Soyasapogenols reduce cellular triglyceride levels in 3T3-L1 mouse adipocyte cells by accelerating triglyceride lipolysis

Abstract

Soyasapogenol is a soyasaponin aglycone, which has been suggested to exert a more potent function than the glycoside form. In this study, the effect of soyasapogenol A and B on cultured adipocyte cell function was investigated using mouse 3T3-L1 adipocyte cells. 3T3-L1 cells were treated with insulin, dexamethasone, and 3-isobutyl-1-methylxanthine for differentiation to adipocytes, and the cells were then cultured in the presence of soyasapogenol A or B (6.25 or 12.5 µM). The media were harvested and refreshed every 2 d. After a 10 d culture, the cells were harvested and the triglyceride content of the cells was determined. The triglyceride content of soyasapogenol B-treated cells was significantly lower than those of vehicle-treated cells. Glycerol and free fatty acid levels in the soyasapogenol-treated cell media were higher than those in vehicle cells. However, there was no difference in the level of adipose triglyceride lipase among soyasapogenol A-, soyasapogenol B-, and vehicle-treated cells. The secreted adiponectin and resistin levels of soyasapogenol-treated cell media were also different compared with those of vehicle-treated cells. Especially, the secreted resistin level in soyasapogenol B-treated cell media was obviously reduced compared with that of vehicle-treated cells. Taken together, these results suggest that soyasapogenol B exerted an anti-obesity and anti-diabetic effect on adipocytes by lowering the cellular triglyceride level by accelerating triglyceride lipolysis with reduced resistin secretion.

Keywords: 3T3-L1 adipocyte; Adipocytokine; Lipolysis; Soyasapogenol A; Soyasapogenol B; Triglyceride.

Fig. 1

Chemical structure of soyasapogenol A and B. Chemical structure of soyasapogenol A (A) and soyasapogenol B (B).

Fig. 2

Effect of soyasapogenol A and B on lipid accumulation for 10 d in 3T3-L1 adipocytes. (A) Oil-red O staining and triglyceride content in 3T3-L1 cells treated with 6.25 µM soyasapogenol A or B; (B) oil-red O staining and triglyceride content in 3T3-L1 cells treated with 12.5 µM soyasapogenol A or B; (C) cytotoxic effect on the viability of 3T3-L1 cells treated with 6.25 µM soyasapogenol A or B; (D) cytotoxic effect on the viability of 3T3-L1 cells treated with 12.5 µM soyasapogenol A or B. Values are expressed as mean ± SE (n = 3). Values that do not share the same letter are significantly different (p < 0.05).

Fig. 3

Effect of soyasapogenol A and B on lipolysis for 10 d in 3T3-L1 adipocytes. (A) Glyceride levels in a medium of 3T3-L1 cells treated with 12.5 µM soyasapogenol A or B; (B) free fatty acid levels in 3T3-L1 cells treated with 12.5 µM soyasapogenol A or B; (C) Western blot analysis showing ATGL activity in 3T3-L1 cells treated with 12.5 µM soyasapogenol A or B. Values are expressed as mean ± SE (n = 3). Values that do not share the same letter are significantly different (p < 0.05).

Fig. 4

Effect of soyasapogenol A and B on lipogenesis for 10 d in 3T3-L1 adipocytes. (A) Western blot analysis showing PPARγ activity in 3T3-L1 cells treated with 12.5 µM soyasapogenol A or B; (B) Western blot analysis showing FAS activity in 3T3-L1 cells treated with 12.5 µM soyasapogenol A or B. Values are expressed as mean ± SE (n = 3).

Fig. 5

Effect of soyasapogenol A and B on adipocytokine secretion for 10 d in 3T3-L1 adipocytes. (A) Adiponectin concentration in a medium of 3T3-L1 cells treated with 12.5 µM soyasapogenol A or B; (B) resistin concentration in a medium of 3T3-L1 cells treated with 12.5 µM soyasapogenol A or B. Values are expressed as mean ± SE (n = 3). Values that do not share the same letter are significantly different (p < 0.05).