Soluble extract of soybean fermented with Aspergillus oryzae GB107 inhibits fat accumulation in cultured 3T3-L1 adipocytes.

BACKGROUND/OBJECTIVES: This study was conducted to investigate the effects of fermented soybean (FS) extract on adipocyte differentiation and fat accumulation using cultured 3T3-L1 adipocytes. MATERIALS/METHODS: 3T3-L1 adipocytes were treated with FS and nonfermented soybean (NFS) extract during differentiation for 10 days in vitro. Oil red O staining was performed and glycerol-3-phosphate dehydrogenase (GPDH) activity was measured for analysis of fat accumulation. Expressions of adipogenic genes were measured. RESULTS: Soluble extract of soybean fermented with Aspergillus oryzae GB107 contained higher levels of low-molecular-weight protein than conventional soybean protein did. FS extract (50 µg/ml) inhibited adipocyte differentiation and fat accumulation during differentiation of 3T3-L1 preadipocytes for 10 days in vitro. Significantly lower GPDH activity was observed in differentiated adipocytes treated with the FS extract than those treated with NFS extract. Treatment with FS extract resulted in decreased expression levels of leptin, adiponectin, and adipogenin genes, which are associated with adipogenesis. CONCLUSIONS: This report is the first to demonstrate that the water-soluble extract from FS inhibits fat accumulation and lipid storage in 3T3-L1 adipocytes. Thus, the soybean extract fermented with A. oryzae GB107 could be used to control lipid accumulation in adipocytes.

The regulation of adipogenesis through GPR120.

Recently, it has been found that long-chain fatty acids activate the G protein-coupled receptors (GPRs), GPR120 and GPR40. However, there have been no reports to date on the possible physiological roles of these GPRs in adipose tissue development and adipocyte differentiation. GPR120 mRNA was highly expressed in the four different adipose tissues, and the amount of mRNA was elevated in adipose tissues of mice fed a high fat diet. However, GPR40 mRNA was not detected in any of the adipose tissues. The expression of GPR120 mRNA was higher in adipocytes compared to stromal-vascular (S-V) cells. The level of GPR120 mRNA increased during adipocyte differentiation in 3T3-L1 cells. Similar results were observed in human adipose tissue, human preadipocytes, and cultured adipocytes. Moreover, use of a small interference RNA (siRNA) to down-regulate GPR120 expression resulted in inhibition of adipocyte differentiation. Our results suggest that GPR120 regulates adipogenic processes such as adipocyte development and differentiation.

Up-regulation of the claudin-6 gene in adipogenesis.

To investigate the role of claudin-6 in adipogenesis, claudin-6 mRNA was examined in adipose tissues and adipocyte differentiation. Claudin-6 mRNA was found to be differentially expressed in four different adipose tissues, and up-regulated in each fat depot of mice fed a high-fat diet as compared to a normal-fat diet. Levels of claudin-6 transcripts were increased during differentiation of 3T3-L1 cells in vitro. Moreover, small interfering RNA (siRNA)-mediated reduction of claudin-6 mRNA inhibited differentiation of 3T3-L1 cells. These results suggest that claudin-6 is another important regulator in adipogenesis and fat deposition.