Sa1620 POLYETHYLENE GLYCOL 3350 CHANGES STOOL CONSISTENCY BUT NOT ANXIETY-LIKE BEHAVIOR OF OUTBRED CD1 MICE Salman Salman, Kent C. Williams, Michael T. Bailey, Ross Maltz Background: Polyethylene Glycol 3350 (PEG-3350) is an over the counter laxative commonly used to treat constipation in pediatric populations. Anecdotal reports of anxiety, lethargy, aggression, mood swings and obsessive compulsive behavior after administration of PEG 3350 have led to parental concerns. However, behavioral problems are common in children with constipation like anxiety, aggression, depression and increased emotional reactivity, and no data have linked PEG 3350 to behavioral changes. In a previous study, we did not find any effects of PEG-3350 on mouse behavior. However, behavior was assessed on multiple time points, which may confound results. Thus, a follow-up experiment was conducted in which behavior was assessed at only a single time point after laxative administration. Aim: Determine if PEG-3350 leads to anxiety-like behavior in male and female mice. Methods: Outbred CD1 mice (8 weeks old) were divided into 6 groups that received: PEG-3350 either at 1g/kg or 4 g/kg, magnesium citrate either at 450mg/kg or 600 mg/kg or water via daily oral gavage for two weeks. In addition, there was an unhandled control group that was not gavaged with vehicle or any of the treatments. Male and female mice were used (n=12 per group) for a total of 144 mice. Stool consistency was assessed 4-6 hours after gavage and was recorded on a scale from 0-3 with 0 indicating normal hard pellets, 1 indicating mildly soft stool, 2 indicating very soft stool, and 3 indicating watery stool. Mice were weighed daily during the gavage period. Behavior on the Light/Dark test, open field test, and elevated plus maze was assessed after 2 weeks of the gavage. Standard measures of anxiety-like behavior were scored during the 5 minutes of the tests. Results: PEG-3350 and magnesium citrate significantly changed stool consistency compared to water and control groups. Although female mice showed increased anxiety-like behavior in the open field task and elevated plus maze, neither PEG-3350 or magnesium citrate affected male or female behavior in the Light/Dark preference test (including latency to enter the dark, time spent in the dark, and number of transitions between light and dark chambers), the open field task (including time spent in the center/periphery, resting time, and distance traveled), or the elevated plus maze (number of entries, time spent in the open arm, and time spent in the closed arm). Conclusion: Daily administration of PEG-3350 does not significantly affect anxiety-like behavior or locomotor activity in male or female mice despite a sufficient laxative affect. Sa1621 EFFECT OF MIRTAZAPINE IN CHILDREN WITH FUNCTIONAL DYSPEPSIA AND FUNCTIONAL NAUSEA Ivonne M. Iglesias Escabi, Lee McDaniel, Paul E. Hyman Mirtazapine is an antidepressant that reduced dyspeptic symptoms in adults. In children, mirtazapine was used for social phobia and reducing panic attacks. We aimed to assess mirtazapine for children meeting Rome criteria for functional dyspepsia and functional nausea. We reviewed charts from 2013-18 documenting indications, symptoms before and after treatment, and side effects of mirtazapine. Response was classified as none, partial (patient feels better, but still with some symptoms), or complete. We treated 62 patients (43 female, age 14.1 ± 3.1 y) for functional dyspepsia (n= 36) or functional nausea (n= 26). Treatment duration ranged from 1 to 1460 days (mean 176±262 days). Most patients (41) received 15 mg, 20 received 7.5 mg and 1 received 30 mg qhs. Responses were complete in 33 (53%), partial in 19 (31%), none in 7 (11%) and 3 (5%) stopped the medicine because of adverse effects before assessment. We documented complete response in 18/36 (50%) with functional dyspepsia and 14/26 (53%) with functional nausea. Complete response occurred in 13/19 (68%) boys and 20/43 (47%) girl, p = 0.19. Of complete responders, 21 patients received 15 mg, 10 received 7.5 mg and 1 received 30 mg. In those with complete response, 16/18 (89%) with dyspepsia and all the nausea patients (14) gained weight. Average weight gain was 3.2 ±2.5 Kg with no sex difference (p = 0.23). Weight gain occurred in 54/62 (87%) patients (18 boys and 36 girls), resulting in discontinuing mirtazapine in 8 patients. There were reports of undesirable behavioral changes (n=5), sleepiness (n=3), increased appetite (n=3), headaches (n=1), dizziness (n=1), sleep walking (n=1), hand tremor (n=1) and allergic reaction (n=1), resulting in stopping mirtazapine in 19 (31%) patients. Only 1 with no response discontinued mirtazapine after 46 days due to increased appetite. Five patients with no GI symptom response continued mirtazapine because it improved comorbid insomnia, and/or reduced panic attacks. Mirtazapine is an option for treating children and adolescents with functional dyspepsia and functional nausea. Sa1622 SLEEP DISTURBANCES IN SCHOOL-AGE CHILDREN WITH FUNCTIONAL GASTROINTESTINAL PAIN DISORDERS AND RELATION TO DEMOGRAPHIC AND CLINICAL CHARACTERISTICS Jennifer Jansen, Teresa Ward, Rona L. Levy, Margaret Heitkemper, Mariella M. Self, Robert J. Shulman Introduction: Research indicates the deleterious effects of sleep disturbances on pain and illness-related functioning across pediatric populations. Sleep problems in youth with func- tional gastrointestinal pain disorders ( FGIDs) are understudied, despite evidence that sleep disturbances increase pain and symptom severity in adults with irritable bowel syndrome. This study sought to better characterize sleep disturbances in school-age children with FGIDs and to assess their relationship with pain and gastrointestinal ( GI) symptoms. Method: Children 7-12 yrs. of age with FGIDs (pediatric Rome IV criteria) and their parents completed the Children’s Sleep Habits Questionnaire and Sleep Self Report, and children completed a 2-week pain and stooling diary. Sleep disturbances were compared to a published normative sample; children above and below the sleep disturbance clinical cutoff scores ( 41 or <41 respectively) were compared on pain/GI symptoms. Results: Mean age was 10.3±1.6; n= S-357 AGA Abstracts 67; 63% female; Black/African American (50.7%) vs White (40.3%). Of the total sample, 61% scored above clinical cutoff for sleep disturbances. Bedtime resistance, sleep onset delay, and daytime sleepiness were significantly higher than the comparison group (Table 1). Children above clinical cutoff score reported greater mean pain interference and greater number of days without bowel movements (Table 2). Compared to White participants, Black/African American participants had greater sleep duration overall ( F=4.49, p=.039), but more frequent night awakenings ( F=4.68, p=.035) and greater symptoms of sleep- disordered breathing (F=4.33, p=.043). In comparison to White participants, Black/African American participants reported lower maximum pain severity ( F=6.40, p=.014), lower overall mean pain severity ( F=5.21, p=.026), and more days without bowel movements ( F=8.96, p=.004). Conclusion: Sleep disturbances in children with FGIDs were common and appear to be related to greater day-to-day pain interference, emphasizing the importance of sleep as a potential intervention target. However, Black/African American children reported greater sleep disruption, but less abdominal pain severity than White children, suggesting sleep- pain relationships may differ across racial/ethnic groups. Further research is needed to assess underlying mechanisms of sleep-pain relationships, particularly across racial groups. Sa1623 URINARY EXOSOMES ISOLATED FROM PEDIATRIC PATIENTS WITH GASTROPARESIS WITH AND WITHOUT HEREDITARY ALPHA TRYPTASEMIA (HAT) REVEAL NOVEL BIOMARKERS AND TARGETS FOR DISEASE MECHANISM Lybil B. Mendoza Alvarez, Mohammad-Zaman Nouri, Nasseem M El moujahid, Nancy D. Denslow, Sarah C Glover, Abdel A. Alli Background: Exosomes are nano-sized vesicles involved in a variety of biological processes including cell differentiation, proliferation, signaling, and intercellular communication. Lip- idomics of urinary exosomes has become an appealing area of investigation due to the potential for biomarker discovery and insight into disease mechanism. The disease mechanism of pediatric gastroparesis is largely unknown, and it is considered idiopathic in 70% of all cases. Hereditary Alpha Tryptasemia (HaT) is an autosomal dominant disorder that represents a subset of individuals with mast cell activation syndrome (MCAS) and likely impacts up to 6% of the general population. It is defined by increased copies of the TPSAB1 encoding alpha-tryptase gene resulting in elevated baseline serum tryptase >8ng/mL. Patients with HaT report symptoms of MCA as well as gastrointestinal (GI) symptoms that could be attributable to either IBS or GI dysmotility (49% in the index NIH cohort). Aim: We investigated differences in lipid species within urinary exosomes between the HaT and control groups in order to identify lipids involved in disease mechanism. Methods: Baseline serum tryptase levels, weight, gastrointestinal symptoms, and gastric emptying scan was recorded in a total of 35 male and female pediatric patients, ages 10-21 years old with clinical symptoms of gastroparesis including nausea, vomiting, bloating, early satiety and abdominal pain. None of the patients had a history of diabetes mellitus, cardiovascular disease, chronic kidney disease, cancer, or any other chronic gastrointestinal disease. HaT patients were classified by tryptase levels and genetic testing. Urinary exosomes were isolated by a series of filtration, centrifugation, and ultracentrifugation steps and the exosomes were characterized by nanoparticle tracking analysis, Western blotting for exosomal markers, and transmission electron microscopy. Lipids were extracted by the Bligh and Dyer method and exosomal lipids in each sample were analyzed using an ultra-high-performance liquid chromatography system. Results: All patients had abnormal gastric emptying with an average half-time of 130min (4-hour protocol), symptoms of nausea and vomiting, and abdominal pain. Eight patients were found to have abnormal tryptases (>8ng/mL) with an average tryptase of 17ng/mL and duplication in the tryptase gene confirming the HaT diagnosis. There was differential expression of various lipid species within the urinary exosomes between the HaT and control groups. Conclusions: Here we show urinary exosomes isolated from the HaT patients have a unique lipidomic profile compared to the control group. These results will allow for further investigation of these differentially expressed lipids in the potential dysregulation of epithelial cell membrane fluidity and permeability coupled to MCA in HaT patients. AGA Abstracts