Investigation of completed suicide and genes involved in cholesterol metabolism

Apolipoproteins and Suicide: A Potential Psychiatric Biomarker

Every year around 800,000 people commit suicide, this represents one death every 40 s. In the search for possible biological biomarkers associated with suicide and/or psychiatric disorders, serum cholesterol levels have been extensively explored. Several studies indicate that cholesterol and associated proteins, especially apolipoproteins (Apos), may play an important role in the diagnosis, prognosis, and susceptibility of suicidal behavior. Here, we describe the current knowledge and findings in the relationship between apolipoproteins and suicide.HIGHLIGHTSThis is the first systematic review of Apos in relation to suicidal behavior.Dysregulations of Apos expression has been observed in patients with suicidal behavior.Apos seem to be associated with cognitive dysfunction in suicide attempters.ApoE is a potential biomarker regarding suicidal behavior.

Possible Association of Cholesterol as a Biomarker in Suicide Behavior

Suicides and suicidal behavior are major causes of mortality and morbidity in public health and are a global problem. Various authors have proposed changes in lipid metabolism (total cholesterol decrease) as a possible biological marker for suicidal behavior. The objective of this study was to review the studies that have demonstrated a relationship between serum cholesterol levels and suicidal behavior and to describe the possible pathophysiological mechanisms that associate changes in cholesterol concentration and suicidal behavior. Relevant literature related to serum cholesterol levels and suicidal behavior was identified through various database searches. The data from the existing literature present the findings that relate low cholesterol levels and possible pathophysiological mechanisms (neuroinflammation, serotonergic neurotransmission), genes related to cholesterol synthesis, pharmacological treatments that alter lipid metabolism and the possible participation in suicidal behavior. Nevertheless, future research is required to describe how serum cholesterol affects cholesterol metabolism in the CNS to establish and understand the role of cholesterol in suicidal behavior.

Evaluation of leptin levels in serum as a biomarker for suicide behavior: systematic review and meta-analysis

Objective: We conducted a meta-analysis of case-control studies to determine whether leptin levels in serum contribute to the pathogenesis of suicide behavior.Methods: PubMed, EBSCO and Science Direct databases were used to search for relevant articles published before January 2020. The systematic review included nine case-control studies that measured leptin levels. The standardized mean difference (d) and 95% confidence intervals were calculated in a fixed-effects model and a random-effects model when appropriate.Results: The results of our meta-analysis indicated that individuals with suicide behavior presented reduced levels of leptin (d: -1.80, 95% CI: -2.21 to -01.38 ng/ml, I² = 0, p(Q) = 0.59). Sensitivity and publication bias analyses confirmed these results.Conclusions: The current meta-analysis suggests that leptin levels might be associated with an increased risk of suicide behavior. However, more studies including larger sample sizes are needed to reach conclusive result.

ABCA1 Polymorphism, a Genetic Risk Factor of Harm Avoidance

Abstract. Even though cholesterol homeostasis and self-harm behaviors have shown to be associated, gene polymorphisms of the cholesterol system have not been studied yet in the context of self-harm related personality traits. Here we present an association study between six ABCA1 polymorphisms and temperament scales measured by Cloninger’s Temperament and Character Inventory on 253 young adults. An association between ABCA1 rs4149264 and harm avoidance has been observed. This association remained significant after Bonferroni correction. Haplotype analysis confirmed an independent association between rs4149264 and harm avoidance. ABCA1, a cholesterol homeostasis gene, is a candidate gene for harm related personality traits.

Plasma apolipoprotein E and severity of suicidal behaviour

There is evidence for association between low cholesterol levels and suicidal behaviour. Since apolipoprotein E (ApoE) is involved in the cholesterol metabolism in both the periphery and in the central nervous system; it may be of particular interest in the neurobiology of suicidal behaviour. Furthermore, hypothalamic-pituitary-adrenal (HPA) axis function, one of the main biological systems implicated in both suicidal behaviour and early-life adversity, affect ApoE levels. Very few studies have assessed plasma ApoE in relation to suicidal behaviour. The purpose of this study was to investigate levels of ApoE in plasma in relation to the severity of suicidal behaviour and life-time adversity in the form of exposure to interpersonal violence in suicide attempters. A total of 100 suicide attempters (67 women and 33 men) were enroled in the study. Information on earlier suicide attempts and age at onset of suicidal behaviour was gathered using the Karolinska Suicide History Interview. The Karolinska Interpersonal Violence Scale was used to assess exposure to interpersonal violence. Plasma ApoE was measured by immunonephelometry according to accredited routines. Patients with at least one earlier suicide attempt had significantly higher ApoE levels compared to suicide attempters debuting with suicidal behaviour at inclusion in the study. A higher number of earlier suicide attempts was significantly correlated with higher plasma ApoE levels. Age at onset was significantly negatively correlated with ApoE after adjusting for age. ApoE showed a significant positive correlation with exposure to interpersonal violence as a child in male suicide attempters. Our findings indicate that ApoE may be related to stress and trauma and the temporal severity of suicidal behaviour.

An overview of the neurobiology of suicidal behaviors as one meta-system

Suicidal behaviors (SB) may be regarded as the outmost consequence of mental illnesses, or as a distinct entity per se. Regardless, the consequences of SB are very large to both society and affected individuals. The path leading to SB is clearly a complex one involving interactions between the subject's biology and environmental influences throughout life. With the aim to generate a representative and diversified overview of the different neurobiological components hypothesized or shown implicated across the entire SB field up to date by any approach, we selected and compiled a list of 212 gene symbols from the literature. An increasing number of novel gene (products) have been introduced as candidates, with half being implicated in SB in only the last 4 years. These candidates represent different neuro systems and functions and might therefore be regarded as competing or redundant explanations. We then adopted a unifying approach by treating them all as parts of the same meta-system, using bioinformatic tools. We present a network of all components connected by physical protein-protein interactions (the SB interactome). We proceeded by exploring the differences between the highly connected core (~30% of the candidate genes) and its peripheral parts, observing more functional homogeneity at the core, with multiple signal transduction pathways and actin-interacting proteins connecting a subset of receptors in nerve cell compartments as well as development/morphology phenotypes and the stress-sensitive synaptic plasticity processes of long term potentiation/depression. We suggest that SB neurobiology might also be viewed as one meta-system and perhaps be explained as intrinsic unbalances acting within the core or as imbalances arising between core and specific peripheral components.

Role of serotonergic-related systems in suicidal behavior: Data from a case-control association study

OBJECTIVE

To investigate whether functional polymorphisms directly (HTR2A and SLC6A4 genes) or indirectly (IL-1 gene complex, APOE and ACE genes) related with serotonergic neurotransmission were associated with suicidal behavior.

SUBJECTS AND METHODS

227 suicide attempters, 686 non-suicidal psychiatric patients, and 420 healthy controls from a homogeneous Spanish Caucasian population were genotyped using standard methods.

RESULTS

There were no differences in genotype frequencies between the three groups. The -1438A/G [χ(2) (df)=9.80 (2), uncorrected p=0.007] and IL-1α -889C/T [χ(2) (df)=8.76 (2), uncorrected p=0.013] genotype frequencies between impulsive and planned suicide attempts trended toward being different (not significant after Bonferroni correction). Suicide attempts were more often impulsive in the presence of -1438G/G or IL-1α -889C/T or C/C genotypes. There was interaction between the polymorphism 5-HTTLPR and age [LRT (df)=6.84 (2), p=0.033] and between the polymorphisms APOE and IL-1RA (86bp)(n) [LRT (df)=12.21 (4), p=0.016] in relation to suicide attempt lethality.

CONCLUSION

These findings further evidence the complexity of the association between genetics and suicidal behavior, the need to study homogenous forms of the behavior and the relevance of impulsive and aggressive traits as endophenotypes for suicidal behavior.

Total serum cholesterol levels and suicide attempts in child and adolescent psychiatric inpatients

Associations between cholesterol and suicidal behavior in adolescent patients have not been explored in depth. In this study, 66 patients consecutively admitted to a psychiatric inpatient unit following attempted suicide were compared with a control group of 54 patients with no history of suicide attempts. The age range of the sample was from 8 to 18 years old. Cholesterol levels were significantly lower in attempted suicide patients than in controls (p < 0.02), supporting the hypothesis that lower cholesterol levels might be associated with suicidal behavior in patients with similar acute phase of their disorder.

(TTA)n polymorphism in 3-hydroxy-3-methylglutaryl-coenzyme A and response to atorvastatin in coronary artery disease patients

3-Hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors have been used clinically for lowering total and low-density lipoprotein cholesterol. Interindividual pharmacological differences observed with this treatment have been attributed to genetic differences. The aim of this study was to assess the association in the low-density lipoprotein cholesterol reduction by atorvastatin and (TTA)n polymorphism in the 3-hydroxy-3-methylglutaryl-coenzyme A reductase gene in patients with coronary artery disease. Changes in total cholesterol levels, triglycerides, high-sensitivity C-reactive protein and free F(2)-isoprostanes were also evaluated. In an open study, patients received 40 mg atorvastatin daily for 8 weeks. Genotyping was done through polymerase chain reaction. The genotype distribution of the 3-hydroxy-3-methylglutaryl-coenzyme A reductase (TTA)n polymorphism was: >10/>10 in 22 out of 64 patients (34%), >10/10 in 14 out of 64 patients (22%) and 10/10 in 28 out of 64 patients (44%). The reduction of low-density lipoprotein cholesterol levels by atorvastatin was not different between allelic variants (TTA)n repeat polymorphism. Reductions in high-sensitivity C-reactive protein were observed in atorvastatin-treated patients with alleles >10/>10 and 10/10. Free F(2)-isoprostanes and total cholesterol were also significantly lower after treatment for all alleles, irrespective of type of polymorphism. In conclusion, the changes induced by atorvastatin treatment on low-density lipoprotein cholesterol, total cholesterol, triglycerides, high-sensitivity C-reactive protein and free F(2)-isoprostane concentrations were not related to the presence of 3-hydroxy-3-methylglutaryl-coenzyme A reductase polymorphism (TTA)n.

The genetics of suicide: a critical review of molecular studies

Genetic epidemiology research has shown that genes contribute to suicide risk. Unfortunately, the first 30 years of candidate-based association studies have provided little information about the specific genetic contributors. This article reviews genetic association studies of suicidal phenotypes published to date. Possible theoretical, methodological, and operational challenges accounting for the modest success of association studies in the field are also discussed. The authors conclude that future research may benefit from using a more systematic and comprehensive selection of candidate genes and variants, examining gene-environment and gene-gene interactions, and investigating higher-order moderators.

Association of APOE genetic polymorphism with cognitive function and suicide history in geriatric depression

Apolipoprotein E (APOE) has been associated with a variety of late-life neuropsychiatric disorders, including geriatric depression. This study determined whether APOE genotypes affect vulnerability to geriatric depression. We also tested the effect of the presence of the APOE epsilon4 (APOE4) allele on age of onset, suicide attempt history and cognitive function in geriatric depressed patients. We genotyped APOE in 111 elderly inpatients diagnosed as having major depression and 144 normal controls. The depressed patients were evaluated at baseline using the Hamilton Rating Scale for Depression and the Mini-Mental State Examination (MMSE) after admission. Age of onset of depression and suicide attempt history in the depressed group were evaluated by interview and medical record. We found no association between APOE genotypes and geriatric depression (p = 0.342) or APOE4 status and age of onset of depression (p = 0.281). However, compared with depressed subjects lacking the APOE epsilon4 allele, depressed subjects who were also APOE4 carriers showed significantly lower MMSE scores (p = 0.021) and an increased suicide attempt history (p = 0.012). The APOE genotype may contribute to cognitive performance and suicidality in geriatric depression, rather than being a specific risk factor for the disorder.

Molecular genetic findings in suicidal behavior: what is beyond the serotonergic system?

Various studies provide consistent evidence for a genetic component in suicidal behavior. First molecular genetic studies concentrated on genes of the serotonergic system based on the biochemical evidence that serotonergic neurotransmission is implicated in this behavior. Furthermore, genes of the dopaminergic and noradrenergic neurotransmitter systems have also been the subjects of investigations in this context. Some epidemical and clinical studies showed that low serum cholesterol levels are associated with suicidal behavior and genes involved in these pathways have been investigated. Microarray experiments provide the possibility of genome-wide gene expression analysis and help to investigate associated molecular mechanisms. The aim of this article is to review molecular genetic studies in suicidal behavior and to emphasize findings on new genes.

Relationship between polymorphisms of 3-hydroxy-3-methylglutaryl coenzyme A reductase gene and hepatitis B virus infection

AIM: To investigate the relationship between exon20 polymorphism of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) gene and clinical outcome of the patients infected with hepatitis B virus (HBV).

METHODS: From the year 2002 to 2004 in Chongqing, the clinical data and blood samples of 2 400 patients with liver diseases were collected. The total DNA was extracted from the blood samples. After amplification, the exon20 polymorphisms of HMGCR gene (locus 18109T/C) were detected polymerase chain reaction (PCR), digestion of restriction enzyme and gel electrophresis.

RESULTS: A total of 1 354 patients were diagnosed with hepatitis B. Hardy-Weinberg equillibrum test showed a favorable goodness for fit (P = 0.016>0.01). Significant differences of genotypes and allele frequency existed between the asymptomatic carriers (AsCs) and patients of any other subgroup except acute hepatitis B and liver cancer (P <0.01). Under the condition of codominance, the polymorphism of HMGCR 18109T/C was significantly correlated with the status of patients after HBV infection (liver cirrhosis/AsC: OR = 0.676, P = 0.004; AsC/severe hepatitis B: OR = 0.672, P = 0.000; AsC/chronic hepatitis B: OR = 0.747, P = 0.000; AsC/chronic hepatitis B+severe hepatitis B+liver cirrhosis: OR = 0.756, P = 0.010), and patients with C/C genotype tended to become AsCs more easily after HBV infection, as compared with patients with T/T and C/T genotype.

CONCLUSION: The exon20 (locus 18109T/C) polymorphism of HMGCR gene is correlated with HBV infection, and patients with C/C genotype are more succeptible to become AsCs after HBV infection.

Decreased density of peripheral benzodiazepine receptors in psychiatric patients after a suicide attempt

To date, two main types of benzodiazepine (BDZ) receptors have been identified: one of these is the so-called central receptor which is found mainly in the cortex, limbic areas and cerebellum, and the other is known as the peripheral receptor, which is found in the kidneys, lungs, ovaries, testes, adrenal glands and blood cells, but is present also in the central nervous system (CNS), in particular in glial cells. Although for some time the peripheral BDZ receptor has been considered an acceptor site with no pharmacological activity, recent data have suggested that it may be involved in a variety of actions, such as the response to stress. The presence of these receptors in blood platelets, which are considered a reliable, peripheral mirror of the same structures located in the SNC, prompted us to evaluate them in a group of psychiatric patients after a suicide attempt, as compared with healthy control subjects, by means of the specific binding of 3H-PK 11195. Suicide, with no doubt, may be considered one of the most stressful situations occurring to humans. The results showed the presence of a significant decrease in the density of 3H-PK 11195 binding sites in the patients, as compared with healthy control subjects. This finding may represent a non-specific indicator of a condition of stress, since peripheral BDZ receptors are modulated by stress and hormones, or it may result more from an abnormal metabolism of steroid substances which could play a pivotal role in the development of vulnerability towards suicide.