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Magnetic resonance imaging cooling–reheating protocol indicates decreased fat fraction via lipid consumption in suspected brown adipose tissue
Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för kirurgiska vetenskaper, Radiologi.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för visuell information och interaktion. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Bildanalys och människa-datorinteraktion.
Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för kirurgiska vetenskaper, Radiologi.
Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för medicinsk cellbiologi.
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2015 (Engelska)Ingår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 10, nr 4, artikel-id e0126705Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

OBJECTIVES: To evaluate whether a water-fat magnetic resonance imaging (MRI) cooling-reheating protocol could be used to detect changes in lipid content and perfusion in the main human brown adipose tissue (BAT) depot after a three-hour long mild cold exposure.

MATERIALS AND METHODS: Nine volunteers were investigated with chemical-shift-encoded water-fat MRI at baseline, after a three-hour long cold exposure and after subsequent short reheating. Changes in fat fraction (FF) and R2*, related to ambient temperature, were quantified within cervical-supraclavicular adipose tissue (considered as suspected BAT, denoted sBAT) after semi-automatic segmentation. In addition, FF and R2* were quantified fully automatically in subcutaneous adipose tissue (not considered as suspected BAT, denoted SAT) for comparison. By assuming different time scales for the regulation of lipid turnover and perfusion in BAT, the changes were determined as resulting from either altered absolute fat content (lipid-related) or altered absolute water content (perfusion-related).

RESULTS: sBAT-FF decreased after cold exposure (mean change in percentage points = -1.94 pp, P = 0.021) whereas no change was observed in SAT-FF (mean = 0.23 pp, P = 0.314). sBAT-R2* tended to increase (mean = 0.65 s-1, P = 0.051) and SAT-R2* increased (mean = 0.40 s-1, P = 0.038) after cold exposure. sBAT-FF remained decreased after reheating (mean = -1.92 pp, P = 0.008, compared to baseline) whereas SAT-FF decreased (mean = -0.79 pp, P = 0.008, compared to after cold exposure).

CONCLUSIONS: The sustained low sBAT-FF after reheating suggests lipid consumption, rather than altered perfusion, as the main cause to the decreased sBAT-FF. The results obtained demonstrate the use of the cooling-reheating protocol for detecting changes in the cervical-supraclavicular fat depot, being the main human brown adipose tissue depot, in terms of lipid content and perfusion.

Ort, förlag, år, upplaga, sidor
2015. Vol. 10, nr 4, artikel-id e0126705
Nationell ämneskategori
Radiologi och bildbehandling
Forskningsämne
Datoriserad bildbehandling
Identifikatorer
URN: urn:nbn:se:uu:diva-254074DOI: 10.1371/journal.pone.0126705ISI: 000353713100132PubMedID: 25928226OAI: oai:DiVA.org:uu-254074DiVA, id: diva2:817004
Tillgänglig från: 2015-04-30 Skapad: 2015-06-04 Senast uppdaterad: 2019-04-15Bibliografiskt granskad
Ingår i avhandling
1. Magnetic Resonance Imaging of Human Brown Adipose Tissue: Methodological Development and Application
Öppna denna publikation i ny flik eller fönster >>Magnetic Resonance Imaging of Human Brown Adipose Tissue: Methodological Development and Application
2019 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Brown adipose tissue (BAT) is a thermogenic organ with the main human depot located in the cervical-supraclavicular (sBAT) region. BAT is proposed as a potential therapeutic target for obesity and diabetes. This thesis aims to contribute to the development of magnetic resonance imaging (MRI)-based methods and to the application of these in studies of human BAT. Water-fat MRI enables separation of water and fat, the dominant contributors to the MR signal, and the quantification of fat fraction (FF) and effective transverse relaxation rate (R2*). FF and R2* are often used in studies of human BAT, e.g. for characterizing the tissue and distinguishing it from white adipose tissue. A Cooling-reheating protocol was introduced for studying changes in sBAT, related to lipid content and perfusion. sBAT FF decreased after cold exposure. The sustained low FF after reheating suggested lipid consumption as the primary cause. This conclusion was based on the assumption of a normalized perfusion after reheating. An automated method for segmentation of sBAT was developed. The method compared well with a semi-automated reference method with respect to segmentation overlap and estimated mean sBAT FF and R2*. A modified version of the automated method was applied to a large-scale study where an association between sBAT FF and glucose tolerance indicated a role for BAT in glucose metabolism, potentially linked to the risk of developing diabetes.  A Cooling-reheating protocol was evaluated with positron emission tomography measurements of perfusion and cold-stimulated BAT activity. Inverse correlations between sBAT FF and BAT activity suggested sBAT FF to predict cold-induced BAT activity. After reheating, the cold-induced increase in perfusion normalized and the cold-induced decrease in FF partially normalized. This suggested potential decreases in FF after reheating to mainly be due to lipid consumption and decreases in FF after cold exposure to possibly be influenced by perfusion.

Ort, förlag, år, upplaga, sidor
Uppsala: Acta Universitatis Upsaliensis, 2019. s. 83
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1572
Nyckelord
Brown adipose tissue, Magnetic resonance imaging, Positron emission tomography, Image segmentation, Glucose metabolism
Nationell ämneskategori
Medicin och hälsovetenskap Radiologi och bildbehandling
Identifikatorer
urn:nbn:se:uu:diva-381766 (URN)978-91-513-0651-3 (ISBN)
Disputation
2019-06-07, Rosénsalen, Entrance 95/96, Akademiska sjukhuset, Uppsala, 09:15 (Engelska)
Opponent
Handledare
Tillgänglig från: 2019-05-17 Skapad: 2019-04-15 Senast uppdaterad: 2019-06-18

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