Influences on skatole formation from tryptophan in the pig colon

Variable amounts of skatole (3-methyl-indole) are formed by microbes out of tryptophan in the colon of pigs. It is resorbed and accumulated in fat, leading to a fecal odor of the meat. We investigated the mechanisms by which differences in diet composition lead to variations in skatole concentrations in blood plasma and fat. The experiments were based on the hypothesis that tryptophan is derived from mucosa cell debris from the small intestine. It was found, that gut cell mitosis is stimulated by the growth factor IGF-I. This factor increases when energy in the diet is high. In addition, the mitotic rate is elevated when high amounts of purines are available in the diet, allowing a more rapid DNA- and RNA-synthesis. Thus, high energy combined with high purines in the diet lead to a remarkable increase of gut cell mitosis which is accompanied by an increase of apoptosis. These apoptotic cells ultimately provide the substrate for skatole formation. In consequence, a dramatically rise of skatole in blood plasma and fat was measurable.