Adiposity and Alzheimer's disease

Lean-to-fat tissue ratio as a risk factor for cognitive impairment in patients undergoing maintenance hemodialysis

OBJECTIVE

The relationship between body mass index (BMI) and cognitive impairment (CI) remains controversial, and no research has been done to explore the effect of lean-to-fat (L/F) tissue ratio on the risk of CI in patients undergoing maintenance hemodialysis (MHD) so far. This study aimed to explore the effect of L/F tissue ratio on the risk of incident CI in patients undergoing MHD.

METHODS

In this observational cohort study, 3356 patients were recruited and followed up for a median of 2 years. Global cognitive function was measured using Mini-Mental State Examination score. Lean tissue mass (LTM) and fat tissue mass (FTM) were analyzed using body composition monitor based on bioimpedance spectroscopy (BCM-BIS), and L/F tissue ratio was calculated by LTM divided by FTM. Hazard ratios (HRs) for incident CI were determined by Cox regression.

RESULTS

The median age of the cohort was 55 years, and 68.7% patients were less educated. During the follow-up period, 1249 patients (37.2%) experienced incident CI. Patients with lower L/F tissue ratios had significantly higher risks of CI (HR 1.51, 95% confidence interval 1.24-1.84; p < 0.001) than those with higher L/F tissue ratios. The association between L/F tissue ratio and incident CI persisted in all subgroups stratified by sex, age, education status, especially in older and less educated participants. Both in all our patients and subgroups, BMI and CI occurrence were not independently relevant.

CONCLUSION

The L/F tissue ratio rather than BMI was an independent risk factor of incident cognitive impairment in patients undergoing MHD.

Cerebral oxygenation and body mass index association with cognitive function in chronic kidney disease patients without dialysis: a longitudinal study

In chronic kidney disease (CKD) patients, the prevalence of cognitive impairment increases with CKD progression; however, longitudinal changes in cognitive performance remain controversial. Few reports have examined the association of cerebral oxygenation with cognitive function in longitudinal studies. In this study, 68 CKD patients were included. Cerebral regional oxygen saturation (rSO₂) was monitored. Cognitive function was evaluated using mini-mental state examination (MMSE) score. Clinical assessments were performed at study initiation and 1 year later. MMSE score was higher at second measurement than at study initiation (p = 0.022). Multivariable linear regression analysis showed that changes in MMSE were independently associated with changes in body mass index (BMI, standardized coefficient: 0.260) and cerebral rSO₂ (standardized coefficient: 0.345). This was based on clinical factors with p < 0.05 (changes in BMI, cerebral rSO₂, and serum albumin level) and the following confounding factors: changes in estimated glomerular filtration rate, hemoglobin level, proteinuria, salt and energy intake, age, presence of diabetes mellitus, history of comorbid cerebrovascular disease, and use of renin–angiotensin system blocker. Further studies with a larger sample size and longer observational period are needed to clarify whether maintaining BMI and cerebral oxygenation improve or prevent the deterioration of cognitive function.

Data-Driven Analyses of Longitudinal Hippocampal Imaging Trajectories: Discrimination and Biomarker Prediction of Change Classes

BACKGROUND

Hippocampal atrophy is a well-known biomarker of neurodegeneration, such as that observed in Alzheimer's disease (AD). Although distributions of hippocampal volume trajectories for asymptomatic individuals often reveal substantial heterogeneity, it is unclear whether interpretable trajectory classes can be objectively detected and used for prediction analyses.

OBJECTIVE

To detect and predict hippocampal trajectory classes in a computationally competitive context using established AD-related risk factors/biomarkers.

METHODS

We used biomarker/risk factor and longitudinal MRI data in asymptomatic adults from the AD Neuroimaging Initiative (n = 351; Mean = 75 years; 48.7% female). First, we applied latent class growth analyses to left (LHC) and right (RHC) hippocampal trajectory distributions to identify distinct classes. Second, using random forest analyses, we tested 38 multi-modal biomarkers/risk factors for their relative importance in discriminating the lower (potentially elevated atrophy risk) from the higher (potentially reduced risk) class.

RESULTS

For both LHC and RHC trajectory distribution analyses, we observed three distinct trajectory classes. Three biomarkers/risk factors predicted membership in LHC and RHC lower classes: male sex, higher education, and lower plasma Aβ1-42. Four additional factors selectively predicted membership in the lower LHC class: lower plasma tau and Aβ1-40, higher depressive symptomology, and lower body mass index.

CONCLUSION

Data-driven analyses of LHC and RHC trajectories detected three classes underlying the heterogeneous distributions. Machine learning analyses determined three common and four unique biomarkers/risk factors discriminating the higher and lower LHC/RHC classes. Our sequential analytic approach produced evidence that the dynamics of preclinical hippocampal trajectories can be predicted by AD-related biomarkers/risk factors from multiple modalities.

Association between Variations in Body Mass Index and Cognitive Function in Older Korean Adults

Background

Although several studies have assessed obesity and cognitive impairment, most of these studies focus on body mass index (BMI) and cognitive impairment. Therefore to better understand the importance of weight maintenance with aging, this study investigated the relationship between variations in weight and cognitive impairment using the Korean version of the Mini-Mental State Examination (K-MMSE) in individuals aged 45 years or older in Korea.

Methods

Data on 3,477 adults with normal cognitive function (K-MMSE ≥24) at baseline were acquired from the Korean Longitudinal Study of Aging (KLoSA) 2006-2016. The association between weight variability and risk of cognitive impairment was assessed using multiple logistic regression models. We also assessed weight variability and change in cognitive function over the 6-year follow-up using multiple linear regression.

Results

Overall, higher variations in BMI were associated with cognitive impairment. Patients in the quintile with the highest variation (Q5) in BMI (mean of BMI changes, 2.69) showed the greatest degree of cognitive impairments (adjusted odds ratio, 1.52; 95% confidence interval [CI], 1.08-2.14; P for trend=0.016). Furthermore, a higher frequency in the number of times (3 times) the patient’s body weight changed was associated with a lower cognitive function (adjusted odds ratio, 3.42; 95% CI, 1.67-7.03; P for trend<0.001).

Conclusion

In this nationally representative study, weight variability was associated with a higher risk of cognitive decline during mid- and late-life stages.

Association of body mass index with risk of cognitive impairment and dementia: A systematic review and meta-analysis of prospective studies

Controversies persist about the associations of body mass index (BMI) with risk of cognitive impairment and dementia. This study aimed to evaluate these associations from various aspects, in which Embase, PubMed and Cochrane databases were searched to identify prospective studies up to May 2019. Random-effects meta-analyses and dose-response meta-analysis were conducted, involving twenty-nine of 20,083 identified literatures. Meta-analysis showed that midlife underweight, obesity and late-life underweight conferred 1.39-, 1.31- and 1.64-fold excess risk for cognitive impairment and dementia, while late-life overweight and obesity conferred 21% and 25% reduced risk. In dose-response meta-analysis, all cause dementia (ACD), Alzheimer's disease (AD) and vascular dementia (VaD) risk in midlife was significantly elevated when BMI surpassed 29, 30 and 32 kg/m2. AD risk in late-life was decreased when BMI was under 27 kg/m2, while this protection for VaD was absent when BMI surpassed 39 kg/m2. Higher BMI produced opposite exerted opposite effects on dementia in mid- and late-age population. Firstly reported, a dose-response relationship further supports the guideline from the standpoint of dementia prevention.

Higher Body Mass Index Is Associated with Lower Cortical Amyloid-β Burden in Cognitively Normal Individuals in Late-Life

BACKGROUND

Both low and high body mass index (BMI) have been associated with an increased risk of dementia, including that caused by Alzheimer's disease (AD). Specifically, high middle-age BMI or a low late-age BMI has been considered a predictor for the development of AD dementia. Less studied is the relationship between BMI and AD pathology.

OBJECTIVE

We explored the association between BMI and cortical amyloid-β (Aβ) burden in cognitively normal participants that were either in mid-life (45-60 years) or late-life (>60).

METHODS

We analyzed cross-sectional baseline data from the Knight Alzheimer Disease Research Center (ADRC) at Washington University. Aβ pathology was measured in 373 individuals with Aβ PET imaging and was quantified using Centiloid units. We split the cohort into mid- and late-life groups for analyses (n = 96 and n = 277, respectively). We ran general linear regression models to predict Aβ levels from BMI while controlling for age, sex, years of education, and APOE4 status. Analyses were also conducted to test the interaction between BMI and APOE4 genotype and between BMI and sex.

RESULTS

Higher BMI was associated with lower cortical Aβ burden in late-life (β= -0.81, p = 0.0066), but no relationship was found in mid-life (β= 0.04, p > 0.5). The BMI×APOE4+ and BMI×male interaction terms were not significant in the mid-life (β= 0.28, p = 0.41; β= 0.64, p = 0.13) or the late-life (β= 0.17, p > 0.5; β= 0.50, p = 0.43) groups.

CONCLUSION

Higher late-life BMI is associated with lower cortical Aβ burden in cognitively normal individuals.

Visual-Constructional Ability in Individuals with Severe Obesity: Rey Complex Figure Test Accuracy and the Q-Score

The aims of this study were to investigate visual-construction and organizational strategy among individuals with severe obesity, as measured by the Rey Complex Figure Test (RCFT), and to examine the validity of the Q-score as a measure for the quality of performance on the RCFT. Ninety-six non-demented morbidly obese (MO) patients and 100 healthy controls (HC) completed the RCFT. Their performance was calculated by applying the standard scoring criteria. The quality of the copying process was evaluated per the directions of the Q-score scoring system. Results revealed that the MO did not perform significantly lower than the HC on Copy accuracy (mean difference −0.302, CI −1.374 to 0.769, p = 0.579). In contrast, the groups did statistically differ from each other, with MO performing poorer than the HC on the Q-score (mean −1.784, CI −3.237 to −0.331, p = 0.016) and the Unit points (mean −1.409, CI −2.291 to −0.528, p = 0.002), but not on the Order points score (mean −0.351, CI −0.994 to 0.293, p = 0.284). Differences on the Unit score and the Q-score were slightly reduced when adjusting for gender, age, and education. This study presents evidence supporting the presence of inefficiency in visuospatial constructional ability among MO patients. We believe we have found an indication that the Q-score captures a wider range of cognitive processes that are not described by traditional scoring methods. Rather than considering accuracy and placement of the different elements only, the Q-score focuses more on how the subject has approached the task.

Modeling the Relationships Among Late-Life Body Mass Index, Cerebrovascular Disease, and Alzheimer's Disease Neuropathology in an Autopsy Sample of 1,421 Subjects from the National Alzheimer's Coordinating Center Data Set

The relationship between late-life body mass index (BMI) and Alzheimer's disease (AD) is poorly understood due to the lack of research in samples with autopsy-confirmed AD neuropathology (ADNP). The role of cerebrovascular disease (CVD) in the interplay between late-life BMI and ADNP is unclear. We conducted a retrospective longitudinal investigation and used joint modeling of linear mixed effects to investigate causal relationships among repeated antemortem BMI measurements, CVD (quantified neuropathologically), and ADNP in an autopsy sample of subjects across the AD clinical continuum. The sample included 1,421 subjects from the National Alzheimer's Coordinating Center's Uniform Data Set and Neuropathology Data Set with diagnoses of normal cognition (NC; n = 234), mild cognitive impairment (MCI; n = 201), or AD dementia (n = 986). ADNP was defined as moderate to frequent neuritic plaques and Braak stageIII-VI. Ischemic Injury Scale (IIS) operationalized CVD. Joint modeling examined relationships among BMI, IIS, and ADNP in the overall sample and stratified by initial visit Clinical Dementia Rating score. Subject-specific random intercept for BMI was the predictor for ADNP due to minimal BMI change (p = 0.3028). Analyses controlling for demographic variables and APOE ɛ4 showed lower late-life BMI predicted increased odds of ADNP in the overall sample (p < 0.001), and in subjects with CDR of 0 (p = 0.0021) and 0.5 (p = 0.0012), but not ≥1.0 (p = 0.2012). Although higher IIS predicted greater odds of ADNP (p < 0.0001), BMI did not predict IIS (p = 0.2814). The current findings confirm lower late-life BMI confers increased odds for ADNP. Lower late-life BMI may be a preclinical indicator of underlying ADNP.

Amyloid precursor protein modulates macrophage phenotype and diet-dependent weight gain

It is well known that mutations in the gene coding for amyloid precursor protein are responsible for autosomal dominant forms of Alzheimer’s disease. Proteolytic processing of the protein leads to a number of metabolites including the amyloid beta peptide. Although brain amyloid precursor protein expression and amyloid beta production are associated with the pathophysiology of Alzheimer’s disease, it is clear that amyloid precursor protein is expressed in numerous cell types and tissues. Here we demonstrate that amyloid precursor protein is involved in regulating the phenotype of both adipocytes and peripheral macrophages and is required for high fat diet-dependent weight gain in mice. These data suggest that functions of this protein include modulation of the peripheral immune system and lipid metabolism. This biology may have relevance not only to the pathophysiology of Alzheimer’s disease but also diet-associated obesity.

Association Between Exercise Capacity and Late Onset of Dementia, Alzheimer Disease, and Cognitive Impairment

OBJECTIVE

To address the association between exercise capacity and the onset of dementia, Alzheimer disease, and cognitive impairment.

PATIENTS AND METHODS

For 6104 consecutive veteran patients (mean ± SD age: 59.2±11.4 years) referred for treadmill exercise testing, the combined end point of dementia, Alzheimer disease, and cognitive impairment was abstracted from the Veterans Affairs computerized patient record system.

RESULTS

After mean ± SD follow-up of 10.3±5.5 years, 353 patients (5.8%) developed the composite end point at a mean ± SD age of 76.7±10.3 years. After correction for confounders in multivariate Cox proportional hazards regression, higher age at exercise testing (hazard ratio [HR]=1.08; 95% CI, 1.07-1.09; P<.001), current smoking (HR=1.44; 95% CI, 1.08-1.93; P=.01), and exercise capacity (HR=0.92; 95% CI, 0.89-0.96; P<.001) emerged as predictors of cognitive impairment. Each 1-metabolic equivalent increase in exercise capacity conferred a nearly 8% reduction in the incidence of cognitive impairment. Meeting the recommendations for daily activity was not associated with a delay in onset of cognitive impairment (HR=1.07; 95% CI, 0.86-1.32; P=.55).

CONCLUSION

Exercise capacity is strongly associated with cognitive function; the inverse association between fitness and cognitive impairment provides an additional impetus for health care providers to promote physical activity.

Effect of resveratrol and environmental enrichment on biomarkers of oxidative stress in young healthy mice

Resveratrol (RESV) and Environmental Enrichment (EE) have been separately reported to protect organisms against various diseases. This study investigated the potential benefit of the combination of RESV and EE on biomarkers of oxidative stress in young healthy mice. Fifty mice of both sexes were randomly divided into five groups of 10 animals each: group I served as control, group II were maintained on alternate day feeding, group III received RESV 50 mg/kg, suspended in caboxymethylcellulose orally per kg/day. Group IV received CMC and kept in an Enriched Environment, group V received RESV + EE. The treatment lasted for 28 days. The animals were sacrificed 24 h after the last treatment and brain samples were collected for biochemical evaluation. The results obtained showed a significant decrease (P < 0.05) in malondialdehyde concentration in EE group and RESV treated group kept EE when compared to the control. A significant decrease was also observed in glutathione peroxidase activity in all the treatment groups when compared to the control. A significant decrease in GPx activities in RESV, EE and RESV + EE treated groups in male and female mice when compared to the control groups respectively. However, a significant increase in GPx activities was observed in EE group in male mice and EODF, RESV groups in female mice when compared to RESV + EE groups respectively. In conclusion, the result of our study indicates that EE possesses antioxidant properties by decreasing MDA concentration and attenuating lipid peroxidation in the brain of young Swiss albino mice.

Low Leptin Availability as a Risk Factor for Dementia in Chilean Older People

OBJECTIVE

The aim was to study the role of leptin in the development of dementia.

METHODS

Follow-up of the ALEXANDROS cohorts, with baseline measurements in 2000. From 1,136 available subjects free of dementia at baseline, 667 subjects had frozen baseline blood samples for measuring leptin and soluble leptin receptor (sOB-R). The free leptin index (FLI) was calculated as the ratio of leptin to sOB-R. Dementia was defined as an MMSE score <22 and a score >5 in the Pfeffer Activities Questionnaire.

RESULTS

After 15 years of follow-up, 42 incident cases of dementia were identified. No difference in serum leptin was observed between people with and without dementia, but sOB-R was higher in demented than in nondemented subjects (sOB-R: 44.94 ± 23.97 vs. 33.73 ± 21.13 ng/ml). The adjusted risk for dementia increased, the higher the log sOB (hazard ratio = 3.58; 95% CI 1.72-7.45, p = 0.001).

CONCLUSION

Lower availability of free leptin was found in demented than in nondemented people, suggesting a role of leptin in cognition.

Cardiovascular risk factors for acute stroke: Risk profiles in the different subtypes of ischemic stroke

Timely diagnosis and control of cardiovascular risk factors is a priority objective for adequate primary and secondary prevention of acute stroke. Hypertension, atrial fibrillation and diabetes mellitus are the most common risk factors for acute cerebrovascular events, although novel risk factors, such as sleep-disordered breathing, inflammatory markers or carotid intima-media thickness have been identified. However, the cardiovascular risk factors profile differs according to the different subtypes of ischemic stroke. Atrial fibrillation and ischemic heart disease are more frequent in patients with cardioembolic infarction, hypertension and diabetes in patients with lacunar stroke, and vascular peripheral disease, hypertension, diabetes, previous transient ischemic attack and chronic obstructive pulmonary disease in patients with atherothrombotic infarction. This review aims to present updated data on risk factors for acute ischemic stroke as well as to describe the usefulness of new and emerging vascular risk factors in stroke patients.

Bone mineral density, adiposity, and cognitive functions

Cognitive decline and dementia due to Alzheimer's disease (AD) have been associated with genetic, lifestyle, and environmental factors. A number of potentially modifiable risk factors should be taken into account when preventive or ameliorative interventions targeting dementia and its preclinical stages are investigated. Bone mineral density (BMD) and body composition are two such potentially modifiable risk factors, and their association with cognitive decline was investigated in this study. 164 participants, aged 34–87 years old (62.78 ± 9.27), were recruited for this longitudinal study and underwent cognitive and clinical examinations at baseline and after 3 years. Blood samples were collected for apolipoprotein E (APOE) genotyping and dual energy x-ray absorptiometry (DXA) was conducted at the same day as cognitive assessment. Using hierarchical regression analysis, we found that BMD and lean body mass, as measured using DXA were significant predictors of episodic memory. Age, gender, APOE status, and premorbid IQ were controlled for. Specifically, the List A learning from California Verbal Learning Test was significantly associated with BMD and lean mass both at baseline and at follow up assessment. Our findings indicate that there is a significant association between BMD and lean body mass and episodic verbal learning. While the involvement of modifiable lifestyle factors in human cognitive function has been examined in different studies, there is a need for further research to understand the potential underlying mechanisms.

Ageing in people with Prader-Willi syndrome: mortality in the UK population cohort and morbidity in an older sample of adults

BACKGROUND

The past two decades have seen a great improvement in the care of people with Prader-Willi syndrome (PWS), particularly with regard to control of diet and behaviour management. Has this affected mortality rates or thrown up new issues regarding premature ageing or dementia? We investigated two aspects of ageing in people with PWS: (1) an estimate of mortality over 9 years in a cohort of people with PWS, originally recruited in 1998-2000; and (2) premature ageing or dementia in people aged ⩾40 years.

METHOD

(1) A follow-up of the population-based 1998-2000 cohort to investigate the subsequent mortality rate; and (2) the recruitment and structured assessment of all members of the Prader-Willi Syndrome Association UK (PWSA-UK) aged ⩾40 years who agreed to participate.

RESULTS

Follow-up of the population-based 1998-2000 cohort gave a mortality rate of at least 7/62 over 9 years (1.25% per annum; 20 untraced), age at death was between 13 and 59 years. Twenty-six members of the PWSA-UK aged ⩾40 years were recruited, 18 of whom had a genetic diagnosis (gd) of PWS. Twenty-two (14 gd) showed no evidence of dementia. Four, with possible symptoms, are described in more detail; all are female, of maternal uniparental disomy (mUPD) genetic subtype, or have a disomic region, and all have a long history of psychotic illness.

CONCLUSIONS

The mortality rate in people with PWS seems to be declining. The subgroup of people with PWS due to UPD or disomic region with female gender and a history of psychosis may be at risk of early onset dementia.

Promotion of cardiovascular health at three stages of life: never too soon, never too late

Cardiovascular disease is the leading cause of death worldwide, with an especially devastating impact in low-to-medium income countries. Cardiovascular disease has been elevated to this position by a combination of factors that include urbanization and its attendant effects, such as obesity, a sedentary lifestyle, changes in dietary habits, and smoking. Given the enormous extent of the problem and the complexity of its causes, which include cultural, social, political, and health care factors, an equally sophisticated and comprehensive strategy is required to combat cardiovascular disease on a global scale. Because exposure to cardiovascular risk factors occurs from early ages, this strategy must be expanded and adjusted throughout the life of an individual. Thus, our efforts should be concentrated not only on cardiovascular disease treatment and prevention, but also on health promotion and primordial prevention. In this review, we present different strategies yielding encouraging results at the population level, from childhood until old age, that aim to protect against the challenges facing the scientific community when combating cardiovascular disease.

Brain-derived neurotrophic factor, but not body weight, correlated with a reduction in depression scale scores in men with metabolic syndrome: a prospective weight-reduction study

BACKGROUND

Obesity, a critical component of metabolic syndrome (MetS), is associated with depression. Deficiency of brain-derived neurotrophic factor (BDNF) is involved in the mechanism of depression. We hypothesized that weight reduction would improve depressive symptoms via increasing BDNF levels in obese men.

METHODS

Male adults with obesity were enrolled in a weight-reduction program for twelve weeks. All subjects underwent daily caloric restriction and an exercise program which was regularly assessed in group classes. Fasting blood samples and Zung Self-Rating Depression Scale (Zung SDS) scores were collected for assessments before and after the study.

RESULTS

A total of 36 subjects completed this program. The average reduction in body weight was 8.4 ± 5.1 kg (8.8 ± 5.1%, P < 0.001). Fasting serum BDNF significantly increased after the study (from 40.4 ± 7.8 to 46.9 ± 8.9 ng/ml, P < 0.001). However, the depression symptoms, as assessed by the Zung Self-Rating Depression Scale (Zung SDS), did not reduce significantly (P = 0.486). Divided into subgroups based on changes in BDNF, Zung SDS scores were significantly reduced in subjects with greater BDNF increase than in those with minor BDNF change (-3.9 ± 6.2 vs. 2.3 ± 6.7, P = 0.009). The increased percentage of BDNF was inversely correlated with the change in Zung SDS (r = -0.380, P = 0.022). Multivariate regression analysis showed that reduction in BDNF was independently associated with change in Zung SDS (95% confidence interval -0.315 to -0.052, P = 0.008).

CONCLUSION

Zung SDS only significantly improved in men with increased fasting BDNF levels after a lifestyle intervention.

TRIAL REGISTRATION

(NCT01065753, ClinicalTrials.gov).

Neurotrophic and metabotrophic potential of nerve growth factor and brain-derived neurotrophic factor: Linking cardiometabolic and neuropsychiatric diseases

One of biggest recent achievements of neurobiology is the study on neurotrophic factors. The neurotrophins are exciting examples of these factors. They belong to a family of proteins consisting of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), NT-4/5, NT-6, and NT-7. Today, NGF and BDNF are well recognized to mediate a dizzying number of trophobiological effects, ranging from neurotrophic through immunotrophic and epitheliotrophic to metabotrophic effects. These are implicated in the pathogenesis of various diseases. In the same vein, recent studies in adipobiology reveal that this tissue is the body’s largest endocrine and paracrine organ producing multiple signaling proteins collectively termed adipokines, with NGF and BDNF being also produced from adipose tissue. Altogether, neurobiology and adipobiology contribute to the improvement of our knowledge on diseases beyond obesity such as cardiometabolic (atherosclerosis, type 2 diabetes, and metabolic syndrome) and neuropsychiatric (e.g., Alzheimer’s disease and depression) diseases. The present review updates evidence for (1) neurotrophic and metabotrophic potentials of NGF and BDNF linking the pathogenesis of these diseases, and (2) NGF- and BDNF-mediated effects in ampakines, NMDA receptor antagonists, antidepressants, selective deacetylase inhibitors, statins, peroxisome proliferator-activated receptor gamma agonists, and purinergic P2X₃ receptor up-regulation. This may help to construct a novel paradigm in the field of translational pharmacology of neuro-metabotrophins, particularly NGF and BDNF.

Sex-specific effects of high fat diet on indices of metabolic syndrome in 3xTg-AD mice: implications for Alzheimer's disease

Multiple factors of metabolic syndrome have been implicated in the pathogenesis of Alzheimer's disease (AD), including abdominal obesity, insulin resistance, endocrine dysfunction and dyslipidemia. High fat diet, a common experimental model of obesity and metabolic syndrome, has been shown to accelerate cognitive decline and AD-related neuropathology in animal models. However, sex interacts with the metabolic outcomes of high fat diet and, therefore, may alter neuropathological consequences of dietary manipulations. This study examines the effects of sex and high fat diet on metabolic and AD-related neuropathological outcomes in 3xTg-AD mice. Three month-old male and female 3xTg-AD mice were fed either standard or high fat diets for 4 months. Obesity was observed in all high fat fed mice; however, ectopic fat accumulation, hyperglycemia and hyperinsulinemia were observed only in males. Interestingly, despite the different metabolic outcomes of high fat diet, the neuropathological consequences were similar: both male and female mice maintained under high fat diet exhibited significant worsening in behavioral performance and hippocampal accumulation of β-amyloid protein. Because high fat diet resulted in obesity and increased AD-like pathology in both sexes, these data support a role of obesity-related factors in promoting AD pathogenesis.

Resveratrol protects the brain of obese mice from oxidative damage

Resveratrol (3,5,4′-trihydroxy-trans-stilbene) is a polyphenolic phytoalexin that exerts cardioprotective, neuroprotective, and antioxidant effects. Recently it has been shown that obesity is associated with an increase in cerebral oxidative stress levels, which may enhance neurodegeneration. The present study evaluates the neuroprotective action of resveratrol in brain of obese (ob/ob) mice. Resveratrol was administered orally at the dose of 25 mg kg⁻¹ body weight daily for three weeks to lean and obese mice. Resveratrol had no effect on body weight or blood glucose levels in obese mice. Lipid peroxides were significantly increased in brain of obese mice. The enzymatic antioxidants superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glucose-6-phosphate dehydrogenase and nonenzymatic antioxidants tocopherol, ascorbic acid, and glutathione were decreased in obese mice brain. Administration of resveratrol decreased lipid peroxide levels and upregulated the antioxidant activities in obese mice brain. Our findings indicate a neuroprotective effect of resveratrol by preventing oxidative damage in brain tissue of obese mice.

Brain-derived neurotrophic factor not associated with metabolic syndrome but inversely correlated with vascular cell adhesion molecule-1 in men without diabetes

BACKGROUND

Excessive visceral fat with unbalanced adipokines is a critical pathogenic factor of metabolic syndrome (MetS), which is associated with disorders of the central nervous system and cardiovascular disease. Because brain-derived neurotrophic factor (BDNF) plays an important role in neurons, we examined the relationship of BDNF to MetS, adipose tissue and biomarkers in men.

METHODS

Thirty-four non-diabetic men with MetS and another 24 age-matched men without MetS were enrolled. In addition to fasting blood samples, the area of adipose tissue at the waist was assessed by magnetic resonance imaging (MRI).

RESULTS

There was no significant difference in serum BDNF concentrations between men with or without MetS (40.9±8.0 vs. 43.2±6.1 ng/ml, P=0.235). However, the serum concentration of soluble vascular cell adhesion molecule-1 (VCAM-1) was higher in the subjects with a lower BDNF level (737±230 vs. 628±115 ng/ml, P=0.025). An inverse correlation between VCAM-1 and BDNF was observed (r=-0.391, P=0.002). After adjusting for visceral adipose tissue, VCAM-1 was found to be independently associated with BDNF [95% confidence interval (-0.025, -0.005), P=0.004].

CONCLUSION

These data show no difference in serum BDNF levels between the men with MetS and controls. However, serum BDNF was inversely correlated with serum VCAM-1 in men without diabetes.

Obesity, leptin, and Alzheimer's disease

Obesity has various deleterious effects on health largely associated with metabolic abnormalities including abnormal glucose and lipid homeostasis that are associated with vascular injury and known cardiac, renal, and cerebrovascular complications. Advanced age is also associated with increased adiposity, decreased lean mass, and increased risk for obesity-related diseases. Although many of these obesity- and age-related disease processes have long been subsumed to be secondary to metabolic or vascular dysfunction, increasing evidence indicates that obesity also modulates nonvascular diseases such as Alzheimer's disease (AD) dementia. The link between peripheral obesity and neurodegeneration will be explored, using adipokines and AD as a template. After an introduction to the neuropathology of AD, the relationship between body weight, obesity, and dementia will be reviewed. Then, population-based and experimental studies that address whether leptin modulates brain health and mitigates AD pathways will be explored. These studies will serve as a framework for understanding the role of adipokines in brain health.

Obesity/hyperleptinemic phenotype adversely affects hippocampal plasticity: effects of dietary restriction

Epidemiological studies estimate that greater than 60% of the adult US population may be categorized as either overweight or obese and there is a growing appreciation that obesity affects the functional integrity of the central nervous system (CNS). We recently developed a lentivirus (LV) vector that produces an insulin receptor (IR) antisense RNA sequence (IRAS) that when injected into the hypothalamus selectively decreases IR signaling in hypothalamus, resulting in increased body weight, peripheral adiposity and plasma leptin levels. To test the hypothesis that this obesity/hyperleptinemic phenotype would impair hippocampal synaptic transmission, we examined short term potentiation (STP) and long term potentiation (LTP) in the hippocampus of rats that received the LV-IRAS construct or the LV-Control construct in the hypothalamus (hypo-IRAS and hypo-Con, respectively). Stimulation of the Schaffer collaterals elicits STP that develops into LTP in the CA1 region of hypo-Con rats; conversely, hypo-IRAS rats exhibit STP that fails to develop into LTP. To more closely examine the potential role of hyperleptinemia in these electrophysiological deficits, hypo-IRAS were subjected to mild food restriction paradigms that would either: 1) prevent the development of the obesity phenotype; or 2) reverse an established obesity phenotype in hypo-IRAS rats. Both of these paradigms restored LTP in the CA1 region and reversed the decreases in the phosphorylated/total ratio of GluA1 Ser845 AMPA receptor subunit expression observed in the hippocampus of hypo-IRAS rats. Collectively, these data support the hypothesis that obesity impairs hippocampal synaptic transmission and support the hypothesis that these deficits are mediated through the impairment of hippocampal leptin activity.

Human cerebral neuropathology of Type 2 diabetes mellitus

The cerebral neuropathology of Type 2 diabetes (CNDM2) has not been positively defined. This review includes a description of CNDM2 research from before the 'Pubmed Era'. Recent neuroimaging studies have focused on cerebrovascular and white matter pathology. These and prior studies about cerebrovascular histopathology in diabetes are reviewed. Evidence is also described for and against the link between CNDM2 and Alzheimer's disease pathogenesis. To study this matter directly, we evaluated data from University of Kentucky Alzheimer's Disease Center (UK ADC) patients recruited while non-demented and followed longitudinally. Of patients who had come to autopsy (N = 234), 139 met inclusion criteria. These patients provided the basis for comparing the prevalence of pathological and clinical indices between well-characterized cases with (N = 50) or without (N = 89) the premortem diagnosis of diabetes. In diabetics, cerebrovascular pathology was more frequent and Alzheimer-type pathology was less frequent than in non-diabetics. Finally, a series of photomicrographs demonstrates histopathological features (including clinical-radiographical correlation) observed in brains of persons that died after a history of diabetes. These preliminary, correlative, and descriptive studies may help develop new hypotheses about CNDM2. We conclude that more work should be performed on human material in the context of CNDM2.

Self-reported vs measured body mass indices in migraineurs

OBJECTIVE

To compare and contrast body mass indices calculated based on self-reported height and weight as compared with measured height and weight in migraine patients.

BACKGROUND

Obesity is a risk factor for multiple neurological disorders including stroke, dementia, and migraine chronification. In addition, several cytokines and adipocytokines associated with migraine are modulated by body mass. The body mass index (BMI) is a commonly used anthropometric measure to estimate total body fat and is often calculated based on patient's self-reported height and weight.

METHODS

This was a retrospective study evaluating consecutive migraine patients presenting to a headache clinic.Demographic characteristics and self-reported height and weight were obtained from a standardized questionnaire that each new patient completes upon presentation to the clinic. In addition, as depression has been shown to be associated with both migraine and obesity, information in regards to major depression utilizing the Patient Healthcare Questionnaire-9 was extracted as well. Following completion of the questionnaire, body mass indices are routinely measured, with height measured to the nearest 0.5 inch utilizing a mounted stadiometer, and weight measured with a standard scale to the nearest 0.5 lb. After this information was extracted from the charts, BMI was then calculated for both self-reported and measured body mass indices.Using the measured body mass indices as a standard, this was then compared and contrasted to the patient's self-reported body mass indices.

RESULTS

A total of 110 patients were included in the study. Patients were predominantly female (91%) with a mean age of 38.6 +/- 11.6 years. Of the total patients included, no significant difference in self-reported height (mean 64.7 +/- 3.1 inches) as compared with measured height (mean 64.5 +/- 3.4 inches) was seen, P = .463. However, self-reported weight (169 +/- 41.3) was underestimated as compared with the measured weight (173.5 +/- 43.2), P = .001. And, the self-reported BMI (28.4 +/- 6.8) was significantly less than the measured BMI (29.4 +/- 7.5), P < .001.

CONCLUSIONS

In our study, the self-reported mean weight and BMI for migraineurs was significantly less than the measured mean weight and BMI, and was of greater magnitude in the obese migraineurs. This suggests that conclusions drawn from studies evaluating obesity utilizing self-reported BMI in migraineurs may undercall the effect of total body obesity.

A look inside the diabetic brain: Contributors to diabetes-induced brain aging

Central nervous system (CNS) complications resulting from diabetes is a problem that is gaining more acceptance and attention. Recent evidence suggests morphological, electrophysiological and cognitive changes, often observed in the hippocampus, in diabetic individuals. Many of the CNS changes observed in diabetic patients and animal models of diabetes are reminiscent of the changes seen in normal aging. The central commonalities between diabetes-induced and age-related CNS changes have led to the theory of advanced brain aging in diabetic patients. This review summarizes the findings of the literature as they relate to the relationship between diabetes and dementia and discusses some of the potential contributors to diabetes-induced CNS impairments.

Risk-reducing effect of education in Alzheimer's disease

OBJECTIVE

To estimate the effect of education on the risk of Alzheimer's disease (AD).

METHODS

373 patients diagnosed with AD and 559 healthy control individuals without first degree relatives with known dementia, were included in a case-control study (2003-2006). All individuals were genotyped for APOE alleles. Odds ratio (OR) for developing AD was calculated by binary logistic regression, with the number of APOE epsilon 4 alleles and educational level as covariates. Analyses were carried out separately for men and women and for different age groups.

RESULTS

Carriers of one APOE epsilon 4 allele had OR of 4.2, and carriers of two APOE epsilon 4 alleles OR of 12.4 for developing AD. When adjusted for the number of APOE epsilon 4 alleles, OR for developing AD was significantly reduced in participants with 8-9 years of education compared to those with only 6-7 years, and was reduced further for those with 10-18 years of education. These findings were obtained for all the age groups studied and for both men and women.

CONCLUSIONS

Education had a consistently protective effect on the risk of developing clinical AD in a dose-dependent manner in both men and women, and in all age groups, also when adjusting for the number of APOE epsilon 4 alleles. Male gender was protective, probably at least in part because of a higher educational level.

Amyloid precursor protein expression is upregulated in adipocytes in obesity

The aim of this study was to determine whether amyloid precursor protein (APP) is expressed in human adipose tissue, dysregulated in obesity, and related to insulin resistance and inflammation. APP expression was examined by microarray expression profiling of subcutaneous abdominal adipocytes (SAC) and cultured preadipocytes from obese and nonobese subjects. Quantitative real-time PCR (QPCR) was performed to confirm differences in APP expression in SAC and to compare APP expression levels in adipose tissue, adipocytes, and stromal vascular cells (SVCs) from subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) specimens. Adipose tissue samples were also examined by western blot and immunofluorescence confocal microscopy. Microarray studies demonstrated that APP mRNA expression levels were higher in SAC (approximately 2.5-fold) and preadipocytes (approximately 1.4) from obese subjects. Real-time PCR confirmed increased APP expression in SAC in a separate group of obese compared with nonobese subjects (P=0.02). APP expression correlated to in vivo indices of insulin resistance independently of BMI and with the expression of proinflammatory genes, such as monocyte chemoattractant protein-1 (MCP-1) (R=0.62, P=0.004), macrophage inflammatory protein-1alpha (MIP-1alpha) (R=0.60, P=0.005), and interleukin-6 (IL-6) (R=0.71, P=0.0005). Full-length APP protein was detected in adipocytes by western blotting and APP and its cleavage peptides, Abeta40 and Abeta42, were observed in SAT and VAT by immunofluorescence confocal microscopy. In summary, APP is highly expressed in adipose tissue, upregulated in obesity, and expression levels correlate with insulin resistance and adipocyte cytokine expression levels. These data suggest a possible role for APP and/or Abeta in the development of obesity-related insulin resistance and adipose tissue inflammation.

Insulin dysfunction induces in vivo tau hyperphosphorylation through distinct mechanisms

Hyperphosphorylated tau is the major component of paired helical filaments in neurofibrillary tangles found in Alzheimer's disease (AD) brains, and tau hyperphosphorylation is thought to be a critical event in the pathogenesis of the disease. The large majority of AD cases is late onset and sporadic in origin, with aging as the most important risk factor. Insulin resistance, impaired glucose tolerance, and diabetes mellitus (DM) are other common syndromes in the elderly also strongly age dependent, and there is evidence supporting a link between insulin dysfunction and AD. To investigate the possibility that insulin dysfunction might promote tau pathology, we induced insulin deficiency and caused DM in mice with streptozotocin (STZ). A mild hyperphosphorylation of tau could be detected 10, 20, and 30 d after STZ injection, and a massive hyperphosphorylation of tau was observed after 40 d. The robust hyperphosphorylation of tau was localized in the axons and neuropil, and prevented tau binding to microtubules. Neither mild nor massive tau phosphorylation induced tau aggregation. Body temperature of the STZ-treated mice did not differ from control animals during 30 d, but dropped significantly thereafter. No change in beta-amyloid (Abeta) precursor protein (APP), APP C-terminal fragments, or Abeta levels were observed in STZ-treated mice; however, cellular protein phosphatase 2A activity was significantly decreased. Together, these data indicate that insulin dysfunction induced abnormal tau hyperphosphorylation through two distinct mechanisms: one was consequent to hypothermia; the other was temperature-independent, inherent to insulin depletion, and probably caused by inhibition of phosphatase activity.