Betaine alleviates fluoride-induced learning and memory impairment in offspring rats through DNA methylation of GNAS

The aim of this study was to explore the DNA methylation mechanisms by which maternal betaine (BET) supplementation during pregnancy alleviates fluoride-induced learning and memory impairments in offspring rats. Female and male rats were mated 2:1 in cage. After pregnancy, they were divided into control group, sodium fluoride (NaF) group, low BET group, and high BET group. The neurobehavioral test showed that slower swimming speed, longer escape latency and fewer platform shuttles were observed in NaF groups, but these were reversed by BET intervention. Furthermore, Hematoxylin and Eosin (H&E) staining revealed disrupted structures of hippocampal neurons in the NaF group, a reduction in intracellular Nissl bodies was evidenced by Nissl staining as well. However, BET treatment could improve the above changes. Targeted Bisulfite Sequencing (TBS) analysis showed that DNA methylation levels in the promoter regions of Guanine nucleotide-binding protein Gs subunit alpha (GNAS) was lower in the NaF group compared to controls, and increased after BET intervention. Furthermore, the NaF group showed significantly increased protein and mRNA expression levels of both GNAS, while it was reduced after low-dose BET intervention. Additionally, the protein and mRNA expression of DNA methyltransferases (DNMTs) were significantly reduced in NaF group, whereas a higher expression levels of these protein and mRNA were observed in the low-dose BET group. Maternal BET supplementation attenuates fluoride-induced learning and memory impairments in rats, potentially by elevating DNA methylation levels in the promoter regions of the GNAS genes.