Glutamine metabolism in fluorosis: Integrated metabolomics and transcriptomics analysis

To identify the potential metabolic biomarkers of fluorosis and the pathogenesis of fluorosis.

Sprague Dawley rats in this study were randomly divided into fluoride exposure and control groups. In the fluoride exposure group, six offspring rats without dental fluorosis were defined as group A, and six offspring rats with dental fluorosis were defined as group C. Eight offspring rats in the control group were defined as group B. The metabolites in plasma were determined using GC-MS, with differential metabolites (DMs) identified using VIP > 1, and P < 0.05. Cluster analysis, KEGG pathway enrichment analysis and Receiver Operating Characteristic (ROC) analysis were subsequently performed. The DMs which were caused by fluoride exposure in the previous study were used to verify our results. The GSE70719 from GEO database were used to support this research at the mRNA level and in vitro experiment were selected to verify above results.

The 13 up-regulated and 4 down-regulated DMs were identified in the group A + C, the 18 up-regulated and 4 down-regulated DMs were identified in group A, and the 12 up-regulated and 2 down-regulated DMs were identified in group C. All groups showed enrichment in Aminoacyl-tRNA synthesis, D-glutamine and D-glutamate metabolism, Nitrogen metabolism, and Purine metabolism pathways. ROC analysis revealed that L-glutamine had excellent diagnostic ability for fluorosis (AUC > 0.85, P < 0.05). Changes in major DMs (L-glutamine, 4-hydroxyproline and L-alanine) were consistent with previous findings. Transcriptomic results showed the significant alteration of GLS gene in the fluoride exposure group. In vitro experiments confirmed decreased GLS and SLC1A5 genes expression.

L-glutamine emerges as a potential biomarker for fluorosis. Glutamine metabolism was involved in the pathogenesis of fluorosis.