Murali Vijayan, P. Hemachandra Reddy
Non-Coding RNAs Based Molecular Links in Type 2 Diabetes, Ischemic Stroke, and Vascular Dementia
Abstract: This article reviews recent advances in the study of microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and their functions in type 2 diabetes mellitus (T2DM), ischemic stroke (IS), and vascular dementia (VaD). miRNAs and lncRNAs are gene regulation markers that both regulate translational aspects of a wide range of proteins and biological processes in healthy and disease states. Recent studies from our laboratory and others have revealed that miRNAs and lncRNAs expressed differently are potential therapeutic targets for neurological diseases, especially T2DM, IS, VaD, and Alzheimer's disease (AD). Currently, the effect of aging in T2DM, IS, and VaD and the cellular and molecular pathways are largely unknown. In this article, we highlight results from the works on the molecular connections between T2DM and IS, and IS and VaD. In each disease, we also summarize the pathophysiology and the differential expressions of miRNAs and lncRNAs. Based on current research findings, we hypothesize that 1) T2DM bi-directionally and age-dependently induces IS and VaD, and 2) these changes are precursors to the onset of dementia in elderly people. Research into these hypotheses is required to examine further whether research efforts on reducing T2DM, IS, and VaD may affect dementia and/or delay the AD disease process in the aged population.
Bo Liu, Jie Liu, Jing-Shan Shi
SAMP8 Mice as a Model of Age-Related Cognition Decline with Underlying Mechanisms in Alzheimer’s Disease
Abstract: Alzheimer’s disease (AD) is a highly age-related cognitive decline frequently attacking the elderly. Senescence-accelerated mouse-prone 8 (SAMP8) is an ideal model to study AD, displaying age-related learning and memory disorders. SAMP8 mice exhibit most features of pathogenesis of AD, including an abnormal expression of anti-aging factors, oxidative stress, inflammation, amyloid-β (Aβ) deposits, tau hyperphosphorylation, endoplasmic reticulum stress, abnormal autophagy activity, and disruption of intestinal flora. SAMP8 mice, therefore, have visualized the understanding of AD, and also provided effective ways to find new therapeutic targets. This review focused on the age-related pathogenesis in SAMP8 mice, to advance the understanding of age-related learning and memory decline and clarify the mechanisms. Furthermore, this review will provide extensive foundations for SAMP8 mice used in therapeutics for AD.
Pravat K. Mandal, Deepika Shukla
KALPANA: Advanced Spectroscopic Signal Processing Platform for Improved Accuracy to Aid in Early Diagnosis of Brain Disorders in Clinical Setting
Abstract: Magnetic resonance spectroscopy (MRS) plays a substantial role in the non-invasive detection of brain neurochemicals, antioxidants, and neurotransmitters. Quantitative monitoring of these neurochemicals and neurotransmitters in the brain has a profound application for the understanding of brain disorders. Significant progress in the MR scanner as well as MR pulse sequence development to detect in vivo neurochemicals has been accomplished. The processing of MR signal from these low abundant neurochemicals/neurotransmitters should be very robust and sensitive in order to provide distinctive observations of disease-related neurochemical alterations and their absolute quantitation to aid in early clinical diagnosis. We highlight the diversity in currently available MRS processing tools, and recently introduced, KALPANA, a promising package integrating the end-to-end processing as well as robust quantitation of neurochemicals in a user-friendly approach through a graphical user interface. This further necessitates the futuristic need for advanced MRS processing pipeline and the respective readout can help in early diagnosis and prognosis of diseases in the clinical environment.
Jing Jin, Jia Guo, Hongbin Cai, Chongchong Zhao, Huan Wang, Zhiyan Liu, Zhao-Ming Ge (Handling Associate Editor: Yuan Zhong)
M2-Like Microglia Polarization Attenuates Neuropathic Pain Associated with Alzheimer’s Disease
Abstract: Many Alzheimer’s disease (AD) patients suffer from persistent neuropathic pain (NP), which is mediated, at least partially, but microglia. Nevertheless, the exact underlying mechanism is unknown. Moreover, a clinically translatable approach through modulating microglia for treating AD-associated NP is not available. Here, in a doxycycline-induced mouse model (rTg4510) for AD, we showed development of NP. We found that the total number of microglia in the CA3 region was not increased, but polarized to pro-inflammatory M1-like phenotype, with concomitant increases in production and secretion of pro-inflammatory cytokines. To examine whether this microglia polarization plays an essential role in the AD-associated NP, we generated an adeno-associated virus (AAV) serotype PHP.B (capable of crossing the blood-brain barrier) carrying shRNA for DNA methyltransferase 1 (DNMT1) under a microglia-specific TMEM119 promoter (AAV-pTMEM119-shDNMT1), which specifically targeted microglia and induced a M2-like polarization in vitro and in vivo in doxycycline-treated rTg4510 mice. Intravenous infusion of AAV-pTMEM119-shDNMT1 induced M2-polarization of microglia and attenuated both AD-associated behavior impairment but also NP in the doxycycline-treated rTg4510 mice. Thus, our data suggest that AD-associated NP may be treated through M2-polarization of microglia.
Chetna Malhotra, Padmini Vishwanath, Jing Rong Yong, Truls Østbye, Dennis Seow, Phillip Yap, Lay Ling Tan, Weng Yew Tham, Janhavi Vaingankar, Jason Foo, Boon Yeow Tan, Kamun Tong, Wai Chong Ng, John Carson Allen Jr., Rahul Malhotra, Weng Mooi Tan, Shiou Liang Wee, Li Ling Ng, Richard Goveas, Vanessa Mok, Alisson Sim, Wei Fern Ng, Hon Khuan Wong, Bharathi Balasundaram, Rui Qi Tan, Pui Sim Ong, Chin Yee Cheong, Alethea Yee Chung Pheng, Christina Tiong, Allyn Hum, Angel Lee, Eric A. Finkelstein (Handling Associate Editor: Christopher Black)
A Prospective Longitudinal Study of Caregivers of Community Dwelling Persons with Severe Dementia (PISCES): Study Protocol
Abstract: Although many persons with severe dementia (PWSDs) are cared for at home by their family caregivers, few studies have assessed end of life (EOL) care experiences of PWSDs. We present the protocol for the PISCES study (Panel study Investigating Status of Cognitively impaired Elderly in Singapore) which aims to describe the clinical course, health care utilization, and expenditures for community-dwelling PWSDs; and perceived burden, coping, resilience, anticipatory and prolonged grief among their caregivers. This ongoing multi-center prospective longitudinal study is recruiting primary informal caregivers of 250 PWSDs from major restructured public hospitals, community hospitals, home care foundations, and hospices in Singapore. Caregivers are surveyed every four months for two years or until the PWSD passes away and then at eight weeks and six months post-death to assess the bereavement of the caregiver. Survey questionnaires included validated tools to assess PWSDs’ quality of life, suffering, behaviors, functional status, resource utilization; and caregiver’s satisfaction with care, awareness of prognosis, care preferences, resilience, coping, perceived burden, distress, positive aspects of caregiving, anticipatory grief, and bereavement adjustment. We also conduct qualitative in-depth interviews with a sub-sample of caregivers. The survey data is being linked with medical and billing records of PWSDs. The study has been approved by an ethics board. Results from the study will be disseminated through publications and presentations targeting researchers, policy makers and clinicians interested in understanding and improving EOL care for PWSDs and their caregivers.
Yi-Fang Chuang, Vijay Varma, Yang An, Toshiko Tanaka, Christos Davatzikos, Susan M. Resnick, Madhav Thambisetty
Interaction between Apolipoprotein E and Butyrylcholinesterase Genes on Risk of Alzheimer’s Disease in a Prospective Cohort Study
Abstract: Background: An epistatic interaction between the ε4 allele of apolipoprotein E (APOE ε4) gene and the K-variant of butyrylcholinesterase (BCHE-K) genes has been previously reported to increase risk of Alzheimer’s disease (AD). However, these observations were largely from case-control studies with small sample sizes. Objective: To examine the interaction between APOE ε4 and BCHE-K on: 1) the risk of incident AD and 2) rates of change in brain volumes and cognitive performance during the preclinical stages of AD in a prospective cohort study. Methods: The study sample for survival analysis included 691 Caucasian participants (age at baseline, 58.4 ± 9.9 years; follow-up time,16.9 ± 9.7 years) from the Baltimore Longitudinal Study of Aging. The neuroimaging sample included 302 participants with 1,388 magnetic resonance imaging (MRI) scans. Cognitive performance was assessed in 703 participants over 4,908 visits. Results: A total of 122 diagnoses (79 AD, 43 mild cognitive impairment [MCI]) were identified. Participants with both APOE ε4 and BCHE-K variants had a 3.7-fold greater risk of AD (Hazard ratio [HR] 95%CI=1.99-6.89, p<0.001) compared to non-carriers of both genes (APOE ε4 x BCHE-K interaction p=0.025). There was no APOE ε4-BCHE-K interaction effect on rate of cognitive decline and brain atrophy. Conclusion: The APOE and BCHE genes interact to influence risk of incident AD/MCI but not rates of brain atrophy and decline in cognitive performance before onset of cognitive impairment. This may suggest the epistatic interaction between APOE ε4 and BCHE-K on AD risk is disease stage-dependent.
Christian Sandøe Musaeus, Helena Sophia Gleerup, Peter Høgh, Gunhild Waldemar, Steen Gregers Hasselbalch, Anja Hviid Simonsen
Cerebrospinal Fluid/Plasma Albumin Ratio as a Biomarker for Blood-Brain Barrier Impairment Across Neurodegenerative Dementias
Abstract: Background: Previous studies have shown an association between disruption of the blood-brain-barrier (BBB) and dementias of different etiologies. The protein concentration of cerebrospinal fluid (CSF) can be used as an indirect measurement for the permeability of the BBB using the CSF/plasma albumin quotient (Q-Alb) or total CSF protein. Objective: In the current study, we wanted to investigate Q-Alb and CSF protein concentration in dementias of different etiologies and the possible confounding factors. Methods: A total of 510 patients and healthy controls were included in the current study. The patients were diagnosed with Alzheimer’s disease (AD), dementia with Lewy bodies (DLB), vascular dementia (VaD), or frontotemporal dementia (FTD). Results: We found that Q-Alb was significantly different between the groups (p = 0.002, F = 3.874). Patients with DLB and VaD showed the largest Q-Alb. Although not significant for CSF total protein, we found the same overall pattern for DLB and VaD. When examining confounding factors, we found a positive association with age and a lower Fazekas score in DLB as compared to VaD. Conclusion: These results suggest that Q-Alb can contribute to our understanding of the pathophysiological mechanisms in DLB, and Q-Alb may serve as a supplementary diagnostic marker. Furthermore, we found a positive association with age, which may be due to differences in vascular co-morbidities. In addition, in patients with DLB, the increased Q-Alb is not due to vascular lesions. Studies are needed to validate the possible diagnostic value of Q-Alb in a larger cohort.
Rebecca L. Robinson, Dorene M. Rentz, Jeffrey Scott Andrews, Anthony Zagar, Yongin Kim, Valerie Bruemmer, Ronald L. Schwartz, Wenyu Ye, Howard M. Fillit
Costs of Early Stage Alzheimer’s Disease in the United States: Cross-Sectional Analysis of a Prospective Cohort Study (GERAS-US)
Abstract: Background: Costs associated with early stages of Alzheimer’s disease (AD; mild cognitive impairment [MCI] and mild dementia [MILD]) are understudied. Objective: To compare costs associated with MCI and MILD due to AD in the United States. Methods: Data included baseline patient/study partner medical history, healthcare resource utilization, and outcome assessments as part of a prospective cohort study. Direct, indirect, and total societal costs were derived by applying standardized unit costs to resources for the 1 month pre-baseline period (USD2017). Costs/month for MCI and MILD cohorts were compared using analysis of variance models. To strengthen the confidence of diagnosis, amyloid-β (Aβ) tests were included and analyses were replicated stratifying within each cohort by amyloid status [+/ ]. Results: Patients (N=1327) with MILD versus MCI had higher total societal costs/month ($4243 versus $2816; p<0.001). These costs were not significantly different within each severity cohort by amyloid status. The largest fraction of overall costs were informal caregiver costs (45.1%) for the MILD cohort, whereas direct medical patient costs were the largest for the MCI cohort (39.0%). Correspondingly, caregiver time spent on basic activities of daily living (ADLs), instrumental ADLs, and supervision time was twice as high for MILD versus MCI (all p<0.001). Conclusion: Early AD poses a financial burden, and despite higher functioning among those with MCI, caregivers were significantly impacted. The major cost driver was the patient’s clinical cognitive-functional status and not amyloid status. Differences were primarily due to rising need for caregiver support.
Wenting He, Man Tu, Yehong Du, Junjie Li, Yayan Pang, Zhifang Dong (Handling Associate Editor: Jin-Tai Yu)
Nicotine Promotes AβPP Nonamyloidogenic Processing via RACK1-Dependent Activation of PKC in SH-SY5Y-AβPP695 Cells
Abstract: Background: Accumulation of amyloid-β (Aβ) peptides, generated from amyloid-β precursor protein (AβPP) amyloidogenic processing, is one of the most salient disease hallmarks of Alzheimer’s disease (AD). Nicotine is able to promote α-secretase-mediated AβPP nonamyloidogenic processing and increase the release of sAβPPα and C-terminal fragment of 83 amino acids (C83). However, the potential molecular mechanism remains elusive. Objective: The aim of the present study was to investigate the effect of nicotine on AβPP processing in SH-SY5Y cells that stably express human Swedish mutant AβPP695 (SH-SY5Y-AβPP695). Methods: The expression of AβPP and its C-terminal fragments including C99, C89, and C83, was measured in SH-SY5Y-AβPP695 cells treated with nicotine for 6 h. Protein kinase C (PKC) antagonist Ro30-8220 or agonist PMA was used to determine the role of PKC in AβPP processing. Lentivirus-mediated shRNA targeting receptor for activated C-kinase 1 (RACK1) gene was added into the media to knockdown RACK1 expression, and then AβPP processing was examined. Results: The results showed that 6 h of nicotine exposure increased the expression of α-secretase (ADAM10) and C83 in a dose dependent manner. While the β-secretase (BACE1), AβPP amyloidogenic processing products C89 and C99 as well as Aβ peptides (including Aβ40 and Aβ42) remained unchanged. We also found that nicotine elevated the expression of phosphorylated PKC (P-PKC) and RACK1 on the cytomembrane. PKC antagonist Ro30-8220 treatment prevented the increase of ADAM10 and C83 by nicotine. Genetic knockdown RACK1 significantly inhibited P-PKC, and consequently abolished the increase of ADAM10 and C83 by nicotine. Conclusion: Taken together, these results indicate that nicotine effectively promotes AβPP nonamyloidogenic processing via RACK1-dependent activation of PKC in SH-SY5Y-AβPP695 cells and could be a potential molecule for AD treatment.
Weiwei Zhang*, Yiming Liu*, Hong Bao, Mengguo Zhang, Feng Gao, Dongmei Kang, Yong Shen *These authors contributed equally to this work.
A New Neurovascular Panel Discriminates Between Patients with Type 2 Diabetes Mellitus with Cognitive Impairment and Cognitive Impairment Alone
Abstract: Background: Recent studies showed that type 2 diabetes mellitus (T2DM) may increase the risk of cognitive impairment, but there are few biomarkers to diagnostically discriminate T2DM-associated cognitive impairment and cognitive impairment alone. In this study, we assessed certain cytokines involved in inflammation and vascular diseases and identified special panel of cytokines that could differentiate between T2DM and cognitive impairment. Objective: To investigate associations and differences between T2DM and cognitive impairment by cytokines analysis. Methods: A total of 264 participants were recruited, their blood samples were collected, and plasma and serum were separated and stored at -80°C until the assessment of amyloid-β (Aβ)42, Aβ40 and 8 kinds of cytokines by Luminex multiplex assays. Results: Plasma Aβ40 is higher whereas Aβ42/40 ratio is lower in cognitive impairment and T2DM-associated cognitive impairment compared to other groups. As compared to health control, YKL-40 level was upregulated in cognitive impairment, PRGN was downregulated in T2DM associated cognitive impairment, OPN was substantially decreased in T2DM, and IL-6 was elevated in cognitive impairment and T2DM-associated cognitive impairment. Interestingly, VEGF and S100B were induced in T2DM when compared with cognitive impairment, and NSE level in T2DM-associated cognitive impairment is significantly lower than in T2DM or cognitive impairment. Conclusion: Aβ42, Aβ40, and Aβ42/40 ratio cannot distinguish T2DM-associated cognitive impairment from cognitive impairment. Certain cytokines (YKL-40, NSE, and VEGF) have good performance in distinguishing T2DM-associated cognitive impairment from simple cognitive impairment. Taken together, this may improve the accuracy of the diagnosis and establishment of individualized therapy.
Margaret S. Blattner, Sunil K. Panigrahi, Cristina D. Toedebusch, Terry J. Hicks, Jennifer S. McLeland, Ian R. Banks, Claire Schaibley, Vitaliy Ovod, Kwasi G. Mawuenyega, Randall J. Bateman, Sharon L. Wardlaw, Brendan P. Lucey (Handling Associate Editor: Sharon Naismith)
Increased Cerebrospinal Fluid Amyloid-β During Sleep Deprivation in Healthy Middle-Aged Adults Is Not Due to Stress or Circadian Disruption
Abstract: Background: Concentrations of soluble amyloid-β (Aβ) oscillate with the sleep-wake cycle in the interstitial fluid of mice and cerebrospinal fluid (CSF) of humans. Further, the concentration of Aβ in CSF increases during sleep deprivation. Stress and disruption of the circadian clock are additional mechanisms hypothesized to increase CSF Aβ levels. Cortisol is a marker for both stress and has an endogenous circadian rhythm. Other factors such as glucose and lactate have been associated with changes in sleep-wake activity and/or Aβ. Objective: In this exploratory study, we used samples collected in a previous study to examine how sleep deprivation affects Aβ, cortisol, lactate, and glucose in plasma and CSF from healthy middle-aged adults (N=11). Methods: Eleven cognitively normal participants without evidence of sleep disturbance were randomized to sleep deprivation or normal sleep control. All participants were invited to repeat the study. Cortisol, lactate, glucose, and Aβ were measured in 2-h intervals over a 36-h period in both plasma and CSF. All concentrations were normalized to the mean prior to calculating mesor, amplitude, acrophase, and other parameters. Results: One night of sleep deprivation increases the overnight concentration of Aβ in CSF approximately 10%, but does not significantly affect cortisol, lactate, or glucose concentrations in plasma or CSF between the sleep-deprived and control conditions. Conclusion: These data suggest that sleep deprivation-related changes in CSF Aβ are not mediated by stress or circadian disruption as measured by cortisol.
Shu-Yi Huang*, Jun-Xia Zhu*, Xue-Ning Shen, Wei Xu, Ya-Hui Ma, Hong-Qi Li, Qiang Dong, Lan Tan, Jin-Tai Yu (Handling Associate Editor: Ling-Qiang Zhu) *These authors contributed equally to this work.
Prevalence of the Preclinical Stages of Alzheimer’s Disease in Cognitively Intact Older Adults: The CABLE Study
Abstract: Background: The National Institute on Aging and Alzheimer’s Association proposed an ATN classification system which divided Alzheimer’s disease biomarkers into three binary classes: amyloid deposition (A), tauopathy (T), and neurodegeneration or neuronal injury (N). Objective: To estimate the prevalence of each profile and to describe the demographic characteristics of each group in Chinese cognitively intact older adults. Methods: In this cross-sectional study, 561 cognitively intact participants from the Chinese Alzheimer’s Biomarker and LifestylE (CABLE) study were classified into eight groups using cerebrospinal fluid amyloid-β 42/40 as A, phosphorylated tau as T, and total tau as N. Multinomial models were used to determine the estimated prevalence of the eight groups. Results: The number and proportion of 561 participants in each ATN profile were 254 A-T-N- (45.3%), 28 A-T+N- (5.0%), 21 A-T-N+ (3.7%), 71 A-T+N+ (12.7%), 78 A+T-N- (13.9%), 14 A+T+N- (2.5%), 21 A+T-N+ (3.7%), and 74 A+T+N+ (13.2%). Individuals in N+ groups tend to be older than N- groups. A+ groups included more female individuals. The prevalence of A-T-N- profile declined with age, while that of A+T+N+ increased continuously. Conclusion: This is the first work to estimate the prevalence of each ATN profile and describe the demographic characteristics of ATN profiles based on a Chinese cohort. The clinical implications of our findings need to be scrutinized further in longitudinal studies of the ATN classification system.
Young Chul Youn, Byoung Sub Lee, Gwang Je Kim, Ji Sun Ryu, Kuntaek Lim, Ryan Lee, Jeewon Suh, Young Ho Park, Jung-Min Pyun, Nayoung Ryu, Min Ju Kang, Hye Ryoun Kim, Sungmin Kang, Seong Soo A. An, SangYun Kim
Blood Amyloid-β Oligomerization as a Biomarker of Alzheimer’s Disease: A Blinded Validation Study
Abstract: Background: Oligomeric amyloid-β (Aβ) is one of the major contributors to the pathomechanism of Alzheimer’s disease (AD); Aβ oligomerization in plasma can be measured using a Multimer Detection System-Oligomeric Aβ (MDS-OAβ) after incubation with spiked synthetic Aβ. Objective: We evaluated the clinical sensitivity and specificity of the MDS-OAβ values for prediction of AD. Methods: The MDS-OAβ values measured using inBloodTM OAβ test in heparin-treated plasma samples from 52 AD patients in comparison with 52 community-based subjects with normal cognition (NC). The inclusion criterion was proposed by the NINCDS-ADRDA and additionally required at least 6 months of follow-up from the initial clinical diagnosis in the course of AD. Results: The MDS-OAβ values were 1.43 ± 0.30 ng/ml in AD and 0.45 ± 0.19 (p<0.001) in NC, respectively. Using a cut-off value of 0.78 ng/ml, the results revealed 100% sensitivity and 92.31% specificity. Conclusion: MDS-OAβ to measure plasma Aβ oligomerization is a valuable blood-based biomarker for clinical diagnosis of AD, with high sensitivity and specificity.
Helen Shiells, Bjoern O. Schelter, Peter Bentham, Thomas C. Baddeley, Christopher M. Rubino, Harish Ganesan, Jeffrey Hammel, Vesna Vuksanovic, Roger T. Staff, Alison D. Murray, Luc Bracoud, Damon J. Wischik, Gernot Riedel, Serge Gauthier, Jianping Jia, Hans J. Moebius, Jiri Hardlund, Christopher M. Kipps, Karin Kook, John M.D. Storey, Charles R. Harrington, Claude M. Wischik
Concentration-Dependent Activity of Hydromethylthionine on Clinical Decline and Brain Atrophy in a Randomized Controlled Trial in Behavioral Variant Frontotemporal Dementia
Abstract: Background: Hydromethylthionine is a potent inhibitor of pathological aggregation of tau and TDP-43 proteins. Objective: To compare hydromethylthionine treatment effects at two doses and to determine how drug exposure is related to treatment response in bvFTD. Methods: We undertook a 52-week Phase III study in 220 bvFTD patients randomized to compare hydromethylthionine at 200 mg/day and 8 mg/day (intended as a control). The principal outcomes were change on the Addenbrookes Cognitive Examination – Revised (ACE-R), the Functional Activities Questionnaire (FAQ), and whole brain volume. Secondary outcomes included Modified Clinical Global Impression of Change (Modified-CGIC). A population pharmacokinetic exposure-response analysis was undertaken in 176 of the patients with available blood samples and outcome data using a discriminatory plasma assay for the parent drug. Results: There were no significant differences between the two doses as randomized. There were steep concentration-response relationships for plasma levels in the range 0.3–0.6 ng/ml at the 8 mg/day dose on clinical and MRI outcomes. There were significant exposure-dependent differences at 8 mg/day for FAQ, Modified-CGIC, and whole brain atrophy comparing patients with plasma levels greater than 0.346 ng/ml with having minimal drug exposure. The exposure-response is biphasic with worse outcomes at the high concentrations produced by 200 mg/day. Conclusions: Hydromethylthionine has a similar concentration-response profile for effects on clinical decline and brain atrophy at the 8 mg/day dose in bvFTD as recently reported in AD. Treatment responses in bvFTD are predicted to be maximal at doses in the range 20–60 mg/day. A confirmatory placebo-controlled trial is now planned.
Hong-Bin Cai, Zhen-Zhen Fan, Ting Tian, Zi-Chao Li, Chon-Chon Zhao, Wen-Ting Guo, Zhao-Ming Ge (Handling Associate Editor: Yong Guo)
Diabetes-Induced H3K9 Hyperacetylation Promotes Development of Alzheimer’s Disease Through CDK5
Abstract: The connection between diabetes and Alzheimer’s disease (AD) is not fully determined. Hyperphosphorylation of tau protein is mediated by binding and stabilization of truncated p25 with cyclin-dependent kinase-5 (CDK5) in AD. We recently showed that diabetes-associated hyperglycemia increased the CDK5 levels to promote development of AD. Here, we examined the underlying mechanisms. Hyperglycemia and glucose intolerance were induced in rats that had received a low dose of streptozotocin (STZ) and a high fat diet (HFD). Compared to the control rats that received no STZ and normal diet-fed, the STZ+HFD rats exhibited poorer performance in the behavioral test and showed hyperacetylation of H3K9 histone on CDK5 promoter, likely resulting from upregulation of a histone acetyltransferase, GCN5. Inhibition of acetylation of H3K9 histone by a specific GCN5 inhibitor, MB3, attenuated activation of CDK5, resulting in decreased tau phosphorylation in rat brain and improved performance of the rats in the behavior test. Thus, these data suggest that diabetes may promote future development of AD through hyperacetylation of H3K9 histone on CDK5 promoter.
Sevil Yasar, Kyle D. Moored, Atif Adam, Fiona Zabel, Yi-Fang Chuang, Vijay R. Varma, Michelle C. Carlson
Angiotensin II Blood Levels Are Associated with Smaller Hippocampal and Cortical Volumes in Cognitively Normal Older Adults
Abstract: Background: There is emerging evidence about possible involvement of the renin-angiotensin system (RAS) in the pathogenesis of Alzheimer’s disease (AD) and decline of cognitive function. However, little is known about associations with brain biomarkers. Objective: Our study aimed to examine associations between blood ACE-1 and ANG II levels and brain MRI based volumes in non-demented participants, and whether these associations were mediated by blood pressure. Methods: This cross-sectional study was conducted in 34 older participants from the Baltimore Experience Corps Trial (BECT) Brain Health Sub-study (BHS). Blood ANGII and ACE-1 levels were measured by ELISA and brain MRI volumes were generated using FreeSurfer 6.0. Multiple linear regression analysis, adjusting for intracranial volume and confounders, was used to determine associations between log transformed ANGII and ACE-1 levels and MRI volumes (mm3). Results: Participants were predominantly female (76%), African-American (94%), with mean age of 66.9 and education of 14.4 years. In the fully adjusted model we observed significant inverse associations between log ANGII levels and total grey matter (β=-14,935.50, ±7,444.83, p=0.05), total hippocampus (β=-129.97, ±105.27, p=0.03), rostral middle frontal (β=-1580.40, ±584.74, p=0.02), and supramarginal parietal (β=-978.90, ±365.54, p=0.02) volumes. There were no associations between ANGII levels and total white matter or entorhinal cortex volumes, or ACE-1 levels and any brain volumes. Conclusion: We observed that increased blood ANGII levels were associated with lower total grey matter, hippocampal, rostral middle frontal, and supramarginal parietal volumes, which are associated with cognitive domains that decline in preclinical AD.
Bo-Hyun Kim, Yong-Ho Choi, Jin-Ju Yang, SangYun Kim, Kwangsik Nho, Jong-Min Lee, for the Alzheimer’s Disease Neuroimaging Initiative (Handling Associate Editor: Keeley Brookes)
Identification of Novel Genes Associated with Cortical Thickness in Alzheimer’s Disease: Systems Biology Approach to Neuroimaging Endophenotype
Abstract: Alzheimer’s disease (AD) is a common neurodegenerative disorder characterized by a heterogeneous distribution of pathological changes in the brain. Cortical thickness is one of the most sensitive imaging biomarkers for AD representing structural atrophy. The purpose of this study is to identify novel genes associated with cortical thickness. We measured the whole-brain mean cortical thickness from magnetic resonance imaging (MRI) scans in 919 subjects from the Alzheimer’s Disease Neuroimaging Initiative cohort, including 163 AD patients, 488 mild cognitive impairment patients, and 268 cognitively normal participants. Based on the single-nucleotide polymorphism (SNP)-based genome-wide association study, we performed gene-based association analysis for mean cortical thickness. Furthermore, we performed expression quantitative trait loci, protein-protein interaction network, and pathway analysis to identify biologically functional information. We identified four genes (B4GALNT1, RAB44, LOC101927583, and SLC26A10), two pathways (cyclin-dependent protein kinase holoenzyme complex and nuclear cyclin-dependent protein kinase holoenzyme complex), and one protein-protein interaction (B4GALNT1 and GALNT8 pair). These genes are involved in protein degradation, GTPase activity, neuronal loss, and apoptosis. The identified pathways are involved in the cellular processes and neuronal differentiation, which contribute to neuronal loss that is responsible for AD. Furthermore, the most significant SNP (rs12320537) in B4GALNT1 is associated with expression levels of B4GALNT1 in several brain regions. Thus, the identified genes and pathways provide deeper mechanistic insight into the molecular basis of brain atrophy in AD.
Samuel T. Henderson, Bruce H. Morimoto, Jeffrey L. Cummings, Martin R. Farlow, Judith Walker (Handling Associate Editor: Russell Swerdlow)
A Placebo-Controlled, Parallel Group, Randomized Clinical Trial of AC-1204 in Mild-to-Moderate Alzheimer’s Disease
Abstract: Background: Alzheimer’s disease (AD) is characterized by amyloid-β plaques, neurofibrillary tangles, and regional cerebral glucose hypometabolism. Providing an alternative metabolic substrate, such as ketone bodies, may be a viable therapeutic option. Objective: The objective was to determine the efficacy and safety of the AC-1204 formulation of caprylic triglyceride administered daily for 26 weeks in APOE4 non-carrier participants with mild-to-moderate AD. Methods: In a double-blind, placebo-controlled, randomized study (AC-12-010, NOURISH AD, NCT 01741194), 413 patients with mild-to-moderate probable AD were stratified by APOE genotype and randomized (1:1) to receive either placebo or AC-1204 for 26 weeks. The primary outcome was the change from baseline to week 26 on the 11-item Alzheimer’s Disease Assessment Scale - Cognitive subscale (ADAS-Cog11) among APOE4 non-carriers. The key secondary outcome was the change from baseline to week 26 in the Alzheimer’s Disease Cooperative Study - Clinician’s Global Impression of Change scale. Results: Administration of AC-1204 was safe and well-tolerated. Mean changes from baseline in the primary outcome at 26 weeks in ADAS-Cog11 for placebo (n=138) was 0.0 and for AC-1204 (n=137) was 0.6 (LS differences of mean – 0.761, p=0.2458) and secondary outcome measures failed to detect any drug effects. Conclusion: The AC-1204 formulation of caprylic triglyceride failed to improve cognition or functional ability in subjects with mild-to-moderate AD. The lack of efficacy observed in this study may have several contributing factors including a lower ketone body formation from AC-1204 than expected and a lack of decline in the patients receiving placebo.
Susan Westfall, Duy M. Dinh, Giulio Maria Pasinetti
Investigation of Potential Brain Microbiome in Alzheimer’s Disease: Implications of Study Bias
Abstract: Background: Dysbiotic microbiota in the gastrointestinal tract promotes and aggravates neurodegenerative disorders. Alzheimer’s disease (AD) has been shown to correlate to dysbiotic bacteria and the immune, metabolic, and endocrine abnormalities associated with abnormal gut-brain-axis signaling. Recent reports also indicate that brain dysbacteriosis may play a role in AD pathogenesis. Objective: To evaluate the presence and differences of brain-region dependent microbiomes in control and AD subjects and the contribution of study bias. Methods: Two independent cohorts of postmortem AD brain samples were collected from separate locations, processed with different extraction protocols and investigated for the presence of bacterial DNA indicative of a brain microbiome with V4 16S next generation sequencing. Results: In both cohorts, few differences between the control and AD groups were observed in terms of alpha and beta diversities, phyla and genera proportions. Independent of study in both AD and control subjects the most abundant phyla were Proteobacteria, Firmicutes, Actinobacteria, and Bacteroidetes. Variations in beta diversity between hippocampal and cerebellum samples were observed indicating an impact of brain region on the presence of microbial DNA. Importantly, differences in alpha and beta diversities between the two independent cohorts were found indicating a significant cohort- and processing-dependent effect on the microbiome. Finally, there were cohort-specific correlations between the gut microbiome and subject demographics indicate that postmortem interval may have a significant impact on brain microbiome determination. Conclusions: Regardless of the study bias, this study concludes that bacterial DNA can be isolated from the human brain suggesting that a brain microbiome may exist; however, more studies are required to understand the variation in AD.
Lin Li*, Dan-Hong Wu*, Hong-Qi Li, Lin Tan, Wei Xu, Qiang Dong, Lan Tan, Jin-Tai Yu, Alzheimer’s Disease Neuroimaging Initiative (Handling Associate Editor: Yong Liu) *These authors contributed equally to this work.
Association of Cerebral Microbleeds With Cognitive Decline: A Longitudinal Study
Abstract: Background: The role of cerebral microbleeds (CMBs) in cognitive impairment remains controversial. Objective: To investigate the possible links between the presence, progression, number, and location of CMBs and cognition. Methods: We assessed 792 subjects from the Alzheimer’s Disease Neuroimaging Initiative who underwent both brain 3 Tesla MRI scans and cognitive testing. The association between CMBs and cognitive change was explored using linear mixed-effects models (LME). Results: Presence and number of CMBs were associated with memory (β = −0.03, p = 0.015; β = −0.01, p = 0.003), executive function (β = −0.04, p = 0.010; β = −0.01, p = 0.014), and global cognitive function (β = −0.06, p = 0.025; β = −0.03, p < 0.001). Progression of CMBs showed significant negative associations with executive function (β = −0.05, p = 0.025) and global cognitive function (β = −0.12, p = 0.015). The relations with cognitive performance (memory, executive function and global cognitive function) were mainly driven by lobar CMBs (β = −0.03, p = 0.041; β = −0.04, p = 0.010; β = −0.07, p = 0.029, respectively), especially those located in temporal lobe (β = −0.08, p = 0.027; β = −0.13, p = 0.001; β = −0.26, p < 0.001, respectively). Furthermore, white matter hyperintensities may mediate the association between CMBs and cognition. Conclusion: The presence, progression, number, and location of CMBs, especially those located in temporal lobe, are associated with cognitive decline. These findings suggest CMBs play a role in cognitive impairment.
Ronaldo D. Piovezan, Déborah Oliveira, Nicole Arias, Daisy Acosta, Martin J. Prince, Cleusa P. Ferri
Mortality Rates and Mortality Risk Factors in Older Adults with Dementia from Low- and Middle-Income Countries: The 10/66 Dementia Research Group Population-Based Cohort Study
Abstract: Background: Dementia is the main cause of disability in older people living in low- and middle-income countries (LMIC). Monitoring mortality rates and mortality risk factors in people with dementia (PwD) may contribute to improving care provision. Objective: We aimed to estimate mortality rates and mortality predictors in PwD from eight LMICs. Methods: This 3-5-year prospective cohort study involved a sample of 1,488 older people with dementia from eight LMIC. Total, age- and gender-specific mortality rates per 1,000 person-years at risk, as well as the total, age- and gender-adjusted mortality rates were estimated for each country’s sub-sample. Cox's regressions were used to establish the predictors of mortality. Results: At follow-up, vital status of 1,304 individuals (87.6%) was established, of which 593 (45.5%) were deceased. Mortality rate was higher in China (65.9%) and lower in Mexico (26.9%). Mortality risk was higher in males (HR=1.57; 95% CI: 1.32,1.87) and increased with age (HR=1.04; 95% CI: 1.03,1.06). Neuropsychiatric symptoms (HR=1.03; 95% CI: 1.01,1.05), cognitive decline (HR 1.04; 95% CI: 1.03,1.05), undernutrition (HR=1.55; 95% CI: 1.19, 2.02), physical impairments (HR=1.15; 95% CI: 1.03,1.29), and disease severity (HR=1.43; 95% CI: 1.22,1.63) predicted higher mortality risk. Conclusion: Several factors predicted higher mortality risk in PwD in LMICs. Males, those with higher age, higher severity of neuropsychiatric symptoms, higher number of physical impairments, higher disease severity, lower cognitive performance, and undernutrition had higher mortality risk. Addressing these indicators of long-term adverse outcomes may potentially contribute to improved advanced care planning, reducing the burden of disease in low-resourced settings.
Clara Domínguez-Vivero, Liwen Wu, Seonjoo Lee, Masood Manoochehri, Sarah Cines, Adam M. Brickman, Batool Rizvi, Anthony Chesebro, Yunglin Gazes, Emer Fallon, Timothy Lynch, Judith L. Heidebrink, Henry Paulson, Jill S. Goldman, Edward Huey, Stephanie Cosentino
Structural Brain Changes in Pre-Clinical FTD MAPT Mutation Carriers
Abstract: Background: Frontotemporal dementia (FTD) is the second most common cause of early-onset neurodegenerative dementia. Several studies have focused on early imaging changes in FTD patients, but once subjects meet full criteria for the FTD diagnosis, structural changes are generally widespread. Objective: This study aims to determine the earliest structural brain changes in asymptomatic MAPT mutation carriers. Methods: This is a cross-sectional multicenter study comparing global and regional brain volume and white matter integrity in a group of MAPT mutation preclinical carriers and controls. Participants belong to multiple generations of six families with five MAPT mutations. All participants underwent a medical examination, neuropsychological tests, genetic analysis, and a magnetic resonance scan (3T, scout, T1-weighted image followed by EPI (BOLD), MPRAGE, DTI, FLAIR, and ASL sequences). Results: Volumes of five cortical and subcortical areas were strongly correlated with mutation status: temporal lobe (left amygdala, left temporal pole), cingulate cortex (left rostral anterior cingulate gyrus, right posterior cingulate), and the lingual gyrus in the occipital lobe. We did not find significant differences in whole brain volume, white matter hyperintensities volume, and white matter integrity using DTI analysis. Conclusion: Temporal lobe, cingulate cortex and the lingual gyrus seem to be early targets of the disease and may serve as biomarkers for FTD prior to overt symptom onset.
Alaa A. Alsharif, Li Wei, Tiantian Ma, Kenneth K.C. Man, Wallis C.Y. Lau, Ruth Brauer, Mansour Almetwazi, Rob Howard, Ian C.K. Wong
Prevalence and Incidence of Dementia in People with Diabetes Mellitus
Abstract: Background: Few studies have shown that an increased risk of dementia is associated with diabetes mellitus. Objective: To estimate the prevalence and incidence of dementia in people with diabetes in primary care in the UK. Methods: We conducted a descriptive study using the UK The Health Improvement Network (THIN) database. People diagnosed with diabetes from 2000 to 2016 were included in the study. Prevalence and incidence rates of dementia were calculated annually, stratified by age and gender. Results: The prevalence of dementia was 0.424% [95%CI (0.420% - 0.427%)] in 2000 and 2.508% [95% CI (2.501% - 2.515%)] in 2016. The highest prevalence was in those aged 85+ from 2.9% [95%CI (2.890% - 2.974%)] in 2000 to 11.3% [95% CI (11.285% - 11.384%)] in 2016. The incidence of dementia increased 3.7 times, from 0.181 cases per 100 persons [95% CI (0.179 – 0.183)] in 2000 to 0.683 cases per 100 persons [95%CI (0.679-0.686)] in 2016, respectively. Women had a higher prevalence and incidence of dementia than men 3.138% [95% CI (3.127% - 3.150%)] versus 2.014% [95% CI (2.006% - 2.022%)] and 0.820 [95% CI (0.814 – 0.826)] versus 0.576 cases per 100 persons [95%CI (0.571-0.580)] in 2016, respectively. Conclusion: There was a trend of increasing prevalence and incidence of dementia in people with diabetes over the period of 2000 to 2016. This study adds to the evidence on dementia prevalence and incidence, particularly in the diabetic population.
Binu P. Thomas, Takashi Tarumi, Min Sheng, Benjamin Tseng, Kyle B. Womack, C. Munro Cullum, Bart Rypma, Rong Zhang, Hanzhang Lu (Handling Associate Editor: Jack de la Torre)
Brain Perfusion Change in Patients with Mild Cognitive Impairment After 12 Months of Aerobic Exercise Training
Abstract: Aerobic exercise (AE) has recently received increasing attention in the prevention of Alzheimer’s disease (AD). There is some evidence that it can improve neurocognitive function in elderly individuals. However, the mechanism of these improvements is not completely understood. In this prospective clinical trial, thirty amnestic mild cognitive impairment participants were enrolled into two groups and underwent 12 months of intervention. One group (n=15) performed AE training (8M/7F, age=66.4 years), whereas the other (n=15) performed stretch training (8M/7F, age=66.1 years) as a control intervention. Both groups performed 25–30 minutes training, 3 times per week. Frequency and duration were gradually increased over time. Twelve-month AE training improved cardiorespiratory fitness (p=0.04) and memory function (p=0.004). Cerebral blood flow (CBF) was measured at pre- and post-training using pseudo-continuous-arterial-spin-labeling MRI. Relative to the stretch group, the AE group displayed a training-related increase in CBF in the anterior cingulate cortex (p=0.016). Furthermore, across individuals, the extent of memory improvement was associated with CBF increases in anterior cingulate cortex and adjacent prefrontal cortex (voxel-wise p<0.05). In contrast, AE resulted in a decrease in CBF of the posterior cingulate cortex, when compared to the stretch group (p=0.01). These results suggest that salutary effects of AE in AD may be mediated by redistribution of blood flow and neural activity in AD-sensitive regions of brain.
Linda H.G. Pagen, Vincent van de Ven, Ed H.B.M. Gronenschild, Nikos Priovoulos, Frans R.J. Verhey, Heidi I.L. Jacobs
Contributions of Cerebro-Cerebellar Default Mode Connectivity Patterns to Memory Performance in Mild Cognitive Impairment
Abstract: Background: The cerebral default mode network (DMN) can be mapped onto specific regions in the cerebellum, which are specifically vulnerable to atrophy in Alzheimer’s disease (AD) patients. Objective: We set out to determine whether there are specific differences in the interaction between the cerebral and cerebellar DMN in amnestic mild cognitive impairment (aMCI) patients compared to healthy controls using resting-state functional MRI and whether these differences are relevant for memory performance. Methods: Eighteen patients with aMCI were age and education-matched to eighteen older adults and underwent 3T MR-imaging. We performed seed-based functional connectivity analysis between the cerebellar DMN seeds and the cerebral DMN. Results: Our results showed that compared to healthy older adults, aMCI patients showed lower anti-correlation between the cerebellar DMN and several cerebral DMN regions. Additionally, we showed that degradation of the anti-correlation between the cerebellar DMN and the medial frontal cortex is correlated with worse memory performance in aMCI patients. Conclusion: These findings provide evidence that the cerebellar DMN and cerebral DMN are negatively correlated during rest in older individuals, and suggest that the reduced anti-correlated impacts the modulatory role of the cerebellum on cognitive functioning, in particular on the executive component of memory functions in neurodegenerative diseases.
Lindsay R. Clark, Megan Zuelsdorff, Derek Norton, Sterling C. Johnson, Mary F. Wyman, Laura M. Hancock, Cynthia Carlsson, Sanjay Asthana, Susan Flowers-Benton, Carey E. Gleason, Heather M. Johnson (Handling Associate Editor: Mariagnese Barbera)
Association of Cardiovascular Risk Factors with Cerebral Perfusion in Whites and African Americans
Abstract: Background: Midlife cardiovascular risk factors increase risk for Alzheimer’s disease (AD). Despite disproportionately high cardiovascular disease and dementia rates, African Americans are under-represented in studies of AD risk and research-based guidance on targeting vascular risk factors is lacking. Objective: This study investigated relationships between specific cardiovascular risk factors and cerebral perfusion in White and African American adults enriched for AD risk. Methods: Participants included 397 cognitively unimpaired White (n=330) and African American (n=67) adults enrolled in the Wisconsin Alzheimer’s Disease Research Center who underwent pseudo-continuous arterial spin labeling MRI. Multiple linear regression models examined independent relationships between cardiovascular risk factors and mean cerebral perfusion. Subsequent interaction and stratified models assessed the role for APOE genotype and race. Results: When risk factor p-values were FDR-adjusted, diastolic blood pressure was significantly associated with mean perfusion. Tobacco use, triglycerides, waist-to-hip ratio, and a composite risk score were not associated with perfusion. Without FDR adjustment, a relationship was also observed between perfusion and obesity, cholesterol, and fasting glucose. Neither APOE genotype nor race moderated relationships between risk factors and perfusion. Conclusion: Higher diastolic blood pressure predicted lower perfusion more strongly than other cardiovascular risk factors. This relationship did not vary by racial group or genetic risk for AD, although the African American sample had greater vascular risk burden and lower perfusion rates. Our findings highlight the need to prioritize inclusion of underrepresented groups in neuroimaging studies and to continue exploring the link between modifiable risk factors, cerebrovascular health, and AD risk in underrepresented populations.
Matteo Vismara, Giovanna Cirnigliaro, Eleonora Piccoli, Federica Giorgetti, Laura Molteni, Laura Cremaschi, Giorgio G. Fumagalli, Claudio D’addario, Bernardo Dell’Osso
Crossing Borders Between Frontotemporal Dementia and Psychiatric Disorders: An Updated Overview
Abstract: Frontotemporal dementia (FTD) includes a group of neurocognitive syndromes, clinically characterized by altered behaviors, impairment of language proficiency, and altered executive functioning. FTD is one of the most frequently observed forms of dementia in the elderly population and the most common in presenile age. As for other subtypes of dementia, FTD incidence is constantly on the rise due to the steadily increasing age of the population, and its recognition is now becoming a determinant for clinicians. FTD and psychiatric disorders can overlap in terms of clinical presentations by sharing a common genetic predisposition and neuropathological mechanism in some cases. Nonetheless, this association is often unclear and underestimated. Since its first reports, research into FTD has constantly grown, with the identification of recent findings related to its neuropathology, genetic, clinical, and therapeutic issues. Literature is thriving on this topic, with numerous research articles published in recent years. In the present review, we aimed to provide an updated description of the clinical manifestations that link and potentially confound the diagnosis of FTD and psychiatric disorders in order to improve their differential diagnosis and early detection. In particular, we systematically reviewed the literature, considering articles specifically focused on the behavioral variant FTD, published after 2015 on the PubMed database.
John Maltby, Mahathir Chan, David Anderson, Elizabeta B. Mukaetova-Ladinska
Validation of the Salzburg Dementia Test Prediction (SDTP) as a Cognitive Screening Tool in an English-Speaking Inpatient Medical Setting
Abstract: Background: The Salzburg Dementia Test Prediction (SDTP), developed using artificial intelligence and based on the Mini-Mental State Examination (MMSE), was recently introduced as a brief cognitive screening tool for cognitive impairment. Objective: In the current study, we investigated whether the STDP can be used as a valid bed-side cognitive screening tool for dementia patients, in an English-speaking, medical inpatient setting. Methods: 216 medically ill older patients who had completed the MMSE (from which the SDTP scores can be calculated), with a subsample 58 patients who had also completed the ACE-R/ACE-III scales. Diagnosis of one of four dementia types (n = 127) and socio-demographic information were also collected. MMSE, SDTP, ACE-R/ACE-III, and dementia diagnosis were used to examine the construct validity of the SDTP through assessments of the structural, concurrent, and convergent validity. Results: The SDTP shows structural validity through demonstrating uni-dimensionality. Construct validity was demonstrated by sufficient correlation sizes with MMSE scores against a benchmark correlation size for most of the subsample, except vascular dementia. Convergent validity was demonstrated for the STDP with equivalent correlations sizes with ACE-R/ACE-III as the MMSE across all samples, though for vascular dementia the magnitude of this correlation was not as strong. Conclusions: Our findings support using STDP as a brief assessment tool among patients who have been diagnosed with Alzheimer’s disease, Lewy body disease, and mixed dementia; however, there is some statistical variability to overall MMSE scores and correlations with the ACE-R/ACE-III among patients diagnosed with vascular dementia.