Current Alzheimer Research - Volume 18, Issue 13, 2021

Dementia is a syndrome resulting from chronic or progressive brain disease. Around 40% of worldwide dementia can be prevented or delayed by modifying 12 risk factors: low educational attainment in early life, mid-life hypertension, mid-life obesity, hearing loss, traumatic brain injury, excessive alcohol consumption, smoking, depression, physical inactivity, social isolation, diabetes mellitus, and air pollution. There is growing evidence that gastrointestinal tract microbiota may significantly contribute to dementia pathogenesis. In particular, gut dysbiosis can trigger metabolic diseases and the progression of low-grade systemic inflammation, being involved in much of the major modifiable risk factors. In this review, we focus on studies that have evaluated the association between modifiable risk factors for dementia and the role of gut microbiota. We also suggest clinical implications for researchers in dementia-gut microbiota related fields.

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder that is increasingly viewed as a complex multi-dimensional disease without effective treatments. Recent randomized, placebo-controlled studies have shown volume losses of ˜0.7% and ˜3.5% per year, respectively, in the basal cholinergic forebrain (CBF) and hippocampus in untreated suspected prodromal AD. One year of donepezil treatment reduced these annualized rates of atrophy to about half of untreated rates. Similar positive although variable results have also been found in volumetric measurements of the cortex and whole brain in patients with mild cognitive impairment as well as more advanced AD stages after treatments with all three currently available acetylcholinesterase (AChE) inhibitors (donepezil, rivastigmine, and galantamine). Here we review the anti-neurodegenerative benefits of AChE inhibitors and the expected parallel disease-accelerating impairments caused by anticholinergics, within a framework of the cholinergic hypothesis of AD and AD-associated loss of nerve growth factor (NGF). Consistent with the “loss of trophic factor hypothesis of AD,” we propose that AChE inhibitors enhance acetylcholine-dependent release and uptake of NGF, thereby sustaining cholinergic neuronal viability and thus slowing AD-associated degeneration of the CBF, to ultimately delay dementia progression. We propose that improved cholinergic therapies for AD started early in asymptomatic persons, especially those with risk factors, will delay the onset, progression, or emergence of dementia. The currently available competitive and pseudo- irreversible AChE inhibitors are not CNS-selective and thus induce gastrointestinal toxicity that limits cortical AChE inhibition to ˜30% (ranges from 19% to 41%) as measured by in vivo PET studies in patients undergoing therapy. These levels of inhibition are marginal relative to what is required for effective symptomatic treatment of dementia or slowing AD-associated neurodegeneration. In contrast, because of the inherently slow de novo synthesis of AChE in the CNS (about one-- tenth the rate of synthesis in peripheral tissues), irreversible AChE inhibitors produce significantly higher levels of inhibition in the CNS than in peripheral tissues. For example, methanesulfonyl fluoride, an irreversible inhibitor reduces CNS AChE activity by ˜68% in patients undergoing therapy and ˜80% in cortical biopsies of non-human primates. The full therapeutic benefits of AChE inhibitors, whether for symptomatic treatment of dementia or disease-slowing, thus would benefit by producing high levels of CNS inhibition. One way to obtain such higher levels of CNS AChE inhibition would be by using irreversible inhibitors.

Objective:Both diabetes mellitus (DM) and poor oral health are common chronic conditions and risk factors of Alzheimer’s disease and related dementia among older adults. This study assessed the effects of DM and complete tooth loss (TL) on cognitive function, accounting for their interactions. Methods: Longitudinal data were obtained from the 2006, 2012, and 2018 waves of the Health and Retirement Study. This cohort study included 7,805 respondents aged 65 years or older with 18,331 person-year observations. DM and complete TL were self-reported. Cognitive function was measured by the Telephone Interview for Cognitive Status. Random-effect regressions were used to test the associations, overall and stratified by sex. Results:Compared with older adults without neither DM nor complete TL, those with both conditions (b = -1.35, 95% confidence interval [CI]: -1.68, -1.02), with complete TL alone (b = -0.67, 95% CI: -0.88, -0.45), or with DM alone (b = -0.40, 95% CI: -0.59, -0.22), had lower cognitive scores. The impact of having both conditions was significantly greater than that of having DM alone (p < .001) or complete TL alone (p = 0.001). Sex-stratified analyses showed the effects were similar in males and females, except having DM alone was not significant in males. Conclusion: The co-occurrence of DM and complete TL poses an additive risk for cognition. Healthcare and family-care providers should pay attention to the cognitive health of patients with both DM and complete TL. Continued efforts are needed to improve older adults’ access to dental care, especially for individuals with DM.

Background: Apolipoprotein E (ApoE) is the major genetic risk factor for sporadic Alzheimer's Disease (AD). Some studies showed a relationship between ApoE4 genotype and the cerebrospinal fluid (CSF) biomarkers (β-amyloid42, p-Tau, t-Tau), as well as with cognitive status. In this sense, it could be interesting to develop an approach to establish amyloid status in a minimally invasive way. Methods: The present study assessed the ApoE genotype in different participant groups (mild cognitive impairment due to AD (MCI-AD), mild/moderate dementia due to AD, MCI not due to AD (MCI not AD), other neurological diseases, healthy participants) (n = 342). Results: As expected, the ApoE4 allele was more prevalent in AD patients, characterized by impairment in CSF β-amyloid42 levels (Aβ +), than in the other groups (Aβ -). In this sense, ApoE4-carrier subjects showed lower CSF levels for β-amyloid42 and higher CSF levels for t-Tau and p-Tau. From this, a multivariate model to predict Aβ status was developed by means of partial least square analysis (PLS) and predictive variables (ApoE genotype, cognitive score, sex, age). This model showed suitable AUC-ROC 0.792 (95% CI, 0.744-0.840) and predictive negative value (81.6%). Conclusion: ApoE genotype could be useful in detecting CSF β-amyloid42 impairment associated with early AD development.

Background: Background: Alzheimer’s disease (AD) is the most common cause of dementia. As a heterogenous disease, there are several clinically and pathobiological defined subtypes with different molecular signatures. Neuroinflammation contributed to AD pathogenesis, however, the roles it played in the heterogeneity of AD was unclear. Objective:We aimed to illustrate the roles neuroinflammation played in the heterogeneity of AD. Method:An integrative network analysis based on transcriptomics, miRNOmics, and proteomics was performed to illustrate the heterogeneous characters of AD. Combined-functional-networks and hypothesis- network were constructed and analyzed to explore the roles neuroinflammation played in AD heterogeneity. Results: Astrocytes, microglia, ‘M2 macrophage-Neuron’, and ‘Microglia- Neuron’ were shown to be enriched in neuroinflammation related functional terms in a cell- and spatial-specific way. The microglia and neurons could interact with each other in three different ways including indirect interactions via intermediate cells, indirect interactions via soluble factors, and direct interactions established localized and functionally distinct signaling, all of which were used to control different biological processes. The combined network analyses exhibited the key roles neuroinflammation plays in the ‘AD hypothesis network’. Conclusion: The AD heterogeneity may be caused by the heterogeneous cells involved in neuroinflammation and the crosstalks between spatial-specific molecular signatures.

Objective: To study the implementation of Global Postural Re-education as a rehabilitative alternative in residence facilities for seniors with Alzheimer, and to verify its effect on psychological and cognitive symptoms. Methods: A quasi-experimental design was employed using month-follow-up assessments at 1,3, and 6 months respectively. Ninety elderly people participated in the composition of the study sample: 69 women and 21 men aged from 67 to 89 years (80.2 ±5.5), grouped in two phases: mild and moderate, according to Alzheimer severity. Patients in both groups received the same treatment twice a week for consecutively 24 weeks. Three follow-up medium-long term assessments were performed at intervals of 1, 3, and 6 months. Outcome measures included Mini-Mental State Examination, Geriatric Depression Scale, Quality of Life in Alzheimer Disease, Barthel Index, and Tinetti Scale. Results: The severity of groups therapy interaction showed significant changes in four outcome measures as cognition [F(1,88)=60.26; p=.000; partial η2= 0.406], depression [F(1,88)=8.24; p=.005; partial η2= 0.086], life quality [F(1,88)= 10.45; p=.002; partial η2= 0.106] and equilibrium [F(1,88)= 6.96; p=.010; partial η2= 0.073]. No changes were found for autonomy [F(1,88)= 1.10; p=.297; partial η2= 0.012]. These changes between the two groups were observed at the sixth month follow-up assessment. Conclusion:Global postural reeducation could be useful as a complementary rehabilitation treatment in Alzheimer patients.