Cold-Activated RNA Eraser Switches On Fat Burning Beyond UCP1

When temperatures drop, mammals do not simply shiver their way to warmth. Beneath the skin, a specialized form of fat begins to burn fuel at a furious pace, converting chemical energy into heat through a process known as non-shivering thermogenesis. For decades, a single mitochondrial protein called UCP1 has dominated the story of how this happens. Now, a study published in Nature Metabolism reveals a surprisingly different player in that story: an RNA-editing enzyme long known for its role in pruning chemical tags from messenger molecules. The research shows that the demethylase ALKBH5 acts as a cold-responsive switch that unlocks a completely separate heat-generating pathway, one built on creatine chemistry and operating even when UCP1 is absent.

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