Role of fasting gastrointestinal motility in the variability of gastrointestinal transit time assessed by hydrogen breath test

Macrophage regulation of the "second brain": CD163 intestinal macrophages interact with inhibitory interneurons to regulate colonic motility - evidence from the Cx3cr1-Dtr rat model

Intestinal macrophages are well-studied for their conventional roles in the immune response against pathogens and protecting the gut from chronic inflammation. However, these macrophages may also have additional functional roles in gastrointestinal motility under typical conditions. This is likely to occur via both direct and indirect influences on gastrointestinal motility through interaction with myenteric neurons that contribute to the gut-brain axis, but this mechanism is yet to be properly characterised. The CX3CR1 chemokine receptor is expressed in the majority of intestinal macrophages, so we used a conditional knockout Cx3cr1-Dtr (diphtheria toxin receptor) rat model to transiently ablate these cells. We then utilized ex vivo video imaging to evaluate colonic motility. Our previous studies in brain suggested that Cx3cr1-expressing cells repopulate by 7 days after depletion in this model, so we performed our experiments at both the 48 hr (macrophage depletion) and 7-day (macrophage repopulation) time points. We also investigated whether inhibitory neuronal input driven by nitric oxide from the enteric nervous system is required for the regulation of colonic motility by intestinal macrophages. Our results demonstrated that CD163-positive resident intestinal macrophages are important in regulating colonic motility in the absence of this major inhibitory neuronal input. In addition, we show that intestinal macrophages are indispensable in maintaining a healthy intestinal structure. Our study provides a novel understanding of the interplay between the enteric nervous system and intestinal macrophages in colonic motility. We highlight intestinal macrophages as a potential therapeutic target for gastrointestinal motility disorders when inhibitory neuronal input is suppressed.

Numerical simulation of peristalsis to study co-localization and intestinal distribution of a macromolecular drug and permeation enhancer

In this work, simulations of intestinal peristalsis are performed to investigate the intraluminal transport of macromolecules (MMs) and permeation enhancers (PEs). Properties of insulin and sodium caprate (C₁₀) are used to represent the general class of MM and PE molecules. Nuclear magnetic resonance spectroscopy was used to obtain the diffusivity of C₁₀, and coarse-grain molecular dynamics simulations were carried out to estimate the concentration-dependent diffusivity of C₁₀. A segment of the small intestine with the length of 29.75 cm was modeled. Peristaltic speed, pocket size, release location, and occlusion ratio of the peristaltic wave were varied to study the effect on drug transport. It was observed that the maximum concentration at the epithelial surface for the PE and the MM increased by 397 % and 380 %, respectively, when the peristaltic wave speed was decreased from 1.5 to 0.5 cm s^-1. At this wave speed, physiologically relevant concentrations of PE were found at the epithelial surface. However, when the occlusion ratio is increased from 0.3 to 0.7, the concentration approaches zero. These results suggest that a slower-moving and more contracted peristaltic wave leads to higher efficiency in transporting mass to the epithelial wall during the peristalsis phases of the migrating motor complex.

European guideline on indications, performance, and clinical impact of hydrogen and methane breath tests in adult and pediatric patients: European Association for Gastroenterology, Endoscopy and Nutrition, European Society of Neurogastroenterology and Motility, and European Society for Paediatric Gastroenterology Hepatology and Nutrition consensus

INTRODUCTION

Measurement of breath hydrogen (H2 ) and methane (CH4 ) excretion after ingestion of test-carbohydrates is used for different diagnostic purposes. There is a lack of standardization among centers performing these tests and this, together with recent technical developments and evidence from clinical studies, highlight the need for a European guideline.

METHODS

This consensus-based clinical practice guideline defines the clinical indications, performance, and interpretation of H2 -CH4 -breath tests in adult and pediatric patients. A balance between scientific evidence and clinical experience was achieved by a Delphi consensus that involved 44 experts from 18 European countries. Eighty eight statements and recommendations were drafted based on a review of the literature. Consensus (≥80% agreement) was reached for 82. Quality of evidence was evaluated using validated criteria.

RESULTS

The guideline incorporates new insights into the role of symptom assessment to diagnose carbohydrate (e.g., lactose) intolerances and recommends that breath tests for carbohydrate malabsorption require additional validated concurrent symptom evaluation to establish carbohydrate intolerance. Regarding the use of breath tests for the evaluation of oro-cecal transit time and suspected small bowel bacterial overgrowth, this guideline highlights confounding factors associated with the interpretation of H2 -CH4 -breath tests in these indications and recommends approaches to mitigate these issues.

CONCLUSION

This clinical practice guideline should facilitate pan-European harmonization of diagnostic approaches to symptoms and disorders, which are very common in specialist and primary care gastroenterology practice, both in adult and pediatric patients. In addition, it identifies areas of future research needs to clarify diagnostic and therapeutic approaches.

Effects of fasting on hematologic and clinical chemical values in cynomolgus monkeys (Macaca fascicularis)

BACKGROUND

Fasting is an important pre-analytical factor that may affect clinical pathology parameters in toxicological and pharmacological studies. Little information is available on how fasting affects clinical pathology parameters in cynomolgus monkeys (Macaca fascicularis).The aim of this study was to evaluate the influence of fasting on clinical pathology parameters in healthy adult cynomolgus monkeys.

METHODS

Five female and six male cynomolgus monkeys were fasted for 0, 8, 16, and 24 hours. Changes in body weight (BW), core hematologic, and serum clinical chemical parameters were evaluated.

RESULTS

The BW significantly decreased after 24 hours of fasting. Significant decreases in red blood cell count, hemoglobin, hematocrit, and mean corpuscular volume and increases in mean cell hemoglobin and mean cell hemoglobin concentration were observed at 16 hours in males. In females, increasing the duration of fasting caused a significant time-dependent increase in platelets. Blood urea nitrogen showed significant decreases in female and male monkeys after fasting. Alkaline phosphatase increased in females after fasting. Aspartate transaminase significantly increased both in females and males at 8 hours. In females, alanine transaminase and lactate dehydrogenase significantly increased at 8 hours. Albumin significantly decreased in males 24 hours, but increased in females 16 hours after fasting. Serum glucose and triglyceride were not affected by fasting. Serum calcium decreased and inorganic phosphorus increased in males after fasting.

CONCLUSION

These results suggested that clinical pathology data would vary after fasting. The decision to feed or fast before blood collection for clinical pathology tests should be made based on careful consideration.

The pathogenesis of gastrointestinal bacterial overgrowth

The normal indigenous intestinal microflora consists of about 10(15) bacteria that under physiological conditions reside mainly in the lower gastrointestinal tract. Bacterial overgrowth implies abnormal bacterial colonization of the upper gut, resulting from failure of specific defense mechanisms restricting colonization under physiological conditions. At present two types of bacterial overgrowth with defined pathogenesis can be distinguished: (1) gastric overgrowth with upper respiratory tract microflora resulting from selective failure of the gastric acid barrier, and (2) gastrointestinal overgrowth with Gram-negative bacilli (enteric bacteria) resulting from failure of intestinal clearance. Helicobacter pylori-induced gastritis of the oxyntic mucosa is the main cause of acquired failure of the gastric acid barrier, which is common among the healthy elderly. Intestinal clearance may fail as the result of impaired intestinal peristalsis or anatomical abnormalities that alter luminal flow. Impaired peristalsis is associated with conditions interfering with intestinal neuromuscular function including myopathic, neuropathic, autoimmune, infectious, inflammatory, metabolic, endocrine, and neoplastic diseases. Anatomical abnormalities are mainly the result of gastrointestinal surgery, intestinal diverticula or fistula. Combined failure of intestinal clearance and the gastric acid barrier results in more severe colonization with Gram-negative bacilli. Gram-negative bacilli are uncommon in the upper gut of otherwise healthy individuals with gastric hypochlorhydria, being acquired (H. pylori) or drug-induced. Significant bacterial overgrowth with Gram-negative bacilli is a rational in the search for an explanation to optimize clinical management. The clinical significance of colonization with upper respiratory tract microflora remains unclear. Translocation of live bacteria, their metabolic products, or antigens from a small bowel colonized by Gram-negative bacilli play a role in the pathogenesis of spontaneous bacterial peritonitis in hepatic disease and in certain types of sepsis, indicating that further studies can point to new patient populations with potential benefit from medical treatment.

Diminished efficacy of colonic adaptation to lactulose occurs in patients with inflammatory bowel disease in remission

Lactulose has been proposed to be beneficial in treating inflammatory bowel disease (IBD). The hypothesis is based on the prebiotic potential of lactulose. A practical approach to testing its usefulness is to determine colonic adaptation to tolerable doses in patients with IBD. Our objective was to determine if a 3-week course of lactulose will decrease BH2 and symptoms in response to an acute lactulose challenge test in control subjects and IBD patients. The design was a prospective cohort study. Subjects were given a 30-g lactulose challenge test (test 1), and then ingested 10 g of lactulose twice a day for 3 weeks before being retested (Test 2). A third test was given after a further 5-week washout period. The main outcomes were the change in 4-hr sum of BH2 (sum(4HrBH2)) values obtained every 30 min, peak BH2, and 4-hr sum of symptom score (sum(4HrSS)) during the lactulose challenge test. In addition, we also report the change in self-reported symptoms and diarrhea during the 3-week administration of lactulose. In controls, sum(4HrBH2) decreased from test 1 (380.5 +/- 56.6 ppm) to test 2 (288.6 +/- 57.4 ppm) (P < 0.05), and returned toward test 1 levels by test 3 (307.5 +/- 53.1, P > 0.5). Unlike controls, the sum(4HrBH2) in patients failed to achieve significance between test 1 (444.5 +/- 55.8 ppm), test 2 (366.5 +/- 80.7 ppm, P > 0.2) or test 3 (411.6 +/- 62.5 ppm, P > 0.2). Sum(4HrSS) results in controls followed a pattern similar to sum(4HrBH2), achieving significance only in test 2 (P < 0.02). Symptoms during the intertest periods decreased by the third week in controls (P < 0.05), but not in patients (P > 0.5). Symptoms were lower in patients and varied insignificantly both in challenges and intertest periods. In conclusion, although controls adapt to a 3-week period of lactulose ingestion, IBD patients fail to meet the criteria for adaptation. However, longer studies may be needed to establish whether IBD patients are slower to adapt.

Orocecal transit time in patients with functional dyspepsia

BACKGROUND

The importance of intestinal dysmotility in functional dyspepsia is a controversial issue.

GOALS

To investigate the orocecal transit time in patients with functional dyspepsia, as well as a possible association between intestinal transit and the presence of anxiety or Helicobacter pylori infection in these patients.

STUDY

The participants in this study were 23 patients with dysmotility-like functional dyspepsia and 24 control subjects. Orocecal transit time was measured by the lactulose hydrogen breath test. The presence of anxiety was assessed by the Hospital Anxiety and Depression (HAD) scale.

RESULTS

No significant difference in orocecal transit times was found between patients (median, 55 minutes; 95% confidence interval [CI], 40-60 minutes) and control subjects (median, 50 minutes; 95% CI, 40-60 minutes; p = 1). In the assessment, 15 patients (73%) scored for anxiety on the HAD scale, and 15 patients (65%) had positive test results for H. pylori. There was no significant difference in orocecal transit times between the patients with (median, 55 minutes; 95% CI, 40-63 minutes) and those without H. pylori infection (50 minutes; 95% CI, 40-68 minutes; p = 0.85), or between the patients with (median, 45 minutes; 95% CI, 40-68 minutes) and those without (60 minutes; 95% CI, 40-63 minutes; p = 0.77) anxiety.

CONCLUSIONS

Orocecal transit time is within the normal range in patients with functional dyspepsia. Anxiety and H. pylori infection do not seem to influence orocecal transit time in these patients.

Duodenal vs. gastric administration of labeled leucine for the study of splanchnic metabolism in humans

Low-rate (6 ml/h) intragastric infusion of stable, isotope-labeled amino acids is commonly used to assess the splanchnic handling of amino acids in humans. However, when used in the postabsorptive state, this method yields unreliable plasma isotopic enrichments, with a coefficient of variation >10%. In this metabolic condition, we confirmed in six subjects that an intragastric infusion of L-[(2)H(3)]leucine at 6 ml/h yields an unreliable isotopic steady state in plasma amino acids with a coefficient of variation of 43 +/- 12% (mean +/- SD). In five additional subjects, we assessed the effects of 1) increasing the rate of delivery of a leucine tracer in an isotonic plasmalike solution at 240 ml/h into the gastric site, and 2) changing the site of infusion from gastric to duodenal with this same high rate of delivery. In contrast to the gastric route, and regardless of the rate of delivery, only the intraduodenal route allowed 1) isotopic plasma steady state (i.e., coefficients of variation were <10%: 5 +/- 3%), and 2) reproducible leucine extraction coefficients (22 +/- 5%). We conclude that an infusion site that bypasses the gastric emptying process, i.e., the duodenal route, along with delivery of a plasmalike solution, is necessary to reach isotopic steady state in plasma when labeled leucine is infused into the gastrointestinal tract in the postabsorptive state.

The patterns of small bowel motility: physiology and implications in organic disease and functional disorders

The physiology and pathophysiology of small bowel motility are reviewed with particular focus on the motility patterns and periods that are detected by intraluminal manometry. Motility patterns are groups of phasic pressure waves resulting from contractions of the circular muscle layer of the small bowel that are organized by the enteric nervous system. Phase III of the migrating motor complex, the hallmark of the fasting motility period, thus reflects enteric neuromuscular function. Response to meal challenge also involves the CNS, reflexes beyond the gut and endocrine responses. Although specific disease diagnosis cannot be made by motility studies of the small bowel, the functional integrity is revealed. The normal occurrence of the essential patterns and periods of motility and the absence of distinctly abnormal patterns evidence preserved function, whereas the opposite indicates clinically significant dysmotility. Certain motility patterns are occasionally seen both in health and disease, and increased prevalence indicates a moderate dysfunction of yet unclear significance. Bacterial overgrowth with Gram-negative bacilli is the consequence of severe small bowel dysmotility, and a diagnosis that can be predicted by a motility study. Testing can be useful in the clinical management of paediatric and adult patients also by predicting the prognosis and response to enteral nutrition and medical therapy. Further studies are, however, needed to take full advantage of motility testing in clinical practise.

Gastrointestinal sounds and migrating motor complex in fasted humans

OBJECTIVE

We investigated the relationships among gastrointestinal sounds, gastrointestinal manometric findings, and small intestinal transit time in healthy fasted humans.

METHODS

Gastrointestinal sounds acquired with two microphones attached to the upper and lower abdominal walls of healthy subjects were quantified with a computer-aided sound analysis program. Antroduodenal contractions were recorded by manometry. Small intestinal transit time was measured by breath hydrogen testing after intraduodenal administration of lactulose.

RESULTS

The sum of the gastrointestinal sound amplitudes (sound index) in both the upper and lower abdomen changed with time, coinciding with the gastric phases of the migrating motor complex. The sound indices in the upper and lower abdomen were 59.0+/-24.8 and 98.1+/-21.6 mV/min in phase 1, 95.5+/-27.9 and 127.4+/-34.9 mV/min in phase 2, and 132.8+/-12.4 and 188.5+/-73.4 mV/min in phase 3, respectively. There were no significant differences among motility phases in terms of the mean duration or frequency of each sound event. Intravenous erythromycin induced phase 3 in the stomach and doubled the sound index. Somatostatin analogue induced phase-3-like clustered contractions in the duodenum, but inhibited antral contractions and decreased the sound index. The small intestinal transit time was shorter and the sound index increased after intravenous metoclopramide, compared with controls. Scopolamine delayed small intestinal transit time and decreased the sound index.

CONCLUSIONS

This study is the first to document the relationships between gastrointestinal sounds and the migrating motor complex. The chronological relation between antral motility and gastrointestinal sounds, and the dissimilar effects of erythromycin and somatostatin, suggest that antral contractions increase gastrointestinal sounds, perhaps by supplying gas into the intestine.

Effects of medium-chain and long-chain triglycerides on antroduodenal motility and small bowel transit time in man

Medium-chain triglycerides are known to induce diarrhea, possibly resulting from accelerated intestinal transit. We performed antroduodenal manometry and lactulose hydrogen breath testing simultaneously in eight healthy subjects in order to determine the effects of intraduodenally administered medium-chain triglycerides (MCT) and long-chain triglycerides (LCT) on gastrointestinal motility and small bowel transit time. LCT (15 mmol/hr) induced a fed motor pattern. In contrast, during MCT, in both equimolar (15 mmol/hr; MCT-1) and equicaloric (30 mmol/hr; MCT-2) amounts comparable to LCT, interdigestive motility was preserved but with a significantly (P < 0.05) shorter MMC cycle length (MCT-1, 65 +/- 7 min; MCT-2, 53 +/- 6 min) compared to control (saline infusion; 127 +/- 14 min). Duodenocecal transit time (DCTT) was significantly (P < 0.05) accelerated during administration of MCT (MCT-1, 56 +/- 6 min; MCT-2, 69 +/- 9 min) and was not affected by LCT (105 +/- 13 min) when compared to control (101 +/- 9 min).

IN CONCLUSION

MCT, in contrast to LCT, preserve interdigestive motility with a shorter MMC cycle length and accelerate DCTT.

Reliability and reproducibility of breath hydrogen and methane in male diabetic subjects

We studied the variability and reliability of breath hydrogen and methane as well as the alterations in intestinal gas profile in response to lactulose ingestion in 13 asymptomatic male patients with diabetes mellitus (DM). Seventeen healthy subjects served as controls. The prevalence of methane producers was 33% in DM and 45% among control subjects (P = NS). The prevalence of nonhydrogen producers was 7.7% and 5.9%, respectively. The coefficient for interday variation of H2 was 72.6 +/- 9.8% in DM and 49.7 +/- 9.8% in controls (P < 0.05). Similarly, the coefficient for interday variation of CH4 was 94.3 +/- 18.8 and 69.4 +/- 16.8% respectively (P = NS). The reproducibility of basal H2 and CH4 among diabetics as assessed by r1 (measure of reliability) was poorer among diabetics when breath analysis was performed on different days (P < 0.001). There was no significant difference between diabetics and controls with respect to basal or peak or area under the curve for H2 and CH4 in response to lactulose. We conclude that there is poor reproducibility of fasting breath gas levels among asymptomatic male subjects with diabetes. In addition, DM is not associated with alterations in hydrogen- or methane-producing potential.

Comparison of scintigraphy and lactulose breath hydrogen test for assessment of orocecal transit: lactulose accelerates small bowel transit

The lactulose breath test (LBT) and gastroenterocolonic scintigraphy (GECS) can both be used to measure orocecal transit time (OCTT). The aims of this study were (1) to measure OCTT by LBT and GECS and (2) to determine whether lactulose alters orocecal transit.

METHODS

Eight normal subjects underwent simultaneous breath hydrogen testing, GECS, and duodenal manometry while receiving either 10 g lactulose or placebo with a radiolabeled solid/liquid test meal during two studies. There was a good correlation between OCTT by LBT and GECS when performed simultaneously (r = 0.95; P < 0.001). OCTT by GECS with lactulose was significantly faster (P = 0.004) than by GECS without lactulose, despite no change in gastric emptying of liquids and slowing of gastric emptying of solids (P = 0.02). The postprandial duodenal motility index was greater with lactulose than with placebo (P = 0.031). This study demonstrates that LBT and GECS (without lactulose) are not equivalent measures of OCTT. The standard LBT accelerates OCTT and slows gastric emptying. Therefore, lactulose has a direct accelerating effect on small intestinal transit.

Intestinal transit in anxiety and depression

BACKGROUND

Patients with anxiety and depression often have bowel symptoms. Until now, studies investigating a link between altered bowel habit and psychological illness have focused on patients with disturbed defecation presenting to gastroenterologists.

AIMS

To determine whether patients with anxiety and depression have objective evidence of abnormal intestinal transit irrespective of any bowel symptoms.

METHODS

21 psychiatric outpatients fulfilling research criteria for generalised anxiety disorder and/or major depression, and 21 healthy volunteers were studied. Orocaecal transit time (OCTT) was measured by lactulose hydrogen breath test. Whole gut transit time (WGTT) was measured by abdominal radiography after ingestion of radio-opaque markers.

RESULTS

Median (range) WGTT was shorter in patients with anxiety (14 (6-29) hours) than in patients with depression (49 (35-71) hours) (p < 0.001), and controls (42 (10-68) hours) (p < 0.001). In patients with anxiety, orocaecal transit time was shorter (60 (10-70) minutes) than in patients with depression (110 (60-180) minutes) (p < 0.01), and shorter than in controls (75 (50-140)) minutes (p < 0.05). The prolongation of transit times in depression compared with controls was not significant. However, WGTT correlated with both the Beck Depression Inventory score (r = 0.59, p < 0.01) and the depression score of the Hospital Anxiety and Depression scale (r = 0.66, p < 0.001).

CONCLUSIONS

These objective measurements of intestinal transit in affective disorders are consistent with clinical impressions that anxiety is associated with increased bowel frequency, and depressed patients tend to be constipated; mood has an effect on intestinal motor function.

Relationship between small-intestinal transit rate and intestinal absorption of (14)C-labelled mannitol and (51)Cr-labelled ethylenediaminetetraacetic acid in healthy subjects

BACKGROUND

Although the small-intestinal transit rate is generally considered to influence the urinary excretion of markers of intestinal permeability, no study has until now formally addressed the importance of this influence in humans.

METHODS

Ten healthy subjects ingested a test solution containing (99m)Tc-labelled diethylenetriaminepentaacetic acid ((99)mTc-DTPA), (14)C-labelled mannitol ((14)C-mannitol), and (51)Cr-labelled ethylenediaminetetraacetic acid ((51)Cr-EDTA). After ingestion, the small-intestinal transit rate of (99)mTc-DTPA was measured with the gamma camera technique. Urine was collected for time periods of 0-2 h, 2-4 h, and 4-6 h to measure the excretion of absorbed (14)C-mannitol and (51)Cr-EDTA. Moreover, the distribution volume and plasma clearance of (14)C-mannitol and (51)Cr-EDTA were determined in each subject.

RESULTS

A positive correlation was found between mean small-intestinal transit time and 0- to 6-h urinary excretion of (14)C-mannitol. The study did not show any correlation between small-intestinal transit rate and 0- to 6-h urinary excretion of (51)Cr-EDTA. Urinary excretion of neither (14)C-mannitol nor (51)Cr-EDTA was affected by distribution volume or urine volume. A positive correlation was observed between plasma clearance and 0- to 6-h urinary excretion of (14)C-mannitol, whereas plasma clearance did not influence the urinary excretion of (51)Cr-EDTA.

CONCLUSIONS

Small-intestinal transit rate seems to have a significant effect on 0- to 6-h urinary excretion of (14)C-mannitol, whereas small intestinal transit rate does not influence the timed urinary excretion of (51)Cr-EDTA.

A comparison of orocaecal transit times assessed by the breath hydrogen test and the sulphasalazine/sulphapyridine method in healthy beagle dogs

Orocaecal transit time (OCTT) was assessed in six healthy beagles by means of the breath hydrogen test (BH2T) and the sulphasalazine/sulphapyridine method (SLZ) after the administration of a test meal of canned food mixed with sulphasalazine. Orocaecal transit time was defined as the time taken from the oral administration of the test meal to the time when the first portion of the meal reached the colon. In five of the dogs the OCTTs assessed by the BH2T were shorter than those measured by the SLZ method by 30, 15, 45, 30 and 45 minutes. However, the median OCTT assessed by the BH2T (135 minutes, range 120 to 195 minutes) was not significantly different from that measured by the SLZ (180 minutes, range 150 to 210 minutes) and was highly correlated with it (r = 0.94, P = 0.016). The sixth dog maintained baseline hydrogen and plasma sulphapyridine readings throughout the monitoring period and the OCTT could not be measured.

Orocecal transit time in humans assessed by sulfapyridine appearance in saliva after sulfasalazine intake

PURPOSE

We propose a noninvasive method for the measurement of orocecal transit time assessed by the sulfapyridine appearance time in saliva after ingestion of sulfasalazine.

METHOD

In 12 healthy volunteers, we studied the correlation between plasma and saliva sulfapyridine appearance times and then the sulfapyridine appearance times in saliva under various experimental conditions to assess the reproducibility, the effects of meals, and the role of the formulation, and the effects of gastrointestinal kinetic drugs.

RESULTS

The correlation between saliva and plasma sulfapyridine appearance times was strong (r = 0.84; p = 0.0004). The sulfapyridine saliva appearance time was significantly delayed by the meal. Compared with placebo, the saliva sulfapyridine appearance time was reduced by cisapride (312 +/- 128 versus 551 +/- 97 minutes; p = 0.0001) and increased by loperamide (674 +/- 267 versus 501 +/- 131 minutes; p = 0.044).

CONCLUSION

We propose the salivary sample method as a validated simplification of the plasma sulfasalazine-sulfapyridine test for the measurement of orocecal transit time.

Fasting breath hydrogen concentrations in gastric and small-intestinal bacterial overgrowth

BACKGROUND

Although elevated fasting breath hydrogen concentrations have been reported in small-intestinal bacterial overgrowth, this diagnosis has been presumptive or based on definitions that vary from study to study. The influence of gastric bacterial overgrowth and gastroduodenal pH has not been documented. Conflicting evidence exists as to the reproducibility of breath hydrogen measurements.

METHODS

Forty-two subjects underwent culture of gastric and duodenal aspirates. The pH was measured by indicator paper. Paired fasting breath hydrogen concentrations were measured by gas chromatography within 7 days of endoscopy.

RESULTS

Paired fasting breath hydrogen concentrations differed in terms of normality or abnormality in 21% of subjects. Paired concentrations correlated significantly in overgrowth but not in culture-negative subjects. Sensitivity for bacterial overgrowth was 4-29%, and specificity 71-100%. No correlation with gastroduodenal pH was found.

CONCLUSIONS

The clinical relevance of a single fasting breath hydrogen concentration is limited. The efficacy of paired measurements for gastric or small-intestinal bacterial overgrowth is poor.

Pharmacokinetic considerations in gastrointestinal motor disorders

Although it has been recognised that alterations in gastrointestinal motility, whether induced by physiological or pathological processes, have significant effects on the pharmacokinetics of orally administered drugs, this subject has received inappropriately little attention. Studies relating to this topic have focused on healthy volunteers and animals and have largely been confined to the effects of single drug doses. There is limited information about the effects of disease on pharmacokinetics under steady-state conditions. Changes in gastrointestinal motility may affect the pharmacokinetics of orally administered drugs by altering the rate of delivery, bioavailability or mucosal absorption of the drug. In general the rate of absorption and time taken to achieve maximal plasma concentrations for well absorbed drugs may be modified by changes in gastrointestinal motility, but overall bioavailability is not usually affected. In these cases the therapeutic and clinical effects of the alteration in pharmacokinetics will, therefore, depend on which parameters are important for the action of the drug. For poorly absorbed drugs both the rate of absorption and bioavailability are likely to be altered by changes in gastrointestinal motility. However, the complex effects of food and disease, as well as the properties and formulation of any drug (solubility, ease of dispersion, delayed release formulation) often make the prediction of the magnitude, or even the direction, of any effect difficult to predict. Drugs with direct effects on gastrointestinal motility may influence their own patterns of absorption. In patients with gastrointestinal motility disorders, drugs administered in a controlled release formulation, or those with poor bioavailability, are most likely to have a poorly predictable therapeutic effect. Care should be taken to ensure that the formulation of the drug, its timing of administration in relation to meals and the use of coadministered drugs optimise, or at least ensure consistent absorption.

Lactulose hydrogen breath test in orocecal transit assessment. Critical evaluation by means of scintigraphic method

Orocecal transit time can be studied easily using the hydrogen breath test with lactulose, but the method has some important limitations. The orocecal transit time of 10 patients suffering from irritable bowel syndrome was measured twice, at a one-week interval, by breath test and scintigraphy simultaneously using an aqueous solution of 20 g lactulose containing 74 MBq of [99mTc]DTPA. Abdominal radioactivity and alveolar hydrogen values obtained every 5 min were noted and used to obtain the following: orocecal transit time by the two methods; ileocecal lactulose flow; total and per gram of lactulose hydrogen production; mean hydrogen concentration during the right colon filling; and measurement error of the breath test with respect to the scintigraphy. In the case of the breath test, the orocecal transit time intrapatient reproducibility was better (coefficient of variation = 13.5%) when a hydrogen threshold increment of 5 ppm was used; the best correlation with the scintigraphic measurement was observed at this threshold (r = 0.90, P < 0.001). The breath test overestimated orocecal transit time with the error correlating negatively and significantly with the total hydrogen production and, particularly, the mean hydrogen concentration (r = 0.79, P < 0.01): for a mean hydrogen concentration of more than 15 ppm, the error was negligible, while within this value there was a noticeable overestimation. To conclude, the lactulose hydrogen breath test is capable of giving an accurate measurement of orocecal transit time if a hydrogen threshold increment of 5 ppm is chosen and if the mean hydrogen concentration in the first 30 min of the right colon filling is taken into account.

Influence of antidepressants on whole gut and orocaecal transit times in health and irritable bowel syndrome

BACKGROUND

Antidepressants are used in the treatment of irritable bowel syndrome but it is unclear whether any symptomatic improvement is due solely to correction of an associated affective disorder, or whether these drugs have effects on bowel function which may be of therapeutic benefit. Intestinal transit is known to be abnormal in some irritable bowel syndrome patients.

METHODS

We have studied the effects of imipramine, a tricyclic antidepressant with mixed pharmacological properties, and paroxetine, a selective 5-hydroxytryptamine re-uptake inhibitor, on intestinal transit times.

RESULTS

Median (range) whole gut transit time was lower in 10 diarrhoea-predominant irritable bowel syndrome patients, 22.2 (3.6-51.6) h, compared to 28 control subjects 39.6 (7.2-68.4) h, (P < 0.05). Similarly, orocaecal transit time was shorter at 55 (30-90) min in diarrhoea-predominant irritable bowel syndrome patients compared to 75 (40-150) min in controls, (P < 0.05). Four days' administration of imipramine increasing to a daily dose of 100 mg prolonged both orocaecal and whole gut transit times in 12 control subjects and six diarrhoea-predominant irritable bowel syndrome patients. In contrast, 30 mg paroxetine daily for 4 days reduced orocaecal transit time in ten controls and eight irritable bowel syndrome patients, but had no effect on whole gut transit time.

CONCLUSION

Short-term administration of antidepressants alters intestinal transit, but the selective 5-hydroxytryptamine re-uptake inhibitor, paroxetine, has different effects to the tricyclic drug, imipramine. These effects on transit precede any effects on mood. Although there is a high prevalence of affective disorder in irritable bowel syndrome clinic patients, these drugs may have additional therapeutic actions on the gut. These actions might be taken into account when prescribing antidepressants in irritable bowel syndrome.

5-Hydroxytryptamine and human small intestinal motility: effect of inhibiting 5-hydroxytryptamine reuptake

Parenteral 5-hydroxytryptamine stimulates small intestinal motility, but the effect of continuous stimulation with 5-hydroxytryptamine on the human migrating motor complex is unknown. Using a selective 5-hydroxytryptamine reuptake inhibitor, paroxetine, this study investigated the effect of indirect 5-hydroxytryptamine agonism on fasting small intestinal motility and transit. Eight healthy subjects were studied while receiving paroxetine 30 mg daily for five days and while receiving no treatment, in random order. Ambulant small intestinal motility was recorded from five sensors positioned from the duodenojejunal flexure to the ileum for 16-18 hours. Paroxetine reduced the migrating motor complex periodicity mean (SEM) from 81 (6) min to 67 (4) min (p < 0.05), and increased the propagation velocity of phase III from 3.1 to 4.7 cm/min in the proximal jejunum (p < 0.01), and from 1.6 to 3.4 cm/min distally (p < 0.001). Orocaecal transit time measured by lactulose hydrogen breath test was reduced by paroxetine from 70 (9) min to 48 (7) min (p < 0.05). These data suggest that 5-hydroxytryptamine participates in the control of migrating motor complexes in humans, and that selective 5-hydroxytryptamine reuptake inhibitors have a prokinetic action in the human small intestine.

Ambulatory small intestinal motility in 'diarrhoea' predominant irritable bowel syndrome

Dysmotility of the duodenum and proximal jejunum has been reported in patients with irritable bowel syndrome. This study extended these findings by recording fasting ambulatory motility from electronic strain gauge sensors sited in the jejunum and ileum of eight diarrhoea predominant irritable bowel syndrome patients and 12 healthy controls. During the day, periodicity of migrating motor complexes mean (SEM) did not differ between patients (92 (10) min) and controls (85 (7) min). At night, periodicity was shorter in both patients and controls, and the daytime dominance of phase II was replaced by phase I. In both groups, aboral progression of phase III fronts was associated with a slowing of propagation velocity and maximum contractile rate, but an increase in mean amplitude of contraction. Discrete clustered contractions were seen in seven patients and 10 controls occupying 14 and 16% of daytime phase II activity, respectively. Pain episodes were not associated with any specific motility patterns. Despite the lack of motility differences between the two groups, orocaecal transit time in the irritable bowel syndrome patients was shorter at 57 (9) min than in the controls, 82 (6) min (p < 0.05). This ambulant study has failed to show any abnormalities of fasting small intestinal motility that might distinguish diarrhoea predominant irritable bowel syndrome patients from healthy controls.

Abnormal progression of a liquid meal through the stomach and small intestine in patients with Chagas' disease

This study describes the abnormal pattern of gastrointestinal progression of a liquid meal in patients with the digestive form of chronic Chagas' disease. This condition is known as a natural model of intramural denervation of the gut. Sixteen patients with clinical and radiographic evidence of esophageal and/or colonic involvement and 18 healthy volunteers were studied. Orocecal transit time after the ingestion of a 10% lactulose solution (180 ml) tagged with 99mtechnetium was measured by a conventional H2 breath technique. Gastric emptying and the arrival of the front of the meal to regions of interest corresponding to proximal and distal areas of the small intestine were assessed by abdominal scintigraphy. Orocecal transit time was significantly greater (P < 0.05) in Chagas' disease patients (N = 13) than in control subjects (N = 18) (mean +/- SD: 100.7 +/- 48.7 min vs 62.9 +/- 18.2 min). Half-time for gastric emptying of liquids in chagasic patients (N = 9) was significantly lower (P < 0.01) than in controls (N = 7) (9.7 +/- 2.7 min vs 26.4 +/- 3.4 min). The time of arrival of the liquid meal to the proximal small intestine was also significantly shorter (P < 0.02) in patients than in controls (5.6 +/- 3.7 vs 11.4 +/- 5.5 min), but there was no difference between the two groups concerning the time the meal first arrived to the distal small intestine (15.0 +/- 11.0 min vs 23.5 +/- 11.4 min, P > 0.05). These results indicate that patients with Chagas' disease have a combination of exceedingly rapid gastric emptying and abnormally delayed transit of liquids through the more distal segments of the small bowel.(ABSTRACT TRUNCATED AT 250 WORDS)

Loperamide. Survey of studies on mechanism of its antidiarrheal activity

In castor oil challenged rats, low doses of loperamide inhibit diarrhea and normalize intestinal propulsion. Unlike other opioids, loperamide is devoid of central opiate-like effects, including blockade of intestinal propulsion, up to the highest subtoxic oral dose. Nevertheless, the antidiarrheal action of loperamide can be considered to be mu-opiate receptor mediated, only a few in vitro effects at rather high concentrations being not naloxone-reversible. There is little evidence that interactions with intestinal opiate receptors directly change epithelial cell function. When secretory stimuli increase mucosal tension, however, loperamide may reverse the elevated hydrostatic tissue pressure that opposes normal absorption. This antisecretory effect at the mucosal level is accompanied by motor effects when loperamide reaches the myenteric mu-opiate receptors. At therapeutic doses for the treatment of acute diarrhea, it is likely that the mucosal effect prevails.