MRI VAT volume and SAT volume ratios: Biomarkers associated with diabetes/prediabetes

Are visceral and subcutaneous adipose tissues indicators of cardiovascular risk factors in individuals with impaired glucose metabolism? A multi-institutional team of researchers in Germany investigated the association between different parameters of fat depots obtainable by magnetic resonance imaging (MRI) and impaired glucose metabolism in individuals who did not have cardiovascular disease. Their research identified several parameters strongly associated with diabetes status. Data from MRI were utilized because this imaging modality can non-invasively quantify the various fat compartments of a human body.

The researchers reported in the September issue of the British Journal of Radiology that MRI-based visceral adipose tissue (VAT)_volume and VAT/subcutaneous adipose tissue (SAT) _volume ratios were associated with prediabetes and diabetes. Specifically, elevated VAT_volume and VAT/SAT_volume ratio are highly associated with prediabetes and diabetes. Lead author Corinna Storz, MD, of the department of diagnostic and interventional radiology of University Hospital Tuebingen, and co-authors wrote that “the quantification of VAT_volume and VAT_area represents a reproducable and reliable biomarker associated with cardiometabolic risk factors such as obesity and glycemic state.”

The study utilized a population-based cohort of 384 individuals who included 52 patients with diabetes, 97 individuals diagnosed as prediabetic, and 235 healthy controls. They ranged in age from 47 to 65 years, with 58% male and 42% female subjects. None had any known prior cardiovascular disease. All were participants in another clinical trial and had had a whole-body MRI scan as part of the trial.

The research team measured volumetric VAT_volume from the femoral head to the cardiac apex. They calculated the volumetric SAT_volume from the femoral head to the diaphram. They defined the volumetric total adipose tissue (TAT_volume) as the summary of VAT and SAT, calculated from the femoral head to the diaphragm and cardiac apex, respectively. They evaluated the association of body adipose tissue on glycemic status, the association of glycemic status to body adipose tissue, and interactions of glycemic status and body mass index (BMI)/waist circumference.

The association of MR parameters with glycemic status showed that (TAT_volume, SAT_volume, and VAT_volume were significantly higher in patients with prediabetes and diabetes as compared to healthy volunteers. This was also true for the VAT/SAT_volume ratio. The authors also reported that the association between VAT_volume  and glycemic status was stronger than for SAT_volume, VAT/SAT_volume ratio, waist circumference, or BMI.

The research conducted also supports findings from a number of other studies, which the authors discuss in detail in their article. While acknowledging that their population cohort consisted of European Caucasians living in Germany, they concluded, “Our results confirm the strong role of VAT_volume in predicting cardiovascular risk and potentially adverse outcome beyond SAT_volume.” 

“For radiologists, this is particularly of interest as this may represent a meaningful measure to be included in radiology reports in the future,” Dr. Storz told Applied Radiology. “As VAT_volume and impaired glucose metabolism is strongly associated, high VAT_volume is an independent, very relevant proxy for high cardiovascular risk. This is mirrored in findings of other studies indicating that VAT portrays a central role in our cardiomeabolic pathophysiology. As such, it is very likely that assessment of VAT will soon be requested by referring physicians and individuals at risk. While further studies are currently ongoing, I think that it is important for us as radiologists to familiarize with these novel emerging markers of cardiometabolic risk.”

REFERENCE

1. Storz C, Heber SD, Rospleszcz S, et al. The role of visceral and subcutaneous adipose tissue measurements and their ratio by magnetic resonance imaging in subjects with prediabetes, diabetes, and health controls from a general population without cardiovascular disease. Br J Radiol. 2018;91(1089):20170808.