New York, July 29 (IANS) A hormone system that controls blood pressure and is often targeted to treat heart disease can also lower metabolism as well as promote obesity, says a study.
Besides regulating BP, the renin-angiotensin system (RAS), also plays a role in controlling energy balance and metabolic rate and therefore may be important in obesity.
But, depending on where in the body this hormone system is operating, it can have opposing effects on weight gain, the researchers said.
When the RAS is elevated in the brain, it increases energy expenditure by increasing resting metabolism, resulting in weight loss.
However, increased activity of the RAS circulating in the body (the peripheral RAS) -- which occurs during obesity in humans and experimental animals -- has the opposite effect, decreasing resting metabolism and increasing weight gain.
"At a very simplistic level, you can think of the brain RAS as the gas pedal on metabolism and the peripheral (circulating) RAS as the brake, with angiotensin as the driver," said Justin Grobe, Assistant Professor at the University of Iowa in the US.
The study conducted on mice showed that the circulating angiotensin reduces resting metabolic rate by activating its less common receptor (angiotensin II type 2 receptor or AT2) specifically on subcutaneous fat cells.
"In multiple ways, activation of the AT2 receptor [by increasing the peripheral RAS] is interfering with the capacity of the cell to make heat," Grobe added.
"It is very consistent with the clinical observation that peripheral angiotensin goes up during obesity. This is probably at least one of the mechanisms by which that excess angiotensin is perpetuating obesity. Because it is telling the body to slow down its metabolism as the body gets bigger," he noted in the work published in the journal Cell Reports.
