Abstract: OBJECTIVE： To investigate subacute effects of polystyrene microplastics (PS-MPs) on the structure and function of adipose tissue in mice. METHODS：Healthy 6-week-old SPF-grade C57BL/6 mice were randomly divided into a control group (normal saline)，an 80 nm PS-MPs group，and a 5 μm PS-MPs group，with 16 mice in each group，half male and half female. The PS-MPs group was orally exposed to 100 mg/kg of PS-MPs continuously for 7 days. Peripheral blood，inguinal fat，perigordal fat，and brown fat of the neck and shoulder were collected，and lipid levels and fat weight were measured. Adipose tissue structure was observed after HE staining，and expression levels of adipocytokines and genes related to lipid metabolism were measured. RESULTS：Compared with the control group，the 80 nm PS-MPs group showed an increase in the number of peripheral blood leukocytes， neutrophils， and lymphocytes in female mice (P <0.05 or P <0.01)，while only the number of leukocytes increased in male mice (P <0.05). Regarding blood lipids， the 80 nm PS-MPs group showed an increase in triglycerides and low-density lipoprotein (LDL) in female mice (both p < 0.05)，while only the triglyceride level increased in male mice (P <0.05). The 80 nm PS-MPs group showed a decrease in subcutaneous fat，an increase in visceral fat，and an increase in white adipocyte area in female mice (all P <0.05). Visceral fat increased by 76.0% in male mice (P <0.05). Serum leptin， adiponectin， and insulin levels increased in female mice (all P <0.05)， while only leptin increased in male mice (P <0.05). Correspondingly，expression of lipid synthesis genes in white fat of female mice was enhanced while expression of oxidative utilization and decomposition genes was inhibited，and the effect was stronger in the female and 80 nm PS-MPs groups. CONCLUSION：Subacute exposure to PS-MPs led to disordered lipid metabolism and white adipose tissue redistribution in mice. The underlying mechanisms involved promotion of lipid synthesis and inhibition of lipid breakdown and utilization， with effects demonstrating sex-specific and size-dependent characteristics. These findings provide evidence supporting the association between MPs exposure and metabolic disorders.

Key words: microplastics, adipose tissue, metabolic disorder, fat redistribution, subacute toxicity