Mitochondria fulfill central cellular functions including energy metabolism, iron-sulfur biogenesis, and regulation of apoptosis and calcium homeostasis. Accumulation of dysfunctional mitochondria is observed in ageing and many human diseases such as cancer and various neurodegenerative disorders. Appropriate quality control of mitochondria is important for cell survival in most eukaryotic cells. One important pathway in this respect is mitophagy, a selective form of autophagy which removes excess and dysfunctional mitochondria. In the past decades a series of essential factors for mitophagy have been identified and characterized. However, little is known about the molecular mechanisms regulating mitophagy. The role of mitochondrial dynamics in mitophagy is controversially discussed. Here we will review recent advances in this context promoting our understanding on the molecular regulation of mitophagy in Saccharomyces cerevisiae and on the role of mitochondrial dynamics in mitochondrial quality control.

Adipocyte dysfunction is a major cause of obesity, which is associated strongly with many disorders including psychological and medical morbidities, metabolic abnormalities, and cardiovascular diseases as well as a series of cancers. This study investigated the antiadipogenic activity of scutellarin (1) in 3T3-L1 preadipocytes as well as the underlying molecular mechanisms. It was observed that 1 reduced adipocyte differentiation of 3T3-L1 cells potently, as evidenced by a decrease in cellular lipid accumulation. At the molecular level, mRNA expression of the master adipogenic transcription factors, PPARγ and C/EBPα, was decreased markedly. However, mRNA levels of C/EBPβ, the upstream regulator of PPARγ and C/EBPα, were not decreased by 1. Moreover, a dose-dependent upregulation of PPARα was observed for 1. Computational modeling indicated that 1 can bind to PPARα, γ, and δ each in a distinct manner, while it can activate PPARα only by forming a hydrogen bond with Y464, thus stabilizing the AF-2 helix and activating PPARα. Therefore, these results suggest that 1, a major component of Scutellaria baicalensis, attenuates fat cell differentiation by upregulating PPARα as well as downregulating the expression of PPARγ and C/EBPα, thus showing therapeutic potential for obesity-related diseases.

A new G-quadruplex (GQ) stabilizer, [Pt(Dip)2](PF6)2 (Dip: 4,7-diphenyl-1,10-phenanthroline), is prepared by the microwave irradiation method. The complex can highly stabilize G-quadruplex, but has negligible interactions with duplex DNA. Aromatic anchors on the polypyridyl ligands bestow the stabilizer with a high binding preference towards parallel GQ.

BackgroundHepatic encephalopathy (HE) is a severe neuropsychiatric syndrome caused by various types of liver failure resulting in hyperammonemia-induced dysfunction of astrocytes. It is unclear whether autophagy, an important pro-survival pathway, is altered in the brains of ammonia-intoxicated animals as well as in HE patients.MethodsUsing primary rat astrocytes, a co-culture model of primary mouse astrocytes and neurons, an in vivo rat HE model, and post mortem brain samples of liver cirrhosis patients with HE we analyzed whether and how hyperammonemia modulates autophagy.FindingsWe show that autophagic flux is efficiently inhibited after administration of ammonia in astrocytes. This occurs in a fast, reversible, time-, dose-, and ROS-dependent manner and is mediated by ammonia-induced changes in intralysosomal pH. Autophagic flux is also strongly inhibited in the cerebral cortex of rats after acute ammonium intoxication corroborating our results using an in vivo rat HE model. Transglutaminase 2 (TGM2), a factor promoting autophagy, is upregulated in astrocytes of in vitro- and in vivo-HE models as well as in post mortem brain samples of liver cirrhosis patients with HE, but not in patients without HE. LC3, a commonly used autophagy marker, is significantly increased in the brain of HE patients. Ammonia also modulated autophagy moderately in neuronal cells. We show that taurine, known to ameliorate several parameters caused by hyperammonemia in patients suffering from liver failure, is highly potent in reducing ammonia-induced impairment of autophagic flux. This protective effect of taurine is apparently not linked to inhibition of mTOR signaling but rather to reducing ammonia-induced ROS formation.InterpretationOur data support a model in which autophagy aims to counteract ammonia-induced toxicity, yet, as acidification of lysosomes is impaired, possible protective effects thereof, are hampered. We propose that modulating autophagy in astrocytes and/or neurons, e.g. by taurine, represents a novel strategy to treat liver diseases associated with HE.FundingSupported by the DFG, CRC974 “Communication and Systems Relevance in Liver Injury and Regeneration“, Düsseldorf (Project number 190586431) Projects A05 (DH), B04 (BG), B05 (NK), and B09 (ASR).

Obesity is associated with an increased risk of many chronic diseases. Recently, a growing body of evidence has shown that phytochemicals may inhibit adipogenesis and obesity. In this study, we report for the first time, the ability of Averrhoa carambola L. peel extract commonly known as star fruit (SFP) to effectively suppress adipocyte differentiation in 3T3-L1 preadipocytes and therefore, address it as a potential candidate to treat obesity and its related diseases. (-)-Epicatechin was identified as a bioactive compound likely responsible for this suppression. As the genetic expression studies revealed that the adipogenic activity of SFP extract was due to the simultaneous downregulation of the C/EBPα and PPARγ as well as the upregulation of PPARα receptor genes, a detailed computational docking study was also elucidated to reveal the likely binding mode of (-)-epicatechin to the receptor of interest, accounting for the likely mechanism that results in the overall suppression of adipocyte differentiation.