Clinicopathologic Study of Sickle Cell-associated Kidney Disease: A Nigerian Experience.

BACKGROUND: Improvements in sickle cell disease (SCD) care have resulted in the survival of many patients into adulthood, although this is accompanied by the increased incidence of end-organ damage, including chronic kidney disease (CKD). OBJECTIVES: This study assessed the prevalence, pattern and predictors of renal dysfunction in SCD patients and investigated the associated renal histopathologic changes. METHODS: We evaluated 105 patients with SCD, for proteinuria, estimated glomerular filtration rate (eGFR), and tubular dysfunction. Renal biopsy was conducted on 22 patients who qualified. Data were analysed using SPSS package version 23. RESULTS: Thirty-seven (35.2%) of the 105 patients had CKD, as defined by an eGFR of 60 ml/min/1.73 m2 and/or proteinuria. The fractional excretion of potassium (FEK) was elevated in all patients, whereas the fractional excretion of sodium (FENa) was elevated in 98.1%. Glomerular filtration rate was negatively correlated with irreversible percentage sickle cell count (r = -0.616, P = 0.0001), FEK (r = -0.448, P = 0.0001) and FENa (r = -0.336, P = 0.004). Age, irreversible percentage sickle cell count, haemoglobin levels and FENa were the major predictors of CKD. The histological pattern in the 22 patients who had biopsies was consistent with mesangioproliferative glomerulonephritis 11 (50%), minimal change disease 6 (27.3%), focal segmental glomerulosclerosis 3 (13.6%) and interstitial nephritis 2 (9.1%). CONCLUSIONS: CKD was prevalent in SCD patients, and it was characterised by tubular dysfunction and mesangioproliferative glomerulonephritis. The main predictors of CKD were increased age, severity of vaso-occlusive crisis, worsening anaemia and tubular dysfunction.

The Effects of Race on Acute Kidney Injury.

Racial disparities in incidence and outcomes of acute kidney injury (AKI) are pervasive and are driven in part by social inequities and other factors. It is well-documented that Black patients face higher risk of AKI and seemingly have a survival advantage compared to White counterparts. Various explanations have been advanced and suggested to account for this, including differences in susceptibility to kidney injury, severity of illness, and socioeconomic factors. In this review, we try to understand and further explore the link between race and AKI using the incidence, diagnosis, and management of AKI to illustrate how race is directly related to AKI outcomes, with a focus on Black and White individuals with AKI. In particular, we explore the effect of race-adjusted estimated glomerular filtration rate (eGFR) equation on AKI prediction and discuss racial disparities in the management of AKI and how this might contribute to racial differences in AKI-related mortality among Blacks with AKI. We also identify some opportunities for future research and advocacy.

Association of chronic inflammation and accelerated atherosclerosis among an indigenous black population with chronic kidney disease.

INTRODUCTION: Inflammation plays a major role in the development of atherosclerosis and cardiovascular morbidity and mortality in chronic kidney disease (CKD) patients. Toll-like receptor-4 (TLR4) is a major receptor for lipopolysaccharides (endotoxin) and other ligands involved in the pathogenesis of inflammation. We determined whether endotoxin levels and the presence of TLR4 polymorphisms are associated with markers of inflammation and atherosclerosis among South African CKD patients. MATERIALS AND METHODS: Endotoxin, lipopolysaccharide binding protein (LBP), serum CD14 (sCD14), interleukin-8 (IL-8), monocyte chemoattractant protein-1 (MCP-1) and carotid intima media thickness (CIMT) were measured in 160 participants (120 CKD patients and 40 controls). Associations between endotoxins and CIMT in the presence of sCD14, IL-8 and MCP-1, were assessed using odds ratios. Participants were screened for the presence of Asp299Gly and Thr399Ile TLR4 polymorphisms, and CIMT and inflammatory markers were compared between subjects with and without TLR4 polymorphisms. RESULTS: Endotoxin levels correlated with sCD14 (r = 0.441, p<0.001) and MCP-1 (r = 0.388, p<0.001) levels while increased CIMT was associated with MCP-1 (r = 0.448, p<0.001), sCD14 levels (r = 0.476, p<0.001), LBP (r = 0.340, p<0.001), and IL-8 (r = 0.395, p<0.001). Atherosclerosis was associated with endotoxin levels (odds ratio: 4.95; 95% confidence interval: 2.52-9.73; p<0.001), and was predicted by higher serum levels of inflammatory markers. Analysis of patients with TLR4 polymorphisms showed reduced serum levels of inflammatory markers and CIMT values compared with the patients carrying the wild type TLR4 alleles. CONCLUSION: The study demonstrated associations between circulating endotoxaemia, systemic inflammation and accelerated atherosclerosis among South African CKD patients, and showed that the atherogenic predictive power of endotoxaemia was significantly increased by the presence of elevated levels of inflammatory markers. Additional findings, which must be confirmed, suggest that TLR4 polymorphisms are associated with low levels of inflammatory markers and CIMT values.

APOL1 Genetic Variants Are Associated with Serum-Oxidized Low-Density Lipoprotein Levels and Subclinical Atherosclerosis in South African CKD Patients.

INTRODUCTION: Apolipoprotein L1 (APOL1) plays an important role in cholesterol metabolism and attenuation of low-density lipoprotein (LDL) oxidation. While protecting against Trypanosoma brucei rhodesiense infection, APOL1 risk alleles confer greater risk for CKD and cardiovascular disease among patients of African descent. OBJECTIVES: We investigated whether APOL1 risk variants are associated with atherosclerosis and oxidized LDL (OxLDL) levels among black South African CKD patients. METHODS: A cross-sectional study of 120 adult CKD patients and 40 controls was undertaken. DNA samples of participants were genotyped for APOL1 G1 and G2 variants. High-sensitivity C-reactive protein, serum lipids, and OxLDL levels were measured, and carotid doppler ultrasonography was performed on all participants. RESULTS: APOL1 alleles rs73885319, rs60910145, and rs71785313 had minor allele frequencies of 9.2, 8.8, and 17.5%, respectively, in the patients, and 8.8, 8.8, and 13.8%, respectively, in the controls. Of the 9 patients with 2 APOL1 risk alleles, 77.8% were compound G1/G2 heterozygotes and 22.2% were G2 homozygotes. Carriers of at least 1 APOL1 risk allele had a 3-fold increased risk of subclinical atherosclerosis (odds ratio 3.19; 95% confidence interval: 1.64-6.19; p = 0.01) compared to individuals with no risk alleles. Patients with 1 or 2 APOL1 risk alleles showed a significant increase in OxLDL levels when compared with those without the APOL1 risk allele. CONCLUSION: These findings suggest an increased risk for atherosclerosis in carriers of a single APOL1 risk variant, and the presence of APOL1 risk variants was associated with increased serum OxLDL levels in black South African CKD patients.

Interleukin-6 gene polymorhisms and interleukin-6 levels are associated with atherosclerosis in CKD patients.

Inflammation is a major risk factor for atherosclerosis. Genetic polymorphisms in the inflammatory cytokine genes have been associated with atherosclerosis. Because levels of inflammatory cytokines are markedly elevated in patients with chronic kidney disease (CKD), we hypothesized that genotypic variations in the interleukin-6 (IL-6) gene are a cause of systemic inflammatory states and atherosclerosis in South African CKD patients. 120 CKD patients and 40 healthy controls were included. Serum IL-6 and high-sensitivity C-reactive protein (hs-CRP) levels were measured. Functional polymorphisms in the IL-6 genes were genotyped using polymerase chain reaction-sequence specific primer (PCR-SSP) methods. Carotid intima-media thickness (CIMT) and the presence of plaque were assessed by B-mode ultrasonography. Serum IL-6 and hs-CRP levels were increased in patients with CKD compared with healthy controls (p < 0.001). In CKD patients, serum IL-6 above the median value was associated with carotid plaque (OR: 2.11; 95% CI: 1.74 - 2.57, p = 0.004), with excess risk confined to the group with high IL-6 levels. Significant associations were found between the IL-6 gene and atherosclerosis in the CKD group (for G/G genotype: OR = 1.21, 95% CI = 1.05 - 1.39, p = 0.012; for GG+GC vs. CC: OR = 1.14, 95% CI = 1.02 - 1.28, p = 0.035). Patients with GG+GC genotype of the IL-6 gene polymorphism had higher levels of IL-6 than those with CC genotype (p = 0.029). In South African CKD patients, the IL-6 gene promoter polymorphism is associated with high serum IL-6 levels and atherosclerosis. The relationship between atherosclerosis and -174G/C polymorphism in the IL-6 gene suggests that IL-6 may be a potential pro-inflammatory mediator of atherosclerosis in CKD patients.

Atherosclerotic vascular disease and its correlates in stable black South African kidney transplant recipients.

BACKGROUND: Despite remarkable improvement in renal function attributable to kidney transplantation, the burden of cardiovascular disease (CVD) among kidney transplant recipients (KTRs) remains high in the post-transplant period. Aggressive use of statins in KTRs may make lipoprotein ratios correlate better with atherosclerotic vascular disease (AsVD) when compared with traditional lipid profile parameters. We therefore evaluated the clinical and echocardiographic correlates of AsVD among non-diabetic, stable, black KTRs in South Africa. METHODS: This was a cross-sectional study of 41 adult (18-65 years), non-diabetic, stable KTRs and 41 age- and sex-matched healthy controls. An interviewer-administered questionnaire was used to obtain information on participants' sociodemographic and cardiovascular risk factors. Anthropometric parameters were measured. Urine and blood samples were obtained and analyzed. Echocardiography was performed and carotid intima media thickness (CIMT) was assessed in both right and left carotid arteries. Spearman's rank correlation and binary logistic regression were performed to determine the relationship between CVD risk factors and AsVD. RESULTS: AsVD was present in 46.3% of KTRs compared to 17.1% of healthy controls (p = 0.004). Left ventricular hypertrophy was present in 92.7% of the KTRs. There were statistically significant differences in waist-hip ratio, systolic blood pressure, mean arterial pressure, urine albumin-creatinine ratio, serum fibrinogen, serum creatinine, estimated glomerular filtration rate, left atrial diameter, left ventricular mass (LVM), and left ventricular mass index (LVMI) between KTRs and controls. A positive relationship was seen between CIMT and certain risk factors for CVD including LVM, LVMI, and mitral valve deceleration time, (p < 0.001). Castelli index 2 and lipoprotein combine index (LCI) showed positive correlation with CIMT. On multivariate analysis, increasing age and kidney transplant status were independent predictors of AsVD after controlling for other risk factors. CONCLUSION: AsVD was common among KTRs. Older age and kidney transplant status independently predicted AsVD. Castelli index 2 and LCI correlated with AsVD better than serum lipid parameters.

Transforming Growth Factor-ß Protects against Inflammation-Related Atherosclerosis in South African CKD Patients.

BACKGROUND: Transforming growth factor-ß (TGF-ß) may inhibit the development of atherosclerosis. We evaluated serum levels of TGF-ß isoforms concurrently with serum levels of endotoxin and various inflammatory markers. In addition, we determined if any association exists between polymorphisms in the TGF-ß1 gene and atherosclerosis in South African CKD patients. METHODS: We studied 120 CKD patients and 40 healthy controls. Serum TGF-ß1, TGF-ß2, TGF-ß3, endotoxin, and inflammatory markers were measured. Functional polymorphisms in the TGF-ß1 genes were genotyped using a polymerase chain reaction-sequence specific primer method and carotid intima media thickness (CIMT) was assessed by B-mode ultrasonography. RESULTS: TGF-ß isoforms levels were significantly lower in the patients with atherosclerosis compared to patients without atherosclerosis (p<0.001). Overall, TGF-ß isoforms had inverse relationships with CIMT. TGF-ß1 and TGF-ß2 levels were significantly lower in patients with carotid plaque compared to those without carotid plaque [TGF-ß1: 31.9 (17.2 - 42.2) versus 45.9 (35.4 - 58.1) ng/ml, p=0.016; and TGF-ß2: 1.46 (1.30 - 1.57) versus 1.70 (1.50 - 1.87) ng/ml, p=0.013]. In multiple logistic regression, age, TGF-ß2, and TGF-ß3 were the only independent predictors of subclinical atherosclerosis in CKD patients [age: odds ratio (OR), 1.054; 95% confidence interval (CI): 1.003 - 1.109, p=0.039; TGF-ß2: OR, 0.996; 95% CI: 0.994-0.999, p=0.018; TGF-ß3: OR, 0.992; 95% CI: 0.985-0.999, p=0.029). TGF-ß1 genotypes did not influence serum levels of TGF-ß1 and no association was found between the TGF-ß1 gene polymorphisms and atherosclerosis risk. CONCLUSION: TGF-ß isoforms seem to offer protection against the development of atherosclerosis among South African CKD patients.

Correlation between volume overload, chronic inflammation, and left ventricular dysfunction in chronic kidney disease patients.

BACKGROUND: Fluid overload is common in chronic kidney disease (CKD) patients, potentially driving chronic inflammation and left ventricular dysfunction. We investigated the association between volume overload, chronic inflammation, and left ventricular dysfunction across subgroups of CKD patients. METHODS: The study included 160 participants, comprising peritoneal dialysis (PD), hemodialysis (HD), stage-3 CKD patients, and age- and sex-matched controls (40 in each group). Fluid status was assessed using a body composition monitor (BCM); serum endotoxin, lipopolysaccharide binding protein (LBP), C-reactive protein (CRP). and interleukin-6 (IL-6) levels were measured as markers of inflammation. Echocardiography was done to assess left ventricular dimension and function. RESULTS: Endotoxemia and volume overload were common across the spectrum of CKD patients and were aggravated by worsening kidney function. Among HD cohorts, postdialysis endotoxemia was increased among patients with dialysis-induced hemodynamic instability and was also closely related to ultrafiltration volume. Endotoxin, IL-6, CRP, and LBP levels were elevated in patients with volume overload compared to euvolemic patients (p < 0.05). Patients with elevated circulating endotoxemia had higher left ventricular mass index (LVMI) compared to patients with lower endotoxin levels. Fluid overload correlated with endotoxin levels, IL-6, and LVMI; while LVMI correlated weakly with LBP and CRP. CONCLUSION: CKD patients typically presented with significant endotoxemia and overt volume overload, which may contribute significantly to chronic low-grade inflammation and left ventricular dysfunction. An additive contribution from hemodialysis treatment may strongly enhance the severity of endotoxemia in HD patients.

Volume overload and its risk factors in South African chronic kidney disease patients: an appraisal of bioimpedance spectroscopy and inferior vena cava measurements.

BACKGROUND: Fluid retention occurs early in chronic kidney disease (CKD) resulting in increased cardiovascular morbidity and mortality. This study aimed to assess volume and nutritional status among South African CKD participants and determine the relationship between malnutrition, inflammation, atherosclerosis, and volume overload using a body composition monitor (BCM). We also evaluated the usefulness of BCM measurement in assessing volume overload. METHODS: 160 participants comprising hemodialysis, peritoneal dialysis, stage 3 CKD patients, and healthy controls (40 in each group) were studied. A BCM was used to assess fluid and nutritional status. Cardiac dimension measurements, and inferior vena cava diameter (IVCD) and carotid intima media thickness were assessed by echocardiography and ultrasonography, respectively. Serum interleukin-6 (IL-6) and C-reactive protein (CRP) levels were measured as markers of inflammation. RESULTS: Fluid overload and malnutrition were present in 68% and 63% of studied patients, respectively. Using physical examination findings as the reference measurements for volume overload, the area under the concentration curves for BCM and IVCD measurements were 0.866 (sensitivity 82%, specificity 74%, p < 0.001) and 0.727 (sensitivity 57%, specificity 70%, p < 0.001), respectively. Lean tissue index, inflammation, and atherosclerosis were associated with volume overload. CONCLUSIONS: Volume overload and malnutrition were common across the spectrum of South African CKD cohorts; volume overload was associated with malnutrition, inflammation, and atherosclerosis. Bioimpedance spectroscopy (BIS) is a useful and sensitive tool for the assessment of fluid status in clinically euvolumic nondialytic CKD patients.