Project description:HSL is a key enzyme in in the mobilization of fatty acids from the triglyceride stores of white adipose tissue. In addition, it is expressed in mice liver. In the present microarray study, changes in the transcript profile of murine liver samples due to global HSL knockout were investigated. Experiment Overall Design: Genetic modification to analyze the impact of a general knockout of the HSL gene on liver metabolism. Experiment Overall Design: HSL knockout (ko) mice versus wildtype (wt) mice. Mice fed a normal diet (ND) versus mice fed a high fat diet (FD) for 6 months. Equal amounts of liver samples from six mice were pooled and total RNA was extracted, except for HSL-null mice on FD were only 4 livers were pooled.
Project description:Lysosomal acid lipase (LAL) is the key enzyme of lysosomal lipid hydrolysis, which degrades cholesteryl esters (CE), triacylglycerols (TG), diacylglycerols (DG), and retinyl esters. The role of LAL in various cellular processes has mostly been studied in LAL-deficient (Lal-/-) mice, which share phenotypical characteristics with humans suffering from LAL deficiency. In vitro, the cell-specific functions of LAL have been commonly investigated by using the LAL inhibitors Lalistat-1 (L1) and Lalistat-2 (L2). Here, we show that pharmacological LAL inhibition but not genetic loss of LAL impairs isoproterenol-stimulated lipolysis and neutral TG hydrolase (TGH) and CE hydrolase (CEH) activities in mature adipocytes, indicating that L1 and L2 inhibit other lipid hydrolases apart from LAL. Since adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL) are the major enzymes that degrade cytosolic TG and CE, respectively, at neutral pH, we hypothesized that L1 and L2 also inhibit ATGL and/or HSL through off-target effects. In fact, both inhibitors drastically reduced neutral CEH activity in cells overexpressing mouse and human HSL and neutral TGH activity in cells overexpressing mouse and human ATGL, albeit to a lesser extent. By performing serine hydrolase-specific activity-based labeling in combination with quantitative proteomics, we confirmed that L2 inhibits HSL and other lipid hydrolases, whereas L1 treatment results in less pronounced inhibition of neutral lipid hydrolases. These results demonstrate that commonly used concentrations of L2 (and L1) are not suitable for investigating the role of LAL-specific lipolysis in lysosomal function, signaling pathways, and autophagy.
Project description:Mammalian hibernation is characterized by metabolic rate depression and a strong decrease in core body temperature that together create energy savings such that most species do not have to eat over the winter months. Brown adipose tissue (BAT), a thermogenic tissue that uses uncoupled mitochondrial respiration to generate heat instead of ATP, plays a major role in rewarming from deep torpor. The present study used label-free phosphoproteomics to investigate changes in BAT from thirteen-lined ground squirrels (Ictidomys tridecemlineatus), comparing euthermic squirrels with squirrels in deep torpor. Differential expression of mitochondrial proteins was also investigated. Surprisingly, mitochondrial membrane and matrix protein expression in BAT was largely constant between active euthermic squirrels and their hibernating counterparts. Validation by immunoblotting confirmed that the protein levels of mitochondrial respiratory chain complexes were largely unchanged. However, phosphoproteomics showed that pyruvate dehydrogenase (PDH) phosphorylation increased during ground squirrel hibernation, and this was confirmed by immunoblotting with phospho-specific antibodies. PDH phosphorylation leads to its inactivation, which suggests that BAT carbohydrate oxidation is inhibited during hibernation. Phosphorylation of hormone-sensitive lipase (HSL) also increased during hibernation, suggesting that HSL would be in a partly activated state in BAT to produce the fatty acids that are likely the primary fuel for thermogenesis during arousal.
Project description:HSL is a key enzyme in in the mobilization of fatty acids from the triglyceride stores of white adipose tissue. In addition, it is expressed in mice liver. In the present microarray study, changes in the transcript profile of murine liver samples due to global HSL knockout were investigated. Keywords: genetic modification
Project description:A major task in dissecting the genetics of complex traits is to identify causal genes for disease phenotypes. We previously developed a method to infer causal relationships among genes through the integration of DNA variation, gene transcription, and phenotypic information. Here we validated our method through the characterization of transgenic and knockout mouse models of candidate genes that were predicted to be causal for abdominal obesity. Perturbation of eight out of the nine genes, with Gas7, Me1 and Gpx3 being novel, resulted in significant changes in obesity related traits. Liver expression signatures revealed alterations in common metabolic pathways and networks contributing to abdominal obesity and overlapped with a macrophage-enriched metabolic network module that is highly associated with metabolic traits in mice and humans. Integration of gene expression in the design and analysis of traditional F2 intercross studies allows high confidence prediction of causal genes, and identification of involved pathways and networks. This SuperSeries is composed of the following subset Series: GSE11991: Liver gene expression profiling of lipoprotein lipase heterozygous knockout mice GSE11992: Liver gene expression profiling of cytosolic malic enzyme knockout mice GSE11993: Liver gene expression profiling of zinc finger binding protein 90 (Zfp90) transgenic mice GSE11994: Liver gene expression profiling of transforming growth factor beta receptor 2 heterozygous knockout (Tgfbr2+/-) mice GSE11995: Liver gene expression profiling of complement component 3a receptor 1 knockout (C3ar1-/-) mice GSE11996: Gas7 male transgenic liver expression vs FVB male wildtype control GSE11997: Gpx3 male transgenic liver expression vs B6/DBA male wildtype control GSE11998: Gyk female heterozygous liver expression vs C57Bl/6J female wildtype control GSE11999: Lactb male transgenic liver expression vs FVB male wildtype control Refer to individual Series