Hyperurikämie und Gicht

Radiosynthesis, Preclinical, and Clinical Positron Emission Tomography Studies of Carbon-11 Labeled Endogenous and Natural Exogenous Compounds

The presence of positron emission tomography (PET) centers at most major hospitals worldwide, along with the improvement of PET scanner sensitivity and the introduction of total body PET systems, has increased the interest in the PET tracer development using the short-lived radionuclides carbon-11. In the last few decades, methodological improvements and fully automated modules have allowed the development of carbon-11 tracers for clinical use. Radiolabeling natural compounds with carbon-11 by substituting one of the backbone carbons with the radionuclide has provided important information on the biochemistry of the authentic compounds and increased the understanding of their in vivo behavior in healthy and diseased states. The number of endogenous and natural compounds essential for human life is staggering, ranging from simple alcohols to vitamins and peptides. This review collates all the carbon-11 radiolabeled endogenous and natural exogenous compounds synthesised to date, including essential information on their radiochemistry methodologies and preclinical and clinical studies in healthy subjects.

Neutrophils as Main Players of Immune Response Towards Nondegradable Nanoparticles

Many nano/microparticles (n/µP), to which our body is exposed, have no physiological way of removal. Our immune system sense these “small particulate objects”, and tries to decrease their harmfulness. Since oxidation, phagocytosis and other methods of degradation do not work with small, chemically resistant, and hydrophobic nanoparticles (nP). This applies to soot from air pollution, nano-diamonds from cosmic impact, polishing and related machines, synthetic polymers, and dietary n/µP. Our body tries to separate these from the surrounding tissue using aggregates from neutrophil extracellular traps (NETs). This effectively works in soft tissues where n/µP are entrapped into granuloma-like structures and isolated. The interactions of hydrophobic nanocrystals with circulating or ductal patrolling neutrophils and the consequent formation of occlusive aggregated NETs (aggNETs) are prone to obstruct capillaries, bile ducts in gallbladder and liver, and many more tubular structures. This may cause serious health problems and often fatality. Here we describe how specific size and surface properties of n/µP can activate neutrophils and lead to aggregation-related pathologies. We discuss “natural” sources of n/µP and those tightly connected to unhealthy diets.

Confined multiple enzymatic (cascade) reactions within poly(dopamine)-based capsosomes

The design of compartmentalized carriers as artificial cells is envisioned to be an efficient tool with potential applications in the biomedical field. The advent of this area has witnessed the assembly of functional, bioinspired systems attempting to tackle challenges in cell mimicry by encapsulating multiple compartments and performing controlled encapsulated enzymatic catalysis. Although capsosomes, which consist of liposomes embedded within a polymeric carrier capsule, are among the most advanced systems, they are still amazingly simple in their functionality and cumbersome in their assembly. We report on capsosomes by embedding liposomes within a poly(dopamine) (PDA) carrier shell created in a solution-based single-step procedure. We demonstrate for the first time the potential of PDA-based capsosomes to act as artificial cell mimics by performing a two-enzyme coupled reaction in parallel with a single-enzyme conversion by encapsulating three different enzymes into separated liposomal compartments. In the former case, the enzyme uricase converts uric acid into hydrogen peroxide, CO2 and allantoin, followed by the reaction of hydrogen peroxide with the reagent Amplex Ultra Red in the presence of the enzyme horseradish peroxidase to generate the fluorescent product resorufin. The parallel enzymatic catalysis employs the enzyme ascorbate oxidase to convert ascorbic acid into 2-L-dehydroascorbic acid.

Conductimetric biosensor for the detection of uric Acid by immobilization uricase on nata de coco membrane-pt electrode

A conductimetric enzyme biosensor for uric acid detection has been developed. The uricase, as enzyme, is isolated from Candida utilis and immobilized on a nata de coco membrane-Pt electrode. The biosensor demonstrates a linear response to urate over the concentration range 1-6 ppm and has good selectivity properties. The response is affected by the membrane thickness and pH change in the range 7.5-9.5. The response time is three minutes in aqueous solutions and in human serum samples. Application of the biosensor to the determination of uric acid in human serum gave results that compared favourably with those obtained by medical laboratory. The operational stability of the biosensor was not less than three days and the relative error is smaller than 10%.

Serum uric acid, hyperuricemia and body mass index in children and adolescents with intellectual disabilities

The aims of the preset study were to describe the profile of serum uric acid, the prevalence of hyperuricemia and its risk factors among children and adolescents with intellectual disabilities. We conducted a cross-sectional study of 941 children and adolescents with intellectual disabilities (aged 4-18 years) who participated in annual health examinations in three special schools in Taiwan. This study indicated 30.6% boys and 17.9% girls with intellectual disabilities were with hyperuricemia in Taiwan. The factors of gender, age and BMI were variables that can significantly predict the hyperuricemia occurrence in this vulnerable population. Those children and adolescents with intellectual disabilities were boys (OR=2.93, 95% CI=2.02-4.26) and older age (OR=6.49, 95% CI=2.19-19.21) were more likely to be hyperuricemia. With regard to BMI to hyperuricemia occurrence, those children and adolescents with intellectual disabilities were overweight (OR=1.16-3.21, 95% CI=1.16-3.21) and being obese (OR=4.95-11.58, 95% CI=4.95-11.58) was more likely to have a hyperuricemia than the normal weight group. This study provides the general profile of serum uric acid, hyperuricemia and its risk factors of children and adolescents with intellectual disabilities. Medical professionals should be highly alert to the possible consequences of hyperuricemia and provide useful information about the clinical manifestation of this condition for caregivers of children and adolescents with intellectual disabilities.

Gout--current diagnosis and treatment

BACKGROUND

Because of the changing dietary habits of an aging population, hyperuricemia is frequently found in combination with other metabolic disorders. Longstanding elevation of the serum uric acid level can lead to the deposition of monosodium urate crystals, causing gout (arthritis, urate nephropathy, tophi). In Germany, the prevalence of gouty arthritis is estimated at 1.4%, higher than that of rheumatoid arthritis. There are no German guidelines to date for the treatment of gout. Its current treatment is based largely on expert opinion.

METHODS

Selective literature review on the diagnosis and treatment of gout.

RESULTS AND CONCLUSIONS

Asymptomatic hyperuricemia is generally not an indication for pharmacological intervention to lower the uric acid level. When gout is clinically manifest, however, acute treatment of gouty arthritis should be followed by determination of the cause of hyperuricemia, and long-term treatment to lower the uric acid level is usually necessary. The goal of treatment is to diminish the body's stores of uric acid crystal deposits (the intrinsic uric acid pool) and thereby to prevent the inflammatory processes that they cause, which lead to structural alterations. In the long term, serum uric acid levels should be kept below 360 micromol/L (6 mg/dL). The available medications for this purpose are allopurinol and various uricosuric agents, e.g., benzbromarone. There is good evidence to support the treatment of gouty attacks by the timely, short-term use of non-steroidal anti-inflammatory drugs (NSAID), colchicine, and glucocorticosteroids.

[New aspects of the pathogenesis of gout. Danger signals, autoinflammation and beyond]

Gout is caused by monosodium urate (MSU) crystal-induced inflammation of the joints and periarticular tissues. MSU crystals activate the NOD-like receptor (NLR) NALP3, which functions as a pattern recognition receptor (PRR). Activated NALP3 mediates interleukin-1b (IL-1b) generation from its inactive pro-form, resulting in the activation of further cells and an IL-8-mediated neutrophil influx into the joint. Based on these new findings on the pathophysiology of gout, an open pilot study has recently demonstrated successful treatment of gout with the soluble IL-1R antagonist anakinra in 10 patients. The physiological role of MSU crystals might be that of a danger signal in peripheral tissues, where they stimulate dendritic cell maturation. The role of PRRs such as the NLR is underlined by NALP3 mutations causing hereditary autoinflammatory syndromes and NOD2 polymorphisms as genetic risk factors for Crohn's disease. In addition to the recognition of danger-associated molecular patterns (e.g. MSU), PRRs confer autoantigen recognition and activation of the innate and adaptive immune system in autoimmune diseases. Detection of RNA and DNA-containing immune complexes by toll-like receptors inducing B-cell activation in systemic lupus erythematosus and of proteinase 3 by the protease-activated receptor-2 inducing dendritic cell maturation in Wegener's granulomatosis have recently been reported.

[Molecular basis of primary renal hyperuricemia : role of the human urate transporter hURAT1]

In highly industrialized countries hyperuricemia is one of the most common metabolic disorders. High uric acid blood levels may lead to the manifestation of gout owing to the precipitation of urate crystals in connective tissue, the skeletal system and kidneys. A primary reduction of renal uric acid excretion can be detected in more than 90% of all cases of hyperuricemia. Despite the identification of several uric acid transporting proteins their pathogenetic role for the induction of primary reduced renal uric acid excretion has not yet been verified. As a result of a case-control study on individuals with normal and reduced renal uric acid excretion, an association of polymorphisms in the human urate transporter 1 gene (hURAT1) with primary reduced urate excretion has been demonstrated for the first time. The hURAT1 gene is an organic anion transporter (SLC22A12), which is preferentially expressed in the apical membrane of proximal renal tubule cells. Functioning as an antiporter, hURAT1 mediates the uptake of urate from the lumen into proximal tubule cells in exchange for organic and inorganic anions. Loss-of-function mutations in the hURAT1 gene are a cause of hereditary renal hypouricemia. The precisely regulated hURAT1 is a candidate gene for hyperuricemia and an important target for the development and optimization of new diagnostic approaches and pharmacological interventions of primary reduced renal uric acid excretion.