Half-life of Glycated Tryptophan in the Plasma of Chickens

Abstract

Tryptophan, an essential amino acid, is enzymatically metabolized to two compounds, kynurenine and serotonin, and 95% of tryptophan is metabolized to kynurenine. As chickens have hyperglycemia and high temperature, tryptophan glycation occurs more easily in chickens than in mammals. Part of tryptophan is non-enzymatically converted to two types of glycated tryptophan, tryptophan-Amadori product and (1R, 3S)-1-(d-gluco-1, 2, 3, 4, 5-pentahydroxypentyl)-1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid (PHP-THβC). Although these compounds are detected in the plasma of chickens, information on the half-life of PHP-THβC in the blood circulation is limited. Therefore, the present study aimed to measure the half-life of plasma PHP-THβC in chickens. PHP-THβC (114 nmol/0.2 mL/70 g body weight) was intravenously administered to chickens via the wing vein, and blood samples were collected at 0, 15, 30, 60, 180, 360, 720, and 1440 min after administration. Plasma concentrations of PHP-THβC were measured by liquid chromatography-mass spectrometry. Plasma PHP-THβC reached to a peak concentration of 16.1 βM at 30 min after administration, and then decreased rapidly to return to the physiological level (0 min) at 360 min after administration. The half-life of plasma PHP-THβC was calculated by non-linear regression analysis, and it was found to be 107 min. This study was the first to measure plasma half-life of glycated tryptophan.

Keywords: PHP-THβC; chicken; glycation; plasma half-life; tryptophan.

Fig. 1.

Time course changes in plasma PHP-THβC concentration in chickens administrated with PHP-THβC intravenously. PHP-THβC dissolved in DPBS at 114 nmol/0.2 mL/70 g body weight was intravenously administrated to chickens via the wing vein. Control groups were administrated DPBS alone. At 15, 30, 60, 180, 360, 720, and 1440 min after administration, blood samples were taken by heart puncture after anesthesia with diethyl ether. Blood samples were also taken from chickens at time 0 as a baseline control. PHP-THβC concentration in the plasma was measured using LC-MS. PHP-THβC concentration (µM)=8.77·exp^{(−0.0065·time (min))} +8.84. Values are means±SEs. n=6.