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Excess iodine induces lipid metabolic disorders by the gut microbiota SCFAs/H2S-p-AMPKα/PPARγ/SREBP-1c pathway in female rats.

With the development of living standards, the problem of excess iodine has long been overlooked. This study aimed to investigate the detrimental effects of long-term excess iodine exposure on lipid metabolism in female Sprague-Dawley rats from the gut-liver axis perspective, and to elucidate the underlying molecular mechanisms by which the gut microbiota and its metabolites mediate iodine-induced lipid metabolic disorders. The results indicated that abnormal iodine nutrition has a negative effect on the health of rats. Specifically, excess iodine not only causes thyroid disorders but also leads to liver lipid metabolism disorders, including elevated serum and hepatic total cholesterol/triglyceride levels and lipid accumulation in the liver. Further investigation revealed that excess iodine causes liver lipid metabolism disorders by altering the gut microbiota, which resulted in an increase in the relative abundance of Desulfovibrio and Lachnospiraceae NK4A136_group, and a decrease in the relative abundance of Akkermansia and Blautia in excess iodine groups. A decrease in the relative abundance of Blautia and an increase in Lachnospiraceae NK4A136_group were strongly correlated with reductions in short-chain fatty acids (acetic, propionic, and valeric acids), whereas an increase in Desulfovibrio was strongly correlated with an increase in H2S. Additionally, acetic acid was negatively correlated with H2S in serum and liver. Excess iodine reduced hepatic p-AMPKα expression while upregulating key regulators of lipid metabolism, including SREBP-1c, PPARγ and ACC1. These changes may represent one of the key mechanisms by which excess iodine induces lipid metabolism disorders through the microbiota-metabolite axis. Overall, these findings suggest that excess iodine influences lipid metabolism through the gut-liver axis. The results of this study provide scientific references and guidance for the appropriate intake of iodine and offer novel insights for early nutritional interventions targeting lipid metabolism disorders.

Journal Article

Increasing gut short-chain fatty acids protects intestinal barrier function but does not spare muscle glycogen or impact aerobic performance.

Animal studies suggest gut microbiota-derived short-chain fatty acids (SCFA) provide an intestinal barrier-protecting, glycogen-sparing energy source that increases aerobic endurance performance, but confirmation in humans is needed. This study aimed to determine whether increasing colonic SCFA availability impacts intestinal barrier function, substrate metabolism, muscle glycogen and aerobic performance in healthy adults. Using a randomized, double-blind, crossover design 12 active men (age 18-30&#xa0;years;40.0&#xa0;&#xb1;&#xa0;7.1&#xa0;mL/kg/min) performed prescribed exercise and consumed a provided diet supplemented with acetylated and butyrylated high-amylose maize starch engineered to deliver SCFA to the colon (HAMS-A/B) or low-amylose maize starch (LAMS) for 7 days, separated by a 2 week washout. Indirect calorimetry, stable isotopes and blood, muscle and urine biomarkers were measured on intervention day 8 while participants completed 90&#xa0;min of steady-state cycle ergometry (ExSS; 60 &#xb1; 5%) followed by a 5&#xa0;km treadmill time trial. HAMS-A/B, relative to LAMS, increased faecal and serum SCFA. Multiple markers of intestinal barrier damage and permeability were lower, and the respiratory exchange ratio during ExSS was higher (0.02 [95% confidence interval (CI): 0.01, 0.03], Ptreatment&#xa0;<&#xa0;0.001) following HAMS-A/B versus LAMS. However no between-treatment difference in glucose turnover, muscle glycogen depletion (14&#xa0;&#xb5;mol/kg/g dry wt. [95% CI: -116, 143], Pinteractio n&#xa0;=&#xa0;0.613) or TT performance (5&#xa0;s [95%CI: -44, 54], Ptreatment&#xa0;=&#xa0;0.816) was observed. Increasing colonic and circulating SCFA modestly altered substrate oxidation and preserved intestinal barrier function during endurance exercise. However effects were not sufficient to spare muscle glycogen or increase aerobic endurance performance, leaving the practical relevance unclear and underscoring challenges inherent in translating promising preclinical findings to humans. KEY POINTS: Animal studies suggest gut microbiota-derived short-chain fatty acids (SCFA) provide an intestinal barrier-protecting, glycogen-sparing energy source that increases aerobic endurance performance, but confirmation in humans is lacking. A gut microbiota-targeted dietary supplementation strategy was used to deliver SCFA to the colon and successfully increased colonic and systemic SCFA concentrations in healthy, physically active adults before and during an endurance exercise bout and aerobic performance test. Increasing colonic and systemic SCFA availability preserved intestinal barrier function but did not impact glucose turnover, alter protein expression in muscle or spare muscle glycogen during endurance exercise. Increasing colonic and systemic SCFA availability did not impact aerobic endurance performance.

Humans

Mechanistic Insights Into the Association Between Gut Microbiota Diversity and Atherosclerosis, Acute Coronary Syndrome, and Peripheral Arterial Disease Progression.

BACKGROUND: The gut microbiome has emerged as a potential contributor to cardiovascular diseases (CVDs), including atherosclerosis, acute coronary syndrome (ACS), and peripheral arterial disease (PAD). While observational studies link dysbiosis to CVD, causal relationships remain uncertain. METHODS: This narrative review synthesizes evidence from human observational studies, clinical interventions, and experimental models to distinguish association from mechanistic plausibility and clinical causality. Literature was searched through July 2026 in PubMed/MEDLINE, Web of Science, and Scopus. RESULTS: Microbial metabolites-including trimethylamine N-oxide (TMAO), short-chain fatty acids (SCFAs), bile acids, and lipopolysaccharide (LPS)-modulate endothelial function, immune cell programming, platelet activity, and plaque stability through receptor-mediated signaling and epigenetic regulation. SCFAs demonstrate potentially protective effects via GPCR and HDAC pathways, while TMAO is associated with atherothrombotic risk. However, much mechanistic evidence derives from preclinical studies. Heterogeneity from diet, geography, host characteristics, renal function, and medications substantially influences microbiota-CVD associations. CONCLUSION: The gut-vascular connection is biologically plausible, but definitive clinical causality remains unproven. Microbiome-directed therapies (dietary modulation, pre/pro/synbiotics, targeted metabolite inhibition) are investigational. Prospective, standardized, adequately powered human studies with clinically meaningful outcomes are essential before routine cardiovascular application.

Gastrointestinal Microbiome

Natural products alleviate exercise-induced fatigue by modulating gut microbiota: a systematic review.

BACKGROUND: Exercise-induced fatigue critically impairs athletic performance and training quality. The gut microbiota, as a key regulator of the "gut-muscle axis," has emerged as a promising anti-fatigue target. Natural products - owing to their diverse sources, structural complexity, and favorable safety profiles - have attracted growing research interest. However, a systematic synthesis comparing their anti-fatigue effects via gut microbiota modulation across different sources is lacking. SCOPE AND APPROACH: We systematically searched PubMed, Web of Science, the Cochrane Library, and CNKI for original studies that administered natural products and concurrently assessed gut microbiota changes and anti-fatigue outcomes. Twenty-six studies (25 animal experiments and 1 human trial) were included and categorized into seven groups by source and chemical characteristics. A descriptive systematic review was conducted to identify common mechanisms and source-specific differentiations. KEY FINDINGS AND CONCLUSIONS: The enrichment of short-chain fatty acid (SCFA)-producing bacteria and the activation of the SCFA-AMPK/PGC-1&#x3b1; axis were shared core events across all product categories. However, source-dependent mechanistic divergences emerged: polysaccharides acted primarily as fermentable substrates with an optimal dose window; polyphenols and saponins exerted dual modulation on both microbiota and host signaling pathways; compound extracts achieved systemic synergy through functional complementation; marine- and animal-derived products exhibited unique targeting profiles and rapid action. Intestinal barrier maintenance and brain-gut axis regulation further extended the anti-fatigue repertoire. Collectively, natural products possess a solid mechanistic basis for alleviating exercise-induced fatigue via gut microbiota remodeling. The differentiated characteristics of these methods in targeting precision and pathway engagement provide a theoretical foundation for designing precision intervention strategies tailored to specific fatigue contexts.

Humans

Probiotic supplementation improves body composition, lipid profiles, and fatty acid metabolism in combat sports athletes during the weight reduction phase.

PURPOSE: Pre-competition weight control for combat sports athletes may alter body composition and fatty acid metabolism. Probiotics have shown potential to regulate overall metabolism; however, their specific effects on fatty acid metabolism during weight control in athletes remain unclear. METHODS: Thirty-two combat sports athletes participating in the 4-week weight reduction period were assigned to either the probiotic group (Group E) or the placebo group (Group C). Body composition, lipid profiles, and fatty acid metabolism were measured before and after the 4-week weight reduction phase. RESULTS: All the athletes experienced a decrease in body weight, body mass index (BMI), body fat percentage, and muscle mass following the 4-week weight loss intervention. Notably, a more significant reduction in body fat percentage (p&#x2009;<&#x2009;0.05) was observed, along with lower levels of triglycerides (TG) and low-density lipoprotein cholesterol (LDL-C), specifically in Group E. Weight loss intervention resulted in increased levels of short-chain fatty acids (SCFAs), specifically acetic acid, propionic acid, and butyric acid. Notably, Group E exhibited higher mean values for SCFAs compared to Group C (p&#x2009;<&#x2009;0.05). Additionally, the serum levels of &#x3b3;-linolenic acid and 8,11,14-eicosatrienoic acid were significantly reduced in Group E (p&#x2009;<&#x2009;0.05). In contrast, the majority of free fatty acids (FFAs) showed significant increases, with greater magnitudes of change observed in Group C (p&#x2009;<&#x2009;0.05). CONCLUSION: Probiotic supplementation can improve body composition, enhance SCFAs levels, and decrease circulating FFAs in combat sports athletes, suggesting that probiotics may have a beneficial impact on pre-competition weight management. TRIAL REGISTRATION NUMBER: chiCTR2400079908 (Reg Date:2024-01-16).

Humans

The gut microbiota-obesity axis in the pathogenesis and prognosis of breast cancer.

BACKGROUND: Breast cancer (BC) remains a major global health concern, accounting for 11.7% of all cancer cases and ranking as the second leading cause of female cancer-related deaths worldwide. Increasing evidence highlights the interplay between&#xa0;gut microbiota (GM) dysbiosis and obesity-associated metabolic dysfunction in BC progression. This review aims to elucidate&#xa0;the role of GM in obese patients with BC. METHODS: A systematic literature search was conducted in PubMed and Web of Science databases for publications from July 2015 to January 2025. Search terms combined BC, GM, obesity, dysbiosis, immunity, and microbiome. Article selection prioritized studies investigating microbial alterations in BC patients, mechanistic links between obesity and cancer progression, and GM-targeted interventions. Both original studies and authoritative reviews were included, supplemented by manual reference screening. DISCUSSION: Obesity may trigger systemic inflammation, altered adipokine secretion, and disrupted steroid hormone metabolism via gut-derived &#x3b2;-glucuronidase activity, thereby exacerbating BC occurrence and recurrence. GM dysbiosis-driven metabolites such as branched-chain amino acids (BCAAs) and short-chain fatty acids (SCFAs) can activate oncogenic signaling pathways and immunosuppressive myeloid-derived suppressor cells (MDSCs), fostering tumor immune evasion. Conversely, dietary interventions, probiotics, and fecal microbiota transplantation (FMT) can alleviate dysbiosis, strengthen gut barriers, and restore anti-tumor immunity, improving chemotherapy response and reducing recurrence. However, challenges persist in deciphering BC subtype-related microbial signatures and optimizing microbiota-targeted therapies. CONCLUSION: Future longitudinal studies are needed to clarify causal relationships, validate microbial biomarkers, and translate preclinical findings into clinical applications. Addressing the gut-breast axis may offer transformative potential for precision oncology in obesity-driven BC.

Humans