Accumulation of albumin-linked and free-form pentosidine in the circulation of uremic patients with end-stage renal failure: renal implications in the pathophysiology of pentosidine.

Pentosidine is an advanced glycation end product and its formation is shown to be closely related to oxidative processes. Recent studies have shown that pentosidine levels are increased not only in plasma and matrix proteins from diabetic patients, but also markedly in nondiabetic hemodialysis patients. Currently, the mechanism of accumulation and kinetics of pentosidine formation in hemodialysis patients remain unknown. Gel filtration of uremic plasma revealed that plasma pentosidine exists in the albumin fraction (approximately 90%) and, interestingly, in free form (approximately 5%) as well. Plasma free pentosidine was undetectable in subjects with normal renal function. There was a significant correlation between the plasma levels of albumin-linked and free pentosidine in hemodialysis patients. Kinetic studies indicated that dietary pentosidine was absorbed into the circulation and that, after either oral or intravenous administration of pentosidine to intact or nephrectomized rats, the plasma free pentosidine level was closely linked to the level of renal function. These findings demonstrate that: (1) Pentosidine accumulates as albumin-linked and in free form in the circulation of uremic patients; (2) dietary pentosidine can be absorbed into the circulation, thus being one possible origin of circulating free pentosidine; (3) free pentosidine may accumulate as a result of decreased glomerular filtration; and (4) the mechanism of accumulation of albumin-linked pentosidine is not related to high glucose levels. It suggests the simultaneous accumulation, during renal failure, of either unknown pentosidine precursor(s) or catalyst(s) of glycoxidation, independent of glucose.