The intensive application of nanomaterials in the food industry has raised concerns about their potential risks to human health. However, limited data are available on the biological safety of nanomaterials in food, especially at the epigenetic level. This study examined the implications of two types of synthetic amorphous silica (SAS), food-grade precipitated silica (S200) and fumed silica Aerosil 200F (A200F), which are nanorange food additives. After 28-day continuous and intermittent subacute exposure to these SAS via diet, whole-genome methylation levels in mouse peripheral leukocytes and liver were significantly altered in a dose- and SAS type-dependent manner, with minimal toxicity detected by conventional toxicological assessments, especially at a human-relevant dose (HRD). The 84-day continuous subchronic exposure to all doses of S200 and A200F induced liver steatosis where S200 accumulated in the liver even at HRD. Genome-wide DNA methylation sequencing revealed that the differentially methylated regions induced by both SAS were mainly located in the intron, intergenic, and promoter regions after 84-day high-dose continuous exposure. Bioinformatics analysis of differentially methylated genes indicated that exposure to S200 or A200F may lead to lipid metabolism disorders and cancer development. Pathway validation experiments indicated both SAS types as potentially carcinogenic. While S200 inhibited the p53-mediated apoptotic pathway in mouse liver, A200F activated the HRAS-mediated MAPK signaling pathway, which is a key driver of hepatocarcinogenesis. Thus, caution must be paid to the risk of long-term exposure to food-grade SAS, and epigenetic parameters should be included as end points during the risk assessment of food-grade nanomaterials.
Keywords: DNA methylation; food-grade; liver steatosis; potential hepatocarcinogenicity; risk assessment; synthetic amorphous silica.