Dicarbonyl-mediated AGEing and diabetic kidney disease

Research advances of advanced glycation end products in milk and dairy products: Formation, determination, control strategy and immunometabolism via gut microbiota

Advanced glycosylation end products (AGEs) are a series of complex compounds which generate in the advanced phase of Maillard reaction, which can pose a non-negligible risk to human health. This article systematically encompasses AGEs in milk and dairy products under different processing conditions, influencing factors, inhibition mechanism and levels among the different categories of dairy products. In particular, it describes the effects of various sterilization techniques on the Maillard reaction. Different processing techniques have a significant effect on AGEs content. In addition, it clearly articulates the determination methods of AGEs and even discusses its immunometabolism via gut microbiota. It is observed that the metabolism of AGEs can affect the composition of the gut microbiota, which further has an impact on intestinal function and the gut-brain axis. This research also provides a suggestion for AGEs mitigation strategies, which are beneficial to optimize the dairy production, especially innovative processing technology application.

Research Progress on Mitochondrial Dysfunction in Diabetic Retinopathy

Diabetic Retinopathy (DR) is one of the most important microvascular complications of diabetes mellitus, which can lead to blindness in severe cases. Mitochondria are energy-producing organelles in eukaryotic cells, which participate in metabolism and signal transduction, and regulate cell growth, differentiation, aging, and death. Metabolic changes of retinal cells and epigenetic changes of mitochondria-related genes under high glucose can lead to mitochondrial dysfunction and induce mitochondrial pathway apoptosis. In addition, mitophagy and mitochondrial dynamics also change adaptively. These mechanisms may be related to the occurrence and progression of DR, and also provide valuable clues for the prevention and treatment of DR. This article reviews the mechanism of DR induced by mitochondrial dysfunction, and the prospects for related treatment.

Advanced Glycation End Products in Health and Disease

Advanced glycation end products (AGEs), formed through the nonenzymatic reaction of reducing sugars with the side-chain amino groups of lysine or arginine of proteins, followed by further glycoxidation reactions under oxidative stress conditions, are involved in the onset and exacerbation of a variety of diseases, including diabetes, atherosclerosis, and Alzheimer’s disease (AD) as well as in the secondary stages of traumatic brain injury (TBI). AGEs, in the form of intra- and interprotein crosslinks, deactivate various enzymes, exacerbating disease progression. The interactions of AGEs with the receptors for the AGEs (RAGE) also result in further downstream inflammatory cascade events. The overexpression of RAGE and the AGE-RAGE interactions are especially involved in cases of Alzheimer’s disease and other neurodegenerative diseases, including TBI and amyotrophic lateral sclerosis (ALS). Maillard reactions are also observed in the gut bacterial species. The protein aggregates found in the bacterial species resemble those of AD and Parkinson’s disease (PD), and AGE inhibitors increase the life span of the bacteria. Dietary AGEs alter the gut microbiota composition and elevate plasma glycosylation, thereby leading to systemic proinflammatory effects and endothelial dysfunction. There is emerging interest in developing AGE inhibitor and AGE breaker compounds to treat AGE-mediated pathologies, including diabetes and neurodegenerative diseases. Gut-microbiota-derived enzymes may also function as AGE-breaker biocatalysts. Thus, AGEs have a prominent role in the pathogenesis of various diseases, and the AGE inhibitor and AGE breaker approach may lead to novel therapeutic candidates.

Introduction to the Theme "Old and New Toxicology: Interfaces with Pharmacology"

The theme of Volume 61 is "Old and New Toxicology: Interfaces with Pharmacology." Old toxicology is exemplified by the authors of the autobiographical articles: B.M. Olivera's work on toxins and venoms from cone snails and P. Taylor's studies of acetylcholinesterase and the nicotinic cholinergic receptor, which serve as sites of action for numerous pesticides and venoms. Other articles in this volume focus on new understanding and new types of toxicology, including (a) arsenic toxicity, which is an ancient poison that, through evolution, has caused most multicellular organisms to express an active arsenic methyltransferase to methylate arsenite, which accelerates the excretion of arsenic from the body; (b) small molecules that react with lipid dicarbonyls, which are now considered the most toxic oxidative stress end products; (c) immune checkpoint inhibitors (ICIs), which have revolutionized cancer therapy but have numerous immune-related adverse events, including cardiovascular complications; (d) autoimmunity caused by the environment; (e) idiosyncratic drug-induced liver disease, which together with the toxicity of ICIs represents new toxicology interfacing with pharmacology; and (f) sex differences in the development of cardiovascular disease, with men more susceptible than women to vascular inflammation that initiates and perpetuates disease. These articles and others in Volume 61 reflect the interface and close integration of pharmacology and toxicology that began long ago but continues today.

AGE/RAGE in diabetic kidney disease and ageing kidney

Diabetic kidney disease (DKD) is the primary cause of chronic kidney disease that inevitably progress to end-stage kidney disease. Intervention strategies such as blood glucose control is effective for preventing DKD, but many patients with DKD still reach end-stage kidney disease. Although comprehensive mechanisms shed light on the progression of DKD, the most compelling evidence has highlighted that hyperglycemia-related advanced glycation end products (AGEs) formation plays a central role in the pathogenesis of DKD. Pathologically, accumulation of AGEs-mediated receptor for AGEs (RAGE) triggers oxidative stress and inflammation, which is the major deleterious effect of AGEs in host and intestinal microenvironment of diabetic and ageing conditions. The activation of AGEs-mediated RAGE could evoke nicotinamide adenine dinucleotide phosphate oxidase-induced reactive oxygen and nitrogen species production and subsequently give rise to oxidative stress in DKD and ageing kidney. Therefore, targeting RAGE with its ligands mediated oxidative stress and chronic inflammation is considered as an additional intervention strategy for DKD and ageing kidney. In this review, we summarize AGEs/RAGE-mediated oxidative stress and inflammation signaling pathways in DKD and ageing kidney, discussing opportunities and challenges of targeting at AGEs/RAGE-induced oxidative stress that could hold the promising potential approach for improving DKD and ageing kidney.

Targeting the Pathobiology of Diabetic Kidney Disease

The pathobiology of diabetic kidney disease (DKD) involves an interplay between all the many different cell types that exist within the kidney and their shared and cumulative dysfunction in response to chronic hyperglycemia. DKD is characteriszed by morphological changes including tubular hypertrophy, podocyte dysfunction, mesangial expansion and mesangiolysis, endothelitis and capillary rarefaction, arteriolar hyalinosis, basement membrane thickening, and ultimately nephron dropout and tubulointerstitial fibrosis. These adaptive but ultimately maladaptive changes accelerate the progression of lesions in the diabetic kidney by increasing mechanical and oxidative stress, hypoxia, fibrogenesis, inflammation, senescence, and apoptosis. In particular, atrophy at the critical junction between Bowman's capsule and the proximal tubule likely represent the leading cause of nephron dropout and kidney function decline in DKD. Preventing, slowing, or reversing these changes should be the target of future "smart" therapies for patients with DKD, many of which are now under development.

Association between glycation biomarkers, hyperglycemia, and micronucleus frequency: A meta -analysis

Micronucleus assay has been used as a biomarker of DNA damage, chromosomal instability, cancer risk and accelerated aging. In this review, a meta-analysis was performed to assess the association between micronuclei (MNi) and diseases with increased advanced glycation end products (AGEs) and HbA1c. The review identified eight studies with 632 subjects with disease and 547 controls. The Mean Ratio (MRi) for AGE levels (MRi = 2.92, 95 %CI: 2.06-4.13, P < 0.00001) and HbA1c levels (MRi = 1.32, 95 %CI: 1.12-1.56, P = 0.001) were significantly higher in the disease group compared to healthy controls. The meta-analysis indicated that the overall estimates of MRi for MNi was 1.83 (95 %CI: 1.38-2.42, p < 0.0001) in subjects with disease compared to controls. Significant increases in MRi for MNi were also observed in the following sub-groups: subjects with disease for elevated AGEs (MRi = 1.62, 95 %CI: 1.12-2.35, P = 0.01), elevated HbA1c (MRi = 2.13, 95 %CI: 1.33-3.39, P = 0.002), lymphocytes MNi (MRi = 1.74, 95 %CI: 1.29-2.33, P = 0.0003), exfoliated buccal cells MNi (MRi = 2.86, 95 %CI: 1.19-6.87, P = 0.02), type 2 diabetes mellitus (T2DM) (MRi = 1.99, 95 %CI: 1.17-3.39, P = 0.01), chronic renal disease (MRi = 1.68, 95 %CI: 1.18-2.38, P = 0.004) and other disease groups (MRi = 2.52, 95 %CI: 1.28-4.96, P = 0.008). The results of this review suggest that MNi could be used as a biomarker of DNA damage and chromosomal instability in degenerative disease where increased AGEs and HbA1c are implicated. The lack of heterogeneity for MN frequency when considered either for all studies or subgroup strengthened the MRi of the meta-analysis. However, the lack of significant association between MRi for MNi and MRi for AGEs or HbA1c indicates that the case-control studies investigated may be confounded by other variables. Thus, larger studies with long term AGE exposure is warranted to further understand the role of MN formation in the initiation and progression of diseases caused by excessive glycation.

Advanced glycation end products and their adverse effects: The role of autophagy

The critical roles played by advanced glycation endproducts (AGEs) accumulation in diabetes and diabetic complications have gained intense recognition. AGEs interfere with the normal functioning of almost every organ with multiple actions like apoptosis, inflammation, protein dysfunction, mitochondrial dysfunction, and oxidative stress. However, the development of a potential treatment strategy is yet to be established. Autophagy is an evolutionarily conserved cellular process that maintains cellular homeostasis with the degradation and recycling systems. AGEs can activate autophagy signaling, which could be targeted as a therapeutic strategy against AGEs induced problems. In this review, we have provided an overview of the adverse effects of AGEs, and we put forth the notion that autophagy could be a promising targetable strategy against AGEs.