Net release and uptake of xenometabolites across intestinal, hepatic, muscle, and renal tissue beds in healthy conscious pigs

Authors: MERCER, KELLY - Arkansas Children'S Nutrition Research Center (ACNC); TEN HAVE, GABRIELLA A.M. - Texas A&M University; PACK, LINDSAY - Arkansas Children'S Nutrition Research Center (ACNC); LAN, RENNY - Arkansas Children'S Nutrition Research Center (ACNC); DEUTZ, NICOLAAS E.P. - Texas A&M University; Ferruzzi, Mario; PICCOLO, BRIAN - Arkansas Children'S Nutrition Research Center (ACNC)

Submitted to: American Journal of Physiology - Gastrointestinal and Liver Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/10/2020
Publication Date: 8/1/2020
Citation: Mercer, K.E., Ten Have, G., Pack, L., Lan, R., Deutz, N., Adams, S.H., Piccolo, B.D. 2020. Net release and uptake of xenometabolites across intestinal, hepatic, muscle, and renal tissue beds in healthy conscious pigs. American Journal of Physiology - Gastrointestinal and Liver Physiology. 319(2):G133-G141. https://doi.org/10.1152/ajpgi.00153.2020.
DOI: https://doi.org/10.1152/ajpgi.00153.2020

Interpretive Summary: There are many non-self originating small molecules (i.e., xenometabolites) that humans and animals can absorb and then either promote beneficial or harmful health outcomes. Many of these xenometabolites are from microbes in our gut. However, there are very few studies that have clearly demonstrated that these microbe xenometabolites are absorbed and which internal organs they interact with in a living model. We used a conscious pig model where one can measure blood samples from surgically implanted catheter ports inserted in arterial and venous sites close to specific organs. Using these measurements, we were then able to calculate the net release or uptake of xenometabolites from the intestines, splanchnic bed (primarily liver and intestines), liver, kidney, and muscle. We found 48 xenometabolites across all ports and 31 of these showed a net difference in either uptake or release from at least one organ. Xenometabolites related to bile acids, indoles, and others were only released from the intestines and only taken up by the liver. Other putative xenometabolites, such as indole-3-carboxaldehyde, p-cresol glucuronide, 4-hydroxyphenyllactic acid, dodecanendioic acid, and phenylacetylglycine, were also released only from the intestines. Most xenometabolites were taken up by the liver and kidneys. Atrolactic acid and dodecanedioic acids showed net release from muscle. This study is the first to describe tissue distribution and flux in a conscious healthy large animal whose gut closely resembles that of a human. Most xenometabolites were taken up by the liver and kidney, likely for modification and excretion pathways. Other xenometabolites appear to have non-gut release, possibly suggesting host related metabolic pathways. These results form the foundation for understanding how the natural, diet-regulated bacteria in the gut (the "microbiome") are trafficked throughout the body to impact health.

Technical Abstract: Xenometabolites from microbial and plant sources are thought to confer beneficial, as well as deleterious, effects on host physiology. Studies determining absorption and tissue uptake of xenometabolites are limited. We utilized a conscious catheterized pig model to evaluate inter-organ flux of annotated known and suspected xenometabolites, derivatives, and bile acids. Female pigs (n=12; 2-3 months old; 25.6 +/- 2.2 kg) had surgically-implanted catheters across portal-drained viscera (PDV), splanchnic area (SPL), liver, kidney, and hindquarter muscle. Overnight fasted arterial and venous plasma was collected simultaneously in a conscious state and stored at -80°C. Thawed samples were analyzed by liquid chromatography-mass spectrometry. Plasma flow was determined with para-aminohippuric acid dilution technology and used to calculate net organ balance for each metabolite. Significant organ uptake or release was determined if net balance differed from zero. A total of 48 metabolites were identified in plasma, and 31 of these had at least one tissue with a significant net release or uptake. All bile acids, indole-3-acetic acid, indole-3-arylic acid, and hydrocinnamic acid were released from the intestine and taken up by the liver. Indole-3-carboxaldehyde, p-cresol glucuronide, 4-hydroxyphenyllactic acid, dodecanendioic acid, and phenylacetylglycine were also released from the intestines. Liver or kidney uptake was noted for indole-3-acetylglycine, p-cresol glucuronide, atrolactic acid, and dodecanedioic acid. Indole-3-carboxaldehyde, atrolactic acid, and dodecanedioic acids showed net release from skeletal muscle. The results confirm gastrointestinal origins for several known xenometabolites in an in vivo overnight-fasted conscious pig model, while non-gut net release of other putative xenometabolites suggests a more complex metabolism.