Effect of deletion of carnitine palmitoyltransferase2 on interscapular BAT gene expression upon adrenergic stimulation in thermoneutral acclimatized mice
ABSTRACT: Ambient temperature affects energy intake and expenditure to maintain homeostasis in a continuously fluctuating environment. Here, mice with an adipose-specific defect in fatty acid oxidation (Cpt2A-/-) were subjected to varying temperature to determine the role of adipose bioenergetics to environmental adaptation. Cpt2A-/- brown adipose tissue (BAT) failed to induce thermogenic genes such as Ucp1 and Pgc1α in response to adrenergic stimulation, which is exacerbated by increasing temperature. Thermoneutrality induced a mitochondrial DNA stress in Cpt2A-/- BAT that resulted in a loss of classical interscapular BAT, but did not affect body weight gain or glucose tolerance in response to a high-fat diet. In this dataset, we include the expression data obtained from dissected mouse interscapular brown adipose tissue from mice acclimatized to thermoneutrality (30C) with and without beta3adrenergic stimulation with and without the deletion of carnitine palmitoyltransferase 2 (i.e., adipose unable to beta-oxidize long chain fatty acids in mitochondria). WildType and Cpt2A KnockOut mice were treated either with or without beta3adrenergic stimulation, thus four classes. Three biologic replicates were compared per class, thus twelve mice.
Project description:Brown adipose tissue (BAT) plays an essential role in metabolic homeostasis by dissipating energy via thermogenesis through uncoupling protein 1 (Ucp1). Previously, we reported that the TATA-binding protein Associated Factor 7L (Taf7l) is an important regulator of white adipose tissue (WAT) differentiation. Here, we show that Taf7l also serves as a molecular switch between brown fat and muscle lineages in vivo and in vitro. In adipose tissue, Taf7l containing TFIID complexes associate with PPAR to mediate DNA looping between distal enhancers and core promoter elements. Our findings suggest that presence of the tissue-specific Taf7l subunit in TFIID functions to promote long-range chromatin interactions during BAT lineage specification. mRNA-seq expression profiling wild type and Taf7l knockout interscapular brown adipose tissue (BAT)
Project description:Adaptive thermogenesis of brown adipose tissue (BAT) is critical for thermoregulation and contributes to total energy expenditure. However, whether BAT has non-thermogenic functions is largely unknown. Here, we describe that mice with a BAT-specific Liver kinase b1 deletion (Lkb1BKO mice) exhibited impaired mitochondrial respiration and thermogenesis in BAT, but reduced adiposity and liver triglyceride accumulation under high-fat-diet feeding at room temperature. Importantly, these metabolic benefits were also present in Lkb1BKO mice at thermoneutrality, where BAT thermogenesis was not required. Mechanistically, decreased mRNA levels of mtDNA-encoded electron transport chain (ETC) subunits and ETC proteome imbalance led to impaired mitochondrial respiration in BAT of Lkb1BKO mice. Furthermore, reducing mtDNA gene expression directly in BAT by removing mitochondrial transcription factor A (Tfam) in BAT also showed ETC proteome imbalance and the tradeoff between BAT thermogenesis and systemic metabolism at both room temperature and thermoneutrality. Collectively, our data demonstrates that ETC proteome imbalance in BAT regulates systemic metabolism independently of BAT thermogenic capacity.
Project description:Brown adipose tissue (BAT) dissipates chemical energy in the form of heat, as a defense against hypothermia and obesity. Current evidence indicates that brown adipocytes arise from Myf5+-dermotomal precursors through the action of a PRDM16-C/EBP-_ transcriptional complex; however, the underlying mechanisms that determine lineage specification and maintenance of brown adipose cells remain poorly understood. Here we study the role of euchromatic histone-lysine N-methyltransferase 1 (EHMT1), a brown fat-enriched lysine methyltransferase, as an essential enzymatic component of the PRDM16 transcriptional complex and controls brown adipose cell fate. To identify targets and function of EHMT1, we performed genome-wide gene expression profiling of BAT from control mouce (Ehmt1flox/flox), Ehmt1Myf5 KO mouse (Myf5-Cre+/-; Ehmt1flox/flox) and Ehmt1adipo KO mouse (Adipo-Cre+/-; Ehmt1flox/flox). Loss of EHMT1 in Myf5+ lineage causes a near total loss of brown fat characteristics and induces muscle-selective gene program in vivo. In addition, adipose-specific deletion of EHMT1 by Adipo-Cre leads to a marked reduction of the thermogenic and fat oxidation genes.
Project description:We applied RNA sequencing (RNA-seq) to map the global changes in gene expression of interscapular brown adipose tissue (iBAT) of mice subjected to acute cold exposure for 3 days. Here we find extensive changes in the iBAT transcriptome in response to cold with a prominent induction of genes associated to lipid-related metabolic processes. RNA-seq of poly-A enriched RNA isolated from brown adipose tissue of 5 mice housed at room temperature (22°C) and 5 mice exposed to cold (4°C) for 3 days.
Project description:Brown adipose tissue (BAT) is a thermogenic organ that dissipates stored energy as heat to maintain body temperature in infants and small mammals. This process may also provide protection from development of diet-induced obesity. We found that the bioactive lipid mediator lysophosphatidic acid (LPA) markedly decreases differentiation of cultured primary brown adipocyte precursors, while potent selective inhibitors of the LPA-generating enzyme autotaxin (ATX) promote differentiation. Transgenic mice overexpressing ATX exhibited reduced expression of BAT-related genes in peripheral white adipose tissue and accumulated significantly more fat than wild-type controls when fed a high fat diet. Our results indicate that ATX and its product LPA are physiologically relevant negative regulators of brown fat adipogenesis and suggest that a decrease in peripheral brown adipose tissue results in increased susceptibility to diet-induced obesity in mice. Primary BAT cell cultures were established as previously reported with some minor modifications (Cannon B., 2001; Néchad M., 1983). Four- to 6-week-old mice were euthanized under aseptic conditions and interscapular BAT (IBAT) dissected, finely minced in digestion buffer containing 123 mM NaCl, 5mM HCl, 1.3 mM CaCl2, 5mM glucose, 1.5% (w/v) crude bovine serum albumin fraction V, 100 mM HEPES, 0.2% collagenase type II (Sigma-Aldrich Corp., St. Louis, MO), pH 7.4, and digested in 10 ml of the same buffer for 30 min at 37°C. The supernatant obtained was then filtered using a 250 µm nylon mesh and kept in ice for 15 minutes to allow fat droplets and mature cells to float. The resulting infranatant was filtered through a 30 µm nylon mesh to enrich the fraction with precursor cells and centrifuged at 700g for 10 min. The pellet obtained was washed once in warm DMEM and resuspended in DMEM medium containing 10% newborn calf serum, 10 mM HEPES, 4mM glutamine, 25 µg/ml sodium ascorbate (Sigma-Aldrich Corp., St. Louis, MO)., 100U/ml penicillin and 100mg/ml streptomycin. Cells were seeded onto 35mm dish plates. Insulin treatment was started on day 1 at 50 nM and the concentration increased to 100 nM at day 5 and 200 nM at day 7. Differentiated/confluent cells were collected for biochemical analysis (~day 9). To identify genes regulated by ATX and LPA signaling, 9 DIV primary BAT cultures were treated with the vehicle (DMSO), specific ATX inhibitor HA155 (2.5µM), or LPA (1-Oleoly-LPA, 5µM) (Avanti Polar Lipids, AL, USA) during differentiation. Treatment of the BAT cultures did not affect confluence or markers of proliferation. RNA was extracted from three cultures per condition using TRIzol reagent (Invitrogen, Carlsbad, CA) as described previously (Blalock EM., 2003).
Project description:Rodents are commonly housed below thermoneutrality (~20°C) 1. Under these conditions there is a substantial effect on rodent physiology including the hyperactivation of brown (BAT) and beige adipose tissue 2. Here, we raised animals from weaning, on an obesogenic diet at thermoneutrality (28°C) to closer mimic human physiology and determine the impact of a) moderate cold exposure (i.e. 20°C, a temperature reduction of ~8°C) or b) treatment with YM-178, a highly-selective, clinically used β3-adrenoreceptor agonist on classical BAT or subcutaneous inguinal (IWAT) beige depots. Under these conditions, uncoupling protein 1 mRNA was undetectable in IWAT in all groups. Maintenance at 20°C drove weight gain and a 125% increase in subcutaneous fat, an effect not seen with YM-178 administration thus suggesting a direct effect of ambient temperature in promoting weight gain and adiposity in obese rats. Using exploratory adipose tissue proteomics we reveal novel processes and pathways associated with cold-induced weight gain in BAT (i.e. histone deacetylation and glycosphingolipid biosynthesis) and IWAT (i.e. NAD+ binding and retinol metabolism). Conversely, YM-178 had minimal metabolic-related effects on BAT and drove a pro-inflammatory phenotype in IWAT. Exercise training elicits diverse effects on brown (BAT) and white adipose tissue (WAT) physiology in rodents housed below their thermoneutral zone (i.e. 28-32°C). In these conditions, BAT is chronically hyperactive and, unlike human residence, closer to thermoneutrality. Therefore, we set out to determine the effects of exercise training in obese animals at 28°C (i.e. thermoneutrality) on BAT and WAT in its basal (i.e. inactive) state. Sprague-Dawley rats (n=12) were housed at thermoneutrality from 3 weeks of age and fed a high-fat diet. At 12 weeks of age half these animals were randomised to 4-weeks of swim-training (1 hour/day, 5 days per week). Following a metabolic assessment interscapular and perivascular BAT and inguinal (I)WAT were taken for analysis of thermogenic genes and the proteome. Exercise attenuated weight gain but did not affect total fat mass or thermogenic gene expression. Proteomics revealed an impact of exercise training on2-oxoglutarate metabolic process, mitochondrial respiratory chain complex IV, carbon metabolism and oxidative phosphorylation. This was accompanied by an upregulation of multiple proteins involved in skeletal muscle physiology suggesting an adipocyte to myocyte switch in BAT. UCP1 mRNA was undetectable in IWAT with proteomics highlighting changes to DNA binding, the positive regulation of apoptosis, HIF-1 signalling and cytokine-cytokine receptor interaction.
Project description:To determine the physiological targets of the RORs in brown adipose tissue. Keywords: Nuclear receptors, RORs, adipose Gene expression analysis was conducted using Agilent whole mouse genome arrays (012694). The analysis was perfomed in duplicate, employing a fluor reversal. RNA was isolated from interscapular brown adipose tissue from C57BL/6 male WT or DKO (RORa-/- and RORg-/-) 8-12 week old mice around circadian time 20. Total RNA was amplified using the Agilent Low RNA Input Fluorescent Linear Amplification Kit protocol. Starting with 500ng of total RNA, Cy3 or Cy5 labeled cRNA was produced according to manufacturer’s protocol. For each two color comparison, 750ng of each Cy3 and Cy5 labeled cRNAs were mixed and fragmented using the Agilent In Situ Hybridization Kit protocol. Hybridizations were performed for 17 hours in a rotating hybridization oven using the Agilent 60-mer oligo microarray processing protocol. Slides were washed as indicated in this protocol and then scanned with an Agilent Scanner. Data were retrieved with the Agilent Feature Extraction software (v7.5), using defaults for all parameters. The Agilent Feature Extraction Software performed error modeling, adjusting for additive and multiplicative noise. The resulting data were processed using the Rosetta Resolver® system (Rosetta Biosoftware, Kirkland, WA).
Project description:Brown adipose tissue (BAT) was suggested to play an important role in lipid and glucose metabolism in rodents and possibly also in humans. In the current study, we used genetic and correlation analyses in the BXH/HXB recombinant inbred (RI) strains, derived from Brown Norway (BN) and spontaneously hypertensive rats (SHR), to identify genetic determinants of BAT function and its role in the pathogenesis of metabolic disturbances. Linkage analyses revealed significant quantitative trait locus (QTL) associated with interscapular BAT mass in the vicinity of the Cd36 (fatty acid translocase) gene on chromosome 4. Additional two closely linked QTL asociated with glucose oxidation and incorporation into BAT lipids were detected near the Wars2 (tryptophanyl tRNA synthetase 2, mitochondrial) candidate gene on chromosome 2.
Project description:Brown adipose tissue (BAT) is a thermogenic organ that requires Uncoupling Protein 1 (UCP1) to dissipate chemical energy as heat, to defend core body temperature against hypothermia, and counteract obesity and metabolic diseases1. However, the transcriptional mechanism ensuring BAT thermogenic capacity for survival prior to environmental cold is unknown. Here we show histone deacetylase 3 (HDAC3) is a required transcriptional regulator of BAT enhancers to ensure thermogenic aptitude and survival. Mice with genetic ablation of HDAC3 become severely hypothermic and fail to survive acute cold exposure. UCP1 is nearly absent in BAT lacking HDAC3 and there is marked down-regulation of mitochondrial oxidative phosphorylation (OXPHOS) genes. Remarkably, although HDAC3 canonically functions as a transcriptional corepressor2, HDAC3 functions as a coactivator of the estrogen-related receptor _ (ERR_) in BAT, and loss of HDAC3 leads to robust global down-regulation of ERR±-driven enhancers. HDAC3 coactivation of ERR_ is mediated through deacetylation of PGC-1_ and is required for basal transcription of Ucp1, OXPHOS, and Pgc-1_. Thus, HDAC3 uniquely primes Ucp1 and thermogenic gene transcription to ensure immediate BAT-driven thermogenesis upon acute exposure to dangerously cold temperatures. Overall design: Interscapular BAT from wild-type and HDAC3 KO animals of C57BL/6 background were adapted to 22C or 29C (thermoneutrality) for ChIP-seq and GRO-seq studies. ChIP-seq studies of HDAC3, ERR- alpha, NCoR, and H3K27ac were performed from individual mice of each genotype and immunoprecipitations were subsequently pooled for sequencing. Nascent transcription changes and eRNAs were measured in WT and HDAC3 KO mice by GRO-seq through pooling 10 interscapular BAT pads from individual mice for nuclei isolation and subsequent nuclear-run on reactions and GRO-seq library construction.