Objectives: 

Leptin is an adipocyte-derived hormone, also secreted by gastric endocrine and exocrine mucosal cells in response to several stimuli, including food intake. Exocrine-delivered leptin is stable in spite of the harsh conditions of the stomach milieu and is able to reach the intestinal lumen. We have previously demonstrated that leptin inhibits sugar and amino acid uptake in rat intestinal everted rings and in the human model of intestinal cells Caco-2. Also, we have shown that the hormone is able to modulate sugar absorption in vivo and that this effect is reversible. Thus, the purpose of the present study was to extend our previous findings and investigate whether leptin can also modulate amino acids absorption in vivo.

Materials: 

In vivo intestinal absorption of proline, beta-alanine and glutamine was measured in rat using the single-pass perfusion system. Pro and beta-Ala absorption was measured at pH 6. Amino acids disappearance from the perfusion medium was measured by radioactivity method, in the absence and presence of luminal leptin in the same animal. Statistical differences were evaluated by the general linear model for repeated measures. Differences were considered statistically significant when p<0.05.

Results: 

Leptin (25 nM) inhibited, by 40 %, Pro (2 mM), beta-Ala (5 mM) and Gln (5 mM) absorption after 5 min of perfusion. This effect was maintained during the whole perfusion period (40 min) and reversed, after removing leptin from the medium, in 5-10 min.

Conclusions: 

These results show that leptin exert a short-term regulation of amino acid absorption, as it happens with sugars. Together with our previous results, they confirm that leptin can be considered as a hormone which modulates nutrients absorption, most probably to permit the adequate nutrients processing by the enterocytes.

This work was supported by Marcelino Botín Foundation.