Serum retinol-binding protein is more highly expressed in visceral than in subcutaneous adipose tissue and is a marker of intra-abdominal fat mass.
Intra-abdominal fat is associated with insulin resistance and cardiovascular risk. Levels of serum retinol-binding protein (RBP4), secreted by fat and liver cells, are increased in obesity and type 2 diabetes (T2D). Here we report that, in 196 subjects, RBP4 is preferentially expressed in visceral (Vis) versus subcutaneous (SC) fat. Vis fat RBP4 mRNA was increased approximately 60-fold and 12-fold in Vis and SC obese subjects respectively versus lean subjects, and approximately 2-fold with impaired glucose tolerance/T2D subjects versus normoglycemic subjects. In obese subjects, serum RBP4 was increased 2- to 3-fold, and serum transthyretin, which stabilizes RBP4 in the circulation, was increased 35%. Serum RBP4 correlated positively with adipose RBP4 mRNA and intra-abdominal fat mass and inversely with insulin sensitivity, independently of age, gender, and body mass index. RBP4 mRNA correlated inversely with GLUT4 mRNA in Vis fat and positively with adipocyte size in both depots. RBP4 levels are therefore linked to Vis adiposity, and Vis fat may be a major source of RBP4 in insulin-resistant states.
Klöting
Nora
N
Department of Internal Medicine III, University of Leipzig, D-04103 Leipzig, Germany.
Graham
Timothy E
TE
Berndt
Janin
J
Kralisch
Susan
S
Kovacs
Peter
P
Wason
Christopher J
CJ
Fasshauer
Mathias
M
Schön
Michael R
MR
Stumvoll
Michael
M
Blüher
Matthias
M
Kahn
Barbara B
BB
D000273:Adipose Tissue / Q000166:cytology / Q000378:metabolism; D000328:Adult; D015415:Biomarkers / Q000378:metabolism*; D015992:Body Mass Index; D003924:Diabetes Mellitus, Type 2 / Q000097:blood* / Q000235:genetics / Q000378:metabolism; D005260:Female; D006801:Humans; D007333:Insulin Resistance; D050152:Intra-Abdominal Fat / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000097:blood*; D011228:Prealbumin / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012177:Retinol-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D054839:Retinol-Binding Proteins, Plasma; D050151:Subcutaneous Fat / Q000378:metabolism* / Q000473:pathology; D013851:Thinness / Q000097:blood
D015415:Biomarkers; D011228:Prealbumin; C101326:RBP4 protein, human; D012333:RNA, Messenger; D012177:Retinol-Binding Proteins; D054839:Retinol-Binding Proteins, Plasma