The difference in gut microbiome composition of melanoma patients regarding their dietary fibre intake

Introduction: The gut microbiome has been recently put in focus for its implications in the pathogenesis and treatment of melanoma, and together with diet may have an influence on the effectiveness of treatment. Dietary fibre (DF) intake impacts gut microbiome composition and metabolic function but greatly varies across individuals whose response to fibres depends on their baseline gut microbiome. This study aimed to determine microbiome differences among melanoma progression-free survival patients regarding their DF intake.

Methods: Croatian metastatic melanoma patients with a complete and sustained response to immunotherapy (N = 15, male 80%, average age 61.0 ±12.2 years) were prospectively profiled for gut (faecal) microbiota signatures and dietary intake (four 24-hour recalls three weeks before the stool sample). Patients were grouped regarding the average DF intake of ≥ 25g/day (high fibre group HFG, N=8) and < 25g/day (low fibre group LFG, N=7).

Results: HFG had significantly higher intake and energy proportion of mono-unsaturated fatty acids (p=0.007) and omega-3 fatty acids (p=0.049), and lower alcohol intake (p=0.046) than LFG patients. HFG patients showed an increase in the proportion of Phocaeicola dorei, Bacteroides cellulosilyticus and Holdemania massiliensis on LEfSE analysis, while LFG exhibited a higher abundance of Ruminococcus, Blautia wexlerae, Anaerobytricum hellii, and Ruthenibacterium edouardi.

Conclusion: DF and omega-3 fatty acids have proven to be associated with promoting intestinal integrity, enhancing short-chain fatty acid production, and altering gut inflammatory state. We demonstrated differences in gut microbiome composition between HFG and LFG metastatic melanoma patients with complete and sustained response to immunotherapy; which further exhibits a potential for health and intestinal homeostasis. The presented difference could be explained by the causal variance in intestinal microbial community ecology that is possibly affected by various environmental involvements, such as diet.