101
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Spreckley E, Murphy KG. The L-Cell in Nutritional Sensing and the Regulation of Appetite. Front Nutr 2015; 2:23. [PMID: 26258126 PMCID: PMC4507148 DOI: 10.3389/fnut.2015.00023] [Citation(s) in RCA: 115] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Accepted: 07/06/2015] [Indexed: 12/25/2022] Open
Abstract
The gastrointestinal (GI) tract senses the ingestion of food and responds by signaling to the brain to promote satiation and satiety. Representing an important part of the gut-brain axis, enteroendocrine L-cells secrete the anorectic peptide hormones glucagon-like peptide-1 (GLP-1) and peptide YY (PYY) in response to the ingestion of food. The release of GLP-1 has multiple effects, including the secretion of insulin from pancreatic β-cells, decreased gastric emptying, and increased satiation. PYY also slows GI motility and reduces food intake. At least part of the gut-brain response seems to be due to direct sensing of macronutrients by L-cells, by mechanisms including specific nutrient-sensing receptors. Such receptors may represent possible pathways to target to decrease appetite and increase energy expenditure. Designing drugs or functional foods to exploit the machinery of these nutrient-sensing mechanisms may offer a potential approach for agents to treat obesity and metabolic disease.
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Affiliation(s)
- Eleanor Spreckley
- Section of Investigative Medicine, Department of Medicine, Imperial College London, Hammersmith Hospital , London , UK
| | - Kevin Graeme Murphy
- Section of Investigative Medicine, Department of Medicine, Imperial College London, Hammersmith Hospital , London , UK
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102
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Ishikawa Y, Hira T, Inoue D, Harada Y, Hashimoto H, Fujii M, Kadowaki M, Hara H. Rice protein hydrolysates stimulate GLP-1 secretion, reduce GLP-1 degradation, and lower the glycemic response in rats. Food Funct 2015; 6:2525-34. [PMID: 26107658 DOI: 10.1039/c4fo01054j] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Rice has historically been consumed in Asia as a major source of carbohydrates, however, little is known regarding the functional roles of rice proteins as dietary factors. In the present study, we investigated whether peptides derived from rice proteins could stimulate GLP-1 secretion, which results in reducing glycemia via the incretin effect in normal rats. Hydrolysates were prepared from the protein fraction of rice endosperm or rice bran, and the effects of these hydrolysates on GLP-1 secretion were examined in a murine enteroendocrine cell line GLUTag. Plasma was collected after oral administration of the rice protein hydrolysates, under anesthesia, or during glucose tolerance tests in rats. In anesthetized rats, plasma dipeptidyl peptidase-IV (DPP-IV) activity was measured after ileal administration of the rice protein hydrolysates. GLP-1 secretion from GLUTag cells was potently stimulated by the rice protein hydrolysates, especially by the peptic digest of rice endosperm protein (REPH) and that of rice bran protein (RBPH). Oral administration of REPH or RBPH elevated plasma GLP-1 concentrations, which resulted in the reduction of glycemia under the intraperitoneal glucose tolerance test. In addition, the plasma DPP-IV activity was attenuated after ileal administration of REPH or RBPH, which resulted in a higher ratio of intact (active) GLP-1 to total GLP-1 in the plasma. These results demonstrate that rice proteins exert potent stimulatory effects on GLP-1 secretion, which could contribute to the reduction of postprandial glycemia. The inhibitory effect of these peptides on the plasma DPP-IV activity may potentiate the incretin effect of GLP-1.
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Affiliation(s)
- Yuki Ishikawa
- Graduate School of Agriculture, Hokkaido University, Sapporo, Japan
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103
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Tarasov AI, Rutter GA. Use of genetically encoded sensors to monitor cytosolic ATP/ADP ratio in living cells. Methods Enzymol 2015; 542:289-311. [PMID: 24862272 DOI: 10.1016/b978-0-12-416618-9.00015-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
ATP is not only recognized as the universal energy "currency" in most cells but also plays a less well-known role as an intracellular and extracellular messenger. Here, we review novel approaches for measuring free ATP (or ATP/ADP ratios) in living mammalian cells by using genetically encoded sensors. We also discuss the key technical aspects of routine real-time ATP/ADP monitoring using as a model one of the last-generation fluorescent probes, a fusion protein commonly known as "Perceval." Finally, we present detailed guidelines for the simultaneous measurement of cytosolic ATP/ADP ratios and Ca(2+) concentrations alongside electrical parameters in individual pancreatic β cells, in which energy metabolism is tightly linked to plasma membrane excitability to control the secretion of insulin. With appropriate variations, this approach can be adapted to the study of cytosolic ATP/ADP ratios and Ca(2+) concentrations in malignant cells, two important aspects of oncometabolism.
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Affiliation(s)
- Andrei I Tarasov
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Oxford, United Kingdom
| | - Guy A Rutter
- Section of Cell Biology, Department of Medicine, Imperial College London, London, United Kingdom.
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104
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Kato M, Tani T, Terahara N, Tsuda T. The Anthocyanin Delphinidin 3-Rutinoside Stimulates Glucagon-Like Peptide-1 Secretion in Murine GLUTag Cell Line via the Ca2+/Calmodulin-Dependent Kinase II Pathway. PLoS One 2015; 10:e0126157. [PMID: 25962102 PMCID: PMC4427495 DOI: 10.1371/journal.pone.0126157] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Accepted: 03/30/2015] [Indexed: 01/10/2023] Open
Abstract
Glucagon-like peptide-1 (GLP-1) is an incretin hormone secreted from enteroendocrine L-cells. Although several nutrients induce GLP-1 secretion, there is little evidence to suggest that non-nutritive compounds directly increase GLP-1 secretion. Here, we hypothesized that anthocyanins induce GLP-1 secretion and thereby significantly contribute to the prevention and treatment of diabetes. Delphinidin 3-rutinoside (D3R) was shown to increase GLP-1 secretion in GLUTag L cells. The results suggested that three hydroxyl or two methoxyl moieties on the aromatic ring are essential for the stimulation of GLP-1 secretion. Notably, the rutinose moiety was shown to be a potent enhancer of GLP-1 secretion, but only in conjunction with three hydroxyl moieties on the aromatic ring (D3R). Receptor antagonist studies revealed that D3R-stimulates GLP-1 secretion involving inositol 1,4,5-trisphosphate receptor-mediated intracellular Ca2+ mobilization. Treatment of GLUTag cells with a Ca2+/calmodulin-dependent kinaseII (CaMKII) inhibitor (KN-93) abolished D3R-stimulated GLP-1 secretion. In addition, treatment of GLUTag cells with D3R resulted in activation of CaMKII. Pre-treatment of cells with a G protein-coupled receptor (GPR) 40/120 antagonist (GW1100) also significantly decreased D3R-stimulated GLP-1 secretion. These observations suggest that D3R stimulates GLP-1 secretion in GLUTag cells, and that stimulation of GLP-1 secretion by D3R is mediated via Ca2+-CaMKII pathway, which may possibly be mediated by GPR40/120. These findings provide a possible molecular mechanism of GLP-1 secretion in intestinal L-cells mediated by foods or drugs and demonstrate a novel biological function of anthocyanins in regards to GLP-1 secretion.
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Affiliation(s)
- Masaki Kato
- College of Bioscience and Biotechnology, Chubu University, Kasugai, Aichi, Japan
| | - Tsubasa Tani
- College of Bioscience and Biotechnology, Chubu University, Kasugai, Aichi, Japan
| | - Norihiko Terahara
- Department of Food Science and Technology, Minami-Kyushu University, Miyazaki, Japan
| | - Takanori Tsuda
- College of Bioscience and Biotechnology, Chubu University, Kasugai, Aichi, Japan
- * E-mail:
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105
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Jiang Y, Rose AJ, Sijmonsma TP, Bröer A, Pfenninger A, Herzig S, Schmoll D, Bröer S. Mice lacking neutral amino acid transporter B(0)AT1 (Slc6a19) have elevated levels of FGF21 and GLP-1 and improved glycaemic control. Mol Metab 2015; 4:406-17. [PMID: 25973388 PMCID: PMC4421019 DOI: 10.1016/j.molmet.2015.02.003] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Revised: 02/05/2015] [Accepted: 02/09/2015] [Indexed: 02/07/2023] Open
Abstract
OBJECTIVE Type 2 diabetes arises from insulin resistance of peripheral tissues followed by dysfunction of β-cells in the pancreas due to metabolic stress. Both depletion and supplementation of neutral amino acids have been discussed as strategies to improve insulin sensitivity. Here we characterise mice lacking the intestinal and renal neutral amino acid transporter B(0)AT1 (Slc6a19) as a model to study the consequences of selective depletion of neutral amino acids. METHODS Metabolic tests, analysis of metabolite levels and signalling pathways were used to characterise mice lacking the intestinal and renal neutral amino acid transporter B(0)AT1 (Slc6a19). RESULTS Reduced uptake of neutral amino acids in the intestine and loss of neutral amino acids in the urine causes an overload of amino acids in the lumen of the intestine and reduced systemic amino acid availability. As a result, higher levels of glucagon-like peptide 1 (GLP-1) are produced by the intestine after a meal, while the liver releases the starvation hormone fibroblast growth factor 21 (FGF21). The combination of these hormones generates a metabolic phenotype that is characterised by efficient removal of glucose, particularly by the heart, reduced adipose tissue mass, browning of subcutaneous white adipose tissue, enhanced production of ketone bodies and reduced hepatic glucose output. CONCLUSIONS Reduced neutral amino acid availability improves glycaemic control. The epithelial neutral amino acid transporter B(0)AT1 could be a suitable target to treat type 2 diabetes.
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Affiliation(s)
- Yang Jiang
- Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia
| | - Adam J. Rose
- Joint Research Division Molecular Metabolic Control, German Cancer Research Center, Center for Molecular Biology, Heidelberg University and Heidelberg University Hospital, 69120 Heidelberg, Germany
| | - Tjeerd P. Sijmonsma
- Joint Research Division Molecular Metabolic Control, German Cancer Research Center, Center for Molecular Biology, Heidelberg University and Heidelberg University Hospital, 69120 Heidelberg, Germany
| | - Angelika Bröer
- Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia
| | - Anja Pfenninger
- Sanofi-Aventis Deutschland GmbH, Industriepark Hoechst, Frankfurt am Main 65926, Germany
| | - Stephan Herzig
- Joint Research Division Molecular Metabolic Control, German Cancer Research Center, Center for Molecular Biology, Heidelberg University and Heidelberg University Hospital, 69120 Heidelberg, Germany
| | - Dieter Schmoll
- Sanofi-Aventis Deutschland GmbH, Industriepark Hoechst, Frankfurt am Main 65926, Germany
| | - Stefan Bröer
- Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia
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106
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Nagamine R, Ueno S, Tsubata M, Yamaguchi K, Takagaki K, Hira T, Hara H, Tsuda T. Dietary sweet potato (Ipomoea batatas L.) leaf extract attenuates hyperglycaemia by enhancing the secretion of glucagon-like peptide-1 (GLP-1). Food Funct 2015; 5:2309-16. [PMID: 25066255 DOI: 10.1039/c4fo00032c] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
'Suioh', a sweet potato (Ipomoea batatas L.) cultivar developed in Japan, has edible leaves and stems. The sweet potato leaves contain polyphenols such as caffeoylquinic acid (CQA) derivatives. It has multiple biological functions and may help to regulate the blood glucose concentration. In this study, we first examined whether sweet potato leaf extract powder (SP) attenuated hyperglycaemia in type 2 diabetic mice. Administration of dietary SP for 5 weeks significantly lowered glycaemia in type 2 diabetic mice. Second, we conducted in vitro experiments, and found that SP and CQA derivatives significantly enhanced glucagon-like peptide-1 (GLP-1) secretion. Third, pre-administration of SP significantly stimulated GLP-1 secretion and was accompanied by enhanced insulin secretion in rats, which resulted in a reduced glycaemic response after glucose injection. These results indicate that oral SP attenuates postprandial hyperglycaemia, possibly through enhancement of GLP-1 secretion.
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Affiliation(s)
- Rika Nagamine
- Research and Development Division, Toyo Shinyaku Co., Ltd., 7-28 Yayoigaoka, Tosu-shi, Saga 841-0005, Japan.
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107
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Tsuda T. Possible abilities of dietary factors to prevent and treat diabetes via the stimulation of glucagon-like peptide-1 secretion. Mol Nutr Food Res 2015; 59:1264-73. [PMID: 25707985 DOI: 10.1002/mnfr.201400871] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Revised: 02/01/2015] [Accepted: 02/09/2015] [Indexed: 12/22/2022]
Abstract
There is a pressing need for countermeasures against diabetes, which has increased in incidence, becoming a global issue. Glucagon-like peptide-1 (GLP-1), a molecule secreted in enteroendocrine L cells in the lower small and large intestines, is thought to be one of the most important molecular targets for the prevention and treatment of diabetes. There has been increasing interest in the possible ability of dietary factors to treat diabetes via modulating GLP-1 secretion. There is thought to be a close relationship between incretin and diet, and the purported best approach for using dietary factors to increase GLP-1 activity is promotion of secretion of endogenous GLP-1. It have been reported that nutrients as well as various non-nutrient dietary factors can function as GLP-1 secretogogues. Here, we present our findings on the GLP-1 secretion-stimulating functions of two dietary factors, curcumin and extract of edible sweet potato leaves, which contain caffeoylquinic acid derivatives. However, it is necessary to reveal in greater detail the stimulation of GLP-1 secretion by dietary factors for preventing and treating diabetes. It is desirable to clarify the exact GLP-1 secretory pathway, the effect of metabolites derived from dietary factors in gut lumen, and the relationship between incretin and meal.
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Affiliation(s)
- Takanori Tsuda
- College of Bioscience and Biotechnology, Chubu University, Kasugai, Aichi, Japan
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108
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Harada K, Kitaguchi T, Tsuboi T. Integrative function of adrenaline receptors for glucagon-like peptide-1 exocytosis in enteroendocrine L cell line GLUTag. Biochem Biophys Res Commun 2015; 460:1053-8. [PMID: 25843795 DOI: 10.1016/j.bbrc.2015.03.151] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2015] [Accepted: 03/26/2015] [Indexed: 01/05/2023]
Abstract
Adrenaline reacts with three types of adrenergic receptors, α1, α2 and β-adrenergic receptors (ARs), inducing many physiological events including exocytosis. Although adrenaline has been shown to induce glucagon-like peptide-1 (GLP-1) secretion from intestinal L cells, the precise molecular mechanism by which adrenaline regulates GLP-1 secretion remains unknown. Here we show by live cell imaging that all types of adrenergic receptors are stimulated by adrenaline in enteroendocrine L cell line GLUTag cells and are involved in GLP-1 exocytosis. We performed RT-PCR analysis and found that α1B-, α2A-, α2B-, and β1-ARs were expressed in GLUTag cells. Application of adrenaline induced a significant increase of intracellular Ca(2+) and cAMP concentration ([Ca(2+)]i and [cAMP]i, respectively), and GLP-1 exocytosis in GLUTag cells. Blockade of α1-AR inhibited adrenaline-induced [Ca(2+)]i increase and exocytosis but not [cAMP]i increase, while blockade of β1-AR inhibited adrenaline-induced [cAMP]i increase and exocytosis but not [Ca(2+)]i increase. Furthermore, overexpression of α2A-AR suppressed the adrenaline-induced [cAMP]i increase and exocytosis. These results suggest that the fine-turning of GLP-1 secretion from enteroendocrine L cells is established by the balance between α1-, α2-, and β-ARs activation.
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Affiliation(s)
- Kazuki Harada
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, Japan
| | - Tetsuya Kitaguchi
- Cell Signaling Group, Waseda Bioscience Research Institute in Singapore (WABIOS), 11 Biopolis Way #05-02 Helios, Singapore 138667, Singapore; Organization for University Research Initiatives, Waseda University, #304, Block 120-4, 513 Wasedatsurumaki-cho, Shinjuku-ku, Tokyo 162-0041, Japan
| | - Takashi Tsuboi
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, Japan.
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109
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L-glutamine and whole protein restore first-phase insulin response and increase glucagon-like peptide-1 in type 2 diabetes patients. Nutrients 2015; 7:2101-8. [PMID: 25811109 PMCID: PMC4425133 DOI: 10.3390/nu7042101] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Revised: 03/10/2015] [Accepted: 03/12/2015] [Indexed: 11/16/2022] Open
Abstract
L-glutamine triggers glucagon-like peptide-1 (GLP-1) release from L cells in vitro and when ingested pre-meal, decreases postprandial glycaemia and increases circulating insulin and GLP-1 in type 2 diabetes (T2D) patients. We aimed to evaluate the effect of oral L-glutamine, compared with whole protein low in glutamine, on insulin response in well-controlled T2D patients. In a randomized study with a crossover design, T2D patients (n = 10, 6 men) aged 65.1 ± 5.8, with glycosylated hemoglobin (HbA1c) 6.6% ± 0.7% (48 ± 8 mmol/mol), received oral L-glutamine (25 g), protein (25 g) or water, followed by an intravenous glucose bolus (0.3 g/kg) and hyperglycemic glucose clamp for 2 h. Blood was frequently collected for analyses of glucose, serum insulin and plasma total and active GLP-1 and area under the curve of glucose, insulin, total and active GLP-1 excursions calculated. Treatments were tested 1-2 weeks apart. Both L-glutamine and protein increased first-phase insulin response (p ≤ 0.02). Protein (p = 0.05), but not L-glutamine (p = 0.2), increased second-phase insulin response. Total GLP-1 was increased by both L-glutamine and protein (p ≤ 0.02). We conclude that oral L-glutamine and whole protein are similarly effective in restoring first-phase insulin response in T2D patients. Larger studies are required to further investigate the utility of similar approaches in improving insulin response in diabetes.
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110
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Resistant maltodextrin promotes fasting glucagon-like peptide-1 secretion and production together with glucose tolerance in rats. Br J Nutr 2015; 114:34-42. [PMID: 25671387 DOI: 10.1017/s0007114514004322] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Glucagon-like peptide-1 (GLP-1), which is produced and released from enteroendocrine L cells, plays pivotal roles in postprandial glycaemia. The ingestion of resistant maltodextrin (RMD), a water-soluble non-digestible saccharide, improves the glycaemic response. In the present study, we examined whether the continuous feeding of RMD to rats affected GLP-1 levels and glycaemic control. Male Sprague-Dawley rats (6 weeks of age) were fed an American Institute of Nutrition (AIN)-93G-based diet containing either cellulose (5 %) as a control, RMD (2.5 or 5 %), or fructo-oligosaccharides (FOS, 2.5 or 5 %) for 7 weeks. During the test period, an intraperitoneal glucose tolerance test (IPGTT) was performed after 6 weeks. Fasting GLP-1 levels were significantly higher in the 5 % RMD group than in the control group after 6 weeks. The IPGTT results showed that the glycaemic response was lower in the 5 % RMD group than in the control group. Lower caecal pH, higher caecal tissue and content weights were observed in the RMD and FOS groups. Proglucagon mRNA levels were increased in the caecum and colon of both RMD and FOS groups, whereas caecal GLP-1 content was increased in the 5 % RMD group. In addition, a 1 h RMD exposure induced GLP-1 secretion in an enteroendocrine L-cell model, and single oral administration of RMD increased plasma GLP-1 levels in conscious rats. The present study demonstrates that continuous ingestion of RMD increased GLP-1 secretion and production in normal rats, which could be stimulated by its direct and indirect (enhanced gut fermentation) effects on GLP-1-producing cells, and contribute to improving glucose tolerance.
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111
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Abstract
The enteroendocrine system is the primary sensor of ingested nutrients and is responsible for secreting an array of gut hormones, which modulate multiple physiological responses including gastrointestinal motility and secretion, glucose homeostasis, and appetite. This Review provides an up-to-date synopsis of the molecular mechanisms underlying enteroendocrine nutrient sensing and highlights our current understanding of the neuro-hormonal regulation of gut hormone secretion, including the interaction between the enteroendocrine system and the enteric nervous system. It is hoped that a deeper understanding of how these systems collectively regulate postprandial physiology will further facilitate the development of novel therapeutic strategies.
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112
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Wang X, Liu H, Chen J, Li Y, Qu S. Multiple Factors Related to the Secretion of Glucagon-Like Peptide-1. Int J Endocrinol 2015; 2015:651757. [PMID: 26366173 PMCID: PMC4558455 DOI: 10.1155/2015/651757] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Revised: 08/02/2015] [Accepted: 08/03/2015] [Indexed: 12/15/2022] Open
Abstract
The glucagon-like peptide-1 is secreted by intestinal L cells in response to nutrient ingestion. It regulates the secretion and sensitivity of insulin while suppressing glucagon secretion and decreasing postprandial glucose levels. It also improves beta-cell proliferation and prevents beta-cell apoptosis induced by cytotoxic agents. Additionally, glucagon-like peptide-1 delays gastric emptying and suppresses appetite. The impaired secretion of glucagon-like peptide-1 has negative influence on diabetes, hyperlipidemia, and insulin resistance related diseases. Thus, glucagon-like peptide-1-based therapies (glucagon-like peptide-1 receptor agonists and dipeptidyl peptidase-4 inhibitors) are now well accepted in the management of type 2 diabetes. The levels of glucagon-like peptide-1 are influenced by multiple factors including a variety of nutrients. The component of a meal acts as potent stimulants of glucagon-like peptide-1 secretion. The levels of its secretion change with the intake of different nutrients. Some drugs also have influence on GLP-1 secretion. Bariatric surgery may improve metabolism through the action on GLP-1 levels. In recent years, there has been a great interest in developing effective methods to regulate glucagon-like peptide-1 secretion. This review summarizes the literature on glucagon-like peptide-1 and related factors affecting its levels.
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Affiliation(s)
- XingChun Wang
- Department of Endocrinology and Metabolism, Shanghai 10th People's Hospital, Tongji University, Shanghai 200072, China
| | - Huan Liu
- Department of Urology, Zhenjiang First People's Hospital, Zhenjiang, Jiangsu 212002, China
| | - Jiaqi Chen
- Department of Endocrinology and Metabolism, Shanghai 10th People's Hospital, Tongji University, Shanghai 200072, China
- Nanjing Medical University, Nanjing, Jiangsu 210029, China
| | - Yan Li
- Department of Endocrinology and Metabolism, Shanghai 10th People's Hospital, Tongji University, Shanghai 200072, China
- Nanjing Medical University, Nanjing, Jiangsu 210029, China
| | - Shen Qu
- Department of Endocrinology and Metabolism, Shanghai 10th People's Hospital, Tongji University, Shanghai 200072, China
- Nanjing Medical University, Nanjing, Jiangsu 210029, China
- *Shen Qu:
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113
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Amino Acid Supplementation to Diet Influences the Activity of the L Cells in Chicken Small Intestine. J Poult Sci 2015. [DOI: 10.2141/jpsa.0150031] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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114
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Takeuti TD, Terra GA, da Silva AA, Terra JA, da Silva LM, Crema E. Effect of the ingestion of the palm oil and glutamine in serum levels of GLP-1, PYY and glycemia in diabetes mellitus type 2 patients submitted to metabolic surgery. ABCD-ARQUIVOS BRASILEIROS DE CIRURGIA DIGESTIVA 2014; 27 Suppl 1:51-5. [PMID: 25409967 PMCID: PMC4743520 DOI: 10.1590/s0102-6720201400s100013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/11/2014] [Accepted: 06/26/2014] [Indexed: 11/22/2022]
Abstract
Background Incretins are hormones produced by the intestine and can stimulate the secretion
of insulin, helping to diminish the post-prandial glycemia. The administration of
an emulsion of palm oil can help in the maintenance of the weight, and can
increase circulating incretins levels. Glutamine increases the concentration of
incretins in diabetic people. Both can help in metabolic syndrome. Aim To analyze the effects of ingestion of palm oil and glutamine in glycemia and in
incretins in patients with diabetes submitted to surgical duodenojejunal exclusion
with ileal interposition without gastrectomy. Methods Eleven diabetic type 2 patients were included and were operated. They were called
to laboratory follow-up without eating anything between eight and 12 hours. They
had there blood collected after the stimulus of the palm oil and glutamine taken
in different days. For the hormonal doses were used ELISA kits. Results The glycemia showed a meaningful fall between the fast and two hours after the
stimulus of the palm oil (p=0,018). With the glutamine the GLP-1 showed an
increase between the fast and one hour (p=0,32), the PYY showed an important
increase between the fast and one hour after the stimulus (p=0,06), the glycemia
showed a meaningful fall after two hours of the administration of the stimulus
(p=0,03). Conclusion Palm oil and glutamine can influence intestinal peptides and glucose
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Affiliation(s)
| | | | | | | | | | - Eduardo Crema
- Universidade Federal do Triângulo Mineiro, Uberaba, MG, Brazil
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115
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Glycemic effects and safety of L-Glutamine supplementation with or without sitagliptin in type 2 diabetes patients-a randomized study. PLoS One 2014; 9:e113366. [PMID: 25412338 PMCID: PMC4239068 DOI: 10.1371/journal.pone.0113366] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Accepted: 10/16/2014] [Indexed: 11/21/2022] Open
Abstract
Background and Aims L-glutamine is an efficacious glucagon-like peptide (GLP)-1 secretagogue in vitro. When administered with a meal, glutamine increases GLP-1 and insulin excursions and reduces postprandial glycaemia in type 2 diabetes patients. The aim of the study was to assess the efficacy and safety of daily glutamine supplementation with or without the dipeptidyl peptidase (DPP)-4 inhibitor sitagliptin in well-controlled type 2 diabetes patients. Methods Type 2 diabetes patients treated with metformin (n = 13, 9 men) with baseline glycated hemoglobin (HbA1c) 7.1±0.3% (54±4 mmol/mol) received glutamine (15 g bd)+ sitagliptin (100 mg/d) or glutamine (15 g bd) + placebo for 4 weeks in a randomized crossover study. Results HbA1c (P = 0.007) and fructosamine (P = 0.02) decreased modestly, without significant time-treatment interactions (both P = 0.4). Blood urea increased (P<0.001) without a significant time-treatment interaction (P = 0.8), but creatinine and estimated glomerular filtration rate (eGFR) were unchanged (P≥0.5). Red blood cells, hemoglobin, hematocrit, and albumin modestly decreased (P≤0.02), without significant time-treatment interactions (P≥0.4). Body weight and plasma electrolytes remained unchanged (P≥0.2). Conclusions Daily oral supplementation of glutamine with or without sitagliptin for 4 weeks decreased glycaemia in well-controlled type 2 diabetes patients, but was also associated with mild plasma volume expansion. Trial Registration ClincalTrials.gov NCT00673894
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Bala V, Rajagopal S, Kumar DP, Nalli AD, Mahavadi S, Sanyal AJ, Grider JR, Murthy KS. Release of GLP-1 and PYY in response to the activation of G protein-coupled bile acid receptor TGR5 is mediated by Epac/PLC-ε pathway and modulated by endogenous H2S. Front Physiol 2014; 5:420. [PMID: 25404917 PMCID: PMC4217307 DOI: 10.3389/fphys.2014.00420] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Accepted: 10/11/2014] [Indexed: 12/19/2022] Open
Abstract
Activation of plasma membrane TGR5 receptors in enteroendocrine cells by bile acids is known to regulate gastrointestinal secretion and motility and glucose homeostasis. The endocrine functions of the gut are modulated by microenvironment of the distal gut predominantly by sulfur-reducing bacteria of the microbiota that produce H2S. However, the mechanisms involved in the release of peptide hormones, GLP-1 and PYY in response to TGR5 activation by bile acids and the effect of H2S on bile acid-induced release of GLP-1 and PYY are unclear. In the present study, we have identified the signaling pathways activated by the bile acid receptor TGR5 to mediate GLP-1 and PYY release and the mechanism of inhibition of their release by H2S in enteroendocrine cells. The TGR5 ligand oleanolic acid (OA) stimulated Gαs and cAMP formation, and caused GLP-1 and PYY release. OA-induced cAMP formation and peptide release were blocked by TGR5 siRNA. OA also caused an increase in PI hydrolysis and intracellular Ca2+. Increase in PI hydrolysis was abolished in cells transfected with PLC-ε siRNA. 8-pCPT-2′-O-Me-cAMP, a selective activator of Epac, stimulated PI hydrolysis, and GLP-1 and PYY release. L-Cysteine, which activates endogenous H2S producing enzymes cystathionine-γ-lyase and cystathionine-β-synthase, and NaHS and GYY4137, which generate H2S, inhibited PI hydrolysis and GLP-1 and PYY release in response to OA or 8-pCPT-2′-O-Me-cAMP. Propargylglycine, an inhibitor of CSE, reversed the effect of L-cysteine on PI hydrolysis and GLP-1 and PYY release. We conclude: (i) activation of Gαs-coupled TGR5 receptors causes stimulation of PI hydrolysis, and release of GLP-1 and PYY via a PKA-independent, cAMP-dependent mechanism involving Epac/PLC-ε/Ca2+ pathway, and (ii) H2S has potent inhibitory effects on GLP-1 and PYY release in response to TGR5 activation, and the mechanism involves inhibition of PLC-ε/Ca2+ pathway.
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Affiliation(s)
- Vanitha Bala
- Gastroenterology Division, Department of Internal Medicine, Virginia Commonwealth University Richmond, VA, USA
| | - Senthilkumar Rajagopal
- Department of Physiology, VCU Program in Enteric Neuromuscular Sciences, Virginia Commonwealth University Richmond, VA, USA
| | - Divya P Kumar
- Department of Physiology, VCU Program in Enteric Neuromuscular Sciences, Virginia Commonwealth University Richmond, VA, USA
| | - Ancy D Nalli
- Department of Physiology, VCU Program in Enteric Neuromuscular Sciences, Virginia Commonwealth University Richmond, VA, USA
| | - Sunila Mahavadi
- Department of Physiology, VCU Program in Enteric Neuromuscular Sciences, Virginia Commonwealth University Richmond, VA, USA
| | - Arun J Sanyal
- Gastroenterology Division, Department of Internal Medicine, Virginia Commonwealth University Richmond, VA, USA
| | - John R Grider
- Department of Physiology, VCU Program in Enteric Neuromuscular Sciences, Virginia Commonwealth University Richmond, VA, USA
| | - Karnam S Murthy
- Department of Physiology, VCU Program in Enteric Neuromuscular Sciences, Virginia Commonwealth University Richmond, VA, USA
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Joo E, Muraoka A, Hamasaki A, Harada N, Yamane S, Kondo Y, Suzuki K, Nasteska D, Shibue K, Harada T, Iwasaki K, Tsuji H, Shide K, Inagaki N. Enteral supplementation with glutamine, fiber, and oligosaccharide modulates incretin and glucagon-like peptide-2 secretion. J Diabetes Investig 2014; 6:302-8. [PMID: 25969715 PMCID: PMC4420562 DOI: 10.1111/jdi.12289] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/16/2014] [Revised: 08/29/2014] [Accepted: 09/15/2014] [Indexed: 12/24/2022] Open
Abstract
Aims/Introduction A dietary supplementation product enriched with glutamine, dietary fiber and oligosaccharide (GFO) is widely applied for enteral nutrition support in Japan. The aim of the present study was to evaluate the effects of GFO ingestion on secretion of incretins, gastric inhibitory polypeptide (GIP) and glucagon-like peptide-1 (GLP-1), and glucagon-like peptide-2 (GLP-2). Materials and Methods We carried out a cross-over study involving 20 healthy Japanese volunteers. The participants received GFO or 17 g of glucose, the equivalent carbohydrate in GFO as the control. Plasma glucose, serum insulin, and plasma total GIP, total GLP-1 and total GLP-2 levels during GFO or glucose loading were determined. Results GFO loading produced significantly higher plasma GLP-1 levels at 30 min and 60 min, area under the curve-GLP-1 value, and area under the curve-GLP-2 value after administration compared with those by glucose loading. In contrast, plasma GIP levels at both 30 and 60 min, and area under the curve-GIP value after glucose loading were significantly higher than those after GFO loading. Conclusions These results show that GFO ingestion stimulates GLP-1 and GLP-2 secretion, and reduces GIP secretion compared with glucose ingestion. Therefore, GFO could have an intestinotrophic effect as well as an ameliorating effect on metabolic disorders through modification of release of gut hormones.
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Affiliation(s)
- Erina Joo
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University Kyoto, Japan
| | - Atsushi Muraoka
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University Kyoto, Japan
| | - Akihiro Hamasaki
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University Kyoto, Japan
| | - Norio Harada
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University Kyoto, Japan
| | - Shunsuke Yamane
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University Kyoto, Japan
| | - Yaeko Kondo
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University Kyoto, Japan
| | - Kazuyo Suzuki
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University Kyoto, Japan
| | - Daniela Nasteska
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University Kyoto, Japan
| | - Kimitaka Shibue
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University Kyoto, Japan
| | - Takanari Harada
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University Kyoto, Japan
| | - Kanako Iwasaki
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University Kyoto, Japan
| | - Hidemi Tsuji
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University Kyoto, Japan
| | - Kenichiro Shide
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University Kyoto, Japan
| | - Nobuya Inagaki
- Department of Diabetes, Endocrinology and Nutrition, Graduate School of Medicine, Kyoto University Kyoto, Japan
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Kim KS, Egan JM, Jang HJ. Denatonium induces secretion of glucagon-like peptide-1 through activation of bitter taste receptor pathways. Diabetologia 2014; 57:2117-25. [PMID: 25016595 PMCID: PMC5160131 DOI: 10.1007/s00125-014-3326-5] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Accepted: 06/16/2014] [Indexed: 10/25/2022]
Abstract
AIMS/HYPOTHESIS This study was designed to ascertain whether human enteroendocrine cells express bitter taste receptors, and whether activation of these receptors with bitter-tasting ligands induces secretion of glucagon-like peptide-1 (GLP-1) and peptide YY (PYY). METHODS We used human enteroendocrine NCI-H716 cells, isolated duodenal segments from mice, and whole mice as our experimental systems for investigating stimuli and mechanisms underlying GLP-1- and PYY-stimulated release. We measured hormone levels by ELISA and determined bitter taste receptor expression by real-time quantitative PCR. We adopted a pharmacological approach using inhibitors and enhancers of downstream signalling pathways known to be involved in bitter taste transduction in taste bud cells to investigate these pathways in NCI-H716 cells. RESULTS Using a pharmacological approach, we identified signalling pathways triggered by the denatonium benzoate (DB)-activated bitter receptors. This involved activation of α-gustducin (Gαgust)-the specific G-protein subunit that is also present in taste bud cells-reduction of intracellular cAMP levels and enhancement of phospholipase C (PLC) activity, which ultimately led to increased intracellular calcium concentrations and hormone release. Gavage of DB, followed by gavage of glucose, to db/db mice stimulated GLP-1 and subsequent insulin secretion, leading to lower blood glucose levels. CONCLUSIONS/INTERPRETATION Our study demonstrates that activation of gut-expressed bitter taste receptors stimulates GLP-1 secretion in a PLC-dependent manner. In diabetic mice, DB (a ligand of bitter taste receptor cells), when given via gavage, lowers blood glucose levels in diabetic mice after oral glucose administration, through increased secretion of GLP-1.
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Affiliation(s)
- Ki-Suk Kim
- Department of Biochemistry, College of Korean Medicine, Kyung Hee University, Hoegi-Dong, Dongdaemun-Gu, Seoul, 130-701, Republic of Korea
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Joshi S, Tough IR, Cox HM. Endogenous PYY and GLP-1 mediate l-glutamine responses in intestinal mucosa. Br J Pharmacol 2014; 170:1092-101. [PMID: 23992397 DOI: 10.1111/bph.12352] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Revised: 08/01/2013] [Accepted: 08/12/2013] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND AND PURPOSE l-glutamine (Gln) is an energy source for gastrointestinal (GI) epithelia and can stimulate glucagon-like peptide 1 (GLP-1) release from isolated enteroendocrine L-cells. GLP-1 and peptide YY (PYY) are co-secreted postprandially and both peptides have functional roles in glucose homeostasis and energy balance. The primary aim of this project was to establish the endogenous mechanisms underpinning Gln responses within intact GI mucosae using selective receptor antagonists. EXPERIMENTAL APPROACH Mouse mucosae from different GI regions were voltage-clamped and short-circuit current (Isc) was recorded to Gln added to either surface in the absence or presence of antagonists, using wild-type (WT) or PYY-/- tissues. The glucose sensitivity of Gln responses was also investigated by replacement with mannitol. KEY RESULTS Colonic apical and basolateral Gln responses (at 0.1 and 1 mM) were biphasic; initial increases in Isc were predominantly GLP-1 mediated. GLP-1 receptor antagonism significantly reduced the initial Gln response in the PYY-/- colon. The slower reductions in Isc to Gln were PYY-Y1 mediated as they were absent from the PYY-/- colon and were blocked selectively in WT tissue by a Y1 receptor antagonist. In jejunum mucosa, Gln stimulated monophasic Isc reductions that were PYY-Y1 receptor mediated. Gln effects were partially glucose sensitive, and Calhex 231 inhibition indicated that the calcium-sensing receptor (CaSR) was involved. CONCLUSION AND IMPLICATIONS Gln stimulates the co-release of endogenous GLP-1 and PYY from mucosal L-cells resulting in paracrine GLP-1 and Y1 receptor-mediated electrogenic epithelial responses. This glucose-sensitive mechanism appears to be CaSR mediated and could provide a significant therapeutic strategy releasing two endogenous peptides better known for their glucose-lowering and satiating effects.
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Affiliation(s)
- S Joshi
- King's College London, Wolfson Centre for Age-Related Diseases, London, UK
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Mansour A, Mohajeri-Tehrani MR, Qorbani M, Heshmat R, Larijani B, Hosseini S. Effect of glutamine supplementation on cardiovascular risk factors in patients with type 2 diabetes. Nutrition 2014; 31:119-26. [PMID: 25466655 DOI: 10.1016/j.nut.2014.05.014] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2014] [Revised: 05/22/2014] [Accepted: 05/24/2014] [Indexed: 12/25/2022]
Abstract
OBJECTIVE The aim of this study was to assess clinical relevance of long-term oral glutamine supplementation on lipid profile and inflammatory and metabolic factors in patients with diabetes. METHOD Sixty-six patients with type 2 diabetes between the ages of 18 and 65 y were randomized to receive glutamine 30 g/d (10 g powder, three times a day) or placebo, in a double-blind, placebo-controlled trial during a 6-wk treatment period. Fifty-three patients completed the trial. Independent samples t test and analysis of covariance were used. RESULTS After a 6-wk treatment period, a significant difference was observed between the two groups in body fat mass (P = 0.01) and percentage of body fat (P = 0.008). Moreover, a significant reduction in waist circumference (P < 0.001) and a tendency for an increase in fat-free mass (P = 0.03), with no change in body weight and body mass index (BMI) was found. Enhancement in body fat-free mass was mainly attributed to trunk (P = 0.03). There was a downward trend in systolic blood pressure (P = 0.005) but not diastolic. Fasting blood glucose (mmol/L) concentration significantly decreased after the 6-wk intervention (P = 0.04). Mean hemoglobin A1c was significantly different between the groups at week 6 (P = 0.04). No significant difference was detected for fasting insulin, homeostasis model assessment for insulin resistance and quantitative insulin sensitivity index between groups (P > 0.05). No significant difference was observed between groups in total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol and triglyceride. No treatment effect on C-reactive protein was found (P = 0.44). CONCLUSION We demonstrated that the 6-wk supplementation with 30 g/d glutamine markedly improved some cardiovascular risk factors, as well as body composition, in patients with type 2 diabetes. Future glutamine dose-response studies are warranted in these areas.
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Affiliation(s)
- Asieh Mansour
- School of Nutritional Sciences and Dietetics, Tehran University of Medical Sciences, Tehran, Iran; Endocrinology and Metabolism Research Center, Endocrinology and Metabolism Research Institute, Tehran University of Medical Sciences, Tehran, Iran
| | - Mohammad Reza Mohajeri-Tehrani
- Endocrinology and Metabolism Research Center, Endocrinology and Metabolism Research Institute, Tehran University of Medical Sciences, Tehran, Iran
| | - Mostafa Qorbani
- Department of Public Health, Alborz University of Medical Sciences, Karaj, Iran; Non-Communicable Diseases Research Center, Endocrinology and Metabolism Research Institute, Tehran University of Medical Sciences, Tehran, Iran
| | - Ramin Heshmat
- Chronic Diseases Research Center, Endocrinology and Metabolism Research Institute, Tehran University of Medical Sciences, Tehran, Iran
| | - Bagher Larijani
- Endocrinology and Metabolism Research Center, Endocrinology and Metabolism Research Institute, Tehran University of Medical Sciences, Tehran, Iran; Diabetes Research Center, Endocrinology and Metabolism Research Institute, Tehran University of Medical Sciences, Tehran, Iran
| | - Saeed Hosseini
- Endocrinology and Metabolism Research Center, Endocrinology and Metabolism Research Institute, Tehran University of Medical Sciences, Tehran, Iran.
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Albrechtsen NJW, Kuhre RE, Deacon CF, Holst JJ. Targeting the intestinal L-cell for obesity and type 2 diabetes treatment. Expert Rev Endocrinol Metab 2014; 9:61-72. [PMID: 30743739 DOI: 10.1586/17446651.2014.862152] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Degradation-resistant glucagon-like peptide-1 (GLP-1) mimetics and GLP-1 enhancers (inhibitors of dipeptidyl peptidase-4, the enzyme which degrades and inactivates GLP-1) have been used for treatment of type 2 diabetes mellitus since 2005-2006. Cutting-edge research is now focusing on uncovering the secretory mechanisms of the GLP-1-producing cells (L-cells) with the purpose of developing agonists that enhance endogenous hormone secretion. Since GLP-1 co-localizes with other anorectic peptides, cholecystokinin, oxyntomodulin/glicentin and peptide YY, L-cell targeting might cause release of several hormones at the same time, providing additive effects on appetite and glucose regulation. In this review, we explore the role of proglucagon-derived peptides and other L-cell co-localizing hormones, in appetite regulation and the mechanism regulating their secretion.
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Affiliation(s)
- Nicolai Jacob Wewer Albrechtsen
- a Faculty of Health and Medical Sciences, NNF Center for Basic Metabolic Research, Section for Translational Metabolism, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark
| | - Rune Ehrenreich Kuhre
- a Faculty of Health and Medical Sciences, NNF Center for Basic Metabolic Research, Section for Translational Metabolism, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark
| | - Carolyn F Deacon
- a Faculty of Health and Medical Sciences, NNF Center for Basic Metabolic Research, Section for Translational Metabolism, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark
| | - Jens Juul Holst
- a Faculty of Health and Medical Sciences, NNF Center for Basic Metabolic Research, Section for Translational Metabolism, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark
- b Department of Biomedical Sciences, Panum Institute, Blegdamsvej 3B, DK-2200 Copenhagen N, Denmark
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González-Abuín N, Martínez-Micaelo N, Blay M, Green BD, Pinent M, Ardévol A. Grape-seed procyanidins modulate cellular membrane potential and nutrient-induced GLP-1 secretion in STC-1 cells. Am J Physiol Cell Physiol 2013; 306:C485-92. [PMID: 24371039 DOI: 10.1152/ajpcell.00355.2013] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Grape-seed procyanidin extracts (GSPE) modulate glucose homeostasis, and it was suggested that GSPE may achieve this by enhancing the secretion of incretin hormones such as glucagon-like peptide-1 (GLP-1). Therefore, the aim of the present study is to examine in detail the effects of GSPE on intestinal endocrine cells (STC-1). GSPE was found to modulate plasma membrane potential in enteroendocrine cells, inducing depolarization at low concentrations (0.05 mg/l) and hyperpolarization at high concentrations (50 mg/l), and surprisingly this was also accompanied by suppressed GLP-1 secretion. Furthermore, how GSPE affects STC-1 cells under nutrient-stimulated conditions (i.e., glucose, linoleic acid, and l-proline) was also explored, and we found that the higher GSPE concentration was effective in limiting membrane depolarization and reducing GLP-1 secretion. Next, it was also examined whether GSPE affected mitochondrial membrane potential, and it was found that this too is altered by GSPE; however, this does not appear to explain the observed effects on plasma membrane potential and GLP-1 secretion. In conclusion, our results show that grape-seed procyanidins modulate cellular membrane potential and nutrient-induced enteroendocrine hormone secretion in STC-1 cells.
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Affiliation(s)
- Noemi González-Abuín
- Departament de Bioquímica i Biotecnologia, Universitat Rovira i Virgili, Tarragona, Spain; and
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Diakogiannaki E, Pais R, Tolhurst G, Parker HE, Horscroft J, Rauscher B, Zietek T, Daniel H, Gribble FM, Reimann F. Oligopeptides stimulate glucagon-like peptide-1 secretion in mice through proton-coupled uptake and the calcium-sensing receptor. Diabetologia 2013; 56:2688-96. [PMID: 24045836 PMCID: PMC3825574 DOI: 10.1007/s00125-013-3037-3] [Citation(s) in RCA: 143] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2013] [Accepted: 08/01/2013] [Indexed: 01/25/2023]
Abstract
AIMS/HYPOTHESIS Ingested protein is a well-recognised stimulus for glucagon-like peptide-1 (GLP-1) release from intestinal L cells. This study aimed to characterise the molecular mechanisms employed by L cells to detect oligopeptides. METHODS GLP-1 secretion from murine primary colonic cultures and Ca(2+) dynamics in L cells were monitored in response to peptones and dipeptides. L cells were identified and purified based on their cell-specific expression of the fluorescent protein Venus, using GLU-Venus transgenic mice. Pharmacological tools and knockout mice were used to characterise candidate sensory pathways identified by expression analysis. RESULTS GLP-1 secretion was triggered by peptones and di-/tripeptides, including the non-metabolisable glycine-sarcosine (Gly-Sar). Two sensory mechanisms involving peptide transporter-1 (PEPT1) and the calcium-sensing receptor (CaSR) were distinguishable. Responses to Gly-Sar (10 mmol/l) were abolished in the absence of extracellular Ca(2+) or by the L-type calcium-channel blocker nifedipine (10 μmol/l) and were PEPT1-dependent, as demonstrated by their sensitivity to pH and 4-aminomethylbenzoic acid and the finding of impaired responses in tissue from Pept1 (also known as Slc15a1) knockout mice. Peptone (5 mg/ml)-stimulated Ca(2+) responses were insensitive to nifedipine but were blocked by antagonists of CaSR. Peptone-stimulated GLP-1 secretion was not impaired in mice lacking the putative peptide-responsive receptor lysophosphatidic acid receptor 5 (LPAR5; also known as GPR92/93). CONCLUSIONS/INTERPRETATION Oligopeptides stimulate GLP-1 secretion through PEPT1-dependent electrogenic uptake and activation of CaSR. Both pathways are highly expressed in native L cells, and likely contribute to the ability of ingested protein to elevate plasma GLP-1 levels. Targeting nutrient-sensing pathways in L cells could be used to mobilise endogenous GLP-1 stores in humans, and could mimic some of the metabolic benefits of bariatric surgery.
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Affiliation(s)
- Eleftheria Diakogiannaki
- Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke’s Hospital, Box 139, Hills Road, Cambridge, CB2 0XY UK
| | - Ramona Pais
- Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke’s Hospital, Box 139, Hills Road, Cambridge, CB2 0XY UK
| | - Gwen Tolhurst
- Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke’s Hospital, Box 139, Hills Road, Cambridge, CB2 0XY UK
| | - Helen E. Parker
- Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke’s Hospital, Box 139, Hills Road, Cambridge, CB2 0XY UK
| | - James Horscroft
- Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke’s Hospital, Box 139, Hills Road, Cambridge, CB2 0XY UK
| | - Beate Rauscher
- Center of Life and Food Sciences Weihenstephan, Technische Universität München, München, Germany
| | - Tamara Zietek
- Center of Life and Food Sciences Weihenstephan, Technische Universität München, München, Germany
| | - Hannelore Daniel
- Center of Life and Food Sciences Weihenstephan, Technische Universität München, München, Germany
| | - Fiona M. Gribble
- Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke’s Hospital, Box 139, Hills Road, Cambridge, CB2 0XY UK
| | - Frank Reimann
- Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke’s Hospital, Box 139, Hills Road, Cambridge, CB2 0XY UK
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The SLC38 family of sodium-amino acid co-transporters. Pflugers Arch 2013; 466:155-72. [PMID: 24193407 DOI: 10.1007/s00424-013-1393-y] [Citation(s) in RCA: 158] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Revised: 10/16/2013] [Accepted: 10/20/2013] [Indexed: 12/13/2022]
Abstract
Transporters of the SLC38 family are found in all cell types of the body. They mediate Na(+)-dependent net uptake and efflux of small neutral amino acids. As a result they are particularly expressed in cells that grow actively, or in cells that carry out significant amino acid metabolism, such as liver, kidney and brain. SLC38 transporters occur in membranes that face intercellular space or blood vessels, but do not occur in the apical membrane of absorptive epithelia. In the placenta, they play a significant role in the transfer of amino acids to the foetus. Members of the SLC38 family are highly regulated in response to amino acid depletion, hypertonicity and hormonal stimuli. SLC38 transporters play an important role in amino acid signalling and have been proposed to act as transceptors independent of their transport function. The structure of SLC38 transporters is characterised by the 5 + 5 inverted repeat fold, which is observed in a wide variety of transport proteins.
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Clemmensen C, Smajilovic S, Smith EP, Woods SC, Bräuner-Osborne H, Seeley RJ, D'Alessio DA, Ryan KK. Oral L-arginine stimulates GLP-1 secretion to improve glucose tolerance in male mice. Endocrinology 2013; 154:3978-83. [PMID: 23959939 PMCID: PMC3800753 DOI: 10.1210/en.2013-1529] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Pharmacological and surgical interventions that increase glucagon-like peptide 1 (GLP-1) action are effective to improve glucose homeostasis in type 2 diabetes mellitus. In light of this, nutritional strategies to enhance postprandial GLP-1 secretion, particularly in the context of diet-induced obesity, may provide an alternative therapeutic approach. Importantly, recent evidence suggests the amino acid L-arginine, a well-known insulin secretagogue, can also stimulate release of GLP-1 from isolated rat intestine. Here we tested the hypothesis that oral L-arginine acts as a GLP-1 secretagogue in vivo, to augment postprandial insulin secretion and improve glucose tolerance. To test this, we administered L-arginine or vehicle by oral gavage, immediately prior to an oral glucose tolerance test in lean and diet-induced obese mice. In both lean and obese mice oral L-arginine increased plasma GLP-1 and insulin and substantially improved glucose clearance. To directly assess the contribution of GLP-1 receptor (GLP-1R)-signaling to these improvements, L-arginine was given to Glp1r knockout mice and their wild-type littermates. In this experiment oral l-arginine significantly augmented insulin secretion and improved glucose clearance in WT mice, but not in Glp1r knockout littermates. Taken together these findings identify L-arginine as a GLP-1 secretagogue in vivo and demonstrate that improvement of glucose tolerance by oral L-arginine depends on GLP-1R-signaling. These findings raise the intriguing possibility that L-arginine-based nutritional and/or pharmaceutical therapies may benefit glucose tolerance by improving the postprandial GLP-1 response in obese individuals.
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Food protein hydrolysates as a source of dipeptidyl peptidase IV inhibitory peptides for the management of type 2 diabetes. Proc Nutr Soc 2013; 73:34-46. [PMID: 24131508 DOI: 10.1017/s0029665113003601] [Citation(s) in RCA: 104] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The prevalence of type 2 diabetes mellitus (T2DM) is increasing and it is estimated that by 2030 approximately 366 million people will be diagnosed with this condition. The use of dipeptidyl peptidase IV (DPP-IV) inhibitors is an emerging strategy for the treatment of T2DM. DPP-IV is a ubiquitous aminodipeptidase that cleaves incretins such as glucagon like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), resulting in a loss in their insulinotropic activity. Synthetic DPP-IV drug inhibitors are being used to increase the half-life of the active GLP-1 and GIP. Dietary intervention is accepted as a key component in the prevention and management of T2DM. Therefore, identification of natural food protein-derived DPP-IV inhibitors is desirable. Peptides with DPP-IV inhibitory activity have been identified in a variety of food proteins. This review aims to provide an overview of food protein hydrolysates as a source of the DPP-IV inhibitory peptides with particular focus on milk proteins. In addition, the proposed modes of inhibition and structure-activity relationship of peptide inhibitors are discussed. Milk proteins and associated peptides also display insulinotropic activity and help regulate blood glucose in healthy and diabetic subjects. Therefore, milk protein derived peptide inhibitors may be a unique multifunctional peptide approach for the management of T2DM.
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Ezcurra M, Reimann F, Gribble FM, Emery E. Molecular mechanisms of incretin hormone secretion. Curr Opin Pharmacol 2013; 13:922-7. [PMID: 24035446 PMCID: PMC3838618 DOI: 10.1016/j.coph.2013.08.013] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2013] [Revised: 08/14/2013] [Accepted: 08/26/2013] [Indexed: 01/06/2023]
Abstract
Incretin peptides (glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP)) are secreted from enteroendocrine cells in the intestinal epithelium, and help to coordinate metabolic responses to food ingestion. A number of molecular mechanisms have recently been defined that underlie carbohydrate, lipid and protein sensing in gut endocrine cells. Knockout mice lacking sodium glucose tranporter-1 (SGLT-1) or the short chain fatty acid sensing receptor FFAR2 (GPR43), for example, have highlighted the importance of these molecules in incretin secretion. This review outlines our current understanding of sensory pathways in incretin secreting cells and highlights the therapeutic potential of targeting them for the development of novel therapies for obesity and diabetes.
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Affiliation(s)
- Marina Ezcurra
- Cambridge Institute for Medical Research, Wellcome Trust, MRC Building, Addenbrooke's Hospital, Box 139, Hills Road, Cambridge CB2 0XY, UK
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128
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Ingestion of leucine + phenylalanine with glucose produces an additive effect on serum insulin but less than additive effect on plasma glucose. JOURNAL OF AMINO ACIDS 2013; 2013:964637. [PMID: 23984046 PMCID: PMC3745835 DOI: 10.1155/2013/964637] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Revised: 03/26/2013] [Accepted: 04/10/2013] [Indexed: 12/02/2022]
Abstract
Most individual amino acids stimulate insulin secretion and attenuate the plasma glucose response when ingested with glucose. We determined whether ingestion of two amino acids simultaneously with glucose would result in an additive effect on the glucose area response compared with ingestion of amino acids individually. Leucine and phenylalanine were chosen because they were two of the most potent glucose-lowering amino acids when given individually. Eight healthy subjects were studied on four separate days. Test meals were given at 0800. The first meal was a water control. Subjects then received 25 g glucose or leucine + phenylalanine (1 mmol/kg fat free body mass each) ±25 g glucose in random order. Glucose, insulin and glucagon were measured frequently for 2.5 hours thereafter. Net areas under the curves were calculated using the mean fasting value as baseline. The insulin response to leucine + phenylalanine was additive. In contrast, the decrease in glucose response to leucine + phenylalanine + glucose was less than additive compared to the individual amino acids ingested with glucose. Interestingly, the insulin response to the combination was largely due to the leucine component, whereas the glucose response was largely due to the phenylalanine component. Glucose was unchanged when leucine or phenylalanine, alone or in combination, was ingested without glucose. This trial is registered with ClinicalTrials.gov NCT01471509.
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129
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Sailer M, Dahlhoff C, Giesbertz P, Eidens MK, de Wit N, Rubio-Aliaga I, Boekschoten MV, Müller M, Daniel H. Increased plasma citrulline in mice marks diet-induced obesity and may predict the development of the metabolic syndrome. PLoS One 2013; 8:e63950. [PMID: 23691124 PMCID: PMC3653803 DOI: 10.1371/journal.pone.0063950] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2012] [Accepted: 04/10/2013] [Indexed: 12/31/2022] Open
Abstract
In humans, plasma amino acid concentrations of branched-chain amino acids (BCAA) and aromatic amino acids (AAA) increase in states of obesity, insulin resistance and diabetes. We here assessed whether these putative biomarkers can also be identified in two different obesity and diabetic mouse models. C57BL/6 mice with diet-induced obesity (DIO) mimic the metabolic impairments of obesity in humans characterized by hyperglycemia, hyperinsulinemia and hepatic triglyceride accumulation. Mice treated with streptozotocin (STZ) to induce insulin deficiency were used as a type 1 diabetes model. Plasma amino acid profiling of two high fat (HF) feeding trials revealed that citrulline and ornithine concentrations are elevated in obese mice, while systemic arginine bioavailability (ratio of plasma arginine to ornithine + citrulline) is reduced. In skeletal muscle, HF feeding induced a reduction of arginine levels while citrulline levels were elevated. However, arginine or citrulline remained unchanged in their key metabolic organs, intestine and kidney. Moreover, the intestinal conversion of labeled arginine to ornithine and citrulline in vitro remained unaffected by HF feeding excluding the intestine as prime site of these alterations. In liver, citrulline is mainly derived from ornithine in the urea cycle and DIO mice displayed reduced hepatic ornithine levels. Since both amino acids share an antiport mechanism for mitochondrial import and export, elevated plasma citrulline may indicate impaired hepatic amino acid handling in DIO mice. In the insulin deficient mice, plasma citrulline and ornithine levels also increased and additionally these animals displayed elevated BCAA and AAA levels like insulin resistant and diabetic patients. Therefore, type 1 diabetic mice but not DIO mice show the “diabetic fingerprint” of plasma amino acid changes observed in humans. Additionally, citrulline may serve as an early indicator of the obesity-dependent metabolic impairments.
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Affiliation(s)
- Manuela Sailer
- Molecular Nutrition Unit, Research Center for Nutrition and Food Sciences, Technische Universität München, Freising-Weihenstephan, Germany
| | - Christoph Dahlhoff
- Molecular Nutrition Unit, Research Center for Nutrition and Food Sciences, Technische Universität München, Freising-Weihenstephan, Germany
- PhD Graduate School ‘Epigenetics, Imprinting and Nutrition’, Research Center for Nutrition and Food Sciences, Technische Universität München, Freising-Weihenstephan, Germany
| | - Pieter Giesbertz
- Molecular Nutrition Unit, Research Center for Nutrition and Food Sciences, Technische Universität München, Freising-Weihenstephan, Germany
| | - Mena K. Eidens
- Molecular Nutrition Unit, Research Center for Nutrition and Food Sciences, Technische Universität München, Freising-Weihenstephan, Germany
| | - Nicole de Wit
- Netherlands Nutrigenomics Centre, TI Food & Nutrition, Wageningen University, Wageningen, The Netherlands
- Division of Human Nutrition, Wageningen University, Wageningen, The Netherlands
| | - Isabel Rubio-Aliaga
- Molecular Nutrition Unit, Research Center for Nutrition and Food Sciences, Technische Universität München, Freising-Weihenstephan, Germany
| | - Mark V. Boekschoten
- Netherlands Nutrigenomics Centre, TI Food & Nutrition, Wageningen University, Wageningen, The Netherlands
- Division of Human Nutrition, Wageningen University, Wageningen, The Netherlands
| | - Michael Müller
- Netherlands Nutrigenomics Centre, TI Food & Nutrition, Wageningen University, Wageningen, The Netherlands
- Division of Human Nutrition, Wageningen University, Wageningen, The Netherlands
| | - Hannelore Daniel
- Molecular Nutrition Unit, Research Center for Nutrition and Food Sciences, Technische Universität München, Freising-Weihenstephan, Germany
- * E-mail:
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130
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Mace OJ, Marshall F. DIGESTIVE PHYSIOLOGY OF THE PIG SYMPOSIUM: Gut chemosensing and the regulation of nutrient absorption and energy supply1. J Anim Sci 2013; 91:1932-45. [DOI: 10.2527/jas.2012-5906] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Affiliation(s)
- O. J. Mace
- Heptares Therapeutics, BioPark, Broadwater Road, Welwyn Garden City, AL7 3AX, United Kingdom
| | - F. Marshall
- Heptares Therapeutics, BioPark, Broadwater Road, Welwyn Garden City, AL7 3AX, United Kingdom
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131
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Takikawa M, Kurimoto Y, Tsuda T. Curcumin stimulates glucagon-like peptide-1 secretion in GLUTag cells via Ca2+/calmodulin-dependent kinase II activation. Biochem Biophys Res Commun 2013; 435:165-70. [DOI: 10.1016/j.bbrc.2013.04.092] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2013] [Accepted: 04/22/2013] [Indexed: 01/05/2023]
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132
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Joo E, Yamane S, Hamasaki A, Harada N, Matsunaga T, Muraoka A, Suzuki K, Nasteska D, Fukushima T, Hayashi T, Tsuji H, Shide K, Tsuda K, Inagaki N. Enteral supplement enriched with glutamine, fiber, and oligosaccharide attenuates experimental colitis in mice. Nutrition 2013; 29:549-55. [DOI: 10.1016/j.nut.2012.09.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2012] [Revised: 08/30/2012] [Accepted: 09/24/2012] [Indexed: 12/12/2022]
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Mansour A, Hosseini S, Larijani B, Pajouhi M, Mohajeri-Tehrani MR. Nutrients related to GLP1 secretory responses. Nutrition 2013; 29:813-20. [PMID: 23415393 DOI: 10.1016/j.nut.2012.11.015] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2012] [Revised: 11/04/2012] [Accepted: 11/23/2012] [Indexed: 12/25/2022]
Abstract
The hormone glucagon-like peptide (GLP-1) is secreted from gut endocrine L cells in response to ingested nutrients. The activities of GLP-1 include stimulating insulin gene expression and biosynthesis, improving β-cell proliferation, exogenesis, and survival. Additionally, it prevents β-cell apoptosis induced by a variety of cytotoxic agents. In extrapancreatic tissues, GLP-1 suppresses hunger, delays gastric emptying, acts as an ileal brake, and increases glucose uptake. The pleiotropic actions of GLP-1, especially its glucose-lowering effect, gave rise to the suggestion that it is a novel approach to insulin resistance treatment. Hormones secreted from the gut including GLP-1, which are involved in the regulation of insulin sensitivity and secretions, have been found to be affected by nutrient intake. In recent years, there has been a growing interest in the effect nutrients may have on GLP-1 secretion; some frequently studied dietary constituents include monounsaturated fatty acids, fructooligosaccharides, and glutamine. This review focuses on the influence that the carbohydrate, fat, and protein components of a meal may have on the GLP-1 postprandial responses.
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Affiliation(s)
- Asieh Mansour
- Endocrinology and Metabolism Research Center, Tehran University of Medical Sciences, Tehran, Iran
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134
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Ojo OO, Conlon JM, Flatt PR, Abdel-Wahab YHA. Frog skin peptides (tigerinin-1R, magainin-AM1, -AM2, CPF-AM1, and PGla-AM1) stimulate secretion of glucagon-like peptide 1 (GLP-1) by GLUTag cells. Biochem Biophys Res Commun 2013; 431:14-8. [PMID: 23291176 DOI: 10.1016/j.bbrc.2012.12.116] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2012] [Accepted: 12/17/2012] [Indexed: 12/25/2022]
Abstract
Skin secretions of several frog species contain host-defense peptides with multiple biological activities including in vitro and in vivo insulin-releasing actions. This study investigates the effects of tigerinin-1R from Hoplobatrachus rugulosus (Dicroglossidae) and magainin-AM1, magainin-AM2, caerulein precursor fragment (CPF-AM1) and peptide glycine leucine amide (PGLa-AM1) from Xenopus amieti (Pipidae) on GLP-1 secretion from GLUTag cells. Tigerinin-1R showed the highest potency producing a significant (P<0.05) increase in GLP-1 release at a concentration of 0.1nM for the cyclic peptide and 0.3nM for the reduced form. All peptides from X. amieti significantly (P<0.05) stimulated GLP-1 release at concentrations ⩾300nM with magainin-AM2 exhibiting the greatest potency (minimum concentration producing a significant stimulation=1nM). The maximum stimulatory response (3.2-fold of basal rate, P<0.001) was produced by CPF-AM1 at a concentration of 3μM. No peptide stimulated release of the cytosolic enzyme, lactate dehydrogenase from GLUTag cells at concentrations up to 3μM indicating that the integrity of the plasma membrane had been preserved. The data indicate that frog skin peptides, by stimulating GLP-1 release as well as direct effects on insulin secretion, show therapeutic potential as agents for the treatment of type 2 diabetes.
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Affiliation(s)
- O O Ojo
- School of Biomedical Sciences, University of Ulster, Coleraine BT52 1SA, UK
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135
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Oya M, Kitaguchi T, Pais R, Reimann F, Gribble F, Tsuboi T. The G protein-coupled receptor family C group 6 subtype A (GPRC6A) receptor is involved in amino acid-induced glucagon-like peptide-1 secretion from GLUTag cells. J Biol Chem 2012; 288:4513-21. [PMID: 23269670 DOI: 10.1074/jbc.m112.402677] [Citation(s) in RCA: 114] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Although amino acids are dietary nutrients that evoke the secretion of glucagon-like peptide 1 (GLP-1) from intestinal L cells, the precise molecular mechanism(s) by which amino acids regulate GLP-1 secretion from intestinal L cells remains unknown. Here, we show that the G protein-coupled receptor (GPCR), family C group 6 subtype A (GPRC6A), is involved in amino acid-induced GLP-1 secretion from the intestinal L cell line GLUTag. Application of l-ornithine caused an increase in intracellular Ca(2+) concentration ([Ca(2+)](i)) in GLUTag cells. Application of a GPRC6A receptor antagonist, a phospholipase C inhibitor, or an IP(3) receptor antagonist significantly suppressed the l-ornithine-induced [Ca(2+)](i) increase. We found that the increase in [Ca(2+)](i) stimulated by l-ornithine correlated with GLP-1 secretion and that l-ornithine stimulation increased exocytosis in a dose-dependent manner. Furthermore, depletion of endogenous GPRC6A by a specific small interfering RNA (siRNA) inhibited the l-ornithine-induced [Ca(2+)](i) increase and GLP-1 secretion. Taken together, these findings suggest that the GPRC6A receptor functions as an amino acid sensor in GLUTag cells that promotes GLP-1 secretion.
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Affiliation(s)
- Manami Oya
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, Japan
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136
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Hosaka H, Kusano M, Zai H, Kawada A, Kuribayashi S, Shimoyama Y, Nagoshi A, Maeda M, Kawamura O, Mori M. Monosodium glutamate stimulates secretion of glucagon-like peptide-1 and reduces postprandial glucose after a lipid-containing meal. Aliment Pharmacol Ther 2012; 36:895-903. [PMID: 22978669 DOI: 10.1111/apt.12050] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2012] [Revised: 06/29/2012] [Accepted: 08/28/2012] [Indexed: 12/25/2022]
Abstract
BACKGROUND Monosodium l-glutamate (MSG) is known to influence the endocrine system and gastrointestinal (GI) motility. The mechanism of postprandial glycemic control by food in the GI tract is mostly unknown and of great interest. AIM To investigate the effect of MSG on glucose homeostasis, incretin secretion and gastric emptying in humans after a lipid-containing meal. METHODS Thirteen healthy male volunteers (mean age, 25.5 years) and with no Helicobcter pylori infection were enrolled. A 400 mL (520 kcal) liquid meal with MSG (2 g, 0.5% wt:vol) or NaCl (control) was ingested in a single-blind placebo-controlled cross-over study. Blood glucose, serum insulin, plasma glucagon, plasma glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide were measured. Gastric emptying was monitored by a 13C acetate breath test. Postprandial symptoms were assessed on a visual analogue scale. RESULTS The 30-min postprandial glucose concentration was significantly reduced by adding MSG to the test meal. The area under the glucose concentration vs. time curve (0-60 min) was also significantly reduced by adding MSG (40.6 ± 3.51 mg·1 hr/dL with MSG vs. 49.2 ± 3.86 mg·1 hr/dL with NaCl, P = 0.047), whereas, the 30-min postprandial plasma GLP-1 level was significantly increased (58.1 ± 15.8 pmol/L with MSG vs. 13.4 ± 15.8 pmol/L with NaCl, P = 0.035). MSG did not affect the half gastric emptying time or postprandial symptoms. CONCLUSIONS Monosodium l-glutamate improved early postprandial glycaemia after a lipid-containing liquid meal. This effect was not associated with a change in gastric emptying, but was possibly related to stimulation of glucagon-like peptide-1 secretion.
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Affiliation(s)
- H Hosaka
- Department of Medicine and Molecular Science, Gunma University Graduate School of Medicine, Maebashi, Japan
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137
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Abstract
Hormones from the gastrointestinal (GI) tract are released following food ingestion and trigger a range of physiological responses including the coordination of appetite and glucose homoeostasis. The aim of this review is to discuss the pathways by which food ingestion triggers secretion of cholecystokinin (CCK), glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) and the altered patterns of gut hormone release observed following gastric bypass surgery. Our understanding of how ingested nutrients trigger secretion of these gut hormones has increased dramatically, as a result of physiological studies in human subjects and animal models and in vitro studies on cell lines and primary intestinal cultures. Specialised enteroendocrine cells located within the gut epithelium are capable of directly detecting a range of nutrient stimuli through a range of receptors and transporters. It is concluded that the arrival of nutrients at the apical surface of enteroendocrine cells is a major stimulus for gut hormone release, thereby coupling these endocrine signals to the arrival of absorbed nutrients in the bloodstream.
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Affiliation(s)
- Fiona M Gribble
- Cambridge Institute for Medical Research, WT/MRC Building, Hills Road, Cambridge CB2 0XY, UK.
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138
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Parker HE, Adriaenssens A, Rogers G, Richards P, Koepsell H, Reimann F, Gribble FM. Predominant role of active versus facilitative glucose transport for glucagon-like peptide-1 secretion. Diabetologia 2012; 55:2445-55. [PMID: 22638549 PMCID: PMC3411305 DOI: 10.1007/s00125-012-2585-2] [Citation(s) in RCA: 140] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Accepted: 04/20/2012] [Indexed: 12/13/2022]
Abstract
AIMS/HYPOTHESIS Several glucose-sensing pathways have been implicated in glucose-triggered secretion of glucagon-like peptide-1 (GLP-1) from intestinal L cells. One involves glucose metabolism and closure of ATP-sensitive K(+) channels, and another exploits the electrogenic nature of Na(+)-coupled glucose transporters (SGLTs). This study aimed to elucidate the role of these distinct mechanisms in glucose-stimulated GLP-1 secretion. METHODS Glucose uptake into L cells (either GLUTag cells or cells in primary cultures, using a new transgenic mouse model combining proglucagon promoter-driven Cre recombinase with a ROSA26tdRFP reporter) was monitored with the FLII(12)Pglu-700 μδ6 glucose sensor. Effects of pharmacological and genetic interference with SGLT1 or facilitative glucose transport (GLUT) on intracellular glucose accumulation and metabolism (measured by NAD(P)H autofluorescence), cytosolic Ca(2+) (monitored with Fura2) and GLP-1 secretion (assayed by ELISA) were assessed. RESULTS L cell glucose uptake was dominated by GLUT-mediated transport, being abolished by phloretin but not phloridzin. NAD(P)H autofluorescence was glucose dependent and enhanced by a glucokinase activator. In GLUTag cells, but not primary L cells, phloretin partially impaired glucose-dependent secretion, and suppressed an amplifying effect of glucose under depolarising high K(+) conditions. The key importance of SGLT1 in GLUTag and primary cells was evident from the impairment of secretion by phloridzin or Sglt1 knockdown and failure of glucose to trigger cytosolic Ca(2+) elevation in primary L cells from Sglt1 knockout mice. CONCLUSIONS/INTERPRETATION SGLT1 acts as the luminal glucose sensor in L cells, but intracellular glucose concentrations are largely determined by GLUT activity. Although L cell glucose metabolism depends partially on glucokinase activity, this plays only a minor role in glucose-stimulated GLP-1 secretion.
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Affiliation(s)
- H. E. Parker
- Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke’s Hospital, Box 139, Hills Road, Cambridge, CB2 0XY UK
| | - A. Adriaenssens
- Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke’s Hospital, Box 139, Hills Road, Cambridge, CB2 0XY UK
| | - G. Rogers
- Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke’s Hospital, Box 139, Hills Road, Cambridge, CB2 0XY UK
| | - P. Richards
- Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke’s Hospital, Box 139, Hills Road, Cambridge, CB2 0XY UK
| | - H. Koepsell
- Institute of Anatomy and Cell Biology, University of Würzburg, Würzburg, Germany
| | - F. Reimann
- Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke’s Hospital, Box 139, Hills Road, Cambridge, CB2 0XY UK
| | - F. M. Gribble
- Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke’s Hospital, Box 139, Hills Road, Cambridge, CB2 0XY UK
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139
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Ahlkvist L, Vikman J, Pacini G, Ahrén B. Synergism by individual macronutrients explains the marked early GLP-1 and islet hormone responses to mixed meal challenge in mice. ACTA ACUST UNITED AC 2012; 178:29-35. [PMID: 22750278 DOI: 10.1016/j.regpep.2012.06.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Revised: 06/01/2012] [Accepted: 06/20/2012] [Indexed: 01/22/2023]
Abstract
Apart from glucose, proteins and lipids also stimulate incretin and islet hormone secretion. However, the glucoregulatory effect of macronutrients in combination is poorly understood. We therefore developed an oral mixed meal model in mice to 1) explore the glucagon-like peptide-1 (GLP-1) and islet hormone responses to mixed meal versus isocaloric glucose, and 2) characterize the relative contribution of individual macronutrients to these responses. Anesthetized C57BL/6J female mice were orally gavaged with 1) a mixed meal (0.285 kcal; glucose, whey protein and peanut oil; 60/20/20% kcal) versus an isocaloric glucose load (0.285 kcal), and 2) a mixed meal (0.285 kcal) versus glucose, whey protein or peanut oil administered individually in their mixed meal caloric quantity, i.e., 0.171, 0.055 and 0.055 kcal, respectively. Plasma was analyzed for glucose, insulin and intact GLP-1 before and during oral challenges. Plasma glucose was lower after mixed meal versus after isocaloric glucose ingestion. In spite of this, the peak insulin response (P=0.02), the peak intact GLP-1 levels (P=0.006) and the estimated β-cell function (P=0.005) were higher. Furthermore, the peak insulin (P=0.004) and intact GLP-1 (P=0.006) levels were higher after mixed meal ingestion than the sum of responses to individual macronutrients. Compared to glucose alone, we conclude that there is a marked early insulin response to mixed meal ingestion, which emanates from a synergistic, rather than an additive, effect of the individual macronutrients in the mixed meal and is in part likely caused by increased levels of GLP-1.
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Affiliation(s)
- L Ahlkvist
- Department of Clinical Sciences, Lund University, Lund, Sweden.
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140
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Diakogiannaki E, Gribble FM, Reimann F. Nutrient detection by incretin hormone secreting cells. Physiol Behav 2012; 106:387-93. [PMID: 22182802 PMCID: PMC3361765 DOI: 10.1016/j.physbeh.2011.12.001] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2011] [Revised: 11/29/2011] [Accepted: 12/03/2011] [Indexed: 12/24/2022]
Abstract
The hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulintropic polypeptide (GIP) are secreted after a meal. Like other enteroendocrine hormones they help to orchestrate the bodies' response to the availability of newly absorbable nutrients and are noteworthy as they stimulate postprandial insulin secretion, underlying what is known as the incretin effect. GLP-1-mimetics are now widely used in the treatment of type 2 diabetes and advantages over older insulinotropic therapies include weight loss. An alternative treatment regime might be the recruitment of endogenous GLP-1, however, very little is known about the physiological control of enteroendocrine responses. This review focuses on the molecular mechanisms to detect nutrient arrival in the gut that have been implicated within the incretin secreting cells.
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Affiliation(s)
| | | | - Frank Reimann
- Cambridge Institute for Medical Research and Department of Clinical Biochemistry, Addenbrooke's Hospital, Hills Road, Cambridge, CB2 0XY, UK
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141
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Mace OJ, Schindler M, Patel S. The regulation of K- and L-cell activity by GLUT2 and the calcium-sensing receptor CasR in rat small intestine. J Physiol 2012; 590:2917-36. [PMID: 22495587 DOI: 10.1113/jphysiol.2011.223800] [Citation(s) in RCA: 188] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Intestinal enteroendocrine cells (IECs) secrete gut peptides in response to both nutrients and non-nutrients. Glucose and amino acids both stimulate gut peptide secretion. Our hypothesis was that the facilitative glucose transporter, GLUT2, could act as a glucose sensor and the calcium-sensing receptor, CasR, could detect amino acids in the intestine to modify gut peptide secretion. We used isolated loops of rat small intestine to study the secretion of gluco-insulinotropic peptide (GIP), glucagon-like peptide-1 (GLP-1) and peptide tyrosine tyrosine (PYY) secretion stimulated by luminal perfusion of nutrients or bile acid. Inhibition of the sodium-dependent glucose cotransporter 1 (SGLT1) with phloridzin partially inhibited GIP, GLP-1 and PYY secretion by 45%, suggesting another glucose sensor might be involved in modulating peptide secretion. The response was completely abolished in the presence of the GLUT2 inhibitors phloretin or cytochalasin B. Given that GLUT2 modified gut peptide secretion stimulated by glucose, we investigated whether it was involved in the secretion of gut peptide by other gut peptide secretagogues. Phloretin completely abolished gut peptide secretion stimulated by artificial sweetener (sucralose), dipeptide (glycylsarcosine), lipid (oleoylethanolamine), short chain fatty acid (propionate) and major rat bile acid (taurocholate) indicating a fundamental position for GLUT2 in the gut peptide secretory mechanism. We investigated how GLUT2 was able to influence gut peptide secretion mediated by a diverse range of stimulators and discovered that GLUT2 affected membrane depolarisation through the closure of K+(ATP)-sensitive channels. In the absence of SGLT1 activity (or presence of phloridzin), the secretion of GIP, GLP-1 and PYY was sensitive to K+(ATP)-sensitive channel modulators tolbutamide and diazoxide. L-amino acids phenylalanine (Phe), tryptophan (Trp), asparagine (Asn), arginine (Arg) and glutamine (Gln) also stimulated GIP, GLP-1 and PYY secretion, which was completely abolished when extracellular Ca2+ was absent. The gut peptide response stimulated by the amino acids was also blocked by the CasR inhibitor Calhex 231 and augmented by the CasR agonist NPS-R568. GLUT2 and CasR regulate K- and L-cell activity in response to nutrient and non-nutrient stimuli.
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142
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Rhee NA, Vilsbøll T, Knop FK. Current evidence for a role of GLP-1 in Roux-en-Y gastric bypass-induced remission of type 2 diabetes. Diabetes Obes Metab 2012; 14:291-8. [PMID: 21951387 DOI: 10.1111/j.1463-1326.2011.01505.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Weight-reducing surgical procedures such as Roux-en-Y gastric bypass (RYGB) have proven efficient as means of decreasing excess body weight. Furthermore, some studies report that up to 80% of patients with type 2 diabetes mellitus (T2DM) undergoing RYGB experience complete remission of their T2DM. Interestingly, the majority of remissions occur almost immediately following the operation and long before significant weight loss has taken place. Following RYGB, dramatic increases in postprandial plasma concentrations of the incretin hormone glucagon-like peptide-1 (GLP-1) have been recorded, and the known antidiabetic effects of GLP-1 are thought to be key mediators in RYGB-induced remission of T2DM. However, the published studies on the impact of RYGB on GLP-1 secretion are few, small and often not controlled properly. Furthermore, mechanistic studies delineating the role of endogenous GLP-1 secretion in RYGB-induced remission of T2DM are lacking. This article critically evaluates the current evidence for a role of GLP-1 in RYGB-induced remission of T2DM.
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Affiliation(s)
- N A Rhee
- Diabetes Research Division, Department of Internal Medicine F, Gentofte Hospital, University of Copenhagen, Niels Andersens Vej 65, Hellerup, Denmark
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143
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Amin A, Murphy KG. Nutritional sensing and its utility in treating obesity. Expert Rev Endocrinol Metab 2012; 7:209-221. [PMID: 30764012 DOI: 10.1586/eem.12.6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Obesity remains a major worldwide health problem, with current medical treatments being poorly effective. Nutrient sensing allows organs such as the GI tract and the brain to recognize and respond to fuel substrates such as carbohydrates, protein and fats. Specialized neural and hormonal pathways exist to facilitate and regulate these chemosensory mechanisms. Manipulation of factors involved in either central or peripheral chemosensory pathways may provide possible targets for the manipulation of appetite. However, further research is required to assess the utility of this approach to developing novel anti-obesity agents.
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Affiliation(s)
- Anjali Amin
- a Section of Investigative Medicine, Faculty of Medicine, Imperial College London, 6th Floor, Commonwealth Building, Hammersmith Hospital, Du Cane Road, London W12 0NN, UK
| | - Kevin G Murphy
- b Section of Investigative Medicine, Faculty of Medicine, Imperial College London, 6th Floor, Commonwealth Building, Hammersmith Hospital, Du Cane Road, London W12 0NN, UK.
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144
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Nerveless and gutsy: intestinal nutrient sensing from invertebrates to humans. Semin Cell Dev Biol 2012; 23:614-20. [PMID: 22248674 PMCID: PMC3712190 DOI: 10.1016/j.semcdb.2012.01.002] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2011] [Revised: 12/27/2011] [Accepted: 01/04/2012] [Indexed: 12/22/2022]
Abstract
The increasingly recognized role of gastrointestinal signals in the regulation of food intake, insulin production and peripheral nutrient storage has prompted a surge of interest in studying how the gastrointestinal tract senses and responds to nutritional information. Identification of metabolically important intestinal nutrient sensors could provide potential new drug targets for the treatment of diabetes, obesity and gastrointestinal disorders. From a more fundamental perspective, the study of intestinal chemosensation is revealing novel, non-neuronal modes of communication involving differentiated epithelial cells. It is also identifying signalling mechanisms downstream of not only canonical receptors but also nutrient transporters, thereby supporting a chemosensory role for “transceptors” in the intestine. This review describes known and proposed mechanisms of intestinal carbohydrate, protein and lipid sensing, best characterized in mammalian systems. It also highlights the potential of invertebrate model systems such as C. elegans and Drosophila melanogaster by summarizing known examples of molecular evolutionary conservation. Recently developed genetic tools in Drosophila, an emerging model system for the study of physiology and metabolism, allow the temporal, spatial and high-throughput manipulation of putative intestinal sensors. Hence, fruit flies may prove particularly suited to the study of the link between intestinal nutrient sensing and metabolic homeostasis.
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145
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Moran-Ramos S, Tovar AR, Torres N. Diet: friend or foe of enteroendocrine cells--how it interacts with enteroendocrine cells. Adv Nutr 2012; 3:8-20. [PMID: 22332097 PMCID: PMC3262619 DOI: 10.3945/an.111.000976] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Gut hormones play a key role in the regulation of food intake, energy expenditure, glucose homeostasis, lipid metabolism, and a wide range of metabolic functions in response to food ingestion. These hormones are altered in metabolic diseases, such as obesity and type 2 diabetes, and are thus proposed to be possible targets for the prevention or treatment of these diseases. It is clear that food composition, macronutrients, and other non-nutrient components as well as the physical properties of food not only modulate the secretion of gut peptides but also modulate transcription and enteroendocrine cell differentiation, which ultimately modifies gut hormone response. The specific mechanisms or sensing machinery that respond to the different components of the diet have been studied for many years; however, over the last few years, new molecular genetic techniques have led to important advances, thereby allowing a deeper understanding of these mechanisms. This review addresses the current knowledge regarding enteroendocrine cells and how diet interacts with this machinery to stimulate and regulate the secretion of gut peptides. The potential for diet interventions as a promising strategy for modulating gut hormone responses to food ingestion and, ultimately, preventing or treating metabolic diseases is being emphasized considering that these diseases are currently a public health burden.
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Affiliation(s)
- Sofia Moran-Ramos
- Departamento de Fisiología de la Nutrición Instituto Nacional de Ciencias Médicas y Nutrición “Salvador Zubirán,” México, México City, México; and,Facultad de Medicina, Universidad Nacional Autónoma de México, México City, México
| | - Armando R. Tovar
- Departamento de Fisiología de la Nutrición Instituto Nacional de Ciencias Médicas y Nutrición “Salvador Zubirán,” México, México City, México; and
| | - Nimbe Torres
- Departamento de Fisiología de la Nutrición Instituto Nacional de Ciencias Médicas y Nutrición “Salvador Zubirán,” México, México City, México; and,To whom correspondence should be addressed. E-mail:
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Abstract
Ingestion of a meal triggers a range of physiological responses both within and outside the gut, and results in the remote modulation of appetite and glucose homeostasis. Luminal contents are sensed by specialised chemosensitive cells scattered throughout the intestinal epithelium. These enteroendocrine and tuft cells make direct contact with the gut lumen and release a range of chemical mediators, which can either act in a paracrine fashion interacting with neighbouring cells and nerve endings or as classical circulating hormones. At the molecular level, the chemosensory machinery involves multiple and complex signalling pathways including activation of G-protein-coupled receptors and solute carrier transporters. This chapter will discuss our current knowledge of the molecular mechanisms underlying intestinal chemosensation with a particular focus on the relatively well-characterised nutrient-triggered secretion from the enteroendocrine system.
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Affiliation(s)
- Gwen Tolhurst
- Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Road, Cambridge, CB2 0XY, UK
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147
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Van Kleef E, Van Trijp JCM, Van Den Borne JJGC, Zondervan C. Successful development of satiety enhancing food products: towards a multidisciplinary agenda of research challenges. Crit Rev Food Sci Nutr 2012; 52:611-28. [PMID: 22530713 PMCID: PMC3662086 DOI: 10.1080/10408398.2010.504901] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
In the context of increasing prevalence of overweight and obesity in societies worldwide, enhancing the satiating capacity of foods may help people control their energy intake and weight. This requires an integrated approach between various food-related disciplines. By structuring this approach around the new product development process, this paper aims to present the contours of such an integrative approach by going through the current state of the art around satiety enhancing foods. It portrays actual food choice as the end result of a complex interaction between internal satiety signals, other food benefits, and environmental cues. Three interrelated routes to satiating enhancement are to change the food composition to develop stronger physiological satiation and satiety signals, anticipate and build on smart external stimuli at the moment of purchase and consumption, and improve palatability and acceptance of satiety enhanced foods. Key research challenges in achieving these routes in the field of nutrition, food technology, consumer, marketing, and communication are outlined.
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Affiliation(s)
- E Van Kleef
- Wageningen University, Marketing & Consumer Behaviour Group, Wageningen, The Netherlands.
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148
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Abstract
The incretin hormones, glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1), are gut peptides which are secreted by endocrine cells in the intestinal mucosa. Their plasma concentrations increase quickly following food ingestion, and carbohydrate, fat, and protein have all been shown to stimulate GLP-1 and GIP secretion. Although neural and hormonal mechanisms have also been proposed to regulate incretin hormone secretion, direct stimulation of the enteroendocrine cells by the presence of nutrients in the intestinal lumen is probably the most important factor in humans. The actions of the incretin hormones are crucial for maintaining normal islet function and glucose homeostasis. Furthermore, it is also now being recognized that incretin hormones may have other actions in addition to their glucoregulatory effects. Studies have shown that GLP-1 and GIP levels and actions may be perturbed in disease states, but interpretation of the precise relationship between disease and incretins is difficult. The balance of evidence seems to suggest that alterations in secretion and/or action of incretin hormones arise secondarily to the development of insulin resistance, glucose intolerance, and/or increases in body weight rather than being causative factors. However, these impairments may contribute to the deterioration of glycemic control in diabetic patients.
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Affiliation(s)
- Carolyn F Deacon
- Department of Biomedical Sciences, University of Copenhagen, DK-2200 Copenhagen N, Denmark.
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149
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Rasouli M, Ahmad Z, Omar AR, Allaudin ZN. Engineering an L-cell line that expresses insulin under the control of the glucagon-like peptide-1 promoter for diabetes treatment. BMC Biotechnol 2011; 11:99. [PMID: 22047106 PMCID: PMC3229441 DOI: 10.1186/1472-6750-11-99] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2011] [Accepted: 11/03/2011] [Indexed: 11/14/2022] Open
Abstract
Background Diabetes mellitus is a complicated disease with a pathophysiology that includes hyperinsulinemia, hyperglycemia and other metabolic impairments leading to many clinical complications. It is necessary to develop appropriate treatments to manage the disease and reduce possible acute and chronic side effects. The advent of gene therapy has generated excitement in the medical world for the possible application of gene therapy in the treatment of diabetes. The glucagon-like peptide-1 (GLP-1) promoter, which is recognised by gut L-cells, is an appealing candidate for gene therapy purposes. The specific properties of L-cells suggest that L-cells and the GLP-1 promoter would be useful for diabetes therapy approaches. Results In this study, L-cells were isolated from a primary intestinal cell line to create suitable target cells for insulin expression studies. The isolated cells displayed L-cell properties and were therefore used as an L-cell surrogate. Next, the isolated L-cells were transfected with the recombinant plasmid consisting of an insulin gene located downstream of the GLP-1 promoter. The secretion tests revealed that an increase in glucose concentration from 5 mM to 25 mM induced insulin gene expression in the L-cells by 2.7-fold. Furthermore, L-cells quickly responded to the glucose stimulation; the amount of insulin protein increased 2-fold in the first 30 minutes and then reached a plateau after 90 minutes. Conclusion Our data showed that L-cells efficiently produced the mature insulin protein. In addition, the insulin protein secretion was positively regulated with glucose induction. In conclusion, GLP-1 promoter and L-cell could be potential candidates for diabetes gene therapy agents.
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Affiliation(s)
- Mina Rasouli
- Laboratory of Vaccines and Immunotherapeutics, Institute of Bioscience, Universiti Putra Malaysia, UPM Serdang, Selangor, Malaysia
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150
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Steinert RE, Beglinger C. Nutrient sensing in the gut: interactions between chemosensory cells, visceral afferents and the secretion of satiation peptides. Physiol Behav 2011; 105:62-70. [DOI: 10.1016/j.physbeh.2011.02.039] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Revised: 02/24/2011] [Accepted: 02/25/2011] [Indexed: 01/01/2023]
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