The correlation between longitudinal changes in hypothalamic-pituitary-adrenal (HPA)-axis activity and changes in neurocognitive function in mixed-state bipolar II disorder

Microbiota-gut-brain axis mechanisms in the complex network of bipolar disorders: potential clinical implications and translational opportunities

Bipolar disorders (BD) represent a severe leading disabling mental condition worldwide characterized by episodic and often progressive mood fluctuations with manic and depressive stages. The biological mechanisms underlying the pathophysiology of BD remain incompletely understood, but it seems that there is a complex picture of genetic and environmental factors implicated. Nowadays, gut microbiota is in the spotlight of new research related to this kind of psychiatric disorder, as it can be consistently related to several pathophysiological events observed in BD. In the context of the so-called microbiota-gut-brain (MGB) axis, it is shown to have a strong influence on host neuromodulation and endocrine functions (i.e., controlling the synthesis of neurotransmitters like serotonin or mediating the activation of the hypothalamic-pituitary-adrenal axis), as well as in modulation of host immune responses, critically regulating intestinal, systemic and brain inflammation (neuroinflammation). The present review aims to elucidate pathophysiological mechanisms derived from the MGB axis disruption and possible therapeutic approaches mainly focusing on gut microbiota in the complex network of BD. Understanding the mechanisms of gut microbiota and its bidirectional communication with the immune and other systems can shed light on the discovery of new therapies for improving the clinical management of these patients. Besides, the effect of psychiatric drugs on gut microbiota currently used in BD patients, together with new therapeutical approaches targeting this ecosystem (dietary patterns, probiotics, prebiotics, and other novelties) will also be contemplated.

Mixed Depression in the Post-COVID-19 Syndrome: Correlation between Excitatory Symptoms in Depression and Physical Burden after COVID-19

The relationship between depression and post-COVID-19 disease syndrome (post-COVID-19 syndrome) is established. Nevertheless, few studies have investigated the association between post-COVID-19 syndrome and mixed depression, i.e., a specific sub-form of depression characterized by high level of excitatory symptoms. Aims of the present study are: (a) to compare the post-COVID-19 syndrome's burden in depressed and non-depressed patients, and (b) to investigate the correlation between post-COVID-19 syndrome's burden and the severity of mixed depression. One thousand and forty six (n = 1460) subjects with post-COVID-19 syndrome were assessed. Subjects were divided into those with (DEP) or without (CONT) depression. Sociodemographically, post-COVID-19 syndrome's symptoms number and type were compared. In DEP, association between levels of excitatory symptoms and the presence of post-COVID-19 syndrome's symptoms were additionally assessed. DEP showed greater percentages of family history of psychiatric disorders than CONT. DEP showed higher percentages of post-COVID-19 symptoms than CONT. A greater level of excitatory symptoms were associated to higher frequencies of post-COVID-19 syndrome' symptoms. Higher levels of post-COVID-19 syndrome's symptoms in DEP corroborate the evidence of a common pathway between these two syndromes. Presence of excitatory symptoms seem to additionally add a greater illness burden. Such findings might help clinicians choose the appropriate treatment for such states. More specifically, therapies aimed to treat excitatory symptoms, such as antipsychotics and mood stabilizers, might help reduce the illness burden in post-COVID-19 patients with mixed depression.

Differential association of cortisol with visual memory/learning and executive function in Bipolar Disorder

The association of cortisol with cognition has been understudied in Bipolar Disorder (BD); available evidence is inconsistent while it is unknown whether cortisol's effects vary across neurocognitive domains implicating different brain structures. This study aimed to examine the association of cortisol with two cognitive tasks targeting visual memory and executive function (planning) in BD, related to the hippocampus and prefrontal lobe, respectively. Cambridge Neuropsychological Test Automated Battery (CANTAB) tasks targeting paired associative learning (PAL) and planning (Stockings of Cambridge; SOC) were administered to 60 BD type I patients. Basal serum cortisol was also measured. Higher cortisol was associated with worse performance in PAL, but not SOC, after controlling for gender, education, illness duration and treatment with mood stabilizers. This is the first study to examine the association of cortisol with neurocognitive function in BD while controlling for clinicodemographic and treatment-related factors. We found a significant association of cortisol with hippocampal-related visual memory/learning but not with prefrontal lobe-related executive function, suggesting domain-specific underlying mechanisms of cognitive dysfunction in BD. Future studies should further explore cortisol's brain structure-specific effects on cognitive functioning in BD.

Genes involved in glucocorticoid receptor signalling affect susceptibility to mood disorders

OBJECTIVES

In mood disorders chronic stress contributes to decreased glucocorticoid receptor signalling in the brain and resistance in the periphery. We hypothesised that aberrant glucocorticoid receptor function may result from genetic predisposition and that decreased GR signalling in the brain correlates with the expression of genes regulating GR complex formation.

METHODS

We performed the association analysis of 698 patients: 490 patients with bipolar disorder and 208 patients with major depressive disorder and 564 control subjects. We genotyped 11 variants using TaqMan assays. Gene expression in the brain tissue was done in male Wistar rats after chronic mild stress protocol. The SRSF5 serum concentration was performed using ELISA. Data were analysed in Statistica and GraphPad.

RESULTS

We found an association of STIP1 and SRSF5 variants with major depressive disorder and BAG1 variant with bipolar disorder. Gene expression analysis in a rat model of depression confirmed significant changes in the expression of SRSF5, BAG1, and FKBP4 in the brain. For SRSF5, we observed significantly increased expression in the serum of depressed females and male rats exposed to chronic stress.

CONCLUSIONS

Our results indicate the involvement of genes associated with GR function, SRSF5, BAG1, and FKBP4 with susceptibility to mood disorders.

Neurobiology of bipolar disorders: a review of genetic components, signaling pathways, biochemical changes, and neuroimaging findings

Bipolar disorder (BD) is a chronic mental illness characterized by changes in mood that alternate between mania and hypomania or between depression and mixed states, often associated with functional impairment. Although effective pharmacological and non-pharmacological treatments are available, several patients with BD remain symptomatic. The advance in the understanding of the neurobiology underlying BD could help in the identification of new therapeutic targets as well as biomarkers for early detection, prognosis, and response to treatment in BD. In this review, we discuss genetic, epigenetic, molecular, physiological and neuroimaging findings associated with the neurobiology of BD. Despite the advances in the pathophysiological knowledge of BD, the diagnosis and management of the disease are still essentially clinical. Given the complexity of the brain and the close relationship between environmental exposure and brain function, initiatives that incorporate genetic, epigenetic, molecular, physiological, clinical, environmental data, and brain imaging are necessary to produce information that can be translated into prevention and better outcomes for patients with BD.

The Neurobiology of Mixed States

Interest in the coexistence of manic and depressive symptoms fostered hypotheses on neurobiological underpinnings of mixed states. Neurobiological properties of mixed states, however, have not been comprehensively described. The authors searched databases for articles on neurobiological markers related to mixed states. Results showed that mixed states are characterized by elevated central and peripheral monoamine levels, greater alterations in hypothalamic-pituitary-adrenal axis, increased inflammation, and greater circadian rhythms dysfunction than nonmixed forms. Furthermore, the magnitude of pathophysiologic alterations in mixed states exceeds those associated with nonmixed mania or depression and suggest that hyperactivation and hyperarousal are core features of mixed states.