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  1. All, As we've discussed elsewhere, the formation of amyloid-beta plaques are known to be an important step in the progression of Alzheimer's disease. Exercise is known to help reduce amyloid plaque buildup, as discussed here. I think the fermented food natto may be beneficial for amyloid clearance as well, but that is more controversial. Sleep is known to be a time when the brain "cleans house", psychologically in terms of memory consolidation and synapse decay, but also literally, through the glymphatic transport system, which flushes toxins from the brain, including beta-amyloid plaques [2]: Clearance [of toxic proteins including beta-amyloid] during sleep is as much as two-fold faster than during waking hours. This new study [1] (popular press article), found that at least in rats, sleep posture influences the rate of glymphatic transport and toxin clearance. In particular, rats that were made to sleep on their (right) side while sleeping had better flow of their glymphatic fluid than rats who were either sitting up or lying on the back although beta-amyloid clearance wasn't much different between the two prone positions. And of course, rat brain morphology and circulatory system is quite a bit different from people, but the authors nevertheless speculate that sleeping on your side may be advantageous for brain health relative to sleeping on your back (or stomach). They didn't compare sleeping on the left vs right side in these rats, but in people it looks like sleeping on one's left side appears to be better for digestion / acid reflux than sleeping on one's right side. --Dean ----- [1] J Neurosci. 2015 Aug 5;35(31):11034-44. doi: 10.1523/JNEUROSCI.1625-15.2015. The Effect of Body Posture on Brain Glymphatic Transport. Lee H(1), Xie L(2), Yu M(3), Kang H(2), Feng T(4), Deane R(2), Logan J(5), Nedergaard M(2), Benveniste H(6). full text: http://www.jneurosci.org.sci-hub.io/content/35/31/11034.long The glymphatic pathway expedites clearance of waste, including soluble amyloid β (Aβ) from the brain. Transport through this pathway is controlled by the brain's arousal level because, during sleep or anesthesia, the brain's interstitial space volume expands (compared with wakefulness), resulting in faster waste removal. Humans, as well as animals, exhibit different body postures during sleep, which may also affect waste removal. Therefore, not only the level of consciousness, but also body posture, might affect CSF-interstitial fluid (ISF) exchange efficiency. We used dynamic-contrast-enhanced MRI and kinetic modeling to quantify CSF-ISF exchange rates in anesthetized rodents' brains in supine, prone, or lateral positions. To validate the MRI data and to assess specifically the influence of body posture on clearance of Aβ, we used fluorescence microscopy and radioactive tracers, respectively. The analysis showed that glymphatic transport was most efficient in the lateral position compared with the supine or prone positions. In the prone position, in which the rat's head was in the most upright position (mimicking posture during the awake state), transport was characterized by "retention" of the tracer, slower clearance, and more CSF efflux along larger caliber cervical vessels. The optical imaging and radiotracer studies confirmed that glymphatic transport and Aβ clearance were superior in the lateral and supine positions. We propose that the most popular sleep posture (lateral) has evolved to optimize waste removal during sleep and that posture must be considered in diagnostic imaging procedures developed in the future to assess CSF-ISF transport in humans. SIGNIFICANCE STATEMENT: The rodent brain removes waste better during sleep or anesthesia compared with the awake state. Animals exhibit different body posture during the awake and sleep states, which might affect the brain's waste removal efficiency. We investigated the influence of body posture on brainwide transport of inert tracers of anesthetized rodents. The major finding of our study was that waste, including Aβ, removal was most efficient in the lateral position (compared with the prone position), which mimics the natural resting/sleeping position of rodents. Although our finding awaits testing in humans, we speculate that the lateral position during sleep has advantage with regard to the removal of waste products including Aβ, because clinical studies have shown that sleep drives Aβ clearance from the brain. Copyright © 2015 the authors 0270-6474/15/3511034-11$15.00/0. PMCID: PMC4524974 [Available on 2016-02-05] PMID: 26245965 ------- [2] Rejuvenation Res. 2013 Dec;16(6):518-23. doi: 10.1089/rej.2013.1530. Sleep facilitates clearance of metabolites from the brain: glymphatic function in aging and neurodegenerative diseases. Mendelsohn AR(1), Larrick JW. Author information: (1)Panorama Research Institute and Regenerative Sciences Institute , Sunnyvale, California. Decline of cognition and increasing risk of neurodegenerative diseases are major problems associated with aging in humans. Of particular importance is how the brain removes potentially toxic biomolecules that accumulate with normal neuronal function. Recently, a biomolecule clearance system using convective flow between the cerebrospinal fluid (CSF) and interstitial fluid (ISF) to remove toxic metabolites in the brain was described. Xie and colleagues now report that in mice the clearance activity of this so-called "glymphatic system" is strongly stimulated by sleep and is associated with an increase in interstitial volume, possibly by shrinkage of astroglial cells. Moreover, anesthesia and attenuation of adrenergic signaling can activate the glymphatic system to clear potentially toxic proteins known to contribute to the pathology of Alzheimer disease (AD) such as beta-amyloid (Abeta). Clearance during sleep is as much as two-fold faster than during waking hours. These results support a new hypothesis to answer the age-old question of why sleep is necessary. Glymphatic dysfunction may pay a hitherto unsuspected role in the pathogenesis of neurodegenerative diseases as well as maintenance of cognition. Furthermore, clinical studies suggest that quality and duration of sleep may be predictive of the onset of AD, and that quality sleep may significantly reduce the risk of AD for apolipoprotein E (ApoE) ɛ4 carriers, who have significantly greater chances of developing AD. Further characterization of the glymphatic system in humans may lead to new therapies and methods of prevention of neurodegenerative diseases. A public health initiative to ensure adequate sleep among middle-aged and older people may prove useful in preventing AD, especially in apolipoprotein E (ApoE) ɛ4 carriers. PMID: 24199995
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