Blog | Tuesday, September 2, 2014

QD: News Every Day--Adiposity, location of fat may influence diseases

The location of body fat, both in the forms of adiposity and the fat that surrounds body organs, may play a role in diseases, studies reported.

First, people with belly fat are at greater risk of developing hypertension when compared to those with similar body-mass index (BMI) but fat concentrations elsewhere on the body, according to a study published in the Journal of the American College of Cardiology. (JACC)

903 patients enrolled in the Dallas Heart Study were followed for an average of 7 years to track development of hypertension, defined as systolic blood pressure of greater or equal to 140, diastolic blood pressure of greater or equal to 90, or starting blood pressure medications. Researchers then did imaging studies of visceral fat, subcutaneous fat, and lower-body fat.

At the end of the study period, 25% of patients developed hypertension. While higher BMI was associated with increased incidence of hypertension (relative risk [RR], 1.24; 95% CI; 1.12 to 1.36, per 1-SD increase), only abdominal fat remained independently associated with hypertension (RR, 1.22; 95% CI, 1.06 to 1.39, per 1-SD increase). The relationship between abdominal fat and hypertension did not change when factoring in gender, age or race.

The strongest correlation between abdominal fat and hypertension was observed with retroperitoneal fat, which could suggest that the effects from fat around the kidneys are influencing the development of hypertension, the authors wrote. This link could open new avenues for the prevention and management of hypertension.

Also, researchers noted, it’s the first time that fat surrounding the kidneys may have an effect. “Though this is a small fat mass in relative terms, similar paracrine effects have recently been suggested between epicardial fat and the occurrence of coronary artery disease,” they wrote.

An editorial stated that, while the results suggest the need for easier ways to measure the location of fat in the body, “it is reasonable health policy at this time to advocate that all obese individuals lose weight via diet and exercise until there is a compelling rationale for any alternate strategy related to regional fat excess.”

Another study, which was also presented as an abstract at the European Society of Cardiology Congress and published online at JACC, suggested that epicardial adipose tissue volume predicts the progression of coronary artery calcification in the general population.

In that study, researchers 3,367 subjects without known coronary artery disease during enrollment in a population-based study.

Subjects with progression of calcification above the median had higher epicarial adipose tissue volume than subjects with less calcification (101.1 ± 47.1 mL vs. 84.4 ± 43.4 mL; P <0.0001).

In regression analysis, 6.3% (95% CI, 2.3% to 10.4%; P=0.0019) of progression of calcification +1 was attributable to 1 SD of epicardial adipose tissue, which persisted after adjustment for risk factors (6.1%; 95% CI: 1.2% to 11.2%; P=0.014).

Because the correlation between epicardial adipose tissue volume and the progression of coronary artery calcification predominantly driven by the youngest people in the cohort, (45 to 55 years of age), epicardial adiposity may influence the atherosclerosis process at early stages, the authors wrote.

“Interestingly, CAC progression was more pronounced in lean subjects, and association of EAT (epicardial adiposity) with CAC (coronary artery calcification) progression was independent of BMI, suggesting that quantification of EAT volume renders substantially different information than measurement of overall obesity despite their distinctive correlation,” the authors wrote. “The present findings describe the paracrine impact of this local visceral adipose tissue on coronary plaque progression that is different from established mechanisms of atherosclerosis development.”