scholarly journals Evidence for alteration of the vitamin D-endocrine system in obese subjects.

1985 ◽  
Vol 76 (1) ◽  
pp. 370-373 ◽  
Author(s):  
N H Bell ◽  
S Epstein ◽  
A Greene ◽  
J Shary ◽  
M J Oexmann ◽  
...  
2005 ◽  
Vol 289 (1) ◽  
pp. F8-F28 ◽  
Author(s):  
Adriana S. Dusso ◽  
Alex J. Brown ◽  
Eduardo Slatopolsky

The vitamin D endocrine system plays an essential role in calcium homeostasis and bone metabolism, but research during the past two decades has revealed a diverse range of biological actions that include induction of cell differentiation, inhibition of cell growth, immunomodulation, and control of other hormonal systems. Vitamin D itself is a prohormone that is metabolically converted to the active metabolite, 1,25-dihydroxyvitamin D [1,25(OH)2D]. This vitamin D hormone activates its cellular receptor (vitamin D receptor or VDR), which alters the transcription rates of target genes responsible for the biological responses. This review focuses on several recent developments that extend our understanding of the complexities of vitamin D metabolism and actions: the final step in the activation of vitamin D, conversion of 25-hydroxyvitamin D to 1,25(OH)2D in renal proximal tubules, is now known to involve facilitated uptake and intracellular delivery of the precursor to 1α-hydroxylase. Emerging evidence using mice lacking the VDR and/or 1α-hydroxylase indicates both 1,25(OH)2D3-dependent and -independent actions of the VDR as well as VDR-dependent and -independent actions of 1,25(OH)2D3. Thus the vitamin D system may involve more than a single receptor and ligand. The presence of 1α-hydroxylase in many target cells indicates autocrine/paracrine functions for 1,25(OH)2D3in the control of cell proliferation and differentiation. This local production of 1,25(OH)2D3is dependent on circulating precursor levels, providing a potential explanation for the association of vitamin D deficiency with various cancers and autoimmune diseases.


Medicina ◽  
2019 ◽  
Vol 55 (9) ◽  
pp. 541 ◽  
Author(s):  
Luka Vranić ◽  
Ivana Mikolašević ◽  
Sandra Milić

Obesity is defined as an excess amount of body fat and represents a significant health problem worldwide. High prevalence of vitamin D (VD) deficiency in obese subjects is a well-documented finding, most probably due to volumetric dilution into the greater volumes of fat, serum, liver, and muscle, even though other mechanisms could not completely be excluded, as they may contribute concurrently. Low VD could not yet be excluded as a cause of obesity, due to its still incompletely explored effects through VD receptors found in adipose tissue (AT). VD deficiency in obese people does not seem to have consequences for bone tissue, but may affect other organs, even though studies have shown inconsistent results and VD supplementation has not yet been clearly shown to benefit the dysmetabolic state. Hence, more studies are needed to determine the actual role of VD deficiency in development of those disorders. Thus, targeting lifestyle through healthy diet and exercise should be the first treatment option that will affect both obesity-related dysmetabolic state and vitamin D deficiency, killing two birds with one stone. However, VD supplementation remains a treatment option in individuals with residual VD deficiency after weight loss.


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