**6. Omega 6 to omega 3 ratio and its related effects**

Normally, the omega 6 to omega 3 ratio has moderate amounts in natural food sources, especially in marine foods. In aquatic creatures, omega 6 to omega 3 ratio in the tissues of molluscs is significantly higher in comparison with others. Also, the omega 6 to omega 3 ratio vary between different organs and different species, as well as marine and freshwater species. There are significant differences in the omega 6 to omega 3 ratio in the gills, foot, mantle and whole body tissues of molluscs species, respectively [12, 14, 35].

Different species of the marine molluscs are generally rich in fatty acid compounds of ω3 (especially C18:3ω3, C20:5ω3 and C22:6ω3). The mussels species in freshwater, however, include a greater proportion of fatty acids compounds of ω6 (especially C18:2ω6 and C20:4ω6). The Σω6/Σω3 ratios is 2:4 in freshwater mussels, but the marine species have ratios of 0.1:1.0 [12].

Obesity disease which is a complex condition along with organs dysregulations and molecular pathways, such as adipose organ, liver, gastrointestinal tract, pancreas, central nervous system (CNS), and genetics. The role of the CNS in this disease needs more attention as obesity rates rise and relating treatments might fail. Since hypothalamus system has long been recognized in the regulation of appetite and food intake, the role of the CNS systems were examined as well as environmental impacts on energy balance. Furthermore, the omega-3 fatty acids have an important role in this disease and in the prevention and management of obesity [3, 4, 6].

for cardiovascular diseases. Marine organisms consume diets rich in n-3 PUFAs and the lipids of the animals can contain up to 50% unsaturated fatty acids, with five or six double bonds,

The term sterol refers to a compound with a fused cyclopentano phenanthrene ring with a 3-hydroxyl moiety. Early studies of gastropod sterols indicated cholesterol as the principal sterol of all species. Most species only one or two types of sterols present. Amino acids are the building blocks of protein molecules. They cause metabolites in the homeostasis of an organisms, due to their role as the regulation of several cellular processes and also as precursors of other molecules, such as hormones and nitrogenous bases. Lipid compositions and storage strategy in molluscs, particularly of bivalves and gastropods, have been studied since lipids constitute a major fraction of molluscan tissues. Almost all the data included in their lipid studies, concern the entire organism and only a few reports on the tissue distribution of fatty acids are available [24, 26, 28, 29].

The lipid in the gill tissue in the marine molluscs has important role for regulate of ions such as Na. In the marine animals, the primary site of Na uptake is gills. In addition to being the initially site of an ion transport, gills also captive food, have roles in gas exchanges and act as a brooding chamber for the larval glochidia in females species. Thus, gills activate in many different functions, regarding that their related importance may vary during the year. From the lipids, C20:4ω6 acid is an active substrate for prostaglandin productions involved in regulating Na uptake and it has relatively high contents in gill lipids. Therefore, high level of C20:4ω6 acid in the gill is probably related to prostaglandin synthesizing in the gills to regulate Na uptake. Finally the accumulation of C20:4ω6 acid in the gills was related to physi-

Fatty acids are organic compounds consist of hydrocarbon chains with terminal carboxyl groups. The fatty acid chains in sea foods differ from vegetables in length. In the presence of Omega-3 fatty acids, prostaglandins actions on epinephrine is diminished and thus constriction or narrowing of blood vessels is prevented. Therefore, marine Mollusca have been regarded as a good source of lipid compounds, and lipids are proper energy sources for ani-

Normally, the omega 6 to omega 3 ratio has moderate amounts in natural food sources, especially in marine foods. In aquatic creatures, omega 6 to omega 3 ratio in the tissues of molluscs is significantly higher in comparison with others. Also, the omega 6 to omega 3 ratio vary between different organs and different species, as well as marine and freshwater species. There are significant differences in the omega 6 to omega 3 ratio in the gills, foot, mantle and

Different species of the marine molluscs are generally rich in fatty acid compounds of ω3 (especially C18:3ω3, C20:5ω3 and C22:6ω3). The mussels species in freshwater, however, include a greater proportion of fatty acids compounds of ω6 (especially C18:2ω6 and C20:4ω6). The Σω6/Σω3 ratios is 2:4 in freshwater mussels, but the marine species have ratios of 0.1:1.0 [12].

including 22:6 n-3 and 20:5 n-3 [18, 19].

238 Biological Resources of Water

ological activities in the organs [22, 30–33].

mals and nutritive foodstuff for human diets [34].

**6. Omega 6 to omega 3 ratio and its related effects**

whole body tissues of molluscs species, respectively [12, 14, 35].

The omega-6 and omega-3 polyunsaturated fatty acids (PUFAs) compounds are very important and essential fatty acids that must be derived from the diet compositions. Since omega-6 and omega-3 polyunsaturated fatty acids (PUFAs) compounds need endogenous enzymes for omega desaturation and there are no endogenous enzymes for omega desaturation in human and other mammals, these compounds cannot be made by man or other mammals and could be made particularly by Mollusca species. Modern agricultural western diets contain excessive concentrations of omega-6 PUFAs but very low concentrations of omega-3 PUFAs, leading to an unhealthy omega-6/omega-3 ratio of 20:1, instead of 1:1 proper for evolution process in the humans [9, 10].

Thus, an unbalanced omega-6/omega-3 ratio in favor of omega-6 PUFAs is highly prothrombotic and proinflammatory, which contributes to the prevalence of atherosclerosis, obesity, and diabetes. In fact, regular and balance of the omega-6/omega-3 ratio have positive effects for of these diseases and is the important factor for improve of these diseases (obesity, diabetes, atherosclerosis and cancer) [23, 24, 26, 30].

As mentioned earlier, omega-6 to omega-3 fatty acids compounds cannot be made and convert in humans and other mammalian cells, therefore, they cannot made enzyme for omega-3 desaturase and so they lack converting enzyme, omega-3 desaturase. Omega-6 and omega-3 fatty acids compounds are not interconvertible, and they are metabolically compounds and functionally distinct. Also they have important opposing physiological influences, therefore, omega-6 to omega-3 fatty acids balance in the diet is very important for better function and body protection [6, 7]. When fish consume by humans or predators, the EPA and DHA from the diet composition partially replace the omega-6 fatty acids, especially AA, in the skin and membranes of almost all body cells, but specifically in the membranes of platelets, erythrocytes, neutrophils, monocytes, and liver cells. The parent compounds for eicosanoid formation, are AA and EPA fatty acids. Because of high levels of omega-6 in the diet, the eicosanoid metabolic products from AA, especially prostaglandins, thromboxane, leukotriene, hydroxyl fatty acids, and lipoids, are formed in larger amounts than those derived from omega-3 fatty acids, especially EPA [32]. The eicosanoids from AA are biologically active in very small concentrations and, if they are formed in high levels, they contribute to the formation of thrombus and atheroma; allergic and inflammatory disorders, particularly in susceptible people; and proliferation of cells. Thus, a diet composition rich in omega-6 fatty acids shifts the physiological state to prothrombotic, proinflammatory, and proaggregatory effects with increases in blood viscosity, vasospasm, and vasoconstriction and cell proliferation. Omega-6 and omega-3 fatty acids balance is a physiological state that is less inflammatory in terms of prostaglandin, gene expression and leukotriene metabolism activity, and interleukin-1 (IL-1) production [28–31].

Novel agricultural technologies, by changing animal feeds for better and short term productions, have decreased the omega-3 fatty acid contents in many foods such as meats, eggs, and even fish. Foods from edible wild plants contain a good balance of omega-6 and omega-3 fatty acids. For instance, *Purslane*, a wild plant, in comparison to *Spinach*, red leaf lettuce, butter crunch lettuce and mustard greens, has eight times more ALA than the cultivated plants [30]. New aquaculture technologies produce fish with less omega-3 fatty acids than naturally grown fish in the ocean or freshwaters. The fatty acid composition in egg yolk from freeranging chicken has an omega-6: omega-3 ratio of 1.3 whereas egg production supervising by the United States Department of Agriculture (USDA) conclude ratio of 19.9. By enriching the chicken feed with fishmeal or flaxseed, the ratio of omega-6: omega-3 decreased to 6.6 and 1.6 respectively [33].

biocompounds in the tissues of animals. Also, salinity of water and pH has effect on the variations in the compounds such as fatty acids. The accumulation of fatty acids in the different tissues of organisms vary in different salinity and pH. Also, the accumulation of fatty acids in the different level of salinity and pH are not similar for different organs, and fatty acid profiles and their amounts in gill tissue for example, has more variations in the

Chemical Ecology of Biocompounds in Molluscs http://dx.doi.org/10.5772/intechopen.72741 241

Levels of proteins, lipids and carbohydrates (glycogen) have been shown to fluctuate with food availability. Food abundance allows for the accumulation of proteins and lipids in the tissues of the different species such as bivalves and gastropods. There are correlations between food type source and biocompounds structure, which increase in the food availability in the aquatic environment could result increasing the amount of the biocompounds in the tissues of the different species of Mollusca. When food availability levels are high in the environment the level of biocompounds are higher in comparison with other situations [17, 20]. The reproductive cycle and time spawning have the key role in the variation of chemistry compounds especially fatty acids, because of the high levels of energy needs for spawning processes and

Lipids generally increase during the course of gametogenesis and decrease upon release of gametes. For proteins, diverging trends have been observed throughout gametogenesis and spawning. During gametogenesis, protein content was found to increase, decrease or even remain stable. During spawning, levels of protein were found to increase or decrease. Differences in food availability and water temperature conditions may partially explain the observed discrepancies since these factors are known to influence protein accumulation [1, 2]. Focusing on proteins and lipids, compounds involved in most biochemical and physiological processes of any organism is therefore useful for the recognition of ecological and physiological changes. Indeed, differences in seasonal trends have been observed among both AAs and FAs. More commonly reported, is the different behavior exhibited among free AAs in relation to salinity and that exhibited among FAs in relation to temperature. The biochemical composition of an organism is determined by endogenous (e.g., gametogenesis, maturation, spawning) and exogenous (e.g., food availability, salinity, temperature) processes. The temporal tests in the field of biochemical compounds permit intercrossing along with chronological and other variables allowing researchers to gain knowledge about ecology and physiology of an organism and also understanding how the surrounding ecosystem

There are significant differences between tissues and their activities for accumulation of amount and structure of natural compounds, and different tissues based on their activities can be accumulated fatty acids, amino acids and other compounds. Therefore, the level of compounds in the tissues are related to their activities. Some tissues such as gonad have highest level of biocompounds in comparison with the other tissues, due to this fact that gonad must have high level of energy for reproductive and spawning process. Since, gonad consume high amount of energy for this process, reproductive and spawning processes need high levels of energy. Also, gills need high energy levels for their metabolism, and so the high

the high level of fatty acids consumed in this process [31, 32].

levels of fatty acids can be accumulate in this tissue [15, 16].

different salinities [4, 6].

may affect [8, 9, 12].

High omega-6/omega-3 ratios cause some disorders such as increasing in the end cannabinoid signaling and related mediators, which could lead to change inflammatory state, energy homeostasis, and mood. In animal experiments a high omega-6 acid intake leads to decreased insulin sensitivity in muscle and promotes fat accumulation in adipose tissues. Nutritional approaches with dietary omega-3 fatty acids reverse the dysregulation of this system, improve insulin sensitivity and control body fat [5, 7].

End cannabinoids are lipids, derived from the omega-6 AA. Their concentrations are regulated by (1) dietary intake of omega-6 and omega-3 fatty acids; and (2) by the activity of biosynthetic and catabolic enzymes involved in the end cannabinoid pathway, which is an important parameter in regulation of appetite and metabolism. The end cannabinoid system is involved in preservation of energy balance and sustained hyperactivity of the end cannabinoid system which result obesity. Finally, omega 6 to omega 3 ratio is important factor in regulation metabolism and enzyme activities, and is important factor in control and improve of the nervous system diseases and genetics [9, 10, 13, 14].
