EXCESS PREVALENCE OF FASTING AND POSTMETHIONINE-LOADING HYPERHOMOCYSTEINEMIA IN STABLE RENAL-TRANSPLANT RECIPIENTS

Hyperhomocysteinemia, either fasting or after methionine loading, may contribute to the increased incidence of cardiovascular disease events experienced by renal transplant recipients. Limited data are availabl e on fasting homocysteine (Hcy) levels, and none on postmethionine-loa ding Hcy levels, in these patients. We assessed the prevalence and pot ential determinants of fasting and postmethionine-loading hyperhomocys teinemia in 29 stable renal transplant recipients and 58 age- and sex- matched, population-based controls free of renal disease with serum cr eatinine levels of 1.5 mg/dL or less. Total (t) plasma Hcy was determi ned fasting and 2 hours after methionine loading, along with fasting d eterminations of the B-vitamin cofactors/substrates for Hcy metabolism , ie, pyridoxal 5'-phosphate, B-12, and folate and serum creatinine. G eometric mean fasting (18.1 versus 9.8 mu M, P<.001) and postmethionin e-loading increase (22.0 versus 15.2, P=.001) in tHcy levels were sign ificantly greater in the renal transplant recipients, as were the prev alence odds (with 95% confidence intervals) for fasting [14.8 (3.4-64. 7)], postmethionine loading [6.9 (1.5-32.8)], combined fasting and pos tmethionine-loading [18.0 (2.3-142.1)] hyperhomocysteinemia, and inade quate circulating folate [4.2 (1.1-16.5)] or pyridoxal 5'-phosphate [3 .2 (0.9-11.0) status. Correlation analyses suggested important potenti al relationships between creatinine and both fasting (+0.64, P<.001) a nd postmethionine-load increase (+0.38, P=.045) in tHcy, folate and fa sting (-0.41, P=.025) tHcy, and pyridoxal 5'-phosphate and postmethion ine-loading increase (-0.33, P=.091) in tHcy. We conclude that there i s an excess prevalence of fasting and postmethionine-loading hyperhomo cysteinemia in stable renal transplant recipients. Renal function is r elated to both fasting and postmethionine loading-hyperhomocysteinemia , inadequate folate status is associated with fasting hyperhomocystein emia, and inadequate vitamin B-6 status may be related to postmethioni ne-loading hyperhomocysteinemia in this patient population.