Genetic differences between bipolar disorder subtypes: A systematic review focused in bipolar disorder type II

Escherichia coli alcohol dehydrogenase YahK is a protein that binds both iron and zinc

Background

Previous studies have highlighted the catalytic activity of Escherichia coli alcohol dehydrogenase YahK in the presence of coenzyme nicotinamide adenine dinucleotide (NAD) and metal zinc. Notably, competitive interaction between iron and zinc ligands has been shown to influence the catalytic efficiency of several key proteases. This study aims to unravel the intricate mechanisms underlying YahK's catalytic action, with a particular focus on the pivotal roles played by metal ions zinc and iron.

Methods

The purified YahK protein from E. coli cells cultivated in LB medium was utilized to investigate its metal-binding properties through UV-visible absorption measurements and determination of metal content. Subsequently, the effects of excess zinc and iron on the metal-binding ability and alcohol dehydrogenase activity of the YahK protein were explored using M9 minimal medium. Furthermore, site-directed mutagenesis technology was employed to determine the iron-binding site location within the YahK protein. Polyacrylamide gel electrophoresis was conducted to examine the relationship between iron and zinc with respect to the YahK protein.

Results

The study confirmed the presence of iron and zinc in the YahK protein, with the zinc-bound form exhibiting enhanced catalytic activity in alcohol dehydrogenation reactions. Conversely, the presence of iron appears to play a pivotal role in maintaining overall stability of the YahK protein. Furthermore, experimental findings indicate that excessive zinc within M9 minimal medium can competitively bind to iron-binding sites on YahK, thereby augmenting its alcohol dehydrogenase activity.

Conclusion

The dynamic binding of YahK to iron and zinc unveils its intricate regulatory mechanism as an alcohol dehydrogenase, thereby highlighting the possible physiological role of YahK in E. coli and its significance in governing cellular metabolic processes. This discovery provides a novel perspective for further investigating the specific impact of metal ion binding on YahK and E. coli cell metabolism.

Pathophysiological Mechanisms of Psychosis-Induced Atrial Fibrillation: The Links between Mental Disorder and Arrhythmia

Atrial fibrillation (AF) is a common phenomenon of sustained arrhythmia leading to heart failure or stroke. Patients with mental disorders (MD), particularly schizophrenia and bipolar disorder, are at a high risk of AF triggered by the dysregulation of the autonomic nervous system, atrial stretch, oxidative stress, inflammation, and electrical or structural remodeling. Moreover, pathophysiological mechanisms underlying MD may also contribute to the genesis of AF. An overactivated hypothalamic-pituitary-adrenal axis, aberrant renin-angiotensin-aldosterone system, abnormal serotonin signaling, disturbed sleep, and genetic/epigenetic factors can adversely alter atrial electrophysiology and structural substrates, leading to the development of AF. In this review, we provide an update of our collective knowledge of the pathophysiological and molecular mechanisms that link MD and AF. Targeting the pathogenic mechanisms of MD-specific AF may facilitate the development of therapeutics that mitigate AF and cardiovascular mortality in this patient population.

Progress and Implications from Genetic Studies of Bipolar Disorder

With the advancements in gene sequencing technologies, including genome-wide association studies, polygenetic risk scores, and high-throughput sequencing, there has been a tremendous advantage in mapping a detailed blueprint for the genetic model of bipolar disorder (BD). To date, intriguing genetic clues have been identified to explain the development of BD, as well as the genetic association that might be applied for the development of susceptibility prediction and pharmacogenetic intervention. Risk genes of BD, such as CACNA1C, ANK3, TRANK1, and CLOCK, have been found to be involved in various pathophysiological processes correlated with BD. Although the specific roles of these genes have yet to be determined, genetic research on BD will help improve the prevention, therapeutics, and prognosis in clinical practice. The latest preclinical and clinical studies, and reviews of the genetics of BD, are analyzed in this review, aiming to summarize the progress in this intriguing field and to provide perspectives for individualized, precise, and effective clinical practice.

White and gray matter alterations in bipolar I and bipolar II disorder subtypes compared with healthy controls - exploring associations with disease course and polygenic risk

Patients with bipolar disorder (BD) show alterations in both gray matter volume (GMV) and white matter (WM) integrity compared with healthy controls (HC). However, it remains unclear whether the phenotypically distinct BD subtypes (BD-I and BD-II) also exhibit brain structural differences. This study investigated GMV and WM differences between HC, BD-I, and BD-II, along with clinical and genetic associations. N = 73 BD-I, n = 63 BD-II patients and n = 136 matched HC were included. Using voxel-based morphometry and tract-based spatial statistics, main effects of group in GMV and fractional anisotropy (FA) were analyzed. Associations between clinical and genetic features and GMV or FA were calculated using regression models. For FA but not GMV, we found significant differences between groups. BD-I patients showed lower FA compared with BD-II patients (ptfce-FWE = 0.006), primarily in the anterior corpus callosum. Compared with HC, BD-I patients exhibited lower FA in widespread clusters (ptfce-FWE < 0.001), including almost all major projection, association, and commissural fiber tracts. BD-II patients also demonstrated lower FA compared with HC, although less pronounced (ptfce-FWE = 0.049). The results remained unchanged after controlling for clinical and genetic features, for which no independent associations with FA or GMV emerged. Our findings suggest that, at a neurobiological level, BD subtypes may reflect distinct degrees of disease expression, with increasing WM microstructure disruption from BD-II to BD-I. This differential magnitude of microstructural alterations was not clearly linked to clinical and genetic variables. These findings should be considered when discussing the classification of BD subtypes within the spectrum of affective disorders.

Differential characteristics of bipolar I and II disorders: a retrospective, cross-sectional evaluation of clinical features, illness course, and response to treatment

BACKGROUND

The distinction between bipolar I and bipolar II disorder and its treatment implications have been a matter of ongoing debate. The aim of this study was to examine differences between patients with bipolar I and II disorders with particular emphasis on the early phases of the disorders.

METHODS

808 subjects diagnosed with bipolar I (N = 587) or bipolar II disorder (N = 221) according to DSM-IV criteria were recruited between April 1994 and March 2022 from tertiary-level mood disorder clinics. Sociodemographic and clinical variables concerning psychiatric and medical comorbidities, family history, illness course, suicidal behavior, and response to treatment were compared between the bipolar disorder types.

RESULTS

Bipolar II disorder patients were more frequently women, older, married or widowed. Bipolar II disorder was associated with later "bipolar" presentation, higher age at first (hypo)mania and treatment, less frequent referral after a single episode, and more episodes before lithium treatment. A higher proportion of first-degree relatives of bipolar II patients were affected by major depression and anxiety disorders. The course of bipolar II disorder was typically characterized by depressive onset, early depressive episodes, multiple depressive recurrences, and depressive predominant polarity; less often by (hypo)mania or (hypo)mania-depression cycles at onset or during the early course. The lifetime clinical course was more frequently rated as chronic fluctuating than episodic. More patients with bipolar II disorder had a history of rapid cycling and/or high number of episodes. Mood stabilizers and antipsychotics were prescribed less frequently during the early course of bipolar II disorder, while antidepressants were more common. We found no differences in global functioning, lifetime suicide attempts, family history of suicide, age at onset of mood disorders and depressive episodes, and lithium response.

CONCLUSIONS

Differences between bipolar I and II disorders are not limited to the severity of (hypo)manic syndromes but include patterns of clinical course and family history. Caution in the use of potentially mood-destabilizing agents is warranted during the early course of bipolar II disorder.

Thalamic nuclei volumes in schizophrenia and bipolar spectrum disorders - Associations with diagnosis and clinical characteristics

BACKGROUND

The thalamus is central to brain functions ranging from primary sensory processing to higher-order cognition. Structural deficits in thalamic association nuclei such as the pulvinar and mediodorsal nuclei have previously been reported in schizophrenia. However, the specificity with regards to clinical presentation, and whether or not bipolar disorder (BD) is associated with similar alterations is unclear.

METHODS

We investigated thalamic nuclei volumes in 334 patients with schizophrenia spectrum disorders (SSD) (median age 29 years, 59 % male), 322 patients with BD (30 years, 40 % male), and 826 healthy controls (HC) (34 years, 54 % male). Volumes of 25 thalamic nuclei were extracted from T1-weighted magnetic resonance imaging using an automated Bayesian segmentation method and compared between groups. Furthermore, we explored associations with clinical characteristics across diagnostic groups, including psychotic and mood symptoms and medication use, as well as diagnostic subtype in BD.

RESULTS

Significantly smaller volumes were found in the mediodorsal, pulvinar, and lateral and medial geniculate thalamic nuclei in SSD. Similarly, smaller volumes were found in BD in the same four regions, but mediodorsal nucleus volume alterations were limited to its lateral part and pulvinar alterations to its anterior region. Smaller volumes in BD compared to HC were seen only in BD type I, not BD type II. Across diagnoses, having more negative symptoms was associated with smaller pulvinar volumes.

CONCLUSIONS

Structural alterations were found in both SSD and BD, mainly in the thalamic association nuclei. Structural deficits in the pulvinar may be of relevance for negative symptoms.

Determinants of three-year clinical outcomes in real-world outpatients with bipolar disorder: The multicenter treatment survey for bipolar disorder in psychiatric outpatient clinics (MUSUBI)

BACKGROUND

There is limited evidence regarding predictors of long-term clinical outcomes in patients with bipolar disorder (BD). The objective of this study was to describe 3-year clinical outcomes and identify their predictors from participants in the multicenter treatment survey for BD in psychiatric outpatient clinics (MUSUBI).

METHODS

The MUSUBI was a naturalistic study investigating patients with BD in real-world clinical practice. Our study extracted data regarding 1647 outpatients with BD from 2016, 2017, and 2019 as baseline, 1-year, and 3-year assessments. As clinical outcomes, we assessed the presence of time ill (depressive and manic) during the 1 year prior to the 3-year assessment and durable remission (53 weeks or more) prior to the 3-year assessment.

RESULTS

Participants with durable remission prior to the 3-year assessment had significant associations with diagnosis of a personality disorder and duration of continuous remission at baseline. Regarding the presence of depressive symptoms during the 1 year prior to the 3-year assessment, work status, Global Assessment of Functioning (GAF) scores, suicidal ideation, and duration of continuous remission at baseline had significant associations with this outcome.

CONCLUSIONS

At the 3-year assessment, 19.3% of participants (318/1647) achieved durable remission, while 47.5% of them (782/1647) were not remitted. Our findings can help clinicians predict the illness course of BD by understanding demographic and clinical characteristics.

Outcomes of Hospitalized Acute Alcoholic Hepatitis (AH) in Patients With Bipolar 1 Disorder (B1D)

Introduction: Alcoholic hepatitis (AH) is a common cause of hospital admissions and is associated with a high mortality rate. AH occurs frequently in patients with heavy alcohol use. Alcohol use disorder (AUD) commonly presents with comorbid psychiatric disorders such as bipolar disorder. Bipolar disorder patients are also known to be at an increased risk for chronic liver diseases. Bipolar 1 disorder (B1D) is often considered the most severe presentation among different types of bipolar disorder. This study assesses the clinical outcomes of patients admitted for AH with concomitant B1D.

Methods: Adult patients with AH were identified within the 2014 National Inpatient Sample (NIS) database. International Classification of Diseases, Ninth Edition Revision, Clinical Modification (ICD-9 CM) codes were used to select for all of the diagnoses for this study. AH patients were subdivided into those with and without B1D. The outcomes of interest were sepsis, hepatic encephalopathy, acute respiratory failure, acute kidney injury, ischemic stroke, hepatic failure, coagulopathy, and inpatient mortality. A multivariate logistic regression analysis was performed to explore whether B1D is an independent predictor for the outcomes.

Results: Among 4,453 patients with AH identified, 166 patients also had B1D. AH patients with comorbid B1D were seen to be younger (42.9 years old vs. 46.2 years old, p < 0.05) and more commonly female (55.4% vs. 36.5%, p < 0.05). The B1D subgroup of AH patients were found to less likely develop acute hepatic failure (adjusted odds ratio (aOR) 0.13, 95% confidence interval (CI): 0.02-0.97, p < 0.05). The adjusted odds ratios for the remaining outcomes were not statistically significant.

Conclusions: Our study indicates that B1D may be an independent protective factor against acute hepatic failure in patients hospitalized with AH. This finding can be explained by frequent laboratory monitoring and psychiatric assessments performed by psychiatrists treating B1D patients, as well as the impact B1D has on cortisol release induced by hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis.

Zebrafish as a potential non-traditional model organism in translational bipolar disorder research: Genetic and behavioral insights

Bipolar disorder (BD) is a severe and debilitating illness that affects 1-2% of the population worldwide. BD is characterized by recurrent and extreme mood swings, including mania/hypomania and depression. Animal experimental models have been used to elucidate the mechanisms underlying BD and different strategies have been proposed to assess BD-like symptoms. The zebrafish (Danio rerio) has been considered a suitable vertebrate system for modeling BD-like responses, due to the genetic tractability, molecular/physiological conservation, and well-characterized behavioral responses. In this review, we discuss how zebrafish-based models can be successfully used to understand molecular, biochemical, and behavioral alterations paralleling those found in BD. We also outline some advantages and limitations of this aquatic species to examine BD-like phenotypes in translational neurobehavioral research. Overall, we reinforce the use of zebrafish as a promising tool to investigate the neural basis associated with BD-like behaviors, which may foster the discovery of novel pharmacological therapies.

Risk of cancer in bipolar disorder and the potential role of lithium: International collaborative systematic review and meta-analyses

We examined bipolar disorder (BD) as a risk factor for developing cancer and the role of lithium on cancer incidence. We conducted two systematic review and meta-analyses of population-based studies providing data on these associations. We screened articles indexed in MEDLINE, Scopus, Embase, and PsycINFO up to August 2020. The first random-effects meta-analysis, based on 4,910,661 individuals from nine studies estimated an increased risk of cancer of any kind [RR = 1.24 (1.05-1.46); p < 0.01], especially breast cancer [RR = 1.33 (1.15-1.55); p < 0.01] in BD. The second random-effects meta-analysis, based on 2,606,187 individuals from five studies did not show increased risk of cancer in people with BD using lithium, and even suggested a small protective effect both in overall [RR = 0.94 (0.72-1.22); p = 0.66] and urinary cancer [RR = 0.93 (0.75-1.14); p = 0.48] although these findings did not reach statistical significance. The current evidence highlights that cancer risk is increased in individuals with BD, particularly breast cancer in women. Lithium may have a potential protective effect on cancer, including urinary cancer. The role of lithium as a mainstay of treatment for BD is reinforced by this study.