The Roles And Mechamisms Of D-4F In Preventing SAMP8 Mice From Alzheimer's Disease Via LncRNA Sirt1-as/SIRT1/reverse Cholesterol Transport Pathway

Background and objective:Alzheimer's disease (AD) with the clinical manifestation of dementia and the pathological feature of amyloid ?-protein (A(3 protein) has been identified as the most common neurodegeneration disease in the elders. Cholesterol plays key roles on A?metabolism and production. D-4F is apolipoprotein A-I (ApoA-I) mimetic peptide which has been revealed a critical role in regulation cholesterol. We aimed at identifying the effects of D-4F on A? production in SAMP8 and the underlying mechanisms as well as the behavioristics of SAMP8 mice.Methods:1. SAMP8 mice (n = 15) were randomized into three groups for treatment with D-4F given in drinking water: high-dose group (0.5 mg/ml), low-dose group (0.3 mg/ml)and control group (just drinking water). After 8 weeks, The heart, kidney, liver and brain were obtained from SAMP8 (9 of them included in the analysis). The long non-coding RNA sirtl-as was measured in all tissues. The immunohistochemistry,western blot qRT-PCR were performed to determine the sirtl-as and the relevant proteins or RNAs levels.2. SAMP8 mice (n = 40) were randomized into three groups for treatment with D-4F by intra-gastric administration: high-dose group (750ug/g/day), medium dose group(125ug/g/day), low-dose group(50ug/g/day) and control group. The mirrorwater maze training and examination were performed to evaluate the memory ability. Further micro PET/CT scan was performed to identify the metabolism and function of SAMP8 mice brain.3. The SAMP8 mice in part 2 (3 mice in each group) were used for the analysis of subtype of high-density lipoprotein (HDLs, HDL-1-HDL-8) levels and the brain tissues were used for the proteomics analysis (iTRAQlabeled method) to identify the cholesterol metabolism and transport associated proteins.Results:1. After treated with D-4F, the sirtl-as has been significantly upregulated in brain,rather than heart, kidney or liver. Specially, sirtl-as was significantly up-regulated by high dose of D-4F in the hippocampus area (p = 0.007) compared with control group. Further analysis revealed that D-4F up-regulates the expression of SIRT1.We also found that D-4F treatment significantly increased the reverse cholesterol transport related protein ATP-binding cassette transporter A1 (ABCA1) and liver X receptor ? (LXR? ,P < 0.05). Finally, the amyloid ?-protein (A? protein) was statistically lower than that in the control group (p < 0.05).2. In the mirrorwater maze training phases, D-4F treated SAMP8 mice showed more advantages in the latent swimming speed and other parameters. Furthermore, in the examination phase, the D-4F treated SAMP8 mice spent more time and a longer distance in the target area. In the micro PET/CT scan examination, only the signal ratio of hippocampus area to lung tissue was significantly different among the four groups (P < 0.05) while other areas showed no significant differences among the D-4F treated groups and control groups (all P values> 0.05).3. The circulating HDL subtypes analysis showed that,the HDL-3 (13.50 ± 0.71,11.50 ± 5.15 and 10.43 ± 4.04vs. 5.50 ± 0.76) and HDL-4 (24.50 ± 6.02, 18.00 ±4.41 and 17.86 ± 5.40vs. 11.75 ± 1.28) were significantly higher in the D-4F treatment groups than that in the control (P=0.011 and 0.008). However,the subtypes of HDL-7 and HDL-8 have been down regulated. In the proteomics analysis on the brain tissues of SAMP8, we have identified more 4000 proteins with differential expression. In addition, the TMEM transmembrane protein family members have been involved in many processes which may participate in the metabolism and transport of cholesterol.Conclusion:1. Our observation indicated that D-4F decreases the expression of A? protein through up-regulating long non coding RNA sirtl-as and its downstream proteins which may involve in reverse cholesterol transport.2. The D-4F treatment may upregulated the SAMP8 spatial performance and memory ability in a water maze. Furthermore, it may also protect the function and metabolism of SAMP8 mice brain from AD.3. We have indicated that the D-4F treatment regulates the balance of various subtypes of HDLs which may be the potential mechanisms of its prevention effect on AD.4. Our study revealed that TMEM transmembrane protein family members have been involved in many processes which may participate in the metabolism and transport of cholesterol.