Zinc is an essential trance element, and its homeostasis is controlled by zinc transporter family members. Various approaches have revealed the important roles of zinc homeostasis by zinc transporters in cellular functions, and manifested a role for zinc as a signaling factor: zinc signaling. This short review introduces the zinc biology and zinc signaling with their basic and historical backgrounds.

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We developed a colorimetric reagent kit for determination of zinc in serum, “ACCURAS AUTO Zn”. The reagent is applicable to all auto-analyzers widely used in hospital laboratories, without any serum pretreatment. This kit enables accurate and immediate assay of zinc.

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Increasing evidence suggests that dyshomeostasis of trace elements are implicated in the pathogenesis of various neurodegenerative diseases such as Alzheimer’s disease, prion diseases, and dementia with Lewy bodies. These diseases share similarity in the formation ofβ-sheet containing amyloid fibrils by disease-related proteins includingβ-amyloid protein (AβP), prion protein, α-synuclein, polyglutamine, and the introduction of apoptotic degeneration. Trace elements can bind to these proteins and cause their conformational changes. Furthermore, these proteins are co-localized in synapses and play crucial roles in the regulation of trace elements. Thus, it is possible that the interactions between the disease-related proteins and trace elements are based on the physiological roles of these proteins. We review here the current understanding of the pathology of the neurodegenerative diseases based on the metal-binding to disease-related proteins and on the disruption of metal homeostasis.

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To evaluate a validity of values for manganese (Mn) and molybdenum (Mo) contents of rice described in the Standard Tables of Food Composition in Japan 2010, 15 samples of Japanese brown rice, 53 samples of Japanese polished rice and 10 samples of Chinese polished rice were collected and their Mn and Mo contents were measured. Mean values of Mn in the Japanese brown rice and polished rice were 1.90 and 0.81 mg/100 g, respectively, which were close to values described in the Standard Tables. Mean value of Mn in the Chinese polished rice was 0.77 mg/100 g, which was also close to the values in the Standard Tables. Among the 53 samples of Japanese polished rice, 45 samples (84.9%) showed the Mn contents ranged from 0.6 to 1.0 mg/100 g. These results indicate that the Mn values of rice described in the Standard Tables are highly reliable. On the other hand, mean values of Mo in the Japanese brown rice and polished rice were 63 and 59 µg/100 g, respectively, which were also close to the Standard Tables. However, 42 samples (79.2%) of the Japanese polished rice showed the Mo content of less than 65 µg/ 100 g and a little sample showed more than 2 times of the values of the Standard Tables. Molybdenum contents in the Chinese rice showed higher values and variation than the Japanese rice. These results indicate that a large part of the Japanese rice showed a little lower Mo value than one described in the Standard Tables.

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