Glycine and N-acetylcysteine (GlyNAC) supplementation in older adults improves glutathione deficiency, oxidative stress, mitochondrial dysfunction, inflammation, insulin resistance, endothelial dysfunction, genotoxicity, muscle strength, and cognition: Results of a pilot clinical trial.

BACKGROUND: Oxidative stress (OxS) and mitochondrial dysfunction are implicated as causative factors for aging. Older adults (OAs) have an increased prevalence of elevated OxS, impaired mitochondrial fuel-oxidation (MFO), elevated inflammation, endothelial dysfunction, insulin resistance, cognitive decline, muscle weakness, and sarcopenia, but contributing mechanisms are unknown, and interventions are limited/lacking. We previously reported that inducing deficiency of the antioxidant tripeptide glutathione (GSH) in young mice results in mitochondrial dysfunction, and that supplementing GlyNAC (combination of glycine and N-acetylcysteine [NAC]) in aged mice improves naturally-occurring GSH deficiency, mitochondrial impairment, OxS, and insulin resistance. This pilot trial in OA was conducted to test the effect of GlyNAC supplementation and withdrawal on intracellular GSH concentrations, OxS, MFO, inflammation, endothelial function, genotoxicity, muscle and glucose metabolism, body composition, strength, and cognition. METHODS: A 36-week open-label clinical trial was conducted in eight OAs and eight young adults (YAs). After all the participants underwent an initial (pre-supplementation) study, the YAs were released from the study. OAs were studied again after GlyNAC supplementation for 24 weeks, and GlyNAC withdrawal for 12 weeks. Measurements included red-blood cell (RBC) GSH, MFO; plasma biomarkers of OxS, inflammation, endothelial function, glucose, and insulin; gait-speed, grip-strength, 6-min walk test; cognitive tests; genomic-damage; glucose-production and muscle-protein breakdown rates; and body-composition. RESULTS: GlyNAC supplementation for 24 weeks in OA corrected RBC-GSH deficiency, OxS, and mitochondrial dysfunction; and improved inflammation, endothelial dysfunction, insulin-resistance, genomic-damage, cognition, strength, gait-speed, and exercise capacity; and lowered body-fat and waist-circumference. However, benefits declined after stopping GlyNAC supplementation for 12 weeks. CONCLUSIONS: GlyNAC supplementation for 24-weeks in OA was well tolerated and lowered OxS, corrected intracellular GSH deficiency and mitochondrial dysfunction, decreased inflammation, insulin-resistance and endothelial dysfunction, and genomic-damage, and improved strength, gait-speed, cognition, and body composition. Supplementing GlyNAC in aging humans could be a simple and viable method to promote health and warrants additional investigation.

Pharmacological disinhibition enhances paced breathing following complete spinal cord injury in rats.

Respiratory dysfunction is one of the most devastating and life-threatening deficits that occurs following cervical spinal cord injury (SCI). Assisted breathing with mechanical ventilators is a necessary part of care for many cervical injured individuals, but it is also associated with increased risk of secondary complications such as infection, muscle atrophy and maladaptive plasticity. Pre-clinical studies with epidural stimulation (EDS) have identified it as an alternative/additional method to support adequate lung ventilation without mechanical assistance. The full potential of EDS, however, may be limited by spinal inhibitory mechanisms within the injured spinal cord. The goal of the present work is to assess the potential improvement for EDS in combination with pharmacological disinhibition of spinal circuits following complete high cervical SCI. All experiments were performed in decerebrate, unanesthetized, non-paralyzed (n = 13) and paralyzed (n = 8) adult Sprague-Dawley rats 6 h following a complete C1 transection. The combination of high-frequency EDS (HF-EDS) at the C4 spinal segment with intrathecal delivery of GABA and glycine receptors antagonists (GABAzine and strychnine, respectively) resulted in significantly increased phrenic motor output, tidal volume and amplitude of diaphragm electrical activity compared to HF-EDS alone. Thus, it appears that spinal fast inhibitory mechanisms limit phrenic motor output and present a new neuropharmacological target to improve paced breathing in individuals with cervical SCI.

Glycine Enhances Satellite Cell Proliferation, Cell Transplantation, and Oligonucleotide Efficacy in Dystrophic Muscle.

The need to distribute therapy evenly systemically throughout the large muscle volume within the body makes Duchenne muscular dystrophy (DMD) therapy a challenge. Cell and exon-skipping therapies are promising but have limited effects, and thus enhancing their therapeutic potency is of paramount importance to increase the accessibility of these therapies to DMD patients. In this study, we demonstrate that co-administered glycine improves phosphorodiamidate morpholino oligomer (PMO) potency in mdx mice with marked functional improvement and an up to 50-fold increase of dystrophin in abdominal muscles compared to PMO in saline. Glycine boosts satellite cell proliferation and muscle regeneration by increasing activation of mammalian target of rapamycin complex 1 (mTORC1) and replenishing the one-carbon unit pool. The expanded regenerating myofiber population then results in increased PMO uptake. Glycine also augments the transplantation efficiency of exogenous satellite cells and primary myoblasts in mdx mice. Our data provide evidence that glycine enhances satellite cell proliferation, cell transplantation, and oligonucleotide efficacy in mdx mice, and thus it has therapeutic utility for cell therapy and drug delivery in muscle-wasting diseases.

Combined Supplementation with Glycine and Tryptophan Reduces Purine-Induced Serum Uric Acid Elevation by Accelerating Urinary Uric Acid Excretion: A Randomized, Single-Blind, Placebo-Controlled, Crossover Study.

The authors previously confirmed the serum uric acid-lowering effects of the combination of glycine and tryptophan in subjects with mild hyperuricemia. This study examined whether combined supplementation with glycine and tryptophan suppressed the elevation in serum uric acid levels caused by purine ingestion and accelerated urinary uric acid excretion in subjects with lower urate excretion using a randomized, single-blind, placebo-controlled, crossover clinical trial design. Healthy Japanese adult males with lower urate excretion ingested water containing purines in addition to dextrin (placebo), tryptophan, glycine, or a glycine and tryptophan mixture. The combined supplementation with glycine and tryptophan significantly reduced the elevated serum uric acid levels after purine ingestion. Glycine alone and in combination with tryptophan significantly increased urinary uric acid excretion and urate clearance compared with the effects of the placebo. Urinary pH increased by the ingestion of the mixture. These results suggested that the improved water solubility of uric acid due to increased urinary pH contributed to the increase of urinary uric acid excretion.

Glycine administration attenuates progression of dystrophic pathology in prednisolone-treated dystrophin/utrophin null mice.

Duchenne muscular dystrophy (DMD) is an X-linked genetic disease characterized by progressive muscle wasting and weakness and premature death. Glucocorticoids (e.g. prednisolone) remain the only drugs with a favorable impact on DMD patients, but not without side effects. We have demonstrated that glycine preserves muscle in various wasting models. Since glycine effectively suppresses the activity of pro-inflammatory macrophages, we investigated the potential of glycine treatment to ameliorate the dystrophic pathology. Dystrophic mdx and dystrophin-utrophin null (dko) mice were treated with glycine or L-alanine (amino acid control) for up to 15 weeks and voluntary running distance (a quality of life marker and strong correlate of lifespan in dko mice) and muscle morphology were assessed. Glycine increased voluntary running distance in mdx mice by 90% (P < 0.05) after 2 weeks and by 60% (P < 0.01) in dko mice co-treated with prednisolone over an 8 week treatment period. Glycine treatment attenuated fibrotic deposition in the diaphragm by 28% (P < 0.05) after 10 weeks in mdx mice and by 22% (P < 0.02) after 14 weeks in dko mice. Glycine treatment augmented the prednisolone-induced reduction in fibrosis in diaphragm muscles of dko mice (23%, P < 0.05) after 8 weeks. Our findings provide strong evidence that glycine supplementation may be a safe, simple and effective adjuvant for improving the efficacy of prednisolone treatment and improving the quality of life for DMD patients.

Targeted Treatment of Individuals With Psychosis Carrying a Copy Number Variant Containing a Genomic Triplication of the Glycine Decarboxylase Gene.

BACKGROUND: The increased mutational burden for rare structural genomic variants in schizophrenia and other neurodevelopmental disorders has so far not yielded therapies targeting the biological effects of specific mutations. We identified two carriers (mother and son) of a triplication of the gene encoding glycine decarboxylase, GLDC, presumably resulting in reduced availability of the N-methyl-D-aspartate receptor coagonists glycine and D-serine and N-methyl-D-aspartate receptor hypofunction. Both carriers had a diagnosis of a psychotic disorder. METHODS: We carried out two double-blind, placebo-controlled clinical trials of N-methyl-D-aspartate receptor augmentation of psychotropic drug treatment in these two individuals. Glycine was used in the first clinical trial, and D-cycloserine was used in the second one. RESULTS: Glycine or D-cycloserine augmentation of psychotropic drug treatment each improved psychotic and mood symptoms in placebo-controlled trials. CONCLUSIONS: These results provide two independent proof-of-principle demonstrations of symptom relief by targeting a specific genotype and explicitly link an individual mutation to the pathophysiology of psychosis and treatment response.

[Efficacy of subgingival glycine air polishing on patients with early peri-implant diseases].

Objective: To compare the clinical efficacies of subgingival glycine air polishing and ultrasonic scaling combined with 0.12% chlorhexidine rinsing on patients with early peri-implant diseases (peri-implant mucositis and early peri-implantitis). Methods: Twenty-two systemically healthy patients with totally 42 implants and early peri-implant diseases, were recruited in this study. The patients were randomly divided into the test group and the control group. Patients in the test group were treated with subgingival glycine air polishing and patients in the control group were treated with ultrasonic scalers combined with 0.12% chlorhexidine rinsing. Periodontal parameters such as probing depth, bleeding index, plaque index and clinical attachment loss, at baseline and 2 months after treatment, respectively, were collected and compared between the test and control groups. Results: For the natural teeth, the parameters of probing depth, bleeding index, plaque index and attachment loss in the two groups were significantly improved after treatments (medians were 0.48 mm vs 0.22 mm, 1.00 vs-0.13, 0.38 vs 0.50, 0.48 mm vs 0.22 mm, respectively for test and control group). There was no statistical difference of median between the two groups after treatment except for that of the attachment loss (medians, 0.48 mm vs 0.22 mm, P=0.034). For the implants, differences of parameters in the two groups at baseline were insignificant. After treatments, the probing depths significantly decreased by 0.67 mm and 0.33 mm in the test group and the control group, respectively. The inter-group differences, however, were insignificant. Significant difference of the bleeding index after treatment was found in the test group (P=0.019), but not in the control group. No adverse reactions were found on patients in the two groups after treatments. Conclusions: Efficacy of subgingival glycine air polishing and ultrasonic scaling combined with 0.12% chlorhexidine rinsing is competitive on patients with early peri-implant diseases. However, the former treatment may be more effective oncontrolling the early peri-implant inflammation.

Association of schizophrenia onset age and white matter integrity with treatment effect of D-cycloserine: a randomized placebo-controlled double-blind crossover study.

BACKGROUND: It has been reported that drugs which promote the N-Methyl-D-aspartate-type glutamate receptor function by stimulating the glycine modulatory site in the receptor improve negative symptoms and cognitive dysfunction in schizophrenia patients being treated with antipsychotic drugs. METHODS: We performed a placebo-controlled double-blind crossover study involving 41 schizophrenia patients in which D-cycloserine 50 mg/day was added-on, and the influence of the onset age and association with white matter integrity on MR diffusion tensor imaging were investigated for the first time. The patients were evaluated using the Positive and Negative Syndrome Scale (PANSS), Scale for the Assessment of Negative Symptoms (SANS), Brief Assessment of Cognition in Schizophrenia (BACS), and other scales. RESULTS: D-cycloserine did not improve positive or negative symptoms or cognitive dysfunction in schizophrenia. The investigation in consideration of the onset age suggests that D-cycloserine may aggravate negative symptoms of early-onset schizophrenia. The better treatment effect of D-cycloserine on BACS was observed when the white matter integrity of the sagittal stratum/ cingulum/fornix stria terminalis/genu of corpus callosum/external capsule was higher, and the better treatment effect on PANSS general psychopathology (PANSS-G) was observed when the white matter integrity of the splenium of corpus callosum was higher. In contrast, the better treatment effect of D-cycloserine on PANSS-G and SANS-IV were observed when the white matter integrity of the posterior thalamic radiation (left) was lower. CONCLUSION: It was suggested that response to D-cycloserine is influenced by the onset age and white matter integrity. TRIAL REGISTRATION: UMIN Clinical Trials Registry (number UMIN000000468 ). Registered 18 August 2006.

Glycinergic inhibition of BAT sympathetic premotor neurons in rostral raphe pallidus.

The rostral raphe pallidus (rRPa) contains sympathetic premotor neurons controlling thermogenesis in brown adipose tissue (BAT). We sought to determine whether a tonic activation of glycineA receptors (GlyAR) in the rRPa contributes to the inhibitory regulation of BAT sympathetic nerve activity (SNA) and of cardiovascular parameters in anesthetized rats. Nanoinjection of the GlyAR antagonist, strychnine (STR), into the rRPa of intact rats increased BAT SNA (peak: +495%), BAT temperature (TBAT, +1.1°C), expired CO2, (+0.4%), core body temperature (TCORE, +0.2°C), mean arterial pressure (MAP, +4 mmHg), and heart rate (HR, +57 beats/min). STR into rRPa in rats with a postdorsomedial hypothalamus transection produced similar increases in BAT thermogenic and cardiovascular parameters. Glycine nanoinjection into the rRPa evoked a potent inhibition of the cooling-evoked increases in BAT SNA (nadir: -74%), TBAT (-0.2°C), TCORE (-0.2°C), expired CO2 (-0.2%), MAP (-8 mmHg), and HR (-22 beats/min) but had no effect on the increases in these variables evoked by STR nanoinjection into rRPa. Nanoinjection of GABA into the rRPa inhibited the STR-evoked BAT SNA (nadir: -86%) and reduced the expired CO2 (-0.4%). Blockade of glutamate receptors in rRPa reduced the STR-evoked increases in BAT SNA (nadir: -61%), TBAT (-0.5°C), expired CO2 (-0.3%), MAP (-9 mmHg), and HR (-33 beats/min). We conclude that a tonically active glycinergic input to the rRPa contributes to the inhibitory regulation of the discharge of BAT sympathetic premotor neurons and of BAT thermogenesis and energy expenditure.

POSTOPERATIVE COMPLICATIONS WITH GLYCINE AND STERILE DISTILLED WATER AFTER TRANSURETHRAL RESECTION OF PROSTATE.

BACKGROUND: Transurethral resection of prostate (TURP) is considered the gold standard for the surgical treatment of BPH. Irrigant fluid absorption by the patient is a potentially serious complication of TURP and can lead to dilutional hyponatremia and TURP syndrome. Other common complications of TURP include urinary tract infection and secondary haemorrhage. The objective of this study was to compare the frequency of postoperative complications (Urinary Tract infection and dilutional hyponatremia) between 1.5% glycine and sterile distilled water used as irrigant in BPH patients after TURP. METHODS: This randomized controlled trial was conducted in department of Urology, PIMS Islamabad, from August 2013 to February 2014. A total of 170 adult male patients between 50-80 years of age undergoing TURP with prostate volume more than 30cc on ultrasound. 85 patients each were randomly allocated to two groups. In group-A, glycine was used as irrigan,t solution during TURP while in group-B distilled water was used. Serum sodium levels were measured at 6th postoperative hour to look for dilutional hyponatremia. On the 15th postoperative day they were inquired about any clinical features of urinary tract infection. Also urine routine examination was performed to look for the presence of WBCs in the urine. RESULTS: Post-operative dilutional hyponatremia was observed in 13 (15.3%) patients in Group A and in 10 (11.8%) patients in group-B. The difference between both the groups being nonsignificant (p-value=0.501).Frequency of postoperative urinary tract infection on 15th postoperative day in group-A was 23(27.1%) while in group-B it was 16 (18.8%), the difference among both the groups being insignificant (p-value=0.202). CONCLUSION: Although the frequency of postoperative complications like UTI and dilutional hyponatremia was less with sterile distilled water, yet, the difference was statistically not significant.

Fluid volume kinetics of dilutional hyponatremia; a shock syndrome revisited.

OBJECTIVE: To evaluate whether the pathophysiology of shock syndromes can be better understood by comparing central hemodynamics with kinetic data on fluid and electrolyte shifts. METHODS: We studied the dilutional hyponatremic shock that developed in response to overhydration with electrolyte-free irrigating fluid - the so-called 'transurethral resection syndrome' - by comparing cardiac output, arterial pressures, and volume kinetic parameters in 17 pigs that were administered 150 ml/kg of either 1.5% glycine or 5% mannitol by intravenous infusion over 90 minutes. RESULTS: Natriuresis appeared to be the key factor promoting hypovolemic hypotension 15-20 minutes after fluid administration ended. Excessive sodium excretion, due to osmotic diuresis caused by the irrigant solutes, was associated with high estimates of the elimination rate constant (k10) and low or negative estimates of the rate constant describing re-distribution of fluid to the plasma after translocation to the interstitium (k21). These characteristics indicated a high urinary flow rate and the development of peripheral edema at the expense of plasma volume and were correlated with reductions in cardiac output. The same general effects of natriuresis were observed for both irrigating solutions, although the volume of infused 1.5% glycine had a higher tendency to enter the intracellular fluid space. CONCLUSION: Comparisons between hemodynamics and fluid turnover showed a likely sequence of events that led to hypovolemia despite intravenous administration of large amounts of fluid.

Fluid volume kinetics of dilutional hyponatremia; a shock syndrome revisited

OBJECTIVE: To evaluate whether the pathophysiology of shock syndromes can be better understood by comparing central hemodynamics with kinetic data on fluid and electrolyte shifts. METHODS: We studied the dilutional hyponatremic shock that developed in response to overhydration with electrolyte-free irrigating fluid - the so-called ‘transurethral resection syndrome' - by comparing cardiac output, arterial pressures, and volume kinetic parameters in 17 pigs that were administered 150 ml/kg of either 1.5% glycine or 5% mannitol by intravenous infusion over 90 minutes. RESULTS: Natriuresis appeared to be the key factor promoting hypovolemic hypotension 15-20 minutes after fluid administration ended. Excessive sodium excretion, due to osmotic diuresis caused by the irrigant solutes, was associated with high estimates of the elimination rate constant (k10) and low or negative estimates of the rate constant describing re-distribution of fluid to the plasma after translocation to the interstitium (k21). These characteristics indicated a high urinary flow rate and the development of peripheral edema at the expense of plasma volume and were correlated with reductions in cardiac output. The same general effects of natriuresis were observed for both irrigating solutions, although the volume of infused 1.5% glycine had a higher tendency to enter the intracellular fluid space. CONCLUSION: Comparisons between hemodynamics and fluid turnover showed a likely sequence of events that led to hypovolemia despite intravenous administration of large amounts of fluid. .

Evaluation of a novel mouse model of intracisternal strychnine-induced trigeminal allodynia.

PURPOSE: Intractable neuropathic dynamic allodynia remains one of the major symptoms of human trigeminal neuropathy and is commonly accepted to be the most excruciatingly painful condition known to humankind. At present, a validated animal model of this disorder is necessary for efficient and effective development of novel drug treatments. Intracisternal strychnine in rats has been shown to result in localized trigeminal dynamic allodynia, thus representing a possible model of trigeminal neuralgia. The purpose of this study was to validate a mouse model of trigeminal glycinergic inhibitory dysfunction using established positive (carbamazepine epoxide) and negative (morphine) controls. METHODS: The actions of conventional first-line treatment (carbamazepine epoxide [CBZe]) and clinically ineffective morphine were tested for trigeminal dynamic mechanical allodynia produced by intracisternal strychnine. In mice under halothane anesthesia, we injected either strychnine (0.3 µg), strychnine with CBZe (4 ng), or artificial cerebrospinal fluid (aCSF) intracisternally (i.c.). In a separate set of experiments, subcutaneous morphine (3 mg·kg(-1) sc) was injected with intracisternal strychnine. Dynamic mechanical allodynia was induced by stroking the fur with polyethylene (PE-10) tubing. The response of each mouse was rated to determine its allodynia score, and scores of each group were compared. In addition, in a separate dichotomous disequilibrium study, pairs of mice were injected with strychnine/saline, strychnine/strychnine-CBZe, or strychnine/strychnine-morphine. A blinded observer recorded which mouse of each pair had the greater global pain behaviour. RESULTS: Strychnine (i.c.) produced higher quantitative allodynia scores in the trigeminal distribution (mean 81.5%; 95% confidence interval [CI] 76.4 to 86.6) vs the aCSF group (mean 11.3%; 95% CI 8.1 to 14.4) (P < 0.0001). Carbamazepine epoxide (i.c.) completely abolished allodynia when co-injected with strychnine (mean 83.2%; 95% CI 78.1 to 88.4) vs strychnine alone (mean 3.2%; 95% CI -0.9 to 7.2) (P < 0.0001). Morphine co-injected with strychnine did not result in reduced allodynia (mean 65.7%; 95% CI 42.0 to 89.4) compared with strychnine alone (mean 87.6%; 95% CI 77.6 to 97.6) (P = 0.16). In a further global allodynia assessment, strychnine (i.c.) produced greater allodynia than both aCSF and strychnine administered with CBZe (P = 0.03). Morphine (ip) administered with strychnine did not result in reduced global allodynia compared with strychnine administered alone (P = 1.0). CONCLUSION: In this study, we have developed and validated a novel murine model of trigeminal dynamic allodynia induced by intracisternal strychnine. The use of mice to study trigeminal allodynia has many benefits, including access to a vast repository of transgenic mouse variants, ease of handling, low cost, and minimal variance of results. The present model may have utility in screening drug treatments for dynamic mechanical allodynia resulting from trigeminal neuropathies.

Safety of an alkalinizing buffer designed for inhaled medications in humans.

BACKGROUND: Airway acidification plays a role in disorders of the pulmonary tract. We hypothesized that the inhalation of alkalinized glycine buffer would measurably alkalinize the airways without compromising lung function or causing adverse events. We evaluated the safety of an inhaled alkaline glycine buffer in both healthy subjects and in subjects with stable obstructive airway disease. METHODS: This work includes 2 open-label safety studies. The healthy controls were part of a phase 1 safety study of multiple inhalations of low-dose alkaline glycine buffer; nebulized saline was used as a comparator in 8 of the healthy controls. Subsequently, a phase 2 study in subjects with stable obstructive airway disease was completed using a single nebulized higher-dose strategy of the alkaline inhalation. We studied 20 non-smoking adults (10 healthy controls and 10 subjects with obstructive airway disease), both at baseline and after inhalation of alkaline buffer. We used spirometry and vital signs as markers of clinical safety. We used changes in fraction of exhaled nitric oxide (NO) and exhaled breath condensate (EBC) pH as surrogate markers of airway pH modification. RESULTS: Alkaline glycine inhalation was tolerated by all subjects in both studies, with no adverse effects on spirometric parameters or vital signs. Airway alkalinization was confirmed by a median increase in EBC pH of 0.235 pH units (IQR 0.56-0.03, P = .03) in subjects after inhalation of the higher-dose alkaline buffer (2.5 mL of 100 mmol/L glycine). CONCLUSIONS: Alkalinization of airway lining fluid is accomplished with inhalation of alkaline glycine buffer and causes no adverse effects on pulmonary function or vital signs.

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.

Glycine intrastriatal administration induces lipid and protein oxidative damage and alters the enzymatic antioxidant defenses in rat brain.

AIMS: We investigated the effects of in vivo intrastriatal administration of glycine (Gly), which is found at high concentrations in the brain of patients affected by nonketotic hyperglycinemia (NKH), on important parameters of oxidative stress. MAIN METHODS: Thiobarbituric acid-reactive substances values (TBA-RS, lipid peroxidation), carbonyl formation (protein oxidative damage), sulfhydryl content, reduced glutathione concentrations, nitric oxide production and the activities of the antioxidant enzymes glutathione peroxidase, glutathione reductase, catalase, superoxide dismutase and glucose-6-phosphate dehydrogenase (antioxidant defenses) were measured in striatum from 30-day-old rats after Gly injection. KEY FINDINGS: Gly administration significantly increased TBA-RS values, implying lipid oxidative damage. Furthermore, Gly-induced increase of TBA-RS was fully prevented by the NMDA receptor antagonist MK-801, indicating the involvement of the NMDA glutamate receptor in this effect. Gly injection also induced protein carbonyl formation, as well as elevation of the activities of glutathione peroxidase, glutathione reductase, catalase and superoxide dismutase. In contrast, glutathione levels, sulfhydryl content, nitric oxide production and the activity of glucose-6-phosphate dehydrogenase were not modified by Gly. SIGNIFICANCE: The data shows that Gly in vivo administration causes lipid peroxidation, probably secondary to NMDA stimulation, induces protein oxidation and modulates the activities of important antioxidant enzymes in the striatum. In case these findings can be extrapolated to the human NKH, it is feasible that oxidative stress may be involved in the pathophysiology of the brain injury observed in patients with this neurometabolic disease.

Transmission of phase-coupling accuracy from the auditory nerve to spherical bushy cells in the Mongolian gerbil.

The phase of low-frequency sinusoids is encoded in phase-coupled discharges of spherical bushy cells (SBCs) of the anteroventral cochlear nucleus and transmitted to the medial superior olive, where binaural input-coincidence is used for processing of sound source localization. SBCs are innervated by auditory nerve fibers through large, excitatory synapses (endbulbs of Held) and by inhibitory inputs, which effectively reduce SBC discharge rates. Here we monitor presynaptic potentials of endbulb-terminals and postsynaptic spikes of SBCs in extracellular single unit recordings in vivo. We compare postsynaptic phase-coupling of SBCs and their presynaptic immediate auditory nerve input. In all but one SBC discharge rates at the characteristic frequency were reduced pre-to-postsynaptically and phase-coupling accuracy was increased in one-third of them. We investigated the contribution of systemic inhibition on spike timing in SBCs by iontophoretic application of glycine- and GABA-receptor antagonists (strychnine, bicuculline). Discharge rate increased in one-third of the units during antagonist application, which was accompanied by a deterioration of phase-coupling accuracy in half of those units. These results suggest that the phase-coupling accuracy is improved in a subpopulation of SBCs during transmission from the auditory nerve to the SBCs by reduction of spike rates.

Antinociceptive effects of systemic lidocaine: involvement of the spinal glycinergic system.

Beside their action on voltage-gated Na(+) channels, local anesthetics are known to exert a variety of effects via alternative mechanisms. The antinociceptive effect of lidocaine is well documented, yet the exact mechanism is not fully understood. Whether glycinergic mechanisms, which play a pivotal role in pain modulation, are involved in lidocaine-induced antinociception is hitherto unclear. In the present study, lidocaine was injected intravenously in rats using the formalin test for acute pain and the chronic constriction injury model for neuropathic pain. The effect of intrathecally administered d-serine (an agonist at the glycine-binding site at the NMDA-receptor), its inactive isomer l-serine, CGP 78608 (antagonist at the glycineB-site of the NMDA-receptor) and strychnine (antagonist at inhibitory glycine-receptors) on lidocaine-induced antinociception was examined. Systemically administered lidocaine was antinociceptive in both acute and chronic pain model. In the formalin test, the effect of lidocaine was antagonized by d-serine, but not by l-serine or strychnine. In the chronic constriction injury model, antinociception evoked by lidocaine was reduced by d-serine, strychnine and CGP 78608, while l-serine had no effect. These results indicate a modulatory effect of lidocaine on the NMDA-receptor. Additionally, since in our study lidocaine-induced antinociception was antagonized by both glycineB-site modulators and strychnine our results may favor the hypothesis of a general glycine-like action of lidocaine or some of its metabolites on inhibitory strychnine-sensitive receptors and on strychnine-insensitive glycine receptors.

High-dose glycine treatment of refractory obsessive-compulsive disorder and body dysmorphic disorder in a 5-year period.

This paper describes an individual who was diagnosed with obsessive-compulsive disorder (OCD) and body dysmorphic disorder (BDD) at age 17 when education was discontinued. By age 19, he was housebound without social contacts except for parents. Adequate trials of three selective serotonin reuptake inhibitors, two with atypical neuroleptics, were ineffective. Major exacerbations following ear infections involving Group A beta-hemolytic streptococcus at ages 19 and 20 led to intravenous immune globulin therapy, which was also ineffective. At age 22, another severe exacerbation followed antibiotic treatment for H. pylori. This led to a hypothesis that postulates deficient signal transduction by the N-methyl-D-aspartate receptor (NMDAR). Treatment with glycine, an NMDAR coagonist, over 5 years led to robust reduction of OCD/BDD signs and symptoms except for partial relapses during treatment cessation. Education and social life were resumed and evidence suggests improved cognition. Our findings motivate further study of glycine treatment of OCD and BDD.

Dietary glycine blunts liver injury after bile duct ligation in rats.

AIM: To investigate the effects of (dietary) glycine against oxidant-induced injury caused by bile duct ligation (BDL). METHODS: Either a diet containing 5% glycine or a standard diet was fed to male Sprague-Dawley (SD) rats. Three days later, BDL or sham-operation was performed. Rats were sacrificed 1 to 3 d after BDL. The influence of deoxycholic acid (DCA) in the presence or absence of glycine on liver cells was determined by measurement of calcium and chloride influx in cultivated Kupffer cells and lactate dehydrogenase (LDH) activity was determined in the supernatant of cultivated hepatocytes. RESULTS: Serum alanine transaminase levels increased to about 600 U/L 1 d after BDL. However, enzyme release was blunted by about two third in rats receiving glycine. Release of the alkaline phosphatase and aspartate aminotransferase was also blocked significantly in the group fed glycine. Focal necrosis was observed 2 d after BDL. Glycine partially blocked the histopathological changes. Incubation of Kupffer cells with DCA led to increased intracellular calcium that could be blocked by incubation with glycine. However, systemic blockage of Kupffer cells with gadolinium chloride had no effects on transaminase release. Incubation of isolated hepatocytes with DCA led to a significant release of LDH after 4 h. This release was largely blocked when incubation with glycine was performed. CONCLUSION: These data indicate that glycine significantly decreased liver injury, most likely by a direct effect on hepatocytes. Kupffer cells do not appear to play an important role in the pathological changes caused by cholestasis.