Succinate signaling attenuates high-fat diet-induced metabolic disturbance and intestinal barrier dysfunction

Understanding how pre- and probiotics affect the gut microbiome and metabolic health

The gut microbiome, a complex assembly of microorganisms, significantly impacts human health by influencing nutrient absorption, the immune system, and disease response. These microorganisms form a dynamic ecosystem that is critical to maintaining overall well-being. Prebiotics and probiotics are pivotal in regulating gut microbiota composition. Prebiotics nourish beneficial bacteria and promote their growth, whereas probiotics help maintain balance within the microbiome. This intricate balance extends to several aspects of health, including maintaining the integrity of the gut barrier, regulating immune responses, and producing metabolites crucial for metabolic health. Dysbiosis, or an imbalance in the gut microbiota, has been linked to metabolic disorders such as type 2 diabetes, obesity, and cardiovascular disease. Impaired gut barrier function, endotoxemia, and low-grade inflammation are associated with toll-like receptors influencing proinflammatory pathways. Short-chain fatty acids derived from microbial fermentation modulate anti-inflammatory and immune system pathways. Prebiotics positively influence gut microbiota, whereas probiotics, especially Lactobacillus and Bifidobacterium strains, may improve metabolic outcomes, such as glycemic control in diabetes. It is important to consider strain-specific effects and study variability when interpreting these findings, highlighting the need for further research to optimize their therapeutic potential. The aim of this report is therefore to review the role of the gut microbiota in metabolic health and disease and the effects of prebiotics and probiotics on the gut microbiome and their therapeutic role, integrating a broad understanding of physiological mechanisms with a clinical perspective.

Trailblazing in adjuvant research: succinate's uncharted territory with neutrophils

The purpose of this study is to investigate the previously unknown connection that succinate has with neutrophils in the setting of adjuvant-mediated immunological enhancement. It has been discovered that succinates stimulate the recruitment of neutrophils in immunization sites, which in turn induces the expression of what is known as neutrophil-derived B cell-activating factor (BAFF). Further amplification of vaccine-induced antibody responses is provided via the succinate receptor 1-interferon regulatory factor 5 (SUCNR1-IRF5)-BAFF signaling pathway, which provides insights into a unique mechanism for immunological enhancement.NEW & NOTEWORTHY This study explores the role of succinate as a vaccine adjuvant, revealing its capacity to enhance neutrophil recruitment at immunization sites, which boosts B cell activation through the succinate receptor 1-interferon regulatory factor 5-B cell-activating factor (SUCNR1-IRF5-BAFF) signaling pathway. Results demonstrate succinate's potential to amplify vaccine-induced antibody responses, highlighting its significance in immunological enhancement and offering new insights into the adjuvant mechanisms of action, particularly in neutrophil-mediated immune responses.

Cellular succinate metabolism and signaling in inflammation: implications for therapeutic intervention

Succinate, traditionally viewed as a mere intermediate of the tricarboxylic acid (TCA) cycle, has emerged as a critical mediator in inflammation. Disruptions within the TCA cycle lead to an accumulation of succinate in the mitochondrial matrix. This excess succinate subsequently diffuses into the cytosol and is released into the extracellular space. Elevated cytosolic succinate levels stabilize hypoxia-inducible factor-1α by inhibiting prolyl hydroxylases, which enhances inflammatory responses. Notably, succinate also acts extracellularly as a signaling molecule by engaging succinate receptor 1 on immune cells, thus modulating their pro-inflammatory or anti-inflammatory activities. Alterations in succinate levels have been associated with various inflammatory disorders, including rheumatoid arthritis, inflammatory bowel disease, obesity, and atherosclerosis. These associations are primarily due to exaggerated immune cell responses. Given its central role in inflammation, targeting succinate pathways offers promising therapeutic avenues for these diseases. This paper provides an extensive review of succinate's involvement in inflammatory processes and highlights potential targets for future research and therapeutic possibilities development.

Large Yellow Tea Polysaccharide Alleviates HFD-Induced Intestinal Homeostasis Dysbiosis via Modulating Gut Barrier Integrity, Immune Responses, and the Gut Microbiome

Long-term high-fat diet (HFD) will induce dysbiosis and a disturbance of intestinal homeostasis. Large yellow tea polysaccharide (LYP) has been shown to improve obesity-associated metabolic disease via modulation of the M2 polarization. However, the contribution of LYP to intestinal barrier impairment and improvement mechanisms in obesity caused by an HFD are still not clear. In this study, we evaluated the impacts of LYP on the mucosal barrier function and microbiota composition in HFD-feeding mice. Results exhibited that dietary LYP supplement could ameliorate the physical barrier function via maintaining intestinal mucosal integrity and elevating tight-junction protein production, strengthen the chemical barrier function via up-regulating the levels of glucagon-like peptide-1 and increasing mucin-producing goblet cell numbers, and enhance the intestinal immune barrier function though suppressing immune cell subsets and cytokines toward pro-inflammatory phenotypes. Moreover, LYP reshaped the constitution and metabolism of intestinal flora by enriching probiotics that produce short-chain fatty acids. Overall, LYP might be used as a critical regulator of intestinal homeostasis to improve host health by promoting gut barrier integrity, modulating intestinal immune response, and inhibiting bowel inflammation.

Possible connection between intestinal tuft cells, ILC2s and obesity

Intestinal tuft cells (TCs) are defined as chemosensory cells that can "taste" danger and induce immune responses. They play a critical role in gastrointestinal parasite invasion, inflammatory bowel diseases and high-fat diet-induced obesity. Intestinal IL-25, the unique product of TCs, is a key activator of type 2 immunity, especially to promote group 2 innate lymphoid cells (ILC2s) to secret IL-13. Then the IL-13 mainly promotes intestinal stem cell (ISCs) proliferation into TCs and goblet cells. This pathway formulates the circuit in the intestine. This paper focuses on the potential role of the intestinal TC, ILC2 and their circuit in obesity-induced intestinal damage, and discussion on further study and the potential therapeutic target in obesity.

Host-microbiota interaction in intestinal stem cell homeostasis

Intestinal stem cells (ISCs) play a pivotal role in gut physiology by governing intestinal epithelium renewal through the precise regulation of proliferation and differentiation. The gut microbiota interacts closely with the epithelium through myriad of actions, including immune and metabolic interactions, which translate into tight connections between microbial activity and ISC function. Given the diverse functions of the gut microbiota in affecting the metabolism of macronutrients and micronutrients, dietary nutrients exert pronounced effects on host-microbiota interactions and, consequently, the ISC fate. Therefore, understanding the intricate host-microbiota interaction in regulating ISC homeostasis is imperative for improving gut health. Here, we review recent advances in understanding host-microbiota immune and metabolic interactions that shape ISC function, such as the role of pattern-recognition receptors and microbial metabolites, including lactate and indole metabolites. Additionally, the diverse regulatory effects of the microbiota on dietary nutrients, including proteins, carbohydrates, vitamins, and minerals (e.g. iron and zinc), are thoroughly explored in relation to their impact on ISCs. Thus, we highlight the multifaceted mechanisms governing host-microbiota interactions in ISC homeostasis. Insights gained from this review provide strategies for the development of dietary or microbiota-based interventions to foster gut health.