Fasting Enhances p-Cresol Production in the Rat Intestinal Tract

• Published in: Experimental Animals Vol. 56; no. 4; pp. 301 - 307
• Main Authors: MAKINO, Ikuyo, KATO, Ikuo, ONOUE, Masaharu, KAWAKAMI, Koji, KOJIMA, Kenji
• Format: Journal Article
• Language: English
• Published: Japan Japanese Association for Laboratory Animal Science 01.07.2007
• Subjects: Ammonia - metabolism; Animals; Bacteria - metabolism; Body Weight; Cecum - metabolism; Cecum - microbiology; Cresols - metabolism; Eating; fasting; Food Deprivation; Hematologic Tests; Indoles - metabolism; Male; microflora metabolite; p-cresol; rat; Rats; Rats, Wistar; Specific Pathogen-Free Organisms; Time Factors
• ISSN: 1341-1357; 1881-7122
• DOI: 10.1538/expanim.56.301

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.