Exercise Ameliorates Insulin Resistance of Type 2 Diabetes through Motivating Short-Chain Fatty Acid-Mediated Skeletal Muscle Cell Autophagy

Role of Akkermansia muciniphila in insulin resistance

Insulin resistance (IR) is a pathogenic factor in numerous metabolic diseases. The gut microbiota plays a crucial role in maintaining the function of the intestinal barrier and overall human health, thereby influencing IR. Dysbiosis of the gut microbiota can contribute to the development of IR. Therefore, it is essential to maintain a balanced and diverse gut microbiota for optimal health. Akkermansia muciniphila, a widely present microorganism in the human intestine, has been shown to regulate gastrointestinal mucosal barrier integrity, reduce endotoxin penetration, decrease systemic inflammation levels, and improve insulin sensitivity. Reduced abundance of A. muciniphila is associated with an increased risk of IR and other metabolic diseases, highlighting its correlation with IR. Understanding the role and regulatory mechanism of A. muciniphila is crucial for comprehending IR pathogenesis and developing novel strategies for preventing and treating related metabolic disorders. Individual variations may exist in both the gut microbiota composition and its impact on IR among different individuals. Further investigation into individual differences between A. muciniphila and IR will facilitate advancements in personalized medicine by promoting tailored interventions based on the gut microbiota composition, which is a potential future direction that would optimize insulin sensitivity while preventing metabolic disease occurrence. In this review, we describe the physiological characteristics of A. muciniphila, emphasize its roles in underlying mechanisms contributing to IR pathology, and summarize how alterations in its abundance affect IR development, thereby providing valuable insights for further research on A. muciniphila, as well as new drug development targeting diabetes.

Gut Microbiota and Polycystic Ovary Syndrome (PCOS): Understanding the Pathogenesis and the Role of Probiotics as a Therapeutic Strategy

Polycystic ovary syndrome (PCOS) is one of the most common disorders among women in modern societies. A variety of factors can contribute to the development of PCOS. These women often exhibit high insulin resistance (IR), hyperandrogenism, irregular periods, and infertility. Dysbiosis of the gut microbiota (GMB) in women with PCOS has attracted the attention of many researchers. Porphyromonas spp., B. coprophilus, and F. prausnitzii are found in higher numbers in the gut of women with PCOS. Short-chain fatty acids (SCFAs), produced by the intestinal microbiota through fermentation, play an essential role in regulating metabolic activities and are helpful in reducing insulin resistance and improving PCOS symptoms. According to studies, the bacteria producing SCFAs in the gut of these women are less abundant than in healthy women. The effectiveness of using probiotic supplements has been proven to improve the condition of women with PCOS. Daily consumption of probiotics improves dysbiosis of the intestinal microbiome and increases the production of SCFAs.

Targeting Autophagy: A Promising Therapeutic Strategy for Diabetes Mellitus and Diabetic Nephropathy

Diabetes mellitus (DM) significantly impairs patients' quality of life, primarily because of its complications, which are the leading cause of mortality among individuals with the disease. Autophagy has emerged as a key process closely associated with DM, including its complications such as diabetic nephropathy (DN). DN is a major complication of DM, contributing significantly to chronic kidney disease and renal failure. The intricate connection between autophagy and DM, including DN, highlights the potential for new therapeutic targets. This review examines the interplay between autophagy and these conditions, aiming to uncover novel approaches to treatment and enhance our understanding of their underlying pathophysiology. It also explores the role of autophagy in maintaining renal homeostasis and its involvement in the development and progression of DM and DN. Furthermore, the review discusses natural compounds that may alleviate these conditions by modulating autophagy.

Low-Molecular-Weight Compounds Produced by the Intestinal Microbiota and Cardiovascular Disease

Cardiovascular disease is the main cause of mortality in industrialized countries, with over 500 million people affected worldwide. In this work, the roles of low-molecular-weight metabolites originating from the gut microbiome, such as short-chain fatty acids, hydrogen sulfide, trimethylamine, phenylacetic acid, secondary bile acids, indoles, different gases, neurotransmitters, vitamins, and complex lipids, are discussed in relation to their CVD-promoting or preventing activities. Molecules of mixed microbial and human hepatic origin, such as trimethylamine N-oxide and phenylacetylglutamine, are also presented. Finally, dietary agents with cardioprotective effects, such as probiotics, prebiotics, mono- and poly-unsaturated fatty acids, carotenoids, and polyphenols, are also discussed. A special emphasis is given to their gut microbiota-modulating properties.

EGCG drives gut microbial remodeling-induced epithelial GPR43 activation to lessen Th1 polarization in colitis

Modulation of immune microenvironment is critical for inflammatory bowel disease (IBD) intervention. Epigallocatechin gallate (EGCG), as a natural low toxicity product, has shown promise in treating IBD. However, whether and how EGCG regulates the intestinal microenvironment is not fully understood. Here we report that EGCG lessens colitis by orchestrating Th1 polarization and self-amplification in a novel manner that required multilevel-regulated intestinal microecosystem. Mechanistically, EGCG activates GPR43 on IEC to inhibit Th1 polarization dependently of short chain fatty acid (SCFA)-producing gut microbiota. Inhibition of GPR43 activity weakens the protective effects of EGCG on colitis development. Moreover, we confirm that fecal SCFAs and/or intestinal GPR43 are limited in patients with colitis and are correlated with Th1 cell number. Taken together, our study reveals an intestinal microenvironment-dependent immunoregulatory effects of EGCG in treating IBD and provides insight into mechanisms of EGCG-based novel immunotherapeutic strategies for IBD.

Crosstalk between intestinal flora and human iron metabolism: the role in metabolic syndrome-related comorbidities and its potential clinical application

The interaction of iron and intestinal flora, both of which play crucial roles in many physiologic processes, is involved in the development of Metabolic syndrome (MetS). MetS is a pathologic condition represented by insulin resistance, obesity, dyslipidemia, and hypertension. MetS-related comorbidities including type 2 diabetes mellitus (T2DM), obesity, metabolism-related fatty liver (MAFLD), hypertension polycystic ovary syndrome (PCOS), and so forth. In this review, we examine the interplay between intestinal flora and human iron metabolism and its underlying mechanism in the pathogenesis of MetS-related comorbidities. The composition and metabolites of intestinal flora regulate the level of human iron by modulating intestinal iron absorption, the factors associated with iron metabolism. On the other hand, the iron level also affects the abundance, composition, and metabolism of intestinal flora. The crosstalk between these factors is of significant importance in human metabolism and exerts varying degrees of influence on the manifestation and progression of MetS-related comorbidities. The findings derived from these studies can enhance our comprehension of the interplay between intestinal flora and iron metabolism, and open up novel potential therapeutic approaches toward MetS-related comorbidities.

Intestinal flora: New perspective of type 2 diabetes

Diabetes comprises a group of metabolic diseases characterized by hyperglycemia stemming from various factors. Current diabetes management primarily focuses on blood glucose control, yet it is inherently progressive, necessitating increased reliance on exogenous blood glucose control methods over time. Therefore, there is an urgent need to explore novel intervention strategies addressing both diabetes and its complications. The human intestinal microbiota, often referred to as the "second genome", exhibits significant diversity and plays a pivotal role in insulin resistance, glucose and lipid metabolism, and inflammatory response. Notably, Li and Guo have elucidated the involvement of intestinal flora in the pathogenesis of type 2 diabetes mellitus (T2DM) and proposed a novel therapeutic approach targeting intestinal microbes. This advancement enhances our comprehension of the multifaceted and multi-target regulation of T2DM by intestinal microflora, thereby offering fresh avenues for understanding its pathogenesis and clinical management. This letter briefly summarizes the role of intestinal flora in T2DM based on findings from animal experiments and clinical studies. Additionally, it discusses the potential clinical applications and challenges associated with targeting intestinal flora as therapeutic interventions.

FFAR2 expressing myeloid-derived suppressor cells drive cancer immunoevasion

BACKGROUND

Emerging evidences suggest that aberrant metabolites contributes to the immunosuppressive microenvironment that leads to cancer immune evasion. Among tumor immunosuppressive cells, myeloid-derived suppressor cells (MDSCs) are pathologically activated and extremely immunosuppressive, which are closely associated with poor clinical outcomes of cancer patients. However, the correlation between MDSCs mediated immunosuppression and particular cancer metabolism remained elusive.

METHODS

Spontaneous lung adenocarcinoma and subcutaneous mouse tumor models, gas chromatography-mass spectrometry (GC-MS) and immunofluorescence assay of patient-derived lung adenocarcinoma tissues, and flow cytometry, RNA sequencing and Western blotting of immune cells, were utilized.

RESULTS

Metabolite profiling revealed a significant accumulation of acetic acids in tumor tissues from both patients and mouse model, which contribute to immune suppression and cancer progression significantly through free fatty acid receptor 2 (FFAR2). Furthermore, FFAR2 is highly expressed in the myeloid-derived suppressor cells (MDSCs) from the tumor of lung adenocarcinoma (LUAD) patients which is greatly associated with poor prognosis. Surprisingly, whole or myeloid Ffar2 gene deletion markedly inhibited urethane-induced lung carcinogenesis and syngeneic tumor growth with reduced MDSCs and increased CD8+ T cell infiltration. Mechanistically, FFAR2 deficiency in MDSCs significantly reduced the expression of Arg1 through Gαq/Calcium/PPAR-γ axis, which eliminated T cell dysfunction through relieving L-Arginine consumption in tumor microenvironment. Therefore, replenishment of L-Arginine or inhibition to PPAR-γ restored acetic acids/FFAR2 mediated suppression to T cells significantly. Finally, FFAR2 inhibition overcame resistance to immune checkpoint blockade through enhancing the recruitment and cytotoxicity of tumor-infiltrating T cells.

CONCLUSION

Altogether, our results demonstrate that the acetic acids/FFAR2 axis enhances MDSCs mediated immunosuppression through Gαq/calcium/PPAR-γ/Arg1 signaling pathway, thus contributing to cancer progression. Therefore, FFAR2 may serve as a potential new target to eliminate pathologically activated MDSCs and reverse immunosuppressive tumor microenvironment, which has great potential in improving clinical outcomes of cancer immunotherapy.

The interplay between gut microbiota, short-chain fatty acids, and implications for host health and disease

Short-chain fatty acids (SCFAs) - acetate, propionate, and butyrate - are important bacterial fermentation metabolites regulating many important aspects of human physiology. Decreases in the concentrations of any or multiple SCFAs are associated with various detrimental effects to the host. Previous research has broadly focused on gut microbiome produced SCFAs as a group, with minimal distinction between acetate, propionate, and butyrate independently, each with significantly different host effects. In this review, we comprehensively delineate the roles of these SCFAs with emphasis on receptor affinity, signaling pathway involvement, and net host physiologic effects. Butyrate is highlighted due to its unique role in gastrointestinal-associated functions, especially maintaining gut barrier integrity. Butyrate functions by promoting epithelial tight junctions, serving as fuel for colonocyte ATP production, and modulating the immune system. Interaction with the immune system occurs locally in the gastrointestinal tract and systemically in the brain. Investigation into research conducted on butyrate production pathways and specific bacterial players involved highlights a unique risk associated with use of gram-positive targeted antibiotics. We review and discuss evidence showing the relationship between the butyrate-producing gram-positive genus, Roseburia, and susceptibility to commonly prescribed, widely used gram-positive antibiotics. Considering gut microbiome implications when choosing antibiotic therapy may benefit health outcomes in patients.

A new perspective in intestinal microecology: lifting the veil of exercise regulation of cardiometabolic diseases

Cardiometabolic diseases (CMDs), encompassing cardiovascular and metabolic dysfunctions, characterized by insulin resistance, dyslipidemia, hepatic steatosis, and inflammation, have been identified with boosting morbidity and mortality due to the dearth of efficacious therapeutic interventions. In recent years, studies have shown that variations in gut microbiota and its own metabolites can influence the occurrence of CMDs. Intriguingly, the composition and function of the gut microbiota are susceptible to exercise patterns, thus affecting inflammatory, immune, and metabolic responses within the host. In this review, we introduce the key mechanisms of intestinal microecology involved in the onset and development of CMDs, discuss the relationship between exercise and intestinal microecology, and then analyze the role of intestinal microecology in the beneficial effects of exercise on CMDs, aiming at elucidating the gut-heart axis mechanisms of exercise mediated protective effect on CMDs, building avenues for the application of exercise in the management of CMDs.

Molecular regulators of exercise-mediated insulin sensitivity in non-obese individuals

Insulin resistance is a significant contributor to the development of type 2 diabetes (T2D) and is associated with obesity, physical inactivity, and low maximal oxygen uptake. While intense and prolonged exercise may have negative effects, physical activity can have a positive influence on cellular metabolism and the immune system. Moderate exercise has been shown to reduce oxidative stress and improve antioxidant status, whereas intense exercise can increase oxidative stress in the short term. The impact of exercise on pro-inflammatory cytokine production is complex and varies depending on intensity and duration. Exercise can also counteract the harmful effects of ageing and inflamm-ageing. This review aims to examine the molecular pathways altered by exercise in non-obese individuals at higher risk of developing T2D, including glucose utilization, lipid metabolism, mitochondrial function, inflammation and oxidative stress, with the potential to improve insulin sensitivity. The focus is on understanding the potential benefits of exercise for improving insulin sensitivity and providing insights for future targeted interventions before onset of disease.

Crosstalk between autophagy and insulin resistance: evidence from different tissues

Insulin is a critical hormone that promotes energy storage in various tissues, as well as anabolic functions. Insulin resistance significantly reduces these responses, resulting in pathological conditions, such as obesity and type 2 diabetes mellitus (T2DM). The management of insulin resistance requires better knowledge of its pathophysiological mechanisms to prevent secondary complications, such as cardiovascular diseases (CVDs). Recent evidence regarding the etiological mechanisms behind insulin resistance emphasizes the role of energy imbalance and neurohormonal dysregulation, both of which are closely regulated by autophagy. Autophagy is a conserved process that maintains homeostasis in cells. Accordingly, autophagy abnormalities have been linked to a variety of metabolic disorders, including insulin resistance, T2DM, obesity, and CVDs. Thus, there may be a link between autophagy and insulin resistance. Therefore, the interaction between autophagy and insulin function will be examined in this review, particularly in insulin-responsive tissues, such as adipose tissue, liver, and skeletal muscle.

The role of autophagy in the treatment of type II diabetes and its complications: a review

Type II diabetes mellitus (T2DM) is a chronic metabolic disease characterized by prolonged hyperglycemia and insulin resistance (IR). Its incidence is increasing annually, posing a significant threat to human life and health. Consequently, there is an urgent requirement to discover effective drugs and investigate the pathogenesis of T2DM. Autophagy plays a crucial role in maintaining normal islet structure. However, in a state of high glucose, autophagy is inhibited, resulting in impaired islet function, insulin resistance, and complications. Studies have shown that modulating autophagy through activation or inhibition can have a positive impact on the treatment of T2DM and its complications. However, it is important to note that the specific regulatory mechanisms vary depending on the target organ. This review explores the role of autophagy in the pathogenesis of T2DM, taking into account both genetic and external factors. It also provides a summary of reported chemical drugs and traditional Chinese medicine that target the autophagic pathway for the treatment of T2DM and its complications.

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.

From Diabetes to Diabetic Complications: Role of Autophagy

Diabetes and its complications reduce quality of life and are life-limiting. At present, diabetes treatment consists of hypoglycemic agents to control blood glucose and the use of insulin-sensitizing drugs to overcome insulin resistance. In diabetes, autophagy is impaired and thus there is poor intracellular environment homeostasis. Pancreatic β-cells and insulin target tissues are protected by enhancing autophagy. Autophagy decreases β-cell apoptosis, promotes β-cell proliferation, and alleviates insulin resistance. Autophagy in diabetes is regulated by the mammalian target of rapamycin (mTOR)/adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) pathway and others. Autophagy enhancers can likely be used as a treatment for diabetes and its complications. This review examines the evidence linking autophagy to diabetes.

The high-intensity interval training (HIIT) and curcumin supplementation can positively regulate the autophagy pathway in myocardial cells of STZ-induced diabetic rats

OBJECTIVE

Targeting autophagy is a new therapeutic strategy for the complications of diabetes,such as diabetic cardiomyopathy (DCM). During diabetes, increased or insufficient autophagic activity causes aberrations in cellular homeostasis. Regarding the conflicting and unclear results regarding the effect of HIIT and curcumin supplementation on the expression of genes associated to autophagy, this study aimed to assess whether 4-week high-intensity interval training (HIIT) and curcumin supplementation are able to influence the expression of autophagy-related genes in myocardial cells of diabetic rats.

METHODS

In an experimental design, 24 male Wistar rats were randomly divided into 4 groups: non-diabetic control (NC), diabetic control (DC), diabetes + HIIT (D + HIIT), and diabetes + curcumin (D + CU). After HIIT program and curcumin treatment, the genes expression of autophagy pathway were assessed in the myocardium by real-time PCR Tanique.

RESULTS

The results indicated that the expression levels of ATG1, Beclin1, ATG5, and LAMP-2 genes were significantly reduced in the DC group compared to the NC group (p < 0.001). Following 4-week HIIT, the expression of Beclin1, ATG-5, and LAMP-2 improved considerably compared to the DC group (p < 0.001, p < 0.001, and p < 0.05, respectively). In addition, after 4 weeks of curcumin supplementation, the expression levels of ATG-5 and Beclin-1 were significantly improved compared to the DC group (p < 0.001, p < 0.05, respectively). It seems HIIT and curcumin supplementation can be an effective approach for inducing autophagy and improving cardiac function in DCM rats.However, HIIT seems more effective than curcumin in this regard.

Protective Effect of Anthocyanins against Neurodegenerative Diseases through the Microbial-Intestinal-Brain Axis: A Critical Review

With the increase in human mean age, the prevalence of neurodegenerative diseases (NDs) also rises. This negatively affects mental and physiological health. In recent years, evidence has revealed that anthocyanins could regulate the functioning of the central nervous system (CNS) through the microbiome-gut-brain axis, which provides a new perspective for treating NDs. In this review, the protective effects and mechanisms of anthocyanins against NDs are summarized, especially the interaction between anthocyanins and the intestinal microbiota, and the microbial-intestinal-brain axis system is comprehensively discussed. Moreover, anthocyanins achieve the therapeutic purpose of NDs by regulating intestinal microflora and certain metabolites (protocateic acid, vanillic acid, etc.). In particular, the inhibitory effect of tryptophan metabolism on some neurotransmitters and the induction of blood-brain barrier permeability by butyrate production has a preventive effect on NDs. Overall, it is suggested that microbial-intestinal-brain axis may be a novel mechanism for the protective effect of anthocyanins against NDs.

Neuregulin-1β increases glucose uptake and promotes GLUT4 translocation in palmitate-treated C2C12 myotubes by activating PI3K/AKT signaling pathway

Insulin resistance (IR) is a feature of type 2 diabetes (T2DM) accompanied by reduced glucose uptake and glucose transporter 4 (GLUT4) translocation by skeletal muscle. Neuregulin-1β (NRG-1β) is essential for myogenesis and the regulation of skeletal muscle metabolism. Neuregulin-1β increases insulin sensitivity, promotes glucose uptake and glucose translocation in normal skeletal muscle. Here, we explored whether Neuregulin-1β increased glucose uptake and GLUT4 translocation in palmitate (PA)-treated C2C12 myotubes. After C2C12 myoblasts differentiated into myotubes, we used palmitate to induce cellular insulin resistance. Cells were incubated with or without Neuregulin-1β and glucose uptake was determined using the 2-NBDG assay. The expression level of glucose transporter 4 (GLUT4) was measured via immunofluorescence and Western blotting. MK2206, an inhibitor of AKT, was employed to reveal the important role played by AKT signaling in PA-treated C2C12 myotubes. We then established an animal model with T2DM and evaluated the effects of Neuregulin-1β on body weight and the blood glucose level. The GLUT4 level in the gastrocnemius of T2DM mice was also measured. NRG-1β not only increased glucose uptake by PA-treated myotubes but also promoted GLUT4 translocation to the plasma membrane. The effect of NRG-1β on PA-treated C2C12 myotubes was associated with AKT activation. In T2DM mice, Neuregulin-1β not only improved diabetes-induced weight loss and diabetes-induced hyperglycemia, but also promoted GLUT4 translocation in the gastrocnemius. In summary, Neuregulin-1β increased glucose uptake and promoted translocation of GLUT4 to the plasma membrane in PA-treated C2C12 myotubes by activating the PI3K/AKT signaling pathway.

Interventions for non-alcoholic liver disease: a gut microbial metabolites perspective

Over the past two decades, non-alcoholic fatty liver disease (NAFLD) has become a leading burden of hepatocellular carcinoma and liver transplantation. Although the exact pathogenesis of NAFLD has not been fully elucidated, recent hypotheses placed more emphasis on the crucial role of the gut microbiome and its derivatives. Reportedly, microbial metabolites such as short-chain fatty acids, amino acid metabolites (indole and its derivatives), bile acids (BAs), trimethylamine N-oxide (TMAO), and endogenous ethanol exhibit sophisticated bioactive properties. These molecules regulate host lipid, glucose, and BAs metabolic homeostasis via modulating nutrient absorption, energy expenditure, inflammation, and the neuroendocrine axis. Consequently, a broad range of research has studied the therapeutic effects of microbiota-derived metabolites. In this review, we explore the interaction of microbial products and NAFLD. We also discuss the regulatory role of existing NAFLD therapies on metabolite levels and investigate the potential of targeting those metabolites to relieve NAFLD.

Beneficial effect of the short-chain fatty acid propionate on vascular calcification through intestinal microbiota remodelling

BACKGROUND

Vascular calcification is a major cause of the high morbidity and mortality of cardiovascular diseases and is closely associated with the intestinal microbiota. Short-chain fatty acids (SCFAs) are derived from the intestinal microbiota and can also regulate intestinal microbiota homeostasis. However, it remains unclear whether exogenous supplementation with propionate, a SCFA, can ameliorate vascular calcification by regulating the intestinal microbiota. This study was conducted to explore the roles of propionate and the intestinal microbiota in the process of vascular calcification.

METHODS

In total, 92 patients were enrolled consecutively as the observational cohort to analyse the relationship between SCFAs and vascular calcification in both blood and faecal samples. A rat model of vascular calcification was induced by vitamin D3 and nicotine (VDN) to validate the effect of propionate. Differences in the intestinal microbiota were analysed by 16S ribosomal RNA gene sequencing. Faecal microbiota transplantation and Akkermansia muciniphila transplantation experiments were performed to evaluate the functions of the intestinal microbiota.

RESULTS

The results of the observational cohort study revealed that the levels of SCFAs (particularly propionate) in both blood and faecal samples independently correlated negatively with calcification scores (P < 0.01). To verify the activities of propionate, it was provided to VDN-treated rats, and oral or rectal propionate delivery reshaped the intestinal microbiota, resulted in elevated SCFA production, improved intestinal barrier function and alleviated inflammation, ultimately ameliorating vascular calcification. Furthermore, we demonstrated that transplantation of the propionate-modulated intestinal microbiota induced beneficial outcomes similar to those with oral or rectal propionate administration. Interestingly, linear discriminant analysis (LDA) effect size (LEfSe) revealed that oral or rectal propionate administration and propionate-modulated intestinal microbiota transplantation both enriched primarily Akkermansia. Subsequently, we demonstrated that Akkermansia supplementation could ameliorate VDN-induced vascular calcification in rats.

CONCLUSIONS

Propionate can significantly ameliorate vascular calcification in VDN-treated rats, and this effect is mediated by intestinal microbiota remodelling. The findings in our study indicate that the intestinal tract-vessel axis is a promising target for alleviating vascular calcification. Video Abstract.

Changes in gut microbiota, metabolite SCFAs, and GPR43 expression in obese diabetic mice after sleeve gastrectomy

AIMS

To evaluate changes in short-chain fatty acid levels and G protein-coupled receptor 43 expression and distribution in gut microbiota and explore their relationships in obese diabetic mice after sleeve gastrectomy.

METHODS AND RESULTS

Diet-induced obese mice and obese diabetic ob/ob mice were established. Changes in glucose metabolism, lipid metabolism, gut microbiota, metabolite short-chain fatty acids, and G protein-coupled receptor 43 expression were assessed in both models 10 weeks postoperatively. Mice that underwent sleeve gastrectomy exhibited sustained weight loss and reduced glucose, insulin, leptin, and cholesterol levels. Metagenomic sequencing revealed significant characteristic alterations in gut microbiota after sleeve gastrectomy, which were correlated with changes in fecal short-chain fatty acid levels. Postoperatively, G protein-coupled receptor 43 expression in the colon tissue was upregulated in both models, whereas its expression in the adipose tissue was downregulated in the diet-induced obese mouse model.

CONCLUSIONS

Metabolic improvement in obese and diabetic mice after sleeve gastrectomy is associated with alterations in gut microbiota, short-chain fatty acid levels, and G protein-coupled receptor 43 expression.

SIGNIFICANCE AND IMPACT OF STUDY

Our findings reveal a possible mechanism through which sleeve gastrectomy improves obesity and diabetes via changes in bacteria producing short-chain fatty acids and G protein-coupled receptor 43.

Exercise for the Diabetic Gut-Potential Health Effects and Underlying Mechanisms

It can be assumed that changes in the gut microbiota play a crucial role in the development of type 2 diabetes mellitus (T2DM). It is generally accepted that regular physical activity is beneficial for the prevention and therapy of T2DM. Therefore, this review analyzes the effects of exercise training on the gut microbiota composition and the intestinal barrier function in T2DM. The current literature shows that regular exercise can influence the gut microbiota composition and the intestinal barrier function with ameliorative effects on T2DM. In particular, increases in the number of short-chain fatty acid (SCFA)-producing bacteria and improvements in the gut barrier integrity with reduced endotoxemia seem to be key points for positive interactions between gut health and T2DM, resulting in improvements in low-grade systemic inflammation status and glycemic control. However, not all aspects are known in detail and further studies are needed to further examine the efficacy of different training programs, the role of myokines, SCFA-producing bacteria, and SCFAs in the relevant metabolic pathways. As microbial signatures differ in individuals who respond differently to exercise training programs, one scientific focus could be the development of computer-based methods for the personalized analysis of the gut microbiota in the context of a microbiota/microbiome-based training program.

Does the gut microbiota contribute to the antiobesity effect of exercise? A systematic review and meta-analysis

OBJECTIVE

The aim of this study was to assess gut microbiota modifications after exercise in humans and animal models with obesity or type 2 diabetes and their role in exercise-induced weight loss.

METHODS

A systematic search of six databases was conducted on July 31, 2021. The extracted data on body fat or body weight from human and animal studies were analyzed using random-effects meta-analysis.

RESULTS

A total of 28 studies were included, with all studies reporting exercise-induced gut microbiota modifications; however, the modified taxa varied among studies. Proteobacteria was the only taxa reported to be altered by exercise in more than one human and one animal study. Taxa belonging to Firmicutes were the most responsive to exercise in humans and mice, whereas Proteobacteria taxa were the most responsive to exercise in rats. A meta-analysis was conducted to examine the weight-lowering effect of exercise based on data subgrouped by altered or unaltered α-diversity or β-diversity. The association between the weight-lowering effect of exercise and altered β-diversity was observed in humans with obesity but not in animals.

CONCLUSIONS

These findings suggest that gut microbiota modifications contribute to exercise-induced weight loss in obesity; however, their precise contributions, especially those of taxon-level variations, remain to be investigated.

Gut microbiota: A new target for T2DM prevention and treatment

Type 2 diabetes mellitus (T2DM), one of the fastest growing metabolic diseases, has been characterized by metabolic disorders including hyperglycemia, hyperlipidemia and insulin resistance (IR). In recent years, T2DM has become the fastest growing metabolic disease in the world. Studies have indicated that patients with T2DM are often associated with intestinal flora disorders and dysfunction involving multiple organs. Metabolites of the intestinal flora, such as bile acids (BAs), short-chain fatty acids (SCFAs) and amino acids (AAs)may influence to some extent the decreased insulin sensitivity associated with T2DM dysfunction and regulate metabolic as well as immune homeostasis. In this paper, we review the changes in the gut flora in T2DM and the mechanisms by which the gut microbiota modulates metabolites affecting T2DM, which may provide a basis for the early identification of T2DM-susceptible individuals and guide targeted interventions. Finally, we also highlight gut microecological therapeutic strategies focused on shaping the gut flora to inform the improvement of T2DM progression.

Pi-Dan-Jian-Qing Decoction Ameliorates Type 2 Diabetes Mellitus Through Regulating the Gut Microbiota and Serum Metabolism

Pi-Dan-Jian-Qing decoction (PDJQ) can been used in the treatment of type 2 diabetes mellitus (T2DM) in clinic. However, the protective mechanisms of PDJQ on T2DM remain unknown. Recent studies have shown that the changes in gut microbiota could affect the host metabolism and contribute to progression of T2DM. In this study, we first investigated the therapeutic effects of PDJQ on T2DM rats. 16S rRNA sequencing and untargeted metabolomics analyses were used to investigate the mechanisms of action of PDJQ in the treatment of T2DM. Our results showed that PDJQ treatment could improve the hyperglycemia, hyperlipidemia, insulin resistance (IR) and pathological changes of liver, pancreas, kidney, and colon in T2DM rats. PDJQ could also decrease the levels of pro-inflammatory cytokines and inhibit the oxidative stress. 16S rRNA sequencing showed that PDJQ could decrease the Firmicutes/Bacteroidetes (F to B) ratio at the phylum level. At the genus level, PDJQ could increase the relative abundances of Lactobacillus, Blautia, Bacteroides, Desulfovibrio and Akkermansia and decrease the relative abundance of Prevotella. Serum untargeted metabolomics analysis showed that PDJQ could regulate tryptophan metabolism, histidine metabolism, tricarboxylic acid (TCA) cycle, phenylalanine, tyrosine and tryptophan biosynthesis and tyrosine metabolism pathways. Correlation analysis indicated that the modulatory effects of PDJQ on the tryptophan metabolism, histidine metabolism and TCA cycle pathways were related to alterations in the abundance of Lactobacillus, Bacteroides and Akkermansia. In conclusion, our study revealed the various ameliorative effects of PDJQ on T2DM, including improving the liver and kidney functions and alleviating the hyperglycemia, hyperlipidemia, IR, pathological changes, oxidative stress and inflammatory response. The mechanisms of PDJQ on T2DM are likely linked to an improvement in the dysbiosis of gut microbiota and modulation of tryptophan metabolism, histamine metabolism, and the TCA cycle.

Does intermittent fasting associated with aerobic training influence parameters related to the gut-brain axis of Wistar rats?

BACKGROUND

Intermittent fasting (IF) and aerobic training have demonstrated beneficial effects on intestinal microbiota composition, but little is known about benefits to the brain through the gut-brain axis. The present study aimed to evaluate gut-brain axis parameters in Wistar rats submitted to IF associated or not with aerobic training.

METHODS

Male rats were evaluated for training performance and then randomized into 4 groups of ten: sedentary control (SC), trained control (TC), sedentary intermittent fasting (SIF), and trained intermittent fasting (TIF), and evaluated during four weeks.

RESULTS

The adiposity index was similar among the TC (2.15±0.43%), SIF (1.98±0.69%) and TIF (1.86±0.51%) groups, and differed from SC (2.98±0.80%). TIF had lower counts of lactic acid bacteria, while SIF had higher counts of Bifidobacterium and Enterococcus. TIF had the highest amount of formic acid in faeces (44.44±2.40 μmol/g) and lowest amount of succinic acid in the gut (0.38±0.00 μmol/g), while SIF had the highest propionic acid amount in the faeces (802.80±00.33 μmol/g) and the lowest amount of lactic acid in the gut (0.85±0.00 μmol/g). TIF demonstrated a tendency towards an anxiolytic effect and SIF showed potential antidepressant effect. IF caused different brain and intestinal injuries. TIF rats presented a diffuse and intense marking of IL-1β in the hippocampus.

CONCLUSION

IF and aerobic exercise, associated or not, can modulate parameters related to the gut-brain axis of Wistar rats, and some benefits may be related to the amounts of organic acids.

Multi-strain probiotic supplement attenuates streptozotocin-induced type-2 diabetes by reducing inflammation and β-cell death in rats

Probiotics are health beneficial bacterial populations colonizing the human gut and skin. Probiotics are believed to be involved in immune system regulation, gut microbiota stabilization, prevention of infectious diseases, and adjustments of host metabolic activities. Probiotics such as Lactobacillus and Bifidobacterium affect glycemic levels, blood lipids, and protein metabolism. However, the interactions between probiotics and metabolic diseases as well as the underlying mechanisms remain unclear. We used streptozotocin (STZ)-induced diabetic animal models to study the effect of Probioglu^TM, a multi-strain probiotic supplement including Lactobaccilus salivarius subsp. salicinius AP-32, L. johnsonii MH-68, L. reuteri GL-104, and Bifidobacterium animalis subsp. lactis CP-9, on the regulation of physiochemical parameters related to type-2 diabetes. Experimental rats were randomly assigned into five groups, control group, streptozotocin (STZ)-treated rats (STZ group), STZ + 1× Probioglu^TM group, STZ + 5× Probioglu^TM group, and STZ + 10× Probioglu^TM group, and physiological data were measured at weeks 0, 2, 4, 6, and 8. Our results indicate that supplementation with Probioglu^TM significantly improved glucose tolerance, glycemic levels, insulin levels, and insulin resistance (HOMA-IR). Furthermore, we observed reduction in urea and blood lipid levels, including low-density lipoprotein (LDL), triglycerides (TG), and total cholesterol (TC). Probioglu^TM administration increased the β-cell mass in STZ-induced diabetic animal models, whereas it reduced the levels of proinflammatory cytokines TNF-α, IL-6, and IL-1β. In addition, the enhancement of oxidative stress biomarkers and superoxide dismutase (SOD) activities was associated with a decrease in malondialdehyde (MDA) levels. We conclude that Probioglu^TM attenuates STZ-induced type-2 diabetes by protecting β-cells, stabilizing glycemic levels, and reducing inflammation. Among all probiotic treating groups, the 10×Probioglu^TM treatment revealed the best results. However, these experimental results still need to be validated by different animal models of type-2 diabetes and human clinical trials in the future.

The role of short-chain fatty acids in the interplay between gut microbiota and diet in cardio-metabolic health

The gut microbiota plays an important role in cardio-metabolic diseases with diet being among the strongest modulators of gut microbiota composition and function. Resistant dietary carbohydrates are fermented to short-chain fatty acids (SCFAs) by the gut bacteria. Fiber and omega-3 rich diets increase SCFAs production and abundance of SCFA-producing bacteria. Likewise, SCFAs can improve gut barrier integrity, glucose, and lipid metabolism, regulate the immune system, the inflammatory response, and blood pressure. Therefore, targeting the gut microbiota with dietary strategies leading to increased SCFA production may benefit cardio-metabolic health. In this review, we provide an overview of the association between diet, SCFAs produced by the gut microbiota and cardio-metabolic diseases. We first discuss the association between the human gut microbiota and cardio-metabolic diseases, then investigate the role of SCFAs and finally explore the beneficial effects of specific dietary interventions that can improve cardio-metabolic outcomes through boosting the SCFA production.

The Impact of Dysmetabolic Sarcopenia Among Insulin Sensitive Tissues: A Narrative Review

Sarcopenia is a common muscular affection among elderly individuals. More recently, it has been recognized as the skeletal muscle (SM) expression of the metabolic syndrome. The prevalence of sarcopenia is increasing along with visceral obesity, to which it is tightly associated. Nonetheless, it is a still underreported entity by clinicians, despite the worsening in disease burden and reduced patient quality of life. Recognition of sarcopenia is clinically challenging, and variability in study populations and diagnostic methods across the clinical studies makes it hard to reach a strong evidence. Impaired insulin activity in SM is responsible for the altered molecular pathways and clinical manifestations of sarcopenia, which is morphologically expressed by myosteatosis. Lipotoxicity, oxidative stress and adipose tissue-derived inflammation lead to both alterations in glucose disposal and protein synthesis in SM, with raising insulin resistance (IR) and SM atrophy. In particular, hyperleptinemia and leptin resistance interfere directly with SM activity, but also with the release of Growth Hormone from the hypohysis, leading to a lack in its anabolic effect on SM. Moreover, sarcopenia is independently associated to liver fibrosis in Non-Alcoholic Fatty Liver Disease (NAFLD), which in turn worsens SM functionality through the secretion of proinflammatory heptokines. The cross-talk between the liver and SM in the IR setting is of crucial relevance, given the high prevalence of NAFLD and the reciprocal impact of insulin-sensitive tissues on the overall disease burden. Along with the efforts of non-invasive diagnostic approaches, irisin and myostatin are two myokines currently evaluated as potential biomarkers for diagnosis and prognostication. Decreased irisin levels seem to be potentially associated to sarcopenia, whereas increased myostatin has shown to negatively impact on sarcopenia in pre-clinical studies. Gene variants in irisin have been explored with regard to the impact on the liver disease phenotype, with conflicting results. The gut-muscle axis has gain relevance with the evidence that insulin resistance-derived gut dysbiosis is responsible for increased endotoxemia and reduction in short-chain free fatty acids, directly affecting and predisposing to sarcopenia. Based on the current evidence, more efforts are needed to increase awareness and improve the management of sarcopenic patients.

The Prospect for Type 2 Diabetes Mellitus Combined with Exercise and Synbiotics: A Perspective

Change in gut microbiome diversity (the so-called dysbiosis) is correlated with insulin resistance conditions. Exercise is typically the first management for people with type 2 diabetes mellitus (T2DM), which is generally well-known for improving glucose regulation. The new prebiotics and probiotics, like synbiotics, designed to target specific diseases, require additional studies. While the effectiveness of exercise combined with synbiotics seems promising, this review discusses these agents' possibility of increasing the gut microbiota's diversity. Therefore, they could enhance short-chain fatty acids (SCFA). In particular, the synbiotic interaction on gut microbiota, the exercise mechanism in improving gut microbiota, and the prospect of the synergistic effect of the combination of synbiotic and exercise to improve insulin sensitivity are addressed.

Intracellular pH Regulation of Skeletal Muscle in the Milieu of Insulin Signaling

Type 2 diabetes (T2D), along with obesity, is one of the leading health problems in the world which causes other systemic diseases, such as cardiovascular diseases and kidney failure. Impairments in glycemic control and insulin resistance plays a pivotal role in the development of diabetes and its complications. Since skeletal muscle constitutes a significant tissue mass of the body, insulin resistance within the muscle is considered to initiate the onset of diet-induced metabolic syndrome. Insulin resistance is associated with impaired glucose uptake, resulting from defective post-receptor insulin responses, decreased glucose transport, impaired glucose phosphorylation, oxidation and glycogen synthesis in the muscle. Although defects in the insulin signaling pathway have been widely studied, the effects of cellular mechanisms activated during metabolic syndrome that cross-talk with insulin responses are not fully elucidated. Numerous reports suggest that pathways such as inflammation, lipid peroxidation products, acidosis and autophagy could cross-talk with insulin-signaling pathway and contribute to diminished insulin responses. Here, we review and discuss the literature about the defects in glycolytic pathway, shift in glucose utilization toward anaerobic glycolysis and change in intracellular pH [pH]_i within the skeletal muscle and their contribution towards insulin resistance. We will discuss whether the derangements in pathways, which maintain [pH]_i within the skeletal muscle, such as transporters (monocarboxylate transporters 1 and 4) and depletion of intracellular buffers, such as histidyl dipeptides, could lead to decrease in [pH]_i and the onset of insulin resistance. Further we will discuss, whether the changes in [pH]_i within the skeletal muscle of patients with T2D, could enhance the formation of protein aggregates and activate autophagy. Understanding the mechanisms by which changes in the glycolytic pathway and [pH]_i within the muscle, contribute to insulin resistance might help explain the onset of obesity-linked metabolic syndrome. Finally, we will conclude whether correcting the pathways which maintain [pH]_i within the skeletal muscle could, in turn, be effective to maintain or restore insulin responses during metabolic syndrome.