Methods to assess advanced glycation end-products

Circulating Concentrations of advanced Glycation end Products, Carboxymethyl Lysine and Methylglyoxal are Associated With Renal Function in Individuals With Diabetes

OBJECTIVE

Diabetic kidney disease (DKD) is one of the most severe chronic complications of diabetes and is associated with higher level of advanced glycation end products (AGEs). The aim of this study was to investigate the diagnostic potential of combined detection of multiple serum AGEs in diagnosing DKD.

METHODS

Serum AGEs, Nε-(carboxymethyl) lysine (CML), Nε-(carboxyethyl) lysine, and methylglyoxal (MGO) levels were measured by enzyme-linked immunosorbent assay in 176 individuals with type 2 diabetes. Participants were classified into normoalbuminuria, microalbuminuria, and macroalbuminuria group according to their urinary albumin to creatinine ratio (UACR).

RESULTS

Higher serum AGEs levels were found to be positively correlated with U-Alb, UACR, and blood urea nitrogen in the study of 176 individuals with type 2 diabetes. CML and MGO levels were positively correlated with U-Alb, UACR, blood urea nitrogen, Scr, and uric acid, and negatively correlated with estimated glomerular filtration rate (P < .05). Multivariate logistic regression analysis showed that elevated levels of AGEs, CML, and MGO were independent risk factors for the progression of DKD (odds ratio = 1.861, 1.016, 7.607, P < .01). The sensitivity, specificity, and area under receiver operating characteristic curve of combined detection of AGEs, MGO, and CML were higher than those of three individual detections (area under the curve = 0.952, 0.772, 0.868, 0905, respectively, P < .05).

CONCLUSION

The combined detection of AGEs, CML, and MGO may improve the reliability of early diagnosis of DKD.

UPLC-MS/MS method for quantitative determination of the advanced glycation endproducts Nε-(carboxymethyl)lysine and Nε-(carboxyethyl)lysine

During blood storage, red blood cells (RBCs) undergo physical, chemical, and metabolic changes that may contribute to post-transfusion complications. Due to the hyperglycemic environment of typical solutions used for RBC storage, the formation of advanced glycation endproducts (AGEs) on the stored RBCs has been implicated as a detrimental chemical change during storage. Unfortunately, there are limited studies involving quantitative determination and differentiation of carboxymethyl-lysine (CML) and carboxyethyl-lysine (CEL), two commonly formed AGEs, and no reported studies comparing these AGEs in experimental storage solutions. In this study, CML and CEL were identified and quantified on freshly drawn blood samples in two types of storage solutions, standard additive solution 1 (AS-1) and a normoglycemic version of AS-1 (AS-1N). To facilitate detection of the AGEs, a novel method was developed to reliably extract AGEs from RBCs, provide Food and Drug Administration (FDA) bioanalytical guidance criteria, and enable acceptable selectivity for these analytes. Ultra-performance liquid chromatography with tandem mass spectrometry (UPLC-MS/MS) was utilized to identify and quantify the AGEs. Results show this method is accurate, precise, has minimal interferences or matrix effects, and overcomes the issue of detecting AGE byproducts. Importantly, AGEs can be detected and quantified in both types of blood storage solutions (AS-1 and AS-1N), thereby enabling long-term (6 weeks) blood storage related studies.

Advanced Glycation End Products and Psoriasis

Advanced glycation end products (AGEs) are biologically active compounds formed physiologically throughout a sequence of chemical reactions, to generate highly oxidant-reactive aldehydes that combine covalently to proteins. They accumulate slowly in tissues during ageing but also in metabolic and selected inflammatory disorders. Accumulation of AGEs occurs more rapidly and intensely in the skin and serum of patients with type 2 diabetes, obesity, cardiovascular diseases, chronic renal insufficiency, and non-alcoholic fatty liver disease and also in the skin of patients with psoriasis. All of the above conditions are intimately associated with psoriasis. Interaction of AGEs with their receptors (RAGEs) stimulates cellular signaling with the formation of reactive oxygen species and activation of nuclear factor kappa light chain enhancer of activated B (NF-kB), which is a key regulator in the expression of inflammatory mediators and the production of oxidative stress. Thus, AGEs may play an interesting pathogenic role in the intersection of inflammatory and metabolic diseases, may represent a biomarker of inflammation and a potential target for novel therapeutic strategies. This is a narrative review with the objective to summarize current evidence on the role of AGEs in psoriasis.

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.

Skin Autofluorescence Measurement as Initial Assessment of Hepatic Parenchyma Quality in Patients Undergoing Liver Resection

Skin autofluorescence (SAF) can detect advanced glycation end products (AGEs) that accumulate in tissues over time. AGEs reflect patients’ general health, and their pathological accumulation has been associated with various diseases. This study aimed to determine whether its measurements can correlate with the liver parenchyma quality. This prospective study included 186 patients who underwent liver resections. Liver fibrosis and/or steatosis > 10% were found in almost 30% of the patients. ROC analysis for SAF revealed the optimal cutoff point of 2.4 AU as an independent predictor for macrovesicular steatosis ≥ 10% with an AUC of 0.629 (95% CI 0.538−0.721, p = 0.006), 59.9% sensitivity, 62.4% specificity, and positive (PPV) and negative (NPV) predictive values of 45.7% and 74.1%, respectively. The optimal cutoff point for liver fibrosis was 2.3 AU with an AUC of 0.613 (95% CI 0.519−0.708, p = 0.018), 67.3% sensitivity, 55.2% specificity, and PPV and NPV of 37.1% and 81.2%, respectively. In the multivariable logistic regression model, SAF ≥ 2.4 AU (OR 2.16; 95% CI 1.05−4.43; p = 0.036) and BMI (OR 1.21; 95% CI 1.10−1.33, p < 0.001) were independent predictors of macrovesicular steatosis ≥ 10%. SAF may enhance the available non-invasive methods of detecting hepatic steatosis and fibrosis in patients prior to liver resection.