Relationship between adipocyte size and adipokine expression and secretion.
BACKGROUND
Adipocytes are known to release a variety of factors that may contribute to the proinflammatory state characteristic for obesity. This secretory function is considered to provide the basis for obesity-related complications such as type 2 diabetes and atherosclerosis.


OBJECTIVE
To get a better insight into possible underlying mechanisms, we investigated the effect of adipocyte size on adipokine production and secretion.


METHODS
Protein secretion and mRNA expression in cultured adipocytes separated according to cell size from 30 individuals undergoing elective plastic surgery were investigated.


RESULTS
The mean adipocyte volume of the four fractions ranged from 205 +/- 146 to 1.077 +/- 471 pl. There were strong linear correlations for the secretion of adipokines over time. Secretion of leptin, IL-6, IL-8, TNF-alpha, monocyte chemoattractant protein-1, interferon-gamma-inducible protein 10, macrophage inflammatory protein-1beta, granulocyte colony stimulating factor, IL-1ra, and adiponectin was positively correlated with cell size. After correction for cell surface, there was still a significant difference between fraction IV (very large) and fraction I (small cells), for leptin, IL-6, IL-8, monocyte chemoattractant protein-1, and granulocyte colony-stimulating factor. In contrast, antiinflammatory factors such as IL-1ra and adiponectin lost their association after correction for cell surface area comparing fraction I and IV. In addition, there was a decrease of IL-10 secretion with increasing cell size.


CONCLUSIONS
The results clearly suggest that adipocyte size is an important determinant of adipokine secretion. There seems to be a differential expression of pro- and antiinflammatory factors with increasing adipocyte size resulting in a shift toward dominance of proinflammatory adipokines largely as a result of a dysregulation of hypertrophic, very large cells.
Skurk
Thomas
T
Else Kröner-Fresenius-Centre for Nutritional Medicine, Technical University Munich, Am Forum 5, D-85350 Freising-Weihenstephan, Germany. nutritional.medicine@wzw.tum.de
Alberti-Huber
Catherine
C
Herder
Christian
C
Hauner
Hans
H
D017667:Adipocytes / Q000166:cytology* / Q000378:metabolism; D052242:Adiponectin / Q000235:genetics* / Q000378:metabolism*; D000328:Adult; D002469:Cell Separation; D048429:Cell Size; D002478:Cells, Cultured; D005260:Female; D006801:Humans; D007378:Interleukins / Q000097:blood / Q000235:genetics* / Q000378:metabolism*; D020738:Leptin / Q000235:genetics* / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D012333:RNA, Messenger / Q000032:analysis; D013997:Time Factors
D052242:Adiponectin; D007378:Interleukins; D020738:Leptin; D012333:RNA, Messenger