Chiyo Hayashi

Nail calcium and magnesium content in relation to age and bone mineral density

In view of the importance of calcium (Ca) and magnesium (Mg) as major bone components and nutrients controlling bone metabolism, and the ready availability of nail samples for analysis, clippings of fingernails and toenails were analyzed for Ca and Mg. The clippings were dissolved in nitric acid and analysis was done, using atomic absorption spectrophotometry, in 169 women and 115 men between 20 and 80 years of age. Fingernail Ca concentration in men decreased from 927 ± 50 ppm (mean ± SEM) in their twenties to 464 ± 50 ppm in their eighties, with a significant negative correlation with age (r = −0.322; P < 0.0001) and such a negative correlation was also shown in the women (r = −0.269; P = 0.0004). Toenail Ca concentrations also decreased significantly with age in men (r = −0.534; P < 0.0001) and women (r = −0.224; P = 0.0016). Fingernail Mg concentration, in contrast, increased significantly with age in both men (r = 0.209; P = 0.0145) and women (r = 0.280; P < 0.0001), but toenail Mg failed to show significant changes with age in either men or women. Multiple stepwise regression analysis of age and lumbar bone mineral density (LBMD) on fingernail Ca concentration eliminated age before LBMD. In a separate group of 33 women in their sixties, a significant positive correlation was noted between fingernail Ca and LBMD (r = 0.544; P = 0.0016) and between toenail Ca and LBMD (r = 0.399; P = 0.0215). A negative correlation was also noted between fingernail Mg concentration and LBMD (r = −0.389; P = 0.0252). Nail mineral content may be utilized as one of the indicators of bone mineral metabolism.

High Cadmium Accumulation Among Humans and Primates: Comparison Across Various Mammalian Species—A Study from Japan

The majority of existing literature reports that cadmium (Cd) is toxic to humans and most living organisms. This paper reports the results of our study that measured Cd levels in the livers and kidneys of humans and other 50 mammalian species under normal conditions in Japan. The study tests the differences in the Cd concentrations across different mammalian species and sexes. Our results revealed that (1) there is a strong correlation between the Cd levels in the livers and kidneys across all examined species, (2) humans exhibit the highest Cd accumulation level in both organs, (3) primates also show a high Cd concentration at a level close to humans, (4) mice and rats show low Cd levels in both organs, indicating that humans accumulate about a few thousand times more Cd than mice and rats, and (5) the Cd concentration of female mammals is more than double of males for both organs. Our results indicate that these cross-sex as well as cross-species discrepancies cannot be explained by the difference in daily Cd intake. While further research is necessary to determine any potential role of Cd accumulation, we speculate that Cd plays some physiological function in the renal cortex of humans and primates.

Cadmium exposure induces expression of the HOXB8 gene in COS-7 cells

Cadmium (Cd) is a serious toxic metal, which is classified as a possible human carcinogen. We assessed the effects of Cd on the expression levels of homeobox genes, which are associated with carcinogenesis. Among 6 homeobox genes examined in this study, only HOXB8 exhibited increased mRNA expression in COS-7 cells treated with 10 microM CdCl(2). Semiquantitative reverse transcription-polymerase chain reaction analysis revealed that the HOXB8 mRNA level was increased by a maximum of 5.4-fold after 6h of Cd exposure. The levels of HOXA7, A9, C4, C9 and C10 mRNAs decreased from 0.1 to 0.3-fold. Silencing of HOXB8 mRNA expression using a siRNA increased HOXC9 and C10 mRNA expression levels by 6.6- and 1.9-fold, respectively. These results suggest that HOXB8 upregulation is associated with suppression of HOXC9 and C10, and that decreased expression of HOXC9 and C10 after Cd exposure is partly due to HOXB8 induction. In conclusion, Cd disrupts the HOX network. Comprehensive analyses of all the HOX gene expression levels in the presence of Cd may afford clues toward understanding Cd-induced carcinogenesis and teratogenesis.

Itai-itai disease is not associated with polymorphisms of the estrogen receptor α gene

Abstract Itai-itai (or ouch-ouch) disease is a syndrome accompanied by bone mineral disorders, and which may be related to oral cadmium exposure. Itai-itai predominantly affects postmenopausal women with a history of multiple childbirths. Recently, it has been reported that polymorphisms of the estrogen receptor α (ERα) gene are associated with postmenopausal reduction of bone mineral density in Japanese women. However, estrogen receptors have never been studied in itai-itai disease. In this study, we examined the genotypic distributions of PvuII and XbaI restriction fragment length polymorphisms (RFLPs) of the ERα gene in patients with itai-itai disease and compared them with those of control subjects. The RFLPs are represented here as Pp (PvuII) and Xx (XbaI); the capital and small letters signify the absence and presence of restriction sites, respectively. The genotypic distributions of the patient group were: PP, 14.8%; Pp, 55.6%; pp, 29.6%; XX, 7.4%; Xx, 29.6%; and xx, 63.0%. These distributions were similar to those observed for the control groups, hence no pattern of genotypic distribution was observed that could be related to itai-itai disease. We conclude that RFLPs of the ERα gene may not be associated with itai-itai disease.