|Van Loan, Marta|
Submitted to: Nutrients
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/21/2013
Publication Date: 8/26/2013
Citation: Piccolo, B.D., Dolnikowski, G., Seyoum, E., Thomas, A., Gertz, E.R., Souza, E.C., Keim, N.L., Adams, S.H., Newman, J.W., Woodhouse, L.R., Van Loan, M.D. 2013. Association between subcutaneous white adipose tissue and serum 25-hydroxyvitamin D in overweight and obese adults. American Journal of Clinical Nutrition. 5(9), 3352-3366. DOI:10.3390/nu5093352. Interpretive Summary: Vitamin D can be obtained from food and from the body’s own metabolic process to make vitamin D from exposure to sunlight. Despite these 2 sources for vitamin D, many individuals have low blood levels of vitamin because of poor food choices and a lack of sun exposure. Epidemiologic data has shown that as body mass index (BMI) increases blood levels of vitamin D are lower. Results from these large cross-sectional studies and animal models suggest that vitamin D may be sequestered in fat tissue and thus lower vitamin D levels in overweight and obese people. Therefore, we conducted a study in which fat tissue samples were obtained from overweight and obese adults before and after weight loss to determine the vitamin D concentration in fat tissue and if the levels in fat tissue change with weight loss. We found a significant positive relationship between vitamin D concentration in fat tissue and in blood, but the levels did not change with weight loss suggesting that vitamin D in fat tissue is not returned to blood with weight and fat loss.
Technical Abstract: Background: Cholecalciferol is known to be deposited in human adipose tissue, but the distribution of 25-hydroxyvitamin D (25(OH)D) in adipose tissue is not known. Objectives: To determine whether 25(OH)D is detectable in subcutaneous white adipose tissue (SWAT) in overweight and obese persons and to determine if SWAT 25(OH)D concentration changed after weight loss. Design: This study was a subset of a larger 15-week weight loss intervention during energy restriction in overweight and obese. Gluteal SWAT biopsies from 20 subjects at baseline and post-intervention were collected. SWAT was analyzed for 25(OH)D by LC/MS/MS. Serum 25(OH)D and 1,25(OH)2D were measured by RIA. Body composition was assessed by dual energy x-ray absorptiometry. Results: SWAT 25(OH)D concentrations were 5.8 ± 2.6 nmol/kg tissue and 6.2 ± 2.7 nmol/kg tissue pre- and post-intervention SWAT, respectively. There was a significant positive association between SWAT 25(OH)D concentration and serum 25(OH)D concentration (r = 0.52, P < 0.01) Conclusion: We detected 25(OH)D in SWAT of overweight and obese adults and these concentrations correlated closely with serum 25(OH)D concentrations. SWAT 25(OH)D concentrations did not significantly change after a moderate reduction in overall adiposity, suggesting that adipose 25(OH)D was not released into circulation with weight loss. More research is needed to understand the interaction between serum and adipose pools of 25(OH)D.