β3-Adrenergic receptors regulate human brown/beige adipocyte lipolysis and thermogenesis

Mitochondrial Calcium Uniporter is Required for Thermogenic Adaptation Mediated by Reactive Oxygen Species Signaling

Mitochondrial Ca2+ influx via mitochondrial calcium uniporter (MCU) accelerates mitochondrial biogenesis and energy metabolism. Nevertheless, the molecular mechanism of MCU-dependent mitochondrial activation and thermogenesis in thermogenic adipose tissues remains elusive. In this study, we demonstrate that MCU governs mitochondrial functions in brown and beige adipocytes via the formation of mitochondrial reactive oxygen species (mtROS). Mice with a brown adipose tissue-specific Mcu knockout (Mcu BKO) mice exhibited decreased oxygen consumption and heat production, accompanied by downregulation of genes related to β-oxidation and thermogenesis. Furthermore, Mcu BKO mice, exhibiting a reduction in mtROS, showed defective thermogenic responses to cold exposure or β-adrenergic stimulation. Downregulation of thermogenic genes including Ucp1 in Mcu BKO mice can be rescued by exogenous ROS through AMP-activated protein kinase (AMPK) activation. Collectively, our results suggest that MCU modulates mtROS formation, which in turn mediates mitonuclear signaling to cellular response with mitochondrial activation.

Fexaramine as the intestine-specific farnesoid X receptor agonist: A promising agent to treat obesity and metabolic disorders

Fexaramine, a gut-restricted farnesoid X receptor (FXR) agonist, promotes glucose and lipid homeostasis, improves insulin sensitivity, promotes white adipose tissue browning, and stimulates nonshivering thermogenesis. Enhancement in energy expenditure due to an increase in amount of energy burned by brown and 'beige' adipocytes results in subsequent weight loss. Fexaramine is poorly absorbed into circulation when delivered orally, which limits systemic FXR activation and toxicity. An increase in β3-adrenoceptor signaling, activation of Takeda G protein-coupled receptor 5/glucagon-like peptide-1 (TGR5/GLP-1) signaling, and induction of fibroblast growth factor (FGF)-19/FGF-15 play crucial roles in fexaramine metabolic actions. Intestinal FXR activation is a promising, potentially safe approach for treating obesity and metabolic syndrome.

Endocrine regulation of metabolic crosstalk between liver and brown adipose tissue by natural active ingredients

The escalating global obesity crisis and its associated metabolic disorders have posed a significant threat to public health, increasing the risk of major health issues such as cardiovascular diseases and type 2 diabetes. Central to metabolic regulation are the liver and brown adipose tissue (BAT), which orchestrate glycolipid metabolism, thermogenesis, and energy homeostasis. Emerging evidence highlights the role of natural bioactive compounds-such as polyphenols (e.g., resveratrol, curcumin), alkaloids (e.g., berberine), and terpenoids (e.g., paeoniflorin, shikonin)-in modulating liver-BAT crosstalk. These compounds influence critical pathways, including AMPK activation, PPAR signaling, and UCP1-mediated thermogenesis, to enhance lipid oxidation, suppress gluconeogenesis, and improve insulin sensitivity. This review systematically examines how these natural agents regulate metabolic interplay between the liver and BAT, addressing their effects on energy expenditure, carbohydrate utilization, and lipid mobilization. Key mechanisms involve the suppression of hepatic lipogenesis, promotion of BAT-mediated thermogenesis, and secretion of hepatokines (e.g., FGF21) and batokines that coordinate interorgan communication. By synthesizing preclinical and clinical findings, we highlight the translational potential of dietary interventions and nutraceuticals targeting liver-BAT axis dysfunction. Future research should prioritize mechanistic studies, dose optimization, and personalized approaches to harness these compounds for combating obesity-related diseases. These insights underscore the promise of natural bioactive molecules as adjuvants to lifestyle modifications, offering innovative strategies for metabolic health restoration.

Obesity prevention by different exercise protocols (HIIT or MICT) involves beige adipocyte recruitment and improved mitochondrial dynamics in high-fat-fed mice

AIM

This study evaluated the effects of high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on UCP1-dependent and UCP1-independent thermogenic and mitochondrial dynamics markers in the inguinal sWAT of high-fat-fed mice.

METHODS

Sixty male C57BL/6 mice (3 months old) were divided into six experimental groups: control diet (C), C + HIIT (C-HIIT), C + MICT (C-MICT), high-fat diet (HF), HF + HIIT (HF-HIIT) and HF + MICT (HF-MICT). The diet and exercise protocols started simultaneously and lasted ten weeks.

RESULTS

HIIT and MICT prevented body mass gain and fat pad expansion, improved insulin sensitivity, and induced browning in C-fed and HF-fed animals. Chronic intake of a HF diet caused adipocyte hypertrophy with a proinflammatory adipokine profile and impaired the expression of thermogenic and mitochondrial dynamics markers. However, both exercise intensities increased anti-inflammatory adipokine concentrations and improved gene markers of mitochondrial dynamics, resulting in sustained UCP1-dependent and UCP1-independent thermogenic markers and maintenance of the beige phenotype in inguinal sWAT. The principal component analysis placed all trained groups opposite the HF group and near the C group, ensuring the effectiveness of HIIT and MICT to prevent metabolic alterations.

CONCLUSIONS

This study provides reliable evidence that, regardless of intensity, exercise is a strategy to prevent obesity by reducing body fat accumulation and inducing browning. The anti-inflammatory adipokine profile and the increased expression of UCP1-dependent and UCP1-independent thermogenic markers sustained active beige adipocytes and mitochondrial enhancement to halt metabolic disturbances due to HF-feeding in exercised mice.

Metabolite 2-aminoadipic acid: implications for metabolic disorders and therapeutic opportunities

Previous evidence has indicated that the role of 2-aminoadipic acid (2-AAA), a derivative of lysine catabolism, in mediating specific detrimental effects on glial cells, notably inhibiting astrocyte activation. In addition, intrathecal administration of 2-AAA has demonstrated significant efficacy in relieving mechanical hyperalgesia. With the growing application of metabolomics in biomedical research, substantial evidence now underscores 2-AAA's pivotal role in regulating glucose and lipid metabolism. As a novel biomarker, 2-AAA is linked to increased susceptibility to diabetes and has emerged as a critical regulator of glucose homeostasis. This review explores recent advancements in understanding 2-AAA's potential therapeutic applications, particularly in the context of metabolic diseases such as diabetes, obesity, and atherosclerosis. It also addresses existing research gaps and outlines future directions for developing 2-AAA-based therapies.

The microprotein C16orf74/MICT1 promotes thermogenesis in brown adipose tissue

Brown and beige adipose tissues are metabolically beneficial for increasing energy expenditure via thermogenesis, mainly through UCP1 (uncoupling protein 1). Here, we identify C16orf74, subsequently named MICT1 (microprotein for thermogenesis 1), as a microprotein that is specifically and highly expressed in brown adipose tissue (BAT) and is induced upon cold exposure. MICT1 interacts with protein phosphatase 2B (PP2B, calcineurin) through the docking motif PNIIIT, thereby interfering with dephosphorylation of the regulatory subunit of protein kinase A (PKA), RIIβ, and potentiating PKA activity in brown adipocytes. Overexpression of MICT1 in differentiated brown adipocytes promotes thermogenesis, showing increased oxygen consumption rate (OCR) with higher thermogenic gene expression during β3-adrenergic stimulation, while knockdown of MICT1 impairs thermogenic responses. Moreover, BAT-specific MICT1 ablation in mice suppresses thermogenic capacity to increase adiposity and insulin resistance. Conversely, MICT1 overexpression in BAT or treating mice with a chemical inhibitor that targets the PP2B docking motif of MICT1 enhances thermogenesis. This results in cold tolerance and increased energy expenditure, protection against diet-induced and genetic obesity and insulin resistance, thus suggesting a therapeutic potential of MICT1 targeting.

Impact of β3-adrenergic receptor agonist on kidney cancer risk in patients with overactive bladder

OBJECTIVES

To determine the effect of β3-adrenergic receptor (AR) agonist on the risk of kidney cancer in patients with overactive bladder (OAB).

PATIENTS AND METHODS

A nationwide population cohort study was conducted using data from the Korean National Health Insurance System database between January 2016 and December 2023. Validation analyses were performed using clinical data from patients with OAB treated with mirabegron or anticholinergics at a tertiary referral hospital between January 2014 and December 2023. The main exposure was intake of β3-AR agonist or anticholinergics, and the main outcome was incidence of kidney cancer.

RESULTS

Of the 1 419 148 patients (61.6% male; median [interquartile range] age, 64 [53-73] years), 3229 developed kidney cancer after OAB treatment. The incidence rate of kidney cancer was 0.7 per 1000 person-years in the mirabegron group and 0.5 per 1000 person-years in the anticholinergic group. Among the validation data of 3108 patients (49.3% male; mean [standard deviation] age, 63.9 [13.3] years), 45 (1.4%) developed kidney cancer after OAB treatment. The mirabegron group had a higher incidence of kidney cancer (1.8%) than the anticholinergic group (0.7%) (P = 0.025).

CONCLUSIONS

Use of β3-AR agonists was associated with an increased risk of kidney cancer compared with anticholinergics. While these findings suggest a potential association between mirabegron use and kidney cancer, further studies are needed to confirm causality. Clinicians should exercise caution when prescribing mirabegron in patients with risk factors for kidney cancer.

Mitochondrial GCN5L1 coordinates with YME1L and MICOS to remodel mitochondrial cristae in white adipocytes and modulate obesity

The relationship between mitochondrial architecture and energy homeostasis in adipose tissues is not well understood. In this study, we utilized GCN5L1-knockout mice in white (AKO) and brown (BKO) adipose tissues to examine mitochondrial homeostasis in adipose tissues. GCN5L1, a regulator of mitochondrial metabolism and dynamics, influences resistance to high-fat-diet-induced obesity in AKO but not BKO mice. This resistance is mediated by an increase in mitochondrial cristae that stabilizes oxidative phosphorylation (OXPHOS) complexes and enhances energy expenditure. Our protein-interactome analysis reveals that GCN5L1 is associated with the mitochondrial crista complex MICOS (MIC13) and the protease YME1L, facilitating the degradation of MICOS and disassembly of cristae during obesity. This interaction results in decreased OXPHOS levels and subsequent adipocyte expansion. Accumulation of GCN5L1 in the mitochondrial intermembrane space is triggered by a high-fat diet. Our findings highlight a regulatory pathway involving YME1L/GCN5L1/MIC13 that remodels mitochondrial cristae in WAT in response to overnutrition-induced obesity.

An NRF2/β3-Adrenoreceptor Axis Drives a Sustained Antioxidant and Metabolic Rewiring Through the Pentose-Phosphate Pathway to Alleviate Cardiac Stress

BACKGROUND

Cardiac β3-adrenergic receptors (ARs) are upregulated in diseased hearts and mediate antithetic effects to those of β1AR and β2AR. β3AR agonists were recently shown to protect against myocardial remodeling in preclinical studies and to improve systolic function in patients with severe heart failure. However, the underlying mechanisms remain elusive.

METHODS

To dissect functional, transcriptional, and metabolic effects, hearts and isolated ventricular myocytes from mice harboring a moderate, cardiac-specific expression of a human ADRB3 transgene (β3AR-Tg) and subjected to transverse aortic constriction were assessed with echocardiography, RNA sequencing, positron emission tomography scan, metabolomics, and metabolic flux analysis. Subsequently, signaling and metabolic pathways were further investigated in vivo in β3AR-Tg and ex vivo in neonatal rat ventricular myocytes adenovirally infected to express β3AR and subjected to neurohormonal stress. These results were complemented with an analysis of single-nucleus RNA-sequencing data from human cardiac myocytes from patients with heart failure.

RESULTS

Compared with wild-type littermates, β3AR-Tg mice were protected from hypertrophy after transaortic constriction, and systolic function was preserved. β3AR-expressing hearts displayed enhanced myocardial glucose uptake under stress in the absence of increased lactate levels. Instead, metabolomic and metabolic flux analyses in stressed hearts revealed an increase in intermediates of the pentose-phosphate pathway in β3AR-Tg, an alternative route of glucose utilization, paralleled with increased transcript levels of NADPH-producing and rate-limiting enzymes of the pentose-phosphate pathway, without fueling the hexosamine metabolism. The ensuing increased content of NADPH and of reduced glutathione decreased myocyte oxidant stress, whereas downstream oxidative metabolism assessed by oxygen consumption was preserved with higher glucose oxidation in β3AR-Tg mice after transaortic constriction compared with wild type, together with increased mitochondrial biogenesis. Unbiased transcriptomics and pathway analysis identified NRF2 (NFE2L2) as an upstream transcription factor that was functionally verified in vivo and in β3AR-expressing cardiac myocytes, where its translocation and nuclear activity were dependent on β3AR activation of nitric oxide synthase and nitric oxide production through S-nitrosation of the NRF2-negative regulator Keap1.

CONCLUSIONS

Moderate expression of cardiac β3AR, at levels observed in human cardiac myocardium, exerts metabolic and antioxidant effects through activation of the pentose-phosphate pathway and NRF2 pathway through S-nitrosation of Keap1, thereby preserving myocardial oxidative metabolism, function, and integrity under pathophysiological stress.

(+)-Terrein exerts anti-obesity and anti-diabetic effects by regulating the differentiation and thermogenesis of brown adipocytes in mice fed a high-fat diet

OBJECTIVE

(+)-Terrein, a low-molecular-weight secondary metabolite from Aspergillus terreus, inhibits adipocyte differentiation in vitro. However, the precise mechanisms underlying the effects of (+)-terrein on adipocytes remain unclear. We hypothesized that (+)-terrein modulates adipogenesis and glucose homeostasis in obesity and diabetes via anti-inflammatory action and regulation of adipocyte differentiation. Hence, in this study, we aimed to investigate the in vivo anti-diabetic and anti-obesity effects of (+)-terrein.

METHODS

Male C57BL/6 J mice were fed normal chow or high-fat (HF) diet and administered (+)-terrein (180 mg/kg) via intraperitoneal injection. Glucose and insulin tolerance tests, serum biochemical assays, and histological analyses were also performed. Rat brown preadipocytes, mouse brown preadipocytes (T37i cells), and inguinal white adipose tissue (ingWAT) preadipocytes were exposed to (+)-terrein during in vitro adipocyte differentiation. Molecular markers associated with thermogenesis and differentiation were quantified using real-time polymerase chain reaction and western blotting.

RESULTS

(+)-Terrein-treated mice exhibited improved insulin sensitivity and reduced serum lipid and glucose levels, irrespective of the diet. Furthermore, (+)-terrein suppressed body weight gain and mitigated fat accumulation by activating brown adipose tissue in HF-fed mice. (+)-Terrein facilitated the in vitro differentiation of rat brown preadipocytes, T37i cells, and ingWAT preadipocytes by upregulating peroxisome proliferator-activated receptor-γ (PPARγ). This effect was synergistic with that of a PPARγ agonist.

CONCLUSION

This study demonstrated that (+)-terrein effectively induces PPARγ expression and brown adipocyte differentiation, leading to reduced weight gain and improved glucose and lipid profiles in HF-fed mice. Thus, (+)-terrein is a potent novel agent with potential anti-obesity and anti-diabetic properties.

Excessive dietary saturated fat or fructose and their combination (found in ultra-processed foods) impair mitochondrial dynamics markers and cause brown adipocyte whitening in adult mice

OBJECTIVE

To investigate the effects of comparable dietary excess of fat or fructose and the combination of these two insults (mimicking ultra-processed foods) on interscapular brown adipose tissue (iBAT) whitening and markers of mitochondrial dynamics in adult male mice.

METHODS

Male C57BL/6 mice were randomly assigned into four groups according to the diet: control diet (C, following AIN-93M), high-fat diet (HF, 32% energy as lard), high-fructose diet (HFRU, 32% energy as fructose) or for high-fat/high-fructose diet (HF-HFRU, 32% as lard and 32% as fructose) for 12 weeks. Data were tested with one-way ANOVA and Dunnet T3 post-test (n=5 per analysis, significance level P < 0.05).

RESULTS

All diets caused insulin resistance and iBAT whitening, albeit with overweight only in the HF and HF-HFRU groups. Principal component analysis indicated that the HFRU scores loaded next to inflammation (Nlrp3) and adipogenesis markers (Pparg), and the HF diet influenced more a mitochondrial gene (Tomm20). However, iBAT whitening in all groups was associated with deficits in mitochondrial dynamics (Ppargc1a, Dnml1, and Pink1), vascularization (Vegfa), and thermogenic markers (Bmp8b, and Ucp1).

CONCLUSION

Similar increases in dietary saturated fat or fructose (32% as energy) and the combination of these two insults (32% / 32%) caused insulin resistance and brown adipocyte dysfunction (whitening) in adult mice after 12 weeks independent of being overweight. In comparison, the PC scores of the HFRU groups were closer to the HF-HFRU group than the HF group, implying a worse outcome and highlighting the importance of limiting saturated fat and fructose intake from ultra-processed foods.

Impact of Western diet on milk miRNAs and target genes in offspring adipose tissue: modulation by betaine during suckling

OBJECTIVE

We investigated how a maternal Western diet (WD) affects milk microRNA (miRNA) profile and associates with metabolic programming in adipose tissues in pups. We also explored the impact of betaine supplementation during suckling, as betaine levels are reported to be reduced in WD-fed dams' milk.

METHODS

A microarray analysis was performed to profile miRNA expression in dams' milk. Betaine levels were measured in the milk of dams and the plasma of their offspring. We also analyzed the expression of miRNA target genes in white and brown adipose tissues through gene expression analysis.

RESULTS

Our findings confirm decreased betaine levels in the milk of WD-fed dams and the plasma of their offspring. The miRNA screening identified 37 deregulated miRNAs (36 downregulated), with the following 6 as the most relevant: miR-223-3p; miR-32-5p; let-7i-5p; miR-140-5p; miR-29a-3p; and miR-29c-3p (downregulated). Some of their target genes were upregulated in brown and white adipose tissues, particularly those related to thermogenesis and browning. Betaine supplementation in pups demonstrated a slight protective effect in females by enhancing thermogenic capacity.

CONCLUSIONS

Our results underscore the profound impact of a maternal WD on milk miRNA composition, potentially influencing gene expression, thermogenesis, and adiposity in the offspring, with sex-related differences.

A narrative review about the intricate crosstalk among endometrium, adipose tissue, and neurons in endometriosis. The multifaceted role of leptin

Endometriosis is a highly prevalent gynecological disease characterized by the presence of endometrium-like tissue outside the uterus, whose etiopathology is far from being elucidated. The most frequent complains of patients are pelvic pain and infertility. Increasing evidence supports the systemic impact of endometriosis suggesting that an intricate crosstalk among distinct organs underlies the development of the disease. In this setting, endometriosis patients present an increased risk for developing other diseases, such as cancer, cardiovascular pathologies, and autoimmune diseases, and manifest neurologic disturbances, including neuropathic hyperalgesia. Whilst the ovary-secreted estrogen dependency of ectopic endometrium growth is well established, we conjecture that adipose tissue-secreted molecules also intervene in endometriosis development and pain manifestation. In fact, women with endometriosis present a peculiar pattern of adipokine secretion that ensues the disease onset. Unexpectedly, the levels of adipose tissue-secreted molecules in those women present similarities with those found in patients with obesity, despite the recognized association of low body mass index with endometriosis. Taking this evidence into consideration, we hypothesize that endometriosis patients present a dysfunctional adipose tissue, which is associated with enhanced metabolism and unregulated browning that not only intervene in the control of body weight but also in peculiar pain processing pathways.

Functional expression mechanisms of food-derived components based on target proteins

Food-derived polyphenols and some alkaloids have reported bioactivities related to the prevention of systemic metabolic disorders such as obesity, glucose intolerance, and dyslipidemia. For food-derived components to exert their functions in vivo, it is essential to interact with biological factors such as proteins, lipids, and nucleic acids. However, it is still unclear whether bioactive components in foods express functions related to their target factors. In this review, I introduce the target proteins in which food-derived components express functions in cells.

Chronic Exposure to Environmental Concentrations of Tetrabromobisphenol A Disrupts Insulin and Lipid Homeostasis in Diet-Induced Obese Mice

Tetrabromobisphenol A (TBBPA), a widely used brominated flame retardant in consumer products, has raised significant health concerns. However, the long-term metabolic effects of chronic exposure to environmentally relevant TBBPA concentrations, particularly in the context of modern high-calorie diets, remain poorly understood. Here, we show that C57BL/6J mice fed a high-fat diet and exposed to 20 or 50 nmol/kg/day TBBPA for 120 days exhibited increased body weight, aggravated fat accumulation, impaired glucose tolerance, insulin resistance, and dyslipidemia. Mechanistic investigations revealed that TBBPA exposure led to decreased norepinephrine levels, consequently reducing energy expenditure. It disrupts hepatic insulin signaling and upregulates G6Pase, thereby increasing the level of liver glucose production. Furthermore, TBBPA enhances hepatic cholesterol synthesis by elevating protein levels of HMGCR, which is the rate-limiting enzyme in cholesterol biosynthesis. This effect is mediated through increased expression of USP20, a specific deubiquitinating enzyme for HMGCR. Additionally, TBBPA modestly enhances fatty acid biosynthesis without significantly affecting lipolysis or fatty acid oxidation. Our research reveals novel molecular pathways through which environmental TBBPA exposure disrupts metabolic balance, potentially exacerbating obesity-related health issues. These findings highlight the synergistic effects between environmental pollutants and modern calorie-dense diets on metabolic health, emphasizing the importance of considering multiple factors in obesity-related disorders.

G-Protein-Coupled Receptor (GPCR) Signaling and Pharmacology in Metabolism: Physiology, Mechanisms, and Therapeutic Potential

G-protein coupled receptors (GPCRs), the largest family of integral membrane proteins, enable cells to sense and appropriately respond to the environment through mediating extracellular signaling to intercellular messenger molecules. GPCRs' pairing with a diverse array of G protein subunits and related downstream secondary messengers, combined with their ligand versatility-from conventional peptide hormone to numerous bioactive metabolites, allow GPCRs to comprehensively regulate metabolism and physiology. Consequently, GPCRs have garnered significant attention for their therapeutic potential in metabolic diseases. This review focuses on six GPCRs, GPR40, GPR120, GLP-1R, and ß-adrenergic receptors (ADRB1, ADRB2, and ADRB3), with GLP-1R recognized as a prominent regulator of system-level metabolism, while the roles of GPR40, GPR120 and ß-adrenergic receptors in central carbon metabolism and energy homeostasis are increasingly appreciated. Here, we discuss their physiological functions in metabolism, the current pharmacological landscape, and the intricacies of their signaling pathways via G protein and ß-arrestin activation. Additionally, we discuss the limitations of existing GPCR-targeted strategies for treating metabolic diseases and offer insights into future perspectives for advancing GPCR pharmacology.

The Role of Active Brown Adipose Tissue in Patients With Pheochromocytoma or Paraganglioma

OBJECTIVES

Metabolically-active brown adipose tissue (aBAT) is a common finding on 18fluorodeoxyglucose positron emission tomography (FDG-PET) imaging in patients with pheochromocytoma or paraganglioma (PPGL). In addition to its clinical significance, we aimed to explore the prevalence of this finding on FDG-PET imaging in patients with PPGL.

METHODS

We conducted a systematic review and meta-analysis of prospective and retrospective studies. Publications were identified through searches in MEDLINE/PubMed, Embase, and SCOPUS from inception until 2022-11-26, with an update check performed on 2024-05-02. Eligible studies included patients with PPGL who had completed FDG-PET imaging. Data on catecholamine levels stratified by the presence of aBAT were extracted and pooled using the random-effects model with the inverse variance method. For the quantitative synthesis, we used standardized mean differences and meta-analysis of proportions. A risk of bias assessment was performed using the Quality in Prognostic Studies tool.

RESULTS

Our search yielded 6 studies suitable for inclusion. Pooled data showed a statistically significant positive difference in isolated demethylated catecholamine levels in aBAT positive groups compared to aBAT negative. No significant differences were found in multiple domains, including tumor size, tumor burden, germline mutations, or location. The proportion of patients with PPGL who present with aBAT stands at approximately 25%.

CONCLUSIONS

The demethylated metabolite levels could have potential use in predicting the presence of active brown adipose tissue in patients with PPGL. There is no convincing evidence of increased aBAT prevalence in patients with PPGL and germline mutations. There was, however, evidence suggesting that the presence of aBAT may confer poorer outcomes and decreased life expectancy.

Absence of MCJ/DnaJC15 promotes brown adipose tissue thermogenesis

Obesity poses a global health challenge, demanding a deeper understanding of adipose tissue (AT) and its mitochondria. This study describes the role of the mitochondrial protein Methylation-controlled J protein (MCJ/DnaJC15) in orchestrating brown adipose tissue (BAT) thermogenesis. Here we show how MCJ expression decreases during obesity, as evident in human and mouse adipose tissue samples. MCJKO mice, even without UCP1, a fundamental thermogenic protein, exhibit elevated BAT thermogenesis. Electron microscopy unveils changes in mitochondrial morphology resembling BAT activation. Proteomic analysis confirms these findings and suggests involvement of the eIF2α mediated stress response. The pivotal role of eIF2α is scrutinized by in vivo CRISPR deletion of eIF2α in MCJKO mice, abrogating thermogenesis. These findings uncover the importance of MCJ as a regulator of BAT thermogenesis, presenting it as a promising target for obesity therapy.

Emerging debates and resolutions in brown adipose tissue research

Until two decades ago, brown adipose tissue (BAT) was studied primarily as a thermogenic organ of small rodents in the context of cold adaptation. The discovery of functional human BAT has opened new opportunities to understand its physiological role in energy balance and therapeutic applications for metabolic disorders. Significantly, the role of BAT extends far beyond thermogenesis, including glucose and lipid homeostasis, by releasing mediators that communicate with other cells and organs. The field has made major advances by using new model systems, ranging from subcellular studies to clinical trials, which have also led to debates. In this perspective, we identify six fundamental issues that are currently controversial and comprise dichotomous models. Each side presents supporting evidence and, critically, the necessary methods and falsifiable experiments that would resolve the dispute. With this collaborative approach, the field will continue to productively advance the understanding of BAT physiology, appreciate the importance of thermogenic adipocytes as a central area of ongoing research, and realize the therapeutic potential.

A natural small molecule pinocembrin resists high-fat diet-induced obesity through GPR120-ERK1/2 pathway

Obesity is a widely concerned health problem. Mobilizing white adipose tissue and reducing fat synthesis are considered as effective strategies in the treatment of obesity. Here, using Connectivity Map (CMap) approach, we identified the pinocembrin (PB), a natural flavonoid primarily found in propolis, as a potential anti-obesity drug. Therefore, high-fat-diet (HFD) mice were randomly divided into two groups and fed a HFD or HFD with PB in this study. In vivo experiments showed that supplementation of PB reduced the body weight gain and ameliorated insulin resistance in HFD-induced mice. More importantly, PB did not cause side effect through detecting the levels of alanine transaminase (ALT), aspartate aminotransferase (AST), creatinine (CRE) and blood urea nitrogen (BUN) in serum of mice. Additionally, PB reduced expansion of white adipose tissue with upregulation of genes related lipolysis and downregulation of genes related lipogenesis. Furthermore, in vitro experiments revealed that PB treatment dose-dependently inhibited lipid droplet formation with upregulation of genes related lipolysis and downregulation of genes related lipogenesis. Molecular docking analysis combined with cellular thermal shift assay (CETSA) suggested that PB has a high affinity to the G protein-coupled receptor 120 (GPR120). Meanwhile, we confirmed that PB efficiently inhibited adipogenic differentiation of preadipocytes by directly binding to GPR120 and subsequently activating the downstream phosphorylation extracellular regulated kinase 1/2 (ERK1/2). Collectively, PB exerted anti-obesity effect through GPR120-ERK1/2 signaling pathway, providing a novel and promising natural drug for the treatment of obesity.

The role of compartmentalized β-AR/cAMP signaling in the regulation of lipolysis in white and brown adipocytes

White and brown adipocytes are central mediators of lipid metabolism and thermogenesis, respectively. Their function is tightly regulated by all three β-adrenergic receptor (β-AR) subtypes which are coupled to the production of the second messenger 3',5'-cyclic adenosine monophosphate (cAMP). While known for decades in other cell types, compartmentation of adipocyte β-AR/cAMP signaling by spatial organization of the pathway and by cAMP degrading phosphodiesterases (PDEs) as well as its role in the regulation of lipolysis is only beginning to emerge. Here, we provide a short overview of recent findings which shed light on compartmentalized signaling using live cell imaging of cAMP in adipocytes and discuss possible future directions of research which could open up new avenues for the treatment of metabolic disorders.

Palm and interesterified palm oil-enhanced brown fat whitening contributes to metabolic dysfunction in C57BL/6J mice

Palm oil is widely used in the food industry owing to its high stability and versatility. The interesterified version has been used as an alternative to oils rich in trans fatty acids. However, the health effects of these vegetable oils are not yet fully understood. We hypothesized that the consumption of palm oil (noninteresterified and interesterified), even without excessive amounts of energy and lipids in the diet, could lead to morphofunctional changes in brown adipose tissue (BAT). To this end, male C57BL/6J mice were divided into 3 dietary groups (n = 10 each): soybean oil (SO), palm oil (PO), and interesterified palm oil (IPO) for 10 weeks. The PO and IPO groups had significant increases in the visceral fat mass and interscapular BAT (iBAT) lipid content. In iBAT, the PO and IPO groups showed lower mRNA expression of Ucp1, Adrb3, and Pgc1a, while the PO also showed lower mRNA levels of Ppara and Ampk, and the IPO showed lower Prdm16 expression. Moreover, PO had higher Il6 expression and lower catalase activity, while the IPO showed an upregulated Tnfa expression and lower catalase activity, but higher antioxidant activity of the glutathione peroxidase (GPx) enzyme. The consumption of PO and IPO had negative effects on weight and body fat, including the impairment of iBAT function. Our findings give rise to apprehensions regarding the safety and consequences of consuming PO and IPO for energy metabolism.

Spotlight on the Mechanism of Action of Semaglutide

Initially intended to control blood glucose levels in patients with type 2 diabetes, semaglutide, a potent glucagon-like peptide 1 analogue, has been established as an effective weight loss treatment by controlling appetite. Integrating the latest clinical trials, semaglutide in patients with or without diabetes presents significant therapeutic efficacy in ameliorating cardiometabolic risk factors and physical functioning, independent of body weight reduction. Semaglutide may modulate adipose tissue browning, which enhances human metabolism and exhibits possible benefits in skeletal muscle degeneration, accelerated by obesity and ageing. This may be attributed to anti-inflammatory, mitochondrial biogenesis, antioxidant and autophagy-regulating effects. However, most of the supporting evidence on the mechanistic actions of semaglutide is preclinical, demonstrated in rodents and not actually confirmed in humans, therefore warranting caution in the interpretation. This article aims to explore potential innovative molecular mechanisms of semaglutide action in restoring the balance of several interlinking aspects of metabolism, pointing to distinct functions in inflammation and oxidative stress in insulin-sensitive musculoskeletal and adipose tissues. Moreover, possible applications in protection from infections and anti-aging properties are discussed. Semaglutide enhancement of the core molecular mechanisms involved in the progress of obesity and diabetes, although mostly preclinical, may provide a framework for future research applications in human diseases overall.

Swertiamarin ameliorates type 2 diabetes by activating ADRB3/UCP1 thermogenic signals in adipose tissue

BACKGROUND AND PURPOSE

Swertiamarin (STM), a secoiridoid glycoside from Swertia chirayita (Roxb.) H. Karst, has been shown to decrease body weight, blood glucose, and blood lipids by inhibiting adipose tissue hypertrophy. However, the underlying mechanisms remain unclear. In particular, adipose thermogenesis is a novel avenue for exploring the pharmacological effects of STM. We aim to investigate the efficacy of STM on type 2 diabetes mellitus (T2DM), with a focus on underlying mechanisms, particularly the activation of ADRB3/UCP1 thermogenic signaling pathways.

METHODS

T2DM model was established by a high-fat diet (HFD) and streptozotocin (STZ) in C57BL/6 J male mice. Mice were given to either 100 or 200 mg kg-1/day of STM, or 200 mg kg-1/day of metformin (Glucophage) via intragastric administration for 7 weeks. In vitro, 3T3-L1 cells were differentiated into adipocytes. Molecular markers related to ADRB3-UCP1 signals, lipolysis, and mitochondrial function were detected.

RESULTS

STM-treated diabetic mice showed a reduction of body weight, fat mass, and blood glucose/lipids and an improvement in insulin sensitivity. Bioinformatics analysis indicated STM promoted lipid metabolism and mitochondrial function, features by closely associated with adipose thermogenesis. STM upregulated the lipolysis-related genes and p-HSL protein in inguinal subcutaneous white adipose tissue (igSWAT) and brown adipose tissue (BAT). STM-treated mice processed a more active energy metabolism. Additionally, the ADRB3-UCP1 signals, mitochondrial-related genes, and oxidative phosphorylation were improved in igSWAT and BAT. In vitro, we found STM interacted with ADRB3, increasing glucose uptake, glycerol release, ADRB3-UCP1 signals, p-HSL expression, mitochondrial content, oxidative phosphorylation complex expression with improved mitochondrial Δψm, as well as reduced lipid accumulation in adipocytes. All these effects were reversed upon ADRB3 inhibition.

CONCLUSION

This study identifies a previously unknown role of STM activating ADRB3/UCP1 signals in adipose tissue, suggesting a potential strategy for treating T2DM.

Establishing Immortalized Brown and White Preadipocyte Cell Lines from Young and Aged Mice

Studying adipogenesis and adipocyte biology requires the isolation of primary preadipocytes from adipose tissues. However, primary preadipocytes have a limited lifespan, can only undergo a finite number of divisions, and often lose their original biological characteristics before becoming senescent. The repeated isolation of fresh preadipocytes, particularly from young pups or aged animals, is costly and time consuming. Immortalization of these cells offers a solution by overcoming cellular senescence and maintaining proliferative capacity, allowing for long-term studies without the continuous need to isolate new cells from animals. Immortalized cell lines thus provide a consistent and reproducible experimental model, significantly reducing variability across different animals. However, successfully establishing immortalized preadipocyte cell lines presents challenges, including selecting appropriate adipose tissue depots, isolating primary preadipocytes, and choosing an effective immortalization strategy. In this article, we present optimized protocols and share first-hand experiences establishing immortalized brown and white preadipocyte cell lines from young and aging mice. These protocols offer a valuable resource for researchers studying adipogenesis and metabolism. © 2024 Wiley Periodicals LLC. Support Protocol 1: Retrovirus production Basic Protocol 1: Isolation and culture of primary brown and white preadipocytes from mouse interscapular brown adipose tissue (iBAT) and subcutaneous white adipose tissue (sWAT) in the same region Basic Protocol 2: Immortalization of mouse brown and white preadipocytes Basic Protocol 3: Selection of immortalized preadipocytes Basic Protocol 4: Selection of single-cell clones of immortalized mouse preadipocytes Basic Protocol 5: Single-cell sorting in a 96-well plate using a flow cytometer for the selection of single-cell clones of immortalized preadipocytes Support Protocol 2: Cryopreservation of immortalized mouse preadipocytes Support Protocol 3: Thawing and culture of cryopreserved immortalized mouse preadipocytes Support Protocol 4: Subculture and expansion of immortalized mouse preadipocytes Basic Protocol 6: Differentiation of immortalized mouse brown and white preadipocytes Support Protocol 5: Identification of differentiated white and brown adipocytes.

Neuroendocrinology of bone

The past decade has witnessed significant advances in our understanding of skeletal homeostasis and the mechanisms that mediate the loss of bone in primary and secondary osteoporosis. Recent breakthroughs have primarily emerged from identifying disease-causing mutations and phenocopying human bone disease in rodents. Notably, using genetically-modified rodent models, disrupting the reciprocal relationship with tropic pituitary hormone and effector hormones, we have learned that pituitary hormones have independent roles in skeletal physiology, beyond their effects exerted through target endocrine glands. The rise of follicle-stimulating hormone (FSH) in the late perimenopause may account, at least in part, for the rapid bone loss when estrogen is normal, while low thyroid-stimulating hormone (TSH) levels may contribute to the bone loss in thyrotoxicosis. Admittedly speculative, suppressed levels of adrenocorticotropic hormone (ACTH) may directly exacerbate bone loss in the setting of glucocorticoid-induced osteoporosis. Furthermore, beyond their established roles in reproduction and lactation, oxytocin and prolactin may affect intergenerational calcium transfer and therefore fetal skeletal mineralization, whereas elevated vasopressin levels in chronic hyponatremic states may increase the risk of bone loss.. Here, we discuss the interaction of each pituitary hormone in relation to its role in bone physiology and pathophysiology.

Disentangling the Neural Circuits of Arousal and Anxiety-Like Behavior

Anxiety disorders are prevalent and debilitating conditions characterized by excessive concern and fear, affecting thoughts, behaviors, and sensations. A critical component of anxiety is arousal, a complex process involving alertness regulation and stimulus salience modulation. While arousal is adaptive in normal circumstances, dysregulation can lead to hypoarousal or hyperarousal, affecting response selection and threat perception. This chapter reviews challenges in studying arousal in preclinical anxiety models, emphasizing the need for multicomponent measurement and analysis. Novel methodologies integrating physiological measurement with activity tracking of neurons with single-cell resolution in awake animals are discussed, with emphasis in current challenges. Understanding these mechanisms is crucial for developing effective treatments for anxiety disorders.

Hyperactive browning and hypermetabolism: potentially dangerous element in critical illness

Brown/beige adipose tissue has attracted much attention in previous studies because it can improve metabolism and combat obesity through non-shivering thermogenesis. However, recent studies have also indicated that especially in critical illness, overactivated brown adipose tissue or extensive browning of white adipose tissue may bring damage to individuals mainly by exacerbating hypermetabolism. In this review, the phenomenon of fat browning in critical illness will be discussed, along with the potential harm, possible regulatory mechanism and corresponding clinical treatment options of the induction of fat browning. The current research on fat browning in critical illness will offer more comprehensive understanding of its biological characteristics, and inspire researchers to develop new complementary treatments for the hypermetabolic state that occurs in critically ill patients.

Actein ameliorates diet-induced obesity through the activation of AMPK-mediated white fat browning

BACKGROUND

Targeting white adipose tissue (WAT) browning to increase systemic energy expenditure is a promising therapeutic strategy to combat obesity. Actein from Actaea cimicifuga L. has recently been reported to ameliorate high fat-induced hepatic steatosis. However, the effect of actein on diet-induced obesity merits more and further investigation.

PURPOSE

We aimed to examine the anti-obesity potential of actein and unravel its actions on WAT browning.

METHODS

The effect of actein on diet-induced obesity was evaluated using a high-fat diet model in C57BL/6 mice. Systemic energy expenditure of mice was measured with a combined indirect calorimetry system. Quantitative real-time PCR analyses were performed to investigate the mRNA levels of genes involved in thermogenesis, browning, and lipolysis. The protein levels were assessed by Western blot. Moreover, WAT explants and a transwell co-culture system consisting of SVFs and adipocytes were constructed to study the mechanisms of actein on promoting WAT browning and lipolysis.

RESULTS

At a dosage of 5 mg/kg/d, actein not only protected mice against diet-induced obesity and insulin resistance, but also reversed pre-established obesity and glucose intolerance in mice. Meanwhile, actein facilitated systemic energy expenditure by activating WAT lipolysis and browning. Further, mechanistic studies revealed that actein indirectly induced epididymal adipocyte lipolysis and directly promoted a white-to-beige conversion of subcutaneous adipocytes by activating the AMPK signaling.

CONCLUSION

Actein ameliorated diet-induced obesity and was discovered as a natural lead compound directly targeting white-to-beige conversion of subcutaneous adipocytes, suggesting the potential of developing new therapies for obesity and associated metabolic disorders.

Unveiling the protective potential of mirabegron against thioacetamide-induced hepatic encephalopathy in rats: Insights into cAMP/PPAR-γ/p-ERK1/2/p S536 NF-κB p 65 and p-CREB/BDNF/TrkB in parallel with oxidative and apoptotic trajectories

Hepatic encephalopathy (HE) is one of the most prevalent and severe hepatic and brain disorders in which escalation of the oxidative, inflammatory and apoptotic trajectories pathologically connects acute liver injury with neurological impairment. Mirabegron (Mira) is a beta3 adrenergic receptor agonist with proven antioxidant and anti-inflammatory activities. The current research pointed to exploring Mira's hepato-and neuroprotective impacts against thioacetamide (TAA)-induced HE in rats. Rats were distributed into three experimental groups: the normal control group, the TAA group, received TAA (200 mg/kg/day for three consecutive days) and the Mira-treated group received Mira (10 mg/kg/day; oral gavage) for 15 consecutive days and intoxicated with TAA from the 13th to the 15th day of the experimental period. Mira counteracted hyperammonemia, enhanced rats' locomotor capability and motor coordination. It attenuated hepatic/neurological injuries by its antioxidant, anti-apoptotic as well as anti-inflammatory potentials. Mira predominantly targeted cyclic adenosine monophosphate (cAMP)/phosphorylated extracellular signal-regulated kinase (p-Erk1/2)/peroxisome proliferator-activated receptor gamma (PPARγ) dependent pathways via downregulation of p S536-nuclear factor kappa B p65 (p S536 NF-κB p 65)/tumor necrosis alpha (TNF-α) axis. Meanwhile, it attenuated nuclear factor erythroid 2-related factor (Nrf2) depletion in parallel with restoring of the neuroprotective defensive pathway by upregulation of cerebral cAMP/PPAR-γ/p-ERK1/2 and p-CREB/BDNF/TrkB besides reduction of GFAP immunoreactivity. Mira showed anti-apoptotic activity through inhibition of Bax immunoreactivity and elevation of Bcl2. To summarize, Mira exhibited a hepato-and neuroprotective effect against TAA-induced HE in rats via shielding antioxidant defense and mitigation of the pathological inflammatory and apoptotic axis besides upregulation of neuroprotective signaling pathways.

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.

Nitric Oxide Signaling and Regulation in the Cardiovascular System: Recent Advances

Nitric oxide (NO) from endothelial NO synthase importantly contributes to vascular homeostasis. Reduced NO production or increased scavenging during disease conditions with oxidative stress contribute to endothelial dysfunction and NO deficiency. In addition to the classical enzymatic NO synthases (NOS) system, NO can also be generated via the nitrate-nitrite-NO pathway. Dietary and pharmacological approaches aimed at increasing NO bioactivity, especially in the cardiovascular system, have been the focus of much research since the discovery of this small gaseous signaling molecule. Despite wide appreciation of the biological role of NOS/NO signaling, questions still remain about the chemical nature of NOS-derived bioactivity. Recent studies show that NO-like bioactivity can be efficiently transduced by mobile NO-ferroheme species, which can transfer between proteins, partition into a hydrophobic phase, and directly activate the soluble guanylyl cyclase-cGMP-protein kinase G pathway without intermediacy of free NO. Moreover, interaction between red blood cells and the endothelium in the regulation of vascular NO homeostasis have gained much attention, especially in conditions with cardiometabolic disease. In this review we discuss both classical and nonclassical pathways for NO generation in the cardiovascular system and how these can be modulated for therapeutic purposes. SIGNIFICANCE STATEMENT: After four decades of intensive research, questions persist about the transduction and control of nitric oxide (NO) synthase bioactivity. Here we discuss NO signaling in cardiovascular health and disease, highlighting new findings, such as the important role of red blood cells in cardiovascular NO homeostasis. Nonclassical signaling modes, like the nitrate-nitrite-NO pathway, and therapeutic opportunities related to the NO system are discussed. Existing and potential pharmacological treatments/strategies, as well as dietary components influencing NO generation and signaling are covered.

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.

Single-cell transcriptomic analysis reveals dynamic activation of cellular signaling pathways regulating beige adipogenesis

PDGFRA+ cells have been identified as adipocyte stem cells (ASCs) that differentiate into beige adipocytes in white adipose tissue (WAT) following thermogenic stimuli. To elucidate the molecular heterogeneity of ASCs, we conducted single-cell transcriptomic profiling of PDGFRA+ cells isolated from the inguinal WAT (iWAT) of mice treated with the beta3 adrenergic receptor agonist CL316243. Single-cell RNA-seq revealed nine major clusters, which were categorized into four groups: resting, proliferating, differentiating, and adipogenic factor-expressing cells (AFECs). Trajectory analysis revealed sequential activation of molecular pathways, including the Hedgehog and Notch signaling pathways, during beige adipogenesis. AFECs expressed Dpp4 and did not differentiate into adipocytes in culture or after transplantation. Furthermore, genetic lineage tracing studies indicated that DPP4+ cells did not differentiate into adipocytes in iWAT during CL316243-induced beige adipogenesis. However, high-fat diet feeding led to the recruitment of adipocytes from DPP4+ cells in iWAT. Overall, this study improved our understanding of the dynamic molecular basis of beige adipogenesis and the potential contribution of DPP4+ adipocyte lineages to the pathological expansion of WAT during diet-induced obesity.

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.

The Interplay between Liver and Adipose Tissue in the Onset of Liver Diseases: Exploring the Role of Vitamin Deficiency

The deficiency of vitamins, a condition known as "hidden hunger", causes comprehensive pathological states. Research over the years has identified a relationship between liver diseases and hypovitaminosis or defects in vitamin metabolism. The exact mechanisms remain elusive; however, the crucial involvement of specific vitamins in metabolic functions, alongside the reclassification of liver disease as metabolic dysfunction-associated steatotic liver disease (MASLD), has prompted researchers to investigate the potential cause-effect dynamics between vitamin deficiency and liver disease. Moreover, scientists are increasingly investigating how the deficiency of vitamins might disrupt specific organ crosstalk, potentially contributing to liver disease. Although the concept of a dysmetabolic circuit linking adipose tissue and the liver, leading to liver disease, has been discussed, the possible involvement of vitamin deficiency in this axis is a relatively recent area of study, with numerous critical aspects yet to be fully understood. In this review, we examine research from 2019 to July 2024 focusing on the possible link between liver-adipose tissue crosstalk and vitamin deficiency involved in the onset and progression of non-alcoholic fatty liver disease (NAFLD). Studies report that vitamin deficiency can affect the liver-adipose tissue axis, mainly affecting the regulation of systemic energy balance and inflammation.

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.

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

Cocoa extract (CE) offers several health benefits, such as antiobesity and improved glucose intolerance. However, the mechanisms remain unclear. Adipose tissue includes white adipose tissue (WAT) and brown adipose tissue. Brown adipose tissue leads to body fat reduction by metabolizing lipids to heat via uncoupling protein 1 (UCP1). The conversion of white adipocytes into brown-like adipocytes (beige adipocytes) is called browning, and it contributes to the anti-obesity effect and improved glucose tolerance. This study aimed to evaluate the effect of CE on glucose tolerance in terms of browning. We found that dietary supplementation with CE improved glucose intolerance in mice fed a high-fat diet, and it increased the expression levels of Ucp1 and browning-associated gene in inguinal WAT. Furthermore, in primary adipocytes of mice, CE induced Ucp1 expression through β3-adrenergic receptor stimulation. These results suggest that dietary CE improves glucose intolerance by inducing browning in WAT.

Association between rs4994 variant in β3-Adrenergic receptor and obesity in Vietnamese preschool-age children, independent of eating behaviors

BACKGROUND

The Arg64 allele of the rs4994 (Trp64Arg) variant in the β3-adrenergic receptor (ADRB3) gene is involved in the control of energy balance by altering lipolysis and thermogenesis in adipocytes, ultimately contributing to the development of obesity. The objective of our study was to investigate the association between the rs4994 variant of the ADRB3 gene and obesity in Hanoi preschool-age children, adjusting for their eating behaviors.

METHODS

A cross-sectional study was performed involving 708 children with normal weight and 304 children with obesity aged 3-5 years from 36 kindergartens in Hanoi, Vietnam. Cheek mucosa cell samples were used for DNA extraction, and genotyping at the ADRB3-rs4994 locus was performed using the polymerase chain reaction-restriction fragment length polymorphism method (PCR-RFLP). Eating behaviors were assessed using the Children's Eating Behaviour Questionnaire (CEBQ). Binary logistic regression analysis was employed to examine the association between the rs4994 variant and obesity, adjusting for confounding factors such as age, sex, residence, birth weight, and eating behaviors.

RESULTS

The frequency of the C allele in the group with obesity was 16.4%, which was higher than in the control group (11.7%, P = 0.003). Children with the CC genotype exhibited significantly greater weight and weight-for-age Z-score compared to those with the TT and TC genotypes (P = 0.004 and 0.03, respectively). Following univariate and multivariate analyses adjusted for age, sex, residence, birth weight, and eating behaviors, a significant association between the rs4994 variant and obesity was observed (P < 0.05).

CONCLUSIONS

This study indicated that the ADRB3-rs4994 variant can be considered as an independent risk factor for obesity in Vietnamese preschool children.

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.

Obesity-induced tissue alterations resist weight loss: A mechanistic review

Interventions aimed at weight control often have limited effectiveness in combating obesity. This review explores how obesity-induced dysfunction in white (WAT) and brown adipose tissue (BAT), skeletal muscle, and the brain blunt weight loss, leading to retention of stored fat. In obesity, increased adrenergic stimulation and inflammation downregulate β-adrenoreceptors and impair catecholaminergic signalling in adipocytes. This disrupts adrenergic-mediated lipolysis, diminishing lipid oxidation in both white and brown adipocytes, lowering thermogenesis and blunting fat loss. Emerging evidence suggests that WAT fibrosis is associated with worse weight loss outcomes; indeed, limiting collagen and laminin-α4 deposition mitigates WAT accumulation, enhances browning, and protects against high-fat-diet-induced obesity. Obesity compromises mitochondrial oxidative capacity and lipid oxidation in skeletal muscle, impairing its ability to switch between glucose and lipid metabolism in response to varying nutrient levels and exercise. This dysfunctional phenotype in muscle is exacerbated in the presence of obesity-associated sarcopenia. Additionally, obesity suppresses sarcolipin-induced sarcoplasmic reticulum calcium ATPase (SERCA) activation, resulting in reduced oxidative capacity, diminished energy expenditure, and increased adiposity. In the hypothalamus, obesity and overnutrition impair insulin and leptin signalling. This blunts central satiety signals, favouring a shift in energy balance toward energy conservation and body fat retention. Moreover, both obese animals and humans demonstrate impaired dopaminergic signalling and diminished responses to nutrient intake in the striatum, which tend to persist after weight loss. This may result in enduring inclinations toward overeating and a sedentary lifestyle. Collectively, the tissue adaptations described pose significant challenges to effectively achieving and sustaining weight loss in obesity.

Genetic evidence for involvement of β2-adrenergic receptor in brown adipose tissue thermogenesis in humans

BACKGROUND

Sympathetic activation of brown adipose tissue (BAT) thermogenesis can ameliorate obesity and related metabolic abnormalities. However, crucial subtypes of the β-adrenergic receptor (AR), as well as effects of its genetic variants on functions of BAT, remains unclear in humans. We conducted association analyses of genes encoding β-ARs and BAT activity in human adults.

METHODS

Single nucleotide polymorphisms (SNPs) in β1-, β2-, and β3-AR genes (ADRB1, ADRB2, and ADRB3) were tested for the association with BAT activity under mild cold exposure (19 °C, 2 h) in 399 healthy Japanese adults. BAT activity was measured using fluorodeoxyglucose-positron emission tomography and computed tomography (FDG-PET/CT). To validate the results, we assessed the effects of SNPs in the two independent populations comprising 277 healthy East Asian adults using near-infrared time-resolved spectroscopy (NIRTRS) or infrared thermography (IRT). Effects of SNPs on physiological responses to intensive cold exposure were tested in 42 healthy Japanese adult males using an artificial climate chamber.

RESULTS

We found a significant association between a functional SNP (rs1042718) in ADRB2 and BAT activity assessed with FDG-PET/CT (p < 0.001). This SNP also showed an association with cold-induced thermogenesis in the population subset. Furthermore, the association was replicated in the two other independent populations; BAT activity was evaluated by NIRTRS or IRT (p < 0.05). This SNP did not show associations with oxygen consumption and cold-induced thermogenesis under intensive cold exposure, suggesting the irrelevance of shivering thermogenesis. The SNPs of ADRB1 and ADRB3 were not associated with these BAT-related traits.

CONCLUSIONS

The present study supports the importance of β2-AR in the sympathetic regulation of BAT thermogenesis in humans. The present collection of DNA samples is the largest to which information on the donor's BAT activity has been assigned and can serve as a reference for further in-depth understanding of human BAT function.

Protective Effects of Beta-3 Adrenoceptor Agonism on Mucosal Integrity in Hyperoxia-Induced Ileal Alterations

Organogenesis occurs in the uterus under low oxygen levels (4%). Preterm birth exposes immature newborns to a hyperoxic environment, which can induce a massive production of reactive oxygen species and potentially affect organ development, leading to diseases such as necrotizing enterocolitis. The β3-adrenoreceptor (β3-AR) has an oxygen-dependent regulatory mechanism, and its activation exerts an antioxidant effect. To test the hypothesis that β3-AR could protect postnatal ileal development from the negative impact of high oxygen levels, Sprague-Dawley rat pups were raised under normoxia (21%) or hyperoxia (85%) for the first 2 weeks after birth and treated or not with BRL37344, a selective β3-AR agonist, at 1, 3, or 6 mg/kg. Hyperoxia alters ileal mucosal morphology, leading to increased cell lipid oxidation byproducts, reduced presence of β3-AR-positive resident cells, decreased junctional protein expression, disrupted brush border, mucin over-production, and impaired vascularization. Treatment with 3 mg/kg of BRL37344 prevented these alterations, although not completely, while the lower 1 mg/kg dose was ineffective, and the higher 6 mg/kg dose was toxic. Our findings indicate the potential of β3-AR agonism as a new therapeutic approach to counteract the hyperoxia-induced ileal alterations and, more generally, the disorders of prematurity related to supra-physiologic oxygen exposure.

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

Obesity is a complex medical condition caused by a positive imbalance between calorie intake and calorie consumption. Brown adipose tissue (BAT), along with the newly discovered "brown-like" adipocytes (called beige cells), functions as a promising therapeutic tool to ameliorate obesity and metabolic disorders by burning out extra nutrients in the form of heat. Many studies in animal models and humans have proved the feasibility of this concept. In this review, we aim to summarize the endeavors over the last decade to achieve a higher number/activity of these heat-generating adipocytes. In particular, pharmacological compounds, especially agonists to the β3 adrenergic receptor (β3-AR), are reviewed in terms of their feasibility and efficacy in elevating BAT function and improving metabolic parameters in human subjects. Alternatively, allograft transplantation of BAT and the transplantation of functional brown or beige adipocytes from mesenchymal stromal cells or human induced pluripotent stem cells (hiPSCs) make it possible to increase the number of these beneficial adipocytes in patients. However, practical and ethical issues still need to be considered before the therapy can eventually be applied in the clinical setting. This review provides insights and guidance on brown- and beige-cell-based strategies for the management of obesity and its associated metabolic comorbidities.

Metabolic trade-offs in Neonatal sepsis triggered by TLR4 and TLR1/2 ligands result in unique dysfunctions in neural breathing circuits

Neonatal sepsis remains one of the leading causes of mortality in newborns. Several brainstem-regulated physiological processes undergo disruption during neonatal sepsis. Mechanistic knowledge gaps exist at the interplay between metabolism and immune activation to brainstem neural circuits and pertinent physiological functions in neonates. To delineate this association, we induced systemic inflammation either by TLR4 (LPS) or TLR1/2 (PAM3CSK4) ligand administration in postnatal day 5 mice (PD5). Our findings show that LPS and PAM3CSK4 evoke substantial changes in respiration and metabolism. Physiological trade-offs led to hypometabolic-hypothermic responses due to LPS, but not PAM3CSK4, whereas to both TLR ligands blunted respiratory chemoreflexes. Neuroinflammatory pathways modulation in brainstem showed more robust effects in LPS than PAM3CSK4. Brainstem neurons, microglia, and astrocyte gene expression analyses showed unique responses to TLR ligands. PAM3CSK4 did not significantly modulate gene expression changes in GLAST-1 positive brainstem astrocytes. PD5 pups receiving PAM3CSK4 failed to maintain a prolonged metabolic state repression, which correlated to enhanced gasping latency and impaired autoresuscitation during anoxic chemoreflex challenges. In contrast, LPS administered pups showed no significant changes in anoxic chemoreflex. Electrophysiological studies from brainstem slices prepared from pups exposed to either TLR4 or PAM3CSK4 showed compromised transmission between preBötzinger complex and Hypoglossal as an exclusive response to the TLR1/2 ligand. Spatial gene expression analysis demonstrated a region-specific modulation of PAM3CSK4 within the raphe nucleus relative to other anatomical sites evaluated. Our findings suggest that metabolic changes due to inflammation might be a crucial tolerance mechanism for neonatal sepsis preserving neural control of breathing.

Optical control of cell-surface and endomembrane-exclusive β-adrenergic receptor signaling

Beta-adrenergic receptors (βARs) are G protein-coupled receptors (GPCRs) that mediate catecholamine hormone-induced stress responses, such as elevation of heart rate. Besides those that are plasma membrane-bound, endomembrane βARs are also signaling competent. Dysregulation of βAR pathways underlies severe pathological conditions. Emerging evidence indicates pathological molecular signatures in deeper endomembrane βARs signaling, likely contributing to conditions such as cardiomyocyte hypertrophy and apoptosis. However, the lack of approaches to control endomembrane β1ARs has impeded linking signaling with pathology. Informed by the β1AR-catecholamine interactions, we engineered an efficient photolabile proligand (OptoIso) to trigger βAR signaling exclusively in endomembrane regions using blue light stimulation. Not only does OptoIso undergo blue light deprotection in seconds, but also efficiently enters cells and allows examination of G protein heterotrimer activation exclusively at endomembranes. OptoIso also allows optical activation of plasma membrane βAR signaling in selected single cells with native fidelity, which can be reversed by terminating blue light. Thus, OptoIso will be a valuable experimental tool to elicit spatial and temporal control of βAR signaling in user-defined endomembrane or plasma membrane regions in unmodified cells with native fidelity.

The novel adrenergic agonist ATR-127 targets skeletal muscle and brown adipose tissue to tackle diabesity and steatohepatitis

OBJECTIVE

Simultaneous activation of β2- and β3-adrenoceptors (ARs) improves whole-body metabolism via beneficial effects in skeletal muscle and brown adipose tissue (BAT). Nevertheless, high-efficacy agonists simultaneously targeting these receptors whilst limiting activation of β1-ARs - and thus inducing cardiovascular complications - are currently non-existent. Therefore, we here developed and evaluated the therapeutic potential of a novel β2-and β3-AR, named ATR-127, for the treatment of obesity and its associated metabolic perturbations in preclinical models.

METHODS

In the developmental phase, we assessed the impact of ATR-127's on cAMP accumulation in relation to the non-selective β-AR agonist isoprenaline across various rodent β-AR subtypes, including neonatal rat cardiomyocytes. Following these experiments, L6 muscle cells were stimulated with ATR-127 to assess the impact on GLUT4-mediated glucose uptake and intramyocellular cAMP accumulation. Additionally, in vitro, and in vivo assessments are conducted to measure ATR-127's effects on BAT glucose uptake and thermogenesis. Finally, diet-induced obese mice were treated with 5 mg/kg ATR-127 for 21 days to investigate the effects on glucose homeostasis, body weight, fat mass, skeletal muscle glucose uptake, BAT thermogenesis and hepatic steatosis.

RESULTS

Exposure of L6 muscle cells to ATR-127 robustly enhanced GLUT4-mediated glucose uptake despite low intramyocellular cAMP accumulation. Similarly, ATR-127 markedly increased BAT glucose uptake and thermogenesis both in vitro and in vivo. Prolonged treatment of diet-induced obese mice with ATR-127 dramatically improved glucose homeostasis, an effect accompanied by decreases in body weight and fat mass. These effects were paralleled by an enhanced skeletal muscle glucose uptake, BAT thermogenesis, and improvements in hepatic steatosis.

CONCLUSIONS

Our results demonstrate that ATR-127 is a highly effective, novel β2- and β3-ARs agonist holding great therapeutic promise for the treatment of obesity and its comorbidities, whilst potentially limiting cardiovascular complications. As such, the therapeutic effects of ATR-127 should be investigated in more detail in clinical studies.

Brown Adipose Tissue Activation in Humans Increases Plasma Levels of Lipid Mediators

CONTEXT

Activation of brown adipose tissue (BAT) thermogenesis improves insulin sensitivity and is beneficial in obesity. Emerging evidence indicates that BAT activation increases lipid mediators that play autocrine and endocrine roles to regulate metabolism and inflammation.

OBJECTIVE

The goal of the study was to determine the relationship between 2 distinct approaches of BAT activation (cold exposure and mirabegron treatment) with lipid mediators in humans.

METHODS

Healthy female subjects (n = 14) were treated with the β3-adrenergic receptor agonist mirabegron (100 mg) daily for 28 days. A subset of female subjects (n = 8) was additionally exposed to cold temperatures (14-16 °C) for 2 hours using a cooling vest prior to initiating mirabegron treatment. A panel of lipid mediators was assessed in plasma using targeted liquid chromatography-tandem mass spectrometry, and their relationship to anthropometric and metabolic parameters was determined.

RESULTS

Activation of BAT with cold exposure acutely increased levels of lipoxygenase and cyclooxygenase products, including 12-hydroxyeicosapentaenoic acid, 12-hydroxyeicosatetraenoic acid (HETE), 5-HETE, 14-hydroxydocosahexaenoic acid (HDHA), an isomer of maresin 2 (MaR2), 17-HDHA, protectin D1 (PD1), and prostaglandin E2. Mirabegron treatment similarly increased these products acutely, although levels of some mediators were blunted after chronic mirabegron treatment. Selected lipid mediators, including an MaR2 isomer, 17-HDHA, 5-HETE, and 15-HETE, positively correlated with nonesterified fatty acids and negatively correlated with the respiratory quotient, while PD1, 15-HETE, and 5-HETE positively correlated with adiponectin.

CONCLUSION

These results indicate that selected lipid mediators may serve as biomarkers of BAT activation.

ENDOGENOUS β 3 -ADRENERGIC RECEPTOR ACTIVATION ALLEVIATES SEPSIS-INDUCED CARDIOMYOCYTE APOPTOSIS VIA PI3K/AKT SIGNALING PATHWAY

ABSTRACT

β 3 -adrenergic receptor (β 3 -AR) has been proposed as a new therapy for several myocardial diseases. However, the effect of β 3 -AR activation on sepsis-induced myocardial apoptosis is unclear. Here, we investigated the effect of β 3 -AR activation on the cardiomyocyte apoptosis and cardiac dysfunction in cecal ligation and puncture (CLP)-operated rats and lipopolysaccharide (LPS)-treated cardiomyocytes. We found that β 3 -AR existed both in adult rat ventricular myocytes (ARVMs) and H9c2 cells. The expression of β 3 -AR was upregulated in LPS-treated ARVMs and the heart of CLP rats. Pretreatment with β 3 -AR agonist, BRL37344, inhibited LPS-induced cardiomyocyte apoptosis and caspase-3, -8, and -9 activation in ARVMs. BRL37344 also reduced apoptosis and increased the protein levels of PI3K, p-Akt Ser473 and p-eNOS Ser1177 in LPS-treated H9c2 cells. Inhibition of PI3K using LY294002 abolished the inhibitory effect of BRL37344 on LPS-induced caspase-3, -8, and -9 activation in H9c2 cells. Furthermore, administration of β 3 -AR antagonist, SR59230A (5 mg/kg), significantly decreased the maximum rate of left ventricular pressure rise (+dP/dt) in CLP-induced septic rats. SR59230A not only increased myocardial apoptosis, reduced p-Akt Ser473 and Bcl-2 contents, but also increased mitochondrial Bax, cytoplasm cytochrome c, cleaved caspase-9, and cleaved caspase-3 levels of the myocardium in septic rats. These results suggest that endogenous β 3 -AR activation alleviates sepsis-induced cardiomyocyte apoptosis via PI3K/Akt signaling pathway and maintains intrinsic myocardial systolic function in sepsis.

Caffeine: a potential mechanism for anti-obesity

Obesity refers to the excessive accumulation of fat caused by a long-term imbalance between energy intake (EI) and energy expenditure (EE). Over recent years, obesity has become a major public health challenge. Caffeine is a natural product that has been demonstrated to exert anti-obesity effects; however, the mechanisms responsible for the effect of caffeine on weight loss have yet to be fully elucidated. Most obesity-related deaths are due to cardiovascular disease. Recent research has demonstrated that caffeine can reduce the risk of death from cardiovascular disease; thus, it can be hypothesized that caffeine may represent a new therapeutic agent for weight loss. In this review, we synthesize data arising from clinical and animal studies over the last decade and discuss the potential mechanisms by which caffeine may induce weight loss, focusing particularly on increasing energy consumption, suppressing appetite, altering lipid metabolism, and influencing the gut microbiota. Finally, we summarize the major challenges associated with caffeine and anti-obesity research and highlight possible directions for future research and development.