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Washington, Feb 21: The fat around arteries may play an important role in keeping the blood vessels healthy, according to a study in rats that may affect how researchers test for treatments related to plaque buildup, as seen in conditions leading to heart attack.

The study, published in the journal Scientific Reports, noted that the fat, known as perivascular adipose tissue, or PVAT, helps arteries let go of muscular tension while under constant strain.

According to the researchers, including Stephanie W. Watts from the Michigan State University in the US, this feature is similar to how the bladder expands to accommodate more liquid, while at the same time keeping it from spilling out.

"In our study, PVAT reduced the tension that blood vessels experience when stretched," Watts said.

"And that's a good thing, because the vessel then expends less energy. It's not under as much stress," she added.

According to Watts and her team, PVAT has largely been ignored by researchers believing its main job was to store lipids and do little more.

Until now, she said, scientists only divided blood vessels into three parts, the innermost layer called the tunica intima, the middle layer called the tunica media, and the outermost layer called the tunica adventitia.

Watts believes PVAT is the fourth layer, which others have called tunica adiposa.

Tunica, she said, meant a membranous sheath enveloping or lining an organ, and adiposa is a synonym for fat.

"For years, we ignored this layer -- in the lab it was thrown out. In the clinic it wasn't imaged. But now we're discovering it may be integral to our blood vessels," Watts said.

"Our finding redefines what the functional blood vessels are, and is part of what can be dysfunctional in diseases that afflict us, including hypertension. We need to pay attention to this layer of a blood vessel because it does far more than we originally thought," she added.

Earlier studies, Watts said, had shown that PVAT plays a role in the functioning of blood vessels, finding that it secretes substances that can cause blood vessels to relax as well as substances that can cause it to contract.

In the current study, the researchers decided to test whether PVAT provides a structural benefit to arteries by assisting the function of stress relaxation.

They tested the thoracic aorta in rats, and found those with intact PVAT had more stress relaxation than those without.

The study revealed that the pieces of artery with surrounding fat had measurably relaxed more than those without.

Watts and her colleagues then tested other arteries, and were able to duplicate the same response.

"It's not something you see only in this particular vessel or this particular species or this particular strain. But that maybe it's a general phenomenon," she said.

After admitting that the world may have a COVID-19 vaccine within one year or even a few months earlier, the World Health Organisation (WHO) on Friday said that UK-based AstraZeneca is leading the vaccine race while US-based pharmaceutical major Moderna is not far behind.

WHO Chief Scientist Soumya Swaminathan stated that the AstraZeneca's coronavirus vaccine candidate is the most advanced vaccine currently in terms of development.

"I think AstraZeneca certainly has a more global scope at the moment in terms of where they are doing and planning their vaccine trials," she told the media.

AstraZeneca's Covid-19 vaccine candidate developed by researchers from the Oxford University will likely provide protection against the disease for one year, the British drug maker's CEO told Belgian radio station Bel RTL this month.

The Oxford University last month announced the start of a Phase II/III UK trial of the vaccine, named AZD1222 (formerly known as ChAdOx1 nCoV-19), in about 10,000 adult volunteers. Other late-stage trials are due to begin in a number of countries.

Last week, Swaminathan had said that nearly 2 billion doses of the COVID-19 vaccine would be ready by the end of next year.

Addressing the media from Geneva, she said that "at the moment, we do not have a proven vaccine but if we are lucky, there will be one or two successful candidates before the end of this year" and 2 billion doses by the end of next year.

Scientists predict that the world may have a COVID-19 vaccine within one year or even a few months earlier, said the Director-General of the World Health Organization even as he underlined the importance of global cooperation to develop, manufacture and distribute the vaccines.

However, making the vaccine available and distributing it to all will be a challenge and will require political will, WHO chief Tedros Adhanom Ghebreyesus said on Thursday during a meeting with the European Parliament's Committee for Environment, Public Health and Food Safety.

One option would be to give the vaccine only to those who are most vulnerable to the virus.

There are currently over 100 COVID-19 vaccine candidates in various stages of development.

Using smartphone for long hours every day may do you more harm than you can probably think of. Researchers have found that spending a lot of time with the device and on social media may lead to mental distress and suicidality among adolescents.

The findings, published in the journal CMAJ (Canadian Medical Association Journal) contains guidance for physicians, parents and teachers on how to help teenagers manage smartphone and social media use for a healthy balance between sleep, academic work, social activity, interpersonal relationships and online activity.

"Physicians, teachers and families need to work together with youth to decrease possible harmful effects of smartphones and social media on their relationships, sense of self, sleep, academic performance, and emotional well-being," said lead author of the study Elia Abi-Jaoude from Toronto Western Hospital in Canada.

This review of evidence, led by the Hospital for Sick Children (SickKids), focuses on smartphone use and does not consider online gaming.

"For adolescents today, who have not known a world without social media, digital interactions are the norm, and the potential benefits of online access to productive mental health information -- including media literacy, creativity, self-expression, sense of belonging and civic engagement -- as well as low barriers to resources such as crisis lines and Internet-based talking therapies cannot be discounted," the authors wrote.

The researchers recommend that doctors should ask teenagers to reduce social media use rather than eradicate it completely and encourage parents to be part of the conversations.

Parents should discuss appropriate smartphone use with teenagers to determine together how to reduce risks and set boundaries.

A recent poll from the US indicates that 54 per cent of teenagers think they spend too much time on their smartphones and about half said they were cutting back on usage.

"Encouragingly, youth are increasingly recognising the negative impact of social media on their lives and starting to take steps to mitigate it," the authors wrote.