Project description:ObjectiveAmong African Americans, the apolipoprotein L1 (APOL1) risk variants have been associated with various types of kidney disease and chronic kidney disease progression. We aimed to determine whether these same risk variants also confer an increased risk for cardiovascular disease.Approach and resultsIn a cohort of African Americans with hypertension-attributed chronic kidney disease followed for up to 12 years, we used Cox proportional hazards models to estimate the relative hazard of a composite cardiovascular disease outcome (cardiovascular death or hospitalization for myocardial infarction, cardiac revascularization procedure, heart failure, or stroke) for the APOL1 high- (2 risk variants) versus low-risk (0-1 risk variant) genotypes. We adjusted for age, sex, ancestry, smoking, heart disease history, body mass index, cholesterol, randomized treatment groups, and baseline and longitudinal estimated glomerular filtration rate, systolic blood pressure, and proteinuria. Among 693 participants with APOL1 genotyping available (23% high risk), the high-risk group had lower mean estimated glomerular filtration rate (44.7 versus 50.1 mL/min per 1.73 m2) and greater proteinuria (median 0.19 versus 0.06) compared with the low-risk group at baseline. There was no significant association between APOL1 genotypes and the composite cardiovascular disease outcome in both unadjusted (hazard ratio=1.23; 95% confidence interval: 0.83-1.81) and fully adjusted (hazard ratio=1.16; 95% confidence interval: 0.77-1.76) models; however, in using an additive model, APOL1 high-risk variants were associated with increased cardiovascular mortality.ConclusionsAmong African Americans with hypertension-attributed chronic kidney disease, APOL1 risk variants were not associated with an overall risk for cardiovascular disease although some signals for cardiovascular mortality were noted.
Project description:BackgroundTwo coding variants in the apo L1 gene (APOL1) are strongly associated with kidney disease in blacks. Kidney disease itself increases the risk of cardiovascular disease, but whether these variants have an independent direct effect on the risk of cardiovascular disease is unclear. Previous studies have had inconsistent results.MethodsWe conducted a two-stage individual participant data meta-analysis to assess the association of APOL1 kidney-risk variants with adjudicated cardiovascular disease events and death, independent of kidney measures. The analysis included 21,305 blacks from eight large cohorts.ResultsOver 8.9±5.0 years of follow-up, 2076 incident cardiovascular disease events occurred in the 16,216 participants who did not have cardiovascular disease at study enrollment. In fully-adjusted analyses, individuals possessing two APOL1 kidney-risk variants had similar risk of incident cardiovascular disease (coronary heart disease, myocardial infarction, stroke and heart failure; hazard ratio 1.11, 95% confidence interval, 0.96 to 1.28) compared to individuals with zero or one kidney-risk variant. The risk of coronary heart disease, myocardial infarction, stroke and heart failure considered individually was also comparable by APOL1 genotype. APOL1 genotype was also not associated with death. There was no difference in adjusted associations by level of kidney function, age, diabetes status, or body-mass index.ConclusionsIn this large, two-stage individual participant data meta-analysis, APOL1 kidney-risk variants were not associated with incident cardiovascular disease or death independent of kidney measures.
Project description:Gene sequence mutations may alter mRNA transcription, transcript stability, protein translation, protein stability and protein folding. Apolipoprotein L1 (APOL1) has two sets of sequence variants that are risk factors for kidney disease development, APOL1G1 (substitution mutation) and APOL1G2 (deletion mutation). Our present study focuses on the impact of these variants on APOL1 mRNA transcription and translation. APOL1 plasmids (EV, G0, G1 and G2) were transfected into human embryonic kidney (HEK) 293T cells. APOL1 variant expression was observed to be significantly lower than that of APOL1G0. Podocyte cell lines stably expressing APOL1 transgenes also showed lower levels of APOL1 expression of APOL1 variants (G1 and G2) compared with APOL1G0 by Western blotting and FACS analysis. The enhanced expression of GRP78 by podocytes expressing APOL1 variants would indicate endoplasmic reticulum (ER) stress. Bioinformatics evaluation using two different programs (MUPro and I-Mutant 2.0) predicted that APOL1 variants were less stable than APOL1G0. Concomitant with protein levels, APOL1 mRNA levels were also depressed following induction of APOL1 variant compared with APOL1G0 in both proliferating and differentiated podocytes. APOL1 mRNA transcript stability was tested after actinomycin D pulsing; APOL1G1 and APOL1G2 mRNAs transcript decayed 10-15% and 15-20% (within a period of 0.5-3 h) respectively. Our data suggest that down-regulated APOL1 protein expression in APOL1 variants is due to compromised transcription and decay of the APOL1 variant transcripts.
Project description:BackgroundAmong patients in the United States with chronic kidney disease, black patients are at increased risk for end-stage renal disease, as compared with white patients.MethodsIn two studies, we examined the effects of variants in the gene encoding apolipoprotein L1 (APOL1) on the progression of chronic kidney disease. In the African American Study of Kidney Disease and Hypertension (AASK), we evaluated 693 black patients with chronic kidney disease attributed to hypertension. In the Chronic Renal Insufficiency Cohort (CRIC) study, we evaluated 2955 white patients and black patients with chronic kidney disease (46% of whom had diabetes) according to whether they had 2 copies of high-risk APOL1 variants (APOL1 high-risk group) or 0 or 1 copy (APOL1 low-risk group). In the AASK study, the primary outcome was a composite of end-stage renal disease or a doubling of the serum creatinine level. In the CRIC study, the primary outcomes were the slope in the estimated glomerular filtration rate (eGFR) and the composite of end-stage renal disease or a reduction of 50% in the eGFR from baseline.ResultsIn the AASK study, the primary outcome occurred in 58.1% of the patients in the APOL1 high-risk group and in 36.6% of those in the APOL1 low-risk group (hazard ratio in the high-risk group, 1.88; P<0.001). There was no interaction between APOL1 status and trial interventions or the presence of baseline proteinuria. In the CRIC study, black patients in the APOL1 high-risk group had a more rapid decline in the eGFR and a higher risk of the composite renal outcome than did white patients, among those with diabetes and those without diabetes (P<0.001 for all comparisons).ConclusionsRenal risk variants in APOL1 were associated with the higher rates of end-stage renal disease and progression of chronic kidney disease that were observed in black patients as compared with white patients, regardless of diabetes status. (Funded by the National Institute of Diabetes and Digestive and Kidney Diseases and others.).
Project description:OBJECTIVE:We sought to evaluate the cardiovascular impact of coding variants in the apolipoprotein L1 gene APOL1 that protect against trypanosome infection but have been associated with kidney disease among African Americans. APPROACH AND RESULTS:As part of the Cardiovascular Health Study, a population-based cohort of Americans aged ?65 years, we genotyped APOL1 polymorphisms rs73885319 and rs71785153 and examined kidney function, subclinical atherosclerosis, and incident cardiovascular disease and death over 13 years of follow-up among 91 African Americans with 2 risk alleles, 707 other African Americans, and 4964 white participants. The high-risk genotype with 2 risk alleles was associated with 2-fold higher levels of albuminuria and lower ankle-brachial indices but similar carotid intima-media thickness among African Americans. Median survival among high-risk African Americans was 9.9 years (95% confidence interval [CI], 8.7-11.9), compared with 13.6 years (95% CI, 12.5-14.3) among other African Americans and 13.3 years (95% CI, 13.0-13.6) among whites (P=0.03). The high-risk genotype was also associated with increased risk for incident myocardial infarction (adjusted hazard ratio 1.8; 95% CI, 1.1-3.0) and mortality (adjusted hazard ratio 1.3; 95% CI 1.0-1.7). Albuminuria and risk for myocardial infarction and mortality were nearly identical between African Americans with 0 to 1 risk alleles and whites. CONCLUSIONS:APOL1 genotype is associated with albuminuria, subclinical atherosclerosis, incident myocardial infarction, and mortality in older African Americans. African Americans without 2 risk alleles do not differ significantly in risk of myocardial infarction or mortality from whites. APOL1 trypanolytic variants may account for a substantial proportion of the excess risk of chronic disease in African Americans.
Project description:Two distinct alleles in the gene encoding apolipoprotein L1 (APOL1), a major component of high-density lipoprotein, confer protection against Trypanosoma brucei rhodesiense infection and also increase risk for chronic kidney disease. Approximately 14% of Americans with African ancestry carry 2 APOL1 risk alleles, accounting for the high chronic kidney disease burden in this population.We tested whether APOL1 risk alleles significantly increase risk for atherosclerotic cardiovascular disease (CVD) in African Americans.We sequenced APOL1 in 1959 randomly selected African American participants in the Jackson Heart Study (JHS) and evaluated associations between APOL1 genotypes and renal and cardiovascular phenotypes. Previously identified association between APOL1 genotypes and chronic kidney disease was confirmed (P=2.4×10(-6)). Among JHS participants with 2 APOL1 risk alleles, we observed increased risk for CVD (50/763 events among participants without versus 37/280 events among participants with 2 risk alleles; odds ratio, 2.17; P=9.4×10(-4)). We replicated this novel association of APOL1 genotype with CVD in Women's Health Initiative (WHI) participants (66/292 events among participants without versus 37/101 events among participants with 2 risk alleles; odds ratio, 1.98; P=8.37×10(-3); JHS and WHI combined, P=8.5×10(-5); odds ratio, 2.12). The increased risk for CVD conferred by APOL1 alleles was robust to correction for both traditional CVD risk factors and chronic kidney disease.APOL1 variants contribute to atherosclerotic CVD risk, indicating a genetic component to cardiovascular health disparities in individuals of African ancestry. The considerable population of African Americans with 2 APOL1 risk alleles may benefit from intensive interventions to reduce CVD.
Project description:Recent studies have identified genetic variants in APOL1 that may contribute to the increased incidence of kidney disease in populations with African ancestry. Here, we review the biology of APOL1 present in the circulation and localized to the kidney as it may contribute to the pathogenesis of APOL1-associated kidney disease.
Project description:African Americans have higher rates of kidney disease than European Americans. Here, we show that, in African Americans, focal segmental glomerulosclerosis (FSGS) and hypertension-attributed end-stage kidney disease (H-ESKD) are associated with two independent sequence variants in the APOL1 gene on chromosome 22 {FSGS odds ratio = 10.5 [95% confidence interval (CI) 6.0 to 18.4]; H-ESKD odds ratio = 7.3 (95% CI 5.6 to 9.5)}. The two APOL1 variants are common in African chromosomes but absent from European chromosomes, and both reside within haplotypes that harbor signatures of positive selection. ApoL1 (apolipoprotein L-1) is a serum factor that lyses trypanosomes. In vitro assays revealed that only the kidney disease-associated ApoL1 variants lysed Trypanosoma brucei rhodesiense. We speculate that evolution of a critical survival factor in Africa may have contributed to the high rates of renal disease in African Americans.
Project description:IntroductionThe relationship of APOL1 renal risk variants to cardiovascular disease (CVD) is controversial and was the subject of this investigation.MethodsAge, cause of death, and nephrosclerosis (the latter defined by glomerulosclerosis) were analyzed in the autopsies of 162 African Americans and 136 whites genotyped for APOL1 risk alleles.ResultsSudden deaths represented >75% of CVD autopsies for both races and all-risk genotypes. The average ages of CVD deaths for African Americans with 1 and 2 APOL1 risk alleles were, respectively, 7.0 years (P = 0.02) and 12.2 years (P < 0.01) younger than African Americans with 0 risk alleles and 8.7 years (P = 0.01) and 13.9 years (P = 0.01) younger than whites. Age differences were not significant between African Americans and whites with 0 risk alleles (P = 0.61). The younger CVD deaths of African Americans were associated with less severe glomerulosclerosis with 2 (P = 0.01), although not 1 (P = 0.09), compared with 0 APOL1 risk alleles. Cardiomyopathy was found in 23% of African Americans with 1 and 2 risk alleles and significantly contributed to the lower age (P = 0.01). For non-CVD deaths, age differences were not seen by race (P = 0.28) or among African Americans by risk allele status (P = 0.38).ConclusionCarriage of 1 or 2 APOL1 risk alleles in African Americans was associated with earlier age deaths due to coronary artery disease and cardiomyopathy. For 2 risk alleles, the early age was independent of nephrosclerosis.