Selenium level is associated with apoE ε4 in rural elderly Chinese

Se is an essential trace element in human nutrition associated with the activity of the antioxidant enzyme glutathione peroxidase. It is considered to be a protective agent against free radicals through enhanced enzyme activity. Associations between low Se and increased risk in various disease indices (cancer, CVD, reproduction and neonatal health, asthma) have been reported(1,2). There is increased interest in using Se as a biomarker for various cancer outcomes(3,4). Measuring Se intake in large cohort studies is often difficult because populations are often mobile and consume foods that were produced and prepared in different areas of the world. Se content in foods, especially grain, is highly variable depending on the Se content of the soils in which they are grown(5). Moreover, supplements containing Se are often ingested particularly by health-conscious individuals, further confounding the results. The rural elderly Chinese population represents a unique opportunity for studying Se exposure. The rural Chinese are unusually stable with most living in the same village throughout their entire life and consuming food that is locally grown. In addition, it is rare for these villagers to take dietary supplements. Chinese scientists have assembled extensive data on Se distributions in many parts of the country; hence it is possible to select sites with differing Se levels so that an extended range can be achieved to maximize statistical power for detecting potential associations. We have recruited a cohort of 2000 elderly Chinese from four rural counties to study Se level and its association with various health outcomes(6). The apoE gene is involved in lipoprotein metabolism and is a risk factor for Alzheimer’s disease and cardiovascular disorders. There are also previous reports that an Se-deficient diet or targeted removal of a gene that causes complete loss of selenoprotein expression results in increased plasma cholesterol concentration with an increase in apoE protein(7–9). Previous studies on predictors of toenail Se or serum Se have mostly concentrated on demographic factors such as age and gender. In the present paper, we examine the association between apoE genotype and Se levels measured in nail samples.