Low levels of testosterone in men could increase their risk of developing Type 2 diabetes, a study funded by Diabetes UK suggests.
Researchers from the University of Edinburgh have found that low testosterone levels are linked to a resistance to insulin – a hormone that controls blood glucose levels.
Testosterone acts on fat cells
This study is the first to directly show how low testosterone levels in fat tissue could be involved in the onset of Type 2 diabetes. Testosterone, which is present throughout the body, acts on fat cells through molecules known as androgen receptors. These receptors enable testosterone to activate genes known to be linked to obesity and diabetes.
Obesity is a known risk factor for Type 2 diabetes. However, the researchers stated that the study showed that low testosterone is a risk factor irrespective of body weight.
The research showed that mice with impaired testosterone function were more likely to be insulin resistant than mice in which testosterone functioned normally. These findings could help explain why older men are more at risk of developing Type 2 diabetes, because testosterone levels fall in men as they age.
Impaired testosterone function linked to weight gain in mice
The study also showed that mice with no androgen receptors in their fat tissue were more likely to show signs of insulin resistance compared to mice with androgen receptors. The mice that lacked androgen receptors also became fatter, compared to other mice and developed full insulin resistance, when both types of mice were fed a high-fat diet.
Scientists believe that a protein called RBP4 plays a crucial role in regulating insulin resistance when testosterone is impaired. They found that levels of RBP4 were higher in mice in which the role of testosterone was impaired.
The Edinburgh team say that its findings could lead to the development of new treatments that regulate production of RBP4 and reduce the risk of Type 2 diabetes in men with lower levels of testosterone.
They are now planning to study people with Type 2 diabetes to see if their levels of testosterone correlate with levels of RBP4.
Healthy balanced diet important to reduce risk
Dr Iain Frame, Director of Research at Diabetes UK, said, “We already know that low testosterone levels are associated with increased obesity and therefore with increased risk of developing Type 2 diabetes, but this study provides evidence that there can be increased risk even when body mass is not affected.
“Yet while testosterone-impaired mice developed insulin resistance whatever diet they were given, the effect was considerably more pronounced on those fed on a high fat diet. This reinforces Diabetes UK advice that a healthy balanced diet is important for everyone, and particularly for those already at high risk of developing Type 2 diabetes.
“Further work is needed to translate these initial findings into clinical practice, as it is important to emphasise that results in mice may not necessarily have direct relevance for humans. But good basic research such as this represents early steps towards potential new treatments, and we are pleased to see research we have funded producing useful results which may benefit people living with diabetes at some point in the future.”