Individual and Combined Associations of Glucose Metabolic Components With Cognitive Function Modified by Obesity

The obesity paradox in cognitive decline: Impact of BMI dynamics and APOE genotypes across various cognitive status

AIMS

To explore the relationship between body mass index (BMI) and its changes in relation to cognitive decline across different cognitive status, while also examining the role of the APOE genotype in these associations.

MATERIALS AND METHODS

A total of 23 255 individuals from the National Alzheimer's Coordinating Center (NACC) were analysed using multivariable logistic and Cox regression to assess BMI and its variability in relation to cognitive decline. Subgroup analyses were conducted to explore how APOE genotype interacts with BMI and cognitive decline.

RESULTS

Compared to individuals with normal cognition and normal BMI, being underweight was associated with a higher risk of developing MCI (HR 3.065, 95% CI: [1.156-8.126]) and dementia (HR 4.057, 95% CI: [1.433-11.483]). Over the 4.07-year follow-up, 9171 individuals experienced cognitive decline. Longitudinal analysis revealed that being overweight or obese was linked to a lower risk of cognitive decline across different cognitive status, including impaired not MCI, MCI and dementia, but had no effect on those with normal cognition. Additionally, compared to stable BMI, the hazard ratios (95% CI) for developing dementia were 2.336 (2.128-2.565) and 2.338 (2.119-2.581) for annual BMI gain or loss greater than 5%. However, different APOE genotypes may influence the effect of BMI and BMI variability on cognitive decline.

CONCLUSIONS

This research supports the 'obesity paradox' and highlights the critical role of APOE in modulating BMI's influence on cognitive health.

Understanding Cognitive Decline in Aging: Mechanisms and Mitigation Strategies - A Narrative Review

Cognitive decline is a natural process that accompanies aging. In some cases, such as in sarcopenia-burdened or diseased older adults, the disease course may be more rapid. Declining cognitive function is associated with changes in the central nervous system per se or peripheral triggers that impair cognition. This review discusses issues related to central, central-peripheral, and peripheral factors that enhance cognitive deterioration, such as cortical thickness, cerebral white matter structure and function, blood-brain barrier (BBB) disruption, insulin resistance, inflammation, and vascular dysfunction. BBB permeability appears to be a critical point for factors associated with aging that may accelerate cognitive decline. Thus, we provide an in-depth analysis of the central-peripheral crosstalk. Additionally, we discuss high-intensity interval training (HIIT) as a promising strategy to counteract changes that accompany the aging process. Resistance (RHIIT) and aerobic (AHIIT) may be beneficial for cognitive health among the elderly, but their lack of empirical confirmation is a huge gap in the research.

Combined impact of neutrophil-to-high-density lipoprotein cholesterol ratio (NHR) and cognitive function on all-cause mortality in older adults: a population-based study

BACKGROUND

The neutrophil-to-high-density lipoprotein cholesterol ratio (NHR) has emerged as a potential biomarker for chronic disease outcomes. Cognitive impairment is a major contributor to mortality in older adults. However, the combined effect of NHR and cognitive function on all-cause mortality remains unclear. This study aims to investigate the joint impact of NHR and cognitive impairment on all-cause mortality in this population.

METHODS

We analyzed participants in the National Health and Nutrition Examination Survey (NHANES) between 2011 and 2014. Participants were grouped according to NHR levels, DSST scores, and the combined NHR and DSST. Weighted Cox regression models assessed the association between NHR, cognitive impairment, and all-cause mortality. Weighted Kaplan-Meier curves estimated survival probabilities.

RESULTS

The study involved 1,486 participants (weighted sample was 54,078,084) aged 60 years and older, of whom 81.76% (n = 1,180) survived and 18.24% (n = 306) died by the end of follow-up. The median follow-up time was 78 months (IQR: 68-94). Weighted multivariable Cox regression revealed that high NHR (HR = 1.82, 95% CI: 1.21-2.74; P = 0.004), cognitive impairment (HR = 1.87, 95% CI: 1.25-2.79; P = 0.002), and the combination of high NHR and cognitive impairment (HR = 2.98, 95% CI: 1.45-6.14; P = 0.003) were independently associated with higher all-cause mortality, after full adjustment in model 3. Kaplan-Meier curves revealed significant survival differences, with the highest survival rate in the NHR Low & Normal cognition and the lowest in the NHR High & Cognitive impairment (P < 0.001).

CONCLUSIONS

High NHR and cognitive impairment in aged 60 years and older have an increased risk of all-cause mortality. These findings underscore the importance of integrating both NHR and cognitive assessments in mortality risk evaluations, offering a potential strategy for early intervention in aging populations.

Triglyceride-glucose index and mortality risks in Helicobacter pylori-infected patients: a national cohort study

BACKGROUND

While Helicobacter pylori (H. pylori) infection is associated with insulin resistance and higher mortality, research on insulin resistance indices and outcomes in H. pylori-infected patients is scarce. This study examines the association between the triglyceride-glucose (TyG) index, an insulin resistance marker, and all-cause and cardiovascular mortality in these patients.

METHODS

This study analyzed NHANES 1999-2000 data to assess the association between the TyG index and all-cause and cardiovascular mortality in H. pylori-infected patients using weighted Cox models and restricted cubic spline analysis.

RESULTS

Among 627 participants with a median follow-up of 20.8 years, 108 all-cause and 28 cardiovascular deaths occurred. Cox models showed that TyG was linked to a hazard ratio (HR) of 1.70 for all-cause mortality (95% CI: 1.23-2.34, P < 0.01) and an HR of 2.90 for cardiovascular mortality (95% CI: 1.91-4.42, P < 0.001). Restricted cubic spline analysis confirmed a linear relationship between the TyG index and both mortality risks. Stratified analyses showed that this relationship was significantly associated in most subgroups, but there was no significant interaction.

CONCLUSION

Higher TyG index is strongly linked to increased risks of both all-cause and cardiovascular mortality in H. pylori-infected patients.

Metformin-induced changes in the gut microbiome and plasma metabolome are associated with cognition in men

BACKGROUND

An altered gut microbiome characterized by reduced abundance of butyrate producing bacteria and reduced gene richness is associated with type 2 diabetes (T2D). An important complication of T2D is increased risk of cognitive impairment and dementia. The biguanide metformin is a commonly prescribed medication for the control of T2D and metformin treatment has been associated with a significant reduction in the risk of dementia and improved cognition, particularly in people with T2D.

AIM

To investigate the associations of metformin use with cognition exploring potential mechanisms by analyzing the gut microbiome and plasma metabolome using shotgun metagenomics and HPLC-ESI-MS/MS, respectively.

METHODS

We explored two independent cohorts: an observational study (Aging Imageomics) and a phase IV, randomized, double-blind, parallel-group, randomized pilot study (MEIFLO). From the two studies, we analyzed four study groups: (1) individuals with no documented medical history or medical treatment (n = 172); (2) people with long-term T2D on metformin monotherapy (n = 134); (3) people with long-term T2D treated with oral hypoglycemic agents other than metformin (n = 45); (4) a newly diagnosed T2D subjects on metformin monotherapy (n = 22). Analyses were also performed stratifying by sex.

RESULTS

Several bacterial species belonging to the Proteobacteria (Escherichia coli) and Verrucomicrobia (Akkermansia muciniphila) phyla were positively associated with metformin treatment, while bacterial species belonging to the Firmicutes phylum (Romboutsia timonensis, Romboutsia ilealis) were negatively associated. Due to the consistent increase in A. muciniphila and decrease in R.ilealis in people with T2D subjects treated with metformin, we investigated the association between this ratio and cognition. In the entire cohort of metformin-treated T2D subjects, the A.muciniphila/R.ilealis ratio was not significantly associated with cognitive test scores. However, after stratifying by sex, the A.muciniphila/R. ilealis ratio was significantly and positively associated with higher memory scores and improved memory in men. Metformin treatment was associated with an enrichment of microbial pathways involved in the TCA cycle, and butanoate, arginine, and proline metabolism in both cohorts. The bacterial genes involved in arginine metabolism, especially in production of glutamate (astA, astB, astC, astD, astE, putA), were enriched following metformin intake. In agreement, in the metabolomics analysis, metformin treatment was strongly associated with the amino acid proline, a metabolite involved in the metabolism of glutamate.

CONCLUSIONS

The beneficial effects of metformin may be mediated by changes in the composition of the gut microbiota and microbial-host-derived co-metabolites.

Metformin, Cognitive Function, and Changes in the Gut Microbiome

The decline in cognitive function and the prevalence of neurodegenerative disorders are among the most serious threats to health in old age. The prevalence of dementia has reached 50 million people worldwide and has become a major public health problem. The causes of age-related cognitive impairment are multiple, complex, and difficult to determine. However, type 2 diabetes (T2D) is linked to an enhanced risk of cognitive impairment and dementia. Human studies have shown that patients with T2D exhibit dysbiosis of the gut microbiota. This dysbiosis may contribute to the development of insulin resistance and increased plasma lipopolysaccharide concentrations. Metformin medication mimics some of the benefits of calorie restriction and physical activity, such as greater insulin sensitivity and decreased cholesterol levels, and hence may also have a positive impact on aging in humans. According to recent human investigations, metformin might partially restore gut dysbiosis related to T2D. Likewise, some studies showed that metformin reduced the risk of dementia and improved cognition, although not all studies are concordant. Therefore, this review focused on those human studies describing the effects of metformin on the gut microbiome (specifically the changes in taxonomy, function, and circulating metabolomics), the changes in cognitive function, and their possible bidirectional implications.

Identification of IGF-1 Effects on White Adipose Tissue and Hippocampus in Alzheimer's Disease Mice via Transcriptomic and Cellular Analysis

Alzheimer's disease (AD) stands as the most prevalent neurodegenerative disorder, characterized by a multitude of pathological manifestations, prominently marked by the aggregation of amyloid beta. Recent investigations have revealed a compelling association between excessive adiposity and glial activation, further correlating with cognitive impairments. Additionally, alterations in levels of insulin-like growth factor 1 (IGF-1) have been reported in individuals with metabolic conditions accompanied by memory dysfunction. Hence, our research endeavors to comprehensively explore the impact of IGF-1 on the hippocampus and adipose tissue in the context of Alzheimer's disease. To address this, we have conducted an in-depth analysis utilizing APP/PS2 transgenic mice, recognized as a well-established mouse model for Alzheimer's disease. Upon administering IGF-1 injections to the APP/PS2 mice, we observed notable alterations in their behavioral patterns, prompting us to undertake a comprehensive transcriptomic analysis of both the hippocampal and adipose tissues. Our data unveiled significant modifications in the functional profiles of these tissues. Specifically, in the hippocampus, we identified changes associated with synaptic activity and neuroinflammation. Concurrently, the adipose tissue displayed shifts in processes related to fat browning and cell death signaling. In addition to these findings, our analysis enabled the identification of a collection of long non-coding RNAs and circular RNAs that exhibited significant changes in expression subsequent to the administration of IGF-1 injections. Furthermore, we endeavored to predict the potential roles of these identified RNA molecules within the context of our study. In summary, our study offers valuable transcriptome data for hippocampal and adipose tissues within an Alzheimer's disease model and posits a significant role for IGF-1 within both the hippocampus and adipose tissue.

Research Progress on Lipocalin-2 in Diabetic Encephalopathy

Diabetic encephalopathy is a central nervous complication of diabetes mellitus which is characterized by cognitive impairment and structural and neurochemical abnormalities, which is easily neglected. Lipocalin-2 (LCN2) is a 25 kDa transporter in the lipocalin family that can transport small molecules, including fatty acids, iron, steroids, and lipopolysaccharides in the circulation. Recently, LCN2 has been found to be a significant regulator of insulin resistance and glucose homeostasis. Numerous studies have shown that LCN2 is connected to central nervous system abnormalities, including neuroinflammation and neurodegeneration, while the latest researches have found that LCN2 is closely related to the development of diabetic encephalopathy. Nevertheless, its precise role in the pathogenesis of diabetic encephalopathy remains to be determined. In this paper, we review recent evidence on the role of LCN2 in diabetic encephalopathy from multiple perspectives in order to decipher the impact of LCN2 in both the aetiology and treatment of diabetic encephalopathy.

The Triglyceride-Glucose Index Is Associated with Longitudinal Cognitive Decline in a Middle-Aged to Elderly Population: A Cohort Study

BACKGROUND

To examine the effect of the triglyceride-glucose (TyG) index on longitudinal cognitive decline in a healthy middle-aged-to-elderly population.

METHODS

We conducted a population-based longitudinal study. A total of 1774 participants without cognitive impairment were enrolled in the 4-year follow-up. They were divided into four groups according to the quartile of the TyG index. Multivariable-adjusted Cox proportional hazard models were performed to examine the association between the TyG index and cognitive decline. Discrimination tests were used to evaluate the incremental predictive value of the TyG index beyond conventional risk factors.

RESULTS

During the follow-up, compared with those in the bottom quartile group, participants in the top TyG quartile group presented a 51% increase in the risk of cognitive decline (OR 1.51 (95% CI: 1.06-2.14)). As shown by discrimination tests, adding the TyG index into the conventional model resulted in a slight improvement in predicting the risk of cognitive decline (NRI 16.00% (p = 0.004)).

CONCLUSION

This study demonstrated that increasing values of the TyG index were positively associated with the risk of cognitive decline. Monitoring the TyG index may help in the early identification of individuals at high risk of cognitive deterioration.

4-Chloro-1,2-phenylenediamine induced structural perturbation and genotoxic aggregation in human serum albumin

4-Chloro-1,2-phenylenediamine (4-Cl-OPD) is a halogenated aromatic diamine used as a precursor in permanent hair color production. Despite its well-documented mutagenic and carcinogenic effects in various in vitro and in vivo models, its role in fibrillar aggregate formation and their genotoxic effect in therapeutic proteins has received less attention. The significance of human serum albumin (HSA) arises from its involvement in bio-regulatory and transport processes. HSA misfolding and aggregation are responsible for some of the most frequent neurodegenerative disorders. We used various complementary approaches to track the formation of amyloid fibrils and their genotoxic effect. Molecular dynamics study demonstrated the complex stability. The impact of 4-Cl-OPD on the structural dynamics of HSA was confirmed by Raman spectroscopy, X-ray diffraction, HPLC and SDS-PAGE. Fibrilllar aggregates were investigated using Congo red assay, DLS, and SEM. The genotoxic nature of 4-Cl-OPD was confirmed using plasmid nicking assay and DAPI staining, which revealed DNA damage and cell apoptosis. 4-Cl-OPD provides a model system for studying fibrillar aggregation and their genotoxic potential in the current investigation. Future studies should investigate the inhibition of the aggregation/fibrillation process, which may yield valuable clinical insights.

4-Chloro-1,2-phenylenediamine induced structural perturbation and genotoxic aggregation in human serum albumin

4-Chloro-1,2-phenylenediamine (4-Cl-OPD) is a halogenated aromatic diamine used as a precursor in permanent hair color production. Despite its well-documented mutagenic and carcinogenic effects in various in vitro and in vivo models, its role in fibrillar aggregate formation and their genotoxic effect in therapeutic proteins has received less attention. The significance of human serum albumin (HSA) arises from its involvement in bio-regulatory and transport processes. HSA misfolding and aggregation are responsible for some of the most frequent neurodegenerative disorders. We used various complementary approaches to track the formation of amyloid fibrils and their genotoxic effect. Molecular dynamics study demonstrated the complex stability. The impact of 4-Cl-OPD on the structural dynamics of HSA was confirmed by Raman spectroscopy, X-ray diffraction, HPLC and SDS-PAGE. Fibrilllar aggregates were investigated using Congo red assay, DLS, and SEM. The genotoxic nature of 4-Cl-OPD was confirmed using plasmid nicking assay and DAPI staining, which revealed DNA damage and cell apoptosis. 4-Cl-OPD provides a model system for studying fibrillar aggregation and their genotoxic potential in the current investigation. Future studies should investigate the inhibition of the aggregation/fibrillation process, which may yield valuable clinical insights.