Intestinal absorption of protein hydrolysis products: a review

Many experimental techniques have allowed researchers to probe the fate of hydrolysis products from proteins in the small intestine. An overview of amino acid and peptide absorption from the small intestine is presented with attention given to historical perspectives that have led to current concepts. Speculation about nutritional significance of these processes is offered. Species differences exist in site of amino acid absorption. Numerous mechanisms are available for the transport of amino acids, including Na(+)-dependent carriers (energy-requiring), Na(+)-independent carriers and diffusion. The relative contribution each transport system makes to absorption is dependent on substrate concentration. Individual amino acids are not absorbed with equal efficiency; methionine usually is absorbed in the greatest proportion. There are interactions among amino acids for transports by specific transport systems. Small peptides (mostly di- and tripeptides) are absorbed from the small intestine more rapidly than are free amino acids; peptides are transported by systems independent of those responsible for transporting free amino acids. Evidence exists that the active transport of these peptides is via a proton gradient. Although the concept that peptides are absorbed intact into the circulation is not universally accepted, evidence supporting the possibility of tissue utilization of these small peptides is accumulating.     

Intestinal digestion of dietary and endogenous proteins along the small intestine of calves fed soybean or potato.

This study was conducted to investigate the quantitative and qualitative changes in dietary and endogenous protein components along the small intestine of calves. They were fed milk replacers in which protein was provided either by skim milk powder alone, as control diet, or by skim milk powder and a soy concentrate, a partially hydrolyzed soy protein isolate, or a potato protein concentrate (1:1 on a CP basis). The calves were continuously infused with the liquid milk substitute diets into the abomasum. Duodenal, jejunal, and ileal digesta were collected through T-piece cannulas. Digestibility (corrected for total endogenous protein) of dietary protein and the concentration of dietary, host endogenous, and bacterial proteins were estimated from the AA composition of digesta using multiple linear regression. The apparent digestibility of feed components increased linearly between the duodenum and the ileum. It was lower with the diets containing plant protein than with the control, especially at the ileum (85% for CP with soy concentrate, 73% with soy isolate, and 81% with potato concentrate vs 91% with skim milk powder). The real digestibility of dietary protein at the ileum was estimated to be 96, 95, 94, and 99%, respectively, for each of the dietary components. The partition of protein components in digesta between dietary, nonspecific endogenous, specific host endogenous, and(or) specific bacterial proteins varied along the small intestine and between diets at a given site. Intestinal apparent reabsorption of host endogenous protein was estimated to be equivalent to at least 86% of the jejunum flow. To conclude, the lower apparent digestibility of the plant protein sources studied resulted more from an enhanced loss of host and bacterial endogenous proteins than from decreased hydrolysis of dietary protein and absorption of their AA.     

Studies on the digestion of carbohydrates in the camel (Camelus dromedarius)

Summary Camels with cannulas in the small intestine were used to study the digestive-absorptive capacities of the small intestine. Solutions of different carbohydrates were infused through the cannulas and the responses in blood glucose levels were measured.Monosaccharides were readily absorbed from the camel small intestine. The pattern of disaccharide absorption indicated that there was high lactase activity and low maltase and sucrase activity, in the camel small intestinal mucosa.

---

Estudios Sobre La Digestión De Carbohidratos En Los Camellos (Camelus Dromediarius)

Resumen Se instalaron cánulas en el intestino delgado de camellos, para estudiar la capacidad digestiva-absortiva, Se utilizaron las cánulas para infundir a través de ellas una serie de soluciones diferentes de carbohidratos, midiendo de esta manera los niveles de glucosa sanguínea.Los monosacáridos se absorbieron fácilmente. El patrón absortivo de los disacáridos indicó que la actividad de la lactosa fue alta y baja la de la maltasa y sucrasa.

---

Etudes Sur La Digestion Des Hydrates De Carbone Chez Le Chameau (Camelus Dromedarius)

Résumé Les capacités digestives et d'absorption du petit intestin du chameau ont été étudiées à l'aide de cannules placées à ce niveau. Des solutions de différents hydrates de carbone ont pu être ainsi introduites dans la lumière du petit intestin avec mesures des taux de glucose dans le sang.Les monosaccharides ont été rapidement absorbés par le petit intestin du chameau. Les essais portant sur l'absorption de disaccharides ont montré l'existence d'une importante activité des lactases et d'une activité basse en ce qui concerne le maltose et le sucrose, dans le mucus du petit intestin du chameau.

     

反刍动物对蛋白质消化、吸收的研究进展

有关营养生理的研究是提出营养价值评定指标和营养调控技术的理论基础。本文对当前反刍动物蛋白质消化、吸收的研究进展作一综述。     

Intestinal absorption and structure in iron deficient piglets

The pattern of faecal egg counts after infection with 10,000 Haemonchus contortus larvae was similar within but not between, four pairs of monozygous twin sheep. Transfer of whole lymph or washed lymph cells from three immune donor sheep to their identical co-twin recipients reduced the susceptibility of the recipients to challenge with 10,000 larvae as measured by faecal egg counts. Cells from a nonimmune donor did not have this effect. In a final experiment, washed cells from an immune triplet sheep, which was actively responding to a repeated challenge infection, transferred a secondary local IgA response to a second recipient triplet and resulted in a marked reduction in worm count when compared with that of a third infectivity control triplet.     

Advanced glycation end products and sorbitol in blood from differently compensated diabetic dogs

Canine diabetes mellitus (DM) is a common metabolic disorder with long term complications, most of which are caused by glycosylation of structural proteins, decreases in antioxidant concentrations, altered osmotic balance and hypoxia due to impaired oxygen transport. Previous studies have demonstrated that under hyperglycemic conditions canine erythrocytes undergo swelling, probably due to activation of the polyol pathway. The present work aimed to assess the plasma concentration of advanced glycation end (AGE) products, stable Amadori-products generated by non-enzymatic glycosylation of proteins and the intracellular concentration of sorbitol, produced by the activation of polyol pathway in 34 blood samples from diabetic dogs and in 14 controls. AGE products were significantly higher (p<0.01) in plasma from diabetic dogs compared with control animals. The sorbitol concentration in erythrocytes was also significantly higher in diabetic dogs and, in particular, in poorly compensated animals and in dogs with ketonuria. In five cases that were analysed before and after clinical improvement, sorbitol concentration was found to correlate with improvement. These results suggest that non-specific glycosylation is increased and that the polyol pathway is activated in diabetic dogs in a manner that is proportionate to the severity of disease. Moreover, the concentration of AGE products and sorbitol may be useful for monitoring the onset of diabetic complications and assessing the most appropriate therapeutic approaches for management of canine DM.     

alpha-Ketoglutarate (AKG) absorption from pig intestine and plasma pharmacokinetics

To study the absorption, metabolism and kinetics, the AKG (in different concentrations) was administered intravenously, intra-portally, orally and directly into the ileum or duodenum of pigs, chronically fitted with portal and jugular catheters and T-shaped cannula at the duodenum and ileum. Additionally, this study was conducted to determine the influence of low pH, Fe(2+) or/and SO on AKG gut absorption and conversely FeSO(4) and FeSO(4)/AKG on Fe(2+) gut absorption. It is concluded that AKG was significantly better absorbed from the upper small intestine than from the distal sections. Furthermore, low pH, Fe(2+) and/or SO ions enhanced AKG absorption. The AKG administered to the portal vein was rapidly eliminated from the blood (half-life less than 5 min). The short lifetime for AKG is probably dependent on quick metabolism in the enteorcyetes and liver. However, the prolonged half-life can be related to its low AKG blood concentration. The Fe(2+) concentrations in blood increased after FeSO(4) and FeSO(4)/AKG duodenal infusion. The implication of above observations is important for practical application of the AKG in animal and human nutrition as well in medicine.     

Intestinal permeability and absorption in dogs with traumatic injury

The objectives of this study were to assess the feasibility of using urinary recovery of sugars to evaluate intestinal permeability and absorption in dogs with traumatic injury and to determine if intestinal permeability and absorption are altered in dogs with traumatic injury. After a 6-hour fast, a sugar solution containing lactulose, rhamnose, 3-0-methyl-D-glucose, and xylose was administered via nasoesophageal tube. Urine was collected and quantitated over the 6-hour study period via closed collection urinary catheters. Urinary sugar recoveries were measured by high-pressure anion exchange liquid chromatography and pulsed amperometric detection. Urinary sugar recoveries in the trauma group at 24, 48, and 72 hours after trauma were compared to normal controls. In addition, severity of trauma was compared to urinary sugar recoveries. Twelve client-owned dogs with traumatic injury and 6 healthy controls were enrolled in the study. Lactulose recovery and the lactulose:rhamnose recovery ratio were significantly higher in the trauma group at 48 hours but were no longer different from controls by 72 hours. Xylose recovery was significantly higher in the trauma group when compared to controls at 72 hours, whereas 3-O-methyl-D-glucose recovery was significantly lower in the trauma group at 24 hours. The xylose: 3-O-methyl-D-glucose ratio was higher in the trauma group at all time points. Significant correlation was found between severity of trauma and xylose and 3-O-methyl-D-glucose recoveries 24 hours after injury. Results of this study support the hypothesis that intestinal permeability and absorption are altered in dogs with traumatic injury.     

疑似猪玉朱赤霉烯酮中毒病的诊治

玉米赤霉烯酮又称F-2霉素属镰刀菌毒素类,是一种类似于雌激素的真菌毒素。玉米赤霉烯酮中毒主要以生殖器官病变为特征,不仅可引起小母猪霉菌性阴道炎,甚至去势过的雄性动物也可发生包皮增长和乳腺突起。本病多发生于猪,尤其以3-5月龄仔猪易感。笔者在临床工作中曾遇到一例疑似病例,现将有关情况报告如下。     

Molecular characterisation of carbohydrate digestion and absorption in equine small intestine

Dietary carbohydrates, when digested and absorbed in the small intestine of the horse, provide a substantial fraction of metabolisable energy. However, if levels in diets exceed the capacity of the equine small intestine to digest and absorb them, they reach the hindgut, cause alterations in microbial populations and the metabolite products and predispose the horse to gastrointestinal diseases. We set out to determine, at the molecular level, the mechanisms, properties and the site of expression of carbohydrate digestive and absorptive functions of the equine small intestinal brush-border membrane. We have demonstrated that the disaccharidases sucrase, lactase and maltase are expressed diversely along the length of the intestine and D-glucose is transported across the equine intestinal brush-border membrane by a high affinity, low capacity, Na+/glucose cotransporter type 1 isoform (SGLT1). The highest rate of transport is in duodenum > jejunum > ileum. We have cloned and sequenced the cDNA encoding equine SGLT1 and alignment with SGLT1 of other species indicates 85-89% homology at the nucleotide and 84-87% identity at the amino acid levels. We have shown that there is a good correlation between levels of functional SGLT1 protein and SGLT1 mRNA abundance along the length of the small intestine. This indicates that the major site of glucose absorption in horses maintained on conventional grass-based diets is in the proximal intestine, and the expression of equine intestinal SGLT1 along the proximal to distal axis of the intestine is regulated at the level of mRNA abundance. The data presented in this paper are the first to provide information on the capacity of the equine intestine to digest and absorb soluble carbohydrates and has implications for a better feed management, pharmaceutical intervention and for dietary supplementation in horses following intestinal resection.     

Intestinal adenomatosis in the pig: histochemical and electron microscopic studies of the mucosa

Histochemical studies of normal and adenomatous intestinal mucosa of the pig showed the adenomatous epithelium to be deficient in enzymes normally found in mature absorptive cells. Electron microscopic studies confirmed that the adenomatous cells closely remsembled the crypt cells of normal mucosa.     

放牧生态系统调控效应Ⅳ.促生长剂对放牧绵羊消化吸收量的调控效应

绵羊瘤胃灌注促生长剂F89，通过神经内分泌途径，调节代谢进行分配的生理性调控，使干物质食入量增加8．74％，蛋白质食入量增加12．08％。十二指肠的干物质流通量比食入量少17．10％，比回肠多18．73％，十二指肠的蛋白质流通量比食入量多42．29％，比回肠多58．25％。干物质消化主要在胃区进行，胃区比小肠多1．60个百分点，比大肠多8．22个百分点，而蛋白质的消化主要在小肠进行，它的消失量占肠道消化总量的71．28％。干物质在消化道中的消化率2组比3组多5．89个百分点，比1组多9．34个百分点，蛋白质依次多1．27个百分点和3．95个百分点，能量分别多7．89个百分点和11．18个百分点。可见，F89有促进采集、消化和提高饲料利用的功能。