Changes in Digestive Microbiota, Rumen Fermentations and Oxidative Stress around Parturition Are Alleviated by Live Yeast Feed Supplementation to Gestating Ewes.

BACKGROUND: In ruminants, physiological and nutritional changes occur peripartum. We investigated if gastro-intestinal microbiota, rumen metabolism and antioxidant status were affected around parturition and what could be the impact of a daily supplementation of a live yeast additive in late gestating ewes. METHODS: Rumen, feces and blood samples were collected from 2 groups of 14 ewes one month and a few days before parturition, and 2 weeks postpartum. RESULTS: In the control ewes close to parturition, slight changes in the ruminal microbiota were observed, with a decrease in the concentration F. succinogenes and in the relative abundance of the Fibrobacteres phylum. Moreover, a decrease in the alpha-diversity of the bacterial community and a reduced relative abundance of the Fibrobacteres phylum were observed in their feces. Control ewes were prone to oxidative stress, as shown by an increase in malondialdehyde (MDA) concentration, a lower total antioxidant status, and higher glutathione peroxidase (GPx) activity in the blood. In the yeast supplemented ewes, most of the microbial changes observed in the control group were alleviated. An increase in GPx activity, and a significant decrease in MDA concentration were measured. CONCLUSIONS: The live yeast used in this study could stabilize gastro-intestinal microbiota and reduce oxidative stress close to parturition.

Fatty acid composition and oxidation in beef muscles as affected by ageing times and cooking methods.

This study aimed to determine how ageing and cooking, each one applied to the beef meat most suitable (pan-fried or grilled ribeye steak, braised chuck and fried or roasted rump steak), induce changes in lipid content, fatty acid (FA) composition and lipid oxidation of muscles from 16 cattle representative of animals raised for France meat production. The fattiest muscle (ribeye) was the richest in saturated and monounsaturated FA leading to poor nutritional indexes. In contrast, the leanest muscle (rump) had the highest proportion of polyunsaturated FA and the highest levels of peroxidation without exceeding critical limits. The impact of cooking methods seemed mainly linked to the moisture loss increasing meat fat content and the culinary fat addition whose FA composition marked the meat. Cooking methods induced oxidation phenomena that could exceed the limit thresholds. In conclusion, short cooking time of rump steak was the best combination to meet nutritional expectations.

Heme-Iron-Induced Production of 4-Hydroxynonenal in Intestinal Lumen May Have Extra-Intestinal Consequences through Protein-Adduct Formation.

Some epidemiological studies show that heme iron consumption, in red meat, is associated to the development of several chronic diseases, including cancers and cardio-metabolic diseases. As heme iron intestinal absorption is finely regulated, we hypothesized that heme iron may act indirectly, through the peroxidation of dietary lipids, in food or in the intestinal lumen during digestion. This heme-iron-induced lipid peroxidation provokes the generation of toxic lipid oxidation products that could be absorbed, such as 4-hydroxynonenal (HNE). In a first experiment, heme iron given to rats by oral gavage together with the linoleic-acid-rich safflower oil induced the formation of HNE in the intestinal lumen. The HNE major urinary metabolite was elevated in the urine of the treated rats, indicating that this compound has been absorbed. In a second experiment, we showed that stable isotope-labeled HNE given orally to rats was able to reach non-intestinal tissues as a bioactive form and to make protein-adducts in heart, liver and skeletal muscle tissues. The presence of HNE-protein adducts in those tissues suggests a putative biological role of diet-originating HNE in extra-intestinal organs. This finding could have major consequences on the onset/development of chronic diseases associated with red meat over-consumption, and more largely to peroxidation-prone food consumption.

Behavioral and patho-physiological response as possible signs of pain in dairy cows during Escherichia coli mastitis: A pilot study.

Bovine mastitis is one of the most common diseases in the dairy industry and it is a major welfare problem. Pain during mastitis is generally assessed through behavior but a combination of indicators would increase the chances of detecting pain and assessing its intensity. The aim of this study was to assess behavioral and patho-physiological responses as possible signs of pain experienced by cows after experimental intramammary challenge (mastitis) with Escherichia coli. Six Holstein-Friesian cows received an inoculation of E. coli P4 in one healthy quarter. Evolution of the disease was assessed using bacteriological growth and somatic cell counts (SCC). Cows' response to the challenge was monitored by direct behavioral and clinical observations, data loggers, rumen temperature sensors, and indicators of inflammation, stress, and oxidative status. From all data recorded, the variables that contributed most to the discrimination of mastitis phases were obtained by factorial discriminant analysis. Baseline levels of all indicators corresponded to values before challenge. Specifically, we weighted data relating to lying behavior by the observations at the same hour of the day before challenge to eliminate the circadian rhythm effect. We identified 3 phases that were discriminated by factorial discriminant analysis with good performance. Nine indicators varied according to the phase of the disease: cows' attitude toward their surroundings, tail position, clinical signs, ear position, variation of postural changes, concentrations of haptoglobin and serum amyloid A (SAA), cortisol blood levels, and rumen temperature (as a surrogate for body temperature). In phase 1 (4 to 8 h postinoculation), E. coli proliferated exponentially in milk but inflammation indicators remained at baseline levels. Cows were less attentive toward their surroundings (median score, 0.63), and postural changes (lying/standing) were less frequent (0.75 times from baseline). In phase 2 (12 to 24 h postinoculation), bacterial concentrations peaked around 12 h and then began to decrease concomitantly with a sharp SCC increase. Cows were less attentive toward their surroundings (score, 0.54), had high plasma cortisol (31.3 ng/mL) and SAA (100.3 µg/mL) concentrations, and rumen temperature was increased (40.3°C). In phase 3 (32 to 80 h postinoculation), bacterial concentrations decreased concomitantly with high SCC levels. Cows had high levels of haptoglobin (0.57 mg/mL) and SAA (269 µg/mL) but showed no behavioral changes. Dairy cows displayed changes of behavioral, inflammatory, and stress parameters after E. coli mammary inoculation. Our results suggest that cows may have experienced discomfort in the preclinical phase (phase 1) and pain in the acute phase (phase 2) but neither discomfort nor pain in the remission phase (phase 3). Although larger controlled studies are needed to confirm our findings, this knowledge could be useful for early detection of E. coli mastitis and for decision-making regarding the initiation of pain-relief treatment during mastitis in dairy cows. This would improve animal welfare and potentially faster disease remission.

Quantification of 4-hydroxy-2-nonenal-protein adducts in the in vivo gastric digesta of mini-pigs using a GC-MS/MS method with accuracy profile validation.

Hydroxyalkenals are lipid oxidation end-products resulting from the oxidation of polyunsaturated fatty acids (PUFA). This study aimed at quantifying the production of 4-hydroxy-2-nonenal-protein adducts (HNE-P) via Michael addition from n-6 PUFA oxidation in the gastric digesta of mini-pigs after the consumption of meat-based meals with different plant antioxidant contents. Using the accuracy profile procedure, we validated an extraction protocol for the quantification of HNE-P by GC-MS/MS in gastric contents. The formation of HNE-P in the gastric compartment was observed for the first time, with concentrations ranging from less than 0.52 to 1.33 nmol HNE-P per 500 mg digesta. Nevertheless, most gastric HNE-P levels were below the limit of quantification of 0.52 nmol HNE-P per 500 mg digesta. In this animal study, the protective effect of plant antioxidant sources on HNE-P formation was not evidenced contrasting with the results using TBARS as markers.

Red meat and colorectal cancer: Nrf2-dependent antioxidant response contributes to the resistance of preneoplastic colon cells to fecal water of hemoglobin- and beef-fed rats.

Epidemiological studies have associated red meat intake with risk of colorectal cancer. Experimental studies explain this positive association by the oxidative properties of heme iron released in the colon. This latter is a potent catalyst for lipid peroxidation, resulting in the neoformation of deleterious aldehydes in the fecal water of heme-fed rats. The toxicity of fecal water of heme-fed rats was associated to such lipid peroxidation. This study demonstrated that fecal water of hemoglobin- and beef-fed rats preferentially induced apoptosis in mouse normal colon epithelial cells than in those carrying mutation on Apc (Adenomatous polyposis coli) gene, considered as preneoplastic. Highlighting the importance of lipid peroxidation and neoformation of secondary aldehydes like 4-hydroxy-2-nonenal (HNE), we optimized the depletion of carbonyl compounds in the fecal water which turned out to abolish the differential apoptosis in both cell lines. To explain the resistance of preneoplastic cells towards fecal water toxicity, we focused on Nrf2, known to be activated by aldehydes, including HNE. Fecal water activated Nrf2 in both cell lines, associated with the induction of Nrf2-target genes related to aldehydes detoxification. However, the antioxidant defense appeared to be higher in preneoplastic cells, favoring their survival, as evidenced by Nrf2 inactivation. Taken together, our results suggest that Nrf2-dependent antioxidant response was involved in the resistance of preneoplastic cells upon exposure to fecal water of hemoglobin- and beef-fed rats. This difference could explain the promoting effect of red meat and heme-enriched diet on colorectal cancer, by initiating positive selection of preneoplastic cells.

Extruded linseed and rapeseed both influenced fatty acid composition of total lipids and their polar and neutral fractions in longissimus thoracis and semitendinosus muscles of finishing Normand cows.

The effects of extruded linseed and rapeseed on lipids and FA composition of total, polar and neutral lipids of longissimus thoracis (LT) and semitendinosus (ST) muscles were investigated in 21 Normand cull cows. Animals were assigned in a 100 d finishing period to straw (30%) and concentrate (70%) based (C) or the same diet supplemented with linseed (L) or with rapeseed (66%) plus linseed (33%) (RL). Beef polar and neutral lipids were purified by liquid chromatography and their FA analysed by GLC. Trans and cis 18:1, purified by HPLC from total FA methyl esters, were analysed by GLC-MS. L and LR diets did not increase beef lipid deposition, but had modified FA composition of both LT and ST muscles in favouring deposition of 18:3n-3 and 9cis,11tr 18:2 (CLA), mainly to the detriment of 18:1∆9 cis (neutral lipids) and 18:2n-6 (polar lipids). However, they did not favour deposition of LC n-3 PUFA in the two muscles, but had increased deposition of trans 18:1 significantly, especially of ∆13tr to ∆16tr isoforms to the detriment of ∆10tr 18:1 (L diet) and of ∆11tr 18:1 (RL diet).

Expression of enzymes and transcription factors involved in n-3 long chain PUFA biosynthesis in limousin bull tissues.

The current low consumption of n-3 long chain polyunsaturated fatty acids (n-3 LCPUFA) led scientists to wonder about the possible enrichment of human food, including meats such as beef, with n-3 LCPUFA. However, their biosynthesis from dietary n-3 PUFA seems limited in mammalian tissues implying that a better understanding of the molecular mechanisms responsible for this down regulation is needed. This study aimed at identifying and comparing the limiting steps of n-3 LCPUFA synthesis in liver, intermuscular adipose tissue (IM-AT) and semitendinosus muscle (ST) from six Limousin bulls. Tissue FA composition was analysed by GLC and mRNA abundance of enzymes and transcription factors involved in n-3 LCPUFA synthesis was assessed by RT-qPCR. In liver, mRNA encoding proteins involved in n-3 LCPUFA synthesis were present in agreement with the significant high content of n-3 LCPUFA (8.4 mol% of total FA, 257 mg/100 g of fresh tissue) in this organ. In IM-AT, these mRNA were all present, but at a tenfold lower intensity than in liver in agreement with the low contents of n-3 LCPUFA in this tissue. In ST muscle, these mRNA were all present except elongase 5 mRNA which was only present as trace, the corresponding protein being undetectable, probably inducing a break of n-3 LCPUFA synthesis from 18:4n-3. In conclusion, Limousin bull ST muscle seemed unable to synthesize n-3 LCPUFA. However, the presence of 20:5n-3 (EPA) and 22:5n-3 (DPAn-3) in muscle raised the question of the origin of these n-3 LCPUFA.

Effect of 6 Weeks of n-3 fatty-acid supplementation on oxidative stress in Judo athletes.

The aim of this investigation was to assess the effects of 6 wk of eicosapentanoic acid (EPA) and docosahexanoic acid (DHA) supplementation on resting and exercise-induced lipid peroxidation and antioxidant status in judoists. Subjects were randomly assigned to receive a placebo or a capsule of polyunsaturated fatty acids (PUFAs; 600 mg EPA and 400 mg DHA). Blood samples were collected in preexercise and postexercise conditions (judo-training session), both before and after the supplementation period. The following parameters were analyzed: α-tocopherol, retinol, lag phase , maximum rate of oxidation (Rmax) during the propagating chain reaction, maximum amount of conjugated dienes (CDmax) accumulated after the propagation phase, nitric oxide (NO) and malondyaldehide (MDA) concentrations, salivary glutathione peroxidase activity, and the lipid profile. Dietary data were collected using a 7-day dietary record. A significant interaction effect between supplementation and time (p < .01) on triglycerides was noted, with values significantly lower in the n-3 long-chain-PUFA (LCPUFA) group after supplementation than in the placebo group. Significant interaction effects between supplementation and time on resting MDA concentrations and Rmax were found (p = .03 and p = .04, respectively), with elevated values in the n-3 LCPUFA group after supplementation and no change in the placebo group's levels. The authors observed a significantly greater NO and oxidative-stress increase with exercise (MDA, Rmax, CDmax, and NO) in the n-3 LCPUFA group than with placebo. No main or interaction effects were found for retinol and α-tocopherol. These results indicate that supplementation with n-3 LCPUFAs significantly increased oxidative stress at rest and after a judo-training session.

Plant extracts combined with vitamin E in PUFA-rich diets of cull cows protect processed beef against lipid oxidation.

The effect of supplementing PUFA-rich cull cow diets with vitamin E (2.8 g/animal/day) or vitamin E plus plant extracts rich in polyphenols (PERP) (126 g/animal/day), for 101+/-3 days preceding slaughter, on the oxidative stability of longissimus thoracis (LT) and semitendinosus (ST) steaks was evaluated after ageing (for 12 d at 4 degrees C either in carcass or under-vacuum) and packaging (14 d under-vacuum (V), 4 d aerobic (A) and 7 d under modified atmosphere (70:30, O(2)/CO(2)) (MA)). The ageing method had no effect on a beef lipid oxidation intensity marker (malondialdehyde (MDA)), whereas packaging systems containing O(2) (A and MA) significantly increased lipid oxidation intensity (5 and 13 times higher than under V, respectively). Adding antioxidants to diets of animals given a PUFA-rich diet significantly improved lipid stability in steaks; the combination of vitamin E and PERP was more efficient than vitamin E alone for the most deleterious beef packaging.

Lipid peroxidation and antioxidant status in rat: effect of food restriction and wheel running.

Using the activity-based anorexia model, the aim of this investigation was to explore antioxidant enzyme activity (catalase, superoxide dismutase), total antioxidant status (TAS), and alpha-tocopherol in blood, liver, and gastrocnemius muscle associated with the food restriction and voluntary wheel running during 8 days. In addition, lipid peroxidation was measured by measurements of malondialdehyde (MDA). Wistars rats (n = 56) were randomly assigned to one of four groups: an ad lib sedentary group, a control wheel activity group, a food restriction-induced hyperactivity group (1 h/day ad lib food, 23 h/day ad lib wheel access), and a food-restricted sedentary group. The animals were killed when the rats in the food-restricted group had lost 25% of their free feeding weight. Antioxidant enzyme activities and TAS in blood, liver, and gastrocnemius muscle were unaffected by voluntary wheel running. A wheel activity effect (P < 0.05) was obtained for the MDA concentrations in plasma, with lower concentrations in trained animals. Food restriction effects were obtained for antioxidant capacity in liver, as well as for CAT activity in the gastrocnemius muscle and plasma MDA concentrations with lower values in the restricted animals. On the other hand, the food-restricted rats showed higher plasma TAS concentrations (P < 0.05) and higher alpha-tocopherol concentrations in the liver (P < 0.05) when compared to animals fed ad libitum. Our results also showed that food restriction coupled to wheel running decreased antioxidant parameters in liver, and plasmatic MDA concentrations and increased TAS plasma concentrations when compared to the ad libitum sedentary situation.

Effect of sunflower-seed oil or linseed oil on milk fatty acid secretion and lipogenic gene expression in goats fed hay-based diets.

Plant oils in the diet are known to alter milk fat composition owing to changes in the supply of fatty acid precursors and/or activity of lipogenic enzymes in the mammary gland. Thirteen mid-lactating Alpine goats were used in a 3 x 3 Latin square design with 28-d periods to evaluate possible mechanisms regulating milk fat synthesis and fatty acid composition on grass hay-based diets containing none (H) or 55 g/kg diet dry matter of sunflower-seed oil (HSO) or linseed oil (HLO). Inclusion of oils in the diet had no effect on milk yield but enhanced (P<0.05) milk fat secretion. Compared with the control, HLO and HSO decreased (P<0.05) C10-C16 secretion and increased (P<0.05) C18 output in milk, responses that were accompanied by reductions in milk fat cis-9 14:1/14:0, cis-9 18:1/18:0 and cis-9, trans-11 18:2/cis-9 18:1 concentration ratios. Plant oil supplements decreased (P<0.05) mammary stearoyl-CoA desaturase (SCD) activity but had no effect on SCD mRNA. Treatments had no effect on glucose-6-phosphate dehydrogenase, malic enzyme and glycerol-3-phosphate dehydrogenase activity, or mRNA abundance and/or activity of lipoprotein lipase, acetyl-CoA carboxylase and fatty acid synthase in mammary, hepatic or adipose tissue. The results provided little support for milk fatty acid secretion responses to HLO and HSO being mediated via changes in mammary, hepatic or adipose mRNA abundance or in the activity of key lipogenic enzymes. In conclusion, plant oils in the diet enhance milk fat synthesis, alter milk fatty acid composition and specifically inhibit mammary SCD activity in the goat. Furthermore, the results suggest that the regulation of mammary lipogenesis in response to plant oils appears related to factors other than altered mammary gene expression or potential lipogenic enzyme activity.

Hepatic metabolism of glucose and linoleic acid varies in relation to susceptibility to fatty liver in ad libitum-fed Muscovy and Pekin ducks.

The susceptibility to develop hepatic steatosis is known to differ between duck species, especially between Muscovy and Pekin ducks. This difference could be explained by either differential responses of species to overfeeding or genetic differences in hepatic lipid metabolism. The aim of the present study was to compare the intensities of the different hepatic pathways (oxidation, lipogenesis, esterification, secretion, etc.) of the two main nutrients (glucose and linoleic acid (LA)) reaching the liver of ad libitum-fed Muscovy (n 6) and Pekin (n 6) ducks using the ex vivo method of liver slices incubated for 16 h with [U-14C]glucose, [1-14C]LA and [35S]methionine added to the survival medium. In such experimental conditions, the lipogenesis pathway from glucose was 2-fold higher (P<0.05) in the liver of the Muscovy duck than in that of the Pekin duck. Furthermore, the hepatic uptake of LA was 2-fold higher (P<0.05) in the Muscovy duck than in the Pekin duck leading to a 2-fold higher (P<0.05) esterification of this fatty acid in the liver of the Muscovy duck. The hepatic secretion of VLDL was higher (P<0.01) in the Muscovy duck than in the Pekin duck but insufficient to prevent lipid accumulation in the liver of the Muscovy duck. In conclusion, these results show the influence of the species on the hepatic metabolism of ducks in relation to their susceptibility to develop fatty liver. These results should shed light on the metabolic regulations that might underlie susceptibility to hepatic steatosis in the the human liver.

Butters varying in trans 18:1 and cis-9,trans-11 conjugated linoleic acid modify plasma lipoproteins in the hypercholesterolemic rabbit.

The experiment was designed to study the effects of butters differing in conjugated linoleic acid (CLA) and trans 18:1 contents on lipoproteins associated with the risk of atherogenesis. New Zealand White male rabbits (9.6 weeks; 2.1 kg) were assigned for 6 or 12 weeks to three diets (n = 6 per diet) made of conventional pellets with 0.2% cholesterol and with 12% fat provided from a butter poor in trans-10 and trans-11 18:1 and in CLA (standard group), or rich in trans-10 18:1 (trans-10 18:1 group) or rich in trans-11 18:1 and in cis-9,trans-11 CLA (trans-11 18:1/CLA group). Blood samples were collected at the end of dietary treatments. Lipoproteins were separated by gradient-density ultracentrifugation. Lipid classes were determined enzymatically and apolipoproteins A-I and B by radial immunodiffusion. Mainly in the 12-week rabbits, higher plasma triglycerides and apolipoprotein B levels shown in the standard and trans-10 18:1 groups compared with those in the trans-11 18:1/CLA group are associated with higher plasma levels of very low density lipoproteins (VLDL) and low density lipoproteins (LDL) also shown in these two groups. In the 12-week rabbits, a shift towards denser LDL, considered as more atherogenic, was shown only in the trans-10 18:1 group. In these animals, the VLDL + LDL to HDL ratio was 1.7-2.3 times higher in the trans-10 18:1 group than in the other groups (P = 0.076). These results suggest a rather neutral effect of trans-11 18:1/CLA butter towards the risk of atherogenesis, whereas trans-10 18:1 butter would tend to be detrimental.

Gestation linked radical oxygen species fluxes and vitamins and trace mineral deficiencies in the ruminant.

In mammals, radical oxygen species (ROS) are essential factors of cell replication, differentiation and growth (oxidative signal), notably during gestation, but are also potentially damaging agents. In Women, ROS play a role in remodeling of uterine tissues, implantation of the embryo, settlement of the villi and development of blood vessels characteristic of gestation. The body stores of vitamins and minerals of gestating females are used to keep ROS fluxes at a level corresponding to oxidative signals and to prevent an imbalance between their production and scavenging (oxidative stress), which would be detrimental to the mother and fetus. There is some evidence that, although based on different regulatory mechanisms, most of the effects of ROS reported in humans also occur in pregnant ruminant females, some of which have been actually reported. Many vitamins and trace elements have dual effects in the organism of mammals: (a) they are involved in the control of metabolic pathways or/and gene expression, (b) but most of the time they also display ROS trapping activity or their deficiencies induce high rates of ROS production. Deficiencies induce different disorders of gestation and can be induced by different kinds of stress. An example is given, corresponding to the decreased contents of cobalt of forages, when exposed to sustained heavy rains, so that the supply of vitamins B12 to the organism of the ruminant that grazes them is reduced and failure of gestation is induced. Outdoor exposure of ruminants to adverse climatic conditions by itself can increase the vitamin and trace element requirements. Adaptation of production systems taking into account these interactions between gestation and sources of stress or change of the quality of feeding stuffs as well as further developments of knowledge in that field is necessary to promote sustainable agricultural practices.

Effect of dietary supply of butters rich either in trans-10-18 : 1 or in trans-11-18 : 1 plus cis-9, trans-11-18 : 2 on rabbit adipose tissue and liver lipogenic activities.

Experimental butters with a high content of trans-18 : 1 fatty acids and/or cis-9,trans-11-18 : 2 (rumenic acid; RA) were fed to thirty-six New Zealand White rabbits to investigate their effects on adipose tissue (AT) and liver lipogenic activities. Animals received one of three atherogenic (0.2 % cholesterol) diets containing 12 % butter with either a standard fatty acid composition (rich in saturated fatty acids), rich in trans-10-18 : 1 (T10 diet) or in trans-11-18 : 1 plus RA (T11+ RA diet) for 6 or 12 weeks. The ingestion of butters rich in trans fatty acids and/or RA for 6 weeks had little or no effect on liver and AT lipogenesis. The ingestion for 12 weeks of butter rich in T11+ RA decreased perirenal AT weight, lipogenic enzyme and lipoprotein lipase activities, without affecting liver lipid concentration or lipogenic activities except for a decrease in glycerol-3-phosphate dehydrogenase activity. Similar trends, but of a lower magnitude, were observed in rabbits fed the T10 diet for 12 weeks. Ingestion of the T10 or T11+ RA diets for 6 or 12 weeks had no significant effect on plasma metabolites and hormones except for glucose which increased at 6 weeks in the T10 group. Plasma leptin concentration was positively correlated with AT weight but did not differ between the three diets. In conclusion, the supply of butters rich in either T10 or T11+ RA in an atherogenic diet for 12 weeks decreased rabbit AT lipogenesis, with a more marked effect of the T11+RA diet, but had no effect on liver lipogenesis.

Beef conjugated linoleic acid isomers reduce human cancer cell growth even when associated with other beef fatty acids.

Although many data are available concerning anticarcinogenic effects of industrial conjugated linoleic acid (CLA), few studies have reported the antitumour properties of CLA mixtures originating from ruminant products. The aim of the present study was to investigate the in vitro antiproliferative effects of beef CLA mixtures on breast, lung, colon, melanoma and ovarian human cancer cell lines. For this purpose, four fatty acid (FA) extracts prepared from beef lipid and varying in their CLA composition, their corresponding purified CLA-enriched fractions, and mixtures of pure synthetic CLA, the composition of which reproduced that of the four selected beef samples, were tested on cancer cell lines. Cancer cells were exposed for 48 h to medium containing 100 microm-FA and their proliferation was determined by quantifying cellular DNA content (Hoechst 33342 dye). Compared with cells incubated without FA, the number of cancer cells was reduced from 25 to 67 % (P<0.0001) following FA treatment. Antiproliferative effects of CLA mixtures varied in magnitude according to the source of FA, the CLA composition and the cell lines. CLA mixtures naturally present in beef inhibited the proliferation of human cancer cell lines, a high content in cis-trans isomers allowing the most important antiproliferative effect. Beef total FA exhibited a greater growth-inhibitory activity than their corresponding CLA-enriched fractions. These results suggested that either beef FA other than beef CLA could possess antiproliferative properties and/or the existence of complementary effects of non-conjugated FA and CLA, which could favour the antiproliferative properties of beef total FA.

Conjugated linoleic acid isomers and their conjugated derivatives inhibit growth of human cancer cell lines.

Conjugated linoleic acid (CLA), mainly c9,t11- and t10,c12-isomers, and polyunsaturated n-3 fatty acids (n-3 PUFA) have been shown to reduce tumor growth. This study compared, on a set of human tumor cells (breast, lung, colon, prostate and melanoma), the antiproliferative effects of: i) trans monounsaturated fatty acids (MUFA) vs. cis MUFA and MUFA vs. PUFA, ii) individual isomers of CLA vs. linoleic acid, iii) CLA-conjugated derivatives vs. their non-conjugated homologues and vs. CLA isomers. Tumor cells were exposed to medium containing individual FA (100 microM) for 48 h and their proliferation was determined by measuring the cellular DNA content (fluorescent Hoechst 33342 dye). The antiproliferative effects of FA varied with the type of cells and were mainly dependent on the degree of unsaturation and on the position and configuration of their double bonds. One isomer of CLA (t9,t11-18:2) and CLA-conjugated derivatives exhibited the strongest growth-inhibitory effect against cancer cells. These results suggest that ruminant products contain active compounds against human tumor cell proliferation.

Effect of site of starch digestion on portal nutrient net fluxes in steers.

Processing of maize grain is known to modulate the site of starch digestion, thus the nature and amount of nutrients delivered for absorption. We assessed the effect of site of starch digestion on nutrient net fluxes across portal-drained viscera (PDV). Three steers, fitted with permanent digestive cannulas and blood catheters, successively received two diets containing 35 % starch as dent maize grain. Diets differed according to maize presentation: dry and cracked (by-pass, BP) v. wet and ground (control, C). Ruminal physicochemical parameters were not significantly affected. Between C and BP, the decrease in ruminal starch digestion was compensated by an increase in starch digestion in the small intestine. The amount of glucose and soluble alpha-glucoside reaching the ileum was not affected. The amount of glucose disappearing in the small intestine increased from 238 to 531 g/d between C and BP, but portal net flux of glucose remained unchanged (-97 g/d). The portal O2 consumption and net energy release were not significantly affected, averaging 16 % and 57 % of metabolizable energy intake, respectively. The whole-body glucose appearance rate, measured by jugular infusion of [6,6-2H2]glucose, averaged 916 g/d. The present study shows that the increase in the amount of glucose disappearing in the small intestine of conventionally fed cattle at a moderate intake level induces no change in portal net flux of glucose, reflecting an increase in glucose utilization by PDV. That could contribute to the low response of whole-body glucose appearance rate observed at this moderate level of intestinal glucose supply.

In vitro metabolism of rumenic acid in bovine liver slices.

Ruminant products are the major source of CLA for humans. However, during periods of fat mobilization, the liver might play an important role in CLA metabolism which would limit the availability of the latter for muscles and milk. In this context, rumenic acid (cis-9, trans-11 CLA) metabolism in the bovine liver (n = 5) was compared to that of oleic acid (n = 3) by using the in vitro liver slice method. Liver slices were incubated for 17 h in a medium containing 0.75 mM of FA mixture and 55 microM of either [1-(14)C] rumenic acid or [1-(14)C] oleic acid at 37 degrees C under an atmosphere of 95% O(2)-5% CO(2). Rumenic acid uptake by liver slices was twice (P = 0.009) that of oleic acid. Hepatic oxidation of both FA (> 50% of incorporated FA) led essentially to the production of acid-soluble products and to a lower extent to CO(2) production. Rumenic acid was partly converted (> 12% of incorporated rumenic acid) into conjugated C18:3. CLA and its conjugated derivatives were mainly esterified into polar lipids (71.7%), whereas oleic acid was preferentially esterified into neutral lipids (59.8%). Rumenic acid secretion as part of VLDL particles was very low and was one-fourth lower than that of oleic acid. In conclusion, rumenic acid was highly metabolized by bovine hepatocytes, especially by the oxidation pathway and by its conversion into conjugated C18:3 for which the biological properties need to be elucidated.