Project description:A growing body of research shows that epigenetic mechanisms are critically involved in normal and pathological aging. The Senescence-Accelerated Mouse Prone 8 (SAMP8) can be considered an useful tool to better understand the dynamics of the global epigenetic landscape during the aging process since its phenotype is not fully explained by genetic factors. Here we investigated dysfunctional age-related transcriptional profiles and epigenetic programming enzymes in the hippocampus of 2- and 9-month-old SAMP8 female mice using the Senescent-Accelerated Resistant 1 (SAMR1) mouse strain as control. SAMP8 mice presented 1,062 genes dysregulated at 2 months of age, and 1,033 genes at 9 months, with 92 genes concurrently dysregulated at both ages in reference to age mated SAMR1. SAMP8 mice showed a significant decrease in global DNA methylation (5-mC) at 2 months while hydroxymethylation (5-hmC) levels were increased in SAMP8 mice at 2 and 9 months of age compared to SAMR1. These changes were accompanied by changes in the expression of several enzymes that regulate 5-mC and methylcytosine oxidation. Acetylated H3 and H4 histone levels were significantly diminished in SAMP8 mice at 2-month-old compared to SAMR1 and altered Histone DeACetylase (HDACs) profiles were detected in both young and old SAMP8 mice. We analyzed 84 different mouse miRNAs known to be altered in neurological diseases or involved in neuronal development. Compared with SAMR1, SAMP8 mice showed 28 and 17 miRNAs differentially expressed at 2 and 9 months of age, respectively, 6 of these miRNAs overlapped at both ages. We used several bioinformatic approaches to integrate our data in mRNA:miRNA regulatory networks and functional predictions for young and aged animals. In sum, our study reveals interplay between epigenetic mechanisms and gene networks that seems to be relevant for the progression towards a pathological aging and provides several potential markers and therapeutic candidates for Alzheimer’s Disease (AD) and age-related cognitive impairment.

Project description:The present study examines the effects of whale meat extract (WME) supplementation on the senescence-accelerated mouse prone 8 (SAMP8) model at the level of learning memory formation and gene expression profiles genome-wide. Our present study builds up on these previous studies by focusing on two sets of experiments examining WME-supplemented diet, on SAMP8 and SAMR1 (senescence-accelerated mouse resistant 1) learning and memory deficits (experiment 1) and whole-genome DNA microarray-based transcriptomics profiling in conjunction with Ingenuity Pathway Analysis (IPA) (experiment 2). We also examined the SAMP8 and SAMR1 mice fed with the regular (control; low-safflower oil, LSO) diets specifically to know the gene profiles in the brain of the SAMP8 mouse. Results revealed that WME supplementation on SAMP8 mouse resulted in an increase in the level of learning memory formation and positive changes in the transcriptome of the brain, suggested through the observation of recovery of gene expressions in the SAMP8 model over the not-supplemented mouse. 6-week-old mice (SAMP8 and SAMR1; CLEA, Tokyo, Japan) were housed at the Animal Institution Facility in Showa University, and maintained in individual cages in a ventilated animal room with controlled temperature and relative humidity under a 12-h light: 12-h dark regime (8:00 AM, lights turned on). Mice were fed chow (CE-2, CLEA Japan) and tap water ad libitum until 24-weeks-old. Then, 24-week-old SAMs mice were given experimental diet, LSO diet as a control diet and WME-supplemented diet, both in a powder form. The WME was made from red meat of Antarctic minke whale (Balaenoptera bonaerensis), taken from the Japanese Whale Research Program under Special Permit in the Antarctic-Phase II in 2009/2010 by heat, enzyme and drying treatments. The quality standard of WE were measured by Marugei Co. Ltd. (Hyogo, Japan). SAMP8 mice were randomly given LSO or WME diet, respectively. SAMR1 mice were given LSO diet only until 50-weeks-old. The behavioral tests were performed at the timing of 49-weeks-old for 8 days. At the end of the experiment (50 weeks of age) following the behavioral analysis (open field test, Y-maze test, new object recognition test (NOR), and water-filled multiple T-maze) and the last day of the feeding, the mice were removed from their cages, decapitated and their brains carefully removed on ice. The whole brains were quickly frozen in liquid nitrogen in a sterile freeze tube and stored at -80ÂºC till extraction of total RNA followed by DNA microarray analysis using a whole-genome mouse chip (Agilent-014868, 4 x 44K (G4122F)) with two-color dye-swap approach in conjunction with IPA bioinformatic analysis. All animal studies were conducted in accordance with the Standards Relating to the Care Management of Experimental Animalsâ (Notice No. 6 of the Office of Prime Minister dated March 27, 1980) and with approval from the Animal Use Committee of Showa University (Approval Number: #04093).

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Analysis of SAMP8 and SAMR1 mice after an exercise intervention

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