The Role of Circulating Slit2, the One of the Newly Batokines, in Human Diabetes Mellitus

Screening and identification of key biomarkers associated with endometriosis using bioinformatics and next-generation sequencing data analysis

Background

Endometriosis is a common cause of endometrial-type mucosa outside the uterine cavity with symptoms such as painful periods, chronic pelvic pain, pain with intercourse and infertility. However, the early diagnosis of endometriosis is still restricted. The purpose of this investigation is to identify and validate the key biomarkers of endometriosis.

Methods

Next-generation sequencing dataset GSE243039 was obtained from the Gene Expression Omnibus database, and differentially expressed genes (DEGs) between endometriosis and normal control samples were identified. After screening of DEGs, gene ontology (GO) and REACTOME pathway enrichment analyses were performed. Furthermore, a protein–protein interaction (PPI) network was constructed and modules were analyzed using the Human Integrated Protein–Protein Interaction rEference database and Cytoscape software, and hub genes were identified. Subsequently, a network between miRNAs and hub genes, and network between TFs and hub genes were constructed using the miRNet and NetworkAnalyst tool, and possible key miRNAs and TFs were predicted. Finally, receiver operating characteristic curve analysis was used to validate the hub genes.

Results

A total of 958 DEGs, including 479 upregulated genes and 479 downregulated genes, were screened between endometriosis and normal control samples. GO and REACTOME pathway enrichment analyses of the 958 DEGs showed that they were mainly involved in multicellular organismal process, developmental process, signaling by GPCR and muscle contraction. Further analysis of the PPI network and modules identified 10 hub genes, including vcam1, snca, prkcb, adrb2, foxq1, mdfi, actbl2, prkd1, dapk1 and actc1. Possible target miRNAs, including hsa-mir-3143 and hsa-mir-2110, and target TFs, including tcf3 (transcription factor 3) and clock (clock circadian regulator), were predicted by constructing a miRNA-hub gene regulatory network and TF-hub gene regulatory network.

Conclusions

This investigation used bioinformatics techniques to explore the potential and novel biomarkers. These biomarkers might provide new ideas and methods for the early diagnosis, treatment and monitoring of endometriosis.

Adipokines in the Crosstalk between Adipose Tissues and Other Organs: Implications in Cardiometabolic Diseases

Adipose tissue was previously regarded as a dormant organ for lipid storage until the identification of adiponectin and leptin in the early 1990s. This revelation unveiled the dynamic endocrine function of adipose tissue, which has expanded further. Adipose tissue has emerged in recent decades as a multifunctional organ that plays a significant role in energy metabolism and homeostasis. Currently, it is evident that adipose tissue primarily performs its function by secreting a diverse array of signaling molecules known as adipokines. Apart from their pivotal function in energy expenditure and metabolism regulation, these adipokines exert significant influence over a multitude of biological processes, including but not limited to inflammation, thermoregulation, immune response, vascular function, and insulin sensitivity. Adipokines are pivotal in regulating numerous biological processes within adipose tissue and facilitating communication between adipose tissue and various organs, including the brain, gut, pancreas, endothelial cells, liver, muscle, and more. Dysregulated adipokines have been implicated in several metabolic diseases, like obesity and diabetes, as well as cardiovascular diseases. In this article, we attempted to describe the significance of adipokines in developing metabolic and cardiovascular diseases and highlight their role in the crosstalk between adipose tissues and other tissues and organs.

An update on the secretory functions of brown, white, and beige adipose tissue: Towards therapeutic applications

Adipose tissue, including white adipose tissue (WAT), brown adipose tissue (BAT), and beige adipose tissue, is vital in modulating whole-body energy metabolism. While WAT primarily stores energy, BAT dissipates energy as heat for thermoregulation. Beige adipose tissue is a hybrid form of adipose tissue that shares characteristics with WAT and BAT. Dysregulation of adipose tissue metabolism is linked to various disorders, including obesity, type 2 diabetes, cardiovascular diseases, cancer, and infertility. Both brown and beige adipocytes secrete multiple molecules, such as batokines, packaged in extracellular vesicles or as soluble signaling molecules that play autocrine, paracrine, and endocrine roles. A greater understanding of the adipocyte secretome is essential for identifying novel molecular targets in treating metabolic disorders. Additionally, microRNAs show crucial roles in regulating adipose tissue differentiation and function, highlighting their potential as biomarkers for metabolic disorders. The browning of WAT has emerged as a promising therapeutic approach in treating obesity and associated metabolic disorders. Many browning agents have been identified, and nanotechnology-based drug delivery systems have been developed to enhance their efficacy. This review scrutinizes the characteristics of and differences between white, brown, and beige adipose tissues, the molecular mechanisms involved in the development of the adipocytes, the significant roles of batokines, and regulatory microRNAs active in different adipose tissues. Finally, the potential of WAT browning in treating obesity and atherosclerosis, the relationship of BAT with cancer and fertility disorders, and the crosstalk between adipose tissue with circadian system and circadian disorders are also investigated.

The integrated bioinformatic analysis identifies immune microenvironment-related potential biomarkers for patients with gestational diabetes mellitus

Background

Gestational diabetes mellitus (GDM), a transient disease, may lead to short- or long-term adverse influences on maternal and fetal health. Therefore, its potential functions, mechanisms and related molecular biomarkers must be comprehended for the control, diagnosis and treatment of GDM.

Methods

The differentially expressed genes (DEGs) were identified using GSE49524 and GSE87295 associated with GDM from the Gene Expression Omnibus database, followed by function enrichment analysis, protein-protein interactions network construction, hub DEGs mining, diagnostic value evaluation and immune infiltration analysis. Finally, hub DEGs, the strongest related to immune infiltration, were screened as immune-related biomarkers.

Results

A hundred and seven DEGs were identified between patients with GDM and healthy individuals. Six hub genes with high diagnostic values, including ALDH1A1, BMP4, EFNB2, MME, PLAUR and SLIT2, were identified. Among these, two immune-related genes (PLAUR and SLIT2) with the highest absolute correlation coefficient were considered immune-related biomarkers in GDM.

Conclusion

Our study provides a comprehensive analysis of GDM, which would provide a foundation for the development of diagnosis and treatment of GDM.

Brown adipose tissue-derived metabolites and their role in regulating metabolism

The discovery and rejuvenation of metabolically active brown adipose tissue (BAT) in adult humans have offered a new approach to treat obesity and metabolic diseases. Beyond its accomplished role in adaptive thermogenesis, BAT secretes signaling molecules known as "batokines", which are instrumental in regulating whole-body metabolism via autocrine, paracrine, and endocrine action. In addition to the intrinsic BAT metabolite-oxidizing activity, the endocrine functions of these molecules may help to explain the association between BAT activity and a healthy systemic metabolic profile. Herein, we review the evidence that underscores the significance of BAT-derived metabolites, especially highlighting their role in controlling physiological and metabolic processes involving thermogenesis, substrate metabolism, and other essential biological processes. The conversation extends to their capacity to enhance energy expenditure and mitigate features of obesity and its related metabolic complications. Thus, metabolites derived from BAT may provide new avenues for the discovery of metabolic health-promoting drugs with far-reaching impacts. This review aims to dissect the complexities of the secretory role of BAT in modulating local and systemic metabolism in metabolic health and disease.

Adipokines from white adipose tissue in regulation of whole body energy homeostasis

Diseases originating from altered energy homeostasis including obesity, and type 2 diabetes are rapidly increasing worldwide. Research in the last few decades on animal models and humans demonstrates that the white adipose tissue (WAT) is critical for energy balance and more than just an energy storage site. WAT orchestrates the whole-body metabolism through inter-organ crosstalk primarily mediated by cytokines named "Adipokines". The adipokines influence metabolism and fuel selection of the skeletal muscle and liver thereby fine-tuning the load on WAT itself in physiological conditions like starvation, exercise and cold. In addition, adipokine secretion is influenced by various pathological conditions like obesity, inflammation and diabetes. In this review, we have surveyed the current state of knowledge on important adipokines and their significance in regulating energy balance and metabolic diseases. Furthermore, we have summarized the interplay of pro-inflammatory and anti-inflammatory adipokines in the modulation of pathological conditions.

New players of the adipose secretome: Therapeutic opportunities and challenges

Adipose tissue is a functional endocrine organ comprised of adipocytes and other cell types that are known to secrete a multiplicity of adipose-derived factors, including lipids and proteins. It is well established that adipose tissue and its secretome can impact systemic energy homeostasis. The endocrine and paracrine effects of adipose-derived factors have been widely studied over the last several decades. Owing to technological advances in genomics and proteomics, several additional adipose-derived protein factors have recently been identified. By learning from previous efforts, the next challenge will be to leverage these discoveries for the prevention or treatment of metabolic disorders. Here, we discuss recently discovered adipose-derived proteins secreted from white or brown adipose tissue and the opportunities and challenges of translating these biological findings into disease therapeutics.

Serum CD14 concentration is associated with obesity and insulin resistance in non-diabetic individuals

OBJECTIVE

CD14 is a lipopolysaccharide-binding protein that serves as a marker of monocytes. The role of circulating CD14 in patients with obesity without diabetes remains unknown. Here, we characterized the relationships between serum CD14 concentration and metabolic parameters related to diabetes and obesity.

METHODS

We performed an observational, prospective case-control study. Eighty participants were evaluated: 26 drug-naïve patients with type 2 diabetes mellitus and 54 healthy individuals. We compared the circulating CD14 concentration and metabolic parameters of the participants with and without diabetes.

RESULTS

The circulating CD14 concentration did not significantly differ between the two groups, but was lower in participants with obesity than in lean controls. No significant associations existed between CD14 concentration and metabolic parameters in the participants with diabetes, but in those without diabetes, the circulating CD14 concentration significantly negatively correlated with body mass index; waist circumference; the concentrations of fasting insulin, 2-hour post-load glucose, 2-h post-load insulin, and low-density lipoprotein-cholesterol; homeostasis model of assessment (HOMA) of insulin resistance; and HOMA beta-cell function.

CONCLUSIONS

This is the first study to show associations of serum CD14 concentration with metabolic parameters in non-diabetic individuals. Circulating CD14 may represent a useful biomarker of metabolic dysfunction in non-diabetic individuals.

The Heartwarming Effect of Brown Adipose Tissue

Brown adipose tissue (BAT) is a metabolically active tissue that improves glucose metabolism and protects against the development of type 2 diabetes and obesity. However, the role of BAT to improve cardiovascular health has only recently been investigated. In this review, we discuss multiple mechanisms through which both the thermogenic and endocrine functions of BAT mediate cardiac health. β-adrenergic stimulation activates the thermogenic function of BAT, resulting in reduced circulating lipids and glucose, and enhanced clearance of hepatic cholesterol-enriched remnants leading to reduced atherosclerotic region size. Additionally, the thermogenic role of BAT has been implicated in activation of the protein kinase B-extracellular-signal-regulated kinase (ERK) 1/2 pathway after myocardial infarction (MI), contributing to reduced injury size. The endocrine function of BAT has also been implicated to improve both systemic metabolic health and cardiac health. Specifically, the batokines fibroblast growth factor 21 (FGF21) and 12,13-diHOME improve cardiovascular health via reduced hypertension, hypertrophy and MI injury size (FGF21) or by directly improving cardiac function via calcium cycling (12,13-diHOME). Finally, we discuss relevant pharmacological treatment methods currently aiming to activate BAT, typically through sympathetic activation. SIGNIFICANCE STATEMENT: This mini-review discusses the role of BAT to improve cardiac health via thermogenic and endocrine effects in both rodents and humans and highlights the need for therapeutic methods which activate or mimic BAT activity.

The Role of Slit-2 in Gestational Diabetes Mellitus and Its Effect on Pregnancy Outcome

BACKGROUND

Slit guidance ligand 2 (Slit-2), as a member of the Slit family, can regulate the inflammatory response and glucose metabolism. The purpose of this study was to explore the expression of Slit-2 in maternal peripheral blood and neonatal cord blood of gestational diabetes mellitus (GDM) patients and its potential importance in disease progression.

METHODS

This study included 57 healthy pregnant women and 61 GDM patients. The levels of Slit-2, C-reactive protein (CRP), monocyte chemoattractant protein-1 (MCP-1), C-peptide (C-P), galectin-3(Gal-3), HbA1c, fasting blood glucose (FBG) and fasting insulin (FINS) in maternal peripheral blood and neonatal cord blood were detected by ELISA. Spearman's rank correlation test was used to assess the association between peripheral Slit-2 and inflammatory indicators, insulin resistance, and pregnancy outcomes. Logistic regression analysis was used to analyze the risk factors of GDM.

RESULTS

Slit-2 levels in maternal peripheral blood and neonatal cord blood of the GDM patients were higher than those of the HC. Slit-2 levels in maternal peripheral blood and neonatal cord blood of the GDM patients were positively correlated with inflammatory factors CRP and MCP-1 levels. The level of Slit-2 in the maternal peripheral blood of the GDM patients was positively correlated with the level of homeostasis model assessment insulin resistance (HOMA-IR) and HbA1c in maternal peripheral blood, but was negatively correlated with the level of homeostasis model assessment -β (HOMA-β). We also found that the Slit-2 level in the maternal peripheral blood of the GDM patients was negatively correlated with neonatal blood glucose, positively correlated with neonatal weight and independent of neonatal total bilirubin.

CONCLUSION

Our study suggests that the abnormal increase in Slit-2 in GDM may be related to its pathogenesis, and it was correlated with neonatal blood glucose and weight in patients with GDM, suggesting that Slit-2 may be a potential biomarker of GDM.

Thermogenic Fat: Development, Physiological Function, and Therapeutic Potential

The concerning worldwide increase of obesity and chronic metabolic diseases, such as T2D, dyslipidemia, and cardiovascular disease, motivates further investigations into preventive and alternative therapeutic approaches. Over the past decade, there has been growing evidence that the formation and activation of thermogenic adipocytes (brown and beige) may serve as therapy to treat obesity and its associated diseases owing to its capacity to increase energy expenditure and to modulate circulating lipids and glucose levels. Thus, understanding the molecular mechanism of brown and beige adipocytes formation and activation will facilitate the development of strategies to combat metabolic disorders. Here, we provide a comprehensive overview of pathways and players involved in the development of brown and beige fat, as well as the role of thermogenic adipocytes in energy homeostasis and metabolism. Furthermore, we discuss the alterations in brown and beige adipose tissue function during obesity and explore the therapeutic potential of thermogenic activation to treat metabolic syndrome.

The relevance of plasma R-spondin 1 and Slit2 as predictive biomarkers in cervical cancer chemotherapy and radiotherapy

Background

R-spondin 1 (Rspol) and Slit2 have been found to play a vital role in cancer development, and have the potential to act as therapeutic adjuvants to increase tolerance to aggressive chemotherapy and/or radiotherapy. This “proof of concept” study evaluates the role of Rspo1 and Slit2 expression in the clinical outcome of cervical cancer patients.

Methods

Using enzyme linked immunosorbent assays (ELISA), we analyzed Rspo1 and Slit2 levels from patients diagnosed with the International Federation of Gynecology and Obstetrics (FIGO) stage IB1–IIA2 cervical cancer (n=34) who received chemotherapy (CT) and/or radiotherapy (RT) and correlated the data with the acute radiation morbidity scoring criteria.

Results

Cervical cancer patients who underwent CT and/or RT showed that neither the level of Rspo1 nor the level of Slit2 changed significantly after the first round of CT (CT1), RT, or the second CT (CT2). However, neurological sensory scores and influence of infection scores were elevated following increasing rounds of therapies. Rspo1 levels correlated negatively with the morbidity score of neutrophils, hemoglobin, platelet, infection score, neurological sensory score, and performance status after CT1, RT, or CT2. We also found that Slit2 levels were negatively correlated with genitourinary, heart, and neurological sensory scores at RT and CT2.

Conclusions

The levels of Rspo1 and Slit2 correlate positively to the tolerance of the patients. In contrast, the levels of Rspo1 and Slit2 showed a negative correlation to the morbidity score of the patients undergoing CT and/or RT. Thus, Rspo1 and Slit2 may be potential predictive biomarkers for patients with cervical cancer receiving CT or RT postoperatively, which supports the current pursuit of the clinical significance of Rspo1 and Slit2.

Brown/Beige adipose tissues and the emerging role of their secretory factors in improving metabolic health: The batokines

Brown and beige adipose tissues are the primary sites for adaptive non-shivering thermogenesis. Although they have been known principally for their thermogenic effects, in recent years, it has emerged that, just like white adipose tissue (WAT), brown and beige adipose tissues also play an important role in the regulation of metabolic health through secretion of various brown adipokines (batokines) in response to various physiological cues. These secreted batokines target distant organs and tissues such as the liver, heart, skeletal muscles, brain, WAT, and perform various local and systemic functions in an autocrine, paracrine, or endocrine manner. Brown and beige adipose tissues are therefore now receiving increasing levels of attention with respect to their effects on various other organs and tissues. Identification of novel secreted factors by these tissues may help in the discovery of drug candidates for the treatment of various metabolic disorders such as obesity, type-2 diabetes, skeletal deformities, cardiovascular diseases, dyslipidemia. In this review, we comprehensively describe the emerging secretory role of brown/beige adipose tissues and the metabolic effects of various brown/beige adipose tissues secreted factors on other organs and tissues in endocrine/paracrine manners, and as well as on brown/beige adipose tissue itself in an autocrine manner. This will provide insights into understanding the potential secretory role of brown/beige adipose tissues in improving metabolic health.

Development of a Cell-Based Assay for the Detection of Neutralizing Antibodies to PF-06730512 Using Homogenous Time-Resolved Fluorescence

The administration of biotherapeutics has the potential to induce potent immune responses. Among these responses, the production of anti-drug antibodies (ADA), including a subset of ADA referred to as neutralizing antibodies (NAb), is of heightened concern. Aside from their capacity to alter the pharmacological profile of a given biotherapeutic, NAb can also pose significant safety risks, especially in instances where an endogenous counterpart to the drug exists. As such, the inclusion of an assay to detect NAb in clinical samples is critical to the effectiveness of a tiered approach to immunogenicity assessment. PF-06730512 is a biotherapeutic protein being developed for the treatment of primary Focal Segmental Glomerulosclerosis (FSGS). To support the immunogenicity assessment of PF-06730512, a cell-based assay was developed for the detection of NAb in FSGS serum samples. Herein, we describe the development of the assay with a focus on the challenges faced, including drug and blood collection tube interferences in NAb detection. The outcome of our efforts was a robust assay capable of detecting 1 μg/mL of a NAb positive control in the presence of clinically relevant drug concentrations up to 30 μg/mL.

Brown Adipose Crosstalk in Tissue Plasticity and Human Metabolism

Infants rely on brown adipose tissue (BAT) as a primary source of thermogenesis. In some adult humans, residuals of brown adipose tissue are adjacent to the central nervous system and acute activation increases metabolic rate. Brown adipose tissue (BAT) recruitment occurs during cold acclimation and includes secretion of factors, known as batokines, which target several different cell types within BAT, and promote adipogenesis, angiogenesis, immune cell interactions, and neurite outgrowth. All these processes seem to act in concert to promote an adapted BAT. Recent studies have also provided exciting data on whole body metabolic regulation with a broad spectrum of mechanisms involving BAT crosstalk with liver, skeletal muscle, and gut as well as the central nervous system. These widespread interactions might reflect the property of BAT of switching between an active thermogenic state where energy is highly consumed and drained from the circulation, and the passive thermoneutral state, where energy consumption is turned off. (Endocrine Reviews 41: XXX - XXX, 2020).

The role of brown and beige adipose tissue in glycaemic control

For the past decade, brown adipose tissue (BAT) has been extensively studied as a potential therapy for obesity and metabolic diseases due to its thermogenic and glucose-consuming properties. It is now clear that the function of BAT goes beyond heat production, as it also plays an important endocrine role by secreting the so-called batokines to communicate with other metabolic tissues and regulate systemic energy homeostasis. However, despite numerous studies showing the benefits of BAT in rodents, it is still not clear whether recruitment of BAT can be utilized to treat human patients. Here, we review the advances on understanding the role of BAT in metabolism and its benefits on glucose and lipid homeostasis in both humans and rodents. Moreover, we discuss the latest methodological approaches to assess the contribution of BAT to human metabolism as well as the possibility to target BAT, pharmacologically or by lifestyle adaptations, to treat metabolic disorders.

Adipose Tissue-Derived Signatures for Obesity and Type 2 Diabetes: Adipokines, Batokines and MicroRNAs

: Obesity is one of the main risk factors for type 2 diabetes mellitus (T2DM). It is closely related to metabolic disturbances in the adipose tissue that primarily functions as a fat reservoir. For this reason, adipose tissue is considered as the primary site for initiation and aggravation of obesity and T2DM. As a key endocrine organ, the adipose tissue communicates with other organs, such as the brain, liver, muscle, and pancreas, for the maintenance of energy homeostasis. Two different types of adipose tissues-the white adipose tissue (WAT) and brown adipose tissue (BAT)-secrete bioactive peptides and proteins, known as "adipokines" and "batokines," respectively. Some of them have beneficial anti-inflammatory effects, while others have harmful inflammatory effects. Recently, "exosomal microRNAs (miRNAs)" were identified as novel adipokines, as adipose tissue-derived exosomal miRNAs can affect other organs. In the present review, we discuss the role of adipose-derived secretory factors-adipokines, batokines, and exosomal miRNA-in obesity and T2DM. It will provide new insights into the pathophysiological mechanisms involved in disturbances of adipose-derived factors and will support the development of adipose-derived factors as potential therapeutic targets for obesity and T2DM.

Serum R-Spondin 1 Is a New Surrogate Marker for Obesity and Insulin Resistance

BACKGROUND

Recent in vivo studies indicated that R-spondin 1 (RSPO1) regulates food intake and increases insulin secretion, but its role in humans remains unknown. This study investigated the association between serum levels of RSPO1 and diverse metabolic parameters in humans.

METHODS

The study population consisted of 43 subjects with newly diagnosed diabetes mellitus, and 79 non-diabetic participants. Serum levels of RSPO1 were measured using the enzyme-linked immunosorbent assay. The relationships between circulating RSPO1 and diverse metabolic parameters were analyzed.

RESULTS

Circulating RSPO1 levels increased to a greater extent in the obese group than in the lean group. Moreover, serum levels of RSPO1 were higher in the insulin-resistant group than in the insulin-sensitive group. Serum levels of RSPO1 were significantly correlated with a range of metabolic parameters including body mass index, fasting C-peptide, homeostasis model assessment of insulin resistance index, and lipid profile. Moreover, levels were significantly associated with insulin resistance and obesity in non-diabetic subjects.

CONCLUSION

This study demonstrated the association between serum levels of RSPO1 and a range of metabolic parameters in humans. Serum levels of RSPO1 are significantly related to obesity and insulin resistance, although the precise mechanisms remain unknown.

Deletion of Robo4 prevents high-fat diet-induced adipose artery and systemic metabolic dysfunction

OBJECTIVE

Accumulating evidence suggests the vascular endothelium plays a fundamental role in the pathophysiology of obesity by regulating the functional status of white adipose and systemic metabolism. Robo4 is expressed specifically in endothelial cells and increases vascular stability and inhibits angiogenesis. We sought to determine the role of Robo4 in modulating cardiometabolic function in response to high-fat feeding.

METHODS

We examined exercise capacity, glucose tolerance, and white adipose tissue artery gene expression, endothelium-dependent dilation (EDD), and angiogenesis in wild type and Robo4 knockout (KO) mice fed normal chow (NC) or a high-fat diet (HFD).

RESULTS

We found Robo4 deletion enhances exercise capacity in NC-fed mice and HFD markedly increased the expression of the Robo4 ligand, Slit2, in white adipose tissue. Deletion of Robo4 increased angiogenesis in white adipose tissue and protected against HFD-induced impairments in white adipose artery vasodilation and glucose intolerance.

CONCLUSIONS

We demonstrate a novel functional role for Robo4 in endothelial cell function and metabolic homeostasis in white adipose tissue, with Robo4 deletion protecting against endothelial and metabolic dysfunction associated with a HFD. Our findings suggest that Robo4-dependent signaling pathways may be a novel target in anti-obesity therapy.

Brown Adipokines

Brown adipokines are regulatory factors secreted by brown and beige adipocytes that exhibit endocrine, paracrine, and autocrine actions. Peptidic and non-peptidic molecules, including miRNAs and lipids, are constituents of brown adipokines. Brown adipose tissue remodeling to meet thermogenic needs is dependent on the secretory properties of brown/beige adipocytes. The association between brown fat activity and a healthy metabolic profile, in relation to energy balance and glucose and lipid homeostasis, is influenced by the endocrine actions of brown adipokines. A comprehensive knowledge of the brown adipocyte secretome is still lacking. Advancements in the identification and characterization of brown adipokines will facilitate therapeutic interventions for metabolic diseases, as these molecules are obvious candidates to therapeutic agents. Moreover, identification of brown adipokines as circulating biomarkers of brown adipose tissue activity may be particularly useful for noninvasive assessment of brown adipose tissue alterations in human pathologies.

Brown and beige fat: From molecules to physiology and pathophysiology

The adipose organ portrays adipocytes of diverse tones: white, brown and beige, each type with distinct functions. Adipocytes orchestrate their adaptation and expansion to provide storage to excess nutrients, the quick mobilisation of fuel to supply peripheral functional demands, insulation, and, in their thermogenic form, heat generation to maintain core body temperature. Thermogenic adipocytes could be targets for anti-obesity and anti-diabetic therapeutic approaches aiming to restore adipose tissue functionality and increase energy dissipation. However, for thermogenic adipose tissue to become therapeutically relevant, a better understanding of its development and origins, its progenitors and their characteristics and the composition of its niche, is essential. Also crucial is the identification of stimuli and molecules promoting its specific differentiation and activation. Here we highlight the structural/cellular differences between human and rodent brown adipose tissue and discuss how obesity and metabolic complication affects brown and beige cells as well as how they could be targeted to improve their activation and improve global metabolic homeostasis. Finally, we describe the limitations of current research models and the advantages of new emerging approaches.