An introduction to pyrrole disorder

Pyrrole Review Article

Dr Antony Underwood MBBS (SYD) FRACP

©Spectrumceuticals 2017 – This article, or parts thereof, may not be reproduced in any form without permission, except in the case of brief quotations embodied in critical articles and reviews.

Introduction

The interest in pyrrole disorder is increasing not only with practitioners but also with the general public. Some of the main reasons for this are improved testing methods in recent years and the clinical response of the condition to zinc and vitamin B6 and their effectiveness in the treatment of many other neuropsychiatric conditions.

Pyrrole was first detected in the urine of psychiatric patients in 1958 by the biochemical unit of a psychiatric research program in Saskatchewan.1 Initially referred to as the ‘unknown substance’ by the unit, it was later called ‘the Mauve Factor’ due to the colour the paper chromatograms turned when it was detected.1 In 1961, Dr D Irvine extracted the compound from the urine of schizophrenic patients and suggested it was part of the pyrrole family.2 Canadian biochemist Dr Abram Hoffer went on to name the disease ‘malvaria’, but it was consequently renamed ‘pyroluria’ by Dr Carl Pfeiffer.1

A correlation between schizophrenia and the levels of mauve in urine was demonstrated by Hoffer and Mahon in 1961. They showed that mauve disappeared from the urine of patients that had recovered from an acute bout of schizophrenia and reappeared when they regressed.1,2 The presence of mauve in urine was found to be associated significantly with symptoms of schizophrenia such as abnormal perception, paranoia and depression.3 High mauve levels were also reported to be present in patients with affective psychosis, alcoholism, psychoneurosis and in ‘disturbed children’. 4

Dr D Irvine misidentified mauve as kryptopyrrole (KP) in a prominent science journal in 1969, and it was also misidentified by Solher in 1970.5,6 Mauve factor is, in fact, hydroxyhemopyrrolin-2-one (HPL), a hydroxylactam of hemopyrrole. This became clear when improvements in technology led to the discovery that KP is not present in human urine.7 In 1978, mauve was identified irrefutably as HPL by synthesis.8,9,2,10 Today pyroluria is called pyrrole disorder, however, it can still be referred to as pyrolleuria, kryptopyroluria, kryptopyrrole or mauve disorder.

The biological origin of HPL

There have been several theories of the biological origin of HPL, which have been explored over the last few decades. The two main theories are that HPL is a result of the breakdown of haem or HPL is a metabolite of porphyrins in the synthesis of haem.

The first theory that HPL is a result of the breakdown of haem was suggested by Dr Carl Pfeiffer and further investigated by Dr D Irvine. When examining the stools of patients with elevated HPL, Irvine discovered a distinctive triad of urobilinoids.11 This finding indicated that HPL could be a result of microbial degradation of bile pigments.

The second theory was hypothesised by Irvine. He reasoned that the structural similarity between HPL and porphyrins, the porphyrinogenicity of HPL and the high levels of HPL found in those with acute intermittent porphyria was evidence for this theory.11 Irvine suggested that porphyrins with a methyl, vinyl or ethyl group found in haemo-configuration on ring I could potentially be a HPL precursor.11 Isocoproporphyrin is one of these potential precursors.

Isocoproporphyrins are produced when there is a polymorphism in the gene that codes for the enzyme coproporphyrinogen oxidase (CPOX).12,13 The altered enzyme produces dehydroisocoproporphyrinogen, which is degraded by bacteria in the gut to form isocoproporphyrin.13 Isocoproporphyrin has the greatest structural similarity to HPL out of all the porphyrins.11 Furthermore, Pfeiffer found that mauve-positive patients excrete significantly more coproporphyrin in their urine than mauve-negative patients.14 Urinary excretion of coproporphyrin in rats quintupled after they were given 0.65 μmol/kg of HPL by intraperitoneal injection.15 Therefore, if isocoproporphyrin is the precursor to HPL, it suggests that both genetics and the gut have a role in the production of HPL.

HPL and the gut

The relationship between HPL and the gut has yet to be conclusively defined, however, there is evidence that such a relationship does exist. It was found that oral dosing with kanamycin, a non-absorbable antibiotic, reversibly eliminated or significantly reduced urinary HPL in nine subjects.11 This is indicative of bacterial involvement in the formation of HPL. Furthermore, there have been multiple observations that suggest urinary excretion of HPL is modulated by intestinal permeability. It is well established that zinc deficiency causes intestinal epithelial damage and increased permeability facilitated by increased nitric oxide in the intestine.16 Since zinc deficiency is a symptom of pyrrole disorder, HPL may therefore have an association with intestinal permeability. Supplementation of zinc has been shown to decrease bowel permeability in animals and humans.17,18,19,20

Therefore, the decrease of HPL in urine associated with the supplementation of zinc and B6 could be due to the positive effect zinc has on intestinal permeability. Laxatives and enemas were found to increase HPL levels in the urine. 11 Laxatives, such as magnesium sulphate and biscodyl, have been shown to increase intestinal permeability 21,22 Furthermore, soap-sud or tap-water enemas cause epithelial loss, which is likely to increase intestinal permeability.23 The effect of laxatives and enemas on urinary HPL is further evidence that HPL is modulated by intestinal permeability. Irvine found that urinary HPL increased significantly when he treated rats and mice with prednisone.11 Prednisone is known to increase gut permeability, therefore this finding is consistent with the theory that gut permeability effects HPL levels.

Testing methods

HPL is present in small quantities in all human urine.24 A survey by Vitamin Diagnostics Laboratory using HPLC/MS methods under strict darkroom conditions determined that the normal concentration of HPL in human urine is 2–25 μg/dL.24 Urinary HPL levels that are over twice the upper limit of normal are considered by clinicians as highly elevated.24

When outside the body, HPL becomes unstable because it frequently interconverts with other structures.5,25 The amount of detectable HPL in urine is reduced by exposure to light and relatively mild chemicals.26 HPL is also heat-labile; one study found it was destroyed when heated to 40°C in a water bath.27 Stabilisation of HPL in urine can be achieved by freezing it to –18°C which is effective for up to four months.28 To prevent the destruction of HPL in the urine and therefore maximise its detection, ascorbate preservative is added to the samples and they are transported in light shielded tubes. In addition, the urine should be collected and analysed in low light environments. If the sample cannot be analysed immediately, overnight delivery and/or freezing is required.

To correct for varying urine concentration, HPL values are normalised using urinary specific gravity (SG) or creatinine.29 Without this adjustment HPL levels could be recorded as higher or lower than they actually are. The BioCenter Laboratory in Wichita, Kansas found that out of 600 colorimetric assays, 20% of HPL values moved into or out of the normal range after adjustment to SG by refractometry. 11 Today HPL levels in urine are determined using Ultraviolet-Visible Spectroscopy (UV-Vis) or High-Pressure Liquid Chromatography/ Mass Spectroscopy (HPLC/MS).

HPL as a biomarker for oxidative stress

Oxidative stress is caused by a deficiency of zinc or vitamin B6 and supplementation of zinc has been found to reduce oxidised biomolecules.30,31,32 P5P (the active form of vitamin B6) protects neurons from damage due to oxidative stress by increasing energy production and lowering cell death in neurons.33,34 Patients with high HPL are deficient in zinc and B6, which is correlated with oxidative stress. Therefore HPL has the potential to indicate oxidative stress.11 Reduced levels of the antioxidant glutathione (GSH) in the plasma is also associated with increased oxidative stress, so it is another marker for oxidative stress.35 Decreased plasma GSH is strongly correlated with HPL, providing another indication that HPL is a biomarker for oxidative stress.11

Treatment of pyrrole disorder

Pfeiffer found that kryptopyrrole (now known as HPL) combined chemically with pyridoxine (vitamin B6) and was then excreted in the urine complexed (along with zinc) with zinc.14 He concluded that this caused symptoms of vitamin B6 and zinc deficiency.14 Pfeiffer found that adequate doses of B6 and zinc relieved the symptoms of pyrrole disorder and reduced urinary excretion of HPL to a normal range.14 The contemporary treatment of pyrrole disorder uses a combination of zinc, magnesium and B6 either as pyridoxine or its active form pyridoxine-5-phosphate or P5P.11,36

Conclusion

Pyrrole disorder is characterised by high levels of HPL in the urine of patients. It is treatable with zinc and vitamin B6. The origins of HPL are unconfirmed but leading theories associate HPL generation with haem synthesis or haem breakdown. A correlation between urinary HPL counts and intestinal permeability has been found. HPL is also associated strongly with oxidative stress, so has the potential to be used as an oxidative stress biomarker. Despite the unknown origins of HPL, its association with oxidative stress, zinc and B6 deficiency allow the successful treatment of pyrrole disorder. This is an important condition that the clinician needs to be aware of in order to diagnosis and treat it effectively. In practice, it is one of the most satisfying conditions to treat and manage as the response to zinc and B6 is often rapid and will frequently lead to good clinical outcomes.

References

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2. DJ. Graham, ‘Quantitative determination of 3-ethyl-5-hydroxy-4,5-dimethyl-delta 3-pyrrolin-2-one in urine using gas-liquid chromatography,’ Clinica Chimica Acta, vol. 85, no. 2, pp. 205-210, 1978.
3. A. Hoffer and Osmond. H, ‘The association between schizophrenia and two objective tests,’ Canadian Medical Association Journal, vol. 87, no. 12, pp. 641-646., 1962.
4. PO. O’Reilly, Ernest M and Hughes G, ‘The incidence of malvaria,’ The British Journal of Psychiatry, vol. 111, pp. 741-744, 1965.
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©Spectrumceuticals 2017 – This article, or parts thereof, may not be reproduced in any form without permission, except in the case of brief quotations embodied in critical articles and reviews.