Future research proposed to link biomarkers with metabolic disorders associated with sleep loss.
Sleep is a fundamental biological necessity, yet the molecular mechanisms through which sleep loss affects the body remain incompletely understood. Reduced sleep duration is epidemiologically linked to a range of metabolic disorders—including weight gain, insulin resistance, diabetes, obesity, and cardiovascular disease—driving renewed efforts to identify biochemical changes that follow sleep restriction. This study reports metabolic signatures that may help explain how insufficient sleep contributes to metabolic dysfunction and points to potential biomarkers for sleep debt.
Published in the Proceedings of the National Academy of Sciences, the study was led by Amita Sehgal, PhD, professor of Neuroscience at the Perelman School of Medicine at the University of Pennsylvania and a Howard Hughes Medical Institute investigator, with co-first authors Aalim M. Weljie, PhD, research assistant professor of Systems Pharmacology and Translational Therapeutics, and Peter Meerlo, PhD, from the University of Groningen, The Netherlands. The investigators performed comprehensive metabolomic profiling of blood from both rats and human participants following periods of normal sleep and controlled sleep restriction.
The cross-species analysis revealed consistent shifts in lipid metabolism and signs of systemic oxidative stress linked to sleep reduction. These findings suggest that sleep loss alters how the body handles fats and may increase oxidative metabolism, both of which are relevant to known metabolic diseases. While the work stops short of proving direct causation, the conserved metabolic changes identified in rats and humans offer targets for further mechanistic and clinical research.
“One possibility is that sleep supports the clearance of metabolic byproducts and helps restore biochemical balance across tissues,” says Sehgal. “Sleep restriction also affects circadian rhythms, and many metabolites show daily oscillations. Disrupting sleep may therefore disrupt metabolite cycles that are important for metabolic health.” Metabolites are small molecules produced or transformed during the processing of fats, carbohydrates, and proteins; beyond serving as intermediates in energy metabolism, they function in cell signaling, enzyme regulation, and growth.
Cross-species metabolic profiling: rats and humans
To model common human sleep patterns, the research team employed chronic sleep restriction rather than total deprivation. Sleep restriction reduces total sleep opportunity without eliminating sleep entirely, a scenario that more accurately mirrors the sleep loss experienced by many people in modern lifestyles. Both rats and human volunteers underwent five days of sleep restriction, and blood samples were collected after baseline sleep and again after the restricted sleep period to measure metabolic changes.
The metabolomic analysis identified a number of metabolites that changed significantly with sleep restriction. In rats, 38 metabolites were uniquely altered by restricted sleep, and roughly half of these were lipids. Human participants showed a similar pattern, with a majority of altered metabolites related to lipids or fatty acids. The researchers observed elevated levels of several phospholipids, including seven distinct plasmalogens in sleep-restricted rats—molecules that are associated with oxidative stress and membrane biology. Overall, the data indicate a consistent shift in lipid metabolism and an increase in oxidative metabolic markers in both species.
In addition to lipid changes, the study detected alterations in certain neurotransmitter-related metabolites and gut-associated compounds, some of which may derive from intestinal microbes. These findings point to multiple physiological systems—central nervous, metabolic, and gut microbiome-related—that are responsive to changes in sleep duration.
Two metabolites emerged as especially noteworthy because they were depleted during sleep restriction and rebounded after recovery sleep in both rats and humans: oxalic acid and diacylglycerol 36:3. Oxalic acid is a small metabolic waste product that arises from the processing of dietary components, including vitamin C and certain amino acids. Diacylglycerol 36:3 is a lipid intermediate involved in the synthesis of triglycerides and also functions in cellular signaling. Because these two molecules showed consistent, reversible changes across species, the authors suggest they may serve as candidate biomarkers for sleep debt.
“Finding the same metabolites in humans and rats is encouraging for two reasons,” says Weljie. “First, there is a clinical need for objective, quantitative markers of sleep debt and sleep quality; metabolites could potentially provide such markers. Second, conserved markers enable mechanistic studies in animal models that could translate into clinical or therapeutic strategies for humans.”
Although further work is required to link these metabolic changes to specific diseases, the study helps bridge epidemiological observations—tying short sleep to metabolic disorders—with biochemical evidence of altered metabolism and oxidative state. “This fits with the broader idea that sleep serves restorative functions, including clearing metabolites from tissues and reestablishing antioxidant balance,” Sehgal notes. “By contrast, sleep loss appears to push the body toward an oxidative metabolic state.”
Co-authors include Namni Goel, Arjun Sengupta, Matthew S. Kayser, Ted Abel, Morris J. Birnbaum (now with industry), and David F. Dinges, all affiliated with the University of Pennsylvania. The authors acknowledge the human volunteers and the staff of the Division of Sleep and Chronobiology for assistance with sample collection and metabolomic analysis. Funding support was provided by the Howard Hughes Medical Institute, the Department of the Navy Office of Naval Research, NASA, the National Institutes of Nursing Research, DARPA, and the US Army Research Office.
Contact: Anna Duerr – University of Pennsylvania
Source: University of Pennsylvania press release
Image Source: Image credited to Ben Mills and Jynto (public domain)
Original Research: Abstract for “Oxalic acid and diacylglycerol 36:3 are cross-species markers of sleep debt” by Aalim M. Weljie, Peter Meerlo, Namni Goel, Arjun Sengupta, Matthew S. Kayser, Ted Abel, Morris J. Birnbaum, David F. Dinges, and Amita Sehgal in PNAS. Published online February 9, 2015, doi:10.1073/pnas.1417432112