Relationship between serum homocysteine and other parameters in renal transplant patients

Nutritional Deficiencies, Bariatric Surgery, and Serum Homocysteine Level: Review of Current Literature

Obesity is currently one of the biggest global health problems. In the case of severe obesity, bariatric surgeries are considered to be the most important method of treatment. The 2 most commonly performed bariatric surgery procedures include Roux-en-Y gastric bypass and sleeve gastrectomy. However, these methods are not free from complications, and the most common ones (moderately long or long term) are micronutrient deficiencies. The deficiency of vitamins B6, B12, and folic acid as cofactors of the folate cycle contributes to the development of hyperhomocysteinemia. It seems that apart from nutritional factors, there are other aspects that have a significant influence on the concentration of homocysteine in blood, such as the type of conducted bariatric surgery, the post-surgical concentration of betaine and creatinine, and the clearance of methionine (i.e., the mutations of the gene that encodes the MTHFR reductase as well as other genes associated with the process of methylation, e.g., methionine synthase). Their presence might be one of the causes of the increased concentration of homocysteine after surgery despite the fact that patients take vitamin-mineral supplementation.

Hyperhomocysteinemia and assessment of its associated factors in renal transplant recipients: a single-center study in northern Iran

INTRODUCTION

Hyperhomocysteinemia (hyperHcy) is an important risk factor for atherosclerosis, which is currently a major cause of death in renal transplant patients (RTRs). The aim of this study was to determine the associated factors of hyperHcy in RTRs in northern Iran.

METHODS

In 148 stable RTRs, total serum homocysteine (tHcy) level, folate, serum albumin and creatinine, creatinine clearance, lipid status, body mass index (BMI), and blood cyclosporine levels (C0 and C2) were determined. The mean doses of cyclosporine A (mg/kg/day) were recorded.

RESULTS

In this analytic cross-sectional study the prevalence of hyperHcy was 70.3%. Hyperhomocysteinemia was defined as total serum homocysteine of 12 μmol/L or greater. The comparison of the group of 44 patients with tHcy level less than 12 and the group of 104 patients with tHcy level of 12 μmol/L or greater revealed that those subjects with hyperHcy were mostly younger, male, with lower BMI, history of glomerulonephritis, higher serum level of uric acid, and blood cyclosporine trough level (C0) and used higher doses of cyclosporine A. Significant correlation was found between tHcy level and recipients age, serum creatinine, BUN, folate concentrations, and creatinine clearance. However, multivariate analysis indicated that serum folate (P=0.01), vitamin B12 (P=0.05), creatinine (P=0.03), and BUN (P=0.05), and blood cyclosporine trough level (C0, P=0.005) were independently associated with tHcy levels.

CONCLUSION

HyperHcy persists after successful kidney transplantation in the majority of RTRs. Serum creatinine, BUN, folate and vitamin B12, and blood cyclosporine trough level (C0) are independently associated with tHcy levels.

Biomarkers of immunosuppressant organ toxicity after transplantation: status, concepts and misconceptions

INTRODUCTION

A major challenge in transplantation is improving long-term organ transplant and patient survival. Immunosuppressants protect the transplant organ from alloimmune reactions, but sometimes also exhibit limiting side effects. The key to improving long-term outcome following transplantation is the selection of the correct immunosuppressive regimen for an individual patient for minimizing toxicity while maintaining immunosuppressive efficacy.

AREAS COVERED

Proteomics and metabolomics have the potential to develop sensitive and specific diagnostic tools for monitoring early changes in cell signal transduction, regulation and biochemical pathways. Here, we review the steps required for the development of molecular markers from discovery, mechanistic and clinical qualification to regulatory approval, and present a critical discussion of the current status of molecular marker development as relevant for the management and individualization of immunosuppressive drug regimens.

EXPERT OPINION

Although metabolomics and proteomics-based studies have yielded several candidate molecular markers, most published studies are poorly designed, statistically underpowered and/or often have not gone beyond the discovery stage. Most molecular marker candidates are still at an early stage. Due to the high complexity of and the resources required for diagnostic marker development, initiatives and consortia organized and supported by funding agencies and regulatory agencies will be critical.

Determinants of hyperhomocysteinemia after gastric bypass surgery in obese subjects

BACKGROUND

Effectiveness of gastric bypass (GBP) on reduction of vascular risk factors is well established, but GBP induces nutritional deficits that could reduce the cardiovascular benefit of weight loss. Particularly, hyperhomocysteinemia, now clearly identified as a vascular risk factor, has been described after GBP. The aim of this study was to clarify the factors associated with increased homocysteine concentration after GBP.

METHODS

Homocysteine concentration and multiple nutritional parameters were measured in 213 consecutive subjects. One hundred and eight subjects were studied before surgery (control (CT)), 115 one to 6 years after GBP, and 41 both before and 6 months after GBP.

RESULTS

Homocysteine concentration did not differ before and after GBP (9.1 ± 3.2 vs 8.6 ± 3.4 μmol/l), but 94% of subjects had been supplemented with a multivitamin preparation after surgery. The nutritional parameters best correlated with homocysteine concentration both before and after GBP were folate and creatinine concentrations (p < 0.0001). In contrast, vitamin B12 and metabolic parameters (including glucose, insulin, lipids and C-reactive protein) were not associated with homocysteine concentration. After GBP, homocysteine concentration was significantly lower in subjects taking a multivitamin supplementation containing a high dose of folate than those who did not (7.7 ± 2.8 vs 10.1 ± 3.9 μmol/l, p < 0.0001).

CONCLUSIONS

The main determinants of homocysteine concentration identified in this study are folate and serum creatinine. Multivitamin supplementation with a high dose of folate prevents hyperhomocysteinemia after GBP.

Hyperhomocysteinemia after kidney transplantation

OBJECTIVE

To determine the prevalence of hyperhomocysteinemia (plasma homocysteine[Hcy] concentration≥15 μmol/L) and evaluate its correlation with allograft function.

MATERIALS AND METHODS

The study included 159 stable renal transplant recipients (104 men and 55 women). The prevalence and severity of hyperhomocysteinemia were compared in the transplant recipients vs 72 patients (48 men and 24 women) receiving hemodialysis therapy.

RESULTS

The mean (SD; range) fasting total Hcy concentration was higher in the hemodialysis group compared with the renal transplantation group: 27.4 (18.3; 10-95) μmol/L vs 16.6 (9.5; 4.5-45.0) μmol/L (P=.00). Hyperhomocysteinemia occurred more frequently in patients receiving hemodialysis therapy (74% vs 49%). No significant correlation was observed between Hcy concentration and recipient sex, cyclosporine trough concentration and concentration at 2 days after dosing, dyslipidemia,cytomegalovirus infection, diabetes mellitus, or aspartate or alanine aminotransferase concentration. Multivariate regression analysis revealed that serum creatinine concentration (P=.02) was the major determinant of increased total Hcy concentration in renal transplant recipients.

CONCLUSION

A high prevalence of moderate hyperhomocysteinemia was observed in renal transplant recipients. There was no correlation between graft function and Hcy concentration.