Vitamin D and adipose tissue—more than storage

Abstract

The pandemic increase in obesity is inversely associated with vitamin D levels. While a higher BMI was causally related to lower 25-hydroxyvitamin D (25(OH)D), no evidence was obtained for a BMI lowering effect by higher 25(OH)D. Some of the physiological functions of 1,25(OH)2D3 (1,25-dihydroxycholecalciferol or calcitriol) via its receptor within the adipose tissue have been investigated such as its effect on energy balance, adipogenesis, adipokine, and cytokine secretion. Adipose tissue inflammation has been recognized as the key component of metabolic disorders, e.g., in the metabolic syndrome. The adipose organ secretes more than 260 different proteins/peptides. However, the molecular basis of the interactions of 1,25(OH)2D3, vitamin D binding proteins (VDBPs) and nuclear vitamin D receptor (VDR) after sequestration in adipose tissue and their regulations are still unclear. 1,25(OH)2D3 and its inactive metabolites are known to inhibit the formation of adipocytes in mouse 3T3-L1 cell line. In humans, 1,25(OH)2D3 promotes preadipocyte differentiation under cell culture conditions. Further evidence of its important functions is given by VDR knock out (VDR−/−) and CYP27B1 knock out (CYP27B1 −/−) mouse models: Both VDR−/− and CYP27B1−/− models are highly resistant to the diet induced weight gain, while the specific overexpression of human VDR in adipose tissue leads to increased adipose tissue mass. The analysis of microarray datasets from human adipocytes treated with macrophage-secreted products up-regulated VDR and CYP27B1 genes indicating the capacity of adipocytes to even produce active 1,25(OH)2D3. Experimental studies demonstrate that 1,25(OH)2D3 has an active role in adipose tissue by modulating inflammation, adipogenesis and adipocyte secretion. Yet, further in vivo studies are needed to address the effects and the effective dosages of vitamin D in human adipose tissue and its relevance in the associated diseases.

Body composition and metabolic profile in adults with vitamin D deficiency

“…The association between vitamin D and fat percentage can be explained by vitamin D storage in the adipose tissue, and there is an inverse correlation between serum 25OHD and total adipose tissue and its fractions [37,38]. High waist circumference was observed in the Vitamin D Deficiency group, which can be attributed to the active role that vitamin D plays in the adipose tissue by modulating the inflammatory response and reducing adipogenesis and adipocyte secretion [39]. A meta-analysis including groups of different ages found an association between vitamin D deficiency and obesity, regardless of age, latitude, cutoff point for vitamin deficiency, and the Human Development Index of the region where the study was carried out [40].…”

Vitamin D modulates adipose tissue biology: possible consequences for obesity?

“…Many studies have examined the role of 1,25(OH) 2 D in the proliferation and differentiation of murine 3T3-L1 pre-adipocytes (52,(58)(59)(60)(61) . Low 1,25(OH) 2 D concentrations were associated with an inhibition of adipogenesis and a reduction of TAG accumulation in 3T3-L1 cells, even if the opposite effects, i.e.…”

Vitamin D deficiency of unknown etiology

“…The only possible explanation for his Vitamin D deficiency could be his obesity [1,2] . It is argued that increase fat sequesters the Vitamin D [2,3] . Usually with this degree of Vitamin D deficiency one with expect secondary hyperparathyroidism.…”