Project description:The β-adrenergic receptor signaling pathway is a major component of adaptive thermogenesis in brown and white adipose tissue during cold acclimation. The β-AR activation highly induces transcriptional coactivator PGC-1α and its splice variant N-terminal (NT)-PGC-1α, promoting the transcription program of mitochondrial biogenesis and thermogenesis. In the present study, we evaluated the role of NT-PGC-1α in brown adipocyte energy metabolism by genome-wide profiling of NT-PGC-1α-responsive genes. Canonical pathway analysis revealed that a number of genes upregulated by NT-PGC-1α are highly enriched in mitochondrial pathways including fatty acid transport and β-oxidation, TCA cycle and electron transport system, thus reinforcing the crucial role of NT-PGC-1α in the enhancement of mitochondrial function. Moreover, gene expression profiling of NT-PGC-1α revealed activation of distinct metabolic pathways such as glucose, lipid and nucleotide metabolism and of signaling pathways such as RAR and PPAR-γ/RXRα activation in brown adipocytes. Together, our data strengthen our previous findings that NT-PGC-1α is a key regulator of mitochondrial oxidative metabolism and thermogenesis in brown adipocytes and further suggest that NT-PGC-1α influences a broader spectrum of thermogenic processes to meet cellular needs for adaptive thermogenesis. Two samples from two groups: NT-PGC-1α overexpression and empty vector. There are technical replicates (A and B) for each group. Two RNA samples were pooled for each group.
Project description:The β-adrenergic receptor signaling pathway is a major component of adaptive thermogenesis in brown and white adipose tissue during cold acclimation. The β-AR activation highly induces transcriptional coactivator PGC-1α and its splice variant N-terminal (NT)-PGC-1α, promoting the transcription program of mitochondrial biogenesis and thermogenesis. In the present study, we evaluated the role of NT-PGC-1α in brown adipocyte energy metabolism by genome-wide profiling of NT-PGC-1α-responsive genes. Canonical pathway analysis revealed that a number of genes upregulated by NT-PGC-1α are highly enriched in mitochondrial pathways including fatty acid transport and β-oxidation, TCA cycle and electron transport system, thus reinforcing the crucial role of NT-PGC-1α in the enhancement of mitochondrial function. Moreover, gene expression profiling of NT-PGC-1α revealed activation of distinct metabolic pathways such as glucose, lipid and nucleotide metabolism and of signaling pathways such as RAR and PPAR-γ/RXRα activation in brown adipocytes. Together, our data strengthen our previous findings that NT-PGC-1α is a key regulator of mitochondrial oxidative metabolism and thermogenesis in brown adipocytes and further suggest that NT-PGC-1α influences a broader spectrum of thermogenic processes to meet cellular needs for adaptive thermogenesis.
Project description:Transcriptional coactivator PGC-1α and its splice variant NT-PGC-1α play crucial roles in regulating cold-induced thermogenesis in brown adipose tissue (BAT). PGC-1α and NT-PGC-1α are highly induced by cold in BAT and subsequently bind to and coactivate many different transcription factors to regulate expression of genes involved in mitochondrial biogenesis, fatty acid oxidation, respiration and thermogenesis. To identify the complete repertoire of PGC-1α and NT-PGC-1α target genes in BAT, we analyzed genome-wide DNA-binding and gene expression profiles. We find that PGC-1α-/NT-PGC-1α binding broadly associates with cold-mediated transcriptional activation. In addition to their known target genes in mitochondrial biogenesis, fatty acid oxidation, respiration and thermogenesis, PGC-1α and NT-PGC-1α target to a broad spectrum of genes involved in diverse biological pathways including ubiquitin-dependent protein catabolism, ribonucleoprotein complex biosynthesis, phospholipid biosynthesis, angiogenesis, glycogen metabolism, phosphorylation, and autophagy. Our findings expand the number of genes and biological pathways that may be regulated by PGC-1α and NT-PGC-1α and provide further insight into the transcriptional regulatory network in which PGC-1α and NT-PGC-1α coordinate a comprehensive transcriptional response in BAT in response to cold.
Project description:Transcriptional coactivator PGC-1α and its splice variant NT-PGC-1α play crucial roles in regulating cold-induced thermogenesis in brown adipose tissue (BAT). PGC-1α and NT-PGC-1α are highly induced by cold in BAT and subsequently bind to and coactivate many different transcription factors to regulate expression of genes involved in mitochondrial biogenesis, fatty acid oxidation, respiration and thermogenesis. To identify the complete repertoire of PGC-1α and NT-PGC-1α target genes in BAT, we analyzed genome-wide DNA-binding and gene expression profiles. We find that PGC-1α-/NT-PGC-1α binding broadly associates with cold-mediated transcriptional activation. In addition to their known target genes in mitochondrial biogenesis, fatty acid oxidation, respiration and thermogenesis, PGC-1α and NT-PGC-1α target to a broad spectrum of genes involved in diverse biological pathways including ubiquitin-dependent protein catabolism, ribonucleoprotein complex biosynthesis, phospholipid biosynthesis, angiogenesis, glycogen metabolism, phosphorylation, and autophagy. Our findings expand the number of genes and biological pathways that may be regulated by PGC-1α and NT-PGC-1α and provide further insight into the transcriptional regulatory network in which PGC-1α and NT-PGC-1α coordinate a comprehensive transcriptional response in BAT in response to cold.
Project description:Mitochondria play an essential role in the ability of brown fat to generate heat, and the PGC-1 coactivators control several aspects of mitochondrial biogenesis. To investigate their specific roles in brown fat cells, we generated immortal preadipocyte lines from the brown adipose tissue of mice lacking PGC-1α. We could then efficiently knockdown PGC-1β expression by shRNA expression. Loss of PGC-1α did not alter brown fat differentiation but severely reduced the induction of thermogenic genes. Cells deficient in either PGC-1α or PGC-1β coactivators showed a small decrease in the differentiation-dependant program of mitochondrial biogenesis and respiration; however, this increase in mitochondrial number and function was totally abolished during brown fat differentiation when both PGC-1α and PGC-1β were deficient. These data show that PGC-1α is essential for brown fat thermogenesis but not brown fat differentiation, and the PGC-1 coactivators play an absolutely essential but complementary function in differentiation-induced mitochondrial biogenesis. Affymetrix microarray analysis of total RNA from wt, PGC-1α KO and PGC-1α KO cells expressing an RNAi specific for PGC-1β knockdown was performed. Of the 461 mitochondrial genes analyzed, 181 were found to be at least 20% different between wt and defective PGC-1α and β adipocytes (p < 0.05). More than 85% of these genes were downregulated in cells deficient for PGC-1alpha and PGC-1beta. Keywords: Analysis of mitochondrial gene expression
Project description:Brown and beige fat share a remarkably similar transcriptional program that supports fuel oxidation and thermogenesis. The chromatin-remodeling machinery that governs genome accessibility and renders adipocytes poised for thermogenic activation remains elusive. BAF60a serves an indispensable role in cold-induced thermogenesis in brown fat. Surprisingly, fat-specific BAF60a inactivation triggers more pronounced browning of inguinal white adipose tissue. These results suggest a dichotomous role of BAF60a-mediated chromatin remodeling in transcriptional control of brown and beige gene programs. To elucidate the mechanism, we performed microarray annalysis in inguinal white adipose tissues from mice after chronic cold exposure.
Project description:Hypoxic conditions in high-altitude environments present unique physiological stressors that drive metabolic adaptations, including adipose tissue browning. In this study, we investigated whether hypoxia (11.6% O₂, simulating 5,300 m altitude) could independently induce browning of adipose tissue in mice, apart from cold-induced mechanisms. Hypoxia significantly promoted the formation of multilocular adipocytes in inguinal white adipose tissue (iWAT) and upregulated thermogenic genes (UCP1, PGC-1α, Cox4i1, VEGF), glucose metabolism-related genes (IRS1/2, PDK2, PPARα), and beige adipocyte markers (Car4, UCP1). In contrast, interscapular brown adipose tissue (iBAT) showed minimal response to hypoxia, with no significant change in UCP1 expression. Notably, hypoxia elevated both Nrg4 and phosphorylated ErbB4 in iWAT. In vitro, Nrg4 overexpression in 3T3-L1 adipocytes increased the expression of PKAcα, PGC-1α, and UCP1, while pharmacological inhibition of ErbB4 phosphorylation using Dacomitinib attenuated Nrg4- and hypoxia-induced browning and lipolysis. In vivo, Dacomitinib treatment impaired hypoxia-mediated improvements in WAT browning and glucose tolerance. To explore the structural basis of this interaction, molecular docking and 100-ns molecular dynamics simulations were conducted, revealing strong and stable binding between Nrg4 and ErbB4, with calculated binding energies of −174.26 kcal/mol (MM/GBSA) and −19.5 kcal/mol (PRODIGY). These findings collectively demonstrate that the Nrg4–ErbB4 axis plays a central role in mediating hypoxia-induced browning and metabolic reprogramming of WAT, providing mechanistic insight into adipose tissue plasticity under low-oxygen conditions.