Inter-organ communication between intestine and liver in vivo and in vitro

The maintenance of body homeostasis requires a finely tuned system of interorgan communication. The intimate metabolic interrelation between intestine and liver is characterized by the unique anatomic position of both tissues using the portal vein as a private channel with the pancreas in optimal position to modulate hepatic metabolism. Gut-derived peptides (such as glucagon-like peptide-1) appear to be involved in the process of liver regeneration by regulating the release of pancreatic hormones (e.g. insulin). Extensive bowel resection or functional exclusion of small intestine may lead to severe liver dysfunction and even cirrhosis, which may be due to the lack of some intestine-derived and as yet unknown factor(s). Here a close cooperation between small intestinal mucosa and hepatocytes is demonstrated leading to the concept of a metabolic gut-liver unit. This metabolic interaction forms a wide spectrum ranging from the secretion of peptide hormones to changes in (portal-venous) substrate availability or hepatocyte cell volume. Further investigation and identification of the mechanisms of such regulatory processes may be facilitated by combined perfusion of isolated rat intestine and liver. Using this in vitro approach we could demonstrate the presence of metabolic interorgan communication between isolated perfused tissues independent of plasma borne hormones or extrinsic neural control.