Functional Evaluation Of Different Flavonoids In The Prevention Of Metabolic Syndrome And Their Mechanisms

The purpose of this paper was to establish an animal model for evaluation of functional foods in the prevention of metabolic syndrome(MS).The intervention effects of 8 flavonoids on body weight growth and glucose and lipid metabolism were evaluated and compared in SD rats.Then,their action targets and mechanisms were studied in chemical and cellular levels.SD rats received a high-fat and high-fructose combination diet,it was found that the body weight was significantly increased,and the glucose tolerance was impaired after 3 weeks.The serum HDL concentration was decreased,and the serum TG level was elevated after 4 weeks.After 7 weeks,the serum TC level was significantly increased,the model group showed fasting hyperglycemia,combined glucose intolerance(CGI)developed.After 10 weeks,liver insulin resistance was observed in the model group.At the end of 13th week,the serum total antioxidant capacity(TAC)level was decreased and the malondialdehyde(MDA)content was increased,oxidative stress occurred.In addition,serous liver steatosis and steatohepatitis were observed in the model group rats.Meanwhile,a small amount of mononuclear lymphocytes and adipocytes were infiltrated in the pancreas tissue,and the proliferation of pancreas islet number was also presented.The treatment groups were separately fed high-fat/high-fructose diet with 8 flavonoids in the same molar concentration by dietary addition for a 13-week period.The results showed that genistein,puerarin,kaempferol,EGCG and apigenin could significantly reduce the growth of body weight.Genistein and puerarin could significantly not only lower the serum TC and LDL-C levels,but also elevate the serum HDL level.Kaempferol and EGCG had no elevation effect on serum HDL level.Quercetin,apigenin,rutin and naringenin presented no obvious reduction in serum TG concentration.Quercetin and rutin showed no lowering serum TC content.Compared with the model control group,the treatment of kaempferol,apigenin,genistein and puerarin could significantly reduce lipid deposition in liver,which were related to inhibition of visceral fat accumulation,enhancement of serum adiponectin level and decrease of serum free fatty acid(FFA)level.IGT was improved by quercetin,kaempferol,apigenin,naringenin,genistein and puerarin,which was associated with increase of peripheral insulin sensitivity.Fasting blood glucose levels were significantly reduced by all flavonoids,which was correlated with improvement of liver insulin resistance.All the flavonoids attenuated oxidative stress by lowering the serum MDA levels and elevating the serum TAC level.Genistein could restore the pathological changes of pancreas to normal.Kaempferol,apigenin and puerarin could significantly diminish the infiltration of adipose cells and inflammatory cells in the pancreas tissue and reduce the proliferation of the pancreas islet.Quercetin and EGCG showed alleviation effect on the proliferation of the pancreas islet.The structure-activity relationship analysis found that isoflavones had the best preventive effect on metabolic syndrome among the 8 flavonoids.The effect of the flavonoids on the activities of lipase,?-amylase and ?-glucosidase were determined in vitro.The results suggested that all the flavonoids showed inhibiting ability on the three enzyme activities.The inhibition efficacy of puerarin,apigenin,kaempferol on lipase activity may be one of the effective approaches for weight control.The inhibition efficacy of,EGCG,quercetin,genistein,kaempferol,apigenin and puerarin on ?-amylase and ?-glucosidase may be one of the effective approaches for pancreas protection.3T3-L1 preadipocytes were differentiationed into mature adipocytes through induction of cocktail inducer.Insulin resisitance cell model was established by treating 3T3-L1 adipocytes with high glucose and high insulin.The effects of the 8 flavonoids on preadipocyte differentiation and insulin resistance were evaluated.The results demonstrated that genistein,kaempferol and apigenin could reduce visceral fat accumulation and body weight growth through inhibiting preadipocytes differentiation.Kaempferol,apigenin and puerarin could significantly lower postprandial blood glucose levels through improving insulin resistance in adipose tissue.Inflammation cell model was established by treating T lymphocytes and macrophages with concanavalin A(ConA)and lipopolysaccharide(LPS)respectively.The anti-inflammatory effects of the flavonoids on T lymphocytes proliferation and macrophages activation were investigated.The results indicated that the 8 flavonoids could reduce insulin resistance in adipose tissue and inflammation in liver tissues,which were related to inhibiting the proliferation of T cells,activation of macrophages and inflammatory cytokine secretion.