Isolated Exopolysaccharides From Lactobacillus Rhamnosus GG Inhibit Adipogenesis In Animals

As a worldwide epidemic associated with many metabolic diseases,human obesity and excessive fat accretion in economic animals impose an enormous burden on individual and public health and animal raising industry.Therefore,it is imminent to look for safe and effective anti-obesity active substances and to study the associated mechanisms.Recent researches have demonstrated that the gut microbiota is involved in obesity and excessive fat accretion in economic animals.Obesity,as a transmissible phenotype by microbiota transplantation,is associated with specific structural and functional configurations of the bacterial gut microbiota.The gut microbiota is,therefore,a potential nutritional and pharmacological target in the management of obesity,and a potential treasure trove/house in the development of anti-obesity molecules.Of all the probiotics,Lactobacillus was one of the most studied species.The fibroblast cell line of 3T3-L1 was used as a cell model for screening and evaluating the feasibility of probiotic components in improving animal lipid metabolisms.The extracts from 12 Lactobacillus strains significantly reduced triacylglycerol(TAG)accumulation with severe inflammation induction in 3T3-L1 adipocytes.Among the 12 strains,LGG(Lactobacillus rhamnosus GG)extracts induced the lowest inflammation induction.Therefore,LGG was chosen for subsequent investigation.We demonstrated that some stable macromoleculars(>50KD)from LGG extracts,such as exopolysaccharides(EPS),may play an important role in reducing the intracellular TAG accumulation of 3T3-L1.Thereafter,LGG EPS was isolated,purified and characterized.The crude EPS was further purified by size-exclusion chromatography on a column of Superdex75(10/300 GE),which showed that EPS was a homogeneous polysaccharide.The molecular weight of the purified EPS determined by GPC/MALLS was 229,300 ± 0.008 kDa.According to TLC and HPLC,EPS was composed of rhamnose,N-acetyl-D-glucosamine and galactose.The FT-IR spectroscopy and NMR analyses were also done to analyze the structure of LGG EPS.Interestingly,LGG EPS significantly decreased the TAG accumulation of 3T3-L1 without any inflammation.The effect of oral administration of LGG EPS was also studied in high-fat-diets fed zebrafish and zebrafish larvae.The results showed that dietary supplemented LGG EPS could ameliorate obesity and fatty liver disease caused by high-fat-diets.However,the molecular mechanisms of the anti-obesity effect of LGG EPS need to be further investigated.Further,the anti-obesity effect of EPS was confirmed in high-fat-diets fed mice.Fat pads of mice injected with LGG EPS(50 mg/kg)every two days for two weeks were significantly reduced with much smaller adipocytes,compared with the controls.The levels of TAG and cholesterol ester in liver,as well as serum TAG,were decreased in LGG EPS injected mice.In addition,down-regulated inflammation was observed in adipose tissue and liver.Interestingly,the expression of TLR2 in adipose tissue and 3T3-L1 cells was significantly increased by LGG EPS addition.Moreover,the reverse of TAG accumulation in TLR2 knockdown3T3-L1 in the presence of LGG EPS confirmed that the inhibition effect of LGG EPS on adipogenesiswas mediated by TLR2.Overall,LGG EPS has the potential for therapeutic development to alleviate lipid metabolic disorders in animals.