Apolipoprotein E gene in physiological and pathological aging

Understanding the interplay between APO E polymorphism and cognition in the Italian oldest old: results from the "Mugello study"

INTRODUCTION

Recent data suggest that the deleterious effect on general health and cognition of ε4 allele of Apolipoprotein E (ApoE) observed in the elderly population, may attenuate in extreme aging. This study aimed to describe the ApoE genotype distribution and its relationship with cognition in a group of nonagenarians living in the Mugello area, Italy.

MATERIAL AND METHODS

Cognition was evaluated using the Mini-Mental-State-Examination (MMSE). DNA was extracted from blood samples to determine ApoE genotyping. Participants were classified into three ApoE groups (ε2, ε3, ε4). Logistic and linear regression models were created, to assess the relationship between ApoE genotype group and dementia diagnosis and cognitive performance, respectively.

RESULTS

169 subjects were included. ApoE ε3 was the most prevalent genotype (76.3%). Dementia prevalence was 26.6% and it was not associated with the presence of ApoE ε4. Participants of ε4 group were significantly more likely to have lower cognitive performances than ε2 and ε3, independently of a dementia diagnosis.

DISCUSSION

Results support that ApoE genotype no longer plays a role in the health condition of the oldest old, however, an interaction is detectable between ApoE polymorphism and cognitive performances at this extreme age.

Diencephalic versus Hippocampal Amnesia in Alzheimer's Disease: The Possible Confabulation-Misidentification Phenotype

BACKGROUND

Alzheimer's disease (AD) is clinically heterogeneous, including the classical-amnesic (CA-) phenotype and some variants.

OBJECTIVE

We aim to describe a further presentation we (re)named confabulation-misidentification (CM-) phenotype.

METHODS

We performed a retrospective longitudinal case-series study of 17 AD outpatients with the possible CM-phenotype (CM-ADs). Then, in a cross-sectional study, we compared the CM-ADs to a sample of 30 AD patients with the CA-phenotype (CA-ADs). The primary outcome was the frequency of cognitive and behavioral features. Data were analyzed as differences in percentage by non-parametric Chi Square and mean differences by parametric T-test.

RESULTS

Anterograde amnesia (100%) with early confabulation (88.2%), disorientation (88.2%) and non-infrequently retrograde amnesia (64.7%) associated with reduced insight (88.2%), moderate prefrontal executive impairment (94.1%) and attention deficits (82.3%) dominated the CM-phenotype. Neuropsychiatric features with striking misidentification (52.9%), other less-structured delusions (70.6%), and brief hallucinations (64.7%) were present. Marked behavioral disturbances were present early in some patients and very common at later stages. At the baseline, the CM-ADs showed more confabulation (p < 0.001), temporal disorientation (p < 0.02), misidentification (p = 0.013), other delusions (p = 0.002), and logorrhea (p = 0.004) than the CA-ADs. In addition, more social disinhibition (p = 0.018), reduction of insight (p = 0.029), and hallucination (p = 0.03) persisted at 12 months from baseline. Both the CA- and CM-ADs showed anterior and medial temporal atrophy. Compared to HCs, the CM-ADs showed more right fronto-insular atrophy, while the CA-ADs showed more dorsal parietal, precuneus, and right parietal atrophy.

CONCLUSION

We described an AD phenotype resembling diencephalic rather than hippocampal amnesia and overlapping the past-century description of presbyophrenia.

APOE ε4 Carrier Status as Mediator of Effects of Psychotropic Drugs on Clinical Changes in Patients With Alzheimer's Disease

OBJECTIVE

Neuropsychiatric syndromes have been associated with memory dysfunction and risk of and earlier onset of dementia, but how psychotropic drugs affect clinical changes in Alzheimer's disease is not entirely clear. This study aimed to assess the prospective effects of psychotropic drugs on cognitive and functional changes in Alzheimer's disease according to APOE ε4 carrier status.

METHODS

The study included consecutive outpatients with late-onset Alzheimer's disease (N=193) and examined score variations at 1 year on the following tests: Clinical Dementia Rating sum of boxes, Mini-Mental State Examination, Severe Mini-Mental State Examination (SMMSE), Brazilian version of the Zarit Caregiver Burden Interview, Index of Independence in Activities of Daily Living, and Lawton's Instrumental Activities of Daily Living Scale. Analyses of score variations accounted for the use of psychotropic drugs or the number of different medications in use, as well as APOE ε4 carrier status, with significance at p<0.05.

RESULTS

For APOE ε4 noncarriers (N=90), cholinesterase inhibitors were beneficial regarding caregiver burden (p=0.030) and basic functionality (p=0.046), memantine was harmful regarding SMMSE score changes (p=0.032), second-generation antipsychotics had nonsignificant harmful effects on SMMSE score changes (p=0.070), and antiepileptic therapy (p=0.001) and the number of different medications in use (p=0.006) were harmful in terms of basic functionality. APOE ε4 carriers (N=103) did not experience any effects of isolated psychotropic drugs on clinical changes, including antidepressants.

CONCLUSIONS

Results support the harmful prospective effects of second-generation antipsychotics and antiepileptic drugs on cognitive and functional changes in Alzheimer's disease, particularly for APOE ε4 noncarriers, whereas antidepressants may be safer options for behavioral enhancement.

VAMP2 Expression and Genotype Are Possible Discriminators in Different Forms of Dementia

Vascular alterations often overlap with neurodegeneration, resulting in mixed forms of dementia (MD) that are hard to differentiate from Alzheimer’s Disease (AD). The 26 bp intergenic polymorphism of VAMP2, a key component of SNARE complex, as well as its mRNA and protein levels are associated with neurological diseases. We evaluated ApoE4 and VAMP2 26 bp Ins/Del genotype distribution in 177 AD, 132 MD, 115 Mild Cognitive Impairment (MCI) and 250 individuals without cognitive decline (CT), as well as VAMP2 gene expression in a subset of 73 AD, 122 MD, 103 MCI and 140 CT. Forty-two MCI evolved to AD (22 MCI-AD) or MD (20 MCI-MD) over time. VAMP2 mRNA was higher in MD compared to AD (p = 0.0013) and CT (p = 0.0017), and in MCI-MD compared to MCI-AD (p < 0.001) after correcting for age, gender, MMSE and ApoE4 +/− covariates (p_c = 0.004). A higher VAMP2 expression was observed in subjects carrying the minor allele Del compared to those carrying the Ins/Ins genotype (p = 0.012). Finally, Del/Del genotype was more frequently carried by MD/MCI-MD compared to CT (p_c = 0.036). These results suggest that VAMP2 mRNA expression can discriminate mixed form of dementia from AD, possibly being a biomarker of AD evolution in MCI patients.

Physiological and Pathological Ageing of Astrocytes in the Human Brain

Ageing is the greatest risk factor for dementia, although physiological ageing by itself does not lead to cognitive decline. In addition to ageing, APOE ε4 is genetically the strongest risk factor for Alzheimer's disease and is highly expressed in astrocytes. There are indications that human astrocytes change with age and upon expression of APOE4. As these glial cells maintain water and ion homeostasis in the brain and regulate neuronal transmission, it is likely that age- and APOE4-related changes in astrocytes have a major impact on brain functioning and play a role in age-related diseases. In this review, we will discuss the molecular and morphological changes of human astrocytes in ageing and the contribution of APOE4. We conclude this review with a discussion on technical issues, innovations, and future perspectives on how to gain more knowledge on astrocytes in the human ageing brain.

The sTREM2 Concentrations in the Blood: A Marker of Neurodegeneration?

Microglia performs a variety of functions during brain development designed to maintain brain homeostasis. Triggering receptor expressed on myeloid cells 2 (TREM2) is expressed in microglial cells modulating phagocytosis, cytokine production, cell proliferation, and cell survival. Interestingly, the levels of soluble TREM2 (the secreted ectodomain of TREM2, sTREM2) were higher in cerebrospinal fluid (CSF) from Alzheimer's disease (AD) patients than subjects without cognitive decline. It is noteworthy that, while CSF sTREM2 levels have been extensively studied, few studies have investigated sTREM2 in blood producing conflicting results. We aimed to investigate the levels of sTREM2 in CSF and blood from a cohort of well-characterized AD comparing the results to those obtained in patients suffering from idiopathic normal pressure hydrocephalus (iNPH), a potentially reversible cognitive impairment. Our findings underlined a significantly lower plasma sTREM2 concentration in AD patients compared to iNPH subjects [39.1 ng/mL (standard deviation (SD), 15.0) and 47.2 ng/mL (SD, 19.5), respectively; p = 0.01], whereas no difference was revealed between the two groups in the CSF sTREM2 levels. The adjusted regression analyses evidenced in AD patients an association between plasma and CSF sTREM2 levels [B = 0.411; 95% confidence interval (CI), 0.137-0.685, p = 0.004], as well as β-amyloid concentrations (B = 0.035; 95% CI, 0.007-0.063, p = 0.01) and an association between CSF sTREM2 and phospho-Tau concentrations (B = 0.248; 95% CI, 0.053-0.443; p = 0.01). No significant relation was found in iNPH patients. In conclusion, these differences in sTREM2 profiles between AD and iNPH reinforce the notion that this receptor has a role in neurodegeneration.

Autonomic function in amnestic and non-amnestic mild cognitive impairment: spectral heart rate variability analysis provides evidence for a brain-heart axis

Mild cognitive impairment (MCI) is a heterogeneous syndrome with two main clinical subtypes, amnestic (aMCI) and non-amnestic (naMCI). The analysis of heart rate variability (HRV) is a tool to assess autonomic function. Cognitive and autonomic processes are linked via the central autonomic network. Autonomic dysfunction entails several adverse outcomes. However, very few studies have investigated autonomic function in MCI and none have considered MCI subtypes or the relationship of HRV indices with different cognitive domains and structural brain damage. We assessed autonomic function during an active orthostatic challenge in 253 oupatients aged ≥ 65, [n = 82 aMCI, n = 93 naMCI, n = 78 cognitively normal (CN), neuropsychologically tested] with power spectral analysis of HRV. We used visual rating scales to grade cerebrovascular burden and hippocampal/insular atrophy (HA/IA) on neuroimaging. Only aMCI showed a blunted response to orthostasis. Postural changes in normalised low frequency (LF) power and in the LF to high frequency ratio correlated with a memory test (positively) and HA/IA (negatively) in aMCI, and with attention/executive function tests (negatively) and cerebrovascular burden (positively) in naMCI. These results substantiate the view that the ANS is differentially impaired in aMCI and naMCI, consistently with the neuroanatomic substrate of Alzheimer's and small-vessel subcortical ischaemic disease.

Klotho Pathways, Myelination Disorders, Neurodegenerative Diseases, and Epigenetic Drugs

In this review we outline a rationale for identifying neuroprotectants aimed at inducing endogenous Klotho activity and expression, which is epigenetic action, by definition. Such an approach should promote remyelination and/or stimulate myelin repair by acting on mitochondrial function, thereby heralding a life-saving path forward for patients suffering from neuroinflammatory diseases. Disorders of myelin in the nervous system damage the transmission of signals, resulting in loss of vision, motion, sensation, and other functions depending on the affected nerves, currently with no effective treatment. Klotho genes and their single-pass transmembrane Klotho proteins are powerful governors of the threads of life and death, true to the origin of their name, Fates, in Greek mythology. Among its many important functions, Klotho is an obligatory co-receptor that binds, activates, and/or potentiates critical fibroblast growth factor activity. Since the discovery of Klotho a little over two decades ago, it has become ever more apparent that when Klotho pathways go awry, oxidative stress and mitochondrial dysfunction take over, and age-related chronic disorders are likely to follow. The physiological consequences can be wide ranging, potentially wreaking havoc on the brain, eye, kidney, muscle, and more. Central nervous system disorders, neurodegenerative in nature, and especially those affecting the myelin sheath, represent worthy targets for advancing therapies that act upon Klotho pathways. Current drugs for these diseases, even therapeutics that are disease modifying rather than treating only the symptoms, leave much room for improvement. It is thus no wonder that this topic has caught the attention of biomedical researchers around the world.

The role of epsilon phenotype in brain glucose consumption in Alzheimer's disease

OBJECTIVE

The aim of our study was to investigate the impact of the epsilon phenotype in brain glucose consumption in a population with Alzheimer's disease.

METHODS

Statistical Parametric Mapping (SPM8) was used to investigate differences in brain glucose consumption (as detectable by means of 18F FDG-PET/CT) in the population examined. A total of 129 patients (72 females and 57 males) with a diagnosis of probable AD according to the NINCDS-ADRDA criteria underwent the PET/CT examination. The mean (SD) age of the patients was 70 (± 7) years; the mean Mini-Mental State Examination was 19(± 5.6). 59 expressed epsilon 4 phenotype (E4) and 70 expressed the epsilon 3 phenotype (E3). Cerebral spinal fluid amyloid, tau, and t-tau have been measured resulting equal to 367.4 (± 149.1), 584.7 (± 312.1), and 79.2(± 45.9) pg/ml, respectively. Patients with confirmed amyloid and Tau changes were classified as AD. Patients with amyloid changes but negative Tau, considered as high risk of AD, were classified as IAD. Age, sex, MMSE, scholarship, and CSF parameters were used as a covariate in the SPM analyses.

RESULTS

We did not find significant differences in age, gender, and MMSE and CSF parameters among groups. In the analysis of the AD group as compared to AD-E3, AD-E4 subjects show a significant reduction of brain glucose consumption in inferior frontal gyrus bilaterally (BA 45, BA 47). In the analysis of the IAD group as compared to IAD-E3, IAD-E4 subjects show a significant reduction of brain glucose consumption in right in medial, middle, and superior frontal gyrus (BA10, BA11), and in left medial and middle frontal gyrus (BA10, BA11). The differences between IAD-E3 and AD-E3 and between IAD-E4 and AD-E4 (and vice versa analysis) resulted not significant.

CONCLUSIONS

APO-e4 is related to a major involvement of the frontal cortex confirming its role of risk factor in AD, while APO-3 seems not related to a specific pattern, supporting the hypothesis of neutral/protective role in AD.

Genetic background, epigenetic factors and dietary interventions which influence human longevity

Longevity is mainly conditioned by genetic, epigenetic and environmental factors. Different genetic modifications seem to be positively associated to longevity, including SNPs in SIRT1, APOE, FOXO3A, ACE, ATM, NOS1 and NOS2 gene. Epigenetic changes as DNA hyper- and hypo-methylation influence significantly human longevity by activating/deactivating different genes involved in physiological mechanisms. Several studies have confirmed that centenarians have a lower DNA methylation content compared to young subjects, which showed more homogeneously methylated DNA region. Also the up-regulation of miR-21 seems to be more associated with longevity in different populations of long-lived subjects, suggesting its role as potential epigenetic biomarkers. A non-pharmacological treatment that seems to contrast age-related diseases and promote longevity is represented by dietary intervention. It has been evaluated the effects of dietary restriction of both single nutrients or total calories to extend lifespan. However, in daily practice it is very difficult to guarantee adherence/compliance of the subjects to dietary restriction and at the same time avoid dangerous nutritional deficiencies. As consequence, the attention has focused on a variety of substances both drugs and natural compounds able to mime the beneficial effects of caloric restriction, including resveratrol, quercetin, rapamycin, metformin and 2-deoxy-D-glucose.