Endocrine and metabolic abnormalities following kidney transplantation

Risk factors for cardiovascular events after successful renal transplantation

BACKGROUND

Cardiovascular disease is a frequent cause of morbidity after renal transplantation. The aims of this study were to evaluate the incidence of cardiovascular events and to identify the main risk factors for cardiovascular complications and mortality in 2071 white adults with a renal transplant functioning for at least 1 year.

METHODS

Clinical events, routine biochemistry, and prescribed drugs at month 1, month 6, and yearly after transplantation were analyzed.

RESULTS

The incidence of cardiovascular events increased over time. At 15 years after transplantation, only 47% of surviving patients had not experienced any cardiovascular event. Risk factors associated with cardiovascular complications were male gender (P=0.04), age (P<0.0001), arterial hypertension before transplantation (P<0.0001), longer pretransplant dialysis (P<0.0001), cardiovascular event before transplantation (P<0.0001), older era of transplantation (P=0.0009), center-specific effect (P=0.003), posttransplant diabetes mellitus (P=0.01), increased pulse pressure after transplantation (P=0.02), intake of corticosteroids (P=0.016), intake of azathioprine (P=0.016), lower serum albumin after transplantation (P=0.004), and higher serum triglyceride levels after transplantation (P=0.007). The risk of death was increased in patients with low or elevated hematocrit, while it was minimal with values around 38%.

CONCLUSIONS

The occurrence of fatal and nonfatal cardiovascular events after successful renal transplantation not only relates to baseline cardiovascular risk factors present at transplantation, but also to immunosuppressive drugs and posttransplantation traditional and nontraditional risk factors.

Renal dysfunction is a strong and independent risk factor for mortality and cardiovascular complications in renal transplantation

Renal transplant recipients (RTR) have shortened life expectancy, primarily due to premature cardiovascular disease (CVD). Traditional CVD risk factors are highly prevalent. In addition, several non-traditional risk factors may contribute to the high risk. The aim of the study was to evaluate the effects of renal dysfunction on mortality and cardiovascular complications in 1052 placebo-treated patients of the Assessment of LEscol in Renal Transplantation (ALERT) trial. Follow-up was 5-6 years and endpoints included cardiac death, non-cardiovascular death, all-cause mortality, major adverse cardiac event (MACE), non-fatal myocardial infarction (MI) and stroke. The effects of serum creatinine at baseline on these endpoints were evaluated. Elevated serum creatinine in RTR was a strong and independent risk factor for MACE, cardiac, non-cardiovascular, and all-cause mortality, but not for stroke or non-fatal MI alone. Serum creatinine was associated with increased mortality and MACE, independent of established CVD risk factors. Graft loss resulted in increased incidences of non-cardiovascular death, all-cause mortality, MACE and non-fatal MI. In conclusion, elevated serum creatinine is a strong risk factor for all-cause, non-cardiovascular and cardiac mortality, and MACE, independent of traditional risk factors, but not for stroke or non-fatal MI alone.

Renal Dysfunction as a Risk Factor for Mortality and Cardiovascular Disease in Renal Transplantation: Experience from the Assessment of Lescol in Renal Transplantation Trial

BACKGROUND

Renal-transplant recipients have shortened life expectancy primarily because of premature cardiovascular disease. Traditional and nontraditional risk factors for cardiovascular disease are prevalent in renal patients. In renal-transplant recipients, immunosuppressive therapy can be nephrotoxic and aggravate cardiovascular disease risk factors. Renal dysfunction has been established as a risk factor for cardiovascular disease and mortality in different populations. We evaluated the effects of baseline renal-transplant function on mortality and cardiovascular and renal endpoints in 1,052 placebo-treated patients of the Assessment of Lescol in Renal Transplantation trial.

METHODS

All renal-transplant recipients were on cyclosporine-based immunosuppressive therapy. Follow-up was 5 to 6 years, and endpoints included cardiac death, noncardiovascular death, all-cause mortality, major adverse cardiac event (MACE), stroke, nonfatal myocardial infarction, and graft loss.

RESULTS

Baseline serum creatinine was strongly and independently associated with increased cardiac, noncardiovascular, and all-cause mortality, as well as MACE and graft loss. Serum creatinine was not a risk factor for stroke or nonfatal myocardial infarction.

CONCLUSIONS

Elevated baseline serum creatinine in renal-transplant recipients is a strong and independent risk factor for all-cause, noncardiovascular and cardiac mortality, MACE, and graft loss.

New insights into the pharmacodynamic and pharmacokinetic properties of statins

The beneficial effects of statins are assumed to result from their ability to reduce cholesterol biosynthesis. However, because mevalonic acid is the precursor not only of cholesterol, but also of many nonsteroidal isoprenoid compounds, inhibition of 3-hydroxy-3-methylglutaryl coenzyme A reductase may result in pleiotropic effects. It has been shown that several statins decrease smooth muscle cell migration and proliferation and that sera from fluvastatin-treated patients interfere with its proliferation. Cholesterol accumulation in macrophages can be inhibited by different statins, while both fluvastatin and simvastatin inhibit secretion of metalloproteinases by human monocyte-derived macrophages. The antiatherosclerotic effects of statins may be achieved by modifying hypercholesterolemia and the arterial wall environment as well. Although statins rarely have severe adverse effects, interactions with other drugs deserve attention. Simvastatin, lovastatin, cerivastatin, and atorvastatin are biotransformed in the liver primarily by cytochrome P450-3A4, and are susceptible to drug interactions when co-administered with potential inhibitors of this enzyme. Indeed, pharmacokinetic interactions (e.g., increased bioavailability), myositis, and rhabdomyolysis have been reported following concurrent use of simvastatin or lovastatin and cyclosporine A, mibefradil, or nefazodone. In contrast, fluvastatin (mainly metabolized by cytochrome P450-2C9) and pravastatin (eliminated by other metabolic routes) are less subject to this interaction. Nevertheless, a 5- to 23-fold increase in pravastatin bioavailability has been reported in the presence of cyclosporine A. In summary, statins may have direct effects on the arterial wall, which may contribute to their antiatherosclerotic actions. Furthermore, some statins may have lower adverse drug interaction potential than others, which is an important determinant of safety during long-term therapy.

Effect of MTHFR 677C>T on plasma total homocysteine levels in renal graft recipients

BACKGROUND

Hyperhomocysteinemia is an established, independent risk factor for vascular disease morbidity and mortality. The 5,10-methylenetetrahydrofolate reductase (MTHFR) gene polymorphism C677T has been shown to result in increased total homocysteine concentrations on the basis of low folate levels caused by a decreased enzyme activity. The effect of this polymorphism on total homocysteine and folate plasma levels in renal transplant patients is unknown.

METHODS

We screened 636 kidney graft recipients for the presence of the MTHFR C677T gene polymorphism. The major determinants of total homocysteine and folate plasma concentrations of 63 patients, who were identified to be homozygous for this gene polymorphism compared with heterozygotes (N = 63), and patients with wild-type alleles (N = 63), who were matched for sex, age, glomerular filtration rate (GFR), and body mass index, were identified by analysis of covariance. The variables included sex, age, GFR, body mass index, time since transplantation, folate and vitamin B12 levels, the use of azathioprine, and the MTHFR genotype. To investigate the impact of the kidney donor MTHFR genotype on total homocysteine and folate plasma concentrations, a similar model was applied in 111 kidney graft recipients with stable graft function, in whom the kidney donor C677T MTHFR gene polymorphism was determined.

RESULTS

The allele frequency of the C677T polymorphism in the MTHFR gene was 0.313 in the whole study population [wild-type (CC), 301; heterozygous (CT), 272; and homozygous mutant (TT), 63 patients, respectively] and showed no difference in the patient subgroups with various renal diseases. The MTHFR C677T gene polymorphism significantly influenced total homocysteine and folate plasma concentrations in renal transplant recipients (P = 0.0009 and P = 0.0002, respectively). Furthermore, a significant influence of the GFR (P = 0.0001), folate levels (P = 0.0001), age (P = 0.0001), body mass index (P = 0.0001), gender (P = 0.0005), and vitamin B12 levels (P = 0.004) on total homocysteine concentrations was observed. The donor MTHFR gene polymorphism had no influence on total homocysteine and folate levels. Geometric mean total homocysteine levels in patients homozygous for the mutant MTHFR allele were 18.6 micromol/liter compared with 14.6 micromol/liter and 14.9 micromol/liter in patients heterozygous for the MTHFR gene polymorphism and those with wild-type alleles (P < 0.05 for TT vs. CT and CC). Geometric mean folate levels were lower in CT and TT patients (11.2 and 10.2 nmol/liter) compared with CC patients (13.6 nmol/liter, P < 0.05 vs. CT and TT).

CONCLUSIONS

This study demonstrates that homozygosity for the C677T polymorphism in the MTHFR gene significantly increases total homocysteine concentrations and lowers folate levels in kidney graft recipients, even in patients with excellent renal function (GFR more than median). These findings have important implications for risk evaluation and vitamin intervention therapy in these patients who carry an increased risk for the development of cardiovascular disease.

Risk factors for premature coronary heart disease after successful liver transplantation in adults

As solid-organ transplantation has evolved into a highly effective treatment for end-stage organ disease, the long-term health implications of chronic exposure of recipients to immunosuppressants and other pharmacological agents are becoming more apparent. Coronary heart disease has long been known to plague kidney transplant recipients and more recently has been found to affect heart transplant recipients disproportionately. Coronary heart disease after liver transplantation, however, is less well known. The purpose of this study was to examine risk factors for premature coronary heart disease in asymptomatic adult recipients of liver transplants. Nutrition-related risk factors for coronary heart disease (obesity and hyperlipidemia) were measured in 29 patients before and after liver transplantation. Changes with respect to primary immunosuppression protocol (cyclosporine plus corticosteroid vs tacrolimus plus corticosteroid) were compared. Risk factors that had not been present before transplantation were apparent in both groups by 6 months after transplantation. Although obesity and hyperlipidemia were not found to be independent risk factors for coronary heart disease, they were clinically important when considered in combination. Cyclosporine was associated with significantly higher serum lipid concentrations than was tacrolimus.

Severe hyperlipoproteinemia in congenital nephrotic syndrome of the Finnish type: effect of dialysis and kidney transplantation

Two children with congenital nephrosis of the Finnish type were studied successively at the three stages of the disease: (A) nephrosis, (B) renal insufficiency/peritoneal dialysis and (C) post-transplantation; two additional patients were studied at two stages. Plasma lipoprotein profiles were determined by density gradient ultracentrifugation and lipids by enzymatic methods. Stage A was characterized by hyperchylomicronemia, low high density lipoprotein (HDL) cholesterol and the presence of dense low density lipoprotein (LDL) and HDL particles. Total cholesterol and triglycerides showed great daily variation (5-14 and 5-33 mmol/l, respectively). During stage B, hyperlipidemia weakened. Yet HDL concentration remained low and the concentration of intermediate density lipoproteins (IDL) increased. At stage C, hyperlipidemia had almost subsided, but the presence of IDL persisted. In conclusion, severe hyperlipoproteinemia of congenital nephrosis at the nephrotic stage is attenuated during renal insufficiency and dialysis, and essentially normalizes after kidney transplantation. Yet the presence of IDL implies an increased risk of atherosclerosis.

Effect of cyclosporin A, azathioprine, and prednisolone on carbohydrate metabolism of rat hepatocytes

The effect of different immunosuppressive drugs (prednisolone, azathioprine, cyclosporin A) on liver carbohydrate metabolism in the rat was investigated. Daily administration of prednisolone (3 mg/kg body weight) and azathioprine (2 mg/kg body weight) intraperitoneally for 2 weeks caused significantly lower liver glycogen content than that in NaCl-treated controls. Liver glucose and lactate content, as well as plasma glucose, glucagon, and serum insulin concentration of these animals, remained unchanged. There were no differences in any of these parameters between cyclosporin A (15 mg/kg body weight)-treated and vehicle (olive oil/ethanol)-treated animals. Prednisolone caused significantly lower glucose production in isolated rat hepatocytes using Na-pyruvate as the substrate, whereas glucose production was unchanged in hepatocytes of azathioprine-treated rats using pyruvate or L-serine as substrates. Glucose production from pyruvate or serine was significantly inhibited by cyclosporin A compared to the vehicle, but did not differ from the effects of azathioprine and prednisolone. Lactate production was significantly lower in cyclosporin-treated animals than in those given either the vehicle or azathioprine. Cyclosporin A completely reversed the inhibition of hepatocyte glycogen consumption caused by the vehicle. However, glycogen production in the presence of cyclosporin A was comparable to the effects of prednisolone and azathioprine. Finally, hepatocyte ketone body production using pyruvate as the substrate was higher in the presence of all immunosuppressive drugs. In the presence of serine, acetoacetate production increased in rats treated with 50 mg/kg body weight cyclosporin A, and beta-hydroxybutyrate production in animals receiving 15 and 50 mg/kg body weight cyclosporin A.