Homocysteine, vitamin B12, and serum and erythrocyte folate in peritoneal dialysis and hemodialysis patients.

BACKGROUND: Plasma homocysteine (Hcy) is an independent risk factor for cardiovascular disease. High levels of plasma Hcy have been observed in end-stage renal disease patients. Few studies have compared peritoneal dialysis (PD) and hemodialysis (HD) patients and few data are available on erythrocyte folate (ery-F) levels in dialysis patients. OBJECTIVES: To evaluate plasma Hcy concentrations, vitamin B12 (B12), and folate status in dialysis patients; to analyze the possible causes of high Hcy levels; to follow up changes in folate and B12 concentrations after 6 months. DESIGN: A cross-sectional observational study. SETTING: Nephrology division and laboratory of hematology in a university and clinical research hospital. PATIENTS: The study included 82 patients treated with PD for 37 + 37 months and 70 patients treated with HD for 136 + 95 months. LABORATORY METHODS: Plasma Hcy was measured by the immunoenzymatic IMx Hcy FPIA method (Abbott Laboratories, Diagnostic Division, Abbott Park, IL, U.S.A.), serum folate (s-F) and ery-F by the Stratus folate fluorometric enzyme-linked assay, and B12 by the Stratus vitamin B12 fluorometric enzyme-linked assay (DADE-Behring, Newark, DE, U.S.A.). RESULTS: Ninety-six percent of PD and 97% of HD patients had Hcy levels above the cutoff (13.5 micromol/L). Homocysteine level was higher in HD than in PD patients, while the prevalence of hyperhomocysteinemia was similar with the two techniques. Erythrocyte folate was significantly higher in PD (1333 +/- 519 pmol/L) than in HD (1049 +/-511 pmol/L, p < 0.01). Statistically significant correlations were observed between Hcy and B12, s-F, ery-F, and dialysis duration. Multivariate analysis showed a strong correlation between s-F and Hcy. After 6 months there were no differences in Hcy, B12, s-F, and ery-F levels. CONCLUSIONS: Plasma Hcy levels were high in more than 95% of our dialysis patients, with no relation to the type of dialysis. Vitamin B12 and folate were normal in the majority of our patients. However, serum folate was the major determinant of Hcy levels. Such a relation between Hcy and folate suggests that levels of folate within the reference interval are inadequate for dialysis patients.     

No association of endocannabinoid genes with bipolar disorder or lithium response in a Sardinian sample

Bipolar disorder (BD) is a chronic and severe psychiatric condition with an underlying component of genetic susceptibility. Mounting evidence suggests a potential role of the endogenous cannabinoid (eCB) system in the pathogenesis of BD. Here we investigated the role of genes encoding for key eCB elements on the risk of developing BD in a sample of 357 BD patients and 422 healthy controls of Sardinian ancestry. Using the HapMap CEU population SNP database, we selected 25 tag Single Nucleotide Polymorphisms (tSNPs) in N-acyl phosphatidylethanolamine phospholipase D (NAPE-PLD), cannabinoid receptor 1 (CNR1) and fatty acid amide hydrolase (FAAH) genes. No significant association was reported for FAAH or CNR1. SNPs rs11487077 and rs6465903 in NAPE-PLD showed nominal association (p=0.033 and p=0.026, respectively) with BD, not significant after permutation testing. These SNPs were also tested for association with lithium response in 204 BD patients characterized for response to long-term lithium treatment, reporting no significant findings. As a whole, our results do not support a clear role of FAAH, CNR1 and NAPE-PLD in BD and lithium response. Additional studies on independent, larger samples are warranted to further explore the involvement of the eCB system in BD.