Botryosphaeran reduces obesity, hepatic steatosis, dyslipidaemia, insulin resistance and glucose intolerance in diet-induced obese rats

Aims Obesity is associated with comorbidities such as diabetes and hepatic steatosis. β-Glucans have been described as effective in treating conditions including dyslipidaemia and diabetes. Thus, the objective of this study was to evaluate the effects of botryosphaeran [(1 → 3)(1 → 6)-β-D-glucan] on obesity and its comorbidities, and understand its mechanism of action. Main methods Obesity was induced in adult male Wistar rats by ingestion of a high-fat diet and water with sucrose (300 g/L) for 8 weeks. Control rats received standard diet. After six weeks, treatment commenced with botryosphaeran (12 mg/kg.b.w., via gavage, 15 days), respective controls received water. Rats were divided into 3 groups: control (C), obese (O), and obese + botryosphaeran (OB). In the 8th week, obesity was characterized. Feed-intake, glucose and lipid profiles, glucose tolerance, and concentrations of glycogen and lipids in liver were analyzed. Protein expression was determined by Western blotting. Key findings Obese rats showed significant increases in weight gain and adipose tissue, presented glucose intolerance, dyslipidaemia, and hepatic steatosis. Botryosphaeran significantly reduced feed intake, weight gain, periepididymal and mesenteric fat, and improved glucose tolerance. Botryosphaeran also reduced triglyceride and VLDL, and increased HDL levels. Furthermore, botryosphaeran increased glycogen and reduced total lipids, triglycerides and cholesterol in liver, and increased AMP-activated protein kinase(AMPK) activity and Forkhead transcription factor 3a(FOXO3a) protein expression in adipose tissue. Significance This study demonstrated that botryosphaeran was effective in reducing obesity, hepatic steatosis, dyslipidaemia insulin resistance and glucose intolerance in diet-induced obese rats, and these effects were, at least in part, associated with reduced feed intake, and AMPK and FOXO3a activities.