Migrating motor complex

Migrating motor complexes (or migrating myoelectric complex or migratory motor complex or migratory myoelectric complex or MMC) are waves of electrical activity that sweep through the intestines in a regular cycle during fasting. These motor complexes trigger peristaltic waves, which facilitate transportation of indigestible substances such as bone, fiber, and foreign bodies from the stomach, through the small intestine, past the ileocecal sphincter, and into the colon. MMC activity varies widely across individuals and within an individual when measured on different days. The MMC occurs every 90-230 minutes during the interdigestive phase (i.e., between meals) and is responsible for the rumbling experienced when hungry.[1][2] It also serves to transport bacteria from the small intestine to the large intestine and to inhibit the migration of colonic bacteria into the terminal ileum and an impairment to the MMC typically results in small intestinal bacterial overgrowth.[3]

PhasesEdit

The MMC originates mostly in the stomach—although ~25% will arise from the duodenum or proximal jejunum—and can travel to the distal end of the ileum.[4] They consist of four distinct phases:

  • Phase I – A prolonged period of quiescence (40-60% of total time);
  • Phase II – Increased frequency of action potentials and smooth muscle contractility (20-30% of total time);
  • Phase III – A few minutes of peak electrical and mechanical activity (5-10 minutes);
  • Phase IV – Declining activity which merges with the next Phase I.[4]

RegulationEdit

Movements of the small bowel are believed to be controlled by the central and enteric nervous systems, intestinal muscles, and numerous peptides and hormones. For example, the MMC is thought to be partially regulated by motilin, which is initiated in the stomach as a response to vagal stimulation, and does not directly depend on extrinsic nerves.[5] Additionally, gastrin, insulin, cholecystokinin, glucagon, and secretin have been reported to disrupt the MMC.

Eating interrupts the MMC. For example, one study found that a continental breakfast of 450 Kcal causes the MMC to disappear for 213 ± 48 minutes.[6] The number of calories and nature of food determine the length of the disruption with fats causing a longer disruption than carbohydrates which in turn cause a longer disruption than protein.[7]

ImpairmentEdit

Autoimmunity following infection by a pathogen producing CdtB, such as C. jejuni, may be the leading cause of MMC impairment.[8] Narcotics are also known to impair the MMC.[9] Stress has been shown to reduce MMC activity as well.[10]

Patients with SIBO and IBS have on average a third as many MMC phase III events with those events being roughly 30% shorter on average.[11]

Therapeutic StimuliEdit

Drugs used to enhance gastrointestinal motility are generally referred to as prokinetics. Serotonin induces phase III of the MMC and so serotonin receptor agonists are commonly administered as prokinetics.[12] Motilin administration causes phase III contractions and so motilin agonists are another common prokinetic.[13]

Eradication of bacterial overgrowth has been shown to partially restore MMC activity.[11]

An elemental diet has been hypothesized to partially restore MCC function.[14]

ReferencesEdit

  1. ^ Dooley CP, Di Lorenzo C, Valenzuela JE (May 1992). "Variability of migrating motor complex in humans". Digestive Diseases and Sciences. 37 (5): 723–8. doi:10.1007/BF01296429. PMID 1563314.
  2. ^ Takahashi T (July 2012). "Mechanism of interdigestive migrating motor complex". Journal of Neurogastroenterology and Motility. 18 (3): 246–57. doi:10.5056/jnm.2012.18.3.246. PMC 3400812. PMID 22837872.
  3. ^ Hasler W (2006). Physiology of the Gastrointestinal Tract (Fourth ed.).
  4. ^ a b Boron WF, Boulpaep EL (2012). Medical physiology : a cellular and molecular approach (Updated second ed.). Philadelphia, Pa.: Saunders. ISBN 978-1-4377-1753-2.
  5. ^ Poitras P, Peeters TL (February 2008). "Motilin". Current Opinion in Endocrinology, Diabetes and Obesity. 15 (1): 54–7. doi:10.1097/MED.0b013e3282f370af. PMID 18185063.
  6. ^ Vantrappen G, Janssens J, Hellemans J, Ghoos Y (June 1977). "The interdigestive motor complex of normal subjects and patients with bacterial overgrowth of the small intestine". The Journal of Clinical Investigation. 59 (6): 1158–66. doi:10.1172/JCI108740. PMC 372329. PMID 864008.
  7. ^ Vantrappen G, Janssens J, Peeters TL (November 1981). "The migrating motor complex". The Medical Clinics of North America. 65 (6): 1311–29. doi:10.1016/S0025-7125(16)31474-2. PMID 7035768.
  8. ^ Pimentel M, Morales W, Pokkunuri V, Brikos C, Kim SM, Kim SE, et al. (May 2015). "Autoimmunity Links Vinculin to the Pathophysiology of Chronic Functional Bowel Changes Following Campylobacter jejuni Infection in a Rat Model". Digestive Diseases and Sciences. 60 (5): 1195–205. doi:10.1007/s10620-014-3435-5. PMID 25424202.
  9. ^ Kueppers PM, Miller TA, Chen CY, Smith GS, Rodriguez LF, Moody FG (March 1993). "Effect of total parenteral nutrition plus morphine on bacterial translocation in rats". Annals of Surgery. 217 (3): 286–92. doi:10.1097/00000658-199303000-00011. PMC 1242782. PMID 8452407.
  10. ^ Kumar D, Wingate DL (November 1985). "The irritable bowel syndrome: a paroxysmal motor disorder". Lancet. 2 (8462): 973–7. doi:10.1016/S0140-6736(85)90525-2. PMID 2865504.
  11. ^ a b Pimentel M, Soffer EE, Chow EJ, Kong Y, Lin HC (December 2002). "Lower frequency of MMC is found in IBS subjects with abnormal lactulose breath test, suggesting bacterial overgrowth". Digestive Diseases and Sciences. 47 (12): 2639–43. doi:10.1023/A:1021039032413. PMID 12498278.
  12. ^ Lördal M, Hellström PM (1998-04-15). "Serotonin induces phase III of the MMC, VIA 5-HT3-receptors dependent on cholinergic mechanisms in the small instestine". Gastroenterology. 114: A795. doi:10.1016/S0016-5085(98)83246-0.
  13. ^ Janssens J, Vantrappen G, Peeters TL (August 1983). "The activity front of the migrating motor complex of the human stomach but not of the small intestine is motilin-dependent". Regulatory Peptides. 6 (4): 363–9. doi:10.1016/0167-0115(83)90265-3. PMID 6635258.
  14. ^ Pimentel M, Constantino T, Kong Y, Bajwa M, Rezaei A, Park S (January 2004). "A 14-day elemental diet is highly effective in normalizing the lactulose breath test". Digestive Diseases and Sciences. 49 (1): 73–7. doi:10.1023/B:DDAS.0000011605.43979.e1. PMID 14992438.

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