Identification of New Genes Involved in Human Adipogenesis and Fat Storage

Abstract

Since the worldwide increase in obesity represents a growing challenge for health care systems, new approaches are needed to effectively treat obesity and its associated diseases. One prerequisite for advances in this field is the identification of genes involved in adipogenesis and/or lipid storage. To provide a systematic analysis of genes that regulate adipose tissue biology and to establish a target-oriented compound screening, we performed a high throughput siRNA screen with primary (pre)adipocytes, using a druggable siRNA library targeting 7,784 human genes. The primary screen showed that 459 genes affected adipogenesis and/or lipid accumulation after knock-down. Out of these hits, 333 could be validated in a secondary screen using independent siRNAs and 110 genes were further regulated on the gene expression level during adipogenesis. Assuming that these genes are involved in neutral lipid storage and/or adipocyte differentiation, we performed InCell-Western analysis for the most striking hits to distinguish between the two phenotypes. Beside well known regulators of adipogenesis and neutral lipid storage (i.e. PPARγ, RXR, Perilipin A) the screening revealed a large number of genes which have not been previously described in the context of fatty tissue biology such as axonemal dyneins. Five out of ten axonemal dyneins were identified in our screen and quantitative RT-PCR-analysis revealed that these genes are expressed in preadipocytes and/or maturing adipocytes. Finally, to show that the genes identified in our screen are per se druggable we performed a proof of principle experiment using an antagonist for HTR2B. The results showed a very similar phenotype compared to knock-down experiments proofing the “druggability”. Thus, we identified new adipogenesis-associated genes and those involved in neutral lipid storage. Moreover, by using a druggable siRNA library the screen data provides a very attractive starting point to identify anti-obesity compounds targeting the adipose tissue.

Effects ofRosmarinus officinalisextract on human primary omental preadipocytes and adipocytes

“…Their weak modulation could be due to the use of visceral human preadipocytes, since PPARg activity is noticeably lower in primary human visceral adipocytes than subcutaneous adipocytes. 53,57 In a recent paper, 58 during 3T3-L1 differentiation, GATA3 was negatively regulated by miR-183 through the inhibition of the canonical Wnt/b-catenin signaling pathway, hence leading to adipogenic differentiation and adipogenesis. Although miR-183 was not listed in miRNAs-seq significant data (Table 2), GATA3 and WNT3A, known as inhibitors of preadipocyte to adipocyte transition, were the significantly (P < 0.001) highest expressed genes.…”

“…52 However, species-related differences in adipose tissue biology are known and also cell line-related artifacts have to be considered. 53 Therefore, to reproduce with higher fidelity the possible effects of RO extract, primary human adipocytes were used as model. Moreover, visceral adipose tissue adipocytes were chosen as target of RO activity, since they are more metabolically active, more sensitive to lipolysis, and more insulin resistant than subcutaneous adipocytes.…”

Epigenetics and human obesity

“…Methylation variation in the promoter of the retinoid X receptor alpha gene (RXRα) in umbilical cord tissue was found to explain up to 26% of the variation in childhood adiposity 79 . RXRα is a nuclear receptor with a known role in adipogenesis 82 ; it forms a heterodimer with the transcription factor PPARγ to activate transcription of genes involved in adipocyte differentiation, glucose metabolism, inflammation and energy homeostasis. DNA methylation appears to be also important in the regulation of PPARγ 83 , and variation in DNA methylation of PGC1A, interacting with PPARγ, has been associated with weight loss, obesity, and risk for T2DM 52 84 85 .…”

Genome-Wide Association Study for Carcass Traits in an Experimental Nelore Cattle Population

“…This gene has been previously associated to fat deposition in humans [24] and it is known that it encodes one of the several different receptors for 5-hydroxytryptamine (serotonin). The serotonin hormone acts as a neurotransmitter, a hormone, and a mitogen.…”