Alterations in the Kynurenine Pathway of Tryptophan Metabolism Are Associated With Depression in People Living With HIV

People living with HIV have increased risk of depression compared with uninfected controls. The determinants of this association are unclear. Alterations in kynurenine (Kyn) metabolism have been associated with depression in uninfected individuals, but whether they are involved in the development of depression in the context of HIV infection is unknown. A total of 909 people living with HIV were recruited from the Copenhagen Comorbidity in HIV infection study. Information regarding demographics and depression was obtained from questionnaires. HIV-related variables and use of antidepressant medication were collected from patient records. Logistic regression models before and after adjustment for confounders were used to test our hypotheses. The prevalence of depression was 11%. Among traditional risk factors, only being unmarried was associated with greater odds of depression. Higher levels of quinolinic-to-kynurenic acid ratio (P = 0.018) and higher concentrations of quinolinic acid (P = 0.048) were found in individuals with depression than in those without. After adjusting for confounders, high levels of quinolinic-to-kynurenic acid ratio and high concentrations of quinolinic acid remained associated with depression [adjusted odds ratio 1.61 (1.01; 2.59) and adjusted odds ratio 1.68 (1.02; 2.77), respectively]. The results from this study suggest that alterations in the kynurenine pathway of tryptophan metabolism are associated with the presence of depression in the context of HIV infection.