Decoding temporal thermogenesis: coregulator selectivity and transcriptional control in brown and beige adipocytes.

In mammals, brown adipose tissue (BAT) and beige adipocytes in white adipose tissue (WAT) play pivotal roles in maintaining body temperature and energy metabolism. In mice, BAT quickly stimulates thermogenesis by activating brown adipocytes upon cold exposure. In the presence of chronic cold stimuli, beige adipocytes are recruited in inguinal WAT to support heat generation. Accumulated evidence has shown that thermogenic execution of brown and beige adipocytes is regulated in a fat depot-specific manner. Recently, we have demonstrated that ubiquitin ligase ring finger protein 20 (RNF20) regulates brown and beige adipocyte thermogenesis through fat-depot-specific modulation. In BAT, RNF20 regulates transcription factor GA-binding protein alpha (GABPα), whereas in inguinal WAT, RNF20 potentiates transcriptional activity of peroxisome proliferator-activated receptor-gamma (PPARγ) through the degradation of nuclear corepressor 1 (NCoR1). This study proposes the molecular mechanisms by which co-regulator(s) selectively and temporally control transcription factors to coordinate adipose thermogenesis in a fat-depot-specific manner. In this Commentary, we provide molecular features of brown and beige adipocyte thermogenesis and discuss the underlying mechanisms of distinct thermogenic processes in two fat depots.

The Effect of KSK-94, a Dual Histamine H3 and Sigma-2 Receptor Ligand, on Adipose Tissue in a Rat Model of Developing Obesity.

BACKGROUND: Numerous studies highlight the critical role that neural histamine plays in feeding behavior, which is controlled by central histamine H3 and H1 receptors. This is the fundamental motivation for the increased interest in creating histamine H3 receptor antagonists as anti-obesity medications. On the other hand, multiple other neurotransmitter systems have been identified as pharmacotherapeutic targets for obesity, including sigma-2 receptor systems. Interestingly, in our previous studies in the rat excessive eating model, we demonstrated a significant reduction in the development of obesity using dual histamine H3/sigma-2 receptor ligands. Moreover, we showed that compound KSK-94 (structural analog of Abbott's A-331440) reduced the number of calories consumed, and thus acted as an anorectic compound. Therefore, in this study, we extended the previous research and studied the influence of KSK-94 on adipose tissue collected from animals from our previous experiment. METHODS: Visceral adipose tissue was collected from four groups of rats (standard diet + vehicle, palatable diet + vehicle, palatable diet + KSK-94, and palatable diet + bupropion/naltrexone) and subjected to biochemical, histopathological, and immunohistochemical studies. RESULTS: The obtained results clearly indicate that compound KSK-94 prevented the hypertrophy and inflammation of visceral adipose tissue, normalized the levels of leptin, resistin and saved the total reduction capacity of adipose tissue, being more effective than bupropion/naltrexon in these aspects. Moreover, KSK-94 may induce browning of visceral white adipose tissue. CONCLUSION: Our study suggests that dual compounds with a receptor profile like KSK-94, i.e., targeting histamine H3 receptor and, to a lesser extent, sigma-2 receptor, could be attractive therapeutic options for patients at risk of developing obesity or with obesity and some metabolic disorders. However, more studies are required to determine its safety profile and the exact mechanism of action of KSK-94.

Thermogenic Fat as a New Obesity Management Tool: From Pharmaceutical Reagents to Cell Therapies.

Obesity is a complex medical condition caused by a positive imbalance between calorie intake and calorie consumption. Brown adipose tissue (BAT), along with the newly discovered "brown-like" adipocytes (called beige cells), functions as a promising therapeutic tool to ameliorate obesity and metabolic disorders by burning out extra nutrients in the form of heat. Many studies in animal models and humans have proved the feasibility of this concept. In this review, we aim to summarize the endeavors over the last decade to achieve a higher number/activity of these heat-generating adipocytes. In particular, pharmacological compounds, especially agonists to the ß3 adrenergic receptor (ß3-AR), are reviewed in terms of their feasibility and efficacy in elevating BAT function and improving metabolic parameters in human subjects. Alternatively, allograft transplantation of BAT and the transplantation of functional brown or beige adipocytes from mesenchymal stromal cells or human induced pluripotent stem cells (hiPSCs) make it possible to increase the number of these beneficial adipocytes in patients. However, practical and ethical issues still need to be considered before the therapy can eventually be applied in the clinical setting. This review provides insights and guidance on brown- and beige-cell-based strategies for the management of obesity and its associated metabolic comorbidities.

Cocoa extract induces browning of white adipocytes and improves glucose intolerance in mice fed a high-fat diet.

Cocoa extract (CE) offers several health benefits, such as anti-obesity and improved glucose intolerance. However, the mechanisms remain unclear. Adipose tissue includes white adipose tissue (WAT) and brown adipose tissue. Brown adipose tissue leads to body fat reduction by metabolizing lipids to heat via uncoupling protein 1 (UCP1). The conversion of white adipocytes into brown-like adipocytes (beige adipocytes) is called browning, and it contributes to the anti-obesity effect and improved glucose tolerance. This study aimed to evaluate the effect of CE on glucose tolerance in terms of browning. We found that dietary supplementation with CE improved glucose intolerance in mice fed a high-fat diet, and it increased the expression levels of Ucp1 and browning-associated gene in inguinal WAT. Furthermore, in primary adipocytes of mice, CE induced Ucp1 expression through ß3-adrenergic receptor stimulation. These results suggest that dietary CE improves glucose intolerance by inducing browning in WAT.

Circulating plasma fibronectin affects tissue insulin sensitivity, adipocyte differentiation, and transcriptional landscape of adipose tissue in mice.

Plasma fibronectin (pFN) is a hepatocyte-derived circulating extracellular matrix protein that affects cell morphology, adipogenesis, and insulin signaling of adipocytes in vitro. In this study, we show pFN accrual to adipose tissue and its contribution to tissue homeostasis in mice. Hepatocyte-specific conditional Fn1 knockout mice (Fn1-/-ALB) show a decrease in adipose tissue FN levels and enhanced insulin sensitivity of subcutaneous (inguinal), visceral (epididymal) adipose tissue on a normal diet. Diet-induced obesity model of the Fn1-/-ALB mouse showed normal weight gain and whole-body fat mass, and normal adipose tissue depot volumes and unaltered circulating leptin and adiponectin levels. However, Fn1-/-ALB adipose depots showed significant alterations in adipocyte size and gene expression profiles. The inguinal adipose tissue on a normal diet, which had alterations in fatty acid metabolism and thermogenesis suggesting browning. The presence of increased beige adipocyte markers Ucp1 and Prdm16 supported this. In the inguinal fat, the obesogenic diet resulted in downregulation of the browning markers and changes in gene expression reflecting development, morphogenesis, and mesenchymal stem cell maintenance. Epididymal adipose tissue showed alterations in developmental and stem cell gene expression on both diets. The data suggests a role for pFN in adipose tissue insulin sensitivity and cell profiles.

Alternative isoform expression of key thermogenic genes in human beige adipocytes.

Background: The beneficial effect of thermogenic adipocytes in maintaining body weight and protecting against metabolic disorders has raised interest in understanding the regulatory mechanisms defining white and beige adipocyte identity. Although alternative splicing has been shown to propagate adipose browning signals in mice, this has yet to be thoroughly investigated in human adipocytes. Methods: We performed parallel white and beige adipogenic differentiation using primary adipose stem cells from 6 unrelated healthy subjects and assessed differential gene and isoform expression in mature adipocytes by RNA sequencing. Results: We find 777 exon junctions with robust differential usage between white and beige adipocytes in all 6 subjects, mapping to 562 genes. Importantly, only 10% of these differentially spliced genes are also differentially expressed, indicating that alternative splicing constitutes an additional layer of gene expression regulation during beige adipocyte differentiation. Functional classification of alternative isoforms points to a gain of function for key thermogenic transcription factors such as PPARG and CITED1, and enzymes such as PEMT, or LPIN1. We find that a large majority of the splice variants arise from differential TSS usage, with beige-specific TSSs being enriched for PPARγ and MED1 binding compared to white-specific TSSs. Finally, we validate beige specific isoform expression at the protein level for two thermogenic regulators, PPARγ and PEMT. Discussion: These results suggest that differential isoform expression through alternative TSS usage is an important regulatory mechanism for human adipocyte thermogenic specification.

Atomic force microscopy characterization of white and beige adipocyte differentiation.

Adipose tissue plays an essential role in systemic metabolism with white adipose tissue (WAT) making up most of the tissue and being involved in the regulation of energy homeostasis, and brown and beige adipose tissue (BAT) exhibiting thermogenic activity. There is promise in the conversion of white adipocytes into beige ones as a therapeutic potential to control and enhance systemic metabolism, but it is difficult to maintain this transformation in vivo because we do not fully understand the mechanism of conversion. In this study, we applied atomic force microscopy (AFM) to characterize beige or white adipocytes during the process of differentiation for morphology, roughness, adhesion, and elasticity at different time points. As cells differentiated to white and beige adipocytes, they exhibited morphological changes as they lipid loaded, transitioning from flattened elongated cells to a rounded shape indicating adipogenesis. While there was an initial decrease in elasticity for both beige and white adipocytes, white adipocytes exhibited a higher elasticity than beige adipocytes at all time points. Beige and white adipogenesis exhibited a decrease in adhesion energy compared to preadipocytes, yet at day 12, white adipocytes had a significant increase in adhesion energy compared to beige adipocytes. This work shows significant differences in the mechanical properties of white vs. beige adipocytes during differentiation. Results from this study contribute to a better understanding of the differentiation of adipocytes which are vital to the therapeutic induction, engineered models, and maintenance of beige adipocytes as a potential approach for enhancing systemic metabolism.

Adipocyte Mitochondria: Deciphering Energetic Functions across Fat Depots in Obesity and Type 2 Diabetes.

Adipose tissue, a central player in energy balance, exhibits significant metabolic flexibility that is often compromised in obesity and type 2 diabetes (T2D). Mitochondrial dysfunction within adipocytes leads to inefficient lipid handling and increased oxidative stress, which together promote systemic metabolic disruptions central to obesity and its complications. This review explores the pivotal role that mitochondria play in altering the metabolic functions of the primary adipocyte types, white, brown, and beige, within the context of obesity and T2D. Specifically, in white adipocytes, these dysfunctions contribute to impaired lipid processing and an increased burden of oxidative stress, worsening metabolic disturbances. Conversely, compromised mitochondrial function undermines their thermogenic capabilities, reducing the capacity for optimal energy expenditure in brown adipocytes. Beige adipocytes uniquely combine the functional properties of white and brown adipocytes, maintaining morphological similarities to white adipocytes while possessing the capability to transform into mitochondria-rich, energy-burning cells under appropriate stimuli. Each type of adipocyte displays unique metabolic characteristics, governed by the mitochondrial dynamics specific to each cell type. These distinct mitochondrial metabolic phenotypes are regulated by specialized networks comprising transcription factors, co-activators, and enzymes, which together ensure the precise control of cellular energy processes. Strong evidence has shown impaired adipocyte mitochondrial metabolism and faulty upstream regulators in a causal relationship with obesity-induced T2D. Targeted interventions aimed at improving mitochondrial function in adipocytes offer a promising therapeutic avenue for enhancing systemic macronutrient oxidation, thereby potentially mitigating obesity. Advances in understanding mitochondrial function within adipocytes underscore a pivotal shift in approach to combating obesity and associated comorbidities. Reigniting the burning of calories in adipose tissues, and other important metabolic organs such as the muscle and liver, is crucial given the extensive role of adipose tissue in energy storage and release.

Epigenetically active chromatin in neonatal iWAT reveals GABPα as a potential regulator of beige adipogenesis.

Background: Thermogenic beige adipocytes, which dissipate energy as heat, are found in neonates and adults. Recent studies show that neonatal beige adipocytes are highly plastic and contribute to >50% of beige adipocytes in adults. Neonatal beige adipocytes are distinct from recruited beige adipocytes in that they develop independently of temperature and sympathetic innervation through poorly defined mechanisms. Methods: We characterized the neonatal beige adipocytes in the inguinal white adipose tissue (iWAT) of C57BL6 postnatal day 3 and 20 mice (P3 and P20) by imaging, genome-wide RNA-seq analysis, ChIP-seq analysis, qRT-PCR validation, and biochemical assays. Results: We found an increase in acetylated histone 3 lysine 27 (H3K27ac) on the promoter and enhancer regions of beige-specific gene UCP1 in iWAT of P20 mice. Furthermore, H3K27ac ChIP-seq analysis in the iWAT of P3 and P20 mice revealed strong H3K27ac signals at beige adipocyte-associated genes in the iWAT of P20 mice. The integration of H3K27ac ChIP-seq and RNA-seq analysis in the iWAT of P20 mice reveal epigenetically active signatures of beige adipocytes, including oxidative phosphorylation and mitochondrial metabolism. We identify the enrichment of GA-binding protein alpha (GABPα) binding regions in the epigenetically active chromatin regions of the P20 iWAT, particularly on beige genes, and demonstrate that GABPα is required for beige adipocyte differentiation. Moreover, transcriptomic analysis and glucose oxidation assays revealed increased glycolytic activity in the neonatal iWAT from P20. Conclusions: Our findings demonstrate that epigenetic mechanisms regulate the development of peri-weaning beige adipocytes via GABPα. Further studies to better understand the upstream mechanisms that regulate epigenetic activation of GABPα and characterization of the metabolic identity of neonatal beige adipocytes will help us harness their therapeutic potential in metabolic diseases.

Aging impairs cold-induced beige adipogenesis and adipocyte metabolic reprogramming.

The energy-burning capability of beige adipose tissue is a potential therapeutic tool for reducing obesity and metabolic disease, but this capacity is decreased by aging. Here, we evaluate the impact of aging on the profile and activity of adipocyte stem and progenitor cells (ASPCs) and adipocytes during the beiging process in mice. We found that aging increases the expression of Cd9 and other fibro-inflammatory genes in fibroblastic ASPCs and blocks their differentiation into beige adipocytes. Fibroblastic ASPC populations from young and aged mice were equally competent for beige differentiation in vitro, suggesting that environmental factors suppress adipogenesis in vivo. Examination of adipocytes by single nucleus RNA-sequencing identified compositional and transcriptional differences in adipocyte populations with aging and cold exposure. Notably, cold exposure induced an adipocyte population expressing high levels of de novo lipogenesis (DNL) genes, and this response was severely blunted in aged animals. We further identified Npr3, which encodes the natriuretic peptide clearance receptor, as a marker gene for a subset of white adipocytes and an aging-upregulated gene in adipocytes. In summary, this study indicates that aging blocks beige adipogenesis and dysregulates adipocyte responses to cold exposure and provides a resource for identifying cold and aging-regulated pathways in adipose tissue.

Perirenal adipose tissue contains a subpopulation of cold-inducible adipocytes derived from brown-to-white conversion.

Perirenal adipose tissue (PRAT) is a unique visceral depot that contains a mixture of brown and white adipocytes. The origin and plasticity of such cellular heterogeneity remains unknown. Here, we combine single-nucleus RNA sequencing with genetic lineage tracing to reveal the existence of a distinct subpopulation of Ucp1-&Cidea+ adipocytes that arises from brown-to-white conversion during postnatal life in the periureter region of mouse PRAT. Cold exposure restores Ucp1 expression and a thermogenic phenotype in this subpopulation. These cells have a transcriptome that is distinct from subcutaneous beige adipocytes and may represent a unique type of cold-recruitable adipocytes. These results pave the way for studies of PRAT physiology and mechanisms controlling the plasticity of brown/white adipocyte phenotypes.

Induction of Browning in White Adipocytes: Fucoidan Characterization and Gold Nanoparticle Synthesis from Undaria pinnatifida Sporophyll Extract.

Seaweed extracts and their specific polysaccharides are widely known for their ability to act as reducing and capping agents during nanoparticle synthesis. Their application is highly favored in green synthesis methods, owing to their eco-friendliness, cost-effectiveness, and remarkable time and energy efficiency. In this study, fucoidan extracted from Undaria pinnatifida sporophyll (UPS) is introduced as a polysaccharide that effectively serves as a dual-function reducing and capping agent for the synthesis of gold nanoparticles (AuNPs). Results from various analyses indicate that AuNPs derived from UPS extract display a uniform spherical shape with an average size of 28.34 ± 1.15 nm and a zeta potential of -37.49 ± 2.13 mV, conclusively confirming the presence of Au. The FT-IR spectra distinctly revealed the characteristic fucoidan bands on the stabilized UPS-AuNPs surface. A 1H-NMR analysis provided additional confirmation by revealing the presence of specific fucoidan protons on the UPS-AuNPs surface. To comprehensively evaluate the impact of UPS extract, UPS-AuNPs, and fucoidan on the biological properties of adipocytes, a rigorous comparative analysis of lipid droplet formation and morphology was conducted. Our findings revealed that adipocytes treated with UPS extract, fucoidan, and UPS-AuNPs, in that order, exhibited a reduction in the total lipid droplet surface area, maximum Ferret diameter, and overall Nile red staining intensity when compared to mature white adipocytes. Furthermore, our analysis of the effects of UPS extracts, UPS-AuNPs, and fucoidan on the expression of key markers associated with white adipose tissue browning, such as UCP1, PGC1a, and PRDM16, demonstrated increased mRNA and protein expression levels in the following order: UPS-AuNPs > fucoidan > UPS extracts. Notably, the production of active mitochondria, which play a crucial role in enhancing energy expenditure in beige adipocytes, also increased in the following order: UPS-AuNPs > fucoidan > UPS extract. These findings underscore the pivotal role of UPS extract, fucoidan, and UPS-AuNPs in promoting adipocyte browning and subsequently enhancing energy expenditure.

Lactate Conversion by Lactate Dehydrogenase B Is Involved in Beige Adipocyte Differentiation and Thermogenesis in Mice.

Adipose tissue (AT) is the primary reservoir of lipid, the major thermogenesis organ during cold exposure, and an important site for lactate production. However, the utilization of lactate as a metabolic substrate by adipocytes, as well as its potential involvement in the regulation of adipocyte thermogenesis, remain unappreciated. In vitro experiments using primary stromal vascular fraction preadipocytes isolated from mouse inguinal white adipose tissue (iWAT) revealed that lactate dehydrogenase B (LDHB), the key glycolytic enzyme that catalyzes the conversion of lactate to pyruvate, is upregulated during adipocyte differentiation, downregulated upon chronic cold stimulation, and regained after prolonged cold exposure. In addition, the global knockout of Ldhb significantly reduced the masses of iWAT and epididymal WAT (eWAT) and impeded the utilization of iWAT during cold exposure. In addition, Ldhb loss of function impaired the mitochondrial function of iWAT under cold conditions. Together, these findings uncover the involvement of LDHB in adipocyte differentiation and thermogenesis.

Dietary Ferulic Acid-Mediated Suppression of Fat Deposits Is Associated with Induction of Beige Adipocyte Formation and Thermogenesis in Inguinal White Adipose Tissue in Mice.

Ferulic acid (FA) is the most abundant phenolic acid in wheat grains. Recent studies have reported that FA intake significantly suppresses body weight gain and accumulation of fat deposits in mice. However, the mechanism by which FA intake affects body fat accumulation remains unclear. We hypothesized that dietary FA induces the formation of beige adipocytes and contributes to the suppression of body fat accumulation. In this study, we investigated whether dietary FA significantly induces beige adipocyte formation and thermogenesis in mice. We found that intake of dietary FA (control diet supplemented with 10 g of FA/kg diet) for 4 wk significantly decreased white adipose tissue (WAT) deposits and body weight gain and significantly induced beige adipocyte formation in inguinal WAT (iWAT) in mice. Furthermore, dietary FA specifically induced thermogenesis in iWAT, dependent upon the significant induction of uncoupling protein 1 expression. These findings suggest that the dietary FA-mediated reduction of WAT accumulation and body weight gain is associated with the induction of beige adipocyte formation and thermogenesis in iWAT, which increases energy expenditure. Our study presents a novel example of dietary FA intake-mediated bioactivity as a functional food-derived factor.

DHA alleviated hepatic and adipose inflammation with increased adipocyte browning in high-fat diet-induced obese mice.

Obesity is associated with accumulation of inflammatory immune cells in white adipose tissue, whereas thermogenic browning adipose tissue is inhibited. Dietary fatty acids are important nutritional components and several clinical and experimental studies have reported beneficial effects of docosahexaenoic acid (DHA) on obesity-related metabolic changes. In this study, we investigated effects of DHA on hepatic and adipose inflammation and adipocyte browning in high-fat diet-induced obese C57BL/6J mice, and in vitro 3T3-L1 preadipocyte differentiation. Since visceral white adipose tissue has a close link with metabolic abnormality, epididymal adipose tissue represents current target for evaluation. A course of 8-week DHA supplementation improved common phenotypes of obesity, including improvement of insulin resistance, inhibition of macrophage M1 polarization, and preservation of macrophage M2 polarization in hepatic and adipose tissues. Moreover, dysregulated adipokines and impaired thermogenic and browning molecules, considered obesogenic mechanisms, were improved by DHA, along with parallel alleviation of endoplasmic reticulum (ER) stress, mitochondrial dysfunction, and mitochondrial DNA stress-directed innate immunity. During 3T3-L1 preadipocytes differentiation, DHA treatment decreased lipid droplet accumulation and increased the levels of thermogenic, browning, and mitochondrial biogenesis molecules. Our study provides experimental evidence that DHA mitigates obesity-associated inflammation and induces browning of adipose tissue in visceral epididymal adipose tissue. Since obesity is associated with metabolic abnormalities across tissues, our findings indicate that DHA may have potential as part of a dietary intervention to combat obesity.

Low Dose of Curcumin Combined with Exercise Synergistically Induces Beige Adipocyte Formation in Mice.

Curcumin (Cur) has various biological effects, including anti-obesity and anti-diabetic properties. However, the molecular mechanisms by which Cur exerts these effects remain unclear. In addition, high doses of Cur have been administered in most animal and human trials to date, due mainly to the poor water solubility of native Cur and its low oral bioavailability. In our previous study, we demonstrated that a highly bioavailable Cur formulation (4.5 mg/kg) induces the formation of beige adipocytes in inguinal white adipose tissue (iWAT) in mice. In the present study, to enhance Cur-mediated beige adipocyte formation and reduce the required functional Cur dose, we investigated whether a low dose of Cur combined with exercise synergistically induced beige adipocyte formation. Cur (1.5 mg Cur/kg, daily) combined with exercise for 4 wk significantly induced beige adipocyte formation in iWAT in mice. This effect was associated with the elevation of interleukin-6 level following subsequent Cur administration combined with exercise. These results indicate that exercise combined with Cur synergistically enhances biological activity and reduces the required Cur dose. These findings suggest that Cur could be used as a dietary supplement during exercise to enhance exercise-mediated health benefits.

Cold-inducible PPA1 is critical for the adipocyte browning in mice.

Promoting the thermogenic capacity of brown/beige adipocytes is becoming a promising strategy to counteract obesity and related metabolic diseases. Inorganic pyrophosphatase 1 (PPA1) is an enzyme that catalyzes the hydrolysis of PPi to Pi, and its presence is required for anabolism to take place in cells. Our previous study demonstrated the importance of PPA1 in maintaining adipose tissue function and whole-body metabolic homeostasis. In this study, we found that the expression of PPA1 was positively associated with the thermogenic capacity of brown/beige adipocytes. PPA1+/- mice exhibited less browning capacity in subcutaneous white adipose tissue compared to wild-type mice and also showed apparent cold intolerance. We found that decreased PPA1 abundance may lead to mitochondrial dysfunction and inhibited adipocyte browning both in vivo and in vitro. Furthermore, our study also revealed that PPA1 worked as a new target gene of nuclear respiratory factor 1 (NRF1), a major transcription regulator of mitochondrial biogenesis. Together, our findings indicated an essential role of PPA1 in mitochondrial function and browning in adipocytes and suggested PPA1 as a new therapeutic target for increasing thermogenesis to combat obesity and metabolic diseases.

H19X-encoded microRNAs induced by IL-4 in adipocyte precursors regulate proliferation to facilitate differentiation.

Adipose tissue, an organ critical for systemic energy homeostasis, is influenced by type 2 immunity in its development and function. The type 2 cytokine interleukin (IL)-4 induces the proliferation of bipotential adipocyte precursors (APs) in white fat tissue and primes these cells for differentiation into beige adipocytes, which are specialized for thermogenesis. However, the underlying mechanisms have not yet been comprehensively examined. Here, we identified six microRNA (miRNA) genes upregulated upon IL-4 stimulation in APs, miR-322, miR-503, miR-351, miR-542, miR-450a, and miR-450b; these are encoded in the H19X locus of the genome. Their expression is positively regulated by the transcription factor Klf4, whose expression also increases upon IL-4 stimulation. These miRNAs shared a large set of target genes, of which 381 genes were downregulated in mRNA expression upon IL-4 stimulation and enriched in Wnt signaling pathways. Two genes with downregulated expression, Ccnd1 and Fzd6, were repressed by H19X-encoded miRNAs. Additionally, the Wnt signaling activator LiCl downregulated the expression of this group of miRNAs in APs, indicating that Wnt signaling-related genes and these miRNAs form a double-negative feedback regulatory loop. This miRNA/Wnt feedback regulation modulated the elevated proliferation of APs induced by IL-4 stimulation and contributed to priming them for beige adipocyte differentiation. Moreover, the aberrant expression of these miRNAs attenuates the differentiation of APs into beige adipocytes. Collectively, our results suggest that H19X-encoded miRNAs facilitate the transition of APs from proliferation to differentiation in the IL-4-mediated regulation.

Androgen Receptor is a Negative Regulator of PRDM16 in Beige Adipocyte.

PRDM16 (PR domain containing protein 16) serves as a dominant activator of brown and beige adipocyte. However, mechanisms underlying the regulation of PRDM16 expression are incompletely understood. A Prdm16 luciferase knockin reporter mouse model is generated, enabling high throughput monitoring of Prdm16 transcription. Single clonal analysis reveals high heterogeneity of Prdm16 expression in the inguinal white adipose tissue (iWAT) cells. Amongst all transcription factors, androgen receptor (Ar) shows the strongest negative correlation with Prdm16. A sex dimorphism for PRDM16 mRNA expression is present in human WAT, with female individuals exhibiting increased expression than males. Androgen-AR signaling mobilization suppresses Prdm16 expression, accompanied by attenuated beiging in beige adipocytes, but not in brown adipose tissue. The suppressive effect of androgens on beiging is abolished upon overexpression of Prdm16. Cleavage under targets and tagmentation mapping reveals direct binding of AR within the intronic region of Prdm16 locus, whereas no direct binding is detected on Ucp1 and other browning-related genes. Adipocyte-selective deletion of Ar potentiates beige cell biogenesis whereas adipocyte-specific overexpression of AR attenuates white adipose beiging. This study highlights an essential role of AR in negative regulation of PRDM16 in WAT and provides an explanation for the observed sex difference in adipose beiging.