Prolonged large bowel transit increases serum deoxycholic acid: a risk factor for octreotide induced gallstones

Growth hormone alters gross anatomy and morphology of the small and large intestines in age- and sex-dependent manners

PURPOSE

Growth hormone (GH) has an important role in intestinal barrier function, and abnormalities in GH action have been associated with intestinal complications. Yet, the impact of altered GH on intestinal gross anatomy and morphology remains unclear.

METHODS

This study investigated the influence of GH signaling on gross anatomy, morphology, and fibrosis by characterizing the small and large intestines in male and female bovine growth hormone transgenic (bGH) mice and GH receptor gene-disrupted (GHR-/-) mice at multiple timepoints.

RESULTS

The length, weight, and circumference of the small and large intestines were increased in bGH mice and decreased in GHR-/- mice across all ages. Colon circumference was significantly increased in bGH mice in a sex-dependent manner while significantly decreased in male GHR-/- mice. Villus height, crypt depth, and muscle thickness of the small intestine were generally increased in bGH mice and decreased in GHR-/- mice compared to controls with age- and sex-dependent exceptions. Colonic crypt depth and muscle thickness in bGH and GHR-/- mice were significantly altered in an age- and sex-dependent manner. Fibrosis was increased in the small intestine of bGH males at 4 months of age, but no significant differences were seen between genotypes at other timepoints.

CONCLUSION

This study observed notable opposing findings in the intestinal phenotype between mouse lines with GH action positively associated with intestinal gross anatomy (i.e. length, weight, and circumference). Moreover, GH action appears to alter morphology of the small and large intestines in an age- and sex-dependent manner.

Acromegaly and Colorectal Neoplasm: An Update

Acromegaly is a systemic disease caused by excessive inappropriate secretion of GH and IGF-I levels, resulting in many systemic complications, including cardiovascular, respiratory, metabolic diseases, and a possible increased risk of some neoplasias. Although many studies on acromegaly and cancer remain uncertain, most data indicate that colorectal cancer (CRC) incidence is increased in this population. The exact mechanism involved in the role of GH-IGF-I axis in CRC has not been fully explained, yet it is associated with local and circulating effects of GH and IGF-I on the colon, promoting angiogenesis, cell proliferation, risk of mutation, inhibition of tumor-suppressor genes and apoptosis, thus facilitating a tumor microenvironment. Nevertheless, population-based studies present controversial findings on CRC incidence and mortality. All worldwide guidelines and expert consensuses agree with the need for colonoscopic screening and surveillance in acromegaly, although there is no consensus regarding the best period to do this. This review aims to analyze the existing data on CRC and acromegaly, exploring its pathophysiology, epidemiological studies and their limitations, colonic polyp characteristics, overall cancer and CRC incidences and mortality, risk factors for colon cancer pathophysiology, and recommendation guideline aspects.

Gastrointestinal defects in gallstone and cholecystectomized patients

BACKGROUND AND AIM

Several gallstone patients complain of dyspeptic symptoms, irrespective of the presence of typical colicky pain. Symptoms often persist after a cholecystectomy. Systematic studies on dyspepsia and dynamic gastrointestinal motor function are missing in gallstone patients with preserved gallbladder or after a cholecystectomy.

MATERIALS AND METHODS

Forty-six gallstone patients (age 55 ± 2 years; 15M, 31F) and 24 cholecystectomized patients (age 57 ± 2 years; 6M, 18F) (no difference in type and volume of gallstones between the two groups) were compared against a group of 65 healthy controls (age 51 ± 2 years; 30M, 35F). Dyspepsia occurring in the prior months was assessed by a questionnaire, gastric and gallbladder emptying by functional ultrasonography and orocecal transit time by a hydrogen breath test using a lactulose-enriched standard liquid meal.

RESULTS

Gallstone patients had significantly greater dyspepsia, fasting and residual gallbladder volumes, and slower gallbladder emptying, gastric emptying and small intestinal transit time than controls. In cholecystectomized patients, gastric emptying further delayed, compared to gallstone patients and controls.

CONCLUSION

Gallstone patients with the gallbladder "in situ" or after a cholecystectomy display dyspeptic symptoms. Symptoms are associated with multiple gastrointestinal motility defects involving the gallbladder, stomach and small intestine. After cholecystectomy, gastric emptying worsens.

Colonic Cancer and Acromegaly

Acromegaly results in a significantly increased morbidity and mortality due to cardiovascular and respiratory complications, as well as malignancies arising mainly from the colon. Furthermore, an increased lifetime risk of malignant transformation of pre-malignant colonic lesions relates to a worse overall prognosis from colorectal cancer, which is currently considered a major disease-related complication. In this review we provide some insight into colonic changes in this condition, summarize current knowledge and evidence on the use of colonoscopic screening in patients with acromegaly, and suggest a recommended screening protocol.

Colonoscopy examination requires a longer time in patients with acromegaly than in other individuals

This study aimed to determine the prevalence of colorectal neoplasms and to investigate the rate of and time required for cecal intubation in patients with acromegaly. A database search performed at our institution identified 29 patients with acromegaly who underwent colonoscopy. Data regarding the endoscopic, biological, and pathological examinations performed were retrospectively reviewed from the clinical records. Subsequently, the rate of and time required for cecal intubation were investigated in 23 patients with acromegaly and compared with the corresponding data of the control group. Control subjects were selected from a 2:1 matched historical control cohort, according to baseline characteristics. The mean age of the acromegaly group (17 female and 12 male) was 60.4 ± 12.6 years. Twelve patients had adenoma (41.4%), eight patients had hyperplastic polyps (27.6%), three patients had sessile serrated adenoma/polyps (10.3%), and three patients had colon cancer (10.3%). Successful cecal intubation was achieved in all patients in both groups. The difference in the time required for successful intubation between the acromegaly group (15.7 ± 9.8 minutes) and the control group (8.7 ± 6.0 minutes) was statistically significant. Linear regression analysis revealed that increased patient age was significantly related to longer colonoscope insertion times. In conclusion, although cecal intubation during colonoscopy was successful in all participants, it required a longer time in patients with acromegaly. Our results underscore the importance of and certain technical difficulties involved in colonoscopy procedures in patients with acromegaly, especially in older patients.

Acromegaly and associated tumours: what should gastroenterologists know?

Acromegaly is a clinical syndrome caused by the excessive production of growth hormone. It is associated with high morbidity and significantly increased mortality, mainly due to cardiovascular and respiratory complications, and cancer. Mortality is reduced to that of the general population following successful treatment, in other words, when insulin-like growth factor (IGF-I) and growth hormone values return to normal levels. Not all tumours associated with this syndrome benefit from cost-effective early diagnosis programmes. An in-depth knowledge on the part of clinicians of the morbidity and mortality associated with acromegaly, allowing them in many cases to anticipate the expected clinical course of the disease, is the best therapeutic and follow-up strategy in these patients.

LONGER CECUM INSERTION TIME AND MORE INADEQUATE COLONIC PREPARATION IN PATIENTS WITH ACROMEGALY: IS A DIFFERENT COLONOSCOPY PREPARATION NEEDED?

Purpose

To investigate whether there is a difference between acromegalic and non-acromegalic cases in terms of bowel preparation and colonoscopic intervention.

Methods

Patients with controlled and uncontrolled acromegaly and as a control group (CG) patients without acromegaly between January 2010 and March 2014 were included. Groups were compared regarding adequacy of bowel preparation, cecal insertion time (CIT) and colonoscopy results.

Results

Fifty-nine patients with acromegaly (controlled n=30, uncontrolled n=29) and 73 age and gender matched volunteers without acromegaly were evaluated. CIT in cases with controlled, uncontrolled acromegaly cases and in CG was 5.33 [4.00-6.00], 7.00 [4.91-11.31], and 3.10 [2.35-4.65] minutes, respectively (p<0.001). Cases in CG had shorter CIT compared to controlled and uncontrolled acromegaly cases ( p=0.014 and p<0.001, respectively). There was no significant difference regarding CIT between controlled and uncontrolled acromegaly cases (p=0.247). Six (20%) of controlled acromegaly patients, 10 (35%) of uncontrolled acromegaly patients and three (4%) of CG had inadequate bowel cleansing (p<0.001). Although statistically insignificant, cases with inadequate bowel cleansing had tendency towards having prolonged CIT in comparison to cases with adequate bowel cleansing (6.00 [3.87-9.00] and 4.16 [2.95-5.70] minutes, respectively, p=0.07).

Conclusion

Inadequate bowel cleansing is one of the main problems encountered during colonoscopic investigation/surveillance in acromegalic patients. Therefore, a different protocol for colonoscopy preparation may be needed for these cases.

Physical Activity and the Biliary Tract in Health and Disease

BACKGROUND

Cholecystitis and gallstones affect a large segment of the population in developed nations, and a small proportion of affected individuals subsequently develop cancer of the gallbladder. However, little is known about the possible beneficial effects of physical activity.

OBJECTIVE

Accordingly, a systematic review examined the influence of both acute and chronic exercise on gallbladder motility, and relationships were examined between habitual physical activity, gallbladder disease, and gallbladder cancer.

METHODS

A search of Ovid/MEDLINE from 1996 to November 2014 yielded 67 articles relating to physical activity and gallbladder function or disease; 18 of these relevant to the objectives of the review were supplemented by 22 papers from personal files and other sources. Because of the limited volume of material, all were considered, although note was taken of the quality of activity measurement, care in excluding covariates, and experimental design (cross-sectional, case-control or randomized controlled trial).

RESULTS

The impact of physical activity upon gallbladder function remains unclear; acute activity could augment emptying by stimulating cholecystokinin release, and one of two training experiments found a small increase in gallbladder motility. The largest and most recent cross-sectional and case-control trials show a reduced risk of gallbladder disease in active individuals. A small number of randomized controlled trials in humans and one animal study generally support these trends, although the number of cases of gallstones are too few for statistical significance. Three studies of gallbladder cancer also show a non-significant trend to benefit from physical activity.

CONCLUSIONS

Although there remains a need for further research, regular physical activity seems likely to reduce the risk of both gallstones and gallbladder cancer. A substantial number of individuals must be persuaded to exercise in order to avoid one case of gallbladder disease, but the attempt appears warranted because of the other health benefits of regular physical activity.

The role of colonoscopic screening in acromegaly revisited: review of current literature and practice guidelines

INTRODUCTION

Acromegaly is a chronic, debilitating and disfiguring condition with a significantly increased morbidity and mortality due to cardiovascular, as well as respiratory complications. Patients with acromegaly are usually diagnosed at the age of 40, however, the duration of symptoms can vary from 5 to 10 years before the formal diagnosis is confirmed. Recent advances in the field of acromegaly have improved survival significantly. A strong association between acromegaly and premalignant colonic lesions and colon cancer has been highlighted. Furthermore, patients with acromegaly have a greater lifetime risk of malignant transformation and a far worse overall prognosis from colorectal cancer, which is now considered a major disease related complication.

MATERIALS AND METHODS

A comprehensive search strategy was applied for the Medline/PubMed electronic database from its inception until April 2014. We considered all human research articles published in English, not classified as case report, editorial, comment, letter, or news.

CONCLUSION

Specific recommendations for large bowel endoscopic screening in patients with acromegaly have been proposed. In this comprehensive review we discuss the current state of knowledge and evidence on colonoscopic screening in patients with acromegaly illustrated by a case of aggressive colorectal cancer presenting late in a young woman with difficult to control acromegaly.

Somatostatin and the gastrointestinal tract

PURPOSE OF REVIEW

Somatostatin influences motility, secretion, and absorption and often has in vivo a modulating, indirect effect on target cells in the gastrointestinal tract. Knowledge on tissue-specific expression of the five somatostatin receptors (SSTRs), their capacities for internalization and downregulation, their subtype-specific intracellular messengers, and the possibility of forming functionally distinct homodimers or heterodimers, has further complicated the actual in-vivo mechanism of action of somatostatin. This review reports recent in-vivo and in-vitro studies on somatostatin effects on the gastrointestinal tract and pancreas, most of them using a new engineered animal model able to define specific roles of somatostatin and/or its receptor subtypes.

RECENT FINDINGS

SSTR2 knockout mice showed normal circulating gastrin and unchanged acid output, suggesting a high degree of plasticity behind gastric acid secretion. Intestinal inflammation significantly increased somatostatin mRNA in SSTR2 null compared to wild type suggesting that somatostatin mediates inflammation also in SSTR2 null mice. In pancreatic islets of SSTR1-5 null mice no variations of islet size, cellular organization or glucagon or insulin content was shown when compared with null SSTRs and control mice.

SUMMARY

Although none of the recent findings produced on somatostatin seem ready to be considered for clinical application, recent developments of animal models such as SSTR knockout mice have highlighted promising results to better understand the direct and indirect effects of somatostatin on gastrointestinal tract functions.

The prevalence and risk factors for gallstone disease

Gallstone disease is one of the most prevalent gastrointestinal disorders. In addition, the costs associated with the diagnosis and treatment of gallstone disease have been rapidly increasing. The etiology and pathogenesis of gallstone disease remains incompletely understood. Gallstone formation may result from a complex interaction of genetic and environmental factors. This article reviews the prevalence and risk factors associated with gallstone disease. Understanding the pathogenesis of gallstone disease could lead to the development of better therapeutic and preventive strategies for dealing with this disease.

Ultrasonic Gallbladder Function in Chronic Kidney Disease: Does Predialysis, Hemodialysis, or CAPD Affect it?

BACKGROUND

There are contradictory reports about the prevalence of cholelithiasis in chronic kidney disease (CKD). The pathogenesis of gallstones is associated with the lithogenic changes of bile composition, increased tendency to nucleation, and decreased gallbladder motility. The studies related to these factors can predict the development of cholelithiasis. The aim of this study was to evaluate the ultrasonic gallbladder function in CKD and to compare it in predialysis (PreD), hemodialysis (HD), and continuous ambulatory peritoneal dialysis (CAPD) patients.

METHODS

Age, gender, and body mass index matched 49 CKD patients (14 PreD, 19 HD, 16 CAPD), and 17 control individuals were included in the study. Diabetic and cirrhotic patients were not included. Ultrasonic gallbladder volume was evaluated in pre- and postprandial period, and ejection fraction was calculated. We also measured several biochemical parameters (cholesterol, triglyceride, blood urea nitrogen (BUN), creatinine, calcium, Phosphorus, parathormone, albumin, total protein) in blood.

RESULTS

Preprandial gallbladder volume in PreD, HD, CAPD, and control groups were 26.7 +/-13.6, 20.8+/-10.4, 23.2+/-14.7, and 26.4+/-14.8 mL, respectively (p > 0.05). Ejection fractions were 54.1 +/- 22.9%, 54.9 +/- 23.9%, 48.6 +/- 15.9%, and 51.8 +/- 19.2% in PreD, HD, CAPD, and control groups, respectively (p > 0.05). Serum triglyceride was higher in PreD patients than control group (207 +/- 144 vs. 110 +/-48 mg/dL) (p<0.05). Serum BUN, Cre, P, and PTH levels were higher in CKD groups than the control group, whereas serum total protein and albumin levels were higher in the control group (p<0.05). Serum Ca was lower in PreD and HD patients than in the controls (p<0.05).

CONCLUSIONS

In conclusion, CKD and renal replacement therapy (HD and CAPD) do not affect gallbladder functions, but more studies are needed to evaluate prevalence of gallstones, gallbladder motility, and the composition of bile in CKD.

Anthropometric measurements, physical activity, and the risk of symptomatic gallstone disease in Chinese women

PURPOSE

Gallstone disease is more common among overweight individuals, particularly in women. We conducted a cross-sectional case-control study of Chinese women nested in the Shanghai Women's Health Study (SWHS) to evaluate the association of gallstone disease with body mass index (BMI), waist to hip ratio (WHR), and physical activity (PA).

METHODS

The study included 8,485 women with self-reported, physician-diagnosed, prevalent gallstone disease and 16,970 frequency-matched controls by birth year and age at gallstone diagnosis (4-year intervals). Information on height, weight history, waist and hip circumferences, physical activities, and other exposures was obtained by in-person interview.

RESULTS

: Usual BMI (p trend < 0.001) and WHR (p trend < 0.001) were both related to a high prevalence of gallstone disease, and a significant interaction between BMI and WHR on gallstone risk was found (odds ratio [OR] = 3.82, 95%CI [95% confidence interval] 2.47-5.23 for those with both highest BMI and WHR relative to those with lowest BMI and WHR, p interaction = 0.03). Gallstone risk was positively associated with cumulative occupational sitting time (p trend = 0.01) and inversely associated with occupational cumulative energy expenditure (p trend = 0.03) as well as with household PA (p trend = 0.02).

CONCLUSIONS

Our findings further support that overall and central excessive adiposity is an independent risk factor for gallstones in women. In addition, regardless of adiposity level, being physically active may ameliorate the risk of this disease.

Somatostatin analogs and gallstones: a retrospective survey on a large series of acromegalic patients

CONTEXT

Development of gallstones (GS) is reported during the use of somatostatin analogs (SA) that are at present the mainstay for the medical treatment of acromegaly.

OBJECTIVE

To review the prevalence and clinical and biochemical correlates of GS in acromegalic patients.

DESIGN AND SETTING

Retrospective survey on hospital records in acromegalic patients followed up in the last 20 yr in tertiary referral centers.

PATIENTS

Four hundred and fifty-nine patients (272 females).

MAIN OUTCOME MEASURES

According to SA use and GS occurrence, patients were divided in 4 groups: 1) treated with SA without GS (SA+GS-), 2) GS developed while on SA (SA+GS+), 3) GS without SA use (SA-GS+), 4) neither GS nor SA (SA-GS-).

RESULTS

Patients were unevenly distributed in the 4 groups: 232, 125, 38, 64, respectively, pointing to a prevalence of GS in acromegaly of 8.3% at diagnosis with an additional 35% developing GS during SA. GS occurred after 3 months-18 yr (median 3 yr) of SA treatment, were diagnosed after symptoms in 17.6%, were associated to steatosis, ultrasound biliary dilation, and biochemical cholestasis, in 25.6%, 12.8%, and 4% of patients, respectively. Ursodehoxicolic acid was administered after GS occurrence, causing their dissolution in 39% of patients after 3-48 months (median 12). Cholecystectomy was performed in 16.8%of patients in group 2. At multivariate analysis obesity, dyslipidemia, and SA treatment were independent predictors of GS onset, whereas gender and age were not.

CONCLUSIONS

GS are a frequent occurrence in acromegalic patients treated with SA, may occur at any time, but are seldom symptomatic or prompt acute surgery. Obesity and dyslipidemia appear to play a major role in the occurrence of GS in acromegalic patients on SA treatment.

Acromegaly: re-thinking the cancer risk

Acromegaly is characterized by sustained elevation of circulating growth hormone (GH) and insulin-like growth factor I (IGF-I), and is clearly associated with increased morbidity and overall mortality mainly due to cardiovascular, metabolic, and respiratory diseases. Although cancer-related mortality varies widely amongst retroperspective studies, it appears to be consistently elevated mainly in patients with uncontrolled disease. We review individual tumor types including neoplasms of the colon, breast, prostate, and thyroid where in vitro, animal studies, and studies in non-acromegalic cancer patients have established a role for the GH/IGF-I axis in tumor progression and possibly initiation. We highlight deficiencies in data in acromegalic patients where the evidence is less convincing. Instead, we explore the hypothesis that acromegaly, independent of hormone secretion, is a disease that heralds genetic and/or epigenetic alterations predisposing to cancer risk elsewhere.

Withdrawal of somatostatin analogue therapy in patients with acromegaly is associated with an increased risk of acute biliary problems

BACKGROUND

The prevalence of gallstones (GS) is increased in acromegaly and further increased by somatostatin analogue (SA) therapy. The incidence is reported at 10-63%, but they are often asymptomatic and rarely require definitive management. Evidence suggests discontinuation of SA may precipitate acute biliary problems.

OBJECTIVE

To determine the frequency of symptomatic gallstones in patients treated with SA.

DESIGN

Retrospective analysis of prospectively followed patients in our centre.

RESULTS

Fifty patients (30 male, mean age 54 +/- 16 years) were on treatment with SA on 1 January 2003. Fifteen (11 male, mean age 50 +/- 17 years) have since discontinued SA with three proceeding to develop acute cholecystitis and two, biliary colic necessitating cholecystectomy. Three of the five had abnormal liver enzymes at or within 3 months of symptomatic presentation. Two of the remaining 35 patients experienced biliary colic necessitating cholecystectomy. These data indicate a highly significant increase in acute biliary problems on discontinuing SA (5 in 27.67 patient 'off-treatment' years vs. 2 in 299 patient treatment years, chi(2), P < 0.0001). All seven patients experiencing problems were male (P = 0.01).

CONCLUSION

This analysis demonstrates the high incidence of symptomatic GS following SA withdrawal, particularly in men. Although liver enzymes were raised no common abnormality was evident to aid as a predictor of future symptoms. We recommend all patients due to stop SA be forewarned of the risk of acute biliary problems. Further work is required to confirm if there is a gender-related difference in the incidence of acute biliary problems on discontinuing SA therapy.

Cancers associated with acromegaly

Acromegaly is characterised by excessive levels of circulating growth hormone and its tissue mediator, insulin-like growth factor (IGF)-I. Prior to effective treatment and lowering of growth hormone and IGF-I, the majority of patients with the disease died by the age of 60 years, largely due to diabetes mellitus, cardiovascular and cerebrovascular diseases. More recently, it has become apparent that patients with acromegaly may also have an increased prevalence of colorectal adenomas and cancer. This may be due to elevated IGF-I, which is implicated in the development of sporadic colorectal cancer, and environmental factors, such as the bile acid deoxycholic acid, the levels of which are also increased in acromegaly. There is some evidence to suggest that breast and prostatic malignancies might also be increased in acromegaly. However, these associations have been based mostly on small epidemiological surveys and circumstantial evidence. Large-scale epidemiological studies are required to clarify this issue.

Physical activity and decreased risk of clinical gallstone disease among post-menopausal women

BACKGROUND

Physical activity may play a role in preventing gallstone disease.

METHODS

The activity/gallstone relationship was examined in post-menopausal women from the Study of Osteoporotic Fractures (SOF; 1986-1988), a prospective study of fracture risk factors in 8010 women (mean age = 71.1 years, SD = 4.9).

RESULTS

Multivariate logistic regression indicated women in the lowest two quartiles of physical activity, according to questionnaire, had a 59% {OR = 1.59 (1.11-2.29), P = 0.02} and a 57% higher risk {OR = 1.57 (1.11-2.23), P = 0.01} of developing gallstone disease compared to women in the highest quartile of activity (PTrend = <0.0001). Additionally, this relationship was examined in a cohort of 182 post-menopausal women (mean age 74.2 years, SD = 4.1) who participated in a randomized controlled trial of a walking intervention. Women in the randomized clinical trial in the lowest tertile of physical activity determined by a physical activity monitor had a higher risk of developing gallstone disease than women in the highest tertile of physical activity, 13% {OR-1.13 (1.01-1.28), P = 0.05, PTrend = <0.04}.

CONCLUSION

Physical activity appears to be inversely related to the development of gallstone disease in post-menopausal women independent of body mass index.

Octreotide induced prolongation of colonic transit increases faecal anaerobic bacteria, bile acid metabolising enzymes, and serum deoxycholic acid in patients with acromegaly

BACKGROUND

Acromegalic patients have slow colonic transit, increased rates of deoxycholic acid formation, and an increased prevalence of cholesterol gall stones, especially during long term octreotide treatment. However, the effects of this prolonged large bowel transit time on the numbers of faecal anaerobes and the activities of the enzyme systems which biotransform conjugated cholic acid into unconjugated deoxycholic acid (cholylglycine hydrolase and 7alpha-dehydroxylase) are unknown.

METHODS

Therefore, in 10 non-acromegalic controls, 11 acromegalic patients not treated with octreotide, and 11 acromegalics on long term (8-48 months) octreotide (100-200 mug three times daily subcutaneously), we measured large bowel transit time and, in freshly voided faeces, the activities of the two bile acid metabolising enzymes, and related the results to the proportion of deoxycholic acid in fasting serum. Moreover, in patients with acromegaly, we measured quantitative bacteriology in faeces.

RESULTS

Mean large bowel transit time in acromegalics not treated with octreotide (35 (SEM 6.5) hours) was 66% longer than that in non-acromegalic controls (21 (3.1) hours; NS) and became further prolonged during octreotide treatment (48 (6.6) hours; p<0.001). These octreotide induced changes in transit were associated, in acromegalic patients, with more total (15.0 (2.5) v 6.3 (1.3)x10(9) colony forming units (cfu)/g; p<0.05) and Gram positive (6.3 (2.3) v 3.2 (1.0)x10(9) cfu/g; p<0.05) faecal anaerobes. Mean faecal cholylglycine hydrolase activity in the long term octreotide group (22.0 (6.0)x10(-2) U/mg protein) was 138% greater than that in non-acromegalic controls (12.0 (6.0)x10(-2); p<0.01). Similarly, mean 7alpha-dehydroxylase activity in octreotide treated acromegalics (11.1 (1.18)x10(-4) U/mg protein) was 78% greater than that in patients not receiving long term octreotide (6.3 (0.5)x10(-4); p<0.001). The mean proportion of deoxycholic acid in fasting serum also increased from 18.0 (2.88)% in the untreated group to 29.6 (2.3)% during long term octreotide (p<0.05). There were significant linear relationships between large bowel transit time and: (i) faecal 7alpha-dehydroxylase activity; and (ii) the proportion of deoxycholic acid in fasting serum and between 7alpha-dehydroxylase activity and the proportion of deoxycholic acid in serum.Summary/interpretation: These data suggest that increased deoxycholic acid formation seen in acromegalics during octreotide treatment is due not only to the greater numbers of faecal anaerobes but also to increased activity of the rate limiting enzyme pathway (7alpha-dehydroxylation) converting cholic acid to deoxycholic acid.

Determination of large bowel length and loop complexity in patients with acromegaly undergoing screening colonoscopy

BACKGROUND

Patients with acromegaly are at moderately increased risk of developing colorectal cancer and may be considered for screening colonoscopy. In turn, large bowel dimensions may be increased in these patients, factors that predict for increased risk of serious complications such as perforation.

OBJECTIVE

To evaluate this risk potential, we measured large bowel length and loop complexity using magnetic endoscopic imaging (MEI).

DESIGN

Case-control study in 25 unselected patients with acromegaly (mean age 56 years) vs. 41 nonacromegalic controls (mean age 60 years) undergoing screening colonoscopy.

MEASUREMENTS

MEI parameters were determined and age- and sex-adjusted mean differences calculated. The dependency of total large bowel length on various demographic and disease-related factors (e.g. GH exposure, IGF-I and IGFBP-3 concentrations) was assessed using regression techniques.

RESULTS

Total large bowel length was increased by 20%[95% confidence interval (CI) 9-31%] in patients with acromegaly compared with controls (unadjusted and adjusted; P-values < 0.001). Acromegaly was also associated with increased time taken to reach the caecum (P = 0.01) and increased pelvic loop complexities (5/25 vs. 1/41, Fisher's exact test: P = 0.03). Total large bowel length was predicted by age at colonoscopy (P = 0.003) and patient height (P = 0.03), but not by surrogate biochemical markers of disease activity.

CONCLUSIONS

Acromegaly is associated with increased large bowel length and loop complexity making colonoscopy technically challenging, and theoretically increasing the risk of serious complications. Patients need to be counselled accordingly, and appropriate resources with experienced staff allocated.

Low-fat, high-carbohydrate and high-fat, low-carbohydrate diets decrease primary bile acid synthesis in humans

BACKGROUND

Dietary fat content influences bile salt metabolism, but quantitative data from controlled studies in humans are scarce.

OBJECTIVE

The objective of the study was to establish the effect of dietary fat content on the metabolism of primary bile salts.

DESIGN

The effects of eucaloric extremely low-fat (0%), intermediate-fat (41%; control diet), and extremely high-fat (83%) diets on kinetic values of cholate and chenodeoxycholate metabolism were determined after 11 d by using stable isotope dilution in 6 healthy men. All diets contained identical amounts of cholesterol.

RESULTS

The total primary bile salt pool size was not significantly affected by dietary fat content, although the chenodeoxycholate pool was significantly higher during the low-fat diet. Fractional turnover rates of both primary bile salts were 30-50% lower during the low- and high-fat diets than during the control diet. Total hepatic bile salt synthesis was approximately 30% lower during both the high- and low-fat diets, but synthesis rates of the 2 primary bile salts were differentially affected. The molar ratio of cholate to total bile salt synthesis increased from 0.50 +/- 0.05 ( +/- SD) to 0.59 +/- 0.05 and 0.66 +/- 0.04 with increasing fat intake, whereas the molar ratio of chenodeoxycholate to total bile salt synthesis decreased from 0.50 +/- 0.05 to 0.41 +/- 0.05 and 0.34 +/- 0.04. The relative concentration of deoxycholate in plasma increased during the low-fat period, which indicated increased absorption from the colon.

CONCLUSIONS

Both low- and high-fat diets reduce the synthesis and turnover rates of primary bile salts in humans, although probably through different mechanisms, and consequently they affect the removal of cholesterol from the body.

Elevated circulating somatostatin levels in acromegaly

GH increases hypothalamic somatostatin (SS) synthesis and secretion but it is unknown if chronic GH excess, as found in acromegaly, may influence circulating SS levels, that are mainly of enteropancreatic source and affect several gastrointestinal functions, including motility. Circulating SS occurs in several post-translational forms including somatostatin-14 (SS-14), somatostatin-28 (SS-28) and other small peptides. The aim of the present study was to characterize the fasting and postprandial pattern of plasma circulating somatostatin in normal subjects and patients with acromegaly. Fasting total SS and SS-28 levels were measured in 32 subjects, 16 acromegalic patients with a new diagnosis (A) (8 F, 8 M, median age 48) and 16 matched healthy volunteers (C) (8 F, 8 M, median age 45). SS was also determined after a standard solid-liquid meal (550 kCal) in 24 of the subjects (12 C and 12 A). Fasting SS and SS-28 were significantly higher in acromegalic patients as compared to healthy subjects. In the former, a positive correlation was found between IGF-I and SS levels (r = 0.525 p < 0.05). Furthermore, the ratio between SS (as pmol equivalent SS-14/I) and SS-28 was higher in the acromegalic patients than in the controls (3.4 +/- 2.1 vs 2.0 +/- 1.6, p < 0.05). The postprandial SS peak, as well as the incremental area above baseline values, was similar in the patients and controls. In conclusion, fasting but not postprandial hypersomatostatinemia, mainly due to an increase in SS-14, characterizes acromegaly. Excess GH/IGF-I could be a causal factor in somatostatin hypersecretion. Conceivably this abnormality might play a role in some alterations of gastrointestinal function of acromegalic patients such as prolonged bowel transit.

Drug-induced cholestasis

Drug-induced cholestasis is a common entity, seen with numerous classes of pharmacological agents. A high index of suspicion is required for the correct diagnosis. Different clinical syndromes may be recognized, with variable degrees of hepatitis in association with cholestasis. The most important aspect of treatment is prompt discontinuation of the offending drug. Several agents have been used for symptomatic relieve of the pruritus associated with cholestasis, including cholestyramine, ursodeoxycholic acid, and opiate antagonists, with limited results. Prognosis is usually good, with few cases of prolonged cholestasis leading to vanishing bile duct syndrome. Liver failure may rarely occur if diagnosis goes unrecognized and the inciting drug is not withdrawn.

Development and application of a polymerase chain reaction assay for the detection and enumeration of bile acid 7alpha-dehydroxylating bacteria in human feces

BACKGROUND

Secondary bile acids are synthesized in the human colon from the bacterial 7alpha-dehydroxylation of primary bile acids. Increased levels of secondary bile acids have been correlated with an increased risk of colon cancer and cholesterol gallstone disease. Based on 16s rDNA sequence analysis, stock cultures of bacterial strains with bile acid 7alpha-dehydroxylation all belong to the genus Clostridium.

METHODS

We developed a polymerase chain reaction (PCR)-based assay that can specifically amplify the baiCD gene, specific to bile acid 7alpha-dehydroxylation pathway. The PCR primer pair was designed using known nucleotide sequences from two different baiCD genes described for Clostridium scindens VPI 12708 and Clostridium hiranonis TO931. Although the DNA sequences of these genes were <70% identical, several regions were conserved enough to design primers with little or no redundancy.

RESULTS

The PCR assay was effective in detecting the baiCD gene in several strains known to exhibit bile acid 7alpha-dehydroxylation activity. The PCR assay also detected the baiCD gene in DNA extracted from fecal dilution series and correlated with the levels of cholic acid 7alpha-dehydroxylating bacteria detected by activity assays. The PCR assay was sensitive enough to detect the baiCD gene in DNA samples extracted directly from as little as 0.5 mg feces.

CONCLUSIONS

This new method should be useful for the monitoring of levels of bile acid 7alpha-dehydroxylating bacteria in human fecal samples.

A comparison of the effects of pegvisomant and octreotide on glucose, insulin, gastrin, cholecystokinin, and pancreatic polypeptide responses to oral glucose and a standard mixed meal

Standard medical therapy for patients with acromegaly includes somatostatin analogs. Owing to the widespread expression of somatostatin receptors, these may be associated with unwanted effects, such as altered glucose tolerance and impaired gut hormone release. Pegvisomant is a novel pegylated GH analog that competes with wild-type GH for GH-receptor binding sites but contains a position 120, amino acid substitution that prevents functional GH receptor dimerization, a known prerequisite for GH signal transduction and generation of IGF-I. We have studied the short-term effects of these two therapies (pegvisomant 20 mg/d for 7 d and octreotide 50 microg thrice daily for 7 d) on glucose tolerance and stimulated gut hormone release in six healthy male volunteers in an open-label, random-order, cross-over study. Subjects were assessed at baseline (oral glucose tolerance test and standard mixed meal) and on d 6 and 7 of each therapy with a minimum washout of 2 wk between treatments. Area under the curve and peak responses were analyzed using one-way repeated-measures ANOVA (on ranks where appropriate). Pegvisomant had no effect on glucose tolerance or stimulated gut hormone response during an oral glucose tolerance test and a standard meal. In contrast, octreotide significantly increased fasting plasma glucose, lowered fasting plasma insulin, and led to deterioration in glucose tolerance; three subjects developed impaired glucose tolerance and one diabetes mellitus by World Health Organization criteria. Octreotide significantly impaired stimulated release of cholecystokinin, gastrin, insulin, and pancreatic polypeptide. In conclusion, pegvisomant, unlike octreotide, is not associated with deterioration in glucose tolerance and impairment of stimulated gut hormone release in normal males.

Effects of cisapride on gall bladder emptying, intestinal transit, and serum deoxycholate: a prospective, randomised, double blind, placebo controlled trial

BACKGROUND

Octreotide inhibits gall bladder emptying and prolongs intestinal transit. This leads to increases in the proportion of deoxycholic acid in, and cholesterol saturation of, gall bladder bile, factors that contribute to the pathogenesis of octreotide induced gall stones.

AIMS

To see if an intestinal prokinetic, cisapride, could overcome these adverse effects of octreotide and if so, be considered as a candidate prophylactic drug for preventing iatrogenic gall bladder stones.

METHODS

A randomised, double blind, placebo controlled, crossover design was used to examine the effects of cisapride (10 mg four times daily) on gall bladder emptying, mouth to caecum and large bowel transit times, and the proportions of deoxycholic acid and other bile acids, in fasting serum from: (i) control subjects (n=6), (ii) acromegalic patients not treated with octreotide (n=6), (iii) acromegalics on long term octreotide (n=8), and (iv) patients with constipation (n=8).

RESULTS

Cisapride had no prokinetic effect on the gall bladder. In fact, it significantly increased both fasting and postprandial gall bladder volumes. However, it shortened mouth to caecum (from 176 (13) to 113 (11) minutes; p<0.001) and large bowel (from 50 (3.0) to 31 (3.4) h; p<0.001) transit times. It also reduced the proportion of deoxycholic acid in serum from 26 (2.3) to 15 (1.8)% (p<0.001), with a reciprocal increase in the proportion of cholic acid from 40 (3.5) to 51 (3.8)% (p<0.01). There were significant linear relationships between large bowel transit time and the proportions of deoxycholic acid (r=0.81; p<0.001) and cholic acid (r=-0.53; p<0.001) in fasting serum. INTERPRETATION/SUMMARY: Cisapride failed to overcome the adverse effects of octreotide on gall bladder emptying but it countered octreotide induced prolongation of small and large bowel transit. Therefore, if changes in intestinal transit contribute to the development of octreotide induced gall bladder stones, enterokinetics such as cisapride may prevent their formation.

Colonic transit influences deoxycholic acid kinetics

BACKGROUND & AIMS

Prolonged large bowel transit, and an increase in the proportion of deoxycholic acid (DCA), have been implicated in the pathogenesis of cholesterol gallstones-including those developing in acromegalics treated with octreotide. However, there are few data on the effects of intestinal transit on bile acid kinetics.

METHODS

We therefore measured the kinetics of DCA and cholic acid (CA) using stable isotopes, serum sampling, and mass spectrometry. The results were related to mouth-to-caecum (MCTT) and large bowel transit times (LBTTs) in 4 groups of 8 individuals: (1) non-acromegalic controls, (2) acromegalics untreated with octreotide, (3) acromegalics on long-term octreotide, and (4) patients with constipation. Paired, before and during octreotide, studies were performed in 5 acromegalics.

RESULTS

In the unpaired and paired studies, octreotide significantly prolonged MCTT and LBTT. In the paired studies, the octreotide-induced prolongation of LBTT caused an increase in the DCA input rate (6.4 +/- 2.8 to 12 +/- 2.6 micromol. kg. d, P < 0.05) and pool size (18 +/- 12 to 40 +/- 13 micromol/kg, P < 0.05), and a decrease in CA pool size (45 +/- 15 to 25 +/- 11 micromol/kg, P < 0.05). Furthermore, during octreotide treatment, the mean conversion of 13C-CA to 13C-DCA (micromoles) was greater (P < 0.05) on study days 3, 4, and 5. There were also positive linear relationships between LBTT and DCA input rate (r = 0.78), pool size (r = 0.82, P < 0.001), and a weak (r = -0.49) negative linear relationship between LBTT and CA pool size (P < 0.01).

CONCLUSIONS

These data support the hypothesis that, by increasing DCA formation and absorption, prolongation of large bowel transit is a pathogenic factor in the formation of octreotide-induced gallstones.

Octreotide increases the proportions of arachidonic acid-rich phospholipids in gall-bladder bile

BACKGROUND AND AIMS

Octreotide treatment of acromegalic patients induces cholesterol gallstone formation, in part by impairing cholecystokinin release and gall-bladder contraction. However, there are few data on the effect of octreotide on biliary arachidonic acid-rich phospholipids or mucin glycoprotein, factors which also influence cholesterol gallstone formation.

METHODS

In acromegalic patients studied before and during 3 months of octreotide treatment, we measured mucin glycoprotein concentrations and the molecular species of phosphatidylcholine, and related the results to the cholesterol saturation and percentage of deoxycholic acid in gall-bladder bile.

RESULTS

The relative proportions of the major arachidonic acid-rich phosphatidylcholine species, PC 16:0-20:4 and PC 18:0-20:4, increased significantly during octreotide treatment. These changes were associated with a rise in the cholesterol saturation index and a non-significant twofold increase in mucin glycoprotein concentration. There were significant correlations between PC 16:0-20:4 and the cholesterol saturation index, percentage of vesicular cholesterol and percentage of deoxycholic acid in gall-bladder bile.

CONCLUSIONS

In acromegalic patients, octreotide increases the proportions of arachidonic acid-rich phospholipids, with associated rises in: (a) the cholesterol saturation index and percentage of vesicular cholesterol, and (b) the percentage of deoxycholic acid in gall-bladder bile-changes similar to those found in patients with cholesterol-rich gall-bladder stones.

Influence of pH on the phase distribution of nascent deoxycholic acid in fresh human cecal aspirates

Prolonged large bowel transit time and an associated increase in the proportion of deoxycholic acid (DCA) in serum and bile have been implicated in the development of cholesterol-rich gallstones and colon cancer. Prolongation of intestinal transit also increases intracolonic pH that, we hypothesized, should favor the solubilization and absorption of newly formed DCA within the colon. To test this hypothesis, we performed in vitro studies on homogenized cecal aspirates (obtained at colonoscopy) that were incubated anaerobically with [14C]cholic acid for 16 h after which the pH was adjusted to between 4.0 and 7.0 in 0.5-pH unit steps. The resultant reaction mixtures were centrifuged to separate the supernatant from the precipitate, and the specific activity of [14C]DCA was quantitated in both phases. As the pH in the aspirates was manipulated from 4.0 to 7.0, the proportion of newly formed, labeled DCA increased in the supernatant and fell in the precipitate, particularly at a hydrogen ion concentration of <100 x 10(-7) (equivalent to pH 5.0-7.0). These results show that the solubility of DCA in colonic contents increases with increasing pH. If solubility is rate limiting, this should lead to increased absorption that, in turn, would explain why the proportion of DCA in serum and bile increases with the prolongation of large bowel transit time.

Association of bowel movement frequency and use of laxatives with the occurrence of symptomatic gallstone disease in a prospective study of women

OBJECTIVES

The authors prospectively examined the association between bowel movement frequency (used as a proxy for intestinal transit), laxative use, and the risk of symptomatic gallstone disease.

METHODS

A total of 79,829 women, aged 36-61 yr, without a history of symptomatic gallstone disease and free of cancer, responded to a mailed questionnaire in 1982 that assessed bowel movement frequency and use of laxatives. Between 1984 and 1996, 4,443 incident cases of symptomatic gallstone disease were documented. Relative risks (RRs) of symptomatic gallstone disease and 95% confidence intervals (CIs) were calculated using logistic regression.

RESULTS

After controlling for age and established risk factors, the multivariate RRs were, compared to women with daily bowel movements, 0.97 (95% CI 0.86-1.08) for women with bowel movements every third day or less, and 1.00 (95% CI 0.91-11.1) for women with bowel movement more than once daily. No trend was evident. As compared to women who never used laxatives in 1982, a significant modest inverse association was seen for monthly laxative use, with a multivariate RR of 0.84 (95% CI 0.72-0.98), and weekly to daily laxative use was associated with a RR of 0.88 (95% CI 0.78-1.02).

CONCLUSIONS

These findings do not support an association between infrequent bowel movements and risk of symptomatic gallstone disease in women, and indicate that simple questions directed at bowel movement frequency are unlikely to enhance our ability to predict risk of symptomatic gallstone disease. The slightly inverse association between use of laxatives and risk of symptomatic gallstone disease may be due to a mechanism that is not related to bowel movement frequency.

Biliary lipid composition in patients with cholesterol and pigment gallstones and gallstone-free subjects: deoxycholic acid does not contribute to formation of cholesterol gallstones

BACKGROUND

Four main disturbances have been attributed to cholesterol gallstone disease: hypersecretion of cholesterol from the liver with cholesterol supersaturation in bile; disturbed motility with defective absorption and secretion by the gallbladder; increased crystallisation of cholesterol in the gallbladder bile; and slow intestinal transit with increased amount of deoxycholic acid in the bile acid pool. We aimed to evaluate the biliary lipid composition in a large series of gallstone patients, with emphasis on the amount of deoxycholic acid and with respect to number of stones, compared to gallstone free subjects.

MATERIALS AND METHODS

Bile was sampled during operations through puncture of the gallbladder from 145 cholesterol gallstone patients, 23 patients with pigment stones and 87 gallstone free patients undergoing cholecystectomy. Biliary lipid composition, cholesterol saturation, bile acid composition, nucleation time and cholesterol crystals were analysed.

RESULTS

The patients with cholesterol gallstones showed higher molar percentage of cholesterol, lower total biliary lipid concentration, higher cholesterol saturation, shorter nucleation time and higher proportion of crystals in bile than the other groups. The nucleation time was significantly shorter in multiple cholesterol gallstone patients, but this was not due to higher cholesterol saturation. Male cholesterol gallstone patients showed higher cholesterol levels, lower total biliary lipid concentration, and higher cholesterol saturation in bile than female patients. There was no difference in biliary content of deoxycholic acid, but significantly lower content of cholic acid in gallstone patients compared to gallstone free patients.

CONCLUSIONS

We conclude that deoxycholic acid does not contribute to gallstone formation in cholesterol gallstone patients. The short nucleation time in patients with multiple cholesterol stones is not due to higher cholesterol saturation.

Hepatolithiasis (intrahepatic stone) during octreotide therapy for acromegaly: a case report

We report a case of hepatolithiasis (intrahepatic stone) complicated by gram-negative sepsis in a 37 year old male with acromegaly being treated with octreotide. As a child, he had suffered a traumatic injury to his liver requiring the surgical repair of a laceration. This is the first reported case of hepatolithiasis during octreotide therapy. Gallstones and bile sludge are common side effects of octreotide therapy but rarely become symptomatic or require treatment. Hepatolithiasis is uncommon in western countries but is quite prevalent in East Asia and is often associated with a predisposing condition that causes intrahepatic bile stasis (eg. bile duct stricture). In addition to its known effect on gallbladder stasis, octreotide alters bile acid composition and may thus hasten intrahepatic sludge and stone formation. Extra caution should be taken in using octreotide or its long-acting analog in patients otherwise predisposed to intrahepatic bile stasis.

Gallstones

At the turn of the millennium, significant advances continue to be made into the epidemiology and pathophysiology of gallstone disease. The NHANES III study, the largest American population-based study of gallstone disease, estimated that more than 20 million Americans have undergone gallbladder surgery or currently have gallstones. Insulin resistance may be an independent risk factor for gallstone disease.Cholecystokinin receptors may be responsible for the altered motility of the gallbladder smooth muscle, and mucin may play an underestimated role as a pronucleating factor. For the first time, researchers have been able to directly observe cholesterol crystallization in human bile. Improved understanding of the multiple factors involved in the pathogenesis of gallstone disease should lead to new therapeutic and preventive strategies.

Mechanism for the transit-induced increase in colonic deoxycholic acid formation in cholesterol cholelithiasis

BACKGROUND & AIMS

Many patients with cholesterol gallbladder stones (GBS) have a high percentage of deoxycholic acid (DCA) in gallbladder bile (all of which are in the conjugated form), probably as a result of prolonged large bowel transit times (LBTT). However, whether the prolonged LBTT increases DCA formation, solubilization, or absorption (or all 3) is not known.

METHODS

In 40 subjects (20 with GBS; age range, 24-74 years), we measured LBTT using radiopaque markers, and intestinal luminal pH by radiotelemetry. We also measured quantitative anaerobic bacteriology and the activities of 2 bile acid-metabolizing enzymes in fresh cecal aspirates obtained during clinically indicated unprepared colonoscopy, and related these results to the percentage of DCA in fasting serum measured by gas chromatography-mass spectrometry.

RESULTS

Compared with controls, GBS patients had longer LBTT (mean 23.1 +/- SEM 2.8 h vs. 36.5 +/- 3.3 h; P < 0.01); more total (2.7 +/- 0.6 x 10(9) vs. 5.9 +/- 1.5 x 10(9) cfu/mL) and Gram-positive (9.5 +/- 3.1 x 10(8) vs. 18.0 +/- 4.1 x 10(8) cfu/mL; P < 0.05) anaerobes; and greater 7alpha-dehydroxylating (7alpha-DH) activity (3.39 +/- 0.59 vs. 10.37 +/- 1.15 x 10(-4) U/mg protein) in the cecal aspirates. They also had higher intracolonic pH values (P < 0.02) and increased percentages of DCA in fasting serum (13.4% +/- 1.52% vs. 21.8% +/- 2. 19%; P < 0.005). Results of univariate and multivariate analyses confirmed that LBTT was critical in determining the percentage of DCA in serum and showed that 7alpha-DH activity and apparent distal colonic pH were also significant independent variables.

CONCLUSIONS

Slow colonic transit (more time), increased Gram-positive anaerobes (more bacteria), and greater 7alpha-DH activity (more enzyme) favor enhanced DCA formation; transit-induced increases in distal colonic luminal pH favor enhanced DCA solubilization/bioavailability; and increases in LBTT (more time) again favor DCA absorption.

Insulin-like growth factor I and the development of colorectal neoplasia in acromegaly

Patients with acromegaly are at increased risk of colorectal neoplasia and, by analogy with high-risk nonacromegalic patients, may require regular colonoscopic screening. However, it is unknown whether the risk is equal in all patients or whether some should be regarded as carrying a particularly high risk. The aims of this study were: 1) to establish the natural history of colorectal neoplasia in acromegaly; 2) to establish which patients are at increased risk of developing neoplasia; and 3) to elucidate the influence of insulin-like growth factor I (IGF-I) in adenoma formation. A prospective colonoscopic evaluation of the development of new premalignant adenomas in the colon was performed in 66 patients with biochemically proven acromegaly who had previously undergone colonoscopic screening and removal of all visible polyps. Twenty-five patients (38%) had a total of 37 polyps detected at the second colonoscopy: nine (14%) had at least one adenoma, and 18 (27%) had one or more hyperplastic polyps (2 patients had both). The development of new adenomas, but not hyperplastic polyps, was associated both with elevated serum IGF-I (P < 0.005) and, to a lesser extent, with a previous adenoma at the original colonoscopy (P < 0.07). In summary, patients with acromegaly and in whom serum IGF-I remains elevated and/or who have had a previous adenoma should be regarded as having an especially high risk for the development of subsequent colorectal neoplasia. Serum IGF-I seems to be implicated in the development of colorectal neoplasia in acromegaly, although the exact mechanisms remain uncertain.

Review article: epidemiology of gall-bladder disease--role of intestinal transit

Recent epidemiological studies have suggested that hyperinsulinaemia may be a central factor in the pathogenesis of cholesterol gallstones, explaining a probable link with physical inactivity as well as abdominal adiposity. There is also increasing evidence for the hypothesis that enrichment of bile with DCA. 'the colonic bile acid', leads to enrichment of bile with cholesterol. Biliary DCA can be raised and lowered by slowing down and speeding up colonic transit, respectively. Slow transit is characteristic of non-obese British women with gallstones and of non-obese peasants in a gallstone-prone mountain community. High biliary DCA predicts recurrence of gallstones and so does laxative usage, a pointer to constipation and therefore to slow transit. In some studies, at least, a high fibre intake is protective against gallstones. Much else besides fibre influences colonic function. Future studies of gallstone aetiology should include measurements of colonic function. Measures that speed up colonic transit should be tested for their ability to prevent gallstone formation in high-risk individuals.

Review: pathogenesis of gallstones

The aim of this article is to review selected aspects of the pathogenesis of cholesterol-rich, gall-bladder stones (GBS)--with emphasis on recent developments in biliary cholesterol saturation, cholesterol microcrystal nucleation, statis within the gall-bladder and, particularly, on the roles of intestinal transit and altered deoxycholic acid (DCA) metabolism, in GBS development. In biliary cholesterol secretion, transport and saturation, recent developments include evidence in humans and animals, that bile lipid secretion is under genetic control. Thus in mice the md-2 gene, and in humans the MDR-3 gene, encodes for a canalicular protein that acts as a 'flippase' transporting phospholipids from the inner to the outer hemi-leaflet of the canalicular membrane. In the absence of this gene, there is virtually no phospholipid or cholesterol secretion into bile. Furthermore, when inbred strains of mice that have 'lith genes' are fed a lithogenic diet, they become susceptible to high rates of GBS formation. The precipitation/nucleation of cholesterol microcrystals from supersaturated bile remains a critical step in gallstone formation. methods of studying this phenomenon have now been refined from the original 'nucleation time' to measurement of cholesterol appearance/detection times, and crystal growth assays. Furthermore, the results of recent studies indicate that, in addition to classical Rhomboid-shape monohydrate crystals, cholesterol can also crystallize, transiently, as needle-, spiral- and tubule-shaped crystals of anhydrous cholesterol. A lengthy list of promoters, and a shorter list of inhibitors, has now been defined. There are many situations where GB stasis in humans is associated with an increased risk of gallstone formation--including iatrogenic stone formation in acromegalic patients treated chronically with octreotide (OT). As well as GB stasis, however, OT-treated patients all have 'bad' bile which is supersaturated with cholesterol, has excess cholesterol in vesicles, rapid microcrystal mulceation times and a two-fold increase in the percentage DCA in bile. This increase in the proportion of DCA seems to be due to OT-induced prolongation of large bowel transit time (LBTT). Thus LBTT is linearly related to (i) the percentage of DCA in serum; (ii) the DCA pool size; and (III) the DCA input or 'synthesis' rate. Furthermore, the intestinal prokinetic, cisapride, counters the adverse effects of OT on intestinal transit, and 'normalizes' the percentage of DCA in serum/bile. Patients with spontaneous gallstone disease also have prolonged LBTTs, more colonic gram-positive anaerobes, increased bile acid metabolizing enzymes and higher intracolonic pH values, than stone-free controls. Together, these changes lead to increased DCA formation, solubilization and absorption, Thus, in addition to the 'lithogenic liver' and 'guilty gall-bladder' one must now add the 'indolent intestine' to the list of culprits in cholesterol gallstone formation.