Publication Database

Mechanisms of methionine absorption in the porcine intestine (2023)

Art

Hochschulschrift

Autor

Romanet, Stella (WE 2)

Quelle

Berlin: Mensch und Buch Verlag, 2023 — X, 82 Seiten

Sprache

Englisch

Verweise

URL (Volltext): https://refubium.fu-berlin.de/handle/fub188/41162

Kontakt

Institut für Veterinär-Physiologie

Oertzenweg 19 b
14163 Berlin
+49 30 838 62600
physiologie@vetmed.fu-berlin.de

Abstract / Zusammenfassung

Ensuring high growth performances is a central subject in the production of livestock. For this reason the diet of pigs is often supplemented with crystalline AA, especially Met as it is an essential and a limiting AA. The objective of this project was to gain insight into the mechanisms of Met absorption in the intestine of weaned pigs and to assess whether different dietary supplements might have different effects on the expression of Met transport systems in the intestinal tract. In the first part of this project, a feeding study was run to give insight whether different Met sources had an effect on the absorption of Met in the small intestine. For this purpose, three groups of each 9 piglets received a pre-feeding which only differed by the Met source supplemented. The three sources were L-Met, D/L-Met and the hydroxy Met analog D/L-2-hydroxy-4-methylthiobutyrate) D/L-HMTBA. In a functional study using the Ussing chamber, we analyzed the mucosal-to-serosal flux rates of L-Met, D-Met and D/L-HMTBA through sections of duodenum, jejunum and ileum. The resulting data showed that a D/L-Metcontaining diet increased the absorptive capacity for D-Met and L-Met. In the jejunum the flux rates of L-Met in the D/L-Met fed group were strongly Na+-dependent, suggesting the induction of a Na+-dependent transport system in the jejunum by a D/L-Met-containing diet. Na+-dependent L-Met transport systems in the apical membrane include B0AT1, ATB0+, ASCT2 and system IMINO. The flux study of D/L-HMTBA in the small intestine showed that the different dietary sources had no influence on the intestinal flux of D/L-HMTBA itself, which was rather surprising as the systems which supposedly accept D/L-HMTBA as a substrate (MCT1 and MCT4) are known to be upregulated in the presence of appropriate substrates. For a better understanding of the functional data obtained in the first part of this project, an analysis of the expression of possible Met transport systems was run along the whole gastrointestinal tract of pigs in the second part of this project. The samples came from the same pigs we used in the Ussing chamber experiments in the first part. Changes in mRNA expression of a total of nine apical or basolateral AA transporters, as well as MCT1 and MCT4, and changes in protein expression of four AA transporters were analyzed. In pigs fed D/L-Met, mRNA expression of ASCT2 was higher when compared to D/L-HMTBA in the small intestine, but this induction was not statistically confirmed on the protein level. B0AT1 protein expression was higher in the distal small intestine where it was upregulated by a D/L-Met containing diet. A D/L-HMTBA-containing diet seemed to upregulate certain basolateral transport systems on gene and protein levels, but also mRNA expression of MCT1. Overall, this part of the project showed that different Met supplements have an effect on the expression of several AA transport systems, especially D/L-Met seemed to have an effect on apical transport systems and D/L-HMTBA more on basolateral transport systems. Overall, this work showed that Met absorption in the intestine is influenced by the diet. Especially a D/L-Met-containing diet increased the L-Met flux in the jejunum of pig in the presence of Na+. Following the functional experiments, the analysis of gene and protein expression showed that this effect might result from expression changes of ASCT2 and B0AT1 which are both Na+-dependent transport systems. They are both excellent candidates for being responsible for the induction of Na+-dependent L-Met flux in the jejunum in the Ussing chamber experiment. To distinguish among those two contenders, more functional data is required to fully understand the mechanisms behind the changes observed in the feeding trial.