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A theoretical analysis of the potential inhibition of human sucrase-isomaltase (SI) by flavonoids was carried out with the aim of identifying potential candidates for an alternative treatment of type 2 diabetes. Two compounds from maize silks, maysin and luteolin, were selected to be studied with the structure-based density functional theory (DFT), molecular docking (MDock), and molecular dynamics (MD) approaches. The docking score and MD simulations suggested that the compounds maysin and luteolin presented higher binding affinities in N-terminal sucrase-isomaltase (NtSI) than in C-terminal sucrase-isomaltase (CtSI). The reactivity parameters, such as chemical hardness (η) and chemical potential (µ), of the ligands, as well as of the active site amino acids of the NtSI, were calculated by the meta-GGA M06 functional in combination with the 6-31G(d) basis set. The lower value of chemical hardness calculated for the maysin molecule indicated that this might interact more easily with the active site of NtSI, in comparison with the values of the acarbose and luteolin structures. Additionally, a possible oxidative process was proposed through the quantum chemical calculations of the electronic charge transfer values (∆N) between the active site amino acids of the NtSI and the ligands. In addition, maysin displayed a higher ability to generate more oxidative damage in the NtSI active site. Our results suggest that maysin and luteolin can be used to develop novel α-glucosidase inhibitors via NtSI inhibition.

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We studied the existence, biochemical characteristics and response to different environmental salinities of amylase, maltase and sucrase activity in the intertidal euryhaline crab Cyrtograpsus angulatus (Dana, 1852) along with the response to distinct salinities of glycogen and free glucose content in storage organs. Amylase, maltase and sucrase activities were kept over a broad range of pH and temperature and exhibited Michaelis-Menten kinetics. Zymography showed the existence of two amylase forms in crabs exposed to 35 (osmoconformation) and low (6-10psu; hyper-regulation) or high (40psu) (hypo-regulation) salinities. Carbohydrases activity in the hepatopancreas and glycemia were not affected in crab exposed to different environmental salinities. In 6 and 40psu, the glycogen content in anterior gills was lower than in 35psu. In 6, 10 and 40psu, glycogen concentration in hepatopancreas, muscle and posterior gills were similar to that in 35psu. Free glucose concentration in chela muscle was higher in 6 and 40psu than in 35psu. The existence and biochemical characteristics of carbohydrases activity and the adjustments in concentration of glycogen in anterior gills and free glucose in chela muscle suggests the ability to perform complete hydrolysis of glycogenic substrates and to keep glucose homeostasis in relation to acclimation to different salinity conditions.

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Many species show diet-induced flexibility of activity of intestinal enzymes; however, molecular and genetic mechanisms responsible for such modulation are less known, particularly in altricial birds. The goal of our study was to test whether a diet-induced increase in activity of intestinal maltase and sucrase in house sparrow nestlings is matched with an increase in maltase-glucoamylase (MG) and sucrase-isomaltase (SI) complex mRNAs respectively. Both enzyme activities were significantly higher in mid-intestine of nestlings fed a medium-starch (MS) diet compared to those fed a starch-free (SF) diet. In contrast to the similar pattern of dietary induction for both enzyme activities, diet MS elevated significantly only the level of MG mRNA, but not SI mRNA. The coordinated increase in activity of maltase and in MG mRNA is consistent with the hypothesis that dietary induction of this enzyme is under transcriptional control. In contrast, the lack of such coordination for changes in activity of sucrase and SI mRNA suggests that upregulation of this enzyme may be achieved by post-translational factor(s). We conclude that genetic mechanisms responsible for diet-induced flexibility of digestive enzymes in birds may differ from that observed in mammals.

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The climatic variability hypothesis (CVH) states that species are geographically more widespread at higher latitudes because individuals have a broader range of physiological tolerance or phenotypic flexibility as latitude and climatic variability increase. However, it remains unclear to what extent climatic variability or latitude, acting on the phenotype, account for any observed geographical gradient in mean range size. In this study, we analyzed the physiological flexibility within the CVH framework by using an intraspecific population experimental approach. We tested for a positive relationship between digestive-tract flexibility (i.e., morphology and enzyme activities) and latitude and climatic and natural diet variability in populations of rufous-collared sparrows (Zonotrichia capensis) captured in desert (27°S), Mediterranean (33°S), and cold-temperate (41°S) sites in Chile. In accordance with the CVH, we observed a positive relationship between the magnitude of digestive-tract flexibility and environmental variability but not latitude. The greatest digestive flexibility was observed in birds at middle latitudes, which experience the most environmental variability (a Mediterranean climate), whereas individuals from the most stable climates (desert and cold-temperate) exhibited little or no digestive-tract flexibility in response to experimental diets. Our findings support the idea that latitudinal gradients in geographical ranges may be strongly affected by the action of regional features, which makes it difficult to find general patterns in the distribution of species.

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Digestive capabilities, such as the rates nutrient hydrolysis and absorption, may affect energy intake and ultimately feeding behavior. In birds, a high diversity in gut biochemical capabilities seems to support the existence of a correlation between the morphology and physiology of the intestinal tract and chemical features of the natural diet. However, studies correlating the activity of digestive enzymes and the feeding habits at an evolutionary scale are scarce. We investigated the effect of dietary habits on the digestive physiological characteristics of eight species of passerine birds from Central Chile. The Order Passeriformes is a speciose group with a broad dietary spectrum that includes omnivorous, granivorous and insectivorous species. We measured the activity of three enzymes: maltase, sucrase and aminopeptidase-N. Using an autocorrelation analysis to remove the phylogenetic effect, we found that dietary habits had no effect on enzymatic activity. However, we found that granivorous and omnivorous species had higher levels of disaccharidase activities and insectivores had the lowest. The major difference in enzymatic activity found at the inter-specific level, compared to the reported lower magnitude of enzyme modulation owing to dietary acclimation, suggests that these differences to some extent have a genetic basis. However, the lack of a clear association between diet categories and gut physiology suggested us that dietary categorizations do not always reflect the chemical composition of the ingested food.

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OBJECTIVE: Flavonoids are naturally occurring compounds widely distributed in plants, which have hypoglycemic potential and have been described as glucosidase inhibitors. This study evaluated the effect of flavonoids on intestinal glucosidase activity after in vivo and in vitro treatment. METHODS: For the in vivo studies animals received quercetin by gavage and for the in vitro assays a segment of the small intestine was used. To obtain the oral glucose tolerance curve fasted normal rats were loaded with glucose plus flavonoids. The glycemia was measured by the glucose oxidase method. RESULTS: Quercetin reduced the effect of sucrase and maltase in the in vivo and in vitro treatments. It was observed in the in vitro studies that the maximum inhibitory effect of kaempferitrin was around 23% for maltase activity. Also, for the sucrose substrate the specific enzyme activity was significantly decreased. Aglycone, flavonoids, and kaempferol decreased significantly the maltase activity at all concentrations assayed. Finally, rutin reduced maltase-specific activity at all concentrations studied. According to the oral glucose tolerance curve, rutin reduced the serum glucose levels at 15, 30, and 60 min when administered by oral gavage 30 min before glucose overload in rats. CONCLUSION: Based on these results, we can conclude that disaccharidases are targets of flavonoids in the regulation of glucose absorption and consequently glucose homeostasis.

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Bird species exhibit great diversity in digestive tract morphology and enzymatic activity that is partly correlated with the chemical composition of their natural diets. However, no studies have assessed whether the activities of digestive enzymes of the enterocytes correlate with dietary chemical composition data analyzed as a continuous variable at an evolutionary scale. We used a phylogenetically explicit approach to examine the effect of diet on the hydrolytic activity of three digestive enzymes (maltase, sucrase, and aminopeptidase-N) in 16 species of songbirds (Order Passeriformes) from Central Chile. The total activities (µmol/min) of these enzymes were positively associated with body mass using both conventional least squares regressions and phylogenetically independent contrasts. After removing mass effects, we found a significant negative correlation between the ratio of aminopeptidase-N and maltase to the proportion of seeds found in the gizzard, but this relationship was no longer significant after controlling for phylogeny. When we analyzed the specific nutritional content of the diet, we found that the percentage of nitrogen in diet was negatively correlated with residual maltase activity and positively correlated with the ratio aminopeptidase-N/maltase. Given the large interspecific differences in biochemical capacity, we conclude that these differences reflect genetically determined evolutionary changes associated with the nutrient contents of each species' natural diet.

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The digestive and metabolic characteristics at the biochemical level underlying between-habitat dietary shift of the SW Atlantic euryhaline burrowing crab Neohelice granulata under natural conditions are unknown. We made studies on adult males of N. granulata from the open mudflat and the vegetated saltmarsh in a SW Atlantic costal lagoon (Mar Chiquita, 37°32'-37°45'S; 57°19'-57°26'W, Argentina). We determined and compared amylase, maltase, sucrase, proteolytic, lipase and alkaline phosphatases activities in the hepatopancreas; glycemia, and glycogen, free glucose, triglycerides and protein concentrations in hepatopancreas, chela muscle, and anterior and posterior gills. The results show that N. granulata exhibits characteristics and between-habitat differences at the biochemical level (i.e. high amylase and disaccharidase activities, differences in total proteolytic, lipase and levamisole-insensitive AP activities in the hepatopancreas, and in the concentrations of glycogen in the gills, triglycerides in the hepatopancreas and of protein in the chela muscle) which could represent adaptive digestive and metabolic strategies to face the differences in environmental conditions (i.e. food availability). The possible relationship between digestive and metabolic characteristics and feeding patterns, type of food available and environmental conditions in each habitat is discussed.

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Digestive capabilities, such as the rates nutrient hydrolysis and absorption, may affect energy intake and ultimately feeding behavior. In birds, a high diversity in gut biochemical capabilities seems to support the existence of a correlation between the morphology and physiology of the intestinal tract and chemical features of the natural diet. However, studies correlating the activity of digestive enzymes and the feeding habits at an evolutionary scale are scarce. We investigated the effect of dietary habits on the digestive physiological characteristics of eight species of passerine birds from Central Chile. The Order Passeriformes is a speciose group with a broad dietary spectrum that includes omnivorous, granivorous and insectivorous species. We measured the activity of three enzymes: maltase, sucrase and aminopeptidase-N. Using an autocorrelation analysis to remove the phylogenetic effect, we found that dietary habits had no effect on enzymatic activity. However, we found that granivorous and omnivorous species had higher levels of disaccharidase activities and insectivores had the lowest. The major difference in enzymatic activity found at the inter-specific level, compared to the reported lower magnitude of enzyme modulation owing to dietary acclimation, suggests that these differences to some extent have a genetic basis. However, the lack of a clear association between diet categories and gut physiology suggested us that dietary categorizations do not always reflect the chemical composition of the ingested food.

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The effect of feed restriction and enzymatic supplementation on intestinal and pancreatic enzyme activities and weight gain was studied in broiler chickens. Quantitative feed restriction was applied to chickens from 7 to 14 d of age. An enzyme complex mainly consisting of protease and amylase was added to the chicken ration from hatching to the end of the experiment. Birds subjected to feed restriction whose diet was not supplemented showed an increase in sucrase, amylase, and lipase activities immediately after the restriction period. Amylase, lipase, and chymotrypsin activities were higher in chickens subjected to feed restriction and fed a supplemented diet than in those only subjected to feed restriction. Trypsin activity increased after feed restriction and after supplementation, but there was no interaction between these effects. Early feed restriction had no effect on enzyme activity in 42-d-old chickens. Chickens subjected to early restriction and fed the supplemented diet presented higher sucrase, maltase, and lipase activities than nonsupplemented ones (P < 0.05). There was no effect of early feed restriction or diet supplementation on weight gain to 42 d. Percentage weight gain from 14 to 42 d of age was equivalent in feed-restricted and ad libitum fed birds. Feed-restricted broilers fed a supplemented diet showed a higher percentage weight gain than nonsupplemented birds. We conclude that enzymatic supplementation potentiates the effect of feed restriction on digestive enzyme activity and on weight gain.

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We studied the ontogeny of the intestinal brush border disaccharidases sucrase and lactase in the precocial rodent Octodon degus. Sucrase hydrolyze sugars from plants while lactase hydrolyzes sugars from milk. Enzyme expression varied inversely with dietary changes according to the developmental pattern. All new-born pups had high lactase and low sucrase activities. Also, a negative correlation between sucrase and lactase activity was found, supporting the economic design hypothesis for the intestinal tract. Profiles for development of sucrase expression exhibit some differences among precocial species, and in O. degus is correlated with the slower transition from milk to solid food consumption at weaning.

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Insectivorous/frugivorous passerine species studied so far lack the ability to modulate intestinal maltase activity, in contrast to galliformes. We tested for dietary modulation of small intestine (SI) enzymes including maltase in house sparrows to understand whether the difference between the galliformes on the one hand, and the passerines on the other, reflects a phylogenetic pattern (maltase modulated in galliformes but not passerines), a dietary pattern (maltase modulated in granivores but not insectivore/frugivores), some other pattern, or chance. We also tested the prediction that intestinal peptidase activity would be increased on a high protein (HP) diet. Birds were fed three diets high in starch, protein, or lipid for 10 days. For birds on the HP diet (60.3% protein) we observed the predicted upward modulation of aminopeptidase-N activity, as compared with the lower-protein, high starch (HS) (12.8% protein) diet. In contrast, birds eating the HS diet had similar maltase and sucrase activities, and only slightly higher isomaltase activity, compared with birds eating the high protein (HP), starch-free diet. Birds eating high lipid (HL) diet had low activities of both carbohydrases and peptidase. Considering that the statistical power of our tests was adequate, we conclude that house sparrows show little or no increase in carbohydrases in response to elevated dietary carbohydrate. We cannot reject the hypothesis that maltase lability among avian species has a phylogenetic component, or that high dietary fat has a depressing effect on both carbohydrase and peptidase activities.

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Culture forms of Leishmania (Leishmania) amazonensis (IFLA/BR/67/PH8) produce an extracellular enzyme that hydrolyzes sucrose molecules into their component monosaccharides. This is important because phlebotomine sand flies, the invertebrate hosts of Leishmania, ingest plant sap or aphid and coccid honeydew rich in sucrose between blood meals and Leishmania promastigotes cannot uptake sucrose. The sucrase was purified and characterized; its molecular weight, estimated by gel filtration chromatography and SDS-PAGE electrophoresis, was about 73 kDa. K(m) and V(max) measured with sucrose as substrate were respectively 4.4 mM and 6.9 mumole glucose.min-1 (mg sucrase)-1, with maximum pH activity at pH 5.5. A series of natural and p-nitrophenyl-derived substrates were assayed, characterizing the enzyme as a highly specific beta-D-fructofuranoside fructohydrolase. When 11 species of Leishmania and 7 genera of trypanosomatids were screened, only the species of the genus Trypanosoma did not produce an enzyme with saccharolytic activity. These data are in agreement with the fact that the latter vectors do not acquire sucrose or raffinose in their meals. Searching for glycolytic enzymes other than sucrase, we found an N-acetyl-beta-D-galactosaminolytic activity. This N-acetyl-galactosaminidase, here described for the first time, might have a role in peritrophic membrane disruption. The importance of sucrase and N-acetyl-beta-D-galactosaminidase in the Leishmania life cycle is discussed.

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Ethanol consumption has a toxic effect on the epithelium of the small bowel, but enterocyte maturity is very difficult to measure under these circumstances. However, when ethanol intake is combined with enterectomy, enterocyte immaturity is greater, permitting an easier separation of these two effects. In a group of rats (13 male Wistar rats weighing approximately 220 g) fed a liquid diet containing 35% ethanol for 4 weeks after resection of the proximal jejunum, the residual small intestine brush border maltase, sucrase, and lactase activities were similar to those of a pair-fed control group (13 animals). However, alkaline phosphatase activity was decreased in the mucosa and in the enterocyte brush border, probably because of the lower activity of this enzyme in the jejunum-ileum remnant of the alcoholic group.

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Bauhinia monandra is a leguminous plant that would be used in human nutrition, however it shows a high hemagglutinating activity against trypsin-treated erythrocytes of rabbit, 2 ml of a NaCl-solution extract of the seeds was given to a group of rats for 10 days. Intestinal disaccharidase activity was determined. Histopathological and histochemical examinations were also performed. Lectins from Bauhinia monandra seeds did not cause any visible intestinal damage even when they seem to be able to bind to the enterocyte brush border. The low disaccharidase activity in the membrane and enterocyte fractions, which represent the enzyme synthesis level, indicates that lectins could reduce the synthesis of these enzymes rather than inhibit the active sites of the enzymes. This effect could be in turn related with the binding action of lectins, because no effect of the autoclaved extract on the disaccharidase activity was observed.

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Se realizó un experimento para evaluar el efecto de la ingestión de pan integral sobre la actividad disacaridásica intestinal. Se utilizó un total de 21 ratas macho, las cuales se agruparon según: a) dieta control con caseína más metionina, b) dieta con blanco, y c) dieta con pan integral. Despúes del periodo experimental de 10 días, se determinó la actividad específica de lactasa, mitasa, sacarasa y trealasa en distintos niveles de localización en la microvellosidad. Todas las enzimas presentaron una disminución significativa (p<0,01) de su actividad en la fracción luminal en las ratas alimentadas con pan integral. Sólo la lactasa y la maltasa mostraron una disminución de su actividad (p<0.01) en la fracción de membrana para dicha dieta. La fracción enterocitaria no mostró diferencia cuando se comparó con la dieta de pan blanco. En todos los nivles de localización la actividad disacaridásica fue mayor en la dieta control (p<0.01). Los resultados obtenidos sugieren que el efecto por "arrastre mecánico" de la fibra dietética contenida en el pan integral es el fundamental en la interacciòn fibra-actividad disacaridásica y que, por tanto, su presencia en el intestino no afecta sensiblemente la biosíntesis de dichas enzimas en el enterocito

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A esquistossomose mansônica compromete vários órgäos, sendo o intestino e o fígado os mais agredidos. Com a intençäo de verificar o comprometimento do intestino delgado, dependente da intensidade e do tempo de infecçäo pelo Schistosoma mansoni, analisou-se a atividade das dissacaridases - lactase, sacarase e maltase - em 112 camundongos, distribuídos em 3 grupos: grupo I - controle, grupo II - infestado com 30 cercárias, grupo III - infestado com 60 cercárias. Observou-se uma diminuiçäo da atividade lactásica, sacarásica e maltásica do intestino delgado, decorrente da infestaçäo esquistossomótica, do tempo de infestaçäo e da alteraçäo entre ambos. O íleo é o segmento que demonstrou maior sensibilidade a esquistossomose, tendo uma diminuiçäo das suas dissacaridases a partir da fase inicial de infestaçäo. Opostamente, o jejuno só mais tardiamente mostra essas alteraçöes, exceto em relaçäo a lactase. Detectou-se um aumento da atividade dissacaridásica, inclusive para a lactase, em todos os grupos, com a evoluçäo etária dos animais, quantitativamente menor nos infestados. Cargas de 30 e 60 cercárias devem ser consideradas do mesmo porte, pois produziram reduçäo semelhante na atividade dissacaridásica

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