Effects of dietary medium-chain triacylglycerols on serum lipoproteins and biochemical parameters in healthy men

The objective of this study was to investigate effects of dietary medium-chain triacylglycerols (MCTs) on serum lipid levels, liver function, and hepatic fat accumulations in healthy men. Eleven subjects consumed 2200-2600 kcal daily, of which 70-80 g was fat; the fat included 40 g of MCTs or else 40 g of long-chain triacylglycerols (blended vegetable oil). The diet was followed for 4 weeks in this controlled double-blind study. At the end of the experiment, significant differences were not found in the concentrations of serum total cholesterol, very low density lipoprotein cholesterol, low density lipoprotein cholesterol, and high density lipoprotein cholesterol between the groups. Serum triglycerol levels were not significantly different in the groups. Adverse effects from ingestion of MCTs on liver functions, the liver-to-spleen ratio on computed tomography (an index of fatty liver), or results of blood tests were not seen. The results suggest that the long-term effects of dietary MCTs on serum cholesterol were similar to those of unsaturated fatty acids found abundantly in vegetable oil, and that consumption of MCTs in the amount of 40 g/day for a month does not cause liver fat accumulation or liver dysfunction.     

Peripheral oestrogen metabolism in postmenopausal women with or without breast cancer: the role of dietary lipids and growth factors

Studies we have carried out have revealed significant differences in oestrogen production and metabolism between normal women and postmenopausal women with breast cancer. The free, biologically available fraction of oestradiol is elevated in plasma from women with breast cancer and we have found that metabolic clearance rates and production rates of oestradiol are also increased. In vitro studies have suggested that lipids can influence the distribution of sex steroids in plasma and we have therefore examined the effect of dietary lipids on the distribution of sex steroids in plasma in vivo. Consumption of a meal with a high saturated fat content or the oral or i.v. administration of "Intralipid", a stabilised emulsion of soya bean oil that is high in unsaturated free fatty acids, had little effect on the available fractions of oestradiol in plasma. However, results from a preliminary study suggest that long-term changes in dietary fat intake can alter the distribution of steroids in plasma. It is concluded that dietary lipids may influence the availability of sex steroids to tissues. Such a mechanism could account for the significant correlation that has been found between dietary fat consumption and the incidence of breast cancer on a world-wide basis.     

Comparative evaluation of rumen‐protected fat,coconut oil and various oilseeds supplemented to fattening bulls

The effects of five different dietary fat supplements on fatty acid composition and oxidative stability of subcutaneous and kidney fat were evaluated in 36 Brown Swiss bulls and compared to a low fat diet in a monofactorial design. The following fat supplements were provided as additional fat at 30 g per kg feed dry matter: crystalline rumen‐protected fat, coconut oil, and three types of crushed whole oilseeds (rapeseed, sunflower seed and linseed). Adipose tissues reflected differences (P < 0.05) in dietary fatty acid composition although to a lower extent. Using protected fat, which contained elevated levels of trans fatty acids, and sunflower seed, containing a high proportion of linoleic acid, significantly increased C18:1 trans fatty acid proportion in the adipose tissues. The use of sunflower seed increased conjugated linoleic acid. The oilseeds resulted in lower amounts of C16:0 in favour of C18:0. Except for linseed, all fat supplemented groups improved oxidative stability of adipose tissues as compared with control. This was explained by lower proportions of unsaturated fatty acids in adipose tissue (protected fat), by elevated α‐tocopherol contents (rapeseed, sunflower seed) or by a combination of both (coconut oil). Fat colour remained unaffected by treatments. Compared to other fat supplements oilseeds, especially sunflower seed and rapeseed, can therefore be recommended to be fed to bulls in order to increase the proportions of C18 unsaturated fatty acids in adipose tissues and to maintain or improve oxidative stability.     

Replacement of Dietary Saturated Fat by PUFA-Rich Pumpkin Seed Oil Attenuates Non-Alcoholic Fatty Liver Disease and Atherosclerosis Development,with Additional Health Effects of Virgin over Refined Oil

Background and Aims

As dietary saturated fatty acids are associated with metabolic and cardiovascular disease, a potentially interesting strategy to reduce disease risk is modification of the quality of fat consumed. Vegetable oils represent an attractive target for intervention, as they largely determine the intake of dietary fats. Furthermore, besides potential health effects conferred by the type of fatty acids in a vegetable oil, other minor components (e.g. phytochemicals) may also have health benefits. Here, we investigated the potential long-term health effects of isocaloric substitution of dietary fat (i.e. partial replacement of saturated by unsaturated fats), as well as putative additional effects of phytochemicals present in unrefined (virgin) oil on development of non-alcoholic fatty liver disease (NAFLD) and associated atherosclerosis. For this, we used pumpkin seed oil, because it is high in unsaturated fatty acids and a rich source of phytochemicals.

Methods

ApoE*3Leiden mice were fed a Western-type diet (CON) containing cocoa butter (15% w/w) and cholesterol (1% w/w) for 20 weeks to induce risk factors and disease endpoints. In separate groups, cocoa butter was replaced by refined (REF) or virgin (VIR) pumpkin seed oil (comparable in fatty acid composition, but different in phytochemical content).

Results

Both oils improved dyslipidaemia, with decreased (V)LDL-cholesterol and triglyceride levels in comparison with CON, and additional cholesterol-lowering effects of VIR over REF. While REF did not affect plasma inflammatory markers, VIR reduced circulating serum amyloid A and soluble vascular adhesion molecule-1. NAFLD and atherosclerosis development was modestly reduced in REF, and VIR strongly decreased liver steatosis and inflammation as well as atherosclerotic lesion area and severity.

Conclusions

Overall, we show that an isocaloric switch from a diet rich in saturated fat to a diet rich in unsaturated fat can attenuate NAFLD and atherosclerosis development. Phytochemical-rich virgin pumpkin seed oil exerts additional anti-inflammatory effects resulting in more pronounced health effects.     

Influence of dietary fatty acids composition, level of dietary fat and feeding period on some parameters of androgen metabolism in male rats

The aim of the present study was to determine the effect of the composition of dietary fatty acids, the duration of feeding period and dietary fat level on androgen metabolism in male rats. One hundred and twelve Wistar rats were divided into 18 groups which were fed three diets containing different types of fat (rapeseed [R], palm [P] and fish [F] oil) at either normal fat level (w/w; 5%) or high fat level (20%) during one, three or six weeks. Blood plasma level of androgen (testosterone+dihydrotestosterone) and testicular activity of 17beta-hydroxysteroid dehydrogenase (17beta-HSD) were investigated. In addition, androgen content in cytosol of the heart, the target organ, was measured. Androgen concentration in both blood plasma and heart cytosol extracts was measured by radioimmunoassay. The activity of 17Beta-HSD was expressed as a conversion of [3H]androstendione to [3H]testosterone in soluble fraction of gonadal homogenates. Plasma androgen concentration was influenced by a type of dietary fat (p<0.05). The highest plasma level of androgen was observed in animals fed R diets rich in unsaturated fatty acids. Significantly lower androgen concentration was demonstrated in rats fed P diets rich in saturated fatty acids. Only the feeding period factor significantly influenced androgen content in cytosol fraction of heart muscle cells (p<0.01). A positive correlation was found between plasma androgen concentration in plasma and cytosol fraction of the heart muscle cells (r=0.63, p<0.001). The feeding period (p<0.001) and dietary fat type (p<0.05) significantly affected the activity of 17beta-HSD. The least 17beta-HSD activity was observed in animals consuming the P-20% diet for six weeks. In summary, dietary fat type and feeding period, but not fat level, significantly affected both testosterone production and testosterone uptake by the target organ in male rats. It was found that a rapeseed diet rich in unsaturated fatty acids stimulated the testicular function in rats.     

Response of rat heart membranes and associated ion-transporting ATPases to dietary lipid

The effects of different dietary fat intake on the lipid composition and enzyme behaviour of sarcolemmal (Na+ + K+)ATPase and sarcoplasmic reticulum Ca2+-ATPase from rat heart were investigated. Rat diets were supplemented with either sunflower seed oil (unsatd./satd. 5.6) or sheep kidney fat (unsatd./satd. 0.8). Significant changes in the phospholipid fatty acid composition were observed in both membranes after 9 weeks dietary lipid treatment. For both membranes, the total saturated/unsaturated fatty acid levels were unaffected by the dietary lipid treatment, however the proportions of the major unsaturated fatty acids were altered. Animals fed the sunflower seed oil diet exhibited an increase in n-6 fatty acids, including linoleic (18:2(n-6] and arachidonic (20:4(n-6] while the sheep kidney fat dietary rats were higher in n-3 fatty acids, principally docosahexaenoic (22:6), with the net result being a higher n-6/n-3 ratio in the sunflower seed oil group compared to sheep kidney fat dietary animals. Fluorescence polarization indicated that the fluidity of sarcoplasmic reticular membrane was greater than that of sarcolemmal membrane, with a dietary lipid-induced decrease in fluidity being observed in the sarcoplasmic reticular membrane from sheep kidney fat dietary animals. Despite these significant changes in membrane composition and physical properties, neither the specific activity nor the temperature-activity relationship (Arrhenius profile) of the associated ATPases were altered. These results suggest that with regard to the parameters measured in this study, the two ion-transporting ATPases are not modulated by changes which occur in the membrane lipid composition as a result of the diet.     

Nutritional factors affecting quantity and quality of carcass fat in chickens.

Nonpathological fattening of a bird occurs when the amount of energy consumed exceeds its requirements for maintenance and growth. Dietary energy and protein levels, particularly the ratio of these two, are the main dietary factors affecting fatness. Consumption of diets low in protein results in excess energy intake and an increased hepatic lipogenesis. Excess protein has the opposite effect. It also increases the energy expenditure required to dispose of excess amino acids in the body. Severe deficiency of a specific amino acid does not increase fattening. The degree of fattening, particularly of the liver, induced by corticosterone injection is greater in birds fed diets containing a wide energy-to-protein ratio in comparison to a narrow ratio. The content of dietary fat per se does not affect carcass fat concentration although it alters the rate of liver fatty acid synthesis. The dietary fatty acid composition affects the composition of tissue fatty acids. Consumption of diets containing vegetable oils or high in protein increases the degree of unsaturation of tissue fat and thereby its susceptibility to oxidation. Dietary dl-alpha-tocopheryl acetate increases the stability of the lipids of adipose and muscle tissue of chicks with relatively saturated body fat, but the dietary effectiveness of this vitamin in improving the stability of tissues of birds having relatively unsaturated fat is limited.     

Dietary fatty acid composition affects the repeat swimming performance of Atlantic salmon in seawater

Repeated critical swimming performance trials (Ucrit) were performed on Atlantic salmon (Salmo salar) to test the null hypothesis that the source of dietary lipids (fish-based, poultry-based, and plant-based) does not influence exercise and recovery performance. Four diets were prepared by extensively replacing supplemental lipid from anchovy oil (AO; 100% AO at 150 g/kg) with cold pressed flaxseed oil (FO; 25% AO, 75% FO), sunflower oil (SO; 25% AO, 75% SO), or poultry fat (PF; 25% AO, 75% PF). These diets had equivalent protein and energy concentrations, but due to the different supplemental lipid sources, varied widely in their fatty acid composition. Fish fed AO had a significantly higher (P<0.05) first Ucrit (2.62+/-0.07 body lenght s(-1)) than those fed PF (2.22+/-0.12 body lenght s(-1)) that had low muscle ratios of n-3 highly unsaturated fatty acids (n-3 HUFA) to saturated fatty acids (SFA) and arachidonic acid (AA), and high levels of oleic acid. Fish in the FO and SO diet groups swam as well as AO-fed fish in both swimming trials. The performance of fish fed AO decreased significantly (P<0.05) during the second swimming trial (i.e. Ucrit2/Ucrit1=0.92+/-0.02). No significant differences occurred between diet groups for the second swim trial. There was a positive correlation between both n-3 HUFA/SFA and n-3 HUFA/AA ratios, and Ucrit1. A negative correlation was found between dietary AA and oleic acids, and Ucrit1. The present study suggests that low dietary n-3 HUFA/ SFA and n-3 HUFA/AA ratios may negatively affect swimming performance. The former possibly can be offset by increasing linoleic acid in the presence of nutritionally adequate n-3 HUFA (e.g. SO diet). Lipid supplements consisting largely of vegetable oils did not compromise fish cardiorespiratory physiology under the conditions of this study.     

Interconversion between Rotenone and Dalpanol

Photosensitized oxidation of trioleoylglycerol (TO), trilinoleoylglycerol (TL), trilinolenoylglycerol (TLn) and vegetable oil triacylglycerols (triglycerides, TG) was carried out in isopropanol using methylene blue as a photosensitizer. Isomeric compositions of hydroperoxy fatty acid components of the oxidized TG were determined by hydrogenation, methanolysis and mass chromatographic analysis of the resulting methyl hydroxy octadecanoate. TO gave 9- and 10-isomers; TL, 9-, 10-, 12- and 13-isomers; and TLn, 9-, 10-, 12-, 13-, 15- and 16-isomers. It was concluded that each unsaturated fatty acid component of vegetable oil TG yields isomeric hydroperoxides during photosensitized oxidation in a manner similar to the corresponding unsaturated fatty acid methyl ester. TL monohydroperoxides were isolated from the photooxidized TL and hydrolyzed by pancreatic lipase. The hydrolysis products consisted of dilinoleoylglycerol, monolinoleoylglycerol, linoleic acid and their respective hydroperoxides. Formation of a hydroperoxy fatty acid component was observed during photoirradiation of vegetable oils in the bulk phase without methylene blue. The isomeric compositions of the resulting methyl hydroxy octadecanoate support the idea that singlet oxygen is responsible for the formation of hydroperoxides in the initial stage of photooxidation.     

The influence of dietary lipid supplementation on cardiac beta-adrenergic receptor adenylate cyclase activity in the marmoset monkey

Dietary lipid supplements high in either saturated fat derived from sheep kidney fat or unsaturated fat derived from sunflower seed oil, and a low mixed fat reference diet were fed to marmoset monkeys for 20 months and the effects on cardiac membrane lipid composition, and myocardial catecholamine-stimulated adenylate cyclase and beta-adrenergic receptor binding activity were investigated. For cardiac membranes enriched for beta-adrenergic binding activity, the dietary lipid treatment resulted in small changes in the proportion of saturated to unsaturated fatty acids and substantial changes in the (n - 6) to (n - 3) series of unsaturated fatty acids in the membrane phospholipids. The sheep kidney fat diet increased the cholesterol-to-phospholipid ratio in cardiac membranes in comparison to the other diets. This diet also significantly elevated basal and isoproterenol-, epinephrine- and norepinephrine-stimulated adenylate cyclase activity. The value of the dissociation constant (Kd) and the receptor number (Bmax) for the binding of [125I]ICYP to the beta-adrenergic receptor was significantly reduced in marmosets fed the sheep kidney fat diet. These results suggest that dietary lipids can influence the activity of the beta-adrenergic/adenylate cyclase system of the heart. Modulation of this transmembrane signalling system may be induced by changes in the properties of the associated membrane lipids, particularly by alteration in the membrane cholesterol-to-phospholipid ratio. This effect may be limited to those animal species in which the nature of the dietary fatty acid intake may be influencing cardiac membrane cholesterol homeostasis, which is in agreement with previous results in rats following dietary cholesterol supplementation (McMurchie et al. (1987) Biochim. Biophys. Acta 898, 137-153). ICYP, (-)-iodocyanopindolol.     

Sensitivity to alcohol in mice with an altered brain fatty acid composition

Ethanol-induced sleep onset times, sleep times and blood alcohol levels upon awakening were measured in mice fed an essential fatty acid deficient, Purina Chow or unsaturated fat diet for nine months. These values in animals fed the essential fatty acid deficient and Purina Chow diets did not differ, but mice fed the unsaturated fat diet had longer sleep times and lower blood alcohol levels upon awakening than mice fed essential fatty acid deficient or Purina Chow diets. Crude brain mitochondrial fractions isolated from mice fed the essential fatty acid deficient diet had decreased levels of docosahexaenoic [22:6(n-3)] and increased levels of eicosatrienoic [20:3(n-9)], docosatrienoic [22:3(n-9)] and docosapentaenoic [22:5(n-6)] acids compared to mice fed the Purina Chow diet. The unsaturated fat diet decreased 22:6(n-3) and increased 22:5(n-6) compared to the Purina Chow dietary regimen. The longer sleep times and lower blood alcohol levels found in mice fed the unsaturated fat diet probably resulted from an artifact due to the obesity of the mice fed this diet and from the hinderance of obesity to the righting reflex (our measure of ethanol potency). We conclude that the alteration of several polyunsaturated fatty acid components in the brain has little or no influence on the sensitivity of the nervous system to alcohol.     

Lipid diet and enterocyte microsomal membrane fluidity in rats

Rats were fed on diets more or less enriched with n-3 and n-6 unsaturated fatty acids, before removal of the small intestine. The global protein, cholesterol and phospholipid contents of enterocyte microsomes were measured. Fatty acids of the total lipid extracts were determined. Acyl coenzyme A: cholesterol acyl transferase (ACAT) was chosen as the enzyme whose activity reflects metabolic changes induced by lipid diets. Fluorescence measurements using diphenylhexatriene as the membrane probe were performed. As dietary fat may change the fatty acid composition of membranes, the order parameter S calculated from fluorescence measurements was studied with regard to dietary fatty acid composition. The S values, distributed over a large range, were not different between rat groups. They were positively correlated with the ratios of cholesterol and proteins to phospholipids and the molar percentage of saturated fatty acids. ACAT activity was negatively correlated with S. Variations in S values among rats, whatever the diet, could in part be attributed to individual factors.     

Lipid peroxidation in the rat-liver S9 fraction: influence of membrane lipid composition

These studies describe the influence of membrane fatty acid composition on peroxidation processes in rat-liver S9 fractions. Lipid peroxidation may be expected to affect enzyme activity and cofactors of importance for the performance of the Salmonella Mutagenicity Test, as well as to contribute to the formation of chemically reactive degradation products that are mutagenic. Lipid peroxidation products were measured as derivatives of 2-thiobarbituric acid (TBA). The amount of TBA-reactive compounds (TBA-C), formed during incubation of S9 fractions from rats fed a diet containing sunflower-seed oil, was 8 times higher than that produced in S9 fractions prepared from rats fed diets containing coconut oil or hydrogenated lard as their only sources of fat. S9 fractions from livers of Aroclor 1254 treated rats showed a marked increase in peroxidation yields for all 3 dietary groups investigated as compared to S9 fractions from non-induced animals. The coconut oil and hydrogenated lard dietary groups showed a 13-fold increase in the yield of TBA-reactive material, while a 2-fold increase was found for the sunflower-seed oil group. The variations in the glutathione (GSH) levels and the degradation of unsaturated fatty acids were also studied in response to Aroclor 1254 treatment, fatty acid composition of the diets and incubation at 37 degrees C. Pronounced variations in the GSH levels were observed in response to Aroclor 1254 treatment and incubation conditions. A positive correlation between production of TBA-reactive material and degradation of unsaturated fatty acids was verified for S9 fractions from the coconut oil and hydrogenated lard dietary groups. Furthermore, the effect of Fe2+ on lipid peroxidation was studied in all 3 dietary groups. The rate of lipid peroxidation was increased in all groups but only the coconut oil and hydrogenated lard dietary groups showed increased total yields of TBA-C upon administration of Aroclor 1254 to rats. Lipid peroxidation processes cause chemical alterations in liver homogenates. Therefore, these effects ought to be considered both in the preparation and in the use of the S9 fraction in different test systems.     

The interaction of dietary fatty acid and cholesterol on catecholamine-stimulated adenylate cyclase activity in the rat heart

Diets supplemented with high levels of saturated or unsaturated fatty acids supplied by addition of sheep kidney fat or sunflower seed oil, respectively, were fed to rats with or without dietary cholesterol. The effects of these diets on cardiac membrane lipid composition, catecholamine-stimulated adenylate cyclase and beta-adrenergic receptor activity associated with cardiac membranes, were determined. The fatty acid-supplemented diets, either with or without cholesterol, resulted in alterations in the proportion of the (n-6) to (n-3) series of unsaturated fatty acids, with the sunflower seed oil increasing and the sheep kidney fat decreasing this ratio, but did not by themselves significantly alter the ratio of saturated to unsaturated fatty acids. However, cholesterol supplementation resulted in a decrease in the proportion of saturated and polyunsaturated fatty acids and a dramatic increase in oleic acid in cardiac membrane phospholipids irrespective of the nature of the dietary fatty acid supplement. The cholesterol/phospholipid ratio of cardiac membrane lipids was also markedly increased with dietary cholesterol supplementation. Although relatively unaffected by the nature of the dietary fatty acid supplement, catecholamine-stimulated adenylate cyclase activity was significantly increased with dietary cholesterol supplementation and was positively correlated with the value of the membrane cholesterol/phospholipid ratio. Although the dissociation constant for the beta-adrenergic receptor, determined by [125I](-)-iodocyanopindolol binding, was unaffected by the nature of the dietary lipid supplement, the number of beta-adrenergic receptors was dramatically reduced by dietary cholesterol and negatively correlated with the value of the membrane cholesterol/phospholipid ratio. These results indicate that the activity of the membrane-associated beta-adrenergic/adenylate cyclase system of the heart can be influenced by dietary lipids particularly those altering the membrane cholesterol/phospholipid ratio and presumably membrane physico-chemical properties. In the face of these dietary-induced changes, a degree of homeostasis was apparent both with regard to membrane fatty acid composition in response to an altered membrane cholesterol/phospholipid ratio, and to down regulation of the beta-adrenergic receptor in response to enhanced catecholamine-stimulated adenylate cyclase activity.     

Phospholipid and triacylglycerol fatty acid composition of major life stages of sunn pest,Eurygaster integriceps (Heteroptera: Scutelleridae)

Phospholipid and triacylglycerol fatty acid compositions of whole animals from all life stages of Eurygaster integriceps, including eggs, nymphs, pre-diapausing adults and diapausing adults, were determined. The fatty acid composition of total lipids of their food, wheat, was also determined. The major components of the insects and their food were the expected C16 and C18 saturated and unsaturated fatty acids. Since fatty acid compositions of third-stadium nymphs were not similar to the profiles of their food, most likely, dietary fatty acids are modified by the insect. The fact is that the food does not provide C20 polyunsaturated fatty acids, but the insect tissue lipids include these components. We suggest biosynthesis of the C20 components by elongation/desaturation of C18:2n-6, an abundant component of the diets. We also show differences in fatty acid profiles from each of the life stages.     

The effect of dietary lipids on the thermotropic behaviour of rat liver and heart mitochondrial membrane lipids

Diets supplemented with relatively high levels of either saturated fatty acids derived from sheep kidney fat (sheep kidney fat diet) or unsaturated fatty acids derived from sunflower seed oil (sunflower seed oil diet) were fed to rats for a period of 16 weeks and changes in the thermotropic behaviour of liver and heart mitochondrial lipids were determined by differential scanning calorimetry (DSC). The diets induced similar changes in the fatty acid composition in both liver and heart mitochondrial lipids, the major change being the omega 6 to omega 3 unsaturated fatty acid ratio, which was elevated in mitochondria from animals on the sunflower seed oil diet and lowered with the mitochondria from the sheep kidney fat dietary animals. When examined by DSC, aqueous buffer dispersions of liver and heart mitochondrial lipids exhibited two independent, reversible phase transitions and in some instances a third highly unstable transition. The dietary lipid treatments had their major effect of the temperature at which the lower phase transition occurred, there being an inverse relationship between the transition temperature and the omega 6 to omega 3 unsaturated fatty acid ratio. No significant effect was observed for the temperature of the higher phase transition. These results indicate that certain domains of mitochondrial lipids, probably containing some relatively higher melting-point lipids, independently undergo formation of the solidus or gel phase and this phenomenon is not greatly influenced by the lipid composition of the mitochondrial membranes. Conversely, other domains, representing the bulk of the membrane lipids and which probably contain the relatively lower melting point lipids, undergo solidus phase formation at temperatures which reflect changes in the membrane lipid composition which are in turn, a reflection of the nature of the dietary lipid intake. These lipid phase transitions do not appear to correlate directly with those events considered responsible for the altered Arrhenius kinetics of various mitochondrial membrane-associated enzymes.     

Differential modulation of rat heart mitochondrial membrane-associated enzymes by dietary lipid

Diets supplemented with high levels of saturated fatty acids derived from sheep kidney (perirenal) fat or unsaturated fatty acids derived from sunflower seed oil were fed to rats and the effect on heart mitochondrial lipid composition and membrane-associated enzyme behaviour was determined. The dietary lipid treatments did not change the overall level of membrane lipid unsaturation but did alter the proportion of various unsaturated fatty acids. This led to a change in the omega 6/omega 3 unsaturated fatty acid ratio, which was highest in the sunflower seed oil fed rats. Arrhenius plots of the mitochondrial membrane associated enzymes succinate-cytochrome c reductase and oligomycin-sensitive adenosinetriphosphatase (ATPase) after dietary lipid treatment revealed different responses in their critical temperature. For succinate-cytochrome c reductase, the critical temperature was 29 degrees C for rats fed the sheep kidney fat diet and 20 degrees C for rats fed the sunflower seed oil diet. In contrast, no shift in the critical temperature for the mitochondrial ATPase was apparent as a result of the differing dietary lipid treatments. The results suggest that the discontinuity in the Arrhenius plot of succinate-cytochrome c reductase is induced by some change in the physical properties of the membrane lipids. In contrast, mitochondrial ATPase appears insensitive, in terms of its thermal behaviour, to changes occurring in the composition of the membrane lipids. However, the specific activity of the mitochondrial ATPase was affected by the dietary lipid treatment being highest for the rats fed the sheep kidney fat diet. No dietary lipid effect was observed for the specific activity of succinate-cytochrome c reductase. This differential response of the two mitochondrial membrane enzymes to dietary-induced changes in membrane lipid composition may affect mitochondrial oxidative phosphorylation.     

Dietary myristic acid at physiologically relevant levels increases the tissue content of C20:5 n-3 and C20:3 n-6 in the rat

This study was designed to investigate the effect of myristic acid on the biosynthesis and metabolism of highly unsaturated fatty acids, when it is supplied in a narrow physiological range in the diet of the rat (0.2-1.2% of total dietary energy). Three experimental diets were designed, containing 22% of total dietary energy as lipids and increasing doses of myristic acid (0.71, 3.00 and 5.57% of total fatty acids). Saturated fat did not exceed 31% of total fat and the C18:3 n-3 amount in each diet was strictly equal (1.6% of total fatty acids). After 7 weeks, the diets had no effect on plasma cholesterol level but greatly modified the liver, plasma and adipose tissue saturated, monounsaturated and polyunsaturated fatty acid profiles. Firstly, daily intakes of myristic acid resulted in a dose-dependent tissue accumulation of myristic acid itself. Palmitic acid was significantly increased in the tissues of the rats fed the higher dose of myristic acid. A dose-response accumulation of tissue C16:1 n-7 as a function of dietary C14:0 was also shown. Secondly, a main finding was that, among n-3 and n-6 polyunsaturated fatty acids, a dose-response accumulation of liver and plasma C20:5 n-3 and C20:3 n-6 (two precursors of eicosanoids) as a function of dietary C14:0 was shown. This result suggests that dietary myristic acid may participate in the regulation of highly unsaturated fatty acid biosynthesis and metabolism.     

Clostridium perfringens challenge and dietary fat type affect broiler chicken performance and fermentation in the gastrointestinal tract

The aim of the present work was to examine how different fats commonly used in the feed industry affect broiler performance, nutrient digestibility and microbial fermentation in the gastrointestinal tract of broiler chickens challenged with virulent Clostridium perfringens strains. Two experiments were carried out, each including 480-day-old male broilers (Ross 308), which were randomly distributed to eight experimental groups using six replicate pens per treatment and 10 birds per pen. In Experiment 1, birds were fed diets containing soybean oil, palm kernel fatty acid distillers, rendered pork fat and lard. In Experiment 2, birds were fed diets containing rapeseed oil, coconut oil, beef tallow and palm oil. In both experiments, the birds were either not challenged or challenged with a mixture of three C. perfringens type A strains. Irrespective of the fat type present in the diet, C. perfringens did not affect broiler chicken body weight gain (BWG) and mortality in either of the two experiments. The BWG was affected by dietary fat type in both experiments, indicating that the fatty acid composition of the fat source affects broiler growth performance. In particular, the inclusion of animal fats tended to improve final BW to a greater extent compared with the inclusion of unsaturated vegetable oils. In Experiment 2, irrespective of the dietary fat type present in the diet, C. perfringens challenge significantly impaired feed conversion ratio in the period from 14 to 28 days (1.63 v. 1.69) and at 42 days (1.65 v. 1.68). In both experiments apparent metabolizable energy values were affected by dietary fat type. Irrespective of the fat type present in the diet, C. perfringens challenge decreased the digesta pH in the crop and ileum, but had no effect in cecal contents. Moreover, in Experiment 1, total organic acid concentration in the ileum was two to three times lower on soybean oil diets as compared with other treatments, indicating that C. perfringens as well as dietary fat type significantly affects microbiota activity in the broiler chicken gastrointestinal tract.