Triglyceride Uptake in Muscles in Rats

Exogenous lipid is assimilated with different priorities in adipose tissue regions and varies in the fasting and fed conditions. The quantitative role of uptake of lipid in muscle has not been evaluated. In order to examine the uptake in other than adipose tissues, U¹⁴C-oleic acid in sesame oil was administered orally to conscious rats, and lipid label measured after different times in serum, heart, liver, mesenteric, retroperitoneal, inguinal and epididymal fat pads, as well as in red and white parts of gastrocnemius, extensor digitorum longus and soleus muscles. Lipid uptake in total adipose tissue was calculated from dissected adipose tissues plus lipids extracted from the eviscerated, skinned carcass. Lipid uptake in total muscle tissue was estimated from label in dissected muscles plus that in the carcass, assuming similar intracellular lipid contents and radioactivity as that averaged from dissected muscles. Lipid uptake in the liver was calculated from directly extracted lipid. Four hours after lipid administration to fed rats lipid radioactivity in heart and serum was minimal and had essentially disappeared at 8 hours. Liver label declined rapidly from peak values at or before 4 hours. Adipose tissue radioactivity increased gradually up to 16 hours and then decreased. Label in muscles was highest at 4 hours in the red gastrocnemius, and then decreased, while the other muscles showed a constant radioactivity over the observation period (24 hours). Radioactivity expressed per unit muscle mass seemed to be proportional to the oxidative capacity of muscles. In comparisons between fed and fasted rats at 16 hours, when adipose tissue label peaked, liver, individual muscles and carcass did not show any significant differences while adipose tissue label was fivefold higher in fed than fasted rats. The distribution of total measured lipid radioactivity between total adipose tissue, total muscle tissue and liver in fed rats at this time-point was 76. 8, 14. 4 and 8. 8% respectively, and in the fasted state 26. 4, 51. 6 and 22. 0%. These estimations suggest that lipid uptake in the fed state is dominated by adipose tissue, while in the fasted state the lipid uptake is higher in muscles than adipose tissues. It was concluded that uptake of absorbed, exogenous triglyceride in muscle is of significance, particularly in the fasted state. This lipid has a half life of several days. It is suggested that this lipid is oxidized in situ, contributing with a hidden fraction to lipid energy needs, or partially transferred to adipose tissue. Lipid uptake in muscle probably constitutes a significant fraction of assimilated exogenous lipid, particularly in the fasting state.     

Production of Poly-beta-Hydroxyalkanoic Acid by Pseudomonas cepacia

The possibility of using the nutritionally versatile bacterium Pseudomonas cepacia to produce poly-beta-hydroxyalkanoic acid was evaluated. Chemostat culture showed that growth of P. cepacia became nitrogen limited when the molar carbon-to-nitrogen ratio of the medium fed into the fermentor was above 15. When grown under nitrogen limitation in batch culture with fructose as the sole source of carbon, P. cepacia accumulated poly-beta-hydroxybutyric acid (PHB) in excess of 50% of the dry weight of its biomass. In batch culture, almost no PHB was produced until the onset of nitrogen limitation. After this point, PHB was produced at a linear rate of 0.12 g liter h (from a constant value of 1.6 g of cellular protein liter). PHB produced by P. cepacia had a weight-average molecular weight of 5.37 x 10 g mol and a polydispersivity index of 3.9. Poly(beta-hydroxybutyric acid-beta-hydroxyvaleric acid) copolymer was produced with a poly-beta-hydroxybutyric acid-poly-beta-hydroxyvaleric acid ratio of up to 30% by weight when propionic acid was added to the medium.     

Dietary neutral lipid level and source in Senegalese sole (Solea senegalensis) larvae: effect on growth, lipid metabolism and digestive capacity

Contrary to larval essential fatty acid (EFA) requirements, the effect of dietary neutral lipid supply has been little investigated in marine fish larvae. The present work investigates the effect of feeding Senegalese sole larvae on Artemia enriched with higher or lower doses of lipid emulsion. Two lipid sources - soybean oil and fish oil - were compared. From 16 days after hatching (DAH) onwards, larvae were fed one of four experimental treatments: Artemia enriched on a high or low dose of soybean oil emulsion (HS and LS) or Artemia enriched on a high or low dose of fish oil emulsion (HF and LF). In terms of growth, the dietary lipid level did not have a significant effect while the soybean oil treatments induced a lower growth than the fish oil-enriched Artemia. The fatty acid (FA) composition of the larvae closely reflected the dietary quantitative and qualitative FA profile. Only slight dietary effects were noted in the activity of trypsin, lipase and alkaline phosphatase. A higher amount of lipid droplets was noticeable in the posterior intestine epithelia and in the hepatocytes of larvae fed Artemia enriched with higher lipid doses, while LS-Artemia induced the lower lipid accumulation on the basal zone of the enterocytes, in accordance with the lowest total lipid level measured in this treatment. These results suggest an important effect of dietary total lipid level on lipid accumulation in the enterocytes and on FA absorption. At 33 DAH a tube feeding trial was conducted with 14C-labelled oleic acid (OA) or triolein (TRI), showing that the lower accumulation of lipid droplets in the larvae fed LS was associated with a significantly higher absorption and retention in the gut and body tissues of the TRI label. For OA no significant differences between treatments were found. TRI label was considerably more evacuated than OA, indicating that sole larvae may have a lower capacity to incorporate a triacylglycerol, which needs to be digested. Finally, OA appears to be preferentially utilized for energy production, accumulating more in larval tissues when absorbed in higher amounts.     

PPARA/RXRA signalling regulates the fate of hepatic non-esterified fatty acids in a sheep model of maternal undernutrition

Maternal undernutrition during late gestation accelerates body fat mobilization to provide more energy for foetal growth and development, which unbalances metabolic homeostasis and results in serious lipid metabolism disorder. However, detailed regulatory mechanisms are poorly understood. Here, a sheep model was used to explore the regulatory role of PPARA/RXRA signalling in hepatic lipid metabolism in undernutrition based on RNA sequencing and cell experiments. KOG function classification showed that lipid transport and metabolism was markedly altered in an undernourished model. In detail, when compared with the controls, fatty acid transport and oxidation and triglyceride metabolism were up-regulated in an undernourished model, while fatty acid synthesis, steroid synthesis, and phospholipid metabolism were down-regulated. Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathway analysis demonstrated that PPARA/RXRA signalling pathway was altered. Moreover, PPARA signalling associated genes were positively correlated with hepatic non-esterified fatty acid (NEFA) levels, while retinol metabolism associated genes were negatively correlated with blood beta-hydroxybutyric acid (BHBA) levels. Results of primary hepatocytes showed that NEFAs could activate PPARA signalling and facilitate fatty acid oxidation (FAO) and ketogenesis, while BHBA could inhibit RXRA signalling and repress FAO and ketogenesis. Excessively accumulated NEFAs in hepatocytes promoted triglyceride synthesis. Furthermore, activation of PPARA/RXRA signalling by WY14643 and 9-cis-retinoic acid could enhance FAO and ketogenesis and reduce NEFAs accumulation and esterification. Our findings elucidate the regulatory mechanisms of NEFAs and BHBA on lipid metabolism as well as the potential role of the PPARA/RXRA signalling pathway in hepatic lipid metabolism, which may contribute to exploring new strategies to maintain lipid metabolic homeostasis in human beings.     

Digestion and absorption of a pure triacylglycerol and a free fatty acid by Clupea harengus L. larvae

The digestion, absorption and post absorptive metabolism of a radiolabelled triacylglycerol (TAG; triolein) and a free fatty acid (FFA; oleic acid), delivered by tube feeding, was studied in herring Clupea harengus larvae, using metabolic chambers and video analysis. In general, a large amount of the delivered lipid was evacuated. Most of the evacuation occurred between 2 and 6 h after tube feeding although a group of larvae responded by rapidly evacuating the lipid (>50% before 2 h). The volume of the tube‐fed lipid affected its utilization. A small volume of triolein (9·2 nl, representing c . 6% of gut filling capacity) resulted in a lower proportion of fast evacuating larvae and improved utilization (lower evacuation and higher absorption: body incorporation and catabolism) compared with 50·6 nl ( c . 17% of gut filling capacity). Increases in the volume of tube fed triolein enhanced only marginally label absorption and led to a steep rise in evacuation. At a comparable high volume (50·6 nl), oleic acid, which does not require digestion, was better absorbed and less evacuated than triolein. The video observation of the lipid digestive process revealed a considerable gut contractile activity that appeared effective in processing the tube fed lipid. Also, the gut wall seemed very sensitive to physical pressure. Signs of chemical degradation during lipid digestion were also noted. The metabolic studies, together with video image analysis, suggested that the limiting step for the utilization of high dietary lipid levels may have been the lipid absorption into the enterocytes and transport into the body, rather than lipid digestion. The results support the notion that the rate of lipid digestion and absorption in fishes is slower than that of mammals.     

Dietary triacylglycerol modulates sodium-dependent D-glucose transport, fluidity and fatty acid composition of rat small intestinal brush-border membrane

Rats were maintained on nutritionally complete diets enriched in unsaturated (menhaden fish oil) or saturated (butter fat) triacylglycerols. After 4 weeks, the animals were killed, proximal small intestinal brush-border membranes were prepared, and examined and compared with respect to their lipid composition, molecular species of phosphatidylcholine, lipid fluidity and sodium-dependent D-glucose transport. Membranes prepared from the two dietary groups were found to possess similar ratios of cholesterol/phospholipid (mol/mol), sphingomyelin/phosphatidylcholine (mol/mol), and protein/lipid (w/w). In contrast to these findings, however, striking differences were noted in the total fatty acid compositions of these membranes. Plasma membranes prepared from animals fed the fish oil diet possessed higher percentages of saturated fatty acids as well as (n - 3) unsaturated fatty acids and lower percentages of monounsaturated and (n - 6) unsaturated fatty acids than those prepared from animals fed the butter fat diet. Analysis of the molecular species of phosphatidylcholine by HPLC, moreover, revealed that membranes from rats fed fish oil had higher levels of 16:0-20:5, 16:0-22:6 and 18:0-20:5 and lower levels of 18:0-18:2 and 16:0-18:1 than their butter fat counterparts. As assessed by steady-state fluorescence polarization, differential polarized phase fluorometric and excimer/monomer fluorescence intensity techniques using various fluorophores, the lipid fluidity of membranes from rats fed fish oil was also found to be significantly lower compared to membranes from rats fed butter fat. Finally, comparison of the kinetic parameters of Na+-dependent D-glucose transport revealed that fish oil-membrane vesicles had a higher maximum velocity (Vmax) than butter fat membrane vesicles but a similar Km for glucose.     

Dietary saturated fatty acid content affects lymph lipoproteins: studies in the rat

We examined effects on intestinal absorption of cholesterol and triglycerides and intestinal lipoprotein formation by feeding rats diets in which saturated fatty acids (palmitic plus stearic) comprised 78%, 68%, 48%, or 38% of triglyceride fatty acids. Absorption into lymph of radiolabeled cholesterol was proportional to triglyceride absorption. The rates of absorption of these lipids were related inversely to the % saturated fatty acids fed. The distribution of newly absorbed cholesterol and triglyceride into intestinal lipoproteins differed. With increasing cholesterol absorption more was recovered in very low density lipoproteins in contrast to the appearance preferentially in chylomicrons of larger quantities of fatty acid. Lymph lipid content did not reflect a consistent pattern in relation to the experimental diet fed. The fatty acid composition of triglyceride-rich lymph lipoproteins resembled the diet closely. One-quarter of the intestinal lymph particles from rats fed the highly saturated diets was flattened and polygonal as judged by electron microscopy if cooled to room temperature; whereas with the same diets, particles collected and isolated at 37 degrees C were round. Proportions of A-I and C apolipoproteins in triglyceride-rich intestinal particles varied inversely; apoA-I increased as fat/cholesterol absorption was greater. Diet-induced alterations in plasma lipoproteins and increased circulating triglycerides in this study in rats were unrelated to the variations in intestinal absorption or lymph lipoprotein formation.     

Biosynthesis of triacylglycerols in the intestines of rainbow trout (Salmo gairdnerii) fed marine zooplankton rich in wax esters

Intestinal preparations from rainbow trout fed a diet rich in wax esters incorporated [1(-14)C]hexadecanoic acid and [1(-14)C]hexadecanol into triacylglycerols at the same rate. The ratio of the number of H atoms from C1 of hexadecanol to the number of molecules of hexadecanol incorporated into triacylglycerols was 1.6 : 3.0. [U-14C]Glucose was incorporated much faster into the glycerol moiety of triacylglycerols than was [U-14C]aspartic acid. We conclude that the oxidation of absorbed fatty alcohol to fatty acid and its subsequent incorporation into triacylglycerols is closely linked with the reductive formation of triacylglycerol-glycerol from glucose. The ability of trout intestines to metabolise fatty alcohol to triacylglycerols was the same in fish fed wax esters as in those fed triacylglycerols.     

Biosynthesis of Poly-beta-Hydroxyalkanoates from Pentoses by Pseudomonas pseudoflava

The potential of Pseudomonas pseudoflava to produce poly-beta-hydroxyalkanoates (PHAs) from pentoses was studied. This organism was able to use a hydrolysate from the hemicellulosic fraction of poplar wood as a carbon and energy source for its growth. However, in batch cultures, growth was inhibited completely at hydrolysate concentrations higher than 30% (vol/vol). When P. pseudoflava was grown on the major sugars present in hemicelluloses in batch cultures, poly-beta-hydroxybutyric acid (PHB) accumulated when glucose, xylose, or arabinose was the sole carbon source, with the final PHB content varying from 17% (wt/wt) of the biomass dry weight on arabinose to 22% (wt/wt) of the biomass dry weight on glucose and xylose. Specific growth rates were 0.58 h on glucose, 0.13 h on xylose, and 0.10 h on arabinose, while the specific PHB production rates based on total biomass ranged from 0.02 g g h on arabinose to 0.11 g g h on glucose. PHB weight-average molecular weights were 640,000 on arabinose and 1,100,000 on glucose and xylose. The absolute amount of PHB in the cells decreased markedly when nitrogen limitation was relaxed by feeding ammonium sulfate at the end of the PHB accumulation stage of the arabinose and xylose fermentations. Copolymers of beta-hydroxybutyric and beta-hydroxyvaleric acids were produced when propionic acid was added to shake flasks containing 10 g of glucose liter. The beta-hydroxyvaleric acid monomer content attained a maximum of 45 mol% when the initial propionic acid concentration was 2 g liter.     

Modulation of antioxidant enzyme activities, platelet aggregation and serum prostaglandins in rats fed spray-dried milk containing n-3 fatty acid

Spray-dried milk enriched with n-3 fatty acids from linseed oil (LSO) or fish oil (FO) were fed to rats to study its influence on liver lipid peroxides, hepatic antioxidant enzyme activities, serum prostaglandins and platelet aggregation. Significant level of α linolenic acid, eicosapentaenoic acid and docosahexaenoic acid were accumulated at the expense of arachidonic acid in the liver of rats fed n-3 fatty acid enriched formulation. The linseed oil and fish oil enriched formulation fed group had 44 and 112% higher level of lipid peroxides in liver homogenate compared to control rats fed groundnut oil enriched formulation. Catalase activity in liver homogenate was increased by 37 and 183% respectively in linseed oil and fish oil formulation fed rats. The glutathione peroxidase activity decreased to an extent of 25–36% and glutathione transferase activity increased to an extent of 34–39% in rats fed n-3 fatty acids enriched formulation. Feeding n-3 fatty acid enriched formulation significantly elevated the n-3 fatty acids in platelets and increased the lipid peroxide level to an extent of 4.2 to 4.5-fold compared to control. The serum thromboxane B₂ level was decreased by 35 and 42% respectively in linseed oil and fish oil enriched formulation fed rats, whereas 6-keto-prostaglandin F1α level was decreased by 17 and 23% respectively in linseed oil and fish oil enriched formulation fed rats. The extent and rate of platelet aggregation was decreased significantly in n-3 fatty acids enriched formulation fed rats. This indicated that n-3 fatty acids enriched formulation beneficially reduces platelet aggregation and also enhances the activities of hepatic antioxidant enzymes such as catalase and glutathione transferase.     

Effects of an organosilicon compound on the tubular apparatus of rat kidney. A histological and enzyme histochemical report

Male adult Wistar rats were treated for 8 weeks with an organosilicone [2,2-dimethyl-4-(chloromethyl)-1,3-dioxa-2-silacyclopentane] employing two different dosages (25 and 50 mg/kg body weight i.p. daily) and the changes in the tubular apparatus of the kidney were investigated employing histological and enzyme-histochemical methods. The effects, more pronounced at the higher dosage, were the following: The brush borders of the proximal tubules were stuck together and disintegrated; only few epithelial cells remained intact showing a decreased activity of nonspecific esterases and the increase of beta-hydroxybutyric acid dehydrogenase. The nuclei of most of the epithelial cells in the distal tubules were dislocated towards the enlarged lumen and the cytoplasma showed a decrease of nonspecific esterases and an increase of beta-hydroxybutyric acid dehydrogenase. The collagen fibers in the walls of the collecting tubules were dislocated and disintegrated with a discontinuous border of Mg2+-ATPase; the nuclei of the epithelial cells were pyknotic, the cytoplasma showed an increase of beta-hydroxybutyric acid dehydrogenase. The induced changes were partially reversible after a recovery period of 8 weeks.     

Supplementation of orotic acid to the casein, but not to egg protein, soy protein, or wheat gluten diets, increases serum ornithine carbamoyltransferase activity

Effects of dietary supplementation of orotic acid to a diet containing the casein protein were compared with diets containing egg protein, soy protein, or wheat gluten on lipid levels in the liver and serum and activities of ornithine carbamoyltransferase (OCT) and alanine aminotransferase in the serum of rats. We found that supplementation of orotic acid to each diet increased the contents of the liver total lipids, triacylglycerol, and phospholipids compared with those not supplemented. The contents of liver total lipids, triacylglycerol, cholesterol, and phospholipids in rats fed the casein diet were significantly higher than those of rats fed the other three diets when orotic acid was supplemented. The levels of triacylglycerol, cholesterol, and phospholipids in the serum of rats fed the casein diet were markedly decreased by addition of orotic acid. The supplementation of orotic acid significantly increased the activities of both serum OCT and alanine aminotransferase in rats fed the casein diet, but not in rats fed the other diets. In conclusion, liver lipid accumulation induced by dietary orotic acid depends on the type of dietary protein. The enhancement of serum OCT activity may result from liver lipid accumulation in rats fed the casein diet supplemented with orotic acid, demonstrating hepatic damage.     

The effects of dietary (n-3) fatty acid supplementation on lipid dynamics and composition in rat lymphocytes and liver microsomes

Rats were fed diets devoid of (n-3) fatty acids (olive oil supplementation) or high in (n-3) fatty acids (fish oil supplementation) for a period of 10 days. In spleen lymphocytes and liver microsomes derived from animals fed fish oil diets, relatively high levels of (n-3) eicosapentaenoic (20:5), docosapentaenoic (22:5) and docosahexaenoic acids (22:6) were obtained compared to minimal levels when fed the olive oil diet. When the average lipid motional properties were examined by measuring the fluorescence anisotropy of diphenylhexatriene, no significant different was found between intact liver microsomes from animals fed the two diets. However, when lipid motion was examined in vesicles of phosphatidylcholine, isolated from the microsomes from fish oil fed animals (21.4% (n-3) fatty acids), the fluorescence anisotropy was significantly less than the corresponding phosphatidylcholine from olive oil fed animals (5.6% (n-3) fatty acids), indicating a more disordered or fluid bilayer in the presence of higher levels of (n-3) fatty acids. Phosphatidylethanolamine (n-3) fatty acids were also elevated after fish oil supplementation (41.3% of total fatty acids), compared to the level after olive oil supplementation (21.4%). The major effect of the fish oil supplementation was a replacement of (n-6) arachidonic acid by the (n-3) fatty acids and when this was 'modeled', using liposomes of synthetic lipids, 1-palmitoyl-2-arachidonyl(n-6) or docosahexaenoyl(n-3)-phosphatidylcholine, significant differences in lipid motional properties were found, with the docosahexaenoate conferring a more disordered or fluid lipid environment. Thus it appears that although lipid order/fluidity can be significantly decreased by increases in the highly unsaturated (n-3) fatty acid levels, alterations in membrane domain organization and/or phospholipid molecular species composition effectively compensated for the changes, at least as far as average lipid motional properties in the intact membranes was concerned.     

Dietary Lipid Levels Influence Lipid Deposition in the Liver of Large Yellow Croaker (Larimichthys crocea) by Regulating Lipoprotein Receptors,Fatty Acid Uptake and Triacylglycerol Synthesis and Catabolism at the Transcriptional Level

Ectopic lipid accumulation has been observed in fish fed a high-lipid diet. However, no information is available on the mechanism by which dietary lipid levels comprehensively regulate lipid transport, uptake, synthesis and catabolism in fish. Therefore, the present study aimed to gain further insight into how dietary lipids affect lipid deposition in the liver of large yellow croaker(Larimichthys crocea). Fish (150.00±4.95 g) were fed a diet with a low (6%), moderate (12%, the control diet) or high (18%) crude lipid content for 10 weeks. Growth performance, plasma biochemical indexes, lipid contents and gene expression related to lipid deposition, including lipoprotein assembly and clearance, fatty acid uptake and triacylglycerol synthesis and catabolism, were assessed. Growth performance was not significantly affected. However, the hepato-somatic and viscera-somatic indexes as well as plasma triacylglycerol, non-esterified fatty acids and LDL-cholesterol levels were significantly increased in fish fed the high-lipid diet. In the livers of fish fed the high-lipid diet, the expression of genes related to lipoprotein clearance (LDLR) and fatty acid uptake (FABP11) was significantly up-regulated, whereas the expression of genes involved in lipoprotein assembly (apoB100), triacylglycerol synthesis and catabolism (DGAT2, CPT I) was significantly down-regulated compared with fish fed the control diet, and hepatic lipid deposition increased. In fish fed the low-lipid diet, the expression of genes associated with lipoprotein assembly and clearance (apoB100, LDLR, LRP-1), fatty acid uptake (CD36, FATP1, FABP3) and triacylglycerol synthesis (FAS) was significantly increased, whereas the expression of triacylglycerol catabolism related genes (ATGL, CPT I) was reduced compared with fish fed the control diet. However, hepatic lipid content in fish fed the low-lipid diet decreased mainly due to low dietary lipid intake. In summary, findings of this study provide molecular insight into the role of lipid deposition in the liver in response to different dietary lipid contents.     

Amino acid transport in the intestine of the caiman

Seventeen amino acids were fed singly to small caimans and the rates of their disappearance from the gut lumen, and of their appearance in intestinal mucosa, whole intestine, whole stomach, and plasma were determined. The results were compared with those in which massive amounts of protein were fed. When single amino acids were fed, only traces of arginine, ornithine, lysine, aspartate and asparagine were absorbed intact. Glycine, alanine and serine were absorbed rapidly reaching mucosal concentrations as high as 40 mM. The others were not concentrated as highly and most were absorbed by the mucosa more slowly than the glycine group. Protein feeding did not result in high amino acid concentrations in the mucosa. Whether amino acids were ingested as protein or in the free state, glycine, alanine and glutamine increased in the mucosa, suggesting these three incorporate nitrogen released from the others. It appeared that several transport systems operate if amino acids are given singly, and that a different more efficient transport system operates during protein digestion.     

Physical training reverses the increased activity of the hepatic ketone body synthesis pathway in chronically diabetic rats

This study was designed to examine whether the training-induced improvement in the plasma concentration of ketone bodies in experimental diabetes mellitus could be explained by changes in the activity of the hepatic ketone body synthesis pathway and/or the plasma free fatty acid levels. Diabetes mellitus was induced by an intravenous injection of streptozotocin (50 mg/kg), and training was carried out on a treadmill. The plasma concentration of beta-hydroxybutyric acid was increased (P < 0.001) in sedentary diabetic rats, and this was partly reversed by training (P < 0.001). The plasma concentration of free fatty acids was increased (P < 0.001) in sedentary diabetic rats, and this was reversed to normal by training (P < 0.001). Diabetes was also associated with an increased activity of the hepatic ketone body synthesis pathway. When the data are expressed as per total liver, physical training decreased the activity of the hepatic ketone body synthesis pathway by 18% in nondiabetic rats (P < 0.05) and by 22% in diabetic rats (P < 0.01), the activity present in trained diabetic rats being not statistically different from that of sedentary control rats. These data suggest that the beneficial effects of physical training on the plasma beta-hydroxybutyric acid levels in the diabetic state are probably explained in part by a decrease in the activity of the hepatic ketone body synthesis pathway and in part by a decrease in plasma free fatty acid levels.     

Changes in biochemical and hemocyte parameters of the Pacific oysters Crassostrea gigas fed T-Iso supplemented with lipid emulsions rich in eicosapentaenoic acid

The aim of this study was to assess the effect of dietary eicosapentaenoic acid (20:5n-3) on hemocyte parameters such as hemocyte concentration, phagocytosis, and non-stimulated reactive oxygen species (ROS) production in Pacific oysters Crassostrea gigas, as well on proximate biochemical and fatty acid compositions. One-year-old oysters (C. gigas) were fed T-Isochrysis aff. galbana (T-Iso), which is low in 20:5n-3, either alone or with supplements of a lipid emulsion rich in 20:5n-3 at 1%, 10% or 50% (dry weight of the algal ration) for up to 7 weeks. Changes in gill fatty acid composition demonstrated that the lipid emulsion was well ingested by oysters during the dietary conditioning. Biochemical analysis indicated that oysters fed supplements of 50% and, to a lesser extent, 10% lipid emulsions had a higher total lipid content compared with oysters fed other diets, suggesting a more advanced reproductive status for the oysters fed high doses of lipid emulsion. Moreover, some oysters in these two treatment groups spawned during the last three weeks of the seven-week feeding experiment. Lipid supplements had a significant influence on hemocyte concentration, phagocytic index and non-stimulated hemocyte ROS production. After 4 weeks, highest hemocyte concentrations were found in oysters fed on a supplement of 50% lipid emulsion compared with those fed on other diets but the hemocytes derived from these oysters had the lowest short-term phagocytic index. After 7 weeks of dietary conditioning, the ROS production in non-stimulated hemocytes of oysters fed 10% and 50% lipid emulsion declined. These results suggested that 20:5n-3, and perhaps its eicosanoid metabolites, affected oyster hemocyte functions; however, the reproductive status of oysters may also have interfered with the 20:5n-3 dietary effect.     

克山病病区粮喂养大鼠红细胞膜脂流动性的变化

本文观察了低硒的克山病病区粮和克山病病区粮补硒后喂养大鼠对其红细胞膜脂流动性的影响。实验结果表明克山病病区粮喂养的大鼠红细胞膜脂流动性较正常对照降低,其原因可能与机体处于低硒状态下红细胞膜结合硒含量降低、红细胞膜胆固醇含量及脂质过氧化产物升高有关,克山病病区粮补硒后喂养大鼠,其红细胞膜脂流动性恢复至正常对照。     

Dietary lipid level influences fatty acid profiles, tissue composition, and lipid peroxidation of soft-shelled turtle, Pelodiscus sinensis

Dietary lipids containing equal portions of soybean oil and fish oil were fed to juvenile Chinese soft-shelled turtle, Pelodiscus sinensis, at supplementation level of 0 to 15% for 8 weeks. Tissue fat contents of turtles increased when dietary lipid concentration increased. Fatty acid profiles for turtles fed diets supplemented with 6% or higher levels of lipids were similar to those in dietary lipids. On absolute value basis, fatty acids of 14-, 16-, and 18-carbons in muscle of turtles fed diet without lipid supplementation were higher than those in the initial turtle muscle. Among them, C16:1 and C18:1 was approximately 4 and 2 fold higher, respectively, than that of the initial turtles. By contrast, absolute amounts of C20:5 and C22:6 in muscle of turtles fed diet without lipid supplementation were slightly less than those in the initial turtles. For turtles fed lipid supplemented diets, tissue C20:5 and C22:6, however, increased when dietary lipid level increased. These results suggest that soft-shelled turtles are capable of synthesizing fatty acids up to 18 carbons from other nutrients and that they may have limited or no ability to synthesize highly unsaturated fatty acids. Lipid peroxidation measured by thiobarbituric acid-reactive substances in tissues of turtles fed 12% and 15% lipids was greater (p<0.05) than that in turtles fed 3% to 9% lipids. This could be due to high lipid and unsaturated fatty acid content in these tissues. On lipid basis, lipid peroxidation in turtles fed diet without lipid supplementation was the highest among all groups suggesting the existence of antioxidant factors in the dietary lipids.     

Dependence of boundary lipid on fatty acid chain length in phosphatidylcholine vesicles containing a hydrophobic protein from myelin proteolipid.

Lipophilin, a hydrophobic protein fraction, purified and delipidated from the proteolipid of human myelin, possesses a layer of boundary lipid surrounding it when incorporated into lipid vesicles. The protein reduces the energy absorbed during the lipid phase transition, indicating that the boundary lipid does not go through the phase transition. The amount of boundary lipid was estimated by plotting the enthalpy of the transition against the protein to lipid mole ratio and extrapolating to deltaH = 0 for a number of synthetic phosphatidylcholines, to determine the ability of fatty acid chains of varying length to interact with the protein. The amount of boundary lipid was found to be similar, 21-25 molecules per molecule of lipophilin, for fatty acid chains of length 14-18 carbons but somewhat less, 16 molecules of lipid per molecule of protein, for a fatty acid chain length of 12 or for one with a trans double bond (18:1tr). No preferential interaction was observed with a lipid containing a particular fatty acid chain length when the protein was incorporated into a mixture of these lipids. These results suggest that the binding of lipids to the boundary layer of other membrane proteins and enzymes may not depend significantly on lipid fatty acid chain length.