Palmitic acid-induced metabolic stress alters differentiation-associated gene expression in human ameloblast-like...

Metabolic stress during enamel development may influence ameloblast differentiation and enamel formation, although the underlying mechanisms remain poorly understood. In this study, we investigated transcriptional and cellular responses to palmitic acid (PA) in the human ameloblast-like cell line HAM3 using a custom quantitative reverse transcription polymerase chain reaction panel based on amelogenesis imperfecta-related genes. PA exposure under both sustained low-dose conditions (50 μM for 24 h) and acute high-dose conditions (500 μM for 4 h) induced coordinated transcriptional changes associated with enamel maturation and cellular stress responses. Expression of the maturation-associated gene AMTN was detectable at baseline and consistently upregulated following PA exposure, whereas that of the epithelial transcription factor gene BCL11B was selectively suppressed under acute high-dose conditions. PA also induced expression of stress-responsive genes including GDF15 and HMOX1. In parallel, immunoblotting demonstrated increased levels of cleaved caspase-3 and LC3-II, while immunofluorescence analysis revealed accumulation of p62-positive structures, consistent with stress-associated apoptosis and altered autophagy-related processes. These findings suggest that PA-induced metabolic stress promotes a stress-associated pseudo-maturation-like transcriptional state in ameloblast-like cells while activating coordinated cellular stress responses. This study provides a potential framework linking metabolic stress environments to altered enamel development.