Effects Of Different Types Of N-3PUFA On Adiponectin And The Mechanism Mediated By CDK5/PPARγ In Rats

ObjectiveAdiponectin is a cytokine secreted by adipocytes,which has positive effects on anti-inflammation,anti atherosclerosis and insulin sensitivity.Improving levels of adiponectin plays a positive role in the prevention and treatment of obesity and relevant diseases.Although n-3 PUFAs(polyunsaturated fatty acids)could regulate the expression of adiponectin,different types of n-3 PUFAs such as ALA(alpha-linolenic acid,C18:3),EPA(eicosapentaenoic acid,C20:5)and DHA(docosahexaenoic acid,C22:6)may have multiple physiological features and functions that may cause their diverse regulatory effects on adiponectin.The molecular mechanism of n-3 PUFA regulate expression of adiponectin is still unclear now,PPARy(peroxisome proliferator-activated receptor y)and(cyclin-dependent kinase 5)CDK5-mediated phosphorylation of PPARy at Ser 273 may be involved.ALA,EPA and DHA are natural ligands of PPARγ,which may involve in the regulation of adiponectin by the above mechanism.In this study,we investigated and compared the different effects of ALA and EPA + DHA on rat adiponectin in normal fat and high fat diet,explored the molecular mechanism mediated by CDK5/PPARy.Results of our study provide scientific evidence for prevention and treatment of obesity and related metabolic diseases.Methods40 male Wistar rats were randomly assigned into four groups:1)NF1:normal fat diet(27%energy from fat)supplemented with EPA+DHA,2)NF2:normal fat diet supplemented with ALA,3)HF1:high fat diet(42%energy from fat)supplemented with EPA+DHA,4)HF2:high fat diet supplemented with ALA.The experiment lasted 12 weeks.Lipid profiles and fasting serum glucose(FSG)were measured at 0th,4th,8th and 12th weeks.At 0th and 12th weeks,concentrations of serum adiponectin and indexes of serum antioxidant were dected.The mRNA and protein levels of adiponectin,PPARy and CDK5,protein levels of phosphorylation of CDK5(p-CDK5)and p-PPARy(273Ser)in rat perirenal adipose tissue were measured at 12th weeks.ResultsThere were no statistical group differences in all the indexes of rats at the baseline,such as levels of lipid profiles,fasting serum glucose and serum adiponectin.In 12th weeks,a significant increasement was observed for high density lipoprotein cholesterol(HDL-C)(P<0.05),but for low density lipoprotein cholesterol(LDL-C)a significant decreasement was detected in NF1 and NF2,NF1 had obvious effect(P<0.05).Serum malondialdehyde(MDA)decreased significantly,but total superoxide dismutase(T-SOD)and glutathione peroxidase(GSH-Px)increased significantly in both NF1 and NF2.Serum adiponectin of normal fat diet groups(NF1 and NF2)increased 2.26μg/mL and 0.70μg/mL(P<0.05)compared with baseline.The mRNA and protein expressions of adiponectin and PPARy in rat perirenal adipose tissue,as well as serum adiponectin of NF1 were significantly higher than NF2(P<0.05).In high fat diet groups(HF1 and HF2),HDL-C levels decreased significantly(P<0.05),but FSG,LDL-C,total cholesterol(TC)and triglyceride(TG)increased significantly in comparison with baseline values(P<0.05).MDA in serum increased significantly,but T-SOD and GSH-Px decreased significantly in both NF1 and NF2,there were no statistical differences between HF1 and HF2(P>0.05).The mRNA and protein levels of adiponectin and PPARy in rat perirenal adipose tissue,also serum adiponectin in high fat diet groups were significantly lower than normal fat diet groups(P<0.05).On the contrary,protein levels of p-CDK5 and p-PPARy(273Ser)in perirenal adipose tissue of high fat diet groups were significantly higher than normal fat diet groups(P<0.05).Serum adiponectin,adiponectin mRNA and protein were positively correlated with PPARγ mRNA and protein,HDL-C,T-SOD and GSH-Px(P<0.01),negatively related to p-PPARγ(273Ser),p-CDK5,FSG,LDL-C,TG,TC and MDA(P<0.05).Conclusion1.Compared with ALA,EPA+DHA more effectively improved levels of serum adiponectin and mRNA and protein levels of adipose tissue adiponectin in normal fat diet rats.The levels of adiponectin in high fat diet groups were lower than that in the normal fat diet groups,and EPA+DHA could increase the protein levels of adiponectin in high fat diet rat perirenal adipose tissue compared with ALA.2.In normal fat diet rats,EPA + DHA and ALA could regulate the expression of adiponectin by PPARy,but EPA + DHA had obvious effect,EPA + DHA and ALA had different effect on adiponectin may be related to its effect on PPARy.3.In high fat diet rats,activated CDK5 and PPARγ phosphorylation increased,CDK5-mediated phosphorylation of PPARy at Ser 273 depressed expression of adiponectin,EPA + DHA and ALA had no difference on the above process.4.EPA+DHA had obvious effect on increasing the serum HDL-C levels and decreasing LDL-C levels of normal fat diet rats,but there was no significant difference in antioxidant capacity like MDA,T-SOD and GSH-Px between the EPA + DHA and ALA groups.