The impact of body mass index in gene expression of reelin pathway mediators in individuals with schizophrenia and mood disorders: A post-mortem study

Expression Profiling of Reelin (RELN) Gene in Patients With Schizophrenia from North Karnataka

Background Schizophrenia is a devastating neuropsychiatric condition of uncertain etiology with significant adverse effects on the affected people, their families, and society. India has a heterogeneous population with a high degree of inbreeding. Hence, it is necessary to screen Indian patients with psychotic disorders to get a true picture of the contribution of Reelin (RELN) mRNA expression in schizophrenia. Mental illness is a leading cause of several metabolic changes and other related complications. It is not clear whether these metabolic changes are due to alterations in the RELN gene expression or because of antipsychotic drug use. Therefore, it is necessary to study the link between RELN gene expression and the metabolic syndrome. Aim and objective The present study aims to study the expression profiling of the RELN gene in patients with schizophrenia and the occurrence of metabolic syndrome in these patients. Methodology Patients with clinically diagnosed schizophrenia were studied for RELN gene expression and the RELN protein was quantified using real-time reverse transcriptase-polymerase chain reaction (RT-PCR). Biochemical parameters like serum random blood sugar (RBS) and lipid profile were analyzed by standard biochemical methods on the semi-auto analyzer and the lipid ratios in the study population were calculated and compared with the age and sex-matched controls. The statistical analyses were performed using IBM SPSS Statistics for Windows, Version 20 (Released 2011; IBM Corp., Armonk, New York, United States). A p-value of <0.05 was considered statistically significant. All statistical tests were two-tailed. Results The present study involved 108 subjects, out of which 54 were patients with schizophrenia (study group) and the remaining 54 were healthy controls (control group). In the former group, 29 were female (53.7%) and 25 were male (46.3%) patients whereas in the latter group, 27 were female (50%) and 27 were male (50%) individuals. Majority of the participants in the study group showed moderate scores on the Brief Psychiatric Rating (BPRS) scale. The levels of RELN mRNA expression were decreased in schizophrenia. Compared to the controls, the levels of RBS, total cholesterol, triglycerides (TGs), and low-density lipoprotein cholesterol (LDL-C) were significantly increased and levels of high-density lipoprotein cholesterol (HDL-C) were significantly decreased in the patients with schizophrenia. Body mass index (BMI), waist circumference (WC), and lipid ratios were also significantly greater in these patients. Conclusion An analysis of the candidate genes in psychotic disorders can be helpful in designing targeted drugs to treat these patients. Early and regular monitoring of patients on antipsychotic drug treatment is needed to find and prevent the risk of developing metabolic syndrome, which is the major cause for atherosclerotic cardiovascular diseases in this group. Appropriate lifestyle modifications and early intervention can help in preventing early deaths in patients with psychotic disorders.

Genetic associations between bipolar disorder and brain structural phenotypes

Patients with bipolar disorder (BD) and their first-degree relatives exhibit alterations in brain volume and cortical structure, whereas the underlying genetic mechanisms remain unclear. In this study, based on the published genome-wide association studies (GWAS), the extent of polygenic overlap between BD and 15 brain structural phenotypes was investigated using linkage disequilibrium score regression and MiXeR tool, and the shared genomic loci were discovered by conjunctional false discovery rate (conjFDR) and expression quantitative trait loci (eQTL) analyses. MiXeR estimated the overall measure of polygenic overlap between BD and brain structural phenotypes as 4-53% on a 0-100% scale (as quantified by the Dice coefficient). Subsequent conjFDR analyses identified 54 independent loci (71 risk single-nucleotide polymorphisms) jointly associated with BD and brain structural phenotypes with a conjFDR < 0.05, among which 33 were novel that had not been reported in the previous BD GWAS. Follow-up eQTL analyses in respective brain regions both confirmed well-known risk genes (e.g. CACNA1C, NEK4, GNL3, MAPK3) and discovered novel risk genes (e.g. LIMK2 and CAMK2N2). This study indicates a substantial shared genetic basis between BD and brain structural phenotypes, and provides novel insights into the developmental origin of BD and related biological mechanisms.

APOE E4 is associated with hyperlipidemia and obesity in elderly schizophrenic patients

Obesity is a critical issue in patients with schizophrenia, which is considered to be brought about by both environmental and genetic factors. Apolipoprotein E (APOE) gene polymorphisms might be involved in the pathogenesis of schizophrenia, however, the effect of APOE gene polymorphism on obesity has never been investigated in Chinese aging with schizophrenia. This cross-sectional study was to investigate the effect of obesity on cognitive and psychiatric symptoms in elderly participants with schizophrenia. At the same time, we also discussed the inner link between APOE E4 and obesity. 301 elderly participants with schizophrenia and 156 normal controls were included in the study. Their cognitive function was assessed using the Montreal Cognitive Assessment (MoCA), psychiatric symptoms were assessed using the Positive and Negative Syndrome Scale (PANSS), and APOE gene polymorphism was determined by polymerase chain reaction (PCR). The prevalence of obesity in elderly schizophrenic patients and healthy controls accounted for 15.9% (48/301) and 10.3% (16/156), respectively, with no statistically significant difference. By using stepwise linear regression analysis, we found that elevated fasting blood glucose, hypertension, and hyperlipidemia were risk factors for obesity in elderly schizophrenic patients. Although there was no direct correlation between APOE E4 and obesity in patients with schizophrenia, it was significantly correlated with hyperlipemia(r = − 0.154, p = 0.008), suggesting that APOE E4 may induce obesity in elderly patients with schizophrenia through hyperlipemia, However, the above conclusions do not apply to the normal elderly. What’s more, we did not find a link between obesity and cognitive function or mental symptoms for both patients with schizophrenia and normal controls. APOE E4 is associated with hyperlipidemia in elderly schizophrenic patients, which may be a risk factor for obesity, however, the above conclusion does not apply to the normal elderly.

Salivary epigenetic biomarkers as predictors of emerging childhood obesity

BACKGROUND

Epigenetics could facilitate greater understanding of disparities in the emergence of childhood obesity. While blood is a common tissue used in human epigenetic studies, saliva is a promising tissue. Our prior findings in non-obese preschool-aged Hispanic children identified 17 CpG dinucleotides for which differential methylation in saliva at baseline was associated with maternal obesity status. The current study investigated to what extent baseline DNA methylation in salivary samples in these 3-5-year-old Hispanic children predicted the incidence of childhood obesity in a 3-year prospective cohort.

METHODS

We examined a subsample (n = 92) of Growing Right Onto Wellness (GROW) trial participants who were randomly selected at baseline, prior to randomization, based on maternal phenotype (obese or non-obese). Baseline saliva samples were collected using the Oragene DNA saliva kit. Objective data were collected on child height and weight at baseline and 36 months later. Methylation arrays were processed using standard protocol. Associations between child obesity at 36 months and baseline salivary methylation at the previously identified 17 CpG dinucleotides were evaluated using multivariable logistic regression models.

RESULTS

Among the n = 75 children eligible for analysis, baseline methylation of Cg1307483 (NRF1) was significantly associated with emerging childhood obesity at 36-month follow-up (OR = 2.98, p = 0.04), after adjusting for child age, gender, child baseline BMI-Z, and adult baseline BMI. This translates to a model-estimated 48% chance of child obesity at 36-month follow-up for a child at the 75th percentile of NRF1 baseline methylation versus only a 30% chance of obesity for a similar child at the 25th percentile. Consistent with other studies, a higher baseline child BMI-Z during the preschool period was associated with the emergence of obesity 3 years later, but baseline methylation of NRF1 was associated with later obesity even after adjusting for child baseline BMI-Z.

CONCLUSIONS

Saliva offers a non-invasive means of DNA collection and epigenetic analysis. Our proof of principle study provides sound empirical evidence supporting DNA methylation in salivary tissue as a potential predictor of subsequent childhood obesity for Hispanic children. NFR1 could be a target for further exploration of obesity in this population.

Evidence that genes involved in hedgehog signaling are associated with both bipolar disorder and high BMI

Patients with bipolar disorder (BD) show higher frequency of obesity and type 2 diabetes (T2D), but the underlying genetic determinants and molecular pathways are not well studied. Using large publicly available datasets, we (1) conducted a gene-based analysis using MAGMA to identify genes associated with BD and body mass index (BMI) or T2D and investigated their functional enrichment; and (2) performed two meta-analyses between BD and BMI, as well as BD and T2D using Metasoft. Target druggability was assessed using the Drug Gene Interaction Database (DGIdb). We identified 518 and 390 genes significantly associated with BD and BMI or BD and T2D, respectively. A total of 52 and 12 genes, respectively, were significant after multiple testing correction. Pathway analyses conducted on nominally significant targets showed that genes associated with BD and BMI were enriched for the Neuronal cell body Gene Ontology (GO) term (p = 1.0E-04; false discovery rate (FDR) = 0.025) and different pathways, including the Signaling by Hedgehog pathway (p = 4.8E-05, FDR = 0.02), while genes associated with BD and T2D showed no specific enrichment. The meta-analysis between BD and BMI identified 64 relevant single nucleotide polymorphisms (SNPs). While the majority of these were located in intergenic regions or in a locus on chromosome 16 near and in the NPIPL1 and SH2B1 genes (best SNP: rs4788101, p = 2.1E-24), five were located in the ETV5 gene (best SNP: rs1516725, p = 1E-24), which was previously associated with both BD and obesity, and one in the RPGRIP1L gene (rs1477199, p = 5.7E-09), which was also included in the Signaling by Hedgehog pathway. The meta-analysis between BD and T2D identified six significant SNPs, three of which were located in ALAS1 (best SNP: rs352165, p = 3.4E-08). Thirteen SNPs associated with BD and BMI, and one with BD and T2D, were located in genes which are part of the druggable genome. Our results support the hypothesis of shared genetic determinants between BD and BMI and point to genes involved in Hedgehog signaling as promising targets.