Systematic Review and Meta-Analysis of the Effects of Endocrine Disrupting Chemicals on Circadian Clock Gene Expression

Background: Endocrine-disrupting chemicals (EDCs) such as bisphenol A (BPA), PFOS, PCBs, DEHP, and dioxins are known to interfere with hormonal systems. Emerging evidence suggests that EDCs can also disrupt circadian rhythm by altering the expression of core clock genes like BMAL1, PER1, CRY1, and CLOCK. However, no prior meta-analysis has comprehensively quantified this impact across multiple biological models. Objective: To systematically review and meta-analyze the effects of EDC exposure on circadian clock gene expression across human, animal, and in vitro studies. Methods: This review followed a PROSPERO-registered protocol (CRD420251068975). Databases searched included PubMed, Scopus, GEO, and ToxNet from January 2000 to June 2025. Inclusion criteria encompassed in vivo, in vitro, or epidemiological studies reporting gene expression data for BMAL1, PER1, CRY1, and CLOCK after EDC exposure. Random-effects meta-analysis was performed using standardized mean differences (SMDs). Risk of bias was assessed using OHAT and the Newcastle-Ottawa Scale. Results: From 342 screened records, 19 studies met inclusion criteria, and 10 were eligible for meta-analysis. EDC exposure was associated with significant downregulation of circadian genes, particularly BMAL1 and PER1. The pooled effect size was SMD = -0.48 (95% CI: -0.59 to -0.37; p <0.001), with moderate heterogeneity (12 = 41%). Funnel plots showed no substantial publication bias. Conclusion: This meta-analysis demonstrates consistent and statistically significant suppression of core circadian genes by chronic EDC exposure. These findings highlight the importance of including chronodisruption markers in toxicological and occupational health surveillance frameworks.. KEYWORDS: Endocrine Disrupting Chemicals, Circadian Rhythm, Gene Expression, BMAL1, PER1, CRY1, CLOCK, Chronodisruption, Toxicogenomics. References 1. Bottalico LN, Weljie AM. Cross-species physiological interactions of endocrine disrupting chemicals with the circadian clock. Gen Comp Endocrinol. 2020;292:113466. 2. Ono M, Dai Y, Fujiwara T, Fujiwara H, Daikoku T, Ando H, et al. Influence of lifestyle and the circadian clock on reproduction. Reprod Med Biol. 2025;24(1):1-11. 3. Sen A, Sellix MT. The circadian timing system and environmental circadian disruption: From follicles to fertility. Endocrinology. 2016;157(10):3364-3376. 4. Yuan W, Liu L, Wei C, Li X, Sun D, Dai C, et al. Identification and meta- analysis of copy number variation-driven circadian clock genes for colorectal cancer. Oncol Lett. 2019;18(6):6090-6098. 5. Rashed N, Liu W, Zhou X, Bode AM, Luo X. The role of circadian gene CLOCK in cancer. Biochim Biophys Acta Mol Cell Res. 2024;1871(1):119097. 6. Škrlec I, Talapko J, Džijan S, Cesar V, Lazić N, Lepeduš H. The association between circadian clock gene polymorphisms and metabolic syndrome: A systematic review and meta-analysis. Biology (Basel). 2021;10(6):462. 7. Crislip GR, Johnston JG, Douma LG, Costello HM, Juffre A, Boyd K, et al. Circadian rhythm effects on the molecular regulation of physiological systems. Compr Physiol. 2021;11(1):127-178. 8. Shilts J, Chen G, Hughey JJ. Evidence for widespread dysregulation of circadian clock progression in human cancer. PeerJ. 2018;6:e4327. 9. Haque SN, Booreddy SR, Welsh DK. Effects of BMAL1 manipulation on the brain's master circadian clock and behavior. Yale J Biol Med. 2019;92(2):251-258. 10. Sharma A. Variable directionality of gene expression changes across generations does not constitute negative evidence of epigenetic inheritance. Environ Epigenet. 2015;1(1):dvv003. 11. Elhassan YH, Alahmadi F, Albadawi EA, Albarakati A, Aljohany AH, Alzaman NS, et al. The relationship between maternal exposure to endocrine-disrupting chemicals and the incidence of congenital heart diseases: A systematic review and meta-analysis. Metabolites. 2024;14(2):149. 12. Sun C, Li C, Liu W, Schiöth HB. Generation of endogenous promoter- driven luciferase reporter system using CRISPR/Cas9 for investigating transcriptional regulation of the core clock gene BMAL1. Biomedicines. 2022;10(10):2440. 13. Leso V, Battistini B, Vetrani I, Reppuccia L, Fedele M, Ruggieri F, et al. The endocrine disrupting effects of nanoplastic exposure: A systematic review. Toxicol Ind Health. 2023;39(5):222-236. 14. Kopp R, Martínez 10, Legradi J, Legler J. Exposure to endocrine disrupting chemicals perturbs lipid metabolism and circadian rhythms. J Environ Sci (China). 2017;61:61-72. 15. Shetty V, Adelman ZN, Slotman MA. Effects of circadian clock disruption on gene expression and biological processes in Aedes aegypti. BMC Genomics. 2024;25(1):102. 16. Ding L, Weger BD, Liu J, Zhou L, Lim Y, Wang D, et al. Maternal high fat diet induces circadian clock-independent endocrine alterations impacting the metabolism of the offspring. iScience. 2024;27(5):107642. 17. Caballero-Gallardo K, Olivero-Verbel J, Freeman JL. Toxicogenomics to evaluate endocrine disrupting effects of environmental chemicals using the zebrafish model. Curr Genomics. 2016;17(3):206-219. 18. Bertram MG, Gore AC, Tyler CR, Brodin T. Endocrine-disrupting chemicals. Curr Biol. 2022;32(15):R869-R874. 19. Wong KH, Durrani TS. Exposures to endocrine disrupting chemicals in consumer products: A guide for pediatricians. Curr Probl Pediatr Adolesc Health Care. 2017;47(5):107-118. 20. Thakkar S, Seetharaman B, Kumar H, Vasantharekha R. Endocrine- disrupting chemicals exposure alter neuroendocrine factors, disrupt cardiac functions and provoke hypoxia conditions in zebrafish model. Arch Environ Contam Toxicol. 2022;82(3):459-468.