Abstract
BackgroundSelenium (Se) status in non-deficient subjects is typically assessed by the Se contents of plasma/serum. That pool comprises two functional, specific selenoprotein components and at least one non-functional, non-specific components which respond differently to changes in Se intake. A more informative means of characterizing Se status in non-deficient individuals is needed.MethodsMultiple biomarkers of Se status (plasma Se, serum selenoprotein P [SEPP1], plasma glutathione peroxidase activity [GPX3], buccal cell Se, urinary Se) were evaluated in relation to selenoprotein genotypes (GPX1, GPX3, SEPP1, SEP15), dietary Se intake, and parameters of single-carbon metabolism in a cohort of healthy, non-Se-deficient men (n = 106) and women (n = 155).ConclusionsPlasma Se concentration was 142.0 ± 23.5 ng/ml, with GPX3 and serum-derived SEPP1 calculated to comprise 20% and 34%, respectively, of that total. The balance, comprised of non-specific components, accounted for virtually all of the interindividual variation in total plasma Se. Buccal cell Se was associated with age and plasma homocysteine (hCys), but not plasma Se. SEPP1 showed a quadratic relationship with body mass index, peaking at BMI 25-30. Urinary Se was greater in women than men, and was associated with metabolic body weight (kg0.75), plasma folate, vitamin B12 and hCys (negatively). One GPX1 genotype (679T/T) was associated with significantly lower plasma Se levels than other allelic variants. Selenium intake, estimated from food frequency questionnaires, did not predict Se status as indicated by any biomarker. These results show that genotype, methyl-group status and BMI contribute to variation in Se biomarkers in Se-adequate individuals.
Highlights
Selenium (Se) status in non-deficient subjects is typically assessed by the Se contents of plasma/ serum
It is well established that Se-deficient individuals show subnormal levels of several Se biomarkers, including some with functional significance, such as the selenoproteins, and others that indicate the amounts of Se in the body, such as the Se contents of tissues and body fluids
Estimation of Dietary Selenium Intake This cohort was of relatively high Se status, as indicated by plasma Se level (142.0 ± 23.5 ng/ml) other biomarkers of Se status (Table 1) and estimated daily Se intake of 109.1 ± 43.6 μg/d
Summary
Selenium (Se) status in non-deficient subjects is typically assessed by the Se contents of plasma/ serum. That selenium (Se) plays roles in cancer prevention has been demonstrated in numerous studies with a variety of animal and cellular models [1,2,3,4] and in several clinical trials [5,6,7]. The largest study, the Selenium and Vitamin E Cancer Prevention Trial (SELECT), failed to detect cancer risk reduction with Se-supplementation [8], indicating that Se-supplementation may not benefit all individuals. Rayman et al [9] pointed out that the results of SELECT are consistent with those of the Nutritional Prevention of Cancer (NPC) Trial [7,10]. In NPC, reduced prostate cancer risk was observed mostly among subjects with baseline plasma Se concentrations. Non-deficient individuals, have maximal selenoenzyme expression [11,12,13], rendering those parameters non-informative regarding changes in Se intake
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