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金沢大学大学院医学部医学系研究科, As is diabetes itself, diabetic vasculopathy is a multifactor disease. Studies conducted in this lab revealed advanced glycation endproducts (AGE) as the major environmental account for vascular cell derangement characteristic of diabetes, and the receptor for AGE (RAGE) as the major genetic factor that responds to them. AGE fractions that caused the vascular derangement were proven to be RAGE ligands. When made diabetic, RAGE-overexpressing transgenic mice exhibited the exacerbation of the indices of nephropathy, and this was prevented by the inhibition of AGE formation. We also created RAGE-deficient mice. They showed marked amelioration of diabetic nephropathy. Extracellular signals and nuclear factors that induce the transcription of human RAGE gene were also identified, which would be regarded as risk factors of diabetic complications. Through an analysis of vascular polysomal poly(A)+ RNA, we came across a novel splice variant coding for a soluble RAGE protein, and named it endogenous secretory RAGE (esRAGE). esRAGE was able to capture AGE ligands and neutralize the AGE action on endothelial cells, suggesting that this variant has a potential to protect blood vessels from diabetes-induced injury. The AGE–RAGE system should thus be regarded as a candidate molecular target for overcoming this life- and quality of life (QOL)-threatening disease.

Compared to long-chain carbohydrates, short-chain sugar aldehydes and dicarbonyls are known to be much more reactive with lysine and arginine. In order to elucidate the potential chemical nature of extracellular matrix cross-links induced by glyceraldehydes (GA), we incubated it with α-amino-protected lysine with or without α-amino-protected arginine at physiological pH and temperature. In this paper, we describe the isolation and the chemical identification of four new advanced glycation endproducts (AGEs). Two acid stable, fluorescent adducts, named lys-hydroxy-triosidine and arg-hydroxy-triosidine were found to be lys–lys and arg–lys cross-links, respectively. The remaining two are nonfluorescent, noncross-linking AGEs formed from one lysine and two GA. Among these latter two adducts, named trihydroxy-triosidine and triosidine-carbaldehyde, only the first one is acid resistant.

Engagement by advanced glycation endproducts (AGE) of the cell surface receptor for AGE (RAGE) leads to perturbation of vascular cell functions. This includes proliferation of endothelial cells (EC), and decrease in pericytes. To clarify these different cellular responses, we analyzed in this study polysomal mRNAs for RAGE from human microvascular EC and pericytes by RT-PCR cloning, and isolated three major variants: novel C-terminally and N-terminally truncated forms and the known full-length form. The protein product of the C-terminally truncated variant was secreted into culture media, whereas the N-terminally truncated form resided on the plasma membrane, when each cDNA was forced to be expressed in COS-7 cells. The former, soluble form of RAGE was actually detected in healthy human sera, and was found capable of neutralizing AGE induction of vascular endothelial growth factor (VEGF) gene in EC. Different degrees of the expression of those RAGE variants may elicit different cellular responses to AGE, and such variation may contribute to the individual susceptibility or resistance to the development of diabetic complications.

Dietary supplement of 0.2% 4 G -α-glucopyranosylrutin (G-rutin) showed the reduction of increases in N e -fructoselysine (FL) and advanced glycation endproducts (AGEs) in kidney and serum proteins of diabetic rats. Furthermore, dietary G-rutin significantly inhibited aldose reductase activity in kidney. Thus, dietary supplement G-rutin has beneficial effects on glycation of serum and kidney proteins.

Nω-carboxymethylarginine (CMA) is a new acid-labile advanced glycation endproduct (AGE). We immunized rabbits with glycated collagen and succeeded in raising the antibody against CMA. The antibody specifically reacted against glycated collagen and CMA, but did not recognize non-glycated collagen or Ne-carboxymethyllysine (CML). The anti-CMA antibody may be applied to estimate CMA as the new diagnostic marker.