Carnosine ameliorates stress-induced glucose metabolism disorder in restrained mice

Antidepressant activity of phytochemicals of Mangifera indica seeds assisted by integrated computational analysis

Mangifera indica L., also known as mango, is a tropical fruit that belongs to the Anacardiaceae family and is prized for its juiciness, unique flavour, and worldwide popularity. The current study aimed to probe into antidepressant power (ADP) of MIS in animals and confirmation of ADP with in silico induced-fit molecular docking. The depression model was prepared by exposing mice to various stressors from 9:00 am to 2:00 pm during 42 days study period. MIS extract and fluoxetine were given daily for 30 min before exposing animals to stressors. ADP was evaluated by various behavioural tests and biochemical analysis. Results showed increased physical activity in mice under behavioural tests, plasma nitrite and malondialdehyde (MDA) levels and monoamine oxidase A (MAO-A) activity decreased dose-dependently in MIS treated mice and superoxide dismutases (SOD) levels increased in treated groups as compared to disease control. With the peculiar behaviour and significant interactions of the functional residues of target proteins with selected ligands along with the best absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties, it is concluded that catechin could be the best MAO-A inhibitor at a binding energy of -8.85 kcal/mol, and two hydrogen bonds were generated with Cys406 (A) and Gly443 (A) residues of the active binding site of MAO-A enzyme. While catechin at -6.86 kcal/mol generated three hydrogen bonds with Ala263 (A) and Gly434 (A) residues of the active site of monoamine oxidase B (MAO-B) enzyme and stabilized the best conformation. Therefore, it is highly recommended to test the selected lead-like compound catechin in the laboratory with biological system analysis to confirm its activity as MAO-A and MAO-B inhibitors so it can be declared as one of the novel therapeutic options with anti-depressant activity. Our findings concluded that M. indica seeds could be a significant and alternative anti-depressant therapy.

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.

Cecal Metabolomic Fingerprint of Unscathed Rats: Does It Reflect the Good Response to a Provocative Decompression?

On one side, decompression sickness (DCS) with neurological disorders lead to a reshuffle of the cecal metabolome of rats. On the other side, there is also a specific and different metabolomic signature in the cecum of a strain of DCS-resistant rats, that are not exposed to hyperbaric protocol. We decide to study a conventional strain of rats that resist to an accident-provoking hyperbaric exposure, and we hypothesize that the metabolomic signature put forward may correspond to a physiological response adapted to the stress induced by diving. The aim is to verify and characterize whether the cecal compounds of rats resistant to the provocative dive have a cecal metabolomic signature different from those who do not dive. 35 asymptomatic diver rats are selected to be compared to 21 rats non-exposed to the hyperbaric protocol. Because our aim is essentially to study the differences in the cecal metabolome associated with the hyperbaric exposure, about half of the rats are fed soy and the other half of maize in order to better rule out the effect of the diet itself. Lower levels of IL-1β and glutathione peroxidase (GPX) activity are registered in blood of diving rats. No blood cell mobilization is noted. Conventional and ChemRICH approaches help the metabolomic interpretation of the 185 chemical compounds analyzed in the cecal content. Statistical analysis show a panel of 102 compounds diet related. 19 are in common with the hyperbaric protocol effect. Expression of 25 compounds has changed in the cecal metabolome of rats resistant to the provocative dive suggesting an alteration of biliary acids metabolism, most likely through actions on gut microbiota. There seem to be also weak changes in allocations dedicated to various energy pathways, including hormonal reshuffle. Some of the metabolites may also have a role in regulating inflammation, while some may be consumed for the benefit of oxidative stress management.

Natural and Synthetic Agents Targeting Reactive Carbonyl Species against Metabolic Syndrome

Reactive carbonyl species (RCS) may originate from the oxidation of unsaturated fatty acids and sugar in conditions of pathology. They are known to have high reactivity towards DNA as well as nucleophilic sites of proteins, resulting in cellular dysfunction. It has been considered that various pathological conditions are associated with an increased level of RCS and their reaction products. Thus, regulating the levels of RCS may be associated with the mitigation of various metabolic and neurodegenerative disorders. In order to perform a comprehensive review, various literature databases, including MEDLINE, EMBASE, along with Google Scholar, were utilized to obtain relevant articles. The voluminous review concluded that various synthetic and natural agents are available or in pipeline research that hold tremendous potential to be used as a drug of choice in the therapeutic management of metabolic syndrome, including obesity, dyslipidemia, diabetes, and diabetes-associated complications of atherosclerosis, neuropathy, and nephropathy. From the available data, it may be emphasized that various synthetic agents, such as carnosine and simvastatin, and natural agents, such as polyphenols and terpenoids, can become a drug of choice in the therapeutic management for combating metabolic syndromes that involve RCS in their pathophysiology. Since the RCS are known to regulate the biological processes, future research warrants detailed investigations to decipher the precise mechanism.

Metformin Attenuates the Metabolic Disturbance and Depression-like Behaviors Induced by Corticosterone and Mediates the Glucose Metabolism Pathway

BACKGROUND

Metabolism disturbances are common in patients with depression. The drug metformin has been reported to exhibit antidepressant activity. The purpose of this study was to investigate metabolism disturbances induced by corticosterone (CORT) and determine if metformin can reverse these effects and their accompanying depression-like behaviors.

METHODS

Rats were exposed to corticosterone with or without metformin administration. Depression-like behaviors were tested. Gene expression was confirmed by quantitative real-time polymerase chain reaction (qRT-PCR) and western blot analysis. In addition, the metabolites were quantified by LC-MS/MS analysis.

RESULTS

Metformin attenuated the depression-like behaviors induced by CORT. Furthermore, metformin reversed disturbances in body weight, serum glucose, and triglyceride levels, as well as hepatic TG levels induced by CORT. Metformin normalized the alterations in the expression of glucose metabolism-related genes (PGC-1α, G6pc, Pepck, Gck, PYGL, Gys2, PKLR, GLUT4) and insulin resistance-related genes (AdipoR1, AdipoR2) in the muscles and livers of rats induced by CORT. Metabolomic analysis showed that metformin reversed the effects of CORT on 11 metabolites involved in the pathways of the tricarboxylic acid cycle, glycolysis, and gluconeogenesis (3-phospho-D-glycerate, β-D-fructose 6-phosphate, D-glucose 6-phosphate, and pyruvate).

CONCLUSION

Our findings suggest that metformin can attenuate metabolism disturbances and depression-like behaviors induced by CORT mediating the glucose metabolism pathway.

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.

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.

Effects of cross-fostering and developmental exposure to mixtures of environmental contaminants on hepatic gene expression in prepubertal 21 days old and adult male Sprague-Dawley rats

The notion that adverse health effects produced by exposure to environmental contaminants (EC) may be modulated by the presence of non-chemical stressors is gaining attention. Previously, our lab demonstrated that cross-fostering (adoption of a litter at birth) acted as a non-chemical stressor that amplified the influence of developmental exposure to EC on the glucocorticoid stress-response in adult rats. Using liver from the same rats, the aim of the current study was to investigate whether cross-fostering might also modulate EC-induced alterations in hepatic gene expression profiles. During pregnancy and nursing, Sprague-Dawley dams were fed cookies laced with corn oil (control, C) or a chemical mixture (M) composed of polychlorinated biphenyls (PCB), organochlorine pesticides (OCP), and methylmercury (MeHg), at 1 mg/kg/day. This mixture simulated the contaminant profile reported in maternal human blood. At birth, some control and M treated litters were cross-fostered to form two additional groups with different biological/nursing mothers (CC and MM). The hepatic transcriptome was analyzed by DNA microarray in male offspring at postnatal days 21 and 78-86. Mixture exposure altered the expression of detoxification and energy metabolism genes in both age groups, but with different sets of genes affected at day 21 and 78-86. Cross-fostering modulated the effects of M on gene expression pattern (MM vs M), as well as expression of energy metabolism genes between control groups (CC vs C). In conclusion, while describing short and long-term effects of developmental exposure to EC on hepatic transcriptomes, these cross-fostering results further support the consideration of non-chemical stressors in EC risk assessments.

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.

A SIRT3/AMPK/autophagy network orchestrates the protective effects of trans-resveratrol in stressed peritoneal macrophages and RAW 264.7 macrophages

Resveratrol gains a great interest for its strong antioxidant properties, while the molecular mechanisms underlie the beneficial effects on psychosocial stress remain controversial. In this study, we demonstrated that resveratrol protected peritoneal macrophages and RAW 264.7 cells from stress-induced decrease in the total cell count, phagocytic capability, reactive oxygen species generation, monodansylcadaverine and mitochondrial membrane potential in stressed mice. Resveratrol promoted stress-induced autophagy in both models. Modulation of autophagy by rapamycin or 3-methyladenine regulated the protective effect of resveratrol, suggesting a role of autophagy in the protective mechanisms of resveratrol. The comparison studies revealed that distinct mechanisms were implicated in the protective effect of resveratrol and other antioxidants (vitamin C and edaravone). Resveratrol promoted autophagy via upregulating SIRT3 expression and phosphorylation of AMP-activated protein kinase (AMPK). Knockdown of SIRT3 resulted in decreased autophagy and abolished protective effect of resveratrol. SIRT1 was also involved in the protective mechanism of resveratrol, although its effect on autophagy was unnoticeable. Pharmacological manipulation of autophagy modulated the effects of resveratrol on SIRT3 and AMPK, revealing the engagement of a positive feedback loop. In sharp contrast, vitamin C and edaravone effectively protected macrophages from stress-induced cytotoxicity, accompanied by downregulated SIRT3 expression and AMPK phosphorylation, and decreased level of autophagy response. Taken together, we conclude that a SIRT3/AMPK/autophagy network orchestrates in the protective effect of resveratrol in macrophages.

Silymarin Prevents Restraint Stress-Induced Acute Liver Injury by Ameliorating Oxidative Stress and Reducing Inflammatory Response

Silymarin is a flavonoid extracted from the milk thistle Silybum marianum. It has been reported to prevent liver injuries induced by various chemicals or toxins. Our recent study suggested that silymarin induces hepatic synthesis of glutathione by increasing cysteine availability, which may consequently contribute to increased antioxidant capacity of the liver. In the present study, we investigated the effects of silymarin on acute liver injury induced by restraint stress. Silymarin (100 mg/kg) was orally administered to BALB/c mice every 12 h (3 times in total). After the last dose, mice were subjected to restraint stress for 6 h, and serum levels of aspartate and alanine aminotransferases, and hepatic levels of lipid peroxidation were determined. Hepatic levels of sulfur-containing metabolites such as methionine, S-adenosylmethionine, cysteine, and glutathione were also measured. The level of pro-inflammatory mediators in both liver and serum was determined. To study the mechanism of the effects of silymarin, we assessed Jun N-terminal kinase (JNK) activation and apoptotic signaling. Restraint stress induced severe oxidative stress and increased mRNA levels of pro-inflammatory mediators; both effects of restraint stress were significantly inhibited by silymarin. Moreover, administration of silymarin significantly prevented acute liver injury induced by restraint stress by blocking JNK activation and subsequently apoptotic signaling. In conclusion, these results suggest that the inhibition of restraint stress-induced liver injury by silymarin is due at least in part to its anti-oxidant activity and its ability to suppress the inflammatory response.

Chronic corticosterone exposure reduces hippocampal glycogen level and induces depression-like behavior in mice

Long-term exposure to stress or high glucocorticoid levels leads to depression-like behavior in rodents; however, the cause remains unknown. Increasing evidence shows that astrocytes, the most abundant cells in the central nervous system (CNS), are important to the nervous system. Astrocytes nourish and protect the neurons, and serve as glycogen repositories for the brain. The metabolic process of glycogen, which is closely linked to neuronal activity, can supply sufficient energy substrates for neurons. The research team probed into the effects of chronic corticosterone (CORT) exposure on the glycogen level of astrocytes in the hippocampal tissues of male C57BL/6N mice in this study. The results showed that chronic CORT injection reduced hippocampal neurofilament light protein (NF-L) and synaptophysin (SYP) levels, induced depression-like behavior in male mice, reduced hippocampal glycogen level and glycogen synthase activity, and increased glycogen phosphorylase activity. The results suggested that the reduction of the hippocampal glycogen level may be the mechanism by which chronic CORT treatment damages hippocampal neurons and induces depression-like behavior in male mice.

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.

Phloridzin improves lipoprotein lipase activity in stress-loaded mice via AMPK phosphorylation

Long-term stress exposure can lead to disturbed homeostasis and cause many life-style diseases. Phloridzin possesses various bioactivities, but the understanding of the effects of phloridzin on stress-related lipid metabolism disorder is limited. Our results demonstrate that phloridzin improved plasma lipoprotein lipase (LPL) activity and triglyceride metabolism in restrained mice. A decrease of angiopoietin-like protein 4 (ANGPTL4) mRNA expression and an increase of AMP-activated protein kinase (AMPK) phosphorylation were observed after phloridzin treatment. After inhibiting AMPK phosphorylation, the effects of phloridzin on the amelioration of plasma LPL activity and suppression of ANGPTL4 expression were blocked. In addition, cardiac AMPK phosphorylation, plasma LPL activity and ANGPTL4 expression were also affected by phloridzin, even if the glucocorticoid receptor was blocked. Taken together, the down-regulation of ANGPTL4 expression by phloridzin was probably via a direct activation of AMPK pathway. This discovery can provide a biochemical and nutritional basis for the use of phloridzin-containing food and beverage in daily life.

Biological functions of histidine-dipeptides and metabolic syndrome

The rapid increase in the prevalence of metabolic syndrome, which is associated with a state of elevated systemic oxidative stress and inflammation, is expected to cause future increases in the prevalence of diabetes and cardiovascular diseases. Oxidation of polyunsaturated fatty acids and sugars produces reactive carbonyl species, which, due to their electrophilic nature, react with the nucleophilic sites of certain amino acids. This leads to formation of protein adducts such as advanced glycoxidation/lipoxidation end products (AGEs/ALEs), resulting in cellular dysfunction. Therefore, an effective reactive carbonyl species and AGEs/ALEs sequestering agent may be able to prevent such cellular dysfunction. There is accumulating evidence that histidine containing dipeptides such as carnosine (β-alanyl-L-histidine) and anserine (β-alanyl-methyl-L-histidine) detoxify cytotoxic reactive carbonyls by forming unreactive adducts and are able to reverse glycated protein. In this review, 1) reaction mechanism of oxidative stress and certain chronic diseases, 2) interrelation between oxidative stress and inflammation, 3) effective reactive carbonyl species and AGEs/ALEs sequestering actions of histidine-dipeptides and their metabolism, 4) effects of carnosinase encoding gene on the effectiveness of histidine-dipeptides, and 5) protective effects of histidine-dipeptides against progression of metabolic syndrome are discussed. Overall, this review highlights the potential beneficial effects of histidine-dipeptides against metabolic syndrome. Randomized controlled human studies may provide essential information regarding whether histidine-dipeptides attenuate metabolic syndrome in humans.

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".

Anti-Depressant Like Effect of Methyl Gallate Isolated from Acer barbinerve in Mice

In the present study, the anti-depressant like effect of methyl gallate (MG) isolated from the stem bark of Acer barbinerve was examined in ICR mice. Body weight (BDW) and blood glucose (BDG) levels significantly decreased in the repeated restraint stress (RRS) group (2 h/day for 14 days) compared to the no stress (NS) group. To examine the effect of MG on RS-induced BDW loss and hypoglycemia, MG (10 mg/kg) and the anti-depressant fluoxetine (10 mg/kg) were administered daily for 14 days. Orally administered MG and fluoxetine significantly attenuated the RS-induced BDW loss and hypoglycemia. Interestingly, MG administered mice showed increased BDG levels in the normal and glucose feeding condition. Chronic RS-subjected mice showed immobilized and depressed behaviors. The effect of MG on the depressed behaviors was evaluated using the tail-suspension test (TST) and the forced swimming test (FST). In both tests, RS-induced immobilized behaviors were significantly reversed in MG and fluoxetine administered groups. Taken together, MG significantly attenuated the RS-induced BDW loss, hypoglycemia, and depressed behaviors. Considering that decreased BDG levels (hypoglycemia) can cause depression, MG may exert its anti-depressant like effect by preventing hypoglycemia. Our results suggest that MG isolated from A. barbinerve can exert anti-depressant like effect, and could be used as a new and natural anti-depressant therapy.

Theacrine, a purine alkaloid obtained from Camellia assamica var. kucha, attenuates restraint stress-provoked liver damage in mice

Theacrine (1,3,7,9-tetramethyluric acid), a purine alkaloid, has proven to be beneficial in maintaining several brain functions and is being studied for potential medicinal uses in recent years. In this study, we isolated theacrine from Camellia assamica var. kucha and investigated its protective effects on liver damage induced by restraint stress in mice. Results showed that 18 h of restraint stress could induce liver damage, with an obvious increase in levels of plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST). This finding was further confirmed by hepatic pathological examination, which showed inflammatory cell infiltration and focal necrosis of hepatocytes. However, oral administration of theacrine (10, 20, 30 mg/kg for 7 consecutive days) was found to decrease plasma ALT and AST levels, reduce hepatic mRNA levels of inflammatory mediators (IL-1β, TNF-α, IL-6, and IFN-γ), and reverse the histologic damages in stressed mice. Simultaneously, theacrine also significantly decreased the content of malondialdehyde and increased oxygen radical absorbance capacity (ORAC) level in the plasma and liver of stressed mice. These results suggested that the protective effects of theacrine on stress-induced liver damage might be correlated with its antioxidative activity. The antioxidative capacity of theacrine was further evaluated by in vitro ORAC and cellular antioxidant activity assay. The results suggested that the antioxidative capacity of theacrine was not due to the direct action on free radical clearance. Moreover, the elevated activities and gene expressions of superoxide dismutase, catalase, and glutathione peroxidase, as well as the reduced activity of xanthine oxidase by theacrine treatment in stressed mice suggested that the antioxidative activity might be due to the strengthening of the antioxidant system in vivo. On the basis of the above results, theacrine is possibly a good candidate for protecting against or treating lifestyle diseases and might contribute to the study of natural products.