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Gałęcka I, Szyryńska N, Całka J. Influence of polyethylene terephthalate (PET) microplastic on selected active substances in the intramural neurons of the porcine duodenum. Part Fibre Toxicol 2024; 21:5. [PMID: 38321545 PMCID: PMC10845528 DOI: 10.1186/s12989-024-00566-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2023] [Accepted: 01/29/2024] [Indexed: 02/08/2024] Open
Abstract
BACKGROUND Currently, society and industry generate huge amounts of plastics worldwide. The ubiquity of microplastics is obvious, but its impact on the animal and human organism remains not fully understood. The digestive tract is one of the first barriers between pathogens and xenobiotics and a living organism. Its proper functioning is extremely important in order to maintain homeostasis. The aim of this study was to determine the effect of microplastic on enteric nervous system and histological structure of swine duodenum. The experiment was carried out on 15 sexually immature gilts, approximately 8 weeks old. The animals were randomly divided into 3 study groups (n = 5/group). The control group received empty gelatin capsules once a day for 28 days, the first research group received daily gelatin capsules with polyethylene terephthalate (PET) particles as a mixture of particles of various sizes (maximum particle size 300 µm) at a dose of 0.1 g/animal/day. The second study group received a dose ten times higher-1 g/animal/day. RESULTS A dose of 1 g/day/animal causes more changes in the enteric nervous system and in the histological structure of duodenum. Statistically significant differences in the expression of cocaine and amphetamine regulated transcript, galanin, neuronal nitric oxide synthase, substance P, vesicular acetylcholine transporter and vasoactive intestinal peptide between control and high dose group was noted. The histopathological changes were more frequently observed in the pigs receiving higher dose of PET. CONCLUSION Based on this study it may be assumed, that oral intake of microplastic might have potential negative influence on digestive tract, but it is dose-dependent.
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Affiliation(s)
- Ismena Gałęcka
- Department of Epizootiology, Faculty of Veterinary Medicine, University of Warmia and Mazury in Olsztyn, Oczapowskiego 13, 10-719, Olsztyn, Poland.
- Deparment of Clinical Physiology, Faculty of Veterinary Medicine, University of Warmia and Mazury in Olsztyn, Oczapowskiego 13, 10-719, Olsztyn, Poland.
| | - Natalia Szyryńska
- Department of Histology and Embryology, Faculty of Veterinary Medicine, University of Warmia and Mazury in Olsztyn, Oczapowskiego 13, 10-719, Olsztyn, Poland
| | - Jarosław Całka
- Deparment of Clinical Physiology, Faculty of Veterinary Medicine, University of Warmia and Mazury in Olsztyn, Oczapowskiego 13, 10-719, Olsztyn, Poland
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Effect of Chemically-Induced Diabetes Mellitus on Phenotypic Variability of the Enteric Neurons in the Descending Colon in the Pig. ANNALS OF ANIMAL SCIENCE 2021. [DOI: 10.2478/aoas-2020-0121] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Abstract
Gastrointestinal neuropathy in diabetes is one of numerous diseases resulting in abnormal functioning of the gastrointestinal tract (GIT), and it may affect any section of the GIT, including the descending colon. In the gastrointestinal system, the neurons are arranged in an interconnecting network defined as the enteric nervous system (ENS) which includes the myenteric plexus and the submucosal plexuses: inner and outer. Regular functioning of the ENS is determined by normal synthesis of the neurotransmitters and neuromodulators. This paper demonstrates the effect of hyperglycaemia on the number of enteric neurons which are immunoreactive to: neural isoform of nitric oxide synthase (nNOS), vasoactive intestinal peptide (VIP), galanin (GAL), calcitonin generelated peptide (CGRP) and cocaine amphetamine-regulated transcript (CART) in the porcine descending colon. It was demonstrated that there was a statistically significant increase in the number of neurons within the myenteric plexus immunoreactive to all investigated substances. In the outer submucosal plexus, the CART-positive neurons were the only ones not to change, whereas no changes were recorded for nNOS or CART in the inner submucosal plexus. This study is the first study to discuss quantitative changes in the neurons immunoreactive to nNOS, VIP, GAL, CGRP and CART in the descending colon in diabetic pigs.
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Bulc M, Całka J, Palus K. Effect of Streptozotocin-Inducted Diabetes on the Pathophysiology of Enteric Neurons in the Small Intestine Based on the Porcine Diabetes Model. Int J Mol Sci 2020; 21:E2047. [PMID: 32192078 PMCID: PMC7139978 DOI: 10.3390/ijms21062047] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Revised: 03/13/2020] [Accepted: 03/14/2020] [Indexed: 12/31/2022] Open
Abstract
Hyperglycemia is one of the main causes of diabetes complications. Gastrointestinal (GI) disturbances are one of the most frequent complications during diabetes. The porcine digestive tract possesses physiological and pathological similarities to the human digestive tract. This also applies to the innervation of the gastrointestinal tract. In this study, the influence of experimentally-inducted hyperglycemia was examined on the expression of vesicular acetylcholine transporter (VAChT), cocaine- and amphetamine-regulated transcript (CART), galanin (GAL), vasoactive intestinal polypeptide (VIP), and calcitonin gene-related peptide (CGRP) in the enteric nervous system (ENS) neurons in the small intestine of the pig. During the current study, an increased number of neurons containing CART, VIP, GAL, and CGRP under streptozotocin injection were observed. The augmentation of expression included all enteric plexuses present in the small intestine. The same results were obtained in the case of VAChT; namely, chronic hyperglycemia led to an increase in the number of neurons utilizing VAChT in all investigated plexuses. The obtained results suggested that the function of neuropeptides studied in this experiment depended on their localization in the ENS structures, as well as part of the GI tract. Diabetes led to alterations in the neurochemical phenotype of small intestine enteric neurons.
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Affiliation(s)
- Michał Bulc
- Department of Clinical Physiology Faculty of Veterinary Medicine, University of Warmia and Mazury, Oczapowskiego Str. 13, 10-719 Olsztyn, Poland; (J.C.); (K.P.)
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Abot A, Lucas A, Bautzova T, Bessac A, Fournel A, Le-Gonidec S, Valet P, Moro C, Cani PD, Knauf C. Galanin enhances systemic glucose metabolism through enteric Nitric Oxide Synthase-expressed neurons. Mol Metab 2018; 10:100-108. [PMID: 29428595 PMCID: PMC5985240 DOI: 10.1016/j.molmet.2018.01.020] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Revised: 01/12/2018] [Accepted: 01/23/2018] [Indexed: 12/14/2022] Open
Abstract
Objective Decreasing duodenal contraction is now considered as a major focus for the treatment of type 2 diabetes. Therefore, identifying bioactive molecules able to target the enteric nervous system, which controls the motility of intestinal smooth muscle cells, represents a new therapeutic avenue. For this reason, we chose to study the impact of oral galanin on this system in diabetic mice. Methods Enteric neurotransmission, duodenal contraction, glucose absorption, modification of gut–brain axis, and glucose metabolism (glucose tolerance, insulinemia, glucose entry in tissue, hepatic glucose metabolism) were assessed. Results We show that galanin, a neuropeptide expressed in the small intestine, decreases duodenal contraction by stimulating nitric oxide release from enteric neurons. This is associated with modification of hypothalamic nitric oxide release that favors glucose uptake in metabolic tissues such as skeletal muscle, liver, and adipose tissue. Oral chronic gavage with galanin in diabetic mice increases insulin sensitivity, which is associated with an improvement of several metabolic parameters such as glucose tolerance, fasting blood glucose, and insulin. Conclusion Here, we demonstrate that oral galanin administration improves glucose homeostasis via the enteric nervous system and could be considered a therapeutic potential for the treatment of T2D. Targeting the enteric nervous system (ENS) is an innovative solution to treat diabetes. The ENS controls duodenal contractions to modulate glycemia via the gut–brain axis. ENS/contractions are targeted by the neuropeptide galanin in the intestine. Oral galanin treatment decreases duodenal hyper-contractility in diabetic mice. Oral galanin restores the gut–brain axis to improve glycemia in diabetic mice.
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Affiliation(s)
- Anne Abot
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1220, Université Paul Sabatier, UPS, Institut de Recherche en Santé Digestive et Nutrition (IRSD), CHU Purpan, Place du Docteur Baylac, CS 60039, 31024 Toulouse Cedex 3, France; NeuroMicrobiota, European Associated Laboratory (EAL) INSERM/UCL, France
| | - Alexandre Lucas
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1048, Université Paul Sabatier, UPS, Institut des Maladies Métaboliques et Cardiovasculaires (I2MC), CHU Rangueil, 1 Avenue Jean Poulhès, BP84225, 31432 Toulouse Cedex 4, France
| | - Tereza Bautzova
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1220, Université Paul Sabatier, UPS, Institut de Recherche en Santé Digestive et Nutrition (IRSD), CHU Purpan, Place du Docteur Baylac, CS 60039, 31024 Toulouse Cedex 3, France; NeuroMicrobiota, European Associated Laboratory (EAL) INSERM/UCL, France
| | - Arnaud Bessac
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1220, Université Paul Sabatier, UPS, Institut de Recherche en Santé Digestive et Nutrition (IRSD), CHU Purpan, Place du Docteur Baylac, CS 60039, 31024 Toulouse Cedex 3, France; NeuroMicrobiota, European Associated Laboratory (EAL) INSERM/UCL, France
| | - Audren Fournel
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1220, Université Paul Sabatier, UPS, Institut de Recherche en Santé Digestive et Nutrition (IRSD), CHU Purpan, Place du Docteur Baylac, CS 60039, 31024 Toulouse Cedex 3, France; NeuroMicrobiota, European Associated Laboratory (EAL) INSERM/UCL, France
| | - Sophie Le-Gonidec
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1048, Université Paul Sabatier, UPS, Institut des Maladies Métaboliques et Cardiovasculaires (I2MC), CHU Rangueil, 1 Avenue Jean Poulhès, BP84225, 31432 Toulouse Cedex 4, France
| | - Philippe Valet
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1048, Université Paul Sabatier, UPS, Institut des Maladies Métaboliques et Cardiovasculaires (I2MC), CHU Rangueil, 1 Avenue Jean Poulhès, BP84225, 31432 Toulouse Cedex 4, France
| | - Cédric Moro
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1048, Université Paul Sabatier, UPS, Institut des Maladies Métaboliques et Cardiovasculaires (I2MC), CHU Rangueil, 1 Avenue Jean Poulhès, BP84225, 31432 Toulouse Cedex 4, France
| | - Patrice D Cani
- NeuroMicrobiota, European Associated Laboratory (EAL) INSERM/UCL, France; Université Catholique de Louvain (UCL), Louvain Drug Research Institute, LDRI, Metabolism and Nutrition Research Group, WELBIO (Walloon Excellence in Life sciences and BIOtechnology), Avenue E. Mounier, 73 B1.73.11, B-1200, Brussels, Belgium.
| | - Claude Knauf
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1220, Université Paul Sabatier, UPS, Institut de Recherche en Santé Digestive et Nutrition (IRSD), CHU Purpan, Place du Docteur Baylac, CS 60039, 31024 Toulouse Cedex 3, France; NeuroMicrobiota, European Associated Laboratory (EAL) INSERM/UCL, France.
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Abot A, Cani PD, Knauf C. Impact of Intestinal Peptides on the Enteric Nervous System: Novel Approaches to Control Glucose Metabolism and Food Intake. Front Endocrinol (Lausanne) 2018; 9:328. [PMID: 29988396 PMCID: PMC6023997 DOI: 10.3389/fendo.2018.00328] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Accepted: 05/31/2018] [Indexed: 12/13/2022] Open
Abstract
The gut is one of the most important sources of bioactive peptides in the body. In addition to their direct actions in the brain and/or peripheral tissues, the intestinal peptides can also have an impact on enteric nervous neurons. By modifying the endogenousproduction of these peptides, one may expect modify the "local" physiology such as glucose absorption, but also could have a "global" action via the gut-brain axis. Due to the various origins of gut peptides (i.e., nutrients, intestinal wall, gut microbiota) and the heterogeneity of enteric neurons population, the potential physiological parameters control by the interaction between the two partners are multiple. In this review, we will exclusively focus on the role of enteric nervous system as a potential target of gut peptides to control glucose metabolism and food intake. Potential therapeutic strategies based on per os administration of gut peptides to treat type 2 diabetes will be described.
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Affiliation(s)
- Anne Abot
- NeuroMicrobiota, European Associated Laboratory (EAL), INSERM, Université catholique de Louvain (UCL), Toulouse, France
- INSERM U1220 Institut de Recherche en Santé Digestive (IRSD), CHU Purpan, Université Toulouse III Paul Sabatier, Paris, France
| | - Patrice D. Cani
- NeuroMicrobiota, European Associated Laboratory (EAL), INSERM, Université catholique de Louvain (UCL), Toulouse, France
- Metabolism and Nutrition Research Group, Louvain Drug Research Institute (LDRI), WELBIO (Walloon Excellence in Life Sciences and BIOtechnology), Université catholique de Louvain (UCL), Brussels, Belgium
| | - Claude Knauf
- NeuroMicrobiota, European Associated Laboratory (EAL), INSERM, Université catholique de Louvain (UCL), Toulouse, France
- INSERM U1220 Institut de Recherche en Santé Digestive (IRSD), CHU Purpan, Université Toulouse III Paul Sabatier, Paris, France
- *Correspondence: Claude Knauf,
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Bulc M, Palus K, Całka J, Zielonka Ł. Changes in Immunoreactivity of Sensory Substances within the Enteric Nervous System of the Porcine Stomach during Experimentally Induced Diabetes. J Diabetes Res 2018; 2018:4735659. [PMID: 30140706 PMCID: PMC6081574 DOI: 10.1155/2018/4735659] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/12/2018] [Revised: 04/30/2018] [Accepted: 05/15/2018] [Indexed: 01/28/2023] Open
Abstract
One of the most frequently reported disorders associated with diabetes is gastrointestinal (GI) disturbance. Although pathogenesis of these complications is multifactorial, the complicity of the enteric nervous system (ENS) in this respect has significant importance. Therefore, this paper analysed changes in substance P- (SP-), calcitonin gene-related peptide- (CGRP-), and leu5-enkephalin- (L-ENK-) like immunoreactivity (LI) in enteric stomach neurons caused by chemically induced diabetes in a porcine model. Using double immunofluorescent labelling, it was found that acute hyperglycaemia led to significant changes in the chemical coding of stomach enteric neurons. Generally, the response to artificially inducted diabetes depended on the "kind" of enteric plexus as well as the stomach region studied. A clear increase in the percentage of neurons immunoreactive to SP and CGRP was visible in the myenteric plexus (MP) in the antrum, corpus, and pylorus as well as in the submucosal plexus (SmP) in the corpus. For L-ENK, an increase in the number of L-ENK-LI neurons was observed in the MP of the antrum and SmP in the corpus, while in the MP of the corpus and pylorus, a decrease in the percentage of L-ENK-LI neurons was noted.
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Affiliation(s)
- Michał Bulc
- Department of Clinical Physiology Faculty of Veterinary Medicine, University of Warmia and Mazury in Olsztyn, Oczapowskiego Str. 13, 10-719 Olsztyn, Poland
| | - Katarzyna Palus
- Department of Clinical Physiology Faculty of Veterinary Medicine, University of Warmia and Mazury in Olsztyn, Oczapowskiego Str. 13, 10-719 Olsztyn, Poland
| | - Jarosław Całka
- Department of Clinical Physiology Faculty of Veterinary Medicine, University of Warmia and Mazury in Olsztyn, Oczapowskiego Str. 13, 10-719 Olsztyn, Poland
| | - Łukasz Zielonka
- Department of Veterinary Prevention and Feed Hygiene, Faculty of Veterinary Medicine, University of Warmia and Mazury in Olsztyn, 10-718 Olsztyn, Poland
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de Souza SRG, de Miranda Neto MH, Martins Perles JVC, Vieira Frez FC, Zignani I, Ramalho FV, Hermes-Uliana C, Bossolani GDP, Zanoni JN. Antioxidant Effects of the Quercetin in the Jejunal Myenteric Innervation of Diabetic Rats. Front Med (Lausanne) 2017; 4:8. [PMID: 28224126 PMCID: PMC5293826 DOI: 10.3389/fmed.2017.00008] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Accepted: 01/19/2017] [Indexed: 12/31/2022] Open
Abstract
Purpose Enteric glial cells (EGCs) exert a critical role in the structural integrity, defense, and metabolic function of enteric neurons. Diabetes mellitus is a chronic disease characterized by metabolic disorders and chronic autonomic neuropathy. Quercetin supplementation, which is a potent antioxidant, has been used in order to reduce the effects of diabetes-induced oxidative stress. The purpose of this research was to investigate the effects of quercetin supplementation in the drinking water at a daily dose of 40 mg on the glial cells and neurons in the jejunum of diabetic rats. Materials and methods Twenty 90-day-old male adult Wistar rats were split into four groups: normoglycemic control (C), normoglycemic control supplemented with quercetin (Q), diabetic (D), and diabetic supplemented with quercetin (DQ). After 120 days, the jejunums were collected, and immunohistochemical technique was performed to label S-100-immunoreactive glial cells and HuC/D-immunoreactive neurons. Results An intense neuronal and glial reduction was observed in the jejunum of diabetic rats. Quercetin displayed neuroprotective effects due to reduced cell body areas of neurons and glial cells in Q and DQ groups compared to their controls (C and D groups). Interestingly, quercetin prevented the glial and neuronal loss with a higher density for the HuC/D-immunoreactive neurons (23.06%) and for the S100-immunoreactive glial cells (14.55%) in DQ group compared to D group. Conclusion Quercetin supplementation promoted neuroprotective effects through the reduction of neuronal and glial body areas and a slight prevention of neuronal and glial density reduction.
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Affiliation(s)
- Sara R Garcia de Souza
- Department of Morphological Sciences, Universidade Estadual de Maringá , Maringá, Paraná , Brazil
| | | | | | | | - Isabela Zignani
- Department of Morphological Sciences, Universidade Estadual de Maringá , Maringá, Paraná , Brazil
| | - Francielle Veiga Ramalho
- Department of Morphological Sciences, Universidade Estadual de Maringá , Maringá, Paraná , Brazil
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Fang P, Yu M, Gu X, Shi M, Zhu Y, Zhang Z, Bo P. Low levels of plasma galanin in obese subjects with hypertension. J Endocrinol Invest 2017; 40:63-68. [PMID: 27538957 DOI: 10.1007/s40618-016-0529-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Accepted: 07/30/2016] [Indexed: 10/21/2022]
Abstract
BACKGROUND Obesity is strongly linked to increased blood pressure, which increases the risk of cardiovascular diseases. To our knowledge, little literature reported the information about galanin levels in obese individuals with hypertension. Therefore, the aim of this study was to investigate the possible involvement of galanin in the pathogenesis of obese subjects with hypertension. METHODS We measured body mass index and blood pressure of 38 obese patients with hypertension, 44 obese controls with normal blood pressure and 44 lean controls with normal blood pressure. Blood samples from all cases were collected at 8:00 a.m. after an overnight fast to determine the fasting plasma concentration of galanin, glucose, insulin, triglyceride, total cholesterol, high- and low-density lipoprotein cholesterol. RESULTS We found that plasma galanin levels were significantly decreased in obese patients with hypertension compared with the obese control group, whereas the galanin levels were significantly increased in obese controls compared with lean controls. Furthermore, in both obese groups the galanin levels were negatively correlative to diastolic blood pressure and positively correlative to insulin and triglyceride levels, but not to heart rate. CONCLUSIONS Low galanin levels were one of characters of obese patients with high blood pressure, and this levels may be taken as a novel biomarker to predict the development of high blood pressure in obese patients.
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Affiliation(s)
- P Fang
- Department of Physiology, Nanjing University of Chinese Medicine Hanlin College, Taizhou, 225300, China
- Department of Endocrinology, Clinical Medical College, Yangzhou University, Yangzhou, 225001, China
- Jiangsu Key Laboratory of Integrated Traditional Chinese and Western Medicine for Prevention and Treatment of Senile Diseases, Medical College, Yangzhou University, Yangzhou, 225001, China
| | - M Yu
- Department of Physiology, Nanjing University of Chinese Medicine Hanlin College, Taizhou, 225300, China
- Department of Endocrinology, Clinical Medical College, Yangzhou University, Yangzhou, 225001, China
| | - X Gu
- Department of Pathology, Clinical Medical College, Yangzhou University, Yangzhou, 225001, Jiangsu, China
| | - M Shi
- Department of Endocrinology, Clinical Medical College, Yangzhou University, Yangzhou, 225001, China
- Jiangsu Key Laboratory of Integrated Traditional Chinese and Western Medicine for Prevention and Treatment of Senile Diseases, Medical College, Yangzhou University, Yangzhou, 225001, China
| | - Y Zhu
- Department of Endocrinology, Clinical Medical College, Yangzhou University, Yangzhou, 225001, China
| | - Z Zhang
- Department of Endocrinology, Clinical Medical College, Yangzhou University, Yangzhou, 225001, China.
| | - P Bo
- Department of Endocrinology, Clinical Medical College, Yangzhou University, Yangzhou, 225001, China.
- Jiangsu Key Laboratory of Integrated Traditional Chinese and Western Medicine for Prevention and Treatment of Senile Diseases, Medical College, Yangzhou University, Yangzhou, 225001, China.
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PEREIRA RENATAV, LINDEN DAVIDR, MIRANDA-NETO MARCÍLIOH, ZANONI JACQUELINEN. Differential effects in CGRPergic, nitrergic, and VIPergic myenteric innervation in diabetic rats supplemented with 2% L-glutamine. ACTA ACUST UNITED AC 2016; 88 Suppl 1:609-22. [DOI: 10.1590/0001-3765201620150228] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Accepted: 06/03/2015] [Indexed: 12/29/2022]
Abstract
ABSTRACT The objective of this study was to investigate the effects of 2% L-glutamine supplementation on myenteric innervation in the ileum of diabetic rats, grouped as follows: normoglycemic (N); normoglycemic supplemented with L-glutamine (NG); diabetic (D); and diabetic supplemented with L-glutamine (DG). The ileums were subjected to immunohistochemical techniques to localize neurons immunoreactive to HuC/D protein (HuC/D-IR) and neuronal nitric oxide synthase enzyme (nNOS-IR) and to analyze varicosities immunoreactive to vasoactive intestinal polypeptide (VIP-IR) and calcitonin gene-related peptide (CGRP-IR). L-Glutamine in the DG group (i) prevented the increase in the cell body area of nNOS-IR neurons, (ii) prevented the increase in the area of VIP-IR varicosities, (iii) did not prevent the loss of HuC/D-IR and nNOS-IR neurons per ganglion, and (iv) reduced the size of CGRP-IR varicosities. L-Glutamine in the NG group reduced (i) the number of HuC/D-IR and nNOS-IR neurons per ganglion, (ii) the cell body area of nNOS-IR neurons, and (iii) the size of VIP-IR and CGRP-IR varicosities. 2% L-glutamine supplementation exerted differential neuroprotective effects in experimental diabetes neuropathy that depended on the type of neurotransmitter analyzed. However, the effects of this dose of L-glutamine on normoglycemic animals suggests there are additional actions of this beyond its antioxidant capacity.
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Expression of Cocaine and Amphetamine Regulated Transcript (CART) in the Porcine Intramural Neurons of Stomach in the Course of Experimentally Induced Diabetes Mellitus. J Mol Neurosci 2015; 57:376-85. [PMID: 26266486 DOI: 10.1007/s12031-015-0618-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Accepted: 07/07/2015] [Indexed: 10/23/2022]
Abstract
In the present study, the effect of streptozotocin-induced diabetes on the cocaine- and amphetamine-regulated transcript-like immunoreactive (CART-LI) enteric nervous structures was investigated within the porcine stomach. To induce diabetes, the pigs were administered intravenously streptozotocin at a dose of 150 mg/kg of body weight. A significant decrease of the number of CART-LI perikarya was observed in the myenteric plexus of the gastric antrum, corpus, and pylorus in the experimental group. In contrast, submucous plexus was devoid of CART-positive neuronal cells both in control and experimental animals. In the control group, the highest densities of CART-LI nerve fibers were observed in the circular muscle layer of antrum and slightly less nerve fibers were present in the muscle layer of corpus and pylorus. In turn, submucous layer of all studied stomach regions revealed relatively smaller number of CART-positive nerve fibers. Diabetes caused statistically significant decrease in the expression of CART-LI nerve fibers only in the antrum circular muscle layer. Also, no changes in the CART-like immunoreactivity in the intraganglionic nerve fibers were observed. The obtained results suggest that acute hyperglycemia produced significant reduction of the CART expression in enteric perikarya throughout entire stomach as well as decrease of density the CART-LI fibers in circular muscle layer of the antrum. Additionally, we suggest that CART might be involved in the regulation of stomach function especially in the gastric motility.
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Yarandi SS, Srinivasan S. Diabetic gastrointestinal motility disorders and the role of enteric nervous system: current status and future directions. Neurogastroenterol Motil 2014; 26:611-24. [PMID: 24661628 PMCID: PMC4104990 DOI: 10.1111/nmo.12330] [Citation(s) in RCA: 123] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/29/2013] [Accepted: 02/18/2014] [Indexed: 02/06/2023]
Abstract
BACKGROUND Gastrointestinal manifestations of diabetes are common and a source of significant discomfort and disability. Diabetes affects almost every part of gastrointestinal tract from the esophagus to the rectum and causes a variety of symptoms including heartburn, nausea, vomiting, abdominal pain, diarrhea and constipation. Understanding the underlying mechanisms of diabetic gastroenteropathy is important to guide development of therapies for this common problem. Over recent years, the data regarding the pathophysiology of diabetic gastroenteropathy is expanding. In addition to autonomic neuropathy causing gastrointestinal disturbances the role of enteric nervous system is becoming more evident. PURPOSE In this review, we summarize the reported alterations in enteric nervous system including enteric neurons, interstitial cells of Cajal and neurotransmission in diabetic animal models and patients. We also review the possible underlying mechanisms of these alterations, with focus on oxidative stress, growth factors and diabetes induced changes in gastrointestinal smooth muscle. Finally, we will discuss recent advances and potential areas for future research related to diabetes and the ENS such as gut microbiota, micro-RNAs and changes in the microvasculature and endothelial dysfunction.
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Affiliation(s)
- S. S. Yarandi
- Division of Digestive Diseases; Emory University; Atlanta GA
- Atlanta VA Medical Center; Decatur Georgia USA
| | - S. Srinivasan
- Division of Digestive Diseases; Emory University; Atlanta GA
- Atlanta VA Medical Center; Decatur Georgia USA
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Bu L, Yao Q, Liu Z, Tang W, Zou J, Qu S. Combined galanin with insulin improves insulin sensitivity of diabetic rat muscles. J Endocrinol 2014; 221:157-65. [PMID: 24501381 DOI: 10.1530/joe-13-0444] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Although administration of galanin or insulin alone may enhance insulin sensitivity and glucose transporter 4 (GLUT4) trafficking, their cooperative effect on insulin sensitivity is still unclear. In the present study, we evaluated the cooperative effect of both reagents compared with solitary treatment with galanin or insulin in type 2 diabetic rats. Galanin and/or insulin were injected singly or together into type 2 diabetic rats once a day for 15 days. The results indicated that coadministration of both reagents compared with treatment with galanin or insulin alone significantly increased glucose infusion rates in euglycemic-hyperinsulinemic clamp tests, 2-deoxy-[(3)H]d-glucose contents, GLUT4 densities, and pAS160 and protein kinase C activity levels, but reduced blood glucose and insulin levels, as well as retinol-binding protein 4 contents, and did not affect Glut4 (Slc2a4) mRNA expression levels in myocytes. The changes in the ratios of GLUT4 immunoreaction in plasma membranes to total cell membranes of myocytes were higher in the coadministrative group compared with either the insulin or the galanin group. These results indicate that cooperation of the two hormones plays a synergic role to improve GLUT4 translocation and insulin sensitivity. This finding indicates the possibility of combining galanin with insulin with the aim of obtaining better antidiabetic efficacy than that of the canonical treatment with insulin alone.
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Affiliation(s)
- Le Bu
- Department of Endocrinology, Shanghai 10th People's Hospital, Tongji University School of Medicine, 301 Yanchang Road, Shanghai 200072, China Key Laboratory of Sichuan Province of Medicinal Chemistry, Chengdu University, Chengdu 610106, China Department of Endocrinology, Changzheng Hospital, Second Military Medical University, Shanghai 200003, China
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13
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Abstract
Autonomic neuropathy complicates diabetes by increasing patient morbidity and mortality. Surprisingly, considering its importance, development and exploitation of animal models has lagged behind the wealth of information collected for somatic symmetrical sensory neuropathy. Nonetheless, animal studies have resulted in a variety of insights into the pathogenesis, neuropathology, and pathophysiology of diabetic autonomic neuropathy (DAN) with significant and, in some cases, remarkable correspondence between rodent models and human disease. Particularly in the study of alimentary dysfunction, findings in intrinsic intramural ganglia, interstitial cells of Cajal and the extrinsic parasympathetic and sympathetic ganglia serving the bowel vie for recognition as the chief mechanism. A body of work focused on neuropathologic findings in experimental animals and human subjects has demonstrated that axonal and dendritic pathology in sympathetic ganglia with relative neuron preservation represents one of the neuropathologic hallmarks of DAN but it is unlikely to represent the entire story. There is a surprising selectivity of the diabetic process for subpopulations of neurons and nerve terminals within intramural, parasympathetic, and sympathetic ganglia and innervation of end organs, afflicting some while sparing others, and differing between vascular and other targets within individual end organs. Rather than resulting from a simple deficit in one limb of an effector pathway, autonomic dysfunction may proceed from the inability to integrate portions of several complex pathways. The selectivity of the diabetic process appears to confound a simple global explanation (e.g., ischemia) of DAN. Although the search for a single unifying pathogenetic hypothesis continues, it is possible that autonomic neuropathy will have multiple pathogenetic mechanisms whose interplay may require therapies consisting of a cocktail of drugs. The role of multiple neurotrophic substances, antioxidants (general or pathway specific), inhibitors of formation of advanced glycosylation end products and drugs affecting the polyol pathway may be complex and therapeutic elements may have both salutary and untoward effects. This review has attempted to present the background and current findings and hypotheses, focusing on autonomic elements including and beyond the typical parasympathetic and sympathetic nervous systems to include visceral sensory and enteric nervous systems.
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Affiliation(s)
- Robert E Schmidt
- Department of Pathology and Immunology, Washington University School of Medicine, Saint Louis, MO, USA.
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LePard KJ, Cellini J. Age-dependent slowing of enteric axonal transport in insulin-resistant mice. World J Gastroenterol 2013; 19:482-91. [PMID: 23382626 PMCID: PMC3558571 DOI: 10.3748/wjg.v19.i4.482] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Revised: 11/20/2012] [Accepted: 12/15/2012] [Indexed: 02/06/2023] Open
Abstract
AIM: To investigate retrograde tracer transport by gastric enteric neurons in insulin resistant mice with low or high glycosylated hemoglobin (Hb).
METHODS: Under anesthesia, the retrograde tracer fluorogold was superficially injected into the fundus or antrum using a microsyringe in KK Cg-Ay/J mice prior to onset of type 2 diabetes mellitus (T2DM; 4 wk of age), at onset of T2DM (8 wk of age), and after 8, 16, or 24 wk of untreated T2DM and in age-matched KK/HIJ mice. Six days later, mice were sacrificed by CO2 narcosis followed by pneumothorax. Stomachs were removed and fixed. Sections from fundus, corpus and antrum were excised and mounted on a glass slide. Tracer-labeled neurons were viewed using a microscope and manually counted. Data were expressed as the number of neurons in short and long descending and ascending pathways and in local fundus and antrum pathways, and the number of neurons in all regions labeled after injection of tracer into either the fundus or the antrum.
RESULTS: By 8 wk of age, body weights of KKAy mice (n = 12, 34 ± 1 g) were heavier than KK mice (n = 17, 29 ± 1 g; F (4, 120) = 4.414, P = 0.002] and glycosylated Hb was higher [KK: (n = 7), 4.97% ± 0.04%; KKAy: (n = 6), 6.57% ± 0.47%; F (1, 26) = 24.748, P < 0.001]. The number of tracer labeled enteric neurons was similar in KK and KKAy mice of all ages in the short descending pathway [F (1, 57) = 2.374, P = 0.129], long descending pathway [F (1, 57) = 0.922, P = 0.341], local fundus pathway [F (1, 53) = 2.464, P = 0.122], local antrum pathway [F (1, 57) = 0.728, P = 0.397], and short ascending pathway [F (1, 53) = 2.940, P = 0.092]. In the long ascending pathway, fewer tracer-labeled neurons were present in KKAy as compared to KK mice [KK: (n = 34), 302 ± 17; KKAy: (n = 29), 230 ± 15; F (1, 53) = 8.136, P = 0.006]. The number of tracer-labeled neurons was decreased in all mice by 16 wk as compared to 8 wk of age in the short descending pathway [8 wk: (n = 15), 305 ± 26; 16 wk: (n = 13), 210 ± 30; F (4, 57) = 9.336, P < 0.001], local antrum pathway [8 wk: (n = 15), 349 ± 20; 16 wk: (n = 13), 220 ± 33; F (4, 57) = 8.920, P < 0.001], short ascending pathway [8 wk: (n = 14), 392 ± 15; 16 wk: (n = 14), 257 ± 33; F (4, 53) = 17.188, P < 0.001], and long ascending pathway [8 wk: (n = 14), 379 ± 39; 16 wk: (n = 14), 235 ± 26; F (4, 53) = 24.936, P < 0.001]. The number of tracer-labeled neurons decreased at 24 wk of age in the local fundus pathway [8 wk: (n = 14), 33 ± 11; 24 wk: (n = 12), 3 ± 2; F (4, 53) = 5.195, P = 0.001] and 32 wk of age in the long descending pathway [8 wk: (n = 15), 16 ± 3; 32 wk: (n = 12), 3 ± 2; F (4, 57) = 2.944, P = 0.028]. The number of tracer-labeled enteric neurons was correlated to final body weight for local fundus and ascending pathways [KK: (n = 34), r = -0.746, P < 0.001; KKAy: (n = 29), r = -0.842, P < 0.001] as well as local antrum and descending pathways [KK (n = 36), r = -0.660, P < 0.001; KKAy (n = 31), r = -0.622, P < 0.001]. In contrast, glycosylated Hb was not significantly correlated to number of tracer-labeled neurons [KK (n = 17), r = -0.164, P = 0.528; KKAy (n = 16), r = -0.078, P = 0.774].
CONCLUSION: Since uncontrolled T2DM did not uniformly impair tracer transport in gastric neurons, long ascending neurons may be more susceptible to persistent hyperglycemia and low effective insulin.
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15
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Neuroprotective effect of quercetin on the duodenum enteric nervous system of streptozotocin-induced diabetic rats. Dig Dis Sci 2012; 57:3106-15. [PMID: 22878915 DOI: 10.1007/s10620-012-2300-7] [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: 04/18/2012] [Accepted: 06/15/2012] [Indexed: 12/12/2022]
Abstract
BACKGROUND In diabetes mellitus (DM), hyperglycemia promotes changes in biochemical mechanisms that induce oxidative stress. Oxidative stress has been closely linked to adverse consequences that affect the function of the gastrointestinal tract caused by injuries to the enteric nervous system (ENS) that in turn cause neurodegeneration and enteric glial loss. Therapeutic approaches have shown that diet supplementation with antioxidants, such as quercetin, reduce oxidative stress. AIMS This work sought to evaluate neurons and enteric glial cells in the myenteric and submucosal plexuses of the duodenum in diabetic rats supplemented with quercetin. METHODS The duodenum of 24 rats, including a control group (C), control quercetin supplementation group (CQ), diabetic group (D), and diabetic quercetin supplementation group (DQ), were used to investigate whole mounts of muscular and submucosal layers subjected to immunohistochemistry to detect vasoactive intestinal peptide in the myenteric layer and double-staining for HuC-D/neuronal nitric oxide synthase (nNOS) and HuC-D/S100. RESULTS A reduction of the general neuronal population (HuC/D) was found in the myenteric and submucosal plexuses (p < 0.001) in the D and DQ groups. The nitrergic subpopulation (nNOS) decreased only in the myenteric plexus (p < 0.001), and glial cells decreased in both plexuses (p < 0.001) in the D and DQ groups. In diabetic rats, quercetin supplementation reduced neuronal and glial loss. Diabetes promoted an increase in the cell body area of both the general and nitrergic populations. Quercetin supplementation only prevented neuronal hypertrophy in the general population. CONCLUSION Supplementation with quercetin eased the damage caused by diabetes, promoting a neuroprotective effect and reducing enteric glial loss in the duodenum.
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16
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Domènech A, Pasquinelli G, De Giorgio R, Gori A, Bosch F, Pumarola M, Jiménez M. Morphofunctional changes underlying intestinal dysmotility in diabetic RIP-I/hIFNβ transgenic mice. Int J Exp Pathol 2011; 92:400-12. [PMID: 22050417 DOI: 10.1111/j.1365-2613.2011.00789.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The pathogenetic mechanisms underlying gastrointestinal dysmotility in diabetic patients remain poorly understood, although enteric neuropathy, damage to interstitial cells of Cajal (ICC) and smooth muscle cell injury are believed to play a role. The aim of this study was to investigate the morphological and functional changes underlying intestinal dysmotility in RIP-I/hIFNβ transgenic mice treated with multiple very low doses of streptozotocin (20 mg/kg, i.p., 5 days). Compared with vehicle-treated mice, streptozotocin-treated animals developed type 1 diabetes mellitus, with sustained hyperglycaemia for 3.5 months, polyphagia, polydipsia and increased faecal output without changes in faecal water content (metabolic cages). Diabetic mice had a longer intestine, longer ileal villi and wider colonic crypts (conventional microscopy) and displayed faster gastric emptying and intestinal transit. Contractility studies showed selective impaired neurotransmission in the ileum and mid-colon of diabetic mice. Compared with controls, the ileal and colonic myenteric plexus of diabetic mice revealed ultrastructural features of neuronal degeneration and HuD immunohistochemistry on whole-mount preparations showed 15% reduction in neuronal numbers. However, no immunohistochemical changes in apoptosis-related markers were noted. Lower absolute numbers of neuronal nitric oxide synthase- and choline acetyltransferase-immunopositive neurons and enhanced vasoactive intestinal polypeptide and substance P immunopositivity were observed. Ultrastructural and immunohistochemical analyses did not reveal changes in the enteric glial or ICC networks. In conclusion, this model of diabetic enteropathy shows enhanced intestinal transit associated with intestinal remodelling, including neuroplastic changes, and overt myenteric neuropathy. Such abnormalities are likely to reflect neuroadaptive and neuropathological changes occurring in this diabetic model.
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Affiliation(s)
- Anna Domènech
- Department of Animal Medicine and Surgery, Universitat Autònoma de Barcelona, Bellaterra, Spain.
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17
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Gangula PRR, Sekhar KR, Mukhopadhyay S. Gender bias in gastroparesis: is nitric oxide the answer? Dig Dis Sci 2011; 56:2520-7. [PMID: 21559738 PMCID: PMC3170494 DOI: 10.1007/s10620-011-1735-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2011] [Accepted: 04/18/2011] [Indexed: 12/27/2022]
Abstract
Accumulating evidence suggests that gender-related differences are prominent in gastric motility functions in both health and disease. Women are more susceptible to gastroparesis than men. Though the mechanism(s) involved are not fully understood, impairment of the nitrergic system is one of the main factors responsible for the disease. Uncoupling of neuronal nitric oxide synthase (nNOS) causes a decreased synthesis of NO leading to a reduction in smooth muscle relaxation. Tetrahydrobiopterin (BH(4)) (an essential cofactor for nNOS) is a key regulator of nNOS activity for stomach dysfunction and gastroparesis. In addition, BH(4) has been shown to be a potent antioxidant and anti-inflammatory agent. Well established by results from our laboratory, a diminished intracellular (BH(4):total biopterin) ratio in diabetic female rats significantly impairs nNOS activity and function. Recent research has been focused on BH(4) biosynthesis and gastroparesis because reduced BH(4) cofactor levels can alter the production of NO by nNOS. Researchers are now paying more attention to the possibility of using BH(4) as a therapeutic strategy in gastroparesis. The purpose of this review is to provide an overview of the regulation and function of nNOS by sex hormones and BH(4) and its potential role in the treatment of gastroparesis.
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Affiliation(s)
- P R R Gangula
- Department of Physiology, Center for Women's Health Research, Meharry Medical College, 1005 Dr. D.B. Todd Jr. Blvd, Nashville, TN 37208, USA.
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18
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Vera G, Castillo M, Cabezos PA, Chiarlone A, Martín MI, Gori A, Pasquinelli G, Barbara G, Stanghellini V, Corinaldesi R, De Giorgio R, Abalo R. Enteric neuropathy evoked by repeated cisplatin in the rat. Neurogastroenterol Motil 2011; 23:370-8, e162-3. [PMID: 21299719 DOI: 10.1111/j.1365-2982.2011.01674.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
BACKGROUND Acute administration of the antitumoral drug cisplatin can induce nausea/emesis and diarrhea. The long-term effects of cisplatin on gastrointestinal motility, particularly after repeated administration, are not well known. Because cisplatin is highly neurotoxic, myenteric neurons can be affected. Our aim was to study the prolonged effects of repeated cisplatin administration in a rat model, focusing on gastrointestinal motor function and myenteric neurons. METHODS Rats received saline or cisplatin (1 or 3 mg kg(-1), i.p.) once weekly for 5 weeks. One week after treatment, both upper gastrointestinal transit and colonic activity were evaluated, and tissue samples from ileum, colon and rectum were processed for histological analysis. Intestinal transit was measured invasively (charcoal method). Colonic activity was determined electromyographically. The gut wall structure was evaluated in sections using conventional histology and immunohistochemistry. Whole-mount preparations from the distal colon were labeled for different markers, including nitric oxide synthase (NOS) and calcitonin-gene related peptide (CGRP) to determine relative proportions of myenteric neurons vs the total neuronal population labeled with HuC/D. KEY RESULTS One week after repeated cisplatin exposure, the upper gastrointestinal transit rate and colonic activity were dose-dependently reduced. The number of NSE- or HuC/D-immunoreactive myenteric neurons per ganglion was decreased; the proportion of CGRP-immunoreactive neurons was decreased, whereas that of NOS-immunoreactive cells was increased. CONCLUSIONS & INFERENCES Chronic cisplatin may induce an enteric neuropathy characterized by changes in myenteric neurons associated with marked gastrointestinal motor dysfunction.
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Affiliation(s)
- G Vera
- Department of Pharmacology and Nutrition, Rey Juan Carlos University, Alcorcón, Spain
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19
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Ishihara E, Nagahama M, Naruse S, Semba R, Miura T, Usami M, Narita M. Neuropathological alteration of aquaporin 1 immunoreactive enteric neurons in the streptozotocin-induced diabetic rats. Auton Neurosci 2008; 138:31-40. [DOI: 10.1016/j.autneu.2007.09.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2007] [Revised: 08/29/2007] [Accepted: 09/06/2007] [Indexed: 01/15/2023]
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20
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Abstract
Diabetes is associated with several changes in gastrointestinal (GI) motility and associated symptoms such as nausea, bloating, abdominal pain, diarrhoea and constipation. The pathogenesis of altered GI functions in diabetes is multifactorial and the role of the enteric nervous system (ENS) in this respect has gained significant importance. In this review, we summarize the research carried out on diabetes-related changes in the ENS. Changes in the inhibitory and excitatory enteric neurons are described highlighting the role of loss of inhibitory neurons in early diabetic enteric neuropathy. The functional consequences of these neuronal changes result in altered gastric emptying, diarrhoea or constipation. Diabetes can also affect GI motility through changes in intestinal smooth muscle or alterations in extrinsic neuronal control. Hyperglycaemia and oxidative stress play an important role in the pathophysiology of these ENS changes. Antioxidants to prevent or treat diabetic GI motility problems have therapeutic potential. Recent research on the nerve-immune interactions demonstrates inflammation-associated neurodegeneration which can lead to motility related problems in diabetes.
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Affiliation(s)
- B Chandrasekharan
- Division of Digestive Diseases, Emory University, Atlanta, GA 30322, USA
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21
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Fehér E, Batbayar B, Vér A, Zelles T. Changes of the different neuropeptide-containing nerve fibers and immunocells in the diabetic rat's alimentary tract. Ann N Y Acad Sci 2007; 1084:280-95. [PMID: 17151308 DOI: 10.1196/annals.1372.023] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Peripheral neuropathy is a common complication of diabetes mellitus, where neuropeptides and immunocells might play important roles in the pathogenesis of the disease. In this article we have quantified the different neuropeptide-containing nerve fibers and immunocells in the streptozotocin-induced diabetic rat's alimentary tract (tongue, duodenum, colon) using immunohistochemical and immunocytochemical methods. The immunoreactive (IR) nerve fibers were found in all layers of the alimentary tract and their distribution pattern was similar in both control and diabetic groups. Mast cell-nerve fiber contacts were rarely found in the controls. However, after 4 weeks duration of diabetes the number of IR nerve fibers and the immunocompetent cells increased significantly (P < 0.05), and the number of mast cell-nerve fiber contacts was even more significantly increased (P < 0.001). The distance between nerve fibers and immunocells was about 1 mum or even less. Some of the mast cells were degranulated in the vicinity of nerve fibers. No immunocompetent cells were IR for any antisera in the control. However, after the streptozotocin treatment, a large number of the immunocompetent cells showed immunoreactivity for SP and NPY. Counting all immunocompetent cells in whole sections showed that 12.3% of them were IR for SP and 25.4% were IR for NPY. Increased number of SP-containing nerve fibers and immunocells in diabetes mellitus might be the reason for painful neuropathy and might amplify the inflammatory reaction in an axon reflex manner; the released histamine and leukotrienes, cytokines, and chemokines might cause inflammations and lesions of the mucosa.
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Affiliation(s)
- Erzsébet Fehér
- Laboratory of Oral Morphology of the Faculty of Dentistry, Department of Anatomy, Histology, and Embryology, Semmelweis University, Tüzoltó u. 58. Budapest, PO Box 95, H-1450, Hungary.
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Dvoráková MC, Pfeil U, Kuncová J, Svíglerová J, Galvis G, Krasteva G, König P, Grau V, Slavíková J, Kummer W. Down-regulation of vasoactive intestinal peptide and altered expression of its receptors in rat diabetic cardiomyopathy. Cell Tissue Res 2005; 323:383-93. [PMID: 16344947 DOI: 10.1007/s00441-005-0001-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2004] [Accepted: 05/03/2005] [Indexed: 12/22/2022]
Abstract
Vasoactive intestinal peptide (VIP) is a vasorelaxant peptide that addresses two receptor subtypes, VPAC1 and VPAC2. It stimulates insulin secretion and mediates anti-inflammatory effects and has been proposed for treatment of type 2 and autoimmune diabetes. In the heart, VIP is produced and released primarily by intrinsic neurons and improves cardiac perfusion and function. Here, we investigated the involvement of this system in the events underlying development of experimentally induced diabetic cardiomyopathy. Rats received a single streptozotocin injection, and cardiac VIP content [radioimmune assay (RIA)], expression of the VIP precursors VPAC1 and VPAC2 [real-time reverse transcription-polymerase chain reaction (RT-PCR)], and VPAC1 and VPAC2 tissue distribution (immunohistochemistry) were assessed 4, 8, and 16 weeks thereafter and compared with corresponding vehicle-treated controls. Cardiac neuropathy manifests progressively during the first 4 months of diabetes at the preproVIP mRNA and VIP peptide level and is accompanied by initial down-regulation of VPAC2 at one prime target of VIP-containing axons, i.e., smooth muscle cells of coronary arterioles. VPAC1 is expressed by macrophages. After initial changes that are specific for atria and ventricles, respectively, VPAC1 and VPAC2 expression return to control levels at 16 weeks despite ongoing loss of VIP. Given the cardioprotective role of the VIP signaling system, the persistence of receptors has therapeutic implications since it is the prerequisite for trials with VPAC2 agonists.
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MESH Headings
- Animals
- Cardiomyopathies/etiology
- Cardiomyopathies/metabolism
- Cardiomyopathies/pathology
- Diabetes Mellitus, Experimental/complications
- Diabetes Mellitus, Experimental/metabolism
- Diabetes Mellitus, Experimental/pathology
- Down-Regulation
- Heart Ventricles/metabolism
- Immunohistochemistry
- Macrophages, Peritoneal/metabolism
- Macrophages, Peritoneal/pathology
- Myocardium/metabolism
- Myocardium/pathology
- Myocytes, Cardiac/metabolism
- Myocytes, Cardiac/pathology
- Protein Precursors/biosynthesis
- Protein Precursors/metabolism
- Radioimmunoassay
- Rats
- Receptors, Vasoactive Intestinal Peptide, Type II/biosynthesis
- Receptors, Vasoactive Intestinal Polypeptide, Type I/biosynthesis
- Reverse Transcriptase Polymerase Chain Reaction
- Vasoactive Intestinal Peptide/biosynthesis
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LePard KJ. Choline acetyltransferase and inducible nitric oxide synthase are increased in myenteric plexus of diabetic guinea pig. Auton Neurosci 2005; 118:12-24. [PMID: 15795174 DOI: 10.1016/j.autneu.2004.12.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2004] [Revised: 12/08/2004] [Accepted: 12/11/2004] [Indexed: 12/16/2022]
Abstract
Alterations in enzymes in myenteric neurons from ileum were investigated in guinea pigs treated with either the pancreatic beta cell toxin streptozotocin or vehicle. After 5-6 weeks, expressions of choline acetyltransferase, neuronal nitric oxide synthase and inducible nitric oxide synthase were determined in longitudinal and myenteric plexus preparations using indirect immunohistochemistry. In ileum from streptozotocin-treated animals, the density of choline acetyltransferase-immunoreactive nerve fibers within the tertiary plexus and the percent total myenteric neurons expressing inducible nitric oxide synthase were increased, but the percent total myenteric neurons expressing neuronal nitric oxide synthase was not changed. Diabetes resulted in selective alterations in myenteric neurons including an increased density of cholinergic tertiary fibers and percentage of neurons expressing the inducible isoform of nitric oxide synthase. These adaptive changes by myenteric neurons to diabetes may contribute to gastrointestinal dysfunctions associated with diabetes.
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Affiliation(s)
- Kathy J LePard
- Department of Physiology, Chicago College of Osteopathic Medicine, Midwestern University, 555 West 31st Street, Downers Grove, IL 60515, USA.
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Chottová Dvoráková M, Kuncová J, Pfeil U, McGregor GP, Svíglerová J, Slavíková J, Kummer W. Cardiomyopathy in streptozotocin-induced diabetes involves intra-axonal accumulation of calcitonin gene-related peptide and altered expression of its receptor in rats. Neuroscience 2005; 134:51-8. [PMID: 15951122 DOI: 10.1016/j.neuroscience.2005.03.058] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2004] [Revised: 03/04/2005] [Accepted: 03/04/2005] [Indexed: 11/19/2022]
Abstract
Calcitonin gene-related peptide (CGRP) is a vasorelaxant and positive inotropic and chronotropic peptide that binds to the calcitonin receptor-like receptor. In the heart, upon stimulation CGRP is released from sensory nerve terminals and improves cardiac perfusion and function. In the present study, we investigated alterations in the components of the CGRP signaling system during development of diabetic cardiomyopathy. Rats received a single injection of streptozotocin. Four, 8, and 16 weeks thereafter cardiac CGRP content (radioimmunoassay), calcitonin receptor-like receptor expression (by real-time RT-PCR), and CGRP and calcitonin receptor-like receptor tissue distribution (immunohistochemistry) were assessed. CGRP content of atria and ventricles progressively increased during the 4 months following streptozotocin-treatment, while the distribution of CGRP-immunoreactive fibers was not visibly altered. Conversely, cardiac expression of calcitonin receptor-like receptor initially (4 weeks after treatment) increased but then gradually declined to 47% of control levels in both atria after 16 weeks. These quantitative changes were not associated with altered cellular distribution patterns (primarily in venous and capillary endothelium). Since sensory neurons have been reported to decrease expression of the CGRP precursor in the course of diabetes, the intra-axonal accumulation of CGRP observed here reflects impaired release, which, coupled with the down-regulation of its cognate receptor, calcitonin receptor-like receptor, may contribute to the well-documented impairment of cardioprotective functions in diabetes.
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Affiliation(s)
- M Chottová Dvoráková
- Department of Physiology, Charles University Plzen, Lidicka 1, 301 67 Plzen, Czech Republic
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Batbayar B, Zelles T, Vér A, Fehér E. Plasticity of the different neuropeptide-containing nerve fibres in the tongue of the diabetic rat. J Peripher Nerv Syst 2004; 9:215-23. [PMID: 15574134 DOI: 10.1111/j.1085-9489.2004.09402.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Common oral complications of diabetes mellitus are xerostomia, impairment of taste, atrophic lesions of the tongue, leukoplakia, lichen oris planus, and tumours, which might be the consequence of chronic inflammation and changes in innervation. In this work, we examined the density of different neuropeptide-containing nerve fibres immunohisto- and immunocytochemically in the root of the control and diabetic rat's tongue. Quantitative analysis showed that the number of immunoreactive (IR) nerve fibres was decreased after 1 week of the streptozotocin treatment, which was prevented by immediate insulin treatment. However, after 4 weeks duration of diabetes, the number of all investigated IR nerve fibres increased significantly (p<0.05), which was further enhanced by the delayed insulin treatment. The numbers of substance P (SP) and vasoactive intestinal polypeptide IR perikarya were also increased by insulin treatment. The electron-microscopic investigations showed that some of the nerve terminals from diabetic animals were found in degeneration. After 4 weeks duration of diabetes, the number of inflammatory cells as well as the mast cell/nerve fibre contacts was also increased. The immunocells also showed IR for SP and neuropeptide Y in the diabetic rats. The insulin treatment decreased both the number and the immunoreactivity of these cells. The increased synthesis and/or regeneration of neuropeptide-containing nerves might indicate the plasticity of nerve fibres in diabetes mellitus, which might happen as a consequence of the changes in the level of neurotrophic factors released by increased number of inflammatory cells or as an effect of insulin.
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26
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Defani MA, Zanoni JN, Natali MRM, Bazotte RB, de Miranda-Neto MH. Effect of acetyl-L-carnitine on VIP-ergic neurons in the jejunum submucous plexus of diabetic rats. ARQUIVOS DE NEURO-PSIQUIATRIA 2004; 61:962-7. [PMID: 14762599 DOI: 10.1590/s0004-282x2003000600014] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The effect of the treatment with acetyl-L-carnitine (ALC) on neurons releasing the vasoactive intestinal polypeptide (VIP) of the submucous plexus in the jejunum of diabetic rats was the purpose of our investigation. Diabetes (DM) was induced by injecting streptozotocin endoveneously (35 mg/kg). After sacrificing the animals, the jejunum was collected and processed for VIP detection. Four groups were used: C (non-diabetic), CC (non-diabetic treated with ALC), D (diabetic), DC (diabetes treated with ALC). We analyzed the immunoreactivity and the cellular profile of 126 cell bodies. The treatment with ALC improved some aspects of DM. However, it promoted a small increase in the area of neurons from group CC, suggesting a possible neurotrophic effect. Neurons from groups D and DC showed a large increase in their cellular profile and immunoreactivity when compared to C and CC, suggesting a larger concentration of this neurotransmitter within the neurons that produce it. This observation constitutes a recurrent finding in diabetic animals, suggesting that ALC does not interfere in the pathophysiological mechanisms that unchain a higher production and/or neurotransmitter accumulation and increase the profile of the VIP-ergic neurons.
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Abstract
The management of diabetic gastroparesis often represents a significant clinical challenge in which the maintenance of nutrition is pivotal. Gastric emptying is delayed in 30% to 50% of patients with longstanding type 1 or type 2 diabetes and upper gastrointestinal symptoms also occur frequently. However, there is only a weak association between the presence of symptoms and delayed gastric emptying. Acute changes in blood glucose concentrations affect gastric motility in diabetes; hyperglycemia slows gastric emptying whereas hypoglycemia may accelerate it; blood glucose concentrations may also influence symptoms. It is now recognized that gastric emptying is a major determinant of postprandial glycemia and, therefore, there is considerable interest in the concept of modulating gastric emptying, by dietary or pharmacologic means, to optimize glycemic control in diabetes.
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Affiliation(s)
- Diana Gentilcore
- Department of Medicine, Royal Adelaide Hospital, North Terrace, Adelaide, South Australia 5000, Australia.
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Schmidt RE. Neuropathology and pathogenesis of diabetic autonomic neuropathy. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2003; 50:257-92. [PMID: 12198813 DOI: 10.1016/s0074-7742(02)50080-5] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Autonomic neuropathy is a significant complication of diabetes resulting in increased patient morbidity and mortality. A number of studies, which have shown correspondence between neuropathologic findings in experimental animals and human subjects, have demonstrated that axonal and dendritic pathology in sympathetic ganglia in the absence of significant neuron loss represents a neuropathologic hallmark of diabetic autonomic neuropathy. A recurring theme in sympathetic ganglia, as well as in the pot-ganglionic autonomic innervation of various end organs, is the involvement of distal portions of axons and nerve terminals by degenerative or dystrophic changes. In both animals and humans, there is a surprising selectivity of the diabetic process for subpopulations of autonomic ganglia, nerve terminals within sympathetic ganglia and end organs, from end organ to end organ, and between vascular and other targets within individual end organs. Although the involvement or autonomic axons in somatic nerves may reflect an ischemic pathogenesis, the selectivity of the diabetic process confounds simple global explanations of diabetic autonomic neuropathy as the result of diminished blood flow with resultant tissue hypoxia. A single unifying pathogenetic hypothesis has not yet emerged from clinical and experimental animal studies, and it is likely that diabetic autonomic neuropathy will be shown to have multiple causative mechanisms, which will interact to result in the variety of presentations of autonomic injury in diabetes. Some of these mechanisms will be shared with aging changes in the autonomic nervous system. The role of various neurotrophic substances and the polyol pathway in the pathogenesis and treatment of diabetic neuropathy likely represents a two-edged sword with both salutary and exacerbating effects. The basic neurobiologic process underlying the diabetes-induced development of neuroaxonal dystrophy, synaptic dysplasia, defective axonal regeneration, and alterations in neurotrophic substance may be mechanistically related.
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Affiliation(s)
- Robert E Schmidt
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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Zanoni JN, Hernandes L, Bazotte RB, Miranda Neto MHD. Terminal ileum submucous plexus: Study of the VIP-ergic neurons of diabetic rats treated with ascorbic acid. ARQUIVOS DE NEURO-PSIQUIATRIA 2002; 60:32-37. [PMID: 11965406 DOI: 10.1590/s0004-282x2002000100007] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The aim of this study was to evaluate the effect of the ascorbic acid (AA) supplementation on the neurons that produce the vasoactive intestinal peptide (VIP) in the submucous plexus of the ileum of rat, four months after the induction of experimental diabetes mellitus with streptozotocin. Three groups of rats were used: C - control, D - diabetic, DA - diabetic receiving AA. We have measured the immunoreactivity and area of 80 cellular bodies of VIP-ergic neurons from each studied group. In the diabetic animals, we have observed hyperphagia, polydipsia, and an increase of glycemia and glycated hemoglobin. The VIP-ergic neurons have presented an increase of their immunoreactivity and the highest profiles when compared to the other groups. In the diabetic animals supplemented with AA it has been observed a small reduction in the glycemia and the water and food intake. We have also noticed smaller immunoreactivity in their VIP-ergic neurons, similar to what we have observed in the control group animals (group C).
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30
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Horowitz M, O'Donovan D, Jones KL, Feinle C, Rayner CK, Samsom M. Gastric emptying in diabetes: clinical significance and treatment. Diabet Med 2002; 19:177-94. [PMID: 11918620 DOI: 10.1046/j.1464-5491.2002.00658.x] [Citation(s) in RCA: 199] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The outcome of recent studies has led to redefinition of concepts relating to the prevalence, pathogenesis and clinical significance of disordered gastric emptying in patients with diabetes mellitus. The use of scintigraphic techniques has established that gastric emptying is abnormally slow in approx. 30-50% of outpatients with long-standing Type 1 or Type 2 diabetes, although the magnitude of this delay is modest in many cases. Upper gastrointestinal symptoms occur frequently and affect quality of life adversely in patients with diabetes, although the relationship between symptoms and the rate of gastric emptying is weak. Acute changes in blood glucose concentration affect both gastric motor function and upper gastrointestinal symptoms. Gastric emptying is slower during hyperglycaemia when compared with euglycaemia and accelerated during hypoglycaemia. The blood glucose concentration may influence the response to prokinetic drugs. Conversely, the rate of gastric emptying is a major determinant of post-prandial glycaemic excursions in healthy subjects, as well as in Type 1 and Type 2 patients. A number of therapies currently in development are designed to improve post-prandial glycaemic control by modulating the rate of delivery of nutrients to the small intestine.
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Affiliation(s)
- M Horowitz
- Department of Medicine, University of Adelaide, Adelaide, South Australia.
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31
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Jenkinson KM, Reid JJ. Altered non-adrenergic non-cholinergic neurotransmission in gastric fundus from streptozotocin-diabetic rats. Eur J Pharmacol 2000; 401:251-8. [PMID: 10924934 DOI: 10.1016/s0014-2999(00)00280-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The influence of streptozotocin-induced diabetes has been investigated on responses to non-adrenergic, non-cholinergic (NANC) nerve stimulation in rat gastric fundus. NANC relaxations in precontracted muscle strips from diabetic rats were smaller than those from control rats. In addition, the relaxations in diabetic but not control rats were followed by rapidly-developing frequency-dependent contractions. In the presence of alpha-chymotrypsin and N(G)-nitro-L-arginine methyl ester (L-NAME), the NANC contractions were markedly enhanced in diabetic rats. Treatment with the aldose reductase inhibitor, sorbinil, did not affect NANC relaxations or contractions in tissues from diabetic rats, and responses remained significantly different from those from control rats. The findings suggest that diabetes impairs relaxations to NANC nerve stimulation in the rat gastric fundus, and that a contractile NANC neurotransmitter(s) is released in diabetic rats. The results also suggest that diabetes-induced alterations in the NANC nerve response are not caused by increased activity of the aldose reductase pathway.
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Affiliation(s)
- K M Jenkinson
- Department of Anatomy and Cell Biology, University of Melbourne, Victoria 3010M, Parkville, Australia.
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Furlan MM, de Miranda Neto MH, Sant'ana DDM, Molinari SL. Number and size of myenteric neurons of the duodenum of adult rats with acute diabetes. ARQUIVOS DE NEURO-PSIQUIATRIA 1999; 57:740-5. [PMID: 10751907 DOI: 10.1590/s0004-282x1999000500003] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
This study had as its purpose to assess the effects of acute diabetes induced by streptozotocin (35 mg/kg body weight) on the number and size of the myenteric neurons of the duodenum of adult rats considering equally the antimesenteric and intermediate regions of the intestinal circumference. Experimental period extended for a week. Neuronal counts were carried out on the same number of fields of both regions of the duodenal circumference and measurements of neuronal and nuclear areas on equal numbers of cells. Number and size of the myenteric neurons stained with Giemsa were not significantly different between groups. On the other hand, the proportion of NADH-positive neurons increased from 18.54% on the controls to 39.33% on the diabetics. The authors discuss that this increased reactivity probably results from a greater NADH/NAD+ ratio, described in many tissues of diabetic animals, which has consequences on the modulation of the enzymes that use these cofactors and whose activity is detected by the NADH-diaphorase technique.
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Affiliation(s)
- M M Furlan
- Departamento de Ciências Morfofisiológicas, Universidade Estadual de Maringá, Brasil
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Calcutt NA, Chen P, Hua XY. Effects of diabetes on tissue content and evoked release of calcitonin gene-related peptide-like immunoreactivity from rat sensory nerves. Neurosci Lett 1998; 254:129-32. [PMID: 10214974 DOI: 10.1016/s0304-3940(98)00692-2] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
We measured the evoked release of calcitonin gene-related peptide-like immunoreactivity (CGRP-LI) from sensory nerve terminals in tracheas from control and diabetic rats using an in vitro perfusion system and also the CGRP-LI content of the vagus nerve and trachea. Diabetes caused a 29% (P < 0.05) reduction in CGRP-LI content of the vagus nerve and a decrease in CGRP-LI release from nerve endings in the trachea evoked by either capsaicin (30% decrease, P < 0.05) or electrical field stimulation (50% decrease: P < 0.05). In contrast, there was a 50% increase in the CGRP-LI content of the unstimulated trachea. Thus, diabetes induces an impairment in neuropeptide release from peripheral terminals of sensory nerves that corresponds to decreased levels in the supplying nerve but is not reflected in tissue measurements that incorporate nerve terminals. Impaired neuropeptide release may contribute to peripheral and central sensory dysfunction in diabetic rats.
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Affiliation(s)
- N A Calcutt
- Department of Pathology, University of California San Diego, La Jolla 92093-0612, USA.
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34
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Abstract
Kinetic studies on the aldose reductase protein (AR2) have shown that it does not behave as a classical enzyme in relation to ring aldose sugars. These results have been confirmed by X-ray crystallography studies, which have pinpointed binding sites for pharmacological "aklose reductase inhibitors" (ARIs). As with non-enzymic glycation reactions, there is probably a free-radical element involved derived from monosaccharide autoxidation. In the case of AR2, there is free radical oxidation of NADPH by autoxidising monosaccharides, enhanced in the presence of the NADPH-binding protein. Whatever the behaviour of AR2, many studies have showed that sorbitol production is not an initiating aetiological factor in the development of diabetic complications in humans. Vitamin E (alpha-tocopherol), other antioxidants and high fat diets can delay or prevent cataract in diabetic animals even though sorbitol and fructose levels are not modified; vitamin C acts as an AR1 in humans. Protein post-translational modification by glyc-oxidation or other events is probably the key factor in the aetiology of diabetic complications. There is now no need to invoke AR2 in xylitol biosynthesis. Xylitol can be produced in the lens from glucose, via a pathway involving the enzymes myo-inositol-oxygen oxidoreductase, D-glucuronate reductase. L-gulonate NAD(+)-3-oxidoreductase and L-iditol-NAD(+)-5-oxidoreductase, all of which have recently been found in bovine and rat lens. This chapter investigates the molecular events underlying AR2 and its binding and kinetics. Induction of the protein by osmotic response elements is discussed, with detailed analysis of recent in vitro and in vivo experiments on numerous ARIs. These have a number of actions in the cell which are not specific, and which do not involve them binding to AR2. These include peroxy-radical scavenging and recently discovered effects of metal ion chelation. In controlled experiments, it has been found that incubation of rat lens homogenate with glucose and the copper chelator o-phenanthroline abolishes production of sorbitol. Taken together, these results suggest AR2 is a vestigial NADPH-binding protein, perhaps similar in function to a number of non-mammalian crystallins which have been recruited into the lens. There is mounting evidence for the binding of reactive aldehyde moieties to the protein, and the involvement of AR2 either as a 'housekeeping' protein, or in a free-radial-mediated 'catalytic' role. Interfering with the NADPH binding and flux levels--possibly involving free radicals and metal ions--has a deleterious effect. We have yet to determine whether aldose reductase is the black sheep of the aldehyde reductase family, or whether it is a skeleton in the cupboard, waiting to be clothed in the flesh of new revelations in the interactions between proteins, metal ions and redox metabolites.
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Affiliation(s)
- M J Crabbe
- Wolfson Laboratory, Division of Cell and Molecular Biology, School of Animal and Microbial Sciences, University of Reading, Whiteknights, Berks, UK.
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