Simultaneous high nutritional single cell oil and lipase production by Candida viswanathii.

BACKGROUND: Omega fatty acids are a family of polyunsaturated fats associated with several health benefits. Lipases are enzymes with potential application in several food processes such as flavor and aroma, surfactants and formulations for the dairy and bakery industries. In this study, single cell oil and lipase production by Candida viswanathii CCR8137 were evaluated simultaneously from renewable carbon sources under nitrogen limitation. METHODS: Enzyme and single cell oil were obtained in submerged cultivations supplemented with triolein, tributyrin, corn oil, sunflower oil, canola oil and olive oil. The effects of glucose on lipid accumulation, fatty acid profile, enzyme production and cell morphology were also evaluated. RESULTS: The highest lipid accumulation (44.5%, w/w) was obtained from triolein, whereas olive oil was the best inducer of lipase synthesis (26.8 U/mL). Nitrogen limiting cultivations were a key parameter for an organic source which showed higher lipid accumulation and enzyme production than the tested inorganic nitrogen source. Glucose was a poor inducer of lipase synthesis, though increased values of lipid accumulation were observed from this carbon source with a maximum of 63.1% (w/w). The fatty acid profile of lipids produced by C. viswanathii CCR8137 showed a high content of omega-9 fatty acid (C18:1 n-9). The addition of glucose to the culture media resulted in the synthesis of essential fatty acids: vaccenic, linolenic and eicosadienoic acids. CONCLUSIONS: Therefore, C. viswanathii CCR8137 strain can be considered as an oleaginous yeast able to accumulate high concentrations of intracellular lipids, which are potential additives for food industry applications as well as being able to simultaneously synthesize high yields of lipase.

Molecular interactions of plant oil components with stratum corneum lipids correlate with clinical measures of skin barrier function.

Plant-derived oils consisting of triglycerides and small amounts of free fatty acids (FFAs) are commonly used in skincare regimens. FFAs are known to disrupt skin barrier function. The objective of this study was to mechanistically study the effects of FFAs, triglycerides and their mixtures on skin barrier function. The effects of oleic acid (OA), glyceryl trioleate (GT) and OA/GT mixtures on skin barrier were assessed in vivo through measurement of transepidermal water loss (TEWL) and fluorescein dye penetration before and after a single application. OA's effects on stratum corneum (SC) lipid order in vivo were measured with infrared spectroscopy through application of perdeuterated OA (OA-d34 ). Studies of the interaction of OA and GT with skin lipids included imaging the distribution of OA-d34 and GT ex vivo with IR microspectroscopy and thermodynamic analysis of mixtures in aqueous monolayers. The oil mixtures increased both TEWL and fluorescein penetration 24 h after a single application in an OA dose-dependent manner, with the highest increase from treatment with pure OA. OA-d34 penetrated into skin and disordered SC lipids. Furthermore, the ex vivo IR imaging studies showed that OA-d34 permeated to the dermal/epidermal junction while GT remained in the SC. The monolayer experiments showed preferential interspecies interactions between OA and SC lipids, while the mixing between GT and SC lipids was not thermodynamically preferred. The FFA component of plant oils may disrupt skin barrier function. The affinity between plant oil components and SC lipids likely determines the extent of their penetration and clinically measurable effects on skin barrier functions.

Trans-11 vaccenic acid reduces hepatic lipogenesis and chylomicron secretion in JCR:LA-cp rats.

Trans-11 vaccenic acid (VA) is the predominant trans isomer in ruminant fat and a major precursor to the endogenous synthesis of cis9,trans11-conjugated linoleic acid in humans and animals. We have previously shown that 3-wk VA supplementation has a triglyceride (TG)-lowering effect in a rat model of dyslipidemia, obesity, and metabolic syndrome (JCR:LA-cp rats). The objective of this study was to assess the chronic effect (16 wk) of VA on lipid homeostasis in both the liver and intestine in obese JCR:LA-cp rats. Plasma TG (P < 0.001), total cholesterol (P < 0.001), LDL cholesterol (P < 0.01), and nonesterified fatty acid concentrations, as well as the serum haptoglobin concentration, were all lower in obese rats fed the VA diet compared with obese controls (P < 0.05). In addition, there was a decrease in the postprandial plasma apolipoprotein (apo)B48 area under the curve (P < 0.05) for VA-treated obese rats compared with obese controls. The hepatic TG concentration and the relative abundance of fatty acid synthase and acetyl-CoA carboxylase proteins were all lower (P < 0.05) in the VA-treated group compared with obese controls. Following acute gastrointestinal infusion of a VA-triolein emulsion in obese rats that had been fed the control diet for 3 wk, the TG concentration was reduced by 40% (P < 0.05) and the number of chylomicron (CM) particles (apoB48) in nascent mesenteric lymph was reduced by 30% (P < 0.01) relative to rats infused with a triolein emulsion alone. In conclusion, chronic VA supplementation significantly improved dyslipidemia in both the food-deprived and postprandial state in JCR:LA-cp rats. The appreciable hypolipidemic benefits of VA may be attributed to a reduction in both intestinal CM and hepatic de novo lipogenesis pathways.

Impairment of 8-iso-PGF(2ALPHA) isoprostane metabolism by dietary conjugated linoleic acid (CLA).

8-iso-PGF(2alpha) isoprostane (IP) is one of the most-used markers of lipid peroxidation in experimental models and humans. After its formation, it is promptly metabolized to 2,3 dinor (DIN) in peroxisomes. Conjugated linoleic acid (CLA) is preferentially beta-oxidized in peroxisomes which may compete with IP, and thereby may affect its metabolism. In order to verify whether CLA is able to influence IP formation and/or metabolism and to explain the mechanism, we challenged rats supplemented with CLA or with triolein (as a control fatty acid), with a single dose of carbon tetrachloride (CCl(4)) or of bacterial lipopolysaccharide (LPS). The results showed that IP and its precursor arachidonic acid hydroperoxide, as well as malondialdehyde (MDA), increase significantly in the liver of rats challenged with CCl(4), irrespective of the diet, while in LPS-treated rats only nitrites in liver and isoprostane in plasma increase. On the other hand, the peroxisomal beta-oxidation products of IP, the DIN, is significantly lower in the CLA group with respect to control and triolein groups. To further investigate whether this is due to competition between CLA and IP at the cellular level, we incubated human fibroblasts from healthy subjects or patients with adrenoleukodystrophy (ALD), with CLA and/or commercially available IP. The rationale of this approach is based on the deficient peroxisomal beta-oxidation of fibroblasts from ALD patients, leading to a reduced formation of DIN. In both normal and ALD cells, the presence of CLA significantly inhibits the formation of DIN from IP. We may conclude that both in vitro and in vivo studies strongly suggest that CLA may impair IP catabolism in peroxisomes. Consequently an increase of IP, as a sole result of CLA intake, cannot be considered as a marker of lipid peroxidation.

The effect of Lorenzo's oil on oxidative stress in X-linked adrenoleukodystrophy.

X-linked adrenoleukodystrophy (X-ALD) is a peroxisomal disorder biochemically characterized by the accumulation of very long chain fatty acids (VLCFA), particularly hexacosanoic acid (C(26:0)) and tetracosanoic acid (C(24:0)), in tissues and biological fluids. Although patients affected by this disorder predominantly present central and peripheral demyelination as well as adrenal insufficiency, the mechanisms underlying the brain damage in X-ALD are poorly known. The current treatment of X-ALD with glyceroltrioleate (C(18:1))/glyceroltrierucate (C(22:1)) (Lorenzo's oil, LO) combined with a VLCFA-poor diet normalizes VLCFA concentrations, but the neurological symptoms persist or even progress in symptomatic patients. Considering that free radical generation is involved in various neurodegenerative disorders and that in a previous study we showed evidence that oxidative stress is probably involved in the pathophysiology of X-ALD symptomatic patients, in the present study we evaluated various oxidative stress parameters, namely thiobarbituric acid reactive species (TBA-RS) and total antioxidant reactivity (TAR) in plasma, as well as the activities of the antioxidant enzymes catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx) in erythrocytes from symptomatic and asymptomatic X-ALD patients and verified whether LO treatment and a VLCFA restricted diet could change these parameters. We observed a significant increase of plasma TBA-RS in symptomatic and asymptomatic X-ALD patients, reflecting induction of lipid peroxidation even before the disease was manifested. In addition, LO treatment did not alter this profile. Furthermore, plasma TAR measurement of X-ALD patients was not different from that of controls. Similarly, the antioxidant enzyme activities CAT, SOD and GPx were not altered in erythrocyte from X-ALD patients as compared to controls. We also examined the in vitro effects of hexacosanoic acid (C(26:0)) and tetracosanoic acid (C(24:0)) alone or combined with oleic (C(18:1))/erucic (C(22:1)) acids on various oxidative stress parameters in cerebral cortex of young rats, namely chemiluminescence, TBA-RS, TAR, CAT, SOD and GPx in order to investigate whether those fatty acids were able to induce oxidative stress. We found that there was a significant increase of TBARS and of chemiluminescence in rat cerebral cortex exposed to C(26:0)/C(24:0), and that the addition of C(18:1)and C(22:1) to the assays did not prevent this effect. Furthermore, TAR measurement was not altered by C(26:0) and C(24:0) acids in rat cerebral cortex. Taken together, our results indicate that lipid peroxidation occurs in X-ALD and that LO treatment does not attenuate or prevent free radical generation in these patients. Therefore, it may be presumed that antioxidants should be considered as an adjuvant therapy for X-ALD patients.

Dietary TAG source and level affect performance and lipase expression in larval sea bass (Dicentrarchus labrax).

The influence of dietary TAG source (fish oil, triolein, and coconut oil) and level (7.5 and 15% of the diet) on growth, lipase activity, and mRNA level was studied in sea bass larvae, from mouth opening until day 24 and from day 37 to 52. Fish oil and triolein induced better growth in both experiments, this being significant at a higher dietary level. Coconut oil significantly decreased growth at the higher level, possibly as the result of an excessive supply of medium-chain TAG. Growth was not related to lipase specific activity, suggesting a production in excess to dietary needs. Body lipid content was positively related to dietary lipid level and was affected by lipid quality. In addition, larval FA composition generally reflected that of the diet. The source of dietary lipid, but not the quantity, was shown to affect lipase activity significantly. Coconut oil diets induced the highest lipase activity, whereas the effect of fish oil was age dependent-it was similar to coconut oil at day 24 but induced the lowest lipase activity in 52-d-old larvae. The differential lipase response was probably caused by differences in the FA composition of the diet, related to the specificity of lipase toward FA differing in chain length and degree of saturation. No significant differences were found in lipase/glyceraldehyde-3-phosphate dehydrogenase mRNA, which suggests the existence of a posttranscriptional regulation mechanism.

Identification, cloning, expression, and purification of three novel human calcium-independent phospholipase A2 family members possessing triacylglycerol lipase and acylglycerol transacylase activities.

Genetic knockout of hormone-sensitive lipase in mice has implicated the presence of other intracellular triacylglycerol (TAG) lipases mediating TAG hydrolysis in adipocytes. Despite intense interest in these TAG lipases, their molecular identities thus far are largely unknown. Sequence data base searches for proteins containing calcium-independent phospholipase A2 (iPLA2) dual signature nucleotide ((G/A)XGXXG) and lipase (GXSXG) consensus sequence motifs identified a novel subfamily of three putative iPLA2/lipase family members designated iPLA2epsilon, iPLA2zeta, and iPLA2eta (previously named adiponutrin, TTS-2.2, and GS2, respectively) of previously unknown catalytic function. Herein we describe the cloning, heterologous expression, and affinity purification of the three human isoforms of this iPLA2 subfamily in Sf9 cells, and we demonstrate that each possesses abundant TAG lipase activity. Moreover, iPLA2epsilon, iPLA2zeta, and iPLA2eta also possess acylglycerol transacylase activity utilizing mono-olein as an acyl donor which, in the presence of mono-olein or diolein acceptors, results in the synthesis of diolein and triolein, respectively. (E)-6-(Bromomethylene)-3-(1-naphthalenyl)-2H-tetrahydropyran-2-one, a mechanism-based suicide substrate inhibitor of all known iPLA2s, inhibits the triglyceride lipase activity of each of the three isoforms similarly (IC50=0.1-0.5 microm). Quantitative PCR revealed dramatically increased expression of iPLA2epsilon and iPLA2zeta transcripts during the hormone-induced differentiation of 3T3-L1 cells into adipocytes and identified the presence of all three iPLA2 isoforms in human SW872 liposarcoma cells. Collectively, these results identify three novel TAG lipases/acylglycerol transacylases that likely participate in TAG hydrolysis and the acyl-CoA independent transacylation of acylglycerols, thereby facilitating energy mobilization and storage in adipocytes.

Diet preferences for specific fatty acids and their effect on composition of fat reserves in migratory Red-eyed Vireos (Vireo olivaceous).

Fatty acid composition of body fat in birds often differs between bird species and between seasons, and changes in diet may be responsible for this variation. We tested two related hypotheses using Red-eyed Vireos, a long-distance migratory songbird: (1) birds prefer diets with certain fatty acids, and (2) fatty acid composition of the diet primarily determines the composition of lipid reserves. During paired-choice experiments, vireos preferred semi-synthetic diets with triolein (81% digestive extraction efficiency) over diets with tristearin (54% digestive extraction efficiency) and, in general, ate more when offered diets with unsaturated fats compared to saturated fats. These results demonstrate that vireos can discriminate between diets differing only in fatty acid composition and prefer diets with long-chain unsaturated fatty acids. When vireos were fed one of two diets for 1 month, the primary fatty acids in each diet also predominated in the tissues of birds fed each diet. However, some fatty acids that were absent in the diet occurred in bird tissues (e.g., 22:4, 22:5) suggesting that selective metabolism of fatty acids along with diet composition determine the fatty acid composition of lipid reserves in migratory birds.

Free fatty acids digested from pollen and triolein in the honeybee (Apis mellifera carnica Pollmann) midgut.

Honey bees satisfy their lipid requirement by consuming pollen. The free fatty acid content of the midgut was used to quantify fat digestion. Midguts extracted from younger workers of known ages and from foragers were divided into three components: endoperitrophic region (peritrophic membrane with gut contents), extraperitrophic region and intestinal wall. Both the total amount of pollen and the amount of free fatty acids in the endoperitrophic region and in the intestinal wall depend on the bee's age. The amounts increase within the 1st 3 days of a honey bee's life, reach maxima around the age of 8 days and then decrease continuously to the lowest values, measured in forager bees. Forced feeding with triacylglycerol results in significantly higher levels of free fatty acids, especially in the endoperitrophic region, in 8-day-old bees and foragers. This indicates that lipolytic activity depends on age and that the free fatty acid content in 8-day-old bees is primarily limited by the amount and availability of lipids ingested. The results show further that fat digestion depends on the functional status of honey bees, as is the case for pollen consumption, speed of transport of pollen bolus through the alimentary canal and protein digestion.

Portal transport of long acyl chain lipids: effect of phosphatidylcholine and low infusion rates.

The transport of absorbed long acyl chain lipids in the portal vein of rats has been shown to be 39% when the duodenal input rate is 135 mumol/h glyceryl trioleate (TO) [C. M. Mansbach II, R. F. Dowell, and D. Pritchett, Am. J. Physiol. 255 (Gastrointest. Liver Physiol. 18): G530-G539, 1991]. These calculations were based on a new experimental model in which portal flux is calculated from the knowledge of portal flow and the concentration of the lipids in excess in the portal vein vs. the carotid artery. To test this model, rats were infused for 6 h with a low rate of [3H]TO (27 mumol/h) with or without phosphatidylcholine (9 mumol/h) or with [3H]TO (135 mumol/h) plus phosphatidylcholine (9 mumol/h) or with [3H]TO (135 mumol/h) plus phosphatidylcholine (9 mumol/h). In all three cases, portal flux was expected to be less. Portal transport was 16.5% of the input rate in the low-dose group, 1.4% in the high-dose group given phosphatidylcholine, and 0.5% in the low-dose plus phosphatidylcholine group. There was no net transport of fatty acid in the portal vein in any of the three cases. These data show that portal lipid transport is dependent on the lipid load and that it is greatly reduced at high loads by including phosphatidylcholine in the lipid infusion.

Inhibition of repairable DNA-damage in Escherichia coli K-12 cells recovered from various organs of nitrosamine-treated mice by vitamin A, phenethylisothiocyanate, oleic acid and triolein.

The influence of various dietary constituents--phenethylisothiocyanate (PEITC), oleic acid (OA), triolein (TO), and vitamin A (ROL)--on the genotoxic activity of nitrosamines (NDMA, NDELA, NPYR) was investigated. For this purpose differential DNA repair assays with Escherichia coli K-12 strains were performed in vitro and in vivo with mice. Under in vitro conditions (liquid holding), all compounds reduced nitrosamine induced DNA-damage in the indicator bacteria in the dose range 1-10 micrograms/ml, the ranking order of efficiency being PEITC greater than OA greater than ROL greater than or equal to TO. In animal-mediated assays, acute oral treatment with PEITC (17-150 mg/kg), 2 h before nitrosamine administration, resulted in a marked decrease of nitrosamine genotoxicity in liver, kidneys, lungs and in the blood. Also in other organs (spleen, testes) an increase in differential survival (which serves as a measure for repairable DNA damage) occurred. With ROL only a comparatively moderate antigenotoxic effect was obtained at a high dose level (250 mg/kg) under identical experimental conditions. OA (2000 mg/kg) and TO (16,000 mg/kg) were completely inactive. Upon repeated treatment (consecutive oral administration of the putative antigenotoxins over 4 days, a final treatment 24 h before nitrosamine administration) PEITC (150 mg/kg/day), ROL (80 mg/kg/day) and OA (2000 mg/kg/day) had no influence on the genotoxic effects of the nitrosamines. Repeated treatment with TO (4000-16,000 mg/kg/day) resulted in a moderate dose-dependent reduction of NDMA-induced DNA-damage in the indicator bacteria, whereas in combination with NPYR only a marginal effect was observed. Biochemical experiments indicated that the antigenotoxic effects of PEITC seen under in vivo conditions were due to inhibition of alpha-hydroxylation of the nitrosamines, whereas ROL and TO appeared not to interfere strongly with this metabolic activation step. Our results indicate that in vitro assays do only partly reflect the antigenotoxic properties of the different food constituents in vivo and that animal-mediated DNA repair assays with E. coli strains are an appropriate approach to study the effects of modifiers of nitrosamine genotoxicity in the living animal.

Dietary fatty acids temporarily alter liver very long-chain fatty acid composition in mice.

To determine the influence of dietary fatty acids on tissue very long-chain fatty acid (VLFA) composition, mice were fed four diets containing 15 g fat/100 g diet derived largely from either safflower oil, peanut oil, olive oil or glycerol trioleate oil. The diets varied widely in the composition of VLFA and other fatty acids. Digestibility of total dietary VLFA ranged from 84.6% in mice fed the glycerol trioleate diet to 96.7% in those fed the safflower oil diet. After 3 mo, the saturated VLFA composition of liver total lipids and sphingomyelin was lower in animals fed the glycerol trioleate oil diet than in mice fed most other diets. Although the saturated VLFA content of the peanut oil diet was more than 15-fold greater than that of the other diets, animals fed the peanut oil diet showed little or no selective increase in liver saturated VLFA. The VLFA composition of brain was comparable in all dietary groups. After 8 mo of feeding, the liver saturated VLFA composition tended to increase and differences between groups disappeared. Liver peroxisomal beta-oxidation of lignocerate (24:0) was similar among all dietary groups. These results demonstrate that dietary fatty acids shorter than VLFA temporarily influence the saturated VLFA composition of liver.

Effect of dietary oils on lipid peroxidation and on antioxidant parameters of rat plasma and lipoprotein fractions.

In order to investigate the influence of fatty acid pattern and antioxidants other than vitamin E on lipid peroxidation and antioxidant levels of plasma very low density and low density lipoproteins (VLDL + LDL), the effects of three diets (equalized for vitamin E) containing soybean oil, olive oil, or an oleate-rich mixture of triglycerides (triolein) were studied in rats. A significantly lower concentration of thiobarbituric acid-reactive substances (TBA-RS) in plasma and lipoproteins was found after the olive oil diet (soybean oil, 3.7 +/- 0.4 nmol/ml; triolein, 2.1 +/- 0.5 nmol/ml; olive oil, 1.5 +/- 0.3 nmol/ml, in plasma) (soybean oil, 0.99 +/- 0.16 nmol/ml; triolein, 0.96 +/- 0.13 nmol/ml; olive oil, 0.38 +/- 0.12 nmol/ml, in the VLDL + LDL fraction). Furthermore, the results from in vitro copper-induced lipid peroxidation, expressed in terms of conjugated dienes, lipid hydroperoxides, and TBA-RS content, showed that VLDL + LDL particles from olive olive oil-fed rats were remarkably resistant to oxidative modification. The results suggest that the fatty acid unsaturation of dietary oils is not the only determining factor of the antioxidant capacity of lipoproteins in this animal model. The maximal protection observed after the olive oil diet may be explained by the presence of other unidentified antioxidants in addition to vitamin E, derived from oil intake. Therefore, the optimal balance between the content of unsaturated fatty acids and natural antioxidants in dietary oils appears to be of major importance.

Regulation of polyunsaturated fatty acid metabolism in tissue phospholipids of obese (fa/fa) and lean (Fa/-) Zucker rats. 1. Effect of dietary lipids on cardiac tissue.

The present investigation addressed three questions: (i) Does the obese syndrome alter the fatty acid composition of cardiac tissue and membrane phospholipids in obese (fa/fa) rats? (ii) Are changes, if they occur, similar to those reported for tissues of the genetically obese (ob/ob) mouse? (iii) Can cardiac tissue phospholipids and their component fatty acids be modified by dietary lipids and if so does this occur to the same extent in both fa/fa and lean (Fa/-) rats? Proportions of polyunsaturated fatty acids (PUFA) in cardiac total phospholipids of fa/fa rats differed significantly from those of Fa/- rats and from those reported for ob/ob mice. Increased 18:2n-6 and decreased 20:4n-6 and 22:6n-3 in fa/fa rats indicated impaired PUFA metabolism, possibly reduced delta 6 and/or delta 5 desaturase activity, compared with Fa/- rats. No differences in hepatic delta 6 and delta 5 desaturase activity between fa/fa and Fa/- were found but enhanced activity of delta 9 desaturase activity in fa/fa as compared to Fa/- was evident. Inclusion of sunflower oil (SO) or triolein (TO) at 5% and 20% by weight in the diet elicited marked changes in the fatty acyl composition of cardiac phospholipids in both fa/fa and Fa/- rats when compared with animals fed the control Oxoid diet alone. Supplementation with triolein was most effective, reducing 18:2n-6 and increasing 20:4n-6 proportions in fa/fa rats so that they resembled those in Fa/- rats fed the control Oxoid diet. The type of fat rather than the amount of its dietary intake appears to be the main determinant of the observed changes in phospholipid composition.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of dietary triolein and sunflower oil on insulin release and lipid metabolism in Zucker rats.

Obese and lean male Zucker rats were fed ad libitum on diets containing either 50 (L) or 200 (H) g/kg diet of either triolein (T) or sunflowerseed oil (S). The specific activity of the hepatic microsomal delta 9 desaturase enzyme was depressed in both lean and obese rats fed the HS diet compared with the other three diets. The fatty acid composition of liver and subcutaneous white adipose tissue lipids were consistent with a lower delta 9 desaturation activity in rats fed the H diets, particularly for the HS diet. In both genotypes, microsomal delta 9 desaturase activity and the ratio of 16:1/(16:0 + 16:1) fatty acids in liver lipids were inversely related to the proportion of 18:2 in liver lipid. Plasma insulin concentrations and rates of glucose-stimulated insulin release in vivo were higher in obese rats compared with lean rats, and plasma insulin levels were higher in rats fed S compared with T. There was no relationship between delta 9 desaturase activity and either plasma insulin concentration or rates of insulin release in vitro. These findings suggest that hepatic delta 9 desaturase activity of Zucker rats is responsive to changes in the proportion of 18:2 in liver lipids but is not affected by changes in insulin secretion.

Factors influencing triacylglycerol delivery into mesenteric lymph.

The transport of triacylglycerol (TG) in mesenteric lymph was studied in rats with duodenal and mesenteric lymphatic cannulas with or without bile fistulas. Rats were infused with 135 mumol glycerol trioleate (TO) for 4 h, followed by 5 h of NaCl infusion. Rats with intact fistulas prefed 20% corn oil had nearly twice the maximum output of TG in lymph as controls. Decay from peak values was zero order for controls and indeterminate for rats prefed corn oil. In rats with bile fistulas, less TG was transported in lymph than in those in which 2 mM phosphatidylcholine (PC) was added to the infusate. The decay from maximum values was zero order for controls and first order for rats infused with PC and TO. Recovery of infused [3H]glycerol trioleate in controls was 43% and increased to 68% on inclusion of PC in the infusate. We conclude that in chow-fed rats lymph TG delivery rates were well below infusion rates, suggesting alternate TG transport routes, TG transport was improved by supplementing the infusate with PC or prefeeding with 20% TG in chow, and PC may be limiting in TG transport in rats with bile fistulas.

Distribution and mobility of omega 3 fatty acids in rainbow trout fed varying levels and types of dietary lipid.

The availability of essential fatty acids in fish neutral lipid to tissue phospholipids was determined under conditions of adequate and inadequate essential fatty acid intake as well as during fasting. Juvenile rainbow trout were fed a semi-purified diet containing varying levels of cod liver oil, with or without supplementary olein. Fatty acid analysis indicated that in all treatments the neutral lipid pool was not turned over during feeding but was enhanced by exogenous or endogenously synthesized fatty acids. Fish that received diets devoid of essential fatty acids maintained virtually all of the docosahexenoic acid originally present in each lipid pool. Fish fed diets containing essential fatty acids deposited them in proportion to the dietary levels. After a 4-week fast, no change was noted in the relative levels of fatty acids in neutral lipid indicating that all fatty acids in neutral lipid were catabolized equally--including essential fatty acids. During fasting there was a selective retention of docosahexenoic and linoleic acids in the phospholipid pool.

Effects of tristearin, triolein and safflower oil diets on cholesterol balance in rats.

Diets containing relatively homogeneous triglycerides composed of 18-carbon chain saturated, monounsaturated or polyunsaturated fatty acids were fed to rats. Cholesterol absorption and turnover were studied. Cholesterol absorption was significantly less in rats fed tristearin than in animals fed triolein or safflower oil. Cholesterol removal from plasma was fastest in rats fed tristearin and slowest with safflower oil and triolein. Plasma cholesterol levels were lowest with tristearin and highest with safflower oil. Increased cholesterol in high density lipoproteins was observed with tristearin and triolein. Lymph and hepatic cholesterol, and lymph triglycerides were highest with safflower oil, suggesting endogenous mobilization. Cholesterol production was least with triolein. Sterol synthesis was greatest with tristearin, perhaps attributable to decreased negative feedback analogous to effects of cholestyramine. Differences in lipoprotein composition observed with the various diets are important since effects on particle size and shape may influence removal mechanisms. The mechanisms underlying the different effects of dietary triglycerides on sterol absorption and metabolism remain to be elucidated.

A unique distribution of laxative-induced spike potentials from the small intestine of the dog.

The effects of castor oil and ricinoleic acid on small bowel electrical activity were studied in the fasted conscious dog and were compared to the effects elicited by two nonlaxative oils (triolein and oleic acid). Spike potential activity was monitored at two jejunal sites using unipolar recording electrodes. Castor oil, ricinoleic acid, and triolein produced an increased incidence of basic electrical rhythm (BER) with associated spike potentials when compared to a fasted control; however, the total electrical spiking activity produced by these oils was not statistically different from that induced by feeding. No treatment altered any of the characteristics of BER. A novel pattern of electrical spiking activity was observed in response to the laxatives. This pattern consisted of short repetitive bursts of spike potentials which migrated the length of the recording site. The laxative-induced electrical pattern persisted for several days after treatment with ricinoleic acid or castor oil, and interdigestive patterns were occasionally interrupted for as long as 72 hr. Electrical activity following feeding or the nonlaxative oils consisted of random spike potentials, and normal interdigestive electrical activity resumed within 24 hr. The laxative-induced electrical pattern was shown to be quantitatively distinct from those produced by feeding, fasting, or nonlaxative oils. This pattern may reflect an action of these laxatives on intestinal motility during a diarrheal state.