A pilot investigation on plasma tenofovir levels and possible side effects in HIV-infected women
Tenofovir disoproxil fumarate (TDF) is a nucleotide reverse transcriptase inhibitor and a prodrug of tenofovir (TFV). It is the currently recommended first line combination treatment of human immunodeficiency virus (HIV) infection in adults. Various clinical studies have associated treatment with a TDF-containing antiretroviral therapy (ART) regimen with reduced bone mineral density (BMD) and renal dysfunction. Hardly any studies to date have correlated plasma TFV concentration with markers of renal function and bone turnover (BTM). This knowledge is also unavailable in the South African public health care system. Hence, the correlations between plasma TFV concentration and renal function markers and BTM in HIV-infected women were investigated. Renal function markers and BTM in HIV-infected women were compared with those in HIV-uninfected control women. A pilot cross-sectional sub-study within the Prospective Urban and Rural Epidemiology (PURE) South Africa study was conducted. Sixty women participated, of which 30 HIV-infected women were matched for age and body mass index with 30 HIV-uninfected ones. Ethics approval was obtained from the North-West University, Human Research Ethics committee (NWU-00016-10-A1) on 12 April 2013 to conduct this sub-study and the North West Department of Health, Mmabatho on 08 August 2013 to access patient health information. A validated high-performance liquid chromatography tandem mass spectrometry method was developed to analyse TFV in plasma. Renal markers measured were the estimated glomerular filtration rate (eGFR), creatinine clearance (CrCl), albuminuria, serum creatinine (SCr), serum urea, serum uric acid, glucosuria, urine sodium (UNa) and maximum tubular reabsorption of phosphate (TmPO4/GFR). The BTM markers measured included C-terminal telopeptide (CTx), alkaline phosphatase (ALP), parathyroid hormone (PTH), total vitamin D (VitD), serum calcium (SrCa), serum phosphate (SrP) and BMD. BMD was assessed using the DTX-200 peripheral DXA system (Osteometer MediTech, Hawthorn, California, USA). Renal and bone markers were analysed on Elecsys® 2010 and COBAS INTERGRA® 400 plus (Roche Diagnostics, Switzerland). Baseline data for HIV-infected participants with regard to CD4+ cell count, SCr prior to TDF initiation, time since TDF initiation, weight prior to TDF initiation and time since HIV diagnosis were collected retrospectively from participants’ public health care files. Statistical analyses applied were linear regression, analysis of covariance, the Mann-Whitney U test, paired t-test and unpaired t-test. IBM® SPSS® Statistics software 22 was used to perform all the statistical analyses. The median and interquartile range of plasma TFV concentration was 113 (74-139.4) ng/mL (n=25) and no TFV was detected in five participants’ plasma. Adjusted analyses showed TFV concentration to be associated with albuminuria (adjusted r2 = 0.339; p = 0.001). Values of CrCl, eGFR and albuminuria (p = 0.032; p = 0.038; p = 0.048, respectively) were significantly higher in HIV-infected women compared to HIV-uninfected women. CrCl [112 (84-137) mL/min] and eGFR [134 (93-153) mL/min/1.73m2] values were abnormally high in HIV-infected women. There was also an increase in both CrCl and eGFR (p = 0.008; p < 0.001, respectively) from baseline to median follow-up of 16.6 (8.8-23.4) months in HIV-infected women. At a TFV plasma concentration of ≥ 120 ng/mL, CTx and ALP correlated positively (r = 0.704; p = 0.016). ALP (112 ± 28 U/L; p < 0.001), CTx (0.68 ± 0.4 ng/mL; p = 0.027) and PTH (56.3 ± 32 pg/mL; p = 0.050) were higher in HIV-infected women compared to HIV-uninfected women. CD4+ cell count increased from baseline to follow-up in HIV-infected women (+250 cells/mm3; p = 0.001). In HIV-infected women on a TDF-based regimen, TFV plasma concentration is associated with an increase in albuminuria, while perturbations in BTM equilibrium occur at ≥ 120 ng/mL of TFV plasma concentration. Abnormally higher CrCl and eGFR are present in HIV-infected women, seen as glomerular hyperfiltration compared with HIV-uninfected women. There was immunological improvement with TDF-based ART in HIV-infected women. Longitudinal studies with larger sample sizes are needed to confirm these findings.
- Health Sciences