Project description:Since the worldwide increase in obesity represents a growing challenge for the health care systems, new approaches are needed to treat obesity and associated disease effectively. The food intake is primarily stored in the adipose tissue and therefore this organ is in focus to develop new anti-obesity treatments. 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. Beside well known regulators of adipogenesis and neutral lipid storage (like PPAR?, RXR, Perilipin A) the screening revealed a large number of genes which were not previously described in the context of fatty tissue biology. An enrichment of genes was observed for axonemal dyneins. Five out of ten anxonemal dyneins were identified in our primary screen and retested positive with independent siRNAs and cell-donors. Quantitative RT-PCR- and immunoblot analysis revealed that axonemal dyneins are expressed in preadipocytes and maturing adipocytes. Using microarray analysis, we further characterize the remaining genes identified in our primary screen to determine their expression pattern during adipogenesis. In the course of fat cell differentiation, 149 among the 459 positive genes were regulated on the gene expression level. Assuming that an adipogenesis-specific expression pattern is another independent hind, that these genes are involved in neutral lipid storage and/or adipocyte differentiation, we retested this gene-pool with independent siRNAs and cell donors. Finally, to show that the genes identified are per se druggable we performed a proof of principle experiment using an antagonist for one randomly chosen gene. 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. For microarray analysis, RNA was isolated at 3 different points in time during adipogenesis (day 0, day 3 and day 7 after induction of differentiation). This experiment was carried out with cells obtained from three different donors. No replicates are included for each point in time.

Project description:Background/aims: Serum concentrations of the hepatokine fibroblast growth factor (FGF) 21 are elevated in obesity, type‐2 diabetes, and the metabolic syndrome. We asked whether FGF21 levels differ between subjects with metabolically healthy vs. unhealthy obesity (MHO vs. MUHO) opening the possibility that FGF21 is a cross‐talker between liver and adipose tissue in MUHO. Furthermore, we studied the effects of chronic FGF21 treatment on adipocyte differentiation, lipid storage, and adipokine secretion. Methods/study design: In 20 morbidly obese donors of abdominal subcutaneous fat biopsies discordant for their whole‐body insulin sensitivity (hereby classified as MHO or MUHO subjects), serum FGF21 was quantified. The impact of chronic FGF21 treatment on differentiation, lipid accumulation, and adipokine release was assessed in isolated preadipocytes differentiated in vitro. Results: Serum FGF21 concentrations were more than two‐fold higher in MUHO as compared to 37 MHO subjects (457 ±378 vs. 211 ±123 pg/mL; p<0.05). FGF21 treatment of human preadipocytes for the entire differentiation period was modestly lipogenic (+15%; p<0.05), reduced the expression of key adipogenic transcription factors (PPARG and CEBPA, ‐15% and ‐40%, respectively; p<0.01 both), reduced adiponectin expression (‐20%; p<0.05), markedly reduced adiponectin release (‐60%; p<0.01), and substantially increased leptin (+60%; p<0.01) and interleukin‐6 (+50%; p<0.001) release. Interpretation/conclusions: The hepatokine FGF21 exerts weak lipogenic and anti‐adipogenic actions and marked adiponectin‐suppressive and leptin and interleukin‐6 release‐promoting effects in human differentiating preadipocytes. Together with the higher serum concentrations in MUHO subjects, our findings reveal FGF21 as a circulating factor promoting the development of metabolically unhealthy adipocytes. We analysed in vitro differentiated preadipocytes from 20 human donors treated with FGF21 or control cultures.

Project description:Since the worldwide increase in obesity represents a growing challenge for the health care systems, new approaches are needed to treat obesity and associated disease effectively. The food intake is primarily stored in the adipose tissue and therefore this organ is in focus to develop new anti-obesity treatments. 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. Beside well known regulators of adipogenesis and neutral lipid storage (like PPAR?, RXR, Perilipin A) the screening revealed a large number of genes which were not previously described in the context of fatty tissue biology. An enrichment of genes was observed for axonemal dyneins. Five out of ten anxonemal dyneins were identified in our primary screen and retested positive with independent siRNAs and cell-donors. Quantitative RT-PCR- and immunoblot analysis revealed that axonemal dyneins are expressed in preadipocytes and maturing adipocytes. Using microarray analysis, we further characterize the remaining genes identified in our primary screen to determine their expression pattern during adipogenesis. In the course of fat cell differentiation, 149 among the 459 positive genes were regulated on the gene expression level. Assuming that an adipogenesis-specific expression pattern is another independent hind, that these genes are involved in neutral lipid storage and/or adipocyte differentiation, we retested this gene-pool with independent siRNAs and cell donors. Finally, to show that the genes identified are per se druggable we performed a proof of principle experiment using an antagonist for one randomly chosen gene. 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.

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RNA-seq identifies IL15-induced adipogenesis and fatty acid metabolism pathways in human adipocytes

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