title: The Relationship between Serum Oxalic Acid, Central Hemodynamic Parameters and Colonization by Oxalobacter formigenes in Hemodialysis Patients.
abstract: OBJECTIVE
  Elevated pulse wave velocity (PWV) and central aortic blood pressures are independent predictors of increased cardiovascular morbidity and mortality in hemodialysis (HD) patients. Oxalic acid is a uremic retention molecule that is extensively studied in the pathogenesis of calcium oxalate stones. Oxalobacter formigenes, a member of the colon microbiota, has important roles in oxalate homeostasis. Data regarding the colonization by and the exact role of O. formigenes in the pathogenesis of oxalic acid metabolism in HD patients are scant. Hence, we aimed to determine the relationship between fecal O. formigenes colonization, serum oxalic acid and hemodynamic parameters in HD patients with regard to the colo-reno-cardiac axis.
  
  
  METHODS
  Fifty HD patients were enrolled in this study. PWV and central aortic systolic (cASBP) and diastolic blood pressures (cADBP) were measured with a Mobil-O-Graph (I.E.M. GmbH, Stolberg, Germany). Serum oxalic acid levels were assessed by ELISA, and fecal O. formigenes DNA levels were isolated and measured by real-time PCR.
  
  
  RESULTS
  Isolation of fecal O. formigenes was found in only 2 HD patients. One of them had 113,609 copies/ml, the other one had 1,056 copies/ml. Serum oxalic acid levels were found to be positively correlated with PWV (r = 0.29, p = 0.03), cASBP (r = 0.33, p = 0.001) and cADBP (r = 0.42, p = 0.002) and negatively correlated with LDL (r = -0.30, p = 0.03). In multivariate linear regression analysis, PWV was independently predicted by oxalic acid, glucose and triglyceride.
  
  
  CONCLUSIONS
  This is the first study that demonstrates the absence of O. formigenes as well as a relation between serum oxalic acid and cASBP, cADBP and PWV in HD patients. Replacement of O. formigenes with pre- and probiotics might decrease serum oxalic acid levels and improve cardiovascular outcomes in HD patients.
authors.affiliation: Department of Microbiology, Erzincan University, Erzincan, Konya, Turkey.
authors.forename: Baris
authors.initials: B
authors.lastname: Gulhan
authors.affiliation: Division of Nephrology, Department of Internal Medicine, Meram School of Medicine, Konya Necmettin Erbakan University, Konya, Turkey.
authors.forename: Kultigin
authors.initials: K
authors.lastname: Turkmen
authors.affiliation: Department of Microbiology, Erzincan University, Erzincan, Konya, Turkey.
authors.forename: Merve
authors.initials: M
authors.lastname: Aydin
authors.affiliation: Department of Biochemistry, School of Medicine, Erzincan University, Erzincan, Konya, Turkey.
authors.forename: Murat
authors.initials: M
authors.lastname: Gunay
authors.affiliation: Department of Microbiology, Erzincan University, Erzincan, Konya, Turkey.
authors.forename: Aytekin
authors.initials: A
authors.lastname: Cıkman
authors.affiliation: Department of Microbiology, Erzincan University, Erzincan, Konya, Turkey.
authors.forename: Murat
authors.initials: M
authors.lastname: Kara
keywords: Central aortic blood pressures; Colo-reno-cardiac axis; Oxalic acid; Oxalobacter formigenes; Pulse wave velocity