Hasan Fattah 3/19/2013

Transcription

1 Hasan Fattah 3/19/2013

2 AASK trial Rational: HTN is a leading cause of (ESRD) in the US, with no known treatment to prevent progressive declines leading to ESRD. Objective: To compare the effects of 2 levels of (BP) control and 3 antihypertensive drug classes on (GFR) decline in HTN. Design Randomized with enrollment from Participants: 1094 AA aged 18 to 70 years with hypertensive renal disease (GFR, ml/min per 1.73 m 2 ) were recruited from 21 clinical centers throughout the US and followed up for 3 to 6.4 years.

3 Interventions: Participants were randomly assigned to 1 of 2 mean arterial pressure goals: to 107 mm Hg (usual; n = 554) mm Hg or less (lower; n = 540), initial treatment with either a β-blocker (metoprolol mg/d; n = 441), an ACEi (ramipril mg/d; n = 436) or a calcium channel blocker, (amlodipine 5-10 mg/d; n = 217). Main Outcome Measures : Rate of change in GFR (GFR slope); clinical composite outcome of reduction in GFR by 50% or more (or 25 ml/min per 1.73 m 2 ) from baseline, ESRD, or death. Three primary treatment comparisons were specified: lower vs usual BP goal; ramipril vs metoprolol; and amlodipine vs metoprolol.

4 JAMA. 2002

5 JAMA. 2002

6 JAMA. 2002

7 JAMA. 2002

8 Proposal of existence of a major nephropathy susceptibility gene underlying several common forms of kidney disease in African Americans in the early 1990s. Freedman et al Am J Kidney Dis. 1993

9 Kopp et al and Kao et al first applied MALD to kidney disease and detected an impressive genetic association between the non-muscle myosin heavy chain 9 gene (MYH9) E1 haplotype and idiopathic FSGS, nondiabetic ESRD, and HIVAN in African Americans Within two years Genovese, Freedman and colleagues demonstrated that two coding variants in APOL1 (termed G1: non-synonymous coding variant 342 G:384 M and G2: a 6 bp deletion) had stronger genetic association with nondiabetic nephropathy than the MYH9 E1 haplotype

10 MALD

11 APOL1 coding variants underlie a spectrum of kidney diseases, including that attributed to hypertension (labeled arteriolar or hypertensive nephrosclerosis), focal segmental glomerulosclerosis, and HIVassociated nephropathy

12 205 AA with biopsy proven FSGS but no FH with 180 AA controls. Genovese et al Science 2010

13 Genotype/Haplotype frequencies for FSGS cases/esrd and controls Genovese et al Science 2010

14 Kopp et al J, Am Nephrol 2011

15 Kopp et al J, Am Nephrol 2011

16 In conclusion: APOL1 genetic variation is a powerful contributor to risk for FSGS and HIVAN. The attributable risk is quantitatively comparable to the role of smoking in non-small-cell lung cancer risk. While only 12 to 13% of African Americans carry two APOL1 risk alleles, these individuals have an estimated 4% lifetime risk for FSGS, and when they develop FSGS, they tend to progress to ESKD rapidly.

17 Clinical Applications of APOL1 Genotyping in Renal Transplantation Kidneys donated by AAs are known to function for shorter periods of time than kidneys donated by European Americans Meier-Kriesche et al Kidney Int 2000

18 The APOL1 gene and allograft survival after kidney transplantation: single center study From March 24, 1998 through September 12, AA deceased organ donors kidneys recovered and typing material procured or delivered to the Wake Forest University Baptist Medical Center (WFUBMC) for transplantation purpose kidney transplant patients were followed longitudinally at our center for at least 1 year and form the study sample. Outcome of interest: time to graft failure Reeves-Daniel et al, A J of transplantation 2011

19 Demographic characteristics of renal allograft donors and recipients Variables Number of APOL1 G1-G2 nephropathy risk variants from kidney donor Two N = 22 Zero or 1 N = 114 p Value Donor age (years) 43.7 ± ± Donor gender (% male) Terminal serum creatinine (mg/dl) 1.34 ± ± Donor African ancestry%) 0.77 ± ± Cold ischemia time (hours) 22.5 ± ± HLA mismatch (N) 4.2 ± ± Recipient gender (% male) Recipient age (years) 45.2 ± ± Recipient race (% African American) Diabetic ESRD in recipients (%)

20 Fully adjusted model for renal allograft survival Parameter APOL1 G1/G2 (2 vs. 0/1 copies) Parameter estimate Standard error p Value Hazard ratio African ancestry Recipient age Gender (female) Donor criteria (standard) HLA mismatch Cold ischemia time PRA* > 0%

21 Renal allograft survival according to APOL1 genotype Reeves-Daniel et al, A J of transplantation 2011

22 Multivariate analysis was repeated excluding graft failures due to hyperacute rejection, two APOL1 G1/G2 risk variants in donors (HR 2.32, p = 0.028) and number of HLA mismatches (HR 1.68, p = 0.025) remained significantly associated with graft survival

23 Outcomes: Differences in graft survival were seen after approximately 20 months. African ancestry did not significantly impact renal allograft survival after transplantation shorter renal allograft survival rates seen in kidneys donated by AAs relative to Caucasians could be substantially related to variation in APOL1.

24 Limitation: Small size sample Lack of APOL1 genotype in recipients Single txp center

25 Does The APOL1 Genotype of AA Kidney Transplant Recipients Impact Allograft Survival Subjects: kidney transplant recipients at the Brigham and Women's Hospital and the University of Alabama at Birmingham, transplanted between 1988 and Of the original cohort (n = 424) only 124 DNA samples identified from kidney transplant recipients of recent African ancestry. Retrospective primary outcome: allograft survival, Differences between subjects in the 2 risk allele group and the 0 or 1 risk allele. Am J Transplant 2012

26 Number of APOL1 genotypes organized by native end-stage renal disease in kidney transplant recipients DM FSGS GN HTN Other/UN K Total (%) WT/WT (21) WT/G (20.2) WT/G (10.1) G1/G (24.2) G1/G (22.7) G2/G (1.7) Total (%) 24 (20.2) 15 (12.6) 17 (14.3) 31 (26.1) 32 (26.9) 119 Am J Transplant 2012

27 Characteristics of kidney transplant recipients 2 Risk alleles 0 or 1 Risk alleles Number of subjects 58 (48.7%) 61 (51.3%) Mean age at transplant (years) p value Cause of ESRD Attributed to HTN Diabetes mellitus 7 19 FSGS 9 6 Type of donor kidney Deceased Living related Donor ethnicity is Black 25 (43.1%) 20 (32.8%) Allograft loss (%) 13 (22.4%) 13 (21.3%) Allograft loss censored by death %) 13 (22.4%) 11 (18.0%) Patient death 1 2 Acute rejection within 1-year posttransplant 2 2

28 Allograft survival of subjects with 0, 1 or 2 risk alleles Am J Transplant 2012

29 having 2 APOL1 risk alleles should not be an impediment to kidney transplantation Future work needs to be done to study the genotypes of kidney transplant recipients and donors together.

30 Potential Mechanisms of APOL1-Associated Nephropathy

31 FIRST PROPOSAL Altered plasma HDL particle concentrations could lead to kidney disease via damage to the renal microcirculation*. ApoL1 is expressed in the liver and may play a role in modifying production of nascent HDL particles that are destined to become the medium-sized HDL subclass upon maturation.

32 Plasma HDL particle subclass concentrations were compared in 73 AA based on APOL1 genotypes to detect differences potentially contributing to renal disease. Freedman et al Nephrol Dial Transplant (2011)

33 Mean (SD) plasma HDL subclass concentrations (lmol/l) HDL subclass No APOL1 risk variants One APOL1 risk variants Two APOL1 risk variants P-value * Unadjusted Adjusted N = 20 N = 17 N = 36 Total HDL particles 36.8 ± 7.6 (34.6) 33.1 ± 7.7 (32.1) 35.6 ± 7.5 (34.3) Large HDL particles ( nm) 5.7 ± 4.1 (4.9) 5.2 ± 2.9 (4.4) 7.0 ± 5.2 (6.3) Medium HDL particles ( nm) 13.1 ± 8.2 (10.7) 10.1 ± 5.5 (8.5) 9.0 ± 5.6 (7.9) Small HDL particles ( nm) 18.1 ± 6.1 (18.5) 17.8 ± 6.6 (17.4) 19.6 ± 6.8 (20.1) Freedman et al Nephrol Dial Transplant (2011)

34 SECOND POSSIBILITY ApoL1 variant proteins bind to HDL particles less avidly, circulate freely, cross the glomerular filtration barrier, and lead to glomerulosclerosis and/or IFTA. This hypothesis is strengthened by the observation that Circulating ApoL1 proteins have been implicated in rapidly recurring FSGS after kidney transplantation; a syndrome that can be improved with plasmapheresis. Gohh et al Am J Transplant. 2005

35 THIRD ONE APOL1 variants may induce apoptosis or autophagy in podocytes, with resultant FSGS or FGGS. messenger RNA encoding ApoL1 protein is expressed in cultured human podocytes and other renal cell types.

36 Apolipoprotein L1, a Novel Bcl-2 Homology Domain 3-only Lipid-binding Protein, Induces Autophagic Cell Death* ApoL1 shares structural and functional similarities with the Bcl2 family of proteins involved in apoptosis. the apoptosis regulating B-cell lymphoma 2 gene (Bcl2) is closely related to APOL1

37 Time- and dose-dependent induction of apol1 and cell death in DLD-1.ApoL1 cells JOURNAL OF BIOLOGICAL CHEMISTRY 2008

38 BH3 domain deletion construct of apol1 failed to induce cell death in DLD-1 cells JOURNAL OF BIOLOGICAL CHEMISTRY 2008

39 ApoL1-induced cell death is through autophagy, not by apoptosis

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