Effect of dietary linolenic and linoleic acids upon growth and lipid metabolism of rainbow trout (Salmo gairdneri)

Composition of uterine milk and its changes with gestational period in red stingrays (Hemitrygon akajei)

Uterine milk is secreted in the uterus for embryo nutrition in several elasmobranch species and may contribute to rapid embryonic growth, but the details of its composition and its functions are poorly understood. In this study, to explore the roles of uterine milk for embryos, its components throughout the gestational period were analysed in detail. Uterine milk was collected from pregnant red stingrays (Hemitrygon akajei) in the early, middle and late gestational periods, respectively (n= 3 for each period). The crude composition, constituent proteins and fatty acids in the milk were analysed. The uterine milk was rich in proteins throughout the gestational period, whereas lipids dramatically increased in the middle period and reduced slightly towards the late period. Some proteins potentially associated with nutrition, cartilage growth and embryonic immunity were found. Several enzymes related to central metabolism were also detected. The constituent fatty acids in the middle and late periods were similar to those in the egg yolks of elasmobranchs, except for C18:2, which was rich only in the uterine milk. The most abundant fatty acid in the milk was C16:1, which could function as a lipokine to promote lipid metabolism in the embryo. This study's data suggest that uterine milk may be secreted in addition to the egg yolk in elasmobranchs to support rapid and healthy embryonic growth.

Partial Dietary Inclusion of Hermetia illucens (Black Soldier Fly) Full-Fat Prepupae in Zebrafish Feed: Biometric, Histological, Biochemical, and Molecular Implications

Due to minimal environmental impact, compared to most conventional feed commodities, insects deserve a growing attention as candidate ingredients for aquafeeds. This study tested, for the first time during zebrafish larval rearing, the effects of an increasing replacement (0%-25%-50%) of fish meal by black soldier fly (BSF) full-fat prepupae meal. All diets were formulated to be isonitrogenous and isolipidic. A multidisciplinary approach, including biometrics, histology, gas chromatography-mass spectrometry, and molecular analyses, was applied to better understand the biological responses of larval zebrafish to the different partial inclusions of BSF in the feed. Generally, results are promising, but a 50% of BSF meal inclusion in the diet affected both lipid composition and accumulation in the larvae.

Alpha-Linolenic Acid, but Not Palmitic Acid, Negatively Impacts Survival, Asexual Reproductive Rate, and Clonal Offspring Size in Hydra oligactis

Hydra, as sit-and-wait predators with limited food selectivity, could serve as model organisms for the analysis of the effect of a particular dietary component on growth and reproduction. We investigated the effect of food quality and of diets enriched with palmitic (PAM) or α-linolenic acid (ALA) on the life history traits of two hydra species: Hydra oligactis and Hydra vulgaris. We tested the hypothesis that a diet enriched with polyunsaturated fatty acids (PUFA) can stimulate growth and reproduction in simple metazoans with a sit-and-wait type of predatory strategy. Our results revealed that a diet based on Artemia nauplii, which are not a natural food for freshwater hydra, stimulated growth, asexual reproduction, and survival in hydra. Artemia nauplii were characterized by the highest lipid content of all used food sources. The analysis of the fatty acid content of hydra indicated the domination the n-6 fatty acids over n-3 (eicosapentaenoic acid [EPA], docosahexaenoic acid [DHA], and ALA). Arachidonic acid appeared to be the dominant PUFA in Hydra, irrespective of diet supplementation with palmitic acid or ALA. The dietary supplementation of ALA negatively affected the survival, asexual reproductive rate, and size of clonal offspring of H. oligactis and had no effect on the life history traits of H. vulgaris. Our results also suggest that the hydras are not able to efficiently convert ALA into other essential fatty acids, such as EPA and DHA. To our knowledge, this is the first report about the adverse effects of n-3 fatty acid supplementation in primitive metazoans such as hydra.

Lipid metabolism and FA composition in tissues of Eurasian perch Perca fluviatilis as influenced by dietary fats

Eurasian perch, Perca fluviatilis, were fed a semipurified fat-free diet for 4 wk, followed by a 16% feeding supplementation of either olive oil (OO), safflower oil (SO), linseed oil (LO), or cod liver oil (CLO) as the only lipid source in each diet for 10 wk. Significant reductions in total lipid of tissues were observed (31.4% in viscera, 66.7% in muscle, and 74.1% in liver) after feeding the fat-free diet. The SO-, LO-, and CLO-fed fish significantly increased lipid deposition in liver and viscera compared to fish fed the OO diet; however, muscle lipid levels were not significantly affected. Large amounts of dietary 18:1 n-9 were incorporated directly into tissue lipids when fish were fed the OO diet. The LO diet significantly elevated 18:4n-3, 20:5n-3, 22:5n-3, and 22:6n-3 in the liver compared to fish fed OO or SO diets, and the n-3/n-6 ratio was 16 times that of the SO group, with significantly high desaturation and elongation products of 18:3n-3. These results suggest that delta6 and delta5 desaturases are highly active in Eurasian perch, and that the enzymes at this dietary n-3/n-6 ratio favor 18:3n-3 over 18:2n-6 as substrate. The SO diet significantly increased 18:3n-6, 20:3n-6, and 22:5n-6 in the liver and significantly decreased EPA and DHA. This indicates that desaturation enzymes were not specifically favoring n-3 over n-6 acids in perch lipid metabolism, and that these elongation and desaturation enzymes were influenced by n-3 and n-6 FA content in the diet. The present study indicates that high tissue content of DHA in the muscle of Eurasian perch was attributable to the greater ability for n-3 acid bioconversion.

Metabolic utilization of linoleate and alpha-linolenate in cultured Sertoli cells

1. The capacity of cultured Sertoli cells to synthesize long-chain polyunsatured fatty acids (PUFA) from the essential fatty acid (EFA) precursors 18:2 n-6 and 18:3 n-3 was tested, and the concentrations of each EFA required to obtain maximal incorporation into membrane lipids were determined. 2. The two EFA were added to the culture medium as free fatty acids complexed to albumin in a molar ratio of 12:1. 3. When the substrates were added individually, the maximal levels of biosynthesis were obtained with 0.7 micrograms/ml of 18:2 n-6 and 2 micrograms/ml of 18:3 n-3. 4. When the two EFA were added together, clear alterations in the behavior of the desaturases with regard to the n-6 and n-3 fatty acids were observed. 5. It was found that a concentration of 0.35 micrograms/ml of each EFA represented the "ideal" required level in order to ensure optimal incorporation of 22-carbon PUFA into the membrane lipids. 6. These results provide the first data on the definition of EFA requirements for Sertoli cells in culture.

n-3 fatty acids as precursors for active metabolic substances: dissonance between expected and observed events

It may be hypothesized that many diseases are associated with an overproduction of eicosanoids from the n-6 acid, arachidonic acid (20:4n-6), and the formation and function of these n-6 eicosanoids can be antagonized by dietary n-3 fats. This hypothesis provides a basis for evaluating the benefits and risks of including various amounts of n-3 and n-6 fats in the diet. Understanding the impact of dietary polyunsaturated fats leads inevitably to a reappraisal of what is 'normal' in terms of what is typical and what is desirable for the fatty acid composition of tissue lipids, the magnitude of eicosanoid-mediated responses, and the frequency and severity of certain diseases.

Na+ transport in perfused intestine and in isolated enterocytes of freshwater trout deprived of essential fatty acid

1. Unidirectional Na+ fluxes obtained in perfused preparation of intestine and Na+ effluxes from enterocytes isolated by a specific method have been determined in the middle intestine of freshwater rainbow trout. 2. Fish were fed semi-purified diets containing 8% by wt of either cod liver oil as reference, grape seed oil or hydrogenated coconut oil which are both deficient in fatty acids (FA) of the (n-3) series essential for the trout. 3. Important modifications in the Na+ intestinal absorption were induced by these deficient diets when measured in perfused intestine. 4. Conversely, no changes were seen in the Na+ active or passive effluxed when measured in enterocytes isolated from trout fed the same diets. 5. Na+,K+-ATPase activities were also unmodified by any diet. 6. It is concluded that deprivation of essential fatty acids reduces Na+ absorption capabilities of trout intestine, an effect which is mainly located at the apical membrane of enterocytes. 7. These results strongly demonstrate that apical entry and active serosal transport are separately modified in trout intestine by EFA deficient diet. 8. Furthermore the FA of the (n-3) series are essential for the retention of functional properties of membranes and ionic permeabilities in particular.

[Use of solid fat in dry mixed feed for rainbow trout (Salmo gairdneri). 2. Fatty acid composition of feed and tissue lipids]

The effect of supplemental dietary fat on the fatty acid composition of some tissue lipids of rainbow trout fingerlings was studied. Data showed that dietary fatty acids were deposited nearly unchanged in the adipose tissue. The level of eicosapentaenoic acid, however, dropped significantly. Muscle showed remarkable capacity for deposition of dietary fat, while only minor changes were observed in the fatty acid composition of liver lipids. Levels of some polyenoic acid (e.g. 18: 2 omega 6, 20:4 omega 6, 20:5 omega 3, 22:6 omega 3) showed, that the fish converted lower unsaturated fatty acids to highly unsaturated fatty acids. It was observed that dietary acids had little effect on the fatty acid composition of tissue phospholipids. This result shows, that 17% fat in the diet are tolerated by trout, without alterations in the fat composition of the liver tissue. Probably the low rearing temperature (11 degrees C) had a more pronounced effect on the fatty acid composition of phospholipids than the diet.

Ovarian and plasma PGE and PGF levels in naturally ovulating brook trout (Salvelinus fontinalis) and the effects of indomethacin on prostaglandin levels

Plasma and ovarian levels of PGE and PGF were measured by radioimmunoassay in naturally ovulating brook trout (Salvelinus fontinalis). At 12 hours post-ovulation, PGF levels in plasma and ovarian tissue were significantly elevated over levels in gravid controls. Plasma PGF levels were still elevated 5-7 days post-ovulation. Indomethacin treatment (10 micrograms/gm body weight) of ovulatory brook trout significantly decreased plasma and ovarian PGF levels by 12 hours post-ovulation. No significant differences were observed in plasma PGE levels, though gravid controls contained significantly elevated ovarian PGE levels as compared to ovulated fish.

Incorporation and turnover of essential fatty acids in phospholipids and neutral lipids of rainbow trout

1. The turnover of rainbow trout (Salmo gairdneri) lipid was monitored in fish receiving essential fatty acids (EFA) replete and EFA deficient diets using [1-14C]-linolenic acid (C18:3 omega 3). 2. Forty percent of administered radioactivity was recovered in total lipid after 7 days. 3. Eighty-five percent of incorporated label was recovered in C18:3 omega 3 derivatives, primarily docosa-hexaenoic acid (22:6 omega 3). 4. Over 10 weeks, 14C activity in neutral lipid (NL) remained constant whereas that in phospholipid (PL) declined due to loss of label from shorter chain omega 3 fatty acids. The mass and specific activity of longer chain omega 3 fatty acids remained constant. 5. There was an accumulation of 14C activity and C22:6 omega 3 in PE at the expense of PC. 6. The pattern of incorporation of 32P inorganic phosphate into molecular classes of phosphatidylcholine (PC) of EFA deficient fish indicated that the rate of turnover of docosahexaenoyl PC was not diminished by EFA deficiency. 7. It is hypothesized that retention of C22:6 omega 3 in EFA deficiency is due to the presence of an efficient recycling system during membrane turnover.

Accumulation of N-3 polyunsaturated fatty acids cultured human Y79 retinoblastoma cells

The metabolism of the n-3 class of polyunsaturated fatty acids, which occur in relatively high quantities in neural tissues, was studied in human Y79 retinoblastoma cells. These cells contained low levels of n-3 polyunsaturates when grown in culture media supplemented with fetal bovine serum. The cells readily incorporated performed docosahexaenoic acid (22.6 n-3) into phospholipids, but human skin fibroblasts did this to a similar extent. When 10 to 30 mumol/ml linolenic acid (18:3 n-3) was added, the cell also accumulated 22:6 in phospholipids. The capacity to convert appreciable amounts of 18:3 to 22:6 appears to be a unique property of the retinoblastoma cells as compared with other continuously cultured cell lines. More 18:3 than linoleic acid (18:2 n-6) was incorporated into phospholipids by the retinoblastoma cultures, and 18:3 was channeled to a larger extent into the ethanolamine glycerophospholipid fraction. These findings indicate that retinoblastoma cells handle n-3 polyunsaturated fatty acids in a manner very similar to neural tissue in vivo. Based on the results obtained with this model system, it appears that three processes may contribute to the accumulation of 22:6 in retina and neural tissue: increased ability to incorporate 18:3, the capacity to convert 18:3 to 22:6, and channeling of 18:3 and its metabolites into ethanolamine glycerophospholipids.

Turnover of label from [1-14C]linolenic acid in phospholipids of coho salmon, Oncorhynchus kisutch

Juvenile coho salmon were injected intraperitoneally with [1-14C] linolenic acid and sampled at 24, 120, and 240 hr. Liver, heart and gill lipids were extracted analyzed, and halflives of individual liver glycerophospholipids and n-3 fatty acids determined from rates of loss of radioactivity. Incorporation of label into gill was much less than into either heart or liver. Total acyl halflife was shorter for the choline phospholipids than for the ethanolamine phospholipids, as were the halflives of all individual n-3 fatty acids. Eicosapentaenoic acid (20:5n-3) had the shortest halflife in both phospholipids (50-60 hr), while docosapentaenoic acid (22:5n-3) and docosahexaenoic acid (22:6n-3) had much longer halflives. Specific activities of the shorter chain n-3 fatty acids were much greater than the longer, more unsaturated homologs at all times, suggesting possible differences in their mechanisms of incorporation into phospholipids. Diacylglycerol analysis indicated that de novo synthesis could be responsible for the incorporation of only a small portion of the labeled long chain fatty acids found in phospholipids. The fatty acid halflives reported here for salmon are in general agreement with those found previously in mammals.

Influence of diet on the acyl composition of phospholipids in endothelial cells and mitochondria of rat brain

The effect of diet on phospholipid acyl groups of rat brain endothelial cells and mitochondria and of liver was determined. Rats were fed high-protein diets with a 4:1 linoleate/linolenate ratio but with 4.4%, 1.9%, or 0.8% of the caloric content provided by these essential fatty acids (cal % EFA) or were fed a fat-free diet. In capillary endothelial cells the greatest change occurred in the plasmalogen ethanolamine fraction, there being a significant reduction in the n-3 series of acyl groups and increase in the n-9 series as the cal % EFA was reduced. Other phospholipid fractions changed little. More pronounced changes occurred in brain mitochondria and liver phospholipids. The small changes in capillary endothelia with cal % EFA are in contrast to the great changes produced by a change in the linoleate/linolenate ratio. As the ratio is reduced, there is a progressive increase in the n-3 series in all phospholipid fractions.

The effect of essential fatty acid deprivation on the metabolic transformations of [1(-14)C]linolenate in developing rat brain

Linolenic acid undergoes rapid metabolism in the brain of 21-day-old rats. Radioactivity is rapidly transferred from linolenic acid to the C20 (n--3) fatty acids while that in docosapentaenoic acid (22 : 5 n--3) and docosahexaenoic acid (22 : 6 n--3) gradually increases. A greater proportion of the radioactivity is associated with the polyunsaturated and less with saturated and monounsaturated fatty acids in essential fatty acid-deprived rats relative to controls.

Linolenic acid deficiency

Linolenic acid deficiency has not been demonstrated clearly in warm blooded animals, yet circumstantial evidence suggests that n-3 fatty acids may have functions in these animals. The fact that several species of fish definitely require dietary n-3 fatty acids indicates that n-3 fatty acids have important and specific functions in these animals and suggests that such functions may also be present in warm blooded animals. It is also true that n-3 fatty acid distribution in tissues of birds and mammals appears to be under strict metabolic control, and that this complex metabolic control mechanism apparently has survived evolutionary pressure for a very long time. So far, attempts to produce linolenic acid deficiency in mammals have not revealed an absolute requirement for n-3 fatty acids. If functions for n-3 fatty acids do exist in warm blooded animals, it seems probable that they may be located in the cerebral cortex or in the retina, because these tissues normally contain high concentrations of n-3 fatty acids.

Effect of various triglycerides on blood and tissue cholesterol of calves

Blood and tissue cholesterol responses were measured in six groups of four calves each fed for 24 weeks reconstituted nonfat dry fat milk in which 30% of calories was derived from one of the following: soybean oil (SBO), beef tallow (T), medium-chain triglycerides (MCT), and 1:1 soybean-oil tallow (SBO/T) combination. Two groups of four calves each also were fed SBO-milk plus dry feed and T-milk plus dry feed, respectively. Blood cholesterol concentration was significantly greater in SBO-fed calves than in T-fed calves. Calves fed MCT-milk had significantly lower blood cholesterol than calves fed T- or SBO-milk. Significant differences in cholesterol concentration were noted for the liver, perianal fat, and for omental fat.

Effect of dietary lipids on fatty acid composition of body lipid in rainbow trout (Salmo gairdneri)

Three isocaloric diets were prepared. Diet 1 (Control) contained 22% herring oil. In diets 2 and 3, a third and a half of the herring oil was replaced, respectively, by an animal fat (lard) which contained a high percentage of saturated fatty acids. Each diet was fed to duplicate groups of rainbow trout for 14 wk. The results of the feeding trial indicated that the concentration of the saturated fatty acids in trout body lipid did not increase despite the high concentration of these fatty acids in Diets 2 and 3. Fish growth, feed efficiency, mortality and the level of fatty acids deposited in fish body lipid and phospholipids are discussed.