Acarbose enhances human colonic butyrate production

Acarbose Impairs Gut Bacteroides Growth by Targeting Intracellular GH97 Enzymes

Acarbose is a type-2 diabetes medicine that inhibits dietary starch breakdown into glucose by inhibiting host amylase and glucosidase enzymes. Numerous gut species in the Bacteroides genus enzymatically break down starch and change in relative abundance within the gut microbiome in acarbose-treated individuals. To mechanistically explain this observation, we used two model starch-degrading Bacteroides, Bacteroides ovatus (Bo) and Bacteroides thetaiotaomicron (Bt). Bt growth is severely impaired by acarbose whereas Bo growth is not. The Bacteroides use a starch utilization system (Sus) to grow on starch. We hypothesized that Bo and Bt Sus enzymes are differentially inhibited by acarbose. Instead, we discovered that although acarbose primarily targets the Sus periplasmic GH97 enzymes in both organisms, the drug affects starch processing at multiple other points. Acarbose competes for transport through the Sus beta-barrel proteins and binds to the Sus transcriptional regulators. Further, Bo expresses a non-Sus GH97 (BoGH97D) when grown in starch with acarbose. The Bt homolog, BtGH97H, is not expressed in the same conditions, nor can overexpression of BoGH97D complement the Bt growth inhibition in the presence of acarbose. This work informs us about unexpected complexities of Sus function and regulation in Bacteroides, including variation between related species. Further, this indicates that the gut microbiome may be a source of variable response to acarbose treatment for diabetes.

Along the microbiota-gut-brain axis: Use of plant polysaccharides to improve mental disorders

With the development of gut microbiota-specific interventions for mental disorders, the interactions between plant polysaccharides and microbiota in the intestinal and their consequent effects are becoming increasingly important. In this review, we discussed the role of plant polysaccharides in improving various mental disorders via the microbiota-gut-brain axis. The chemical and structural characteristics and metabolites of these plant polysaccharides were summarised. Plant polysaccharides and their metabolites have great potential for reshaping gut microbiota profiles through gut microbiota-dependent fermentation. Along the microbiota-gut-brain axis, the consequent pharmacological processes that lead to the elimination of the symptoms of mental disorders include 1) regulation of the central monoamine neurotransmitters, amino acid transmitters and cholinergic signalling system; 2) alleviation of central and peripheral inflammation mainly through the NLRP3/NF-κB-related signalling pathway; 3) inhibition of neuronal apoptosis; and 4) enhancement of antioxidant activities. According to this review, monosaccharide glucose and structure -4-α-Glcp-(1→ are the most potent compositions of the most reported plant polysaccharides. However, the causal structure-activity relationship remains to be extensively explored. Moreover, mechanistic elucidation, safety verification, and additional rigorous human studies are expected to advance plant polysaccharide-based product development targeting the microbiota-gut-brain axis for people with mental disorders.

Butyrate's (a short-chain fatty acid) microbial synthesis, absorption, and preventive roles against colorectal and lung cancer

Butyrate, a short-chain fatty acid (SCFA) produced by bacterial fermentation of fiber in the colon, is a source of energy for colonocytes. Butyrate is essential for improving gastrointestinal (GI) health since it helps colonocyte function, reduces inflammation, preserves the gut barrier, and fosters a balanced microbiome. Human colonic butyrate producers are Gram-positive firmicutes, which are phylogenetically varied. The two most prevalent subgroups are associated with Eubacterium rectale/Roseburia spp. and Faecalibacterium prausnitzii. Now, the mechanism for the production of butyrate from microbes is a very vital topic to know. In the present study, we discuss the genes encoding the core of the butyrate synthesis pathway and also discuss the butyryl-CoA:acetate CoA-transferase, instead of butyrate kinase, which usually appears to be the enzyme that completes the process. Recently, butyrate-producing microbes have been genetically modified by researchers to increase butyrate synthesis from microbes. The activity of butyrate as a histone deacetylase inhibitor (HDACi) has led to several clinical trials to assess its effectiveness as a potential cancer treatment. Among various significant roles, butyrate is the main energy source for intestinal epithelial cells, which helps maintain colonic homeostasis. Moreover, people with non-small-cell lung cancer (NSCLC) have distinct gut microbiota from healthy adults and frequently have dysbiosis of the butyrate-producing bacteria in their guts. So, with an emphasis on colon and lung cancer, this review also discusses how the microbiome is crucial in preventing the progression of certain cancers through butyrate production. Further studies should be performed to investigate the underlying mechanisms of how these specific butyrate-producing bacteria can control both colon and lung cancer progression and prognosis.

Calorie restriction mimetic drugs could favorably influence gut microbiota leading to lifespan extension

Calorie restriction (CR) can prolong human lifespan, but enforcing long-term CR is difficult. Thus, a drug that reproduces the effects of CR without CR is required. More than 10 drugs have been listed as CR mimetics (CRM), and some of which are conventionally categorized as upstream-type CRMs showing glycolytic inhibition, whereas the others are categorized as downstream-type CRMs that regulate or genetically modulate intracellular signaling proteins. Intriguingly, recent reports have revealed the beneficial effects of CRMs on the body such as improving the host body condition via intestinal bacteria and their metabolites. This beneficial effect of gut microbiota may lead to lifespan extension. Thus, CRMs may have a dual effect on longevity. However, no reports have collectively discussed them as CRMs; hence, our knowledge about CRM and its physiological effects on the host remains fragmentary. This study is the first to present and collectively discuss the accumulative evidence of CRMs improving the gut environments for healthy lifespan extension, after enumerating the latest scientific findings related to the gut microbiome and CR. The conclusion drawn from this discussion is that CRM may partially extend the lifespan through its effect on the gut microbiota. CRMs increase beneficial bacteria abundance by decreasing harmful bacteria rather than increasing the diversity of the microbiome. Thus, the effect of CRMs on the gut could be different from that of conventional prebiotics and seemed similar to that of next-generation prebiotics.

α-Glucosidase inhibitors boost gut immunity by inducing IgA responses in Peyer's patches

Peyer's patches (PPs) are specialized gut-associated lymphoid tissues that initiate follicular helper T (Tfh)-mediated immunoglobulin A (IgA) response to luminal antigens derived from commensal symbionts, pathobionts, and dietary sources. IgA-producing B cells migrate from PPs to the small intestinal lamina propria and secrete IgA across the epithelium, modulating the ecological balance of the commensal microbiota and neutralizing pathogenic microorganisms. α-glucosidase inhibitors (α-GIs) are antidiabetic drugs that inhibit carbohydrate digestion in the small intestinal epithelium, leading to alterations in the commensal microbiota composition and metabolic activity. The commensal microbiota and IgA responses exhibit bidirectional interactions that modulate intestinal homeostasis and immunity. However, the effect of α-GIs on the intestinal IgA response remains unclear. We investigated whether α-GIs affect IgA responses by administering voglibose and acarbose to mice via drinking water. We analyzed Tfh cells, germinal center (GC) B cells, and IgA-producing B cells in PPs by flow cytometry. We also assessed pathogen-specific IgA responses. We discovered that voglibose and acarbose induced Tfh cells, GCB cells, and IgA-producing B cells in the PPs of the proximal small intestine in mice. This effect was attributed to the modification of the microbiota rather than a shortage of monosaccharides. Furthermore, voglibose enhanced secretory IgA (S-IgA) production against attenuated Salmonella Typhimurium. Our findings reveal a novel mechanism by which α-GIs augment antigen-specific IgA responses by stimulating Tfh-GCB responses in PPs, and suggest a potential therapeutic application as an adjuvant for augmenting mucosal vaccines.

The effects of macronutrients metabolism on cellular and organismal aging

Evidence supports the notion that metabolic pathways are major regulators of organismal aging, and that metabolic perturbations can extend health- and lifespan. For this reason, dietary interventions and compounds perturbing metabolism are currently explored as anti-aging strategies. A common target for metabolic interventions delaying aging is cellular senescence, a state of stable growth arrest that is accompanied by various structural and functional changes including the activation of a pro-inflammatory secretome. Here, we summarize the current knowledge on the molecular and cellular events associated with carbohydrate, lipid and protein metabolism, and define how macronutrients can regulate induction or prevention of cellular senescence. We discuss how various dietary interventions can achieve prevention of disease and extension of healthy longevity by partially modulating senescence-associated phenotypes. We also emphasize the importance of developing personalized nutritional interventions that take into account the current health and age status of the individual.

Characterizing the Effect of Amylase Inhibitors on Maltodextrin Metabolism by Gut Bacteria Using Fluorescent Glycan Labeling

Diet-derived polysaccharides are an important carbon source for gut bacteria and shape the human gut microbiome. Acarbose, a compound used clinically to treat type 2 diabetes, is known to inhibit the growth of some bacteria on starches based on its activity as an inhibitor of α-glucosidases and α-amylases. In contrast to acarbose, montbretin A, a new drug candidate for the treatment of type 2 diabetes, has been reported to be more specific for the inhibition of α-amylase, notably human pancreatic α-amylase. However, the effects of both molecules on glycan metabolism across a larger diversity of human gut bacteria remain to be characterized. Here, we used ex vivo metabolic labeling of a human microbiota sample with fluorescent maltodextrin to identify gut bacteria affected by amylase inhibitors. Metabolic labeling was performed in the presence and absence of amylase inhibitors, and the fluorescently labeled bacteria were identified by fluorescence-activated cell sorting coupled with 16S rDNA amplicon sequencing. We validated the labeling results in cultured isolates and identified four gut bacteria species whose metabolism of maltodextrin is inhibited by acarbose. In contrast, montbretin A slowed the growth of only one species, supporting the fact that it is more selective. Metabolic labeling is a valuable tool to characterize glycan metabolism in microbiota samples and could help understand the untargeted impact of drugs on the human gut microbiota.

Recent Updates on Phytoconstituent Alpha-Glucosidase Inhibitors: An Approach towards the Treatment of Type Two Diabetes

Diabetes is a common metabolic disorder marked by unusually high plasma glucose levels, which can lead to serious consequences such as retinopathy, diabetic neuropathy and cardiovascular disease. One of the most efficient ways to reduce postprandial hyperglycemia (PPHG) in diabetes mellitus, especially insulin-independent diabetes mellitus, is to lower the amount of glucose that is absorbed by inhibiting carbohydrate hydrolyzing enzymes in the digestive system, such as α-glucosidase and α-amylase. α-Glucosidase is a crucial enzyme that catalyzes the final stage of carbohydrate digestion. As a result, α-glucosidase inhibitors can slow D-glucose release from complex carbohydrates and delay glucose absorption, resulting in lower postprandial plasma glucose levels and control of PPHG. Many attempts have been made in recent years to uncover efficient α-glucosidase inhibitors from natural sources to build a physiologic functional diet or lead compound for diabetes treatment. Many phytoconstituent α-glucosidase inhibitors have been identified from plants, including alkaloids, flavonoids, anthocyanins, terpenoids, phenolic compounds, glycosides and others. The current review focuses on the most recent updates on different traditional/medicinal plant extracts and isolated compounds' biological activity that can help in the development of potent therapeutic medications with greater efficacy and safety for the treatment of type 2 diabetes or to avoid PPHG. For this purpose, we provide a summary of the latest scientific literature findings on plant extracts as well as plant-derived bioactive compounds as potential α-glucosidase inhibitors with hypoglycemic effects. Moreover, the review elucidates structural insights of the key drug target, α-glucosidase enzymes, and its interaction with different inhibitors.

A Bayesian method for identifying associations between response variables and bacterial community composition

Determining associations between intestinal bacteria and continuously measured physiological outcomes is important for understanding the bacteria-host relationship but is not straightforward since abundance data (compositional data) are not normally distributed. To address this issue, we developed a fully Bayesian linear regression model (BRACoD; Bayesian Regression Analysis of Compositional Data) with physiological measurements (continuous data) as a function of a matrix of relative bacterial abundances. Bacteria can be classified as operational taxonomic units or by taxonomy (genus, family, etc.). Bacteria associated with the physiological measurement were identified using a Bayesian variable selection method: Stochastic Search Variable Selection. The output is a list of inclusion probabilities ([Formula: see text]) and coefficients that indicate the strength of the association ([Formula: see text]) for each bacterial taxa. Tests with simulated communities showed that adopting a cut point value of [Formula: see text] ≥ 0.3 for identifying included bacteria optimized the true positive rate (TPR) while maintaining a false positive rate (FPR) of ≤ 5%. At this point, the chances of identifying non-contributing bacteria were low and all well-established contributors were included. Comparison with other methods showed that BRACoD (at [Formula: see text] ≥ 0.3) had higher precision and a higher TPR than a commonly used center log transformed LASSO procedure (clr-LASSO) as well as higher TPR than an off-the-shelf Spike and Slab method after center log transformation (clr-SS). BRACoD was also less likely to include non-contributing bacteria that merely correlate with contributing bacteria. Analysis of a rat microbiome experiment identified 47 operational taxonomic units that contributed to fecal butyrate levels. Of these, 31 were positively and 16 negatively associated with butyrate. Consistent with their known role in butyrate metabolism, most of these fell within the Lachnospiraceae and Ruminococcaceae. We conclude that BRACoD provides a more precise and accurate method for determining bacteria associated with a continuous physiological outcome compared to clr-LASSO. It is more sensitive than a generalized clr-SS algorithm, although it has a higher FPR. Its ability to distinguish genuine contributors from correlated bacteria makes it better suited to discriminating bacteria that directly contribute to an outcome. The algorithm corrects for the distortions arising from compositional data making it appropriate for analysis of microbiome data.

Anti-Diabetic Intestinal Mechanisms: Foods, Herbs, and Western Medicines

The role of intestinal factors in the pathogenesis of diabetes, such as a decrease in the incretin effect, has recently attracted considerable attention. An imbalance in the gut microbiota inhibits the secretion of incretins, which are metabolic hormones can reduce blood glucose levels, and promotes the occurrence and development of diabetes. Numerous studies have demonstrated that foods are environmental factors that are important in the modulation of gut microbial-mediated glucose metabolism. In general, functional foods trigger the gut microbiota to produce beneficial metabolites or reduce harmful products through metabolic pathways and then regulate glucose and lipid metabolism. Recent studies have shown that similar to functional foods, the regulatory effects of some herbs and Western medicines are closely related to alterations in the gut microbiota. In this review, the intestinal mechanism of foods, herbs, and Western medicine in affecting the process of glucose metabolism is summarized.

The Relationships between Gut Microbiota and Diabetes Mellitus, and Treatments for Diabetes Mellitus

Diabetes mellitus is considered to be a global epidemic. The combination of genetic susceptibility and an unhealthy lifestyle is considered to be the main trigger of this metabolic disorder. Recently, there has been increased interest in the roles of gut microbiota as a new potential contributor to this epidemic. Research, in recent years, has contributed to an in-depth characterization of the human microbiome and its associations with various diseases, including metabolic diseases and diabetes mellitus. It is known that diet can change the composition of gut microbiota, but it is unclear how this, in turn, may influence metabolism. The main objective of this review is to evaluate the pathogenetic association between microbiota and diabetes and to explore any new therapeutic agents, including nutraceuticals that may modulate the microbiota. We also look at several mechanisms involved in this process. There is a clear, bidirectional relationship between microbiota and diabetes. Current treatments for diabetes influence microbiota in various ways, some beneficial, but others with still unclear effects. Microbiota-aimed treatments have seen no real-world significant effects on the progression of diabetes and its complications, with more studies needed in order to find a really beneficial agent.

Extension of the Life Span by Acarbose: Is It Mediated by the Gut Microbiota?

Acarbose can extend the life span of mice through a process involving the gut microbiota. Several factors affect the life span, including mitochondrial function, cellular senescence, telomere length, immune function, and expression of longevity-related genes. In this review, the effects of acarbose-regulated gut microbiota on the life span-influencing factors have been discussed. In addition, a novel theoretical basis for improving our understanding of the mechanisms by which acarbose extends the life span of mice has been suggested.

Muribaculaceae Genomes Assembled from Metagenomes Suggest Genetic Drivers of Differential Response to Acarbose Treatment in Mice

The drug acarbose is used to treat diabetes and, by inhibiting α-amylase in the small intestine, increases the amount of starch entering the lower digestive tract. This results in changes to the composition of the microbiota and their fermentation products. Acarbose also increases longevity in mice, an effect that has been correlated with increased production of the short-chain fatty acids propionate and butyrate. In experiments replicated across three study sites, two distantly related species in the bacterial family Muribaculaceae were dramatically more abundant in acarbose-treated mice, distinguishing these responders from other members of the family. Bacteria in the family Muribaculaceae are predicted to produce propionate as a fermentation end product and are abundant and diverse in the guts of mice, although few isolates are available. We reconstructed genomes from metagenomes (MAGs) for nine populations of Muribaculaceae to examine factors that distinguish species that respond positively to acarbose. We found two closely related MAGs (B1A and B1B) from one responsive species that both contain a polysaccharide utilization locus with a predicted extracellular α-amylase. These genomes also shared a periplasmic neopullulanase with another, distantly related MAG (B2) representative of the only other responsive species. This gene differentiated these three MAGs from MAGs representative of nonresponding species. Differential gene content in B1A and B1B may be associated with the inconsistent response of this species to acarbose across study sites. This work demonstrates the utility of culture-free genomics for inferring the ecological roles of gut bacteria, including their response to pharmaceutical perturbations.

IMPORTANCE The drug acarbose is used to treat diabetes by preventing the breakdown of starch in the small intestine, resulting in dramatic changes in the abundance of some members of the gut microbiome and its fermentation products. In mice, several of the bacteria that respond most positively are classified in the family Muribaculaceae, members of which produce propionate as a primary fermentation product. Propionate has been associated with gut health and increased longevity in mice. We found that genomes of the most responsive Muribaculaceae showed signs of specialization for starch fermentation, presumably providing them a competitive advantage in the large intestine of animals consuming acarbose. Comparisons among genomes enhance existing models for the ecological niches occupied by members of this family. In addition, genes encoding one type of enzyme known to participate in starch breakdown were found in all three genomes from responding species but none of the other genomes.

Prebiotics, Probiotics, Synbiotics, Paraprobiotics and Postbiotic Compounds in IBD

The increasing incidence of inflammatory bowel diseases (IBD) and the increasing severity of the course of these diseases create the need for developing new methods of therapy. The gut microbiome is extensively studied as a factor influencing the development and course of IBD. The composition of intestinal microbiota can be relatively easily modified by diet (i.e., prebiotics, mainly dietary fibers) and bacterial supplementation using beneficial bacteria strains called probiotics. Additionally, the effects of the improved microbiome could be enhanced or gained by using paraprobiotics (non-viable, inactivated bacteria or their components) and/or postbiotics (products of bacterial metabolism or equal synthetic products that beneficially modulate immunological response and inflammation). This study summarizes the recent works on prebiotics, probiotics, synbiotics (products merging pre- and probiotics), paraprobiotics and postbiotics in IBD.

Mechanistic basis and preliminary practice of butyric acid and butyrate sodium to mitigate gut inflammatory diseases: a comprehensive review

A key event featured in the early stage of chronic gut inflammatory diseases is the disordered recruitment and excess accumulation of immune cells in the gut lamina propria. This process is followed by the over-secretion of pro-inflammatory factors and the prolonged overactive inflammatory responses. Growing evidence has suggested that gut inflammatory diseases may be mitigated by butyric acid (BA) or butyrate sodium (NaB). Laboratory studies show that BA and NaB can enhance gut innate immune function through G-protein-mediated signaling pathways while mitigating the overactive inflammatory responses by inhibiting histone deacetylase. The regulatory effects may occur in both epithelial enterocytes and the immune cells in the lamina propria. Prior to further clinical trials, comprehensive literature reviews and rigid examination concerning the underlying mechanism are necessary. To this end, we collected and reviewed 197 published reports regarding the mechanisms, bioactivities, and clinical effects of BA and NaB to modulate gut inflammatory diseases. Our review found insufficient evidence to guarantee the safety of clinical practice of BA and NaB, either by anal enema or oral administration of capsule or tablet. The safety of clinical use of BA and NaB should be further evaluated. Alternatively, dietary patterns rich in "fruits, vegetables and beans" may be an effective and safe approach to prevent gut inflammatory disease, which elevates gut microbiota-dependent production of BA. Our review provides a comprehensive reference to future clinical trials of BA and NaB to treat gut inflammatory diseases.

Association between α-glucosidase inhibitor use and psoriatic disease risk in patients with type 2 diabetes mellitus: A population-based cohort study

AIMS

To investigate the association between the use of alpha-glucosidase inhibitors (AGIs) and the risk of psoriatic disease (ie, psoriasis and psoriatic arthritis) in patients with type 2 diabetes mellitus (T2DM) treated with metformin.

METHODS

Using the 1999-2013 Taiwanese Longitudinal Cohort of Diabetes Patients Database, we identified patients with T2DM who initiated hypoglycaemic treatment between 2003 and 2012. After excluding patients with a history of psoriatic disease (International Classification of Disease, Ninth Revision, Clinical Modification codes 696.0-1) before T2DM diagnosis, patients who received antidiabetic treatment for <90 days, and patients aged <20 or >100 years, we identified 1390 patients who received metformin+AGIs (AGI exposure group) and 47 514 patients who received metformin only (comparison group). We matched the two groups at a 1:10 ratio by age, sex, and index date of T2DM drug use. The association between AGI use and psoriatic disease risk was analysed using a Cox proportional hazard mode; time-dependent covariates for factors were reported in terms of hazard ratios (HRs) with 95% confidence intervals (CIs) after age, sex, T2DM duration, and comorbidities were controlled for.

RESULTS

After adjusting the AGI exposure and comparison groups for potential confounders, we found that psoriatic disease risk was associated with metformin+AGI use when AGI was discontinued for 30 days (HR, 8.77; 95% CI, 1.58-48.5) and when a high AGI dose was administered; furthermore, the risk declined during AGI discontinuation.

CONCLUSIONS

This population-based study reports that AGI use and interruption of AGI use may be associated with increased psoriatic disease risk in treated patients with T2DM.

Aquaporin5-Targeted Treatment for Dry Eye Through Bioactive Compounds and Gut Microbiota

Dry eye and dry mouth are the principal sources of morbidity for patients with Sjögren's syndrome (SS). There are few effective treatments, particularly systemic ones. Targeting aquaprin-5 (AQP5)-mediated tear secretion has been tested as a novel ancillary strategy and has proved promising. Patients have a great interest in using complementary medicine, including nutraceuticals and bioactive compounds to alleviate their symptoms. Potential mechanisms by which phytocompounds and bioactive compounds may benefit SS ocular and mouth symptoms through modulation of AQP5 activity are presented within this review. Supplementation with prebiotics (such as polyphenols with high bioavailability) in SS patients with lower Firmicutes/Bacteroides (F/B) community ratio phenotype, through administration of butyrate-producing diets, is proposed as ancillary strategy for dry eye and mouth. The potential use of natural bioactive compounds to treat dry eye could also apply to dry mouth occurring in the context of aging and SS. This novel hypothesis could have implications with respect to planning a successful dietary regimen for achieving and maintaining a normal gut microbiota in SS patients. This regimen would include augmenting butyrate-producing foodstuffs and/or polyphenol-rich syrups, and high amounts of some specific probiotic-rich foodstuffs such as yogurt, soy yogurt, or as probiotic supplements. There are applications for pharmaceutical and nutraceutical products aiming to relieve dry eye and mouth.

Habitual Dietary Intake Affects the Altered Pattern of Gut Microbiome by Acarbose in Patients with Type 2 Diabetes

The aim of this research was to reveal the characteristics of gut microbiome altered by acarbose intervention in Japanese patients with type 2 diabetes (T2D) and its possible association with habitual dietary intake. Eighteen patients with T2D were administered acarbose for four weeks. The abundances of two major phyla, namely Actinobacteria and Bacteroidetes, were reciprocally changed accompanied by the acarbose intervention. There were also significant changes in the abundances of ten genera, including the greater abundance of Bifidobacterium, Eubacterium, and Lactobacillus and the lower abundance of Bacteroides in the group after the intervention than that before the intervention. Hierarchical clustering of habitual dietary intake was performed based on the pattern of changes in the gut microbiota and were classified into distinct three clusters. Cluster I consisted of sucrose, cluster II mainly included fat intake, and cluster III mainly included carbohydrate intake. Moreover, the amount of change in Faecalibacterium was positively correlated with the intake of rice, but negatively correlated with the intake of bread. The intake of potato was negatively correlated with the amount of change in Akkermansia and Subdoligranulum. Acarbose altered the composition of gut microbiome in Japanese patients with T2D, which might be linked to the habitual dietary intake.

Diabetes medications as potential calorie restriction mimetics-a focus on the alpha-glucosidase inhibitor acarbose

The field of aging research has grown rapidly over the last half-century, with advancement of scientific technologies to interrogate mechanisms underlying the benefit of life-extending interventions like calorie restriction (CR). Coincident with this increase in knowledge has been the rise of obesity and type 2 diabetes (T2D), both associated with increased morbidity and mortality. Given the difficulty in practicing long-term CR, a search for compounds (CR mimetics) which could recapitulate the health and longevity benefits without requiring food intake reductions was proposed. Alpha-glucosidase inhibitors (AGIs) are compounds that function predominantly within the gastrointestinal tract to inhibit α-glucosidase and α-amylase enzymatic digestion of complex carbohydrates, delaying and decreasing monosaccharide uptake from the gut in the treatment of T2D. Acarbose, an AGI, has been shown in pre-clinical models to increase lifespan (greater longevity benefits in males), with decreased body weight gain independent of calorie intake reduction. The CR mimetic benefits of acarbose are further supported by clinical findings beyond T2D including the risk for other age-related diseases (e.g., cancer, cardiovascular). Open questions remain regarding the exclusivity of acarbose relative to other AGIs, potential off-target effects, and combination with other therapies for healthy aging and longevity extension. Given the promising results in pre-clinical models (even in the absence of T2D), a unique mechanism of action and multiple age-related reduced disease risks that have been reported with acarbose, support for clinical trials with acarbose focusing on aging-related outcomes and incorporating biological sex, age at treatment initiation, and T2D-dependence within the design is warranted.

One Month of Classic Therapeutic Ketogenic Diet Decreases Short Chain Fatty Acids Production in Epileptic Patients

Ketogenic diet (KD), a high fat and very low carbohydrates diet, is used worldwide for the treatment of drug resistant epilepsy but, due to its composition, it might exert an impact on gut health. Even though data of KD effects on intestinal microbiota changes are recently emerging, its influence on the gut environment has been scarcely addressed so far. The aim of this study was to investigate whether 1 month of KD affects the gut environment in epileptic patients, by analyzing short chain fatty acids (SCFA) production and fecal water toxicity. A total of seven patients were enrolled. Stool samples were collected before (T0) and after 1 month of KD (4:1 ketogenic ratio) (T1). SCFA were determined by GC-FID and fecal water toxicity in Caco-2 cell culture by comet assay. Concentrations of SCFA significantly decreased after KD (p < 0.05): in particular, we found a 55% reduction of total SCFA level, a 64% reduction of acetate, 33% of propionate, and 20% of butyrate (p < 0.05). Cytotoxicity of fecal water extracted from stool samples was not significantly altered by diet, while genotoxicity was slightly decreased after KD (p < 0.05). Genotoxicity values were consistent with data previously obtained from a healthy Italian population. The present study suggests that 1 month of KD significantly reduce SCFA production. Since SCFA produced by gut microbiota exert many health promoting effects on either the gut environment or human metabolism, these results open a new branch of investigation into KD effects.

Modulation of Gut Microbiota Profile and Short-Chain Fatty Acids of Rats Fed with Taro Flour or Taro Starch

To investigate the effect of flour and starch of the Indonesian native tuber “taro” on the composition and activity of the gut microbiota in diabetic rats, streptozotocin (STZ)-induced diabetic rats were fed normal chow (AIN), or AIN in which corn starch was replaced by either taro flour or purified taro starch for 4 weeks. Fecal samples were collected at baseline and after 4 weeks, and the composition of microbial communities was measured using 16S rRNA sequencing, while SCFAs were measured using ion chromatography. Bodyweight declined upon DM induction with STZ. Feeding taro starch led to a lower reduction in bodyweight than feeding taro starch, but this was only significant for taro starch in weeks 2, 3, and 4 (p = 0.02, p = 0.01, and p < 0.01, respectively). Both taro starch and taro flour induced changes in the gut microbiota composition compared to AIN, which were different for taro flour and taro starch. Bifidobacterium, Sutterella, and Prevotella were markers for taro flour feeding, while Anaerostipes was a marker for taro starch feeding. Induction of diabetes also led to changes in the microbiota composition. Random Forest correctly predicted for 16 of 18 samples whether rats were diabetic or not and correctly predicted 6 of 12 microbiota samples belonging to either taro flour- or taro starch-fed groups, indicating also some significant overlap in the substrate, as expected. Taro starch and taro flour both led to a significant increase in the fecal concentrations of acetate, propionate, and butyrate.

Changes in the gut microbiome and fermentation products concurrent with enhanced longevity in acarbose-treated mice

BACKGROUND

Treatment with the α-glucosidase inhibitor acarbose increases median lifespan by approximately 20% in male mice and 5% in females. This longevity extension differs from dietary restriction based on a number of features, including the relatively small effects on weight and the sex-specificity of the lifespan effect. By inhibiting host digestion, acarbose increases the flux of starch to the lower digestive system, resulting in changes to the gut microbiota and their fermentation products. Given the documented health benefits of short-chain fatty acids (SCFAs), the dominant products of starch fermentation by gut bacteria, this secondary effect of acarbose could contribute to increased longevity in mice. To explore this hypothesis, we compared the fecal microbiome of mice treated with acarbose to control mice at three independent study sites.

RESULTS

Microbial communities and the concentrations of SCFAs in the feces of mice treated with acarbose were notably different from those of control mice. At all three study sites, the bloom of a single bacterial taxon was the most obvious response to acarbose treatment. The blooming populations were classified to the largely uncultured Bacteroidales family Muribaculaceae and were the same taxonomic unit at two of the three sites. Propionate concentrations in feces were consistently elevated in treated mice, while the concentrations of acetate and butyrate reflected a dependence on study site. Across all samples, Muribaculaceae abundance was strongly correlated with propionate and community composition was an important predictor of SCFA concentrations. Cox proportional hazards regression showed that the fecal concentrations of acetate, butyrate, and propionate were, together, predictive of mouse longevity even while controlling for sex, site, and acarbose.

CONCLUSION

We observed a correlation between fecal SCFAs and lifespan in mice, suggesting a role of the gut microbiota in the longevity-enhancing properties of acarbose. Treatment modulated the taxonomic composition and fermentation products of the gut microbiome, while the site-dependence of the responses illustrate the challenges facing reproducibility and interpretation in microbiome studies. These results motivate future studies exploring manipulation of the gut microbial community and its fermentation products for increased longevity, testing causal roles of SCFAs in the observed effects of acarbose.

Impact of Gut Dysbiosis on Neurohormonal Pathways in Chronic Kidney Disease

Chronic kidney disease (CKD) is a worldwide major health problem. Traditional risk factors for CKD are hypertension, obesity, and diabetes mellitus. Recent studies have identified gut dysbiosis as a novel risk factor for the progression CKD and its complications. Dysbiosis can worsen systemic inflammation, which plays an important role in the progression of CKD and its complications such as cardiovascular diseases. In this review, we discuss the beneficial effects of the normal gut microbiota, and then elaborate on how alterations in the biochemical environment of the gastrointestinal tract in CKD can affect gut microbiota. External factors such as dietary restrictions, medications, and dialysis further promote dysbiosis. We discuss the impact of an altered gut microbiota on neuroendocrine pathways such as the hypothalamus⁻pituitary⁻adrenal axis, the production of neurotransmitters and neuroactive compounds, tryptophan metabolism, and the cholinergic anti-inflammatory pathway. Finally, therapeutic strategies including diet modification, intestinal alpha-glucosidase inhibitors, prebiotics, probiotics and synbiotics are reviewed.

The Glucoamylase Inhibitor Acarbose Has a Diet-Dependent and Reversible Effect on the Murine Gut Microbiome

The gut microbial community has a profound influence on host physiology in both health and disease. In diabetic individuals, the gut microbiota can affect the course of disease, and some medications for diabetes, including metformin, seem to elicit some of their benefits via an interaction with the microbiota. Here, we report that acarbose, a glucoamylase inhibitor for type 2 diabetes, changes the murine gut bacterial community structure in a reversible and diet-dependent manner. In both high-starch and high-fiber diet backgrounds, acarbose treatment results in increased short-chain fatty acids, particularly butyrate, as measured in stool samples. As we learn more about how human disease is affected by the intestinal bacterial community, the interplay between medications such as acarbose and the diet will become increasingly important to evaluate.

Acarbose is a safe and effective medication for type 2 diabetes that inhibits host glucoamylases to prevent starch digestion in the small intestines and thus decrease postprandial blood glucose levels. This results in an increase in dietary starch in the distal intestine, where it becomes food for the gut bacterial community. Here, we examined the effect of acarbose therapy on the gut community structure in mice fed either a high-starch (HS) or high-fiber diet rich in plant polysaccharides (PP). The fecal microbiota of animals consuming a low dose of acarbose (25 ppm) was not significantly different from that of control animals that did not receive acarbose. However, a high dose of acarbose (400 ppm) with the HS diet resulted in a substantial change to the microbiota structure. Most notably, the HS diet with a high dose of acarbose lead to an expansion of the Bacteroidaceae and Bifidobacteriaceae and a decrease in the Verrucomicrobiaceae (such as Akkermansia muciniphila) and the Bacteroidales S24-7. Once acarbose treatment ceased, the community composition quickly reverted to mirror that of the control group, suggesting that acarbose does not irreversibly alter the gut community. The high dose of acarbose in the PP diet resulted in a distinct community structure with increased representation of Bifidobacteriaceae and Lachnospiraceae. Short-chain fatty acids (SCFAs) measured from stool samples were increased, especially butyrate, as a result of acarbose treatment in both diets. These data demonstrate the potential of acarbose to change the gut community structure and increase beneficial SCFA output in a diet-dependent manner.

IMPORTANCE The gut microbial community has a profound influence on host physiology in both health and disease. In diabetic individuals, the gut microbiota can affect the course of disease, and some medications for diabetes, including metformin, seem to elicit some of their benefits via an interaction with the microbiota. Here, we report that acarbose, a glucoamylase inhibitor for type 2 diabetes, changes the murine gut bacterial community structure in a reversible and diet-dependent manner. In both high-starch and high-fiber diet backgrounds, acarbose treatment results in increased short-chain fatty acids, particularly butyrate, as measured in stool samples. As we learn more about how human disease is affected by the intestinal bacterial community, the interplay between medications such as acarbose and the diet will become increasingly important to evaluate.

Impacts of dietary silver nanoparticles and probiotic administration on the microbiota of an in-vitro gut model

Ingestion of silver nanoparticles (AgNPs) is inevitable linked to their widespread use in food, medicines and other consumer products. However, their effects on human microbiota at non-lethal concentrations remain poorly understood. In this study, the interactions among 1 μg mL^-1 AgNPs, the intestinal microbiota, and the probiotic Bacillus subtilis (BS) were tested using in-vitro batch fermentation models inoculated with human fecal matter. Results from metagenomic investigations revealed that the core bacterial community was not affected by the exposure of AgNPs and BS at the later stage of fermentation, while the proportions of rare species changed drastically with the treatments. Furthermore, shifts in the Firmicutes/Bacteriodetes (F/B) ratios were observed after 24 h with an increase in the relative abundance of Firmicutes species and a decrease in Bacteroidetes in all fermentation cultures. The co-exposure to AgNPs and BS led to the lowest F/B ratio. Fluorescent in-situ hybridization analyses indicated that non-lethal concentration of AgNPs negatively affected the relative percentage of Faecalibacterium prausnitzii and Clostridium coccoides/Eubacterium rectales taxa in the fermentation cultures after 24 h. However, exposure to single and combined treatments of AgNPs and BS did not change the overall diversity of the fecal microflora. Functional differences in cell motility, translation, transport, and xenobiotics degradation occurred in AgNPs-treated fermentation cultures but not in AgNPs+BS-treated samples. Compared to the control samples, treated fecal cultures showed no significant statistical differences in terms of short-chain fatty acids profiles, cytotoxic and genotoxic effects on Caco-2 cell monolayers. Overall, AgNPs did not affect the composition and diversity of the core fecal microflora and its metabolic and toxic profiles. This work indicated a chemopreventive role of probiotic on fecal microflora against AgNPs, which were shown by the decrease of F/B ratio and the unaltered state of some key metabolic pathways.

Nondigestible carbohydrates, butyrate, and butyrate-producing bacteria

Nondigestible carbohydrates (NDCs) are fermentation substrates in the colon after escaping digestion in the upper gastrointestinal tract. Among NDCs, resistant starch is not hydrolyzed by pancreatic amylases but can be degraded by enzymes produced by large intestinal bacteria, including clostridia, bacteroides, and bifidobacteria. Nonstarch polysaccharides, such as pectin, guar gum, alginate, arabinoxylan, and inulin fructans, and nondigestible oligosaccharides and their derivatives, can also be fermented by beneficial bacteria in the large intestine. Butyrate is one of the most important metabolites produced through gastrointestinal microbial fermentation and functions as a major energy source for colonocytes by directly affecting the growth and differentiation of colonocytes. Moreover, butyrate has various physiological effects, including enhancement of intestinal barrier function and mucosal immunity. In this review, several representative NDCs are introduced, and their chemical components, structures, and physiological functions, including promotion of the proliferation of butyrate-producing bacteria and enhancement of butyrate production, are discussed. We also describe the strategies for achieving directional accumulation of colonic butyrate based on endogenous generation mechanisms.

Comparisons of Effects on Intestinal Short-Chain Fatty Acid Concentration after Exposure of Two Glycosidase Inhibitors in Mice

Acarbose and voglibose are the most widely used diabetes drugs as glycosidase inhibitors. In this study, the use of these two inhibitors significantly increased the content of starch in large intestine, and altered the concentration of short-chain fatty acids (SCFAs) by affecting the intestinal microbiota. However, there are some differences in the intestinal microbiome of the two groups of mice, mainly in bacteria such as Bacteroidaceae bacteroides and Desulfovibrionaceae desulfovibrio. The productions of acetate and propionate in caecum in voglibose group were significantly higher than those in acarbose group and two kinds of glycosidase inhibitors were close in the production of butyrate in caecum. The Tax4Fun analysis based on Kyoto Encyclopedia of Genes and Genomes (KEGG) data indicated that different productions of acetate and propionate between acarbose group and voglibose group may be related to 2-oxoisovalerate dehydrogenase and pyruvate oxidase. In addition, in-vitro experiments suggested that voglibose had less effect on epithelial cells than acarbose after direct stimulation. According to the recent researches of SCFAs produced by intestinal microbiota, our comparative study shown higher concentration of these beneficial fatty acids in the lumen of voglibose-treated mice, which implied a lower level of inflammation.

Effect of dietary fat to starch content on fecal microbiota composition and activity in dogs1

Dietary fat is known to modulate the hindgut microbiota in rodents; however, there is no clear evidence on the impact of high-fat diets on canine gut microbiota. The purpose of this study was to investigate the effect of feeding of diets differing in the amount of ME provided by fat and starch on the composition and activity of canine fecal microbiota. Twelve adult (3 to 7 yr of age) spayed Beagle dogs received a low-fat-high-starch diet (LF-HS; approximately 23%, 42%, and 25% ME provided by fat, starch, and CP, respectively) and a high-fat-low-starch diet (HF-LS; approximately 43%, 22%, and 25% ME provided by fat, starch, and CP, respectively) following a 2-period crossover arrangement. The higher amount of fat in the HF-LS diet was provided by lard, whereas the higher amount of starch in the LF-HS diet was provided primarily by maize and broken rice. Each period lasted 7 wk and included 4 wk for diet adaptation. Dogs were fed to meet their daily energy requirements (set at 480 kJ ME/kg BW0.75). Fecal samples were collected on weeks 5 and 6 of each period for the analysis of bacterial richness, diversity, and composition [by Ion-Torrent next-generation sequencing], bile acids, ammonia, and VFA. Additional fecal samples were collected from four dogs per diet and period to use as inocula for in vitro fermentation using xylan and pectin as substrates. Gas production was measured at 2, 4, 6, 9, 12, and 24 h of incubation. On week 7, blood samples were collected at 0- and 180-min postfeeding for the analysis of bacterial lipopolysaccharide (LPS). Feeding the HF-LS diet led to a greater (P < 0.05) fecal bile acid concentration compared with the LF-HS diet. Bacterial richness and diversity did not differ between diets (P > 0.10). However, dogs showed a lower relative abundance of Prevotella (P < 0.01), Solobacterium (P < 0.05), and Coprobacillus (P ˂ 0.05) when fed of the HF-LS diet. Fecal ammonia and VFA contents were not affected by diet (P > 0.10). Relative to the LF-HS diet, in vitro fermentation of xylan using feces of dogs fed the HF-LS diet produced less gas at 6 h (P < 0.01) and 9 h (P < 0.05). Blood LPS did not increase at 180-min postfeeding with either diet (P < 0.10). These findings indicate that feeding a HF-LS diet to dogs does not affect bacterial diversity or fermentative end products in feces, but may have a negative impact on Prevotella and xylan fermentation.

The influence of diabetes and antidiabetic medications on the risk of pancreatic cancer: a nationwide population-based study in Korea

This study investigated the effects of diabetes and antidiabetic medications on the risk of pancreatic cancer(PaC). We extracted data on Koreans with newly diagnosed diabetes and selected age- and sex-matched controls provided by the National Health Insurance Corporation. Incident PaC was defined as a new registration in the Korea Central Cancer Registry under ICD-10 C25 with admission history until 2015. During 19,429,617.1 person-years, 8,589 PaCs were identified in 1,005,409 subjects for diabetes group and 4,021,636 subjects for control group. The diabetes group showed more than a two-fold risk for PaC compared with the control group. Among antidiabetic medications, metformin, thiazolidinedione, and dipeptidyl peptidase-4 inhibitor exposure was associated with decreased risk for future PaC(hazard ratio[95% confidence interval] = 0.86[0.77–0.96], 0.82[0.68–0.98], 0.57[0.51–0.64], respectively), whereas sulfonylurea and insulin exposure was related to increased risk(hazard ratio[95% CI] = 1.73[1.57–1.91], 2.86[1.43–5.74], respectively) compared to subjects with no drug exposure. Moreover, subjects with dual exposure history to metformin plus thiazolidinedione or metformin plus dipeptidyl peptidase-4 inhibitor had a lower risk of PaC compared to metformin-only treated subjects. In conclusion, Korean adults with diabetes are at higher risk of PaC compared with nondiabetic individuals, and this risk may be modified by antidiabetic medications.

Phenylketonuric diet negatively impacts on butyrate production

BACKGROUND AND AIMS

Phenylalanine (Phe) restricted diet, combined with Phe-free l-amino acid supplementation, is the mainstay of treatment for phenylketonuria (PKU). Being the diet a key factor modulating gut microbiota composition, the aim of the present paper was to compare dietary intakes, gut microbiota biodiversity and short chain fatty acids (SCFAs) production in children with PKU, on low-Phe diet, and in children with mild hyperphenylalaninemia (MHP), on unrestricted diet.

METHODS AND RESULTS

We enrolled 21 PKU and 21 MHP children matched for gender, age and body mass index z-score. Dietary intakes, including glycemic index (GI) and glycemic load (GL), and fecal microbiota analyses, by means of denaturing gradient gel electrophoresis (DGGE) and Real-time PCR were assessed. Fecal SCFAs were quantified by gas chromatographic analysis.

RESULTS

We observed an increased carbohydrate (% of total energy), fiber and vegetables intakes (g/day) in PKU compared with MHP children (p = 0.047), as well a higher daily GI and GL (maximum p < 0.001). Compared with MHP, PKU showed a lower degree of microbial diversity and a decrease in fecal butyrate content (p = 0.02). Accordingly, two of the most abundant butyrate-producing genera, Faecalibacterium spp. and Roseburia spp., were found significantly depleted in PKU children (p = 0.02 and p = 0.03, respectively).

CONCLUSION

The low-Phe diet, characterized by a higher carbohydrate intake, increases GI and GL, resulting in a different quality of substrates for microbial fermentation. Further analyses, thoroughly evaluating microbial species altered by PKU diet are needed to better investigate gut microbiota in PKU children and to eventually pave the way for pre/probiotic supplementations.

Sex-dependent Differences in Liver and Gut Metabolomic Profiles With Acarbose and Calorie Restriction in C57BL/6 Mice

Acarbose, an alpha-glucosidase inhibitor used in treating type 2 diabetes, impairs complex carbohydrate digestion and absorption and extends life span in mice (without a requisite reduction in food intake). To assess sex-differential effects coincident with calorie restriction versus a nonrestricted longevity enhancing intervention, we evaluated the metabolite profiles (by liquid chromatography-mass spectroscopy) from livers and cecal contents of C57BL/6J mice (n = 4/sex/group), which were maintained for 10 months under one of the three diet treatments: ad libitum control diet (CON), ad libitum control diet containing 0.1% acarbose (ACA), or 40% calorie restriction using the control diet (CR). Principal component analysis revealed sex-differential profiles with ACA in livers. Of the identified metabolites (n = 621) in liver, CR significantly altered ~44% (males:187↑/131↓, females:74↑/148↓) compared with CON, in contrast with ACA (M:165↑/61↓, F:52↑/60↓). Dissimilarity in ACA-F liver metabolites was observed for ~50% of common metabolites from ACA-M and CR-M/F. CR resulted in fewer significant cecal metabolite differences (n = 615 metabolites; M:86↑/66↓, F:51↑/48↓ vs CON), relative to ACA treatment (M:32↑/189↓, F:36↑/137↓). Metabolomic profiling identifies sex-differential and tissue-specific effects with amino acid metabolism sub-pathways including those involving tryptophan, branch-chain and sulfur amino acids, and the urea cycle, as well as bile acid, porphyrin, and cofactor metabolism pathways.

Diet, Microbiota, and Metabolic Health: Trade-Off Between Saccharolytic and Proteolytic Fermentation

The intestinal microbiota have emerged as a central regulator of host metabolism and immune function, mediating the effects of diet on host health. However, the large diversity and individuality of the gut microbiota have made it difficult to draw conclusions about microbiota responses to dietary interventions. In the light of recent research, certain general patterns are emerging, revealing how the ecology of the gut microbiota profoundly depends on the quality and quantity of dietary carbohydrates and proteins. In this review, I provide an overview of the dependence of microbial ecology in the human colon on diet and how the effects of diet on host health depend partially on the microbiota. Understanding how the individual-specific microbiota respond to short- and long-term dietary changes and how they influence host energy homeostasis will enable targeted interventions to achieve specific outcomes, such as weight loss in obesity or weight gain in malnutrition.

The Relationship between Frequently Used Glucose-Lowering Agents and Gut Microbiota in Type 2 Diabetes Mellitus

Metabolic diseases, especially diabetes mellitus, have become global health issues. The etiology of diabetes mellitus can be attributed to genetic and/or environmental factors. Current evidence suggests the association of gut microbiota with metabolic diseases. However, the effects of glucose-lowering agents on gut microbiota are poorly understood. Several studies revealed that these agents affect the composition and diversity of gut microbiota and consequently improve glucose metabolism and energy balance. Possible underlying mechanisms include affecting gene expression, lowering levels of inflammatory cytokines, and regulating the production of short-chain fatty acids. In addition, gut microbiota may alleviate adverse effects caused by glucose-lowering agents, and this can be especially beneficial in diabetic patients who experience severe gastrointestinal side effects and have to discontinue these agents. In conclusion, gut microbiota may provide a novel viewpoint for the treatment of patients with diabetes mellitus.

Effects of Antidiabetic Drugs on Gut Microbiota Composition

Gut microbiota forms a catalog of about 1000 bacterial species; which mainly belong to the Firmicutes and Bacteroidetes phyla. Microbial genes are essential for key metabolic processes; such as the biosynthesis of short-chain fatty acids (SCFA); amino acids; bile acids or vitamins. It is becoming clear that gut microbiota is playing a prevalent role in pathologies such as metabolic syndrome; type 2 diabetes (T2D); inflammatory and bowel diseases. Obesity and related diseases; notably type 2 diabetes, induce gut dysbiosis. In this review; we aim to cover the current knowledge about the effects of antidiabetic drugs on gut microbiota diversity and composition as well as the potential beneficial effects mediated by specific taxa. Metformin is the first-line treatment against T2D. In addition to its glucose-lowering and insulin sensitizing effects, metformin promotes SCFA-producing and mucin-degrading bacteria. Other antidiabetic drugs discussed in this review show positive effects on dysbiosis; but without any consensus specifically regarding the Firmicutes to Bacteroidetes ratio. Thus, beneficial effects might be mediated by specific taxa.

Microbiota in anorexia nervosa: The triangle between bacterial species, metabolites and psychological tests

Anorexia nervosa (AN) is a psychiatric disease with devastating physical consequences, with a pathophysiological mechanism still to be elucidated. Metagenomic studies on anorexia nervosa have revealed profound gut microbiome perturbations as a possible environmental factor involved in the disease. In this study we performed a comprehensive analysis integrating data on gut microbiota with clinical, anthropometric and psychological traits to gain new insight in the pathophysiology of AN. Fifteen AN women were compared with fifteen age-, sex- and ethnicity-matched healthy controls. AN diet was characterized by a significant lower energy intake, but macronutrient analysis highlighted a restriction only in fats and carbohydrates consumption. Next generation sequencing showed that AN intestinal microbiota was significantly affected at every taxonomic level, showing a significant increase of Enterobacteriaceae, and of the archeon Methanobrevibacter smithii compared with healthy controls. On the contrary, the genera Roseburia, Ruminococcus and Clostridium, were depleted, in line with the observed reduction in AN of total short chain fatty acids, butyrate, and propionate. Butyrate concentrations inversely correlated with anxiety levels, whereas propionate directly correlated with insulin levels and with the relative abundance of Roseburia inulinivorans, a known propionate producer. BMI represented the best predictive value for gut dysbiosis and metabolic alterations, showing a negative correlation with Bacteroides uniformis (microbiota), with alanine aminotransferase (liver function), and with psychopathological scores (obsession-compulsion, anxiety, and depression), and a positive correlation with white blood cells count. In conclusion, our findings corroborate the hypothesis that the gut dysbiosis could take part in the AN neurobiology, in particular in sustaining the persistence of alterations that eventually result in relapses after renourishment and psychological therapy, but causality still needs to be proven.

Effects of Acarbose on the Gut Microbiota of Prediabetic Patients: A Randomized, Double-blind, Controlled Crossover Trial

INTRODUCTION

The α-glucosidase inhibitor acarbose is an efficacious medicine for the treatment and prevention of type 2 diabetes mellitus (T2DM). However, the response of gut microbiota to acarbose is important, as the microbiota may have a critical role in the development of metabolic diseases, and acarbose is metabolized exclusively within the gastrointestinal tract. We explored the changes in the proportion and diversity of gut microbiota before and after treatment with acarbose in patients with prediabetes.

METHODS

We designed a randomized, double-blind, controlled crossover trial in which 52 Chinese patients with prediabetes by an oral glucose tolerance test (OGTT) with a BMI of 18-35 kg/m² were randomly allocated to treatment with acarbose or placebo. Gut microbiota characterizations were determined with 16S rDNA-based high-throughput sequencing.

RESULTS

Of the 52 participants who entered the study, 40 (76.9%) completed the protocol. On the basis of the operational taxonomic unit (OTU) profiles, a total of 107 OTUs were significantly altered after acarbose treatment, with 76 (71%) assigned to the order of Clostridiales. Ruminococcaceae (15 OTUs) and Lachnospiraceae (22 OTUs) decreased in response to acarbose, and 48 OTUs increased by 12.8-fold, including Lactobacillaceae (8 of 9 belonging to Lactobacillus), Ruminococcaceae (6 of 11 belonging to Faecalibacterium), and Veillonellaceae (8 of 15 belonging to Dialister). At genera level, five flourished after treatment with acarbose, including Lactobacillus and Dialister, while Butyricicoccus, Phascolarctobacterium, and Ruminococcus were inhibited.

CONCLUSION

This study suggests that the benefits of acarbose for T2DM may correlate with the selective modulation of the gut microbiota.

TRIAL REGISTRATION

Chinese Clinical Trial Register number, ChiCTR-TTRCC-13004112.

Rett Syndrome: A Focus on Gut Microbiota

Rett syndrome (RTT) is an X-linked neurodevelopmental disorder affecting 1 in 10,000 live female births. Changes in microbiota composition, as observed in other neurological disorders such as autism spectrum disorders, may account for several symptoms typically associated with RTT. We studied the relationship between disease phenotypes and microbiome by analyzing diet, gut microbiota, and short-chain fatty acid (SCFA) production. We enrolled eight RTT patients and 10 age- and sex-matched healthy women, all without dietary restrictions. The microbiota was characterized by 16S rRNA gene sequencing, and SCFAs concentration was determined by gas chromatographic analysis. The RTT microbiota showed a lower α diversity, an enrichment in Bacteroidaceae, Clostridium spp., and Sutterella spp., and a slight depletion in Ruminococcaceae. Fecal SCFA concentrations were similar, but RTT samples showed slightly higher concentrations of butyrate and propionate, and significant higher levels in branched-chain fatty acids. Daily caloric intake was similar in the two groups, but macronutrient analysis showed a higher protein content in RTT diets. Microbial function prediction suggested in RTT subjects an increased number of microbial genes encoding for propionate and butyrate, and amino acid metabolism. A full understanding of these critical features could offer new, specific strategies for managing RTT-associated symptoms, such as dietary intervention or pre/probiotic supplementation.

Effect of miglitol on the suppression of nonalcoholic steatohepatitis development and improvement of the gut environment in a rodent model

BACKGROUND

The gut environment has been considered to play a role in the development of nonalcoholic steatohepatitis (NASH). α-glucosidase inhibitors (α-GIs) delay carbohydrate absorption and may change the gut environment. We considered that the protective effect of α-GIs against NASH development is related to changes in the gut environment and thus investigated the effects of miglitol, an α-GI, on NASH development and the gut environment.

METHODS

Mice were divided into three groups and fed a normal chow diet (NCD), a high-fat high-sucrose diet (HFHSD), or HFHSD plus 0.04% miglitol (HFHSD plus M) for 12 weeks.

RESULTS

Insulin resistance developed more in the HFHSD group than in the NCD group, whereas it was suppressed in the HFHSD plus M group. NASH was evaluated histologically, biochemically, and on the basis of messenger RNA expression levels. Miglitol treatment suppressed HFHSD-induced NASH development with the suppression of hepatic Toll-like receptor 4 expression, increased glucagon-like peptide 1 (GLP-1) concentration, and reduced lipopolysaccharide concentration in portal plasma. Regarding the gut environment, the intestinal transit time was shortened and colon inflammation was suppressed in the HFHSD plus M group compared with the HFHSD group. Regarding the gut microbiota, the abundances of Erysipelotrichaceae and Coriobacteriaceae were increased in the HFHSD group compared with the NCD group, whereas the increase was suppressed in the HFHSD plus M group.

CONCLUSIONS

We demonstrated that miglitol has a protective effect against HFHSD-induced NASH development. The increased GLP-1 secretion and the suppression of endotoxemia, associated with the changes in the gut environment, including the gut microbiota, could contribute to the underlying mechanisms.

Targeting glucose metabolism for healthy aging

Advancing age is the greatest single risk factor for numerous chronic diseases. Thus, the ability to target the aging process can facilitate improved healthspan and potentially lifespan. Lack of adequate glucoregulatory control remains a recurrent theme accompanying aging and chronic disease, while numerous longevity interventions result in maintenance of glucoregulatory control. In this review, we propose targeting glucose metabolism to enhance regulatory control as a means to ameliorate the aging process. We highlight that calorie restriction improves glucoregulatory control and extends both lifespan and healthspan in model organisms, but we also indicate more practical interventions (i.e., calorie restriction mimetics) are desirable for clinical application in humans. Of the calorie restriction mimetics being investigated, we focus on the type 2 diabetes drug acarbose, an α-glucosidase inhibitor that when taken with a meal, results in reduced enzymatic degradation and absorption of glucose from complex carbohydrates. We discuss alternatives to acarbose that yield similar physiologic effects and describe dietary sources (e.g., sweet potatoes, legumes, and berries) of bioactive compounds with α-glucosidase inhibitory activity. We indicate future research should include exploration of how non-caloric compounds like α-glucosidase inhibitors modify macronutrient metabolism prior to disease onset, which may guide nutritional/lifestyle interventions to support health and reduce age-related disease risk.

Use of an α-Glucosidase Inhibitor and the Risk of Colorectal Cancer in Patients With Diabetes: A Nationwide, Population-Based Cohort Study

OBJECTIVE

Acarbose, an α-glucosidase inhibitor, has been shown to have antineoplastic effects on colorectal cancer in biomarker studies. We assessed the association between acarbose use in patients with diabetes and incident colorectal cancer.

RESEARCH DESIGN AND METHODS

We conducted a nationwide, population-based study using a large cohort with diabetes in the Taiwan National Health Insurance Research Database. Patients with newly diagnosed diabetes (n = 1,343,484) were enrolled between 1998 and 2010. One control subject not using acarbose was randomly selected for each subject using acarbose after matching for age, sex, diabetes onset, and comorbidities. Cox proportional hazards regression with a competing risks analysis was used to calculate the hazard ratios (HRs) and 95% CIs for the association between acarbose use and incident colorectal cancer for each eligible case-control pair (n = 199,296).

RESULTS

There were 1,332 incident cases of colorectal cancer in the cohort with diabetes during the follow-up period of 1,487,136 person-years. The overall incidence rate was 89.6 cases per 100,000 person-years. Patients treated with acarbose had a 27% reduction in the risk of colorectal cancer compared with control subjects. The adjusted HRs were 0.73 (95% CI 0.63-0.83), 0.69 (0.59-0.82), and 0.46 (0.37-0.58) for patients using >0 to <90, 90 to 364, and ≥365 cumulative defined daily doses of acarbose, respectively, compared with subjects who did not use acarbose (P for trend < 0.001).

CONCLUSIONS

Acarbose use reduced the risk of incident colorectal cancer in patients with diabetes in a dose-dependent manner.

Acarbose: safe and effective for lowering postprandial hyperglycaemia and improving cardiovascular outcomes

α-Glucosidase inhibitors (AGIs) are a class of oral glucose-lowering drugs used exclusively for treatment or prevention of type 2 diabetes mellitus. AGIs act by altering the intestinal absorption of carbohydrates through inhibition of their conversion into simple sugars (monosaccharides) and thus decrease the bioavailability of carbohydrates in the body, significantly lowering blood glucose levels. The three AGIs used in clinical practice are acarbose, voglibose and miglitol. This review will focus on the cardiovascular properties of acarbose. The current available data suggest that AGIs (particularly acarbose) may be safe and effective for the treatment of prediabetes and diabetes.

Kiwifruit fibre level influences the predicted production and absorption of SCFA in the hindgut of growing pigs using a combined in vivo-in vitro digestion methodology

Combined in vivo (ileal cannulated pig) and in vitro (faecal inoculum-based fermentation) digestion methodologies were used to predict the production and absorption of SCFA in the hindgut of growing pigs. Ileal and faecal samples were collected from animals (n 7) fed diets containing either 25 or 50 g/kg DM of kiwifruit fibre from added kiwifruit for 14 d. Ileal and faecal SCFA concentrations normalised for food DM intake (DMI) and nutrient digestibility were determined. Ileal digesta were collected and fermented for 38 h using a fresh pig faecal inoculum to predict SCFA production. The predicted hindgut SCFA production along with the determined ileal and faecal SCFA were then used to predict SCFA absorption in the hindgut and total tract organic matter digestibility. The determined ileal and faecal SCFA concentrations (e.g. 8·5 and 4·4 mmol/kg DMI, respectively, for acetic acid for the low-fibre diet) represented only 0·2-3·2 % of the predicted hindgut SCFA production (e.g. 270 mmol/kg DMI for acetic acid). Predicted production and absorption of acetic, butyric and propionic acids were the highest for the high-fibre diet (P0·05). In conclusion, determined ileal and faecal SCFA concentrations represent only a small fraction of total SCFA production, and may therefore be misleading in relation to the effect of diets on SCFA production and absorption. Considerable quantities of SCFA are produced and absorbed in the hindgut of the pig by the fermentation of kiwifruit.

Sex differences in gut fermentation and immune parameters in rats fed an oligofructose-supplemented diet

BACKGROUND

Mechanistic data to support health claims is often generated using rodent models, and the influence of prebiotic supplementation has largely been evaluated using male rodents. Given that sex-based differences in immune parameters are well recognized and recent evidence suggests differences in microbiota composition between sexes, validation of the effectiveness of prebiotics merits assessment in both males and females. Here, we have compared the effect of oligofructose (OF) supplementation on the fecal bacterial community, short chain fatty acid profiles, and gut mucosal and systemic immune parameters in male and female rats.

METHODS

Male and female rats were fed rodent chow or chow supplemented with OF (5 % w/w). Fecal community change was examined by analyzing 16S rRNA gene content. To compare effects of OF between sexes at the gut microbial and mucosal immune level, fecal short chain fatty acid and tissue cytokine profiles were measured. Serum lipopolysaccharide levels were also evaluated by the limulus amebocyte lysate assay as an indirect means of determining gut permeability between sexes.

RESULTS

In the fecal community of females, OF supplementation altered community structure by increasing abundance in the Phylum Bacteroidetes. In male rats, no changes in fecal community structure were observed, although fecal butyrate levels significantly increased. Liver Immunoglobulin A (IgA) levels were higher in males relative to females fed OF, and serum LPS concentrations were higher in males independent of diet. Females had higher basal levels of the regulatory cytokine interleukin-10 (IL-10) in the colon and liver, while males had higher basal levels of the pro-inflammatory cytokines IL-6 and cytokine-induced neutrophil chemoattractant-1 (CINC-1) in the cecum and liver.

CONCLUSIONS

We have shown that male and female rat gut communities metabolize an OF-supplemented diet differently. Sex-specific responses in both the fecal community and systemic immune parameters suggest that this difference may result from an increase in the availability of gut peptidyl-nitrogen in the males. These findings demonstrate the importance of performing sex-comparative studies when investigating potential health effects of prebiotics using rodent models.

Temporal change in the gut community of rats fed high amylose cornstarch is driven by endogenous urea rather than strictly on carbohydrate availability

AIM

To examine change in the gut community of rats fed high amylose maize starch (HAMS).

METHODS AND RESULTS

Rats were fed AIN93G diets containing HAMS (5% resistant starch type 2) or alphacell (control). HAMS increased faecal short-chain fatty acid output, faecal propionate and total bacteria output but reduced gut pH and blood urea concentrations compared with rats ingesting the control diet. Feeding HAMS resulted in a gut community dominated by four phylotypes homologous with Ruminococcus bromii, Bacteroides uniformis and with yet to be cultivated organisms aligning into the Family Porphyromonadaceae. Enrichment of phylotypes aligning within the Bacteroidetes occurred primarily in the caecum, whereas those homologous with R. bromii were found primarily in the faeces. HAMS altered community structure such that the phylum Bacteroidetes represented the dominant gut lineage and progressively reduced faecal community phylotype richness over the duration of feeding.

CONCLUSIONS

Feeding HAMS resulted in a caecal and faecal community dominated by organisms that require ammonia as a primary nitrogen source. Gut ammonia derived from endogenous urea represents an important factor contributing to caecal community composition in addition to the ability to utilize HAMS. Increases in faecal propionate, rather than butyrate as is often observed following resistant starch feeding, reflected a gut community dominated by the Bacteroidetes.

SIGNIFICANCE

Diet-mediated change is often viewed strictly in terms of available carbohydrate. Here, we have shown that ammonia derived from endogenous urea is an important factor contributing to gut community composition and structure in rats fed this substrate.