Caffeine ameliorates the metabolic syndrome in diet-induced obese mice through regulating the gut microbiota and serum metabolism

Fu brick tea supplementation ameliorates non-alcoholic fatty liver disease and associated endotoxemia via maintaining intestinal homeostasis and remodeling hepatic immune microenvironment

Non-alcoholic fatty liver disease (NAFLD) is a prevalent disorder of excessive fat accumulation and inflammation in the liver that currently lacks effective therapeutic interventions. Fu brick tea (FBT) has been shown to ameliorate liver damage and modulate gut microbiota dysbiosis in NAFLD, but the potential mechanisms have not been comprehensively elucidated, especailly whether its hepatoprotective effects are determined to depend on the homeostasis of gut microbiota, intestinal barrier function and hepatic immune microenvironment. In this study, our results further demonstrated that FBT not only alleviated NAFLD symptoms and related endotoxemia in high-fat diet (HFD)-fed rats, but also attenuated intestinal barrier dysfunction and associated inflammation, also confirmed in Caco-2 cell experiment. Meanwhile, FBT intervention significantly relieved HFD-induced gut microbiota dysbiosis, characterized by increased diversity and composition, particularly facilitating beneficial microbes, including short chain fatty acids (SCFAs) and bile acids producers, such as Blautia and Fusicatenibacter, and inhibiting Gram-negative bacteria, such as Prevotella_9 and Phascolarctobacterium. Also, the gut microbiota-dependent hepatoprotective effects of FBT were verified by fecal microbiota transplantation (FMT) experiment. Thus, the beneficial moulation of gut microbiota altered by FBT in levels of SCFAs, bile acids and lipopolysaccharides, intestinal barrier function and TLR4/NF-κB pathway contributed to alleviate liver steatosis and inflammation. Additionally, the hepatoprotective effects of FBT was further demonstrated by suppressing Kupffer cell activation and regulating lipid metabolism using an ex vivo model of liver organoid. Therefore, FBT supplementation can maintain intenstinal homeostasis and remodel hepatic immune microenvironment to prevent NAFLD and associated endotoxemia.

Unveiling roles of beneficial gut bacteria and optimal diets for health

The gut microbiome plays a pivotal role in human health, influencing digestion, immunity, and disease prevention. Beneficial gut bacteria such as Akkermansia muciniphila, Adlercreutzia equolifaciens, and Christensenella minuta contribute to metabolic regulation and immune support through bioactive metabolites like short-chain fatty acids (SCFAs). Dietary patterns rich in prebiotics, fermented foods, and plant-based bioactive compounds, including polyphenols and flavonoids, promote microbiome diversity and stability. However, challenges such as individual variability, bioavailability, dietary adherence, and the dynamic nature of the gut microbiota remain significant. This review synthesizes current insights into gut bacteria's role in health, emphasizing the mechanisms by which dietary interventions modulate microbiota. Additionally, it highlights advancements in microbiome-targeted therapies and the transformative potential of personalized nutrition, leveraging microbiota profiling and artificial intelligence (AI) to develop tailored dietary strategies for optimizing gut health and mitigating chronic inflammatory disorders. Addressing these challenges requires a multidisciplinary approach that integrates scientific innovation, ethical frameworks, and practical implementation strategies.

Lauric-α-linolenic lipids modulate gut microbiota, preventing obesity, insulin resistance and inflammation in high-fat diet mice

Medium- and long-chain triacylglycerols (MLCTs) are regarded as healthy premium oils; however, the health benefits of novel MLCTs enriched with lauric and α-linolenic acids are still not fully understood. This study examined the health benefits of lauric-α-linolenic structural lipids (ALSL) and physical mixture (PM) with a similar fatty acid composition in mice with obesity induced by the high-fat diet (HFD). The data indicated that ALSL is more effective than PM in counteracting obesity, insulin resistance, hyperlipidaemia, liver injury, and systemic inflammation in HFD-induced mice. These effects may be associated with the regulation of gut microbiota. ALSL significantly upregulated the abundance of Dubosiella, Lactobacillus, and Bifidobacterium while reducing the abundance of Ileibacterium. Furthermore, ALSL therapy increased the levels of acetic acid, propionic acid, and total short-chain fatty acids. Correlation analysis found that the positive changes in these gut microbes correlated positively with the anti-inflammatory, insulin-sensitizing, and anti-obesity effects of ALSL.

Stabilization of hypoxia-inducible factor 1α and regulation of specific gut microbes by EGCG contribute to the alleviation of ileal barrier disorder and obesity

Tea polyphenols have a regulatory effect on metabolic-related diseases, however, the underlying mechanism remains elusive. Our study aims to explore the dietary intervention effect of Epigallocatechin gallate (EGCG), the major polyphenol in green tea, on obesity and intestinal barrier disorders in mice fed a high-fat diet. By supplementing with 50 mg kg-1 EGCG, we observed a significant amelioration in body weight gain, fat accumulation, and liver dysfunction. Furthermore, EGCG modulated the HFD-induced metabolomic alterations. In particular, EGCG intervention restored the ileal barrier by enhancing the expression of tight junction proteins and antimicrobial peptides. At the mechanistic level, EGCG treatment stabilized hypoxia-inducible factor 1α (HIF1α) both in vitro and in vivo. Meanwhile, EGCG significantly increased the abundance of Dubosiella and Akkermansia, along with the elevated SCFA contents. These findings suggest that the ability of EGCG to stabilize HIF1α and regulate specific gut microbes is pivotal in mitigating ileal barrier dysfunction and obesity. Moreover, serum metabolomics revealed potential biomarkers following EGCG intervention. This study supports the intake of EGCG or green tea in obesity management and offers a novel perspective for investigating the metabolic regulatory mechanism of other dietary polyphenols.

Effects of Coffee on Gut Microbiota and Bowel Functions in Health and Diseases: A Literature Review

Background and objectives: As one of the most popular beverages in the world, coffee has long been known to affect bowel functions such as motility, secretion, and absorption. Recent evidence obtained in human and animal studies suggests that coffee has modulating impacts on gut microbiota. We aim to present an overview of the specific effects of coffee on gut microbiota composition, diversity, and growth. We will also critically review the impacts of coffee on bowel functions in health and diseases and discuss whether gut microbiota play a role in the coffee-associated functional changes in the gastrointestinal tract. Methods: We searched the literature up to June 2024 through PubMed, Web of Science, and other sources using search terms such as coffee, caffeine, microbiota, gastrointestinal infection, motility, secretion, gut-brain axis, absorption, and medication interaction. Clinical research in patients and preclinical studies in rodent animals were included. Results: A majority of the studies found that moderate consumption of coffee (<4 cups a day) increased the relative abundance of beneficial bacterial phyla such as Firmicutes and Actinobacteria and decreased Bacteroidetes. Moderate coffee consumption also increased Bifidobacterium spp. and decreased the abundance of Enterobacteria. Coffee consumption is reported to increase gut microbiota diversity. Although the effects of coffee on bowel functions have been known for a long time, it is not until recently that we have recognized that some of the effects of coffee may be partly due to its impacts on microbiota. Conclusions: The current literature suggests that moderate coffee consumption has beneficial effects on oral and gut microbiota and motility function. However, excessive coffee intake (>5 cups a day) is implicated in reflux disorders, periodontal diseases, and progression of Crohn's disease. Further research in the field is needed, as there are many conflicting results regarding the impacts of coffee in the gastrointestinal tract.

The effects of caffeine on pancreatic diseases: the known and possible mechanisms

Caffeine, a controversial substance, was once known to be addictive and harmful. In recent years, new effects of caffeine on the human body have been confirmed. Recent research over the past few decades has shown the potential of caffeine in treating pancreas-related diseases. This review aims to analyze the known and possible mechanisms of caffeine on pancreatic diseases and provides an overview of the current research status regarding the correlation between caffeine and pancreatic disease, while enhancing our understanding of their relationship.

Effect of coffee, tea and alcohol intake on circulating inflammatory cytokines: a two sample-Mendelian randomization study

BACKGROUND

Despite the abundance of research examining the effects of coffee, tea, and alcohol on inflammatory diseases, there is a notable absence of conclusive evidence regarding their direct causal influence on circulating inflammatory cytokines. Previous studies have primarily concentrated on established cytokines, neglecting the potential impact of beverage consumption on lesser-studied but equally important cytokines.

METHODS

Information regarding the consumption of coffee, tea, and alcohol was collected from the UK Biobank, with sample sizes of 428,860, 447,485, and 462,346 individuals, respectively. Data on 41 inflammatory cytokines were obtained from summary statistics of 8293 healthy participants from Finnish cohorts.

RESULTS

The consumption of coffee was found to be potentially associated with decreased levels of Macrophage colony-stimulating factor (β = -0.57, 95% CI -1.06 ~ -0.08; p = 0.022) and Stem cell growth factor beta (β = -0.64, 95% CI -1.16 ~ -0.12; p = 0.016), as well as an increase in TNF-related apoptosis-inducing ligand (β = 0.43, 95% CI 0.06 ~ 0.8; p = 0.023) levels. Conversely, tea intake was potentially correlated with a reduction in Interleukin-8 (β = -0.45, 95% CI -0.9 ~ 0; p = 0.045) levels. Moreover, our results indicated an association between alcohol consumption and decreased levels of Regulated on Activation, Normal T Cell Expressed and Secreted (β = -0.24, 95% CI -0.48 ~ 0; p = 0.047), as well as an increase in Stem cell factor (β = 0.17, 95% CI 0.02 ~ 0.31; p = 0.023) and Stromal cell-derived factor-1 alpha (β = 0.20, 95% CI 0.04 ~ 0.36; p = 0.013).

CONCLUSION

Revealing the interactions between beverage consumption and various inflammatory cytokines may lead to the discovery of novel therapeutic targets, thereby facilitating dietary interventions to complement clinical disease treatments.

Caffeine: a potential mechanism for anti-obesity

Obesity refers to the excessive accumulation of fat caused by a long-term imbalance between energy intake (EI) and energy expenditure (EE). Over recent years, obesity has become a major public health challenge. Caffeine is a natural product that has been demonstrated to exert anti-obesity effects; however, the mechanisms responsible for the effect of caffeine on weight loss have yet to be fully elucidated. Most obesity-related deaths are due to cardiovascular disease. Recent research has demonstrated that caffeine can reduce the risk of death from cardiovascular disease; thus, it can be hypothesized that caffeine may represent a new therapeutic agent for weight loss. In this review, we synthesize data arising from clinical and animal studies over the last decade and discuss the potential mechanisms by which caffeine may induce weight loss, focusing particularly on increasing energy consumption, suppressing appetite, altering lipid metabolism, and influencing the gut microbiota. Finally, we summarize the major challenges associated with caffeine and anti-obesity research and highlight possible directions for future research and development.

Causal effect between gut microbiota and metabolic syndrome in European population: a bidirectional mendelian randomization study

BACKGROUND

Observational studies have reported that gut microbiota composition is associated with metabolic syndrome. However, the causal effect of gut microbiota on metabolic syndrome has yet to be confirmed.

METHODS

We performed a bidirectional Mendelian randomization study to investigate the causal effect between gut microbiota and metabolic syndrome in European population. Summary statistics of gut microbiota were from the largest available genome-wide association study meta-analysis (n = 13,266) conducted by the MiBioGen consortium. The summary statistics of outcome were obtained from the most comprehensive genome-wide association studies of metabolic syndrome (n = 291,107). The inverse-variance weighted method was applied as the primary method, and the robustness of the results was assessed by a series of sensitivity analyses.

RESULTS

In the primary causal estimates, Actinobacteria (OR = 0.935, 95% CI = 0.878-0.996, P = 0.037), Bifidobacteriales (OR = 0.928, 95% CI = 0.868-0.992, P = 0.028), Bifidobacteriaceae (OR = 0.928, 95% CI = 0.868-0.992, P = 0.028), Desulfovibrio (OR = 0.920, 95% CI = 0.869-0.975, P = 0.005), and RuminococcaceaeUCG010 (OR = 0.882, 95% CI = 0.803-0.969, P = 0.009) may be associated with a lower risk of metabolic syndrome, while Lachnospiraceae (OR = 1.130, 95% CI = 1.016-1.257, P = 0.025), Veillonellaceae (OR = 1.055, 95% CI = 1.004-1.108, P = 0.034) and Olsenella (OR = 1.046, 95% CI = 1.009-1.085, P = 0.015) may be linked to a higher risk for metabolic syndrome. Reverse MR analysis demonstrated that abundance of RuminococcaceaeUCG010 (OR = 0.938, 95% CI = 0.886-0.994, P = 0.030) may be downregulated by metabolic syndrome. Sensitivity analyses indicated no heterogeneity or horizontal pleiotropy.

CONCLUSIONS

Our Mendelian randomization study provided causal relationship between specific gut microbiota and metabolic syndrome, which might provide new insights into the potential pathogenic mechanisms of gut microbiota in metabolic syndrome and the assignment of effective therapeutic strategies.

Dose-Dependent Effects of Lipopolysaccharide on the Endothelium-Sepsis versus Metabolic Endotoxemia-Induced Cellular Senescence

The endothelium, the innermost cell layer of blood vessels, is not only a physical barrier between the bloodstream and the surrounding tissues but has also essential functions in vascular homeostasis. Therefore, it is not surprising that endothelial dysfunction is associated with most cardiovascular diseases. The functionality of the endothelium is compromised by endotoxemia, the presence of bacterial endotoxins in the bloodstream with the main endotoxin lipopolysaccharide (LPS). Therefore, this review will focus on the effects of LPS on the endothelium. Depending on the LPS concentration, the outcomes are either sepsis or, at lower concentrations, so-called low-dose or metabolic endotoxemia. Sepsis, a life-threatening condition evoked by hyperactivation of the immune response, includes breakdown of the endothelial barrier resulting in failure of multiple organs. A deeper understanding of the underlying mechanisms in the endothelium might help pave the way to new therapeutic options in sepsis treatment to prevent endothelial leakage and fatal septic shock. Low-dose endotoxemia or metabolic endotoxemia results in chronic inflammation leading to endothelial cell senescence, which entails endothelial dysfunction and thus plays a critical role in cardiovascular diseases. The identification of compounds counteracting senescence induction in endothelial cells might therefore help in delaying the onset or progression of age-related pathologies. Interestingly, two natural plant-derived substances, caffeine and curcumin, have shown potential in preventing endothelial cell senescence.

Metabolic Insights into Caffeine's Anti-Adipogenic Effects: An Exploration through Intestinal Microbiota Modulation in Obesity

Obesity, a chronic condition marked by the excessive accumulation of adipose tissue, not only affects individual well-being but also significantly inflates healthcare costs. The physiological excess of fat manifests as triglyceride (TG) deposition within adipose tissue, with white adipose tissue (WAT) expansion via adipocyte hyperplasia being a key adipogenesis mechanism. As efforts intensify to address this global health crisis, understanding the complex interplay of contributing factors becomes critical for effective public health interventions and improved patient outcomes. In this context, gut microbiota-derived metabolites play an important role in orchestrating obesity modulation. Microbial lipopolysaccharides (LPS), secondary bile acids (BA), short-chain fatty acids (SCFAs), and trimethylamine (TMA) are the main intestinal metabolites in dyslipidemic states. Emerging evidence highlights the microbiota's substantial role in influencing host metabolism and subsequent health outcomes, presenting new avenues for therapeutic strategies, including polyphenol-based manipulations of these microbial populations. Among various agents, caffeine emerges as a potent modulator of metabolic pathways, exhibiting anti-inflammatory, antioxidant, and obesity-mitigating properties. Notably, caffeine's anti-adipogenic potential, attributed to the downregulation of key adipogenesis regulators, has been established. Recent findings further indicate that caffeine's influence on obesity may be mediated through alterations in the gut microbiota and its metabolic byproducts. Therefore, the present review summarizes the anti-adipogenic effect of caffeine in modulating obesity through the intestinal microbiota and its metabolites.

Comparative profiling of gut microbiota and metabolome in diet-induced obese and insulin-resistant C57BL/6J mice

Diet-based models are commonly used to investigate obesity and related disorders. We conducted a comparative profiling of three obesogenic diets HFD, high fat diet; HFHF, high fat high fructose diet; and HFCD, high fat choline deficient diet to assess their impact on the gut microbiome and metabolome. After 20 weeks, we analyzed the gut microbiota and metabolomes of liver, plasma, cecal, and fecal samples. Fecal and plasma bile acids (BAs) and fecal short-chain fatty acids (SCFAs) were also examined. Significant changes were observed in fecal and cecal metabolites, with increased Firmicutes and decreased Bacteroidetes in the HFD, HFHF, and HFCD-fed mice compared to chow and LFD (low fat diet)-fed mice. Most BAs were reduced in plasma and fecal samples of obese groups, except taurocholic acid, which increased in HFCD mice's plasma. SCFAs like acetate and butyrate significantly decreased in obesogenic diet groups, while propionic acid specifically decreased in the HFCD group. Pathway analysis revealed significant alterations in amino acid, carbohydrate metabolism, and nucleic acid biosynthesis pathways in obese mice. Surprisingly, even LFD-fed mice showed distinct changes in microbiome and metabolite profiles compared to the chow group. This study provides insights into gut microbiome dysbiosis and metabolite alterations induced by obesogenic and LFD diets in various tissues. These findings aid in selecting suitable diet models to study the role of the gut microbiome and metabolites in obesity and associated disorders, with potential implications for understanding similar pathologies in humans.