Sugar responsive regulatory network that controls organismal carbohydrate, amino acid and lipid homeostasis [set 2]
Ontology highlight
ABSTRACT: Maintaining metabolic homeostasis in response to fluctuating nutrient intake requires intricate coordination between tissues of multicellular animals. The insulin/glucagon axis is well known to hormonally coordinate organism-wide carbohydrate metabolism. The ChREBP/Mondo-Mlx transcription factors regulate glycolytic and lipogenic genes locally in hepatocytes and adipocytes, but its role in systemic metabolic homeostasis has remained poorly understood. We demonstrate that Mondo-Mlx controls gene activity in several peripheral tissues of Drosophila melanogaster, where it regulates nutrient digestion and transport as well as carbohydrate, amino acid and lipid metabolism. In addition to directly regulating metabolic genes Mondo-Mlx controls a regulatory network composed of the Activin ligand Dawdle and GLI similar transcription factor Sugarbabe. Dawdle and Sugarbabe contribute to the regulation of a subset of Mondo-Mlx-dependent processes, including sugar-induced de novo synthesis of serine and fatty acids. In summary, our study establishes Mondo-Mlx sugar sensor as a master regulator of organismal metabolic homeostasis upon sugar feeding.
Project description:Maintaining metabolic homeostasis in response to fluctuating nutrient intake requires intricate coordination between tissues of multicellular animals. The insulin/glucagon axis is well known to hormonally coordinate organism-wide carbohydrate metabolism. The ChREBP/Mondo-Mlx transcription factors regulate glycolytic and lipogenic genes locally in hepatocytes and adipocytes, but its role in systemic metabolic homeostasis has remained poorly understood. We demonstrate that Mondo-Mlx controls gene activity in several peripheral tissues of Drosophila melanogaster, where it regulates nutrient digestion and transport as well as carbohydrate, amino acid and lipid metabolism. In addition to directly regulating metabolic genes Mondo-Mlx controls a regulatory network composed of the Activin ligand Dawdle and GLI similar transcription factor Sugarbabe. Dawdle and Sugarbabe contribute to the regulation of a subset of Mondo-Mlx-dependent processes, including sugar-induced de novo synthesis of serine and fatty acids. In summary, our study establishes Mondo-Mlx sugar sensor as a master regulator of organismal metabolic homeostasis upon sugar feeding.
Project description:Nutrient-dependent gene regulation critically contributes to homeostatic control of animal physiology in changing nutrient landscape. In Drosophila, dietary sugars activate transcription factors (TFs), such as Mondo-Mlx, Sugarbabe and Cabut, which control metabolic gene expression to mediate physiological adaptation to high sugar diet. TFs that correspondingly control sugar responsive metabolic genes under conditions of low dietary sugar remain, however, poorly understood. We have used de novo motif prediction to uncover a significant over-representation of GATA-like motifs on the promoters of sugar-responsive genes in Drosophila larvae. GATA TF Grain was found to contribute to the regulation of sugar-responsive genes, and consequently to central carbon and lipid metabolism, primarily on low sugar diet. Grain targets include known sugar responsive TFs, cabut and smad on X (smox). Moreover, Grain promotes the expression of genes involved in de novo lipogenesis. Grain chromatin binding sites significantly converge with those of Sugarbabe. Grain and Sugarbabe both activate lipogenic genes, but display functional predominance on low and high sugar conditions, respectively. Collectively, our data provides evidence for a metazoan GATA transcription factor in nutrient-responsive metabolic regulation in vivo.
Project description:Feeding on high sugar diet reprograms metabolism, partially mediated through a gene regulatory network controlled by intracellular sugar sensor Mondo/ChREBP-Mlx. Sugar-induced gene expression changes include activation of genes encoding enzymes of glycolysis, pentose phosphate pathways, and de novo lipogenesis, collectively driving the flux of sugar-derived carbon into triacylglycerides. These sugar-induced metabolic changes are likely to trigger compensatory responses to avoid depletion of necessary metabolites, but they remain poorly characterized. Through a global temporal clustering analysis of sugar-induced gene expression in Drosophila we identify new gene expression programs controlled by sugar feeding. These include rapid and transient downregulation of ribosome biogenesis genes, known targets of transcription factor Myc. Through in silico motif predictions and experimental validation, we identify transcriptional repressor Clockwork orange (CWO) as a mediator of this response. CWO expression is directly activated by Mondo-Mlx and it counteracts Myc through repression of its expression as well as through binding to overlapping regulatory regions of ribosome biogenesis genes. Loss of CWO function leads to depletion of UDP-GlcNAc pools and impaired viability on high sugar diet. Analysis of CWO orthologs, BHLHE40 and BHLHE41, in mouse hepatocytes revealed a conserved role for BHLHE41 in repressing ribosome biogenesis genes. Collectively, our data uncover a gene regulatory circuit balancing the activities of lipid and protein biosynthesis to maintain homeostasis during high sugar feeding.
Project description:Feeding on high sugar diet reprograms metabolism, partially mediated through a gene regulatory network controlled by intracellular sugar sensor Mondo/ChREBP-Mlx. Sugar-induced gene expression changes include activation of genes encoding enzymes of glycolysis, pentose phosphate pathways, and de novo lipogenesis, collectively driving the flux of sugar-derived carbon into triacylglycerides. These sugar-induced metabolic changes are likely to trigger compensatory responses to avoid depletion of necessary metabolites, but they remain poorly characterized. Through a global temporal clustering analysis of sugar-induced gene expression in Drosophila we identify new gene expression programs controlled by sugar feeding. These include rapid and transient downregulation of ribosome biogenesis genes, known targets of transcription factor Myc. Through in silico motif predictions and experimental validation, we identify transcriptional repressor Clockwork orange (CWO) as a mediator of this response. CWO expression is directly activated by Mondo-Mlx and it counteracts Myc through repression of its expression as well as through binding to overlapping regulatory regions of ribosome biogenesis genes. Loss of CWO function leads to depletion of UDP-GlcNAc pools and impaired viability on high sugar diet. Analysis of CWO orthologs, BHLHE40 and BHLHE41, in mouse hepatocytes revealed a conserved role for BHLHE41 in repressing ribosome biogenesis genes. Collectively, our data uncover a gene regulatory circuit balancing the activities of lipid and protein biosynthesis to maintain homeostasis during high sugar feeding.
Project description:Feeding on high sugar diet reprograms metabolism, partially mediated through a gene regulatory network controlled by intracellular sugar sensor Mondo/ChREBP-Mlx. Sugar-induced gene expression changes include activation of genes encoding enzymes of glycolysis, pentose phosphate pathways, and de novo lipogenesis, collectively driving the flux of sugar-derived carbon into triacylglycerides. These sugar-induced metabolic changes are likely to trigger compensatory responses to avoid depletion of necessary metabolites, but they remain poorly characterized. Through a global temporal clustering analysis of sugar-induced gene expression in Drosophila we identify new gene expression programs controlled by sugar feeding. These include rapid and transient downregulation of ribosome biogenesis genes, known targets of transcription factor Myc. Through in silico motif predictions and experimental validation, we identify transcriptional repressor Clockwork orange (CWO) as a mediator of this response. CWO expression is directly activated by Mondo-Mlx and it counteracts Myc through repression of its expression as well as through binding to overlapping regulatory regions of ribosome biogenesis genes. Loss of CWO function leads to depletion of UDP-GlcNAc pools and impaired viability on high sugar diet. Analysis of CWO orthologs, BHLHE40 and BHLHE41, in mouse hepatocytes revealed a conserved role for BHLHE41 in repressing ribosome biogenesis genes. Collectively, our data uncover a gene regulatory circuit balancing the activities of lipid and protein biosynthesis to maintain homeostasis during high sugar feeding.
Project description:To cope with food scarcity, animals store energy as lipids, which are produced from carbohydrates via de novo lipogenesis (DNL). The carbohydrate-responsive ChREBP-MLX complex is a master transcriptional regulator for DNL and lipid storage. However, our understanding of molecular mechanisms, particularly signaling pathways, controlling ChREBP-MLX complex remains incomplete. Here, we show that mammalian MLX is phosphorylated on an evolutionarily conserved motif and that MLX phosphorylation is necessary for ChREBP-MLX transcriptional activity. In Drosophila, MLX phosphorylation is essential for lipid storage and sugar tolerance during fly development. Furthermore, we identified CK2 as an MLX kinase. Although glucose phosphorylation is required for ChREBP-MLX activity, accumulation of glucose-6-phosphate (G6P) inhibits CK2-mediated MLX phosphorylation and thereby ChREBP-MLX activity. We propose that the evolutionarily conserved MLX phosphorylation is a rheostat that adjusts ChREBP-MLX activity in response to the carbohydrate availability ultimately controlling energy homeostasis.
Project description:Organisms need to assess their nutritional state and adapt their digestive capacity to the demands for various nutrients. Modulation of digestive enzyme production represents a potential step to regulate nutriment intake. However, the role of digestion in nutrient homeostasis has been largely neglected. In this study, we analyzed the mechanism underlying glucose repression of amylase in the adult Drosophila midgut. We demonstrated that glucose represses many carbohydrases and lipases. Our data shows that the consumption of nutritious sugars stimulates the secretion of the TGFβ ligand, Dawdle. Dawdle then acts via the circulation to activate TGFβ/Activin signaling in the midgut, culminating in the repression of digestive enzyme expression. Thus, our study not only identifies a mechanism coupling sugar sensing to digestive enzyme expression but points to an important role of TGFβ/Activin signaling in sugar metabolism. RNA-sequencing of whole guts from Drosophila melannogaster OregonR adult females was performed under three feeding conditions: Standard medium, glucose, and agar. Three biological repeats were performed for each condition.
Project description:Organisms need to assess their nutritional state and adapt their digestive capacity to the demands for various nutrients. Modulation of digestive enzyme production represents a rational step to regulate nutriment uptake. However, the role of digestion in nutrient homeostasis has been largely neglected. In this study, we analyzed the mechanism underlying glucose repression of digestive enzymes in the adult Drosophila midgut. We demonstrate that glucose represses the expression of many carbohydrases and lipases. Our data reveal that the consumption of nutritious sugars stimulates the secretion of the transforming growth factor β (TGF-β) ligand, Dawdle, from the fat body. Dawdle then acts via circulation to activate TGF-β/Activin signaling in the midgut, culminating in the repression of digestive enzymes that are highly expressed during starvation. Thus, our study not only identifies a mechanism that couples sugar sensing with digestive enzyme expression but points to an important role of TGF-β/Activin signaling in sugar metabolism.
Project description:Metabolic stress and changes in nutrient levels modulate many aspects of skeletal muscle function during aging and disease. Growth factors and cytokines secreted by skeletal muscle, known as myokines, are important signaling factors but it is largely unknown whether they modulate muscle growth and differentiation in response to nutrients. Here, we find that changes in glucose levels increase the activity of the glucose-responsive transcription factor MLX, which promotes and is necessary for myoblast fusion. MLX promotes myogenesis not via an adjustment of glucose metabolism but rather by inducing the expression of several myokines, including insulin like-growth factor-2 (IGF2), whereas RNAi and dominant-negative MLX reduce IGF2 expression and block myogenesis. This phenotype is rescued by conditioned media from control muscle cells and by recombinant IGF2, which activates the myogenic kinase Akt. Importantly, MLX null mice display decreased IGF2 induction and diminished muscle regeneration in response to injury, indicating that the myogenic function of MLX is conserved in vivo. Thus, glucose is a signaling molecule that regulates myogenesis and muscle regeneration via MLX/IGF2/Akt signaling.â??The data pproided are histome H4 acetlation data for MLX DN and MLX wt samples; 3 MLX DN H4 Ac Chip seq samples , 3 Inputs, 3 MLX WT H4 Ac samples and 3 WT inputs