Effects Of Chia Seed Supplementation On Cognitive Function And Cellular Senescence

Alzheimer's disease(AD),a progressive neurodegenerative disease,is one of the main reasons resulting in increased global incidence of dementia.The case and molecular mechanisms of AD are complex,and there is no effective measure for the prevention and treatment of AD.Cellular senescence is that cells detach from the cell cycle,showing a senescence-associated secretory phenotype(SASP),which can cause chronic inflammation,dysfunction of adipose tissue,diabetes,and insulin resistance.Adipose tissue is the key organ of substantial senescent cell accumulation under both obesity and aging condition.Chia is a plateau desert plant that grows in North America,such as Mexico and Guatemala.Chia seeds are its seeds.It contains the richest plant source of ?-linolenic acid(ALA).In the peripheral tissues,Chia seeds have the effect of improving the risk factors of AD,such as improving blood lipids and insulin resistance,but there is currently an inconsistency in the relationship between ALA and AD.Therefore,it is of great theoretical significance to study the effects of Chia seed on AD and cell senescence of adipose tissue.Objective:To investigate the effects of Chia seed supplementation on SAMP8 mice induced by high-fat(HFD)diet.1.Whether it can improve cognitive dysfunction and AD-related pathological parameters in SAMP8 mice.2.Whether it can improve the expression of key markers of cell senescence of adipose tissues and explore the possible mechanisms.Methods:Twenty-four SAMP8 male mice were randomly divided into 3 groups: low-fat group(P8LF,the ratio of carbohydrate,protein and fat was,70%:20%:10%);high-fat diet group(P8HF,the ratio was,20%: 20%: 60%);high-fat diet + Chia seed group(HC,10% Chia seed added to the above high-fat diet);SAMR1 mice as a control group(R1LF),were fed a low-fat diet(energy supply was the same as P8 LF group).At the end of the 18 weeks' intervention,we examined:1.Cognitive function and AD patholog of SAMP8 mice1.1 Behavior functional test: Morris water maze experiment were conducted to measure cognitive function in mice.1.2 Abeta pathology: The protein of A? generating pathway,such as APP,BACE1,cathepsin B,and the clearance of A?,such as IDE and ADAM10,as well as protein expression of A?42 in hippocampus and cortex were measured via Western blot.1.3 Tau pathology: The phosphorylated of Tau at serine 396 and serine404 and tau related protein kinase in hippocampus and cortex,such as CDK5,P25/P35 and PP2 A were measured via Western blot.1.4 Neuroinflammation: Western blot was used to measure GFAP in hippocampus and cortex.Immunohistochemistry was used to measure the expression of A?42 and Ib?-1 in hippocampus.2.GTT & ITT tests and blood biochemical indexesGlucose tolerance test(GTT)and insulin tolerance(ITT)tests were used.And we also measured levels of glucose,insulin,adiponectin,glycerol,triglycerides,and total cholesterol of serum.3.Cell senescence of adipose tissue3.1 T1-weighted magnetic resonance imaging(MRI): to determine the body composition of y fat in mice.3.2 HE staining:to observe the morphology of subcutaneous adipose tissue and epididymal adipose tissue in mice.3.3 Real-time PCR(RT-PCR)experiments: to measure the m RNA expression of p16,p21,p53,CD68 and PAI-1 in subcutaneous and epididymal adipose tissue.3.4 Western blot:to measure the protein expression of p-AMPK and SIRT1 in the subcutaneous and epididymal adipose tissue.Results:1.Cognitive function and AD pathological indicators in SAMP8 imce1.1 Cognitive function: during navigation trials,compared to R1 LF group,P8 LF group demonstrated longer escape latency to platform at day1 and day3,and P8 HC group also shown longer escape latency to platform at day 3.During the spatial memorytesting,there was no difference for time spent in target quadrant and the number of crossings among groups.1.2 A? pathology: In hippocampus,in terms of the generation pathway of A?,compared to R1 LF group,P8 HF group had increased APP and A?42;P8HC group had elevated BACE1,cathepsin B and A?42.In terms of the clearance pathway of A?,compared to R1 LF group,P8 HF group had reduced ADAM10,and P8 HC group had elevated IDE;compared to P8 HF group,P8 HC group also had elevated ADAM10.In cortex,compared to R1 LF group,P8 HC group had elevated IDE;P8HF group had elevated cathepsin B.P8 HF and P8 HC groups also had elevated BACE1 compared to R1 LF group and P8 LF group.1.3 Tau pathology: in hippocampus,compared to R1 LF group,there was elevated phosphorylation of tau at serine 404(p-Tauser404)in P8 LF and P8 HF groups.And P8 HC group had reduced phosphorylation of tau at serine 404 compared to P8 HF group.Compared to R1 LF group,the protein expression of CDK5 was significantly increased from P8 HF group,while p25/p35 was significantly reduced from P8 HC group.There was no difference for protein expression of p-Tau at serine 396 and 404,as well as P25/P35,CDK5 and PP2 A protein expression from cortex among groups.1.4 Neuroinflammation: in hippocampus,compared to R1 LF group,there was elevated protein expression of GFAP from P8 LF,P8HF and P8 HC group.In cortex,compared to R1 LF,the protein expression of GFAP was also significantly increased from P8 HC group.We also measured A?42&Ib?-1 via immunofluorescence,increased Ib?-1 activation was observed from P8 LF,P8HF and P8 HC group surrounding A?42 in hippocampus area.2.GTT & ITT tests and blood biochemical indexes2.1 Serum glucose,insulin,adiponectin,triglyceride,cholesterol and glycerol levels: Fasting serum glucose was higher in P8 LF and P8 HF than R1 LF group.Serum insulin in P8 LF and P8 HC group was lower than R1 LF group,and serum insulin in P8 HC group was also reduced compared with P8 LF group.P8 HC group had significantly reduced HOMA-IR compared with R1 LF group.P8 LF,P8HF and P8 HC had reduced adiponectin level.2.2 Glucose and insulin tolerance tests: In GTT test,P8 HF group had significantly increased area under curve(AUC)compared with R1 LF and P8 LF group;and compared to P8 HF group,P8 HC group had significantly reduced total AUC.In ITT test,comparedto R1 LF group,P8 LF,P8HF and P8 HC group all had increased AUC.And the total AUC in P8 HF and P8 HC group were also significantly higher compared to P8 LF group.3.Cell senescence markers of SAMP8 mice3.1 Body composition: compared to R1 LF group,P8 HF and P8 HC group showed significant signal strengthen according to the result of MRI.3.2 Result of HE staining: compared to both R1 LF and P8 LF group,P8 HF group had significantly enlarged adipocytes in both EPI and SC fat;meanwhile,the adipocytes in SC fat from P8 HC group were also significantly enlarged.3.3 Markers of cellular senescence m RNA expression in EPI and SC fat: Compared to R1 LF group,the m RNA expression of p16,CD68 and PAI-1 in EPI fat from P8 HF group were significantly increased;compared to P8 HF group,the m RNA expression of p16 and CD68 in EPI fat from P8 HC group were significantly reduced.As for SC fat,in comparison with R1 LF group,P8 HF group had significantly increased p16,p21 and CD68 m RNA expression;P8HC group also had significantly increased p16 m RNA expression.3.4 p-AMPK and SIRT1 protein expression in EPI and SC fat: Compared to R1 LF group,the protein expression of p-AMPK in EPI and SC fat from P8 HF group were significantly reduced;while there was no difference for SIRT1 protein expression among groups.Conclusion:1.HFD utilized in our present model couldn't worsen the impaired learning ability,and chia seed had no effect on learning and memory ability for HFD fed SAMP8 mice.This may be related to the fact that chia seed not only increased non-amyloidgenic processing of APP and A? degradation,but also increased amyloidogenic pathway and neuro-inflammation.2.HFD resulted in impaired glucose tolerance and insulin tolerance in SAMP8 mice,and chia seed is able to reverse HFD induced glucose intolerance.However,it can not effectively improve the impaired insulin resistance.3.HFD resulted in elevated markers of cell senescence in both EPI and SC fat.The reduction in AMPK activity may be one of the reasons for causing this.And chia seed supplementation is able to reduce senescence associated markers at least in epididymal adipose tissue.