Senescence-accelerated Mouse Prone 8 Research Articles

The Effects of LW-AFC on the Hippocampal Transcriptome in Senescence-Accelerated Mouse Prone 8 Strain, a Mouse Model of Alzheimer's Disease.

The senescence-accelerated mouse prone 8 (SAMP8) strain is considered a robust experimental model for developing preventative and therapeutic treatments for Alzheimer's disease (AD), a neurodegenerative disease which cannot be effectively prevented, halted, or cured. Our previous studies showed that LW-AFC, a new formula derived from the classical traditional Chinese medicinal prescription Liuwei Dihuang decoction, ameliorates cognitive deterioration in PrP-hAβPPswe/PS1ΔE9 transgenic mice and SAMP8 mice. This study aims to investigate the mechanism that mediates how LW-AFC improves cognitive deficit on the basis of the transcriptome. We conducted a genome-wide survey of gene expression in the hippocampus in mice from the senescence accelerated mouse resistant 1 (SAMR1) strain, from SAMP8 and from LW-AFC treated SAMP8. The results showed that LW-AFC reversed the transcriptome in the hippocampus of SAMP8 mice. The specific investigation of altered gene expression in subtypes defined by cognitive profiles indicated that the systemic lupus erythematosus pathway, spliceosomes, amyotrophic lateral sclerosis, and the insulin signaling were involved in the improvement of cognitive ability by LW-AFC. The expression of genes Enpp2, Etnk1, Epdr1, and Gm5900 in the hippocampus were correlated with that of LW-AFC's ameliorating cognitive impairment in SAMP8 mice. Because LW-AFC is composed of polysaccharides, glycosides, and oligosaccharides, we infer that LW-AFC has direct or indirect effects on altering gene expressions and regulating pathways in the hippocampus of SAMP8 mice. These data are helpful for the enhanced identification of LW-AFC as new therapeutic modalities to AD.

Analyses of mRNA Profiling through RNA Sequencing on a SAMP8 Mouse Model in Response to Ginsenoside Rg1 and Rb1 Treatment

Ginsenoside Rg1 and Rb1 are the major ingredients in two medicines called QiShengLi (Z20027165) and QiShengJing (Z20027164) approved by China. These ingredients are believed to mitigate forgetfulness. Numerous studies have confirmed that GRg1 and GRb1 offer protection against Alzheimer's disease (AD), and our morris water maze (MWM) experiment also indicated that GRg1 and GRb1 may attenuate memory deficits in the 7-month-old SAMP8 mice; however, comprehensive understanding of their roles in AD remains limited. This study systematically explored the mechanism at the genome level of the anti-AD effects of GRg1 and GRb1 in a senescence-accelerated mouse prone 8 (SAMP8) model through deep RNA sequencing. A total of 74,885 mRNA transcripts were obtained. Expression analysis showed that 1,780 mRNA transcripts were differentially expressed in SAMP8 mice compared with the SAMP8+GRg1 mice. Moreover, 1,066 significantly dysregulated mRNA transcripts were identified between SAMP8 and SAMP8+GRb1 mice. Analyses according to gene ontology and the Kyoto Encyclopedia of Genes and Genomes revealed that oral administration of GRg1 and GRb1 improved the learning performance of the SAMP8 mouse model from various aspects, such as nervous system development and mitogen-activated protein kinase signaling pathway. The most probable AD-related transcriptional responses after medication were predicted and discussed in detail. This study is the first to provide a systematic dissection of mRNA profiling in SAMP8 mouse brain in response to GRg1 and GRb1 treatment. We explained their efficacy thoroughly from the source (gene-level explanation). The findings serve as a theoretical basis for the exploration of GRg1 and GRb1 as functional drugs with anti-AD activity.

Effects of electroacupuncture at Guanyuan (CV 4) or Sanyinjiao (SP 6) on hypothalamus-pituitary-ovary axis and spatial learning and memory in female SAMP8 mice

OBJECTIVETo investigate the effects of electroacupuncture (EA) at the Guanyuan (CV 4) or Sanyinjiao (SP 6) acupoints on the hypothalamus-pituitary-ovary (HPO) axis and spatial learning and memory in female mice. METHODSNine-month-old female mice with senescence-accelerated mouse prone 8 (SAMP8) were divided into three groups: the disease model, EA-Guanyuan and EA-Sanyinjiao groups. Concurrently, 9-month old female mice with senescence-accelerated mouse resistance 1 (SAMR1) were set as the control model group. The two treatment groups were given the same pattern of EA stimulation. Gonadotropin-releasing hormone, luteinizing hormone, follicle-stimulating hormone (FSH) and Serum estradiol levels in the Hypothalamus-pituitary-ovary axis were assessed by enzyme-linked immunosorbent assay to determine the HPO axis function level. Spatial learning and memory were assessed by the Morris Water Maze (MWM) test. RESULTS(a) HPO axis: compared with the control model group, the disease model group displayed a decrease in E2 levels (P < 0.01), and an increase in GnRH, LH and FSH levels (P < 0.01). E2 levels were increased in EA treatment groups compared with the disease model group (P < 0.05). In contrast, GnRH and LH and FSH levels were reduced (P < 0.05). EA-Sanyinjiao group was superior than EA-Guanyuan group on increasing E2 and declining GnRH levels (P < 0.01). (b) The MWM test demonstrated that the response latency in the EA-Sanyinjiao treatment group declined from day 2 to day 5 compared with the disease model group (P < 0.05), whereas the EA-Guanyuan treatment group showed no significant difference. CONCLUSIONEA can regulate hormone (E2, FSH, LH, GnRH) levels in the HPO axis and the spatial learning and memory ability in female SAMP8 mice. Moreover, this effect may have been more pronounced in the EA-Sanyinjiao group than the EA-Guanyuan group. The underlying mechanism of the EA-induced changes may be related to gonadal hormone shifts in the HPO axis, followed by an improvement in spatial learning and memory.

Effect of an Enhanced Nose-to-Brain Delivery of Insulin on Mild and Progressive Memory Loss in the Senescence-Accelerated Mouse.

Insulin is now considered to be a new drug candidate for treating dementias, such as Alzheimer's disease, whose pathologies are linked to insulin resistance in the brain. Our recent work has clarified that a noncovalent strategy involving cell-penetrating peptides (CPPs) can increase the direct transport of insulin from the nasal cavity into the brain parenchyma. The present study aimed to determine whether the brain insulin level increased by intranasal coadministration of insulin with the CPP penetratin has potential for treating dementia. The pharmacological actions of insulin were investigated at different stages of memory impairment using a senescence-accelerated mouse-prone 8 (SAMP8) model. The results of spatial learning tests suggested that chronic intranasal administration of insulin with l-penetratin to SAMP8 slowed the progression of memory loss in the early stage of memory impairment. However, contrary to expectations, this strategy using penetratin was ineffective in recovering the severe cognitive dysfunction in the progressive stage, which involves brain accumulation of amyloid β (Aβ). Immunohistological examination of hippocampal regions of samples from SAMP8 in the progressive stage suggested that accelerated nose-to-brain insulin delivery had a partial neuroprotective function but unexpectedly increased Aβ plaque deposition in the hippocampus. These findings suggest that the efficient nose-to-brain delivery of insulin combined with noncovalent CPP strategy has different effects on dementia during the mild and progressive stages of cognitive dysfunction.

Age-related alterations of neuronal excitability and voltage-dependent Ca2+ current in a spontaneous mouse model of Alzheimer’s disease

Alzheimer’s disease (AD) is the most common age-dependent neurodegenerative disorder, characterized by a progressive dysfunction of central neurons, and senescence-accelerated mouse prone 8 (SAMP8), a spontaneous AD mouse model, appears to be an excellent model to investigate the process of AD. Previous studies have indicated that neuronal excitability is impaired in transgenic AD mice. In this study, the cognition of SAMP8 mice was tested using the passive avoidance task and Morris water maze; whole-cell current-clamp recordings were used to evaluate the neuronal excitability, including the resting membrane potential, the number of action potentials, and after-hyperpolarization; and the voltage-dependent Ca2+ current in hippocampal slices was measured using whole-cell voltage-clamp recordings. We found that compared to the young mice, the performance in the learning and memory behavior tasks was impaired in aged mice, and the hippocampal CA1 pyramidal neurons of the aged mice showed a significantly depolarized resting membrane potential, increased numbers of action potentials after injection of depolarizing current, and increased after-hyperpolarization after the action potentials. Consistent with the above changes, the voltage-dependent Ca2+ current was larger in aged mice than in young mice. These data suggested that the aged SAMP8 neurons were hyperexcitable, and the alterations in the voltage-dependent Ca2+ current of aged neurons occurred in parallel to the elevation in excitability.

Neuroprotective effect of the Chinese medicine Tiantai No. 1 and its molecular mechanism in the senescence-accelerated mouse prone 8.

Tiantai No. 1, a Chinese medicine predominantly composed of powdered Rhizoma Gastrodiae, Radix Ginseng, and Ginkgo leaf at a ratio of 2:1:2 and dissolved in pure water, is neuroprotective in animal models of various cognitive disorders, but its molecular mechanism remains unclear. We administered Tiantai No. 1 intragastrically to senescence-accelerated mouse prone 8 (SAMP8) mice (a model of Alzheimer's disease) at doses of 50, 100 or 150 mg/kg per day for 8 weeks and evaluated their behavior in the Morris water maze and expression of Alzheimer's disease-related proteins in the brain. Tiantai No. 1 shortened the escape latency in the water maze training trials, and increased swimming time in the target quadrant during the spatial probe test, indicating that Tiantai No. 1 improved learning and memory in SAMP8 mice. Immunohistochemistry revealed that Tiantai No. 1 restored the proliferation potential of Ki67-positive cells in the hippocampus. In addition, mice that had received Tiantai No. 1 had fewer astrocytes, and less accumulation of amyloid-beta and phosphorylated tau. These results suggest that Tiantai No. 1 is neuroprotective in the SAMP8 mouse model of Alzheimer's disease and acts by restoring neuronal number and proliferation potential in the hippocampus, decreasing astrocyte infiltration, and reducing the accumulation of amyloid-beta and phosphorylated tau.

MicroRNA-139 modulates Alzheimer's-associated pathogenesis in SAMP8 mice by targeting cannabinoid receptor type 2.

Alzheimer's disease (AD) is a neurodegenerative disorder, and is the most common type of dementia in the elderly population. Growing evidence indicates that microRNAs (miRNAs) play a crucial role in neuroinflammation associated with AD progression. In this study, we analyzed the expression of microRNA-139 (miR-139) as well as the learning and memory function in AD. We observed that the miR-139 expression was significantly higher in the hippocampus of aged senescence accelerated mouse prone 8 (SAMP8) mice (2.92 ± 0.13) than in the control mice (1.49 ± 0.08). Likewise, the overexpression of miR-139 by means of hippocampal injection impaired the hippocampus-dependent learning and memory formation. In contrast, the downregulation of miR-139 in mice improved learning and memory function in the mice. The level of cannabinoid receptor type 2 (CB2), a potential target gene of miR-139, was inversely correlated with the miR-139 expression in primary hippocampal cells. Furthermore, we demonstrated that miR-139 inversely modulated the responses to proinflammatory stimuli. Together, our findings demonstrate that miR-139 exerts a pathogenic effect in AD by modulating CB2-meditated neuroinflammatory processes.

LW-AFC Effects on N-glycan Profile in Senescence-Accelerated Mouse Prone 8 Strain, a Mouse Model of Alzheimer's Disease.

Glycosylation is one of the most common eukaryotic post-translational modifications, and aberrant glycosylation has been linked to many diseases. However, glycosylation and glycome analysis is a significantly challenging task. Although several lines of evidence have indicated that protein glycosylation is defective in Alzheimer’s disease (AD), only a few studies have focused on AD glycomics. The etiology of AD is unclear and there are no effective disease-modifying treatments for AD. In this study, we found that the object recognition memory, passive avoidance, and spatial learning and memory of senescence-accelerated mouse prone 8 (SAMP8) strain, an AD animal model, were deficient, and LW-AFC, which was prepared from the traditional Chinese medicine prescription Liuwei Dihuang decoction, showed beneficial effects on the deterioration of cognitive capability in SAMP8 mice. Forty-three and 56 N-glycan were identified in the cerebral cortex and serum of SAMP8 mice, respectively. The N-glycan profile in SAMP8 mice was significantly different from that of senescence accelerated mouse resistant 1 (SAMR1) strains, the control of SAMP8 mice. Treatment with LW-AFC modulated the abundance of 21 and 6 N-glycan in the cerebral cortex and serum of SAMP8 mice, respectively. The abundance of (Hex)3(HexNAc)5(Fuc)1(Neu5Ac)1 and (Hex)2(HexNAc)4 decreased in the cerebral cortex and serum of SAMP8 mice compared with SAMR1 mice, decreases that were significantly correlated with learning and memory measures. The administration of LW-AFC could reverse or increase these levels in SAMP8 mice. These results indicated that the effects of LW-AFC on cognitive impairments in SAMP8 mice might be through modulation of N-glycan patterns, and LW-AFC may be a potential anti-AD agent.

Invited

To investigate the effects of electroacupuncture (EA) at the Guanyuan (CV 4) or Sanyinjiao (SP 6) acupoints on the hypothalamus-pituitary-ovary (HPO) axis and spatial learning and memory in female mice.Nine-month-old female mice with senescence-accelerated mouse prone 8 (SAMP8) were divided into three groups: the disease model, EA-Guanyuan and EA-Sanyinjiao groups. Concurrently, 9-month old female mice with senescence-accelerated mouse resistance 1 (SAMR1) were set as the control model group. The two treatment groups were given the same pattern of EA stimulation. Gonadotropin-releasing hormone, luteinizing hormone, follicle-stimulating hormone (FSH) and Serum estradiol levels in the Hypothalamus-pituitary-ovary axis were assessed by enzyme-linked immunosorbent assay to determine the HPO axis function level. Spatial learning and memory were assessed by the Morris Water Maze (MWM) test.(a) HPO axis: compared with the control model group, the disease model group displayed a decrease in E2 levels (P < 0.01), and an increase in GnRH, LH and FSH levels (P < 0.01). E2 levels were increased in EA treatment groups compared with the disease model group (P < 0.05). In contrast, GnRH and LH and FSH levels were reduced (P < 0.05). EA-Sanyinjiao group was superior than EA-Guanyuan group on increasing E2 and declining GnRH levels (P < 0.01). (b) The MWM test demonstrated that the response latency in the EA-Sanyinjiao treatment group declined from day 2 to day 5 compared with the disease model group (P < 0.05), whereas the EA-Guanyuan treatment group showed no significant difference.EA can regulate hormone (E2, FSH, LH, GnRH) levels in the HPO axis and the spatial learning and memory ability in female SAMP8 mice. Moreover, this effect may have been more pronounced in the EA-Sanyinjiao group than the EA-Guanyuan group. The underlying mechanism of the EA-induced changes may be related to gonadal hormone shifts in the HPO axis, followed by an improvement in spatial learning and memory.

Fuzheng Quxie Decoction Ameliorates Learning and Memory Impairment in SAMP8 Mice by Decreasing Tau Hyperphosphorylation.

Hyperphosphorylation of the microtubule-associated protein, tau, is critical to the progression of Alzheimer's disease (AD). Fuzheng Quxie Decoction (FQD), a Chinese herbal complex, is an effective clinical formula used to treat AD. In the current study, we employed high-performance liquid chromatography and liquid chromatography tandem mass spectrometry to identify the components of FQD. Three major components (ginsenoside Rg1, ginsenoside Re, and coptisine) were detected in the brain of FQD-fed mice, indicating their ability to cross the blood-brain barrier. We further evaluated the efficacy of FQD on Senescence-Accelerated Mice Prone-8 (SAMP8) mice. FQD significantly ameliorated learning and memory deficits in SAMP8 mice on the Morris Water Maze, decreasing escape latency (p < 0.01) and increasing swim time within the original platform-containing quadrant (p < 0.05). Further, FQD increased the number of neurons and intraneuronal Nissl bodies in the hippocampal CA1 region. FQD also decreased the expression of phosphorylated tau protein and increased the expression of protein phosphatase 2A (PP2A) and the N-methyl-D-aspartate receptor subunit, NR2A (p < 0.01). Our results indicate that FQD improves the learning and memory ability of SAMP8 mice. Moreover, our findings suggest that the protective effect of FQD is likely mediated through an inhibition of hippocampal tau hyperphosphorylation via NMDAR/PP2A-associated proteins.

SS31 ameliorates age-related activation of NF-κB signaling in senile mice model, SAMP8.

Aging has been attributed to oxidative stress and inflammatory response, in which NF-κB and Nrf2-ARE signaling pathways play significant roles. Senescence accelerated mouse prone 8 (SAMP8) is generally used an animal model for aging studies. Here, we investigated the NF-κB and Nrf2-ARE signaling pathways in SAMP8 brains at different ages and their responses to SS31 peptide treatment. Thirty six SAMP8 mice were separated into aging groups and SS31-treatment groups. The hippocampus from each mouse was dissected for RNA and protein extraction. Cytokines and ROS levels were measured using ELISA and standardised method. Gene expressions of NF-κB, Nrf2 and HO-1 were measured by RT-qPCR. Total protein amount of NF-κB and HO-1, as well as the concentrations of nuclear and cytoplasmic Nrf2 were measured using Western blots. Our data showed that aging could activate both NF-κB and Nrf2-ARE signaling pathways, which could be suppressed and activated by SS31 treatment respectively. Regression analysis revealed that NF-κB gene expression was the most important parameter predicting aging process and SS31 treatment effects in SAMP8. Our findings suggested that SS31 treatment may modulate the inflammatory and oxidative stress status of the aged brains and exert protective effects during brain aging.

Long-term cilostazol administration ameliorates memory decline in senescence-accelerated mouse prone 8 (SAMP8) through a dual effect on cAMP and blood-brain barrier

Phosphodiesterases (PDEs), which hydrolyze and inactivate 3′, 5′-cyclic adenosine monophosphate (cAMP) and 3′, 5′-cyclic guanosine monophosphate (cGMP), play an important role in synaptic plasticity that underlies memory. Recently, several PDE inhibitors were assessed for their possible therapeutic efficacy in treating cognitive disorders. Here, we examined how cilostazol, a selective PDE3 inhibitor, affects brain functions in senescence-accelerated mouse prone 8 (SAMP8), an animal model of age-related cognitive impairment. Long-term administration of cilostazol restored the impaired context-dependent conditioned fear memory of SAMP8 to match that in normal aging control substrain SAMR1. Cilostazol also increased the number of cells containing phosphorylated cAMP-responsive element binding protein (CREB), a downstream component of the cAMP pathway. Finally, cilostazol improves blood-brain barrier (BBB) integrity, demonstrated by reduced extravasation of 2-deoxy-2-18F-fluoro-d-glucose and Evans Blue dye in the brains of SAMP8. This improvement in BBB integrity was associated with an increased amount of zona occludens protein 1 (ZO-1) and occludin proteins, components of tight junctions integral to the BBB. The results suggest that long-term administration of cilostazol exerts its beneficial effects on age-related cognitive impairment through a dual mechanism: by enhancing the cAMP system in the brain and by maintaining or improving BBB integrity.

Exercise restores muscle stem cell mobilization, regenerative capacity and muscle metabolic alterations via adiponectin/AdipoR1 activation in SAMP10 mice.

BackgroundExercise train (ET) stimulates muscle response in pathological conditions, including aging. The molecular mechanisms by which exercise improves impaired adiponectin/adiponectin receptor 1 (AdipoR1)‐related muscle actions associated with aging are poorly understood. Here we observed that in a senescence‐accelerated mouse prone 10 (SAMP10) model, long‐term ET modulated muscle‐regenerative actions.Methods25‐week‐old male SAMP10 mice were randomly assigned to the control and the ET (45 min/time, 3/week) groups for 4 months. Mice that were maintained in a sedentary condition served controls.ResultsET ameliorated aging‐related muscle changes in microstructure, mitochondria, and performance. The amounts of proteins or mRNAs for p‐AMPKα, p‐Akt, p‐ERK1/2, p‐mTOR, Bcl‐XL, p‐FoxO3, peroxisome proliferators‐activated receptor‐γ coactivator, adiponectin receptor1 (adpoR1), and cytochrome c oxidase‐IV, and the numbers of CD34+/integrin‐α7 + muscle stem cells (MuSCs) and proliferating cells in the muscles and bone‐marrow were enhanced by ET, whereas the levels of p‐GSK‐3α and gp91phox proteins and apoptotic cells were reduced by ET. The ET also resulted in increased levels of plasma adiponectin and the numbers of bone‐marrow (BM)‐derived circulating CD34+/integrin‐α7 + MuSCs and their functions. Integrin‐α7 + MuSCs of exercised mice had improved changes of those beneficial molecules. These ET‐mediated aged muscle benefits were diminished by adiponectin and AdipoR1 blocking as well as AMPK inhibition. Finally, recombinant mouse adiponectin enhanced AMPK and mTOR phosphorylations in BM‐derived integrin‐α7 + cells.ConclusionsThese findings suggest that ET can improve aging‐related impairments of BM‐derived MuSC regenerative capacity and muscle metabolic alterations via an AMPK‐dependent mechanism that is mediated by an adiponectin/AdipoR1 axis in SAMP10 mice.

Tooth loss early in life suppresses neurogenesis and synaptophysin expression in the hippocampus and impairs learning in mice

ObjectiveTooth loss induced neurological alterations through activation of a stress hormone, corticosterone. Age-related hippocampal morphological and functional changes were accelerated by early tooth loss in senescence-accelerated mouse prone 8 (SAMP8). In order to explore the mechanism underlying the impaired hippocampal function resulting from early masticatory dysfunction due to tooth loss, we investigated the effects of early tooth loss on plasma corticosterone levels, learning ability, neurogenesis, and synaptophysin expression in the hippocampus later in life of SAMP8 mice. DesignWe examined the effects of tooth loss soon after tooth eruption (1 month of age) on plasma corticosterone levels, learning ability in the Morris water maze, newborn cell proliferation, survival and differentiation in the hippocampal dentate gyrus, and synaptophysin expression in the hippocampus of aged (8 months of age) SAMP8 mice. ResultsAged mice with early tooth loss exhibited increased plasma corticosterone levels, hippocampus-dependent learning deficits in the Morris water maze, decreased cell proliferation, and cell survival in the dentate gyrus, and suppressed synaptophysin expression in the hippocampus. Newborn cell differentiation in the hippocampal dentate gyrus, however, was not affected by early tooth loss. ConclusionThese findings suggest that learning deficits in aged SAMP8 mice with tooth loss soon after tooth eruption are associated with suppressed neurogenesis and decreased synaptophysin expression resulting from increased plasma corticosterone levels, and that long-term tooth loss leads to impaired cognitive function in older age.

Moderate-dose Regular Lifelong Alcohol Intake Changes the Intestinal Flora, Protects against Aging, and Keeps Spatial Memory in the Senescence-accelerated Mouse Prone 8 (SAMP8) Model.

Heavy and long-term alcohol consumption increase the risk of alcohol-related diseases. Epidemiological studies show moderate drinking reduces the risk of mortality, cardiovascular diseases, and brain infarction in the J-shaped or U-shaped curve effect. However, why moderate drinkers may be healthy and non-drinkers may be ill in diverse populations remains controversial. Herein, we examined the relationship between moderate/lifelong alcohol intake and aging, especially aging-related cognitive functions in senescence-accelerated mouse prone 8 (SAMP8) model. Methods: SAMP8 model (5-week-old, male, n = 36), a model of age-related cognitive deficit, were group-housed (n = 6/cage) and provided free access to water (water group, n = 18) or 1% ethanol (EtOH group, n = 18, intake started when mice were 9 weeks old). The object recognition test (ORT) and object location test (OLT) were used to evaluate cognitive functions. The intestinal flora at the age of 87 weeks was analyzed by terminal restriction fragment length polymorphism (T-RFLP). The lifespan of the EtOH-group mice was about 4 weeks longer than that of the water-group mice. In the EtOH group, spatial recognition impairment, assessed by OLT, was observed later (age, 73 weeks) than that in the water group (age, 52 weeks). The spinal curvature and skin conditions progressed significantly slower in the EtOH group than in the water group. Moreover, diarrhea symptoms only appeared in the water group, at the age of 82 weeks. The T-RFLP analysis of the intestinal flora indicated higher Lactobacillales order and lower Clostridium cluster XI in the EtOH group than in the water group, although those were extremely high in some mice close to death in both groups. Water-group mice with diarrhea presented significantly higher Clostridium cluster XI than did those without diarrhea (P = 0.017). Moderate alcohol intake changes intestinal flora and positively affects aging of SAMP8 model.

L-Lysine suppresses myofibrillar protein degradation and autophagy in skeletal muscles of senescence-accelerated mouse prone 8.

Sarcopenia is a condition of the loss of muscle mass that is associated with aging and that increases the risk for bedridden state, thereby warranting studies of interventions that attenuate sarcopenia. Here the effects of 2-month dietary L-lysine (Lys) supplementation (1.5-3.0%) on myofibrillar protein degradation and major proteolytic systems were investigated in senescence-accelerated mouse prone 8 (SAMP8). At 36weeks of age, skeletal muscle and lean body mass was reduced in SAMP8 when compared with control senescence-accelerated mouse resistant 1 (SAMR1). The myofibrillar protein degradation, which was evaluated by the release of 3-methylhistidine, was stimulated in SAMP8, and the autophagy activity, which was evaluated by light chain 3-II, was stimulated in the skeletal muscle of SAMP8. The activation of ubiquitin-proteasome system was not observed in the muscles of SAMP8. However, myofibrillar protein degradation and autophagic activity in skeletal muscles of SAMP8 were suppressed by dietary intake of 3.0% Lys. The present data indicate that myofibrillar protein degradation by bulk autophagy is stimulated in the skeletal muscles of SAMP8 and that dietary Lys supplementation attenuates sarcopenia in SAMP8 by suppressing autophagic proteolysis.

MiR-195 dependent roles of mitofusin2 in the mitochondrial dysfunction of hippocampal neurons in SAMP8 mice

Abnormal gene expression, including mRNAs, and microRNAs (miRNA), have been identified in the development of Alzheimer's disease (AD). Although mitofusin2 (mfn2) has been found to be down-regulated in the neurons from hippocampus and cortex in AD patients, little is known about its roles and the regulatory mechanisms in the pathogenesis of AD. This study was performed to investigate the roles of mfn2 protein and its upstream regulatory mechanism in the progression of AD using a senescence accelerated mouse prone-8 (SAMP8) model. The results of quantitative real-time PCR and western blot revealed that mfn2 expression displayed a consistent decrease with aging in the hippocampus of SAMP8 than did age-matched SAMR1 mice. The luciferase activity assay combined with mutational analysis confirmed the binding site of miR-195 to the 3′ -untranslated region (3′-UTR) of mfn2 mRNA. Furthermore, miR-195 inhibitor or antigomir induced the higher level expression of mfn2 protein in vitro and in vivo. In addition, exogenous expression of miR-195 decreased the mitochondrial membrane potential (MMP) of the HT-22 cells by targeting mfn2. In conclusion, these results indicated that deregulation of mfn2 might be involved in mitochondrial dysfunction during the progression of AD, and its decreased expression was regulated at least in part by miR-195 in AD mice. The abnormal expression of miR-195 played a potential role in mitochondrial disorder by targeting mfn2 in hippocampus of SAMP8 mice. Therefore, upregulation of mfn2 protein by inhibiting miR-195 might be a potential new therapeutic strategy for treatment of AD.

Neuroprotective Effects of Electroacupuncture Preventive Treatment in Senescence-Accelerated Mouse Prone 8 Mice

To investigate the preventive treatment effects of electroacupuncture (EA) on cognitive changes and brain damage in senescence-accelerated mouse prone 8 (SAMP8) mice. The 5-month-old male SAMP8 and age-matched homologous normal aging mice (SAMR1) were adopted in this study. EA stimulation at Baihui (GV 20) and Yintang (EX-HN 3) was performed every other day for 12 weeks, 4 weeks as a course. Morris water maze test and Nissl-stained with cresyl violet were used for cognitive impairments evaluation and brain morphometric analysis. Amyloid-β (A β) expression in hippocampus and parietal cortex was detected by immunohistochemistry, and apoptosis was observed by TUNEL staining. After 3 courses of EA preventive treatment, the escape latencies of 8-month-old SAMP8 mice in EA group were significantly shortened than those of un-pretreated SAMP8 mice. Compared with SAMR1 mice, extensive neuronal changes were visualized in the CA1 area of hippocampus in SAMP8 mice, while these pathological changes and attenuate cell loss in hippocampal CA1 area of SAMP8 mice markedly reduced after EA preventive treatment. Furthermore, A β expression in hippocampus and parietal cortex of SAMP8 mice decreased significantly after EA treatment, and neuronal apoptosis decreased as well. EA preventive treatment at GV 20 and EX-HN 3 might improve cognitive deficits and neuropathological changes in SAMP8 mice, which might be, at least in part, due to the effects of reducing brain neuronal damage, decreasing neuronal apoptosis and inhibiting A β-containing aggregates.

Treadmill running exercise prevents senile osteoporosis and upregulates the Wnt signaling pathway in SAMP6 mice.

This study examined the effects of different exercise intensities and durations on bone mineral density (BMD) and bone strength in senescence-accelerated mouse prone 6 (SAMP6) and determined the involvement of the Wnt signaling pathway in exercise-induced osteogenesis. Three-month-old male SAMP6 mice were randomly assigned to different speeds of treadmill running exercise representing low, medium and high intensity, with the duration of five and nine weeks, respectively. We showed that medium-intensity exercise had positive effects on skeletal health, including BMD and bone strength, and the efficacy was higher than that of low-intensity exercise. Interestingly, high-intensity exercise can maintain or even increase bone strength, despite its negative effects on bone mass. Nine weeks of exercise was superior to 5 weeks of exercise, particularly for low-intensity exercise. Furthermore, these effects of exercise-induced osteogenesis are accompanied by activation of the Wnt signaling pathway. Taken together, these results suggest that the positive effects of exercise on osteoporosis prevention are intensity and duration-dependent, and may involve the regulation of Wnt signaling pathways.

Behavioral and omics analyses study on potential involvement of dipeptide balenine through supplementation in diet of senescence-accelerated mouse prone 8

This study investigates effects of dipeptide balenine, as a major component of whale meat extract (hereafter, WME), supplementation on senescence-accelerated mouse prone 8 (SAMP8), an Alzheimer's disease (AD) model at level of learning and memory formation and brain expression profiles genome-wide in brain. Mice fed experimental balenine (+WME) supplemented diet for 26weeks were subjected to four behavioral tests – open field, Y-maze, novel object recognition, and water-filled multiple T-maze – to examine effects on learning and memory. Brain transcriptome of SAMP8 mice-fed the WME diet over control low-safflower oil (LSO) diet-fed mice was delineated on a 4×44K mouse whole genome DNA microarray chip. Results revealed the WME diet not only induced improvements in the learning and memory formation but also positively modulated changes in the brain of the SAMP8 mouse; the gene inventories are publically available for analysis by the scientific community. Interestingly, the SAMP8 mouse model presented many genetic characteristics of AD, and numerous novel molecules (Slc2a5, Treh, Fbp1, Aldob, Ppp1r1a, DNase1, Agxt2l1, Cyp2e1, Acsm1, Acsm2, and Pah) were revealed over the SAMR1 (senescence-accelerated mouse resistant 1) mouse, to be oppositely regulated/recovered under the balenine (+WME) supplemented diet regime by DNA microarray and bioinformatics analyses. Our present study demonstrates an experimental strategy to understand the effects of dipeptide balenine, prominetly contained in meat diet, on SAMP8, providing new insight into whole brain transcriptome changes genome-wide. The gene expression data has been deposited into the Gene Expression Omnibus (GEO): GSE76459. The data will be a valuable resource in examining the effects of natural products, and which could also serve as a human model for further functional analysis and investigation.