Characterization of the inhibitory effect of growth hormone on primary preadipocyte differentiation

LH Hansen, B Madsen, B Teisner… - Molecular …, 1998 - academic.oup.com
LH Hansen, B Madsen, B Teisner, JH Nielsen, N Billestrup
Molecular endocrinology, 1998academic.oup.com
GH exerts adipogenic activity in several preadipocyte cell lines, whereas in primary rat
preadipocytes, GH has an antiadipogenic activity. To better understand the molecular
mechanism involved in adipocyte differentiation, the expression of adipocyte-specific genes
was analyzed in differentiating preadipocytes in response to GH. We found that the
expression of both adipocyte determination and differentiation factor 1 (ADD1) and
peroxisome proliferator activated receptor γ (PPARγ) was induced in preadipocytes during …
Abstract
GH exerts adipogenic activity in several preadipocyte cell lines, whereas in primary rat preadipocytes, GH has an antiadipogenic activity. To better understand the molecular mechanism involved in adipocyte differentiation, the expression of adipocyte-specific genes was analyzed in differentiating preadipocytes in response to GH. We found that the expression of both adipocyte determination and differentiation factor 1 (ADD1) and peroxisome proliferator activated receptor γ (PPARγ) was induced in preadipocytes during differentiation. In the presence of GH, which markedly inhibited triglyceride accumulation, no reduction in the expression level of ADD1 was observed in response to GH, whereas there was a 50% reduction in the expression of PPARγ. The DNA binding activity of the PPARγ/retinoid X receptor-α (RXRα) to the ARE7 element from the aP2 gene was also reduced by approximately 50% in response to GH. GH inhibited the expression of late markers of adipocyte differentiation, fatty acid synthase, aP2, and hormone-sensitive lipase by 70–80%. The antiadipogenic effect of GH was not affected by the mitogen-activated protein (MAP) kinase/extracellular-regulated protein (ERK) kinase inhibitor PD 98059, indicating that the mitogen-activated protein kinase pathway was not involved in GH inhibition of preadipocyte differentiation. The expression of preadipocyte factor-1/fetal antigen 1 was decreased during differentiation, and GH treatment prevented this down-regulation of Pref-1/FA1. A possible role for Pref-1/FA1 in mediating the antiadipogenic effect of GH was indicated by the observation that FA1 inhibited differentiation as effectively as GH. These data suggest that GH exerts its inhibitory activity in adipocyte differentiation at a step after the induction of ADD1 but before the induction of genes required for terminal differentiation.
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