Development of Evaluation Methods for Anti-Glycation Activity and Functional Ingredients Contained in Coriander and Fennel Seeds

Spices are known to have various physiological functions. We focused on the anti-glycation effects of spices, researched anti-glycation active ingredients in coriander (Coriandrum sativum L.) and fennel (Foeniculum vulgare) seeds, and conducted experiments using human skin-derived fibroblast TIG-110 cells as a model of glycation. We isolated 11 compounds from two spice seeds and found several substances that showed anti-glycation activity. A new compound (5,5′-diallyl-2,2′-diglucopyranosyl-3,3′-dimethoxy diphenyl ether) was isolated from fennel seeds and showed high anti-glycation activity with an IC50 value of 0.08 mM, thereby indicating a high anti-glycosylation activity. In this study, we established a glyoxal (GO)-induced glycation test method for human skin cells, confirmed the anti-glycation effect of spice seeds using this glycation induction model, and found that the exposure of TIG-110 human skin-derived fibroblast cells to GO reduced cell viability. The most stable conditions for cell viability were found to be a GO concentration of 1.25 mM and a culture time of 48 h. We evaluated extracts and isolates of spice seeds using this model as a model test for glycation induction. We conducted qualitative and quantitative analyses of carboxymethyl lysine (CML), a type of AGE, to determine the relationship between cell viability and AGEs. The relationship between cell viability and the amount of CML was correlated. Establishing a glycation induction model test using skin cells makes it possible to quickly screen extracts of natural ingredients in the future. Moreover, the results of this model showed that extracts of two spice seeds and their isolates have high anti-glycation activity, and they are expected to be used as cosmetics, health foods, and pharmaceutical ingredients.

Advanced Glycation End Products (AGEs): Biochemistry, Signaling, Analytical Methods, and Epigenetic Effects

The advanced glycation end products (AGEs) are organic molecules formed in any living organisms with a great variety of structural and functional properties. They are considered organic markers of the glycation process. Due to their great heterogeneity, there is no specific test for their operational measurement. In this review, we have updated the most common chromatographic, colorimetric, spectroscopic, mass spectrometric, and serological methods, typically used for the determination of AGEs in biological samples. We have described their signaling and signal transduction mechanisms and cell epigenetic effects. Although mass spectrometric analysis is not widespread in the detection of AGEs at the clinical level, this technique is highly promising for the early diagnosis and therapeutics of diseases caused by AGEs. Protocols are available for high-resolution mass spectrometry of glycated proteins although they are characterized by complex machine management. Simpler procedures are available although much less precise than mass spectrometry. Among them, immunochemical tests are very common since they are able to detect AGEs in a simple and immediate way. In these years, new methodologies have been developed using an in vivo novel and noninvasive spectroscopic methods. These methods are based on the measurement of autofluorescence of AGEs. Another method consists of detecting AGEs in the human skin to detect chronic exposure, without the inconvenience of invasive methods. The aim of this review is to compare the different approaches of measuring AGEs at a clinical perspective due to their strict association with oxidative stress and inflammation.

Ameliorating Effect of Akebia quinata Fruit Extracts on Skin Aging Induced by Advanced Glycation End Products

The accumulation of free radicals and advanced glycation end products (AGEs) in the skin plays a very important role in skin aging. Both are known to interact with each other. Therefore, natural compounds or extracts that possess both antioxidant and antiglycation activities might have great antiageing potential. Akebia quinata fruit extract (AQFE) has been used to treat urinary tract inflammatory disease in traditional Korean and Chinese medicines. In the present study, AQFE was demonstrated to possess antioxidant and antiglycation activity. AQFE protects human dermal fibroblasts (HDFs) from oxidative stress and inhibits cellular senescence induced by oxidative stress. We also found that AQFE inhibits glycation reaction between BSA and glucose. The antiglycation activity of AQFE was dose-dependent. In addition, the antiglycation activity of AQFE was confirmed in a human skin explant model. AQFE reduced CML expression and stimulated fibrillin-1 expression in comparison to the methyglyoxal treatment. In addition, the possibility of the extract as an anti-skin aging agent has also been clinically validated. Our analysis of the crow’s feet wrinkle showed that there was a decrease in the depth of deep furrows in RI treated with AQFE cream over an eight-week period. The overall results suggest that AQFE may work as an anti-skin aging agent by preventing oxidative stress and other complications associated with AGEs formation.

Protective activity of gallic acid against glyoxal -induced renal fibrosis in experimental rats

This study was designed to evaluate the protective activity of gallic acid (GA) against glyoxal (GO) an advanced glycation intermediate-induced renal fibrosis in experimental rats. Glyoxal (i.p) at a dose of 15 mg/Kg body weight/day for 4 weeks induces renal fibrosis. GA was administered orally (100 mg/Kg body weight/day) along with GO for 4 weeks. The anti-fibrotic activity of GA was analyzed by measuring the collagen synthesis and deposition in renal tissues using mRNA expression analysis and Masson trichrome staining (MTS), respectively. The nephroprotective potential of GA was assessed by quantifying the markers of kidney damage such as serum blood-urea-nitrogen (BUN), creatinine (CR) and alkaline phosphatase (AP). Moreover, basement membrane damage in renal tissues was analysed by periodic acid Schiff’s (PAS) staining. GA co-treatment markedly suppressed the GO-induced elevation in mRNA expression of collagenIand III, MMP-2, MMP-9 and NOX (p < 0.05, respectively) genes as compared with GO alone infused rats. In addition, GA co-treatment significantly attenuated the GO -induced elevation in serum markers such as BUN, CR and AP levels (p < 0.05, respectively). Furthermore, GA co-treatment restored back the decreased renal super oxide dismutase (SOD) activity (p < 0.05) thereby assuage the reactive oxygen species (ROS) generation, and maintained the normal architecture of glomerulus. The present study clearly indicates that GO -induces renal fibrosis by enhancing GO/receptor of advanced glycation end product (RAGE) induced ROS generation and GA effectively counteracted GO-induced renal fibrosis by its ROS quenching and anti-glycation activity.

Strategies to target mitochondria and oxidative stress by antioxidants: key points and perspectives

For several decades, many antioxidants studies have emphasized the marked disparity between the beneficial effect of the antioxidants shown in preclinical studies and their inability to show beneficial effects in clinical trials. Besides, it is not uncommon to find highly contradictory clinical results, which may explain why consumers are less enthusiastic for antioxidant uses. This perspective article aims to highlights the critical role of Reactive Oxygen Species (ROS) and antioxidants, the potential mechanisms that might account for these discrepancies in clinical trials and some strategies to target oxidative stress and mitochondria by antioxidants. We need urgently to set up standard methods to evaluate antioxidants and oxidative stress in human and in particular at mitochondria level. The determination of what the basal level of ROS is in normal human may be used to identify pathologic ROS levels in patients and ultimately guide antioxidants treatment.

Hyperglycemic oxoaldehyde, glyoxal, causes barrier dysfunction, cytoskeletal alterations, and inhibition of angiogenesis in vascular endothelial cells: aminoguanidine protection

Vascular endothelium is vulnerable to the attack of glucose-derived oxoaldehydes (glyoxal and methylglyoxal) during diabetes, through the formation of advanced glycation end products (AGEs). Although aminoguanidine (AG) has been shown to protect against the AGE-induced adverse effects, its protection against the glyoxal-induced alterations in vascular endothelial cells (ECs) such as cytotoxicity, barrier dysfunction, and inhibition of angiogenesis has not been reported and we investigated this in the bovine pulmonary artery ECs (BPAECs). The results showed that glyoxal (1-10 mM) significantly induced cytotoxicity and mitochondrial dysfunction in a dose- and time-dependent (4-12 h) fashion in ECs. Glyoxal was also observed to significantly inhibit EC proliferation. The study also revealed that glyoxal induced EC barrier dysfunction (loss of trans-endothelial electrical resistance), actin cytoskeletal rearrangement, and tight junction alterations in BPAECs. Furthermore, the results revealed that glyoxal significantly inhibited in vitro angiogenesis on the Matrigel. For the first time, this study demonstrated that AG significantly protected against the glyoxal-induced cytotoxicity, barrier dysfunction, cytoskeletal rearrangement, and inhibition of angiogenesis in BPAECs. Therefore, AG appears as a promising protective agent in the treatment of AGE-induced vascular endothelial alterations and dysfunction during diabetes, presumably by blocking the reactivity of the sugar-derived dicarbonyls such as glyoxal and preventing the formation of AGEs.

Maillard reaction, mitochondria and oxidative stress: potential role of antioxidants

Glycation and oxidative stress are two important processes known to play a key role in complications of many disease processes. Oxidative stress, either via increasing reactive oxygen species (ROS), or by depleting the antioxidants may modulate the genesis of early glycated proteins in vivo. Maillard Reactions, occur in vivo as well as in vitro and are associated with the chronic complications of diabetes, aging and age-related diseases. Hyperglycaemia causes the autoxidation of glucose, glycation of proteins, and the activation of polyol metabolism. These changes facilitate the generation of reactive oxygen species and decrease the activity of antioxidant enzymes such as Cu,Zn-superoxide dismutase, resulting in a remarkable increase of oxidative stress. A large body of evidence indicates that mitochondria alteration is involved and plays a central role in various oxidative stress-related diseases. The damaged mitochondria produce more ROS (increase oxidative stress) and less ATP (cellular energy) than normal mitochondria. As they are damaged, they cannot burn or use glucose or lipid and cannot provide cell with ATP. Further, glucose, amino acids and lipid will not be correctly used and will accumulate outside the mitochondria; they will undergo more glycation (as observed in diabetes, obesity, HIV infection and lipodystrophia). The objective of this paper is to discuss how to stop the vicious circle established between oxidative stress, Maillard Reaction and mitochondria. The potential application of some antioxidants to reduce glycation phenomenon and to increase the antioxidant defence system by targeting mitochondria will be discussed. Food and pharmaceutical companies share the same challenge, they must act now, urgently and energetically.

Advanced glycation end products inhibit the expression of collagens type I and III by human gingival fibroblasts

BACKGROUND

It is evident that diabetes and periodontal disease are closely interrelated. Accumulation of advanced glycation end products (AGEs), coupled with exaggerated host responses to bacterial infection, may account for the increased periodontal destruction observed in patients with uncontrolled diabetes. The present study investigated the effects of AGEs on the viability of human gingival fibroblasts (HGFs) and the expression of types I and III collagen in HGFs.

METHODS

The cell viability of HGFs was examined by methylthiazolet-etrazolium assay, whereas the expression of types I and III collagen message and protein was detected by real-time quantitative reverse transcription-polymerase chain reaction and sandwich enzyme-linked immunosorbent assay, respectively.

RESULTS

AGEs significantly suppressed the cell viability of HGFs from 24 to 72 hours (P <0.01). A high concentration of glucose (25 mmol/l) in the culture media exaggerated the inhibition of the survival rate of HGFs (P <0.01). The expression of collagen types I and III messages and proteins was significantly downregulated at 72 hours by AGEs in a concentration-dependent manner (P <0.05). Moreover, the synthesis of intracellular types I and III collagen protein was markedly inhibited by AGEs (P <0.05).

CONCLUSIONS

AGEs may suppress the cell viability of HGFs and downregulate the expression of types I and III collagen by the cells. Further investigations are warranted to clarify the molecular mechanisms of AGEs in the regulation of cell function and collagen metabolism in patients with diabetes and periodontitis.