CONTRASTING ADRENERGIC EFFECTS ON LIPOPROTEIN-LIPASE GENE-EXPRESSION IN THE BROWN ADIPOSE-TISSUE OF INTACT MICE AND IN CULTURED BROWN ADIPOCYTES FROM MICE
P. Kuusela et al., CONTRASTING ADRENERGIC EFFECTS ON LIPOPROTEIN-LIPASE GENE-EXPRESSION IN THE BROWN ADIPOSE-TISSUE OF INTACT MICE AND IN CULTURED BROWN ADIPOCYTES FROM MICE, Biochimica et biophysica acta, L. Lipids and lipid metabolism, 1345(3), 1997, pp. 327-337
To examine the regulation of lipoprotein lipase (LPL) gene expression,
LPL mRNA levels in the brown adipose tissue of intact mice and in mou
se brown adipocyte cultures were examined. In intact mice, exposure to
cold resulted in a rapid, transient, 5-fold increase in LPL mRNA leve
l. Norepinephrine (NE) injection could fully mimic the effect of acute
exposure to cold, and LPL mRNA and enzymatic activity were increased
in parallel after NE injection. These results indicated positive adren
ergic control of LPL gene expression in the brown adipose tissue of in
tact mice. In cultured mouse brown adipocytes, the level of spontaneou
sly expressed LPL mRNA decreased in parallel with the progression of b
rown adipocyte differentiation. NE treatment of undifferentiated cells
led to a decrease in LPL mRNA levels. In brown adipocytes that had re
ached a mature state, NE had a small negative or no effect on LPL mRNA
levels, irrespective of whether the experiment was performed in the p
resence or absence of insulin or of newborn-calf serum. It was conclud
ed that LPL gene expression in brown adipose tissue in intact mice is
under adrenergic control but that this gene is not under positive. adr
energic control in cultured brown adipocytes from mice, although these
cells are otherwise adrenergically sensitive. The presence of additio
nal factors may be necessary to confer adrenergic sensitivity to I:he
LPL gene in the cultured brown adipocytes; alternatively, cells other
than the mature brown adipocytes may confer the positive adrenergic se
nsitivity to the brown adipose tissue depots in situ. (C) 1997 Elsevie
r Science B.V.