Delphine Rousseau

AMP-Activated Protein Kinase α2 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 AMPKα2, the main cardiac catalytic isoform, alters mitochondrial function and biogenesis. Body weight, heart weight, and AMPKα1 expression were similar in control littermate and AMPKα2−/− mice. Despite normal oxygen consumption in perfused hearts, maximal oxidative capacity, measured using saponin permeabilized cardiac fibers, was ∼30% lower in AMPKα2−/− 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 AMPKα2 subunit in the regulation of cardiac muscle oxidative capacity via cardiolipin homeostasis.

Dietary n-3 polyunsaturated fatty acids affect the development of renovascular hypertension in rats

The consequences of a dietary n‐3 PUFA supply was investigated on the blood pressure (BP) increase elicited by left renal artery stenosis in rats distributed in 3 groups (n = 8) fed for 8 weeks a semi‐purified diet either as control diet or enriched diets (docosahexaenoic acid, DHA, or eicosapentaenoic acid, EPA). The PUFA intake induced large alterations in heart and kidney phospholipid fatty acid profile, but did not influence body weight, cardiac hypertrophy, renal left atrophy and right hypertrophy. Within 4 weeks, BP raised from 120–180 ± 2 mm Hg in the control group, but only to 165 ± 3 mm Hg in the n‐3 PUFA groups. After stabilization of BP in the 3 groups, the rats received a short administration of increasing dose of perindopril. The lower dose (0.5 mg/kg) moderately decreased BP only in the control group. With higher doses (1, 5 and 10 mg/kg) BP was normalized in the 3 groups, with a higher amplitude of the BP lowering effect in the control group. A moderate n‐3 PUFA intake can contribute to prevent the development of peripheral hypertension in rats by a mechanism that may involve angiotensin converting enzyme.

IS A DIETARY N-3 FATTY ACID SUPPLEMENT ABLE TO INFLUENCE THE CARDIAC EFFECT OF THE PSYCHOLOGICAL STRESS?

Epidemiological studies suggest that n-3 polyunsaturated fatty acids (PUFA) are involved in the prevention of cardiovascular disease. Stress is known to increase the incidence of CVD and the present study was realised to evaluate some physiological and biochemical effects of dietary docosahexaenoic acid (DHA) in male Wistar rats subjected to a psycho social stress. Rats were fed for 8 weeks a semi-purified diet containing 10% of either sunflower seed oil or the same oil supplemented with DHA. This food supply represented 50% of their daily requirement. The remaining 50% were supplied as 45 mg food pellets designed to induce stress in rats by an intermittent-feeding schedule process. The control group (n = 12) was fed the equivalent food ration as a single daily feeding. The physiological cardiovascular parameters were recorded by telemetry through a transmitter introduced in the abdomen. At the end of the experimentation, the heart and adrenals were withdrawn and the fatty acid composition and the catecholamine store were determined. Dietary DHA induced a pronounced alteration of the fatty acid profile of cardiac phospholipids (PL). The level of all the n-6 PUFAs was reduced while 22:6 n-3 was increased. The stress induced a significant increase in heart rate which was not observed in DHA-fed group. The time evolution of the systolic blood pressure was not affected by the stress and was roughly similar in the stressed rats of either dietary group. Conversely, the systolic blood pressure decreased in the unstressed rats fed DHA. Similar data were obtained for the diastolic blood pressure. The beneficial effect of DHA was also observed on cardiac contractility, since the dP/dtmax increase was prevented in the DHA-fed rats. The stress-induced modifications were associated with an increase in cardiac noradrenaline level which was not observed in DHA-fed rats. The fatty acid composition of adrenals was significantly related to the fatty acid intake particularly the neutral lipid fraction (NL) which incorporated a large amount of DHA. Conversely, n-3 PUFAs were poorly incorporated in adrenal phospholipids. Moreover the NL/PL ratio was significantly increased in the DHA fed rats. The amount of adrenal catecholamines did not differ significantly between the groups. These results show that a supplementation of the diet with DHA induced cardiovascular alterations which could be detected in conscious animals within a few weeks. These alterations were elicited by a reduced heart rate and systolic and diastolic blood pressure.

Influence of Trimetazidine on the synthesis of complex lipids in the heart and other target organs

Trimetazidine exerts antianginal properties at the cellular level, without haemodynamic effect in clinical and experimental conditions. This cytoprotection was attributed to a decreased utilization of fatty acids for energy production, balanced by an increased incorporation in structural lipids. This study evaluated the influence of Trimetazidine on complex lipid synthesis from [2‐3H] glycerol, in ventricular myocytes, isolated rat hearts and in vivo in the myocardium and several other tissues. In cardiomyocytes, Trimetazidine increased the synthesis of phosphatidyl‐choline (+ 80%), phosphatidyl‐ethanolamine (+ 210%), phosphatidyl‐inositol (+ 250%) and cardiolipid (+ 100%). The common precursor diacylglycerol was also increased (+ 40%) whereas triacylglycerol was decreased (−70%). Similar results were obtained in isolated hearts with 10 μM Trimetazidine (phosphatidyl‐choline + 60%, phosphatidyl‐ethanolamine + 60%, phosphatidyl‐inositol + 100% and cardiolipid + 50%), the last two phospholipids containing 85% of the radioactivity. At 1 μM, Trimetazidine still stimulated the phospholipid synthesis although the difference was found significant only in phosphatidyl‐inositol and cardiolipid. In vivo studies (10 mg/kg per day for 7 days and 5 mg/kg, i.p. before the experiment) revealed significant changes in the intracellular lipid biosynthesis, with increased labelling of phospholipids and reduced incorporation of glycerol in nonphosphorous lipids. Trimetazidine increased the glycerol uptake from plasma to the other tissues (liver, cochlea, retina), resulting in an altered lipid synthesis. The anti‐anginal properties of Trimetazidine involve a reorganisation of the glycerol‐based lipid synthesis balance in cardiomyocytes, associated with an increased uptake of plasma glycerol that may contribute to explain the pharmacological properties reported in other organs.

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.

BackgroundOlive 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.MethodsIn 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 μM, 1 hour). Effects on reactive oxygen species generation, mitochondria and caveolin-1 expression were studied using microcytofluorometry, flow cytometry and confocal microscopy.ResultsOur 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.ConclusionOleic acid, a potential potent modulator of oxidative stress, could be added to PUFA-rich oils to prevent oxidative stress-linked corneal pathology.