Circadian and sleep phenotypes in a mouse model of Alzheimer's disease characterized by intracellular accumulation of amyloid ß oligomers.

Disturbances in sleep-wake and circadian rhythms may reportedly precede the onset of cognitive symptoms in the early stages of Alzheimer's disease (AD); however, the underlying mechanisms of these AD-induced sleep disturbances remain unelucidated. To specifically evaluate the involvement of amyloid ß (Aß) oligomers in AD-induced sleep disturbances, we examined circadian and sleep phenotypes using an Aß-GFP transgenic (Aß-GFP Tg) mouse characterized by intracellular accumulation of Aß oligomers. The circadian rhythm and free-running period of wheel running activity were identical between Aß-GFP Tg and littermate wild-type mice. The durations of rapid eye movement (REM) sleep were elongated in Aß-GFP Tg mice; however, the durations of non-REM sleep and wakefulness were unaffected. The Aß-GFP Tg mice exhibited shifts in the electroencephalogram (EEG) power spectra toward higher frequencies in the inactive light phase. These findings suggest that the intracellular accumulation of Aß oligomers might be associated with sleep quality; however, its impact on circadian systems is limited.

Supplementation with Ashitaba (Angelica keiskei) Yellow Stem Exudate Prevents Aging-Induced Thrombotic Tendencies and Systemic Inflammation Without Affecting Body Weight Gain in Mice.

Angelica keiskei Koidzumi (Ashitaba) is a traditional folk medicine and health supplement in Japan. Ashitaba yellow stem exudate (AYE) contains abundant chalcones and thus has the potential to treat and prevent many pathological states such as cancer, inflammation, obesity, diabetics, thrombosis, and hypertension. Levels of plasminogen activator inhibitor 1 (PAI-1), a key regulator of the fibrinolytic system, increase with age in mouse plasma. Therefore, we aimed to determine the effects of AYE on plasma thrombotic parameters in aging mice. Long-term (52 weeks) AYE supplementation significantly decreased age-induced increases of PAI-1 in mouse plasma. Supplementation with AYE decreased levels of the acute-phase and fibrinolytic protein plasma plasminogen, and significantly decreased those of tumor necrosis factor α. These results suggested that continuous intake of AYE throughout life decreases age-induced systemic inflammation and prevents thrombotic tendencies without affecting body weight gain in aged mice. Our findings showed that supplementing diets with AYE might help to prevent thrombotic diseases in elderly individuals.

Metabolic profiles of saliva in male mouse models of chronic sleep disorders induced by psychophysiological stress.

Disordered sleep is a global social problem and an established significant risk factor for psychological and metabolic diseases. We profiled non-targeted metabolites in saliva from mouse models of chronic sleep disorder (CSD). We identified 288 and 55 metabolites using CE-FTMS and LC-TOFMS, respectively, among which concentrations of 58 (CE-FTMS) and three (LC-TOFMS) were significantly changed by CSD. Pathway analysis revealed that CSD significantly suppressed glycine, serine and threonine metabolism. Arginine and proline metabolic pathways were among those that were both upregulated and downregulated. Pathways of alanine, aspartate and glutamate metabolism, genetic information processing, and the TCA cycle tended to be downregulated, whereas histidine metabolism tended to be upregulated in mice with CSD. Pyruvate, lactate, malate, succinate and the glycemic amino acids alanine, glycine, methionine, proline, and threonine were significantly decreased, whereas 3-hydroxybutyric and 2-hydroxybutyric acids associated with ketosis were significantly increased, suggesting abnormal glucose metabolism in mice with CSD. Increases in the metabolites histamine and kynurenic acid that are associated with the central nervous system- and decreased glycine, might be associated with sleep dysregulation and impaired cognitive dysfunction in mice with CSD. Our findings suggested that profiling salivary metabolites could be a useful strategy for diagnosing CSD.

A ketogenic diet containing medium-chain triglycerides reduces REM sleep duration without significant influence on mouse circadian phenotypes.

Ketogenic diets (KDs) affect the circadian rhythms of behavior and clock gene expression in experimental animals. However, these diets were designed to simulate a fasting state; thus, whether these effects are caused by diet-induced ketogenesis or persistent starvation is difficult to distinguish. The present study aimed to define the effects of a KD containing medium-chain triglycerides (MCT-KD) that increase blood ketone levels without inducing carbohydrate starvation, on circadian rhythms and sleep regulation. Mice were fed with a normal diet (CTRL) or MCT-KD for 2 weeks. Blood ß-hydroxybutyrate levels were significantly increased up to 2 mM by the MCT-KD, whereas body weight gain and blood glucose levels were identical between the groups, suggesting that ketosis accumulated without carbohydrate starvation in the MCT-KD mice. Circadian rhythms of wheel-running activity and core body temperature were almost identical, although wheel-running was slightly reduced in the MCT-KD mice. The circadian expression of the core clock genes, Per1, Per2, Bmal1, and Dbp in the hypothalamus, heart, liver, epididymal adipose tissues, and skeletal muscle were almost identical between the CTRL and MCT-KD mice, whereas the amplitude of hepatic Per2 and adipose Per1 expression was increased in MCT-KD mice. The MCT-KD reduced the duration of rapid-eye-movement (REM) sleep without affecting the duration of non-REM sleep and the duration of wakefulness. These findings suggested that the impact of ketone bodies on circadian systems are limited, although they might reduce locomotor activity and REM sleep duration.

Identification of salivary microRNA profiles in male mouse model of chronic sleep disorder.

Chronic sleep disorders (CSD) comprise a potential risk factor for metabolic and cardiovascular diseases, obesity and stroke. Thus, the identification of biomarkers for CSD is an important step in the early prevention of metabolic dysfunctions induced by sleep dysfunction. Diagnostic saliva samples can be easily and noninvasively collected. Thus, we aimed to identify whole microRNA (miRNA) profiles of saliva in control and psychophysiologically stressed CSD mouse models and compare them at Zeitgeber time (ZT) 0 (lights on) and ZT12 (lights off). The findings of two-way ANOVA revealed that the expression of 342 and 109 salivary miRNAs was affected by CSD and the time of day, respectively. Interactions were found in 122 miRNAs among which, we identified 197 (ZT0) and 62 (ZT12) upregulated, and 40 (ZT0) and seven (ZT12) downregulated miRNAs in CSD mice. We showed that miR-30c-5p, which is elevated in the plasma of patients with hypersomnia, was upregulated in the saliva of CSD mice collected at ZT0. The miRNAs, miR-10a-5p, miR-146b-5p, miR-150-5p, and miR-25-3p are upregulated in the serum of humans with poor sleep quality, and these were also upregulated in the saliva of CSD mice collected at ZT0. The miRNAs miR-30c, miR146b-5p, miR150, and miR-25-5p are associated with cardiovascular diseases, and we found that plasma concentrations of brain natriuretic peptides were significantly increased in CSD mice. The present findings showed that salivary miRNA profiles could serve as useful biomarkers for predicting CSD.

Memory dysfunction and anxiety-like behavior in a mouse model of chronic sleep disorders.

Sleep disturbances can contribute to cognitive decline and neuropsychiatric disorders. However, the underlying mechanisms of these processes are poorly understood. The present study evaluated the effects of a chronic sleep disorder (CSD) on long-term memory formation and anxiety-like behavior in our originally established mouse model of psychophysiological stress-induced CSD characterized by disrupted circadian rhythms of wheel-running activity and sleep-wake cycles. Model mice are continuously exposed to mild stress imposed by perpetually staying on a running-wheel to avoid water. The findings of novel object recognition (NORT) and open field (OFT) tests showed that CSD impaired recognition memory and elicited anxiety-like behavior, respectively. These results suggested that the CSD impaired cognitive function and emotional status. Thus, this CSD model could be useful for studying the underlying mechanisms of neurobehavioral difficulties caused by sleep disorders. We then examined the hippocampal mRNA expression of genes associated with learning and memory, and anxiety and depression. The CSD increased the mRNA expression of Crhr1, Ngf and Phlpp1, and suppressed that of Ace, Egr2 and Slc6a4. Based on the functions of these genes, we inferred that the increase in Crhr1 mRNA was associated with the pathogenesis of psychiatric conditions, whereas mRNA levels of the other five genes were directed towards symptom relief. Upregulating hippocampal Crhr1 expression might contribute in part to the activation of corticotropin-releasing hormone (CRH)-CRH receptor1 signaling that mediates CSD-evoked mental disorders.

Dietary natural cocoa ameliorates disrupted circadian rhythms in locomotor activity and sleep-wake cycles in mice with chronic sleep disorders caused by psychophysiological stress.

OBJECTIVES: Cocoa contains many chemical compounds that affect the physiological functions of experimental animals and humans. The present study used a mouse model characterized by disrupted circadian rhythms of locomotor activity and sleep-wake cycles to determine whether natural cocoa improves chronic sleep disorders (CSDs) induced by psychophysiological stress. METHODS: Mice were fed a high-fat, high-sucrose diet supplemented with 2.0% natural cocoa and stressed for 30 d to induce CSDs. RESULTS: Dietary cocoa restored the amplitude reduction of day-night activity rhythms by improving reduced nocturnal wheel-running activities during CSDs. Electroencephalography revealed that dietary cocoa significantly ameliorated CSD-induced increases in wakefulness during the first half of the inactive phase and in nonrapid eye movement sleep during the first half of the active phase. The attenuation of circadian rapid eye movement sleep rhythms and increased electroencephalography slow-wave activity (a marker of nonrapid eye movement sleep intensity) induced by CSDs improved in mice supplemented with cocoa. Dietary cocoa notably did not affect wheel-running activity rhythms or sleep-wake cycles under normal conditions. Dietary cocoa significantly increased the hypothalamic mRNA expression of Hspa1 a that encodes HSP70 and is associated with sleep regulation. Furthermore, Hspa1 a expression was not induced by CSDs in mice supplemented with cocoa. CONCLUSIONS: These findings suggest that dietary cocoa exerts beneficial effects on insomnia and circadian sleep disorders induced by psychophysiological stress.

Chronically skipping breakfast impairs hippocampal memory-related gene expression and memory function accompanied by reduced wakefulness and body temperature in mice.

Acute or chronic effects of consuming or skipping breakfast on cognitive performance in humans are controversial. To evaluate the effects of chronically skipping breakfast (SB) on hippocampus-dependent long-term memory formation, we examined hippocampal gene expression and applied the novel object recognition test (NORT) after two weeks of repeated fasting for six hours from lights off to mimic SB in mice. We also examined the effects of SB on circadian rhythms of locomotor activity, food intake, core body temperature (CBT) and sleep-wake cycles. Skipping breakfast slightly but significantly decreased total daily food intake without affecting body weight gain. Locomotor activity and CBT significantly decreased during the fasting period under SB. The degree of fasting-dependent CBT reduction gradually increased and then became stabilized after four days of SB. Electroencephalographic data revealed that repeated SB significantly decreased the duration of wakefulness and increased that of rapid eye movement (REM) and of non-REM (NREM) sleep during the period of SB. Furthermore, total daily amounts of wakefulness and NREM sleep were significantly decreased and increased, respectively, under SB, suggesting that SB disrupts sleep homeostasis. Skipping breakfast significantly suppressed mRNA expression of the memory-related genes, Camk2a, Fkbp5, Gadd45b, Gria1, Sirt1 and Tet1 in the hippocampus. Recognition memory assessed by NORT was impaired by SB in accordance with the gene expression profiles. These findings suggested that chronic SB causes dysregulated CBT, sleep-wake cycles and hippocampal gene expression, which results in impaired long-term memory formation.

Dietary Heat-Killed Lactobacillus brevis SBC8803 Attenuates Chronic Sleep Disorders Induced by Psychophysiological Stress in Mice.

We previously reported that dietary heat-killed Lactobacillus brevis SBC8803 affects sleep in mice and humans. The present study examined whether SBC8803 improves psychophysiological stress-induced chronic sleep disorders (CSD) using a mouse model characterized by disrupted circadian rhythms of wheel-running activity and sleep-wake cycles. Mice were fed with a diet supplemented with 0.5% heat-killed SBC8803 for 6 wk and imposed stress-induced CSD for last 2 wk. Dietary SBC8803 suppressed the reduction in wheel-running activity induced by CSD. Electroencephalography (EEG) revealed that SBC8803 significantly restored wakefulness and increased non-rapid eye movement (NREM) sleep during the second half of the active phase during CSD. The CSD-induced reduction in EEG slow wave activity, a marker of NREM sleep intensity, during the beginning of the inactive phase was significantly improved by SBC8803 supplementation. These findings suggest that dietary heat-killed SBC8803 confers beneficial effects on insomnia and circadian sleep disorders induced by psychophysiological stress.

Chronic sleep disorder induced by psychophysiological stress induces glucose intolerance without adipose inflammation in mice.

Sleep disturbances are associated with various metabolic diseases such as hypertension and diabetes. We had previously established a mouse model of a psychophysiological stress-induced chronic sleep disorder (CSD) characterized by disrupted circadian rhythms of wheel-running activity, core body temperature, and sleep-wake cycles. To evaluate the underlying mechanisms of metabolic disorders induced by CSD, we created mice with CSD for six weeks and fed them with a high-fat diet. Glucose intolerance with hyperglycemia resulted, although plasma insulin levels and body weight increases were identical between control and CSD mice. Gluconeogenesis and glycolysis were enhanced and suppressed, respectively, in the livers of CSD mice, because the mRNA expression of Pck1 was significantly increased, whereas that of Gck and Pklr were significantly decreased in the CSD mice. Adipose inflammation induced by the high-fat diet seemed suppressed by the CSD, because the mRNA expression levels of Adgre1, Ccl2, and Tnf were significantly downregulated in the adipose tissues of CSD mice. These findings suggest that CSD impair glucose tolerance by inducing gluconeogenesis and suppressing glycolysis. Hyperphasia with hypoleptinemia, hypercorticosteronemia, and increased plasma free fatty acids might be involved in the impaired glucose metabolism under a CSD. Further studies are needed to elucidate the endocrine and molecular mechanisms underlying the associations between sleep disorders and impaired glucose homeostasis that consequently causes diabetes.