Visceral and subcutaneous fat mass association with serum 25(OH)D concentrations in Brazilian adults

Abstract

Vitamin D status is influenced by a number of factors including dietary intake, skin pigmentation and sun exposure. Serum concentration of 25(OH)D may also decrease due to its sequestration by fat tissue. We herein investigated whether fat compartments (visceral and subcutaneous) are differently associated with vitamin D status. We evaluated 514 adults (33–79 y; 266 women and 248 men) who are part of a cohort of employees at a university in Rio de Janeiro, the “Estudo Pró‐Saúde”. Serum 25(OH) concentrations were analyzed by using a chemiluminescent enzyme‐labeled immunometric assay. Fat distribution was assessed by DXA (IDXA, GE Health Care). Analysis of visceral adipose tissue (VAT) was performed by CoreScan VAT software. Total subcutaneous adipose tissue (SAT) was obtained by subtracting the visceral fat from total fat mass of each individual. An objective estimate of natural and sun‐induced skin color was measured by reflectance colorimetry using a Chroma Meter CR‐400 (Konica Minolta) followed by calculation of Individual Typology Angle (ITA°) and Sun Exposure Index (SEI). Serum 25(OH)D association with visceral and subcutaneous fat mass was investigated using multivariate linear regression models that also included ITA°, SEI, month and year of blood collection, as independent variables. Additionally, differences in mean serum 25(OH)D by quartiles of visceral and subcutaneous fat mass were evaluated by ANCOVA with adjustment for month and year of blood collection, and SEI. 72% of the participants were overweight or obese, 54% had serum 25(OH)D concentrations below 20ng/ml and 92% below 30ng/ml. Both SAT (β=−0.129, P=0.022) and VAT (β=−0.109, P=0.046) appeared as significant predictors of serum 25(OH)D in a stepwise linear regression that also tested ITA°, SEI, month and year of blood collection, as independent variables. Compared to the first quartile of SAT (<20.6Kg of SAT; 22.87±0.69ng/ml), individuals in the second, third and fourth quartiles had lower serum 25(OH)D (19.14±0.69, 18.56±0.69 and 16.77±0.69ng/ml, respectively, p<0.001). Compared to the first quartile of VAT (<0.7Kg of VAT; 20.70±0.71ng/ml), only individuals in the fourth quartile had lower serum 25(OH)D (17.24±0.71ng/ml, P<0.01). Having SAT or VAT higher than median (26.0Kg and 1.15Kg, respectively) significantly increased the chance of having serum 25(OH)D lower than 20ng/mL (SAT: OR 2.00; 95% CI 1.41–2.86 and VAT: OR 1.58; 95% CI 1.11–2.24; P<0.05) or lower than 30ng/mL (SAT: OR 2.05; 95% CI 1.05–4.00 and VAT: OR 2.29; 95% CI 1.16–4.52; P<0.05). Our results suggest that the excess of both subcutaneous and visceral fat compartments may contribute to decrease serum 25(OH)D concentrations, independently of skin pigmentation and sun exposure.Support or Funding InformationFundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ, grant number E‐26/102.201/2013 and E‐26/110.116/2014, for FFB), Brazil.