Western-style diet linked to state-dependent memory inhibition

Obesity may ultimately be a disease of the brain, involving a progressive deterioration of various cognitive processes that influence eating. Researchers at Macquarie University have now shown that memory inhibition -- the useful ability to 'block out' memories that are no longer useful, which depends on a brain area called the hippocampus -- is linked to dietary excess. Usually, food-related memories should be at the forefront during hunger but then inhibited during fullness, so that thoughts of food are set aside when eating is no longer top priority.

Prior animal studies have shown that a Western diet -- one high in fats and sugars and low in fruit, vegetable and fiber -- impairs the memory inhibition abilities of the hippocampus. Practically, this could mean that a Western-style diet makes it harder to inhibit pleasant memories triggered by seeing or smelling palatable food. This would make it hard to resist delicious treats even if one were full.
The Macquarie researchers have now found evidence for this problem in humans, they reported this week at the annual meeting of the Society for the Study of Ingestive Behavior (SSIB), the foremost society for research into all aspects of eating and drinking behaviour. The study supported by the Australian Research Council and led by PhD student Tuki Attuquayefio looked at healthy young people, some of whom ate a Western-style diet.
Participants completed learning and memory tests that depend on the hippocampus and also rated their liking and wanting of palatable snack foods before and after a filling lunch. Participants who habitually ate a Western-style diet were slower at learning and poorer at remembering than those who ate a healthier diet, and more importantly showed much smaller reductions in wanting palatable snacks when tested full compared to hungry.
The key finding is that memory performance and snack food ratings were linked. "Even though they were full, they still wanted to eat the sweet and fatty junk food," explained Tuki Attuquayefio. "What was even more interesting was that this effect was strongly related to their performance on the learning and memory task, suggesting that there is a link between the two via the hippocampus."
In agreement with the animal research, people with greater intake of a high fat, high sugar diet may do more poorly on the learning and memory tests because of how the diet impacts the hippocampus. The Macquarie University researchers believe inability to inhibit food memories when in a satiated physiological state could then explain the persistent desire for snacks. For otherwise healthy, lean, young people who routinely consume high-fat high-sugar diets, compromised hippocampal function may make it harder to regulate food intake and set them upon the road towards obesity.

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The above post is reprinted from materials provided by Society for the Study of Ingestive Behavior. Note: Materials may be edited for content and length.

Sixth DNA base discovered?

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DNA illustration (stock image). New research describes the possible existence of a sixth DNA base, the methyl-adenine (mA), which also help determine the epigenome and would therefore be key in the life of the cells.

Credit: © abhijith3747 / Fotolia

DNA (deoxyribonucleic acid) is the main component of our genetic material. It is formed by combining four parts: A, C, G and T (adenine, cytosine, guanine and thymine), called bases of DNA combine in thousands of possible sequences to provide the genetic variability that enables the wealth of aspects and functions of living beings.

Two more bases: the Methyl- cytosine and Methyl-adenine
In the early 80s, to these four "classic" bases of DNA was added a fifth: the methyl-cytosine (mC) derived from cytosine. And it was in the late 90's when mC was recognized as the main cause of epigenetic mechanisms: it is able to switch genes on or off depending on the physiological needs of each tissue.
In recent years, interest in this fifth DNA base has increased by showing that alterations in the methyl-cytosine contribute to the development of many human diseases, including cancer.
Today, an article published in Cell by Manel Esteller, director of the Epigenetics and Cancer Biology Program of the Bellvitge Biomedical Research Institute (IDIBELL), ICREA researcher and Professor of Genetics at the University of Barcelona, describes the possible existence of a sixth DNA base, the methyl-adenine (mA), which also help determine the epigenome and would therefore be key in the life of the cells.
In bacteria and in complex organisms
"It was known for years that bacteria, evolutionarily very distant living organisms of us, had mA in its genome with a protective function against the insertion of genetic material from other organisms. But it was believed that this was a phenomenon of primitive cells and it was very static" describes Manel Esteller.
"However, this issue of Cell publishes three papers suggesting that more complex cells called eukaryotes such as the human body cells, also present the sixth DNA base. These studies suggest that algae, worms and flies possess mA and it acts to regulate the expression of certain genes, thus constituting a new epigenetic mark. This work has been possible thanks to the development of analytical methods with high sensitivity because levels of mA in described genomes are low. In addition it seems that mA would play a specific role in stem cells and early stages of development, "explains the researcher.
"Now the challenge we face is to confirm this data and find out whether mammals, including humans, we also have this sixth DNA base, and consider what its role is."

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The above post is reprinted from materials provided by IDIBELL-Bellvitge Biomedical Research Institute. Note: Materials may be edited for content and length.

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Journal Reference:

1. Holger Heyn, Manel Esteller. An Adenine Code for DNA: A Second Life for N6-Methyladenine. Cell, 2015; DOI: 10.1016/j.cell.2015.04.021

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IDIBELL-Bellvitge Biomedical Research Institute. "Sixth DNA base discovered?." ScienceDaily. ScienceDaily, 4 May 2015. .

How new HIV drugs lock virus in immaturity

 

Study provides insights into workings of new HIV drugs and how virus becomes resistant

Date:

July 15, 2016

Source:

European Molecular Biology Laboratory

Summary:

A new type of HIV drug currently being tested works in an unusual way, scientists have found. They also discovered that when the virus became resistant to early versions of these drugs, it did not do so by blocking or preventing their effects, but rather by circumventing them. The study presents the most detailed view yet of part of the immature form of HIV.

 

 

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For HIV to mature, a crucial cutting point has to be severed. EMBL scientists determined the cutting site's 3-D structure in whole HIV particles, and found that it is hidden in a position where the virus' cutting machinery can't sever it. So for the virus to mature, the structure first has to change, to expose that cutting point.

Credit: Copyright Florian Schur/EMBL

A new type of HIV drug currently being tested works in an unusual way, scientists in the Molecular Medicine Partnership Unit, a collaboration between EMBL and Heidelberg University Hospital, have found. They also discovered that when the virus became resistant to early versions of these drugs, it did not do so by blocking or preventing their effects, but rather by circumventing them. The study, published online today in Science, presents the most detailed view yet of part of the immature form of HIV.

HIV, the virus that causes AIDS, comes in two forms: immature and mature. The immature form is assembled inside an infected person's cells. After an immature virus particle has left the cell, it has to change into the mature form before it can infect other human cells. A new group of drugs that inhibit this maturation is currently undergoing clinical trials, but so far it was unclear how exactly these drugs act.
To go from immature to mature, HIV has to cut the connections between its main building blocks, and rearrange those pieces. John Briggs' lab at EMBL and Hans-Georg Kräusslich's lab at Heidelberg University Hospital looked at a particularly important cutting point. It connects building blocks known as the capsid protein and the spacer peptide 1, and if it is not cut, the virus cannot mature. The scientists used a combination of cryo-electron tomography and subtomogram averaging to reveal exactly what this part of the immature form of HIV looks like in 3D. They found that the cutting site is hidden in a position where the virus' cutting machinery can't sever it. So for the virus to mature, the structure first has to change, to expose that cutting point.
"When we looked at the virus with one of these inhibitor drugs on it, we found that the inhibitor doesn't prevent the cutting machinery from getting in, as you might expect," says Florian Schur, who carried out the work in Briggs' lab. "Rather, the drug locks the immature virus structure in place, so that it can't be cut."
When the new inhibitor drugs were first developed, scientists found that HIV viruses with certain mutations in their genetic sequence were unaffected by the drugs -- they were resistant. Having determined what the cutting point looks like and how the drugs act, Briggs and colleagues are now able to understand the effects of those mutations.
"Rather than stopping the drug from binding, the virus becomes resistant through mutations that destabilise the immature structure," says Kräusslich. "This allows it to rearrange and be cut even when the drug is in place."
The researchers would now like to probe the virus and the inhibitor drugs in even greater detail, to understand exactly how the drugs attach themselves to the viral proteins, and potentially gather data that could help to search for better drugs -- or to design them.
The method used in this study -- combined cryo-electron tomography and subtomogram averaging -- enables scientists to study structures inside irregular viruses like HIV, or within cells. In essence, the scientists use an electron microscope to obtain a 3D image of the sample -- in this case, whole HIV-1 particles. They then identify all the copies of the object they want to study -- all the instances of the capsid protein-spacer peptide 1 cutting point -- and use software to rotate the 3D image of each copy so that they are all facing the same way. By repeating this procedure with thousands of images, the scientists can obtain an accurate picture. With this approach, researchers can study such samples without having to purify them in a test-tube, which means that they see them in their real state. The EMBL scientists' work now proves that the method can provide the level of detail that is crucial to understanding how molecular machines work and to informing drug design.

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The above post is reprinted from materials provided by European Molecular Biology Laboratory. Note: Materials may be edited for content and length.

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Journal Reference:

1. F. K. M. Schur, M. Obr, W. J. H. Hagen, W. Wan, A. J. Jakobi, J. M. Kirkpatrick, C. Sachse, H.-G. Krausslich, J. A. G. Briggs. An atomic model of HIV-1 capsid-SP1 reveals structures regulating assembly and maturation. Science, 2016; DOI: 10.1126/science.aaf9620

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European Molecular Biology Laboratory. "How new HIV drugs lock virus in immaturity: Study provides insights into workings of new HIV drugs and how virus becomes resistant." ScienceDaily. ScienceDaily, 15 July 2016. .

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Sleeping healthy toddler (stock image). Bedtimes after 9 p.m. appeared to double the likelihood of obesity later in life, according to a new study.

Credit: © Kenishirotie / Fotolia

Preschoolers who are regularly tucked into bed by 8 p.m. are far less likely to become obese teenagers than young children who go to sleep later in the evening, new research has found.

Bedtimes after 9 p.m. appeared to double the likelihood of obesity later in life, according to a study from The Ohio State University College of Public Health.
"For parents, this reinforces the importance of establishing a bedtime routine," said Sarah Anderson, lead author and associate professor of epidemiology.
It also arms pediatricians with scientifically based advice for parents.
"It's something concrete that families can do to lower their child's risk and it's also likely to have positive benefits on behavior and on social, emotional and cognitive development," Anderson said.
Excess weight in children is a major health concern in the United States. Approximately 17 percent -- 12.7 million -- of children and adolescents are obese, according to the latest figures from the Centers for Disease Control and Prevention.
Obesity can set kids up for a lifelong struggle with weight and health complications that can accompany it, including diabetes and heart disease.
The new research, which appears in the The Journal of Pediatrics, used data from 977 children who were part of the Study of Early Child Care and Youth Development. That project followed healthy babies born at 10 U.S. sites in 1991.
Anderson and her co-authors divided preschool bedtimes into three categories: 8 p.m. or earlier, between 8 p.m. and 9 p.m., and after 9 p.m. The children were about 4 ½ years old when their mothers reported their typical weekday bedtime.
The researchers linked preschoolers' bedtimes to obesity when the kids were teens, at an average age of 15.
They found a striking difference: Only 1 in 10 of the children with the earliest bedtimes were obese teens, compared to 16 percent of children with mid-range bedtimes and 23 percent of those who went to bed latest. Half the kids in the study fell into the middle category. A quarter had early bedtimes and another quarter went to bed late.
Because the emotional climate at home can influence routines such as bedtime, Anderson and her colleagues also examined interactions between mothers and their children during a videotaped playtime. Scientists call the measurement "maternal sensitivity" and it factors in maternal support, respect for the child's autonomy and lack of hostility.
Regardless of the quality of the maternal-child relationship, there was a strong link between bedtimes and obesity, the researchers found. But the children who went to bed latest and whose moms had the lowest sensitivity scores faced the highest obesity risk.
The researchers also found that later bedtimes were more common in children who were not white, whose moms had less education and who lived in lower-income households.
Previous research has established a relationship between short sleep duration and obesity. And one study found a correlation between late bedtimes and obesity risk five years later. This new bedtime study is the first to use data on obesity collected about a decade after the children were in preschool, Anderson said.
Her team's previous research has illustrated the importance of household routines for preschool-aged children and this builds on that work, she said.
Anderson said she and her co-authors focused on bedtimes because they have a greater impact on the duration of sleep than do wake times, over which parents have less control.
When parents and older siblings must get up and out the door early, that often means young children rise early as well.
Putting a child to bed early doesn't guarantee he or she will fall immediately into a deep sleep, Anderson said, but establishing a consistent bedtime routine makes it more likely that children will get the amount of sleep they need to be at their best, Anderson said.
Recommending early bedtimes for young children may help to prevent obesity, and pediatricians are in a position to talk with parents about the importance of sleep for children's overall health. Pediatricians can also help to address obstacles families may face, she said.
"It's important to recognize that having an early bedtime may be more challenging for some families than for others," Anderson said.
"Families have many competing demands and there are tradeoffs that get made. For example, if you work late, that can push bedtimes later in the evening."
The majority of young children are biologically pre-programmed to be ready to fall asleep well before 9 p.m., according to previous research.
The study doesn't answer questions about how sleep time intertwines with a variety of other factors that can contribute to weight gain in childhood, including physical activity and nutrition, Anderson said, and that remains an active area of research.

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Story Source:
The above post is reprinted from materials provided by Ohio State University. The original item was written by Misti Crane. Note: Materials may be edited for content and length.

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Journal Reference:

1. Sarah E. Anderson, Rebecca Andridge, Robert C. Whitaker. Bedtime in Preschool-Aged Children and Risk for Adolescent Obesity. The Journal of Pediatrics, July 2016 DOI: 10.1016/j.jpeds.2016.06.005

The tongue of a blue whale can weigh as much as an elephant

The tongue of a blue whale can weigh as much as an elephant, and its heart is about the size of a Volkswagen Beetle car and can weigh up to 992 lbs (450 kg). Their aorta, the major blood vessel of the heart, is big enough for a human child to crawl through.

The largest living organism on Earth

The largest living organism on Earth may well be a honey fungus in the Malheur National Forest, Oregon, U.S.A.. It’s estimated to be roughly 2.4 miles (3.7 kilometers) across and may be more than 8,000 years old