Many gut peptides have been shown to influence energy intake. Most of them act to increase satiety and decrease food intake (anorexigenic peptides, i.e glucagon-like peptides), others stimulate the appetite (orexigenic peptides i.e orexins). Circulating gut hormones have been shown to act either directly on neurons in hypothalamic and brainstem centres of appetite control and/or indirectly via neural reflex arcs. However, local effects on gastrointestinal (GI) motility might contribute to modifications in energy intake altering the rate at which nutrients are processed and delivered in the blood. Interestingly, most of the gut peptides influences also the cardiovascular system or through central autonomic neurons or through a direct impact on the heart. In consideration that gut peptides may represent an attractive therapeutic target in the treatment of human disease related to alterations of the food intake, we plan to define if and how peptides with orexigenic [orexin A (OXA) and orexin B (OXB)] and anorexigenic [glucagons-like peptides (GLP-1 and GLP-2)] property exert a peripheral modulation of GI motility and cardiac activity. In this view, studies will performed in vitro to analyze, in rodents, the effects induced by OXA, OXB, GLP-1 and GLP-2 on GI motility and cardiac activity, and to examine their mechanism of action, the location of the receptors, the signal transduction mechanism and the interactions with other chemical mediators. In addition, the impact of feeding on the responses caused by the peptides and on the expression of the receptors will be evaluated performing the study on fed ad libitum and 12/24h fasted animals. Peptide effects will be studied on the spontaneous mechanical and electrical activity of stomach, small and large intestinal segments using organ bath technique and microelectrode intracellular recording. Priority will be given to stomach because the slowing of the gastric emptying is considered an important mechanism for the satiating effect of gut peptide signalling. To analyze whether OXA, OXB, GLP-1 and GLP-2 directly affect cardiac performance the isolated and spontaneously beating Langendorff perfused rat heart will be utilized. The effects of peptides will be examined after treatment with specific receptor antagonists to establish which receptor type is involved in the observed action. To obtain qualitative and quantitative indication about the putative interactions between orexigenic and anorexigenic peptides, the effects of each peptide will be compared with those obtained by the simultaneous administration of the others. Possible indirect effects of the peptides, due to neurotransmitter and/or chemical mediator release, on the contractility of the gastrointestinal segments will be taken into account, using well known pharmacological antagonists for endogenous mediators. In addition, the excitatory and/or inhibitory responses induced by neural activation in GI preparations will be analysed before and after treatment with OXA, OXB, GLP-1 and GLP-2 to verify a possible modulator effect of orexigenic and anorexigenic peptides on the neurotransmission. At cardiac level in the light of the importance of cholinergic system and of nitric oxide (NO) in the cardiac regulation, the interactions between orexigenic and anorexigenic peptides and acetylcholine or NO will be examined using selective muscarinic receptor antagonists or inhibitor of NO pathway. In order to examine, in both system, the signal transduction coupled to the receptors, the responses induced by the peptides will be tested in the presence of drugs able to inhibit the different steps of the signal transduction pathways. Parallel experiments by immunohistochemistry/immunofluorescence will be performed in order to evaluate, in the GI tract of the two groups of animals, presence, distribution and cellular location (enteric neurons, muscle and/or enteroendocrine cells) of the molecules presently investigated. Attention will be focus
|Data di inizio/fine effettiva||9/22/08 → 10/21/10|
Esplora i temi di ricerca toccati da questo progetto. Queste etichette sono generate sulla base dei riconoscimenti/sovvenzioni sottostanti. Insieme formano una fingerprint unica.