Promising avenues of therapeutics for bipolar illness

Toward a neurocircuit-based sequential transcranial magnetic stimulation treatment of pediatric bipolar II disorder

BACKGROUND

Abnormalities in large-scale neuronal networks-the frontoparietal central executive network (CEN)-are consistent findings in bipolar disorder and potential therapeutic targets for transcranial magnetic stimulation (TMS).

OBJECTIVE

The present study aimed to assess the effects of CEN neurocircuit-based sequential TMS on the clinical symptoms and cognitive functions of adolescents with bipolar II disorder.

METHODS

The study was a single-blinded, randomized, placebo-control trial. Participants with DSM-5-defined bipolar disorder II were recruited and randomized to receive either a sham treatment (n = 20) or an active TMS treatment (n = 22). The active group patients were taking medication, with intermittent theta burst stimulation (iTBS) treatment provided as adjunctive treatment targeting the left DLPFC, the left ITG, and the left PPC nodes consecutively. Patients completed the measurements of HAMD and the Das-Naglieri Cognition Assessment System at baseline and 3 weeks after the intervention.

RESULTS

A significant group-by-time interaction was observed in the HAMD, total cognition, and planning. Post-hoc analysis revealed that patients in the active group significantly improved HAMD scores following neurostimulation. Moreover, within-subject analysis indicated that the active group significantly improved in scores of total cognition and planning, while the sham group did not. No significant differences were seen in the other cognitive measures.

CONCLUSION

The neurocircuit-based sequential TMS protocol targeting three CEN nodes, in conjunction with medication, safely and effectively improved depressive symptoms and cognitive function in adolescents with bipolar II disorder.

Novel routes to bipolar disorder drug discovery

INTRODUCTION

Bipolar disorder (BD) is a severe and chronic medical condition typified by episodic recurrent mania (or hypomania) in addition to major depression. BD is associated with a number of negative outcomes including premature death, reduced quality of life and can also lead to other complications including impaired cognitive function. Unfortunately, the currently available pharmacological treatments for BD are insufficient for many with the condition.

AREAS COVERED

This review focuses on known therapeutic targets of mood stabilizing drugs including: the glycogen synthase kinase-3 (GSK-3), the phosphoinositide pathway and protein kinase C (PKC), the brain-derived neurotrophic factor (BDNF), and histone deacetylases (HDACs). This article also presents new promising therapeutic targets including: the glutamatergic pathway, mitochondrial modulators, neuropeptide-converting endopeptidases, the insulin transduction pathway, the purinergic system and the melatoninergic system.

EXPERT OPINION

Challenges in improving methods and tools to generate, integrate and analyze high-dimensional data are required to allow opening novel routes to BD drug discovery. Through the application of systems biology approaches and the use of bioinformatical tools to integrate all omics data, it will be possible in the near future to gain deeper insights into pathophysiology of BD. This will in turn lead to the identification and exploitation of new potential therapeutic approaches.

Brain glutamatergic characteristics of pediatric offspring of parents with bipolar disorder

We wished to determine whether decreases in prefrontal glutamate concentrations occur in offspring of parents with bipolar disorder with and at high risk for mania. Sixty children and adolescents, 9-18 years old, of parents with bipolar I or II disorder (20 offspring with established history of mania, "BD", 20 offspring with symptoms subsyndromal to mania, "SS", and 20 healthy controls "HC") were examined using proton magnetic resonance spectroscopy at 3T to study glutamatergic metabolite concentrations in the anterior cingulate cortex (ACC). A signal for reductions in absolute glutamate concentrations in the ACC was seen in the BD compared with HC and SS groups. No other statistically significant differences among groups were found. Offspring of parents with BD with prior histories of mania may have disruptions in glutamatergic function compared with HC or children at risk for BD who have not yet developed mania. Longitudinal studies are necessary to confirm whether prefrontal glutamate decreases only after the onset of full mania.

The potential use of biomarkers as an adjunctive tool for staging bipolar disorder

Recent data show that biomarkers differ in early and late-stage bipolar disorder (BD). Here we propose a model of staging for bipolar disorder that emphasizes the potential use of biomarkers for differentiating early and late-stage BD patients in the inter-episodic period. The proposed model includes a Latent phase: patients at "ultra-high-risk" for developing BD, characterized by a family history of BD, temperament traits, mood, and anxiety symptoms as well as genetic vulnerability for developing the disorder; Stage I: patients who return to their baseline level of functioning when mood episodes resolve; Stage II: biomarkers and functioning impairment are related to comorbidities or rapid-cycling presentations; Stage III: persistent cognitive and functioning impairment in the inter-episode period as well as changes in biomarkers; and Stage IV: same findings as in Stage III associated with extreme cognitive and functioning impairment, to the point that patients are unable to live autonomously. Empirical testing will determine the ability of the present model to inform patients and clinicians about both prognosis and response to treatment.