Impairment of health-related quality of life in functional dyspepsia and chronic liver disease: the influence of depression and anxiety

BACKGROUND

Health-related quality of life (HRQOL) is a marker of disease severity. Data on the relative impairment of HRQOL in chronic liver disease (CLD) and functional gastrointestinal disorders are lacking and no studies have assessed the link between impairment of HRQOL and psychosocial factors yet.

AIM

To assess predictors for, and the impairment of, HRQOL in CLD and FD.

METHODS

In 181 functional dyspepsia (FD) patients, 204 CLD patients and 337 healthy blood donors, HRQOL was assessed with the Short Form-36 (mental and physical component), and anxiety and depression utilizing the Hospital Anxiety and Depression Scale.

RESULTS

Compared with HC, HRQOL is significantly lower in FD and CLD (P-value for all <0.001). The mental but not physical component of HRQOL was significantly more impaired in FD compared with CLD (P < 0.05). After adjusting for confounders, impairment of mental (P < 0.001) and physical (P = 0.005) component of HRQOL was associated with the severity of CLD and FD. In FD, the multivariate analysis revealed depression and severity of symptoms as the most important predictors of HRQOL (R2 = 21.9 and 7.1). In CLD, the mental component of HRQOL was associated with depression and anxiety (R(2) = 9.9 and 9.7).

CONCLUSIONS

In tertiary care, HRQOL is more severely impaired in FD compared with CLD. Co-morbid psychiatric conditions significantly contribute to the impairment of HRQOL.

[Frequency, relevance, causes of and strategies for prevention of medication errors]

Drug therapy has led to major advances in medicine. The beneficial effects of drug therapy are coupled with the inevitable risk of adverse drug reactions especially in elderly patients. Many adverse drug reactions are preventable. The electronic health card that will be introduced in Germany starting in 2006 is designed to support electronic decision support to prevent medication errors. Studies have demonstrated that CPOES can reduce medication errors by 80%. The necessary steps to improve medication safety in Germany are outlined and discussed.

[Is an evidence-based therapy of inpatients with type 2 diabetes possible from studies used for formulating therapy guidelines?]

BACKGROUND AND OBJECTIVE

Evidence-based guidelines are based on controlled trials and expert knowledge. Controlled trials often exclude elderly patients and those with diseases of several organs. It was the aim of this study to assess to what extent evidence-based guidelines of the German Diabetes Society (DDG) for antihyperglycaemic treatment were applicable to hospitalized patients with type 2 diabetes.

PATIENTS AND METHODS

The exclusion criteria of the clinical trials listed in the guidelines of the DDG (Diabetes und Stoffwechsel 12/2003; supplement 2, 29-31) were analysed. The study cohort consisted of all patients on drug treatment of type 2 diabetes who had been hospitalized during August and September 2003 in the two medical units of the Saarbrucken University Hospital. Current data on diabetes-associated and diabetes-dependent diseases were recorded.

RESULTS

91 of 125 literature citations (72%) contained clinical studies of evidence class I-III. 33.3% od studies had explicitly excluded patients with renal disease, 31.1% with liver disease, 10.9% with an age >75 years, 15.2% with coronary heart disease and 12.3% with heart failure. These exclusion criteria were used regardless of the drugs used. In 153 of 982 patients (15.5%) had drug-treated type 2 diabetes mellitus, median age was 73 years. In 138 of 153 patients (90.1%) medical and and social data could be obtained. 18.1% of these patients would have been excluded because their creatinine was >1.5 mg/dl, 45.5% because they were older then 75 years, 50.7% because they had coronary heart disease, and 15.9% because of heart failure (some patients met more than one of these items).

CONCLUSION

Treatment of hospitalized patients with type 2 diabetes with cardiac, hepatic and/or renal disease or older than 75 years was not possible if medical management was based on clinical studies with an evidence level I-III.

[Chronic abdominal pain--internistic-psychosomatic aspects]

Abdominal pain is considered to be chronic when it persists for at least three months or when a patient experiences such pain for a total of three months during the course of a year. Pathophysiologically, nociceptive/neuropathic functional pain syndrome, mental disorders with the cardinal symptom of chronic pain, and mixed forms can be distinguished. In 50% of the patients, the cause of chronic abdominal pain is a functional gastrointestinal disorder e.g. functional dyspepsia irritable bowel syndrome. On the basis of a structured pain history, a physical examination and a basic "technical" diagnostic program (laboratory investigations, abdominal ultrasonography, Esophagogastroduodenoscopy, colonoscopy), correct assignment to one of the above-mentioned can be achieved in most of the cases.

Validation of the Inflammatory Bowel Disease Questionnaire IBDQ-D, German Version, for Patients with Ileal Pouch Anal Anastomosis for Ulcerative Colitis

BACKGROUND AND AIMS

The inflammatory bowel disease questionnaire (IBDQ) is the standard instrument for assessment of health-related quality of life (HRQOL) in patients with inflammatory bowel diseases. It has not been validated for patients with ileal pouch anal anastomosis (IPAA) and ulcerative colitis (UC).

METHODS

To determine acceptance (percentage of completed items), reliability (Cronbach's alpha of the IBDQ-D subscales) and convergent validity (correlations of the IBDQ subscales with the questionnaires used for validation) 61 patients with UC (age 52.7 +/- 13.9 years; 47 % female, 53 % male) and IPAA completed the German (Competence Network IBD) version of the Inflammatory Bowel Disease Questionnaire (IBDQ-D), the Short Form Health Survey (SF-36) the Hospital Anxiety and Depression Scale German Version (HADS-D) and the Giessener Symptom List (GBB 24). Face validity was assessed by a physicians' and patients' panel. All 37 patients underwent endoscopy making it possible to differentiate between patients with and without pouchitis (discriminant validity).

RESULTS

With 97.7 % completed items the acceptance was high. Cronbach's alpha value for the subscales ranged from 0.71 to 0.93. Missing items covering extraintestinal manifestations of IBD were criticized by patients. The correlation coefficients with comparable subscales of other instruments ranged between 0.41 and 0.76. Patients with clinical pouchitis scored significantly lower in all subscales than patients without pouchitis (p < 0.001).

CONCLUSION

The IBDQ-D has good acceptance, reliability, convergent and discriminant validity, but limited face and construct validity in patients with IPAA and UC.

Validierung der deutschen Version der Fatigue Impact Scale FIS-D

OBJECTIVE

The Fatigue Impact Scale, FIS, is an internationally used instrument for the assessment of the impact of fatigue on Health-Related Quality of Life, HRQOL, also in patients with chronic liver diseases. In the German-speaking countries a validated instrument for measuring the impact of fatigue on patients with chronic liver diseases has not been available so far.

METHODS

The German linguistic adaptation of the FIS using a forward-backward procedure was administered to 204 patients (age 52,7 +/- 13,9 years; 47 % female, 53 % male, 45 % no cirrhosis, 22 % Child's A, 15 % Child's B and 17 % Child's C cirrhosis; 53 % with chronic viral hepatitis, 32 % with alcoholic and 15 % with other liver diseases) of a secondary care hospital. The following internationally accepted instruments were used for validation: The Short Form Health Survey, SF 36, the Hospital Anxiety and Depression Scale German Version, HADS-D, and the Giessener Symptom Scale, GBB 24. Fifty patients in clinically stable situation filled out the FIS-D within 3 - 8 days.

RESULTS

The acceptance of the FIS-D was high with 98 % answered items. The internal consistency of the three subscales was excellent (0.94 - 0.96), the test-retest reliability of the three subscales was good (0.72 - 0.83). The correlation coefficients with the validation instruments ranged between 0.49 and 0.80 (all p < 0 001). No differences in the FIS-D subscale scores were found in patients with and without cirrhosis and between the different Child-Pugh stages of liver cirrhosis. Patients treated with tranquilizer or antidepressants scored higher in the FIS-D than patients without this treatment (p < 0.05).

CONCLUSION

The FIS-D is well accepted by patients in clinical routine care and has been shown to have good acceptance and reliability in the assessment of fatigue in chronic liver patients.

[Psychophysiology of visceral pain syndromes]

Psychosomatics of visceral pain syndromes. From a psychosomatic point of view visceral pain syndromes can be classified into nociceptive (somatic and visceral) pain syndromes without and with maladaptive pain coping resp.psychic comorbidity, functional pain syndromes (typical symptom clusters without biochemical or structural abnormalities in clinical routine diagnostics) and psychic disorders with pain as main symptom. With regard to the etiology and the course of chronic inflammatory bowel diseases (IBD) as representatives of somatic pain syndromes and of irritable bowel syndrome/chronic pelvic pain as representatives of functional pain syndromes empirically validated psychosocial aspects are summarized: Personality traits, illness behavior, daily hassles, life events and psychic comorbidity and effects of psychotherapy. Psychosocial factors are decisive in the etiology and the course of functional pain syndromes as determinants of their severity (psychosomatic disease in a narrow sense). Psychosocial factors are not decisive for the etiology, but for the course of IBD (psychosomatic disease in a broader sense). Within general pain therapy of visceral pain syndromes a biopsychosocial approach should be applied right from the beginning (psychosomatic basic care). Within special pain therapy of visceral pain syndromes a qualified psychiatric - psychotherapeutic diagnostics and co-therapy should be mandatory.

[Tobacco associated gastrointestinal disorders: smoking cessation therapy - a task for gastroenterologists]

Tobacco smoking is an independent risk factor in the etiology of Crohn's disease, functional dyspepsia, GERD, chronic pancreatitis and gastrointestinal carcinomas (oesophagus, stomach, colon, pancreas and liver). The current knowledge of the effects of tobacco smoking on the gastrointestinal tract is summarised. Non-smoking should be recommended to everybody as primary prevention against cardiopulmonary and gastrointestinal diseases. Despite lacking of clinical studies tobacco abstinence should be recommended as a secondary preventive therapy of Crohn's disease, functional dyspepsia, GERD and chronic pancreatitis because of epidemiological studies and pathophysiological considerations. All gastroenterologists should help patients with the above mentioned diseases to stop smoking. Evidence based methods of smoking cessation and methods suited to routine clinical care are presented. Pharmacological (nicotine replacement therapy) and psychological therapies (cognitive behavioural group therapies) should be adapted to the prior experiences of the patient, his stage of motivation to stop smoking and his co-morbidity. In refractory ulcerative colitis controlled tobacco smoking can be recommended to ex-smokers.

[Colitis ulcerosa and opioid addiction]

The occurrence of an opioid addiction within an opioid treatment of pain or diarrhoea in inflammatory bowel disease is rarely reported. We report on a 36-year-old male with a 14 years lasting left sided chronic ulcerative colitis who developed after the initiation of a therapy with tincture of opium because of abdominal pain and diarrhoea an opioid addiction with the consumption of opium and later buprenorphin. Additionally to the diagnostics and therapy of the ulcerative colitis a detoxication was carried out. The diarrhoea slightly increased during the buprenorphin withdrawal. Diarrhoea refractory to other treatment should be treated by loperamid because of its lacking effects on the central nervous system. In chronic abdominal or musculoskeletal pain in inflammatory bowel disease opioids can be used if no surgical or other medical pain relief is possible. A consequent control of the therapeutic and side effects of the opioid therapy is necessary, especially of an abuse of opioid medication. The published case reports of a therapeutic induction of opioid addiction demonstrate that psychiatric comorbidity is an essential or even necessary risk factor. A checklist with seven criteria of opioid addiction during opioid therapy is presented.

[Smoking cessation. A physician's responsibility]

Giving up smoking is a cost-effective measure in the secondary prevention of chronic arterial disease and chronic obstructive pulmonary disease. The involvement of the physician in the primary prevention of smoking and kicking the habit in the case of tobacco-related disease, must receive greater emphasis than has so far been the case in Germany. Weaning smokers suffering from tobacco-related disease from their habit is a task for the physician, and may take the form either of a single minimal intervention, or successive consultations that can be integrated in every medical activity. The concept of stepwise smoking dishabituation is supported by evidence-based consensus recommendations on the part of relevant national and international medical societies and public institutions.

[Chronic intestinal pseudo-obstruction. Clinical symptomatology and course]

BACKGROUND AND OBJECTIVE

Chronic intestinal pseudoobstruction (CIP) is a motility disorder clinically characterized by recurrent symptoms of small intestinal or large bowel obstruction without organic stenosis. The aim of the present study was to assess the clinical presentation and course of the disease.

PATIENTS AND METHODS

During a four year period all available data including the symptoms as assessed by the bowel disease questionnaire (BDQ) of all patients with newly established diagnosis of CIP were analyzed including duration of symptoms and previous surgical interventions due to the abdominal symptoms.

RESULTS

Data of nine patients (five females, four males, age 20 - 64 years) with newly diagnosed CIP were available for analysis. Median age at initial onset of symptoms were 24 years. The final diagnosis of CIP was established after a median of 7 years (range 1 - 20). Initially, the majority of patients suffered from uncharacteristic symptoms such as abdominal fullness and abdominal pain. All patients had undergone repeated abdominal surgical interventions for suspected mechanical bowel obstruction. On average, the first surgical intervention was performed 5 years after the onset of symptoms and there was a median number of 10 treatments as in-patients. Suspected acute bowel obstruction occurred between 1 and 14 times and laparotomies were performed in 50 % of these events.

CONCLUSION

The diagnosis of CIP is usually preceded by several years with uncharacteristic abdominal symptoms. During this time, most patients undergo multiple surgical interventions. Thus, in patients with repeated suspected acute bowel obstruction without definite proof of mechanical obstruction, CIP has to be taken into consideration as differential diagnosis. In this context, small bowel manometry is an important diagnostic tool.

[Measuring quality of life in gastroenterology--concepts, instruments and problems]

Health-related quality of life (HRQOL) is becoming an increasingly more important primary or secondary end point of clinical studies. Patients and their self help organizations demand a greater regard to their subjective experience of their disease and its treatment. Cost-effectiveness analyses measuring quality-adjusted life years are becoming more and more decisive in health politics. Therefore it is important for gastroenterologists to know the concepts and methods of HRQOL-measurement. The present article discusses the definitions of (health-related) quality of life and reviews generic- and disease-specific quality of life instruments in gastroenterology including quality criteria. Rules for the adaptation of Anglo-American questionnaires into German-speaking countries are pointed out. Finally the limitations of the concepts of HRQUOL and its measurement are discussed.

Antisecretory mechanisms of peptide YY in rat distal colon

Peptide YY (PYY) is a potent regulator of intestinal secretion. These studies investigated the role of Y1 and Y2 receptor subtypes in mediating the antisecretory effects of PYY on mucosa-submucosa preparations of rat distal colon. Addition of vasoactive intestinal peptide (VIP) to these tissues resulted in a 140 +/- 18% increase in basal short-circuit current (Isc) and the induction of Cl- secretion. VIP-stimulated increases in Isc were abolished by the addition of each of PYY, (Pro34)-PYY, a Y1 receptor-selective agonist, and PYY-(3-36), an endogenous Y2 receptor-selective ligand. However, when tissue neural transmission was blocked with tetrodotoxin, neither PYY nor its receptor subtype-selective analogs were able to inhibit VIP-stimulated increases in Isc. These results suggest that in the rat distal colon, the antisecretory actions of PYY are mediated through a combination of Y1 and Y2 receptor subtypes or through a novel receptor subtype that is unable to discriminate between (Pro34)-PYY and PYY-(3-36).

Altered postprandial motility in chronic pancreatitis: role of malabsorption

BACKGROUND & AIMS

Intraileal nutrients modulate gastrointestinal motility, but effects of maldigestion on postprandial motility are unknown. The aim of this study was to compare motor responses with ileal nutrient exposure in health and pancreatic insufficiency after a meal or intraluminal perfusion.

METHODS

After oroileal multilumen intubation for duodeno-jejuno-ileal sampling, marker perfusion, and motility recording, 14 normal subjects and 12 patients with severe pancreatic insufficiency received a labeled liquid meal twice, either with placebo or pancreatin. Effects of intraileal nutrient perfusion on fed motility induced by duodenal amino acid perfusion were also investigated.

RESULTS

Compared with normals, untreated patients had greater cumulative ileal nutrient delivery (69 +/- 21 vs. 487 +/- 232 kJ), shorter fed pattern (196 +/- 22 vs. 131 +/- 14 minutes), greater 90% gastric emptying (163 +/- 12 vs. 128 +/- 10 minutes), and faster small intestinal transit (86 +/- 9 vs. 44 +/- 6 minutes). Pancreatin reversed these changes. Ileal nutrient perfusion converted fed into interdigestive-like motility in normals (7 of 8) and patients (4 of 5).

CONCLUSIONS

In subjects with pancreatic insufficiency, a low-energy liquid meal induces shorter fed motor pattern associated with accelerated gastric emptying and intestinal transit compared with healthy subjects. Because changes responded to enzyme treatment and could be reproduced by ileal nutrient perfusion, ileal delivery of malabsorbed chyme may be involved as a mechanism.

Neuropeptide Y 3-36 is an endogenous ligand selective for Y2 receptors

Neuropeptide Y (NPY 1-36) binds to Y1 and Y2 receptors with similar affinity. No endogenous molecular form of NPY with selectivity for Y1 or Y2 receptors has been described so far. We report the presence of an endogenous fragment of NPY in porcine brain, NPY 3-36, which lacks the amino-terminal dipeptide Tyr-Pro of NPY 1-36. NPY 3-36 accounts for 35% of NPY-like immunoreactivity in porcine brain. We have compared binding of NPY 3-36 and NPY 1-36 in model systems of Y1-like (SK-N-MC cells) and Y2-like receptors (CHP234 cells). NPY 3-36 and NPY 1-36 had similarly high affinity for Y2-like receptors on CHP234 cells, but NPY 3-36 had a 1000-fold lower affinity than NPY 1-36 for Y1-like receptors on SK-N-MC cells. Thus amino-terminal cleavage of NPY 1-36 generating NPY 3-36 converts an unselective Y1/Y2 receptor ligand into a highly Y2 selective ligand. This may be a means of fine tuning NPY biological actions.

Inhibition of canine exocrine pancreatic secretion by peptide YY is mediated by PYY-preferring Y2 receptors

It is still unclear, which receptor subtype, Y1 and/or Y2, mediates the inhibitory action of PYY on exocrine pancreatic secretion. The present study was undertaken to characterize functionally the Y receptor subtype that mediates the inhibition of exocrine pancreatic secretion by peptide YY (PYY). In eight conscious dogs with chronic gastric and pancreatic fistulas, we compared the action of intravenous infusion of 200 and 400 pmol/kg/h of the Y receptor agonists PYY 1-36, PYY 3-36, PYY 13-36, Pro34PYY 1-36, and NPY 1-36 on the pancreatic secretory response to secretin (20.5 pmol/kg/h) and cerulein (29.6 pmol/kg/h). PYY 13-36, Pro34PYY 1-36, and NPY 1-36 were also studied by giving a fivefold dose (1,000 and 2,000 pmol/kg/h). PYY 1-36 and the Y2 receptor agonist PYY 3-36 significantly inhibited pancreatic secretory responses to secretin and cerulein, whereas inhibition by NPY 1-36 and the Y2 receptor agonist PYY 13-36 was attainable only at doses of 1,000 and 2,000 pmol/kg/h. The Y1 receptor agonist Pro34PYY 1-36 was without effect on pancreatic secretion. We conclude that in dogs the inhibition of exocrine pancreatic secretion by PYY is mediated via Y2 receptors of a PYY-preferring subtype.

Reversal by NPY, PYY and 3-36 molecular forms of NPY and PYY of intracisternal CRF-induced inhibition of gastric acid secretion in rats

1. The Y receptor subtype involved in the antagonism by neuropeptide Y (NPY) of intracisternal corticotropin-releasing factor (CRF)-induced inhibition of gastric acid secretion was studied in urethane-anaesthetized rats by use of peptides with various selectivity for Y1, Y2 and Y3 subtypes: NPY, a Y1, Y2 and Y3 agonist, peptide YY (PYY), a Y1 and Y2 agonist, [Leu31, Pro34]-NPY, a Y1 and Y3 agonist, NPY(3-36) and PYY(3-36), highly selective Y2 agonists and NPY(13-36) a weak Y2 and Y3 agonist. Peptides were injected intracisternally 10 min before intracisternal injection of CRF (10 micrograms) and gastric acid secretion was measured by the flushed technique for 1 h before and 2 h after pentagastrin-(10 micrograms kg-1 h-1, i.v.) infusion which started 10 min after CRF injection. 2. Intracisternal injection of CRF (10 micrograms) inhibited by 56% gastric acid secretion stimulated by pentagastrin. Intracisternal injection of NPY and PYY (0.1-0.5 microgram) did not influence the acid response to pentagastrin but blocked CRF-induced inhibition of pentagastrin-stimulated acid secretion. NPY(3-36) (0.5 microgram) and PYY(3-36) (0.25 and 0.5 microgram) also completely blocked the inhibitory action of CRF on pentagastrin-stimulated acid secretion. 3. [Leu31, Pro34]-NPY (0.5-5 micrograms) and NPY(13-36) (0.5-5 micrograms) injected intracisternally did not modify gastric acid secretion induced by pentagastrin or CRF inhibitory action. 4. The sigma antagonist, BMY 14802 (1 mg kg-1, s.c.) did not influence the acid response to pentagastrin but prevented the antagonism by PYY(3-36) (0.5 microgram) of the CRF antisecretory effect. 5. These results show that both PYY and NPY and the 3-36 forms of PYY and NPY are equipotent in blocking central CRF-induced inhibition of pentagastrin-stimulated gastric acid secretion. The structure-activity profile suggests a mediation through Y2 receptor subtype and the involvement of sigma binding sites.

Inhibitory effect of PYY on vagally stimulated acid secretion is mediated predominantly by Y1 receptors

Two molecular forms of peptide YY (PYY), PYY-(1--36) and PYY-(3--36), are abundant in rabbit intestine and blood. We have previously shown that PYY-(1--36) (PYYI) activates equipotently Y1 and Y2 receptors and PYY-(3--36) (PYY II) is a highly selective agonist for Y2 receptors. In the present study, we examined the effect of exogenous infusion of PYY on vagally stimulated gastric acid secretion in awake rabbits with chronic gastric fistula. To determine the specific PYY receptor(s) that mediates this effect, we used a highly selective Y1 agonist, Pro34-PYY, a synthetic PYY, and a Y2-selective agonist, PYY II. Vagal stimulation of acid secretion was elicited by an intravenous bolus injection of insulin (0.125 U/kg) 30 min after beginning a 180-min intravenous infusion of either PYY I, PYY II, or [Pro34]-PYY after a 50 micrograms/kg i.v. bolus of atropine followed immediately by a 500 micrograms/kg sc injection. During infusion of 200 pmol.kg 1.h-1 PYY I, acid output was significantly inhibited to 45 +/- 13% of maximum acid output 60 min after injection of insulin. Similarly, acid output during infusion of 200 pmol.kg-1.h-1 [Pro34]-PYY was significantly inhibited to 52 +/- 12% of maximum. In contrast, acid output during infusion of 200 pmol.kg-1.h-1 of PYY II was not significantly inhibited (101 +/- 18% of maximum). Infusion of double the dose (400 pmol.kg-1.h-1) of PYY II resulted in acid inhibition (51 = 15% of maximum), whereas infusion of the same dose did not significantly enhance acid inhibition by infusion of either PYY I or [Pro34]-PYY (28 +/- 11 and 42 +/- 15% of maximum). These results indicate that PYY, acting predominantly at Y1 receptors, is a potent inhibitor of vagally stimulated acid secretion in adult rabbits.

Ileal release of glucagon-like peptide-1 (GLP-1). Association with inhibition of gastric acid secretion in humans

There is evidence that the distal intestine participates in the regulation of gastric motor and secretory function. It was the aim of this study to examine in greater detail the effects of ileal nutrient exposure on human gastric acid secretion and to investigate potential intermediary mechanisms. Twelve normal subjects were intubated with an oroileal multilumen tube assembly for gastric, duodenal, and ileal perfusion of marker and test solutions, aspiration, and intestinal manometry. We studied ileal effects on gastric acid output in the unstimulated, interdigestive state (during early phase II, N = 6), and during endogenous stimulation by intraduodenal essential amino acid perfusion, N = 6) and on release of candidate humoral mediators, peptide YY (PYY) and glucagonlike peptide-1 (GLP-1), both known inhibitors of human gastric acid secretion. Compared with ileal saline perfusion, ileal carbohydrate (total caloric load: 60 kcal) decreased interdigestive gastric acid output by 64% (P < 0.01), and endogenously stimulated output by 68%, respectively (P < 0.005). Under all experimental conditions, ileal carbohydrate increased plasma GLP-1 by 80-100% (all P < 0.005). Ileal lipid perfusion had similar inhibitory effects on gastric acid output and stimulatory effects on GLP-1 release as had ileal carbohydrate. By contrast, ileal perfusion with peptone had no or only weak effects on either acid output or plasma GLP-1. Plasma PYY concentrations and suppression of gastric secretion in response to ileal perfusions were not correlated. In humans, both interdigestive and endogenously stimulated gastric acid output are inhibited in response to intraileal carbohydrate or lipids, but not protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Peptide YY inhibits exocrine pancreatic secretion in isolated perfused rat pancreas by Y1 receptors

Peptide YY (PYY) inhibits exocrine pancreatic secretion in several species. Two receptors, Y1 and Y2, are known to mediate PYY actions. While PYY 1-36 binds equally to both receptor subtypes, a second endogenous form of PYY, PYY 3-36, selectively activates Y2 receptors. The importance of Y receptor subtypes for inhibition of exocrine pancreatic secretion by PYY is unknown. We studied the effects of PYY 1-36 on cholecystokinin octapeptide (CCK-8)-stimulated amylase secretion in an isolated perfused rat pancreas model. To characterize functionally the receptors involved we determined the effects of a Y1-selective agonist, [Pro34]PYY; a Y2 selective agonist, PYY 3-36; and neuropeptide Y (NPY) in this model. PYY 1-36 significantly inhibited stimulated amylase secretion in the denervated rat pancreas. [Pro34]PYY and NPY both inhibited exocrine pancreatic secretion as potently as PYY 1-36. Contrary to that, the Y2 selective agonist, PYY 3-36, was inactive. We conclude that PYY inhibits exocrine pancreatic secretion in this extrinsically denervated rat pancreas model by Y1 receptors.

[Pro34]peptide YY is a Y1-selective agonist at peptide YY/neuropeptide Y receptors

We have investigated binding and functional effects of a new peptide YY analogue, [Pro34]peptide YY, at Y1 and Y2-like subtypes of receptors for peptide YY and neuropeptide Y. In binding studies [Pro34]peptide YY had a similarly high affinity as peptide YY to human Y1-like receptors in SK-N-MC cells, a human neuroblastoma cell line of presumed neurogenic origin, and HEL cells, a human cell line derived from a patient with Hodgkin's disease. In functional studies [Pro34]peptide YY stimulated Ca2+ elevations in both Y1-like receptor cell lines with similar potency and efficacy as peptide YY. In contrast to peptide YY [Pro34]peptide YY was 1000-fold less potent in binding to Y2-like receptors in porcine splenic membranes and lacked agonistic effects in another Y2-like receptor-mediated model system, i.e. inhibition of [3H]serotonin release from rat cerebral cortical slices. Thus, [Pro34]peptide YY is a highly Y1-selective full agonist of peptide YY/neuropeptide Y receptors. [Pro34]peptide YY could be useful for studying the importance of Y receptor subtypes in mediating peptide YY physiological actions.

Two molecular forms of peptide YY (PYY) are abundant in human blood: characterization of a radioimmunoassay recognizing PYY 1-36 and PYY 3-36

Two endogenous forms of PYY are abundant in man and dog, PYY 1-36 (PYY-I) and PYY 3-36 (PYY-II). PYY-II is a major molecular form of PYY in human colon, but it is not known, whether PYY-II is also released into the circulating blood. Several radioimmunoassays for measuring PYY-I in plasma have been developed, but it has not been reported, whether they equally detect PYY-II. We characterize a radioimmunoassay for measuring PYY in human plasma which equally recognizes PYY-I and PYY-II. Using this radioimmunoassay and reversed phase HPLC we demonstrate the existence of two forms of PYY in human blood, coeluting with synthetic PYY-I and PYY-II.

Characterization of two forms of peptide YY, PYY(1-36) and PYY(3-36), in the rabbit

Peptide YY (PYY) has been purified as a 36 amino acid peptide from intestinal extracts of several mammalian species including pig, rat, dog, and man. The primary structure of rabbit PYY is still unknown, although rabbit tissues have extensively been used for characterization of PYY receptor subtypes and receptor subtype-mediated actions. We report the purification and primary structure of PYY(1-36) (PYY-I) from rabbit intestinal mucosa, and the existence of a second endogenous molecular form of PYY, PYY(3-36) (PYY-II). The amino acid sequence of PYY-I is YPSKPEAPGEDASPEELNRYYASLRHYLNLVTRQRY-amide. Rabbit PYY differs from porcine PYY, which is identical to rat and canine PYY, by two amino acid substitutions at positions 3 (Ser instead of Ala) and 18 (Asp instead of Ser), whereas rabbit PYY and human PYY differ by only one residue at position 3 (Ser instead of Ile). The existence of two endogenous forms of PYY in the rabbit, with PYY-II lacking the amino-terminal dipeptide Tyr-Pro of PYY-I, is consistent with previously reported findings, demonstrating the existence of PYY-II in man and dog (9,11). We have previously demonstrated that PYY-I is an unselective Y1/Y2 agonist, whereas PYY-II is a highly selective Y2 agonist. Thus, proteolytic processing of PYY-I controls the peptide's receptor selectivity. The existence of PYY-I and PYY-II in the rabbit supports the assumption of a physiological role of Y receptor heterogeneity for PYY.

Proteolytic processing of neuropeptide Y and peptide YY by dipeptidyl peptidase IV

Neuropeptide Y, peptide YY and pancreatic polypeptide share an evolutionary conserved proline-rich N-terminal sequence, a structure generally known to be inert to the attack of common proteinases, but a potential target for specialized proline-specific aminopeptidases. Purified human dipeptidyl peptidase IV (also termed CD 26) liberated N-terminal Tyr-Pro from both, neuropeptide Y and peptide YY, with very high specific activities and Km values in the micromolar range, but almost no Ala-Pro from pancreatic polypeptide. Other proline-specific aminopeptidases exhibited low (aminopeptidase P, liberation of N-terminal Tyr) or totally no activity (dipeptidyl peptidase II), as was also observed with less-specific aminopeptidases (aminopeptidase M, leucine aminopeptidase). When human serum was incubated with neuropeptide Y or peptide YY at micro- and nanomolar concentrations, Tyr-Pro was detected as a metabolite of both peptides. Formation of Tyr-Pro in serum was blocked in the presence of Lys-pyrrolidine and diprotin A (Ile-Pro-Ile), specific, competitive inhibitors of dipeptidyl peptidase IV. Incubation of neuropeptide Y or peptide YY with immunocytochemically defined, cultivated endothelial cells from human umbilical cord also yielded Tyr-Pro. Dipeptidyl peptidase IV could be immunostained on most endothelial cells by a specific antibody. We suggest that dipeptidyl peptidase IV might be involved in the degradation of neuropeptide Y and peptide YY to N-terminal truncated neuropeptide Y(3-36) and peptide YY(3-36). Since specific binding to Y1, but not to Y2 subtype of neuropeptide Y/peptide YY receptors requires intact N- as well as C-termini of neuropeptide Y and peptide YY, removal of their amino-terminal dipeptides by dipeptidyl peptidase IV inactivates them for binding to one receptor subtype.

Comparison of clearance and metabolism of infused cholecystokinins 8 and 58 in dogs

BACKGROUND

Cholecystokinin (CCK) 58 is the predominant molecular form of CCK in canine and human intestine and circulating blood. There is no report on the metabolism and clearance rate of CCK-58. The aim of this study was to compare the in vivo half-life and metabolism of CCK-58 with that of synthetic CCK-8.

METHODS

CCK-58 was purified from canine intestine by consecutive high-performance liquid chromatographic (HPLC) and fast protein liquid chromatographic steps. The peptides were given to 12 dogs as an intravenous (IV) bolus injection to determine the half-life of circulating CCK. Six dogs were given CCK-58 or CCK-8 as a constant IV infusion to determine plasma clearance rates and stability in circulating blood. Circulating molecular forms of CCK were determined by radioimmunoassay after extraction of CCK from plasma and characterization by HPLC.

RESULTS

The half-life of CCK-58 was 4.4 +/- 0.6 minutes compared with 1.3 +/- 0.1 minutes for CCK-8. Less than 5% of CCK-58 could be detected as smaller forms during constant IV infusion.

CONCLUSIONS

The longer half-life of CCK-58 compared with CCK-8 and the minimal conversion into smaller forms during constant IV infusion are consistent with the finding that CCK-58 is not only the major stored form but also the circulating form of CCK after endogenous stimulation in dogs.

[Proteolytic processing by dipeptidyl aminopeptidase IV generates receptor selectivity for peptide YY (PYY)]

Two receptor subtypes, Y1 and Y2, are known to mediate PYY biological activity. PYY 1-36 binds to Y1 and Y2 receptors with equal affinity, whereas the second endogenous form of PYY, PYY 3-36, selectively binds to Y2 receptors. Dipeptidyl cleavage thus transforms an unselective Y agonist into a highly selective Y2 agonist, PYY 3-36. The enzyme responsible for this processing is unknown. Since PYY has a proline in the penultimate position it is protected from the attack of most unspecific exopeptidases. Only a few exopeptidases are theoretically capable of generating PYY 3-36 from PYY 1-36. Of the enzymes tested only the dipeptidyl aminopeptidase IV (DPP IV, E.C. 3.4.14.5) cleaved Tyr-Pro from PYY 1-36 with high activity. Since DPP IV is found on the endothelial surface and brush border membranes it can be considered a candidate enzyme for generating PYY 3-36 in vivo, thereby regulating the ratio of Y1/Y2 receptor stimulation by PYY.

[The terminal ileum as a co-regulator of cyclic interdigestive pancreatic secretion in man]

Nutrients present in the ileum of humans can modulate endogenously stimulated pancreatic secretion. To determine whether cyclic interdigestive pancreatic secretion can also be influenced by nutrients in the ileum, six fasting volunteers were intubated with an oro-ileal multi-lumen tube for perfusing test and marker solutions, aspiration of duodenal contents and recording of motility. At the beginning of the interdigestive cycle, the ileum was perfused intermittently with solutions of carbohydrates, proteins or lipids in the physiological amounts observed in the ileum after a meal; saline solution was perfused as a control. After saline, protein and calcium perfusion, the expected periodic increase in chymotrypsin secretion was observed during phase II of the interdigestive cycle (p < 0.05 vs phase I). In contrast, carbohydrates and lipids inhibited the phase-II-associated increase in pancreatic secretion. These findings indicate that the ileum may be involved in the regulation of human interdigestive pancreatic secretion.

[Y1 receptors mediate inhibitory and stimulatory effects of peptide YY in isolated small intestine and large intestine muscles of the rabbit]

Peptide YY has been shown to have stimulatory and inhibitory effects on gastrointestinal motility. However, the receptors mediating these effects are unknown. To determine if specific YY receptor agonists can mediate the effects on gastrointestinal motility we studied the effects of peptide YY (PYY), of Pro34PYY, a selective Y1 agonist, and of PYY 3-36, a selective Y2 agonist, on the motility in isolated smooth muscle strips from rabbit small and large intestine. In strips from distal colon, PYY stimulated spontaneous motility whereas it inhibited spontaneous contractions in circular strips from distal ileum. In distal circular colon maximal inotropic response (10.1 +/- 2.1% of a maximal response to carbachol 10(-5) M) was found at PYY 10(-8) M; (ED50 3.1 +/- 1.2 x 10(-9) M). In distal circular ileum maximal inhibition (by 39 +/- 20% of basal motility index) was found at 10(-7) M; (ID50 6.2 +/- 1.4 x 10(-9) M). PYY caused a dose-dependent inhibition of the on-contraction induced by electrical field stimulation. This inhibition could not be reversed by alpha- or beta-adrenergic blockade. PYY had no influence on the inotropic response evoked by carbachol. Both the stimulatory effect of PYY observed in distal colon and the inhibitory effect in distal ileum could be reproduced by the Y1 agonist Pro34PYY, but not by the Y2 agonist PYY 3-36. In distal circular colon the maximal inotropic response evoked by the Y1 agonist was 10 +/- 1.4%; (ED50 1.2 +/- 0.5 x 10(-8) M).(ABSTRACT TRUNCATED AT 250 WORDS)

Novel generation of hormone receptor specificity by amino terminal processing of peptide YY

The physiological significance of multiple Y receptors has not been determined since until recently only one form of endogenous agonists was known, namely PYY1-36 and NPY1-36. Recently, a new molecular form of PYY was characterized as des(Tyr-Pro)PYY (PYY3-36 or PYY-II). Its ability to interact at various Y receptors was not characterized. Analytical chromatography of fresh canine colon extracts shows two peaks of immunoreactivity eluting in the positions of PYY-II and PYY1-36 (PYY). PYY-II was about 40% of the total PYY immunoreactivity indicating that it is one of the major forms of PYY expressing its biological activity. It is shown that PYY-II will not displace label from the Y1 receptors found on a human neuroblastoma cell line. It is further shown that PYY-II is as potent as PYY for the inhibition of pancreatic secretion, which must occur through Y2 receptors. The enzymatic removal of Tyr-Pro from PYY to form PYY-II must therefore regulate the relative expression of a non-selective agonist (PYY) to a highly selective Y2 agonist (PYY-II). Amino terminal processing of PYY represents a novel type of regulation of peptide hormone specificity. It has important biological implications for PYY and potential relevance for other peptide hormone receptor systems.

Patterns of prohormone processing. Order revealed by a new procholecystokinin-derived peptide

An 83-amino acid cholecystokinin peptide with a sulfated tyrosine and an amidated carboxyl terminus (CCK-83) was purified from human intestinal mucosa. The purified peptide was chemically characterized, and its bioactivity was compared to CCK-8. Several post-translational processing steps such as cleavage at basic residues, sulfation, and amidation are necessary to form biologically active cholecystokinin from its nascent prepropeptide. The discovery of CCK-83 gives new insight into the order of preprohormone processing. The processing of prepro-CCK appears to be in the order of: 1) signal peptidase cleavage, 2) tyrosine sulfation, 3) cleavage after a carboxyl-terminal pair of basic residues, 4) carboxypeptidase B-like cleavage of these basic residues, 5) amidation (which results in the formation of CCK-83), and 6) cleavage at monobasic residues by endopeptidases (which results in the smaller molecular forms of cholecystokinin). The characterization of biologically active CCK-83 with a sulfated tyrosine and an amidated carboxyl terminus establishes the site of signal peptidase action and suggests an order of post-translational modifications that give rise to the various molecular forms of cholecystokinin.

Determination of various molecular forms of cholecystokinin from canine mucosa by radioimmunoassay and bioassay

Bioassays using amylase release from isolated pancreatic acini measure only cholecystokinin (CCK) forms with an intact carboxyl terminus ending with phenylalanine amide, but it cannot be excluded that peptides not structurally related to CCK are also responsible for CCK-like bioactivity. CCK exists in several molecular forms in intestinal mucosa which are released into the circulating blood. We studied the molecular forms of CCK in canine intestinal extracts after separation by high performance liquid chromatography by bioassay and compared them with those detected by radioimmunoassay. For the radioimmunoassay, an antibody was used which needs the carboxyl terminal phenylalanine amide for recognition. Three immunoreactive peaks were reproducibly seen in HPLC eluates which eluted in the regions of synthetic CCK-8, purified porcine CCK-33-39 (which co-elute using this gradient) and purified canine CCK-58. All these peaks were bioactive for amylase release from isolated pancreatic acini. No further bioactive peaks were detected in the HPLC eluates. When an antibody was used which recognizes the midregion of CCK-58, an additional peak was detected which eluted between CCK-33-39 and CCK-58. This form presumably represents an amino terminal fragment of CCK lacking the carboxyl terminus. It can be concluded that bioassays of CCK measure only CCK bioactivity in intestinal mucosal extracts, whereas radioimmunoassays may detect biologically inactive forms depending on the antibody recognition site.

Molecular variants of cholecystokinin after endogenous stimulation in humans: a time study

The time-dependent release of molecular variants of cholecystokinin (CCK) into the circulation was studied before and 1, 2, and 4 h after a test meal in six healthy volunteers. At each time period, 100 ml of blood were drawn in a manner to inhibit CCK degradation. Plasma was formed and CCK concentrated by Sep-Pak C18 cartridge chromatography. Molecular variants of CCK and gastrin were well separated from each other by high-performance liquid chromatography (HPLC). Molecular forms of CCK and gastrin were measured by radioimmunoassay using an antibody that requires the presence of the carboxyl-terminal phenylalanine amide for full recognition, implying that biologically active forms were detected. HPLC elution positions of gastrin forms were determined using a gastrin-specific antibody. Chromatographic separation of CCK from gastrin forms was complete, allowing separate integration of gastrin and CCK forms. Therefore no subtraction of gastrin-like immunoreactivity from CCK-like immunoreactivity (CCK-LI) was necessary and CCK-LI could be directly determined. Peaks of CCK-LI were integrated in the column eluates and the plasma concentrations were calculated. Total plasma CCK-LI rose from a value of 2.4 +/- 0.6 pM before the test meal to 6.4 +/- 0.8, 6.6 +/- 0.9, and 5.8 +/- 1.2 pM 1, 2, and 4 h postprandially. The major molecular forms released into the circulation eluted on HPLC in the position of CCK-58 and CCK-39 (which coelutes with CCK-33). Minor amounts were detected in the position of CCK-8. There was no significant difference in the relative proportions of the molecular forms released at the different time periods.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of the major form of cholecystokinin in human intestine: CCK-58

Acid extracts of human intestines obtained from surgical samples or from organ donors contain cholecystokinin (CCK) immunoreactivity. From surgical samples, extracted and eluted quickly, greater than 75% of the CCK immunoreactivity eluted in the same region as purified canine CCK-58 during analytical reverse-phase high-pressure liquid chromatography (HPLC). A major portion of the CCK immunoreactivity from donor intestinal extracts also eluted in this region. This immunoreactivity has been purified from human intestinal extracts by a series of several reverse-phase and cation-exchange chromatographies. Amino acid and microsequence analysis showed that this immunoreactivity is human CCK-58. Tryptic digestion of purified human CCK-58 produced another immunoreactive form that eluted in the position of CCK-8 during analytical reverse-phase HPLC. The immunoreactivity of the trypsin-digested material was 2.6-fold higher than that of an identical sample of CCK-58 incubated without trypsin. Thus the carboxyl-terminal antibody used for radioimmunoassay cross-reacts greater than twofold less with human CCK-58. This diminished cross-reactivity would lead to an underestimation of the relative proportions of CCK-58 in tissue and plasma extracts. If CCK-58 is the major circulating form this diminished cross-reactivity would also lead to underestimations of the circulating levels of total CCK. Determination of human CCK-58 structure confirms that one of the major components of human CCK that expresses biological activity is CCK-58.

Structural characterization of canine PYY

PYY was purified from canine colonic mucosa by sequential steps of reverse phase HPLC and ion-exchange FPLC. Microsequence, amino acid and mass spectral analyses of the purified peptide and its tryptic fragments were consistent with the structure: YPAKPEAPGEDASPEELSRYYASLRHYLNLVTRQRY-amide. Canine PYY(1-36) has the identical sequence as porcine and rat PYY but differs from human PYY at position 3, with Ala instead of Ile, and position 18, with Ser instead of Asn. A smaller form, PYY(3-36), was also purified and characterized. It may differ in its biological activity from the intact peptide and could act as a partial antagonist or agonist of PYY(1-36).

A new molecular form of PYY: structural characterization of human PYY(3-36) and PYY(1-36)

A radioimmunoassay was developed using an antibody raised in rabbits against synthetic porcine PYY. This radioimmunoassay was used to detect PYY immunoreactivity in human intestinal extracts. Human colonic mucosa was extracted with acid, centrifuged and the supernatant concentrated by low pressure preparative reverse phase chromatography. A subsequent C-18 reverse phase HPLC step separated two peaks of PYY immunoreactivity. Each peak was purified by sequential steps of ion-exchange FPLC and reverse phase HPLC. In the final purification step single absorbance peaks were associated with PYY immunoreactivity. Microsequence, amino acid, and mass spectral analysis of the intact and tryptic fragments of the two peptides were consistent with the structures: YPIKPEAPGEDASPEELNRYYASLRHYLNLVTRQRY-amide [human PYY(1-36)] and--IKPEAPGEDASPEELNRYYASLRHYLNLVTRQRY-amide [human PYY(3-36)]. Human PYY(1-36) differs from porcine PYY only at position 3, with Ile instead of Ala, and position 18, with Asn instead of Ser. PYY(3-36) may differ in its biological activity from the intact peptide. Its high proportions in the colon suggest that it is released into the circulation where it could act as a partial antagonist of PYY(1-36).