Spotlight On: Preeclampsia

Pregnant woman holding hands over belly on black background

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Lady Sybil Crawley—the feisty youngest sister of a wealthy British family on the PBS television series “Downton Abbey”—made her way into viewers’ hearts. Devotees of the show were shocked when, in a surprise twist, she died soon after giving birth. Lady Sybil died from high blood pressure during pregnancy (preeclampsia) that developed into a more serious condition called eclampsia in which high blood pressure causes potentially fatal seizures.

Unfortunately, this type of tragedy is not a distant memory from the early 1900s when “Downton Abbey” was set. Preeclampsia still causes too many deaths—or near deaths—in the U.S. each year. However, when diagnosed properly, preeclampsia is manageable.

Preeclampsia develops in about 5–8 percent of all pregnancies. Symptoms include headaches, nausea, vomiting, and excessive swelling of the feet, hands and face.

There are also invisible symptoms, such as damage to internal organs like the liver and kidneys. Preeclampsia occurs when a woman’s blood pressure rises too high (140/90 mmHg or above) during mid- to late-pregnancy (more than 20 weeks of gestation). The increased blood pressure limits the amount of blood that the baby receives and can slow down fetal growth. Babies born to women with preeclampsia are frequently smaller and weigh less than those born to women with normal blood pressure. Preeclampsia is often connected with other health conditions such as obesity, diabetes, kidney disease and a history of high blood pressure.

A woman’s age, race and where she lives can also increase the likelihood of developing preeclampsia. Women over age 40, black women and women from the southern U.S. also have an increased risk of developing high blood pressure during pregnancy. The reasons why Southern women have greater risk are not clear, but it may be linked to the prevalence of obesity and diabetes, especially in the Deep South.

It is important for expectant women and their families to know the symptoms of preeclampsia, talk openly with their doctors about their potential risks and speak up when something doesn’t feel right. May is Preeclampsia Awareness Month. Talk to the pregnant women in your life and learn about preeclampsia together.

Jessica Taylor, PhDJessica C. Taylor, PhD, is the Senior Manager of Higher Education Programs at the American Physiological Society. She is a cardiovascular physiologist, the mother of one and hails from Mississippi.

Hypertension: Silent and Unequal

Nurse checking blood pressure for mature African American man

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High blood pressure has been coined the “silent killer” because it has no symptoms, which causes many people to go undiagnosed. A blood pressure reading that stays high for long periods of time is called hypertension. It’s one of the leading risk factors for heart disease.

In addition to being silent, hypertension is also unequal—rates in black people are much higher than in any other racial group in the U.S. An estimated 46 percent of black adults in the U.S. have hypertension. But because guidelines for diagnosis changed recently, this number is likely to be underestimated.

The physiological reasons behind this racial discrepancy are unclear. Some studies suggest differences in the response to stress. One study showed that young black men had greater nervous system responses than white men when faced with a physically stressful situation—in this case, plunging their hand into an ice water bath.

The researchers looked at activity (called sympathetic activity) in a part of the nervous system that regulates heart rate, force of heart contractions and can decrease the size (constriction) of the blood vessels. Constriction of blood vessels during exercise is good, as it redirects blood and oxygen to the muscles. However, too much sympathetic activity can result in unneeded blood vessel constriction and an increase in heart rate that significantly raises blood pressure. The black participants’ surge in sympathetic activity in the ice water test was accompanied by large spikes in blood pressure, which has been linked to future development of hypertension.

A more recent study suggests that the racial disparity may also lie in the blood vessels’ response to nervous system activity during periods of rest. The researchers inserted a tiny probe into a nerve of the leg to measure sympathetic activity in the muscles. They also looked at blood flow in the artery of the leg and blood pressure throughout the resting period. They found that black men had greater vessel constriction and higher blood pressure than white men, even when accounting for other variables that may affect blood pressure such as weight.

Seeing how blood vessels react—or overreact— to nervous system activity helps scientists understand more about the factors that potentially increase the risk of hypertension in black adults. The next step is to find ways to reduce these responses and lower the risks of hypertension and heart disease in this population.

April is National Minority Health Month. Visit the U.S. Department of Health and Human Services’ Office of Minority Health to learn how people from diverse cultures can stay healthy.

Yasina Somani cropYasina Somani, MS, is a PhD student in the Cardiovascular Aging and Exercise Lab at Penn State. She is interested in studying the effects of novel exercise and nutritional therapies on cardiovascular outcomes in both healthy and clinical populations.

Childhood Stress + Immune Overactivity = High Blood Pressure in Adulthood?

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About 35 million adults in the U.S. may develop high blood pressure because of negative events that happened to them during childhood. Researchers are exploring how an event you experience when you’re a kid can cause high blood pressure as an adult.

About 35 million children in the U.S. experience early-life stress (ELS). ELS is any traumatic event that occurs for an extended period of time to a child younger than 10. These experiences may range from emotional, sexual or physical abuse to parental divorce or growing up in a low-income household. ELS often has negative health effects—including high blood pressure—throughout a person’s adult life.

High blood pressure occurs when the force of the blood passing through the blood vessels remains higher than normal. If the pressure is not controlled, the blood vessels become stiff over time, which reduces blood flow and oxygen to the heart and increases the risk of heart failure or heart attack. High blood pressure can also cause severe damage to blood vessels in the kidneys and may eventually lead to chronic kidney disease, a condition in which the kidneys are no longer able to filter blood to remove toxic waste from the body. People with severe chronic kidney disease require a treatment called dialysis to keep them alive. During dialysis, a machine removes waste and excess water from the blood, effectively acting as an artificial kidney outside the body.

Because of these potential complications, it’s important to understand how ELS puts people at risk for high blood pressure. Numerous studies have shown that activation of immune cells can make high blood pressure worse. A recent study explored how ELS affects the immune system in rat kidneys, the organs responsible for long-term blood pressure control. The study found that rats exposed to ELS had higher numbers of immune cell markers and more immune cell activation in their adult life. Prolonged immune cell activation can prevent the kidneys from working properly, which may cause high blood pressure later on.

Interestingly, the study also found that when the immune cells in the kidneys of ELS rats were stimulated they showed that the immune cells were overactive. This finding is important because it shows researchers are starting to understand more about the link between ELS and high blood pressure. However, more research is needed to fully establish a connection between childhood trauma, the immune response of the kidneys and high blood pressure in adulthood.

Ijeoma ObiIjeoma Obi, MS, is a PhD candidate in the University of Alabama at Birmingham’s Department of Medicine, Nephrology Division, Section of Cardio-Renal Physiology and Medicine.

Of Ice Swims and Mountain Marathons (and So Much More)

If you regularly read this blog, you may know that the research questions that physiologists ask relate to wide range of topics—cells, tissues and organs, insects and animals, and how the environment influences all of these things. Nowhere is this more apparent than at the annual Experimental Biology meeting. This year, thousands of physiology-based research abstracts were presented over five days. Read on to learn about two research studies on extreme sports that caught our eye.

Glacier Dive

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Ice swimming is growing in popularity, with hundreds of athletes worldwide giving this chilly sport a try. Human performance in water this cold—swims must take place in water that’s 5 degrees Celsius or colder—has not been well-studied. In a study presented at the EB meeting, researchers looked at how age, gender and environmental factors such as wind chill affected athletes during one-mile ice swims. Among other results, they found that age doesn’t have a large effect on swim times, suggesting that athletes can be competitive in the sport well into their 30s and 40s. This is significantly older than the average age of the athletes on the most recent U.S. Winter Olympic team (26 years old), giving hope to older athletes as the sport is being considered as a new Winter Olympics event.

Man Running Uphill

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Fifty kilometer (~31 mile) mountain ultramarathons test athletes aerobic and anaerobic fitness through changes in elevation, terrain and weather. Aerobic fitness refers to how the body uses energy when there is enough oxygen, such as the energy burn that occurs when running at a comfortable pace. Anaerobic fitness refers to the body’s ability to exercise when there’s not enough oxygen, such as during a sprint to the finish line at the end of a race. While it may seem that aerobic fitness would be a better predictor of how fast a person would finish an ultramarathon, researchers found that competitors with the best anaerobic fitness finished faster. That’s why exercises that build anaerobic endurance, such as uphill sprints, would be a worthwhile addition to the training regimen of anyone preparing for this type of race.

These studies were just the tip of the iceberg. Read more physiology research highlights from the EB meeting:

How exercise to protect the blood vessels from stress

Why a high-salt and high-sugar diet is a fast track to high blood pressure

The benefits of gastric bypass surgery that occur before the weight comes off

Elephant seals that protect themselves with CO2

What tobacco hornworms can tell us about fat metabolism

How an inhaler could protect against life-threatening accumulation of fluid in the lungs

Stacy Brooks

Beyond Mars and Venus: Three Ways Gender Can Affect your Blood Pressure

Blood Pressure

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Much of what we know about human health and disease comes from studies in male animals. However, researchers are finding that for blood pressure control, what’s true for male animals is not necessarily true for females. One in three adults in the U.S. has high blood pressure (hypertension) and of those, only half have their hypertension under control, according to the Centers for Disease Control and Prevention. Understanding sex differences in the way the disease develops and behaves is important to improve hypertension care for both men and women.

Here are some of the newest findings on hypertension-related sex differences, presented in November at the American Physiological Society’s Physiology and Gender conference:

Women’s kidneys maintain the body’s salt levels differently than men’s. The kidneys are very important organs in the control of blood pressure. They do this by managing levels of sodium (salt) and potassium. Luciana Veiras, PhD, of the University of Southern California showed that female rats that were put on a fast and then fed a diet high in potassium had higher levels of sodium in their urine than their male counterparts did. This demonstrates that female and male kidneys respond differently to increases in blood potassium and suggests that blood pressure control also differs between men and women.

Different hormones may drive obesity-related high blood pressure in men and women. Research has shown that obesity causes hypertension. Fat cells create a hormone called leptin that stimulates the brain to increase blood pressure. However, the reason it increases blood pressure has primarily been studied only in male animals. It was unknown if the same was true for obese female animals. Eric Belin de Chantemele, PhD, of Georgia Regents University, presented findings suggesting that another hormone contributed to obesity-induced high blood pressure in females: aldosterone.

The immune cells that cause hypertension in men may not be the same in women. Studies in male research animals show that inflammation-promoting immune cells are involved in the development of high blood pressure. Jennifer Sullivan, PhD, of Georgia Regents University, presented work suggesting that the immune system actions in cardiovascular disease are not the same in men and women. She found that hypertensive female rats have more anti-inflammatory immune cells. Additionally, the immune cells that cause high blood pressure in male animals aren’t as common in female animals with high blood pressure.

As research studies continue to include more gender diversity, science will uncover more ways that men and women differ in health and disease, making personalized medicine and therapies better for both male and female patients.

Jessica Faulkner

 

Jessica Faulkner, PhD, is a postdoctoral fellow at Augusta University.

Why the Y Difference in High Blood Pressure?

Doctor Checking Blood Pressure Of Businessman

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One in three adults in the U.S. has high blood pressure (hypertension). Although men and women are just as likely to develop hypertension during their lifetimes, men younger than 45 have hypertension more often than women that age do. Scientists wondered if this difference is because the male hormone testosterone affects physiological processes differently than the female hormone estrogen does. In the case of hypertension, the suspicion was correct, but it wasn’t the entire story. Recent studies have shown that the gene that gives men the physiological traits to produce testosterone—the SRY gene—may influence blood pressure, too.

Called the sex-determining region of the Y chromosome, SRY is found only on the Y chromosome and carries out its main job after conception when the embryo is developing. SRY turns on the genes involved in the development of male sex organs, triggering the testes to develop and produce the male hormone testosterone. Females don’t have a Y chromosome, nor the SRY gene. Instead, they develop ovaries and produce the female hormone estrogen.

SRY is part of a family of genes whose job is to turn other genes on or off. It is directly related to another gene found on the X chromosome, SOX3. Men have both SRY and SOX3, while women only have SOX3. However, because SRY and SOX3 are from the same family, they control the same genes. In a new study in Physiological Genomics, researchers wanted to know if SRY and SOX3 controlled the genes involved in blood pressure regulation in the same way: Did both of them turn on the genes or did one turn off and the other turn on the genes?

The researchers found that SRY and SOX3 had the same effects on several blood pressure genes except for one gene that produced renin, a protein that raises blood pressure. SRY turned renin production on, while SOX3 turned it off. SRY’s protein was also found in male rats’ kidneys, where renin is made, while SOX3’s was not. This led researchers to believe that renin is only controlled by SRY in males and that blood pressure is controlled differently in men, offering an explanation for why hypertension risks are different between the sexes.

Maggie KuoMaggie Kuo, PhD, is the former Communications and Social Media Coordinator for APS. Catch more of her writing in the Careers Section of Science Magazine.

Heart-Healthy Diets: Why the Low Sodium?

BloodEat less salt. It’s advice often recommended as a way to reduce blood pressure, but why? And if the body needs sodium (salt) to work properly, how does eating too much of it become unhealthy? In the cardiovascular system, excess sodium changes the body’s physiological processes to encourage high blood pressure, or hypertension. Sodium affects blood volume and the way two key organs—the kidneys and the heart—do their jobs.

Blood is made up of blood cells suspended in plasma—water containing proteins, nutrients, dissolved minerals and cellular waste. The kidneys purify blood by moving the water and everything in it, besides the proteins, out of the bloodstream into its ducts. The nutrients and minerals the body uses, including sodium, are then moved back into the bloodstream. Water is attracted to salt, so it follows sodium back into the bloodstream. The extra minerals and water left behind are filtered out, joined with waste products and excreted as urine.

Eating salt raises the sodium level in the plasma. As a result, more water gets reabsorbed into the blood and the total volume of the blood increases. The heart senses blood volume through how much its chambers are filled. When more blood is present, the heart contracts with greater force and pumps more blood out to the body. This increase in output causes blood pressure to rise.

The kidneys are eventually able to filter out excess sodium into the urine. However, constantly eating a lot of sodium maintains the elevated plasma sodium concentration, slowing down the return to normal blood volume levels and keeping already high blood pressure high.

Limiting dietary salt breaks this cycle. Blood volume decreases, the heart does not pump as strongly and blood pressure falls towards a healthy range. This is why “eat less salt” is heart-healthy advice to remember during American Heart Month and beyond.

Maggie KuoMaggie Kuo, PhD, is the former Communications and Social Media Coordinator for APS. Catch more of her writing in the Careers Section of Science Magazine.

Reviewed by Barbara E. Goodman, PhD

 

Correction (3/16/15): An earlier version had said “The kidneys purify blood by moving plasma and everything in it out of the bloodstream into its duct.” Protein actually remains in the blood vessels and do not filter into the kidneys’ ducts. The text has been edited accordingly.