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Melatonin & irritable bowel syndrome.

Frequent arousals occur in 26%-55% of people with the disorder irritable bowel syndrome (IBS). Sleep problems can result from IBS symptoms such as abdominal or rectal pain but poor sleep itself can intensify IBS symptoms. Recently, scientists have found that the sleep-promoting hormone melatonin can provide relief.

A person with IBS suffers with abdominal pain that usually manifests after eating and is relieved on defecation; the pain may be either episodic or chronic. Other symptoms are bloating; mucus in the feces; and problems with defecation (i.e., constipation and/or diarrhea). Some IBS sufferers have alternating bouts of constipation and diarrhea. Since no physical or biochemical abnormalities can be found as a cause of these symptoms IBS is considered a functional bowel disorder.

Until recent years, scientists described IBS in terms of impaired motility of the GI tract. In support of this, some studies found that the passage of stool is delayed in constipation-predominant IBS sufferers but accelerated in diarrhea-predominant IBS sufferers. A more current view sees IBS as the result of an individual's hypersensitivity to GI sensations.

Yet another recent view sees IBS as a result of a malfunctioning brain-gut axis. The brain-gut axis is a two-way neural pathway which links cortical centers in the brain with intestinal sensation and intestinal motor function. The two-way neural pathway allows for a continual interplay between emotions, thought, and intestinal function. Positron emission tomography studies show that certain areas in the brain that process negative emotions and interpret visceral sensations are more activated in IBS sufferers than in people without the disorder.

Two cells of interest in the brain-gut axis are pinealocytes and enterochromaffin cells. Both types of cells produce melatonin. Pinealocytes, the major cell of the pineal gland, produce melatonin in the brain and enterochromaffin cells, which are scattered throughout the surface of the GI tract, produce melatonin in the gut.

Pineal melatonin synthesis is affected by the intensity of light. Strong light intensity suppresses its production and darkness sets pineal melatonin production into motion. Scientists believe that light impacts pineal melatonin production because the pineal gland has connections to vision.

Pinealocytes secrete melatonin into nearby blood vessels in the brain. In this way, the hormone enters the bloodstream and some pineal melatonin travels to the gut. However, the amount of melatonin produced in the GI tract by enterochromaffin cells is 400 times greater than that produced by the pineal gland. Unlike pineal gland melatonin, GI melatonin is not influence by light intensity but instead by food intake. In particular, foods containing a high tryptophan level stimulate the enterochromaffin cells to synthesize of GI melatonin.

Enterochromaffin cells release melatonin into nearby blood vessels of the mucous membrane of the inner lining of the stomach and intestines. It is through these vessels that melatonin is transported into the blood stream from the gut. Some of the melatonin, however, remains in the GI tract to exert a protective action on the GI tissues. Protective actions of melatonin are: it reduces hydrochloric acid production, it stimulates the immune system, it plays a role in the regeneration of epithelial cells in the GI tract, it acts as an anti-oxidant, and it has anti-excitatory properties These characteristics may play a role in the relief from IBS symptoms.

Because of melatonin's role in sleep, various studies investigated the impact of melatonin on the sleep of IBS sufferers. University of Singapore researchers gave melatonin to 20 IBS sufferers who had sleep problems and a placebo to 20 other IBS sufferers who also had sleep problems.

Before and after treatment, subjects completed questionnaires, underwent rectal manometry, and had overnight polysomnography. The two groups underwent the drug regimen (melatonin or placebo) for two weeks. Afterwards, the researchers discovered that the melatonin group had significantly reduced abdominal pain and increased tolerance to rectal pain. However, bloating, stool type (i.e., constipation or diarrhea), stool frequency, and anxiety and depression scores remained the same before and after treatment in both groups. Sleep parameters--total sleep time, sleep latency, sleep efficiency, sleep onset latency, arousals, duration of stages 1-4 and rapid eye movement (REM) sleep, and REM onset latency--remained the same as before treatment. Song et al. concluded that melatonin could be beneficial for relieving abdominal pain in people with IBS although it does not improve sleep quality in people with IBS.

Another University of Singapore study compared the efficacy of placebo vs. melatonin treatment on sleep in healthy subjects and IBS sufferers. They had similar results and concluded that melatonin was effective in reducing IBS symptoms but not in improving sleep.

Both Song and Lu concede that their studies may have shown no improvement in sleep quality since they were done for a short period of time (a few weeks) and with a small sample size. They nevertheless are optimistic that melatonin could be a treatment for IBS.

Problems with going to sleep, awakening at night, and early morning awakening in IBS sufferers can result from abdominal pain, the need to defecate frequently, diarrhea, or discomfort from constipation. Conversely, a poor night's sleep can intensify IBS symptoms. Melatonin treatment may be a key in breaking this cycle. More studies that investigate the melatoninergic aspects of IBS may reveal to what extent sleep problems and IBS share a common etiology, how melatonin can be used to improve the sleep of IBS sufferers and which sufferers would most benefit from melatonin treatment.

by Regina Patrick RPSGT
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Title Annotation:SLEEP MEDICINE
Author:Patrick, Regina
Publication:FOCUS: Journal for Respiratory Care & Sleep Medicine
Date:Mar 22, 2015
Words:902
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