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Microbe diet interactions influence the effects of fiber on host metabolismEnergy metabolism and dietary fiber -
Diets naturally high in fiber can be considered to bring about several main physiological consequences: [1]. Fiber is defined by its physiological impact, with many heterogenous types of fibers. Some fibers may primarily impact one of these benefits i. Defining fiber physiologically allows recognition of indigestible carbohydrates with structures and physiological properties similar to those of naturally occurring dietary fibers.
In this definition, "edible parts of plants" indicates that some parts of a plant that are eaten—skin, pulp, seeds, stems, leaves, roots—contain fiber. Both insoluble and soluble sources are in those plant components. A food resistant to this process is undigested, as insoluble and soluble fibers are.
They pass to the large intestine only affected by their absorption of water insoluble fiber or dissolution in water soluble fiber. Fermentation occurs through the action of colonic bacteria on the food mass, producing gases and short-chain fatty acids.
These short-chain fatty acids have been shown to have significant health properties. As an example of fermentation, shorter-chain carbohydrates a type of fiber found in legumes cannot be digested, but are changed via fermentation in the colon into short-chain fatty acids and gases which are typically expelled as flatulence.
According to a journal article, [97] fiber compounds with partial or low fermentability include:. When fermentable fiber is fermented, short-chain fatty acids SCFA are produced.
SCFAs that are absorbed by the colonic mucosa pass through the colonic wall into the portal circulation supplying the liver , and the liver transports them into the general circulatory system. Overall, SCFAs affect major regulatory systems, such as blood glucose and lipid levels, the colonic environment, and intestinal immune functions.
The major SCFAs in humans are butyrate , propionate , and acetate , where butyrate is the major energy source for colonocytes , propionate is destined for uptake by the liver, and acetate enters the peripheral circulation to be metabolized by peripheral tissues.
The United States FDA allows manufacturers of foods containing 1. Soluble fiber from foods such as [name of soluble fiber source, and, if desired, name of food product], as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease.
The allowed label may state that diets low in saturated fat and cholesterol and that include soluble fiber from certain of the above foods "may" or "might" reduce the risk of heart disease. As discussed in FDA regulation 21 CFR Soluble fiber from consuming grains is included in other allowed health claims for lowering risk of some types of cancer and heart disease by consuming fruit and vegetables 21 CFR In December , FDA approved a qualified health claim that consuming resistant starch from high- amylose corn may reduce the risk of type 2 diabetes due to its effect of increasing insulin sensitivity.
The allowed claim specified: "High-amylose maize resistant starch may reduce the risk of type 2 diabetes.
FDA has concluded that there is limited scientific evidence for this claim. Contents move to sidebar hide. Article Talk. Read Edit View history. Tools Tools. What links here Related changes Upload file Special pages Permanent link Page information Cite this page Get shortened URL Download QR code Wikidata item.
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Retrieved 8 June Retrieved 11 October BAT weight of the XGC group was higher than that of the DLC group Figure 7. The influence of region and diet on other indexes of E.
miletus were not significant Table 4. Figure 7. Effects of region and high-fiber food on morphological indicators of Eothenomys miletus. A : Body mass, B : food intake, C RMR, D : liver weight, E : small intestine length, F : cecum length, G : WAT weight, H : BAT weight.
Data are mean ± SE. Different letters denote significant differences among treatments in the same region, capital letters refer to the DL region, and lowercase letters refer to the XGLL region. XGLL on the same day. Table 4.
Effects of region and high-fiber food on physiological indicators in Eothenomys miletus. Leptin and UCP1 of E. Leptin in DL was higher than that of XGLL, and UCP1 in XGLL was higher than that of DL. The SCFAs of the DLC and XGC group were significantly different, and the difference in DL was higher than that in XGLL.
Diet had a significant effect on LBP in E. miletus [ F 3. LBP in DLRe group was higher than that in DLHF group Figure 8. miletus were not significant Table 5. Figure 8. Effects of region and high-fiber food on physiological indices of Eothenomys miletus. A : Leptin, B : Glu, C : Tg, D : SCFAs, E : LBP, F : TNT-α.
Table 5. Effects of region and high-fiber food on serum physiological indicators in Eothenomys miletus. Figure 9. Correlation heat map between physiological indicators and dominant microorganisms of Eothenomys miletus.
A : Physiological indicators in DL, B : serum physiological indicators in DL, C : physiological indicators in XGLL, D : serum physiological indicators in XGLL.
The correlation between the detection indicators in DL and the dominant genera of E. miletus feces the top ten relative abundance of all samples was shown in Figure 9B. The correlation between the physiological indicators in XGLL and the dominant genera of E.
miletus feces the top ten relative abundance of all samples was shown in Figure 9C. The correlation between the detection indicators in XGLL and the dominant genera of E. miletus feces the top ten relative abundance of all samples was shown in Figure 9D. The correlation between the physiological indicators in different regions and the dominant OTU in the feces of E.
miletus is shown in Figure The physiological indicators that have a major impact on the microbial community were TNF-α, Tg, UCP1, SCFAs, and leptin. The RDA results showed that the explanatory power of these physiological indicators on microorganisms with main axes were 5.
Figure Redundancy analyses RDA of the correlation between physiological indicators and dominant microbial communities in Eothenomys miletus. RDA was used to assess the correlation between dominant genera top 9 and physicochemical factors using Canoco 5. The dominant OTUs correlation network of E.
miletus feces in different regions was shown in Figure The network analysis included the top OTUs with relative abundance, and based on Gephi 0. It means that the microorganisms in the advantage OTU co-occurrence network were mainly cooperative.
Dominant OTU co-occurrence network of Eothenomys miletus between two regions. Nodes were colored according to their modular characteristics, and the same color represented a close correlation within the module.
The colors of the edges were consistent with their corresponding node. The size of a node was positively correlated with the degree, and the larger it was, the more connections it had in the network. Animal species are abundant and their feeding habits are complex, and these complex ecological characteristics also shape the different gut microbiota characteristics.
Previous researches results have shown that gut microbiota in E. miletus were highly adapted to their herbivorous habits Yan and Zhu, In the present study, the main dominant organisms in the gut microflora of E. The dominant organisms in E. miletus gut microbiota at the genus level were the same as in previous studies, Lactobacillus , Clostridiales UG and S UG , but with different proportions.
Lactobacillus had the highest percentage of It has been shown that Lactobacillus , Clostridiales UG and S UG were associated with the digestive degradation of cellulose, and Lactobacillus also assists the host in releasing phytochemicals with potent antioxidant and anti-inflammatory activities from ingested fiber, and from the results of the present experiments, it is hypothesized that Lactobacillus may possess a higher level of fitness for high-fiber foods Van Dyke and McCarthy, ; Russell and Duthie, ; Geirnaert et al.
miletus enhanced their adaptability to high-fiber foods. Body mass directly reflects the energy balance in mammals Zhu et al. In the present study, high fiber food had no significant effect on body mass of E. miletus , but it had a significant effect on food intake, which was higher in the HF group than in the other groups.
For high-fiber food, which was difficult to digest to obtain nutrients, E. miletus may regulate their body weight homeostasis by increasing the amount of food intake so as to obtain more energy. Compensating for decreased digestibility by increasing food intake is a common strategy in small mammals, such as the herbivorous Dicrostonyx groenlandicus and Meriones unguiculatus , and has also been adopted by E.
miletus for high-fiber foods Nagy and Negus, ; Zhao and Wang, Following a high-fiber diet, small intestine grew in length, and the mass of the digestive tract except the stomach also increased, E.
miletus showed similar responding to high-fiber foods Kass et al. Host food resources are the main factor affecting gut microbiota diversity, and a high-fiber diet can increase gut microbiota diversity Hu et al. According to the results of PERMANOVA, it was found that the differences in β-diversity between XGC group and XGHF group, and between XGRe and DLRe groups were significant, indicating that there were structural differences in the gut microorganisms.
Venn diagram results showed that HF group contained the most species of gut microbiota, followed by the control group, and the Re group had the smallest number. The high-fiber food might increase the β-diversity of intestinal microorganisms in E.
The gut microbiota can assist the host in digesting difficultly decomposed food, providing nutrients that were originally unavailable, and allowing the host to flexibly respond to constantly changing environments Salyers et al.
In the present study, through the enrichment of intestinal microorganisms in each group of E. miletus , it was found that Bacteroidales and Bacteroides were enriched among DLC, XGC and XGRe groups.
Studies have shown that Bacteroides could supplement eukaryotic genome by degrading enzymes targeting resistant dietary polymers, and it is believed that Bacteroidota had the higher fiber degradation potential compared with other phyla Martínez et al. In addition to typical cellulose degrading bacteria, some probiotics capable of digesting cellulose were enriched in the intestinal microorganisms of E.
Between the DLC group and the DLRe group, Blautia was enriched, which can prevent pathogen colonization by producing bacteriocin, and exhibited anti-inflammatory properties and maintained glucose homeostasis by up-regulating the production of regulatory T cells and SCFAs Liu et al.
Alistipes , Sporobacter and Rikenellaceae enriched in the DLHF group were all probiotic bacteria, and studies have shown that Alistipes , Rikenellaceae, and Sporobacter all produced acetic acid and were involved in the uptake and metabolism of SCFAs, and Rikenellaceae could degraded aromatic compounds and produced SCFAs, SCFAs play an important role in appetite regulation, energy metabolism, inflammation and disease as end products of fermentation of dietary fiber and resistant starch, moreover, Rikenellaceae were considered to be a key bacterium for the control of intestinal infections or inflammation in the treatment of non-infectious colitis Morrison and Preston, ; Parker et al.
Anoxybacillus was enriched in the XGHF group, and research suggested that it was beneficial for the proliferation of probiotics such as fecal bacteria and Lactobacillus rosenbergii Liu et al. Current research suggested that high-fiber foods as prebiotics can promote the growth of specific members of the resident gut microbiota, stimulated the production of SCFAs, lower pH, and maintain intestinal homeostasis Scott et al.
However, it is worth noting that Methylobacteriaceae , which was enriched in the XGHF and XGRe group, was an opportunistic pathogen that poses a threat to human health and has been found to be able to enter the silkworm gut through food Consiglieri et al.
In our study, the abundance of dominant fiber degrading bacteria increased after the high-fiber diet in E. miletus , thus digesting more fiber to provide energy for them. At the same time, it promoted the proliferation of probiotics, participated in the regulation of immunity and energy metabolism of E.
miletus through SCFAs and other metabolites, and maintained the energy balance and health of E. Through redundancy analysis, it was found that SCFAs, leptin, UCP1, and Tg may have a major impact on the microbial community.
Studies have found that SCFAs not only play an important role in maintaining energy balance and increasing energy regulation such as insulin, but also promote intestinal barrier function and intestinal immune homeostasis through various mechanisms, thereby regulating the affinity of fibers in the intestine through immune regulation and increasing the proportion of beneficial bacteria in the gut microbiota Chawla and Patil, In the current experiment, there was a significant negative correlation between the WAT weight and the relative abundance of Ruminococcus , and between Tg and the relative abundance of Rikenellaceae UG in DL; There was a significant negative correlation between BAT mass and the relative abundance of Prevotella , Rikenellaceae UG and Oscillospira in XGLL.
Research showed that Ruminococcus , Rikenellaceae and Prevotella were all fiber degrading bacteria, which can degrade structural carbohydrates and starch, and can produce SCFAs such as acetate and propionate Bi et al. In this experiment, under the condition of high-fiber food, it is speculated that the metabolites of E.
miletus after their intestinal microorganisms digested cellulose may participate in the regulation of energy metabolism of E. miletus by inhibiting the production of BAT and WAT.
Moreover, the relative abundance of LBP was significantly negatively correlated with the relative abundance of Rikenellaceae and positively correlated with the relative abundance of Lactobacillus in DL, while the relative abundance of Lachnospiraceae UG and Clostridiales UG were significantly positively correlated with the relative abundance of Lactobacillus in XGLL.
Research has shown that Lachnospiraceae utilizes lactic acid and acetic acid to produce butyric acid; Lactobacillus can improve intestinal integrity, reduce systemic LBP level, regulate lipid metabolism, and regulate the composition of gut microbiota and SCFAs Lim et al.
In our experiment, it showed that E. miletus can regulate body immunity by inhibiting LBP by specific flora and promoting the production of LBP inhibitory factor FIAF, so as to maintain body health.
Liver is one of the thermogenic organs of small mammals Zhu et al. In the present study, after high-fiber diet acclimation, the liver weight of DL increased, while that of XGLL decreased, and increased after refeeding. Analyses of gut microorganisms on related indicators revealed that liver weight of DL was significantly negatively correlated with the relative abundance of Bacteroides and positively correlated with the relative abundance of Lachnospiraceae UG , while liver weight of XGLL was positively correlated with the relative abundance of Bacteroides , and negatively correlated with the relative abundance of Clostridiales UG and Lachnospiraceae UG.
Prevotella relative abundance is positively correlated with leptin and UCP1 Pfannenberg et al. miletus through metabolites, and Prevotella metabolites may be involved in the regulation of thermogenesis by modulating the contents of leptin and UCP1, and thus enhancing its adaptation to the high-fiber food environment.
Specific flora had a preference for certain specific food components in different environments, and the metabolites of the flora would participate in the regulation of the intestinal microenvironment and host homeostasis, and the intestinal microenvironment will be more conducive to the reproduction and growth of the relevant flora in large quantities and colonization, so as to maintain the balance of the host homeostasis Moeller and Sanders, In the present study, under the condition of high-fiber food, different bacterial groups participated in food digestion or energy metabolism etc.
The co-occurrence network results showed that intestinal microorganisms were dominated by cooperation, and positive cooperation played an important role in adaptation to high-fiber food Abbas et al.
Under the condition of high-fiber diet, body mass, food intake, RMR, liver weight, cecum length, BAT weight, leptin, UCP1 and SCFAs of E. miletus were significantly different between DL group and XGLL group. The elevation of XGLL was higher than that of DL, and the winter temperature and food stress were greater in XGLL.
The higher metabolism in XGLL may related to heavier liver and BAT mass, and higher UCP1 content was its adaptation to low temperature environment and longer cecum is an adaptation to the high-fiber food, which was similar to our previous results Scott et al.
However, it is worth noting that the DL E. miletus decreased its RMR while increased its intake of high-fiber food, whereas the XGLL E. miletus adopted higher food intake and RMR. It is assumed that the DL E. miletus was not able to digest the high-fiber food fast enough to obtain energy, and instead, it adopted a lower metabolism to maintain its energy balance.
The results of this experiment showed that the composition of intestinal microorganisms in the XGLL group was more than that in the DL group. After the high-fiber diet, the difference between the two regions was reduced, and there was structural difference in intestinal microorganisms in the refeeding groups.
It showed that the food diversity of the XGLL was higher than that of Dali, and the high-fiber food increased the diversity of intestinal microorganisms, indicating that food resources were poorer and the food contains higher levels of indigestible cellulose in the winter of XGLL, and that gut microorganisms assist the XGLL E.
miletus in facing the stress of winter food resources by altering their structure and diversity Varel and Dehority, The intestinal microorganisms in DL and XGLL were also different in control groups. In addition to the dominant bacteria for cellulose degradation, more probiotics appeared in DL after the high-fiber diet, while pathogenic bacteria appeared in XGLL.
Therefore, for the herbivorous E. miletus , high-fiber food may also enrich pathogenic bacteria in addition to reducing the digestibility and increasing the stress for E. miletus in winter. In conclusion, the present study for the first time explored the effects of high-fiber food on the intestinal microorganisms of E.
miletus at different altitudes. It was found that high-fiber food affected the diversity and enrichment of intestinal microorganisms, and there were similarities and differences in the effects of high-fiber food on E.
Under the condition of high-fiber food, the intestinal microorganisms assist E. miletus to obtain energy from indigestible cellulose through the enrichment of fiber degrading bacteria, produced SCFAs, participated in energy metabolism, immune regulation, etc.
High-fiber food also promoted the enrichment of probiotics in the intestinal microbiota of E. A diverse and responsive microbial community may be a key strategy for living in extreme climates Tsuji et al.
Therefore, the plasticity of the composition of the gut microbiota in combination with the large metabolic reservoir of microorganisms of E. miletus provided an important adaptation to a high-altitude environment with low winter temperatures and scarce food resources.
Moreover, we found that there had relationships between the physiological processes and the changes of relative intestinal bacteria; however, further follow-up research is still needed on these relationships.
The datasets presented in this study can be found in online repositories. All animal procedures were within the rules of Animals Care and Use Committee of School of Life Sciences, Yunnan Normal University. This study was approved by the committee The study was conducted in accordance with the local legislation and institutional requirements.
WeZ: Investigation, Methodology, and Writing—original draft. TJ: Investigation, Methodology, and Writing—original draft. HZ: Methodology, Resources, and Writing—original draft. WaZ: Software, Writing—original draft, and Writing—review and editing. This work was financially supported by the National Natural Science Foundation of China , the Yunnan Ten Thousand Talents Plan Young and Elite Talents Project YNWR-QNRC , and the Yunnan Provincial Middle-Young Academic and Technical Leader Candidate HB We wish to thank Pro.
Burkart Engesser at Historisches Museum Basel, Switzerland for correcting the English usage in the draft. We thank you for the three reviewers and the editor of the journal for their valuable comments.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The reviewer LZ declared a past co-authorship with the authors TJ, HZ, and WaZ to the handling editor. All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers.
Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher. Abbas, W. Influence of host genetics in shaping the rumen bacterial community in beef cattle.
doi: PubMed Abstract CrossRef Full Text Google Scholar. Alberdi, A. On the other hand, diet is necessary for growth, health and defense, as well as regulating and assisting the symbiotic gut microbial communities that inhabit in the digestive tract, referred to as the gut microbiota.
Diet influences the composition of the gut microbiota. The quality and quantity of diet affects their metabolism which creates a link between diet. The microorganisms in response to the type and amount of dietary intake.
Dietary fibers, which includes non-digestible carbohydrates NDCs are neither neither-digested nor absorbed and are subjected to bacterial fermentation in the gastrointestinal tract resulting in the formation of different metabolites called SCFAs.
The SCFAs have been reported to effect metabolic activities at the molecularlevel. The NDCs via gut microbiota dependent pathway regulate glucose homeostasis, gut integrity and hormone by GPCR, NF-kB, and AMPK-dependent processes.
In this chapter, we will focus on dietary fibers, which interact directly with gut microbes and lead to the production of metabolites and discuss how dietary fiber impacts gut microbiota ecology, host physiology, and health and molecule mechanism of dietary fiber on signaling pathway that linked to the host health.
The human gut harbors a plethora of a complex community of micro-organisms that are vital for host development and physiology. The host creates a stable environment for the microbes while the microbes offer the host with an array of functions such as digestion of complex dietary macronutrients, minerals and vitamins production, pathogen protection, and immune system maintenance.
Studies have shown that the gut microbiota comprises of about 3. Dietary fibers DFs are vital modulators of the gut microbiota composition which directly impacts individual biological processes and homeostasis via the metabolites, a consequent of microbial fermentation of nutrients such as, short-chain unsaturated fats SCFAs [ 5 ].
The gut microbiota plays a key and essential role in the metabolization of DFs including non-digestible carbohydrates NDCs , proteins and peptides, which has escape digestion by host enzymes in the upper gut and absorption in the lower digestive tract.
From among the different SCFAs produced Acetate is the most abundant and it is used by many gut commensals to produce propionate and butyrate in a growth-promoting cross-feeding process. Moreover, the SCFA, have been shown a to regulate metabolic activities. The FFAR2 signaling pathway regulates the insulin-stimulated lipid accumulation in adipocytes and inflammation however peptide tyrosine-tyrosine and glucagon-like peptide 1 regulate appetite.
The NDCs via microbiota dependent pathway regulate glucose homeostasis, gut integrity, and hormone by GPCR, NF-kB, and AMPK-dependent processes. Hence in this chapter, emphasis is given to address the effects of dietary fibers metabolites as prime signaling molecules, through different signaling pathways and their link between gut microbiota and the host health.
Dietary fibles defined by codex alimentarius commission are edible carbohydrate polymers with varying monomeric units that are impervious to the host digestive enzymes and thus has escape absorption in the small intestines.
These includes, 1 edible naturally occurring carbohydrate polymers present in foods such as fruits, vegetables, legumes, and cereals 2 edible carbohydrate polymers obtained from food raw materials by physical, enzymatic, and chemical means and 3 synthetic carbohydrate polymers.
In addition, DFs are further divided either into polysaccharides non-starchpolysaccharides [NSPs], resistant starch [RS], and resistant oligosaccharides [ROs] or into insoluble and soluble forms [ 7 ]. Soluble fibers are fermented by the gut bacteria giving rise to metabolites such as short-chain fatty acids SCFAs , insoluble forms of fibers such as cellulose and hemi-cellulose may or slowly digested by the gut bacteria and contributes to a fecal bulking effect, as they reach the colon.
Delay absorption of glucose and lipids influencing post-prandial metabolism on the other hand are caused by most soluble NSPs, especially polymers with high molecular weight such as guar gum, certain pectins, b-glucans, and psyllium, are viscous, meaning that they are able to form a gel structure in the intestinal tract that can [ 7 ].
Recently, due to low consumption of DFs in the Industrialized Western world Fortification of foods with extracted or synthesized non-digestible carbohydrates is carried out as a strategy to increase fiber intake.
However, contrastingly, studies have reported that irrespective of the types of fibers, virtually all fibers will induce specific shifts in microbiota composition as a result of competitive interactions, and which of these compositional shifts may be beneficial for health, has not yet been established [ 10 ].
Furthermore, the mechanisms that have been established to be beneficial to health, is not calculative on the selective utilization of the carbohydrates but on an integrative effect of bacterial fermentation, producing metabolic compounds e.
Hence, a change in the emphasis of the prebiotic concept away from the selective effect of specific dietary components on gut microbial communities towards the effects of ecological and functional consequences of fiber fermentation, is more significant for host physiology and health [ 10 ].
Microorganisms including several species of bacteria, yeast, and viruses make up the Gut microbiota. Out of the different Bacterial phyla, a few phyla represented, by about species [ 14 ] composed the gut microbiota.
Clostridium, Enterococcus, Lactobacillus, Bacillus, and Ruminicoccus are among the more than genera in the Firmicutes phylum. Phylum Bacteroidetes consists of Bacteroides and Prevotella as predominant genera. The Actinobacteria a less abundant phylumis mainly represented by the Bifidobacterium genus [ 15 ].
Besides, the gut microbiome is to a very large extent affected by dietary administration of fiber, which alters the gut microbiota by providing substrates for microbial growth, and expansion of their populations [ 7 ].
The possession of different enzymes, about glycoside hydrolase, 22 polysaccharidelyase, and 16 carbohydrate esterase enzyme families, allows the gut microbiome to switch between different energy sources of fibers depending on their availability [ 16 ]. Bacteria such as Firmicutes and Actinobacteria has been found to be prime species, which initiates the degradation of complex substrates [ 7 ].
Species such as Bifidobacteriumadolescentis , Ruminoccocusbromii , Eubacteriumrectale , and Parabacteroides distasonis play significant roles in degrading resistant Starch [ 1 , 17 ]. The consumption of galactooligosaccharides mainly induces Bifidobacterium species possessing the enzymatic machinery to utilize the substrate [ 18 ].
Reports have also suggested that, degradation of complex substates, occurs in a cascade where, different species will contribute equally at different stages towards production of metabolites [ 7 ].
Although R. bromii does not make butyrate, it is considered a keystone species for the breakdown of RS and contributes significantly to butyrate generation in the colon. Other dietary fiber types are expected to have similar keystone species, although they have yet to be discovered.
Dietary fibers, are metabolized by the microbiota in the cecum and colon [ 20 ] resulting in the formation of major products such as particular, acetate, propionate, and butyrate [ 21 ]. However, studies have reported that, microbes can utilize amino acids from dietary proteins and triglycerols from fats [ 22 , 23 ] to facilitate diminished supply of dietary fermentable fibers resulting in reduced fermentative activity and formation of SCFAs as minor end products [ 24 ].
Although, protein fermentation was observed to the SCFA pool but, however dietary proteins mostly give rise to branched-chain fatty acids such asisobutyrate, 2-methylbutyrate, and isovalerate, [ 25 ] which are may have a concerning effect as a result of insulin resistance [ 26 ].
Acetate C2 is a major SCFA metabolite produced from pyruvate. Many gut bacteria produce Acetate from pyruvate via acetyl-CoA or the Wood-Ljungdahl pathway, which produces acetate via two branches: 1 the C1-body branch also known as the Eastern branch via CO 2 reduction to formate and 2 the carbon monoxide branch also known as the Western branch via CO 2 reduction to CO, which is then combined with a methyl group.
Propionate is created when succinate is converted to methylmalonyl-CoA through the succinate pathway. Furthermore, propionate, can also be synthesized from acrylate using lactate as a precursor via the acrylate pathway [ 27 ] and via the propanediol pathway using deoxyhexose sugars as substrates [ 28 ].
Butyrate, the third main SCFA, is produced by the condensation of two molecules of acetyl-CoA and subsequent reduction to butyryl-CoA, which can then be converted to butyrate by phosphotrans butyrylase and butyrate kinase via the classical pathway [ 29 ].
The butyryl-CoA: acetate CoA-transferase enzyme can also convert butyryl-CoA to butyrate [ 30 ]. Besides, reports have also shown that some microbes can use both lactate and acetate to synthesize butyrate.
Butyrate can also be produced from proteins via the lysine pathway, according to a recent analysis of metagenome data [ 31 ], implying that microorganisms in the gut can adjust to dietary changes in order to sustain the synthesis of important metabolites like SCFAs.
SCFA levels vary along the length of the gut, with the highest concentrations in the cecum and proximal colon and decreasing towards the distal colon [ 21 ]. The metabolites of dietary fibers DFs are SCFAs that play a significant role in metabolic diseases prevention and treatment along with some contradictory research finding [ 32 ].
The SCFAs formate, lactate, acetate, propionate, and butyrate are produces by the saccharolytic fermentation of the dietary fibrous [ 33 ] which have a significant role in the maintenance of health by reducing the chances of development of different disease. The various physiological functions in the gut including adding the energy to colonocytes, maintaining their mobility, blood flow, and regularize the movements of electrolytes and nutrients within the lumen activate and modulate by SCAFs [ 35 ].
Propionate maintains glucose homeostasis by gluconeogenic pathway [ 37 ]. The expression of leptin has enhanced by propionate and acetate.
Leptin is a potent anorectic hormone, in adipocytes [ 38 ]. Acetate is a lipogenic SCFAs, reduced levels of acetate would result in decreased lipogenesis [ 37 ]. In the rat hepatocytes, acetate act as de novo lipogenesis and cholesterol synthesis, and these two pathways are to be inhibited by propionate [ 39 ].
The increased levels of propionate SCFAs would assist in the inhibition of acetate conversion into lipid in adipose tissue and the liver. The DFs via gut microbiota increase the rate of acetate synthesis while reducing the level of propionate in cells [ 40 ].
Acetate SCFAs is inversely related to plasma insulin levels [ 41 ] and acetate also activates leptin secretion in murine adipocytes [ 42 ]. High-fat diet-fed rats have increased acetate C2 production due to gut microbiota that leads to ghrelin secretion and glucose-stimulated insulin secretion by activation of the parasympathetic nervous system PNS , apart from these high calorically dense diet through gut microbiota-brain-β-cell axis promotes obesity and health complications by regimenting glucose and lipids homeostasis [ 43 ].
New study finding by many researchers groups have suggested that [ 44 , 45 ] the loss of gut microbiota species from the colonic microbiota is associated to consumption of the high-fat, low-dietary fiber diets and other nutrient intake and diversity of gut microbiome [ 46 , 47 ].
The fermentable dietary fibers directly govern the diversity of the gut microbiota [ 48 ], SCFAs regulate the different physiological activity of host. The majority of SCFAs transported across the mucosa by active transport, mediated by two receptors.
The monocarboxylate transporter 1 MCT-1 and the sodium-coupled monocarboxylate transporter 1 SMCT-1 receptors. Direct inhibition of histone deacetylases HDACs to directly regulate gene expression and SCFA also effects signaling through G-protein-coupled receptors GPCRs , this may influence host physiology by modulate biological responses of the host.
All physiological activities occurring in the body are gut metabolites driven and SCFAs are connecting the link between the gut immunity with microbiota. The crucial role of SCFA has been signified in shaping and regulating both local and peripheral immune systems that respond to host metabolism via inflammatory pathways.
Therefore, SCFAs modulate functions of the different systems including the enteric, nervous, endocrine, and blood vascular system serving as a key factor to regulate metabolic disorders and immunity.
Gut bacteria produced SCFAs from indigestible saccharides diet precursors and SCFAs transported across the mucosa by active transport mediated by two receptors, monocarboxylate transporter 1 MCT-1 and sodium-coupled monocarboxylate transporter 1 SMCT-1 receptors which influence host physiological functions and modulate biological responses of the host.
The main mechanism is direct inhibition of histone deacetylases HDACs to directly regulate gene expression. HDACs remove acetyl groups deacetylation from lysine residues of histones [ 50 ]. Transcription of genes is enhanced through inhibition of HDACs function by increasing histone acetylation.
Dietary fibers SCFAs inhibit HDACs activity and therefore suppress expression of gene in different cells. The SCFAs-mediated HDACs inhibition, acts as an anti-inflammatory immune response mediated by less production of inflammatory cytokines IL-8, IL-6, and TNFα [ 52 ].
Apart from these butyrate and propionate reduced NF-kB activity and inflammatory cytokines [ 53 ], showing that the anti-inflammatory effects of SCFAs are mediated through the modulation of NF-kB signaling pathway. Beside this the SCFAs also affect signaling through GPCRs.
The SCFAs activate different GPCRs e. propionate C3 is a most potent activator of GPR The expression of GPR43 has been reported in the entire gastrointestinal tract GIT along with cells of the immune and nervous systems. In GIT, GPR43 is highly expressed in endocrine L-cells of the ileum and colon of intestinal PYY and GLP-1 [ 54 ] producing cells as well as on colonocytes and enterocytes.
The SCFAs control the body weight through the release of leptin in adipose tissue by the expression of GPR41 [ 56 ]. The SCFAs play crucial role in metabolic functions of hepatic cells through the FFAR3 signaling pathway without influencing the intestinal environment [ 57 ].
Niacin receptor 1 GPRa is activated by C4 at low concentration while highly expressed in adipocytes with a lesser extent is also expressed on immune cells. Activation of GPRa in adipocytes suppresses lipolysis and the lowering of plasma-free fatty acid levels FFAs [ 58 ]. Through epigenetic mechanisms via histone acetylation acetate also increases fatty acid synthesis [ 59 ].
Therefore these finding could helpful to promote the development of functional foods using SCFAs or dietary significance of non-digestible carbohydrates fiber.
Gut microbes regulates the host metabolism by secretion of gut hormone. Gut microbiota induced signal to nearby intestinal enteroendocrine cells through microbial metabolites of DFs.
These enteroendocrine cells release metabolically active hormones like GLP-1, PYY, GIP, 5-HT, and CCK which influence feeding behavior, glucose metabolism, insulin sensitivity and adiposity. Dietary components also impact on the composition of gut microbiota which may have further downstream consequences on gut hormone secretion and host metabolism.
Enterochromaffin cells EC of the gut are the main source of serotonin 5-HT, 5-hydroxytryptamine. The EC is dispersed throughout the GI tract of the host and constitutes about half of all enteroendocrine cells.
The gut microbiota influences 5-HT levels in the host. The antibiotic-treated mice study showed that significantly lower levels of EC cell-derived 5-HT when compared to antibiotic free animals.
The EC cells can sense microbial metabolites by FFAR2 and FFAR3 signaling mechanisms [ 60 ]. PYY Peptide tyrosine-tyrosine regulates food intake and satiety through activation of central G protein-coupled Y2 receptors on neuropeptide Y NPY and AgRP neurons in arcuate nucleus of hypothalamic part of brain [ 61 ].
The ability of gut microbiota to influence PYY secretion, therefore, gut microbiota has significant implications for the development of metabolic disease and obesity. Glucagon-like peptide 1 GLP-1 augments insulin and inhibits glucagon secretion from the pancreas cells. GLP-1 inhibits gastric emptying and influences satiety and food intake [ 64 , 65 ].
Orally administrated sodium butyrate in mice has been shown to transiently increase GIP and GLP-1 secretion and GIP level were associated with adiposity reported the ileal infusion of acetate, propionate, and butyrate during feeding in pigs, increased plasma CCK levels and paradoxically inhibit pancreatic secretion [ 66 ].
SCFAs are influence insulin function via their receptors [ 67 , 68 ]. Glucose homeostasis in type 2 diabetes mellitus patients managed by fiber reaches diet that alters the gut microbiota. The deficiency in SCFAs production in host has associated with type 2 diabetes by interfering HbA1c levels in circulation [ 69 ].
Diet plat a major role in gut microbiota composition and gut microbiota regulates metabolism via metabolites produces by plant-based diets and intake of probiotics increases secretion of carbohydrate-active enzymes [ 70 ] in luminal of GIT.
Dietary fibers and its gut microbial metabolite SCFAs have been known to exert metabolic benefits to the host [ 71 ]. Various health benefits have been reported whereby Dietary fibers via SCFA increase plasma SCFA levels to active FFAR3 which has been shown to improve hepatic metabolic conditions.
Furthermore, Dietary fibers consumption reduced HFD-induced liver weight growth and hepatic TG accumulation, as well as a shift in hepatic lipid metabolism.
Open Energy metabolism and dietary fiber peer-reviewed ane. Submitted: 27 Fibr Reviewed: 21 July Nad 24 September Lycopene antioxidant properties com Enery cbspd. Food is a basic requirement for human life and well-being. On the other hand, diet is necessary for growth, health and defense, as well as regulating and assisting the symbiotic gut microbial communities that inhabit in the digestive tract, referred to as the gut microbiota. Diet influences the composition of the gut microbiota.
Dietary fiber in Commonwealth English fibre or roughage is the portion of plant-derived food that Ejergy Visceral fat and obesity completely broken metabolisj by fibet digestive Energy metabolism and dietary fiber. Food sources fibdr dietary fiber have traditionally Robust Orange Aroma divided according xietary whether they provide soluble or Energy metabolism and dietary fiber fiber. Plant foods contain both types of fiber in meabolism amounts, according to the fiber characteristics of viscosity and fermentability. Soluble fiber fermentable fiber or prebiotic fiber — which dissolves in water — is generally fermented in the colon into gases and physiologically active by-productssuch as short-chain fatty acids produced in the colon by gut bacteria. Examples are beta-glucans in oats, barley, and mushrooms and raw guar gum. Psyllium — a soluble, viscous, nonfermented fiber — is a bulking fiber that retains water as it moves through the digestive systemeasing defecation. Soluble fiber is generally viscous and delays gastric emptying which, in humans, can result in an extended feeling of fullness.
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