Clinical Characteristics, Life Adversities and Personality Traits in Monozygotic Twins With, at Risk of and Without Affective Disorders

APOE Genotype, ApoE Plasma Levels, Lipid Metabolism, and Cognition in Monozygotic Twins with, at Risk of, and without Affective Disorders

Background: Lipids influence brain function and mental health. Understanding the role of apolipoproteins in affective disorders could provide valuable insights and potentially pave the way for novel therapeutic approaches. Methods: We examined the apolipoprotein E genotype and ApoE-levels, lipid profiles, and the correlation with cognition in 204 monozygotic (MZ) twins with unipolar or bipolar disorder in remission or partial remission (affected, AT), their unaffected co-twins (high-risk, HR), and twins with no personal or family history of affective disorder (low-risk, LR). Results: The APOE genotype was not associated with affective disorders. No significant group differences in ApoE levels were found between the three risk groups. Post hoc analysis group-wise comparisons showed higher ApoE levels in the AT than HR twins and in the concordant AT twin pairs relative to the discordant twin pairs. Within the discordant twin pairs, higher ApoE levels were observed in the affected twins (AT = 39.4 mg/L vs. HR = 36.8 mg/L, p = 0.037). Limitations: The present study could benefit from a larger sample size. We did not assess dietary habits. Conclusions: The results did not support our main hypothesis. However, exploratory post hoc analysis suggests a role for plasma ApoE and triglycerides in affective disorders. Future research is needed.

Neural responses during down-regulation of negative emotion in patients with recently diagnosed bipolar disorder and their unaffected relatives

BACKGROUND

Aberrant emotion regulation has been posited as a putative endophenotype of bipolar disorder (BD). We therefore aimed to compare the neural responses during voluntary down-regulation of negative emotions in a large functional magnetic resonance imaging study of BD, patients' unaffected first-degree relatives (URs), and healthy controls (HCs).

METHODS

We compared neural activity and fronto-limbic functional connectivity during emotion regulation in response to aversive v. neutral pictures in patients recently diagnosed with BD (n = 78) in full/partial remission, their URs (n = 35), and HCs (n = 56).

RESULTS

Patients showed hypo-activity in the left dorsomedial, dorsolateral, and ventrolateral prefrontal cortex (DMPFC and DLPFC) during emotion regulation while viewing aversive pictures compared to HCs, with URs displaying intermediate neural activity in these regions. There were no significant differences between patients with BD and HCs in functional connectivity from the amygdala during emotion regulation. However, exploratory analysis indicated that URs displayed more negative amygdala-DMPFC coupling compared with HCs and more negative amygdala-cingulate DLPFC coupling compared to patients with BD. At a behavioral level, patients and their URs were less able to dampen negative emotions in response aversive pictures.

CONCLUSIONS

The findings point to deficient recruitment of prefrontal resources and more negative fronto-amygdala coupling as neural markers of impaired emotion regulation in recently diagnosed remitted patients with BD and their URs, respectively.

Association between lifetime and recent stressful life events and the early course and psychopathology in patients with newly diagnosed bipolar disorder, first-degree unaffected relatives and healthy controls: Cross-sectional results from a prospective study

OBJECTIVE

There is an accumulation of stressful life events prior to the first mood episode, but the impact of previous severe life events on psychopathology in patients with bipolar disorder (BD) is not well studied. We aimed to examine the number of recent and lifetime life events in patients with newly diagnosed BD, their unaffected relatives (UR), and healthy controls (HC) as well as the impact of severe lifetime life events on the early course of BD.

METHODS

We compared the number of recent and lifetime life events in 398 patients with newly diagnosed BD, 109 UR, and 214 HC. We subsequently dichotomized the patients with BD by >2 lifetime life events to investigate the associations of severe lifetime life events with clinical characteristics and affective symptoms.

RESULTS

Patients with newly diagnosed BD reported significantly more life events in the last 12 months and lifetime before compared with UR and HC. Patients who reported >2 lifetime life events (n = 160) compared with patients with 0-2 life events (n = 238) had a significantly longer diagnostic delay (9.5 years ± 8.2 vs. 6.2 years ± 6.9), presented with more anxiety and depressive symptoms and had at least one previous suicide attempt (30.6% vs. 15.6%) and one previous admission (51.3% vs. 36.6%).

CONCLUSION

The experience of severe lifetime life events seems to impact the early course in BD in terms of longer diagnostic delay, more severe psychopathology including more admissions and a more than doubled risk for previous suicide attempts.

Associations between childhood maltreatment and oxidative nucleoside damage in affective disorders

Background

Childhood maltreatment is an established risk factor for incident unipolar disorder and bipolar disorder. It is separately observed that affective disorders (AD) are also associated with higher nucleoside damage by oxidation. Childhood maltreatment may induce higher levels of nucleoside damage by oxidation and thus contribute to the development of AD; however, this relation is only sparsely investigated.

Methods

In total, 860 participants (468 patients with AD, 151 unaffected first-degree relatives, and 241 healthy control persons) completed the Childhood Trauma Questionnaire (CTQ). The association between CTQ scores and markers of systemic DNA and RNA damage by oxidation as measured by urinary excretion of 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodG) and 8-oxo-7,8-dihydroguanosine (8-oxoGuo) levels, respectively, was investigated.

Results

In multiple regression models adjusted for sex- and age, 8-oxodG and 8-oxoGuo levels were found to be higher in individuals who had experienced more childhood maltreatment. These associations persisted in models additionally adjusted for body mass index, alcohol, and current smoking status. Emotional abuse, sexual abuse, and emotional neglect were principally responsible for the foregoing associations.

Conclusions

Our findings of an association between childhood maltreatment and oxidative stress markers suggest that childhood maltreatment overall, notably emotional abuse and emotional neglect, is associated with enhanced systemic damage to DNA and RNA in adulthood. Further, individuals with AD reported a higher prevalence of childhood maltreatment, which may induce higher levels of nucleoside damage by oxidation in adulthood, possibly leading to increased risk of developing AD. Longitudinal studies are needed to clarify this relationship further.

Affective disorders impact prevalence of Flavonifractor and abundance of Christensenellaceae in gut microbiota

Background Affective disorders (AD) have been associated with a higher prevalence of the gut Flavonifractor genus and a lower abundance of the gut Christensenellaceae family. Objective and methods By pooling two independent study samples of patients with AD (n = 176), their unaffected first-degree relatives (n = 70) and healthy controls (n = 101) we aimed to replicate and extend our prior findings of differential Flavonifractor prevalence and Christensenellaceae abundance when comparing patients with AD and healthy controls. The gut microbiota was profiled using 16S rRNA gene amplicon sequencing. Results The pattern of higher prevalence of Flavonifractor and lower Centered Log-Ratio (CLR) abundance of Christensenellaceae was associated with AD. In generalized linear models the CLR abundance of Christensenellaceae was lower in patients with AD (p = 0.024), and in smokers (p = 1.9*10^-4), and inversely associated with increasing waist circumference (p = 0.031). The prevalence of Flavonifractor was higher in patients with AD (p = 0.033) and in smokers (p = 0.036). No impact of psychotropic medication was found. The CLR abundance of Christensenellaceae (p = 0.041), but not the prevalence of Flavonifractor (p = 0.20) could distinguish non-smoking patients with AD from non-smoking healthy controls, whereas no such associations were found in smokers. Unaffected relatives neither differed from patients with AD nor from healthy controls. Conclusion Compared with findings in healthy controls, AD was associated with a significantly lower CLR abundance of the health-linked Christensenellaceae and a significantly higher prevalence of Flavonifractor; findings that are associated with enhanced oxidative stress and systemic low-grade inflammation. If our observations are validated in future independent studies, they support the notion that parts of aberrant gut microbiota are shared by AD and states of dysmetabolism.

Reduced frontostriatal response to expected value and reward prediction error in remitted monozygotic twins with mood disorders and their unaffected high-risk co-twins

BACKGROUND

Depressive episodes experienced in unipolar (UD) and bipolar (BD) disorders are characterized by anhedonia and have been associated with abnormalities in reward processes related to reward valuation and error prediction. It remains however unclear whether these deficits are associated with familial vulnerability to mood disorders.

METHODS

In a functional magnetic resonance imaging study, we evaluated differences in the expected value (EV) and reward prediction error (RPE) signals in ventral striatum (VS) and prefrontal cortex between three groups of monozygotic twins: affected twins in remission for either UD or BD (n = 53), their high-risk unaffected co-twins (n = 34), and low-risk twins with no family history of mood disorders (n = 25).

RESULTS

Compared to low-risk twins, affected twins showed lower EV signal bilaterally in the frontal poles and lower RPE signal bilaterally in the VS, left frontal pole and superior frontal gyrus. The high-risk group did not show a significant change in the EV or RPE signals in frontostriatal regions, yet both reward signals were consistently lower compared with low-risk twins in all regions where the affected twins showed significant reductions.

CONCLUSION

Our findings strengthen the notion that reduced valuation of expected rewards and reduced error-dependent reward learning may underpin core symptom of depression such as loss of interest in rewarding activities. The trend reduction in reward-related signals in unaffected co-twins warrants further investigation of this effect in larger samples and prospective follow-up to confirm possible association with increased familial vulnerability to mood disorders.

Hippocampal subfield morphology in monozygotic twins discordant for affective disorders

Unipolar and bipolar disorders aggregate in families and have been associated with a reduced gray-matter volume in hippocampal and prefrontal cortex. Here we used structural MRI to clarify whether abnormalities in hippocampal subfield and prefrontal cortical morphology are associated with familial vulnerability (i.e., changes present both in patients and unaffected relatives compared to healthy individuals), resilience (i.e., changes differentiating unaffected relatives and patients), or sequalae of illness in a sample of monozygotic twins. We investigated regional differences in gray-matter volume extracted using FreeSurfer 6.0 between remitted affected twins (AT) with either unipolar or bipolar disorder (n = 67), unaffected discordant co-twins (UT, n = 39), and low-risk twins (LT, n = 31) with no personal or first-degree family history of affective disorders. The UT showed greater bilateral hippocampal volumes compared to AT. Between group differences in left hippocampal volume were driven by greater cornu ammonis 1-3 and 4, subiculum and subfield of dentate gyrus. For the right hippocampus, differences were driven by greater hippocampal tail and subiculum. There was a trend for UT having a larger left hippocampus than LT, but no significant differences in hippocampal volumes between AT and LT. Outside the hippocampus, AT showed a smaller volume of left dorsomedial prefrontal cortex compared to LT. Our results suggest that larger volume of specific hippocampal subfields may be associated with resilience in healthy relatives of patients with an affective illness. Moreover, a smaller volume of left dorsomedial prefrontal cortex may reflect a sequalae of illness.

S100B and brain derived neurotrophic factor in monozygotic twins with, at risk of and without affective disorders

BACKGROUND

The calcium binding protein S100B and brain derived neurotrophic factor (BDNF) are both biomarkers implicated in neuronal processes in the central nervous system and seem to be associated with affective disorders. Here we investigated both markers in a sample of monozygotic (MZ) twins with, at risk of and without affective disorders, aiming to evaluate whether these markers have a role as causal factors- or trait markers for affective disorders.

METHOD

We measured serum S100B and plasma BDNF levels in 204 monozygotic twins (MZ) with unipolar or bipolar disorder in remission or partial remission (affected), their unaffected co-twins (high-risk) and twins with no personal or family history of affective disorder (low-risk).

RESULTS

No significant group differences in S100B and BDNF levels were found between the three groups. Exploratory analysis revealed that higher S100B levels were correlated with lower cognitive performance.

LIMITATIONS

The cross-sectional design cannot elucidate the two neuronal biomarkers role as causal factors. We would have preferred a higher sample size in the high- and low-risk groups.

CONCLUSION

The present result did not support a role for S100B and BDNF as neither causal factors nor trait markers for affective disorders. Elevated S100B levels may associate with impaired cognition, but further studies are warranted.

Are remitted affective disorders and familial risk of affective disorders associated with metabolic syndrome, inflammation and oxidative stress? - a monozygotic twin study

BACKGROUND

Metabolic syndrome (MetS) is associated with reduced life expectancy in patients with affective disorders, however, whether MetS also plays a role before the onset of affective disorder is unknown. We aimed to investigate whether MetS, inflammatory markers or oxidative stress act as risk factors for affective disorders, and whether MetS is associated with increased inflammation and oxidative stress.

METHODS

We conducted a high-risk study including 204 monozygotic (MZ) twins with unipolar or bipolar disorder in remission or partial remission (affected), their unaffected co-twins (high-risk) and twins with no personal or family history of affective disorder (low-risk). Metabolic Syndrome was ascertained according to the International Diabetes Federation (IDF) criteria. Inflammatory markers and markers of oxidative stress were analyzed from fasting blood and urine samples, respectively.

RESULTS

The affected and the high-risk group had a significantly higher prevalence of MetS compared to the low-risk group (20% v. 15% v. 2.5%, p = 0.0006), even after adjusting for sex, age, smoking and alcohol consumption. No differences in inflammatory and oxidative markers were seen between the three groups. Further, MetS was associated with alterations in inflammatory markers, and oxidative stress was modestly correlated with inflammation.

CONCLUSION

Metabolic syndrome is associated with low-grade inflammation and may act as a risk factor and a trait marker for affective disorders. If confirmed in longitudinal studies, this suggests the importance of early intervention and preventive approaches targeted towards unhealthy lifestyle factors that may contribute to later psychopathology.

Remitted affective disorders and high familial risk of affective disorders associate with aberrant intestinal microbiota

OBJECTIVE

Affective disorders seem associated with aberrant intestinal microbiota but whether this pattern also occurs in individuals at increased heritable risk is unknown. We investigated associations between gut microbiota profiles and affective disorders by comparing monozygotic (MZ) twins concordant (affected twins with unipolar or bipolar disorder in remission) and discordant to affective disorders (high-risk) with MZ twins without affective disorders (low-risk).

METHODS

Stool samples were collected from 128 MZ twins and the microbiome was profiled using 16S rDNA sequencing of the V3-V4 region.

RESULTS

Affected twins had a lower diversity and an absence of a specific operational taxonomical unit (OTU) in comparison with low-risk twins. The high-risk twins exhibited the same pattern although the lower diversity was only at a trend level. The OTU belonged to the family Christensenellaceae. The findings were not explained by lifestyle factors (smoking, alcohol consumption, body mass index, or psychotropic medication).

CONCLUSION

Affected twins in remission and high-risk twins presented aberrant gut microbiota with depletion of a specific OTU. If replicated, this reduced relative sequence absence may together with the globally altered microbiota composition act as a vulnerability marker by accentuating the effect of gene-environment interactions in individuals genetically disposed for an affective disorder.

Emotional Mental Imagery Abnormalities in Monozygotic Twins With, at High-Risk of, and Without Affective Disorders: Present in Affected Twins in Remission but Absent in High-Risk Twins

Background: Mental imagery abnormalities feature across affective disorders including bipolar disorder (BD) and unipolar depression (UD). Maladaptive emotional imagery has been proposed as a maintenance factor for affective symptomatology and a target for mechanism-driven psychological treatment developments. Where imagery abnormalities feature beyond acute affective episodes, further opportunities for innovation arise beyond treatments, such as for tertiary/relapse prevention (e.g., in remitted individuals) or primary prevention (e.g., in non-affected but at-risk individuals). The aim of our study was to investigate for the first time the presence of possible mental imagery abnormalities in affected individuals in remission and at-risk individuals for affective disorders using a familial risk design. Methods: A population-based cohort of monozygotic twins was recruited through linkage between the Danish national registries (N=204). Participants were grouped as: affected (remitted BD/UD; n = 115); high-risk (co-twin with history of BD/UD; n = 49), or low-risk (no co-twin history of BD/UD; n = 40). Twins completed mental imagery measures spanning key subjective domains (spontaneous imagery use and emotional imagery) and cognitive domains (imagery inspection and imagery manipulation). Results: Affected twins in remission reported enhanced emotional mental imagery compared to both low- and high-risk twins. This was characterized by greater impact of i) intrusive prospective imagery (Impact of Future Events Scale) and ii) deliberately-generated prospective imagery of negative scenarios (Prospective Imagery Task). There were no significant differences in these key measures between affected BD and UD twins in remission. Additionally, low- and high-risk twins did not significantly differ on these emotional imagery measures. There were also no significant differences between the three groups on non-emotional measures including spontaneous imagery use and cognitive stages of imagery. Conclusions: Abnormalities in emotional prospective imagery are present in monozygotic twins with affective disorders in remission-despite preserved cognitive stages of imagery-but absent in unaffected high-risk twins, and thus do not appear to index familial risk (i.e., unlikely to qualify as "endophenotypes"). Elevated emotional prospective imagery represents a promising treatment/prevention target in affective disorders.