The levels of the nitrogenous metabolite PAGN were also increased in PDAC compared to CP in the present study (Fig. 5b). PAGN is a product of gut microbiota-host co-metabolism found in urine and blood (Barrios et al. 2015), and there are indications that the gut microbiota has an important role in carcinogenesis (Schwabe and Jobin 2013).