Effects of lead and cadmium co-exposure on bone mineral density in a Chinese population.

It has been indicated that both cadmium (Cd) and lead (Pb) may have adverse effects on the bone. However, most studies have only focused on a single factor. The primary and main and interactive effects of Cd and Pb on bone mineral density (BMD) in a Chinese population were observed in this study. A total of 321 individuals (202 women and 119 men), aged 27 years and older, living in control and polluted areas, were recruited to participate in this study. The BMD was measured through dual energy X-ray absorptiometry (DXA) at the proximal radius and ulna. The samples of urine and blood were collected to determine the levels of Cd and Pb in the urine (UCd and UPb) and blood (BCd and BPb). The Cd and Pb levels of people living in the polluted area were significantly higher than those living in the control area (p<0.05). The BMD of women living in polluted area was significantly lower than that of women living in the control area (p<0.05). Furthermore, the BMD decreased with increasing of BCd (p<0.05), BPb and UPb in women. The likelihood of low BMD was associated with higher BCd in women (OR=2.5, 95% CI: 1.11-5.43) and BPb in men (OR=4.49, 95% CI: 1.37-14.6). The relative extra risk index of low BMD for female and male subjects with both high levels of BCd and BPb was 0.45 and 1.16, respectively. This study strengthens previous evidence that cadmium and lead may influence the bone and also demonstrates that cadmium and lead may have interactive effects on BMD.

Environmental level of cadmium exposure stimulates osteoclasts formation in male rats.

Low level of cadmium (Cd) exposure may enhance osteoclasts formation in vitro. The aim of the study was to observe the effects of Cd on osteoclasts formation in vivo. Sprague-Dawley male rats were divided into 4 groups which were given Cd via drinking water at concentrations of 0, 2, 10 and 50 mg/L for 12 weeks. At the 12th week, urine samples were collected from all of the rats. All rats were then sacrificed and the blood was collected for biomarkers assay. Bone tissues were dissected for mineral density determinations, histological investigation, tartrate resistant acid phosphatase staining and immunohistochemical staining. The bone mineral density and bone microstructure index of rats treated with 50mg Cd/L were obviously lower than in control rats. Histochemical investigation showed that Cd could induce osteoclasts formation in a dose-dependent manner. Tartrate resistant acid phosphatase 5b levels in rats treated with Cd were higher than the control. Immunohistochemical investigation showed that Cd could enhance receptor-activated nuclear factor kappa B ligand expression (RANKL) and inhibit osteoprotegerin (OPG) expression. Our study evidences in vivo that excessive bone resorption mediated via osteoclasts is an important way for Cd toxic effects on bone and OPG/RANKL may play an important role.

Benchmark dose for estimation of cadmium reference level for osteoporosis in a Chinese female population.

In this study, the reference level of cadmium in urine and blood related with bone damage was assessed using benchmark dose in a Chinese female population. Total of 338 women was recruited, and urine and blood samples were collected from each individual for determination of cadmium in urine (UCd) and blood (BCd). Bone mineral density was measured by dual energy X-ray absorptiometry. BMD and BMDL were calculated corresponding to additional risk of 5% and 10%. With benchmark response (BMR) of 5%/10%, the BMD of BCd, UCd related with osteoporosis was 1.88µg/L/3.23µg/L and 5.30µg/g crea/9.06µg/g crea, and the BMDL-05 was 1.39µg/L/2.38µg/L and 3.78µg/g crea/6.36µg/g crea; the BMD of BCd, UCd related with low bone mass was 0.95µg/L/3.12µg/L and 3.12µg/g crea/5.87µg/g crea, and the BMDL-05 was 0.72µg/L/1.35µg/L and 2.14µg/g crea/3.99µg/g crea. The BMD of UCd in people over 60years old was much lower than that of people less than 60years old. BMD value was related with ages and effects biomarkers. Our data showed that BMD of UCd associated with osteoporosis was lower than that previously estimated.