Finding the Narcolepsy Target

A new study provides evidence to support the idea that narcolepsy is an autoimmune disorder.

A decade ago it was discovered that people with narcolepsy lack brain cells that make “hypocretin.” This is a hormone that helps promote wakefulness. The finding helped explain why people with narcolepsy have episodes of uncontrollable sleepiness.

But why do these brain cells die in people with narcolepsy? Last year the Sleep Education Blog reported on a new study. It suggested that the immune system attacks and destroys the brain cells by mistake. In August another study reported that this attack may be triggered by an infection.

Now Swiss and French researchers report that they may have identified a specific target of the autoimmune attack that causes narcolepsy. It is a protein called Tribbles homolog 2 – or “Trib2.”

They believe that Trib2 is an “autoantigen” in narcolepsy. An autoantigen is the target of an attack by autoantibodies. These antibodies attack a natural protein in the body rather than a protein from an infectious agent.

First they found that Trib2 was enriched in hypocretin-producing neurons in mice. Then they compared people who have narcolepsy with healthy controls. They also compared narcoleptics with people who have other disorders such as idiopathic hypersomnia and multiple sclerosis.

They found that the levels of Trib2-specific antibodies were much higher in people with narcolepsy. These levels of circulating autoantibodies against Trib2 were highest soon after narcolepsy symptoms appeared. They sharply decreased within two to three years.

Then the levels of Trib2-specific antibodies stabilized for up to 30 years. But these levels remained much higher than those of controls.

“These results indicate for the first time to our knowledge that Trib2 is an autoantigen in human narcolepsy,” the authors wrote. “Trib2-specific antibodies specifically target hypocretin neurons, ultimately leading to their disappearance and hypocretin deficiency.”

They cautioned that Trib2 may not be the only autoantigen in narcolepsy. Several autoantibodies may be involved.

But they are optimistic about treating narcolepsy with intravenous immunoglobulins soon after symptoms appear. In 2003 and 2004 they reported success at using IVIg treatment for people with narcolepsy. Last year they reported that hypocretin levels normalized in a narcolepsy patient after immunotherapy.

Read more about narcolepsy.

Image by Op.dan

Infections May Trigger Narcolepsy

In May the Sleep Education Blog reported that narcolepsy may be an autoimmune disorder. Research suggests that narcolepsy may develop when the immune system attacks and destroys hypocretin-producing brain cells by mistake. Hypocretin is a hormone that helps promote wakefulness.

But what causes this immune system response? A study in the Aug. 1 issue of the journal Sleep shows that bacterial infection may be one trigger.

The study involved 200 people with narcolepsy and 200 healthy controls. They were recruited from the U.S., the Czech Republic, Italy and South Korea. Their blood was tested for antibodies that are markers of bacterial infection.

Results show that the levels of antibodies related to “streptococcus” were much higher in people with narcolepsy. These levels were highest when blood was drawn soon after narcolepsy symptoms began.

Streptococcus is the name of a group of bacteria. Some types of the bacteria can cause disease in humans; examples include scarlet fever, strep throat and tonsillitis.

The authors note that the levels of anti-streptococcal antibodies vary widely across people groups. About 90 percent of the people with narcolepsy in this study were Caucasian; so the study needs to be replicated among other ethnic groups.

But the results show that streptococcal infections are probably an important trigger for narcolepsy.

New Study Suggests that Narcolepsy is an Autoimmune Disorder

Scientists have made another major breakthrough in understanding the sleep disorder narcolepsy. A new study suggests that it is an autoimmune disorder.

Results show that people with narcolepsy are more likely to have a unique variant of a specific gene belonging to T cells. These cells play an important role in the response of the immune system.

“Our discovery clearly shows narcolepsy is an autoimmune disease,” study author Dr. Emmanuel Mignot said in a Stanford statement. “We’re now getting the main pieces of what’s happening in narcolepsy.”

The NIH reports that one of those pieces involves a human leukocyte antigen (HLA) gene. People with narcolepsy are likely to have a variant of an HLA gene. Along with T cells, HLA proteins help the immune system identify invaders such as bacteria and viruses.

Another piece of the puzzle was the discovery that people with narcolepsy lack brain cells that make hypocretin. This is a hormone that helps promote wakefulness. The finding helped explain why people with narcolepsy have episodes of uncontrollable sleepiness.

But the loss of hypocretin-producing brain cells occurs over time; narcolepsy typically appears after 15 years of age.

Why do these brain cells die in people with narcolepsy? The new study suggests that the immune system attacks and destroys the brain cells by mistake.

So is the case closed? Not yet. The HLA and T-cell variants fail to fully explain narcolepsy. Some people with these genetic variations never develop the disorder.

Why? That is still unclear. But Dr. Mignot believes that a chain reaction is involved.

"Narcolepsy is probably the result of a series of unfortunate events,” he told BBC News.

Mignot said that the genetic variations “predispose” you to have narcolepsy; they put you at risk. But it may take some kind of “trigger” - such as in infection - to set the disorder in motion. This trigger may activate the immune system response that kills hypocretin cells.

There is still more to learn about narcolepsy. But this new discovery may help doctors learn how to stop the disorder from developing.

Sleep & the H1N1 “Swine Flu” Virus

The H1N1 flu virus, or “swine flu,” has infected people in 20 countries. This includes people in the U.S., Canada and Mexico.

How can you protect yourself from this new virus?

The CDC advises you to get plenty of sleep. This will help your body to maintain a strong immune system.

In January the Sleep Education Blog reported on a study linking sleep and the immune system. Participants were exposed to a “rhinovirus” – the common cold.

People who reported sleeping less than seven hours per night were three times more likely to develop a cold. The AASM recommends that adults get seven to eight hours of sleep each night.

To keep from getting the flu, the CDC also recommends that you wash your hands often. Keep active, eat a healthy diet and drink plenty of fluids. Avoid close contact with people who are sick.

The CDC advises you to stay home from work or school if you develop symptoms of the flu. These include a fever, sore throat, body aches, chills and fatigue. Stay home for seven days after your symptoms begin or until you have been symptom-free for 24 hours.

If you feel sick you may want to contact your doctor. He or she will determine if flu testing or treatment is needed.

Your doctor may prescribe an antiviral drug for you. This type of medicine can make your illness milder and help you feel better faster.

The two antiviral drugs approved by the FDA for treating the H1N1 flu virus are Tamiflu and Relenza. Currently there are no licensed vaccines for the H1N1 flu virus.

The FDA, FTC and Health Canada all report that some Internet sites may sell products with the false claim that they will prevent or cure the H1N1 virus. You should contact your doctor before buying any of these products online.

Image by Robert Terrell

Sleep to Keep from Catching a Cold

It turns out that your mother was right all along. Getting more sleep can help you avoid catching a cold.

A new study shows that sleeping less than seven hours per night may make you three times more likely to develop a cold. There also was a link to “sleep efficiency.”

This is the percentage of time in bed that you are asleep. A high efficiency means that almost all your time in bed was spent sleeping. A low efficiency means that you were awake for much of your time in bed. Maybe you had trouble falling asleep. Or you woke up in the middle of the night and struggled to return to sleep.

To find your sleep efficiency, divide your total sleep time by your time in bed. For example, maybe you slept for 6.5 hours of the seven hours you spent in bed. This would give you a sleep efficiency of 93%.

The study found that those with an average sleep efficiency of less than 92% were 5.5 times more likely to develop a cold. Results remained significant after controlling for other factors.

The study involved 153 healthy men and women. They were between 21 and 55 years of age. For 14 days they reported their sleep duration and sleep efficiency from the previous night.

Then they were given nasal drops containing a rhinovirus. Their symptoms were monitored for five days while they were kept in isolation.

You can improve your sleep efficiency by following the tips of good sleep hygiene. Seek help at a sleep center if you have an ongoing problem that keeps you from sleeping well.

Now if only someone would do a study to see if Mom was right about chicken soup. Oh wait – it’s already been done.