Identification and determination of selenoneine, 2-selenyl-N α , N α , N α -trimethyl-L-histidine, as the major organic selenium in blood cells in a fish-eating population on remote Japanese Islands.

Selenoneine is the major selenium compound in fish muscles, and fish appears to be an important source of selenium in the fish-eating population. Selenoneine has strong antioxidant activity and a detoxifying function against methylmercury (MeHg) toxicity. Dietary intake, bioaccumulation, and metabolism of selenoneine have not been characterized in humans. A nutritional survey was conducted in remote islands of the Kagoshima Prefecture in Japan. To evaluate the potential risks and benefits of fish consumption for health, we measured concentrations of selenoneine, total selenium, MeHg, inorganic mercury, and polyunsaturated fatty acid (LC-PUFA) in the blood of a fish-eating human population. The erythrocyte, leukocyte, and platelet residues following removal of serum (cellular fraction) contained 0.510 µg Se/g, 0.212 µg selenoneine Se/g, and 0.262 µg Se-containing proteins Se/g, whereas the serum contained 0.174 µg total Se/g. Selenoneine was highly concentrated in the cellular fraction in a manner that was dependent on subjects' frequency of fish consumption. Concentrations of selenoneine were closely correlated with concentrations of MeHg in the cellular fraction. Selenoneine is the major chemical form of selenium in the blood cells of this fish-eating human population and may be an important biomarker for selenium redox status.

Relationship between RBC mercury levels and serum n3 polyunsaturated fatty acid concentrations among Japanese men and women.

AIMS: To evaluate potential health risk and benefits of fish consumption, the association of fish consumption with total mercury levels in red blood cells (RBCs) and serum eicosapentaenoic acid (EPA) concentrations was examined. SUBJECTS AND METHODS: Study subjects were 269 Japanese (98 men and 171 women) living in a remote island of Kagoshima, and their blood was drawn in 1994. RESULTS: Total mercury levels were related to weekly fish consumption among women (P = 0.035) but not among men (P = 0.643). However, serum EPA levels were not related to fish consumption in both women and men. In contrast, EPA levels in the high-density ipoprotein (HDL) fraction of the sera were significantly related to fish consumption (P values for men and women were 0.014 and 0.073, resp.). Interestingly, mercury levels were related to serum EPA levels and EPA in the HDL fraction of the sera (P = 0.001) among women (P = 0.005) but not among men. Sex differences in fish species consumed may be an explanation for the observed sex difference. CONCLUSION: Those findings suggest that the health benefit of fish consumption can be maximized by the careful selection of fish species consumed.

Scalp hair mercury concentrations in Pakistan.

The presence of mercury in the environment is widespread and persistent, but the extent of exposure of Pakistanis to mercury is virtually unknown. We collected toenail and scalp hair samples from 158 subjects (83 males and 75 females) residing in Lahore and its suburbs. We also conducted a questionnaire survey and personal interviews to obtain information on demographic factors, lifestyles, and socioeconomic factors, among others. Mercury concentration in hair samples was measured by cold vapor atomic absorption spectrometry (CVAAS). In addition, the concentration of selenium in the toenail and hair samples was determined by inductively coupled plasma mass spectrometry (ICP-MS). The mean hair mercury concentration was 0.45 ppm (95% CI = 0.34-0.60) and did not show correlation with fish consumption, age, area of origin, or present residence. Mercury concentration was higher (p = 0.021) in females than in males, and was also higher in subjects with 11 or more years of education (p for trend = 0.013). There were 13 subjects with mercury concentration higher than 10 ppm. Most of them were young females and a few were middle-aged males. When the analysis was confined to subjects with mercury concentrations lower than 0.6 ppm, the amount of fish consumed showed correlation with hair mercury concentration with a marginal statistical significance (p = 0.065). The geometric means of selenium in hair and toenails were 0.87 and 1.01 ppm, respectively. Mercury and selenium concentrations in hair showed no correlation (correlation coefficient = 0.057, p = 0.478). This study shows that mercury exposure levels among residents in Lahore and its suburban areas are relatively low, except among outliers, wherein mercury exposure might be brought about by the use of mercury-containing soaps.

Toenail arsenic levels among residents in Amami-Oshima Island, Japan.

In order to evaluate the current arsenic exposure status and its determinants in Japan, we collected toenail samples from 212 subjects residing in a town with a population of 6,900 in Amami-Oshima Island in August 1999. We measured arsenic concentrations of the toenails using inductively coupled plasma mass spectrometry. In addition, we examined the association of arsenic levels with lifestyles and dietary habits, including the consumption of fish, seaweed, and rice. The mean toenail arsenic level was 0.41 ppm (95% confidence interval, 0.36-0.47), which was about 3-fold higher than those observed in other populations of mainland Kagoshima. Arsenic levels were elevated among current smokers (mean = 0.65; 95% confidence interval, 0.32-1.29) when compared with non-smokers (mean = 0.40; 95% confidence interval, 0.34-0.46), and among the residents consuming 4 bowls or more, of rice every day (mean = 1.97; 95% confidence interval, 0.25-15.75) when compared to residents consuming 3 bowls or less (mean = 0.39; 95% confidence interval, 0.34-0.45). Sex, age, alcohol intake, fish consumption, or seaweed consumption was not associated with toenail arsenic concentration. Further studies seem warranted to examine the cause of relatively high arsenic levels in our study area.

Long-term follow-up study of health status in population living in methylmercury-polluted area.

At present, it is important to follow-up on the health condition of inhabitants living in a methylmercury-polluted area surrounding Minamata City, paying attention to subclinical disorders not only of the central nervous system, which have been concentrically studied for more than 40 years, but also to other health issues as well. We have performed annual follow-up multiple health examinations on about 1,500 persons of ages more than 40 years old in Tsunagi Town near Minamata City each summer from 1984 to 2004. Case-control studies were designed to estimate the role of risk factors for various health issues using geographical differences to compare the verified patients. The results of the study are summarized as follows: (1) There were no significant differences in the prevalence of diseases associated with Minamata disease (MD) (e.g., liver diseases, renal diseases). (2) Subjective complaints, which were related not only to neurological but also to general complaints were consistently much more common in the polluted area than in the control area. (3) Five percent of the inhabitants who were not certified as MD patients had a high predicting index of MD. They could be affected by methylmercury poisoning. It is important to make a differential diagnosis. (4) No significant differences with respect to ADL by residential area were observed. However, MD patients who stayed in their homes showed some impairments of instrumental ADL. (5) It is important to take into consideration mental distress not only from the physical effects but also from the secondary social damage experienced through MD in these area.

Serial study on the association between body mass index and hypertension in rural Japanese.

The objective of this study was to examine the association between body mass index (BMI) and blood pressure. Two sets of cross-sectional data were obtained from annual health examinations for adults aged 40 years and over (n=1,327 in 1993; n=1,302 in 2000) in Tsunagi area of Kumamoto Prefecture, Japan. BMI was associated with mean blood pressure and with prevalence of hypertension both in 1993 and 2000. The association was independent of age, smoking status and alcohol consumption. A significant increase in risk of hypertension was found in most categories of BMI 25.0 and above, and a greater than three fold increase in those with BMI of 27 and above compared with those with BMI of 18.5-22.9. Although mean blood pressure and prevalence of hypertension sharply decreased in 2000 compared with that in 1993, BMI was positively and independently associated with increased blood pressure.

Logistic model analysis of neurological findings in Minamata disease and the predicting index.

OBJECTIVE: To establish a statistical diagnostic method to identify patients with Minamata disease (MD) considering factors of aging and sex, we analyzed the neurological findings in MD patients, inhabitants in a methylmercury polluted (MP) area, and inhabitants in a non-MP area. MATERIALS AND METHODS: We compared the neurological findings in MD patients and inhabitants aged more than 40 years in the non-MP area. Based on the different frequencies of the neurological signs in the two groups, we devised the following formula to calculate the predicting index for MD: predicting index = 1/(1+e(-x)) x 100 (The value of x was calculated using the regression coefficients of each neurological finding obtained from logistic analysis. The index 100 indicated MD, and 0, non-MD). RESULTS: Using this method, we found that 100% of male and 98% of female patients with MD (95 cases) gave predicting indices higher than 95. Five percent of the aged inhabitants in the MP area (598 inhabitants) and 0.2% of those in the non-MP area (558 inhabitants) gave predicting indices of 50 or higher. CONCLUSION: Our statistical diagnostic method for MD was useful in distinguishing MD patients from healthy elders based on their neurological findings.