The study, led by Yinliang Zhang, Xiaochen Gai, Dong Zhao and Yongsheng Chang, with contributions from a team at Tianjin Medical University, Capital Medical University and Westlake University, began with a deceptively simple observation. When mice were exposed to cold, or when their fat cells were bathed in norepinephrine, the sympathetic neurotransmitter that surges during cold exposure, levels of ALKBH5 rose sharply in brown and subcutaneous fat. ALKBH5 belongs to a small family of enzymes that remove N6-methyladenosine, or m6A, the most abundant internal chemical modification on messenger RNA. By stripping these methyl marks, ALKBH5 can alter how long particular mRNA molecules survive before being degraded, and therefore how much protein the cell can manufacture from them.

Tracing the signal upstream, the investigators found that ALKBH5 expression is not a passive side effect of cold. Instead, norepinephrine binding to adrenergic receptors triggers the classic thermogenic signaling cascade: cyclic AMP accumulates, protein kinase A is activated, and the transcription factor CREB is phosphorylated and dispatched to the ALKBH5 gene, switching it on. Pharmacological tools confirmed the pathway’s logic. Forskolin and CW 008, which elevate cAMP signaling, boosted ALKBH5 expression in both mouse and human adipocytes, while the CREB inhibitor 666-15 and the PKA inhibitor H89 blunted that induction. In other words, the same sympathetic signal that commands fat cells to burn also instructs them to reprogram their RNA landscape.

The consequences of losing that reprogramming became clear when the team generated mice lacking ALKBH5 specifically in adipose tissue. Both male and female animals showed reduced thermogenic capacity, dropping their body temperature faster during acute cold exposure and dissipating less energy overall. When fed a high-fat diet, the knockout mice gained more weight, accumulated more fat mass and developed impaired glucose homeostasis compared with controls. Crucially, the metabolic defect appeared without changes in food intake or locomotor activity, pointing squarely at energy expenditure rather than appetite as the underlying problem. The findings applied across sexes, strengthening the physiological relevance of the pathway.

The mirror-image experiment proved equally striking. When the researchers delivered an ALKBH5 gene into brown and subcutaneous fat using adeno-associated virus, the treated animals became metabolic overachievers. They maintained higher core body temperatures in the cold, generated greater total energy expenditure, and resisted the weight gain and glucose intolerance induced by a high-fat diet. Human data added a correlative dimension: analysis of gene expression from public cohorts, including the Genotype-Tissue Expression project, showed that ALKBH5 levels in human subcutaneous fat inversely correlate with obesity, suggesting that the mouse findings may translate to human biology.

The deepest insight, however, came from the mechanistic work. Searching for the thermogenic machinery that ALKBH5 controls, the team landed on CKB, creatine kinase B, an enzyme central to the so-called futile creatine cycle. In this circuit, creatine kinase pumps phosphate onto creatine to build phosphocreatine, and a mitochondrial enzyme hydrolyzes it back again, forcing the cell to burn ATP in a loop that generates heat rather than useful work. Deleting ALKBH5 from fat lowered CKB expression and creatine kinase activity, while boosting ALKBH5 raised them. When the researchers depleted creatine with beta-guanidinopropionic acid, the thermogenic benefits of ALKBH5 overexpression largely evaporated, confirming that creatine metabolism is the load-bearing element of the pathway.

Molecularly, the connection between the demethylase and the creatine kinase is an elegant piece of RNA biology. ALKBH5 removes m6A marks from the CKB transcript itself. Those methyl tags, when present, are recognized by YTHDF2, a reader protein that escorts methylated mRNAs to degradation machinery. By demethylating CKB mRNA, ALKBH5 shields it from YTHDF2-mediated destruction, lengthening the transcript’s half-life and allowing more creatine kinase B protein to be produced. Experiments with mutated CKB constructs, methylated RNA immunoprecipitation, and YTHDF2 knockdown in both mouse brown and human beige adipocytes pieced this mechanism together site by site, and the m6A peaks identified on CKB mRNA matched the canonical DRACH sequence motifs predicted from genomic analysis.

Perhaps the most provocative result concerns UCP1, the long-reigning icon of thermogenesis. In mice genetically engineered to lack UCP1 entirely, ALKBH5 overexpression still raised energy expenditure and protected against cold exposure, demonstrating that the creatine-driven pathway operates in parallel with, and independently of, the classical uncoupling mechanism. This echoes recent single-cell studies suggesting that thermogenic fat contains distinct subpopulations of cells, some defined by UCP1 and others by futile cycling enzymes. The new work provides the first known regulatory link between an adrenergic signal and the creatine branch, effectively giving that parallel pathway its own commander.

The therapeutic implications are considerable. Obesity treatments based on increasing energy expenditure have long sought safe ways to activate thermogenic fat, but UCP1-centric strategies face hurdles, including uncertainty about how much functional brown fat adult humans carry and concerns about off-target adrenergic stimulation. A target that works through mRNA stabilization rather than receptor agonism, and that functions even without UCP1, opens a genuinely different door. The authors caution that ALKBH5 is a broad-acting demethylase implicated in diverse processes, from fertility to cancer metabolism to cardiac fibrosis, so any obesity therapy built on it would need careful tissue specificity. Still, the demonstration that a single RNA modification enzyme can rewire cellular fuel chemistry in response to cold reframes thermogenesis as an epitranscriptomic phenomenon, and it hands obesity researchers a new molecular lever precisely where they need it most: the fat that burns.

Subject of Research: The role of the m6A demethylase ALKBH5 in regulating creatine-driven non-shivering thermogenesis in adipose tissue

Article Title: ALKBH5 activates creatine-driven thermogenesis by stabilizing CKB mRNA in response to cold

Article References: Zhang, Y., Du, C., Qiao, W., Qiu, P., Xu, C., Yang, X., Hao, J., Zhao, D., Gai, X., & Chang, Y. (2026). ALKBH5 activates creatine-driven thermogenesis by stabilizing CKB mRNA in response to cold. Nature Metabolism. https://doi.org/10.1038/s42255-026-01592-y

Image Credits: AI Generated

DOI: 10.1038/s42255-026-01592-y

Keywords: ALKBH5, thermogenesis, brown fat, m6A methylation, CKB, creatine kinase, UCP1, obesity, YTHDF2, norepinephrine, CREB signaling, metabolism

Brown adipose tissue, commonly called brown fat, differs fundamentally from white adipose tissue. White fat primarily stores excess energy in large lipid droplets, whereas brown fat is specialized for dissipating chemical energy as heat. Its cells contain abundant mitochondria and high levels of uncoupling protein 1, or UCP1, a protein embedded in the inner mitochondrial membrane. Under cold conditions, UCP1 allows mitochondria to release the energy of nutrient oxidation as heat rather than capture it entirely in the form of ATP. This process, known as non-shivering thermogenesis, helps maintain body temperature without the rapid muscle contractions associated with shivering.

The study places calcium at the center of this metabolic response. Calcium ions are widely known for their roles in muscle contraction, neurotransmitter release and gene regulation, but they also act as rapid intracellular signals that coordinate energy use. Orai1 is a highly selective calcium channel located in the plasma membrane. It is best known as part of the store-operated calcium entry system, in which depletion of calcium inside the endoplasmic reticulum activates sensor proteins called STIM1. STIM1 then communicates with Orai1, opening the channel and allowing extracellular calcium to flow into the cell. In brown adipocytes, this influx appears to connect external physiological signals with the internal machinery responsible for mobilizing fuel and activating heat-producing mitochondria.

The connection begins with lipolysis, the enzymatic process that releases fatty acids from triglycerides stored in lipid droplets. These liberated fatty acids serve two purposes in brown fat. They provide mitochondria with substrates for oxidation, and they directly support the activity of UCP1. Without adequate fatty-acid delivery, brown adipocytes may possess mitochondria and UCP1 but lack the fuel and regulatory inputs required for robust thermogenesis. By identifying Orai1 as a regulator of lipolysis, the research suggests that calcium entry is not merely a secondary response to metabolic activation. Instead, it may help determine whether brown-fat cells can efficiently unlock their stored energy when heat production is needed.

The second major link is mitochondrial activation. Mitochondria must rapidly adjust their activity when brown fat is exposed to cold or stimulated by signals associated with increased energy expenditure. Calcium can influence mitochondrial metabolism by coordinating the supply of metabolic intermediates and modifying the activity of enzymes involved in fuel oxidation. Carefully controlled calcium transfer can therefore accelerate energy production, while excessive or poorly regulated calcium may damage mitochondria and promote cellular stress. The findings described in the study support a model in which Orai1-dependent calcium entry helps brown adipocytes reach the level of mitochondrial activity required for thermogenesis while coordinating that activity with the release of fatty acids.

This mechanism may help explain how brown fat integrates several layers of physiological regulation. Cold exposure activates the sympathetic nervous system, which releases norepinephrine and stimulates receptors on brown adipocytes. Those signals increase cyclic AMP and activate protein kinase A, a pathway traditionally regarded as the dominant controller of lipolysis and UCP1-dependent heat production. The new work indicates that this established pathway may operate in concert with calcium signaling through Orai1. Rather than acting as isolated switches, sympathetic signals, lipid-droplet enzymes, calcium channels and mitochondria may form an interconnected circuit that allows brown fat to respond quickly and proportionately to changes in body temperature.

The implications extend beyond the biology of cold adaptation. Brown-fat activity has attracted intense interest because it consumes glucose and fatty acids and can raise whole-body energy expenditure. Adults retain smaller amounts of brown or brown-like thermogenic fat than infants, but measurable depots can remain active, particularly under cold exposure. Researchers have therefore explored whether stimulating thermogenesis could contribute to strategies for obesity, insulin resistance or metabolic disease. The Orai1 pathway may represent one possible molecular target, although translating a cellular mechanism into a safe treatment would require substantial additional research. Calcium channels participate in many organs, so manipulating Orai1 systemically could affect immune cells, muscle, the nervous system or other tissues.

The study also underscores why the regulation of thermogenesis cannot be reduced to a single “on” switch. Heat production depends on timing, intensity and cellular context. Brown adipocytes must release fuel, transport it into mitochondria, oxidize it and direct the resulting energy toward heat. Each stage is vulnerable to imbalance. Excessive lipolysis could produce harmful lipid intermediates, while uncontrolled calcium accumulation could impair mitochondrial function. Understanding how Orai1 is activated, how long calcium signals persist and how those signals are terminated will be essential for determining whether the pathway promotes healthy metabolic flexibility or contributes to cellular stress under pathological conditions.

For now, the research adds Orai1-mediated calcium entry to the molecular map of brown-fat thermogenesis and presents calcium signaling as a functional bridge between fat mobilization and mitochondrial heat production. The findings do not mean that activating Orai1 alone would automatically cause weight loss, nor do they establish a ready-made therapy for metabolic disease. They do, however, reveal a mechanism that may help explain how brown adipose tissue synchronizes fuel availability with energy dissipation. As scientists continue to investigate thermogenic fat, this calcium-controlled connection could become an important part of efforts to understand—and eventually influence—the body’s capacity to burn energy as heat.

Subject of Research: Orai1-mediated calcium entry, lipolysis, mitochondrial activation and brown adipose tissue thermogenesis

Article Title: Orai1-mediated Ca²⁺ entry regulates lipolysis and mitochondrial activation in brown adipose thermogenesis

Article References: Kim, S., Nguyen, P.A., Park, KS. et al. “Orai1-mediated Ca²⁺ entry regulates lipolysis and mitochondrial activation in brown adipose thermogenesis.” Experimental & Molecular Medicine (2026). https://doi.org/10.1038/s12276-026-01808-x

Image Credits: AI Generated

DOI: 10.1038/s12276-026-01808-x; published 13 August 2026

Keywords: Orai1, calcium signaling, Ca²⁺ entry, brown adipose tissue, brown fat, thermogenesis, lipolysis, mitochondria, UCP1, metabolism

Brown adipose tissue, unlike its white counterpart, is specialized for generating heat through non-shivering thermogenesis, a process critical for maintaining body temperature and metabolic health. Central to this function is the nuclear receptor peroxisome proliferator-activated receptor gamma (PPARγ), a transcription factor extensively studied for its role in adipocyte differentiation and lipid metabolism. However, this new research highlights an unexpected regulatory layer wherein PPARγ’s activity is modulated by a novel post-translational modification, specifically HMGylation—a modification involving the addition of a hydroxy-methylglutaryl group—which has not been previously linked to BAT physiology.

At the heart of this mechanism is AUH (AU RNA-binding protein/enoyl-CoA hydratase), an enzyme traditionally appreciated for catalyzing a key step in leucine catabolism. The enzyme’s ability to catalyze the conversion of methylglutaconyl-CoA to 3-hydroxy-3-methylglutaryl-CoA, a vital intermediate in leucine metabolism, was well documented, yet this study reveals a bifunctional role. Besides enzymatic catalysis, AUH exerts a RNA-binding function that appears to modulate thermogenic gene expression at a post-transcriptional level, suggesting that AUH acts as a metabolic sensor linking amino acid catabolism to thermogenic control.

The researchers utilized a combination of advanced proteomics, transcriptomics, and metabolic phenotyping to demonstrate that in male mice, loss of AUH dampens BAT thermogenesis and decreases energy expenditure, leading to increased adiposity and impaired glucose homeostasis. Mechanistically, AUH facilitates the HMGylation of PPARγ, which augments its transcriptional activity, thereby enhancing the expression of thermogenic genes such as Ucp1. This post-translational modification represents a previously unrecognized mode of fine-tuning PPARγ function in the context of energy metabolism.

Moreover, the RNA-binding aspect of AUH adds a new dimension to thermogenic regulation. The study shows that AUH interacts with specific RNA transcripts in BAT, which likely influences their stability and translation. This dual enzymatic and RNA-binding capability allows AUH to coordinate metabolic inputs from leucine catabolism with gene networks responsible for heat production, effectively coupling nutrient status with energy expenditure.

Another striking element of the study is the sex-specific nature of AUH’s function. The authors report that the regulatory axis involving AUH, PPARγ HMGylation, and RNA-binding predominantly impacts male mice, underscoring complex sexual dimorphisms in BAT biology. This raises exciting questions about how metabolic pathways diverge between sexes and suggests that AUH-targeted therapies might require sex-specific considerations.

This discovery could radically enhance our understanding of the multifaceted control of energy balance, as BAT has been recognized as a promising target for combating metabolic diseases due to its ability to dissipate excess calories as heat. By revealing that an amino acid catabolic enzyme interacts integratively with nuclear receptor signaling and RNA biology, the study broadens the scope of metabolic regulation beyond classical pathways, suggesting new therapeutic targets that capitalize on multifunctional protein enzymes like AUH.

The methodology employed by Jiang and colleagues is equally noteworthy. They combined genetic manipulation techniques, including BAT-specific AUH knockout and overexpression models, with sophisticated mass spectrometry assays capable of detecting PTMs like HMGylation in situ. This allowed for precise mapping of modification sites on PPARγ and assessment of the functional consequences on transcriptional activity. Concurrent RNA immunoprecipitation and sequencing helped delineate AUH’s RNA interaction partners, unveiling a complex post-transcriptional regulatory network.

In addition to the molecular and cellular insights, the physiological assessments confirmed the systemic impacts of AUH modulation. Male mice deficient in AUH exhibited reduced cold tolerance and diminished whole-body energy expenditure, aligning molecular observations with organismal phenotypes. These systemic manifestations underscore the enzyme’s critical role in maintaining metabolic health.

The link between leucine metabolism and thermogenic regulation through AUH also suggests an intriguing metabolic feedback loop. Leucine, a branched-chain amino acid, is an essential nutrient with known effects on mTOR signaling and metabolic health. The coupling of its catabolism to BAT function via AUH implies that dietary and metabolic states could directly influence thermogenic capacity, positioning AUH as a metabolic rheostat that senses nutrient flux and calibrates energy dissipation accordingly.

Furthermore, this research prompts a reevaluation of the functional repertoire of PTMs in nuclear receptor biology. While phosphorylation, acetylation, and ubiquitination of PPARγ have been extensively studied, the identification of HMGylation introduces a new biochemical layer that may have broader implications across different nuclear receptors and transcription factors with pivotal roles in metabolic control.

From a translational perspective, the multifaceted role of AUH holds promise for innovative intervention strategies. Targeting the enzymatic activity or the RNA-binding function of AUH could selectively modulate BAT thermogenesis, offering novel approaches to enhance energy expenditure without the side effects associated with global PPARγ agonists traditionally used in diabetes treatment.

Moreover, the sex-specific findings highlight the importance of personalized medicine in metabolic disease management. Future studies could investigate whether variations in AUH activity contribute to sex-related differences in metabolic disease prevalence and response to therapy, potentially leading to tailored treatments for men and women.

The data also invite closer scrutiny into the role of RNA-binding proteins in metabolism, an emerging field bridging RNA biology with metabolic regulation. AUH exemplifies how multi-domain proteins integrate metabolic cues with gene regulation, potentially inspiring the search for similar multifunctional enzymes in other metabolic tissues.

As exciting as these findings are, the research community must now explore the detailed molecular mechanisms governing AUH’s dual functions and their integration under physiological and pathological states. Questions remain about how HMGylation is dynamically regulated, the spectrum of RNA targets for AUH in BAT and perhaps other tissues, and whether similar mechanisms exist in humans.

In conclusion, the discovery that AUH regulates brown adipose tissue thermogenesis via PPARγ HMGylation and RNA-binding function represents a significant stride forward in metabolic research. It illuminates a nuanced biochemical nexus linking amino acid catabolism to energy expenditure, expanding our grasp of how the body maintains its thermal and metabolic balance. This integrative mechanism not only enhances fundamental understanding but also lays the groundwork for novel therapeutic strategies targeting metabolic diseases through modulation of multifunctional enzymes like AUH.

Subject of Research: Regulation of brown adipose tissue thermogenesis by the leucine catabolic enzyme AUH through PPARγ HMGylation and RNA-binding in male mice.

Article Title: Leucine catabolic enzyme AUH regulates BAT thermogenesis via PPARγ HMGylation and RNA-binding function in male mice.

Article References: Jiang, H., Ni, S., Li, Z. et al. Leucine catabolic enzyme AUH regulates BAT thermogenesis via PPARγ HMGylation and RNA-binding function in male mice. Nat Commun (2026). https://doi.org/10.1038/s41467-026-71581-y

Image Credits: AI Generated

Brown adipose tissue has captivated metabolism scientists for decades due to its unique thermogenic abilities. Unlike white fat, which primarily stores energy, brown fat specializes in burning calories to generate heat, a process termed non-shivering thermogenesis. This heat production is crucial not only for maintaining body temperature in cold environments but also plays a role in systemic metabolic processes, including glucose regulation. Despite insights into BAT’s metabolic functions, how the sympathetic nervous system orchestrates these responses through precise neural pathways remained elusive—until now.

The research, conducted by Neri, Lee, Fohn, and colleagues, reveals that sympathetic projections to BAT are not monolithic but rather consist of distinct populations of neurons with discrete functional roles. Using cutting-edge neuroanatomical tracing, optogenetics, and metabolic phenotyping, the investigators mapped these pathways with unparalleled clarity. They demonstrated that one set of sympathetic neurons predominantly regulates BAT-mediated thermogenesis, while another set modulates glucose tolerance—thereby dissociating two fundamental metabolic functions attributable to brown fat.

This dualistic neural control model signifies a paradigm shift. It suggests that the sympathetic nervous system exerts differentiated control over thermogenic activation and endocrine-metabolic adaptations, rather than a single, uniform output. This nuanced regulation involves distinct circuits emerging from separate nodes in the central nervous system and converging onto BAT, each modulating specific downstream metabolic outcomes. Such specificity offers potential therapeutic leverage points to selectively boost thermogenesis or improve glucose metabolism in metabolic diseases.

Detailed neuroanatomical analyses identified key brainstem and hypothalamic regions as origins of these specialized sympathetic projections. Importantly, these divergent pathways exhibited characteristic molecular markers, underscoring their unique identities. For instance, neurons governing thermogenesis displayed heightened expression of adrenergic receptor components, essential for activating BAT’s heat-producing machinery. Conversely, neurons implicated in glucose regulation interfaced with systemic metabolic networks, influencing insulin sensitivity and glucose uptake dynamics.

Functionally, optogenetic stimulation experiments substantiated the dissociation of these circuits. Selective activation of thermogenesis-related sympathetic pathways led to increased energy expenditure and heat production without significantly affecting systemic glucose metrics. Conversely, stimulating glucose-modulatory projections improved glucose tolerance independently of thermogenic changes. This functional delineation deepens our mechanistic understanding of the sympathetic control over metabolic tissues.

Importantly, the study employed a rodent model of diet-induced obesity to probe translational relevance. In this context, selective modulation of the glucose-regulating sympathetic pathway ameliorated hyperglycemia and insulin resistance, demonstrating therapeutic potential. The capacity to target discrete sympathetic outputs may pave the way for next-generation interventions aimed at distinct metabolic endpoints, bypassing the side effects associated with broad sympathetic activation.

At a cellular level, the team explored how sympathetic neurotransmitters interact with adipocyte receptors within BAT. They found that noradrenaline released from thermogenesis-specific neurons robustly activated uncoupling protein 1 (UCP1), driving mitochondrial heat production. Meanwhile, the glucose-control circuit modulated adipocyte insulin sensitivity through alternative adrenergic signaling cascades, highlighting complex intercellular communication mechanisms that orchestrate systemic metabolism.

This research also challenges current dogma by suggesting that the sympathetic nervous system’s influence extends beyond immediate metabolic toggling. It appears capable of inducing long-term adaptations in brown adipose tissue function and systemic glucose homeostasis. Such plasticity implies that sympathetic circuits may be amenable to reprogramming or fine-tuning as a durable therapeutic strategy against obesity and type 2 diabetes.

Furthermore, the elucidation of these distinct pathways enriches our understanding of brown fat’s physiological heterogeneity. Brown adipocytes have been traditionally viewed as a uniform cell type, but this study suggests that their functional diversity partly reflects the differential sympathetic innervation patterns they receive. This finding invites further exploration into the interplay between neural inputs and adipose tissue phenotypes.

The authors also discuss the implications of their findings in the context of human health. Given that brown fat activity inversely correlates with obesity and metabolic disease in humans, decoding the neuronal control mechanisms offers a translational bridge towards targeted neuromodulatory therapies. Precision interventions that selectively amplify thermogenesis could enhance energy expenditure, while those that improve BAT-driven glucose clearance could mitigate hyperglycemia without impacting thermal regulation.

Future directions proposed by the researchers include delineating the molecular signals that specify sympathetic neuron subtype identities during development and adulthood, as well as investigating how these circuits adapt to environmental stimuli such as cold exposure or dietary shifts. Such work will deepen insights into the dynamic regulation of energy balance by neuro-metabolic networks.

The study’s methodological advancements are also noteworthy. By integrating viral tracing techniques with in vivo neural manipulation and sophisticated metabolic assays, the research sets new standards for dissecting neuro-adipose tissue crosstalk. This multimodal approach promises to accelerate discoveries in the emerging field of neuro-metabolism, fostering innovations to combat metabolic diseases at the neural circuit level.

Ultimately, the identification of functionally distinct sympathetic projections controlling BAT thermogenesis and glucose tolerance marks a milestone in metabolism research. It underlines the complexity of sympathetic outputs and gently overturns simplistic views of autonomic regulation. As we unearth the molecular and circuit-based architecture underpinning metabolic control, we edge closer to novel therapies that harness the body’s own neural networks to restore and maintain metabolic health.

This landmark discovery opens a new chapter in metabolic neuroscience, promising to inspire a wave of innovative research focused on exploiting symmetrically specialized neural circuits. By bridging the gap between brain, fat, and systemic metabolism, we stand on the cusp of transformative advances that could dramatically reshape how metabolic diseases are treated in the years to come.

Subject of Research: Sympathetic nervous system regulation of brown adipose tissue thermogenesis and glucose metabolism.

Article Title: Distinct sympathetic projections to brown fat regulate thermogenesis and glucose tolerance.

Article References:
Neri, D., Lee, S., Fohn, A.M. et al. Distinct sympathetic projections to brown fat regulate thermogenesis and glucose tolerance. Nat Metab (2026). https://doi.org/10.1038/s42255-025-01429-0

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s42255-025-01429-0