Meder Kamalov

Synthesis of monolysyl advanced glycation endproducts and their incorporation into collagen model peptides.

The synthesis of advanced glycation endproducts (AGEs), CML, CEL, and pyrraline and their incorporation into collagen model peptides is reported. AGEs are modified amino acids that form on proteins such as collagen and are thought to play a significant role in the pathogenesis of many diseases, particularly diabetes. The synthesis and incorporation of these compounds into synthetic peptides is a key step in developing model systems with which to investigate AGE-modified proteins.

Diabetes-induced alterations in tissue collagen and carboxymethyllysine in rat kidneys: Association with increased collagen-degrading proteinases and amelioration by Cu(II)-selective chelation

Advanced glycation end-products (AGEs) comprise a group of non-enzymatic post-translational modifications of proteins and are elevated in diabetic tissues. AGE-modification impairs the digestibility of collagen in vitro but little is known about its relation to collagen-degrading proteinases in vivo. N(ε)-carboxymethyllysine (CML) is a stable AGE that forms on lysyl side-chains in the presence of glucose, probably via a transition metal-catalysed mechanism. Here, rats with streptozotocin-induced diabetes and non-diabetic controls were treated for 8weeks with placebo or the Cu(II)-selective chelator, triethylenetetramine (TETA), commencing 8weeks after disease induction. Actions of diabetes and drug treatment were measured on collagen and collagen-degrading proteinases in kidney tissue. The digestibility and CML content of collagen, and corresponding levels of mRNAs and collagen, were related to changes in collagen-degrading-proteinases. Collagen-degrading proteinases, cathepsin L (CTSL) and matrix metalloproteinase-2 (MMP-2) were increased in diabetic rats. CTSL-levels correlated strongly and positively with increased collagen-CML levels and inversely with decreased collagen digestibility in diabetes. The collagen-rich mesangium displayed a strong increase of CTSL in diabetes. TETA treatment normalised kidney collagen content and partially normalised levels of CML and CTSL. These data provide evidence for an adaptive proteinase response in diabetic kidneys, affected by excessive collagen-CML formation and decreased collagen digestibility. The normalisation of collagen and partial normalisation of CML- and CTSL-levels by TETA treatment supports the involvement of Cu(II) in CML formation and altered collagen metabolism in diabetic kidneys. Cu(II)-chelation by TETA may represent a treatment option to rectify collagen metabolism in diabetes independent of alterations in blood glucose levels.

Intermolecular Peptide Cross‐Linking by Using Diaminodicarboxylic Acids

Synthetic methods aimed at preparing peptides cross-linked by diaminodiacids remain an important chemical challenge. These cross-links are known to play a crucial role on the activity, structural stability, and folding of the host peptides and proteins. Recent developments in the syntheses of such systems have led to intriguing advances in the understanding of intermolecular side-chain cross-linking and the role that these structural motifs play in the biochemistry of proteins. Herein we provide an overview of the existing synthetic methodology that has been developed to effect protein cross-linking using diaminodiacids.

196 Strategies for Inhibiting Advanced Glycation Endproduct (Age) Induced Vascular Calcification in a Smooth Muscle Cell Culture Model

Vascular calcification is implicated in a range of cardiovascular disease mechanisms, leading to an associated increase in morbidity and mortality. One such trigger are advanced glycation endproducts (AGEs), the tissue accumulation of which increases with age and is more prevalent in diabetic subjects due to oxidative stress and poor glycaemic control. The aim of this study was to investigate the osteogenic potential of AGEs and elucidate mechanisms of inhibiting these processes in a smooth muscle cell (SMC) culture model. Osteogenic differentiation of SMCs was induced using β-glycerophosphate (β-GP), carboxymethyllysine (CML), carboxyethyllysine (CEL) methylglyoxal (MGO) and glycated low density lipoprotein (gly-LDL). The cells were subsequently treated with aminoguanidine (AG), an inhibitor of AGE formation, and novel glycomimetic compounds in order to determine their anti-calcification potential in vitro using qPCR, ELISA, Alkaline phosphatase (ALP) activity and Alizarin red staining. Gly-LDL (10 µg/ml) and CML (2.5nM) increased the level of calcification observed compared to the β-GP (5 mM) positive control after 21 days (p < 0.05), with gly-LDL induced calcification apparent after 14 days. Both AG (250 µM) and the novel glycomimetic compounds reduced the level of mineralisation observed at 21 days compared with osteogenic treatments (p < 0.05). CEL (2.5 nM) and MGO (0.1 mM) both induced calcification, however mineralization was not as extensive as with β-GP. When compared to the structure of CML, the side-chain of CEL contains an extra methyl group, suggesting this group impacts RAGE receptor binding. It was also shown that β-GP combined with increased glucose concentration induced more extensive calcification unlike low glucose levels and β-GP alone. ALP activity, when stimulated with β-GP, CML and gly-LDL was greater at day 4 than at day 7, with AG reducing ALP activity measurements at day 4. Gly-LDL increases gene expression of OCN at day 4 compared with β-GP and CML, however this was reduced at day 7, corresponding with an increased expression of OPN and OPG. NOTCH-3 gene expression was also reduced at day 7. Gene expression of OPN, OPG and NOTCH-3 were reduced at both day 4 and day 7 compared with osteogenic treatments (β-GP, CML and gly-LDL). In summary, we conclude that gly-LDL and CML are potent inducers of calcification compared with β-GP, and that their osteogenic potential can be modulated by both AG and novel glycomimetic compounds.