The newborn rat gastric emptying rate is volume and not developmentally dependent

Adiponectin and the regulation of gastric content volume in the newborn rat

BACKGROUND

Oral intake is dependent on the gastric ability to accommodate the food bolus. Comparatively, neonates have a smaller gastric capacity than adults and this may limit the volume of their milk intake. Yet, we previously reported that the newborn rat gastric milk volume is greatest after birth and, when normalized to body weight, decreases with postnatal age. Such age-dependent changes are not the result of intake differences, but greater gastric accommodation and reduced emptying rate.

AIM

Hypothesizing that breastmilk-derived adiponectin is the factor regulating gastric accommodation in neonates, we comparatively evaluated its effects on the rat fundic muscle tone at different postnatal ages.

METHODS

In freshly dispersed smooth muscle cells (SMC), we measured the adiponectin effect on the carbachol-induced length changes.

RESULTS

Adiponectin significantly reduced the carbachol-stimulated SMC shortening independently of age. In the presence of the inhibitor iberiotoxin, the adiponectin effect on SMC shortening was suppressed, suggesting that it is mediated via large-conductance Ca²⁺ sensitive K⁺ channel activation. Lastly, we comparatively measured the newborn rat gastric milk curd adiponectin content in one- and two-week-old rats and found a 50% lower value in the latter.

CONCLUSION

Adiponectin, a major component of breastmilk, downregulates fundic smooth muscle contraction potential, thus facilitating gastric volume accommodation. This rodent’s adaptive response maximizes breastmilk intake volume after birth.

Smart Responsive Quercetin-Conjugated Glycol Chitosan Prodrug Micelles for Treatment of Inflammatory Bowel Diseases

The incidence and progression of inflammatory bowel disease are closely related to oxidative stress caused by excessive production of reactive oxygen species (ROS). To develop an efficacious and safe nanotherapy against inflammatory bowel diseases (IBD), we designed a novel pH/ROS dual-responsive prodrug micelle GC-B-Que as an inflammatory-targeted drug, which was comprised by active quercetin (Que) covalently linked to biocompatible glycol chitosan (GC) by aryl boronic ester as a responsive linker. The optimized micelles exhibited well-controlled physiochemical properties and stability in a physiological environment. Time-dependent NMR spectra traced the changes in the polymer structure in the presence of H₂O₂, confirming the release of the drug. The in vitro drug release studies indicated a low release rate (<20 wt %) in physiological conditions, but nearly complete release (>95 wt % after 72 h incubation) in a pH 5.8 medium containing 10 μM H₂O₂, exhibiting a pH/ROS dual-responsive property and sustained release behavior. Importantly, the negligible drug release in a simulated gastric environment in 1 h allowed us to perform intragastric administration, which has potential to achieve the oral delivery by mature enteric-coating modification in future. Further in vivo activities and biodistribution experiments found that the GC-B-Que micelles tended to accumulate in intestinal inflammation sites and showed better therapeutic efficacy than the free drugs (quercetin and mesalazine) in a colitis mice model. Typical inflammatory cytokines including TNF-α, IL-6, and iNOS were significantly suppressed by GC-B-Que micelle treatment. Our work promoted inflammatory-targeted delivery and intestinal drug accumulation for active single drug quercetin and improved the therapeutic effect of IBD. The current study also provided an alternative strategy for designing a smart responsive nanocarrier for a catechol-based drug to better achieve the target drug delivery.

Caffeine and Gastric Emptying Time in Very Preterm Neonates

Background: Caffeine has been commonly used for prevention and treatment of apnea-related symptoms in premature infants. However, its side effects have not been thoroughly studied. We investigated whether caffeine affects gastric motility in very-preterm (VP) neonates. Methods: The study is a randomized crossover clinical trial. Twenty-two neonates with mean birth weight (BW) (standard deviation—SD) 1077 (229) g and mean gestational age (GA) (SD) 28.6 (2.1) weeks were recruited. Each neonate had its gastric emptying time checked twice with ultrasound assessment of changes in antral cross sectional area (ACSA). All neonates were sequentially allocated to the caffeine group (A) and the control group (B). Complications from the gastrointestinal tract were documented throughout the study. Results: Statistically significant difference was found with regards to the gastric emptying time [median, (range)] between caffeine and control group (p = 0.040). Additionally, in the neonates with BW 1000–1500 g and GA ≥ 28 weeks, the gastric emptying time (minutes) was significantly longer during caffeine treatment [44.5 (36–68.2)] and [40 (34.5–66.5)] respectively, as compared to the gastric emptying time during no caffeine treatment [27 (24.2–30)] (p = 0.002) and [27 (24.5–30)] (p = 0.001). The incidence of gastrointestinal (GI) complications was significantly greater in neonates receiving caffeine [6 (27.%)] as compared with those without caffeine treatment [1 (4.6%)] (p = 0.039). Conclusions: During caffeine treatment, a significantly delayed gastric emptying time was noted in all study neonates, especially in these with BW 1000–1500 g and those with GA ≥ 28 weeks. Further larger studies are necessary in order to confirm this interesting finding.