RESUMO
PURPOSE: Peptide YY (PYY) is a gastrointestinal hormone with physiological actions regulating appetite and energy homoeostasis. The cellular mechanisms by which nutrients stimulate PYY secretion from intestinal enteroendocrine cells are still being elucidated. METHODS: This study comprehensively evaluated the suitability of intestinal STC-1 cells as an in vitro model of PYY secretion. PYY concentrations (both intracellular and in culture media) with other intestinal peptides (CCK, GLP-1 and GIP) demonstrated that PYY is a prominent product of STC-1 cells. Furthermore, acute and chronic PYY responses to 15 short (SCFAs)- and long-chain (LCFAs) dietary fatty acids were measured alongside parameters for DNA synthesis, cell viability and cytotoxicity. RESULTS: We found STC-1 cells to be reliable secretors of PYY constitutively releasing PYY into cell culture media (but not into non-stimulatory buffer). We demonstrate for the first time that STC-1 cells produce PYY mRNA transcripts; that STC-1 cells produce specific time- and concentration-dependent PYY secretory responses to valeric acid; that linoleic acid and conjugated linoleic acid 9,11 (CLA 9,11) are potent PYY secretagogues; and that chronic exposure of SCFAs and LCFAs can be detrimental to STC-1 cells. CONCLUSIONS: Our studies demonstrate the potential usefulness of STC-1 cells as an in vitro model for investigating nutrient-stimulated PYY secretion in an acute setting. Furthermore, our discovery that CLA directly stimulates L-cells to secrete PYY indicates another possible mechanism contributing to the observed effects of dietary CLA on weight loss.
Assuntos
Enterócitos/metabolismo , Ácido Linoleico/metabolismo , Ácidos Linoleicos Conjugados/metabolismo , Ácidos Pentanoicos/metabolismo , Peptídeo YY/metabolismo , Via Secretória , Regulação para Cima , Animais , Linhagem Celular , Sobrevivência Celular , Colecistocinina/metabolismo , Replicação do DNA , Ácidos Graxos não Esterificados/efeitos adversos , Ácidos Graxos não Esterificados/metabolismo , Ácidos Graxos Voláteis/efeitos adversos , Ácidos Graxos Voláteis/metabolismo , Polipeptídeo Inibidor Gástrico/metabolismo , Peptídeo 1 Semelhante ao Glucagon/metabolismo , Cinética , Camundongos , Peptídeo YY/genética , RNA Mensageiro/metabolismoRESUMO
OBJECTIVE: GIP is a peptide hormone of therapeutic interest in type 2 diabetes and obesity. This study evaluated pGIP/neo STC-1 as a potential K-cell model for studying GIP secretion. METHODS: We evaluated cellular storage and medium accumulation of GIP along with other gastrointestinal peptides cholecystokinin (CCK), peptide YY (PYY), obestatin and ghrelin over 72 h and probed possible intracellular signals (PKA, PKC, Ca(2+) and GPCR) involved in peptide hormone synthesis/secretion. RESULTS: Results demonstrate for the first time that pGIP/Neo STC-1 cells produce and secrete 3 to 6 times more GIP than STC-1. The cells clearly retain the ability to synthesize and secrete CCK and PYY but reduced levels indicate a shift towards a predominantly K-cell phenotype. Furthermore, gastric peptides such as obestatin and ghrelin are not produced in either STC-1 or pGIP/Neo STC-1 cells. DISCUSSION: This study demonstrates the potential usefulness of pGIP/Neo cells for studying GIP secretion and further investigations will establish its suitability for investigating hormone release in vitro.
Assuntos
Colecistocinina/metabolismo , Células Enteroendócrinas/metabolismo , Polipeptídeo Inibidor Gástrico/metabolismo , Grelina/metabolismo , Peptídeo YY/metabolismo , Linhagem Celular , Hormônios Gastrointestinais/metabolismo , HumanosRESUMO
Cholecystokinin (CCK) is a peptide hormone secreted from the I-cells of the intestine and it has important physiological actions related to appetite regulation and satiety. In this study we used STC-1 cells to investigate the effects of common dietary-derived fatty acids (FAs) on I-cell secretory function and metabolism. We extend earlier studies by measuring the acute and chronic effects of 11 FAs on CCK secretion, cellular CCK content, CCK mRNA levels, cellular DNA synthesis, cellular viability and cytotoxicity. FAs were selected in order to assess the importance of chain length, degree of saturation, and double bond position and conformation. The results demonstrate that secretory responses elicited by dietary FAs are highly selective. For example, altering the conformation of a double bond from cis to trans (i.e. oleic acid versus elaidic acid) completely abolishes CCK secretion. Lauric acid appears to adversely affect I-cell metabolism and arachidonic acid suppresses DNA synthesis. Our studies reveal for the first time that conjugated linoleic acid isoforms are particularly potent CCK secretagogues, which also boost intracellular stores of CCK. These actions of conjugated linoleic acid may explain satiating actions observed in dietary intervention studies.
Assuntos
Colecistocinina/genética , Gorduras na Dieta/farmacologia , Animais , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Colecistocinina/efeitos dos fármacos , Colecistocinina/metabolismo , Primers do DNA , Replicação do DNA/efeitos dos fármacos , Ácidos Graxos/farmacologia , Regulação Neoplásica da Expressão Gênica , Camundongos , Camundongos Transgênicos , RNA Mensageiro/genética , RNA Neoplásico/genéticaRESUMO
Increasing evidence from both clinical and experimental studies indicates that the insulin-releasing hormone, glucagon-like peptide-1 (GLP-1) may exert additional protective/reparative effects on the cardiovascular system. The aim of this study was to examine vasorelaxant effects of GLP-1(7-36)amide, three structurally-related peptides and a non-peptide GLP-1 agonist in rat aorta. Interestingly, all GLP-1 compounds, including the established GLP-1 receptor antagonist, exendin (9-39) caused concentration-dependent relaxation. Mechanistic studies employing hyperpolarising concentrations of potassium or glybenclamide revealed that these relaxant effects are mediated via specific activation of ATP-sensitive potassium channels. Further experiments using a specific membrane-permeable cyclic AMP (cAMP) antagonist, and demonstration of increased cAMP production in response to GLP-1 illustrated the critical importance of this pathway. These data significantly extend previous observations suggesting that GLP-1 may modulate vascular function, and indicate that this effect may be mediated by the GLP-1 receptor. However, further studies are required in order to establish whether GLP-1 related agents may confer additional cardiovascular benefits to diabetic patients.