Obese ZDF rats fermented resistant starch with effects on gut microbiota but no reduction in abdominal fat

A type 4 resistant potato starch alters the cecal microbiome, gene expression and resistance to colitis in mice fed a Western diet based on NHANES data

Four major types of resistant starch (RS1-4) are present in foods and can be fermented to produce short-chain fatty acids (SCFAs), alter the microbiome and modulate post-prandial glucose metabolism. While studies in rodents have examined the effects of RS4 consumption on the microbiome, fewer have examined its effect on gene expression in the cecum or colon or resistance to bacterial-induced colitis, and those that have, use diets that do not reflect what is typically consumed by humans. Here we fed mice a Total Western Diet (TWD), based on National Health and Nutrition Examination Survey (NHANES) data for 6-7 weeks and then supplemented their diet with 0, 2, 5, or 10% of the RS4, Versafibe 1490™ (VF), a phosphorylated and cross-linked potato starch. After three weeks, mice were infected with Citrobacter rodentium (Cr) to induce colitis. Infected mice fed the 10% VF diet had the highest levels of Cr fecal excretion at days 4, 7 and 11 post-infection. Infected mice fed the 5% and 10%VF diets had increased hyperplasia and colonic damage compared with the control. Changes in bacterial genera relative abundance, and alpha and beta diversity due to diet were most evident in mice fed 10% VF. Cr infection also resulted in specific changes to the microbiome and gene expression both in the cecum and the colon compared with diet alone, including the expression of multiple antimicrobial genes, Reg3b, Reg3g, NOS2 and Ifng. These results demonstrate that VF, a RS4, alters cecal and colonic gene expression, the microbiome composition and resistance to bacterial-induced colitis.

Vertical heterogeneity enhances network complexity and stability of co-occurrence microbes in the eastern Indian Ocean

Microbes are core to driving biogeochemical cycles and differ between sun-drenched surface and relatively dark deep oceans. However, their distinct contributions to the organization and association of communities are still remaining elusive. Here, their assembly and co-occurrence stability are systematically researched along the surface and vertical gradients in the eastern Indian Ocean. The distribution of surface microbes was grouped tightly with closer phylogenetic distance and broader niche breadth, and separately from those vertical samples. Clear distance-decay of community similarity was observed in surface microbes with lower richness, while more diverse microeukaryotes and prokaryotes were observed in surface and vertical environments, respectively. Co-occurrence microbes along vertical gradients had a more complex network that was dominated by prokaryotes, while exhibited a lower modularity compared to the surface network. Microbial associations along vertical gradients were more stable and resilient, with lower robustness, higher vulnerability, and a relatively consistent fragmentation. Moreover, prokaryotes contribute greatly to the network topology and stability compared to microeukaryotes in surface environments, emphasizing their distinct functions and survival strategies in maintaining community stability across spatial variations. Environmental selection and community differentiation led to the divergence in organization and potential function of microbes. This study shed light on new perspectives on how marine microbes were associated with and influenced by spatial heterogeneity and their distinct roles in community organization in the face of environmental fluctuations.

Deleterious Effects of Yoyo Dieting and Resistant Starch on Gastrointestinal Morphology

BACKGROUND

Obesity is associated with structural deterioration in the gut. Yoyo dieting, which refers to repeated phases of dieting and non-dieting periods leading to cyclic weight loss and regain, is a common occurrence in individuals with obesity. However, there is limited evidence on how gut structures are affected in yoyo dieting. There is good evidence suggesting that increased intake of resistant starch (RS) may be beneficial in promoting structural improvements in the gut. This investigation aimed to explore the effect of yoyo dieting on gastrointestinal structure and whether RS has beneficial effects in improving obesity-related gastrointestinal damage.

METHOD

In this study, male and female C57BL/6 mice were assigned to six different diets for 20 weeks: (1) control diet, (2) high fat diet (HF), (3) yoyo diet (alternating HF and control diets every 5 weeks), (4) control diet with RS, (5) HF with RS, and (6) yoyo diet with RS. Distal colon was collected for epithelial barrier integrity measurement. The small and large intestines were collected for histological assessment.

RESULTS

After 20 weeks, yoyo dieting resulted in increased colonic inflammation and exacerbated mucosal damage in comparison with continuous HF diet feeding. RS supplemented in HF and yoyo diets reduced mucosal damage in comparison to diets without RS. However, RS supplementation in a control diet significantly increased inflammation, crypt length, and goblet cell density. There were no significant differences in epithelial change and epithelial barrier integrity across diet groups.

CONCLUSIONS

This study suggests that yoyo dieting worsens gut damage, and incorporating high levels of RS may be detrimental in the absence of dietary challenge.

Increasing degree of substitution inhibits acetate while promotes butyrate production during in vitro fermentation of citric acid-modified rice starch

Citric acid-modified starch functions as a resistant starch, while the combined effects of its fine molecular structure and degree of substitution on gut microbiota are not well understood. To this end, citric acid-modified starches with varying degrees of substitution were synthesized from rice starches with distinct molecular structures and their impact on gut microbiota composition and short-chain fatty acid (SCFA) production was analyzed. Notably, rice starch with a higher degree of substitution significantly reduced acetate production, while promoted butyrate production. Correlation analysis further suggested that amylopectin chains with 12 < DP ≤ 36 and amylose chains with 100 < DP ≤ 500 alter the growth of Faecalibacterium_prausnitzii and Bacteroides_vulgatus, consequentially determining the production of SCFAs. Collectively, these findings indicate that citric acid-modified rice starch with different degrees of substitution can target specific gut bacteria and SCFA production, thus conferring beneficial impact on human health.

The Impact of Yoyo Dieting and Resistant Starch on Weight Loss and Gut Microbiome in C57Bl/6 Mice

Cyclic weight loss and subsequent regain after dieting and non-dieting periods, a phenomenon termed yoyo dieting, places individuals at greater risk of metabolic complications and alters gut microbiome composition. Resistant starch (RS) improves gut health and systemic metabolism. This study aimed to investigate the effect of yoyo dieting and RS on the metabolism and gut microbiome. C57BL/6 mice were assigned to 6 diets for 20 weeks, including control, high fat (HF), yoyo (alternating HF and control diets every 5 weeks), control with RS, HF with RS, and yoyo with RS. Metabolic outcomes and microbiota profiling using 16S rRNA sequencing were examined. Yoyo dieting resulted in short-term weight loss, which led to improved liver health and insulin tolerance but also a greater rate of weight gain compared to continuous HF feeding, as well as a different microbiota profile that was in an intermediate configuration between the control and HF states. Mice fed HF and yoyo diets supplemented with RS gained less weight than those fed without RS. RS supplementation in yoyo mice appeared to shift the gut microbiota composition closer to the control state. In conclusion, yoyo dieting leads to obesity relapse, and increased RS intake reduces weight gain and might help prevent rapid weight regain via gut microbiome restoration.

Dietary fiber and polyphenols from whole grains: effects on the gut and health improvements

Cereals are the main source of energy in the human diet. Compared to refined grains, whole grains retain more beneficial components, including dietary fiber, polyphenols, proteins, vitamins, and minerals. Dietary fiber and bound polyphenols (biounavailable) in cereals are important active substances that can be metabolized by the gut microorganisms and affect the intestinal environment. There is a close relationship between the gut microbiota structures and various disease phenotypes, although the consistency of this link is affected by many factors, and the specific mechanisms are still unclear. Remodeling unfavorable microbiota is widely recognized as an important way to target the gut and improve diseases. This paper mainly reviews the interaction between the gut microbiota and cereal-derived dietary fiber and polyphenols, and also summarizes the changes to the gut microbiota and possible molecular mechanisms of related glycolipid metabolism. The exploration of single active ingredients in cereals and their synergistic health mechanisms will contribute to a better understanding of the health benefits of whole grains. It will further help promote healthier whole grain foods by cultivating new varieties with more potential and optimizing processing methods.

A type 4 resistant potato starch alters the cecal microbiome and gene expression in mice fed a western diet based on NHANES data

Four major types of resistant starch (RS1-4) are present in foods, all of which can alter the microbiome and are fermented in the cecum and colon to produce short-chain fatty acids (SCFAs). Type 4 RSs are chemically modified starches, not normally found in foods, but have become a popular food additive as their addition increases fiber content. Multiple studies, in humans and rodents, have explored how different RS4 affect post-prandial glucose metabolism, but fewer studies have examined the effects of RS4 consumption on the microbiome. In addition, many RS studies conducted in rodents use high-fat diets that do not approximate what is typically consumed by humans. To address this, mice were fed a Total Western Diet (TWD), based on National Health and Nutrition Examination Survey (NHANES) data that mimics the macro and micronutrient composition of a typical American diet, for six weeks, and then supplemented with 0, 2, 5, or 10% of the RS4, Versafibe 1490™ (VF), a phosphorylated and cross-linked potato starch, for an additional three weeks. The cecal contents were analyzed for SCFA content and microbiota composition. Butyrate production was increased while branched chain SCFA production decreased. The alpha-diversity of the microbiome decreased in mice fed the TWD with 10% VF 1490 added while the beta-diversity plot showed that the 5% and 10% VF groups were distinct from mice fed the TWD. Similarly, the largest changes in relative abundance of various genera were greatest in mice fed the 10% VF diet. To examine the effect of VF consumption on tissue gene expression, cecal and distal colon tissue mRNA abundance were analyzed by RNASeq. Gene expression changes were more prevalent in the cecum than the colon and in mice fed the 10% VF diet, but the number of changes was substantially lower than we previously observed in mice fed the TWD supplemented with native potato starch (RPS). These results provide additional evidence that the structure of the RS is a major factor determining its effects on the microbiome and gene expression in the cecum and colon.

A Study on the Structural and Digestive Properties of Rice Starch-Hydrocolloid Complexes Treated with Heat-Moisture Treatment

Rice starch-hydrophilic colloid complexes (SHCs) were prepared by incorporating xanthan gum and locust bean gum into natural rice starch. Subsequently, they underwent hygrothermal treatment (H-SHC) to investigate their structural and digestive properties with varying colloid types and added amounts of H-SHC. The results demonstrated that heat-moisture treatment (HMT) led to an increase in resistant starch (RS) content in rice starch. This effect was more pronounced after the addition of hydrophilic colloid, causing RS content to surge from 8.42 ± 0.39% to 38.36 ± 3.69%. Notably, the addition of locust bean gum had a more significant impact on enhancing RS content, and the RS content increased with the addition of hydrophilic colloids. Enzyme digestion curves indicated that H-SHC displayed a lower equilibrium concentration (C∞), hydrolysis index (HI), and gluconeogenesis index (eGI). Simultaneously, HMT reduced the solubility and swelling power of starch. However, the addition of hydrophilic colloid led to an increase in the solubility and swelling power of the samples. Scanning electron microscopy revealed that hydrophilic colloid encapsulated the starch granules, affording them protection. X-ray diffraction (XRD) showed that HMT resulted in the decreased crystallinity of the starch granules, a trend mitigated by the addition of hydrophilic colloid. Infrared (IR) results demonstrated no formation of new covalent bonds but indicated increased short-range ordering in H-SHC. Rapid viscosity analysis and differential scanning calorimetry indicated that HMT substantially decreased peak viscosity and starch breakdown, while it significantly delayed the onset, peak, and conclusion temperatures. This effect was further amplified by the addition of colloids. Rheological results indicated that H-SHC displayed lower values for G', G″, and static rheological parameters compared to natural starch. In summary, this study offers valuable insights into the development of healthy, low-GI functional foods.

Neuroactive Steroid-Gut Microbiota Interaction in T2DM Diabetic Encephalopathy

The pathological consequences of type 2 diabetes mellitus (T2DM) also involve the central nervous system; indeed, T2DM patients suffer from learning and memory disabilities with a higher risk of developing dementia. Although several factors have been proposed as possible contributors, how neuroactive steroids and the gut microbiome impact brain pathophysiology in T2DM remain unexplored. On this basis, in male Zucker diabetic fatty (ZDF) rats, we studied whether T2DM alters memory abilities using the novel object recognition test, neuroactive steroid levels by liquid chromatography-tandem mass spectrometry, hippocampal parameters using molecular assessments, and gut microbiome composition using 16S next-generation sequencing. Results obtained reveal that T2DM worsens memory abilities and that these are correlated with increased levels of corticosterone in plasma and with a decrease in allopregnanolone in the hippocampus, where neuroinflammation, oxidative stress, and mitochondrial dysfunction were reported. Interestingly, our analysis highlighted a small group of taxa strictly related to both memory impairment and neuroactive steroid levels. Overall, the data underline an interesting role for allopregnanolone and microbiota that may represent candidates for the development of therapeutic strategies.

Raw potato starch alters the microbiome, colon and cecal gene expression, and resistance to Citrobacter rodentium infection in mice fed a Western diet

Resistant starches (RS) are fermented in the cecum and colon to produce short-chain fatty acids and other microbial metabolites that can alter host physiology and the composition of the microbiome. We previously showed that mice fed a Total Western Diet (TWD) based on NHANES data that mimics the composition of a typical American diet, containing resistant potato starch (RPS), produced concentration dependent changes to the cecal short-chain fatty acids, the microbiome composition as well as gene expression changes in the cecum and colon that were most prevalent in mice fed the 10% RPS diet. We were then interested in whether feeding TWD/RPS would alter the resistance to bacterial-induced colitis caused by Citrobacter rodentium (Cr), a mouse pathogen that shares 66.7% of encoded genes with Enteropathogenic Escherichia coli. Mice were fed the TWD for 6 weeks followed by a 3-weeks on the RPS diets before infecting with Cr. Fecal Cr excretion was monitored over time and fecal samples were collected for 16S sequencing. Mice were euthanized on day 12 post-infection and cecal contents collected for 16S sequencing. Cecum and colon tissues were obtained for gene expression analysis, histology and to determine the level of mucosa-associated Cr. Feeding RPS increased the percentage of mice productively infected by Cr and fecal Cr excretion on day 4 post-infection. Mice fed the TWD/10% RPS diet also had greater colonization of colonic tissue at day 12 post-infection and colonic pathology. Both diet and infection altered the fecal and cecal microbiome composition with increased levels of RPS resulting in decreased α-diversity that was partially reversed by Cr infection. RNASeq analysis identified several mechanistic pathways that could be associated with the increased colonization of Cr-infected mice fed 10% RPS. In the distal colon we found a decrease in enrichment for genes associated with T cells, B cells, genes associated with the synthesis of DHA-derived SPMs and VA metabolism/retinoic acid signaling. We also found an increase in the expression of the potentially immunosuppressive gene, Ido1. These results suggest that high-level consumption of RPS in the context of a typical American diet, may alter susceptibility to gastrointestinal bacterial infections.

Influence of Resistant Starch in Whole Rice on Human Gut Microbiota─From Correlation Implications to Possible Causal Mechanisms

Rice is the main staple food for a large population around the world, while it generally has a high glycemic index and low resistant starch (RS) content. Although many strategies have been applied to develop healthier rice products with increased RS contents, their actual effects on gut microbiota and human health remain elusive. In this review, currently available production methods of rice RS are briefly summarized, followed by a critical discussion on their interactions with gut microbiota and subsequent effects on human health, from correlation implications to causal mechanisms. Different contents, types, and structures of RS have been produced by strategies such as genetic manipulation and controlling cooking conditions. The difference can largely determine effects of rice RS on gut microbiota composition and metabolites by specific RS-gut microbiota interactions. This review can thus help the rice industry develop rice products with desirable RS contents and structures to generally improve human health.

Insoluble dietary fibers: structure, metabolism, interactions with human microbiome, and role in gut homeostasis

Consumption of food rich in dietary fibers (DFs) has been long recognized to exert an overall beneficial effect on human health. This review aims to provide a holistic overview on how IDFs impact human gut health either directly, or through modulation of the gut microbiome. Several databases were searched for collecting papers such as PubMed, Google Scholar, Web of Science, Scopus and Reaxys from 2000 till 2022. Firstly, an overview of the chemical structure of the various IDFs and the pathways employed by gut microbiota for their degradation is provided. The impact of IDFs on microbial community structure and pathogens colonization inside the human gut was discussed. Finally, the impact of IDFs on gut homeostasis and systemic effects at the cellular level, as well as the overall immunological benefits of IDFs consumption were analyzed. IDFs viz., cellulose, hemicellulose, resistant starch, and lignin found enriched in food are discussed for these effects. IDFs were found to induce gut immunity, improve intestinal integrity and mucosal proliferation, and favor adhesion of probiotics and hence improve human health. Also, IDFs were concluded to improve the bioavailability of plant polyphenols and improve their health-related functional roles. Ultimately, dietary fibers processing by modification shows potential to enhance fibers-based functional food production, in addition to increase the economic value and usage of food-rich fibers and their by-products.

A Review: Cereals on Modulating the Microbiota/Metabolome for Metabolic Health

PURPOSE OF REVIEW

Diet can modulate both the composition and functionality of the human gut microbiota. Cereals are rich in specific macro and functional elements that are considered important dietary components for maintaining human health; therefore, it is important to examine precise nutritional mechanism involved in exerting the health benefits via modulating gut microbiota. The purpose of this review is to summarize recent research on how different cereals in the diet can regulate the microbiota for health and disease.

RECENT FINDINGS

There is an increased interest in targeting the gut microbiome for the treatment of chronic diseases. Cereals can alter the gut microbiome and may improve energy and glucose homeostasis, interfere with host energy homeostasis, appetite, blood glucose regulation, insulin sensitivity, and regulation of host metabolism. However, more human research is necessary to confirm the beneficial health outcomes of cereals via modulating gut microbiota. Cereals play an essential role in shaping the intestinal microbiota that contributes to exerting health effects on various diseases.

Resistant Potato Starch Alters the Cecal Microbiome and Gene Expression in Mice Fed a Western Diet Based on NHANES Data

Several studies indicate that the four major types of resistant starch (RS1-4) are fermented in the cecum and colon to produce short-chain fatty acids (SCFAs) and can alter the microbiome and host physiology. However, nearly all these studies were conducted in rodents fed with a diet that does not approximate what is typically consumed by humans. To address this, mice were fed a Total Western Diet (TWD) based on National Health and Nutrition Examination Survey (NHANES) data that mimics the macro and micronutrient composition of a typical American diet for 6 weeks and then supplemented with 0, 2, 5, or 10% of the RS2, resistant potato starch (RPS), for an additional 3 weeks. The cecal microbiome was analyzed by 16S sequencing. The alpha-diversity of the microbiome decreased with increasing consumption of RPS while a beta-diversity plot showed four discreet groupings based on the RPS level in the diet. The relative abundance of various genera was altered by feeding increasing levels of RPS. In particular, the genus Lachnospiraceae NK4A136 group was markedly increased. Cecal, proximal, and distal colon tissue mRNA abundance was analyzed by RNASeq. The cecal mRNA abundance principal component analysis showed clear segregation of the four dietary groups whose separation decreased in the proximal and distal colon. Differential expression of the genes was highest in the cecum, but substantially decreased in the proximal colon (PC) and distal colon (DC). Most differentially expressed genes were unique to each tissue with little overlap in between. The pattern of the observed gene expression suggests that RPS, likely through metabolic changes secondary to differences in microbial composition, appears to prime the host to respond to a range of pathogens, including viruses, bacteria, and parasites. In summary, consumption of dietary RPS led to significant changes to the microbiome and gene expression in the cecum and to a lesser extent in the proximal and distal colon.

Gut Microbiota Composition and Predicted Microbial Metabolic Pathways of Obesity Prone and Obesity Resistant Outbred Sprague-Dawley CD Rats May Account for Differences in Their Phenotype

Like humans, outbred Sprague-Dawley CD rats exhibit a polygenic pattern of inheritance of the obese phenotype and not all individuals exposed to a high calorie intake develop obesity. We hypothesized that differences in gut microbiota composition account for phenotype differences between obese prone (OP) and obese resistant (OR) rats. We studied the gut microbiota composition of OPand OR rats after a high fat (HF) diet and how they respond to fermentation of resistant starch (RS). In phase 1 of the study 28 OP and 28 OR rats were fed a HF diet. In order to determine causal role of microbiota on phenotypes, In phase 2, a microbiota transplant between the two phenotypes was performed before switching all rats to a HF diet supplemented with 20% RS. We determined microbiota composition by 16S sequencing and predicted microbiota function by PICRUSt2. Despite a similar calorie intake, in phase 2 OP rats gained more weight and accumulated more abdominal fat in both phase 1 and 2 compared to OR rats (P < 0.001; n = 6). The OP rats fermented RS more robustly compared with OR rats with an increase in total bacteria, short chain fatty acids, and increased weight of the cecum, but microbiota of OP rats had much lower alpha diversity and evenness. The microbiota of OP rats, had higher amounts of bacteria from order Bacteroidales, specifically family Muribaculaceae (S24-7), which is known to possess several starch degrading enzymes and was reported in previous studies to increase with fermentation of RS. The OR rats fermented RS less but had higher bacterial diversity and evenness and had significantly higher bacterial counts from phylum Firmicutes particularly order Clostridiales, genus Clostridium and an uncultured bacterium of the genus Akkermansia. The microbiota of OR rats had enhanced bacterial chemotaxis, phosphotransferase system (PTS), and fatty acid biosynthesis compared to OP rats whose microbiota had higher glycan degradation and LPS biosynthesis pathways. The microbiota transplant did not change obesity phenotype or microbiota composition. In conclusion, a higher alpha-diversity and evenness of the microbiota and higher proportions of Clostridiales and Akkermansia in OR rats were associated with a better metabolic phenotype with lower body fat. However, robust RS fermentation caused a lower diversity and evenness and did not result in a leaner phenotype.

Effects of sago starch on body weight, food intake, caecum short chain fatty acids, adipose tissue, and hepatic lipid content of fat-induced Sprague Dawley rats

Sago starch which naturally contains high amount of resistant starch, comes to the attention due to its ability to confer health benefits as functional food i.e., prebiotic. The present work aimed to investigate the effects of sago starch consumption on body weight, satiation, caecum short chain fatty acids body, and hepatic lipid content on diet-induced obese rats for obesity management. A total of 36 male Sprague Dawley rats were fat-induced and divided into the obesity-prone and obesity-resistant groups. Eight percent and sixteen percent resistant starch from sago and Hi-maize260 were incorporated into the standardised feed formulation. Food intake was weighed throughout the intervention period. The caecum sample was subjected to short chain fatty acids analysis using HPLC. Hepatic lipid content was measured using the Folch method. Both dosages of sago starch (8 and 16% SRS) promoted body weight loss with a reduction of food intake, which suggested satiety. No significant differences was observed in the production of lactate, acetate, propionate, and butyrate from the caecum sample. Both dosages of sago starch (8 and 16% SRS) also showed lower hepatic lipid content and visceral adipose tissue than the baseline and control groups. However, 8% sago starch showed the lowest hepatic lipid content in obesity-prone and obesity-resistant groups. Overall results demonstrated that sago starch has the potential as an obesity and overweightness control regime as it promotes satiety, lowers visceral adipose tissue, and reduces hepatic lipid content. Consumers should consider adding sago starch in their daily meals.

Effects of Differences in Resistant Starch Content of Rice on Intestinal Microbial Composition

The aim of this study was to evaluate the effects of resistant starch (RS) and fat levels on the gut microbiome in C57BL/6 mice. Three levels of RS from three varieties of rice were the major source of carbohydrates and fat levels were low (10%) and high (39%). We confirmed that RS decreased the Firmicutes to Bacteroidetes ratio, increased SCFA production by higher Bacteroidaceae and S24-7 abundance, and enriched predicted gene families of glycosidases and functional pathways associated with carbohydrate and glycan metabolism. We also found correlations between microbial taxa and tissue gene expression related to carbohydrate and lipid metabolism. Moreover, increasing RS levels resulted in a molecular ecological network with enhanced modularity and interspecific synergy, which is less sensitive to high fat intervention. Overall, RS as low as 0.44% from cooked rice can modulate gut microbiome in mice, which correlated to a protective effect against deleterious effects of an obesogenic diet.

Health beneficial effects of resistant starch on diabetes and obesity via regulation of gut microbiota: a review

Resistant starch (RS) is well known to prevent type 2 diabetes mellitus (T2DM) and obesity. Recently, attention has been paid to gut microbiota which mediates the RS's impact on T2DM and obesity, while a mechanistic understanding of how RS prevents T2DM and obesity through gut microbiota is not clear yet. Therefore, this review aims at exploring the underlying mechanisms of it. RS prevents T2DM and obesity through gut microbiota by modifying selective microbial composition to produce starch-degrading enzymes, promoting the production of intestinal metabolites, and improving gut barrier function. Therefore, RS possessing good functional features can be used to increase the fiber content of healthier food. Furthermore, achieving highly selective effects on gut microbiota based on the slight differences of RS's chemical structure and focusing on the effects of RS on strain-levels are essential to manipulate the microbiota for human health.

Structural rearrangement of native and processed pea starches following simulated digestion in vitro and fermentation characteristics of their resistant starch residues using human fecal inoculum

Pea starches, in both native (NPS) and retrograded-autoclaved forms (RAPS), were subjected to simulated gastrointestinal (GI) digestion in vitro, their multi-scale structural characteristics, morphological features, molecular distribution and thermal properties were characterized. A gradual increase in the short-/long-range crystallinity, melting enthalpy of gelatinization on increasing digestion time was observed for both the native and retrograded-autoclaved pea starch samples based on the X-ray diffraction, Fourier-transform infrared spectra, solid-state 13CNMR and differential scanning calorimetry measurements. It was especially noticed that the growth rate of crystallinity and double helices, as well as the decrease in Mw values were evidently greater for RAPS than for NPS. To investigate how different molecular fine structure of pea starch substrate affects the gut microbiota shifts and dynamic short-chain fatty acid profile, their resistant starch residues obtained from both native and retrograded-autoclaved pea starch after 8 h of simulated GI tract digestion was used as the fermentation substrate. The levels of acetate, propionate and butyrate gradually increased with the increasing fermentation time for NPS and RAPS. In comparison to the blank control (i.e., the group without the addition of carbohydrate), the fermented NPS and RAPS obviously resulted in an increased abundance of Firmicutes and Bacteroidetes, accompanied by a decrease in Proteobacteria, Actinobacteria and Verrucomicrobia. Both NPS and RAPS promoted different shifts in the microbial community at the genus level, with an increase in the abundance of Bacteroides, Megamonas and Bifidobacterium, as well as a reduction in the abundance of Fusobacterium, Faecalibacterium and Lachnoclostridium in comparison to the blank control samples.

Effects of Berberine on the Gastrointestinal Microbiota

The gastrointestinal microbiota is a multi-faceted system that is unraveling novel contributors to the development and progression of several diseases. Berberine has been used to treat obesity, diabetes mellitus, atherosclerosis, and metabolic diseases in China. There are also clinical trials regarding berberine use in cardiovascular, gastrointestinal, and endocrine diseases. Berberine elicits clinical benefits at standard doses and has low toxicity. The mechanism underlying the role of berberine in lipid‐lowering and insulin resistance is incompletely understood, but one of the possible mechanisms is related to its effect on the gastrointestinal microbiota. An extensive search in electronic databases (PubMed, Scopus, Embase, Web of Sciences, Science Direct) was used to identify the role of the gastrointestinal microbiota in the berberine treatment. The aim of this review was to summarize the pharmacologic effects of berberine on animals and humans by regulation of the gastrointestinal microbiota.

Effects of Rice with Different Amounts of Resistant Starch on Mice Fed a High-Fat Diet: Attenuation of Adipose Weight Gain

Increasing the amount of resistant starch (RS) in the diet may confer protective effects against chronic diseases. Rice, a good dietary source of carbohydrates, also contains RS. However, it remains unclear if RS at the amount consumed in cooked rice has a health benefit. To address the question, we examined the effects of cooked rice containing different levels of RS in a diet-induced obesity rodent model. Rice containing RS as low as 1.07% attenuated adipose weight and adipocyte size gain, induced by a moderately high-fat (HF) diet, which correlated with lower leptin levels in plasma and adipose tissue. Rice with 8.61% RS increased fecal short-chain fatty acid levels, modulated HF-diet-induced adipose triacylglycerol metabolism and inflammation-related gene expression, and increased fecal triglyceride excretion. Hence, including rice with RS level at ≥1.07% may attenuate risks associated with the consumption of a moderately HF diet.

Abundance of the species Clostridium butyricum in the gut microbiota contributes to differences in obesity phenotype in outbred Sprague-Dawley CD rats

OBJECTIVES

Gut microbiota profiles contribute to differences in obesity phenotype. We examined the abundance of the species Clostridium butyricum in relation to obesity phenotype.

METHODS

In outbred Sprague -Dawley rats we examined effects of dietary fat, resistant starch (RS), and a microbiota transplant on obesity phenotype. Using targeted qPCR, we examined the abundance of total gut bacteria and C. butyricum in relation to the propensity of obesity prone and obesity resistant rats to accumulate abdominal fat.

RESULTS

Before inclusion of dietary RS, obesity resistant (OR) rats had higher amounts of total bacteria, and C. butyricum compared to obesity prone (OP) rats (P < 0.005 in study I, P < 0.0001 in study II). A high fat diet (HF) lowered C. butyricum levels while RS had no effect. Dietary RS elicited robust fermentation and increased total bacteria only in OP rats. In preparation for the transplant, antibiotics were administered to recipient rats. Four weeks thereafter, total bacteria levels were restored but, C. butyricum levels were not. The transplant between the two phenotypes had no effect on abundance of C. butyricum and obesity phenotype.

CONCLUSIONS

While C. butyricum is a known saccharolytic, its proliferation is not enhanced by fermentation of resistant starch. C. butyricum maybe one of the species that constitute a core microbiota involved in energy storage and metabolism through mechanisms that are not yet known.

In Vivo Colonic Fermentation of Sorghum (Sorghum bicolor L.): Important Correlations Observed among the Physiological Parameters of Cecum, Liver, Adipose Tissue and Fasting Serum Lipid Profile

High amylose corn starch (HAS), whole grain sorghum (S-Wh), refined sorghum (S-Rf) and α-corn starch (CON) diets were fed to animals for 1 mo aiming to examine the physiological effects of resistant starch inclusion in the diet from grains. HAS exhibited significantly lower feed intake, final body weight, serum lipid profile with significantly higher cecal parameters and short chain fatty acid (SCFA) contents. S-Wh group exhibited significantly higher body weight, feed intake and serum lipid parameters compared to other 3 groups. Cecal fermentation was not seemed to be prominent in the CON, S-Wh and S-Rf groups with respect to lower cecal parameters and SCFA contents. The cecal microbial compositions in HAS, S-Wh and CON/S-Rf exhibited 3 distinct clusters suggesting a significant effect of the cecal microbial composition on cecal parameters, SCFA contents and physiological parameters.

Conserved and variable responses of the gut microbiome to resistant starch type 2

Resistant starch type 2 (RS2), a dietary fiber comprised solely of glucose, has been extensively studied in clinical trials and animal models for its capacity to improve metabolic and systemic health. Because the health modulatory effects of RS2 and other dietary fibers are thought to occur through modification of the gut microbiome, those studies frequently include assessments of RS2-mediated changes to intestinal microbial composition and function. In this review, we identify the conserved responses of the gut microbiome among 13 human and 35 animal RS2 intervention studies. Consistent outcomes of RS2 interventions include reductions in bacterial α-diversity; increased production of lumenal short-chain fatty acids; and enrichment of Ruminococcus bromii, Bifidobacterium adolescentis, and other gut taxa. Different taxa are usually responsive in animal models, and many RS2-mediated changes to the gut microbiome vary within and between studies. The root causes for this variation are examined with regard to methodological and analytical differences, host genetics and age, species differences (eg, human, animal), health status, intervention dose and duration, and baseline microbial composition. The significant variation found for this single dietary compound highlights the challenges in targeting the gut microbiome to improve health with dietary interventions. This knowledge on RS2 also provides opportunities to improve the design of nutrition studies targeting the gut microbiome and to ultimately identify the precise mechanisms via which dietary fiber benefits human health.

Novel Resistant Starch Type 4 Products of Different Starch Origins, Production Methods, and Amounts Are Not Equally Fermented when Fed to Sprague-Dawley Rats

SCOPE

The possible mechanisms of production of four novel resistant starch type 4 (RS4) products for total cecal fermentation in an in vivo rodent model are evaluated.

METHODS AND RESULTS

Forty weanling rats are randomly assigned to five groups (n = 8) for a 3-week study. Starches are the RS type 4 products, as 10% of weight of RS diets (RSA-RSD), and AMIOCA starch (100% amylopectin) comprises 53.6% weight of control (CON) and 43.6% weight of RS diets. The RS products vary by percent purity and origin (potato, corn, tapioca). At euthanasia, cecal contents, serum, GI tract, and abdominal fat are collected. RSB, RSC, and RSD fed rats have greater empty cecum weights, lower cecal content pH, higher cecal content wet weight, and higher total cecal content acetate and propionate than the CON and RSA fed rats. Two other indicators of fermentation, total cecal contents butyrate and glucagon-like peptide 1, do not have significant ANOVA F values, which require more subjects for 80% power.

CONCLUSION

RS4 products that are produced from different starch origins with varying amounts of RS4 content and different methods of production are not uniformly fermented in an in vivo model.

Attenuation of metabolic syndrome in the ob/ob mouse model by resistant starch intervention is dose dependent

The current study applied an ob/ob mouse model of obesity for investigating the impact of different RS doses in a high-fat (HF) diet on the attenuation of metabolic syndrome. Although a significant reduction of body weight was not achieved, RS intervention significantly decreased liver weight with suppressed lipid accumulation in the liver tissue and reduced adipocyte size in the fat tissue. All levels of RS intervention were associated with significantly enriched pathways for PPAR, NAFLD and cGMP-PKG signaling. In contrast, either a medium or a higher RS intake (MRS and HRS, respectively) led the AMPK signaling pathway to be significantly enriched but not a diet with lower RS intake. More importantly, sphingolipid biosynthesis activity was noted with MRS and HRS intervention, which is highly associated with the improvement in insulin resistance, and the pathway of type II diabetes mellitus was correspondingly significantly enriched in the HRS group, demonstrating a dose-dependent manner. Similarly, there was no significant difference in the ratio of Bacteroidetes and Firmicutes between high-fat diet and RS groups until RS reached a certain level (i.e. in the HRS group). Furthermore, increased profiles of both Prevotellaceae and Coriobacteriaceae in the HF group were noted for the first time with a revised function from RS intervention, which is consistent with the content of lipopolysaccharides in their corresponding serum. Gut microbiota functional analysis showed that primary and secondary bile acid biosynthesis was also noted to be enriched following the RS intervention, benefiting cholesterol homeostasis. This study further highlights the association of RS consumption with the attenuation of metabolic syndrome in an obesity model, and its functionality is characterized by dose-dependence.

Understanding the Role of the Gut Microbiome and Microbial Metabolites in Obesity and Obesity-Associated Metabolic Disorders: Current Evidence and Perspectives

PURPOSE

In this review, we summarize current evidence on the gut microbiome and microbial metabolites in relation to obesity and obesity-associated metabolic disorders. Special emphasis is given on mechanisms interconnecting gut microbiome and microbial metabolites with metabolic disorders as well as on potential preventive and therapeutic perspectives with a "bench to bedside" approach.

RECENT FINDINGS

Recent data have highlighted the role of gut dysbiosis in the etiology and pathogenesis of metabolic disorders, including obesity, metabolic syndrome, type 2 diabetes mellitus, and non-alcoholic fatty liver disease. Overall, most studies have demonstrated a reduction in gut microbiome diversity and richness in obese subjects, but there is still much debate on the exact microbial signature of a healthy or an obese gut microbiome. Despite the controversial role of an altered gut microbiome as a cause or consequence of obesity in human studies, numerous animal studies and certain human studies suggest beneficial metabolic effects of certain microbial intestinal metabolites, such as butyrate, that could be used in the prevention and treatment of obesity and its comorbidities. More randomized controlled trials and larger prospective studies including well-defined cohorts as well as a multi-omics approach are warranted to better identify the associations between the gut microbiome, microbial metabolites, and obesity and its metabolic complications.

Dynamic Development of Fecal Microbiome During the Progression of Diabetes Mellitus in Zucker Diabetic Fatty Rats

Background: Although substantial efforts have been made to link the gut microbiota to type 2 diabetes, dynamic changes in the fecal microbiome under the pathological conditions of diabetes have not been investigated.

Methods: Four male Zucker diabetic fatty (ZDF) rats received Purina 5008 chow [protein = 23.6%, Nitrogen-Free Extract (by difference) = 50.3%, fiber (crude) = 3.3%, ash = 6.1%, fat (ether extract) = 6.7%, and fat (acid hydrolysis) = 8.1%] for 8 weeks. A total of 32 stool samples were collected from weeks 8 to 15 in four rats. To decipher the microbial populations in these samples, we used a 16S rRNA gene sequencing approach.

Results: Microbiome analysis showed that the changes in the fecal microbiome were associated with age and disease progression. In all the stages from 8 to 15 weeks, phyla Firmicutes, Bacteroidetes, Actinobacteria, and Proteobacteria primarily dominated the fecal microbiome of the rats. Although Lactobacillus and Turicibacter were the predominant genera in 8- to 10-week-old rats, Bifidobacterium, Lactobacillus, Ruminococcus, and Allobaculum were the most abundant genera in 15-week-old rats. Of interest, compared to the earlier weeks, relatively greater diversity (at the genus level) was observed at 10 weeks of age. Although the microbiome of 12-week-old rats had the highest diversity, the diversity in 13–15-week-old rats was reduced. Spearman’s correlation analysis showed that F/B was negatively correlated with age. Random blood glucose was negatively correlated with Lactobacillus and Turicibacter but positively correlated with Ruminococcus and Allobaculum and Simpson’s diversity index.

Conclusion: We demonstrated the time-dependent alterations of the abundance and diversity of the fecal microbiome during the progression of diabetes in ZDF rats. At the genus level, dynamic changes were observed. We believe that this work will enhance our understanding of fecal microbiome development in ZDF rats and help to further analyze the role of the microbiome in metabolic diseases. Furthermore, our work may also provide an effective strategy for the clinical treatment of diabetes through microbial intervention.

Beneficial Effect of Intestinal Fermentation of Natural Polysaccharides

With the rapid development of modern society, many chronic diseases are increasing including diabetes, obesity, cardiovascular diseases, etc., which further cause an increased death rate worldwide. A high caloric diet with reduced natural polysaccharides, typically indigestible polysaccharides, is considered a health risk factor. With solid evidence accumulating that indigestible polysaccharides can effectively prevent and/or ameliorate symptoms of many chronic diseases, we give a narrative review of many natural polysaccharides extracted from various food resources which mainly contribute their health beneficial functions via intestinal fermentation.

CD Obesity-Prone Rats, but not Obesity-Resistant Rats, Robustly Ferment Resistant Starch Without Increased Weight or Fat Accretion

OBJECTIVE

This study used CD obesity-prone (OP) and obesity-resistant (OR) rats to examine how weight gain and fat accretion relate to fermentation levels and microbiota composition after feeding resistant starch (RS).

METHODS

After feeding OP rats and OR rats a high-fat (HF) diet for 4 weeks, rats were stratified into three groups: they were fed either an HF diet (group 1: HF-HF) or were switched to a low-fat (LF) diet (group 2: HF-LF) or an LF diet supplemented with 20% RS by weight for 4 weeks (group 3: HF-LFRS). Energy intake, body weight, fermentation variables, and microbiota composition were determined.

RESULTS

In OP rats, RS elicited robust fermentation (increased cecal contents, short-chain fatty acids, and serum glucagon-like peptide 1). Total bacteria, species of the Bacteroidales family S24-7, and the archaean Methanobrevibacter smithii increased. The robust fermentation did not elicit higher weight or fat accretion when compared with that of control rats fed the same isocaloric diets (HF-LF ± RS). In OR rats, body weight and fat accretion were also not different between HF-LF ± RS diets, but RS elicited minimal changes in fermentation and microbiota composition.

CONCLUSIONS

Robust fermentation did not contribute to greater weight. Fermentation levels and changes in microbiota composition in response to dietary RS differed by obesity phenotype.

Short Chain Fatty Acids in the Colon and Peripheral Tissues: A Focus on Butyrate, Colon Cancer, Obesity and Insulin Resistance

Increased dietary fiber consumption has been associated with many beneficial effects, including amelioration of obesity and insulin resistance. These effects may be due to the increased production of short chain fatty acids, including propionate, acetate and butyrate, during fermentation of the dietary fiber in the colon. Indeed, oral and dietary supplementation of butyrate alone has been shown to prevent high fat-diet induced obesity and insulin resistance. This review focuses on sources of short chain fatty acids, with emphasis on sources of butyrate, mechanisms of fiber and butyrate metabolism in the gut and its protective effects on colon cancer and the peripheral effects of butyrate supplementation in peripheral tissues in the prevention and reversal of obesity and insulin resistance.

How to Feed the Mammalian Gut Microbiota: Bacterial and Metabolic Modulation by Dietary Fibers

The composition of the gut microbiota of mammals is greatly influenced by diet. Therefore, evaluation of different food ingredients that may promote changes in the gut microbiota composition is an attractive approach to treat microbiota disturbances. In this study, three dietary fibers, such as inulin (I, 10%), resistant starch (RS, 10%), and citrus pectin (3%), were employed as supplements to normal chow diet of adult male rats for 2 weeks. Fecal microbiota composition and corresponding metabolite profiles were assessed before and after prebiotics supplementation. A general increase in the Bacteroidetes phylum was detected with a concurrent reduction in Firmicutes, in particular for I and RS experiments, while additional changes in the microbiota composition were evident at lower taxonomic levels for all the three substrates. Such modifications in the microbiota composition were correlated with changes in metabolic profiles of animals, in particular changes in acetate and succinate levels. This study represents a first attempt to modulate selectively the abundance and/or metabolic activity of various members of the gut microbiota by means of dietary fiber.