Glycine ingestion improves subjective sleep quality in human volunteers, correlating with polysomnographic changes

Dietary Collagen Peptides Ameliorate the Mood Status of Fatigue and Vigor: A Randomized, Double-Blinded, Placebo-Controlled, Parallel-Group Comparative Trial

The mood status of fatigue can impact daily activities. Dietary collagen peptides have been reported to be beneficial for health conditions. A randomized, double-blinded, placebo-controlled, parallel-group study investigated the effects of collagen peptides on mood status including fatigue, physical condition, and immunological status. The participants who were healthy but easily fatigued consumed active food containing collagen peptides (10 g/day) (n = 33) or placebo food (n = 33) for eight weeks. POMS® 2 was used to assess the perceived fatigue and other mood status. The primary outcome was the T-scores of Fatigue-Inertias at eight weeks. In addition, their physical condition and immunological parameters were evaluated. The data set was a per protocol set of 31 participants each in both groups. As for POMS® 2, the T-score of Fatigue-Inertias at eight weeks was significantly lower in the active group than in the placebo group (47.0 ± 7.4 versus 51.5 ± 9.0, p = 0.045). The T-score of Vigor-Activity was significantly higher in the active group than in the placebo group after eight weeks (53.9 ± 10.7 versus 47.3 ± 9.6, p = 0.002). Regarding the questionnaire on the physical condition, the Likert scale score on fatigue after a night's sleep at eight weeks was significantly lower in the active group than in the placebo group (median; 3.0 versus 4.0, p = 0.038). There were no significant differences in the measured values of immunological parameters. No safety-related issues were reported in this trial. The intake of collagen peptides (10 g/day) for eight weeks ameliorated the mood status of fatigue and vigor and increased the feeling of sleep restfulness. Dietary collagen peptides were efficient and safe nutritional ingredients for healthy but easily fatigued individuals.Clinical trial registry number and website: UMIN-CTR, UMIN000042291 https://center6.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000048280.

Collagen peptide supplementation before bedtime reduces sleep fragmentation and improves cognitive function in physically active males with sleep complaints

PURPOSE

The primary aim of this study was to examine whether a glycine-rich collagen peptides (CP) supplement could enhance sleep quality in physically active men with self-reported sleep complaints.

METHODS

In a randomized, crossover design, 13 athletic males (age: 24 ± 4 years; training volume; 7 ± 3 h·wk1) with sleep complaints (Athens Insomnia Scale, 9 ± 2) consumed CP (15 g·day1) or a placebo control (CON) 1 h before bedtime for 7 nights. Sleep quality was measured with subjective sleep diaries and actigraphy for 7 nights; polysomnographic sleep and core temperature were recorded on night 7. Cognition, inflammation, and endocrine function were measured on night 7 and the following morning. Subjective sleepiness and fatigue were measured on all 7 nights. The intervention trials were separated by ≥ 7 days and preceded by a 7-night familiarisation trial.

RESULTS

Polysomnography showed less awakenings with CP than CON (21.3 ± 9.7 vs. 29.3 ± 13.8 counts, respectively; P = 0.028). The 7-day average for subjective awakenings were less with CP vs. CON (1.3 ± 1.5 vs. 1.9 ± 0.6 counts, respectively; P = 0.023). The proportion of correct responses on the baseline Stroop cognitive test were higher with CP than CON (1.00 ± 0.00 vs. 0.97 ± 0.05 AU, respectively; P = 0.009) the morning after night 7. There were no trial differences in core temperature, endocrine function, inflammation, subjective sleepiness, fatigue and sleep quality, or other measures of cognitive function or sleep (P > 0.05).

CONCLUSION

CP supplementation did not influence sleep quantity, latency, or efficiency, but reduced awakenings and improved cognitive function in physically active males with sleep complaints.

The effect of glycine administration on the characteristics of physiological systems in human adults: A systematic review

Functional decline of physiological systems during ageing leads to age-related diseases. Dietary glycine increases healthy lifespan in model organisms and might decrease inflammation in humans, suggesting its geroprotective potential. This review summarises the evidence of glycine administration on the characteristics of eleven physiological systems in adult humans. Databases were searched using key search terms: 'glycine', 'adult', 'supplementation'/ 'administration'/ 'ingestion'/ 'treatment'. Glycine was administered to healthy and diseased populations (18 and 34 studies) for up to 14 days and 4 months, respectively. The nervous system demonstrated the most positive effects, including improved psychiatric symptoms from longer-term glycine administration in psychiatric populations. While longer-term glycine administration improved sleep in healthy populations, these studies had small sample sizes with a high risk of bias. Larger and long-term studies with more robust study designs in healthy populations to examine the effects of glycine administration on preventing, delaying or reversing the ageing process are warranted.

Nutritional Modulation of Sleep Latency, Duration, and Efficiency: A Randomized, Repeated-Measures, Double-Blind Deception Study

PURPOSE

This study aimed to test the hypothesis that a novel nutritional blend composed of tryptophan, glycine, magnesium, tart cherry powder, and l -theanine enhances subjective and objective measures of sleep during free living conditions.

METHODS

In a randomized, repeated-measures crossover and double-blind deception design, participants ( n = 9 males and 7 females, age = 24 ± 3 yr, body mass = 69.8 ± 11.6 kg, stature = 170.8 ± 9.1 cm) completed a 3-d familiarization period, followed by 3-d intervention and placebo trials. Subjective Pittsburgh Quality Sleep Index, Core Consensus Sleep Diary, and Karolinska Sleepiness Scale survey tools, alongside objective actigraphy measures of sleep, were assessed, with daily nutritional intake, activity, and light exposure standardized between trials. Participants provided daily urine samples for assessment of targeted and untargeted metabolomes.

RESULTS

The intervention trial reduced sleep onset latency (-24 ± 25 min; P = 0.002), increased total sleep time (22 ± 32 min; P = 0.01), and increased sleep efficiency (2.4% ± 3.9%; P = 0.03), while also reducing morning sleepiness ( P = 0.02). Throughout the study, 75% of participants remained blinded to sleep assessment as a primary outcome measure, with 56% subjectively indicating improved sleep during the intervention trial. Metabolomic analysis highlighted several significantly altered metabolomes related to sleep regulation between trials, inclusive of 6-sulfatoxymelatonin, d -serine, and l -glutamic acid.

CONCLUSIONS

Data demonstrate that using the proposed blend of novel nutritional ingredients during free living conditions reduced sleep onset latency, increased total sleep duration, and increased sleep efficiency, leading to reduced perceptions of morning sleepiness. These effects may be mediated by the upregulation of key metabolites involved in the neurophysiological modulation of the sleep/wake cycle.

Development of a one-step analysis method for several amino acids using a microfluidic paper-based analytical device

A one-step analysis method was developed for four types of amino acids using a microfluidic paper-based analytical device fabricated from chromatography filtration paper and laminate films. Aminoacyl-tRNA synthetase was used to detect each amino acid. The obtained laminated paper-based analytical device (LPAD) contained four enzymatic reaction areas. Colorimetric detection was performed based on the molybdenum blue reaction. A model method for the simple, easy, and simultaneous detection of several amino acid concentrations was suggested, in contrast to the conventional methods such as HPLC or LC-MS. The method provided a selective quantification at the ranges of 3.6-100 μM for tryptophan, 10.1-100 μM for glycine, 5.9-100 μM for histidine and 5.6-100 μM for lysine with a detection limit of 1.1 μM, 3.3 μM, 1.9 μM and 1.8 μM, respectively. LPAD fabrication was considerably simple, and the subsequent detection process was easy and required a short period of time (within 15 min).

Excitation-independent and fluorescence-reversible N-GQD for picomolar detection of inhibitory neurotransmitter in milk samples ‒ an alleyway for possible neuromorphic computing application

N‒GQDs with an average size of ca. 20-30 nm are utilized for the picomolar detection of inhibitory neurotransmitters, glycine (Gly), in pH ca. 7.0. The crystalline nature, morphology, elemental composition, and chemical state of N-GQDs are investigated by XRD, FE-SEM, HR-TEM, XPS, and FT-IR techniques. The addition of Gly (100 × 10^-9 M; 0 → 1.0 mL) steadily quenches the fluorescence intensity of N-GQD (1 × 10^-6 M) at 432 nm (λ_ex 333 nm) due to inner filter effect (IFE) through the formation of ground-state complex, N-GQD•Gly. The excitation-independent N‒GQDs showed an outstanding selectivity and sensitivity towards Gly with binding constant (K_a = 8.97 × 10^-3 M^-1) and LoD (21.04 pM; S/N = 3). Time-correlated single-photon counting experiment confirms the static quenching of N-GQD (8.77 → 8.85 ns) in the presence of Gly. The interference of other amino acids on the strong binding of the N-GQD•Gly complex in H₂O is examined. Combinatorial Ex-OR and NOT gate logic circuits that could be useful in neuromorphic computing are developed based on the reversible fluorescence intensity changes of N-GQD upon the addition of Gly (Ф_F 0.54 → 0.39). The real-time application of N-GQD was investigated using commercially available relevant milk samples. Remarkably, not less than 99% cytotoxic reactivity of N-GQDs is attained against HeLa cells.

Biochemical composition of some Echinodermata (Holothuroidea, Echinoidea) from the Red Sea, Egypt

In the present study, the biochemical composition of some Echinodermata (Holothuroidea, Echinoidea) from the Red Sea, Egypt was investigated. The results showed that the highest percentage of saturated fatty acids (SFA) was in Holothuria nobilis and the lowest percentage was recorded in Holothuria scabra. The highest percentage of monounsaturated fatty acids (MUFA) was recorded in Pearsonothuria graeffei while the lowest percentage was recorded in Holothuria atra. The highest percentage of polyunsaturated fatty acids (PUFA) was recorded in Holothuria nobilis and the lowest percentage was recorded in Holothuria atra. The highest percentage of omega-3 fatty acids was recorded in Stichopus hermanni however, the lowest percentage was recorded in Diadema setosum. The highest percentage of omega-6 fatty acids was recorded in Bohadschia vitiensis where, the lowest percentage was recorded in Holothuria atra. In addition, nonessential amino acid (NEAA) glycine were the highest in all species and serine was the lowest while Essential amino acid (EAA) arginine was the highest and cysteine was the lowest. All of the NEAA recorded highest concentrations in S. hermanni except proline. The recorded essential amino acids were histidine, isoleucine, phenylalanine, and leucine. The latter was high in Pearsonothuria graeffei. Tyrosine, valine, threonine, and arginine were high in Stichopus hermanni. The present study proved that sea cucumbers has great nutritional value.

Nutritional Interventions to Improve Sleep in Team-Sport Athletes: A Narrative Review

Athletes often experience sleep disturbances and poor sleep as a consequence of extended travel, the timing of training and competition (i.e., early morning or evening), and muscle soreness. Nutrition plays a vital role in sports performance and recovery, and a variety of foods, beverages, and supplements purportedly have the capacity to improve sleep quality and quantity. Here, we review and discuss relevant studies regarding nutrition, foods, supplements, and beverages that may improve sleep quality and quantity. Our narrative review was supported by a semi-systematic approach to article searching, and specific inclusion and exclusion criteria, such that articles reviewed were relevant to athletes and sporting environments. Six databases—PubMed, Scopus, CINAHL, EMBASE, SPORTDiscus, and Google Scholar—were searched for initial studies of interest from inception to November 2020. Given the paucity of sleep nutrition research in the athlete population, we expanded our inclusion criteria to include studies that reported the outcomes of nutritional interventions to improve sleep in otherwise healthy adults. Carbohydrate ingestion to improve sleep parameters is inconclusive, although high glycemic index foods appear to have small benefits. Tart cherry juice can promote sleep quantity, herbal supplements can enhance sleep quality, while kiwifruit and protein interventions have been shown to improve both sleep quality and quantity. Nutritional interventions are an effective way to improve sleep quality and quantity, although further research is needed to determine the appropriate dose, source, and timing in relation to training, travel, and competition requirements.

Dietary glycine improves urine storage symptoms in urology outpatients

OBJECTIVES

Spinal glycinergic mechanisms inhibit the micturition reflex, and administration of glycine inhibits bladder activity in rats. Therefore, we examined whether dietary glycine would improve storage symptoms in urological outpatients.

METHODS

We enrolled 20 participants (16 men and four women) with an overactive bladder symptom score (OABSS) ≥ 3. All participants took 3 g of glucose (placebo) twice a day for the first four weeks, then 3 g of glycine twice a day for the next four weeks. We evaluated blood pressure, international prostate symptom score (IPSS), nocturia quality of life (N-QOL) score, OABSS, frequency of urination, sleep latency, time to first nighttime void, bladder pain, global self-assessment (GSA) evaluated urinary symptom improvement, and adverse events.

RESULTS

Glucose administered as a placebo improved urinary frequency, urine force on the IPSS, and five of the 13 items on the N-QOL. However, compared to the results before and after glucose administration, glycine treatment decreased the number of nocturnal voids, urgency, and total score for urine storage items on the IPSS. It also reduced blood pressure and improved IPSS-QOL. For the OABSS, improvements with glycine were noted in the number of nocturnal urinations, urinary urgency, urge incontinence, and total score. For the N-QOL, eight of 13 items, and the total score, improved. The actual number of nighttime urinations, sleep latency, latency to first nighttime urination, bladder pain, and GSA also improved. There were no adverse events.

CONCLUSIONS

Glycine might improve urine storage symptoms, cardiovascular function, pain, and sleep.

Effects of onion extract containing concentrated cysteine sulfoxides on sleep quality: a randomized, double-blind, placebo-controlled, crossover study

The objective of this randomized, double-blind, placebo-controlled, crossover study was to examine the effects of onion extract containing concentrated cysteine sulfoxides on improving sleep quality. In total, 30 healthy men and women who were dissatisfied with their sleep consumed the test food sample (onion extract tablets) for 5 days. The delta power during non-rapid eye movement sleep and the delta power per minute in the first sleep cycle increased significantly with the intake of onion extract containing concentrated cysteine sulfoxides compared with the intake of placebo. A significant decline in sleep latency was also observed. Salivary α-amylase level, a stress indicator, decreased significantly with the intake of onion extract containing concentrated cysteine sulfoxides compared with the intake of placebo. These findings indicate that onion extract containing concentrated cysteine sulfoxides alleviates stress, improves the quality of sleep and promotes smooth transition into sleep.

Improvement of Aspects of Subjective Sleep Quality of Healthy Volunteers by Ingestion of Porcine Placental Extract: A Randomized Cross-Over Pilot Study

Objectives: This study assessed the effects of oral porcine placental extract (PPE) on sleep quality of healthy volunteers not satisfied with their sleep.

Design: This study used a randomized, placebo-controlled, double-blind, cross-over clinical pilot study.

Setting: This study was conducted under an outpatient multicenter setting in Japan.

Interventions: A total of 20 healthy Japanese volunteers aged between 28 and 73, whose Pittsburgh Sleep Quality Index global scores were between 6 and 10, successfully completed the study. At first, PPE at 300 mg/kg or placebo was ingested for 2 weeks. Then, after a 2-week washout period, each group ingested under a cross-over setting the opposite sample (placebo or PPE) for another 2 weeks.

Main Outcome Measures: Objective measurement of the sleep made with an activity tracker and subjective measurements of sleep quality by use of St. Mary's Hospital Sleep Questionnaire were done just before and after the administration time slots.

Results: No effect of PPE on the sleep length was observed. Several measures in the subjective St. Mary's Hospital Sleep Questionnaire, i.e., changes in Q5 (sleep depth) and Q9 (sleep wellness) between pre- and post-ingestions, were significantly different between groups in the direction of improvement of subjective sleep quality in the PPE group.

Conclusions: Although oral PPE at 300 mg/day for 2 weeks did not affect the length of sleep itself, it significantly improved several measures of subjective sleep quality. These results suggest that PPE might be a way to improve sleep quality without hypnotic drugs.

Clinical Trial Registration:www.umin.ac.jp/ctr/, identifier: UMIN000026468.

The Future of Shift Work: Circadian Biology Meets Personalised Medicine and Behavioural Science

Shift work is commonplace in modern societies, and shift workers are predisposed to the development of numerous chronic diseases. Disruptions to the circadian systems of shift workers are considered important contributors to the biological dysfunction these people frequently experience. Because of this, understanding how to alter shift work and zeitgeber (time cue) schedules to enhance circadian system function is likely to be key to improving the health of shift workers. While light exposure is the most important zeitgeber for the central clock in the circadian system, diet and exercise are plausible zeitgebers for circadian clocks in many tissues. We know little about how different zeitgebers interact and how to tailor zeitgeber schedules to the needs of individuals; however, in this review we share some guidelines to help shift workers adapt to their work schedules based on our current understanding of circadian biology. We focus in particular on the importance of diet timing and composition. Going forward, developments in phenotyping and "envirotyping" methods may be important to understanding how to optimise shift work. Non-invasive, multimodal, comprehensive phenotyping using multiple sources of time-stamped data may yield insights that are critical to the care of shift workers. Finally, the impact of these advances will be reduced without modifications to work environments to make it easier for shift workers to engage in behaviours conducive to their health. Integrating findings from behavioural science and ergonomics may help shift workers make healthier choices, thereby amplifying the beneficial effects of improved lifestyle prescriptions for these people.

Methanol extract of Spathodea campanulata P. (Beauv.) leaves demonstrate sedative and anxiolytic like actions on swiss albino mice

Background

Spathodea campanulata P. Beauv. (Bignoniaceae) is a very common plant in Bangladesh which is locally called “Rudrapalash”. In Nigeria leaves extract of S. campanulata has a reputation of being used as an anticonvulsant. In this connection, the aim of this study was to investigate other neuropharmacological effects like sedative and anxiolytic activities of methanol extract of S. campanulata (MESC) leaves in different mice tests.

Methods

To assay sedative activity mice were subjected to open field and hole-cross test, whereas anxiolytic activity was checked by the elevated-plus maze, light-dark box, and hole-board test. For each test, mice were divided into control group (deionized water, 0.1 ml/mouse, p.o.), standard group (diazepam, 1 mg/kg, i.p) and three test groups (200, 400 and 600 mg/kg MESC, p.o.). The acute toxicity test and phytochemical screening of MESC were performed before the pharmacological study.

Results

The result demonstrated strong sedative and anxiolytic activity of MESC in a dose-dependent manner. All doses of MESC (200, 400 & 600 mg/kg) reduced the number of (square & hole) crossed by mice in both open field and hole cross tests (p < 0.001). On the other hand, in elevated plus-maze and light-dark box test mice opted to stay more in open arms and light box instead of close arms and dark box (p < 0.001). In hole-board test MESC (200, 400 & 600 mg/kg) elevated the number of head dipping (p < 0.001) dose-dependently. Phytochemical investigation indicated the presence of alkaloid, saponin, glycoside, carbohydrate, flavonoid, and tannin in MESC.

Conclusion

The experimental results explicit that S. campanulata leaves possess sedative and anxiolytic activities, hence suggest further chemical investigation to identify specific phytoconstituents responsible for sedative and anxiolytic effects.

Diet and sleep health: a scoping review of intervention studies in adults

BACKGROUND

Recent research has demonstrated an association between dietary intake and sleep health that can influence chronic disease risk factors. A scoping review of research studies investigating dietary intake and sleep was undertaken to determine the extent and scope of research in laboratory-based, free-living and mixed settings. Additionally, this review determines how well subpopulations and geographical locations are represented and the methodologies used to assess outcome measures.

METHODS

Five online databases were used to identify papers published between 1970 and 2017. Included studies were those conducted in adults and reported both outcomes of interest: (i) sleep health, including sleep restriction and sleep hygiene and (ii) dietary outcomes, including altered nutrients, dietary patterns and supplements.

RESULTS

In total, 129 publications were included with the majority being dietary interventions investigating sleep outcomes (n = 109) with fewer being sleep interventions investigating and reporting dietary outcomes (n = 20). Dietary interventions were most often carried out in free-living environments, in contrast to sleep interventions that were most often carried out in laboratory-based environments. The majority of dietary interventions investigated use of a supplement (n = 66 studies), which was predominantly caffeine (n = 49). Sleep interventions investigated sleep duration only, with the majority (n = 17) investigating the effect of partial sleep restriction under 5.5 h per night on dietary intake, while three studies investigating total sleep deprivation.

CONCLUSIONS

Investigating broader aspects of dietary such as overall diet quality and dietary patterns and other components of sleep health such as quality,  timing and sleep hygiene are important aspects for future research.

Sleep-promoting effects of threonine link amino acid metabolism in Drosophila neuron to GABAergic control of sleep drive

Emerging evidence indicates the role of amino acid metabolism in sleep regulation. Here we demonstrate sleep-promoting effects of dietary threonine (SPET) in Drosophila. Dietary threonine markedly increased daily sleep amount and decreased the latency to sleep onset in a dose-dependent manner. High levels of synaptic GABA or pharmacological activation of metabotropic GABA receptors (GABA_B-R) suppressed SPET. By contrast, synaptic blockade of GABAergic neurons or transgenic depletion of GABA_B-R in the ellipsoid body R2 neurons enhanced sleep drive non-additively with SPET. Dietary threonine reduced GABA levels, weakened metabotropic GABA responses in R2 neurons, and ameliorated memory deficits in plasticity mutants. Moreover, genetic elevation of neuronal threonine levels was sufficient for facilitating sleep onset. Taken together, these data define threonine as a physiologically relevant, sleep-promoting molecule that may intimately link neuronal metabolism of amino acids to GABAergic control of sleep drive via the neuronal substrate of sleep homeostasis.

Editorial note: This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter).

Dietary Protein and Amino Acid Intake: Links to the Maintenance of Cognitive Health

With the rapid growth in the aging population, there has been a subsequent increase in the rates of Alzheimer's disease and related dementias (ADRD). To combat these increases in ADRD, scientists and clinicians have begun to place an increased emphasis on preventative methods to ameliorate disease rates, with a primary focus area on dietary intake. Protein/amino acid intake is a burgeoning area of research as it relates to the prevention of ADRD, and consumption is directly related to a number of disease-related risk factors as such low-muscle mass, sleep, stress, depression, and anxiety. As a result, the role that protein/amino acid intake plays in affecting modifiable risk factors for cognitive decline has provided a robust area for scientific exploration; however, this research is still speculative and specific mechanisms have to be proven. The purpose of this review is to describe the current understanding of protein and amino acids and the preventative roles they play with regard to ADRD, while providing future recommendations for this body of research. Additionally, we will discuss the current recommendations for protein intake and how much protein older adults should consume in order to properly manage their long-term risk for cognitive decline.

Review: Amino acid concentration of high protein food products and an overview of the current methods used to determine protein quality

Quality of the dietary protein in foods rather than amount of dietary protein may be of greater importance from a human health and wellness standpoint. Various systems are in place to determine the value of dietary protein. Protein digestibility-corrected amino acid score (PDCAAS) and digestible indispensable amino acid score (DIAAS) are the two major protein standards used to determine the completeness of proteins by their unique concentration and digestibility of indispensable amino acids. The purpose of this review was to provide a comprehensive comparison of the amino acid concentration of high protein foods and provide the current status of the use and practicality of the PDCAAS and DIAAS system. This review builds upon previous research analyzing the total nutrient density of protein-rich foods and expands scientific research investigating the quality of proteins. In summary, the average sum of indispensable amino acids for meat and fish products is much more consistent than that of non-meat and plant-based food products. However, some non-meat products have relatively similar amounts of indispensable amino acids on a similar serving size basis. The overwhelming aspect of determining protein quality is that greater research is needed to determine protein digestibility of food products.

A Comparative Randomized Controlled Clinical Trial on the Effectiveness, Safety, and Tolerability of a Homeopathic Medicinal Product in Children with Sleep Disorders and Restlessness

A prospective, multicenter, randomized, open-label, controlled clinical trial was performed to evaluate the effectiveness and safety of the homeopathic product ZinCyp-3-02 in children with sleep disorders for ≥ one month compared to glycine. Children ≤ six years old received either ZinCyp-3-02 (N = 89) or comparator glycine (N = 90). After treatment for 28 days, total sleep-disorder-associated complaints severity scores decreased in both groups from median 7.0 (out of maximum 11.0) points to 2.0 (ZinCyp-3-02) and 4.0 (glycine) points, respectively, with overall higher odds of showing improvement for ZinCyp-3-02 (odds ratio: 4.45 (95% CI: 2.77-7.14), p < 0.0001, POM overall treatment related effect). Absence of individual complaints (time to sleep onset, difficulties maintaining sleep, sleep duration, troubled sleep (somniloquism), physical inactivity after awakening, restlessness for unknown reason, and sleep disorders frequency) at study end were significantly higher with ZinCyp-3-02 (all p values < 0.05). More children with ZinCyp-3-02 were totally free of complaints (p = 0.0258). Treatment effectiveness (p < 0.0001) and satisfaction assessments (p < 0.0001) were more favorable for ZinCyp-3-02. Few nonserious adverse drug reactions were reported (ZinCyp-3-02: N = 2, glycine: N = 1) and both treatments were well tolerated. Treatment with the homeopathic product ZinCyp-3-02 was found to be safe and superior to the comparator glycine in the treatment of sleep disorders in children.

New Functions and Potential Applications of Amino Acids

Currently, several types of amino acids are being produced and used worldwide. Nevertheless, several new functions of amino acids have been recently discovered that could result in other applications. For example, oral stimulation by glutamate triggers the cephalic phase response to prepare for food digestion. Further, the stomach and intestines have specific glutamate-recognizing systems in their epithelial mucosa. Regarding clinical applications, addition of monosodium glutamate to the medicinal diet has been shown to markedly enhance gastric secretion in a vagus-dependent manner. Branched-chain amino acids (BCAAs) are the major components of muscles, and ingestion of BCAAs has been found to be effective for decreasing muscle pain. BCAAs are expected to be a solution for the serious issue of aging. Further, ingestion of specific amino acids could be beneficial. Glycine can be ingested for good night's sleep: glycine ingestion before bedtime significantly improved subjective sleep quality. Ingestion of alanine and glutamine effectively accelerates alcohol metabolism, and ingestion of cystine and theanine effectively prevents colds. Finally, amino acids could be used in a novel clinical diagnostic method: the balance of amino acids in the blood could be an indicator of the risk of diseases such as cancer. These newly discovered functions of amino acids are expected to contribute to the resolution of various issues.

Investigation of sedative and hypnotic effects of Amygdalus communis L. extract: behavioral assessments and EEG studies on rat

Amygdalus communis L. (almond) has been traditionally used as a natural medicine in the treatment of various diseases. The present research studied the sedative and hypnotic effects of the aqueous fraction of seeds of almond in rats. In order to investigate these effects, a combination of behavioral methods (open field test and loss of righting reflex test) as well as quantitative and analytic methods (EEG and EMG) were applied. The results of the open field test showed that a dose of 400 mg/kg of the almond extract significantly inhibited the locomotion activity of rats compared to normal. The results also illustrated that the almond extract affected pentobarbital-induced sleep through increasing the number of fallings asleep and prolongation of sleeping time. Analysis of EEG recordings of the animals which had received the same dose of the almond extract as the open field test demonstrated marked changes in the animals' sleep architecture. Significant prolongation of total sleeping time as well as significant increase in NREM sleep were the main observed changes compared to the normal condition. These results suggest that the aqueous extract of almond has significant sedative and hypnotic effects, which may support its therapeutic use for insomnia.

The sleep-promoting and hypothermic effects of glycine are mediated by NMDA receptors in the suprachiasmatic nucleus

The use of glycine as a therapeutic option for improving sleep quality is a novel and safe approach. However, despite clinical evidence of its efficacy, the details of its mechanism remain poorly understood. In this study, we investigated the site of action and sleep-promoting mechanisms of glycine in rats. In acute sleep disturbance, oral administration of glycine-induced non-rapid eye movement (REM) sleep and shortened NREM sleep latency with a simultaneous decrease in core temperature. Oral and intracerebroventricular injection of glycine elevated cutaneous blood flow (CBF) at the plantar surface in a dose-dependent manner, resulting in heat loss. Pretreatment with N-methyl-D-aspartate (NMDA) receptor antagonists AP5 and CGP78608 but not the glycine receptor antagonist strychnine inhibited the CBF increase caused by glycine injection into the brain. Induction of c-Fos expression was observed in the hypothalamic nuclei, including the medial preoptic area (MPO) and the suprachiasmatic nucleus (SCN) shell after glycine administration. Bilateral microinjection of glycine into the SCN elevated CBF in a dose-dependent manner, whereas no effect was observed when glycine was injected into the MPO and dorsal subparaventricular zone. In addition, microinjection of D-serine into the SCN also increased CBF, whereas these effects were blocked in the presence of L-701324. SCN ablation completely abolished the sleep-promoting and hypothermic effects of glycine. These data suggest that exogenous glycine promotes sleep via peripheral vasodilatation through the activation of NMDA receptors in the SCN shell.

Sleep in elite athletes and nutritional interventions to enhance sleep

Sleep has numerous important physiological and cognitive functions that may be particularly important to elite athletes. Recent evidence, as well as anecdotal information, suggests that athletes may experience a reduced quality and/or quantity of sleep. Sleep deprivation can have significant effects on athletic performance, especially submaximal, prolonged exercise. Compromised sleep may also influence learning, memory, cognition, pain perception, immunity and inflammation. Furthermore, changes in glucose metabolism and neuroendocrine function as a result of chronic, partial sleep deprivation may result in alterations in carbohydrate metabolism, appetite, food intake and protein synthesis. These factors can ultimately have a negative influence on an athlete’s nutritional, metabolic and endocrine status and hence potentially reduce athletic performance. Research has identified a number of neurotransmitters associated with the sleep–wake cycle. These include serotonin, gamma-aminobutyric acid, orexin, melanin-concentrating hormone, cholinergic, galanin, noradrenaline, and histamine. Therefore, nutritional interventions that may act on these neurotransmitters in the brain may also influence sleep. Carbohydrate, tryptophan, valerian, melatonin and other nutritional interventions have been investigated as possible sleep inducers and represent promising potential interventions. In this review, the factors influencing sleep quality and quantity in athletic populations are examined and the potential impact of nutritional interventions is considered. While there is some research investigating the effects of nutritional interventions on sleep, future research may highlight the importance of nutritional and dietary interventions to enhance sleep.

Effects of L-serine ingestion on human sleep

To investigate the effects of L-serine intake on human sleep, we conducted two randomized double-blinded crossover studies. In Study 1, healthy subjects who were dissatisfied with their sleep were given L-serine or a placebo 30 min before going to bed. After waking the next morning, subjective sleep quality was rated using the Ogri-Shirakawa-Azumi subjective sleep rating scale. In Study 2, subjective sleep quality was rated using the St. Mary's Hospital sleep questionnaire, and objective parameters, including sleep initiation time, number of nighttime awakenings, and hours of sleep, were evaluated using actigraphy. In Study 1, factors related to "sleep initiation" and "sleep maintenance" during the L-serine intake period were significantly improved compared to the placebo intake period (p = 0.02 and p = 0.008, respectively). In Study 2, scores for "How well did you sleep last night?" and "How satisfied were you with last night's sleep?" were significantly better during L-serine intake compared to placebo (p = 0.04 and p = 0.03, respectively). Subjective evaluation of sleep quality on waking was thus improved. In addition, objective evaluation using actigraphy showed that the "number of nighttime awakenings" tended to be decreased (p = 0.08). These findings suggest that intake of L-serine before going to bed may improve human sleep.

The glycine deportation system and its pharmacological consequences

The glycine deportation system is an essential component of glycine catabolism in man whereby 400 to 800mg glycine per day are deported into urine as hippuric acid. The molecular escort for this deportation is benzoic acid, which derives from the diet and from gut microbiota metabolism of dietary precursors. Three components of this system, involving hepatic and renal metabolism, and renal active tubular secretion help regulate systemic and central nervous system levels of glycine. When glycine levels are pathologically high, as in congenital nonketotic hyperglycinemia, the glycine deportation system can be upregulated with pharmacological doses of benzoic acid to assist in normalization of glycine homeostasis. In congenital urea cycle enzymopathies, similar activation of the glycine deportation system with benzoic acid is useful for the excretion of excess nitrogen in the form of glycine. Drugs which can substitute for benzoic acid as substrates for the glycine deportation system have adverse reactions that may involve perturbations of glycine homeostasis. The cancer chemotherapeutic agent ifosfamide has an unacceptably high incidence of encephalopathy. This would appear to arise as a result of the production of toxic aldehyde metabolites which deplete ATP production and sequester NADH in the mitochondrial matrix, thereby inhibiting the glycine deportation system and causing de novo glycine synthesis by the glycine cleavage system. We hypothesize that this would result in hyperglycinemia and encephalopathy. This understanding may lead to novel prophylactic strategies for ifosfamide encephalopathy. Thus, the glycine deportation system plays multiple key roles in physiological and neurotoxicological processes involving glycine.

New therapeutic strategy for amino acid medicine: glycine improves the quality of sleep

Glycine is a non-essential amino acid that has indispensable roles in both excitatory and inhibitory neurotransmission via N-methyl-D-aspartate type glutamate receptors and glycine receptors, respectively. We recently reported that glycine ingestion before bedtime significantly ameliorated subjective sleep quality in individuals with insomniac tendencies. Oral administration of glycine to rats was found to induce a significant increase in the plasma and cerebrospinal fluid glycine concentrations and a significant decrease in the core body temperature associated with an increase in cutaneous blood flow. The decline in the core body temperature might be a mechanism underlying glycine's effect on sleep, as the onset of sleep is known to involve a decrease in the core body temperature. Moreover, a low core body temperature is maintained during sleep in humans. Pharmacological studies investigating the mechanisms of glycine on sleep were also performed. In this review, we will describe both our recent findings regarding how and where orally administered glycine acts and findings from our rat study and human trials.

Orexin neurons receive glycinergic innervations

Glycine, a nonessential amino-acid that acts as an inhibitory neurotransmitter in the central nervous system, is currently used as a dietary supplement to improve the quality of sleep, but its mechanism of action is poorly understood. We confirmed the effects of glycine on sleep/wakefulness behavior in mice when administered peripherally. Glycine administration increased non-rapid eye movement (NREM) sleep time and decreased the amount and mean episode duration of wakefulness when administered in the dark period. Since peripheral administration of glycine induced fragmentation of sleep/wakefulness states, which is a characteristic of orexin deficiency, we examined the effects of glycine on orexin neurons. The number of Fos-positive orexin neurons markedly decreased after intraperitoneal administration of glycine to mice. To examine whether glycine acts directly on orexin neurons, we examined the effects of glycine on orexin neurons by patch-clamp electrophysiology. Glycine directly induced hyperpolarization and cessation of firing of orexin neurons. These responses were inhibited by a specific glycine receptor antagonist, strychnine. Triple-labeling immunofluorescent analysis showed close apposition of glycine transporter 2 (GlyT2)-immunoreactive glycinergic fibers onto orexin-immunoreactive neurons. Immunoelectron microscopic analysis revealed that GlyT2-immunoreactive terminals made symmetrical synaptic contacts with somata and dendrites of orexin neurons. Double-labeling immunoelectron microscopy demonstrated that glycine receptor alpha subunits were localized in the postsynaptic membrane of symmetrical inhibitory synapses on orexin neurons. Considering the importance of glycinergic regulation during REM sleep, our observations suggest that glycine injection might affect the activity of orexin neurons, and that glycinergic inhibition of orexin neurons might play a role in physiological sleep regulation.

Pharmacokinetics and cerebral distribution of glycine administered to rats

High doses of glycine have been reported to improve negative schizophrenic symptoms, suggesting that ingested glycine activates glutamatergic transmission via N-methyl-D-aspartate (NMDA) receptors. However, the pharmacokinetics of administered glycine in the brain has not been evaluated. In the present study, the time- and dose-dependent distributions of administered glycine were investigated from a pharmacokinetic viewpoint. Whole-body autoradiography of radiolabeled glycine was performed, and time-concentration curves for glycine and serine in plasma, cerebrospinal fluid (CSF), and brain tissues were obtained. Furthermore, pharmacokinetic parameters were calculated. For a more detailed analysis, the amount of glycine uptake in the brain was evaluated using the brain uptake index method. Radiolabeled glycine was distributed among periventricular organs in the brain. Oral administration of 2 g/kg of glycine significantly elevated the CSF glycine concentration above the ED50 value for NMDA receptors. The glycine levels in CSF were 100 times lower than those in plasma. Glycine levels were elevated in brain tissue, but with a slower time-course than in CSF. Serine, a major metabolite of glycine, was elevated in plasma, CSF, and brain tissue. Glycine uptake in brain tissue increased in a dose-dependent manner. Time-concentration curves revealed that glycine was most likely transported via the blood-CSF barrier and activated NMDA receptors adjacent to the ventricles. The pharmacokinetic analysis and the brain uptake index for glycine suggested that glycine was transported into brain tissue by passive diffusion. These results provide further insight into the potential therapeutic applications of glycine.

Sleep health and asynchronization

Recent surveys in Japan reported that more than half of children interviewed complained of daytime sleepiness, approximately one quarter reported insomnia, and some complained of both nocturnal insomnia and daytime sleepiness. To explain the pathophysiology of this type of sleep disturbance, a novel clinical concept of asynchronization has been proposed. Asynchronization involves disturbances in various aspects of biological rhythms that normally exhibit circadian oscillations. The putative major triggers for asynchronization include a combination of nighttime light exposure, which can disturb the biological clock and decrease melatonin secretion, and a lack of morning light exposure, which can prohibit normal synchronization of the biological clock to a 24-h cycle and decrease activity in the serotonergic system. The early phase of asynchronization may be caused by inadequate sleep hygiene, is likely to be functional, and to be relatively easily resolved by establishing a regular sleep-wakefulness cycle. However, without adequate intervention, these disturbances may gradually worsen, resulting into the chronic phase. No single symptom appears to be specific for the clinical phases, and the chronic phase is defined in terms of the response to interventions. The factors causing the transition from the early to chronic phase of asynchronization and those producing the difficulties of recovering patients with the chronic phase of asynchronization are currently unclear.

Oral administration of glycine increases extracellular serotonin but not dopamine in the prefrontal cortex of rats

AIM

Glycine, one of the non-essential amino acids, has been reported to be effective in reducing negative symptoms of schizophrenia. Recently, we found that glycine improves subjective sleep quality in humans. The aim of this study was to investigate the effects of oral glycine administration on endogenous 5-hydroxytryptamine (5-HT) and dopamine in the prefrontal cortex (PFC) of living rats.

METHODS

Microdialysis probes were inserted stereotaxically into the rat prefrontal cortex. Cortical levels of 5-HT and dopamine were measured following oral administration of 1 or 2 g/kg glycine, 2 g/kg d-serine, or 2 g/kg L-serine.

RESULTS

Both glycine and d-serine significantly increased extracellular 5-HT levels for 10 min, whereas dopamine levels remained unchanged. L-serine, in contrast, had no significant effects on 5-HT levels.

CONCLUSIONS

It is possible that the increase in 5-HT in response to glycine and d-serine was mediated by N-methyl-D-aspartate receptors. The transient increase in 5-HT in the PFC might be associated with the alleviation of negative symptoms in patients with schizophrenia and the amelioration of sleep quality in patients with insomnia.