Specific Short-chain Fatty Acids Research Articles

Butyrate Alleviates Cytokine-Induced Barrier Dysfunction by Modifying Claudin-2 Levels.

Simple SummaryThe influence of Short-chain fatty acids (SCFAs) on barrier function under pathological conditions has not been assessed, and the regulation of the tight junction (TJ) proteins by SCFAs under pathological conditions has not been fully elucidated. We therefore aimed to evaluate the effect of SCFAs on intestinal barrier function under cytokine-stimulated conditions. Butyrate, but not acetate, propionate, or succinate, ameliorated the tumor necrosis factor-alpha (TNF-α)/interferon-gamma (IFN-γ)-induced decrease in transepithelial electrical resistance (TEER). TNF-α/IFN-γ stimulation significantly increased the protein level of claudin-2 and decreased the level of claudin-3. Butyrate significantly attenuated the upregulation of claudin-2 induced by TNF-α/IFN-γ. Similarly, butyrate blocked the decrease in TEER and the upregulation of claudin-2 induced by interleukin-13, without changing the level of other TJ proteins. Our results suggested that butyrate is the main component of SCFAs to alleviate barrier dysfunction and that claudin-2 is the major target of this SCFA. It is hoped that these results will facilitate the development of treatments for diseases related to intestinal barrier impairment.Gastrointestinal (GI) disorders such as celiac disease and inflammatory bowel disease are attributed to intestinal barrier disruption. Imbalance of cytokines has been reported in the intestinal epithelium of patients with GI disorders. Short-chain fatty acids (SCFAs), derived from the fermentation of dietary fiber in the intestine, have been reported to benefit the intestinal barrier. Accordingly, we evaluated the effect of specific SCFAs on intestinal barrier function under cytokine-stimulated conditions. Caco-2 cells were cultured on insert membranes to generate monolayers, which then were used to investigate the effects of SCFAs. Tumor necrosis factor-alpha (TNF-α), interferon-gamma (IFN-γ), or interleukin-13 (IL-13) was added to the basolateral side of the membrane while SCFAs were added to the apical side. After a 24 h stimulation, transepithelial electrical resistance (TEER) was measured, and the protein levels of claudin-1, claudin-2, claudin-3, claudin-4, occludin, and zonula occludens-1 (ZO-1) were evaluated by Western blot. Butyrate, but not acetate, propionate, or succinate, ameliorated the TNF-α/IFN-γ-induced decrease in TEER. TNF-α/IFN-γ stimulation significantly increased the protein level of claudin-2 and decreased the level of claudin-3. Butyrate significantly attenuated the upregulation of claudin-2 induced by TNF-α/IFN-γ. Butyrate blocked the decrease in TEER and the upregulation of claudin-2 induced by IL-13 without changing the level of other tight junction proteins. Our results suggested that butyrate is the main component of SCFAs to alleviate barrier dysfunction and that claudin-2 is the major target of this SCFA.

Microbiota fermentation characteristics of acylated starches and the regulation mechanism of short-chain fatty acids on hepatic steatosis.

Starches acylated with specific short-chain fatty acids (SCFAs) have the potential to provide specificity in SCFA delivery. It is well documented that SCFAs are involved in lipid metabolism, but the underlying mechanism is still unclear. For characterizing the fermentation properties of acylated starches with various SCFAs in terms of SCFA production, three different acylated starches were prepared following the esterification of high amylose maize starch (HAMS) using acetic anhydride, propionic anhydride and butyric anhydride, respectively. Compared with HAMS, the gut microbiota fermentation of acetylated, propionylated and butylated starches specifically increased the production of acetic acid, propionic acid, and butyric acid, respectively, indicating that the introduced acyl group can be effectively released during the fermentation process. Furthermore, the utilization of these starches generated more total SCFAs, suggesting that they can be effectively fermented by the microbiota as a carbohydrate substrate. Study on an in vitro model of cultured rat hepatocytes indicated that either mixed SCFAs or butyrate play an important role in regulating lipid metabolism via activating AMPK and PPAR signaling pathways, implying the importance of butyrate in the improvement of lipid metabolism and accumulation. This study may provide further understanding of the individual function of the corresponding SCFA.

Diet-dependent gut microbiota impacts on adult neurogenesis through mitochondrial stress modulation.

The influence of dietary factors on brain health and mental function is becoming increasingly recognized. Similarly, mounting evidence supports a role for gut microbiota in modulating central nervous system function and behaviour. Still, the molecular mechanisms responsible for the impact of diet and associated microbiome in adult neurodegeneration are still largely unclear. In this study, we aimed to investigate whether and how changes in diet-associated microbiome and its metabolites impact on adult neurogenesis. Mice were fed a high-fat, choline-deficient diet, developing obesity and several features of the metabolic syndrome, including non-alcoholic steatohepatitis. Strikingly, our results showed, for the first time, that animals fed with this specific diet display premature increased neurogenesis, possibly exhausting the available neural stem cell pool for long-term neurogenesis processes. The high-fat, choline-deficient diet further induced neuroinflammation, oxidative stress, synaptic loss and cell death in different regions of the brain. Notably, this diet-favoured gut dysbiosis in the small intestine and cecum, up-regulating metabolic pathways of short-chain fatty acids, such as propionate and butyrate and significantly increasing propionate levels in the liver. By dissecting the effect of these two specific short-chain fatty acids in vitro, we were able to show that propionate and butyrate enhance mitochondrial biogenesis and promote early neurogenic differentiation of neural stem cells through reactive oxygen species- and extracellular signal-regulated kinases 1/2-dependent mechanism. More importantly, neurogenic niches of high-fat, choline-deficient-fed mice showed increased expression of mitochondrial biogenesis markers, and decreased mitochondrial reactive oxygen species scavengers, corroborating the involvement of this mitochondrial stress-dependent pathway in mediating changes of adult neurogenesis by diet. Altogether, our results highlight a mitochondria-dependent pathway as a novel mediator of the gut microbiota–brain axis upon dietary influences.

Microbial hydrogen economy alleviates colitis by reprogramming colonocyte metabolism and reinforcing intestinal epithelial barrier

Abstract Several studies have found exogenous H2 treatment can alleviate inflammatory damage in inflammatory bowel disease (IBD) animal models, but the mechanisms behind it are less clearly understood. The present study aimed to investigate whether hydrogen-rich saline (HS) attenuates IBD in mice model and the underlying mechanisms. The results showed that HS administration significantly inhibit weight loss and reduce inflammatory damage in dextran sulfate sodium (DSS)-induced acute ulcerative colitis (UC) mice model. We observed that H2 regulates the composition of microbiota by up-regulating the abundance of intestinal specific short chain fatty acids (SCFAs)-producing bacteria. Increased butyrate-producing microbes activated the intracellular butyrate sensor peroxisome proliferator–activated receptor γ (PPAR-γ) signaling pathway, meanwhile decreased the epithelial expression of Nos2, the gene encoding inducible nitric oxide synthase, and thus promoted the recovery of colonic anaerobic environment. Our results also indicated that HS administration reduce intestinal epithelial barrier permeability by decreasing the dextran concentrations in serum, inhibit dysbiotic Enterobacteriaceae expansion, increasing mucus secretion in the colonic lumen, and promoting the expression of intestinal interepithelial tight junction protein. Taken together, we identified the mechanism by which exogenous H2-improved “microbial hydrogen economy” regulates metabolic reprogramming of colonocyte through microbiota-activated PPAR-γ signaling pathway to provide colonic anaerobic environment, and reinforces intestinal epithelial barrier function, thereby promoting the recovery of intestinal homeostasis.

Acetic acid and butyric acid released in large intestine play different roles in the alleviation of constipation

Abstract Constipation is a disorder that affects people of all ages. Previous study showed Bifidobacterium spp. altered the faecal concentrations of short-chain fatty acids (SCFAs) while relieving constipation. Therefore, we speculated SCFAs might relieve constipation. We evaluated constipation-related indicators, SCFA levels and the faecal microbiota of constipated mice that were fed acylated starches derived from specific SCFAs for 1 month. It confirmed application of acylated starches resolved the issue of SCFAs absorption in small intestine by measuring the concentration of different SCFA in various tissues. Acetylated starch relieved constipation by increasing acetic acid-producing bacteria that were correlated positively with the small intestinal transit rate and water content of faeces, while butylated starch relieved constipation by increasing butyric acid-producing bacteria that were correlated negatively with the time to the first black stool defecation. These results indicated acetic acid and butyric acid play different roles in relieving constipation.

In vitro fecal fermentation of propionylated high-amylose maize starch and its impact on gut microbiota

Resistant starch (RS) acylated with propionate groups is of particular interest in terms of their capacity to deliver specific short-chain fatty acids (SCFAs) to the colon with health benefits. In the present study, we fabricated propionylated high-amylose maize starches with different degrees of substitution (DS), and monitored the in vitro human fecal fermentation profiles. Propionylated modification did not change the slow gas production properties of high-amylose maize starch throughout the whole fermentation period. The final concentration of propionate (13.68–21.10 mM) produced by propionylated starch fermentation enhanced gradually with increase of DS value, resulting from the release of introduced propionyl groups. Certain beneficial gut microbiota such as Roseburia, and Blautia were obviously promoted, suggesting that propionylated starch could regulate the composition of gut microbiota. The results may facilitate the design and manufacture of functional food products with the aim of improving colonic health.

The Gut Microbiome Influences Host Endocrine Functions.

The gut microbiome is considered an organ contributing to the regulation of host metabolism. Since the relationship between the gut microbiome and specific diseases was elucidated, numerous studies have deciphered molecular mechanisms explaining how gut bacteria interact with host cells and eventually shape metabolism. Both metagenomic and metabolomic analyses have contributed to the discovery of bacterial-derived metabolites acting on host cells. In this review, we examine the molecular mechanisms by which bacterial metabolites act as paracrine or endocrine factors, thereby regulating host metabolism. We highlight the impact of specific short-chain fatty acids on the secretion of gut peptides (i.e., glucagon-like peptide-1, peptide YY) and other metabolites produced from different amino acids and regulating inflammation, glucose metabolism, or energy homeostasis. We also discuss the role of gut microbes on the regulation of bioactive lipids that belong to the endocannabinoid system and specific neurotransmitters (e.g., γ-aminobutyric acid, serotonin, nitric oxide). Finally, we review the role of specific bacterial components (i.e., ClpB, Amuc_1100) also acting as endocrine factors and eventually controlling host metabolism. In conclusion, this review summarizes the recent state of the art, aiming at providing evidence that the gut microbiome influences host endocrine functions via several bacteria-derived metabolites.

Fermentation characteristics of resistant starch, arabinoxylan, and β-glucan and their effects on the gut microbial ecology of pigs: Areview.

Dietary fibers (DF) contain an abundant amount of energy, although the mammalian genome does not encode most of the enzymes required to degrade them. However, a mutual dependence is developed between the host and symbiotic microbes, which has the potential to extract the energy present in these DF. Dietary fibers escape digestion in the foregut and are fermented in the hindgut, producing short-chain fatty acids (SCFA) that alter the microbial ecology in the gastrointestinal tract (GIT) of pigs. Most of the carbohydrates are fermented in the proximal part, allowing protein fermentation in the distal part, resulting in colonic diseases. The structures of resistant starch (RS), arabinoxylan (AX), and β-glucan (βG) are complex; hence, makes their way into the hindgut where these are fermented and provide energy substrates for the colonic epithelial cells. Different microbes have different preferences of binding to different substrates. The RS, AX and βG act as a unique substrate for the microbes and modify the relative composition of the gut microbial community. The granule dimension and surface area of each substrate are different, which influences the penetration capacity of microbes. Arabinose and xylan are 2 different hemicelluloses, but arabinose is substituted on the xylan backbone and occurs in the form of AX. Fermentation of xylan produces butyrate primarily in the small intestine, whereas arabinose produces butyrate in the large intestine. Types of RS and forms of βG also exert beneficial effects by producing different metabolites and modulating the intestinal microbiota. Therefore, it is important to have information of different types of RS, AX and βG and their roles in microbial modulation to get the optimum benefits of fiber fermentation in the gut. This review provides relevant information on the similarities and differences that exist in the way RS, AX, and βG are fermented, and their positive and negative effects on SCFA production and gut microbial ecology of pigs. These insights will help nutritionists to develop dietary strategies that can modulate specific SCFA production and promote beneficial microbiota in the GIT of swine.

Cigarette smoke reduces short chain fatty acid production by a Porphyromonas gingivalis clinical isolate.

ObjectivesWe hypothesized that short chain fatty acid (SCFA) production by oral pathogens is suppressed by exposure to cigarette smoke extract (CSE).BackgroundTobacco smoking is a major risk factor for plaque‐induced periodontal diseases. Despite increased disease susceptibility, overt oral inflammation is suppressed in smokers, presenting a diagnostic conundrum. Bacterial‐derived SCFAs can penetrate into oral tissues where they influence multiple components of immune and healing responses. Indeed, the SCFA burden has been correlated with the inflammatory condition of the gingiva. However, the influence of cigarette consumption on SCFA production is unknown.MethodsGC/MS was employed to monitor the production of several SCFAs (propionic acid, isobutyric acid, butyric acid, and isovaleric acid) by representative anaerobic oral pathogens (Filifactor alocis 35896, Fusobacterium nucleatum 25586, Porphyromonas gingivalis 33277) that were exposed, or not, to a physiologically relevant dose of CSE (2000 ng/ml nicotine equivalents) generated from 3R4F reference cigarettes.ResultsThe growth of all three bacterial species was unaffected by CSE. The capacity to produce SCFAs by these bacteria was highly varied. F alocis produced the highest concentration of a specific SCFA (butyrate); P gingivalis provided the most robust overall SCFA signal, while F alocis and F nucleatum did not release detectable levels of isobutyrate or isovalerate. As P gingivalis 33277 was the broadest SCFA producer, three low‐passage clinical isolates (10208C, 5607, and 10512) were also examined. Compared to unconditioned microbes, reduced SCFA release was apparent in CSE‐exposed low‐passage clinical isolates of P gingivalis which reached significance for one of the three isolates (propionic, isobutyric, butyric, and isovaleric acids, all P < 0.05).ConclusionsThere is high disparity in the SCFA profiles of variant chronic periodontitis‐associated bacteria, while CSE exposure reduces SCFA production by a specific clinical strain of P gingivalis. If the latter phenomenon occurs in vivo, a reduced SCFA burden may help explain the reduced vascular response to dental plaque in tobacco smokers.

A pectic polysaccharide from peach palm fruits (Bactris gasipaes) and its fermentation profile by the human gut microbiota in vitro

Depending on their chemical structure, pectic polymers may be fermented by different bacteria in the human gut and, therefore, display a different metabolite profile. We aimed to investigate the chemical structure of pectins from peach palm fruits and to evaluate their in vitro fecal fermentation profiles. A fraction (PW-AP) containing a linear highly methyl esterified homogalacturonan (degree of esterification of 70%) with minor portions of xylogalacturonan and type I rhamnogalacturonan was submitted to fermentation by the human gut microbiota. It produced significantly less gas than fructooligosaccharides (FOS) at all evaluated time points, and in 24h presented a cumulative gas production ~27% lower than FOS. Drops in pH could be observed during fermentation of both FOS and PW-AP. Moreover, the pectin was slower fermented than FOS, though with a similar production of total short chain fatty acids (SCFA) and a lower production of branched chain fatty acids. The amounts of specific SCFA differed from that of FOS, with higher production of acetate (16.2%) and propionate (6.2%) and lower production butyrate (112%). The ratio of total SCFA production to gas production was 4.0mL/µmol and 5.5mL/µmol for FOS and PW-AP, respectively, indicating that the latter leads to less gas formation per µmol of produced SCFA. Overall, the understanding of how pectic structures are fermented brings new insights into the fiber utilization by the human gut microbiota and its relation to biological outcomes.

Organocatalytic route for the synthesis of propionylated starch

In recent years acetylated, propionylated and butyrylated starches have received special attention due to their capacity to deliver specific short chain fatty acids (SCFAs) to the colon in a sustained and predictable manner, and thus contribute to maintaining the normal physiologic function of the large bowel and preventing specific diseases.In the current contribution a non-conventional organocatalytic solventless route for the eco-friendly propionylation of corn starch is proposed. The catalyst used in the acylation is a naturally occurring α-hydroxy acid (l-tartaric acid). Propionylated starches with degree of substitution (DS) in the 0.05–1.59 interval were obtained and characterized in terms of chemical structure, morphology, crystallinity, thermal stability and hydrophilicity. Results showed that by the proposed methodology propionylated starch with the DS required for clinical use (i.e. 0.2–0.3) could be obtained within 2–3h of reaction. Characterization results evidenced the progressive loss of crystallinity of starch granules as higher substitution levels were conferred.

Short-chain fatty acid profiles from flaxseed dietary fibres after in vitro fermentation of pig colonic digesta: Structure–function relationship

Abstract Flaxseed (Linum usitatissimum L.) is rich in dietary fibres. There are four major soluble dietary fibre fractions, and their molecular structures have been characterised; however, the structure–function relationship on the short-chain fatty acid (SCFA) profiles is still unknown. SCFA profiles produced by in vitro fermentation of pig colonic digesta with soluble flaxseed dietary fibre fractions were determined by gas chromatography with psyllium arabinoxylans as the reference fibres. The results revealed that total SCFA production from all tested dietary fibres were significantly higher than negative control (NC) after 72 h fermentation. Acetic acid was the major SCFA produced, followed by propionic acid and butyric acid during 72 h fermentation. The acetic acid production from flaxseed kernel xyloglucans, and butyric acid production from flaxseed mucilage arabinoxylans were significantly higher than negative control (NC) after 48 h fermentation. Both psyllium and flaxseed mucilage arabinoxylans promoted butyric acid production more effectively than other tested dietary fibres during 48 h fermentation, while flaxseed kernel xyloglucans and flaxseed RG-I were more effective on promoting acetic acid production. The dietary fibre strucutre played major roles on promoting specific SCFAs, and the conformational characteristics might contribute to the difference of fermentability rates. Flaxseed dietary fibres were relatively slower fermentable dietary fibres as compared with psyllium fibres, and all flaxseed dietary fibres had higher level of total SCFA production than psyllium fibres after 72 h incubation. This research should further promotes the utilisation of flaxseed dietary fibres, and contributes to the optimisation of colonic health based on more balanced diets with both grain and oilseed.

Intestinal microbiology in early life: specific prebiotics can have similar functionalities as human-milk oligosaccharides

Human milk is generally accepted as the best nutrition for newborns and has been shown to support the optimal growth and development of infants. On the basis of scientific insights from human-milk research, a specific mixture of nondigestible oligosaccharides has been developed, with the aim to improve the intestinal microbiota in early life. The mixture has been extensively studied and has been shown to be safe and to have potential health benefits that are similar to those of human milk. The specific mixture of short-chain galacto-oligosaccharides and long-chain fructo-oligosaccharides has been found to affect the development of early microbiota and to increase the Bifidobacterium amounts as observed in human-milk-fed infants. The resulting gut ecophysiology is characterized by high concentrations of lactate, a slightly acidic pH, and specific short-chain fatty acid profiles, which are high in acetate and low in butyrate and propionate. Here, we have summarized the main findings of dietary interventions with these specific oligosaccharides on the gut microbiota in early life. The gut ecophysiology in early life may have consequences for the metabolic, immunologic, and even neurologic development of the child because reports increasingly substantiate the important function of gut microbes in human health. This review highlights major findings in the field of early gut colonization and the potential impact of early nutrition in healthy growth and development.

Butyrate esterified to starch is released in the human gastrointestinal tract

Short-chain fatty acids (SCFAs) maintain human colonic function and may help prevent colonic disease. A study with ileostomists showed that starches acylated with specific SCFAs largely survive passage through the small intestine, but the percentage released in the colon has not been established. The objective was to determine the percentage of ingested esterified butyrate released in the human gastrointestinal tract. The study was a randomized, crossover, controlled trial consisting of baseline and four 2-wk periods during which 16 volunteers consumed diets low in resistant starch plus 20 and 40 g cooked high-amylose maize starch (HAMS: HAMS20 or HAMS40) or butyrylated HAMS (HAMSB20 or HAMSB40) daily. HAMSB20 contained 31.8 mmol esterified butyrate. Complete 48-h fecal collections were made on days 2-3 and 12-13 of each period. Free fecal butyrate concentrations were higher after HAMSB40 than after HAMSB20 (P < 0.005) and HAMS (P < 0.0001) and higher than baseline data (P < 0.0001). Fecal esterified butyrate concentrations were highest in the HAMSB40 (days 12-13; P < 0.0001) group, and concentrations in the HAMSB40 (days 2-3) and HAMSB20 groups were higher than those in the HAMS groups and those at baseline (P < 0.0001). Ingestion of HAMSB20 and HAMSB40 resulted in the release of 26.8 ± 1.0 and 50.2 ± 2.4 mmol butyrate/d (days 12-13) (84.2 ± 3.0% and 79.0 ± 3.1% of total ingested esterified butyrate), respectively, in the gastrointestinal tract. By calculation, ∼57.2% of ingested esterified butyrate was released in the colon. Microbial analysis showed that this release was probably facilitated mainly by Parabacteroides distasonis, which increased in abundance with HAMSB40 (days 12-13) (P < 0.001). This study shows that cooked butyrylated starch delivers esterified butyrate to the human colon effectively and has the potential to improve human bowel health. This trial is registered in the Australian Clinical Trials Registry as ACTRN012606000398505.

Hindgut Plasticity in Wallabies Fed Hay either Unchopped or Ground and Pelleted: Fiber Is Not the Only Factor

Phenotypic plasticity of the gastrointestinal tract is crucial for optimal food processing and nutrient balance in many vertebrate species. For mammalian herbivores, gut plasticity is typically correlated with the fiber content of forage; however, we show here that other factors such as ingesta particle size may effect profound phenotypic plasticity of the fermentative hindgut in a medium-sized (10-kg body mass) marsupial herbivore, the red-necked wallaby (Macropus rufogriseus). When dietary fiber contents were comparable, red-necked wallabies that were fed a finely ground, pelleted hay for 60-72 d had hindguts that were some 28% heavier (empty wet mass) than those fed unchopped hay. The hindguts of pellet-fed wallabies contained more wet ingesta, which was also of a finer particle size, than those fed hay, indicating some separation of large- and small-particle fermentation between the foregut and the hindgut, respectively. Such a digestive strategy would benefit animals by allowing fermentation of a range of ingesta particle sizes that are expected for free-ranging animals faced with a spectrum of diet types and qualities. The heavier hindgut of pellet-fed wallabies was correlated with increased concentrations of short-chain fatty acids (SCFAs) in the fermentative hindgut (cecum and proximal colon) and particularly with increases in the molar proportions of n-butyric acid. The mechanisms facilitating gut plasticity in herbivorous mammals are uncertain, but we suggest that manipulating ingesta particle size rather than dietary fiber could provide a useful tool for evaluating causal explanations. In particular, altering ingesta particle size could help to distinguish possible direct processes (e.g., the favoring of smaller intestinal microbes and production of specific SCFAs) from indirect affects of feed structure (e.g., muscular hypertrophy to compensate for increased intakes and digesta bulk or the fermentation of mucus secreted to promote the flow of viscous, fine-particle material).

The Potent Deacetylase Inhibitor Trichostatin a (TSA) Increases CXCR4 Expression in Hematopoietic Stem/Progenitor Cells by Chromatin Remodelling

Stromal-cell derived factor (SDF)-1α/CXCL12 and its cognate receptor, CXCR4, play a crucial role in the trafficking of normal hematopoietic stem/progenitor cells (HSPC) and their homing/retention in bone marrow. Consequently, modulation of CXCR4 expression in HSPC could be applied therapeutically to improve the efficiency of HSPC transplantation. It is known that gene expression can be regulated by chromatin remodelling. Two groups of histone modifying enzymes, histone acetyltransferase (HAT) and histone deacetylase (HDAC) participate in the regulation of chromatin structure, and hence gene expression. Disruption of normal HAT or HDAC activities has been found in many human cancers. Recently, several structurally diverse and highly specific HDAC inhibitors (HDI) have been reported. They act as strong modulators of growth, differentiation and apoptosis in several types of cancer, particularly acute myeloid leukemia (AML). However, very little is known regarding the effects of HDI on HSPC. We have previously shown that a specific short-chain fatty acid HDI, valproic acid (VPA), enhances CXCR4 expression and function in normal HSPC (Blood 2007: 110; 425a). In order to determine whether other structurally diverse classes of HDI are able to influence CXCR4 expression in HSPC through chromatin remodelling, we investigated the effect of potent hydroxamic acid HDI Trichostatin A (TSA) on CXCR4 in normal HSPC. We examined the effect of TSA on CXCR4 expression (by FACS and real-time RT-PCR), modulation of CXCR4 transcription (chromatin immunoprecipitation (X-ChIP) analysis) and on functional response towards an SDF-1α gradient (by chemotaxis assay) of HSPC (CD34+ cells from cord blood (CB) and the models of immature hematopoietic cells expressing CD34 antigen, namely AML cell lines KG-1a and KG-1). Cells were incubated for 24 h in IMDM supplemented with 20% FCS in the presence of TSA (0.1 μM). We found that TSA increases the percentage of CXCR4-expressing CB CD34+, KG-1a, KG-1 cells (2.5-, 8- and 3-fold, respectively). This effect was also confirmed at the mRNA level in CB CD34+, KG-1a and KG-1 cells (by about 2.5-, 5- and 2.5-fold up-regulation, respectively). Moreover, X-ChIP analysis showed a significant increase in association of acetyl-histone H4 binding to the CXCR4 promoter in CB CD34+ and KG-1 cells (2- and 1.7-fold, respectively). TSA was also shown to significantly increase the chemotaxis of KG-1a cells towards SDF-1α (20 ng/mL), which was inhibited by AMD3100, a potent antagonist of CXCR4. We conclude that other HDI such as TSA regulate CXCR4 expression in HSPC by chromatin remodelling and we suggest that priming of HSPC with HDI may improve their homing and engraftment into bone marrow, especially in CB transplantation.

Resistant starches as a vehicle for delivering health benefits to the human large bowel

Non-starch polysaccharides (NSP; major components of dietary fibre) have been rather disappointing in the prevention and management of large bowel inflammatory diseases (IBD) or colorectal cancer (CRC). Resistant starch (RS) is that starch which escapes small intestinal digestion and enters the large bowel. RS contributes to total dietary fibre and could be as important as NSP in promoting large bowel health and preventing IBD and CRC. Indeed, it appears that some societies historically at low risk for these conditions eat relatively little NSP but have diets high in RS through their culinary practices. RS acts largely through its large bowel bacterial fermentation products which are, in adults, short chain fatty acids (SCFA). Collectively, SCFA have several non-specific positive actions on large bowel physiology including lowering of luminal pH. Of the major acids, butyrate has attracted the most attention. It is a major metabolic fuel for and promoter of a normal phenotype in colonocytes. Recent data from our laboratory support the latter suggestion. We have shown that, in rats, higher dietary protein (as casein, red meat or soy) increases colonocyte genetic damage and thinning of the colonic mucus barrier. However, feeding of RS as a high amylose maize starch opposed both of these changes in proportion to increased colonic butyrate. These data accord with prospective population data showing lower CRC risk with consumption of total dietary fibre. RS intakes appear to be low in most affluent industrialized countries, so increasing its consumption by modifying consumer foods is one strategy to improve public health. CSIRO and its partners are developing new high amylose cereal cultivars for this purpose. Colonic delivery of specific SCFA could also be useful clinically and we have shown that acetylated, propionylated and butyrylated starches resist small intestinal amylolysis. The bound SCFA are released by the large bowel microflora, raising their digesta levels, with the greatest increase being in the esterified acid. Feeding studies with butyrylated starch in rats have confirmed the opposition of diet-induced genetic damage, supporting a role for this SCFA in lowering risk of CRC and IBD. Further human and animal interventions are planned to determine the potential of these new types of RS in enhancing colonic health.

Excretion of starch and esterified short-chain fatty acids by ileostomy subjects after the ingestion of acylated starches

Background: Short-chain fatty acids (SCFAs) have a role in maintaining bowel health and can assist in the prevention and treatment of colonic disease. The ability of acylated starches to deliver SCFAs to the large bowel has been shown in animal studies but has not been established in humans.Objective: The aim was to determine whether cooked, highly acylated starches were resistant to small intestinal digestion in ileostomy volunteers.Design: Volunteers consumed single doses of custards containing 20 g cooked acetylated, propionylated, or butyrylated high-amylose maize starches (HAMSA, HAMSP, and HAMSB, respectively) on each collection day. The amounts of starch and of esterified SCFAs ingested and subsequently excreted in the stoma effluent were measured. Custards containing unacylated high-amylose maize starch (Hylon VII, HAMS) and low-amylose maize starch (3401C, LAMS) were consumed as controls.Results: Between 73% and 76% of the esterified SCFAs survived small intestinal digestion, which showed the potential of acylated starches to deliver specific SCFAs to the large bowel. The resistance of starches to small intestinal digestion as measured by ileal excretion was significantly greater for HAMSA, HAMSP, HAMSB, and HAMS than for LAMS (P < 0.001). The concentration of acetate in stoma digesta was higher than expected in all groups; this additional acid may have been derived from endogenous sources.Conclusions: Acylated starches are a potentially effective method of delivering significant quantities of specific SCFAs to the colon in humans. These products have potential application in the treatment and prevention of bowel disorders amenable to modulation by SCFAs.

Down-Regulation of the Monocarboxylate Transporter 1 Is Involved in Butyrate Deficiency During Intestinal Inflammation

Butyrate oxidation is impaired in intestinal mucosa of patients with inflammatory bowel diseases (IBD). Butyrate uptake by colonocytes involves the monocarboxylate transporter (MCT) 1. We aimed to investigate the role of MCT1 in butyrate oxidation deficiency during colonic inflammation. Colonic tissues were collected from patients with IBD or healthy controls and from rats with dextran sulfate sodium (DSS)-induced colitis. The intestinal epithelial cell line HT-29 was treated with interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha). MCT1 expression was analyzed by real-time reverse-transcription polymerase chain reaction, Western blot, and immunofluorescence. Butyrate uptake and oxidation in HT-29 cells was assessed using [(14)C]-butyrate. The mechanism of MCT1 gene regulation was analyzed by nuclear run-on and reporter gene assays. MCT1 messenger RNA (mRNA) and protein levels were markedly decreased in inflamed colonic mucosa of IBD patients and rats. In HT-29 cells, down-regulation of MCT1 mRNA and protein abundance by IFN-gamma and TNF-alpha correlated with a decrease in butyrate uptake and subsequent oxidation. IFN-gamma and TNF-alpha did not affect MCT1 mRNA stability but rather down-regulated gene transcription. We demonstrate that the cytokine response element is located in the proximal -111/+213 core region of the MCT1 promoter. The data suggest that butyrate oxidation deficiency in intestinal inflammation is a consequence of reduction in MCT1-mediated butyrate uptake. This reinforces the proposition that butyrate oxidation deficiency in IBD is not a primary defect.

Colonic Health: Fermentation and Short Chain Fatty Acids

Interest has been recently rekindled in short chain fatty acids (SCFAs) with the emergence of prebiotics and probiotics aimed at improving colonic and systemic health. Dietary carbohydrates, specifically resistant starches and dietary fiber, are substrates for fermentation that produce SCFAs, primarily acetate, propionate, and butyrate, as end products. The rate and amount of SCFA production depends on the species and amounts of microflora present in the colon, the substrate source and gut transit time. SCFAs are readily absorbed. Butyrate is the major energy source for colonocytes. Propionate is largely taken up by the liver. Acetate enters the peripheral circulation to be metabolized by peripheral tissues. Specific SCFA may reduce the risk of developing gastrointestinal disorders, cancer, and cardiovascular disease. Acetate is the principal SCFA in the colon, and after absorption it has been shown to increase cholesterol synthesis. However, propionate, a gluconeogenerator, has been shown to inhibit cholesterol synthesis. Therefore, substrates that can decrease the acetate: propionate ratio may reduce serum lipids and possibly cardiovascular disease risk. Butyrate has been studied for its role in nourishing the colonic mucosa and in the prevention of cancer of the colon, by promoting cell differentiation, cell-cycle arrest and apoptosis of transformed colonocytes; inhibiting the enzyme histone deacetylase and decreasing the transformation of primary to secondary bile acids as a result of colonic acidification. Therefore, a greater increase in SCFA production and potentially a greater delivery of SCFA, specifically butyrate, to the distal colon may result in a protective effect. Butyrate irrigation (enema) has also been suggested in the treatment of colitis. More human studies are now needed, especially, given the diverse nature of carbohydrate substrates and the SCFA patterns resulting from their fermentation. Short-term and long-term human studies are particularly required on SCFAs in relation to markers of cancer risk. These studies will be key to the success of dietary recommendations to maximize colonic disease prevention.