Propionate suppresses hepatic gluconeogenesis via GPR43/AMPK signaling pathway. Arch Biochem Biophys. 2019;672:108057. [PMID: 31356781 DOI: 10.1016/j.abb.2019.07.022]

Gut Microbiota Disorders and Metabolic Syndrome: Tales of a Crosstalk Process

The microbiota in humans consists of trillions of microorganisms that are involved in the regulation of the gastrointestinal tract and immune and metabolic homeostasis. The gut microbiota (GM) has a prominent impact on the pathogenesis of metabolic syndrome (MetS). This process is reciprocal, constituting a crosstalk process between the GM and MetS. In this review, GM directly or indirectly inducing MetS via the host-microbial metabolic axis has been systematically reviewed. Additionally, the specifically altered GM in MetS are detailed in this review. Moreover, short-chain fatty acids (SCFAs), as unique gut microbial metabolites, have a remarkable effect on MetS, and the role of SCFAs in MetS-related diseases is highlighted to supplement the gaps in this area. Finally, the existing therapeutics are outlined, and the superiority and shortcomings of different therapeutic approaches are discussed, in hopes that this review can contribute to the development of potential treatment strategies.

Integration strategies involving 16S rDNA sequencing combined with untargeted metabolomics revealed the mechanism of Selaginella tamariscina (Beauv.) Spring in db/db diabetic mice

Selaginella tamariscina extracts (STS), total flavonoids of Selaginella tamariscina (TFST) and the main active component amentoflavone (AMT) have hypoglycaemic-mitigating effects, but their efficacy and mechanism of action in db/db mice are unknown. This study aimed to evaluate the hypoglycaemic effects of Selaginella tamariscina and its extracts in db/db diabetic mice and explore their mechanisms through gut microbiota modulation and metabolomics. Sixty male db/db mice were divided into model (db/db), STS (1.1 g/kg), TFST (140 mg/kg), AMT (60 mg/kg), mulberry twig alkaloid tablets (MTA, 24 mg/kg), and metformin (Met, 160 mg/kg) groups. Another 10 db/m mice served as controls. Treatments lasted 4 weeks. Blood glucose, body weight, diabetes symptoms, lipid levels, pathological changes, oxidative stress markers and liver damage levels were assessed. The gut microbiota composition was analyzed via 16S rDNA sequencing, and urinary metabolomics was conducted to understand metabolic changes. Selaginella tamariscina and its extracts significantly improved hyperglycaemia, insulin sensitivity, lipid metabolism, oxidative stress and liver injury in db/db mice, among which TFST was the most effective, with an effect comparable to that of Met and superior to that of MTA. TFST regulates gut microbiota disorders and metabolic profiles in db/db diabetic mice and modulates Alloprevotella levels, affecting butyric acid content and, thus, exerting a hypoglycaemic effect. These findings suggest that TFST modulates Alloprevotella, influencing butyric acid levels, which improves glycaemic control, enhances insulin sensitivity, and prevents oxidative stress and tissue damage. In conclusion, TFST has potential as a natural therapeutic agent for the control of T2DM.

Targeting inflammation and gut microbiota with antibacterial therapy: Implications for central nervous system health

The complex symbiotic relationship between inflammation, the gut microbiota, and the central nervous system (CNS) has become a pivotal focus of contemporary biomedical research. Inflammation, as a physiological defense mechanism, plays a dual role as both a protective and pathological factor, and is intricately associated with gut microbiota homeostasis, often termed the "second brain." The gutbrain axis (GBA) exemplifies this multifaceted interaction, where gut health exerts significantly regulatory effects on CNS functions. Antibacterial therapies represent both promising and challenging strategies for modulating inflammation and gut microbiota composition to confer CNS benefits. However, while such therapies may exert positive modulatory effects on the gut microbiota, they also carry the potential to disrupt microbial equilibrium, potentially exacerbating neurological dysfunction. Recent advances have provided critical insights into the therapeutic implications of antibacterial interventions; nevertheless, the application of these therapies in the context of CNS health warrants a judicious and evidence-based approach. As research progresses, deeper investigation into the microbial-neural interface is essential to fully realize the potential of therapies targeting inflammation and the gut microbiota for CNS health. Future efforts should focus on refining antibacterial interventions to modulate the gut microbiota while minimizing disruption to microbial balance, thereby reducing risks and enhancing efficacy in CNS-related conditions. In conclusion, despite challenges, a more comprehensive understanding of the GBA, along with precise modulation through targeted antibacterial therapies, offers significant promise for advancing CNS disorder treatment. Continued research in this area will lead to innovative interventions and improved patient outcomes.

Harnessing Prebiotics to Improve Type 2 Diabetes Outcomes

The gut microbiota, a complex ecosystem of microorganisms in the human gastrointestinal tract (GI), plays a crucial role in maintaining metabolic health and influencing disease susceptibility. Dysbiosis, or an imbalance in gut microbiota, has been linked to the development of type 2 diabetes mellitus (T2DM) through mechanisms such as reduced glucose tolerance and increased insulin resistance. A balanced gut microbiota, or eubiosis, is associated with improved glucose metabolism and insulin sensitivity, potentially reducing the risk of diabetes-related complications. Various strategies, including the use of prebiotics like inulin, fructooligosaccharides, galactooligosaccharides, resistant starch, pectic oligosaccharides, polyphenols, β-glucan, and Dendrobium officinale have been shown to improve gut microbial composition and support glycemic control in T2DM patients. These prebiotics can directly impact blood sugar levels while promoting the growth of beneficial bacteria, thus enhancing glycemic control. Studies have shown that T2DM patients often exhibit a decrease in beneficial butyrate-producing bacteria, like Roseburia and Faecalibacterium, and an increase in harmful bacteria, such as Escherichia and Prevotella. This review aims to explore the effects of different prebiotics on T2DM, their impact on gut microbiota composition, and the potential for personalized dietary interventions to optimize diabetes management and improve overall health outcomes.

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.

A systematic framework for understanding the microbiome in human health and disease: from basic principles to clinical translation

The human microbiome is a complex and dynamic system that plays important roles in human health and disease. However, there remain limitations and theoretical gaps in our current understanding of the intricate relationship between microbes and humans. In this narrative review, we integrate the knowledge and insights from various fields, including anatomy, physiology, immunology, histology, genetics, and evolution, to propose a systematic framework. It introduces key concepts such as the 'innate and adaptive genomes', which enhance genetic and evolutionary comprehension of the human genome. The 'germ-free syndrome' challenges the traditional 'microbes as pathogens' view, advocating for the necessity of microbes for health. The 'slave tissue' concept underscores the symbiotic intricacies between human tissues and their microbial counterparts, highlighting the dynamic health implications of microbial interactions. 'Acquired microbial immunity' positions the microbiome as an adjunct to human immune systems, providing a rationale for probiotic therapies and prudent antibiotic use. The 'homeostatic reprogramming hypothesis' integrates the microbiome into the internal environment theory, potentially explaining the change in homeostatic indicators post-industrialization. The 'cell-microbe co-ecology model' elucidates the symbiotic regulation affecting cellular balance, while the 'meta-host model' broadens the host definition to include symbiotic microbes. The 'health-illness conversion model' encapsulates the innate and adaptive genomes' interplay and dysbiosis patterns. The aim here is to provide a more focused and coherent understanding of microbiome and highlight future research avenues that could lead to a more effective and efficient healthcare system.

Systems Biology of Human Microbiome for the Prediction of Personal Glycaemic Response

The human gut microbiota is increasingly recognized as a pivotal factor in diabetes management, playing a significant role in the body's response to treatment. However, it is important to understand that long-term usage of medicines like metformin and other diabetic treatments can result in problems, gastrointestinal discomfort, and dysbiosis of the gut flora. Advanced sequencing technologies have improved our understanding of the gut microbiome's role in diabetes, uncovering complex interactions between microbial composition and metabolic health. We explore how the gut microbiota affects glucose metabolism and insulin sensitivity by examining a variety of -omics data, including genomics, transcriptomics, epigenomics, proteomics, metabolomics, and metagenomics. Machine learning algorithms and genome-scale modeling are now being applied to find microbiological biomarkers associated with diabetes risk, predicted disease progression, and guide customized therapy. This study holds promise for specialized diabetic therapy. Despite significant advances, some concerns remain unanswered, including understanding the complex relationship between diabetes etiology and gut microbiota, as well as developing user-friendly technological innovations. This mini-review explores the relationship between multiomics, precision medicine, and machine learning to improve our understanding of the gut microbiome's function in diabetes. In the era of precision medicine, the ultimate goal is to improve patient outcomes through personalized treatments.

Double-side role of short chain fatty acids on host health via the gut-organ axes

Short chain fatty acids (SCFA) exist in dietary foods and are produced by the fermentation of gut microbiota, and are considered an important element for regulating host health. Through blood circulation, SCFA produced in the gut and obtained from foods have an impact on the intestinal health as well as vital organs of the host. It has been recognized that the gut is the "vital organ" in the host. As the gut microbial metabolites, SCFA could create an "axis" connecting the gut and to other organs. Therefore, the "gut-organ axes" have become a focus of research in recent years to analyze organism health. In this review, we summarized the sources, absorption properties, and the function of SCFA in both gut and other peripheral tissues (brain, kidney, liver, lung, bone and cardiovascular) in the way of "gut-organ axes". Short chain fatty acids exert both beneficial and pathological role in gut and other organs in various ways, in which the beneficial effects are more pronounced. In addition, the beneficial effects are reflected in both preventive and therapeutic effects. More importantly, the mechanisms behinds the gut and other tissues provided insight into the function of SCFA, assisting in the development of novel preventive and therapeutic strategies for maintaining the host health.

Different Short-Chain Fatty Acids Unequally Modulate Intestinal Homeostasis and Reverse Obesity-Related Symptoms in Lead-Exposed High-Fat Diet Mice

Our previous study showed that heavy metal lead (Pb) exposure exacerbates high-fat-diet (HFD)-induced metabolic damage and significantly depletes the gut microbiota-derived metabolite short-chain fatty acid (SCFA) levels. However, it remains unclear whether SCFA is a key metabolite involved in accelerating adverse consequences after Pb exposure. In this study, we explored the effects of exogenous supplementation of acetate, propionate, and butyrate on a metabolic disorder model in Pb-exposed HFD mice. We found that three SCFA interventions attenuated glycolipid metabolism disorders and liver damage, with butyrate performing the best effects in improving obesity-related symptoms. All three SCFA promoted the abundance of Muribaculaceae and Muribaculum, acetate specifically enriched Christensenellaceae, Blautia, and Ruminococcus, and butyrate specifically enriched Parasutterella, Rikenella, Prevotellaceae_UCG-001, and Bacteroides, which contributed to the positive promotion of SCFA production forming a virtuous cycle. Besides, butyrate inhibited Gram-negative bacteria Escherichia-Shigella. All of these events alleviated the intestinal Th17/Treg imbalance and inflammatory response through crosstalk between the G protein-coupled receptor (GPR)/histone deacetylase 3 (HDAC3) and lipopolysaccharide (LPS)/toll-like receptors 4 (TLR4)/nuclear factor κ-B (NF-κB) pathways and ultimately improved the intestinal barrier function. SCFA further upregulated the monocarboxylate transporter 1 (MCT1) and GPR43/adenosine 5'-monophosphate-activated protein kinase (AMPK) pathways to inhibit hepatic lipid accumulation. Overall, SCFA, especially butyrate, is an effective modulator to improve metabolic disorders in obese individuals exposed to heavy metals by targeting gut microecology.

Influence of Northern Wild Rice on Gut Dysbiosis and Short Chain Fatty Acids: Correlation with Metabolic and Inflammatory Markers in Mice on High Fat Diet

Wild rice (WLD) attenuated hyperglycemia, hyperlipidemia and chronic inflammation in mice receiving a high-fat diet (HFD) versus white rice (WHR), but the underlying mechanism is not well understood. We examined the influence of HFD + WLD on gut microbiota, short chain fatty acids (SCFAs) and the correlation with metabolic or inflammatory markers in mice versus HFD + WHR. C57BL/6J mice received HFD + 26 g weight (wt) % WHR or WLD or 13 g wt% WHR + 13 g wt% WLD (WTWD) for 12 weeks. Plasma levels of glucose, cholesterol and triglycerides, insulin resistance and inflammatory markers after overnight fasting were lower, and the abundances of fecal Lactobacillus gasseri and propionic acid were higher in HFD + WLD-fed mice than in HFD + WHR-fed mice. The anti-inflammatory effects of HFD + WTWD were weaker than HFD + WLD but were greater than those in HFD + WHR-fed mice. Abundances of fecal Lactobacillus gasseri and propionic acid in mice receiving HFD + WLD were higher than those in mice fed with HFD + WHR. The abundances of fecal L. gasseri and propionic acid negatively correlated with metabolic and inflammatory markers. The findings of the present study suggest that WLD attenuated metabolic and inflammatory disorders in mice on HFD. Interactions between WLD components and gut microbiota may upregulate fecal SCFAs, and the latter may be attributed to the benefits of WLD on metabolism and inflammation in mice on HFD.

Dynamic Changes in the Nutrient Digestibility, Rumen Fermentation, Serum Parameters of Perinatal Ewes and Their Relationship with Rumen Microbiota

Changes in physiological and biochemical parameters are crucial for the reproductive performance and health of perinatal ewes. This study investigated the temporal variations in feed intake, nutrient digestibility, serum parameters, and ruminal fermentation on days 21, 14, and 7 before lambing (Q21, Q14, and Q7) and days 3, 7, and 14 after lambing (H3, H7, and H14). The results showed that dry matter intake (DMI) and glucose (Glu) gradually decreased (p < 0.05) before lambing and increased (p < 0.05) after lambing. The digestibility of dry matter (DMD), crude protein (CPD), and acid detergent fiber (ADFD) increased (p < 0.05) before lambing, then decreased (p < 0.05) on day H3, and then increased (p < 0.05) on day H14. The rumen pH, NH3-N, and triglycerides (TG) gradually increased (p < 0.05) before lambing and were higher (p < 0.05) on day Q7 than after lambing. The concentrations of acetate, butyrate, and total volatile fatty acids (T-VFA) were lower (p < 0.05) on day Q7 than those on days Q21 and Q14, then increased (p < 0.05) after lambing. Total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) concentrations gradually decreased (p < 0.05) in perinatal ewes. BHBA and NEFA concentrations were lower (p < 0.05) on day Q21 than those from days Q14 to H14. The rumen microbiota compositions were different (p < 0.05) in perinatal ewes, and g_Anaerovibrio, g_Lachnobacterium, and g_Schwartzia were positively correlated (p < 0.05) with DMI, Glu, acetate, propionate, and T-VFA, and negatively correlated (p < 0.05) with LDL-C. g_Bacillus was negatively correlated (p < 0.05) with DMI, Glu, acetate, propionate, butyrate, and T-VFA, but positively correlated (p < 0.05) with rumen pH and LDL-C. In summary, the DMI, nutrient digestibility, rumen fermentation, and serum parameters changed during the perinatal period of ewes, and the changes in DMI, serum glucose, acetate, propionate, and T-VFA were related to the rumen bacteria.

Mechanisms of regulation of glycolipid metabolism by natural compounds in plants: effects on short-chain fatty acids

BACKGROUND

Natural compounds can positively impact health, and various studies suggest that they regulate glucose‒lipid metabolism by influencing short-chain fatty acids (SCFAs). This metabolism is key to maintaining energy balance and normal physiological functions in the body. This review explores how SCFAs regulate glucose and lipid metabolism and the natural compounds that can modulate these processes through SCFAs. This provides a healthier approach to treating glucose and lipid metabolism disorders in the future.

METHODS

This article reviews relevant literature on SCFAs and glycolipid metabolism from PubMed and the Web of Science Core Collection (WoSCC). It also highlights a range of natural compounds, including polysaccharides, anthocyanins, quercetins, resveratrols, carotenoids, and betaines, that can regulate glycolipid metabolism through modulation of the SCFA pathway.

RESULTS

Natural compounds enrich SCFA-producing bacteria, inhibit harmful bacteria, and regulate operational taxonomic unit (OTU) abundance and the intestinal transport rate in the gut microbiota to affect SCFA content in the intestine. However, most studies have been conducted in animals, lack clinical trials, and involve fewer natural compounds that target SCFAs. More research is needed to support the conclusions and to develop healthier interventions.

CONCLUSIONS

SCFAs are crucial for human health and are produced mainly by the gut microbiota via dietary fiber fermentation. Eating foods rich in natural compounds, including fruits, vegetables, tea, and coarse fiber foods, can hinder harmful intestinal bacterial growth and promote beneficial bacterial proliferation, thus increasing SCFA levels and regulating glucose and lipid metabolism. By investigating how these compounds impact glycolipid metabolism via the SCFA pathway, novel insights and directions for treating glucolipid metabolism disorders can be provided.

Gut microbiota-derived acetate attenuates lung injury induced by influenza infection via protecting airway tight junctions

BACKGROUND

Gut microbiota (GM) have been implicated as important regulators of gastrointestinal symptom which is commonly occurred along with respiratory influenza A virus (IAV) infection, suggesting the involvement of the gut-to-lung axis in a host's response to IAV. IAV primarily destroys airway epithelium tight junctions (TJs) and consequently causes acute respiratory disease syndrome. It is known that GM and their metabolism produce an anti-influenza effect, but their role in IAV-induced airway epithelial integrity remains unknown.

METHODS

A mouse model of IAV infection was established. GM were analyzed using 16S rRNA gene sequencing, and short-chain fatty acids (SCFAs) levels were measured. GM depletion and fecal microbiota transplantation (FMT) were conducted to validate the role of GM in IAV infection. A pair-feeding experiment was conducted to reveal whether IAV-induced GM dysbiosis is attributed to impaired food intake. Furthermore, human bronchial epithelial (HBE) cells were cocultured with IAV in the presence or absence of acetate. TJs function was analyzed by paracellular permeability and transepithelial electronic resistance (TEER). The mechanism of how acetate affects TJs integrity was evaluated in HBE cells transfected with G protein-coupled receptor 43 (GPR43) short hairpin RNA (shRNA).

RESULTS

IAV-infected mice exhibited lower relative abundance of acetate-producing bacteria (Bacteroides, Bifidobacterium, and Akkermansia) and decreased acetate levels in gut and serum. These changes were partly caused by a decrease in food consumption (due to anorexia). GM depletion exacerbated and FMT restored IAV-induced lung inflammatory injury. IAV infection suppressed expressions of TJs (occludin, ZO-1) leading to disrupted airway epithelial barrier function as evidenced by decreased TEER and increased permeability. Acetate pretreatment activated GPR43, partially restored IAV-induced airway epithelial barrier function, and reduced inflammatory cytokines levels (TNF-α, IL-6, and IL-1β). Such protective effects of acetate were absent in HBE cells transfected with GPR43 shRNA. Acetate and GPR43 improved TJs in an AMP-activated protein kinase (AMPK)-dependent manner.

CONCLUSION

Collectively, our results demonstrated that GM protected airway TJs by modulating GPR43-AMPK signaling in IAV-induced lung injury. Therefore, improving GM dysbiosis may be a potential therapeutic target for patients with IAV infection.

Galactooligosaccharides: Synthesis, metabolism, bioactivities and food applications

Prebiotics are non-digestible ingredients that exert significant health-promoting effects on hosts. Galactooligosaccharides (GOS) have remarkable prebiotic effects and structural similarity to human milk oligosaccharides. They generally comprise two to eight sugar units, including galactose and glucose, which are synthesized from substrate lactose by microbial β-galactosidase. Enzyme sources from probiotics have received particular interest because of their safety and potential to synthesize specific structures that are particularly metabolized by intestinal probiotics. Owing to advancements in modern analytical techniques, many GOS structures have been identified, which vary in degree of polymerization, glycosidic linkage, and branch location. After intake, GOS adjust gut microbiota which produce short chain fatty acids, and exhibit excellent biological activities. They selectively stimulate the proliferation of probiotics, inhibit the growth and adhesion of pathogenic bacteria, alleviate gastrointestinal, neurological, metabolic and allergic diseases, modulate metabolites production, and adjust ion storage and absorption. Additionally, GOS are safe and stable, with high solubility and clean taste, and thus are widely used as food additives. GOS can improve the appearance, flavor, taste, texture, viscosity, rheological properties, shelf life, and health benefits of food products. This review systemically covers GOS synthesis, structure identifications, metabolism mechanisms, prebiotic bioactivities and wide applications, focusing on recent advances.

Dietary inclusion of Clostridium butyricum cultures alleviated impacts of high-carbohydrate diets in largemouth bass (Micropterus salmoides)

A 60-d feeding trial was conducted to explore the potential regulatory effects of dietary Clostridium butyricum cultures (CBC) supplementation in high-carbohydrate diet (HCD) on carbohydrate utilisation, antioxidant capacity and intestinal microbiota of largemouth bass. Triplicate groups of largemouth bass (average weight 35·03 ± 0·04 g), with a destiny of twenty-eight individuals per tank, were fed low-carbohydrate diet and HCD supplemented with different concentration of CBC (0 %, 0·25 %, 0·50 % and 1·00 %). The results showed that dietary CBC inclusion alleviated the hepatic glycogen accumulation induced by HCD intake. Additionally, the expression of hepatic ampkα1 and insulin signaling pathway-related genes (ira, irb, irs, p13kr1 and akt1) increased linearly with dietary CBC inclusion, which might be associated with the activation of glycolysis-related genes (gk, pfkl and pk). Meanwhile, the expression of intestinal SCFA transport-related genes (ffar3 and mct1) was significantly increased with dietary CBC inclusion. In addition, the hepatic antioxidant capacity was improved with dietary CBC supplementation, as evidenced by linear decrease in malondialdehyde concentration and expression of keap1, and linear increase in antioxidant enzyme activities (total antioxidative capacity, total superoxide dismutase and catalase) and expression of antioxidant enzyme-related genes (nrf2, sod1, sod2 and cat). The analysis of bacterial 16S rRNA V3-4 region indicated that dietary CBC inclusion significantly reduced the enrichment of Firmicutes and potential pathogenic bacteria genus Mycoplasma but significantly elevated the relative abundance of Fusobacteria and Cetobacterium. In summary, dietary CBC inclusion improved carbohydrate utilization, antioxidant capacity and intestinal microbiota of largemouth bass fed HCD.

Butyrate and Propionate are Negatively Correlated with Obesity and Glucose Levels in Patients with Type 2 Diabetes and Obesity

Background

Growing evidence has demonstrated the important roles of gut microbiota and short chain fatty acids, especially acetate, propionate and butyrate, in the development of obesity and metabolic diseases. To date, the effects of acetate, propionate and butyrate on human adiposity and glucose metabolism remain controversial. This study aimed to explore the associations of systemically acetate, propionate and butyrate with obesity and glucose homeostasis in patients with type 2 diabetes (T2D) and obesity.

Methods

A total of 12 patients with T2D and obesity and 8 age- and sex-matched healthy individuals with BMI <24 kg/m2 were enrolled in this study. Height, weight, body composition, blood pressure, biochemical indices, a 75-g oral glucose tolerance test, and plasma acetate, propionate and butyrate were measured at baseline. Then, participants in T2D group were given a weight control therapy, in addition to conventional medication, and all the measurements were repeated 12 months from baseline. The direct segmental multi-frequency bioelectrical impedance analysis was used to assess body composition. Acetate, propionate and butyrate levels were determined by liquid chromatography coupled to tandem mass spectrometry.

Results

Butyrate concentration significantly increased from baseline after obvious weight loss (P<0.05). Correlation analysis showed that propionate was negatively correlated with percent of body fat (PBF) and 2-h plasma glucose (2-h PG) (P<0.05), and butyrate was negatively associated with body mass index, visceral fat area, PBF and 2-h PG (P<0.05). No association was found between acetate and obesity.

Conclusion

Butyrate and propionate are negatively correlated with obesity and glucose levels in patients with T2D and obesity.

Highland barley β-glucan supplementation attenuated hepatic lipid accumulation in Western diet-induced non-alcoholic fatty liver disease mice by modulating gut microbiota

Non-alcoholic fatty liver disease (NAFLD) has become one of the most common chronic liver diseases worldwide. NAFLD is caused by numerous factors, including the genetic susceptibility, oxidative stress, unhealthy diet, and gut microbiota dysbiosis. Among these, gut microbiota is a key factor and plays an important role in the development of NAFLD. Therefore, modulating the composition and structure of gut microbiota might provide a new intervention strategy for NAFLD. Highland barley β-glucan (HBG) is a polysaccharide that can interact with gut microbiota after entering the lower gastrointestinal tract and subsequently improves NAFLD. Therefore, a Western diet was used to induce NAFLD in mouse models and the intervention effects and underlying molecular mechanisms of HBG on NAFLD mice based on gut microbiota were explored. The results indicated that HBG could regulate the composition of gut microbiota in NAFLD mice. In particular, HBG increased the abundance of short-chain fatty acids (SCFA)-producing bacteria (Prevotella-9, Bacteroides, and Roseburia) as well as SCFA contents. The increase in SCFA contents might activate the adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) signaling pathway, thereby improving the liver lipid metabolism disorder and reducing liver lipid deposition.

Recent advances in the extraction, purification, structural-property correlations, and antiobesity mechanism of traditional Chinese medicine-derived polysaccharides: a review

Traditional Chinese medicine (TCM) has displayed preventive and therapeutic effects on many complex diseases. As natural biological macromolecules, TCM-derived antiobesogenic polysaccharides (TCMPOs) exhibit notable weight-loss effects and are seen to be a viable tactic in the fight against obesity. Current studies demonstrate that the antiobesity activity of TCMPOs is closely related to their structural characteristics, which could be affected by the extraction and purification methods. Therefore, the extraction, purification and structural-property correlations of TCMPOs were discussed. Investigation of the antiobesity mechanism of TCMPOs is also essential for their improved application. Herein, the possible antiobesity mechanisms of TCMPOs are systematically summarized: (1) modulation of appetite and satiety effects, (2) suppression of fat absorption and synthesis, (3) alteration of the gut microbiota and their metabolites, and (4) protection of intestinal barriers. This collated information could provide some insights and offer a new therapeutic approach for the management and prevention of obesity.

The impact of lipopolysaccharide on cerebrovascular function and cognition resulting from obesity-induced gut dysbiosis

Obesity is a worldwide epidemic coinciding with a concomitant increase in the incidence of neurodegenerative diseases, particularly dementia. Obesity is characterised by increased adiposity, chronic low-grade systemic inflammation, and oxidative stress, which promote endothelial dysfunction. Endothelial dysfunction reduces cerebrovascular function leading to reduced cerebral blood flow and, eventually, cognitive decline, thus predisposing to a neurodegenerative disease. Obesity is also characterised by gut dysbiosis and a subsequent increase in the lipopolysaccharide which increasingly activates toll-like receptor 4 (TLR4) and further promotes chronic low-grade systemic inflammation. This also disrupts the crosstalk within the gut-brain axis, thus influencing the functions of the central nervous system, including cognition. However, the mechanisms by which obesity-related increases in oxidative stress, inflammation and endothelial dysfunction are driven by, or associated with, increased systemic lipopolysaccharide leading to reduced cerebrovascular function and cognition, beyond normal ageing, have not been elucidated. Hence, this review examines how increased concentrations of lipopolysaccharide and the subsequent increased TLR4 activation observed in obesity exacerbate the development of obesity-induced reductions in cerebrovascular function and cognition.

Akkermansia muciniphila protects the intestine from irradiation-induced injury by secretion of propionic acid

Intestinal dysbiosis frequently occurs in abdominal radiotherapy and contributes to irradiation (IR)-induced intestinal damage and inflammation. Akkermansia muciniphila (A. muciniphila) is a recently characterized probiotic, which is critical for maintaining the dynamics of the intestinal mucus layer and preserving intestinal microbiota homeostasis. However, the role of A. muciniphila in the alleviation of radiation enteritis remains unknown. In this study, we reported that the abundance of A. muciniphila was markedly reduced in the intestines of mice exposed to abdominal IR and in the feces of patients who received abdominal radiotherapy. Abundance of A. muciniphila in feces of radiotherapy patients was negatively correlated with the duration of diarrhea in patients. Administration of A. muciniphila substantially mitigated IR-induced intestinal damage and prevented mouse death. Analyzing the metabolic products of A. muciniphila revealed that propionic acid, a short-chain fatty acid secreted by the microbe, mediated the radioprotective effect. We further demonstrated that propionic acid bound to G-protein coupled receptor 43 (GRP43) on the surface of intestinal epithelia and increased histone acetylation and hence enhanced the expression of tight junction proteins occludin and ZO-1 and elevated the level of mucins, leading to enhanced integrity of intestinal epithelial barrier and reduced radiation-induced intestinal damage. Metformin, a first-line agent for the treatment of type II diabetes, promoted intestinal epithelial barrier integrity and reduced radiation intestinal damage through increasing the abundance of A. muciniphila. Together, our results demonstrated that A. muciniphila plays a critical role in the reduction of abdominal IR-induced intestinal damage. Application of probiotics or their regulators, such as metformin, could be an effective treatment for the protection of radiation exposure-damaged intestine.

ACT001 Alleviates chronic kidney injury induced by a high-fat diet in mice through the GPR43/AMPK pathway

BACKGROUND

Roughly 10 -15% of global populace suffer from Chronic Kidney Disease(CKD). A major secondary disease that can progress to end-stage renal disease (ESRD) is obesity-associated kidney disease (ORG). Although clinical management strategies are currently available, morbidity and mortality rates are increasing. Thus, new solutions are needed. Intestinal permeability, systemic inflammation, and aberrant intestinal metabolites have all been linked to ORG.

PURPOSE

ACT001 has anti-inflammatory, redox-regulatory and antitumour activities. The current study was designed to examine how ACT001 affects ORG and analyze the fundamental processes.

METHODS

A high-fat diet (HFD) was used to generate ORG in female C57BL/6 J mice. ORG mice were divided into three groups at random: HFD, HFD + ACT001, HFD + polyphosphocholine (PPC). To assess renal and colonic damage, periodic acid-Schiff (PAS) and hematoxylin-eosin (HE) staining were used. Following that, renal inflammation, oxidative stress, lipid deposition, colonic inflammation, and intestinal permeability were evaluated by protein blotting, polymerase chain reaction (PCR), immunohistochemistry, and immunofluorescence staining. Lastly, the SCFAs content was assessed by gas chromatographymass spectrometry.

RESULTS

Mice in the HFD group displayed more severe albuminuria, glomerular hypertrophy, renal oxidative damage, inflammation, and lipid accumulation than mice with the normal diet (ND) group, as well as lower levels of intestinal SCFA valproic acid, colonic inflammation, and tight junction protein downregulation. ACT001 treatment restores the content of valproic acid in intestinal SCFAs, promotes the binding of SCFAs to renal GPR43, activates the AMPK signalling pathway. Therefore, it promotes the Nrf2-Keap1 signalling pathway and inhibits the NF-κB signalling pathway. SCFAs, additionally, augment colonic GPR43 concentrations, diminishing NLRP3 inflammasome expression and restoring ZO-1 and occludin protein levels.

CONCLUSION

This study is the first to look at ACT001's potential as a treatment for obesity-related kidney disease. Regulating GPR43 and AMPK signalling pathways, By controlling the GPR43 and AMPK signalling pathways, ACT001 improves colitis and the intestinal mucosal barrier, decreases renal lipid deposition, and suppresses inflammation and oxidative stress in the kidneys. According to this study, ACT001 could be a viable ORG therapy option.

Angelica sinensis polysaccharide ameliorates nonalcoholic fatty liver disease via restoring estrogen-related receptor α expression in liver

Angelica sinensis polysaccharide (ASP) showed increasingly recognized hepatoprotective effects and lipid regulation. Because polysaccharides are typically degraded into fragments or short-chain fatty acids in the gut, rather than being absorbed in their intact form, it is worth pondering why ASP can regulate hepatic lipid metabolism and protect the liver from damage caused by lipid accumulation. In vivo and in vitro nonalcoholic fatty liver disease (NAFLD) models with lipid accumulation were established to investigate the effect and potential mechanisms of ASP on hepatic fat accumulation. Our results showed that ASP remodeled the composition and abundance of the gut microbiota in high-fat diet-fed mice and increased their levels of propionate (0.92 ± 0.30 × 107 vs. 2.13 ± 0.52 × 107 ) and butyrate (1.83 ± 1.31 × 107 vs. 6.39 ± 1.44 × 107 ). Sodium propionate significantly increased the expression of estrogen-related receptor α (ERRα) in liver cells (400 mM sodium propionate for 2.19-fold increase) and alleviated the progress of NAFLD in methionine-choline-deficient diet model. Taken together, our study demonstrated that ASP can regulate hepatic lipid metabolism via propionate/ERRα pathway and ultimately relieving NAFLD. Our findings demonstrate that ASP can be used as a health care product or food supplement to prevent NAFLD.

Development and Validation of a Propionate Metabolism-Related Gene Signature for Prognostic Prediction of Hepatocellular Carcinoma

Background

Studies have demonstrated that propionate metabolism-related genes (PMRGs) are associated with cancer progression. PMRGs are not known to be involved in Hepatocellular carcinoma (HCC).

Methods

In this study, The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases were accessed for HCC-related transcriptome data and clinical information. First, DE-PMRGs were derived by intersecting PMRGs and DEGs between HCC tissues and normal controls. The clusterProfiler R package was then used to enrich DE-PMRGs. In addition, biomarkers of HCC were identified, and a prognostic model was developed. Using functional analysis and tumor microenvironment analysis, new insights were obtained into HCC. The expression of biomarkers was validated using quantitative real-time polymerase chain reaction (qRT-PCR).

Results

132 DE-PMRGs were obtained by intersecting 3690 DEGs and 291 PMRGs. Steroid and organic acid metabolism were associated with these genes. For the construction of the risk model for HCC samples, five biomarkers were identified, including Acyl-CoA dehydrogenase short chain (ACADS), CYP19A1, formiminotransferase cyclodeaminase (FTCD), glucose-6-phosphate dehydrogenase (G6PD), and glutamic-oxaloacetic transaminase (GOT2). ACADS, FTCD, and GOT2 were positive factors, whereas CYP19A1 and G6PD were negative. HCC patients with AUC greater than 0.6 were predicted to survive 1/2/3/4/5 years, indicating decent efficiency of the model. The probability of 1/3/5-survival for HCC was also predicted by the nomogram using the risk score, pathologic T stage, and cancer status. Moreover, functional enrichment analysis revealed the high-risk genes were associated with invasion and epithelial-mesenchymal transition. Significantly, immune cell infiltration and immune checkpoint expression were linked to HCC development.

Conclusion

This study identified five biomarkers of propionate metabolism that can predict HCC prognosis. This finding may provide a deeper understanding of PMRG function in HCC.

Gut-derived short-chain fatty acids bridge cardiac and systemic metabolism and immunity in heart failure

Heart failure (HF) represents a group of complex clinical syndromes with high morbidity and mortality and has a significant global health burden. Inflammation and metabolic disorders are closely related to the development of HF, which are complex and depend on the severity and type of HF and common metabolic comorbidities such as obesity and diabetes. An increasing body of evidence indicates the importance of short-chain fatty acids (SCFAs) in regulating cardiac function. In addition, SCFAs represent a unique class of metabolites and play a distinct role in shaping systemic immunity and metabolism. In this review, we reveal the role of SCFAs as a link between metabolism and immunity, which regulate cardiac and systemic immune and metabolic systems by acting as energy substrates, inhibiting the expression of histone deacetylase (HDAC) regulated genes and activating G protein-coupled receptors (GPCRs) signaling. Ultimately cardiac efficiency is improved, cardiac inflammation alleviated and cardiac function in failing hearts enhanced. In conclusion, SCFAs represent a new therapeutic approach for HF.

Penthorum chinense Pursh improves type 2 diabetes mellitus via modulating gut microbiota in db/db mice

Penthorum chinense Pursh (P. chinense) has been traditionally used as hepatoprotective food and medicine for hundreds of years due to its significant antioxidant and anti-inflammatory activities. However, the efficacy and mechanisms of action of P. chinense in type 2 diabetes mellitus were not fully understood. In this study, we found that P. chinense extract (PCP) supplementation resulted in reduced body weight and hyperglycemia, improved pancreatic tissue injury and insulin sensitivity, and decreased inflammatory cytokines expression in spontaneously diabetic db/db mice. 16S rRNA gene sequencing of fecal samples showed that PCP administration decreased the abundance of Firmicutes and increased the proportion of Bacteroidetes at the phylum level. Moreover, Muribaculum, Barnesiella, Prevotella, and Mucinivorans were enriched, with Desulfovibrio and Lactobacillus lowered at the genus level in db/db mice with PCP supplementation. These results suggested that PCP may ameliorate hyperglycemia, insulin resistance, and inflammation by remodeling the gut microbiota in db/db mice.

Role of hypoxia in cellular senescence

Senescent cells persist and continuously secrete proinflammatory and tissue-remodeling molecules that poison surrounding cells, leading to various age-related diseases, including diabetes, atherosclerosis, and Alzheimer's disease. The underlying mechanism of cellular senescence has not yet been fully explored. Emerging evidence indicates that hypoxia is involved in the regulation of cellular senescence. Hypoxia-inducible factor (HIF)- 1α accumulates under hypoxic conditions and regulates cellular senescence by modulating the levels of the senescence markers p16, p53, lamin B1, and cyclin D1. Hypoxia is a critical condition for maintaining tumor immune evasion, which is promoted by driving the expression of genetic factors (such as p53 and CD47) while triggering immunosenescence. Under hypoxic conditions, autophagy is activated by targeting BCL-2/adenovirus E1B 19-kDa interacting protein 3, which subsequently induces p21WAF1/CIP1 as well as p16Ink4a and increases β-galactosidase (β-gal) activity, thereby inducing cellular senescence. Deletion of the p21 gene increases the activity of the hypoxia response regulator poly (ADP-ribose) polymerase-1 (PARP-1) and the level of nonhomologous end joining (NHEJ) proteins, repairs DNA double-strand breaks, and alleviates cellular senescence. Moreover, cellular senescence is associated with intestinal dysbiosis and an accumulation of D-galactose derived from the gut microbiota. Chronic hypoxia leads to a striking reduction in the amount of Lactobacillus and D-galactose-degrading enzymes in the gut, producing excess reactive oxygen species (ROS) and inducing senescence in bone marrow mesenchymal stem cells. Exosomal microRNAs (miRNAs) and long noncoding RNAs (lncRNAs) play important roles in cellular senescence. miR-424-5p levels are decreased under hypoxia, whereas lncRNA-MALAT1 levels are increased, both of which induce cellular senescence. The present review focuses on recent advances in understanding the role of hypoxia in cellular senescence. The effects of HIFs, immune evasion, PARP-1, gut microbiota, and exosomal mRNA in hypoxia-mediated cell senescence are specifically discussed. This review increases our understanding of the mechanism of hypoxia-mediated cellular senescence and provides new clues for anti-aging processes and the treatment of aging-related diseases.

Microbial-Derived Tryptophan Metabolites and Their Role in Neurological Disease: Anthranilic Acid and Anthranilic Acid Derivatives

The gut microbiome provides the host access to otherwise indigestible nutrients, which are often further metabolized by the microbiome into bioactive components. The gut microbiome can also shift the balance of host-produced compounds, which may alter host health. One precursor to bioactive metabolites is the essential aromatic amino acid tryptophan. Tryptophan is mostly shunted into the kynurenine pathway but is also the primary metabolite for serotonin production and the bacterial indole pathway. Balance between tryptophan-derived bioactive metabolites is crucial for neurological homeostasis and metabolic imbalance can trigger or exacerbate neurological diseases. Alzheimer's, depression, and schizophrenia have been linked to diverging levels of tryptophan-derived anthranilic, kynurenic, and quinolinic acid. Anthranilic acid from collective microbiome metabolism plays a complex but important role in systemic host health. Although anthranilic acid and its metabolic products are of great importance for host-microbe interaction in neurological health, literature examining the mechanistic relationships between microbial production, host regulation, and neurological diseases is scarce and at times conflicting. This narrative review provides an overview of the current understanding of anthranilic acid's role in neurological health and disease, with particular focus on the contribution of the gut microbiome, the gut-brain axis, and the involvement of the three major tryptophan pathways.

The pathogenic role of intestinal flora metabolites in diabetic nephropathy

With the increasing incidence of diabetes, diabetic kidney disease has become a major cause of chronic kidney disease. The role of the gut microbiota in diabetes and its related complications have been extensively investigated; the modulatory effect of the gut microbiota on the host depends on several gut microbial metabolites, particularly short-chain fatty acids, secondary bile acids, and trimethylamine N-oxide. In this review, we focused on the evidence related to the pathogenic role of each of the gut microbial metabolites in diabetic nephropathy. The main novel therapies targeting the gut microbiota include probiotics, dietary prebiotics, synbiotic supplements, and faecal microbiota transplants, although there is no standard treatment principle. Further research is therefore needed to elucidate the link between gut microbes and diabetic nephropathy, and more therapeutic targets should be explored to treat diabetic nephropathy with dysbiosis of the gut microbes.

Gut Microbiota and Aging: Traditional Chinese Medicine and Modern Medicine

The changing composition of gut microbiota, much like aging, accompanies people throughout their lives, and the inextricable relationship between both has recently attracted extensive attention as well. Modern medical research has revealed that a series of changes in gut microbiota are involved in the aging process of organisms, which may be because gut microbiota modulates aging-related changes related to innate immunity and cognitive function. At present, there is no definite and effective method to delay aging. However, Nobel laureate Tu Youyou's research on artemisinin has inspired researchers to study the importance of Traditional Chinese Medicine (TCM). TCM, as an ancient alternative medicine, has unique advantages in preventive health care and in treating diseases as it already has formed an independent understanding of the aging system. TCM practitioners believe that the mechanism of aging is mainly deficiency, and pathological states such as blood stasis, qi stagnation and phlegm coagulation can exacerbate the process of aging, which involves a series of organs, including the brain, kidney, heart, liver and spleen. Our current understanding of aging has led us to realise that TCM can indeed make some beneficial changes, such as the improvement of cognitive impairment. However, due to the multi-component and multi-target nature of TCM, the exploration of its mechanism of action has become extremely complex. While analysing the relationship between gut microbiota and aging, this review explores the similarities and differences in treatment methods and mechanisms between TCM and Modern Medicine, in order to explore a new approach that combines TCM and Modern Medicine to regulate gut microbiota, improve immunity and delay aging.

Impact of the gut microbiota on angiotensin Ⅱ-related disorders and its mechanisms

The renin-angiotensin system (RAS) consists of multiple angiotensin peptides and performs various biological functions mediated by distinct receptors. Angiotensin II (Ang II) is the major effector of the RAS and affects the occurrence and development of inflammation, diabetes mellitus and its complications, hypertension, and end-organ damage via the Ang II type 1 receptor. Recently, considerable interest has been given to the association and interaction between the gut microbiota and host. Increasing evidence suggests that the gut microbiota may contribute to cardiovascular diseases, obesity, type 2 diabetes mellitus, chronic inflammatory diseases, and chronic kidney disease. Recent data have confirmed that Ang II can induce an imbalance in the intestinal flora and further aggravate disease progression. Furthermore, angiotensin converting enzyme 2 is another player in RAS, alleviates the deleterious effects of Ang II, modulates gut microbial dysbiosis, local and systemic immune responses associated with coronavirus disease 19. Due to the complicated etiology of pathologies, the precise mechanisms that link disease processes with specific characteristics of the gut microbiota remain obscure. This review aims to highlight the complex interactions between the gut microbiota and its metabolites in Ang II-related disease progression, and summarize the possible mechanisms. Deciphering these mechanisms will provide a theoretical basis for novel therapeutic strategies for disease prevention and treatment. Finally, we discuss therapies targeting the gut microbiota to treat Ang II-related disorders.

Steroid hormone 20-hydroxyecdysone disturbs fat body lipid metabolism and negatively regulates gluconeogenesis in Hyphantria cunea larvae

The steroid hormone 20-hydroxyecdysone (20E) has been described to regulate fat body lipid metabolism in insects, but its accurate regulatory mechanism, especially the crosstalk between 20E-induced lipid metabolism and gluconeogenesis remains largely unclear. Here, we specially investigated the effect of 20E on lipid metabolism and gluconeogenesis in the fat body of Hyphantria cunea larvae, a notorious pest in forestry. Lipidomics analysis showed that a total of 1 907 lipid species were identified in the fat body of H. cunea larvae assigned to 6 groups and 48 lipid classes. The differentially abundant lipids analysis showed a significant difference between 20E-treated and control samples, indicating that 20E caused a remarkable alteration of lipidomics profiles in the fat body of H. cunea larvae. Further studies demonstrated that 20E accelerated fatty acid β-oxidation, inhibited lipid synthesis, and promoted lipolysis. Meanwhile, the activities of pyruvate carboxylase, phosphoenolpyruvate carboxykinase, fructose-1,6-bisphosphatase, and glucose-6-phosphatase were dramatically suppressed by 20E in the fat body of H. cunea larvae. As well, the transcriptions of genes encoding these 4 rate-limiting gluconeogenic enzymes were significantly downregulated in the fat body of H. cunea larvae after treatment with 20E. Taken together, our results revealed that 20E disturbed fat body lipid homeostasis, accelerated fatty acid β-oxidation and promoted lipolysis, but negatively regulated gluconeogenesis in H. cunea larvae. The findings might provide a new insight into hormonal regulation of glucose and lipid metabolism in insect fat body.

Short-Chain Fatty-Acid-Producing Bacteria: Key Components of the Human Gut Microbiota

Short-chain fatty acids (SCFAs) play a key role in health and disease, as they regulate gut homeostasis and their deficiency is involved in the pathogenesis of several disorders, including inflammatory bowel diseases, colorectal cancer, and cardiometabolic disorders. SCFAs are metabolites of specific bacterial taxa of the human gut microbiota, and their production is influenced by specific foods or food supplements, mainly prebiotics, by the direct fostering of these taxa. This Review provides an overview of SCFAs' roles and functions, and of SCFA-producing bacteria, from their microbiological characteristics and taxonomy to the biochemical process that lead to the release of SCFAs. Moreover, we will describe the potential therapeutic approaches to boost the levels of SCFAs in the human gut and treat different related diseases.

Gut microbiome as a therapeutic target for liver diseases

The prominent role of gut in regulating the physiology of different organs in a human body is increasingly acknowledged, to which the bidirectional communication between gut and liver is no exception. Liver health is modulated via different key components of gut-liver axis. The gut-derived products mainly generated from dietary components, microbial metabolites, toxins, or other antigens are sensed and transported to the liver through portal vein to which liver responds by secreting bile acids and antibodies. Therefore, maintaining a healthy gut microbiome can promote homeostasis of this gut-liver axis by regulating the intestinal barrier function and reducing the antigenic molecules. Conversely, liver secretions also regulate the gut microbiome composition. Disturbed homeostasis allows luminal antigens to reach liver leading to impaired liver functioning and instigating liver disorders. The perturbations in gut microbiome, permeability, and bile acid pool have been associated with several liver disorders, although precise mechanisms remain largely unresolved. Herein, we discuss functional fingerprints of a healthy gut-liver axis while contemplating mechanistic understanding of pathophysiology of liver diseases and plausible role of gut dysbiosis in different diseased states of liver. Further, novel therapeutic approaches to prevent the severity of liver disorders are discussed in this review.

Production of Food-Derived Bioactive Peptides with Potential Application in the Management of Diabetes and Obesity: A Review

The prevalence of diabetes mellitus and obesity is increasing worldwide. Bioactive peptides are naturally present in foods or in food-derived proteins. Recent research has shown that these bioactive peptides have an array of possible health benefits in the management of diabetes and obesity. First, this review will summarize the top-down and bottom-up production methods of the bioactive peptides from different protein sources. Second, the digestibility, bioavailability, and metabolic fate of the bioactive peptides are discussed. Last, the present review will discuss and explore the mechanisms by which these bioactive peptides help against obesity and diabetes based on in vitro and in vivo studies. Although several clinical studies have demonstrated that bioactive peptides are beneficial in alleviating diabetes and obesity, more double-blind randomized controlled trials are needed in the future. This review has provided novel insights into the potential of food-derived bioactive peptides as functional foods or nutraceuticals to manage obesity and diabetes.

A Combination of Acetate, Propionate, and Butyrate Increases Glucose Uptake in C2C12 Myotubes

BACKGROUND

Dietary fibers are subjected to saccharolytic fermentation by the gut microbiota, leading to the production of short chain fatty acids (SCFAs). SCFAs act as signaling molecules to different cells in the human body including skeletal muscle cells. The ability of SCFAs to induce multiple signaling pathways, involving nuclear erythroid 2-related factor 2 (Nrf2), may contribute to the redox balance, and thereby may be involved in glucose homeostasis. The aim of this study is to investigate whether SCFAs increase glucose uptake by upregulating the endogenous antioxidant glutathione (GSH) in C2C12 myotubes.

METHODS

C2C12 myotubes were exposed to 1, 5, or 20 mM of single (acetate, propionate, or butyrate) or mixtures of SCFAs for 24 h. Cytotoxicity, glucose uptake, and intracellular GSH levels were measured.

RESULTS

20 mM of mixture but not separate SCFAs induced cytotoxicity. Exposure to a mixture of SCFAs at 5 mM increased glucose uptake in myotubes, while 20 mM of propionate, butyrate, and mixtures decreased glucose uptake. Exposure to single SCFAs increased GSH levels in myotubes; however, SCFAs did not prevent the menadione-induced decrease in glucose uptake in myotubes.

CONCLUSIONS

The effect of SCFAs on modulating glucose uptake in myotubes is not associated with the effect on endogenous GSH levels.

Study on mechanism of action of total flavonoids from Cortex Juglandis Mandshuricae against alcoholic liver disease based on "gut-liver axis"

The objective of this study was to investigate the effects and molecular mechanisms of total flavonoids from Cortex Juglandis Mandshuricae (TFC) on preventing alcohol-induced chronic liver injury and regulating gut microbiota in mice. The results showed that oral administration of TFC significantly attenuated alcoholic liver injury in mice. TFC improved lipid accumulation in mice with chronic alcoholic liver injury through activation of the AMPK/PPARα pathway. In addition, TFC maintained the integrity of the intestinal barrier in alcoholic mice, reducing endotoxin leakage from the intestine and further inhibiting the TLR4/NF-κB inflammatory pathway. More importantly, TFC regulated the intestinal microbiota composition and certain bacteria, including Akkermansia muciniphila, Lactobacillus and others. At the same time, reduced levels of short-chain fatty acids due to alcohol consumption were restored. In summary, TFC upregulated AMPK/PPARα signaling pathway to improve hepatic fat accumulation and oxidative stress; TFC positively regulated intestinal flora composition to reduce intestinal disorders caused by alcohol consumption, and further inhibited alcohol-induced inflammatory responses through the intestinal-liver axis. The above findings may be the mechanism of TFC's pharmacological effects against alcoholic liver injury.

Polysaccharide-rich fractions from Enteromorpha prolifera improve hepatic steatosis and gut barrier integrity in high-fat diet-induced obese mice linking to modulation of gut microbiota

Polysaccharides from Enteromorpha prolifera (EP) possess important benefits in the management of obesity and associated metabolic diseases, but to date, the underlying mechanism linking this alleviative effect of EP to gut microbiota remains obscure. This study aimed to investigate the effects of EP in improving lipid metabolism disorders and intestinal barrier disruption in mice with high-fat diet (HFD), and its association with modulation of gut microbiota. C57BL/6 mice were fed a control diet or a HFD with or without 5% EP for 12 weeks. Factors related to lipid metabolism, insulin signaling and intestinal barrier integrity, as well as the involvement of gut microbiota and metabolites, were measured. EP supplementation reduced HFD-induced adiposity and mitigated insulin resistance, hepatic steatosis and elevation of serum lipopolysaccharides (LPS). HFD impaired intestinal barrier integrity while improved due to EP. Moreover, EP administration ameliorated HFD-induced gut dysbiosis, as revealed by the increased short-chain fatty acid (SCFA)-producing bacteria (e.g., Bacteroides, Parabacteroides, Alloprevotella, and Ruminococcus) and gut barrier-protective Akkermansia muciniphila and decreased endotoxin-producing bacteria (e.g., Desulfovibrionaceae and Bilophila), accompanied by enrichment in intestinal SCFA content and reduction in circulating LPS level. The change of dominant bacterial genera is significantly correlated with improved metabolic profiles and intestinal permeability induced by EP. In conclusion, our results indicate that EP can attenuate HFD-induced metabolic disorders along with restoration of gut barrier integrity and lowering of circulating endotoxin, and these improvements are associated with modulation of gut microbiota composition and related metabolites. These data deepen mechanistic understanding of the anti-obesity and metabolic improving effects of EP.

Gut microbiota: The key to the treatment of metabolic syndrome in traditional Chinese medicine - a case study of diabetes and nonalcoholic fatty liver disease

Metabolic syndrome mainly includes obesity, type 2 diabetes (T2DM), alcoholic fatty liver (NAFLD) and cardiovascular diseases. According to the ancient experience philosophy of Yin-Yang, monarch-minister compatibility of traditional Chinese medicine, prescription is given to treat diseases, which has the advantages of small toxic and side effects and quick effect. However, due to the diversity of traditional Chinese medicine ingredients and doubts about the treatment theory of traditional Chinese medicine, the mechanism of traditional Chinese medicine is still in doubt. Gastrointestinal tract is an important part of human environment, and participates in the occurrence and development of diseases. In recent years, more and more TCM researches have made intestinal microbiome a new frontier for understanding and treating diseases. Clinically, nonalcoholic fatty liver disease (NAFLD) and diabetes mellitus (DM) often co-occur. Our aim is to explain the mechanism of interaction between gastrointestinal microbiome and traditional Chinese medicine (TCM) or traditional Chinese medicine formula to treat DM and NAFLD. Traditional Chinese medicine may treat these two diseases by influencing the composition of intestinal microorganisms, regulating the metabolism of intestinal microorganisms and transforming Chinese medicinal compounds.

Utility of Human Relevant Preclinical Animal Models in Navigating NAFLD to MAFLD Paradigm

Fatty liver disease is an emerging contributor to disease burden worldwide. The past decades of work established the heterogeneous nature of non-alcoholic fatty liver disease (NAFLD) etiology and systemic contributions to the pathogenesis of the disease. This called for the proposal of a redefinition in 2020 to that of metabolic dysfunction-associated fatty liver disease (MAFLD) to better reflect the current understanding of the disease. To date, several clinical cohort studies comparing NAFLD and MAFLD hint at the relevancy of the new nomenclature in enriching for patients with more severe hepatic injury and extrahepatic comorbidities. However, the underlying systemic pathogenesis is still not fully understood. Preclinical animal models have been imperative in elucidating key biological mechanisms in various contexts, including intrahepatic disease progression, interorgan crosstalk and systemic dysregulation. Furthermore, they are integral in developing novel therapeutics against MAFLD. However, substantial contextual variabilities exist across different models due to the lack of standardization in several aspects. As such, it is crucial to understand the strengths and weaknesses of existing models to better align them to the human condition. In this review, we consolidate the implications arising from the change in nomenclature and summarize MAFLD pathogenesis. Subsequently, we provide an updated evaluation of existing MAFLD preclinical models in alignment with the new definitions and perspectives to improve their translational relevance.

The Intestinal Microbiota and Short-Chain Fatty Acids in Association with Advanced Metrics of Glycemia and Adiposity Among Young Adults with Type 1 Diabetes and Overweight or Obesity

Background

Comanagement of glycemia and adiposity is the cornerstone of cardiometabolic risk reduction in type 1 diabetes (T1D), but targets are often not met. The intestinal microbiota and microbiota-derived short-chain fatty acids (SCFAs) influence glycemia and adiposity but have not been sufficiently investigated in longstanding T1D.

Objectives

We evaluated the hypothesis that an increased abundance of SCFA-producing gut microbes, fecal SCFAs, and intestinal microbial diversity were associated with improved glycemia but increased adiposity in young adults with longstanding T1D.

Methods

Participants provided stool samples at ≤4 time points (NCT03651622: https://clinicaltrials.gov/ct2/show/NCT03651622). Sequencing of the 16S ribosomal RNA gene measured abundances of SCFA-producing intestinal microbes. GC-MS measured total and specific SCFAs (acetate, butyrate, propionate). DXA (body fat percentage and percentage lean mass) and anthropometrics (BMI) measured adiposity. Continuous glucose monitoring [percentage of time in range (70-180 mg/dL), above range (>180 mg/dL), and below range (54-69 mg/dL)] and glycated hemoglobin (i.e., HbA1c) assessed glycemia. Adjusted and Bonferroni-corrected generalized estimating equations modeled the associations of SCFA-producing gut microbes, fecal SCFAs, and intestinal microbial diversity with glycemia and adiposity. COVID-19 interrupted data collection, so models were repeated restricted to pre-COVID-19 visits.

Results

Data were available for ≤45 participants at 101 visits (including 40 participants at 54 visits pre-COVID-19). Abundance of Eubacterium hallii was associated inversely with BMI (all data). Pre-COVID-19, increased fecal propionate was associated with increased percentage of time above range and reduced percentage of time in target and below range; and abundances of 3 SCFA-producing taxa (Ruminococcus gnavus, Eubacterium ventriosum, and Lachnospira) were associated inversely with body fat percentage, of which two microbes were positively associated with percentage lean mass. Abundance of Anaerostipes was associated with reduced percentage of time in range (all data) and with increased body fat percentage and reduced percentage lean mass (pre-COVID-19).

Conclusions

Unexpectedly, fecal propionate was associated with detriment to glycemia, whereas most SCFA-producing intestinal microbes were associated with benefit to adiposity. Future studies should confirm these associations and determine their potential causal linkages in T1D.This study is registered at clinical.trials.gov (NCT03651622; https://clinicaltrials.gov/ct2/show/NCT03651622).

Health Benefits and Side Effects of Short-Chain Fatty Acids

The gut microbiota and their metabolites could play an important role in health and diseases of human beings. Short-chain fatty acids (SCFAs) are mainly produced by gut microbiome fermentation of dietary fiber and could also be produced by bacteria of the skin and vagina. Acetate, propionate, and butyrate are three major SCFAs, and their bioactivities have been widely studied. The SCFAs have many health benefits, such as anti-inflammatory, immunoregulatory, anti-obesity, anti-diabetes, anticancer, cardiovascular protective, hepatoprotective, and neuroprotective activities. This paper summarizes health benefits and side effects of SCFAs with a special attention paid to the mechanisms of action. This paper provides better support for people eating dietary fiber as well as ways for dietary fiber to be developed into functional food to prevent diseases.

Mulberry Leaf Extract Improves Metabolic Syndrome by Alleviating Lipid Accumulation In Vitro and In Vivo

Metabolic syndrome (MS) is a metabolic disease with multiple complications. Mulberry leaf extract (MLE) is rich in flavonoids and has great potential in alleviating glucose and lipid metabolism disorders. This study evaluated the effect and mechanism of MLE on the alleviation of MS. The components of the MLE were analyzed, and then the regulation of lipid metabolism by MLE in vitro and in vivo was determined. In a hepatocyte model of oleic acid-induced lipid accumulation, it was found that MLE alleviated lipid accumulation and decreased the expression of genes involved in lipogenesis. Furthermore, MLE improved obesity, insulin resistance, plasma lipid profile, and liver function in MS mice after a 15-week intervention. MLE decreased the expression of SREBP1, ACC, and FAS through the AMPK signaling pathway to inhibit lipid synthesis and increase the level of CPT1A to promote lipid decomposition to achieve its hypolipidemic effect. Meanwhile, MLE was also shown to affect the composition of the gut microbiota and the production of short-chain fatty acids, which contributed to the alleviation of lipid accumulation. Our results suggest that MLE can improve MS by improving lipid metabolism through multiple mechanisms and can be developed into dietary supplements for the improvement of MS.

Short-Chain Fatty Acids in the Metabolism of Heart Failure – Rethinking the Fat Stigma

Heart failure (HF) remains a disease with immense global health burden. During the development of HF, the myocardium and therefore cardiac metabolism undergoes specific changes, with decreased long-chain fatty acid oxidation and increased anaerobic glycolysis, diminishing the overall energy yield. Based on the dogma that the failing heart is oxygen-deprived and on the fact that carbohydrates are more oxygen-efficient than FA, metabolic HF drugs have so far aimed to stimulate glucose oxidation or inhibit FA oxidation. Unfortunately, these treatments have failed to provide meaningful clinical benefits. We believe it is time to rethink the concept that fat is harmful to the failing heart. In this review we discuss accumulating evidence that short-chain fatty acids (SCFAs) may be an effective fuel for the failing heart. In contrast to long-chain fatty acids, SCFAs are readily taken up and oxidized by the heart and could serve as a nutraceutical treatment strategy. In addition, we discuss how SCFAs activate pathways that increase long chain fatty acid oxidation, which could help increase the overall energy availability. Another potential beneficial effect we discuss lies within the anti-inflammatory effect of SCFAs, which has shown to inhibit cardiac fibrosis – a key pathological process in the development of HF.

Glucagon, cyclic AMP, and hepatic glucose mobilization: A half‐century of uncertainty

For at least 50 years, the prevailing view has been that the adenylate cyclase (AC)/cyclic AMP (cAMP)/protein kinase A pathway is the predominant signal mediating the hepatic glucose‐mobilizing actions of glucagon. A wealth of evidence, however, supports the alternative, that the operative signal most of the time is the phospholipase C (PLC)/inositol‐phosphate (IP3)/calcium/calmodulin pathway. The evidence can be summarized as follows: (1) The consensus threshold glucagon concentration for activating AC ex vivo is 100 pM, but the statistical hepatic portal plasma glucagon concentration range, measured by RIA, is between 28 and 60 pM; (2) Within that physiological concentration range, glucagon stimulates the PLC/IP3 pathway and robustly increases glucose output without affecting the AC/cAMP pathway; (3) Activation of a latent, amplified AC/cAMP pathway at concentrations below 60 pM is very unlikely; and (4) Activation of the PLC/IP3 pathway at physiological concentrations produces intracellular effects that are similar to those produced by activation of the AC/cAMP pathway at concentrations above 100 pM, including elevated intracellular calcium and altered activities and expressions of key enzymes involved in glycogenolysis, gluconeogenesis, and glycogen synthesis. Under metabolically stressful conditions, as in the early neonate or exercising adult, plasma glucagon concentrations often exceed 100 pM, recruiting the AC/cAMP pathway and enhancing the activation of PLC/IP3 pathway to boost glucose output, adaptively meeting the elevated systemic glucose demand. Whether the AC/cAMP pathway is consistently activated in starvation or diabetes is not clear. Because the importance of glucagon in the pathogenesis of diabetes is becoming increasingly evident, it is even more urgent now to resolve lingering uncertainties and definitively establish glucagon’s true mechanism of glycemia regulation in health and disease.

The effects of SCFAs on glycemic control in humans: a systematic review and meta-analysis

BACKGROUND

Noncommunicable disease development is related to impairments in glycemic and insulinemic responses, which can be modulated by fiber intake. Fiber's beneficial effects upon metabolic health can be partially attributed to the production of SCFAs via microbial fermentation of fiber in the gastrointestinal tract.

OBJECTIVES

We aimed to determine the effects of SCFAs, acetate, propionate, and butyrate on glycemic control in humans.

METHODS

The CENTRAL, Embase, PubMed, Scopus, and Web of Science databases were searched from inception to 7 December 2021. Papers were included if they reported a randomized controlled trial measuring glucose and/or insulin compared to a placebo in adults. Studies were categorized by the type of SCFA and intervention duration. Random-effects meta-analyses were performed for glucose and insulin for those subject categories with ≥3 studies, or a narrative review was performed.

RESULTS

We identified 43 eligible papers, with 46 studies within those records (n = 913), and 44 studies were included in the meta-analysis. Vinegar intake decreased the acute glucose response [standard mean difference (SMD), -0.53; 95% CI, -0.92 to -0.14; n = 67] in individuals with impaired glucose tolerance or type 2 diabetes and in healthy volunteers (SMD, -0.27; 95% CI, -0.54 to 0.00; n = 186). The meta-analyses for acute acetate, as well as acute and chronic propionate studies, showed no significant effect.

CONCLUSIONS

Vinegar decreased the glucose response acutely in healthy and metabolically unhealthy individuals. Acetate, propionate, butyrate, and mixed SCFAs had no effect on blood glucose and insulin in humans. Significant heterogeneity, risks of bias, and publication biases were identified in several study categories, including the acute vinegar glucose response. As evidence was very uncertain, caution is urged when interpreting these results. Further high-quality research is required to determine the effects of SCFAs on glycemic control.

Akkermansia muciniphila Ameliorates Acetaminophen-Induced Liver Injury by Regulating Gut Microbial Composition and Metabolism

The gut microbiota drives individual sensitivity to excess acetaminophen (APAP)-mediated hepatotoxicity. It has been reported that the bacterium Akkermansia muciniphila protects hosts against liver disease via the liver-gut axis, but its therapeutic potential for drug-induced liver injury remains unclear. In this study, we aimed to investigate the effect of A. muciniphila on APAP-induced liver injury and the underlying mechanism. Administration of A. muciniphila efficiently alleviated APAP-induced hepatotoxicity and reduced the levels of serum alanine aminotransferase (ALT) and aspartate transaminase (AST). A. muciniphila significantly attenuated APAP-induced oxidative stress and the inflammatory response, as evidenced by restoration of the reduced glutathione/oxidized glutathione (GSH/GSSG) balance, enhanced superoxide dismutase (SOD) activity, reduced proinflammatory cytokine production, and alleviation of macrophage and neutrophil infiltration. Moreover, A. muciniphila maintained gut barrier function, reshaped the perturbed microbial community and promoted short-chain fatty acid (SCFA) secretion. The beneficial effects of A. muciniphila were accompanied by alterations in hepatic gene expression at the transcriptional level and activation of the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway. Our results suggested that A. muciniphila could be a potential pretreatment for APAP-induced liver injury.

IMPORTANCE Our work revealed that A. muciniphila attenuated APAP-induced liver injury by alleviating oxidative stress and inflammation in the liver, and its hepatoprotective effect was accompanied by activation of the PI3K/Akt pathway and mediated by regulation of the composition and metabolic function of the intestinal microbiota. This finding suggested that the microbial community is a non-negligible impact on drug metabolism and probiotic administration could be a potential therapy for drug-induced liver injury.

Bifidobacterium animalis subsp. lactis A6 Enhances Fatty Acid β-Oxidation of Adipose Tissue to Ameliorate the Development of Obesity in Mice

Fatty acid β-oxidation (FAO) is confirmed to be impaired in obesity, especially in adipose tissues. We previously proved that Bifidobacterium animalis subsp. lactis A6 (BAA6) had protective effects against diet-induced obesity. However, whether BAA6 enhances FAO to ameliorate the development of obesity has not been explored. After being fed with high-fat diet (HFD) for 9 weeks, male C57BL/6J mice were fed HFD or BAA6 for 8 weeks. In vitro study was carried out using 3T3-L1 adipocytes to determine the effect of BAA6 culture supernatant (BAA6-CM). Here, we showed that administration of BAA6 to mice fed with HFD decreased body weight gain (by 5.03 g) and significantly up-regulated FAO in epididymal adipose tissues. In parallel, FAO in 3T3-L1 cells was increased after BAA6-CM treatment. Acetate was identified as a constituent of BAA6-CM that showed a similar effect to BAA6-CM. Furthermore, acetate treatment activated the GPR43-PPARα signaling, thereby promoting FAO in 3T3-L1 cells. The levels of acetate were also elevated in serum and feces (by 1.92- and 2.27-fold) of HFD-fed mice following BAA6 administration. The expression levels of GPR43 and PPARα were increased by 55.45% and 69.84% after BAA6 supplement in the epididymal fat of mice. Together, these data reveal that BAA6 promotes FAO of adipose tissues through the GPR43-PPARα signaling, mainly by increasing acetate levels, leading to alleviating the development of obesity.