COPH researcher: heart fat matters

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Where the body stores fat can have serious systemic effects on health, according to Dr. Amy Alman, assistant professor in the USF College of Public Health’s Department of Epidemiology and Biostatistics.

Alman’s research found that higher levels of pericardial fat, which is fat deposited around the heart, is associated with higher rates of diabetes in adults.

Rather than focusing on visceral body fat, the total body mass index or the total amount of fat on the body, Alman decided to focus on ectopic fat around the heart, also known as pericardial adipose tissue.

Ectopic fat is the type of fat that accumulates in areas of the body that normally does not store large amounts of fat, such as the liver, in between muscles and the heart.

“A lot of research has shown associations between visceral adipose tissue and health outcomes like cardiovascular disease and diabetes. But, fat accumulates in other areas as well,” Alman said.

CT scan of heart

CT scan of the heart illustrating pericardial adipose tissue (in yellow) and lean tissue (red). (Photo courtesy of Amy Alman)

 

Alman’s research “Higher pericardial adiposity is associated with prevalent diabetes: The Coronary Artery Risk Development in Young Adults,” was published online in Dec. 2015 in Nutrition, Metabolism & Cardiovascular Disease.

“We have a big epidemic of obesity and Type 2 diabetes in this country, and obesity and Type 2 diabetes are very strongly linked,” Alman said. “The question is whether fat distribution is more important than overall volume.”

Alman used data from the Coronary Artery Risk Development in Young Adults (CARDIA) study to examine the impact of pericardial adipose tissue and prevalence of diabetes.

The CARDIA study began in 1985 to 1986, enrolling young adults, aged 18 to 30 years old, who have been followed for 30 years to examine risk factors for cardiovascular disease, according to Alman.

Participants were from one of four cities: Birmingham, Chicago, Minneapolis and Oakland. In total, Alman examined data pulled from 3,107 participants during their year 25 exams.

“The reason it’s a good study is, one, it’s so large, and, two, it’s prospective,” she said. “When they enrolled they didn’t have cardiovascular disease and weren’t selected to have particular outcomes. They are a good cohort to look at for novel risk factors and what might lead to cardiovascular disease. It’s a well done study and you can robustly control for the traditional risk factors while identifying novel risk factors.”

Alman said that while numerous studies have examined the relationship between visceral fat, such as the fat around the waist or abdomen, and diabetes, very few examine the effect of ectopic fat.

“We’re really showing that yes, visceral abdominal fat is important, but guess what? So is pericardial fat and it’s independent of visceral fat,” she said.

Amy Alman

Amy Alman, PhD

 

Alman said some participants of CARDIA exhibited low visceral fat but high ectopic fat, which indicated that some individuals might appear physically healthy and with normal BMI, but actually have high concentrations of fat around their hearts.

“[Fat] has function that goes beyond what we see. So, understanding the biological characteristics, how it varies from individual to individual and what can we do to switch functioning from metabolically unhealthy to metabolically healthy has the potential to have a huge public health impact,” Alman said.

While the body commonly deposits fat around the abdomen, Alman said it may be more important to recognize where ectopic fat is accumulating rather than one’s total volume of fat.

Alman also said an important characteristic of her study is that it points to the importance of understanding the biological functioning of fat to better understand how to make appropriate interventions for individuals.

Heart

It is possible that one may not exhibit signs of visceral fat, but have fat concentrated around the heart. (iStock photo)

 

“When we advise people that they need to lose weight there may be more we need to know than just what the weight number is on the scale or what their BMI is,” she said. “The BMI number misses a lot of the story.”

Alman hopes to continue her research in this field to keep examining the systemic effects ectopic fat is having on the body and, particularly, the factors that lead to ectopic fat storage.

“I think that you can’t say it doesn’t have systemic effects and that is what is really driving me to keep looking at this,” she said. “I do think that ectopic fat does have systemic effects and that fat distribution is an important characteristic that we need to understand on a broader level in order to identify those at higher risk and provide better inventions for those at risk.”

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Alman, A.C., et al. Higher pericardial adiposity is associated with prevalent diabetes: The Coronary Artery Risk Development in Young Adults Study. Nutrition, Metabolism & Cardiovascular Disease (2016), http://dx.doi.org/10.1016/j.numecd.2015.12.011

 

Story by Anna Mayor, USF College of Public Health.