Hederagenin from Hedera helix Promotes Fat Browning in 3T3-L1 Adipocytes

Abstract

The prevalence of obesity is increasing globally, with approximately 700 million obese people worldwide. Currently, regulating energy homeostasis by increasing energy expenditure is attracting attention as a strategy for treating obesity. White adipose tissue is known to play a role in accumulating energy by storing excess energy, while brown adipose tissue expends energy and maintains body temperature. Thus, the browning of white adipose tissue has been shown to be effective in controlling obesity. Hedera helix (H. helix) has been widely used as a traditional medicine for various diseases. In several previous studies, hederagenin (HDG) from H. helix has demonstrated many biological activities. In this study, we investigated the antiobesity effect of HDG on fat browning in 3T3-L1 adipocytes. Consequent to HDG treatment, a reduction in lipid accumulation was measured through oil red O staining. In addition, this study investigated that HDG increases energy expenditure by upregulating the expression of several targets related to thermogenesis, including uncoupling protein 1 (UCP1). This process involves inhibiting lipogenesis via the adenosine monophosphate-activated protein kinase (AMPK) signaling pathway and promoting lipolysis through the protein kinase A (PKA) pathway. HDG is expected to be effective in promoting fat browning, indicating its potential as a natural antiobesity candidate.

Keywords: 3T3-L1; Hedera helix; fat browning; hederagenin; uncoupling protein 1.

Figure 1

Chemical structure of hederagenin (HDG).

Figure 2

Effects of HDG on cell viability of 3T3-L1 preadipocytes. The cells were treated with the compound and incubated for 48 h. All data are presented as mean ± SEM (n = 3). ** p < 0.01 compared with the control. Statistical analysis was conducted using Student’s t-test.

Figure 3

Effects of HDG on lipid accumulation in 3T3-L1 cells. The cells were differentiated for 7 days and stained with ORO (magnification: ×100, scale bar = 100 µm) (A). The stained cells were eluted with 100% isopropanol. Lipid accumulation was quantified using a microplate reader at 520 nm (B). All data are presented as mean ± SEM (n = 3). * p < 0.05 or ** p < 0.01 compared with the control. Statistical analysis was performed using Student’s t-test.

Figure 4

Effects of HDG on the expression of thermogenesis markers (A), beige-specific markers (B), and mitochondrial biogenesis markers (C). All data are presented as mean ± SEM (n = 3). * p < 0.05, ** p < 0.01, and *** p < 0.001 compared with the control. Statistical analysis was conducted using Student’s t-test.

Figure 5

Effect of HDG on UCP1 and mitochondria measured using immunofluorescence staining. 3T3-L1 adipocytes treated with 20 μM HDG for 7 days were stained for UCP1-FITC, MitoTracker Red, and DAPI. The images were captured at 60× magnification (scale bars = 20 µm). The blue, red, and green arrows indicate the adipocyte nucleus, mitochondria, and UCP1, respectively.

Figure 6

Effects of HDG on the expression of lipogenesis pathway proteins (A), fatty acid oxidation markers (B), and lipolysis markers (C). All data are presented as mean ± SEM (n = 3). * p < 0.05, ** p < 0.01, and *** p < 0.001 compared with the control. Statistical analysis was conducted using Student’s t-test.

Figure 7

Fat browning process mediated by HDG. Stimulation: →, inhibition: ┫, increase: ↑, decrease: ↓.