Expression profiles of thyroid hormone transporters Mct10 and Lat2 within the different intestinal segments of young and aged wild-type mice

Localized in the basolateral membrane of human small intestines, thyroid hormone transporters MCT10 and LAT2 are the proposed molecules involved in visceral thyroid hormone metabolism. To our best knowledge, the age-dependent expression patterns of these transporters have not been evaluated. Yet, alterations in transcription may be anticipated, because thyroid metabolism in general changes with age. We therefore analyzed the expression profiles of primary and secondary thyroid hormone transporters Mct8, Mct10, Lat1 & 2, Ntcp and Oatps within the intestines of young and aged C57BL/6-mice by quantitative PCR. Young mice (age = 4 months) and old mice (age = 18 months) were sacrificed and RNA was isolated from the different intestinal segments. Highest expression levels were shown for candidate molecules Mct10 and Lat2, confirming their assumed role in small intestine. Other thyroid transporters could be neglected due to low transcription in intestinal tissues. We now examined Mct10- and Lat2-expression of old compared to young mice (Fig. 1). An age-dependent down-regulation may be estimated in ileum for Mct10 and both in jejunum and ileum for Lat2. In the remaining intestinal parts transcription of both molecules seems to be unaffected from age and in general no up-regulation was observed. In summary, our results have to be classified as preliminary and further analysis based on larger mouse groups and additional immunohistochemistry will be necessary.

Tab. 1

	Mct 10	Lat2
Duodenum n = 8 (old) n = 5 (young)	↔	↔
Jejunum n = 6 (old) n = 4 (young)	↔	↓
Ileum n = 8 (old) n = 5 (young)	↓	↓
Colon n = 8 (old) n = 4 (young)	↔	↔
Expression pattern of Mct10 and Lat2 in the respective tissues. Old C57BL/6-mice (mean age = 18 months) were compared to young (mean age = 4 months). ↓: down-regulation. ↑: up-regulation. ↔: stable expression

This project is funded by DFG SPP 1629 FU356/8 – 1.