(HFF) for 12-16 weeks; lean mice fed 10% calories from fat (LFF) were used as controls.In Vitro extracellular recordings were performed from jejunal afferents. Nodose ganglionneurons (NGNs) were dissociated and plated onto coverslips. Whole cell patch clamprecordings or Fura-2AM calcium imaging experiments on NGNs were performed 18-24 hpost-dissociation. Results: In recordings from jejunal afferents, responses to 100nM CCK(11.5 ± 3.2 vs. 3.35 ± 1.0 spikes/s n=10, p<0.05) and 10μM 5-HT (4.85 ± 1.4 vs. 1.75 ±0.25, n=10, p<0.05) were decreased in HFF mice compared to LFF controls. Howeverresponses to non satiety related compounds such as nicotine, and baseline firing rate werealso decreased, suggesting a global decrease in excitability. Current clamp experiments wereperformed on NGNs to assess the membrane properties in LFF and HFF neurons. Restingmembrane potentials were similar -46.6 ± 3.5 mV (LFF, n=5) and -43.1 ± 2.5mV (HFF,n=5). Rheobase was significantly increased (34.0 ± 9.3 vs. 128.0 ± 24.6 pA, n=5, P < 0.05)and the number of action potentials at 2X rheobase was decreased (3.0 ± 0.8 vs. 1 ± 0, n=5 p<0.05) in HFF compared to LFF, and there was a large, but non statistically significantreduction in input resistance (LFF, 725.6 ± 266.9 MΩ vs. HFF, 141 ± 15.6 MΩ). In Calciumimaging studies on HFF neurons, 0.5% (1/21) and 9.5% (2/21) of the neurons respondedto 100nM CCK-8s and 1μM 5-HT respectively. The number of responsive neurons washigher in LFF mice CCK; 18.9 % (7/37), 5-HT; 21.6% (8/37). Conclusions: Responses tothe satiety mediators CCK and 5-HT are significantly attenuated in gut vagal afferents. Thisreduction in response appears to be due at least in part to a global reduction in excitabilityof vagal afferents in diet induced obese mice, raising the possibility that high fat diet cancause vagal hyposensitivity, impairing normal satiety signals from the GI tract.

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Effects of Rimonabant on Gastrointestinal Transit in DogsJieyun Yin, Sidney S. Chen, Jun Song, Jiande Chen

Rimonabant (Rim), a highly selective cannabinoid (CB) receptor 1 blocker, was developedfor treating obesity. While CBs are known to alter gastrointestinal motility that plays animportant role in food intake and nutrient absorption, it is however, unknown whetheralterations in gastrointestinal motility are involved in the anti-obesity mechanisms of .Rim.The aim of this study was therefore to investigate the effects of Rim on gastric emptying,small intestinal and colonic transit in dogs. Methods: Six dogs equipped with one duodenalcannula and one colonic cannula were studied a number of paired sessions: control andRim at 1mg/kg. Gastric emptying was assessed by ingesting a can of solid food, collectingsamples via the duodenal cannula and drying them in the air. Small intestinal transit wasmeasured by injecting a 30ml phenol red solution into the small intestine via the duodenalcannula after a solid test meal, collecting phenol red samples through the colonic cannulaevery 15min for 3 hrs. Five of the dogs were used for studying the effect of Rim on colonictransit using abdominal X-ray. Colonic transit was assessed by counting the numbers ofradiopaque markers that were inserted to the proximal colon through the colon cannula atdifferent time points (2 hours, 4 hours and 6 hours after insertion of the markers) alongthe colon. Seven areas including ascending colon, hepatic flexure, transverse colon, splenicflexure, descending colon, rectum and out of the rectum were used to calculate the geometriccenter (GC) of the markers. Results: 1) Rim significantly delayed gastric emptying of solidduring 120 min to 180 min after the meal (P< 0.05 vs. control). The gastric emptying was80.8 ± 3.0% in the control session and was significantly reduced to 57.5 ± 7.8% with Rim(P = 0.02). 2) Rim substantially accelerated small intestinal transit. The first appearancetime of phenol red was reduced from 137.8 ± 19.3 min in the controls to 39 ± 14.1 withRim (P = 0.001). 3) Rim significantly accelerated colonic transit. The GC after 2, 4 and 6hours of inserting markers were 1.9 ± 0.6, 3.9 ± 0.5 and 5.0 ± 0.1 in the control session,and was significantly increased to 4.8 ± 0.8, 5.4 ± 0.6 and 6.2 ± 0.4 respectively (P<0.03vs. corresponding control). Conclusions: Selectively block of CB1 receptor by Rim delaysgastric emptying but accelerates small intestinal and colonic transit potently. The delay ingastric emptying but acceleration in intestinal transit may partly explain anti-obesity mechan-isms of Rim as delayed gastric emptying may lead to reduced food intake whereas accelerationin intestinal transit may lead a reduction in nutrient absorption.

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Colon Electrical Stimulation: A Potential Treatment for ObesityHanaa S. Sallam, Jiande Chen

Obesity is one of the most prevalent health problems in the United States. Current therapeuticstrategies for the treatment of obesity are unsatisfactory. Recently, gastric electrical stimula-tion, as a potential therapy for obesity, has been extensively studied and has shown promisingresults in the reduction of food intake and induction of weight loss. Instead of gastricelectrical stimulation, we hypothesized the use of colon electrical stimulation (CES) to reduceupper gastrointestinal motility and food intake. In this preliminary study, we aimed atstudying the effects of CES on solid gastric emptying, intestinal motility and food intake indogs. Six dogs, equipped with serosal colon electrodes and a duodenal cannula, wererandomly assigned to receive sham CES or CES during the assessment of: 1) solid gastricemptying, 2) postprandial intestinal motility and 3) food intake. Solid gastric emptying wasassessed by collecting the gastric effluent from the intestinal cannula over three hours,following the consumption of a one can of dog food. Intestinal motility recording was donein the fed state by means of a manometry catheter that was inserted into the intestinethrough the intestinal cannula. For the food intake study, following a week training to eatover a two-hour period each day, the dogs were offered abundant food in their home cagewhile sham CES or CES were applied over the two-hour period during which food wasprovided using a portable stimulator attached to the back of the animal. The amount offood intake was noted. We found that 1) CES delayed solid gastric emptying by 77%(p≤0.0001 vs. sham). The percentages of solid gastric emptying at 3 hours were 10%±3and 87%±3 with CES and sham-CES, respectively (p≤0.0001). The difference in the solidgastric emptying between CES and sham was consistent over the entire three hours of thestudy. 2) CES significantly reduced intestinal contractility; an effect that lasted throughoutthe recovery period. The motility indices were 3.5±0.3 and 5.2±0.6 with CES and sham-CES, respectively (p=0.02). 3) CES resulted in a reduction of 61% in food intake (p=0.04).Colon electrical stimulation delays gastric emptying of solid, inhibits intestinal motility and

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reduces food intake. Further studies are warranted to investigate the therapeutic potentialof CES for obesity.

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Differential Distribution of Ghrelin-O-Acyltransferase (Goat) ImmunoreactiveCells in the Mouse and Rat Gastric Oxyntic MucosaMiriam Goebel, Andreas Stengel, Lixin Wang, Yvette Tache, George Sachs, Nils W.Lambrecht

Background: The enzyme that acylates ghrelin has been recently identified in mice as amember of the superfamily of membrane-bound O-acyltransferases (MBOATs) and namedghrelin-O-acyltransferase (GOAT). Only one report showed GOAT mRNA expression inghrelin-expressing cells of the mouse stomach. Aim: To investigate the cellular source ofGOAT in the stomach of rats and mice. Methods: Expression of GOAT protein was deter-mined by Western blot and immunohistochemistry using a custom made anti-GOAT poly-clonal antibody which was raised against amino acids 273-286 of rat MBOAT4 (GOAT).Gastric corpus tissue was collected from male Sprague-Dawley rats and C57/Bl mice andprocessed for paraffin embedding and protein extraction. Results: Western blot analysisrevealed two immunoreactive bands in rat and mouse gastric corpus mucosal proteins, a50 kDa band corresponding to the monomeric GOAT protein and a 100 kDa band corres-ponding to a SDS stable dimer. These bands were also observed, surprisingly, in plasmaprotein fractions. Moreover, the 50 kDa GOAT monomer in mice plasma proteins wasincreased in concentration after a 24 h fasting period. Double labeling immunohistochemistryon rat and mouse gastric mucosal sections was performed for GOAT, ghrelin, and histidinedecarboxylase (HDC). In mice, GOAT-immunoreactive cells were distributed throughoutmiddle and lower portions of the oxyntic glands whereas in rats they were localized mainlyin the lower portion of the glands. Double labeling showed that the vast majority (90%) ofGOAT-immunoreactive cells in mice co-labeled with ghrelin whereas only 40% of GOAT-positive cells in rats showed co-expression of ghrelin. In the rat, a considerable portion ofGOAT-positive cells co-expressed HDC. Immuno-positivity in rat or mouse tissue wasabolished after pre-absorption of the GOAT antibody with GOAT peptide. Conclusion:These data suggest species differences between rats and mice in gastric GOAT expressionperhaps suggesting a different role for the GOAT enzyme in the rat stomach. Westernanalysis of plasma proteins in mice revealed increased concentrations of soluble GOAT inthe fasted state which implies release of GOAT enzyme into the circulation according tometabolic state. This warrants further investigation (supported by DK 41301).

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Contribution of Serotonin 2C Receptor Activation to “Ghrelin Resistance” andPossible Therapy for Cisplatin-Induced AnorexiaKoji Yakabi, Shoki Ro, Shino Ohno, Toru Aoyama, Junichi Kawashima, Katsuya Chinen,Chiharu Sadakane, Masamichi Noguchi, Tomohisa Hattori

Background/Aim: It is well known that peripheral ghrelin regulates appetite via vagal nerveactivation, but there is little information that clarifies the effect of central ghrelin on thegut-brain axis. In addition, it has been demonstrated that in patients with cancer cachexiaor anorexia nervosa plasma ghrelin concentration neither decreases nor increases. Thus,appetite loss under high plasma ghrelin concentration has been termed “ghrelin resistance”.This study was performed to investigate the association between decreased hypothalamicacylated ghrelin secretion in cisplatin-induced anorexia and ghrelin resistance. Methods:Seven-week-old male SD rats were used. Cisplatin or serotonin receptor agonist was adminis-tered alone (i.p.) or coadministered with the 5-HT2C receptor antagonist SB242084 (i.c.v.).After a fixed time, the amount of ghrelin secreted as well as plasma ghrelin concentrationwere measured in the blood and hypothalamus by ELISA. Alternatively, rikkunshito (RKT),an endogenous ghrelin secretion stimulator (p.o.) (Gastroenterology 2008 Vol.134, BiologicalPsychiatry 2009 Vol.65) or exogenous rat ghrelin (i.c.v.) was administered alone or coadmin-istered with cisplatin to clarify the effect of endogenous hypothalamic ghrelin secretion onfood intake. Results: In 19.1% of rats treated with either cisplatin or the 5-HT2C receptoragonist mCPP, food intake and hypothalamic acylated ghrelin secretion decreased signific-antly compared with saline-treated rats. In addition, RKT treatment alone markedly enhancedhypothalamic acylated ghrelin secretion (291.7%). In rats treated with cisplatin + SB242084,but not granisetron, decrease in food intake and hypothalamic acylated ghrelin secretionwas completely inhibited as shown in Table 1. Further, coadministration of RKT or ratghrelin with cisplatin also inhibited the decrease in food intake and ghrelin secretion (cisplatin+ vehicle 57.3 ± 2.4% vs. cisplatin + RKT, 117.0 ± 11.8%, p = 0.002). Conclusion: Decreasedhypothalamic ghrelin secretion seems to play an important role in cisplatin-induced anorexia.Serotonin 2C activation was implicated as a possible mechanism. The present results indicatethe possibility that the regulation of central ghrelin secretion by treatment with 5-HT2Creceptor antagonist or RKT may contribute to a cure for ghrelin resistance in cisplatin-induced anorexia.Changes in hypothalamic ghrelin secretion

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