In Vitro and In Vivo Antiglycation Effects of Connarus ruber Extract

Accumulation of advanced glycation end products (AGEs) of the Maillard reaction has been implicated in the pathogenesis of diabetes and its complications. Connarus ruber has been used as a folk remedy for several diseases, including diabetes; however, its underlying mechanism has not yet been investigated. This study investigated the effects of C. ruber extract against glycation on collagen-linked AGEs in vitro and streptozotocin-induced diabetic rats (STZ-DM rats) in vivo. The antiglycation activities of C. ruber extract and aminoguanidine (AG) were examined using a collagen glycation assay kit. Nonfluorescent AGE, Nε-carboxymethyl lysine (CML), Nω-carboxymethyl arginine, and Nε-carboxyethyl lysine levels were measured via electrospray ionization-liquid chromatography-tandem mass spectrometry. The effect of the extract on the cytotoxicity of methylglyoxal (MG), a precursor of AGEs, was examined in HL60 cells. STZ-DM rats were treated with the extract for 4 wk, and the effect was assessed using biochemical markers in the serum and CML-positive cells in renal tissues. C. ruber extract dose-dependently inhibited the glycation of collagen and formation of nonfluorescent AGEs, which was comparable to AG, and it significantly attenuated MG-induced cytotoxicity in HL60 cells. Furthermore, the glycated albumin levels in STZ-DM rats decreased, the increase in serum lipid levels was reversed, and immunohistochemistry demonstrated that CML deposition in the glomerulus of STZ-DM rats significantly decreased. Although further studies are needed, C. ruber could be a potential therapeutic for preventing and progressing many pathological conditions, including diabetes.

The Antioxidant and Tyrosinase-Inhibiting Activities of 4-Hydroxycinnamoyl-Malate from a Citrus junos Callus Extract

We evaluated the antioxidant and skin-lightening activities of 4-hydroxycinnamoyl-malate (4-HCM) in vitro; the material is a water-soluble component of Citrus junos callus. 4-HCM was waterextracted from callus grown on MS medium containing picloram to enhance growth. The antioxidant activity of 4-HCM was determined using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2′-azinobis-(3-ethylbenzoline-6-sulfonate) (ABTS) free-radical-scavenging assays. 4-HCM-mediated inhibition of extracellular matrix protein glycation was assessed using the elastin and collagen glycation assays. Inhibition of skin pigmentation was evaluated by measuring anti-tyrosinase activity and melanogenesis in melanoma cells. 4-HCM was then incorporated into elastic nanoliposomes (ENLs) and delivered topically to enhance percutaneous absorption. At 5 mM, the free-radical-scavenging activity of 4-HCM was 54.2±0.631% in the ABTS assay, comparable to that of 1 mM ascorbic acid (46.5± 0.17%). The IC50 value for inhibition of advanced glycation end-product formation from elastin was 1.25±0.23 mM; collagen glycation was completely inhibited when the 4-HCM level was >5 mM. At 0.5 mM, the material afforded 49.2±3.09% inhibition of tyrosinase activity and, at 10 mM, reduced the melanocyte melanin content by 78% without significant cellular toxicity. Moreover, 4-HCM-loaded ENLs exhibited 569% enhanced permeation of 4-HCM across the human epidermis, which may afford skin-lightening if included in cosmetic formulations.

Modulatory Effect of Glycated Collagen on Oral Streptococcal Nanoadhesion

Biofilm-mediated oral diseases such as dental caries and periodontal disease remain highly prevalent in populations worldwide. Biofilm formation initiates with the attachment of primary colonizers onto surfaces, and in the context of caries, the adhesion of oral streptococci to dentinal collagen is crucial for biofilm progression. It is known that dentinal collagen suffers from glucose-associated crosslinking as a function of aging or disease; however, the effect of collagen crosslinking on the early adhesion and subsequent biofilm formation of relevant oral streptococci remains unknown. Therefore, the aim of this work was to determine the impact of collagen glycation on the initial adhesion of primary colonizers such as Streptococcus mutans UA159 and Streptococcus sanguinis SK 36, as well as its effect on the early stages of streptococcal biofilm formation in vitro. Type I collagen matrices were crosslinked with either glucose or methylglyoxal. Atomic force microscopy nanocharacterization revealed morphologic and mechanical changes within the collagen matrix as a function of crosslinking, such as a significantly increased elastic modulus in crosslinked fibrils. Increased nanoadhesion forces were observed for S. mutans on crosslinked collagen surfaces as compared with the control, and retraction curves obtained for both streptococcal strains demonstrated nanoscale unbinding behavior consistent with bacterial adhesin-substrate coupling. Overall, glucose-crosslinked substrates specifically promoted the initial adhesion, biofilm formation, and insoluble extracellular polysaccharide production of S. mutans, while methylglyoxal treatment reduced biofilm formation for both strains. Changes in the adhesion behavior and biofilm formation of oral streptococci as a function of collagen glycation could help explain the biofilm dysbiosis seen in older people and patients with diabetes. Further studies are necessary to determine the influence of collagen crosslinking on the balance between acidogenic and nonacidogenic streptococci to aid in the development of novel preventive and therapeutic treatment against dental caries in these patients.

NEUROTOXICOLOGICAL PROPERTIES OF THE COMPOUND AV-19 FOR PROPHYLAXIS AND TREATMENT OF COMPLICATIONS OF DIABETES MELLITUS

The article presents the results of a study of the neurotoxicological profile of the new compound AB-19, acting on collagen glycation end products (AGE) and their receptors (RAGE), for the prevention and treatment of diabetes complications. The multi-test method «S. Irwin» was used. The test results were evaluated in parallel groups receiving the substance in doses starting with the average effective dose (ED50) and with a multiple increase by 5, 10, 20 and 50 times. It was found that the compound AB-19 in doses of 20, 100 and 200 mg / kg does not affect the functional and behavioral status of animals. However, with an increase to 400 mg / kg, typical manifestations of intoxication were observed: a decrease in muscle tone, hypothermia, sedation, tachypnea. As a result of the study, it was revealed that the neurotoxicological properties of the compound AB-19 are characterized by dose-dependent activity. A minimum toxic dose of 400 mg / kg ≤ Tdmin ≤ 1000 mg / kg was also indicated.

Basement Membrane Collagen Glycation Prevents Endothelial Cell Response to Strain due to Altered Focal Adhesion Formation

Vascular morbidity and mortality are primary complications of diabetes and have been correlated with unregulated blood glucose control. Endothelial cells that line the vasculature are known to be dysfunctional in hyperglycemia (1). Furthermore, the high glucose environment promotes basement membrane protein glycation and enhanced cross-linking. This can increase matrix stiffness, decrease matrix degradation, and potentially alter the spatial distribution of cell-matrix binding sites.