Phenotypic Frailty Assessment in SAMP8 Mice: Sex Differences and Potential Role of miRNAs as Peripheral Biomarkers

Geniposide attenuates muscle atrophy via the inhibition of FoxO1 in senescence-accelerated mouse prone-8

BACKGROUND

Geniposide (GP) is an iridoid glycoside that is present in nearly 40 species, including Gardenia jasminoides Ellis. GP has been reported to exhibit neuroprotective effects in various Alzheimer's disease (AD) models; however, the effects of GP on AD models of Caenorhabditis elegans (C. elegans) and aging-accelerated mouse predisposition-8 (SAMP8) mice have not yet been evaluated.

PURPOSE

To determine whether GP improves the pathology of AD and sarcopenia.

METHODS

AD models of C. elegans and SAMP8 mice were employed and subjected to behavioral analyses. Further, RT-PCR, histological analysis, and western blot analyses were performed to assess the expression of genes and proteins related to AD and muscle atrophy.

RESULTS

GP treatment in the AD model of C. elegans significantly restored the observed deterioration in lifespan and motility. In SAMP8 mice, GP did not improve cognitive function deterioration by accelerated aging but ameliorated physical function deterioration. Furthermore, in differentiated C2C12 cells, GP ameliorated muscle atrophy induced by dexamethasone treatment and inhibited FoxO1 activity by activating AKT.

CONCLUSION

Although GP did not improve the AD pathology in SAMP8 mice, we suggest that GP has the potential to improve muscle deterioration caused by aging. This effect of GP may be attributed to the suppression of FoxO1 activity.

Differential Epigenetic Changes in the Dorsal Hippocampus of Male and Female SAMP8 Mice: A Preliminary Study

Alzheimer's disease (AD) is the most common age-related neurodegenerative disease characterized by memory loss and cognitive impairment. The causes of the disease are not well understood, as it involves a complex interaction between genetic, environmental, and epigenetic factors. SAMP8 mice have been proposed as a model for studying late-onset AD, since they show age-related learning and memory deficits as well as several features of AD pathogenesis. Epigenetic changes have been described in SAMP8 mice, although sex differences have never been evaluated. Here we used western blot and qPCR analyses to investigate whether epigenetic markers are differentially altered in the dorsal hippocampus, a region important for the regulation of learning and memory, of 9-month-old male and female SAMP8 mice. We found that H3Ac was selectively reduced in male SAMP8 mice compared to male SAMR1 control mice, but not in female mice, whereas H3K27me3 was reduced overall in SAMP8 mice. Moreover, the levels of HDAC2 and JmjD3 were increased, whereas the levels of HDAC4 and Dnmt3a were reduced in SAMP8 mice compared to SAMR1. In addition, levels of HDAC1 were reduced, whereas Utx and Jmjd3 were selectively increased in females compared to males. Although our results are preliminary, they suggest that epigenetic mechanisms in the dorsal hippocampus are differentially regulated in male and female SAMP8 mice.