[Joint session of the National Academy of Medicine and the National Academy of Pharmacy, November 26, 2002].
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Food, Genetically Modified↗
Biomedical subjects
A Rérat
Publications and source records attributed to A Rérat.
[Synopsis and recommendations].
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Agriculture↗
[Summary and conclusions].
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Food, Genetically Modified↗
Influence of the nature of carbohydrate intake on the absorption chronology of reducing sugars and volatile fatty acids in the pig.
The results of three successive experiments were compared in order to analyse the chronology of absorbed energy amounts resulting from enzymatic or microbial digestion, respectively. These experiments were undertaken in the pig to study the absorption kinetics of reducing sugars and amino-nitrogen formed during enzymatic digestion and of volatile fatty acids (VFA) formed through the action of the digestive flora. The animals were given well-balanced semi-synthetic diets containing poorly digestible or indigestible carbohydrates. These diets contained the following ingredients: (Experiment A) purified cellulose at two levels of incorporation (LC diet 6%, HC diet 16%); (Experiment B) alfalfa meal (22%) supplying 6% crude fibre (HA diet) versus lactose (22%) with an addition of 6% purified cellulose (HL diet); (Experiment C) sorbitol in the form of maltitol (53%) with an addition of 6% purified cellulose (SHyd diet) versus maltose under the same conditions (53%, SNat diet). Each diet was fed to five pigs fitted with catheters placed in the portal vein and carotid artery and with a flow probe around the portal vein, which made it possible to study the nutrient absorption after one meal (800 g). Under our experimental conditions (intake: 2 200-2 300 kcal, except HC 1 930 kcal) the higher level of crude fibre or the presence of osides in the diet which are poorly digestible in the small intestine (lactose, maltitol), depressed the absorption of reducing sugars (RS) (amount absorbed within 12 h relative to intake %: SNat 92.8; LC 82.7; HL 78.7; HA 76.0; HC 72.5; SHyd 71.3). The absorbed energy supply resulting from the VFA increased accordingly, in the presence of poorly digestible or indigestible carbohydrates (as a percentage of the total energy absorbed as RS, lactic acid (LA) and VFA: SNat 3.4; LC 7.1; HL 8.9; HC 10.4; SHyd 13.1) with one exception (HA: 6.0%). For all diets, the greatest energy absorption (42-63% according to the diet) occurred during the first 4 h after the meal, the larger fraction resulting from RS (86.8-94.8% according to the diet). The energy supply due to the absorption of VFA became large between the 5th and the 12th hour, and was larger for diets containing poorly digestible or indigestible carbohydrates (as a percentage of the total RS + LA + VFA: SNat 6.5; LC 8.7; HC 14.3; HC 14.4; SHyd 23.3) with one exception (HA: 9.0%). Although the late absorption of VFA was insufficient to compensate for the energy deficit due to a lower of RS, it may bridge the energy gap during the interprandial period.
Animals↗
Kinetics of amino acid and glucose absorption following pancreatic diversion in the pig.
An experiment was conducted in the pig to determine the consequences of deprivation of exocrine pancreatic secretion on the composition and quantity of nutrients absorbed after intake of a balanced diet. Five growing pigs (53.8 kg body weight) were fitted with permanent catheters in the portal vein and the carotid artery and with an electromagnetic flow probe around the portal vein to measure the exchanges between the blood and the intestinal lumen. They were also fitted with a permanent catheter in the duct of Wirsung to educe the exocrine pancreatic secretion and another one in the duodenum in order to reintroduce it. In each animal, glucose, amino-N and amino acid absorption as well as insulin and glucagon production were measured over a period of 10 h after the meal (semi-purified diet based on purified starch and containing 180 g fish meal/kg, DM content of the meal 731 g), either in the presence of pancreatic juice (group C: immediate reintroduction), or in the absence of pancreatic juice (group D: deprivation). The deprivation of pancreatic juice provoked a marked depression in the absorption of glucose (D 67.9 (SEM 27.9) g/10 h, C 437.7 (SEM 39.5) g/10 h, P < 0.001), and of amino-N (D 7.55 (SEM 0.54) g/10 h, C 15.80 (SEM 0.79) g/10 h, P < 0.001). The composition of the mixture of amino acids in the portal blood was only slightly modified: only the levels of histidine (P < 0.05) and of valine (P < 0.06, NS) decreased in the absence of pancreatic juice. Insulin production was much lower (by 64%, P < 0.05) in the absence of pancreatic juice whereas that of glucagon was not affected.
Amino Acids↗
Mathematical modeling of digestion and nutrient absorption in pigs.
A simple simulation model of digestion and absorption in pigs was developed. The structure of the model is a set of four anatomical compartments for DM: stomach, two portions of small intestine, and the large intestine. In each of these anatomical compartments, subcompartments correspond to the major biochemical components of feed and their products of degradation. The major degradation and absorption events are considered as well as the effect of microbial activity in the large intestine. The total number of compartments is 44. The numerical integration with a time step of 1 min allows prediction of kinetic features of digestion phenomena such as absorption patterns and transit flows. First validation of the model shows that the global dynamic behavior of the model is realistic and promising. However, some additional factors must be considered for improved accuracy, in particular the susceptibility of the feed components to enzymatic degradation. The outputs of such a model could be used as inputs for metabolic or growth models running with time steps smaller than the 24-h basis often used in nutrition.
Animals↗
[Bovine spongiform encephalopathy. Review of data collected since the statement of February 6, 1996].
The observation in 1995 and 1996 of 10 cases of a new variant of Creutzfeldt-Jakob disease (V-CJD) in U.K. suggested a possible relation between this human cases and bovine spongiform encephalopathy (BSE). Recent papers about this topic are reviewed : hypothesis of a possible genetic link between man and cattle, hypothesis of a acquired resistance against the agent of BSE after a previous infection by a less virulent agent of ovine origin, importance of polymorphism at codon 129 according to the hypothesis of a virus-induced amyloidosis, diagnostic test with cerebrospinal fluid, epidemiology of BSE and prediction of future BSE spread.
Animals↗
[Relationship between world food production and the environment].
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Agriculture↗
[Human and animal spongiform encephalopathy. Update on December 17, 1996].
Recent papers about bovine spongiform encephalopathy (BSE) and new variant of Creutzfeldt-Jakob disease (nvCJD) are reviewed: new data, maternal transmission of BSE, epidemiology of BSE in British cattle, structure of the PrP(res), biochemical signature of PrP(res), chronic pesticide-initiated modification of the prion protein, protein markers in cerebrospinal fluid.
Animals↗
Nutritional value of protein hydrolysis products (oligopeptides and free amino acids) as a consequence of absorption and metabolism kinetics.
When pigs were submitted to duodenal infusion of solutions containing a large percentage of small peptides (PEP) or free amino acids with the same pattern (AAL) amino acids appear in the portal blood more rapidly and more uniformly after infusion of PEP then after infusion of AAL, with the notable exception of methionine for which the opposite was true. These differences were lowered when a carbohydrate (maltose dextrin) was present in the solution, but nevertheless remained significant for the first hour after the infusion. The long-term (8-hour) uptake of free amino acids into the liver and the peripheral tissues differed in profile according to the nature of the duodenal infusion. Peripheral uptake was appreciably less well balanced after infusion of free amino acids (deficiency of threonine and phenylalanine) than after infusion of small peptides (deficiency of methionine). Accordingly, in the rat, under conditions of discontinuous enteral nutrition the mixture of small peptides was of greater nutritive value than the mixture of free amino acids. It thus appears that the absorption kinetics which results in important variations in the temporal distribution of free amino acids in the tissues may be at the origin of transitory imbalances in tissue amino acid uptake, and as a result of a lower nutritive value.
Amino Acids↗
Exogenous and endogenous contributions to nitrogen fluxes in the digestive tract of pigs fed a casein diet. III. Recycling of endogenous nitrogen.
The aim of the present study was to measure the incorporation of infused 15N in blood fractions, urine, digesta, faeces and in the exocrine pancreatic and biliary secretions, in order to estimate the endogenous part of nitrogen in the ileal digesta and in the faeces of pigs fed a casein diet and to calculate the total endogenous nitrogen secretion as well as its recycling in the digestive tract. For 8 d 11 Large White female pigs (50.1 +/- 1.8 kg) received a continuous infusion of L-[15N]leucine via a catheter in the jugular vein. The 15N-enrichment was measured in several fractions. The 15N-level of the pancreatic juice was higher than that in the biliary secretion, TCA-blood fractions, and urine during the whole experimental period. Using the 15N-isotope dilution method it was found that casein was completely digested up to the terminal ileum and that all the nitrogen in the ileal digesta was of endogenous origin. The total endogenous secretion was estimated at approximately 11 g N/d. The reabsorption of endogenous nitrogen amounted to 79% up to the end of the small intestine and 88% over the whole digestive tract.
Absorption↗
Intestinal absorption and liver uptake of medium-chain fatty acids in non-anaesthetized pigs.
In order to study the rate of intestinal absorption and hepatic uptake of medium-chain fatty acids (MCFA), six growing pigs, mean body weight 65 kg, were fitted with a permanent fistula in the duodenum and with three catheters in the portal vein, carotid artery and hepatic vein respectively. Two electromagnetic flow probes were also set up, one around the portal vein and one around the hepatic artery. A mixture of octanoic and decanoic acids, esterified as medium-chain triacylglycerols, together with maltose dextrine and a nitrogenous fraction was continuously infused for 1 h into the duodenum. Samples of blood were withdrawn from the three vessels at regular intervals for 12 h and further analysed for their non-esterified octanoic and decanoic acid contents. The concentration of non-esterified octanoic and decanoic acids in the portal blood rose sharply after the beginning of each infusion and showed a biphasic time-course with two maximum values, one after 15 min and a later one between 75 and 90 min. Only 65% of octanoic acid infused into the duodenum and 54% of decanoic acid were recovered in the portal flow throughout each experiment. The amounts of non-esterified MCFA taken up per h by the liver were close to those absorbed from the gut via the portal vein within the same periods of time, showing that the liver is the main site of utilization of MCFA in pigs. These results have been discussed with a special emphasis laid on the possible mechanisms of the biphasic time-course of MCFA absorption and the incomplete recovery in the portal blood of the infused fatty acids.
Animals↗
Absorption balances and kinetics of nutrients and bacterial metabolites in conscious pigs after intake of maltose- or maltitol-rich diets.
Because sorbitol is poorly absorbed in the small intestine, it may be the origin of large amounts of residues reaching the large intestine and may be substrate for microbial activity. An experiment was conducted to study the quantitative appearance in the portal blood of nutrients and metabolites derived from enzymatic hydrolysis and microbial fermentation in the fore- and hindgut. Five Large White, castrated male pigs (mean BW of 61.2 +/- 1.7 kg) were fitted under anesthesia with an electromagnetic flow probe around the portal vein and with permanent cannulas in the portal vein and the carotid artery. From 10 d before surgery, they were accustomed to one of the two semisynthetic, well-balanced diets, containing a high level (53% of DM) of either a maltose-rich glucose syrup (SNat) or of a maltitol-rich hydrogenated glucose syrup (SHyd). Eight days after surgery and after an 18-h fast, each animal was given a last meal (800 g) of the diet to which it was formerly accustomed. For 12 h after this meal, blood samples were taken at 30- to 60-min intervals for glucose, sorbitol, amino N, VFA, D- and L-lactic acids, insulin, and glucagon determinations, and portal blood flow was continuously recorded. The absorption coefficients (amounts appearing for 12 h in the portal blood: amounts ingested, percentage) of glucose and of amino N were not significantly different between the two diets. The amount of sorbitol that appeared within 12 h in the portal blood after SHyd intake was 44 g (25% intake). The amount of VFA that appeared in the portal blood within 12 h was 2.7 times larger (P < .05) after intake of the maltitol-rich diet (SHyd:808 mmol) than after intake of the maltose-rich diet (300 mmol). This difference was due to an increase in absorbed amounts of propionate (SHyd 402 vs SNat 56 mmol, P < .05), butyrate (SHyd 63 vs SNat 17 mmol, P < .01), isovalerate (SHyd 17 vs SNat 5 mmol, P < .05), and acetate (SHyd 298 vs SNat 219 mmol, P < .13). There were no significant changes in insulin and glucagon production. Intake of the maltitol-rich diet resulted in less available energy (82.0%) than did intake of the maltose-rich diet (92.6%).
Absorption↗
[Relation between food intake and oxygen consumption of organs drained by the portal vein in the conscious pig].
The intestinal absorption of glucose and alpha-amino nitrogen, the appearance of D-and L-lactic acids in the protal vein and the consumption of oxygen by the organs of the abdominal extrahepatic splanchnic area were studied simultaneously in pigs either during the postprandial period or during a fasting period of the same length. For this purpose, 5 growing pigs (59.4 +/- 3.5 kg live weight) were fitted with permanent catheters in the portal vein and carotid artery and with an electro-magnetic flowmeter probe around the portal vein. This device was used to measure the exchanges between the blood and the intestinal lumen. For a period of 1 wk, the animal received a semi-synthetic diet containing 6% purified cellulose (R6) and then during the next wk, a diet containing 16% purified cellulose (R16), the order of distribution being alternated from one animal to the next. During each of these 2 wk and after a fasting period of 16 h, they were subjected to 2 successive tests of 5 h, either after intake of an 800-g meal (R) (R6 or R16), or after no meal intake (J6 or J16). During these tests, blood samplings were made at 15 to 30-min intervals, the consumption of oxygen was recorded by an ABL3 radiometer and the afore mentioned nutrients and metabolites analysed in these samples. The consumption of oxygen was higher (P > 0.01) during the postprandial period (5.41 +/- 0.19 mmol/kg/h) than during the fasting period (4.64 +/- 0.19 mmol/kg/h) while the availability of oxygen only increased slightly (P < 0.05) (14.01 +/- 0.66 vs 13.08 +/- 0.76 mmol/kg/h). By contrast, the oxygen extraction coefficient did not significantly increase with meal intake. The appearance of L-lactic acid in the portal blood was higher (P < 0.001) during the postprandial period (3.83 +/- 0.32 g/h) than during the fasting period (1.23 +/- 0.23 g/h). The energy expenditure due to the aerobic metabolism of the organs drained by the portal vein ranged from 35.7 to 37.8 kcal/h after meal intake, ie 1-18% more than after fasting. The anaerobic metabolism only represented 0.3-0.4% (fasting) and 1.1-1.3% (postprandial period) of this aerobic metabolism. Oxygen consumption was not changed by the dietary cellulose content.
Animals↗
Splanchnic fluxes of amino acids after duodenal infusion of carbohydrate solutions containing free amino acids or oligopeptides in the non-anaesthetized pig.
Seven non-anaesthetized pigs (mean body-weight 64.6 kg) were used to study the intestinal absorption and hepatic metabolism of glucose and amino acids (AA) using carbohydrate solutions (maltose dextrin; 440 g/2 I), containing 110 g of either an enzymic milk-protein hydrolysate (PEP) with a large percentage of small peptides (about 50% with less than five AA residues) and very few free AA (8%) or a mixture of free AA (AAL) with an identical pattern, infused intraduodenally. Each pig was previously fitted under anaesthesia with electromagnetic flow probes around the portal vein and the hepatic artery, and with permanent catheters in the portal vein, carotid artery, one hepatic vein and the duodenum. Each solution was infused for 1 h after a fasting period (18 h) and each pig received both solutions at 8 d intervals. The observation period lasted 8 h. For most AA (his, lys, phe, thr, arg, tyr, pro) the absorption rate after infusion of PEP was significantly higher than after that of AAL during the 1st hour, but the differences quickly disappeared. After 8 h, the only differences concerned his and tyr (PEP > AAL) and met, glu and asp (AAL > PEP). There was a large uptake of blood AA by gut-wall cells, higher after AAL infusion than after PEP infusion, particularly for branched-chain AA (BCAA). The absorption of ammonia-nitrogen after both infusions was equivalent to two-thirds of urea-N passing from blood to intestinal tissues and lumen. Glucose absorbed within 8 h represented only 76% (PEP) or 69% (AAL) of the infused amounts. The cumulative hepatic total AA (TAA) uptake increased from 13 to 27% of the infused amounts between the 1st and the 8th hour after PEP infusion, and from 8 to 31% after AAL infusion. Most essential AA were largely taken up by the liver, with the exception of met (PEP) and thr and of BCAA, which were poorly retained for both solutions; there was a high uptake of ala and gly, and a release of asp, glu, and gln. Urea-N released by the liver within 8 h was equivalent to 23-25% absorbed amino-N and to around 1.5 times ammonia-N taken up by the liver within 8 h. Glucose was highly taken up by the liver during the first hours then released, the total uptake within 8 h representing about half the absorbed amount.(ABSTRACT TRUNCATED AT 400 WORDS)
Amino Acids↗
Hepatic and portal-drained viscera balances of amino acids, insulin, glucagon and gastrin in the pig after ingestion of casein or rapeseed proteins.
Hepatic and intestinal balances of amino acids, insulin, glucagon and gastrin were studied in 6 non-anaesthetized Large White pigs (mean body weight 64 +/- 4.8 kg) after ingestion of casein or rapeseed proteins. The animals were fitted with permanent catheters in the portal vein, the brachiocephalic artery and the right hepatic vein. In addition, 2 electromagnetic flow probes were implanted, one around the portal vein and the other around the hepatic artery. After a preliminary adaptation to each diet the animals received at 1-wk intervals and according to a double latin square design, 3 test meals of 800 g each, one containing 23.2% of rapeseed concentrate (diet RA 12) and the others 13.9 or 27.8% of hydrochloric casein (diets CA 12 and CA 24). Each observation period lasted 12 h. Amino acids from all diets were very well absorbed. In 12 h, the absorption of total amino acids as a percentage of the ingested quantities was 99% for CA 12, 102% for CA 24 and 104% for RA 12. Hepatic uptake of total amino acids in 12 h expressed as a percentage of the absorbed quantities was 13% for CA 12, 66% for CA 24 and 25% for RA 12. Differences in the hepatic extraction rate of essential amino acids appeared between the 2 levels of casein ingestion and for Arg between the 2 protein sources. Whatever the nature of the ingested protein or the level of casein, the liver showed a net production of Asp and Glu. The production and hepatic balance of insulin were the lowest after ingestion of RA 12. No differences were noted in the same parameters for glucagon and gastrin. Independently of the nutritional situation, the hepatic extraction rate of insulin appeared to be higher than those of glucagon and gastrin. Our results showed that the nature as well as the level of dietary proteins have large effects on the sequence and volume of absorptive phenomena, the hepatic metabolism of nutrients, the production of gastrointestinal hormones and the non-hepatic tissue disposal of absorbed nutrients.
Absorption↗
Exogenous and endogenous contributions to nitrogen fluxes in the digestive tract of pigs fed a casein diet. II. Ileal and faecal digestibilities and absorption of amino acids.
The present work aimed at quantifying nitrogen (N) and amino acid (AA) fluxes in the digestive tract of growing pigs fed a casein diet. In this paper we report on digesta passage at the terminal ileum, on apparent balances at the ileal and faecal levels, and on nutrients appearance in the portal vein. Digesta flow-rate at the terminal ileum was maximum between 6 and 12 h after the meal. About 10% of N and 5% of total AA ingested were recovered within 24 h. AA absorption started 30 min after the meal, and was measurable until 13 to 14 h. The total AA absorbed in 24 h accounted for 128% of the AA ingested. The AA composition of ileal digesta was very different from that of casein, closely resembling that of endogenous proteins. The AA composition of faeces was very close to that of bacterial proteins. The ileal digestibilities of AA, though lower than their faecal values, were very high. This was confirmed by AA absorption balances greater than 100%. These data suggest that casein was almost totally digested by the terminal ileum, and that endogenous AA were substantially reabsorbed. These findings are supported by data on endogenous N recycling (15N), reported in a following paper.
Amino Acids↗
Comparative digestion of maltitol and maltose in unanesthetized pigs.
Four Large White pigs (mean body weight 62.8 +/- 0.6 kg) were fitted with permanent catheters in the portal vein, carotid artery and duodenum, and with an electromagnetic flow probe around the portal vein. Eight days after surgery each animal received at 4-d intervals two duodenal infusions for 1 h each of solutions (1000 mL) containing 110 g of mild enzymic milk protein hydrolysate and 440 g of either a maltose-rich glucose syrup (54.6% maltose, 5.2% free glucose) or a maltitol-rich hydrogenated glucose syrup (54.2% maltitol, 6% free sorbitol). For 8 h after the beginning of each infusion, portal blood flow rate was recorded continuously, and blood samples were collected at various intervals (15 to 30 min) for the analysis of aminonitrogen, glucose and sorbitol. Maltitol was hydrolyzed substantially in the small gut. The absorption coefficient of glucose (percentage of infused glucose appearing in the portal blood) was the same 8 h after infusion of maltitol (78.1%) and maltose (78.8%). Sorbitol was poorly absorbed, with an absorption coefficient of 7.2% after 8 h. Its presence in the gut lumen did not inhibit the absorption of glucose. Aminonitrogen from milk oligopeptides appeared more rapidly in the portal vein during the first 4 h after infusion of maltitol than after that of maltose. This was probably due to a reduced competition between absorption of glucose and oligopeptides because of the smaller amount of glucose in the digestive lumen after maltitol hydrolysis.
Animals↗