We previously showed that an ethanolic extract of the edible brown algae Petalonia binghamiae promotes the differentiation of 3T3-L1 preadipocytes and decreases hyperglycemia in streptozotocin-induced diabetic mice. Here, we report that a water-soluble extract of P. binghamiae thalli, prepared by enzymatic digestion, inhibits preadipocyte differentiation and adipogenesis in a dose-dependent manner. In differentiating 3T3-L1 preadipocytes, the extract (designated PBEE) decreased the expression of peroxisome proliferator-activated receptor γ, CCAAT/enhancer-binding proteins α and β, and fatty acid-binding protein aP2. It also inhibited the mitotic clonal expansion process of adipocyte differentiation, and it inhibited insulin-stimulated uptake of glucose into mature 3T3-L1 adipocytes by reducing phosphorylation of insulin receptor substrate-1. In rats with high-fat diet (HFD)-induced obesity, PBEE exhibited potent anti-obesity effects. In this animal model, increases in body weight and fat storage were suppressed by the addition of PBEE to the drinking water at 500 mg/L for 30 days. PBEE supplementation reduced serum levels of glutamic pyruvic and glutamic oxaloacetic transaminases and increased the serum level of high-density lipoprotein cholesterol. Moreover, it significantly decreased the accumulation of lipid droplets in liver tissue, suggesting a protective effect against HFD-induced hepatic steatosis. Taken together, these data demonstrate that PBEE inhibits preadipocyte differentiation and adipogenesis in cultured cells and in rodent models of obesity.
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