Brown vs white adipocytes: The PPARγ coregulator story

AbstractThe development of adipose tissue is a process which involves the concerted cooperation of numerous transcription factors together with their coactivators and corepressors. The peroxisome proliferator-activated receptor γ (PPARγ) is considered to be one of the master regulators of adipocyte differentiation. The presence of two functionally distinct types of adipose tissue, white and brown (WAT and BAT), requires an even more complex regulation of adipose tissue development. In this review we will focus on the role of PPARγ coregulators in adipogenesis and especially on the role of PPARγ coregulators in white and brown adipose tissue. Specificity in coregulator function in WAT and BAT may form an additional level of regulation of adipose tissue development

Current practice for the treatment of acute paracetamol intoxication with N-acetylcysteine in Dutch hospitals

Background Nationally and internationally a discussion is ongoing on the effectiveness, the dose required and the treatment duration of N-acetylcysteine to treat acute paracetamol intoxication. Objective In this paper we present the results of a national survey among hospital pharmacists. In this research the present treatment duration and dosing of N-acetylcysteine is reviewed. Design and methods An electronic survey consisting of 15 questions on the treatment of acute paracetamol intoxications in hospitals has been sent to hospital pharmacists. Results Hospital pharmacists of 67 of the 69 Dutch hospitals (97%) have responded. The majority (52 centres, 78%) indicated to treat acute paracetamol intoxications according to the treatment guideline of the NVZA/NVKFB on toxicologie.org. 64 centres (96%) used the dosing regimen of the above-mentioned treatment guideline, namely 150 mg/kg in 1 hour, followed by 450 mg/kg in 24 hours. The toxicologie.org treatment guideline of 150 mg/L at 4 hours after intake, (or 75 mg/L at 4 hours after intake for sensitive patients) to start N-acetylcysteine therapy, is used by 61 centres (91%). 30% of the centres indicate that there are differences in the treatment of an acute paracetamol intoxication in children and adults. In general, in these centres, it is preferred to start early with N-acetylcysteine in children. Conclusion Despite local differences, in the majority of the hospitals acute paracetamol intoxications are treated according to the toxicologie.org treatment guideline. Because of this, toxicologie.org is an appropriate medium to implement possible future adaptations in the N-acetylcysteine dosing regime in Dutch hospitals.</p

A Novel RNAi Lethality Rescue Screen to Identify Regulators of Adipogenesis

Adipogenesis, the differentiation of fibroblast-like mesenchymal stem cells into mature adipocytes, is tightly regulated by a complex cascade of transcription factors, including the nuclear receptor Peroxisome proliferator activator receptor γ (PPARγ). RNAi-mediated knock down libraries may present an atractive method for the identification of additional adipogenic factors. However, using in vitro adipogenesis model systems for high-throughput screening with siRNA libraries is limited since (i) differentiation is not homogeneous, but results in mixed cell populations, and (ii) the expression levels (and activity) of adipogenic regulators is highly dynamic during differentiation, indicating that the timing of RNAi-mediated knock down during differentiation may be extremely critical. Here we report a proof-of-principle for a novel RNAi screening method to identify regulators of adipogenesis that is based on lethality rescue rather than differentiation, using microRNA expression driven by a PPARγ responsive RNA polymerase II promoter. We validated this novel method through screening of a dedicated deubiquitinase knock down library, resulting in the identification of UCHL3 as an essential deubiquitinase in adipogenesis. This system therefore enables the identification of novel genes regulating PPARγ-mediated adipogenesis in a high-throughput setting

Effect of Synthetic Dietary Triglycerides: A Novel Research Paradigm for Nutrigenomics

The effect of dietary fats on human health and disease are likely mediated by changes in gene expression. Several transcription factors have been shown to respond to fatty acids, including SREBP-1c, NF-kappaB, RXRs, LXRs, FXR, HNF4alpha, and PPARs. However, it is unclear to what extent these transcription factors play a role in gene regulation by dietary fatty acids in vivo

PPARγ lipodystrophy mutants reveal intermolecular interactions required for enhancer activation

Peroxisome proliferator-activated receptor γ (PPARγ) is the master regulator of adipocyte differentiation, and mutations that interfere with its function cause lipodystrophy. PPARγ is a highly modular protein, and structural studies indicate that PPARγ domains engage in several intra- and inter-molecular interactions. How these interactions modulate PPARγ's ability to activate target genes in a cellular context is currently poorly understood. Here we take advantage of two previously uncharacterized lipodystrophy mutations, R212Q and E379K, that are predicted to interfere with the interaction of the hinge of PPARγ with DNA and with the interaction of PPARγ ligand binding domain (LBD) with the DNA-binding domain (DBD) of the retinoid X receptor, respectively. Using biochemical and genome-wide approaches we show that these mutations impair PPARγ function on an overlapping subset of target enhancers. The hinge region-DNA interaction appears mostly important for binding and remodelling of target enhancers in inaccessible chromatin, whereas the PPARγ-LBD:RXR-DBD interface stabilizes the PPARγ:RXR:DNA ternary complex. Our data demonstrate how in-depth analyses of lipodystrophy mutants can unravel molecular mechanisms of PPARγ function