A translational study across zebrafish, CUMS mice, and a human trial provides evidence that a combination of walnut peptide and theanine (WPT) effectively improves chronic stress-induced sleep disorders by regulating HPA axis function and restoring the duration and quality of slow-wave sleep.
Key Findings
Results
WPT treatment reduced waking activity and duration in pentylenetetrazole (PTZ)-induced zebrafish, demonstrating a sedative-like effect in the initial screening model.
Zebrafish were used as a high-throughput screening model prior to mammalian and human studies.
PTZ (pentylenetetrazole) was used to induce a hyperactivity/wakefulness state in zebrafish.
WPT treatment reduced both waking activity levels and waking duration in this model.
This zebrafish screen served as the first step in a translational research paradigm.
Results
In CUMS mice, WPT significantly improved sleep architecture by restoring the duration of slow-wave sleep (SWS).
A chronic unpredictable mild stress (CUMS) mouse model was used to replicate stress-induced sleep disorders.
WPT combination restored SWS duration, which is characteristically reduced by chronic stress.
Sleep quality was enhanced as measured by increased delta wave power density.
Delta wave power density is a key electrophysiological marker of deep, restorative sleep.
Results
WPT corrected HPA axis hyperactivity in CUMS mice by lowering elevated serum corticosterone (CORT) levels.
Chronic stress induces hyperactivation of the hypothalamic-pituitary-adrenal (HPA) axis, a key mechanistic driver of sleep disruption.
WPT intervention reduced elevated serum corticosterone (CORT), a primary stress hormone and marker of HPA axis activity.
Normalization of CORT levels was identified as a central mechanistic pathway of WPT's effects.
HPA axis dysregulation is described as mechanistically linked to disrupted sleep architecture.
Results
WPT modulated central neurotransmitters in CUMS mice, reversing stress-induced deficits by increasing levels of GABA and tryptophan.
Chronic stress caused deficits in inhibitory and sleep-promoting neurotransmitters.
WPT increased levels of GABA, described as 'the inhibitory neurotransmitter.'
WPT increased tryptophan, described as 'a key precursor for serotonin and melatonin.'
These neurochemical changes provide a mechanistic basis for the observed improvements in sleep architecture.
Results
In an eight-week randomized, placebo-controlled human trial, WPT restored sleep duration and improved subjective sleep quality scores in adults with sleep disturbances.
The human trial was an eight-week randomized, placebo-controlled design.
Participants were adults with a Pittsburgh Sleep Quality Index (PSQI) score ≥ 7, indicating clinically meaningful sleep disturbance.
WPT restored sleep duration in participants.
Subjective sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI), and scores improved with WPT treatment.
Methods
The study employed a translational research paradigm across three biological systems to evaluate WPT efficacy.
The three-stage paradigm consisted of: zebrafish screening, a CUMS mouse model, and a human clinical trial.
This sequential, multi-species approach was designed to provide translational validation of findings.
The paradigm connected mechanistic findings in animal models to outcomes observed in human participants.
The authors describe this as providing 'robust evidence' for WPT efficacy.
What This Means
This research suggests that a combination of walnut peptide and theanine (WPT) — two naturally derived compounds — may help improve sleep problems caused by chronic stress. The study used a progressive, three-stage approach: first testing WPT in zebrafish (where it reduced wakefulness), then in mice subjected to ongoing stress (where it restored deep sleep and improved brain wave patterns associated with restorative sleep), and finally in a clinical trial with human adults who had reported sleep difficulties. The human trial lasted eight weeks and was randomized and placebo-controlled, meaning participants were randomly assigned to receive either WPT or a dummy treatment, making it a more rigorous test of the supplement's effects.
The research also investigated how WPT works at a biological level. In the stressed mice, WPT appeared to calm down an overactive stress-response system (the HPA axis) by reducing levels of the stress hormone corticosterone. It also increased levels of GABA, a brain chemical that promotes calm and inhibits excessive neural activity, as well as tryptophan, a building block for the mood and sleep-regulating chemicals serotonin and melatonin. These findings suggest WPT does not just mask sleep symptoms but may address underlying stress-related biological imbalances.
This research suggests that a walnut peptide and theanine combination is a potentially promising nutritional approach for adults experiencing stress-related sleep disturbances, particularly those affecting deep, slow-wave sleep. Because this was a single study with specific participant eligibility criteria (PSQI score ≥ 7), more independent research would be needed to confirm these findings across broader populations and to determine optimal dosing and long-term safety.
Gong J, Jia X, Wang L, Lu Y, Guo R, Gong R, et al.. (2026). Walnut peptide and theanine combination ameliorates sleep disorders: a multi-species study including a human trial.. Food & function. https://doi.org/10.1039/d5fo03867g