Novel nutraceutical combination restores hepatic deiodinase expression and protein levels under inflammatory conditions: evidence from an in vitro model

Background/objectives Thyroid hormone activation depends on the conversion of T4 to T3 by the selenoenzyme DIO1, whose expression is suppressed by inflammation and oxidative stress. This study evaluated whether a combination of vitamin A, selenium, taurine, oleic acid, and resveratrol could counteract Lipopolysaccaride (LPS)-induced downregulation of DIO1 in HepG2 cells. Methods Cytotoxicity of Taurine, Resveratrol, Retinol, and Oleic acid was assessed in FB789 and HepG2 cells by MTT assay. Non-toxic, biologically active concentrations (2.5 μM Taurine; 2.5 μM Resveratrol; 50 μM Retinol; 100 μM Oleic Acid) were used to test DIO1 modulation following LPS exposure (1 μg/mL). DIO1 mRNA and protein levels were quantified by qRT-PCR and Western blot. Results All compounds exhibited acceptable cell viability profiles at low-to-mid range doses. LPS markedly suppressed DIO1 mRNA expression, whereas each nutrient partially restored its levels. Notably, the combined treatment completely prevented LPS-mediated DIO1 downregulation and significantly increased DIO1 protein abundance compared with both medium and LPS-treated controls. Conclusion In this in vitro model, a specific combination of bioactive nutrients effectively restored DIO1 expression under inflammatory conditions, supporting peripheral thyroid hormone activation. These findings provide mechanistic rationale for nutrition-based strategies aimed at mitigating inflammation-related impairment of T4-to-T3 conversion in vulnerable or catabolic clinical populations.