Glycation is a non-enzymatic reaction between reducing sugars and amino group proteins which leads to the formation of advanced glycation end products (AGEs). The buildup of AGEs in the body is a key factor in the onset of aging and lifestyle-related diseases. In this study, the inhibitory effect on the formation of AGEs by rice water was investigated. Rice water is a common ingredient used traditionally as a beautifying agent but lacks proper scientific research. 14 Japonica and Indica rice varieties were used to prepare rice water samples using three different methods, namely type 1, type 2, and type 3 (n = 42). The human serum albumin (HSA) glycation model was used to evaluate the inhibitory effect on the formation of fluorescent AGEs by rice water. The total phenolic content (TPC) in rice water was determined according to the Folin-Ciocalteau procedure. All 42 rice water samples showed an inhibitory effect on the formation of fluorescent AGEs, and positive correlations were observed between the inhibitory effect and the TPC at p ‹ 0.05; type 1 rice water (r = 0.906), type 2 rice water (r = 0.918), and type 3 rice water (r = 0.765). It was also observed that rice water prepared from pigmented rice varieties showed the highest inhibitory values, for example, type 1 sample number 1 (66.4 ± 0.4%), type 2 sample number 1 (66.6 ± 0.7%), and type 3 sample number 12 (69.6 ± 0.8%). Consequently, the results from this study verifies the anti-glycative effect of rice water and suggests the TPC plays a role on the anti-glycative effect of rice water.

View full abstract

The Maillard reaction is a reaction between the carbonyl group of reducing sugars and the amino group of amino acids, which proceeds not only in foods but also in the body. In the early stage of this reaction, Amadori rearrangement products are formed, followed by oxidation and condensation reactions, and finally forming advanced glycation end products (AGEs). In this study, AGEs, which are still difficult to quantify, were simply measured using a plate reader and compared with an ELISA using an antibody against N^ε-(carboxymethyl) lysine (CML). It was evaluated how the formation of these AGEs changed with different types (ribose, fructose, glucose) and concentrations (5 mM, 30 mM) of carbohydrates that are predicted to alter AGE formation. In the results, changes were observed depending on the incubation period and the type of carbohydrate. Furthermore, the effect was more pronounced with higher concentrations of carbohydrates. The correlation between the fluorescence measurement and the CML measurement using antibodies was confirmed, suggesting that the plate reader method can be used to evaluate glycation conveniently.

View full abstract

Glycation is a non-enzymatic reaction that occurs under physiological conditions which contributes to the pathogenesis aging and related diseases. Staphylococcus aureus is a frequent cause of infection, whose overabundance on the skin is linked to conditions involving elevated glycative stress such as atopic dermatitis and diabetes mellitus. The influence of glycative stress on host-pathogen interactions is still poorly understood. Therefore, we conducted a small-scale observational study of the human skin, alongside in vitro experiments to determine the effects on S. aureus of exposure to advanced glycation endproducts (AGEs). In contrast to that of young adults, the elderly skin was characterized by significantly increased fluorescent AGE content, a 10-fold increase in S. aureus abundance, and a 20% reduction in coagulase-negative Staphylococcus carriage. Glycated keratin triggered the formation of large multicellular S. aureus aggregates in vitro. Under static conditions, glycated keratin promoted biofilm formation in a dose-dependent manner (ED₅₀ = 0.64 mg/mL). AGE accumulation in the skin may play a crucial role in dysbiosis and recurring S. aureus infection. Preventative treatments to reduce glycative stress could reduce the risk of disease and avoid overuse of antibiotics.

View full abstract

Aims: Neutrophils play a key role in infection control via two main mechanisms: phagocytosis and neutrophil extracellular trap (NET) release. Despite their role in infection, NETs can also promote cancer growth and metastasis, inflammatory diseases, and vascular thrombosis. However, the relationship between NET formation and the diet, which are critical factors in the progression of metabolic syndrome, remains unclear. In this study, we examined whether blood NET formation is increased after food intake and sought to identify the dietary components that trigger NET formation. Methods: Using flow cytometry, we analysed NET formation in the blood of mice fed with four different nutritional diets: normal moderate-fat diet (MF), high-fat diet (HF), high-fat and cholesterol diet (HFHC), and dietary fiber Bacto Agar (BA). Results: The highest NET formation was found in HF-fed mice, while no increase was found in BA-fed mice. Moreover, we observed peaks in NET formation _~2 h and 6–24 h after meal consumption. NET formation was abolished after intestinal bacteria were depleted by antibiotic treatment, even when the mice were fed the HF meal. Furthermore, we observed NET formation in human peripheral blood 6 h after meal consumption. Conclusions: These findings suggest that NET formation in peripheral blood may be induced after intake of a high-fat diet, and that this phenomenon is closely associated with the gut microbiota. Further investigations are warranted to unveil the involvement of food components, the gut microbiota, and blood NET formation in the pathogenesis of lifestyle-related diseases.

View full abstract

Purpose: In recent years, the role of advanced glycation end products (AGEs) in promoting and exacerbating metabolic and skin abnormalities has attracted much attention. In this study, we elucidated the relationship between AGE accumulation and skin characteristics, commonalities, and features in metabolic syndrome (MS) patients and controls. Methods: Caucasian male and female patients (n = 296) living in Riga, Latvia, divided into MS (n = 149) and non-MS (n = 147), were analyzed by skin lesion (epidermoid nigricans, seborrheic keratosis, actinic keratosis, age-related wrinkles, gravitational wrinkles, and facial telangiectasia). MS was diagnosed using IDF criteria. For glycative stress index, skin autofluorescence (SAF) was measured using AGE Reader, and skin AGE accumulation was evaluated. Skin findings were assessed using Dermatoscopy Dermlite for facial teleangiectasia, dermatosis and dyspigmentation. Blood biochemical analysis included oxidative stress indices (glutathione: GSH, selenoprotein: Se, superoxide dismutase: SOD, glutathione peroxidase glutathione peroxidase: GPx, and malondialdehyde: MDA). Results: The MS group showed higher body mass index (BMI) (p < 0.001, Mann-Whitney test), higher triglyceride (TG) (p < 0.001, Mann-Whitney test), lower HDL-C (p < 0.001, Mann-Whitney test), and lower Vitamin D (p = 0.05 compared to the non-MS group. For inflammatory response and oxidative stress, the MS group showed higher C-reactive protein (CRP) (p = 0.007, Mann-Whitney test), higher MDA (p = 0.006, Mann-Whitney test), and significantly equal SOD (p = 0.291). SAF, an index of glycative stress, was significantly equal in the MS group (p = 0.468). Next, we conducted a Spearman rank correlation analysis between SAF and each item. Significant correlations were found for the following items: FPG: r = 0.345 (p = 0.036, n = 37), TC: r = 0.328 (p = 0.023, n = 48), HDL-C: r = −0.399 (p = 0.019, n = 34), CRP: r = 0.372 (p = 0.028, n = 37), and CRP: r = 0.372 (p = 0.028, n = 37). No significant correlations were found with other items. Skin lesions were classified as seborrheic keratosis (n = 109), actinic keratosis (n = 25), acanthosis nigricans (n = 16), aging wrinkles (n = 126), gravity wrinkles (n = 34), facial telangiectasia (n = 242), and lentigo pigmentosa (n = 204). SAF was positively correlated with skin aging parameters of seborrheic keratosis and lentigo pigmentosa (p < 0.05) and associated with the severity of skin aging on the face using the skin aging index (p < 0.05). In skin biopsies, the expression of GLUT-1 was increased, accompanied by a decrease in the number of regulatory T cells. Conclusion: MS was associated with excess ROS and reduced antioxidant capacity. Accumulation of AGEs in the skin was strongly associated with clinical aging-related changes (seborrheic keratosis, telangiectasia, and skin wrinkles). The AGE accumulation was associated with inflammatory processes, indicating that SAF may be closely related to skin health.

View full abstract

Intermediate carbonyl compounds produced by abnormalities in glucose and lipid metabolism in vivo induce amino carbonyl reactions that modify proteins in a non-enzymatic manner. This reaction is further accelerated with the progression of lifestyle-related diseases, eventually leading to the formation of advanced glycation end-products (AGEs). Also, alcoholic beverages are consumed as a luxury item. Acetaldehyde (AA), which is produced as an intermediate metabolite of alcohol metabolism, has a highly reactive carbonyl group and may modify proteins in the same manner as AGEs are produced. In this study, we attempted to identify the structure of AA-modified amino acids (AA-A) and measure their amount by immunochemical methods using monoclonal antibodies in order to detect the modification of proteins by AA. The spleens of mice immunized with AA-keyhole limpet hemocyanin (AA-KLH) were fused with myeloma cells, and antibody-producing cells reactive with AA-bovine serum albumin (AA-BSA) were isolated. The amino acid analysis of AA-BSA showed that lysine (Lys) and histidine were highly modified. Focusing on Lys with amino groups on its side chain, AA-Lys was isolated from the product generated from N^α-benzyloxycarbonyl-L-lysine (N^α-Cbz-Lys) and AA by HPLC and the structure was analyzed by nuclear magnetic resonance (NMR) and mass spectrometry. As a result, m/z 385 and m/z 411 were detected, and the structure was identified by NMR. The reactivity of these three fractions with antibodies against monoclonal anti-AA-modified proteins was evaluated and the structures were analyzed. In addition, the three fractions in AA-modified BSA incubated in phosphate buffer (pH 7.4) at 37 ^oC for 7 days were evaluated by ELISA. As a result, the structures of the three fractions were identified, and the highest reactivity with antibodies was observed in fraction 2. These increased in a concentration-dependent manner with AA-modified BSA. These results indicate that three new AA-derived Lys structures have been identified and are formed under physiological conditions, and that this structure will be one of the tools to evaluate protein modification by AA.

View full abstract