MG-HCr, the Methylglyoxal-Derived Hydroimidazolone of Creatine, a Biomarker for the Dietary Intake of Animal Source Food

In the course of the Maillard reaction in vivo or in food, creatine reacts with the 1,2-dicarbonyl compound methylglyoxal to N-(4-methyl-5-oxo-1-imidazolin-2-yl)sarcosine (MG-HCr). We studied whether the urinary excretion of MG-HCr is affected by its intake with meat or by the intake of creatine and subsequent in vivo formation of MG-HCr. Therefore, 24 h urine of 30 subjects with different dietary habits was analyzed with HPLC-MS/MS. The daily MG-HCr excretion via urine varied between omnivores (0.39-9.67 μmol/day, n = 24), vegetarians (0.18-0.97 μmol/day, n = 19), and vegans (0.10-0.27 μmol/day, n = 8). An intervention study with 18 subjects demonstrated the bioavailability of MG-HCr (ca. 54%) from 200 g of heated meat and its quick excretion with urine. A creatine intervention of 0.44 g did not increase MG-HCr excretion. Thus, the differences in MG-HCr excretion between different diets are mainly caused by the dietary uptake of MG-HCr. We additionally found MG-HCr in milk and egg products, where it is formed during heat treatment. This partly explains differences in MG-HCr excretion of vegetarians and vegans. Hence, MG-HCr in urine is a short-term marker for the intake of heat-processed animal source food.