Vitamin D is sequestered in Fat: total body, adipose, and liver – Dec 2018

Associations of different body fat deposits with serum 25-hydroxyvitamin D concentrations.

Clin Nutr. 2018 Dec 18. pii: S0261-5614(18)32586-X. doi: 10.1016/j.clnu.2018.12.018

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All analyses were adjusted for age, ethnicity, educational level, chronic diseases, smoking, alcohol use and physical activity.
Analyses of abdominal subcutaneous and visceral adipose tissue were additionally adjusted for total body fat.
Analyses of hepatic fat were additionally adjusted for total body fat and visceral adipose tissue.

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Rafiq R1, Walschot F2, Lips P2, Lamb HJ3, de Roos A3, Rosendaal FR4, Heijer MD5, de Jongh RT2, de Mutsert R4.

• 1 Department of Internal Medicine and Endocrinology, VU University Medical Center, Amsterdam Movement Sciences, Amsterdam, the Netherlands. ra.rafiq at vumc.nl.
• 2 Department of Internal Medicine and Endocrinology, VU University Medical Center, Amsterdam Movement Sciences, Amsterdam, the Netherlands.
• 3 Department of Radiology, Leiden University Medical Center, Leiden, the Netherlands.
• 4 Department of Clinical Epidemiology, Leiden University Medical Center, Leiden, the Netherlands.
• 5 Department of Internal Medicine and Endocrinology, VU University Medical Center, Amsterdam Movement Sciences, Amsterdam, the Netherlands; Department of Clinical Epidemiology, Leiden University Medical Center, Leiden, the Netherlands.

BACKGROUND & AIMS:
Obesity is a well-established risk factor of vitamin D deficiency. However, it is unclear which fat deposit is most strongly related to serum 25-hydroxyvitamin D (25(OH)D) concentrations. Our aim was to distinguish the specific contributions of total body fat (TBF), abdominal subcutaneous adipose tissue (aSAT), visceral adipose tissue (VAT) and hepatic fat on 25(OH)D concentrations.

METHODS:
We performed a cross-sectional analysis of the Netherlands Epidemiology of Obesity study, a population-based cohort study. We used linear regression analyses to examine associations of TBF, aSAT, VAT (n = 2441) and hepatic fat (n = 1980) with 25(OH)D concentrations. Standardized values were used to compare the different fat deposits.

RESULTS:
Mean (SD) age and 25(OH)D concentrations of the study population was 56 (6) years and 70.8 (24.2) nmol/L, respectively. TBF was inversely associated with 25(OH)D concentrations in women, but not in men. One percent higher TBF was associated with 0.40 nmol/L (95%CI: -0.67 to -0.13) lower 25(OH)D. aSAT was not associated with 25(OH)D concentrations. One cm2 higher VAT was associated with 0.05 nmol/L (-0.09 to -0.02) lower 25(OH)D in men, and 0.06 nmol/L (-0.10 to -0.01) lower 25(OH)D in women. Hepatic fat was only associated with 25(OH)D in men. A tenfold increase in hepatic fat was associated with 6.21 nmol/L (-10.70 to -1.73) lower 25(OH)D. Regressions with standardized values showed VAT was most strongly related to 25(OH)D.

CONCLUSIONS: In women, TBF and VAT were inversely related to 25(OH)D concentrations. In men, VAT and hepatic fat were inversely related to 25(OH)D concentrations. In both groups, VAT was most strongly associated with 25(OH)D concentrations.