Formaldehyde alters triglyceride synthesis and very low-density lipoprotein secretion in a time-dependent manner

Formaldehyde is a common indoor air pollutant that is toxic to the liver. This study aimed to investigate the effects of formaldehyde on triglyceride metabolism in human hepatocellular carcinoma cells (HepG2). Cell viability was detected using a MTT (3-(4,5-dimethylthiazol-2-Yl)-2,5-diphenyltetrazolium bromide) assay. Following treatment with different concentrations of formaldehyde for 24 and 48 h, the intra and extra-hepatocellular triglyceride (TG) content was determined using a chemical-enzymatic method; Western blotting was used to detect the levels of fatty acid synthesis and VLDL-related proteins. Our results showed that cell viability significantly decreased after formaldehyde treatment (0.5–12.5 mM, 24/48 h). Extracellular TG levels in the hepatocytes increased after formaldehyde treatment at 0.004 mM–0.1 mM for 24 h. SREBP-1c, ACC, FASN, and MTP, CES3 and DGAT1 proteins increased significantly after 24 h of formaldehyde treatment. Intracellular TG levels decreased for 48 h treatment of formaldehyde. AMPKα increased significantly in all tested groups and p-AMPK increased significantly after 0.1 mM formaldehyde treatment for 48 h. Our results indicated that short–term formaldehyde exposure balances triglyceride metabolism by promoting hepatocellular TG synthesis and VLDL secretion; Long-term formaldehyde disturbs the TG metabolism balance in the hepatocytes.