Project description:Insufficient mitochondrial quantity in brown adipose tissue (BAT) causes defective thermogenesis and positive energy balance, which is coupled with the development of obesity. Whether disturbance of mitochondrial quality affects BAT function remains unknown. Here, we describe that the brown adipocyte-specific Leucine-rich PPR motif-containing protein knockout mice (LrpprcBKO) exhibited mitochondrial electron transport chain (ETC) proteome imbalance and a complete loss of the -adrenergic-stimulated thermogenesis at room temperature (RT), due to specific reduction of mtDNA-encoded genes. However, the LrpprcBKO mice were lean at normal chow and were protected against high-fat-diet-induced metabolic abnormalities, such as obesity, insulin resistance, adipose inflammation, hepatic steatosis, and hypertriglyceridemia. The beige adipocytes in inguinal white adipose tissue were expanded in LrpprcBKO mice at RT, but not at thermoneutrality. However, BAT thermogenic defects and metabolic benefits were present in LrpprcBKO mice regardless of ambient temperatures. Collectively, our results reveal that a thermogenesis-incapable BAT with mitochondrial ETC proteome imbalance can improve systemic metabolism, suggesting BAT’s contributions to thermoregulation and systemic metabolism can be uncoupled.
Project description:We performed a genome-wide deep sequencing analysis of the microRNAs abundant in mesenchymal stem cells (MSCs) derived from murine brown adipose tissue and in in vitro differentiated mature brown adipocytes. Several microRNAs were identified as differentially regulated when comparing datasets from MSCs vs. mature fat cells. These microRNAs may have an implication in the regulation of adipogenesis as well as thermogenesis in brown adipose tissue (BAT).
Project description:Brown adipose tissue plays a crucial role in modulating whole-body energy expenditure through the thermogenic function of its mitochondrial respiratory chain. Pharmacological interventions targeting this function hold significant therapeutic promise. Thus, gaining a comprehensive understanding of the pathophysiological regulation of brown adipose tissue is imperative for future therapeutic applications. In this study, we investigated the metabolic mechanisms underlying the regulation of mature brown adipocyte function by the mitochondrial respiratory chain. Our findings indicate that deficiency in mitochondrial complex I in mature brown adipocytes leads to lipidomic remodeling. This remodeling results in an increase in arachidonic acid content and prostaglandin E2 (PGE2) production, leading to reduced transcriptional activity of peroxisome proliferator-activated receptor gamma (PPARγ) and peroxisome proliferator-activated receptor alpha (PPARα) and alterations in the content of PPAR activator complexes, which consequently result in reduced brown adipocyte thermogenesis and peroxisomal gene expression in mature brown adipocyte. In summary, our study elucidates that the mitochondrial-derived arachidonic acid signal regulates brown adipocyte thermogenesis and peroxisome biogenesis by modulating the PPAR activator complex."
Project description:Non-shivering thermogenesis in adipocytes is mediated by brown adipose tissue, purportedly through the sole action of uncoupling protein 1 (UCP1). The physiological relevance of UCP1-dependent thermogenesis has primarily been inferred from the attenuation of thermogenic output of mice genetically lacking Ucp1 from birth (germline Ucp1-/-). However, germline Ucp1-/- mice harbor secondary changes within brown adipose tissue beyond UCP1, such as reduced electron transport chain abundance. We show here that these secondary changes also encompass reduced expression of genes regulating fuel liberation, changes that would attenuate the capacity of any thermogenic pathway. Therefore, the quantitative contribution of UCP1-dependent and -independent thermogenesis is not fully understood. To mitigate the potentially confounding ancillary changes to brown adipose tissue of germline Ucp1-/- mice, we constructed mice with inducible adipocyte-selective disruption of Ucp1. We find that, while germline Ucp1-/- mice succumb to cold-induced hypothermia with complete penetrance, most mice with inducible deletion of Ucp1 maintain homeothermy in the cold. However, inducible adipocyte-selective co-deletion of Ucp1 and creatine kinase B (Ckb, an effector of UCP1-independent thermogenesis) exacerbates cold-intolerance, indicative of a negative genetic interaction and thus a parallel thermogenic function. We find no evidence for impairments in insulation or non-shivering thermogenesis in skeletal muscle that would drive this phenotype. Furthermore, following UCP1 deletion or UCP1/CKB co-deletion from mature adipocytes, moderate cold exposure triggers the regeneration of mature adipocytes that coordinately restore UCP1 and CKB to brown adipose tissue, providing further evidence of their parallel thermogenic relationship. Our findings suggest that thermogenic adipocytes utilize non-paralogous protein redundancy – through UCP1 and CKB – to promote cold-induced energy dissipation.
Project description:The proteome cargo of extracellular vesicles released from brown adipose tissue (BAT) and from white adipose tissue (WAT) of mice subjected to cold exposure (4°C) was analysed by a TMT-based quantitative proteomic procedure in order to obtain new information on the processes of thermogenesis.
Project description:Various physiological stimuli, such as cold environment, diet, and hormones, trigger brown adipose tissue (BAT) to produce heat through sympathetic nervous system (SNS)- and -adrenergic receptors (ARs). The AR stimulation increases intracellular cAMP levels through heterotrimeric G proteins and adenylate cyclases, but the processes by which cAMP modulates brown adipocyte function are not fully understood. Here we described that specific ablation of cAMP production in brown adipocytes led to reduced lipolysis, mitochondrial biogenesis, uncoupling protein 1 (Ucp1) expression, and consequently defective adaptive thermogenesis. Elevated cAMP signaling by sympathetic activation inhibited Salt-inducible kinase 2 (Sik2) through protein kinase A (PKA)-mediated phosphorylation in brown adipose tissue. Inhibition of SIKs enhanced Ucp1 expression in differentiated brown adipocytes and Sik2 knockout mice exhibited enhanced adaptive thermogenesis at thermoneutrality in an Ucp1-dependent manner. Taken together, our data indicate that suppressing Sik2 by PKA-mediated phosphorylation is a requisite for SNS-induced Ucp1 expression and adaptive thermogenesis in BAT, and targeting Sik2 may present a novel therapeutic strategy to ramp up BAT thermogenic activity in humans.
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. Here we found that BAF60a, a subunit of the SWI/SNF chromatin-remodeling complexes, serves an indispensible role in cold-induced thermogenesis in brown fat. BAF60a maintains chromatin accessibility for key thermogenic genes in close proximity to PPARg and EBF2 binding sites. Surprisingly, fat-specific BAF60a inactivation triggers more pronounced browning of inguinal white adipose tissue that is linked to induction of MC2R, a receptor for the pituitary hormone ACTH. Elevated MC2R expression sensitizes adipocytes and BAF60a-deficient adipose tissue to thermogenic activation in response to ACTH stimulation. These observations reveal an unexpected dichotomous role of BAF60a-mediated chromatin remodeling in transcriptional control of brown and beige gene programs and illustrate a pituitary-adipose signaling axis in the control of thermogenesis.
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:We performed a genome-wide deep sequencing analysis of the microRNAs abundant in mesenchymal stem cells (MSCs) derived from murine brown adipose tissue and in in vitro differentiated mature brown adipocytes. Several microRNAs were identified as differentially regulated when comparing datasets from MSCs vs. mature fat cells. These microRNAs may have an implication in the regulation of adipogenesis as well as thermogenesis in brown adipose tissue (BAT). Examination of BAT-derived MSCs (BAT-MSC; 1 sample) and in vitro differentiated mature brown fat cells (BAT-DIFF; 1 sample) vertis biotechnologie AG, D-85354 Freising, Germany (library construction and sequencing)
Project description:Family with sequence similarity 172 member A (FAM172A) protein acts as a key physiological repressor of brown adipose tissue (BAT) activity that plays a key role in energy metabolism. Its expression in BAT is suppressed by cold and other adrenergic stimulators. Mechanistically, FAM172A inhibits BAT activity and thermogenesis, in part, by binding to 3-hydroxybutyrate dehydrogenase 1 (BDH1), which subsequently affects the levels of beta-hydroxybutyrate (BHB), a ketone body metabolite closely involved in adipose mitochondrial biogenesis.