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

The associations of BMI with mean diffusivity of basal ganglia among young adults with mild obesity and without obesity

Obesity causes a wide range of systemic diseases and is associated with mood and anxiety disorders. It is also associated with dopaminergic reward system function. However, the relationships between microstructural properties of the dopaminergic system and body mass index (BMI) have not been investigated. In this study, we investigated the associations of BMI with mean diffusivity (MD), diffusion tensor imaging measure in areas of the dopaminergic system (MDDS) in 435 healthy young adults with mild obesity and without obesity (BMI < 40). We detected the association between greater BMI and lower MD of the right globus pallidus and the right putamen. These results suggest that the property of the dopaminergic system is associated with BMI among young adults with mild obesity and without obesity.

Brain white matter microstructure in obese women with binge eating disorder

OBJECTIVE

Research on potential brain circuit abnormalities in binge eating disorder (BED) is limited. Here, we assess white matter (WM) microstructure in obese women with BED.

METHOD

Diffusion tensor imaging data were acquired, and tract-based spatial statistics used to examine WM in women with BED who were obese (n = 17) compared to normal-weight (NWC) (n = 17) and to women who were obese (OBC) (n = 13). Body mass index (BMI) was a covariate in the analyses.

RESULTS

The BED group (vs. NWC) had greater axial diffusion (AD) in the forceps minor, anterior thalamic radiation, superior and inferior longitudinal fasciculus, that is, in pathways connecting fronto-limbic regions. Microstructures differences in AD between the BED and OBC groups were seen in fronto-limbic pathways extending to temporoparietal pathways. The BED (vs. OBC) group had greater fractional anisotropy in the forceps minor and greater AD in the superior longitudinal fasciculus, cingulate gyrus, and corpus callosum, consistent with fronto-tempoparietal pathways.

CONCLUSION

Women with BED show WM alterations in AD in fronto-limbic and parietal pathways that are important in decision-making processes. As BMI was a covariate in the analyses, alterations in BED may be part of the pathology, but whether they are a cause or effect of illness is unclear.

Evaluating the Sensitivity of Resting-State BOLD Variability to Age and Cognition after Controlling for Motion and Cardiovascular Influences: A Network-Based Approach

Recent functional magnetic resonance imaging (fMRI) studies report that moment-to-moment variability in the BOLD signal is related to differences in age and cognition and, thus, may be sensitive to age-dependent decline. However, head motion and/or cardiovascular health (CVH) may contaminate these relationships. We evaluated relationships between resting-state BOLD variability, age, and cognition, after characterizing and controlling for motion-related and cardiovascular influences, including pulse, blood pressure, BMI, and white matter hyperintensities (WMH), in a large (N = 422) resting-state fMRI sample of cognitively normal individuals (age 43-89). We found that resting-state BOLD variability was negatively related to age and positively related to cognition after maximally controlling for head motion. Age relationships also survived correction for CVH, but were greatly reduced when correcting for WMH alone. Our results suggest that network-based machine learning analyses of resting-state BOLD variability might yield reliable, sensitive measures to characterize age-related decline across a broad range of networks. Age-related differences in resting-state BOLD variability may be largely sensitive to processes related to WMH burden.

Is Midlife Metabolic Syndrome Associated With Cognitive Function Change? The Study of Women's Health Across the Nation

CONTEXT

Metabolic syndrome (MetS) affects cognitive function in late life, particularly in women. But longitudinal research is scarce on associations of MetS with cognitive function during midlife.

OBJECTIVE

To determine associations between MetS exposure and cognitive function trajectories in midlife women.

DESIGN AND SETTING

This is a 17-year prospective, longitudinal study of multiracial/ethnic women in 7 US communities, with annual/biennial assessments.

PARTICIPANTS

Participants were 2149 US women traversing menopause.

EXPOSURE

Exposure consisted of MetS assessments (median 4 assessments over 4 years).

MAIN OUTCOME MEASURES

Main outcome measures were assessments of cognitive function in 3 domains: perceptual speed (symbol digit modalities test, SDMT), episodic memory (East Boston Memory Test, EBMT), and working memory (Digit Span Backward Test, DSB).

RESULTS

By their first cognitive assessment (age 50.7 ± 2.9 years), 29.5% met the criteria for MetS. Women completed a median (interquartile range [IQR]) of 6 (IQR 4-7) follow-up cognitive assessments over 11.2 (IQR 9.2-11.5) years. Women with MetS, compared with those without, had a larger 10-year decline in SDMT z-score (estimate -0.087, 95% confidence interval, -0.150 to -0.024; P = 0.007), after adjustment for cognitive testing practice effects, sociodemographics, lifestyle, mood, and menopause factors. As such, MetS accelerated the 10-year loss of perceptual speed by 24%. MetS did not differentially affect the rate of decline in either immediate (P = 0.534) or delayed (P = 0.740) episodic memory or in working memory (P = 0.584).

CONCLUSIONS

In midlife women MetS exposure was associated with accelerated decline in perceptual speed, but not episodic or working memory.

The impact of neuroimaging advancement on neurocognitive evaluation in pediatric brain tumor survivors: A review

Pediatric brain tumors are a type of tumors that are commonly present in children and young adults. With the improvement of treatment, the quality of life, especially the cognitive functioning, is gaining increasingly more attention. Apart from cognitive evaluations, neuroimaging studies begin to play an important part in neurocognitive functioning investigation. In this way, the brain tissue changes caused by tumor variables (including tumor location and tumor size) and treatment variables (including surgery, chemotherapy and radiotherapy) can be detected by neuroimaging. Recent advancement of neuroimaging techniques, such as functional-MRI (fMRI) and diffusion tensor imaging (DTI), made great contributions to understanding cognitive dysfunction and quantifying the effects of tumor variables and treatment variables. In recent years, laminar-fMRI provided a potentially valuable tool for examining the exact origins of neural activity and cognitive function. On the other hand, molecular fMRI might guide diagnosis and treatment of brain disease in the future by using new biomarkers, and DTI can detect white matter changes and obtain some anatomically specific information.

Neuroinflammation and White Matter Alterations in Obesity Assessed by Diffusion Basis Spectrum Imaging

Human obesity is associated with low-grade chronic systemic inflammation, alterations in brain structure and function, and cognitive impairment. Rodent models of obesity show that high-calorie diets cause brain inflammation (neuroinflammation) in multiple regions, including the hippocampus, and impairments in hippocampal-dependent memory tasks. To determine if similar effects exist in humans with obesity, we applied Diffusion Basis Spectrum Imaging (DBSI) to evaluate neuroinflammation and axonal integrity. We examined diffusion-weighted magnetic resonance imaging (MRI) data in two independent cohorts of obese and non-obese individuals (Cohort 1: 25 obese/21 non-obese; Cohort 2: 18 obese/41 non-obese). We applied Tract-based Spatial Statistics (TBSS) to allow whole-brain white matter (WM) analyses and compare DBSI-derived isotropic and anisotropic diffusion measures between the obese and non-obese groups. In both cohorts, the obese group had significantly greater DBSI-derived restricted fraction (DBSI-RF; an indicator of neuroinflammation-related cellularity), and significantly lower DBSI-derived fiber fraction (DBSI-FF; an indicator of apparent axonal density) in several WM tracts (all corrected p < 0.05). Moreover, using region of interest analyses, average DBSI-RF and DBSI-FF values in the hippocampus were significantly greater and lower, respectively, in obese relative to non-obese individuals (Cohort 1: p = 0.045; Cohort 2: p = 0.008). Hippocampal DBSI-FF and DBSI-RF and amygdalar DBSI-FF metrics related to cognitive performance in Cohort 2. In conclusion, these findings suggest that greater neuroinflammation-related cellularity and lower apparent axonal density are associated with human obesity and cognitive performance. Future studies are warranted to determine a potential role for neuroinflammation in obesity-related cognitive impairment.

Brain microstructural abnormalities in type 2 diabetes mellitus: A systematic review of diffusion tensor imaging studies

Type 2 diabetes mellitus (T2DM) is associated with deficits in the structure and function of the brain. Diffusion tensor imaging (DTI) is a highly sensitive method for characterizing cerebral tissue microstructure. Using PRISMA guidelines, we identified 29 studies which have demonstrated widespread brain microstructural impairment and topological network disorganization in patients with T2DM. Most consistently reported structures with microstructural abnormalities were frontal, temporal, and parietal lobes in the lobar cluster; corpus callosum, cingulum, uncinate fasciculus, corona radiata, and internal and external capsules in the white matter cluster; thalamus in the subcortical cluster; and cerebellum. Microstructural abnormalities were correlated with pathological derangements in the endocrine profile as well as deficits in cognitive performance in the domains of memory, information-processing speed, executive function, and attention. Altogether, the findings suggest that the detrimental effects of T2DM on cognitive functions might be due to microstructural disruptions in the central neural structures.

White matter microstructure mediates the association between physical fitness and cognition in healthy, young adults

We aimed to extend our knowledge on the relationship between physical fitness (PF) and both white matter microstructure and cognition through in-depth investigation of various cognitive domains while accounting for potentially relevant nuisance covariates in a well-powered sample. To this end, associations between walking endurance, diffusion-tensor-imaging (DTI) based measures of fractional anisotropy (FA) within brain white matter and cognitive measures included in the NIH Toolbox Cognition Battery were investigated in a sample of n = 1206 healthy, young adults (mean age = 28.8; 45.5% male) as part of the human connectome project. Higher levels of endurance were associated with widespread higher FA (p_FWE < 0.05) as well as with enhanced global cognitive function (p < 0.001). Significant positive relationships between endurance and cognitive performance were similarly found for almost all cognitive domains. Higher FA was significantly associated with enhanced global cognitive function (p < 0.001) and FA was shown to significantly mediate the association between walking endurance and cognitive performance. Inclusion of potentially relevant nuisance covariates including gender, age, education, BMI, HBA1c, and arterial blood pressure did not change the overall pattern of results. These findings support the notion of a beneficial and potentially protective effect of PF on brain structure and cognition.

Chronic exposure to high fat diet triggers myelin disruption and interleukin-33 upregulation in hypothalamus

Background

Hypothalamic inflammation including astrogliosis and microglia activation occurs after intake of high fat diet (HFD) in rodent models or in obese individuals. However, the effect of chronic HFD feeding on oligodendrocytes (OLGs), a myelin-producing glial population in the central nervous system (CNS), remains unclear. In this study, we used 8-week old male C57BL/6 mice fed by HFD for 3–6 months to induce chronic obesity.

Results

The transmission electron microscopy imaging analysis showed that the integrity of hypothalamic myelin was disrupted after HFD feeding for 4 and 6 months. Moreover, the accumulation of Iba1⁺-microglia with an amoeboid hypertrophic form was continually observed in arcuate nucleus of HFD-fed mice during the entire feeding time period. Interleukin-33 (IL-33), a tissue alarmin upon injury to the CNS, was detected with an increased level in hypothalamus after HFD feeding for 3 and 4 months. Furthermore, the in vitro study indicated that exposure of mature OLGs to IL-33 impaired OLG cell structure along with a decline in the expression of myelin basic protein.

Conclusions

Altogether, our findings demonstrate that chronic HFD feeding triggers hypothalamic myelin disruption in accompany with IL-33 upregulation and prolonged microglial activation in hypothalamus. Given that the addition of exogenous IL-33 was harmful for the maturation of OLGs, an increase in IL-33 by chronic HFD feeding might contribute to the induction of hypothalamic myelin disruption.

Electronic supplementary material

The online version of this article (10.1186/s12868-019-0516-6) contains supplementary material, which is available to authorized users.

Effect of resveratrol on metabolic syndrome components: A systematic review and meta-analysis

We summarized 16 controlled studies and evaluated the correlation of resveratrol supplementation with metabolic parameters such as the body weight, waist circumference (WC), systolic blood pressure (sbp), HDL, total cholesterol, triglyceride and glucose levels. This meta-analysis was carried out to determine the association between the resveratrol intake with metabolic parameters in metabolic syndrome patients. PubMed, Scopus, Cochrane and Google Scholar were searched from inception to December 2018 using relevant keywords. All articles were independently reviewed by two authors using predetermined selection criteria. We have selected the studies that investigated the effects of resveratrol on metabolic parameters. Of 16 studies, 10 were performed on human subjects, and in 6 studies animal models were used. Standard mean difference (SMD) with 95% confidence interval were determined using Der Simonian and Laird random-effects modeling, when there was a significant heterogeneity between studies. Funnel plot and Egger's test were conducted to examine the risk of publication bias. Pooled effect sizes in human studies indicated a significant impact of resveratrol supplementation on glucose level [-1.73 (-2.99, -0.47); p = 0.007)] and WC [-1.73 (-2.79, -0.67); p = 0.001] compared with the control group. Also combining the results of studies on rat samples (n = 6), indicated significant effect of resveratrol on decreasing weight [-22.95 (-44.74, -1.17); p = 0.04], TGs [-6.76 (-11.10, -2.42); p = 0.001], sbp [-7.30 (-12.48, -2.13); p = 0.006], and it can influence significantly on increasing HDL level (4.75 (1.87, 7.63); p = 0.001). However, resveratrol was not significantly effective on total cholesterol in both samples. The results of subgroup analysis of human studies showed that resveratrol has significant effect on metabolic parameters (glucose level and WC) at the dosage of > 500 mg and with long-term interventions ≥ 10 weeks. Administration of resveratrol can meaningfully reduce the BW, WC, TGs, and glucose level, also it can increase HDL, but not total cholesterol.

Sex-specific effects of central adiposity and inflammatory markers on limbic microstructure

Midlife obesity is a risk factor of late onset Alzheimer's disease (LOAD) but why this is the case remains unknown. As systemic inflammation is involved in both conditions, obesity-related neuroinflammation may contribute to damage in limbic structures important in LOAD. Here, we investigated the hypothesis that systemic inflammation would mediate central obesity related effects on limbic tissue microstructure in 166 asymptomatic individuals (38-71 years old). We employed MRI indices sensitive to myelin and neuroinflammation [macromolecular proton fraction (MPF) and kf] from quantitative magnetization transfer (qMT) together with indices from neurite orientation dispersion and density imaging (NODDI) to investigate the effects of central adiposity on the fornix, parahippocampal cingulum, uncinate fasciculus (compared with whole brain white matter and corticospinal tract) and the hippocampus. Central obesity was assessed with the Waist Hip Ratio (WHR) and abdominal visceral and subcutaneous fat area fractions (VFF, SFF), and systemic inflammation with blood plasma concentrations of leptin, adiponectin, C-reactive protein and interleukin 8. Men were significantly more centrally obese and had higher VFF than women. Individual differences in WHR and in VFF were negatively correlated with differences in fornix MPF and kf, but not with any differences in neurite microstructure. In women, age mediated the effects of VFF on fornix MPF and kf, whilst in men differences in the leptin and adiponectin ratio fully mediated the effect of WHR on fornix MPF. These results suggest that visceral fat related systemic inflammation may damage myelin-related properties of the fornix, a key limbic structure known to be involved in LOAD.

BMI-related cortical morphometry changes are associated with altered white matter structure

BACKGROUND

While gross measures of brain structure have shown alterations with increasing body mass index (BMI), the extent and nature of such changes has varied substantially across studies. Here, we sought to determine whether small-scale morphometric measures might prove more sensitive and reliable than larger scale measures and whether they might offer a valuable opportunity to link cortical changes to underlying white matter changes. To examine this, we explored the association of BMI with millimetre-scale Gaussian curvature, in addition to standard measures of morphometry such as cortical thickness, surface area and mean curvature. We also assessed the volume and integrity of the white matter, using white matter signal intensity and fractional anisotropy (FA). We hypothesised that BMI would be linked to small-scale changes in Gaussian curvature and that this phenomenon would be mediated by changes in the integrity of the underlying white matter.

METHODS

The association of global measures of T1-weighted cortical morphometry with BMI was examined using linear regression and mediation analyses in two independent groups of healthy young to middle aged human subjects (n1 = 52, n2 = 202). In a third dataset of (n3 = 897), which included diffusion tensor images, we sought to replicate the significant associations established in the first two datasets, and examine the potential mechanistic link between BMI-associated cortical changes and global FA.

RESULTS

Gaussian curvature of the white matter surface showed a significant, positive association with BMI across all three independent datasets. This effect was mediated by a negative association between the integrity of the white matter and BMI.

CONCLUSIONS

Increasing BMI is associated with changes in white matter microstructure in young to middle-aged healthy adults. Our results are consistent with a model whereby BMI-linked cortical changes are mediated by the effects of BMI on white matter microstructure.

Vascular burden and APOE ε4 are associated with white matter microstructural decline in cognitively normal older adults

White matter microstructure can be measured with diffusion tensor imaging (DTI). While increasing age is a predictor of white matter (WM) microstructure changes, roles of other possible modifiers, such as cardiovascular risk factors, APOE ε4 allele status and biological sex have not been clarified. We investigated 665 cognitively normal participants from the Baltimore Longitudinal Study of Aging (age 50-95, 56.7% female) with a total of 1384 DTI scans. WM microstructure was assessed by fractional anisotropy (FA) and mean diffusivity (MD). A vascular burden score was defined as the sum of five risk factors (hypertension, obesity, elevated cholesterol, diabetes and smoking status). Linear mixed effects models assessed the association of baseline vascular burden on baseline and on rates of change of FA and MD over a mean follow-up of 3.6 years, while controlling for age, race, and scanner type. We also compared DTI trajectories in APOE ε4 carriers vs. non-carriers and men vs. women. At baseline, higher vascular burden was associated with lower FA and higher MD in many WM structures including association, commissural, and projection fibers. Higher baseline vascular burden was also associated with greater longitudinal decline in FA in the hippocampal part of the cingulum and the fornix (crus)/stria terminalis and splenium of the corpus callosum, and with greater increases in MD in the splenium of the corpus callosum. APOE ε4 carriers did not differ from non-carriers in baseline DTI metrics but had greater decline in FA in the genu and splenium of the corpus callosum. Men had higher FA and lower MD in multiple WM regions at baseline but showed greater increase in MD in the genu of the corpus callosum. Women showed greater decreases over time in FA in the gyrus part of the cingulum, compared to men. Our findings show that modifiable vascular risk factors (1) have a negative impact on white matter microstructure and (2) are associated with faster microstructural deterioration of temporal WM regions and the splenium of the corpus callosum in cognitively normal adults. Reducing vascular burden in aging could modify the rate of WM deterioration and could decrease age-related cognitive decline and impairment.

Local Diffusion Homogeneity Provides Supplementary Information in T2DM-Related WM Microstructural Abnormality Detection

Objectives: We aimed to investigate whether an inter-voxel diffusivity metric (local diffusion homogeneity, LDH), can provide supplementary information to traditional intra-voxel metrics (i.e., fractional anisotropy, FA) in white matter (WM) abnormality detection for type 2 diabetes mellitus (T2DM). Methods: Diffusion tensor imaging was acquired from 34 T2DM patients and 32 healthy controls. Voxel-based group-difference comparisons based on LDH and FA, as well as the association between the diffusion metrics and T2DM risk factors [i.e., body mass index (BMI) and systolic blood pressure (SBP)], were conducted, with age, gender and education level controlled. Results: Compared to the controls, T2DM patients had higher LDH in the pons and left temporal pole, as well as lower FA in the left superior corona radiation (p < 0.05, corrected). In T2DM, there were several overlapping WM areas associated with BMI as revealed by both LDH and FA, including right temporal lobe and left inferior parietal lobe; but the unique areas revealed only by using LDH included left inferior temporal lobe, right supramarginal gyrus, left pre- and post-central gyrus (at the semiovale center), and right superior radiation. Overlapping WM areas that associated with SBP were found with both LDH and FA, including right temporal pole, bilateral orbitofrontal area (rectus gyrus), the media cingulum bundle, and the right cerebellum crus I. However, the unique areas revealed only by LDH included right inferior temporal lobe, right inferior occipital lobe, and splenium of corpus callosum. Conclusion: Inter- and intra-voxel diffusivity metrics may have different sensitivity in the detection of T2DM-related WM abnormality. We suggested that LDH could provide supplementary information and reveal additional underlying brain changes due to diabetes.

Group cognitive remediation therapy for adults with obesity prior to behavioural weight loss treatment: study protocol for a randomised controlled superiority study (CRT study)

INTRODUCTION

Individuals with obesity show deficits in executive functioning which have been implicated in decreased weight loss outcome. Preliminary evidence suggests that cognitive remediation therapy (CRT) improves executive functioning and weight loss in obesity. However, confirmatory support, especially for pre-weight loss use, is lacking. The CRT study aims at determining the efficacy of CRT versus no treatment control in patients with obesity before entering behavioural weight loss (BWL) treatment. It is hypothesised that individuals who receive CRT will show better weight loss outcome, improved executive functioning, greater weight loss-related behavioural changes and higher attendance of BWL treatment, 6 and 12 months after cessation of CRT.

METHODS AND ANALYSIS

In a single-centre, assessor-blinded, randomised, two-armed parallel-group superiority trial, 260 adults with body mass index ≥35.0 kg/m2 are centrally randomised to 8-week group-based CRT versus no treatment, before entering BWL treatment. Primary outcome is the amount of weight loss (%) at 6-month follow-up, compared with pre-treatment, derived from measured body weight. Secondary outcomes include improvement in executive functioning post-treatment and in weight loss-related behaviour, mental and physical health, and attendance to BWL treatment at 6-month and 12-month follow-up. Maintenance of weight loss at 12-month follow-up will be determined. Mixed model analyses based on intent-to-treat will be used to compare the CRT and control groups with respect to differences in weight change between pre-treatment and 6-month follow-up. Similar models will be used for analysing 12-month follow-up data and secondary outcomes. Further analyses will include additional covariates to identify predictors of treatment outcome.

ETHICS AND DISSEMINATION

The study was approved by the Ethical Committee of the University of Leipzig (256-15-13072015, version 'Final 1.0 from 28 May 2015). The study results will be disseminated through peer-reviewed publications.

TRIAL REGISTRATION NUMBER

DRKS00009333; Pre-results.

Associations between waist circumference, metabolic risk and executive function in adolescents: A cross-sectional mediation analysis

The main objective of this study was to investigate the associations between waist circumference, metabolic risk factors, and executive function in adolescents. Methods: The study was cross-sectional and included 558 adolescents (mean age 14.2 years). Anthropometrics and systolic blood pressure (sysBP) were measured and fasting blood samples were analyzed for metabolic risk factors. A metabolic risk factor cluster score (MetS-cluster score) was computed from the sum of standardized sysBP, triglycerides (TG), inverse high-density lipid cholesterol (HDLc) and insulin resistance (homeostasis model assessment). Cognitive control was measured with a modified flanker task. Results: Regression analyses indicated that after controlling for demographic variables, HDLc exhibited a negative and TG a positive association with flanker reaction time (RT). Waist circumference did not demonstrate a statistically significant total association with the cognitive outcomes. In structural equation modeling, waist circumference displayed an indirect positive association with incongruent RT through a higher MetS-cluster score and through lower HDLc. The only statistically significant direct association between waist circumference and the cognitive outcomes was for incongruent RT in the model including HDLc as mediator. Conclusions: These findings are consonant with the previous literature reporting an adverse association between certain metabolic risk factors and cognitive control. Accordingly, these results suggest specificity between metabolic risk factors and cognitive control outcomes. Further, results of the present study, although cross-sectional, provide new evidence that specific metabolic risk factors may mediate an indirect association between adiposity and cognitive control in adolescents, even though a direct association between these variables was not observed. However, taking the cross-sectional study design into consideration, these results should be interpreted with caution and future longitudinal or experimental studies should verify the findings of this study.

Abscisic Acid Supplementation Rescues High Fat Diet-Induced Alterations in Hippocampal Inflammation and IRSs Expression

Accumulated evidence indicates that neuroinflammation induces insulin resistance in the brain. Moreover, both processes are intimately linked to neurodegenerative disorders, including Alzheimer's disease. Potential mechanisms underlying insulin resistance include serine phosphorylation of the insulin receptor substrate (IRS) or insulin receptor (IR) misallocation. However, only a few studies have focused on IRS expression in the brain and its modulation in neuroinflammatory processes. This study used the high-fat diet (HFD) model of neuroinflammation to study the alterations of IR, an insulin-like growth factor receptor (IGF1R) and IRS expressions in the hippocampus. We observed that HFD effectively reduced mRNA and protein IRS2 expression. In contrast, a HFD induced the upregulation of the IRS1 mRNA levels, but did not alter an IR and IGF1R expression. As expected, we observed that a HFD increased hippocampal tumor necrosis factor alpha (TNFα) and amyloid precursor protein (APP) levels while reducing brain-derived neurotrophic factor (BDNF) expression and neurogenesis. Interestingly, we found that TNFα correlated positively with IRS1 and negatively with IRS2, whereas APP levels correlated positively only with IRS1 but not IRS2. These results indicate that IRS1 and IRS2 hippocampal expression can be affected differently by HFD-induced neuroinflammation. In addition, we aimed to establish whether abscisic acid (ABA) can rescue hippocampal IRS1 and IRS2 expression, as we had previously shown that ABA supplementation prevents memory impairments and improves neuroinflammation induced by a HFD. In this study, ABA restored HFD-induced hippocampal alterations, including IRS1 and IRS2 expression, TNFα, APP, and BDNF levels and neurogenesis. In conclusion, this study highlights different regulations of hippocampal IRS1 and IRS2 expression using a HFD, indicating the important differences of these scaffolding proteins, and strongly supports ABA therapeutic effects.

Elevated body-mass index is associated with reduced white matter integrity in two large independent cohorts

Obesity has been associated with a variety of neurobiological alterations. Recent neuroimaging research has pointed to the relevance of brain structural and functional alterations in the development of obesity. However, while the role of gray matter atrophy in obesity has been evidenced in several well powered studies, large scale evidence for altered white matter integrity in obese subjects is still absent. With this study, we therefore aimed to investigate potential associations between white matter abnormalities and body mass index (BMI) in two large independent samples of healthy adults. Associations between BMI values and whole brain fractional anisotropy (FA) were investigated in two independent cohorts: A sample of n = 369 healthy subjects from the Münster Neuroimaging Cohort (MNC), as well as a public available sample of n = 1064 healthy subjects of the Humane Connectome Project (HCP) were included in the present study. Tract based spatial statistics (TBSS) analyses of BMI on whole brain FA were conducted including age and sex as nuisance covariates using the FMRIB library (FSL Version 5.0). Threshold-free cluster enhancement was applied to control for multiple comparisons. In both samples higher BMI was significantly associated with strong and widespread FA reductions. These effects were most pronounced in the corpus callosum, bilateral posterior thalamic radiation, bilateral internal capsule and external capsule, bilateral inferior longitudinal fasciculus and inferior fronto-occipital fasciculus. The association was found to be independent of age, sex and other cardiovascular risk factors. No significant positive associations between BMI and FA occurred. With this highly powered study, we provide robust evidence for globally reduced white matter integrity associated with elevated BMI including replication in an independent sample. The present work thus points out the relevance of white matter alterations as a neurobiological correlate of obesity.

Non-invasive imaging modalities to study neurodegenerative diseases of aging brain

The aim of this article is to highlight current approaches for imaging elderly brain, indispensable for cognitive neuroscience research with emphasis on the basic physical principles of various non-invasive neuroimaging techniques. The first part of this article presents a quick overview of the primary non-invasive neuroimaging modalities used by cognitive neuroscientists such as transcranial magnetic stimulation (TMS), transcranial electrical stimulation (tES), electroencephalography (EEG), magnetoencephalography (MEG), single photon emission computed tomography (SPECT), positron emission tomography (PET), magnetic resonance spectroscopic imaging (MRSI), Profusion imaging, functional magnetic resonance imaging (fMRI), near infrared spectroscopy (NIRS) and diffusion tensor imaging (DTI) along with tractography and connectomics. The second part provides a comprehensive overview of different multimodality imaging techniques for various cognitive neuroscience studies of aging brain.