Ultrasonic assessment of calcaneus in inhabitants in a cadmium-polluted area

Osteoporosis and renal dysfunction in a general population exposed to cadmium in China

Osteoporosis is a common metabolic disease characterized by low bone mass and microarchitectural deterioration of bone tissue. Many factors are involved in the occurrence of osteoporosis. Cadmium can cause both osteomalacia and osteoporosis and these effects have long been investigated through various epidemiological or experimental studies. The present study examines a possible relationship between cadmium nephropathy and its effects on the skeleton in populations living in a polluted area in southeast China. Monophoton absorptiometry was used to measure bone mineral density in the population and the Z score (the number of SD from the difference between the measured bone density of the individual and the group mean value for sex- and age-matched controls) was introduced to define osteoporosis (Z score < -2). Osteoporosis caused by cadmium exposure was demonstrated in this study on a general population environmentally exposed to cadmium in China. It was found that there were significant differences in the prevalence of osteoporosis among the different urinary cadmium groups (chi2 = 18.84, P = 0.0008). The linear trend test gave chi2 = 16.281, P = 0.00005. There was a dose-response relationship between cadmium exposure (urinary cadmium) and prevalence of osteoporosis. Of 31 subjects with osteoporosis, 23 subjects were suffering from renal dysfunction. The prevalence of renal dysfunction (74.19%) was significantly higher than that in those without osteoporosis (chi2 = 16.53, P < 0.001). Stratum analysis was performed to further assess the relationship between bone damage and renal impairment caused by cadmium. There was a significant difference between those with and without tubular damage (chi2 = 19.92, P = 0.000) but not in those with and without glomerular damage (chi2 = 0.08, P = 0.114). This showed that glomerular dysfunction plays a smaller role than tubular dysfunction in the causation of bone damage. It was found that the prevalence of osteoporosis increases with increasing values of parameters of tubular damage. Osteoporosis caused by cadmium is thus related to kidney dysfunction and especially to tubular damage and its severity but not to glomerular damage. The present study has thus demonstrated the combined adverse effects (osteoporosis and renal dysfunction) caused by environmental exposure to cadmium for the first time in Asia outside the endemic area in Japan.

Urinary cadmium excretion is correlated with calcaneal bone mass in Japanese women living in an urban area

Nine hundred eight women aged 40-88 years living in a non-Cd-polluted area in Japan were analyzed for urinary cadmium (Cd), N-acetyl-beta-D-glucosaminidase (NAG) activity, beta(2)-microglobulin (B2MG) concentration, and for the stiffness index (STIFF) of calcaneal bone using an ultrasound method. The urinary Cd in the subjects, with a mean and range of 2.87 and 0.25-11.4 microg/g creatinine, respectively, showed a significant correlation with NAG but not with B2MG. STIFF was significantly inversely correlated with urinary Cd, and the association remained significant after adjusting for age, body weight, and menstrual status, suggesting a significant effect of Cd on the bone loss in these subjects without signs of Cd-induced kidney damage. A two-fold increase in urinary Cd was accompanied by a decrease in STIFF corresponding to a 1.7-year rise in age. These results emphasize the need for reassessment of the significance of Cd exposure in the general Japanese population.

Assessment of bone metabolism in cadmium-induced renal tubular dysfunction by measurements of biochemical markers

Bone metabolism related to the severity of cadmium (Cd)-induced renal tubular dysfunction (RTD) was assessed by measuring several bone biochemical markers. Fifty-three female subjects with RTD aged 65-76 years (mean 70.0+/-3.3 years) and who lived in the Cd-polluted Jinzu River basin in Toyama, Japan were studied. Bone alkaline phosphatase (bone-ALP), intact bone Gla-protein (intact-BGP) and carboxy-terminal propeptide of type I collagen (PICP) in serum as bone formation markers and pyridinoline (Pyr) and deoxypyridinoline (Dpyr) in urine as bone resorption markers were measured. All markers of bone turnover were increased and significantly correlated with each other, suggesting that bone formation and resorption were coupled and increased in Cd-induced RTD. Fractional excretion of beta(2)-microglobulin (beta(2)-m, FE(beta 2-m)) as an index of severity of Cd-induced RTD was extremely varied ranging from 0.45 to 53%. There were no significant correlations between FE(beta 2-m) and each of the five bone biochemical markers. The bone turnover in Cd-induced RTD appeared to be determined by the glomerular filtration rate (GFR): in subjects with GFRs above 50 ml/min, the levels of bone-ALP or intact-BGP tended to be inversely related to the GFRs, whereas in subjects with GFRs below 40 ml/min, those levels tended to decrease. These results suggest that the bone turnover, in particular the bone formation, was influenced by renal tubular function as assessed by the levels of GFR in Cd-induced RTD.

Low-level cadmium exposure and osteoporosis

Osteoporosis is a major cause of morbidity worldwide. A number of risk factors, such as age and gender, are well established. High cadmium exposure causes renal damage and in severe cases also causes osteoporosis and osteomalacia. We have examined whether long-term low-level cadmium exposure increases the risk of osteoporosis. Bone mineral density (BMD) in the forearm was measured in 520 men and 544 women, aged 16-81 years, environmentally or occupationally exposed to cadmium, using dual-energy X-ray absorptiometry (DXA) technique. Cadmium in urine was used as the dose estimate and protein HC was used as a marker of renal tubular damage. There was a clear dose-response relation between cadmium dose and the prevalence of tubular proteinuria. Inverse relations were found between cadmium dose, tubular proteinuria, and BMD, particularly apparent in persons over 60 years of age. There was a dose-response relation between cadmium dose and osteoporosis. The odds ratios (ORs) for men were 2.2 (95% CI, 1.0-4.8) in the dose group 0.5-3 nmol Cd/mmol creatinine and 5.3 (2.0-14) in the highest dose category (> or = 3 nmol/mmol creatinine) compared with the lowest dose group (< 0.5 nmol Cd/mmol creatinine). For women, the OR was 1.8 (0.65-5.3) in the dose group 0.5-3 nmol Cd/mmol creatinine. We conclude that exposure to low levels of cadmium is associated with an increased risk of osteoporosis.

Variation in blood concentrations of cadmium and lead in the elderly

This study aims at characterizing blood concentrations of cadmium (B-Cd) and lead (B-Pb) in a group of 176 men and 248 women, 49-92 years of age (mean 68 years), selected from the Swedish Twin Registry. Metal concentrations were determined using graphite furnace atomic absorption spectrophotometry. B-Cd ranged from 0.05 to 6.8 microg Cd/L (median 0.36 microg Cd/L) and B-Pb from 5.6 to 150 microg Pb/L (median 27 microg Pb/L). As expected, smokers had higher B-Cd than nonsmokers (median 1.3 versus 0.32 microg Cd/L), while B-Pb was not significantly related to smoking habits. Among nonsmokers, women had higher B-Cd than men (median 0.35 versus 0.25 microg Cd/L). In men, but not women, B-Cd increased with age and consequently the gender-related difference in B-Cd was most obvious in the youngest age group. On the other hand, women had lower B-Pb than men (median 24 versus 30 microg Pb/L). In both men and women, B-Pb decreased between 50 and 70 years of age, perhaps reflecting decreased energy intake. In women, the highest B-Pb in the 50-55 years age group is probably related to an increased release of Pb from the skeleton during postmenopausal bone demineralization. After about 70 years, B-Pb tended to increase, which probably is a cohort effect due to much higher Pb exposure 10-30 years ago when leaded gasoline was used.