Endocrine cells producing peptide hormones in the intestine of Nile tilapia: distribution and effects of feeding and fasting on the cell density

Abstract

Endocrine cells (ECs) act as a luminal surveillance system responding to either the presence or absence of food in the gut through the secretion of peptide hormones. The aim of this study was to analyze the effects of feeding and fasting on the EC peptide-specific distribution along the intestine of Nile tilapia. We assessed the density of ECs producing gastrin (GAS), cholecystokinin-8 (CCK-8), neuropeptide Y (NPY), and calcitonin gene-related peptide (CGRP) in nine segments of the intestine using immunohistochemistry. Our results show that ECs immunoreactive to CCK-8, GAS, NPY, and CGRP can be found along all the intestinal segments sampled, from the midgut to hindgut, although differences in their distribution along the gut were observed. Regarding nutrient status, we found that the anterior segments of the midgut seem to be the main site responding to luminal changes in Nile tilapia. The NPY+ and CGRP+ EC densities increased in the fasted group, while the amount of CCK-8+ ECs were higher in the fed group. No effects of fasting or feeding were found in the GAS+ EC densities. Changes in ECs density were found only at the anterior segments of the intestine which may be due to the correlation between vagus nerve anatomy, EC location, and peptide turnover. Lastly, ECs may need to be considered an active cell subpopulation that may adapt and respond to different nutrient status as stimuli. Due to the complexity of the enteroendocrine system and its importance in fish nutrition, much remains to be elucidated and it deserves closer attention.

Effect of fasting and feeding on growth, intestinal morphology and enteroendocrine cell density in Rhamdia quelen juveniles

“…However, it was observed that fish fed with the lower protein level (T1) presented low density of CCK‐IR cells. Similar to our results, fasted Nile tilapia ( Oreochromis niloticus ) presented lower density of CCK‐8 + cells compared to fed ones (Pereira et al., ) and high concentrations of fish meal in the diet have a more potent effect on the stimulation of CCK synthesis and digestive enzymes secretion than other protein sources in yellowtail ( Seriola quinqueradiata ) Furutani, Masumoto and Fukada (). This demonstrates that the source or dietary protein level can positively influence CCK synthesis and promote digestive activities such as pancreatic activity, fluid secretion and intestinal motility (Gribble, ; Murashita et al., ).…”

Distribution of goblet and endocrine cells in the intestine: A comparative study in Amazonian freshwater Tambaqui and hybrid catfish

“…Together our current results and previous (Pereira et al, , ) highlight the restricted distribution of NPY in the first midgut segments, regardless feeding habits, which might play a role as the main signaling area in the intestine to hypothalamic center that modulates food intake.…”

“…Unlike Tambaqui but similar to hybrid catfish, the EC CCK in O . niloticus (Pereira et al, ) and gobie, C . gulosus (Hur et al, ), were mainly concentrated in the midgut segment close to the stomach (Table ).…”

“…In accordance with our results, both omnivorous O . niloticus (Pereira et al, ) and as well as carnivorous S . brasiliensis (Pereira et al, ) showed larger number of NPY+ cells in the midgut segment, near by the stomach.…”

“…The polyclonal antibodies used herein were selected according to their accuracy at recognizing peptide hormones CCK‐8 and NPY, produced by intestinal ECs in other fishes, including Nile tilapia ( Oreochromis niloticus ; Pereira et al, ), dorado ( Salminus brasiliensis ; Pereira et al, ), South American catfish ( Rhamdia quelen ; Hernández et al, ), and pejerrey ( Odontesthes bonariensis ; Vigliano et al, ).…”