Fasting Enhances p -Cresol Production in the Rat Intestinal Tract

摘要

p -Cresol is a metabolite of aromatic amino acid metabolism produced by intestinal microflora, and its formation is influenced by intestinal conditions. Fasting drastically changes intestinal conditions. However, the effect of fasting on p -cresol production is unclear. In this study, serum and cecal p -cresol levels were determined in non-fasted rats and in rats fasting for either 12 or 18 h. Serum p -cresol increased significantly with 12-h fasting (3.44 ± 2.15 nmol/ml; P <0.05) and 18-h fasting (5.40 ± 2.20; P <0.001) as compared to the level in the non-fasted rats (1.02 ± 0.50). Cecal p -cresol levels of the 12-h fasted (272.6 ± 313.2 nmol/cecum) and 18-h fasted rats (436.6 ± 190.8; P <0.01) were higher than those in non-fasted rats (27.1 ± 21.9). The total cecal protein in content did not change with 18-h fasting. However, the cecal protein concentration increased significantly with fasting ( P <0.001), and correlated closely with total cecal p -cresol contents ( P <0.001). These results indicate that fasting enhances p -cresol production in the rat cecum, resulting in accumulation of serum p -cresol. We presume that the increase in p -cresol produced by fasting is related to the enhancement of bacterial nitrogen metabolism via an increased concentration of endogenous protein in the cecum.