A Short-term Diet High in Carboxymethyl-lysine (CML) Increases Urinary Excretion but Not Serum CML Levels (P12-012-19)

Objectives

Dietary advanced glycation end products (AGEs) are a group of compounds formed by the Maillard reaction. Carboxymethyl-lysine (CML), a marker of AGEs in foods, may contribute to cardiometabolic diseases. However, CML health effects and its absorption and excretion in healthy individuals remained controversial. For this reason, the aim of this study was to evaluate serum and urinary excretion CML levels in healthy adults after a short-term diet high in CML.

Methods

A randomized clinical trial was conducted in 30 healthy adults (18–35 years old). After signing the informed consent, subjects were randomly assigned to a low or a high CML diet. All participant followed a diet with low CML content for seven days (washing period) before the 5-days intervention. During the 5 days participants received all the foods according to their group. Blood and 24-hour urine samples were collected before and after the intervention to evaluate serum and urinary CML levels. CML measurement in foods, serum, and urine was carried out by HPLC-ESI-ITMS/MS. Comparison between groups was carried out by a t-test. The research was approved by the Institutional Review Board and the clinical trial registration number NCT03208946.

Results

Biochemical and anthropometric variables were similar between groups (P > 0.05). The average consumption of CML was 1.93 ± 1.47 mg/day for the low CML diet and 5.03 ± 2.22 mg/day for the high CML diet, whereas caloric, protein and fat intake were similar. Serum levels decreased significantly in both groups (low diet: basal 488.1 ± 135.4 μg/L, final 383.2 ± 78.6 μg/L (P = 0.007)) (high diet: basal 463.5 ± 90.3 μg/L, final 390.3 ± 99.1 μg/L (P = 0.02)). No significant difference was found when comparing the final CML levels between groups (P = 0.47). The excretion of CML in urine was adjusted by creatinine (mg) and the high CML group had a greater excretion (4.5 ± 8.0 ug CML/mg) when compared to the low CML group (−1.5 ± 7.2 ug CML/mg) (P = 0.04).

Conclusions

A high CML diet increases urinary CML excretion levels in healthy adults when compared to a low CML diet. There were no significant differences in serum CML levels between both groups. However, a greater decrease was observed in the subjects who followed a diet with a low content of AGEs.

Funding Sources

University of Guanajuato. CONACYT.