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      Soft-shelled turtle eggs inhibit the formation of AGEs in the serum and skin of diabetic rats

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          Abstract

          Although soft-shelled turtle eggs (STE) have been used as a folk medicine for revitalization and the prevention of lifestyle-related diseases, the scientific evidence to support the use of STE in this manner is scarce. To clarify the physiological evidence, STE was administered to diabetic rats and the inhibitory effects on the formation of advanced glycation end-products (AGEs), which are known to increase with the progression of lifestyle-related diseases, were examined. STE and citric acid were administered to diabetic rats for 3 months, and serum N ε-(carboxymethyl)lysine (CML) contents were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Although the administration of STE did not affect the body weight, glycoalbumin or ketone body levels, it significantly reduced the serum level of CML. The accumulation of AGEs, which was measured by fluorescence intensity in the auricle skin and the lower gums, was also reduced by the administration of STE to a similar extent to that observed with citric acid. This report provides the first evidence that the oral administration of STE reduces the formation of AGEs, suggesting that one of the health effects of STE may be the inhibition of AGEs formation.

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          Advanced glycation end-product Nε-carboxymethyl-Lysine accelerates progression of atherosclerotic calcification in diabetes.

          Vascular calcification is an active deposition process of calcium phosphate which resembles bone formation and is highly regulated by osteoblast-like cells. Existing studies demonstrate that advanced glycation end-products (AGEs) may play a pathogenic role in the vascular calcification process. However, their mechanism remains poorly understood. The aim of our current study is to investigate how non-cross-link and non-fluorescent N(ε)-carboxymethyl-Lysine (CML), a major immunogen of AGEs, affect the progression of atherosclerotic calcification in diabetes. The present study consisted of an in vivo investigation and two in vitro investigations. In study I, male apoE(-/-) mice were first rendered diabetic by the administration of 5 daily intraperitoneal injections of streptozotocin (STZ, 40 mg/kg), and then given a semi-synthetic high-fat diet (HFD) plus daily injections of CML (10mg/kg/day). The mice were euthanized and analyzed at 0 month (group 0M, n = 10), 2 months (group 2M, n = 10), and 4 months (group 4M, n = 10) after the triple administrations of STZ-CML-HFD. In study II, the effects of CML on the apoptosis in macrophages were investigated. RAW264.7 cells were incubated with or without 50 μg/mL oxLDL plus various concentrations of CML for 48 h. In study III, we investigated whether A7r5 aortic smooth muscle cells were induced into osteoblast-like phenotypes by incubation with or without 80 μg/mL of RAW264.7-derived-apoptotic bodies and 50 μg/mL of oxLDL plus various concentrations of CML (or high-glucose) for 7 days. Related analyses (i.e., H&E staining, Masson staining, von Kossa staining, TUNEL staining, immunohistochemical staining, calcium content assay, annexin V-FITC/PI double-staining, and Western blot) were performed. Morphological analysis showed that early atherosclerotic plaques appeared 2 months after the triple administrations of STZ-CML-HFD, and that typically advanced plaques with extensive calcification lesions, abundant cholesterol crystals, and proliferative collagen were formed 4 months after the triple administrations of STZ-CML-HFD. Furthermore, CML deposition signals and the expression of receptor for advanced glycation end-products (RAGE) in the aortic wall were mainly restricted in the atherosclerotic plaques. After the incubation of A7r5 smooth muscle cells with 10 μmol/L CML plus 50 μg/mL oxLDL, and 80 μg/mL apoptotic bodies (ABs) for 7 days, semi-quantitative analysis of bone morphogenetic protein 2 (BMP-2), core-binding factor α1 (cbfα1), and alkaline phosphatase (ALP) expression showed 5.0-, 2.0-, and 2.9-fold increases, respectively, compared with those in 50 μg/mL oxLDL and 80 μg/mL ABs. Subsequently, a similar trend was observed in the calcium deposition of the cell layer. However, high-glucose had no effects on the ALP activity and calcium deposition of A7r5 cell layer under high-lipid, apoptosis-coexisting conditions. Both animal and cell studies consistently demonstrated that the CML/RAGE axis may first initiate the apoptosis of macrophages in atherosclerotic lesions and then induce BMP-2-cbfα1-ALP-calcification cascade in a high-lipid, apoptosis-coexisting environment. The CML/RAGE axis may play an important role in atherosclerotic calcification of diabetes through the mechanism that induces the apoptosis of macrophages followed by the osteogenic differentiation of aortic smooth muscle cells. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.
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            Advanced glycation end-products: modifiable environmental factors profoundly mediate insulin resistance

            Advanced glycation end-products are toxic by-products of metabolism and are also acquired from high-temperature processed foods. They promote oxidative damage to proteins, lipids and nucleotides. Aging and chronic diseases are strongly associated with markers for oxidative stress, especially advanced glycation end-products, and resistance to peripheral insulin-mediated glucose uptake. Modifiable environmental factors including high levels of refined and simple carbohydrate diets, hypercaloric diets and sedentary lifestyles drive endogenous formation of advanced glycation end-products via accumulation of highly reactive glycolysis intermediates and activation of the polyol/aldose reductase pathway producing high intracellular fructose. High advanced glycation end-products overwhelm innate defenses of enzymes and receptor-mediated endocytosis and promote cell damage via the pro-inflammatory and pro-oxidant receptor for advanced glycation end-products. Oxidative stress disturbs cell signal transduction, especially insulin-mediated metabolic responses. Here we review emerging evidence that restriction of dietary advanced glycation end-products significantly reduces total systemic load and insulin resistance in animals and humans in diabetes, polycystic ovary syndrome, healthy populations and dementia. Of clinical importance, this insulin sensitizing effect is independent of physical activity, caloric intake and adiposity level.
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              Age-dependent accumulation of N epsilon-(carboxymethyl)lysine and N epsilon-(carboxymethyl)hydroxylysine in human skin collagen.

              N epsilon-(Carboxymethyl)lysine (CML) is formed on oxidative cleavage of carbohydrate adducts to lysine residues in glycated proteins in vitro [Ahmed et al. (1988) J. Biol. Chem. 263, 8816-8821; Dunn et al. (1990) Biochemistry 29, 10964-10970]. We have shown that, in human lens proteins in vivo, the concentration of fructose-lysine (FL), the Amadori adduct of glucose to lysine, is constant with age, while the concentration of the oxidation product, CML, increases significantly with age [Dunn et al. (1989) Biochemistry 28, 9464-9468]. In this work we extend our studies to the analysis of human skin collagen. The extent of glycation of insoluble skin collagen was greater than that of lens proteins (4-6 mmol of FL/mol of lysine in collagen versus 1-2 mmol of FL/mol of lysine in lens proteins), consistent with the lower concentration of glucose in lens, compared to plasma. In contrast to lens, there was a slight but significant age-dependent increase in glycation of skin collagen, 33% between ages 20 and 80. As in lens protein, CML, present at only trace levels in neonatal collagen, increased significantly with age, although the amount of CML in collagen at 80 years of age, approximately 1.5 mmol of CML/mol of lysine, was less than that found in lens protein, approximately 7 mmol of CML/mol of lysine. The concentration of N epsilon-(carboxymethyl)hydroxylysine (CMhL), the product of oxidation of glycated hydroxylysine, also increased with age in collagen, in parallel with the increase in CML, from trace levels at infancy to approximately 5 mmol of CMhL/mol of hydroxylysine at age 80.(ABSTRACT TRUNCATED AT 250 WORDS)
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                Author and article information

                Journal
                J Clin Biochem Nutr
                J Clin Biochem Nutr
                JCBN
                Journal of Clinical Biochemistry and Nutrition
                the Society for Free Radical Research Japan (Kyoto, Japan )
                0912-0009
                1880-5086
                March 2016
                22 January 2016
                : 58
                : 2
                : 130-134
                Affiliations
                [1 ]Laboratory of Food and Regulation Biology, Graduate School of Agriculture, Tokai University, Kawayou, Minamiaso, Aso-gun, Kumamoto 869-1404, Japan
                [2 ]Healthcare Business Development Department I, Medical and Healthcare Business Development Unit, Business Solution Company, SHARP Corporation, 2613-1 Ichinomoto-cho, Tenri, Nara 632-8567, Japan
                [3 ]Department of Orthopaedic Surgery, Jikei University School of Medicine, 3-25-8 Nishi-Shimbashi, Minato-ku, Tokyo 105-8461, Japan
                Author notes
                *To whom correspondence should be addressed. E-mail: nagai-883@ 123456umin.ac.jp
                Article
                JCBN15-131
                10.3164/jcbn.15-131
                4788400
                27013779
                4464f45c-dd6c-4021-b1bb-c59e2925faa2
                Copyright © 2016 JCBN

                This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 19 October 2015
                : 1 November 2015
                Categories
                Original Article

                Biochemistry
                ages,soft-shelled turtle eggs,diabetes mellitus,cml,oxidation
                Biochemistry
                ages, soft-shelled turtle eggs, diabetes mellitus, cml, oxidation

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