Hyperglycemia-induced accumulation of advanced glycosylation end products in fibroblast-like synoviocytes promotes knee osteoarthritis

Osteoarthritis (OA) is significantly associated with diabetes, but how hyperglycemia induces or aggravates OA has not been shown. The synovium plays a critical role in cartilage metabolism and substance exchange. Herein, we intended to investigate whether and how hyperglycemia affects the occurrence and progression of OA by influencing the synovium. In patients with knee OA and diabetes (DM OA), we found a more severe inflammatory response, higher endoplasmic reticulum stress (ERS) levels, and more advanced glycosylation end products (AGEs) accumulation in the synovium than in patients without diabetes. Subsequently, we found similar results in the DM OA group in a rat model. In the in vitro cocultivation system, high glucose-stimulated AGEs accumulation, ERS, and inflammation in rat fibroblast-like synoviocytes (FLSs), which resulted in chondrocyte degeneration due to inflammatory factors from FLSs. Furthermore, in the synovium of the DM OA group and FLSs treated with high glucose, the expression of glucose transporter 1 (GLUT1) and its regulatory factor hypoxia-inducible factor (HIF)-1α was increased significantly. Inhibitors of HIF-1α, GLUT1 or AGEs receptors attenuated the effect of high glucose on chondrocyte degradation in the FLS-chondrocyte coculture system. In summary, we demonstrated that hyperglycemia caused AGEs accumulation in FLSs via the HIF-1α-GLUT1 pathway, which increases the release of inflammatory factors from FLSs, subsequently inducing chondrocyte degradation and promoting OA progression.

UVA Exposure Combined with Glycation of the Dermis Are Two Catalysts for Skin Aging and Promotes a Favorable Environment to the Appearance of Elastosis

Skin aging is the result of superimposed intrinsic (individual) and extrinsic (e.g., UV exposure or nutrition) aging. Previous works have reported a relationship between UV irradiation and glycation in the aging process, leading, for example, to modified radical species production and the appearance of AGEs (advanced glycosylation end products) in increasing quantities, particularly glycoxidation products like pentosidine. In addition, the colocalization of AGEs and elastosis has also been observed. We first investigated the combination of the glycation reaction and UVA effects on a reconstructed skin model to explain their cumulative biological effect. We found that UVA exposure combined with glycation had the ability to intensify the response for specific markers: for example, MMP1 or MMP3 mRNA, proteases involved in extracellular matrix degradation, or proinflammatory cytokine, IL1α, protein expression. Moreover, the association of glycation and UVA irradiation is believed to promote an environment that favors the onset of an elastotic-like phenomenon: mRNA coding for elastin, elastase, and tropoelastin expression is increased. Secondly, because the damaging effects of UV radiation in vivo might be more detrimental in aged skin than in young skin due to increased accumulation of pentosidine and the exacerbation of alterations related to chronological aging, we studied the biological effect of soluble pentosidine in fibroblasts grown in monolayers. We found that pentosidine induced upregulation of CXCL2, IL8, and MMP12 mRNA expression (inflammatory and elastotic markers, respectively). Tropoelastin protein expression (elastin precursor) was also increased. In conclusion, fibroblasts in monolayers cultured with soluble pentosidine and tridimensional in vitro skin constructs exposed to the combination of AGEs and UVA promote an inflammatory state and an alteration of the dermal compartment in relation to an elastosis-like environment.

Advanced glycosylation end products inhibit the proliferation of bone-marrow stromal cells through activating MAPK pathway

Background The purpose of present study was to explore the mechanism of nuclear factor-kappa B (NF-κB), phosphatidylinositol 3-kinase (PI3K)/protein kinase B(PKB/Akt) and mitogen-activated protein kinase (MAPK) signaling pathways after intervention of advanced glycosylation end products (AGEs) on rat bone-marrow stromal cells (BMSCs). Methods Prepare and identify AGEs. BMSCs were isolated from 16 SD rats and cultured with different concentration of AGEs. Cell viability was detected by cell counting kit-8 (CCK-8). BMSCs were cultured with AGEs (0.25 mg/ml) for 30 min, 12 h, 24 h, 72 h and 120 h. In addition, BMSCs were cultured with AGEs, AGEs + JNK inhibitor and AGEs + P38 inhibitor for 24 h and 48 h, respectively. Western blotting and RT-PCR were used to determine the protein and mRNA expression levels, respectively. Results Cell viability of BMSCs was significantly correlated with concentration and effect time of AGEs (P < 0.05), and the most appropriate concentration was 0.25 mg/ml. AGEs stimulation significantly increased the protein expression levels of NF-κB p65, JNK, p38 (P < 0.05), decreased IκB (P < 0.05), but had no effect on the protein expression of Akt in BMSCs (P > 0.05). At the mRNA level, JNK and p38 inhibitors significantly reduced the levels of NF-κB p65, p38 and JNK, increased IκB (P > 0.05), but had no effect on Akt in BMSCs (P > 0.05). At the protein level, JNK and p38 inhibitors notably decreased the expression of NF-κB p65, p38, p-JNK, P-IκB and JNK (P < 0.001), and increased IκB (P < 0.05). Conclusion Advanced glycosylation end products can inhibit the proliferation of bone-marrow stromal cells through activating MAPK pathway.

How Does Glycation Affect Binding Parameters of the Albumin-Gliclazide System in the Presence of Drugs Commonly Used in Diabetes? In Vitro Spectroscopic Study

In this research, the selected drugs commonly used in diabetes and its comorbidities (gliclazide, cilazapril, atorvastatin, and acetylsalicylic acid) were studied for their interactions with bovine serum albumin—native and glycated. Two different spectroscopic methods, fluorescence quenching and circular dichroism, were utilized to elucidate the binding interactions of the investigational drugs. The glycation process was induced in BSA by glucose and was confirmed by the presence of advanced glycosylation end products (AGEs). The interaction between albumin and gliclazide, with the presence of another drug, was confirmed by calculation of association constants (0.11–1.07 × 104 M−1). The nature of changes in the secondary structure of a protein depends on the drug used and the degree of glycation. Therefore, these interactions may have an influence on pharmacokinetic parameters.

Therapeutic Applications of Type 2 Diabetes Mellitus Drug Metformin in Patients with Osteoarthritis

Type 2 diabetes mellitus (T2DM) and osteoarthritis (OA) are common chronic diseases that frequently co-exist. The link between OA and T2DM is attributed to common risk factors, including age and obesity. Several reports suggest that hyperglycemia and accumulated advanced glycosylation end-products might regulate cartilage homeostasis and contribute to the development and progression of OA. Metformin is used widely as the first-line treatment for T2DM. The drug acts by regulating glucose levels and improving insulin sensitivity. The anti-diabetic effects of metformin are mediated mainly via activation of adenosine monophosphate (AMP)-activated protein kinase (AMPK), which is an energy sensing enzyme activated directly by an increase in the AMP/ATP ratio under conditions of metabolic stress. Dysregulation of AMPK is strongly associated with development of T2DM and metabolic syndrome. In this review, we discuss common risk factors, the association between OA and T2DM, and the role of AMPK. We also address the adaptive use of metformin, a known AMPK activator, as a new drug for treatment of patients with OA and T2DM.

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.

The receptor for advanced glycosylation end products, RAGE (AGER) is differentially expressed in non-small cell lung cancer and associates with patient survival.

Non-small cell lung cancer (NSCLC) is the leading cause of cancer death in the United States (1). We mined published microarray data (2, 3, 4) to identify differentially expressed genes in NSCLC. We found that the gene encoding the advanced glycosylation end-product specific receptor, AGER (5), also known as RAGE, was among the genes whose expression was most quantitatively different in tumors from patients with NSCLC as compared to the lung. AGER expression was significantly decreased in NSCLC tumors as compared to the lung, and lower expression of AGER in patient tumors was significantly associated with worse overall survival. AGER may be important for initiation or progression of non-small cell lung cancer in humans.

Combination Assay for Tumor Markers in Saliva of Potentially Malignant Disorders and Oral Squamous Cell Carcinoma

Potentially malignant disorders are “the risk of malignancy being present in a lesion or condition either at the time of initial diagnosis or at a future date” include mainly leukoplakia, erythroplakia, oral lichen planus, oral submucous fibrosis. Biomarkers were of immense help in diagnosis in recent years but a very few molecular biomarkers have been reported in the literature which are not significantly accurate. The current study aims at quantifying the levels of Transforming growth factor (TGF- β), Platelet derived growth factors (PDGF) and receptor of advanced glycosylation end products (RAGE) in saliva of patients with potentially malignant disorders and oral squamous cell carcinoma. Unstimulated saliva of oral squamous cell carcinoma and potentially malignant disorder patients was collected and stored in sub zero temperature. Further biochemical analysis was performed with Raybio ELISA kits. One way ANOVA was performed. The mean concentration of RAGE, PDGF and TGF- β was increased in oral squamous cell carcinoma groups and potentially malignant disorders when compared to healthy controls.p-0.000 (p<0.05).These combined assays can be used as potential biomarkers for indicating the prognosis of the disease and can be used as a diagnostic tool for screening and early detection as these combined assays give more reliable and accurate diagnosis when compared to single biomarker assays.

Influences of advanced glycosylation end products on the inner blood–retinal barrier in a co-culture cell model in vitro

Advanced glycosylation end products (AGEs) are harmful factors that can damage the inner blood–retinal barrier (iBRB). Rat retinal microvascular endothelial cells (RMECs) were isolated and cultured, and identified by anti-CD31 and von Willebrand factor polyclonal antibodies. Similarly, rat retinal Müller glial cells (RMGCs) were identified by H&E staining and with antibodies of glial fibrillary acidic protein and glutamine synthetase. The transepithelial electrical resistance (TEER) value was measured with a Millicell electrical resistance system to observe the leakage of the barrier. Transwell cell plates for co-culturing RMECs with RMGCs were used to construct an iBRB model, which was then tested with the addition of AGEs at final concentrations of 50 and 100 mg/L for 24, 48, and 72 h. AGEs in the in vitro iBRB model constructed by RMEC and RMGC co-culture led to the imbalance of the vascular endothelial growth factor (VEGF) and pigment epithelial derivative factor (PEDF), and the permeability of the RMEC layer increased because the TEER decreased in a dose- and time-dependent manner. AGEs increased VEGF but lowered PEDF in a dose- and time-dependent manner. The intervention with AGEs led to the change of the transendothelial resistance of the RMEC layer likely caused by the increased ratio of VEGF/PEDF.