Low molecular weight proteinuria in human immunodeficiency virus-infected patients

Profiling Biomarkers in HIV Glomerular Disease – Potential for the Non-Invasive Diagnosis of HIVAN?

Background

There is a wide spectrum of kidney pathology in human immunodeficiency virus (HIV) infection, affecting all structures of the kidney. The histology of HIV chronic kidney disease (CKD) is diverse, ranging from HIV-associated nephropathy (HIVAN) to focal glomerulosclerosis (FSGS), HIV-immune complex disease (HIV-ICD), other glomerulopathies and tubulo-interstitial nephritis. Definitive diagnosis is by kidney biopsy, an invasive procedure. However, serum and urinary biomarkers may be useful in predicting the histological diagnosis of HIVAN.

Purpose

We wished to determine the utility of serum and urinary biomarkers in predicting the histological diagnosis of HIVAN.

Patients and Methods

We measured neutrophil gelatinase-associated lipocalin (NGAL), cystatin C, transforming growth factor (TGF)-β isoforms and bone morphogenetic protein (BMP)-7 in the serum and urine in patients with different histological forms of HIV glomerular disease.

Results

In HIVAN, we demonstrated increased levels of serum cystatin C and increased levels of serum and urinary NGAL. Urinary TGF-β1 and TGF-β2 levels were elevated in HIV-positive patients with CKD but were not significantly different in the different HIV histologies, while urinary BMP-7 levels were elevated in minimal change disease.

Conclusion

This study confirmed the presence of increased serum and urinary biomarkers of tubular injury in patients with HIVAN, and increased urinary biomarkers of fibrosis in HIV CKD, and may indicate their value as a non-invasive diagnostic tool for the diagnosis of HIVAN.

Pharmacokinetics and renal safety of tenofovir alafenamide with boosted protease inhibitors and ledipasvir/sofosbuvir

BACKGROUND

Ledipasvir/sofosbuvir increases tenofovir plasma exposures by up to 98% with tenofovir disoproxil fumarate (TDF), and exposures are highest with boosted PIs. There are currently no data on the combined use of the newer tenofovir prodrug, tenofovir alafenamide (TAF), boosted PIs and ledipasvir/sofosbuvir.

OBJECTIVES

To compare the plasma and intracellular pharmacokinetics and renal safety of TAF with ledipasvir/sofosbuvir when co-administered with boosted PIs.

METHODS

Persons with HIV between 18 and 70 years and on a boosted PI with TDF were eligible. The study was comprised of four phases: (1) TDF 300 mg with boosted PI; (2) TAF 25 mg with boosted PI; (3) TAF 25 mg with boosted PI and ledipasvir/sofosbuvir; and (4) TAF 25 mg with boosted PI. Pharmacokinetic sampling, urine biomarker collection [urine protein (UPCR), retinol binding protein (RBP) and β2 microglobulin (β2M) normalized to creatinine] and safety assessments occurred at the end of each phase. Plasma, PBMCs and dried blood spots were collected at each visit.

RESULTS

Ten participants were enrolled. Plasma tenofovir exposures were 76% lower and tenofovir-diphosphate (TFV-DP) concentrations in PBMCs increased 9.9-fold following the switch to TAF. Neither of these measures significantly increased with ledipasvir/sofosbuvir co-administration, nor did TAF plasma concentrations. No significant changes in estimated glomerular filtration rate or UPCR occurred, but RBP:creatinine and β2M:creatinine improved following the switch to TAF.

CONCLUSIONS

Ledipasvir/sofosbuvir did not significantly increase plasma tenofovir or intracellular TFV-DP in PBMCs with TAF. These findings provide reassurance that the combination of TAF, boosted PIs and ledipasvir/sofosbuvir is safe in HIV/HCV-coinfected populations.

Brief Report: Subclinical Kidney Dysfunction in HIV-Infected Children: A Cross-Sectional Study

OBJECTIVE

Most of the kidney dysfunction in HIV-positive children receiving antiretroviral therapy (ART) is attributed to tenofovir. There is a paucity of data on kidney dysfunction in tenofovir-naive children. The primary objective was to know the point prevalence of albuminuria and β2-microglobulinuria in HIV-infected children aged 3-18 years receiving ART. Albuminuria and β2-microglobulinuria were used as surrogates for glomerular and tubular dysfunction, respectively. The secondary objective was to determine their predictors.

DESIGN

Cross-sectional study-design.

METHODS

One hundred consecutive HIV-positive children (3-18 years) on ART were included. Spot urine sample was analyzed for urinary creatinine, total protein, microalbumin, and β2-microglobulin. Albuminuria was defined as albumin to creatinine ratio of >30 mg/g; proteinuria as urine dipstick ≥trace or spot urine protein to creatinine ratio (uPCR) of ≥0.2. β2-microglobulinuria was defined as β2-microglobulin levels of >350 µg/L.

RESULTS

There were 71 boys and 29 girls. Most of the children had WHO clinical stage I and were getting zidovudine-based regimen. Only 7 children were getting tenofovir. estimated Glomerular Filtration Rate and serum creatinine were normal in all children. Approximately half (48%) had renal dysfunction in the form of glomerular dysfunction (26%), tubular dysfunction (27%), or both (5%). Age at diagnosis was significantly associated with β2-microglobulinuria (P = 0.044). None of the selected variables were associated with albuminuria.

CONCLUSIONS

HIV-associated glomerular and tubular dysfunction is common in children receiving ART other than tenofovir. The standard guidelines should consider including routine urinary biomarker monitoring in children on ART.

Predictive factors and prevalence of microalbuminuria in HIV-infected patients: a cross-sectional analysis

Background

Renal dysfunction is a common problem in the HIV+ population, due to the effect of both the HIV virus and the several classes of ARV drugs such as tenofovir (TDF). It is also known that the presence of renal damage correlates with cardiovascular risk and therefore with the risk of mortality of the patients accordingly. The detection of early renal damage is very important. Albuminuria and microalbuminuria are markers of early kidney disease and cardiovascular risk. The aim of the study is to evaluate the prevalence of microalbuminuria in a large polycentric sample, of unselected and consecutive HIV-patients followed as outpatients, and to assess its association with different therapeutic regimens.

Methods

We studied 326 patients with a mean age of 48.4 ± 1.6 years, treated at the Infectious Diseases Clinics of Chieti and Perugia for 48 weeks. The main metabolic parameters and the microalbuminuria levels in a single sample of urine were evaluated.

Results

Microalbuminuria was detected in 61.0% of patients at T0 and in 49.7% after 48 weeks of observation with a median values of 1.1 mg/L (IQR: 0-2.7) vs. 0 mg/L (IQR: 0-2.0). 70% of the enrolled population did not show changes in microalbuminuria levels over time, 19% showed improvement, and 11% of the population had a worsening of microalbuminuria levels without any alteration of creatinine, uric acid and GFR-MDRD. We also found a statistically significant association between the development of microalbuminuria and gender (p < 0.035), Arterial Hypertension (AH) (p < 0.028) and therapy with TDF (p < 0.050).

Conclusion

We showed a very high prevalence of microalbuminuria, much higher than the literature data; the use of TDF affects the renal function in a statistically significant way and should therefore be considered a risk factor for kidney damage, which can be early assessed with the measurement of microalbuminuria.

Longitudinal Assessment of Proximal Tubular Dysfunction in HIV Seropositive and Seronegative Persons: Correlates and Implications

BACKGROUND

Proximal tubular dysfunction (PTD) is common in HIV-positive persons and has been associated with tenofovir disoproxil fumarate (TDF). However, few studies have assessed the natural history PTD in HIV-positive and -negative individuals, or the association of PTD with the subsequent trajectory of directly measured glomerular filtration rate (mGFR).

METHODS

We followed 192 HIV-positive and 100 HIV-negative, nondiabetic participants for 3 years. We measured 3 PTD markers (normoglycemic glycosuria, fractional excretion of phosphorus, and tubular proteinuria) and mGFR (by iohexol disappearance from serum) annually. We used univariate and multivariate generalized estimating equation logistic regression to identify factors associated with PTD across all visits and linear mixed effects models to assess the association between baseline PTD and mGFR slope.

RESULTS

Compared with HIV-negative participants, HIV-positive persons that were not taking antiretroviral therapy were at increased risk of PTD (adjusted odds ratio 3.33; 95% confidence interval: 1.65 to 6.71), whereas those taking a TDF-based or a TDF-sparing regimen were not at significantly increased risk of PTD. Among HIV-positive participants, uncontrolled viremia was a strong correlate of PTD. Forty-nine of 55 (89%) participants with PTD at baseline had at least 1 subsequent visit without PTD. There was no association between baseline PTD and rate of decline in mGFR over time.

CONCLUSIONS

Poorly controlled HIV may be a stronger risk factor for PTD than TDF use. The individual-level variability of the PTD markers over time was high, potentially limiting their usefulness for routine screening in unselected patients. Baseline PTD was not associated with subsequent mGFR slope.

Profiling of Kidney Injury Biomarkers in Patients Receiving Cisplatin: Time-dependent Changes in the Absence of Clinical Nephrotoxicity

The success of cisplatin-containing regimens to treat solid tumors is limited, in part, by nephrotoxicity. In rodents, several urinary proteins have emerged that are sensitive indicators of cisplatin-induced kidney injury. We sought to characterize time-dependent changes in the urinary concentrations of 12 proteins, including kidney injury molecule-1 (KIM-1), calbindin, beta 2-microglobulin (β2M), and trefoil factor 3 (TFF3) after cisplatin therapy. Urine was collected at baseline, 3 days (range, 2-5 days), and 10 days (range, 9-11 days) from 57 patients with solid tumors receiving outpatient cisplatin therapy (≥25 mg/m2 ). Serum creatinine was largely unchanged after cisplatin infusion. However, compared with baseline values, several novel biomarkers were significantly increased in the urine, including β2M, which was threefold higher by day 3 (P < 0.0001). Urinary KIM-1 and TFF3 were elevated twofold by day 10 (P = 0.002 and P = 0.002, respectively), whereas calbindin levels were increased eightfold (P < 0.0001). We report novel time-dependent changes in the urinary excretion of noninvasive markers of subclinical kidney injury after cisplatin treatment.

The Relationship between Vitamin A Deficiency and Hiv Infection: Review of Scientific Studies

Review of the literature shows that in adults there are variations in the association of hyporetinemia with disease progression as well as variations in the response to supplementation. Populations that are likely to be deficient in vitamin A show the biggest responses. Additional vitamin A supplementation may not be necessary, and may even be harmful, in adults who already have a good dietary intake of vitamin A and who take many other vitamin supplements. Vitamin A supplementation does not appear to have any impact on mother-to-child transmission of HIV; nevertheless, vitamin A supplementation of pregnant women in the third trimester may be useful to reduce the incidence of low-birthweight and premature infants. the impact of vitamin A on mother-to-child transmission of HIV in preterm infants is awaiting further investigation. Vitamin A supplementation of HIV-infected children appears to be beneficial to reduce the incidence and severity of diarrhea in particular. Randomized, placebo-controlled trials in pregnant women and adults have shown that the association between vitamin A and HIV is probably an association of reverse causality.

Altered Underlying Renal Tubular Function in Patients With Chronic Hepatitis B Receiving Nucleos(t)ide Analogs in a Real-World Setting: The MENTE Study

BACKGROUND

Cases of renal tubular dysfunction have been reported in patients with hepatitis B and in patients with human immunodeficiency virus who are undergoing tenofovir treatment. However, little is known about the impact on tubular function in patients with chronic hepatitis B (CHB) under long-term use of entecavir (ETV) and tenofovir disoproxil fumarate (TDF). We evaluated markers of renal tubular function and bone turnover in patients with CHB treated with ETV or TDF.

PATIENTS AND METHODS

A multicenter, cross-sectional study was performed on markers of renal tubular function and bone turnover in hepatitis B virus-monoinfected patients on long-term treatment with Entecavir or Tenofovir (the MENTE study). The analyzed parameters were: retinol-binding protein/creatinine, neutrophil gelatinase-associated lipocalin/creatinine, excretion of phosphates, uric acid excretion, glomerular filtrate, protein/creatinine, albumin/creatinine, serum creatinine, phosphate, CTX, P1NP, vitamin D, and parathormone.

RESULTS

A total of 280 patients (ETV: 89, TDF: 69, control: 122) were included in this study. The TDF group was associated with altered levels of retinol-binding protein (RBP)/creatinine (TDF 25% vs. 7% ETV and control; P<0.001). Protein/creatinine, uric acid excretion, P1NP1, and parathormone were higher in the TDF group. The proportion of patients with serum phosphate <2.5 mg/dL was higher in both the ETV and the TDF groups compared with the control. The multivariate analysis showed that the use of TDF was independently associated with a higher risk of altered excretion of RBP/creatinine (4.4; interquartile range: 1.4 to 14; P=0.013).

CONCLUSIONS

We found an independent association between TDF use and altered RBP excretion. This finding indicates subclinical tubular damage. Because tubular dysfunction can precede the decline of renal function, close monitoring of RBP levels in patients with CHB on nucleos(t)ide analog treatment must be performed for early detection of TDF-related renal toxicity. In this study, these differences in tubular function were not associated with concomitant changes in markers of bone turnover.

Urinary Markers of Tubular Injury in HIV-Infected Patients

Renal disease is a common complication of HIV-infected patients, associated with increased risk of cardiovascular events, progression to AIDS, AIDS-defining illness, and mortality. Early and accurate identification of renal disease is therefore crucial to improve patient outcomes. The use of serum creatinine, along with proteinuria, to detect renal involvement is essentially to screen for markers of glomerular disease and may not be effective in detecting earlier stages of renal injury. Therefore, more sensitive and specific markers are needed in order to early identify HIV-infected patients at risk of renal disease. This review article summarizes some new and important urinary markers of tubular injury in HIV-infected patients and their clinical usefulness in the renal safety follow-up of TDF-treated patients.

Epidemiology, clinical characteristics, and management of chronic kidney disease in human immunodeficiency virus-infected patients

Antiretroviral therapy has markedly reduced acquired immune deficiency syndrome-related deaths and opportunistic infectious diseases. This has resulted in prolonged survival of individuals infected with the human immunodeficiency virus (HIV). However, this improvement in survival has been accompanied by an increase in the incidence of chronic kidney disease (CKD) and end-stage renal disease. CKD is now epidemic among HIV-infected populations in both Western and Eastern countries. Risk factors associated with CKD in HIV-infected populations include aging, hypertension, diabetes mellitus, co-infection with hepatitis C virus, a low CD4 cell count, and a high HIV viral load. Clinical experience has shown that HIV-infected individuals often have one or more concurrent risk factors for CKD. The cumulative effect of multiple risk factors on the development of CKD should be noted in this population. Glomerular disease directly related to HIV infection, so-called HIV-associated nephropathy, remains an important cause of CKD among a limited HIV population of African descent, but is less likely to be common among other urban HIV populations. The impact of exposure to nephrotoxic antiretroviral agents on the development of kidney disease is both an old and a new concern. In particular, the association of tenofovir with kidney tubular injury has been an area of great interest. The findings regarding tenofovir's adverse effect on long-term kidney function vary among studies. The early identification and treatment of CKD is recommended for reducing the burden of patients requiring dialysis in HIV-infected populations. Periodic monitoring of urinary concentrations of albumin, protein, and tubular injury markers such as low-molecular-weight proteins may be useful for the early diagnosis of patients at risk for incident CKD. This review focuses on recent epidemiology, clinical characteristics, and management of CKD in a contemporary HIV-infected population.

Urine alpha1-microglobulin is a better marker for early tubular dysfunction than beta2-microglobulin among tenofovir-exposed human immunodeficiency virus-infected men who have sex with men

OBJECTIVES

Men who have sex with men are at risk of tenofovir nephrotoxicity due to its wide use in both treatment and prophylaxis for human immunodeficiency virus infection, but little is known about the urinary biomarkers of early renal dysfunction in this population. This study aims to identify useful biomarkers of early renal dysfunction among human immunodeficiency virus-infected men who have sex with men exposed to tenofovir.

METHODS

In a cross-sectional study urinary alpha1-microglobulin, beta2-microglobulin, N-acetyl-β-d-glucosaminidase and albumin were measured and expressed as the ratio-to-creatinine in 239 human immunodeficiency virus-infected men who have sex with men who were treatment naïve or receiving antiretroviral therapy with tenofovir-containing or non-tenofovir-containing regimens. Additionally, 56 patients in the non-antiretroviral therapy group started a tenofovir-containing regimen and were assessed after 3 and 6 months on antiretroviral therapy.

RESULTS

Both the frequency of alpha1-microglobulin proteinuria (alpha1-microglobulin-creatinine ratio >25.8mg/g) and the median urinary alpha1-microglobulin-creatinine ratio were higher in the tenofovir disoproxil fumarate group than the other two groups (all p<0.05). A higher frequency of beta2-microglobulin proteinuria (beta2-microglobulin-creatinine ratio >0.68mg/g) was also observed in the tenofovir group (28.9%) compared to the non-tenofovir group (13.6%, p=0.024). There were no significant differences between groups for N-acetyl-β-d-glucosaminidase and albumin. In the longitudinal study, the median urinary alpha1-microglobulin-creatinine ratio after 3 and 6 months on tenofovir-containing therapy (16.8 and 17.3mg/g) was higher than baseline (12.3mg/g, p=0.023 and 0.011, respectively), while no statistically important changes were observed in urinary beta2-microglobulin-creatinine ratio or in the other biomarkers after 3 and 6 months on antiretroviral therapy (all p>0.05).

CONCLUSION

Urinary alpha1-microglobulin seems to be a more sensitive and stable indicator of tubular dysfunction than urinary beta2-microglobulin for assessing tenofovir-related nephrotoxicity and can be significantly altered after tenofovir exposure.

β2-microglobulin induces epithelial-mesenchymal transition in human renal proximal tubule epithelial cells in vitro

Background

The objective of this study was to investigate the influence of β2-microglobulin (β2-M) on the epithelial-mesenchymal transition (EMT) in renal tubular epithelial cells.

Methods

A human kidney proximal tubular cell line (HK-2) was used as the proximal tubular cell model. HK-2 cells were exposed to different concentrations of β2-M (5, 10, 25, and 50 μM) for up to 24, 48 and 72 h. The effects of β2-M on cell morphology were observed by phase contrast microscopy, and the possible associated mechanisms were assessed by immunofluorescence staining, western blot, RNA interference, immunoprecipitation, and induced coupled plasma mass spectroscopy.

Results

β2-M induced marked morphological alterations in the HK-2 cells, accompanied by the increased expression of extracellular matrix components and α-smooth muscle actin (α-SMA), vimentin and fibronectin and the reduced expression of E-cadherin. Our results also revealed that β2-M could induce the EMT in the HK-2 cells without significant affecting cell viability. Excess β2-M in the HK-2 cells led to a decrease in iron and an increase in hypoxia inducible factor-1α (HIF-1α), which induced EMT in the HK-2 cells. Additionally, disrupting the function of the β2-M/hemochromatosis (HFE) complex by HFE knockdown was sufficient to reverse β2-M-mediated EMT in the HK-2 cells.

Conclusion

These findings demonstrate that the activity of β2-M is mediated by the β2-M/HFE complex, which regulates intracellular iron homeostasis and HIF-1α and ultimately induces EMT in HK2 cells.

Proximal renal tubular dysfunction related to antiretroviral therapy among HIV-infected patients in an HIV clinic in Mexico

Proximal renal tubular dysfunction (PRTD) of varying severity has been associated with antiretroviral toxicity, especially related to the use of tenofovir (TDF). The aim of this study was to investigate whether HIV-infected patients who use a tenofovir-based regimen are at increased risk of tubular dysfunction. We conducted an observational, comparative, longitudinal, prospective study. Estimated glomerular filtration rate (eGFR) and markers of tubular damage to assess tubular dysfunction (fractional excretion of phosphate and uric acid, glycosuria, and proteinuria) were measured at baseline and at weeks 12 and 24. Of 111 participants, PRTD was found in 6.3% at week 12 and 9% at week 24, with no statistically significant difference between those on an abacavir (ABC)-containing regimen or a TDF-containing regimen. We also found an increase in triglycerides associated with the ABC-containing regimen compared with the TDF group. The use of an ABC- or TDF-containing regimen was independently associated with tubular dysfunction, but we found no significant differences between these groups, except when TDF was combined with a protease inhibitor. A better and more complete assessment of renal function is needed, because the presence of tubular dysfunction and proteinuria without impairment of eGFR may affect the renal safety of HIV-infected patients.

Relationships between renal parameters and serum and urine markers of inflammation in those with and without HIV infection

We sought to determine the relationships among intrarenal and systemic inflammation and renal disease in HIV. We compared paired serum and urinary levels (normalized to urine creatinine) of monocyte chemotactic protein-1 (MCP-1), regulated on activation normal T cell expressed and secreted (RANTES), interferon-γ-induced protein-10 (IP-10), interleukin-8 (IL-8), and β2-microglobulin (B2M) between two groups of HIV-infected subjects not receiving antiretroviral therapy (ART) [A: not expecting to initiate ART immediately due to having CD4 cell counts ≥350/μl, N=26; B: about to initiate ART, N=19], a group of HIV-infected subjects receiving virologically suppressive antiretroviral therapy [C, N=30], and a group of HIV-uninfected, healthy volunteers [D, N=45]. We then correlated these inflammatory biomarker levels with urine protein/creatinine ratios (uPCR), urine albumin/creatinine ratios (uACR), and estimated glomerular filtration rates (eGFR). Urine inflammatory biomarker levels were highest in Group B. When combining all four study groups, statistically significant positive correlations included uPCR with urine IL-8, urine MCP-1, urine IP-10, and serum IP-10 and uACR with urine IL-8, urine B2M, serum IP-10, and serum B2M. eGFR was statistically significantly negatively correlated with serum MCP-1 and serum B2M. Paired serum and urine levels of IP-10 and B2M (but not IL-8, RANTES, or MCP-1) were significantly correlated with each other in the overall group. The levels of urine inflammatory markers tested differed by HIV status and use of virologically suppressive ART. These urine and serum inflammatory markers were differentially correlated with uPCR, uACR, and eGFR, suggesting that different intrarenal and systemic inflammatory pathways may contribute to different measures of nephropathy.

Detection of renal brush border membrane enzymes for evaluation of renal injury in neonatal scleredema

OBJECTIVE

To evaluate renal brush border membrane enzymes in urine as an indicator for renal injury in neonatal scleredema (NS).

METHODS

Sixty nine NS patients in our hospital were enrolled and divided into mild group and moderate/severe group. Patients were further randomly divided into therapy and control subgroups for 7 days ligustrazine administration. Urine samples were collected to detect renal brush border membrane enzymes (RBBME) by ELISA and β2-microglobulin (β2-MG) by radioimmunoassay (RIA). The results were compared with those of 30 normal neonates. Data were statistically analyzed using SPSS13.0 software.

RESULTS

Both RBBME and β2-MG were found to be higher in urine in NS patients than normal controls (P < 0.01). Level of RBBME increased with the severity of NS (P <0.05), while urinary β2-MG did not (P >0.05). After being treated with ligustrazine, a medicine for renal function recovery, both RBBME and β2-MG were similarly significantly decreased comparing to untreated groups (P < 0.05). 79.7% of NS patients showed abnormal RBBME while only 52.2% had an abnormal urinary β2-MG (χ (2)=11.65，P < 0.01).

CONCLUSION

RBBME was more sensitive than β2-MG in reflecting the renal injury in NS. Examination of RBBME effectively reflected the recovery of renal injury after treatment with ligustrazine.

Cystatin C: a new renal marker and its potential use in small animal medicine

The occurrence of chronic kidney disease is underestimated in both human and veterinary medicine. Glomerular filtration rate (GFR) is considered the gold standard for evaluating kidney function. However, GFR assessment is time-consuming and labor-intensive and therefore not routinely used in practice. The commonly used indirect GFR markers, serum creatinine (sCr) and urea, are not sufficiently sensitive or specific to detect early renal dysfunction. Serum cystatin C (sCysC), a proteinase inhibitor, has most of the properties required for an endogenous GFR marker. In human medicine, numerous studies have evaluated its potential use as a GFR marker in several populations. In veterinary medicine, this marker is gaining interest. The measurement is easy, which makes it an interesting parameter for clinical use. This review summarizes current knowledge about cystatin C (CysC) in humans, dogs, and cats, including its history, assays, relationship with GFR, and biological and clinical variations in both human and veterinary medicine.

How to manage HIV-infected patients with chronic kidney disease in the HAART era

As human immunodeficiency virus (HIV)-infected patients now live longer while receiving highly active antiretroviral therapy (HAART), chronic kidney disease (CKD) has emerged as a significant cause of morbidity and mortality among urban HIV population. Risk factors associated with CKD in such HIV-infected population include aging, hypertension, diabetes mellitus, co-infection with hepatitis C virus, low CD4 cell count, and high HIV viral load. Clinical experience has shown that HIV-infected individuals often have one or more concurrent risk factors for CKD. The cumulative effect of multiple risk factors on the development of CKD should be noted in this population. Glomerular disease directly related to HIV infection, so-called HIV-associated nephropathy, remains an important cause of CKD among limited HIV population of African descent. The impact of exposure to nephrotoxic antiretroviral agents on the development of kidney disease is both an old and a new concern. In particular, the association of tenofovir with kidney disease has been an area of great interest. The findings regarding tenofovir's adverse effect on long-term kidney function vary among studies. Early identification and treatment of kidney disease is imperative for reducing the burden of patients requiring dialysis in HIV-infected populations. Periodic monitoring of urinary albumin excretion, tubular parameters such as low-molecular-weight proteinuria, and the estimated glomerular filtration rate may be useful for early diagnosis of patients at risk for incident CKD. This review focuses on recent developments in epidemiology, risk factors, identification, estimation, and management of CKD in HIV-infected population in the HAART era.

Detection and diagnostic applicability of human urinary kininogen in kala-azar patients

The present study was aimed to detect urinary proteins excreted in kala-azar patients. Urinary proteins were isolated by ammonium sulfate precipitation and purified by Amicon ultra using 3 kDa cutoff membrane device. The proteins were resolved on 12% sodium dodecyl sulfate polyacrylamide gel electrophoresis and blots were developed with the patients sera. The excretion of urinary proteins was differential in kala-azar patients. A total eight proteins of molecular weights 25, 28, 46, 54, 57, 60, 72, and 95 kDa were detected in the urine of visceral leishmaniasis (VL) patients. On blot, the 57 kDa protein was found to be host origin and characterized as human kininogen. All other proteins were leishmanial origin. Out of 50 urine samples analyzed, the kininogen was detected in 45 urine samples. Following treatment, this protein was not detectable in the urine samples of any patient. The appearance of kininogen in urine of VL patients offers a novel possibility for the development of diagnostic tool and a test of cure.

Persistent decline in estimated but not measured glomerular filtration rate on tenofovir may reflect tubular rather than glomerular toxicity

BACKGROUND

Tenofovir disoproxil fumarate (TDF) has been associated with proximal renal tubulopathy and reduction in estimated glomerular filtration rate (eGFR), without accounting for the tubular secretion of creatinine.

METHODS

A substudy was performed among 19 participants of a randomized 48-week trial, comparing continuing first-line zidovudine/lamivudine (ZDV/3TC) with switching to TDF/emtricitabine (FTC). GFR was measured with [(125)I]-iothalamate (mGFR) and effective renal plasma flow (ERPF) with [(131)I]-hippuran. eGFR and tubular effects were assessed using plasma and urine samples.

RESULTS

Of the 19 patients, 18 were men, 15 whites, mean (SD) age 46.0 (8.9) years, plasma HIV-1 RNA less than 50 copies/ml in all. After 48 weeks, eGFR using Cockcroft-Gault equation and ERPF, but not mGFR, had significantly decreased, and urinary α1-microglobulin/creatinine and microalbumin/creatinine significantly increased in patients on TDF. Although phosphate metabolism on TDF was affected at week 4, differences between groups disappeared during follow-up.

CONCLUSION

Replacing ZDV/3TC with TDF/FTC in this limited sample of virologically suppressed HIV-1-infected adults was associated with mild persistent tubular but not glomerular dysfunction over 48 weeks. The observed persistent decrease in Cockcroft-Gault-based eGFR, but not mGFR, rather than being indicative of glomerular dysfunction may be explained by TDF inhibiting tubular creatinine excretion.

Tenofovir-associated kidney toxicity in HIV-infected patients: a review of the evidence

Tenofovir (TDF) is an effective and widely used treatment for both human immunodeficiency virus (HIV) and hepatitis B virus infection. Although studies suggest that TDF has a low overall toxicity profile and only a modest effect on estimated glomerular filtration rate, numerous case reports have since appeared in the literature describing TDF-associated renal tubular dysfunction, and this is now a significant source of HIV-related referrals to nephrologists. The main target of toxicity appears to be the proximal tubule, and in severe cases, patients can develop renal Fanconi syndrome. We review findings from recent studies in this area performed by ourselves and others and discuss our direct experience as practicing nephrologists. In particular, we discuss: (1) the nature and extent of TDF-associated kidney toxicity in the HIV-infected population, (2) potential underlying mechanisms of toxicity in the proximal tubule, (3) risk factors for developing tubular dysfunction, and (4) suggested strategies to monitor patients on TDF therapy.

Biomarkers of impaired renal function

PURPOSE OF REVIEW

Renal disease is increasingly common as life expectancy of HIV-infected persons continues to improve. Several biomarkers are available for monitoring renal function, although no consensus exists on how best to apply these tools in HIV infection. This review describes recent findings for the more common renal biomarkers.

RECENT FINDINGS

Although widely used in clinical practice, creatinine-based estimates of glomerular filtration rate have not been validated in HIV infection. Serum cystatin C has been proposed as a more sensitive marker of renal dysfunction in HIV infection, although it may also reflect systemic inflammation. Screening for proteinuria and albuminuria allows identification of patients at higher risk of kidney disease and other adverse outcomes. Fanconi syndrome, which has been associated with tenofovir use, is associated with severe tubular proteinuria, and several low molecular weight proteins, including retinol-binding protein, β2-microglobulin, and neutrophil gelatinase-associated lipocalin have been studied as markers of tubular dysfunction. Studies have reported a high prevalence of subclinical proximal tubular dysfunction in patients receiving antiretroviral therapy.

SUMMARY

Future studies are needed to determine the optimal biomarkers for the detection and monitoring of renal disease in HIV.

Prospective study of renal function in HIV-infected pediatric patients receiving tenofovir-containing HAART regimens

AIM

to describe the impact of tenofovir disoproxil fumarate (TDF) use on renal function in HIV-infected pediatric patients.

DESIGN

it is a prospective, multicenter study. The setting consisted of five third-level pediatric hospitals in Spain. The study was conducted on patients aged 18 years and younger who had received TDF for at least 6 months. The intervention was based on the study of renal function parameters by urine and serum analyses. The main outcome measures were renal function results following at least 6 months of TDF therapy.

RESULTS

forty patients were included (32 were white and 26 were diagnosed with AIDS). Median (range) duration of TDF treatment was 77 months (16-143). There were no significant changes in the estimated creatinine clearance. Urine osmolality was abnormal in eight of 37 patients, a decrease in tubular phosphate absorption was documented in 28 of 38 patients, and 33 of 37 patients had proteinuria. A statistically significant decrease in serum phosphate and potassium concentrations was observed during treatment (P = 0.005 and P = 0.003, respectively), as well as a significant relationship between final phosphate concentration and tubular phosphate absorption (P = 0.010). A negative correlation was found between phosphate concentration and time on TDF.

CONCLUSIONS

TDF use showed a significant association with renal tubular dysfunction in HIV-infected pediatric patients. Periodic assessment of tubular function may be advisable in the follow-up of this population.

Microalbuminuria predicts overt proteinuria among patients with HIV infection

BACKGROUND

This study examines the association between microalbuminuria and the development of proteinuria among HIV-infected persons.

METHODS

A total of 948 subjects provided urine samples for albumin, protein and creatinine measurements semiannually. Microalbuminuria was defined as an albumin-to-creatinine ratio of >30 mg/g. Proteinuria was defined as a protein-to-creatinine ratio of > or =0.350 mg/mg. The progression from microalbuminuria to proteinuria was described.

RESULTS

At baseline, 69.4% of the subjects had no detectable proteinuria, 20.2% had microalbuminuria, and 10.4% had proteinuria. Subjects with microalbuminuria and proteinuria were more likely to be black (P=0.02), have lower CD4 cell counts (P=0.02 comparing subjects without abnormal urine protein excretion to subjects with microalbuminuria; P=0.0001 comparing subjects with microalbuminuria to subjects with proteinuria), and have a higher HIV RNA level (P=0.08 and 0.04, respectively). Among 658 subjects with normal urine protein, 82.7% continued to have no abnormality, 14.3% developed microalbuminuria, and 3.0% developed proteinuria. Subjects without baseline proteinuria (i.e. either normal protein excretion or microalbuminuria) who developed proteinuria were more likely to have microalbuminuria (P=0.001), a lower CD4 cell count (P=0.06), and a higher plasma HIV RNA (P=0.03) than those who did not progress to proteinuria. In multivariate analysis, only microalbuminuria remained associated with the development of proteinuria (odds ratio 2.9; 95% confidence interval 1.5, 5.5; P=0.001).

CONCLUSION

Microalbuminuria predicts the development of proteinuria among HIV-infected persons. Because proteinuria has been linked to poorer outcomes, strategies to affect microalbuminuria should be tested.

Tenofovir-associated renal and bone toxicity

OBJECTIVES

The aims of the study were to describe the clinical presentation and renal and bone abnormalities in a case series of HIV-infected patients receiving treatment with tenofovir (TDF), and to recommend appropriate screening for toxicity related to TDF.

METHODS

Patients were identified from referrals to a specialist HIV renal clinic. Patients were included if treatment with TDF was assessed as the primary cause of the renal function impairment and clinical data were available prior to and following discontinuation of TDF treatment. Data were collected from case note review and clinic databases.

RESULTS

Twenty-two patients (1.6% of all those who received TDF) were identified with TDF-associated renal toxicity. All had normal serum creatinine prior to TDF therapy. All presented with proteinuria. On stopping TDF, renal function improved. Eight patients had confirmed Fanconi syndrome. Twelve patients presented with bone pain and osteomalacia was confirmed on an isotope bone scan in seven of these patients. The findings (in those patients tested) of tubular proteinuria, reduced tubular transport maximum of phosphate (TmP), and glycosuria were all consistent with the proximal tubule being the site of toxicity.

CONCLUSION

Renal toxicity remains a concern in patients treated with TDF. Clinical presentation may be with renal dysfunction, Fanconi syndrome or osteomalacia. Our investigations suggest proximal tubular toxicity as a common pathogenic mechanism.

Progressive renal tubular dysfunction associated with long-term use of tenofovir DF

It became evident that tenofovir DF (TDF) causes a modest and gradual decline in GFR, however, the impact of long-term use of TDF on tubular function has not been fully evaluated. In 40 patients treated with TDF and 23 patients treated with other NRTIs, urine beta(2)-microglobulin (U-BMG), percentage tubular reabsorption of phosphate (%TRP), alkaline phosphatase (ALP), serum creatinine, and calculated GFR were prospectively measured for 96 weeks. In patients receiving TDF, median U-BMG rose from 188 microg/liter at baseline to 555 microg/liter at week 96 (p = 0.02), median %TRP declined from 94% at baseline to 90% at week 96 (p = 0.002), median ALP ratio compared with baseline persistently increased from 1 to 1.278 at week 96 (p = 0.001), and serum creatinine showed significant but minimal change from 0.64 mg/dl to 0.74 mg/dl at week 96 (p = 0.02). The GFR level declined minimally but significantly in TDF-receiving patients (-17 ml/min/1.73 m(2)), whereas it did not change in other NRTI-receiving patients [+ 3 ml/min/1.73 m(2); mixed models analysis of variance (MMANOVA) p = 0.03 for overall change from baseline to week 96]. U-BMG, %TRP, ALP, or serum creatinine did not change significantly in other NRTI-receiving patients during the observation period. In five patients with marked changes in U-BMG (>10,000 microg/liter) and %TRP (<80%), both U-BMG and %TRP immediately recovered in all patients after discontinuing TDF, whereas GFR levels did not fully recover for 6 months in three patients. Prolonged treatment with TDF caused progressive renal tubular dysfunction as well as a modest decline in GFR. If U-BMG levels >10,000 microg/liter and %TRP values <80% are observed, discontinuing TDF may be beneficial.

Determination of Clara cell protein urinary elimination as a marker of tubular dysfunction

Clara cell 16-kDa protein (CC16) is a protein expressed primarily by the bronchial cells. It is rapidly eliminated by glomerular filtration, reabsorbed almost entirely, and catabolized in proximal tubule cells. To date, normal values for urinary CC16 in healthy children have not been determined. We have studied 63 pediatric patients (mean age 8.17 +/- 3.91 years) and 31 healthy children (control group; mean age 8.83 +/- 3.65 years). In the control group, the CC16/creatinine ratio was 1.22 +/- 1.52 microg/g. In 16 out of 31 control children, the value of the ratio was zero. Fourteen patients (22.2%) showed a high CC16/creatinine ratio; in contrast, among these same patients, the ratio N-acetyl-beta-D: -glucosaminidase (NAG)/creatinine was elevated in seven cases (11.1%) and the ratio beta2-microglobulin/creatinine was elevated in seven cases (11.1%). The three parameters were in agreement in 51 patients (80.9%). Among the patients, the CC16/creatinine ratio was correlated with both the beta2-microglobulin/creatinina ratio (r = 0.76, P < 0.001) and the NAG/creatinine ratio (r = 0.6, P < 0.001). Our findings indicate that CC16 is a good marker of proximal tubular function in childhood. The highest observed values were in children with proximal tubulopathies, in children with chronic renal failure, and in those treated with cyclosporine.

Kidney tubular abnormalities in the absence of impaired glomerular function in HIV patients treated with tenofovir

BACKGROUND

Tenofovir (TDF) is the most widely prescribed antiretroviral drug. Kidney abnormalities are the main concern using the drug. As glomerular function is infrequently affected in patients treated with TDF, herein, we report the results of an extensive examination of tubular function.

METHODS

Cross-sectional study of plasma and 24 h urine markers of kidney tubulopathy (glucosuria, hyperaminoaciduria, hyperphosphaturia, hyperuricosuria and beta2-microglobulinuria) could be allocated in three groups: patients under a TDF-containing HAART; patients on HAART never exposed to TDF; and antiretroviral-naive individuals. Significant tubular damage was defined when at least two of these parameters were repeatedly present, being at least one part of the Fanconi syndrome criteria (glucosuria, hyperaminoaciduria and hyperphosphaturia). Glomerular function was assessed using creatinine clearance.

RESULTS

A total of 284 consecutive HIV patients were examined, 154 on TDF, 49 on other HAART regimens and 81 drug-naive. No significant differences in creatinine clearance were observed when comparing distinct groups. The proportion of patients with tubular damage in groups 1, 2 and 3 were 22, 6 and 12%, respectively. In a multivariate analysis [odds ratio (OR) {95% confidence interval (CI)} P], the only independent predictors of tubular dysfunction were TDF use (21.6, 4.1-113, <0.001) and older age (1.1 per year, 1.0-1.1, 0.01).

CONCLUSION

Exposure to TDF is associated with an increased risk over time of kidney tubular abnormalities in the absence of significant impaired glomerular function. Although long-term consequences of this tubulopathy are unknown, close monitoring of accelerated bone mineral loss and renal insufficiency are warranted. Periodic screening of tubular function parameters should be recommended to patients receiving TDF.

Microalbuminuria associated with indicators of inflammatory activity in an HIV-positive population

Background. The survival of human immunodeficiency virus (HIV)-infected patients has increased significantly since the introduction of combination antiretroviral therapy, leading to the development of important long-term complications including cardiovascular disease (CVD) and renal disease. Microalbuminuria, an indicator of glomerular injury, is associated with an increased risk of progressive renal deterioration, CVD and mortality. However, the prevalence of microalbuminuria has barely been investigated in HIV-infected individuals.

Methods. Based on three prospective urine samples in an unselected nonhypertensive, nondiabetic HIV-positive cohort (n = 495), we analysed the prevalence of microalbuminuria and compared the Caucasian share with that of a nonhypertensive, nondiabetic population-based control group (n = 2091). Significant predictors for microalbuminuria were analysed within the HIV-positive cohort.

Results. The prevalence of microalbuminuria was 8.7% in the HIV-infected cohort, which is three to five times higher than that in the general population. HIV-infected patients with microalbuminuria were older, and had higher blood pressure, longer duration of HIV infection, higher serum beta 2-microglobulin, higher serum creatinine and a reduced glomerular filtration rate of ≤90 mL/min, compared with those with normal albumin excretion. In multivariate analysis, systolic blood pressure, serum beta 2-microglobulin and duration of HIV infection were found to be independent predictors of microalbuminuria.

Conclusions. Our findings indicate that in addition to haemodynamic effects, inflammatory activity may be implicated as a cause of the development of microalbuminuria. With respect to the increasing risk of developing CVD or renal diseases and mortality, the high prevalence of microalbuminuria in HIV-infected individuals warrants special attention.

Human immunodeficiency virus-associated nephropathy (HIVAN) in Nigerian children

Human immunodeficiency virus-associated nephropathy (HIVAN) has rarely been reported in African children. In this single-center study, we analyzed ten children diagnosed with HIVAN from January 2000 to October 2006. There were eight boys and two girls, with a male:female ratio of 4:1. Their ages were from 5 months to 15 years (mean 6.8+/-6.2 years), with a peak age of 5-9 years. The presenting complaints included generalized edema (60%) and hypertension (50%). All patients had proteinuria on urine dipstick, with four (40%) at nephrotic range (proteinuria >or=500 mg/dl). Nine (90%) patients were in renal failure, with elevated serum creatinine (6.3-24 mg/dl) and serum urea (70-120 mg/dl). Renal disease was the first manifestation of HIV infection in six patients, whereas the diagnosis was made on autopsy in three. The duration from HIV infection to development of HIVAN ranged from 5 months to 10 years. CD4(+) cell count, done in only three patients due to financial constraints, was below 200/mm(3). The kidneys were hyperechoic on abdominal ultrasound in all patients, and three (30%) showed grossly enlarged kidneys. Histology of renal tissues available by autopsy in three patients showed mainly collapsing focal segmental glomerulosclerosis. Treatments given were angiotensin-converting enzyme (ACE) inhibitors and highly active antiretroviral therapy (HAART) in four and two patients, respectively, and one patient underwent peritoneal dialysis. On outcome analysis, seven (70%) patients died, two were lost to follow-up, and one was alive on HAART therapy at the writing of this article. In conclusion, HIVAN occurs in Nigeria children, and the mortality is very high from uremia.

Serum and urine cystatin C levels in children with post-pyelonephritic renal scarring: a pilot study

AIM

We aimed to investigate in children with a history of acute pyelonephritis the influence of unilateral post-pyelonephritic renal scarring detected by DMSA scan on serum (S(CysC)) and urine cystatin C (U(CysC)) as well as upon other traditional markers of renal damage.

METHODS

Children with DMSA proven pyelonephritis (n = 28) were grouped as either scar [+] (n = 19, unilateral renal scarring) or scar [-] (no scarring, n = 9). The scar [+] group was further divided into scar-1 (differential DMSA uptake, Delta(DMSA) </= 10%; n = 8) and scar-2 (Delta(DMSA) > 10%, n = 11) subgroups. S(CysC), serum creatinine, urine NAG, microalbumin, protein, fractional sodium excretion (FE(Na)), tubular phosphate reabsorption (TPR), and U(CysC/Cr) were evaluated in all patients.

RESULTS

Neither S(CysC) nor U(CysC) were affected by age, height, and weight. scar [+] versus scar [-] groups and scar-1 versus scar-2 subgroups were not different with regard to all studied parameters. S(CysC) did not increase in children with post-pyelonephritic unilateral renal scarring. However, 11 children with slightly increased (>0.95 mg/l) S(CysC) levels in scar [+] group tended to have higher Delta(DMSA), albeit not significantly. Furthermore, U(CysC/Cr) correlated well with urine microalbumin, NAG, and FE(Na) in all children and the scar [+] group (P < 0.05).

CONCLUSION

S(CysC) and U(CysC) did not differ among pediatric patients with and without unilateral post-pyelonephritic renal scarring. However, Delta(DMSA) uptake between the two kidneys tended to be raised in children with S(CysC) levels higher than the reference ranges. Additionally, U(CysC/Cr) exhibits parallelism with tubular functions.

Microalbuminuria in HIV infection

OBJECTIVE

Microalbuminuria is associated with increased risk of cardiovascular disease and mortality. The objective of the study was to evaluate if HIV infection was an independent risk factor for microalbuminuria.

DESIGN

Cross sectional.

METHODS

The relationship between HIV infection and microalbuminuria was assessed using subjects enrolled in the study of Fat Redistribution and Metabolic Change in HIV Infection, which consists of HIV-positive and control men and women. Participants with proteinuria (dipstick >or= 1+) were excluded.

RESULTS

Microalbuminuria (urinary albumin/creatinine ratio, ACR > 30 mg/g) was present in 11% of HIV infected, and 2% of control participants (P < 0.001); a fivefold odds after multivariate adjustment (odds ratio, 5.11; 95% confidence interval, 1.97-13.31; P=0.0008). Several cardiovascular risk factors were associated with higher ACR in HIV participants: insulin resistance (HOMA > 4; 32%, P < 0.0001), systolic blood pressure (21%, P = 0.01 for 120-140 versus < 120 mmHg, and 43%, P = 0.06 for > 140 versus < 120 mmHg), and family history of hypertension (17%, P = 0.03). Higher CD4 cell count was associated with lower albumin/creatinine ratio (-24%, P = 0.009 for 200-400 versus < 200 cells/ml and -26%, P = 0.005 for > 400 versus < 200 cells/ml).

CONCLUSION

HIV infection had a strong and independent association with microalbuminuria, the severity of which was predicted by markers of insulin resistance, hypertension, and advanced HIV infection. These associations warrant further investigation, as the increased prevalence of microalbuminuria in HIV infection may be a harbinger of future risk of cardiovascular and kidney diseases.

Urinary Cystatin C as a Marker of Tubular Dysfunction

Cystatin C (CysC) is a nonglycosylated 13 KD protein that belongs to the type II cystatin gene family. It is a strong inhibitor of cysteine proteinases, freely filtered by the kidney glomerulus and reabsorbed by the tubulus, where it is almost totally catabolized. Remainder of the nonmetabolized CysC is eliminated in urine and may represent a useful marker of tubular dysfunction. The aim of the study was to confirm the clinical importance of the quantitative determination of CysC by an automated immunonephelometric method (DADE Behring). Two groups of patients were examined: one with glomerular (GD, n=36) and one with tubular dysfunction (TD, n=31), and compared with the control group (CG, n=31) of healthy males and females from laboratory personnel (n=11) and patients on routine systematic examination (n=20), from 25 to 58 years old. The patient groups were categorised according to the urine analysis of total proteins, creatinine and adequate proteins electrophoretic panel. CysC concentration in CG was in the range of 0.02-0.15 mg/L; 0.01-0.48 mg/L and 0.25-18 mg/L in GD and TD groups respectively. Values of means ± SD for patient groups (GD=0.11 ± 0.14; TD=3.92 ± 3.75 mg/L) showed statistical significance (p<0.001) in the TD group in relation to GD and CG groups. It confirms that quantitative determination of CysC in one urine portion, with a fast laboratory method, might be a useful marker of tubular dysfunction, especially in emergency situations, taking into account that there is no interference of circadian variation on its concentration.

A cross-sectional study of HIV-seropositive patients with varying degrees of proteinuria in South Africa

Human immunodeficiency virus (HIV)-associated nephropathy (HIVAN) is the most common finding on renal biopsy in HIV-infected black patients and is also the commonest cause of end-stage renal disease in these patients. Early detection of HIVAN may be beneficial in evaluating early treatment. This study examined the pattern of renal diseases in HIV-infected South Africans and also attempted to diagnose HIVAN at an early stage. In this single-center cross-sectional study, 615 HIV-infected patients were screened for proteinuria. Thirty patients with varying degrees of proteinuria underwent renal biopsy. Patients with diabetes mellitus, uncontrolled hypertension, known causes of chronic kidney disease, and serum creatinine above 250 mumol/l were excluded. Patients in this study were not on antiretroviral therapy. HIVAN was found in 25 (83%) patients. Six of them (24%) had microalbuminuria. Altogether, seven patients with persistent microalbuminuria were biopsied and six (86%) showed HIVAN. Other biopsy findings included membranoproliferative nephropathy in two (7%) and interstitial nephritis in three (10%). Four patients with HIVAN had associated membranous nephropathy. HIVAN is the commonest biopsy finding among our study patients with HIV infection who present with varying degrees of proteinuria. Microalbuminuria is a manifestation of HIVAN in our study patients. Therefore, microalbuminuria may be an early marker of HIVAN, and screening for its presence may be beneficial. Renal biopsy may be considered in seropositive patients who present with persistent microalbuminuria, especially with low CD4 counts irrespective of good renal function. This will allow diagnosis and treatment of HIVAN at an early stage and may prevent further disease progression.

Recommended dose for repair of serum vitamin A levels in patients with HIV infection/AIDS may be insufficient because of high urinary losses

OBJECTIVE

Retinol deficiency is quite frequent in the population of human immunodeficiency virus (HIV)-infected individuals. Serum retinol levels of less than 1.05 micromol/L determine a 3.5 to five times higher death risk. However, studies evaluating the efficacy of retinol supplementation in HIV-seropositive individuals have reported conflicting results. The World Health Organization recommends the treatment of vitamin A deficiency in seropositive individuals in the same manner as for seronegative individuals, but clinical studies proving the efficacy of this scheme are lacking. The proposal of the present study was to assess the efficacy of supplementation with high retinol doses in HIV-infected patients with vitamin A deficiency.

METHODS

Twenty-five adult HIV-seropositive individuals were monitored over a period of 9 months, with determination of serum and urinary retinol every 3 months. The subjects received retinol palmitate doses ranging from 300,000 IU to 600,000 IU. Patients whose retinol levels were higher than 1.60 micromol/L were only observed.

RESULTS

Eighteen patients received supplementation during clinical monitoring. The dose of 600,000 IU induced a significant mean increase in serum levels of 0.47 micromol/L (P = 0.049) within a period of three months. Those who received 300,000 IU presented a mean increase of 0.29 micromol/L. In contrast, the patients who did not receive replacement therapy presented a significant decrease (P = 0.017) in serum retinol levels, with initial and final values of 1.77 micromol/L and 1.55 micromol/L. The individuals with the worst response to supplementation presented a higher urinary loss of retinol at the beginning of the study. Even with a mean retinol supplementation of 771,428 IU during the study period, six patients had marginal serum retinol levels at the end of the study.

CONCLUSION

We conclude that, in view of the high urinary loss of this nutrient, there is the need to redefine the ideal dose for the treatment of HIV-infected individuals.

Renal tubular toxicity associated with tenofovir assessed using urine-beta 2 microglobulin, percentage of tubular reabsorption of phosphate and alkaline phosphatase levels

Despite its wide use, the renal tubular toxicity of tenofovir has not been fully evaluated. Twelve weeks after initiating a tenofovir-containing HAART regimen, a high urine-beta 2 microglobulin level was observed in 12 out of 17 patients, the percentage of tubular reabsorption of phosphate decreased from 96.0 to 91.1% and alkaline phosphatase increased from 294 to 365 U/l, whereas serum creatinine and phosphorus remained largely unchanged. Patients with the above findings should be monitored carefully for renal tubular toxicity.

Cystatin C--properties and use as diagnostic marker

This chapter focuses on the most well characterized inhibitors—cystatin C—and provide some information on its structure, biochemical properties, its role in normal and abnormal physiological processes, as well as on its use as a diagnostic marker. A major part of the cysteine proteases are evolutionary related to the structurally well–defined cysteine protease papain and are called papain–like cysteine proteases. The biological roles and the cystatin superfamily inhibitors of papain–like cystein proteases are also discussed. The aminoacid sequence and schematic structure of human cystatin C is also presented. The evolutionary relationships among all known inhibitory active human cystatins and kininogen cystatin domains are diagrammatically represented. The distribution of cystatins in body fluids and additional functions attributed to cystatin C are described. The serum or plasma cystatin C is used as a marker for glomerular filtration rate (GFR). The urine cystatin C is used as a marker for proximal tubular damage. The two types of brain hemorrhage associated with Cystatin C amyloid deposits are also demonstrated. The conditions connected with deposition of amyloid β–protein in cystatin C and cerebral hemorrhage is also provided.

Comparison of a neural network approach with five traditional methods for predicting creatinine clearance in patients with human immunodeficiency virus infection

STUDY OBJECTIVE

To compare the results of an artificial neural network approach with those of five published creatinine clearance (Cl(cr)) prediction equations and with the measured (true) Cl(cr) in patients infected with the human immunodeficiency virus (HIV).

DESIGN

Six-month prospective study.

SETTINGS

Two university medical centers.

PATIENTS

Sixty-five HIV-infected patients: 18 relatively healthy outpatients and 47 inpatients.

INTERVENTIONS

All subjects had urine collected for 24 hours to determine Cl(cr).

MEASUREMENTS AND MAIN RESULTS

The 16 input variables were age, ideal body weight, actual body weight, body surface area, height, and the following blood chemistries: sodium, potassium, aspartate aminotransferase, alanine aminotransferase, red blood cell count, platelet count, white blood cell count, glucose, serum creatinine, blood urea nitrogen, and albumin. The only output variable was Cl(cr). A training set of 55 subjects was used to develop the relationship between input variables and the output variable. The trained neural network was then used to predict Cl(cr) of a validation set of 10 subjects. Mean differences between predicted Cl(cr) and actual Cl(cr) (bias) were 4.1, 28.7, 29.4, 26.0, 31.8, and 55.8 ml/min/1.73 m2 for the artificial neural network, Cockcroft and Gault, Jelliffe 1, Jelliffe 2, Mawer et al, and Hull et al methods, respectively.

CONCLUSION

The accuracy of predicting Cl(cr) in subjects with HIV infection by the artificial neural network is superior to that of the five equations that are currently used in clinical settings.

Evidence for an essential role of megalin in transepithelial transport of retinol

Transepithelial transport of retinol is linked to retinol-binding protein (RBP), which is taken up and also synthesized in a number of epithelia. By immunocytochemistry of human, rat, and mouse renal proximal tubules, a strong staining in apical endocytic vacuoles, lysosomes, endoplasmic reticulum, Golgi, and basal vesicles was observed, in accordance with luminal endocytic uptake as well as a constitutive synthesis and basal secretion of RBP. Analysis of mice with target disruption of the gene for the major endocytic receptor of proximal tubules, megalin, revealed no RBP in proximal tubules of these mice. Western blotting and HPLC of the urine of the megalin-deficient mice instead revealed a highly increased urinary excretion of RBP and retinol, demonstrating that glomerular filtered RBP-retinol of megalin-deficient mice escapes uptake by proximal tubules. A direct megalin-mediated uptake of purified RBP-retinol was indicated by surface plasmon resonance analysis and uptake in immortalized rat yolk sac cells. Uptake was partially inhibited by a polyclonal megalin antibody and the receptor-associated protein. The present data show that the absence of RBP-binding megalin causes a significantly increased loss of RBP and retinol in the urine, demonstrating a crucial role of megalin in vitamin A homeostasis.

Micronutrients and the pathogenesis of human immunodeficiency virus infection

Micronutrient deficiencies may be common during human immunodeficiency virus (HIV) infection. Insufficient dietary intake, malabsorption, diarrhoea, and impaired storage and altered metabolism of micronutrients can contribute to the development of micronutrient deficiencies. Low plasma or serum levels of vitamins A, E, B6, B12 and C, carotenoids, Se, and Zn are common in many HIV-infected populations. Micronutrient deficiencies may contribute to the pathogenesis of HIV infection through increased oxidative stress and compromised immunity. Low levels or intakes of micronutrients such as vitamins A, E, B6 and B12, Zn and Se have been associated with adverse clinical outcomes during HIV infection, and new studies are emerging which suggest that micronutrient supplementation may help reduce morbidity and mortality during HIV infection.