Fatty acid patterns in iron-deficient maternal and neonatal rats

To determine the effects of maternal iron deficiency on lipid composition and fatty acid patterns in offspring, rats were fed ad libitum diets containing 5 ppm iron (deficient) (n=8) or 320 ppm iron (control) (n=7) and deionized water from day-1 of gestation through day-18 of lactation. On day-2 of lactation, litters were standardized to three male and three female pups. On day-18, pups were fasted for 4 hr before tissue and blood collection. Significant changes in serum and liver lipid concentrations and fatty acid patterns were observed in deficient pups. Serum triglycerides, cholesterol and phospholipids and liver triglycerides, cholesterol, and cholesteryl esters were increased. In deficient pups, percentage total fatty acids of 14∶0, 16∶1, 18∶1, 18∶2 from serum lipids were increased; in liver, 14∶0, 18∶2, 18∶3 were increased; 18∶0 and 20∶4 were decreased in both serum and liver. Dam serum lipid levels did not differ between groups. Lipid changes observed in iron-deficient pups did not consistently reflect the milk, serum or liver lipid patterns observed in dams. Altered lipid composition and fatty acid patterns of iron-deficient pups thus appear to be of endogenous origin.     

Dietary saturated fat level alters the competition between α-linolenic and linoleic acid

Male weanling rats were fed semi-synthetic diets high in saturated fat (beef tallow) vs high in linoleic acid (safflower oil) with or without high levels of α-linolenic acid (linseed oil) for a period of 28 days. The effect of feeding these diets on cholesterol content and fatty acid composition of serum and liver lipids was examined. Feeding linseed oil with beef tallow or safflower oil had no significant effect on serum levels of cholesterol. Serum cholesterol concentration was higher in animals fed the safflower oil diet than in animals fed the beef tallow diet without linseed oil. Feeding linseed oil lowered the cholesterol content in liver tissue for all dietary treatments tested. Consumption of linseed oil reduced the arachidonic acid content with concomitant increase in linoleic acid in serum and liver lipid fractions only when fed in combination with beef tallow, but not when fed with safflower oil. Similarly, ω3 fatty acids (18∶3ω3, 20∶5ω3, 22∶5ω3, 22∶6ω3) replaced ω6 fatty acids (20∶4ω6, 22∶4ω6) in serum and liver lipid fractions to a greater extent when linseed oil was fed with beef tallow than with safflower oil. The results suggest that the dietary ratio of linoleic acid to saturated fatty acids or of 18∶3ω3 to 18∶2ω6 may be important to determine the cholesterol and arachidonic acid lowering effect of dietary α-linolenic acid.     

Chronic administration of eicosapentaenoic acid and docosahexaenoic acid as ethyl esters reduced plasma cholesterol and changed the fatty acid composition in rat blood and organs

Fish oils rich in n-3 fatty acids have been shown to decrease plasma lipid levels, but the underlying mechanism has not yet been elucidated. This investigation was performed in order to further clarify the effects of purified ethyl esters of eicosapentaenoic acid (EPA-EE) and docosahexaenoic acid (DHA-EE) on lipid metabolism in rats. The animals were fed EPA-EE, DHA-EE, palmitic acid, or corn oil (1 g/kg/d) by orogastric intubation along with a chow background diet for three months. At the end the animals were sacrificed. Plasma and liver lipids were measured, as well as lipid-related enzyme activities and mRNA levels. The fatty acid composition of plasma and different tissues was also determined. This study shows that, compared to the corn oil control, EPA-EE and DHA-EE lowered plasma cholesterol level, whereas only EPA-EE lowered the amount of plasma triacylglycerol. In liver peroxisomes, both EE preparations increased fatty acyl-CoA oxidase FAO activities, and neither altered 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase activities. In liver microsomes, EPA-EE raised HMG-CoA reductase and acyl-CoAicholesterol acyltransferase activities, whereas DHA-EE lowered the former and did not affect the latter. Neither product altered mRNA levels for HMG-CoA reductase, low density lipoprotein-receptor, or low density lipoprotein-receptor related protein. EPA-EE lowered plasma triacylglycerol, reflecting lowered very low density lipoprotein secretion, thus the cholesterol lowering effect in EPA-EE-treated rats may be secondary to the hypotriacylglycerolemic effect. An inhibition of HMG-CoA reductase activity in DHA-EE treated rats may contribute to the hypocholesterolemic effect. The present study reports that 20∶5n-3, and not 22∶6n-3, is the fatty acid primarily responsible for the triacylglycerol lowering effect of fish oil. Finally, 20∶5n-3 was not converted to 22∶6n-3, whereas retroconversion of 22∶6n-3 to 20∶5n-3 was observed.     

Fatty acid specificity in the inhibition of cell proliferation and its relationship to lipid peroxidation and prostaglandin biosynthesis

Primary cultures of smooth muscle cells were established from the medial layer of guinea pig aorta. Cells at passage level 4 were treated with different series of fatty acids belonging to the n-9, n-6 and n-3 families. Lipid peroxidation was measured by the thiobarbituric acid assay and prostaglandin biosynthesis was measured by the radioimmunoassay of PGE and 6-keto-PGF_1α. Cell proliferation was estimated from the total cell number of cultures seeded at low density. 18∶1(n-9) did not form lipid peroxides and this fatty acid stimulated cell proliferation. All fatty acids which generated lipid peroxides inhibited cell proliferation, but inhibition was correlated with the degree of lipid peroxidation only in the n-9 fatty acid family. 22∶4(n-6) and 22∶6(n-3) inhibited prostaglandin biosynthesis. 18∶2(n-6), 18∶2(n-9), 18∶3(n-3), 20∶2(n-9), 20∶3(n-3) and 20∶5(n-3) had no effect on prostaglandin biosynthesis. 18∶3(n-6), 20∶3(n-6) and 20∶4(n-6) generated prostaglandins. 20∶3(n-9) generated metabolites with prostaglandin immunoreactivity. The inhibition of cell proliferation did not correlate with enhanced or inhibited prostaglandin synthesis. The inhibition of cell proliferation was related to the structures of the different polyunsaturated fatty acid families decreasing in the order n-9>n-6>n-3. Eicosatrienoic acids were the most effective inhibitors of cell proliferation in each fatty acid family and 20∶3(n-9) was the most potent eicosatrienoic acid. These data show that specific as yet unrecognized products of fatty acid metabolism are responsible for the inhibition of cell proliferation. Fatty acids are designated by the number of carbon atoms: number of double bonds and the position of the first double bond from the methyl terminus of the acyl chain is noted in parenthesis: 18∶1(n-9), 9-octadecenoic acid; 18∶2(n-9), 6,9-octadecadienoic acid; 18∶2(n-6), 9,12-octadecadienoic acid; 18∶3(n-6), 6,9,12-octadecatrienoic acid, 18∶3(n-3), 9,12,15-octadecatrienoic acid; 20∶2(n-9), 8,11-eicosadienoic acid; 20∶3(n-9), 5,8,11-eicosatrienoic acid; 20∶3(n-6), 8,11,-14-eicosatrienoic acid, 20∶4(n-6), 5,8,11,14-eicosatetraenoic acid; 20∶5(n-3), 5,8,11,14,17-eicosapentaenoic acid; 22∶4-(n-6), 7,10,13,16-docosatetraenoic acid, 22∶6(n-3), 4,7,10,13,16,19-docosahexaenoic acid. Presented at the 73rd AOCS annual meeting, Toronto, Canada, May 1982.     

Specific inhibition of hepatic fatty acid synthesis exerted by dietary linoleate and linolenate in essential fatty acid adequate rats

Dietary linoleate and linolenate were investigated for their ability to specifically inhibit liver and adipose tissue lipogenesis in meal-fed (access to food 900-1,200 hr), essential fatty acid (EFA) adequate rats. Supplementing a high carbohydrate diet containing 2.5% safflower oil with 3% palmitate 16∶0, oleate 18∶1, or linoleate 18∶2 did not affect in vivo liver or adipose tissue fatty acid synthesis. However, 18∶2 addition to the basal diet did result in a significant (P<0.05) decline of liver fatty acid synthetase (FAS) and glucose-6-phosphate dehydrogenase (G6PD) activities. When the safflower oil content of the basal diet was reduced to 1%, the addition of 3% 18∶2 or linolenate 18∶3 significantly (P<0.05) depressed hepatic FAS, G6PD, and in vivo fatty acid synthesis by 50%. Addition of 18∶1 caused no depression in hepatic FAS activity but did result in a significant (P<0.05) decline in liver G6PD activity and fatty acid synthesis which was intermediate between basal and basal +18∶2-or+18∶3-fed animals. Adipose tissue rates of lipogenesis were completely unaffected by dietary fatty acid supplementation. Similarly, the addition of 3 or 5% 18∶3 to a basal diet for only one meal resulted in no change in lipogenesis relative to that in animals fed the basal diet. The data indicate that, like rats fed EFA-deficient diets, dietary 18∶2 and 18∶3 exert a specific capacity to depress rat liver FAS and G6PD activities and rate of fatty acid synthesis. Michigan Agricultural Experiment station Journal Article No. 7581. D.R. Romsos is the recipient of Career Development Award K04 AM 00112     

Effect of eicosatetraynoic acid on liver and plasma lipids

Groups of rats were fed a fat-free diet supplemented with 0.5% safflower oil (control) or the control diet containing 0.5% of 5,8,11,14-eicosatetraynoic acid (TYA). Blood was collected weekly and plasma lipids analyzed. After 4 weeks, the animals were killed and the liver lipids were analyzed in detail. The acetylenic fatty acid perturbed plasma neutral lipid and phospholipid class concentrations and reduced growth rates. Liver triglyceride concentrations were reduced dramatically in the TYA fed animals, suggesting interference with complex lipid synthesis. Plasma and liver triglycerides were shifted to higher molecular weight species suggesting that TYA affected fatty acid metabolism. The phospholipids showed an accumulation of 18∶2 and a fall in 20∶4 percentages indicating an inhibition in the conversion of linoleate to arachidonate. All major lipid classes exhibited an increase in 18∶1 levels. Analysis of the octadecenoate positional isomers indicated the proportion of oleate increased substantually in all lipid classes whereas vaccenate proportions had fallen dramatically. All of the data collectively suggest that TYA inhibits the elongation of unsaturated fatty acids. A group of rats bearing hepatoma 7288CTC were also fed the TYA diet. Host liver lipids were affected by TYA similar to normal TYA fed animals, but the effects on hepatoma lipids were marginal.     

Dietary fatty acid composition induces comparable changes in cardiolipin fatty acid profile of heart and brain mitochondria

The fatty acid profile of cardiolipin (CL) from brain and cardiac mitochondria was measured to determine whether CL isolated from these two tissue sources responded similarly to alterations in dietary fat composition. Male Wistar rats were fed 20% (w/w) diets containing 2 to 12% (w/w) 18∶2n-6 for four weeks. Despite higher baseline levels of CL 18∶2n-6 in cardiac (54±1% of total fatty acids) compared to brain (13±1%) mitochondria, CL 18∶2n-6 levels increased in proportion to dietary 18∶2 levels. The degree of change in 18∶2n-6 was comparable with both tissues showing an approximate 1.5- to 2-fold increase. The time course of changes in CL fatty acid profile was examined in a subsequent experiment in which animals were fed 20% (w/w) fat diets containing either 3 or 15% α-linoleate. Changes in cardiac CL 18∶1, 18∶2n-6, and 22∶6n-3 levels were observed within one week of feeding. While statistically significant differences were not observed in brain CL until the second week of feeding, the time course did not differ substantively from that observed in heart. The results from this study suggest that while baseline fatty acid profile of cardiac and neural CL differ, mitochondria from both tissues show comparable sensitivity to changes in dietary fat composition. Furthermore, it would appear that the turnover rate of fatty acids in CL is similar in both tissues.     

A relationship between essential fatty acid and vitamin E deficiency

To test whether vitamin E deficiency might influence the course of essential fatty acid (EFA) deficiency, Long Evans rats were fed diets containing a marginal amount (1.5% of calories) of 18∶2ω6 or 18∶3ω3 fatty acid with complete absence of the other and with or without vitamin E. Vitamin E contents decreased continuously in serum and liver in all rats fed the E-free diets but in the brains of only the rats fed the marginal 18∶3ω3, E-free diet. It is considered that the vitamin E is cooxidized in the liver with 22∶6ω3, since this fatty acid is very low in livers of the rats fed the marginal 18∶2ω6 diet but much higher in livers of the rats fed the marginal 18∶3ω3 diet. Brain 22∶6ω3 values are comparable for both groups. The source of 22∶6ω3 is evidently in the mother's milk, since following weaning there is a precipitous drop in 22∶6ω3 in serum, liver and carcass of rats on the 18∶2ω6-containing diet. No significant signs of EFA deficiency were seen in the E-deficient rats. Operated for the U.S. Department of Energy by the University of California under contract no. DE-AC03-76-SF00012.     

Effect of diet on the fatty acid and molecular species composition of dog retina phospholipids

Dogs were born to mothers fed commercial diets low or enriched in n-3 fatty acids and raised on those diets until they were about 50 d old. Retinas were removed, lipids were extracted, and total phospholipids were anlyzed for fatty acid and molecular species composition. Animals from the low n-3 group had significantly lower retinal levels of 22∶6n-3 and higher levels of n-6 fatty acids, especially 20∶4n-6 and 22∶5n-6. There was no difference in the retinal levels of 18∶2n-6, and only small differences were found in saturated and monounsaturated fatty acids. The most dramatic differences in molecular species occurred in 22∶6n-3-22∶6n-3 (4.7 vs. 0.8%) and 18∶0-22∶6n-3 (27.6 vs. 14.4%); total molecular species containing 22∶6n-3 were significantly lower in the low n-3 group (45.5 vs. 24.0%). Molecular species containing 20∶4n-6 and 22∶5n-6 were greater in the low n-3 animals (13.0 vs. 25.7%), as were molecular species containing only saturated and monounsaturated fatty acids (40.8 vs. 35.4%). These results show that modest differences in the amount of n-3 fatty acids in the diets of dogs can have profound effects on the fatty acid and molecular species composition of their retinas.     

Relationship between dietary supply of long-chain fatty acids and membrane composition of long- and very long chain essential fatty acids in developing rat photoreceptors

The present study was designed to determine if dietary supply of long-chain fatty acid (LCFA, C20∶4n-6, and/or C22∶6n-3), reflecting levels that might be incorporated into infant formulas, influences the fatty acid composition of the visual cell membrane. The rod outer segment (ROS) of the retina was analyzed from rats fed diets varying in the ratio of 18∶2n-6 to 18∶3n-3 with or without 20∶4n-6 [arachidonic acid (AA)] and 22∶6n-3 (docosahexaenoic acid) from birth to six weeks of age. The level of very long chain fatty acids (VLCFA, C₂₄−C₃₆) was identified using gas chromatography and gas chromatography-mass spectrometry. In the ROS, the highest relative percent of AA was attained in phosphatidylcholine (PC) and phosphatidylethanolamine (PE) of animals fed 1% AA diet, whereas feeding 0.7% docosahexaenoic acid (DHA) diet significantly increased the DHA level in PC, phosphatidylserine, and phosphatidylinositol compared to feeding diets containing AA. VLCFA of n-6 and n-3 up to C₃₆ were found in PC, with the most abundant fatty acids being C₃₂ and C₃₄. In PC, phosphatidylserine and PE, the n-6 tetraenoic VLCFA level was highly increased in animals fed 1% AA compared to other dietary groups. This study suggests that dietary fat containing small amounts of AA or DHA is an important factor influencing membrane fatty acid composition of the visual cell during development. Based on a presentation at the AOCS Annual Meeting & Expo in San Antonio, Texas, May 7–11, 1995.     

Effect of dietary fatty acid composition on the biosynthesis of unsaturated fatty acids in rat liver microsomes

A study was made of the influence of semisynthetic diets of low and high unsaturation on the fatty acid composition and desaturation-chain elongation enzymatic activity of the liver microsomal fractions of male Sprague-Dawley rats of different ages. Groups of rats were fed 5 or 20% coconut oil (CO), or a 5 or 20% mixture of corn and menhaden oils (3∶7) (CME) from weaning to 100 wk of age. Growth rate and food consumption were measured during this period in which animals were sacrificed at 36, 57, 77 and 100 wk of age. Both the level and composition of the dietary fat supplements produced marked effects on the fatty acid composition of the liver microsomal lipids. In general, the fatty acid composition of the microsomal fractions reflected that of the dietary fat and was more unsaturated with the higher level of fat fed. The rate of conversion of linoleic to arachidonic acid in assays performed in vitro with liver microsomal preparations from animals of the different groups also showed marked differences. The 6-desaturase-chain elongation activity was higher in the 5% than 20% group and corresponded to the essential fatty acid (EFA) status of the animals in these groups as represented by the triene-tetraene ratio of the microsomal lipid. The relationship of the 6-desaturase activity to fatty acid composition of the microsomal lipid indicated that if varied directly with the level of 20∶3ω9, 18∶1 and 16∶1 and was inhibited by arachidonic acid. The activity of the 6-desaturase enzyme system was lowest in the liver microsomal fraction obtained from the animals fed the CME diets and appeared to be suppressed by the high levels of 20∶5 and 22∶6 that accumulated in the microsomal lipid. Accordingly, the levels of arachidonic acid were lower in the microsomal lipid of these groups than those of the corresponding CO groups in spite of a greater abundance of linoleic acid in the diet. The data suggest that the activity of the 6-desaturase-chain elongation system is regulated by the fatty acid composition of the microsomal lipid as influenced by the composition of the dietary fat.     

Influence of dietary fat on metabolism of (14-14C)erucic acid in the perfused rat liver. Distribution of metabolites in lipid classes

Two groups of rats were fed diets containing 20% by weight of either partially hydrogenated marine oil supplemented with sunflower seed oil (PHMO) or palm oil (PO) for 8 wk. Using a liver perfusion system, the effect of dietary long chain monoenoic fatty acids on the uptake and metabolism of [14-¹⁴C]erucic acid was studied. The perfusion times were 15 and 60 min, respectively. The two groups showed equal ability for erucic acid uptake in the liver but differed in the channeling of the fatty acids into various metabolic pathways. A higher metabolic turnover of 22∶1 in the PHMO livers relative to the PO livers was demonstrated by an increased recovery of total [¹⁴C]labeling in the triglyceride (TG) and phospholipid (PL) fractions, already evident after 15 min of perfusion. The chainshortening capacity was highest in the PHMO group, reflected by a higher [¹⁴C]18∶1 incorporation in both TG and PL, and increasing from 15 to 60 min of perfusion. The amount of [¹⁴C]18∶1 found in PL and TG after 60 min of perfusion of livers from rats fed PO corresponded to that shown for the PHMO group after 15 min. The PL demonstrated a discrimination against 22∶1 compared to TG, and, when available, 18∶1 was highly preferred for PL-synthesis. The total fatty acid distribution in the TG, as determined by gas liquid chromatography (GLC), reflected the composition of the dietary fats. In the total liver PL, 22∶1 and 20∶1 were present in negligible amounts, although the PHMO diet contained 12–13% of both 22∶1 and 20∶1. In the free fatty acid fraction (FFA), the major part of the radioactivity (≈80%) was [14-¹⁴C]erucic acid, and only small amounts of [¹⁴C]18∶1(<2%) were presents, even after 60 min of perfusion. The shortened-chain 18∶1 was readily removed from the FFA pool and preferentially used for lipid esterification.     

Effects of dietary vegetable oil on atlantic salmon hepatocyte fatty acid desaturation and liver fatty acid compositions

Fatty acyl desaturase activities, involved in the conversion of the C₁₈ EFA 18∶2n−6 and 18∶3n−3 to the highly unsaturated fatty acids (HUFA) 20∶4n−6, 20∶5n−3, and 22∶6n−3, are known to be under nutritional regulation. Specifically, the activity of the desaturation/elongation pathway is depressed when animals, including fish, are fed fish oils rich in n−3 HUFA compared to animals fed, vegetable oils rich in C₁₈ FFA. The primary aims of the present study were (i) to establish the relative importance of product inhibition (n−3 HUFA) vs. increased substrate concentration (C₁₈ EFA) and (ii) to determine whether 18∶2n−6 and 18∶3n−3 differ in their effects on the hepatic fatty acyl desaturation/elongation pathway in Atlantic salmon (Salmo salar). Smolts were fed 10 experimental diets containing blends of two vegetable oils, linseed (IO), and rapeseed oil (RO), and fish oil (FO) in a triangular mixture design for 50 wk. Fish were sampled after 32 and 50 wk, lipid and FA composition of liver determined, fatty acyl desaturation/elongation activity estimated in hepatocytes using [1-¹⁴C]18∶3n−3 as substrate, and the data subjected to regression analyses. Dietary 18∶2n−6 was positively correlated, and n−3 HUFA negatively correlated, with lipid content of liver. Dietary 20∶5n−3 and 22∶6n−3 were positively correlated with liver FA with a slope greater than unity suggesting relative retention and deposition of these HUFA. In contrast, dietary 18∶2n−6 and 18∶3n−3 were positively correlated with liver FA with a slope of less than unity suggesting metabolism via β-oxidation and/or desaturation/elongation. Consistent with this, fatty acyl desaturation/elongation in hepatocytes was significantly increased by feeding diets containing vegetable oils. Dietary 20∶5n−3 and 22∶6n−3 levels were negatively correlated with hepatocyte fatty acyl desaturation. At 32 wk, 18∶2n−6 but not 18∶3n−3 was positively correlated with hepatocyte fatty acyl desaturation, wheres the reverse was true at 50 wk. The data indicate that both feedback inhibition through increased n−3 HUFA and decreased C₁₈ fatty acyl substrate concentration are probably important in determining the level of hepatocyte fatty acyl desaturation and that 18∶2n−6 and 18∶3n−3 may differ in their effects on this pathway.     

Influence of dietary arachidonic acid on metabolism in vivo of 8 cis, 11 cis, 14-eicosatrienoic acid in humans

This study investigated the influence of dietary arachidonic acid (20∶4n-6) on Δ5 desaturation and incorporation of deuterium-labeled 8cis, 11cis, 14-eicosatrienoic acid (20∶3n-6) into human plasma lipids. Adult male subjects (n=4) were fed diets containing either 1.7 g/d (H120∶4 diet) or 0.21 g/d (LO20∶4 diet) of arachidonic acid for 50 d and then dosed with a mixture containing ethyl esters of 20∶3n-6[d4] and 18∶1n-9[d2]. A series of blood samples was sequentially drawn over a 72-h period, and methyl esters of plasma total lipid, triacylglycerol, phospholipids, and cholesteryl ester were analyzed by gas chromatography-mass spectrometry. Based on the concentration of 20∶3n-6[d4] in total plasma lipid, the estimated conversion of 20∶3n-6[d4] to 20∶4n-6[d4] was 17.7.±0.79% (HI20∶4 diet) and 2.13±1.44% (LO20∶4 diet). The concentrations of 20∶4n-6[d4] in total plasma lipids from subjects fed the HI20∶4 and LO20∶4 diets were 2.10±0.6 and 0.29±0.2 μmole/mL plasma/mmole of 20∶3n-6[d4] fed/kg of body weight. These data indicate that conversion of 20∶3n-6[d4] to 20∶4n-6[d4] was stimulated 7-8-fold by the HI20∶4 diet. Phospholipid acyltransferase was 2.5-fold more selective for 20∶3n-6[d4] than 18∶1n-9[d2], and lecithin:cholesterol acyltransferase was 2-fold more selective for 18∶1n-9[d2] than 20∶3n-6[d4]. These differences in selectivity were not significantly influenced by diet. Absorption of ethyl 20∶3n-6[d4] was about 33% less than ethyl 18∶1n-9[d2]. The sum of the n-6 retroconversion products from 20∶3n-6[d4] in total plasma lipids was about 2% of the total deuterated fatty acids. Neither absorption nor retroconversion appears to be influenced by diet.     

Effect of selenium and vitamin E supplements on tissue lipids, peroxides, and fatty acid distribution in experimental diabetes

The protective role of selenium (Se), given as a Se-rich yeast, selenomethionine or selenomethionine+vitamin E supplement, toward changes in lipid, peroxide, and fatty acid distribution in tissues of streptozotocin-induced diabetic rats, was investigated, after 24 wk of disease. Diabetes increased liver thiobarbituric acid-reactive substances and conjugated dienes; Se supplement completely corrected these changes. In kidney, as in heart, the peroxide levels were not significantly changed by diabetes. In diabetic rat liver, a significant drop in triglycerides and phospholipids (P<0.05) was observed; this was modulated by Se+vitamin F supplementation. Se+vitamin E supplementation also inhibited the decrease in 18∶2n-6 and the increase in 22∶6n-3 observed in liver of diabetic rats, changes which reflect altered glycemic control. In kidney, heart, and aorta, diabetes produced some changes in lipid content and fatty acid distribution, especially an increase in heart triglycerides which was also corrected by the Se supplement. Se supplementation to diabetic rats also increased 18∶0 etherlinked alcohol, 20∶4 n-6, and 22∶5 n-3 in cardiac lipids. In aorta, Se + vitamin E significanlty increased 20∶5 n-3. These polyunsaturated fatty acids are precursors, in situ, of prostaglandin l₂ (PGl₂) and PGl₃ which may protect against cardiovascular dysfunction. In kidney, converrely, Se decreased 20∶4 n-6, the precursor of thromboxane A₁ implicated in diabetic glomerular injury. thus Se, and more efficiently Se + vitamin E supplementation, in experimental diabetes could play a role in controlling oxidative status and altered lipid metabolism in liver, thereby maintaining favorable fatty acid distribution in the major tissues affected by diabetic complications.     

The prevention of alcoholic fatty liver using dietary supplements: Dihydroxyacetone,pyruvate and riboflavin compared to arachidonic acid in pair-fed rats

Male Sprague-Dawley rats were fed for 30 days a high-fat liquid ethanol diet with dihydroxyacetone, pyruvate and riboflavin added as supplements (AMA-). Plasma triglyceride (TG) levels were 6-fold greater in these rats than in those fed and alcohol with without the supplements (AA-). The liver TG content in rats fed the AMA-diet was similar to that of rats fed a control diet (CA-) in which alcohol was replaced with isocaloric amounts of dextrose. Livers of rats fed the AA- diet had 3 times more TG than controls. Alcohol ingestion also enhanced the hepatic content of cholesteryl esters (CE) and phospholipids (PL). These lipids were reduced to levels found in livers of rats fed the control diet (CA-) when dihydroxyacetone, pyruvate and riboflavin were included in the alcohol diet. The fatty acid compositions of TG, CE and PL from livers of rats fed the AMA-diet were similar to those of corresponding lipids from rats fed the control diet (CA-) but differed from compositions when fed the alcohol diet (AA-). Regardless of the diet fed, TG had the same fatty acid composition in plasma and liver. The same was true of PL fatty acid composition. However, the fatty acid composition of CE differed between liver and plasma. The major fatty acid in liver CE was 18∶1 whereas in plasma it was arachidonic acid (20∶4). Reduced fatty liver was observed in an earlier study when rats were fed ad libitum an ethanol diet containing 20∶4. In the present study, we pair-fed the same diet and fatty liver was not reduced. Dihydroxyacetone, pyruvate and riboflavin did not prevent alcohol-induced fatty liver when 20∶4 was included in the AMA-diet. Our results confirm that dietary dihydroxyacetone, pyruvate and riboflavin prevent alcohol-induced fatty liver, and show that this effect may result from increased mobilization of fat from liver.     

The signature 10-hydroxy stearic acid thought to correlate with infectivity in oocysts of Cryptosporidium species is an artifact

Heating or freezing leads to loss in infectivity of oocysts of Cryptosporidium parvum toward neonatal BALB/c mice and is reflected in the profile of the polar lipid fatty acids. Upon loss of infectivity, the ratio of polar lipid to neutral lipid fatty acid decreased and the relative proportions of 18∶1n-9 also decreased; proportions of 18∶2n-6 and 20∶5n-6 increased, whereas the proportions of 16∶0 remained constant with freezing. During these investigations, a novel fatty acid, 10-OH 18∶0, was discovered in the glycolipid fraction. The identification of a fatty acid unique to species of Cryptosporidium was thought to provide a specific biomarker for this organism. Cryptosporidium also demonstrated fluctuations in absolute quantities of 10-OH 18∶0 with events that lead to loss of infectivity. This led to the presumed correlation of this biomarker with infectious Cryptosporidium. The 10-OH 18∶0 was putatively localized at the sn-2 position of phosphatidylethanolamine. High-performance liquid chromatography/electrospray ionization mass spectrometry revealed that the 10-OH 18∶0 existed principally in the free fatty acid form. Herein, we establish that the free fatty acid 10-OH 18∶0 was, in actuality, an artifact of the procedures for sample preparation.     

The effects of a dietary oxidized oil on lipid metabolism in rats

This study was carried out to investigate the effects of a dietary oxidized oil on lipid metabolism in rats, particularly the desaturation of fatty acids. Two groups of rats were fed initially for a period of 35 d diets containing 10% of either fresh oil or thermally treated oil (150°C, 6d). The dietary fats used were markedly different for lipid peroxidation products (peroxide value: 94.5 vs. 3.1 meq O₂/kg; thiobarbituric acid-reactive substances: 230 vs. 7 μmol/kg) but were equalized for their fatty acid composition by using different mixtures of lard and safflower oil and for tocopherol concentrations by individual supplementation with dl-α-tocopherol acetate. In the second period which lasted 16 d, the same diets were supplemented with 10% linseed oil to study the effect of the oxidized oil on the desaturation of α-linolenic acid. During the whole period, all the rats were fed identical quantities of diet by a restrictive feeding system in order to avoid a reduced food intake in the rats fed the oxidized oil. Body weight gains and food conversion rates were only slightly lower in the rats fed the oxidized oil compared to the rats fed the fresh oil. Hence, the effects of lipid peroxidation products could be studied without a distortion by a marked reduced food intake and growth. To assess the rate of fatty acid desaturation, the fatty acid composition of liver and heart total lipids and phospholipids was determined and ratios between product and precursor of individual desaturation reactions were calculated. Rats fed the oxidized oil had reduced ratios of 20∶4n−6/18∶2n−6, 20∶5n−3/18∶3n−3, 20∶4n−6/20∶3n−6, and 22∶6n−3/22∶5n−3 in liver phospholipids and reduced ratios of 20∶4n−6/18∶2n−6, 22∶5n−3/18∶3n−3, and 22∶6n−3/18∶3n−3 in heart phospholipids. Those results suggest a reduced rate of desaturation of linoleic acid and α-linolenic acid by microsomal Δ4-, Δ5-, and Δ6-desaturases. Furthermore, liver total lipids of rats fed the oxidized oil exhibited a reduced ratio between total monounsaturated fatty acids and total saturated fatty acids, suggesting a reduced Δ9-desaturation. Besides those effects, the study observed a slightly increased liver weight, markedly reduced tocopherol concentrations in liver and plasma, reduced lipid concentrations in plasma, and an increased ratio between phospholipids and cholesterol in the liver. Thus, the study demonstrates that feeding an oxidized oil causes several alterations of lipid and fatty acid metabolism which might be of great physiologic relevance.     

Major clofibrate effects on liver and plasma lipids are independent of changes in polyunsaturated fatty acid composition induced by dietary fat

The effects of clofibrate on the content and composition of liver and plasma lipids were studied in mice fed for 4 wk on diets enriched in n−6 or n−3 polyunsaturated fatty acids (PUFA) from sunflower oil (SO) or fish oil (FO), respectively; both oils were fed at 9% of the diet (dry weight basis). Only FO was hypolipidemic. Both oil regimes led to slightly increased concentrations of phospholipids (PL) and triacylglycerols (TG) in liver as compared with a standard chow diet containing 2% fat. Clofibrate promoted hypolipidemia only in animals fed SO. Its main effect was to enlarge the liver, such growth increasing the amounts of major glycerophospholipids while depleting the TG. SO and FO consumption changed the proportion of n−6 or n−3 PUFA in liver and plasma lipids in opposite ways. After clofibrate action, the PUFA of liver PL were preserved better than in the absence of oil supplementation. However, most of the drug-induced changes (e.g., increased 18∶1n−9 and 20∶3n−6, decreased 22∶6/20∶5 ratios) occurred inrrespective of lipids being rich in n−6 or n−3 PUFA. The concentration of sphingomyelin (SM), a minor liver lipid that virtually lacks PUFA, increased with the dietary oils, decreased with clofibrate, and changed its fatty acid composition in both situations. Thus. oil-increased SM had more 22∶0 and 24∶0 than clofibrate-decreased SM, which was significantly richer in 22∶1 and 24∶1.     

Lipogenic enzyme activities in primary cultures of adult mouse hepatocytes

The effects of various unsaturated fatty acids such as oleic (18∶1n−9), linoleic (18∶2n−6) and arachidonic (20∶4n−6) on the activities of fatty acid synthetase (FAS), malic enzyme (ME), glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH) all were determined in primary cultures of mouse hepatocytes. Activities of FAS and ME were found to decrease with time in culture regardless of whether hepatocyte donors were fed diets containing polyunsaturated fatty acid-free hydrogenated cottonseed oil (HCTO) or corn oil (CO). On the other hand, while G6PDH activity also declined in cultured hepatocytes obtained from HCTO-fed mice, the activity of this enzyme increased in cells cultured from CO-fed mice. 6PGDH activity was found to increase in hepatocytes obtained from both diet groups. Neither 18∶2 nor 20∶4 when added to media could alter FAS or ME activities compared with those observed with either 18∶1-containing or fatty acid-free media. Since lactic dehydrogenase activity and the rate of incorporation of [³H] leucine into FAS protein were unaltered with time in hepatocyte cultures, the decreased activities of FAS and ME cannot be attributed to a loss in cell viability during culture but rather appear to be specific for those enzymes which respond to diet hormones in vivo. Examination of the fatty acid contents of the cells after the culture period showed that the values for the ratios of 16∶0/16∶1 and of 18∶0/18∶1 were elevated when either 18∶2 or 20∶4 was added to the medium even though there was no evidence for elongation of the added 18∶2 or for 20∶4 being converted to 22∶4. This result suggest that Δ9-desaturase activity was inhibited by these polyunsaturated fatty acids and that conversion of 18∶2 to 20∶4 was not required for such action. The rate of synthesis determined by the relative rate of incorporation of [³H]leucine into FAS was two to five times higher in hepatocytes prepared from mice fed the HCTO diet than in hepatocytes from mice fed the CO diet. We have concluded that the mechanisms for long-term regulation may not be contained entirely within the liver.