Alkaptonuria is a rare disorder of tyrosine catabolism caused by deficiency of homogentisate 1,2-dioxygenase that leads to accumulation of homogentisic acid (HGA). Deposition of HGA-derived polymers in connective tissue causes progressive arthropathy of the spine and large joints, cardiac valvular disease, and genitourinary stones beginning in the fourth decade of life. Nitisinone, a potent inhibitor of the upstream enzyme, 4-hydroxyphenylpyruvate dioxygenase, dramatically reduces HGA production. As such, nitisinone is a proposed treatment for alkaptonuria. A randomized clinical trial of nitisinone in alkaptonuria confirmed the biochemical efficacy and tolerability of nitisinone for patients with alkaptonuria but the selected primary outcome did not demonstrate significant clinical benefit. Given that alkaptonuria is a rare disease with slow progression and variable presentation, identifying outcome parameters that can detect significant change during a time-limited clinical trial is challenging. To gain insight into patient-perceived improvements in quality of life and corresponding changes in physical function associated with nitisinone use, we conducted a post-hoc per protocol analysis of patient-reported outcomes and a functional assessment. Analysis revealed that nitisinone-treated patients showed significant improvements in complementary domains of the 36-Item Short-Form Survey (SF-36) and 6-min walk test (6MWT). Together, these findings suggest that nitisinone improves both quality of life and function of patients with alkaptonuria. The observed trends support nitisinone as a therapy for alkaptonuria.

The interaction between Nitisinone (NTBC) and bovine serum albumin (BSA) as the transport protein in a circulating system was investigated for the first time utilizing various analytical (UV-Vis spectrophotometry, fluorescence spectroscopy, dynamic light scattering, and differential scanning calorimetry) and computational (molecular docking and molecular dynamics simulations) methods. The BSA fluorescence intensity was quenched upon interaction with NTBC, and the quenching mechanism was observed as static. The interaction between NTBC and BSA was examined at 288 K, 298 K, and 308 K where the binding constants were found to be 1.44 × 105 ± 0.22 M-1, 5.18 × 104 ± 0.20 M-1, and 3.02 × 104 ± 0.22 M-1 respectively, suggesting an intermediate binding affinity between NTBC and BSA. Changes in the microenvironment surrounding tryptophan and tyrosine residues of BSA were elucidated using 3-D fluorescence spectroscopy. Thermodynamic studies revealed the calculated values of ΔH =  - 54.34 ± 5 kJ/mol and ΔS =  - 0.0908 ± 0.24 kJ/mol K-1, indicating the involvement of van der Waals forces and hydrogen bonds in the interaction between NTBC and BSA. Moreover, the interaction\'s spontaneous nature was evidenced by negative ΔG values across all temperatures. Using dynamic light scattering, it was observed that higher NTBC concentrations led to a gradual rise in hydrodynamic diameter and notable aggregation of the NTBC-BSA complex. Moreover, changing signal values and shifted peaks of BSA, NTBC, and complex in differential scanning calorimetry curves, meant there were molecular interactions between the NTBC and BSA. In silico approaches also elucidated how NTBC binds to active sites on BSA, further supporting other findings. Moreover, molecular docking studies offer a more profound insight into the changing dynamics of hydrophobic, hydrogen, and halogen bonding involved in stabilizing the NTBC-BSA complex.

A rare metabolic condition called alkaptonuria (AKU) is caused by a decrease in homogentisate 1,2 dioxygenase (HGO) activity due to a mutation in homogentisate dioxygenase (HGD) gene. Homogentisic acid is a byproduct of the catabolism of tyrosine and phenylalanine that darkens the urine and accumulates in connective tissues which causes an agonizing arthritis. Employing the use of deep learning artificial intelligence (AI) drug design, this study aims to alleviate the current toxicity of the AKU drugs currently in use, particularly nitisinone, by utilizing the natural flavanol kaempferol molecule as a 4-hydroxyphenylpyruvate dioxygenase inhibitor. Kaempferol was employed to generate three effective de novo drug candidates targeting the enzyme 4-hydroxyphenylpyruvate dioxygenase using an AI drug design tool. We present novel AIK formulations in the present study. The AIK\'s (Artificial Intelligence Kaempferol) examination of drug-likeliness among the three led to its choice as a possible target. The toxicity assessment research of AIK demonstrates that it is not only safer to use than other treatments, but also more efficient. The docking of the AIGT with 4-hydroxyphenylpyruvate dioxygenase, which revealed a binding affinity of around -9.099 kcal/mol, highlights the AIK\'s potential as a therapeutic candidate. An innovative approach to deal with challenging circumstances is thus presented in this study by new formulations kaempferol that have been meticulously designed by AI. The results of the in vitro tests must be confirmed in vivo, even though AI-designed AIK is effective and sufficiently safe as computed.

UNASSIGNED: Increased homogentisic acid (HGA) in alkaptonuria (AKU) causes severe arthritis. Nitisinone reduces the production of HGA, but whether it also decreases arthroplasty was examined in 237 AKU patients.
UNASSIGNED: Patients attending the United Kingdom National Alkaptonuria Centre (NAC) and the Suitability of Nitisinone in Alkaptonuria 2 (SONIA 2) study were studied. Assessments included questionnaires eliciting details of arthroplasty. Nitisinone was administered from baseline, 2 mg in the NAC and 10 mg in SONIA 2. In SONIA 2, subgroups consisted of those with baseline arthroplasty on and not on nitisinone (BR + N+, BR + N-), as well as those without baseline arthroplasty on and not on nitisinone (BR-N+, BR-N-).
UNASSIGNED: In the SONIA2 subgroups, new joint replacement (JR) probabilities after baseline were significantly different (BR + N+, BR + N-, BR-N+, BR-N-) (χ2 = 23.3, p < 0.001); mean (SD) was 3.8 (0.1) years in BR-N-, 3.7 (0.1) years in BR-N+, 3.4 (0.3) years in BR + N-, and 3.0 (0.3) years in BR + N+. Further, the BR + N- showed more JR than the BR-N- subgroup (p < 0.01), while BR + N+ similarly showed more JR than the BR-N+ subgroup (p < 0.001).In the NAC, the BR- group had a mean age of 51.6 (7.0) years at baseline but 57.7 (8.7) years at final follow up during nitisinone therapy and showed only 7 incident JR. The BR+ group had an age at baseline of 57.4 (8.5) years and had undergone 94 JRs at baseline.
UNASSIGNED: The incidence of arthroplasty was earlier and more frequent after the first JR and was not affected by nitisinone.

Osteoarthritis (OA) is a chronic degenerative joint disease characterized by cartilage degeneration and subchondral bone remodelling. Currently, conservative treatment strategies cannot effectively alleviate the progression of OA. In this study, we used computer network analysis to show that Nitisinone (NTBC) is closely related to extracellular matrix degradation in OA and mainly interferes with the TNF-α signaling pathway. NTBC is an orphan drug used to treat hereditary type I tyrosinemia by altering phenylalanine/tyrosine metabolic flow. In this study, we found that NTBC effectively reduced chondrocyte inflammation and extracellular matrix degradation induced by TNF-α. Mechanistically, NTBC inhibited the cGAS/STING signaling pathway and reduced activation of the STING-dependent NF-κB pathway to alleviate inflammation. In addition, NTBC inhibited osteoclastogenesis and delayed the occurrence of subchondral bone remodelling. In mice with ACLT-induced osteoarthritis, intra-articular injection of NTBC significantly reduced cartilage degradation and subchondral bone remodelling. NTBC showed impressive therapeutic efficacy as a potential pharmaceutical intervention for the treatment of OA.

BACKGROUND: Nitisinone is a medium-sized organic molecule that is used in treating hereditary tyrosinemia type 1 (HT-1). The structurally analogous mesotrione, however, is used as a pesticide/herbicide. What molecular properties are responsible for the similarity/dissimilarity of these molecules is investigated here. The solvent effect reduces the electron affinity to rather negative values and causes the negative electron affinity which manifests itself in a very high positive absolute reduction potential.
METHODS: B3LYP method was utilized for a geometry optimization of nitisinone and mesotrione in their neural and ionized (L0, L+, L-) forms of 6 structures. The calculations were conducted in water as a solvent using conductor-like polarizable continuum model (CPCM), nitisinone also in vacuo. The complete vibrational analysis at the true energy minimum allows evaluating the thermodynamic functions with focus to the zero-point energy and overall entropic term. The change of the Gibbs energy on reductions and/or oxidation facilitates evaluating the absolute reduction and absolute oxidation potentials. Also, DLPNO-CCSD(T) method that involves the major part of the correlation energy has been applied to nitisinone and mesotrione and their molecular ions.

Amongst a cohort of 88 alkaptonuria (AKU) patients attending the United Kingdom National Alkaptonuria Centre (NAC), four unrelated patients had co-existing Parkinson\'s disease (PD). Two of the NAC patients developed PD before receiving nitisinone (NIT) while the other two developed overt PD during NIT therapy. NIT lowers redox-active homogentisic acid (HGA) and profoundly increases tyrosine (TYR). A further unpublished case of a Dutch patient with AKU and PD on deep brain stimulation is included in this report. A Pubmed search revealed a further five AKU patients with PD, all without NIT usage. The prevalence of PD in AKU in the NAC appears to be nearly 20-times higher than in the non-AKU population (p < 0.001) even when adjusted for age. We propose that life-long exposure to redox-active HGA may account for the higher prevalence of PD in AKU. Furthermore, the appearance of PD in AKU patients during NIT therapy may be due to unmasking dopamine deficiency in susceptible individuals, as a result of the tyrosinaemia during NIT therapy inhibiting the rate-limiting brain tyrosine hydroxylase.

Alkaptonuria (AKU) is an ultra-rare inherited inborn error of metabolism that afflicts the tyrosine metabolic pathway, resulting in the accumulation of homogentisic acid (HGA) in the circulation, and significant excretion in urine. Clinical manifestations, typically observed from the third decade of life, are lifelong and significantly affect the quality of life. This review provides a comprehensive overview of the natural history of AKU, including clinical, biochemical and genetic perspectives. An update on the major advances on studies in murine models and human subjects, providing mechanistic insight into the molecular and biochemical processes that underlie pathophysiology and its response to treatment are presented. The impact of treatment with nitisinone is also presented with a specific emphasis on hypertyrosinemia, as uncertainty on this topic remains. Future perspectives are explored, such as novel approaches to treat hypertyrosinemia including the use of binding agents and amino acid transporter inhibitors, as well as advanced potentially curative gene and cell therapy initiatives.

Alkaptonuria is a rare genetic metabolic disorder of autosomal recessive inheritance characterised by the accumulation of homogentisic acid in the body. It is diagnosed upon identification of characteristic symptoms, using various biochemical investigations, radiographic pictures, and a variety of specialised tests. Here we are discussing the case of an 80-year-old female patient with incidental findings of alkaptonuria. It is crucial to understand the fundamental diagnostic investigations that can be used in low-income nations or facilities where investigations like genetic testing, gas chromatography, and mass spectrometry are not readily available for the diagnosis of alkaptonuria.

Alkaptonuria (AKU) is a rare genetic autosomal recessive disorder characterized by elevated serum levels of homogentisic acid (HGA). In this disease, tyrosine metabolism is interrupted because of the alterations in homogentisate dioxygenase (HGD) gene. The patient suffers from ochronosis, fractures, and tendon ruptures. To date, no medicine has been approved for the treatment of AKU. However, physiotherapy and strong painkillers are administered to help mitigate the condition. Recently, nitisinone, an FDA-approved drug for type 1 tyrosinemia, has been given to AKU patients in some countries and has shown encouraging results in reducing the disease progression. However, this drug is not the targeted treatment for AKU, and causes keratopathy. Therefore, the foremost aim of this study is the identification of potent and druggable inhibitors of AKU with no or minimal side effects by targeting 4-hydroxyphenylpyruvate dioxygenase. To achieve our goal, we have performed computational modelling using BioSolveIT suit. The library of ligands for molecular docking was acquired by fragment replacement of reference molecules by ReCore. Subsequently, the hits were screened on the basis of estimated affinities, and their pharmacokinetic properties were evaluated using SwissADME. Afterward, the interactions between target and ligands were investigated using Discovery Studio. Ultimately, compounds c and f were identified as potent inhibitors of 4-hydroxyphenylpyruvate dioxygenase.