Suffering from obesity or overweight is a major risk factor for developing hypertension and cardiovascular disease. There are several factors that could be involved; however, precise explanation of the relationship between the two conditions has not yet been clarified.
A team of researchers led by Professor Michael Cowley, director of the Institute of Obesity and Diabetes in the School of Biomedical Sciences at Monash University in Australia, in collaboration with Sadaf Farooqi, University of Cambridge, UK, studied mice and humans who have problems producing or processing the hormone leptin and compared them with ‘healthy’ individuals to see whether this hormone could provide the link.
Leptin hormone is composed of fat and travels through the bloodstream to reach the brain, where it acts as a signal to the energy reserves, adjusting both energy expenditure and the sensation of hunger, hence it is also referred to as ‘satiety hormone’.
The group found that some people with obesity, who are lacking the hormone leptin because of a genetic disorder, had low blood pressure despite being very heavy. This was also the case for those lacking the gene for the leptin receptor in the brain, which means that the brain was unable to respond to the hormone.
Modelling the human condition, Professor Cowley’s team showed that mice with normal leptin signaling developed an increase in blood pressure when they became obese on a high fat diet. These effects were not seen in mice that lacked leptin or where leptin was unable to work because of a defect or block on the leptin receptor.
These experiments demonstrate that leptin signaling is necessary for obesity-induced increased blood pressure. The clinical studies in severely obese humans showed that these observations are relevant to humans.
“High blood pressure is a well-known consequence of obesity. Our study explains the mechanism behind this link, showing that leptin, a hormone secreted by fat, increases blood pressure,” explained Professor Cowley.
The researchers are now investigating the precise pathways in the brain by which leptin acts to regulate blood pressure.
“We now know that leptin regulates both our weight and our blood pressure through its action on the brain. Targeting this action could offer a useful way of helping people fight obesity and associated problems such as high blood pressure and heart disease,” Professor Farooqi, from the Wellcome Trust-Medical Research Council Institute of Metabolic Science added.
The study was published in the journal Cell.
Through: University of Cambridge