Hormone therapy with the male sex hormone testosterone could stop men becoming diabetic, according to new research.
Men with low levels of the hormone are more likely to develop the condition which affects over 3.5 million Britons.
A study found it helps them regulate blood sugar by triggering chemicals in cells within the pancreas that produce the hormone insulin.
Scientists say it could help identify new treatments for type 2 diabetes, the form linked to lifestyle, in the large number of patients lacking the male sex hormone because of age or prostate cancer therapies.
Testosterone is present throughout the body and low levels are associated with increased obesity, a known risk factor for developing type 2 diabetes.
It could help explain why older men are more at risk of developing diabetes because testosterone levels fall in men as they age.
Professor Franck Mauvais-Jarvis, of Tulane University, New Orleans, said: “We have found the cause, and a potential treatment pathway, for type 2 diabetes in testosterone deficient men.
“Our study shows testosterone is an anti-diabetic hormone in men. If we can modulate its action without side effects, it is a therapeutic avenue for type 2 diabetes.”
His researchers used specially bred male mice with pancreatic beta cells lacking a testosterone gene, known as the androgen receptor.
They fed them a Western style diet rich in fats and sugar and tested their response to glucose.
The mice without androgen receptors all developed lower insulin secretion, leading to glucose intolerance compared with normal mice in the control group.
To better understand how testosterone interacted with insulin production within the pancreas, researchers administered testosterone and glucose directly to human pancreatic cells treated with an androgen receptor inhibitor and those harvested from mice without androgen receptors.
In both cases the cells showed decreased insulin production compared to those whose testosterone gene was not blocked or missing.
Further experiments in cultured mouse and human cells showed the insulin-producing effect of testosterone could be abolished by inhibiting the hormone GLP-1, which the body produces after a meal.
The study, published in the journal Cell Metabolism, suggests testosterone boosts the impact of the hormone, which is currently used as a diabetes treatment.