TGF-b/Smad3 inhibition synergizes with PPARg agonism to reduce fibrosis and enhance functional beige adipogenesis

Adipose tissue depots vary markedly in their ability to store and metabolize triglycerides, undergo beige adipogenesis and be susceptibile to metabolic disease. The molecular mechanisms that underlie such heterogeneity are not entirely clear. Previously, we showed that TGF-b signaling regulates the browning of white adipose tissue via recruitment of dedicated beige progenitors. Here, we find that TGF-b signals dynamically regulate the balance between adipose tissue fibrosis and beige adipogenesis. Elevated basal and high-fat diet inducible activation of TGF-b/Smad3 signaling was observed in the visceral (epididymal) adipose tissue depot. Activation of TGF-b/Smad3 signaling was associated with increased adipose tissue fibrosis. RNA-seq combined with fluorescence-activated cell sorting of stromal vascular fraction of epididymal white adipose tissue depot resulted in identification of TGF-b/Smad3 regulated ITGA5+ fibrogenic progenitors. TGF-b/Smad3 signal inhibition, genetically or pharmacologically, reduced fibrosis and increased functional beige adipogenesis. TGF-b/Smad3 antagonized the beneficial effects of PPARγ , activation whereas TGF-b receptor 1 inhibition synergized with actions of rosiglitazone, a PPARγ agonist, to dampen fibrosis and promote beige adipogenesis. There was a positive correlation between TGF-b activation and levels of fibrosis marker, ITGA5, in human adipose tissue samples , with visceral (omental) adipose tissue depot exhibiting higher fibrosis potential than subcutaneous or brown adipose tissue depots. Taken together, out data provide TGF-b/Smad3 signaling operates at the nexus of adipose tissue fibrosis and functional beige adipogenesis.