Fibroblast growth factor 23 is elevated in tenofovir-related hypophosphatemia

Fanconi Syndrome in Patients With Human Immunodeficiency Virus Treated With Tenofovir-Based Antiretroviral Therapy: A Systematic Literature Review

OBJECTIVE

Several cases of Fanconi syndrome (FS), a severe form of nephrotoxicity, have been reported in patients with HIV on tenofovir-containing antiretroviral therapy. A systematic review of the published literature on tenofovir-related FS in patients with HIV was conducted.

DATA SOURCES

PubMed and Embase were queried to identify articles in English published between January 2005 and June 2023, reporting tenofovir-related FS in adults with HIV. Preclinical studies, conference/poster abstracts, commentaries and responses, and review papers were excluded.

STUDY SELECTION AND DATA EXTRACTION

Of the 256 articles screened, 57 met the inclusion criteria. These comprised 37 case reports, 11 case series, 1 cross-sectional study, 1 case-control study, 4 cohort studies, 1 single-arm open-label clinical trial, 1 sub-analysis of clinical trials, and 1 pooled analysis of clinical trials.

DATA SYNTHESIS

Among 56 cases on which information was abstracted, median age at FS diagnosis was 50 years, 51.8% were men, and duration of tenofovir use ranged from 6 weeks to 11 years. Ritonavir was co-prescribed in almost half the cases. In observational and interventional studies, incidence of FS was low. Many studies reported resolution of FS symptoms after tenofovir discontinuation. All FS occurrences were identified in those on tenofovir disoproxil fumarate (TDF), except for one patient on tenofovir alafenamide (TAF).

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

Continuous monitoring of signs and symptoms of renal and bone toxicity is essential for patients with HIV on tenofovir-containing therapy.

CONCLUSIONS

Occurrence of FS is low in patients with HIV treated with tenofovir-based regimens. Concomitant use of ritonavir may increase risk of FS. TAF may be a safer alternative than TDF in terms of nephrotoxicity.

Impact of Tenofovir Disoproxil-Induced Fanconi Syndrome on Bone Material Quality: A Case Report

Tenofovir is a nucleotide analog reverse‐transcriptase inhibitor (NtARTI) used for treatment of chronic hepatitis B and human immunodeficiency virus (HIV). Fanconi syndrome (FS) is a condition affecting the proximal tubules of the kidney, leading to increased passage and impaired reabsorption of various small molecules such as glucose, phosphate, bicarbonate, and amino acids. Tenofovir disoproxil fumarate (TDF) is one of two pro‐drugs of tenofovir associated with a greater nephrotoxicity and renal complications such as FS with subsequent osteomalacia, acute kidney injury, and reduction of glomerular filtration rate (GFR) compared with tenofovir alafenamide (TAF). We present the case of a 33‐year‐old white woman treated with TDF because of chronic hepatitis B infection suffering four atraumatic fractures over the period of 2 years. The patient was taken off the TDF regimen 3 months before presentation. Initial blood and urine samples suggested the presence of TDF‐induced osteomalacia, which was confirmed by transiliac bone biopsy and histomorphometry. Moreover, bone mineral density distribution (BMDD) by quantitative backscattered electron imaging (qBEI) analysis showed that approximately 56% of the bone surface was normally mineralized and 44% showed a reduced mineralization consistent with the presence of osteomalacia. The patient made a significant recovery upon cessation of the causative agent. This case report emphasizes the use of bone biopsy, histomorphometry and qBEI in confirming the diagnosis of drug‐induced Fanconi syndrome and associated osteomalacia. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Bone loss in hepatitis B virus-infected patients can be associated with greater osteoclastic activity independently of the retroviral use

Nucleoside/nucleotide analogs such as tenofovir, have been used as long-term therapy for the treatment of hepatitis B and side effects such as the reduction in bone mineral density have been associated with their use. To determine the relationships between bone, hormonal, biochemical, and mineral parameters in patients with hepatitis B treated with nucleoside/nucleotide antiviral. A cross-sectional study was conducted with 81 adult patients with chronic hepatitis B infection. Dual-energy X-ray absorptiometry (DXA) was performed to assess bone mineral density. Biochemical analyses were performed for osteocalcin, deoxypyridinoline, parathyroid hormone, vitamin D, IGF-1, TSH, testosterone, estradiol, FSH, transaminases, urea, creatinine, calcium, serum and urinary phosphorus, magnesium, and FGF-23, body composition was performed by DXA. Participants, both gender, were divided according to the use of antiretrovirals: Group1: 27 inactive virus carriers without medication; Group2: 27 patients using tenofovir; and Group3: 27 patients using lamivudine or entecavir. DXA readings diagnosed osteopenia in the lumbar spine for 7.4% of individuals in Group1, 15% in Group2, and 3.7% in Group3. For all groups, we observed normal values in bone formation markers, osteocalcin levels as well as parathyroid hormone, insulin growth factor 1, and FGF-23. In all groups, we found increased levels of urinary deoxypyridinoline, a bone resorption marker. Increased levels in the bone resorption markers indicated a high resorptive activity of bone tissue. These data suggested high resorption activity of bone tissue in hepatitis B virus-infected patients independent of the use of antiretrovirals.

Consensus Recommendations for the Diagnosis and Management of X-Linked Hypophosphatemia in Belgium

X-linked hypophosphatemia (XLH) is the most common genetic form of hypophosphatemic rickets and osteomalacia. In this disease, mutations in the PHEX gene lead to elevated levels of the hormone fibroblast growth factor 23 (FGF23), resulting in renal phosphate wasting and impaired skeletal and dental mineralization. Recently, international guidelines for the diagnosis and treatment of this condition have been published. However, more specific recommendations are needed to provide guidance at the national level, considering resource availability and health economic aspects. A national multidisciplinary group of Belgian experts convened to discuss translation of international best available evidence into locally feasible consensus recommendations. Patients with XLH may present to a wide array of primary, secondary and tertiary care physicians, among whom awareness of the disease should be raised. XLH has a very broad differential-diagnosis for which clinical features, biochemical and genetic testing in centers of expertise are recommended. Optimal care requires a multidisciplinary approach, guided by an expert in metabolic bone diseases and involving (according to the individual patient's needs) pediatric and adult medical specialties and paramedical caregivers, including but not limited to general practitioners, dentists, radiologists and orthopedic surgeons. In children with severe or refractory symptoms, FGF23 inhibition using burosumab may provide superior outcomes compared to conventional medical therapy with phosphate supplements and active vitamin D analogues. Burosumab has also demonstrated promising results in adults on certain clinical outcomes such as pseudofractures. In summary, this work outlines recommendations for clinicians and policymakers, with a vision for improving the diagnostic and therapeutic landscape for XLH patients in Belgium.

Serum Levels of Fibroblast Growth Factor 23 in People Living with HIV

BACKGROUND

Fibroblast growth factor (FGF) 23 is a well-known phosphaturic hormone produced mainly by bone cells to maintain phosphate and mineral homeostasis. Serum FGF23 levels are elevated in patients with chronic kidney disease (CKD), and elevated FGF23 might increase the risk of cardiovascular disease (CVD). Several reports have documented an increased incidence of risk factors for osteopenia, CKD, and CVD in people living with HIV (PLWH). However, few reports related to FGF23 in PLWH have been published.

METHODS

Male HIV patients who presented to the outpatient clinic of Teikyo University Hospital, Tokyo, Japan, in 2015 and were treated with antiretroviral therapy (ART) for > 6 months were enrolled in the study. In addition to serum FGF23 measurements, the clinical factors assessed included age, ART regimens, and laboratory data. Spearman correlation and multiple regression analysis were performed to determine factors significantly associated with FGF23.

RESULTS

In total, 67 patients were enrolled in the present study. The median age was 43.7 years, the median CD4 count was 529 cells/μL, and the median serum FGF23 level was 36.0 pg/mL. Based on correlation and multiple regression analyses, serum FGF23 levels were significantly correlated with HIV RNA > 50 copies (correlation analysis: t = 3.4259, P = 0.0011 / multiple regression analysis: P = 0.00106) or abacavir (ABC)/lamivudine (3TC) use (t = 2.8618, P = 0.0057 / P = 0.02704).

CONCLUSION

Factors significantly associated with elevated serum FGF23 levels included poor virologic control and ABC/3TC use.

Influence of antiretroviral therapy on bone metabolism of patients with chronic hepatitis B: a review

Hepatitis B is a major public health problem worldwide and associated with significant mortality. To prevent or delay the deleterious effects of chronic infection by the hepatitis B virus, patients should be carefully followed, and antiviral therapy indicated according to specific recommendations. Currently, available drugs inhibit viral replication and slow or stop the progression of inflammation and fibrosis of the liver. However, the drugs for oral use in the treatment of hepatitis B, jointly referred to as nucleoside/nucleotide analogs, are indicated for prolonged use and have potential side effects. The reduction in bone mineral density was associated with the use of tenofovir, already evaluated in patients infected with HIV because the drug is also part of the therapeutic arsenal for this viral infection. There are few studies on the effects of tenofovir in patients with mono hepatitis B. Therefore, this literature review proposes to examine how hepatitis B acts in the body and the mechanisms by which antiretroviral drugs (especially tenofovir) can affect bone metabolism.

Effect of Vitamin D Supplementation on Bone Turnover Markers During HIV Pre-Exposure Prophylaxis Using Tenofovir Disoproxil Fumarate-Emtricitabine in Men Who Have Sex with Men

Pre-exposure prophylaxis (PrEP) with tenofovir disoproxil fumarate-emtricitabine (TDF-FTC) reduces bone mineral density in HIV-uninfected men who have sex with men (MSM). We hypothesized that PrEP with TDF-FTC would increase bone turnover markers (BTMs) at week 24 and that vitamin D supplementation from weeks 24 to 48 would blunt this increase. Participants were from a cohort of 398 MSM and transgender women who received daily TDF-FTC for PrEP. At week 24, a prospective intervention group initiated vitamin D3 4,000 IU daily. Concurrent controls were selected from the cohort who took ≤400 IU/day of vitamin D3 matched by age, race, and body mass index. The primary endpoint was the change in procollagen-I N-terminal propeptide (P1NP) from weeks 24 to 48. Paired t-tests were used to compare changes in BTMs between intervention and controls. Among 48 intervention-control pairs, median age was 33 years. At baseline, 68.9% of the intervention group and 77.3% of controls were vitamin D sufficient (≥20 ng/mL, p = .94). P1NP, C-telopeptide, parathyroid hormone (PTH), and 25-OH vitamin D3 did not increase significantly at week 24. P1NP fell by a mean ± SD of -27.6 ± 49.9 pg/mL from weeks 24 to 48 with vitamin D and -2.5 ± 40.2 pg/mL in controls (p = .01). There were no significant between-group differences in the weeks 24-48 change in C-telopeptide, PTH, or 25-OH vitamin D3. Vitamin D3 supplementation with 4,000 IU/day resulted in a significant reduction in the BTM P1NP compared with controls, suggesting that this intervention has potential to improve bone health during PrEP.

The prevalence of low serum free testosterone and the short-term effect of anti-retroviral therapy in male Japanese treatment-naïve HIV patients

OBJECTIVES

The prevalence of hypogonadism in HIV patients is still a matter of debate. Today, serum free testosterone (fTST) is thought to be more important than serum testosterone in the diagnosis of hypogonadism in patients with HIV. This study aimed to determine the prevalence of low fTST levels and the effects of anti-retroviral therapy (ART) on fTST levels in treatment-naïve male Japanese patients with HIV.

METHODS

Patients who visited Teikyo University Hospital, Japan between 2010 and 2016 were enrolled. Patients' fTST levels were evaluated twice with a radioimmunoassay in the morning, at the onset of ART and one year later. Clinical factors were also reviewed. The patients were divided into two groups ('hypogonadism' and 'normal') based on Japanese criteria. To determine factors related to low fTST in treatment-naïve patients, the Mann-Whitney U test and a multiple-regression analysis were used. Changes in fTST levels after ART initiation were evaluated with a paired t-test.

RESULTS

Data from 25 patients were collected. Their median age was 36.0 years, and the median fTST level was 8.00 pg/ml in the treatment-naïve state. Thirteen patients (52%) were in the hypogonadism group. Low levels of fibroblast growth factor 23 were significantly related to low fTST levels. After the start of ART, fTST levels increased significantly (median 8.00 interquartile range [6.40-9.70] to 9.60 [7.60-13.10] pg/ml, p = 0.0081).

CONCLUSIONS

Subnormal fTST levels occurred frequently among the present study patients in treatment-naïve settings. Free testosterone levels in patients with HIV were significantly increased one year after the start of ART.

Adefovir-induced Fanconi syndrome associated with osteomalacia

Fanconi syndrome is a dysfunction of the proximal renal tubules that results in impaired reabsorption and increased urinary loss of phosphate and other solutes. The pathophysiology of drug-induced Fanconi syndrome is unclear. Here we report the case of a 36-year-old woman who presented with pain in multiple bones and proteinuria. She had a 7-year history of taking adefovir at 10 mg/day for chronic hepatitis B. Three years previously she had received surgery for a nontraumatic right femur neck fracture, after which she continued to complain of pain in multiple bones, and proteinuria, glycosuria, and phosphaturia were noted. The findings of a light-microscope examination of a renal biopsy sample were normal, but mitochondrial damage of the proximal tubules was evident in electron microscopy. Western blot analysis revealed that the level of serum fibroblast growth factor 23 (FGF23) was lower than in normal controls. After 2 months of treatment, hypophosphatemia and proximal tubular dysfunction were reversed, and serum FGF23 had normalized. This case suggests that direct mitochondrial damage in proximal tubules can cause drug-induced Fanconi syndrome associated with osteomalacia.

Hypocalcaemic and hypophosphatemic rickets

Rickets refers to deficient mineralization at the growth plate and is usually associated with abnormal serum calcium and/or phosphate. There are several subtypes of rickets, including hypophosphatemic rickets (vitamin-D-resistant rickets secondary to renal phosphate wasting), vitamin D-dependent rickets (defects of vitamin D metabolism) and nutritional rickets (caused by dietary deficiency of vitamin D, and/or calcium, and/or phosphate). Most rickets manifest as bone deformities, bone pain, and impaired growth velocity. Diagnosis of rickets is established through the medical history, physical examination, biochemical tests and radiographs. It is of crucial importance to determine the cause of rickets, including the molecular characterization in case of vitamin D resistant rickets, and initiate rapidly the appropriate therapy. In this review, we describe the different causes and therapies of genetic and nutritional rickets, supported by the recent progress in genetics and development of novel molecules such as anti-FGF23 antibody.

Bone Health and Impact of Tenofovir Treatment in Men with Hepatitis-B Related Chronic Liver Disease

BACKGROUND

Chronic Liver Disease (CLD) has been shown to have an adverse impact on bone health. Hepatitis-B related CLD and its treatment with tenofovir may have additional effects on skeleton.

OBJECTIVE

To study the impact of HBV related CLD and its treatment with Tenofovir on bone health in Indian subjects.

METHODS

This cross sectional study included men (18-60 years) and comprised of three groups: Group-1 was treatment naïve HBV related CLD (n = 79), Group-2 those with HBV related CLD on tenofovir for at least 1 year (n = 136), Group-3 age, sex and Body Mass Index (BMI) matched healthy controls (n = 58). Bone biochemistry and Bone Mineral Density (BMD) at spine, Femoral Neck (FN) and forearm were studied. Independent t-test or ANOVA was used to compare the means of continuous variables and chi-square test for categorical variables. Multiple logistic regression was used to assess the factors causing Low Bone Mass (LBM) at FN.

RESULTS

A significantly greater proportion (P < 0.05) of patients (40%) with CLD (group 1 and group 2) had vitamin D deficiency (<20 ng/ml) in comparison with control group (22%). The mean serum C-Terminal telopeptide was significantly higher (P < 0.05) and the mean BMD was significantly lower (P < 0.05) in subjects with HBV related CLD than controls. The prevalence of LBM was higher in group 1 at the spine (31%) and forearm (18.4%) when compared to controls (8.1% and 7.8% respectively) (P < 0.05). The proportion of patients with LBM at FN was highest in group 2 (12.3%) compared to those in group 1 (8%) and group 3 (4%) (P < 0.05). Advanced age, low BMI, and high viral load (>10,000 IU/ml) emerged as significant risk factors for LBM at FN.

CONCLUSION

The impact of hepatitis-B related CLD as well as its treatment on bone health is significant. Bone health need to be periodically evaluated in these subjects especially in older men who are lean and have a higher viral load.

Serum FGF23 levels may not be associated with serum phosphate and 1,25-dihydroxyvitamin D levels in patients with Fanconi syndrome-induced hypophosphatemia

Fibroblast growth factor 23 (FGF23) is regulated by sustained phosphate supplementation and restriction. However, few studies have investigated FGF23 levels in patients with Fanconi syndrome. Therefore, we evaluated intact and C-terminal FGF23 and FGF23-associated parameters in four patients with Fanconi syndrome. Serum intact and C-terminal FGF23 levels were extremely low. Although serum phosphate and 1,25-dihydroxyvitamin D levels improved to or above the normal range within 1 year of treatment with oral phosphate and calcitriol, serum FGF23 levels remained low. Serum FGF23 levels in patients with Fanconi syndrome might be regulated by novel factors other than serum phosphate and 1,25-dihydroxyvitamin D levels.

Correlates and Longitudinal Renal and Cardiovascular Implications of FGF23 Levels in HIV-Positive Individuals

Fibroblast growth factor23 (FGF23), an early marker of kidney dysfunction, is associated with cardiovascular death. Its role in HIV-positive individuals is unknown. We measured FGF23 in 100 HIV-negative and 191 HIV-positive nondiabetic adults with normal baseline estimated glomerular filtration rate (GFR). We measured GFR by iohexol annually, albumin-creatinine ratio (ACR) every 6 months, as well as pulse wave velocity, carotid plaque, and carotid intima media thickness (IMT) at baseline and 2 years. Progressive albuminuria was defined as follow-up ACR ≥2-fold than baseline and ≥30 mg/g. Regression models assessed associations of FGF23 with baseline factors and longitudinal changes in disease markers. FGF23 levels were similar in HIV serostatus. Among HIV-positive persons, factors independently associated with higher baseline FGF23 levels included female (adjusted ratio of geometric means [95% CI],1.46 [1.21,1.76]), serum phosphorus (1.20 [1.03,1.40]), HCV (1.31 [1.10,1.56]) and non-suppressed HIV RNA (1.27 [1.01,1.76]). At baseline, FGF23 was not associated with GFR, albuminuria, carotid plaque, or carotid IMT in cross-sectionally adjusted analysis of HIV-positive individuals. However, higher baseline FGF23 was associated with progressive albuminuria (odds ratio1.48 [95% CI]:1.05,2.08) and a more rapid increase in IMT (13 μm/year, 95% CI,3,24). These findings suggest a role for FGF23 in HIV-positive populations in identifying patients at greater risk for cardiovascular and kidney disease.

Tenofovir monotherapy for hepatitis B after 1 year does not produce renal dysfunction, but is associated with hyperparathyroidism not related to vitamin D

INTRODUCTION

Viral hepatitis B (VHB) represents a major public health problem. Studies from HIV multidrug patients have associated the use of tenofovir disoproxil fumarate (TDF) with renal dysfunction and phosphate wasting.

OBJECTIVE

The aim of this study was to examine the effect of year-long TDF monotherapy on renal function in VHB patients.

PATIENTS AND METHODS

We evaluated adult patients diagnosed with VHB before treatment initiation (T0), and after 3 and 12 months (T3 and T12) of TDF initiation. Estimated glomerular filtration rate (eGFR) was estimated by serum cystatin C and creatinine. In addition, urinary electrolytes and tubular biomarkers (cystatin C, β2-microglobulin and neutrophil gelatinase-associated lipocalin) were analyzed, as well as parathyroid hormone (PTH) and 25(OH)vitamin D levels.

RESULTS

After 1 year, 32 patients completed the study, 22 (68.7%) men and 12 (37.5%) Whites, mean age 44.1±12.0 years. We found that serum electrolytes were similar at baseline and 3 or 12 months after initiation of TDF monotherapy. In addition, urinary fractional excretions of electrolytes as well as proteinuria, albuminuria, urinary β2-microglobulin, and urinary cystatin C showed no significant differences across the treatment timeline. There were also no statistical differences in the eGFR. There was a statistically significant increase in the PTH (Friedman's test, P=0.012), but the 25(OH)vitamin D levels were in the normal range in the beginning and did not change at the follow-up. Moreover, there was no correlation between the initial levels of vitamin D and the corresponding increases in the PTH values.

CONCLUSION

If used as monotherapy in hepatitis B patients for a 12-month period, TDF is not associated with changes in either eGFR or a panel of urinary biomarkers. Serum and urinary electrolytes also remained unchanged. Of note, a significant increase in the PTH was found, although not related to the 25(OH)vitamin D initial status.