Objective  To explore the therapeutic mechanism of tetrahydropalmatine (THP) on high glucose-induced insulin resistance (IR) in HepG2 cells.

Methods  An IR model was established using HepG2 cells, which were divided into three groups: the control group (CON), the model group (HG), and the THP intervention group (HG+THP). Cell viability, glucose uptake, and phosphorylated Akt levels were detected to, evaluated the alleviating effect of THP on IR in HepG2 cells. Oxidative stress was assessed by measuring antioxidant enzyme activities [glutathione peroxidase (GSH-PX), superoxide dismutase (SOD), catalase (CAT)], reactive oxygen species (ROS) levels, and lipid peroxidation products [malondialdehyde (MDA), 4-hydroxynonenal (4-HNE)]. Western blot, qPCR, and cell transfection were used to detect the impact of THP on the nuclear factor-erythroid 2-related factor 2 (Nrf2)/antioxidant response element (ARE) signaling pathway related genes and protein expression, and verify the mechanism of THP activating the Nrf2/ARE pathway to alleviate IR induced by high glucose.

Results  Compared to CON group, HG group showed lower 2-NBDG uptake and phosphorylated Akt levels, increased intracellular ROS activity, and reduced antioxidant enzyme activities of GSH-PX, CAT and SOD, with higher MDA and 4-HNE levels. THP intervention improved oxidative stress and restored glucose uptake. Western blot revealed increased Nrf2 and phosphorylated Nrf2 protein levels in HG+THP group, along with upregulated transcription levels of downstream antioxidant genes NAD(P)H: quinine oxidoreductase 1 (Nqo1), heme oxygenase-1 (Ho-1) and CAT. Nrf2 knockdown could inhibit THP's therapeutic effects on the IR induced by high glucose.

Conclusion  THP enhances antioxidant defenses and glucose uptake in HepG2 cells, and alleviates high glucose-induced oxidative stress and IR by activating the Nrf2/ARE pathway, which has the potential to be developed as a drug for the treatment of IR and metabolic diseases.

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