Project description:The suprachiasmatic nucleus (SCN), the central circadian pacemaker, orchestrates daily metabolic rhythms, yet its role in substrate selection and thermogenic adaptation remains insufficiently understood. Here, we show that SCN lesioning abolishes the adaptive suppression of brown adipose tissue (BAT) thermogenesis typically observed during time-restricted feeding in subthermoneutral environments (TRF-STE), a condition that imposes concurrent nutrient and thermal challenges. Contrary to wild-type responses, SCN-lesioned mice maintain elevated BAT thermogenic activity, driven by enhanced sympathetic tone and β3-adrenergic receptor (ADRB3) signaling. This compensatory response promotes a shift from lipid oxidation to glucose utilization, enabling heat production despite impaired lipolysis. Mechanistically, we identify a SCN-regulated ADRB3-S100B signaling axis underlying this metabolic reprogramming. S100B, a nutrient-sensitive protein calcium-binding protein, is upregulated in BAT following SCN disruption, where it enhances thermogenic capacity by stimulating brown adipocyte proliferation and suppressing senescence. Functional studies reveal that S100B is both necessary and sufficient for sustaining BAT thermogenesis under TRF-STE. Furthermore, diverse SCN disruption models, including light-induced circadian arrhythmia, N - Methyl - D - aspartic acid (NMDA) excitotoxicity, and Caspase-3-mediated ablation, consistently elevates S100B expression in BAT, reinforcing its role as a convergent effector of SCN-regulated metabolic adaptation. These findings uncover a previously unrecognized role of the SCN in coordinating thermogenic flexibility and fuel partitioning under stress. The identification of the ADRB3-S100B axis as a key mediator of this adaptation provides new mechanistic insight into the neural regulation of energy balance, with potential therapeutic relevance for circadian misalignment, obesity, and resistance to diet-induced weight loss.
Project description:Ten-eleven translocation (TET) proteins oxidize 5-methylcytosine in DNA to 5- hydroxymethylcytosine and further oxidized derivatives. Here we show that TET proteins are key epigenetic suppressors of adipocyte thermogenesis and energy expenditure in both white and brown adipose tissues in vivo. Tet expression in adipocytes decreases upon cold or adrenergic stimulation but increases following high-fat diet (HFD) consumption. Mice with triple deletion of all three Tet genes in adipocytes have higher energy expenditure due to enhanced fat browning and thermogenesis. They also show significantly enhanced lipolysis because of elevated expression of Adrb3 and key lipases including Atgl and Hsl. Consequently, the knockout mice display improved cold tolerance and are substantially resistant to obesity, inflammation, and associated metabolic complications including insulin resistance. Mechanistically, TET deficiency substantially prevents the HFD-induced transcriptional alterations in adipose tissues. TET proteins recruit histone deacetylases (HDACs) to the key thermogenic gene loci including Adrb3, Ppargc1a, and Ucp1, leading to transcriptional repression through histone deacetylation. Thus, the TET-HDAC axis may be therapeutically targeted to treat obesity and related metabolic diseases.
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: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:Activation of brown fat thermogenesis increases energy expenditure and alleviates obesity. Sympathetic nervous system (SNS) is important in brown/beige adipocyte thermogenesis. Here we discover a novel fat-derived “adipokine” neurotrophic factor neurotrophin 3 (NTF3) and its receptor Tropomyosin receptor kinase C (TRKC) as key regulators of SNS growth and innervation in adipose tissue. NTF3 is highly expressed in brown/beige adipocytes, and potently stimulates sympathetic neuron neurite growth. NTF3/TRKC regulates a plethora of pathways in neuronal axonal growth and elongation. Adipose tissue sympathetic innervation is significantly increased in mice with adipocyte-specific NTF3 overexpression, but profoundly reduced in mice with TRKC haploinsufficiency (TRKC+/-). Increasing NTF3 via pharmacological or genetic approach promotes beige adipocyte development, enhances cold-induced thermogenesis and protects against diet-induced obesity (DIO); whereas TRKC+/- mice or SNS TRKC deficient mice are cold intolerant and prone to DIO. Thus, NTF3 is an important fat-derived neurotrophic factor regulating SNS innervation, energy metabolism and obesity.
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 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:A persistent influx of energy due to intake over expenditure leads to obesity. Increasing energy expenditure through activation of brown fat thermogenesis is a promising therapeutic strategy for the treatment of obesity. Epigenetic regulation has emerged as a key player in regulating brown fat development and thermogenic program. Here we aimed to study the role of DNA methyltransferase 3b (Dnmt3b), a DNA methyltransferase involved in de novo DNA methylation, in the regulation of brown fat function and energy homeostasis during diet-induced obesity (DIO). We have generated a genetic model with Dnmt3b deletion in brown fat-skeletal lineage precursor cells (3bKO mice) by crossing Dnmt3b-floxed (fl/fl) mice with Myf5-Cre mice. Female 3bKO mice were prone to diet-induced obesity and were insulin resistant. This was associated with decreased energy expenditure, which may largely account for the obese phenotype as there was no difference in food intake and locomotor activity between 3bKO and fl/fl mice. Dnmt3b deficiency impaired mitochondrial and thermogenic program in brown fat. Surprisingly, further RNA-seq analysis revealed a profound up-regulation of myogenic markers in the brown fat of 3bKO mice, suggesting a myocyte-like remodeling in brown fat, which may explain the impaired thermogenic program in brown fat. Further motif enrichment and pyrosequencing analysis suggested myocyte enhancer factor 2C (Mef2c) as a mediator for the myogenic alteration in Dnmt3b-deficient brown fat as indicated by decreased methylation at its promoter. Our data demonstrate that brown fat Dnmt3b is a key regulator of brown fat development, energy metabolism and obesity in female mice.