Microplastics are linked to a number of health problems. (Photo by SIVStockStudio on Shutterstock)
In a Nutshell
- Male mice exposed to microplastics before conception produced female offspring with insulin resistance on a high-fat diet, while male offspring remained largely unaffected
- Microplastic exposure altered more than 4,000 small RNA molecules in sperm that can influence gene expression in developing embryos
- Female offspring from exposed fathers had elevated inflammatory proteins in their livers linked to insulin resistance, despite normal body weight
- The findings suggest microplastic exposure may have intergenerational health consequences, though whether similar effects occur in humans requires further research
Fathers exposed to microplastics before conception may be setting their daughters up for metabolic problems later in life. A new mouse study shows when male mice consumed plastic particles before breeding, their female offspring developed insulin resistance on a high-fat diet while male offspring remained largely unaffected.
Research from the University of California, Riverside found an unusual pattern. Female descendants of microplastic-exposed fathers showed significantly impaired insulin tolerance despite maintaining normal body weight and fat mass. Their brothers had reduced fat deposits but normal insulin function.
Male mice received microplastics daily for four weeks before mating with unexposed females. The dose matched amounts humans might encounter through everyday exposure to contaminated food and water. The fathers themselves showed no health changes from the exposure.
Daughters Develop Insulin Resistance
When fed a Western-style high-fat diet after weaning, female offspring from exposed fathers failed insulin tolerance tests. Blood glucose levels dropped more slowly after insulin injection compared to controls, showing their bodies struggled to respond properly to the hormone. This condition, called insulin resistance, increases risk for Type 2 diabetes and cardiovascular disease.
Examining liver tissue revealed why. Female offspring from microplastic-exposed fathers had elevated levels of inflammatory proteins. One protein called IKKβ acts as a central coordinator of inflammatory responses and has been directly linked to obesity-related insulin resistance in previous research. None of these changes appeared in male offspring.
Sperm RNA Carries Environmental Signals
The study, published in the Journal of the Endocrine Society, identifies a potential mechanism behind these sex-specific effects. Microplastic exposure substantially changed small RNA molecules in sperm. These molecular fragments act like instructions that can influence which genes turn on or off in developing embryos.
Scientists used an advanced sequencing technique that overcomes limitations of traditional methods by detecting chemically modified RNA molecules. The analysis uncovered more than 4,000 changes in small RNAs from sperm of microplastic-exposed mice.
To test whether these altered RNAs could affect development, researchers introduced three candidates into mouse embryonic stem cells. All three changed expression of genes important for metabolism and development. One RNA fragment increased expression of an inflammatory gene while decreasing a gene that helps cells respond to insulin. Two other RNA fragments decreased expression of genes involved in muscle development, gut formation, and glucose transport.
These experimental results in stem cells match some problems observed in female offspring: elevated inflammation and impaired insulin signaling.
Why Female Offspring Are More Vulnerable
The sex-specific pattern observed in this study fits with findings from other research on paternal environmental exposures. Studies have found that fathers fed high-fat diets or exposed to arsenic produced female offspring with glucose intolerance, while male offspring remained unaffected.
Scientists don’t fully understand why female offspring appear more vulnerable. Possibilities include differences in sex chromosomes, sex hormone effects, and distinct patterns in how male versus female embryos reset their gene activity patterns during early development.
Male offspring weren’t completely unaffected by paternal microplastic exposure, but their changes differed from their sisters. Males from exposed fathers had significantly reduced belly fat despite similar overall body weight. Female offspring showed the opposite pattern—reduced muscle mass with normal fat mass.
Human Microplastic Exposure
Humans face widespread exposure to microplastics through contaminated food, water, and air. Recent studies have detected plastic particles in human blood, placentas, liver, kidneys, and brain tissue. Researchers have also found them in testicular tissue, semen, and placentas.
The health consequences need more investigation, though emerging evidence links microplastics to increased cardiovascular disease risk, metabolic dysfunction, and premature aging. Most research has focused on direct exposure effects rather than potential impacts on future generations.
This study suggests parental microplastic exposure may carry consequences across generations. The four-week exposure period in fathers preceded conception, indicating the plastic particles affected sperm development rather than directly contaminating embryos. Whether similar mechanisms operate in humans requires direct investigation.
The study focused on polystyrene microplastics at one dose level and examined only first-generation offspring. Questions remain about other plastic types, dose-response relationships, and whether effects would persist across multiple generations.
Paper Notes
Limitations: The study has several notable limitations. Sample sizes were relatively small, with 4-12 animals for most metabolic tests and 3 samples for PANDORA-seq sperm RNA sequencing experiments. The research only examined F1 (first generation) offspring, so whether effects persist across multiple generations is unknown. Researchers did not measure energy expenditure or food intake, which could help explain the observed body composition changes in offspring. The study used a single dose of polystyrene microplastics, so dose-response relationships and effects of other plastic types were not evaluated. While the study demonstrates associations between sperm RNA changes and offspring phenotypes, establishing definitive causation would require additional experiments such as sperm RNA injection studies into normal zygotes.
Funding and Disclosures: This work was partially supported by National Institutes of Health grants R35ES035015 and R01HL167206 to Changcheng Zhou. The authors declare they have no conflicts of interest to disclose. The small RNA sequencing data generated in this study have been deposited in the GEO database under accession code GSE306011.
Publication Information: Seung Hyun Park, Jianfei Pan, Xudong Zhang, Ting-An Lin, Sijie Tang, Xiuchun Li, Sihem Cheloufi, Qi Chen, Tong Zhou, and Changcheng Zhou. “Paternal microplastic exposure alters sperm small non-coding RNAs and affects offspring metabolic health in mice.” Journal of the Endocrine Society, 2025. DOI: 10.1210/jendso/bvaf214. The authors are affiliated with the Division of Biomedical Sciences at University of California Riverside School of Medicine, Molecular Medicine Program at University of Utah School of Medicine, Department of Biochemistry at UC Riverside, and Department of Physiology and Cell Biology at University of Nevada Reno School of Medicine.
