Free water alterations in different inflammatory subgroups in schizophrenia

Cognitive impairment and vulnerability of cholinergic brain network in the Alzheimer's continuum: free-water imaging based on diffusion tensor imaging

Background

Increased extracellular free water (FW) is considered to provide better pathophysiological information than conventional diffusion tensor imaging (DTI) metrics. The cholinergic brain network is a key hub for cognitive function, and microstructural changes detected by free water imaging in this system may be associated with cognitive impairment in Alzheimer's disease (AD). However, the specific impact of FW changes in the cholinergic brain network on cognitive domains across the AD continuum and their diagnostic value remain unclear.

Methods

Here, we investigated the basal forebrain cholinergic free water alterations based on free water-corrected diffusion tensor imaging in healthy controls (n = 36), amnestic mild cognitive impairment (aMCI; n = 31), the AD group (n = 33). The cholinergic basal forebrain subregions were divided into the Broca diagonal band (Ch1-3) and the Meynert basal nucleus (Ch4). The cognitive domains performance was measured using the Montreal Cognitive Assessment (MoCA). Additionally, we evaluated the diagnostic value of free water fraction (FWf) within the cholinergic system.

Results

FWf in the bilateral Ch1-3 and Ch4 regions increased with age, and was significantly higher in aMCI and AD (p < 0.001). In AD, the FWf within Ch4 was correlated with total MoCA score (R = -0.42, p = 0.015), especially with visual spatial/executive (R = -0.47, p = 0.006) and orientation deficits (R = -0.38, p = 0.029). No significant correlations were found in the aMCI group. ROC curve analysis showed that FWf within the cholinergic brain network had high diagnostic efficacy for AD versus HC (AUC = 0.958, 95% CI = 0.909-1.00), and moderate diagnostic efficacy for aMCI versus HC (AUC = 0.795, 95% CI = 0.685-0.905) and aMCI versus AD (AUC = 0.719, 95% CI = 0.589-0.850).

Conclusion

FW imaging captures microstructural damage in the cholinergic brain network across the entire AD continuum. These changes occur early in aMCI but selectively affect domain-specific cognition in the later stages of AD, possibly through cholinergic network dysfunction. Our results highlight the potential of free water imaging as a biomarker for cognitive decline.

Association between peripheral inflammation and body mass index on white matter integrity and free water in bipolar II depression

Immuno-metabolic dysregulation is implicated in mood disorders and elucidating non-invasive brain correlates may aid clinical translation of pathomechanism. This study aims to investigate the interrelationship between peripheral inflammation and body mass index (BMI) and their effects on white matter (WM) microstructure and free water (FW) in bipolar II depression (BDII-D). Voxel-wise FW and FW-corrected fractional anisotropy (FAt) were compared between 146 BDII-D and 151 healthy controls (HCs) using FSL Randomise. Partial correlations were used to explore associations between BMI, peripheral inflammation, FW measures, and psychiatric symptoms. Moderation analysis examined the interrelationships among BMI, peripheral inflammation, and FW measures. BDII-D showed lower FAt in the genu of the corpus callosum (CC) and bilateral anterior corona radiata, and higher FW in the body of the CC compared with HCs. Higher BMI was linked to lower global FAt (q < 0.001), while higher peripheral inflammation was associated with higher global FW (q ≤ 0.01) in BDII-D. Lower FAt in the genu of the CC and higher FW in the body of CC were significantly related to higher BMI, inflammation, and greater depressive symptoms (q < 0.05). Low-grade Inflammation moderated the relationship between higher BMI and lower FAt in the genu of the CC in BDII-D (B = -3.094e-05, p < 0.001). We found evidence for a mechanistic link between immune-metabolic dysregulation and altered connection in BDII-D. Next to mediating BMI effects on WM integrity, there seems to exist specific relationships between inflammation and BMI with different MR-based tract markers that need further investigation.

Imaging Biomarker Studies of Antipsychotic-Naïve First-Episode Schizophrenia in China: Progress and Future Directions

BACKGROUND AND HYPOTHESIS

Identifying biomarkers at onset and specifying the progression over the early course of schizophrenia is critical for better understanding of illness pathophysiology and providing novel information relevant to illness prognosis and treatment selection. Studies of antipsychotic-naïve first-episode schizophrenia in China are making contributions to this goal.

STUDY DESIGN

A review was conducted for how antipsychotic-naïve first-episode patients were identified and studied, the investigated biological measures, with a focus on neuroimaging, and how they extend the understanding of schizophrenia regarding the illness-related brain abnormality, treatment effect characterization and outcome prediction, and subtype discovery and patient stratification, in comparison to findings from western populations. Finally, how biomarker studies should be conducted in the future was also discussed.

STUDY RESULTS

Gray matter reduction has been most robust within temporo-frontal regions and cerebellum, whereas altered brain function has been most pronounced in cerebello-cortical connections and default mode network, each might be related to long-standing illness alterations and acute physiological alterations at measurement. By studying untreated patients, the progressive alterations in temporal and frontal regions and enlargements in bilateral putamen were found more likely effects of illness, not just treatment. Some of these changes were found with potential to predict clinical outcomes and differentiate biologically patient subgroups.

CONCLUSIONS

Mostly with data-driven approaches, the studies from China are helping identify candidate imaging biomarkers in schizophrenia that are related to early-stage illness, treatment effects, and biological subgroup differentiation. Future work is needed to translate these biomarkers for clinical application.

White matter alterations in episodic migraine without aura patients assessed with diffusion MRI: effect of free water correction

OBJECTIVE

To assess the effect of modeling free water (FW) on the identification of white matter (WM) microstructure alterations using diffusion Magnetic Resonance Imaging (dMRI) in episodic migraine without aura patients compared with healthy controls.

BACKGROUND

Diffusion tensor imaging (DTI) studies examining WM in migraine patients previously overlooked the potential influence of FW partial volume effects. Correcting FW effects could offer a clearer understanding of WM changes in migraine. This study is the first to incorporate FW effects when evaluating alterations in WM tracts in migraine patients, offering a comparison to standard DTI analysis.

METHODS

A group of 14 patients with low-frequency episodic menstrual-related migraine without aura and 15 healthy controls matched for the phase of the menstrual cycle were recruited and underwent dMRI acquisitions. FW partial volume fraction was estimated, the diffusion signal corrected and the diffusion parameters calculated from both FW-corrected and uncorrected signals. Tract-Based Spatial Statistics (TBSS) and WM skeleton regions of interest (ROI) analyses were used to compare between groups.

RESULTS

Comparisons between control subjects and migraine patients with TBSS and ROI analyses revealed significantly lower axial diffusivity (AD), both with and without FW correction, as well as altered FW values in migraine patients in some WM tracts. TBSS detected MD changes only after FW correction.

CONCLUSIONS

These findings suggest WM alterations in these migraine patients in comparison with control subjects, in accordance with other migraine studies. Differences in the diffusion parameters might point to inflammatory processes in migraine related to cellular swelling.

Distinguishing Early from Late Mild Cognitive Impairment Using Magnetic Resonance Free-Water Diffusion Tensor Imaging

Mild Cognitive Impairment (MCI) is a transitional stage between normal aging and Alzheimer's disease. Differentiating early MCI (EMCI) from late MCI (LMCI) is crucial for early diagnosis and intervention. This study used free-water diffusion tensor imaging (fw-DTI) to investigate white matter differences and voxel-based correlations with Mini-Mental State Examination (MMSE) scores. Data from the Alzheimer's Disease Neuroimaging Initiative included 476 healthy controls (CN), 137 EMCI participants, and 62 LMCI participants. Significant MMSE differences were found between the CN and MCI groups, but not between EMCI and LMCI. However, distinct white matter changes were observed: LMCI showed a higher f-index and lower fw-fractional anisotropy (fw-FA) compared to EMCI in several white matter regions. These findings indicate specific white matter tracts involved in MCI progression. Voxel-based correlations between fw-DTI metrics and MMSE scores further supported these results. In conclusion, this study provides crucial insights into white matter changes associated with EMCI and LMCI, offering significant implications for future research and clinical practice.

Poor self-reported sleep is associated with prolonged white matter T2 relaxation in psychotic disorders

Background

Psychotic disorders are characterized by white matter (WM) abnormalities; however, their relationship with the various aspects of illness presentation remains unclear. Sleep disturbances are common in psychosis, and emerging evidence suggests that sleep plays a critical role in WM physiology. Therefore, it is plausible that sleep disturbances are associated with impaired WM integrity in these disorders. To test this hypothesis, we examined the association of self-reported sleep disturbances with WM transverse (T2) relaxation times in a cross-diagnostic sample of patients with psychosis.

Methods

A total of 28 patients with psychosis (11 schizophrenia spectrum disorders and 17 bipolar disorder with psychotic features) were included. Metabolite (N-acetyl aspartate, choline, and creatine) and water T2 relaxation times were measured in the anterior corona radiata at 4T. Sleep was evaluated using the Pittsburgh Sleep Quality Index (PSQI).

Results

PSQI total score showed a moderate to strong positive correlation with water T2 (r = 0.64, p< 0.001). Linear regressions showed that this association was independent of the overall severity of depressive, manic, or psychotic symptoms. In our exploratory analysis, sleep disturbance was correlated with free water percentage, suggesting that increased extracellular water may be a mechanism underlying the association of disturbed sleep and prolonged water T2 relaxation.

Conclusion

Our results highlight the connection between poor sleep and WM abnormalities in psychotic disorders. Future research using objective sleep measures and neuroimaging techniques suitable to probe free water is needed to further our insight into this relationship.

Cellular and extracellular white matter alterations after childhood trauma experience in individuals with schizophrenia

BACKGROUND

Childhood trauma (CT) is related to altered fractional anisotropy (FA) in individuals with schizophrenia (SZ). However, it remains unclear whether CT may influence specific cellular or extracellular compartments of FA in SZ with CT experience. We extended our previous study on FA in SZ (Costello et al., 2023) and examined the impact of CT on hypothesized lower free water-corrected FA (FAT) and higher extracellular free water (FW).

METHOD

Thirty-seven SZ and 129 healthy controls (HC) were grouped into the 'none/low' or 'high' CT group. All participants underwent diffusion-weighted magnetic resonance imaging. We performed tract-based spatial statistics to study the main effects of diagnostic group and CT, and the interaction between CT and diagnostic group across FAT and FW.

RESULTS

SZ displayed lower FAT within the corpus callosum and corona radiata compared to HC (p < 0.05, Threshold-Free Cluster Enhancement (TFCE)). Independent of diagnosis, we observed lower FAT (p < 0.05, TFCE) and higher FW (p < 0.05, TFCE) in both SZ and HC with high CT levels compared to SZ and HC with none or low CT levels. Furthermore, we did not identify an interaction between CT and diagnostic group (p > 0.05, TFCE).

CONCLUSIONS

These novel findings suggest that the impact of CT on lower FAT may reflect cellular rather than extracellular alterations in established schizophrenia. This highlights the impact of CT on white matter microstructure, regardless of diagnostic status.

Imaging neuroglia

Imaging can help us understand the role neuroglia plays in health and during the course of neurologic disorders. In vivo microscopy has had a great impact on our understanding of how neuroglia behaves during health and disease. While initially the technique was hindered by the limited penetration depth in brain tissue, recent advancements lead to increasing possibilities for imaging of deeper brain structures, even at super-resolution. Unfortunately, in vivo microscopy cannot be applied in a clinical setting and thus cannot be used to study neuroglia in patient populations. However, noninvasive imaging techniques like positron emission tomography (PET) and magnetic resonance imaging (MRI) can. PET has provided valuable information on the involvement of neuroglia in neurologic disorders. To more specifically image microglia and astrocytes, many new PET biomarkers have been defined for which PET tracers are continuously developed, evaluated, and improved. A cell-type specific PET tracer with favorable imaging characteristics can have a huge impact on neuroglia research. While being less sensitive than PET, MRI is a more accessible imaging technique. Initially, only general neuroinflammation processes could be imaged with MRI, but newly developed methods and sequences allow for increasing cell-type specificity. Overall, while each imaging method comes with limitations, improvements are continuously made, all with the aim to truly understand the role that neuroglia play in health and disease.

Mendelian randomization analysis of causal and druggable circulating inflammatory proteins in schizophrenia

Background

Schizophrenia (SZ) is a severe mental disorder with complex origins. Observational studies suggested that inflammatory factors may play a role in the pathophysiology of SZ and we aim to investigate the potential genetic connection between them by examining the causal impact of circulating inflammatory proteins on SZ.

Methods

We utilized Mendelian randomization (MR) analysis to assess the causal relationship between circulating inflammatory proteins and SZ and the GWAS summary datasets were sourced from public databases. The SZ dataset comprised 74,776 cases and 101,023 controls, while the summary results for 91 plasma proteins in 14,824 participants were obtained through the Olink Target platform. Moreover, to identify and evaluate potential drug targets, we searched the Drug-Gene Interaction Database (DGIdb).

Results

The results of the MR study confirmed that nine inflammatory proteins had a causal effect on SZ. Among these proteins, IL1A (OR: 0.93), TNFB (OR: 0.94), TNFSF14 (OR: 0.96), and CD40 (OR: 0.95) exhibited protective effects against SZ. Conversely, CCL23 (OR: 1.04), CCL19 (OR: 1.04), 4EBP1 (OR: 1.06), TWEAK (OR: 1.08), and DNER (OR: 1.10) were associated with an increased risk of SZ. The MR-Egger and weighted median methods also supported the direction of these effects. According to the Gene-Drug analysis, LTA, IL1A, CD40, and 4EBP1 can serve as drug targets.

Conclusions

Our study established causal relationships between circulating inflammatory proteins and SZ. It may be beneficial to personalize the treatment of SZ by incorporating inflammation management into the treatment regimen.

Poor Self-Reported Sleep is Associated with Prolonged White Matter T2 Relaxation in Psychotic Disorders

Background

Schizophrenia (SZ) and bipolar disorder (BD) are characterized by white matter (WM) abnormalities, however, their relationship with illness presentation is not clear. Sleep disturbances are common in both disorders, and recent evidence suggests that sleep plays a critical role in WM physiology. Therefore, it is plausible that sleep disturbances are associated with impaired WM integrity in these disorders. To test this hypothesis, we examined the association of self-reported sleep disturbances with WM transverse (T2) relaxation times in patients with SZ spectrum disorders and BD with psychotic features.

Methods

28 patients with psychosis (17 BD-I, with psychotic features and 11 SZ spectrum disorders) were included. Metabolite and water T2 relaxation times were measured in the anterior corona radiata at 4T. Sleep was evaluated using the Pittsburgh Sleep Quality Index.

Results

PSQI total score showed a moderate to strong positive correlation with water T2 (r = 0.64, p<0.001). Linear regressions showed that this association was specific to sleep disturbance but was not a byproduct of exacerbation in depressive, manic, or psychotic symptoms. In our exploratory analysis, sleep disturbance was correlated with free water percentage, suggesting that increased extracellular water may be a mechanism underlying the association of disturbed sleep and prolonged water T2 relaxation.

Conclusion

Our results highlight the connection between poor sleep and WM abnormalities in psychotic disorders. Future research using objective sleep measures and neuroimaging techniques suitable to probe free water is needed to further our insight into this relationship.

The associations of peripheral interleukin alterations and hippocampal subfield volume deficits in schizophrenia

The hippocampus is one of the brain regions most vulnerable to inflammatory insults, and the relationships between peripheral inflammation and hippocampal subfields in patients with schizophrenia remain unclear. In this study, forty-six stably medicated patients with schizophrenia and 48 demographically matched healthy controls (HCs) were recruited. The serum levels of IL - 1β, IL-6, IL-10, and IL-12p70 were measured, and 3D high-resolution T1-weighted magnetic resonance imaging was performed. The IL levels and hippocampal subfield volumes were both compared between patients and HCs. The associations of altered IL levels with hippocampal subfield volumes were assessed in patients. Patients with schizophrenia demonstrated higher serum levels of IL-6 and IL-10 but lower levels of IL-12p70 than HCs. In patients, the levels of IL-6 were positively correlated with the volumes of the left granule cell layer of the dentate gyrus (GCL) and cornu Ammonis (CA) 4, while the levels of IL-10 were negatively correlated with the volumes of those subfields. IL-6 and IL-10 might have antagonistic roles in atrophy of the left GCL and CA4. This suggests a complexity of peripheral cytokine dysregulation and the potential for its selective effects on hippocampal substructures, which might be related to the pathophysiology of schizophrenia.