## 3 Discussion
In addition, when we compared the flavonoid contents in the two materials, we found that SH was 19.4 and UA 20.9 mg QE/g, indicating that the two materials were analyzed similarly. To confirm whether the SH and UA extracts affect adipocyte formation, they were applied at concentrations equal to or lower than 500 \(\upmu\)g/mL, which do not exhibit cytotoxicity during the differentiation process. The results confirmed that adipocyte differentiation was inhibited in a concentration-dependent manner. During the differentiation of preadipocyte 3T3-L1 cells, fat is accumulated in the cells, mostly as neutral fat [40]. The TG content in the cells decreased in a concentration-dependent manner. After treatment with SH and UA extracts at a concentration of 500 \(\upmu\)g/mL, TG content decreased by more than 30%. A previous study on the inhibition of adipocyte differentiation using SH reported that TG content decreased by 23% in the experimental group treated with SH at 1 mg/mL for 8 d [41]. In contrast, in our results, TG content was considerably reduced when the extract was applied at a concentration of 500 \(\upmu\)g/mL. This difference may be due to differences in the drying method, extraction solvent, and seaweed extraction method. Preadipocytes were treated with the 3-isobutyl-1-methylxanthine (IBMX) complex, and specific genes were expressed during the differentiation process into adipocytes. Several transcription factors, including _PPAR\(\gamma\)_, _C/EBPa_, and _SREBP1c_, play a pivotal role in regulating the differentiation and accumulation of adipocytes [42; 43]. _PPAR\(\gamma\)_ is a predominantly liver-distributed transcription factor that, when activated, produces marked changes in fat morphology, fat accumulation, and insulin sensitivity [44]. _C/EBPa_ plays an important role in adipogenesis. Expressions of _PPAR\(\gamma\)_ and _C/EBPa_ are mutually regulated at the preadipocyte differentiation stage, and the two genes cooperate to promote adipogenesis and regulate the expression of _SREBP1c_ and _FAS_[45; 46]. The results of our analysis confirmed that the expression of transcription factors of adipogenesis was downregulated in a concentration-dependent manner. In addition, evidence suggests that differentiation into adipocytes is inhibited by the suppression of _FAS_ expression [47], an important metabolic enzyme acting on adipogenesis and lipogenesis. Therefore, our results confirmed that the two seaweed extracts function as suppressors of the expression of key transcription factors that act during the fat differentiation process and that UA regulates the expression of transcription factors more effectively than SH. The HFD mouse model has been widely used to investigate anti-obesity effects and for the development of anti-obesity drugs [48]. Obese mice fed an HFD are characterized by increased body weight and adipocyte size, fatty liver development, and increased plasma GLU and TG levels [47]. In the present study, to confirm the effect of preventing obesity in C57 BL/6 mice induced by an HFD, the extract was added to drinking water at 1% concentration and administered for 12 weeks. In general, extracts have been administrated mainly via the oral route, but they may also be supplied through feed or water [26,49]. Since the extracts were added to the drinking water, we investigated potential differences between feed and drinking water intake. The results showed no differences in diet and water intake between the HFD and the extract administration groups, and no issues were observed regarding palatability. The weight gain rate significantly decreased in the group administered the SH and UA extracts compared to that in the HFD group. A previous obesity study using SH showed a protective effect against obesity when the substance was added to a high-fat diet at 2% and 6% and fed to mice [26]. However, this study found that adding the extract to drinking water at a concentration of 1% showed anti-obesity effects despite a lower treatment concentration than the previous results.