Brain Glucose Metabolism Research Articles

Role of Aging, Genetics after Exposure to Airborne Particulate matter and High Temperatures on a Mouse Model of Alzheimer's Disease

Background: Elevated temperatures are usually accompanied by corresponding increases in concentrations of air pollutants increasing mortality or morbidity, which may feasibly be attributed to an interaction between the two factors. High temperatures and high levels of air pollution are increasingly linked to cognitive decline in individuals over 65 years. We hypothesize that the combined exposures to particulate matter (PM2.5) and heat stress (HS) may alter brain glucose metabolism and gut dysbiosis leading to increased cognitive impairment and accelerated AD phenotype.

Dynamic Human Brain Imaging with a Portable PET Camera: Comparison to a Standard Scanner.

Portable, cost-effective PET cameras can radically expand the applicability of PET. We present here a within-participant comparison of fully quantified [18F]FDG dynamic scans in healthy volunteers using the standard Biograph mCT scanner and portable CerePET scanner. Methods: Each of 20 healthy volunteers underwent dynamic [18F]FDG imaging with both scanners (1-154 d apart) and concurrent arterial blood sampling. Tracer SUV, net influx rate (Ki), and the corresponding cerebral metabolic rate of glucose (CMRglu) were quantified at regional and voxel levels. Results: At the regional level, CerePET outcome measure estimates within participants robustly correlated with Biograph mCT estimates in the neocortex, wherein the average Pearson correlation coefficients across participants ± SD were 0.83 ± 0.07 (SUV) and 0.85 ± 0.08 (Ki and CMRglu). There was also strong agreement between CerePET and Biograph mCT estimates, wherein the average regression slopes across participants were 0.84 ± 0.17 (SUV), 0.83 ± 0.17 (Ki), and 0.85 ± 0.18 (CMRglu). There was similar bias across participants but higher correlation and less variability in subcortical regions than in cortical regions. Pearson correlation coefficients for subcortical regions equaled 0.97 ± 0.02 (SUV) and 0.97 ± 0.03 (Ki and CMRglu), and average regression slopes equaled 0.79 ± 0.14 (SUV), 0.83 ± 0.11 (Ki), and 0.86 ± 0.11 (CMRglu). In voxelwise assessment, CerePET and Biograph mCT estimates across outcome measures were significantly different only in a cluster of left frontal white matter. Conclusion: Our results indicate robust correlation and agreement between semi- and fully quantitative brain glucose metabolism measurements from portable CerePET and standard Biograph mCT scanners. The results obtained with a portable PET scanner in this comparison in humans require follow-up but lend confidence to the feasibility of more flexible and portable brain imaging with PET.

Characteristics of brain glucose metabolism and metabolic connectivity in noise-induced hearing loss

The purpose of this study was to evaluate the differences in cerebral glucose metabolism and metabolic connectivity between noise-induced hearing loss (NIHL) subjects and normal subjects. Eighty-nine subjects who needed close observation for NIHL or were diagnosed with NIHL and 89 normal subjects were enrolled. After pre-processing of positron emission tomography images including co-registration, spatial normalization, and smoothing, a two-sample t-test was conducted to compare cerebral glucose metabolism between the two groups. To evaluate metabolic connectivity between two groups, BRAPH–BRain Analysis using graPH theory, a software package to perform graph theory analysis of the brain connectome was used. NIHL subjects showed hypometabolism compared to normal subjects in both insulae (x − 38, y − 18, z 4; × 42, y − 12, z 4) and right superior temporal gyrus (× 44, y 16, z − 20). No brain regions showed hypermetabolism in the NIHL subjects. In metabolic connectivity analysis, NIHL subjects showed decreased average strength, global efficiency, local efficiency, and mean clustering coefficient when compared with normal subjects. Decreased glucose metabolism and metabolic connectivity in NIHL subject might reflect decreased auditory function. It might be characteristic of sensorineural hearing loss.

Association between plasma inflammatory biomarkers and [18F]FDG‐PET signal in a transgenic amyloid rat model

AbstractBackgroundNeuroinflammation is thought to play an important role in the pathogenesis of Alzheimer’s disease (AD). It has recently been demonstrated that [18F]FDG positron emission tomography (PET) signal is sensitive to central inflammatory changes in AD. However, it is unknown whether blood cytokines, which are important signaling molecules that regulate the peripheral inflammatory process, are associated with the cerebral [18F]FDG‐PET signal. In this work, we aimed to investigate whether plasma cytokines are associated with brain glucose metabolism in a transgenic amyloid rat model.MethodBrain metabolism of 4‐ and 10‐month‐old wild‐type (WT) and APP/PS1 rats (TgF344‐AD) were assessed with [18F]FDG‐PET imaging. Plasma inflammatory markers (IFN‐γ, IL‐1α, IL‐1β, IL‐6, IL‐10 and TNF‐α) were measured by multiplex immunoassay. [18F]FDG‐SUVr was calculated with pons as the reference region. Correlation between inflammatory markers and [18F]FDG‐PET signal was conducted at the voxel level (RMINC; p<0.05 and t>2).ResultAt 4 months, IL‐10 levels significantly associate with [18F]FDG‐PET signal in the frontal and temporoparietal cortices (FCx and TPCx) and hippocampus (Fig1A), whereas other biomarkers present only small clusters associated with [18F]FDG‐PET signal (Fig1A). At 10 months, a positive association with [18F]FDG‐PET was found between IL‐1α and IL‐1β at FCx and TPCx, while IL‐10 showed a positive correlation at the TPCx (Fig1B). Additionality, IFN‐γ and TNF‐α presented small correlation clusters at the TPCx, and IL‐6 at the TPCx and CxF (Fig1B).ConclusionAt the pre‐amyloid plaque stage, only an anti‐inflammatory cytokine, IL‐10, presented positive associations with brain glucose metabolism. However, multiple pro‐inflammatory cytokines correlated with brain glucose metabolism at the amyloid plaque stage. These findings suggest a dual peripheral inflammatory response impacting brain metabolism, which can be associated with amyloid species and deposition.

GABA transporters gene expression associates with [18F]FDG‐PET signal in regions typically hypometabolic in Alzheimer’s disease

AbstractBackgroundIt is suggested that the [18F]fluorodeoxyglucose(FDG)‐PET signal reflects astrocyte and neuronal activity, with the excitatory glutamate uptake by astrocytes as the trigger for brain glucose metabolism. The inhibitory neurotransmitter γ‐aminobutyric acid (GABA) is taken up by neurons and astrocytes through the GABA transporters (GAT) 1 and 3. However, its role in the [18F]FDG‐PET signal in healthy aging and Alzheimer’s disease (AD) remains poorly investigated. Thus, we aimed to explore associations between neuronal and astrocytic GABA transporters gene expression with [18F]FDG‐PET in cognitively unimpaired (CU) and AD individuals.MethodWe obtained [18F]FDG‐PET imaging data of CU and AD from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) (Table 1). GAT1 and GAT3 gene expression in the brain was obtained from the Allen Brain Atlas (Table 1, Figure 1). We extracted SUVr (pons as reference region) and mRNA values using the RMINC package and performed Pearson’s correlation to test the association between [18F]FDG‐PET and GABA transporters mRNA (p‐value < 0.05).ResultIn brain regions typically hypometabolic in AD, we observed a strong positive association of [18F]FDG‐PET SUVr with GAT1 and GAT3 gene expression in CU (GAT1: r = 0.93; p < 0.0001; Figure 2A, GAT3: r = 0.94; p < 0.0001; Figure 2B) and AD individuals (GAT1: r = 0.9; p < 0.0001; Figure 2A, GAT3: r = 0.92; p < 0.0001; Figure 2B). By contrast, in brain regions typically resilient, we found a weak correlation with CU individuals (GAT1: r = 0.32; p = 0.016; Figure 2C, GAT3: r = 0.26; p = 0.04; Figure 2D) and no significant correlation in AD patients (GAT1: r = 0.24; p = 0.07; Figure 2C, GAT3: r = 0.24; p = 0.059; Figure 2D).ConclusionOur results demonstrate a significant strong positive association between [18F]FDG‐PET SUVr and GABA transporters gene expression in CU and AD in hypometabolic regions. These findings suggest that GABA transporters are involved with brain glucose metabolism in regions classically vulnerable to AD pathology.

Blood‐derived mitochondrial DNA copy number is associated with Alzheimer’s Disease through the regulation of plasma lipid and amino acid metabolism

AbstractBackgroundBlood‐derived mitochondrial DNA copy number (mtDNA‐CN) is the proxy measurement of mitochondrial function in the peripheral and central systems. Abnormal mtDNA‐CN not only indicates impaired mtDNA replication and transcription machinery but also dysregulated biological processes such as energy and lipid metabolism. However, the relationship between mtDNA‐CN and Alzheimer’s Disease (AD) and the underlying mechanisms of mitochondrial dysfunction in the pathogenesis of AD are still unclear.MethodTo investigate the causal relationship between mtDNA‐CN and AD, we performed two‐sample Mendelian randomization (MR) using publicly available summary statistics from GWAS for mtDNA‐CN and AD. Further, we estimated mtDNA‐CN using whole‐genome sequence data from blood samples of 1,521 ADNI participants and used a Cox proportional hazard model, adjusted for age, sex, and study phase, to assess the association between mtDNA‐CN and AD risk. The association of AD biomarkers measured in brain and plasma metabolites with mtDNA‐CN was evaluated using linear regression. We conducted causal mediation analysis to test the natural indirect effects of mtDNA‐CN change on AD risk through the significantly associated biomarkers and metabolites.ResultMR analysis using a profile likelihood approach suggested a causal relationship between decreased blood‐derived mtDNA‐CN and increased risk of AD (OR = 0.71; P = 0.023). Survival analysis showed that decreased mtDNA‐CN was significantly associated with increased risk of conversion from mild cognitive impairment to AD (HR = 0.80; P = 0.0017). We also identified significant associations between mtDNA‐CN and brain glucose metabolism (β = 0.050; P = 0.047) and amyloid‐β (Aβ) (β = 0.069; P = 0.015) and CSF Aβ (β = ‐0.051; P = 0.048). Plasma Aβ was, however, not associated. Several lipid species, amino acids, biogenic amines, and inflammatory proteins in plasma were also significantly associated with mtDNA‐CN. Finally, causal mediation analyses showed that the effect of change in mtDNA‐CN on AD risk is mediated by plasma neurofilament light (β = ‐0.055; P = 0.010), glycine (β = 0.016; P = 0.044), and hexadecenoylcarnitine (β = ‐0.017; P = 0.049).ConclusionOur study indicates that mtDNA‐CN measured in blood is predictive of AD risk. Associations of mtDNA‐CN with Aβ in CSF and brain, but not plasma, suggest cross‐tissue regulation of mitochondria. Decreased mtDNA‐CN might increase AD risk through lipid and amino acid metabolism. These results also suggest potential development of mtDNA‐CN as a blood‐based biomarker.

The relationship between [18F]FDG‐PET signal and key‐players of brain glucose metabolism

AbstractBackgroundNeuronal activity is supported by activity‐dependent lactate production from astrocytes, as postulated by the astrocyte–neuron lactate shuttle (ANLS) hypothesis. Indeed, astrocytic glutamate uptake is a main trigger for brain glucose consumption. [18F]fluorodeoxyglucose (FDG)‐PET showing a hypometabolic signature has been used as an index of neurodegeneration in Alzheimer’s disease (AD). In the early stages of the disease, soluble amyloid‐beta (Aβ) has been associated with neuronal hyperactivity due to decreased astrocytic glutamate uptake. It is hypothesized that this phenomenon occurs especially in regions with high ongoing baseline activity. Over time, neurodegeneration and hypometabolism in such regions may contribute to the progress of the AD continuum. Thus, we investigated whether the [18F]FDG‐PET signal in typical hypometabolic regions in AD is associated with the expression of ANLS transporters and enzymes in the healthy brain.MethodGene expression of GLUT1, GLUT3, MCT1, MCT2, MCT4, LDHA, and LDHB (ANLS genes) from postmortem brain tissue of healthy individuals were obtained from the Allen Human Brain Atlas. [18F]FDG‐PET data from cognitively unimpaired individuals were obtained from the Alzheimer’s Disease Neuroimaging Initiative (ADNI). Pearson correlations were performed between the mean gene expression and the mean [18F]FDG‐PET SUVr across typically hypometabolic brain regions in AD (precuneus, angular and temporal gyri, and parietal and cingulate regions) and non‐vulnerable regions (uncorrected p‐value < 0.05).ResultsThe expression of ANLS genes had a stronger positive correlation with [18F]FDG‐PET SUVr across the AD hypometabolic regions than the non‐vulnerable regions (p < 0.05). Of note, the astrocytic glucose transporter GLUT1 presented a stronger correlation with [18F]FDG‐PET than the neuronal transporter GLUT3 in AD‐vulnerable regions. Figure 1 presents all correlations.ConclusionOur results show that the physiological expression of transporters and enzymes responsible for the brain glucose metabolism correlate more with the [18F]FDG‐PET signal in typical brain regions of the AD hypometabolic signature. This suggests these regions present a higher baseline activity and may be more susceptible to Aβ‐induced hyperactivation in early AD, which could lead to a bioenergetic collapse in later disease stages, as shown in the [18F]FDG‐PET of AD individuals.

Therapeutic targeting of TREM2: A novel approach for treatment of AD?

AbstractBackgroundGenome‐wide association studies have revealed risk genes for developing late‐onset AD many of which are exclusively expressed by microglia in the brain. One of these microglial genes is TREM2. Studies employing mouse models of amyloid pathology have shown that TREM2 function is essential for microglia to mount a proper response to amyloid pathology. The fact that microglia exert protective effects via TREM2 at least at the early stages of amyloid deposition suggests that boosting TREM2 function pharmacologically during the early stages of AD may be a promising novel therapeutic approach.MethodWe have developed and evaluated the protective potential of agonistic anti‐TREM2 antibodies boosting TREM2 function in preclininal models of amyloid pathology and related disorders employing immunoblotting, ELISA, immunohistochemistry, scRNA‐seq, lipidomics, and TSPO‐ as well as FDG‐PET imaging.ResultOur agonistic anti‐TREM2 antibody 4D9 binds 12 amino acids N‐terminal of the ectodomain cleavage site, inhibits proteolytic TREM2 cleavage, and potently activates downstream pSYK signaling. Boosting TREM2 signaling by 4D9 leads to improved survival of macrophages, enhanced phagocytic activity of primary microglia, lower amyloid burden in an AD mouse model as well as accelerated recovery in mouse models of demyelination. In more recent work we focused on the development of a version of 4D9 with an engineered Fc part, which allows very efficient transcytosis of the antibody across the blood brain barrier (ATV:4D9; ATV: antibody transport vehicle). We demonstrate in an AD mouse model by TSPO and FDG PET imaging that a human specific version of the antibody enhances microglial activation and brain glucose metabolism, respectively.ConclusionSeveral independent studies including our own efforts have convincingly shown amelioration of amyloid pathology in preclinical models of AD upon administration of agonistic anti‐TREM2 antibodies. Together with findings demonstrating reduced cognitive decline in patients with higher levels of CSF soluble TREM2, which serves as a surrogate marker for TREM2‐dependent microglial activity, this suggests that TREM2‐boosting therapies should be actively explored in the clinical setting. In addition, our work indicates that TSPO‐ and FDG‐PET imaging may be used to assess target engagement.

Understanding the progression of Alzheimer’s Disease in 5XFAD transgenic female mice using 1H‐[13C]‐NMR Spectroscopy

AbstractBackground5XFAD female mice have been reported to exhibit severe plaque loading at an early age. However, brain glucose metabolism is poorly understood in this model. The objective of the current study was to understand neurometabolism and its role in disease progression and pathophysiology in female transgenic mice at various age points.MethodThe current study uses a tracer‐based approach, which involves infusion of [1,6]13C2 labeled glucose into AD mouse model 5XFAD, to observe the changes in the neuronal glucose oxidation in this pathological condition with the progression of age.ResultThere was a significant memory loss in the 6 months‐old (6M) transgenic females compared to the 15 months‐old (15M) animals through Novel Object Recognition and Y‐Maze tests. The neurochemical profile showed higher myo‐inositol levels in the cerebral cortex in the 15M mice wrt. the 6M ones, which implies that there is increased gliosis and neuroinflammation in the former. There is also an increased level of glutamine in the 15M mice, which is known to act as an osmolyte and cause brain edema. However, the cerebral metabolic rates of glucose oxidation in Glutamatergic and GABAergic neurons did not show a significant difference in 5xFAD female mice when compared with wild‐type mice of the same age.ConclusionThe imperturbation in the female mice might be linked to some active underlying neuroprotective mechanism and needs to be explored further. Also, to get a clear picture of the gender‐dependent AD progression, studies need to be conducted in the age‐matched male mice as well.

GABA transporters gene expression associates with [18F]FDG‐PET signal in regions typically hypometabolic in Alzheimer’s disease

AbstractBackgroundIt is suggested that the [18F]fluorodeoxyglucose(FDG)‐PET signal reflects astrocyte and neuronal activity, with the excitatory glutamate uptake by astrocytes as the trigger for brain glucose metabolism. The inhibitory neurotransmitter γ‐aminobutyric acid (GABA) is taken up by neurons and astrocytes through the GABA transporters (GAT) 1 and 3. However, its role in the [18F]FDG‐PET signal in healthy aging and Alzheimer’s disease (AD) remains poorly investigated. Thus, we aimed to explore associations between neuronal and astrocytic GABA transporters gene expression with [18F]FDG‐PET in cognitively unimpaired (CU) and AD individuals.MethodWe obtained [18F]FDG‐PET imaging data of CU and AD from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) (Table 1). GAT1 and GAT3 gene expression in the brain was obtained from the Allen Brain Atlas (Table 1, Figure 1). We extracted SUVr (pons as reference region) and mRNA values using the RMINC package and performed Pearson’s correlation to test the association between [18F]FDG‐PET and GABA transporters mRNA (p‐value < 0.05).ResultIn brain regions typically hypometabolic in AD, we observed a strong positive association of [18F]FDG‐PET SUVr with GAT1 and GAT3 gene expression in CU (GAT1: r = 0.93; p < 0.0001; Figure 2A, GAT3: r = 0.94; p < 0.0001; Figure 2B) and AD individuals (GAT1: r = 0.9; p < 0.0001; Figure 2A, GAT3: r = 0.92; p < 0.0001; Figure 2B). By contrast, in brain regions typically resilient, we found a weak correlation with CU individuals (GAT1: r = 0.32; p = 0.016; Figure 2C, GAT3: r = 0.26; p = 0.04; Figure 2D) and no significant correlation in AD patients (GAT1: r = 0.24; p = 0.07; Figure 2C, GAT3: r = 0.24; p = 0.059; Figure 2D).ConclusionOur results demonstrate a significant strong positive association between [18F]FDG‐PET SUVr and GABA transporters gene expression in CU and AD in hypometabolic regions. These findings suggest that GABA transporters are involved with brain glucose metabolism in regions classically vulnerable to AD pathology. ”

Plasma biomarkers of Alzheimer’s Disease associate with gray matter volume and cerebral glucose metabolism in older adults with Mild Cognitive Impairment

AbstractBackgroundAlzheimer’s Disease (AD) pathology in vivo has traditionally been measured in the cerebrospinal fluid or by positron emission tomography (PET). Developments in measuring plasma biomarkers present less invasive, cheaper ways to quantify AD pathology. However, the associations between these new plasma markers and neuroimaging markers of AD are not fully understood. We examined the relationship between plasma biomarkers of AD and measures of whole brain gray matter volume (GMV) and cerebral glucose metabolism in both cognitively unimpaired (n = 83) and impaired (n = 30) individuals.MethodWe collected data from individuals within the University of Kansas Alzheimer’s Disease Research Center’s (KU ADRC) Clinical Cohort who underwent MRI and FDG‐PET scans and had available plasma data. Participants included 64 females, and age of the neuroimaging cohort was 76.0 ± 6. Plasma biomarkers were measured in EDTA plasma using the Quanterix Simoa® HD‐X, and included NfL, Aβ42, Aβ40, GFAP, and p‐tau181. GMV was estimated using MPRAGE MRI processed in FreeSurfer. Cerebral glucose metabolism was estimated from FDG‐PET data using SUVR values calculated through SPM12, with standardization to pons. We used linear regression to examine the relationship between each biomarker to whole brain GMV and glucose metabolism. ANCOVA was used to evaluate differences in the plasma biomarkers between diagnosis groups. Analyses included sex and age as covariates.ResultWhole brain GMV (F = 8.4, p = .004) and cerebral glucose metabolism (F = 10.9, p = .002) differed between diagnostic groups. In the linear regression, we observed an interaction effect between cognitive diagnosis and each biomarker, such that the slopes of regressions between each plasma biomarker and neuroimaging marker was significant in the impaired group, but not significant in the unimpaired. In the impaired group, the strongest association observed was between plasma NFL and whole brain GMV (β = ‐1.4, p = .020) and cerebral glucose metabolism (β = ‐1.7, p = .014). Additionally, all plasma biomarkers were found to differ between diagnostic groups.ConclusionWe show that plasma markers of AD pathology associate with whole brain GMV and cerebral glucose metabolism in individuals with cognitive impairment. Further work will examine the relationship between biomarkers and regional neuroimaging measures

Correlational analysis of plasma metabolome and brain imaging in a humanized APOE mouse model

AbstractBackgroundApolipoprotein E (APOE) ε4 is the strongest genetic risk factor for the development of late‐onset Alzheimer’s disease (LOAD). Additionally, females have a 2x greater risk of developing LOAD than males. LOAD patients show brain glucose hypometabolism and severe reduction in hippocampal volume. Hippocampal atrophy has also been linked with plasma ceramide and phosphotidylcholine (PC) levels in these patients. This study explores the effects of sex and genotype on the plasma metabolome and potential correlations to brain imaging metrics in an aged humanized APOE (hAPOE) mouse model.MethodPlasma samples from 23–25‐month‐old hAPOE mice (37M/32F) expressing ε3/3, ε3/4 or ε4/4 genotypes were analyzed via mass spectrometry using the Biocrates MxP® Quant 500 platform. In a subset of these animals (24M/20F), in‐vivo FDG‐PET and high‐resolution ex‐vivo MRI were obtained. Cerebral FDG‐PET standardized uptake values were normalized to cerebellum (SUVr). Cerebral SUVr and regional volumes were correlated with detected metabolites and metabolic indicators using Pearson correlations. Two‐way ANOVAs were used to identify sex and genotype effects with post‐hoc t‐tests to determine statistical significance.ResulthAPOE ε3/3 mice had significantly greater cholesteryl ester (54%; p < 0.026) and lysophosphotidylcholine (lysoPC; 27%; p < 0.031) levels compared to ε4/4 mice. Females had lower levels of PCs (93%; p < 0.007), lysoPCs (82%; p < 0.018), triglycerides (62%; p < 0.045), and 1‐Met‐His (p = 5.84E‐25) than males. Significant positive correlations were observed between cerebral SUVr and PCs (45%; p < 0.049) as well as lysoPCs (82%; p <0.017). Total brain volume was negatively correlated with plasma 3‐Met‐His:creatinine ratio, indicative of muscle protein degradation (r = ‐0.44; p = 0.003) and positively correlated with (LysoPC+ arachidonic acid): PC ratio, indicative of phospholipase A2 activity (r = 0.42; p = 0.004). Right hippocampal volume percentage was significantly positively correlated with PCs (64%; p < 0.045) and 1‐Met‐His (p = 0.00067).ConclusionAt a comparable human age of ∼ 70 years, within the humanized APOE mouse, sex was the major contributing factor to metabolic differences in peripheral blood plasma. Levels of peripheral metabolites correlated with brain volumetrics and glucose metabolism, highlighting potential therapeutic targets for interventions designed to preserve neuronal health in AD.

Associations between brain TSPO and [18F]FDG‐PET signals in neurodegenerative disorders

AbstractBackgroundRecent evidence indicates that activated microglial cells contribute to the brain FDG‐PET signal changes in neurodegenerative disorders. Radiopharmaceuticals targeting the 18‐kDa translocator protein (TSPO) have been used to measure microglial activation. The combination of FDG‐PET and TSPO‐PET allows for assessing, in‐vivo and non‐invasively, whether they associate in brain regions vulnerable to neurodegeneration. So far, multiple studies have used FDG‐PET and TSPO‐PET concomitantly, but to our knowledge, no systematic evaluation has been conducted to assess whether they are associated. We aimed to systematically summarize the current data on brain TSPO‐PET and FDG‐PET signals in individuals with neurodegenerative disorders.MethodStudies performing TSPO‐ and FDG‐PET in neurodegenerative disorders were searched in PubMed and Web of Science. Included articles must have performed PET images concomitantly with both tracers in healthy controls and individuals presenting with neurodegenerative disorders. This review complied with PRISMA (2020) guidelines and was registered at PROSPERO (CRD42022354523).ResultA total of 272 articles were found after a search on PubMed and Web of Science, with eight meeting the inclusion criteria. We included clinical studies with individuals presenting Alzheimer’s Disease (AD), Parkinson’s Disease (PD), corticobasal syndrome and progressive supranuclear palsy, behavioral variant frontotemporal dementia, and progressive nonfluent aphasia. In AD, five studies presented negative associations, and one presented a positive association between TSPO and FDG signals in brain regions vulnerable to AD. In PD (3 studies) and the other related neurodegenerative disorders (2 studies) evaluated, we found a negative correlation between FDG‐PET and TSPO‐PET signals in vulnerable regions.ConclusionAll studies presented associations between FDG‐ and TSPO‐PET signals. These findings suggest that microglia, indexed by TSPO binding, negatively impacts brain glucose metabolism indexed by FDG‐PET. Further studies are needed to address associations between TSPO‐PET and FDG‐PET in the asymptomatic and early stages of neurodegenerative disorders.

Development of a selective estrogen β‐receptor phytoestrogen formulation – PhytoSERM – for the reduction of Alzheimer’s risk and relief of menopausal symptoms in women: a phase 2 randomized clinical trial framework

AbstractBackgroundThe greatest risk factors for Alzheimer’s disease (AD) are age, APOɛ4 allele and female sex. The estimated lifetime risk for AD is 19.5% for women compared to 10.3% in men. Accumulating evidence points to life‐time estrogen exposure as a protective factor against cognitive decline and AD in women, and to the menopause transition as a trigger for an existing AD predisposition. Estrogen replacement therapy (ERT) is effective for sustaining neurological health, but fear of breast cancer is the principal reason menopausal women reject it. Instead, women utilize over the counter products labeled as natural and considered to be safer. Thus, to attain brain protection and address breast protection we developed a rationally designed combination of select ERβ‐selective phytoestrogens that promote brain health to reduce AD risk without increasing breast cell proliferation.MethodA total of 100 participants, 50 per treatment arm, will be enrolled. Eligible participants are woman, 45‐60 years, peri or post‐menopausal (last menstrual period completed ≥ 60 days and ≤ 4 years), MoCA≥22, and experiencing ≥7 hot flashes per day. Participants will be randomized to 50 mg of PhytoSERM or placebo (orally, once‐per‐day) for a 24‐week period. FDG‐PET scans will be conducted at baseline and 24 weeks. Cognitive measures and clinical ratings will be assessed. Hot flashes will be measured both subjectively with a diary and objectively with a digital wristband measuring electrodermal activity.ResultPrimary endpoint is change from baseline to 24 weeks in regional brain glucose metabolism standardized uptake value ratio (SUVR). Secondary outcome measures include cognitive test battery scores, hot flash score and clinical ratings scores. Exploratory measures will include MRI brain volumes, fractional anisotropy, quantitative anisotropy, functional connectivity, and cerebral blood perfusion.ConclusionHerein we present a phase 2 proof‐of‐concept framework to assess the efficacy of PhytoSERM as a potential non‐pharmacologic therapeutic to improve cognitive health and reduce menopausal symptoms. Results from this study will validate previous findings that indicate that PhytoSERM is a safe alternative to hormone therapy and has the potential to sustain neurological health during the menopausal transition.

Banxia Xiexin Decoction Alleviated Cerebral Glucose Metabolism Disorder by Regulating Intestinal Microbiota in APP/PS1 Mice.

To identify whether Banxia Xiexin Decoction (BXD) alleviates cerebral glucose metabolism disorder by intestinal microbiota regulation in APP/PS1 mice. Forty-five 3-month-old male APP/PS1 mice were divided into 3 groups using a random number table (n=15 per group), including a model group (MG), a liraglutide group (LG) and a BXD group (BG). Fifteen 3-month-old male C57BL/6J wild-type mice were used as the control group (CG). Mice in the BG were administered BXD granules by gavage at a dose of 6 g/(kg•d) for 3 months, while mice in the LG were injected intraperitoneally once daily with Liraglutide Injection (25 nmol/kg) for 3 months. Firstly, liquid chromatography with tandem-mass spectrometry was used to analyze the active components of BXD granules and the medicated serum of BXD. Then, the cognitive deficits, Aβ pathological change and synaptic plasticity markers, including synaptophysin (SYP) and postsynaptic density protein 95 (PSD95), were measured in APP/PS1 mice. Brain glucose uptake was detected by micropositron emission tomography. Intestinal microbial constituents were detected by 16S rRNA sequencing. The levels of intestinal glucagon-like peptide 1 (GLP-1) and cerebral GLP-1 receptor (GLP-1R), as well as the phosphoinositide-3-kinase/protein kinase B/glycogen synthase kinase-3β (PI3K/Akt/GSK3β) insulin signaling pathway were determined by immunohistochemical (IHC) staining and Western blot analysis, respectively. BXD ameliorated cognitive deficits and Aβ pathological features (P<0.01). The expressions of SYP and PSD95 in the BG were higher than those in the MG (P<0.01). Brain glucose uptake in the BG was higher than that in the MG (P<0.01). The intestinal microbial composition in the BG was partially reversed. The levels of intestinal GLP-1 in the BG were higher than those in the MG (P<0.01). Compared with the MG, the expression levels of hippocampal GLP-1R, Akt, PI3K and p-PI3K in the BG were significantly increased (P<0.01), while the levels of GSK3β were reduced (P<0.01). BXD exhibited protective effects against Alzheimer's disease by regulating the gut microbiota/GLP-1/GLP-1R, enhancing PI3K/Akt/GSK3β insulin signaling pathway, and improving brain glucose metabolism.

Regional cerebral metabolism alterations and functional connectivity in individuals with opioid use disorder: An integrated resting-state PET/fMRI study

Individuals with opioid use disorder (OUD) have been reported to show abnormal brain metabolism and impaired coupling among brain networks such as the default mode network (DMN), salience network (SN), and executive control network (ECN). However, the characteristics of brain glucose metabolism and its related functions in the brain networks in individuals with OUD remain unknown. Thirty-six individuals with OUD and thirty matched healthy controls (HCs) were recruited in this integrated positron emission tomography/magnetic resonance imaging (PET/MRI) study. Differences in glucose metabolism were analyzed by using 18F-fluorodeoxyglucose (18F-FDG), and the corresponding coupling characteristics of the individuals with OUD were also analyzed. The individuals with OUD showed widespread bilateral hypometabolism in the middle temporal gyrus (MTG), superior temporal gyrus, angular gyrus, supramarginal gyrus, inferior parietal lobe, Rolandic operculum, and left insula, but obvious hypermetabolism in the brainstem and left cerebellum. Meanwhile, in individuals with OUD, the hypometabolism of right MTG which is included in the DMN was accompanied by decreased coupling with the left superior frontal gyrus and right superior parietal gyrus which are included in the ECN. Furthermore, individuals with OUD showed a positive correlation between the duration of heroin use and glucose metabolism of the left MTG. The individuals with OUD were characterized by widespread bilateral hypometabolism in the temporal and parietal regions but obvious hypermetabolism in the brainstem and left cerebellum. The results suggest that the hypometabolism in the temporal and parietal regions might be related to DMN dysfunction and the hypermetabolism in the brainstem and left cerebellum may be compensate for other brain regions showing hypometabolism. In particular, hypometabolism in the self-referential-related DMN regions in OUD might attenuate their relationships with the inhibitory-control-related ECN regions. These findings highlight the importance of evaluating the metabolic and functional profiles of the right MTG in future studies on the treatment of OUD.

Short-term consumption of highly processed diets varying in macronutrient content impair the sense of smell and brain metabolism in mice

ObjectiveFood processing greatly contributed to increased food safety, diversity, and accessibility. However, the prevalence of highly palatable and highly processed food in our modern diet has exacerbated obesity rates and contributed to a global health crisis. While accumulating evidence suggests that chronic consumption of such foods is detrimental to sensory and neural physiology, it is unclear whether its short-term intake has adverse effects. Here, we assessed how short-term consumption (<2 months) of three diets varying in composition and macronutrient content influence olfaction and brain metabolism in mice. MethodsThe diets tested included a grain-based standard chow diet (CHOW; 54% carbohydrate, 32% protein, 14% fat; #8604 Teklad Rodent diet , Envigo Inc.), a highly processed control diet (hpCTR; 70% carbohydrate, 20% protein, 10% fat; #D12450B, Research Diets Inc.), and a highly processed high-fat diet (hpHFD; 20% carbohydrate, 20% protein, 60% fat; #D12492, Research Diets Inc.). We performed behavioral and metabolic phenotyping, electro-olfactogram (EOG) recordings, brain glucose metabolism imaging, and mitochondrial respirometry in different brain regions. We also performed RNA-sequencing (RNA-seq) in the nose and across several brain regions, and conducted differential expression analysis, gene ontology, and network analysis. ResultsWe show that short-term consumption of the two highly processed diets, but not the grain-based diet, regardless of macronutrient content, adversely affects odor-guided behaviors, physiological responses to odorants, transcriptional profiles in the olfactory mucosa and brain regions, and brain glucose metabolism and mitochondrial respiration. ConclusionsEven short periods of highly processed food consumption are sufficient to cause early olfactory and brain abnormalities, which has the potential to alter food choices and influence the risk of developing metabolic disease.

Ketone bodies mediate alterations in brain energy metabolism and biomarkers of Alzheimer's disease.

Alzheimer's disease (AD) is the most common form of dementia. AD is a progressive neurodegenerative disorder characterized by cognitive dysfunction, including learning and memory deficits, and behavioral changes. Neuropathology hallmarks of AD such as amyloid beta (Aβ) plaques and neurofibrillary tangles containing the neuron-specific protein tau is associated with changes in fluid biomarkers including Aβ, phosphorylated tau (p-tau)-181, p-tau 231, p-tau 217, glial fibrillary acidic protein (GFAP), and neurofilament light (NFL). Another pathological feature of AD is neural damage and hyperactivation of astrocytes, that can cause increased pro-inflammatory mediators and oxidative stress. In addition, reduced brain glucose metabolism and mitochondrial dysfunction appears up to 15 years before the onset of clinical AD symptoms. As glucose utilization is compromised in the brain of patients with AD, ketone bodies (KBs) may serve as an alternative source of energy. KBs are generated from the β-oxidation of fatty acids, which are enhanced following consumption of ketogenic diets with high fat, moderate protein, and low carbohydrate. KBs have been shown to cross the blood brain barrier to improve brain energy metabolism. This review comprehensively summarizes the current literature on how increasing KBs support brain energy metabolism. In addition, for the first time, this review discusses the effects of ketogenic diet on the putative AD biomarkers such as Aβ, tau (mainly p-tau 181), GFAP, and NFL, and discusses the role of KBs on neuroinflammation, oxidative stress, and mitochondrial metabolism.

Subject classification and cross-time prediction based on functional connectivity and white matter microstructure features in a rat model of Alzheimer’s using machine learning

BackgroundThe pathological process of Alzheimer’s disease (AD) typically takes decades from onset to clinical symptoms. Early brain changes in AD include MRI-measurable features such as altered functional connectivity (FC) and white matter degeneration. The ability of these features to discriminate between subjects without a diagnosis, or their prognostic value, is however not established.MethodsThe main trigger mechanism of AD is still debated, although impaired brain glucose metabolism is taking an increasingly central role. Here, we used a rat model of sporadic AD, based on impaired brain glucose metabolism induced by an intracerebroventricular injection of streptozotocin (STZ). We characterized alterations in FC and white matter microstructure longitudinally using functional and diffusion MRI. Those MRI-derived measures were used to classify STZ from control rats using machine learning, and the importance of each individual measure was quantified using explainable artificial intelligence methods.ResultsOverall, combining all the FC and white matter metrics in an ensemble way was the best strategy to discriminate STZ rats, with a consistent accuracy over 0.85. However, the best accuracy early on was achieved using white matter microstructure features, and later on using FC. This suggests that consistent damage in white matter in the STZ group might precede FC. For cross-timepoint prediction, microstructure features also had the highest performance while, in contrast, that of FC was reduced by its dynamic pattern which shifted from early hyperconnectivity to late hypoconnectivity.ConclusionsOur study highlights the MRI-derived measures that best discriminate STZ vs control rats early in the course of the disease, with potential translation to humans.

The clinical application value of brain 18F-FDG PET/CT in the diagnostics of Parkinsonian syndromes

Objective: To analyze the PET/CT imaging features of fluoride 18F-fluorodeoxyglucose (18F-FDG) in patients with various types of Parkinson's syndrome (PS), and to establish a "diagnostic tree" model of 18F-FDG PET/CT for PS. Methods: Data of patients with Parkinson's disease (PD), patients with multiple system atrophy cerebellar type (MSA-C), and patients with multiple system atrophy Parkinson's type (MSA-P)admitted to the Neurology Department of Huashan Hospital affiliated to Fudan University from January 2019 to December 2021. 18F-FDG PET/CT examination was conducted in all patients. Clinical and follow-up data was collected to determine clinical diagnosis. The specific patterns of brain glucose metabolism in patients with various types of Parkinsonism were observed and their utility in the differential diagnosis of the disease was analyzed. 18F-FDG PET/CT imaging"diagnostic tree"model was established and its value in the differential diagnosis of Parkinsonism was verified. Results: A total of 320 patients, 187 males and 133 females, aged (62±9) years, were enrolled in our study, including 80 PD, 90 PSP, 114 MSA-C and 36 MSA-P patients. The differential diagnostic features of cerebral glucose metabolism of Parkinsonism were as follows: the metabolism of putamen increased in PD patients, the metabolism of caudate nucleus, thalamus, midbrain, and frontal lobe decreased in PSP patients, the metabolism of cerebellum decreased in MSA-C patients, and the metabolism of putamen and cerebellum decreased in MSA-P patients. The sensitivity and specificity of the"diagnostic tree"model are 88.75% and 91.25% for PD diagnosis, 54.44% and 96.96% for PSP diagnosis, 87.72% and 86.41% for MSA-C diagnosis, and 55.56% and 91.55% for MSA-P diagnosis, respectively. It could correctly classify 75%(240/320) of patients. Conclusions: Characteristic metabolism patterns of brain in 18F-FDG PET/CT imaging is significant for the differential diagnosis of PD, PSP, MSA-C and MSA-P. The"diagnostic tree"model is valuable for clinical diagnosis.