Some aspects of lipid metabolism in the liver of Wistar rats with fat diet-induced obesity

Diet-induced obesity in rats can be produced by high-fat feeding. Comparing high-fat with low-fat feeding, the present study was designed to characterize the phases of development of obesity. In the dynamic phase, male rats were investigated at the age of 9-10 weeks after feeding the diets for 4-5 weeks. In the static phase, the animals at the age of 24-26 weeks were tested after 20-22 weeks of the nutritional regime. In this phase, the effects of switching high-fat to low-fat diet for 4 weeks were also examined. Fractionating lipid extracts by thin layer chromatography the concentrations of several lipids in epididymal adipose tissue, in serum, and in liver were determined. In liver, the enhancement of cholesteryl-ester (CE) concentration after high-fat feeding besides the accumulation of triglycerides (TG) is remarkable. Cell fractionation studies of the livers by differential ultracentrifugation showed the major part of the accumulated CE in the supernatant. In vitro incorporation of (1-14C)acetate and (2-14C)mevalonate into liver slices indicated that cholesterol synthesis in the liver of the obese rats was not increased. Although the offered fat diet with 0.1% of cholesterol can not be considered as high in cholesterol, the 2.5-fold higher amount of the high-fat diet in comparison with the low-fat diet (0.04% cholesterol) could be responsible for the enlargement of CE in the liver of the fat fed rats. This possibility was proved by measurement of the cholesterol absorption and transport to the liver after oral administration of (4-14C)cholesterol. Estimation of TG secretion rates of the liver using Triton WR 1339 pointed out higher rates in the obese rats in the dynamic phase. In the static phase, the rates were not different between both feeding groups, while fat restriction in the food produced a striking increase of TG secretion. It is assumed that only in the dynamic phase metabolism is able to compensate the liver TG accumulation by an enhanced transport to the adipose tissue. In the static phase this ability is diminished but not lost.     

Prepartum nutrition alters fatty acid composition in plasma, adipose tissue, and liver lipids of periparturient dairy cows

The fatty acyl profile of phospholipids (PL) determines the fluidity of cell membranes and affects cell function. The degree to which long-chain fatty acid (LCFA) composition of PL and triacylglycerols (TG) in liver and total lipids in adipose tissue can be altered by prepartum nutrition in peripartal dairy cows is unclear. Multiparous Holsteins (n = 25) were assigned to 1 of 4 prepartal diets: 1) CA, the control diet fed to meet 120% of energy requirements; 2) CR, a control diet fed to meet 80% of requirements; 3) S, a diet supplemented with mostly saturated free fatty acids (47% 16:0, 36% 18:0, 14% cis-18:1) and fed to meet 120% of requirements; or 4) U, a diet similar to S except that cows were abomasally infused with soybean oil so that the diet plus infused fat would meet 120% of requirements. Diets were fed for 40 d prepartum; all cows received a lactation diet postpartum. Groups CR and U had lower prepartum intakes of dry matter and net energy, but glucose concentrations in plasma were similar among treatments. Cows fed S, U, or CR had greater nonesterified fatty acids in plasma prepartum, but cows fed U had decreased β-hydroxybutyrate postpartum. Postpartal concentrations of total lipids and glycogen in liver tissue were similar among treatments. Cows in group U had a greater percentage of 18:2 but less 16:0, 18:0, and 20:4 in plasma total lipids than cows fed S. Treatment U increased 18:2 and 18:3 and decreased 18:1 in subcutaneous adipose tissue at 1 d postpartum. Across diets, percentages of 16:0 and trans-18:1 were increased, and 18:0, 20:3, and 20:5 were decreased, in hepatic PL at d 1 postpartum. Significant treatment × time interactions indicated that treatment U increased 18:2 in hepatic PL at the expense of 18:1, 20:3, 20:4, 22:6, and 24:0 on d 1 postpartum, but changes were normalized by d 65 postpartum. The unsaturation index of hepatic PL was lower at d 1 than at d −45 or 65, which implies that hepatic membrane fluidity decreased around parturition. The unsaturation index at d 1 was greater for cows fed S than those fed CA or U. Percentages of 16:0, 18:1, and 22:0 were increased, and 18:0, 20:3, 20:4, 20:5, 24:0, and 26:0 were decreased, in hepatic TG at d 1. Prepartal feed restriction modestly affected tissue LCFA profiles. The LCFA profile of adipose tissue, liver PL, and liver TG can be altered by dietary LCFA supply prepartum; changes in liver are normalized by 65 d postpartum.     

Fatty acid composition of the lipids of the mantle and liver of cephalopod mollusks

The authors studied tissue lipids of flesh and liver of squids, the most important industrial objects in the Far East basin. Among them there were Todarodes pacificus, Ommastrephes bartrami, Berrytenthis magester, Sepia officinalis. Total lipids in flesh fluctuated from 0.50 to 2.61%. The liver of all squid species contains from 15.00 to 54.6% of lipids. The sum of lipids in the cuttlefish liver is from 5.43 to 12.30%. Lipids in edible tissues contain high amounts (50-55%) of phospholipids and monoglycerides. The following saturated fatty acids (SFA) prevail: C16:0 (from 14.68 to 28.64%). C14:0 (from 0.24 to 2.23%), C12:0 (from 0.25 to 2.82%). The cuttlefish lipids are characterized by the highest level of monounsaturated fatty acids: C16:1 (10.51%). C22:1 (13.59%). The content of polyunsaturated fatty acids in lipids of Bartram and Comandor squids and cuttlefish comprises 47.59-49.84%. C20:5 (5.40-20.20%) promotes a normal functioning of the cardiovascular system. The level of SFA in the Bartram squid liver lipids is more than 2 times lower (33.28/14.17) than in the tissue lipids, while in the Pacific Ocean (17.59/13.23), Comandor (39.20/30.71) squids and cuttlefish (20.39/17.82) they are at about the same level. The lipids of Comandor squid liver contain 22.98% of C16:0. The levels of the following acids are especially high: C18:1 (5.66-25.18%), C16:1 (1.49-20.32%), C22:1 (2.49-8.69%), C22:5 (4.13-6.83%), C20:5 (6.16-10.68%), C22:6 (3.10-10.18%), C20:4 (2.4-22.06%).     

Fatty acid composition of the lipids of whitefish

The fatty-acid composition of lipids was studied in the muscular tissue and internal organs of whitefish living in Siberian rivers, that had been moved to lakes where it had not lived before. Changes in the lipid composition were recorded in mature fish moved into the lakes and in this year's brood. It was found that lipids of mature fish were resistant to oxidizing damage.     

Fatty acid composition of adipose tissue and muscle from Jersey steers was affected by finishing diet and tissue location

To determine the impacts of finishing diet and tissue type and location on fatty acid composition and palatability of Jersey beef, twenty steers were assigned to a factorial treatment design with initial weight (Light vs. Heavy) and finishing diet (70 vs. 85% concentrate) as treatments. Ribeye steaks were collected for sensory evaluation. Muscle, seam and subcutaneous (s.c.) fat from steaks, kidney fat (KF) and omental fat (OMF) were collected for fatty acid analysis. Initial weight and finishing diet had little impact on beef palatability. The 85% concentrate decreased polyunsaturated fatty acids (PUFA) in muscle and increased trans fatty acids in all tissues (P < 0.05). The monounsaturated:saturated fatty acid ratio (MUFA:SFA) was highest in s.c. fat, intermediate in muscle and seam fat, and lowest in KF and OMF. The PUFA:SFA was highest in muscle, intermediate in s.c. and seam fat, and lowest in KF and OMF. Fatty acid composition differed greatly among tissues and the lower concentrate diet increased omega-3 and PUFA percentages in muscle.     

Fatty acid composition of goat diets vs intramuscular fat

Twenty Boer x Spanish goats, at the age range of 90–118 days, were assigned to two dietary treatments, with 10 animals fed a grain ration (G) and the other 10 grazed in rangeland. The grain ration contained sorghum grain (67.5%), cottonseed hulls, dehydrated alfalfa meal, cottonseed meal, soybean meal, molasses, and mineral and vitamin supplements. Animals were slaughtered at the age range of 206–234 days. Intramuscular fat (IF) and the diet specimens — representative samples of G and the parts of range plants (RPs) that goats were expected to have consumed — were analyzed for fatty acid composition. The percentage of 16:0 was higher in RPs than in G, but not different between IF from range goats and that from grain-fed goats. Total unsaturated fatty acid (UFA) percentage was higher in G than in RPs. The major UFAs were 18:2 and 18:3 in RPs, and 18:1 and 18:2 in G. In IF, 18:1 constituted more than two-thirds of UFAs, regardless of diet type.     

Fatty acid and glyceride composition of Astrocaryum vulgare kernel fat

The kernel composition, lipid classes, fatty acid composition, fatty acid distribution on triglycerides and triglyceride composition of kernel fat from Astrocaryum vulgare Mart palms grown in Nigeria have been studied. Kernels had a high fat content. Lauric acid was the predominant fatty acid in the whole fat and was also the major fatty acid in the triglycerides and in the 2-monoglycerides derived from them by pancreatic lipase hydrolysis. All the fatty acids exhibited a preference for the 1-and-3, positions of triglycerides, except for lauric which showed a preference for the 2-position and oleic which exhibited a random distribution. The trisaturated triglycerides were the predominant triglyceride type and the fatty acid composition of the various triglycerides suggested an absence of completely unsaturated triglycerides.     

Dietary CLA alters intramuscular fat and fatty acid composition of pig skeletal muscle and subcutaneous adipose tissue

The present study was conducted to determinate the responsiveness of different levels of dietary conjugated linoleic acid (CLA) on intramuscular fat (IMF) and fatty acid composition of skeletal muscle and fat in pigs fed from 59.5 to 133.5 kg. Forty female Large White × (Large White × Landrace) pigs were used. Four levels (0%, 0.5%, 1% and 2%) of a commercial enriched CLA oil supplementation (60% of CLA isomers, 30% cis-9, trans-11 and 30% trans-10, cis-12) were fed to pigs. Carcass, ham, foreleg and loin weights were recorded. Dietary CLA enrichment increased the loin weight (P < 0.01) and the combined weights of hams + forelegs + loins (P < 0.02). IMF content in Longissimus dorsi was also increased by dietary CLA treatment (P < 0.001) and a linear response was observed. Dietary CLA increased saturated fatty acids (SFA) and decreased monounsaturated fatty acids (MUFA) in muscle and adipose tissue (P < 0.001). Feeding 1% CLA to finishing swine increases IMF in heavy pigs slaughtered at an average weight of 133.5 kg.     

Fatty acid composition and intramolecular structure of triglycerides from adipose tissue of the red deer and the reindeer

Rowett Research Institute, Bucksburn, Aberdeen, AB2 9SB Triglycerides extracted from perinephric, omental and subcutaneous adipose tissue of six female red deer and of two male and one female reindeer were analysed for the composition and intramolecular disposition of their component fatty acids. In their overall fatty acid composition, the triglycerides of normal and pregnant red deer were similar and resembled those of domesticated ruminants; trans-unsaturated acids were present and the perinephric triglycerides contained a relatively high proportion of stearic acid compared with triglycerides from other bodily sites. The triglycerides from corresponding adipose tissue of lactating hinds contained much less stearic acid and relatively more myristic, palmitic and palmitoleic acids, suggesting that fatty acids of exogenous origin were not being deposited because they were in demand for milk fat synthesis. The adipose tissue triglycerides of the reindeer were unusual in that they were, apparently, mainly of endogenous origin and showed a notable resemblance to the triglycerides of lambs reared on a virtually lipid-free diet. This was reflected in a comparatively low content of stearic acid in the perinephric triglycerides, and the absence of trans-unsaturated acids from all the triglycerides. Analysis of the principal feed (‘reindeer moss’, Cladonia) showed that, compared with normal herbage, it is a very poor source of exogenous fatty acids. Regardless of their fatty acid composition, the intramolecular structure of the triglycerides of the red deer and the reindeer conformed to the general distribution pattern common to most animals. Stearic acid was, for the most part, esterified to the primary alcoholic groups of the glycerol moiety (positions 1 and 3), as was palmitic acid, except when it was present in lower overall proportion than stearic acid. Unsaturated acids and the medium-chain acid, myristic acid, were mainly esterified to the secondary alcohol group (position 2).     

Fatty acid composition of total lipids from some tropical storage organs

The fatty acids of the total lipid extracts made from 10 tropical storage organs (Alocasia macrorrhiza, Colocasia esculenta, Dioscorea alata, D. bulbifera, D. cayensis, D. rotundata, Ipomea batatas, etc.) were studied. The high occurrence of the C₁₈ unsaturated fatty acids (linoleate and linolenate which together contributed over 50 % on average of the total fatty acids), conferred a high level of unsaturation on almost species. Compared with similar storage organs of temperate regions, there was a definite reduction in the degree of unsaturation. This was brought about by a general increase in the intrinsic values of palmitate and oleate.     

Fatty acid make-up of the muscle tissue lipids of ocean fish

Consequent upon the results of investigating fatty acids composition in the tissue lipids of a number of marine fish (marmoreal and green nototenia, merow, stavrida, klykach, lufar, marine perch and marine bream) of different degrees of fatness there were ascertained substantial differences in the correlation of basic acid components and the nutritional value of the lipids. A comparison between the overall lipid content and the quantity of highly unsaturated acids enabled it to disclose a possible relative resistance of the studied fish to the oxidative lipids decay.     

Temporal changes in milk fatty acid composition during diet-induced milk fat depression in lactating cows

Diet-induced milk fat depression (MFD) in lactating cows has been attributed to alterations in ruminal lipid metabolism leading to the formation of specific fatty acid (FA) biohydrogenation intermediates that directly inhibit milk fat synthesis. However, the mechanisms responsible for decreased lipid synthesis in the mammary gland over time are not well defined. The aim of this study was to evaluate the effect of diet on milk FA composition and milk fat production over time, especially during MFD, and explore the associations between MFD and FA biohydrogenation intermediates in omasal digesta and milk. Four lactating Finnish Ayrshire cows used in a 4 × 4 Latin square with a 2 × 2 factorial arrangement of treatments and 35-d experimental periods were fed diets formulated to cause differences in ruminal and mammary lipid metabolism. Treatments consisted of an iso-nitrogenous total mixed ration based on grass silage with a forage to concentrate ratio of 65:35 or 35:65 without added oil, or with sunflower oil at 50 g/kg of diet dry matter. The high-concentrate diet with sunflower oil (HSO) induced a 2-stage drop in milk fat synthesis that was accompanied by specific temporal changes in the milk FA composition. The MFD on HSO was associated especially with trans-10 18:1 and also with trans-9,cis-11 conjugated linoleic acid (CLA) in milk and omasal digesta across all diets and was accompanied by the appearance of trans-10,cis-15 18:2. Trans-10,cis-12 CLA was increased in HSO, but milk fat secretion was not associated with omasal or milk trans-10,cis-12 CLA. The temporal changes in milk fat content and yield and milk FA composition reflect the shift from the predominant ruminal biohydrogenation pathway to an alternative pathway. The ambiguous role of trans-10,cis-12 CLA suggests that trans-10 18:1, trans-9,cis-11 CLA and trans-10,cis-15 18:2 or additional mechanisms contributed to the diet-induced MFD in lactating cows.     

Quality of pig adipose tissue: relationship between solid fat content and lipid composition

The dependence of solid fat content at 20°C of adipose tissues on their fatty acid and triacylglycerol compositions was studied on lipids extracted from tissues from 166 pigs. The solid fat content (SFC20) was 20% on average but varied widely (9-35%). The SFC20 variability was closely related to the proportions of disaturated triacylglycerols and more specifically to palmitoyl-stearoyl-oleoyl-glycerol (R(2)=0.92). The SFC20 variability was also related to the proportions of the saturated fatty acids, palmitic and stearic acids (R(2)=0.94). The part of the variance of SFC20 explained by the proportion of polyunsaturated fatty acids was lower (R(2)=0.48). The iodine value showed a high correlation with SFC20 (R(2)=0.81) but carcass lean content was a poor indicator of the solid fat content of adipose tissues (R(2)=0.06).