Differential homocysteine levels in renal transplant patients receiving neoral versus tacrolimus

Polymorphisms in the methylenetetrahydrofolate reductase gene are determinant for vascular complications after liver transplantation

OBJECTIVE

The aim of this study was to evaluate the role of the C677T-MTHFR (methylenetetrahydrofolate reductase)-polymorphism (CC, CT and TT) for vascular complications in liver transplant recipients.

DESIGN

Retrospective study.

SETTING

Hepatology-Transplantation-Unit, Johann Wolfgang Goethe-University, Frankfurt am Main.

SUBJECTS

48 liver transplant recipients were included, no dropouts.

METHODS

MTHFR polymorphism was detected by PCR amplification and digestion with Hinfl restriction enzyme. Vascular complications after liver transplantation were detected from the patients' records. The total serum homocysteine (HCY) was analyzed with high-pressure liquid chromatography.

RESULTS

In the wild-type group (CC), the HCY levels were slightly high (14.0+/-1 micro M). Among the patients with the CT polymorphism, the HCY values were elevated (22.5+/-3 micro M). In the homozygous TT group, there was a significant increase (31.2+/-6 micro M, P<0.01) of the HCY values. The percentage of vascular complications was higher in the heterozygous CT (47%) and homozygous TT (62.5%) group compared with wild-type CC (21%). Patients with a homozygous TT genotype of the MTHFR polymorphism with a vascular complication had a highly significant elevated HCY level compared to the other genotype groups, both with and without any vascular complications (P<0.001). Recipients with an elevated HCY and the TT polymorphism have a higher probability of developing a vascular complication after transplantation (odds ratio: 4.3 and 11.0; 95% confidence interval: 1.15, 12.25 and 1.41, 85.24).

CONCLUSIONS

The C677T polymorphism in the MTHFR gene and subsequent elevation of the total serum HCY is significantly associated with an increased incidence of vascular complications in liver transplant recipients.

Tacrolimus versus cyclosporin as primary immunosuppression for kidney transplant recipients

BACKGROUND

Kidney transplantation is the treatment of choice for most patients with end-stage renal disease (ESRD). Standard protocols in use typically involve three drug groups each directed to a site in the T-cell activation or proliferation cascade which are central to the rejection process: calcineurin inhibitors (e.g. cyclosporin, tacrolimus), anti-proliferative agents (e.g. azathioprine, mycophenolate mofetil) and steroids (prednisolone). It remains unclear whether new regimens are more specific or simply more potent immunosuppressants.

OBJECTIVES

To compare the effects of tacrolimus with cyclosporin as primary therapy for kidney transplant recipients.

SEARCH STRATEGY

MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials, the Cochrane Renal Group's specialist register and conference proceedings were searched to identify relevant reports of randomised controlled trials (RCTs). Two reviewers assessed trials for eligibility, quality and extracted data independently.

SELECTION CRITERIA

All RCTs where tacrolimus was compared with cyclosporin for the initial treatment of kidney transplant recipients

DATA COLLECTION AND ANALYSIS

Data were synthesised (random effects model) and results expressed as relative risk (RR), values <1 favouring tacrolimus, with 95% confidence intervals (CI). Subgroup analysis and meta-regression were used to examine potential effect modification by differences in trial design and immunosuppressive co-interventions.

MAIN RESULTS

123 reports from 30 trials (4102 patients) were included. At six months graft loss was significantly reduced in tacrolimus-treated recipients (RR 0.56, 95% CI 0.36 to 0.86), and this effect was persistent up to three years. Meta-regression showed that this benefit diminished as higher trough levels of tacrolimus were targeted (P = 0.04), after allowing for differences in cyclosporin formulation (P = 0.97) and cyclosporin target trough level (P = 0.38). At one year, tacrolimus patients suffered less acute rejection (RR 0.69, 95% CI 0.60 to 0.79), and less steroid-resistant rejection (RR 0.49, 95% CI 0.37 to 0.64), but more insulin-requiring diabetes mellitus (RR 1.86, 1.11 to 3.09), tremor, headache, diarrhoea, dyspepsia and vomiting. Cyclosporin-treated recipients experienced significantly more constipation and cosmetic side-effects. We demonstrated no differences in infection or malignancy.

AUTHORS' CONCLUSIONS

Tacrolimus is superior to cyclosporin in improving graft survival and preventing acute rejection after kidney transplantation, but increases post-transplant diabetes, neurological and gastrointestinal side effects. Treating 100 recipients with tacrolimus instead of cyclosporin would avoid 12 suffering acute rejection, two losing their graft but cause an extra five to become insulin-requiring diabetics.

Effect of immunosuppressive agents on long-term survival of renal transplant recipients: focus on the cardiovascular risk

In the control of acute rejection, attention is being focused more and more on the long-term adverse effects of the immunosuppressive agents used. Since cardiovascular disease is the main cause of death in renal transplant recipients, optimal control of cardiovascular risk factors is essential in the long-term management of these patients. Unfortunately, several commonly used immunosuppressive drugs interfere with the cardiovascular system. In this review, the cardiovascular adverse effects of the immunosuppressive agents currently used for maintenance immunosuppression are thoroughly discussed. Optimising immunosuppression means finding a balance between efficacy and safety. Corticosteroids induce endothelial dysfunction, hypertension, hyperlipidaemia and diabetes mellitus, and impair fibrinolysis. The use of corticosteroids in transplant recipients is undesirable, not only because of their cardiovascular effects, but also because they induce such adverse effects as osteoporosis, obesity, and atrophy of the skin and vessel wall. Calcineurin inhibitors are the most powerful agents for maintenance immunosuppression. The calcineurin inhibitor ciclosporin (cyclosporine) not only induces these same adverse effects as corticosteroids but is also nephrotoxic. Tacrolimus has a more favourable cardiovascular risk profile than ciclosporin and is also less nephrotoxic. It has little or no effect on blood pressure and serum lipids; however, its diabetogenic effect is more prominent in the period immediately following transplantation, although at maintenance dosages, the diabetogenic effect appears to be comparable to that of ciclosporin. The diabetogenic effect of tacrolimus can be managed by reducing the dose of tacrolimus and early corticosteroid withdrawal. The effect of tacrolimus on endothelial function has not been completely elucidated. The proliferation inhibitors azathioprine and mycophenolate mofetil (MMF) have little effect on the cardiovascular system. Yet, indirectly, by inducing anaemia, they may lead to left ventricular hypertrophy. MMF is an attractive alternative to azathioprine because of its higher potency and possibly lower risk of malignancies. Sirolimus also induces anaemia, but may be promising because of its antiproliferative features. Whether the hyperlipidaemia induced by sirolimus counteracts its beneficial effects is, as yet, unknown. It may be combined with MMF, however, initial attempts resulted in severe mouth ulcers.

Abdominal aortic aneurysm and its correlation to plasma homocysteine, and vitamins

BACKGROUND

Hyperhomocysteinemia is a recognised independent risk factor in the genesis of atherosclerotic diseases. However, very little is known about the relationship between homocysteine and abdominal aortic aneurysm (AAA). Vitamins, namely B12 and folic acid have been implicated in the regulation of plasma homocysteine levels. However, there has been no prospective study that has analysed the relationship of AAA and plasma homocysteine in light of serum vitamin levels.

AIMS

To study the relationship between plasma homocysteine, serum B12 and folic acid levels, and AAA.

METHOD

Case control study including 38 AAA patients and 36 controls. Fasting homocysteine, B12 and folic acid were determined in serum separated within 1 h of blood collection using a fluorescence polarisation immunoassay technique (FPIA).

RESULTS

Twenty-six (68%) of the AAA patients had elevated levels of homocysteine compared to 2 (6%) in the case control group. The mean homocysteine level in the AAA group was 19.4 micromol/L (SE +/- 1.1) (95% CI 17.17-21.65) and in the control group was 10.9 micromol/L (SE +/- 1) (95% CI 9.95-11.88) (p<0.001). Mean vitamin B12 levels in the AAA and the controls was 332.11 pg/L (SE +/- 16.44) and 414.33 pg/L (SE +/- 19.72), respectively (p<0.004). Mean folic acid in the AAA was 8.02 (SE +/- 0.71) and the control was 9.8 etagm/L (SE +/- 0.69), (ns).

CONCLUSION

This study confirms significantly higher levels of plasma homocysteine in AAA patients but lower levels of B12. Use of supplemental vitamins that should lower plasma homocysteine may modify vascular disease progression. Clinical trials in this direction are warranted.

Plasma homocysteine levels in renal transplant patients on tacrolimus therapy

Increased plasma total homocysteine levels afford an independent risk factor to assess cardiovascular morbidity in patients with normal and impaired renal function, including stable transplant recipients. The purpose of this study was to evaluate plasma homocysteine levels and factors known to influence homocysteine metabolism (folate and Vitamin B(12)) in renal transplanted patients treated with tacrolimus. Plasma homocysteine, serum folate and serum vitamin B(12) concentrations were measured in 18 cadaveric renal transplant patients with stable function both before and 3 months after the renal transplantation. While the mean plasma homocysteine level in the renal transplant group was significantly higher than in the control group, no significant change was observed following renal transplantation under tacrolimus therapy (16.84 +/- 6.43 micromol/L vs 16.02 +/- 6.54 micromol/L). The levels of folate before and after transplantation were considerably lower than the control group; a significant effect of tacrolimus has not been observed (7.32 +/- 4.68 ng/mL and 7.55 +/- 5.20 ng/mL). Serum vitamin B(12) levels in the transplant group were significantly lower than the control group; a significant decline was seen 3 months after the renal transplantation (448.94 +/- 230.03 pg/mL vs 334.38 +/- 240.61 pg/mL). Consequently, although plasma homocysteine levels of renal transplant recipients are higher, a lowering effect of tacrolimus therapy was not observed on plasma homocysteine levels. The lower levels of folate and Vitamin B(12) in the transplant group compared to a control group supports therapy with folate and Vitamin B(12) to decrease homocysteine concentrations.