Whole-body FDG-PET scans revealed that visceral adipose tissue (VAT) has increased glucose uptake compared with subcutaneous adipose tissue (SAT) and the differences in stromal metabolic activity can aid in cardiovascular risk stratification, according to a study published in this month’s Journal of American College of Cardiology: Cardiovascular Imaging.
VAT burden correlates better with cardiovascular risk than does SAT burden. In the study, Thomas Christen, MD, PhD, from the division of cardiovascular medicine at Brigham and Women’s Hospital in Boston, and colleagues retrospectively studied tissue-specific glucose uptake in vivo in clinically obtained whole-body FDG-PET scans in humans.
Whole-body FDG-PET scans from 31 obese and 26 lean patients revealed that VAT exhibited higher FDG uptake compared with SAT independent of age, sex, body mass index, comorbidities and medications, according to Christen and colleagues.
The researchers also assessed glucose uptake in vitro, using stromal vascular cells isolated from SAT and VAT of diet-induced obese C57BL/6 mice and found that stromal vascular cells from VAT exhibited higher glucose uptake than those from SAT.
Christen and colleagues also evaluated the expression of glucose transporters and hexokinases and found that there was increased expression of hexokinase-1in VAT-derived compared with SAT-derived stromal vascular cells. This affirms that different fat deposits associated with distinct clinical outcomes exhibit differential metabolic activity, noted the authors.
“This article moves our understanding beyond the initial findings that 1) not all adipose tissue is alike and 2) adipocytes can make and respond to hormones and cytokines to realizing that adipose tissue is a complex environment composed of varying amounts of many different types of cells including the stromal vascular cell fraction,” wrote Robert J. Gropler, MD, professor of radiology and Linda R. Peterson, MD, associate professor of medicine and radiology, both with the cardiovascular division at Washington University School of Medicine in St. Louis, in an accompanying editorial.
The study highlights the potential of imaging techniques to delineate how biological events remote from the cardiovascular system may influence disease involving this system, according to Gropler and Peterson.
The findings also underscore the limitations of more generalized biological imaging techniques such as the measurement of glucose uptake and emphasize the need for the development of molecular imaging approaches that noninvasively target specific cell types and/or biological processes that comprise VAT and contribute to cardiovascular disease, Gropler and Peterson concluded.