Anti-Obesity Effects of Sargassum thunbergii via Downregulation of Adipogenesis Gene and Upregulation of Thermogenic Genes in High-Fat Diet-Induced Obese Mice

Abstract

Obesity is a metabolic disease characterized by an increased risk of type 2 diabetes, hypertension, and cardiovascular disease. We have previously reported that compounds isolated from brown alga, Sargassum thunbergii (ST; Sargassum thunbergii (Mertens ex Roth) Kuntze), inhibit adipogenesis in 3T3-L1 cells. However, the in vivo anti-obesity effects of these compounds have not been previously reported. Therefore, the objective of this study was to determine the effects of ST on weight loss, fat accumulation, as well as risk factors for type 2 diabetes and cardiovascular disease in high-fat diet (HFD)-induced obese mice. ST treatment significantly decreased body weight and fat accumulation in HFD-induced obese mice, while reducing insulin and factors related to cardiovascular diseases (triglyceride and total cholesterol) in serum. ST-induced downregulation of PPARγ in white adipose tissue, and upregulation of the thermogenic genes, UCP-1 and UCP-3, in brown adipose tissue was also observed. In addition, oral administration of ST reduced the occurrence of fatty liver, as well as the amount of white adipose tissue in HFD mice. Cumulatively, these results suggest that ST exerts anti-obesity effects and may serve as a potential anti-obesity therapeutic agent.

Keywords: Sargassum thunbergia; anti-obesity; high-fat diet; seaweed.

Figure 1

Effects of Sargassum thunbergii on body weight and fat accumulation. (A) Mouse body weight gain over seven weeks. (B) Weight of different types of fats. Epi: epididymal fat; Sub: subcutaneous fat; Mes: mesenteric fat; Peri: perirenal fat. All data is expressed as mean ± SD (n = 5/group). Significant differences were identified at * p < 0.05, as compared to the HFD group. ST: Sargassum thunbergia ethanol extract.

Figure 2

Histopathologic analysis of white adipose and hepatic tissues. (A) Histological changes in the central vein and portal area of white adipose tissue as assessed using Image J software. (B) Histological changes in the liver. The liver and white adipose tissue sections were stained with hematoxylin and eosin (H&E). Significant differences were identified at * p < 0.05, as compared to the high-fat diet (HFD) group. Gar: Garcinia cambogia; Gpo: Garcinia cambogia positive control; Ori: Orlistat; ST: Sargassum thunbergii ethanol extract.

Figure 3

Effects of Sargassum thunbergii on the expression of adipogenesis (PPARγ) and thermogenic uncoupling protein 1 and uncoupling protein 3 (UCP-1, UCP-3) genes in white adipose tissue and brown adipose tissue. All data was obtained via RT-PCR analysis. Significant differences were identified at * p < 0.05, as compared to the HFD group.