## 4 Discussion
Future studies will investigate the molecular mechanisms involved in TGF\(\beta\) induction. In the second part of this study, the conditioned medium that contained a fair amount of TGF\(\beta\) was used on human pancreatic cancer cells to verify that the cytokine secreted by dysmetabolic adipocytes exerted the metabolic and pro-cancerogenic effects previously characterized when commercial TGF\(\beta\) was studied [29]. Indeed, after this treatment the tumor cells increased the transcription of the elements of mitochondrial respiration,and EMT and cellular migration were enhanced. This investigation can be considered a novel proof-of-concept study in which we tested an in vitro model that could mimic the causes and the effects of an inflammatory condition occurring in vivo; for example, in the tumor microenvironment. In fact, the metabolic failure that could affect every tissue could trigger TGF\(\beta\) synthesis and secretion, particularly in adipocytes; in response to metabolic impairment, the cytokine would stimulate adipocytes and neighbor cells by autocrine and paracrine activity, to reinforce energy metabolism, contain the dysmetabolic energy loss and sustain cell survival, in a positive feedback loop. Unfortunately, the pro-tumorigenic activity of TGF\(\beta\) would also support cancer progression and spreading. This model is depicted in Figure 5.  
Some works in the literature [79; 80] and our recent article [29] report that TGF\(\beta\) acts as a stimulant of mitochondrial metabolism and subsequent energy production. From this evidence and the results obtained in this study, we believe that the synthesis of this cytokine can be considered an adaptive response to signals of dysmetabolism or mitochondrial deregulation, which lead to an energy deficiency; in these conditions, TGF\(\beta\) stimulates the cells to overcome these difficulties by increasing the activity of the respiratory chain and oxidative phosphorylation. This study lays the foundations for a further investigation of the role of inflamed adipose tissue as a predisposing factor to carcinogenesis. The signaling of TGF\(\beta\) is a crucial regulator of intestinal homeostasis and inflammation; therefore, dysregulation of this pathway could be associated with inflammatory carcinogenesis of the gastrointestinal tract [81]. In the study of [PERSON] et al. carried out in the KrasG12D conditional mouse model of pancreatic cancer, a high-fat diet generated an inflammatory environment at the level of peri-pancreatic fat, suggesting that an initial inflammation of adipose tissue may extend to nearby organs, through the secretion of inflammatory cytokines [69]. Measuring cytokine levels at the tumor site in vivo is complex and often the tumor cells themselves are resistant to its activity; it is plausible that the final effect of the cytokine in vivo could be comparable to that observed in vitro at low doses. [PERSON] et al. have quantified the amounts of TGF\(\beta\) in 11 tumor effusions and reported a concentration range between 0.5 and 2 ng/mL [82]. Similarly to previous studies in which the cytokine was used at low doses of 1 ng/mL [61; 62], in our experimental setting, the conditioned medium of the dysmetabolic adipocytes was used on pancreatic cancer at a concentration of TGF\(\beta\) corresponding to 0.35 ng/mL. Although from this study we can draw some conclusions on TGF\(\beta\) secretion and activity, we cannot exclude the presence of other inflammatory factors  
Figure 5: A schematic representation of the role of TGF\(\beta\) as a response to mitochondrial dysfunction. The cytokine produced by dysmetabolic adipocytes exerts its stimulatory activity on pancreatic transformed cells and enhances cancer progression by increasing energy availability, reprogramming the cells toward the epithelial-mesenchymal transition (EMT) and inducing migration. OXPHOS: oxidative phosphorylation. Created with BioRender.com. in the conditioned medium, which would reinforce the metabolic and pro-tumoral effects of TGF\(\beta\) measured in our model.