N-acetylaspartate, choline, myoinositol, glutamine and glutamate (glx) concentration changes in proton MR spectroscopy (1H MRS) in patients with mild cognitive impairment (MCI)

Magnetic Resonance Spectroscopy (MRS) in Alzheimer's Disease

MRS is a noninvasive technique to measure different metabolites in the brain. Changes in the levels of certain metabolites can be used as surrogate markers for Alzheimer's disease. They can potentially be used for diagnosis, prediction of prognosis, or even assessing response to treatment.There are different techniques for MRS acquisitions including STimulated Echo Acquisition Mode (STEAM) and Point Resolved Spectroscopy (PRESS). In terms of localization, single or multi-voxel methods can be used. Based on current data: 1. NAA, marker of neuronal integrity and viability, reduces in AD with longitudinal changes over the time as the disease progresses. There are data claiming that reduction of NAA is associated with tau accumulation, early neurodegenerative processes, and cognitive decline. Therefore, it can be used as a stage biomarker for AD to assess the severity of the disease. With advancement of disease modifying therapies, there is a potential role for NAA in the future to be used as a marker of response to treatment. 2. mI, marker of glial cell proliferation and activation, is associated with AB pathology and has early changes in the course of the disease. The NAA/mI ratio can be predictive of AD development with high specificity and can be utilized in the clinical setting to stratify cases for further evaluation with PET for potential treatments. 3. The changes in the level of other metabolites such as Chol, Glu, Gln, and GABA are controversial because of the lack of standardization of MRS techniques, current technical limitations, and possible region specific changes. 4. Ultrahigh field MRS and more advanced techniques can overcome many of these limitations and enable us to measure more metabolites with higher accuracy. 5. Standardization of MRS techniques, validation of metabolites' changes against PET using PET-guided technique, and longitudinal follow-ups to investigate the temporal changes of the metabolites in relation to other biomarkers and cognition will be crucial to confirm the utility of MRS as a potential noninvasive biomarker for AD.

Testosterone administration affects 1H-MRS metabolite spectra in transgender men

BACKGROUND

Recently, a variety of studies using different neuroimaging techniques attempted to identify the existence of a brain endophenotype in people with gender dysphoria (GD). However, despite mounting neuroimaging work, brain gender differences and effects of gender-affirming hormone therapy (GAHT) at the metabolite level remain understudied.

METHODS

Thirty-one transgender men (TM) before and after testosterone administration (7.7 months ± 3.5 months), relative to 30 cisgender men (CM) and 35 cisgender women (CW) underwent magnetic resonance spectroscopy (1H-MRS) at two time points. Two brain regions were assessed, i.e. the lateral parietal cortex and the amygdala/anterior hippocampus. Associated metabolites that were measured include N-acetyl aspartate (NAA), creatine (Cr), choline (Cho), glutamate and glutamine (Glx), myo-inositol (mI), glycine (Gly) and their respective ratios.

RESULTS

A critical time by group interaction revealed an effect of GAHT in the lateral parietal cortex of TM. MI+Gly/Cr ratios decreased upon initiation of GAHT. In addition, NAA/Cr and Cho/Cr ratios were lower in CW when compared to CM in the lateral parietal cortex. Glx levels and Glx/Cr ratios in TM differed from those in CW in the amygdala/anterior hippocampus. Interestingly, pubertal age of onset of gender dysphoria (i.e. GD) in TM differentially affected testosterone-mediated effects on Cr concentration and NAA/Cr ratios when compared to childhood and adult GD onset in the amygdala/anterior hippocampus.

CONCLUSION

This 1H-MRS study demonstrated that testosterone administration shifts mI+Gly/Cr ratios in the parietal cortex. In the amygdala/anterior hippocampus, modulation of metabolite concentrations by age of onset of GD is suggestive for a possible developmental trend.

Insight into Early Diagnosis of Multiple Sclerosis by Targeting Prognostic Biomarkers

Multiple sclerosis (MS) is a central nervous system (CNS) immune-mediated disease that mainly strikes young adults and leaves them disabled. MS is an autoimmune illness that causes the immune system to attack the brain and spinal cord. The myelin sheaths, which insulate the nerve fibers, are harmed by our own immune cells, and this interferes with brain signal transmission. Numbness, tingling, mood swings, memory problems, exhaustion, agony, vision problems, and/or paralysis are just a few of the symptoms. Despite technological advancements and significant research efforts in recent years, diagnosing MS can still be difficult. Each patient's MS is distinct due to a heterogeneous and complex pathophysiology with diverse types of disease courses. There is a pressing need to identify markers that will allow for more rapid and accurate diagnosis and prognosis assessments to choose the best course of treatment for each MS patient. The cerebrospinal fluid (CSF) is an excellent source of particular indicators associated with MS pathology. CSF contains molecules that represent pathological processes such as inflammation, cellular damage, and loss of blood-brain barrier integrity. Oligoclonal bands, neurofilaments, MS-specific miRNA, lncRNA, IgG-index, and anti-aquaporin 4 antibodies are all clinically utilised indicators for CSF in MS diagnosis. In recent years, a slew of new possible biomarkers have been presented. In this review, we look at what we know about CSF molecular markers and how they can aid in the diagnosis and differentiation of different MS forms and treatment options, and monitoring and predicting disease progression, therapy response, and consequences during such opportunistic infections.

Neuroimaging of Mouse Models of Alzheimer’s Disease

Magnetic resonance imaging (MRI) and positron emission tomography (PET) have made great strides in the diagnosis and our understanding of Alzheimer’s Disease (AD). Despite the knowledge gained from human studies, mouse models have and continue to play an important role in deciphering the cellular and molecular evolution of AD. MRI and PET are now being increasingly used to investigate neuroimaging features in mouse models and provide the basis for rapid translation to the clinical setting. Here, we provide an overview of the human MRI and PET imaging landscape as a prelude to an in-depth review of preclinical imaging in mice. A broad range of mouse models recapitulate certain aspects of the human AD, but no single model simulates the human disease spectrum. We focused on the two of the most popular mouse models, the 3xTg-AD and the 5xFAD models, and we summarized all known published MRI and PET imaging data, including contrasting findings. The goal of this review is to provide the reader with broad framework to guide future studies in existing and future mouse models of AD. We also highlight aspects of MRI and PET imaging that could be improved to increase rigor and reproducibility in future imaging studies.

Frontal Metabolites and Alzheimer's Disease Biomarkers in Healthy Older Women and Women Diagnosed with Mild Cognitive Impairment

BACKGROUND

Women account for two thirds of the prevalence and incidence of Alzheimer's disease (AD) and mild cognitive impairment (MCI). Evidence suggest that sex may differently influence the expression of proteins amyloid-beta (Aβ1-42) and tau, for which early detection is crucial in prevention of the disease.

OBJECTIVE

We investigated the effect of aging and cerebrospinal fluid (CSF) levels of Aβ1-42 and tau on frontal metabolites measured with proton magnetic resonance spectroscopy (MRS) in a cohort of cognitively normal older women and women with MCI.

METHODS

3T single-voxel MRS was performed on the medial frontal cortex, using Point Resolved Spectroscopy (PRESS) and Mescher-Garwood Point Resolved Spectroscopy (MEGA-PRESS) in 120 women (age range 50-85). CSF samples of Aβ1-42 and tau and scores of general cognition were also obtained.

RESULTS

Levels of frontal gamma aminobutyric acid (GABA+) were predicted by age, independently of disease and CSF biomarkers. Importantly, levels of GABA+ were reduced in MCI patients. Additionally, we found that levels of N-acetylaspartate relative to myo-inositol (tNAA/mI) predicted cognition in MCI patients only and were not related to CSF biomarkers.

CONCLUSION

This study is the first to demonstrate a strong association between frontal GABA+ levels and neurological aging in a sample consisting exclusively of healthy older women with various levels of CSF tau and Aβ1-42 and women with MCI. Importantly, our results show no correlation between CSF biomarkers and MRS metabolites in this sample.

Glutamine + glutamate level predicts the magnitude of microstructural organization in the gray matter in the healthy elderly

BACKGROUND

Diffusion tensor imaging (DTI), which is a technique for measuring the degree and direction of movement of water molecules in tissue, has been widely used to noninvasively assess white matter (WM) or gray matter (GM) microstructures in vivo. Mean diffusivity (MD), which is the average diffusion across all directions, has been considered as a marker of WM tract degeneration or extracellular space enlargement in GM. Recent lines of evidence suggest that cortical MD can better identify early-stage Alzheimer's disease than structural morphometric parameters in magnetic resonance imaging. However, knowledge of the relationships between cortical MD and other biological factors in the same cortical region, e.g. metabolites, is still limited.

METHODS

Thirty-three healthy elderly individuals [aged 50-77 years (mean, 63.8±7.4 years); 11 males and 22 females] were enrolled. We estimated the associations between cortical MD and neurotransmitter levels. Specifically, we measured levels of γ-aminobutyric acid (GABA) and glutamate + glutamine (Glx), which are inhibitory and excitatory neurotransmitters, respectively, in medial prefrontal cortex (mPFC) and posterior cingulate cortex (PCC) using MEGA-PRESS magnetic resonance spectroscopy, and we measured regional cortical MD using DTI.

RESULTS

Cortical MD was significantly negatively associated with Glx levels in both mPFC and PCC. No significant association was observed between cortical MD and GABA levels in either GM region.

CONCLUSION

Our findings suggest that degeneration of microstructural organization in GM, as determined on the basis of cortical MD measured by DTI, is accompanied by the decline of Glx metabolism within the same GM region.

Electroacupuncture ameliorate learning and memory by improving N-acetylaspartate and glutamate metabolism in APP/PS1 mice

Objective

To explore the precise mechanism of electroacupuncture (EA) to delay cognitive impairment in Alzheimer disease.

Methods

N-Acetylaspartate (NAA), glutamate (Glu) and myoinositol (mI) metabolism were measured by magnetic resonance spectroscopy, learning and memory of APP/PS1 mouse was evaluated by the Morris water maze test and the step-down avoidance test, neuron survival number and neuronal structure in the hippocampus were observed by Nissl staining, and BDNF and phosphorylated TrkB detected by Western blot.

Results

EA at DU20 acupuncture significantly improve learning and memory in behavioral tests, up-regulate NAA, Glu and mI metabolism, increase the surviving neurons in hippocampus, and promote the expression of BDNF and TrkB in the APP/PS1 transgenic mice.

Conclusion

These findings suggested that EA is a potential therapeutic for ameliorate cognitive dysfunction, and it might be due to EA could improve NAA and Glu metabolism by upregulation of BDNF in APP/PS1 mice.

Decreased Glutamate Levels in Patients with Amnestic Mild Cognitive Impairment: An sLASER Proton MR Spectroscopy and PiB-PET Study

BACKGROUND AND PURPOSE

Glutamate levels may be informative about the declining neuronal health in the central nervous system. We used an advanced proton MR spectroscopy (¹ H-MRS) protocol composed of semi-localization by adiabatic selective refocusing (sLASER) localization and FAST(EST)MAP shimming for detection of alterations in brain glutamate concentrations in patients with amnestic mild cognitive impairment.

METHODS

Participants with amnestic mild cognitive impairment (n = 14; median age = 80) and age- and sex-matched clinically normal controls (n = 32; median age = 79) from the population-based Mayo Clinic Study of Aging were recruited prospectively to the 3T single-voxel ¹ H-MRS study that examined metabolite changes in the posterior cingulate gyri. To be included, controls had to have low β-amyloid load on [¹¹ C] Pittsburgh Compound B (PiB)-PET (standard uptake value ratio; SUVr < 1.42) and patients with amnestic mild cognitive impairment had to have high β-amyloid load (SUVr ≥ 1.42).

RESULTS

Glutamate concentration and the glutamate/myo-inositol ratio were lower in patients with amnestic mild cognitive impairment than clinically normal controls (P < .05). Higher global cortical PiB-PET SUVr correlated with lower glutamate/myo-inositol (r = -.3, P = .04).

CONCLUSIONS

The advanced sLASER with FAST(EST)MAP shimming is a promising protocol for identifying glutamate alterations. Advanced ¹ H-MRS protocols may add to the understanding of early Alzheimer's disease pathophysiology through detection of glutamate concentration in posterior cingulate gyri of individuals with amnestic mild cognitive impairment.

Hydrogen Proton Magnetic Resonance Spectroscopy in Multidomain Amnestic Mild Cognitive Impairment and Vascular Cognitive Impairment Without Dementia

To investigate the value of hydrogen proton magnet resonance spectroscopy ((1)H-MRS) in the differential diagnosis of multiple-domain amnestic mild cognitive impairment (M-aMCI) and vascular cognitive impairment with no dementia (VCIND); (1)H-MRS was performed in patients with M-aMCI and VCIND. The level was determined for N-acetylaspartate (NAA), glutamate (Glu), inositol (mI), choline (Cho), and creatine (Cr). Compared with the normal control group, the NAA-Cr ratio in all regions studied was significantly lower in the M-aMCI and VCIND groups. The Glu-Cr ratio in the posterior cingulate gyrus of the M-aMCI group was significantly lower than in the VCIND. The mI-Cr ratio in the frontal white matter of the VCIND was significantly higher than in the M-aMCI group. In the white matter adjacent to the lateral ventricles, the Cho-Cr ratio was significantly higher in the VCIND than the M-aMCI. Our results suggested (1)H-MRS is an effective method in the differential diagnosis of M-aMCI and VCIND.

Analysis of the posterior cingulate cortex with [18F]FDG-PET and Naa/mI in mild cognitive impairment and Alzheimer's disease: Correlations and differences between the two methods

Reduction of regional brain glucose metabolism (rBGM) measured by [18F]FDG-PET in the posterior cingulate cortex (PCC) has been associated with a higher conversion rate from mild cognitive impairment (MCI) to Alzheimer's disease (AD). Magnetic Resonance Spectroscopy (MRS) is a potential biomarker that has disclosed Naa/mI reductions within the PCC in both MCI and AD. Studies investigating the relationships between the two modalities are scarce.

OBJECTIVE

To evaluate differences and possible correlations between the findings of rBGM and NAA/mI in the PCC of individuals with AD, MCI and of cognitively normal volunteers.

METHODS

Patients diagnosed with AD (N=32) or MCI (N=27) and cognitively normal older adults (CG, N=28), were submitted to [18F]FDG-PET and MRS to analyze the PCC. The two methods were compared and possible correlations between the modalities were investigated.

RESULTS

The AD group exhibited rBGM reduction in the PCC when compared to the CG but not in the MCI group. MRS revealed lower NAA/mI values in the AD group compared to the CG but not in the MCI group. A positive correlation between rBGM and NAA/mI in the PCC was found. NAA/mI reduction in the PCC differentiated AD patients from control subjects with an area under the ROC curve of 0.70, while [18F]FDG-PET yielded a value of 0.93.

CONCLUSION

rBGM and Naa/mI in the PCC were positively correlated in patients with MCI and AD. [18F]FDG-PET had greater accuracy than MRS for discriminating AD patients from controls.

Magnetic resonance spectroscopy in the diagnosis of dementia with Lewy bodies

Dementia with Lewy bodies (DLB) is considered to be the second most frequent primary degenerative dementing illness after Alzheimer's disease (AD). DLB, together with Parkinson's disease (PD), Parkinson's disease with dementia (PDD) belong to α-synucleinopathies—a group of neurodegenerative diseases associated with pathological accumulation of the α-synuclein protein. Dementia due to PD and DLB shares clinical symptoms and neuropsychological profiles. Moreover, the core features and additional clinical signs and symptoms for these two very similar diseases are largely the same. Neuroimaging seems to be a promising method in differential diagnosis of dementia studies. The development of imaging methods or other objective measures to supplement clinical criteria for DLB is needed and a method which would accurately facilitate diagnosis of DLB prior to death is still being searched. Proton magnetic resonance spectroscopy (¹H-MRS) provides a noninvasive method of assessing an in vivo biochemistry of brain tissue. This review summarizes the main results obtained from the application of neuroimaging techniques in DLB cases focusing on ¹H-MRS.

Advances in high-field magnetic resonance spectroscopy in Alzheimer's disease

Alzheimer's disease (AD) affects several important molecules in brain metabolism. The resulting neurochemical changes can be quantified non-invasively in localized brain regions using in vivo single-voxel proton magnetic resonance spectroscopy (SV 1H MRS). Although the often heralded diagnostic potential of MRS in AD largely remains unfulfilled, more recent use of high magnetic fields has led to significantly improved signal-to-noise ratios and spectral resolutions, thereby allowing clinical applications with increased measurement reliability. The present article provides a comprehensive review of SV 1H MRS studies on AD at high magnetic fields (3.0 Tesla and above). This review suggests that patterned regional differences and longitudinal alterations in several neurometabolites are associated with clinically established AD. Changes in multiple metabolites are identifiable even at early stages of AD development. By combining information of neurochemicals in different brain regions revealing either pathological or compensatory changes, high field MRS can be evaluated in AD diagnosis and in the detection of treatment effects. To achieve this, standardization of data acquisition and analytical approaches is needed.

Metabolic changes in acute cerebral infarction: Findings from proton magnetic resonance spectroscopic imaging

The purpose of this study was to investigate the clinical role of proton magnetic resonance spectroscopy (¹H-MRS) in the diagnosis of acute cerebral infarction. Using databases available at the Fifth Affiliated Hospital of Zhengzhou University (Zhengzhou, China), the medical records of 47 patients with acute cerebral infarction treated between April 2010 and March 2012 were retrospectively reviewed. The patients underwent routine magnetic resonance imaging (MRI), diffusion-weighted imaging (DWI) and multiple-voxel ¹H-MRS examination within 12 h after the onset of stroke. The patients then received normal medical treatment for 2 weeks and underwent follow-up ¹H-MRS examination at 1–2 months after stroke. The concentrations of the main metabolites [N-acetylaspartic acid (NAA), creatine (Cr), choline (Cho) and lactate (Lac)] in the infarct center, the infarction border region and the contralateral brain areas (control) were analyzed. The 47 patients experienced changes in NAA, Cho and Lac levels at different stages after stroke. In the infarction center, the NAA/Cr and NAA/Cho ratios decreased, while the Lac/Cr ratio increased within 12 h compared with those in the contralateral side. Within 6–12 h after stroke, the Lac/Cr ratio increased and the NAA/Cho ratio decreased compared with those <6 h after stroke. During the 1–2 months post-stroke, significant reductions in the NAA/Cr, NAA/Cho, Cho/Cr and Lac/Cr ratios were observed in the infarction center. In the infarction border region, the Lac/Cr ratio increased significantly at 12 h and decreased during the 1–2 months after stroke. The NAA/Cr, NAA/Cho and Cho/Cr ratios were significantly increased in the infarction border regions of patients who received thrombolytic therapy for 1–2 months compared with those in patients who did not undergo thrombolysis. Our results highlight the usefulness of ¹H-MRS-based metabolomics as a feasible and efficient prognostic tool for assessing the treatment effect of acute cerebral infarction.

Relationships among serum C-reactive protein, receptor for advanced glycation products, metabolic dysfunction, and cognitive impairments

Background

We examined the clinical value of two serum markers of low-grade inflammation, C-reactive protein (CRP) and receptor of advanced glycation products (RAGE), as prognostic indices for cognitive decline.

Methods

Patients with cognitive impairment (n = 377) and controls (n = 66) were examined by blood biochemistry tests, including ELISAs of serum CRP and RAGE, the Mini-mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA), and STEAM 1H-MRS of the left hippocampus and thalamus.

Results

Compared to the control group, the cognitive impairment group was older (63.10 ± 9.70 years vs. 55.09 ± 10.77 years, P = 0.000) and had fewer years of formal education (9.01 ± 4.01 vs. 12.94 ± 3.0, P = 0.000). There were no significant differences in the frequencies of type 2 diabetes, hypertension, or hyperlipidemia between groups. Serum CRP and RAGE were higher in the cognitive impairment group (CRP: 2.08 mg/L, range 1.07 − 3.36 mg/L vs. 0.21 mg/L, range 0.18 − 0.42 mg/L; RAGE: 4.01, range 2.49 − 5.71, vs. 2.28, range 1.84 − 3.03; P < 0.05 for both). In patients with cognitive impairment, there were negative correlations between cognitive function (as measured by MMSE and MoCA) and both CRP and RAGE levels (P < 0.05). Patients over 55 years exhibited a positive correlation between CRP and myo-inositol peak area in the left hippocampus (P < 0.05), while there was no relationship between RAGE and any metabolite (P > 0.05). Multiple linear regression revealed that CRP was influenced by hypertension (P = 0.026) and cognitive impairment (P = 0.042).

Conclusions

Chronic low-grade inflammation is present in patients with cognitive impairment. Serum CRP, RAGE, and left hippocampal myo-inositol may provide prognostic information on cognitive decline.

Magnetic resonance spectroscopy in mild cognitive impairment: systematic review and meta-analysis

Research using proton magnetic resonance spectroscopy (MRS) can potentially elucidate metabolite changes representing early degeneration in Mild Cognitive Impairment (MCI), an early stage of dementia. We integrated the published literature using meta-analysis to identify patterns of metabolite changes in MCI. 29 MRS studies (with a total of 607 MCI patients and 862 healthy controls) were classified according to brain regions. Hedges' g was used as effect size in a random effects model. N-Acetyl Aspartate (NAA) measures were consistently reduced in posterior cingulate (PC), hippocampus, and the paratrigonal white matter (PWM). Creatine (Cr) concentration was reduced in the hippocampus and PWM. Choline (Cho) concentration was reduced in the hippocampus while Cho/Cr ratio was raised in the PC. Myo-inositol (mI) concentration was raised in the PC and mI/Cr ratio was raised in the hippocampus. NAA/mI ratio was reduced in the PC. NAA may be the most reliable marker of brain dysfunction in MCI though mI, Cho, and Cr may also contribute towards this.

Nuclear magnetic resonance spectroscopy is highly sensitive for lipid-soluble metabolites

Although the water-soluble metabolite profile of human mesenchymal stem cells is known, the lipid profile still needs further investigation. In this study, methanol-chloroform was used to extract pid-soluble metabolites and perchloric acid was used to extract water-soluble metabolites. Furthermore, a dual phase extraction method using methanol-chloroform and water was used to obtain both water and lipid fractions simultaneously. All metabolite extractions were analyzed on a 9.4T high-resolution nuclear magnetic resonance spectrometer. Metabolite resonance peaks were assigned in the acquired spectra according to the chemical shift, and the extraction efficiency of ferent methods was compared. Results showed that in the spectra of water-soluble extracts, major metabolites comprised low molecular weight metabolites, including lactate, acetic acid, fatty acids, threonine, glutamic acid, creatine, choline and its derivatives, while in the spectra of lipid-soluble extracts, most metabolites were assigned to fatty acids. Among the different extraction procedures, perchloric acid was more efficient in extracting water-soluble metabolites and methanol-chloroform was efficient in extracting organic components compared with the dual phase extraction method. Nuclear magnetic resonance spectroscopy showed that as low as 0.7 mg organic yield was enough to obtain clear resonance peaks, while about 6.0 mg water-soluble yield was needed to obtain relatively favorable spectral lines. These results show that the efficiency of extracting water and lipid fractions is higher using perchloric acid and methanol-chloroform compared with dual phase extraction and that nuclear magnetic resonance spectroscopy is highly sensitive for analyzing lipid-soluble extracts.