Researchers from University of Wisconsin (UW)-Madison have developed an MRI-based fat quantification method that separately measures brown adipose tissue (BAT) and white adipose tissue (WAT).

Previously regarded as a simple thermoregulator useful for infants and hibernating animals, BAT may in fact have health promoting properties. In addition, low levels of dermal WAT (dWAT) may be positively correlated with the activation of BAT’s anti-obesity and anti-inflammatory properties, according to UW Professor of Oncology Caroline Alexander, PhD.

The seed for this imaging technique was planted in 2010, when UW’s James T Ntambi, PhD, mapped the effects of an obesity-resistant gene not to fat or liver or muscle, but to skin. After seeing Ntambi talk about his conclusions, Alexander measured the dermal fat in obesity-resistant mice, finding that it was much thinner than normal. However, when they measured dWAT in a group of 10 normal human subjects, they found that it varied from person to person, with no correlation to overall body fat.

“dWAT could be an independent genetic determinant of metabolic health, obesity and diabetes,” said Alexander. “The question is: How to we integrate this knowledge into MRI to start asking the right questions?”

Enter UW Assistant Professor Diego Hernando, PhD. A longtime member of UW’s MRI Research Group, Hernando designed chemical shift-encoded, fat-only imaging that allows measurement of both bWAT and dWAT on existing MRI scanners.

“We applied techniques we’ve been working on for years to rapidly generate a map of fat distribution—not just dermal, but white and brown adipose tissue as well,” said Hernando.

Another wrinkle was reproducibility; the scan had to be compatible with as many MRI scanners as possible, to ensure consistency across clinical studies, Alexander explained.

The next step is testing the thickness of dWAT for connections with other conditions, including diabetes, obesity and lipodystrophy. A thicker layer of dWAT may correspond to non-activation of BAT, increasing the risk of diabetes or obesity.

“This offers the opportunity to identify molecular factors that promote obesity, and to stratify the population as obesity resistant or susceptible. In addition, the scan could be used to assess the response of dWAT to interventions such as drug treatments, diet changes and environmental conditions,” wrote Alexander et al.