Invited review: Mineral absorption mechanisms, mineral interactions that affect acid–base and antioxidant status, and diet considerations to improve mineral status

The physiology and pathophysiology of small bowel motility are reviewed with particular focus on the motility patterns and periods that are detected by intraluminal manometry. Motility patterns are groups of phasic pressure waves resulting from contractions of the circular muscle layer of the small bowel that are organized by the enteric nervous system. Phase III of the migrating motor complex, the hallmark of the fasting motility period, thus reflects enteric neuromuscular function. Response to meal challenge also involves the CNS, reflexes beyond the gut and endocrine responses. Although specific disease diagnosis cannot be made by motility studies of the small bowel, the functional integrity is revealed. The normal occurrence of the essential patterns and periods of motility and the absence of distinctly abnormal patterns evidence preserved function, whereas the opposite indicates clinically significant dysmotility. Certain motility patterns are occasionally seen both in health and disease, and increased prevalence indicates a moderate dysfunction of yet unclear significance. Bacterial overgrowth with Gram-negative bacilli is the consequence of severe small bowel dysmotility, and a diagnosis that can be predicted by a motility study. Testing can be useful in the clinical management of paediatric and adult patients also by predicting the prognosis and response to enteral nutrition and medical therapy. Further studies are, however, needed to take full advantage of motility testing in clinical practise.

The patterns of small bowel motility: physiology and implications in organic disease and functional disorders.

To elucidate the specific function of the three phases (I-III) of the migrating motor complex (MMC) by manometry, detailed analysis of individual pressure waves in the proximal duodenum was performed. Twenty healthy subjects (10 men and 10 women of whom 11 were tube-naive) underwent computerized manometry for 5 h during fasting followed by 45 min after a meal using an 8-channel water perfused catheter. Three recording points were in the antrum, three in the proximal duodenum (2 cm apart), one in the distal duodenum and one in the proximal jejunum. In all subjects at least one phase III (median 2) was observed during the 5-h fasting recording. In the proximal duodenum the mean proportion of retrograde pressure waves, out of all propagating waves, was significantly increased in the last part of phase III (85 +/- 9%, mean, SE), compared with early phase III (6 +/- 5%), late phase II (5 +/- 4%) and the feeding phase (10 +/- 5%), irrespective of gender or previous tube-experience. The median length of the MMCs was 108.5 min. There was no statistically significant difference between men and women or between tube-naive and tube-experienced subjects for the duodeno-jejunal motility indices of phase II and phase III, nor for duration or migration of phase III. The postprandial motility index of the small intestine was increased compared with the interdigestive late phase II, particularly in the jejunum (P < 0.02). The last part of the duodenal interdigestive phase III in healthy subjects shows the feature of a retrosperistaltic pump. This cyclic sequence of retropropagation coincides with the reported rapid alkalinization of the duodenal bulb and the gastric antrum occurring in early antral phase I.

Interdigestive gastroduodenal manometry in humans. Indication of duodenal phase III as a retroperistaltic pump.

Transport of water and salt across the intestinal mucosa is a major function of the gastrointestinal tract and is regulated by the enteric nervous system. The details of this regulation vary between intestinal regions and between species. However, there are many common elements including that the major output neurons of the secretomotor pathways contain vasoactive intestinal peptide and are located in the submucosal plexus and that there are secretomotor circuits in both the myenteric and submucosal plexuses. These circuits are not simple feed-forward pathways, but include recurrent excitatory networks of intrinsic sensory neurons in both myenteric and submucosal plexuses. These neurons are excited by many sensory stimuli including major nutrients acting via mucosal enteroendocrine cells, and their excitability is enhanced in various diarrheal diseases, which often show disturbed coupling between secretion and motility, suggesting a central role for these circuits.

Enteric Neural Regulation of Mucosal Secretion

Upper gastrointestinal motor function and incretin hormone secretion are major determinants of postprandial glycemia and insulinemia. However, the impact of small intestinal flow events on glucose ...

https://www.physiology.org/doi/pdf/10.1152/ajpgi.00519.2006

Concurrent duodenal manometric and impedance recording to evaluate the effects of hyoscine on motility and flow events, glucose absorption, and incretin release.

In 22 healthy volunteers distal duodenal fluid absorption was related to the interdigestive motility cycle. Fluid absorption was measured with a triple-lumen perfusion technique, and motility was registered with a low-compliance pneumohydraulic system. Pancreatic and biliary secretions were estimated by measurement of bilirubin and amylase release into the duodenal segment. Duodenal fluid absorption rate changed during the interdigestive motility cycle; the highest absorption rate was registered during phase I (low-motor activity) and absorption rate then decreased in parallel with increasing motor activity during phase II (r = -0.69, P less than 0.001). In late phase II a net fluid secretion was frequently registered, together with an increased release of bilirubin into the duodenal lumen. This pattern was seen during perfusion with both glucose-containing (30 mM) and glucose-free solutions. The results show that duodenal fluid absorption rate changes markedly during the interdigestive motility cycle. This effect may be a hydrodnamic phenomenon or may be due to activation of a neural secretory mechanism during phase II.

Relationship between interdigestive duodenal motility and fluid transport in humans

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Relationship between interdigestive duodenal motility and fluid transport in humans