In dogs with heart failure, a great production of free-radical sources occurs, which are the main causes of cellular dysunction, leading to oxidative stress.
A proper food intake of fatty acids and antioxidants plays an important role in restricting this phenomenon: the presence of fatty acids decreases the sensitivity of cells to free radicals and represents the first defense against the oxidative stress; the coenzyme Q10, vitamin E and polyphenols, are fat-soluble vitamins with antioxidant properties, too.
Heart failure represents one of the main causes of death in domestic carnivores. Cell oxygenation does not work properly in these animals, leading to cellular metabolism dysfunction.
In a chronic way, the heart work of a dog with heart failure is insufficient to provide the normal oxygenation of all cells, which implies a dioxygen cellular chronic deficit and thus a regular production of free radicals.
In an acute way, during the phenomenon of ischemia reperfusion, the cell ischemia induces a massive production of free radicals that are released in the organism.
Usually free radicals are produced via cellular metabolism, and in physiological conditions, antioxidant enzymes regulate this phenomenon
However, when a large amount of free radicals is produced, these enzymes are overloaded, and free radicals generate cellular damages leading to oxidative stress.
These molecules are very unstable and toxic for cells and they induce a membrane lipid peroxidation, altering the stability and the permeability of these membranes. These cellular lesions are so important that they can lead to the apoptosis of cells, and so the death. So, cardiac insufficiency is at the origin of a noxious state of cellular oxidative stress, which increases the cardiac cell dysfunctions and thus amplifies the phenomenon of oxidative stress.
ROLE OF OMEGA 3 ESSENTIAL FATTY ACIDS
The unsaturated fatty acids of cell membranes are the first damaged by the free radicals produced during cardiac insufficiency, this results in cell disorganization and cellular dysfunction. The presence of essential fatty acids in the composition of cell membranes decreases their sensitivity to free radicals and constitutes a first protection against the oxidative stress
Some fatty acids are called “essentials” as mammals do not synthesize them, and they must then be present in the food to satisfy the organism needs. This is the case of long omega 3 and omega 6 fatty acids
However, all essential fatty acids are not equivalent: for example, the omega 6 fatty acids, which are commonly known to be inflammation activators, do not induce the same benefits for the cardiac cells as omega 3 fatty acids do.
Indeed, a study led in rats revealed that a 7% daily supplementation in omega 3 essential fatty acids increases the cellular concentration of super oxide dismutase in heart, making it more available to neutralize the free radicals produced by cellular metabolism
Omega 3 fatty acids can be found mainly in fat fishes, soya, colza, or linen oils
Although the optimal dose of omega 3 essential fatty acids still remains to be determined, it would seem that the ratio omega 6 : omega 3 is very important. Indeed, if the quantity of fatty acids omega 3 brought is too important, there is a risk of lipid peroxidation. Then, the most adapted ratio of these two acids seems to be 5 : 1 ratio.
ROLE OF ANTIOXIDANTS
COENZYME Q10
It is now well known that a supplementation of coenzyme Q10 plays an important role in the heart function. Indeed, the coenzyme Q10, which is a part of the respiratory chains of mitochondria, is important in the cell energy production.
This coenzyme, with its antioxidant properties, helps to fight against the free radicals released later during reperfusion, thanks to two mechanisms: directly, by scavenging free radicals produced, and indirectly, by regenerating the active form of other antioxidant molecules.
Moreover, the coenzyme Q10 also intervenes in the energy production resumption after an ischemia phenomenon, improving the myocytes functioning
Coenzyme Q10 can be synthesized from phenylalanine, acetyl Coenzyme A, tyrosine and by seven vitamins (B2, B3, B5, B6, B9, B12, and C). However, food can also supply coenzyme Q10: meat is particularly rich in coenzyme Q10. The dose most frequently recommended is an intake from 30 to 90 mg by oral route, twice a day.
VITAMINE E AND SELENIUM
All the eight vitamin E isomers are fat-soluble vitamins with antioxidant properties, but the most active form is αtocopherol, acting as cellular barrier for the oxidant molecules.
When the vitamin E is exceeded, glutathione peroxidase relieves vitamin E to neutralize the oxidant molecules. The main cofactor of this enzyme is selenium, and it is easily understandable which impact could have a deficit in selenium on its activity. On the other hand, an increase of the selenium intake seems to have no effect on the activity of glutathione peroxidase
Vitamin E is a molecule synthesized by plants. The minimum food contribution recommended by AAFCO is 50 UI/kg DM. Its intestinal absorption is widely influenced by the ration composition: the presence of polyunsaturated fatty acids oxidant agents implies an increase of vitamin E need; on the contrary, a ration containing monounsaturated fatty acids or selenium leads to a decrease of vitamin E necessary. However, in dog food, the recommended dose is fixed to a maximum of 1000 UI/kg.
POLYPHENOLS
Polyphenols are synthesized by plants to respond to an environmental stress. They have antioxidant properties which allow them to catch the free radicals produced during oxidative stress.
In food, polyphenols are mainly found in vegetables. However, the determination of the food polyphenols composition is difficult because of the important variety of molecules (8000 different organic molecules). There is a big difference between the quantity of polyphenols contained in the food and the quantity effectively absorbed and used by the body: cooking, peeling fruits and vegetables, and preservation are so many factors which decrease the effective contribution of polyphenols in the body. The smallest polymers are more easily absorbed and have a better systemic action, which implies a better nutritional value.
There is no study on the effect of polyphenols in domestic carnivores, but it is likely that the quantity of polyphenols ingested by pets via industrial or domestic food is very low
A well-studied diet is the main resource for the well-being and life expectancy of these animals.A suitable supplementation of antioxidants and essential fatty acids can play a major role maintaining cardiac cell homeostasis and especially in managing oxidative stress.
In practice, dietary feed for cardiac insufficient animals are only supplemented with essential fatty acids with an omega 6/omega 3 report which can vary from 2 to 10.
Regarding the antioxidant molecule supplementations, they are often absent or below the contributions needed to have benefit for the heart. This is probably due to the difficulty to preserve a sufficient amount of antioxidants during the manufacturing process.