Molecular Basis of Human Gut

In addition to the hardwired program of gut development discussed above, it is clear that environmental influences, such as diet (27) and the microbial community of the gut (28), play important roles in the differentiation and function of the gut. For example, in mammals, the changing dietary input in the pre- and postnatal periods imposes different demands on the intestine and influences its morphology, enzymatic diversity, and transport. In addition, the diet contains substances such as polyamines and epidermal growth factor that do not play a nutritional role but appear to directly stimulate the growth of the intestinal epithelium (27). Similarly, C. elegans worms adjust the size of their pharynx, intestine, and intestinal microvilli depending on their nutritional state (29), and such plasticity is also seen in the willow ptarmigan, in which the winter consumption of fibrous food is associated with relatively long caecae. Investigations into the cellular and molecular underpinnings of such phenomena are just beginning