Prevention of age-associated dementia

Reconsidering the overdiagnosis of mild cognitive impairment for dementia prevention among adults aged ≥80 years

A diagnosis at the stage of mild cognitive impairment (MCI) is encouraged to promote dementia prevention since intensive intervention during the mild stage is thought to be effective for dementia prevention. Many adults aged ≥80 years hope to prevent dementia; however, several issues should be considered regarding the diagnosis of MCI. First, the diagnosis of MCI is not clear-cut in actual medical practice, with the differentiation of MCI from normal states and mild dementia being blurred. Second, although MCI due to Alzheimer's disease can be differentiated from MCI without pathological changes, interventions specific to MCI due to Alzheimer's disease have not been developed. Third, the diagnosis of MCI can cause self-stigma, leading to psychological effects such as depression and anxiety for both the patients and their families, which can be risk factors for developing dementia for patients. In addition, medical resources are limited and diagnosing MCI is costly in medical human resources. Considering these issues, diagnosing MCI to promote dementia prevention should be viewed from the perspective of the individual patient's interests, especially for those aged ≥80 years. The final decision regarding receiving a diagnosis or not should be the patient's; therefore, it is necessary to increase patients' health literacy, which requires medical professionals to provide them with appropriate evidence-based information. At the same time, it is important to provide psychological support to people who have been diagnosed.

The Role of Gut Bacterial Metabolites in Brain Development, Aging and Disease

In the last decade, emerging evidence has reported correlations between the gut microbiome and human health and disease, including those affecting the brain. We performed a systematic assessment of the available literature focusing on gut bacterial metabolites and their associations with diseases of the central nervous system (CNS). The bacterial metabolites short-chain fatty acids (SCFAs) as well as non-SCFAs like amino acid metabolites (AAMs) and bacterial amyloids are described in particular. We found significantly altered SCFA levels in patients with autism spectrum disorder (ASD), affective disorders, multiple sclerosis (MS) and Parkinson’s disease (PD). Non-SCFAs yielded less significantly distinct changes in faecal levels of patients and healthy controls, with the majority of findings were derived from urinary and blood samples. Preclinical studies have implicated different bacterial metabolites with potentially beneficial as well as detrimental mechanisms in brain diseases. Examples include immunomodulation and changes in catecholamine production by histone deacetylase inhibition, anti-inflammatory effects through activity on the aryl hydrocarbon receptor and involvement in protein misfolding. Overall, our findings highlight the existence of altered bacterial metabolites in patients across various brain diseases, as well as potential neuroactive effects by which gut-derived SCFAs, p-cresol, indole derivatives and bacterial amyloids could impact disease development and progression. The findings summarized in this review could lead to further insights into the gut–brain–axis and thus into potential diagnostic, therapeutic or preventive strategies in brain diseases.

Hyperoside attenuates renal aging and injury induced by D-galactose via inhibiting AMPK-ULK1 signaling-mediated autophagy

The kidney is a typical organ undergoing age and injury. Hyperoside is reported to be useful for preventing aging induced by D-galactose (D-gal). However, therapeutic mechanisms remain unclear. We thereby aimed to verify whether hyperoside, compared to vitamin E (VE), could alleviate renal aging and injury by regulating autophagic activity and its related signaling pathways. In vivo, rats were administered with either hyperoside or VE after renal aging modeling induced by D-gal. Changes in renal aging and injury markers, autophagic activity and AMPK-ULK1 signaling pathway in the kidneys were analysed. In vitro, the NRK-52E cells exposed to D-gal were used to investigate regulative actions of hyperoside and VE on cell viability, renal tubular cellular aging markers, autophagic activity and its related signaling pathways by histomorphometry, immunohistochemistry, immunofluorescence, lentiviral transfection and Western blot. Aging and injury in the kidneys and renal tubular cells induced by D-gal were ameliorated by hyperoside and VE. Hyperoside and VE inhibited autophagic activity through mTOR-independent and AMPK-ULK1 signaling pathways. Hyperoside, as a component of phytomedicine similar to VE, attenuated renal aging and injury induced by D-gal via inhibiting AMPK-ULK1-mediated autophagy. This study provides the first evidence that hyperoside contributes to the prevention of age-associated renal injury.

Vitamin E Supplementation Reduces Cellular Loss in the Brain of a Premature Aging Mouse Model

BACKGROUND

Aging is a highly complex biological process driven by multiple factors. Its progression can partially be influenced by nutritional interventions. Vitamin E is a lipid-soluble anti-oxidant that is investigated as nutritional supplement for its ability to prevent or delay the onset of specific aging pathologies, including neurodegenerative disorders.

PURPOSE

We aimed here to investigate the effect of vitamin E during aging progression in a well characterized mouse model for premature aging.

METHOD

Xpg-/- animals received diets with low (~2.5 mg/kg feed), medium (75 mg/kg feed) or high (375 mg/kg feed) vitamin E concentration and their phenotype was monitored during aging progression. Vitamin E content was analyzed in the feed, for stability reasons, and in mouse plasma, brain, and liver, for effectiveness of the treatment. Subsequent age-related changes were monitored for improvement by increased vitamin E or worsening by depletion in both liver and nervous system, organs sensitive to oxidative stress.

RESULTS

Mice supplemented with high levels of vitamin E showed a delayed onset of age-related body weight decline and appearance of tremors when compared to mice with a low dietary vitamin E intake. DNA damage resulting in liver abnormalities such as changes in polyploidy, was considerably prevented by elevated amounts of vitamin E. Additionally, immunohistochemical analyses revealed that high intake of vitamin E, when compared with low and medium levels of vitamin E in the diet, reduces the number of p53-positive cells throughout the brain, indicative of a lower number of cells dying due to DNA damage accumulated over time.

CONCLUSIONS

Our data underline a neuroprotective role of vitamin E in the premature aging animal model used in this study, likely via a reduction of oxidative stress, and implies the importance of improved nutrition to sustain health.

Effects of vitamin E on cognitive performance during ageing and in Alzheimer's disease

Vitamin E is an important antioxidant that primarily protects cells from damage associated with oxidative stress caused by free radicals. The brain is highly susceptible to oxidative stress, which increases during ageing and is considered a major contributor to neurodegeneration. High plasma vitamin E levels were repeatedly associated with better cognitive performance. Due to its antioxidant properties, the ability of vitamin E to prevent or delay cognitive decline has been tested in clinical trials in both ageing population and Alzheimer’s disease (AD) patients. The difficulty in performing precise and uniform human studies is mostly responsible for the inconsistent outcomes reported in the literature. Therefore, the benefit of vitamin E as a treatment for neurodegenerative disorders is still under debate. In this review, we focus on those studies that mostly have contributed to clarifying the exclusive function of vitamin E in relation to brain ageing and AD.

Comparison the neuropreotective effect of Cortex Phellodendri chinensis and Cortex Phellodendri amurensis against beta-amyloid-induced neurotoxicity in PC12 cells

Cortex Phellodendron chinensis (CPC) and Cortex Phellodendron amurensis (CPA) derived from the dried bark of Phellodendron chinense Schneid. or Phellodendron amurense Rupr., respectively, are used interchangeably in clinical practice under the name "Huang Bai" for centuries in Chinese medicine for the treatment of various inflammatory conditions. Previous study in our laboratory demonstrated that CPC and CPA had different anti-diarrheal, anti-bacterial and anti-inflammatory effects. In this present study, we aimed to compare the protective effect of ethanol extract of Cortex Phellodendri chinensis (ECPC) and Cortex Phellodendri Amurensis (ECPA) against beta-amyloid (Aβ)-induced neurotoxicity in PC12 cells, a typical model of Alzheimer's disease. The results showed that ECPC and ECPA contain four common chemical markers such as berberine, but palmatine and jatrorrhizin were not found in CPC in contrast to the presence in CPA. In addition, both ECPC and ECPA can significantly increase the cell viability in Aβ-treated PC12 cells. Moreover, ECPC and ECPA can markedly elevate the ratio of the protein and mRNA levels of Bcl-2/Bax, while remarkably decrease the release of cytochrome c, and the protein and mRNA expression of caspase-3. Interestingly, ECPA has better protective effect than ECPC against Aβ-induced neurotoxicity in PC12 cells. These results indicate that both ECPC and ECPA have potential protective effect against Aβ-induced neurotoxicity in PC12 cells, and ECPA is more potential of the two species to be used in traditional medicine as a neuroprotective agent for the treatment of AD. The neuroprotective effect of the two species may be mediated, at least in part, via suppressing of the cellular apoptosis.

Can healthy lifestyle modify risk factors for dementia? Findings from a pilot community-based survey in Chennai (India) and Newcastle (UK)

BACKGROUND

Currently there are no effective treatments available for dementia. Attention has turned to defining preventive strategies and identifying modifying effects of lifestyle, including physical activity, diet, alcohol intake and smoking, in reducing cognitive decline and overt memory problems in the elderly.

METHODS

In this study, we addressed the modifying aspects of various components of lifestyle in two ageing samples and explored the possible effects that exercise, diet and spiritual and religious beliefs have upon physical and mental health. A total of 251 subjects (128 in Chennai, India, and 123 in Newcastle, UK) filled in a questionnaire regarding their lifestyle habits. Data were analysed with χ² analysis.

RESULTS

Our findings highlight that spiritual and religious beliefs promoted good physical and mental health and were negatively associated with risk factors for dementia, such as high blood pressure, high cholesterol level and diabetes. Lifelong diet and physical activity also contributed to better overall well-being in both samples.

CONCLUSIONS

Our study suggests substantial lifestyle variations between two urban populations in Chennai, India, and Newcastle-upon-Tyne, UK. Further detailed work is required to identify the lifestyle components that have the greatest impact on modifying the known risk factors for dementia.

The aging brain and neurodegenerative diseases

This article reviews the current thoughts on the effects of aging on the brain. Mechanisms of neurodegeneration are discussed, particularly those associated with Alzheimer's and Parkinson's diseases. Strategies of early detection of presymptomatic disease and potential future treatments are explored. Modification of risk factors and lifestyles for disease prevention is discussed.

Oral folic acid and vitamin B-12 supplementation to prevent cognitive decline in community-dwelling older adults with depressive symptoms--the Beyond Ageing Project: a randomized controlled trial

BACKGROUND

Evidence remains unclear as to whether folic acid (FA) and vitamin B-12 supplementation is effective in reducing depressive symptoms.

OBJECTIVES

The objective was to determine whether oral FA + vitamin B-12 supplementation prevented cognitive decline in a cohort of community-dwelling older adults with elevated psychological distress.

DESIGN

A randomized controlled trial (RCT) with a completely crossed 2 × 2 × 2 factorial design comprising daily oral 400 μg FA + 100 μg vitamin B-12 supplementation (compared with placebo), physical activity promotion, and depression literacy with comparator control interventions for reducing depressive symptoms was conducted in 900 adults aged 60-74 y with elevated psychological distress (Kessler Distress 10-Scale; scores >15). The 2-y intervention was delivered in 10 modules via mail with concurrent telephone tracking calls. Main outcome measures examined change in cognitive functioning at 12 and 24 mo by using the Telephone Interview for Cognitive Status-Modified (TICS-M) and the Brief Test of Adult Cognition by Telephone (processing speed); the Informant Questionnaire on Cognitive Decline in the Elderly was administered at 24 mo.

RESULTS

FA + vitamin B-12 improved the TICS-M total (P = 0.032; effect size d = 0.17), TICS-M immediate (P = 0.046; d = 0.15), and TICS-M delayed recall (P = 0.013; effect size d = 0.18) scores at 24 mo in comparison with placebo. No significant changes were evident in orientation, attention, semantic memory, processing speed, or informant reports.

CONCLUSION

Long-term supplementation of daily oral 400 μg FA + 100 μg vitamin B-12 promotes improvement in cognitive functioning after 24 mo, particularly in immediate and delayed memory performance. This trial was registered at clinicaltrials.gov as NCT00214682.

Neuroprotective effects of puerarin against beta-amyloid-induced neurotoxicity in PC12 cells via a PI3K-dependent signaling pathway

Epidemiological data have indicated that estrogen replacement therapy (ERT) can decrease the risk of developing Alzheimer's disease (AD). Phytoestrogens have been proposed as potential alternatives to ERT. The aim of the present study was to assess the neuroprotective effects of puerarin, a phytoestrogen isolated from Pueraria lobata, against the toxicity of beta-amyloid (Aβ) in relation to the mitochondria-mediated cell death process, and to elucidate the role the activation of Akt and modulation of the pro- and antiapoptotic proteins in puerarin-induced neuroprotection. The present study shows that puerarin afforded protection against Aβ-induced toxicity through inhibiting apoptosis in PC12 cells. This result was also confirmed by the activated caspase-3 assay. P-Akt, Bcl-2 and p-Bad expression increased after pretreatment with puerarin in PC12 cells exposed to Aβ(25-35), whereas Bax expression and cytochrome c release decreased. Interestingly, these effects of puerarin against Aβ(25-35) insult were abolished by wortmannin, an inhibitor of PI3K phosphorylation. These findings suggest that puerarin prevent Aβ-induced neurotoxicity through inhibiting neuronal apoptosis, and might be a potential preventive or therapeutic agent for AD.

Stress, exercise, and Alzheimer's disease: a neurovascular pathway

Genetic factors are known to play a role in Alzheimer's disease (AD) vulnerability, yet less than 1% of incident AD cases are directly linked to genetic causes, suggesting that environmental variables likely play a role in the majority of cases. Several recent human and animal studies have examined the effects of behavioral factors, specifically psychological stress and exercise, on AD vulnerability. Numerous animal studies have found that, while stress exacerbates neuropathological changes associated with AD, exercise reduces these changes. Some human studies suggest that psychological stress can increase the risk of developing AD, while other studies suggest that exercise can significantly reduce AD risk. Most animal studies investigating the mechanisms responsible for the effects of these behavioral factors have focused on neuronal processes, including the effects of stress hormones and neurotrophic factors on the neuropathological hallmarks of AD, namely amyloid-beta (Aβ) deposition and tau-phosphorylation. However, cumulative evidence indicates that, in humans, AD is associated with the presence of cerebrovascular disease, and cardiovascular risk factors are associated with increased risk of developing AD. There is an extensive literature demonstrating that behavioral factors, particularly stress and exercise, can powerfully modulate the pathophysiology of vascular disease. Thus, the following model proposes that the influence of stress and exercise on AD risk may be partially due to the effects of these behavioral factors on vascular homeostasis and pathology. These effects are likely due to both indirect modification of AD risk through alterations in vascular risk factors, such as hypertension, diabetes, and aortic stiffening, as well as direct influence on the cerebrovasculature, including changes in cerebral blood flow, angiogenesis, and vascular disease. Future studies examining the effects of behavioral factors on AD risk should incorporate measures of both peripheral and cerebral vascular function to further our understanding of the mechanisms by which behavior can modify AD susceptibility. Greater knowledge of the molecular mechanisms behind these behavioral effects would further our understanding of the disease and lead to innovative treatment and preventive approaches.

The role of the ubiquitin proteasome system in Alzheimer's disease

Today, Alzheimer's disease (AD) is one of the most important age-related neurodegenerative diseases, but its etiology remains still unknown. Since the discovery that the hallmark structures of this disease i.e. the formation of amyloid fibers could be the product of ubiquitin-mediated protein degradation defects, it has become clear that the ubiquitin–proteasome system (UPS), usually essential for protein repair, turnover and degradation, is perturbed in this disease. Different aspects of normal and pathological aging are discussed with respect to protein repair and degradation via the UPS, as well as consequences of a deficit in the UPS in AD. Selective protein oxidation may cause protein damage, or protein mutations may induce a dysfunction of the proteasome. Such events eventually lead to activation of cell death pathways and to an aberrant aggregation or incorporation of ubiquitinated proteins into hallmark structures. Aggresome formation is also observed in other neurodegenerative diseases, suggesting that an activation of similar mechanisms must occur in neurodegeneration as a basic phenomenon. It is essential to discuss therapeutic ways to investigate the UPS dysfunction in the human brain and to identify specific targets to hold or stop cell decay.

Neurogenesis in Alzheimer's disease

It is widely acknowledged that neural stem cells generate new neurons through the process of neurogenesis in the adult brain. In mammals, adult neurogenesis occurs in two areas of the CNS: the subventricular zone and the subgranular zone of the dentate gyrus of the hippocampus. The newly generated cells display neuronal morphology, generate action potentials and receive functional synaptic inputs, their properties being equivalent to those of mature neurons. Alzheimer's disease (AD) is the widespread cause of dementia, and is an age-related, progressive and irreversible neurodegenerative disease that results in massive neuronal death and deterioration of cognitive functions. Here, we overview the relations between adult neurogenesis and AD, and try to analyse the controversies in the field. We also summarise recent data obtained in the triple transgenic model of AD that show time- and region-specific impairment of neurogenesis, which may account for the early changes in synaptic plasticity and cognitive impairments that develop prior to gross neurodegenerative alterations and that could underlie new rescue therapies.

Design, synthesis, and biological evaluation of coumarin derivatives tethered to an edrophonium-like fragment as highly potent and selective dual binding site acetylcholinesterase inhibitors

A large series of substituted coumarins linked through an appropriate spacer to 3-hydroxy-N,N-dimethylanilino or 3-hydroxy-N,N,N-trialkylbenzaminium moieties were synthesized and evaluated as acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitors. The highest AChE inhibitory potency in the 3-hydroxy-N,N-dimethylanilino series was observed with a 6,7-dimethoxy-3-substituted coumarin derivative, which, along with an outstanding affinity (IC(50)=0.236 nM) exhibits excellent AChE/BChE selectivity (SI>300 000). Most of the synthesized 3-hydroxy-N,N,N-trialkylbenzaminium salts display an AChE affinity in the sub-nanomolar to picomolar range along with excellent AChE/BChE selectivities (SI values up to 138 333). The combined use of docking and molecular dynamics simulations permitted us to shed light on the observed structure-affinity and structure-selectivity relationships, to detect two possible alternative binding modes, and to assess the critical role of pi-pi stacking interactions in the AChE peripheral binding site.

Age, Alzheimer's disease and dementia in the Baltimore Longitudinal Study of Ageing

Recent studies suggest that dementia in the most elderly (90 years of age and above) is only modestly related to Alzheimer's disease pathology. This raises the possibility that other, as yet unknown, disease processes may underlie dementia in this rapidly growing demographic group, and that efforts designed to combat Alzheimer's disease may not be appropriate for treating dementia in very elderly subjects. To study this question more closely, we examined the relationship between neocortical Alzheimer-type brain pathology and dementia in consecutive autopsies from 209 participants in the Baltimore Longitudinal Study of Ageing, a prospective longitudinal cohort study of the effect of ageing on cognition. Almost half of the cohort was older than 90 years of age at death. We found that several measures of neocortical Alzheimer's pathology, including the Consortium to Establish a Registry of Alzheimer's Disease neuritic plaque score and the Braak neurofibrillary tangle score, remained significant predictors of dementia, independent of age. In participants older than 90 years of age, intracranial atherosclerosis emerged as an important predictor of dementia in subjects with low Alzheimer's pathology scores, but did not mitigate the importance or population attributable risk of high Alzheimer's pathology scores on the odds of dementia. There was evidence that the threshold score for neurofibrillary pathology to cause dementia increased in the oldest subjects, but this was offset by an overall increase in neurofibrillary pathology in this age group. We conclude that neocortical Alzheimer's disease pathology remains significantly correlated with dementia, independent of age. In the most elderly, atherosclerosis also emerged as a cause of dementia in subjects with low Alzheimer's pathology scores. We found no evidence for a significant number of elderly subjects having dementia without an apparent cause.