Long-term supplementation with eicosapentaenoic acid salvages cardiomyocytes from hypoxia/reoxygenation-induced injury in rats fed with fish-oil-deprived diet

Antioxidant and Cardioprotective Effects of EPA on Early Low-Severity Sepsis through UCP3 and SIRT3 Upholding of the Mitochondrial Redox Potential

Sepsis still causes death, often through cardiac failure and mitochondrial dysfunction. Dietary ω3 polyunsaturated fatty acids are known to protect against cardiac dysfunction and sepsis lethality. This study set out to determine whether early low-severity sepsis alters the cardiac mitochondrial function in animals fed a Western-type diet and whether dietary eicosapentaenoic acid (EPA) administration protects the myocardium against the deleterious effects of sepsis and if so to seek possible mechanisms for its effects. Rats were divided into two groups fed either an ω3 PUFA-deficient diet (“Western diet,” DEF group) or an EPA-enriched diet (EPA group) for 5 weeks. Each group was subdivided into two subgroups: sham-operated rats and rats subjected to cecal ligation and puncture (CLP). In vivo cardiac mechanical function was examined, and mitochondria were harvested to determine their functional activity. Oxidative stress was evaluated together with several factors involved in the regulation of reactive oxygen species metabolism. Sepsis had little effect on cardiac mechanical function but strongly depressed mitochondrial function in the DEF group. Conversely, dietary EPA greatly protected the mitochondria through a decreased oxidative stress of the mitochondrial matrix. The latter was probably due to an increased uncoupling protein-3 expression, already seen in the sham-operated animals. CLP rats in the EPA group also displayed increased mitochondrial sirtuin-3 protein expression that could reinforce the upholding of oxidative phosphorylation. Dietary EPA preconditioned the heart against septic damage through several modifications that protect mitochondrial integrity. This preconditioning can explain the cardioprotective effect of dietary EPA during sepsis.

About the controversies of the cardioprotective effect of n-3 polyunsaturated fatty acids (PUFAs) between animal studies and clinical meta-analyses: a review with several strategies to enhance the beneficial effects of n-3 PUFAs

Several meta-analyses describing the effect of n-3 polyunsaturated fatty acids on the survival rate of the victims of an acute coronary event do not clearly support a beneficial impact of these fatty acids. Yet, animal studies consistently show n-3 PUFA-induced protection against ischemia-reperfusion-induced myocardial injuries. The impact on reperfusion arrhythmias of these PUFAs is more controversial. The literature shows the anti-arrhythmic properties of circulating n-3 PUFAs. However, when these fatty acids are incorporated in the cardiac membrane, they protect the myocardial tissue vis a vis cellular damage but they can be either pro- or anti-arrhythmic during reperfusion, depending on the severity of tissue injuries. The latter elements can explain the lack of beneficial effect observed in the meta-analyses, but a proper use of n-3 PUFAs may provide advantages in terms of survival rate. This review discusses the different results obtained in humans and animals and presents several strategies to enhance the beneficial effects of n-3 PUFAs.

Eicosapentaenoic acid preserves diaphragm force generation following endotoxin administration

Introduction

Infections produce severe respiratory muscle weakness, which contributes to the development of respiratory failure. An effective, safe therapy to prevent respiratory muscle dysfunction in infected patients has not been defined. This study examined the effect of eicosapentaenoic acid (EPA), an immunomodulator that can be safely administered to patients, on diaphragm force generation following endotoxin administration.

Methods

Rats were administered the following (n = 5/group): (a) saline, (b) endotoxin, 12 mg/kg IP, (c) endotoxin + EPA (1.0 g/kg/d), and (d) EPA alone. Diaphragms were removed and measurements made of the diaphragm force-frequency curve, calpain activation, caspase activation, and protein carbonyl levels.

Results

Endotoxin elicited large reductions in diaphragm specific force generation (P < 0.001), and increased diaphragm caspase activation (P < 0.01), calpain activation (P < 0.001) and protein carbonyl levels (P < 0.01). EPA administration attenuated endotoxin-induced reductions in diaphragm specific force, with maximum specific force levels of 27 ± 1, 14 ± 1, 23 ± 1, and 24 ± 1 N/cm², respectively, for control, endotoxin, endotoxin + EPA, and EPA treated groups (P < 0.001). EPA did not prevent endotoxin induced caspase activation or protein carbonyl formation but significantly reduced calpain activation (P < 0.02).

Conclusions

These data indicate that endotoxin-induced reductions in diaphragm specific force generation can be partially prevented by administration of EPA, a nontoxic biopharmaceutical that can be safely given to patients. We speculate that it may be possible to reduce infection-induced skeletal muscle weakness in critically ill patients by administration of EPA.

Increased myocardial susceptibility to repetitive ischemia with high-fat diet-induced obesity

Obesity and diabetes are frequently associated with cardiovascular disease. When a normal heart is subjected to brief/sublethal repetitive ischemia and reperfusion (I/R), adaptive responses are activated to preserve cardiac structure and function. These responses include but are not limited to alterations in cardiac metabolism, reduced calcium responsiveness, and induction of antioxidant enzymes. In a model of ischemic cardiomyopathy inducible by brief repetitive I/R, we hypothesized that dysregulation of these adaptive responses in diet-induced obese (DIO) mice would contribute to enhanced myocardial injury. DIO C57BL/6J mice were subjected to 15 min of daily repetitive I/R while under short-acting anesthesia, a protocol that results in the development of fibrotic cardiomyopathy. Cardiac lipids and candidate gene expression were analyzed at 3 days, and histology at 5 days of repetitive I/R. Total free fatty acids (FFAs) in the cardiac extracts of DIO mice were significantly elevated, reflecting primarily the dietary fatty acid (FA) composition. Compared with lean controls, cardiac FA oxidation (FAO) capacity of DIO mice was significantly higher, concurrent with increased expression of FA metabolism gene transcripts. Following 15 min of daily repetitive I/R for 3 or 5 days, DIO mice exhibited increased susceptibility to I/R and, in contrast to lean mice, developed microinfarction, which was associated with an exaggerated inflammatory response. Repetitive I/R in DIO mice was associated with more profound significant downregulation of FA metabolism gene transcripts and elevated FFAs and triglycerides. Maladaptive metabolic changes of FA metabolism contribute to enhanced myocardial injury in diet-induced obesity.