Sargassum thunbergii Extract Attenuates High-Fat Diet-Induced Obesity in Mice by Modulating AMPK Activation and the Gut Microbiota

Abstract

<i>Sargassum thunbergii</i> (Mertens ex Roth) Kuntze (ST) is a brown alga rich in indole-2-carboxaldehyde. This study aimed to investigate the anti-obesity effects of ethanol extract from ST in in vitro and in vivo models. In 3T3-L1 cells, ST extract significantly inhibited lipid accumulation in mature adipocytes while lowering adipogenic genes (<i>C/epba</i> and <i>Pparg</i>) and enhancing metabolic sensors (<i>Ampk</i>, <i>Sirt1</i>), thermogenic genes (<i>Pgc-1a</i>, <i>Ucp1</i>), and proteins (p-AMPK/AMPK and UCP1). During animal investigation, mice were administered a chow diet, a high-fat diet (HF), or an HF diet supplemented with ST extract (at dosages of 150 and 300 mg/kg bw per day) for 8 weeks (n = 10/group). ST extract administration decreased weight gain, white adipose tissue weight, LDL-cholesterol, and serum leptin levels while improving glucose intolerance. In addition, ST extract increased the expression of <i>Ampk</i> and <i>Sirt1</i> in adipose tissue and in the liver, as well as p-AMPK/AMPK ratio in the liver, compared to HF-fed mice. The abundance of <i>Bacteroides vulgatus</i> and <i>Faecalibacterium prausnitzii</i> in the feces increased in response to ST extract administration, although levels of <i>Romboutsia ilealis</i> decreased compared with those in HF-fed mice. ST extract could prevent obesity in HF-fed mice via the modulation of AMPK activation and gut microbiota composition.