Adiponectin receptors in human adipose tissue: effects of obesity, weight loss, and fat depots.
OBJECTIVE
To investigate the presence and regulatory properties of the adiponectin receptors, AdipoR1 and AdipoR2, in human adipose tissue (AT) and in isolated human adipocytes.


METHODS
The effect of obesity, weight loss, and gender on expression of AdipoR1 and AdipoR2 was investigated in subcutaneous AT. The influence of fat distribution on these receptors was investigated in paired samples of subcutaneous and omental AT. Gene expression of these receptors was quantified by reverse transcriptase-polymerase chain reaction.


RESULTS
AdipoR1 mRNA levels were approximately 10-fold higher than adipoR2 in both AT fragments and in isolated adipocytes. AdipoR1 expression was lower in AT from obese subjects (p < 0.05) compared with that from normal-weight subjects, and AdipoR1 displayed a negative correlation with BMI (r = -0.53, p < 0.01). In obese subjects, weight loss (approximately 12 kg) increased AdipoR1 expression by 80% in AT (p < 0.01). Concerning regional differences, AdipoR1 showed significantly lower expression in omental AT than in subcutaneous AT (p < 0.01). No gender difference was observed in the expression of these receptors. In human preadipocyte cultures, AdipoR1 expression was not induced during the differentiation process, whereas AdipoR2 was induced by 5-fold (p < 0.05).


CONCLUSIONS
AdipoR1 is highly expressed in human AT, indicating that adiponectin may have biological effects in AT in an autocrine/paracrine manner. AdipoR1 expression in AT is reduced in obese subjects and is increased after weight loss. Thus, it can be suggested that adiponectin might have reduced biological effects in AT due to low levels of adiponectin receptors in obese subjects and in omental adipocytes, which may further aggravate the negative metabolic effect of low levels of adiponectin characterizing the obese state.
Department of Endocrinology and Metabolism C, Aarhus University Hospital, Aarhus Sygehus, Tage Hansensgade 2, DK-8000 Aarhus C, Denmark.
Maria S
MS
Rasmussen
Aina S
AS
Lihn
Steen B
SB
Pedersen
Jens M
JM
Bruun
Mads
M
Rasmussen
Bjørn
B
Richelsen
D017667:Adipocytes / Q000378:metabolism*; D052242:Adiponectin / Q000378:metabolism; D000328:Adult; D015992:Body Mass Index; D016022:Case-Control Studies; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D008875:Middle Aged; D009765:Obesity / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D054419:Receptors, Adiponectin; D011956:Receptors, Cell Surface / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015431:Weight Loss
C499918:ADIPOQ protein, human; C475418:ADIPOR1 protein, human; C475420:ADIPOR2 protein, human; D052242:Adiponectin; D012333:RNA, Messenger; D054419:Receptors, Adiponectin; D011956:Receptors, Cell Surface