Lipid Biomarker Research in Bipolar Disorder: A Scoping Review of Trends, Challenges, and Future Directions.

Bipolar disorder (BD) is a disabling disorder with heterogeneous symptom profiles and trajectories. Like many other neuropsychiatric disorders, clinical decision making related to diagnoses and choice of treatment is based on clinical assessments alone, and risk prediction for treatment success or resistance at an individual level remains sparse. An enormous effort to add biological markers to this risk prediction is ongoing. The role of lipids in normal brain functioning is well established, and several hypotheses about the role of lipids in the pathogenesis of neuropsychiatric disorders, including BD, have been made. The frequent comorbidity between neuropsychiatric disorders and cardiovascular disease, the genetic overlap of risk genes for severe mental disorders and genes involved in lipid regulation, and the lipid-altering effects of antipsychotics and mood stabilizers indicate that lipids could hold promise as biomarkers for neuropsychiatric disorders, including BD. To date, reviews of lipid biomarkers in schizophrenia and major depression have noted caveats for future investigations, while reviews of lipid biomarker research in BD is missing. In the current scoping review, we present a comprehensive overview of trends in previous research on lipid biomarkers in BD. The current literature varies greatly in the phenotypes investigated and study designs, leading to divergent findings. Small sample size; potential confounders related to physical activity, nutritional status, and medication use; and cross-sectional designs were frequently reported limitations. Future research may benefit from pivoting toward utilization of newer laboratory techniques such as lipidomics, but consistent use of study methods across cohorts is also needed.

Characterizing the Shared Genetic Underpinnings of Schizophrenia and Cardiovascular Disease Risk Factors.

OBJECTIVE: Schizophrenia is associated with increased risk of cardiovascular disease (CVD), although there is variation in risk among individuals. There are indications of shared genetic etiology between schizophrenia and CVD, but the nature of the overlap remains unclear. The aim of this study was to fill this gap in knowledge. METHODS: Overlapping genetic architectures between schizophrenia and CVD risk factors were assessed by analyzing recent genome-wide association study (GWAS) results. The bivariate causal mixture model (MiXeR) was applied to estimate the number of shared variants and the conjunctional false discovery rate (conjFDR) approach was used to pinpoint specific shared loci. RESULTS: Extensive genetic overlap was found between schizophrenia and CVD risk factors, particularly smoking initiation (N=8.6K variants) and body mass index (BMI) (N=8.1K variants). Several specific shared loci were detected between schizophrenia and BMI (N=304), waist-to-hip ratio (N=193), smoking initiation (N=293), systolic (N=294) and diastolic (N=259) blood pressure, type 2 diabetes (N=147), lipids (N=471), and coronary artery disease (N=35). The schizophrenia risk loci shared with smoking initiation had mainly concordant effect directions, and the risk loci shared with BMI had mainly opposite effect directions. The overlapping loci with lipids, blood pressure, waist-to-hip ratio, type 2 diabetes, and coronary artery disease had mixed effect directions. Functional analyses implicated mapped genes that are expressed in brain tissue and immune cells. CONCLUSIONS: These findings indicate a genetic propensity to smoking and a reduced genetic risk of obesity among individuals with schizophrenia. The bidirectional effects of the shared loci with the other CVD risk factors may imply differences in genetic liability to CVD across schizophrenia subgroups, possibly underlying the variation in CVD comorbidity.

Shared Genetic Loci Between Schizophrenia and White Blood Cell Counts Suggest Genetically Determined Systemic Immune Abnormalities.

BACKGROUND: Immune mechanisms are indicated in schizophrenia (SCZ). Recent genome-wide association studies (GWAS) have identified genetic variants associated with SCZ and immune-related phenotypes. Here, we use cutting edge statistical tools to identify shared genetic variants between SCZ and white blood cell (WBC) counts and further understand the role of the immune system in SCZ. STUDY DESIGN: GWAS results from SCZ (patients, n = 53 386; controls, n = 77 258) and WBC counts (n = 56 3085) were analyzed. We applied linkage disequilibrium score regression, the conditional false discovery rate method and the bivariate causal mixture model for analyses of genetic associations and overlap, and 2 sample Mendelian randomization to estimate causal effects. STUDY RESULTS: The polygenicity for SCZ was 7.5 times higher than for WBC count and constituted 32%-59% of WBC count genetic loci. While there was a significant but weak positive genetic correlation between SCZ and lymphocytes (rg = 0.05), the conditional false discovery rate method identified 383 shared genetic loci (53% concordant effect directions), with shared variants encompassing all investigated WBC subtypes: lymphocytes, n = 215 (56% concordant); neutrophils, n = 158 (49% concordant); monocytes, n = 146 (47% concordant); eosinophils, n = 135 (56% concordant); and basophils, n = 64 (53% concordant). A few causal effects were suggested, but consensus was lacking across different Mendelian randomization methods. Functional analyses indicated cellular functioning and regulation of translation as overlapping mechanisms. CONCLUSIONS: Our results suggest that genetic factors involved in WBC counts are associated with the risk of SCZ, indicating a role of immune mechanisms in subgroups of SCZ with potential for stratification of patients for immune targeted treatment.

Triple trouble: uncovering the risks and benefits of early fetal reduction in trichorionic triplets in a large national Danish cohort study.

BACKGROUND: Triplet pregnancies are high risk for both the mother and the infants. The risks for infants include premature birth, low birthweight, and neonatal complications. Therefore, the management of triplet pregnancies involves close monitoring and may include interventions, such as fetal reduction, to prolong the pregnancy and improve outcomes. However, the evidence of benefits and risks associated with fetal reduction is inconsistent. OBJECTIVE: This study aimed to compare the outcomes of trichorionic triplet pregnancies with and without fetal reduction and with nonreduced dichorionic twin pregnancies and primary singleton pregnancies. STUDY DESIGN: All trichorionic triplet pregnancies in Denmark, including those with fetal reduction, were identified between 2008 and 2018. In Denmark, all couples expecting triplets are informed about and offered fetal reduction. Pregnancies with viable fetuses at the first-trimester ultrasound scan and pregnancies not terminated were included. Adverse pregnancy outcome was defined as a composite of miscarriage before 24 weeks of gestation, stillbirth at 24 weeks of gestation, or intrauterine fetal death of 1 or 2 fetuses. RESULTS: The study cohort was composed of 317 trichorionic triplet pregnancies, of which 70.0% of pregnancies underwent fetal reduction to a twin pregnancy, 2.2% of pregnancies were reduced to singleton pregnancies, and 27.8% of pregnancies were not reduced. Nonreduced triplet pregnancies had high risks of adverse pregnancy outcomes (28.4%), which was significantly lower in triplets reduced to twins (9.0%; difference, 19.4%, 95% confidence interval, 8.5%-30.3%). Severe preterm deliveries were significantly higher in nonreduced triplet pregnancies (27.9%) than triplet pregnancies reduced to twin pregnancies (13.1%; difference, 14.9%, 95% confidence interval, 7.9%-21.9%). However, triplet pregnancies reduced to twin pregnancies had an insignificantly higher risk of miscarriage (6.8%) than nonreduced twin pregnancies (1.1%; difference, 5.6%; 95% confidence interval, 0.9%-10.4%). CONCLUSION: Triplet pregnancies reduced to twin pregnancies had significantly lower risks of adverse pregnancy outcomes, severe preterm deliveries, and low birthweight than nonreduced triplet pregnancies. However, triplet pregnancies reduced to twin pregnancies were potentially associated with a 5.6% increased risk of miscarriage.

First-trimester prediction of preterm prelabour rupture of membranes incorporating cervical length measurement.

OBJECTIVES: To examine early pregnancy risk factors for preterm prelabour rupture of membranes (PPROM) and develop a predictive model. STUDY DESIGN: Retrospective analysis of a cohort of mixed-risk singleton pregnancies screened in the first and second trimesters in three Danish tertiary fetal medicine centres, including a cervical length measurement at 11-14 weeks, at 19-21 weeks and at 23-24 weeks of gestation. Univariable and multivariable logistic regression analyses were employed to identify predictive maternal characteristics, biochemical and sonographic factors. Receiver operating characteristic (ROC) curve analysis was used to determine predictors for the most accurate model. RESULTS: Of 3477 screened women, 77 (2.2%) had PPROM. Maternal factors predictive of PPROM in univariable analysis were nulliparity (OR 2.0 (95% CI 1.2-3.3)), PAPP-A < 0.5 MoM (OR 2.6 (1.1-6.2)), previous preterm birth (OR 4.2 (1.9-8.9)), previous cervical conization (OR 3.6 (2.0-6.4)) and cervical length ≤ 25 mm on transvaginal imaging (first-trimester OR 15.9 (4.3-59.3)). These factors all remained statistically significant in a multivariable adjusted model with an AUC of 0.72 in the most discriminatory first-trimester model. The detection rate using this model would be approximately 30% at a false-positive rate of 10%. Potential predictors such as bleeding in early pregnancy and pre-existing diabetes mellitus affected very few cases and could not be formally assessed. CONCLUSIONS: Several maternal characteristics, placental biochemical and sonographic features are predictive of PPROM with moderate discrimination. Larger numbers are required to validate this algorithm and additional biomarkers, not currently used for first-trimester screening, may improve model performance.

Risks and pregnancy outcome after fetal reduction in dichorionic twin pregnancies: a Danish national retrospective cohort study.

BACKGROUND: Twin pregnancies carry a higher risk of congenital and structural malformations, and pregnancy complications including miscarriage, stillbirth, and intrauterine fetal death, compared with singleton pregnancies. Carrying a fetus with severe malformations or abnormal karyotype places the remaining healthy fetus at an even higher risk of adverse outcome and pregnancy complications. Maternal medical conditions or complicated obstetrical history could, in combination with twin pregnancy, cause increased risks for both the woman and the fetuses. To our knowledge, no previous studies have evaluated and compared the outcomes of all dichorionic twin pregnancies and compared the results of reduced twins with those of nonreduced and primary singletons in a national cohort. These data are important for clinicians when counseling couples about fetal reduction and its implications. OBJECTIVE: This study aimed to describe and compare the risks of adverse pregnancy outcomes, including the risk of pregnancy loss, in a national cohort of all dichorionic twins-reduced, nonreduced, and primary singletons. In addition, we examined the implications of gestational age at fetal reduction on gestational age at delivery. STUDY DESIGN: This was a retrospective cohort study of all Danish dichorionic twin pregnancies, including pregnancies undergoing fetal reduction and a large proportion of randomly selected primary singleton pregnancies with due dates between January 2008 and December 2018. The primary outcome measures were adverse pregnancy outcomes (defined as miscarriage before 24 weeks, stillbirth from 24 weeks, or single intrauterine fetal death in nonreduced twin pregnancies), preterm delivery, and obstetrical pregnancy complications. Outcomes after fetal reduction were compared with those of nonreduced dichorionic twins and primary singletons. RESULTS: In total, 9735 dichorionic twin pregnancies were included, of which 172 (1.8%) were reduced. In addition, 16,465 primary singletons were included. Fetal reductions were performed between 11 and 23 weeks by transabdominal needle-guided injection of potassium chloride, and outcome data were complete for all cases. Adverse pregnancy outcome was observed in 4.1% (95% confidence interval, 1.7%-8.2%) of reduced twin pregnancies, and 2.4% (95% confidence interval, 0.7%-6.1%) were delivered before 28 weeks, and 4.2% (95% confidence interval, 1.7%-8.5%) before 32 weeks. However, when fetal reduction was performed before 14 weeks, adverse pregnancy outcomes occurred in only 1.4% (95% confidence interval, 0.0%-7.4%), and delivery before 28 and 32 weeks diminished to 0% (95% confidence interval, 0.0%-5.0%) and 2.8% (95% confidence interval, 0.3%-9.7%), respectively. In contrast, 3.0% (95% confidence interval, 2.7%-3.4%) of nonreduced dichorionic twins had an adverse pregnancy outcome, and 1.9% (95% confidence interval, 1.7%-2.1%) were delivered before 28 weeks, and 7.3% (95% confidence interval, 6.9%-7.7%) before 32 weeks. Adverse pregnancy outcomes occurred in 0.9% (95% confidence interval, 0.7%-1.0%) of primary singletons, and 0.2% (95% confidence interval, 0.1%-0.3%) were delivered before 28 weeks, and 0.7% (95% confidence interval, 0.6%-0.9%) before 32 weeks. For reduced twins, after taking account of maternal factors and medical history, it was demonstrated that the later the fetal reduction was performed, the earlier the delivery occurred (P<.01). The overall risk of pregnancy complications was significantly lower among reduced twin pregnancies than among nonreduced dichorionic twin pregnancies (P=.02). CONCLUSION: In a national 11-year cohort including all dichorionic twin pregnancies, transabdominal fetal reduction by needle guide for fetal or maternal indication was shown to be safe, with good outcomes for the remaining co-twin. Results were best when the procedure was performed before 14 weeks.

Inflammatory markers are altered in severe mental disorders independent of comorbid cardiometabolic disease risk factors.

BACKGROUND: Inflammation and immune activation have been implicated in the pathogenesis of severe mental disorders and cardiovascular disease (CVD). Despite high level of comorbidity, many studies of the immune system in severe mental disorders have not systematically taken cardiometabolic risk factors into account. METHODS: We investigated if inflammatory markers were increased in schizophrenia (SCZ) and affective (AFF) disorders independently of comorbid CVD risk factors. Cardiometabolic risk factors (blood lipids, body mass index and glucose) and CVD-related inflammatory markers CXCL16, soluble interleukin-2 receptor (sIL-2R), soluble CD14 (sCD14), macrophage inhibitory factor and activated leukocyte cell adhesion molecule (ALCAM) were measured in n = 992 patients (SCZ, AFF), and n = 647 healthy controls. We analyzed the inflammatory markers before and after controlling for comorbid cardiometabolic risk factors, and tested for association with psychotropic medication and symptom levels. RESULTS: CXCL16 (p = 0.03) and sIL-2R (p = 7.8 × 10-5) were higher, while sCD14 (p = 0.05) were lower in patients compared to controls after controlling for confounders, with significant differences in SCZ for CXCL16 (p = 0.04) and sIL-2R (p = 1.1 × 10-5). After adjustment for cardiometabolic risk factors higher levels of sIL-2R (p = 0.001) and lower sCD14 (p = 0.002) remained, also in SCZ (sIL-2R, p = 3.0 × 10-4 and sCD14, p = 0.01). The adjustment revealed lower ALCAM levels (p = 0.03) in patients. We found no significant associations with psychotropic medication or symptom levels. CONCLUSION: The results indicate that inflammation, in particular enhanced T cell activation and impaired monocyte activation, are associated with severe mental disorders independent of comorbid cardiometabolic risk factors. This suggests a role of novel pathophysiological mechanisms in severe mental disorders, particularly SCZ.

Outcomes of monoamniotic twin pregnancies managed primarily in outpatient care-a Danish multicenter study.

INTRODUCTION: Monoamniotic twin pregnancies are high-risk pregnancies, and management by inpatient or frequent outpatient care is recommended. We report the outcomes of a national cohort of monoamniotic twin pregnancies managed primarily as outpatients. MATERIAL AND METHODS: We prospectively analyzed the recorded data from the Danish Fetal Medicine Database, local databases, and medical records of all monoamniotic twin pregnancies diagnosed at the first trimester scan or later, and managed at the six major fetal medicine centers in Denmark over a 10-year period. RESULTS: Sixty-one monoamniotic twin pregnancies were included. Thirteen pregnancies were terminated early. Of the remaining 48 pregnancies with a normal first trimester scan, there were 36 fetal losses (25 spontaneous miscarriages <22+0  weeks, 3 late terminations and 8 intrauterine deaths >22 weeks) and 60 liveborn children (62.5%), all of whom were delivered by cesarean delivery at a median gestational age of 33+0  weeks. Three children had minor malformations and there was 1 pregnancy with twin-to-twin transfusion syndrome. After 26+0  weeks, 78.8% were managed as outpatients. Intrauterine death occurred in 3.8% of outpatients and in 28.6% of inpatients (admitted due to complications). At weeks 32, 33 and 34, the prospective risk of intrauterine death was 6.9%, 4.2% and 5.9%, respectively. CONCLUSION: In this nationwide, unselected population, only 62.5% of fetuses with a normal first trimester scan were born alive. In contrast, the mortality was 3.8% after 26 weeks among the 78.8% of the cohort that was managed as outpatients. More knowledge is still needed to predict which pregnancies are at the highest risk of intrauterine death.

Exploring the Wnt signaling pathway in schizophrenia and bipolar disorder.

The Wnt signaling pathway plays a crucial role in neurodevelopment and in regulating the function and structure of the adult nervous system. Schizophrenia (SCZ) and bipolar disorder (BD) are severe mental disorders with evidence of subtle neurodevelopmental, structural and functional neuronal abnormalities. We aimed to elucidate the role of aberrant regulation of the Wnt system in these disorders by evaluating plasma levels of secreted Wnt modulators in patients (SCZ = 551 and BD = 246) and healthy controls (HCs = 639) using enzyme immune-assay. We also investigated the expression of 141 Wnt-related genes in whole blood in a subsample (SCZ = 338, BD = 241, and HCs = 263) using microarray analysis. Both SCZ and BD had dysregulated mRNA expression of Wnt-related genes favoring attenuated canonical (beta-catenin-dependent) signaling, and there were also indices of enhanced non-canonical Wnt signaling. In particular, FZD7, which may activate all Wnt pathways, but favors non-canonical signaling, and NFATc3, a downstream transcription factor and readout of the non-canonical Wnt/Ca2+ pathway, were significantly increased in SCZ and BD (p < 3 × 10-4). Furthermore, patients had lower plasma levels of soluble dickkopf 1 and sclerostin (p < 0.01) compared with HC. Our findings suggest that SCZ and BD are characterized by abnormal Wnt gene expression and plasma protein levels, and we propose that drugs targeting the Wnt pathway may have a role in the treatment of severe mental disorders.

Attenuated Notch signaling in schizophrenia and bipolar disorder.

The Notch signaling pathway plays a crucial role in neurodevelopment and in adult brain homeostasis. We aimed to further investigate Notch pathway activity in bipolar disorder (BD) and schizophrenia (SCZ) by conducting a pathway analysis. We measured plasma levels of Notch ligands (DLL1 and DLK1) using enzyme immunoassays in a large sample of patients (SCZ n = 551, BD n = 246) and healthy controls (HC n = 639). We also determined Notch pathway related gene expression levels by microarray analyses from whole blood in a subsample (SCZ n = 338, BD n = 241 and HC n = 263). We found significantly elevated Notch ligand levels in plasma in both SCZ and BD compared to HC. Significant gene expression findings included increased levels of RFNG and KAT2B (p < 0.001), and decreased levels of PSEN1 and CREBBP in both patient groups (p < 0.001). RBPJ was significantly lower in SCZ vs HC (p < 0.001), and patients using lithium had higher levels of RBPJ (p < 0.001). We provide evidence of altered Notch signaling in both SCZ and BD compared to HC, and suggest that Notch signaling pathway may be disturbed in these disorders. Lithium may ameliorate aberrant Notch signaling. We propose that drugs targeting Notch pathway could be relevant in the treatment of psychotic disorders.

Increase in serum HDL level is associated with less negative symptoms after one year of antipsychotic treatment in first-episode psychosis.

BACKGROUND: A potential link between increase in total cholesterol and triglycerides and clinical improvement has been observed during antipsychotic drug treatment in chronic schizophrenia patients, possibly due to drug related effects on lipid biosynthesis. We examined whether changes in serum lipids are associated with alleviation of psychosis symptoms after one year of antipsychotic drug treatment in a cohort of first-episode psychosis (FEP) patients. METHODS: A total of 132 non-affective antipsychotic-treated FEP patients were included through the Norwegian Thematically Organized Psychosis (TOP) project. Data on antipsychotic usage, serum lipids (total cholesterol, high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol and triglycerides (TG)), body mass index (BMI) and clinical state were obtained at baseline and after 12months. The Positive and Negative Syndrome Scale (PANSS) was used to assess psychotic symptoms. Mixed-effects models were employed to examine the relationship between serum lipids and psychotic symptoms while controlling for potential confounders including BMI. RESULTS: An increase in HDL during one year of antipsychotic treatment was associated with reduction in PANSS negative subscores (B=-0.48, p=0.03). This relationship was not affected by concurrent change in BMI (adjusted HDL: B=-0.54, p=0.02). No significant associations were found between serum lipids, BMI and PANSS positive subscores. CONCLUSION: We found that an increase in HDL level during antipsychotic treatment is associated with improvement in negative symptoms in FEP. These findings warrant further investigation to clarify the interaction between lipid pathways and psychosis.

Childhood maltreatment severity is associated with elevated C-reactive protein and body mass index in adults with schizophrenia and bipolar diagnoses.

BACKGROUND: Several studies have described an association between childhood maltreatment and inflammatory markers in the psychotic disorders (schizophrenia [SZ] and bipolar disorder [BD]). Previous studies have been relatively small (<50 participants), and the severity of abuse and the putative influence of body mass index (BMI) have not been properly investigated. METHODS: The combined effects of childhood abuse severity and clinical diagnosis on inflammatory markers were investigated in a large sample (n=483) of patients with a disorder on the psychosis spectrum and in healthy controls (HCs). Plasma levels of inflammatory markers (high-sensitivity C-reactive protein [hs-CRP], soluble tumor necrosis factor receptor type 1 [TNFR-R1], glycoprotein 130 [gp130]) were analyzed, and BMI and data on childhood trauma events, on the basis of the Childhood Trauma Questionnaire (CTQ), were obtained from all participants. RESULTS: Patients had increased levels of hs-CRP (P<0.001, Cohens d=0.4), lower levels of gp130 (P<0.001, Cohens d=0.5), higher BMI (P<0.001, Cohens d=0.5) and reported more childhood maltreatment experiences (P<0.001, Cohens d=1.2) than the HC group. The severity of childhood abuse (up to three types of abuse: sexual abuse, physical abuse, and emotional abuse) was associated with elevated BMI (f=8.46, P<0.001, Cohen's d=0.5) and hs-CRP (f=5.47, P=0.001, Cohen's d=0.3). Combined effects of patient status and severity of childhood abuse were found for elevated hs-CRP (f=4.76, P<0.001, Cohen's d=0.4). Differences among the groups disappeared when BMI was added to the model. DISCUSSION: Trauma-altered immune activation via elevated hs-CRP in patients with SZ and BD may be mediated by higher BMI; however, the direction of this association needs further clarification.

A Study of TNF Pathway Activation in Schizophrenia and Bipolar Disorder in Plasma and Brain Tissue.

Objective: A proinflammatory imbalance in the tumor necrosis factor (TNF) system may contribute to the pathogenesis of schizophrenia (SCZ) and bipolar disorders (BDs) and related comorbidities. We investigated the relative distribution of TNF-related molecules in blood and dorsolateral prefrontal cortex (DLPFC) in these disorders. Method: We measured plasma levels of TNF, soluble TNF receptor 1 (sTNFR1), soluble TNF receptor 2 (sTNFR2), and a disintegrin and metalloprotease-17 (ADAM17) using enzyme immunoassays and calculated the TNF/sTNFRs ratio (TNF/sTNFR1+sTNFR2) in a sample of 816 SCZ and BD spectrum patients and 624 healthy controls (HCs). TNF, TNFRSF1A (TNFR1), TNFRSF1B (TNFR2), and ADAM17 mRNA levels were determined in whole blood, and postmortem DLPFC obtained from an independent cohort (n = 80 SCZ, n = 44 BD, and n = 86 HC). Results: In peripheral blood, we show increased TNF-related measures in patients compared to HC, with an increased TNF/sTNFRs ratio (p = 6.00 × 10-5), but decreased TNF mRNA expression (p = 1 × 10-4), with no differences between SCZ and BD. Whole blood ADAM17 mRNA expression was markedly higher in BD vs SCZ patients (p = 1.40 × 10-14) and vs HC (p = 1.22 × 10-8). In postmortem DLPFC, we found no significant differences in mRNA expression of TNF pathway genes between any groups. Conclusions: SCZ and BD patients have increased plasma TNF pathway markers without corresponding increase in blood cell gene expression. ADAM17 expression in leukocytes is markedly different between the two disorders, while alterations in TNF-related gene expression in DLPFC are uncertain. Further studies are necessary to elucidate the aberrant regulation of the TNF pathway in severe mental disorders.

VRK2 gene expression in schizophrenia, bipolar disorder and healthy controls.

BACKGROUND: Common variants in the Vaccinia-related kinase 2 (VRK2) gene have been associated with schizophrenia, but the relevance of its encoded protein VRK2 in the disorder remains unclear. AIMS: To identify potential differences in VRK2 gene expression levels between schizophrenia, bipolar disorder, psychosis not otherwise specified (PNOS) and healthy controls. METHOD: VRK2 mRNA level was measured in whole blood in 652 individuals (schizophrenia, n = 201; bipolar disorder, n = 167; PNOS, n = 61; healthy controls, n = 223), and compared across diagnostic categories and subcategories. Additionally, we analysed for association between 1566 VRK2 single nucleotide polymorphisms and mRNA levels. RESULTS: We found lower VRK2 mRNA levels in schizophrenia compared with healthy controls (P<10(-12)), bipolar disorder (P<10(-12)) and PNOS (P = 0.0011), and lower levels in PNOS than in healthy controls (P = 0.0042) and bipolar disorder (P = 0.00026). Expression quantitative trait loci in close proximity to the transcription start site of the short isoforms of the VRK2 gene were identified. CONCLUSIONS: Altered VRK2 gene expression seems specific for schizophrenia and PNOS, which is in accordance with findings from genome-wide association studies. These results suggest that reduced VRK2 mRNA levels are involved in the underlying mechanisms in schizophrenia spectrum disorders.

Inflammatory markers are associated with general cognitive abilities in schizophrenia and bipolar disorder patients and healthy controls.

BACKGROUND: The mechanisms underlying cognitive impairment in schizophrenia and bipolar disorders are largely unknown. Immune abnormalities have been found in both disorders, and inflammatory mediators may play roles in cognitive function. We investigated if inflammatory markers are associated with general cognitive abilities. METHODS: Participants with schizophrenia spectrum (N=121) and bipolar spectrum (N=111) disorders and healthy controls (N=241) were included. General intellectual abilities were assessed using the Wechsler Abbreviated Scale of Intelligence (WASI). Serum concentrations of the following immune markers were measured: Soluble tumor necrosis factor receptor 1 (sTNF-R1), interleukin 1 receptor antagonist (IL-1Ra), osteoprotegerin, von Willebrand factor, C-reactive protein, interleukin-6 and CD40 ligand. RESULTS: After adjusting for age, sex and diagnostic group, significant negative associations with general cognitive function were found for sTNF-R1 (p=2×10(-5)), IL-1Ra (p=0.002) and sCD40 ligand (p=0.003). Among patients, the associations remained significant (p=0.006, p=0.005 and p=0.02) after adjusting for possible confounders including education, smoking, psychotic and affective symptoms, body mass index, cortisol, medication and time of blood sampling. Subgroup analysis, showed that general cognitive abilities were significantly associated with IL-1Ra and sTNF-R1 in schizophrenia patients, with sCD40L and IL-1Ra in bipolar disorder patients and with sTNF-R1 in healthy controls. CONCLUSION: The study shows significant negative associations between inflammatory markers and general cognitive abilities after adjusting for possible confounders. The findings strongly support a role for inflammation in the neurophysiology of cognitive impairment.