Protective effects of Radix Isatidis polysaccharide ameliorates obesity via promotion AMPK pathway in high-fat-diet-induced obese rats and 3T3-L1 adipocyte cells

Abstract

Objectives: The purpose of this paper is to ascertain the effect and mechanism of Radix Isatidis polysaccharide (RIP) on obesity. Methods: High fat diet (HFD)-induced obese rats and the MDI-induced 3T3-L1 adipocyte cells were established to evaluate the ameliorated obesity effect and mechanism from RIP. Key findings: Experiments in vivo show that oral administration of RIP has significant preventive effects on HFD-induced obesity and metabolic disorders in rats. With treatment of RIP (20, 40 and 80 mg/kg BW), the body weight, fat accumulation, adipocyte cell size, serum lipid levels and antioxidant enzyme activity were progressively improved. On the other hand, the treatment of 3T3-L1 cells with RIP (25, 50 and 100 mg/L) led to a decrease in lipid accumulation and glucose consumption. In addition, during adipogenesis in 3T3-L1 cells, RIP remarkably down-regulated mRNA levels of peroxisome proliferator-activated receptor-γ(PPARγ), CCAAT/enhancer binding protein-α (C/EBPα), sterol regulatory element-binding protein-1c (SREBP-1c), fatty acid synthase (FAS), acetyl-CoA carboxylase and glycerol-3-phosphate dehydrogenase. Furthermore, after RIP treatment, the protein expression of PPARγ, C/EBPα, FAS, HMG-CoA reductase and acetyl-CoA synthetase-1 (AceCS1) were significantly decreased and the expression of p-AMPK was increased. Conclusion: These results highlight the potential of RIP for obesity interventions and suggest that RIP inhibited adipocyte differentiation and lipid synthesis by activating adenosine 5′-monophosphate (AMP)-activated protein kinase (AMPK) signalling pathway and down-regulating the expression of major adipogenic transcription factors, PPARγ, C/EBPα, etc.