IMPDH activity in thiopurine-treated patients with inflammatory bowel disease - Relation to TPMT activity and metabolite concentrations
2008 (English)In: British Journal of Clinical Pharmacology, ISSN 0306-5251, E-ISSN 1365-2125, Vol. 65, no 1, 69-77 p.Article in journal (Refereed) Published
AIMS: Azathioprine and 6-mercaptopurine are steroid-sparing drugs used in inflammatory bowel disease (IBD). The polymorphic enzyme thiopurine S-methyltransferase (TPMT) is of importance for thiopurine metabolism and occurrence of adverse events. The role of other thiopurine-metabolizing enzymes is less well known. This study investigated the role of inosine-5′- monophosphate dehydrogenase (IMPDH), which is a key enzyme in the de novo synthesis of guanine nucleotides and also strategically positioned in the metabolic pathway of thiopurines. METHODS: IMPDH was measured in 100 healthy blood donors. IMPDH, TPMT and metabolite concentrations were studied in 50 patients with IBD on stable thiopurine therapy. IMPDH activity was measured in peripheral blood mononuclear cells. TPMT activity, 6-methylthioinosine 5′-monophosphate (meTIMP) and 6-thioguanine nucleotide (6-TGN) concentrations were measured in red blod cells, which is the current practice in clinical monitoring of thiopurines. Enzyme activities were related to metabolite concentrations and clinical characteristics. RESULTS: A wide range of IMPDH activity was observed both in healthy blood donors (median 13.1, range 4.7-24.2 nmol mg-1 protein h-1) and IBD patients (median 14.0, range 7.0-21.7). There was a negative correlation between IMPDH activity and dose-normalized meTIMP concentrations (rs = -0.31, P = 0.03), but no evident correlation to 6-TGN concentration or the meTIMP/6-TGN ratio. There were no significant correlations between TPMT activity and metabolite concentrations. CONCLUSION: Even though the meTIMP concentrations correlated inversely to the IMPDH activity, the role of IMPDH in balancing the formation of methylated and phosphorylated metabolites was not evident. Taken together, the results give cause to question established opinions about thiopurine metabolism. © 2007 The Authors.
Place, publisher, year, edition, pages
2008. Vol. 65, no 1, 69-77 p.
6-Mercaptopurine/*pharmacology Adult Aged Aged, 80 and over Azathioprine/*pharmacology Biological Markers Female Humans IMP Dehydrogenase/genetics/*metabolism Immunosuppressive Agents/*pharmacology Inflammatory Bowel Diseases/*drug therapy Male Methyltran
Medical and Health Sciences
IdentifiersURN: urn:nbn:se:liu:diva-43268DOI: 10.1111/j.1365-2125.2007.02985.xLocal ID: 73262OAI: oai:DiVA.org:liu-43268DiVA: diva2:264127