Taste receptors (TR1s, TR2s) for sweet and bitter along with related G-proteins (α-transducin and α-gustducin) have been localized in the GI tract mucosa of several mammals. Taste signalling molecules are now conceived to be part of a wide chemosensing system contributing to sense luminal contents. In the pig model (resembling the human gut) we established whether feeding changes, i.e. fasting and re-feeding, wereable to affect: 1) the expression of α-transducin throughout the GI tract; 2) neuropeptide coding of the cells expressing α-transducin; and 3) the spatial relationship between α-transducin cells and nerves supplying the gut. Pig stomach-to-rectum specimens (n= 12; 45 days of age), subdivided in 3 groups, i.e. control (C), fasted for 24h (F) and re-fed (R), were fixed in 4%-paraformaldehyde, embedded either in paraffin and processed for single and double labelling immunofluorescence with antibodies to: α-transducin, chromogranin-A (CgA), gastrin/cholecystokinin (Gas/CCK), somatostatin (SOM) and PGP9.5. The highest density of α-transducin-immunoreactive (IR) cells has been shown in the pylorus (C: 191±22, F: 99±28 and R: 112±51) and in the cardial mucosa (C: 79±46, F: 29±13 and R: 57±10), whereas in the intestine the highest α-transducin cell density was observed in the duodenum of C (54±22) vs. F and R (41±20,14±6, respectively). The density of α-transducin-IR cells decreased along the large intestine. The percentage of α-transducin/CgA-IR cells was reduced in the GI tract of F and R vs. C. In the jejunum,α -transducin/CCK cells decreased in F and R vs. C. Gas/α-transducin and SOM/α -transducin colocalizations have never been detected. PGP9.5 varicose nerve fibers, running either singly or in small fascicles, throughout the lamina propria of the small bowe l mucosa were seen in close spatial relationship with α-transducin cells. In conclusion, changes to α-transducin expression in neuropeptide-containing cells following F and R provide a basis to the concept that these cells participate to luminal chemosensing in the GI tract. The identification of chemosensory molecule plasticity in response to fasting and nutrients in specialized GI cells could open novel therapeutic strategies in feeding behaviour or metabolic disorders.

Modifications to α-transducin and neuropeptide immunoreactivities evoked by feeding in the GI tract

CLAVENZANI, PAOLO;MAZZONI, MAURIZIO;BOSI, PAOLO;TREVISI, PAOLO;LATORRE, ROCCO;LALATTA COSTERBOSA, GIOVANNA;CHIOCCHETTI, ROBERTO;BARBARA, GIOVANNI;STANGHELLINI, VINCENZO;CORINALDESI, ROBERTO;BORTOLAMI, RUGGERO;GORI, ALESSANDRA;DE GIORGIO, ROBERTO
2009

Abstract

Taste receptors (TR1s, TR2s) for sweet and bitter along with related G-proteins (α-transducin and α-gustducin) have been localized in the GI tract mucosa of several mammals. Taste signalling molecules are now conceived to be part of a wide chemosensing system contributing to sense luminal contents. In the pig model (resembling the human gut) we established whether feeding changes, i.e. fasting and re-feeding, wereable to affect: 1) the expression of α-transducin throughout the GI tract; 2) neuropeptide coding of the cells expressing α-transducin; and 3) the spatial relationship between α-transducin cells and nerves supplying the gut. Pig stomach-to-rectum specimens (n= 12; 45 days of age), subdivided in 3 groups, i.e. control (C), fasted for 24h (F) and re-fed (R), were fixed in 4%-paraformaldehyde, embedded either in paraffin and processed for single and double labelling immunofluorescence with antibodies to: α-transducin, chromogranin-A (CgA), gastrin/cholecystokinin (Gas/CCK), somatostatin (SOM) and PGP9.5. The highest density of α-transducin-immunoreactive (IR) cells has been shown in the pylorus (C: 191±22, F: 99±28 and R: 112±51) and in the cardial mucosa (C: 79±46, F: 29±13 and R: 57±10), whereas in the intestine the highest α-transducin cell density was observed in the duodenum of C (54±22) vs. F and R (41±20,14±6, respectively). The density of α-transducin-IR cells decreased along the large intestine. The percentage of α-transducin/CgA-IR cells was reduced in the GI tract of F and R vs. C. In the jejunum,α -transducin/CCK cells decreased in F and R vs. C. Gas/α-transducin and SOM/α -transducin colocalizations have never been detected. PGP9.5 varicose nerve fibers, running either singly or in small fascicles, throughout the lamina propria of the small bowe l mucosa were seen in close spatial relationship with α-transducin cells. In conclusion, changes to α-transducin expression in neuropeptide-containing cells following F and R provide a basis to the concept that these cells participate to luminal chemosensing in the GI tract. The identification of chemosensory molecule plasticity in response to fasting and nutrients in specialized GI cells could open novel therapeutic strategies in feeding behaviour or metabolic disorders.
Atti XIX Convegno Nazionale GISN
46
46
CLAVENZANI P.; MAZZONI M.; BOSI P.; TREVISI P.; LATORRE R.; LALATTA COSTERBOSA G.; CHIOCCHETTI R.; BARBARA G.; STANGHELLINI V.; CORINALDESI R.; BORTOLAMI R.; TONINI M.; GORI A.; STERNINI C.; DE GIORGIO R.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11585/99111
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