Plasma amyloid-beta oligomer is related to subjective cognitive decline and brain amyloid status.

BACKGROUND: Subjective cognitive decline (SCD) is a target for Alzheimer's disease prediction. Plasma amyloid-beta oligomer (AßO), the pathogenic form of Aß in blood, has recently been proposed as a novel blood-based biomarker of AD prediction by representing brain Aß deposition. The relationship between plasma AßO, brain Aß deposition, and SCD in individuals with normal objective cognition has not been investigated. METHODS: In this cross-sectional study, we analyzed 126 participants with normal objective cognition. More SCD symptoms were expressed as higher scores of the Subjective Cognitive Decline Questionnaire (SCDQ) and Memory Age-associated Complaint Questionnaire (MACQ). The plasma AßO level of each participant was measured twice for validation and expressed as a concentration (ng/mL) and a ratio relative to the mean value of two internal standards. Brain Aß deposition was assessed by [18F] flutemetamol positron emission tomography (PET) and expressed as standard uptake value ratio (SUVR). Associations of SCDQ and MACQ with plasma AßO levels or SUVR were analyzed in multiple linear regression models. The association between plasma AßO level and flutemetamol PET positivity was assessed in logistic regression and receiver operative characteristic analyses. RESULTS: Overall, participants were 73.3 years old with female predominance (69.0%). After adjustment for confounders, high SCDQ and MACQ scores were associated with the high plasma AßO levels as both concentrations and ratios (ratios: standardized coefficient = 0.246 and p = 0.023 for SCDQ, standardized coefficient = 0.209 and p = 0.029 for MACQ; concentrations: standardized coefficient = 0.257 and p = 0.015 for SCDQ, standardized coefficient = 0.217 and p = 0.021 for MACQ). In contrast, SCDQ and MACQ were not significantly associated with SUVRs (p = 0.134 for SCDQ, p = 0.079 for MACQ). High plasma AßO levels were associated with flutemetamol PET (+) with an area under the curve of 0.694 (ratio) or 0.662 (concentration). Combined with APOE e4, plasma AßO presented area under the curves of 0.789 (ratio) and 0.783 (concentration). CONCLUSIONS: Our findings indicate that the high plasma AßO level could serve as a potential surrogate biomarker of severe SCD and the presence of brain Aß deposition in individuals with normal objective cognition.

Pioglitazone use associated with reduced risk of the first attack of ischemic stroke in patients with newly onset type 2 diabetes: a nationwide nested case-control study.

BACKGROUND: Pioglitazone use is known to be associated with a reduced risk of recurrent stroke in patients with diabetes mellitus (DM) who have a history of stroke. However, it is unclear whether this benefit extends to patients without a history of stroke. We aimed to evaluate the association between pioglitazone use and development of first attack of ischemic stroke in patients with newly diagnosed type 2 DM. METHODS: Using longitudinal nationwide data from the 2002-2017 Korean National Health Insurance Service DM cohort, we analyzed the association between pioglitazone use and incidence of primary ischemic stroke using a nested case-control study. Among 128,171 patients with newly onset type 2 DM who were stroke-free at the time of DM diagnosis, 4796 cases of ischemic stroke were identified and matched to 23,980 controls based on age, sex, and the onset and duration of DM. The mean (standard deviation) follow-up time was 6.08 (3.34) years for the cases and controls. Odds ratios (ORs) and 95% confidence intervals (CIs) for the association between ischemic stroke and pioglitazone use were analyzed by multivariable conditional logistic regression analyses adjusted for comorbidities, cardiometabolic risk profile, and other oral antidiabetic medications. RESULTS: Pioglitazone use was associated with a reduced risk of first attack of ischemic stroke (adjusted OR [AOR] 0.69, 95% CI 0.60-0.80) when compared with non-use. Notably, pioglitazone use was found to have a dose-dependent association with reduced rate of ischemic stroke emergence (first cumulative defined daily dose [cDDD] quartile AOR 0.99, 95% CI 0.74-1.32; second quartile, AOR 0.77, 95% CI 0.56-1.06; third quartile, AOR 0.51, 95% Cl 0.36-0.71; highest quartile, AOR 0.48, 95% CI 0.33-0.69). More pronounced risk reduction was found in patients who used pioglitazone for more than 2 years. A further stratified analysis revealed that pioglitazone use had greater protective effects in patients with risk factors for stroke, such as high blood pressure, obesity, and current smoking. CONCLUSIONS: Pioglitazone use may have a preventive effect on primary ischemic stroke in patients with type 2 DM, particularly in those at high risk of stroke.

Exposure of ultrafine particulate matter causes glutathione redox imbalance in the hippocampus: A neurometabolic susceptibility to Alzheimer's pathology.

Particulate matter (PM) exposure is related to an increased risk of sporadic Alzheimer's disease (AD), the pathogenesis of which is explained by chronic neurometabolic disturbance. Therefore, PM-induced alterations in neurometabolism might herald AD. We aimed to identify brain region-specific changes in metabolic pathways associated with ultrafine particle (UFP) exposure and to determine whether such metabolic alterations are linked to susceptibility to AD. We constructed UFP exposure chambers and generated UFP by the pyrolysis method, which produces no toxic oxidized by-products of combustion, such as NOx and CO. Twenty male C57BL6 mice (11-12 months old) were exposed either to UFP or room air in the chambers for 3 weeks. One week following completion of UFP exposure, regional brain tissues, including the olfactory bulb, cortex, hippocampus, and cerebellum, were obtained and analyzed by metabolomics based on GC-MS and LC-MS, western blot analysis, and immunohistochemistry. Our results demonstrated that the metabolomic phenotype was distinct within the 4 different anatomical regions following UFP exposure. The highest level of metabolic change was identified in the hippocampus, a vulnerable region involved in AD pathogenesis. In this region, one of the key changes was perturbed redox homeostasis via alterations in the methionine-glutathione pathway. UFP exposure also induced oxidative stress and neuroinflammation, and importantly, increased Alzheimer's beta-amyloid levels in the hippocampus. These results suggest that inhaled UFP-induced perturbation in hippocampal redox homeostasis has a role in the pathogenesis of AD. Therefore, chronic exposure to UFP should be regarded as a cumulative environmental risk factor for sporadic AD.

Particulate matter increases beta-amyloid and activated glial cells in hippocampal tissues of transgenic Alzheimer's mouse: Involvement of PARP-1.

Exposure to air pollutants, such as particulate matter (PM), has been implicated in neurodegenerative disorders including Alzheimer's disease (AD). However, direct effects of PM on production of ß-amyloid (Aß), a key pathogenic molecule in AD, and its underlying mechanism are still elusive. Given PM's potential to induce oxidative stress in other tissues, we hypothesized that poly(ADP-ribose) polymerase (PARP-1) might be involved in PM-induced neurotoxicity. To address this, we used an ex vivo model of AD, the organotypic hippocampal slice tissue culture from old (12-14 months-of-age) triple transgenic 3xTg-AD mice. First, we observed that fine PM (aerodynamic diameter < 4 µm) can dose-dependently activate PARP-1 and decrease NAD+ levels in Neuro2A cells. PARP-1 activation did occur under concentrations of PM which did not affect cell viability. Next, we observed that direct treatment of PM increased Aß levels and activated glial cells in the ex vivo hippocampal tissues of 3xTg-AD mice. PM-induced glial activation was most prominent in CA1 region of the hippocampal tissue. Notably, we found that pharmacological inhibition of PARP-1 reversed both PM-induced Aß increase and glial activation, arguing the possible involvement of PARP-1 in PM-induced AD pathogenesis. Our findings suggest that PARP-1 might be a potential molecular target, responsible for mediating negative effects of PM on the brain. Modulating PARP-1 activity could be a promising approach to prevent or alleviate PM-related environmental neurotoxicity which could initiate AD pathogenesis.

Suppression of AIMP1 protects cognition in Alzheimer's disease model mice 3xTg-AD.

Neuroinflammation has been raised as a candidate of unifying pathogenesis and a target of a disease-modifying strategy for Alzheimer's disease (AD). Aminoacyl-tRNA synthetase complex (ARS)-interacting multifunctional protein 1 (AIMP1) is a cytokine that is known to amplify the actions of tumor necrosis factor-α and to be involved in microglial activation and neuronal death. In this respect, AIMP1 could be a plausible target for the treatment of AD. Therefore, we aimed to examine whether anti-AIMP1 antibody could exert therapeutic effects against cognitive impairment using 3xTg-AD mice. Through the passive avoidance test, we found that an intraperitoneal injection of anti-AIMP1 antibody over 4 weeks was effective in protecting memory function in 3xTg-AD mice (16 weeks old). In addition, to address the translational implications of AIMP1, we measured blood AIMP1 levels in patients with AD (n=22), mild cognitive impairment (n=25), and normal cognition (n=23). Blood AIMP1 levels were associated negatively with global cognitive function and were significantly higher in individuals with a higher degree of medial temporal lobe atrophy, which is one of the representative clinical markers of AD. Our results suggested a possible association of AIMP1 with AD pathogenesis, as well as the potential of the anti-AIMP1 antibody as a novel therapeutic option for AD.

Blunted response of hippocampal AMPK associated with reduced neurogenesis in older versus younger mice.

The rate of hippocampal neurogenesis declines with aging. This is partly explained by decreased neural responsiveness to various cues stimulating metabolism. AMP-activated protein kinase (AMPK), a pivotal enzyme regulating energy homeostasis in response to metabolic demands, showed the diminished sensitivity in peripheral tissues during aging. AMPK is also known to be involved in neurogenesis. We aimed to see whether AMPK reactivity is also blunted in the aged hippocampus, and thus is associated with aging-related change in neurogenesis. Following subchronic (7days) intraperitoneal and acute intracerebroventricular (i.c.v.) administration of either 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR; AMPK activator) or saline (sham) to young (16-week-old) and old (72-week-old) mice, we measured changes in AMPK activity, brain-derived neurotrophic factor (BDNF) expression or neurogenesis in the hippocampus. AICAR-induced changes in AMPK activity were observed in the hippocampus of young mice after acute i.c.v. injection. However, neither subchronic nor acute treatment induced significant changes in AMPK activity in old mice. Intriguingly, directions of AICAR-induced changes in AMPK activity were opposite between the hippocampus (decrease) and skeletal muscle (increase). ATP levels were inversely correlated with hippocampal AMPK activity, suggesting that the higher energy levels achieved by AICAR treatment might deactivate neuronal AMPK in young mice. The blunted response of AMPK to AICAR in old age was also indicated by the observations that the levels of neurogenesis and BDNF expression were significantly changed only in young mice upon AICAR treatment. Our findings suggest that the blunted response of neuronal AMPK in old age might be responsible for aging-associated decline in neurogenesis. Therefore, in addition to activation of AMPK, recovering its sensitivity may be necessary to enhance hippocampal neurogenesis in old age.

Calcium influx-mediated translocation of m-calpain induces Ku80 cleavage and enhances the Ku80-related DNA repair pathway.

Proteomic analysis of ionomycin-treated and untreated mammary epithelial MCF10A cells elucidated differences in Ku80 cleavage. Ku80, a subunit of the Ku protein complex, is an initiator of the non-homologous, end-joining (NHEJ), double-strand breaks (DSBs) repair pathway. The nuclear Ku80 was cleaved in a calcium concentration-dependent manner by m-calpain but not by m-calpain. The cleavage of nuclear Ku80 at its α/ß domain was validated by Western blotting analysis using flag-tagged expression vectors of truncated versions of Ku80 and a flag antibody and was confirmed in m-calpain knock-down cells and in vitro cell-free evaluation with recombinant proteins of calpains, Ku70, and Ku80. In addition, the cleaved Ku80 still formed a Ku heterodimer and promoted DNA DSB repair activity. Taken together, these findings indicate that translocated m-calpain enhances the NHEJ pathway through the cleavage of Ku80. Based on the present study, m-calpain in DNA repair pathways might be a novel anticancer drug target, or its mechanism might be a possible route for resistance acquisition of DNA damage-inducing chemotherapeutics.

Cholinesterase Inhibitor Donepezil Increases Mitochondrial Biogenesis through AMP-Activated Protein Kinase in the Hippocampus.

OBJECTIVE: Donepezil, a widely prescribed drug for Alzheimer's disease (AD), is now considered to have multimodal actions beyond cholinesterase inhibition. We aimed to see whether donepezil enhances mitochondrial biogenesis and relevant signaling pathways since mitochondrial dysfunction is a key feature of the hypometabolic AD brain. METHODS: As a metabolic gauge, AMP-activated protein kinase (AMPK) was investigated as a tentative mediator of neurometabolic action of donepezil. Changes in phospho-AMPK levels, mitochondrial biogenesis, and ATP levels were measured upon donepezil treatment using neuroblastoma cells, primary cultured neurons and ex vivo hippocampal tissue of adult mice. RESULTS: Donepezil dose-dependently increased mitochondrial biogenesis and ATP levels as well as expression of PGC-1α and NRF-1 in neuroblastoma cells. Donepezil dose-dependently activated AMPK; however, inhibition of AMPK abolished the observed effects of donepezil, indicating that AMPK is a key mediator of donepezil's action. Notably, mitochondrial biogenesis upon donepezil treatment was mainly observed within dendritic regions of primary cultured hippocampal neurons. Levels of synaptic markers were also increased by donepezil. Finally, AMPK- dependent mitochondrial biogenesis by donepezil was confirmed in organotypic hippocampal tissue. CONCLUSIONS: Our findings indicate that AMPK/PGC-1α signaling is involved in beneficial actions of donepezil on neurometabolism. Pharmacological activation of AMPK might be a promising approach to counteract AD pathogenesis associated with brain hypometabolism.

Utility of the Montreal Cognitive Assessment (MoCA) and its subset in HIV-associated neurocognitive disorder (HAND) screening.

OBJECTIVES: The Montreal Cognitive Assessment (MoCA) is a useful screening tool for mild cognitive impairment. We aimed to know whether the full MoCA and subsets of the full test are effective for detecting HIV-associated neurocognitive disorder (HAND). METHODS: We examined the socio-demographic, clinical, functional, and neuropsychological levels of 194 HIV-infected patients. We compared total scores and scores from each cognitive domain of MoCA between patients with and without HAND. We also examined the utility of subsets of the full test using a few selective domains. The diagnostic accuracies of MoCA and subset composition were evaluated. RESULTS: The total scores of MoCA (P<0.001) and scores from Trail Making Test-B (P=0.020), attention domain (P=0.005), and immediate (P=0.003) and delayed recall (P=0.002) differed between patients with and without HAND. A subset composed of Trail Making Test-B, rescored serial subtraction, and immediate/delayed recall showed a 69.2% accuracy. CONCLUSIONS: Our results suggest that the MoCA and its subsets alone are not sufficient in screening for HAND. Further studies will be needed to develop a simpler and easier screening tool for HAND based on this study.

Requirement of AMPK activation for neuronal metabolic-enhancing effects of antidepressant paroxetine.

Reduced glucose metabolism has been implicated as a pathophysiology of depressive disorder. Normalization of such impaired neurometabolism has been related to the therapeutic actions of antidepressant medication. However, the molecular mechanism underlying the neurometabolic actions of antidepressants has not been fully understood. Given that AMP-activated protein kinase (AMPK) is a master switch for energy homeostasis, we aimed to determine whether selective serotonin reuptake inhibitor paroxetine enhances energy metabolism by activating AMPK in neuroblastoma cells. We found that paroxetine dose dependently increased mitochondrial biogenesis, which involves the AMPK-peroxisome proliferator-activated receptor-γ coactivator-1α pathway. In addition, paroxetine-induced AMPK activation increases glucose uptake and ATP production. These neurometabolic effects of paroxetine were suppressed by cotreatment with compound C (CC), an AMPK inhibitor. These findings suggest a possibility that modulation of the AMPK pathway might be a previously unrecognized mechanism underlying the neurometabolic action of antidepressants. Further study is warranted to examine the region-specific and time-specific effects of AMPK modulation by antidepressants on mood-related behaviors.

Metabolomic signatures in peripheral blood associated with Alzheimer's disease amyloid-ß-induced neuroinflammation.

Discovery of biomarkers in peripheral blood is a crucial step toward the early diagnosis and repetitive monitoring of treatment response for Alzheimer's disease (AD). Metabolomics is a promising technology that can identify unbiased biomarkers. To explore potential blood biomarkers for AD via metabolic profiling with high-resolution magic angle spinning nuclear magnetic resonance techniques, we identified changes in peripheral blood metabolomic profiles in response to amyloid-ß (Aß)-induced neuroinflammation and co-treatment with gallate, a phytochemical known to have anti-neuroinflammatory properties. Alzheimer's-like (AL) model mice were produced by intracerebroventricular infusion of Aß and compared with normal control mice with infusion of vehicle. AL mice were treated with either gallate (treated AL mice) or vehicle (untreated AL mice). Metabolomic analyses of both whole blood and plasma showed a clear separation between untreated AL mice and the other two groups, with levels of several metabolites involved in energy metabolism, including pyruvate and creatine, being significantly reduced in untreated AL mice compared with control and treated AL mice. Gallate treatment suppressed Aß-induced overproduction of the inflammatory cytokine tumor necrosis factor-α in the hippocampus and normalized plasma levels of the affected metabolites. These results suggest that plasma levels of several metabolites could be indicative of both brain pathology and therapeutic responses, supporting the possibility of a close relationship between central neuroinflammation and systemic metabolic disturbance. These findings also suggest the potential of NMR-based metabolomics as a method to identify novel plasma biomarkers for AD, which could be confirmed by future translational research with human patients.

AMPK γ2 subunit gene PRKAG2 polymorphism associated with cognitive impairment as well as diabetes in old age.

Metabolic and cognitive disorders are closely related. However, the molecular mechanism underlying this association is still elusive. Given the importance of energy metabolism in neuronal cells, AMP-activated protein kinase (AMPK), a master switch of energy metabolism, could be an independent factor affecting cognitive as well as metabolic functions. Therefore, we examined the relationship between the AMPK γ2 gene, the PRKAG2 -26C/T polymorphism and cognitive impairment or diabetes in 1609 subjects aged from 60 to 80. We performed multivariate logistic regression analyses with adjustment for age, gender, education, smoking, alcohol, depression, waist circumference, APOE e4, and stroke history. We found a significant association between the -26C/T polymorphism (CC vs. CT/TT) and cognitive impairment (OR, 1.6; 95% CI, 1.1-2.3). Moreover, this polymorphism (CC/CT vs. TT) was also related to the presence of diabetes (OR, 1.8; 95% CI, 1.2-2.8). Importantly, the relationship with cognitive impairment was still significant in non-diabetic individuals (OR, 1.6; 95% CI, 1.1-2.4). Further analyses with a subpopulation (n=611) revealed that CC homozygotes relative to T-allele carriers had significantly better performances in verbal memory and attentional tasks. These findings collectively support a hypothesis that AMPK has a role not only in metabolic functioning but also in cognitive functioning in humans. Extended longitudinal study with a larger number of samples is warranted.

A preliminary investigation of alpha-lipoic acid treatment of antipsychotic drug-induced weight gain in patients with schizophrenia.

Weight gain and other metabolic disturbances have now become discouraging, major side effects of atypical antipsychotic drugs (AAPDs). The novel strategies required to counteract these serious consequences, however, should avoid modulating the activities of the neurotransmitter receptors involved because those receptors are the therapeutic targets of AAPDs. Adenosine monophosphate-activated protein kinase is an enzyme that plays a pivotal role in energy homeostasis. We hypothesized that alpha-lipoic acid (ALA), which is known to modulate adenosine monophosphate-activated protein kinase activity in the hypothalamus and peripheral tissues, would ameliorate AAPD-induced weight gain. We describe the case series of a 12-week ALA trial in schizophrenia patients treated with AAPDs. Two of 7 enrolled subjects were dropped from the study because of noncompliance and demand for new medication to treat depressive symptoms, respectively. The mean (SD) weight loss was 3.16 (3.20) kg (P = 0.043, last observation carried forward; median, 3.03 kg; range, 0-8.85 kg). On average, body mass index showed a significant reduction (P = 0.028) over the 12 weeks. During the same period, a statistically significant reduction was also observed in total cholesterol levels (P = 0.042), and there was a weak trend toward the reduction in insulin resistance (homeostasis model assessment of insulin resistance) (P = 0.080). Three subjects reported increased energy subjectively. The total scores on the Brief Psychiatric Rating Scale and the Montgomery-Asberg Depression Rating Scale did not vary significantly during the study. These preliminary data suggest the possibility that ALA can ameliorate the adverse metabolic effects induced by AAPDs. To confirm the benefits of ALA, more extended study is warranted.