Prenatal And Early Postnatal Exposure To Low-dose Cadmium Accelerates Liver Cancer Caused By High-fat Choline-deficient Diet Combined DEN In Mice

Background:Cadmium is an ubiquitous non-essential trace metal,which is hazardous substance to humans.Cadmium is regarded as a metoblic disturbance,and the effects of long-term cadmium exposure include increased risks of diabetes,obesty,cardiovascular disorders and cancer.Maternal exposure to cadmium,causes obesity and metabolic changes in offspring,including nonalcoholic fatty liver disease(NAFLD)-like pathology in the liver.The obesity related liver pathology,such as steatosis and steatohepatitis can proceed to HCC.However,whether maternal cadmium exposure accelerating liver cancer in the offspring is unknown.Aim:This study aims to investigate the impact of early-life(preconception,gestational and weaning)exposure to cadmium chloride(Cd Cl₂)in drinking water on the incidence of and potential mechanisms for HCC in the offspring subjected to postweaning HCC-induction.Methods:Seven-week-old parental male and female C57BL/6J mice were divided at random into two groups:the control group and the cadmium group.The mice in the cadmium group were exposed to drinking water containing Cd Cl₂(8.15 mg/L for 5ppm of Cd).After 16 weeks,male and female mice were housed together to mate.At weaning,the control offspring were subdivided at random into Control and HCC-induction(Con-Can)groups.Similarly,female and male offspring with early-life cadmium chloride exposure(Cd group)were allocated to the HCC induction(Cd-Can)group.The Con-Can and Cd-Can group mice received an intraperitoneal injection of N-Nitrosodiethylamine(DEN)at 25 mg/kg immediately after weaning and were fed a HFCD diet(58%kcal from fat).After 23 and 26 weeks treatment,the mice received intraperitoneal glucose tolerance test(IPGTT).Then they were sacrificed to record tumor number on the liver surface and collect the blood and liver tissues.Measure the cadmium,triglyceride(TG)and malondialdehyde(MDA)levels in the liver tissues,as well as the alanine transaminase(ALT),TG,and cholesterol levels in the blood.The proteins of the peri-tumor liver tissue was extracted to detedct the expression of inflammatory response and fatty acid(FA)metabolism related proteins.Perform pathological and immunohistochemistry staining of the liver tissue to observe the morphology and specific molecular expression changes.Results:At the point of weaning,the liver cadmium content is significantly higher in mice with cadmium chloride exposure compared to mice without exposure.The difference disappears at the age of 26 and 29 weeks old.Both male and female mice showed higher body weight gain in the cadmium chloride exposure group.For females,the early-life cadmium chloride exposure also worse insulin intolerance without significant promotion of DEN/HFCD-induced liver tumor.In contrast,the early-life cadmium chloride exposure induced earlier,more and larger size tumors.The liver peri-tumor tissue of mice with early-life cadmium chloride exposure exhibited higher phosphorylation of Nuclear factor kappa B(NF-?B)and Signal transducer and activator of transcription 3(STAT3),and higher expression of Vascular adhesion molecule(VCAM),NOD-,LRR-and pyrin domain-containing protein 3(NLRP3),and Interlukin-1 beta(IL-1?),also displayed higher Cluster of differentiation 36(CD36)expression and lower Fatty acid-binding protein 1(FABP1),Peroxisome proliferator-activated receptor alpha(PPAR?),and Peroxisome proliferator activated receptor?coantivator 1 alpha(PGC1?)expression,accompanied with higher MDA and lower esterified TG content,than that of mice without exposure.Conclusions:In summary,the early-life exposure to low cadmium chloride accelerates the development of liver cancer induced by DEN/HFCD diet in male mice,which may attribute to inflammation followed lipotoxicity,caused by increased fatty acid uptake but decreased fatty acid consumption.