Alzheimer's Disease and Functional Foods: An Insight on Neuroprotective Effect of its Combination

Comparison between sub-chronic and chronic sleep deprivation-induced behavioral and neuroimmunological abnormalities in mice: Focusing on glial cell phenotype polarization

BACKGROUND

Sleep disorders, depression, and Alzheimer's disease (AD) are extensively reported as comorbidity. Although neuroinflammation triggered by microglial phenotype M1 activation, leading to neurotransmitter dysfunction and Aβ aggregation, is considered as the leading cause of depression and AD, whether and how sub-chronic or chronic sleep deprivation (SD) contribute to the onset and development of these diseases remains unclear.

METHODS

Memory and depression-like behaviors were evaluated in both SDs, and then circadian markers, glial cell phenotype polarization, cytokines, depression-related neurotransmitters, and AD-related gene/protein expressions were measured by qRT-PCR, enzyme-linked immunosorbent assay, high-performance liquid chromatography, and western-blotting respectively.

RESULTS

Both SDs induced give-up behavior and anhedonia and increased circadian marker period circadian regulator 2 (PER2) expression, which were much worse in chronic than in the sub-chronic SD group, while brain and muscle ARNT-like protein-1 only decreased in the chronic-SD. Furthermore, increased microglial M1 and astrocyte A1 expression and proinflammatory cytokines, interleukin (IL)-1β, IL-6, and tumor necrosis factor-α was observed in both SDs, which were more significant in chronic SD. Similarly, decreased norepinephrine and 5-hydroxytryptamine/5-hydroxyindoleacetic acid ratio were more significant, which corresponds to the worse depression-like behavior in chronic than sub-chronic-SD. With regard to AD, increased amyloid precursor protein (APP) and soluble (s)-APPβ and decreased sAPPα in both SDs were more significant in the chronic. However, sAPPα/sAPPβ ratio was only decreased in chronic SD.

CONCLUSION

These findings suggest that both SDs induce depression-like changes by increasing PER2, leading to neuroinflammation and neurotransmitter dysfunction. However, only chronic SD induced memory impairment likely due to severer circadian disruption, higher neuroinflammation, and dysregulation of APP metabolism.

Preventive Impact of Long-Term Ingestion of Chestnut Honey on Glucose Disorders and Neurodegeneration in Obese Mice

The purpose of the present study was to evaluate the impact of long-term honey ingestion on metabolic disorders and neurodegeneration in mice fed a high-fat diet (HFD). Three groups of mice were fed with a standard diet (STD), HFD or HFD supplemented with honey (HFD-H) for 16 weeks. Biochemical, histological, Western blotting, RT-PCR and Profiler PCR array were performed to assess metabolic parameters, peripheral and central insulin resistance and neurodegeneration. Daily honey intake prevented the HFD-induced glucose dysmetabolism. In fact, it reduced plasma fasting glucose, insulin and leptin concentrations and increased adiponectin levels. It improved glucose tolerance, insulin sensitivity and HOMA index without affecting plasma lipid concentration. HFD mice showed a significantly higher number of apoptotic nuclei in the superficial and deep cerebral cortex, upregulation of Fas-L, Bim and P27 (neuronal pro-apoptotic markers) and downregulation of Bcl-2 and BDNF (anti-apoptotic factors) in comparison with STD- and HFD-H mice, providing evidence for honey neuroprotective effects. PCR-array analysis showed that long-term honey intake increased the expression of genes involved in insulin sensitivity and decreased genes involved in neuroinflammation or lipogenesis, suggesting improvement of central insulin resistance. The expressions of p-AKT and p-GSK3 in HFD-H mice, which were decreased and increased, respectively, in HFD mouse brain, index of central insulin resistance, were similar to STD animals supporting the ability of regular honey intake to protect brain neurons from insulin resistance. In conclusion, the present results provide evidence for the beneficial preventative impact of regular honey ingestion on neuronal damage caused by HFD.