Deep subcutaneous adipose tissue: a distinct abdominal adipose depot.
OBJECTIVE
Abdominal visceral (VAT) and subcutaneous adipose tissue (SAT) display significant metabolic differences, with VAT showing a functional association to metabolic/cardiovascular disorders. A third abdominal adipose layer, derived by the division of SAT and identified as deep subcutaneous adipose tissue (dSAT), may play a significant and independent metabolic role. The aim of this study was to evaluate depot-specific differences in the expression of proteins key to adipocyte metabolism in a lean population to establish a potential physiologic role for dSAT.


METHODS
Adipocytes and preadipocytes were isolated from whole biopsies taken from superficial SAT (sSAT), dSAT, and VAT samples obtained from 10 healthy normal weight patients (7 women and 3 men), with a mean age of 56.4 +/- 4.04 years and a mean BMI of 23.1 +/- 0.5 kg/m2. Samples were evaluated for depot-specific differences in insulin sensitivity using adiponectin, glucose transport protein 4 (GLUT4), and resistin mRNA and protein expression, glucocorticoid metabolism by 11beta-hydroxysteroid dehydrogenase type-1 (11beta-HSD1) expression, and alterations in the adipokines leptin and tumor necrosis factor-alpha (TNF-alpha).


RESULTS
Although no regional differences in expression were observed for adiponectin or TNF-alpha, dSAT whole biopsies and adipocytes, while intermediary to both sSAT and VAT, reflected more of the VAT expression profile of 11beta-HSD1, leptin, and resistin. Only in the case of the intracellular pool of GLUT4 proteins in whole biopsies was an independent pattern of expression observed for dSAT. In an evaluation of the homeostatic model, dSAT 11beta-HSD1 protein (r = 0.9573, p = 0.0002) and TNF-alpha mRNA (r = 0.8210, p = 0.0236) correlated positively to the homeostatic model.


CONCLUSIONS
Overall, dSAT seems to be a distinct abdominal adipose depot supporting an independent metabolic function that may have a potential role in the development of obesity-associated complications.
Walker
Gillian E
GE
Laboratory of Molecular Biology, Istituto Auxologico Italiano, Via L. Cadorna, 90, Piancavallo, VB 28921, Italy. walkergi68@yahoo.com
Verti
Barbara
B
Marzullo
Paolo
P
Savia
Guilio
G
Mencarelli
Monica
M
Zurleni
Francesco
F
Liuzzi
Antonio
A
Di Blasio
Anna Maria
AM
D043205:11-beta-Hydroxysteroid Dehydrogenase Type 1 / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D017667:Adipocytes / Q000378:metabolism; D052242:Adiponectin / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D015153:Blotting, Western; D005260:Female; D005938:Glucocorticoids / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D051275:Glucose Transporter Type 4 / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007041:Hypoxanthine Phosphoribosyltransferase / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D050152:Intra-Abdominal Fat / Q000166:cytology / Q000378:metabolism*; D020738:Leptin / Q000235:genetics / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D040262:Receptors, Vascular Endothelial Growth Factor / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D052243:Resistin / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050151:Subcutaneous Fat / Q000166:cytology / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism
D052242:Adiponectin; D005938:Glucocorticoids; D051275:Glucose Transporter Type 4; D020738:Leptin; C499624:RETN protein, human; D012333:RNA, Messenger; D052243:Resistin; C495692:SLC2A4 protein, human; D014409:Tumor Necrosis Factor-alpha; D043205:11-beta-Hydroxysteroid Dehydrogenase Type 1; D007041:Hypoxanthine Phosphoribosyltransferase; D040262:Receptors, Vascular Endothelial Growth Factor; D005947:Glucose