Plasma metabolic alterations and potential biomarkers in individuals at clinical high risk for psychosis

Cross-sectional association between metabolic parameters and psychotic-like experiences in a population-based sample of middle-aged and elderly individuals

BACKGROUND

Metabolic alterations are often found in patients with clinical psychosis early in the course of the disorder. Psychotic-like experiences are observed in the general population, but it is unclear whether these are associated with markers of metabolism.

METHODS

A population-based cohort of 1890 individuals (mean age 58.0 years; 56.3% women) was included. Metabolic parameters were measured by body-mass index (BMI), concentrations of low-density and high-density lipoprotein cholesterol (LDL-C and HDL-C), total cholesterol, triglycerides, and fasting glucose and insulin in blood. Frequency and distress ratings of psychotic-like experiences from the positive symptom dimension of the Community Assessment of Psychic Experience questionnaire were assessed. Cross-sectional associations were analysed using linear regression analyses.

RESULTS

Higher BMI was associated with higher frequency of psychotic-like experiences (adjusted mean difference: 0.04, 95% CI 0.02-0.06) and more distress (adjusted mean difference: 0.02, 95% CI 0.01-0.03). Lower LDL-C was associated with more psychotic-like experiences (adjusted mean difference: -0.23, 95% CI -0.40 to -0.06). When restricting the sample to those not using lipid-lowering medication, the results of BMI and LDL-C remained and an association between lower HDL-C and higher frequency of psychotic-like experiences was found (adjusted mean difference: -0.37, 95% CI -0.69 to -0.05). We observed no significant associations between cholesterol, triglycerides, glucose, insulin or homeostatic model assessment and psychotic-like experiences.

CONCLUSIONS

In a population-based sample of middle-aged and elderly individuals, higher BMI and lower LDL-C were associated with psychotic-like experiences. This suggests that metabolic markers are associated with psychotic-like experiences across the vulnerability spectrum.

Recent Updates on Predicting Conversion in Youth at Clinical High Risk for Psychosis

PURPOSE OF REVIEW

This review highlights recent advances in the prediction and treatment of psychotic conversion. Over the past 25 years, research into the prodromal phase of psychotic illness has expanded with the promise of early identification of individuals at clinical high risk (CHR) for psychosis who are likely to convert to psychosis.

RECENT FINDINGS

Meta-analyses highlight conversion rates between 20 and 30% within 2-3 years using existing clinical criteria while research into more specific risk factors, biomarkers, and refinement of psychosis risk calculators has exploded, improving our ability to predict psychotic conversion with greater accuracy. Recent studies highlight risk factors and biomarkers likely to contribute to earlier identification and provide insight into neurodevelopmental abnormalities, CHR subtypes, and interventions that can target specific risk profiles linked to neural mechanisms. Ongoing initiatives that assess longer-term (> 5-10 years) outcome of CHR participants can provide valuable information about predictors of later conversion and diagnostic outcomes while large-scale international biomarker studies provide hope for precision intervention that will alter the course of early psychosis globally.

Prognostic models predicting transition to psychotic disorder using blood-based biomarkers: a systematic review and critical appraisal

Accumulating evidence suggests individuals with psychotic disorder show abnormalities in metabolic and inflammatory processes. Recently, several studies have employed blood-based predictors in models predicting transition to psychotic disorder in risk-enriched populations. A systematic review of the performance and methodology of prognostic models using blood-based biomarkers in the prediction of psychotic disorder from risk-enriched populations is warranted. Databases (PubMed, EMBASE and PsycINFO) were searched for eligible texts from 1998 to 15/05/2023, which detailed model development or validation studies. The checklist for Critical Appraisal and Data Extraction for Systematic Reviews of Prediction Modelling Studies (CHARMS) was used to guide data extraction from eligible texts and the Prediction Model Risk of Bias Assessment Tool (PROBAST) was used to assess the risk of bias and applicability of the studies. A narrative synthesis of the included studies was performed. Seventeen eligible studies were identified: 16 eligible model development studies and one eligible model validation study. A wide range of biomarkers were assessed, including nucleic acids, proteins, metabolites, and lipids. The range of C-index (area under the curve) estimates reported for the models was 0.67-1.00. No studies assessed model calibration. According to PROBAST criteria, all studies were at high risk of bias in the analysis domain. While a wide range of potentially predictive biomarkers were identified in the included studies, most studies did not account for overfitting in model performance estimates, no studies assessed calibration, and all models were at high risk of bias according to PROBAST criteria. External validation of the models is needed to provide more accurate estimates of their performance. Future studies which follow the latest available methodological and reporting guidelines and adopt strategies to accommodate required sample sizes for model development or validation will clarify the value of including blood-based biomarkers in models predicting psychosis.

Plasma levels of neurotrophin 4/5, NGF and pro-BDNF influence transition to mental disorders in a sample of individuals at ultra-high risk for psychosis

BACKGROUND

Neurotrophins (NTs) and their precursors (pro-NTs) are polypeptides with important roles in neuronal development, differentiation, growth, survival and plasticity, as well as apoptosis and neuronal death. Imbalance in NT levels were observed in schizophrenia spectrum disorders, but evidence in ultra-high risk for psychosis (UHR) samples is scarce.

METHODS

A naturalistic sample of 87 non-help-seeking UHR subjects and 55 healthy controls was drawn from the general population. Blood samples were collected and NT-3, NT-4/5, BDNF, pro-BDNF, NGF, pro-NGF were analyzed through enzyme linked immunosorbent assay (ELISA). Information on cannabis and tobacco use was also collected. Logistic regression models and path analysis were used to control for confounders (tobacco, age, cannabis use).

RESULTS

NT-4/5 was significantly decreased, and pro-BDNF was significantly increased in UHR individuals compared to controls. Cannabis use and higher NGF levels were significantly related to transition to psychiatric disorders among UHR subjects. Increased pro-BDNF and decreased NT-4/5 influenced transition by the mediation of perceptual abnormalities.

CONCLUSIONS

Our study shows for the first time that NTs are altered in UHR compared to healthy control individuals, and that they can be a predictor of transition to psychiatric illnesses in this population. Future studies should employ larger naturalistic samples to confirm the findings.

Eye movement indices as predictors of conversion to psychosis in individuals at clinical high risk

Eye movement abnormalities have been established as an "endophenotype" of schizophrenia. However, less is known about the possibility of these abnormalities as biomarkers for psychosis conversion among clinical high risk (CHR) populations. In the present study, 108 CHR individuals and 70 healthy controls (HC) underwent clinical assessments and eye-tracking tests, comprising fixation stability and free-viewing tasks. According to three-year follow-up outcomes, CHR participants were further stratified into CHR-converter (CHR-C; n = 21) and CHR-nonconverter (CHR-NC; n = 87) subgroups. Prediction models were constructed using Cox regression and logistic regression. The CHR-C group showed more saccades of the fixation stability test (no distractor) and a reduced saccade amplitude of the free-viewing test than HC. Moreover, the CHR-NC group exhibited excessive saccades and an increased saccade amplitude of the fixation stability test (no distractor; with distractor) compared with HC. Furthermore, two indices could effectively discriminate CHR-C from CHR-NC with an area under the receiver-operating characteristic (ROC) curve of 0.80, including the saccade number of the fixation stability test (no distractor) and the saccade amplitude of the free-viewing test. Combined with negative symptom scores of the Scale of Prodromal Symptoms, the area was 0.81. These findings support that eye movement alterations might emerge before the onset of clinically overt psychosis and could assist in predicting psychosis transition among CHR populations.

Different patterns of association between white matter microstructure and plasma unsaturated fatty acids in those with high risk for psychosis and healthy participants

Background

Disrupted white matter (WM) microstructure has been commonly identified in youth at clinical high risk (CHR) for psychosis. Several lines of evidence suggest that fatty acids, especially unsaturated fatty acids (UFAs), might play a crucial role in the WM pathology of early onset psychosis. However, evidence linking UFA and WM microstructure in CHR is quite sparse.

Aims

We investigated the relationship between the plasma UFA level and WM microstructure in CHR participants and healthy controls (HC).

Methods

Plasma fatty acids were assessed and diffusion tensor imaging (DTI) data were performed with tract-based spatial statistics (TBSS) analysis for 66 individuals at CHR for psychosis and 70 HC.

Results

Both the global and regional diffusion measures showed significant between-group differences, with decreased fractional anisotropy (FA) but increased mean diffusivity (MD) and radial diffusivity (RD) found in the CHR group compared with the HC group. On top of that, we found that in the HC group, plasma arachidic acid showed obvious trend-level associations with higher global FA, lower global MD and lower global RD, which regionally spread over the corpus callosum, right anterior and superior corona radiata, bilateral anterior and posterior limb of the internal capsule, and bilateral superior longitudinal fasciculus. However, there were no associations between global WM measures and any UFA in the CHR group. Conversely, we even found negative associations between arachidic acid levels and regional FA values in the right superior longitudinal fasciculus and right retrolenticular part of the internal capsule in the CHR group.

Conclusions

Compared with the HC group, CHR subjects exhibited a different pattern of association between WM microstructure and plasma UFA, with a neuroprotective effect found in the HC group but not in the CHR group. Such discrepancy could be due to the excessively upregulated UFAs accumulated in the plasma of the CHR group, highlighting the role of balanced plasma-membrane fatty acids homeostasis in WM development.