Interaction of Vitamin D-BODIPY With Fat Cells and the Link to Obesity-associated Vitamin D Deficiency.

BACKGROUND/AIM: Obese individuals often exhibit vitamin D deficiency, potentially due to sequestration in fat cells. Little is known about how vitamin D3 enters adipocytes and associates with the intracellular lipid droplet.

MATERIALS AND

METHODS

Newly differentiated human and mouse (3T3-L1) adipocytes and primary mouse adipocytes were treated with vitamin D3 covalently linked to green fluorescent BODIPY (VitD-B) or Green BODIPY (GB) as control. Cells were exposed to 10-100 nM concentrations for various lengths of time (1-48 h). Fluorescence microscopy assessed vitamin D distribution.

RESULTS

VitD-B demonstrated stable incorporation into adipocytes without enzymatic cleavage, as HPLC showed no free vitamin D3 after 72 h. Fluorescence microscopy showed GB uptake was rapid and persisted for 48 h. VitD-B uptake was more gradual compared to GB in the human and 3T3-L1 adipocytes. Primary mouse adipocytes exhibited similar uptake patterns, with VitD-B appearing within 1 h and fluorescence intensity increasing 1.2-fold at 8 h and 5.7-fold at 24 h. GB exhibited rapid fluorescence uptake in these same cells, 29-fold higher than VitD-B at 1 h. At 24 h, some VitD-B treated cells exhibited greater fluorescence intensity around the surface of the lipid droplets, which was not observed in GB. Isolated lipid droplets exhibited rapid and immediate uptake of both VitD-B and GB, indicating a strong affinity for these lipid structures. The time-dependent accumulation of vitamin D3 in human adipocytes mirrored VitD-B uptake.

CONCLUSION

VitD-B is a reliable proxy for studying the dynamics of vitamin D3 uptake in adipocytes.