Mapping glucose-mediated gut-to-brain signalling pathways in humans.

OBJECTIVES: Previous fMRI studies have demonstrated that glucose decreases the hypothalamic BOLD response in humans. However, the mechanisms underlying the CNS response to glucose have not been defined. We recently demonstrated that the slowing of gastric emptying by glucose is dependent on activation of the gut peptide cholecystokinin (CCK1) receptor. Using physiological functional magnetic resonance imaging this study aimed to determine the whole brain response to glucose, and whether CCK plays a central role. EXPERIMENTAL DESIGN: Changes in blood oxygenation level-dependent (BOLD) signal were monitored using fMRI in 12 healthy subjects following intragastric infusion (250ml) of: 1M glucose+predosing with dexloxiglumide (CCK1 receptor antagonist), 1M glucose+placebo, or 0.9% saline (control)+placebo, in a single-blind, randomised fashion. Gallbladder volume, blood glucose, insulin, and GLP-1 and CCK concentrations were determined. Hunger, fullness and nausea scores were also recorded. PRINCIPAL OBSERVATIONS: Intragastric glucose elevated plasma glucose, insulin, and GLP-1, and reduced gall bladder volume (an in vivo assay for CCK secretion). Glucose decreased BOLD signal, relative to saline, in the brainstem and hypothalamus as well as the cerebellum, right occipital cortex, putamen and thalamus. The timing of the BOLD signal decrease was negatively correlated with the rise in blood glucose and insulin levels. The glucose+dex arm highlighted a CCK1-receptor dependent increase in BOLD signal only in the motor cortex. CONCLUSIONS: Glucose induces site-specific differences in BOLD response in the human brain; the brainstem and hypothalamus show a CCK1 receptor-independent reduction which is likely to be mediated by a circulatory effect of glucose and insulin, whereas the motor cortex shows an early dexloxiglumide-reversible increase in signal, suggesting a CCK1 receptor-dependent neural pathway.

Using read codes to identify patients with irritable bowel syndrome in general practice: a database study.

BACKGROUND: Estimates of the prevalence of irritable bowel syndrome (IBS) vary widely, and a large proportion of patients report having consulted their general practitioner (GP). In patients with new onset gastrointestinal symptoms in primary care it might be possible to predict those at risk of persistent symptoms. However, one of the difficulties is identifying patients within primary care. GPs use a variety of Read Codes to describe patients presenting with IBS. Furthermore, in a qualitative study, exploring GPs' attitudes and approaches to defining patients with IBS, GPs appeared reluctant to add the IBS Read Code to the patient record until more serious conditions were ruled out. Consequently, symptom codes such as 'abdominal pain', 'diarrhoea' or 'constipation' are used. The aim of the current study was to investigate the prevalence of recorded consultations for IBS and to explore the symptom profile of patients with IBS using data from the Salford Integrated Record (SIR). METHODS: This was a database study using the SIR, a local patient sharing record system integrating primary, community and secondary care information. Records were obtained for a cohort of patients with gastrointestinal disorders from January 2002 to December 2011. Prevalence rates, symptom recording, medication prescribing and referral patterns were compared for three patient groups (IBS, abdominal pain (AP) and Inflammatory Bowel Disease (IBD)). RESULTS: The prevalence of IBS (age standardised rate: 616 per year per 100,000 population) was much lower than expected compared with that reported in the literature. The majority of patients (69%) had no gastrointestinal symptoms recorded in the year prior to their IBS. However a proportion of these (22%) were likely to have been prescribed NICE guideline recommended medications for IBS in that year. The findings for AP and IBD were similar. CONCLUSIONS: Using Read Codes to identify patients with IBS may lead to a large underestimate of the community prevalence. The IBS diagnostic Read Code was rarely applied in practice. There are similarities with many other medically unexplained symptoms which are typically difficult to diagnose in clinical practice.

GP perspectives of irritable bowel syndrome--an accepted illness, but management deviates from guidelines: a qualitative study.

BACKGROUND: The estimated prevalence of irritable bowel syndrome (IBS) is 10%. Up to one third of patients develop chronic symptoms, which impact on everyday functioning and psychological wellbeing. Guidelines suggest an increased role for primary care in the management of patients with IBS, and referral for psychological interventions. Literature reports dissatisfaction and frustration experienced by both patients with IBS and healthcare professionals. The aim of this study was to explore the perspectives of general practitioners (GPs) in relation to the diagnosis and management of IBS and their views on the potential use of a risk assessment tool to aid management decisions for patients with IBS in primary care. METHODS: This was a qualitative study using face-to-face semi-structured interviews with GPs in North West England. Interviews were fully transcribed and data analyzed using constant comparison across interviews. Tensions between GP accounts and the NICE guideline for the management of IBS were highlighted. RESULTS: GPs described IBS as a diagnosis of exclusion and the process as tentative and iterative, with delay in adding a Read code to the patient record until they were confident of the diagnosis. Whilst GPs accepted there was a link between IBS and psychological symptoms they suggested that the majority of patients could be managed within primary care without referral for psychological interventions, in conflict with the NICE guideline. They did not feel that a risk assessment tool for patients with IBS would be helpful. CONCLUSIONS: This study highlights the tensions between evidence recognizing the need to identify patients whose symptoms may become chronic and offer pro-active care, including referral for psychological therapies, and the perspectives of GPs managing patients in every-day clinical practice. The reluctance of GPs to refer patients for evidence-based psychological treatments may have implications for commissioning services and patient care.

Synthesis, characterization and luminescence studies of gold(I)-NHC amide complexes.

A flexible, efficient and straightforward methodology for the synthesis of N-heterocyclic carbene gold(I)-amide complexes is reported. Reaction of the versatile building block [Au(OH)(IPr)] (1) (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) with a series of commercially available (hetero)aromatic amines leads to the synthesis of several [Au(NRR')(IPr)] complexes in good yields and with water as the sole byproduct. Interestingly, these complexes present luminescence properties. UV-vis and fluorescence measurements have allowed the identification of their excitation and emission wavelengths (λmax). These studies revealed that by selecting the appropriate amine ligand the emission can be easily tuned to achieve a variety of colors, from violet to green.

Functional neuroimaging demonstrates that ghrelin inhibits the central nervous system response to ingested lipid.

OBJECTIVE: Gut-derived humoural factors activate central nervous system (CNS) mechanisms controlling energy intake and expenditure, and autonomic outflow. Ghrelin is secreted from the stomach and stimulates food intake and gastric emptying, but the relevant mechanisms are poorly understood. Nutrient-activated CNS systems can be studied in humans by physiological/pharmacological MRI (phMRI). This method has been used to examine the CNS responses to exogenous ghrelin. DESIGN: phMRI was used to study the CNS responses in healthy people to a ghrelin bolus (0.3 nmol/kg, intravenous) in the post-prandial state, and an intravenous infusion of ghrelin (1.25 pmol/kg/min) alone and after intragastric lipid (dodecanoate, C12) in people who have fasted. RESULTS: A ghrelin bolus decreased the blood oxygenation level dependent (BOLD) signal detected by phMRI in feeding-activated areas of the CNS in the post-prandial state. Infusion of ghrelin reversed the effect of C12 in delaying gastric emptying but had no effect on hunger. Intragastric C12 caused strong bilateral activation of a matrix of CNS areas, including the brain stem, hypothalamus and limbic areas which was attenuated by exogenous ghrelin. Ghrelin infusion alone had a small but significant stimulatory effect on CNS BOLD signals. CONCLUSION: Ghrelin inhibits activation of the hypothalamus and brain stem induced by ingested nutrients, suggesting a role in suppression of gut-derived satiety signals in humans.

Expression of cannabinoid CB1 receptors by vagal afferent neurons: kinetics and role in influencing neurochemical phenotype.

The intestinal hormone cholecystokinin (CCK) inhibits food intake via stimulation of vagal afferent neurons (VAN). Recent studies suggest that CCK also regulates the expression of some G protein-coupled receptors and neuropeptide transmitters in these neurons. The aim of the present study was to characterize the expression of cannabinoid (CB)1 receptors in VAN and to determine whether stimulation of these receptors plays a role in regulating neurochemical phenotype. Expression of CB1 in rat VAN was detectable by in situ hybridization or immunohistochemistry after 6 h of fasting and increased to a maximum after 24 h when approximately 50% of neurons in the mid and caudal regions expressed the receptor. Melanin-concentrating hormone (MCH)1 receptors also increased with fasting, but the changes were delayed compared with CB1; in contrast Y2 receptors (Y2R) exhibited reciprocal changes in expression to CB1. Administration of CCK8s (10 nmol ip) to fasted rats decreased expression of CB1 with a t(1/2) of approximately 1 h compared with 3 h for MCH1. The action of CCK8s was inhibited by ghrelin and orexin-A. The CB1 agonist anandamide (intraperitoneally) reversed the effect of CCK8s on CB1, MCH1, and Y2 receptor expression. In contrast, in rats fasted for 18 h, administration of a CB1 antagonist/inverse agonist (AM281 ip) downregulated CB1 expression and increased Y2 receptor expression. Activation of vagal CB1 receptors therefore influences the neurochemical phenotype of these neurons, indicating a new and hitherto unrecognized role for endocannabinoids in gut-brain signaling.

Cholecystokinin regulates expression of Y2 receptors in vagal afferent neurons serving the stomach.

The intestinal hormones CCK and PYY3-36 inhibit gastric emptying and food intake via vagal afferent neurons. Here we report that CCK regulates the expression of Y2R, at which PYY3-36 acts. In nodose ganglia from rats fasted up to 48 h, there was a fivefold decrease of Y2R mRNA compared with rats fed ad libitum; Y2R mRNA in fasted rats was increased by administration of CCK, and by refeeding through a mechanism sensitive to the CCK1R antagonist lorglumide. Antibodies to Y2R revealed expression in both neurons and satellite cells; most of the former (89 +/- 4%) also expressed CCK1R. With fasting there was loss of Y2R immunoreactivity in CCK1R-expressing neurons many of which projected to the stomach, but not in satellite cells or neurons projecting to the ileum or proximal colon. Expression of a Y2R promoter-luciferase reporter (Y2R-luc) in cultured vagal afferent neurons was increased in response to CCK by 12.3 +/- 0.1-fold and by phorbol ester (16.2 +/- 0.4-fold); the response to both was abolished by the protein kinase C inhibitor Ro-32,0432. PYY3-36 stimulated CREB phosphorylation in rat nodose neurons after priming with CCK; in wild-type mice PYY3-36 increased Fos labeling in brainstem neurons but in mice null for CCK1R this response was abolished. Thus Y2R is expressed by functionally distinct subsets of nodose ganglion neurons projecting to the stomach and ileum/colon; in the former expression is dependent on stimulation by CCK, and there is evidence that PYY3-36 effects on vagal afferent neurons are CCK dependent.

Sweetness and bitterness taste of meals per se does not mediate gastric emptying in humans.

In cell line and animal models, sweet and bitter tastants induce secretion of signaling peptides (e.g., glucagon-like peptide-1 and cholecystokinin) and slow gastric emptying (GE). Whether human GE and appetite responses are regulated by the sweetness or bitterness per se of ingested food is, however, unknown. We aimed to determine whether intragastric infusion of "equisweet" (Study A) or "equibitter" (Study B) solutions slow GE to the same extent, and whether a glucose solution made sweeter by the addition of saccharin will slow GE more potently than glucose alone. Healthy nonobese subjects were studied in a single-blind, randomized fashion. Subjects received 500-ml intragastric infusions of predetermined equisweet solutions of glucose (560 mosmol/kgH(2)O), fructose (290 mosmol/kgH(2)O), aspartame (200 mg), and saccharin (50 mg); twice as sweet glucose + saccharin, water (volumetric control) (Study A); or equibitter solutions of quinine (0.198 mM), naringin (1 mM), or water (Study B). GE was evaluated using a [(13)C]acetate breath test, and hunger and fullness were scored using visual analog scales. In Study A, equisweet solutions did not empty similarly. Fructose, aspartame, and saccharin did not slow GE compared with water, but glucose did (P < 0.05). There was no additional effect of the sweeter glucose + saccharin solution (P > 0.05, compared with glucose alone). In Study B, neither bitter tastant slowed GE compared with water. None of the solutions modulated perceptions of hunger or fullness. We conclude that, in humans, the presence of sweetness and bitterness taste per se in ingested solutions does not appear to signal to influence GE or appetite perceptions.

Predicting aspiration after hemispheric stroke from timing measures of oropharyngeal bolus flow and laryngeal closure.

Deglutitive aspiration is common after stroke, affecting up to 50% of patients and predisposing them to pneumonia, yet it is virtually impossible to predict those patients at greatest risk. The aim of this study was to develop a robust predictive model for aspiration after stroke. Swallowing was assessed by digital videofluoroscopy (VF) in 90 patients following hemispheric stroke. Lesion characteristics were determined by computerized tomography (CT) brain scan using the Alberta Stroke Programme Early CT Score (ASPECTS). Aspiration severity was measured using a validated penetration-aspiration scale. The probability of aspiration was then determined from measures of swallowing pathophysiology and lesion location by discriminant analysis. Aspiration was observed in 47 (52%) patients, yet despite disrupted swallowing physiology, intrasubject aspiration scores were variable. The best discriminant model combined pharyngeal transit time, swallow response time, and laryngeal closure duration to predict 73.11% of those aspirating (sensitivity = 66.54, specificity = 80.22, p > 0.001). The addition of lesion location did not add anything further to the predictive model. We conclude that the pathophysiology of poststroke aspiration is multifactorial but in most cases can be predicted by three key swallowing measurements. These measurements, if translatable into clinical bedside evaluation, may assist with the development of novel measurement and intervention techniques to detect and treat poststroke aspiration.

Ultrasensitive DNA detection using oligonucleotide-silver nanoparticle conjugates.

Oligonucleotide-gold nanoparticle (OGN) conjugates are powerful tools for the detection of target DNA sequences due to the unique properties conferred upon the oligonucleotide by the nanoparticle. Practically all the research and applications of these conjugates have used gold nanoparticles to the exclusion of other noble metal nanoparticles. Here we report the synthesis of oligonucleotide-silver nanoparticle (OSN) conjugates and demonstrate their use in a sandwich assay format. The OSN conjugates have practically identical properties to their gold analogues and due to their vastly greater extinction coefficient both visual and absorption analyses can occur at much lower concentrations. This is the first report of OSN conjugates being successfully used for target DNA detection and offers improved sensitivity which is of interest to a range of scientists.

The relationship between somatisation and outcome in patients with severe irritable bowel syndrome.

OBJECTIVE: This study aimed to assess the relationship between somatisation and outcome in patients with severe irritable bowel syndrome (IBS). METHOD: Two hundred fifty-seven patients with severe IBS included in a randomised controlled trial were assessed at baseline and divided into four quartiles on the basis of their somatisation score. The patients were randomised to receive the following over 3 months: brief interpersonal psychotherapy, 20 mg daily of the SSRI antidepressant paroxetine, or treatment as usual. Outcome 1 year after treatment was assessed using the Short Form-36 physical component summary (PCS) score and total costs for posttreatment year. RESULTS: The patients in the quartile with the highest baseline somatisation score had the most severe IBS, the most concurrent psychiatric disorders, and the highest total costs for the year prior to baseline. At 1 year after the end of treatment, however, the patients with marked somatisation, who received psychotherapy or antidepressant, had improved health status compared to those who received usual care: mean (S.E.) PCS scores at 15 months were 36.6 (2.2), 35.5 (1.9), and 26.4 (2.7) for psychotherapy, antidepressant, and treatment-as-usual groups, respectively (adjusted P=.014). Corresponding data for total costs over the year following the trial, adjusted for baseline costs, were pound 1092 (487), pound 1394 (443), and pound 2949 (593) (adjusted P=.050). CONCLUSIONS: Patients with severe IBS who have marked somatisation improve with treatment like other IBS patients and show a greater reduction of costs. Antidepressants and psychotherapy are cost-effective treatments in severe IBS accompanied by marked somatisation.

Severe chronic abdominal pain in the absence of adhesions.

Management of the patient with chronic severe abdominal pain in the absence of adhesions remains one of the major challenges of the gastroenterologist. Given that extensive investigation will inevitably take place of such individual, the role of the gastroenterologist who is asked to review such a problem, is to identify unusual manifestations of common disorders from new, previously-unidentified causes, and to assess the degree to which somatisation and psychological overlay are exacerbating the problem. Investigations must be targeted against clinically-generated hypotheses rather than to repeat a non-systematic approach. Therapy in the absence of a newly-identified disorder is generally targeted at alleviating rather than removing symptoms, addressing an individual's personal pain and management needs, and avoiding ever more complex and invasive investigations.

Induction of G2/M phase cell cycle arrest by carnosol and carnosic acid is associated with alteration of cyclin A and cyclin B1 levels.

Carnosol and carnosic acid, two antioxidant polyphenols present in Rosmarinus officinalis (rosemary), were investigated for their antiproliferative properties toward Caco-2 cells. Twenty hours of treatment with both carnosol and carnosic acid inhibited 3H-thymidine incorporation in a dose-dependent manner, with a 50% inhibitory concentration of 23 microM and significantly increased the doubling time of Caco-2 cells from 29.5 to 140 and 120 h, respectively. These effects were associated with accumulation of treated cells in the G2/M phase of the cell cycle. Carnosol was found to exert its major cell cycle effect after prometaphase, and caused an increase in cyclin B1 protein levels whereas carnosic acid arrested cells prior to prometaphase, and caused a reduction in cyclin A levels. These structurally related phytochemicals, therefore, appear to arrest cells at different phases of the cell cycle possibly through influencing the levels of different cyclin proteins.

Constitutive cyclo-oxygenase-2 does not contribute to the development of human visceral pain hypersensitivity.

BACKGROUND AND AIMS: Central sensitisation (CS), contributes to the development and maintenance of gastrointestinal pain hypersensitivity. Constitutive cyclo-oxygenase-2 (COX-2) contributes to central sensitisation in somatic pain hypersensitivity but its role in mediating visceral pain hypersensitivity is unknown. We therefore conducted a study to determine if COX-2 inhibition with Valdecoxib attenuates the development or early maintenance of CS in a validated human oesophageal pain hypersensitivity model. METHODS: Healthy volunteers were studied in two randomised, double blind, crossover studies in which pain thresholds (PT) to electrical stimulation were assessed in the proximal oesophagus, chest wall and foot, prior to and following a distal oesophageal acid infusion. Protocol 1: Valdecoxib, (40 mg) or matching placebo was given orally for 4 days prior to oesophageal acid infusion. Protocol 2: IV Parecoxib (40 mg) or saline was given 120 min after oesophageal acid infusion. RESULTS: Valdecoxib did not prevent the induction of secondary allodynia in the proximal oesophagus nor did it attenuate it following its establishment. Chest wall PT fell following oesophageal acid but foot PT remained unchanged; highlighting the development viscero-somatic convergence due to CS. Valdecoxib had no analgesic or anti-hyperalgesic effect on chest wall or foot PT. CONCLUSIONS: Neither the induction nor initial maintenance of acid induced oesophageal pain hypersensitivity is prevented by Valdecoxib, suggesting that constitutive spinal COX-2 does not contribute to the development or early maintenance of acute visceral central sensitisation.

Neurogastroenterology: imaging of the sensory and motor control of the GI tract.

The central nervous system plays a major role in the receipt and processing of gastrointestinal signals both at a conscious and subconscious level. It also provides major input into the motor control of the gut, most particularly with regard to swallowing and defecation. This review indicates how this control operates and provides recent experimental evidence of mechanisms underlying it both in health and disease.

Expression of cannabinoid CB1 receptors by vagal afferent neurons is inhibited by cholecystokinin.

Both inhibitory (satiety) and stimulatory (orexigenic) factors from the gastrointestinal tract regulate food intake. In the case of the satiety hormone cholecystokinin (CCK), these effects are mediated via vagal afferent neurons. We now report that vagal afferent neurons expressing the CCK-1 receptor also express cannabinoid CB1 receptors. Retrograde tracing established that these neurons project to the stomach and duodenum. The expression of CB1 receptors determined by RT-PCR, immunohistochemistry and in situ hybridization in rat nodose ganglia was increased by withdrawal of food for > or =12 hr. After refeeding of fasted rats there was a rapid loss of CB1 receptor expression identified by immunohistochemistry and in situ hybridization. These effects were blocked by administration of the CCK-1 receptor antagonist lorglumide and mimicked by administration of CCK to fasted rats. Because CCK is a satiety factor that acts via the vagus nerve and CB1 agonists stimulate food intake, the data suggest a new mechanism modulating the effect on food intake of satiety signals from the gastrointestinal tract.

Reported sexual abuse predicts impaired functioning but a good response to psychological treatments in patients with severe irritable bowel syndrome.

OBJECTIVE: We assessed the effect of reported sexual abuse on symptom severity and health-related quality of life in patients with severe irritable bowel syndrome (IBS) undergoing psychological treatments. METHODS: IBS patients entering a treatment trial who reported prior sexual abuse were compared with the remainder in terms of symptom severity and health-related quality of life (SF-36) at trial entry and 15 months later. Analyses used ANCOVA with age, sex, marital status, and treatment group as covariates. We assessed possible mediators using multiple regression analysis. RESULTS: Of 257 patients with severe IBS, 31 (12.1%) reported a history of rape and 28 (10.9%) reported forced, unwanted touching. People who reported abuse were more impaired than the remainder on the SF-36 scales for pain (adjusted p = .023) and physical function (p = .029); these relationships followed a "dose-response" relationship and were mediated by SCL-90 somatization score. At 15 months follow-up, the associations between reported abuse and SF-36 scores were lost because people with reported abuse, especially rape, improved more than the remainder when treated with psychotherapy or paroxetine (selective serotonin reuptake inhibitor antidepressant); this improvement was mediated by change in SCL-90 somatization score. CONCLUSIONS: In severe IBS, the association between self-reported sexual abuse and impaired functioning is mediated by a general tendency to report numerous bodily symptoms. A reported history of abuse is associated with a marked improvement following psychological treatment.

SERS enhancement of silver nanoparticles prepared by a template-directed triazole ligand strategy.

Two advances in the development of a one-pot method to prepare silver nanoparticles (AgNPs) using the Tollens' reagent are described. First, a template-directed process of AgNP synthesis using resorcinol triazole ligands bearing two pendent galactose sugars is shown. Second, the conversion of these AgNPs into SERS nanotags is demonstrated using malachite green isothiocyanate as the Raman reporter molecule.

Palladium(0) NHC complexes: a new avenue to highly efficient phosphorescence.

We report the first examples of highly luminescent di-coordinated Pd(0) complexes. Five complexes of the form [Pd(L)(L')] were synthesized, where L = IPr, SIPr or IPr* NHC ligands and L' = PCy3, or IPr and SIPr NHC ligands. The photophysical properties of these complexes were determined in degassed toluene solution and in the solid state and contrasted to the poorly luminescent reference complex [Pd(IPr)(PPh3)]. Organic light-emitting diodes were successfully fabricated but attained external quantum efficiencies of between 0.3 and 0.7%.

Changes in tolerance to rectal distension correlate with changes in psychological state in patients with severe irritable bowel syndrome.

OBJECTIVE: Reduced tolerance to rectal distension has been regarded as a biological marker for irritable bowel syndrome (IBS), but longitudinal studies are few. This study determined whether change in tolerance to rectal distension after psychological treatments was associated with: 1) change in abdominal pain; 2) change in psychological symptoms; 3) a reported history of sexual abuse. METHODS: Participants completed a visual analogue scale of abdominal pain, SCL-90 and Hamilton rating scale of depression; discomfort threshold to rectal distension was determined using a double random staircase protocol. These were measured at entry to a trial of psychotherapy or paroxetine (selective serotonin reuptake inhibitor antidepressant) and 3 months later (N = 52). Analysis of change scores were adjusted for treatment group and baseline values. RESULTS: Increased tolerance to distension after treatment was associated with reduction in depression (r = -0.37, p =.008) but not abdominal pain. Patients who reported prior sexual abuse showed greater increase in tolerance than the remainder (changes in volume threshold: -24.7 ml [SEM = 12.1] vs. 3.6 ml [SEM = 6.2], adjusted p =.045; changes in pressure threshold: -4.7 [SEM = 1.7] mm Hg vs. 0.96 [SEM=0.9], adjusted p =.005). Multiple regression indicated that reduction in depression score and a reported history of sexual abuse were independently associated with improved tolerance to distension. CONCLUSIONS: In patients with severe IBS, increased tolerance to rectal distension after psychological treatment is significantly associated with improved depression and reported sexual abuse. These results suggest that in some patients with severe IBS psychological rather than biological processes are primarily responsible for reduced tolerance to rectal distension.