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Biomedical subjects

A B Thomson

Publications and source records attributed to A B Thomson.

At least 73 records · Page 4Linked to original sources
PubMed1997

Inhibition of lipid absorption as an approach to the treatment of obesity.

A reduction in fat intake may be achieved by making educated choices to reduce total calorie intake, to consume a lower quantity of total fats, or to modify the ratio of saturated-to-polyunsaturated lipids. Leptin agonists or NPY or CCK antagonists may prove to be useful to diminish appetite and thereby reduce the total intake of food. But eating has such cultural, social, and hedonistic attributes that such a single-pronged approach is unlikely to be successful. The use of fat substitutes may prove to be popular to provide a wide range of snack food options, but these are likely to be of minimal use in weight reduction programs because of their distribution of additives in only a limited number of foods. The inhibitors of lipid digestion will be modestly successful in the short term; their long-term success will be influenced by gastrointestinal adverse effects and the need to consume fat-soluble vitamin supplements to prevent the development of fat-soluble vitamin deficiencies. The inhibition of lipid absorption is an attractive targeted approach for the treatment of obesity, since this would reduce the uptake of visible as well as invisible fats, which would potentially offer convenient dosing, and could also be a means to inhibit secondarily the uptake of carbohydrate calories.

Animals↗
PubMed1997

Adaptation of intestinal nutrient transport in health and disease. Part I.

Why is it important to understand the mechanisms controlling intestinal adaptation? There are two major answers to this question. Firstly, in establishing the cellular and molecular events associated with intestinal adaptation, we will formulate a general framework that may be applied to the understanding of adaptation of other cell membranes. For example, alterations in the synthesis of glucose carriers and their subsequent insertion into membranes may alter sugar entry across the intestinal brush border membrane (BBM) using the sodium-dependent D-glucose transporter, SGLT1, or the BBM sodium-independent facultative fructose transporter, GLUT5, and may alter facilitated sugar exit across the basolateral membrane (BLM) using GLUT2. The precise role of transcriptional and translational processes in the up- or down-regulation of sugar transport requires further definition. Alterations in enterocyte microsomal lipid metabolic enzyme expression occurring during the course of intestinal adaptation will direct the synthesis of lipids destined for trafficking to the BBM and BLM domains of the enterocyte. This will subsequently alter the passive permeability properties of these membranes and ultimately influence lipid absorption. Therefore, establishing the physiological, cellular and molecular mechanisms of adaptation in the intestine will define principles that may be applied to other epithelia. Secondly, enterocyte membrane adaptation is subject to dietary modification, and these may be exploited as a means to enhance a beneficial or to reduce a detrimental aspect of the intestinal adaptive process in disease states. Alterations in membrane function occur in association with changes in dietary lipids, and these are observed in a variety of cells and tissues including lymphocytes, testes, liver, adipocytes, nerve tissue, nuclear envelope and mitochondria. Therefore, the elucidation of the mechanisms of intestinal adaptation and the manner whereby dietary manipulation modulates these processes affords the future possibility of dietary engineering aimed at using food as a therapeutic agent. It is hoped this approach will form the centerpiece for future investigation that would focus on disease prevention, as well as on the development of better therapeutic strategies to prevent the development or to treat the complications of conditions such as diabetes mellitus, obesity, hyperlipidemia and inflammatory bowel diseases. This review deals with the physiology of glucose transport with specific emphasis on transporters of the brush border membrane (BBM) and the basolateral membrane (BLM). On the BBM the sodium (Na)/glucose transporters (SGLT1 and SGLT2), the Na-independent transporter (GLUT5), and on the BLM the hexose transporter (GLUT2) are discussed. The molecular biology of these transporters is also reviewed.

Adaptation, Physiological↗
PubMed1997

Adaptation of intestinal nutrient transport in health and disease. Part II.

The first part of this review dealt with the physiology of glucose transport with specific emphasis on transporters of the brush border membrane (BBM) and the basolateral membrane (BLM). On the BBM, the sodium (Na)/glucose transporters (SGLT1 and SGLT2), the Na-independent transporter (GLUT5) and on the BLM the hexose transporter (GLUT2) are discussed. The molecular biology of these transporters is also reviewed. In the second part of the review, we discuss the manner in which intestinal adaptation may be modified by alterations in the diet, especially the lipid constituents, and two important examples of intestinal adaptation will be given: diabetes mellitus and inflammatory bowel disease.

Adaptation, Physiological↗
PubMed1997

Short-chain fatty acid-supplemented total parenteral nutrition enhances functional adaptation to intestinal resection in rats.

BACKGROUND & AIMS: Intestinal adaptation is a complex physiological process that is not completely understood. Total parenteral nutrition (TPN) induces intestinal atrophy that is prevented by the systemic administration of short-chain fatty acids (SCFAs) as measured by morphological indices (i.e., mucosal weight and mucosal DNA, RNA, and protein concentration). The aim of this study was to examine the effect of SCFA-supplemented TPN on functional markers of intestinal adaptation. METHODS: Forty-eight male Sprague-Dawley rats underwent an 80% jejunoileal resection and jugular catheterization. Rats received standard TPN or an isoenergetic, isonitrogenous TPN supplemented with SCFA (TPN + SCFA). Animals were further randomized to receive nutrient solutions for 3 or 7 days. RESULTS: Ileal uptakes of D-glucose were higher (P < 0.05) in both TPN + SCFA groups. Expression of glucose transporter (GLUT)2 messenger RNA (mRNA) was higher (P < 0.007) in the TPN + SCFA group at day 3. Expression of sodium-dependent glucose transporter 1 tended to be higher in both TPN + SCFA groups (P = 0.1). Na+,K+-adenosine triphosphatase mRNA was significantly more abundant in the TPN groups. GLUT5 and sucrase-isomaltase mRNA abundance did not differ between groups. CONCLUSIONS: Intravenous SCFAs facilitate intestinal adaptation after resection by increasing basolateral intestinal nutrient transport. The addition of SCFAs to current TPN formulations may be warranted to improve functional characteristics of the gastrointestinal tract.

Adaptation, Physiological↗
PubMed1997

A physiological level of rhubarb fiber increases proglucagon gene expression and modulates intestinal glucose uptake in rats.

Previous work demonstrated that a high fiber diet upregulates proglucagon mRNA and secretion of glucagon-like peptide-1 [GLP-1(7-37)] and insulin compared with an elemental fiber-free diet. This study examined whether similar intakes of fibers differing in physiochemical and fermentative properties alter the expression of intestinal hormones and intestinal absorptive properties. Sprague-Dawley rats were fed either a 50 g/kg cellulose or rhubarb fiber diet for 14 d. Ileal proglucagon mRNA levels were significantly higher in rats fed rhubarb fiber than in those fed cellulose fiber (9.3 +/- 0.9 vs. 6.2 +/- 1.0 densitometer units). Proglucagon mRNA in the colon did not differ between diet treatments. Plasma c-peptide concentrations were significantly higher 30 min after an oral glucose tolerance test in the rhubarb vs. cellulose group (1627 +/- 67 vs. 1290 +/- 71 pmol/L). Passive permeability, measured by the uptake of L-glucose, was significantly higher in the jejunum of rats fed cellulose compared with those fed rhubarb fiber. Adjusting total glucose uptake for passive permeability and unstirred water layer resistance resulted in a higher Km being calculated for the jejunum and ileum of the cellulose fiber group. Jejunal and ileal carrier-mediated uptakes (Vmax) were not altered by diet and reflected the lack of difference between groups in sodium-dependent glucose cotransporter (SGLT-1) and sodium-independent glucose transporter (GLUT2) mRNA levels. Replacing cellulose fiber with rhubarb fiber in a diet upregulated ileal proglucagon mRNA and resulted in a reduced passive permeability but did not affect glucose transport of the small intestine. This work establishes the importance of dietary fiber fermentability in modulating intestinal proglucagon expression and possibly glucose homeostasis.

Animals↗
PubMed1997

Nutrient uptake into undifferentiated and differentiated HT-29 cells in culture.

HT-29 human colon carcinoma cells in culture have many characteristics of enterocytes, and these cells have been used by others to study intestinal drug and nutrient transport and metabolism. When grown in glucose-containing medium, HT-29 cells are largely undifferentiated (HT-29glu), but when grown in the absence of glucose but in the presence of galactose (HT-29gal), the population of cells is mostly differentiated. This study was undertaken with HT-29glu and HT-29gal cells to study the uptake of palmitic acid (16:0), linoleic acid (18:2), and cholesterol. The relationship between concentration and uptake of 16:0, 18:2, and cholesterol was linear in HT-29glu and HT-29gal cells, with the relative values of the slopes of this relationship being 18:2 > > 16:0 > > cholesterol. The rates of uptake of these lipids were at least three times higher in HT-29gal than in HT-29glu cells. In HT-29glu cells, the relative rates of uptake of the sugars at 32 mM were D-glucose = galactose > fructose > > alpha-methylglucose. Uptake of these sugars was much greater in HT-29gal than in HT-29glu cells. When 100 microM forskolin was added to the incubation medium for 7 days post-confluency, which stimulates the activity of adenylate cyclase and thereby increases the intracellular synthesis of cAMP, there was no effect on the uptake of the lipids or the sugars in either HT-29glu or HT-29gal cells. Thus, (i) differentiated HT-29gal cells transport larger amounts of lipids and sugars than do undifferentiated HT-29glu cells; (ii) forskolin has no effect on the uptake of lipids or sugars in these cells. This human cell culture system may be useful to study the in vitro transport of lipids, to establish the role of cell differentiation on these uptake processes, and to determine the potential role of selected intracellular signals.

Absorption↗
PubMed1997

Ontogeny of intestinal adaptation in rats in response to isocaloric changes in dietary lipids.

Alterations in dietary lipids of the nursing mother result in variations in the lipid content of her milk. Maternal rats, weanlings, and 10-wk-old animals were fed chow or a semisynthetic isocaloric diet enriched with either saturated fatty acids (S) or polyunsaturated fatty acids (P). The jejunal and ileal in vitro uptake of varying concentrations (4-64 mM) of D-glucose and D-fructose or single concentrations of medium- and long-chain fatty acids and cholesterol were assessed in 18- to 21-day-old suckling rats, in 5-wk-old weanling animals, and in 12-wk-old young adults. The rate of uptake of D-glucose and D-fructose was unaffected in suckling rats by changing the lipid content of the diet of the nursing dams, whereas sugar uptake was greater in weanlings or adults fed S compared with P. The jejunal uptake of long-chain fatty acids was not influenced in suckling by changing the mother's diet, whereas in weanlings the uptake of 18:0 and 18:3 was higher with feeding S vs. P. In summary, jejunal uptake of cholesterol was greater in sucklings than in weanlings fed S vs. P. In suckling animals there are different adaptive patterns between the jejunum and the ileum and varying patterns of adaptation in response to alterations in the lipids in the diet when comparing suckling vs. weanling rats. These differences in nutrient uptake could not be explained by age- or diet-associated alterations in villus height. It is concluded that the age of the rat influences the intestinal adaptation of nutrient transport, which occurs in response to changes in dietary lipids, and dietary lipids fed to nursing dams and their offspring are important in the development of the intestine.

Animals↗
PubMed1997

Small bowel review: Part I.

Significant advances have been made in the study of the small bowel. Part I of this two-part review of the small bowel examines carbohydrates, including brush border membrane hydrolysis and sugar transport; amino acids, dipeptides, proteins and food allergy, with a focus on glutamine, peptides and macromolecules, and nucleosides, nucleotides and polyamines; salt and water absorption, and diarrhea, including antidiarrheal therapy and oral rehydration treatment; lipids (digestion and absorption, fatty acid binding proteins, intracellular metabolism, lipoproteins and bile acids); and metals (eg, iron) and vitamins.

Animals↗
PubMed1997

Budesonide in the management of patients with Crohn's disease.

Modern medical therapy is increasingly based on evidence. The evidence presented here is that budesonide (Entocort, Astra Pharma) 9 mg/day is superior to placebo and equivalent to systemically active glucocorticosteroids in achieving disease remission in patients with active Crohn's disease, and in prolonging the recurrence time of symptomatic disease. Budesonide causes less disturbance to adrenal function than prednisone or prednisolone and may cause fewer steroid-associated symptoms. Thus, budesonide is the safer, more effective steroid of choice to treat patients with Crohn's disease.

Anti-Inflammatory Agents↗
PubMed1997

A suggested approach to patients with dyspepsia.

A comprehensive review of dyspepsia is presented. Topics include causes of dyspepsia, prevalence, causes of symptoms (motility abnormalities, visceral hypersensitivity, psychosocial aspects, role of Helicobacter pylori), investigations of patients with dyspepsia and, finally, whether there is effective treatment.

Diagnosis, Differential↗
PubMed1997

Endoscopists' opinions of indications for upper gastrointestinal endoscopy.

OBJECTIVE: To determine whether endoscopists and general internists agreed with the characterization of appropriateness for endoscopy of various clinical scenarios, as previously reported by the RAND Corporation. DESIGN: Mail survey. STUDY SAMPLE: All endoscopists in western Canada and a random sample of general internists who did not perform endoscopy. METHODS: Questionnaires were sent to 179 endoscopists in western Canada who were asked to rate the 53 scenarios for endoscopy on a nine-point scale ranging from most appropriate to most inappropriate. A similar questionnaire was sent to 39 general internists practising in the province of Alberta. RESULTS: Response rate was 72% of endoscopists (n = 128) and 64% of general internists (n = 25). Among the endoscopists, there was agreement with the RAND classification for 32 scenarios. All 18 indications previously thought to be appropriate were considered to be appropriate. However, endoscopists agreed with only six of 16 equivocal and eight of 19 indications considered inappropriate. Discrepancies were reviewed by five experienced endoscopists and most appeared to be related to a concern regarding possible malignancy linked in part with the definition of failure to respond to medical therapy; and to a refusal to request a barium meal before endoscopy. Among general internists, there was agreement with RAND in 26 scenarios. When the appropriateness rankings of endoscopists and general internists were compared, there was agreement in 40 of 53 scenarios. Significant discrepancies in ratings were identified in scenarios in which barium studies were described as being normal, known or not done. CONCLUSIONS: The equivocal and inappropriate ratings developed by the RAND Corporation are not uniformly accepted by the endoscopy community or general internists. Use of the RAND indications for assessing quality assurance can be challenged.

Adult↗
PubMed1997

A double-blind randomized study of cisapride in the treatment of nonulcer dyspepsia. The Canadian Cisapride Nud Study Group.

Cisapride is a substituted benzamide with gastrointestinal prokinetic effects presumed to be due to the enhancement of the physiological release of acetylcholine at the myenteric plexus. In a multicentre study, 189 patients with nonulcer dyspepsia (NUD) received single-blind placebo treatment for two weeks. A total of 123 patients with no or minimal response to placebo and epigastric pain of at least moderate severity and frequency were randomly assigned to one of the three parallel double-blind treatments for six weeks: cisapride 10 mg tid, cisapride 20 mg tid or placebo. The severity and frequency of individual symptoms (epigastric pain, heartburn, nausea, vomiting anorexia, postprandial discomfort, regurgitation, lower abdominal pain, bloating and constipation) were assessed on a four- and five-point categorical scale, respectively, by the investigator at three on treatment visits and by patients in a daily diary. Analysis of investigator and patient assessments for differences in symptom severity x frequency composite scores among the three treatment groups showed no statistically significant differences for individual symptoms or symptom clusters. As assessed by the investigator, and compared with baseline, cisapride 20 mg tid significantly (P < 0.05) improved epigastric pain, bloating and early satiety as well as improved the total symptom cluster. Investigator evaluation of the five most severe and frequent symptoms for each patient showed statistically significant improvement in each treatment group. For patient diary assessments, statistically significant within-treatment improvement of the total symptom cluster, the five most severe symptoms cluster, bloating and early satiety was observed for both cisapride 20 mg and placebo, whereas epigastric pain significantly (P < 0.05) improved in all three treatment groups. Investigator evaluation of global response (good+excellent) rate at the end of the six week treatment period was 38% for cisapride 20 mg, 47% for cisapride 10 mg and 33% for placebo. No statistically significant difference in this parameter among treatments was noted. Cisapride was well tolerated at both doses with a side effect profile comparable with that of placebo. It is concluded that in this double-blind multicentre study with a single-blind two-week placebo run in phase, cisapride 10 mg tid and 20 mg tid were not effective compared with placebo in improving symptoms in NUD patients. This study re-emphasizes the good prognosis of patients with NUD, with 14% of patients improving in the two-week placebo run-in phase and a further 33% improving in the next six weeks while on placebo. Within-treatment analysis of investigator assessments showed improvement for cisapride 20 mg tid suggesting a trend of efficacy at this dose.

Administration, Oral↗
PubMed1997

Small bowel review: Part II.

Significant advances have been made in the study of the small bowel. Part II of this two-part review of the small bowel examines the early development and later ageing of the small bowel; the effect of diabetes, alcohol, radiation and HIV on the small bowel; enteral and parenteral nutrition; the brush border membrane and enterocyte proliferation; and peptide hormones (including transforming growth factors, motilin peptide YY and cholecystokinin).

Aging↗
PubMed1997

Small bowel review--Part II.

The small bowel has undergone intense study. Part II of this review of the small bowel summarizes the current knowledge about the permeability of the gastrointestinal epithelium, the brush border membrane, motility, carbohydrates, diabetes, ethanol, diet, and diagnostic procedures.

Carbohydrate Metabolism↗
PubMed1997

Helicobacter pylori: from bench to bedside.

With the exponential increase in research in the field of Helicobacter pylori a paradigm shift has occurred. It is now recognized that H pylori is a chronic infection of the stomach causing inflammation. Some patients remain asymptomatic, while others may develop dyspepsia, duodenal or gastric ulcer, gastric cancer or a mucosa-associated lymphoid tissue lymphoma. However, the role of H pylori in contributing to nonulcer dyspepsia or nonsteroidal anti-inflammatory drug gastropathy remains controversial. An effective vaccine against H pylori is years away. Major interest has focused on the questions "who should be investigated and therefore treated" and "what is the latest gold standard for eradication of H pylori"? In Europe, guidelines have been developed to help the practitioner answer these important questions. Canadian guidelines will soon be available. For persons with known peptic ulcer disease there should be unequivocal acceptance that the good clinical practice of eradicating H pylori will result in substantial savings in health care expenses. The original 'classical triple therapy' (bismuth, metronidazole and tetracycline [BMT]) has now been surpassed by the combination of a proton pump inhibitor (PPI) plus two antibiotics (metronidazole plus clarithromycin; amoxicillin plus clarithromycin; or amoxicillin plus metronidazole), each given twice a day for one week. In Canada, the regimen of omeprazole plus one antibiotic (amoxicillin or clarithromycin) was approved recently but gives an eradication rate that is lower than the current target of 90%. According to the European (Mäastricht) recommendations, if a single treatment attempt with PPI plus two antibiotics fails, PPI plus BMT is recommended.

Antacids↗
PubMed1997

A high cholesterol diet blocks the effect of calcium channel blockers on the uptake of sugars in rabbit intestine.

Two classes of calcium channel blockers, nisoldipine (NIS) and verapamil (VER), alter the intestinal uptake of sugars, and varying the lipid composition of the diet also modifies intestinal transport function. This study was undertaken in adult male New Zealand rabbits to assess the effect of 3 weeks of dosing with NIS (1 mg.kg-1.day-1) or VER (4 mg.kg-1.day-1) on the in vitro jejunal uptake of D-galactose and L- or D-glucose. The value of the maximal transport rate of D-galactose (Vmax) increased with NIS and VER, compared with control vehicle. The value of the apparent Michaelis constant (K(m)) rose with NIS and fell with VER, and the value of the passive permeability coefficient (Pd) estimated from the uptake of L-glucose fell with NIS and rose with VER. These effects of NIS and VER on Vmax, K(m), and Pd were prevented by feeding a high cholesterol (2.8%) supplemented chow diet (HCD), as compared with chow alone. These effects were not due to any change in the animal's weight gain or intestinal mucosal surface area. The acute exposure of the jejunal tissue in vitro to varying concentrations of NIS but not VER reduced the uptake of D-glucose but had no effect on basal short circuit current (Isc) in either chow or HCD. Isc stimulated with glucose or theophylline was less in chow-fed rabbits compared with HCD-fed rabbits given NIS or VER. Thus, the active transport of sugars by the sodium-dependent transporter in the brush-border membrane, SGLT1, and the passive uptake by the paracellular route are variably influenced by these two classes of calcium channel blockers, and this effect is modified by the cholesterol content of the diet.

Animals↗
PubMed1997

The Second Canadian Consensus Conference on the Management of Patients with Gastroesophageal Reflux Disease.

The Second Canadian Consensus Conference on the Management of Patients with Gastroesophageal Reflux Disease (GERD) was organized by the Canadian Association of Gastroenterology to address major advances in the understanding of the pathophysiology of GERD, to review the new methods of investigation and therapy introduced since the first conference in 1992 and to examine the issue of relevant health economics. The changes that have taken place over the past four years have been sufficiently dramatic to necessitate reassessment of the recommendations made following the first conference. The second conference dealt with the investigation and treatment of uncomplicated GERD and the complex issues of esophageal and extraesophageal complications such as chest pain, Barrett's esophagus, and reflux-related pulmonary and laryngeal disorders. The role of laparoscopic surgery was also discussed. A decision tree for investigation and treatment of patients with GERD was developed. The 38 participants represented a broad spectrum of experience, location of practice and special interests. The distribution of participants conformed to the recommendations of the Canadian Medical Association guidelines for consensus documents in that there should be input from all possible interested parties. A list of the state-of-the-art lectures presented during the conference, the small group sessions, the session chairpersons and participants are appended to this document. CONCLUSIONS. UNCOMPLICATED GERD: GERD with alarm symptoms must be investigated immediately. There was no consensus about when to investigate uncomplicated GERD, ie, whether to perform endoscopy immediately or after initial therapy fails. There was controversy regarding 'step up' (H2 receptor antagonist [H2RA] or prokinetic [PK] first therapy) versus 'step down' therapy (proton pump inhibitor [PPI] first therapy). The majority decision was for short term 'step up' therapy and investigation if symptoms do not improve or recur. Maintenance therapy should be carried out with the initial therapy that was effective. H2RAs and PKs may suffice for maintenance therapy in milder GERD; however, for severe esophagitis, PPIs should be used. SURGERY: Indications for laparoscopic surgery should be the same as for conventional antireflux operations. NONCARDIAC ANGINA-LIKE CHEST PAIN: After exclusion of nonesophageal causes, the majority decided that eight weeks of therapy with a PPI should be performed, while some suggested work-up before a therapeutic test. In the absence of response or recurrence, esophagogastroduodenoscopy (EGD) and, depending on the circumstances, 24 h ambulatory pH/motility may be indicated. BARRETT'S ESOPHAGUS: Only patients who, in case of future discovery of cancer or dysplasia, are able or willing to undergo therapy should have surveillance. In the absence of dysplasia EGD should be performed every two years, and in the presence of mild dysplasia every three to six months. All agreed that for severe dysplasia, esophagectomy or poor risk patients, esophageal mucosal ablation is indicated. ESTRAESOPHAGEAL COMPLICATONS (EECs): Asthma, chronic cough and posterior laryngitis were considered EECs. Although PPIs may decrease symptoms, improvement alone is not diagnostic of the presence of EEC. Ambulatory pH studies with two pH probes or ambulatory pH/motility may be useful in establishing causation. HEALTH ECONOMICS: There are limited data for an economic comparison among the different drugs or between medical and surgical therapy.

Canada↗