(PTFS14-04-26) Early-Life High-Fat Diet-Driven Mammary microRNA Remodeling Bridges Gut Microbiome Dysbiosis and Breast Microenvironment Alterations

Objectives: Childhood and adolescence represent critical windows of susceptibility when dietary exposures may influence later breast cancer risk. However, how diet during early life impacts the gut-breast axis remains poorly defined. This study investigated how miRNA bridges the gut microbiome dysbiosis induced by early-life high-fat diet (HF) and mammary microenvironment disruption that may predispose to breast cancer in later life.

Methods: Female C57BL/6J mice were fed LF diet (10 kcal% fat) or HF diet (60 kcal% fat) from 4 to 12 weeks of age (equivalent to human childhood and adolescence). Animals were euthanized at 12 weeks of age or at 24 weeks of age after maintenance chow. Mammary miRNAs were quantified by qPCR. Fecal microbiome was profiled. Breast/blood biomarkers were summarized as pathways by calculating the mean z-score of their constituent parameters. Spearman correlations and Cytoscape networks (|r|≥0.5, p≤0.05) were used to identify cross-omics modules and hubs.

Results: HF altered mammary miRNAs at both time points, surprisingly with stronger effects at 24 weeks. At 12 weeks, 9/27 microRNAs differed (FDR q < 0.05; HF n=4, LF n=5), including higher miR-221/320a/190b/9 and lower miR-193b; at 24 weeks, 21/27 miRNAs differed (q < 0.05; HF n=5, LF n=5), with higher miR-27a/190b and lower miR-137/324/140/200b. Pathway analyses connected miRNA with inflammation (miR-146a-), adipogenesis (miR-304+, miR-200b+), Wnt pathway (miR-200+, miR-146a-), and proliferation (miR-320a+; miR-146a-). Interestingly, folate/one-carbon metabolism showed strongest coupling, with miR-146a-, miR-193b-, miR-320a+, and miR-27b+. Taxa–miRNA analysis identified miR-103/107 and miR-21/221/155 positively linked to taxa such as Bilophila/Alistipes and inversely linked to Roseburia. Network hubs included Enterorhabdus, folate status, miRNAs (miR-103/107/146a), Wnt-signaling components (Wisp1, Cyclin D1, and C-Myc), inflammatory cytokines (TNF-α/COX2/IL6).

Conclusions: Early-life HF diet induces persistent miRNA remodeling associated with gut microbiome shift and the breast microenvironment alteration, supporting the presence of a disrupted gut–miRNA–breast axis, collectively suggesting a potential predisposition to breast tumorigenesis.

Funding Sources: USDA/NIFA AFRI grants (2025-67017-45104, ZL) and USDA//NIFA Hatch project (MAS00586, ZL).