DHA or EPA diet. Our results suggested that EPA- or DHA-supplemented diet did not exhibit any beneficial effect against LPC-induced inhibition of endothelium-dependent aortic relaxation in Golden Syrian hamsters. These LPC effects were associated in our study not only with an inhibition of nitric oxide-dependent vasorelaxation, but also with a concomitant activation of a compensatory vasorelaxant pathway depending both on PLA(2) metabolites and on K(Ca) channel opening.

Enhanced removal of cholesterol from macrophage foam cells to serum from type IV hypertriglyceridemic subjects.

Hypertriglyceridemia being an independent cardiovascular risk factor, we have compared the potential of sera from asymptomatic hypertriglyceridemic (HTG) type IIb, type IV or normolipidemic (NLP) subjects to promote both fractional cholesterol efflux and cellular cholesterol mass changes using macrophage foam cells. The J774 cells loaded with cholesterol by incubation with acetylated LDL were incubated in the absence or presence of cAMP to upregulate ABCA1 (ATP binding cassette transporter A1) and then incubated for 24h with 1% serum. Compared with NLP, type IV sera exhibited a major increase in ABCA1-dependent efflux while type IIb sera exhibited a moderate but not significant increased ABCA1-mediated efflux. Moreover, positive correlations were established between ABCA1-dependent efflux and the serum prebeta-HDL or TG concentrations. The major finding was that the sera from type IV induced higher total cholesterol and cholesteryl ester mass depletions from ABCA1-expressing cells compared with other groups. Moreover, negative correlations were obtained between total cholesterol or cholesteryl ester mass changes and serum prebeta-HDL levels. In conclusion, we demonstrated for the first time that the serum prebeta-HDL present in high proportions in type IV HTG subjects are not only responsible for higher cholesterol efflux potential but also for increased abilities to promote net removal of cholesterol from macrophage foam cells.

Long-term effect of dietary {alpha}-linolenic acid or decosahexaenoic acid on incorporation of decosahexaenoic acid in membranes and its influence on rat heart in vivo.

The present study was designed to evaluate whether long-term intake of dietary alpha-linolenic acid (ALA), supplied as whole grain-extruded linseed, can increase endogenous production of n-3 long-chain polyunsaturated fatty acids (FAs) in healthy adult rats and influence the heart rate (HR) and adrenergic response in the same way as docosahexaenoic acid (DHA)-rich diets. DHA enrichment was evaluated using FA analysis of tissue phospholipids after 8, 16, 24, and 32 wk of feeding in male Wistar rats randomly assigned to three dietary groups (n = 8 in each group): a reference fat diet (RFD), an ALA-rich (ALA) diet, and a DHA-rich (DHA) diet. At 1 wk before the animals were killed, under anesthesia, HR was measured from ECG recordings during an adrenergic stimulation challenge (n = 8). There was a significant increase of DHA in the cardiac membrane in the ALA group compared with the RFD group. DHA content in the cardiac membrane was approximately 10% in the ALA group vs. 20% in the DHA group and 4% in the RFD group. The cardiac FA profile was established after 2 mo and remained essentially unchanged thereafter. Regardless of the diet, DHA in the heart decreased with age. Nevertheless, DHA content in the heart remained at >15% in the DHA group and remained greater in older rats fed the ALA diet than in younger RFD-fed rats. Basal HR decreased in the ALA group (395 +/- 24.9 beats/min) to a level between that of the DHA and RFD groups (375 +/- 26.4 and 407 +/- 36.7 beats/min, respectively). Both n-3 dietary intakes contribute to enhancement of the chronotropic response to adrenergic agonist stimulation. Regulation of HR by neurohumoral mediators may be controlled by lower content of DHA, e.g., by a dietary supply of extruded linseed (ALA).

AMP-activated protein kinase alpha2 deficiency affects cardiac cardiolipin homeostasis and mitochondrial function.

AMP-activated protein kinase (AMPK) plays an important role in controlling energy homeostasis and is envisioned as a promising target to treat metabolic disorders. In the heart, AMPK is involved in short-term regulation and in transcriptional control of proteins involved in energy metabolism. Here, we investigated whether deletion of AMPKalpha2, the main cardiac catalytic isoform, alters mitochondrial function and biogenesis. Body weight, heart weight, and AMPKalpha1 expression were similar in control littermate and AMPKalpha2(-/-) mice. Despite normal oxygen consumption in perfused hearts, maximal oxidative capacity, measured using saponin permeabilized cardiac fibers, was approximately 30% lower in AMPKalpha2(-/-) mice with octanoate, pyruvate, or glutamate plus malate but not with succinate as substrates, showing an impairment at complex I of the respiratory chain. This effect was associated with a 25% decrease in mitochondrial cardiolipin content, the main mitochondrial membrane phospholipid that is crucial for complex I activity, and with a 13% decrease in mitochondrial content of linoleic acid, the main fatty acid of cardiolipins. The decrease in cardiolipin content could be explained by mRNA downregulation of rate-limiting enzymes of both cardiolipin synthesis (CTP:PA cytidylyltransferase) and remodeling (acyl-CoA:lysocardiolipin acyltransferase 1). These data reveal a new role for AMPKalpha2 subunit in the regulation of cardiac muscle oxidative capacity via cardiolipin homeostasis.