The aim of this study was to investigate modifiable predictors of vitamin D status in healthy individuals, aged 55-74, and living across the USA. Vitamin D status [serum 25-hydroxyvitamin D (25(OH)D)] was measured along with age and season at blood collection, demographics, anthropometry, physical activity (PA), diet, and other lifestyle factors in 1357 male and 1264 female controls selected from the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO) cohort. Multivariate linear and logistic regression analyses were used to identify associations with vitamin D status. Three, 29 and 79% of the population had serum 25(OH)D levels <25, <50 and <80 nmol/L, respectively. The major modifiable predictors of low vitamin D status were low vitamin D dietary and supplement intake, body mass index (BMI) >30 kg/m 2 , physical inactivity (PA) and low milk and calcium supplement intake. In men, 25(OH)D was determined more by milk intake on cereal and in women, by vitamin D and calcium supplement and menopausal hormone therapy (MHT) use. Thus targeting an increase in vigorous activity and vitamin D and calcium intake and decreasing obesity could be public health interventions independent of sun exposure to improve vitamin D status in middle-aged Americans.© 2010 Elsevier Ltd. All rights reserved. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. NIH Public Access

Little is known about the mechanism for the prolonged residence time of 25-hydroxyvitamin D (25OHD) in blood. Several lines of evidence led us to propose that skeletal muscle could function as the site of an extravascular pool of 25OHD. In vitro studies investigated the capacity of differentiated C2 murine muscle cells to take up and release 25OHD, in comparison with other cell types and the involvement of the membrane protein megalin in these mechanisms. When C2 cells are differentiated into myotubes, the time-dependent uptake of labeled 25OHD is 2-3 times higher than in undifferentiated myoblasts or nonmuscle osteoblastic MG63 cells (P < .001). During in vitro release experiments (after 25OHD uptake), myotubes released only 32% ± 6% stored 25OHD after 4 hours, whereas this figure was 60% ± 2% for osteoblasts (P < .01). Using immunofluorescence, C2 myotubes and primary rat muscle fibers were, for the first time, shown to express megalin and cubilin, endocytotic receptors for the vitamin D binding protein (DBP), which binds nearly all 25OHD in the blood. DBP has a high affinity for actin in skeletal muscle. A time-dependent uptake of Alexafluor-488-labeled DBP into mature muscle cells was observed by confocal microscopy. Incubation of C2 myotubes (for 24 hours) with receptor-associated protein, a megalin inhibitor, led to a 40% decrease in 25OHD uptake (P < .01). These data support the proposal that 25OHD, after uptake into mature muscle cells, is held there by DBP, which has been internalized via membrane megalin and is retained by binding to actin.

OBJECTIVE: The aim of this study was to identify speci®cally which biochemical indices predict excessive weight gain over time in a cohort of pre-pubertal children. SUBJECTS: Fifty nine healthy pre-pubertal children (age: 6.3 ± 9.8 y). MEASUREMENTS: Children were de®ned anthropometrically and biochemically at baseline. Height and weight measurements were then repeated after six (n 52) and 12 months (n 37). RESULTS: Weight change after six months (de®ned by a change in body mass index (BMI) z-score from baseline) demonstrated no correlation with fasting plasma levels of leptin, insulin, insulin:glucose (IG) ratio, cholesterol, triglyceride or high density lipoprotein (HDL) cholesterol. However, after 12 months there was a signi®cant negative correlation between BMI z-score change and initial plasma leptin (r À0.35, P 0.048) and this relationship strengthened when adjusted for body fat (from bio-electrical impedance; r À0.46, P 0.009). In addition, there was a signi®cant positive relationship between plasma total cholesterol and BMI z score change (r 0.38, P 0.03) and this relationship remained unchanged when adjusted for body fat. No relationship was observed between weight change after 12 months and plasma levels of insulin, IG ratio, HDL cholesterol or triglyceride. CONCLUSION: Plasma leptin and total cholesterol were found to be predictive of weight gain over 12 months in a cohort of pre-pubertal children. These two potential predictors can be readily measured in clinical practice and these ®ndings may represent a method of de®ning the`at risk of obesity' state in childhood.

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In this qualitative study, researchers examined cultural and attitudinal factors that might be related to sun-exposure behaviors among East Asian women living in Australia. Researchers asked Chinese (n = 20) and Korean (n = 16) immigrant women who participated in a larger cross-sectional quantitative study of vitamin D blood levels to volunteer to participate in an in-depth interview in 2010. These women reported a number of cultural factors related to their attitudes and behaviors with regard to sun exposure. They expressed preference for fair skin, a tradition of covering skin when outdoors, and no sunbathing culture. They believed that fair skin was more beautiful than tanned skin. They reported that beauty was the reason for active avoidance of sunlight exposure. Although they reported knowledge of the need for sun avoidance due to skin cancer risk, few reported knowledge about the benefits of sun exposure for adequate vitamin D levels. These findings may provide some reasons for vitamin D deficiency previously reported in these populations. Thus, researchers recommend that these attitudes of excessive sun protection and limiting sun exposure be further investigated as they may have implications for planning and delivery of health promotion programs to this growing population of immigrants in Australia.