Health In Focus
  • Mechanism associated with hypertension during sleep apnea identified.
  • Carotid body resection controlled hypertension but lead to side effects.
  • Drugs found to inhibit cystathionine-y-lyase could aid hypertension.

Sleep apnea is a common condition in which the airways are blocked and there is reduced intake of air or pauses in breathing. The period of obstruction or lowered intake of air can last from a few seconds to half an hour.
Drug to Control Hypertension During Sleep Apnea Identified
Drug to Control Hypertension During Sleep Apnea Identified

People at higher risk for sleep apnea are

  • Overweight individuals
  • Men
  • People with nasal blocks or obstruction
  • Small airways
  • Children with tonsils
People with untreated sleep apnea have a nearly three fold increase in the risk of death when compared with people who do not have sleep apnea. Heavy snoring can also disturb a partner and lead to poor sleep and ill health.

Terry Young who is a professor at the University of Wisconsin's Department of Population of Health Sciences says "We have been studying the effects of sleep apnea in the Wisconsin Sleep Cohort for more than a decade and have reported links between sleep apnea and hypertension, stroke and depression."

Hypertension is a serious effect of sleep apnea that dramatically increases the risk of death for individuals. Scientists from The University of Chicago have identified a mechanism with which there is an increase in blood pressure in the body due to sleep apnea.

Mechanism of Hypertension Due to Sleep Apnea

Dr. Nanduri Prabhakar who is the lead author of the study and the director of The University of Chicago's Institute for Integrative Physiology and Center for Systems Biology of Oxygen Sensing reveals "Our results, using a rodent model, establish a mechanism that is the cause of apnea-associated hypertension. They also offer a novel way to block the process, preventing this form of hypertension and restoring normal blood pressures."

The carotid arteries have a small group of cells called the carotid bodies that are present on the left and the right side of the neck. These carotid bodies have chemosensory cells in them that assess the level of oxygen in the blood to regulate breathing.

Drop in Oxygen Levels in the Blood

When there is a drop in oxygen levels in the blood due to sleep apnea, the carotid bodies initiate

  • Generation of reactive oxygen species
  • Reactive oxygen species increase the level of hydrogen sulphide in the body
  • Increase in hydrogen sulphide signals carotid bodies to signal the increase in intake of oxygen.
  • The sympathetic nervous system is stimulated leading to constriction of the blood vessel.
The constricted blood vessels result in hypertension.

Carotid Body Resection

In an earlier study, an association was found between asthma and carotid bodies. Since carotid bodies were found to play a role in increasing blood pressure, they were surgically removed. However, this lead to serious side effects. Due to the absence of the carotid body, the body loses the urge to breathe more and this was highly risky during exercising.

Method to Lower Hypertension

The researchers involved in the study suggest a new method of controlling hypertension during sleep apnea. During sleep apnea, the elevated level of hydrogen sulphide leads to increase in the signaling for intake of oxygen. The scientists suggest that a drug that inhibits the enzyme cystathionine-y-lyase would be effective as the enzyme is involved in the increase of hydrogen sulphide.

Rodent Studies

The research team found that blocking the enzyme aided in controlling levels of hydrogen sulphide in the body. When they tested the effect of cystathionine-y-lyase inhibitor L-propargylglycine (L-PAG) on rodents, they found that it "Restored normal carotid body function, sympathetic nerve activity and blood pressure, and blocked hypertensive responses to simulated apneas".

Sleep apnea is a condition in which there is a pause in breathing while the individual is sleeping. Though it is very difficult to control sleep apnea, controlling the risk of hypertension using a drug, without increasing the risk for any side effects, would give these people a good night's sleep.

Source: Medindia

Most Popular on Medindia