The research, conducted at the University of Toyama, focused on macrophages, the versatile immune cells that populate nearly every tissue in the body. Within injured or inflamed skeletal muscle, macrophages transition from a pro-inflammatory M1 state, which initiates the response to damage, to an anti-inflammatory M2 state, which supports repair and remodelling. M2 macrophages are supposed to be the good guys, secreting factors that help satellite cells, the resident muscle stem cells, differentiate and rebuild tissue. Yet previous work had shown that CD206-positive macrophages accumulate in ageing muscle in both mice and humans, and that their presence correlates with declining muscle mass. The paradox — repair-promoting cells associated with deterioration — suggested that one or more of the molecules these cells produce might, under conditions of chronic metabolic stress such as obesity, turn from healer to saboteur. TGF-β1, a potent cytokine with well-known fibrotic and anti-myogenic effects, emerged as the prime suspect.

To test this hypothesis directly, the team engineered a conditional knockout mouse model by crossing CD206-CreER T2 mice, in which Cre recombinase activity is restricted to CD206-expressing cells and can be pharmacologically controlled, with mice carrying floxed alleles of the Tgf-β1 gene. Administering tamoxifen at six weeks of age selectively excised the Tgf-β1 gene from CD206-positive macrophages, leaving the cytokine production of all other cell types untouched. One week later, the mice — both knockout animals and floxed controls — were placed on a high-fat diet deriving sixty percent of calories from fat for twelve weeks, a regimen that reliably produces obesity, insulin resistance and measurable skeletal muscle impairment. Crucially, body weight and food intake remained comparable between the two groups throughout the experiment, meaning that any differences in muscle function could not be attributed to differences in how much the animals ate or weighed.

The functional results were striking. In an exhaustive treadmill protocol in which running distance and time were recorded alongside the number of electric shocks received, the knockout mice ran roughly twice as far before exhaustion, a difference the authors report with a p-value of 0.0008. The knockout animals also hung from a wire mesh for significantly longer before dropping and generated measurably greater forelimb grip strength. Gene expression analysis confirmed the molecular validity of the model: Tgfb1 transcript levels were markedly reduced in the tibialis anterior muscle of knockout mice, and immunohistochemistry revealed a loss of the CD206 and TGF-β1 double-positive signal that characterised macrophages in control tissue. In other words, removing one cytokine from one immune cell population was sufficient to produce a whole-animal improvement in physical performance under obesogenic conditions.

The mechanisms behind this improvement proved to operate through two distinct and complementary routes. The first involves fibro-adipogenic progenitors, or FAPs, a population of mesenchymal-like cells resident in skeletal muscle that normally support repair by secreting paracrine factors. Using magnetic-activated cell sorting to isolate PDGFRα-positive FAPs from muscle tissue, the researchers found that deleting macrophage-derived TGF-β1 unleashed these progenitors: expression of follistatin (Fst) rose 1.70-fold and follistatin-like protein 1 (Fstl1) rose 2.60-fold in the tibialis anterior. Follistatin is a well-characterised antagonist of myostatin and activin, two powerful brakes on muscle growth, and its induction is a textbook signature of enhanced myogenesis. Consistent with this, myogenic regulatory genes were upregulated across both soleus and tibialis anterior muscles, and fibrosis-related gene expression declined, suggesting that removing TGF-β1 also relieved the profibrotic pressure that stiffens and scars obese muscle.

The second route ran through metabolism rather than directly through muscle. Analysis of muscle fibre type genes revealed that knockout mice had significantly elevated expression of Myh7 (type I fibres, 2.40-fold), Myh2 (type IIa, 1.50-fold) and Myh1 (type IIx, 2.35-fold) in the soleus, along with increased Myh4 (type II, 1.76-fold) in the tibialis anterior. Because type I fibres are rich in mitochondria and resistant to fatigue, this shift pointed toward enhanced oxidative metabolism, and downstream analyses confirmed it: genes governing mitochondrial biogenesis, all five oxidative phosphorylation complexes, fatty acid oxidation and fatty acid uptake were broadly upregulated in the muscles of knockout animals. At the centre of this metabolic reprogramming sat the AMPK/SIRT1/PGC-1α axis, the canonical energy-sensing cascade that orchestrates mitochondrial biogenesis. Phosphorylation of the AMPKα subunit at threonine 172 increased 1.5-fold, PGC-1α protein rose 2.2-fold, and Sirt1 expression climbed in parallel — a coordinated activation pattern that, in the knockout mice, restored the mitochondrial programme that obesity normally suppresses.

What connected an immune-cell gene deletion in muscle to mitochondrial activation in muscle? The answer turned out to lie in adipose tissue. Adiponectin, a hormone secreted by fat cells that sensitises tissues to insulin and activates AMPK in muscle through its receptor AdipoR1, was significantly elevated in the knockout mice. In epididymal white adipose tissue, Tgfb1 expression dropped while Adipoq expression rose, and serum adiponectin measured by ELISA increased 1.23-fold. Correspondingly, AdipoR1 mRNA increased 1.8-fold in both soleus and tibialis anterior muscle, closing the loop: macrophage-derived TGF-β1 was suppressing adiponectin production in fat, and its removal liberated the adiponectin–AdipoR1–AMPK signalling axis that drives mitochondrial function in muscle. Insulin signalling improved as well, with insulin-stimulated Akt phosphorylation rising 2.14-fold in adipose tissue and 1.62-fold in liver, and both glucose tolerance and insulin tolerance tests showed significantly better metabolic profiles in the knockout animals. Histology of adipose tissue told a matching story, with fewer crown-like structures — the histological scars of dying, inflamed adipocytes — and a trend toward smaller, metabolically healthier fat cells.

The significance of these findings extends beyond the mouse cage. Sarcopenic obesity is a growing public health concern as populations age and obesity rates climb, and current therapeutic options are limited largely to exercise and nutritional intervention, neither of which fully restores regenerative capacity in metabolically compromised muscle. By identifying macrophage-derived TGF-β1 as a node that simultaneously suppresses FAP-mediated myogenesis, dampens adiponectin secretion, blunts insulin sensitivity and throttles mitochondrial biogenesis, the study reframes sarcopenic obesity not simply as a passive consequence of carrying excess fat, but as an actively maintained state orchestrated in part by misbehaving immune cells. It also resolves the earlier paradox of CD206-positive macrophage accumulation in ageing muscle: these cells may indeed be present to repair, but the TGF-β1 they secrete in an obese or aged environment may prevent them from doing so effectively, or even actively contribute to fibrosis and metabolic dysfunction.

The authors are careful to note the limitations of their work. The study does not disentangle the relative contributions of the myogenic and adiponectin-mediated mechanisms to the overall improvement in muscle strength, and the experiments were performed exclusively in mice on a defined high-fat diet protocol. Whether human CD206-positive macrophages behave identically, whether pharmacological TGF-β1 blockade — an approach already in clinical use for other fibrotic conditions — could reproduce the benefits without unacceptable side effects, and how the two mechanisms interact over longer time courses all remain open questions. TGF-β1 is a pleiotropic molecule with essential roles in immune regulation and wound healing, so systemic inhibition carries real risks; the appeal of the macrophage-specific strategy demonstrated here is precisely its selectivity.

Even with those caveats, the study delivers a conceptually important message: the immune system is not a bystander in metabolic muscle disease but an active participant whose output can be reprogrammed. The demonstration that deleting a single cytokine from a single macrophage subset can simultaneously enhance regeneration, improve whole-body glucose metabolism, boost circulating adiponectin and reactivate mitochondrial biogenesis suggests that carefully targeted immunomodulation could one day complement or even substitute for lifestyle interventions in patients whose muscle function is collapsing under the combined weight of obesity and age. For now, the treadmill mice — running twice as far on the same obese body mass — offer the most vivid evidence yet that the key to rescuing failing muscle may lie not in the muscle fibres themselves, but in the immune cells that surround them.

Macrophages are highly adaptable cells. Rather than existing in a single fixed state, they respond continuously to signals from damaged tissue, cancer cells, cytokines, metabolites and neighboring immune cells. In simplified laboratory terminology, macrophages with an M1-like profile are associated with inflammatory and antimicrobial activity, whereas M2-like macrophages are often linked to tissue repair, immune suppression and tumor progression. In real tumors, macrophage states form a spectrum rather than two sharply separated categories. Nevertheless, the balance between inflammatory and immunosuppressive functions can strongly influence the outcome of cancer. TAMs that suppress immune responses may protect malignant cells from attack, stimulate blood-vessel formation and assist invasion into surrounding tissues. Reprogramming these cells has therefore become an important objective in cancer immunotherapy.

The new work focuses on Gsα, the alpha subunit of the stimulatory heterotrimeric G protein. This molecule is best known as a component of signaling downstream from G protein-coupled receptors, a vast family of cell-surface receptors that detect hormones, neurotransmitters, lipids and other extracellular signals. When activated, Gsα commonly stimulates adenylyl cyclase, increasing intracellular cyclic AMP and activating downstream effectors such as protein kinase A. However, G protein signaling is not confined to a single linear route. Depending on the receptor, cellular context and regulatory proteins present, Gsα-associated signals can influence several networks, including the mitogen-activated protein kinase pathway. MAPK signaling includes interconnected kinase cascades such as ERK, p38 and JNK, which regulate gene expression, differentiation, stress responses and inflammatory behavior.

To investigate the role of Gsα in macrophages, the researchers used mice in which the protein was selectively removed from these immune cells. These animals, referred to as GsαMKO mice, were compared with control mice carrying the intact Gsα gene. The team examined tumor development using two widely used experimental systems: B16 melanoma cells and MC38 colorectal cancer cells. In both models, the absence of macrophage Gsα was associated with faster tumor growth. Experiments involving metastatic B16 disease also indicated a greater burden of cancer spread in mice lacking Gsα in macrophages. These findings suggest that the protein affects more than the size of the primary tumor; it may also influence the ability of the tumor microenvironment to support dissemination and colonization of distant organs.

The researchers then examined the molecular identity and behavior of macrophages inside the tumors. Macrophages containing Gsα showed increased expression of CD86, CCR5, Il1b and Nos2, genes and proteins commonly associated with inflammatory activation and immune stimulation. CD86 can provide important co-stimulatory signals during interactions between antigen-presenting cells and T cells. CCR5 is a chemokine receptor involved in immune-cell trafficking, while Il1b encodes interleukin-1 beta, a potent inflammatory mediator. Nos2, also known as inducible nitric oxide synthase, enables macrophages to produce nitric oxide, a reactive molecule involved in antimicrobial and immune effector functions. In contrast, Gsα activity was associated with lower levels of CD206 and Il10, markers linked in this context to alternative, immunosuppressive macrophage behavior.

These changes were not merely molecular labels. The study indicates that Gsα-positive macrophages were better able to contribute to antitumor immunity. Their altered chemokine-receptor profile could affect how macrophages are recruited and positioned within tumors, while their inflammatory gene program could improve their ability to oppose malignant cells. The researchers also observed increased effector activity among CD8-positive T cells in tumors from control animals compared with animals lacking macrophage Gsα. CD8-positive T cells are cytotoxic lymphocytes capable of recognizing and killing abnormal cells, but their effectiveness can be weakened by suppressive conditions within the tumor microenvironment. The results suggest that macrophage Gsα may indirectly strengthen T-cell responses by making the surrounding immune environment less tolerant of cancer.

At the mechanistic level, the investigators linked this macrophage reprogramming to MAPK activity. They reported that Gsα promoted phosphorylation of ERK, p38 and JNK—chemical modifications that activate these kinases and allow them to transmit signals toward the nucleus and other cellular targets. Once activated, MAPK pathways can alter transcription factors and inflammatory gene networks, changing how macrophages respond to tumor-derived signals. The simultaneous involvement of ERK, p38 and JNK is notable because these branches can control overlapping yet distinct aspects of macrophage biology. ERK often participates in proliferation and differentiation signals, p38 is strongly associated with stress and inflammatory responses, and JNK can regulate cytokine production, apoptosis and transcriptional remodeling. Together, their activation may help maintain the proinflammatory state observed in macrophages containing Gsα.

Additional cell-based experiments supported the conclusion that the effect was intrinsic to macrophages rather than simply a consequence of unrelated differences between the animals. Bone marrow-derived macrophages from Gsα-deficient mice displayed altered activation patterns, and restoring exogenous Gsα changed the molecular profile of these cells. The study also used tumor-conditioned media, which contains soluble factors released by cancer cells, to model some of the signals macrophages encounter in the tumor microenvironment. These experiments point to a system in which cancer-derived signals can push macrophages toward tumor-supporting behavior when Gsα is absent, whereas Gsα helps preserve or restore inflammatory functions. The investigators further reported increased CD31 expression in tumors from GsαMKO mice, consistent with enhanced vascular features that could facilitate tumor expansion and metastatic escape, although the precise relationship between macrophage Gsα and blood-vessel formation requires further study.

The findings are especially relevant because many current cancer treatments focus primarily on malignant cells or on immune checkpoints, such as the PD-1 and PD-L1 pathway. Checkpoint inhibitors can release T cells from inhibitory signals, but their success depends on the broader immune environment. Immunosuppressive TAMs are one reason tumors may remain resistant even when cytotoxic lymphocytes are present. A therapy designed to preserve Gsα activity in macrophages, enhance its downstream signaling or selectively activate the relevant MAPK branches could theoretically complement existing immunotherapies. However, the study does not establish a treatment for patients, and directly manipulating G protein signaling would carry substantial risks. Gsα operates in many tissues and participates in physiological processes ranging from hormone responses to metabolism, so a systemic drug could produce effects far beyond the tumor. Any future strategy would need to target macrophages with high precision and determine which receptors or intracellular intermediates connect Gsα to ERK, p38 and JNK in different cancers.

The authors emphasize that their conclusions arise from B16 and MC38 mouse models and from experimental macrophage systems. Human tumors contain diverse macrophage populations shaped by genetics, treatment history, tissue origin and metabolic conditions, and these cells may not respond identically to Gsα manipulation. The study also highlights an important complexity in cell signaling: the same molecular pathway can have different consequences depending on the cell type and biological setting. While Gsα-associated cyclic AMP signaling has been linked in other contexts to anti-inflammatory or M2-like macrophage behavior, this work identifies a macrophage-specific role in which Gsα supports inflammatory antitumor activity through MAPK phosphorylation. Further research will be needed to validate Gsα expression and MAPK activity in human TAMs, establish whether the relationship predicts patient outcomes and determine whether selectively reprogramming this pathway can improve responses to immunotherapy without provoking harmful inflammation. For now, the study adds Gsα to the growing list of molecular switches that may decide whether the immune cells surrounding a tumor become its allies—or its enemies.

Subject of Research: Gsα signaling in tumor-associated macrophages and its influence on tumor growth, metastasis and antitumor immunity

Article Title: Gsα deficiency in macrophages promotes tumor progression via the MAPK signaling pathway

Article References: Yan W, Yang J, Tan S, et al. “Gsα deficiency in macrophages promotes tumor progression via the MAPK signaling pathway.” Journal of Molecular Medicine 104, article 52 (2026).

Image Credits: AI Generated

DOI: 10.1007/s00109-026-02660-2

Keywords: Gsα, tumor-associated macrophages, TAMs, macrophage polarization, MAPK signaling, ERK, p38, JNK, cancer immunotherapy, tumor progression, metastasis

The study highlights how VHL exerts its suppressive effects on angiogenesis via modulation of the hypoxia-inducible factor 1-alpha (HIF-1α). Under normal oxygen levels, VHL functions as an essential regulator, promoting the degradation of HIF-1α, which is crucial for the transcription of several angiogenic factors. An accumulation of HIF-1α can lead to the increased expression of vascular endothelial growth factor (VEGF) and other pro-angiogenic factors, which can trigger tumor growth and metastasis. By elucidating this suppressive mechanism, the authors pave the way for potential therapeutic interventions targeting HIF-1α in pathological angiogenesis.

In their investigation, Zou and colleagues employed a combination of molecular biology techniques to demonstrate that VHL not only targets HIF-1α but also influences the Angiopoietin/Tie2 signaling pathway. This pathway is paramount in maintaining the stability of blood vessels and regulating endothelial cell function. In TEMs, the interaction between Angiopoietins and Tie2 receptors plays a pivotal role in modulating angiogenesis, and VHL’s ability to inhibit this pathway presents a novel angle for potential therapeutic targets.

An important finding of this research is the role of AMP-activated protein kinase (AMPK) within the VHL-mediated signaling network. AMPK, a central energy sensor in cells, has been previously implicated in the regulation of metabolism and cell growth. The researchers unveiled that VHL’s action on HIF-1α and subsequent AMPK activation leads to a downregulation of VEGF expression, thereby diminishing the pro-angiogenic response. This novel connection indicates that VHL may serve as a crucial regulator that integrates cellular energy status with angiogenic signaling.

The implications of these findings extend far beyond basic scientific understanding. As various pathological conditions are characterized by aberrant angiogenesis, the manipulation of the VHL-HIF-1α-AMPK axis could represent a viable therapeutic strategy. For instance, in cancer biology, tumoral angiogenesis is often a hallmark that enables tumor growth and metastasis; therefore, targeting this pathway could enhance the efficacy of existing cancer therapies. Furthermore, the potential to develop small molecules or other modalities that can mimic or enhance VHL activity presents exciting therapeutic avenues.

The researchers utilized in vitro systems alongside animal models to validate their findings. By employing TEMs and analyzing gene expression profiles, the study demonstrated that VHL’s suppression of angiogenesis is not merely correlative but causative. This level of rigor strengthens the conclusions drawn from the study and highlights its relevance in a broader context where aberrant angiogenesis is a pathological concern.

Additionally, the findings raise questions about the broader implications for macrophage biology. TEMs, which play essential roles in wound healing and tissue repair, could be influenced significantly by the VHL-HIF-1α pathway. The research indicates that the balance between pro-angiogenic and anti-angiogenic signals could determine the function of these macrophages in different tissue environments, thus revealing an additional layer of complexity in the immune response and tissue homeostasis.

Moreover, the interaction of VHL with the Tie2 receptor adds another dimension to the understanding of TEM functionality. By unveiling this relationship, the researchers not only enhance our knowledge of macrophage biology but also suggest novel strategies to exploit these cells in therapeutic contexts. For instance, engineered macrophages that maintain VHL expression could be employed to control angiogenesis during tissue regeneration or to counteract pathological angiogenesis in tumor settings.

As researchers probe deeper into the cellular pathways that regulate angiogenesis, the connection between VHL and the Angiopoietin/Tie2 signaling pathway emphasizes the need for comprehensive approaches to understanding tumor microenvironments. The discovery calls for additional studies to unravel the precise regulatory networks that govern these processes, and to explore how they might be leveraged for therapeutic benefit.

In conclusion, Zou et al.’s research elegantly illustrates the multifaceted role of VHL in suppressing angiogenesis through the modulation of HIF-1α, AMPK, and the Angiopoietin/Tie2 signaling pathways within TEMs. Their findings not only highlight potential therapeutic targets but also reshape the current understanding of macrophage-mediated angiogenesis. Future research in this domain promises to provide further insights that could lead to innovative therapeutic approaches in a multitude of diseases characterized by dysregulated angiogenesis.

The urgency for novel therapeutic strategies has never been more critical, particularly in the face of rising cancer incidences and the plethora of conditions marked by excessive angiogenesis. By harnessing the power of VHL and related pathways, researchers could pave the way for exciting new treatments that may significantly improve patient outcomes. As the scientific community continues to validate and build upon these findings, the potential for translation into clinical practice becomes ever more tangible.

This study serves as a timely reminder of the power of fundamental research in unlocking the complexities of disease mechanisms and fostering new avenues for treatment. As we continue to explore the intricacies of cellular signaling and the underlying biology of diseases, findings such as those reported by Zou and colleagues will undoubtedly bear fruit in efforts to combat serious health challenges surrounding angiogenesis.

Subject of Research: The role of VHL in suppressing angiogenesis via HIF-1α-Mediated Ang/Tie2/AMPK/VEGF signaling pathway in Tie-2 Expressed Macrophages (TEMs).

Article Title: VHL Suppresses Angiogenesis Through HIF-1a-Mediated Ang/Tie2/AMPK/VEGF Signaling Pathway in Tie-2 Expressed Macrophages (TEMs).

Article References:

Zou, MC., Yang, YH., Mao, YP. et al. VHL Suppresses Angiogenesis Through HIF-1a-Mediated Ang/Tie2/AMPK/VEGF Signaling Pathway in Tie-2 Expressed Macrophages (TEMs).
Biochem Genet (2025). https://doi.org/10.1007/s10528-025-11175-3

Image Credits: AI Generated

DOI: 10.1007/s10528-025-11175-3

Keywords: VHL, HIF-1α, Angiogenesis, Tie2, Macrophages, AMPK, VEGF, Tumor Biology, Angiopoietin.