Advanced glycation end products (AGEs) promote melanogenesis through receptor for AGEs

Unveiling the mechanism of high sugar diet induced advanced glycosylation end products damage skin structure via extracellular matrix-receptor interaction pathway

BACKGROUND

AGEs accumulate in the skin as a result of a high-sugar diet and play an important role in the skin aging process.

OBJECTIVES

The aim of this study was to characterize the mechanism underlying the effect of a high-sugar diet on skin aging damage at a holistic level.

METHODS

We established a high-sugar diet mouse model to compare and analyze differences in physiological indexes. The effect of a high-sugar diet on skin aging damage was analyzed by means of a transcriptome study and staining of pathological sections. Furthermore, the differences in the protein expression of AGEs and ECM components between the HSD and control groups were further verified by immunohistochemistry.

RESULTS

The skin in the HSD group mice tended toward a red, yellow, dark, and deep color. In addition, the epidermis was irregular with anomalous phenomena, the epidermis was thinned, and the dermis lost its normal structure and showed vacuolated changes. Transcriptomics results revealed significant downregulation of the ECM-receptor interaction pathway, significant upregulation of the expression of AGEs and significant downregulation of the expression levels of COLI, FN1, LM5, and TNC, among others ECM proteins and ECM receptors.

CONCLUSIONS

High-sugar diets cause skin aging damage by inducing the accumulation of AGEs, disrupting the expression of ECM proteins and their receptors, and downregulating the ECM-receptor interaction pathway, which affects cellular behavioral functions such as cell proliferation, migration, and adhesion, as well as normal skin tissue structure.

The effects of advanced glycation end-products on skin and potential anti-glycation strategies

The advanced glycation end-products (AGEs) are produced through non-enzymatic glycation between reducing sugars and free amino groups, such as proteins, lipids or nucleic acids. AGEs can enter the body through daily dietary intake and can also be generated internally via normal metabolism and external stimuli. AGEs bind to cell surface receptors for AGEs, triggering oxidative stress and inflammation responses that lead to skin ageing and various diseases. Evidence shows that AGEs contribute to skin dysfunction and ageing. This review introduces the basic information, the sources, the metabolism and absorption of AGEs. We also summarise the detrimental mechanisms of AGEs to skin ageing and other chronic diseases. For the potential strategies for counteracting AGEs to skin and other organs, we summarised the pathways that could be utilised to resist glycation. Chemical and natural-derived anti-glycation approaches are overviewed. This work offers an understanding of AGEs to skin ageing and other chronic diseases and may provide perspectives for the development of anti-glycation strategies.

Association between advanced glycation end products and uveitis/scleritis activity in patients with active immune-mediated ocular inflammatory diseases

PURPOSE

To investigate for association between skin autofluorescence (SAF) advanced glycation end products (AGEs) and uveitis/scleritis activity in systemic inflammatory disease-related active non-infectious uveitis/scleritis patients.

METHODS

This cross-sectional study was conducted at Siriraj Hospital during October 2019 to March 2020. AGEs were measured by SAF method in systemic immune-related disease patients with active uveitis/scleritis, and those results were compared with those of healthy age-matched controls.

RESULTS

Thirty-one active non-infectious uveitis/scleritis patients and 31 age-matched controls were enrolled. The mean age of patients was 40.0 ± 12.8 years, and most were female (55.0%). The most common associated systemic immune-related disease was Vogt-Koyanagi-Harada disease (n = 14). Mean SAF AGE level in the study group compared to the control group was 2.38 ± 0.66 arbitrary units (AU) versus 2.58 ± 0.56 AU, respectively (p = 0.20). Multivariate analysis showed decreased SAF AGE level to be significantly associated with active ocular inflammation, (odds ratio: 0.01, 95% confidence interval: 0.00004-0.81; p = 0.04).

CONCLUSIONS

SAF AGE level was not so far found to be a reliable biomarker for indicating uveitis/scleritis activity in systemic immune-related disease patients with active ocular inflammation.

CLINICAL TRIAL REGISTRATION

Thai Clinical Trials Registry, https://www.thaiclinicaltrials.org/ . (Reg. No. TCTR20200114004, registered date 01/01/2020, beginning date of the trial 10/01/2019).

A20 ameliorates advanced glycation end products-induced melanogenesis by inhibiting NLRP3 inflammasome activation in human dermal fibroblasts

BACKGROUND

Advanced glycation end products (AGEs) promote melanogenesis through activating NLRP3 inflammasome in fibroblasts. Although A20 has been highlighted to inhibit NLRP3 inflammasome activation, its roles and mechanisms remain elusive in photoaging-associated pigmentation.

OBJECTIVES

To determine the significance of fibroblast A20 in AGEs-induced NLRP3 inflammasome activation and pigmentation.

METHODS

The correlation between A20 and AGEs or melanin was studied in sun-exposed skin and lesions of melasma and solar lentigo. We then investigated A20 level in AGEs-treated fibroblast and the effect of fibroblast A20 overexpression or knockdown on AGEs-BSA-induced NLRP3 inflammasome activation and pigmentation, respectively. Finally, the severity of NLRP3 inflammasome activation and pigmentation was evaluated after mice were injected intradermally with A20-overexpression adeno-associated virus and AGEs-BSA.

RESULTS

Dermal A20 expression was decreased and exhibited negative correlation with either dermal AGEs deposition or epidermal melanin level in sun-exposed skin and pigmentary lesions. Moreover, both AGEs-BSA and AGEs-collagen robustly decreased A20 expression via binding to RAGE in fibroblasts. Further, A20 overexpression or depletion significantly decreased or augmented AGEs-BSA-induced activation of NF-κB pathway and NLRP3 inflammasome and IL-18 production and secretion in fibroblasts, respectively. Importantly, fibroblast A20 potently repressed AGEs-BSA-stimulated melanin content，tyrosinase activity，and expression of microphthalmia-associated transcription factor and tyrosinase in melanocytes. Particularly, fibroblast A20 significantly abrogated AGEs-BSA-promoted melanogenesis in ex vivo skin and mouse models. Additionally, fibroblast A20 inhibited AGEs-BSA-activated MAPKs in melanocytes and the epidermis of ex vivo skin.

CONCLUSIONS

Fibroblast A20 suppresses AGEs-stimulate melanogenesis in photoaging-associated hyperpigmentation disorders by inhibiting NLRP3 inflammasome activation.

Ingestion of a collagen peptide containing high concentrations of prolyl-hydroxyproline and hydroxyprolyl-glycine reduces advanced glycation end products levels in the skin and subcutaneous blood vessel walls: a randomized, double-blind, placebo-controlled study

In this randomized, double-blind, placebo-controlled study, we investigated the effects of collagen peptides (CP) containing high concentrations of prolyl-hydroxyproline and hydroxyprolyl-glycine on advanced glycation end products (AGEs) levels in the skin and subcutaneous blood vessel walls. A total of 31 individuals aged 47-87 years were randomly assigned to receive either 5 g/day of fish-derived CP or a placebo for 12 weeks. Body and blood compositions and AGEs levels were measured at the beginning and end of the study. No adverse events were observed, and both groups' blood and body compositions did not change significantly. However, the CP group had significantly lower AGEs levels and a slightly lower insulin resistance index (homeostasis model assessment ratio [HOMA-R]) than the placebo group. In addition, the percentage changes in AGEs and HOMA-R levels were positively and strongly correlated in both groups. These findings suggest that fish-derived CP may be effective in reducing AGEs levels and improving insulin resistance.

AGEs Blocker™ (Goji Berry, Fig, and Korean Mint Mixed Extract) Inhibits Skin Aging Caused by Streptozotocin-Induced Glycation in Hairless Mice

Glycation is a cause of skin aging. This study investigated in a glycation-induced skin aging mouse model the effects on skin and mechanism of action of AGEs Blocker™ (AB), which contains goji berry, fig, and Korean mint mixed extract. This study sought to demonstrate the antiglycation effect of streptozotocin, thereby improving skin aging, by measuring advanced glycation end products (AGEs) and various skin parameters, including collagen; matrix metalloproteinases (MMPs); inflammatory cytokines; activities of oxidative enzymes; and skin wrinkles, elasticity, and hydration. This study found that skin wrinkles, elasticity, and hydration improved with AB. Particularly, the oral administration of AB suppressed AGEs, receptors of AGEs, and carboxymethyl lysine in blood and skin tissue. In addition, AB increased the activities of antioxidative enzymes, reduced inflammatory cytokines, suppressed MMP-9 expression, and increased the contents of collagen and hyaluronic acid, ultimately suppressing skin wrinkles and increasing skin elasticity and hydration. Therefore, AB can inhibit skin aging through its antiglycation effect and is thus considered a good ingredient for skin care products.

Autophagy Activation Promoted by Pulses of Light and Phytochemicals Counteracting Oxidative Stress during Age-Related Macular Degeneration

The seminal role of autophagy during age-related macular degeneration (AMD) lies in the clearance of a number of reactive oxidative species that generate dysfunctional mitochondria. In fact, reactive oxygen species (ROS) in the retina generate misfolded proteins, alter lipids and sugars composition, disrupt DNA integrity, damage cell organelles and produce retinal inclusions while causing AMD. This explains why autophagy in the retinal pigment epithelium (RPE), mostly at the macular level, is essential in AMD and even in baseline conditions to provide a powerful and fast replacement of oxidized molecules and ROS-damaged mitochondria. When autophagy is impaired within RPE, the deleterious effects of ROS, which are produced in excess also during baseline conditions, are no longer counteracted, and retinal degeneration may occur. Within RPE, autophagy can be induced by various stimuli, such as light and naturally occurring phytochemicals. Light and phytochemicals, in turn, may synergize to enhance autophagy. This may explain the beneficial effects of light pulses combined with phytochemicals both in improving retinal structure and visual acuity. The ability of light to activate some phytochemicals may further extend such a synergism during retinal degeneration. In this way, photosensitive natural compounds may produce light-dependent beneficial antioxidant effects in AMD.

Enzymatic Deglycation of Damaged Skin by Means of Combined Treatment of Fructosamine-3-Kinase and Fructosyl-Amino Acid Oxidase

The consensus in aging is that inflammation, cellular senescence, free radicals, and epigenetics are contributing factors. Skin glycation through advanced glycation end products (AGEs) has a crucial role in aging. Additionally, it has been suggested that their presence in scars leads to elasticity loss. This manuscript reports fructosamine-3-kinase (FN3K) and fructosyl-amino acid oxidase (FAOD) in counteracting skin glycation by AGEs. Skin specimens were obtained (n = 19) and incubated with glycolaldehyde (GA) for AGE induction. FN3K and FAOD were used as monotherapy or combination therapy. Negative and positive controls were treated with phosphate-buffered saline and aminoguanidine, respectively. Autofluorescence (AF) was used to measure deglycation. An excised hypertrophic scar tissue (HTS) (n = 1) was treated. Changes in chemical bonds and elasticity were evaluated using mid-infrared spectroscopy (MIR) and skin elongation, respectively. Specimens treated with FN3K and FAOD in monotherapy achieved an average decrease of 31% and 33% in AF values, respectively. When treatments were combined, a decrease of 43% was achieved. The positive control decreased by 28%, whilst the negative control showed no difference. Elongation testing of HTS showed a significant elasticity improvement after FN3K treatment. ATR-IR spectra demonstrated differences in chemical bounds pre- versus post-treatment. FN3K and FAOD can achieve deglycation and the effects are most optimal when combined in one treatment.

The Essential Role of Light-Induced Autophagy in the Inner Choroid/Outer Retinal Neurovascular Unit in Baseline Conditions and Degeneration

The present article discusses the role of light in altering autophagy, both within the outer retina (retinal pigment epithelium, RPE, and the outer segment of photoreceptors) and the inner choroid (Bruch's membrane, BM, endothelial cells and the pericytes of choriocapillaris, CC). Here autophagy is needed to maintain the high metabolic requirements and to provide the specific physiological activity sub-serving the process of vision. Activation or inhibition of autophagy within RPE strongly depends on light exposure and it is concomitant with activation or inhibition of the outer segment of the photoreceptors. This also recruits CC, which provides blood flow and metabolic substrates. Thus, the inner choroid and outer retina are mutually dependent and their activity is orchestrated by light exposure in order to cope with metabolic demand. This is tuned by the autophagy status, which works as a sort of pivot in the cross-talk within the inner choroid/outer retina neurovascular unit. In degenerative conditions, and mostly during age-related macular degeneration (AMD), autophagy dysfunction occurs in this area to induce cell loss and extracellular aggregates. Therefore, a detailed analysis of the autophagy status encompassing CC, RPE and interposed BM is key to understanding the fine anatomy and altered biochemistry which underlie the onset and progression of AMD.

Resveratrol Alleviates Diabetic Periodontitis-Induced Alveolar Osteocyte Ferroptosis Possibly via Regulation of SLC7A11/GPX4

The mode and mechanism of diabetic periodontitis-induced alveolar-osteocyte death are still unclear. This study aimed to investigate the occurrence of ferroptosis in alveolar osteocytes during diabetic periodontitis and the therapeutic potential of resveratrol to alleviate osteocyte ferroptosis. Diabetic periodontitis was induced in C57/BL6-male mice and treated with or without resveratrol. Periodontitis pathogenicity was analyzed by micro-CT and histology, and alveolar-osteocyte ferroptosis was analyzed by immunohistochemistry. MLOY4 osteocytes were treated with P. gingivalis-derived lipopolysaccharide (LPS)+advanced glycosylated end products (AGEs) mimicking diabetic periodontitis condition in vitro, with or without resveratrol or ferrostatin-1 (ferroptosis inhibitor). Osteocyte ferroptosis and expression of inflammatory mediators were analyzed. Diabetic periodontitis aggravated periodontitis pathogenicity and inhibited the expression of GPX4 and SLC7A11 in alveolar osteocytes and resveratrol alleviated these effects. LPS+AGEs triggered osteocyte ferroptosis in vitro as indicated by the downregulated GPX4 and SLC7A11, upregulated malondialdehyde, disrupted mitochondrial morphology, and overexpressed pro-inflammatory mediators IL-1β, TNF-α, SOST, RANKL, and IL-6, and ferrostatin-1 or resveratrol treatment reversed these effects. LPS+AGEs upregulated pIKBα and pNF-κB p65 expression in osteocytes, and resveratrol or ferrostatin-1 reversed this effect. In conclusion, diabetic periodontitis triggers alveolar osteocyte ferroptosis possibly via disruption of the SLC7A11/GPX4 axis, and resveratrol has therapeutic potential to correct this biological event.

Anti-cyclooxygenase, anti-glycation, and anti-skin aging effect of Dendrobium officinale flowers’ aqueous extract and its phytochemical validation in aging

Introduction

Dendrobium officinale Kimura et Migo (D. officinale) , widely called as “life-saving immortal grass” by Chinese folk, is a scarce and endangered species. The edible stems of D. officinale have been extensively studied for active chemical components and various bioactivities. However, few studies have reported the well-being beneficial effects of D. officinale flowers (DOF). Therefore, the present study aimed to investigate the in vitro biological potency of its aqueous extract and screen its active components.

Methods

Antioxidant tests, including 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), the ferric reducing ability of plasma (FRAP), and intracellular reactive oxygen species (ROS) level analyses in primary human epidermal keratinocytes, anti-cyclooxygenase2 (COX-2) assay, anti-glycation assay (both fluorescent AGEs formation in a BSA fructose/glucose system and glycation cell assay), and anti-aging assay (quantification of collagen types I and III, and SA-β-gal staining assay) were conducted to determine the potential biological effects of DOF extracts and its major compounds. Ultra-performance liquid chromatography-electrospray ionisation-quadrupole-time-of-flight-mass spectrometry (UPLC-ESI-QTOF-MS/MS) was performed to investigate the composition of DOF extracts. Online antioxidant post-column bioassay tests were applied to rapidly screen major antioxidants in DOF extracts.

Results and discussion

The aqueous extract of D. officinale flowers was found to have potential antioxidant capacity, anti-cyclooxygenase2 (COX-2) effect, anti-glycation potency, and anti-aging effects. A total of 34 compounds were identified using UPLC-ESI-QTOF-MS/MS. Online ABTS radical analysis demonstrated that 1-O-caffeoyl-β-D-glucoside, vicenin-2, luteolin-6-C-β-D-xyloside-8-C-β--D-glucoside, quercetin-3-O-sophoroside, rutin, isoquercitrin, and quercetin 3-O-(6″-O-malonyl)-β-D-glucoside are the major potential antioxidants. In addition, all selected 16 compounds exerted significant ABTS radical scavenging ability and effective AGE suppressive activities. However, only certain compounds, such as rutin and isoquercitrin, displayed selective and significant antioxidant abilities, as shown by DPPH and FRAP, as well as potent COX-2 inhibitory capacity, whereas the remaining compounds displayed relatively weak or no effects. This indicates that specific components contributed to different functionalities. Our findings justified that DOF and its active compound targeted related enzymes and highlighted their potential application in anti-aging.

The Association between the Level of Advanced Glycation End Products and Objective Skin Quality Parameters

Advanced glycation end products (AGEs) represent an endogenously produced or exogenously derived group of compounds derived from nonenzymatic glycation. Recent experimental studies are suggesting that AGEs could play an important role in the skin's quality and its aging process. Hence, the aim of this study was to clinically evaluate the AGEs and skin quality parameters across different age groups in the general population. The study included 237 participants. Melanin, erythema, hydration, friction and transepidermal water loss (TEWL) were evaluated using noninvasive probes, while AGEs were evaluated using a skin autofluorescence reader. There was a significant positive correlation between AGEs and the amount of melanin (p < 0.001), erythema (p < 0.001) and TEWL (p < 0.001), while there was a significant negative correlation between AGEs and hydration (p < 0.001) and friction (p < 0.001). After dividing the sample into three groups depending on their age, in all three groups, there was a significant positive correlation between AGEs and the melanin count (p < 0.001) and TEWL (p < 0.001), while there was a significant negative correlation between AGEs and skin hydration (p < 0.001). Multiple linear regression analysis showed that the level of AGEs as a dependent variable retained a significant association with age (p < 0.001), melanin (p < 0.001), erythema (p = 0.005) and TEWL (p < 0.001) as positive predictors. Moreover, AGEs retained a significant association with skin hydration (p < 0.001) and friction (p = 0.017) as negative predictors. These outcomes imply that AGEs could be linked with the complex physiology of the skin and its aging process.

Compounds in Indonesian Ginger Rhizome Extracts and Their Potential for Anti-Skin Aging Based on Molecular Docking

Skin aging is a condition caused by reactive oxygen species (ROS) and advanced glycation end products (AGEs). Indonesian gingers (Zingiber officinale), which consists of Gajah (GG), Red (MM), and Emprit (EE) ginger, are thought to produce anti-skin aging compounds through enzyme inhibition. The enzymes used in the molecular docking study were collagenase, hyaluronidase, elastase, and tyrosinase. This study aimed to determine the compounds contained in Indonesian ginger rhizome ethanolic extracts using liquid chromatography–mass spectrometry/mass spectrometry to differentiate metabolites contained in the different Indonesian ginger rhizome extracts. A principal component analysis (PCA) and a heat map analysis were used in order to determine which compounds and extracts contained potential anti-skin aging properties based on a molecular docking study. Ascorbic acid was used as a control ligand in the molecular docking study. Ninety-eight compounds were identified in three different ginger rhizomes extracts and were grouped into three separate quadrants. The most potent compound for anti-skin aging in the Indonesian ginger rhizome extracts was octinoxate. Octinoxate showed a high abundance in the EE ginger rhizome extract. Therefore, the EE ginger extract was the Indonesian ginger rhizome extract with the greatest potential for anti-skin aging.

Research Advances on the Damage Mechanism of Skin Glycation and Related Inhibitors

Our skin is an organ with the largest contact area between the human body and the external environment. Skin aging is affected directly by both endogenous factors and exogenous factors (e.g., UV exposure). Skin saccharification, a non-enzymatic reaction between proteins, e.g., dermal collagen and naturally occurring reducing sugars, is one of the basic root causes of endogenous skin aging. During the reaction, a series of complicated glycation products produced at different reaction stages and pathways are usually collectively referred to as advanced glycation end products (AGEs). AGEs cause cellular dysfunction through the modification of intracellular molecules and accumulate in tissues with aging. AGEs are also associated with a variety of age-related diseases, such as diabetes, cardiovascular disease, renal failure (uremia), and Alzheimer's disease. AGEs accumulate in the skin with age and are amplified through exogenous factors, e.g., ultraviolet radiation, resulting in wrinkles, loss of elasticity, dull yellowing, and other skin problems. This article focuses on the damage mechanism of glucose and its glycation products on the skin by summarizing the biochemical characteristics, compositions, as well as processes of the production and elimination of AGEs. One of the important parts of this article would be to summarize the current AGEs inhibitors to gain insight into the anti-glycation mechanism of the skin and the development of promising natural products with anti-glycation effects.

Evaluation of Skin Biophysical Parameters and Angiogenesis Using CD34 as a Biomarker in Older Diabetic Women Treated with Radiofrequency

Background

The prevalence of type 2 diabetes mellitus (t2DM) has been steadily increasing. Patients with t2DM need to slow down the skin ageing processes and to obtain a rejuvenating effect. Treatments that do not damage the superficial layers of the epidermis could be a promising solution for those patients.

Purpose

The aim of this study was to evaluate the effects of radiofrequency therapy on the biophysical parameters and angiogenesis of facial skin, using CD34 as a biomarker in older diabetic women treated with metformin.

Patients and Methods

A total of 45 subjects with phototype 2 or 3 (Fitzpatrick scale) were investigated (25 t2DM – study group, 20 – healthy controls). A series of 6 treatments (once a week) with a Radio Frequency Skin Rejuvenation System device was used on facial skin. Measurements of skin hydration, transepidermal water loss (TEWL), melanin and erythema index, temperature, and pH, at baseline and after radiofrequency therapy were performed with the Courage + Khazaka MPA-9 device. Immunohistochemistry on paraffin-embedded sections was used to evaluate the intensity of CD34 expression.

Results

Radiofrequency treatment significantly improved facial skin hydration (p < 0.0001). Enhancement of the epidermal barrier observed, by reduced TEWL as a result of a series of treatments with radiofrequency on the facial skin (p < 0.0001), was observed. CD34 was more abundantly expressed after radiofrequency treatment. No side effects were observed.

Conclusion

Treatment with radiofrequency is an effective and non-invasive method of facial skin rejuvenation in older women with t2DM, with a relatively short post-procedure recovery time and low potential for severe adverse effects.

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.

Non-invasive and rapid diagnosis of type 2 diabetes mellitus based on the analysis of hair by front-face fluorescence spectroscopy

Rapid and early detection of pathologies for screening purposes is not always easy with traditional methods. New low-cost optical techniques that are suitable for preventive detection and, more specifically, for developing countries must be developed. The objective of this work is to propose UV-VIS fluorescence of hair as a promising technique for a simple and rapid preliminary diagnosis of type II diabetes. In this work, we analyzed 130 hair samples taken from volunteers of different ages at the Habib Thameur Hospital in Tunis, Tunisia. These samples were analyzed clinically beforehand, and 50 were classified as healthy acting as a control, 24 were classified as low-level diabetics with a glycated hemoglobin A1C (HbA1c) <7%, and the other 56 were classified as high-level diabetics having an HbA1c >7%. The fluorescence of the patients' hair led to several interesting results. Indeed, a clear discrimination was obtained not only between the healthy and patients with a disease, but also a discrimination between diabetics with low levels and high levels or diabetics with and without complication. Also, a strong correlation between fluorescence spectra and glycated HbA1c for the diabetic population was clearly established. A linear discriminant analysis shows that it is possible to predict the status of test patients after having trained a fraction of the population. All these results show the ability of the front-face fluorescence (FFF) technique to detect disease and predict advanced states simply by capturing the fluorescence of the hair illuminated by a single LED. This work shows for the first time, to our knowledge, the capability of the FFF technique on hair samples for the diagnosis of diabetes.

Advanced glycation end products promote melanogenesis via activating NLRP3 inflammasome in human dermal fibroblasts

Advanced glycation end products (AGEs) accumulation is significantly increased in the dermis of photoaged skin and plays crucial roles in photoaging. Although AGEs have been found to contribute to the yellowish discoloration of photoaged skin, their roles in photoaging-associated hyperpigmentation disorders have not been extensively studied. In this study, we observed that AGEs, NLRP3 and IL-18 were increased in the dermis of sun-exposed skin and lesions of melasma and solar lentigo and that dermal deposition of AGEs was positively correlated with epidermal melanin levels. Additionally, we found AGEs-BSA potently activated NLRP3 inflammasome and promoted IL-18 production and secretion in cultured fibroblasts, which was mediated by RAGE/NF-κB pathway. Moreover, AGEs-BSA significantly promoted melanogenesis through increasing tyrosinase activity and expression of microphthalmia-associated transcription factor and tyrosinase, which was dependent on NLRP3 inflammasome activation and IL-18 secretion in fibroblasts. Notably, AGEs-collagen could activate NLRP3 inflammasome in fibroblasts and enhance melanogenesis. Further, we found IL-18 enhanced melanogenesis through binding to its receptor and activating p38 MAPK and ERK1/2 signaling pathways in melanocytes. Importantly, the pro-melanogenesis of AGEs-BSA was verified in ex vivo cultured skin and mice models. These findings suggest that dermal AGEs stimulate melanogenesis and contribute to the development of photoaging-associated hyperpigmentation disorders.

Serial Passaging of RAW 264.7 Cells Modulates Intracellular AGE Formation and Downregulates RANKL-Induced In Vitro Osteoclastogenesis

The passage number of cells refers to the number of subculturing processes that the cells have undergone. The effect of passage number on morphological and phenotypical characteristics of cells is of great importance. Advanced glycation end products have also been associated with cell functionality and characteristics. Murine monocyte RAW 264.7 cells differentiate into osteoclasts upon receptor activation caused by nuclear factor-kappa-Β ligand (RANKL) treatment. This study aims to identify the role of passage number on intracellular advanced glycation end products (AGEs) formation and osteoclastogenic differentiation of RAW 264.7 cells. Western blotting was performed to check intracellular AGE formation along with fluorometric analysis using a microplate reader. Tartrate-resistant acid phosphatase (TRAP) staining was performed to check osteoclastogenic differentiation, and qPCR was realized to check the responsible mRNA expression. Immunofluorescence was used to check the morphological changes. Intracellular AGE formation was increased with passaging, and the higher passage number inhibited multinucleated osteoclastogenic differentiation. Osteoclastogenic gene expression also showed a reducing trend in higher passages, along with a significant reduction in F-actin ring size and number. Lower passages should be used to avoid the effects of cell subculturing in in vitro osteoclastogenesis study using RAW 264.7 cells.

A Dunaliella salina Extract Counteracts Skin Aging under Intense Solar Irradiation Thanks to Its Antiglycation and Anti-Inflammatory Properties

Glycation, and the resulting buildup of advanced glycation end products (AGEs), is recognized as a key driver of cumulative skin damage and skin aging. Dunaliella salina is a halophile microalga adapted to intense solar radiation through the production of carotenoids. We present a natural supercritical CO₂ extract of Dunaliella salina rich in the colorless carotenoids phytoene and phytofluene. The extract exhibited antiglycation and anti-inflammatory activities in ex vivo testing, showing strongly reduced formation of N-ε-carboxy-methyl-lysine with exposure to methylglyoxal, reduced AGE receptor levels, and significantly reduced interleukins 6 and 8. In a placebo-controlled clinical study under intense solar exposure, the extract significantly reduced the skin’s glycation scores and its sensitivity to histamine; key skin aging parameters were also significantly improved vs. placebo, including wrinkle counts and spots. These results demonstrate the value of this Dunaliella salina extract, rich in colorless carotenoids, as an antiglycative, anti-inflammatory, and antiaging active ingredient, including in high-irradiation contexts.

Protective effects of mycosporine-like amino acid-containing emulsions on UV-treated mouse ear tissue from the viewpoints of antioxidation and antiglycation

Mycosporine-like amino acids (MAAs) are promising natural antioxidative compounds with cosmetic applications for the prevention of skin aging. In this study, we evaluated the protective effects of natural resources-derived MAA-containing emulsions on mouse ear tissue exposed to UV irradiation. DBA/2CrSlc male mice were irradiated by UV light at 120 mJ/cm²/day for 9 days. MAA-containing emulsions were prepared using mycosporine-2-glycine (M2G), shinorine (SHI), or porphyra-334 (P334) and applied to mice ears at a dose of 50 mg/ear/day. After that, collected ear skin tissues were subjected to the observation of melanocytes, investigation for antioxidative stress markers, and measurement of advanced glycation-end products (AGEs). In addition, the antiglycative effects of MAAs were investigated in vitro. MAA-containing emulsions prepared in this study upregulated the activities of total superoxide dismutase (SOD) and catalase (CAT) in mouse ear tissue exposed to UV irradiation. Increased accumulation of copper/zinc (Cu/Zn) -SOD and/or CAT was also found in mouse ear tissue on which M2G- or P334-containing emulsion had been applied. Furthermore, P334 exhibited an antiglycative effect on elastin in vitro. Although MAA-containing emulsions have antioxidative effects as well as in vitro antiglycation, a protective effect by the accumulation of AGEs in mice ears exposed to UV was not observed. Thus, application of MAA-containing emulsions stimulated or protected the expression of antioxidant-associated proteins, thereby leading to upregulation of antioxidative activities in mouse ear skin samples tissues under UV irradiation. Additional optimization of MAA-containing emulsions, including composition, process, and dosage should be considered for further improvement of efficacy.

Lipopolysaccharides induce a RAGE-mediated sensitization of sensory neurons and fluid hypersecretion in the upper airways

Thoracic dorsal root ganglia (tDRG) contribute to fluid secretion in the upper airways. Inflammation potentiates DRG responses, but the mechanisms remain under investigation. The receptor for advanced glycation end-products (RAGE) underlies potentiation of DRG responses in pain pathologies; however, its role in other sensory modalities is less understood. We hypothesize that RAGE contributes to electrophysiological and biochemical changes in tDRGs during inflammation. We used tDRGs and tracheas from wild types (WT), RAGE knock-out (RAGE-KO), and with the RAGE antagonist FPS-ZM1, and exposed them to lipopolysaccharides (LPS). We studied: capsaicin (CAP)-evoked currents and action potentials (AP), tracheal submucosal gland secretion, RAGE expression and downstream pathways. In WT neurons, LPS increased CAP-evoked currents and AP generation, and it caused submucosal gland hypersecretion in tracheas from WT mice exposed to LPS. In contrast, LPS had no effect on tDRG excitability or gland secretion in RAGE-KO mice or mice treated with FPS-ZM1. LPS upregulated full-length RAGE (encoded by Tv1-RAGE) and downregulated a soluble (sRAGE) splice variant (encoded by MmusRAGEv4) in tDRG neurons. These data suggest that sensitization of tDRG neurons contributes to hypersecretion in the upper airways during inflammation. And at least two RAGE variants may be involved in these effects of LPS.

Skin Pigmentation Abnormalities and Their Possible Relationship with Skin Aging

Skin disorders showing abnormal pigmentation are often difficult to manage because of their uncertain etiology or pathogenesis. Abnormal pigmentation is a common symptom accompanying aging skin. The association between skin aging and skin pigmentation abnormalities can be attributed to certain inherited disorders characterized by premature aging and abnormal pigmentation in the skin and some therapeutic modalities effective for both. Several molecular mechanisms, including oxidative stress, mitochondrial DNA mutations, DNA damage, telomere shortening, hormonal changes, and autophagy impairment, have been identified as involved in skin aging. Although each of these skin aging-related mechanisms are interconnected, this review examined the role of each mechanism in skin hyperpigmentation or hypopigmentation to propose the possible association between skin aging and pigmentation abnormalities.

Involvement of RAGE and Oxidative Stress in Inflammatory and Infectious Skin Diseases

The surface receptor for advanced glycosylation end-products (RAGE) and its soluble (sRAGE) and endogenous secretory (EN-RAGE) forms belong to the superfamily of toll-like receptors and play important roles in inflammation and autoimmunity, directly or through binding with advanced glycosylation end-products (AGE) and advanced oxidation protein products (AOPP). We reviewed the literature on the role of RAGE in skin diseases. Research in this field is still rather limited (28 articles) but suggests the involvement of RAGE and RAGE-related pathways in chronic inflammatory diseases (lupus, psoriasis, atopic dermatitis, and lichen planus), infectious diseases (leprosy, Staphylococcus aureus-induced skin lesions), alterations of the repairing processes in diabetic skin, systemic sclerosis, and ulcers. These data prompt further research in this field, which not only will be useful to better understand the pathogenetic mechanisms of diseases, but is also likely to have intriguing clinical implications. Indeed, when their role in the complex and multifactorial inflammatory balance will be adequately defined, RAGE and related molecules could be used as markers of disease severity and/or response to treatment. Moreover, future promising therapeutic perspectives could be topical administration of some of these molecules (e.g., sRAGE) to modulate local inflammatory response and/or the development of anti-RAGE antibodies for systemic treatment.

Glyoxalase System in the Progression of Skin Aging and Skin Malignancies

Dicarbonyl compounds, including methylglyoxal (MGO) and glyoxal (GO), are mainly formed as byproducts of glucose metabolism. The main glyoxalase system consists of glyoxalase I and II (Glo1 and Glo2) and is the main enzyme involved in the detoxification of dicarbonyl stress, which occurs as an accumulation of MGO or GO due to decreased activity or expression of Glo1. Dicarbonyl stress is a major cause of cellular and tissue dysfunction that causes various health issues, including diabetes, aging, and cancer. The skin is the largest organ in the body. In this review, we discuss the role of the glyoxalase system in the progression of skin aging, and more importantly, skin malignancies. We also discuss the future prospects of the glyoxalase system in other skin abnormalities such as psoriasis and vitiligo, including hyperpigmentation. Finally, in the present review, we suggest the role of glyoxalase in the progression of skin aging and glyoxalase system as a potential target for anticancer drug development for skin cancer.

Casein Hydrolysate Containing Milk-Derived Peptides Reduces Facial Pigmentation Partly by Decreasing Advanced Glycation End Products in the Skin: A Randomized Double-Blind Placebo-Controlled Trial

Casein hydrolysate has been shown to improve arterial stiffness as estimated by brachial-ankle pulse wave velocity (baPWV) in untreated hypertensive patients. Facial pigmentation is associated with atherosclerosis, both of which are supposed to be modulated by tissue accumulation of advanced glycation end products (AGEs). However, effects of casein hydrolysate on facial pigmentation and AGEs remain largely unknown. This randomized double-blind placebo-controlled trial evaluated whether and how casein hydrolysate improves facial pigmentation in 80 nonhypertensive Japanese patients. Study participants were randomly assigned to receive either active tablets containing casein hydrolysate or placebo for 48 weeks. Facial pigmentation area, baPWV, and skin accumulation levels of AGEs were evaluated by Robo Skin Analyzer RSA50S II, volume-plethysmographic apparatus, and AGE Reader, respectively, at baseline and at the end of the intervention. Treatment with casein hydrolysate, but not placebo significantly reduced triglycerides and facial pigmentation area. There were significant differences of changes in triglycerides, facial pigmentation area, skin accumulation levels of AGEs, and baPWV between the two groups. Furthermore, changes in triglycerides and skin accumulation levels of AGEs were positively and independently associated with those in facial pigmentation area, whereas changes in baPWV were not. This study suggests that casein hydrolysate reduces facial pigmentation area in nonhypertensive participants partly by decreasing skin accumulation levels of AGEs. Clinical-Trials.gov ID: UMIN000027675.

2,5-diketopiperazines mitigate the amount of advanced glycation end products accumulated with age in human dermal fibroblasts

OBJECTIVE

Glycation is a common non-enzymatic reaction between proteins and sugars, resulting in the formation of advanced glycation end products (AGEs) in the human body. As can be seen in diabetic patients, the accumulation of AGEs in the skin has aesthetic consequences (wrinkles, brown spots and yellowish complexion). Therefore, the objective of this work was to find compounds isolated from natural sources that could eliminate the final AGEs accumulated in the skin with ageing.

METHODS AND RESULTS

A preliminary screening performed on a bank of microbial extracts and pure compounds showed that 2,5-Diketopiperazines (DKPs), as well as the extract of Sphingobacterium sp (SNB-CN13), reduced the presence of AGEs in fibroblasts by -28% and -23%, respectively. In this article, we present the dereplication approach used to reveal the presence of 26 different DKPs in the crude extract of Sphingobacterium sp. Bioguided fractionation has led to the isolation of 12 of them, whose identity has been confirmed by HRMS and NMR. A green synthesis approach has been developed to synthesize 3 symmetrical DKPs. The biological activity of all DKPs was evaluated by the development of an in vitro test using immunocytochemistry to reveal the presence of AGE carboxymethyl-lysine in human dermal fibroblasts.

CONCLUSION

Our work shows for the first time that DKPs decrease the amount of carboxymethyl-lysine AGE in elderly human dermal fibroblasts grown in vitro. Therefore, diketopiperazines can be considered as compounds of interest for dermatological and cosmetic applications with an anti-ageing aim.

Optimizing skin pharmacotherapy for older patients: the future is at hand but are we ready for it?

Age-related changes affect both the local pharmacotherapy of skin diseases and the transdermal administration of drugs. The development of aged skin models disregards the highly individual process of aging, facilitating general conclusions for older patients. Nevertheless, 'omics technology, high-content screening, and non-invasive imaging, as well as bioprinting, CRISPR-Cas, and, patients-on-a-chip, can retrieve personalized information for the generation of in vitro models. Herein, we suggest a strategy to optimize pharmacotherapy for older patients. The technology for relevant human cell-based models is at hand and the consideration of patient heterogeneity is required to unlock their full potential.

Anti-tyrosinase and Anti-oxidative Activities by Asana: the Heartwood ofPterocarpusmarsupium

Asana (the heartwood of Pterocarpus marsupium) has been utilized as an agent for diabetes mellitus in Ayurveda traditional medicine. In our research program to explore novel functions of asana extract, we focused on its skin-whitening effect because asana has been used as a remedy for chronic skin diseases. In addition, the authors have already reported an improvement in blood fluidity that brightens dull facial skin. Based on these effects, asana is a promising candidate agent that possesses both blood fluidity and anti-tyrosinase activities. We focused on the anti-tyrosinase activity and anti-oxidative activities of asana and the results are summarized in this report. We found that a 50% ethanolic extract obtained from asana (PM-ext) showed 23%, 53%, and 71% inhibition against mushroom tyrosinase at 12.5, 50, and 200 µg/mL. Oxyresveratrol and isoliquiritigenin were identified as the active compounds by activity-guided purification. Oxyresveratrol has higher potency than isoliquiritigenin and the IC50of oxyresveratrol was estimated to be 2.1 µM. On the other hand, isoliquiritigenin showed 21%, 28%, and 38% inhibition at 10, 50, and 100 µM, respectively. The inhibitory activity of oxyresveratrol was compared with 3 stilbenes, pterostilbene, resveratrol, and piceatannol. Although oxyresveratrol showed 72.8%, 81.0%, and 85.4% inhibition at 2, 5, and 10 µM, respectively, pterostilbene, resveratrol, and piceatannol showed no effects at the same concentration; these compounds also demonstrated anti-melanogenesis activity on B16 murine melanoma cells. As a result, oxyresveratrol showed the most potent activity, without cytotoxicity, with 38%, 74%, and 84% inhibition at 2, 10, and 20 µM, respectively, while pterostilbene showed 26%, 71%, and 79% inhibition at the same concentration with cytotoxicity at 10 and 20 µM. Resveratrol showed 20%, 41%, and 57% inhibition without cytotoxicity at 2, 10, and 20 µM, respectively. Auto-oxidation is one of the major factors in melanin biosynthesis and anti-oxidative activity is suitable for an anti-melanogenesis agent. We investigated the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity by PM-ext. As a result, PM-ext showed 16%, 33%, and 73% DPPH radical-scavenging activity at 10, 20, and 50 µg/mL, respectively. Oxyresveratrol showed 19%, 31%, and 59% scavenging activity at 10, 20, and 50 µM, respectively, similar to piceatannol. In addition, PM-ext showed 29%, 48%, and 80% suppressive activity on AGEs production at 3.1, 12.5, and 50 µg/mL, respectively. Oxyresveratrol showed 32%, 47%, and 55% activity at 10, 50, and 100 µM, respectively, and this was the most potent among the stilbenes tested. These results suggest that PM-ext could be a promising candidate as skin-whitening agent.

Determination of (+)-Dihydrorobinetin as An Active Constituent of the Radical-Scavenging Activity of Asana (Pterocarpus marsupium) Heartwood

Asana used in Ayurveda medicine originates from the heartwood of Fabaceae Pterocarpus marsupium. In our previous report, we demonstrated that a 50% ethanolic extract (PM-ext) of Asana was a promising candidate as a skin-whitening agent based on its anti-tyrosinase and antioxidative activities. Moreover, the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity of PM-ext was demonstrated and one of the active constituents was identified as oxyresveratrol. However, the potency of oxyresveratrol was low and the other active constituent has not yet been investigated. Activity-guided purification led us to isolate (+)-dihydrorobinetin (DHR). DHR had a potent DPPH radical-scavenging activity (half-maximal inhibitory concentration [IC50] = 1.3 µM) and also showed suppressive activity of advanced glycation end products (AGEs) production (IC50=132 µM), as well as superoxide dismutase (SOD)-like activity (half-maximal effective concentration=27 µM). In a PM-ext, this is the first report to identify DHR and to demonstrate the suppressive activity of AGEs production and SOD-like activity of DHR. From these results, PM-ext containing DHR is a promising candidate as a multifunctional material with multiple anti-oxidant activities.

Protein Glycation: An Old Villain is Shedding Secrets

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The glycation of proteins is non-physiological post-translational incorporation of carbohydrates onto the free amines or guanidines of proteins and some lipids. Although the existence of glycated proteins has been known for forty years, a full understanding of their pathogenic nature has been slow in accruing. In recent years, however, glycation has gained widespread acceptance as a contributing factor in numerous metabolic, autoimmune, and neurological disorders, tying together several confounding aspects of disease etiology. From diabetes, arthritis, and lupus, to multiple sclerosis, amyotrophic lateral sclerosis, Alzheimer’s, and Parkinson’s diseases, an emerging glycation/inflammation paradigm now offers significant new insight into a physiologically important toxicological phenomenon. It exposes novel drug targets and treatment options, and may even lay foundations for long-awaited breakthroughs.

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This ‘current frontier’ article briefly profiles current knowledge regarding the underlying causes of glycation, the structural biology implications of such modifications, and their pathological consequences. Although several emerging therapeutic strategies for addressing glycation pathologies are introduced, the primary purpose of this mini-review is to raise awareness of the challenges and opportunities inherent in this emerging new medicinal target area.

Glycation Damage: A Possible Hub for Major Pathophysiological Disorders and Aging

Glycation is both a physiological and pathological process which mainly affects proteins, nucleic acids and lipids. Exogenous and endogenous glycation produces deleterious reactions that take place principally in the extracellular matrix environment or within the cell cytosol and organelles. Advanced glycation end product (AGE) formation begins by the non-enzymatic glycation of free amino groups by sugars and aldehydes which leads to a succession of rearrangements of intermediate compounds and ultimately to irreversibly bound products known as AGEs. Epigenetic factors, oxidative stress, UV and nutrition are important causes of the accumulation of chemically and structurally different AGEs with various biological reactivities. Cross-linked proteins, deriving from the glycation process, present both an altered structure and function. Nucleotides and lipids are particularly vulnerable targets which can in turn favor DNA mutation or a decrease in cell membrane integrity and associated biological pathways respectively. In mitochondria, the consequences of glycation can alter bioenergy production. Under physiological conditions, anti-glycation defenses are sufficient, with proteasomes preventing accumulation of glycated proteins, while lipid turnover clears glycated products and nucleotide excision repair removes glycated nucleotides. If this does not occur, glycation damage accumulates, and pathologies may develop. Glycation-induced biological products are known to be mainly associated with aging, neurodegenerative disorders, diabetes and its complications, atherosclerosis, renal failure, immunological changes, retinopathy, skin photoaging, osteoporosis, and progression of some tumors.

Photoaging protective effects of BIOGF1K, a compound-K-rich fraction prepared from Panax ginseng

BACKGROUND

BIOGF1K, a compound-K-rich fraction, has been shown to display anti-inflammatory activity. Although Panax ginseng is widely used for the prevention of photoaging events induced by UVB irradiation, the effect of BIOGF1K on photoaging has not yet been examined. In this study, we investigated the effects of BIOGF1K on UVB-induced photoaging events.

METHODS

We analyzed the ability of BIOGF1K to prevent UVB-induced apoptosis, enhance matrix metalloproteinase (MMP) expression, upregulate anti-inflammatory activity, reduce sirtuin 1 expression, and melanin production using reverse transcription-polymerase chain reaction, melanin content assay, tyrosinase assay, and flow cytometry. We also evaluated the effects of BIOGF1K on the activator protein-1 signaling pathway, which plays an important role in photoaging, by immunoblot analysis and luciferase reporter gene assays.

RESULTS

Treatment of UVB-irradiated NIH3T3 fibroblasts with BIOGF1K prevented UVB-induced cell death, inhibited apoptosis, suppressed morphological changes, reduced melanin secretion, restored the levels of type I procollagen and sirtuin 1, and prevented mRNA upregulation of MMP-1, MMP-2, and cyclo-oxygenase-2; these effects all occurred in a dose-dependent manner. In addition, BIOGF1K markedly reduced activator-protein-1-mediated luciferase activity and decreased the activity of mitogen-activated protein kinases (extracellular response kinase, p38, and C-Jun N-terminal kinase).

CONCLUSION

Our results strongly suggest that BIOGF1K has anti-photoaging activity and that BIOGF1K could be used in anti-aging cosmeceutical preparations.

Biological impact of advanced glycation endproducts on estrogen receptor-positive MCF-7 breast cancer cells

Diabetes mellitus potentiates the risk of breast cancer. We have previously described the pro-tumorigenic effects of advanced glycation endproducts (AGEs) on estrogen receptor (ER)-negative MDA-MB-231 breast cancer cell line mediated through the receptor for AGEs (RAGE). However, a predominant association between women with ER-positive breast cancer and type 2 diabetes mellitus has been reported. Therefore, we have investigated the biological impact of AGEs on ER-positive human breast cancer cell line MCF-7 using in vitro cell-based assays including cell count, migration, and invasion assays. Western blot, FACS analyses and quantitative real time-PCR were also performed. We found that AGEs at 50-100μg/mL increased MCF-7 cell proliferation and cell migration associated with an enhancement of pro-matrix metalloproteinase (MMP)-9 activity, without affecting their poor invasiveness. However, 200μg/mL AGEs inhibited MCF-7 cell proliferation through induction of apoptosis indicated by caspase-3 cleavage detected using Western blotting. A phospho-protein array analysis revealed that AGEs mainly induce the phosphorylation of extracellular-signal regulated kinase (ERK)1/2 and cAMP response element binding protein-1 (CREB1), both signaling molecules considered as key regulators of AGEs pro-tumorigenic effects. We also showed that AGEs up-regulate RAGE and ER expression at the protein and transcript levels in MCF-7 cells, in a RAGE-dependent manner after blockade of AGEs/RAGE interaction using neutralizing anti-RAGE antibody. Throughout the study, BSA had no effect on cellular processes. These findings pave the way for future studies investigating whether the exposure of AGEs-treated ER-positive breast cancer cells to estrogen could lead to a potentiation of breast cancer development and progression.

Hypoxia driven glycation: Mechanisms and therapeutic opportunities

Tumor masses are deprived of oxygen and characterized by enhanced glucose uptake followed by glycolysis. Elevated glucose levels induce non-enzymatic glycosylation or glycation of proteins which leads to accumulation of advanced glycation end products (AGE). These AGE molecules bind to their respective receptors called the receptor for advanced glycation end products (RAGE) and initiate several aberrant signaling pathways leading to onset of diseases such as diabetes, Alzheimer's, atherosclerosis, heart failure and cancer. The role of AGE in cancer progression is being extensively studied in recent years. As cancer cells are hypoxic in nature and adapted to glycolysis, which induces glycation, its effects need to be understood in greater detail. Since AGE-RAGE signaling is involved in cancer progression, inhibition of AGE-RAGE interaction could be a potential therapeutic target. The purpose of this review is to highlight the role of AGE-RAGE interaction in hypoxic cancer cells.

The effects of advanced glycation end products (AGEs) on dermal wound healing and scar formation: a systematic review

Introduction:

With ageing, the skin gradually loses its youthful appearance and functions like wound healing and scar formation. The pathophysiological theory of Advanced Glycation End products (AGEs) has gained traction during the last decade. This review aims to document the influence of AGEs on the mechanical and physiologic properties of the skin, how they affect dermal wound healing and scar formation in high-AGE populations like elderly patients and diabetics, and potential therapeutic strategies.

Methods:

This systematic literature study involved a structured search in Pubmed and Web of Science with qualitative analysis of 14 articles after a three-staged selection process with the use of in- and exclusion criteria.

Results:

Overall, AGEs cause shortened, thinned, and disorganized collagen fibrils, consequently reducing elasticity and skin/scar thickness with increased contraction and delayed wound closure. Documented therapeutic strategies include dietary AGE restriction, sRAGE decoy receptors, aminoguanidine, RAGE-blocking antibodies, targeted therapy, thymosin β4, anti-oxidant agents and gold nanoparticles, ethyl pyruvate, Gal-3 manipulation and metformin.

Discussion:

With lack of evidence concerning scars, no definitive conclusions can yet be made about the role of AGEs on possible appearance or function of scar tissue. However, all results suggest that scars tend to be more rigid and contractile with persistent redness and reduced tendency towards hypertrophy as AGEs accumulate.

Conclusion:

Abundant evidence supports the pathologic role of AGEs in ageing and dermal wound healing and the effectiveness of possible therapeutic agents. More research is required to conclude its role in scar formation and scar therapy.

Our skin is the body’s first line of defense. It is the barrier that protects us from chemical and biological threats such as viruses, bacteria or corrosive liquids. It is the sensor that allows us to detect physical threats like extreme temperatures, pressure and pain. And when these preventative measures fail, the skin has yet another property: the ability to heal.

Skin changes visibly with age, most notably with the appearance of wrinkles. However, there is more to ageing than meets the eye; invisible alterations cause the decline of various functions of the skin, such as wound healing and scar formation. An array of non-conclusive research has been done in this field. One theory that has gained traction during the last decade is the Advanced Glycation End products (AGEs) theory. The theory states that AGEs play an important role in skin aging, wound healing and the effectiveness of different therapeutic options. Their presence supposedly indicates a diminished ability for wound healing and scar formation.

AGEs are proteins to which sugar molecule is bound. The sugar molecule inhibits the original protein from functioning properly. As skin contains many proteins like collagen, the formation of these AGEs could be a viable explanation for the diminished functioning with ageing. In this review, we investigated whether the accumulation of AGEs affects wound healing and scar formation.

Normal scar formation results in a thin scar. However, it may happen that scarring results in thick, large, painful and itchy scars. We investigated whether people with a high AGE content in their skin, like diabetics and elderly, have difficulties forming aesthetically pleasing scars. Secondly, we investigated which therapies reduce the AGE content and, if so, whether these therapies can improve wound healing and scarring. This literature study involved research in scientific databases with qualitative analysis of 14 articles after a three-staged selection process with the use of set criteria.

We found the different ways in which AGEs affect skin properties and wound healing. Collagen, one of the most important proteins in the skin, is affected by these AGEs. Once a sugar binds to it, the collagen strings becomes thinner and shorter, and the different collagen proteins cross-link with each other in an unstructured way. The result of these alterations is a reduced elasticity, i.e. the skin becomes stiffer. The scar will be thinner and the time for wounds to close is longer. We also found strategies to diminish the AGE content, including dietary AGE restriction and Metformin, a drug used in diabetes.

We can conclude that there is proof of AGEs playing an important role in skin ageing, wound healing and the effectiveness of different therapeutic options. However, more research is required to conclude the exact role of AGEs in scar formation and scar therapy.