Basal leptin regulates amino acid uptake in polarized Caco-2 cells

Abstract

Leptin is secreted by gastric mucosa and is able to reach the intestinal lumen where its receptors are located in the apical membrane of the enterocytes. We have previously demonstrated that apical leptin inhibits sugar and amino acids uptake in vitro and glucose absorption in vivo. Since leptin receptors are also expressed in the basolateral membrane of the enterocytes, the aim of the present work was to investigate whether leptin acting from the basolateral side could also regulate amino acid uptake. Tritiated Gln and β-Ala were used to measure uptake into Caco-2 cells grown on filters, in the presence of basal leptin at short incubation times (5 and 30 min) and after 6 h of preincubation with the hormone. In order to compare apical and basal leptin effect, Gln and β-Ala uptake was measured in the presence of leptin acting from the apical membrane also in cells grown on filters. Basal leptin (8 mM) inhibited by ~15-30% the uptake of 0.1 mM Gln and 1 mM β-Ala quickly, after 5 min exposure, and the effect was maintained after long preincubation periods. Apical leptin had the same effect. Moreover, the inhibition was rapidly and completely reversed when leptin was removed from the apical or basolateral medium. These results extend our previous findings and contribute to the vision of leptin as an important hormonal signal for the regulation of intestinal absorption of nutrients.

Transport Mechanisms of Butyrate Modified Nanoparticles: Insight into “Easy Entry, Hard Transcytosis” of Active Targeting System in Oral Administration

“…To further elucidate the function of receptors in each stage of NP transport, the hormone leptin was used. Leptin receptors are present all along the intestine within the brush border, and leptin can regulate expression of various transporters and the absorption of nutrients. , According to previous reports, leptin also affected free butyrate absorption and regulated MCT-1 expression. , Here, after preincubation with leptin for 18 h, cells were exposed to both NPs. It was found that only Bu-PEG NPs showed greatly reduced internalization (only ∼40% of control group) at the concentration of leptin ranging from 1 to 200 nM (Figures B and S3A).…”

“…Leptin receptors are present all along the intestine within the brush border, and leptin can regulate expression of various transporters and the absorption of nutrients. 27,28 According to previous reports, leptin also affected free butyrate absorption and regulated MCT-1 expression. 29,30 Here, after preincubation with leptin for 18 h, cells were exposed to both NPs.…”

Hto, Tritiated Amino Acid Exposure and External Exposure Induce Differential Effects on Hematopoiesis and Iron Metabolism

“…By contrast, amino acids may be distributed more heterogeneously, since they enter cell cytoplasm and participate in cell metabolic processes. For example, the intestinal epithelium, and especially the basal part of the villi where amino acids are absorbed by enterocytes 50 , may concentrate TAA before transport into the blood. Moreover, the AAs are absorbed mainly by the duodenum and the upper part of the jejunum 42 .…”