Possible mediators of metabolic endotoxemia in women with obesity and women with obesity-diabetes in The Gambia

Interkingdom signaling between gastrointestinal hormones and the gut microbiome

The interplay between the gut microbiota and gastrointestinal hormones plays a pivotal role in the health of the host and the development of diseases. As a vital component of the intestinal microecosystem, the gut microbiota influences the synthesis and release of many gastrointestinal hormones through mechanisms such as modulating the intestinal environment, producing metabolites, impacting mucosal barriers, generating immune and inflammatory responses, and releasing neurotransmitters. Conversely, gastrointestinal hormones exert feedback regulation on the gut microbiota by modulating the intestinal environment, nutrient absorption and utilization, and the bacterial biological behavior and composition. The distributions of the gut microbiota and gastrointestinal hormones are anatomically intertwined, and close interactions between the gut microbiota and gastrointestinal hormones are crucial for maintaining gastrointestinal homeostasis. Interventions leveraging the interplay between the gut microbiota and gastrointestinal hormones have been employed in the clinical management of metabolic diseases and inflammatory bowel diseases, such as bariatric surgery and fecal microbiota transplantation, offering promising targets for the treatment of dysbiosis-related diseases.

Bacterial lipopolysaccharide inhibits free thiamin uptake along the intestinal tract via interference with membrane expression of thiamin transporters 1 and 2

This study examined the effect of exposure of small and large intestinal epithelial cells to the bacterial lipopolysaccharide (LPS) on uptake of free form of vitamin B1, i.e., thiamin. The intestinal tract encounters two sources of thiamin: diet and the gut microbiota. Absorption of thiamin in both the small and large intestine occurs via a carrier-mediated process that involves thiamin transporters 1 and 2 (THTR-1 and -2). Complementary in vitro (human duodenal epithelial HuTu-80 cells and human colonic epithelial NCM460 cells), in vivo (mice), and ex vivo (human primary differentiated enteroid and colonoid monolayers) models were used. The results showed that exposure to LPS causes a significant inhibition in carrier-mediated [3H]-thiamin uptake by small and large intestinal epithelia, with no change in the levels of expression of THTR-1 and -2 mRNAs and their total cellular proteins. However, a significant decrease in the fractions of the THTR-1 and -2 proteins that are expressed at the cell membranes of these epithelial cells was observed. These effects of LPS appeared to involve a protein kinase A (PKA) signaling pathway as activating this pathway caused a reversal in the inhibition of thiamin uptake and level of expression of its transporters at the cell membrane. These findings demonstrate that exposure of gut epithelia to LPS (a situation that occurs under different pathological conditions) leads to inhibition in thiamin uptake due to a decrease in level of expression of its transporters at the cell membrane that is likely mediated via a PKA signaling pathway. NEW & NOTEWORTHY This study shows that the exposure of gut epithelial cells to bacterial LPS negatively impact the uptake process of the free form of vitamin B1 (i.e., thiamin). This appears to be mediated via suppression in the level of thiamin transporters 1 and 2 (THTR-1 and -2) expression at the cell membrane and involves a protein kinase A (PKA) signaling pathway.

The Degree of Inulin Polymerization Is Important for Short-Term Amelioration of High-Fat Diet (HFD)-Induced Metabolic Dysfunction and Gut Microbiota Dysbiosis in Rats

Inulin, a non-digestible polysaccharide, has gained attention for its prebiotic properties, particularly in the context of obesity, a condition increasingly understood as a systemic inflammatory state linked to gut microbiota composition. This study investigates the short-term protective effects of inulin with different degrees of polymerization (DPn) against metabolic health deterioration and gut microbiota alterations induced by a high-fat diet (HFD) in Sprague Dawley rats. Inulin treatments with an average DPn of 7, 14, and 27 were administered at 1 g/kg of bodyweight to HFD-fed rats over 21 days. Body weight, systemic glucose levels, and proinflammatory markers were measured to assess metabolic health. Gut microbiota composition was analyzed through 16S rRNA gene sequencing. The results showed that inulin27 significantly reduced total weight gain and systemic glucose levels, suggesting a DPn-specific effect on metabolic health. The study also observed shifts in gut microbial populations, with inulin7 promoting several beneficial taxa from the Bifidobacterium genera, whilst inducing a unique microbial composition compared to medium-chain (DPn 14) and long-chain inulin (DPn: 27). However, the impact of inulin on proinflammatory markers and lipid metabolism parameters was not statistically significant, possibly due to the short study duration. Inulin with a higher DPn has a more pronounced effect on mitigating HFD-induced metabolic health deterioration, whilst inulin7 is particularly effective at inducing healthy microbial shifts. These findings highlight the benefits of inulin as a dietary adjuvant in obesity management and the importance of DPn in optimizing performance.

The potential of short-chain fatty acid epigenetic regulation in chronic low-grade inflammation and obesity

Obesity and chronic low-grade inflammation, often occurring together, significantly contribute to severe metabolic and inflammatory conditions like type 2 diabetes (T2D), cardiovascular disease (CVD), and cancer. A key player is elevated levels of gut dysbiosis-associated lipopolysaccharide (LPS), which disrupts metabolic and immune signaling leading to metabolic endotoxemia, while short-chain fatty acids (SCFAs) beneficially regulate these processes during homeostasis. SCFAs not only safeguard the gut barrier but also exert metabolic and immunomodulatory effects via G protein-coupled receptor binding and epigenetic regulation. SCFAs are emerging as potential agents to counteract dysbiosis-induced epigenetic changes, specifically targeting metabolic and inflammatory genes through DNA methylation, histone acetylation, microRNAs (miRNAs), and long non-coding RNAs (lncRNAs). To assess whether SCFAs can effectively interrupt the detrimental cascade of obesity and inflammation, this review aims to provide a comprehensive overview of the current evidence for their clinical application. The review emphasizes factors influencing SCFA production, the intricate connections between metabolism, the immune system, and the gut microbiome, and the epigenetic mechanisms regulated by SCFAs that impact metabolism and the immune system.

Gut microbiota dysbiosis -associated obesity and its involvement in cardiovascular diseases and type 2 diabetes. A systematic review

INTRODUCTION

Obesity is a complex, multifactorial disease caused by various factors. Recently, the role of the gut microbiota in the development of obesity and its complications has attracted increasing interest.

PURPOSE

This article focuses on the mechanisms by which gut microbiota dysbiosis induces insulin resistance, type 2 diabetes, and cardiovascular diseases linked to obesity, highlighting the mechanisms explaining the role of gut microbiota dysbiosis-associated inflammation in the onset of these pathologies.

METHODS

A systematic study was carried out to understand and summarize the published results on this topic. More than 150 articles were included in this search, including different types of studies, consulted by an online search in English using various electronic search databases and predefined keywords related to the objectives of our study.

RESULTS

We have summarized the data from the articles consulted in this search, and we have found a major gut microbiota alteration in obesity, characterized by a specific decrease in butyrate-producing bacteria and the production of metabolites and components that lead to metabolic impairments and affect the progression of various diseases associated with obesity through distinct signaling pathways, including insulin resistance, type 2 diabetes, and cardiovascular diseases (CVD). We have also focused on the major role of inflammation as a link between gut microbiota dysbiosis and obesity-associated metabolic complications by explaining the mechanisms involved.

CONCLUSION

Gut microbiota dysbiosis plays a crucial role in the development of various obesity-related metabolic abnormalities, among them type 2 diabetes and CVD, and represents a major challenge for chronic disease prevention and health. Indeed, the intestinal microbiota appears to be a promising target for the nutritional or therapeutic management of these diseases.

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.