Tadataka Tsuji

Adipose tissue has emerged as a dynamic endocrine organ that coordinates systemic energy balance and cardiometabolic health. This Review highlights the dual humoral and neuronal pathways through which adipose tissue regulates systemic metabolism. Humoral signals include peptide hormones, lipid mediators, metabolites, chemokines and exosomal microRNAs secreted by adipose depots. Neuronal circuits control adipose function rapidly and precisely: sympathetic efferents trigger lipolysis in white adipose tissue and thermogenesis in brown adipose tissue, whereas sensory afferents detect chemical, thermal and mechanical signals to adjust sympathetic activity. Nutritional and environmental stimuli (for example, diet, cold exposure and exercise), along with pathological states (for example, obesity, type 2 diabetes mellitus, lipodystrophy and ageing-associated disorders), dynamically modulate these endocrine and neural outputs. Methodological innovations, such as omics based on mass spectrometry or liquid chromatography-mass spectrometry, secretome labelling, adipose tissue organoid models and click chemistry, enable high-resolution characterization of adipose-derived signals and their targets. Finally, we discuss translational opportunities, including synthetic analogues of lipophilic hormones, and future therapeutic strategies that harness adipose communication networks.

Three-dimensional genome organization underlies gene regulation, yet how acute hormonal signalling reshapes chromatin structure to control metabolism remains unclear. β3-adrenergic receptor (β3-AR) hormonal signalling drives adipocyte thermogenesis. Here, we show three-dimensional genome maps of mouse and primary human brown adipocytes during thermogenesis using Micro-C. We find that β3-AR signalling rapidly reorganizes chromatin loops within 4 h, with dynamically gained loops coupled to thermogenic gene activation in both species. Mechanistically, β3-AR stimulation promotes histone variant H2A.Z deposition to enhance chromatin accessibility at loop anchors, facilitating the recruitment of bridging factor MED1. Loss of H2A.Z compromises loop formation and thermogenic gene activation across species. Brown fat-specific H2A.Z deficiency in mice impairs thermogenic activity and glucose tolerance. Integration with genome-wide association studies links H2A.Z-occupied loops to genetic variants associated with obesity and related metabolic disorders. Together, our findings uncover a cross-species conserved β3-AR signalling–H2A.Z axis that rapidly reorganizes chromatin interactions in adipocyte thermogenesis, providing mechanistic and translational insights into metabolic regulation.

N⁶-methyladenosine (m⁶A) is among the most abundant mRNA modifications, yet its cell-type-specific regulatory roles remain unclear. Here we show that m⁶A methyltransferase-like 14 (METTL14) differentially regulates transcriptome in brown versus white adipose tissue (BAT and WAT), leading to divergent metabolic outcomes. In humans and mice with insulin resistance, METTL14 expression differs significantly from BAT and WAT in the context of its correlation with insulin sensitivity. Mettl14-knockout in BAT promotes prostaglandin secretion, improving systemic insulin sensitivity. Conversely, Mettl14-knockout in WAT triggers adipocyte apoptosis and systemic insulin resistance. m⁶A-seq and RNA-seq integration revealed upregulated prostaglandin biosynthesis pathways in BAT and apoptotic pathways in WAT with Mettl14 deficiency. Stable METTL14-knockout hBAs/hWAs show METTL14-mediated m⁶A promotes mRNA decay of PTGES2 and CBR1 in hBAs and TRAIL and TNFR1 in hWAs. These data shed light on the ability of m⁶A to impact metabolism in a cell-type-specific manner with implications for influencing the pathophysiology of metabolic diseases.

Thermogenic adipose tissue, consisting of brown and beige fat, regulates nutrient utilization and energy metabolism. Human brown fat is relatively scarce and decreases with obesity and aging. Hence, inducing thermogenic differentiation of white fat offers an attractive way to enhance whole-body metabolic capacity. Here, we show the role of endothelin 3 (EDN3) and endothelin receptor type B (EDNRB) in promoting the browning of white adipose tissue (WAT). EDNRB overexpression stimulates thermogenic differentiation of human white preadipocytes through cAMP-EPAC1-ERK activation. In mice, cold induces the expression of EDN3 and EDNRB in WAT. Deletion of EDNRB in adipose progenitor cells impairs cold-induced beige adipocyte formation in WAT, leading to excessive weight gain, glucose intolerance, and insulin resistance upon high-fat feeding. Injection of EDN3 into WAT promotes browning and improved whole-body glucose metabolism. The findings shed light on the mechanism of WAT browning and offer potential therapeutics for obesity and metabolic disorders.

Light is fundamental for biological life, with most mammals possessing light-sensing photoreceptors in various organs. Opsin3 is highly expressed in adipose tissue which has extensive communication with other organs, particularly with the brain through the sympathetic nervous system (SNS). Our study reveals a new light-triggered crosstalk between adipose tissue and the hypothalamus. Direct blue-light exposure to subcutaneous white fat improves high-fat diet-induced metabolic abnormalities in an Opsin3-dependent manner. Metabolomic analysis shows that blue light increases circulating levels of histidine, which activates histaminergic neurons in the hypothalamus and stimulates brown adipose tissue (BAT) via SNS. Blocking central actions of histidine and denervating peripheral BAT blunts the effects of blue light. Human white adipocytes respond to direct blue light stimulation in a cell-autonomous manner, highlighting the translational relevance of this pathway. Together, these data demonstrate a light-responsive metabolic circuit involving adipose-hypothalamus communication, offering a potential strategy to alleviate obesity-induced metabolic abnormalities.

We developed MEBOCOST, an algorithm for quantitatively inferring metabolite-mediated intercellular communications using single-cell RNA-seq data. The algorithm identifies cell-cell communications in which metabolites, such as lipids, are secreted by sender cells and traveled to interact with sensor proteins of receiver cells. The sensors on the receiver cell include the cell surface receptors, transporters across the cell membrane, or nuclear receptors. MEBOCOST relies on a comprehensive database of metabolite-sensor partners, which we manually curated from the literature and other public sources. MEBOCOST defines sender and receiver cells for an extracellular metabolite based on the expression levels of the enzymes and sensors, respectively, thus identifies metabolite-sensor communications between the cells. Applying MEBOCOST to mouse brown adipose tissue (BAT) successfully recaptured known metabolite-mediated cell communications and further identified new communications. Additionally, MEBOCOST identified a set of intercellular metabolite-sensor communications regulated by cold exposure in mouse BAT. MEBOCOST will be useful to researchers for investigation of metabolite-mediated cell-cell communications in many biological and disease models. The MEBOCOST software is freely available at https://github.com/zhengrongbin/MEBOCOST.

Obesity induces chronic inflammation resulting in insulin resistance and metabolic disorders. Cold exposure can improve insulin sensitivity in humans and rodents, but the mechanisms have not been fully elucidated. Here, we find that cold resolves obesity-induced inflammation and insulin resistance and improves glucose tolerance in diet-induced obese mice. The beneficial effects of cold exposure on improving obesity-induced inflammation and insulin resistance depend on brown adipose tissue (BAT) and liver. Using targeted liquid chromatography with tandem mass spectrometry, we discovered that cold and β3-adrenergic stimulation promote BAT to produce maresin 2 (MaR2), a member of the specialized pro-resolving mediators of bioactive lipids that play a role in the resolution of inflammation. Notably, MaR2 reduces inflammation in obesity in part by targeting macrophages in the liver. Thus, BAT-derived MaR2 could contribute to the beneficial effects of BAT activation in resolving obesity-induced inflammation and may inform therapeutic approaches to combat obesity and its complications.

We developed MEBOCOST, a computational algorithm for quantitatively inferring metabolite-mediated intercellular communications using single cell RNA-seq data. The algorithm identifies cell-cell communications in which metabolites, such as lipids, are secreted by sender cells and traveled to interact with sensor proteins of receiver cells. The sensor proteins on receiver cell might be cell surface receptors, transporters across the cell membrane, or nuclear receptors. MEBOCOST relies on a comprehensive database of metabolite-sensor partners, which we manually curated from the literatures and other public sources. MEBOCOST defines sender and receiver cells for an extracellular metabolite based on the expression levels of the enzymes and sensors, respectively, thus identifies metabolite-sensor communications between the cells. Applying MEBOCOST to mouse brown adipose tissue (BAT) successfully recaptured known metabolite-mediated cell communications and further identified new communications. Additionally, MEBOCOST identified a set of BAT intercellular metabolite-sensor communications that was regulated by cold exposure of the mice. MEBOCOST will be useful to numerous researchers to investigate metabolite-mediated cell-cell communications in many biological and disease models. The MEBOCOST software is freely available at https://github.com/zhengrongbin/MEBOCOST .

A balanced omega (ω)-6/ω-3 polyunsaturated fatty acids (PUFAs) ratio has been linked to metabolic health and the prevention of chronic diseases. Brown adipose tissue (BAT) specializes in energy expenditure and secretes signaling molecules that regulate metabolism via inter-organ crosstalk. Recent studies have uncovered that BAT produces different PUFA species and circulating oxylipin levels are correlated with BAT-mediated energy expenditure in mice and humans. However, the impact of BAT ω-6/ω-3 PUFAs on metabolic phenotype has not been fully elucidated. The Fat-1 transgenic mice can convert ω-6 to ω-3 PUFAs. Here, we demonstrated that mice receiving Fat-1 BAT transplants displayed better glucose tolerance and higher energy expenditure. Expression of genes involved in thermogenesis and nutrient utilization was increased in the endogenous BAT of mice receiving Fat-1 BAT, suggesting that the transplants may activate recipients’ BAT. Using targeted lipidomic analysis, we found that the levels of several ω-6 oxylipins were significantly reduced in the circulation of mice receiving Fat-1 BAT transplants than in mice with wild-type BAT transplants. The major altered oxylipins between the WT and Fat-1 BAT transplantation were ω-6 arachidonic acid-derived oxylipins via the lipoxygenase pathway. Taken together, these findings suggest an important role of BAT-derived oxylipins in combating obesity-related metabolic disorders.