Evidence of glucuronidation of the glycation product LW-1: tentative structure and implications for the long-term complications of diabetes

Autor: Vincent M. Monnier, David R. Sell, Zhili Liang, Ina Nemet
Rok vydání: 2018
Předmět:
Zdroj: Glycoconjugate Journal. 35:177-190
ISSN: 1573-4986
0282-0080
DOI: 10.1007/s10719-017-9810-7
Popis: LW-1 is a collagen-linked blue fluorophore whose skin levels increase with age, diabetes and end-stage renal disease (ESRD), and correlate with the long-term progression of microvascular disease and indices of subclinical cardiovascular disease in type 1 diabetes. The chemical structure of LW-1 is still elusive, but earlier NMR analyses showed it has a lysine residue in an aromatic ring coupled to a sugar molecule reminiscent of advanced glycation end-products (AGEs). We hypothesized and demonstrate here that the unknown sugar is a N-linked glucuronic acid. LW-1 was extracted and highly purified from ~99 g insoluble skin collagen obtained at autopsy from patients with diabetes/ESRD using multiple rounds of proteolytic digestion and purification by liquid chromatography (LC). Advanced NMR techniques ((1)H-NMR, (13)C-NMR, (1)H-(13)C HSQC, (1)H-(1)H TOCSY, (1)H-(13)C HMBC) together with LC-mass spectrometry (MS) revealed a loss of 176 amu (atomic mass units) unequivocally point to the presence of a glucuronic acid moiety in LW-1. To confirm this data, LW-1 was incubated with β-glycosidases (glucosidase, galactosidase, glucuronidase) and products were analyzed by LC-MS. Only glucuronidase could cleave the sugar from the parent molecule. These results establish LW-1 as a glucuronide, now named glucuronidine, and for the first time raise the possible existence of a “glucuronidation pathway of diabetic complications”. Future research is needed to rigorously probe this concept and elucidate the molecular origin and biological source of a circulating glucuronidine aglycone.
Databáze: OpenAIRE
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