Plasma levels of advanced glycation end products in healthy, long-term vegetarians and subjects on a western mixed diet

Katarína Šebeková, Marica Krajčovičová-Kudláčková, Reinhard Schinzel, Veronika Faist, Jana Klvanová, August Heidland

Evidence indicates that food-derived Maillard's reaction products are absorbed and yet can be detected in the circulation. We postulated that consumption of the heat-treated food by omnivores could be reflected by higher plasma levels of advanced glycation end products (AGEs) in comparison with vegetarians, who in cooking (by keeping away from meat) use lower temperatures and less time for heating. Plasma fluorescent AGEs (350/450 nm) and N(epsilon)-(carboxymethyl)lysine (CML, competitive ELISA) levels were investigated in 3 groups of healthy vegetarians (9 vegans-V, 19 lactoovo-vegetarians--VLO and 14 semi-vegetarians--VS) and compared with those of age-matched omnivores (O, n=19). Mean duration of vegetarian diet was V: 7.2 +/- 1.0,VLO: 8.2 +/- 0.8 and VS: 7.9 +/- 1.1 years. Both fluorescent AGE (O: 9.9 +/- 0.5; V: 10.8 +/- 0.7, LO: 13.1 +/- 0.8* and SV: 11.6 +/- 1.2 x 10(3) AU), and CML levels (O: 427.1 +/- 15.0,V: 514.8 +/- 24.6*, LO: 525.7 +/- 29.5**, SV: 492.6 +/- 18.0* ng/ml) were significantly lower in omnivores than in vegetarians. Plasma glucose, parameters of renal function (plasma concentration of creatinine and cystatin C, calculated glomerular filtration rate--GFR) as well as C-reactive protein levels were within the normal range and did not differ significantly between the groups. Thus, neither decline of kidney function nor inflammatory processes contributed to the rise in plasma AGEs. Enhanced plasma AGE levels in vegetarians in comparison to omnivores are herein presented for the first time. Mechanisms of AGE elevation and potential pathophysiological relevance of this finding are to be elucidated in prospective studies.