Repressive effects of oat extracts on intracellular lipid-droplet formation in adipocytes and a three-dimensional subcutaneous adipose tissue model

We assessed the repression of lipid-droplet formation in mouse mesenchymal stromal preadipocytes OP9 by specified oat extracts (Hatomugi, Coix lacryma-jobi var. ma-yuen) named “SPH” which were proteolytically and glucosyl-transferredly prepared from finely-milled oat whole-grain. Stimulation of OP9 preadipocytes with insulin-containing serum-replacement promoted differentiation to adipocytes, concurrently with an increase in the intracellular lipid droplets by 51.5%, which were repressed by SPH-bulk or SPH-water-extract at 840 ppm, to 33.5% or 46.9%, respectively, but not by SPH-ethanol-extract at the same dose, showing the hydrophilic property of the anti-adipogenetic ingredients. The intracellular lipid droplets were scanty for intact preadipocytes, small-sized but abundant for the SPH-unadministered adipocytes, and large-sized but few for SPH-bulk-administered adipocytes being coexistent with many lipid-droplet-lacking viable cells, suggesting “the all-or-none rule” for lipid-droplet generation in cell-to-cell. Hydrogen-peroxide-induced cell death in human epidermal keratinocytes HaCaT was prevented by SPH-bulk at 100 or 150 ppm by 5.6–8.1%, being consistent with higher viabilities of SPH-bulk-administered OP9 cells, together with repressions of both cell shrinkage and cell detachment from the culture substratum. In three-dimensional subcutaneous adipose tissue models reconstructed with HaCaT-keratinocytes and OP9-preadipocytes, lipid droplets were accumulated in dermal OP9-cell-parts, and repressed to 43.5% by SPH-bulk at 840 ppm concurrently with marked diminishment of huge aggregates of lipid droplets. Thus SPH-bulk suppresses adipogenesis-associated lipid-droplet accumulation during differentiation of OP9 preadipocytes together with lowered cytotoxicity to either HaCaT keratinocytes or the preadipocytes.