Elucidating the role of UCP1 and FGF21 for metabolic homeostasis in the cold
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ABSTRACT: Global RNA sequencing analysis of the hypothalamus, BAT, inguinal WAT and muscle of long-term cold exposed WT, FGF21 KO, UCP1 KO and UCP1/FGF21 double KO mice
Project description:Global RNA sequencing analysis of brown fat (BAT), inguinal white fat (iWAT), liver and muscle (quadriceps) of high-fat diet fed WT, FGF21 KO, UCP1 KO and UCP1/FGF21 double KO mice.
Project description:Fibroblast growth factor 21 (FGF21) is a key metabolic regulator which was recently discovered as stress-induced myokine and common denominator of muscle mitochondrial disease. However, its precise function and pathophysiological relevance remains unknown. Here we demonstrate that white adipose tissue (WAT) is the major target of muscle mitochondrial stress-induced FGF21. Strikingly, substantial browning and metabolic remodeling of subcutaneous WAT, together with the reduction of circulating triglycerides and cholesterol are fully FGF21 dependent. Unexpectedly and in contrast to prior expectations, we found a negligible role of FGF21 in muscle stress-related improved glycemic control, obesity resistance and hepatic lipid homeostasis. Furthermore, we show that the protective muscle mitohormesis and metabolic stress adaptation does not require FGF21 action. Taken together, our data imply that although FGF21 drives WAT remodeling, this effect and FGF21 as stress hormone per se may not be essential for the adaptive response under muscle mitochondrial stress conditions. Wildtype male mice and FGF21-knockout male mice, together with muscle specific UCP1-transgenic male animals, and double cross of FGF21-KO with UCP1-Tg male mice, were kept on a standardized low fat diet for 40 weeks. After sacrifice, subcutaneous white adipose tisseu (scWAT) was rapidly removed, weighed, and snap frozen in liquid nitrogen and used for RNA isolation and whole genome gene expression microarray hybridisation using Agilent arrays.
Project description:A comparison of the translating RNAs in UCP1-positive cells from the classical BAT, the inguinal WAT, and the perigonadal WAT. We find genes common to all UCP1-positive cells independent of anatomical location, as well as genes specifically enriched in one group versus the others. Results provide a portrait of gene expression in UCP1-positive cells in vivo. Translating RNAs in UCP1-positive cells were purified from 6 week old female UCP1-TRAP mice after 2 weeks at 4 degC. N=3 for iWAT, N=2 for pgWAT, and N=3 for BAT.
Project description:Atlas of UCP1-KO Beiging inguinal adipose tissue and tissue in which beta adrenergic signaling is blocked provides further insight into UCP1-independent mechanisms of beiging.
Project description:A comparison of the translating RNAs in UCP1-positive cells from the classical BAT, the inguinal WAT, and the perigonadal WAT. We find genes common to all UCP1-positive cells independent of anatomical location, as well as genes specifically enriched in one group versus the others. Results provide a portrait of gene expression in UCP1-positive cells in vivo.
Project description:Coenzyme Q is an essential component of mitochondrial function and required for thermogenic activity in brown adipose tissues (BAT). BAT CoQ deficiency (50-75%) by genetic or pharmacological means does not interfere with basal or maximal mitochondrial respiration in brown adipocytes but increases mitochondrial oxidants and induces UPRmt, ISR, and repression of UCP1 expression. ATF4, the master regulator of ISR, is required for UCP1 suppression in BAT CoQ deficiency. In animals, BAT CoQ deficiency causes cold intolerance but activates compensatory thermogenic mechanisms in BAT and other tissues via greatly induced BAT FGF21 expression resulting in paradoxically upregulated whole-body respiration rates and protection from obesity at room temperature and thermoneutrality. BAT-specific loss of either ATF4 or FGF21 abolishes these metabolic benefits demonstrating a central role for CoQ in the modulation of whole-body energy expenditure and thus for the etiology of primary and secondary CoQ deficiencies.
Project description:Single cell level analysis of transcriptional circuits regulating UCP1-indepednent theremogensis through Lgr6 in inguinal Adipose tissue. We previously identified an increase in Lgr6 gene expression in the beige adipocyte population of UCP1-KO mice and hypothesized its involvement in UCP1-independent thermogensis. Consistent with our previous data the scATAC-seq data reveals that chromatin accessibility at the Lgr6 loci is significantly higher in Ucp1- KO beige adipocytes as compared to WT and the promter is also more accessible in Ucp1- KO beige adipocytes. Other DNA-binding motifs involved in UCP-1 indepedent thermogensis were also analyzed and found to be upregulated in the KO model.
Project description:Since brown adipose tissue (BAT) dissipates energy through UCP1, BAT has garnered attention as a therapeutic intervention for obesity and metabolic diseases including type 2 diabetes. As we better understand the roles of classical brown and beige adipocytes, increased beige fat mass in response to a variety of external/internal cues is associated with significant improvements in glucose and lipid homeostasis that may not be entirely mediated by UCP1. We aim to analyze transcriptome of wild type and UCP1-null beige adipocyte to identify the UCP1-independent function.
Project description:Differentiation of brown adipocytes is a crucial process for adaptive thermogenesis, which is stimulated by various factors. We found robust browning of inguinal white adipose tissue in UCP1/ApoE-DKO mice, but not in ApoE-KO mice, under high-fat diet condition. We used microarray to determine the genes specifically regulated in the browning white adipose tissue in UCP1/ApoE-DKO mice.