Initial exploration of the health effects on Qinghai-Tibetan Plateau yaks following short-term exposure to polystyrene microplastics: Analysis of rumen microbiota, host metabolism, antioxidant function and inflammatory responses.

Microplastics (MPs) are ubiquitous across environments including the Qinghai-Tibet Plateau. Most existing MPs studies focus on aquatic animals and rodents, while MPs influences on yaks (Bos grunniens) remain poorly understood. Using yaks as animal models, we combined metagenomics and metabolomics to explore short-term polystyrene-MPs (PS-MPs) impacts on ruminal microbiota, metabolism, antioxidant capacity and inflammation. Seven-day PS-MPs exposure reshaped rumen microbiota and elevated β-diversity. Four KEGG pathways (peptidoglycan synthesis, vitamin B6/riboflavin metabolism, terpenoid backbone biosynthesis) were enriched alongside altered extracellular polysaccharides composition. Serum metabolomics revealed elevated L-glutamine and indole-3-propionic acid, coupled with reduced 2-C-methyl-D-erythritol 2,4-cyclodiphosphate and indole-3-lactic acid post-exposure. Urinary metabolomics revealed decreased D-erythrose 4-phosphate, dimethyl allyl pyrophosphate, and 2-C-methyl-D-erythritol 2,4-cyclodiphosphate, collectively indicating inhibited terpenoid backbone biosynthesis in yaks. Additionally, PS-MPs triggered inflammatory responses, evidenced by elevated levels of pro-inflammatory cytokines (interferon-γ, interleukin-1β, interleukin-6, interleukin-17, interleukin-22, tumor necrosis factor-α, transforming growth factor-α), yet antioxidant function indexes (total antioxidant capacity, superoxide dismutase, glutathione peroxidase, catalase and malondialdehyde) showed no significant changes. Multi-omics suggested Prevotella ruminicola may help resist PS-MPs invasion. In summary, rumen microbes may alleviate PS-MPs adverse effects, explaining yaks' mild responses to short-term PS-MPs exposure. Long-term MPs effects, tissue deposition and related molecular mechanisms warrant further study.