Gut microbiota disorders cause type 2 diabetes mellitus and homeostatic disturbances in gut-related metabolism in Japanese subjects

Association of short-chain fatty acids and the gut microbiome with type 2 diabetes: Evidence from the Henan Rural Cohort

BACKGROUND AND AIMS

Human studies about short-chain fatty acids (SCFAs), the gut microbiome, and Type 2 diabetes (T2DM) are limited. Here we explored the association between SCFAs and T2DM and the effects of gut microbial diversity on glucose status in rural populations.

METHODS AND RESULTS

We performed a cross-sectional study from the Henan Rural Cohort and collected stool samples. Gut microbiota composition and faecal SCFA concentrations were measured by 16S rRNA and GC-MS. The population was divided based on the tertiles of SCFAs, and logistic regression models assessed the relationship between SCFAs and T2DM. Generalized linear models tested the interactions between SCFAs and gut microbial diversity on glucose indicators (glucose, HbAlc and insulin). Compared to the lowest tertile of total SCFA, acetate and butyrate, the highest tertile exhibited lower T2DM prevalence, with ORs and 95% CIs of 0.291 (0.085-0.991), 0.160 (0.044-0.574) and 0.171 (0.047-0.620), respectively. Restricted cubic spline demonstrated an approximately inverse S-shaped association. We also noted interactions of the ACE index with the highest tertile of valerate on glucose levels (P-interaction = 0.022) and the Shannon index with the middle tertile of butyrate on insulin levels (P-interaction = 0.034). Genus Prevotella_9 and Odoribacter were inversely correlated with T2DM, and the genus Blautia was positively associated with T2DM. These bacteria are common SCFA-producing members.

CONCLUSIONS

Inverse S-shaped associations between SCFAs (total SCFA, acetate, and butyrate) and T2DM were observed. Valerate and butyrate modify glucose status with increasing gut microbial diversity.

Modulating the Gut Microbiota and Metabolites with Traditional Chinese Medicines: An Emerging Therapy for Type 2 Diabetes Mellitus and Its Complications

Currently, an estimated 537 million individuals are affected by type 2 diabetes mellitus (T2DM), the occurrence of which is invariably associated with complications. Glucose-lowering therapy remains the main treatment for alleviating T2DM. However, conventional antidiabetic agents are fraught with numerous adverse effects, notably elevations in blood pressure and lipid levels. Recently, the use of traditional Chinese medicines (TCMs) and their constituents has emerged as a preferred management strategy aimed at curtailing the progression of diabetes and its associated complications with fewer adverse effects. Increasing evidence indicates that gut microbiome disturbances are involved in the development of T2DM and its complications. This regulation depends on various metabolites produced by gut microbes and their interactions with host organs. TCMs' interventions have demonstrated the ability to modulate the intestinal bacterial microbiota, thereby restoring host homeostasis and ameliorating metabolic disorders. This review delves into the alterations in the gut microbiota and metabolites in T2DM patients and how TCMs treatment regulates the gut microbiota, facilitating the management of T2DM and its complications. Additionally, we also discuss prospective avenues for research on natural products to advance diabetes therapy.

Gut microbial dysbiosis in the pathogenesis of leukemia: an immune-based perspective

Leukemias are a set of clonal hematopoietic malignant diseases that develop in the bone marrow. Several factors influence leukemia development and progression. Among these, the gut microbiota is a major factor influencing a wide array of its processes. The gut microbial composition is linked to the risk of tumor development and the host's ability to respond to treatment, mostly due to the immune-modulatory effects of their metabolites. Despite such strong evidence, its role in the development of hematologic malignancies still requires attention of investigators worldwide. In this review, we make an effort to discuss the role of host gut microbiota-immune crosstalk in leukemia development and progression. Additionally, we highlight certain recently developed strategies to modify the gut microbial composition that may help to overcome dysbiosis in leukemia patients in the near future.

Gut microbes in metabolic disturbances. Promising role for therapeutic manipulations?

The prevalence of overweight, obesity, type 2 diabetes, metabolic syndrome and steatotic liver disease is rapidly increasing worldwide with a huge economic burden in terms of morbidity and mortality. Several genetic and environmental factors are involved in the onset and development of metabolic disorders and related complications. A critical role also exists for the gut microbiota, a complex polymicrobial ecology at the interface of the internal and external environment. The gut microbiota contributes to food digestion and transformation, caloric intake, and immune response of the host, keeping the homeostatic control in health. Mechanisms of disease include enhanced energy extraction from the non-digestible dietary carbohydrates, increased gut permeability and translocation of bacterial metabolites which activate a chronic low-grade systemic inflammation and insulin resistance, as precursors of tangible metabolic disorders involving glucose and lipid homeostasis. The ultimate causative role of gut microbiota in this respect remains to be elucidated, as well as the therapeutic value of manipulating the gut microbiota by diet, pre- and pro- synbiotics, or fecal microbial transplantation.

Does symbiotic supplementation which contains Bacillus Coagulans Lactobacillus rhamnosus, Lactobacillus acidophilus and fructooligosaccharide has favourite effects in patients with type-2 diabetes? A randomised, double-blind, placebo-controlled trial

This study aimed to determine the effect of Bacillus Coagulans symbiotic supplementation on metabolic factors and inflammation in patients with type-2 diabetes. In this clinical trial, 50 patients with type-2 diabetes were randomly assigned to the symbiotic (containing Bacillus Coagulans + Lactobacillus rhamnosus + Lactobacillus acidophilus and fructooligosaccharide) or placebo groups to receive one sachet daily for 12 weeks. Glycaemic Index, lipid profile, and hs-CRP were measured at the beginning and end of the study. Analysis of covariance demonstrated that fasting blood glucose (FBG), insulin, homeostatic Model Assessment for Insulin Resistance (HOMA-IR), β-cell function (HOMA-β) (p <.05) and hs-CRP (p <.05) significantly declined in the treatment group compared with the placebo group. So, the current study indicated that Bacillus Coagulans symbiotic supplementation could improve metabolic factors and inflammation in patients with type-2 diabetes.

Enhanced trimethylamine metabolism and gut dysbiosis in type 2 diabetes mellitus with microalbumin

Background

Abnormal gut microbiota and blood trimethylamine-N-oxide (TMAO) metabolome have been reported in patients with type 2 diabetes mellitus (T2DM) and advanced diabetic nephropathy. This study aimed to investigate the gut microbiota profiles and a group of targeted urine metabolic characteristics in T2DM patients with or without microalbuminuria, to determine the correlation between the gut microbiota composition, trimethylamine (TMA) metabolism, and the clinical features during progression of diabetic kidney disease (DKD).

Methods

This study included 26 T2DM patients with microalbuminuria (Micro), 26 T2DM patients with normoalbuminuria (Normo), and 15 healthy controls (HC). Urine and Fecal samples were detected using ultra performance liquid chromatography tandem mass spectrometry and 16S ribosomal DNA gene sequencing, respectively.

Results

The TMAO/TMA ratio decreased gradually during the HC-Normo-Micro transition. The levels of TMA, choline and betaine were significantly different between the HC group and the T2DM patients belonging to both Normo and Micro groups. At the operational taxonomic unit (OTU) level, the gut microflora diversity was significantly reduced in the Micro groups compared to the HC groups and the Normo groups. Taxonomic analyses revealed significant consumption in the relative abundances of eight bacterial genera and significant enrichment of two bacterial genera during the HC-Normo-Micro transition. Furthermore, the relative abundances of six bacterial genera, namely, Ruminococcus_1, [Eubacterium]_ruminantium_group, Roseburia, Faecalibacterium, Fusicatenibacter and Coprococcus_3 exhibited significant differences, and were associated with elevated urinary albumin creatinine ratio (UACR), TMAO/TMA, TMA and its precursors in the Micro group compared with the other groups.

Conclusion

The imbalance of gut microbiota has occurred in patients with early-stage DKD, and the consumption of short-chain fatty acid-producing bacteria were associated with the accumulation of TMA and UACR.

Effects of Shenlian formula on microbiota and inflammatory cytokines in adults with type 2 diabetes: a double-blind randomized clinical trial

OBJECTIVES

To observe the efficacy of Shenlian formula (SL formula, ), which consist of Huanglian () and Renshen (), in the treatment of type 2 diabetes mellitus (T2DM) and explore the effects on gut microbiota and serum inflammatory cytokines.

METHODS

In a double-blind, randomized, placebo-controlled parallel-group clinical trial, 31 adults with T2DM were randomly allocated to receive the SL formula or placebo for 12 weeks. Body mass index (BMI), blood lipid indices, glycemic biomarkers including glycated hemoglobin (HbA1C), fasting plasma glucose (FPG), postprandial blood glucose (PBG), fasting insulin levels (FIL), fasting C-peptide (C-P), homoeostasis model assessment for insulin resistance (HOMA-IR) and inflammatory cytokines were assessed at baseline and 12 weeks. The contents of gut microbiota were determined by pyrosequencing of the V3-V4 regions of 16S rRNA genes.

RESULTS

Sixteen cases were allocated in the treatment group and 15 in the placebo group. Compared with the placebo, SL formula resulted in a higher significant reduction in PBG [(?1.318 ± 0.772)(?0.008 ± 1.404) mmol/L, 0.003], BMI [(?0.611 ± 0.524)(0.957 ± 2.212) kg/m, 0.01], FIL [(?1.627 ± 6.268)(3.976 ± 6.85) μIU/mL, 0.02], HOMA-IR [(?0.530 ± 1.461)(1.511 ± 2.288), 0.006], and C-reactive protein (CRP) [(?1.307 ± 0.684)(0.828 ± 0.557) mg/L, 0.04]. In terms of gut microbiota, compared with the placebo, the SL formula resulted in a significant decrease in species richness and evenness.

CONCLUSIONS

The SL formula showed the efficacy to improve postprandial blood glucose, insulin resistance, BMI and CRP levels. In addition, it could reduce the total number, richness and evenness of species, meanwhile increase the abundance of probiotics to modulate the structure of gut microbiota in patients with T2DM. However, further studies are required for exploring the deeper mechanism of TCM on gut microbiota.

The roles of gut microbiota and its metabolites in diabetic nephropathy

Diabetic nephropathy (DN) is a severe microvascular complication of diabetes, which increases the risk of renal failure and causes a high global disease burden. Due to the lack of sustainable treatment, DN has become the primary cause of end-stage renal disease worldwide. Gut microbiota and its metabolites exert critical regulatory functions in maintaining host health and are associated with many pathogenesis of aging-related chronic diseases. Currently, the theory gut-kidney axis has opened a novel angle to understand the relationship between gut microbiota and multiple kidney diseases. In recent years, accumulating evidence has revealed that the gut microbiota and their metabolites play an essential role in the pathophysiologic processes of DN through the gut-kidney axis. In this review, we summarize the current investigations of gut microbiota and microbial metabolites involvement in the progression of DN, and further discuss the potential gut microbiota-targeted therapeutic approaches for DN.

The Interplay of Dietary Fibers and Intestinal Microbiota Affects Type 2 Diabetes by Generating Short-Chain Fatty Acids

Foods contain dietary fibers which can be classified into soluble and insoluble forms. The nutritional composition of fast foods is considered unhealthy because it negatively affects the production of short-chain fatty acids (SCFAs). Dietary fiber is resistant to digestive enzymes in the gut, which modulates the anaerobic intestinal microbiota (AIM) and fabricates SCFAs. Acetate, butyrate, and propionate are dominant in the gut and are generated via Wood-Ljungdahl and acrylate pathways. In pancreatic dysfunction, the release of insulin/glucagon is impaired, leading to hyperglycemia. SCFAs enhance insulin sensitivity or secretion, beta-cell function, leptin release, mitochondrial function, and intestinal gluconeogenesis in human organs, which positively affects type 2 diabetes (T2D). Research models have shown that SCFAs either enhance the release of peptide YY (PYY) and glucagon-like peptide-1 (GLP-1) from L-cells (entero-endocrine), or promotes the release of leptin hormone in adipose tissues through G-protein receptors GPR-41 and GPR-43. Dietary fiber is a component that influences the production of SCFAs by AIM, which may have beneficial effects on T2D. This review focuses on the effectiveness of dietary fiber in producing SCFAs in the colon by the AIM as well as the health-promoting effects on T2D.

Key Stratification of Microbiota Taxa and Metabolites in the Host Metabolic Health-Disease Balance

Human gut microbiota seems to drive the interaction with host metabolism through microbial metabolites, enzymes, and bioactive compounds. These components determine the host health-disease balance. Recent metabolomics and combined metabolome-microbiome studies have helped to elucidate how these substances could differentially affect the individual host pathophysiology according to several factors and cumulative exposures, such as obesogenic xenobiotics. The present work aims to investigate and interpret newly compiled data from metabolomics and microbiota composition studies, comparing controls with patients suffering from metabolic-related diseases (diabetes, obesity, metabolic syndrome, liver and cardiovascular diseases, etc.). The results showed, first, a differential composition of the most represented genera in healthy individuals compared to patients with metabolic diseases. Second, the analysis of the metabolite counts exhibited a differential composition of bacterial genera in disease compared to health status. Third, qualitative metabolite analysis revealed relevant information about the chemical nature of metabolites related to disease and/or health status. Key microbial genera were commonly considered overrepresented in healthy individuals together with specific metabolites, e.g., Faecalibacterium and phosphatidylethanolamine; and the opposite, Escherichia and Phosphatidic Acid, which is converted into the intermediate Cytidine Diphosphate Diacylglycerol-diacylglycerol (CDP-DAG), were overrepresented in metabolic-related disease patients. However, it was not possible to associate most specific microbiota taxa and metabolites according to their increased and decreased profiles analyzed with health or disease. Interestingly, positive association of essential amino acids with the genera Bacteroides were observed in a cluster related to health, and conversely, benzene derivatives and lipidic metabolites were related to the genera Clostridium, Roseburia, Blautia, and Oscillibacter in a disease cluster. More studies are needed to elucidate the microbiota species and their corresponding metabolites that are key in promoting health or disease status. Moreover, we propose that greater attention should be paid to biliary acids and to microbiota-liver cometabolites and its detoxification enzymes and pathways.

Gut Microbiome and Its Impact on Obesity and Obesity-Related Disorders

PURPOSE OF REVIEW

The prevalence of overweight and obesity has been increasing worldwide at an alarming rate. Gut microbiota intimately influence host energy metabolism, and immune response. Studies indicate a prominent role of gut dysbiosis in propagating inflammation that is associated with the development of obesity and obesity-related disorders such as type 2 diabetes mellitus, metabolic syndrome, and non-alcoholic fatty liver disease. This article will review the current literature on gut microbiome and its impact on obesity and obesity-related disorders.

RECENT FINDINGS

An altered gut microbial composition in obesity and obesity-related disorders is associated with enhanced energy extraction from the non-digestible dietary carbohydrates, increased gut permeability, increased production of proinflammatory metabolites, such as lipopolysaccharides, resulting in systemic inflammation and insulin resistance. Gut microbiota modulation can be achieved either by dietary manipulation or by administration of probiotics, prebiotics, synbiotics, and/or fecal microbiota transplantation aiming at the improvement of the gut dysbiosis in obesity and metabolic disorders. Further clinical trials are required to better elucidate the dose, and frequency of these interventions and also their long-term impact on host metabolism.

Shorter sleep time relates to lower human defensin 5 secretion and compositional disturbance of the intestinal microbiota accompanied by decreased short-chain fatty acid production

Sleep is essential for our health. Short sleep is known to increase disease risks via imbalance of intestinal microbiota, dysbiosis. However, mechanisms by which short sleep induces dysbiosis remain unknown. Small intestinal Paneth cell regulates the intestinal microbiota by secreting antimicrobial peptides including α-defensin, human defensin 5 (HD5). Disruption of circadian rhythm mediating sleep-wake cycle induces Paneth cell failure. We aim to clarify effects of short sleep on HD5 secretion and the intestinal microbiota. Fecal samples and self-reported sleep time were obtained from 35 healthy middle-aged Japanese (41 to 60-year-old). Shorter sleep time was associated with lower fecal HD5 concentration (r = 0.354, p = 0.037), lower centered log ratio (CLR)-transformed abundance of short-chain fatty acid (SCFA) producers in the intestinal microbiota such as [Ruminococcus] gnavus group (r = 0.504, p = 0.002) and Butyricicoccus (r = 0.484, p = 0.003), and lower fecal SCFA concentration. Furthermore, fecal HD5 positively correlated with the abundance of these genera and SCFA concentration. These findings suggest that short sleep relates to disturbance of the intestinal microbiota via decreased HD5 secretion.

Oral administration of Blautia wexlerae ameliorates obesity and type 2 diabetes via metabolic remodeling of the gut microbiota

The gut microbiome is an important determinant in various diseases. Here we perform a cross-sectional study of Japanese adults and identify the Blautia genus, especially B. wexlerae, as a commensal bacterium that is inversely correlated with obesity and type 2 diabetes mellitus. Oral administration of B. wexlerae to mice induce metabolic changes and anti-inflammatory effects that decrease both high-fat diet–induced obesity and diabetes. The beneficial effects of B. wexlerae are correlated with unique amino-acid metabolism to produce S-adenosylmethionine, acetylcholine, and l-ornithine and carbohydrate metabolism resulting in the accumulation of amylopectin and production of succinate, lactate, and acetate, with simultaneous modification of the gut bacterial composition. These findings reveal unique regulatory pathways of host and microbial metabolism that may provide novel strategies in preventive and therapeutic approaches for metabolic disorders.

Here, the authors inversely associate Blautia wexlerae with obesity and type 2 diabetes mellitus in humans and further show that administration of B. wexlerae to mice decrease both high-fat diet–induced obesity and diabetes via modulating gut microbial metabolism.

Gut microbiota diversity in middle-aged and elderly patients with end-stage diabetic kidney disease

BACKGROUND

Diabetic kidney disease (DKD) is the most common cause of end-stage renal disease (ESRD), but the mechanism between DKD and ESRD remains unclear. Some experts have put forward the "microbial-centered ESRD development theory", believing that the bacterial load caused by gut microecological imbalance and uremia toxin transfer are the core pathogenic links. The purpose of this study was to analyze the genomic characteristics of gut microbiota in patients with ESRD, specifically DKD or non-diabetic kidney disease (NDKD).

METHODS

In this cross-sectional study, patients with ESRD were recruited in a community, including 22 DKD patients and 22 NDKD patients matched using gender and age. Fecal samples of patients were collected for 16S rDNA sequencing and gut microbiota analysis. The distribution structure, diversity, and abundance of microflora in DKD patients were analyzed by constructing species evolutionary trees and analyzing alpha diversity, beta diversity, and linear discriminant analysis effect size (LEfSe).

RESULTS

The results of our study showed that there were statistically significant differences in the richness and species of gut microbiota at the total level between DKD patients and NDKD patients. The analysis of genus level between the two groups showed significant differences in 16 bacterial genera. Among them, Oscillibacter, Bilophila, UBA1819, Ruminococcaceae UCG-004, Anaerotruncus, Ruminococcaceae, and Ruminococcaceae NK4A214 bacteria in DKD patients were higher than those in NDKD patients.

CONCLUSIONS

16S rDNA sequencing technology was used in this study to analyze the characteristics of intestinal flora in ESRD patients with or without diabetes. We found that there was a significant difference in the intestinal flora of ESRD patients caused by DKD and NDKD, suggesting that these may be potential causative bacteria for the development of ERSD in DKD patients.

Gut microbiota-derived metabolites as key actors in type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is one of the most risk factors threatening human health. Although genetic and environmental factors contribute to the development of T2DM, gut microbiota has also been found to be involved. Gut microbiota-derived metabolites are a key factor in host-microbe crosstalk, and have been revealed to play a central role in the physiology and physiopathology of T2DM. In this review, we provide a timely and comprehensive summary of the microbial metabolites that are protective or causative for T2DM, including some amino acids-derived metabolites, short-chain fatty acids, trimethylamine N-oxide, and bile acids. The mechanisms by which metabolites affect T2DM have been elaborated. Knowing more about these processes will increase our understanding of the causal relationship between gut microbiota and T2DM. Moreover, some frontier therapies that target gut microbes and their metabolites to improve T2DM, including dietary intervention, fecal microbiota transplantation, probiotics, prebiotics or synbiotics intervention, and drugging microbial metabolism, have been critically discussed. This review may provide novel insights for the development of targeted and personalized treatments for T2DM based on gut microbial metabolites. More high-quality clinical trials are needed to accelerate the clinical translation of gut-targeted therapies for T2DM.

The Effect of Gut Microbe Dysbiosis on the Pathogenesis of Alzheimer's Disease (AD) and related conditions

It has been hypothesized that the shift in gut microbiota composition, known as gut microbe dysbiosis, may be correlated with the onset of Alzheimer's disease (AD), which is the most common cause of dementia characterized by a gradual deterioration in cognitive function associated with the development of amyloid-beta (Aβ) plaques. The gut microbiota dysbiosis induces the release of significant amounts of amyloids, lipopolysaccharides, and neurotoxins, which might play a role in modulating signaling pathways and immune activation, leading to the production of proinflammatory cytokines related to the pathogenesis of AD. The dysbiosis of gut microbe is associated with various diseases such as type 2 diabetes, obesity, hypertension, and some neuropsychiatric disorders like depression, anxiety, and stress. It is conceivable that these diseases trigger the onset of AD. Thus, modifying the gut microbiota composition with probiotic and prebiotic supplementation can reduce depression and anxiety symptoms, lower stress reactivity, and improve memory. This narrative review aimed to examine the possible role of gut microbe dysbiosis in AD's pathogenesis.

Treatment with broad-spectrum antibiotics upregulates Sglt1 and induces small intestinal villous hyperplasia in mice

Although extensive evidence indicates that the gut microbiota plays a crucial role in regulating glucose homeostasis, the exact regulatory mechanism remains unclear. This study aimed to investigate the effect of broad-spectrum antibiotics on the expression of glucose transporters, histomorphology of the small intestine, and glucose metabolism in mice. C57BL/6 mice were administered drinking water with or without a broad-spectrum antibiotic combination for 4 weeks. Thereafter, an oral glucose tolerance test was performed. Body weight, small intestine histopathology, mRNA levels of glucose transporters (SGLT1 and GLUT2) and intestinal transcription factors (CDX1 and CDX2) were evaluated. SGLT1 and CDX1 were upregulated in the small intestine upon antibiotic administration compared with that in the control group. The height and surface area of the jejunal villi were significantly higher upon antibiotic administration than in the control group. Fasting glucose levels were significantly higher upon antibiotic administration than in the control group. The present results indicate that treatment with broad-spectrum antibiotics upregulates SGLT1 and CDX1 and induces hyperplasia in the small intestine, thus increasing fasting blood glucose levels. Our results further the current understanding of the effects of broad-spectrum antibiotics on the gut microbiota and glucose homeostasis that may have future clinical implications.

Is Intestinal Dysbiosis-Associated With Immunosuppressive Therapy a Key Factor in the Pathophysiology of Post-Transplant Diabetes Mellitus?

Post-transplant diabetes mellitus (PTDM) is one of the most common and deleterious comorbidities after solid organ transplantation (SOT). Its incidence varies depending on the organs transplanted and can affect up to 40% of patients. Current research indicates that PTDM shares several common features with type 2 diabetes mellitus (T2DM) in non-transplant populations. However, the pathophysiology of PTDM is still poorly characterized. Therefore, ways should be sought to improve its diagnosis and therapeutic management. A clear correlation has been made between PTDM and the use of immunosuppressants. Moreover, immunosuppressants are known to induce gut microbiota alterations, also called intestinal dysbiosis. Whereas the role of intestinal dysbiosis in the development of T2DM has been well documented, little is known about its impacts on PTDM. Functional alterations associated with intestinal dysbiosis, especially defects in pathways generating physiologically active bacterial metabolites (e.g., short-chain fatty acids, trimethylamine N-oxide, indole and kynurenine) are known to favour several metabolic disorders. This publication aims at discussing the potential role of intestinal dysbiosis and dysregulation of bacterial metabolites associated with immunosuppressive therapy in the occurrence of PTDM.

Unique Habitual Food Intakes in the Gut Microbiota Cluster Associated with Type 2 Diabetes Mellitus

This cross-sectional study aimed to clarify the characteristic gut microbiota of Japanese patients with type 2 diabetes (T2DM) using t-distributed stochastic neighbor embedding analysis and the k-means method and to clarify the relationship with background data, including dietary habits. The gut microbiota data of 383 patients with T2DM and 114 individuals without T2DM were classified into red, blue, green, and yellow groups. The proportions of patients with T2DM in the red, blue, green, and yellow groups was 86.8% (112/129), 69.8% (81/116), 76.3% (90/118), and 74.6% (100/134), respectively; the red group had the highest prevalence of T2DM. There were no intergroup differences in sex, age, or body mass index. The red group had higher percentages of the Bifidobacterium and Lactobacillus genera and lower percentages of the Blautia and Phascolarctobacterium genera. Higher proportions of patients with T2DM in the red group used α-glucosidase inhibitors and glinide medications and had a low intake of fermented soybean foods, including miso soup, than those in the other groups. The gut microbiota pattern of the red group may indicate characteristic changes in the gut microbiota associated with T2DM in Japan. These results also suggest that certain diabetes drugs and fermented foods may be involved in this change. Further studies are needed to confirm the relationships among traditional dietary habits, the gut microbiota, and T2DM in Japan.

Therapeutic Potential of Butyrate for Treatment of Type 2 Diabetes

Metagenomics studies have shown that type 2 diabetes (T2D) is associated with an altered gut microbiota. Whereas different microbiota patterns have been observed in independent human cohorts, reduction of butyrate-producing bacteria has consistently been found in individuals with T2D, as well as in those with prediabetes. Butyrate is produced in the large intestine by microbial fermentations, particularly of dietary fiber, and serves as primary fuel for colonocytes. It also acts as histone deacetylase inhibitor and ligand to G-protein coupled receptors, affecting cellular signaling in target cells, such as enteroendocrine cells. Therefore, butyrate has become an attractive drug target for T2D, and treatment strategies have been devised to increase its intestinal levels, for example by supplementation of butyrate-producing bacteria and dietary fiber, or through fecal microbiota transplant (FMT). In this review, we provide an overview of current literature indicating that these strategies have yielded encouraging results and short-term benefits in humans, but long-term improvements of glycemic control have not been reported so far. Further studies are required to find effective approaches to restore butyrate-producing bacteria and butyrate levels in the human gut, and to investigate their impact on glucose regulation in T2D.

Effects of ad libitum free-choice access to freshly squeezed domestic white asparagus juice on intestinal microbiota composition and universal biomarkers of immuno-metabolic homeostasis and general health in middle-aged female and male C57BL/6 mice

BACKGROUND AND PURPOSE

Asparagus contains different bioactive and volatile components including pyrazines, sulphur-containing compounds, and polyphenols. Asparagus juice is a new low-calorie LAB-containing natural juice product, the usage of which is expanding. Pyrazines and sulphur-containing compounds are degraded by bacteria on one hand, but on the other hand, dietary polyphenols prevent human colorectal diseases as modulators of the composition and/or activity of gut microbiota. However, the utility of these asparagus compounds for reversal of age-associated microbial dysbiosis and the immunometabolic disorders that dysbiosis incites body inflammatory reactions was not much explored so far. Hence, using middle-aged mice, we conducted the current study to verify the effect of freshly squeezed domestic white asparagus juice on the biomarkers reflecting immuno-metabolic pathways linking age-related dysbiosis and metabolic events.

MATERIALS AND METHODS

Thirty-two conventional Harlan Laboratories C57BL/6 mice aged between 11-12 months were randomly divided into two groups (n=16). Mice in control group 1 received sterile tap water. Animals in group 2 had 60 days ad libitum free-choice access to sterile tap water supplemented with 5% (v/v) freshly squeezed domestic white asparagus juice. Clinical signs of general health, hydration, and inflammation were monitored daily. Caecal content samples were analysed by qPCR for microbial composition. Histology of relevant organs was carried out on day 60 after sacrificing the mice. Universal markers of metabolic- and liver function were determined in serum samples. Caecal SCFAs contents were measured using HPLC.

RESULTS

Overall, no significant differences in general health or clinical signs of inflammation between the two groups were observed. The liver to body weight ratio in asparagus juice-drank mice was lowered. The qPCR quantification showed that asparagus juice significantly decreased the caecal Clostridium coccoides group while causing an enhancement in Clostridium leptum, Firmicutes, and bifidobacterial groups as well as total caecal bacterial count. Asparagus juice significantly elevated the caecal contents of SCFAs. Enhanced SCFAs (acetate, butyrate, and propionate) in mice receiving asparagus juice, however, did coincide with altered lipid levels in plasma or changes in the abundance of relevant bacteria for acetate-, butyrate-, and propionate production.

DISCUSSION

To the best of our knowledge, this is the first study aiming at evaluating the effect of freshly squeezed German domestic white asparagus juice on universal markers of metabolic- and liver function in middle-aged mice and the role of gut microbiota in this regard. The effectiveness of asparagus juice to improve metabolism in middle-aged mice was associated with alterations in intestinal microbiota but maybe also due to uptake of higher amounts of SCFAs. Hence, the key signal pathways corresponding to improved immune-metabolic homeostasis will be an important research scheme in the future.

Faecal biomarkers in type 1 diabetes with and without diabetic nephropathy

Gastrointestinal dysbiosis is common among persons with type 1 diabetes (T1D), but its potential impact on diabetic nephropathy (DN) remains obscure. We examined whether faecal biomarkers, previously associated with low-grade gastrointestinal inflammation, differ between healthy controls and T1D subjects with and without DN. Faecal samples were analyzed for levels of calprotectin, intestinal alkaline phosphatase (IAP), short-chain fatty acids (SCFA) and immunoglobulins in subjects with T1D (n = 159) and healthy controls (NDC; n = 50). The subjects with T1D were stratified based on albuminuria: normoalbuminuria (< 30 mg/g; n = 49), microalbuminuria (30-299 mg/g; n = 50) and macroalbuminuria (≥ 300 mg/g; n = 60). aecal calprotectin, IAP and immunoglobulin levels did not differ between the T1D albuminuria groups. However, when subjects were stratified based on faecal calprotectin cut-off level (50 µg/g), macroalbuminuric T1D subjects exceeded the threshold more frequently than NDC (p = 0.02). Concentrations of faecal propionate and butyrate were lower in T1D subjects compared with NDC (p = 0.04 and p = 0.03, respectively). Among T1D subjects, levels of branched SCFA (BCFA) correlated positively with current albuminuria level (isobutyrate, p = 0.03; isovalerate, p = 0.005). In our study cohort, fatty acid metabolism seemed to be altered among T1D subjects and those with albuminuria compared to NDC. This may reflect gastrointestinal imbalances associated with T1D and renal complications.

Role of Postbiotics in Diabetes Mellitus: Current Knowledge and Future Perspectives

In the last decade, the gastrointestinal microbiota has been recognised as being essential for health. Indeed, several publications have documented the suitability of probiotics, prebiotics, and symbiotics in the management of different diseases such as diabetes mellitus (DM). Advances in laboratory techniques have allowed the identification and characterisation of new biologically active molecules, referred to as “postbiotics”. Postbiotics are defined as functional bioactive compounds obtained from food-grade microorganisms that confer health benefits when administered in adequate amounts. They include cell structures, secreted molecules or metabolic by-products, and inanimate microorganisms. This heterogeneous group of molecules presents a broad range of mechanisms and may exhibit some advantages over traditional “biotics” such as probiotics and prebiotics. Owing to the growing incidence of DM worldwide and the implications of the microbiota in the disease progression, postbiotics appear to be good candidates as novel therapeutic targets. In the present review, we summarise the current knowledge about postbiotic compounds and their potential application in diabetes management. Additionally, we envision future perspectives on this topic. In summary, the results indicate that postbiotics hold promise as a potential novel therapeutic strategy for DM.

Sodium acetate ameliorated systemic and renal oxidative stress in high-fructose insulin-resistant pregnant Wistar rats

Pregnancy is an insulin-resistant condition especially at near term predisposing maternal kidneys to hyperinsulinemia-induced oxidative stress. The impact of fructose on renal metabolic dysregulation and oxidative stress in pregnancy requires elucidation. Short-chain fatty acids (SCFAs) are known for protective roles in oxidative stress conditions. Therefore, the study aimed at investigating fructose-induced glucose dysregulation and renal oxidative stress in pregnant and non-pregnant rats and the possible preventive role of SCFA, acetate. Thirty female Wistar rats were grouped (n = 5/group). Three groups were made pregnant (P); the other three remained non-pregnant (NP). Both pregnant and non-pregnant rats received drinking water (control), 10% fructose (w/v) (NP+F or P+F), and 10% (w/v) fructose plus sodium acetate (200 mg/kg) (NP+F+A or P+F+A) for 3 weeks. Renal and plasma glutathione antioxidant index (GSH/GSSG), G6PDH, and adenosine were significantly lower in NP+F and P+F groups compared with control while renal and plasma adenosine deaminase (ADA), xanthine oxidase (XO), uric acid (UA), lactate dehydrogenase (LDH), and malonaldehyde (MDA) were significantly elevated in NP+F and P+F groups compared with controls. HOMA-IR showed marked impairment in both NP+F and P+F groups. The P+F group revealed greater suppression in plasma and renal G6PDH-dependent antioxidant index, adenosine, and aggravation of LDH, MDA compared with the NP+F group (p < 0.05). Sodium acetate reduces plasma and renal surrogate oxidative stress markers, improved G6PD-dependent antioxidant index, and HOMA-IR in NP+F and P+F groups. Pregnancy exacerbates fructose-induced insulin resistance and renal oxidative stress whereas acetate ameliorated fructose-induced redox and glucose dysregulation in pregnant and non-pregnant rats.

Role of Polyphenols on Gut Microbiota and the Ubiquitin-Proteasome System in Neurodegenerative Diseases

Today, neurodegenerative diseases have become a remarkable public health challenge due to their direct relation with aging. Accordingly, understanding the molecular and cellular mechanisms occurring in the pathogenesis of them is essential. Both protein aggregations as a result of the ubiquitin-proteasome system (UPS) inefficiency and gut microbiota alternation are the main pathogenic hallmarks. Polyphenols upregulating this system may decrease the developing rate of neurodegenerative diseases. Most of the dietary intake of polyphenols is converted into other microbial metabolites, which have completely different biological properties from the original polyphenols and should be thoroughly investigated. Herein, several prevalent neurodegenerative diseases are pinpointed to explain the role of gut microbiota alternations and the role of molecular changes, especially UPS down-regulation in their pathogenesis. Some of the most important polyphenols found in our diet are explained along with their microbial metabolites in the body.

Metabolic Syndrome in an Aging Society - Role of Oxidant-Antioxidant Imbalance and Inflammation Markers in Disentangling Atherosclerosis

INTRODUCTION

The prevalence of metabolic syndrome among the elderly population is growing. The elements of metabolic syndrome in an aging society are currently being researched. Atherosclerosis is a slow process in which the first symptoms may be observed after many years. The mechanisms underlying the progression of atherosclerosis are oxidative stress and inflammation. Inflammation and oxidative stress are associated with the increased incidence of metabolic syndrome. Taking the above into consideration, metabolic syndrome is thought to be a clinical equivalent of atherosclerosis.

AIM

The aim of this paper is to review the impact of the interplay of oxidant-antioxidant and inflammation markers in metabolic syndrome in general as well as its components in the pathophysiology which underlies development of atherosclerosis in elderly individuals.

METHODS

A systematic scan of online resources designed for elderly (≥65 years) published from 2005 to the end of 2020 were reviewed. This was supplemented with grey literature and then all resources were narratively analyzed. The analysis included the following terms: "atherosclerosis or metabolic syndrome" and "oxidative stress or inflammation" and "elderly" to find reports of atherosclerotic disease from asymptomatic to life-threatening among the elderly population with metabolic syndrome .

RESULTS

The work summarizes articles that were applicable to this study, including systematic reviews, qualitative studies and opinion pieces. Current knowledge focuses on monitoring the inflammation and oxidant-antioxidant imbalance in disentangling atherosclerosis in patients diagnosed with metabolic syndrome. The population-based studies described inflammation, increased oxidative stress and weak antioxidant defense systems as the mechanisms underlying atherosclerosis development. Moreover, there are discussions that these targets could potentially be a point of intervention to reduce the development of atherosclerosis in the elderly, especially those with altered glucose and lipid metabolism. Specific markers may be used as an approach for the prevention and lifestyle modification of atherosclerotic disease in such population.

CONCLUSION

Metabolic syndrome and its components are important contributors in the progression of atherosclerotic disease in the elderly population but constant efforts should be made to broaden our knowledge of elderly groups who are the most susceptible for the development of atherosclerosis complications.

Differential gut microbiota composition between type 2 diabetes mellitus patients and healthy controls: A systematic review

AIMS

This systematic review summarised the latest findings on differential composition of gut microbiota in T2DM.

METHODS

Literature search was performed using electronic databases. Relevant studies were identified, extracted and assessed for risk of bias. The primary outcome of this systematic review was the composition of gut microbiota in healthy controls and T2DM while the secondary outcomes included the correlation of gut microbiota with metabolic parameters.

RESULTS

Thirteen case-control studies involving 575 T2DM and 840 healthy controls were included. T2DM patients exhibited a marked increase in lactobacilli. Six studies found lactobacilli to predominate the gut of T2DM patients; however, this could be confounded by the types of antihyperglyacemic medications. Conversely, butyrate producers dominate the gut of healthy controls. In T2DM patients, butyrate producers were surprisingly higher in those taking metformin intake than those not taking the drug. Whilst lactobacilli were found to be higher with increased plasma glucose, conflicting correlations were observed between various genera and anthropometric measurements, dietary intake, lipid profiles and inflammatory markers. There were moderate to strong significant positive correlations between the class Clostridia and phylum Firmicutes with pro-inflammatory IFN-γ as well as between Negativicutes and IL-6.

CONCLUSIONS

Altogether, butyrate-producing bacteria are negatively correlated to glycaemic parameters. Lactobacilli are higher in T2DM patients and Firmicutes is correlated with inflammation.

A Pilot Study for Metabolic Profiling of Obesity-Associated Microbial Gut Dysbiosis in Male Wistar Rats

Obesity is one of the most incident and concerning disease worldwide. Definite strategies to prevent obesity and related complications remain elusive. Among the risk factors of the onset of obesity, gut microbiota might play an important role in the pathogenesis of the disease, and it has received extensive attention because it affects the host metabolism. In this study, we aimed to define a metabolic profile of the segregated obesity-associated gut dysbiosis risk factor. The study of the metabolome, in an obesity-associated gut dysbiosis model, provides a relevant way for the discrimination on the different biomarkers in the obesity onset. Thus, we developed a model of this obesity risk factors through the transference of gut microbiota from obese to non-obese male Wistar rats and performed a subsequent metabolic analysis in the receptor rats. Our results showed alterations in the lipid metabolism in plasma and in the phenylalanine metabolism in urine. In consequence, we have identified metabolic changes characterized by: (1) an increase in DG:34:2 in plasma, a decrease in hippurate, (2) an increase in 3-HPPA, and (3) an increase in o-coumaric acid. Hereby, we propose these metabolites as a metabolic profile associated to a segregated dysbiosis state related to obesity disease.

Short-Chain Fatty Acids: A Soldier Fighting Against Inflammation and Protecting From Tumorigenesis in People With Diabetes

Converging evidences showed that people with diabetes mellitus (DM) have significantly higher risk for different cancers, of which the exact mechanism underlying the association has not been fully realized. Short-chain fatty acids (SCFAs), the fermentation products of the intestinal microbiota, are an essential source for energy supply in gut epithelial cells. They have been reported to improve intestinal barrier integrity, prevent microbial translocation, and further dampen inflammation. Gut dysbiosis and reduction in SCFA-producing bacteria as well as SCFAs production in the intestine are commonly seen in metabolic disorders including DM and obesity. Moreover, inflammation can contribute to tumor initiation and progression through multiple pathways, such as enhancing DNA damage, accumulating mutations in tumor suppressor genes Tp53, and activating nuclear factor-kappa B (NF-κB) signaling pathways. Based on these facts, we hypothesize that lower levels of microbial SCFAs resulted from gut dysbiosis in diabetic individuals, enhance microbial translocation, and increase the inflammatory responses, inducing tumorigenesis ulteriorly. To this end, we will discuss protective properties of microbial SCFAs and explore the pivotal roles SCFAs played in the link of DM with cancer, so as to take early precautions to reduce the risk of cancer in patients with DM.

Genetic Basis of Tiller Dynamics of Rice Revealed by Genome-Wide Association Studies

A tiller number is the key determinant of rice plant architecture and panicle number and consequently controls grain yield. Thus, it is necessary to optimize the tiller number to achieve the maximum yield in rice. However, comprehensive analyses of the genetic basis of the tiller number, considering the development stage, tiller type, and related traits, are lacking. In this study, we sequence 219 Korean rice accessions and construct a high-quality single nucleotide polymorphism (SNP) dataset. We also evaluate the tiller number at different development stages and heading traits involved in phase transitions. By genome-wide association studies (GWASs), we detected 20 significant association signals for all traits. Five signals were detected in genomic regions near known candidate genes. Most of the candidate genes were involved in the phase transition from vegetative to reproductive growth. In particular, HD1 was simultaneously associated with the productive tiller ratio and heading date, indicating that the photoperiodic heading gene directly controls the productive tiller ratio. Multiple linear regression models of lead SNPs showed coefficients of determination (R²) of 0.49, 0.22, and 0.41 for the tiller number at the maximum tillering stage, productive tiller number, and productive tiller ratio, respectively. Furthermore, the model was validated using independent japonica rice collections, implying that the lead SNPs included in the linear regression model were generally applicable to the tiller number prediction. We revealed the genetic basis of the tiller number in rice plants during growth, By GWASs, and formulated a prediction model by linear regression. Our results improve our understanding of tillering in rice plants and provide a basis for breeding high-yield rice varieties with the optimum the tiller number.

Characterisation of gut microbiota of obesity and type 2 diabetes in a rodent model

Various studies have suggested that the gut microbiome interacts with the host and may have a significant role in the aetiology of obesity and Type 2 Diabetes (T2D). It was hypothesised that bacterial communities in obesity and T2D differ from control and compromise normal interactions between host and microbiota. Obesity and T2D were developed in rats by feeding a high-fat diet or a high-fat diet plus a single low-dose streptozotocin administration, respectively. The microbiome profiles and their metabolic potentials were established by metagenomic 16S rRNA sequencing and bioinformatics. Taxonomy and predicted metabolism-related genes in obesity and T2D were markedly different from controls and indeed from each other. Diversity was reduced in T2D but not in Obese rats. Factors likely to compromise host intestinal, barrier integrity were found in Obese and T2D rats including predicted, decreased bacterial butyrate production. Capacity to increase energy extraction via ABC-transporters and carbohydrate metabolism were enhanced in Obese and T2D rats. T2D was characterized by increased proinflammatory molecules. While obesity and T2D show distinct differences, results suggest that in both conditions Bacteroides and Blautia species were increased indicating a possible mechanistic link.

Changes in the Gut Microbiota are Associated with Hypertension, Hyperlipidemia, and Type 2 Diabetes Mellitus in Japanese Subjects

The human gut microbiota is involved in host health and disease development. Therefore, lifestyle-related diseases such as hypertension (HT), hyperlipidemia (HL), and type 2 diabetes mellitus (T2D) may alter the composition of gut microbiota. Here, we investigated gut microbiota changes related to these diseases and their coexistence. This study involved 239 Japanese subjects, including healthy controls (HC). The fecal microbiota was analyzed through the isolation of bacterial genomic DNA obtained from fecal samples. Although there were no significant differences in the microbial structure between groups, there was a significant difference in the α-diversity between HC and the patients in whom two diseases coexisted. Moreover, Actinobacteria levels were significantly increased, whereas Bacteroidetes levels were significantly decreased in all disease groups. At the genus level, Bifidobacterium levels were significantly increased in the HL and T2D groups, as were those of Collinsella in all disease groups. In contrast, Alistipes levels were significantly lower in the HL group. Furthermore, metabolic enzyme families were significantly increased in all disease groups. Interestingly, the structure and function of the gut microbiota showed similar profiles in all the studied diseases. In conclusion, several changes in the structure of the gut microbiota are associated with T2D, HT, and HL in Japanese subjects.

The role of gut microbiota (GM) and GM-related metabolites in diabetes and obesity. A review of analytical methods used to measure GM-related metabolites in fecal samples with a focus on metabolites' derivatization step

Disruption of gut microbiota (GM) composition is increasingly related to the pathogenesis of various metabolic diseases. Additionally, GM is responsible for the production and transformation of metabolites involved in the development of metabolic disorders, such as obesity and type 2 diabetes mellitus (T2DM). The current state of knowledge regarding the composition of GM and GM-related metabolites in relation to the progress and development of obesity and T2DM is presented in this review. To understand the relationships between GM-related metabolites and the development of metabolic disorders, their accurate qualitative and quantitative measurement in biological samples is needed. Feces represent a valuable biological matrix which composition may reflect the health status of the lower gastrointestinal tract and the whole organism. Mass spectrometry (MS), mainly in combination with gas chromatography (GC) or liquid chromatography (LC), is commonly used to measure fecal metabolites. However, profiling metabolites in such a complex matrix as feces is challenging from both analytical chemistry and biochemistry standpoints. Chemical derivatization is one of the most effective methods used to overcome these problems. In this review, we provide a comprehensive summary of the derivatization methods of GM-related metabolites prior to GC-MS or LC-MS analysis, which have been published in the last five years (2015-2020). Additionally, analytical methods used for the analysis of GM-related metabolites without the derivatization step are also presented.

The Effects of Metformin on the Gut Microbiota of Patients with Type 2 Diabetes: A Two-Center, Quasi-Experimental Study

Metformin is reported to affect human gut microbiota; however, the nature of this association in Japanese patients with type 2 diabetes mellitus (T2DM) is unknown. We enrolled 31 patients with T2DM who took metformin for the first time in this study. We compared them before and after four weeks of taking metformin. Fecal samples were collected and 16S rDNA sequences were performed to identify the gut microbiota. Blood samples and Gastrointestinal Symptom Rating Scale (GSRS) questionnaire results, denoting gastro-intestinal symptoms, were also collected. In the whole-group analysis, no significant differences were found at the phylum level. In a subgroup of 21 patients that excluding those using medications affecting gut microbiota, there was a significant decrease of the phylum Firmicutes (p = 0.042) and of the ratio of the Firmicutes and Bacteroidetes abundances (p = 0.04) after taking metformin. Changes in abdominal pain (r = −0.56, p = 0.008) and regurgitation (r = −0.53, p = 0.01) were associated with Parabacteroides. Despite there being no direct association with abdominal symptoms, our study revealed that the composition of gut microbiota in Japanese individuals with T2DM partially changed after starting metformin.

Intake of sucrose affects gut dysbiosis in patients with type 2 diabetes

Aims/Introduction

Gut dysbiosis is generally associated with type 2 diabetes mellitus. However, the effect of habitual dietary intake on gut dysbiosis in Japanese patients with type 2 diabetes mellitus has not yet been explicated. This study investigated whether alteration of the gut microbiota was influenced by dietary intake of sucrose in Japanese patients with type 2 diabetes mellitus.

Materials and Methods

In this cross‐sectional study, 97 patients with type 2 diabetes mellitus and 97 healthy individuals were matched by age and sex, and then, fecal samples were obtained. Next‐generation sequencing of the 16S ribosomal ribonucleic acid gene was carried out, and functional profiles for the gut microbiota were analyzed. We selected the top 30 gut microbial genera and top 20 functional profiles for the gut microbiota specified by the weighted average difference method. The association between gut microbial genera or functional profiles and habitual dietary intake was investigated by Spearman’s rank correlation coefficient, and then, clustering analysis was carried out to clarify the impact of habitual dietary intake.

Results

The Actinobacteria phylum was highly abundant in patients with type 2 diabetes mellitus, whereas the Bacteroidetes phylum was less abundant. Diabetic‐type gut microbes, specifically Bacteroides and Bifidobacterium, were altered by sucrose intake at the genus level. Furthermore, sucrose intake was associated with glycolysis/gluconeogenesis in the diabetic‐type functional profiles of the gut microbiota.

Conclusions

The gut microbiota and functional profiles for the gut microbiota in patients with type 2 diabetes mellitus were significantly different from those in healthy individuals. Furthermore, we showed that sucrose intake was closely associated with these differences.

Metformin effect on gut microbiota: insights for HIV-related inflammation

The gut microbiota is emerging as a prominent player in maintaining health through several metabolic and immune pathways. Dysregulation of gut microbiota composition, also known as dysbiosis, is involved in the clinical outcome of diabetes, inflammatory bowel diseases, cancer, aging and HIV infection. Gut dysbiosis and inflammation persist in people living with HIV (PLWH) despite receiving antiretroviral therapy, further contributing to non-AIDS comorbidities. Metformin, a widely used antidiabetic agent, has been found to benefit microbiota composition, promote gut barrier integrity and reduce inflammation in human and animal models of diabetes. Inspired by the effect of metformin on diabetes-related gut dysbiosis, we herein critically review the relevance of metformin to control inflammation in PLWH. Metformin may improve gut microbiota composition, in turn reducing inflammation and risk of non-AIDS comorbidities. This review will pave the way towards innovative strategies to counteract dysregulated microbiota and improve the lives of PLWH.

Controversial Roles of Gut Microbiota-Derived Short-Chain Fatty Acids (SCFAs) on Pancreatic β-Cell Growth and Insulin Secretion

In the past 15 years, gut microbiota emerged as a crucial player in health and disease. Enormous progress was made in the analysis of its composition, even in the discovery of novel species. It is time to go beyond mere microbiota-disease associations and, instead, provide more causal analyses. A key mechanism of metabolic regulation by the gut microbiota is through the production of short-chain fatty acids (SCFAs). Acting as supplemental nutrients and specific ligands of two G-protein-coupled receptors (GPCRs), they target the intestines, brain, liver, and adipose tissue, and they regulate appetite, energy expenditure, adiposity, and glucose production. With accumulating but sometimes conflicting research results, key questions emerged. Do SCFAs regulate pancreatic islets directly? What is the effect of β-cell-specific receptor deletions? What are the mechanisms used by SCFAs to regulate β-cell proliferation, survival, and secretion? The receptors FFA2/3 are normally expressed on pancreatic β-cells. Deficiency in FFA2 may have caused glucose intolerance and β-cell deficiency in mice. However, this was contrasted by a double-receptor knockout. Even more controversial are the effects of SCFAs on insulin secretion; there might be no direct effect at all. Unable to draw clear conclusions, this review reveals some of the recent controversies.

Differences in gut microbial patterns associated with salivary biomarkers in young Japanese adults

Recent evidence suggests that psychological stress is associated with gut microbiota; however, there are no reports of its association with gut microbial structure. This cross-sectional study examined the relationship between psychological stress and gut microbial patterns in young Japanese adults. Analysis of fecal microbiota was performed using terminal restriction fragment length polymorphism (T-RFLP). Psychological stress was assessed using salivary biomarkers, including cortisol, alpha-amylase, and secretory IgA (S-IgA). Fecal microbial patterns were defined using principal component analysis of the T-RFLP profile and were classified into two enterotype-like clusters, which were defined by the B (microbiota dominated by Bacteroides) and BL patterns (microbiota dominated by Bifidobacterium and Lactobacillales), respectively. The Simpson index was significantly higher for the BL pattern than for the B pattern. The salivary cortisol level was significantly lower for the BL pattern than for the B pattern. Salivary alpha-amylase and S-IgA levels showed a negative correlation with the Simpson index. Our results raise the possibility that salivary biomarkers may be involved in the observed differences in microbial patterns.

A sea cucumber (Holothuria leucospilota) polysaccharide improves the gut microbiome to alleviate the symptoms of type 2 diabetes mellitus in Goto-Kakizaki rats

Diabetes mellitus has become a worldwide concern in recent years. In this study, the effect of Holothuria leucospilota polysaccharide (HLP) on type 2 diabetes mellitus (T2DM) was investigated in Goto-Kakizaki (GK) rats. The results showed that HLP significantly improved glucose intolerance and regulated blood lipid and hormone levels (p < 0.05). Pathological analysis showed that HLP repaired the impairments of the pancreas and colon in diabetic rats. In addition, a high dose of HLP (200 mg/kg) significantly upregulated the gene expression of peroxisome proliferator-activated receptor-α (PPAR-α), peroxisome proliferator-activated receptor-γ (PPAR-γ), phosphoinositide 3-kinase (PI3K), protein kinase B (PKB/AKT), glucose transporter-4 (GLUT4) and anti-apoptotic (Bcl-2), and downregulated the mRNA levels of pro-apoptotic (Bax) and cluster of differentiation 36 (CD36) in diabetic rats (p < 0.05). Furthermore, HLP treatment increased the short-chain fatty acid-producing bacteria and decreased the opportunistic bacterial pathogen in the feces of diabetic rats. These results demonstrated that HLP has the potential to ameliorate T2DM in GK rats.

Changes in Plasma Free Fatty Acids Associated with Type-2 Diabetes

Type 2 diabetes mellitus (T2DM) is associated with increased total plasma free fatty acid (FFA) concentrations and an elevated risk of cardiovascular disease. The exact mechanisms by which the plasma FFA profile of subjects with T2DM changes is unclear, but it is thought that dietary fats and changes to lipid metabolism are likely to contribute. Therefore, establishing the changes in concentrations of specific FFAs in an individual’s plasma is important. Each type of FFA has different effects on physiological processes, including the regulation of lipolysis and lipogenesis in adipose tissue, inflammation, endocrine signalling and the composition and properties of cellular membranes. Alterations in such processes due to altered plasma FFA concentrations/profiles can potentially result in the development of insulin resistance and coagulatory defects. Finally, fibrates and statins, lipid-regulating drugs prescribed to subjects with T2DM, are also thought to exert part of their beneficial effects by impacting on plasma FFA concentrations. Thus, it is also interesting to consider their effects on the concentration of FFAs in plasma. Collectively, we review how FFAs are altered in T2DM and explore the likely downstream physiological and pathological implications of such changes.