Low densities of serotonin and peptide YY cells in the colon of patients with irritable bowel syndrome.

BACKGROUND: The gut hormones are important in regulating gastrointestinal motility. Disturbances in gastrointestinal motility have been reported in patients with irritable bowel syndrome (IBS). Reduced endocrine cell density, as revealed by chromogranin A, has been reported in the colon of IBS patients. AIMS: To investigate a possible abnormality in the colonic endocrine cells of IBS patients. METHODS: A total of 41 patients with IBS according to Rome Criteria III and 20 controls were included in the study. Biopsies from the right and left colon were obtained from both patients and controls during colonoscopy. The biopsies were immunostained for serotonin, peptide YY (PYY), pancreatic polypeptide (PP), entroglucagon, and somatostatin cells. Cell densities were quantified by computerized image analysis. RESULTS: Serotonin and PYY cell densities were reduced in the colon of IBS patients. PP, entroglucagon, and somatostatin-immunoreactive cells were too few to enable reliable quantification. CONCLUSION: The cause of these observations could be primary genetic defect(s), secondary to altered serotonin and/or PYY signaling systems and/or subclinical inflammation. Serotonin activates the submucosal sensory branch of the enteric nervous system and controls gastrointestinal motility and chloride secretion via interneurons and motor neurons. PYY stimulates absorption of water and electrolytes, and inhibits prostaglandin (PG) E2, and vasoactive intestinal peptide, which stimulates intestinal fluid secretion and is a major regulator of the "ileal brake". Although the cause and effect relationship of these findings is difficult to elucidate, the abnormalities reported here might contribute to the symptoms associated with IBS.

Ghrelin in patients with irritable bowel syndrome.

General gastrointestinal dysmotility occurs in patients with irritable bowel syndrome (IBS). Ghrelin seems to play an important role in regulating gastrointestinal motility. The present study was undertaken, therefore, to establish the possible role of ghrelin in the pathophysiology of IBS. Thirty-seven patients with IBS (19 had IBS-constipation and 18 IBS-diarrhoea) were included in this study. Ten healthy volunteers served as controls. After overnight fast, blood samples were drawn from patients and controls, and a gastroduodenal endoscopy was performed. Biopsies were taken from oxyntic mucosa and duodenum. Ghrelin cell density was determined by computer image analysis after immunohistochemical staining of the tissues. Total and active ghrelin were detected in tissue extracts and plasma by commercially available RIA and ELISA Kits. The density of ghrelin-immunoreactive cells in the oxyntic mucosa was significantly lower in IBS-constipation and significantly higher in IBS-diarrhoea patients than healthy controls (P<0.0001 and <0.0001, respectively). There was no statistical difference in total or active ghrelin between IBS patients and controls, regarding tissue extracts or plasma. In order to compensate for the increase and decrease in the ghrelin cell density, the synthesis and release of ghrelin may be decreased and increased in IBS-diarrhoea and IBS-constipation patients, respectively. It has been speculated that this compensatory mechanism may be subjected from time to time to fatigue with the subsequent increased and decreased synthesis and release of ghrelin in IBS-diarrhoea and IBS-constipation with a subsequent intermittent diarrhoea or constipation seen in these patients, respectively.

Dietary guidance normalizes large intestinal endocrine cell densities in patients with irritable bowel syndrome.

BACKGROUND/OBJECTIVES: To determine the large intestinal endocrine cell types affected following dietary guidance in patients with irritable bowel syndrome (IBS). SUBJECTS/METHODS: The study included 13 IBS patients and 13 control subjects. The patients received three sessions of individualized dietary guidance. Both the control subjects and the patients were scheduled for colonoscopies at baseline and again for the patients at 3-9 months after dietary guidance. Biopsy samples were taken from the colon and rectum and were immunostained for all types of large intestinal endocrine cells. The endocrine cells were quantified using computerized image analysis. RESULTS: The daily total consumption (mean±s.e.m. values) of fruits and vegetables rich in FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides and polyols) decreased significantly from 16.2±5.3 g before receiving dietary guidance to 9.2±3.2 g after receiving dietary guidance (P=0.02). In the total colon, the densities of serotonin cells were 46.8±8.9, 10.5±2.1 and 22.6±3.2 cells/mm(2) in control subjects and in IBS patients before and after receiving dietary guidance, respectively (P=0.007); the corresponding densities of peptide YY cells were 11.6±1.8, 10.8±1.7 and 16.8±2.1 cells/mm(2), respectively (P=0.06). The cell densities for both serotonin and peptide YY did not change significantly in the rectum. The densities of somatostatin cells in the rectum were 13.5±3.0, 13.2±3.0, and 22.3±3.2 cells/mm(2) for control subjects and for IBS patients before and after receiving dietary guidance, respectively (P=0.01). CONCLUSIONS: The densities of the large intestinal endocrine cells tend to normalize following dietary guidance that may have contributed to the improvement of the patients with IBS symptoms.

Comparison between triple therapy with octreotide, galanin and serotonin vs. irinotecan or oxaliplatin in combination with 5-fluorouracil/leukovorin in human colon cancer.

Human colon cancer cells were injected sub-cutaneously into 30 nude mice. After 8 days, the animals were divided into 3 equal groups. The first and second groups received an i.p. injection with 5-fluorouracil/leukovorin (5-FU/LV) for 5 days (20 mg and 10 mg/kg body weight respectively). On the first day of 5-FU/LV treatment, the first group received an i.p. injection of irinotecan (2.5 mg/kg body weight), and the second group received an i.p. injection with oxaliplatin (1 mg/kg body weight). The third group were injected i.p. with 100 microl saline solution containing octreotide, galanin and serotonin. Injections were given 3 times daily for 5 days with a total dose of 150 microg/kg body weight/day. Three days after the treatment, the animals were sacrificed. Whereas the animals treated with triple therapy held a stable body weight, animals treated with 5-FU/LV-irinotecan and 5-FU/LV-oxaliplatin had gradual weight loss, which amounted to approximately 25% of their body weight at the end of the experiment. Moreover, 2 mice in the group treated with 5-FU/LV-irinotecan died, most probably due to side effects. There was no statistically significant difference between the 3 groups regarding tumour proliferation, apoptosis, blood vessel density, EGF- and VEGF-expression. Treatment with triple therapy using octreotide, galanin and serotonin appear to be comparable to 5-FU/LV in combination with irinotecan and oxaliplatin. However, triple therapy seems to have a better safety profile.

Effects of triple therapy with octreotide, galanin and serotonin on a human colon cancer cell line implanted in mice: comparison between different routes of administration.

A human colon cancer cell line was implanted subcutaneously in nude mice. After 7 days, the animals were divided into four groups. The first group received an intraperitoneal (i.p.) continuous infusion by an osmotic pump, the second was given i.p. bolus injections, the third received continuous subcutaneous (s.c.) infusion by an osmotic pump and the fourth group was given bolus s.c. injections. Each group was divided into 2 subgroups. The first subgroup received triple treatment with octreotide, galanin, and serotonin, 40 microg/kg body weight/day of each. The second subgroup was given sterile saline solution. Treatment lasted for 14 days. The volume and wet weight of the tumours in all treated groups tended to decrease, but was statistically significant only in the group with continuous i.p. infusion. The number of viable cells tended to decrease in all the treated groups, but was not statistically significant. Proliferation index was significantly reduced in mice given triple therapy i.p. as bolus injection and as continuous infusion, as compared with their respective controls. The apoptotic index increased significantly in mice receiving triple therapy as continuous i.p. infusion as revealed by both the TUNEL method and by poly (ADP-ribose) polymerase (PARP) expression. The number of tumour blood vessels was significantly reduced in the mice given triple therapy as continuous i.p. infusion, as compared with controls. There was no statistical difference between animals treated by different routes, regarding proliferation or apoptosis of the cancer cells, or the number or mean luminal area of tumour blood vessels. The present investigation showed that regardless of the route of administration, triple therapy with octreotide, galanin and serotonin generally reduced the volumes, weights, viable cells, vascularization and proliferation of the tumours, as well as inducing apoptosis. Continuous i.p. infusion appears, however, to be the most effective route of administration.

Effects of single, double or triple combinations of octreotide, galanin and serotonin on a human pancreatic cancer cell line.

The human pancreatic cancer cell line (SW 1990) was exposed to 0.2 microg/ml of octreotide, galanin or serotonin as single, double or triple combinations. The tumor cells were checked at 3, 6 and 12 hours. In order to determine the number of viable cancer cells, the MTT-assay was used. Proliferation, apoptosis and the expression of epidermal growth factor were detected with immunohistochemistry using the avidin-biotin complex method. In addition, apoptosis was also detected with (TUNEL) method. The primary antibodies used were proliferating cell nuclear antigen (PCNA), anti-poly (ADP-ribose) polymerase (PARP) and anti-human epidermal growth factor. Single treatment with octreotide or serotonin reduced, the number of viable cells and the proliferation index at all observation times. Galanin increased the number of viable cells and the proliferation index. Whereas double treatments containing octreotide reduced the number of viable cells, those containing galanin increased the number. The effect of single, double or triple treatment on the apoptotic index obtained with both TUNEL method and PARP expression varied depending on the combination and the observation time. Octreotide did not affect the tumor cell expression of EGF. Galanin and serotonin, on the other hand, increased the expression of EGF. Whereas triple combination increased the expression of EGF after 6 h, all the other double combinations decreased this expression. It has been concluded that treatment with a combination of octreotide and serotonin may be useful in clinical settings.

Effects of triple treatment with octreotide, galanin and serotonin on a human pancreas cancer cell line in xenografts.

Human pancreas cancer cells were implanted s.c. in nude mice. After 11 days, the mice were divided into two groups of 13. The first group received sterile saline solution and the second received triple therapy containing octreotide, galanin and serotonin, 40 microg/kg/day as a continuous i.p. infusion via an implanted osmotic pump for 14 days. Triple therapy prolonged the survival rate of the mice bearing human pancreatic carcinoma. Both the volume and weight of tumours in mice given triple therapy were less than in controls (not statistically significant). The proliferation index and the labelling index for epidermal growth factor (EGF) increased significantly in mice given triple therapy vis-a-vis controls. There was no statistically significant difference between control and treated tumours as regards, apoptotic index, necrosis, or number of tumour blood vessels. The increased survival rate was attributed to the reduced tumour load, since both weight and volume were reduced. It is most probable that octreotide was the responsible agent. Further investigation with single and double combinations of octreotide, galanin and serotonin are needed to identify the cause of increased cell proliferation in tumours subjected to these bioactive substances. Identifying the agent(s) inducing pancreatic cancer cell proliferation may be useful in combining a new treatment, as antagonists to these bioactive substances are available.

Effect of dietary management on the gastric endocrine cells in patients with irritable bowel syndrome.

BACKGROUND/OBJECTIVES: The gastric endocrine cells in patients with irritable bowel syndrome (IBS) tend to normalize following dietary guidance. The aim of the present study was to identify the gastric endocrine cell types that are changed following such dietary guidance. SUBJECTS/METHODS: Fourteen IBS patients and 14 healthy subjects were included in the study. Patients received three sessions of individual dietary management guidance. Gastroscopy was performed on both the controls and the patients at baseline and then again for the patients at 3-9 months after dietary guidance. Biopsy samples from the corpus and antrum were immunostained for all gastric endocrine cell types. Endocrine cells were quantified by computerized image analysis. RESULTS: The densities of the ghrelin cells for the controls and IBS patients before and after dietary guidance were 149.6 ± 36.2 (mean ± s.e.m.; 95% confidence interval (CI) 71.3-227.8), 114.5 ± 32.7 and 161.8 ± 37.8 cells/mm(2), respectively. The densities of the gastrin cells in these groups were 155.8 ± 21.0 (95% CI 110.3-201.2), 159.4 ± 24.3 and 211.6 ± 28.0 cells/mm(2), respectively; the corresponding densities of serotonin cells in the corpus were 18.2 ± 3.9 (95% CI 9.8-26.6), 10.6 ± 3.4 and 14 ± 2.0 cells/mm(2) and in the antrum were 44.6 ± 12.2 (95% CI 18.1-71.1), 1.7 ± 0.5 and 14.7 ± 6.3 cells/mm(2). The densities of the somatostatin cells in the corpus were 40.0 ± 7.7 (95% CI 23.5-56.5), 23.0 ± 3.0 and 37.3 ± 4.2 cells/mm(2), respectively, and in the antrum were 138.9 ± 22.0 (95% CI 91.4-186.3), 95.6 ± 15.9 and 86.0 ± 16.9 cells/mm(2), respectively. CONCLUSIONS: The densities of all of the gastric endocrine cell types changed towards the healthy control values in the IBS patients following a change in food intake.

Human rectal endocrine cells and aging.

Endocrine cells of the human rectum were investigated by immunocytochemistry and quantified by computerized image analysis in three different age groups. The age intervals were 20-29, 40-49 and 60-69 years. No statistically significant differences were found between the age groups, regarding the numbers of all endocrine cell types investigated, namely peptide YY (PYY)-, pancreatic polypeptide (PP)-, enteroglucagon-, somatostatin- and serotonin-immunoreactive cells. Nor was there any difference regarding the cell secretory index. Nuclear volume was significantly greater in the 40-49 year olds than the other age groups. There was no statistically significant difference between females and males regarding numbers of the endocrine cell types investigated. It is concluded that age does not affect the endocrine cells of the human large intestine as it was earlier found in animal models of aging. It is imperative that caution should be taken when applying results obtained in animal models of aging in humans.

Ageing and endocrine cells of human duodenum.

Motility and secretory disorders of the gastrointestinal tract and associated glands increase with ageing. The duodenum contains several peptide/amine producing cells that play an important role in regulating gastrointestinal motility and secretion. The present study was performed to elucidate changes in these cells that may have arisen as a result of ageing. A total of four age groups of subjects, aged 1-2, 20-29, 40-49 and 60-69 years were studied. The various endocrine cell types were identified by immunohistochemistry and quantified by computerized image analysis, and two parameters were determined; the number of cells/mm3 epithelial cells and the cell secretory index (CSI), which indicates the immunoreactive secretory granule content of the endocrine cells. Chromogranin A- and serotonin-immunoreactive (IR) cells were fewer in 1-2-year-olds than in 20-29-year-olds. Gastrin/CCK-IR cells were significantly more numerous in 1-2-year-olds and 60-69 years-olds than in 20-29-year-olds. Somatostatin-IR cells were more numerous in the 40-49-year-olds than in the 20-29 years-olds. The CSI was higher in chromogranin A-, gastric inhibitory polypeptide (GIP)-, somatostatin- and gastrin/CCK-IR cells in 1-2-year-olds than in 20-29-year-olds. There was no significant sex difference regarding the numbers and CSI of other endocrine cell types. This study established the absence of sex-related differences in all endocrine cell types investigated, regarding numbers and physiological activity. Age, on the other hand, was shown to be associated with changes in the numbers of CCK-, somatostatin- and serotonin-IR, which may have some bearing on the gastrointestinal disorders of the elderly.

Age-induced changes in the enteric nervous system in the mouse.

The enteric nervous system of the murine gut was investigated by immunocytochemistry in 1-, 3-, 12- and 24-month-old mice, using protein gene product 9.5, a general marker for nerve elements. Myenteric and submucosal plexi were quantified by computerized image analysis. In antrum, there were significantly fewer neurones per ganglion in both myenteric and submucosal ganglia of 12- and 24-month-old mice than in 3-month-old animals. The same was true of duodenum and colon. The relative volume density of nerve fibres in antral muscularis propria was significantly greater in the 1-, 12- and 24-month-old mice than in the 3-month-old mice. In colon, there were fewer submucosal ganglia per millimetre baseline in 1-month-old mice than in 3-month-old mice. The colonic myenteric ganglion in 1-, 12- and 24-month-old mice was smaller than in 3-month-old mice. There was no statistical difference between females and males regarding the number of ganglia per millimetre baseline, ganglionic area, number of neurones per ganglion or the relative volume density of nerve fibres in either the myenteric or submucosal plexi. As the enteric nervous system is responsible for coordinating and integrating the motility of the gut, the ageing-related changes reported here may well be of some relevance for the increased gastrointestinal motility dysfunction in the elderly persons.

Liver transplantation restores endocrine cells in patients with familial amyloidotic polyneuropathy.

BACKGROUND: The aim of this study was to investigate familial amyloidotic polyneuropathy, Portuguese type patients' endocrine cell content in the stomach and duodenum before and after liver transplantation, and to relate the findings to the patients' gastrointestinal disturbances. METHODS: Ten liver-transplanted familial amyloidotic polyneuropathy, Portuguese type patients and 10 healthy controls were seen. Endocrine cells were identified by immunohistochemistry and quantified with computerized image analysis. The activity of the cells was appraised by measurements of the cell secretory index and nuclear area. Clinical symptoms were obtained from the patients' medical records. RESULTS: After transplantation, a significant increase of several endocrine cell types were noted, and the pretransplant depletion of several types of endocrine cells disappeared. For no type of endocrine cell was any difference compared with controls noted after transplantation. There was no significant decrease of the amount of amyloid in the biopsies after liver transplantation. The patients' symptoms remained generally unchanged after transplantation, although a substantial time lapse between pretransplant evaluation and transplantation was present. CONCLUSIONS: Liver transplantation restores the endocrine cells in the upper part of the gastrointestinal tract. The restoration was not correlated with an improvement of the patients' symptoms. No decrease of the amyloid deposits was noted.

Glucagon and glucagon-like immunoreactive cells in mid- and hindgut carcinoids.

The occurrence of glucagon/glucagon-like immunoreactivity in 31 small intestinal, 34 rectal and 18 appendiceal carcinoids were investigated immunocytochemically using, sequence specific antisera. Glucagon/GLI immunoreactive cells were found in five small-intestinal and five rectal carcinoids, but none were observed in any of the appendiceal carcinoids examined. Glucagon/GLI immunoreactive cells constituted a minor cell population, except in one rectal carcinoid, where most of the tumour cells were of this type. Glucagon/GLI immunoreactive cells were detected with only some sequence-specific antisera, and not with antisera directed against the rest of the glucagon/glicentin molecule. This might indicate that these cells contain a molecule which shares some antigenic binding sites with glucagon/glicentin rather than genuine glucagon/glicentin. It is concluded that this finding contributes to explain why hindgut carcinoids rarely give rise to symptoms related to neuro-endocrine product(s).

The possible role of the gut neuroendocrine system in diabetes gastroenteropathy.

Gastrointestinal symptoms such as nausea and vomiting, heartburn, abdominal pain, diarrhoea, constipation and faecal incontinence are common in patients with diabetes. Diabetes gastroenteropathy is a clinically relevant problem. In addition to the increased morbidity it causes, it results in severely impaired metabolic control, which in turn increases the risk of hyper-/hypoglycaemia. Moreover, the poorly controlled blood glucose level increases the risk of secondary diabetes complications, namely, retinopathy, nephropathy, neuropathy and cardiovascular affection. Gastrointestinal symptoms may also cause malnutrition in patients with diabetes, which, together with the disturbed immune defence in diabetes, may cause intercurrent infections. Gastrointestinal symptoms in patients with diabetes are attributed to disturbed gastrointestinal motility. Gastrointestinal dysmotility in diabetes is believed to be caused by autonomic neuropathy and/or hyperglycaemia. The neuroendocrine system of the gut secretes peptides/amines that play an important role in regulating gastrointestinal motility. It is conceivable, therefore, to assume that a disturbance in this regulatory system may contribute to the pathogenesis of gastrointestinal complications in diabetes. The present review gives an updated overview of the abnormalities in the gastrointestinal neuroendocrine system in diabetes, speculates upon the possible role of these abnormalities in the pathogenesis of diabetes gastroenteropathy and, finally, predicts the possible clinical implications of these findings.

The nature and implication of intestinal endocrine cell changes in coeliac disease.

Coeliac disease is associated with intestinal lesion. This lesion causes architectural derangement of the mucosa in the form of villus atrophy, increased crypt length and increased volume of the lamina propria. Several changes in the intestinal endocrine cells have been reported over the years, e.g. the number of secretin cells and increased numbers of GIP, CCK/gastrin, motilin, and serotonin cells. There is no consensus about the nature of the changes in somatostatin-cells. It has been postulated that the changes in the endocrine cells are a selective process to meet the new demands exerted by the dramatic decrease in intestinal absorptive area. It has been speculated further that the changes in the endocrine cells would cause an incomplete digestion of the ingested food and its rapid elimination from the intestine. These changes may be responsible for the diarrhoea and steatorrhoea that occur in patients with coeliac disease.

A comparison between double and triple therapies of octreotide, galanin and serotonin on a rat colon carcinoma.

Sixty female nude mice (C578L/6jBom-nu) were injected with 100 microl cell suspension containing 2 x 10(6) viable cells of an N-methyl-N-nitroguanidine-induced rat colonic adenocarcinoma. After seven days the animals were divided into five groups. The first group received only saline and served as a control group. The second group received a triple therapy of octreotide, galanin and serotonin (20 microg/kg). The last three groups received double therapies of octreotide/galanin, octreotide/serotonin or galanin/serotonin (20 microg/kg). They were treated twice a day for five days. Tumour volume and weight, relative volume density of tumour-feeding blood vessels and of tumour necrotic tissue, as well as apoptotic and proliferation indices were determined. Animal weight, food consumption, faeces weight and its water content were recorded before and after treatment. Tumour volume was significantly reduced only in the group that received the triple therapy. The volume density of the tumour-feeding blood vessels was significantly reduced in the treated groups with the exception of the group that received octreotide and serotonin. Increased relative volume density of tumour necrotic tissue occurred only in the group treated with triple therapy. Apoptotic indices were significantly increased in all treated groups. No statistical difference was found between treated animals and controls regarding proliferation indices, food consumption, faeces weight and water content or animal weight. In conclusion, double therapy using two of the gastrointestinal bioactive substances, octreotide, galanin and serotonin, has certain effects on colon cancer cells. To cause a considerable tumour necrosis, triple therapy seems to be required. Both double and triple therapy seem to lack obvious side-effects.

Myenteric plexus in the gastrointestinal tract of non-obese diabetic mice.

The myenteric plexus was investigated in the gastrointestinal tract of pre-diabetic and diabetic non-obese diabetic (NOD) mice. The plexus was immunostained by the avidin-biotin complex method, using a general marker for nerve elements, namely protein gene-product 9.5. The nerve fibres were quantified by point-counting and the number of ganglia and their area were determined by image analysis. The relative volume density of the nerve fibres in duodenal muscularis propria was found to be significantly reduced in of both pre-diabetic and diabetic NOD mice. There was no statistical difference between controls and NOD mice regarding relative volume density of nerve fibres in antral and colonic muscularis propria. The number of myenteric ganglia/mm baseline was significantly decreased in the duodenum of diabetic NOD mice, and showed a non-statistically significant tendency to decrease in pre-diabetic mice. In the antrum and colon, there was no difference between the controls and NOD mice regarding the number of ganglia/mm baseline. Nor was there any significant difference between controls and NOD mice in the area of myenteric ganglia in either antrum, duodenum or colon. It is concluded that the changes in the duodenal myenteric plexus of NOD mice are prior to the onset of diabetes. It is suggested that the absence of changes in the antral and colonic myenteric plexus when using a general marker for neuroelements does not preclude a possible change in cholinergic, adrenergic or peptidergic innervation.

Duodenal endocrine cells in mice with particular regard to age-induced changes.

Duodenal endocrine cell types in four age groups of NMRI mice (1, 3, 12 and 24 months old) were identified by immunocytochemistry and quantified by computerized image analysis. Whereas the number of secretin-immunoreactive cells was significantly increased in the 24-month-old group, the number of GIP-immunoreactive cells was reduced in 12-month-old compared with 3-month-old mice. The number of somatostatin-immunoreactive cells was fewer in both the 12- and 24-month-olds vis-à-vis the 3-month-old mice. Whereas serotonin-immunoreactive cells were fewer in both 1-month-old and 12-month-old mice, they were more numerous in 24-month-old mice then in the 3-month-old ones. The number of gastrin/CCK-immunoreactive cells was unaffected by age. The cell secretory index (CSI) of secretin- and serotonin-immunoreactive cells was increased in the 24-month-old mice vis-à-vis the 3-month-old ones and the CSI of GIP- and somatostatin-immunoreactive cells was increased in 12-month-old mice vis-à-vis 3-month-old mice. In contrast, the CSI of somatostatin- and serotonin-immunoreactive cells in 1-month-old mice was lower than that of 3-month-old-mice. The nuclear volume of secretin-, GIP-, gastrin/CCK- and serotonin-immunoreactive cells was less in 1-month-olds than in 3-month-old mice. Whereas the nuclear volume of somatostatin-immunoreactive cells was decreased in 12-month-old animals, that of gastrin/CCK- and serotonin-immunoreactive cells was greater in 24-month-old mice than in 3-month-old ones. It is concluded that these changes may be secondary to structural and functional changes in the gastrointestinal tract caused by ageing. It is possible that these changes are involved in the development of dysfunction of the gut observed at advanced age.

Myenteric plexus of obese diabetic mice (an animal model of human type 2 diabetes).

The myenteric plexus of the gastrointestinal tract was investigated in the obese diabetic mouse, an animal model of human type 2 diabetes. Sections were immunostained by the avidin-biotin complex method, using a general nerve marker, protein gene product 9.5 (PGP 9.5), as well as antibodies to several important neurotransmitters. Computerized image analysis was used for quantification. When diabetic mice were compared with controls, no difference was found in the density of PGP 9.5-immunoreactive (IR) nerve fibres in antrum, duodenum or colon. In antrum and duodenum, diabetic mice showed a decreased number of vasoactive intestinal peptide (VIP)-IR neurons in myenteric ganglia as well a decreased relative volume density in myenteric plexus (though not significantly in antrum, p=0.073). No difference was found regarding VIP-IR nerves in colon. The volume density of nitric oxide synthase (NOS)-IR nerve fibres was decreased in antrum and duodenum of diabetic mice, whereas no difference was found in colon. The density of galanin-IR nerve fibres was decreased in duodenum. Whereas neuropeptide Y (NPY)- and vesicular acetylcholine transporter (VAChT)-IR nerve fibres was increased in density in colon of diabetic mice, no difference was found in antrum and duodenum. Regarding substance P, there was no difference between diabetic and control mice in antrum, duodenum or colon. The present study shows that gut innervation is affected in this animal model of human type 2 diabetes. It is possible that the present findings may have some relevance for the gastrointestinal dysfunctions seen in patients with type 2 diabetes.

Colonic endocrine cells in rats with chemically induced colon carcinoma.

Colonic carcinoma was induced in male Sprague-Dawley rats by injecting them with 1,2-dimethylhydrazine dihydrochloride. Control rats were injected with EDTA solution. Tissue specimens of colon from four groups of animals: (i) rats without tumour, (ii) with dysplasia and lymphoid hyperplasia, (iii) with colonic adenocarcinoma, and (iv) controls, were investigated. The colonic endocrine cells were detected by immunocytochemistry and quantified by computerised image analysis. Peptide YY (PYY)- and serotonin-immunoreactive cells were found in the colon of all the groups investigated. There were few somatostatin- or enteroglucagon-immunoreactive cells and no pancreatic polypeptide (PP)-immunoreactive cells in the colon of any of the groups studied. The density of PYY-immunoreactive cells increased significantly in rats with dysplasia and lymphoid hyperplasia and in rats with colon carcinoma. There was no statistically significant difference as regards cell secretory index (CSI) or nuclear area of PYY-immunoreactive cells in any of treated groups examined. Nor was there any statistically significant difference between all treated animal groups and controls, as regards cell density, CSI, or nuclear area of serotonin-immunoreactive cells. The present observations in an animal model of human colon carcinoma support the assumption that neuroendocrine peptides in the gut are involved in the carcinogenesis of colorectal carcinoma. However, The nature of the changes in the colonic endocrine cells observed here differed from those in patients with colon carcinoma, possibly due to a difference between the response of young rats to an induced colon carcinoma and a spontaneously developed carcinoma in elderly humans, or due to a species difference.