Activities of amino acid metabolizing enzymes in the stomach and small intestitine of developing rats

The activities of aspartate and alanine transaminase, serine dehydratase, arginase, glutamate dehydrogenase, adenylate deaminase and glutamine synthetase were determined in the stomach and small intestine of developing rats. Despite the common embryonic origin of the intestine and stomach, their enzymes showed quite different activity levels and patterns of development, depending on their roles. Most enzyme activities were low during late intrauterine life and after birth, attaining adult levels with the change of diet at weaning. No arginase activity was found in the stomach and no changes were detected in adenylate deaminase in the stomach or intestine throughout the period studied. Alanine transaminase, serine dehydratase and, to some extent, glutamine synthetase levels, significantly higher in late intrauterine life, decreased after birth, suggesting that the foetal stomach has a transient ability to handle amino acids.

Positional bias of general and tissue-specific regulatory motifs in mouse gene promoters

Background: The arrangement of regulatory motifs in gene promoters, or promoterarchitecture, is the result of mutation and selection processes that have operated over manymillions of years. In mammals, tissue-specific transcriptional regulation is related to the presence ofspecific protein-interacting DNA motifs in gene promoters. However, little is known about therelative location and spacing of these motifs. To fill this gap, we have performed a systematic searchfor motifs that show significant bias at specific promoter locations in a large collection ofhousekeeping and tissue-specific genes.Results: We observe that promoters driving housekeeping gene expression are enriched inparticular motifs with strong positional bias, such as YY1, which are of little relevance in promotersdriving tissue-specific expression. We also identify a large number of motifs that show positionalbias in genes expressed in a highly tissue-specific manner. They include well-known tissue-specificmotifs, such as HNF1 and HNF4 motifs in liver, kidney and small intestine, or RFX motifs in testis,as well as many potentially novel regulatory motifs. Based on this analysis, we provide predictionsfor 559 tissue-specific motifs in mouse gene promoters.Conclusion: The study shows that motif positional bias is an important feature of mammalianproximal promoters and that it affects both general and tissue-specific motifs. Motif positionalconstraints define very distinct promoter architectures depending on breadth of expression andtype of tissue.

Cocoa flavonoid-enriched diet modulates systemic and intestinal immunoglobulin synthesis in adult Lewis rats

Previous studies have reported that a diet containing 10% cocoa, a rich source of flavonoids, has immunomodulatory effects on rats and, among others effects, is able to attenuate the immunoglobulin (Ig) synthesis in both systemic and intestinal compartments. The purpose of the present study was focused on investigating whether these effects were attributed exclusively to the flavonoid content or to other compounds present in cocoa. To this end, eight-week-old Lewis rats were fed, for two weeks, either a standard diet or three isoenergetic diets containing increasing proportions of cocoa flavonoids from different sources: one with 0.2% polyphenols from conventional defatted cocoa, and two others with 0.4% and 0.8% polyphenols, respectively, from non-fermented cocoa. Diet intake and body weight were monitored and fecal samples were obtained throughout the study to determine fecal pH, IgA, bacteria proportions, and IgA-coated bacteria. Moreover, IgG and IgM concentrations in serum samples collected during the study were quantified. At the end of the dietary intervention no clear changes of serum IgG or IgM concentrations were quantified, showing few effects of cocoa polyphenol diets at the systemic level. However, in the intestine, all cocoa polyphenol-enriched diets attenuated the age-related increase of both fecal IgA and IgA-coated bacteria, as well as the proportion of bacteria in feces. As these effects were not dependent on the dose of polyphenol present in the diets, other compounds and/or the precise polyphenol composition present in cocoa raw material used for the diets could be key factors in this effect.

The problem of nitrogen disposal in the obese

Amino-N is preserved because of the scarcity and nutritional importance of protein. Excretion requires its conversion to ammonia, later incorporated into urea. Under conditions of excess dietary energy, the body cannot easily dispose of the excess amino-N against the evolutively adapted schemes that prevent its wastage; thus ammonia and glutamine formation (and urea excretion) are decreased. High lipid (and energy) availability limits the utilisation of glucose, and high glucose spares the production of ammonium from amino acids, limiting the synthesis of glutamine and its utilisation by the intestine and kidney. The amino acid composition of the diet affects the production of ammonium depending on its composition and the individual amino acid catabolic pathways. Surplus amino acids enhance protein synthesis and growth, and the synthesis of non-protein-N-containing compounds. But these outlets are not enough; consequently, less-conventional mechanisms are activated, such as increased synthesis of NO∙ followed by higher nitrite (and nitrate) excretion and changes in the microbiota. There is also a significant production of N(2) gas, through unknown mechanisms. Health consequences of amino-N surplus are difficult to fathom because of the sparse data available, but it can be speculated that the effects may be negative, largely because the fundamental N homeostasis is stretched out of normalcy, forcing the N removal through pathways unprepared for that task. The unreliable results of hyperproteic diets, and part of the dysregulation found in the metabolic syndrome may be an unwanted consequence of this N disposal conflict.

Hepatocyte nuclear factor 4alpha transactivates the mitochondrial alanine aminotransferase gene in the kidney of Sparus aurata

Alanine aminotransferase (ALT) plays an important role in amino acid metabolism and gluconeogenesis. The preference of carnivorous fish for protein amino acids instead of carbohydrates as a source of energy lead us to study the transcriptional regulation of the mitochondrial ALT (mALT) gene and to characterize the enzyme kinetics and modulation of mALT expression in the kidney of gilthead sea bream (Sparus aurata) under different nutritional and hormonal conditions. 5′-Deletion analysis of mALT promoter in transiently transfected HEK293 cells, site-directed mutagenesis and electrophoretic mobility shift assays allowed us to identify HNF4α as a new factor involved in the transcriptional regulation of mALT expression. Quantitative RT-PCR assays showed that starvation and the administration of streptozotocin (STZ) decreased HNF4α levels in the kidney of S. aurata, leading to the downregulation of mALT transcription. Analysis of the tissue distribution showed that kidney, liver, and intestine were the tissues with higher mALT and HNF4α expression. Kinetic analysis indicates that mALT enzyme is more efficient in catalyzing the conversion of L-alanine to pyruvate than the reverse reaction. From these results, we conclude that HNF4α transactivates the mALT promoter and that the low levels of mALT expression found in the kidney of starved and STZ-treated fish result from a decreased expression of HNF4α. Our findings suggest that the mALT isoenzyme plays a major role in oxidazing dietary amino acids, and points to ALT as a target for a biotechnological action to spare protein and optimize the use of dietary nutrients for fish culture.

Mechanisms involved in down-regulation of intestinal IgA in rats by high cocoa intake

Previous studies have shown that rat intestinal immunoglobulin A (IgA) concentration and lymphocyte composition of the intestinal immune system were influenced by a highly enriched cocoa diet. The aim of this study was to dissect the mechanisms by which a long-term high cocoa intake was capable of modifying gut secretory IgA in Wistar rats. After 7 weeks of nutritional intervention, Peyer's patches, mesenteric lymph nodes and the small intestine were excised for gene expression assessment of IgA, transforming growth factor ß, C-C chemokine receptor-9 (CCR9), interleukin (IL)-6, CD40, retinoic acid receptors (RAR¿ and RARß), C-C chemokine ligand (CCL)-25 and CCL28 chemokines, polymeric immunoglobulin receptor and toll-like receptors (TLR) expression by real-time polymerase chain reaction. As in previous studies, secretory IgA concentration decreased in intestinal wash and fecal samples after cocoa intake. Results from the gene expression showed that cocoa intake reduced IgA and IL¿6 in Peyer's patches and mesenteric lymph nodes, whereas in small intestine, cocoa decreased IgA, CCR9, CCL28, RAR¿ and RARß. Moreover, cocoa-fed animals presented an altered TLR expression pattern in the three compartments studied. In conclusion, a high-cocoa diet down-regulated cytokines such as IL-6, which is required for the activation of B cells to become IgA-secreting cells, chemokines and chemokine receptors, such as CCL28 and CCR9 together with RAR¿ and RARß, which are involved in the gut homing of IgA-secreting cells. Moreover, cocoa modified the cross-talk between microbiota and intestinal cells as was detected by an altered TLR pattern. These overall effects in the intestine may explain the intestinal IgA down-regulatory effect after the consumption of a long-term cocoa-enriched diet.

Estudio multidisciplinario del ecosistema manglar en la comunidad tradicional de Curral Velho : Análisis de los servicios ecosistémicos producidos por los manglares a partir de la percepción de la comunidad de Curral Velho

Existe un número elevado de sectores de la sociedad que identifican los beneficios ofrecidos por el ecosistema del manglar así como la interacción entre ellos y el bienestar humano. Aún así, los servicios ecosistémicos (ESs) ofrecidos por la naturaleza son poco visibles y reconocidos legislativamente. Se puede observar que el manglar es uno de los ecosistemas más productivos del planeta. Tienen gran importancia tanto económica, social, ambiental como cultural, pero en las últimas décadas se ha hecho más notable una degradación progresiva debida, en gran parte, a la cría de camarón en cautividad, la camaronicultura. Por esta causa, se observa que la legislación y las políticas que pretenden gestionar estos ecosistemas, no actúan en consecuencia al no imponer ciertas medidas necesarias para esta vital protección, ni considera la importancia de los ecosistemas para la vida de las comunidades tradicionales que dependen de sus servicios para sobrevivir. Por ello es necesario producir un conocimiento sobre ESs a partir de la percepción por parte de la comunidad y que la comunidad se implique en la resolución de esta problemática, ya sea en la toma de decisiones o mediante ciertas actividades o acciones que puedan denunciar estas prácticas insostenibles. Frente a este contexto, este trabajo fue realizado a partir de la información obtenida en la comunidad de Curral Velho (Ceará, Brasil), con el objetivo de realizar un estudio sobre los ESs proveídos por los manglares a partir de la percepción de la comunidad para demostrar la importancia que éstos tienen para el bienestar de los habitantes de la comunidad que se benefician. Los resultados fueron alcanzados a partir de una combinación de metodologías sociales que hacen posible la participación por parte de los habitantes: free listing, encuestas de valoración, grupos focales y observación participante. En la aplicación de estos métodos fueron identificados nuevos ESs de carácter psicológico por los pescadores/as de la pesca artesanal. Por lo que se concluye que es importante tener en cuenta la opinión de las comunidades adyacentes para preservar los flujos ecosistémicos que proporciona el manglar.

Estudio multidisciplinario del ecosistema manglar en la comunidad tradicional de Curral Velho : Estudio sobre la pesca artesanal y análisis de sus diferencias con la acuicultura del camarón

Curral Velho es una comunitat tradicional, situada al nord-est de Brasil, que manté una relació directa amb els ecosistemes que la envolten. La comunitat depèn del estat de conservació del medi natura, ja que obtenen diferents serveis ecositemics. En aquest territori es desenvolupen dos tipus d’economies amb unes bases molt diferents. Una economia tradicional, desenvolupada per la pròpia comunitat, que es basa en la propietat col·lectiva del territori i en optimitzar a llarg termini els beneficis que s’obtenen del medi; y un altre com la camaronicultura, la base de la qual es la obtenció de beneficis a curt termini i amb un territori de propietat privada. Aquesta superposició de models de producció genera impactes ambientals, i un conflicte socio-ambiental entre la comunitat i els que desenvolupen la camaronicultura. L’objectiu es realitzar un estudi econòmic de la pesca artesanal de Curral Velho caracteritzant manera de viure, creant una base de dades sobre pesca artesanal i elaborant indicador de beneficis econòmics generats per la pesca artesanal. Per contextualitzar els resultats es va fer un anàlisis de les dos economies existents a la comunitat. Els resultats obtinguts en primer lloc són que l’economia d’explotació intensiva aporta més guanys per les persones de la comunitat que tenen un relació directa que les que es dediquen a la pesca artesanal, però es important no aturar-se aquí: s’ha de realitzar un anàlisis més profund. Com a conclusió, la activitat pesquera es més rentable a llarg termini ja que els recursos extrets de manera sostenible i així són il·limitats y accessibles a tota la comunitat. A diferència de la camaronicultura, la pesca artesanal no genera desigualtats socials ni vulneracions dels drets humans. Tot el contrari, genera forts vincles entre els individus de la comunitat basats en el treball en equip i l’aprenentatge vivencial e intergeneracional.