Identification of a biomarker for sleep drive in flies and humans

Abstract

It is a common experience to sacrifice sleep to meet the demands of our 24-h society. Current estimates reveal that as a society, we sleep on average 2 h less than we did 40 years ago. This level of sleep restriction results in negative health outcomes and is sufficient to produce cognitive deficits and reduced attention and is associated with increased risk for traffic and occupational accidents. Unfortunately, there is no simple quantifiable marker that can detect an individual who is excessively sleepy before adverse outcomes become evident. To address this issue, we have developed a simple and effective strategy for identifying biomarkers of sleepiness by using genetic and pharmacological tools that dissociate sleep drive from wake time in the model organism Drosophila melanogaster. These studies have identified a biomarker, Amylase, that is highly correlated with sleep drive. More importantly, both salivary Amylase activity and mRNA levels are also responsive to extended waking in humans. These data indicate that the fly is relevant for human sleep research and represents a first step in developing an effective method for detecting sleepiness in vulnerable populations.Drosophila ͉ saliva ͉ sleep deprivation I t has been suggested that forced and self-inflicted sleep loss have reached epidemic proportions in Western industrialized populations (1, 2), costing billions of dollars in lost productivity and creating hazardous conditions on our roadways (3), in our skies (4), and in our hospitals (5). The National Highway Traffic Safety Administration estimates that 20% of motor vehicle crashes are attributed to sleepiness and fully 37% of adult drivers report falling asleep at the wheel at some point in their lives. Moreover, both regional and long-haul pilots accumulate sleep debt during trips, fall asleep in the cockpit, and experience levels of sleepiness that are associated with performance decrements (6, 7). In the hospital setting, training demands frequently disrupt the sleep of medical residents, which is then associated with increased attentional failures and medical errors (8). Indeed, after a heavy call rotation, the driving performance of medical residents was similar to those with a blood alcohol level of 0.05 g % (9) and is associated with increased risk of falling asleep while driving (10).Given the magnitude of this problem, it is not surprising that the sleep community, public health officials, and others have devoted considerable attention toward minimizing the negative impact of sleep loss on public health and safety (11). In addition to more focused basic research and increased educational campaigns to create public awareness, both regulatory and legislative initiatives have been implemented to address this problem. A general theme that has emerged from all of these efforts has been the importance of identifying a simple and quantifiable biomarker of sleepiness (11)(12)(13). A biomarker of sleepiness should be responsive to increasing levels of sleep debt and should only be activated by period...

Changes in Gene Expression with Sleep

“…A similar disassociation between wake time and sleep homeostasis can be achieved by comparing flies treated with caffeine or methamphetamine. 1,7 Both caffeine and methamphetamine each produce sustained periods of waking and similar locomoter activity profiles. However, unlike caffeine, flies do not compensate for the lost sleep accrued during methamphetamine-induced waking.…”

“…With that in mind, a goal of our laboratories has been to develop a rational strategy to expedite the identification of candidate biomarkers. 1 We began with the assumption that since both the genetic and environmental context of a gene can influence its behavior, an effective test of sleep loss will likely be composed of a panel of multiple biomarkers. That is, we believe that it is premature to exclude a candidate analyte simply because it might also be modulated in response to other conditions (e.g., illness, metabolism, sympathetic tone, etc.).…”

Salivary mRNA targets for cancer diagnostics

“…In an extension of this undertaking, salivary RNA was also applied successfully to array analysis by an independent group to identify new saliva identifying mRNAs [19]. Lastly, salivary amylase mRNA (and protein) were shown to be highly correlated with sleep deprivation [20].…”

Salivary Biomarkers of Physical Fatigue as Markers of Sleep Deprivation

“…A gene expression study identified salivary amylase as a biomarker of sleep drive in both fruit flies (Drosophila melanogaster) and humans. 49 Indeed, heterozygote individuals with a single copy of the c.22G > A (rs73598374) polymorphism for adenosine deaminase differ significantly from homozygote individuals with respect to vulnerability to sleep loss, exhibiting both a reduction in sustained attention and an elevation in salivary α-amylase activity during periods of prolonged waking. 55 Although many of these measures of sleepiness appear promising, the lack of specificity among many, if not all, of the sleep reporter and regulatory substances identified to date has led some to suggest that proper measurement of sleepiness will ultimately require simultaneous monitoring of numerous analytes.…”

“…Methods of quantifying sleepiness have been proposed based on changes in behavioral factors such as response time 6,46 and other measures of attention, as well as various electrophysiological factors such as changes in the power for a particular type of electroencephalographic wave. 47 Other methods for measuring sleepiness have focused on changes in the composition of serum, 48 saliva, 49 cerebrospinal fluid, 50,51 exhaled breath, and exhaled breath condensate. 52 Inflammatory factors such as IL-6, TNF-α, von Willebrand factor, and C-reactive protein 53,54 have drawn considerable attention.…”