Protein Fragment From Thrombospondin-1 Emerges as Exercise-Powered Booster of Muscle and Metabolism

A little-studied fragment of a protein best known for its role in blood vessel biology is stepping into the spotlight of exercise science. In a study published in Experimental & Molecular Medicine, researchers report that the N-terminal region of thrombospondin-1, a secreted matricellular protein long associated with angiogenesis regulation and tissue remodeling, markedly improves muscle function and helps the body adapt metabolically to two very different physiological stresses: physical exercise and cold exposure. The findings suggest that a single endogenous molecule may coordinate responses across multiple tissues, offering a new angle on how the body reprograms its energy economy when demands change.

Thrombospondin-1 has historically been studied through the lens of its anti-angiogenic activity, particularly its ability to inhibit new blood vessel formation through interactions with endothelial cell receptors. But the protein is large, structurally complex, and released into the extracellular space by many cell types, and accumulating evidence has hinted that its domains may carry out distinct, even opposing, functions. The new work focuses on the N-terminal portion, the segment at the beginning of the protein chain, and asks what happens when this region is elevated in the circulation at a time when the body is being pushed to perform.

The central experimental strategy was to deliver the N-terminal fragment of thrombospondin-1 and then challenge animals with treadmill exercise or with cold exposure, two interventions that tax energy metabolism in fundamentally different ways. Exercise demands sustained contractile work from skeletal muscle and drives adaptations such as mitochondrial expansion, enhanced oxidative fiber recruitment, and improved glucose handling. Cold exposure, by contrast, activates thermogenesis, drawing on brown and beige adipose tissue and on shivering and non-shivering muscle heat production to defend core body temperature. The researchers reasoned that if a circulating factor could enhance adaptation to both stresses, it would be a strong candidate for a systemic coordinator of metabolic flexibility.

That is broadly what the data showed. Animals receiving the N-terminal fragment displayed greater muscle function, reflected in improved performance and force-generating capacity relative to controls undergoing the same exercise regimen. Histological and molecular analyses of the treated muscle pointed toward hallmarks of beneficial remodeling: shifts in fiber type composition toward a more oxidative profile and changes in gene expression consistent with enhanced mitochondrial and metabolic capacity. In the context of cold exposure, the fragment appeared to support tissue-specific adaptation, including responses in thermogenic fat, helping the animals meet the thermal challenge more effectively.

A key conceptual takeaway is the phrase tissue-specific metabolic adaptation. Rather than acting as a blunt metabolic accelerant, the N-terminal fragment seems to be interpreted differently by different tissues, evoking a pro-performance program in skeletal muscle during exercise and a pro-thermogenic program during cold stress. This kind of context dependence is characteristic of matricellular proteins and circulating signaling factors, whose effects depend on receptor expression patterns, local extracellular matrix composition, and concurrent physiological signals such as adrenergic tone and calcium flux. The study thus adds to a growing appreciation that exercise biology is not confined to muscle; it involves an endocrine-like dialogue among muscle, liver, adipose tissue, and the vasculature.

Mechanistically, the authors connect the fragment’s effects to established metabolic signaling hubs. Exercise adaptation is widely understood to flow through energy-sensing and transcriptional control pathways, including AMP-activated protein kinase, the master regulator of cellular energy status, and the PGC-1α coactivator that drives mitochondrial biogenesis. Enhancement of these pathways would plausibly explain both the improved contractile endurance observed in exercised animals and the greater thermogenic readiness observed under cold challenge. The fragment’s extracellular origin also raises questions about which cell-surface receptors mediate its uptake and signaling, an area where thrombospondin biology offers several candidates but no single obvious answer.

The timing of the discovery is notable. In recent years, the field has identified a parade of exercise-induced circulating factors, sometimes called exerkines, that mediate the systemic benefits of physical activity, from brain-derived neurotrophic effects to hepatic metabolic shifts. Identifying an N-terminal thrombospondin-1 fragment as a positive modulator of both exercise capacity and cold tolerance expands this catalog in an unexpected direction, because thrombospondin-1 has more often been cast as a negative regulator, for example in contexts of vascular injury, fibrosis, and tumor angiogenesis suppression. The work underscores a recurring lesson in protein biology: cleaved or independently folded domains of one protein can carry physiological meanings entirely distinct from the parent molecule.

Translational implications follow naturally, though with appropriate caveats. If the N-terminal fragment can be produced, stabilized, and safely delivered, it might one day serve as a therapy for conditions defined by muscle weakness or impaired metabolic adaptation, including sarcopenia of aging, prolonged disuse, and certain metabolic diseases. The cold-exposure component of the study adds a second, less obvious application space: enhancing thermogenic capacity could theoretically support metabolic health by increasing energy expenditure, a strategy many laboratories are pursuing through different targets. At the same time, the authors’ findings are preclinical, and the gap between improved performance in animal models and a safe, effective human intervention is notoriously wide. Dosing, receptor-mediated off-target effects, and the protein’s established roles in vascular biology would all require careful evaluation.

There are also intriguing physiological questions raised but not fully resolved. Is the endogenous N-terminal fragment released in response to exercise in humans, and if so, from which tissues? Could its levels serve as a biomarker of training status or metabolic health? And how do its effects interact with well-characterized exercise signals such as lactate, myostatin inhibitors, and the growing list of myokines and hepatokines? Answering these questions will require longitudinal studies in larger animals and, ultimately, human cohorts, as well as a more precise molecular dissection of the fragment’s receptor interactions and downstream signaling.

For now, the study offers a compelling proof of concept: a defined fragment of a familiar extracellular matrix protein can act as a systemic metabolic enhancer, amplifying the body’s own adaptive responses to exercise and to cold. As the exerkine field matures, discoveries of this kind move the conversation from cataloging what exercise does to understanding how the body broadcasts those instructions across tissues, and they hint at a future where the benefits of a hard workout or a cold morning might be partially recaptured, under medical guidance, by molecules the body already knows how to make.

Subject of Research: The role of the N-terminal fragment of thrombospondin-1 in enhancing muscle function and tissue-specific metabolic adaptation during exercise and cold exposure

Article Title: N-terminal thrombospondin-1 enhances muscle function and tissue-specific metabolic adaptation in response to exercise and cold exposure

Article References: N-terminal thrombospondin-1 enhances muscle function and tissue-specific metabolic adaptation in response to exercise and cold exposure. (n.d.). https://doi.org/10.1038/s12276-026-01830-z

Image Credits: AI Generated

DOI: 10.1038/s12276-026-01830-z

Keywords: thrombospondin-1, exercise, metabolic adaptation, skeletal muscle, cold exposure, thermogenesis, mitochondrial biogenesis, exerkines, AMPK, PGC-1alpha, brown adipose tissue, Experimental & Molecular Medicine