 These alterations of gut microbiota can impact on several mechanisms in ESRD. Gut bacteria produce vitamin K and the microbiome composition might therefore play a pivotal role in providing enough vitamin K for a sufficient carboxylation of MGP, a potent inhibitor of arterial calcification. Treatment with vitamin K antagonists, for example, has been associated with a 10 fold increased risk for the development of calcification and calciphylaxis, a life threatening calcifying arteriolopathy in CKD-patients. Furthermore the gut is a potential source of endotoxin in patients with ESRD, due to translocation of bacterial products across the gastrointestinal barrier. In ESRD the presence of endotoxin is an independent predictor for mortality. Ultrafiltration during hemodialysis treatment leads to critical ischemia in the splanchnic vascular bed, thus adversely affecting the integrity of the gut barrier. Disruption of gut barrier function in ESRD allows translocation of endotoxin and bacterial metabolites to the systemic circulation, which contributes to inflammation and uremia and prompts progression of the disease. Furthermore, subclinical inflammation in ESRD-patients has been shown to promote progression of cardiovascular disease as well. The gut microbiome also impacts on glucose metabolism and plays a critical role in obesity and the development of insulin resistance and type 2 diabetes. Protein fermentation by gut microbiota generates toxic metabolites and many of the known uremic toxins are of intestinal origin, including p-cresol and indoxyl sulfate. Modulation of the microbiome can contribute to the reductionelimination of uremic toxins. 