Metabolic Disturbances Induced by Sleep Restriction as Potential Triggers for Alzheimer's Disease

Sleep restriction promotes brain oxidative stress and inflammation, and aggravates cognitive impairment in insulin-resistant mice

Sleep deprivation and insulin resistance (IR) are two risk factors for Alzheimer's disease. As the population of people with IR increases and sleep restriction (SR) due to staying up late becomes the "new normal", it is necessary to investigate the effects and molecular pathogenesis of chronic SR on cognitive function in insulin resistance. In this study, 4-week-old mice were fed a high-fat diet (HFD) for 8 weeks to establish IR model, and then the mice were subjected to SR for 21 days, and related indicators were assessed, including cognitive capacity, apoptosis, oxidative stress, glial cell activation, inflammation, blood-brain barrier (BBB) permeability and adiponectin levels, for exploring the potential regulatory mechanisms. Compared with control group, IR mice showed impaired cognitive capacity, meanwhile, SR not only promoted Bax/Bcl2-induced hippocampal neuronal cell apoptosis and Nrf2/HO1- induced oxidative stress, but also increased microglia activation and inflammatory factor levels and BBB permeability, thus aggravating the cognitive impairment in IR mice. Consequently, changing bad living habits and ensuring sufficient sleep are important intervention strategies to moderate the aggravation of IR-induced cognitive impairment.

Association between sleep problems and functional disability in community-dwelling older adults

BACKGROUND

Sleep problems are frequently observed in older adults. They can lead to changes in the individual's physical, occupational, cognitive, and social functioning, compromising the performance of activities of daily living and contributing to the occurrence of functional disability. This study evaluated the association between sleep problems and functional disability in community-dwelling older adults.

METHODS

This was a cross-sectional study with data from 10,507 Brazilian community-dwelling older adults participating in the 2013 National Health Survey. The exposure variable was self-reported sleep problems in the last two weeks. The outcome measure was functional disability assessed from self-reported questionnaires, categorized into basic activities of daily living (BADL) and instrumental activities of daily living (IADL), and defined as not being able to perform or having little or a lot of difficulty in at least one of the activities investigated in the domain of interest.

RESULTS

Older adults who reported sleep problems had 1.53 (95%CI: 1.34; 1.75) and 1.42 (95%CI: 1.26; 1.59) greater odds of having a disability in BADL and IADL when compared to individuals who reported having no sleep problems.

CONCLUSIONS

Older adults with sleep problems were more likely to have a functional disability, both in BADL and IADL. Thus, it is important to implement strategies to screen for sleep problems in older adults in primary health care as a preventive strategy for functional disability.

[Chronic sleep restriction in rats leads to a weakening of compensatory reactions in response to acute sleep deprivation]

OBJECTIVE

To identify features in the compensatory mechanisms of sleep regulation in response to acute sleep deprivation after chronic sleep restriction in rats.

MATERIAL AND METHODS

Male Wistar rats 7-8 months old underwent 5-day sleep restriction: 3 h of sleep deprivation and 1 h of sleep opportunity repeating throughout each day. Six-hour acute total sleep deprivation was performed at the beginning of daylight hours on the 3rd day after sleep restriction. Polysomnogramms were recorded throughout the day before chronic sleep restriction, on the 2nd recovery day after chronic sleep restriction and after acute sleep deprivation. The control group was not subjected to chronic sleep restriction.

RESULTS

The animals after chronic sleep restriction had the compensatory increase in total sleep time in response to acute sleep deprivation weaker than in control animals. Animals after sleep restriction had the compensatory increase in the time of slow-wave sleep (SWS) only in the first 6 hours after acute sleep deprivation, whereas in control animals the period of compensation of SWS lasted 12 hours. A compensatory increase in slow-wave activity (SWA) was observed in both groups of animals, but in animals experiencing chronic sleep restriction the amplitude of SWA after acute sleep deprivation was less than in control animals. A compensatory increase in REM sleep in sleep restricted animals occurred immediately after acute sleep deprivation and coincides with a compensatory increase in SWS and SWA, whereas in control conditions these processes are spaced in time.

CONCLUSION

Compensatory reactions in response to acute sleep deprivation (sleep homeostasis) are weakened in animals subjected to chronic sleep restriction, as the reaction time and amplitude are reduced.

Circadian Synchrony: Sleep, Nutrition, and Physical Activity

The circadian clock in mammals regulates the sleep/wake cycle and many associated behavioral and physiological processes. The cellular clock mechanism involves a transcriptional negative feedback loop that gives rise to circadian rhythms in gene expression with an approximately 24-h periodicity. To maintain system robustness, clocks throughout the body must be synchronized and their functions coordinated. In mammals, the master clock is located in the suprachiasmatic nucleus (SCN) of the hypothalamus. The SCN is entrained to the light/dark cycle through photic signal transduction and subsequent induction of core clock gene expression. The SCN in turn relays the time-of-day information to clocks in peripheral tissues. While the SCN is highly responsive to photic cues, peripheral clocks are more sensitive to non-photic resetting cues such as nutrients, body temperature, and neuroendocrine hormones. For example, feeding/fasting and physical activity can entrain peripheral clocks through signaling pathways and subsequent regulation of core clock genes and proteins. As such, timing of food intake and physical activity matters. In an ideal world, the sleep/wake and feeding/fasting cycles are synchronized to the light/dark cycle. However, asynchronous environmental cues, such as those experienced by shift workers and frequent travelers, often lead to misalignment between the master and peripheral clocks. Emerging evidence suggests that the resulting circadian disruption is associated with various diseases and chronic conditions that cause further circadian desynchrony and accelerate disease progression. In this review, we discuss how sleep, nutrition, and physical activity synchronize circadian clocks and how chronomedicine may offer novel strategies for disease intervention.

Circadian Synchrony: Sleep, Nutrition, and Physical Activity

The circadian clock in mammals regulates the sleep/wake cycle and many associated behavioral and physiological processes. The cellular clock mechanism involves a transcriptional negative feedback loop that gives rise to circadian rhythms in gene expression with an approximately 24-h periodicity. To maintain system robustness, clocks throughout the body must be synchronized and their functions coordinated. In mammals, the master clock is located in the suprachiasmatic nucleus (SCN) of the hypothalamus. The SCN is entrained to the light/dark cycle through photic signal transduction and subsequent induction of core clock gene expression. The SCN in turn relays the time-of-day information to clocks in peripheral tissues. While the SCN is highly responsive to photic cues, peripheral clocks are more sensitive to non-photic resetting cues such as nutrients, body temperature, and neuroendocrine hormones. For example, feeding/fasting and physical activity can entrain peripheral clocks through signaling pathways and subsequent regulation of core clock genes and proteins. As such, timing of food intake and physical activity matters. In an ideal world, the sleep/wake and feeding/fasting cycles are synchronized to the light/dark cycle. However, asynchronous environmental cues, such as those experienced by shift workers and frequent travelers, often lead to misalignment between the master and peripheral clocks. Emerging evidence suggests that the resulting circadian disruption is associated with various diseases and chronic conditions that cause further circadian desynchrony and accelerate disease progression. In this review, we discuss how sleep, nutrition, and physical activity synchronize circadian clocks and how chronomedicine may offer novel strategies for disease intervention.