Glucose is a component of carbohydrates, and the main energy source used by brain cells.
By studying rats, a team at Imperial College London identified a mechanism that appears to sense how much glucose is reaching the brain, and prompts animals to seek more if it detects a shortfall.
The researchers believe it may play a role in driving our preference for sweet and starchy foods.
The study, funded by the Biotechnology and Biological Sciences Research Council, is published in the Journal of Clinical Investigation.
Dr James Gardiner, from the Department of Medicine, who led the study, said: "Our brains rely heavily on glucose for energy. It's clearly a very important nutrient, but in our evolutionary past it would have been hard to come by. So we have a deep-rooted preference for glucose-rich foods and seek them out."
The researchers hypothesised that an enzyme called glucokinase might play a role in driving our desire for glucose. Glucokinase is involved in sensing glucose in the liver and pancreas. It is present in the hypothalamus, an area of the brain that regulates a variety of essential functions including food intake, but its exact role was unclear.
They first discovered that when rats go for 24 hours without eating, the activity of glucokinase in an appetite-regulating centre in the hypothalamus increases sharply.
The rats were given access to a glucose solution as well as their normal food pellets, called chow. When the researchers increased the activity of glucokinase in the hypothalamus using a virus, rats consumed more glucose in preference to chow. When glucokinase activity was decreased, they consumed less glucose.
"This is the first time anyone has discovered a system in the brain that responds to a specific nutrient, rather than energy intake in general. It suggests that when you're thinking about diet, you have to think about different nutrients, not just count calories," Dr Gardiner said.
Dr Gardiner suggested that in humans it might be possible to reduce cravings for glucose by altering one's diet and a drug acting on this system could potentially prevent obesity.
"People are likely to have different levels of this enzyme, so different things will work for different people. For some people, eating more starchy foods at the start of a meal might be a way to feel full more quickly by targeting this system, meaning they eat less overall."
For more information please contact:
Research Media Officer
Imperial College London
Tel: +44(0)20 7594 2198
Out of hours duty press officer: +44(0)7803 886 248
Notes to editors:
1. Syed Hussain et al. 'Glucokinase activity in the arcuate nucleus regulates glucose intake.' Journal of Clinical Investigation, 2014.
2. About Imperial College London
Imperial College London is one of the world's leading universities. The College's 14,000 students and 7,500 staff are expanding the frontiers of knowledge in science, medicine, engineering and business, and translating their discoveries into benefits for society.
Founded in 1907, Imperial builds on a distinguished past - having pioneered penicillin, holography and fibre optics - to shape the future. Imperial researchers work across disciplines to improve global health, tackle climate change, develop sustainable energy technology and address security challenges. This blend of academic excellence and its real-world application feeds into Imperial's exceptional learning environment, where students participate in research to push the limits of their degrees.
Imperial nurtures a dynamic enterprise culture, where collaborations with industrial, healthcare and international partners are the norm. In 2007, Imperial College London and Imperial College Healthcare NHS Trust formed the UK's first Academic Health Science Centre. This unique partnership aims to improve the quality of life of patients and populations by taking new discoveries and translating them into new therapies as quickly as possible.
Imperial has nine London campuses, including Imperial West: a new 25 acre research and innovation centre in White City, west London. At Imperial West, researchers, businesses and higher education partners will co-locate to create value from ideas on a global scale.