Two disorders that often occur together — type 2 diabetes and high blood pressure — may have a common link in a hormone called aldosterone, researchers suggest.
Aldosterone has already been implicated in the development of high blood pressure (hypertension). Now, a new study reports that people with higher levels of aldosterone had more than twice the odds of developing type 2 diabetes. Researchers also found that the link between aldosterone and diabetes was stronger among some racial groups.
Aldosterone is a hormone that helps the body hold onto sodium. It also helps regulate the body's fluid levels, according to the researchers.
"The hormone aldosterone is one potential link between the development of hypertension and diabetes," said the study's lead author, Dr. Joshua Joseph. He's an endocrinologist at Ohio State Wexner Medical Center, in Columbus.
Joseph explained that aldosterone can increase how much sodium the kidneys take in. When this happens, overall fluid levels in the body increase and blood vessels constrict. These factors can lead to high blood pressure.
In type 2 diabetes, he said, aldosterone can affect how the body uses another hormone — insulin. Insulin ushers sugar from foods into the body's cells so it can be used as fuel to provide energy.
"The two major causes of type 2 diabetes are an inability to utilize insulin — 'insulin resistance' — or impaired insulin secretion from the pancreas," Joseph explained. "Aldosterone has been shown to cause insulin resistance in muscle, and impair insulin secretion from the pancreas."
Almost 30 million Americans have diabetes, according to the U.S. Centers for Disease Control and Prevention.
Dr. Joel Zonszein, director of the Clinical Diabetes Center at Montefiore Medical Center, in New York City, is not convinced that aldosterone plays a significant role in type 2 diabetes.
"When we use spironolactone [a drug that can treat high blood pressure and reduce aldosterone levels], we don't see a reduction in insulin resistance or an improvement in insulin sensitivity," Zonszein said.
"If aldosterone plays of role in the development of type 2 diabetes, it's a very minimal role," he added.
Joseph and his colleagues are already planning a clinical trial to show whether there is a cause-and-effect relationship between aldosterone and type 2 diabetes. They've received a grant from the U.S. National Institutes of Health for the future research.
The current study looked at data on almost 1,600 people from a previous study designed to track hardening of the blood vessels over time. Participants were from diverse populations in the United States. During 10.5 years of follow-up, just over 100 people developed type 2 diabetes.
Overall, the study found that people who had elevated aldosterone levels were more than twice as likely to develop type 2 diabetes. Black people with higher aldosterone levels had almost triple the risk. Chinese-Americans were almost 10 times more likely to develop diabetes if they had high aldosterone, the findings showed.
Joseph said, "We still don't know why there are differences among diverse populations." He suggested that differences in genetics or salt sensitivity might play a role.
Zonszein said the study findings were interesting, but he doesn't think aldosterone will be shown to have a significant role in the way the body uses and controls blood sugar.
Although it's too early to apply these findings to clinical care, Joseph said people can lower their aldosterone levels through a healthy lifestyle. That includes eating healthy foods, maintaining a healthy weight, exercising regularly and not smoking.
The study findings were published online Sept. 4 in the Journal of the American Heart Association.
Learn more about preventing type 2 diabetes from the U.S. National Institute of Diabetes and Digestive and Kidney Diseases.
SOURCES: Joshua Joseph, M.D., endocrinologist, Ohio State Wexner Medical Center, Columbus, Ohio; Joel Zonszein, M.D., director, Clinical Diabetes Center, Montefiore Medical Center, New York City; Sept. 4, 2018, Journal of the American Heart Association, online