Higher Dietary Intake of Advanced Glycation End Products Is Associated with Faster Cognitive Decline in Community-Dwelling Older Adults

The RAGE Axis: A Relevant Inflammatory Hub in Human Diseases

In 1992, a transcendental report suggested that the receptor of advanced glycation end-products (RAGE) functions as a cell surface receptor for a wide and diverse group of compounds, commonly referred to as advanced glycation end-products (AGEs), resulting from the non-enzymatic glycation of lipids and proteins in response to hyperglycemia. The interaction of these compounds with RAGE represents an essential element in triggering the cellular response to proteins or lipids that become glycated. Although initially demonstrated for diabetes complications, a growing body of evidence clearly supports RAGE's role in human diseases. Moreover, the recognizing capacities of this receptor have been extended to a plethora of structurally diverse ligands. As a result, it has been acknowledged as a pattern recognition receptor (PRR) and functionally categorized as the RAGE axis. The ligation to RAGE leads the initiation of a complex signaling cascade and thus triggering crucial cellular events in the pathophysiology of many human diseases. In the present review, we intend to summarize basic features of the RAGE axis biology as well as its contribution to some relevant human diseases such as metabolic diseases, neurodegenerative, cardiovascular, autoimmune, and chronic airways diseases, and cancer as a result of exposure to AGEs, as well as many other ligands.

Communal interaction of glycation and gut microbes in diabetes mellitus, Alzheimer's disease, and Parkinson's disease pathogenesis

Diabetes and its complications, Alzheimer's disease (AD), and Parkinson's disease (PD) are increasing gradually, reflecting a global threat vis-à-vis expressing the essentiality of a substantial paradigm shift in research and remedial actions. Protein glycation is influenced by several factors, like time, temperature, pH, metal ions, and the half-life of the protein. Surprisingly, most proteins associated with metabolic and neurodegenerative disorders are generally long-lived and hence susceptible to glycation. Remarkably, proteins linked with diabetes, AD, and PD share this characteristic. This modulates protein's structure, aggregation tendency, and toxicity, highlighting renovated attention. Gut microbes and microbial metabolites marked their importance in human health and diseases. Though many scientific shreds of evidence are proposed for possible change and dysbiosis in gut flora in these diseases, very little is known about the mechanisms. Screening and unfolding their functionality in metabolic and neurodegenerative disorders is essential in hunting the gut treasure. Therefore, it is imperative to evaluate the role of glycation as a common link in diabetes and neurodegenerative diseases, which helps to clarify if modulation of nonenzymatic glycation may act as a beneficial therapeutic strategy and gut microbes/metabolites may answer some of the crucial questions. This review briefly emphasizes the common functional attributes of glycation and gut microbes, the possible linkages, and discusses current treatment options and therapeutic challenges.

Association of Advanced Glycation End Products with Cognitive Function: HealthyDance Study

Background

The current research on advanced glycosylation end products (AGEs) and cognitive function is limited.

Objective

We aimed to investigate the relationship between multiple plasma AGEs and cognitive function and mild cognitive impairment (MCI).

Methods

Baseline data from The Lifestyle and Healthy Aging of Chinese Square Dancer Study was used in this cross-sectional study. Ultra-high-performance liquid chromatography tandem mass spectrometry was used to determine plasma levels of carboxymethyl lysine (CML), carboxyethyl lysine (CEL), and methyl imidazolinone (MG-H1). Four cognitive tests were used to obtain the four cognitive domain scores and the composite z scores. The Petersen criteria were used to diagnose MCI. The data were analyzed by multivariable linear and logistic regression models.

Results

This study included 1,018 participants (median age 61.0 years, 87.3% female). After multivariate adjustment, the βs of the highest quartile of CML and CEL compared to the lowest quartile were -0.28 (-0.38, -0.17) and -0.13 (-0.23, -0.03), respectively, for the composite z score. For the four cognitive domains, CML was negatively correlated with memory, attention, and executive function, and CEL was negatively associated with memory and language function. In addition, higher CML was associated with a higher odds of MCI. MG-H1 was not associated with cognitive function.

Conclusions

High plasma AGE levels were correlated with poorer cognitive function, particularly CML and CEL, higher levels of CML were also associated with higher odds of MCI. To clarify the effects of different AGEs on cognitive function and the underlying mechanisms, further longitudinal and experimental studies are needed.

Higher dietary advanced glycation products intake is associated with increased risk of dementia, independent from genetic predisposition

BACKGROUND

Dietary advanced glycation end products (AGEs) might exert adverse effects on cognition. The associations between dietary AGEs and long-term risk of dementia are yet to be assessed in large population studies. We aimed to explore whether elevated dietary AGEs intake is associated with increased risk of dementia, and whether this association might be affected by genetic risk.

METHODS

A prospective cohort study, which included a total of 93,830 participants (aged≥ 50 years) free from dementia at baseline of the UK Biobank study (2006-2010) and had at least two 24-h dietary assessments and were followed up until 2021. Dietary AGEs, including Nε-(1-Carboxyethyl)-l-lysine (CEL), Nε-(carboxymethyl) lysine (CML), and Nδ-(5-hydro-5-methyl-4-imidazolon-2-yl)-ornithine (MG-H1) were estimated via averaged data from the multiple 24-h food assessments according to the ultra-performance LC-tandem MS based dAGEs database. Incidence of all-cause dementia was ascertained through hospital inpatient and mortality records. Multivariable Cox regression models were utilized to estimate hazards ratios (HRs) and 95% confidence interval (CI) of dementia risk associated with dietary AGEs.

RESULTS

During a median follow-up of 11.9 years, 728 participants developed dementia. In multivariable adjusted model, when comparing the highest with the lowest tertile of intake level, HRs (95% CI) of dementia were 1.43 (1.16, 1.76) for total AGEs Z score, 1.53 (1.25, 1.89) for CEL, 1.27 (1.03, 1.56) for CML and 1.24 (1.02, 1.52) for MG-H1 (all P trend<0.01). There was no significant interaction between dietary AGEs intake, genetic risk and APOE ε4 carrier status for dementia.

CONCLUSIONS

Higher intakes of dietary AGEs including CEL, CML and MG-H1 were associated with a higher risk of dementia, independent from genetic risk, highlighting the significance of dietary AGEs restriction for dementia prevention.