Carnosine-induced antidepressant-like activity in rats

Histidine-containing dipeptide deficiency links to hyperactivity and depression-like behaviors in old female mice

Carnosine, anserine, and homocarnosine are histidine-containing dipeptides (HCDs) abundant in the skeletal muscle and nervous system in mammals. To date, studies have extensively demonstrated effects of carnosine and anserine, the predominant muscular HCDs, on muscular functions and exercise performance. However, homocarnosine, the predominant brain HCD, is underexplored. Moreover, roles of homocarnosine and its related HCDs in the brain and behaviors remain poorly understood. Here, we investigated potential roles of endogenous brain homocarnosine and its related HCDs in behaviors by using carnosine synthase-1-deficient (Carns1-/-) mice. We found that old Carns1-/- mice (female 12 months old) exhibited hyperactivity- and depression-like behaviors with higher plasma corticosterone levels on light-dark transition and forced swimming tests, but had no defects in spontaneous locomotor activity, repetitive behavior, olfactory functions, and learning and memory abilities, as compared with their age-matched wild-type (WT) mice. We confirmed that homocarnosine and its related HCDs were deficient across brain areas of Carns1-/- mice. Homocarnosine deficiency exhibited small effects on its constituent γ-aminobutyric acid (GABA) in the brain, in which GABA levels in hypothalamus and olfactory bulb were higher in Carns1-/- mice than in WT mice. In WT mice, homocarnosine and GABA were highly present in hypothalamus, thalamus, and olfactory bulb, and their brain levels did not decrease in old mice when compared with younger mice (3 months old). Our present findings provide new insights into roles of homocarnosine and its related HCDs in behaviors and neurological disorders.

The cross-sectional association between dietary total, animal, and plant-based protein intake and the prevalence and severity of depressive symptoms in Dutch adults with type 2 diabetes: The Hoorn Diabetes Care System cohort

OBJECTIVE

This study aimed to investigate cross-sectional associations of total, animal, and plant-based protein intake and depressive symptoms in Dutch adults with type 2 diabetes (T2D).

METHODS

We included 1137 individuals with T2D (aged 68.6 ± 9.0) from the Hoorn Diabetes Care System cohort. Energy-adjusted protein intake was assessed using a validated Food Frequency Questionnaire. The nine-item Patient Health Questionnaire (PHQ-9) was used to assess the prevalence of depressive symptoms (PHQ-9 ≥ 10 and/or anti-depressant use) and the severity of depressive symptoms (continuous PHQ-9 score). Associations between total, animal, and plant-based protein (quartiles) with depressive symptoms were assessed using multiple logistic and linear regression.

RESULTS

Highest intake of total, animal, and plant-based protein was not associated with the prevalence of depressive symptoms, compared to lowest intake (e.g., total protein, ORQ4vsQ1:0.75, 95%CI 0.42;1.32). For the severity of depressive symptoms, highest total protein intake was significantly associated with lower PHQ-9 scores (ORQ4vsQ1:0.87, 95%CI 0.75;1.00), compared to lowest intake. Animal protein was not associated with the severity of depressive symptoms (β ∼ 1), while the association for plant-based protein was marginally non-significant (βQ4vsQ1:0.88, 95%CI 0.76;1.02).

CONCLUSION

In individuals with T2D, higher total protein intake was associated with reduced severity of depressive symptoms, but not with the prevalence of depressive symptoms. Further prospective research with a larger sample size is needed to confirm these associations.

The contribution of polyamine pathway to determinations of diagnosis for treatment-resistant depression: A metabolomic analysis

OBJECTIVES

Approximately one-third of major depressive disorder (MDD) patients do not respond to standard antidepressants and develop treatment-resistant depression (TRD). We aimed to reveal metabolic differences and discover promising potential biomarkers in TRD.

METHODS

Our study recruited 108 participants including healthy controls (n = 40) and patients with TRD (n = 35) and first-episode drug-naive MDD (DN-MDD) (n = 33). Plasma samples were presented to ultra performance liquid chromatography-tandem mass spectrometry. Then, a machine-learning algorithm was conducted to facilitate the selection of potential biomarkers.

RESULTS

TRD appeared to be a distinct metabolic disorder from DN-MDD and healthy controls (HCs). Compared to HCs, 199 and 176 differentially expressed metabolites were identified in TRD and DN-MDD, respectively. Of all the metabolites that were identified, spermine, spermidine, and carnosine were considered the most promising biomarkers for diagnosing TRD and DN-MDD patients, with the resulting area under the ROC curve of 0.99, 0.99, and 0.93, respectively. Metabolic pathway analysis yielded compelling evidence of marked changes or imbalances in both polyamine metabolism and energy metabolism, which could potentially represent the primary altered pathways associated with MDD. Additionally, L-glutamine, Beta-alanine, and spermine were correlated with HAMD score.

CONCLUSIONS

A more disordered metabolism structure is found in TRD than in DN-MDD and HCs. Future investigations should prioritize the comprehensive analysis of potential roles played by these differential metabolites and disturbances in polyamine pathways in the pathophysiology of TRD and depression.

Antidepressant-like Effects of Representative Types of Food and Their Possible Mechanisms

Depression is a mental disorder characterized by low mood, lack of motivation, negative cognitive outlook, and sleep problems. Suicide may occur in severe cases, although suicidal thoughts are not seen in all cases. Globally, an estimated 350 million individuals grapple with depression, as reported by the World Health Organization. At present, drug and psychological treatments are the main treatments, but they produce insufficient responses in many patients and fail to work at all in many others. Consequently, treating depression has long been an important topic in society. Given the escalating prevalence of depression, a comprehensive strategy for managing its symptoms and impacts has garnered significant attention. In this context, nutritional psychiatry emerges as a promising avenue. Extensive research has underscored the potential benefits of a well-rounded diet rich in fruits, vegetables, fish, and meat in alleviating depressive symptoms. However, the intricate mechanisms linking dietary interventions to brain function alterations remain largely unexplored. This review delves into the intricate relationship between dietary patterns and depression, while exploring the plausible mechanisms underlying the impact of dietary interventions on depression management. As we endeavor to unveil the pathways through which nutrition influences mental well-being, a holistic perspective that encompasses multidisciplinary strategies gains prominence, potentially reshaping how we approach and address depression.

Maternal stress-induced changes in adolescent and adult offspring: Neurobehavioural improvement and telomere maintenance

Maternal stress (MS) during gestation is known to increase the risk for the development of behavioural and physiological disorders and advances cellular aging. In this study, we investigated whether the supplementation of standardized Bacopa monnieri extract (CDRI-08/BME) or l-Carnosine (L-C) to the mother exposed to social stress during gestation modify the effect on their offspring's neurobehaviour, antioxidant defence gene expression, telomere length, and telomere biology. To test this, timed pregnant rats were subjected to social stress during the gestational day (GD) 16-18. A subset of stressed pregnant rats received either BME [80 mg/kg in 0.5% gum acacia (per-orally; p.o)] or L-C [1 mg/kg (p.o)] every day from GD-10 to until their pup's attained postnatal day (PND)-23. We observed that MS induced anxiety-like behaviour, altered inter-limb coordination, antioxidant defence genes [Superoxide dismutase (SOD1,2), Catalase (CAT), Glutathione peroxidase-3 (GPX3)], telomerase reverse transcriptase (TERT), shelterin complex subunits (TRF1, RAP1B, POT1) protein level and shorten telomere length. Notably, supplementation of BME/L-C dampens the MS, thus the effect on neurobehaviour, antioxidant defence gene expression, and telomere biology is minimized in their offspring. Together, our results suggest that supplementation of BME/L-C during gestation dampens the MS and reduced oxidative stress-mediated changes in telomere shortening/biology and associated neurobehaviour in offspring born following MS.

Dietary protein intake affects the association between urinary iodine and clinically relevant depression: Evidence from NHANES 2007-2018

Both iodine concentration and protein intake are important nutritional factors that may influence the development of depressive symptoms. However, there are no studies on the effect of protein intake on the relationship between iodine concentration and the risk of depression. The study aimed to explore the relationship between iodine and the risk of clinically relevant depression (CRD) according to protein intake. This study analyzed the adults (≥18 years) who participated in the 2007-2018 National Health and Nutrition Cross-sectional Survey (N = 10,462). CRD was assessed using the Patient Health Questionnaire (PHQ-9). Protein intake was assessed using two 24-h dietary recalls and urinary iodine concentration (UIC) was measured using inductively coupled plasma dynamic response cell mass spectrometry. Weighted multivariate logistic regression and restrictive cubic splines were performed to assess the relationship between UIC and CRD according to protein category (low protein intake <0.8 g/kg/day; high protein intake: ≥0.8 g/kg/day). After controlling for sociodemographic, behavioral, chronic diseases, and dietary factors, a positive correlation was observed between UIC (log10) and CRD (OR: 1.36, 95% CI: 1.026, 1.795). Low UIC (<100 μg/L) was associated with a lower prevalence of CRD (OR: 0.73, 95% CI: 0.533, 0.995) in high protein intake individuals, whereas this relationship did not exist in those with low protein intake. Moreover, restrictive cubic splines confirmed a near L-shaped relationship between UIC and CRD in the low-protein group (nonlinear p = .042) and a linear relationship between them in the high-protein group (nonlinear p = .392). This study illustrates that protein intake affects the relationship between UIC and CRD. Combining lower UIC and high protein intake may help reduce the prevalence of CRD, which would have significant implications for managing patients with depressive CRD in the clinical setting.

Serum levels of carnosine may be associated with the duration of MDD episodes

BACKGROUND

Major depressive disorder (MDD) is a recurrent disorder that incurs a high societal burden. However, the etiology of MDD remains unclear. The functioning of several systems associated with the etiopathogenesis of MDD, such as inflammatory and stress systems, is partially modulated by the dipeptide carnosine.

METHODS

The study comprised 99 MDD patients and 253 non-depressed controls aged 20-71 years. Fasting serum samples were analyzed using ultra-performance liquid chromatography coupled to mass spectrometry to determine the serum levels of carnosine and its constituent, histidine. We compared these metabolites in three different settings: 1) MDD patients vs. non-depressed controls and 2) remitted vs. non-remitted MDD patients, as well as 3) changes in the metabolite levels during the follow-up period within a) the remitted group and b) the non-remitted group. In addition, we assessed the possible effect of medications on the measured metabolites.

RESULTS

We observed higher serum levels of carnosine in the MDD group compared to the control group at baseline (OR = 1.895, 95%CI = 1.223-2.937, p = 0.004). Elevated serum levels of carnosine were also associated with a longer duration of the depressive episode (Z = 0.406, p = 0.001). However, the use of any antipsychotic medication (n = 36) was associated with lowered carnosine levels (p = 0.010 for use vs. non-use). At the follow-up, remitted and non-remitted participants displayed no significant differences in their carnosine levels (Z = -0.14, p = 0.891) or histidine (Z = -1.39 p = 0.164).

CONCLUSIONS

An increase in circulating carnosine may characterize depressive episodes and may represent a protective homeostatic reaction against MDD-related oxidative stress and inflammation.

Stimulation of uncoupling protein 1 expression by β-alanine in brown adipocytes

Carnosine, which is abundant in meat, is a dipeptide composed of β-alanine and histidine, known to afford various health benefits. It has been suggested that carnosine can elicit an anti-obesity effect via induction and activation of brown/beige adipocytes responsible for non-shivering thermogenesis. However, the relationship between carnosine and brown/beige adipocytes has not been comprehensively elucidated. We hypothesized that β-alanine directly modulates brown/beige adipogenesis and performed an in vitro assessment to test this hypothesis. HB2 brown preadipocytes were differentiated using insulin from day 0. Cells were treated with various concentrations of β-alanine (12.5-100 μM) during adipogenesis (days 0-8) and differentiation (days 8-10). Then, cells were further stimulated with or without forskolin, an activator of the cAMP-dependent protein kinase pathway, on day 8 or day 10 for 4 h before harvesting. We observed that HB2 cells expressed molecules related to the transport and signal transduction of β-alanine. Treatment with β-alanine during brown adipogenesis dose-dependently enhanced forskolin-induced Ucp1 expression; this was not observed in differentiated brown adipocytes. Consistent with these findings, treatment with β-alanine during days 0-8 increased phosphorylation levels of CREB in forskolin-treated HB2 cells. In addition, β-alanine treatment during brown adipogenesis increased the expression of Pparα, known to induce brown/beige adipogenesis, in a dose-dependent manner. These findings revealed that β-alanine could target HB2 adipogenic cells and enhance forskolin-induced Ucp1 expression during brown adipogenesis, possibly by accelerating phosphorylation and activation of CREB. Thus, β-alanine, a carnosine-constituting amino acid, might directly act on brown adipogenic cells to stimulate energy expenditure.

Unveiling the Hidden Therapeutic Potential of Carnosine, a Molecule with a Multimodal Mechanism of Action: A Position Paper

Carnosine (β-alanyl-L-histidine) is a naturally occurring endogenous dipeptide and an over-the-counter food supplement with a well-demonstrated multimodal mechanism of action that includes the detoxification of reactive oxygen and nitrogen species, the down-regulation of the production of pro-inflammatory mediators, the inhibition of aberrant protein formation, and the modulation of cells in the peripheral (macrophages) and brain (microglia) immune systems. Since its discovery more than 100 years ago, a plethora of in vivo preclinical studies have been carried out; however, there is still substantial heterogeneity regarding the route of administration, the dosage, the duration of the treatment, and the animal model selected, underlining the urgent need for "coordinated/aligned" preclinical studies laying the foundations for well-defined future clinical trials. The main aim of the present position paper is to critically and concisely consider these key points and open a discussion on the possible "alignment" for future studies, with the goal of validating the full therapeutic potential of this intriguing molecule.

Neuropeptide Y modifies a part of diencephalic catecholamine but not indolamine metabolism in chicks depending on feeding status

The role of the monoaminergic system in the feeding behavior of neonatal chicks has been reported, but the functional relationship between the metabolism of monoamines and appetite-related neuropeptides is still unclear. This study aimed to investigate the changes in catecholamine and indolamine metabolism in response to the central action of neuropeptide Y (NPY) in different feeding statuses and the underlying mechanisms. In Experiment 1, the diencephalic concentrations of amino acids and monoamines following the intracerebroventricular (ICV) injection of NPY (375 pmol/10 μl/chick), saline solution under ad libitum, and fasting conditions for 30 min were determined. Central NPY significantly decreased L-tyrosine concentration, the precursor of catecholamines under feeding condition, but not under fasting condition. Central NPY significantly increased dopamine metabolites, including 3,4-dihydroxyphenylacetic acid and homovanillic acid (HVA). The concentration of 3-methoxy-4-hydroxyphenylglycol was significantly reduced under feeding condition, but did not change under fasting condition by NPY. However, no effects of NPY on indolamine metabolism were found in either feeding status. Therefore, the mechanism of action of catecholamines with central NPY under feeding condition was elucidated in Experiment 2. Central NPY significantly attenuated diencephalic gene expression of catecholaminergic synthetic enzymes, such as tyrosine hydroxylase, L-aromatic amino acid decarboxylase, and GTP cyclohydrolase I after 30 min of feeding. In Experiment 3, co-injection of α-methyl-L-tyrosine, an inhibitor of tyrosine hydroxylase with NPY, moderately attenuated the orexigenic effect of NPY, accompanied by a significant positive correlation between food intake and HVA levels. In Experiment 4, there was a significant interaction between NPY and clorgyline, an inhibitor of monoamine oxidase A with ICV co-injection which implies that co-existence of NPY and clorgyline enhances the orexigenic effect of NPY. In conclusion, central NPY modifies a part of catecholamine metabolism, which is illustrated by the involvement of dopamine transmission and metabolism under feeding but not fasting conditions.

Green Tea Suppresses Brain Aging

Epidemiological studies have demonstrated that the intake of green tea is effective in reducing the risk of dementia. The most important component of green tea is epigallocatechin gallate (EGCG). Both EGCG and epigallocatechin (EGC) have been suggested to cross the blood–brain barrier to reach the brain parenchyma, but EGCG has been found to be more effective than EGC in promoting neuronal differentiation. It has also been suggested that the products of EGCG decomposition by the intestinal microbiota promote the differentiation of nerve cells and that both EGCG and its degradation products act on nerve cells with a time lag. On the other hand, the free amino acids theanine and arginine contained in green tea have stress-reducing effects. While long-term stress accelerates the aging of the brain, theanine and arginine suppress the aging of the brain due to their anti-stress effect. Since this effect is counteracted by EGCG and caffeine, the ratios between these green tea components are important for the anti-stress action. In this review, we describe how green tea suppresses brain aging, through the activation of nerve cells by both EGCG and its degradation products, and the reductions in stress achieved by theanine and arginine.

Theanine, Antistress Amino Acid in Tea Leaves, Causes Hippocampal Metabolic Changes and Antidepressant Effects in Stress-Loaded Mice

By comprehensively measuring changes in metabolites in the hippocampus of stress-loaded mice, we investigated the reasons for stress vulnerability and the effect of theanine, i.e., an abundant amino acid in tea leaves, on the metabolism. Stress sensitivity was higher in senescence-accelerated mouse prone 10 (SAMP10) mice than in normal ddY mice when these mice were loaded with stress on the basis of territorial consciousness in males. Group housing was used as the low-stress condition reference. Among the statistically altered metabolites, depression-related kynurenine and excitability-related histamine were significantly higher in SAMP10 mice than in ddY mice. In contrast, carnosine, which has antidepressant-like activity, and ornithine, which has antistress effects, were significantly lower in SAMP10 mice than in ddY mice. The ingestion of theanine, an excellent antistress amino acid, modulated the levels of kynurenine, histamine, and carnosine only in the stress-loaded SAMP10 mice and not in the group-housing mice. Depression-like behavior was suppressed in mice that had ingested theanine only under stress loading. Taken together, changes in these metabolites, such as kynurenine, histamine, carnosine, and ornithine, were suggested to be associated with the stress vulnerability and depression-like behavior of stressed SAMP10 mice. It was also shown that theanine action appears in the metabolism of mice only under stress loading.

Intracerebroventricular injection of L-arginine and D-arginine induces different effects under an acute stressful condition

Central administration of L-arginine was reported to attenuate stress responses in neonatal chicks. The present study aimed to elucidate the differential effects of centrally administered L-arginine and its enantiomer, D-arginine, on the stress response in chicks and the associated mechanisms. Intracerebroventricular injection of L-arginine attenuated acute isolation stress by inducing sleep-like behavior, while central administration of D-arginine potentiated the stress response, reducing the time spent standing motionless with eyes open and increasing distress vocalizations compared to the control. The brain concentrations of amino acids and monoamines following L- and D-arginine administration during stress were also determined. L-Arginine significantly increased the mesencephalic L-glutamine concentration. D-Arginine administration did not affect the levels of L-arginine or other amino acids in the examined brain regions. 3,4-Dihydroxyphenylacetic acid (DOPAC) level and dopamine (DA) metabolic rate (DOPAC/DA) were significantly higher in the diencephalon in the D-arginine group compared to the L-arginine group, while the mesencephalic DA level was significantly lower in the D-arginine group compared to the control. In vitro experiment using the brain slice culture demonstrated that extracellular perfusion of D-arginine significantly elevated the mRNA expression level of monoamine oxidase B, the major enzyme involved in DA metabolism, in the locus coeruleus region of the brainstem. In conclusion, in neonatal chicks, central administration of D-arginine exerted a stimulant effect on the stress response, in contrast to the stress-attenuating effects of L-arginine, partly through an effect on brain dopaminergic metabolism and not through competition with the L-stereoisomer.

Effects of Dietary Defatted Meat Species on Metabolomic Profiles of Murine Liver, Gastrocnemius Muscle, and Cecal Content

In both humans and animals, meat not only constitutes one of the sources of protein, but also includes various water-soluble bioactive substances such as imidazole peptides (carnosine and anserine) and taurine. Previous studies demonstrated that dietary meat species could differently affect physiological functions; however, the mechanisms of this remain unclear. To explore the physiological effects of dietary defatted meat species, especially on metabolism, we investigated their influence on the metabolomic profiles of the liver, gastrocnemius muscle, and cecal content in mice. Casein (control) or a defatted meat species (beef leg, pork leg, chicken leg, or chicken breast) was supplied as the major protein source in the diet for four weeks, and metabolism-related molecules were measured by gas chromatography–mass spectrometry. We found that various metabolite levels in tissues and cecal content differed according to the types of dietary protein consumed. Specifically, differences in carnosine, 1,5-anhydro-glucitol, inositol, butyric acid, and propionic acid were clearly observed. Among them, the highest carnosine intake by dietary pork leg was clearly related to the highest carnosine level in the liver. In addition, taurine intake was suggested to be linked to some metabolic pathways including taurine and hypotaurine metabolism in cecal content. These results provide additional knowledge of the effects of different dietary meat species on human and animal health.

Inflammation as the Common Biological Link Between Depression and Cardiovascular Diseases: Can Carnosine Exert a Protective Role?

Several epidemiological studies have clearly shown the high co-morbidity between depression and Cardiovascular Diseases (CVD). Different studies have been conducted to identify the common pathophysiological events of these diseases such as the overactivation of the hypothalamic- pituitary-adrenal axis and, most importantly, the dysregulation of immune system which causes a chronic pro-inflammatory status. The biological link between depression, inflammation, and CVD can be related to high levels of pro-inflammatory cytokines, such as IL-1β, TNF-α, and IL-6, released by macrophages which play a central role in the pathophysiology of both depression and CVD. Pro-inflammatory cytokines interfere with many of the pathophysiological mechanisms relevant to depression by upregulating the rate-limiting enzymes in the metabolic pathway of tryptophan and altering serotonin metabolism. These cytokines also increase the risk to develop CVD, because activation of macrophages under this pro-inflammatory status is closely associated with endothelial dysfunction and oxidative stress, a preamble to atherosclerosis and atherothrombosis. Carnosine (β-alanyl-L-histidine) is an endogenous dipeptide which exerts a strong antiinflammatory activity on macrophages by suppressing reactive species and pro-inflammatory cytokines production and altering pro-inflammatory/anti-inflammatory macrophage polarization. This dipeptide exhibits antioxidant properties scavenging reactive species and preventing oxidative stress-induced pathologies such as CVD. In the present review we will discuss the role of oxidative stress and chronic inflammation as common pathophysiological events both in depression and CVD and the preclinical and clinical evidence on the protective effect of carnosine in both diseases as well as the therapeutic potential of this dipeptide in depressed patients with a high co-morbidity of cardiovascular diseases.

Polaprezinc (Zinc-L-Carnosine Complex) as an Add-on Therapy for Binge Eating Disorder and Bulimia Nervosa, and the Possible Involvement of Zinc Deficiency in These Conditions: A Pilot Study

BACKGROUND

Zinc plays an important role in appetite regulation. L-Carnosine, an endogenous dipeptide, may also regulate eating behavior via its histaminergic and antiglutamatergic properties. Polaprezinc (zinc-L-carnosine complex) is a medication for gastric ulcers. A small case series reported successful treatment of binge eating with add-on polaprezinc.

METHODS

This was an open trial of add-on polaprezinc in patients with binge eating disorder (BED; n = 22) or bulimia nervosa (BN; n = 7) receiving antidepressants. A 4-week baseline period was followed by a 16-week polaprezinc treatment at 150 mg/d (containing 34 mg zinc and 116 mg L-carnosine) in addition to ongoing psychotropic medications. We also assessed their zinc status via a laboratory index and zinc deficiency-related symptoms.

RESULTS

At the study end, both conditions showed a significant reduction in the 4-week frequency of combined objective and subjective binge eating episodes, the 4-week frequency of days when at least 1 such episode occurred (only in BED), several aspects of eating disorder psychopathology (rated by the Eating Disorder Examination-Questionnaire), and comorbid depressive symptoms (rated by the 16-item Quick Inventory of Depressive Symptomatology [Self-Report]). Serum copper/zinc ratio decreased from 1.4 to 1.1 on average in both conditions. All patients had multiple zinc deficiency-related symptoms at baseline that substantially improved after polaprezinc treatment. Overall, the effectiveness of polaprezinc was greater in BED patients than in BN patients, with minor adverse effects.

CONCLUSIONS

These findings offer preliminary evidence for the effectiveness of polaprezinc in treating BED and BN and suggest the involvement of zinc deficiency in these conditions.

Effect of β-alanine supplementation on carnosine and histidine content in the hippocampus of 14-month-old rats

Carnosine and histidine content in the hippocampus of 14-month-old male rats was examined following 30 days of β-alanine supplementation. All animals were provided identical diets; however, 100 mg of β-alanine was mixed with glucomannan (80:20 blend) in the water of β-alanine supplemented animals. Hippocampal carnosine content was significantly greater (p = 0.005) for β-alanine compared with control, while no differences (p = 0.438) were noted in histidine content between groups. Results provide initial evidence that β-alanine supplementation increases carnosine content in the hippocampus of middle-aged rats, without compromising histidine content. β-Alanine supplementation increases hippocampal carnosine content without compromising histidine content in middle-aged rats.

Heat-killed Lactobacillus helveticus strain MCC1848 confers resilience to anxiety or depression-like symptoms caused by subchronic social defeat stress in mice

The gut microbiota is involved in the pathogenesis of stress-related disorders. Probiotics can benefit the central nervous system via the microbiota–gut–brain axis, which raises the possibility that probiotics are effective in managing depression. In the present study, we examined the effects of heat-killed Lactobacillus helveticus strain MCC1848 in subchronic and mild social defeat stress (sCSDS) model mice (a widely used animal model of depression). MCC1848 supplementation significantly enhanced the interaction time in the social interaction test and sucrose preference ratio in the sucrose preference test, suggesting that MCC1848 improved anxiety- or depressive-like behaviors in sCSDS mice. The gene expression profile analysis of the nucleus accumbens, which plays an important role in stress resilience, indicated that MCC1848 ameliorated sCSDS-induced gene expression alterations in signal transduction or nervous system development. These findings suggest that MCC1848 supplementation is useful as a preventive strategy for chronic-stress-induced depression.

The Potential of Carnosine in Brain-Related Disorders: A Comprehensive Review of Current Evidence

Neurological, neurodegenerative, and psychiatric disorders represent a serious burden because of their increasing prevalence, risk of disability, and the lack of effective causal/disease-modifying treatments. There is a growing body of evidence indicating potentially favourable effects of carnosine, which is an over-the-counter food supplement, in peripheral tissues. Although most studies to date have focused on the role of carnosine in metabolic and cardiovascular disorders, the physiological presence of this di-peptide and its analogues in the brain together with their ability to cross the blood-brain barrier as well as evidence from in vitro, animal, and human studies suggest carnosine as a promising therapeutic target in brain disorders. In this review, we aim to provide a comprehensive overview of the role of carnosine in neurological, neurodevelopmental, neurodegenerative, and psychiatric disorders, summarizing current evidence from cell, animal, and human cross-sectional, longitudinal studies, and randomized controlled trials.

Daily consumption of essence of chicken improves cognitive function: a systematically searched meta-analysis of randomized controlled trials

Essence of chicken (EC) is a dietary supplement with potential benefits on one's cognitive performance. The purpose of this meta-analysis is to evaluate the effects of consuming EC on cognitive function, applying extensively represented domains. Six databases were systematically searched to yield 1760 articles. These articles were independently screened to obtain 8 eligible articles with a pooled population of 794 subjects which is more than twice the population size considered in the previous meta-analyses. Largely, favorable effects on cognitive function were observed following daily EC intake, specifically in the working memory domain (standardized mean difference: 0.31, 95% CI: 0.16, 0.46), one of the core components in executive function which showed statistically significant results. Furthermore, the observed results were also robust to sensitivity analyses and subgroup analyses. This suggests that when consumed daily, EC may improve the mental processing aspect of cognitive function amongst the healthy population.

Effects of β-alanine supplementation on physical performance, cognition, endocrine function, and inflammation during a 24 h simulated military operation

Sustained military operations (SUSOPs) are associated with performance decrements and cognitive dysfunction. β-Alanine (BA) supplementation may have a role in increasing soldier resiliency by enhancing muscle-buffering capacity and reducing oxidative stress. The purpose of this study was to examine the effects of BA on physical performance, cognition, endocrine function, and inflammation during a 24 h simulated SUSOP. Nineteen males were randomized into one of two groups: BA (n = 10) or placebo (n = 9; PLA) (12 g/day) for 14 days preceding the 24 h SUSOP. Assessments were performed at 0 h (0H), 12 h (12H), and 24 h (24H) during the SUSOP. No changes in visual tracking ability, jump power, or upper-body muscular endurance were observed between groups or time points (P's > 0.05). Increases in subjective feelings of soreness and fatigue were noted at 12H compared to 0H (P < 0.05) in PLA, but not in BA. Visual reaction time for PLA was slower at 24H compared to 0H (P = 0.035), and PLA made more errors on reaction time testing at 12H compared to BA (P = 0.048), but motor reaction time was faster (P = 0.016) for PLA. Simulated litter carry and 1 km run completion times increased at 24H compared to 0H in both groups (P < 0.05), however, PLA had a longer 1 km time compared to BA at 24H (P = 0.050). Increases in inflammatory and endocrine markers were observed over the SUSOP, with no differences between groups. BA supplementation appears to maintain some aspects of cognition and physical performance during a 24 h SUSOP, with no effects on endocrine function or inflammation.

Carnosine as an effective neuroprotector in brain pathology and potential neuromodulator in normal conditions

Carnosine (b-alanyl-L-histidine) is an endogenous dipeptide widely distributed in excitable tissues, such as muscle and neural tissues-though in minor concentrations in the latter. Multiple benefits have been attributed to carnosine: direct and indirect antioxidant effect, antiglycating, metal-chelating, chaperone and pH-buffering activity. Thus, carnosine turns out to be a multipotent protector against oxidative damage. However, the role of carnosine in the brain remains unclear. The key aspects concerning carnosine in the brain reviewed are as follows: its concentration and bioavailability, mechanisms of action in neuronal and glial cells, beneficial effects in human studies. Recent literature data and the results of our own research are summarized here. This review covers studies of carnosine effects on both in vitro and in vivo models of cerebral damage, such as neurodegenerative disorders and ischemic injuries and the data on its physiological actions on neuronal signaling and cerebral functions. Besides its antioxidant and homeostatic properties, new potential roles of carnosine in the brain are discussed.

Mechanisms of carnosine-induced activation of neuronal cells

Carnosine (β-Ala-l-His), an imidazole dipeptide, is known to have many functions. Recently, we demonstrated in a double-blind randomized controlled trial that carnosine is capable of preserving cognitive function in elderly people. In the current study, we assessed the ability of carnosine to activate the brain, and we tried to clarify the molecular mechanisms behind this activation. Our results demonstrate that carnosine permeates the blood brain barrier and activates glial cells within the brain, causing them to secrete neurotrophins, including BDNF and NGF. These results point to a novel mechanism of carnosine-induced neuronal activation. Our results suggest that carnosine should be recognized as a functional food factor that helps achieve anti-brain aging.

Murine Depression Model and its Potential Applications for Discovering Foods and Farm Products with Antidepressant-Like Effects

Advanced societies face increased health problems related to various stresses. Chronic psychological stress is a major risk factor for psychiatric disorders such as depression. Although therapeutic agents reduce several symptoms of depression, most have side effects in a broad range of the population. Furthermore, some victims of depression do not show significant improvement with any drugs, so alternative approaches are needed. Good dietary habits may potentially reduce depressive symptoms, but there is little scientific evidence thus far. Murine depression models are useful to test nutritional approaches in vivo. Our model mice subjected to a subchronic mild social defeat stress (sCSDS) paradigm show several alterations in physiological parameters and social behavior. These stress-induced symptoms in sCSDS mice can be used as cues to identify antidepressant-like natural resources including foods and farm products. We previously discovered that sCSDS mice show more vulnerability to social stress by changing dietary condition. In addition, we developed a more objective system for analyzing mouse behavior using a 3D depth-sensing camera to understand relationships between diet and behavior. The combination of sCSDS mice with 3D behavioral analysis is a powerful method for screening ingredients in foods and farm products for antidepressant-like effects.

Central Injection of Glucose Modifies Behavior, Amino Acid and Monoamine Metabolism in Neonatal Chicks under Acute Stressful Conditions

The effect of intracerebroventricular (i.c.v.) injection of a wide range of glucose concentrations on the behavioral response, central amino acid and monoamine contents was investigated in chicks exposed to a social isolation stressful condition. The chicks were given an i.c.v. injection of 0.21, 0.42, 0.84, and 1.68 µmol of D-glucose, and then behavioral changes were observed over 10 min. The behavioral stress response was dose-dependently decreased and calm behavior was increased by i.c.v. administration of glucose. In the diencephalon, glutamine was positively correlated, whereas glycine was negatively correlated with the dose of glucose. In the telencephalon, the dopamine metabolite and dopamine turnover rates were positively correlated, whereas dopamine was negatively correlated with doses of glucose. In the plasma, isoleucine and hydroxyproline were positively correlated with the dose of glucose, and several amino acids were also influenced by glucose levels.

These results suggest that the possible pathways of the sedative effect of glucose include: (1) amino acids synthesized from injected glucose, which can induce the sedative and/or hypnotic effects; (2) amino acids modified by injected glucose transported in the brain from the peripheral tissues; and (3) injected glucose-induced decreases in brain dopamine levels. In conclusion, these changes induced by central glucose interact and induce the sedative effect in neonatal chicks.

Carnosine and Related Peptides: Therapeutic Potential in Age-Related Disorders

Imidazole dipeptides (ID), such as carnosine (β-alanyl-L-histidine), are compounds widely distributed in excitable tissues of vertebrates. ID are also endowed of several biochemical properties in biological tissues, including antioxidant, bivalent metal ion chelating, proton buffering, and carbonyl scavenger activities. Furthermore, remarkable biological effects have been assigned to such compounds in age-related human disorders and in patients whose activity of serum carnosinase is deficient or undetectable. Nevertheless, the precise biological role of ID is still to be unraveled. In the present review we shall discuss some evidences from clinical and basic studies for the utilization of ID as a drug therapy for age-related human disorders.

Possible Benefit of Dietary Carnosine towards Depressive Disorders

Many stress-related and depressive disorders have been shown to be associated with one or more of the following; shortened telomeres, raised cortisol levels and increased susceptibility to age-related dysfunction. It is suggested here that insufficient availability of the neurological peptide, carnosine, may provide a biochemical link between stress- and depression-associated phenomena: there is evidence that carnosine can enhance cortisol metabolism, suppress telomere shortening and exert anti-aging activity in model systems. Dietary supplementation with carnosine has been shown to suppress stress in animals, and improve behaviour, cognition and well-being in human subjects. It is therefore proposed that the therapeutic potential of carnosine dietary supplementation towards stress-related and depressive disorders should be examined.

Changes in free amino acid and monoamine concentrations in the chick brain associated with feeding behavior

Domesticated chicks are precocial and therefore have relatively well-developed feeding behavior. The role of hypothalamic neuropeptides in food-intake regulation in chicks has been reported for decades. However, we hypothesized that nutrients and their metabolites in the brain may be involved in food intake in chicks because these animals exhibit a very frequent feeding pattern. Therefore, the purpose of this study was to examine the feeding behavior of chicks as well as the associated changes in free amino acid and monoamine concentrations in the chick brain. The feeding behavior of chicks was recorded continuously for 6 h. The next day, brain and blood samples were collected when the chicks either attempted to have food (hungry group) or turned food down (satiated group), in order to analyze the concentrations of the free amino acids and monoamines. We confirmed that the feeding behavior of neonatal chicks was characterized by short resting periods between very brief times spent on food intake. Several free amino acids in the mesencephalon were significantly lower in the satiated group than in the hungry group, while l-histidine and l-glutamine were significantly higher. Notably, there was no change in the free amino acid concentrations in other brain regions or plasma. As for monoamines, serotonin and norepinephrine were significantly lower in the mesencephalon of the hungry group compared with the satiated group, but 5 hydroxyindolacetic acid (5-HIAA) was higher. In addition, serotonin and norepinephrine levels were significantly higher in the brain stem of the hungry chicks compared with the satiated group, but levels of 5-HIAA and homovanillic acid were lower. Levels of both dopamine and its metabolite, 3,4-dihydroxyphenylacetic acid, were significantly higher in the diencephalon and telencephalon of the chicks in the hungry group. In conclusion, the changes in the free amino acids and monoamines in the brain may have some role in the feeding behavior of neonatal chicks.

β-Alanine supplemented diets enhance behavioral resilience to stress exposure in an animal model of PTSD

This study investigated the effects of β-alanine (BA) ingestion on the behavioral and neuroendocrine response of post-traumatic stress disorder (PTSD) in a murine model. Animals were fed a normal diet with or without (PL) BA supplementation (100 mg kg(-1)) for 30 days. Animals were then exposed to a predator-scent stress (PSS) or a sham (UNEX). Behaviors were evaluated using an elevated plus maze (EPM) and acoustic startle response (ASR) 7 days following exposure to the PSS. Corticosterone concentrations (CS), expression of brain-derived neurotrophic factor (BDNF), and brain carnosine concentrations were analyzed a day later. Animals in PSS+PL spent significantly less time in the open arms and in the number of entries in the EPM than PSS+BA, UNEX+BA, or UNEX+PL. Animals in PSS+BA had comparable scores to UNEX+BA. Anxiety index was higher (p < 0.05) in PSS+PL compared to PSS+BA or animals that were unexposed. ASR and freezing were greater (p < 0.05) in animals exposed to PSS compared to animals unexposed. CS expression was higher (p < 0.05) in animals exposed to PSS compared to unexposed animals. Brain carnosine concentrations in the hippocampus and other brain sections were significantly greater in animals supplemented with BA compared to PL. BDNF expression in the CA1 and DG subregions of the hippocampus was lower (p < 0.05) in animals exposed and fed a normal diet compared to animals exposed and supplemented with BA, or animals unexposed. In conclusion, BA supplementation in rats increased brain carnosine concentrations and resulted in a reduction in PTSD-like behavior, which may be mediated in part by maintaining BDNF expression in the hippocampus.

The effect of chicken extract on mood, cognition and heart rate variability

Chicken extract, which is rich in anserine and carnosine, has been widely taken in Asian countries as a traditional remedy with various aims, including attenuation of psychological fatigue. The effects of consuming BRAND’S Essence of Chicken (EOC) or a placebo on 46 young adults’ responses to a standard psychological “stressor” were considered. Heart rate variability (HRV), cortisol responses, mood and cognition were measured at baseline and after ten days supplementation. EOC resulted in feeling less anxious, depressed and confused and more agreeable and clearheaded. A decrease in HRV was observed after EOC but only in females. Cognition and cortisol levels were not influenced by EOC. Findings suggest that EOC may be a promising supplement to improve mood in a healthy population.

Macronutrient intake and depressive symptoms among Japanese male workers: the Furukawa Nutrition and Health Study

This study was aimed to examine the cross-sectional association of protein, carbohydrate, and fat intake with depressive symptoms among 1794 Japanese male workers aged 18-69 years who participated in a health survey. Dietary intake was assessed with a validated self-administered diet history questionnaire. Depressive symptoms were assessed using the Center for Epidemiologic Studies Depression (CES-D) scale. Odds ratio of depressive symptoms (CES-D scale of ≥16) was estimated by using multiple logistic regression with adjustment for covariates including folate, vitamin B6, vitamin B12, polyunsaturated fatty acid, magnesium, and iron intake. Multivariable-adjusted odds ratio of depressive symptoms for the highest quartile of protein intake was 26%, albeit not statistically significant, lower compared with the lowest. The inverse association was more evident when a cutoff value of CES-D score ≥19 was used. The multivariable-adjusted odds ratios (95% confidence intervals) for the highest through lowest quartile of protein intake were 1.00 (reference), 0.69 (0.47-1.01), 0.69 (0.44-1.09), and 0.58 (0.31-1.06) (P for trend=0.096). Neither carbohydrate nor fat intake was associated with depressive symptoms. Our findings suggest that low protein intake may be associated with higher prevalence of depressive symptoms in Japanese male workers.

Orally administered whole egg demonstrates antidepressant-like effects in the forced swimming test on rats

OBJECTIVE

Several studies have reported that vegetarian diets are associated with a higher prevalence of major depression. Therefore, we hypothesised that the consumption of animal products, especially eggs, may have positive effects on mental health, especially on major depression, because a previous study reported that egg consumption produces numerous beneficial effects in humans. The purpose of the present study was to evaluate the effects of chronic whole-egg treatment on depression-like behaviours in Wistar rats, a control strain, and Wistar Kyoto rats, an animal model of depression.

METHODS

In both the rats, either whole-egg solution (5 ml/kg) or distilled water (5 ml/kg) was orally administrated for 35 days. During these periods, the open-field test (OFT) was conducted on the 21st day, and a forced swimming test (FST) was enforced on the 27th and 28th days. On the 36th day, the plasma and brain were collected.

RESULTS

Chronic whole-egg treatment did not affect line crossing in the OFT, whereas it reduced the total duration of immobility in the FST on both strains. Furthermore, interestingly, the results indicated the possibility that whole-egg treatment elevated the incorporation of tryptophan into the brain, and the tryptophan concentration in the prefrontal cortex was actually increased by the treatment.

CONCLUSION

This study demonstrated that whole-egg treatment exerts an antidepressant-like effect in the FST. It is suggested that whole egg may be an excellent food for preventing and alleviating the conditions of major depression.

Inhibition of tumour cell growth by carnosine: some possible mechanisms

The naturally occurring dipeptide carnosine (β-alanyl-L-histidine) has been shown to inhibit, selectively, growth of transformed cells mediated, at least in part, by depleting glycolytic ATP levels. The mechanism(s) responsible has/have yet to be determined. Here, we discuss a number of probable and/or possible processes which could, theoretically, suppress glycolytic activity which would decrease ATP supply and generation of metabolic intermediates required for continued cell reproduction. Possibilities include effects on (i) glycolytic enzymes, (ii) metabolic regulatory activities, (iii) redox biology, (iv) protein glycation, (v) glyoxalase activity, (vi) apoptosis, (vii) gene expression and (viii) metastasis. It is possible, by acting at various sites that this pluripotent dipeptide may be an example of an endogenous "smart drug".

Effects of beta-alanine supplementation and interval training on physiological determinants of severe exercise performance

INTRODUCTION

We aimed to manipulate physiological determinants of severe exercise performance. We hypothesized that (1) beta-alanine supplementation would increase intramuscular carnosine and buffering capacity and dampen acidosis during severe cycling, (2) that high-intensity interval training (HIT) would enhance aerobic energy contribution during severe cycling, and (3) that HIT preceded by beta-alanine supplementation would have greater benefits.

METHODS

Sixteen active men performed incremental cycling tests and 90-s severe (110 % peak power) cycling tests at three time points: before and after oral supplementation with either beta-alanine or placebo, and after an 11-days HIT block (9 sessions, 4 × 4 min), which followed supplementation. Carnosine was assessed via MR spectroscopy. Energy contribution during 90-s severe cycling was estimated from the O2 deficit. Biopsies from m. vastus lateralis were taken before and after the test.

RESULTS

Beta-alanine increased leg muscle carnosine (32 ± 13 %, d = 3.1). Buffering capacity and incremental cycling were unaffected, but during 90-s severe cycling, beta-alanine increased aerobic energy contribution (1.4 ± 1.3 %, d = 0.5), concurrent with reduced O2 deficit (-5.0 ± 5.0 %, d = 0.6) and muscle lactate accumulation (-23 ± 30 %, d = 0.9), while having no effect on pH. Beta-alanine also enhanced motivation and perceived state during the HIT block. There were no between-group differences in adaptations to the training block, namely increased buffering capacity (+7.9 ± 11.9 %, p = 0.04, d = 0.6, n = 14) and glycogen storage (+30 ± 47 %, p = 0.04, d = 0.5, n = 16).

CONCLUSIONS

Beta-alanine did not affect buffering considerably, but has beneficial effects on severe exercise metabolism as well as psychological parameters during intense training phases.

Effects of essence of chicken on cognitive brain function: a near-infrared spectroscopy study

The aim of this study was to investigate the effects of the essence of chicken on brain function by near-infrared spectroscopy. Twelve healthy elderly subjects took the essence of chicken or a placebo for 7 d in a double-blind cross-over design study. Changes in oxy-hemoglobin concentrations in the bilateral prefrontal areas of the brain were measured while the subjects performed the simple reaction task, the Groton Maze Learning Test, and the working memory task. In the latter case, there were significant interactions in the changes in oxy-hemoglobin concentrations between treatment and period of intake according to two-way repeated ANOVA. The changes in oxy-hemoglobin concentrations significantly increased in several regions of the prefrontal areas of the brain in those taking essence of chicken for 7 d. These results suggest that essence of chicken is useful as a nutritional supplement to enhance or maintain brain function in the elderly.

Changes in brain monoamine metabolism of neonatal chicks under two different acute stress conditions

1. The purpose of the present study was to clarify brain monoamine metabolism during two different conditions of acute stress by quantifying changes in the brain of neonatal chicks exposed to either restraint with isolation, or fasting stress. 2. Under restraint with isolation-induced stress, dopaminergic metabolism was clearly stimulated. 3. During fasting stress, dopaminergic activity, serotonergic and norepinephrinergic metabolisms were stimulated. 4. It was concluded that brain monoamine metabolism of chicks is differentially affected by stressors.