Short-chain fatty acids as a link between diet and cardiometabolic risk: a narrative review

Alterations of the gut microbiota in patients with diabetic nephropathy and its association with the renin-angiotensin system

Objective

Type 2 Diabetes Mellitus (T2DM) is a global health concern, with complications such as diabetic nephropathy (DN) affecting 16.6% of patients and contributing to end-stage renal failure. Emerging research suggests that gut microbial communities may influence DN progression, potentially through mechanisms involving the renin-angiotensin system (RAS). This study aimed to evaluate changes in specific microbial genera in individuals with T2DM, both with and without DN, and to explore their associations with renal function markers and RAS activation.

Methods

A total of 120 participants were categorized into three groups: healthy controls, T2DM without DN, and T2DM with DN. Microbial abundances of genera including Escherichia, Prevotella, Bifidobacterium, Lactobacillus, Roseburia, Bacteroides, Faecalibacterium, and Akkermansia were quantified using qPCR targeting the bacterial 16 S rRNA gene. Gene expression levels of RAS-associated markers (ACE, AGT1R, AT2R, and Ang II) and inflammation-related genes (TNF-α, TLR4) were analyzed in peripheral blood mononuclear cells via qPCR.

Results

The study identified significant alterations in microbial composition. Genera such as Faecalibacterium, Akkermansia, Roseburia (butyrate producers), and Bifidobacterium (a potential probiotic) were markedly reduced in T2DM and DN groups compared to controls. Increased mRNA expression of RAS-related genes, including ACE, AGT1R, and Ang II, was observed in these groups. We also foun correlations between altered microbial genera, RAS gene expression, and clinical markers of renal dysfunction.

Conclusion

The findings suggest that specific microbial genera may influence the pathogenesis of DN through RAS activation and inflammatory pathways. These insights highlight potential therapeutic targets for mitigating DN progression in T2DM patients.

Research Progress in the Extraction, Structural Characteristics, Bioactivity, and Commercial Applications of Oat β-Glucan: A Review

Oats (Avena sativa L.) are an important cereal crop with diverse applications in both food and forage. Oat β-glucan has gained attention for its beneficial biological activities, such as reducing cardiovascular risk, preventing diabetes, and enhancing intestinal health. Despite its potential, more comprehensive research is required to explore its preparation, modification, bioactivities, and applications. This review highlights recent advancements in the determination and preparation of oat β-glucan, explores its biological activities and mechanisms, and examines the impact of food processing techniques on its properties. This review is intended to provide a theoretical foundation and reference for the development and application of oat β-glucan in the functional food industry.

Short-chain fatty acids as a novel intervention for high-fat diet-induced metabolic syndrome

Metabolic syndrome (MetS) is driven by a complex interplay of genetic, lifestyle, and dietary factors, leading to weight gain, insulin resistance, dyslipidemia, and chronic inflammation. Gut microbiota dysbiosis has been recently recognized as a key contributor to MetS, leading to advancements in gut microbiome-based interventions to improve health outcomes. Considering the unique challenges associated with the use of pre/probiotics, short-chain fatty acids (SCFA), also known as postbiotics, have emerged as promising therapeutic agents due to their role in modulating host metabolism and physiology. Considering this, the aim of the current study was to explore the therapeutic potential of SCFA (butyrate, propionate, and acetate) supplementation against a high-fat diet (HFD)-induced experimental model of MetS in male Wistar rats. Alterations in body weight, lipid profile, histopathology, and adipose tissue accumulation were assessed to establish SCFA-mediated amelioration of experimental MetS. Further, the enzymatic (GPx, Catalase, GR, and GST) and non-enzymatic (LPO, total ROS, and Redox ratio were evaluated. The results indicated that SCFA supplementation could effectively mitigate key features of MetS. A significant reduction in body weight gain and fasting blood glucose levels, along with markedly lowered triglycerides, total cholesterol, and LDL levels, with partial restoration of HDL levels was observed following SCFA supplementation. SCFA administration also attenuated MetS-associated hepatic damage as studied by histopathological investigation and analysis of liver function marker enzyme activities. Such ameliorative effects of SCFA against HFD-induced MetS were owed to potential redox modulation studied using enzymatic and non-enzymatic oxidative stress markers. In conclusion, the study's outcomes show that SCFA supplementation could potentially be used against managing MetS. It underscores the therapeutic potential of SCFA by placing them as a novel gut microbiome-based dietary approach to improve metabolic health and reduce the risk of MetS-associated complications. However, more detailed mechanistic explorations are warranted in the future, leading to their beneficial role in MetS contributing to holistic health outcomes.

Quantifying fecal and plasma short-chain fatty acids in healthy Thai individuals

Short-chain fatty acids (SCFAs) are involved in important physiological processes such as gut health and immune response, and changes in SCFA levels can be indicative of disease. Despite the importance of SCFAs in human health and disease, reference values for fecal and plasma SCFA concentrations in healthy individuals are scarce. To address this gap in current knowledge, we developed a simple and reliable derivatization-free GC-TOFMS method for quantifying fecal and plasma SCFAs in healthy individuals. We targeted six linear- and seven branched-SCFAs, obtaining method recoveries of 73-88% and 83-134% in fecal and plasma matrices, respectively. The developed methods are simpler, faster, and more sensitive than previously published methods and are well suited for large-scale studies. Analysis of samples from 157 medically confirmed healthy individuals showed that the total SCFAs in the feces and plasma were 34.1 ± 15.3 µmol/g and 60.0 ± 45.9 µM, respectively. In fecal samples, acetic acid (Ace), propionic acid (Pro), and butanoic acid (But) were all significant, collectively accounting for 89% of the total SCFAs, whereas the only major SCFA in plasma samples was Ace, constituting of 93% of the total plasma SCFAs. There were no statistically significant differences in the total fecal and plasma SCFA concentrations between sexes or among age groups. The data revealed, however, a positive correlation for several nutrients, such as carbohydrate, fat, iron from vegetables, and water, to most of the targeted SCFAs. This is the first large-scale study to report SCFA reference intervals in the plasma and feces of healthy individuals, and thereby delivers valuable data for microbiome, metabolomics, and biomarker research.

The Interactions Between Diet and Gut Microbiota in Preventing Gestational Diabetes Mellitus: A Narrative Review

Recent studies have revealed that dysbiosis, defined as alterations in gut microbiota, plays an important role in the development and the progression of many non-communicable diseases, including metabolic disorders, such as type 2 diabetes mellitus and gestational diabetes mellitus (GDM). The high frequency of GDM makes this disorder an important public health issue, which needs to be addressed in order to reduce both the maternal and fetal complications that are frequently associated with this disease. The studies regarding the connections between gut dysbiosis and GDM are still in their early days, with new research continuously emerging. This narrative review seeks to outline the mechanisms through which a healthy diet that protects the gut microbiota is able to prevent the occurrence of GDM, thus providing medical nutritional therapeutic perspectives for the management of GDM.

Modulation of the gut microbiota by dietary intervention with Acanthocereus tetragonus improves the health status of Wistar rats with metabolic syndrome

The gastrointestinal tract is an ecosystem with heterogeneous patterns, distributions, and environments, resulting in different microbial compositions in each gut segment. The relationship between diet and microbiota determines this heterogeneity. Consumption of diets high in fat and carbohydrates (HLHC) is associated with gut dysbiosis, low microbial diversity, and metabolic syndrome (MetS). Functional fiber consumption improves the profile and diversity of the gut microbiota (GM); it stimulates the production of short-chain fatty acids (SCFAs), which act as signaling molecules that maintain the gut barrier integrity and induce hormone synthesis that regulates satiety and glucose metabolism, reducing some MetS parameters. The effect of a dietary intervention with Acanthocereus tetragonus (At), a cactus rich in fiber, antioxidants, amino acids, and minerals traditionally consumed by the Mexican population, is reported here. For this purpose, Wistar rats were randomly divided into three study groups: a control (C) group, a MetS group, and an At-supplemented group. In the MetS and At groups, an HLHC was administered for 12 weeks, inducing MetS. After 18 weeks, stool samples were collected for microbiota sequencing. HLHC administration favored Firmicutes and decreased the abundance of Bacteriodetes at the phylum level in the MetS group. At the genus level, the dietary intervention with At increased the presence of Roseburia, Ruminococcus, Blautia, Bacteroides, and Christensenella, reflecting the effect of A. tetragonus consumption on GM. At diet administration reduced body weight; the plasma glucose, insulin, and lipid levels; and insulin resistance.

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

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

Gut microbiome: A revolution in type II diabetes mellitus

Type II diabetes mellitus (T2DM) has experienced a dramatic increase globally across countries of various income levels over the past three decades. The persistent prevalence of T2DM is attributed to a complex interplay of genetic and environmental factors. While numerous pharmaceutical therapies have been developed, there remains an urgent need for innovative treatment approaches that offer effectiveness without significant adverse effects. In this context, the exploration of the gut microbiome presents a promising avenue. Research has increasingly shown that the gut microbiome of individuals with T2DM exhibits distinct differences compared to healthy individuals, suggesting its potential role in the disease's pathogenesis and progression. This emerging field offers diverse applications, particularly in modifying the gut environment through the administration of prebiotics, probiotics, and fecal microbiome transfer. These inter-ventions aim to restore a healthy microbiome balance, which could potentially alleviate or even reverse the metabolic dysfunctions associated with T2DM. Although current results from clinical trials have not yet shown dramatic effects on diabetes management, the groundwork has been laid for deeper investigation. Ongoing and future clinical trials are critical to advancing our understanding of the microbiome's impact on diabetes. By further elucidating the mechanisms through which microbiome alterations influence insulin resistance and glucose metabolism, researchers can develop more targeted interventions. The potential to harness the gut microbiome in developing new therapeutic strategies offers a compelling prospect to transform the treatment landscape of T2DM, potentially reducing the disease's burden significantly with approaches that are less reliant on traditional pharmaceuticals and more focused on holistic, systemic health improvements.

Critical Role of Mitochondrial Fatty Acid Metabolism in Normal Cell Function and Pathological Conditions

There is a "popular" belief that a fat-free diet is beneficial, supported by the scientific dogma indicating that high levels of fatty acids promote many pathological metabolic, cardiovascular, and neurodegenerative conditions. This dogma pressured scientists not to recognize the essential role of fatty acids in cellular metabolism and focus on the detrimental effects of fatty acids. In this work, we critically review several decades of studies and recent publications supporting the critical role of mitochondrial fatty acid metabolism in cellular homeostasis and many pathological conditions. Fatty acids are the primary fuel source and essential cell membrane building blocks from the origin of life. The essential cell membranes phospholipids were evolutionarily preserved from the earlier bacteria in human subjects. In the past century, the discovery of fatty acid metabolism was superseded by the epidemic growth of metabolic conditions and cardiovascular diseases. The association of fatty acids and pathological conditions is not due to their "harmful" effects but rather the result of impaired fatty acid metabolism and abnormal lifestyle. Mitochondrial dysfunction is linked to impaired metabolism and drives multiple pathological conditions. Despite metabolic flexibility, the loss of mitochondrial fatty acid oxidation cannot be fully compensated for by other sources of mitochondrial substrates, such as carbohydrates and amino acids, resulting in a pathogenic accumulation of long-chain fatty acids and a deficiency of medium-chain fatty acids. Despite popular belief, mitochondrial fatty acid oxidation is essential not only for energy-demanding organs such as the heart, skeletal muscle, and kidneys but also for metabolically "inactive" organs such as endothelial and epithelial cells. Recent studies indicate that the accumulation of long-chain fatty acids in specific organs and tissues support the impaired fatty acid oxidation in cell- and tissue-specific fashion. This work, therefore, provides a basis to challenge these established dogmas and articulate the need for a paradigm shift from the "pathogenic" role of fatty acids to the critical role of fatty acid oxidation. This is important to define the causative role of impaired mitochondrial fatty acid oxidation in specific pathological conditions and develop novel therapeutic approaches targeting mitochondrial fatty acid metabolism.

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.

Relationship between dietary fiber and all-cause mortality, cardiovascular mortality, and cardiovascular disease in patients with chronic kidney disease: a systematic review and meta-analysis

BACKGROUND

The potential protective effects of dietary fiber against all-cause mortality, cardiovascular mortality, and cardiovascular disease in patients with chronic kidney disease have not been definitively established. To verify this relationship, a systematic review and a meta-analysis were undertaken.

METHODS

PubMed, The Cochrane Library, Web of Science, Embase, ProQuest, and CINAHL were used to systematically search for prospective cohort studies that investigate the association between dietary fiber and all-cause mortality, cardiovascular mortality, and cardiovascular disease in individuals with chronic kidney disease (CKD). This search was conducted up to and including March 2023.

RESULTS

The analysis included 10 cohort studies, with a total of 19,843 patients who were followed up for 1.5-10.1 y. The results indicated a significant negative correlation between dietary fiber and all-cause mortality among patients with CKD (HR 0.80, 95% CI 0.58-0.97, P < 0.001). Subgroup analysis further revealed that the study population and exposure factors were significantly associated with all-cause mortality (P < 0.001). Increased dietary fiber intake was associated with a reduced risk of cardiovascular mortality (HR 0.78; 95% CI 0.67-0.90) and a reduced incidence of cardiovascular disease (HR 0.87; 95% CI 0.80-0.95) among patients with CKD.

CONCLUSIONS

The pooled results of our meta-analysis indicated an inverse association between dietary fiber intake and all-cause mortality, cardiovascular mortality, and cardiovascular disease.

Reassessing the Effects of Dietary Fat on Cardiovascular Disease in China: A Review of the Last Three Decades

Cardiovascular disease (CVD) is a leading cause of global mortality, and is considered one of diseases with the most rapid growth rate in China. Numerous studies have indicated a closed relationship between an increased incidence of CVD and dietary factors. Dietary fat is one of the three primary nutrients of consumption; however, high fat dietary in causing CVD has been neglected in some official dietary guidelines. Our present review has analyzed the relationship between dietary fat consumption and CVD in China over the past 30 years (from 1990 to 2019). There is a significant correlation between CVD incidence and mortality for consumption of both vegetable oils and animal fats, per capita consumption, and the relative weight of dietary fat exceeding that of other food ingredients (e.g., salt, fruit, and marine food). For fatty acid species, the proportion of ω6 fatty acid consumption increased, causing a significant increase in the ratios of ω6/ω3 fatty acids, whereas the proportion of monounsaturated fatty acid consumption decreased. Such changes have been considered a characteristic of dietary fat consumption in Chinese residents over the past 30 years, and are closely related to the incidence of CVD. Therefore, we suggest that the government should spread awareness regarding the consumption of dietary fat intake to prevent CVD and related health disorders. The public should be educated to avoid high fat diet and increase the intake of monounsaturated fatty acids and ω3 fatty acids.

Contributions of the microbiota to the systemic inflammatory response

The health of the intestinal microbiota impacts tolerance at homeostasis and the strength of the inflammation response during acute bloodstream infections. A complete understanding of the feedback loop between systemic inflammation and dysregulation of the gut microbiota is necessary for inflammation management. Here we will review the many ways in which the microbiota can influence the systemic pro-inflammatory response. Short-chain fatty acids, produced through the microbial metabolism of dietary fibers, can suppress inflammation systemically; in the absence of a balanced diet or disruption of the microbiota through antibiotics, there is disrupted metabolite production, leading to systemic inflammation. Dysbiosis or inflammation in the intestines can lead to a breakdown of the sturdy intestinal-epithelial barrier. When this barrier is perturbed, immunogenic lipopolysaccharides or extracellular vesicles enter the bloodstream and induce excessive inflammation. Necessary clinical treatments, such as antifungals or antibacterials, induce microbiota dysregulation and thus increased risk of endotoxemia; though probiotics may aid in improving the microbiota health and have been shown to deflate inflammation during sepsis. Within this complicated relationship: What is in control, the dysbiotic microbiota or the systemic inflammation?