No association between APOE and major depressive disorder in a community sample of 17,507 adults

ApoE4 dysregulation incites depressive symptoms and mitochondrial impairments in mice

Apolipoprotein E4 (ApoE4) is involved in the stress-response processes and is hypothesized to be a risk factor for depression by means of mitochondrial dysfunction. However, their exact roles and underlying mechanisms are largely unknown. ApoE4 transgenic mice (B6. Cg-ApoEtm1Unc Cdh18Tg( GFAP-APOE i4)1Hol /J) were subjected to stress (lipopolysaccharides, LPS) to elucidate the aetiology of ApoE4-induced depression. LPS treatment significantly aggravated depression-like behaviours, concurrent with neuroinflammation and impaired mitochondrial changes, and melatonin/Urolithin A (UA) + 5-aminoimidazole-4-carboxamide 1-β-D-ribofuranoside (AICAR) reversed these effects in ApoE4 mice. Concurrently, ApoE4 mice exhibited mitophagy deficits, which could be further exacerbated by LPS stimulation, as demonstrated by reduced Atg5, Beclin-1 and Parkin levels, while PINK1 levels were increased. However, these changes were reversed by melatonin treatment. Additionally, proteomic profiling suggested mitochondria-related signalling and network changes in ApoE4 mice, which may underlie the exaggerated response to LPS. Furthermore, HEK 293T cells transfected with ApoE4 showed mitochondria-associated protein and mitophagy defects, including PGC-1α, TFAM, p-AMPKα, PINK1 and LC3B impairments. Additionally, it aggravates mitochondrial impairment (particularly mitophagy), which can be attenuated by triggering autophagy. Collectively, ApoE4 dysregulation enhanced depressive behaviour upon LPS stimulation.

Association of APOE E2 and low-density lipoprotein with depressive symptoms in Chinese senile schizophrenia inpatients: A cross-sectional study

Background

Schizophrenia is considered to occur due to both environmental and genetic factors. Depressive symptoms and apolipoprotein E (APOE) gene polymorphisms are involved in the pathogenesis of schizophrenia. However, the effect of APOE gene polymorphism on depressive symptoms has never been investigated among Chinese elderly schizophrenia patients.

Objective

This cross-sectional study aimed to determine the effect of APOE gene polymorphism on blood lipid metabolism and depressive symptoms among elderly schizophrenia patients.

Method

A total of 301 elderly schizophrenia patients (161 males, age ranges from 60 to 92 years, with an average age of 67.31 ± 6.667) were included in the study. Depressive symptoms were assessed using the Geriatric Depression Scale (GDS). APOE gene polymorphisms were determined by polymerase chain reaction (PCR). Correlations between GDS and serum low-density lipoprotein (LDL) levels with APOE genotypes were assessed.

Results

The concentration of LDL in the APOE E2 group was significantly lower than those in the APOE E3 and APOE E4 groups, and the GDS scores in the APOE E2 and APOE E3 groups were higher than those in the APOE E4 group. Using partial correlation analysis and controlling the duration of disease and hyperlipidemia, we found that GDS scores were significantly correlated with LDL (r = −0.179, p = 0.025).

Conclusions

The APOE E2 genotype is associated with more depressive symptoms and lower serum LDL in elderly Chinese schizophrenia patients, and there is a negative correlation between depressive symptoms and LDL.

Role of apolipoprotein E epsilon 4 (APOE*ε4) as an independent risk factor for incident depression over a 12-year period in cognitively intact adults across the lifespan

BACKGROUND

The apolipoprotein E ε4 allele (APOE*ε4) is indicated as a risk for Alzheimer's disease and other age-related diseases. The risk attributable to APOE*ε4 for depression is less clear and may be because of confounding of the relationship between dementia and depression.

AIMS

We examined the risk of APOE* ε4 for incident depression and depressive symptomology over a 12-year period across the adult lifespan.

METHOD

Participants were from the Personality and Total Health Through Life study, aged 20 to 24 (n = 1420), 40 to 44 (n = 1592) or 60-64 (n = 1768) at baseline, and interviewed every 4 years since 1999. Ethnicities other than White, those without genotyping and those with depression at baseline, or who reported strokes and scores on the Mini-Mental State Examination <27 at any observation, were excluded.

RESULTS

Over the study period, there was no evidence that APOE*ε4+ was a risk factor for depression, including any depression (odds ratio (OR) = 0.94, 95% CI 0.77-1.16, P = 0.573), major depression (OR = 0.96, 95% CI 0.60-1.53, P = 0.860), minor depression (OR = 0.94, 95% CI 0.67-1.30, P = 0.695) or depressive symptomology (incidence rate ratio (IRR) = 1.02, 95% CI 0.97-1.08, P = 0.451). APOE*ε4 was unrelated to incident depression. Findings were consistent for all age cohorts.

CONCLUSIONS

Among cognitively intact Australian adults who were free of depression at baseline, there was little evidence that APOE*ε4+ carriers are at increased risk for depression over a 12-year period among those who are cognitively intact.

Chronic depressive symptomatology and CSF amyloid beta and tau levels in mild cognitive impairment

OBJECTIVES

To investigate the association between chronic subsyndromal symptoms of depression (SSD), cerebrospinal fluid (CSF) biomarkers, and neuropsychological performance in individuals with mild cognitive impairment (MCI).

METHODS

Participants included 238 older adults diagnosed with MCI from the Alzheimer's Disease Neuroimaging Initiative repository with cognitive and CSF amyloid beta (Aβ_1-42 ), total tau (t-tau), and phosphorylated tau (p-tau) data. The Neuropsychiatric Inventory identified individuals with chronic endorsement (SSD group N = 80) or no endorsement (non-SSD group N = 158) of depressive symptoms across timepoints. CSF biomarker and cognitive performance were evaluated with linear regression models adjusting for age, education, gender, APOE genotype, global cognitive status, and SSD group.

RESULTS

As compared to the non-SSD group, the SSD group displayed lower CSF Aβ_1-42 levels (β = -24.293, S.E. = 6.345, P < 0.001). No group differences were observed for CSF t-tau (P = 0.497) or p-tau levels (P = 0.392). Lower CSF Aβ_1-42 levels were associated with poorer performance on learning (β = 0.041, S.E. = 0.018, P = 0.021) and memory (β = -0.012, S.E. = 0.005, P = 0.031) measures, whereas higher CSF t-tau levels were associated with poorer performance on measures of global cognition (β = 0.022, S.E = 0.008, P = 0.007) and language (β = -0.010, S.E = 0.004, P = 0.019). SSD was independently associated with diminished global cognition, learning and memory, language, and executive function performance over and above the effects of CSF biomarkers (all P < 0.05).

CONCLUSIONS

MCI participants with SSD displayed diminished CSF Aβ_1-42 levels but did not differ from non-SSD controls in CSF tau levels. Additionally, CSF biomarkers and SSD independently accounted for variance in cognitive performance, suggesting that these factors may uniquely confer cognitive risk in MCI.

Understanding the pathophysiology of depression: From monoamines to the neurogenesis hypothesis model - are we there yet?

A number of factors (biogenic amine deficiency, genetic, environmental, immunologic, endocrine factors and neurogenesis) have been identified as mechanisms which provide unitary explanations for the pathophysiology of depression. Rather than a unitary construct, the combination and linkage of these factors have been implicated in the pathogenesis of depression. That is, environmental stressors and heritable genetic factors acting through immunologic and endocrine responses initiate structural and functional changes in many brain regions, resulting in dysfunctional neurogenesis and neurotransmission which then manifest as a constellation of symptoms which present as depression.

Shared Genetic Risk Factors for Late-Life Depression and Alzheimer's Disease

BACKGROUND

Considerable evidence has been reported for the comorbidity between late-life depression (LLD) and Alzheimer's disease (AD), both of which are very common in the general elderly population and represent a large burden on the health of the elderly. The pathophysiological mechanisms underlying the link between LLD and AD are poorly understood. Because both LLD and AD can be heritable and are influenced by multiple risk genes, shared genetic risk factors between LLD and AD may exist.

OBJECTIVE

The objective is to review the existing evidence for genetic risk factors that are common to LLD and AD and to outline the biological substrates proposed to mediate this association.

METHODS

A literature review was performed.

RESULTS

Genetic polymorphisms of brain-derived neurotrophic factor, apolipoprotein E, interleukin 1-beta, and methylenetetrahydrofolate reductase have been demonstrated to confer increased risk to both LLD and AD by studies examining either LLD or AD patients. These results contribute to the understanding of pathophysiological mechanisms that are common to both of these disorders, including deficits in nerve growth factors, inflammatory changes, and dysregulation mechanisms involving lipoprotein and folate. Other conflicting results have also been reviewed, and few studies have investigated the effects of the described polymorphisms on both LLD and AD.

CONCLUSION

The findings suggest that common genetic pathways may underlie LLD and AD comorbidity. Studies to evaluate the genetic relationship between LLD and AD may provide insights into the molecular mechanisms that trigger disease progression as the population ages.

Gene-Environment Interplay in Physical, Psychological, and Cognitive Domains in Mid to Late Adulthood: Is APOE a Variability Gene?

Despite emerging interest in gene-environment interaction (GxE) effects, there is a dearth of studies evaluating its potential relevance apart from specific hypothesized environments and biometrical variance trends. Using a monozygotic within-pair approach, we evaluated evidence of G×E for body mass index (BMI), depressive symptoms, and cognition (verbal, spatial, attention, working memory, perceptual speed) in twin studies from four countries. We also evaluated whether APOE is a 'variability gene' across these measures and whether it partly represents the 'G' in G×E effects. In all three domains, G×E effects were pervasive across country and gender, with small-to-moderate effects. Age-cohort trends were generally stable for BMI and depressive symptoms; however, they were variable-with both increasing and decreasing age-cohort trends-for different cognitive measures. Results also suggested that APOE may represent a 'variability gene' for depressive symptoms and spatial reasoning, but not for BMI or other cognitive measures. Hence, additional genes are salient beyond APOE.

A 9-year prospective population-based study on the association between the APOE*E4 allele and late-life depression in Sweden

BACKGROUND

It is well established that there is an association between the apolipoprotein E (APOE) ε4 allele (APOE*E4) and Alzheimer's disease. It is less clear whether there is also an association with geriatric depression. We examined the relationship between APOE*E4 and 5-year incidence of depression in a Swedish population-based sample of older adults without dementia and excluding older adults who developed dementia within 4 years after the diagnosis of depression.

METHODS

In 2000-2001, 839 women and men (age range, 70-92 years; mean age, 73.8 years) free from dementia and depression underwent neuropsychiatric and neuropsychological examinations and genotyping of the APOE*E4 allele. Follow-up evaluations were conducted in 2005 and 2009.The association between APOE*E4 allele and 5-year incidence of depression was examined, while avoiding possible confounding effects of clinical or preclinical dementia by excluding participants who had dementia at study entry, subsequently developed dementia during the 9-year follow-up period, or had a decline in Mini-Mental State Examination score of ≥5 points.

RESULTS

Among subjects without depression at study entry and without dementia or significant cognitive decline during the subsequent 9 years, APOE*E4 was prospectively associated with more severe depressive symptoms (b = 1.56, p = .007), incident minor depression (odds ratio = 1.99 [confidence interval = 1.11-3.55], p = .020), and any depression (odds ratio = 1.75 [confidence interval = 1.01-3.03], p = .048).

CONCLUSIONS

The presence of the APOE*E4 allele predicted future depression in this Swedish population study, even after excluding depressed individuals who later developed dementia, suggesting that the APOE*E4 allele could potentially identify people at high risk for clinically significant depression.

Interactions between the apolipoprotein E ε4 allele status and adverse childhood experiences on depressive symptoms in older adults

BACKGROUND

The influence of childhood adversity on depression is modulated by genetic vulnerability. The apolipoprotein E ε4 (APOE-ε4) allele is a strong genetic risk factor for Alzheimer's disease (AD). Because late-life depressive symptoms could be a part of the preclinical course of AD, the APOE-ε4 allele may contribute to depression in old age.

OBJECTIVE

The aim of this study was to evaluate whether an APOE-ε4 carrier status was associated with depressive symptoms in older adults and to detect the gene-environment interaction between APOE-ε4 status and childhood adversity in relation to depressive symptoms in old age.

METHOD

The participants consisted of 137 older adults (age range 50-70) without any psychiatric history or clinically significant cognitive impairment. APOE genotypes and measures of childhood adversity and depressive symptoms were obtained.

RESULTS

There was a significant positive association between adverse childhood experiences (ACE) scores and depressive symptoms (B=0.60; 95% CI=0.26, 0.93 for a 1 score increase in ACE scores; p=0.001). Although APOE-ε4 status per se was not associated with depressive symptoms, there was a significant interaction of the ACE scores with the APOE genotype in relation to depressive symptoms (B=0.78; 95% CI=0.02, 1.55; p=0.044). There was a significantly higher effect of childhood adversity on depressive symptoms in APOE-ε4 carriers than non-carriers (t=2.13, p=0.035).

CONCLUSIONS

Our results suggest that the APOE-ε4 may modulate the association between childhood adversity and depressive symptoms in older adults. However, more research in a larger sample is needed to gain a better understanding of the relationship between the APOE-ε4, childhood adversity, and depression.

Apolipoprotein E and depressive symptoms: shared or independent routes to age-related cognitive decline?

Variation in the apolipoprotein E (APOE) genotype is associated with cognitive decline in normal aging. Increased symptoms of depression are also associated with greater cognitive impairment and risk of dementia in old age. Unlike APOE, where the direction of the effect is from genotype to cognitive decline, the causal relationship between depressed mood and cognitive impairment is not known. Rather than being a reaction to worsening cognitive performance with age, depressive symptoms might be a risk factor for age-related cognitive decline. The study by Rajan and colleagues (published in this issue of Psychosomatic Medicine) speaks to this possibility and, importantly, considers the association between depressive symptoms and age-related cognitive decline in the context of APOE variation. This editorial discusses these findings in relation to causal pathways and highlights how longitudinal studies of this nature will improve our understanding of the biological underpinnings of cognitive decline and classification of its risk in the general population.

ApoE4 is not associated with depression when mild cognitive impairment is considered

OBJECTIVE

The aim of the study was to examine the relationship between apolipoprotein E4 allele (ApoE4) and depression among an older Japanese population. Mild cognitive impairment (MCI) was taken into consideration.

METHODS

This is a community-based cross-sectional study. We assessed the mood and cognitive function of Japanese community-dwelling individuals aged 65 years or older. In the first phase of the study, we evaluated the mood and cognitive function. In the second phase, face-to-face structured interviews were conducted. Individuals with dementia and other mental diseases were excluded on the basis of a consensus meeting of psychiatrists and neuropsychologists; 738 subjects with full data were included in the analyses. We subdivided depression into major depressive episode (MDE) and depressive symptoms cases (DSCs). DSC was defined as a score of 6 or more on the Geriatric Depression Scale but not having a diagnosis of MDE. The relationship between depression (MDE and DSC) and ApoE4 was examined by multivariate logistic regression.

RESULTS

The adjusted odds ratio (OR) of ApoE4 on DSC was not significant (OR = 0.82, 95%CI = 0.48-1.39, p < 0.46). Sex (OR = 2.53, 95%CI = 1.33-4.79, p < 0.01), MCI (1.95, 1.21-3.14, p < 0.01), years of education (0.87, 0.79-0.95, p < 0.01), and Nishimura's activities of daily living scores (0.75, 0.63-0.89, p < 0.01) significantly correlated with prevalence of DSC. There were no significant risk factors for MDE.

CONCLUSION

Apolipoprotein E4 allele contributed to neither DSC nor MDE. The association of MCI with ApoE4 and DSC suggested that MCI is a confounder for the association between ApoE4 and DSC.

Increasing depressive symptoms in children of Alzheimer parents

Children of persons with Alzheimer disease (AD) are at increased risk of developing AD themselves, but specific factors that predict AD in this population have yet to be elucidated. Various studies indicate depressive symptoms may predate clinical AD and represent a risk factor and/or prodrome of incipient dementia, but their relevance for AD offspring remains uncertain. As part of a longitudinal family study of AD, we assessed depressive symptomatology in 30 middle aged AD offspring (mean age at baseline: 41.2). Their mean total scores on the Hamilton Depression Rating scale increased from 1.8 to 5.3 (P < .001) across a 20-year interval. Neurocognitive performance remained stable in a subset of this cohort (N = 25) over the same interval. Findings from this small convenience sample suggest emerging depressive symptoms may be among the earliest signs of subsequent dementia in this high-risk population but require confirmation through further longitudinal follow-up and replication in larger populations.

Genetic variation in apolipoprotein E alters regional gray matter volumes in remitted late-onset depression

BACKGROUND

The apolipoprotein E (ApoE) gene has been confirmed as the major genetic risk factor for late-onset Alzheimer's disease (AD). The effect of ApoE polymorphism on brain morphology still remains unclear in remitted late-onset depression (RLOD).

METHODS

A total of 37 patients with remitted geriatric depression were investigated with optimized voxel-based morphometry. We tested for differences in gray matter volume between ApoE epsilon4 allele noncarriers (n=25) and ApoE epsilon4 allele carriers (n=12) in RLOD patients.

RESULTS

The volumes of right medial frontal gyrus, left middle frontal gyrus and left inferior occipital gyrus were significantly smaller in RLOD patients with ApoE epsilon4 allele carriers as compared to ApoE epsilon4 allele noncarriers. There was a significant positive correlation between gray matter volume of right medial frontal gyrus and Digit Span Test score in RLOD patients with ApoE epsilon4 allele carriers.

LIMITATIONS

This study is cross-sectional, therefore it cannot determine whether abnormal gray matter volume is a state marker or trait marker of RLOD with ApoE epsilon4 allele carriers.

CONCLUSION

Our findings support the hypothesis that the ApoE genotype might be associated with structural changes in RLOD.