Published online Sep 7, 2021. doi: 10.3748/wjg.v27.i33.5566
Peer-review started: March 9, 2021
First decision: May 1, 2021
Revised: May 12, 2021
Accepted: August 12, 2021
Article in press: August 12, 2021
Published online: September 7, 2021
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.
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.
In freshly dispersed smooth muscle cells (SMC), we measured the adiponectin effect on the carbachol-induced length changes.
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.
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.
Core Tip: Gastric accommodation regulates the stomach content volume. Lactating rats continuously breastfeed to keep a full gastric milk volume and their gastric emptying time is directly related to the gastric content volume. Little is known about the gastric fundic accommodation regulatory factors early in life. In this study, breastmilk-derived adiponectin is shown to promote gastric fundic relaxation, thus playing an important regulatory role during the lactating period.