Plasma Apolipoprotein L1 Levels Do Not Correlate with CKD

Polymorphisms in APOL1 are associated with CKD, including HIV-related CKD, in individuals of African ancestry. The apolipoprotein L1 (APOL1) protein circulates and is localized in kidney cells, but the contribution of APOL1 location to CKD pathogenesis is unclear. We examined associations of plasma APOL1 levels with plasma cytokine levels, dyslipidemia, and APOL1 genotype in a nested case-control study (n=270) of HIV-infected African Americans enrolled in a multicenter prospective observational study. Patients were designated as having CKD when estimated GFR (eGFR) decreased to <60 ml/min per 1.73 m² (eGFR<60 cohort) or protein-to-creatinine ratios became >3.5 g/g (nephrotic proteinuria cohort). Circulating APOL1 levels did not associate with APOL1 genotype, CKD status, or levels of proinflammatory cytokines, but did correlate with fasting cholesterol, LDL cholesterol, and triglyceride levels. At ascertainment, CKD-associated polymorphisms (risk variants) in APOL1 associated with the eGFR<60 cohort, but not the nephrotic-range proteinuria cohort. Of note, in both the eGFR<60 and nephrotic proteinuria cohorts, CKD cases with two APOL1 risk variants had significant declines in eGFR over a median of 4 years compared with individuals with one or no risk variants. APOL1 risk genotype was not associated with changes in proteinuria. Higher circulating proinflammatory cytokine levels were independently associated with CKD but not APOL1 genotype. In conclusion, the function of variant APOL1 proteins derived from circulation or synthesized in the kidney, but not the level of circulating APOL1, probably mediates APOL1-associated kidney disease in HIV-infected African Americans.Nondiabetic CKD in individuals of African ancestry have been linked to polymorphisms in the gene for apolipoprotein L1 (APOL1),^1–5 a protein component of HDL particles with a known function in the immune clearance of Trypanosoma brucei infections.⁶ CKD is associated with two coding variants of the APOL1 gene known as G1 and G2, both of higher allele frequency in African and African descendent populations compared with white populations where they are almost absent. Evidence suggests that the prevalence of the G1 and G2 variants may have increased in African populations because of a selective advantage from their ability to kill a broader range of Trypanosoma species.^1,2,7 Individuals carrying at least one G1 or G2 allele have additional protection from trypanosomiasis; however, individuals with two G1 or G2 alleles are at increased risk for nondiabetic CKD.^2,4,5The pathogenic mechanisms responsible for CKD associated with APOL1 risk variants are unknown. We recently showed that, in addition to being secreted and circulated in the blood,⁸ APOL1 is localized in podocytes, proximal tubular epithelial cells, and small-artery endothelium in normal kidney.⁹ Thus, the contribution of circulating versus kidney-localized variant APOL1s to CKD pathogenesis is unknown. In kidney transplantation, two studies suggest that graft loss is associated with the APOL1 genotype of the allograft, not the recipient.^10,11 However, the association of APOL1 plasma levels with CKD phenotypes or APOL1 genotype has not been studied.To address these issues, we examined circulating APOL1 levels with APOL1 genotype and renal function in HIV-infected African Americans in the AIDS Clinical Trials Group (ACTG) Longitudinal Linked Randomized Trials (ALLRT) cohort because the occurrence of HIV-associated nephropathy (HIVAN) and renal outcomes in HIV-infected patients are strongly associated with APOL1 risk alleles.^12–14 In addition, we examined the relationship between circulating APOL1 levels and proinflammatory cytokines known to induce APOL1 expression and previously associated with CKD and HIV/AIDS progression.^15,16 Additional analyses examined associations of APOL1 levels with dyslipidemia and the role of APOL1 genotype on CKD progression using longitudinal data.     

The vaso-occlusive pain crisis in sickle cell disease: Definition,pathophysiology, and management

Early diagnosis, treatment, and prevention of a vaso-occlusive crisis (VOC) are critical to the management of patients with sickle cell disease. It is essential to differentiate between VOC-associated pain and chronic pain, hyperalgesia, neuropathy, and neuropathic pain. The pathophysiology of VOCs includes polymerization of abnormal sickle hemoglobin, inflammation, and adhesion. Hydroxyurea, L-glutamine, crizanlizumab, and voxelotor have been approved by the US Food and Drug Administration for reducing the frequency of VOCs; the European Medicines Agency has approved only hydroxyurea. Other novel treatments are in late-stage clinical development in both the United States and the European Union. The development of agents for prevention and treatment of VOCs should be driven by our understanding of its pathophysiology.     

Pattern of microbial translocation in patients living with HIV-1 from Vietnam,Ethiopia and Sweden

Introduction

The role of microbial translocation (MT) in HIV patients living with HIV from low- and middle-income countries (LMICs) is not fully known. The aim of this study is to investigate and compare the patterns of MT in patients from Vietnam, Ethiopia and Sweden.

Methods

Cross-sectional samples were obtained from treatment-naïve patients living with HIV-1 and healthy controls from Vietnam (n=83; n=46), Ethiopia (n=9492; n=50) and Sweden (n=51; n=19). Longitudinal samples were obtained from a subset of the Vietnamese (n=24) in whom antiretroviral therapy (ART) and tuberculostatics were given. Plasma lipopolysaccharide (LPS), sCD14 and anti-flagellin IgG were determined by the endpoint chromogenic Limulus Amebocyte Assay and enzyme-linked immunosorbent assay.

Results

All three biomarkers were significantly increased in patients living with HIV-1 from all countries as compared to controls. No differences were found between males and females. Vietnamese and Ethiopian patients had significantly higher levels of anti-flagellin IgG and LPS, as compared to Swedes. ART reduced these levels for the Vietnamese. Vietnamese patients given tuberculostatics at initiation of ART had significantly lower levels of anti-flagellin IgG and higher sCD14. The biomarkers were lower in Vietnamese who did not develop opportunistic infection.

Conclusions

Higher MT is common in patients living with HIV compared to healthy individuals, and in patients from LMICs compared to patients from a high-income country. Treatment with tuberculostatics decreased MT while higher levels of MT are associated with a poorer clinical outcome.