Impact of VKORC1 Haplotypes on Long-Term Graft Function in Kidney Transplantation

Phylloquinone and vitamin D status: associations with incident chronic kidney disease in the Framingham Offspring cohort

BACKGROUND

Cardiovascular risk factors are associated with the development of chronic kidney disease (CKD), and CKD and vascular disease are etiologically linked. Evidence suggests deficiencies of vitamins D and K may adversely affect the cardiovascular system, but data from longitudinal studies are lacking. We hypothesized that deficiencies of vitamins D and K may be associated with incident CKD and/or incident albuminuria amongst members of the general population.

METHODS

We analyzed 1,442 Framingham Heart Study participants (mean age 58 years; 50.5% women), free of CKD (eGFR <60 ml/min/1.73 m(2)), with a mean follow-up of 7.8 years in 2005-2008. Incident albuminuria was defined using sex-specific cut-offs of urine albumin-to-creatinine ratio (≥17 mg/g men and ≥25 mg/g women). Baseline log plasma phylloquinone (vitamin K(1)) and 25(OH)D levels, analyzed as continuous variables and by quartile, were related to risk of incident CKD (n = 108) and incident albuminuria (n = 106) using logistic regression models adjusted for standard risk factors.

RESULTS

Participants in the highest phylloquinone quartile (≥1.78 nmol/l) had an increased risk of CKD (multivariable-adjusted OR Q(4) vs. Q(1) 2.39; p = 0.006) and albuminuria at follow-up (multivariable-adjusted OR Q(4) vs. Q(1) 1.95; p = 0.05), whereas no association was observed with continuous phylloquinone levels for either endpoint. Deficiency of 25(OH)D was not associated with incident CKD or albuminuria in either analysis.

CONCLUSIONS

Contrary to our hypothesis, higher plasma phylloquinone levels are associated with an increased risk of incident CKD. Whether plasma phylloquinone is a marker for another unmeasured risk factor requires further study. External validation is necessary given the unexpected nature of these results.

SLCO1B1 genetic polymorphism influences mycophenolic acid tolerance in renal transplant recipients

AIMS

This study aimed to determine the influence of gene candidates on mycophenolic acid (MPA) response during the first year of renal transplantation.

MATERIALS & METHODS

A total of 218 renal transplant recipients who received MPA from the first day of transplantation at a fixed dose of 2 g/day were genotyped for ABCB1, ABCC2, UGT2B7, UGT1A9, SLCO1B1, SLCO1B3 and IMPDH1 polymorphisms. Clinical end points were MPA-related adverse drug reactions (ADRs) and acute rejection episodes during the first year post-transplantation.

RESULTS

After correction for multiple statistical testing, SLCO1B1 (encoding the hepatic uptake transporter OATP1B1) was the only gene associated with MPA-related ADRs, showing a 75% risk reduction in favor of a protective effect of the SLCO1B1*5 allele (p = 0.002). In vitro experiments showed that MPA metabolites MPA-phenyl-glucuronide and MPA-acyl-glucuronide are substrates of OATP1B1. Their transport was decreased in the presence of the variant transporter (OATP1B1*5).

CONCLUSION

These results suggest for the first time that carriers of the SLCO1B1*5 allele seem to be protected from MPA-related ADRs.