Plasma protein glycation in Alzheimer's disease.

Recent studies have suggested that formation of advanced glycation end-products (AGEs) in some brain proteins could be associated with Alzheimer's disease. These AGEs can be produced by various sugars (hexose, pentose, glyceraldehyde and oxidative products of vitamin C). In this study, we quantified plasma protein glycation specifically derived from glucose in patients with Alzheimer's disease with different grades of cognitive disorders. Two groups of Alzheimer patients were studied: a group with moderate Alzheimer's disease (n = 6, 9<MMS<20) and a severe Alzheimer group (n = 13, MMS<9) who were compared with an age-matched control group (n = 10, MMS>23) and a group of subjects with diabetes (n = 31). Protein glycation was evaluated in plasma with a highly specific HPLC-UV technique, using furosine, which is the acid hydrolysis product of epsilon-deoxy-fructosyl-lysine Plasma furosine was almost two times higher in subjects with Alzheimer's disease (p<.005) than in controls, but still 50% lower than in diabetic patients (P<.02). Fasting plasma glucose levels were significantly correlated to the furosine concentration. To explain these results, an eventual impairment in glucose peripheral use or an increase in protein glycation rate associated with Alzheimer's disease should be explored.