Effects of dietary wheat bran on absorption and accumulation of PCBs in rats.

Polychlorinated biphenyls (PCBs) are toxic environmental contaminants, which tend to accumulate in the food chain. Since dietary intake is the most important exposure route, PCB body burden may be affected by taking proper dietary measures. In the present study, diets were supplemented with either wheat bran or its cellulose based placebo in order to study the effect of bran consumption on the absorption of dietary PCBs and the excretion of initially stored PCBs. During the period of PCB intake, faecal PCB excretion was elevated by consumption of wheat bran as compared to the placebo. Hence, apparent faecal PCB digestibilities as well as PCB retentions in the whole body were lower in the wheat bran consuming rats. After ending PCB consumption, dietary wheat bran had only a minor effect on faecal PCB output while accumulation in the body was not affected. When PCBs were consumed for a longer time, a small but significant reduction of apparent faecal PCB digestibility was found. However, PCB content in the body kept increasing while PCB retention as percent of intake remained almost constant. Furthermore, differences among individual PCB congeners in metabolic susceptibility and hydrophobic characteristics had an impact on their accumulation in the body.

Polychlorinated biphenyl distribution and faecal excretion in rats fed wheat bran.

Polychlorinated biphenyls (PCBs) are abundant and persistent environmental contaminants, which tend to accumulate through the food chain. Because of the toxic potential of these compounds, body burden should be kept as low as possible e.g. by taking dietary measures. In the present report, the effect of wheat bran consumption on absorption of dietary PCBs as well as on excretion of previously absorbed PCBs was investigated in rats. Moreover, the accumulation of 7 reference PCB congeners in liver and abdominal adipose tissue was studied. Faecal excretion of dietary PCBs was significantly higher in rats fed wheat bran compared to its placebo. As a result, apparent PCB digestibility was diminished, but not enough to significantly affect PCB accumulation in liver and abdominal adipose tissue. Furthermore, excretion of previously absorbed PCBs following switching of the rats to a control diet without added PCBs was enhanced by wheat bran fibre intake, although to a much lesser extent than excretion of PCBs originating directly from the diet. Consequently, stimulation of PCB clearance from liver and abdominal adipose tissue due to wheat bran consumption was not detectable. Although no preferential absorption of PCB congeners was observed, PCB patterns in tissues obviously differed from the dietary PCB pattern. This was mainly due to PCBs 52 and 101, which were metabolised in the body. Moreover, reduced levels of PCB 138 were found in liver, while PCB 28 and 138 were predominantly present in adipose tissue. The experiment also demonstrated that PCB redistribution from the liver to the adipose tissue occurs.

Digestibility, retention and incorporation of low-level dietary PCB contents in laying hens.

Polychlorinated biphenyls (PCBs) are persistent and hazardous environmental contaminants, which tend to bioaccumulate in the food chain. In the present report the long-term effect of low-level dietary PCB concentrations was studied on performance, egg quality, apparent PCB digestibility, apparent PCB retention and PCB accumulation in laying hens that were fed experimental diets for 41 weeks. The tested dietary concentrations of supplemented PCBs, based on the sum of seven reference congeners, were 0, 1.5 and 6 ng/g. PCB ingestion did not significantly affect performance or egg quality parameters. The PCB concentration in egg yolk reached a nearly constant level after approximately 40 and 70 days of consumption of the diets containing 1.5 and 6 ng PCBs/g, respectively. Apparent faecal PCB digestibility and apparent retention were not influenced by dietary levels of added fat varying between 1.5% and 4.5%, but were significantly higher in hens fed diets containing added PCBs. Moreover, apparent PCB digestibility and retention increased significantly with age. Among the seven individual PCB congeners, no systematically significant differences with regard to apparent faecal digestibility were observed throughout the experiment. Accumulation of PCBs in the fat fraction of egg yolk, abdominal adipose tissue and thigh and breast muscle greatly depended upon PCB intake, but never exceeded the maximally allowed concentration of 200 ng/g. As PCBs 52 and 101 were hardly found in egg yolks and hen tissues, it was concluded that both congeners were greatly metabolised. Comparison of relative contents of individual PCB congeners revealed that PCBs 118, 138 and 153 were preferentially incorporated in yolk and body tissues.

Accumulation and tissue distribution of selected polychlorinated biphenyl congeners in chickens.

During one to three consecutive periods of 2 weeks, broiler chickens (n = 108) received test dies to which different amount of PCBs (7 congeners) were added. The relationship between exposure time and accumulation of individual congeners in different chicken tissues, such as breast, thigh and abdominal fat tissue, was observed. In all tissues, the vast majority of the PCB accumulation occurred during the first 2 weeks of exposures. After that, PCB concentrations only increased in the abdominal fat tissue of the animals. The individual PCBs were distributed differently in the various tissues. While CBs 28, 118, 138, 153 and 180 accumulated in the chickens, CBs 52 and 101 were metabolized, but no methyl sulphone metabolites of these congeners could be detected. Our results provide information on the absorption, tissue distribution and biotransformation of the individual PCB congeners and confirm the structure-activity relationships for metabolism of PCBs in birds, which are different from those in fish or mammalian species.

Polychlorinated biphenyls in broiler diets: their digestibility and incorporation in body tissues.

The influence of dietary amounts of polychlorinated biphenyls (PCBs) was studied on performance, apparent PCB digestibility and PCB accumulation in broiler chickens that were maintained until 42 days of age. Dietary concentrations of supplemented PCBs, based on the sum of seven reference congeners, ranged from 0 to 12 ng/g, which was below the legal maximum of 200 ng PCBs/g fat in Belgian feeds. PCB ingestion did not significantly affect body weight and feed intake. Apparent PCB digestibility was not influenced by dietary levels of added fat varying between 4% and 8%, but was significantly higher in broilers fed diets containing added PCBs. Accumulation of PCBs in the fat fraction of abdominal adipose tissue and breast and thigh muscle greatly depended upon PCB intake. However, PCB contents in the various body fat fractions within the same animal differed, even within muscle tissues, indicating an unequal PCB distribution in body fats.

The influence of enzyme-resistant starch on cholesterol metabolism in rats fed on a conventional diet.

Male Wistar rats were fed on a conventional diet containing normal corn starch or 6% enzyme-resistant starch originating from either raw or retrograded high-amylose corn starch. Furthermore, the diets were either cholesterol-free or contained 1% cholesterol and 0.1% cholic acid. The main objective of this study was to investigate whether the addition of enzyme-resistant starch to a rat conventional diet had any effect on cholesterol metabolism. Therefore, plasma and liver cholesterol concentrations, plasma HDL:LDL cholesterol ratios and neutral steroid and bile acid excretion were determined. No significant effect of enzyme-resistant starch feeding on plasma and liver cholesterol concentrations was found. However, consumption of raw or retrograded high-amylose corn starch resulted in a decrease in esterified and total liver cholesterol concentrations of 24 and 22%, respectively. This was accompanied by a reduction in plasma esterified and total cholesterol levels of 4% and a tendency to higher daily faecal coprostanol and total bile acid excretion.

Effect of route and frequency of administration of apomorphine on growth hormone release in African catfish (Clarias gariepinus).

Apomorphine is known to stimulate growth hormone release in African catfish following an intraperitoneal (IP) injection. In the present study the effect of apomorphine (5 or 20 mg/kg body weight) on plasma GH levels was evaluated after gastro-intestinal or parenteral delivery. Apomorphine increased the plasma GH concentration regardless of the route of administration, indicating that apomorphine can be absorbed from the intestinal tract. The effect of repeated administration of apomorphine differed clearly between the tested doses. Although a single IP injection with 20 mg apomorphine/kg body weight resulted in a clear increase in plasma GH levels, a second injection given 12 hours later was ineffective. In contrast the last of 4 consecutive injections with 5 mg apomorphine/kg body weight given at intervals of 12 hours stimulated the plasma GH levels in a similar way to a single IP injection with the same dose.

Determination of phospholipid content of intramuscular fat by Fourier Transform Infrared spectroscopy.

A method has been developed to determine the phospholipid content in fat extract with FTIR (Fourier Transform Infrared). l-α-Phosphatidylcholine from egg yolk in hexane solution was used as a reference for band identification at different concentrations. Phosphate bands were determined at different wavenumbers as described in the literature. A dilution series was made from meat extract and from 1-α-phosphatidylcholine. A linear calibration curve was obtained between the FTIR-results and the Iatroscan results, which were used as a reference. The band between 1282 cm(-1) and 1020 cm(-1) can be used for determination of phospholipid content.

Dose-response relationships between dietary (n-3) fatty acids and plasma and tissue lipids, steroid excretion and urinary malondialdehyde in rats.

For a 28-d experimental period, rats were fed a nonpurified, cereal-based diet containing 9.1% supplemental beef tallow or fish oil or one of the following beef tallow:fish oil blends: 95:5; 90:10; 80:20 and 50:50. All diets provided between 21.3 and 22.7 g linoleic acid/kg. Higher fish oil intake was paralleled by elevated incorporation of long-chain (n-3) fatty acids in plasma total lipid, mainly at the expense of arachidonic acid. Significant inverse relationships were found between plasma total (n-3) fatty acid concentration and plasma triglyceride, cholesterol or free fatty acid concentrations. Fish oil intake did not lead to a shift of triglycerides or cholesterol from the plasma to the tissues (liver, heart, kidneys). Reduced plasma cholesterol concentrations in the fish oil-fed rats could not be explained by higher fecal excretion of neutral sterols and bile acids. In vivo lipid peroxidation, assessed by urinary malondialdehyde excretion, was enhanced when diets containing greater than 1.8% fish oil were fed.

Cholesterol-lowering effects and utilization of protein, lipid, fiber and energy in rats fed unprocessed and baked oat bran.

The effects of the addition of 15% or 30% non-heated oat bran or 30% baked oat bran to a purified diet on apparent digestibility of dry matter, protein, lipid and fiber were measured in balance experiments with male Wistar rats. The effects of oat bran on dietary metabolizable energy, fecal bulking capacity and transit time of the ingested food were also studied. Heat processing of oat bran occurred in conditions of moisture and temperature similar to those of bread baking. Compared with the unprocessed oat bran, the baked product had a higher content of insoluble fiber, mainly due to higher Klason lignin content and a shift from soluble to insoluble beta-glucans. Relative to the fiber-free control diet, feeding the oat bran diets increased wet and dry fecal weight and decreased the transit time of the food. Fecal bulking capacity increased proportionally with oat fiber intake. Metabolizable energy of the diets, as well as apparent digestibility of dry matter and protein decreased with oat bran supplementation; on the other hand, lipid digestibility was not significantly changed. Baking of oat brain resulted in no statistically significant effects on dietary metabolizable energy or apparent digestibility of dry matter, protein, lipid and fiber. The measured metabolizable energy of oat bran ranged between 12.7 and 13.2 MJ/kg. Total plasma cholesterol concentration diminished with oat brain intake; non-heated and baked oat bran had comparable effects on plasma cholesterol. An inverse linear relationship (r = -0.80, P less than 0.1) was found between plasma cholesterol concentration and fecal excretion of bile acids.

Lipid metabolism responses in rats fed beef tallow, native or randomized fish oil and native or randomized peanut oil.

In experiments with male Wistar rats, we measured the effects of nonpurified diets containing 9.1% added fat (beef tallow, native or randomized fish oil, native or randomized peanut oil) on apparent digestibility of total fat and individual fatty acids. We also investigated the effects of the diets on plasma contents of triglyceride, cholesterolesters and free and total cholesterol as well as on the fatty acid profiles of plasma and liver phospholipids. Randomization of fish oil or peanut oil had no significant effect on any of the lipid measurements. Fat digestibility was significantly lower in the rats fed beef tallow. Apparent absorption of 18:1(n-9) and polyunsaturated fatty acids was not dependent on the fatty acid profile of the dietary fat. Apparent absorption of 16:1(n-7) and saturated fatty acids was generally highest in the rats fed fish oil. Intake of fish oil or peanut oil significantly decreased plasma triglyceride content. Intake of fish oil resulted in substantially decreased contents of total cholesterol and cholesterolesters in plasma, but intake of peanut oil did not. Efficiency of conversion of 18:2(n-6) into 20:4(n-6) was inhibited by long-chain (n-3) fatty acids.

Digestion and absorption of free and esterified fish oil fatty acids in rats.

This study was designed to test the hypotheses that digestibility and post-absorption metabolism of fish oil are influenced by impaired lipolysis and by the stereospecific composition of its triacylglycerols. Male Wistar rats were fed nonpurified diets containing one of the following fat sources: 9% native fish oil (NFO), 9% autorandomized fish oil (RFO), 8.1% fish oil-derived free fatty acids (FO-FFA) plus 0.9% glycerol, or 9% soybean oil (SO) as a reference fat. In a 24-day balance study, apparent digestibility of total dietary fat averaged 93.1% in the SO, NFO and RFO groups, and 90.9% in the FO-FFA group. Randomization of fish oil had no effect on apparent digestibility of individual fatty acids. In rats fed FO-FFA, apparent absorption of saturated and monounsaturated fatty acids was lower when compared to the NFO and RFO groups. Feeding the FO-FFA diet tended to increase plasma triglyceride content. The hypocholesterolemic effect of polyunsaturated n-3 fatty acids was not influenced by the dietary source. Similar effects on fatty acid profiles of plasma and liver phospholipids were caused by the NFO, RFO and the FO-FFA diets. We conclude that once polyunsaturated n-3 fatty acids are absorbed, their effect on lipid metabolism is not determined by the dietary source.

Flavomycin effects on performance of beef bulls and nutrient digestibility in wethers.

For 28 weeks a feeding experiment was conducted to determine the effects of dietary flavomycin on performance of beef bulls. In the first and second half of the trial, 40 animals (average initial weight 352 kg) had free access to corn silage or beet pulp, respectively, both supplemented with an appropriate concentrate containing 0 or 10 mg/kg of the antibiotic. Daily flavomycin intake was 39 to 46 mg when the animals were on the corn silage diet and 51 to 54 mg when they were fed the beet pulp diet. The animals fed the corn silage-based diet supplemented with flavomycin showed a non-significant improvement of daily gain (1.4%) and feed conversion (2.3%). When the beet pulp-based diet was fed, flavomycin significantly increased daily gain (15.2%, P less than 0.002) and feed conversion efficiency (9.1%, P less than 0.03). For the overall feeding experiment the positive effect of flavomycin feeding was 6.7% on body weight gain (P less than 0.09) and 5.2% on feed conversion (P less than 0.13). Flavomycin did not affect carcass yield of beef bulls. Also the effect of flavomycin on diet digestibility was studied in wethers fed a mixture of beet pulp and concentrate, containing 0 or 10 ppm flavomycin. No significant effect from the antibiotic on digestion of dry matter, crude protein, fibre, fat, ash and N-free extract was observed.

Separation and quantitation of phospholipids in animal tissues by Iatroscan TLC/FID.

A procedure has been developed to separate and quantitate phospholipids, including phosphatidylinositol and phosphatidylserine, from animal tissues by means of the Iatroscan TLC/FID technique. The method is based on the use of 0.01 M oxalic acid impregnated Chromarods-SII and stepwise resolution of the phospholipids in the presence of 1,2-dipalmitoyl-sn-glycero-3-phospho (N,N-dimethylethanolamine) as internal standard. To remove the neutral lipids, the rods are initially developed in a non-polar solvent mixture followed by partial scanning. Next, the rods are impregnated with oxalic acid, developed twice in CHCl3/CH3OH/CH3COOH/HCOOH/H2O (80:35:2:1:3, v/v/v/v/v) and partially scanned for measuring lysophosphatidylcholine, sphingomyelin and phosphatidylcholine. The subsequent step involves double development in CHCl3/CH3OH/30% NH4OH (60:35:0.9, v/v/v) to resolve cardiolipin, internal standard, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine and phosphatidic acid. For each phospholipid a linear calibration curve with a highly significant correlation coefficient was obtained. However, the calibration lines extrapolated to negative intercepts on the ordinate, indicating declining sensitivity at low phospholipid loads.

Cholesterol metabolism in mature and immature rats fed animal and plant protein.

In two feeding experiments immature (180 g) and mature rats (370 g) were fed a semi-purified diet containing 20% of a protein source (casein, wheat gluten, soybean or potato protein) for 4 wk. Food supply was restricted to 15 g daily. As compared to casein, plant proteins induced significantly lower concentrations of plasma total cholesterol and high density lipoprotein (HDL) cholesterol. The plasma cholesterol increase associated with aging was not prevented by consumption of casein, soybean or potato protein, but wheat gluten seemed to be effective. Lecithin-cholesterol acyltransferase (LCAT) activity was not significantly different in rats of the same age fed different plant proteins, whereas the esterification rate was lower in rats fed casein. With aging the LCAT activity generally decreased. As compared to the casein groups, the rats fed plant proteins showed higher excretion of fecal neutral and acidic steroids. Among the groups fed plant proteins, the fecal output of steroids was variable. Significantly negative correlations were found between fecal total sterol excretion and plasma total cholesterol or HDL cholesterol, respectively. Plant proteins showed a faster migration rate in the stomach, whereas their migration and absorption were slower in the first half of the small intestine. A relation between nonabsorbed nitrogen-containing substances and sterol excretion was hypothesized.

Supplementing salinomycin to diets for growing-finishing pigs.

Feeding experiments with growing-finishing pigs were carried out to study the effect of different dietary salinomycin concentrations upon animal performance. Besides a dietary treatment without antibiotic, three treatments consisted of 20/10 mg/kg, 40/20 mg/kg and 60/30 mg/kg salinomycin (the first and second number refer to the salinomycin content in grower and finisher diet, respectively). Compared to the control group, feeding diets with 20 or 40 mg/kg salinomycin resulted in significantly higher weight gain in the grower period (25-45 kg body weight), while also feed conversion was lower (although not statistically significant). In the finisher period (45-100 kg body weight) salinomycin had no significant effect upon weight gain or feed conversion efficiency, but the 20 and 30 mg/kg treatments yielded the best results. Considering the grower and finisher period together the dietary treatments 40/20 mg/kg and 60/30 mg/kg showed highest growth rate and most favourable feed conversion, although not statistically significant. Carcass characteristics (dressing percentage, carcass length, backfat thickness, percent meat) were not affected by dietary salinomycin supplementation.

Energetic efficiency and mitochondrial function in rats fed trans fatty acids.

Nutritional experiments with growing rats were conducted to study the effect of dietary t18:1 and t,t18:2 in mixtures with safflower oil (77.1% linoleate) on oxidative phosphorylation of isolated liver mitochondria and on energetic efficiency as measured in energy balance experiments. Partially hydrogenated soybean oil (PHSO) with 45% t18:1 and an ethyl ester concentrate of trans fatty acids (TRANS) containing 52% t,t18:2 were used. Six groups of male rats were fed diets with 10% (wt/wt) fat supplements: 1, safflower oil (SAF); 2, 8% PHSO + 2% SAF; 3, 0.5% TRANS + 9.5% SAF; 4, 1% TRANS + 9% SAF; 5, 2% TRANS + 8% SAF; and 6, 5% TRANS + 5% SAF. These fat supplements contained 77.1, 17.1, 73.3, 69.4, 61.7 and 38% linoleate for groups 1-6, respectively. The basal metabolic rate was not affected by dietary treatments, neither were the metabolizable energy values. As compared to the SAF group, rats receiving the 8% PHSO + 2% SAF showed no different effect on energy utilization or mitochondrial respiratory function. TRANS was found to reduce the efficiency of metabolizable energy utilization at the 5% level (group 6), while mitochondrial ATP synthesis was significantly depressed in both the 2% and the 5% TRANS groups. A parallelism was observed between t,t18:2 incorporation in liver mitochondria, reduced mitochondrial oxidative function and depressed energetic efficiency. The experiments indicated that t,t18:2 exerted a significantly negative effect on energy utilization at 1.0 and 2.5% levels in the diet even when fed with relatively high concentrations of linoleate.

Hepatic fatty acids and acyl desaturases in rats: effects of dietary carbohydrate and essential fatty acids.

For a 9-week period, six groups of weanling male rats were fed either a fat-free diet or a diet containing 10% hydrogenated coconut oil (HCO) or 10% safflower oil (SAF), respectively. Each of these diets contained either glucose or sucrose as the only carbohydrate. In the fat-free diets, the carbohydrate level was 67.3% and in the fat-supplemented diets 44.8%. Including HCO in the fat-free diet did not significantly alter hepatic 5-, 6-, and 9-desaturase activity, whereas addition of SAF significantly depressed all these activities. As compared to glucose, sucrose induced higher 9-desaturase activity in the rats on the fat-free diets. Adding HCO or SAF to the diet, simultaneously with lowering the carbohydrate level, diminished the stimulatory effect of dietary sucrose versus glucose on 9-desaturase activity. Levels of 20:4n6 and 20:3n9 in the fatty acid profiles of the liver microsomes were not influenced by dietary carbohydrate source, neither were the activities of the 5- and 6-desaturases, providing indirect evidence that dietary sucrose, as compared to glucose, did not differently affect biosynthesis of 20:4n6 and 20:3n9.

Effects of dietary long-chain fatty acids on the rat biosynthesis of unsaturated fatty acids in the rat.

Menhaden oil (ME) was included in semisynthetic diets to study the effect of long-chain fatty acids, mainly 20:5n3 and 22:6n3, on the biosynthesis of polyunsaturated fatty acids and on the 6- and 9-desaturase activities in liver microsomes. Five experimental diets, with the following fat supplements, were fed to male rats from weaning for a period of 33 weeks: 5% safflower oil (SAF) + 10% hydrogenated coconut oil (HCO), 5% SAF + 5% HCO + 5% ME, 5% SAF + 10% ME, 15% HCO and 5% HCO + 10% ME. The last two diets were deficient in linoleic acid. The three nondeficient diets contained similar amounts of linoleic acid. Including ME in the diets depressed the 6- and 9-desaturase activities, especially in the linoleic acid--deficient rats. The synthesis of 20:4n6, 22:4n6 and 22:5n6 were depressed. These effects were related to the preferential accumulation of dietary 20:5n3 and 22:6n3 in the liver microsomes, as compared to the n6 fatty acids. It is hypothesized that dietary 20:5n3 and 22:6n3 increase the minimum requirement for linoleic acid in the diet.

Interrelationship between dietary trans Fatty acids and the 6- and 9-desaturases in the rat.

Studies are reported on the effects of dietary trans fatty acids on the 6- and 9-acyl desaturase activities in the liver microsomes of rats fed essential fatty acid (EFA)-deficient and non-EFA-deficient diets. In experiment I, weanling male rats were fed a semisynthetic diet with either 10% safflower oil (SAF) or 10% hydrogenated coconut oil (HCO). At the age of one year, half of the dietary fat was replaced by a supplement containing elaidate, linolelaidate and cis, trans-trans,cis-18:2 (TRANS) for 12 weeks. In experiment II, male rats which were kept from weaning on a 10% (SAF + TRANS, or 5% HCO + 5% TRANS. Feeding TRANS depressed the 6-desaturase activity in the liver microsomes, especially in the EFA-deficient rats (HCO + TRANS group of experiment I). Unlike the 6-deaturase activity, the 9-desaturase activity was not inhibited by the dietary trans fatty acids and was significantly stimulated in the non-EFA-deficient rats (SAF + TRANS group of experiment I and HCO + TRANS groups of experiment II). This was evidence by incubation reaction and by comparisons of fatty acid consumptions and microsomal fatty acid levels, showing extra biosynthesis of 16:1 and 18:1 when TRANS was fed. The biosynthesis of essential (n-6) fatty acids was depressed by the TRANS supplement in EFA-deficient as well as in non-EFA-deficient animals.