Effects of fat emulsions with different fatty acid composition on plasma and hepatic lipids in rats receiving total parenteral nutrition

Effects of different fatty acids on the development of hepatic steatosis were studied in rats receiving total parenteral nutrition (TPN). 65 rats, with internal jugular catheters, were divided into one control group (n = 8), and four experimental groups (n = 13-15 each). The control group was fed a chow diet and all experimental groups received TPN. TPN provided 300 kcal/kg/day with 40% of the non-protein energy provided as fat. All TPN solutions were isonitrogenous and identical in nutrient composition except for the fatty acid composition of the fat emulsion. Four kinds of fat emulsions rich in: 1) medium chain fatty acids (C8:0,C10:0), 2) oleic acid (C18:1 n-9), 3) linoleic acid (C18:2 n-6), 4) eicosapentaenoic acid (C20:5 n-3)/docosahexaenoic acid (C22:6 n-3), were used. These fat emulsions were prepared with: 1) a mixture of medium chain triglycerides (MCT) and soybean oil (9:1), 2) olive oil, 3) safflower oil, 4) fish oil, respectively. The results of the study demonstrated a higher hepatic lipid content in the olive oil and safflower oil groups than in the control group, whereas no significant difference was seen between the MCT and control groups. Also, no difference was observed between the fish oil and control groups. With regard to the plasma lipids, the MCT group and olive oil group produced hyperlipidaemia. The plasma of the safflower oil and fish oil groups, however, had a low lipid concentration comparable to the control group. These results suggest that TPN with a fat emulsion prepared with fish oil does not cause hyperlipidaemia nor induce hepatic steatosis in normal rats.     

Effects on biotin,fat type and sodium nitrite on organ size,plasma constituents and liver fatty acid composition in rats

The role of biotin in the metabolism of fatty acids (FA) and as an anti-oxidant in an in vivo system under oxidant stress produced by sodium nitrite (NaNO₂)-induced methemoglobinemia was studied in Sprague-Dawley male rats. This report deals with basic data on growth, food intakes, changes in organ size, constituents in plasma and fatty acids in livers. Twelve groups of 14–16 weanlings were given a basal diet with 15% by weight of either biotin (0 or 150 μg/rat/week by mouth) and with or without NaNO₂ (250 or 500 mg/liter in the drinking water) for 6–7 weeks. Biotin-supplemented (B-S) rats ate more, gained more weight and drank more fluid; had larger organs; higher blood lipids and glucose, but had lower blood urea nitrogen (BUN) than did biotin-deprived (B-D) rats. Of the major FA, B-S rats had the highest % of 16:0 and 18:1n?9 but B-D rats had the highest % of 18:0, 18:2n?6 and 20:4n?6. As expected, CO-fed rats had the highest % of 18:2n?6, 20:4n?6 and 22:5n?6. L-fed rats had the highest % of 16:0 and 18:0. BT-fed rats had the highest % of 18:1n?9. Of the ratios calculated for 16:0/18:0 and of 20:4n?6/18:2n?6, L-fed rats had the highest, with BT-fed rats next and CO-fed rats the lowest. B-S rats had the highest ratios of 20:4n?6/18:2n?6, but the results were influenced by the type of dietary fat. CO-fed rats showed no difference in the ratio when biotin was given. The results suggest a role for biotin in essential FA metabolism with implications for integrity of membrane structure and fuction, and prostaglandin precursor biosynthesis.     

Effects of conjugated linoleic acid supplementation on fatty acid composition in the plasma, liver, and epididymal fat pads of male-Sprague Dawley rats

The purpose of this study was to investigate the effects of conjugated linoleic acid (CLA) on the fatty acid composition of plasma, liver, and epididymal fat pads in rats. Seventy-two male Sprague-Dawley rats were divided into four groups and received beef tallow (BT), fish oil (FO), beef tallow with CLA (BTC), and fish oil with CLA (FOC). All the rats were fed an experimental diet containing 12% (wt/wt) total fat, including CLA at 1%, for 30 weeks. The fatty acid analyses of the plasma, liver, and epididymal fat pads were performed by the one-step methylation method, followed by gas chromatography. Monounsaturated fatty acid (MUFA) levels in the plasma were significantly reduced in the BTC group as compared to the BT group. The levels of C18:1 and C20:4 in the liver were significantly lower in the BTC group than in the BT group (P < .05). CLA was detected in the epididymal fat pads of the rats that did not receive supplemental CLA (the BT and FO groups), indicating de novo synthesis. CLA caused significant decreases in C18:1 fatty acid levels in both the BTC and FOC groups in epididymal fat pads. C22:6 was significantly higher in the liver microsomes of the BTC group, as compared to the BT group. MUFA was stored at higher levels in the epididymal fat pads and was significantly lower in level in the CLA-supplemented (BTC and FOC) groups as compared to the BT and FO groups (P < .05). In conclusion, dietary CLA supplementation in rats altered fatty acid composition in a tissue-specific manner. CLA was stored mainly in the epididymal fat pad. The results also suggested that CLA may inhibit the conversions of C18:0 to C18:1 and C18:2 to C20:4 fatty acid, resulting in significantly lower levels of C18:1 and C20:4 in the livers of the BTC group as compared to the BT group.     

Effects of dietary fatty acid composition on macronutrient selection and synaptosomal fatty acid composition in rats

Our previous work showed that rats consuming 20% (wt/wt) lard diets selected more protein and less carbohydrate than did rats fed 20% (wt/wt) soybean oil diets. To determine if this effect is specific to saturated fat source and to measure changes in fatty acid composition of synaptosomal phospholipids, male Wistar rats were fed a 20% (wt/wt) soybean oil or tallow diet with 24% protein and 48% carbohydrate for 2 wk. Rats then self-selected from two diets with the same fat previously fed but different protein and carbohydrate composition (5% protein, 67% carbohydrate and 55% protein, 17% carbohydrate). Tallow-fed rats selected more protein and less carbohydrate than did soybean oil-fed rats. Dietary fat also affected fatty acid composition of synaptosomal phospholipids, phosphatidylcholine being most affected and phosphatidylinositol most resistant. Later studies determined if selection differences were due to taste. When rats self-selected without prior exposure to diets, tallow-fed rats selected more protein and less carbohydrate than did soybean oil-fed rats during the last 2 wk but not the first 2 wk. When rats selected from diets with identical protein and carbohydrate composition but different dietary fat, rats consumed slightly greater amounts of the tallow diet at each protein level. The relative intake of tallow and soybean oil diets, however, did not vary significantly with dietary protein treatment. These results confirm that rats fed saturated fat diets select more protein and less carbohydrate than do rats fed polyunsaturated fat diets and suggest this difference is not due to taste factors.     

Diet (n-3) polyunsaturated fatty acid content and parity affect liver and erythrocyte phospholipid fatty acid composition in female rats

The fatty acid composition of membrane phospholipids affects the physicochemical properties of the membrane and thus influences cell function. In this study, the effects of 1-4 sequential pregnancies on the phospholipid fatty acid compositions of the maternal liver and erythrocytes were determined in female rats fed diets containing alpha-linolenic acid (ALA), ALA and preformed docosahexaenoic acid (DHA; ALA+DHA), or minimal ALA (low ALA). Virgin females, fed the diets for commensurate durations, served as a control for reproduction. Liver and erythrocyte total phospholipid compositions were determined at weaning by TLC/GC. In both tissues, significant main effects of diet and reproductive status were detected for many fatty acids, but a significant interaction of diet, reproductive status, and duration of treatment (no. of reproductive cycles or equivalent time period for virgins) was detected only for DHA, 22:6(n-3). Primiparous dams fed the ALA and low ALA diet had decreased liver DHA content of 31% and 74%, respectively, compared with virgin females fed the ALA diet. Liver DHA did not decrease further after additional reproductive cycles. Liver DHA content was unchanged in parous dams fed the ALA+DHA diet, but virgin females fed this diet exhibited a 50% increase in liver DHA after 13 wk of treatment. Changes in erythrocyte DHA were of similar magnitude and time course to those observed in liver, suggesting that this tissue may serve as a marker for liver DHA status.     

Effects of capsinoid on serum and liver lipids in hyperlipidemic rats

We compared the effects of capsinoid, a non-pungent component, on serum and liver lipids, with that of synthetic capsaicin in hyperlipidemic rats. Male Wistar rats of 9 wk old were divided into 4 groups: a control group receiving a high-fat diet containing 1% cholesterol, and capsaicin, capsinoid-I and capsinoid-II groups supplemented with 0.1 mmol of N-pelargonylvanillylamide (synthetic capsaicin), and 0.1 mmol and 1.0 mmol of capsinoid (capsiate: dihydrocapsiate=63 : 37) per kg of control diet, respectively. All groups were pair-fed for 4 wk. Compared with the control group, serum lipid levels in both capsinoid groups and liver lipid contents in the capsinoid-II group showed the same reduction as that of the capsaicin group. In the capsaicin and capsinoid-I groups, fatty acid synthase (FAS) activities were lower and hepatic triacylglycerol lipase (HTGL) [EC 3.1.1.3] activities tended to be higher than those of control group. Lipoprotein lipase (LPL) [EC 3.1.1.34] activity in adipose tissue was higher in the capsaicin and capsinoid-II groups than in the control group. These results showed that capsinoid can improve serum and liver lipid metabolism comparable to synthetic capsaicin.     

Long-chain fatty acid composition of maternal liver lipids during pregnancy and lactation in the rat: comparison of triglyceride to phospholipid

The change in long-chain fatty acid composition in maternal liver was studied during pregnancy and lactation in the rat. Maternal liver triglycerides and phospholipids transiently accumulated and were depleted of long-chain fatty acids during pregnancy and lactation. During pregnancy, maternal liver accumulated triglyceride, but triglyceride fatty acid composition changed little. However, maternal liver total phospholipid fatty acid composition changed significantly without a change in the total pool size throughout pregnancy or lactation. The change in composition of (n-3) and (n-6) essential fatty acids in maternal liver triglyceride and total phospholipid occurred in an apparently dyssynchronous manner throughout pregnancy and lactation.     

Dietary trans fatty acids alter diaphragm phospholipid fatty acid composition, triacylglycerol content and glucose transport in rats

The present study evaluates the effect of dietary trans fatty acids on diaphragm phospholipid fatty acid composition, intramyocellular triacylglycerol content and insulin-stimulated glucose uptake in comparison with dietary saturated fatty acids. Male weanling WNIN rats were divided into three groups and fed for 3 months on one of the following diets containing 10 % oil differing in fatty acid composition: control diet, saturated fatty acid diet and trans fatty acid diet. Dietary trans fatty acids increased the intramyocellular triacylglycerols and decreased the ratio of 20 : 4n-6 to 18 : 2n-6 and long-chain PUFA levels (20 %) in diaphragm phospholipids, indicating inhibition of PUFA biosynthesis. However, saturated fatty acids decreased both 18 : 2n-6 and 20 : 4n-6 without change in the ratio. Trans fatty acid-induced alterations in diaphragm phospholipid fatty acid composition and intramyocellular triacylglycerol content were associated with decreased insulin-stimulated glucose transport in the diaphragm. These observations suggest that dietary trans fatty acids decrease diaphragm insulin sensitivity, possibly due to increased intramyocellular triacylglycerol accumulation and decreased long-chain PUFA in phospholipids.     

Effect of methyl linoleate administration on phospholipid fatty acid composition and osmotic fragility of erythrocytes in essential fatty acid deficient rats

Methyl linoleate (18:2 omega 6) was administered to rats deficient in essential fatty acids (EFA) and the effects on osmotic fragility and lipid composition of their red blood cells were studied. Even if they remained deficient in omega-3 fatty acids, the fragile red cells of EFA-deficient rats were remarkably strengthened by the linoleate treatment. It is concluded that omega-3 fatty acids are not essential for the maintenance of cell membrane integrity in rats. Since the cholesterol/phospholipid ratio in red cells was lower in untreated than in treated rats, it is suggested that this factor might be responsible in part for the higher fragility of red cells in EFA-deficient rats. Despite the prolonged administration of overload quantities of methyl linoleate, the proportion of 18:2 omega 6 in the red blood cell phospholipids of treated rats was actually lower than that in rats fed a regular stock diet, while the relative content of other omega-6 fatty acids (20:4 omega 6, 22:4 omega 6, and 22:5 omega 6) increased. These results indicate that the metabolic processes of omega-6 fatty acids in treated rats were stimulated, probably as a result of the lack of competition from omega-3 fatty acids for the same enzyme systems.     

Influence of a fiber mixture on serum and liver lipids and on fecal fat excretion in rats

Male Sprague-Dawley rats (8 per group) were fed a modified AIN-76A diet containing either 10% cellulose or 10% of a proprietary fiber mixture for 21 days. Weight gain and liver weight were similar in the 2 groups but feed efficiency was higher in the test group. Serum cholesterol and triglycerides were lowered by 11% and 15%, respectively, by the test diet. Liver cholesterol was lowered significantly in the fiber-fed rats whereas liver triglycerides were elevated. Twenty-four–hour fecal collections were made on days 12 and 19. The weight of feces was unaffected by the test diet, but water content and fecal fat were increased by 27% and 44% and by 99% and 100%, respectively, on days 12 and 19. The amount of Liebermann-Burchard–positive material in the feces was significantly higher in rats fed the test material. The increases on days 12 and 19 were 139% and 105%, respectively.     

Effect of methyl linoleate administration on phospholipid fatty acid composition and osmotic fragility of erythrocytes in essential fatty acid deficient rats.

Methyl linoleate (18:2 omega 6) was administered to rats deficient in essential fatty acids (EFA) and the effects on osmotic fragility and lipid composition of their red blood cells were studied. Even if they remained deficient in omega-3 fatty acids, the fragile red cells of EFA-deficient rats were remarkably strengthened by the linoleate treatment. It is concluded that omega-3 fatty acids are not essential for the maintenance of cell membrane integrity in rats. Since the cholesterol/phospholipid ratio in red cells was lower in untreated than in treated rats, it is suggested that this factor might be responsible in part for the higher fragility of red cells in EFA-deficient rats. Despite the prolonged administration of overload quantities of methyl linoleate, the proportion of 18:2 omega 6 in the red blood cell phospholipids of treated rats was actually lower than that in rats fed a regular stock diet, while the relative content of other omega-6 fatty acids (20:4 omega 6, 22:4 omega 6, and 22:5 omega 6) increased. These results indicate that the metabolic processes of omega-6 fatty acids in treated rats were stimulated, probably as a result of the lack of competition from omega-3 fatty acids for the same enzyme systems.     

碘氟联用对大鼠脑细胞膜磷脂和脂肪酸组成的影响

目的　研究不同浓度碘和高浓度氟联合作用对大鼠脑细胞膜磷脂和脂肪酸组成的影响。方法　给大鼠饮用高浓度的氟化钠 (15 0mg L) ,同时分别加入低、中、高浓度碘化钾(0 0 0 3、0 0 3和 3mg L)的溶液共 5个月 ,然后用液相色谱法分离和测定大鼠脑细胞磷脂和脂肪酸组成。结果　实验各组中各种磷脂含量无显著变化。高浓度氟和高浓度碘加氟 (15 0mg L + 3mg L)可使大鼠脑细胞膜脂肪酸构成比发生了明显的变化 ,饱和脂肪酸中的月桂酸(C12 :0 )显著增加 (P <0 0 5 ) ,不饱和脂肪酸中的亚油酸 (C18:2 )显著减少 ;中浓度碘对氟的这种作用有明显的拮抗作用 ,而高浓度时则反而有协同毒性作用。结论　氟中毒所致大鼠脑细胞膜脂肪酸组成的变化可能与氟致脂质过氧化作用有关 ,而 0 0 3mg L的碘化钾是本实验条件下拮抗氟中毒对大鼠脑细胞脂肪酸组成的最佳浓度