Regional differences in cortical benzodiazepine receptors of Alzheimer, vascular, and mixed dementia patients

The link between metabolic syndrome and Alzheimer disease: A mutual relationship and long rigorous investigation

It has been illustrated that metabolic syndrome (MetS) is associated with Alzheimer disease (AD) neuropathology. Components of MetS including central obesity, hypertension, insulin resistance (IR), and dyslipidemia adversely affect the pathogenesis of AD by different mechanisms including activation of renin-angiotensin system (RAS), inflammatory signaling pathways, neuroinflammation, brain IR, mitochondrial dysfunction, and oxidative stress. MetS exacerbates AD neuropathology, and targeting of molecular pathways in MetS by pharmacological approach could a novel therapeutic strategy in the management of AD in high risk group. However, the underlying mechanisms of these pathways in AD neuropathology are not completely clarified. Therefore, this review aims to elucidate the association between MetS and AD regarding the oxidative and inflammatory mechanistic pathways.

Forest Biomass as a Promising Source of Bioactive Essential Oil and Phenolic Compounds for Alzheimer's Disease Therapy

Alzheimer’s disease (AD) is the most common neurodegenerative disorder affecting elderly people worldwide. Currently, there are no effective treatments for AD able to prevent disease progression, highlighting the urgency of finding new therapeutic strategies to stop or delay this pathology. Several plants exhibit potential as source of safe and multi-target new therapeutic molecules for AD treatment. Meanwhile, Eucalyptus globulus extracts revealed important pharmacological activities, namely antioxidant and anti-inflammatory properties, which can contribute to the reported neuroprotective effects. This review summarizes the chemical composition of essential oil (EO) and phenolic extracts obtained from Eucalyptus globulus leaves, disclosing major compounds and their effects on AD-relevant pathological features, including deposition of amyloid-β (Aβ) in senile plaques and hyperphosphorylated tau in neurofibrillary tangles (NFTs), abnormalities in GABAergic, cholinergic and glutamatergic neurotransmission, inflammation, and oxidative stress. In general, 1,8-cineole is the major compound identified in EO, and ellagic acid, quercetin, and rutin were described as main compounds in phenolic extracts from Eucalyptus globulus leaves. EO and phenolic extracts, and especially their major compounds, were found to prevent several pathological cellular processes and to improve cognitive function in AD animal models. Therefore, Eucalyptus globulus leaves are a relevant source of biological active and safe molecules that could be used as raw material for nutraceuticals and plant-based medicinal products useful for AD prevention and treatment.

[123I]Iomazenil SPECT Detects a Reversible Lesion of the Left Medial Temporal Lobe in a Case of Global Autobiographical Amnesia

Global autobiographical amnesia is a rare disorder that is characterized by a sudden loss of autobiographical memories covering many years of an individual's life. Generally, routine neuroimaging studies such as CT and MRI yield negative findings in individuals with global autobiographical amnesia. However, in recent case reports, functional analyses such as SPECT and fMRI have revealed changes in activity in various areas of the brain when compared with controls. Studies using iomazenil (IMZ) SPECT with individuals with global autobiographical amnesia have not been reported. We report the case of a 62-year-old Japanese woman with global autobiographical amnesia who had disappeared for ∼4 weeks. [123I]-IMZ SPECT showed reduced IMZ uptake in her left medial temporal lobe and no significant reduction on N-isopropyl-[123I] p-iodoamphetamine (IMP) SPECT in the identical region. Because IMZ binds to the central benzodiazepine receptor, this dissociation between IMZ and IMP SPECT was thought to reflect the breakdown of inhibitory neurotransmission in the left medial temporal lobe. Moreover, when the woman recovered most of her memory 32 months after fugue onset, the IMZ SPECT-positive lesion had decreased in size. Because the woman had long suffered verbal abuse from her former husband's sister and brother, which can also cause global autobiographical amnesia, it is difficult to conclude whether the IMZ SPECT-positive lesion in the left medial temporal lobe was the cause or the result of her global autobiographical amnesia. Although only one case, these observations suggest that IMZ SPECT may be useful in uncovering the mechanisms underlying global autobiographical amnesia.

Age-related increase in GABAA receptor distribution in the prefrontal cortex

Profound insight into age-related changes in γ-aminobutyric acid type A receptor (GABAA-R) distribution using iodine-123-iomazenil single photon emission computed tomography (IMZ-SPECT) can contribute to accurate in vivo evaluation. We evaluated the age-related changes in prefrontal cortex (PFC), which is the key region involved in various neurological and psychiatric diseases. In this study, IMZ-SPECT imaging data of 21 healthy males with an age range of 22-59 (mean, 38 ± 12) years were analyzed using three-dimensional stereotactic surface projection (3D-SSP). The Z-score images of the younger group (age < 40, n = 11) and the older group (age ≥ 40, n = 10) were compared. Subsequently, the mean RI-count ratios calculated for each Brodmann area (BA) by stereotactic extraction estimation method were compared between these groups. Thereafter, linear regression analysis between age and RI-count ratio was performed for all enrolled subjects. In the result, IMZ accumulation increased in bilateral BA10, 11, and the BA47 (left hemisphere) in the older group compared with the younger group. Furthermore, regression analysis demonstrated a significant positive correlation between age and RI-count ratio in these areas. Our findings indicate that GABAA-R distribution in the PFC relatively increases with age. Therefore, we concluded that the age-related changes should be considered to accurately evaluate pathophysiology of neurological and psychiatric diseases.

γ-Aminobutyric acid type A receptor binding affinity in the right inferior frontal gyrus at resting state predicts the performance of healthy elderly people in the visual sustained attention test

ABSTRACTBackground:Although recent studies have suggested that the γ-aminobutyric acid type A (GABAA) receptor binding affinity can be a more sensitive marker of age-related neuronal loss than regional gray matter (GM) volume, knowledge about the relationship between decreased GABAA receptor binding affinity and cognitive decline during normal aging is still limited.

METHODS

Thirty-seven healthy elderly individuals (aged 50-77 years (mean, 64.5 ± 7.3 years); 15 males and 22 females) were enrolled in this study. We investigated the association of the performance of the healthy elderly in the attentional function test with regional GM volume, regional cerebral bold flow (rCBF), and GABAA receptor binding affinity in the resting state by structural magnetic resonance imaging (MRI), arterial spin labeling (ASL), and 123I-iomazenil (IMZ) SPECT, with the analysis focusing on the bilateral inferior frontal gyri.

RESULTS

The score of the rapid visual information processing (RVP) test, which is used to assess visual sustained attention, showed a positive correlation with GABAA receptor binding affinity in the right inferior frontal gyrus. No significant correlation was found between RVP test score and regional GM volume or rCBF.

CONCLUSION

The findings of 123I-IMZ SPECT, but not those of structural MRI or ASL, suggest that a decreased GABAA receptor binding affinity can be a sensitive marker of cognitive impairment.

Differences in peripheral oxidative stress markers in Alzheimer's disease, vascular dementia and mixed dementia patients

AIMS

We determined whether the possible roles of oxidative stress differ in the pathophysiology and cognitive decline of Alzheimer's disease (AD), vascular dementia (VaD) and mixed Alzheimer's/vascular dementia (MD).

METHODS

We measured the levels of diacron reactive oxygen metabolite (dROM), reflecting the amount of organic hydroperoxides, and biological anti-oxidant potential (BAP), measuring the ferric reducing ability of blood plasma, in 72 patients with AD, 27 with VaD, 24 with MD and 53 non-demented outpatients (control group). In addition, endogenous plasma anti-oxidants, such as albumin, total bilirubin and uric acid, were compared among the groups. All participants with VaD and MD showed extensive white matter hyperintensity, in addition to multiple lacunes.

RESULTS

The dROM levels were significantly higher in the AD and MD groups than in the control group. The BAP levels were significantly lower in the MD group than in the control, AD and VaD groups. The AD group showed significantly lower levels of bilirubin and uric acid than the control group. The MD group showed a significantly lower level of albumin than the control and AD groups, and a significantly lower level of bilirubin than the control group. The Mini-Mental State examination scores correlated significantly with dROM levels and BAP/dROM ratios in the AD group.

CONCLUSIONS

An imbalance in pro-oxidant and anti-oxidant defenses is apparently involved in the pathophysiology of the AD and MD groups. The extent of oxidative stress damage might differ in subtypes of dementia by being greater in the MD group than in other types of dementia. Synergic effects of the degenerative element of AD and white matter lesions might be associated with oxidative stress damage in the MD group.

Potential neuroimaging biomarkers of pathologic brain changes in Mild Cognitive Impairment and Alzheimer's disease: a systematic review

Background

Neuroimaging-biomarkers of Mild Cognitive Impairment (MCI) allow an early diagnosis in preclinical stages of Alzheimer’s disease (AD). The goal in this paper was to review of biomarkers for Mild Cognitive Impairment (MCI) and Alzheimer’s disease (AD), with emphasis on neuroimaging biomarkers.

Methods

A systematic review was conducted from existing literature that draws on markers and evidence for new measurement techniques of neuroimaging in AD, MCI and non-demented subjects. Selection criteria included: 1) age ≥ 60 years; 2) diagnosis of AD according to NIAAA criteria, 3) diagnosis of MCI according to NIAAA criteria with a confirmed progression to AD assessed by clinical follow-up, and 4) acceptable clinical measures of cognitive impairment, disability, quality of life, and global clinical assessments.

Results

Seventy-two articles were included in the review. With the development of new radioligands of neuroimaging, today it is possible to measure different aspects of AD neuropathology, early diagnosis of MCI and AD become probable from preclinical stage of AD to AD dementia and non-AD dementia.

Conclusions

The panel of noninvasive neuroimaging-biomarkers reviewed provides a set methods to measure brain structural and functional pathophysiological changes in vivo, which are closely associated with preclinical AD, MCI and non-AD dementia. The dynamic measures of these imaging biomarkers are used to predict the disease progression in the early stages and improve the assessment of therapeutic efficacy in these diseases in future clinical trials.

MicroPET imaging and transgenic models: a blueprint for Alzheimer's disease clinical research

Over the past decades, developments in neuroimaging have significantly contributed to the understanding of Alzheimer's disease (AD) pathophysiology. Specifically, positron emission tomography (PET) imaging agents targeting amyloid deposition have provided unprecedented opportunities for refining in vivo diagnosis, monitoring disease propagation, and advancing AD clinical trials. Furthermore, the use of a miniaturized version of PET (microPET) in transgenic (Tg) animals has been a successful strategy for accelerating the development of novel radiopharmaceuticals. However, advanced applications of microPET focusing on the longitudinal propagation of AD pathophysiology or therapeutic strategies remain in their infancy. This review highlights what we have learned from microPET imaging in Tg models displaying amyloid and tau pathology, and anticipates cutting-edge applications with high translational value to clinical research.

Decreased γ-aminobutyric acid levels in the parietal region of patients with Alzheimer's disease

PURPOSE

To determine whether there are in vivo differences of γ-aminobutyric acid (GABA) levels in frontal and parietal regions of Alzheimer's disease (AD) patients, compared with healthy controls using magnetic resonance spectroscopy ((1) H-MRS).

MATERIALS AND METHODS

Fifteen AD patients and fifteen age- and gender-matched healthy controls underwent (1) H-MRS of the frontal and parietal lobes using the "MEGA-Point Resolved Spectroscopy Sequence" (MEGA-PRESS) technique, and cognitive levels of subjects were evaluated using Mini-Mental State Examination (MMSE) tests. MRS data were processed using the Gannet program. Because the signal detected by MEGA-PRESS includes contributions from GABA, macromolecules and homocarnosine, it is labeled as "GABA+" rather than GABA. Differences of GABA+/Cr ratios between AD patients and controls were tested using covariance analysis, adjusting for gray matter fraction. The relationship between GABA+/Cr and MMSE scores was also analyzed.

RESULTS

Significant lower GABA+/Cr ratios were found in the parietal region of AD patients compared with controls (P = 0.041). In AD patients, no significant correlations between GABA+/Cr and MMSE scores were found in either the frontal (r = -0.164; P = 0.558) or parietal regions (r = 0.025; P = 0.929).

CONCLUSION

Decreased GABA+/Cr levels were present in the parietal region of patients with AD in vivo, suggesting that abnormalities of the GABAergic system may be present in the pathogenesis of AD.