13C metabolic tracing in human SGBS cells provides a potential new approach methodology for assessing metabolism-disrupting properties of environmental chemicals

Human exposure to certain environmental chemicals, including phthalates, is linked to metabolic disruption and may thereby contribute to diseases like obesity. However, regulatory methods to evaluate such effects are lacking. DINCH was introduced as a substitute for banned phthalate plasticizers, but its primary metabolite, MINCH, has been shown to promote adipogenesis in human preadipocytes and alter the lipid metabolism of mature adipocytes. To investigate its potential metabolism-disrupting effects, we assessed changes in the central carbon metabolism activity of human preadipocytes and mature adipocytes by ¹³C metabolic tracing. In preadipocytes, MINCH increased glycolysis, pentose phosphate pathway activity, acetyl-CoA production from glucose and glutamine, and pyruvate anaplerosis, indicating a metabolic shift toward adipogenesis. In mature adipocytes, MINCH enhanced glycolysis, glyceroneogenesis, fatty acid oxidation, and oxidative TCA cycle activity, pathways associated with the browning of adipocytes. Elevated UCP1 expression confirmed MINCH-induced browning. Most pronounced effects occurred at micromolar concentrations, whereas subtle changes were already observed at nanomolar concentrations in preadipocytes, the biological relevance of which should be further investigated. Overall, our findings demonstrate the utility of ¹³C metabolic tracing as a New Approach Methodology for detecting chemical-induced metabolic alterations, thus providing a new perspective for the hazard and risk assessment of environmental contaminants.