The transforming growth factor-β (TGF-β) signaling plays a critical role in the development and tissue homeostasis in metazoans, and deregulation of TGF-β signaling leads to many pathological conditions. Mounting evidence suggests that TGF-β signaling can actively alter metabolism in diverse cell types. Furthermore, metabolic pathways, beyond simply regarded as biochemical reactions, are closely intertwined with signal transduction. Here, we discuss the role of TGF-β in glucose, lipid, amino acid, redox and polyamine metabolism with an emphasis on how TGF-β can act as a metabolic modulator and how metabolic changes can influence TGF-β signaling. We also describe how interplay between TGF-β signaling and cell metabolism regulates cellular homeostasis as well as the progression of multiple diseases, including cancer.

Transforming growth factor beta (TGF‐β), a multifunctional cytokine, plays critical roles in immune responses. However, the precise role of TGF‐β in colitis and colitis‐associated cancer remains poorly defined. Here, it is demonstrated that TGF‐β promotes the colonic inflammation and related tumorigenesis in the absence of Smad family member 4 (Smad4). Smad4 loss in intestinal epithelium aggravates colitis and colitis‐associated neoplasia induced by dextran sulfate sodium (DSS) and azoxymethane/dextran sulfate sodium (AOM/DSS), leading to over‐activated immune responses and increased TGF‐β1 levels. In Smad4‐deficient organoids, TGF‐β1 stimulates spheroid formation and impairs intestinal stem cell proliferation and lineage specification. YAP, whose expression is directly upregulated by TGF‐β1 after Smad4 deletion, mediates the effect of TGF‐β1 by interacting with Smad2/3. Attenuation of YAP/TAZ prevents TGF‐β1‐induced spheroid formation in Smad4−/– organoids and alleviates colitis and colitis‐associated cancer in Smad4‐deficient mice. Collectively, these results highlight an integral role of the TGF‐β/Smad4 axis in restraining intestinal inflammation and tumorigenesis and suggest TGF‐β or YAP signaling as therapeutic targets for these gastrointestinal diseases intervention.

Paracrine signals play pivotal roles in organ homeostasis. Mesenchymal stromal cells (MSCs) play a key role in regulating epithelium homeostasis in the intestine while their paracrine effects are poorly characterized. Here, we identified prostaglandin E2 (PGE2) secreted by cyclooxygenase (COX)-expressing MSCs as a vital factor to maintain the intestinal mucosal barrier. We found that MSCs-induced organoid swelling through paracrine effect in vitro, a process due to enhanced water adsorption and is mediated by the COX-PGE2-EP4 axis. To further explore the regulatory effect of this axis on the intestinal epithelial barrier in vivo, we established the conditional knockout mouse model to specifically delete COX in MSCs and found that PGE2 reduction downregulated the gene Muc2 and induced a gastric metaplasia-like phenotype. Moreover, PGE2 defects increased the susceptibility of intestinal epithelium to colitis. Our study uncovers the paracrine signaling of COX-expressing MSCs in intestinal mucosal barrier maintenance, providing a basis for understanding the role of mesenchymal cells in the pathophysiological function of the intestine.