Advanced Glycation End Products: New Clinical and Molecular Perspectives

Metformin attenuates high-carbohydrate diet-induced redox imbalance, inflammation, and mitochondrial dysfunction in Megalobrama amblycephala

This study aimed to investigate the effects of dietary metformin supplementation on the redox balance, inflammation, mitochondrial biogenesis, and function in blunt snout bream fed a high-carbohydrate (HC) diet. Fish (45.12 ± 0.36 g) were randomly offered four diets, including a control diet (33% carbohydrate), an HC diet (45% carbohydrate), and the HC diet supplemented with 0.06% (HCM1) and 0.12% (HCM2) metformin respectively for 12 weeks. Compared with the control, feeding the HC diet significantly increased the hepatosomatic index (HSI), the mesenteric fat index, liver and muscle glycogen contents, liver and adipose tissue lipid contents, plasma glucose and glycation end products (AGES) levels and aspartate transaminase activity, plasma and liver malondialdehyde (MDA) contents, hepatic adenosine triphosphate (ATP) and adenosine monophosphate (AMP) contents, mitochondrial cytochrome c content, mitochondrial complex IV activity and ATP 6 transcription, but decreased plasma catalase (CAT) activity, muscle superoxide dismutase (SOD) activity, hepatic antioxidant enzymes activities, and the transcriptions of transforming growth factor β (tgfβ) and interleukin 10 (il10). Compared with the HC group, metformin treatment (especially the HCM2 group) significantly elevated tissue glycogen contents, muscle SOD activity, plasma and liver antioxidant enzymes activities, the transcriptions of tgfβ and il10, the sodium/potassium ATPase activity, the contents of mitochondrial protein and AMP, the level of p-AMP activated protein kinase (AMPK), and the p-AMPK/t-AMPK ratio, but lowered the HSI, tissue lipid contents, plasma levels of glucose, AGES and glycated serum protein, plasma, and liver MDA contents, the transcriptions of il1β, NADH dehydrogenase subunit 1 and ATP 6, the contents of ATP and cytochrome c, the ATP/AMP ratio, and the activities of complexes I and IV. In conclusion, metformin could attenuate the HC diet-induced redox imbalance, inflammation, and mitochondrial dysfunction in blunt snout bream.

Metabolic Syndrome and Biotherapeutic Activity of Dairy (Cow and Buffalo) Milk Proteins and Peptides: Fast Food-Induced Obesity Perspective-A Narrative Review

Metabolic syndrome (MS) is defined by the outcome of interconnected metabolic factors that directly increase the prevalence of obesity and other metabolic diseases. Currently, obesity is considered one of the most relevant topics of discussion because an epidemic heave of the incidence of obesity in both developing and underdeveloped countries has been reached. According to the World Obesity Atlas 2023 report, 38% of the world population are presently either obese or overweight. One of the causes of obesity is an imbalance of energy intake and energy expenditure, where nutritional imbalance due to consumption of high-calorie fast foods play a pivotal role. The dynamic interactions among different risk factors of obesity are highly complex; however, the underpinnings of hyperglycemia and dyslipidemia for obesity incidence are recognized. Fast foods, primarily composed of soluble carbohydrates, non-nutritive artificial sweeteners, saturated fats, and complexes of macronutrients (protein-carbohydrate, starch-lipid, starch-lipid-protein) provide high metabolic calories. Several experimental studies have pointed out that dairy proteins and peptides may modulate the activities of risk factors of obesity. To justify the results precisely, peptides from dairy milk proteins were synthesized under in vitro conditions and their contributions to biomarkers of obesity were assessed. Comprehensive information about the impact of proteins and peptides from dairy milks on fast food-induced obesity is presented in this narrative review article.

Prunin from Poncirus trifoliata (L.) Rafin Inhibits Aldose Reductase and Glucose-Fructose-Mediated Protein Glycation and Oxidation of Human Serum Albumin

Diabetes complications are associated with aldose reductase (AR) and advanced glycation end products (AGEs). Using bioassay-guided isolation by column chromatography, 10 flavonoids and one coumarin were isolated from Poncirus trifoliata Rafin and tested in vitro for an inhibitory effect against human recombinant AR (HRAR) and rat lens AR (RLAR). Prunin, narirutin, and naringin inhibited RLAR (IC50 0.48-2.84 μM) and HRAR (IC50 0.68-4.88 μM). Docking simulations predicted negative binding energies and interactions with the RLAR and HRAR binding pocket residues. Prunin (0.1 and 12.5 μM) prevented the formation of fluorescent AGEs and nonfluorescent Nε-(carboxymethyl) lysine (CML), as well as the fructose-glucose-mediated protein glycation and oxidation of human serum albumin (HSA). Prunin suppressed the formation of the β-cross-amyloid structure of HSA. These results indicate that prunin inhibits oxidation-dependent protein damage, AGE formation, and AR, which may help prevent diabetes complications.

An overview on glycation: molecular mechanisms, impact on proteins, pathogenesis, and inhibition

The formation of a heterogeneous set of advanced glycation end products (AGEs) is the final outcome of a non-enzymatic process that occurs in vivo on long-life biomolecules. This process, known as glycation, starts with the reaction between reducing sugars, or their autoxidation products, with the amino groups of proteins, DNA, or lipids, thus gaining relevance under hyperglycemic conditions. Once AGEs are formed, they might affect the biological function of the biomacromolecule and, therefore, induce the development of pathophysiological events. In fact, the accumulation of AGEs has been pointed as a triggering factor of obesity, diabetes-related diseases, coronary artery disease, neurological disorders, or chronic renal failure, among others. Given the deleterious consequences of glycation, evolution has designed endogenous mechanisms to undo glycation or to prevent it. In addition, many exogenous molecules have also emerged as powerful glycation inhibitors. This review aims to provide an overview on what glycation is. It starts by explaining the similarities and differences between glycation and glycosylation. Then, it describes in detail the molecular mechanism underlying glycation reactions, and the bio-molecular targets with higher propensity to be glycated. Next, it discusses the precise effects of glycation on protein structure, function, and aggregation, and how computational chemistry has provided insights on these aspects. Finally, it reports the most prevalent diseases induced by glycation, and the endogenous mechanisms and the current therapeutic interventions against it.

Protective effect of Inonotus obliquus polysaccharide on MGO-induced nonenzymatic glycation fibroblasts

Background

The nonenzymatic glycation of fibroblasts causes functional downregulation and behavioral disorders in the skin.

Methods

To investigate the effect of Inonotus obliquus on the nonenzymatic glycation of skin, we examined the inhibition of advanced glycation end products (AGEs) using four extraction methods: n-butanol, ethyl acetate, n-hexane and aqueous alcohol precipitation. The physical properties and chemical structure of the most effective, purified, crude I. obliquus polysaccharide (IOP) were examined. The effects of IOP on carboxymethyl lysine (CML) accumulation, inflammatory factor release, reactive oxygen species (ROS) production, key extracellular matrix (ECM) protein (MMP 1, 2 and 9; FN-1, LM-5 and COL-1) mRNA expression, and cell survival, migration and adhesion were also examined via cellular assays.

Results

IOP is a polysaccharide with a molecular weight (Mw) of 2.396 × 104 (±6.626%) that is composed mainly of glucose, galactose, xylose, mannose and arabinose (29.094:21.705:14.857:9.375:7.709). In addition, a cellular antiglycation assay showed that IOP, which can promote ECM formation by inhibiting the accumulation of CML, inhibiting the release of inflammatory factors (IL-1β, IL-6, and TNF-α), inhibiting the production of reactive oxygen species (ROS), inhibiting the expression of matrix metalloproteinases (MMP-1\-2\-9), promoting the synthesis of ECMs (COL1, FN1, and LM5), and improving cellular dysfunction, had strong antiglycation activity at concentrations in the range of 6-24 μg/mL.

Conclusion

IOP effectively reduced the levels of inflammatory factors and reactive oxygen species produced by AGEs, further preventing the impairment of cell behavior (decreased migration and reduced cell adhesion) and preventing the downregulation of the expression of key extracellular matrix proteins induced by AGEs. The results indicate the potential application of IOP as an AGE inhibitor in skin care.

(+)-Catechin mitigates impairment in insulin secretion and beta cell damage in methylglyoxal-induced pancreatic beta cells

BACKGROUND

The formation of advanced glycation end products (AGEs) is the central process contributing to diabetic complications in diabetic individuals with sustained and inconsistent hyperglycemia. Methylglyoxal, a reactive carbonyl species, is found to be a major precursor of AGEs, and its levels are elevated in diabetic conditions. Dysfunction of pancreatic beta cells and impairment in insulin secretion are the hallmarks of diabetic progression. Exposure to methylglyoxal-induced AGEs alters the function and maintenance of pancreatic beta cells. Hence, trapping methylglyoxal could be an ideal approach to alleviate AGE formation and its influence on beta cell proliferation and insulin secretion, thereby curbing the progression of diabetes to its complications.

METHODS AND RESULTS

In the present study, we have explored the mechanism of action of (+)-Catechin against methylglyoxal-induced disruption in pancreatic beta cells via molecular biology techniques, mainly western blot. Methylglyoxal treatment decreased insulin synthesis (41.5%) via downregulating the glucose-stimulated insulin secretion pathway (GSIS). This was restored upon co-treatment with (+)-Catechin (29.9%) in methylglyoxal-induced Beta-TC-6 cells. Also, methylglyoxal treatment affected the autocrine function of insulin by disrupting the IRS1/PI3k/Akt pathway. Methylglyoxal treatment suppresses Pdx-1 and Maf A levels, which are responsible for beta cell maintenance and cell proliferation. (+)-Catechin could significantly augment the levels of these transcription factors.

CONCLUSION

This is the first study to examine the impact of a natural compound on methylglyoxal with the insulin-mediated autocrine and paracrine activities of pancreatic beta cells. The results indicate that (+)-Catechin exerts a protective effect against methylglyoxal exposure in pancreatic beta cells and can be considered a potential anti-glycation agent in further investigations on ameliorating diabetic complications.

Optimization of guideline-directed medical therapies in patients with diabetes and chronic kidney disease

Diabetes is the leading cause of chronic kidney disease (CKD) and kidney failure worldwide. CKD frequently coexists with heart failure and atherosclerotic cardiovascular disease in the broader context of cardio-kidney-metabolic syndrome. Diabetes and CKD are associated with increased risk of all-cause and cardiovascular death as well as decreased quality of life. The role of metabolic and hemodynamic abnormalities has long been recognized as an important contributor to the pathogenesis and progression of CKD in diabetes, while a more recent and growing body of evidence supports activation of both systemic and local inflammation as important contributors. Current guidelines recommend therapies targeting pathomechanisms of CKD in addition to management of traditional risk factors such as hyperglycemia and hypertension. Sodium-glucose cotransporter-2 inhibitors are recommended for treatment of patients with CKD and type 2 diabetes (T2D) if eGFR is ≥20 ml/min/173 m2 on a background of renin-angiotensin system inhibition. For patients with T2D, CKD, and atherosclerotic cardiovascular disease, a glucagon-like peptide-1 receptor agonist is recommended as additional risk-based therapy. A non-steroidal mineralocorticoid receptor antagonist is also recommended as additional risk-based therapy for persistent albuminuria in patients with T2D already treated with renin-angiotensin system inhibition. Implementation of guideline-directed medical therapies is challenging in the face of rapidly accumulating knowledge, high cost of medications, and lack of infrastructure for optimal healthcare delivery. Furthermore, studies of new therapies have focused on T2D and CKD. Clinical trials are now planned to inform the role of these therapies in people with type 1 diabetes (T1D) and CKD.

Advanced glycation end products of dietary origin and their association with inflammation in diabetes - A minireview

Advanced glycation end products (AGEs) are a diverse group of compounds that are formed as a result of the non-enzymatic reaction between a reducing sugar such as glucose and the free NH2 groups of an amino acid in a protein or other biomolecule. The chemical reaction, by which these products are generated, is known as the Maillard reaction and occurs as a part of the body's normal metabolism. Such a reaction is enhanced during diabetes due to hyperglycemia, but it can also occur during the preparation, processing, and preservation of certain foods. Therefore, AGEs can also be obtained from the diet (d-AGE) and contribute to an increase of the total serum pool of these compounds. They have been implicated in a wide variety of pathological processes, mainly because of their ability to induce inflammatory responses and oxidative stress increase. They are extensively accumulated as a part of the normal aging, especially in tissues rich in long half-life proteins, which can compromise the physiology of these tissues. d-AGEs are abundant in diets rich in processed fats and sugars. This review is addressed to the current knowledge on these products and their impact on the immunomodulation of various mechanisms that may contribute to exacerbation of the diabetes pathophysiology.

Incretin Therapies for Patients with Type 2 Diabetes and Chronic Kidney Disease

Since the early 2000s, an influx of novel glucose-lowering agents has changed the therapeutic landscape for treatment of diabetes and diabetes-related complications. Glucagon-like peptide-1 (GLP-1) receptor agonists represent an important therapeutic class for the management of type 2 diabetes (T2D), demonstrating benefits beyond glycemic control, including lowering of blood pressure and body weight, and importantly, decreased risk of development of new or worsening chronic kidney disease (CKD) and reduced rates of atherosclerotic cardiovascular events. Plausible non-glycemic mechanisms that benefit the heart and kidneys with GLP-1 receptor agonists include anti-inflammatory and antioxidant effects. Further supporting their use in CKD, the glycemic benefits of GLP-1 receptor agonists are preserved in moderate-to-severe CKD. Considering current evidence, major guideline-forming organizations recommend the use of GLP-1 receptor agonists in cases of T2D and CKD, especially in those with obesity and/or in those with high cardiovascular risk or established heart disease. Evidence continues to build that supports benefits to the heart and kidneys of the dual GLP-1/glucose-dependent insulinotropic polypeptide (GIP) receptor agonist tirzepatide. Ongoing outcome and mechanistic studies will continue to inform our understanding of the role of GLP-1 and dual GLP-1/GIP receptor agonists in diverse patient populations with kidney disease.

Methylglyoxal in Cardiometabolic Disorders: Routes Leading to Pathology Counterbalanced by Treatment Strategies

Methylglyoxal (MGO) is the major compound belonging to reactive carbonyl species (RCS) responsible for the generation of advanced glycation end products (AGEs). Its upregulation, followed by deleterious effects at the cellular and systemic levels, is associated with metabolic disturbances (hyperglycemia/hyperinsulinemia/insulin resistance/hyperlipidemia/inflammatory processes/carbonyl stress/oxidative stress/hypoxia). Therefore, it is implicated in a variety of disorders, including metabolic syndrome, diabetes mellitus, and cardiovascular diseases. In this review, an interplay between pathways leading to MGO generation and scavenging is addressed in regard to this system's impairment in pathology. The issues associated with mechanistic MGO involvement in pathological processes, as well as the discussion on its possible causative role in cardiometabolic diseases, are enclosed. Finally, the main strategies aimed at MGO and its AGEs downregulation with respect to cardiometabolic disorders treatment are addressed. Potential glycation inhibitors and MGO scavengers are discussed, as well as the mechanisms of their action.

Advanced glycation end products: Key mediator and therapeutic target of cardiovascular complications in diabetes

The incidence of type 2 diabetes mellitus is growing in epidemic proportions and has become one of the most critical public health concerns. Cardiovascular complications associated with diabetes are the leading cause of morbidity and mortality. The cardiovascular diseases that accompany diabetes include angina, myocardial infarction, stroke, peripheral artery disease, and congestive heart failure. Among the various risk factors generated secondary to hyperglycemic situations, advanced glycation end products (AGEs) are one of the important targets for future diagnosis and prevention of diabetes. In the last decade, AGEs have drawn a lot of attention due to their involvement in diabetic patho-physiology. AGEs can be derived exogenously and endogenously through various pathways. These are a non-homogeneous, chemically diverse group of compounds formed non-enzymatically by condensation between carbonyl groups of reducing sugars and free amino groups of protein, lipids, and nucleic acid. AGEs mediate their pathological effects at the cellular and extracellular levels by multiple pathways. At the cellular level, they activate signaling cascades via the receptor for AGEs and initiate a complex series of intracellular signaling resulting in reactive oxygen species generation, inflammation, cellular proliferation, and fibrosis that may possibly exacerbate the damaging effects on cardiac functions in diabetics. AGEs also cause covalent modifications and cross-linking of serum and extracellular matrix proteins; altering their structure, stability, and functions. Early diagnosis of diabetes may prevent its progression to complications and decrease its associated comorbidities. In the present review, we recapitulate the role of AGEs as a crucial mediator of hyperglycemia-mediated detrimental effects in diabetes-associated complications. Furthermore, this review presents an overview of future perspectives for new therapeutic interventions to ameliorate cardiovascular complications in diabetes.

Maternal n-7 Unsaturated Fatty Acids Protect the Fetal Brain from Neuronal Degeneration in an Intrauterine Hyperglycemic Animal Model

We previously reported that glycation induces insulin resistance in the hearts of newborn pups from a gestational diabetes mellitus (GDM) rat model. Administration of n-3 unsaturated fatty acids suppressed glycation and improved signaling in GDM rat pups. In this study, we investigated their effects on cranial neurons using the GDM rat model and PC12 cells derived from rat adrenal pheochromocytomas. Additionally, we examined whether n-3 and n-7 unsaturated fatty acids (cis-palmitoleic acid [CPA] and trans-palmitoleic acid [TPA]) ameliorate the detrimental effects of high glucose exposure on rats. In the neonatal cerebrum of GDM rats, increased levels of advanced glycation end products (AGEs) inhibited Akt phosphorylation; however, CPA and TPA intake during pregnancy ameliorated these abnormalities. Furthermore, exposure to high-glucose-induced apoptosis in PC12 cells compared to the cells cultured in control glucose. PC12 cells exposed to high-glucose with fatty acids exhibited reduced AGE production and apoptosis induction compared to the high-glucose group. These findings suggest that a hyperglycemic environment during pregnancy promotes AGE formation in brain neuronal proteins and induces apoptosis. Both TPA and CPA mitigated these abnormalities; however, CPA is cytotoxic, highlighting its safety in pregnant women.

Sudomotor dysfunction in diabetic peripheral neuropathy (DPN) and its testing modalities: A literature review

Long term consequences of diabetes mellitus (DM) may include multi-organ complications such as retinopathy, cardiovascular disease, neuronal, and kidney damage. One of the most prevalent complication is diabetic peripheral neuropathy (DPN), occurring in half of all diabetics, and is the main cause of disability globally with profound impact on a patient's quality of life. Small fiber neuropathy (SFN) can develop in the pre-diabetes stage preceding large fiber damage in DPN. Asymptomatic SFN is difficult to diagnose in early stages, with sudomotor dysfunction considered one of the earliest manifestations of autonomic neuropathy. Early detection is crucial as it can prevent potential cardiovascular events. Although punch skin biopsy is the gold-standard method for SFN diagnosis, implementation as routine screening is hindered due to its invasive, impractical, and time-consuming nature. Other sudomotor testing modalities, most of which evaluate the postganglionic cholinergic sympathetic nervous system, have been developed with varying sensitivity and specificity for SFN diagnosis. Here, we provide an overview on the general mechanism of DPN, the importance of sudomotor assessment for early detection of autonomic dysfunction in DPN, the benefits and disadvantages of current testing modalities, factors that may affect testing, and the importance of future discoveries on sudomotor testing for successful DPN diagnosis.

Post-synthesis of covalent organic frameworks as a hydrophilic platform for specific detection of egg ovalbumin under physiological pH

Ovalbumin (OVA) is an important protein source in our daily life. Unfortunately, the food safety problem has become more and more serious, such as protein allergy and contaminated protein. Therefore, it is necessary to detect vital proteins efficiently and rapidly. Mass spectrometry (MS) is a powerful tool for the detection of proteins. Herein, dual amino acids functionalized covalent organic frameworks containing disulfide covalent bonds (COF@SS@GC, where G is glutathione and C is cysteine) were facilely prepared for OVA enrichment through hydrophilic interaction liquid chromatography (HILIC) under physiological pH. The results showed that COF@SS@GC had displayed sensitive detection (0.1 fmol), good selectivity (OVA: BSA = 1:100), adsorption capacity (311 mg/g), stability, reproducibility, linearity, LOQ level (42 μg/mL) and recovery ratio (64.83 %) for OVA. COF@SS@GC also demonstrated satisfactory purification ability in the enrichment of egg white, indicating that COF@SS@GC had great potential in the enrichment of protein from complex samples.

Oxidative Stress in Diabetic Peripheral Neuropathy: Pathway and Mechanism-Based Treatment

Diabetic peripheral neuropathy (DPN) is a major complication of diabetes mellitus with a high incidence. Oxidative stress, which is a crucial pathophysiological pathway of DPN, has attracted much attention. The distortion in the redox balance due to the overproduction of reactive oxygen species (ROS) and the deregulation of antioxidant defense systems promotes oxidative damage in DPN. Therefore, we have focused on the role of oxidative stress in the pathogenesis of DPN and elucidated its interaction with other physiological pathways, such as the glycolytic pathway, polyol pathway, advanced glycosylation end products, protein kinase C pathway, inflammation, and non-coding RNAs. These interactions provide novel therapeutic options targeting oxidative stress for DPN. Furthermore, our review addresses the latest therapeutic strategies targeting oxidative stress for the rehabilitation of DPN. Antioxidant supplements and exercise have been proposed as fundamental therapeutic strategies for diabetic patients through ROS-mediated mechanisms. In addition, several novel drug delivery systems can improve the bioavailability of antioxidants and the efficacy of DPN.

Clinical significance of skin autofluorescence for diabetic macroangiopathy and comparison with conventional markers of atherosclerosis: a cross-sectional and prospective study

Background

Skin autofluorescence (SAF) is a marker for the accumulation of advanced glycation end products (AGEs), and is associated with diabetic macroangiopathy. However, whether SAF is superior to conventional markers of atherosclerosis such as carotid intima-media thickness (IMT) and pulse wave velocity (PWV) in detecting macroangiopathy remains unclear.

Methods

We recruited 845 patients with type 2 diabetes enrolled in a community diabetes cohort (ViNA cohort) who had SAF, IMT, and PWV measured at baseline. The prevalence of macroangiopathy at baseline and new cardiovascular events during the 2-year follow-up period was investigated. SAF was measured using an AGE reader. Coronary artery calcification (CAC) was measured by computed tomography in 485 patients. Peripheral artery disease (PAD) was defined as the ankle-brachial blood pressure ratio of ≤ 0.9.

Results

SAF, IMT, and PWV were significantly correlated with each other, and age, diabetes duration, and estimated glomerular filtration rate were their strong confounders. SAF was associated with baseline stroke and new stroke after adjusting for confounders, but not with coronary artery disease (CAD) or PAD. The nonsignificant relationship between SAF and CAD was consistent with the relationship between SAF and CAC. Multivariate analysis showed a significant association of SAF with baseline and new stroke independent of IMT and PWV. Maximum-IMT was significantly associated with baseline CAD, PAD, and stroke, but not with a new stroke, whereas PWV was associated with a new stroke.

Conclusion

Among diabetic macroangiopathies, SAF is a good stroke biomarker, but not for CAD and PAD.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13340-022-00608-8.

Oxidative Stress in Type 2 Diabetes: The Case for Future Pediatric Redoxomics Studies

Considerable evidence supports the role of oxidative stress in adult type 2 diabetes (T2D). Due to increasing rates of pediatric obesity, lack of physical activity, and consumption of excess food calories, it is projected that the number of children living with insulin resistance, prediabetes, and T2D will markedly increase with enormous worldwide economic costs. Understanding the factors contributing to oxidative stress and T2D risk may help develop optimal early intervention strategies. Evidence suggests that oxidative stress, triggered by excess dietary fat consumption, causes excess mitochondrial hydrogen peroxide emission in skeletal muscle, alters redox status, and promotes insulin resistance leading to T2D. The pathophysiological events arising from excess calorie-induced mitochondrial reactive oxygen species production are complex and not yet investigated in children. Systems medicine is an integrative approach leveraging conventional medical information and environmental factors with data obtained from “omics” technologies such as genomics, proteomics, and metabolomics. In adults with T2D, systems medicine shows promise in risk assessment and predicting drug response. Redoxomics is a branch of systems medicine focusing on “omics” data related to redox status. Systems medicine with a complementary emphasis on redoxomics can potentially optimize future healthcare strategies for adults and children with T2D.

Advanced Glycation End Products in the Skin: Molecular Mechanisms, Methods of Measurement, and Inhibitory Pathways

Advanced glycation end products (AGEs) are a series of stable compounds produced under non-enzymatic conditions by the amino groups of biomacromolecules and the free carbonyl groups of glucose or other reducing sugars commonly produced by thermally processed foods. AGEs can cause various diseases, such as diabetes, atherosclerosis, neurodegeneration, and chronic kidney disease, by triggering the receptors of AGE (RAGEs) in the human body. There is evidence that AGEs can also affect the different structures and physiological functions of the skin. However, the mechanism is complicated and cumbersome and causes various harms to the skin. This article aims to identify and summarise the formation and characteristics of AGEs, focussing on the molecular mechanisms by which AGEs affect the composition and structure of normal skin substances at different skin layers and induce skin issues. We also discuss prevention and inhibition pathways, provide a systematic and comprehensive method for measuring the content of AGEs in human skin, and summarise and analyse their advantages and disadvantages. This work can help researchers acquire a deeper understanding of the relationship between AGEs and the skin and provides a basis for the development of effective ingredients that inhibit glycation.

Advanced Glycation End-Products (AGEs): Formation, Chemistry, Classification, Receptors, and Diseases Related to AGEs

Advanced glycation end-products (AGEs) constitute a non-homogenous, chemically diverse group of compounds formed either exogeneously or endogeneously on the course of various pathways in the human body. In general, they are formed non-enzymatically by condensation between carbonyl groups of reducing sugars and free amine groups of nucleic acids, proteins, or lipids, followed by further rearrangements yielding stable, irreversible end-products. In the last decades, AGEs have aroused the interest of the scientific community due to the increasing evidence of their involvement in many pathophysiological processes and diseases, such as diabetes, cancer, cardiovascular, neurodegenerative diseases, and even infection with the SARS-CoV-2 virus. They are recognized by several cellular receptors and trigger many signaling pathways related to inflammation and oxidative stress. Despite many experimental research outcomes published recently, the complexity of their engagement in human physiology and pathophysiological states requires further elucidation. This review focuses on the receptors of AGEs, especially on the structural aspects of receptor-ligand interaction, and the diseases in which AGEs are involved. It also aims to present AGE classification in subgroups and to describe the basic processes leading to both exogeneous and endogeneous AGE formation.

The Role of Advanced Glycation End Products and Its Soluble Receptor in Kidney Diseases

Patients with chronic kidney disease (CKD) are more prone to oxidative stress and chronic inflammation, which may lead to an increase in the synthesis of advanced glycation end products (AGEs). Because AGEs are mostly removed by healthy kidneys, AGE accumulation is a result of both increased production and decreased kidney clearance. On the other hand, AGEs may potentially hasten decreasing kidney function in CKD patients, and are independently related to all-cause mortality. They are one of the non-traditional risk factors that play a significant role in the underlying processes that lead to excessive cardiovascular disease in CKD patients. When AGEs interact with their cell-bound receptor (RAGE), cell dysfunction is initiated by activating nuclear factor kappa-B (NF-κB), increasing the production and release of inflammatory cytokines. Alterations in the AGE-RAGE system have been related to the development of several chronic kidney diseases. Soluble RAGE (sRAGE) is a decoy receptor that suppresses membrane-bound RAGE activation and AGE-RAGE-related toxicity. sRAGE, and more specifically, the AGE/sRAGE ratio, may be promising tools for predicting the prognosis of kidney diseases. In the present review, we discuss the potential role of AGEs and sRAGE as biomarkers in different kidney pathologies.

Pancreatic Stellate Cells and Metabolic Alteration: Physiology and Pathophysiology

Pancreatic stellate cells play a pivotal role in the development of pancreatic fibrosis. A wide variety of external stimuli can cause PSC activation accompanied by metabolic changes, which alters the tissue microenvironment by producing extracellular matrix proteins, cytokines, growth factors, and other mediators. Several metabolites aggravate fibrosis and inflammation by acting as key activating factors for PSCs. In other words, PSCs sense systemic metabolic changes. The detrimental effects of PSC activation on normal pancreatic cells, especially islet cells, further complicate metabolic imbalance through the dysregulation of glucose metabolism. PSC activation promotes cancer by altering the metabolism in pancreatic cancer cells, which collaborate with PSCs to efficiently adapt to environmental changes, promoting their growth and survival. This collaboration also contributes to the acquisition of chemoresistance. PSCs sequester chemotherapeutic agents and produce competing molecules as additional resistance mechanisms. The application of these metabolic targets for novel therapeutic strategies is currently being explored. This mini-review summarizes the role of PSCs in metabolic regulation of normal and cancerous cells.

Stasis dermatitis: A skin manifestation of poor prognosis in patients with heart failure

BACKGROUND

 The relationship between stasis dermatitis (SD), clinical factors, and heart failure (HF) outcomes in outpatients has not been previously assessed.

METHODS

 This observational cross-sectional study evaluated 324 patients admitted to the HF outpatient clinic. A total of 158 HF outpatients (100 males and 58 females) were enrolled in the study and were divided into two groups depending on whether they were diagnosed with SD within six months before attending the outpatient clinic. Forty-one patients (26 %) diagnosed with SD in the preceding six months were designated group 1, and 117 (74 %) not diagnosed were designated group 2.

RESULTS

 Diabetes mellitus (DM) (OR =5.473, p <0.001), chronic obstructive pulmonary disease (COPD) (OR =2.623, p =0.039), and increased systolic pulmonary artery pressure (SPAP) (OR =1.061, p =0.001) values were independently associated with SD in multivariate logistic regression analysis. During the follow-up of 12 ± 4 months, no significant difference was documented between group 1 and group 2 regarding the death ratio (17 % vs. 19 %, p =0.991). In the multivariate Cox proportional-hazards model with a stepwise forward method, the presence of SD diagnosis [hazard ratio (HR) =2.933, 95 % Confidence Interval (CI): 1.660-5.181, p <0.001] and coronary artery disease (CAD) (HR=2.492, 95%CI: 1.238-5.018, p= 0.011) remained independently associated with the risk of HF-related hospitalization.

CONCLUSION

SD was found, for the first time, to be independently associated with DM, COPD, and increased SPAP values and determined as an independent predictor for HF-related hospitalization.HIPPOKRATIA 2022, 26 (1):13-18.

Exploration of Noninvasive Detection of Advanced Glycation End Products in the Lens to Screen for Diabetic Kidney Disease

Diabetic kidney disease (DKD) is a complication of diabetes, which is the most common cause of end-stage renal disease (dialysis). DKD has a high mortality rate, and only early detection can nip this disease in the bud. Advanced glycation end products (AGEs)are generally believed to be involved in the occurrence of DKD. Studies have shown that the lens AGEs fluorescence for noninvasive detection has high consistency with the gold standard OGTT, has high sensitivity and specificity, and could be used as a practical tool for the early screening of type 2 diabetes mellitus (T2DM).Therefore, we speculated that the noninvasive lens AGEs fluorescence detection method can be used to predict the occurrence of DKD. This study detected levels of AGEs in multiple cellular and tissues and analyzed the relationships between AGEs and lens, eyeballs, peripheral blood mononuclear cell (PBMC), serum, and kidney. Additionally, we examined the possible role of lens AGEs fluorescence in DKD screening. Our preexperimental study found that lens AGE levels in patients with T2DM were positively correlated with PBM and serum AGE levels. Lens AGE levels in patients with T2DM were negatively correlated with eGFR and positively correlated with urinary ACR. The animal and cell experiments showed that the AGE levels in the eyeballs of DM mice were also positively correlated with those in the serum and kidney. To increase the reliability of the experiment, we increased the sample size. In our results, lens AGEs levels were positively correlated with the occurrence of DKD, and the incidence of DKD in the high lens AGEs group was 2.739 times that in the low lens AGEs group. The receiver operating characteristic (ROC) curves showed that patients with T2DM with a lens AGEs value ≥ 0.306 were likely to have DKD. The area under the ROC curve of the noninvasive technique for identifying DKD was 0.757 (95% Cl: 0.677-0.838, p<0.001), and the sensitivity and specificity were 70.0% and 78.7%, respectively. These results suggest that noninvasive lens AGEs detection technology has certain clinical value in diagnosing whether patients with T2DM have DKD.