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L R Ranganath - One of the best experts on this subject based on the ideXlab platform.

  • characterizing the alkaptonuria joint and spine phenotype and assessing the effect of homogentisic acid lowering therapy in a large cohort of 87 patients
    Journal of Inherited Metabolic Disease, 2021
    Co-Authors: Milad Khedr, L R Ranganath, Sobhan Vinjamuri, J A Gallagher
    Abstract:

    A large alkaptonuria (AKU) cohort was studied to better characterize the poorly understood spondyloarthropathy of rare disease AKU. Eighty-seven patients attended the National Alkaptonuria Centre (NAC) between 2007 and 2020. Seven only attended once. Fifty-seven attended more than once and received Nitisinone 2 mg daily. Twenty-three attended at least twice without receiving Nitisinone. Assessments included questionnaire analysis, 18F Positron emission tomography computerised tomography (PETCT), as well as photographs of ochronotic pigment in eyes and ears at baseline when 2 mg Nitisinone was commenced and yearly thereafter. Blood and urine samples were collected for chemical measurement. The prevalence of ochronosis, as well as pain, PETCT and combined pain and PETCT scores, was greatly increased at 90.5%, 85.7%, 100%, and 100%, respectively. Joint pain scores were greatest in proximal joints in upper and lower limbs. PETCT joint scores were higher in proximal joints in upper limb but higher in distal joints in the lower limb. Spine pain scores were highest in lumbar, followed by cervical, thoracic, and cervical regions at 77.4%, 59.5%, 46.4%, and 25%, respectively. PETCT spine scores were highest in thoracic followed by lumbar, cervical, and sacroiliac regions at 74.4%, 70.7%, 64.6%, and 47.8% respectively; ochronosis associated closely with spondyloarthropathy scores (R = .65; P < .0001). Nitisinone reversed ochronosis significantly, with a similar pattern of decreased joint and spine disease. Spondyloarthropathy is a highly prevalent feature in this NAC cohort. Ochronosis appears to be associated with spondyloarthropathy. Nitisinone decreases ochronosis and had a similar nonsignificant effect pattern on spondyloarthropathy.

  • characterising the arthroplasty in spondyloarthropathy in a large cohort of eighty seven patients with alkaptonuria
    Journal of Inherited Metabolic Disease, 2020
    Co-Authors: J A Gallagher, L R Ranganath, John S Davidson, Sobhan Vinjamuri
    Abstract:

    Arthroplasty in the spondyloarthropathy (SPOND) of alkaptonuria (AKU) in incompletely characterised. The aim was to improve the understanding of arthroplasty in AKU through a study of patients attending the National Alkaptonuria Centre (NAC). Eighty-seven patients attended the NAC between 2007 and 2020. Seven only attended once. Fifty-seven attended more than once and received Nitisinone 2 mg daily. Twenty-three attended at least twice without receiving Nitisinone. Assessments including questionnaire analysis eliciting details of arthroplasty and other surgical treatments for SPOND, 18 FPETCT and CT densitometry at the neck of hip and lumbar spine, as well as photographs of the eyes and ears were acquired from patients attending the National Alkaptonuria Centre (NAC) at baseline when 2 mg Nitisinone was commenced, and yearly thereafter. Photographs were scored to derive ochronosis scores. Blood and urine samples were collected for chemical analyses. The prevalence of arthroplasty was 36.8%, similar in males and females, occurring especially in the knees, hips and shoulders. Multiple arthroplasties were found in 29 patients (33.3%) in this cohort. Incident arthroplasty was 6.5% in the Nitisinone group and 7.1% in the no-Nitisinone group. Incident arthroplasty was 11.3% in the group with baseline arthroplasty and 3.51% in the group without. A strong association of arthroplasty with SPOND (R = 0.5; P << .0001) and ochronosis (R = 0.54; P < .0001) was seen. Nitisinone had no significant effect on incident arthroplasty. Arthroplasty due to ochronosis and SPOND is common in AKU. Nitisinone decreased ochronosis but had no effect on arthroplasty in this cohort.

  • efficacy and safety of once daily Nitisinone for patients with alkaptonuria sonia 2 an international multicentre open label randomised controlled trial
    The Lancet Diabetes & Endocrinology, 2020
    Co-Authors: L R Ranganath, Daniela Braconi, Eftychia E. Psarelli, Trevor Cox, Anders Broijersen, Jean Baptiste Arnoux, Michael E Briggs, Nadia Loftus, Helen Bygott, Andrew S Davison
    Abstract:

    Summary Background Alkaptonuria is a rare, genetic, multisystem disease characterised by the accumulation of homogentisic acid (HGA). No HGA-lowering therapy has been approved to date. The aim of SONIA 2 was to investigate the efficacy and safety of once-daily Nitisinone for reducing HGA excretion in patients with alkaptonuria and to evaluate whether Nitisinone has a clinical benefit. Methods SONIA 2 was a 4-year, open-label, evaluator-blind, randomised, no treatment controlled, parallel-group study done at three sites in the UK, France, and Slovakia. Patients aged 25 years or older with confirmed alkaptonuria and any clinical disease manifestations were randomly assigned (1:1) to receive either oral Nitisinone 10 mg daily or no treatment. Patients could not be masked to treatment due to colour changes in the urine, but the study was evaluator-blinded as far as possible. The primary endpoint was daily urinary HGA excretion (u-HGA24) after 12 months. Clinical evaluation Alkaptonuria Severity Score Index (cAKUSSI) score was assessed at 12, 24, 36, and 48 months. Efficacy variables were analysed in all randomly assigned patients with a valid u-HGA24 measurement at baseline. Safety variables were analysed in all randomly assigned patients. The study was registered at ClinicalTrials.gov ( NCT01916382 ). Findings Between May 7, 2014, and Feb 16, 2015, 139 patients were screened, of whom 138 were included in the study, with 69 patients randomly assigned to each group. 55 patients in the Nitisinone group and 53 in the control group completed the study. u-HGA24 at 12 months was significantly decreased by 99·7% in the Nitisinone group compared with the control group (adjusted geometric mean ratio of Nitisinone/control 0·003 [95% CI 0·003 to 0·004], p Interpretation Nitisinone 10 mg daily was well tolerated and effective in reducing urinary excretion of HGA. Nitisinone decreased ochronosis and improved clinical signs, indicating a slower disease progression. Funding European Commission Seventh Framework Programme.

  • reversal of ochronotic pigmentation in alkaptonuria following Nitisinone therapy analysis of data from the united kingdom national alkaptonuria centre
    JIMD reports, 2020
    Co-Authors: L R Ranganath, Andrew T. Hughes, Andrew S Davison, Milad Khedr, Anna M. Milan, Peter Wilson, Elizabeth West, J P Dillon, J A Gallagher
    Abstract:

    Background Increased homogentisic acid (HGA) causes ochronosis. Nitisinone decreases HGA. The aim was to study the effect of Nitisinone on the ochronosis progression. Methods Photographs of the eyes and ears were acquired from patients attending the National Alkaptonuria Centre (NAC) at V-1 (pre-baseline visit), V0 (baseline visit when 2 mg Nitisinone was commenced), and yearly at V1, V2, and V3 visits. Photographs were inspected for evolution of ochronotic pigment and also scored categorically to derive eye, ear, and combined ochronosis scores. An ear cartilage biopsy was also carried out at V0 and one year after V3 (V4) and ochronotic pigment was assessed and quantitated. Visits were compared for changes in pigment. Fasting blood and 24-hour urine samples were collected for measurement of HGA. Results There were 80 AKU patients at V0, and 52, 47, and 40 at V1, V2, and V3 in the group with variable numbers (VAR Group) respectively; 23 patients attended once before V0, in the V-1 visit. Photographs of patients show increase in eye pigment between V-1 and V0, followed by decrease post-Nitisinone at V1, V2, and V3. Ear and combined ochronosis semiquantitative scoring showed an increase between V-1 and V0 (P < .01), followed by a decrease at V1, V2, and V3, in the VAR group (P < .01). Ochronotic pigment in ear biopsy between V0 and V4 showed a 19.1% decrease (P < .05). Conclusions Nitisinone decreases HGA and partially reverses ochronosis.

  • Fatal acute haemolysis and methaemoglobinaemia in a man with renal failure and Alkaptonuria - Is Nitisinone the solution?
    'Elsevier BV', 2020
    Co-Authors: As Davison, Luangrath E, Selvi E, L R Ranganath
    Abstract:

    Haemolysis and methaemoglobinaemia (MetHb) are rare metabolic complications that can occur in Alkaptonuria (AKU), for which there is no curative treatment. Presented is a case of a man who had AKU, and serves as a reminder of life-threatening complications that can occur with haemolysis and MetHb. This case presents an opportunity to revisit important considerations relating to the investigation and treatment of haemolysis and MetHb with a view to raising awareness, and in doing so hopefully reducing the uniformly fatal outcome. Additionally it is proposed that treatment of haemolysis and MetHb with Nitisinone is considered as a potentially lifesaving treatment as it is believed that reducing the concentration of circulating homogentisic acid will reduce oxidative stress

Andrew S Davison - One of the best experts on this subject based on the ideXlab platform.

  • efficacy and safety of once daily Nitisinone for patients with alkaptonuria sonia 2 an international multicentre open label randomised controlled trial
    The Lancet Diabetes & Endocrinology, 2020
    Co-Authors: L R Ranganath, Daniela Braconi, Eftychia E. Psarelli, Trevor Cox, Anders Broijersen, Jean Baptiste Arnoux, Michael E Briggs, Nadia Loftus, Helen Bygott, Andrew S Davison
    Abstract:

    Summary Background Alkaptonuria is a rare, genetic, multisystem disease characterised by the accumulation of homogentisic acid (HGA). No HGA-lowering therapy has been approved to date. The aim of SONIA 2 was to investigate the efficacy and safety of once-daily Nitisinone for reducing HGA excretion in patients with alkaptonuria and to evaluate whether Nitisinone has a clinical benefit. Methods SONIA 2 was a 4-year, open-label, evaluator-blind, randomised, no treatment controlled, parallel-group study done at three sites in the UK, France, and Slovakia. Patients aged 25 years or older with confirmed alkaptonuria and any clinical disease manifestations were randomly assigned (1:1) to receive either oral Nitisinone 10 mg daily or no treatment. Patients could not be masked to treatment due to colour changes in the urine, but the study was evaluator-blinded as far as possible. The primary endpoint was daily urinary HGA excretion (u-HGA24) after 12 months. Clinical evaluation Alkaptonuria Severity Score Index (cAKUSSI) score was assessed at 12, 24, 36, and 48 months. Efficacy variables were analysed in all randomly assigned patients with a valid u-HGA24 measurement at baseline. Safety variables were analysed in all randomly assigned patients. The study was registered at ClinicalTrials.gov ( NCT01916382 ). Findings Between May 7, 2014, and Feb 16, 2015, 139 patients were screened, of whom 138 were included in the study, with 69 patients randomly assigned to each group. 55 patients in the Nitisinone group and 53 in the control group completed the study. u-HGA24 at 12 months was significantly decreased by 99·7% in the Nitisinone group compared with the control group (adjusted geometric mean ratio of Nitisinone/control 0·003 [95% CI 0·003 to 0·004], p Interpretation Nitisinone 10 mg daily was well tolerated and effective in reducing urinary excretion of HGA. Nitisinone decreased ochronosis and improved clinical signs, indicating a slower disease progression. Funding European Commission Seventh Framework Programme.

  • reversal of ochronotic pigmentation in alkaptonuria following Nitisinone therapy analysis of data from the united kingdom national alkaptonuria centre
    JIMD reports, 2020
    Co-Authors: L R Ranganath, Andrew T. Hughes, Andrew S Davison, Milad Khedr, Anna M. Milan, Peter Wilson, Elizabeth West, J P Dillon, J A Gallagher
    Abstract:

    Background Increased homogentisic acid (HGA) causes ochronosis. Nitisinone decreases HGA. The aim was to study the effect of Nitisinone on the ochronosis progression. Methods Photographs of the eyes and ears were acquired from patients attending the National Alkaptonuria Centre (NAC) at V-1 (pre-baseline visit), V0 (baseline visit when 2 mg Nitisinone was commenced), and yearly at V1, V2, and V3 visits. Photographs were inspected for evolution of ochronotic pigment and also scored categorically to derive eye, ear, and combined ochronosis scores. An ear cartilage biopsy was also carried out at V0 and one year after V3 (V4) and ochronotic pigment was assessed and quantitated. Visits were compared for changes in pigment. Fasting blood and 24-hour urine samples were collected for measurement of HGA. Results There were 80 AKU patients at V0, and 52, 47, and 40 at V1, V2, and V3 in the group with variable numbers (VAR Group) respectively; 23 patients attended once before V0, in the V-1 visit. Photographs of patients show increase in eye pigment between V-1 and V0, followed by decrease post-Nitisinone at V1, V2, and V3. Ear and combined ochronosis semiquantitative scoring showed an increase between V-1 and V0 (P < .01), followed by a decrease at V1, V2, and V3, in the VAR group (P < .01). Ochronotic pigment in ear biopsy between V0 and V4 showed a 19.1% decrease (P < .05). Conclusions Nitisinone decreases HGA and partially reverses ochronosis.

  • studies in alkaptonuria reveal new roles beyond drug clearance for phase i and ii biotransformations in tyrosine metabolism
    bioRxiv, 2020
    Co-Authors: Brendan P Norman, Andrew T. Hughes, Hazel Sutherland, Andrew S Davison, Anna M. Milan, Juliette H Hughes, Peter Wilson, Neil G Berry, Jonathan C. Jarvis
    Abstract:

    Background and Purposealkaptonuria (AKU) is an inherited disorder of tyrosine metabolism caused by lack of the enzyme homogentisate 1,2-dioxygenase (HGD). The primary biochemical consequence of HGD-deficiency is increased circulating homogentisic acid (HGA), which is central to AKU disease pathology. The aim of this study was to investigate the wider metabolic consequences of targeted Hgd disruption. Experimental Approachthe first metabolomic analysis of the Hgd-/- AKU mouse model was performed. Urinary metabolites altered in Hgd-/- were further validated by showing that the HGA-lowering drug Nitisinone reversed their direction of alteration in AKU Key Resultscomparison of Hgd-/- (AKU) versus Hgd+/- (heterozygous control) urine revealed increases in HGA and a group of 8 previously unreported HGA-derived transformation products from phase I and II metabolism. HGA biotransformation products HGA-sulfate, HGA-glucuronide, HGA-hydrate and hydroxymethyl-HGA were also decreased in urine from both mice and patients with AKU on the HGA-lowering agent Nitisinone. Hgd knockout also revealed a host of previously unrecognised associations between tyrosine, purine and TCA cycle metabolic pathways. Conclusion and ImplicationsAKU is rare, but our findings further what is currently understood about tyrosine metabolism more generally, and show for the first time that phase I and II detoxification is recruited to prevent accumulation of endogenously-produced metabolites in inborn errors of metabolism. The data highlight the misconception that phase I and II metabolic biotransformations are reserved solely for drug clearance; these are ancient mechanisms, which represent new potential treatment targets in inherited metabolic diseases. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=141 SRC="FIGDIR/small/044347v1_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@12b0b2forg.highwire.dtl.DTLVardef@eb4bacorg.highwire.dtl.DTLVardef@1b511e1org.highwire.dtl.DTLVardef@a8ef8e_HPS_FORMAT_FIGEXP M_FIG C_FIG Bullet point summaryWhat is already known O_LIIncreased circulating homogentisic acid is central to disease pathology in the inherited metabolic disease alkaptonuria C_LIO_LIThe Hgd knockout mouse, created in our laboratory, accurately models human alkaptonuria C_LI What this study adds O_LIPhase I and II biotransformations are recruited in alkaptonuria for detoxification of homogentisic acid C_LIO_LIThese data challenge misconceptions that phase I and II metabolism is solely for drug clearance C_LI Clinical significance O_LIPhase I and II metabolic processes represent new treatment targets in inherited metabolic diseases C_LIO_LIThe molecular pathology of AKU extends much further than the known alteration to tyrosine metabolism C_LI

  • Nitisinone causes acquired tyrosinosis in alkaptonuria
    Journal of Inherited Metabolic Disease, 2020
    Co-Authors: Milad Khedr, Andrew T. Hughes, Hazel Sutherland, Andrew S Davison, Jonathan C. Jarvis, Brendan P Norman, Anna M. Milan, Richard Fitzgerald, Maggie S Cooper, Louise Markinson
    Abstract:

    For over two decades, Nitisinone (NTBC) has been successfully used to manipulate the tyrosine degradation pathway and save the lives of many children with hereditary tyrosinaemia type 1. More recently, NTBC has been used to halt homogentisic acid accumulation in alkaptonuria (AKU) with evidence suggesting its efficacy as a disease modifying agent. NTBC-induced hypertyrosinaemia has been associated with cognitive impairment and potentially sight-threatening keratopathy. In the context of a non-lethal condition (ie, AKU), these serious risks call for an evaluation of the wider impact of NTBC on the tyrosine pathway. We hypothesised that NTBC increases the tyrosine pool size and concentrations in tissues. In AKU mice tyrosine concentrations of tissue homogenates were measured before and after treatment with NTBC. In humans, pulse injection with l-[13 C9 ]tyrosine and l-[d8 ]phenylalanine was used along with compartmental modelling to estimate the size of tyrosine pools before and after treatment with NTBC. We found that NTBC increased tyrosine concentrations in murine tissues by five to nine folds. It also significantly increased the tyrosine pool size in humans (P < .001), suggesting that NTBC increases tyrosine not just in serum but also in tissues (ie, acquired tyrosinosis). This study provides, for the first time, the experimental proof for the magnitude of NTBC-related acquired tyrosinosis which should be overcome to ensure the safe use of NTBC in AKU.

  • quantification of the flux of tyrosine pathway metabolites during Nitisinone treatment of alkaptonuria
    Scientific Reports, 2019
    Co-Authors: Andrew T. Hughes, Andrew S Davison, Milad Khedr, Anna M. Milan, J Rovensky, Eftychia E. Psarelli, Trevor Cox
    Abstract:

    Nitisinone decreases homogentisic acid (HGA) in Alkaptonuria (AKU) by inhibiting the tyrosine metabolic pathway in humans. The effect of different daily doses of Nitisinone on circulating and 24 h urinary excretion of phenylalanine (PA), tyrosine (TYR), hydroxyphenylpyruvate (HPPA), hydroxyphenyllactate (HPLA) and HGA in patients with AKU was studied over a four week period. Forty AKU patients, randomised into five groups of eight patients, received doses of 1, 2, 4 or 8 mg of Nitisinone daily, or no drug (control). Metabolites were analysed by tandem mass spectrometry in 24 h urine and serum samples collected before and after Nitisinone. Serum metabolites were corrected for total body water and the sum of 24 hr urine plus total body water metabolites of PA, TYR, HPPA, HPLA and HGA were determined. Body weight and urine urea were used to check on stability of diet and metabolism over the 4 weeks of study. The sum of quantities of urine metabolites (PA, TYR, HPPA, HPLA and HGA) were similar pre- and post-Nitisinone. The sum of total body water metabolites were significantly higher post-Nitisinone (p < 0.0001) at all doses. Similarly, combined 24 hr urine:total body water ratios for all analytes were significantly higher post-Nitisinone, compared with pre-Nitisinone baseline for all doses (p = 0.0002 – p < 0.0001). Significantly higher concentrations of metabolites from the tyrosine metabolic pathway were observed in a dose dependant manner following treatment with Nitisinone and we speculate that, for the first time, experimental evidence of the metabolite pool that would otherwise be directed towards pigment formation, has been unmasked.

Anna M. Milan - One of the best experts on this subject based on the ideXlab platform.

  • reversal of ochronotic pigmentation in alkaptonuria following Nitisinone therapy analysis of data from the united kingdom national alkaptonuria centre
    JIMD reports, 2020
    Co-Authors: L R Ranganath, Andrew T. Hughes, Andrew S Davison, Milad Khedr, Anna M. Milan, Peter Wilson, Elizabeth West, J P Dillon, J A Gallagher
    Abstract:

    Background Increased homogentisic acid (HGA) causes ochronosis. Nitisinone decreases HGA. The aim was to study the effect of Nitisinone on the ochronosis progression. Methods Photographs of the eyes and ears were acquired from patients attending the National Alkaptonuria Centre (NAC) at V-1 (pre-baseline visit), V0 (baseline visit when 2 mg Nitisinone was commenced), and yearly at V1, V2, and V3 visits. Photographs were inspected for evolution of ochronotic pigment and also scored categorically to derive eye, ear, and combined ochronosis scores. An ear cartilage biopsy was also carried out at V0 and one year after V3 (V4) and ochronotic pigment was assessed and quantitated. Visits were compared for changes in pigment. Fasting blood and 24-hour urine samples were collected for measurement of HGA. Results There were 80 AKU patients at V0, and 52, 47, and 40 at V1, V2, and V3 in the group with variable numbers (VAR Group) respectively; 23 patients attended once before V0, in the V-1 visit. Photographs of patients show increase in eye pigment between V-1 and V0, followed by decrease post-Nitisinone at V1, V2, and V3. Ear and combined ochronosis semiquantitative scoring showed an increase between V-1 and V0 (P < .01), followed by a decrease at V1, V2, and V3, in the VAR group (P < .01). Ochronotic pigment in ear biopsy between V0 and V4 showed a 19.1% decrease (P < .05). Conclusions Nitisinone decreases HGA and partially reverses ochronosis.

  • studies in alkaptonuria reveal new roles beyond drug clearance for phase i and ii biotransformations in tyrosine metabolism
    bioRxiv, 2020
    Co-Authors: Brendan P Norman, Andrew T. Hughes, Hazel Sutherland, Andrew S Davison, Anna M. Milan, Juliette H Hughes, Peter Wilson, Neil G Berry, Jonathan C. Jarvis
    Abstract:

    Background and Purposealkaptonuria (AKU) is an inherited disorder of tyrosine metabolism caused by lack of the enzyme homogentisate 1,2-dioxygenase (HGD). The primary biochemical consequence of HGD-deficiency is increased circulating homogentisic acid (HGA), which is central to AKU disease pathology. The aim of this study was to investigate the wider metabolic consequences of targeted Hgd disruption. Experimental Approachthe first metabolomic analysis of the Hgd-/- AKU mouse model was performed. Urinary metabolites altered in Hgd-/- were further validated by showing that the HGA-lowering drug Nitisinone reversed their direction of alteration in AKU Key Resultscomparison of Hgd-/- (AKU) versus Hgd+/- (heterozygous control) urine revealed increases in HGA and a group of 8 previously unreported HGA-derived transformation products from phase I and II metabolism. HGA biotransformation products HGA-sulfate, HGA-glucuronide, HGA-hydrate and hydroxymethyl-HGA were also decreased in urine from both mice and patients with AKU on the HGA-lowering agent Nitisinone. Hgd knockout also revealed a host of previously unrecognised associations between tyrosine, purine and TCA cycle metabolic pathways. Conclusion and ImplicationsAKU is rare, but our findings further what is currently understood about tyrosine metabolism more generally, and show for the first time that phase I and II detoxification is recruited to prevent accumulation of endogenously-produced metabolites in inborn errors of metabolism. The data highlight the misconception that phase I and II metabolic biotransformations are reserved solely for drug clearance; these are ancient mechanisms, which represent new potential treatment targets in inherited metabolic diseases. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=141 SRC="FIGDIR/small/044347v1_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@12b0b2forg.highwire.dtl.DTLVardef@eb4bacorg.highwire.dtl.DTLVardef@1b511e1org.highwire.dtl.DTLVardef@a8ef8e_HPS_FORMAT_FIGEXP M_FIG C_FIG Bullet point summaryWhat is already known O_LIIncreased circulating homogentisic acid is central to disease pathology in the inherited metabolic disease alkaptonuria C_LIO_LIThe Hgd knockout mouse, created in our laboratory, accurately models human alkaptonuria C_LI What this study adds O_LIPhase I and II biotransformations are recruited in alkaptonuria for detoxification of homogentisic acid C_LIO_LIThese data challenge misconceptions that phase I and II metabolism is solely for drug clearance C_LI Clinical significance O_LIPhase I and II metabolic processes represent new treatment targets in inherited metabolic diseases C_LIO_LIThe molecular pathology of AKU extends much further than the known alteration to tyrosine metabolism C_LI

  • Nitisinone causes acquired tyrosinosis in alkaptonuria
    Journal of Inherited Metabolic Disease, 2020
    Co-Authors: Milad Khedr, Andrew T. Hughes, Hazel Sutherland, Andrew S Davison, Jonathan C. Jarvis, Brendan P Norman, Anna M. Milan, Richard Fitzgerald, Maggie S Cooper, Louise Markinson
    Abstract:

    For over two decades, Nitisinone (NTBC) has been successfully used to manipulate the tyrosine degradation pathway and save the lives of many children with hereditary tyrosinaemia type 1. More recently, NTBC has been used to halt homogentisic acid accumulation in alkaptonuria (AKU) with evidence suggesting its efficacy as a disease modifying agent. NTBC-induced hypertyrosinaemia has been associated with cognitive impairment and potentially sight-threatening keratopathy. In the context of a non-lethal condition (ie, AKU), these serious risks call for an evaluation of the wider impact of NTBC on the tyrosine pathway. We hypothesised that NTBC increases the tyrosine pool size and concentrations in tissues. In AKU mice tyrosine concentrations of tissue homogenates were measured before and after treatment with NTBC. In humans, pulse injection with l-[13 C9 ]tyrosine and l-[d8 ]phenylalanine was used along with compartmental modelling to estimate the size of tyrosine pools before and after treatment with NTBC. We found that NTBC increased tyrosine concentrations in murine tissues by five to nine folds. It also significantly increased the tyrosine pool size in humans (P < .001), suggesting that NTBC increases tyrosine not just in serum but also in tissues (ie, acquired tyrosinosis). This study provides, for the first time, the experimental proof for the magnitude of NTBC-related acquired tyrosinosis which should be overcome to ensure the safe use of NTBC in AKU.

  • dietary restriction of tyrosine and phenylalanine lowers tyrosinemia associated with Nitisinone therapy of alkaptonuria
    Journal of Inherited Metabolic Disease, 2020
    Co-Authors: Juliette H Hughes, Andrew T. Hughes, Hazel Sutherland, Jonathan C. Jarvis, S. Judd, Anna M. Milan, Lakshminarayan R. Ranganath, Peter Wilson, George Bougharios, J A Gallagher
    Abstract:

    BACKGROUND: Alkaptonuria (AKU) is caused by homogentisate 1,2-dioxygenase deficiency that leads to homogentisic acid (HGA) accumulation, ochronosis and severe osteoarthropathy. Recently, Nitisinone treatment, which blocks HGA formation, has been effective in AKU patients. However, a consequence of Nitisinone is elevated tyrosine that can cause keratopathy. The effect of tyrosine and phenylalanine dietary restriction was investigated in Nitisinone-treated AKU mice, and in an observational study of dietary intervention in AKU patients. METHODS: Nitisinone-treated AKU mice were fed tyrosine/phenylalanine-free and phenylalanine-free diets with phenylalanine supplementation in drinking water. Tyrosine metabolites were measured pre-Nitisinone, post-Nitisinone, and after dietary restriction. Subsequently an observational study was undertaken in 10 patients attending the National Alkaptonuria Centre (NAC), with tyrosine >700μmol/L who had been advised to restrict dietary protein intake and where necessary, to use tyrosine/phenylalanine-free amino acid supplements. RESULTS: Elevated tyrosine (813μmol/L) was significantly reduced in Nitisinone-treated AKU mice fed a tyrosine/phenylalanine-free diet in a dose responsive manner. At 3 days of restriction, tyrosine was 389.3μmol/L, 274.8μmol/L and 144.3μmol/L with decreasing phenylalanine doses. In contrast, tyrosine was not effectively reduced in mice by a phenylalanine-free diet; at 3 days tyrosine was 757.3μmol/L, 530.2μmol/L and 656.2μmol/L, with no dose response to phenylalanine supplementation. In NAC patients, tyrosine was significantly reduced (p=0.002) when restricting dietary protein alone, and when combined with tyrosine/phenylalanine-free amino acid supplementation; 4 out of 10 patients achieved tyrosine <700μmol/L. CONCLUSION: Tyrosine/phenylalanine dietary restriction significantly reduced Nitisinone-induced tyrosinaemia in mice, with phenylalanine restriction alone proving ineffective. Similarly, protein restriction significantly reduced circulating tyrosine in AKU patients.

  • quantification of the flux of tyrosine pathway metabolites during Nitisinone treatment of alkaptonuria
    Scientific Reports, 2019
    Co-Authors: Andrew T. Hughes, Andrew S Davison, Milad Khedr, Anna M. Milan, J Rovensky, Eftychia E. Psarelli, Trevor Cox
    Abstract:

    Nitisinone decreases homogentisic acid (HGA) in Alkaptonuria (AKU) by inhibiting the tyrosine metabolic pathway in humans. The effect of different daily doses of Nitisinone on circulating and 24 h urinary excretion of phenylalanine (PA), tyrosine (TYR), hydroxyphenylpyruvate (HPPA), hydroxyphenyllactate (HPLA) and HGA in patients with AKU was studied over a four week period. Forty AKU patients, randomised into five groups of eight patients, received doses of 1, 2, 4 or 8 mg of Nitisinone daily, or no drug (control). Metabolites were analysed by tandem mass spectrometry in 24 h urine and serum samples collected before and after Nitisinone. Serum metabolites were corrected for total body water and the sum of 24 hr urine plus total body water metabolites of PA, TYR, HPPA, HPLA and HGA were determined. Body weight and urine urea were used to check on stability of diet and metabolism over the 4 weeks of study. The sum of quantities of urine metabolites (PA, TYR, HPPA, HPLA and HGA) were similar pre- and post-Nitisinone. The sum of total body water metabolites were significantly higher post-Nitisinone (p < 0.0001) at all doses. Similarly, combined 24 hr urine:total body water ratios for all analytes were significantly higher post-Nitisinone, compared with pre-Nitisinone baseline for all doses (p = 0.0002 – p < 0.0001). Significantly higher concentrations of metabolites from the tyrosine metabolic pathway were observed in a dose dependant manner following treatment with Nitisinone and we speculate that, for the first time, experimental evidence of the metabolite pool that would otherwise be directed towards pigment formation, has been unmasked.

J A Gallagher - One of the best experts on this subject based on the ideXlab platform.

  • characterizing the alkaptonuria joint and spine phenotype and assessing the effect of homogentisic acid lowering therapy in a large cohort of 87 patients
    Journal of Inherited Metabolic Disease, 2021
    Co-Authors: Milad Khedr, L R Ranganath, Sobhan Vinjamuri, J A Gallagher
    Abstract:

    A large alkaptonuria (AKU) cohort was studied to better characterize the poorly understood spondyloarthropathy of rare disease AKU. Eighty-seven patients attended the National Alkaptonuria Centre (NAC) between 2007 and 2020. Seven only attended once. Fifty-seven attended more than once and received Nitisinone 2 mg daily. Twenty-three attended at least twice without receiving Nitisinone. Assessments included questionnaire analysis, 18F Positron emission tomography computerised tomography (PETCT), as well as photographs of ochronotic pigment in eyes and ears at baseline when 2 mg Nitisinone was commenced and yearly thereafter. Blood and urine samples were collected for chemical measurement. The prevalence of ochronosis, as well as pain, PETCT and combined pain and PETCT scores, was greatly increased at 90.5%, 85.7%, 100%, and 100%, respectively. Joint pain scores were greatest in proximal joints in upper and lower limbs. PETCT joint scores were higher in proximal joints in upper limb but higher in distal joints in the lower limb. Spine pain scores were highest in lumbar, followed by cervical, thoracic, and cervical regions at 77.4%, 59.5%, 46.4%, and 25%, respectively. PETCT spine scores were highest in thoracic followed by lumbar, cervical, and sacroiliac regions at 74.4%, 70.7%, 64.6%, and 47.8% respectively; ochronosis associated closely with spondyloarthropathy scores (R = .65; P < .0001). Nitisinone reversed ochronosis significantly, with a similar pattern of decreased joint and spine disease. Spondyloarthropathy is a highly prevalent feature in this NAC cohort. Ochronosis appears to be associated with spondyloarthropathy. Nitisinone decreases ochronosis and had a similar nonsignificant effect pattern on spondyloarthropathy.

  • characterising the arthroplasty in spondyloarthropathy in a large cohort of eighty seven patients with alkaptonuria
    Journal of Inherited Metabolic Disease, 2020
    Co-Authors: J A Gallagher, L R Ranganath, John S Davidson, Sobhan Vinjamuri
    Abstract:

    Arthroplasty in the spondyloarthropathy (SPOND) of alkaptonuria (AKU) in incompletely characterised. The aim was to improve the understanding of arthroplasty in AKU through a study of patients attending the National Alkaptonuria Centre (NAC). Eighty-seven patients attended the NAC between 2007 and 2020. Seven only attended once. Fifty-seven attended more than once and received Nitisinone 2 mg daily. Twenty-three attended at least twice without receiving Nitisinone. Assessments including questionnaire analysis eliciting details of arthroplasty and other surgical treatments for SPOND, 18 FPETCT and CT densitometry at the neck of hip and lumbar spine, as well as photographs of the eyes and ears were acquired from patients attending the National Alkaptonuria Centre (NAC) at baseline when 2 mg Nitisinone was commenced, and yearly thereafter. Photographs were scored to derive ochronosis scores. Blood and urine samples were collected for chemical analyses. The prevalence of arthroplasty was 36.8%, similar in males and females, occurring especially in the knees, hips and shoulders. Multiple arthroplasties were found in 29 patients (33.3%) in this cohort. Incident arthroplasty was 6.5% in the Nitisinone group and 7.1% in the no-Nitisinone group. Incident arthroplasty was 11.3% in the group with baseline arthroplasty and 3.51% in the group without. A strong association of arthroplasty with SPOND (R = 0.5; P << .0001) and ochronosis (R = 0.54; P < .0001) was seen. Nitisinone had no significant effect on incident arthroplasty. Arthroplasty due to ochronosis and SPOND is common in AKU. Nitisinone decreased ochronosis but had no effect on arthroplasty in this cohort.

  • reversal of ochronotic pigmentation in alkaptonuria following Nitisinone therapy analysis of data from the united kingdom national alkaptonuria centre
    JIMD reports, 2020
    Co-Authors: L R Ranganath, Andrew T. Hughes, Andrew S Davison, Milad Khedr, Anna M. Milan, Peter Wilson, Elizabeth West, J P Dillon, J A Gallagher
    Abstract:

    Background Increased homogentisic acid (HGA) causes ochronosis. Nitisinone decreases HGA. The aim was to study the effect of Nitisinone on the ochronosis progression. Methods Photographs of the eyes and ears were acquired from patients attending the National Alkaptonuria Centre (NAC) at V-1 (pre-baseline visit), V0 (baseline visit when 2 mg Nitisinone was commenced), and yearly at V1, V2, and V3 visits. Photographs were inspected for evolution of ochronotic pigment and also scored categorically to derive eye, ear, and combined ochronosis scores. An ear cartilage biopsy was also carried out at V0 and one year after V3 (V4) and ochronotic pigment was assessed and quantitated. Visits were compared for changes in pigment. Fasting blood and 24-hour urine samples were collected for measurement of HGA. Results There were 80 AKU patients at V0, and 52, 47, and 40 at V1, V2, and V3 in the group with variable numbers (VAR Group) respectively; 23 patients attended once before V0, in the V-1 visit. Photographs of patients show increase in eye pigment between V-1 and V0, followed by decrease post-Nitisinone at V1, V2, and V3. Ear and combined ochronosis semiquantitative scoring showed an increase between V-1 and V0 (P < .01), followed by a decrease at V1, V2, and V3, in the VAR group (P < .01). Ochronotic pigment in ear biopsy between V0 and V4 showed a 19.1% decrease (P < .05). Conclusions Nitisinone decreases HGA and partially reverses ochronosis.

  • dietary restriction of tyrosine and phenylalanine lowers tyrosinemia associated with Nitisinone therapy of alkaptonuria
    Journal of Inherited Metabolic Disease, 2020
    Co-Authors: Juliette H Hughes, Andrew T. Hughes, Hazel Sutherland, Jonathan C. Jarvis, S. Judd, Anna M. Milan, Lakshminarayan R. Ranganath, Peter Wilson, George Bougharios, J A Gallagher
    Abstract:

    BACKGROUND: Alkaptonuria (AKU) is caused by homogentisate 1,2-dioxygenase deficiency that leads to homogentisic acid (HGA) accumulation, ochronosis and severe osteoarthropathy. Recently, Nitisinone treatment, which blocks HGA formation, has been effective in AKU patients. However, a consequence of Nitisinone is elevated tyrosine that can cause keratopathy. The effect of tyrosine and phenylalanine dietary restriction was investigated in Nitisinone-treated AKU mice, and in an observational study of dietary intervention in AKU patients. METHODS: Nitisinone-treated AKU mice were fed tyrosine/phenylalanine-free and phenylalanine-free diets with phenylalanine supplementation in drinking water. Tyrosine metabolites were measured pre-Nitisinone, post-Nitisinone, and after dietary restriction. Subsequently an observational study was undertaken in 10 patients attending the National Alkaptonuria Centre (NAC), with tyrosine >700μmol/L who had been advised to restrict dietary protein intake and where necessary, to use tyrosine/phenylalanine-free amino acid supplements. RESULTS: Elevated tyrosine (813μmol/L) was significantly reduced in Nitisinone-treated AKU mice fed a tyrosine/phenylalanine-free diet in a dose responsive manner. At 3 days of restriction, tyrosine was 389.3μmol/L, 274.8μmol/L and 144.3μmol/L with decreasing phenylalanine doses. In contrast, tyrosine was not effectively reduced in mice by a phenylalanine-free diet; at 3 days tyrosine was 757.3μmol/L, 530.2μmol/L and 656.2μmol/L, with no dose response to phenylalanine supplementation. In NAC patients, tyrosine was significantly reduced (p=0.002) when restricting dietary protein alone, and when combined with tyrosine/phenylalanine-free amino acid supplementation; 4 out of 10 patients achieved tyrosine <700μmol/L. CONCLUSION: Tyrosine/phenylalanine dietary restriction significantly reduced Nitisinone-induced tyrosinaemia in mice, with phenylalanine restriction alone proving ineffective. Similarly, protein restriction significantly reduced circulating tyrosine in AKU patients.

  • interference of hydroxyphenylpyruvic acid hydroxyphenyllactic acid and tyrosine on routine serum and urine clinical chemistry assays implications for biochemical monitoring of patients with alkaptonuria treated with Nitisinone
    Clinical Biochemistry, 2019
    Co-Authors: S L Curtis, Brendan P Norman, Anna M. Milan, J A Gallagher, L R Ranganath, Birgitta Olsson, N B Roberts
    Abstract:

    Abstract Objectives We have assessed the effect of elevated concentrations of hydroxyphenylpyruvic acid (HPPA), hydroxyphenyllactic acid (HPLA) and tyrosine, on a range of chemistry tests in serum and urine to explore the potential for chemical interference on routine laboratory analyses in patients with alkaptonuria (AKU) treated with Nitisinone and similarly implications for patients with hereditary tyrosinemia type 1 (HT-1). Materials and methods HPPA, HPLA and tyrosine were added separately to pooled serum from subjects without AKU in a range of assays with Roche Modular chemistries. Effects on urine were assessed by changes in urine strip chemistries after mixing a positive control urine with various amounts of the test compounds and reading on a Siemens urine strip meter. Results No significant effect (p > 0.1) was observed up to 225 μmol/L of HPPA and HPLA, and up to 5000 μmol/L tyrosine, on any of the serum-based assays including those with peroxidase-coupled reaction systems of enzymatic creatinine, urate, total cholesterol, HDL cholesterol and triglyceride. Both the monohydroxy HPPA, and the dihydroxy homogentisic acid (HGA), at increased urine concentrations typical of Nitisinone-treated AKU and non-treated AKU respectively, did however show marked negative interference in strip assays for glucose and leucocytes; i.e. those with peroxide-linked endpoints. The effect of increased HPLA was less marked. Conclusions In patients with AKU or on Nitisinone treatment and HT-1 patients on Nitisinone, urine strip chemistry testing should be used sparingly, if at all, to avoid false negative reporting. It is recommended that urine assays should be organised with a suitable specialist laboratory.

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  • reversal of ochronotic pigmentation in alkaptonuria following Nitisinone therapy analysis of data from the united kingdom national alkaptonuria centre
    JIMD reports, 2020
    Co-Authors: L R Ranganath, Andrew T. Hughes, Andrew S Davison, Milad Khedr, Anna M. Milan, Peter Wilson, Elizabeth West, J P Dillon, J A Gallagher
    Abstract:

    Background Increased homogentisic acid (HGA) causes ochronosis. Nitisinone decreases HGA. The aim was to study the effect of Nitisinone on the ochronosis progression. Methods Photographs of the eyes and ears were acquired from patients attending the National Alkaptonuria Centre (NAC) at V-1 (pre-baseline visit), V0 (baseline visit when 2 mg Nitisinone was commenced), and yearly at V1, V2, and V3 visits. Photographs were inspected for evolution of ochronotic pigment and also scored categorically to derive eye, ear, and combined ochronosis scores. An ear cartilage biopsy was also carried out at V0 and one year after V3 (V4) and ochronotic pigment was assessed and quantitated. Visits were compared for changes in pigment. Fasting blood and 24-hour urine samples were collected for measurement of HGA. Results There were 80 AKU patients at V0, and 52, 47, and 40 at V1, V2, and V3 in the group with variable numbers (VAR Group) respectively; 23 patients attended once before V0, in the V-1 visit. Photographs of patients show increase in eye pigment between V-1 and V0, followed by decrease post-Nitisinone at V1, V2, and V3. Ear and combined ochronosis semiquantitative scoring showed an increase between V-1 and V0 (P < .01), followed by a decrease at V1, V2, and V3, in the VAR group (P < .01). Ochronotic pigment in ear biopsy between V0 and V4 showed a 19.1% decrease (P < .05). Conclusions Nitisinone decreases HGA and partially reverses ochronosis.

  • studies in alkaptonuria reveal new roles beyond drug clearance for phase i and ii biotransformations in tyrosine metabolism
    bioRxiv, 2020
    Co-Authors: Brendan P Norman, Andrew T. Hughes, Hazel Sutherland, Andrew S Davison, Anna M. Milan, Juliette H Hughes, Peter Wilson, Neil G Berry, Jonathan C. Jarvis
    Abstract:

    Background and Purposealkaptonuria (AKU) is an inherited disorder of tyrosine metabolism caused by lack of the enzyme homogentisate 1,2-dioxygenase (HGD). The primary biochemical consequence of HGD-deficiency is increased circulating homogentisic acid (HGA), which is central to AKU disease pathology. The aim of this study was to investigate the wider metabolic consequences of targeted Hgd disruption. Experimental Approachthe first metabolomic analysis of the Hgd-/- AKU mouse model was performed. Urinary metabolites altered in Hgd-/- were further validated by showing that the HGA-lowering drug Nitisinone reversed their direction of alteration in AKU Key Resultscomparison of Hgd-/- (AKU) versus Hgd+/- (heterozygous control) urine revealed increases in HGA and a group of 8 previously unreported HGA-derived transformation products from phase I and II metabolism. HGA biotransformation products HGA-sulfate, HGA-glucuronide, HGA-hydrate and hydroxymethyl-HGA were also decreased in urine from both mice and patients with AKU on the HGA-lowering agent Nitisinone. Hgd knockout also revealed a host of previously unrecognised associations between tyrosine, purine and TCA cycle metabolic pathways. Conclusion and ImplicationsAKU is rare, but our findings further what is currently understood about tyrosine metabolism more generally, and show for the first time that phase I and II detoxification is recruited to prevent accumulation of endogenously-produced metabolites in inborn errors of metabolism. The data highlight the misconception that phase I and II metabolic biotransformations are reserved solely for drug clearance; these are ancient mechanisms, which represent new potential treatment targets in inherited metabolic diseases. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=141 SRC="FIGDIR/small/044347v1_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@12b0b2forg.highwire.dtl.DTLVardef@eb4bacorg.highwire.dtl.DTLVardef@1b511e1org.highwire.dtl.DTLVardef@a8ef8e_HPS_FORMAT_FIGEXP M_FIG C_FIG Bullet point summaryWhat is already known O_LIIncreased circulating homogentisic acid is central to disease pathology in the inherited metabolic disease alkaptonuria C_LIO_LIThe Hgd knockout mouse, created in our laboratory, accurately models human alkaptonuria C_LI What this study adds O_LIPhase I and II biotransformations are recruited in alkaptonuria for detoxification of homogentisic acid C_LIO_LIThese data challenge misconceptions that phase I and II metabolism is solely for drug clearance C_LI Clinical significance O_LIPhase I and II metabolic processes represent new treatment targets in inherited metabolic diseases C_LIO_LIThe molecular pathology of AKU extends much further than the known alteration to tyrosine metabolism C_LI

  • Nitisinone causes acquired tyrosinosis in alkaptonuria
    Journal of Inherited Metabolic Disease, 2020
    Co-Authors: Milad Khedr, Andrew T. Hughes, Hazel Sutherland, Andrew S Davison, Jonathan C. Jarvis, Brendan P Norman, Anna M. Milan, Richard Fitzgerald, Maggie S Cooper, Louise Markinson
    Abstract:

    For over two decades, Nitisinone (NTBC) has been successfully used to manipulate the tyrosine degradation pathway and save the lives of many children with hereditary tyrosinaemia type 1. More recently, NTBC has been used to halt homogentisic acid accumulation in alkaptonuria (AKU) with evidence suggesting its efficacy as a disease modifying agent. NTBC-induced hypertyrosinaemia has been associated with cognitive impairment and potentially sight-threatening keratopathy. In the context of a non-lethal condition (ie, AKU), these serious risks call for an evaluation of the wider impact of NTBC on the tyrosine pathway. We hypothesised that NTBC increases the tyrosine pool size and concentrations in tissues. In AKU mice tyrosine concentrations of tissue homogenates were measured before and after treatment with NTBC. In humans, pulse injection with l-[13 C9 ]tyrosine and l-[d8 ]phenylalanine was used along with compartmental modelling to estimate the size of tyrosine pools before and after treatment with NTBC. We found that NTBC increased tyrosine concentrations in murine tissues by five to nine folds. It also significantly increased the tyrosine pool size in humans (P < .001), suggesting that NTBC increases tyrosine not just in serum but also in tissues (ie, acquired tyrosinosis). This study provides, for the first time, the experimental proof for the magnitude of NTBC-related acquired tyrosinosis which should be overcome to ensure the safe use of NTBC in AKU.

  • dietary restriction of tyrosine and phenylalanine lowers tyrosinemia associated with Nitisinone therapy of alkaptonuria
    Journal of Inherited Metabolic Disease, 2020
    Co-Authors: Juliette H Hughes, Andrew T. Hughes, Hazel Sutherland, Jonathan C. Jarvis, S. Judd, Anna M. Milan, Lakshminarayan R. Ranganath, Peter Wilson, George Bougharios, J A Gallagher
    Abstract:

    BACKGROUND: Alkaptonuria (AKU) is caused by homogentisate 1,2-dioxygenase deficiency that leads to homogentisic acid (HGA) accumulation, ochronosis and severe osteoarthropathy. Recently, Nitisinone treatment, which blocks HGA formation, has been effective in AKU patients. However, a consequence of Nitisinone is elevated tyrosine that can cause keratopathy. The effect of tyrosine and phenylalanine dietary restriction was investigated in Nitisinone-treated AKU mice, and in an observational study of dietary intervention in AKU patients. METHODS: Nitisinone-treated AKU mice were fed tyrosine/phenylalanine-free and phenylalanine-free diets with phenylalanine supplementation in drinking water. Tyrosine metabolites were measured pre-Nitisinone, post-Nitisinone, and after dietary restriction. Subsequently an observational study was undertaken in 10 patients attending the National Alkaptonuria Centre (NAC), with tyrosine >700μmol/L who had been advised to restrict dietary protein intake and where necessary, to use tyrosine/phenylalanine-free amino acid supplements. RESULTS: Elevated tyrosine (813μmol/L) was significantly reduced in Nitisinone-treated AKU mice fed a tyrosine/phenylalanine-free diet in a dose responsive manner. At 3 days of restriction, tyrosine was 389.3μmol/L, 274.8μmol/L and 144.3μmol/L with decreasing phenylalanine doses. In contrast, tyrosine was not effectively reduced in mice by a phenylalanine-free diet; at 3 days tyrosine was 757.3μmol/L, 530.2μmol/L and 656.2μmol/L, with no dose response to phenylalanine supplementation. In NAC patients, tyrosine was significantly reduced (p=0.002) when restricting dietary protein alone, and when combined with tyrosine/phenylalanine-free amino acid supplementation; 4 out of 10 patients achieved tyrosine <700μmol/L. CONCLUSION: Tyrosine/phenylalanine dietary restriction significantly reduced Nitisinone-induced tyrosinaemia in mice, with phenylalanine restriction alone proving ineffective. Similarly, protein restriction significantly reduced circulating tyrosine in AKU patients.

  • quantification of the flux of tyrosine pathway metabolites during Nitisinone treatment of alkaptonuria
    Scientific Reports, 2019
    Co-Authors: Andrew T. Hughes, Andrew S Davison, Milad Khedr, Anna M. Milan, J Rovensky, Eftychia E. Psarelli, Trevor Cox
    Abstract:

    Nitisinone decreases homogentisic acid (HGA) in Alkaptonuria (AKU) by inhibiting the tyrosine metabolic pathway in humans. The effect of different daily doses of Nitisinone on circulating and 24 h urinary excretion of phenylalanine (PA), tyrosine (TYR), hydroxyphenylpyruvate (HPPA), hydroxyphenyllactate (HPLA) and HGA in patients with AKU was studied over a four week period. Forty AKU patients, randomised into five groups of eight patients, received doses of 1, 2, 4 or 8 mg of Nitisinone daily, or no drug (control). Metabolites were analysed by tandem mass spectrometry in 24 h urine and serum samples collected before and after Nitisinone. Serum metabolites were corrected for total body water and the sum of 24 hr urine plus total body water metabolites of PA, TYR, HPPA, HPLA and HGA were determined. Body weight and urine urea were used to check on stability of diet and metabolism over the 4 weeks of study. The sum of quantities of urine metabolites (PA, TYR, HPPA, HPLA and HGA) were similar pre- and post-Nitisinone. The sum of total body water metabolites were significantly higher post-Nitisinone (p < 0.0001) at all doses. Similarly, combined 24 hr urine:total body water ratios for all analytes were significantly higher post-Nitisinone, compared with pre-Nitisinone baseline for all doses (p = 0.0002 – p < 0.0001). Significantly higher concentrations of metabolites from the tyrosine metabolic pathway were observed in a dose dependant manner following treatment with Nitisinone and we speculate that, for the first time, experimental evidence of the metabolite pool that would otherwise be directed towards pigment formation, has been unmasked.