Animals studies should always be treated with caution. This is because animals have different physiologies to humans. In addition, animal nutrition is different to human nutrition and what is good for a dog, cat, rat or rabbit, may not be good for a human. However, animal studies are perfectly valid if you are interested in animals. Not all animals studies need to be extrapolated to humans, some can be applied quite reasonably to animals. Pet rats for example often suffer from respiratory infections as they age, particularly mycoplasma. These infections can be eliminated through basic changes to the care of the rat, but if left untreated can eventually lead to congestive heart failure in the rats. Symptoms include shortness of breath, lack of vitality and energy as well as other complications that can seriously impair the health of the rat. Anyone who has kept pet rats will likely have come across this. A study that investigates treatment of congestive heart failure in rats might therefore be of interest to rat owners.
For example, one study1 investigated the effects of the fish oils eicosapentaenoic acid (EPA, C20:5 (n-3)) and docosahexaenoic acid (DHA, C22:6 (n-3)) on the normal cardiac function of rats. Rats were fed 1 gram per kg body weight EPA, DHA or a control for 28 days. The results showed that the QT intervals on the electrocardiogram were significantly shortened (suggesting faster heart rate) in the EPA and DHA fed rats compared to the controls. Analysis showed that the EPA content of the myocardium was significantly higher in the EPA fed rats and the EPA and DHA content higher in the DHA fed rats, compared to the controls. Therefore both EPA and DHA were accumulating in the myocardium of the rats. In addition, the arachidonic acid (AA, C20:4 (n-6)) content of the rat myocardium was lower than that of control rat myocardium. This suggests that the omega-3 fatty acids EPA and DHA were able to inhibit synthesis of arachidonic acid, probably through the inhibition of the delta 5-desaturase enzyme.
The authors then exposed some rats to monocrotaline to induce coronary heart failure. Those rats fed DHA at 1 gram per kg body weight had shorter QT intervals in their electrocardiograms similar to control rats. In contrast, rats exposed to monocrotaline had elongated QT waves suggesting heart pathology. Therefore administration of DHA may be protective of coronary heart disease. Both DHA and EPA appear to show cardioprotective effects in humans, and some of this effects may come from their ability to accumulate in heart tissue and protect heart function. The authors speculated that the changes to the heart muscle in the rats might be due to ion channel modification by the downstream metabolites of EPA, possibly resolvin E1, and downstream metabolites of DHA, possibly protectin1, 17S resolvin D1, and 17R resolvin D1. These metabolites are relatively newly discovered derivatives of EPA and DHA that are synthesised through a novel alternative pathway not related to eicosanoid synthesis.
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