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Genes regulated by nuclear Lipin in the fed and fasting state

ABSTRACT: Lipins are eukaryotic proteins with functions in lipid synthesis and the homeostatic control of energy balance. They execute these functions by acting as phosphatidate phosphatase enzymes in the cytoplasm and by changing gene expression after translocation into the cell nucleus, in particular under fasting conditions. Here, we asked how gene expression changes, under both fed and fasting conditions, when nuclear translocation of Lipin is impaired. To address this question, we created a Drosophila mutant expressing Lipin lacking a nuclear localization signal (LipinDNLS). Notably, adult LipinDNLS flies were not only viable but also exhibited improved life expectancy. In contrast, they were highly susceptible to starvation. To examine how these phenotypes correlate with changes in gene expression, we carried out an RNA-seq analysis with mRNA from female and male LipinDNLS and control flies that had been kept under fed or fasting conditions. We found that genes involved in metabolism, feeding behavior, and the immune response were mis-regulated in LipinDNLS flies. The changed expression of these genes supports hypotheses explaining improved life expectancy under fed and decreased life expectancy under fasting conditions. For instance, metabolic rate measurements confirmed the prediction based on the RNA-seq data that energy production by oxidative phosphorylation is reduced in fed LipinDNLS flies.

ORGANISM(S): Drosophila melanogaster

PROVIDER: GSE158189 | GEO | 2020/09/19

REPOSITORIES: GEO

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Project description:Mutations in the gene encoding lipin 1 cause hepatic steatosis in fld mice, a genetic model of lipodystrophy. Lipin 1 appears to be highly involved in the control of fatty acid metabolism. Lipin 1 is most often located in the nucleus, but other studies suggest that lipin also has effects in the cytoplasm. However, the molecular function of lipin 1 is unclear. To evaluate the effects of activation of the lipin 1 system in liver, lipin 1beta was overexpressed in mouse liver using an adenoviral vector. We found that lipin 1 overexpression increased the expression of many genes involved in mitochondrial fatty acid oxidation while repressing expression of genes involved in lipogenesis. We believe that lipin is a transcriptional coactivator of the peroxisome proliferator-activated receptor (PPAR) complex. However, the many molecular aspects of its function remain unclear. Abstract of published manuscript follows: Lipin 1 is an inducible amplifier of the hepatic PGC-1alpha/PPARalpha regulatory pathway.Finck BN, Gropler MC, Chen Z, Leone TC, Croce MA, Harris TE, Lawrence JC Jr, Kelly DP. Center for Cardiovascular Research and Washington University School of Medicine, St. Louis, Missouri 63110; Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110. Perturbations in hepatic lipid homeostasis are linked to the development of obesity-related steatohepatitis. Mutations in the gene encoding lipin 1 cause hepatic steatosis in fld mice, a genetic model of lipodystrophy. However, the molecular function of lipin 1 is unclear. Herein, we demonstrate that the expression of lipin 1 is induced by peroxisome proliferator-activated receptor gamma (PPARgamma) coactivator 1alpha (PGC-1alpha), a transcriptional coactivator controlling several key hepatic metabolic pathways. Gain-of-function and loss-of-function strategies demonstrated that lipin selectively activates a subset of PGC-1alpha target pathways, including fatty acid oxidation and mitochondrial oxidative phosphorylation, while suppressing the lipogenic program and lowering circulating lipid levels. Lipin activates mitochondrial fatty acid oxidative metabolism by inducing expression of the nuclear receptor PPARalpha, a known PGC-1alpha target, and via direct physical interactions with PPARalpha and PGC-1alpha. These results identify lipin 1 as a selective physiological amplifier of the PGC-1alpha/PPARalpha-mediated control of hepatic lipid metabolism. Keywords: response to lipin 1 activation

Project description:Mutations in the gene encoding lipin 1 cause hepatic steatosis in fld mice, a genetic model of lipodystrophy. Lipin 1 appears to be highly involved in the control of fatty acid metabolism. Lipin 1 is most often located in the nucleus, but other studies suggest that lipin also has effects in the cytoplasm. However, the molecular function of lipin 1 is unclear. To evaluate the effects of activation of the lipin 1 system in liver, lipin 1beta was overexpressed in mouse liver using an adenoviral vector. We found that lipin 1 overexpression increased the expression of many genes involved in mitochondrial fatty acid oxidation while repressing expression of genes involved in lipogenesis. We believe that lipin is a transcriptional coactivator of the peroxisome proliferator-activated receptor (PPAR) complex. However, the many molecular aspects of its function remain unclear. Abstract of published manuscript follows:; Lipin 1 is an inducible amplifier of the hepatic PGC-1alpha/PPARalpha regulatory pathway.Finck BN, Gropler MC, Chen Z, Leone TC, Croce MA, Harris TE, Lawrence JC Jr, Kelly DP. Center for Cardiovascular Research and Washington University School of Medicine, St. Louis, Missouri 63110; Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110. Perturbations in hepatic lipid homeostasis are linked to the development of obesity-related steatohepatitis. Mutations in the gene encoding lipin 1 cause hepatic steatosis in fld mice, a genetic model of lipodystrophy. However, the molecular function of lipin 1 is unclear. Herein, we demonstrate that the expression of lipin 1 is induced by peroxisome proliferator-activated receptor gamma (PPARgamma) coactivator 1alpha (PGC-1alpha), a transcriptional coactivator controlling several key hepatic metabolic pathways. Gain-of-function and loss-of-function strategies demonstrated that lipin selectively activates a subset of PGC-1alpha target pathways, including fatty acid oxidation and mitochondrial oxidative phosphorylation, while suppressing the lipogenic program and lowering circulating lipid levels. Lipin activates mitochondrial fatty acid oxidative metabolism by inducing expression of the nuclear receptor PPARalpha, a known PGC-1alpha target, and via direct physical interactions with PPARalpha and PGC-1alpha. These results identify lipin 1 as a selective physiological amplifier of the PGC-1alpha/PPARalpha-mediated control of hepatic lipid metabolism. Experiment Overall Design: Adult male C57BL6 mice were injected with adenovirus driving expression of mouse lipin 1beta or green fluorescent protein (GFP). Mice were recovered and sacrificed 6 days after injection. Total RNA was isolated and analyzed using Affymetrix microarray.

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Genes regulated by nuclear Lipin in the fed and fasting state

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