Brush Border Digestive Enzymes Research Articles

Effects of Polyphenols on Glucose-Induced Metabolic Changes in Healthy Human Subjects and on Glucose Transporters.

Dietary polyphenols interact with glucose transporters in the small intestine and modulate glucose uptake after food or beverage consumption. This review assesses the transporter interaction in vitro and how this translates to an effect in healthy volunteers consuming glucose. As examples, the apple polyphenol phlorizin inhibits sodium-glucose linked transporter-1; in the intestinal lumen, it is converted to phloretin, a strong inhibitor of glucose transporter-2 (GLUT2), by the brush border digestive enzyme lactase. Consequently, an apple extract rich in phlorizin attenuates blood glucose and insulin in healthy volunteers after a glucose challenge. On the other hand, the olive phenolic, oleuropein, inhibits GLUT2, but the strength of the inhibition is not enough to modulate blood glucose after a glucose challenge in healthy volunteers. Multiple metabolic effects and oxidative stresses after glucose consumption include insulin, incretin hormones, fatty acids, amino acids, and protein markers. However, apart from acute postprandial effects on glucose, insulin, and some incretin hormones, very little is known about the acute effects of polyphenols on these glucose-induced secondary effects. In summary, attenuation of the effect of a glucose challenge in vivo is only observed when polyphenols are strong inhibitors of glucose transporters.

The effect of weaning diet type on grey mullet (Mugil cephalus) juvenile performance during the trophic shift from carnivory to omnivory

In captive grey mullet (Mugil cephalus) juveniles, the weaning stage overlaps the period where there are changes in the ontogeny of digestive enzymes as the fry transit from carnivory to omnivory. The aim of this study was to evaluate growth, survival, weight distribution and the activity of pancreatic and brush border digestive enzymes when fry are fed a carnivorous, herbivorous or omnivorous weaning diet.Fifteen 17-L aquaria in a flow through system with 40‰, UV treated, temperature (24.5 ± 0.5 °C) controlled seawater were stocked with eighty-five 23 dph grey mullet larvae per aquarium. This allowed the testing of three weaning dietary treatments, differing in their protein and carbohydrate content, in 5 replicate aquaria per treatment from 24 to 53 dph. Diet 1 was the dried macroalgal species Ulva lactuca and was designated as a low protein: high carbohydrate herbivorous diet. Diet 2 was a commercial microencapsulated starter feed designated as a high protein: low carbohydrate carnivorous diet. Diet 3 was a 1:1 ww mixture of diets 1 and diet 2 representing an omnivorous feeding regime.The average final weight of the omnivorous feeding fish was significantly (P < .05) higher (203.9 ± 10.0 mg dry weight, dw) than their carnivorous (163.3 ± 7.1 mg dw) and herbivorous feeding (111.8 ± 14.0 mg dw) cohorts. The population of fish fed the herbivorous diet demonstrated a significantly (P = .02) higher percentage of smaller fish (<100 mg) than the omnivorous and carnivorous feeding fish. In contrast, there was a markedly (P = .008 and P = .001) higher percentage of larger (200–400 mg) fish from the carnivorous and omnivorous treatments, respectively, than fish fed the herbivorous diet. Pancreatic α-amylase, alkaline protease and trypsin activity significantly rose when dietary carbohydrate increased, whereas chymotrypsin and lipase activities were independent of the type of diet (P > .05). The activity levels of brush border alkaline phosphatase and intracellular leucine alanine peptidase were similar in grey mullet fry fed the carnivorous and omnivorous diets, but were higher than those in fish fed the herbivorous diet (P < .05). The intestinal maturation index exhibited the highest and lowest values in mullet fry fed the carnivorous and herbivorous diets, respectively, whereas those from the omnivorous group showed intermediate values (P = .03). This study broadly suggests that aquaculture feeds for juvenile grey mullet should be designed for omnivorous feeding habits.

The Secretion and Action of Brush Border Enzymes in the Mammalian Small Intestine.

Microvilli are conventionally regarded as an extension of the small intestinal absorptive surface, but they are also, as latterly discovered, a launching pad for brush border digestive enzymes. Recent work has demonstrated that motor elements of the microvillus cytoskeleton operate to displace the apical membrane toward the apex of the microvillus, where it vesiculates and is shed into the periapical space. Catalytically active brush border digestive enzymes remain incorporated within the membranes of these vesicles, which shifts the site of BB digestion from the surface of the enterocyte to the periapical space. This process enables nutrient hydrolysis to occur adjacent to the membrane in a pre-absorptive step. The characterization of BB digestive enzymes is influenced by the way in which these enzymes are anchored to the apical membranes of microvilli, their subsequent shedding in membrane vesicles, and their differing susceptibilities to cleavage from the component membranes. In addition, the presence of active intracellular components of these enzymes complicates their quantitative assay and the elucidation of their dynamics. This review summarizes the ontogeny and regulation of BB digestive enzymes and what is known of their kinetics and their action in the peripheral and axial regions of the small intestinal lumen.

Effects of protease, phytase and a Bacillus sp. direct-fed microbial on nutrient and energy digestibility, ileal brush border digestive enzyme activity and cecal short-chain fatty acid concentration in broiler chickens.

Two experiments were conducted to determine the effects of protease and phytase (PP) and a Bacillus sp. direct-fed microbial (DFM) on dietary energy and nutrient utilization in broiler chickens. In the first experiment, Ross 308 broiler chicks were fed diets supplemented with PP and DFM in a 2×2 factorial arrangement. The 4 diets (control (CON), CON + PP, CON + DFM, and CON + PP + DFM) were fed from 15–21 days of age. In Experiment 1, significant interaction (P≤0.01) between PP and DFM on the apparent ileal digestibility coefficient for starch, crude protein, and amino acid indicated that both additives increased the digestibility. Both additives increased the nitrogen retention coefficient with a significant interaction (P≤0.01). Although no interaction was observed, significant main effects (P≤0.01) for nitrogen-corrected apparent ME (AMEn) for PP or DFM indicated an additive response. In a follow-up experiment, Ross 308 broiler chicks were fed the same experimental diets from 1–21 days of age. Activities of ileal brush border maltase, sucrase, and L-alanine aminopeptidase were increased (P≤0.01) by PP addition, while a trend (P = 0.07) for increased sucrase activity was observed in chickens fed DFM, in Experiment 2. The proportion of cecal butyrate was increased (P≤0.01) by DFM addition. Increased nutrient utilization and nitrogen retention appear to involve separate but complementary mechanisms for PP and DFM, however AMEn responses appear to have separate and additive mechanisms.

Effects of genetic strain and holding facility on the characteristics of alkaline phosphatase and brush border enzymes in silver perch (Bidyanus bidyanus)

The activity of the enzymes located in the digestive tract (pyloric caeca and intestine) in two strains and F1 crosses of the Australian freshwater fish silver perch [Murray River (M) and Cataract Dam (C)] was evaluated. The effect of the fish holding system (cages or ponds) on the activity of alkaline phosphatase (AP) and the brush border enzymes: maltase, leucine amino peptidase (LAP) and γ-glutamyl transferase (γ-GT) was examined. The enzymatic activity was tested in three intestinal sections: the pyloric caeca, upper and lower intestine. All the tested enzyme activities were influenced by an interaction between the intestinal section and the strain or cross of silver perch. For fish maintained in ponds, there were two distinct enzymatic activity patterns, one for the pure strains (C × C and M × M) and one for the crosses (C × M and M × C). Significantly higher (P<0.05) enzymatic activities of the crosses compared with the pure strains were particularly noticeable in the pyloric caeca. In fish held in cages, there was a significantly higher (P<0.05) enzymatic activity in the pyloric caeca of the C × C strain. The total enzymatic activities in the fish reared in the ponds were significantly higher (P<0.05) than those in the fish held in cages. The results of the present investigation confirm that the different genetic background of the silver perch in the Murray River and in the Cataract Dam influences the activity of the brush border digestive enzymes. This activity also varies between maintenance systems.

Effects of the partial substitution of dietary fish meal by differently processed soybean meals on growth performance, nutrient digestibility and activity of intestinal brush border enzymes in the European sea bass ( Dicentrarchus labrax)

This study evaluated the effects of replacing fish meal (FM) in the diet of European sea bass ( Dicentrarchus labrax) with differently processed soybean meals on growth performance; apparent digestibility coefficients (ADCs); the activity of alkaline phosphatase and the brush border digestive enzymes: leucine amino peptidase, maltase and γ-glutamyl transpeptidase; and the fish morphometric and flesh quality. European sea bass with an initial average body weight of 187.8 ± 1.4 g, were fed either a FM based (control) diet or a soy replacement isoproteic, isolipidic and isocaloric diet. The treatments consisted replacing FM protein by: 25% toasted, dehulled and solvent-extracted soybean meal (SE25); 50% dehulled and toasted soy seeds subjected to dry extrusion and mechanical oil extraction (ME50); 50% enzyme-treated soybean meal (ET50) and an inclusion of 60% composed of 30% toasted, dehulled and solvent-extracted soybean meal and 30% enzyme-treated soybean meal (SE + ET/60). ADCs values of dry matter, crude protein, crude lipid and gross energy did not significantly differ between ME50 and SE + ET/60 but both of them were inferior to the other treatments ( P < 0.05). Compared with the control FM-based diet, only the group that consumed the ME50 diet had lower specific growth rate, feed conversion ratio and gross protein retention efficiency values ( P < 0.05). The protein efficiency ratio did not differ between the FM-based control group and all other soy derivate groups ( P > 0.05). In order to gain more insight on the effects of the diet on fish growth, activity of the brush border enzymes was measured. No significant differences were found in leucine amino peptidase and maltase activities, between the control group and the other soy derivate groups. The activity of γ-glutamyl transpeptidase was significantly higher in the upper section in fish that consumed the control diet compared with fish that consumed the soy derivate diets. Yet, the main activity of this enzyme was found in the lower intestinal section. In all the soy derivate diets except for the SE25 diet, the activity of alkaline phosphatase was significantly lower than its activity in the control diet. Feeding diets that include various types and levels of soybean derivatives did not affect the whole body composition and slaughter yield but significantly reduced liver weight. The results show that in methionine supplemented diets, FM can be replaced in terms of protein by 25% SE, 50% ET or 60% soy composed of 30% SE and 30% ET without hampering fish performance. The inclusion of 50% protein from ME resulted in significantly lower growth performance and feed utilization.

Posthatch growth of the digestive system in wild and domesticated ducks

1. Our study was designed to test the hypothesis that domestication and artificial selection have influenced the posthatch growth and functioning of the gastrointestinal (GI) tract of ducks. The mass and length of the GI tract organs, the growth of intestinal villi, the intestinal surface area and the activities of brush border digestive enzymes were measured in a commercial strain of Pekin duck and its wild ancestor, the mallard (Anas platyrhynchos), at regular intervals between hatch and 16 weeks of age. 2. The growth of the digestive organs, with respect to body mass, was described using allometry. Allometric mass exponents were then used to calculate body ‘mass-corrected’, or ‘relative’ organ masses, relative surface areas and relative enzyme activities. There were appreciable differences between data presented on a mass-specific (g/kg) and a mass-corrected (g/kg b ) basis, which highlighted the importance of correcting for the complete effects of body mass when comparing the growth and function of the digestive system between strains. 3. While the process of domestication has induced major changes in the absolute characteristics of the GI tract, it has failed to have the same effect on the relative characteristics. During the first 2 weeks posthatch, the relative masses of the majority of digestive organs, and the GI tract as a whole, were the same in both strains. During weeks 3 to 5, domesticated ducks maintained higher absolute growth rates of the body and the GI tract, with the support of relatively smaller digestive organs. The relative masses of the small intestine and the GI tract as a whole were 45 and 66% higher respectively in mallards than in Pekin ducks during this period. 4. Domesticated ducks had elevated digestive enzyme activity and a greater absorptive surface area than mallards throughout development, both in absolute and relative terms. This appears to compensate for the failure of the relative masses of digestive organs in domesticated ducks to accompany the increased body mass and growth rate. 5. At 5 weeks posthatch, the absolute mass of the small intestine in domesticated ducks declined by 38%. There is no obvious explanation for this decline because the masses of other digestive organs, daily feed intake and body mass continued to rise.

Morphological, molecular, and functional changes in the chicken small intestine of the late-term embryo

The rapid development of the gastrointestinal tract posthatch has been described; however, little information exists concerning the development of the small intestine in the prehatch period. The present study examined the morphological, cellular, and molecular changes occurring in the small intestine toward the end of the incubation period by examining the expression of intestinal genes that code for brush border digestive enzymes and transporters, their biochemical activities, and the morphological changes in the mucosal layer. The results indicated that during the last 3 d of incubation the weight of the intestine, as a proportion of embryo weight, increased from approximately 1% on d 17 of embryonic age to 3.5% at hatch. At this time the villi could be divided into two main developmental stages, differing in their length and shape, with the larger villi often being pear-shaped and the smaller villi being narrower and having a rocket-like shape. However, on d 19 a further stage of villus development was observed. Activities of maltase, aminopeptidase, sodium-glucose transporter (SGLT)-1, and ATPase began to increase on d 19 and further increased on the day of hatch. The expression of mRNA for these brush-border membrane (BBM) enzymes and transporters was detected from d 15. Determining quantities relative to beta-actin indicated that expression of all parameters examined was low on d 15 and 17, increased 9- to 25-fold on d 19, and all decreased again on the day of hatch. Relative expression of mRNA of the different enzymes and transporters were correlated as were their activities (r = 0.75 to 0.96); however, expression was not correlated with enzymatic activities. The role of these parameters in the ontogeny of absorption is discussed. Thus, major changes in the expression and localization of the functional brush-border proteins prepare the framework for ingestion of carbohydrate- and protein-rich exogenous feed posthatch.

Experimental evidences on the potential of prebiotic fructans to reduce the risk of colon cancer

Inulin is extracted from the chicory root. It is a set of fructans with its monomers linked by means of beta(2-1) bonds. This linkage cannot be hydrolysed by either pancreatic or by brush border digestive enzymes in the upper intestinal tract of humans. As such the carbohydrates arrive in the colon, where they are fermented by bifidobacteria and other lactic acid producing bacteria, thus enhancing their relative populations in the gut. Recent research in experimental animal models revealed that inulin has significant anticarcinogenic properties. It acts chemopreventively by reducing the incidence of azoxymethane (AOM) - induced aberrant crypt foci and tumours in the colon. These effects may be due to the stimulation of bifidobacteria, which themselves have been shown to act as antigenotoxic in the colon and to reduce AOM-induced tumours. Also fermentation products, including the short-chain fatty acid butyrate, could contribute to the protective effects. In this case a mechanism may be the induction of apoptosis of already transformed cells. The experimental evidence from animal studies and from studies elucidating potential mechanisms strongly supports the possibility that inulin will contribute to reducing risks for colon cancer in humans. In order to obtain more insight into this possibility, human dietary intervention studies relating biomarkers of reduced risk to inulin consumption are needed.

Experimental evidences on the potential of prebiotic fructans to reduce the risk of colon cancer

Inulin is extracted from the chicory root. It is a set of fructans with its monomers (n=2–65) linked by means of β(2–1) bonds. This linkage cannot be hydrolysed by either pancreatic or by brush border digestive enzymes in the upper intestinal tract of humans. As such the carbohydrates arrive in the colon, where they are fermented by bifidobacteria and other lactic acid producing bacteria, thus enhancing their relative populations in the gut. Recent research in experimental animal models revealed that inulin has significant anticarcinogenic properties. It acts chemopreventively by reducing the incidence of azoxymethane (AOM) — induced aberrant crypt foci and tumours in the colon. These effects may be due to the stimulation of bifidobacteria, which themselves have been shown to act as antigenotoxic in the colon and to reduce AOM-induced tumours. Also fermentation products, including the short-chain fatty acid butyrate, could contribute to the protective effects. In this case a mechanism may be the induction of apoptosis of already transformed cells. The experimental evidence from animal studies and from studies elucidating potential mechanisms strongly supports the possibility that inulin will contribute to reducing risks for colon cancer in humans. In order to obtain more insight into this possibility, human dietary intervention studies relating biomarkers of reduced risk to inulin consumption are needed.

Does neomucosa induced by small bowel stem cell transplantation have adequate function?

Small intestinal epithelium digests and absorbs nutrients. Crypt stem cell transplantation can generate neomucosa with normal morphology, but the digestive and absorptive capacities of this neomucosa are unknown. This study evaluates stem cell induced neomucosal brush border digestive enzyme activity and nutrient transport function. Rodent small intestinal epithelial stem cells were isolated by enzymatic digestion, then grafted to inbred recipients. Grafts were retrieved at 25 days, and apical brush border membrane vesicles prepared for quantitative assays. Neomucosal lactase, sucrase, aminopeptidase N, and alkaline phosphatase activity was determined by incubation with enzyme specific substrate. Neomucosal sodium dependent D-glucose transport was evaluated by incubation with D-[U-14C] glucose. Comparative assays were performed in age-matched control intestine. Neomucosal digestive enzyme activities and D-glucose transport were all similar in neomucosa and control small intestine.

The potential use of tomato lectin for oral drug delivery. 1. Lectin binding to rat small intestine in vitro

Tomato lectin, an apparently non-toxic dietary glycoprotein with a molecular mass of 71 kDa, was isolated from ripe tomato fruits. Its potential as an intestinal bioadhesive was examined using an in vitro organ culture system and Western blotting. The lectin was shown to bind avidly to rings of small intestine and this binding could be inhibited with specific competing sugars. After electrophoretic separation and transfer onto nitrocellulose, several of the proteins located on the small intestinal brush border membranes were found to bind tomato lectin, particularly those in the 160-116 kDa molecular mass range. These correspond to intestinal brush border digestive enzymes, which are known to be complex glycoproteins. The specific binding of tomato lectin to the enterocyte cell surface may give it potential for increasing the gastrointestinal residence time as a component of an oral drug formulation.

Neurotensin stimulates growth of small intestine in rats.

Neurotensin has many actions on digestive tract motility and secretion and stimulates pancreatic growth. We examined effects of chronic administration of neurotensin on growth of small intestine and colon. Four groups of 10 rats were injected with saline or neurotensin (33, 100, or 300 micrograms/kg) every 8 h for 5 days. The small intestine was divided into four segments of equal length, weighed, and assayed for DNA, protein, and brush-border digestive enzymes. The colon was weighed and assayed for DNA and protein. Neurotensin caused dose-related increases in growth of small intestine; at the highest dose, similar increases in weight (12-20%), DNA (23-35%), and protein content (33-39%) occurred in each segment of small intestine. Maltase, sucrase, and leucine aminopeptidase (but not lactase) contents were also significantly increased after neurotensin, but the largest effects were seen in the proximal small intestine. Neurotensin had no effect on weight, DNA, or protein content of the colon. These results suggest a role for neurotensin in regulating growth of small intestine.

Enhancement of ileal adaptation by prednisolone after proximal small bowel resection in the rat.

The effect of prednisolone on the adapted ileum of the rat after jejunal resection was examined. Three weeks after 50% proximal small bowel resection animals were fed pharmacological doses of soluble prednisolone (0.75 mg/kg/day) over a one week period, and killed at four weeks. Animals treated with prednisolone showed significant increases in brush border alpha-glucosidase, leucyl-2-napththylamidase and gamma-glutamyl transferase (P less than 0.01) per unit length of intestine compared with resection alone and transection reanastomosis control groups. This increase was the result of a significant enhancement (P less than 0.01) of brush border digestive enzyme activity per milligram of epithelial cell DNA-that is, per enterocyte-and was associated with a similar increase in enterocyte RNA content. In contrast, the activities of lysosomal and mitochondrial marker enzymes per milligran of DNA were similar in each group. Cell proliferation was not further stimulated by prednisolone. Thus prednisolone can selectively enhance brush border digestive capacity after intestinal resection without increasing cell proliferation. The increase in enterocyte RNA suggests that enzyme induction may be the mechanism of this effect.