Beige adipocytes are a distinct type of thermogenic fat cell in mouse and human

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.

PRDM16 in thermogenic adipocytes mediates an inter-organ protective signaling against alcohol-associated liver disease

Alcohol-associated liver disease (ALD) is one of the major chronic liver diseases and despite the dire clinical needs and extensive research efforts, no effective therapies are available for late-stages of ALD except for liver transplantation. Adipose tissue dysfunction has been implicated in the progression of ALD. Furthermore, it has been previously suggested that thermogenic fat can be activated after alcohol consumption. In this study, increased thermogenic gene expression was detected in both classical brown adipose tissue and beige adipocytes in mice that were given alcohol challenges even when housed at thermoneutrality. In particular, higher expression level of Prdm16, the key transcriptional co-component for beige fat function, was observed in the subcutaneous fat of mice after alcohol challenges. The objective of the present study is to explore the functional significance of adipocyte PRDM16 in the context of ALD. Even though Prdm16 adipocyte-specific-deleted mice (Prdm16-adKO) did not show liver defects at the basal level, following two different alcohol challenge regimens, exacerbated ALD phenotypes were observed in Prdm16-adKO mice compared to that of the control Prdm16fl/fl mice. Mechanistic investigation suggests that adipose dysfunction after alcohol abuse, including alcohol-induced changes in adipose lipolytic activity, fatty acid oxidation and adipokine levels, may render the worsened ALD phenotype in Prdm16-adKO mice. These results indicate PRDM16-mediated signaling in fat plays a protective role against liver injury caused by alcohol abuse, suggesting it may represent a potential therapeutic target against ALD.

Polyamine metabolism in macrophage-adipose tissue function and homeostasis

Intracellular metabolism is a crucial regulator of macrophage function. Recent evidence revealed that the polyamine pathway and subsequent hypusination of eukaryotic initiation factor 5A (eIF5A) are master regulators of immune cell functions. In brown adipose tissue (BAT), macrophages show an impressive degree of heterogenicity, with specific subsets supporting adaptive thermogenesis during cold exposure. In this review, we discuss the impact of polyamine metabolism on macrophage diversity and function, with a particular focus on their role in adipose tissue homeostasis. Thus, we highlight the exploration of how polyamine metabolism in macrophages contributes to BAT homeostasis as an attractive and exciting new field of research.

Differential mitochondrial adaptation and FNDC5 production in brown and white adipose tissue in response to cold and obesity

OBJECTIVE

Fibronectin type III domain-containing protein 5 (FNDC5) modulates adipocyte metabolism by increasing white and brown adipose tissue (WAT and BAT) browning and activity, respectively. We investigated whether FNDC5 can regulate visceral WAT and BAT adaptive thermogenesis by improving mitochondrial homeostasis in response to cold and obesity.

METHODS

Adipose tissue expression of FNDC5 and factors involved in mitochondrial homeostasis were determined in patients with normal weight and obesity (n = 159) and in rats with diet-induced obesity after 1 week of cold exposure (n = 61). The effect of different FNDC5 concentrations on mitochondrial biogenesis, dynamics, and mitophagy was evaluated in vitro in human adipocytes.

RESULTS

In human visceral adipocytes, FNDC5/irisin triggered mitochondrial biogenesis (TFAM) and fusion (MFN1, MFN2, and OPA1) while inhibiting peripheral fission (DNM1L and FIS1) and mitophagy (PINK1 and PRKN). Circulating and visceral WAT expression of FNDC5 was decreased in patients and experimental animals with obesity, whereas its receptor, integrin αV, was upregulated. Obesity increased mitochondrial fusion while decreasing mitophagy in visceral WAT from patients and rats. By contrast, in rat BAT, an upregulation of Fndc5 and genes involved in mitochondrial biogenesis and fission was observed. Cold exposure promoted mitochondrial biogenesis and healthy peripheral fission while repressing Fndc5 expression and mitophagy in BAT from rats.

CONCLUSIONS

Depot differences in FNDC5 production and mitochondrial adaptations in response to obesity and cold might indicate a self-regulatory mechanism to control thermogenesis in response to energy needs.

Deciphering adipose development: Function, differentiation and regulation

The overdevelopment of adipose tissues, accompanied by excess lipid accumulation and energy storage, leads to adipose deposition and obesity. With the increasing incidence of obesity in recent years, obesity is becoming a major risk factor for human health, causing various relevant diseases (including hypertension, diabetes, osteoarthritis and cancers). Therefore, it is of significance to antagonize obesity to reduce the risk of obesity-related diseases. Excess lipid accumulation in adipose tissues is mediated by adipocyte hypertrophy (expansion of pre-existing adipocytes) or hyperplasia (increase of newly-formed adipocytes). It is necessary to prevent excessive accumulation of adipose tissues by controlling adipose development. Adipogenesis is exquisitely regulated by many factors in vivo and in vitro, including hormones, cytokines, gender and dietary components. The present review has concluded a comprehensive understanding of adipose development including its origin, classification, distribution, function, differentiation and molecular mechanisms underlying adipogenesis, which may provide potential therapeutic strategies for harnessing obesity without impairing adipose tissue function.

Two Regions with Different Expression of Lipogenic Enzymes in Rats' Posterior Subcutaneous Fat Depot

Lipid metabolism in various adipose tissue depots can differ vastly. This also applies to lipogenesis, the process of synthesizing fatty acids from acetyl-CoA. This study compared the expression of some lipogenic enzymes: fatty acid synthase (FASN), ATP-citrate lyase (ACLY), and malic enzyme 1 (ME1) in different regions of the posterior subcutaneous adipose tissue in rats. Methods and Results: Posterior subcutaneous adipose tissue collected from twelve-month-old Wistar rats was divided into six parts (A-F). The expression of genes encoding lipogenic enzymes was assessed by measuring their activity and mRNA levels using real-time PCR. In the gluteal region of the fat pad, there were much higher levels of activity and mRNA for these lipogenic enzymes compared to the dorsolumbar region. The mRNA level of FASN increased by more than twentyfold, whereas the level of ME1 and ACLY increased eight- and fivefold respectively. This phenomenon was observed in both old and young animals. Furthermore, the lack of uncoupling protein one (Ucp1) expression suggests that neither the presence of brown adipocytes in the gluteal part nor the transformation of white adipocytes into beige contributed to the observed differences. Conclusion: These results indicate that the gluteal white adipose tissue appears to be a unique and separate subcutaneous fat depot.

TGF-β antagonism synergizes with PPARγ agonism to reduce fibrosis and enhance beige adipogenesis

OBJECTIVES

Adipose tissue depots vary markedly in their ability to store and metabolize triglycerides, undergo beige adipogenesis and susceptibility to metabolic disease. The molecular mechanisms that underlie such heterogeneity are not entirely clear. Previously, we showed that TGF-β signaling suppresses beige adipogenesis via repressing the recruitment of dedicated beige progenitors. Here, we find that TGF-β signals dynamically regulate the balance between adipose tissue fibrosis and beige adipogenesis.

METHODS

We investigated adipose tissue depot-specific differences in activation of TGF-β signaling in response to dietary challenge. RNA-seq and fluorescence activated cell sorting was performed to identify and characterize cells responding to changes in TGF-β signaling status. Mouse models, pharmacological strategies and human adipose tissue analyses were performed to further define the influence of TGF-β signaling on fibrosis and functional beige adipogenesis.

RESULTS

Elevated basal and high-fat diet inducible activation of TGF-β/Smad3 signaling was observed in the visceral adipose tissue depot. Activation of TGF-β/Smad3 signaling was associated with increased adipose tissue fibrosis. RNA-seq combined with fluorescence-activated cell sorting of stromal vascular fraction of epididymal white adipose tissue depot resulted in identification of TGF-β/Smad3 regulated ITGA5+ fibrogenic progenitors. TGF-β/Smad3 signal inhibition, genetically or pharmacologically, reduced fibrosis and increased functional beige adipogenesis. TGF-β/Smad3 antagonized the beneficial effects of PPARγ whereas TGF-β receptor 1 inhibition synergized with actions of rosiglitazone, a PPARγ agonist, to dampen fibrosis and promote beige adipogenesis. Positive correlation between TGF-β activation and ITGA5 was observed in human adipose tissue, with visceral adipose tissue depots exhibiting higher fibrosis potential than subcutaneous or brown adipose tissue depots.

CONCLUSIONS

Basal and high-fat diet inducible activation of TGF-β underlies the heterogeneity of adipose tissue depots. TGF-β/Smad3 activation promotes adipose tissue fibrosis and suppresses beige progenitors. Together, these dual mechanisms preclude functional beige adipogenesis. Controlled inhibition of TβRI signaling and concomitant PPARγ stimulation can suppress adipose tissue fibrosis and promote beige adipogenesis to improve metabolism.

Depot-specific mRNA expression programs in human adipocytes suggest physiological specialization via distinct developmental programs

Adipose tissue is distributed in diverse locations throughout the human body. Not much is known about the extent to which anatomically distinct adipose depots are functionally distinct, specialized organs, nor whether depot-specific characteristics result from intrinsic developmental programs, as opposed to reversible physiological responses to differences in tissue microenvironment. We used DNA microarrays to compare mRNA expression patterns of isolated human adipocytes and cultured adipose stem cells, before and after ex vivo adipocyte differentiation, from seven anatomically diverse adipose tissue depots. Adipocytes from different depots display distinct gene expression programs, which are most closely shared with anatomically related depots. mRNAs whose expression differs between anatomically diverse groups of depots (e.g., subcutaneous vs. internal) suggest important functional specializations. These depot-specific differences in gene expression were recapitulated when adipocyte progenitor cells from each site were differentiated ex vivo, suggesting that progenitor cells from specific anatomic sites are deterministically programmed to differentiate into depot-specific adipocytes. Many developmental transcription factors show striking depot-specific patterns of expression, suggesting that adipocytes in each anatomic depot are programmed during early development in concert with anatomically related tissues and organs. Our results support the hypothesis that adipocytes from different depots are functionally distinct and that their depot-specific specialization reflects distinct developmental programs.

Effective Prevention and Treatment of Acute Leukemias in Mice by Activation of Thermogenic Adipose Tissues

Acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL) are common hematological malignancies in adults. Despite considerable research advances, the development of standard therapies, supportive care, and prognosis for the majority of AML and ALL patients remains poor and the development of new effective therapy is urgently needed. Here, it is reported that activation of thermogenic adipose tissues (TATs) by cold exposure or β3-adrenergic receptor agonists markedly alleviated the development and progression of AML and ALL in mouse leukemia models. TAT activation (TATA) monotherapy substantially reduces leukemic cells in bone marrow and peripheral blood, and suppresses leukemic cell invasion, including hepatomegaly and splenomegaly. Notably, TATA therapy prolongs the survivals of AML- and ALL-bearing mice. Surgical removal of thermogenic brown adipose tissue (BAT) or genetic deletion of uncoupling protein 1 (UCP1) largely abolishes the TATA-mediated anti-leukemia effects. Metabolomic pathway analysis demonstrates that glycolytic metabolism, which is essential for anabolic leukemic cell growth, is severely impaired in TATA-treated leukemic cells. Moreover, a combination of TATA therapy with chemotherapy produces enhanced anti-leukemic effects and reduces chemotoxicity. These data provide a new TATA-based therapeutic paradigm for the effective treatment of AML, ALL, and likely other types of hematological malignancies.

Maintenance of thermogenic adipose tissues despite loss of the H3K27 acetyltransferases p300 or CBP

Brown and beige adipose tissues are specialized for thermogenesis and are important for energy balance in mice. Mounting evidence suggests that chromatin-modifying enzymes are integral for the development, maintenance, and functioning of thermogenic adipocytes. p300 and cAMP-response element binding protein (CREB)-binding protein (CBP) are histone acetyltransferases (HATs) responsible for writing the transcriptionally activating mark H3K27ac. Despite their homology, p300 and CBP do have unique tissue- and context-dependent roles, which have yet to be examined in brown and beige adipocytes specifically. We assessed the requirement of p300 or CBP in thermogenic fat using uncoupling protein 1 (Ucp1)-Cre-mediated knockdown in mice to determine whether their loss impacted tissue development, susceptibility to diet-induced obesity, and response to pharmacological induction via β3-agonism. Despite successful knockdown, brown adipose tissue mass and expression of thermogenic markers were unaffected by loss of either HAT. As such, knockout mice developed a comparable degree of diet-induced obesity and glucose intolerance to that of floxed controls. Furthermore, "browning" of white adipose tissue by the β3-adrenergic agonist CL-316,243 remained largely intact in knockout mice. Although p300 and CBP have nonoverlapping roles in other tissues, our results indicate that they are individually dispensable within thermogenic fats specifically, possibly due to functional compensation by one another.NEW & NOTEWORTHY The role of transcriptionally activating H3K27ac epigenetic mark has yet to be examined in mouse thermogenic fats specifically, which we achieved here via Ucp1-Cre-driven knockdown of the histone acetyltransferases (HAT) p300 or CBP under several metabolic contexts. Despite successful knockdown of either HAT, brown adipose tissue was maintained at room temperature. As such, knockout mice were indistinguishable to controls when fed an obesogenic diet or when given a β3-adrenergic receptor agonist to induce browning of white fat. Unlike other tissues, thermogenic fats are resilient to p300 or CBP ablation, likely due to sufficient functional overlap between them.

SGLT2 inhibitor canagliflozin reduces visceral adipose tissue in db/db mice by modulating AMPK/KLF4 signaling and regulating mitochondrial dynamics to induce browning

Obesity is characterized by excessive accumulation of adipose tissue (mainly visceral). The morphology and function of mitochondria are crucial for regulating adipose browning and weight loss. Research suggests that the SGLT2 inhibitor canagliflozin may induce weight loss through an unknown mechanism, particularly targeting visceral adipose tissue. While Krueppel-Like Factor 4 (KLF4) is known to be essential for energy metabolism and mitochondrial function, its specific impact on visceral adipose tissue remains unclear. We administered canagliflozin to db/db mice for 8 weeks, or exposed adipocytes to canagliflozin for 24 h. The expression levels of browning markers, mitochondrial dynamics, and KLF4 were assessed. Then we validated the function of KLF4 through overexpression in vivo and in vitro. Adenosine monophosphate-activated protein kinase (AMPK) agonists, inhibitors, and KLF4 si-RNA were employed to elucidate the relationship between AMPK and KLF4. The findings demonstrated that canagliflozin significantly decreased body weight in db/db mice and augmented cold-induced thermogenesis. Additionally, canagliflozin increased the expression of mitochondrial fusion-related factors while reducing the levels of fission markers in epididymal white adipose tissue. These consistent findings were mirrored in canagliflozin-treated adipocytes. Similarly, overexpression of KLF4 in both adipocytes and db/db mice yielded comparable results. In all, canagliflozin mitigates obesity in db/db mice by promoting the brown visceral adipocyte phenotype through enhanced mitochondrial fusion via AMPK/KLF4 signaling.

Lipid Droplets Big and Small: Basic Mechanisms That Make Them All

Lipid droplets (LDs) are dynamic storage organelles with central roles in lipid and energy metabolism. They consist of a core of neutral lipids, such as triacylglycerol, which is surrounded by a monolayer of phospholipids and specialized surface proteins. The surface composition determines many of the LD properties, such as size, subcellular distribution, and interaction with partner organelles. Considering the diverse energetic and metabolic demands of various cell types, it is not surprising that LDs are highly heterogeneous within and between cell types. Despite their diversity, all LDs share a common biogenesis mechanism. However, adipocytes have evolved specific adaptations of these basic mechanisms, enabling the regulation of lipid and energy metabolism at both the cellular and organismal levels. Here, we discuss recent advances in the understanding of both the general mechanisms of LD biogenesis and the adipocyte-specific adaptations controlling these fascinating organelles.

Characterization of Ucp1-iCre knockin mice reveals the recombination activity in male germ cells

Ucp1 promoter-driven Cre transgenic mice are useful in the manipulation of gene expression specifically in thermogenic adipose tissues. However, the wildly used Ucp1-Cre line was generated by random insertion into the genome and showed ectopic activity in some tissues beyond adipose tissues. Here, we characterized a knockin mouse line Ucp1-iCre generated by targeting IRES-Cre cassette immediately downstream the stop codon of the Ucp1 gene. The Cre insertion had little to no effect on uncoupling protein 1 (UCP1) levels in brown adipose tissue. Ucp1-iCre mice of both genders exhibited normal thermogenesis and cold tolerance. When crossed with Rosa-tdTomato reporter mice, Ucp1-iCre mice showed robust Cre activity in thermogenic adipose tissues. In addition, limited Cre activity was sparsely present in the ventromedial hypothalamus (VMH), choroid plexus, kidney, adrenal glands, ovary, and testis in Ucp1-iCre mice, albeit to a much lesser extent and with reduced intensity compared with the conventional Ucp1-Cre line. Single-cell transcriptome analysis revealed Ucp1 mRNA expression in male spermatocytes. Moreover, male Ucp1-iCre mice displayed a high frequency of Cre-mediated recombination in the germline, whereas no such effect was observed in female Ucp1-iCre mice. These findings suggest that Ucp1-iCre mice offer promising utility in the context of conditional gene manipulation in thermogenic adipose tissues, while also highlighting the need for caution in mouse mating and genotyping procedures.NEW & NOTEWORTHY Ucp1 promoter-driven Cre transgenic mice are useful in the manipulation of gene expression specifically in thermogenic adipose tissues. The widely used Ucp1-Cre mouse line (Ucp1-CreEvdr), which was generated using the bacterial artificial chromosome (BAC) strategy, exhibits major brown and white fat transcriptomic dysregulation and ectopic activity beyond adipose tissues. Here, we comprehensively validate Ucp1-iCre knockin mice, which serve as another optional model besides Ucp1-CreEvdr mice for specific genetic manipulation in thermogenic tissue.

Keys to the switch of fat burning: stimuli that trigger the uncoupling protein 1 (UCP1) activation in adipose tissue

As one of the main pathogenic factors of cardiovascular and cerebrovascular diseases, the incidence of metabolic diseases such as adiposity and metabolic dysfunction-associated steatotic liver disease (MASLD) is increasing annually. It is urgent and crucial to find more therapeutic targets to treat these diseases. Mainly expressed in brown adipocytes, mitochondrial uncoupling protein 1 (UCP1) is key to the thermogenesis of classical brown adipose tissue (BAT). Furthermore, white adipose tissue (WAT) is likely to express more UCP1 and subsequently acquire the ability to undergo thermogenesis under certain stimuli. Therefore, targeting and activating UCP1 to promote increased BAT thermogenesis and browning of WAT are helpful in treating metabolic diseases, such as adiposity and MASLD. In this case, the stimuli that activate UCP1 are emerging. Therefore, we summarize the thermogenic stimuli that have activated UCP1 in recent decades, among which cold exposure is one of the stimuli first discovered to activate BAT thermogenesis. As a convenient and efficient therapy with few side effects and good metabolic benefits, physical exercise can also activate the expression of UCP1 in adipose tissue. Notably, for the first time, we have summarized and demonstrated the stimuli of traditional Chinese medicines that can activate UCP1, such as acupuncture, Chinese herbal formulas, and Chinese medicinal herbs. Moreover, pharmacological agents, functional foods, food ingredients, and the gut microbiota are also commonly associated with regulating and activating UCP1. The identification and analysis of UCP1 stimuli can greatly facilitate our understanding of adipose tissue thermogenesis, including the browning of WAT. Thus, it is more conducive to further research and therapy for glucose and lipid metabolism disorders.

The Therapeutic Potential of Theobromine in Obesity: A Comprehensive Review

Obesity, characterized by chronic low-grade inflammation, is a significant health concern. Phytochemicals found in plants are being explored for therapeutic use, particularly in combating obesity. Among these, theobromine, commonly found in cocoa and chocolate, shows promise. Although not as extensively studied as caffeine, theobromine exhibits positive effects on human health. It improves lipid profiles, aids in asthma treatment, lowers blood pressure, regulates gut microbiota, reduces tumor formation, moderates blood glucose levels, and acts as a neuroprotective agent. Studies demonstrate its anti-obesity effects through mechanisms such as browning of white adipose tissue, activation of brown adipose tissue, anti-inflammatory properties, and reduction of oxidative stress. This study aims to suggest theobromine as a potential therapeutic agent against obesity-related complications.

Effects of Cryolipolysis on the Conversion of White Adipose Tissue: Pilot Study

INTRODUCTION

Cryolipolysis (CLL) is a widely employed noninvasive procedure for body fat reduction. It operates by inducing cooling, leading to the crystallization of cytoplasmic lipids, loss of cellular integrity, and apoptosis/necrosis of adipocytes, accompanied by local inflammation. Ongoing discussions revolve around CLL's potential to transform white adipocytes into brown adipocytes, potentially yielding more significant effects compared to alternative procedures.

OBJECTIVE

Thus, this randomized, blinded clinical study aimed to investigate the effects of CLL on adipose tissue and elucidate the mechanisms involved in its application and capacity for adipocyte conversion.

METHODOLOGY

Tissue samples from six patients were assessed at intervals of 45, 60, and 90 days following the application of the CLL protocol during abdominoplasty surgeries.

RESULTS

The samples underwent immunohistochemical analyses targeting various markers, revealing higher expression of PPAR-gamma, PPAR-alpha, and UCP-1 markers in CLL-treated samples.

CONCLUSION

Therefore, the present study suggests that CLL has the ability to intervene in adipocyte conversion.

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 in vivo but has been difficult to model in vitro; 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.

Single-nucleus transcriptomics identifies separate classes of UCP1 and futile cycle adipocytes

Adipose tissue can recruit catabolic adipocytes that utilize chemical energy to dissipate heat. This process occurs either by uncoupled respiration through uncoupling protein 1 (UCP1) or by utilizing ATP-dependent futile cycles (FCs). However, it remains unclear how these pathways coexist since both processes rely on the mitochondrial membrane potential. Utilizing single-nucleus RNA sequencing to deconvolute the heterogeneity of subcutaneous adipose tissue in mice and humans, we identify at least 2 distinct subpopulations of beige adipocytes: FC-adipocytes and UCP1-beige adipocytes. Importantly, we demonstrate that the FC-adipocyte subpopulation is highly metabolically active and utilizes FCs to dissipate energy, thus contributing to thermogenesis independent of Ucp1. Furthermore, FC-adipocytes are important drivers of systemic energy homeostasis and linked to glucose metabolism and obesity resistance in humans. Taken together, our findings identify a noncanonical thermogenic adipocyte subpopulation, which could be an important regulator of energy homeostasis in mammals.

Unravelling the function of prdm16 in human tumours: A comparative analysis of haematologic and solid tumours

Extensive research has shown that PR domain 16 (PRDM16) plays a critical role in adipose tissue metabolism, including processes such as browning and thermogenesis of adipocytes, beigeing of adipocytes, and adipogenic differentiation of myoblasts. These functions have been associated with diseases such as obesity and diabetes. Additionally, PRDM16 has been correlated with various other conditions, including migraines, heterochromatin abnormalities, metabolic syndrome, cardiomyopathy, sarcopenia, nonsyndromic cleft lip, and essential hypertension, among others. However, there is currently no systematic or comprehensive conclusion regarding the mechanism of PRDM16 in human tumours, including haematologic and solid tumours. The aim of this review is to provide an overview of the research progress on PRDM16 in haematologic and solid tumours by incorporating recent literature findings. Furthermore, we explore the prospects of PRDM16 in the precise diagnosis and treatment of human haematologic and solid tumours.

Gene expression and characterization of clonally derived murine embryonic brown and brite adipocytes

White adipocytes store energy, while brown and brite adipocytes release heat via nonshivering thermogenesis. In this study, we characterized two murine embryonic clonal preadipocyte lines, EB5 and EB7, each displaying unique gene marker expression profiles. EB5 cells differentiate into brown adipocytes, whereas EB7 cells into brite (also known as beige) adipocytes. To draw a comprehensive comparison, we contrasted the gene expression patterns, adipogenic capacity, as well as carbohydrate and lipid metabolism of these cells to that of F442A, a well-known white preadipocyte and adipocyte model. We found that commitment to differentiation in both EB5 and EB7 cells can be induced by 3-Isobutyl-1-methylxanthine/dexamethasone (Mix/Dex) and staurosporine/dexamethasone (St/Dex) treatments. Additionally, the administration of rosiglitazone significantly enhances the brown and brite adipocyte phenotypes. Our data also reveal the involvement of a series of genes in the transcriptional cascade guiding adipogenesis, pinpointing GSK3β as a critical regulator for both EB5 and EB7 adipogenesis. In a developmental context, we observe that, akin to brown fat progenitors, brite fat progenitors make their appearance in murine development by 11-12 days of gestation or potentially earlier. This result contributes to our understanding of adipocyte lineage specification during embryonic development. In conclusion, EB5 and EB7 cell lines are valuable for research into adipocyte biology, providing insights into the differentiation and development of brown and beige adipocytes. Furthermore, they could be useful for the characterization of drugs targeting energy balance for the treatment of obesity and metabolic diseases.

Exercise-Induced cytokines, diet, and inflammation and their role in adipose tissue metabolism

Background

Obesity poses a significant global health challenge, necessitating effective prevention and treatment strategies. Exercise and diet are recognized as pivotal interventions in combating obesity. This study reviews the literature concerning the impact of exercise-induced cytokines, dietary factors, and inflammation on adipose tissue metabolism, shedding light on potential pathways for therapeutic intervention.

Methodology

A comprehensive review of relevant literature was conducted to elucidate the role of exercise-induced cytokines, including interleukin-6 (IL-6), interleukin-15 (IL-15), brain-derived neurotrophic factor (BDNF), irisin, myostatin, fibroblast growth factor 21 (FGF21), follistatin (FST), and angiopoietin-like 4 (ANGPTL4), in adipose tissue metabolism. Various databases were systematically searched using predefined search terms to identify relevant studies. Articles selected for inclusion underwent thorough analysis to extract pertinent data on the mechanisms underlying the influence of these cytokines on adipose tissue metabolism.

Results and Discussion

Exercise-induced cytokines exert profound effects on adipose tissue metabolism, influencing energy expenditure (EE), thermogenesis, fat loss, and adipogenesis. For instance, IL-6 activates AMP-activated protein kinase (AMPK), promoting fatty acid oxidation and reducing lipogenesis. IL-15 upregulates peroxisome proliferator-activated receptor delta (PPARδ), stimulating fatty acid catabolism and suppressing lipogenesis. BDNF enhances AMPK-dependent fat oxidation, while irisin induces the browning of white adipose tissue (WAT), augmenting thermogenesis. Moreover, myostatin, FGF21, FST, and ANGPTL4 each play distinct roles in modulating adipose tissue metabolism, impacting factors such as fatty acid oxidation, adipogenesis, and lipid uptake. The elucidation of these pathways offers valuable insights into the complex interplay between exercise, cytokines, and adipose tissue metabolism, thereby informing the development of targeted obesity management strategies.

Conclusion

Understanding the mechanisms by which exercise-induced cytokines regulate adipose tissue metabolism is critical for devising effective obesity prevention and treatment modalities. Harnessing the therapeutic potential of exercise-induced cytokines, in conjunction with dietary interventions, holds promise for mitigating the global burden of obesity. Further research is warranted to delineate the precise mechanisms underlying the interactions between exercise, cytokines, and adipose tissue metabolism.

Kinin B1 receptor deficiency promotes enhanced adipose tissue thermogenic response to β3-adrenergic stimulation

OBJECTIVE AND DESIGN

Kinin B1 receptor (B1R) has a key role in adipocytes to protect against obesity and glycemic metabolism, thus becoming a potential target for regulation of energy metabolism and adipose tissue thermogenesis.

MATERIAL OR SUBJECTS

Kinin B1 knockout mice (B1KO) were subjected to acute induction with CL 316,243 and chronic cold exposure.

METHODS

Metabolic and histological analyses, gene and protein expression and RNA-seq were performed on interscapular brown adipose tissue (iBAT) and inguinal white adipose tissue (iWAT) of mice.

RESULTS

B1KO mice, under acute effect of CL 316,243, exhibited increased energy expenditure and upregulated thermogenic genes in iWAT. They were also protected from chronic cold, showing enhanced non-shivering thermogenesis with increased iBAT mass (~ 90%) and recruitment of beige adipocytes in iWAT (~ 50%). Positive modulation of thermogenic and electron transport chain genes, reaching a 14.5-fold increase for Ucp1 in iWAT. RNA-seq revealed activation of the insulin signaling pathways for iBAT and oxidative phosphorylation, tricarboxylic acid cycle, and browning pathways for iWAT.

CONCLUSION

B1R deficiency induced metabolic and gene expression alterations in adipose tissue, activating thermogenic pathways and increasing energy metabolism. B1R antagonists emerge as promising therapeutic targets for regulating obesity and associated metabolic disorders, such as inflammation and diabetes.

The Different Shades of Thermogenic Adipose Tissue

PURPOSE OF REVIEW

By providing a concise overview of adipose tissue types, elucidating the regulation of adipose thermogenic capacity in both physiological contexts and chronic wasting diseases (a protracted hypermetabolic state that precipitates sustained catabolism and consequent progressive corporeal atrophy), and most importantly, delving into the ongoing discourse regarding the role of adipose tissue thermogenic activation in chronic wasting diseases, this review aims to provide researchers with a comprehensive understanding of the field.

RECENT FINDINGS

Adipose tissue, traditionally classified as white, brown, and beige (brite) based on its thermogenic activity and potential, is intricately regulated by complex mechanisms in response to exercise or cold exposure. This regulation is adipose depot-specific and dependent on the duration of exposure. Excessive thermogenic activation of adipose tissue has been observed in chronic wasting diseases and has been considered a pathological factor that accelerates disease progression. However, this conclusion may be confounded by the detrimental effects of excessive lipolysis. Recent research also suggests that such activation may play a beneficial role in the early stages of chronic wasting disease and provide potential therapeutic effects. A more comprehensive understanding of the changes in adipose tissue thermogenesis under physiological and pathological conditions, as well as the underlying regulatory mechanisms, is essential for the development of novel interventions to improve health and prevent disease.

Natriuretic peptide receptor-C perturbs mitochondrial respiration in white adipose tissue

Natriuretic peptide receptor-C (NPR-C) is highly expressed in adipose tissues and regulates obesity-related diseases; however, the detailed mechanism remains unknown. In this research, we aimed to explore the potential role of NPR-C in cold exposure and high-fat/high-sugar (HF/HS) diet-induced metabolic changes, especially in regulating white adipose tissue (WAT) mitochondrial function. Our findings showed that NPR-C expression, especially in epididymal WAT (eWAT), was reduced after cold exposure. Global Npr3 (gene encoding NPR-C protein) deficiency led to reduced body weight, increased WAT browning, thermogenesis, and enhanced expression of genes related to mitochondrial biogenesis. RNA-sequencing of eWAT showed that Npr3 deficiency enhanced the expression of mitochondrial respiratory chain complex genes and promoted mitochondrial oxidative phosphorylation in response to cold exposure. In addition, Npr3 KO mice were able to resist obesity induced by HF/HS diet. Npr3 knockdown in stromal vascular fraction (SVF)-induced white adipocytes promoted the expression of proliferator-activated receptor gamma coactivator 1α (PGC1α), uncoupling protein one (UCP1), and mitochondrial respiratory chain complexes. Mechanistically, NPR-C inhibited cGMP and calcium signaling in an NPR-B-dependent manner but suppressed cAMP signaling in an NPR-B-independent manner. Moreover, Npr3 knockdown induced browning via AKT and p38 pathway activation, which were attenuated by Npr2 knockdown. Importantly, treatment with the NPR-C-specific antagonist, AP-811, decreased WAT mass and increased PGC-1α, UCP1, and mitochondrial complex expression. Our findings reveal that NPR-C deficiency enhances mitochondrial function and energy expenditure in white adipose tissue, contributing to improved metabolic health and resistance to obesity.

Adaptive Induction of Nonshivering Thermogenesis in Muscle Rather Than Brown Fat Could Counteract Obesity

Warm-blooded animals such as birds and mammals are able to protect stable body temperature due to various thermogenic mechanisms. These processes can be facultative (occurring only under specific conditions, such as acute cold) and adaptive (adjusting their capacity according to long-term needs). They can represent a substantial part of overall energy expenditure and, therefore, affect energy balance. Classical mechanisms of facultative thermogenesis include shivering of skeletal muscles and (in mammals) non-shivering thermogenesis (NST) in brown adipose tissue (BAT), which depends on uncoupling protein 1 (UCP1). Existence of several alternative thermogenic mechanisms has been suggested. However, their relative contribution to overall heat production and the extent to which they are adaptive and facultative still needs to be better defined. Here we focus on comparison of NST in BAT with thermogenesis in skeletal muscles, including shivering and NST. We present indications that muscle NST may be adaptive but not facultative, unlike UCP1-dependent NST. Due to its slow regulation and low energy efficiency, reflecting in part the anatomical location, induction of muscle NST may counteract development of obesity more effectively than UCP1-dependent thermogenesis in BAT.

Cold-induced phosphatidylethanolamine synthesis in liver and brown adipose tissue of mice

Increasing energy expenditure in brown adipose (BAT) tissue by cold-induced lipolysis is discussed as a potential strategy to counteract imbalanced lipid homeostasis caused through unhealthy lifestyle and cardiometabolic disease. Yet, it is largely unclear how liberated fatty acids (FA) are metabolized. We investigated the liver and BAT lipidome of mice housed for 1 week at thermoneutrality, 23 °C and 4 °C using quantitative mass spectrometry-based lipidomics. Housing at temperatures below thermoneutrality triggered the generation of phosphatidylethanolamine (PE) in both tissues. Particularly, the concentrations of PE containing polyunsaturated fatty acids (PUFA) in their acyl chains like PE 18:0_20:4 were increased at cold. Investigation of the plasma's FA profile using gas chromatography coupled to mass spectrometry revealed a negative correlation of PUFA with unsaturated PE in liver and BAT indicating a flux of FA from the circulation into these tissues. Beta-adrenergic stimulation elevated intracellular levels of PE 38:4 and PE 40:6 in beige wildtype adipocytes, but not in adipose triglyceride lipase (ATGL)-deficient cells. These results imply an induction of PE synthesis in liver, BAT and thermogenic adipocytes after activation of the beta-adrenergic signaling cascade.

New Insights into Adipose Tissue Metabolic Function and Dysfunction, 2nd Edition

The adipose organ is well recognized for its role in energy storage and mobilization, responding to nutrient availability, the body's needs, and thermogenesis, thereby regulating the organism's energy balance [...].

Association of monoaminergic gene polymorphisms in chronic inflammatory pulmonary disease patients with successful smoking cessation

BACKGROUND

Albeit smoking cessation has unequivocal health benefits, attempts to quit are not unanimous, even in patient populations at high risk for smoking-related diseases cessation. Allelic variations of enzymes involved in dopamine metabolism are being considered as candidates for nicotine addiction. We set out to assess whether rs4680 G/A and rs2235186 G/A polymorphisms of COMT and MAO-A, respectively are associated with the ability to quit smoking in chronic inflammatory pulmonary disease patients.

METHODS

Patients managed for chronic inflammatory pulmonary disease by the Department of Pulmonology (University of Debrecen, Hungary), with a current or past smoking habit were included in the current analysis. The study was designed in line with the STROBE statement for cross-sectional studies and was approved by the National Center for Public Health, Hungary. Genomic DNA was extracted from peripheral blood specimens. SNPs were genotyped using TaqMan SNP genotyping assays.

RESULTS

rs4680 COMT polymorphism showed significant effect for successful smoking cessation in patients with pulmonary disease. Accordingly, A/A subjects had lower odds for successful smoking cessation (odds ratio 0.37; 95% confidence interval 0.20-0.69, p = 0.002 (additive model). On the other hand, patients homozygous for the minor allele (A) at rs2235186 of MAO-A showed a non-significant trend toward increased odds for successful smoking cessation.

CONCLUSIONS

The presence of the minor allele for rs4680 COMT was shown to decrease the odds for successful smoking cessation, a finding that may be interpreted in view of the altered balance between tonic and phasic dopamine release.

Cold Exposure Rejuvenates the Metabolic Phenotype of Panx1-/- Mice

Pannexin1 (Panx1) ATP channels are important in adipocyte biology, potentially influencing energy storage and expenditure. We compared the metabolic phenotype of young (14 weeks old) and mature (20 weeks old) wild-type (WT) and Panx1-/- mice exposed or not to cold (6 °C) during 28 days, a condition promoting adipocyte browning. Young Panx1-/- mice weighed less and exhibited increased fat mass, improved glucose tolerance, and lower insulin sensitivity than WT mice. Their energy expenditure and respiratory exchange ratio (RER) were increased, and their fatty acid oxidation decreased. These metabolic effects were no longer observed in mature Panx1-/- mice. The exposure of mature mice to cold exacerbated their younger metabolic phenotype. The white adipose tissue (WAT) of cold-exposed Panx1-/- mice contained more small-sized adipocytes, but, in contrast to WT mice, white adipocytes did not increase their expression of Ucp1 nor of other markers of browning adipocytes. Interestingly, Glut4 expression was already enhanced in the WAT of young Panx1-/- mice kept at 22 °C as compared to WT mice. Thus, Panx1 deletion exerts overall beneficial metabolic effects in mice that are pre-adapted to chronic cold exposure. Panx1-/- mice show morphological characteristics of WAT browning, which are exacerbated upon cold exposure, an effect that appears to be associated with Ucp1-independent thermogenesis.

Physiological and metabolic functions of the β3-adrenergic receptor and an approach to therapeutic achievements

A specific type of beta-adrenergic receptor was discovered in the decade of 1980s and subsequently recognized as a new type of beta-adrenergic receptor, called beta3-adrenoceptor (β3-AR). β3-AR expresses in different tissues, including adipose tissue, gall bladder, stomach, small intestine, cardiac myocytes, urinary bladder, and brain. Structurally, β3-AR is very similar to β1- and β2-AR and belongs to a G-protein coupled receptor that uses cAMP as an intracellular second messenger. Alternatively, it also activates the NO-cGMP cascade. Stimulation of the β3-AR increases lipolysis, fatty acid oxidation, energy expenditure, and insulin action, leading to anti-obesity and anti-diabetic activity. Moreover, β3-AR differentially regulates the myocardial contraction and relaxes the urinary bladder to balance the cardiac activity and delay the micturition reflex, respectively. In recent years, this receptor has served as an attractive target for the treatment of obesity, type 2 diabetes, congestive heart failure, and overactive bladder syndrome. Several β3-AR agonists are in the emerging stage that can exert novel pharmacological benefits in different therapeutic areas. The present review focuses on the structure, signaling, physiological, and metabolic activities of β3-AR. Additionally, therapeutic approaches of β3-AR have also been considered.

From development to future prospects: The adipose tissue & adipose tissue organoids

Living organisms store their energy in different forms of fats including lipid droplets, triacylglycerols, and steryl esters. In mammals and some non-mammal species, the energy is stored in adipose tissue which is the innervated specialized connective tissue that incorporates a variety of cell types such as macrophages, fibroblasts, pericytes, endothelial cells, adipocytes, blood cells, and several kinds of immune cells. Adipose tissue is so complex that the scope of its function is not only limited to energy storage, it also encompasses to thermogenesis, mechanical support, and immune defense. Since defects and complications in adipose tissue are heavily related to certain chronic diseases such as obesity, cardiovascular diseases, type 2 diabetes, insulin resistance, and cholesterol metabolism defects, it is important to further study adipose tissue to enlighten further mechanisms behind those diseases to develop possible therapeutic approaches. Adipose organoids are accepted as very promising tools for studying fat tissue development and its underlying molecular mechanisms, due to their high recapitulation of the adipose tissue in vitro. These organoids can be either derived using stromal vascular fractions or pluripotent stem cells. Due to their great vascularization capacity and previously reported incontrovertible regulatory role in insulin sensitivity and blood glucose levels, adipose organoids hold great potential to become an excellent candidate for the source of stem cell therapy. In this review, adipose tissue types and their corresponding developmental stages and functions, the importance of adipose organoids, and the potential they hold will be discussed in detail.

Lesson on obesity and anatomy of adipose tissue: new models of study in the era of clinical and translational research

Obesity is a serious global illness that is frequently associated with metabolic syndrome. Adipocytes are the typical cells of adipose organ, which is composed of at least two different tissues, white and brown adipose tissue. They functionally cooperate, interconverting each other under physiological conditions, but differ in their anatomy, physiology, and endocrine functions. Different cellular models have been proposed to study adipose tissue in vitro. They are also useful for elucidating the mechanisms that are responsible for a pathological condition, such as obesity, and for testing therapeutic strategies. Each cell model has its own characteristics, culture conditions, advantages and disadvantages. The choice of one model rather than another depends on the specific study the researcher is conducting. In recent decades, three-dimensional cultures, such as adipose spheroids, have become very attractive because they more closely resemble the phenotype of freshly isolated cells. The use of such models has developed in parallel with the evolution of translational research, an interdisciplinary branch of the biomedical field, which aims to learn a scientific translational approach to improve human health and longevity. The focus of the present review is on the growing body of data linking the use of new cell models and the spread of translational research. Also, we discuss the possibility, for the future, to employ new three-dimensional adipose tissue cell models to promote the transition from benchside to bedsite and vice versa, allowing translational research to become routine, with the final goal of obtaining clinical benefits in the prevention and treatment of obesity and related disorders.

Brown adipose tissue-derived FGF21 mediates the cardioprotection of dexmedetomidine in myocardial ischemia/reperfusion injury

Brown adipose tissue (BAT) plays a critical role in regulating cardiovascular homeostasis through the secretion of adipokines, such as fibroblast growth factor 21 (FGF21). Dexmedetomidine (DEX) is a selective α2-adrenergic receptor agonist with a protection against myocardial ischemia/reperfusion injury (MI/RI). It remains largely unknown whether or not BAT-derived FGF21 is involved in DEX-induced cardioprotection in the context of MI/RI. Herein, we demonstrated that DEX alleviated MI/RI and improved heart function through promoting the release of FGF21 from interscapular BAT (iBAT). Surgical iBAT depletion or supplementation with a FGF21 neutralizing antibody attenuated the beneficial effects of DEX. AMPK/PGC1α signaling-induced fibroblast growth factor 21 (FGF21) release in brown adipocytes is required for DEX-mediated cardioprotection since blockade of the AMPK/PGC1α axis weakened the salutary effects of DEX. Co-culture experiments showed that DEX-induced FGF21 from brown adipocytes increased the resistance of cardiomyocytes to hypoxia/reoxygenation (H/R) injury via modulating the Keap1/Nrf2 pathway. Our results provided robust evidence that the BAT-cardiomyocyte interaction is required for DEX cardioprotection, and revealed an endocrine role of BAT in DEX-mediating protection of hearts against MIRI.

Perivascular Adipose Tissue and Perivascular Adipose Tissue-Derived Extracellular Vesicles: New Insights in Vascular Disease

Perivascular adipose tissue (PVAT) is a special deposit of fat tissue surrounding the vasculature. Previous studies suggest that PVAT modulates the vasculature function in physiological conditions and is implicated in the pathogenesis of vascular diseases. Understanding how PVAT influences vasculature function and vascular disease progression is important. Extracellular vesicles (EVs) are novel mediators of intercellular communication. EVs encapsulate molecular cargo such as proteins, lipids, and nucleic acids. EVs can influence cellular functions by transferring the carried bioactive molecules. Emerging evidence indicates that PVAT-derived EVs play an important role in vascular functions under health and disease conditions. This review will focus on the roles of PVAT and PVAT-EVs in obesity, diabetic, and metabolic syndrome-related vascular diseases, offering novel insights into therapeutic targets for vascular diseases.

Obesity-induced chronic low-grade inflammation in adipose tissue: A pathway to Alzheimer's disease

Alzheimer's disease (AD) is a leading cause of cognitive impairment worldwide. Overweight and obesity are strongly associated with comorbidities, such as hypertension, diabetes, and insulin resistance (IR), which contribute substantially to the development of AD and subsequent morbidity and mortality. Adipose tissue (AT) is a highly dynamic organ composed of a diverse array of cell types, which can be classified based on their anatomic localization or cellular composition. The expansion and remodeling of AT in the context of obesity involves immunometabolic and functional shifts steered by the intertwined actions of multiple immune cells and cytokine signaling within AT, which contribute to the development of metabolic disorders, IR, and systemic markers of chronic low-grade inflammation. Chronic low-grade inflammation, a prolonged, low-dose stimulation by specific immunogens that can progress from localized sites and affect multiple organs throughout the body, leads to neurodystrophy, increased apoptosis, and disruption of homeostasis, manifesting as brain atrophy and AD-related pathology. In this review, we sought to elucidate the mechanisms by which AT contributes to the onset and progression of AD in obesity through the mediation of chronic low-grade inflammation, particularly focusing on the roles of adipokines and AT-resident immune cells.

Cationic polymer effect on brown adipogenic induction of dedifferentiated fat cells

Obesity and its associated comorbidities place a substantial burden on public health. Given the considerable potential of brown adipose tissue in addressing metabolic disorders that contribute to dysregulation of the body's energy balance, this area is an intriguing avenue for research. This study aimed to assess the impact of various polymers, including collagen type I, fibronectin, laminin, gelatin, gellan gum, and poly-l-lysine (PLL), on the in vitro brown adipogenic differentiation of dedifferentiated fat cells within a fibrin gel matrix. The findings, obtained through RT-qPCR, immunofluorescent imaging, ELISA assay, and mitochondria assessment, revealed that PLL exhibited a significant browning-inducing effect. Compared to fibrin-only brown-like drops after two weeks of incubation in brown adipogenic medium, PLL showed 6 (±3) times higher UCP1 gene expression, 5 (±2) times higher UCP1 concentration by ELISA assay, and 2 (±1) times higher mitochondrial content. This effect can be attributed to PLL's electrostatic properties, which potentially facilitate the cellular uptake of crucial brown adipogenic inducers such as the thyroid hormone, triiodothyronine (T3), and insulin from the induction medium.

Inhibition of IL-11 signalling extends mammalian healthspan and lifespan

For healthspan and lifespan, ERK, AMPK and mTORC1 represent critical pathways and inflammation is a centrally important hallmark1-7. Here we examined whether IL-11, a pro-inflammatory cytokine of the IL-6 family, has a negative effect on age-associated disease and lifespan. As mice age, IL-11 is upregulated across cell types and tissues to regulate an ERK-AMPK-mTORC1 axis to modulate cellular, tissue- and organismal-level ageing pathologies. Deletion of Il11 or Il11ra1 protects against metabolic decline, multi-morbidity and frailty in old age. Administration of anti-IL-11 to 75-week-old mice for 25 weeks improves metabolism and muscle function, and reduces ageing biomarkers and frailty across sexes. In lifespan studies, genetic deletion of Il11 extended the lives of mice of both sexes, by 24.9% on average. Treatment with anti-IL-11 from 75 weeks of age until death extends the median lifespan of male mice by 22.5% and of female mice by 25%. Together, these results demonstrate a role for the pro-inflammatory factor IL-11 in mammalian healthspan and lifespan. We suggest that anti-IL-11 therapy, which is currently in early-stage clinical trials for fibrotic lung disease, may provide a translational opportunity to determine the effects of IL-11 inhibition on ageing pathologies in older people.

Butein derivatives prevent obesity and improve insulin resistance through the induction of energy expenditure in high-fat diet-fed obese mice

Obesity is a global public health problem and is related with fatal diseases such as cancer and cardiovascular and metabolic diseases. Medical and lifestyle-related strategies to combat obesity have their limitations. White adipose tissue (WAT) browning is a promising strategy for increasing energy expenditure in individuals with obesity. Uncoupling protein 1 (UCP1) drives WAT browning. We previously screened natural products that enable induction of Ucp1 and demonstrated that these natural products induced WAT browning and increased energy expenditure in mice with diet-induced obesity. In this study, we aimed to extensively optimise the structure of compound 1, previously shown to promote WAT browning. Compound 3 s exhibited a significantly higher ability to induce Ucp1 in white and brown adipocytes than did compound 1. A daily injection of compound 3 s at 5 mg/kg prevented weight gain by 13.6 % in high-fat diet-fed mice without any toxicological observation. In addition, compound 3 s significantly improved glucose homeostasis, decreased serum triacylglycerol levels, and reduced total cholesterol and LDL cholesterol levels, without altering dietary intake or physical activity. Pharmaceutical properties such as solubility, lipophilicity, and membrane permeability as well as metabolic stability, half-life (T1/2), and blood exposure ratio of i.p to i.v were significantly improved in compound 3 s when compared with those in compound 1. Regarding the mode of action of WAT browning, the induction of Ucp1 and Prdm4 by compounds 1 and 3 s was dependent on Akt1 in mouse embryonic fibroblasts. Therefore, this study suggests the potential of compound 3 s as a therapeutic agent for individuals with obesity and related metabolic diseases, which acts through the induction of WAT browning as well as brown adipose tissue activation.

Mitochondrial lipidomes are tissue specific - low cholesterol contents relate to UCP1 activity

Lipid composition is conserved within sub-cellular compartments to maintain cell function. Lipidomic analyses of liver, muscle, white and brown adipose tissue (BAT) mitochondria revealed substantial differences in their glycerophospholipid (GPL) and free cholesterol (FC) contents. The GPL to FC ratio was 50-fold higher in brown than white adipose tissue mitochondria. Their purity was verified by comparison of proteomes with ER and mitochondria-associated membranes. A lipid signature containing PC and FC, calculated from the lipidomic profiles, allowed differentiation of mitochondria from BAT of mice housed at different temperatures. Elevating FC in BAT mitochondria prevented uncoupling protein (UCP) 1 function, whereas increasing GPL boosted it. Similarly, STARD3 overexpression facilitating mitochondrial FC import inhibited UCP1 function in primary brown adipocytes, whereas a knockdown promoted it. We conclude that the mitochondrial GPL/FC ratio is key for BAT function and propose that targeting it might be a promising strategy to promote UCP1 activity.

A combination of Citrus aurantifolia fruit rind and Theobroma cacao seed extracts supplementation enhances metabolic rates in overweight subjects: a randomized, placebo-controlled, cross-over study

Background and objective

LN19183 is a proprietary, synergistic combination of Citrus aurantifolia fruit rind and Theobroma cacao seed extracts that increased resting energy expenditure (REE) in high-fat diet (HFD)-fed obese rats. The objective of this study was to validate the thermogenic potential of LN19183 in obese Sprague Dawley (SD) rats and to assess its clinical efficacy in a proof-of-concept, randomized, placebo-controlled, cross-over human trial.

Methods

In the rat study, HFD-fed obese rats were supplemented with either HFD alone or with 45, 90, or 180 mg LN19183 per kg body weight (BW) for 28 days. In the human study, 60 overweight adults (male and female, aged 20-39 years) were randomized. Subjects took LN19183 (450 mg) or a matched placebo capsule on two consecutive days in phases one and two of the study, separated by a 10-day washout period. In each phase, on day 1, REE at pre-dose, 60-, 120-, and 180-min post-dose, and on day 2, metabolic rates at pre-dose and post-dose during and 20 min after exercise were measured using indirect calorimetry.

Results

In rats, LN19183 significantly increased REE, reduced BW gain and fat masses, and increased fat and carbohydrate metabolism marker proteins including beta 3 adrenergic receptor (β3-AR), phospho-AMP-activated protein kinase (AMPK), glucagon-like peptide-1 receptor (GLP-1R) in the liver, and serum adiponectin levels. Furthermore, LN19183-supplemented human volunteers increased (P < 0.05, vs. placebo) the metabolic rates at rest and with exercise; their fat oxidation was increased (P < 0.05, vs. placebo) at rest and 20 min post-exercise. The groups' systolic and diastolic blood pressure (BP), heart rates (HR), and safety parameters were comparable.

Conclusion

These observations suggest that LN19183 is a thermogenic botanical composition with no stimulatory effects on BP and HR.

The Role of Adipocytes Recruited as Part of Tumor Microenvironment in Promoting Colorectal Cancer Metastases

Adipose tissue dysfunction, which is associated with an increased risk of colorectal cancer (CRC), is a significant factor in the pathophysiology of obesity. Obesity-related inflammation and extracellular matrix (ECM) remodeling promote colorectal cancer metastasis (CRCM) by shaping the tumor microenvironment (TME). When CRC occurs, the metabolic symbiosis of tumor cells recruits adjacent adipocytes into the TME to supply energy. Meanwhile, abundant immune cells, from adipose tissue and blood, are recruited into the TME, which is stimulated by pro-inflammatory factors and triggers a chronic local pro-inflammatory TME. Dysregulated ECM proteins and cell surface adhesion molecules enhance ECM remodeling and further increase contractibility between tumor and stromal cells, which promotes epithelial-mesenchymal transition (EMT). EMT increases tumor migration and invasion into surrounding tissues or vessels and accelerates CRCM. Colorectal symbiotic microbiota also plays an important role in the promotion of CRCM. In this review, we provide adipose tissue and its contributions to CRC, with a special emphasis on the role of adipocytes, macrophages, neutrophils, T cells, ECM, and symbiotic gut microbiota in the progression of CRC and their contributions to the CRC microenvironment. We highlight the interactions between adipocytes and tumor cells, and potential therapeutic approaches to target these interactions.

The impacts of obesity in rheumatoid arthritis and insights into therapeutic purinergic modulation

Rheumatoid Arthritis (RA) is an autoimmune condition responsible for the impairment of synovia and joints, endangering the functionality of individuals and contributing to mortality. Currently, obesity is increasing worldwide, and recent studies have suggested an association between such condition and RA. In this sense, obese individuals present a lower capacity for achieving remission and present more intense symptoms of the disease, demonstrating a link between both disorders. Different studies aim to understand the possible connection between the conditions; however, few is known in this sense. Therefore, knowing that obesity can alter the activity of multiple body systems, this work's objective is to evaluate the main modifications caused by obesity, which can be linked to the pathophysiology of RA, highlighting as relevant topics obesity's negative impact triggering systemic inflammation, intestinal dysbiosis, endocrine disbalances. Furthermore, the relationship between oxidative stress and obesity also deserves to be highlighted, considering the influence of reactive oxygen species (ROS) accumulation in RA exacerbation. Additionally, many of those characteristics influenced by obesity, along with the classic peculiarities of RA pathophysiology, can also be associated with purinergic signaling. Hence, this work suggests possible connections between the purinergic system and RA, proposing potential therapeutic targets against RA to be studied.

Genetic variation in NOTCH1 is associated with overweight and obesity in Brazilian elderly

Excessive weight (overweight and obesity) is a common disorder involving genetic and environmental factors, associated with cardiovascular diseases, type-2 diabetes, and others. NOTCH1 is critical for the maintenance of stem cells and adult tissues, being reported as a key player in metabolism and adipogenesis in animals. Thus, we test the hypothesis that NOTCH1 Single Nucleotide Polymorphisms (SNPs) are associated with excessive weight. Participants from the census-based cohort SABE (Saúde, Bem Estar e Envelhecimento-Health, Well-Being, and Aging), carried out in the city of São Paulo-Brazil, were stratified into cases and controls according to BMI. We filter the SNPs located at the start and end positions of NOTCH1 and 50 Kb on both sides. We selected SNPs with minor allelic frequency (MAF) greater than or equal to 0.01 and Hardy-Weinberg equilibrium (p > 0.05) and r2 ≥ 0.8. We performed an association study with genotypes and haplotypes, as well as in silico functional analysis of the identified SNPs. We observed an association of the SNP rs9411207 with the risk of excessive weight, under log-additive model, and the genotype distribution showed an increased frequency of homozygous TT (OR 1.50, CI 1.20-1.88; p = 0.0002). The haplotype GAT constructed from this and other SNPs in high Linkage Disequilibrium was more frequent in excessive-weight individuals (p = 0.003). In silico analyses suggested that these SNPs are likely to affect the transcription of NOTCH1 and other genes involved in adipogenesis and metabolism. This is the first study reporting association between NOTCH1 SNPs and the risk of excessive weight. Considering the possibility of NOTCH1 modulation, additional population studies are important to replicate these data and confirm the usefulness of risk genotypes for management strategies of excessive weight.

Navigating Lipodystrophy: Insights from Laminopathies and Beyond

Recent research into laminopathic lipodystrophies-rare genetic disorders caused by mutations in the LMNA gene-has greatly expanded our knowledge of their complex pathology and metabolic implications. These disorders, including Hutchinson-Gilford progeria syndrome (HGPS), Mandibuloacral Dysplasia (MAD), and Familial Partial Lipodystrophy (FPLD), serve as crucial models for studying accelerated aging and metabolic dysfunction, enhancing our understanding of the cellular and molecular mechanisms involved. Research on laminopathies has highlighted how LMNA mutations disrupt adipose tissue function and metabolic regulation, leading to altered fat distribution and metabolic pathway dysfunctions. Such insights improve our understanding of the pathophysiological interactions between genetic anomalies and metabolic processes. This review merges current knowledge on the phenotypic classifications of these diseases and their associated metabolic complications, such as insulin resistance, hypertriglyceridemia, hepatic steatosis, and metabolic syndrome, all of which elevate the risk of cardiovascular disease, stroke, and diabetes. Additionally, a range of published therapeutic strategies, including gene editing, antisense oligonucleotides, and novel pharmacological interventions aimed at addressing defective adipocyte differentiation and lipid metabolism, will be explored. These therapies target the core dysfunctional lamin A protein, aiming to mitigate symptoms and provide a foundation for addressing similar metabolic and genetic disorders.

Hyaluronan Mediates Cold-Induced Adipose Tissue Beiging

Adipose tissue beiging refers to the process by which beige adipocytes emerge in classical white adipose tissue depots. Beige adipocytes dissipate chemical energy and secrete adipokines, such as classical brown adipocytes, to improve systemic metabolism, which is beneficial for people with obesity and metabolic diseases. Cold exposure and β3-adrenergic receptor (AR) agonist treatment are two commonly used stimuli for increasing beige adipocytes in mice; however, their underlying biological processes are different. Transcriptional analysis of inguinal white adipose tissue (iWAT) has revealed that changes in extracellular matrix (ECM) pathway genes are specific to cold exposure. Hyaluronic acid (HA), a non-sulfated linear polysaccharide produced by nearly all cells, is one of the most common components of ECM. We found that cold exposure significantly increased iWAT HA levels, whereas the β3-AR agonist CL316,243 did not. Increasing HA levels in iWAT by Has2 overexpression significantly increases cold-induced adipose tissue beiging; in contrast, decreasing HA by Spam1 overexpression, which encodes a hyaluronidase that digests HA, significantly decreases cold-induced iWAT beiging. All these data implicate a role of HA in promoting adipose tissue beiging, which is unique to cold exposure. Given the failure of β3-AR agonists in clinical trials for obesity and metabolic diseases, increasing HA could serve as a new approach for recruiting more beige adipocytes to combat metabolic diseases.

From fasting to fat reshaping: exploring the molecular pathways of intermittent fasting-induced adipose tissue remodeling

Obesity, characterised by excessive fat accumulation, is a complex chronic condition that results from dysfunctional adipose tissue expansion due to prolonged calorie surplus. This leads to rapid adipocyte enlargement that exceeds the support capacity of the surrounding neurovascular network, resulting in increased hypoxia, inflammation, and insulin resistance. Intermittent fasting (IF), a dietary regimen that cycles between periods of fasting and eating, has emerged as an effective strategy to combat obesity and improve metabolic homeostasis by promoting healthy adipose tissue remodeling. However, the precise molecular and cellular mechanisms behind the metabolic improvements and remodeling of white adipose tissue (WAT) driven by IF remain elusive. This review aims to summarise and discuss the relationship between IF and adipose tissue remodeling and explore the potential mechanisms through which IF induces alterations in WAT. This includes several key structural changes, including angiogenesis and sympathetic innervation of WAT. We will also discuss the involvement of key signalling pathways, such as PI3K, SIRT, mTOR, and AMPK, which potentially play a crucial role in IF-mediated metabolic adaptations.

Dietary Pectin from Premna microphylla Turcz Leaves Prevents Obesity by Regulating Gut Microbiota and Lipid Metabolism in Mice Fed High-Fat Diet

The present study was designed to investigate the protective effects of pectin extracted from Premna microphylla Turcz leaves (PTP) against high-fat-diet (HFD)-induced lipid metabolism disorders and gut microbiota dysbiosis in obese mice. PTP was made using the acid extraction method, and it was found to be an acidic pectin that had relative mole percentages of 32.1%, 29.2%, and 26.2% for galacturonic acid, arabinose, and galactose, respectively. The administration of PTP in C57BL/6J mice inhibited the HFD-induced abnormal weight gain, visceral obesity, and dyslipidemia, and also improved insulin sensitivity, as revealed by the improved insulin tolerance and the decreased glucose levels during an insulin sensitivity test. These effects were linked to increased energy expenditure, as demonstrated by the upregulation of thermogenesis-related protein UCP1 expression in the brown adipose tissue (BAT) of PTP-treated mice. 16S rRNA gene sequencing revealed that PTP dramatically improved the HFD-induced gut dysbiosis by lowering the ratio of Firmicutes to Bacteroidetes and the quantity of potentially harmful bacteria. These findings may provide a theoretical basis for us to understand the functions and usages of PTP in alleviating obesity.

The essential role of architectural noncoding RNA Neat1 in cold-induced beige adipocyte differentiation in mice

Neat1 is an architectural RNA that provides the structural basis for nuclear bodies known as paraspeckles. Although the assembly processes by which Neat1 organizes paraspeckle components are well-documented, the physiological functions of Neat1 are not yet fully understood. This is partly because Neat1 knockout (KO) mice, lacking paraspeckles, do not exhibit overt phenotypes under normal laboratory conditions. During our search for conditions that elicit clear phenotypes in Neat1 KO mice, we discovered that the differentiation of beige adipocytes-inducible thermogenic cells that emerge upon cold exposure-is severely impaired in these mutant mice. Neat1_2, the architectural isoform of Neat1, is transiently upregulated during the early stages of beige adipocyte differentiation, coinciding with increased paraspeckle formation. Genes with altered expression during beige adipocyte differentiation typically cluster at specific chromosomal locations, some of which move closer to paraspeckles upon cold exposure. These observations suggest that paraspeckles might coordinate the regulation of these gene clusters by controlling the activity of certain transcriptional condensates that coregulate multiple genes. We propose that our findings highlight a potential role for Neat1 and paraspeckles in modulating chromosomal organization and gene expression, potentially crucial processes for the differentiation of beige adipocytes.

Role of Brown Adipose Tissue in Metabolic Health and Efficacy of Drug Treatment for Obesity

(1) Background: Brown adipose tissue (BAT) is responsible for non-shivering thermogenesis, and its activation has become a new object as both a determinant of metabolic health and a target for therapy. This study aimed to identify the relationships between the presence of BAT, parameters that characterize metabolic health (glucose, lipids, blood pressure (BP)), and the dynamics of body mass index (BMI) during weight-reducing therapy. (2) Methods: The study included 72 patients with obesity. We investigated metabolic parameters, anthropometric parameters, and BP. Dual-energy X-ray absorptiometry (DXA) and positron emission tomography and computed tomography (PET/CT) imaging with 18F-fluorodeoxyglucose (18F-FDG) were performed. (3) Results: Before weight-reducing therapy, BAT was revealed only in 19% patients with obesity. The presence of BAT was associated with a lower risk of metabolic deviations that characterize metabolic syndrome: shorter waist circumference (WC) (p = 0.02) and lower levels of glucose (p = 0.03) and triglycerides (p = 0.03). Thereafter, patients were divided into four groups according to the type of therapy (only lifestyle modification or with Liraglutide or Reduxin or Reduxin Forte). We did not find a relationship between the presence of BAT and response to therapy: percent weight reduction was 10.4% in patients with BAT and 8.5% in patients without BAT (p = 0.78) during six months of therapy. But we noted a significant positive correlation between the volume of BAT and the effectiveness of weight loss at 3 months (r = 0.52, p = 0.016). The dynamic analysis of BAT after 6 months of therapy showed a significant increase in the volume of cold-induced metabolically active BAT, as determined by PET/CT with 18F-FDG in the Liraglutide group (p = 0.04) and an increase in the activity of BAT standardized uptake value (SUV mean and SUV max) in the Reduxin (p = 0.02; p = 0.01, respectively) and Liraglutide groups (p = 0.02 in both settings). (4) Conclusions: The presence of brown adipose tissue is associated with a lower risk of metabolic abnormalities. In general, our study demonstrated that well-established drugs in the treatment of obesity (Liraglutide and Reduxin) have one more mechanism for implementing their effects. These drugs have the ability to increase the activity of BAT. A significant positive relationship between the total volume of BAT and the percentage of weight loss may further determine the priority mechanism of the weight-reducing effect of these medicaments.

Carnosic Acid (CA) Induces a Brown Fat-like Phenotype, Increases Mitochondrial Biogenesis, and Activates AMPK in 3T3-L1 Adipocytes

Adipose tissue plays a crucial role in regulating metabolic homeostasis, and its dysfunction in obesity leads to insulin resistance and type 2 diabetes (T2D). White adipose tissue (WAT) primarily stores energy as lipids, while brown adipose tissue (BAT) regulates thermogenesis by dissipating energy as heat. The process of browning involves the transdifferentiation of WAT into brown-like or beige adipocytes, which exhibit a similar phenotype as BAT. The browning of WAT is an attractive approach against obesity and T2D, and the activation of the energy sensor AMP-activated protein kinase (AMPK) has been shown to play a role in browning. Carnosic acid (CA), a polyphenolic diterpene, found in many plants including rosemary, is reported to possess potent antioxidant, anti-inflammatory, and anti-hyperglycemic properties. The limited evidence available indicates that CA activates AMPK and may have anti-obesity and antidiabetic potential; however, the effects in adipocyte browning remain largely unexplored. This study aimed to examine the effects of CA on the markers of adipocyte browning. The treatment of 3T3L1 adipocytes with CA activated AMPK, reduced lipid accumulation, and increased the expression of browning protein markers (UCP-1, PGC-1α, PRDM16, and TFAM) and mitochondrial biogenesis. The use of compound C, an AMPK inhibitor, significantly attenuated the effects of CA, indicating AMPK involvement. These studies demonstrate that CA can activate AMPK and stimulate the browning of white adipocytes. Future animal and human studies are required to examine the effects of CA in vivo.