In vitro differentiation of mouse brown preadipocytes is enhanced by IGFBP-3 expression and reduced by IGFBP-3 silencing.
OBJECTIVE
White adipocyte metabolism is regulated by insulin-like growth factor-binding protein (IGFBP)-3, but its effect on brown adipocytes is not known. This study investigated whether IGFBP-3 influences the proliferation and differentiation of brown preadipocytes in primary culture.


METHODS
In vitro growth and differentiation of brown preadipocytes from wild-type mice, transgenic mice overexpressing human IGFBP-3 (PGKBP3), or its non-IGF-binding Gly56/Gly80/Gly81-mutant (PGKmutBP3), and wild-type brown preadipocytes transfected with IGFBP-3 siRNA were studied by us. In addition to IGF-I and IGFBP-3 expression, brown preadipocyte growth and differentiation were assessed by antiproliferating cell nuclear antigen, oil red O, brown fat gene expression, and phosphorylation states of Akt and ERK.


RESULTS
Akt phosphorylation and IGF-I expression were paralleled by initial growth and differentiation and were slower for PGKBP3 brown preadipocytes than PGKmutBP3 and wild-type preadipocytes. Terminal adipocyte differentiation as assessed by lipid accumulation coincided with ERK inhibition and was greatest in PGKmutBP3 cells, followed by PGKBP3 cells and then wild-type cells, whereas adipocyte differentiation was poor after IGFBP-3 siRNA treatment. Thermogenic genes were increased by IGFBP-3 overexpression, but lower in differentiated PGKmutBP3 than PGKBP3 cells.


CONCLUSIONS
Brown adipocyte growth and differentiation in vitro were affected by the manipulation of IGFBP-3 expression, suggesting that IGFBP-3 is a factor regulating brown adipocyte fate.
Department of Internal Medicine, University of Manitoba, Winnipeg, Canada.
K Hoa
KH
Nguyen
Department of Internal Medicine, University of Manitoba, Winnipeg, Canada.
Suresh
S
Mishra
Department of Internal Medicine, University of Manitoba, Winnipeg, Canada.
B L Grégoire
BL
Nyomba
D052437:Adipocytes, Brown / Q000378:metabolism*; D000818:Animals; D002454:Cell Differentiation; D020868:Gene Silencing / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D010766:Phosphorylation; D014162:Transfection
D018972:Insulin-Like Growth Factor Binding Protein 3; D007334:Insulin-Like Growth Factor I