A study of the age-related acceleration of glycation of tissue proteins in rats

The relationship between age-related glycation and a fluorescent product attributable to the advanced Maillard reaction was investigated in the aortas of rats between 4 and 120 weeks of age. The early-stage product of the Maillard reaction was measured using furosine (epsilon-N-(2-furoylmethyl)-L-lysine) as a marker. The advanced product was measured by fluorescence high-performance liquid chromatography. The level of furosine in the aorta increased with aging to reach a maximum value in rats of 50 to 70 weeks of age, and decreased in rats from 90 to 120 weeks of age. By contrast, the level of the putative advanced product reached a maximum in 90-week-old rats and remained at the maximum level in 120-week-old rats. The level of glycated hemoglobin showed no significant change in rats of more than 14 weeks of age. The advanced Maillard products may play an important role in the pathophysiology of aging arteries.     

Increased cholesterol concentration in intermediate density lipoprotein fraction of normolipidemic non-insulin-dependent diabetics

There is increasing agreement about the atherogenicity of intermediate density lipoprotein (IDL). In order to determine whether normocholesterolemic diabetics are at a higher risk of atherosclerosis, cholesterol concentrations in three subclasses of triglyceride-rich lipoprotein fraction (Sf 12-400) were examined. Their plasma triglyceride and cholesterol levels were limited to below 150 and 250 mg/dl, respectively. They were divided into 3 groups according to their treatment: insulin injection (group I), sulphonylurea (group S) and diet alone (group D). Age-matched healthy normolipidemic non-obese subjects served as controls (group C). Triglyceride-rich lipoproteins were separated by ultracentrifugation: very low density lipoprotein (VLDL), Sf 60-400; intermediate density lipoprotein (IDL1), Sf 20-60; IDL2; Sf 12-20. Cholesterol concentrations in total plasma, VLDL, IDL2 and high density lipoprotein (HDL) were all identical in every group. A significant increase in cholesterol concentration was found in IDL1 of groups S and D. Low density lipoprotein-cholesterol of group I was also increased. These findings indicate an increased risk factor in normolipidemic diabetics.