Intermittent fasting alleviates ulcerative colitis via lithocholic acid-mediated macrophage reprogramming

Ulcerative colitis (UC) is a chronic gut inflammatory disease that flares and remits unpredictably. This study tested whether a 5:2 intermittent fasting (IF) pattern — eating freely five days a week and restricting calories sharply on two days — could reduce intestinal inflammation in a mouse model of chronic colitis. The researchers found that this dietary rhythm reshaped the gut microbiome in ways that boosted production of a specific bile acid called lithocholic acid (LCA). LCA, in turn, switched macrophages (key immune cells in the gut lining) away from a pro-inflammatory state by improving how their mitochondria burn fuel. To test clinical relevance, the team also analyzed tissue and blood samples from UC patients and found that people with higher LCA levels tended to have milder disease, lower erythrocyte sedimentation rate (ESR), and lower fecal calprotectin — two standard markers of intestinal inflammation. The study provides a plausible molecular chain from an eating pattern to microbiome change, to a specific metabolite, to immune reprogramming. While promising, the findings are largely preclinical and require controlled human trials before they can inform patient care.

• 5:2 intermittent fasting (5 days ad libitum, 2 days low-calorie) promoted remission in a chronic murine colitis model, establishing the dietary intervention as effective at the preclinical level.
• IF reshaped gut microbiota composition and enhanced bile acid metabolic flux, with lithocholic acid (LCA) identified as the key elevated metabolite mediating anti-inflammatory effects.
• LCA directly inhibited pro-inflammatory (M1-like) macrophage polarization by inducing metabolic reprogramming — specifically by enhancing mitochondrial oxidative respiration rather than glycolysis.
• In human UC patient samples, higher colonic or systemic LCA levels correlated with milder disease severity, lower erythrocyte sedimentation rate (ESR), and reduced fecal calprotectin, supporting translational relevance.

The study used a 5:2 intermittent fasting protocol applied to a chronic experimental colitis mouse model (specific chemical agent not named in abstract, but consistent with DSS-based chronic colitis). Gut microbiota composition was assessed by 16S rRNA amplicon sequencing, and bile acid profiles were measured by metabolomics. Mechanistic experiments examined LCA's effect on macrophage polarization and mitochondrial function in vitro and/or ex vivo. Human validation used UC patient samples correlated with LCA levels and clinical inflammatory markers (ESR, calprotectin); sample sizes for both animal and human cohorts were not specified in the abstract.

The study is primarily preclinical, and causal inference in the human cohort is limited by its correlational, cross-sectional design — it cannot confirm that raising LCA drives clinical improvement in patients. The specific gut microbial taxa responsible for LCA elevation under IF remain uncharacterized, leaving the microbiome-to-metabolite link mechanistically incomplete. The 5:2 IF model may not translate directly to human compliance, tolerability, or safety in active UC, where caloric restriction could worsen nutritional status. The next critical experiment would be a randomized, controlled pilot trial of 5:2 IF in UC patients with serial LCA measurement, macrophage phenotyping from mucosal biopsies, and validated disease activity indices.

This article extends the bile acid–gut immune axis literature captured in the corpus by providing a dietary intervention lever — intermittent fasting — that elevates lithocholic acid and downstream macrophage reprogramming, a mechanistic layer not addressed by polysaccharide-based approaches seen in [§118], which also alleviates DSS colitis via microbiota modulation but through structurally distinct phytochemicals without a bile acid intermediary. It parallels [§119], where macrophage dysfunction in UC is targeted therapeutically (via ZBP1-driven pyroptosis suppression by Emapunil), confirming that macrophage polarization is a convergent therapeutic node in UC regardless of the upstream trigger. The gut microbiota–metabolite–immune axis logic also parallels [§120], which demonstrates that Eubacterium rectale alleviates IBD through glutamine metabolism and GLS2/NF-κB signaling — a complementary but mechanistically distinct microbial metabolic route to mucosal protection. Together, these articles collectively strengthen the case that intestinal macrophage reprogramming, whether reached through bile acids, amino acid metabolism, or direct pharmacology, represents a tractable therapeutic strategy in UC.

• Emapunil attenuates ulcerative colitis by suppressing Z-DNA binding protein 1 driven pyroptosis and pro-inflammatory polarization in macrophages
  Both target macrophage dysfunction in UC but via entirely different upstream mechanisms (LCA-mitochondrial respiration vs. ZBP1-pyroptosis suppression by Emapunil), making direct comparison informative for understanding which macrophage axis is most druggable.
• Anti-inflammatory and gut microbiota-modulating effects of a novel mannan from Scilla scilloides on DSS-induced colitis in mice
  Both use a DSS-colitis preclinical model and intervene through gut microbiota modulation, but the mannan polysaccharide in [id=118] does not invoke bile acid signaling, allowing readers to isolate the bile acid pathway as a distinguishing mechanistic feature of IF.
• Eubacterium rectale Mitigates Inflammatory Bowel Disease via Modulation of Glutamine Metabolism Through the GLS2 and NF-κB Pathway
  Both identify a gut microbiota-derived metabolite (LCA vs. glutamine/GLS2) as the functional mediator of IBD relief, offering a comparative view of how different microbial metabolic outputs converge on mucosal immune suppression.
• The Role of Vitamin D in Inflammatory Bowel Disease: Clinical Relevance and Therapeutic Potential
  Vitamin D shares with LCA an immunomodulatory role in IBD and acts partly through macrophage polarization and barrier function, making [id=147] a useful comparator for gauging whether LCA's effects are mechanistically distinct or overlapping with established nutritional modulators of UC.