A functional common polymorphism of the ABCB1 gene is associated with chronic kidney disease and hypertension in Chinese

The Effect of Platelet Activity, ABCB1 Genetic Polymorphism, and Renal Function on the Development of Ticagrelor-Related Dyspnea in Patients with Acute Coronary Syndrome

Purpose

The aim of this study was to determine the effect of ABCB1 genetic polymorphism and renal function on the occurrence of ticagrelor-related dyspnea.

Patients and Methods

A total of 299 patients with acute with type 1, 2, or 3 myocardial infarction (with and without ST-segment elevation), who underwent coronary angiography and PTCA with stent implantation and were treated with antiplatelet drugs (ticagrelor and aspirin), were enrolled in this prospective study. For all enrolled patient's platelet aggregation (induction with high-sensitivity adenosine diphosphate, ADP HS) testing was performed using a MULTIPLATE® analyzer. Venous blood was also collected for genotyping.

Results

Patients experiencing ticagrelor-related dyspnea had lower ADP HS value (ADP HS ≤ 19.5 U; OR = 2.254; P = 0.009), higher creatinine concentration (>90 µmol/l; OR = 3.414; P = 0.019), and lower GFR value (<60 mL/min/1.73 m2; OR = 2.211; P = 0.035). ABCB1 T allele was associated with ticagrelor-related dyspnea (OR = 2.550; P = 0.04).

Conclusion

Ticagrelor-related dyspnea was found to be related to low platelet aggregation, increased plasma creatinine concentration, decreased GFR, and ABCB1 T allele. Carriers of the ABCB1 T allele had a higher plasma creatinine concentration that could be associated with an inhibitory effect of ticagrelor on P-glycoprotein function.

The role of candidate genetic polymorphisms in the interaction between voriconazole and cyclosporine in patients undergoing allogeneic hematopoietic cell transplantation: An explorative study

PURPOSE

To evaluate polymorphisms in genes of drug metabolizing enzymes and transporters involved in cyclosporine and/or voriconazole disposition among patients undergoing allogeneic hematopoietic cell transplantation (allo-HCT).

METHODS

DNA from forty patients was genotyped using the DMETPlus array. The average ratio of cyclosporine concentration/dose (C/D in (ng/mL)/(mg/kg)) per participant's weight was computed using available trough levels and daily doses.

RESULTS

The C/D cyclosporine ratio was significantly higher when it was administered with voriconazole as compared to when it was administered alone: median: 116.75 vs. 25.40 (ng/mL)/(mg/kg) with and without voriconazole respectively, (P < 0.001). There was also a significant association between the C/D cyclosporine ratio combined with voriconazole and the ABCB1 2677 G > T > A (rs2032582) genetic polymorphism (P = 0.05). In parallel, ABCB1 variant allele carriers had higher creatinine in combination therapy with a median creatinine (mg/dL) of 0.74 vs. 0.56 for variant allele carriers vs. reference; P = 0.003. Interestingly, CYP2C9, CYP2C19, and CYP3A5 extensive metabolizers tended to be associated with lower cyclosporine C/D ratio when combined with voriconazole, but the results were not statistically significant.

CONCLUSION

To the best of our knowledge, this is the first pharmacogenetic study on the interaction between voriconazole and cyclosporine in patients undergoing allo-HCT. Results suggest that the ABCB1 2677 G > T > A genetic polymorphism plays a role in this interaction with cyclosporine related nephrotoxicity. Pre-emptive genotyping for this genetic variant may be warranted for cyclosporine dose optimization. Larger studies are needed to potentially show significant associations with more candidate genes such as CYP3A4/5, CYP2C9, and CYP2C19, among others.

Hypertension in High School Students: Genetic and Environmental Factors

Hypertension and obesity in the young population are major risk factors for renal and cardiovascular events, which could arise in adulthood. A candidate-gene approach was applied in a cohort observational study, in which we collected data from 2638 high school adolescent students. Participants underwent anthropometric and blood pressure (BP) measurements, as well as saliva and urine sample collection for genomic DNA extraction and renal function evaluation, respectively. We tested whether candidate genes previously implicated in salt-sensitive hypertension in adults impact BP also among adolescents. Since inflammatory mechanisms may be involved in pathophysiology of hypertension and in endothelial dysfunction and atherosclerosis through reactive oxygen species, the baseline urinary excretion of inflammatory and oxidative stress markers in a subgroup of adolescents stratified according to ADD1 (alpha adducin) rs4961 genotypes was assessed. Regression analysis of BP values with genetic polymorphisms, highlighted an association with a missense variant of LSS (lanosterol synthase, rs2254524), a gene coding for an enzyme involved in endogenous ouabain synthesis. Higher diastolic and systolic BP were associated with LSS A allele ( P =0.011 and P =0.023, respectively). BP resulted associated with 5 more SNPs. The KL (klotho) rs9536314 missense variant was associated with 24 hour urinary Na + excretion ( P =0.0083). Urinary protein tests showed a greater excretion of IL1β (interleukin 1β) and interleukin 10 ( P <0.0001) in carriers of the ADD1 rs4961 T allele. In conclusion, 3 missense gene variants already implicated in adult hypertension impact BP or Na + excretion among adolescents, and, together with activated pro-inflammatory pathways, might predispose to early cardiovascular damage.

Recipient rs1045642 Polymorphism Is Associated With Office Blood Pressure at 1-Year Post Kidney Transplantation: A Single Center Pharmacogenetic Cohort Pilot Study

Background: Corticosteroids are associated with reduced bone mineral density (BMD), as well as water and salt retention, leading to hypertension. They are substrates for P-glycoprotein, a protein coded by the highly polymorphic ABCB1 gene. We hypothesized that one ABCB1 polymorphism, rs1045642, is associated with blood pressure and BMD parameters at 1-year post kidney transplantation (KT).

Methods: Rs1045642 was genotyped using pyrosequencing in 40 KT recipients. Both dominant (CC vs. CT + TT) and codominant (CC vs. CT vs. TT) genetic models (analysis of variance from linear regressions) were adjusted for confounding variables (age, sex, type of nephropathy, glomerular filtration rate, and corticosteroid use at 1 year).

Results: Rs1045642 genotypes were significantly associated with systolic (SBP) and diastolic (DBP) blood pressure 1-year post-transplantation, independent of the genetic model used (adjusted codominant model: SBP p-value = 0.015, DBP p-value = 0.038; adjusted dominant model: SBP p-value = 0.003, DBP p-value = 0.011). A non-statistically significant trend was observed for an association between rs1045642 and BMD change at 1-year post-KT.

Conclusions: Rs1045642 is significantly associated with higher BP 1 year after KT. Further investigations are necessary to confirm the role of rs1045642 in corticosteroid-related adverse effects.

Diurnal Blood Pressure Rhythmicity in Relation to Environmental and Genetic Cues in Untreated Referred Patients

No previous study has addressed the relative contributions of environmental and genetic cues to the diurnal blood pressure rhythmicity. From 24-hour ambulatory recordings of systolic blood pressure obtained in untreated patients (51% women; mean age, 51 years), we computed the night-to-day ratio in 897 and morning surge in 637. Environmental cues included season, mean daily outdoor temperature, atmospheric pressure, humidity and weekday, and the genetic cues 14 single nucleotide polymorphisms in 10 clock genes. Systolic blood pressure averaged (±SD) 126.7±11.9 mm Hg, night-to-day ratio 0.86±0.07, and morning surge 24.8±10.7 mm Hg. In adjusted analyses, night-to-day ratio was 2.4% higher in summer and 1.8% lower in winter ( P <0.001) compared with the annual average with a small effect of temperature ( P =0.079); morning surge was 1.7 mm Hg lower in summer and 1.1 mm Hg higher in winter ( P <0.001). The other environmental cues did not add to the night-to-day ratio or morning surge variance ( P ≥0.37). Among the 14 genetic variations, only CLOCK rs180260 was significantly associated with morning surge after adjustment for season, temperature, and other host factors and after Bonferroni correction ( P =0.044). In CLOCK rs1801260 C allele carriers (n=83), morning surge was 3.7 mm Hg higher than in TT homozygotes (n=554). Of the night-to-day ratio and morning surge variance, season and temperature explained ≈8% and ≈3%, while for genetic cues, these proportions were ≈1% or less. In conclusion, environmental compared with genetic cues are substantially stronger drivers of the diurnal blood pressure rhythmicity.

Progress in risk prediction for people with chronic kidney disease

PURPOSE OF REVIEW

Chronic kidney disease is common, but the associated risk of adverse outcomes is heterogeneous and methods for risk stratification are, therefore, required. We have reviewed recent progress in developing clinically applicable risk scores for people with chronic kidney disease.

RECENT FINDINGS

Large epidemiological studies have confirmed that lower glomerular filtration rate and albuminuria are the most important risk factors for adverse outcomes in all populations studied. Ongoing research has identified several potentially important novel risk factors, including genetic factors, metabolomic factors, fibroblast growth factor 23, novel cardiovascular risk factors [CXC motif, ligand 12 (CXCL12) and ceruloplasmin], skin autofluorescence and inflammatory markers (serum-free light chains and circulating receptors for tumour necrosis factor). Several risk scores have been developed and one in particular (by Tangri et al.) performs well, uses variables commonly assessed in clinical practice and has been externally validated. Further studies are required to assess its performance in populations outside of secondary care and its usefulness in guiding decision making in clinical practice.

SUMMARY

Although substantial progress has been made, the goal of achieving simple robust risk scores which are widely applicable and effective in guiding clinical decision making remains to be achieved.

Nephrosclerosis: update on a centenarian

Nephrosclerosis is an umbrella term defining changes in all compartments of the kidney, changes caused by hypertension and by ageing. Among other lesions, arteriolosclerosis and arteriolohyalinosis play a major role in inducing glomerular ischaemic shrinking and sclerosis along with glomerulomegaly and focal-segmental glomerulosclerosis (FSGS). These lesions are accompanied by tubulointerstitial inflammation and fibrosis that predict the decline of renal function. Nephrosclerosis is a major cause of renal insufficiency in blacks of African descent with a severe, early form of renovasculopathy and a rapid course to renal failure with predominant lesions of FSGS. It seems that in blacks, separate genetic factors independently lead to vascular lesions and to hypertension with a different time-scale of their onset and of their progression, nephroangiosclerosis preceding the onset of hypertension. Conversely, true and histologically identified nephrosclerosis in white Europeans rarely leads to end-stage renal disease in the absence of malignant hypertension. Various animal models demonstrate that renal vascular lesions may exist in the absence of hypertension. These experiments also point to a major role of angiotensin II and of a number of independent and overlapping cellular and molecular pathways in a cascade of inflammatory events that end in renal fibrosis. Two pathophysiologic mechanisms are at work in inducing glomerular lesions and tubulointerstitial fibrosis: a loss of autoregulation of the renal blood flow caused by an arteriolohyalinosis of the glomerular afferent arteriole and ischaemia that fosters the generation of hypoxia inducible-fibrosing factors. Not all antihypertensive drugs equally protect the kidney from nephrosclerosis. Angiotensin II antagonists exert a favourable effect on hyperfiltration. Conversely, dihydropyridine calcium-channel blockers and vasodilators do not withstand the derangement of renal autoregulation.

Developments in renal pharmacogenomics and applications in chronic kidney disease

Chronic kidney disease (CKD) has shown an increasing prevalence in the last century. CKD encompasses a poor prognosis related to a remarkable number of comorbidities, and many patients suffer from this disease progression. Once the factors linked with CKD evolution are distinguished, it will be possible to provide and enhance a more intensive treatment to high-risk patients. In this review, we focus on the emerging markers that might be predictive or related to CKD progression physiopathology as well as those related to a different pattern of response to treatment, such as inhibitors of the renin–angiotensin system (including angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers; the vitamin D receptor agonist; salt sensitivity hypertension; and progressive kidney-disease markers with identified genetic polymorphisms). Candidate-gene association studies and genome-wide association studies have analyzed the genetic basis for common renal diseases, including CKD and related factors such as diabetes and hypertension. This review will, in brief, consider genotype-based pharmacotherapy, risk prediction, drug target recognition, and personalized treatments, and will mainly focus on findings in CKD patients. An improved understanding will smooth the progress of switching from classical clinical medicine to gene-based medicine.

Calcineurin inhibitors and hypertension: a role for pharmacogenetics?

Hypertension is a common side effect of calcineurin inhibitors (CNIs), which are drugs used to prevent rejection after transplantation. Hypertension after kidney transplantation has been associated with earlier graft failure and higher cardiovascular mortality in the recipient. Recent data indicate that enzymes and transporters involved in CNI pharmacokinetics and pharmacodynamics, including CYP3A5, ABCB1, WNK4 and SPAK, are also associated with salt-sensitive hypertension. These insights raise the question whether polymorphisms in the genes encoding these proteins increase the risk of CNI-induced hypertension. Predicting who is at risk for CNI-induced hypertension may be useful for when selecting specific interventions, including dietary salt restriction, thiazide diuretics or a CNI-free immunosuppressive regimen. This review aims to explore the pharmacogenetics of CNI-induced hypertension, highlighting the knowns and unknowns.