Tryptophan metabolism in patients with chronic kidney disease secondary to type 2 diabetes: Relationship to inflammatory markers

Subrata Debnath, Chakradhar Velagapudi, Laney Redus, Farook Thameem, Balakuntalam Kasinath, Claudia E. Hura, Carlos Lorenzo, Hanna E. Abboud, Jason C. O'Connor

Research output: Contribution to journalArticlepeer-review

34 Scopus citations

Abstract

Objecti ve: Type 2 diabetes (T2D) is the primary case of chronic kidney disease (CKD). Inflammation is associated with metabolic dysregulation in patients with T2D and CKD. Tryptophan (TRP) metabolism may have relevance to the CKD outcomes and associated symptoms. We investigated the relationships of TRP metabolism with inflammatory markers in patients with T2D and CKD. Methods: Data were collected from a well-characterized cohort of type 2 diabetic individuals with all stages of CKD, including patients on hemodialysis. Key TRP metabolites (kynurenine [KYN], kynurenic acid [KYNA], and quinolinic acid [QA]), proinflammatory cytokines (tumor necrosis factor-α [TNF-α] and interleukin-6 [IL-6]), and C-reactive protein were measured in plasma. The KYN/TRP ratio was utilized as a surrogate marker for indoleamine 2,3-dioxygenase 1 (IDO1) enzyme activity. Results: There was a significant inverse association between circulating TRP level and stages of CKD (P < 0.0001). Downstream bioactive TRP metabolites KYN, KYNA, and QA were positively and robustly correlated with the severity of kidney disease (P < 0.0001). In multiple linear regression, neither TNF-α nor IL-6 was independently related to KYN/TRP ratio after adjusting for estimated glomerular filtration rate (eGFR). Only TNF-α was independently related to KYN after taking into account the effect of eGFR. Conclusio ns: Chronic kidney disease secondary to T2D may be associated with accumulation of toxic TRP metabolites due to both inflammation and impaired kidney function. Future longitudinal studies to determine whether the accumulation of KYN directly contributes to CKD progression and associated symptoms in patients with T2D are warranted.

Original languageEnglish (US)
JournalInternational Journal of Tryptophan Research
Volume10
Issue number1
DOIs
StatePublished - 2017

Keywords

  • Chronic kidney disease
  • Indoleamine 2,3-dioxygenase 1
  • Inflammatory cytokines
  • Kynurenine
  • Tryptophan
  • Type 2 diabetes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology

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