Vitamin D deficiency and persistent proteinuria among HIV-infected and uninfected injection drug users

Objective: Proteinuria occurs commonly among HIV-infected and uninfected injection drug users (IDUs) and is associated with increased mortality risk. Vitamin D deficiency, highly prevalent among IDUs and potentially modifiable, may contribute to proteinuria. To determine whether vitamin D is associated with proteinuria in this population, we conducted a cross-sectional study in the AIDS Linked to the IntraVenous Experience (ALIVE) Study. Methods: 25(OH)-vitamin D levels were measured in 268 HIV-infected and 614 HIV-uninfected participants. The association between vitamin D deficiency (<10ng/ml) and urinary protein excretion was evaluated by linear regression. The odds of persistent proteinuria (urine protein-to-creatinine ratio >200mg/g on two occasions) associated with vitamin D deficiency was examined using logistic regression. Results: One-third of participants were vitamin D-deficient. Vitamin D deficiency was independently associated with higher urinary protein excretion (P<0.05) among HIV-infected and diabetic IDUs (P-interaction<0.05 for all). Persistent proteinuria occurred in 18% of participants. Vitamin D deficiency was associated with greater than six-fold odds of persistent proteinuria among diabetic IDUs [odds ratio (OR) 6.29, 95% confidence interval (CI) 1.54, 25.69] independent of sociodemographic characteristics, comorbid conditions, body mass index, and impaired kidney function [estimated glomerular filtration rate (eGFR) <60ml/min per 1.73m]; no association, however, was observed among nondiabetic IDUs (OR 1.06, 95% CI 0.64, 1.76) (P-interaction <0.05). Conclusions: Vitamin D deficiency was associated with higher urinary protein excretion among those with HIV infection and diabetes. Vitamin D deficiency was independently associated with persistent proteinuria among diabetic IDUs, although not in nondiabetic persons. Whether vitamin D repletion ameliorates proteinuria in these patients requires further study.