Visceral adiposity predicts subclinical white matter hyperintensities in middle-aged adults

Visceral adiposity is associated with iron deposition and myelin loss in the brains of aged mice

Iron deposition and myelin loss are observed in the brain with aging, and iron accumulation is suggested to be involved in myelin damage. However, the exact mechanism of iron deposition with aging remains unclear. This study was aimed to determine whether expanded visceral adipose tissue contributes to iron deposition and myelin loss by inducing hepcidin in the brains of aged male mice. Compared with young adult mice, levels of hepcidin in the brain, epididymal adipose tissue, and circulation were increased in aged mice, which had expanded visceral adipose tissue with inflammation. An increase in expressions of ferritin, an indicator of intracellular iron status, was accompanied by decreased levels of proteins related to myelin sheath in the brains of aged mice. These age-related changes in the brain were improved by visceral fat removal. In addition, IL-6 level, activation of microglia/macrophages, and nuclear translocation of phosphorylated Smad1/5 (pSmad1/5) inducing hepcidin expression were reduced in the brains of aged mice after visceral fat removal, accompanied by decreases of pSmad1/5- and ferritin-positive microglia/macrophages and mature oligodendrocytes. These findings indicate that visceral adiposity contributes to hepcidin-mediated iron deposition and myelin loss with inflammation in the aged brain. Our results support the importance of preventing visceral adiposity for maintaining brain health in older individuals.

Insulin resistance-related features are associated with cognitive decline: a cross-sectional study in adult patients with type 1 diabetes

BACKGROUND

To investigate the associations between insulin resistance (IR)-related features and cognitive function in type 1 diabetes (T1D).

METHODS

A total of 117 adult patients with T1D were recruited in this cross-sectional study. IR-related features include overweight/obesity/central obesity, hypertension, atherogenic dyslipidemia, and decreased estimated insulin sensitivity (eIS). The Wechsler Memory Scale-Chinese Revision, Wisconsin Card Sorting Test, and Sustained Attention to Response Task was used to assess memory, executive function and sustained attention, respectively. A z-score was generated from each test, and a composite measure of global cognitive performance was calculated by averaging the z-scores of all tests. Cognitive differences were measured between T1D patients with and without IR-related features. The associations between IR-related features and and cognitive performance were analyzed using: logistic regression, partial correlation, and multivariate linear regression analysis.

RESULTS

A total of 53 (45.3%) T1D patients were defined as having IR-related features. Individuals with IR-related features displayed worse overall cognitive scores compared to those without and had a 4-fold increase in the risk for having global cognitive z-score < 0. Among the IR-related features, higher triglyceride (TG) and lower eIS showed linear correlation with lower global cognitive performance. And the subsequent regression analysis identified eIS as the factor independently associated with global cognitive performance.

CONCLUSIONS

We have provided evidence linking IR-related features to deteriorated cognitive function in adult patients with T1D. And eIS showed an independent positive correlation with global cognitive performance. Although no causal relationship can be drawn, IR emerges as an important factor reflecting cognitive function.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03610984.

Cardiometabolic health across menopausal years is linked to white matter hyperintensities up to a decade later

Introduction

The menopause transition is associated with several cardiometabolic risk factors. Poor cardiometabolic health is further linked to microvascular brain lesions, which can be detected as white matter hyperintensities (WMHs) using T2-FLAIR magnetic resonance imaging (MRI) scans. Females show higher risk for WMHs post-menopause, but it remains unclear whether changes in cardiometabolic risk factors underlie menopause-related increase in brain pathology.

Methods

In this study, we assessed whether cross-sectional measures of cardiometabolic health, including body mass index (BMI) and waist-to-hip ratio (WHR), blood lipids, blood pressure, and long-term blood glucose (HbA1c), as well as longitudinal changes in BMI and WHR, differed according to menopausal status at baseline in 9,882 UK Biobank females (age range 40-70 years, n premenopausal = 3,529, n postmenopausal = 6,353). Furthermore, we examined whether these cardiometabolic factors were associated with WMH outcomes at the follow-up assessment, on average 8.78 years after baseline.

Results

Postmenopausal females showed higher levels of baseline blood lipids (HDL β  = 0.14, p < 0.001, LDL β  = 0.20, p < 0.001, triglycerides β  = 0.12, p < 0.001) and HbA1c (β  = 0.24, p < 0.001) compared to premenopausal women, beyond the effects of age. Over time, BMI increased more in the premenopausal compared to the postmenopausal group (β  = -0.08, p < 0.001), while WHR increased to a similar extent in both groups (β  = -0.03, p = 0.102). The change in WHR was however driven by increased waist circumference only in the premenopausal group. While the group level changes in BMI and WHR were in general small, these findings point to distinct anthropometric changes in pre- and postmenopausal females over time. Higher baseline measures of BMI, WHR, triglycerides, blood pressure, and HbA1c, as well as longitudinal increases in BMI and WHR, were associated with larger WMH volumes (β range = 0.03-0.13, p ≤ 0.002). HDL showed a significant inverse relationship with WMH volume (β  = -0.27, p < 0.001).

Discussion

Our findings emphasise the importance of monitoring cardiometabolic risk factors in females from midlife through the menopause transition and into the postmenopausal phase, to ensure improved cerebrovascular outcomes in later years.

Lower Body Mass Index at Baseline Is Related to Steeper Cognitive Decline in the Alzheimer's Disease Neuroimaging Initiative Cohort

OBJECTIVE

Midlife obesity is a risk factor for dementia, whereas obesity in older age may be protective of cognition, a phenomenon known as the "obesity paradox." The mechanisms underlying this phenomenon and the relationship between body mass index (BMI) and cognitive function over time remain unclear.

METHODS

In 1399 adults with and without mild cognitive impairment (median age 73.6 years) from the Alzheimer's Disease Neuroimaging Initiative, we modeled the effects of baseline BMI on within-person trajectories of cognitive decline using Latent Growth Curve Modeling. We also tested if the effects of BMI on cognitive decline are global or specific to memory, executive function, or language.

RESULTS

Higher baseline BMI was associated with better memory ( βBMI = 0.06, p < .05) and worse executive function ( βBMI = -0.05, p < .05) and not associated with language. Independent of baseline diagnosis, higher baseline BMI was associated with slower rate of decline in executive function, memory, and language ( βBMI = 0.13, 0.12, and 0.12, respectively; p < .01). Higher BMI was not associated with the intercept ( βBMI = 0.04, p = .059) or change ( βBMI = 0.04, p = .415) in a global cognitive factor.

CONCLUSIONS

We found that higher baseline BMI was associated with slower cognitive decline in participants with and without mild cognitive impairment diagnosis. Higher BMI in this context seems to be protective of cognitive function for people at risk for dementia. Our findings also support domain-specific effects of obesity on various cognitive functions rather than a final common pathway.

Assessment of correlation between conventional anthropometric and imaging-derived measures of body fat composition: a systematic literature review and meta-analysis of observational studies

BACKGROUND

In studies of the association of adiposity with disease risk, widely used anthropometric measures of adiposity (e.g. body-mass-index [BMI], waist circumference [WC], waist-hip ratio [WHR]) are simple and inexpensive to implement at scale. In contrast, imaging-based techniques (e.g. magnetic resonance imaging [MRI] and dual x-ray absorptiometry [DXA]) are expensive and labour intensive, but can provide more accurate quantification of body fat composition. There is, however, limited evidence about the relationship between conventional and imaging-derived measures of adiposity.

METHODS

We searched Scopus and Web of Science for published reports in English of conventional versus imaging-derived measurements of adiposity. We identified 42 articles (MRI = 22; DXA = 20) that met selection criteria, involving 42,556 (MRI = 15,130; DXA = 27,426) individuals recruited from community or hospital settings. Study-specific correlation coefficients (r) were transformed using Fisher's Z transformation, and meta-analysed to yield weighted average correlations, both overall and by ancestry, sex and age, where feasible. Publication bias was investigated using funnel plots and Egger's test.

RESULTS

Overall, 98% of participants were 18 + years old, 85% male and 95% White. BMI and WC were most strongly correlated with imaging-derived total abdominal (MRI-derived: r = 0.88-; DXA-derived: 0.50-0.86) and subcutaneous abdominal fat (MRI-derived: 0.83-0.85), but were less strongly correlated with visceral abdominal fat (MRI-derived: 0.76-0.79; DXA-derived: 0.80) and with DXA-derived %body fat (0.76). WHR was, at best, strongly correlated with imaging-derived total abdominal (MRI-derived: 0.60; DXA-derived: 0.13), and visceral abdominal fat (MRI-derived: 0.67; DXA-derived: 0.65), and moderately with subcutaneous abdominal (MRI-derived: 0.54), and with DXA-derived %body fat (0.58). All conventional adiposity measures were at best moderately correlated with hepatic fat (MRI-derived: 0.36-0.43). In general, correlations were stronger in women than in men, in Whites than in non-Whites, and in those aged 18 + years.

CONCLUSIONS

In this meta-analysis, BMI and WC, but not WHR, were very strongly correlated with imaging-derived total and subcutaneous abdominal fat. By comparison, all three measures were moderately or strongly correlated with imaging-based visceral abdominal fat, with WC showing the greatest correlation. No anthropometric measure was substantially correlated with hepatic fat. Further larger studies are needed to compare these measures within the same study population, and to assess their relevance for disease risks in diverse populations.

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.

A Potential Link Between Visceral Obesity and Risk of Alzheimer's Disease

Alzheimer's disease (AD) is the most common type of dementia characterized by the deposition of amyloid beta (Aβ) plaques and tau-neurofibrillary tangles in the brain. Visceral obesity (VO) is usually associated with low-grade inflammation due to higher expression of pro-inflammatory cytokines by adipose tissue. The objective of the present review was to evaluate the potential link between VO and the development of AD. Tissue hypoxia in obesity promotes tissue injury, production of adipocytokines, and release of pro-inflammatory cytokines leading to an oxidative-inflammatory loop with induction of insulin resistance. Importantly, brain insulin signaling is involved in the pathogenesis of AD and lower cognitive function. Obesity and enlargement of visceral adipose tissue are associated with the deposition of Aβ. All of this is consonant with VO increasing the risk of AD through the dysregulation of adipocytokines which affect the development of AD. The activated nuclear factor kappa B (NF-κB) pathway in VO might be a potential link in the development of AD. Likewise, the higher concentration of advanced glycation end-products in VO could be implicated in the pathogenesis of AD. Taken together, different inflammatory signaling pathways are activated in VO that all have a negative impact on the cognitive function and progression of AD except hypoxia-inducible factor 1 which has beneficial and neuroprotective effects in mitigating the progression of AD. In addition, VO-mediated hypoadiponectinemia and leptin resistance may promote the progression of Aβ formation and tau phosphorylation with the development of AD. In conclusion, VO-induced AD is mainly mediated through the induction of oxidative stress, inflammatory changes, leptin resistance, and hypoadiponectinemia that collectively trigger Aβ formation and neuroinflammation. Thus, early recognition of VO by visceral adiposity index with appropriate management could be a preventive measure against the development of AD in patients with VO.

Sharing Circulating Micro-RNAs between Osteoporosis and Sarcopenia: A Systematic Review

Background: Osteosarcopenia, a combination of osteopenia/osteoporosis and sarcopenia, is a common condition among older adults. While numerous studies and meta-analyses have been conducted on osteoporosis biomarkers, biomarker utility in osteosarcopenia still lacks evidence. Here, we carried out a systematic review to explore and analyze the potential clinical of circulating microRNAs (miRs) shared between osteoporosis/osteopenia and sarcopenia. Methods: We performed a systematic review on PubMed, Scopus, and Embase for differentially expressed miRs (p-value < 0.05) in (i) osteoporosis and (ii) sarcopenia. Following screening for title and abstract and deduplication, 83 studies on osteoporosis and 11 on sarcopenia were identified for full-text screening. Full-text screening identified 54 studies on osteoporosis, 4 on sarcopenia, and 1 on both osteoporosis and sarcopenia. Results: A total of 69 miRs were identified for osteoporosis and 14 for sarcopenia. There were 9 shared miRs, with evidence of dysregulation (up- or down-regulation), in both osteoporosis and sarcopenia: miR-23a-3p, miR-29a, miR-93, miR-133a and b, miR-155, miR-206, miR-208, miR-222, and miR-328, with functions and targets implicated in the pathogenesis of osteosarcopenia. However, there was little agreement in the results across studies and insufficient data for miRs in sarcopenia, and only three miRs, miR-155, miR-206, and miR-328, showed the same direction of dysregulation (down-regulation) in both osteoporosis and sarcopenia. Additionally, for most identified miRs there has been no replication by more than one study, and this is particularly true for all miRs analyzed in sarcopenia. The study quality was typically rated intermediate/high risk of bias. The large heterogeneity of the studies made it impossible to perform a meta-analysis. Conclusions: The findings of this review are particularly novel, as miRs have not yet been explored in the context of osteosarcopenia. The dysregulation of miRs identified in this review may provide important clues to better understand the pathogenesis of osteosarcopenia, while also laying the foundations for further studies to lead to effective screening, monitoring, or treatment strategies.

Bidirectional communication between brain and visceral white adipose tissue: Its potential impact on Alzheimer's disease

A variety of axes between brain and abdominal organs have been reported, but the interaction between brain and visceral white adipose tissue (vWAT) remains unclear. In this review, we summarized human studies on the association between brain and vWAT, and generalized their interaction and the underlying mechanisms according to animal and cell experiments. On that basis, we come up with the concept of the brain-vWAT axis (BVA). Furthermore, we analyzed the potential mechanisms of involvement of BVA in the pathogenesis of Alzheimer's disease (AD), including vWAT-derived fatty acids, immunological properties of vWAT, vWAT-derived retinoic acid and vWAT-regulated insulin resistance. The proposal of BVA may expand our understanding to some extent of how the vWAT impacts on brain health and diseases, and provide a novel approach to study the pathogenesis and treatment strategies of neurodegenerative disorders.

Associations between abdominal adipose tissue, reproductive span, and brain characteristics in post-menopausal women

The menopause transition involves changes in oestrogens and adipose tissue distribution, which may influence female brain health post-menopause. Although increased central fat accumulation is linked to risk of cardiometabolic diseases, adipose tissue also serves as the primary biosynthesis site of oestrogens post-menopause. It is unclear whether different types of adipose tissue play diverging roles in female brain health post-menopause, and whether this depends on lifetime oestrogen exposure, which can have lasting effects on the brain and body even after menopause. Using the UK Biobank sample, we investigated associations between brain characteristics and visceral adipose tissue (VAT) and abdominal subcutaneous adipose tissue (ASAT) in 10,251 post-menopausal females, and assessed whether the relationships varied depending on length of reproductive span (age at menarche to age at menopause). To parse the effects of common genetic variation, we computed polygenic scores for reproductive span. The results showed that higher VAT and ASAT were both associated with higher grey and white matter brain age, and greater white matter hyperintensity load. The associations varied positively with reproductive span, indicating more prominent associations between adipose tissue and brain measures in females with a longer reproductive span. The effects were in general small, but could not be fully explained by genetic variation or relevant confounders. Our findings indicate that associations between abdominal adipose tissue and brain health post-menopause may partly depend on individual differences in cumulative oestrogen exposure during reproductive years, emphasising the complexity of neural and endocrine ageing processes in females.

Gut Microbiome, Inflammation, and Cerebrovascular Function: Link Between Obesity and Cognition

Obesity affects 13% of the adult population worldwide and this number is only expected to increase. Obesity is known to have a negative impact on cardiovascular and metabolic health, but it also impacts brain structure and function; it is associated with both gray and white matter integrity loss, as well as decreased cognitive function, including the domains of executive function, memory, inhibition, and language. Especially midlife obesity is associated with both cognitive impairment and an increased risk of developing dementia at later age. However, underlying mechanisms are not yet fully revealed. Here, we review recent literature (published between 2010 and March 2021) and discuss the effects of obesity on brain structure and cognition, with a main focus on the contributions of the gut microbiome, white adipose tissue (WAT), inflammation, and cerebrovascular function. Obesity-associated changes in gut microbiota composition may cause increased gut permeability and inflammation, therewith affecting cognitive function. Moreover, excess of WAT in obesity produces pro-inflammatory adipokines, leading to a low grade systemic peripheral inflammation, which is associated with decreased cognition. The blood-brain barrier also shows increased permeability, allowing among others, peripheral pro-inflammatory markers to access the brain, leading to neuroinflammation, especially in the hypothalamus, hippocampus and amygdala. Altogether, the interaction between the gut microbiota, WAT inflammation, and cerebrovascular integrity plays a significant role in the link between obesity and cognition. Future research should focus more on the interplay between gut microbiota, WAT, inflammation and cerebrovascular function to obtain a better understanding about the complex link between obesity and cognitive function in order to develop preventatives and personalized treatments.

Relationship between obesity and structural brain abnormality: Accumulated evidence from observational studies

We aimed to evaluate the relationship between obesity and structural brain abnormalities assessed by magnetic resonance imaging using data from 45 observational epidemiological studies, where five articles reported prospective longitudinal results. In cross-sectional studies' analyses, the pooled weighted mean difference for total brain volume (TBV) and gray matter volume (GMV) in obese/overweight participants was -11.59 (95 % CI: -23.17 to -0.02) and -10.98 (95 % CI: -20.78 to -1.18), respectively. TBV was adversely associated with BMI and WC, GMV with BMI, and hippocampal volume with BMI, WC, and WHR. WC/WHR are associated with a risk of lacunar and white matter hyperintensity (WMH). In longitudinal studies' analyses, BMI was not statistically associated with the overall structural brain abnormalities (for continuous BMI: RR = 1.02, 95 % CI: 0.94-1.12; for categorial BMI: RR = 1.18, 95 % CI: 0.75-1.85). Small sample size of prospective longitudinal studies limited the power of its pooled estimates. A higher BMI is associated with lower brain volume while greater WC/WHR, but not BMI, is related to a risk of lacunar infarct and WMH. Future longitudinal research is needed to further elucidate the specific causal relationships and explore preventive measures.

Serum concentrations of oxytocin, DHEA and follistatin are associated with osteoporosis or sarcopenia in community-dwelling postmenopausal women

Background

Osteoporosis and sarcopenia are major health issues in postmenopausal women due to their high prevalence and association with several adverse outcomes. However, no biomarkers may be used for screening and diagnosis. The current study investigated potential biomarkers for osteoporosis and/or sarcopenia in postmenopausal women.

Methods

A cross-sectional study on 478 healthy community-dwelling postmenopausal women aged 50–90 years was performed. Osteoporosis and sarcopenia were defined according to the World Health Organization (WHO) and Asian Working Group for Sarcopenia (AWGS).

Results

Dehydroepiandrosterone (DHEA) was related to muscle strength (β = 0.19, p = 0.041) and function (β = 0.58, p = 0.004). Follistatin (β = − 0.27, p = 0.01) was related to muscle mass. Oxytocin (β = 0.59, p = 0.044) and DHEA (β = 0.51, p = 0.017) were related to bone mass. After adjusting for age, oxytocin (odds ratio (OR) 0.75; 95% confidence intervals (CI) 0.63–0.98; p = 0.019) was associated with osteoporosis, and DHEA (OR 0.73; 95% CI 0.51–0.96; p = 0.032) and follistatin (OR 1.66; 95% CI 1.19–3.57; p = 0.022) were associated with sarcopenia.

Conclusions

Postmenopausal women with sarcopenia were more likely to have lower DHEA levels and higher follistatin levels, and postmenopausal women with osteoporosis were more likely to have lower oxytocin levels.

Obesity and Race May Explain Differential Burden of White Matter Hyperintensity Load

OBJECTIVE

Compared to European Americans, research indicates that African Americans have higher white matter hyperintensity (WMH) load; however, the clinical and biological bases underlying this higher burden are poorly understood. We hypothesize that obesity may explain differences in WMH between African and European Americans.

METHODS

Participants enrolled in longitudinal brain aging studies (n=292; 61% Female; 92% European American; mean age=69.6±7.7) completed evaluations including medical exams, neuroimaging, and sociodemographic surveys. Overweight/obese status defined as body mass index ≥30 kg/m2, and WMH load, captured by FLAIR images, as sum of deep and periventricular volumes, scored using the Fazekas scale (0-6), WMH≥4 considered high.

RESULTS

Logistic regression analyses, adjusted for age, sex, hypertension, and smoking history, indicated that age and interaction between race and obesity were significant predictors of WMH, demonstrating that obesity significantly moderated the relationship between race and WMH. Age independently increased the odds of high WMH by 16% (OR=1.16, 95% CI=1.09-1.23, p<0.001). Stratified analysis indicates that older European Americans had increased WMH (OR=1.17, 95% CI=1.09-1.23, p<0.001), while obese African Americans had increased WMH (OR=27.65, 95% CI=1.47-519.13, p<0.05). In a case controlled subgroup matched by age, sex, and education (n=48), African Americans had significantly higher WMH load (27% vs 4%, Χ 2=5.3, p=0.02).

CONCLUSION

Results denote that age predicted WMH among European Americans, while obesity predicted WMH among African Americans. Matched sample analyses indicate that obesity increases the odds of WMH, though more pronounced in African Americans. These findings suggest that obesity may explain the differential burden of white matter hyperintensity load, signifying public health and clinical importance.

Network Modeling Sex Differences in Brain Integrity and Metabolic Health

Hypothesis-driven studies have demonstrated that sex moderates many of the relationships between brain health and cardiometabolic disease, which impacts risk for later-life cognitive decline. In the present study, we sought to further our understanding of the associations between multiple markers of brain integrity and cardiovascular risk in a midlife sample of 266 individuals by using network analysis, a technique specifically designed to examine complex associations among multiple systems at once. Separate network models were constructed for male and female participants to investigate sex differences in the biomarkers of interest, selected based on evidence linking them with risk for late-life cognitive decline: all components of metabolic syndrome (obesity, hypertension, dyslipidemia, and hyperglycemia); neuroimaging-derived brain-predicted age minus chronological age; ratio of white matter hyperintensities to whole brain volume; seed-based resting state functional connectivity in the Default Mode Network, and ratios of N-acetyl aspartate, glutamate and myo-inositol to creatine, measured through proton magnetic resonance spectroscopy. Males had a sparse network (87.2% edges = 0) relative to females (69.2% edges = 0), indicating fewer relationships between measures of cardiometabolic risk and brain integrity. The edges in the female network provide meaningful information about potential mechanisms between brain integrity and cardiometabolic health. Additionally, Apolipoprotein ϵ4 (ApoE ϵ4) status and waist circumference emerged as central nodes in the female model. Our study demonstrates that network analysis is a promising technique for examining relationships between risk factors for cognitive decline in a midlife population and that investigating sex differences may help optimize risk prediction and tailor individualized treatments in the future.

Central Obesity, Cardiometabolic Risk, and Cognitive Change in the Study of Latinos - Investigation of Neurocognitive Aging

BACKGROUND

The relationships between obesity and cognitive decline in aging are mixed and understudied among Hispanics/Latinos.

OBJECTIVE

To understand associations between central obesity, cognitive aging, and the role of concomitant cardiometabolic abnormalities among Hispanics/Latinos.

METHODS

Participants included 6,377 diverse Hispanics/Latinos enrolled in the Hispanic Community Health Study/Study of Latinos (HCHS/SOL) and SOL-Investigation for Neurocognitive Aging (SOL-INCA). Participants were 45 years and older at the first cognitive testing session (Visit 1). Cognitive outcomes (z-score units) included global composite and domain specific (learning, memory, executive functioning, processing speed) measures at a second visit (SOL-INCA, on average, 7 years later), and 7-year change. We used survey linear regression to examine associations between central obesity (waist circumference≥88 cm and≥102 cm for women and men, respectively) and cognition. We also tested whether the relationships between obesity and cognition differed by cardiometabolic status (indication of/treatment for 2 + of the following: high triglycerides, hypertension, hyperglycemia, low high-density lipoprotein cholesterol).

RESULTS

Central obesity was largely unassociated with cognitive outcomes, adjusting for covariates. However, among individuals with central obesity, cardiometabolic abnormality was linked to poorer cognitive function at SOL-INCA (ΔGlobalCognition =-0.165, p < 0.001) and to more pronounced cognitive declines over the average 7 years (ΔGlobalCognition = -0.109, p < 0.05); this was consistent across cognitive domains.

CONCLUSION

Central obesity alone was not associated with cognitive function. However, presence of both central obesity and cardiometabolic abnormalities was robustly predictive of cognition and 7-year cognitive declines, suggesting that in combination these factors may alter the cognitive trajectories of middle-aged and older Hispanics/Latinos.

Spatial distribution and cognitive impact of cerebrovascular risk-related white matter hyperintensities

OBJECTIVES

White matter hyperintensities (WMHs) are considered macroscale markers of cerebrovascular burden and are associated with increased risk of vascular cognitive impairment and dementia. However, the spatial location of WMHs has typically been considered in broad categories of periventricular versus deep white matter. The spatial distribution of WHMs associated with individual cerebrovascular risk factors (CVR), controlling for frequently comorbid risk factors, has not been systematically investigated at the population level in a healthy ageing cohort. Furthermore, there is an inconsistent relationship between total white matter hyperintensity load and cognition, which may be due to the confounding of several simultaneous risk factors in models based on smaller cohorts.

METHODS

We examined trends in individual CVR factors on total WMH burden in 13,680 individuals (aged 45-80) using data from the UK Biobank. We estimated the spatial distribution of white matter hyperintensities associated with each risk factor and their contribution to explaining total WMH load using voxel-wise probit regression and univariate linear regression. Finally, we explored the impact of CVR-related WMHs on speed of processing using regression and mediation analysis.

RESULTS

Contrary to the assumed dominance of hypertension as the biggest predictor of WMH burden, we show associations with a number of risk factors including diabetes, heavy smoking, APOE ε4/ε4 status and high waist-to-hip ratio of similar, or greater magnitude to hypertension. The spatial distribution of WMHs varied considerably with individual cerebrovascular risk factors. There were independent effects of visceral adiposity, as measured by waist-to-hip ratio, and carriage of the APOE ε4 allele in terms of the unique spatial distribution of CVR-related WMHs. Importantly, the relationship between total WMH load and speed of processing was mediated by waist-to-hip ratio suggesting cognitive consequences to WMHs associated with excessive visceral fat deposition.

CONCLUSION

Waist-to-hip ratio, diabetes, heavy smoking, hypercholesterolemia and homozygous APOE ε4 status are important risk factors, beyond hypertension, associated with WMH total burden and warrant careful control across ageing. The spatial distribution associated with different risk factors may provide important clues as to the pathogenesis and cognitive consequences of WMHs. High waist-to-hip ratio is a key risk factor associated with slowing in speed of processing. With global obesity levels rising, focused management of visceral adiposity may present a useful strategy for the mitigation of cognitive decline in ageing.

Increasing body mass index in an elderly cohort: Effects on the quantitative MR parameters of the brain

BACKGROUND

Body mass index (BMI) is increasing in a large number of elderly persons. This increase in BMI is known to put one at risk for many "diseases of aging," although less is known about how a change in BMI may affect the brains of the elderly.

PURPOSE

To investigate the relationship between BMI and quantitative water content, T₁ , T₂ *, and the semi-quantitative magnetization transfer ratio (MTR) of various structures in elderly brains.

STUDY TYPE

Cross-sectional.

SUBJECTS

Forty-two adults (BMI range: 19.1-33.5 kg/m² , age range: 58-80 years).

FIELD STRENGTH

3T MRI (two multi-echo gradient echoes, actual flip angle imaging, magnetization prepared rapid gradient echo, fluid attenuated inversion recovery).

ASSESSMENT

The 3D two-point method was used to derive (semi-)quantitative parameters in global white (WM) and gray matter (GM) and their regions as defined by the Johns Hopkins University and the Montreal Neurological Institute atlases.

STATISTICAL TESTS

Multivariate linear regression with BMI as principal regressor, corrected for the additional regressors age, gender, and glycated hemoglobin. Spearman correlation between quantitative parameters of the regions showing significant changes and the lipid spectra / C-reactive protein (CRP). Voxel-based morphometry and analysis of covariance (ANCOVA) to explore changes in the GM volume.

RESULTS

T₁ increased significantly (P < 0.05) in the frontal, temporal, and parietal cortices, while the bilateral corona radiata, right superior longitudinal fasciculus, as well as the corpus callosum showed significant changes in the WM regions. T₂ * increased significantly in the global WM and left corona radiata. Changes in MTR and the free water content did not reach significance. No significant correlation between any quantitative parameter and the lipid spectra or CRP could be identified.

DATA CONCLUSION

These results suggest that an elevated BMI predominantly affects T₁ in WM as well as GM structures in the elderly human brain.

LEVEL OF EVIDENCE

3 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2020;51:514-523.

Physical activity mitigates adverse effect of metabolic syndrome on vessels and brain

Metabolic syndrome (MetS) adversely affects the vasculature and cerebral white matter (CWM) integrity. Arterial stiffening has been associated with diminished CWM integrity. Physical activity (PA) can ameliorate components of MetS and subsequently affect arterial stiffening and CWM integrity. Our aim was to determine the role of PA on mitigating the adverse influence of MetS on arterial stiffness and CWM integrity. In a cross-sectional study design, sixty-six middle-aged adults (40-62 years) composed of 18 sedentary MetS (Sed MetS), 21 physically active MetS (Active MetS), and 27 healthy individuals absent of MetS risk factors were studied. Carotid artery stiffness was assessed via simultaneous ultrasound and tonometry. CWM integrity was measured using diffusion tensor imaging (DTI) through metrics of fractional anisotropy (FA) and mean diffusivity (MD). Carotid β-stiffness index in Active MetS was lower than Sed MetS but was not different from Healthy controls (6.6 ± 1.5, 7.7 ± 2.1, and 5.6 ± 1.6 au, p = 0.001). CWM integrity was significantly greater in Active MetS subjects compared to Sed MetS subjects but statistically equal to Healthy controls in the anterior limb of the internal capsule, and splenium of the corpus callosum, uncinate fasciculus, and superior corona radiata (all p < 0.05). Middle-aged individuals with MetS who habitually perform PA demonstrated lower arterial stiffness and more favorable CWM integrity than their sedentary peers, indicating that PA may be effective in mitigating the adverse effects of MetS on the vasculature and brain at midlife.

MRI adipose tissue and muscle composition analysis-a review of automation techniques

MRI is becoming more frequently used in studies involving measurements of adipose tissue and volume and composition of skeletal muscles. The large amount of data generated by MRI calls for automated analysis methods. This review article presents a summary of automated and semi-automated techniques published between 2013 and 2017. Technical aspects and clinical applications for MRI-based adipose tissue and muscle composition analysis are discussed based on recently published studies. The conclusion is that very few clinical studies have used highly automated analysis methods, despite the rapidly increasing use of MRI for body composition analysis. Possible reasons for this are that the availability of highly automated methods has been limited for non-imaging experts, and also that there is a limited number of studies investigating the reproducibility of automated methods for MRI-based body composition analysis.

Phenotypic heterogeneity of obesity-related brain vulnerability: one-size interventions will not fit all

Intact memory and problem solving are key to functional independence and quality of life in older age. Considering the unprecedented demographic shift toward a greater number of older adults than children in the United States in the next few decades, it is critically important for older adults to maintain work productivity and functional independence for as long as possible. Implementing early interventions focused on modifiable risk factors for cognitive decline at midlife is a strategy with the highest chance of success at present, bearing in mind the current lack of dementia cures. We present a selective, narrative review of evidence linking nutrition, body composition, vascular health, and brain function in midlife to highlight the phenotypic heterogeneity of obesity-related brain vulnerability and to endorse the development of individually tailored lifestyle modification plans for primary prevention of cognitive decline.

Association of neck circumference and cognitive impairment among Chinese elderly

OBJECTIVES

To investigate the association between neck circumference (NC) and cognitive impairment and interactions between relevant variables to the risk of cognitive impairment.

METHODS

A population-based survey was conducted among elderly inhabitants aged 60 years and over from a community in Shanghai suburb. Multivariate logistic regression analyses were performed to evaluate associations and log likelihood ratio tests to examine interactions.

RESULTS

Cognitive impairment was identified in 269 (10.8%) subjects from 2,500 participants. Higher BMI (OR = 1.55; 95% CI = 1.11-2.16), higher WHR (OR = 1.44; 95% CI = 1.07-1.95), and higher total cholesterol (TC) (OR = 1.52; 95% CI = 1.09-2.13) were significantly associated with the increased risk of cognitive impairment. Significant interactions were observed between TC and a few other relevant variables, respectively.

CONCLUSIONS

NC was associated with the high risk of cognitive impairment. Additive effects of NC with TC on cognitive impairment were observed.

White Matter Hyperintensity in Elderly Patients with Diabetes Mellitus Is Associated with Cognitive Impairment, Functional Disability, and a High Glycoalbumin/Glycohemoglobin Ratio

Aims: Although evidence has accumulated that white matter hyperintensity (WMH) is associated with the deterioration of cognitive function and impairment of activities of daily living (ADL), the clinical relevance of WMH in elderly patients with diabetes mellitus (DM) is not still clear. The aim of this study was to examine whether WMH volume is associated with ADL and cognitive function and whether glucose control and glucose variability can affect WMH volume in these patients.

Methods: This cross-sectional study investigated the associations of WMH with cognitive function and instrumental ADL (IADL), as well as metabolic and vascular risk factors in a total of 178 elderly patients with diabetes. The study assessed WMH volumes and the functional status of cognition and IADL. WMH volumes were evaluated by obtaining axial T2-weighted and fluid-attenuated inversion recovery sequence images on brain magnetic resonance imaging and assessing the images using Software for Neuro-Image Processing in Experimental Research.

Results: We found a significant association between WMH volumes and Mini-Mental State Examination (MMSE) scores (p = 0.039) and between WMH and IADL status (p = 0.006). Furthermore, we found significant relations of large WMH volumes with a high glycoalbumin/glycohemoglobin ratio (GA/HbA1c) (p < 0.001). Large WMH volumes were also found to be associated with a low body mass index (p = 0.014) and a low diastolic blood pressure (p = 0.024), but not with HbA1c. Multiple regression analysis showed that high GA/HbA1c, which reflects high glucose variability, was a significant determining factor for large WMH volumes. We also found that GA/HbA1c was negatively associated with both MMSE (p = 0.036) and IADL (p < 0.001).

Conclusion: GA/HbA1c, which is a marker of glucose variability, was independently associated with WMH volumes, which could lead to the decline of cognition and IADL in elderly patients with DM.

Body-Brain Connections: The Effects of Obesity and Behavioral Interventions on Neurocognitive Aging

Obesity is a growing public health problem in the United States, particularly in middle-aged and older adults. Although the key factors leading to a population increase in body weight are still under investigation, there is evidence that certain behavioral interventions can mitigate the negative cognitive and brain ("neurocognitive") health consequences of obesity. The two primary behaviors most often targeted for weight loss are caloric intake and physical activity. These behaviors might have independent, as well as overlapping/synergistic effects on neurocognitive health. To date obesity is often described independently from behavioral interventions in regards to neurocognitive outcomes, yet there is conceptual and mechanistic overlap between these constructs. This review summarizes evidence linking obesity and modifiable behaviors, such as physical activity and diet, with brain morphology (e.g., gray and white matter volume and integrity), brain function (e.g., functional activation and connectivity), and cognitive function across the adult lifespan. In particular, we review evidence bearing on the following question: Are associations between obesity and brain health in aging adults modifiable by behavioral interventions?