Gastrointestinal hormones and pathophysiology of functional gastrointestinal disorders

Neural correlates of a single-session massage treatment

The current study investigated the immediate neurophysiological effects of different types of massage in healthy adults using functional magnetic resonance imaging (fMRI). Much attention has been given to the default mode network, a set of brain regions showing greater activity in the resting state. These regions (i.e. insula, posterior and anterior cingulate, inferior parietal and medial prefrontal cortices) have been postulated to be involved in the neural correlates of consciousness, specifically in arousal and awareness. We posit that massage would modulate these same regions given the benefits and pleasant affective properties of touch. To this end, healthy participants were randomly assigned to one of four conditions: 1. Swedish massage, 2. reflexology, 3. massage with an object or 4. a resting control condition. The right foot was massaged while each participant performed a cognitive association task in the scanner. We found that the Swedish massage treatment activated the subgenual anterior and retrosplenial/posterior cingulate cortices. This increased blood oxygen level dependent (BOLD) signal was maintained only in the former brain region during performance of the cognitive task. Interestingly, the reflexology massage condition selectively affected the retrosplenial/posterior cingulate in the resting state, whereas massage with the object augmented the BOLD response in this region during the cognitive task performance. These findings should have implications for better understanding how alternative treatments might affect resting state neural activity and could ultimately be important for devising new targets in the management of mood disorders.

Natural Parenting — Back to Basics in Infant Care

This review examines an age-old approach to parenting recently rediscovered in Western industrialized societies and known by names such as natural parenting, attachment parenting, and instinctive parenting. Its leading principle is utmost sensitivity to the child's innate emotional and physical needs, resulting in extended breastfeeding on demand, extensive infant carrying on the caregiver's body, and cosleeping of infant and parents. The described practices prevailed during the evolutionary history of the human species and reflect the natural, innate rearing style of the human species to which the human infant has biologically adapted over the course of evolution. An overview of research from diverse areas regarding psychological as well as physiological aspects of early care provides evidence for the beneficial effects of natural parenting. Cross-cultural and historical data is cited to reveal the widespread use of the investigated parenting style. It is concluded that the described approach to parenting provides the human infant with an ideal environment for optimal growth both psychologically and physiologically. It is yet to be determined how much departure from this prototype of optimal human parenting is possible without compromising infant and parental wellbeing. The review also invites a critical reevaluation of current Western childrearing practices.

Autonomic reactivity during viewing of an unpleasant film

The effect of an aversive, high-arousing film on heart rate, respiratory sinus arrhythmia, and electrogastrographic activity (EGG) was investigated. Previous studies have indicated a larger heart-rate deceleration for visual stimuli depicting surgery or blood compared to neutral content, and this phenomenon is similar to the bradycardia observed in animals in response to fear. The heart-rate deceleration is clearly parasympathetically driven, and it is considered a general index of attention. An accurate index of cardiac vagal tone can be obtained by means of quantification of the amplitude of respiratory sinus arrhythmia. The relationship between cardiac vagal tone and EGG is complex, but animal research has shown that suppressing vagal activity dampens gastric motility. We have investigated whether a movie depicting surgery is associated with greater heart-rate deceleration, larger increase in respiratory sinus arrhythmia, and greater increase in EGG activity compared to a neutral movie. In addition, if both respiratory sinus arrhythmia and EGG are indices of vagal tone, a positive correlation between these physiological responses was expected. Analysis indicated an effect of the surgery movie on heart rate and respiratory sinus arrhythmia, but not on EGG activity. Moreover, the expected correlation was not found. Implications for future studies are discussed.

The polyvagal theory: phylogenetic substrates of a social nervous system

The evolution of the autonomic nervous system provides an organizing principle to interpret the adaptive significance of physiological responses in promoting social behavior. According to the polyvagal theory, the well-documented phylogenetic shift in neural regulation of the autonomic nervous system passes through three global stages, each with an associated behavioral strategy. The first stage is characterized by a primitive unmyelinated visceral vagus that fosters digestion and responds to threat by depressing metabolic activity. Behaviorally, the first stage is associated with immobilization behaviors. The second stage is characterized by the sympathetic nervous system that is capable of increasing metabolic output and inhibiting the visceral vagus to foster mobilization behaviors necessary for 'fight or flight'. The third stage, unique to mammals, is characterized by a myelinated vagus that can rapidly regulate cardiac output to foster engagement and disengagement with the environment. The mammalian vagus is neuroanatomically linked to the cranial nerves that regulate social engagement via facial expression and vocalization. As the autonomic nervous system changed through the process of evolution, so did the interplay between the autonomic nervous system and the other physiological systems that respond to stress, including the cortex, the hypothalamic-pituitary-adrenal axis, the neuropeptides of oxytocin and vasopressin, and the immune system. From this phylogenetic orientation, the polyvagal theory proposes a biological basis for social behavior and an intervention strategy to enhance positive social behavior.

Motilin- and neuropeptide Y-like immunoreactivity in a psychophysiological stress experiment on patients with functional dyspepsia

BACKGROUND

The aim of the study was to compare plasma motilin-like immunoreactivity (MOT-LI) and neuropeptide Y (NPY)-like immunoreactivity (NPY-LI) in patients with functional dyspepsia (FD) during a controlled psychophysiological experiment.

METHOD

25 patients (12 men, 13 women), age 24-50, with recurrent FD, and 25 pair-wise sex- and age-matched community control subjects were studied. In an experiment, after a rest period, subjects were studied during a 15-min stress interview. The aim of the interview was to elicit anxiety. Before and during the intervention blood samples were drawn for peptide analyses. Outcome measures were the Gastrointestinal Symptom Rating Scale, fasting blood glucose, heart rate and blood pressure as well as the subjects' self-ratings on visual analogue scales. The plasma concentrations of MOT-LI and NPY-LI are given as anti-logarithms.

RESULTS

Mean plasma MOT-LI concentration was 7.3 (CI: 5.7-9.4) pmol/L in the patient group, and 7.9 (CI: 6.1-10.2) pmol/L in the control group. Mean plasma NPY-LI concentration was 14.2 (CI: 12.3-16.4) pmol/L in the patient group, and 13.4 (Cl: 11.8-15.3) pmol/L in the control group. Using ANCOVA (covariates: group, gender, age, body mass index and smoking) MOT-LI was related to lower indigestion symptomatology (p<0.04) and positive change in joyfulness during the interview (p<0.03). In the patient group delta motilin correlated with increased joyfulness (p<0.03) and decreased sadness (p<0.03). The NPY-LI increase during the interview was related to higher fasting blood glucose before the interview (p<0.01) and a stronger increase in systolic blood pressure during the test (p<0.05).

CONCLUSION

During a stress interview plasma MOT-LI is positively related to less indigestion symptomatology and joyfulness, while changes in plasma NPY-LI were positively related to sympathetic nervous system activity, but not to gastrointestinal symptoms.

Love: an emergent property of the mammalian autonomic nervous system

The evolution of the autonomic nervous system provides an organizing principle to interpret the adaptive significance of mammalian affective processes including courting, sexual arousal, copulation, and the establishment of enduring social bonds. According to the Polyvagal Theory (Porges, 1995, 1996, 1997), the well-documented phylogenetic shift in the neural regulation of the autonomic nervous system passes through three stages, each with an associated behavioral strategy. The first stage is characterized by a primitive unmyelinated visceral vagus that fosters digestion and responds to threat by depressing metabolic activity. Behaviorally, the first stage is associated with immobilization behaviors. The second stage is characterized by the sympathetic nervous system that is capable of increasing metabolic output and inhibiting the visceral vagus to foster mobilization behaviors necessary for 'fight or flight'. The third stage, unique to mammals, is characterized by a myelinated vagus that can rapidly regulate cardiac output to foster engagement and disengagement with the environment. The mammalian vagus is neuroanatomically linked to the cranial nerves that regulate social engagement via facial expression and vocalization. The Polyvagal Theory provides neurobiological explanations for two dimensions of intimacy: courting and the establishment of enduring pair-bonds. Courting is dependent upon the social engagement strategies associated with the mammalian vagus. The establishment of enduring pair-bonds is dependent upon a co-opting of the visceral vagus from an immobilization system associated with fear and avoidance to an immobilization system associated with safety and trust. The theory proposes that the phylogenetic development of the mammalian vagus is paralleled by a specialized communication, via oxytocin and vasopressin, between the hypothalamus and the medullary source nuclei of the viscera vagus, which facilitates sexual arousal, copulation, and the development of enduring pair-bonds.

Age-related decrease in plasma levels of gastrin, cholecystokinin and somatostatin

Newborn babies have higher concentrations of gastrointestinal hormones than adults. The aim of the present study was to investigate the relationship between age and plasma levels of the three peptides gastrin, cholecystokinin and somatostatin in healthy children aged 1-15 years. Gastrin, cholecystokinin and somatostatin concentrations were twice as high at 1-2 years of age compared with children older than 10 years. Significant negative correlations between age and hormone concentrations were established. It is suggested that these age-dependent differences are related to the growth rate and relative energy consumption during the early years of life.

Orienting in a defensive world: mammalian modifications of our evolutionary heritage. A Polyvagal Theory

The vagus, the 10th cranial nerve, contains pathways that contribute to the regulation of the internal viscera, including the heart. Vagal efferent fibers do not originate in a common brainstem structure. The Polyvagal Theory is introduced to explain the different functions of the two primary medullary source nuclei of the vagus: the nucleus ambiguus (NA) and the dorsal motor nucleus (DMNX). Although vagal pathways from both nuclei terminate on the sinoatrial node, it is argued that the fibers originating in NA are uniquely responsible for respiratory sinus arrhythmia (RSA). Divergent shifts in RSA and heart rate are explained by independent actions of DMNX and NA. The theory emphasizes a phylogenetic perspective and speculates that mammalian, but not reptilian, brainstem organization is characterized by a ventral vagal complex (including NA) related to processes associated with attention, motion, emotion, and communication. Various clinical disorders, such as sudden infant death syndrome and asthma, may be related to the competition between DMNX and NA.

Cardiac vagal tone: a physiological index of stress

Cardiac vagal tone is proposed as a novel index of stress and stress vulnerability in mammals. A model is described that emphasizes the role of the parasympathetic nervous system and particularly the vagus nerve in defining stress. The model details the importance of a branch of the vagus originating in the nucleus ambiguus. In mammals the nucleus ambiguus not only coordinates sucking, swallowing, and breathing, but it also regulates heart rate and vocalizations in response to stressors. In mammals it is possible, by quantifying the amplitude of respiratory sinus arrhythmia, to assess the tonic and phasic regulation of the vagal pathways originating in the nucleus ambiguus. Measurement of this component of vagal tone is proposed as a method to assess, on an individual basis, both stress and the vulnerability to stress.

Symptoms and personality in patients with chronic functional dyspepsia

Twenty-five patients, 12 men and 13 women, aged 24-50 yr, who had consulted physicians and had received the diagnosis functional dyspepsia after extensive examination 6-8 years prior to this study, and were still suffering from this condition, were compared with community control subjects pair-wise matched for age and sex. Control subjects who had ever consulted a physician for gastrointestinal symptoms were excluded. Questionnaires measuring symptoms, job strain, social support and personality traits were used. Relatively few differences were found between groups. Compared to the community controls, however, the patients reported more gastrointestinal and nervous symptoms, and higher somatization, measured by Symptom Check List-90. The extent of reported overall distress was greater in patients than in control subjects. The detachment score (Karolinska Scales of Personality) was significantly lower in patients than in control subjects; this difference was also significant in separate analysis for men. Female patients had lower socialization and higher suspicion scores than female control subjects. Male patients reported more decision latitude (job control) than male control subjects.

Glucose translocation and metabolism in the rat jejunum perfused in once-through mode in vitro

Simultaneous once-through luminal and vascular perfusions with glucose of rat jejunum in vitro were used in an attempt to resolve conflicting reports on glucose metabolism in jejuna perfused in once-through mode in vivo and in recirculation mode in vitro. Results include: (a) respiration rates during each perfusion, (b) CO2 production from absorbed glucose, (c) absolute rates of glucose absorption from the lumen into the epithelium, (d) absolute rates of glucose translocation from lumen to vascular bed, (e) absolute rates of lactate excretion into the two perfusion media, (f) recoveries of absorbed glucose, (g) the distribution of radioactivity among translocated glucose and its metabolites. About 50% of the total lactate originates in the glucose extracted from the vascular medium during concomitant absorption and translocation of luminal glucose. The results suggest what further experiments need to be done. Results from recirculation perfusions in vitro cannot contest or confirm the results quoted from experiments conducted with once-through perfusions in vivo.

Role of efferent and afferent vagal nerve activity during reproduction: integrating function of oxytocin on metabolism and behaviour

The vagal nerves convey information between the brain and the gastrointestinal tract in both afferent and efferent direction. The efferent vagal nerves regulate gastrointestinal secretory and motor function and also the activity in the endocrine system of the gut. Gastrointestinal function and anabolic metabolism is optimized during gestation and lactation as a means of saving energy for this calorie-demanding process. This enhanced activity seems to involve central oxytocinergic transmission which increases efferent vagal nerve activity as reflected by altered levels of gastrointestinal hormones in plasma. In parallel a behaviour pattern characterized by sedation is induced. In addition, vagal afferents transfer information from the gut to the brain, e.g. as to the presence or absence of calories in the gastrointestinal tract. It is well known that satiety and sedation following a meal is in part caused by an activation of vagal afferents in response to food intake. Cholecystokinin released from the intestine is one of the factors that triggers the afferent vagal nerve activity. Also reproductive "interactive behaviours" such as milk ejection and maternal behaviour can be induced by CCK via afferent activation of vagal nerves. In contrast, when no food reaches the gut, milk production and ejection is blocked. Parts of these effects are vagally mediated, since they can be observed in vagotomized rats receiving full amounts of calories.

Elevated cholecystokinin concentrations in plasma in children with recurrent abdominal pain

The objective of the present study was to measure plasma concentrations of the gastrointestinal hormones gastrin, somatostatin and cholecystokinin in plasma of children with recurrent abdominal pain, since these hormones affect gastrointestinal function. Forty-four children (7-16 years old) with recurrent abdominal pain and 36 control children (matched for age and sex) participated in the study. In a blood sample collected after an overnight fast, gastrin, somatostatin and cholecystokinin concentrations were measured by radioimmunoassay. The children with recurrent abdominal pain had higher plasma cholecystokinin levels (p < 0.001) than the controls. Whether or not this aberration is related to the clinical symptoms of children with recurrent abdominal pain remains to be established.

The relationships between personality traits and plasma gastrin, cholecystokinin, somatostatin, insulin, and oxytocin levels in healthy women

In earlier studies performed on a group of women with gastrointestinal symptoms, significant positive correlations between the gastrointestinal hormone gastrin and anxiety, and a negative correlation with socialization were obtained. These and other relationships were tested on 33 healthy women. A comprehensive and concise statistical model was used for the analysis of correlations between, on one hand, the levels of oxytocin and the gastrointestinal hormones gastrin, cholecystokinin, somatostatin and insulin, and, on the other hand, personality traits. Almost all explained variance of the hormone levels could be referred to three personality trait factors, Anxiety, Aggressive non-conformity, and Detachment. The statistical explanation of the gastrin level variance was most successful, the three personality trait factors explaining 48% of this variance. Gastrin "increased" Anxiety while reducing Aggressive non-conformity and Detachment. A similar pattern for insulin was also reliable. Considering general trends, the negative correlations between all hormones and Detachment are interesting. Present data suggest that there is a psychoendocrinological antithesis to the fight-flight individual, characterized by high activity in the sympathoadrenal system: these contrasting persons, with high levels of the gastrointestinal hormones gastrin and insulin, tend to be warm and caring and non-aggressive--but often not free from anxiety. We do not think that the demonstrated associations between hormone levels and personality traits implicate a direct causal relationship. They rather may mirror the activity of centrally acting or hypothalamic control systems which influence both behavioural and endocrine profiles.

Somatostatin levels in plasma in nonsmoking and smoking breast-feeding women

The objective of the study was to record how somatostatin levels in plasma are altered in response to breast-feeding during the lactation period and to relate somatostatin levels to the success of the lactational performance and to smoking habits. Fifty-two women were investigated 4 days post partum and 3-4 months later. Blood samples were collected and the levels of somatostatin-like immunoreactivity (below referred to as SLI) were measured with radioimmunoassay. The periods of exclusive breast-feeding and of mixed feeding were assessed as well as the milk yield. Smoking habits were noted. SLI levels were found to be significantly lower on day 4 after delivery, compared to 3-4 months later. Also the type of response to breast-feeding was different. Thus, a significant fall of SLI was seen during breast-feeding at the maternity unit, but not 3-4 months later. Smoking women breast-fed fully for a significantly shorter time than nonsmokers and had significantly higher SLI levels at onset of breast-feeding day 4 post partum. Whether the high somatostatin levels recorded in connection with breast-feeding in smokers are related to the shorter period of breast-feeding seen in this group remains to be established. In addition, the highest levels of somatostatin were seen the day after the very last breast-feeding and a possible role for somatostatin in the weaning process should be explored.

Gastrin, somatostatin and oxytocin levels in patients with functional disorders of the gastrointestinal tract and their response to feeding and interaction

Twenty-four individuals with functional disorders of the gastrointestinal tract participated in the study. Symptoms from the upper and lower gastrointestinal tract were recorded by means of a self-administered questionnaire before, 3 months and 3 yr after participation in group therapy. Blood was sampled from the patients while they were subjected to three different provocations (a friendly greeting, a food stimulus and a stress stimulus). Ten subjects without gastrointestinal symptoms participated in an identical experiment. Gastrin, somatostatin and oxytocin levels were measured with radioimmunoassay. Both gastrin and somatostatin levels were influenced by the provocations and by the greeting and the stress stimulus in particular. In principle, the controls tended to react with a parasympathetic response pattern following the interactive stimuli, whereas the individuals with functional disorders of the gastrointestinal tract reacted with an activation of the sympathetic nervous system. Somatostatin levels were significantly higher and oxytocin levels lower in patients than in controls and gastrin levels tended to be higher in patients than in controls. Most individuals reported both gastric as well as intestinal symptoms. Gastrin levels correlated positively with total symptom level and somatostatin levels with intestinal symptoms scores reported by the patients.

Quantitative relationships between suckling-induced teat stimulation and the release of prolactin, gastrin, somatostatin, insulin, glucagon and vasoactive intestinal polypeptide in sows

The pituitary hormones prolactin and oxytocin play important roles in the production and ejection of milk. In addition, some gastrointestinal peptides are released in response to suckling. During suckling, the piglets massage the udder of the sow both before and after let-down and the duration of suckling is correlated to the amount of milk produced by the sow. The aim of this study was to investigate whether there is a quantitative relation between the release of prolactin, gastrin, somatostatin, insulin, glucagon and vasoactive intestinal polypeptide (VIP) and the amount of stimulation of the sow's teats by the piglets. Repeated blood samples were drawn from three Swedish Landrace sows during three consecutive nursings by each sow on days 1, 3, 7 and 14 after parturition. The duration of massage by the piglets was noted, as was the number of piglets massaging. Hormone levels were quantified by radioimmunoassay. The release of prolactin, somatostatin, insulin, glucagon and VIP but not of gastrin were found to be significantly related to the amount of teat massage performed by the piglets during the first 2 weeks of lactation. The release was related to the duration of piglet massage or to the combined effect of duration and the number of piglets massaging but not to the number of piglets massaging per se. The basal level of prolactin was found to decrease during this time.

Personality traits in a group of individuals with functional disorders of the gastrointestinal tract and their correlation with gastrin, somatostatin and oxytocin levels

The Karolinska Scales of Personality (KSP) and some dimensions of the Bergman scale reflecting social dependency and self-confidence were used in 24 individuals with functional disorders of the gastrointestinal tract. Patients showed higher scores of somatic anxiety, indirect aggression and irritability and lower scores in socialization when compared with a reference group. The levels of gastrointestinal symptoms as well as the levels of some hormones related to vagal nerve activity in this patient group have been reported in a previous publication. When the scores obtained in personality inventories were related to symptom levels, we found significant correlations with intestinal but not abdominal symptoms. Gastrin levels correlated inversely with socialization. Somatostatin levels on the other hand, correlated negatively with social dependency and positively with self-confidence in the Bergman scale. Interestingly, oxytocin levels correlated positively with social dependency and in addition with indirect aggression and verbal aggression. The correlation between hormone levels and scores of personality dimensions will be interpreted and discussed within a physiological context.

Maternal somatostatin levels and their correlation with infant birth weight

Samples of blood were obtained from 52 primiparous breast-feeding women 4 days post partum. Thirty-six of the mothers were still breast-feeding 3-4 months later and had further blood samples taken. Somatostatin levels were analyzed by radioimmunoassay. A highly significant rank correlation (P = 0.0001) between average somatostatin levels on the two occasions was established, although somatostatin levels recorded 3-4 months post partum were significantly higher than those found 4 days post partum (P less than 0.01). Furthermore, somatostatin levels obtained 4 days and 3-4 months post partum were inversely related to the birth weight of their children (P = 0.006 and P = 0.03). The significant negative correlation between somatostatin levels recorded 4 days post partum and birth weight of the infants persisted only when non-smokers were investigated. A strong positive correlation between infant birth weight and weight of placenta was found (P = 0.0001) and a negative correlation (P = 0.04) between somatostatin levels and placental weight. A stepwise regression was performed to explain the importance of somatostatin levels in birth weight. Somatostatin levels and smoking had an almost equal influence on the variation in birth weight (approximately 10%). It is suggested that low maternal somatostatin levels are related to an efficient storage of nutrients in the fetoplacental unit, thereby leading to a high birth weight.

Plasma concentrations of gastrin and somatostatin after breast feeding in 4 day old infants

The plasma concentrations of gastrin and somatostatin were measured by radioimmunoassay before and after breast feeding in healthy 4 day old infants who had been born at full term. The mean (SD) concentrations of gastrin and somatostatin before breast feeding were 120 (30) pmol/l and 35 (12) pmol/l, respectively. Breast feeding in these infants was not followed by increased concentrations of gastrin and somatostatin in peripheral blood. High preprandial peptide concentrations, as seen during the neonatal period may limit the further release of peptide after feeding.