Bladder control drug may help control weight

Dr Cypess

Mirabegron (Myrbetriq), an oral drug approved by FDA in 2012 for treating incontinence, may help control weight by boosting the metabolic abilities of brown fat, a form of fat that can help to expend energy, according to an early phase clinical study.

Unlike the far more common white fat, brown fat can speed up metabolism in people who are subjected to cold. Scientists had long known that this form of fat is present in babies and young children, and scientists from Joslin Diabetes Center and other institutions demonstrated in 2009 that these cells can be found in adults as well. Experiments in animals revealed that the cells can be activated by various agents, among them drugs that link to a protein on the cell surface called a Beta3-adrenergic receptor.

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A team of investigators led by Joslin Diabetes Center researchers and funded in part by the NIH’s National Institute of Diabetes and Digestive and Kidney Diseases successfully activated brown adipose tissue and increased energy expenditure in 12 lean adult men using mirabegron, a drug that stimulates β3-adrenergic receptors. Brown adipose tissue (BAT), often called brown fat, consumes calories from fat and sugar to generate heat and is normally activated when a person is exposed to cold. At peak effect, the drug boosted energy consumption by more than a tenth in the trial volunteers, suggesting that it might help in losing weight.

“This report is the first showing that human brown fat can be activated in a targeted pharmacological manner,” according to Aaron M. Cypess, MD, PhD, MMSc, investigator and section head, Translational Physiology Diabetes, Endocrinology, and Obesity Branch, NIDDK, NIH.

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“Given that mirabegron is already approved by FDA for the treatment of overactive bladder, there could be increased attempts at off-label use of mirabegron for the purpose of weight loss,” Dr Cypress said. “We strongly recommend against this approach since there is no published evidence to show that chronic use of mirabegron yields any benefit for weight reduction or glucose metabolism.”

There is now an accessible, pharmacological means that can be used to study human brown fat,  Dr Cypress said. “Studies in rodents have already shown that chronic pharmacological activation of brown fat can lead to prevention of obesity and improved glucose metabolism. New studies are under way to determine if similar health benefits can be achieved in humans.”