Background & Objective: Advanced Glycation End Products (AGEs), commonly seen in western diets, are known to affect glycaemic control. Despite this, little is known about AGE gastrointestinal absorption and subsequent trafficking. We therefore aimed to determine this using near infrared (near-IR) labelled AGE-modified albumin.
Methods: AGE-modified bovine serum albumin (BSA) and unmodified BSA (66kDa protein) were labelled with a near-IR ester. Twenty week old, male, C57BL/6 mice were orally gavaged with near-IR AGE-BSA or BSA control (5 mg/kg bolus, n= 3 mice/group). Control mice received IR dye only or water. Plasma and urine were collected at 15 minutes, 1, 4 and 8 hours post-gavage following euthanasia of the mice and imaged by SDS-PAGE.
Results: Fifteen minutes post-bolus, 60% of mice in both BSA and AGE-BSA groups demonstrated the presence of a 66kDa band in plasma (6.00, IQR: 6.3 RFU vs 2.34, IQR 5.4 RFU; respectively (as determined by densitometry)). No intact near IR-labelled proteins were observed in plasma after 1 and 4 hours, with the exception of a single mouse that had received near IR-BSA. However, at 8 hours post-gavage, a 66kDa band reappeared in the circulation in 30% of mice administered with AGE-BSA and 30% of mice administered BSA. The urine contained cleavage products of approximately 30kDa and 15kDa at all timepoints and treatments when compared with water only controls. However, there was some variation in the profile of cleavage products between replicate animals with some animals only demonstrating the 15kDa band and others demonstrating both.
Conclusions: These data suggest that intact AGE-modified BSA may enter the circulation within 15 minutes of ingestion, traffic to tissues and later reappear in the circulation after 4 and 8 hours. Further analysis of organs and tissues from these animals remains to be completed.