Beige Fat Cells Research Articles

Development of a functional beige fat cell line uncovers independent subclasses of cells expressing UCP1 and the futile creatine cycle

Although uncoupling protein 1 (UCP1) is established as a major contributor to adipose thermogenesis, recent data have illustrated an important role for alternative pathways, particularly the futile creatine cycle (FCC). How these pathways co-exist in cells and tissues has not been explored. Beige cell adipogenesis occurs invivo but has been difficult to model invitro; here, we describe the development of a murine beige cell line that executes a robust respiratory response, including uncoupled respiration and the FCC. The key FCC enzyme, tissue-nonspecific alkaline phosphatase (TNAP), is localized almost exclusively to mitochondria in these cells. Surprisingly, single-cell cloning from this cell line shows that cells with the highest levels of UCP1 express little TNAP, and cells with the highest expression of TNAP express little UCP1. Immunofluorescence analysis of subcutaneous fat from cold-exposed mice confirms that the highest levels of these critical thermogenic components are expressed in distinct fat cell populations.

Poly-L-Lactic Acid Reduces the Volume of Dermal Adipose Tissue Through its Metabolite Lactate.

Poly-L-lactic acid (PLLA), a well-established biostimulator that induces collagenases, is widely used among clinical practice to treat skin aging. However, the precise regulatory effect of PLLA on different dermal cell subsets beyond fibroblast has not been fully elucidated. In this study, we constructed in vivo PLLA injection and in vitro PLLA-adipocyte co-culture models to analyze the regulatory effects of PLLA on the volume, differentiation, lipolysis, and thermogenic capacity of dermal adipocyte. We found that PLLA injection significantly reduced the thickness of dermal fat in mice. In co-culture assay, PLLA showed no effect on adipogenesis, but stimulated the lipolysis activity. Interestingly, PLLA also enhanced the differentiation of fat cells into beige fat cells, which possess higher thermogenic capacity. In mechanical study, we blocked adipocyte lactate uptake with a monocarboxylate transporter (MCT1/4) inhibitor and found that the regulatory effect of PLLA on dermal adipocyte relies on its metabolite lactate. In summary, our results suggest that PLLA has complex regulatory effects on the dermal cells, and its ability to improve skin aging is not fully attributed to stimulating collagen synthesis, but also partially involves adipocytes.No Level Assigned This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Mouse vascularized adipose spheroids: an organotypic model for thermogenic adipocytes.

Adipose tissues, particularly beige and brown adipose tissue, play crucial roles in energy metabolism. Brown adipose tissues' thermogenic capacity and the appearance of beige cells within white adipose tissue have spurred interest in their metabolic impact and therapeutic potential. Brown and beige fat cells, activated by environmental factors like cold exposure or by pharmacology, share metabolic mechanisms that drive non-shivering thermogenesis. Understanding these two cell types requires advanced, yet broadly applicable in vitro models that reflect the complex microenvironment and vasculature of adipose tissues. Here we present mouse vascularized adipose spheroids of the stromal vascular microenvironment from inguinal white adipose tissue, a tissue with 'beiging' capacity in mice and humans. We show that adding a scaffold improves vascular sprouting, enhances spheroid growth, and upregulates adipogenic markers, thus reflecting increased adipocyte maturity. Transcriptional profiling via RNA sequencing revealed distinct metabolic pathways upregulated in our vascularized adipose spheroids, with increased expression of genes involved in glucose metabolism, lipid metabolism, and thermogenesis. Functional assessment demonstrated increased oxygen consumption in vascularized adipose spheroids compared to classical 2D cultures, which was enhanced by β-adrenergic receptor stimulation correlating with elevated β-adrenergic receptor expression. Moreover, stimulation with the naturally occurring adipokine, FGF21, induced Ucp1 mRNA expression in the vascularized adipose spheroids. In conclusion, vascularized inguinal white adipose tissue spheroids provide a physiologically relevant platform to study how the stromal vascular microenvironment shapes adipocyte responses and influence activated thermogenesis in beige adipocytes.

Beyond the Cold: Activating Brown Adipose Tissue as an Approach to Combat Obesity.

With a dramatic increase in the number of obese and overweight people, there is a great need for new anti-obesity therapies. With the discovery of the functionality of brown adipose tissue in adults and the observation of beige fat cells among white fat cells, scientists are looking for substances and methods to increase the activity of these cells. We aimed to describe how scientists have concluded that brown adipose tissue is also present and active in adults, to describe where in the human body these deposits of brown adipose tissue are, to summarize the origin of both brown fat cells and beige fat cells, and, last but not least, to list some of the substances and methods classified as BAT promotion agents with their benefits and side effects. We summarized these findings based on the original literature and reviews in the field, emphasizing the discovery, function, and origins of brown adipose tissue, BAT promotion agents, and batokines. Only studies written in English and with a satisfying rating were identified from electronic searches of PubMed.

Ubiquitin ligase RNF20 coordinates sequential adipose thermogenesis with brown and beige fat-specific substrates

In mammals, brown adipose tissue (BAT) and inguinal white adipose tissue (iWAT) execute sequential thermogenesis to maintain body temperature during cold stimuli. BAT rapidly generates heat through brown adipocyte activation, and further iWAT gradually stimulates beige fat cell differentiation upon prolonged cold challenges. However, fat depot-specific regulatory mechanisms for thermogenic activation of two fat depots are poorly understood. Here, we demonstrate that E3 ubiquitin ligase RNF20 orchestrates adipose thermogenesis with BAT- and iWAT-specific substrates. Upon cold stimuli, BAT RNF20 is rapidly downregulated, resulting in GABPα protein elevation by controlling protein stability, which stimulates thermogenic gene expression. Accordingly, BAT-specific Rnf20 suppression potentiates BAT thermogenic activity via GABPα upregulation. Moreover, upon prolonged cold stimuli, iWAT RNF20 is gradually upregulated to promote de novo beige adipogenesis. Mechanistically, iWAT RNF20 mediates NCoR1 protein degradation, rather than GABPα, to activate PPARγ. Together, current findings propose fat depot-specific regulatory mechanisms for temporal activation of adipose thermogenesis.

P03-079-23 New Approach To Weight Loss by Changing White Fat Cells To Beige Fat Cells. Can Dietary Bioactive Components Be Safely Used to Reduce Obesity?

P03-079-23 New Approach To Weight Loss by Changing White Fat Cells To Beige Fat Cells. Can Dietary Bioactive Components Be Safely Used to Reduce Obesity?

The Effect of Exercise Training on Irisin Secretion in Patients with Type 2 Diabetes: A Systematic Review

Irisin is a myokine considered to be a potential mediator of exercise-induced energy metabolism and its secretion is known to promote the browning of beige fat cells in white adipose tissue. However, it is currently not known which exercise protocol is the best to enhance irisin concentration in patients with type 2 diabetes (T2D). The purpose of this study is to provide a review investigating the irisin response to different exercise training modalities and intensities in T2D. A systematic literature search was performed in May 2022. After the selection process from 938 articles, six studies were included. Selected papers presented different exercise training interventions regarding intensity and modality. One study reported no significant differences in serum irisin levels after exercise training, whereas the other five showed a higher increase in serum irisin levels after exercise training with higher differences in irisin secretion after high-intensity training (HIT). No consideration was possible on exercise modalities. The impact of training intensity and modality was found to be partly discordant but data seem to suggest that HIT promotes greater irisin secretion. Despite the limited evidence, HIT, both in interval and continuous modalities, could be suggested as valid exercise training to increase circulating irisin in patients with T2D.

Beta-hydroxybutyrate dampens adipose progenitors’ profibrotic activation through canonical Tgfβ signaling and non-canonical ZFP36-dependent mechanisms

Background/PurposeAdipose tissue contains progenitor cells that contribute to beneficial tissue expansion when needed by de novo adipocyte formation (classical white or beige fat cells with thermogenic potential). However, in chronic obesity, they can exhibit an activated pro-fibrotic, extracellular matrix (ECM)-depositing phenotype that highly aggravates obesity-related adipose tissue dysfunction. MethodsGiven that progenitors' fibrotic activation and fat cell browning appear to be antagonistic cell fates, we have examined the anti-fibrotic potential of pro-browning agents in an obesogenic condition. ResultsIn obese mice fed a high fat diet, thermoneutral housing, which induces brown fat cell dormancy, increases the expression of ECM gene programs compared to conventionally raised animals, indicating aggravation of obesity-related tissue fibrosis at thermoneutrality. In a model of primary cultured murine adipose progenitors, we found that exposure to β-hydroxybutyrate selectively reduced Tgfβ-dependent profibrotic responses of ECM genes like Ctgf, Loxl2 and Fn1. This effect is observed in both subcutaneous and visceral-derived adipose progenitors, as well as in 3T3-L1 fibroblasts. In 30 patients with obesity eligible for bariatric surgery, those with higher circulating β-hydroxybutyrate levels have lower subcutaneous adipose tissue fibrotic scores. Mechanistically, β-hydroxybutyrate limits Tgfβ-dependent collagen accumulation and reduces Smad2-3 protein expression and phosphorylation in visceral progenitors. Moreover, β-hydroxybutyrate induces the expression of the ZFP36 gene, encoding a post-transcriptional regulator that promotes the degradation of mRNA by binding to AU-rich sites within 3′UTRs. Importantly, complete ZFP36 deficiency in a mouse embryonic fibroblast line from null mice, or siRNA knock-down in primary progenitors, indicate that ZFP36 is required for β-hydroxybutyrate anti-fibrotic effects. ConclusionThese data unravel the potential of β-hydroxybutyrate to limit adipose tissue matrix deposition, a finding that might exploited in an obesogenic context.

PWWP2B Fine-Tunes Adipose Thermogenesis by Stabilizing HDACs in a NuRD Subcomplex.

Histone deacetylases (HDACs) are widely involved in many biological processes, as well as in control of brown and beige adipose physiology, but the precise molecular mechanisms by which HDACs are assembled into transcriptional machinery to fine‐tune thermogenic program remain ill‐defined. PWWP domain containing 2b (PWWP2B), which is identified as a component of the nucleosome remodeling and deacetylation complex (NuRD), interacts and stabilizes HDAC1/2 at the thermogenic gene promoters to suppress their expression. Ablation of Pwwp2b promotes adipocyte thermogenesis and ameliorates diet‐induced obesity in vivo. Intriguingly, Pwwp2b is not only a brown fat‐enriched gene but also dramatically induced by cold and sympathetic stimulation, which may serve as a physiological brake to avoid over‐activation of thermogenesis in brown and beige fat cells.

Control of Adipose Cell Browning and Its Therapeutic Potential.

Adipose tissue is the largest endocrine organ in humans and has an important influence on many physiological processes throughout life. An increasing number of studies have described the different phenotypic characteristics of fat cells in adults. Perhaps one of the most important properties of fat cells is their ability to adapt to different environmental and nutritional conditions. Hypothalamic neural circuits receive peripheral signals from temperature, physical activity or nutrients and stimulate the metabolism of white fat cells. During this process, changes in lipid inclusion occur, and the number of mitochondria increases, giving these cells functional properties similar to those of brown fat cells. Recently, beige fat cells have been studied for their potential role in the regulation of obesity and insulin resistance. In this context, it is important to understand the embryonic origin of beige adipocytes, the response of adipocyte to environmental changes or modifications within the body and their ability to transdifferentiate to elucidate the roles of these cells for their potential use in therapeutic strategies for obesity and metabolic diseases. In this review, we discuss the origins of the different fat cells and the possible therapeutic properties of beige fat cells.

Can eosinophils in adipose tissue add fuel to the fire?

In inguinal adipose tissue, beige adipocytes are interspersed among white adipocytes and in close communication with dynamic populations of immune cells. Recent data have demonstrated that anti-inflammatory macrophages (M2) increase thermogenic activity of beige adipocytes, although the mechanism is currently under debate. ILC2, cells via secretion, of methionine enkephalin peptide were found to be able to increase beige thermogenesis. Knights et al. have recently generated a whole-body knock-out of KLF3 (KLF3-/-) to explore its contribution to thermogenesis and weight gain in a diet-induced obesity animal model.

KMT5c modulates adipocyte thermogenesis by regulating Trp53 expression

Brown and beige adipocytes harbor the thermogenic capacity to adapt to environmental thermal or nutritional changes. Histone methylation is an essential epigenetic modification involved in the modulation of nonshivering thermogenesis in adipocytes. Here, we describe a molecular network leading by KMT5c, a H4K20 methyltransferase, that regulates adipocyte thermogenesis and systemic energy expenditure. The expression of Kmt5c is dramatically induced by a β3-adrenergic signaling cascade in both brown and beige fat cells. Depleting Kmt5c in adipocytes in vivo leads to a decreased expression of thermogenic genes in both brown and subcutaneous (s.c.) fat tissues. These mice are prone to high-fat-diet-induced obesity and develop glucose intolerance. Enhanced transformation related protein 53 (Trp53) expression in Kmt5c knockout (KO) mice, that is due to the decreased repressive mark H4K20me3 on its proximal promoter, is responsible for the metabolic phenotypes. Together, these findings reveal the physiological role for KMT5c-mediated H4K20 methylation in the maintenance and activation of the thermogenic program in adipocytes.

Urolithin A Induces Brown-like Phenotype in 3T3-L1 White Adipocytes via β3-adrenergic Receptor-p38 MAPK Signaling Pathway

Recently, pharmacological activation of thermogenesis in brown fat and induction of white fat browning (beiging) have been considered as promising strategies in the development of anti-obesity drugs. During the screening of natural compounds that may stimulate thermogenesis, urolithin A (UroA), which is metabolized from pomegranate ellagitannins by gut microflora, was identified as a potent anti-obesity candidate. In the present study, we elucidated the role of UroA to induce the brown-like phenotype in 3T3-L1 white adipocytes. UroA treatments of up to 50 µM were non-toxic to cells. UroA at 15 µM significantly increased the protein expression levels of brown-fatspecific markers such as UCP1, PRDM16, PGC-1α, C/EBPβ, and PPARα. In addition, it remarkably increased the expression of beige-specific genes, including Cd137, Cidea, Cited1, Tbx1, and Tmen26, in 3T3-L1 white adipocytes and significantly elevated expressions of the brown-fatspecific genes (Ppargc1, Prdm16, and Ucp1) in white adipocytes. Furthermore, UroA treatment of 3T3-L1 white adipocytes cells reduced the expression of key adipogenic transcription factors, whereas enhanced lipolysis and the fat oxidation process. Mechanistic study revealed that UroA treatment induces browning in white adipocytes via activation of β3-AR- and p38 MAPK-dependent signaling pathways. Taken together, UroA has the potential to treat obesity by its capacity to recruit beige fat cells in white adipocyte tissue, thereby contributing to an increase in thermogenesis.

Stepping Up Human Beige Fat Cell Production

Beige fat cells hold significant promise for reducing obesity and metabolic disease. Su etal. (2018) present a robust method to produce human beige adipocytes from pluripotent stem cells via the generation of an expandable intermediary population of mesenchymal progenitor cells.

Obesity-Associated miR-199a/214 Cluster Inhibits Adipose Browning via PRDM16-PGC-1α Transcriptional Network.

miRNAs are important regulators of differentiation, development, and function of brown and beige fat cells. In this study, we identify the role of the miR-199a/214 cluster in the regulation of brown and beige adipocyte development and thermogenesis in vitro and in vivo. We show that expression of the miR-199a/214 cluster is dramatically decreased during brown and beige adipocyte differentiation and in response to cold exposure or β-adrenergic receptor activation. The cluster levels are significantly upregulated in the adipose tissues of obese mice and human subjects. Overexpression of the miR-199a/214 cluster suppresses brown adipocyte differentiation and inhibits thermogenic gene expression and mitochondrial respiration, whereas knockdown of the cluster increases thermogenic gene expression and mitochondrial function in beige adipocytes. In addition, inhibition of the miR-199a/214 cluster promotes beiging effects in vivo. We further show that miR-199a/214 suppresses brown adipocyte differentiation and beige fat development by directly targeting PRDM16 and peroxisome PGC-1α, two key transcriptional regulators of adipose browning. Together, these observations reveal that the miR-199a/214 cluster is a key negative regulator of brown and beige fat development and thermogenesis.

VEGF-A-Expressing Adipose Tissue Shows Rapid Beiging, Enhanced Survival after Transplantation

Adipocyte-derived VEGF-A plays a crucial role in angiogenesis and contributes to adipocyte function and systemic metabolism, such as insulin resistance, chronic inflammation and beigeing of subcutaneous adipose tissue. Utilizing a doxycycline (Dox)-inducible adipocyte-specific VEGF-A overexpressing mouse model, we investigated the dynamics of local VEGF-A effects on tissue beiging of adipose tissue transplants. VEGF-A overexpression in adipocytes triggers angiogenesis. We also observe a rapid appearance of beige fat cells in subcutaneous white adipose tissue (sWATs) within as early as 2 days post induction of VEGF-A. In contrast to conventional cold-induced beiging, VEGF-A-induced beiging is independent of IL-4. We subjected metabolically healthy VEGF-A overexpressing adipose tissue to autologous transplantation. Transfer of subcutaneous adipose tissues taken from VEGF-A overexpressing mice into diet-induced obese mice resulted in systemic metabolic benefits, associated with improved survival of adipocytes and a concomitant reduced inflammatory response. These effects of VEGF-A are tissue autonomous, inducing WAT beigeing and angiogenesis within the transplanted tissue. Our findings indicate that manipulation of adipocyte functions with a bona fide angiogenic factor, such as VEGF-A, significantly improves the survival and volume retention of fat grafts and can convey metabolically favorable properties on the recipient on the basis of beiging. Disclosure M. Kim: None. Y.A. An: None. H. Bang: None. P.E. Scherer: None. J. Park: None.

Molecular dynamics simulation and steered molecular dynamics simulation on irisin dimers.

Irisin is found closely associated with promoting the browning of beige fat cells in white adipose tissue. The crystal structure reveals that irisin forms a continuous inter-subunit β-sheet dimer. Here, molecular dynamics (MD) simulation and steered molecular dynamics (SMD) simulation were performed to investigate the dissociation process and the intricate interactions between the two irisin monomers. In the process of MD, the interactions between the monomers were roughly analyzed through the average numbers of both hydrophobic contacts and H-bonds. Then, SMD was performed to investigate the accurate interaction energy between the monomers. By the analysis of dissociation energy, the van der Waals (vdW) force was identified as the major energy to maintain the dimer structure, which also verified the results of MD simulation. Meanwhile, 11 essential residues were discovered by the magnitude of rupture force during dissociation. Among them, residues Arg75, Glu79, Ile77, Ala88, and Trp90 were reported in a previous study using the method of mutagenesis and size exclusion chromatography, and several new important residues (Arg72, Leu74, Phe76, Gln78, Val80, and Asp91) were also identified. Interestingly, the new important residues that we discovered and the important residues that were reported are located in the opposite side of the β-sheet of the dimer.

Circulating molecules that control brown/beige adipocyte differentiation and thermogenic capacity.

Obesity may be counteracted by increased energy expenditure. Circulating molecules act in the adipose tissue to influence brown and beige adipocyte function, differentiation, and thermogenic capacity, which in turn affects substrate utilization and impacts energy balance at the organismal level. These molecules have been envisioned as biomarkers and potential candidates for pharmacological interventions to treat obesity. Here we summarize studies that demonstrate the roles of endogenous circulating molecules of a wide variety in regulating the thermogenic potential of brown and beige fat cells. This review describes the state-of-the-art in the field and helps researchers to prioritize their targets in future studies.

Caloric Restriction and Diet-Induced Weight Loss Do Not Induce Browning of Human Subcutaneous White Adipose Tissue in Women and Men with Obesity

Caloric restriction (CR) is standard lifestyle therapy inobesity management. CR-induced weight loss improves the metabolic profile of individuals with obesity. In mice, occurrence of beige fat cells in white fat depots favors a metabolically healthy phenotype, and CR promotes browning of white adipose tissue (WAT). Here, human subcutaneous abdominal WAT samples were analyzed in 289 individuals with obesity following a two-phase dietary intervention consisting of an 8week very low calorie diet and a 6-month weight-maintenance phase. Before the intervention, we show sex differences and seasonal variation, with higher expression of brown and beige markers in women with obesity and during winter, respectively. The very low calorie diet resulted in decreased browning of subcutaneous abdominal WAT. During the whole dietary intervention, evolution of body fat and insulin resistance was independent of changes in brown and beige fat markers. These data suggest that diet-induced effects on body fat and insulin resistance are independent of subcutaneous abdominal WAT browning in people with obesity.

Lsd1 prevents age-programed loss of beige adipocytes

Aging is accompanied by major changes in adipose tissue distribution and function. In particular, with time, thermogenic-competent beige adipocytes progressively gain a white adipocyte morphology. However, the mechanisms controlling the age-related transition of beige adipocytes to white adipocytes remain unclear. Lysine-specific demethylase 1 (Lsd1) is an epigenetic eraser enzyme positively regulating differentiation and function of adipocytes. Here we show that Lsd1 levels decrease in aging inguinal white adipose tissue concomitantly with beige fat cell decline. Accordingly, adipocyte-specific increase of Lsd1 expression is sufficient to rescue the age-related transition of beige adipocytes to white adipocytes in vivo, whereas loss of Lsd1 precipitates it. Lsd1 maintains beige adipocytes by controlling the expression of peroxisome proliferator-activated receptor α (Ppara), and treatment with a Ppara agonist is sufficient to rescue the loss of beige adipocytes caused by Lsd1 ablation. In summary, our data provide insights into the mechanism controlling the age-related beige-to-white adipocyte transition and identify Lsd1 as a regulator of beige fat cell maintenance.