Butyrate and other short-chain fatty acids increase the rate of lipolysis in 3T3-L1 adipocytes

Dose-Dependent Effects of Short-Chain Fatty Acids on 3T3-L1 Adipocyte Adipokine Secretion and Metabolic Function

BACKGROUND

Short-chain fatty acids (SCFAs) produced from microbial fermentation of non-digestible carbohydrates and protein have been shown to modulate adipocyte adipokine secretion and metabolic function, which has implications for mitigating dysfunction in obese adipose tissue; however, the individual effects of different SCFAs and the optimal concentration required is unknown. The purpose of this study was to dose-dependently determine the effects of individual SCFAs on adipocyte adipokine secretion and metabolic function.

METHODS

We recapitulated the obese adipocyte inflammatory conditions using mature 3T3-L1 adipocytes and a physiological concentration of lipopolysaccharide (LPS) ± individual SCFAs, namely acetate, propionate, and butyrate, in a dose-dependent manner (0.25 mM, 0.5 mM, and 1 mM) for 24 h.

RESULTS

SCFAs dose-dependently affected inflammatory adipokine secretion, wherein at 1 mM, all three SCFAs reduced the secretion of leptin, IL-6 and IL-1β, but only propionate and butyrate reduced MCP-1/CCL2 and MIP-1α/CCL3 compared to control (p < 0.05). Interestingly, 1 mM acetate increased RANTES/CCL5 secretion versus control, whereas propionate and butyrate decreased RANTES/CCL5 secretion, and only 1 mM propionate reduced MCP-3/CCL7 secretion (p < 0.05). At the lower 0.5 mM concentration, both propionate and butyrate reduced IL-6 and IL-1β secretion compared to control (p < 0.05), and there was no difference in adipokine secretion between groups at the 0.25 mM SCFA concentration (p > 0.05). Intracellular protein expression in the ratio of phosphorylated-to-total STAT3 was reduced by all SCFAs at 1 mM and by propionate and butyrate at 0.5 mM versus control (p < 0.05). The ratio fo phosphorylated-to-total NFκB p65 expression was reduced by propionate and butyrate at 1 mM and by butyrate alone at 0.5 mM compared to control (p < 0.05). Basal (no insulin stimulation) and insulin-stimulated glucose uptake did not differ between control and any 1 mM SCFA treatment conditions (p > 0.05).

CONCLUSIONS

Individual SCFAs exert different dose-dependent effects on LPS-stimulated adipocyte function.

Butyrate: A potential mediator of obesity and microbiome via different mechanisms of actions

Butyrate, a short-chain fatty acid, is a crucial product of gut microbial fermentation with significant implications for various metabolic and physiological processes. Dietary sources of butyrate are limited, primarily derived from the fermentation of dietary fibers by butyrate-producing gut bacteria. Butyrate exerts its effects primarily as a histone deacetylase (HDAC) inhibitor and through signaling pathways involving G protein-coupled receptors (GPCRs). Its diverse benefits include promoting gut health, enhancing energy metabolism, and potentially alleviating complications associated with obesity. However, the exact role of butyrate in obesity is still under investigation, with a limited number of human trials necessitating further research to determine its efficacy and safety profile. Moreover, butyrate impact on the gut-brain axis and its modulation of microbiome effect on behavior highlight its broader importance in regulating host physiology. A thorough understanding of the metabolic pathways and mechanisms of butyrate is essential for developing targeted interventions for metabolic disorders. Continued research is crucial to fully realize its therapeutic potential and optimize its clinical applications in human health. In summary, this review illuminates the multifaceted role of butyrate as a potential mediator of obesity and related metabolic changes.

Sodium Butyrate, A Gut Microbiota Derived Metabolite in Type 2 Diabetes Mellitus and Cardiovascular Disease: A Review

Type 2 diabetes is characterized by elevated blood glucose levels, leading to an increased risk of cardiovascular diseases. Sodium butyrate, the sodium salt of the short-chain fatty acid butyric acid produced by gut microbiota fermentation, has shown promising effects on metabolic diseases, including type 2 diabetes and cardiovascular diseases. Sodium butyrate demonstrates anti-inflammatory, anti-oxidative, and lipid-lowering properties and can improve insulin sensitivity and reduce hepatic steatosis. In this review, we investigate how sodium butyrate influences cardiovascular complications of type 2 diabetes, including atherosclerosis (AS), heart failure (HF), hypertension, and angiogenesis. Moreover, we explore the pathophysiology of cardiovascular disease in type 2 diabetes, focusing on hyperglycemia, oxidative stress, inflammation, and genetic factors playing crucial roles. The review suggests that sodium butyrate can be a potential preventive and therapeutic agent for cardiovascular complications in individuals with type 2 diabetes.

The Role of Gut Microbiota in the Onset and Progression of Obesity and Associated Comorbidities

Obesity, a global public health problem, is constantly increasing, so the concerns in preventing and combating it are increasingly focused on the intestinal microbiota. It was found that the microbiota is different in lean people compared to obese individuals, but the exact mechanisms by which energy homeostasis is influenced are still incompletely known. Numerous studies show the involvement of certain bacterial species in promoting obesity and associated diseases such as diabetes, hypertension, cancer, etc. Our aim is to summarize the main findings regarding the influence of several factors such as lifestyle changes, including diet and bariatric surgery, on the diversity of the gut microbiota in obese individuals. The second purpose of this paper is to investigate the potential effect of various microbiota modulation techniques on ameliorating obesity and its comorbidities. A literature search was conducted using the PubMed database, identifying articles published between 2019 and 2024. Most studies identified suggest that obesity is generally associated with alterations of the gut microbiome such as decreased microbial diversity, an increased Firmicutes-to-Bacteroidetes ratio, and increased SCFAs levels. Our findings also indicate that gut microbiota modulation techniques could represent a novel strategy in treating obesity and related metabolic diseases. Although some mechanisms (e.g., inflammation or hormonal regulation) are already considered a powerful connection between gut microbiota and obesity development, further research is needed to enhance the knowledge on this particular topic.

Application of tongue image characteristics and oral-gut microbiota in predicting pre-diabetes and type 2 diabetes with machine learning

Background

This study aimed to characterize the oral and gut microbiota in prediabetes mellitus (Pre-DM) and type 2 diabetes mellitus (T2DM) patients while exploring the association between tongue manifestations and the oral-gut microbiota axis in diabetes progression.

Methods

Participants included 30 Pre-DM patients, 37 individuals with T2DM, and 28 healthy controls. Tongue images and oral/fecal samples were analyzed using image processing and 16S rRNA sequencing. Machine learning techniques, including support vector machine (SVM), random forest, gradient boosting, adaptive boosting, and K-nearest neighbors, were applied to integrate tongue image data with microbiota profiles to construct predictive models for Pre-DM and T2DM classification.

Results

Significant shifts in tongue characteristics were identified during the progression from Pre-DM to T2DM. Elevated Firmicutes levels along the oral-gut axis were associated with white greasy fur, indicative of underlying metabolic changes. An SVM-based predictive model demonstrated an accuracy of 78.9%, with an AUC of 86.9%. Notably, tongue image parameters (TB-a, perALL) and specific microbiota (Escherichia, Porphyromonas-A) emerged as prominent diagnostic markers for Pre-DM and T2DM.

Conclusion

The integration of tongue diagnosis with microbiome analysis reveals distinct tongue features and microbial markers. This approach significantly improves the diagnostic capability for Pre-DM and T2DM.

Fatty acids and epigenetics in health and diseases

Lipids are crucial for human health and reproduction and include diverse fatty acids (FAs), notably polyunsaturated FAs (PUFAs) and short-chain FAs (SCFAs) that are known for their health benefits. Bioactivities of PUFAs, including ω-6 and ω-3 FAs as well as SCFAs, have been widely studied in various tissues and diseases. Epigenetic regulation has been suggested as a significant mechanism affecting the progression of various diseases, including cancers and metabolic and inflammatory diseases. Epigenetics encompasses the reversible modulation of gene expression without altering the DNA sequence itself, mediated by mechanisms such as DNA methylation, histone acetylation, and chromatin remodeling. Bioactive FAs have been demonstrated to regulate gene expression via epigenetic modifications that are potentially important for modulating metabolic control and disease risk. This review paper discusses the evidence in support of bioactive FAs, including ω-6 and ω-3 FAs and SCFAs, eliciting various disease prevention via epigenetic regulation including methylation or acetylation.

Graphical abstract

Microbiota-derived short chain fatty acids in pediatric health and diseases: from gut development to neuroprotection

The infant gut microbiota undergoes significant changes during early life, which are essential for immune system maturation, nutrient absorption, and metabolic programming. Among the various microbial metabolites, short-chain fatty acids (SCFAs), primarily acetate, propionate, and butyrate, produced through the fermentation of dietary fibers by gut bacteria, have emerged as critical modulators of host-microbiota interactions. SCFAs serve as energy sources for colonic cells and play pivotal roles in regulating immune responses, maintaining gut barrier integrity, and influencing systemic metabolic pathways. Recent research highlights the potential neuroprotective effects of SCFAs in pediatric populations. Disruptions in gut microbiota composition and SCFA production are increasingly associated with a range of pediatric health issues, including obesity, allergic disorders, inflammatory bowel disease (IBD), and neurodevelopmental disorders. This review synthesizes current knowledge on the role of microbiota-derived SCFAs in pediatric health, emphasizing their contributions from gut development to neuroprotection. It also underscores the need for further research to unravel the precise mechanisms by which SCFAs influence pediatric health and to develop targeted interventions that leverage SCFAs for therapeutic benefits.

Consumption of yacon flour and energy-restricted diet increased the relative abundance of intestinal bacteria in obese adults

Prebiotics can alter the gastrointestinal environment, favoring the growth of health-promoting bacteria. Although yacon is a functional food, with prebiotic properties (fructooligosaccharides), its effects on the intestinal microbiota have not been investigated yet. The objective of this study was to evaluate the effects of yacon flour consumption and energy-restricted diet in the intestinal microbiota in adults with excess body weight. Twenty-one adults with excess body weight were included in this randomized, parallel, double-blind, placebo-controlled, 6-week clinical trial. Subjects daily consumed at breakfast a drink containing 25 g of yacon flour (n = 11) or not containing yacon (n = 10) and received the prescription of energy-restricted diets. Fecal samples were collected on the first and on last day of the study. 16S rRNA sequencing was assessed to evaluate the effect of yacon fermentation on intestinal microbiota bacterial composition. There was an increase in the genera Bifidobacterium, Blautia, Subdoligranulum, and Streptococcus after the consumption of yacon and energy-restricted diet. In the yacon group, we also observed a positive correlation between the concentrations of short-chain fatty acids versus the genera Coprococcus and Howardella, besides a negative correlation between the concentrations of advanced glycation end products and early glycation products versus the genera Ruminococcus and Prevotella, respectively. Consumption of yacon flour and energy-restricted diet selectively changed the intestinal microbiota composition in adults with excess body weight. TRIAL REGISTRATION: Register number: RBR-6YH6BQ. Registered 23 January, 2018.

Adipokines and Bacterial Metabolites: A Pivotal Molecular Bridge Linking Obesity and Gut Microbiota Dysbiosis to Target

Adipokines are essential mediators produced by adipose tissue and exert multiple biological functions. In particular, adiponectin, leptin, resistin, IL-6, MCP-1 and PAI-1 play specific roles in the crosstalk between adipose tissue and other organs involved in metabolic, immune and vascular health. During obesity, adipokine imbalance occurs and leads to a low-grade pro-inflammatory status, promoting insulin resistance-related diabetes and its vascular complications. A causal link between obesity and gut microbiota dysbiosis has been demonstrated. The deregulation of gut bacteria communities characterizing this dysbiosis influences the synthesis of bacterial substances including lipopolysaccharides and specific metabolites, generated via the degradation of dietary components, such as short-chain fatty acids, trimethylamine metabolized into trimethylamine-oxide in the liver and indole derivatives. Emerging evidence suggests that these bacterial metabolites modulate signaling pathways involved in adipokine production and action. This review summarizes the current knowledge about the molecular links between gut bacteria-derived metabolites and adipokine imbalance in obesity, and emphasizes their roles in key pathological mechanisms related to oxidative stress, inflammation, insulin resistance and vascular disorder. Given this interaction between adipokines and bacterial metabolites, the review highlights their relevance (i) as complementary clinical biomarkers to better explore the metabolic, inflammatory and vascular complications during obesity and gut microbiota dysbiosis, and (ii) as targets for new antioxidant, anti-inflammatory and prebiotic triple action strategies.

Prebiotic effects of plant-derived (poly)phenols on host metabolism: Is there a role for short-chain fatty acids?

The gut microbiota has been extensively investigated during the last decade because of its effects on host neuroendocrine pathways and other processes. The imbalance between beneficial and pathogenic bacteria, known as dysbiosis, may be a determining predisposing factor for many noncommunicable chronic diseases, such as obesity, type 2 diabetes mellitus, metabolic syndrome, and Alzheimer's disease. On the other hand, interventions aiming to reestablish the balance between microbiota components have been suggested as potential preventive therapeutic strategies against these disorders. Among these interventions, dietary supplementation with (poly)phenols has been highlighted due to the modulatory effects exerted by those compounds on the gut microbiota. In addition, (poly)phenol consumption is associated with increased production of short-chain fatty acids (SCFAs), a set of microbial metabolites whose actions are ascribed to improving the abovementioned metabolic disorders. Thus, this review discusses the modulation of the gut microbiota by prebiotic (poly)phenols based on in vivo studies performed with isolated (poly)phenolic compounds, their interaction with the gut microbiota and the production of SCFAs in pursuit of the molecular mechanisms underlying the health effects of (poly)phenols on host metabolism.

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.

Epigenetic effects of short-chain fatty acids from the large intestine on host cells

Adult humans harbor at least as many microbial cells as eukaryotic ones. The largest compartment of this diverse microbial population, the gut microbiota, encompasses the collection of bacteria, archaea, viruses, and eukaryotic organisms that populate the gastrointestinal tract, and represents a complex and dynamic ecosystem that has been increasingly implicated in health and disease. The gut microbiota carries ∼100-to-150-times more genes than the human genome and is intimately involved in development, homeostasis, and disease. Of the several microbial metabolites that have been studied, short-chain fatty acids emerge as a group of molecules that shape gene expression in several types of eukaryotic cells by multiple mechanisms, which include DNA methylation changes, histone post-translational modifications, and microRNA-mediated gene silencing. Butyric acid, one of the most extensively studied short-chain fatty acids, reaches higher concentrations in the colonic lumen, where it provides a source of energy for healthy colonocytes, and its concentrations decrease towards the bottom of the colonic crypts, where stem cells reside. The lower butyric acid concentration in the colonic crypts allows undifferentiated cells, such as stem cells, to progress through the cell cycle, pointing towards the importance of the crypts in providing them with a protective niche. In cancerous colonocytes, which metabolize relatively little butyric acid and mostly rely on glycolysis, butyric acid preferentially acts as a histone deacetylase inhibitor, leading to decreased cell proliferation and increased apoptosis. A better understanding of the interface between the gut microbiota metabolites and epigenetic changes in eukaryotic cells promises to unravel in more detail processes that occur physiologically and as part of disease, help develop novel biomarkers, and identify new therapeutic modalities.

Interaction between β-glucans and gut microbiota: a comprehensive review

Gut microbiota (GMB) in humans plays a crucial role in health and diseases. Diet can regulate the composition and function of GMB which are associated with different human diseases. Dietary fibers can induce different health benefits through stimulation of beneficial GMB. β-glucans (BGs) as dietary fibers have gained much interest due to their various functional properties. They can have therapeutic roles on gut health based on modulation of GMB, intestinal fermentation, production of different metabolites, and so on. There is an increasing interest in food industries in commercial application of BG as a bioactive substance into food formulations. The aim of this review is considering the metabolizing of BGs by GMB, effects of BGs on the variation of GMB population, influence of BGs on the gut infections, prebiotic effects of BGs in the gut, in vivo and in vitro fermentation of BGs and effects of processing on BG fermentability.

Gut Microbial-Derived Short Chain Fatty Acids: Impact on Adipose Tissue Physiology

Obesity is a global public health issue and major risk factor for pathological conditions, including type 2 diabetes, dyslipidemia, coronary artery disease, hepatic steatosis, and certain types of cancer. These metabolic complications result from a combination of genetics and environmental influences, thus contributing to impact whole-body homeostasis. Mechanistic animal and human studies have indicated that an altered gut microbiota can mediate the development of obesity, leading to inflammation beyond the intestine. Moreover, prior research suggests an interaction between gut microbiota and peripheral organs such as adipose tissue via different signaling pathways; yet, to what degree and in exactly what ways this inter-organ crosstalk modulates obesity remains elusive. This review emphasizes the influence of circulating gut-derived short chain fatty acids (SCFAs) i.e., acetate, propionate, and butyrate, on adipose tissue metabolism in the scope of obesity, with an emphasis on adipocyte physiology in vitro and in vivo. Furthermore, we discuss some of the well-established mechanisms via which microbial SCFAs exert a role as a prominent host energy source, hence regulating overall energy balance and health. Collectively, exploring the mechanisms via which SCFAs impact adipose tissue metabolism appears to be a promising avenue to improve metabolic conditions related to obesity.

Modulation of adipose tissue metabolism by microbial-derived metabolites

Obesity and its complications, including type 2 diabetes, cardiovascular disease, and certain cancers, have posed a significant burden on health and healthcare systems over the years due to their high prevalence and incidence. Gut microbial derivatives are necessary for the regulation of energy metabolism and host immunity, as well as for maintaining homeostasis of the intestinal environment. Gut flora metabolites may be a link between gut microbes and diseases, such as obesity, and help understand why alterations in the microbiota can influence the pathophysiology of human disease. This is supported by emerging evidence that microbial-derived metabolites, such as short-chain fatty acids, bile acids, tryptophan, trimethylamine-N-oxide, and lipopolysaccharides, can be beneficial or detrimental to the host by affecting organs outside the gut, including adipose tissue. Adipose tissue is the largest lipid storage organ in the body and an essential endocrine organ that plays an indispensable role in the regulation of lipid storage, metabolism, and energy balance. Adipose tissue metabolism includes adipocyte metabolism (lipogenesis and lipolysis), thermogenesis, and adipose tissue metabolic maladaptation. Adipose tissue dysfunction causes the development of metabolic diseases, such as obesity. Here, we review the current understanding of how these microbial metabolites are produced and discuss both established mechanisms and the most recent effects of microbial products on host adipose tissue metabolism. We aimed to identify novel therapeutic targets or strategies for the prevention and treatment of obesity and its complications.

Butyrate to combat obesity and obesity-associated metabolic disorders: Current status and future implications for therapeutic use

Evidence is increasing that disturbances in the gut microbiome may play a significant role in the etiology of obesity and type 2 diabetes. The short chain fatty acid butyrate, a major end product of the bacterial fermentation of indigestible carbohydrates, is reputed to have anti-inflammatory properties and positive effects on body weight control and insulin sensitivity. However, whether butyrate has therapeutic potential for the treatment and prevention of obesity and obesity-related complications remains to be elucidated. Overall, animal studies strongly indicate that butyrate administered via various routes (e.g., orally) positively affects adipose tissue metabolism and functioning, energy and substrate metabolism, systemic and tissue-specific inflammation, and insulin sensitivity and body weight control. A limited number of human studies demonstrated interindividual differences in clinical effectiveness suggesting that outcomes may depend on the metabolic, microbial, and lifestyle-related characteristics of the target population. Hence, despite abundant evidence from animal data, support of human data is urgently required for the implementation of evidence-based oral and gut-derived butyrate interventions. To increase the efficacy of butyrate-focused interventions, future research should investigate which factors impact treatment outcomes including baseline gut microbial activity and functionality, thereby optimizing targeted-interventions and identifying individuals that merit most from such interventions.

Central and peripheral regulations mediated by short-chain fatty acids on energy homeostasis

The human gut microbiota influences obesity, insulin resistance, and the subsequent development of type 2 diabetes (T2D). The gut microbiota digests and ferments nutrients resulting in the production of short-chain fatty acids (SCFAs), which generate various beneficial metabolic effects on energy and glucose homeostasis. However, their roles in the central nervous system (CNS)-mediated outputs on the metabolism have only been minimally studied. Here, we explore what is known and future directions that may be worth exploring in this emerging area. Specifically, we searched studies or data in English by using PubMed, Google Scholar, and the Human Metabolome Database. Studies were filtered by time from 1978 to March 2022. As a result, 195 studies, 53 reviews, 1 website, and 1 book were included. One hundred and sixty-five of 195 studies describe the production and metabolism of SCFAs or the effects of SCFAs on energy homeostasis, glucose balance, and mental diseases through the gut-brain axis or directly by a central pathway. Thirty of 195 studies show that inappropriate metabolism and excessive of SCFAs are metabolically detrimental. Most studies suggest that SCFAs exert beneficial metabolic effects by acting as the energy substrate in the TCA cycle, regulating the hormones related to satiety regulation and insulin secretion, and modulating immune cells and microglia. These functions have been linked with AMPK signaling, GPCRs-dependent pathways, and inhibition of histone deacetylases (HDACs). However, the studies focusing on the central effects of SCFAs are still limited. The mechanisms by which central SCFAs regulate appetite, energy expenditure, and blood glucose during different physiological conditions warrant further investigation.

Short-chain fatty acid: An updated review on signaling, metabolism, and therapeutic effects

Fatty acids are good energy sources (9 kcal per gram) that aerobic tissues can use except for the brain (glucose is an alternative source). Apart from the energy source, fatty acids are necessary for cell signaling, learning-related memory, modulating gene expression, and functioning as cytokine precursors. Short-chain fatty acids (SCFAs) are saturated fatty acids arranged as a straight chain consisting minimum of 6 carbon atoms. SCFAs possess various beneficial effects like improving metabolic function, inhibiting insulin resistance, and ameliorating immune dysfunction. In this review, we discussed the biogenesis, absorption, and transport of SCFA. SCFAs can act as signaling molecules by stimulating G protein-coupled receptors (GPCRs) and suppressing histone deacetylases (HDACs). The role of SCFA on glucose metabolism, fatty acid metabolism, and its effect on the immune system is also reviewed with updated details. SCFA possess anticancer, anti-diabetic, and hepatoprotective effects. Additionally, the association of protective effects of SCFA against brain-related diseases, kidney diseases, cardiovascular damage, and inflammatory bowel diseases were also reviewed. Nanotherapy is a branch of nanotechnology that employs nanoparticles at the nanoscale level to treat various ailments with enhanced drug stability, solubility, and minimal side effects. The SCFA functions as drug carriers, and nanoparticles were also discussed. Still, much research was not focused on this area. SCFA functions in host gene expression through inhibition of HDAC inhibition. However, the study has to be focused on the molecular mechanism of SCFA against various diseases that still need to be investigated.

Gut and obesity/metabolic disease: Focus on microbiota metabolites

Obesity is often associated with the risk of chronic inflammation and other metabolic diseases, such as diabetes, cardiovascular disease, and cancer. The composition and activity of the gut microbiota play an important role in this process, affecting a range of physiological processes, such as nutrient absorption and energy metabolism. The active gut microbiota can produce a large number of physiologically active substances during the process of intestinal metabolism and reproduction, including short-chain/long-chain fatty acids, secondary bile acids, and tryptophan metabolites with beneficial effects on metabolism, as well as negative metabolites, including trimethylamine N-oxide, delta-valerobetaine, and imidazole propionate. How gut microbiota specifically affect and participate in metabolic and immune activities, especially the metabolites directly produced by gut microbiota, has attracted extensive attention. So far, some animal and human studies have shown that gut microbiota metabolites are correlated with host obesity, energy metabolism, and inflammation. Some pathways and mechanisms are slowly being discovered. Here, we will focus on the important metabolites of gut microbiota (beneficial and negative), and review their roles and mechanisms in obesity and related metabolic diseases, hoping to provide a new perspective for the treatment and remission of obesity and other metabolic diseases from the perspective of metabolites.

Polysaccharides from Callerya speciosa alleviate metabolic disorders and gut microbiota dysbiosis in diet-induced obese C57BL/6 mice

Callerya speciosa ("Niu Dali" in Chinese) is a well-known edible plant in Southeast China. C. speciosa roots contain a high level of polysaccharides, which have been reported to show multiple health-promoting effects. In the current study, the anti-obesity effects of a crude extract of C. speciosa polysaccharides (NP) and its underlying mechanisms of action are investigated. C57BL/6 mice were divided into three groups and fed either a standard diet or a high-fat diet (HFD). The HFD + NP group mice received oral administration of NP (100 mg per kg per day) every other day for 10 weeks. NP supplementation alleviated HFD-induced diabetic biomarkers including body weight gain, hyperlipidemia, liver steatosis, and adipocyte hypertrophy. Western blot and RT-PCR analyses revealed that NP inhibited hepatic de novo lipogenesis and adipogenesis (i.e. decreased expression of Srebp1c, Fas, Cebpα, and Pparγ), stimulated adipocyte lipolysis (enhanced mRNA expression of Hsl and Mgl), and attenuated HFD-induced hepatic inflammation (decreased expression of TNF-α and NF-κB p65). Furthermore, 16S rDNA and GC-MS analyses showed that NP supplementation restored the Firmicutes/Bacteroidetes proportion, elevated colon-derived SCFAs, especially acetic acid content, and increased the relative abundance of genera associated with SCFA production in HFD-fed mice. Findings from this study suggest that NP alleviated HFD-induced obesity in a mouse model, which was possibly due to its ameliorative effects on diet-induced gut dysbiosis. Polysaccharides from C. speciosa are promising prebiotics and they may be further developed as functional foods for the management of obesity.

Role of Butyrate, a Gut Microbiota Derived Metabolite, in Cardiovascular Diseases: A comprehensive narrative review

Cardiovascular diseases (CVD) are major causes of death worldwide. Recently, new roles for intestinal microbiota in pathology and treatment of CVD have been proposed. Butyrate, a bacterial metabolite, is synthesized in the gut and performs most of its functions in there. However, researchers have discovered that butyrate could enter to portal vein and interact with various organs. Butyrate exhibits a broad range of pharmacological activities, including microbiome modulator, anti-inflammatory, anti-obesity, metabolic pathways regulator, anti-angiogenesis, and antioxidant. In this article we review evidence supporting a potentially therapeutic role for butyrate in CVD and the mechanisms and pathways involved in the cardio-protective effects of butyrate from the gut and circulation to the nervous system. In summary, although butyrate exhibits a wide variety of biological activities in different pathways including energy homeostasis, glucose and lipid metabolism, inflammation, oxidative stress, neural signaling, and epigenetic modulation in experimental settings, it remains unclear whether these findings are clinically relevant and whether the molecular pathways are activated by butyrate in humans.

Dysbiotic Gut Bacteria in Obesity: An Overview of the Metabolic Mechanisms and Therapeutic Perspectives of Next-Generation Probiotics

Obesity, a worldwide health concern with a constantly rising prevalence, is a multifactorial chronic disease associated with a wide range of physiological disruptions, including energy imbalance, central appetite and food reward dysregulation, and hormonal alterations and gut dysbiosis. The gut microbiome is a well-recognized factor in the pathophysiology of obesity, and its influence on host physiology has been extensively investigated over the last decade. This review highlights the mechanisms by which gut dysbiosis can contribute to the pathophysiology of obesity. In particular, we discuss gut microbiota’s contribution to host energy homeostatic changes, low-grade inflammation, and regulation of fat deposition and bile acid metabolism via bacterial metabolites, such as short-chain fatty acids, and bacterial components, such as lipopolysaccharides, among others. Finally, therapeutic strategies based on next-generation probiotics aiming to re-shape the intestinal microbiota and reverse metabolic alterations associated with obesity are described.

The effect of adenosine monophosphate-activated protein kinase on lipolysis in adipose tissue: an historical and comprehensive review

CONTEXT

Lipolysis is one of the most important pathways for energy management, its control in the adipose tissue (AT) is a potential therapeutic target for metabolic diseases. Adenosine Mono Phosphate-activated Protein Kinase (AMPK) is a key regulatory enzyme in lipids metabolism and a potential target for diabetes and obesity treatment.

OBJECTIVE

The aim of this work is to analyse the existing information on the relationship of AMPK and lipolysis in the AT.

METHODS

A thorough search of bibliography was performed in the databases Scopus and Web of Knowledge using the terms lipolysis, adipose tissue, and AMPK, the unrelated publications were excluded, and the documents were analysed.

RESULTS

Sixty-three works were found and classified in 3 categories: inhibitory effects, stimulatory effect, and diverse relationships; remarkably, the newest researches support an upregulating relationship of AMPK over lipolysis.

CONCLUSION

The most probable reality is that the relationship AMPK-lipolysis depends on the experimental conditions.

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

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

mTOR and ERK1/2 signaling participate in the process of acetate regulating lipid metabolism and HSL expression

Objective

Acetate plays an important role in host lipid metabolism. However, the network of acetate-regulated lipid metabolism remains unclear. Previous studies show that mitogen-activated protein kinases (MAPKs) and mechanistic target of rapamycin (mTOR) play a crucial role in lipid metabolism. We hypothesize that acetate could affect MAPKs and/or mTOR signaling and then regulate lipid metabolism. The present study investigated whether any cross talk occurs among MAPKs, mTOR and acetate in regulating lipid metabolism.

Methods

The ceramide C6 (an extracellular signaling-regulated kinases 1 and 2 [ERK1/2] activator) and MHY1485 (a mTOR activator) were used to treat rabbit adipose-derived stem cells (ADSCs) with or without acetate, respectively.

Results

It indicated that acetate (9 mM) treatment for 48 h decreased the lipid deposition in rabbit ADSCs. Acetate treatment decreased significantly phosphorylated protein levels of ERK1/2 and mTOR but significantly increased mRNA level of hormone-sensitive lipase (HSL). Acetate treatment did not significantly alter the phosphorylated protein level of p38 MAPK and c-Jun aminoterminal kinase (JNK). Activation of ERK1/2 and mTOR by respective addition in media with ceramide C6 and MHY1485 significantly attenuated decreased lipid deposition and increased HSL expression caused by acetate.

Conclusion

Our results suggest that ERK1/2 and mTOR signaling pathways are associated with acetate regulated HSL gene expression and lipid deposition.

Modulation of Adipocyte Metabolism by Microbial Short-Chain Fatty Acids

Obesity and its complications—including type 2 diabetes, cardiovascular disease, and certain cancers—constitute a rising global epidemic that has imposed a substantial burden on health and healthcare systems over the years. It is becoming increasingly clear that there is a link between obesity and the gut microbiota. Gut dysbiosis, characterized as microbial imbalance, has been consistently associated with obesity in both humans and animal models, and can be reversed with weight loss. Emerging evidence has shown that microbial-derived metabolites such as short-chain fatty acids (SCFAs)—including acetate, propionate, and butyrate—provide benefits to the host by impacting organs beyond the gut, including adipose tissue. In this review, we summarize what is currently known regarding the specific mechanisms that link gut-microbial-derived SCFAs with adipose tissue metabolism, such as adipogenesis, lipolysis, and inflammation. In addition, we explore indirect mechanisms by which SCFAs can modulate adipose tissue metabolism, such as via perturbation of gut hormones, as well as signaling to the brain and the liver. Understanding how the modulation of gut microbial metabolites such as SCFAs can impact adipose tissue function could lead to novel therapeutic strategies for the prevention and treatment of obesity.

Butyrate Alters Pyruvate Flux and Induces Lipid Accumulation in Cultured Colonocytes

Butyrate is considered the primary energy source of colonocytes and has received wide attention due to its unique health benefits. Insight into the mechanistic effects of butyrate on cellular and metabolic function relies mainly on research in in-vitro-cultured cells. However, cells in culture differ from those in vivo in terms of metabolic phenotype and nutrient availability. For translation, it is therefore important to understand the impact of different nutrients on the effects of butyrate. We investigated the metabolic consequences of butyrate exposure under various culturing conditions, with a focus on the interaction between butyrate and glucose. To investigate whether the effects of butyrate were different between cells with high and low mitochondrial capacity, we cultured HT29 cells under either low- (0.5 mM) or high- (25 mM) glucose conditions. Low-glucose culturing increased the mitochondrial capacity of HT29 cells compared to high-glucose (25 mM) cultured HT29 cells. Long-term exposure to butyrate did not alter mitochondrial bioenergetics, but it decreased glycolytic function, regardless of glucose availability. In addition, both high- and low-glucose-grown HT29 cells showed increased lipid droplet accumulation following long-term butyrate exposure. Acute exposure of cultured cells (HT29 and Caco-2) to butyrate increased their oxygen consumption rate (OCR). A simultaneous decrease in extracellular acidification rate (ECAR) was observed. Furthermore, in the absence of glucose, OCR did not increase in response to butyrate. These results lead us to believe that butyrate itself was not responsible for the observed increase in OCR, but, instead, butyrate stimulated pyruvate flux into mitochondria. Indeed, blocking of the mitochondrial pyruvate carrier prevented a butyrate-induced increase in oxygen consumption. Taken together, our results indicate that butyrate itself is not oxidized in cultured cells but instead alters pyruvate flux and induces lipid accumulation.

The Effects of Erchen Decoction on Gut Microbiota and Lipid Metabolism Disorders in Zucker Diabetic Fatty Rats

Obesity is a chronic metabolic disease caused by genetic and environmental factors that has become a serious global health problem. There is evidence that gut microbiota is closely related to the occurrence and development of obesity. Erchen Decoction (ECD), a traditional Chinese medicine, has been widely used for clinical treatment and basic research of obesity and related metabolic diseases in recent years. It can significantly improve insulin resistance (IR) and lipid metabolism disorders. However, there is no microbiological study on its metabolic regulation. In this study, we investigated the effects of ECD on obesity, especially lipid metabolism and the composition and function of gut microbiota in Zucker diabetic fatty (ZDF) rats, and explored the correlation between the biomarkers of gut microbiota and metabolite and host phenotype. The results showed that ECD could reduce body weight, improve IR and lipid metabolism, and reduce the concentration of free fatty acids (FFA) released from white adipose tissue (WAT) due to excessive lipolysis by interfering with the insulin receptor substrate 1 (IRS1)/protein kinase B (AKT)/protein kinase A (PKA)/hormone-sensitive triglyceride lipase (HSL) signaling pathway in ZDF rats. Additionally, ECD gradually adjusted the overall structure of changed gut microbiota, reversed the relative abundance of six genera, and changed the function of gut microbiota by reducing the content of propionic acid, a metabolite of gut microbiota, in ZDF rats. A potentially close relationship between biomarkers, especially Prevotella, Blautia, and Holdemania, propionic acid and host phenotypes were demonstrated through correlation analysis. The results suggested that the beneficial effects of ECD on obesity, especially lipid metabolism disorders, are related to the regulation of gut microbiota in ZDF rats. This provides a basis for further research on the mechanism and clinical application of ECD to improve obesity via gut microbiota.

Transcriptomic Responses Induced in Muscle and Adipose Tissues of Growing Pigs by Intravenous Infusion of Sodium Butyrate

Simple Summary

The present study was constructed to determine the effects of short-term intravenous sodium butyrate (SB) administration on metabolism through transcriptomic responses in muscle and adipose tissue of pigs. We found that systemic butyrate displayed a discriminative metabolic regulation in muscle and adipose tissue. Intravenous SB infusion decreased amino acid metabolism pathways both in muscle and adipose tissues. Intravenous SB infusion increased glucose catabolism in muscle tissue and decreased glucose utilization in adipose tissue. Moreover, intravenous SB infusion decreased lipolysis in muscle tissue but increased lipolysis in adipose tissue. These findings support the direct role of the SCFA butyrate in the regulation of the metabolism.

Abstract

Butyrate has a central function in the regulation of energy metabolism as a metabolite of bacterial fermentation. This study evaluated the effects of intravenous sodium butyrate (SB) administration on the transcriptome of muscle and adipose tissue of pigs. Twelve crossbred barrows (Duroc × Landrace × Large White) were fitted with a medical polyethylene cannula via the internal jugular vein and were daily infused with 10 mL SB (200 mmol/L) or the same volume of physiological saline. Muscle transcriptome showed 11 DEGs related to carbohydrate metabolism, 28 DEGs related to lipid metabolism, and 10 DEGs related to amino acid metabolism. Among these, carbohydrate catabolic process-related genes (PPP1R3B, PRPS2, ALDOC), fatty acid synthase (FASN), and lipolysis-related genes (PLIN1) were upregulated, while the carbohydrate biosynthetic process-related genes (PCK1) and most amino acid metabolism-related genes were downregulated. Adipose transcriptome showed 12 DEGs related to carbohydrate metabolism, 27 DEGs related to lipid metabolism, and 10 DEGs related to amino acid metabolism. Among these, carbohydrate metabolism-related genes (IGF1, LEP, SLC2A4) and lipolysis-related genes (LPL) were upregulated, while lipolysis-related genes (ANGPTL4) and most amino acid metabolism-related genes were downregulated. The results suggest that short-term intravenous SB infusion could modulate the muscle and adipose tissue metabolism at the transcriptional level by decreasing amino acid metabolism pathways. Additionally, intravenous SB increased the glucose catabolism in muscle tissue and decreased the glucose utilization in adipose tissue. Intravenous SB increased the fatty acid synthesis, decreased the lipolysis in muscle tissue, and increased the lipolysis in adipose tissue. This suggests that systemic butyrate may display discriminative metabolic regulation in different tissues of barrows.

A comprehensive review on the impact of β-glucan metabolism by Bacteroides and Bifidobacterium species as members of the gut microbiota

β-glucans are polysaccharides which can be obtained from different sources, and which have been described as potential prebiotics. The beneficial effects associated with β-glucan intake are that they reduce energy intake, lower cholesterol levels and support the immune system. Nevertheless, the mechanism(s) of action underpinning these health effects related to β-glucans are still unclear, and the precise impact of β-glucans on the gut microbiota has been subject to debate and revision. In this review, we summarize the most recent advances involving structurally different types of β-glucans as fermentable substrates for Bacteroidetes (mainly Bacteroides) and Bifidobacterium species as glycan degraders. Bacteroides is one of the most abundant bacterial components of the human gut microbiota, while bifidobacteria are widely employed as a probiotic ingredient. Both are generalist glycan degraders capable of using a wide range of substrates: Bacteroides spp. are specialized as primary degraders in the metabolism of complex carbohydrates, whereas Bifidobacterium spp. more commonly metabolize smaller glycans, in particular oligosaccharides, sometimes through syntrophic interactions with Bacteroides spp., in which they act as secondary degraders.

Identification of novel functional CpG-SNPs associated with Type 2 diabetes and birth weight

Genome-wide association studies (GWASs) have identified hundreds of genetic loci for type 2 diabetes (T2D) and birth weight (BW); however, a large proportion of the total trait heritability remains unexplained. The previous studies were generally focused on individual traits and largely failed to identify the majority of the variants that play key functional roles in the etiology of the disease. Here, we aim to identify novel functional loci for T2D, BW and the pleiotropic variants shared between them by performing a targeted conditional false discovery rate (cFDR) analysis that integrates two independent GWASs with summary statistics for T2D (n = 26,676 cases and 132,532 controls) and BW (n = 153,781) which entails greater statistical power than individual trait analyses. In this analysis, we considered CpG-SNPs, which are SNPs that may influence DNA methylation status, and are therefore considered to be functionally important. We identified 103 novel CpG-SNPs for T2D, 182 novel CpG-SNPs for BW (cFDR < 0.05), and 52 novel pleiotropic loci for both (conjunction cFDR [ccFDR] < 0.05). Among the identified novel CpG-SNPs, 33 were annotated as methylation quantitative trait loci (meQTLs) in whole blood, and 145 displayed at least some effects on meQTL, metabolic QTL (metaQTL), and/or expression QTL (eQTL). These findings may provide further insights into the shared biological mechanisms and functional genetic determinants that overlap between T2D and BW, thereby providing novel potential targets for treatment/intervention development.

Modulation of Short-Chain Fatty Acids as Potential Therapy Method for Type 2 Diabetes Mellitus

In recent years, the relationship between intestinal microbiota (IM) and the pathogenesis of type 2 diabetes mellitus (T2DM) has attracted much attention. The beneficial effects of IM on the metabolic phenotype of the host are often considered to be mediated by short-chain fatty acids (SCFAs), mainly acetate, butyrate, and propionate, the small-molecule metabolites derived from microbial fermentation of indigestible carbohydrates. SCFAs not only have an essential role in intestinal health but might also enter the systemic circulation as signaling molecules affecting the host's metabolism. In this review, we summarize the effects of SCFAs on glucose homeostasis and energy homeostasis and the mechanism through which SCFAs regulate the function of metabolically active organs (brain, liver, adipose tissue, skeletal muscle, and pancreas) and discuss the potential role of modulation of SCFAs as a therapeutic method for T2DM.

Low and high concentrations of butyrate regulate fat accumulation in chicken adipocytes via different mechanisms

The present study investigated the effects of varying concentrations of sodium butyrate (SB) on fat accumulation and cell proliferation in chicken adipocytes. High and low serial concentrations of SB used significantly reduced adipocytic fat accumulation. However, they were observed to exhibit differences in cell morphology and distinctions in lipogenic genes expression profiles. At lower concentration (0.01 mM), fat accumulation was decreased with an associated downregulation in the expression of lipogenic genes, which was mediated by free fatty acid receptors (FFARs). Contarily, at higher concentration (1 mM), the fat droplets laden in adipocytes were enlarged, and this was accompanied with activation of lipogenic genes expression. However, the total accumulated fat was also decreased largely due to reduction in cell numbers, which was partially attributable to the reduction in histone deacetylase (HDAC) activity. Animal experiments further indicated that dietary supplementation of lower dose coated SB (0.1% wt/wt) inhibited fat deposition in livers and abdominal fat tissues of broilers, suggesting the potential application of sodium butyrate as feed additive in the regulation of fat deposition.

Butyrate generated by gut microbiota and its therapeutic role in metabolic syndrome

Metabolic syndrome (MetS) and the associated incidence of cardiovascular disease and type 2 diabetes represents a significant contributor to morbidity and mortality worldwide. Butyrate, a short-chain fatty acid produced by the gut microbiome, has long been known to promote growth in farmed animals and more recently has been reported to improve body weight and composition, lipid profile, insulin sensitivity and glycaemia in animal models of MetS. In vitro studies have examined the influence of butyrate on intestinal cells, adipose tissue, skeletal muscle, hepatocytes, pancreatic islets and blood vessels, highlighting genes and pathways that may contribute to its beneficial effects. Butyrate's influences in these cells have been attributed primarily to its epigenetic effects as a histone deacetylase inhibitor, as well as its role as an agonist of free fatty acid receptors, but clear mechanistic evidence is lacking. There is also uncertainty whether results from animal studies can translate to human trials due to butyrate's poor systemic availability and rapid clearance. Hitherto, several small-scale human clinical trials have failed to show significant benefits in MetS patients. Further trials are clearly needed, including with formulations designed to improve butyrate's availability. Regardless, dietary intervention to increase the rate of butyrate production may be a beneficial addition to current treatment. This review outlines the current body of evidence on the suitability of butyrate supplementation for MetS, looking at mechanistic effects on the various components of MetS and highlighting gaps in the knowledge and roadblocks to its use in humans.

Short chain fatty acids could prevent fat deposition in pigs via regulating related hormones and genes

Short chain fatty acids (SCFAs) are produced when indigestible carbohydrates, such as fiber and resistant starch, undergo fermentation by specific microbiota in the hindgut.

Butyrate attenuated fat gain through gut microbiota modulation in db/db mice following dapagliflozin treatment

We investigated the effect of a combination treatment with dapagliflozin (Dapa), a sodium-glucose cotransporter-2 inhibitor and butyrate on weight change in db/db mice. Six-week-old male db/db mice were assigned to four groups: vehicle with normal chow diet (NCD), Dapa with NCD, vehicle with 5% sodium butyrate-supplemented NCD (NaB), or Dapa with 5% NaB. After six weeks of treatment, faecal microbiota composition was analysed by sequencing 16S ribosomal RNA genes. In the vehicle with NaB and Dapa + NaB groups, body weight increase was attenuated, and amount of food intake decreased compared with the vehicle with the NCD group. The Dapa + NaB group gained the least total and abdominal fat from baseline. Intestinal microbiota of this group was characterized by a decrease of the Firmicutes to Bacteroidetes ratio, a decrease of Adlercreutzia and Alistipes, as well as an increase of Streptococcus. In addition, the proportion of Adlercreutzia and Alistipes showed a positive correlation with total fat gain, whereas Streptococcus showed a negative correlation. Inferred metagenome function revealed that tryptophan metabolism was upregulated by NaB treatment. We demonstrated a synergistic effect of Dapa and NaB treatment on adiposity reduction, and this phenomenon might be related to intestinal microbiota alteration.

Free Fatty Acid Receptors in Health and Disease

Fatty acids are metabolized and synthesized as energy substrates during biological responses. Long- and medium-chain fatty acids derived mainly from dietary triglycerides, and short-chain fatty acids (SCFAs) produced by gut microbial fermentation of the otherwise indigestible dietary fiber, constitute the major sources of free fatty acids (FFAs) in the metabolic network. Recently, increasing evidence indicates that FFAs serve not only as energy sources but also as natural ligands for a group of orphan G protein-coupled receptors (GPCRs) termed free fatty acid receptors (FFARs), essentially intertwining metabolism and immunity in multiple ways, such as via inflammation regulation and secretion of peptide hormones. To date, several FFARs that are activated by the FFAs of various chain lengths have been identified and characterized. In particular, FFAR1 (GPR40) and FFAR4 (GPR120) are activated by long-chain saturated and unsaturated fatty acids, while FFAR3 (GPR41) and FFAR2 (GPR43) are activated by SCFAs, mainly acetate, butyrate, and propionate. In this review, we discuss the recent reports on the key physiological functions of the FFAR-mediated signaling transduction pathways in the regulation of metabolism and immune responses. We also attempt to reveal future research opportunities for developing therapeutics for metabolic and immune disorders.

Circulating but not faecal short-chain fatty acids are related to insulin sensitivity, lipolysis and GLP-1 concentrations in humans

Microbial-derived short-chain fatty acids (SCFA) acetate, propionate and butyrate may provide a link between gut microbiota and whole-body insulin sensitivity (IS). In this cross-sectional study (160 participants, 64% male, BMI: 19.2–41.0 kg/m², normal or impaired glucose metabolism), associations between SCFA (faecal and fasting circulating) and circulating metabolites, substrate oxidation and IS were investigated. In a subgroup (n = 93), IS was determined using a hyperinsulinemic-euglycemic clamp. Data were analyzed using multiple linear regression analysis adjusted for sex, age and BMI. Fasting circulating acetate, propionate and butyrate concentrations were positively associated with fasting GLP-1 concentrations. Additionally, circulating SCFA were negatively related to whole-body lipolysis (glycerol), triacylglycerols and free fatty acids levels (standardized (std) β adjusted (adj) −0.190, P = 0.023; std β adj −0.202, P = 0.010; std β adj −0.306, P = 0.001, respectively). Circulating acetate and propionate were, respectively, negatively and positively correlated with IS (M-value: std β adj −0.294, P < 0.001; std β adj 0.161, P = 0.033, respectively). We show that circulating rather than faecal SCFA were associated with GLP-1 concentrations, whole-body lipolysis and peripheral IS in humans. Therefore, circulating SCFA are more directly linked to metabolic health, which indicates the need to measure circulating SCFA in human prebiotic/probiotic intervention studies as a biomarker/mediator of effects on host metabolism.

Lipid-regulating properties of butyric acid and 4-phenylbutyric acid: Molecular mechanisms and therapeutic applications

In the past two decades, significant advances have been made in the etiology of lipid disorders. Concomitantly, the discovery of liporegulatory functions of certain short-chain fatty acids has generated interest in their clinical applications. In particular, butyric acid (BA) and its derivative, 4-phenylbutyric acid (PBA), which afford health benefits against lipid disorders while being generally well tolerated by animals and humans have been assessed clinically. This review examines the evidence from cell, animal and human studies pertaining to the lipid-regulating effects of BA and PBA, their molecular mechanisms and therapeutic potential. Collectively, the evidence supports the view that intakes of BA and PBA benefit lipid homeostasis across biological systems. We reviewed the evidence that BA and PBA downregulate de novo lipogenesis, ameliorate lipotoxicity, slow down atherosclerosis progression, and stimulate fatty acid β-oxidation. Central to their mode of action, BA appears to function as a histone deacetylase (HDAC) inhibitor while PBA acts as a chemical chaperone and/or a HDAC inhibitor. Areas of further inquiry include the effects of BA and PBA on adipogenesis, lipolysis and apolipoprotein metabolism.

Growth performance, lipid metabolism, and health status of grass carp (Ctenopharyngodon idella) fed three different forms of sodium butyrate

Sodium butyrate (SB) can be coated with fatty acid matrix. In this study, the effects of three SB forms, being zero-lipid-coated (SB-A), half-lipid-coated (SB-B), and 2/3 lipid-coated (SB-C) (w/w), on growth, lipid metabolism, and health status of grass carp (Ctenopharyngodon idella) were investigated. The three forms of SB were added to a control diet to form three SB diets, Con., SB-A, SB-B, and SB-C, where the pure SB in each SB diet was kept at the same level (500 mg kg^-1). A total of 216 C. idella (14.10 ± 0.60 g/fish) were allotted into four groups (triplicate per group) and fed the four diets respectively for 56 days, and then fish were sampled and determined. Fish growth was not affected by any of the three forms of SB. Viscerosomatic index, intraperitoneal fat index, and crude lipid of hepatopancreas and muscle were significantly decreased and villus height of intestine and mRNA expression of MyD88 and TLR22 in hepatopancreas were significantly improved in SB diets compared with control (p < 0.05), respectively. MiSeq sequencing of the V3-V4 region of bacterial 16S rRNA gene revealed that SB increased the relative abundances of intestinal healthy bacteria, Fusobacteria and Bacteroides, and the abundances of Cetobacterium decreased in the SB-C group. In conclusion, the present results showed that three forms of SB, without affecting the growth of fish, respectively decreased lipid accumulation and probably have a beneficial effect on health of C. idella.

Antidiabetic Drugs in NAFLD: The Accomplishment of Two Goals at Once?

Non-Alcoholic Fatty Liver Disease (NAFLD) is the most common cause of chronic liver disease in Western countries, accounting for 20–30% of general population and reaching a prevalence of 55% in patients with type 2 diabetes mellitus (T2DM). Insulin resistance plays a key role in pathogenic mechanisms of NAFLD. Many drugs have been tested but no medications have yet been approved. Antidiabetic drugs could have a role in the progression reduction of the disease. The aim of this review is to summarize evidence on efficacy and safety of antidiabetic drugs in patients with NAFLD. Metformin, a biguanide, is the most frequently used drug in the treatment of T2DM. To date 15 randomized controlled trials (RCTs) and four meta-analysis on the use of metformin in NAFLD are available. No significant improvement in histological liver fibrosis was shown, but it can be useful in the treatment of co-factors of NAFLD, like body weight, transaminase or cholesterol levels, and HbA1c levels. A possible protective role in various types of cancer has been reported for Metformin. Thiazolidinediones modulate insulin sensitivity by the activation of PPAR-γ. The RCTs and the meta-analysis available about the role of these drugs in NAFLD show an improvement in ballooning, lobular inflammation, and perhaps fibrosis, but some side effects, in particular cardiovascular, were showed. GLP-1 analogues stimulate insulin secretion by pancreatic beta cell and inhibit glucagon release; Liraglutide is the most used drug in this class and significantly improves steatosis, hepatocyte ballooning and transaminase levels. Scanty data about the role of DPP-4 and SGLT inhibitors were published. No data about insulin effects on NAFLD are available but it was showed a possible association between insulin use and the development of solid neoplasms, in particular HCC. In conclusion, antidiabetic drugs seem to be promising drugs, because they are able to treat both NAFLD manifestations and diabetes, preventing worsening of hepatic damage, but data are still conflicting. All antidiabetic drugs can be safely used in patients with compensated cirrhosis, while insulin is the preferred drug in decompensated Child C cirrhosis.

Fermentation and germination improve nutritional value of cereals and legumes through activation of endogenous enzymes

Cereals and legumes are outstanding sources of macronutrients, micronutrients, phytochemicals, as well as antinutritional factors. These components present a complex system enabling interactions with different components within food matrices. The interactions result in insoluble complexes with reduced bioaccessibility of nutrients through binding and entrapment thereby limiting their release from food matrices. The interactions of nutrients with antinutritional factors are the main factor hindering nutrients release. Trypsin inhibitors and phytates inherent in cereals and legumes reduce protein digestibility and mineral release, respectively. Interaction of phytates and phenolic compounds with minerals is significant in cereals and legumes. Fermentation and germination are commonly used to disrupt these interactions and make nutrients and phytochemicals free and accessible to digestive enzymes. This paper presents a review on traditional fermentation and germination processes as a means to address myriad interactions through activation of endogenous enzymes such as α‐amylase, pullulanase, phytase, and other glucosidases. These enzymes degrade antinutritional factors and break down complex macronutrients to their simple and more digestible forms.

Sodium butyrate supplementation ameliorates diabetic inflammation in db/db mice

Endotoxemia has been recognized to be closely accompanied with type 2 diabetes mellitus (T2DM) and is responsible for many diabetic complications. Recent study suggests the potential role of butyrate, a short-chain fatty acid (SCFA) from microbiota metabolite, on T2DM. Gut-leak is a key event in diabetic-endotoxemia. To investigate if butyrate could ameliorate diabetic-endotoxemia, both in vivo and in vitro experiments were carried out in the present study. The effect of butyrate supplementation on blood HbA1c and inflammatory cytokines were determined in db/db mice; gut barrier integrity and expression of tight junction proteins were investigated both in vivo and in vitro Oral butyrate administration significantly decreased blood HbA1c, inflammatory cytokines and LPS in db/db mice; inflammatory cell infiltration was reduced, and gut integrity and intercellular adhesion molecules were increased as detected by HE staining, immunohistochemistry and Western blot. By gut microbiota assay, ratio of Firmicutes:Bacteroidetes for gut microbiota was reduced by butyrate. In Caco-2 cells, butyrate significantly promoted cell proliferation, decreased inflammatory cytokines' secretion, enhanced cell anti-oxidative stress ability and preserved the epithelial monocellular integrity, which was damaged by LPS. The present findings demonstrated that butyrate supplementation could ameliorate diabetic-endotoxemia in db/db mice via restoring composition of gut microbiota and preserving gut epithelial barrier integrity.

β-adrenergic Receptor Stimulation Revealed a Novel Regulatory Pathway via Suppressing Histone Deacetylase 3 to Induce Uncoupling Protein 1 Expression in Mice Beige Adipocyte

Browning of adipose tissue has been prescribed as a potential way to treat obesity, marked by the upregulation of uncoupling protein 1 (Ucp1). Several reports have suggested that histone deacetylase (HDAC) might regulate Ucp1 by remodelling chromatin structure, although the mechanism remains unclear. Herein, we investigate the effect of β-adrenergic receptor (β-AR) activation on the chromatin state of beige adipocyte. β-AR-stimulated Ucp1 expression via cold (in vivo) and isoproterenol (in vitro) resulted in acetylation of histone activation mark H3K27. H3K27 acetylation was also seen within Ucp1 promoter upon isoproterenol addition, favouring open chromatin for Ucp1 transcriptional activation. This result was found to be associated with the downregulation of class I HDAC mRNA, particularly Hdac3 and Hdac8. Further investigation showed that although HDAC8 activity decreased, Ucp1 expression was not altered when HDAC8 was activated or inhibited. In contrast, HDAC3 mRNA and protein levels were simultaneously downregulated upon isoproterenol addition, resulting in reduced recruitment of HDAC3 to the Ucp1 enhancer region, causing an increased H3K27 acetylation for Ucp1 upregulation. The importance of HDAC3 inhibition was confirmed through the enhanced Ucp1 expression when the cells were treated with HDAC3 inhibitor. This study highlights the novel mechanism of HDAC3-regulated Ucp1 expression during β-AR stimulation.