Pathogenesis of Dementia

Risk of Dementia and Alzheimer's Disease Associated With Antidiabetics: A Bayesian Network Meta-Analysis

INTRODUCTION

Dementia risk is substantially elevated in patients with diabetes. However, evidence on dementia risk associated with various antidiabetic regimens is still limited. This study aims to comprehensively investigate the risk of dementia and Alzheimer's disease (AD) associated with various antidiabetic classes.

METHODS

Cochrane Central Register of Controlled Trials, Embase, MEDLINE (PubMed), and Scopus were searched from inception to March 2024 (PROSPERO CRD 42022365927). Observational studies investigating dementia and AD incidences after antidiabetic initiation were identified. Bayesian network meta-analysis was performed to determine dementia and AD risks associated with antidiabetics. Preferred Reporting Items for Systematic Reviews-Network Meta-Analyses (PRISMA-NMA) guidelines were followed. Statistical analysis was performed and updated in November 2023 and March 2024, respectively.

RESULTS

A total of 1,565,245 patients from 16 studies were included. Dementia and AD risks were significantly lower with metformin and sodium glucose co-transporter-2 inhibitors (SGLT2i). Metformin displayed the lowest risk of dementia across diverse antidiabetics, whereas α-glucosidase inhibitors demonstrated the highest risk. SGLT2i exhibited the lowest dementia risk across second-line antidiabetics. Dementia risk was significantly higher with dipeptidyl peptidase-4 inhibitor (DPP4i), metformin, sulfonylureas, and thiazolidinediones (TZD) compared to SGLT2i in the elderly (≥75 years). Dementia risk associated with metformin was substantially lower, regardless of diabetic complication status or baseline A1C.

DISCUSSION

Metformin and SGLT2i demonstrated lower dementia risk than other antidiabetic classes. Patient-specific factors may affect this relationship and cautious interpretation is warranted as metformin is typically initiated at an earlier stage with fewer complications. Hence, further large-scaled clinical trials are required.

Hepatopancreatic metabolic disorders and their implications in the development of Alzheimer's disease and vascular dementia

Dementia has been faced with significant public health challenges and economic burdens that urges the need to develop safe and effective interventions. In recent years, an increasing number of studies have focused on the relationship between dementia and liver and pancreatic metabolic disorders that result in diseases such as diabetes, obesity, hypertension and dyslipidemia. Previous reports have shown that there is a plausible correlation between pathologies caused by hepatopancreatic dysfunctions and dementia. Glucose, insulin and IGF-1 metabolized in the liver and pancreas probably have an important influence on the pathophysiology of the most common dementias: Alzheimer's and vascular dementia. This current review highlights recent studies aimed at identifying convergent mechanisms, such as insulin resistance and other diseases, linked to altered hepatic and pancreatic metabolism, which are capable of causing brain changes that ultimately lead to dementia.

Association between Mediterranean diet and dementia and Alzheimer disease: a systematic review with meta-analysis

BACKGROUND

Dementia affects 5-8% of the population aged over 65 years (~50 million worldwide). Several factors are associated with increased risk, including diet. The Mediterranean diet (MedDiet) has shown potential protective effects against several chronic diseases.

AIMS

This systematic review with meta-analysis aim was to assess the association between adherence to the MedDiet and the risk of dementia in the elderly.

METHODS

PRISMA-2020 guidelines were followed. PubMed/MEDLINE and Scopus were searched on 17 July 2023. The Newcastle-Ottawa Scale tool was used to assess the risk of bias. The protocol was pre-registered in PROSPERO (registration number: CRD 42023444368). Heterogeneity was assessed using the I2 test. Publication bias was assessed by visual inspection of the funnel plot and by Egger's regression asymmetry test. The final effect size was reported as OR or HR, depending on the study design of the included studies.

RESULTS

Out of 682 records, 21 were included in the analysis. The pooled OR was 0.89 (95% CI = 0.84-0.94) based on 65,955 participants (I2 = 69.94). When only cohort studies were included, HR was 0.84 (95% CI = 0.76-0.94) based on 55,205 participants (I2 = 89.70). When only Alzheimer Disease was considered OR was 0.73 (95% CI = 0.62-0.85) based on 38,292 participants (I2 = 63.85).

DISCUSSION

Despite the relatively low risk reduction associated with higher adherence to MedDiet among elderly, it should be considered that this population is the most affected.

CONCLUSIONS

Adherence to MedDiet could be an effective non-pharmacological measure to reduce the burden of dementia, even among elderly.

Mitigating cellular aging and enhancing cognitive functionality: visual arts-mediated Cognitive Activation Therapy in neurocognitive disorders

The growing phenomenon of population aging is redefining demographic dynamics, intensifying age-related conditions, especially dementia, projected to triple by 2050 with an enormous global economic burden. This study investigates visual arts-mediated Cognitive Activation Therapy (CAT) as a non-pharmacological CAT intervention targets both biological aging [leukocyte telomere length (LTL), DNA methylation age (DNAmAge)] and cognitive functionality. Aligning with a broader trend of integrating non-pharmacological approaches into dementia care. The longitudinal study involved 20 patients with mild to moderate neurocognitive disorders. Cognitive and functional assessments, and biological aging markers -i.e., LTL and DNAmAge- were analyzed before and after CAT intervention. Change in LTL was positively correlated with days of treatment (p =0.0518). LTL significantly elongated after intervention (p =0.0269), especially in men (p =0.0142), correlating with younger age (p =0.0357), and higher education (p =0.0008). DNAmAge remained instead stable post-treatment. Cognitive and functional improvements were observed for Copy of complex geometric figure, Progressive Silhouettes, Position Discrimination, Communication Activities of Daily Living-Second edition, Direct Functional Status (p < 0.0001) and Object decision (p =0.0594), but no correlations were found between LTL and cognitive gains. Visual arts-mediated CAT effectively mitigates cellular aging, especially in men, by elongating LTL. These findings underscore the potential of non-pharmacological interventions in enhancing cognitive and functional status and general well-being in dementia care. Further research with larger and longer-term studies is essential for validation.

Changes in cognitive ability and serum microRNA levels during aging in mice

Mild cognitive impairment (MCI) is an early stage that can result in dementia. MCI can be reversed, and diagnosis at an early stage is crucial to control the progression to dementia. Dementia is currently diagnosed based on interviews and screening tests; however, novel biomarkers must be identified to allow early MCI detection. Therefore, the present study aimed to identify novel biomarkers in the form of blood microRNAs (miRNAs/miRs) for the diagnosis of MCI or early dementia. Blood samples were collected from C57BL/6NJcl male mice at four time points, including 4-week-old (4W), 8-week-old (8W), 36-week-old (36W) and 58-week-old (58W), and serum was isolated. Body weight and blood total cholesterol levels were increased, and blood alkaline phosphatase was decreased with aging. The 8W mice exhibited the highest cognitive ability in the Morris water maze test, whereas the 58W mice demonstrated decreased cognitive ability. The serum RNA concentrations of the 4W, 8W, 36W and 58W mice demonstrated no significant differences. Furthermore, small RNA levels were detected in the serum of all mice. miRNA microarray analysis revealed a >1.5-fold increase in the serum expression of two miRNAs (miR-21a-5p and miR-92a-3p) and a >1.5-fold decrease in the serum expression of two other miRNAs (miR-6769b-5p and miR-709) in 58W mice compared with those in 8W mice. In the future, we aim to further analyze aged mice to discover novel MCI biomarkers.

Relationship between cognitive function and weight-adjusted waist index in people ≥ 60 years old in NHANES 2011-2014

BACKGROUND

Widespread attention has been given to the detrimental effects of obesity on cognitive function. However, there is no evidence on the connection between low cognitive performance and the WWI (weight-adjusted waist index). This study looked into the connection between poor cognitive performance and the WWI in senior Americans.

METHODS

A cross-sectional research study was carried out with information from the NHANES 2011-2014. With multivariate linear regression models, the pertinence between the WWI and low cognitive function in persons older than 60 years was examined. The nonlinear link was described using threshold effect analyses and fitted smoothed curves. Interaction tests and subgroup analysis were also conducted.

RESULTS

The study had 2762 individuals in all, and subjects with higher WWI values were at greater risk for low cognitive function. In the completely adjusted model, the WWI was positively connected with low cognitive performance assessed by CERAD W-L (OR = 1.22, 95% CI 1.03-1.45, p = 0.0239), AFT (OR = 1.30, 95% CI 1.09-1.54, p = 0.0029), and DSST (OR = 1.59, 95% CI 1.30-1.94, p < 0.0001). The effect of each subgroup on the positive correlation between the WWI and low cognitive performance was not significant. The WWI and low cognitive performance as determined by CERAD W-L and AFT had a nonlinear connection (log-likelihood ratio < 0.05).

CONCLUSION

Among older adults in the United States, the risk of low cognitive performance may be positively related to the WWI.

Early depressive manifestations in patients with dementia caused by Alzheimer's disease

Previous studies on the complex interplay between depression and dementia in patients with Alzheimer's disease revealed that early-life depression is a risk factor for dementia. Both depression and dementia appear to share common etiopathological mechanisms. In the present study, a comprehensive retrospective analysis was performed on a study group of patients with dementia suffering from previously diagnosed depression. The aim was to assess potentially relevant clinical and imaging parameters that can be used to characterize depression as a risk factor for dementia in later life. Statistically significant data correlating cognitive scores with the moment of depression onset and the length of time period to the diagnosis of dementia were identified. Furthermore, at the moment of depression diagnosis, structural cerebral alterations tended to appear more frequently in women compared with men. However, this sex-associated difference is not maintained after the moment of dementia diagnosis. Results from the present study contributed additional data to the evidence supporting a relationship between a history of depression and the occurrence of Alzheimer's disease, discussing relevant clinical and imaging parameters featured in patients with dementia and their inter-relations.

Combining Experimental and Computational Methods to Produce Conjugates of Anticholinesterase and Antioxidant Pharmacophores with Linker Chemistries Affecting Biological Activities Related to Treatment of Alzheimer's Disease

Effective therapeutics for Alzheimer's disease (AD) are in great demand worldwide. In our previous work, we responded to this need by synthesizing novel drug candidates consisting of 4-amino-2,3-polymethylenequinolines conjugated with butylated hydroxytoluene via fixed-length alkylimine or alkylamine linkers (spacers) and studying their bioactivities pertaining to AD treatment. Here, we report significant extensions of these studies, including the use of variable-length spacers and more detailed biological characterizations. Conjugates were potent inhibitors of acetylcholinesterase (AChE, the most active was 17d IC50 15.1 ± 0.2 nM) and butyrylcholinesterase (BChE, the most active was 18d: IC50 5.96 ± 0.58 nM), with weak inhibition of off-target carboxylesterase. Conjugates with alkylamine spacers were more effective cholinesterase inhibitors than alkylimine analogs. Optimal inhibition for AChE was exhibited by cyclohexaquinoline and for BChE by cycloheptaquinoline. Increasing spacer length elevated the potency against both cholinesterases. Structure-activity relationships agreed with docking results. Mixed-type reversible AChE inhibition, dual docking to catalytic and peripheral anionic sites, and propidium iodide displacement suggested the potential of hybrids to block AChE-induced β-amyloid (Aβ) aggregation. Hybrids also exhibited the inhibition of Aβ self-aggregation in the thioflavin test; those with a hexaquinoline ring and C8 spacer were the most active. Conjugates demonstrated high antioxidant activity in ABTS and FRAP assays as well as the inhibition of luminol chemiluminescence and lipid peroxidation in mouse brain homogenates. Quantum-chemical calculations explained antioxidant results. Computed ADMET profiles indicated favorable blood-brain barrier permeability, suggesting the CNS activity potential. Thus, the conjugates could be considered promising multifunctional agents for the potential treatment of AD.

Transcript-Level In Silico Analysis of Alzheimer's Disease-Related Gene Biomarkers and Their Evaluation with Bioactive Flavonoids to Explore Therapeutic Interactions

Alzheimer's disease (AD) is a progressive brain disorder that can significantly affect the quality of life. We used a variety of in silico tools to investigate the transcript-level mutational impact of exonic missense rare variations (single nucleotide polymorphisms, SNPs) on protein function and to identify potential druggable protein cavities that correspond to potential therapeutic targets for the management of AD. According to the NIA-AA (National Institute on Aging-Alzheimer's Association) framework, we selected three AD biomarker genes (APP, NEFL, and MAPT). We systematically screened transcript-level exonic rare SNPs from these genes with a minor allele frequency of 1% in 1KGD (1000 Genomes Project Database) and gnomAD (Genome Aggregation Database). With downstream functional effect predictions, a single variation (rs182024939: K > N) of the MAPT gene with nine transcript SNPs was identified as the most pathogenic variation from the large dataset of mutations. The machine learning consensus classifier predictor categorized these transcript-level SNPs as the most deleterious variations, resulting in a large decrease in protein structural stability (ΔΔG kcal/mol). The bioactive flavonoid library was screened for drug-likeness and toxicity risk. Virtual screening of eligible flavonoids was performed using the MAPT protein. Identification of druggable protein-binding cavities showed VAL305, GLU655, and LYS657 as consensus-interacting residues present in the MAPT-docked top-ranked flavonoid compounds. The MM/PB(GB)SA analysis indicated hesperetin (-5.64 kcal/mol), eriodictyol (-5.63 kcal/mol), and sakuranetin (-5.60 kcal/mol) as the best docked flavonoids with the near-native binding pose. The findings of this study provide important insights into the potential of hesperetin as a promising flavonoid that can be utilized for further rational drug design and lead optimization to open new gateways in the field of AD therapeutics.

Variety and Duration of Different Sedentary Behaviors, Inflammation, Genetic Susceptibility, and New-Onset Dementia in the Older Population

OBJECTIVES

We aimed to evaluate the relationship of the variety and duration of different sedentary behaviors (TV-watching, driving, and nonoccupational computer use) with the risk of dementia in older participants, and examine whether inflammation and genetic susceptibility may modify the relationship.

DESIGN

A prospective cohort study.

SETTING AND PARTICIPANTS

173,829 older participants (≥60 years) without prior dementia in the UK Biobank were enrolled.

METHODS

A healthy sedentary behavior score was calculated as the number of the 3 major sedentary behaviors with a duration associated with the lowest risk of dementia. The primary outcome was new-onset all-cause dementia.

RESULTS

During a median follow-up of 12.4 years, 4965 (2.9%) participants developed new-onset dementia. There were U-shaped associations for TV-watching and driving time, and a reversed J-shaped association for nonoccupational computer use time with new-onset all-cause dementia, with the lowest dementia risk at >0-<2 hours/day for all the 3 sedentary behaviors. Moreover, a higher healthy sedentary behavior score was significantly associated with a lower risk of all-cause dementia (per 1 score increment: hazard ratio 0.78, 95% CI 0.75-0.81), with a stronger inverse association in those with higher levels of high-sensitivity C-reactive protein and monocytes (both P-interactions <.05). Genetic risks of dementia did not significantly modify the association. Similar trends were found for new-onset Alzheimer's disease and vascular dementia.

CONCLUSIONS AND IMPLICATIONS

The associations between the duration of different sedentary behaviors and new-onset dementia were different in the older population. Moreover, the variety of sedentary behavior was inversely associated with new-onset dementia, especially among those with higher levels of inflammation.

Molecular Mechanisms of Dementia

The various forms of dementia and the other neurodegenerative disorders that affect memory, cognition, and behavior have become a public health priority across the developed world [...].

Metabolites of Life: Phosphate

The process of aging and escalating the failure of all body organs has become the center of interest in contemporary science and medicine. The leading role of phosphate-calcium tandem deficiency as a pacemaker of metabolic senescence has emerged recently. Most of the phosphates in the human body are stored in the bones, which seem to play a pivotal role in all metabolic and energetic processes. Bone metabolism combines physical activity with adaptive changes in the internal environment of the body, which is necessary for its survival. Phosphate-calcium signaling is the primary mechanism for controlling homeostasis and its recovery after exercise-induced disorders. Phosphates play an important role in the regulation of energy metabolism both by regulating postprandial glucose storage in the muscles and in the liver, as well as the distribution and adaptation of energy metabolites to the needs of the brain and skeletal muscles. The bone-driven energy metabolism is of decisive importance for maintaining all vital functions of the body organs, including their proper functioning and integrated interplay. The phosphate-calcium tandem contributes to the development and proper functioning of the organism, whereas energy dysmetabolism is the main cause of aging and the final termination of life.

Thermogenic Capacity of Human Supraclavicular Brown Fat and Cold-Stimulated Brain Glucose Metabolism

Human brain metabolism is susceptible to temperature changes. It has been suggested that the supraclavicular brown adipose tissue (BAT) protects the brain from these fluctuations by regulating heat production through the presence of uncoupling protein 1 (UCP-1). It remains unsolved whether inter-individual variation in the expression of UCP-1, which represents the thermogenic capacity of the supraclavicular BAT, is linked with brain metabolism during cold stress. Ten healthy human participants underwent 18F-FDG PET scanning of the brain under cold stimulus to determine brain glucose uptake (BGU). On a separate day, an excision biopsy of the supraclavicular fat—the fat proximal to the carotid arteries supplying the brain with warm blood—was performed to determine the mRNA expression of the thermogenic protein UCP-1. Expression of UCP-1 in supraclavicular BAT was directly related to the whole brain glucose uptake rate determined under cold stimulation (rho = 0.71, p = 0.03). In sub-compartmental brain analysis, UCP-1 expression in supraclavicular BAT was directly related to cold-stimulated glucose uptake rates in the hypothalamus, medulla, midbrain, limbic system, frontal lobe, occipital lobe, and parietal lobe (all rho ≥ 0.67, p < 0.05). These relationships were independent of body mass index and age. When analysing gene expressions of BAT secretome, we found a positive correlation between cold-stimulated BGU and DIO2. These findings provide evidence of functional links between brain metabolism under cold stimulation and UCP-1 and DIO2 expressions in BAT in humans. More research is needed to evaluate the importance of these findings in clinical outcomes, for instance, in examining the supporting role of BAT in cognitive functions under cold stress.

Mitochondria-Targeted Antioxidants, an Innovative Class of Antioxidant Compounds for Neurodegenerative Diseases: Perspectives and Limitations

Neurodegenerative diseases comprise a wide spectrum of pathologies characterized by progressive loss of neuronal functions and structures. Despite having different genetic backgrounds and etiology, in recent years, many studies have highlighted a point of convergence in the mechanisms leading to neurodegeneration: mitochondrial dysfunction and oxidative stress have been observed in different pathologies, and their detrimental effects on neurons contribute to the exacerbation of the pathological phenotype at various degrees. In this context, increasing relevance has been acquired by antioxidant therapies, with the purpose of restoring mitochondrial functions in order to revert the neuronal damage. However, conventional antioxidants were not able to specifically accumulate in diseased mitochondria, often eliciting harmful effects on the whole body. In the last decades, novel, precise, mitochondria-targeted antioxidant (MTA) compounds have been developed and studied, both in vitro and in vivo, to address the need to counter the oxidative stress in mitochondria and restore the energy supply and membrane potentials in neurons. In this review, we focus on the activity and therapeutic perspectives of MitoQ, SkQ1, MitoVitE and MitoTEMPO, the most studied compounds belonging to the class of MTA conjugated to lipophilic cations, in order to reach the mitochondrial compartment.