Why is motilin active in some studies with mice, rats, and guinea pigs, but not in others? Implications for functional variability among rodents

The influence of herbal medicine on serum motilin and its effect on human and animal model: a systematic review

Introduction: Motilin (MLN) is a gastrointestinal (GI) hormone produced in the upper small intestine. Its most well understood function is to participate in Phase III of the migrating myoelectric complex component of GI motility. Changes in MLN availability are associated with GI diseases such as gastroesophageal reflux disease and functional dyspepsia. Furthermore, herbal medicines have been used for several years to treat various GI disorders. We systematically reviewed clinical and animal studies on how herbal medicine affects the modulation of MLN and subsequently brings the therapeutic effects mainly focused on GI function. Methods: We searched the PubMed, Embase, Cochrane, and Web of Science databases to collect all articles published until 30 July 2023, that reported the measurement of plasma MLN levels in human randomized controlled trials and in vivo herbal medicine studies. The collected characteristics of the articles included the name and ingredients of the herbal medicine, physiological and symptomatic changes after administering the herbal medicine, changes in plasma MLN levels, key findings, and mechanisms of action. The frequency patterns (FPs) of botanical drug use and their correlations were investigated using an FP growth algorithm. Results: Nine clinical studies with 1,308 participants and 20 animal studies were included in the final analyses. Herbal medicines in clinical studies have shown therapeutic effects in association with increased levels of MLN, including GI motility regulation and symptom improvement. Herbal medicines have also shown anti-stress, anti-tumor, and anti-inflammatory effects in vivo. Various biochemical markers may correlate with MLN levels. Markers may have a positive correlation with plasma MLN levels included ghrelin, acetylcholine, and secretin, whereas a negative correlation included triglycerides and prostaglandin E2. Markers, such as gastrin and somatostatin, did not show any correlation with plasma MLN levels. Based on the FP growth algorithm, Glycyrrhiza uralensis and Paeonia japonica were the most frequently used species. Conclusion: Herbal medicine may have therapeutic effects mainly on GI symptoms with involvement of MLN regulation and may be considered as an alternative option for the treatment of GI diseases. Further studies with more solid evidence are needed to confirm the efficacy and mechanisms of action of herbal medicines. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=443244, identifier CRD42023443244.

Phlorizin attenuates postoperative gastric ileus in rats

BACKGROUND

Postoperative ileus (POI) is a major complication of abdominal surgery (AS). Impaired gut barrier mediated via Toll-like receptor 4 (TLR4) and interleukin-1 (IL-1) receptor is involved in the development of POI. Phlorizin is a nonselective inhibitor of sodium-linked glucose transporters (SGLTs) and is known to improve lipopolysaccharide (LPS)-induced impaired gut barrier. This study aimed to clarify our hypothesis that AS-induced gastric ileus is mediated via TLR4 and IL-1 signaling, and phlorizin improves the ileus.

METHODS

AS consisted of a celiotomy and manipulation of the cecum for 1 min. Gastric emptying (GE) in 20 min with liquid meal was determined 3 h after the surgery in rats. The effect of subcutaneous (s.c.) injection of LPS (1 mg kg-1 ) was also determined 3 h postinjection.

KEY RESULTS

AS delayed GE, which was blocked by TAK-242, an inhibitor of TLR4 signaling and anakinra, an IL-1 receptor antagonist. LPS delayed GE, which was also mediated via TLR4 and IL-1 receptor. Phlorizin (80 mg kg-1 , s.c.) significantly improved delayed GE induced by both AS and LPS. However, intragastrical (i.g.) administration of phlorizin did not alter it. As gut mainly expresses SGLT1, SGLT2 may not be inhibited by i.g. phlorizin. The effect of phlorizin was blocked by ghrelin receptor antagonist in the LPS model.

CONCLUSIONS & INFERENCES

AS-induced gastric ileus is mediated via TLR4 and IL-1 signaling, which is simulated by LPS. Phlorizin improves the gastric ileus via activation of ghrelin signaling, possibly by inhibition of SGLT2. Phlorizin may be useful for the treatment of POI.

The Acute Effect of Hydroxychloroquine Sulfate on Hunger, the Plasma Concentration of Orexigenic Peptides and Hedonic Food Intake: A Pilot Study

The direct infusion of bitter solutions in the gastrointestinal tract can reduce the secretion of orexigenic hormones and influence appetite and food intake. We aimed to explore whether oral ingestion of the bitter tastant hydroxychloroquine sulfate can exert similar effects. Ten lean adult women were included in this double-blind, randomized, two-visit, crossover study. After an overnight fast, each volunteer received film-coated tablets containing 400 mg of hydroxychloroquine sulfate (Plaquenil®) or placebo. Plasma-ghrelin, -motilin, -insulin and blood-glucose concentrations were determined every 10 min before and 30 min after feeding; appetite was scored every 10 min. Hunger scores were investigated with a special interest 50-60 min after the ingestion of hydroxychloroquine sulfate, right before a rewarding chocolate milkshake was offered to drink ad libitum. Compared with the placebo, hydroxychloroquine sulfate tended to reduce hunger at the time of interest (p = 0.10). No effect was found upon subsequent milkshake intake. Motilin plasma concentrations were unaltered, but acyl-ghrelin plasma concentrations decreased after the ingestion of hydroxychloroquine sulfate (t = 40-50; p < 0.05). These data suggest that the oral intake of hydroxychloroquine sulfate tablets reduces subjective hunger via a ghrelin-dependent mechanism but does not affect motilin release, hedonic food intake or insulin levels in healthy women.

Structural basis for motilin and erythromycin recognition by motilin receptor

Motilin is an endogenous peptide hormone almost exclusively expressed in the human gastrointestinal (GI) tract. It activates the motilin receptor (MTLR), a class A G protein-coupled receptor (GPCR), and stimulates GI motility. To our knowledge, MTLR is the first GPCR reported to be activated by macrolide antibiotics, such as erythromycin. It has attracted extensive attention as a potential drug target for GI disorders. We report two structures of G_q-coupled human MTLR bound to motilin and erythromycin. Our structures reveal the recognition mechanism of both ligands and explain the specificity of motilin and ghrelin, a related gut peptide hormone, for their respective receptors. These structures also provide the basis for understanding the different recognition modes of erythromycin by MTLR and ribosome. These findings provide a framework for understanding the physiological regulation of MTLR and guiding drug design targeting MTLR for the treatment of GI motility disorders.