Migrating motor complex, also known asmigrating myoelectric complex,migratory motor complex,migratory myoelectric complex andMMC, is a cyclic, recurring motility pattern that occurs in the stomach and small bowel duringfasting; it is interrupted byfeeding.[1] A pattern of electrical activity is also observed in thegastrointestinal tract in a regular cycle during this interdigestive period.
MMC was discovered and characterized in fasting dogs in 1969 by Joseph H. Szurszewski at theMayo Clinic.[2] He also showed that this activity stops upon eating a meal, and suggested that it induces a motor activity that acts as an "interdigestive housekeeper" in the small intestine.[2] These motor complexes triggerperistaltic waves, which facilitate transportation of indigestible substances such asbone,fiber, andforeign bodies from thestomach, through thesmall intestine, past theileocecal sphincter, and into thecolon. 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 therumbling experienced when hungry.[3][4] It also serves to transportbacteria from the small intestine to the large intestine and to inhibit the migration of colonic bacteria into theterminal ileum; an impairment to the MMC typically results insmall intestinal bacterial overgrowth.[5]
The MMC originates mostly in the stomach—although ~25% will arise from theduodenum or proximaljejunum—and can travel to the distal end of theileum.[6] 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.[6]
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 initiated bymotilin, and it does not directly depend on extrinsic nerves.[7] 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.[8] 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.[9]
Most of the cleaning waves in the MMC happen at night while we are asleep. For many people this will be sufficient to help maintain a healthy, balanced environment in the digestive tract. For others, it may be beneficial to space out food intake to allow for a couple of cleaning waves to occur between meals throughout the day as well.[10]
Autoimmunity following infection by a pathogen producingCdtB, such asC. jejuni, may be the leading cause of MMC impairment.[11]Narcotics are also known to impair the MMC.[12] Stress has been shown to reduce MMC activity as well.[13]
Patients withSIBO andIBS have on average a third as many MMC phase III events with those events being roughly 30% shorter on average.[14]
Drugs used to enhance gastrointestinal motility are generally referred to asprokinetics. Serotonin induces phase III of the MMC, and so serotonin receptor agonists are commonly administered as prokinetics.[15] Motilin administration causes phase III contractions, and so motilin agonists are another common prokinetic.[16]
Eradication of bacterial overgrowth has been shown to partially restore MMC activity.[14]
Anelemental diet has been hypothesized to partially restore MMC function.[17]
^Deloose E, Janssen P, Depoortere I, Tack J. The migrating motor complex: control mechanisms and its role in health and disease. Nat Rev Gastroenterol Hepatol. 2012;9(5):271-285. Published 2012 Mar 27. doi:10.1038/nrgastro.2012.57
^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.PMID1563314.
^Hasler W (2006).Physiology of the Gastrointestinal Tract (Fourth ed.).
^abBoron WF, Boulpaep EL (2012).Medical physiology : a cellular and molecular approach (Updated second ed.). Philadelphia, Pa.: Saunders.ISBN978-1-4377-1753-2.
^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.PMID7035768.
^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.PMID25424202.
^abPimentel 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.PMID12498278.
^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.PMID6635258.
^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.PMID14992438.
