Association of proton density fat fraction in adipose tissue with imaging-based and anthropometric obesity markers in adults

Abstract

Background/Objectives:The purpose of this study was to examine the relationship of the proton density fat fraction (PDFF), measured by magnetic resonance imaging (MRI), of supraclavicular and gluteal adipose tissue with subcutaneous and visceral adipose tissue (SAT and VAT) volumes, liver fat fraction and anthropometric obesity markers. The supraclavicular fossa was selected as a typical location where brown adipocytes may be present in humans and the gluteal region was selected as a typical location enclosing primarily white adipocytes.Subjects/Methods:In this cross-sectional study, 61 adults (44 women, median age 29.3 years, range 21–68 years) underwent an MRI examination of the neck and the abdomen/pelvis (3T, Ingenia, Philips Healthcare). PDFF maps of the supraclavicular and gluteal adipose tissue and the liver were generated. Volumes of SAT and VAT were calculated and supraclavicular and subcutaneous fat were segmented using custom-built post-processing algorithms. Body mass index (BMI), waist circumference and waist-to-height ratio were recorded. Statistical analysis was conducted using the Student's t-test and Pearson correlation analysis.Results:Mean supraclavicular PDFF was 75.3±4.7% (range 65.4–83.8%) and mean gluteal PDFF was 89.7±2.9% (range 82.2-94%), resulting in a significant difference (P<0.0001). Supraclavicular PDFF was positively correlated with VAT (r=0.76, P<0.0001), SAT (r=0.73, P<0.0001), liver PDFF (r=0.42, P=0.0008) and all measured anthropometric obesity markers. Gluteal subcutaneous PDFF also correlated with VAT (r=0.59, P<0.0001), SAT (r=0.63, P<0.0001), liver PDFF (r=0.3, P=0.02) and anthropometric obesity markers.Conclusions:The positive correlations between adipose tissue PDFF and imaging, as well as anthropometric obesity markers suggest that adipose tissue PDFF may be useful as a biomarker for improving the characterization of the obese phenotype, for risk stratification and for selection of appropriate treatment strategies.

Differentiating supraclavicular from gluteal adipose tissue based on simultaneous PDFF and T2* mapping using a 20‐echo gradient‐echo acquisition

“…The significant difference between the PDFF in different fat regions for both 6‐ and 20‐echo data detected in the present analysis is in accordance with results from other studies where the MRI fat fraction differed between supraclavicular and subcutaneous adipose tissue, presumably due to differences in adipose tissue composition and the presence of BAT in the supraclavicular, but not in the subcutaneous adipose tissue . The assumption of a difference in T 2 * relaxation times in BAT compared with WAT is based on the knowledge about differences in tissue composition, with BAT having more mitochondria and thus a higher iron content as well as denser vasculature.…”

“…Exclusion criteria for MRI measurements were pregnancy and standard contraindications for MRI examinations. The study design as well as the results regarding associations between MR and clinical parameters have been previously described in detail . For this analysis, we focused on a subset of subjects where a 20‐multiecho gradient echo acquisition of the supraclavicular and pelvic region had been performed.…”

“…For the segmentation of the supraclavicular fat depot, an in‐house semiautomatic segmentation tool implemented in MatLab was used, as previously described in detail . Average PDFF‐values (in %) as well as T 2 * times of each resulting volume of interest were recorded.…”

“…These MRI techniques can be used for differentiating the compositional difference between WAT and BAT based on simultaneous mapping of the proton density fat fraction (PDFF) and T 2 * relaxation time . Specifically, there have been multiple studies showing that PDFF is lower in the BAT‐containing supraclavicular region compared with WAT depots, presumably due to the lower lipid content and higher water content of BAT compared with WAT . T 2 * relaxation times also have been reported to be shorter in supraclavicular fat compared with WAT, accounting for the increased microscopic magnetic field inhomogeneity due to the increased water content, the presence of mitochondria, and the different perfusion and oxygenation of the supraclavicular fat.…”

Magnetic Resonance Imaging of Adipose Tissue in Metabolic Dysfunction

“…PDFF has been validated in the liver against reference histological methods [23 -25]. In adipose tissues, PDFF shows a high variability, ranging from values as low as 50 -65 % in BAT up to 90 -100 % in WAT [13,26,27].…”