Ke Cheng

Plasma Metabonomics as a Novel Diagnostic Approach for Major Depressive Disorder

Major depressive disorder (MDD) is a socially detrimental psychiatric disorder, contributing to increased healthcare expenditures and suicide rates. However, no empirical laboratory-based tests are available to support the diagnosis of MDD. In this study, a NMR-based plasma metabonomic method for the diagnosis of MDD was tested. Proton nuclear magnetic resonance ((1)H NMR) spectra of plasma sampled from first-episode drug-naı̈ve depressed patients (n = 58) and healthy controls (n = 42) were recorded and analyzed by orthogonal partial least-squares discriminant analysis (OPLS-DA). The OPLS-DA score plots of the spectra demonstrated that the depressed patient group was significantly distinguishable from the healthy control group. Moreover, the method accurately diagnosed blinded samples (n = 26) in an independent replication cohort with a sensitivity and specificity of 92.8% and 83.3%, respectively. Taken together, NMR-based plasma metabonomics may offer an accurate empirical laboratory-based method applicable to the diagnosis of MDD.

Proteomics reveals energy and glutathione metabolic dysregulation in the prefrontal cortex of a rat model of depression

Major depressive disorder (MDD) is a prevalent debilitating psychiatric mood that contributes to increased rates of disability and suicide. However, the pathophysiology underlying MDD remains poorly understood. A growing number of studies have associated dysfunction of the prefrontal cortex (PFC) with depression, but no proteomic study has been conducted to assess PFC protein expression in a preclinical model of depression. Using the chronic unpredictable mild stress (CUMS) rat model of depression, differential protein expression between the PFC proteomes of CUMS and control rats was assessed through two-dimensional electrophoresis followed by matrix-assisted laser desorption ionization-time of flight-tandem mass spectrometry. Differential protein expression was analyzed for Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway over-representation. Four differential proteins were selected for Western blotting validation. Twenty-nine differential proteins were identified in the PFC of CUMS rats relative to control rats. Through KEGG analysis, energy and glutathione metabolic pathways were determined to be the most significantly altered biological pathways. Two of the four differential proteins selected for Western blotting validation - glyoxalase 1 and dihydropyrimidinase-related protein 2 - were found to be significantly downregulated in CUMS relative to control rats. In conclusion, proteomic analysis reveals that energy and glutathione metabolism are the most significantly altered biological pathways in the CUMS rat model of depression. Further investigation on these processes and proteins in the PFC is key to a better understanding of the underlying pathophysiology of MDD.

Reduced neurogenesis and pre-synaptic dysfunction in the olfactory bulb of a rat model of depression

A variety of evidence has a connection with hippocampal neurogenesis in the pathophysiology of depression. However, whether other neurogenic regions in the adult central nervous system would likewise be involved is a highly interesting question. The olfactory bulb (OB) is one of the post-developmental neurogenesis areas in the adult mammalian brain. Clinical studies have shown a decreased olfactory sensitivity in depressed patients, and a recent study disclosed cases of reduced OB volume in acute major depression, indicating the OB may be also affected. Here, animal models are superior to human studies, which may provide further insight into such complex processes. We therefore investigated OB neurogenesis using a chronic unpredictable mild stress (CUMS) rat model of depression. Considering the functional analysis of adult neurogenesis which has been carried out at the synaptic level as well as animal behavior level, we detected pre-synaptic and olfactory function in the OB of rats after 4 weeks of chronic stress. Immunohistochemistry and Western blot analysis showed a dramatic reduction of immature neurons marked by polysialylated neural cell adhesion molecule and doublecortin as well as mature neurons labeled by neuronal nuclei. Moreover, chronic stress down-regulated the expression of synaptophsin but up-regulated syntaxin in the OB, as demonstrated by Western blot, whereas a significant variation at the mRNA level was lacking. Notably, in the rat model of depression, both a decreased OB volume and olfactory dysfunction were present at the same time, which is consistent with clinical findings in depressed patients. In summary, reduced OB neurogenesis and pre-synaptic dysfunction were observed in the rat model, which may at least in part correspond to the reduced OB volume and olfactory malfunction in patients suffering from depression.

Amino acid metabolic dysfunction revealed in the prefrontal cortex of a rat model of depression

Major depressive disorder (MDD) is a debilitating mood disorder. However, the molecular mechanism(s) underlying depression remain largely unknown. Here, we applied a GC-MS-based metabonomic approach in the chronic unpredictable mild stress (CUMS) model, a well-established rodent model of depression, to investigate significant metabolic changes in the rat prefrontal cortex (PFC). Multivariate statistical analysis - including principal component analysis, partial least squares-discriminate analysis, and pair-wise orthogonal projections to latent structures discriminant - was applied to identify differential PFC metabolites between CUMS rats and healthy controls. As compared to healthy control rats, CUMS rats were characterized by lower levels of isoleucine and glycerol in combination with higher levels of N-acetylaspartate and β-alanine. These findings should provide insight into the pathophysiological mechanism(s) underlying MDD and preliminary leads relevant to diagnostic biomarker discovery for depression.

Age- and Sex-Based Hematological and Biochemical Parameters for Macaca fascicularis

Background The cynomolgus monkey (Macaca fascicularis) has been increasingly used in biomedical research, making knowledge of its blood-based parameters essential to support the selection of healthy subjects and its use in preclinical research. As age and sex affect these blood-based parameters, it is important to establish baseline indices for these parameters on an age and sex basis and determine the effects of age and sex on these indices. Methods A total of 917 cynomolgus monkeys (374 males and 543 females) were selected and segregated by age (five groups) and sex. A total of 30 hematological and 22 biochemical parameters were measured, and the effects of age and sex were analyzed. Results Baseline indices for hematological and biochemical parameters were separately established by age and sex. Significant effects by age, sex, and age-sex interaction were observed in a number of blood parameters. In the 49–60 months and 61–72 months age groups, red blood cell count, hemoglobulin, and hematocrit showed significantly lower values (P<0.01) in females than males. Serum alkaline phosphatase varied with age in both sexes (P<0.01) and was significantly higher in females than males (P<0.05) in the groups aged 13–24 months and 25–36 months; however, in the three groups aged over 25–36 months, serum alkaline phosphatase was significantly lower in females than males (P<0.01). Creatinine concentration increased with age (P<0.01) in all age groups; specifically in the groups aged 49–60 months and 61–72 months, creatinine was significantly higher (P<0.01) in males than females. Total protein and globulin both increased with age (P<0.01). Conclusion The baseline values of hematological and biochemical parameters reported herein establish reference indices of blood-based parameters in the cynomolgus monkey by age and sex, thereby aiding researchers in selecting healthy subjects and evaluating preclinical studies using this species.

Increased apoptosis and different regulation of pro-apoptosis protein bax and anti-apoptosis protein bcl-2 in the olfactory bulb of a rat model of depression

Reduced olfactory bulb (OB) volume and olfactory sensitivity have been observed in depressed patients, the exact mechanisms underlying, however, are still unknown. Our previous study found that decreased neurogenesis and pre-synaptic dysfunction in the OB of a rat model of depression may be responsible for the phenomena. Nevertheless, whether the apoptosis would also play a certain role in this process is not clear. In this study, we investigated the apoptosis in the OB of a chronic unpredictable mild stress (CUMS) rat model of depression using terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining. Simultaneously, the pro-apoptosis protein bax and anti-apoptosis protein bcl-2 were detected by Western blot. The results showed that the number of TUNEL-positive cells increased dramatically in the glomerular layer of the OB of the CUMS rats, accompanied with up-regulated expression of bax protein and down-regulated expression of bcl-2 protein. The findings indicate that increased apoptosis may be attributed to explain at some level for the reduced OB volume and olfactory dysfunction in depressed patients. Moreover, the mitochondria-dependent death pathway might be involved in apoptosis in the OB of the CUMS rats.

Construction and Validation of a Systematic Ethogram of Macaca fascicularis in a Free Enclosure

Behavioral studies in non-human primates have become ideal models for further investigations into advanced cognitive function in humans. To date, there is no systematic ethogram of the cynomolgus monkey (Macaca fascicularis) in a free enclosure. In a field observation of 6012 subjects, 107 distinct behaviors of M. fascicularis were preliminarily described. 83 of these behaviors were then independently validated through a randomized cohort and classified into 12 behavioral categories. 53 of these behaviors were then selected to accurately reflect the daily mundane activity of the species in a free enclosure. These findings systematically document the behavior of M. fascicularis in a free enclosure for use in further investigations.

Elevated host lipid metabolism revealed by iTRAQ-based quantitative proteomic analysis of cerebrospinal fluid of tuberculous meningitis patients.

PURPOSE Tuberculous meningitis (TBM) remains to be one of the most deadly infectious diseases. The pathogen interacts with the host immune system, the process of which is largely unknown. Various cellular processes of Mycobacterium tuberculosis (MTB) centers around lipid metabolism. To determine the lipid metabolism related proteins, a quantitative proteomic study was performed here to identify differential proteins in the cerebrospinal fluid (CSF) obtained from TBM patients (n = 12) and healthy controls (n = 12). METHODS CSF samples were desalted, concentrated, labelled with isobaric tags for relative and absolute quantitation (iTRAQ™), and analyzed by multi-dimensional liquid chromatography-tandem mass spectrometry (LC-MS/MS). Gene ontology and proteomic phenotyping analysis of the differential proteins were conducted using Database for Annotation, Visualization, and Integrated Discovery (DAVID) Bioinformatics Resources. ApoE and ApoB were selected for validation by ELISA. RESULTS Proteomic phenotyping of the 4 differential proteins was invloved in the lipid metabolism. ELISA showed significantly increased ApoB levels in TBM subjects compared to healthy controls. Area under the receiver operating characteristic curve analysis demonstrated ApoB levels could distinguish TBM subjects from healthy controls and viral meningitis subjects with 89.3% sensitivity and 92% specificity. CONCLUSIONS CSF lipid metabolism disregulation, especially elevated expression of ApoB, gives insights into the pathogenesis of TBM. Further evaluation of these findings in larger studies including anti-tuberculosis medicated and unmedicated patient cohorts with other center nervous system infectious diseases is required for successful clinical translation.

Effects of gut microbiota on the microRNA and mRNA expression in the hippocampus of mice

Backgrounds Gut microbiota is increasingly recognized as an important environmental factor that could influence the brain function and behaviors through the microbiota‐gut‐brain axis. Method Here, we used the germ‐free (GF) mice to explore the effect of gut microbiota on hippocampal microRNA (miRNA) and messenger RNAs (mRNAs) expression. Results Behavioral tests showed that, compared to specific pathogen‐free (SPF) mice, the GF mice displayed more center time, center distance and less latency to familiar food. Colonization of the GF mice with gut microbiota from SPF mice did not reverse these behaviors. However, 7 differentially expressed miRNAs and 139 mRNAs were significantly restored. Through microRNA Target Filter analysis, 4 of 7 restored miRNAs had 2232 target mRNAs. Among these target mRNAs, 21 target mRNAs levels were decreased. Further analysis showed that the most significant GO terms were metabolic process (GO: 0008152), binding (GO: 0005488) and cell part (GO: 0044464) for biological process, molecular function and cellular component, respectively, and the most significantly altered pathway was axon guidance (mmu04360). Conclusions These findings indicated that colonization of gut microbiota to adolescent GF mice was not sufficient to reverse the behavioral alterations. Gut microbiota could significantly influence the expression levels of miRNAs and mRNAs in hippocampus. Our results could provide original and valuable data for researchers to further study the microbiota‐gut‐brain axis. Highlights7 miRNA in the hippocampus was related with gut microbiota.139 mRNA in the hippocampus was related with gut microbiota.4 miRNA and 21 target mRNAs resulted in 22 miRNA‐mRNA interactions.

Differential urinary metabolites related with the severity of major depressive disorder

&NA; Major depressive disorder (MDD) is a common mental disorder that affects a persons general health. However, there is still no objective laboratory test for diagnosing MDD. Here, an integrated analysis of data from our previous studies was performed to identify the differential metabolites in the urine of moderate and severe MDD patients. A dual platform approach (NMR spectroscopy and GC–MS) was used. Consequently, 14 and 22 differential metabolites responsible for separating moderate and severe MDD patients, respectively, from their respective healthy controls (HCs) were identified. Meanwhile, the moderate MDD‐specific panel (N‐Methylnicotinamide, Acetone, Choline, Citrate, vanillic acid and azelaic acid) and severe MDD‐specific panel (indoxyl sulphate, Taurine, Citrate, 3‐hydroxyphenylacetic acid, palmitic acid and Lactate) could discriminate moderate and severe MDD patients, respectively, from their respective HCs with high accuracy. Moreover, the differential metabolites in severe MDD were significantly involved in three metabolic pathways and some biofunctions. These results showed that there were divergent urinary metabolic phenotypes in moderate and severe MDD patients, and the identified potential urinary biomarkers might be useful for future developing objective diagnostic tests for MDD diagnosis. Our results could also be helpful for researchers to study the pathogenesis of MDD. HighlightsModerate MDD‐specific panel consisting of five metabolites was identified.Severe MDD‐specific panel consisting of five metabolites was identified.Moderate and severe MDD patients have divergent urinary metabolic phenotypes.