Malnutrition Risk in Kidney Recipients Treated With Mycophenolate Mofetil Is Associated With IMPDH1 rs2278294 Polymorphism.

BACKGROUND: Malnutrition is known to increase morbidity and mortality in renal transplant recipients, whereas little is known about genetic predisposition to low body mass index (BMI) in the transplant setting. Inosine monophosphate dehydrogenase (IMPDH) regulates intracellular fat accumulation, pre-adipicytes maturation, and is a target of mycophenolic acid (MPA) used as a standard immunosuppressant. We hypothesized that MPA may interfere with fat tissue formation and weight gain in kidney transplant recipients and this process may be modified by IMPDH1 or IMPDH2 (genes encoding constitutive and inducible IMPDH) small nucleotide polymorphism variants. STUDY DESIGN: In an observational longitudinal study of kidney transplant recipients treated with mycophenolate mofetil, genetic factors were IMPDH1 (rs2278294, rs2278293) and IMPDH2 (rs11706052) allelic variants, the main outcome was the time-dependent change in BMI, and secondary outcomes were occurrence of BMI below 18.5 or 20 kg/m2. RESULTS: In a study group of 190 patients, no association was found between BMI changes and rs11706052 and rs2278293 variants. In terms of rs2278294, we found that allele G was associated with significantly slower BMI gain in a dominant model of inheritance. Concerning secondary endpoints, none of the AA carriers were underweight at 6 months post-implantation, while at least 2% of G allele carriers were underweight. From the first post-transplant year, all AA carriers had BMI above 20 kg/m2, while among G allele carriers at least 10% had BMI < 20 kg/m2 by generalized estimating equations. CONCLUSION: Based on our results, we postulate that MPA derivates influence post-transplant BMI and potentially also body fat content. In consequence, genotyping rs2278294 would potentially allow clinicians to personalize MPA treatment.

Recipient uridine 5'-diphospho-glucuronosyltransferase UGT1A9 c.98T>C variant determines transplanted kidney filtration rate.

Mycophenolic acid preparations are commonly used in prophylaxis of kidney allograft acute rejection. The medication is metabolized by uridine diphosphate glucuronosyltransferases, mainly UGT1A9 present in liver, kidney, and intestine. The effect of UGT1A9 allelic variants on drug metabolism in healthy volunteers and transplant recipients has been previously evaluated; these studies included the UGT1A9 c.98T>C polymorphism (rs72551330, p.Met33Thr) causing methionine-to-threonine substitution in the polypeptide chain. The study objective was to evaluate the relationship between UGT1A9 c.98T>C polymorphism and kidney graft function and survival and the risk of acute allograft rejection. Kidney recipients who underwent transplantation between 2000 and 2007 at the Medical University of Warsaw were included. Clinical data originated from standard medical records, UGT1A9 c.98T>C was genotyped using a polymerase chain reaction-restriction fragment length polymorphism method. A group of 243 kidney transplant recipients was enrolled in the study. The frequency of the c.98C allele was 2.4% (12 of 486). Most of the carriers of the allelic variant (10 of 12) received cyclosporine A at transplantation. In the c.98C allele carriers, worse function of the renal allograft, manifested by a significantly lower glomerular filtration rate, was found in the first posttransplantation month and persisted at a lower level for 8 years after the procedure (for comparison of the UGT1A9 c.98 TT vs the UGT1A9 c.98 TC groups, P = .03). No association was found between the presence of the UGT1A9 c.98C allele and the risk of delayed renal graft function, acute rejection, dysfunction of the renal graft, or dialysis treatment reintroduction. Significantly lower estimated glomerular filtration rate of the renal allograft in UGT1A9 c.98C carriers did not translate into decreased allograft survival.

Uridine diphosphate glucuronosyltransferase 2B7 variant p.His268Tyr as a predictor of kidney allograft early acute rejection.

BACKGROUND: Uridine diphosphate glucuronosyltransferase (UGT2B7) is responsible for conversion of mycophenolic acid to mycophenolic acyl-glucuronide (acylMPAG). Conflicting data exist regarding the role of UGT2B7 p.His268Tyr (802C>T, rs7439366) variant in the clinical course following organ transplantation. STUDY AIM: The aim of this study was to reveal an association between UGT2B7 p.His268Tyr (802C>T, rs7439366) polymorphism and kidney transplantation outcome. STUDY DESIGN, PATIENTS, AND METHOD: Genomic DNA of 235 kidney transplant recipients was genotyped for UGT2B7 802C>T using TagMan single nucleotide polymorphism (SNP) genotyping assay. Maintenance immunosuppression used mycophenolate mofetil (MMF) and cyclosporine A (n = 137) or tacrolimus (n = 98). Primary end-point was biopsy-confirmed acute rejection within 3 and 12 post-transplantation months. Secondary end-points included gastrointestinal side effects, leukopenia, lymphopenia, neutropenia, and infections. Statistical analysis was performed with the aid of SAS System using kernel-smoothed estimates of acute graft rejection hazard function. The log-rank test and hazard ratio were used to reflect association between UGT2B7 802C>T variant and risk of acute graft rejection. RESULTS: Within 3 postimplantation months 38 (16.2%) patients experienced acute rejection; 33 were allele C carriers in UGT2B7 802C>T SNP and 5 were TT homozygotes (P < .0457). Allele C-associated risk of rejection was 2.50 and remained between 2.19 and 3.02 after adjustment for clinical confounders, ie, HLA mismatch, panel-reactive antibodies, donor age, repeated transplantation, induction therapy, donor type, delayed graft function, applied calcineurin inhibitor, or MMF dosing. We found no association between the polymorphism and gastrointestinal side effects, leukopenia, lymphopenia, neutropenia, and infections. CONCLUSION: UGT2B7 802C>T genotyping may help identify patients with excessive early acute rejection risk.

Lymphocyte counts in kidney allograft recipients are associated with IMPDH2 3757T>C gene polymorphism.

Inosine monophosphate dehydrogenase (IMPDH), the rate-limiting enzyme for de novo synthesis of guanine nucleotides, is required for lymphocyte proliferation. Inhibition of IMPDH by mycophenolic acid (MPA) constitutes part of an immunosuppressive therapy in kidney allograft recipients. The 3757T>C polymorphic variant (rs11706052) of the IMPDH2 gene, which encodes 1 of 2 IMPDH isoenzymes, has been associated with increased IMPDH activity and reduced ability of MPA to exert antiproliferative effects on lymphocytes. The association of IMPDH2 3757T>C SNP with posttransplant courses of kidney allograft recipients remains unclear. Therefore, the aim of the present study was to evaluate associations between this single nucleotide polymorphism and common posttransplant complications among Polish kidney allotransplant recipients. We observed that the frequency of IMPDH2 3757C allele in this group (n=177) did not differ significantly from a control cohort representing the background population of Poland (n=550). There were no significant differences between patients carrying the IMPDH2 3757CT and TT genotypes with respect to acute rejection risk, neutropenia, or incidences of serious infections or gastrointestinal side effects. However, we noted that the 3757C allele was associated with higher lymphocyte counts and a reduced incidence of lymphopenia among kidney allograft recipients. Our findings may be of practical significance to tailor immunosuppressive regimens in kidney transplant recipients.

Prevalence of unidirectional Na+-dependent adenosine transport and altered potential for adenosine generation in diabetic cardiac myocytes.

Adenosine is an important physiological regulator of the cardiovascular system. The goal of our study was to assess the expression level of nucleoside transporters (NT) in diabetic rat cardiomyocytes and to examine the activities of adenosine metabolizing enzymes. Isolated rat cardiomyocytes displayed the presence of detectable amounts of mRNA for ENT1, ENT2, CNT1, and CNT2. Overall adenosine (10 microM) transport in cardiomyocytes isolated from normal rat was 36 pmol/mg/min. The expression level of equilibrative transporters (ENT1, ENT2) decreased and of concentrative transporters (CNT1, CNT2) increased in myocytes isolated from diabetic rat. Consequently, overall adenosine transport decreased by 30%, whereas Na(+)-dependent adenosine uptake increased 2-fold, and equilibrative transport decreased by 60%. The activity ratio of AMP deaminase/5'-nucleotidase in cytosol of normal cardiomyocytes was 11 and increased to 15 in diabetic cells. The activity of ecto-5'-nucleotidase increased 2-fold in diabetic cells resulting in a rise of the activity ratio of ecto-5'-nucleotidase/adenosine deaminase from 28 to 56.These results indicate that in rat cardiomyocytes diabetes alters activities of adenosine metabolizing enzymes in such a way that conversion of AMP to IMP is favored in the cytosolic compartment, whereas the capability to produce adenosine extracellularly is increased. This is accompanied by an increased unidirectional Na(+)-dependent uptake of adenosine and significantly reduced bidirectional adenosine transport.

Altered expression of adenosine receptors in heart of diabetic rat.

Diabetes results in functional, biochemical, and morphological abnormalities in the heart. Some of these changes may be attributed to altered adenosine action. This study aimed to examine the expression level of adenosine receptors (AR) in heart of streptozotocin-induced diabetic rat. Performed analyses revealed detectable levels of A1-AR, A2a-AR, A2b-AR, A3-AR mRNA and protein in whole heart and isolated cardiac myocytes. An increase in A1-AR protein content with no changes in mRNA level was observed in isolated cardiac myocytes. Diabetes resulted in an increase of A3-AR mRNA and protein levels in heart and in cardiac myocytes. The level of A2a-AR mRNA was increased in whole diabetic heart, but it decreased in cardiac myocytes with no detectable changes in protein content. We did not observe any changes in expression level of A2b-AR in diabetic heart and isolated cardiac myocytes. Administration of insulin to diabetic rat for four days resulted in returning of the ARs mRNA and protein to the levels observed in heart of normal rat. These changes in ARs genes expression, and receptors protein content correspond to some abnormalities characteristic of the diabetic heart, suggesting involvement in pathogenesis of diabetic cardiomyopathy.

Polyethylene glycol enzyme immunoassay for screening anti-haptoglobin monoclonal antibodies.

An enzyme immunoassay for the screening of anti-haptoglobin activities in supernatants of hybridoma cell cultures is described. The sandwich technique was greatly improved by the addition of 2% polyethylene glycol 6000 to all the reagents. It allowed a six-fold shortening in the incubation time compared with the standard method without sacrificing either sensitivity or accuracy.