Increased plasma noradrenaline and serum gastrin in patients with duodenal ulcer

The effect of the human gut-signalling hormone, norepinephrine, on the growth of the gastric pathogen Helicobacter pylori

BACKGROUND AND AIMS

Helicobacter pylori is an important human pathogen, infecting around half the population of the world. It has developed a number of refinements to allow it to persist in the human stomach. Catecholamine hormones have been shown to enhance growth of other bacterial species and are found in the gastric niche. We aimed to study growth enhancement of H. pylori by the human catecholamine hormones epinephrine and norepinephrine.

METHODS

Growth studies were carried out in complex and defined media containing the hormones epinephrine, norepinephrine, and normetanephrine, the main host metabolite of norepinephrine. Bacterial density was measured by viable count or optical density. Intracellular ATP was measured using a bioluminescence assay technique.

RESULTS

Both epinephrine and norepinephrine enhanced H. pylori growth in a dose-dependent strain-independent fashion, with norepinephrine being more effective than epinephrine. We showed a rapid (4 hours) dose-dependent effect on metabolic activity, as measured by intracellular ATP levels. We used a chemically defined medium to study mechanisms: chelation of ferric iron blocked H. pylori growth, which could be overcome by addition of norepinephrine. Disruption of the catechol group of norepinephrine abrogated its H. pylori-growth-promoting activity.

CONCLUSIONS

Norepinephrine stimulates growth of H. pylori under otherwise growth-restricted conditions, and this effect is related to the ability of norepinephrine to bind ferric iron. This supports the notion that norepinephrine may aid H. pylori persistence in the stomach.

The role of catecholamines in clinical medicine

The sympathetic nervous system is of major importance for the regulation of several physiological functions. Drugs which inhibit the actions of catecholamines and adrenergic drugs are used in the treatment of many clinical disorders. The potential role of catecholamines in a number of human diseases has, however, until recent years been studied to a limited extent only due to lack of methods for quantitation of sympathetic nervous activity. After the development of enzymatic isotope-derivative assays, reliable measurements of noradrenaline and adrenaline in plasma became available. Studies in man have shown that plasma noradrenaline is an index of sympathetic nervous activity. The present survey deals with sympathetic nervous activity and plasma adrenaline in a number of clinical disorders viz. arterial hypertension, duodenal ulcer, thyrotoxicosis, diabetes mellitus and ketotic hypoglycemia.

Sympathoadrenal activity and psychosocial stress. The significance of aging, long-term smoking, and stress models

Recent studies have indicated that the increase in plasma norepinephrine and sympathetic activity with aging in healthy subjects is largely due to long-term cigarette smoking. In patients who have or have had duodenal ulcer the increase in plasma norepinephrine with age was markedly increased. These patients as a group perceive their lives somewhat more stressful than the general population and they tend to die prematurely due to smoking-associated diseases. These patients may select dysfunctional coping strategies like smoking, which may result in organ pathologies and a compensatory increase in plasma norepinephrine. No close correlation has been established between plasma epinephrine and "ill health." High plasma epinephrine levels may have a deleterious effect on the cardiovascular system in elderly subjects during certain conditions. In a population study, we found, however, that low resting plasma epinephrine levels were associated with an unfavorable survival rate. We speculate that an inadequate response to psychosocial stress and the choice of dysfunctional coping strategies may be more harmful and cause more "ill health" than hypersecretion of stress hormones like epinephrine and cortisol, which has been the traditional view. We suggest that there are different stress states. Stress hormones like epinephrine and cortisol may play a major role during situations like combat, illness, and strenuous exercise. In response to psychosocial stress, dysfunctional coping strategies are, however, largely responsible for harmful effects of stress.

Hypovolaemia inhibits acid-induced alkaline transport in the rat duodenum via an alpha-2 adrenergic mechanism

Acid exposure of the duodenal mucosa is a well-known stimulant of the mucosal alkaline secretion. We have previously reported that a minor blood loss inhibits this secretory increment via activation of the splanchnic nerves. In the present study the pharmacological characteristics of the splanchnic neural inhibition of the alkaline secretion were investigated. Duodenal HCO3- secretion was measured by in-situ titration in chloralose-anaesthetized rats. Exposure of the duodenal mucosa to hydrochloric acid (0.01 M, 5 min) increased the secretion by approximately 60%. A 10% decrease in blood volume simultaneously to the luminal acidification abolished the secretory increase, as previously reported. Treatment with either guanethidine or yohimbine blocked the bleeding-induced inhibition of the secretion after acid-exposure. Neither prazosin nor propranolol did prevent such hypovolaemia-induced inhibition of duodenal alkaline secretion. The present results suggest that the splanchnic neural inhibition of acid-induced duodenal HCO3- secretion is mediated via adrenergic nerve fibres and alpha-2 adrenoceptors.

Plasma neurotransmitters and cortisol in duodenal ulcer patients. Role of stress

Levels of noradrenaline, adrenaline, dopamine, free serotonin, platelet serotonin, and cortisol were measured in the plasma of duodenal ulcer patients and controls. All subjects received antacids, and these substances were also measured. During relapse, all patients showed raised noradrenaline, adrenaline, dopamine, free serotonin, and cortisol values. In contrast, platelet serotonin showed very low values, which correlated negatively with all the former, except free serotonin. No correlations were found in parameters of the controls. After healing, significant reductions of noradrenaline, adrenaline, dopamine, free serotonin, and cortisol and significant increases of platelet serotonin values were observed. However, only dopamine, free serotonin, and cortisol reached normal values. Noradrenaline and adrenaline remained higher and platelet serotonin lower, both significantly more so than normals. These still-altered parameters showed similar correlations to those found during relapses. The present results demonstrate that some baseline autonomic system imbalance exists in patients, amplified and accentuated during relapse. We discuss the possibility that stress plays some role in triggering duodenal ulcer relapse.

Adrenaline stimulates acid production in isolated pig and human parietal cells

To investigate the mechanisms of adrenergic stimulation of the parietal cell and to study the possible relationship between the stress hormone adrenaline and duodenal ulcer, the effects of adrenaline and various adrenoceptor agonists and antagonists were investigated in parietal cells isolated from pig stomachs and from endoscopic biopsy specimens taken from the gastric mucosa of patients. Parietal cell acid production was assayed by the aminopyrine accumulation technique. Adrenaline as the sole drug showed poor or no stimulatory effect but potentiated histamine-stimulated acid production. In the presence of histamine, beta-adrenoceptor agonists caused a stimulation of acid formation with the potency order isoproterenol greater than adrenaline greater than noradrenaline. The beta-2-selective antagonist ICI118551 was a more potent inhibitor of acid production than both the beta-1 antagonist practolol and the H2-receptor antagonist cimetidine. Studies of (3H)-dihydroalprenolol (DHA) binding to purified parietal cell membranes showed a protein-concentration-dependent and specific binding of 2.2 +/- 0.6 pmol DHA/microgram. Adrenaline increased gastric acid production in both pig and human parietal cells, most likely through a beta-2 receptor on the parietal cell. The adrenaline stimulatory effect in cells obtained from patients with peptic ulcer was more pronounced than in cells from non-ulcer patients, which indicates a possible role of adrenaline in some types of ulcer disease.

Gastrin responses in patients with adrenergic insufficiency

High basal gastrin levels in pure autonomic failure could result from peripheral vagus nerve involvement, whereas the increased response during hypoglycaemia may reflect adrenergic supersensitivity. A reduced gastrin increment in multiple system atrophy was found following insulin-hypoglycaemia and is consistent with decreased gastrin release secondary to diminished central sympathetic nervous system activation in the absence of peripheral denervation supersensitivity.

Effects of physiological increases of plasma noradrenaline on gastric acid secretion and gastrointestinal hormones

It is not known if the increased plasma concentration of noradrenaline in patients with chronic duodenal ulcer disease is a pathogenetic factor or not. The aim of the present study was to investigate if physiologic changes of noradrenaline would evoke any alterations in gastric acid secretion or in the plasma concentration of some gastrointestinal hormones (gastrin, secretin, PP, PYY, and GIP) known to affect gastric physiology. The results show that basal plasma noradrenaline concentration was 1.8 nM and after infusion with noradrenaline at 0.04 or 0.2 nmol/kg/min plasma levels of 2.5 and 4.4 nM were obtained. No appreciable changes could be found in basal or pentagastrin stimulated acid secretion or in any of the gastrointestinal peptides studied. If the elevated plasma noradrenaline concentration observed in duodenal ulcer patients is a pathogenetic factor; it is probable that it interferes with other variables such as blood flow, bicarbonate secretion, or prostaglandin synthesis.

Basal and food-stimulated levels of gastrin and pancreatic polypeptide in non-ulcer dyspepsia and duodenal ulcer

Basal and food-stimulated levels of gastrin and pancreatic polypeptide (PP) were studied in 86 patients with non-ulcer dyspepsia (NUD), defined as chronic or recurrent epigastric pain without anatomical antecedents and without concomitant symptoms of irritable bowel. Thirteen patients with endoscopically confirmed duodenal ulcer disease (DU) and 13 healthy subjects constituted the reference groups. The mean basal gastrin concentration was moderately but significantly (p less than 0.05) higher in the NUD group than in the reference groups (24.3 +/- 1.6 (SEM) pmol/l in NUD, compared with 15.0 +/- 1.5 and 13.6 +/- 1.0 pmol/l among DU patients and healthy subjects, respectively). The well-established postprandial hypergastrinemia in duodenal ulcer patients could be confirmed in this study, and their gastrin response to food was significantly (p less than 0.01) greater than the responses observed both in healthy subjects and in NUD patients. The two latter groups did not differ significantly with regard to gastrin increments, but there was a tendency towards greater increases in the NUD group. A significantly (p less than 0.05) enhanced PP response to the test meal was observed among the DU patients, whereas the response pattern in NUD was closely similar to that in healthy subjects.

Plasma norepinephrine is abnormal in patients with duodenal ulcer. The significance of age

Previous studies indicate that the forearm venous plasma norepinephrine (NE) concentration is abnormally high in patients with duodenal ulcer. The aim of the present study was to examine the relationship between age and plasma NE concentration in patients with duodenal ulcer and controls. Eleven male patients with duodenal ulcer and 12 male control subjects were examined. Plasma NE concentration was approximately twofold greater in duodenal ulcer patients in both the resting seated position and during exercise than values obtained in controls (2 p less than 0.02, less than 0.05). There was a strong correlation between plasma NE and age in patients with duodenal ulcer but not in controls (r = 0.69, 2 p less than 0.05). Our results suggest that the increase in plasma NE with age is greater in patients with duodenal ulcer than in normal healthy subjects or in patients with minor surgical diseases. Patients with duodenal ulcer may have a higher functional age than healthy subjects.

Adrenergic mechanisms in selected diseases: arterial hypertension, duodenal ulcer, primary depressive illness, malignant tumors, and ketotic hypoglycemia

The sympathetic nervous system is of major importance for the regulation of several physiologic functions. Drugs that inhibit the actions of catecholamines and adrenergic drugs are used in the treatment of many clinical disorders. The potential role of catecholamines in a number of human diseases has, however, until recent years been studied to a limited extent only due to lack of methods for quantitation of sympathetic nervous activity. After the development of enzymatic isotope-derivative assays, reliable measurements of noradrenaline and adrenaline became available. Studies in man have shown that plasma noradrenaline is an index of sympathetic nervous activity. The present survey deals with noradrenaline and adrenaline concentrations in blood, tissue, and cerebrospinal fluid in a number of clinical disorders viz. arterial hypertension, duodenal ulcer, malignant tumors, primary depressive illness, and ketotic hypoglycemia.

Plasma catecholamines in human and experimental hypertension

Plasma levels of norepinephrine reflect the rate of its release from sympathetic nerves. In patients with hypertension and in spontaneously hypertensive (SHR) rats basal plasma NE levels are normal. SHR rats are abnormally reactive to stress, as are the normotensive (WKY) strain from which they were derived. The amounts of NE released by sympathetic stimulation are similar in pithed SHR and WKY rats, but SHR rats have greater blood pressure responses. This may be due to diminished beta-adrenoceptor-mediated vasodilation in young SHR rats and structural changes in arterioles of older SHR rats. It is concluded that in SHR rats separate abnormalities of centrally-mediated responses to stress and of peripheral sensitivity to catecholamines contribute to the development and maintenance of elevated blood pressure.

Increased sensitivity of gastrin release to adrenaline in duodenal ulcer

Serum gastrin concentrations were measured in patients with duodenal ulcer and controls before, during, and after one-hour intravenous infusion of various doses of adrenaline (0.12 microgram to 6 microgram/min). Gastrin concentrations in the basal state were significantly increased in duodenal ulcer patients compared to controls. The maximal rise in serum gastrin concentrations was obtained at a dose of 4 microgram/min adrenaline in both groups of subjects, and the increase was significantly higher in duodenal ulcer patients than in controls. Adrenaline increased predominantly the gastrin III component (gastrin-17 like) in both duodenal ulcer patients and controls. The threshold level of adrenaline-induced gastrin release was significantly lower in duodenal ulcer patients: intravenous infusion of adrenaline in a dose of 0.12 microgram and 0.25 microgram/min increased serum gastrin concentrations 23 and 43%, respectively, but had no effect in controls. Rises in plasma adrenaline concentrations were similar in both groups of subjects in response to the various doses of adrenaline employed. Only the smallest dose of adrenaline (0.12 microgram/min) resulted in clearly physiological variations in plasma adrenaline concentrations. The results indicate that endogenous adrenaline may stimulate the secretion of gastrin during physiological conditions in patients with duodenal ulcer.