Sex-Related Differences in Brain Volumes and Cerebral Blood Flow Among Overweight and Obese Adults With Type 2 Diabetes: Exploratory Analyses From the Action for Health in Diabetes Brain Magnetic Resonance Imaging Study

Non-invasive in vivo measurements of metabolic alterations in the type 2 diabetic brain by 1H magnetic resonance spectroscopy

Type 2 diabetes (T2D) is a complex chronic metabolic disorder characterized by hyperglycemia because of insulin resistance. Diabetes with chronic hyperglycemia may alter brain metabolism, including brain glucose and neurotransmitter levels; however, detailed, longitudinal studies of metabolic alterations in T2D are lacking. To shed insight, here, we characterized the consequences of poorly controlled hyperglycemia on neurochemical profiles that reflect metabolic alterations of the brain in both humans and animal models of T2D. Using in vivo 1H magnetic resonance spectroscopy, we quantified 12 metabolites cross-sectionally in T2D patients and 20 metabolites longitudinally in T2D db/db mice versus db+ controls. We found significantly elevated brain glucose (91%, p < 0.001), taurine (22%, p = 0.02), glucose+taurine (56%, p < 0.001), myo-inositol (12%, p = 0.02), and choline-containing compounds (10%, p = 0.01) in T2D patients versus age- and sex-matched controls, findings consistent with measures in T2D db/db versus control db+ littermates. In mice, hippocampal and striatal neurochemical alterations in brain glucose, ascorbate, creatine, phosphocreatine, γ-aminobutyric acid, glutamate, glutamine, glutathione, glycerophosphoryl-choline, lactate, myo-inositol, and taurine persisted in db/db mice with chronic disease progression from 16 to 48 weeks of age, which were distinct from control db+ mice. Overall, our study demonstrates the utility of 1H magnetic resonance spectroscopy as a non-invasive tool for characterizing and monitoring brain metabolic changes with T2D progression.

Sex Specific Associations of Sex hormone With Brain Volumes and Cerebral Blood Flow: A Cross Sectional Observational Study Within the Look AHEAD Type 2 Diabetes Cohort

Background

Females have greater brain volume and cerebral blood flow than males when controlling for intracranial volume and age. Brain volume decreases after menopause, suggesting a role of sex hormones. We studied the association of sex hormones with brain volume, white matter hyperintensity volumes and cerebral blood flow in people with Type 2 Diabetes and with overweight and obesity conditions that accelerate brain atrophy.

Methods

We analyzed data from 215 participants with overweight or obesity and Type 2 Diabetes from the Look AHEAD Brain Magnetic Resonance Imaging ancillary study (mean age 68 years, 73% postmenopausal female). Estradiol and total testosterone levels were measured with electrochemoluminescence assays. The ratio of brain measurements to intracranial volume was analyzed to account for body size. We analyzed sex hormones as quantitative measures in males, whereas in females we grouped those with detectable vs. undetectable hormone levels (Estradiol <73 pmol/L [20 pg/mL]: 79%; Total Testosterone < 0.07 mmol/L [0.02 ng/mL]: 37% undetectable in females).

Results

Females with detectable total testosterone levels had higher brain volume to intracranial volume ratio (median [25th, 75th percentile]: 0.85 [0.84, 0.86]) as compared to those with undetectable Total Testosterone levels (0.84 [0.83, 0.86]; rank sum p=0.04). This association was attenuated after age and body mass index adjustment (p=0.08). Neither white matter hyperintensity volumes or cerebral blood flow in females, nor any brain measures in males, were significantly associated with Estradiol or Total Testosterone.

Conclusions

In postmenopausal females with Type 2 Diabetes with overweight and obesity, detectable levels of total testosterone were associated greater brain volume relative to intracranial volume, suggesting a protective role for testosterone in female brain health. Our findings are limited by a small sample size and low sensitivity of hormone assays. Our suggestive findings can be combined with future larger studies to assess clinically important differences.

Trial Registration

NCT00017953.

New Insights and Potential Therapeutic Interventions in Metabolic Diseases

Endocrine homeostasis and metabolic diseases have been the subject of extensive research in recent years. The development of new techniques and insights has led to a deeper understanding of the mechanisms underlying these conditions and opened up new avenues for diagnosis and treatment. In this review, we discussed the rise of metabolic diseases, especially in Western countries, the genetical, psychological, and behavioral basis of metabolic diseases, the role of nutrition and physical activity in the development of metabolic diseases, the role of single-cell transcriptomics, gut microbiota, epigenetics, advanced imaging techniques, and cell-based therapies in metabolic diseases. Finally, practical applications derived from this information are made.

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.

Hormonal factors moderate the associations between vascular risk factors and white matter hyperintensities

To examine the moderation effects of hormonal factors on the associations between vascular risk factors and white matter hyperintensities in men and women, separately. White matter hyperintensities were automatically segmented and quantified in the UK Biobank dataset (N = 18,294). Generalised linear models were applied to examine (1) the main effects of vascular and hormonal factors on white matter hyperintensities, and (2) the moderation effects of hormonal factors on the relationship between vascular risk factors and white matter hyperintensities volumes. In men with testosterone levels one standard deviation higher than the mean value, smoking was associated with 27.8% higher white matter hyperintensities volumes in the whole brain. In women with a shorter post-menopause duration (one standard deviation below the mean), diabetes and higher pulse wave velocity were associated with 28.8% and 2.0% more deep white matter hyperintensities, respectively. These findings highlighted the importance of considering hormonal risk factors in the prevention and management of white matter hyperintensities.

Changes of brain function in patients with type 2 diabetes mellitus measured by different analysis methods: A new coordinate-based meta-analysis of neuroimaging

Objective

Neuroimaging meta-analysis identified abnormal neural activity alterations in patients with type 2 diabetes mellitus (T2DM), but there was no consistency or heterogeneity analysis between different brain imaging processing strategies. The aim of this meta-analysis was to determine consistent changes of regional brain functions in T2DM via the indicators obtained by using different post-processing methods.

Methods

Since the indicators obtained using varied post-processing methods reflect different neurophysiological and pathological characteristics, we further conducted a coordinate-based meta-analysis (CBMA) of the two categories of neuroimaging literature, which were grouped according to similar data processing methods: one group included regional homogeneity (ReHo), independent component analysis (ICA), and degree centrality (DC) studies, while the other group summarized the literature on amplitude of low-frequency fluctuation (ALFF) and cerebral blood flow (CBF).

Results

The final meta-analysis included 23 eligible trials with 27 data sets. Compared with the healthy control group, when neuroimaging studies were combined with ReHo, ICA, and DC measurements, the brain activity of the right Rolandic operculum, right supramarginal gyrus, and right superior temporal gyrus in T2DM patients decreased significantly. When neuroimaging studies were combined with ALFF and CBF measurements, there was no clear evidence of differences in the brain function between T2DM and HCs.

Conclusion

T2DM patients have a series of spontaneous abnormal brain activities, mainly involving brain regions related to learning, memory, and emotion, which provide early biomarkers for clarifying the mechanism of cognitive impairment and neuropsychiatric disorders in diabetes.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=247071, PROSPERO [CRD42021247071].

A scoping review of resting-state brain functional alterations in Type 2 diabetes

Resting-state functional magnetic resonance imaging (rs-fMRI) has been actively used in the last decade to investigate brain functional connectivity alterations in Type 2 Diabetes Mellitus (T2DM) to understand the neuropathophysiology of T2DM in cognitive degeneration. Given the emergence of new analysis techniques, this scoping review aims to map the rs-fMRI analysis techniques that have been applied in the literature and reports the latest rs-fMRI findings that have not been covered in previous reviews. Graph theory, the contemporary rs-fMRI analysis, has been used to demonstrate altered brain topological organisations in people with T2DM, which included altered degree centrality, functional connectivity strength, the small-world architecture and network-based statistics. These alterations were correlated with T2DM patients' cognitive performances. Graph theory also contributes to identify unbiased seeds for seed-based analysis. The expanding rs-fMRI analytical approaches continue to provide new evidence that helps to understand the mechanisms of T2DM-related cognitive degeneration.

Cerebrovascular Function, Vascular Risk, and Lifestyle Patterns in Resistant Hypertension

BACKGROUND

Impaired cerebrovascular reactivity (CVR) and blunted cerebral hemodynamic recruitment are thought to be important mechanisms linking hypertension to cerebrovascular and cognitive outcomes. Few studies have examined cardiovascular or dietary correlates of CVR among hypertensives.

OBJECTIVE

To delineate associations between cardiometabolic risk, diet, and cerebrovascular functioning among individuals with resistant hypertension from the TRIUMPH trial (n = 140).

METHODS

CVR was assessed by examining changes in tissue oxygenation (tissue oxygenation index [TOI] and oxygenated hemoglobin [HBO2]) using functional near-infrared spectroscopy (fNIRS) during a breath holding test, a standardized CVR assessment to elicit a hypercapnic response. Participants also underwent fNIRS during three cognitive challenge tasks. Vascular function was assessed by measurement of brachial artery flow mediated dilation and hyperemic flow response. Cardiometabolic fitness was assessed from peak VO2 on an exercise treadmill test and body mass index. Dietary patterns were quantified using the DASH eating score. Cognitive function was assessed using a 45-minute test battery assessing Executive Function, Processing Speed, and Memory.

RESULTS

Greater levels fitness (B = 0.30, p = 0.011), DASH compliance (B = 0.19, p = 0.045), and lower obesity (B = -0.30, p = 0.004), associated with greater changes in TOI, whereas greater flow-mediated dilation (B = 0.19, p = 0.031) and lower stroke risk (B = -0.19, p = 0.049) associated with greater HBO2. Similar associations were found for cerebral hemodynamic recruitment, and associations between CVR and cognition were moderated by duration of hypertension.

CONCLUSION

Impaired CVR elevated cardiometabolic risk, obesity, vascular function, and fitness among hypertensives.

Multimodal brain imaging effect of "Adjust Zang-fu and Arouse Spirit" electroacupuncture on diabetic cognitive impairment: study protocol of a randomized, sham-controlled pilot trial

BACKGROUND

Diabetic cognitive impairment (DCI) is a serious chronic complication caused by diabetes. The pathogenesis of DCI is complex, but brain nerve injury and brain nerve cell apoptosis are important pathological changes. Multimodal brain imaging is one of the most important techniques to study the neural mechanism of the brain. For the clinical treatment of DCI, there is no effective targeted Western medicine and a lack of clear drug intervention methods. Therefore, there is an urgent need to find effective complementary and alternative methods and clarify their mechanism. This research seeks to explore the multimodal brain imaging effect of "Adjust Zang-fu and Arouse Spirit" electroacupuncture for DCI.

METHODS

This clinical research will be a randomized, sham-controlled pilot trial. Eligible participants will be randomly assigned to the intervention group (n = 60) and the control group (n = 30). The intervention group will be divided into the "Adjust Zang-fu and Arouse Spirit" electroacupuncture group (n = 30) and sham electroacupuncture group (n = 30). All participants will continue to receive routine hypoglycemic therapy. The treatment period is the same in both groups. The primary outcomes include functional magnetic resonance imaging (fMRI), magnetic resonance spectroscopy (MRS), Montreal Cognitive Assessment Scale (MoCA), and Clinical Dementia Rating (CDR). The secondary outcomes include blood glucose and blood lipid tests, Instrumental Activities of Daily Living Scale (IADL), Hachinski Ischemic Scale (HIS), Self-Rating Anxiety Scale (SAS), and Self-Rating Depression Scale (SDS). Outcomes will be assessed at baseline and before and after treatment, and adverse events will be examined. Inter- and intragroup analyses will be performed.

DISCUSSION

This randomized controlled study, combined with multimodal brain imaging techniques and a clinical evaluation scale, was designed to explore the mechanism of "Adjust Zang-fu and Arouse Spirit" electroacupuncture in improving the central nervous system in DCI.

TRIAL REGISTRATION

Chinese Clinical Trial Registration ChiCTR2000040268 . Registered on 26 November 2020.

Legacy of a 10-Year Multidomain Lifestyle Intervention on the Cognitive Trajectories of Individuals with Overweight/Obesity and Type 2 Diabetes Mellitus

INTRODUCTION

Weight loss and increased physical activity interventions are commonly recommended for individuals with type 2 diabetes (T2D) and overweight or obesity. We examined the impact of randomization to an intensive lifestyle intervention (ILI) on trajectories of cognitive function over 10 years in a cohort of participants in a randomized clinical trial who had T2D and overweight/obesity at baseline.

METHODS

Participants aged 45-76 years were enrolled in 2001-2004 and were randomized to the ILI or a diabetes support and education (DSE) condition. Cognitive function was assessed in 3,938 participants at up to 4 time points 8-18 years after randomization. General linear mixed effects models examined cognitive trajectories over time. Subgroup analyses focused on sex, individuals with baseline body mass index >30, those carrying the APOE ε4 allele, and those with a baseline history of cardiovascular disease (CVD).

RESULTS

Overall, there were no differences in the rate of cognitive decline by intervention arm. Subgroup analyses showed that participants who had a baseline history of CVD and were randomized to the ILI arm of the study performed significantly worse on the Stroop Color Word Test than those in the DSE arm.

DISCUSSION/CONCLUSIONS

The ILI did not result in preserved cognitive function or slower rates of cognitive decline in this cohort of individuals who had T2D and were overweight or obese at baseline.

A multimodal meta-analysis of regional structural and functional brain alterations in type 2 diabetes

Neuroimaging studies have identified brain structural and functional alterations of type 2 diabetes mellitus (T2DM) patients; however, there is no systematic information on the relations between abnormalities in these two domains. We conducted a multimodal meta-analysis of voxel-based morphometry and regional resting-state functional MRI studies in T2DM, including fifteen structural datasets (693 patients and 684 controls) and sixteen functional datasets (378 patients and 358 controls). We found, in patients with T2DM compared to controls, conjoint decreased regional gray matter volume (GMV) and altered intrinsic activity mainly in the default mode network including bilateral superior temporal gyrus/Rolandic operculum, left middle and inferior temporal gyrus, and left supramarginal gyrus; decreased GMV alone in the limbic system; and functional abnormalities alone in the cerebellum, insula, and visual cortex. This meta-analysis identified complicated patterns of conjoint and dissociated brain alterations in T2DM patients, which may help provide new insight into the neuropathology of T2DM.

Cerebral perfusion alterations in type 2 diabetes mellitus - a systematic review

Type 2 diabetes mellitus (T2DM) is related to abnormal brain structure and function, increasing the risk of cognitive impairment and dementia. We systematically reviewed the published literature focusing on cerebral perfusion in patients with T2DM. Although no significant difference was found in global cerebral blood flow (CBF) between the T2DM group and the healthy control group, the regional cerebral perfusion in T2DM was significantly reduced in multiple locations, including the occipital lobe, domains involved in the default mode network and the cerebellum. The decline in regional CBF was associated with a wide range of cognitive disorders in T2DM, including learning, memory, attention, and executive processing, as well as visual function. In addition, diabetes-related biochemical indicators, such as glycated hemoglobin and insulin resistance, were negatively correlated with regional CBF. In general, these functional perfusion imaging studies indicate that decreased CBF in T2DM may be a potential cause of cognitive impairment.

Sex-related differences in cognitive trajectories in older individuals with type 2 diabetes and overweight or obesity

INTRODUCTION

It is unknown whether rates of cognitive decline differ between older women and men with type 2 diabetes (T2D) and overweight or obesity.

METHODS

Two to four cognitive assessments were obtained across up to 10 years from 2799 adults (mean age 68 years; 62% women) with T2D who had been enrolled in a clinical trial of weight loss intervention. Sex-related differences in means and rates of decline of cognitive scores were assessed.

RESULTS

Women outperformed men in verbal learning and processing speed (P < 0.001), but not executive function (P = 0.22). The rates of decline over time for women and men were similar (P ≥  0.10); however women, but not men, with apolipoprotein E (APOE) ε4 alleles had steeper declines in verbal learning (P = 0.02) and processing speed (P = 0.007) than those without these alleles.

DISCUSSION

Cognitive advantages for women with T2D and overweight/obesity over men are preserved as they age; however, these are eroded by the APOE ε4 genotype.

The influence of obesity on cerebral blood flow in young adults using arterial spin labeling MRI

Obesity causes damage to several organs, including the brain. Recent studies have been focusing on understanding the mechanisms through which obesity affects brain structure and function using neuroimaging techniques. A functional biomarker, such as cerebral blood flow (CBF), is a powerful tool that can be used to explore neural dysfunction. However, there is currently limited information regarding the association between CBF and obesity. The study was conducted to investigate the potential effect of obesity on brain perfusion in a young cohort aged 20-30 years. A total of 21 obese (body mass index (BMI) > 26 kg/m² ) and 21 lean (BMI < 24 kg/m² ) right-handed volunteers were included in this study. CBF was acquired using the 2D single post-labeling delay (PLD) arterial spin labeling (ASL) technique on a 3 T MRI scanner. A multiple regression analysis was performed to examine the difference in global and regional gray matter (GM) CBF between the groups. CBF value was assigned as the dependent variable, whereas age, sex, and group (obese or lean) were considered as the independent variables. Results showed that group-related differences in CBF were homogeneous across brain regions, as obese subjects had significantly lower global GM CBF than lean subjects (P < 0.05). In the voxelwise analysis, obese individuals had significantly lower CBF in the left pulvinar of the thalamus and visual association areas, including Brodmann area (BA) 7, BA18, and BA19, than lean subjects. Although the signal-to-noise ratio was slightly compromised for 2D sequences and subject-specific arterial transit time was not estimated due to a single PLD sequence, this study demonstrated alterations in CBF in obese subjects, particularly in regions of the pulvinar of the thalamus and its synchronously related areas such as visual association areas. These results suggest that ASL provides a potential platform for further obesity-related research.

TREM-2-p38 MAPK signaling regulates neuroinflammation during chronic cerebral hypoperfusion combined with diabetes mellitus

Background

Diabetes mellitus (DM) and chronic cerebral hypoperfusion(CCH)are both risk factors for cognitive impairment. However, whether DM and CCH can synergistically promote cognitive impairment and the related pathological mechanisms remain unknown.

Methods

To investigate the effect of DM and CCH on cognitive function, rats fed with high-fat diet (HFD) and injected with low-dose streptozotocin (STZ) followed by bilateral common carotid artery occlusion (BCCAO) were induced to mimic DM and CCH in vivo and mouse BV2 microglial cells were exposed to hypoxia and/or high glucose to mimic CCH complicated with DM pathologies in vitro. To further explore the underlying mechanism, TREM-2-specific small interfering RNA and TREM-2 overexpression lentivirus were used to knock out and overexpress TREM-2, respectively.

Results

Cognitive deficits, neuronal cell death, neuroinflammation with microglial activation, and TREM-2-MAPK signaling were enhanced when DM was superimposed on CCH both in vivo and in vitro. Manipulating TREM-2 expression levels markedly regulated the p38 MAPK signaling and the inflammatory response in vitro. TREM-2 knockout intensified while TREM-2 overexpression suppressed the p38 MAPK signaling and subsequent pro-inflammatory mediator production under high glucose and hypoxia condition.

Conclusions

These results suggest that TREM-2 negatively regulates p38 MAPK-mediated inflammatory response when DM was synergistically superimposed on CCH and highlight the importance of TREM-2 as a potential target of immune regulation in DM and CCH.