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  • 1.
    Haglund, Sofie
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Gastroenterologi och hepatologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Endokrin- och magtarmmedicinska kliniken US.
    Interindividual differences in thiopurine metabolism: studies with focus on inflammatory bowel disease2011Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The thiopurines, 6-mercaptopurine and its prodrug azathioprine, are used in the treatment of inflammatory bowel disease, ulcerative colitis and Crohn´s disease. The main active metabolites are the phosphorylated thioguanine nucleotides (6-TGNs) and methylated thioinosine monophosphate (meTIMP). Both groups contribute to the immunomodulatory effects. About 30-40% of patients fail to benefit from thiopurine treatment. A well-known cause of adverse reactions is decreased or absent thiopurine S-methyltransferase (TPMT) activity. Low TPMT activity is inherited as an autosomal codominant recessive trait and is present in approximately 10% of the population. Although several clinical issues can be solved from determination of TPMT activity, there are cases where it is not possible. In Sweden approximately 25% of IBD-patients display suboptimal 6-TGN concentrations and unexpectedly high concentrations of meTIMP despite a normal TPMT activity. A high meTIMP/6-TGN concentration ratio has been associated with both unresponsiveness to therapy and emergence of adverse reactions. Inosine 5’-monophosphate dehydrogenase (IMPDH) may constitute a candidate gene to explain this metabolite profile, as it is strategically positioned in the metabolic pathway of thiopurines where it competes with TPMT for their common substrate 6-TIMP.

    In paper I a pyrosequencing method was developed for genotyping of at that time all known genetic variants of TPMT. The concordance between genotype and phenotype in 30 individuals was 93%. The allele frequencies of TPMT*3A, *3B, *3C and *2 in a Swedish background population (n=800) were in agreement with those in other Caucasian or European populations. In Paper II-IV we explored the molecular basis of different metabolite profiles, i.e. low, normal and high meTIMP/6-TGN concentration ratios. The activity of IMPDH was measured in mononuclear cells (MNC). Patients with high metabolite ratios had lower IMPDH activity than patients with normal or low ratios, explained by an inverse correlation to red blood cells concentration of meTIMP. No correlation to 6-TGN was observed. Downregulation of IMPDH activity in HEK293 cells with genetically engineered TPMT activity was associated with an increase in meTIMP, but unexpectedly also of 6-TGN, irrespective of the TPMT status. These results suggest effects of pharmacogenes other than TPMT and IMPDH. A whole genome expression analysis was performed, (1) to identify new candidate genes that could explain differences in metabolite profiles, and (2) to study genes with known associations to the metabolic pathway of (thio)purines. The whole genome expression analysis did not identify any significant group differences. In analysis of the thiopurine related genes, three clusters of co-regulated genes were defined. A co-operation between expression levels of SLC29A1 and NT5E in explaining the meTIMP/6-TGN concentration ratio was observed, and individually SLC29A1 and NT5E correlated to 6-TGN and meTIMP, respectively.

    Pysosequencing is a convenient and flexible method which is now run in parallel to phenotyping in our laboratory. Our results also illustrate the complexity of the thiopurine metabolism and suggest that differences between metabolite profiles are explained either by interactions between several genes, each with a small contribution, or at the post-transcriptional level. Search for more precise tools to explain differences in metabolite profiles is needed. Furthermore, in order to investigate small effects it is necessary to analyse metabolite concentrations and gene expression levels, as well as enzyme activities in the target cells of therapy (MNC).

    Delarbeid
    1. Pyrosequencing of TPMT Alleles in a General Swedish Population and in Patients with Inflammatory Bowel Disease
    Åpne denne publikasjonen i ny fane eller vindu >>Pyrosequencing of TPMT Alleles in a General Swedish Population and in Patients with Inflammatory Bowel Disease
    Vise andre…
    2004 (engelsk)Inngår i: Clinical Chemistry, ISSN 0009-9147, E-ISSN 1530-8561, Vol. 50, nr 2, s. 288-295Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Background: Interindividual differences in therapeutic efficacy in patients treated with thiopurines might be explained by the presence of thiopurine S-methyltransferase (TPMT) alleles that encode for reduced TPMT enzymatic activity. It is therefore of value to know an individual's inherent capacity to express TPMT. Method: We developed a pyrosequencing method to detect 10 single-nucleotide polymorphisms (SNPs) in TPMT. A Swedish population (n = 800) was examined for TPMT*3A, TPMT*3B, TPMT*3C, and TPMT*2. Patients with inflammatory bowel disease (n = 24) and healthy volunteers (n = 6), selected on the basis of TPMT enzymatic activity, were investigated for all 10 SNPs to determine the relationship between TPMT genotype and phenotype. Results: In the general population we identified the following genotypes with nonfunctional alleles: TPMT*1/*3A (*3A allelic frequency, 3.75%), TPMT*1/*3C (*3C allelic frequency, 0.44%), TPMT*1/*3B (*3B allelic frequency, 0.13%), and TPMT*1/*2 (*2 allelic frequency, 0.06%). All nine individuals with normal enzymatic activity were wild-type TPMT*1/*1. Thirteen individuals with intermediate activity were either TPMT*1/*3A (n = 12) or TPMT*1/*2 (n = 1). Eight individuals with low enzymatic activity were TPMT*3A/*3A (n = 4), TPMT*3A/*3C (n = 2), or TPMT*1/*3A (n = 2). Conclusion: Next to wild type, the most frequent alleles in Sweden are TPMT*3A and TPMT*3C. A previously established phenotypic cutoff for distinguishing normal from intermediate metabolizers was confirmed. To identify the majority of cases (90%) with low or intermediate TPMT activity, it was sufficient to analyze individuals for only 3 of the 10 SNPs investigated. Nevertheless, this investigation indicates that other mutations might be of relevance for decreased enzymatic activity. © 2004 American Association for Clinical Chemistry.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-45829 (URN)10.1373/clinchem.2003.023846 (DOI)
    Tilgjengelig fra: 2009-10-11 Laget: 2009-10-11 Sist oppdatert: 2017-12-13
    2. IMPDH activity in thiopurine-treated patients with inflammatory bowel disease - Relation to TPMT activity and metabolite concentrations
    Åpne denne publikasjonen i ny fane eller vindu >>IMPDH activity in thiopurine-treated patients with inflammatory bowel disease - Relation to TPMT activity and metabolite concentrations
    2008 (engelsk)Inngår i: British Journal of Clinical Pharmacology, ISSN 0306-5251, E-ISSN 1365-2125, Vol. 65, nr 1, s. 69-77Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    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.

    Emneord
    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
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-43268 (URN)10.1111/j.1365-2125.2007.02985.x (DOI)73262 (Lokal ID)73262 (Arkivnummer)73262 (OAI)
    Tilgjengelig fra: 2009-10-10 Laget: 2009-10-10 Sist oppdatert: 2017-12-13bibliografisk kontrollert
    3. The Role of Inosine-5'-Monophosphate Dehydrogenase in Thiopurine Metabolism in Patients With Inflammatory Bowel Disease
    Åpne denne publikasjonen i ny fane eller vindu >>The Role of Inosine-5'-Monophosphate Dehydrogenase in Thiopurine Metabolism in Patients With Inflammatory Bowel Disease
    Vise andre…
    2011 (engelsk)Inngår i: Therapeutic Drug Monitoring, ISSN 0163-4356, E-ISSN 1536-3694, Vol. 33, nr 2, s. 200-208Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    BACKGROUND:: There is a large interindividual variability in thiopurine metabolism. High concentrations of methylthioinosine-5'-monophosphate (meTIMP) and low concentrations of 6-thioguanine nucleotides (6-TGNs) have been associated with a lower response rate and an increased risk of adverse events. In this study, the role of inosine-5'-monophosphate dehydrogenase (IMPDH) for differences in metabolite patterns of thiopurines was investigated.

    METHODS:: IMPDH activity and thiopurine metabolite concentrations were determined in patients with inflammatory bowel disease and a normal thiopurine methyltransferase (TPMT) phenotype and meTIMP/6-TGN concentration ratio > 20 (n = 26), in patients with a metabolite ratio ≤20 (n = 21), in a subgroup with a metabolite ratio <4 (n = 6), and in 10 patients with reduced TPMT activity. In vitro studies were conducted on human embryonic kidney cells (HEK293) with genetically engineered IMPDH and TPMT activities.

    RESULTS:: Patients with metabolite ratios >20 had lower IMPDH activity than those with ratios ≤20 (P < 0.001). Metabolic ratios >20 were only observed in patients with normal TPMT activity. Downregulation of IMPDH activity in HEK293 cells was associated with an increase in the concentration of meTIMP (fold change: 17 up to 93, P < 0.001) but, unexpectedly, also of 6-thioguanosine monophosphate (fold change: 2.6 up to 5.0, P < 0.001).

    CONCLUSIONS:: These data question the general view of IMPDH as the rate-limiting enzyme in the phosphorylation of thiopurines. Investigations of other mechanisms are needed to more fully explain the various metabolite patterns and outcomes in patients under treatment.

    sted, utgiver, år, opplag, sider
    Lippincott Williams & Wilkins, 2011
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-66431 (URN)10.1097/FTD.0b013e31820b42bb (DOI)000288498100010 ()21311411 (PubMedID)
    Tilgjengelig fra: 2011-03-15 Laget: 2011-03-15 Sist oppdatert: 2017-12-11bibliografisk kontrollert
    4. Pharmacotranscriptomics in thiopurine treated IBD patients with different metabolite profiles
    Åpne denne publikasjonen i ny fane eller vindu >>Pharmacotranscriptomics in thiopurine treated IBD patients with different metabolite profiles
    2008 (engelsk)Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Background: Thiopurine drugs are used to induce and maintain remission in inflammatory bowel disease. The methyl thioinosine monophosphate (meTIMP)/6-thioguanine nucleotide (6-TGN) concentration ratio has been related to drug response and adverse reactions. Here we investigated for differences in gene expression levels between patients with different metabolite profiles.

    Methods: Transcriptional profiles in blood samples from an exploratory patient cohort (n=21) comprising three groups; patients with normal thiopurine S-methyltransferase phenotype and meTIMP/6-TGN concentration ratio >20, ratio 10.0-14.0 and ratio ≤4, respectively, were assessed by hybridization to microarrays. Results were further evaluated with reverse transcription qPCR [exploratory and a validation cohort of patients (n=33)]. Additionally, known genes of the thiopurine metabolic pathway were analysed separately.

    Results: The whole genome expression analysis did not identify any significant differences between metabolite profiles. Analysis of thiopurine related genes revealed a large interindividual variation in gene expression, but only small differences between metabolite profiles. Three clusters of co-regulated genes were defined based on correlations between gene expression levels. The concentration of meTIMP correlated to the expression of NT5E (rs = 0.33, P = 0.02) and TPMT (rs = - 0.37, P = 0.007). The concentration of 6-TGN correlated to the expression of HPRT1 (rs = - 0.31, P = 0.03) and SLC29A1 (rs = 0.33, P = 0.02). With the exception of SLC29A1, these genes belonged to the same cluster of genes.

    Conclusions: Our results illustrates the complexity of the thiopurine metabolism and suggest that differences between metabolite profiles are explained either by interactions between several genes, each with a small contribution, or at the post-transcriptional level. Search for more precise tools in order to explain differences in metabolite profiles is needed.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-66432 (URN)
    Tilgjengelig fra: 2011-03-15 Laget: 2011-03-15 Sist oppdatert: 2011-03-15bibliografisk kontrollert
  • 2.
    Haglund, Sofie
    et al.
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Gastroenterologi och hepatologi. Linköpings universitet, Hälsouniversitetet.
    Almer, Sven
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Gastroenterologi och hepatologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Magtarmmedicinska kliniken.
    Peterson, Curt
    Linköpings universitet, Institutionen för medicin och hälsa, Klinisk farmakologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Onkologiska kliniken US.
    Söderman, Jan
    Ryhov County Hospital, Jönköping, Sweden .
    Gene Expression and Thiopurine Metabolite Profiling in Inflammatory Bowel Disease: Novel Clues to Drug Targets and Disease Mechanisms?2013Inngår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, nr 2Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background and Aims

    Thiopurines are effective to induce and maintain remission in inflammatory bowel disease (IBD). The methyl thioinosine monophosphate (meTIMP)/6-thioguanine nucleotide (6-TGN) concentration ratio has been associated with drug efficacy. Here we explored the molecular basis of differences in metabolite profiles and in relation to disease activity.

    Methods

    Transcriptional profiles in blood samples from an exploratory IBD-patient cohort (n = 21) with a normal thiopurine S-methyltransferase phenotype and meTIMP/6-TGN ratios >20, 10.0–14.0 and ≤4, respectively, were assessed by hybridization to microarrays. Results were further evaluated with RT qPCR in an expanded patient cohort (n = 54). Additionally, 30 purine/thiopurine related genes were analysed separately.

    Results

    Among 17 genes identified by microarray-screening, there were none with a known relationship to pathways of purines/thiopurines. For nine of them a correlation between expression level and the concentration of meTIMP, 6-TGN and/or the meTIMP/6-TGN ratio was confirmed in the expanded cohort. Nine of the purine/thiopurine related genes were identified in the expanded cohort to correlate with meTIMP, 6-TGN and/or the meTIMP/6-TGN ratio. However, only small differences in gene expression levels were noticed over the three different metabolite profiles. The expression levels of four genes identified by microarray screening (PLCB2, HVCN1, CTSS, and DEF8) and one purine/thiopurine related gene (NME6) correlated significantly with the clinical activity of Crohn’s disease. Additionally, 16 of the genes from the expanded patient cohort interacted in networks with candidate IBD susceptibility genes.

    Conclusions

    Seventeen of the 18 genes which correlated with thiopurine metabolite levels also correlated with disease activity or participated in networks with candidate IBD susceptibility genes involved in processes such as purine metabolism, cytokine signaling, and functioning of invariant natural killer T cells, T cells and B cells. Therefore, we conclude that the identified genes to a large extent are related to drug targets and disease mechanisms of IBD.

  • 3.
    Haglund, Sofie
    et al.
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Gastroenterologi och hepatologi. Linköpings universitet, Hälsouniversitetet.
    Almer, Sven
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för klinisk och experimentell medicin, Gastroenterologi och hepatologi. Östergötlands Läns Landsting, Medicincentrum, Endokrin- och magtarmmedicinska kliniken US.
    Peterson, Curt
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och hälsa, Klinisk farmakologi. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Onkologiska kliniken US.
    Söderman, Jan
    Division of Medical Diagnostics, Laboratory medicine, Ryhov Hospital, Jönköping, Sweden.
    Pharmacotranscriptomics in thiopurine treated IBD patients with different metabolite profiles2008Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Background: Thiopurine drugs are used to induce and maintain remission in inflammatory bowel disease. The methyl thioinosine monophosphate (meTIMP)/6-thioguanine nucleotide (6-TGN) concentration ratio has been related to drug response and adverse reactions. Here we investigated for differences in gene expression levels between patients with different metabolite profiles.

    Methods: Transcriptional profiles in blood samples from an exploratory patient cohort (n=21) comprising three groups; patients with normal thiopurine S-methyltransferase phenotype and meTIMP/6-TGN concentration ratio >20, ratio 10.0-14.0 and ratio ≤4, respectively, were assessed by hybridization to microarrays. Results were further evaluated with reverse transcription qPCR [exploratory and a validation cohort of patients (n=33)]. Additionally, known genes of the thiopurine metabolic pathway were analysed separately.

    Results: The whole genome expression analysis did not identify any significant differences between metabolite profiles. Analysis of thiopurine related genes revealed a large interindividual variation in gene expression, but only small differences between metabolite profiles. Three clusters of co-regulated genes were defined based on correlations between gene expression levels. The concentration of meTIMP correlated to the expression of NT5E (rs = 0.33, P = 0.02) and TPMT (rs = - 0.37, P = 0.007). The concentration of 6-TGN correlated to the expression of HPRT1 (rs = - 0.31, P = 0.03) and SLC29A1 (rs = 0.33, P = 0.02). With the exception of SLC29A1, these genes belonged to the same cluster of genes.

    Conclusions: Our results illustrates the complexity of the thiopurine metabolism and suggest that differences between metabolite profiles are explained either by interactions between several genes, each with a small contribution, or at the post-transcriptional level. Search for more precise tools in order to explain differences in metabolite profiles is needed.

  • 4.
    Haglund, Sofie
    et al.
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Gastroenterologi och hepatologi. Linköpings universitet, Hälsouniversitetet.
    Lindqvist Appell, Malin
    Linköpings universitet, Institutionen för medicin och hälsa, Klinisk farmakologi. Linköpings universitet, Hälsouniversitetet.
    Almer, Sven
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för klinisk och experimentell medicin, Gastroenterologi och hepatologi. Östergötlands Läns Landsting, Medicincentrum, Endokrin- och magtarmmedicinska kliniken US.
    Peterson, Curt
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och hälsa, Klinisk farmakologi. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Onkologiska kliniken US.
    Taipalensuu, J.
    Div. of R. and D. in Lab. Medicine, Ryhov County Hospital, SE-551 85 Jönköping, Sweden.
    Pyrosequencing of TPMT Alleles in a General Swedish Population and in Patients with Inflammatory Bowel Disease2004Inngår i: Clinical Chemistry, ISSN 0009-9147, E-ISSN 1530-8561, Vol. 50, nr 2, s. 288-295Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background: Interindividual differences in therapeutic efficacy in patients treated with thiopurines might be explained by the presence of thiopurine S-methyltransferase (TPMT) alleles that encode for reduced TPMT enzymatic activity. It is therefore of value to know an individual's inherent capacity to express TPMT. Method: We developed a pyrosequencing method to detect 10 single-nucleotide polymorphisms (SNPs) in TPMT. A Swedish population (n = 800) was examined for TPMT*3A, TPMT*3B, TPMT*3C, and TPMT*2. Patients with inflammatory bowel disease (n = 24) and healthy volunteers (n = 6), selected on the basis of TPMT enzymatic activity, were investigated for all 10 SNPs to determine the relationship between TPMT genotype and phenotype. Results: In the general population we identified the following genotypes with nonfunctional alleles: TPMT*1/*3A (*3A allelic frequency, 3.75%), TPMT*1/*3C (*3C allelic frequency, 0.44%), TPMT*1/*3B (*3B allelic frequency, 0.13%), and TPMT*1/*2 (*2 allelic frequency, 0.06%). All nine individuals with normal enzymatic activity were wild-type TPMT*1/*1. Thirteen individuals with intermediate activity were either TPMT*1/*3A (n = 12) or TPMT*1/*2 (n = 1). Eight individuals with low enzymatic activity were TPMT*3A/*3A (n = 4), TPMT*3A/*3C (n = 2), or TPMT*1/*3A (n = 2). Conclusion: Next to wild type, the most frequent alleles in Sweden are TPMT*3A and TPMT*3C. A previously established phenotypic cutoff for distinguishing normal from intermediate metabolizers was confirmed. To identify the majority of cases (90%) with low or intermediate TPMT activity, it was sufficient to analyze individuals for only 3 of the 10 SNPs investigated. Nevertheless, this investigation indicates that other mutations might be of relevance for decreased enzymatic activity. © 2004 American Association for Clinical Chemistry.

  • 5.
    Haglund, Sofie
    et al.
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Gastroenterologi och hepatologi. Linköpings universitet, Hälsouniversitetet.
    Taipalensuu, Jan
    1Research and Development in Laboratory Medicine Laboratory Medicine, Ryhov Hospital, Jönköping.
    Peterson, Curt
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och hälsa, Klinisk farmakologi. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Onkologiska kliniken US.
    Almer, Sven
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för klinisk och experimentell medicin, Gastroenterologi och hepatologi. Östergötlands Läns Landsting, Medicincentrum, Endokrin- och magtarmmedicinska kliniken US.
    IMPDH activity in thiopurine-treated patients with inflammatory bowel disease - Relation to TPMT activity and metabolite concentrations2008Inngår i: British Journal of Clinical Pharmacology, ISSN 0306-5251, E-ISSN 1365-2125, Vol. 65, nr 1, s. 69-77Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 6.
    Haglund, Sofie
    et al.
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Gastroenterologi och hepatologi. Linköpings universitet, Hälsouniversitetet.
    Vikingsson, Svante
    Linköpings universitet, Institutionen för medicin och hälsa, Klinisk farmakologi. Linköpings universitet, Hälsouniversitetet.
    Söderman, Jan
    Division of Medical Diagnostics, Laboratory Medicine, Ryhov Hospital, Jönköping;.
    Hindorf, Ulf
    Department of Gastroenterology, Lund University Hospital, Lund.
    Grännö, Christer
    Department of Medicine, Ryhov Hospital, Jönköping.
    Danelius, Margareta
    Department of Internal Medicine, Ersta Hospital, Stockholm, Sweden.
    Coulthard, Sally
    Northern Institute for Cancer Research, Newcastle University, Newcastle upon Tyne, United Kingdom.
    Peterson, Curt
    Linköpings universitet, Institutionen för medicin och hälsa, Klinisk farmakologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Onkologiska kliniken US.
    Almer, Sven
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Gastroenterologi och hepatologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Endokrin- och magtarmmedicinska kliniken US.
    The Role of Inosine-5'-Monophosphate Dehydrogenase in Thiopurine Metabolism in Patients With Inflammatory Bowel Disease2011Inngår i: Therapeutic Drug Monitoring, ISSN 0163-4356, E-ISSN 1536-3694, Vol. 33, nr 2, s. 200-208Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    BACKGROUND:: There is a large interindividual variability in thiopurine metabolism. High concentrations of methylthioinosine-5'-monophosphate (meTIMP) and low concentrations of 6-thioguanine nucleotides (6-TGNs) have been associated with a lower response rate and an increased risk of adverse events. In this study, the role of inosine-5'-monophosphate dehydrogenase (IMPDH) for differences in metabolite patterns of thiopurines was investigated.

    METHODS:: IMPDH activity and thiopurine metabolite concentrations were determined in patients with inflammatory bowel disease and a normal thiopurine methyltransferase (TPMT) phenotype and meTIMP/6-TGN concentration ratio > 20 (n = 26), in patients with a metabolite ratio ≤20 (n = 21), in a subgroup with a metabolite ratio <4 (n = 6), and in 10 patients with reduced TPMT activity. In vitro studies were conducted on human embryonic kidney cells (HEK293) with genetically engineered IMPDH and TPMT activities.

    RESULTS:: Patients with metabolite ratios >20 had lower IMPDH activity than those with ratios ≤20 (P < 0.001). Metabolic ratios >20 were only observed in patients with normal TPMT activity. Downregulation of IMPDH activity in HEK293 cells was associated with an increase in the concentration of meTIMP (fold change: 17 up to 93, P < 0.001) but, unexpectedly, also of 6-thioguanosine monophosphate (fold change: 2.6 up to 5.0, P < 0.001).

    CONCLUSIONS:: These data question the general view of IMPDH as the rate-limiting enzyme in the phosphorylation of thiopurines. Investigations of other mechanisms are needed to more fully explain the various metabolite patterns and outcomes in patients under treatment.

  • 7.
    Haglund, Sofie
    et al.
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Gastroenterologi och hepatologi. Linköpings universitet, Hälsouniversitetet.
    Zimdahl Kahlin, Anna
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för läkemedelsforskning. Linköpings universitet, Hälsouniversitetet.
    Vikingsson, Svante
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för läkemedelsforskning.
    Almér, Stefan
    Linköpings universitet, Institutionen för klinisk och experimentell medicin. Linköpings universitet, Hälsouniversitetet.
    Söderman, Jan
    Division of Medical Diagnostics, Ryhov County Hospital, Jönköping, Sweden.
    P658 Effects of allopurinol on thiopurine metabolism and gene expression levels in HepG2 cells2014Konferansepaper (Annet vitenskapelig)
  • 8.
    Lindqvist Appell, Malin
    et al.
    Linköpings universitet, Institutionen för medicin och vård, Klinisk farmakologi. Linköpings universitet, Hälsouniversitetet.
    Haglund, Sofie
    Linköpings universitet, Institutionen för molekylär och klinisk medicin, Gastroenterologi och hepatologi. Linköpings universitet, Hälsouniversitetet.
    Almer, Sven
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för molekylär och klinisk medicin, Gastroenterologi och hepatologi. Östergötlands Läns Landsting, Medicincentrum, Endokrin- och magtarmmedicinska kliniken US.
    Peterson, Curt
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk farmakologi. Östergötlands Läns Landsting, Laboratoriemedicinskt centrum, Klinisk farmakologi.
    Taipalensuu, Jan
    Division of Research and Development in Laboratory Medicine, Ryhov County Hospital, Jönköping.
    Hertervig, Erik
    dDepartment of Medicine, Lund University Hospital, Lund.
    Lyrenäs, Ebbe
    Department of Medicine, Blekinge County Hospital, Karlskrona.
    Söderkvist, Peter
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för biomedicin och kirurgi, Avdelningen för medicinsk cellbiologi.
    Identification of two novel sequence variants affecting thiopurine methyltransferase enzyme activity2004Inngår i: Pharmacogenetics, ISSN 0960-314X, E-ISSN 1473-561X, Vol. 14, nr 4, s. 261-265Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The polymorphic enzyme thiopurine methyltransferase (TPMT) is involved in the methylation of thiopurines. On comparing the phenotype with the genotype in Swedish patients with inflammatory bowel disease and healthy individuals, we found two discordant cases with low TPMT enzyme activity (0.3 and 0.4 U/ml packed red blood cells (pRBC). Genotyping by pyrosequencing revealed that they carried the nucleotide substitutions 460G>A and 719A>G, giving two possible genotypes (TPMT*1/*3A or TPMT*3B/ *3C). DNA sequencing of exon III to X was performed in the patients and their parents. We identified an A>G transition in the start codon (exon III, 1A>G, Met>Val, TPMT*14) in one of the patients and her father (6.3 U/ml pRBC). The mother in this family carried the 460G>A and 719A>G nucleotide substitutions (TPMT*3A, 5.0 U/ml pRBC). In the second family, sequencing revealed a G>A transition in the acceptor splice site in intron VII/exon VIII (IVS7 - 1G>A, TPMT*15) in the patient and his mother (6.9 U/ml pRBC). His father was genotyped as TPMT*1/*3A (6.0 U/ml pRBC). Hence, we report the identification of two novel sequence variants, present in highly conserved nucleotide positions of the human TPMT gene, resulting in a loss of enzyme activity.

  • 9.
    Rajani, Rupesh
    et al.
    Linköpings universitet, Institutionen för klinisk och experimentell medicin. Linköpings universitet, Hälsouniversitetet.
    Haglund, Sofie
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Gastroenterologi och hepatologi. Linköpings universitet, Hälsouniversitetet.
    Bergquist, Annika
    Department of Gastroenterology & Hepatology, Karolinska University Hospital, Stockholm.
    Melin, Tor
    Division of Gastroenterology & Hepatology, University Hospital, Lund.
    Friis-Liby, Ingalill
    Department of Medicine, Sahlgrenska University Hospital, Gothenburg.
    Verbaan, Hans
    Department of Medicine, University Hospital, Malmö.
    Kapraali, Marjo
    Karolinska Institutet, Department of Clinical Sciences Danderyd Hospital, Division of Medicine, Stockholm.
    Lindahl, Tomas
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Klinisk kemi. Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för klinisk och experimentell medicin, Klinisk kemi.
    Almer, Sven
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Gastroenterologi och hepatologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Medicincentrum, Endokrin- och magtarmmedicinska kliniken US.
    High prevalence of the germline JAK2 46/1 haplotype and V617-mutationin Swedish patients with Budd-Chiari syndrome and Portal Vein Thrombosis2010Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Background & Aims: To determine the prevalence of the somatic JAK2 V617F mutation and distribution of the germline JAK2 46/1 haplotype in Budd-Chiari Syndrome (BCS) and portal vein thrombosis (PVT).

    Methods: Real-time PCR was performed to genotype for the JAK2V 617F mutation and the 46/1 haplotype (tag-SNPs rs12343867, T>C and rs12340895, C>G) in blood samples of 19 BCS and 91 PVT patients (without intra-abdominal malignancy), and 283 controls from a background population.

    Results: The prevalence of JAK2 V617F-mutation was 63% in BCS and 14% in PVT patients. 10% in BCS and 2% in PVT had V617F negative MPD. Conversely, V617F positive subjects without known MPD was found in 5% of the BCS and in 1% of PVT patients. The frequency of the JAK2 46/1 haplotype was significantly higher in BCS (53%) and PVT (36%) patients compared to controls (27%) (p=0.02; OR=3.0; 95% CI 1.5-5.9 and OR=1.51; 95% CI 1.1-2.1, respectively). In PVT patients the JAK2 haplotype was highly enriched in non-cirrhotic patients (41%) (p <0.01 ; OR=1.8; 95% CI 1.2-2.6) but not in cirrhotic patients (23%) (p=0.53 ; OR= 0.8; 95% CI 0.4-1.7). An increased JAK2 46/1 haplotype frequency was evident only in V617F mutation positive patients.

    Conclusions: The prevalence of JAK2 V617F was high in BCS (63%) and non-cirrhotic PVT (14%), facilitating detection of latent MPD. A negative result dose not rule out MPD. The occurrence of the JAK2 46/1 haplotype was significantly higher in V617F mutation positive patients but not in mutation negative patients, suggesting that the haplotype may not have an independent role separated from the V617F mutation in BCS and PVT patients.

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