Human Brown Adipose Tissue Temperature and Fat Fraction Are Related to Its Metabolic Activity.
The metabolic activity of human brown adipose tissue (BAT) has been previously examined using positron emission tomography (PET). The aim of this study was to use proton magnetic resonance spectroscopy (1H MRS) to investigate whether the temperature and the fat fraction (FF) of BAT and white adipose tissue (WAT) are associated with BAT metabolic activity determined by deoxy-2-18F-fluoro-d-glucose (18F-FDG)-PET.



Ten healthy subjects (four women, six men; 25 to 45 years of age) were studied using PET-magnetic resonance imaging during acute cold exposure and at ambient room temperature. BAT and subcutaneous WAT 1H MRS were measured. The tissue temperature and the FF were derived from the spectra. Tissue metabolic activity was studied through glucose uptake using dynamic FDG PET scanning during cold exposure. A 2-hour hyperinsulinemic euglycemic clamp was performed on eight subjects.



The metabolic activity of BAT associated directly with the heat production capacity and inversely with the FF of the tissue. In addition, the lipid-burning capacity of BAT associated with whole-body insulin sensitivity. During cold exposure, the FF of BAT was lower than at room temperature, and cold-induced FF of BAT associated inversely with high-density lipoprotein and directly with low-density lipoprotein cholesterol.



Both 1H MRS-derived temperature and FF are promising methods to study BAT activity noninvasively. The association between the lipid-burning capacity of BAT and whole-body insulin sensitivity emphasizes the role of BAT in glucose handling. Furthermore, the relation of FF to high-density lipoprotein and low-density lipoprotein cholesterol suggests that BAT has a role in lipid clearance, thus protecting tissues from excess lipid load.
Turku PET Centre and.|Turku PET Centre.
Kalle
K
Koskensalo
Turku PET Centre and.|Turku PET Centre.
Juho
J
Raiko
Turku PET Centre and.|Turku PET Centre.
Teemu
T
Saari
Turku PET Centre.|Department of Medical Physics.
Virva
V
Saunavaara
Turku PET Centre and.|Turku PET Centre.
Olli
O
Eskola
Turku PET Centre and.|Turku PET Centre.
Pirjo
P
Nuutila
Department of Medical Physics.
Jani
J
Saunavaara
Department of Radiology, University of Turku, 20520 Turku, Finland.|Medical Imaging Centre of Southwest Finland, and.|Department of Radiology, Turku University Hospital, 20520 Turku, Finland.
Riitta
R
Parkkola
Turku PET Centre and.|Turku PET Centre.
Kirsi A
KA
Virtanen
D002001:Adipose Tissue, Brown / Q000000981:diagnostic imaging / Q000378:metabolism*; D050154:Adiposity / Q000502:physiology*; D000328:Adult; D001833:Body Temperature Regulation / Q000502:physiology*; D003080:Cold Temperature; D005240:Feasibility Studies; D005260:Female; D019788:Fluorodeoxyglucose F18; D015309:Glucose Clamp Technique; D064368:Healthy Volunteers; D006801:Humans; D007333:Insulin Resistance; D008075:Lipoproteins, HDL / Q000378:metabolism; D008077:Lipoproteins, LDL / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D050151:Subcutaneous Fat / Q000378:metabolism; D062125:Thermometry / Q000379:methods*
D008075:Lipoproteins, HDL; D008077:Lipoproteins, LDL; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18