Identification of regulatory elements in the human adipose most abundant gene transcript-1 (apM-1) promoter: role of SP1/SP3 and TNF-? as regulatory pathways

Abstract

Aims/hypothesis. The human adipocyte-specific apM-1 (adipose most abundant gene transcript-1) gene encodes for a secretory protein of the adipose tissue that seems to play a role in the pathogenesis of obesityrelated insulin resistance and its expression is inhibited by TNF-α. Our aim was to characterize the tissuespecific regulation of the recently cloned apM-1 promoter and the mechanisms of TNF-α-induced downregulation of the apM-1 gene. Methods. We characterised the apM-1 gene by electrophoretic mobility shift assays (EMSA) and luciferase reporter gene assays (LRA). Results. Although several putative binding sites for transcription factors known to be involved in adipogenesis such as C/EBP and PPARγ are present in the promoter, we could not detect any binding of these nuclear proteins from differentiated adipocytes. However, a proximal SP1 binding site specifically binds both, recombinant SP1 protein and SP1 derived from adipocyte nuclear extracts. Since the expression of SP1 during adipocyte differentiation has not yet been analysed, we could show by using EMSA, that binding activity of SP1 is increased during adipocyte differentiation. The stimulatory activity of SP1 was confirmed in LRA by cotransfection experiments in S2 Schneider cells lacking endogenous SP factors. An inhibitory activity of SP3 on the stimulatory effect of SP1 could be confirmed in LRA by contransfection experiments in adipocytes. Nuclear extracts from adipocytes incubated with TNF-α showed a reduced binding activity of SP1. Conclusion/interpretation. SP1 is expressed and its binding activity is enhanced during adipocyte differentiation. SP1 has stimulatory effects, SP3 has inhibitory effects on apM-1 promoter activity, mediated by a proximal SP1 binding site. The mechanism of TNF-α-induced inhibition of apM-1 gene expression is, at least in part, due to a decrease of transcriptional SP1 binding activity caused by TNF-α and thus provides a new mechanism of TNF-α-dependent signalling. [Diabetologia (2002[Diabetologia ( ) 45:1425[Diabetologia ( -1433 Keywords apM-1, adipocyte, promoter, SP1, SP3, TNF-α, transcription, differentiation, diabetes, obesity. The adipose tissue has been considered as a special type of connective tissue, that stores energy in the form of triglycerides and releases energy in the form of non-esterified fatty acids whenever needed. However, increasing evidence suggests that the adipose tissue produces and secretes several highly active molecules. During the last 5 years it has become widely accepted that adipocytes do function as endocrine cells by secreting a variety of highly active molecules. These so-called adipocytokines [1] are secreted from the adipose tissue into the blood stream.

SIRT1 Regulates Adiponectin Gene Expression through Foxo1-C/Enhancer-binding Protein α Transcriptional Complex

“…Of note, it has been reported that C/EBP␣ up-regulates adiponectin expression through a C/EBP consensus sequence at the human adiponectin promoter (29). Although a putative C/EBP␣ binding site in the murine adiponectin promoter can be found by sequence scan, most studies did not demonstrate binding of C/EBP␣ to this site (14,26,30). Our study indicated that C/EBP␣ and Foxo1 up-regulate adiponectin promoter activity in a synergistic manner.…”

Sleep Fragmentation During Late Gestation Induces Metabolic Perturbations and Epigenetic Changes in Adiponectin Gene Expression in Male Adult Offspring Mice

“…It is well known that AdipoQ abundance is inversely associated with obesity, insulin resistance and type 2 diabetes, inflammatory markers, and endothelial dysfunction as well as with the development of cardiovascular disease (37). The production of AdipoQ by adipocytes is controlled at the level of gene expression through specific promoter regions (38) as well as by epigenetic mechanisms (28). Histone modifications of the AdipoQ gene were examined in mice exposed to a maternal high-fat diet (HFD) (39), and increased DNA methylation in the AdipoQ promoter region was reported in mice fed an HFD during late gestation (35).…”

Interaction between β-hexachlorocyclohexane and ADIPOQ genotypes contributes to the risk of type 2 diabetes mellitus in East Chinese adults

“…SNP rs182052 is located in intron 1 of ADIPOQ gene, and its minor allele A results in a loss of a Sp1-binding site and gain of a CCAAT/enhancer-binding protein (C/EBP) b-binding site, reducing adipocyte differentiation3839. SNP rs182052 was reported to be significantly associated with lower plasma adiponectin40, a strong predictor of diabetes41, which was reflected in our finding that cases had lower adiponectin levels than controls (Fig.…”