White matter microstructure and cognitive decline in metabolic syndrome: a review of diffusion tensor imaging

Increased dementia risk in patients with Parkinson's disease attributed to metabolic syndrome

INTRODUCTION

Metabolic syndrome (MetS) manifests resembling pathophysiological mechanisms with Parkinson's disease (PD). Current research on the overall population has emphasized MetS as a freestanding risk factor for cognition. This research aims to explore the impact of MetS on cognition in Parkinson's patients.

METHOD

We involved subjects identified as having early-stage PD patients. The MetS was diagnosed dependent on parameters overviewed in the National Cholesterol Education Program's Adult Treatment Panel III. The clinical severity and stages in patients with PD were dependent on the disease rating scales. The cognition was evaluated by the Turkısh version of the Montreal Cognitive Assessment Scale (MoCA-TR). The cases were categorized according to cognitive failure: mild cognitive impairment in PD (PD-MCI), and PD dementia (PDD).

RESULTS

Metabolic syndrome was present in 39.6% of the participants. 22.0% of patients were in the normal cognition, 29.1% in the PD-MCI group, and 48.9% in the PD-D group. The cognitive scores in patients with MetS is considerably lower than MetS negative group. A statistically notable inverse association was detected between fasting blood glucose levels and the visual-spatial/executive functions, naming, language, and orientation scores. The multivariate logistic regression analysis showed individuals with MetS were found to have an 11.308 times higher risk of PD-D (odds ratio [OR]: 11,3, 95% confidence interval [CI]: 1.61-79.2 ).

CONCLUSION

We discerned the occurrence of MetS in PD raises the possibility of advancing dementia. This suggests that considering MetS in this patient group could contribute to the effective management of dementia.

Exploring the reduction in aquaporin-4 and increased expression of ciliary neurotrophic factor with the frontal-striatal gliosis induced by chronic high-fat dietary stress

High-fat diet (HFD)-induced obesity induces peripheral inflammation and hypothalamic pathogenesis linking the activation of astrocytes and microglia. Clinical evidence indicates a positive correlation between obesity and psychiatric disorders, such as depression. The connectivity of the frontal-striatal (FS) circuit, involving the caudate putamen (CPu) and anterior cingulate cortex (ACC) within the prefrontal cortex (PFC), is known for its role in stress-induced depression. Thus, there is a need for a thorough investigation into whether chronic obesity-induced gliosis, characterized by the activation of astrocytes and microglia, in these brain regions of individuals with chronic obesity. The results revealed increased S100β+ astrocytes and Iba1+ microglia in the CPu and ACC of male obese mice, along with immune cell accumulation in meningeal lymphatic drainage. Activated GFAP+ astrocytes and Iba1+ microglia were observed in the corpus callosum of obese mice. Gliosis in the CPu and ACC was linked to elevated cleaved caspase-3 levels, indicating potential neural cell death by chronic HFD feeding. There was a loss of myelin and adenomatous polyposis coli (APC)+ oligodendrocytes (OLs) in the corpus callosum, an area known to be linked with injury to the CPu. Additionally, reduced levels of aquaporin-4 (AQP4), a protein associated within the glymphatic systems, were noted in the CPu and ACC, while ciliary neurotrophic factor (CNTF) gene expression was upregulated in these brain regions of obese mice. The in vitro study revealed that high-dose CNTF causing a trend of reduced astrocytic AQP4 expression, but it significantly impaired OL maturation. This pathological evidence highlights that prolonged HFD consumption induces persistent FS gliosis and demyelination in the corpus callosum. An elevated level of CNTF appears to act as a potential regulator, leading to AQP4 downregulation in the FS areas and demyelination in the corpus callosum. This cascade of events might contribute to neural cell damage within these regions and disrupt the glymphatic flow.

Relationships between abdominal adipose tissue and neuroinflammation with diffusion basis spectrum imaging in midlife obesity

OBJECTIVE

This study investigated how obesity, BMI ≥ 30 kg/m2, abdominal adiposity, and systemic inflammation relate to neuroinflammation using diffusion basis spectrum imaging.

METHODS

We analyzed data from 98 cognitively normal midlife participants (mean age: 49.4 [SD 6.2] years; 34 males [34.7%]; 56 with obesity [57.1%]). Participants underwent brain and abdominal magnetic resonance imaging (MRI), blood tests, and amyloid positron emission tomography (PET) imaging. Abdominal visceral and subcutaneous adipose tissue (VAT and SAT, respectively) was segmented, and Centiloids were calculated. Diffusion basis spectrum imaging parameter maps were created using an in-house script, and tract-based spatial statistics assessed white matter differences in high versus low BMI values, VAT, SAT, insulin resistance, systemic inflammation, and Centiloids, with age and sex as covariates.

RESULTS

Obesity, high VAT, and high SAT were linked to lower axial diffusivity, reduced fiber fraction, and increased restricted fraction in white matter. Obesity was additionally associated with higher hindered fraction and lower fractional anisotropy. Also, individuals with high C-reactive protein showed lower axial diffusivity. Higher restricted fraction correlated with continuous BMI and SAT particularly in male individuals, whereas VAT effects were similar in male and female individuals.

CONCLUSIONS

The findings suggest that, at midlife, obesity and abdominal fat are associated with reduced brain axonal density and increased inflammation, with visceral fat playing a significant role in both sexes.

Linking metabolic syndrome, cerebral small vessel disease, and cognitive health: insights from a subclinical population study using TriNetX

Metabolic syndrome (MetS) has been linked to accelerated cognitive decline and Alzheimer's disease and related dementias (ADRDs) via cerebral small vessel disease (CSVD); however, this relation in MetS without overt cardiometabolic disease comorbidities is unknown and may represent a population amenable to preventative strategies. Our study aimed to determine risk profiles for neurocognitive decline and ADRDs in early-stage MetS with evidence of CSVD using the TriNetX electronic health records (EHR) research network. Patients aged 50 to 80 years old meeting MetS criteria were identified utilizing TriNetX data from 76 healthcare organizations. Propensity score matching controlled for demographic and confounding factors. Cohorts included MetS-only, non-MetS, and a MetS subset with evidence of CSVD (MetS-CSVD) created by clustering relevant ICD-codes for diagnoses, imaging, and lab work. Contingency analyses determined odds of developing neurocognitive decline, ADRDs, and CSVD in MetS vs non-MetS and MetS-CSVD vs. MetS-only, using odd ratios with 95% confidence intervals (p-value < 0.05). After propensity score matching, there were 57,347 men and 52,259 women in each of the MetS and non-MetS cohorts and 2,810 men and 2,862 women in each of the MetS-CSVD and MetS-only cohorts. Compared to non-MetS, the MetS cohort exhibited higher odds of developing neurocognitive decline (men: RR = 1.82, p < 0.001; women: RR = 1.34, p = 0.015) and CSVD (men: RR = 2.83, p < 0.001; women: RR = 2.14, p < 0.001), but only women exhibited significantly higher odds of developing ADRDs (men: RR = 1.13, p = 0.38; women: RR = 1.52, p < 0.001). Compared to MetS-only, the MetS-CSVD showed elevated odds in developing neurocognitive decline (men: RR = 1.81, p = 0.040; women: RR = 1.87, p = 0.018) and ADRDs (men: RR = 2.39, p = 0.009; women: RR = 1.65, p = 0.041). A large, predominantly US, sample of subclinical MetS demonstrated heightened odds for developing neurocognitive decline and ADRDs, with even higher odds when evidence of CSVD was also present. TriNetX facilitated a robust exploration of these associations, and our findings warrant further investigation of interventions that target this subclinical at-risk population.

Insulin resistance and white matter microstructural abnormalities in nondiabetic adult: A population-based study

BACKGROUND

Insulin resistance (IR) is of growing concern yet its association with white matter integrity remains controversial. We aimed to investigate the association between IR and white matter integrity in nondiabetic adults.

METHODS

This cross-sectional analysis was conducted based on the PolyvasculaR Evaluation for Cognitive Impairment and vaScular Events (PRECISE) study. A total of 1709 nondiabetic community-dwelling adults with available diffusion-weighted imaging based on brain magnetic resonance imaging and completed oral glucose tolerance test were included. IR was measured noninvasively by insulin sensitivity indices (ISI), including ISIcomposite and ISI0,120, as well as homeostasis model assessment of insulin resistance (HOMA-IR). White matter microstructure abnormalities were identified by diffusion-weighted imaging along with tract-based spatial statistical analysis to compare diffusion metrics between groups. The multivariable linear regression models were applied to measure the association between white matter microstructure abnormalities and IR.

RESULTS

A total of 1709 nondiabetic individuals with a mean age of 60.8 ± 6.4 years and 54.1% female were included. We found that IR was associated with a significant increase in mean diffusivity, axial diffusivity, and radial diffusivity extensively in cerebral white matter in regions such as the anterior corona radiata, superior corona radiata, anterior limb of internal capsule, external capsule, and body of corpus callosum. The pattern of associations was more marked for ISIcomposite and ISI0,120. However, the effect of IR on white matter integrity was attenuated after, in addition, adjustment for history of hypertension and cardiovascular disease and antihypertensive medication use.

CONCLUSION

Our findings indicate a significant association between IR and white matter microstructural abnormalities in nondiabetic middle-aged community residents, while these associations were greatly influenced by the history of hypertension and cardiovascular disease, and antihypertensive medication use. Further investigation is needed to clarify the role of IR in white matter integrity, whereas prophylactic strategies of maintaining a low IR status may ameliorate disturbances in white matter integrity.

DATA ACCESSIBILITY STATEMENT

The data that support the findings of this study are available from the corresponding authors upon reasonable request.

Associations of metabolic syndrome with cognitive function and dementia risk: Evidence from the UK Biobank cohort

AIM

To investigate the associations of metabolic syndrome (MetS) with cognitive function, dementia and its subtypes.

METHODS

Based on the participants recruited by UK Biobank, this study aims to investigate the associations of MetS with cognitive function, dementia and its subtypes. Generalized estimating equations, Cox proportional risk models, and multiple linear regression models were respectively used to assess associations between MetS and dementia-related outcomes.

RESULTS

Among the 363,231 participants, 95,713 had MetS at baseline. The results showed that MetS was significantly associated with cognitive function related to fluid intelligence and prospective memory at follow-up. Among participants aged ≥60 years, MetS was correlated with elevated risk of all-cause dementia, particularly vascular dementia (VaD) [hazard ratio 1.115 (95% confidence interval: 1.047, 1.187), hazard ratio 1.393 (95% confidence interval: 1.233, 1.575), respectively]. With increasing MetS components, the risk of all-cause dementia and VaD tended to be elevated. MetS has also been associated with dementia-related structural changes in the brain, including alterations in overall brain volume, white matter volume, grey matter volume and white matter integrity.

CONCLUSION

MetS was associated with poorer cognitive performance and might increase the risk of all-cause dementia as well as VaD, but the effect on Alzheimer's disease was not significant. Holistic control of the MetS may benefit the prevention and control of cognitive impairment and dementia.

Cerebral white matter myelination is associated with longitudinal changes in processing speed across the adult lifespan

Myelin's role in processing speed is pivotal, as it facilitates efficient neural conduction. Its decline could significantly affect cognitive efficiency during ageing. In this work, myelin content was quantified using our advanced MRI method of myelin water fraction mapping. We examined the relationship between myelin water fraction at the time of MRI and retrospective longitudinal change in processing speed among 121 cognitively unimpaired participants, aged 22-94 years, from the Baltimore Longitudinal Study of Aging and the Genetic and Epigenetic Signatures of Translational Aging Laboratory Testing (a mean follow-up duration of 4.3 ± 6.3 years) using linear mixed-effects models, adjusting for demographics. We found that higher myelin water fraction values correlated with longitudinally better-maintained processing speed, with particularly significant associations in several white matter regions. Detailed voxel-wise analysis provided further insight into the specific white matter tracts involved. This research underscores the essential role of myelin in preserving processing speed and highlights its potential as a sensitive biomarker for interventions targeting age-related cognitive decline, thereby offering a foundation for preventative strategies in neurological health.

Targeting leptin/CCL3-CCL4 axes in NAFLD/MAFLD: A novel role for BPF in counteracting thalamic inflammation and white matter degeneration

Non-alcoholic fatty liver disease (NAFLD), redefined as Metabolic Associated Fatty Liver Disease (MAFLD), is characterized by an extensive multi-organ involvement. MAFLD-induced systemic inflammatory status and peripheral metabolic alteration lead to an impairment of cerebral function. Herein, we investigated a panel of leptin-related inflammatory mediators as predictive biomarkers of neuroinflammation and evaluated the possible role of Bergamot Polyphenolic Fraction (BPF) in counteracting this MAFLD-induced inflammatory cascade. Male DIAMOND mice were randomly assigned to fed chow diet and tap water or high fat diet with sugar water. Starting from week 16, mice were further divided and treated with vehicle or BPF (50 mg/kg/day), via gavage, until week 30. Magnetic resonance imaging was performed at the baseline and at week 30. Correlation and regression analyses were performed to discriminate the altered lipid metabolism in the onset of cerebral alterations. Steatohepatitis led to an increase in leptin levels, resulting in a higher expression of proinflammatory mediators. The inflammatory biomarkers involved in leptin/CCL3-CCL4 axes were correlated with the altered thalamus energetic metabolism and the white matter degeneration. BPF administration restored leptin level, improved glucose and lipid metabolism, and reduced chronic low-grade inflammatory mediators, resulting in a prevention of white matter degeneration, alterations of thalamus metabolism and brain atrophy. The highlighted positive effect of BPF, mediated by the downregulation of the inflammatory biomarkers involved in leptin/CCL3-CCL4 axes, affording novel elements to candidate BPF for the development of a therapeutic strategy aimed at counteracting MAFLD-related brain inflammation.

Structural Brain Alterations in Metabolic Syndrome: A Comprehensive MRI Volumetric Analysis of Subcortical and Associated Structures

Objective: This study aims to elucidate the comprehensive effects of metabolic syndrome (MetS) on the structural integrity of subcortical brain regions and associated structures through high-resolution magnetic resonance imaging (MRI) volumetric analysis, thereby contributing to a deeper understanding of the neuroanatomical dimensions of MetS and its potential implications for cognitive functions and overall brain health. Methods: A cross-sectional design was implemented, involving 25 individuals diagnosed with MetS for at least one year and a healthy control group of 15 individuals at a tertiary hospital's family medicine clinic in Eastern Turkey. Participants underwent a high-resolution MRI scan using a 1.5T Siemens Aera scanner. The MRICloud platform was employed for comprehensive segmentation and quantitative analysis of various brain structures. Results: The study revealed significant volumetric reductions in all measured subcortical brain regions among individuals with MetS compared to the control group (all P < 0.05). Notable differences were observed in key structures such as the substantia nigra, corpus callosum, and thalamus. In subcortical structures, the largest volumetric differences were noted in the basal ganglia L (1322.4 mm³), while the most significant percentage differences were seen in the substantia nigra R (25.24%) and caudate nucleus L (21.02%). Conclusion: The findings from this study underscore the significant neuroanatomical changes associated with MetS, manifesting as volumetric reductions in critical subcortical brain areas. These alterations underscore the necessity for further research into the comprehensive influence of MetS on cognitive processes and the potential for early therapeutic interventions.

Association between metabolic syndrome and white matter integrity in young and mid-age post-9/11 adult Veterans

Metabolic syndrome has been associated with reduced brain white matter integrity in older individuals. However, less is known about how metabolic syndrome might impact white matter integrity in younger populations. This study examined metabolic syndrome-related global and regional white matter integrity differences in a sample of 537 post-9/11 Veterans. Metabolic syndrome was defined as ≥3 factors of: increased waist circumference, hypertriglyceridemia, low high-density lipoprotein cholesterol, hypertension, and high fasting glucose. T1 and diffusion weighted 3 T MRI scans were processed using the FreeSurfer image analysis suite and FSL Diffusion Toolbox. Atlas-based regions of interest were determined from a combination of the Johns Hopkins University atlas and a Tract-Based Spatial Statistics-based FreeSurfer WMPARC white matter skeleton atlas. Analyses revealed individuals with metabolic syndrome (n = 132) had significantly lower global fractional anisotropy than those without metabolic syndrome (n = 405), and lower high-density lipoprotein cholesterol levels was the only metabolic syndrome factor significantly related to lower global fractional anisotropy levels. Lobe-specific analyses revealed individuals with metabolic syndrome had decreased fractional anisotropy in frontal white matter regions compared with those without metabolic syndrome. These findings indicate metabolic syndrome is prevalent in this sample of younger Veterans and is related to reduced frontal white matter integrity. Early intervention for metabolic syndrome may help alleviate adverse metabolic syndrome-related brain and cognitive effects with age.

Pathophysiological relationships between cognitive deficit in bipolar affective disorder and metabolic syndrome

INTRODUCTION AND OBJECTIVES

Bipolar disorder (BD) has been related to various cognitive dysfunctions as well as to a high prevalence of metabolic syndrome (MS), which seems to influence the cognitive performance of patients with BD. Therefore, different hypotheses have been generated to try to explain the pathophysiological relationship between cognitive deficit in BD and MS. The objective was to review the current literature regarding the possible pathophysiological explanation of the relationship between BD and MS and its effect on cognitive performance of patients with BD.

METHODS

A bibliographic search was carried out using MEDLINE, ClinicalKey, EMBASE, Literatura Latino-Americana y del Caribe en Ciencias de la Salud [Latin American and Caribbean Literature in Health Sciences] (LILACS), APA PsycNet, Scopus and Scielo databases, and the Pan-American Medical Electronic Library; using the following search terms: "bipolar disorder"[MeSH Terms] OR "bipolar disorder"[All Fields] OR "mood disorders"[All Fields] AND "cognitive deficit"[MeSH Terms] OR "cognitive deficit"[All Fields] OR "cognitive dysfunction"[All Fields] OR "cognitive impairment"[All Fields] OR "cognitive decline"[All Fields] AND "metabolic syndrome" [MeSH Terms] OR "metabolic abnormalities"[All Fields] OR "metabolic effects"[All Fields] OR "obesity" [All Fields] OR "abdominal obesity" [All Fields] OR "overweight" [All Fields] OR "diabetes" [All Fields] OR "hypertension" [All Fields] AND "antipsychotics" [MeSH Terms] OR "antipsychotics"[All Fields] AND "antidepressants" [MeSH Terms] OR "antidepressants"[All Fields] AND "mood stabilizers" [MeSH Terms] OR "mood stabilizers"[All Fields]. Filters: free full text, full text, from 2001 to 2022. A total of 80 articles in Spanish and English, of any type of design, were selected. Selection and reading were carried out by all the authors.

RESULTS AND CONCLUSIONS

The various pathophysiological hypotheses proposed, inflammatory, endocrine, drug, environmental and social, suggest that a series of changes at the macro and microcellular level are correlated in patients with BD and MS with a negative effect on cognition of patients both globally and in specific domains, mainly executive function, memory, attention, and perceptual motor skills. Research processes should be continued to explore the various hypotheses that support the relationship between BD, MS and cognition.

Bridging metabolic syndrome and cognitive dysfunction: role of astrocytes

Metabolic syndrome (MetS) and cognitive dysfunction pose significant challenges to global health and the economy. Systemic inflammation, endocrine disruption, and autoregulatory impairment drive neurodegeneration and microcirculatory damage in MetS. Due to their unique anatomy and function, astrocytes sense and integrate multiple metabolic signals, including peripheral endocrine hormones and nutrients. Astrocytes and synapses engage in a complex dialogue of energetic and immunological interactions. Astrocytes act as a bridge between MetS and cognitive dysfunction, undergoing diverse activation in response to metabolic dysfunction. This article summarizes the alterations in astrocyte phenotypic characteristics across multiple pathological factors in MetS. It also discusses the clinical value of astrocytes as a critical pathologic diagnostic marker and potential therapeutic target for MetS-associated cognitive dysfunction.

Dissecting unique and common variance across body and brain health indicators using age prediction

Ageing is a heterogeneous multisystem process involving different rates of decline in physiological integrity across biological systems. The current study dissects the unique and common variance across body and brain health indicators and parses inter-individual heterogeneity in the multisystem ageing process. Using machine-learning regression models on the UK Biobank data set (N = 32,593, age range 44.6-82.3, mean age 64.1 years), we first estimated tissue-specific brain age for white and gray matter based on diffusion and T1-weighted magnetic resonance imaging (MRI) data, respectively. Next, bodily health traits, including cardiometabolic, anthropometric, and body composition measures of adipose and muscle tissue from bioimpedance and body MRI, were combined to predict 'body age'. The results showed that the body age model demonstrated comparable age prediction accuracy to models trained solely on brain MRI data. The correlation between body age and brain age predictions was 0.62 for the T1 and 0.64 for the diffusion-based model, indicating a degree of unique variance in brain and bodily ageing processes. Bayesian multilevel modelling carried out to quantify the associations between health traits and predicted age discrepancies showed that higher systolic blood pressure and higher muscle-fat infiltration were related to older-appearing body age compared to brain age. Conversely, higher hand-grip strength and muscle volume were related to a younger-appearing body age. Our findings corroborate the common notion of a close connection between somatic and brain health. However, they also suggest that health traits may differentially influence age predictions beyond what is captured by the brain imaging data, potentially contributing to heterogeneous ageing rates across biological systems and individuals.

Interactions between overweight/obesity and alcohol dependence impact human brain white matter microstructure: evidence from DTI

There is inconsistent evidence for an association of obesity with white matter microstructural alterations. Such inconsistent findings may be related to the cumulative effects of obesity and alcohol dependence. This study aimed to investigate the possible interactions between alcohol dependence and overweight/obesity on white matter microstructure in the human brain. A total of 60 inpatients with alcohol dependence during early abstinence (44 normal weight and 16 overweight/obese) and 65 controls (42 normal weight and 23 overweight/obese) were included. The diffusion tensor imaging (DTI) measures [fractional anisotropy (FA) and radial diffusivity (RD)] of the white matter microstructure were compared between groups. We observed significant interactive effects between alcohol dependence and overweight/obesity on DTI measures in several tracts. The DTI measures were not significantly different between the overweight/obese and normal-weight groups (although widespread trends of increased FA and decreased RD were observed) among controls. However, among the alcohol-dependent patients, the overweight/obese group had widespread reductions in FA and widespread increases in RD, most of which significantly differed from the normal-weight group; among those with overweight/obesity, the alcohol-dependent group had widespread reductions in FA and widespread increases in RD, most of which were significantly different from the control group. This study found significant interactive effects between overweight/obesity and alcohol dependence on white matter microstructure, indicating that these two controllable factors may synergistically impact white matter microstructure and disrupt structural connectivity in the human brain.

Correlates of axonal content in healthy adult span: Age, sex, myelin, and metabolic health

As the emerging treatments that target grey matter pathology in Alzheimer's Disease have limited effectiveness, there is a critical need to identify new neural targets for treatments. White matter's (WM) metabolic vulnerability makes it a promising candidate for new interventions. This study examined the age and sex differences in estimates of axonal content, as well the associations of with highly prevalent modifiable health risk factors such as metabolic syndrome and adiposity. We estimated intra-axonal volume fraction (ICVF) using the Neurite Orientation Dispersion and Density Imaging (NODDI) in a sample of 89 cognitively and neurologically healthy adults (20-79 years). We showed that ICVF correlated positively with age and estimates of myelin content. The ICVF was also lower in women than men, across all ages, which difference was accounted for by intracranial volume. Finally, we found no association of metabolic risk or adiposity scores with the current estimates of ICVF. In addition, the previously observed adiposity-myelin associations (Burzynska et al., 2023) were independent of ICVF. Although our findings confirm the vulnerability of axons to aging, they suggest that metabolic dysfunction may selectively affect myelin content, at least in cognitively and neurologically healthy adults with low metabolic risk, and when using the specific MRI techniques. Future studies need to revisit our findings using larger samples and different MRI approaches, and identify modifiable factors that accelerate axonal deterioration as well as mechanisms linking peripheral metabolism with the health of myelin.

Interaction Between a High-Fat Diet and Tau Pathology in Mice: Implications for Alzheimer's Disease

BACKGROUND

Obesity is a modifiable risk factor for Alzheimer's disease (AD). However, its relation with tau pathology (i.e., aberrant tau protein behavior in tauopathies such as AD) has been inconclusive.

OBJECTIVE

This study investigated the interaction between a high-fat diet (HFD) and tau pathology in adult male mice.

METHODS

Transgenic mice overexpressing human P301S Tau (those with the pathology) and wild-type (WT) littermates were subjected to behavioral tests, functional magnetic resonance imaging (fMRI), diffusion tensor imaging (DTI), and western blotting analysis to investigate the effects of prolonged HFD versus regular diet during adulthood.

RESULTS

HFD increased body weight in both WT and P301S mice but had minimal effect on blood glucose levels. The brain response to HFD was tau genotype-specific. WT mice exhibited decreased recognition memory and enhanced network connectivity in fMRI, while P301S mice exhibited white matter tract disorganization in DTI as the sole significant finding. The reduction of insulin receptor β, insulin downstream signaling, neuronal nuclear protein, CD68-positive phagocytic activity, and myelin basic protein level were confined to the cortex of WT mice. In contrast to P301S mice, WT mice showed significant changes in the tau protein and its phosphorylation levels along with increased soluble neurofilament light levels in the hippocampus.

CONCLUSIONS

HFD-induced brain dysfunction and pathological changes were blunted in mice with the pathology and more profound in healthy mice. Our findings highlight the need to consider this interaction between obesity and tau pathology when tailoring treatment strategies for AD and other tauopathies.

A latent clinical-anatomical dimension relating metabolic syndrome to brain structure and cognition

The link between metabolic syndrome (MetS) and neurodegenerative as well cerebrovascular conditions holds substantial implications for brain health in at-risk populations. This study elucidates the complex relationship between MetS and brain health by conducting a comprehensive examination of cardiometabolic risk factors, cortical morphology, and cognitive function in 40,087 individuals. Multivariate, data-driven statistics identified a latent dimension linking more severe MetS to widespread brain morphological abnormalities, accounting for up to 71% of shared variance in the data. This dimension was replicable across sub-samples. In a mediation analysis we could demonstrate that MetS-related brain morphological abnormalities mediated the link between MetS severity and cognitive performance in multiple domains. Employing imaging transcriptomics and connectomics, our results also suggest that MetS-related morphological abnormalities are linked to the regional cellular composition and macroscopic brain network organization. By leveraging extensive, multi-domain data combined with a dimensional stratification approach, our analysis provides profound insights into the association of MetS and brain health. These findings can inform effective therapeutic and risk mitigation strategies aimed at maintaining brain integrity.

Metabolic syndrome and cognitive deficits in the Greek cohort of Epirus Health Study

BACKGROUND

Metabolic syndrome is considered an important risk factor for cognitive decline and dementia. However, the evidence in middle-aged individuals is still conflicting. The aim of the study was to explore the association between metabolic syndrome and its individual components with cognitive function and to investigate possible interaction between sex, age and genetic predisposition for metabolic syndrome and Alzheimer's disease in a middle-aged Greek cohort.

METHODS

A total of 2,077 healthy adults (mean age: 46.7 years) were included in the primary cross-sectional analysis and 305 of them in secondary prospective analyses. Metabolic syndrome was defined by the revised National Cholesterol Education-Adult Treatment Panel III and the International Diabetes Federation criteria. Cognitive function was measured primarily with the Trail Making, Verbal fluency and Logical Memory test, and in secondary prospective analyses with online versions of Posner cueing task, an emotional recognition task, Corsi block-tapping task and Stroop task.

RESULTS

Multivariable linear regressions showed an association of metabolic syndrome with lower performance in attention (β=1.62 seconds, 95% CI=0.20, 3.04) and memory (β=-0.62 words, 95% CI=-1.19, -0.05) that could be driven by associations with elevated fasting glucose and abdominal obesity. Similar associations were observed in the secondary prospective analyses.

CONCLUSION

In summary, metabolic syndrome was associated with cognitive deficits in domains related with the cognitive profile of vascular cognitive impairment.

Brain response in asthma: the role of "lung-brain" axis mediated by neuroimmune crosstalk

In addition to typical respiratory symptoms, patients with asthma are frequently accompanied by cognitive decline, mood disorders (anxiety and depression), sleep disorders, olfactory disorders, and other brain response manifestations, all of which worsen asthma symptoms, form a vicious cycle, and exacerbate the burden on families and society. Therefore, studying the mechanism of neurological symptoms in patients with asthma is necessary to identify the appropriate preventative and therapeutic measures. In order to provide a comprehensive reference for related research, we compiled the pertinent literature, systematically summarized the latest research progress of asthma and its brain response, and attempted to reveal the possible "lung-brain" crosstalk mechanism and treatment methods at the onset of asthma, which will promote more related research to provide asthmatic patients with neurological symptoms new hope.

Metabolic syndrome and adiposity: Risk factors for decreased myelin in cognitively healthy adults

Metabolic syndrome (MetS) is a cluster of conditions that affects ∼25% of the global population, including excess adiposity, hyperglycemia, dyslipidemia, and elevated blood pressure. MetS is one of major risk factors not only for chronic diseases, but also for dementia and cognitive dysfunction, although the underlying mechanisms remain poorly understood. White matter is of particular interest in the context of MetS due to the metabolic vulnerability of myelin maintenance, and the accumulating evidence for the importance of the white matter in the pathophysiology of dementia. Therefore, we investigated the associations of MetS risk score and adiposity (combined body mass index and waist circumference) with myelin water fraction measured with myelin water imaging. In 90 cognitively and neurologically healthy adults (20-79 years), we found that both high MetS risk score and adiposity were correlated with lower myelin water fraction in late-myelinating prefrontal and associative fibers, controlling for age, sex, race, ethnicity, education and income. Our findings call for randomized clinical trials to establish causality between MetS, adiposity, and myelin content, and to explore the potential of weight loss and visceral adiposity reduction as means to support maintenance of myelin integrity throughout adulthood, which could open new avenues for prevention or treatment of cognitive decline and dementia.

Neuroprotection in metabolic syndrome by environmental enrichment. A lifespan perspective

Metabolic syndrome (MetS) is defined by the concurrence of different metabolic conditions: obesity, hypertension, dyslipidemia, and hyperglycemia. Its incidence has been increasingly rising over the past decades and has become a global health problem. MetS has deleterious consequences on the central nervous system (CNS) and neurological development. MetS can last several years or be lifelong, affecting the CNS in different ways and treatments can help manage condition, though there is no known cure. The early childhood years are extremely important in neurodevelopment, which extends beyond, encompassing a lifetime. Neuroplastic changes take place all life through - childhood, adolescence, adulthood, and old age - are highly sensitive to environmental input. Environmental factors have an important role in the etiopathogenesis and treatment of MetS, so environmental enrichment (EE) stands as a promising non-invasive therapeutic approach. While the EE paradigm has been designed for animal housing, its principles can be and actually are applied in cognitive, sensory, social, and physical stimulation programs for humans. Here, we briefly review the central milestones in neurodevelopment at each life stage, along with the research studies carried out on how MetS affects neurodevelopment at each life stage and the contributions that EE models can provide to improve health over the lifespan.

Paediatric obesity and metabolic syndrome associations with cognition and the brain in youth: Current evidence and future directions

Obesity and components of the metabolic syndrome (MetS) are associated with differences in brain structure and function and in general and food-related cognition in adults. Here, we review evidence for similar phenomena in children and adolescents, with a focus on the implications of extant research for possible underlying mechanisms and potential interventions for obesity and MetS in youth. Current evidence is limited by a relative reliance on small cross-sectional studies. However, we find that youth with obesity and MetS or MetS components show differences in brain structure, including alterations in grey matter volume and cortical thickness across brain regions subserving reward, cognitive control and other functions, as well as in white matter integrity and volume. Children with obesity and MetS components also show some evidence for hyperresponsivity of food reward regions and hyporesponsivity of cognitive control circuits during food-related tasks, altered brain responses to food tastes, and altered resting-state connectivity including between cognitive control and reward processing networks. Potential mechanisms for these findings include neuroinflammation, impaired vascular reactivity, and effects of diet and obesity on myelination and dopamine function. Future observational research using longitudinal measures, improved sampling strategies and study designs, and rigorous statistical methods, promises to further illuminate dynamic relationships and causal mechanisms. Intervention studies targeted at modifiable biological and behavioural factors associated with paediatric obesity and MetS can further inform mechanisms, as well as test whether brain and behaviour can be altered for beneficial outcomes.

The association between regional adiposity, cognitive function, and dementia-related brain changes: a systematic review

Background

Adiposity has been previously associated with cognitive impairment and Alzheimer's disease and related disorders (ADRD). Body mass index (BMI) is the most common measure of global adiposity, but inconsistent results were found since it is a global measurement. BMI does not represent regional fat distribution which differs between sexes, race, and age. Regional fat distribution may contribute differently to cognitive decline and Alzheimer's disease (AD)-related brain changes. Fat-specific targeted therapies could lead to personalized improvement of cognition. The goal of this systematic review is to explore whether regional fat depots, rather than central obesity, should be used to understand the mechanism underlying the association between adiposity and brain.

Methods

This systematic review included 33 studies in the English language, conducted in humans aged 18 years and over with assessment of regional adiposity, cognitive function, dementia, and brain measures. We included only studies that have assessed regional adiposity using imaging technics and excluded studies that were review articles, abstract only or letters to editor. Studies on children and adolescents, animal studies, and studies of patients with gastrointestinal diseases were excluded. PubMed, PsychInfo and web of science were used as electronic databases for literature search until November 2022.

Results

Based on the currently available literature, the findings suggest that different regional fat depots are likely associated with increased risk of cognitive impairment, brain changes and dementia, especially AD. However, different regional fat depots can have different cognitive outcomes and affect the brain differently. Visceral adipose tissue (VAT) was the most studied regional fat, along with liver fat through non-alcoholic fatty liver disease (NAFLD). Pancreatic fat was the least studied regional fat.

Conclusion

Regional adiposity, which is modifiable, may explain discrepancies in associations of global adiposity, brain, and cognition. Specific regional fat depots lead to abnormal secretion of adipose factors which in turn may penetrate the blood brain barrier leading to brain damage and to cognitive decline.

Sex-specific relationships between obesity, physical activity, and gray and white matter volume in cognitively unimpaired older adults

Independently, obesity and physical activity (PA) influence cerebral structure in aging, yet their interaction has not been investigated. We examined sex differences in the relationships among PA, obesity, and cerebral structure in aging with 340 participants who completed magnetic resonance imaging (MRI) acquisition to quantify grey matter volume (GMV) and white matter volume (WMV). Height and weight were measured to calculate body mass index (BMI). A PA questionnaire was used to estimate weekly Metabolic Equivalents. The relationships between BMI, PA, and their interaction on GMV Regions of Interest (ROIs) and WMV ROIs were examined. Increased BMI was associated with higher GMV in females, an inverse U relationship was found between PA and GMV in females, and the interaction indicated that regardless of BMI greater PA was associated with enhanced GMV. Males demonstrated an inverse U shape between BMI and GMV, and in males with high PA and had normal weight demonstrated greater GMV than normal weight low PA revealed by the interaction. WMV ROIs had a linear relationship with moderate PA in females, whereas in males, increased BMI was associated with lower WMV as well as a positive relationship with moderate PA and WMV. Males and females have unique relationships among GMV, PA and BMI, suggesting sex-aggregated analyses may lead to biased or non-significant results. These results suggest higher BMI, and PA are associated with increased GMV in females, uniquely different from males, highlighting the importance of sex-disaggregated models. Future work should include other imaging parameters, such as perfusion, to identify if these differences co-occur in the same regions as GMV.

Prenatal alcohol exposure causes persistent microglial activation and age- and sex- specific effects on cognition and metabolic outcomes in an Alzheimer's Disease mouse model

Background: Prenatal alcohol exposure (PAE) causes behavioral deficits and increases risk of metabolic diseases. Alzheimer's Disease (AD) is a neurodegenerative disease that has a higher risk in adults with metabolic diseases. Both present with persistent neuroinflammation.Objectives: We tested whether PAE exacerbates AD-related cognitive decline in a mouse model (3xTg-AD; presenilin/amyloid precursor protein/tau), and assessed associations among cognition, metabolic impairment, and microglial reactivity.Methods: Alcohol-exposed (ALC) pregnant 3xTg-AD mice received 3 g/kg alcohol from embryonic day 8.5-17.5. We evaluated recognition memory and associative memory (fear conditioning) in 8-10 males and females per group at 3 months of age (3mo), 7mo, and 11mo, then assessed glucose tolerance, body composition, and hippocampal microglial activation at 12mo.Results: ALC females had higher body weights than controls from 5mo (p < .0001). Controls showed improved recognition memory at 11mo compared with 3mo (p = .007); this was not seen in ALC mice. Older animals froze more during fear conditioning than younger, and ALC mice were hyper-responsive to the fear-related cue (p = .017). Fasting blood glucose was lower in ALC males and higher in ALC females than controls. Positive associations occurred between glucose and fear-related context (p = .04) and adiposity and fear-related cue (p = .0002) in ALC animals. Hippocampal microglial activation was higher in ALC than controls (p < .0001); this trended to correlate with recognition memory.Conclusions: ALC animals showed age-related cognitive impairments that did not interact with AD risk but did correlate with metabolic dysfunction and somewhat with microglial activation. Thus, metabolic disorders may be a therapeutic target for people with FASDs.

Asthma, the central nervous system, and neurocognition: Current findings, potential mechanisms, and treatment implications

Accumulating behavioral evidence suggests that asthma is associated with cognitive deficits. A number of studies have identified potential biological contributions to cognition in asthma; however, mechanistic pathways of central nervous system (CNS) involvement in asthma are yet to be established. We therefore conducted a literature review to identify studies examining potential CNS contributions to cognition in asthma. In this review, we discuss our general understanding of the CNS in asthma in the context of cognitive performance and outline a working model of mechanistic pathways linking the proposed neural influences of asthma pathology with cognition. To this extent, we incorporate neural, behavioral, psychological, social and environmental factors. Finally, we underscore the clinical significance of the CNS and neurocognitive sequelae in asthma, highlighting potential opportunities for routine monitoring, therapeutic intervention, and recommend key areas for future research.

Neuroimaging findings related to glymphatic system alterations in older adults with metabolic syndrome

OBJECTIVE

The glymphatic system is a glial-based perivascular network that promotes brain metabolic waste clearance. Reduced glymphatic flow has been observed in rat models of type 2 diabetes and hypertension, indicating the role of vascular risk factors in the glymphatic system. However, little is known about how vascular risk factors affect the human glymphatic system. The present study aims to assess the relationships between metabolic syndrome (MetS), a cluster of vascular risk factors, and the glymphatic system function using diffusion magnetic resonance imaging (MRI)-based measures of water diffusivity in the glymphatic compartments, including the brain interstitial space and perivascular spaces around the deep medullary vein. We hypothesized that vascular risk factors are associated with glymphatic dysfunction, leading to cognitive impairment in older adults.

METHODS

This cross-sectional study assessed 61 older adults (age range, 65-82 years) who had participated in the Bunkyo Health Study, including 15 healthy controls (mean age, 70.87 ± 4.90 years) and 46 individuals with MetS (mean age, 71.76 ± 4.61 years). Fractional volume of extracellular-free water (FW) and an index of diffusion tensor imaging along the perivascular space (DTI-ALPS) were used as indirect indicators of water diffusivity in the interstitial extracellular and perivenous spaces of white matter, respectively.

RESULTS

After adjusting for age, sex, years of education, total Fazekas scale, Pittsburgh sleep quality index (PSQI) score, and intracranial volume (ICV), a significantly (P = 0.030; Cohen's d = 1.01) higher FW was observed in individuals with MetS than in the healthy controls. Furthermore, individuals with MetS had a significantly (P = 0.031; Cohen's d = 0.86) lower ALPS index than the healthy controls, with age, sex, years of education, total Fazekas scale, PSQI score, ICV, fractional anisotropy, and mean diffusivity included as confounding factors. Higher FW was significantly associated with lower ALPS index (r = -0.37; P = 0.004). Multiple linear regression (MLR) with backward elimination analyses showed that higher diastolic blood pressure (BP; standardized β = 0.33, P = 0.005) was independently associated with higher FW, whereas higher fasting plasma glucose levels (standardized β = -0.63, P = 0.002) or higher Brinkman index of cigarette consumption cumulative amount (standardized β = -0.27, P = 0.022) were associated with lower ALPS index. The lower ALPS index (standardized β, 0.28; P = 0.040) was associated with poorer global cognitive performance, which was determined using the Japanese version of the Montreal Cognitive Assessment (MOCA-J) scores. Finally, partial correlation analyses showed a significant correlation between higher FW and lower MOCA-J scores (r = -0.35; P = 0.025) and between higher FW and higher diastolic BP (r = 0.32, P = 0.044).

CONCLUSION

The present study shows the changes in diffusion MRI-based measures reflected by the higher FW and lower ALPS index in older adults with MetS, possibly due to the adverse effect of vascular risk factors on the glymphatic system. Our findings also indicate the associations between the diffusion MRI-based measures and elevated diastolic BP, hyperglycemia, smoking habit, and poorer cognitive performance. However, owing to the limitations of this study, the results should be cautiously interpreted.

Insulin Resistance and Cognitive Impairment: Evidence From Neuroimaging

Insulin is a peptide well known for its role in regulating glucose metabolism in peripheral tissues. Emerging evidence from human and animal studies indicate the multifactorial role of insulin in the brain, such as neuronal and glial metabolism, glucose regulation, and cognitive processes. Insulin resistance (IR), defined as reduced sensitivity to the action of insulin, has been consistently proposed as an important risk factor for developing neurodegeneration and cognitive impairment. Although the exact mechanism of IR-related cognitive impairment still awaits further elucidation, neuroimaging offers a versatile set of novel contrasts to reveal the subtle cerebral abnormalities in IR. These imaging contrasts, including but not limited to brain volume, white matter (WM) microstructure, neural function and brain metabolism, are expected to unravel the nature of the link between IR, cognitive decline, and brain abnormalities, and their changes over time. This review summarizes the current neuroimaging studies with multiparametric techniques, focusing on the cerebral abnormalities related to IR and therapeutic effects of IR-targeting treatments. According to the results, brain regions associated with IR pathophysiology include the medial temporal lobe, hippocampus, prefrontal lobe, cingulate cortex, precuneus, occipital lobe, and the WM tracts across the globe. Of these, alterations in the temporal lobe are highly reproducible across different imaging modalities. These structures have been known to be vulnerable to Alzheimer's disease (AD) pathology and are critical in cognitive processes such as memory and executive functioning. Comparing to asymptomatic subjects, results are more mixed in patients with metabolic disorders such as type 2 diabetes and obesity, which might be attributed to a multifactorial mechanism. Taken together, neuroimaging, especially MRI, is beneficial to reveal early abnormalities in cerebral structure and function in insulin-resistant brain, providing important evidence to unravel the underlying neuronal substrate that reflects the cognitive decline in IR. EVIDENCE LEVEL: 5 TECHNICAL EFFICACY: Stage 2.

Metabolic syndrome and cognition: A systematic review across cognitive domains and a bibliometric analysis

The aim of this review is to investigate the association between metabolic syndrome (MetS) and cognitive decline in distinct cognitive domains, and to perform a complementary study description through the bibliometric analysis. PubMed and Scopus databases were searched from inception to 15 December 2021 to identify longitudinal studies that examined the association of MetS with incident decline, in order to prevent reverse causality. The Preferred Reporting Items for Systematic Review and Meta-Analysis checklist was used to conduct the present systematic review. Thirty studies were included and results were analyzed across the cognitive domains of global cognition, memory, executive functions, attention, visuoconstructive abilities, and language. The majority of the studies reviewed did not report statistically significant results for most cognitive domains investigated, and decline in specific cognitive domains was not consistently associated with the presence of MetS. Meta-analyses were not conducted due to the high degree of between-study heterogeneity regarding the MetS definitions, the cognitive domains examined, the specific tests used for each cognitive domain and the different measures of association used. Bibliometric analysis revealed that most studies are conducted by research teams from USA and China, and that cognitive tasks that reflect real-life abilities are rarely examined. Future studies should employ larger sample sizes, longer follow-up periods, a global consensus for MetS definition and standardized tests of the above mentioned cognitive domains as well as problem-solving tasks with high sensitivity and specificity to clarify the impact of MetS on cognition and its underlying mechanisms.

Sex- and age-specific associations between cardiometabolic risk and white matter brain age in the UK Biobank cohort

Cardiometabolic risk (CMR) factors are associated with accelerated brain aging and increased risk for sex-dimorphic illnesses such as Alzheimer's disease (AD). Yet, it is unknown how CMRs interact with sex and apolipoprotein E-ϵ4 (APOE4), a known genetic risk factor for AD, to influence brain age across different life stages. Using age prediction based on multi-shell diffusion-weighted imaging data in 21,308 UK Biobank participants, we investigated whether associations between white matter Brain Age Gap (BAG) and body mass index (BMI), waist-to-hip ratio (WHR), body fat percentage (BF%), and APOE4 status varied (i) between males and females, (ii) according to age at menopause in females, and (iii) across different age groups in males and females. We report sex differences in associations between BAG and all three CMRs, with stronger positive associations among males compared to females. Independent of APOE4 status, higher BAG (older brain age relative to chronological age) was associated with greater BMI, WHR, and BF% in males, whereas in females, higher BAG was associated with greater WHR, but not BMI and BF%. These divergent associations were most prominent within the oldest group of females (66-81 years), where greater BF% was linked to lower BAG. Earlier menopause transition was associated with higher BAG, but no interactions were found with CMRs. In conclusion, the findings point to sex- and age-specific associations between CMRs and brain age. Incorporating sex as a factor of interest in studies addressing CMR may promote sex-specific precision medicine, consequently improving health care for both males and females.

Overview of therapeutic targets in management of dementia

Dementia is defined as a gradual cognitive impairment that interferes with everyday tasks, and is a leading cause of dependency, disability, and mortality. According to the current scenario, millions of individuals worldwide have dementia. This review provides with an overview of dementia before moving on to its subtypes (neurodegenerative and non-neurodegenerative) and pathophysiology. It also discusses the incidence and severity of dementia, focusing on Alzheimer's disease with its different hypotheses such as Aβ cascade hypothesis, Tau hypothesis, inflammatory hypothesis, cholinergic and oxidative stress hypothesis. Alzheimer's disease is the most common type and a progressive neurodegenerative illness distinct by neuronal loss and resulting cognitive impairment, leading to dementia. Alzheimer's disease (AD) is considered the most familiar neurodegenerative dementias that affect mostly older population. There are still no disease-modifying therapies available for any dementias at this time, but there are various methods for lowering the risk to dementia patients by using suitable diagnostic and evaluation methods. Thereafter, the management and treatment of primary risk elements of dementia are reviewed. Finally, the future perspectives of dementia (AD) focusing on the impact of the new treatment are discussed.

Mechanisms linking obesity and its metabolic comorbidities with cerebral grey and white matter changes

Obesity is a preventable risk factor for cerebrovascular disorders and it is associated with cerebral grey and white matter changes. Specifically, individuals with obesity show diminished grey matter volume and thickness, which seems to be more prominent among fronto-temporal regions in the brain. At the same time, obesity is associated with lower microstructural white matter integrity, and it has been found to precede increases in white matter hyperintensity load. To date, however, it is unclear whether these findings can be attributed solely to obesity or whether they are a consequence of cardiometabolic complications that often co-exist with obesity, such as low-grade systemic inflammation, hypertension, insulin resistance, or dyslipidemia. In this narrative review we aim to provide a comprehensive overview of the potential impact of obesity and a number of its cardiometabolic consequences on brain integrity, both separately and in synergy with each other. We also identify current gaps in knowledge and outline recommendations for future research.

Impact of Weight Loss on Brain Age: Improved Brain Health Following Bariatric Surgery

Individuals living with obesity tend to have increased brain age, reflecting poorer brain health likely due to grey and white matter atrophy related to obesity. However, it is unclear if older brain age associated with obesity can be reversed following weight loss and cardiometabolic health improvement. The aim of this study was to assess the impact of weight loss and cardiometabolic improvement following bariatric surgery on brain health, as measured by change in brain age estimated based on voxel-based morphometry (VBM) measurements. We used three distinct datasets to perform this study: 1) CamCAN dataset to train the brain age prediction model, 2) Human Connectome Project (HCP) dataset to investigate whether individuals with obesity have greater brain age than individuals with normal weight, and 3) pre-surgery, as well as 4, 12, and 24 month post-surgery data from participants (n=87, age: 44.0±9.2 years, BMI: 43.9±4.2 kg/m2) who underwent a bariatric surgery to investigate whether weight loss and cardiometabolic improvement as a result of bariatric surgery lowers the brain age. As expected, our results from the HCP dataset showed a higher brain age for individuals with obesity compared to individuals with normal weight (T-value = 7.08, p-value < 0.0001). We also found significant improvement in brain health, indicated by a decrease of 2.9 and 5.6 years in adjusted delta age at 12 and 24 months following bariatric surgery compared to baseline (p-value < 0.0005 for both). While the overall effect seemed to be driven by a global change across all brain regions and not from a specific region, our exploratory analysis showed lower delta age in certain brain regions (mainly in somatomotor, visual, and ventral attention networks) at 24 months. This reduced age was also associated with post-surgery improvements in BMI, systolic/diastolic blood pressure, and HOMA-IR (T-value_BMI=4.29, T-value_SBP=4.67, T-value_DBP=4.12, T-value_HOMA-IR=3.16, all p-values < 0.05). In conclusion, these results suggest that obesity-related brain health abnormalities (as measured by delta age) might be reversed by bariatric surgery-induced weight loss and widespread improvements in cardiometabolic alterations.

White matter fiber-specific degeneration in older adults with metabolic syndrome

OBJECTIVE

Metabolic syndrome (MetS) is defined as a complex of interrelated risk factors for type 2 diabetes and cardiovascular disease, including glucose intolerance, abdominal obesity, hypertension, and dyslipidemia. Studies using diffusion tensor imaging (DTI) have reported white matter (WM) microstructural abnormalities in MetS. However, interpretation of DTI metrics is limited primarily due to the challenges of modeling complex WM structures. The present study used fixel-based analysis (FBA) to assess the effect of MetS on the fiber tract-specific WM microstructure in older adults and its relationship with MetS-related measurements and cognitive and locomotor functions to better understand the pathophysiology of MetS.

METHODS

Fixel-based metrics, including microstructural fiber density (FD), macrostructural fiber-bundle cross-section (FC), and a combination of FD and FC (FDC), were evaluated in 16 healthy controls (no components of MetS; four men; mean age, 71.31 ± 5.06 years), 57 individuals with premetabolic syndrome (preMetS; one or two components of MetS; 29 men; mean age, 72.44 ± 5.82 years), and 46 individuals with MetS (three to five components of MetS; 27 men; mean age, 72.15 ± 4.97 years) using whole-brain exploratory FBA. Tract of interest (TOI) analysis was then performed using TractSeg across 14 selected WM tracts previously associated with MetS. The associations between fixel-based metrics and MetS-related measurements, neuropsychological, and locomotor function tests were also analyzed in individuals with preMetS and MetS combined. In addition, tensor-based metrics (i.e., fractional anisotropy [FA] and mean diffusivity [MD]) were compared among the groups using tract-based spatial statistics (TBSS) analysis.

RESULTS

In whole-brain FBA, individuals with MetS showed significantly lower FD, FC, and FDC compared with healthy controls in WM areas, such as the splenium of the corpus callosum (CC), corticospinal tract (CST), middle cerebellar peduncle (MCP), and superior cerebellar peduncle (SCP). Meanwhile, in fixel-based TOI, significantly reduced FD was observed in individuals with preMetS and MetS in the anterior thalamic radiation, CST, SCP, and splenium of the CC compared with healthy controls, with relatively greater effect sizes observed in individuals with MetS. Compared with healthy controls, significantly reduced FC and FDC were only demonstrated in individuals with MetS, including regions with loss of FD, inferior cerebellar peduncle, inferior fronto-occipital fasciculus, MCP, and superior longitudinal fasciculus part I. Furthermore, negative correlations were observed between FD and Brinkman index of cigarette consumption cumulative amount and between FC or FDC and the Trail Making Test (parts B-A), which is a measure of executive function, waist circumference, or low-density lipoprotein cholesterol. Finally, TBSS analysis revealed that FA and MD were not significantly different among all groups.

CONCLUSIONS

The FBA results demonstrate that substantial axonal loss and atrophy in individuals with MetS and early axonal loss without fiber-bundle morphological changes in those with preMetS within the WM tracts are crucial to cognitive and motor function. FBA also clarified the association between executive dysfunction, abdominal obesity, hyper-low-density lipoprotein cholesterolemia, smoking habit, and compromised WM neural tissue microstructure in MetS.

Determinants and Temporal Dynamics of Cerebral Small Vessel Disease: 14-Year Follow-Up

BACKGROUND

The aim of this study is to investigate the temporal dynamics of small vessel disease (SVD) and the effect of vascular risk factors and baseline SVD burden on progression of SVD with 4 neuroimaging assessments over 14 years in patients with SVD.

METHODS

Five hundred three patients with sporadic SVD (50-85 years) from the ongoing prospective cohort study (RUN DMC [Radboud University Nijmegen Diffusion Tensor and Magnetic Resonance Cohort]) underwent baseline assessment in 2006 and follow-up in 2011, 2015, and 2020. Vascular risk factors and magnetic resonance imaging markers of SVD were evaluated. Linear mixed-effects model and negative binomial regression model were used to examine the determinants of temporal dynamics of SVD markers.

RESULTS

A total of 382 SVD patients (mean [SD] 64.1 [8.4]; 219 men and 163 women) who underwent at least 2 serial brain magnetic resonance imaging scans were included, with mean (SD) follow-up of 11.15 (3.32) years. We found a highly variable temporal course of SVD. Mean (SD) WMH progression rate was 0.6 (0.74) mL/y (range, 0.02-4.73 mL/y) and 13.6% of patients had incident lacunes (1.03%/y) over the 14-year follow-up. About 4% showed net WMH regression over 14 years, whereas 38 out of 361 (10.5%), 5 out of 296 (2%), and 61 out of 231 (26%) patients showed WMH regression for the intervals 2006 to 2011, 2011 to 2015, and 2015 to 2020, respectively. Of these, 29 (76%), 5 (100%), and 57 (93%) showed overall progression across the 14-year follow-up, and the net overall WMH change between first and last scan considering all participants was a net average WMH progression over the 14-year period. Older age was a strong predictor for faster WMH progression and incident lacunes. Patients with mild baseline WMH rarely progressed to severe WMH. In addition, both baseline burden of SVD lesions and vascular risk factors independently and synergistically predicted WMH progression, whereas only baseline SVD burden predicted incident lacunes over the 14-year follow-up.

CONCLUSIONS

SVD shows pronounced progression over time, but mild WMH rarely progresses to clinically severe WMH. WMH regression is noteworthy during some magnetic resonance imaging intervals, although it could be overall compensated by progression over the long follow-up.

Aging-Related Behavioral, Adiposity, and Glucose Impairments and Their Association following Prenatal Alcohol Exposure in the C57BL/6J Mouse

People that experience prenatal alcohol exposure (PAE) may have behavioral and metabolic impairments, and it is unclear whether these remain stable or change with age. We assessed behavioral and metabolic endpoints across the lifespan in a mouse model of fetal alcohol spectrum disorder (FASD). Pregnant C57BL/6J mice received alcohol (ALC; 3 g/kg) or maltose-dextrin (control, CON) daily from embryonic day 8.5 to 17.5. Offspring were tested on accelerating rotarod, Y-maze, novel object recognition, and fear conditioning at 6 weeks and 10 and 17 months; females were also tested at 24 months. Body composition, fasting glucose, and glucose clearance were assessed at 18 months. Female but not male ALC mice had greater adiposity than age-matched CON from 7 months onward. At 18 months, male but not female ALC mice had reduced glucose clearance and ALC mice were more likely to have elevated fasting glucose. In the rotarod training session, ALC females performed worse than CON. In the Y-maze, significant exposure-age interactions affected ALC performance in both sexes versus age-match CON. For fear conditioning, all animals acquired the task and froze more at older ages. In both the context and cued tasks, there were exposure-age interactions and ALC animals frozen less than CON at 10 months. Correlation analysis revealed that fasting glucose and glucose clearance correlated with % of body fat in ALC but not in CON mice. Additionally, glucose intolerance and % body fat negatively correlated with performance in the rotarod, context learning, and novel object recognition tasks in ALC but not CON mice. All mice exhibit worsening of behavioral performance as they age, and PAE did not further exacerbate this. ALC but not CON mice displayed adiposity and glucose intolerance that correlate with their cognitive impairments, suggesting that these may be mechanistically related in PAE. Findings emphasize that FASD should be considered a whole-body disorder.

Recurrent moderate hypoglycemia accelerates the progression of cognitive deficits through impairment of TRPC6/GLUT3 pathway in diabetic APP/PS1 mice

Currently, the most effective strategy for dealing with Alzheimer’s disease (AD) is delaying the onset of dementia. Severe hypoglycemia is strongly associated with dementia; however, the effects of recurrent moderate hypoglycemia (RH) on the progression of cognitive deficits in patients with diabetes with genetic susceptibility to AD remain unclear. Here, we report that insulin-controlled hyperglycemia slightly aggravated AD-type pathologies and cognitive impairment; however, RH significantly increased neuronal hyperactivity and accelerated the progression of cognitive deficits in streptozotocin-induced (STZ-induced) diabetic APP/PS1 mice. Glucose transporter 3–mediated (GLUT3-mediated) neuronal glucose uptake was not significantly altered under hyperglycemia but was markedly reduced by RH, which induced excessive mitochondrial fission in the hippocampus. Overexpression of GLUT3, specifically in the dentate gyrus (DG) area of the hippocampus, enhanced mitochondrial function and improved cognitive deficits. Activation of the transient receptor potential channel 6 (TRPC6) increased GLUT3-mediated glucose uptake in the brain and alleviated RH-induced cognitive deficits, and inactivation of the Ca²⁺/AMPK pathway was responsible for TRPC6-induced GLUT3 inhibition. Taken together, RH impairs brain GLUT3-mediated glucose uptake and further provokes neuronal mitochondrial dysfunction by inhibiting TRPC6 expression, which then accelerates progression of cognitive deficits in diabetic APP/PS1 mice. Avoiding RH is essential for glycemic control in patients with diabetes, and TRPC6/GLUT3 represents potent targets for delaying the onset of dementia in patients with diabetes.

Metabolic Syndrome and Cognitive Function

PURPOSE OF REVIEW

Metabolic syndrome (MetS) is a cluster of cardiovascular disease risk factors that are related to several adverse health outcomes, including poor cognitive function. This review seeks to summarize and critically review select recent findings on the association between MetS and cognition.

RECENT FINDINGS

MetS was associated with lower domain-specific and global cognitive function in most cross-sectional studies, but findings from longitudinal studies are not consistent. The associations varied depending on age, sex, cognitive test, genetic susceptibility, and the duration of follow-up in prospective studies. MetS was associated with a higher risk of mild cognitive impairment (MCI) and progression from MCI to dementia, particularly vascular dementia. Among MetS components, high blood pressure, high waist circumference, and hyperglycemia were the strongest predictors of cognitive function. MetS is associated with higher risk of cognitive impairment. Research is needed on how preventing or treating MetS affects cognition.

In vivo evaluation of the levator ani muscle in primiparous women using diffusion tensor imaging and fiber tractography

OBJECTIVE

To characterize the levator ani muscle (LAM) injury after first vaginal delivery and investigate the clinical application of diffusion tensor imaging (DTI) and fiber tractography in evaluating the LAM.

METHODS

Fifty-eight primiparous women at 6 weeks after vaginal delivery and 27 nulliparous women as controls underwent T2-weighted sequence and DTI sequence of the pelvic floor. A LAM scoring system was used to characterize the morphological changes. Fiber tractography of each major subdivision of LAM was performed, followed by assessment of the quality of fiber tracking. Fractional anisotropy (FA), apparent diffusion coefficient (ADC), fiber volume, and length were calculated.

RESULTS

Puborectalis and iliococcygeus injuries were observed in 30/58 (51.7%) and 10/58 (17.2%) primiparae, respectively. No LAM defects were identified in the control group. For the puborectalis, the FA values were lower (P = 0.010) and ADC values were higher (P = 0.024) in the primiparous group than in the control group. For the iliococcygeus, the fiber volume values were lower in the primiparous group than in the control group (P = 0.004).

CONCLUSION

Vaginal delivery can result in LAM injury at the puborectalis. DTI parameters can assist in the quantitative diagnosis of the LAM injury.

Burning Fog: Cognitive Impairment in Burning Mouth Syndrome

Background: Due to its common association with chronic pain experience, cognitive impairment (CI) has never been evaluated in patients with burning mouth syndrome (BMS). The purpose of this study is to assess the prevalence of CI in patients with BMS and to evaluate its relationship with potential predictors such as pain, mood disorders, blood biomarkers, and white matter changes (WMCs).

Methods: A case-control study was conducted by enrolling 40 patients with BMS and an equal number of healthy controls matched for age, gender, and education. Neurocognitive assessment [Mini Mental State Examination (MMSE), Digit Cancellation Test (DCT), the Forward and Backward Digit Span task (FDS and BDS), Corsi Block-Tapping Test (CB-TT), Rey Auditory Verbal Learning Test (RAVLT), Copying Geometric Drawings (CGD), Frontal Assessment Battery (FAB), and Trail Making A and B (TMT-A and TMT-B)], psychological assessment [Hamilton Rating Scale for Depression and Anxiety (HAM-D and HAM-A), Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESS), and 36-Item Short Form Health Survey (SF-36)], and pain assessment [Visual Analogic Scale (VAS), Total Pain Rating index (T-PRI), Brief Pain Inventory (BPI), and Pain DETECT Questionnaire (PD-Q)] were performed. In addition, blood biomarkers and MRI of the brain were recorded for the detection of Age-Related WMCs (ARWMCs). Descriptive statistics, the Mann-Whitney U-test, the Pearson Chi-Squared test and Spearman's correlation analysis were used.

Results: Patients with BMS had impairments in most cognitive domains compared with controls (p < 0.001^**) except in RAVLT and CGD. The HAM-D, HAM-A, PSQI, ESS, SF-36, VAS, T-PRI, BPI and PD-Q scores were statistically different between BMS patients and controls (p < 0.001^**) the WMCs frequency and ARWMC scores in the right temporal (RT) and left temporal (LT) lobe were higher in patients with BMS (p = 0.023^*).

Conclusions: Meanwhile, BMS is associated with a higher decline in cognitive functions, particularly attention, working memory, and executive functions, but other functions such as praxis-constructive skills and verbal memory are preserved. The early identification of CI and associated factors may help clinicians to identify patients at risk of developing time-based neurodegenerative disorders, such as Alzheimer's disease (AD) and vascular dementia (VD), for planning the early, comprehensive, and multidisciplinary assessment and treatment.

Abnormalities of Brain White Matter in Type 2 Diabetes Mellitus: A Meta-Analysis of Diffusion Tensor Imaging

Aims: The study aimed to conduct a meta-analysis to determine the abnormalities of white matter in patients with type 2 diabetes mellitus (T2DM) by identifying the consistency of diffusion tensor imaging (DTI). Method: The literature for DTI comparing patients with T2DM with controls published before October 30, 2020, were reviewed in PubMed, Web of Science, Embase, CNKI, and Wan Fang databases. The meta-analysis was performed using the activation likelihood estimation (ALE) method, including 12 reports and 381 patients with T2DM. Results: The meta-analysis identified 10 white matter regions that showed a consistent reduction of fractional anisotropy (FA) in patients with T2DM, including genu of the corpus callosum, the body of corpus callosum, bilateral anterior corona radiata, bilateral superior corona radiata, bilateral cingulum, and bilateral superior fronto-occipital fasciculus. Conclusion: This study revealed the abnormal characteristics of white matter in T2DM, which would be helpful to understand the underlying neuropathological and physiological mechanisms of T2DM and provide evidence for clinical diagnosis and treatment.

Association between metabolic syndrome and resting-state functional brain connectivity

The objective of this study is to examine whether metabolic syndrome (MetS), the clustering of 3 or more cardiovascular risk factors, disrupts the resting-state functional connectivity (FC) of the large-scale cortical brain networks. Resting-state functional magnetic resonance imaging data were collected from seventy-eight middle-aged and older adults living with and without MetS (27 MetS; 51 non-MetS). FC maps were derived from the time series of intrinsic activity in the large-scale brain networks by correlating the spatially averaged time series with all brain voxels using a whole-brain seed-based FC approach. Participants with MetS showed hyperconnectivity across the core brain regions with evidence of loss of modularity when compared with non-MetS individuals. Furthermore, patterns of higher between-network MetS-related effects were observed across most of the seed regions in both right and left hemispheres. These findings indicate that MetS is associated with altered intrinsic communication across core neural networks and disrupted between-network connections across the brain due to the co-occurring vascular risk factors in MetS.

Spontaneous neural activity changes after bariatric surgery: A resting-state fMRI study

BACKGROUND

Metabolic disorders associated with obesity could lead to alterations in brain structure and function. Whether these changes can be reversed after weight loss is unclear. Bariatric surgery provides a unique opportunity to address these questions because it induces marked weight loss and metabolic improvements which in turn may impact the brain in a longitudinal fashion. Previous studies found widespread changes in grey matter (GM) and white matter (WM) after bariatric surgery. However, findings regarding changes in spontaneous neural activity following surgery, as assessed with the fractional amplitude of low frequency fluctuations (fALFF) and regional homogeneity of neural activity (ReHo), are scarce and heterogenous. In this study, we used a longitudinal design to examine the changes in spontaneous neural activity after bariatric surgery (comparing pre- to post-surgery), and to determine whether these changes are related to cardiometabolic variables.

METHODS

The study included 57 participants with severe obesity (mean BMI=43.1 ± 4.3 kg/m²) who underwent sleeve gastrectomy (SG), biliopancreatic diversion with duodenal switch (BPD), or Roux-en-Y gastric bypass (RYGB), scanned prior to bariatric surgery and at follow-up visits of 4 months (N = 36), 12 months (N = 29), and 24 months (N = 14) after surgery. We examined fALFF and ReHo measures across 1022 cortical and subcortical regions (based on combined Schaeffer-Xiao parcellations) using a linear mixed effect model. Voxel-based morphometry (VBM) based on T1-weighted images was also used to measure GM density in the same regions. We also used an independent sample from the Human Connectome Project (HCP) to assess regional differences between individuals who had normal-weight (N = 46) or severe obesity (N = 46).

RESULTS

We found a global increase in the fALFF signal with greater increase within dorsolateral prefrontal cortex, precuneus, inferior temporal gyrus, and visual cortex. This effect was more significant 4 months after surgery. The increase within dorsolateral prefrontal cortex, temporal gyrus, and visual cortex was more limited after 12 months and only present in the visual cortex after 24 months. These increases in neural activity measured by fALFF were also significantly associated with the increase in GM density following surgery. Furthermore, the increase in neural activity was significantly related to post-surgery weight loss and improvement in cardiometabolic variables, such as blood pressure. In the independent HCP sample, normal-weight participants had higher global and regional fALFF signals, mainly in dorsolateral/medial frontal cortex, precuneus and middle/inferior temporal gyrus compared to the obese participants. These BMI-related differences in fALFF were associated with the increase in fALFF 4 months post-surgery especially in regions involved in control, default mode and dorsal attention networks.

CONCLUSIONS

Bariatric surgery-induced weight loss and improvement in metabolic factors are associated with widespread global and regional increases in neural activity, as measured by fALFF signal. These findings alongside the higher fALFF signal in normal-weight participants compared to participants with severe obesity in an independent dataset suggest an early recovery in the neural activity signal level after the surgery.

White matter integrity differences in obesity: A meta-analysis of diffusion tensor imaging studies

Some Diffusion Tensor Imaging studies have shown a loss of white matter (WM) integrity linked to impaired cognitive function in obese individuals. However, inconsistent WM integrity changes have been reported. We aimed to identify which WM tracts show consistent changes with obesity. We conducted a systematic search to find studies examining the association between obesity-related measures and Fractional Anisotropy (FA) or Mean Diffusivity. We performed a meta-analysis with FA datasets using Anisotropic Effect Size-Signed Differential Mapping software. The meta-analysis showed that increased obesity measurements were related to reduced FA in the genu of the corpus callosum. We validated our findings using an independent sample from the Human Connectome Project dataset, which supports lower FA in this region in individuals with obesity compared to those with normal weight (p = 0.028). Our findings provide evidence that obesity is associated with reduced WM integrity in the genu of the corpus callosum, a tract linking frontal areas involved in executive function. Future studies are needed on the mechanisms linking obesity with loss of WM integrity.

Similar Theory of Mind Deficits in Community Dwelling Older Adults with Vascular Risk Profile and Patients with Mild Cognitive Impairment: The Case of Paradoxical Sarcasm Comprehension

Recent studies deal with disorders and deficits caused by vascular syndrome in efforts for prediction and prevention. Cardiovascular health declines with age due to vascular risk factors, and this leads to an increasing risk of cognitive decline. Mild cognitive impairment (MCI) is defined as the negative cognitive changes beyond what is expected in normal aging. The purpose of the study was to compare older adults with vascular risk factors (VRF), MCI patients, and healthy controls (HC) in social cognition and especially in theory of mind ability (ToM). The sample comprised a total of 109 adults, aged 50 to 85 years (M = 66.09, SD = 9.02). They were divided into three groups: (a) older adults with VRF, (b) MCI patients, and (c) healthy controls (HC). VRF and MCI did not differ significantly in age, educational level or gender as was the case with HC. Specifically, for assessing ToM, a social inference test was used, which was designed to measure sarcasm comprehension. Results showed that the performance of the VRF group and MCI patients is not differentiated, while HC performed higher compared to the other two groups. The findings may imply that the development of a vascular disorder affecting vessels of the brain is associated from its “first steps” to ToM decline, at least regarding specific aspects of it, such as paradoxical sarcasm understanding.

Altered White Matter Microstructures in Type 2 Diabetes Mellitus: A Coordinate-Based Meta-Analysis of Diffusion Tensor Imaging Studies

Objective

Type 2 diabetes mellitus (T2DM) is often accompanied by cognitive decline and depressive symptoms. Numerous diffusion tensor imaging (DTI) studies revealed microstructural white matter (WM) abnormalities in T2DM but the findings were inconsistent. The present study aimed to conduct a coordinate-based meta-analysis (CBMA) to identify statistical consensus of DTI studies in T2DM.

Methods

We performed a systematic search on relevant studies that reported fractional anisotropy (FA) differences between T2DM patients and healthy controls (HC). The anisotropic effect size seed-based d mapping (AES-SDM) approach was used to explore WM alterations in T2DM. A meta-regression was then used to analyze potential influences of sample characteristics on regional FA changes.

Results

A total of eight studies that comprised 245 patients and 200 HC, along with 52 coordinates were extracted. The meta-analysis identified FA reductions in three clusters including the left inferior network, the corpus callosum (CC), and the left olfactory cortex. Besides, FA in the CC was negatively correlated with body mass index (BMI) in the patients group.

Conclusions

T2DM could lead to subtle WM microstructural alterations, which might be associated with cognitive deficits or emotional distress symptoms. This provides a better understanding of the pathophysiology of neurodegeneration and complications in T2DM.

Systematic Review Registration

Registered at PROSPERO (http://www.crd.york.ac.uk/PROSPERO), registration number: CRD42020218737.

Rats with elevated genetic risk for metabolic syndrome exhibit cognitive deficiencies when young

Metabolic syndrome (MetS) is a known risk factor for cognitive decline. Using polygenic rat models selectively bred for high and low intrinsic exercise capacity and simultaneously modelling as low and high innate risk factor for MetS respectively, we have previously shown that adult animals with lower exercise capacity/higher MetS risk perform poorly in tasks requiring flexible cognition. However, it is not known whether these deficits in cognition are present already at young age. Also, it is unclear whether the high risk genome is related also to lower-level cognition, such as sensory gating measured as prepulse inhibition. In this study, young and adult (5-8 weeks and ~9 months) rats selectively bred for 36 generations as High-Capacity Runners (HCR) or Low-Capacity Runners (LCR) were tested for behavior in an open field task, modulation of startle reflex, and spatial learning in a T-maze. HCR rats were more active in the open field than LCR rats independent of age. Responses to the startle stimulus habituated to the same extent in LCR compared to HCR rats when young, but as adults, stronger habituation was seen in the HCR animals. The prepulse inhibition of startle response was equally strong in young HCR and LCR animals but the effect was shorter lasting in HCR animals. In T-maze, adult HCR animals unexpectedly showed attenuated learning, but we interpret this finding to stem from differences in motivation rather than learning ability. Overall, in the LCR rats with the risk genome for poor aerobic fitness and MetS, indications of compromised cognitive function are present already at a young age.

Variation of HbA1c affects cognition and white matter microstructure in healthy, young adults

The metabolic serum marker HbA1c has been associated with both impaired cognitive performance and altered white matter integrity in patients suffering from diabetes mellitus. However, it remains unclear if higher levels of HbA1c might also affect brain structure and function in healthy subjects. With the present study we therefore aimed to investigate the relationship between HbA1c levels and cognitive performance as well as white matter microstructure in healthy, young adults. To address this question, associations between HbA1c and cognitive measures (NIH Cognition Toolbox) as well as DTI-derived imaging measures of white matter microstructure were investigated in a publicly available sample of healthy, young adults as part of the Humane Connectome Project (n = 1206, mean age = 28.8 years, 45.5% male). We found that HbA1c levels (range 4.1-6.3%) were significantly inversely correlated with measures of cognitive performance. Higher HbA1c levels were associated with significant and widespread reductions in fractional anisotropy (FA) controlling for age, sex, body mass index, ethnicity, and education. FA reductions were furthermore found to covary with measures of cognitive performance. The same pattern of results could be observed in analyses restricted to participants with HBA1c levels below 5.7%. The present study demonstrates that low-grade HbA1c variation below diagnostic threshold for diabetes is related to both cognitive performance and white matter integrity in healthy, young adults. These findings highlight the detrimental impact of metabolic risk factors on brain physiology and underscore the importance of intensified preventive measures independent of the currently applied diagnostic HbA1c cutoff scores.

Glucose-level dependent brain hypometabolism in type 2 diabetes mellitus and obesity

BACKGROUND

Metabolic syndrome and its individual components lead to wide-ranging consequences, many of which affect the central nervous system. In this study, we compared the [18F]FDG regional brain metabolic pattern of participants with type 2 diabetes mellitus (T2DM) and non-DM obese individuals.

METHODS

In our prospective study, 51 patients with controlled T2DM (ages 50.6 ± 8.0 years) and 45 non-DM obese participants (ages 52.0 ± 9.6 years) were enrolled. Glucose levels measured before PET/CT examination (pre-PET glucose) as well as laboratory parameters assessing glucose and lipid status were determined. NeuroQ application (NeuroQTM 3.6, Syntermed, Philips) was used to evaluate regional brain metabolic differences. [18F]FDG PET/CT (AnyScan PC, Mediso) scans, estimating brain metabolism, were transformed to MNI152 brain map after T1 registration and used for SPM-based group comparison of brain metabolism corrected for pre-PET glucose, and correlation analysis with laboratory parameters.

RESULTS

NeuroQ analysis did not reveal significant regional metabolic defects in either group. Voxel-based group comparison revealed significantly (PFWE<0.05) decreased metabolism in the region of the precuneus and in the right superior frontal gyrus (rSFG) in the diabetic group as compared to the obese patients. Data analysis corrected for pre-PET glucose level showed a hypometabolic difference only in the rSFG in T2DM. Voxel-based correlation analysis showed significant negative correlation of the metabolism in the following brain regions with pre-PET glucose in diabetes: precuneus, left posterior orbital gyrus, right calcarine cortex and right orbital part of inferior frontal gyrus; whilst in the obese group only the right rolandic (pericentral) operculum proved to be sensitive to pre-PET glucose level.

CONCLUSIONS

To our knowledge, this is the first study to perform pre-PET glucose level corrected comparative analysis of brain metabolism in T2DM and obesity. We also examined the pre-PET glucose level dependency of regional cerebral metabolism in the two groups separately. Large-scale future studies are warranted to perform further correlation analysis with the aim of determining the effects of metabolic disturbances on brain metabolism.

Elevated Circulating Microparticle Subpopulations in Incidental Cerebral White Matter Hyperintensities: A Multimodal Study

Asymptomatic (or "silent") manifestations of cerebral small vessel disease (CSVD) are widely recognized through incidental findings of white matter hyperintensities (WMHs) as a result of magnetic resonance imaging (MRI). This study aims to examine the potential associations of surrogate markers for the evaluation of white matter integrity in CSVD among asymptomatic individuals through a battery of profiling involving QRISK2 cardiocerebrovascular risk prediction, neuroimaging, neurocognitive evaluation, and microparticles (MPs) titers. Sixty asymptomatic subjects (mean age: 39.83 ± 11.50 years) with low to moderate QRISK2 scores were recruited and underwent neurocognitive evaluation for memory and cognitive performance, peripheral venous blood collection for enumeration of selected MPs subpopulations, and 3T MRI brain scan with specific diffusion MRI (dMRI) sequences inclusive of diffusion tensor imaging (DTI). WMHs were detected in 20 subjects (33%). Older subjects (mean age: 46.00 ± 12.00 years) had higher WMHs prevalence, associated with higher QRISK2 score and reduced processing speed. They also had significantly higher mean percentage of platelet (CD62P)- and leukocyte (CD62L)-derived MPs. No association was found between reduced white matter integrity-especially at the left superior longitudinal fasciculus (LSLF)-with age and neurocognitive function; however, LSLF was associated with higher QRISK2 score, total MPs, and CD62L- and endothelial cell-derived MPs (CD146). Therefore, this study establishes these multimodal associations as potential surrogate markers for "silent" CSVD manifestations in the well-characterized cardiocerebrovascular demographic of relatively young, neurologically asymptomatic adults. Furthermore, to the best of our knowledge, this study is the first to exhibit elevated MP counts in asymptomatic CSVD (i.e., CD62P and CD62L), which warrants further delineation.