Research progress of Eubacterium and its metabolite short-chain fatty acids in regulating type 2 diabetes mellitus / 中华预防医学杂志

Intestinal flora and its metabolites are closely related to the progression of type 2 diabetes mellitus(T2DM). Eubacterium is one of the dominant intestinal flora, and its metabolites short-chain fatty acids (SCFAs) play a leading role in regulating intestinal metabolic balance. It has been reported that SCFAs can regulate the secretion of glucagon-like peptide-1, improve the function of pancreatic β cells, participate in bile acids metabolism and regulate the production of inflammatory factors in T2DM. Based on the above research background, this article mainly reviews the relationship between Eubacterium and its metabolite SCFAs and T2DM and its regulatory mechanism.

Ammonia determines transcriptional profile of microorganisms in anaerobic digestion

ABSTRACT Anaerobic digestion is important for the management of livestock manure with high ammonia level. Although ammonia effects on anaerobic digestion have been comprehensively studied, the molecular mechanism underlying ammonia inhibition still remains elusive. In this study, based on metatranscriptomic analysis, the transcriptional profile of microbial community in anaerobic digestion under low (1500 mg L-1) and high NH4 + (5000 mg L-1) concentrations, respectively, were revealed. The results showed that high NH4 + concentrations significantly inhibited methane production but facilitated the accumulations of volatile fatty acids. The expression of methanogenic pathway was significantly inhibited by high NH4 + concentration but most of the other pathways were not significantly affected. Furthermore, the expressions of methanogenic genes which encode acetyl-CoA decarbonylase and methyl-coenzyme M reductase were significantly inhibited by high NH4 + concentration. The inhibition of the co-expressions of the genes which encode acetyl-CoA decarbonylase was observed. Some genes involved in the pathways of aminoacyl-tRNA biosynthesis and ribosome were highly expressed under high NH4 + concentration. Consequently, the ammonia inhibition on anaerobic digestion mainly focused on methanogenic process by suppressing the expressions of genes which encode acetyl-CoA decarbonylase and methyl-coenzyme M reductase. This study improved the accuracy and depth of understanding ammonia inhibition on anaerobic digestion.

The use of Prevotella bryantii 3C5 for modulation of the ruminal environment in an ovine model

Abstract In the Southern Hemisphere, ruminants are mostly raised in grazing systems where animals consume forage and are supplemented with low amounts of concentrates. Concentrates are usually given separately and are rapidly ingested. This practice leads to changing rumen environment conditions during the day, may alter the rumen microbial metabolism and could affect host performance. The native ruminal Prevotella bryantii strain 3C5 was administered every 48 h to wethers under experimental conditions simulating Southern-Hemisphere feeding to evaluate its potential as a rumen fermentation modulator. The inoculum potential was assessed on day 17. The ammonia nitrogen (NH3-N), volatile fatty acids and ruminal pH were monitored on a 24-h basis 19 days after the beginning of the experiment, and the microbial community structure was assessed by pyrosequencing. The administration of P. bryantii modified the fermentation products and daily pH values compared to the control. The NH3-N concentration in the rumen of treated animals was significantly higher than that of the untreated animals. Modification of the ruminal environment and fermentation pathways was achieved without altering the general structure of the microbial community or the potential methane production. P. bryantii 3C5 could be considered in potential probiotic formulations for ruminants in semi-intensive systems.

An overview of biotechnological production of propionic acid: from upstream to downstream processes

The increasing demand for propionic acid (PA) production and its wide applications in several industries, especially the food industry (as a preservative and satiety inducer), have led to studies on the low-cost biosynthesis of this acid. This paper gives an overview of the biotechnological aspects of PA production and introduces Propionibacterium as the most popular organism for PA production. Moreover, all process variables influencing the production yield, different simple and complex carbon sources, the metabolic pathway of production, engineered mutants with increased productivity, and modified tolerance against high concentrations of acid have been described. Furthermore, possible methods of extraction and analysis of this organic acid, several applied bioreactors, and different culture systems and substrates are introduced. It can be concluded that maximum biomass and PA production may be achieved using metabolically engineered microorganisms and analyzing the most significant factors influencing yield. To date, the maximum reported yield for PA production is 0.973 g·g-1, obtained from Propionibacterium acidipropionici in a three-electrode amperometric culture system in medium containing 0.4 mM cobalt sepulchrate. In addition, the best promising substrate for PA bioproduction may be achieved using glycerol as a carbon source in an extractive continuous fermentation. Simultaneous production of PA and vitamin B12 is suggested, and finally, the limitations of and strategies for competitive microbial production with respect to chemical process from an economical point of view are proposed and presented. Finally, some future trends for bioproduction of PA are suggested.

Volatile fatty acids influence on the structure of microbial communities producing PHAs

Polyhydroxyalkanoates (PHAs) can be produced by microorganisms and are a biodegradable alternative to fossil-fuel based plastics. Currently, the focus is on reducing production costs by exploring alternative substrates for PHAs production, and on producing copolymers which are less brittle than monomers. Accordingly, this study used a substrate consisting of wastewater from waste-glycerol fermentation, supplemented with different amounts of acetic and propionic acids. These substrates were used to feed mixed microbial communities enriched from activated sludge in a sequencing batch reactor. A reactor supplemented with 2 mL of acetic acid produced 227.8 mg/L of a homopolymer of hydroxybutyrate (3HB); 4 mL of acetic acid produced 279.8 mg/L 3HB; whereas 4 mL of propionic acid produced 673.0 mg/L of a copolymer of 3HB and 3HV (hydroxyvalerate). Ribosomal Intergenic Spacer Analysis (RISA) was used to show the differences between the communities created in the reactors. Thauera species predominated in biomass that produced 3HB; Paracoccus denitrificans in the biomass that produced 3HB-co-3HV. Because P. denitrificans produced the more desirable copolymer, it may be advantageous to promote its growth in PHAs-producing reactors by adding propionate.

Fermentação ruminal de ovinos alimentados com alto concentrado e grãos de girassol ou gordura protegida / Ruminal fermentation of sheep fed high-concentrated diet containing sunflower grains or protected fat

Seis ovinos machos, não castrados, da raça Santa Inês, com média de peso de 30kg, fistulados no rúmen, foram distribuídos em delineamento de quadrado-latino duplo (3x3). Três períodos e três dietas, uma controle, sem inclusão de fonte de lipídio, e duas com inclusão de grãos de girassol ou gordura protegida, foram testados quanto aos parâmetros ruminais. Foram verificadas diferenças (P<0,05) entre as dietas quanto à concentração ruminal de amônia (18mg/dL), mas não houve efeito sobre o pH (6,1), a produção total de ácidos graxos de cadeia curta (98mM), a proporção de acetato (66,4 por cento), de propionato (20 por cento) e de butirato (13 por cento) e sobre a razão acetato:propionato (3,2:1). As bactérias sólido-aderidas isoladas do conteúdo ruminal dos animais recebendo a dieta-controle apresentaram maior teor de nitrogênio (10,7 por cento) que as das dietas com gordura protegida (9,8 por cento) ou com grãos de girassol (9,1 por cento). A produção de nitrogênio pelas bactérias sólido-aderidas da dieta-controle (170mg/g) não diferiu da dieta com grãos de girassol (153mg/kg) ou com gordura protegida (160mg/kg). A inclusão de grãos de girassol ou gordura protegida na dieta com alto concentrado para ovinos propiciou ambiente adequado para fermentação ruminal.

Six not castrated Santa Inês breed male sheep, weighing 30kg, fistulated in the rumen, were randomly alloted in a double Latin-Square design (3x3). Three periods and three diets, a control without addition of the lipid source, and two with addition of sunflower seeds or protected fat, were tested on the ruminal fermentation. Differences (P<0.05) between diets for ruminal ammonia concentration (18mg/dL) were observed. However, effects were not detected on pH (6.1); the total production of short-chain fatty acids (98mM); proportions of acetate (66.4 percent), propionate (20 percent), and butyrate (13 percent); and acetate:propionate ratio (3.2:1). The solid-adherent bacteria isolated from the rumen content of animals fed control diet had higher nitrogen content (10.7 percent) than those fed protected fat diet (9.8 percent) or sunflower seeds diet (9.1 percent). The production of nitrogen by bacteria attached to solid-control diet (170mg/kg) did not differ from sunflower seeds (153mg/kg) or protected fat diets (160mg/kg). The inclusion of sunflower seeds or protected fat in diets with high concentrate for sheep provided suitable environment for rumen fermentation.

Anaerobic degradation of coconut husk leachate using UASB-reactor.

Reffing of coconut husk, the majorprocess in quality coir fibre extraction, causes serious pollution with brackish water lagoons of Kerala. An attempt is made to treat the coconut husk leachate by using a laboratory scale UASB-reactor The experiment was conducted with loading of leachate from 1 kg of fresh coconut husk. The anaerobic treatment was done continuously The parameters like VFA, pH, COD and polyphenols were analysed regularly during the evaluation of the reactor performance. The polyphenol, VFA and COD were diminished gradually with time. The pH of the reactor during the study was found to be in the range of 6-8. The biogas production was increased with loading and about 82% of the total COD/kg husk could be converted to biogas. The maximum polyphenol loading in the reactor was reached to about 298.51 mg/l of husk.

Treatment of spent wash in anaerobic thermophilic suspended growth reactor (ATSGR).

Pollution through spent wash is a major problem in India. There is an urgent need to develop wastewater treatment technologies for safer disposal. In the present investigation, an attempt has been made to examine a few aspects of thermophilic anaerobic digestion of spent wash collected from a distillery. The study was carried out in a 4 liter laboratory scale anaerobic thermophilic suspended growth reactor After the successful startup, the organic loading was increased stepwise to assess the performance of the reactor. During the study period, biogas generated was recorded and the maximum gas generated was found to be 11.9 liter at an organic loading rate (OLR) of 29 g COD/l. A 500% increase in the volatile fatty acid (VFA) concentration (1850 mg/l) was observed, when the OLR was increased from 29 to 30 g COD/l. During the souring phase the removal of COD, total solids (TS) and volatile solids (VS) were in the order of 52%, 40% and 46% respectively The methane content in the biogas varied from 65% to 75%.

Necrotising enterocolitis: the state of the science.

Necrotizing enterocolitis is the most common gastrointestinal emergency of the neonate, affecting 5-10% of infants, yet the pathogenesis remains unclear. Widely accepted risk factors include prematurity, enteral feeds, bacterial colonization and mucosal injury. How these or other yet identified factors come together to create the classic clinical and pathologic features is the subject of much research. The activation of the cytokine cascade, in part by bacterial ligands, appears to play a key role in mucosal injury. Two mediators that may also contribute are platelet activating factor and intestinal toll-like receptors. Short chain fatty acids, the products of bacterial fermentation of carbohydrates, have been thought to cause mucosal injury. Overgrowth of pathogenic bacteria in the face of a decreased commensal population may play a key role. A current focus of clinical research involves probiotics, enterally fed forms of commsenal bacteria. This may set the stage for a healthier intestinal ecosystem and possibly, decreased risk of NEC.

Participação do ruminoretículo e omaso na superfície absortiva total do proventrículo de bovinos / Participation of the reticulorumen and omasum in the total absorptive surface of the bovine forestomach

Cerca de 50% dos ácidos graxos voláteis (AGV) produzidos no ruminoretículo são absorvidos nesse compartimento e outros 50% passam com a fase fluida para o omaso e são absorvidos antes do duodeno. O objetivo deste trabalho foi mensurar a superfície de absorção do ruminoretículo e do omaso comparando-as com a magnitude de absorção. Oito bovinos adultos tiveram seu estômago removido imediatamente após o abate. Os compartimentos do estômago foram separados, pesados e tiveram fragmentos coletados em diversas regiões anatômicas. Procedeu-se a mensuração da área total da superfície interna por meio de captura e análise de imagens digitalizadas. A superfície absortiva do ruminoretículo (7,7 m²) foi maior (P<0,001) do que a do omaso (2,1 m²). A relação superfície/digesta, entretanto, foi maior (P=0,07) no omaso (0,22 m²/Kg) que no ruminoretículo (0,12m²/Kg), representando uma área superficial 83,3% maior no omaso por unidade de digesta. A área de um fragmento do saco ventral do rúmen apresentou correlação positiva (0,84) com a área total da superfície do rúmen, indicando ser possível a estimativa da área total do órgão por meio de biópsia. A superfície absortiva dos compartimentos parece ser compatível com a magnitude de absorção, entretanto, estudos que comparem a taxa fracional de absorção de AGV entre os compartimentos devem ser realizados.

About 50% of volatile fatty acids (VFA) produced in the reticulorumen are absorbed in this compartment. The other 50% pass with the fluid phase to the omasum and are absorbed before the duodenum. The objective of this experiment was to measure the absorption surface of the reticulorumen and omasum aiming to compare it with the absorption magnitude. Eight adult bovines had their stomachs removed immediately after slaughtering. The stomach compartments were separated and weighed. Fragments were collected from several anatomical regions. Measurements of the total area of the internal surface were taken through image capture and analysis. The reticulorumen absorptive surface (7.7 m²) was larger (P<0.001) than the omasum absorptive surface (2.1 m²). The surface/digest ratio, however, was larger (P=0.07) in the omasum (0.22 m²/kg) than in the reticulorumen (0.12m²/kg), representing an omasum surface area for each digest unit 83.3% larger. The area of one of the rumen ventral sac fragments showed a positive correlation (0.84) with the total rumen surface area, indicating that it is possible to estimate the total rumen area by biopsy. The absorptive surface of the forestomach compartments seem to be compatible with absorption magnitude. However, further studies comparing VFA fractional absorption rate among forestomach compartments should be carried out.

Methanogenic activity test as an aid in evaluating performance and stability of anaerobic bioreactors.

The correlation between methanogenic activity and anaerobic reactor performance is intuitive. In this paper, an attempt has been made to suggest a new parameter, defined on the basis of the relative activity of acetoclastic and hydrogen oxidising methanogens, to aid in evaluating the performance and stability of anaerobic reactors. Performance of three bench scale reactors was assessed at different relative populations of the trophic groups of methanogens as estimated through acetoclastic and total methanogenic activity tests. Results indicated that the acetoclastic to total methanogenic activity ratio 0.7 yielded stable and optimal reactor performance. The acetoclastic and total methanogenic activity tests provide a simple technique that may aid in evaluating the performance and stability of anaerobic bioreactors.

Acidos graxos de cadeia curta e doenças colorretais / Short-chain fatty acids and colorectal diseases

O cólon humano contribui de maneira importante para a fermentaçäo de polissacárides näo absorvidos, produzindo ácidos graxos de cadeia curta (AGCC). Este artigo analisa a importância fisiológica dos AGCC para os colonócitos e as perspectivas de sua utilizaçäo clínica no tratamento das doenças colorretais. Diversos efeitos benéficos säo atribuídos ao processo de fermentaçäo e à subsequente produçäo de AGCC, como a contribuiçäo às necessidades energéticas, à manutençäo da integridade e funçäo da mucosa colônica e implicaçöes no metabolismo nitrogenado, de lipídes e glicídios. Além disso, diversas afecçöes colorretais tem sido relacionadas a deficiência de AGCC, como a colite por desuso, colite ulcerativa, bolsite pós-proctocolectomia com anastomose íleo-anal e câncer colorretal. Por este motivo, o fornecimento de AGCC diretamente à mucosa intestinal ou por via intravenosa tem sido preconizado em diversas condiçöes clínicas

Heat or gamma irradiation sterilization affects the hypocholesterolemic effect of guar gum in axenic and heteroxenic rats

1. Twenty-two axenic (germfree) or thirty heteroxenic (axenic colonized with human flora) 2.5-3.5 months old female Fisher rats were fed for four weeks either a hypercholesterolemic (HYPER) diet or a HYPER diet containing 5 per cent guar gum (GG) sterilized by heat or by gamma irradiation. 2. Axenic rats fed the irradiated GG diet had higher cholesterolemia than their counterparts fed an autoclaved diet (4.50 vs 2.29 mmol/l), whereas the method of sterilization had no effect on plasma cholesterol in axenic HYPER or heteroxenic animals (7.35 vs 6.51 mg/dl). 3. The levels of hepatic esterified cholesterol were higher in heteroxenic animals fed the irradiated GG diet than in their counterparts fed the autoclaved GG diet (5.65 vs 3.57 mmol/g tissue). 4. The composition of volatile fatty acids in the cecal content of heteroxenic rats was dependent on the method of sterilization regardless of the presence of fiber: the levels of butyrate were 2.88 and 0.85 mumol/g for rats fed the autoclaved and irradiated diets, respectively. 5. Gamma irradiation abolished the cholesterol-lowering effect of guar gum, whereas sterilization by heat preserved this effect. 6. The hypocholesterolemic effect of guar was reduced by gamma irradiation sterilization and was probably mediated by qualitative changes in the intestinal microflora which interfered with bile acid absorption

Concentración fecal de ácidos grasos volátiles y ácido láctico en pacientes con sindrome de instestino corto / Fecal concentration in volatile fatty acids and latic acids in patients with short bowel syndrome

El sindrome de intestino corto (SIC) está caracterizado por diarrea y mala absorción de nutrientes. Los carbohidratos no absorbidos en el intestino delgado pueden contribuir a la diarrea a través de un efecto osmótico mediado por los propios azúcares sin absorber o por sus productos de fermentación bacteriana. En condiciones de normalidad los ácidos grasos volátiles (AGV) son los principales metabolitos bacterianos, son parcialmente absorbidos por la mucosa colónica estimulando la absorción de sodio y agua el acido láctico esta en muy bajas concentraciones, su absorción es lenta y trabajos experimentales demuestran que puede ocasionar daño a la mucosa colónica. En este trabajo se estudió la composición del agua fecal (pH,Na+,K+, osmolaridad, AGV y ácidos D y L-láctico) de pacientes con SIC comparando los resultados con un grupo control. El agua fecal de los pacientes con SIC mostró una disminución en la concentración de K+, de la relación K+/Na+, y un incremento del gap osmótico. Los AGV fueron los principales aniones orgánicos en las heces de los sujetos controles mientras que el ácido láctico fue el anion preponderante en el agua fecal obtenida de pacientes con SIC. Estos resultados sugieren que este cambio metabólico bacteriano puede contribuir a la diarrea observada en los pacientes con SIC.

La acción de los diferentes isómeros del acido láctico en el colón de la rata / The action of different lactic acid isomers in the colon of rats

La presencia de ácido láctico en la luz colónica según su calidad y/o cantidad, puede asociarse con un daño metabólico del colonocito. En este trabajo se estudio la influencia de los diferentes isómeros del ácido lático y su recêmico en dos concentraciones extremas (20 y 100 mEq/l) en la luz colônica de la rata. Las modificaciones sobre el pH, el agua y los electrólitos se asociaron con la acción absortivo secretora de la pared colónica. Por otro lado se determinó la influencia del ácido láctico sobre el mucus colônico y la permeación de albúmina. Se efectuó el estudio histopatológico del ciego y del colon izquierdo. Se demuestra que existen diferencias en el comportamiento de la pared colónica frente a los distintos isómeros y al recémico del ácido láctico; (una) mayor absorción de agua, Na+ y Cl- para el isómero D(-) a baja concentración; comportándose en forma opuesta a altas concentraciones. El pH final es más alto con la forma D(-), no habiendo grandes variaciones en la permeación de albunina entre los diferentes isómeros. A altas concentraciones se frena la absorción de Cl-. Llama la atención el porcentaje alto de erosiones especialmente en el ciego dondo se halla el isómero (+) a alta concentración. Las presentes observaciones sugieren que la presencia de ácido láctico en la colitis ulcerosa merece mayor atención sobretudo en determinar la cantidad y calidad del mismo

Acidos grasos de cadena corta: futuras aplicaciones en clínica / Short chain fatty acids: future clinical applications

Los ácidos grasos de cadena larga, son isotónicos, aportan un alto contenido calorico (9 kcal por gramo), previenen la defeciencia de ácidos grasos esenciales, se pueden administrar conjuntamente con aminoácidos y glucosa por via periférica. Entre los efectos metabolicos desfavorables, se puede anotar que requieren camitina para su oxidacion y son metabolizados lentamente en situaciones de estres. Por otra parte, se ha informado bloqueo del sistema reticuloendotelial en modelos in vitro y con dosis mayores de 3 gr, esteatosis hepática y disminucion de la capacidad de difusion pulmonar en hombres sanos. Los acidos grasos de cadena media no requieren camitina para su oxidación, y entran rapidamente a la mitocondria, pero no previenen la deficiencia de acidos grasos esenciales. Los acidos grasos de cadena corta (AGCC), son metabolizados en el ciego, con produccion de acido acetico, ácido propionico y acido butirico. Este ultimo es el principal sustrato del colonocito. Por otra parte, lo AGCC estimulan la absorcion de sodio y agua en el colon, son troficos intestinales y facilitan la cicatrizacion. Son solubles en agua y podrian administrarse como acidos libres o como sales. Podrian constituir adicionalmente un aporte calorico complementario. Su uso potencial debe ser comprobado en estudios clinicos subsiguientes.

Effect of loperamide and bisacodyl on intestinal transit time, fecal weight and short chain fatty acid excretion in the rat

En esta experiencia se estudió el efecto de drogas que modifican la motilidad colónica sobre el tiempo de tránsito intestinal (TTI), (medidos con marcadores radiopacos) el peso fecal (PF) y la concentración fecal de ácidos grasos de cadena corta (AGCC) (medidos por cromatografía gaseosa) en un grupo de 8 ratas durante 4 semanas mantenidad con una dieta convencional. Para acortar el TTI se usó bisacordyl y para alargar el TTI se usó loperamida. La primera y la tercera semana fueron períodos controles sin administración de drogas. El valor promedio de estos períodos fue, para el TTI: 28,9 ñ 1,9 h, para el PF: 9,2 ñ 1,2 g/24h, para la concentración fecal de AGCC: 60,6 ñ 17,9 mmoles/g. Durante la administración de loperamida (2da semana) se observó un incremento del TTI con respecto al período control: 40,4 ñ 8,0h una disminución en el PF: 4,8 ñ 3,6g/24h y en la concentración fecal de AGCC: 32,2 ñ 5,8 mmoles/g. Con la adminstración de Bisacodyl (4ta semana) se obtuvo una disminución en TTI: 24,8 ñ 2,5h un incremento en el PF: 27,5 ñ 3,7g/24h, y un incremento de la concentración fecal de AGCC: 108,2 ñ 39,9 mmoles/g. Se observó una correlación negativa entre el TTI y el PF (R=0,67 p < 0,01) y una correlación positiva entre la concentración de AGCC y el PF (R=0,71 p < 0,01). El análisis individual de los AGCC fecales muestra una correlación positiva del ácido acético, propiónico y butírico con el PF y una correlación negativa para el ácido isovalérico y caproico. Los resultados de este trabajo muestan que el PF y la concentración de AGCC fecales pueden ser influenciados por modificaciones del tránsito intestinal