Curcumin Treatment Ameliorates Hepatic Insulin Resistance Induced by Sub-chronic Oral Exposure to Cadmium LOAEL Dose via NF-κB and Nrf2 Pathways.

Abstract

Cadmium (Cd) is a global pollutant, and its accumulation in the liver causes oxidative stress, inflammation, insulin resistance (IR), and metabolic complications. This study investigated whether curcumin treatment could alleviate hepatic IR in Wistar rats exposed to sub-chronic cadmium and explored the underlying molecular pathways. Male Wistar rats were divided into a control group (standard normocaloric diet + cadmium-free water) and a cadmium group (standard normocaloric diet + drinking water with 32.5 ppm CdCl₂) for 30 days. Oral glucose tolerance, insulin response, and IR were assessed using mathematical models. Liver tissue was analyzed for markers of oxidative stress, inflammation, and key regulatory pathways, including NF-κB, Nrf2, MAPKs (JNK and p38), and the IRS1-Akt pathway. We established an effective curcumin dose of 250 mg/kg for 5 days orally. Results demonstrated that after 30 days of exposure, cadmium accumulated in the liver, inducing an oxidative and inflammatory state. This was characterized by increased expression of NF-κB, JNK, and p38, along with diminished Nrf2 expression, hepatic IR, hyperglycemia, and hyperinsulinemia. Curcumin treatment effectively alleviated these metabolic disorders by restoring the balance between NF-κB and Nrf2 in the liver, modulating the MAPK pathway, and, consequently, improving oxidative and inflammatory balance. In conclusion, this study suggests that cadmium induces hepatic IR through an imbalance between NF-κB and Nrf2 signaling pathways. Curcumin treatment appears to improve these pathways, thereby ameliorating hepatic IR.