Plasma BDNF and Cytokines Correlated with Protein Biomarkers for Bipolar II Disorder

Chronic exposure to imipramine induces a switch from depression-like to mania-like behavior in female serotonin transporter knockout rats: Role of BDNF signaling in the infralimbic cortex

BACKGROUND

Bipolar disorder (BD) is a highly burdensome psychiatric disorder characterized by alternating states of mania and depression. A major challenge in the clinic is the switch from depression to mania, which is often observed in female BD patients during antidepressant treatment such as imipramine. However, the underlying neural basis is unclear.

METHODS

To investigate the potential neuronal pathways, serotonin transporter knockout (SERT KO) rats, an experimental model of female BD patients, were subjected to a battery of behavioral tests under chronic treatment of the antidepressant imipramine. In addition, the expression of brain-derived neurotrophic factor (BDNF) and its downstream signaling was examined in the prefrontal cortex.

RESULTS

Chronic exposure to imipramine reduced anxiety and sociability and problem-solving capacity, and increased thigmotaxis and day/night activity in all animals, but specifically in female SERT KO rats, compared to female wild-type (WT) rats. Further, we found an activation of BDNF-TrkB-Akt pathway signaling in the infralimbic, but not prelimbic, cortex after chronic imipramine treatment in SERT KO, but not WT, rats.

LIMITATIONS

Repeated testing behaviors could potentially affect the results. Additionally, the imipramine induced changes in behavior and in the BDNF system were measured in separate animals.

CONCLUSIONS

Our study indicates that female SERT KO rats, which mirror the female BD patients with the 5-HTTLPR s-allele, are at higher risk of a switch to mania-like behaviors under imipramine treatment. Activation of the BDNF-TrkB-Akt pathway in the infralimbic cortex might contribute to this phenotype, but causal evidence remains to be provided.

Correlation of potential diagnostic biomarkers (circulating miRNA and protein) of bipolar II disorder

OBJECTIVES

We previously identified certain peripheral biomarkers of bipolar II disorder (BD-II) including circulating miRNAs (miR-7-5p, miR-142-3p, miR-221-5p, and miR-370-3p) and proteins (Matrix metallopeptidase 9 (MMP9), phenylalanyl-tRNA synthetase subunit beta (FARSB), peroxiredoxin 2 (PRDX2), carbonic anhydrase 1 (CA-1), and proprotein convertase subtilisin/kexin type 9 (PCSK9)). We try to explore the connection between these biomarkers.

METHODS

We explored correlations between the peripheral levels of above circulating miRNAs and proteins in our previously collected BD-II (N = 96) patients and control (N = 115) groups. We further searched TargetScan and BioGrid websites to identify direct and indirect interactions between these protein-coding genes and circulating miRNAs.

RESULTS

In the BD-II group, we identified significant correlations between the miR-221-5p and CA-1 (rho = -0.323, P = 0.001), FARSB (rho = 0.251, P = 0.014), MMP-9 (rho = 0.313, P = 0.002) and PCSK9 (rho = 0.252, P = 0.014). The miR-370-3p also significantly correlated with FARSB expression (rho = 0.330, P = 0.001) and PCSK9 expression (rho = 0.221, P = 0.031) in the BD-II group. Our findings were in line with the modulating axis identified from TargetScan and BioGrid, miR-221-5p/CA-1/MMP9 and miR-370-3p/FARSB/PCSK9, suggesting their association with BD-II.

CONCLUSION

Our result supported that peripheral candidate miRNA and protein biomarkers may interact in BD-II. We concluded that miR-221-5p/CA-1/MMP9 and miR-370-3p/FARSB/PCSK9 axes might act a critical role in the pathomechanism of BD-II.

Levels of Matrix Metalloproteinase 9 Are Elevated in Persons With Schizophrenia or Bipolar Disorder: The Role of Modifiable Factors

Background

Matrix metalloproteinases (MMPs) are a diverse set of enzymes associated with inflammation. MMP-9 is of particular interest because it has been associated with autoimmune and cardiopulmonary disorders, tobacco smoking, and obesity, prevalent in psychiatric populations.

Methods

Sensitive enzyme immunoassays measured MMP-9 in blood samples from 1121 individuals (mean age = 35.6 [SD = 13.0] years; 47.7% male; 440 with schizophrenia, 399 with bipolar disorder, and 282 without a psychiatric disorder). We estimated the odds of diagnosis associated with MMP-9, demographic variables, tobacco smoking, and obesity, and also the partial explained variance using regression methods. We also determined the association between psychiatric medications and MMP-9 levels.

Results

Individuals with elevated MMP-9 levels had higher odds of schizophrenia or bipolar disorder compared with the nonpsychiatric group adjusted for demographic variables. Partial correlation analyses indicated the demographic-adjusted variance associated with MMP-9, smoking, obesity, and their interaction explained 59.6% for schizophrenia and 39.9% for bipolar disorder. Levels of MMP-9 were substantially lower in individuals receiving valproate, particularly relatively high doses.

Conclusions

Individuals with higher levels of MMP-9 have significantly higher odds of schizophrenia or bipolar disorder. Individuals receiving valproate had substantially lower levels of MMP-9, possibly related to its ability to inhibit histone deacetylation. A substantial portion of the variance in clinical disorders associated with MMP-9 can be attributed to smoking or obesity. Interventions to reduce smoking and obesity might reduce the morbidity and mortality associated with elevated MMP-9 levels and improve the health outcomes of individuals with these disorders.