Stable Isotope-Resolved Metabolomics Reveals the Abnormal Brain Glucose Catabolism in Depression Based on Chronic Unpredictable Mild Stress Rats

Stevioside Ameliorates Prenatal Obesity Induced Postpartum Depression: The Potential Role of Gut Barrier Homeostasis

SCOPE

Postpartum depression and cognitive impairment are the common complications of prenatal obesity. Stevioside is a non-nutritive natural sweetener with antioxidant and anti-inflammatory. However, its effects on depression behaviors and cognitive impairment induced by a high-fat diet (HFD) remain unclear.

METHODS AND RESULTS

An 8-week HFD is used to establish a prenatal obesity model in female C57BL/6J mice to explore the improvement effects of stevioside (0.5 mg mL-1 in drinking water) on maternal depression and cognitive dysfunction after weaning. The results demonstrated that stevioside improves behavioral performance of obese maternal mice, and inhibits neuronal damage and 5-hydroxytryptamine (5-HT) abnormality induced by HFD. In addition, stevioside inhibits oxidative stress by reducing malondialdehyde (MDA) and increasing superoxide dismutase (SOD) and glutathione (GSH) activities in the brains of obese maternal mice. Additionally, stevioside improves gut barrier integrity and prevented lipopolysaccharide (LPS) extravasation, and alleviates neuroinflammation. Correlation analysis shows that gut barrier and serum LPS are closely related to behavioral performance and brain biochemical indicators.

CONCLUSION

Stevioside is capable to prevent prenatal obesity-induced cognitive and mood disorders by restoring intestinal barrier damage and inhibiting inflammation.

Stable Isotope Tracer Technique and Network Pharmacology to Reveal Antidepressant Targets and Active Components of Xiaoyao San

In recent years, the research of mitochondrial dysfunction in depression has drawn the focus of researchers. Our research group previously found that Xiaoyao San (XYS) has improved the mitochondrial structure and the blocked tricarboxylic acid cycle (TCA cycle) in the hippocampal tissue of chronic unpredictable mild stress (CUMS) rats. However, the specific targets and active components of XYS remain unclear, and the potential to improve hippocampal mitochondrial TCA cycle disorder was also unexplored. In this research, a strategy to combine stable isotope-resolved metabolomics (SIRM), network pharmacology and transmission electron microscopy (TEM) was used to explore the potential, targets of action, and active components of XYS to improve hippocampal mitochondrial TCA cycle disorder of CUMS rats. The results of TEM showed that the ultrastructure of hippocampal mitochondria could be improved by XYS. A combination of SIRM and molecular docking showed that pyruvate carboxylase (PC), ATP citrate lyase (ACLK), glutamate dehydrogenase (GLDH), glutamate oxaloacetate transaminase (GOT) and pyruvate dehydrogenase (PDH) were targets of XYS to improve TCA cycle disorder. In addition, troxerutin was found to be the most potential active component of XYS to improve TCA cycle disorder. The above research results can provide new insights for the development of antidepressant drugs.

Mitochondria in depression: The dysfunction of mitochondrial energy metabolism and quality control systems

BACKGROUND

Depression is the most disabling neuropsychiatric disorder, causing difficulties in daily life activities and social interactions. The exact mechanisms of depression remain largely unclear. However, some studies have shown that mitochondrial dysfunction would play a crucial role in the occurrence and development of depression.

AIMS

To summarize the known knowledge about the role of mitochondrial dysfunction in the pathogenesis of depression.

METHODS

We review the recent literature， including 105 articles, to summarize the mitochondrial energy metabolism and quality control systems in the occurrence and development of depression. Some antidepressants which may exert their effects by improving mitochondrial function are also discussed.

RESULTS

Impaired brain energy metabolism and (or) damaged mitochondrial quality control systems have been reported not only in depression patients but in animal models of depression. Although the classical antidepressants have not been specially designed to target mitochondria, the evidence suggests that many antidepressants may exert their effects by improving mitochondrial function.

CONCLUSIONS

This brief review focuses on the findings that implicate mitochondrial dysfunction and the quality control systems as important etiological factors in the context of depressive disorders. It will help us to understand the various concepts of mitochondrial dysfunction in the pathogenesis of depression, and to explore novel and more targeted therapeutic approaches for depression.

Transcutaneous auricular vagus nerve stimulation ameliorates adolescent depressive- and anxiety-like behaviors via hippocampus glycolysis and inflammation response

BACKGROUND

Transcutaneous auricular vagus nerve stimulation (taVNS) is a crucial neuromodulation therapy for depression, yet its molecular mechanism remains unclear. Here, we aim to unveil the underlying mechanisms of antidepression by systematically evaluating the change of gene expression in different brain regions (i.e., hippocampus, anterior cingulate cortex, and medial prefrontal cortex).

METHODS

The adolescent depression rat model was established by chronic unpredictable mild stress (CUMS), followed by the taVNS treatment for 3 weeks. The open field test (OFT), forced swimming test (FST), elevated plus maze test (EPM), and new object recognition (NOR) test were used to evaluate depressive- and anxiety-like behaviors. Gene expression analysis of three brain regions was conducted by RNA sequencing (RNA-seq) and further bioinformatics methods.

RESULTS

The depressive- and anxiety-like behaviors in CUMS-exposed rats were manifested by decreased spontaneous locomotor activity of OFT, increased immobility time of FST, increased entries and time in the closed arms of EPM, and decreased new object index of NOR. Furthermore, CUMS exposure also led to alterations in gene expression within the hippocampus (HIP), anterior cingulate cortex (ACC), and medial prefrontal cortex (mPFC), suggesting a potential link between adolescent stress and pathological changes within these brain regions. TaVNS could significantly ameliorate depressive- and anxiety-like behaviors. Its effects on these three brain regions were found related to regulation of the metabolism, and there were some brain region-specific findings. Compared with ACC and mPFC, taVNS has a more concrete effect on HIP by regulating the inflammation response and glycolysis.

CONCLUSION

taVNS is capable of ameliorating adolescent depressive- and anxiety-like behaviors by regulating plenty of genes in the three brain regions. Suppressed level of inflammatory response and enhanced glycolysis manifests the dominant role of taVNS in HIP, which provides a theoretical foundation and data support for the molecular mechanism of antidepression by taVNS.

Recent Progress in Mass Spectrometry-Based Metabolomics in Major Depressive Disorder Research

Major depressive disorder (MDD) is a serious mental illness with a heavy social burden, but its underlying molecular mechanisms remain unclear. Mass spectrometry (MS)-based metabolomics is providing new insights into the heterogeneous pathophysiology, diagnosis, treatment, and prognosis of MDD by revealing multi-parametric biomarker signatures at the metabolite level. In this comprehensive review, recent developments of MS-based metabolomics in MDD research are summarized from the perspective of analytical platforms (liquid chromatography-MS, gas chromatography-MS, supercritical fluid chromatography-MS, etc.), strategies (untargeted, targeted, and pseudotargeted metabolomics), key metabolite changes (monoamine neurotransmitters, amino acids, lipids, etc.), and antidepressant treatments (both western and traditional Chinese medicines). Depression sub-phenotypes, comorbid depression, and multi-omics approaches are also highlighted to stimulate further advances in MS-based metabolomics in the field of MDD research.

Paclitaxel Induces Neurotoxicity by Disrupting Tricarboxylic Acid Cycle Metabolic Balance in the Mouse Hippocampus

Objective

It is well known that paclitaxel (PTX)-induced neurotoxicity seriously affects the quality of life of patients and is the main reason for reducing the dose of chemotherapy or even stopping chemotherapy. The current data are limited, and further information is required for practice and verification. The aims of this study were to clarify the molecular mechanism underlying PTX-induced neurotoxicity by combining in vivo and in vitro metabolomics studies and provide new targets for the prevention and treatment of PTX-induced neurotoxicity.

Methods

In the in vivo study, a PTX-induced neurotoxicity mouse model was established by intraperitoneal injection of PTX (6 mg/kg every three days) for two consecutive weeks. After verification by water maze tests and HE staining of pathological sections, hippocampal metabolites were measured and the differential metabolites and related metabolic pathways were identified by multivariate statistical analysis. In the in vitro study, we investigated the effects of PTX on mouse hippocampal neuron cells, assessing the concentration and time of administration by MTT assays. After modeling, the relevant metabolites in the TCA cycle were quantified by targeted metabolomics using stable isotope labeling. Finally, the key enzymes of the TCA cycle in tissues and cells were verified by RT-PCR.

Results

Administration of PTX to model mice resulted in neurological damage, shown by both water-maze tests and hippocampal tissue sections. Twenty-four metabolites and five associated metabolic pathways were found to differ significantly between the hippocampal tissues of the model and control groups. These included metabolites and pathways related to the TCA cycle and pyruvate metabolism. Metabolomics analysis using stable isotope labeling showed significant changes in metabolites associated with the TCA cycle compared with the control group (P < 0.05). Finally, RT-PCR verified that the expression of key enzymes in the TCA cycle was changed to different degrees in both hippocampal tissues and cells.

Conclusion

Our results showed that PTX neurotoxicity in hippocampal tissue and neuron cells was associated with inhibition of the TCA cycle. This inhibition leads to brain insufficiency and impaired metabolism, resulting in various neurotoxic symptoms.

Metabolic Alterations and Related Biological Functions of Post-Stroke Depression in Ischemic Stroke Patients

Background

Post-stroke depression (PSD) is one of the most common neuropsychiatric complications after stroke. However, the underlying mechanisms of PSD remain ambiguous, and no objective diagnosis tool is available to diagnose PSD. Previous metabolomic studies on PSD included patients with ischemic and hemorrhagic stroke indiscriminately, which is not conducive to elucidating and predicting the occurrence of PSD. The aim of this study is to elucidate the pathogenesis of PSD and provide potential diagnostic markers for PSD in ischemic stroke patients.

Methods

In total, 51 ischemic stroke patients at 2 weeks were included in this study. Those with depressive symptoms were assigned to the PSD group, while the others were assigned to the non-PSD group. Plasma metabolomics based on liquid chromatography-mass spectrometry (LC-MS) was performed to explore the differential plasma metabolites between the PSD and non-PSD groups.

Results

Principal component analysis (PCA), partial least squares discriminant analysis (PLS-DA) and orthogonal partial least-squares discriminant analysis (OPLS-DA) showed significant metabolic alterations between PSD patients and non-PSD patients. In total, 41 differential metabolites were screened out, mainly including phosphatidylcholines (PCs), L-carnitine and acyl carnitines, succinic acid, pyruvic acid and L-lactic acid. Metabolite-related pathway analysis revealed that alanine, aspartate and glutamate metabolism, glycerophospholipid metabolism and the citrate cycle (TCA cycle) may contribute to the pathogenesis of PSD. A panel of three signature metabolites [PC(22:5(7Z,10Z,13Z,16Z,19Z)/15:0), LysoPA(18:1(9Z)/0:0) and 1,5-anhydrosorbitol] was determined as potential biomarkers for PSD in ischemic stroke patients.

Conclusion

These findings are conducive to providing new insights into the pathogenesis of PSD and developing objective diagnostic tools for PSD in ischemic stroke patients.

Reduced energy metabolism contributing to aging of skeletal muscle by serum metabolomics and gut microbiota analysis

AIMS

Sarcopenia is an age-related syndrome characterized by a gradual loss of the muscle mass, strength, and function. It is associated with a high risk of adverse consequences such as poorer quality of life, falls, disability and mortality among the elderly. The aim in this study is to investigate the pathological mechanism of sarcopenia.

MAIN METHODS

The aging of skeletal muscle was investigated by the D-galactose induced accelerated aging model combining with constrained motion. After 10 weeks, muscle function and gastrocnemius muscle index, and morphology of muscle fibers were evaluated, and myostatin, IGF-1 and ATP in skeletal muscle were also determined. Then the mechanism of aging-related skeletal muscle dysfunctions was investigated based on untargeted serum metabolomics and 16S rRNA gene sequencing. Four key metabolites were validated by the D-galactose-induced C2C12 senescent cell model in vitro.

KEY FINDINGS

Results showed that gastrocnemius muscle mass was decreased significantly, morphology of muscle fibers was altered, and muscle function was damaged in the aged group. Furthermore, increased MSTN, and decreased IGF-1 and ATP were also observed in the aging skeletal muscle. Importantly, alteration of the key pathways including riboflavin biosynthesis and energy metabolism contributed to the aging of skeletal muscle. Four key metabolites, including riboflavin, α-ketoglutaric acid and two dicarboxylic acids, which were involved in these metabolic pathways, could promote the proliferation of C2C12 cells.

SIGNIFICANCE

These findings provide novel insights into pathological mechanism of sarcopenia, and will facilitate the development of therapeutic and preventive strategies for sarcopenia.

A novel insight for high-rate and low-efficiency glucose metabolism in depression through stable isotope-resolved metabolomics in CUMS-induced rats

BACKGROUND

Existing research has suggested that depression results in disorders of glucose metabolism in the organism which causing insufficient energy supply. However, the overall changes in glucose metabolism that arise from depression have not been clarified.

METHODS

In this study, the depression-like behavior in chronically unpredictable mild stressed rats was investigated, and the fate of glucose was tracked through isotope tracing and mass spectrometry, with a focus on metabolite changes in cecal contents.

RESULTS

As indicated by the results, the isotopic results of cecal contents can indicate the metabolic end of the organism. Moreover, the TCA cycle activity was notably reduced, and the gluconeogenesis pathway was abnormally up-regulated in the CUMS-induced rats. The organism expedited other glucose metabolism pathways to make up for the insufficiency of energy. As a result, the activity of the inefficient glycolysis pathway was increased.

LIMITATIONS

Existing research has only investigated the metabolism of 13C-glucose, and lipids and proteins have been rarely explored.

CONCLUSIONS

The chronic unpredictable mild stress can inhibit the entry of pyruvate into mitochondria in SD rats, such that the activity of TCA is reduced, and insufficient energy supply is caused. The organism is capable of expediting other glucose metabolism rate pathways to make up for the insufficiency of energy, whereas it still cannot compensate for the loss of energy. As a result, CUMS-induced rats exhibited high-rate and low-efficiency glucose metabolism.

A unique insight for Xiaoyao San exerts antidepressant effects by modulating hippocampal glucose catabolism using stable isotope-resolved metabolomics

ETHNOPHARMACOLOGICAL RELEVANCE

In traditional Chinese medicine (TCM) theory, depression is an emotional disease, which is thought to be related to stagnation of liver qi and dysfunction of the spleen in transport. Xiaoyao San (XYS) is considered to have the effects of soothing liver-qi stagnation and invigorating the spleen. The spleen has the function to transport and transform nutrients. The liver has also termed the center of energy metabolism in the body. Therefore, exploring the antidepressant effects of XYS from the perspective of energy metabolism may reveal new findings.

AIM OF THE STUDY

Glucose catabolism is an important part of energy metabolism. In recent years, several researchers have found that XYS can exert antidepressant effects by modulating abnormalities in glucose catabolism-related metabolites. The previous research of our research group found that the hippocampus glucose catabolism was disordered in depression. However, the antidepressant potential of XYS through modulating the disorders of hippocampal glucose catabolism and the specific metabolic pathways and targets of XYS action were still unknown. The aim of this study was to address the above scientific questions.

MATERIALS AND METHODS

In this research, the CUMS (chronic unpredictable mild stress) model was used as the animal model of depression. The antidepressant effect of XYS was evaluated by behavioral indicators. The specific pathways and targets of XYS modulating the disorders of glucose catabolism in the hippocampus of CUMS rats were obtained by stable isotope-resolved metabolomics. Further, the isotope tracing results were also verified by molecular biology and electron transmission electron microscopy.

RESULTS

The results demonstrated that XYS pretreatment could significantly improve the depressive symptoms induced by CUMS. More importantly, it was found that XYS could modulate the disorders of glucose catabolism in the hippocampus of CUMS rats. Stable isotope-resolved metabolomics and enzyme activity tests showed that Lactate dehydrogenase (LDH), Pyruvate carboxylase (PC), and Pyruvate dehydrogenase (PDH) were targets of XYS for modulating the disorders of glucose catabolism in the hippocampus of CUMS rats. The Succinate dehydrogenase (SDH) and mitochondrial respiratory chain complex V (MRCC-Ⅴ) were targets of XYS to improve abnormal mitochondrial oxidative phosphorylation in the hippocampus of CUMS rats. XYS was also found to have the ability to improve the structural damage of mitochondria and nuclei in the hippocampal caused by CUMS.

CONCLUSIONS

This study was to explore the antidepressant effect of XYS from the perspective of glucose catabolism based on a strategy combining stable isotope tracing, molecular biology techniques, and transmission electron microscopy. We not only obtained the specific pathways and targets of XYS to improve the disorders of glucose catabolism in the hippocampus of CUMS rats, but also revealed the specific targets of the pathways of XYS compared with VLF.

Low levels of serum LDH are associated with depression and suicide attempts

BACKGROUND

A huge body of evidence has signaled a correlation between adult depression and energy metabolism. The key links are the energy supply and substrates for brain energy metabolism and the crucial signaling molecule lactate. Nevertheless, the association between lactate metabolism and depression remains elusive.

OBJECTIVE

The primary objective of this study was to explore the difference in serum LDH levels between patients with major depressive disorder (MDD) and the normal population and to determine whether LDH can be employed as a predictor of suicide attempt (SA) in MDD patients.

METHODS

Serum LDH levels were measured in 232 patients with MDD and 110 healthy controls. Depressive symptoms were assessed using the 24-item Hamilton Depression Scale (HAMD-24). The data were collected and analyzed with SPSS 22.0.

RESULTS

The serum LDH level of the control group was (196.50 ± 34.40) U/L, while that of the MDD group was (177.94 ± 25.89) U/L (P < 0.001). Notably, the LDH level [(169.96 ± 25.31) U/L] in the SA group was significantly lower than that in the control and non-SA groups [(181.25 ± 25.47) U/L] (P < 0.01); There was no significant correlation with HAMD-24 score (P > 0.05). Collectively, this study demonstrated that a decrease in serum LDH levels is an independent risk factor for SA in MDD patients.

CONCLUSION

Our results imply that a decrease in LDH levels may be associated with MDD and suicidal behaviors. Early identification of suicide risk and evaluation of the prognosis of depression is critical.

Tryptophan-5-HT pathway disorder was uncovered in the olfactory bulb of a depression mice model by metabolomic analysis

Major depression (MD) is a severe mental illness that creates a heavy social burden, and the potential molecular mechanisms remain largely unknown. Lots of research demonstrate that the olfactory bulb is associated with MD. Recently, gas chromatography-mass spectrometry-based metabolomic studies on depressive rats indicated that metabolisms of purine and lipids were disordered in the olfactory bulb. With various physicochemical properties and extensive concentration ranges, a single analytical technique could not completely cover all metabolites, hence it is necessary to adopt another metabolomic technique to seek new biomarkers or molecular mechanisms for depression. Therefore, we adopted a liquid chromatography-mass spectrometry metabonomic technique in the chronic mild stress (CMS) model to investigate significant metabolic changes in the olfactory bulb of the mice. We discovered and identified 16 differential metabolites in the olfactory bulb of the CMS treatments. Metabolic pathway analysis by MetaboAnalyst 5.0 was generated according to the differential metabolites, which indicated that the tryptophan metabolism pathway was the core pathogenesis in the olfactory bulb of the CMS depression model. Further, the expressions of tryptophan hydroxylase (TpH) and aromatic amino acid decarboxylase (AAAD) were detected by western blotting and immunofluorescence staining. The expression of TpH was increased after CMS treatment, and the level of AAAD was unaltered. These results revealed that abnormal metabolism of the tryptophan pathway in the olfactory bulb mediated the occurrence of MD.

Novel targets for ameliorating energy metabolism disorders in depression through stable isotope-resolved metabolomics

The severe harm of depression to human health and life has attracted global attention, but the exact mechanism is not yet known due to the complicated pathogenesis. The existing antidepressants are far from ideal, indicating it is urgently needed to seek safe and effective drugs from a unique perspective. Based on the hypothesis of "mitochondrial dysfunction" proposed recently, we attempt to focus on the substrates supply of energy metabolism. We applied stable isotope-resolved metabolomics, and revealed that significantly decreased TCA cycle and abnormally increased gluconeogenesis pathway in CUMS rats. Pyruvate dehydrogenase (PDH) and pyruvate carboxylase (PC) maybe the key metabolic enzymes. This metabolic reprogramming was confirmed through ELISA assays and Western blot analysis. To explore the causes of substrates supply disorder in depression, we conducted the mitochondrial structure-function evaluation. Interestingly, the levels of the mitochondrial pyruvate carrier (MPC) decreased significantly, which is essential for the entry of pyruvic acid into the TCA cycle. Together, MPC, PDH and PC are expected to become potential novel therapeutic targets for treating depressive disorders. This research provides a unique insight for re-cognizing the pathological mechanisms of depression, the novel targets for development of ideal antidepressants, as well as a paradigm for deciphering abnormal metabolic pathways in other metabolic diseases.

Stable Isotope-Resolved Metabolomics Studies on Corticosteroid-Induced PC12 Cells: A Strategy for Evaluating Glucose Catabolism in an in Vitro Model of Depression

Depression is a common psychopathological state or mood disorder syndrome. The serious risks to human life and the inadequacy of the existing antidepressant drugs have driven us to understand the pathogenesis of depression from a new perspective. Our research group has found disturbances in glucose catabolism in both depression and nephrotic syndrome. What are the specific metabolic pathways and specificities of glucose catabolism disorders caused by depression? To address the above scientific questions, we creatively combined traditional metabolomics technology with stable isotope-resolved metabolomics to research the glucose catabolism of the corticosterone-induced PC12 cell damage model and the adriamycin-induced glomerular podocyte damage model. The results showed an increased flux of pyruvate metabolism in depression. The increased flux of pyruvate metabolism led to an activation of gluconeogenesis in depression. The disturbed upstream metabolism of succinate caused the tricarboxylic acid cycle (TCA cycle) to be blocked in depression. In addition, there were metabolic disturbances in the purine metabolism and pentose phosphate pathways in depression. Compared with nephrotic syndrome, pyruvate metabolism, the TCA cycle, and gluconeogenesis metabolism in depression were specific. The metabolic pathways researched above are likely to be important targets for the efficacy of antidepressants.