title: PET imaging reveals distinctive roles for different regional adipose tissue depots in systemic glucose metabolism in nonobese humans.
abstract: Excess amounts of abdominal subcutaneous (SAT) and visceral (VAT) adipose tissue (AT) are associated with insulin resistance, even in normal-weight subjects. In contrast, gluteal-femoral AT (GFAT) is hypothesized to offer protection against insulin resistance. Dynamic PET imaging studies were undertaken to examine the contributions of both metabolic activity and size (volume) of these depots in systemic glucose metabolism. Nonobese, healthy volunteers (n = 15) underwent dynamic PET imaging uptake of [¹⁸F]FDG at a steady-state (20 mU·m⁻²·min⁻¹) insulin infusion. PET images of tissue [¹⁸F]FDG activity were coregistered with MRI to derive K values for insulin-stimulated rates of fractional glucose uptake within tissue. Adipose tissue volume was calculated from DEXA and MRI. VAT had significantly higher rates of fractional glucose uptake per volume than SAT (P < 0.05) or GFAT (P < 0.01). K(GFAT) correlated positively (r = 0.67, P < 0.01) with systemic insulin sensitivity [glucose disappearance rate (R(d))] and negatively with insulin-suppressed FFA (r = -0.71, P < 0.01). SAT (r = -0.70, P < 0.01) and VAT mass (r = -0.55, P < 0.05) correlated negatively with R(d), but GFAT mass did not. We conclude that rates of fractional glucose uptake within GFAT and VAT are significantly and positively associated with systemic insulin sensitivity in nonobese subjects. Furthermore, whereas SAT and VAT amounts are confirmed to relate to systemic insulin resistance, GFAT amount is not associated with insulin resistance. These dynamic PET imaging studies indicate that both quantity and quality of specific AT depots have distinct roles in systemic insulin resistance and may help explain the metabolically obese but normal-weight phenotype.
authors.affiliation: Division of Endocrinology and Metabolism, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.
authors.forename: Jason M
authors.initials: JM
authors.lastname: Ng
authors.forename: Koichiro
authors.initials: K
authors.lastname: Azuma
authors.forename: Carol
authors.initials: C
authors.lastname: Kelley
authors.forename: Richard
authors.initials: R
authors.lastname: Pencek
authors.forename: Zofia
authors.initials: Z
authors.lastname: Radikova
authors.forename: Charles
authors.initials: C
authors.lastname: Laymon
authors.forename: Julie
authors.initials: J
authors.lastname: Price
authors.forename: Bret H
authors.initials: BH
authors.lastname: Goodpaster
authors.forename: David E
authors.initials: DE
authors.lastname: Kelley
mesh_terms: D015502:Absorptiometry, Photon; D000273:Adipose Tissue / Q000000981:diagnostic imaging* / Q000378:metabolism* / Q000473:pathology; D050154:Adiposity; D000328:Adult; D015992:Body Mass Index; D015331:Cohort Studies; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D019788:Fluorodeoxyglucose F18; D005947:Glucose / Q000378:metabolism*; D015309:Glucose Clamp Technique; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D007333:Insulin Resistance; D050152:Intra-Abdominal Fat / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology; D035002:Lower Extremity; D008279:Magnetic Resonance Imaging; D008297:Male; D050177:Overweight / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000473:pathology; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D050507:Subcutaneous Fat, Abdominal / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology
chemical_list: D005230:Fatty Acids, Nonesterified; D007328:Insulin; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D005947:Glucose