When food porn holds no allure: the science behind satiety

New research from the University of British Columbia is shedding light on why enticing pictures of food affect us less when we’re full.

“We’ve known that insulin plays a role in telling us we’re satiated after eating, but the mechanism by which this happens is unclear,” says Stephanie Borgland, an assistant professor in UBC’s Dept. of Anesthesiology, Pharmacology and Therapeutics and the study’s senior author.

In the new study published online this week in Nature Neuroscience, Borgland and colleagues found that insulin – prompted by a sweetened, high-fat meal – affects the ventral tegmental area (VTA) of the brain, which is responsible for reward-seeking behaviour. When insulin was applied to the VTA in mice, they no longer gravitated towards environments where food had been offered.

“Insulin dulls the synapses in this region of the brain and decreases our interest in seeking out food,” says Borgland, “which in turn causes us to pay less attention to food-related cues.”

“There has been a lot of discussion around the environmental factors of the obesity epidemic,” Borgland adds, pointing to fast food advertising bans in Quebec, Norway, the U.K., Greece and Sweden. “This study helps explain why pictures or other cues of food affect us less when we’re satiated – and may help inform strategies to reduce environmental triggers of overeating.”

The VTA has also been shown to be associated with addictive behaviours, including illicit drug use. Borgland says better understanding of the mechanism in this region of the brain could, in the long run, inform diagnosis and treatment.

(Image: Shutterstock)

How insulin binds to cells

A landmark discovery about how insulin docks on cells could help in the development of improved types of insulin for treating both type 1 and type 2 diabetes.

For the first time, researchers have captured the intricate way in which insulin uses the insulin receptor to bind to the surface of cells. This binding is necessary for the cells to take up sugar from the blood as energy.

The research team was led by the Walter and Eliza Hall Institute and used the Australian Synchrotron in Melbourne. The study was published in the journal Nature.

For more than 20 years scientists have been trying to solve the mystery of how insulin binds to the insulin receptor. A research team led by Associate Professor Mike Lawrence, Dr Colin Ward and Dr John Menting have now found the answer.

Associate Professor Lawrence from the institute’s Structural Biology division said the team was excited to reveal for the first time a three-dimensional view of insulin bound to its receptor. “Understanding how insulin interacts with the insulin receptor is fundamental to the development of novel insulins for the treatment of diabetes,” Associate Professor Lawrence said. “Until now we have not been able to see how these molecules interact with cells. We can now exploit this knowledge to design new insulin medications with improved properties, which is very exciting.”

The Australian Synchrotron’s MX2 microcrystallography beamline was critical to the project’s success. “If we did not have this fantastic facility in Australia and their staff available to help us, we would simply not have been able to complete this project,” Associate Professor Lawrence said.

Associate Professor Lawrence assembled an international team of project collaborators, including researchers from Case Western Reserve University, the University of Chicago, the University of York and the Institute of Organic Chemistry and Biochemistry in Prague. “Collaborations in this field are essential,” he said. “No one laboratory has all the resources, expertise and experience to take on a project as difficult as this one.”

“We have now found that the insulin hormone engages its receptor in a very unusual way,” Associate Professor Lawrence said. “Both insulin and its receptor undergo rearrangement as they interact – a piece of insulin folds out and key pieces within the receptor move to engage the insulin hormone. You might call it a ‘molecular handshake’.”

Australia is facing an increasing epidemic of type 2 diabetes. There are now approximately one million Australians living with diabetes and around 100,000 new diagnoses each year.

“Insulin controls when and how glucose is used in the human body,” Associate Professor Lawrence said. “The insulin receptor is a large protein on the surface of cells to which the hormone insulin binds. The generation of new types of insulin have been limited by our inability to see how insulin docks into its receptor in the body.

“Insulin is a key treatment for diabetics, but there are many ways that its properties could potentially be improved,” Associate Professor Lawrence said. “This discovery could conceivably lead to new types of insulin that could be given in ways other than injection, or an insulin that has improved properties or longer activity so that it doesn’t need to be taken as often. It may also have ramifications for diabetes treatment in developing nations, by creating insulin that is more stable and less likely to degrade when not kept cold, an angle being pursued by our collaborators. Our findings are a new platform for developing these kinds of medications.”

Scientists announce new treatment for type II diabetes

According to the World Health Organization, there are currently 347 million diabetics worldwide, with 90 percent of those people having type II diabetes specifically. It occurs when fat accumulates in places such as muscles, blood vessels and the heart, causing the cells in those areas to no longer be sufficiently responsive to insulin. This insulin resistance, in turn, causes blood glucose levels to rise to dangerous levels. Ultimately, it can result in things such as heart disease, strokes, blindness, kidney failure, and amputations. Fortunately, however, an international team of scientists has just announced a new way of treating the disease.

Currently, one of the main ways of treating type II diabetes involves switching the patient to a healthier diet and increasing the amount of exercise they get – the disease is most often caused by obesity. Additionally, oral medication can be used to increase insulin production and the body’s sensitivity to it, or to decrease glucose production. For approximately 30 percent of patients, however, such medication ceases to be effective after a few years, and they end up having to receive regular insulin injections.

The new treatment focuses on VEGF-B, a protein within the body that affects how fat is transported and stored. Using an antibody/drug known as 2H10, the scientists were able to block the signaling of VEGF-B in mice and rats, which subsequently kept fat from accumulating in the “wrong” areas of the animals – namely their muscles, blood vessels and hearts.

Using ultrasound waves, MIT engineers have found a way to enhance the permeability of skin to drugs, making transdermal drug delivery more efficient. This technology could pave the way for noninvasive drug delivery or needle-free vaccinations, according to the researchers.

“This could be used for topical drugs such as steroids — cortisol, for example — systemic drugs and proteins such as insulin, as well as antigens for vaccination, among many other things,” says Carl Schoellhammer, an MIT graduate student in chemical engineering and one of the lead authors of a recent paper on the new system.

Ultrasound — sound waves with frequencies greater than the upper limit of human hearing — can increase skin permeability by lightly wearing away the top layer of the skin, an effect that is transient and pain-free.

In a paper appearing in the Journal of Controlled Release, the research team found that applying two separate beams of ultrasound waves — one of low frequency and one of high frequency — can uniformly boost permeability across a region of skin more rapidly than using a single beam of ultrasound waves.