Antidepressant treatment was associated with elevated REM sleep without atonia (RSWA) even without REM sleep behavior disorder (RBD), suggesting that antidepressants, not depression, promote RSWA. Differences in RSWA distribution and type were also seen, with higher anterior tibialis RSWA in antidepressant-treated patients and higher tonic RSWA in Parkinson disease-RBD patients, which could aid distinction between RBD subtypes. These findings suggest that antidepressants may mediate different RSWA mechanisms or, alternatively, that RSWA type and distribution evolve during progressive neurodegeneration. Further prospective RSWA analyses are necessary to clarify the relationships between antidepressant treatment, psychiatric disease, and RBD.

BACKGROUND: Oral monosaccharides and disaccharides are used to measure in vivo human gut permeability through urinary excretion. AIMS: The aims were as follows: (1) to obtain normative data on small intestinal and colonic permeability; (2) to assess variance on standard 16 g fiber diet performed twice;(3) to determine whether dietary fiber influences gut permeability measurements; and (4) to present pilot data using 2 selected probes in patients with diarrhea-predominant irritable bowel syndrome (IBS-D). METHODS: Sixty healthy female and male adults, age 18-70 years, participated in 3 randomized studies (2 studies on 16.25 g and 1 study on 32.5 g fiber) in otherwise standardized diets. At each test, the following sugars were ingested: 12 C-mannitol, 13 C-mannitol, rhamnose (monosaccharides), sucralose, and lactulose (disaccharides). Standardized meals were administered from 24 hours before and during 24 hours post-sugars with 3 urine collections: 0-2, 2-8, and 8-24 hours. Sugars were measured using highperformance liquid chromatography-tandem mass spectrometry. Eighteen patients with IBS-D underwent 24-hour excretion studies after oral 13 C-mannitol and lactulose. RESULTS: Baseline sugars (>3-fold above lower limits of quantitation) were identified in the 3 studies: 12 C-mannitol in all participants; sucralose in 4-8, and rhamnose in 1-3. Median excretions/24 h (percentage of administered dose) for 13 Cmannitol, rhamnose, lactulose, and sucralose were w30%, w15%, 0.32%, and 2.3%, respectively. 13 C-mannitol and rhamnose reflected mainly small intestinal permeability. Intraindividual saccharide excretions were consistent, with minor differences with 16.25 g vs 32.5 g fiber diets. Median interindividual coefficient of variation was 76.5% (10-90 percentile: 34.6-111.0). There were no significant effects of sex, age, or body mass index on permeability measurements in health. 13 C-mannitol measurements are feasible in IBS-D. CONCLUSIONS: Baseline 12 C-mannitol excretion precludes its use; 13 C-mannitol is the preferred probe for small intestinal permeability.

Abnormal gastric accommodation (GA) and gastric emptying contribute to pathophysiology in functional dyspepsia (FD). Secretin is a key regulator of GA in animal studies. Our aim was to study the effects of secretin on gastric motility, satiation, postprandial symptoms, and key hormones. We performed two double-blind, randomized, saline-controlled crossover trials in 10 healthy volunteers and 10 patients with FD by Rome IV criteria. We used measured GA (by validated SPECT method) after a 111In radiolabeled Ensure 300-mL meal and quantified gastric emptying for 30 min by scintigraphy. Satiation was measured by volume to fullness (VTF) and maximum tolerated volume (MTV) on an Ensure nutrient drink test and postprandial symptoms 30 min post-MTV. Fasting and postprandial GLP-1, GIP, and HPP were measured. The ages and sex distribution of healthy controls and patients with FD were similar. Compared with placebo, secretin delayed gastric emptying at 30 min in both health [−11% (−16, −4), P = 0.004]; and FD [−8% (−9, 0), P = 0.03]. Satiation (VTF and MTV), GA, and plasma levels of GLP-1, GIP, and HPP did not differ between treatment arms in health or FD. On ANCOVA analysis (adjusting for age and sex), secretin did not consistently increase postprandial symptoms in health or FD. Secretin delayed gastric emptying in both health and FD without significantly altering GA, VTF, or MTV or selected hormones. Thus, secretin receptor activation may provide a novel therapeutic mechanism for patients with FD and rapid gastric emptying. NEW & NOTEWORTHY The naturally occurring hormone secretin retards gastric emptying of solids without deleteriously affecting gastric accommodation, satiation, other upper gastrointestinal hormones, or postprandial symptoms. Given these findings, a subset of patients with rapid gastric emptying (e.g., the estimated 20% of patients with functional dyspepsia) could be candidates for treatments that stimulate a secretin receptor such as sacubitril, which inhibits neprilysin, an enzyme that degrades secretin.

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