Alzheimer Disease Pathology and Neurodegeneration in Midlife Obesity: A Pilot Study

Estimating global prevalence of mild cognitive impairment and dementia in elderly with overweight, obesity, and central obesity: A systematic review and meta-analysis

BACKGROUND AND AIM

Previous studies have demonstrated that adiposity, particularly obesity during midlife, may have a detrimental effect on cognitive function. This study aims to estimate the global prevalence of mild cognitive impairment (MCI) and dementia in elderly aged 60 years or above with overweight, obesity, and central obesity.

METHODS

We searched PubMed, Embase, Web of Science, and Cochrane Library from inception to November 2023. DerSimonian-Laird random-effects model with Logit transformation was used. Sensitivity analysis, meta-regression, and subgroup analysis were employed to investigate determinants of the prevalence of MCI and dementia.

RESULTS

A total of 72 studies involving 2,980,947 elderly with distinct adiposity status were included. Pooled prevalence of MCI and dementia in elderly with overweight and obesity was 32.54% and 9.47%, respectively. Univariate meta-regression analysis indicated that the heterogeneity in dementia prevalence was attributable to variations in study size (R2 = 0.01, p < 0.05), while the multivariable analysis underscored that the income of country or area had the most significant predictive importance (60.3% and 90.3%) for both MCI and dementia prevalence. Subgroup analysis revealed regional disparities and diagnostic technique variations contributing to heterogeneity. Based on currently available but inadequate epidemiological data, the pooled prevalence of MCI and dementia in elderly with central obesity was calculated as 10.18% and 9.75%, respectively.

CONCLUSION

Strategies to address adiposity-associated cognitive impairment should consider multifaceted interventions beyond simple weight reduction. Macro-level initiatives such as improvement of income levels and micro-level interventions including the adoption of accurate diagnostic techniques also represent equally pivotal components.

Feasibility of the MIND+SOUL Culturally Tailored Brain Healthy Diet: A Pilot Study

Alzheimer's disease (AD) disproportionately impacts Black Americans, who are three times more likely to develop AD. While heart-healthy diets have shown potential in reducing AD risk, research on adapted dietary interventions for Black American communities remains limited. This pilot study assessed the feasibility and acceptability of an adapted brain healthy diet intervention (MIND + SOUL) and explored changes in cardiometabolic risk and cognition. Twenty-nine participants completed the 12-week intervention, which included culturally tailored health education, cooking classes, health coaching, and groceries. Feasibility was assessed by attendance and retention rates, while acceptability was measured by two questionnaires. Participants had a mean age of 70.3, with 10.3% male. The intervention demonstrated high feasibility (89.3% retention) and acceptability (mean = 71.9, SD = 8.59), with meaningful improvements in body mass index (estimate = -0.54, P = 0.009), dietary intake (estimate = 28.39, P = 0.042), and executive function (estimate = 3.32, P < 0.001). However, no significant changes in blood-based biomarkers were observed. The MIND + SOUL intervention demonstrated high feasibility and acceptability, improvements in body composition, cognitive function, and dietary behaviors, despite no significant changes in blood-based biomarkers. Findings suggest potential benefits for reducing AD risk factors and promoting healthy aging. Clinical Trials Registry: ClinicalTrials.Gov; NCT05414682.

Nasal lymphatic obstruction of CSF drainage as a possible cause of Alzheimer's disease and dementia

Alzheimer's disease, the most common form of dementia among older adults, slowly destroys memory and thinking skills. In recent years, scientists have made tremendous progress in understanding Alzheimer's disease, still, they do not yet fully understand what causes the disease. This article proposes a novel etiology for Alzheimer's disease. Our hypothesis developed from a review of nuclear medicine scans, in which the authors observed a significant increase in nasal turbinate vasodilation and blood pooling in patients with hypertension, sleep apnea, diabetes and/or obesity, all risk factors for Alzheimer's disease. The authors propose that nasal turbinate vasodilation and resultant blood pooling lead to the obstruction of normal nasal lymphatic clearance of cerebrospinal fluid and its waste products from the brain. The nasal turbinate vasodilation, due to increased parasympathetic activity, occurs alongside the well-established increased sympathetic activity of the cardiovascular system as seen in patients with hypertension. The increased parasympathetic activity is likely due to an autonomic imbalance secondary to the increase in worldwide consumption of highly processed food associated with dysregulation of the glucose regulatory system. The authors' hypothesis offers a novel mechanism and a new paradigm for the etiology of Alzheimer's disease and helps explain the rapid worldwide rise in the disease and other dementias which are expected to double in the next 20 years. This new paradigm provides compelling evidence for the modulation of the parasympathetic nervous system as a novel treatment strategy for Alzheimer's disease and other degenerative brain diseases, specifically targeting nasal turbinate lymphatic flow.

Iron accumulation/overload and Alzheimer's disease risk factors in the precuneus region: A comprehensive narrative review

Alzheimer's disease (AD) is a neurodegenerative disease that is characterized by amyloid plaques, neurofibrillary tangles, and neuronal loss. Early cerebral and body iron dysregulation and accumulation interact with AD pathology, particularly in the precuneus, a crucial functional hub in cognitive functions. Quantitative susceptibility mapping (QSM), a novel post-processing approach, provides insights into tissue iron levels and cerebral oxygen metabolism and reveals abnormal iron accumulation early in AD. Increased iron deposition in the precuneus can lead to oxidative stress, neuroinflammation, and accelerated neurodegeneration. Metabolic disorders (diabetes, non-alcoholic fatty liver disease (NAFLD), and obesity), genetic factors, and small vessel pathology contribute to abnormal iron accumulation in the precuneus. Therefore, in line with the growing body of literature in the precuneus region of patients with AD, QSM as a neuroimaging method could serve as a non-invasive biomarker to track disease progression, complement other imaging modalities, and aid in early AD diagnosis and monitoring.

Vascular Contributions to Healthy Aging and Dementia

Vascular pathologies are among the most common contributors to neurodegenerative changes across the spectrum of normal aging to dementia. Cerebral small vessel disease (SVD) encompasses a wide range of conditions affecting capillaries, small arteries, and arterioles, as well as perivascular spaces and fluid dynamics in the brain, playing a significant role in vascular contributions to cognitive impairment and dementia (VCID). These factors can accelerate the progression of SVD and neuronal degeneration. Since aging is the primary risk factor for Alzheimer's disease (AD) and AD-related dementias (ADRD), this Research Topic aims to gather recent research to better understand vascular contributions to healthy aging and age-related cognitive impairment. Other risk factors include diabetes, lifestyle factors, high cholesterol, vascular inflammation, and immune remodeling, all of which can accelerate cognitive dysfunction progression. This special issue includes a total of 21 articles comprising Reviews, Perspectives, and Original Research articles. The articles cover various technical and biological aspects related to recent progress in aging and dementia research. We aim to promote research exchange across different fields, including imaging, VCID, molecular biology, neuroinflammation, and immunology. Most papers in this special issue focus on understanding the disease mechanisms of AD/ADRD and developing new therapeutic strategies.

CMS121: a novel approach to mitigate aging-related obesity and metabolic dysfunction

BACKGROUND

Modulated by differences in genetic and environmental factors, laboratory mice often show progressive weight gain, eventually leading to obesity and metabolic dyshomeostasis. Since the geroneuroprotector CMS121 has a positive effect on energy metabolism in a mouse model of type 2 diabetes, we investigated the potential of CMS121 to counteract the metabolic changes observed during the ageing process of wild type mice.

METHODS

Control or CMS121-containing diets were supplied ad libitum for 6 months, and mice were sacrificed at the age of 7 months. Blood, adipose tissue, and liver were analyzed for glucose, lipids, and protein markers of energy metabolism.

RESULTS

The CMS121 diet induced a 40% decrease in body weight gain and improved both glucose and lipid indexes. Lower levels of hepatic caspase 1, caspase 3, and NOX4 were observed with CMS121 indicating a lower liver inflammatory status. Adipose tissue from CMS121-treated mice showed increased levels of the transcription factors Nrf1 and TFAM, as well as markers of mitochondrial electron transport complexes, levels of GLUT4 and a higher resting metabolic rate. Metabolomic analysis revealed elevated plasma concentrations of short chain acylcarnitines and butyrate metabolites in mice treated with CMS121.

CONCLUSIONS

The diminished de novo lipogenesis, which is associated with increased acetyl-CoA, acylcarnitine, and butyrate metabolite levels, could contribute to safeguarding not only the peripheral system but also the aging brain. By mimicking the effects of ketogenic diets, CMS121 holds promise for metabolic diseases such as obesity and diabetes, since these diets are hard to follow over the long term.

Causal effects of nonalcoholic fatty liver disease on cerebral cortical structure: a Mendelian randomization analysis

Background

Previous studies have highlighted changes in the cerebral cortical structure and cognitive function among nonalcoholic fatty liver disease (NAFLD) patients. However, the impact of NAFLD on cerebral cortical structure and specific affected brain regions remains unclear. Therefore, we aimed to explore the potential causal relationship between NAFLD and cerebral cortical structure.

Methods

We conducted a Mendelian randomization (MR) study using genetic predictors of alanine aminotransferase (ALT), NAFLD, and percent liver fat (PLF) and combined them with genome-wide association study (GWAS) summary statistics from the ENIGMA Consortium. Several methods were used to assess the effect of NAFLD on full cortex and specific brain regions, along with sensitivity analyses.

Results

At the global level, PLF nominally decreased SA of full cortex; at the functional level, ALT presented a nominal association with reduced SA of parahippocampal gyrus, TH of pars opercularis, TH of pars orbitalis, and TH of pericalcarine cortex. Besides, NAFLD presented a nominal association with reduced SA of parahippocampal gyrus, TH of pars opercularis, TH of pars triangularis and TH of pericalcarine cortex, but increased TH of entorhinal cortex, lateral orbitofrontal cortex and temporal pole. Furthermore, PLF presented a nominal association with reduced SA of parahippocampal gyrus, TH of pars opercularis, TH of cuneus and lingual gyrus, but increased TH of entorhinal cortex.

Conclusion

NAFLD is suggestively associated with atrophy in specific functional regions of the human brain.