Asthma may contribute to childhood obesity epidemic

Toddlers with asthma are more likely to become obese children, according to an international study led by USC scientists.

The finding is a turnabout for children's health as obesity has often been seen as a precursor to asthma in children, not the other way around. The study, conducted by a team of 40 scientists including researchers at the Keck School of Medicine of USC, was recently published in the European Respiratory Journal.

This is the largest study yet about early-onset asthma and obesity. It focused on more than 20,000 youths across Europe. It shows that, beyond wheezing and shortness of breath, asthma can lead to bodies that make young people more susceptible to other health problems later in life.

Lida Chatzi, the senior author and professor of preventive medicine at USC, says asthma and obesity pack a one-two punch against children's health, which raises concern about a public health crisis due to their prevalence.

"We care about this issue because asthma affects approximately 6.5 million children -- about one in 10 -- in the United States," Chatzi said. "It's a chronic childhood disorder and if it increases the risk of obesity, we can advise parents and physicians on how to treat it and intervene to help young children grow up to enjoy healthy, adult lives."

For two decades, scientists have documented the parallel epidemics of childhood asthma and obesity, with focus on how obesity is a risk factor for asthma. In adults, obesity is an important risk factor for new asthma, especially among women, but the relationships appear to differ in children. Few studies look at the problem the other way around to understand how asthma contributes to obesity in kids, which prompted scientists to undertake this research.

Drawing upon big data on children's health collected across Europe, the scientists investigated 21,130 children born between 1990 and 2008 across nine countries, including Denmark, France, Germany, Greece, Italy, the Netherlands, Spain, Sweden and the United Kingdom.

The children were diagnosed by physicians with asthma at 3 to 4 years old and the scientists followed toddlers into childhood up to 8 years of age. Their goal was to focus on health risks of early-onset asthma.

On average, the scientists found that children diagnosed with asthma had a 66 percent higher risk of becoming obese than those without an asthma diagnosis. For children with persistent wheezing symptoms, their risk of developing obesity was 50 percent greater compared to children without such symptoms. Children with active asthma were nearly twice as likely to develop obesity than those without asthma and wheezing, according to the study. The findings are consistent with previous, but smaller, longitudinal studies conducted in the United States that observed asthma increased the risk of obesity.

The causal direction between asthma and obesity is not well understood. Asthma is regarded as a barrier to children's physical activity that might lead to accumulation of fat in the body, while higher doses of inhaled corticosteroids had been hypothesized to increase risk of obesity in children with asthma. According to the study, children with asthma who used medication had the strongest risk of developing obesity.

Since both asthma and obesity have their origins early in life, it is possible that the asthma-obesity association is also established in this critical time window of child development. Previous studies have shown that in utero exposures, such as prenatal diet or maternal obesity, are associated with increased risk of both disorders.

"Asthma may contribute to the obesity epidemic. We urgently need to know if prevention and adequate treatment of asthma can reduce the trajectory toward obesity," said Frank Gilliland, professor of preventive medicine at the Keck School of Medicine, who participated in the study.

According to the U.S. Centers for Disease Control and Prevention, about 40 percent of Americans, or 93 million, are obese. The estimated annual medical cost of obesity nationwide was $147 billion in 2008, the CDC estimates. Obesity is linked to diseases such as diabetes, high blood pressure and stroke.

The CDC reports the number of people with asthma in the United States is growing every year. About one in 12 Americans is afflicted with the illness. In smoggy places, like California's San Joaquin Valley, about 1 in 6 children suffer from asthma, the highest rate in the country.

In Europe, 1 in 8 people die due to lung diseases -- or about one person per minute. It includes well-known diseases like asthma and lung cancer and other less-known diseases like chronic obstructive pulmonary disease, which is now the third most common cause of death, according to the European Respiratory Society.

Testosterone explains why women more prone to asthma

An international research team has revealed for the first time that testosterone protects males against developing asthma, helping to explain why females are two times more likely to develop asthma than males after puberty.

The study showed that testosterone suppresses the production of a type of immune cell that triggers allergic asthma. The finding may lead to new, more targeted asthma treatments.

One in nine Australians (2.5 million people) and around one in 12 Americans (25 million) have asthma, an inflammatory airway condition. During an asthma attack, the airways swell and narrow, making it difficult to breathe. In adults asthma is two times more prevalent and more severe in women than men, despite more being more common in boys than girls before puberty.

In 2016, the city of Melbourne, Australia, experienced a 'thunderstorm asthma' event that was unprecedented internationally in its scale and severity of consequences, with almost 10,000 people visiting hospitals over a two-day period. Thunderstorm asthma refers to allergic asthma thought to be initiated by an allergy to grass pollen. Many people with no history of asthma experienced severe asthma attacks.

Dr Cyril Seillet and Professor Gabrielle Belz from Melbourne's Walter and Eliza Hall Institute, with Dr Jean-Charles Guéry and his team at the Physiopathology Center of Toulouse-Purpan, France, led the study, published today in the Journal of Experimental Medicine.

Dr Seillet said hormones were speculated to play a significant role in the incidence and severity of asthma in women. "There is a very interesting clinical observation that women are more affected and develop more severe asthma than men, and so we tried to understand why this was happening," Dr Seillet said.

"Our research shows that high levels of testosterone in males protect them against the development of allergic asthma. We identified that testosterone is a potent inhibitor of innate lymphoid cells, a newly-described immune cell that has been associated with the initiation of asthma."

The research team found that innate lymphoid cells -- or ILC2s -- 'sensed' testosterone and responded by halting production of the cells.

"Testosterone directly acts on ILC2s by inhibiting their proliferation," Dr Seillet said. "So in males, you have less ILC2s in the lungs and this directly correlates with the reduced severity of asthma."

ILC2s are found in the lungs, skin and other organs. These cells produce inflammatory proteins that can cause lung inflammation and damage in response to common triggers for allergic asthma, such as pollen, dust mites, cigarette smoke and pet hair.

Professor Belz said understanding the mechanism that drives the sex differences in allergic asthma could lead to new treatments for the disease.

"Current treatments for severe asthma, such as steroids, are very broad based and can have significant side effects," Professor Belz said.

"This discovery provides us with a potential new way of treating asthma, by targeting the cells that are directly contributing to the development of allergic asthma. While more research needs to be done, it does open up the possibility of mimicking this hormonal regulation of ILC2 populations as a way of treating or preventing asthma. Similar tactics for targeting hormonal pathways have successfully been used for treating other diseases, such as breast cancer."

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