Could hibernating animals be key to war on diabetes?

05/07/05 Brown bears, squirrels, bats and frogs could hold the key to why western populations are facing an epidemic of type 2 diabetes, according to professor of medicine Peter Grant. If his theory is proven, it will “completely change the view of diabetes and its cause.”

By 2025, 300 million people worldwide will suffer from type 2 diabetes, up to 85 per cent of whom will die of related heart disease. The condition, associated with obesity, develops when the body’s fat cells secrete proteins involved in both cardiovascular disease and the development of insulin resistance, preventing the body from using glucose as an energy source.

Professor Grant, director of the University’s new £10m Leeds Institute of Genetics, Health and Therapeutics (LIGHT), believes the body wouldn’t become resistant to insulin action and hoard fat in this way without a reason. “It’s a physiological process so there must be some kind of benefit,” he said. “The question is, under what circumstances?” When the body’s fat cells – or adipocytes – become full, they send messages to the brain to slow down and conserve energy. There is one circumstance where these responses are vital – animal hibernation.

He suggests that animals have a basic metabolic response that stores energy and develops insulin resistance in preparation for deprivation, usually during long winter months. In hibernating animals, this response is accompanied by prolonged periods of torpor, but in humans and other animals seasonal variations in light and food are critical in regulating energy utilisation, even though man probably never formally hibernated.

What has changed for man is that we now have constant supplies of food and light. As a result, whilst hibernating animals become insulin resistant to conserve energy in response to fat storage for the winter, then lose it during hibernation, we just continue to put on weight. “We have fractured our relationship with our environment – we no longer respond to seasons and we don’t have a fluctuating food supply. As a result we get obese and what should be a short term protective response to help us over winter becomes chronic, harmful and leads to diabetes and cardiovascular disease,” he said.

The theory will be tested in the LIGHT and could give important insights into potential treatments. “If we could identify the genes analogous to those in hibernating animals there is the real potential to develop novel targets for the prevention and treatment of both diabetes and cardiovascular disease.”

The news comes as research finds that adult lifestyle has more influence on your chances of developing diabetes than childhood experience, according to new research whose findings contradict previously-held beliefs.

A team from the University of Newcastle upon Tyne, UK, studied 412 men and women and found that fatter adults were more likely to have increased insulin resistance, a risk marker for Type 2 diabetes.

Childhood factors, such as birth weight and nutrition, were found to have limited impact, whereas they were previously thought to be significant. The study is published in the academic journal, Diabetes/Metabolism Research and Reviews.

The Newcastle University study measured participants’ percentage body fat and waist-hip ratio, along with other lifestyle elements. Men and women with a higher body fat and higher waist-hip ratio were more likely to demonstrate increased insulin resistance.

The data was collected as part of the Thousand Families Study, a Newcastle University project which has examined the health of children born in Newcastle in May and June 1947 throughout their lives. The study was funded by the Wellcome Trust, the Minnie Henderson Trust, the Sir John Knott Trust and the Special Trustees of the Newcastle Hospitals.

Study leader Dr Mark Pearce, who is also director of the Thousand Families Study, said promotion of healthier lifestyles throughout life would be the public health interventions most likely to reduce insulin resistance in later life.

He said: “Previous studies have suggested that risk of poor health in later life is programmed by impaired development in the womb, and that poor growth in fetal and infant life is associated with impaired insulin secretion and sensitivity. However, not all of these studies have not had access to complete data on later life.
“Our study, which has examined people from birth to adulthood, suggests that the life you lead as an adult has the biggest influence on your health, in terms of diabetes risk, in later life.

Dr Pearce, of Newcastle University’s School of Clinical Medical Sciences, added: “It’s never too late to start living a healthy lifestyle – and even though our study shows that childhood experience had limited impact on insulin resistance in adulthood, parents still have a role to play in introducing their children to eating a healthy diet and physical exercise, so they can develop good habits that will hopefully last throughout adulthood and old age.”

Amanda Vezey, care advisor at Diabetes UK, said, “We already know that lifestyle factors play a large part in the development of Type 2 diabetes. This study further emphasises the importance of eating a healthy, balanced diet and taking part in regular physical activity.

"To reduce the risks of developing Type 2 diabetes in earlier years, it's essential to start leading a healthy lifestyle as early as possible."