Deciphering the regulatory role of selenium on cadmium bioavailability and toxicity: From the perspective of gut microbiota

Residents in areas naturally rich in cadmium (Cd) and selenium (Se) frequently exhibit exceptional longevity, raising intriguing questions about the interplay between the two elements. However, whether co-exposure affects the bioavailability of Cd remains unclear. Meanwhile, it is necessary to unclose the antagonistic mechanisms between Se and Cd. Here, a mouse bioassay was conducted to assess the impact of Se addition at low (0.1 mg/kg), medium (0.5 mg/kg) and high (2 mg/kg) doses, and duration (10 and 30 d) on Cd bioavailability of rice and Cd-induced hepatic toxicity. Results showed that Se cannot reduce Cd bioavailability. Medium Se addition for a duration of 10 days (MSe10) exhibited the highest efficacy in attenuating hepatic inflammation, as evidenced by augmented antioxidant enzyme activity, alleviated pathological damage, and increased levels of anti-inflammatory metabolites within the liver. The benefit was associated with its restoration of the gut microbiota and changes in key metabolic pathways. Notably, MSe10 increased the abundance of Faecalibaculum and Dubosiella, and enhanced the levels of secondary bile acids. Neither 0.1 mg/kg, 2 mg/kg nor long time addition of Se was beneficial for liver recovery. The hepatic lesions were fecal microbiota-dependent, as supported by fecal microbiota transplantation. Microbiota from MSe10 were capable to ameliorate hepatic inflammation, strengthen the intestinal barrier, and inhibit lipopolysaccharides (LPS) accumulation in blood. Additionally, the study provided insights into Se as an intervention for Cd toxicity, highlighting the appropriate dosage and its potential to reduce health risks.