Treatment options in acute porphyria, porphyria cutanea tarda, and erythropoietic protoporphyria

Acute Intermittent Porphyria’s Symptoms and Management: A Narrative Review

Acute intermittent porphyria (AIP) is an autosomal dominant disorder of heme biosynthesis in the liver that is caused by the accumulation of toxic heme metabolites aminolevulinic acid (ALA) and porphobilinogen (PBG) due to a deficiency in the enzyme hydroxymethylbilane synthase (HMBS). The prevalence of AIP is found to commonly affect females of reproductive age (ages 15-50) and people of Northern European descent. The clinical manifestations of AIP include acute and chronic symptoms that can be outlined into three phases: the prodromal phase, the visceral symptom phase, and the neurological phase. Major clinical symptoms involve severe abdominal pain, peripheral neuropathy, autonomic neuropathies, and psychiatric manifestations. Symptoms are often heterogeneous and vague, which can lead to life-threatening signs if not treated and managed appropriately. Whether treating AIP in its acute or chronic form, the cornerstone of treatment consists of the suppression of the production of ALA and PBG. The mainstay of managing acute attacks continues to comprise discontinuing porphyrogenic agents, adequate caloric support, heme treatment, and the treatment of symptoms. In recurrent attacks and chronic management, prevention is key with the consideration of liver transplantation and/or renal transplantation. In recent years, there has been great interest in emerging treatments that focus on a molecular level such as enzyme replacement therapy, ALAS1 gene inhibition, and even liver gene therapy (GT), which has changed the way of traditionally managing this disease and will pave the way for innovative therapies to come.

Disease burden in patients with acute hepatic porphyria: experience from the phase 3 ENVISION study

Background

Acute hepatic porphyria (AHP) is a family of four rare genetic diseases, each involving deficiency in a hepatic heme biosynthetic enzyme. Resultant overproduction of the neurotoxic intermediates δ-aminolevulinic acid (ALA) and porphobilinogen (PBG) leads to disabling acute neurovisceral attacks and progressive neuropathy. We evaluated the AHP disease burden in patients aged ≥ 12 years in a post hoc analysis of the Phase 3, randomized, double-blind, placebo-controlled ENVISION trial of givosiran (NCT03338816), an RNA interference (RNAi) therapeutic that targets the enzyme ALAS1 to decrease ALA and PBG production. We analyzed baseline AHP severity via chronic symptoms between attacks, comorbidities, concomitant medications, hemin-associated complications, and quality of life (QOL) and evaluated givosiran (2.5 mg/kg monthly) in patients with and without prior hemin prophylaxis on number and severity of attacks and pain scores during and between attacks.

Results

Participants (placebo, n = 46; givosiran, n = 48) included patients with low and high annualized attack rates (AARs; range 0–46). At baseline, patients reported chronic symptoms (52%), including nausea, fatigue, and pain; comorbidities, including neuropathy (38%) and psychiatric disorders (47%); concomitant medications, including chronic opioids (29%); hemin-associated complications (eg, iron overload); and poor QOL (low SF-12 and EuroQol visual analog scale scores). A linear relationship between time since diagnosis and AAR with placebo suggested worsening of disease over time without effective treatment. Givosiran reduced the number and severity of attacks, days with worst pain scores above baseline, and opioid use versus placebo.

Conclusions

Patients with AHP, regardless of annualized attack rates, have considerable disease burden that may partly be alleviated with givosiran.

Hypertensive Crisis in Patients with Acute Intermittent Porphyria

Introduction: Acute intermittent porphyria (AIP) is the most common and the most severe form of acute hepatic porphyria.

Case report: Patient, 39 years old, was admitted to the Emergency Department because of abdominal pain. Abdominal pain started 5 days before the admission. The diagnostic research in his hospital showed presence of a stone in the right kidney, and the patient was transported to the other Clinical Centre, where a common urine test showed: high values of delta - aminolevulinic acid and porphobilinogen. The patient was transported to our Clinical Centre. At the admission, abdominal pain decreased, but the patient had a hypertensive crisis with a headache, tearing eyes, swelling, anxiety.Common laboratory tests were in reference range, except creatinine, CRP, arterial blood gas analysis, urine test. The hypertensive crisis was treated by beta blockers and diuretics in maximal doses, but without a positive effect, so we decided to try with Glyceryl trinitrate intravenously. Control blood pressure was 170/100mmHg….130/80mmHg.

Discussion: Porphyria can be a diagnostic problem, because one of the manifestations can be abdominal pain.

Conclusions: Comorbidities can be critical in the therapy of life threating conditions.

Therapeutic RNA-silencing oligonucleotides in metabolic diseases

Recent years have seen unprecedented activity in the development of RNA-silencing oligonucleotide therapeutics for metabolic diseases. Improved oligonucleotide design and optimization of synthetic nucleic acid chemistry, in combination with the development of highly selective and efficient conjugate delivery technology platforms, have established and validated oligonucleotides as a new class of drugs. To date, there are five marketed oligonucleotide therapies, with many more in clinical studies, for both rare and common liver-driven metabolic diseases. Here, we provide an overview of recent developments in the field of oligonucleotide therapeutics in metabolism, review past and current clinical trials, and discuss ongoing challenges and possible future developments.

Porphyria cutanea tarda and patterns of long-term sick leave and disability pension: a 24-year nationwide matched-cohort study

BACKGROUND

Porphyria cutanea tarda (PCT) is a skin disorder caused by a defect in the liver enzyme uroporphyrinogen decarboxylase and is associated with hepatitis C virus infection, high alcohol intake, smoking and iron overload. Data on the long-term morbidity of PCT is lacking.

METHODS

We conducted a nationwide matched cohort study over a 24-year period. The study sample included 534 persons aged 18-67 years with a biochemically confirmed PCT diagnosis and a sample of 21,360 persons randomly selected from the working age population, matched on age, sex and educational attainment. We investigated if persons with sporadic and familial PCT had an increased risk of long-term sick leave (LTSL) or disability pension. We further assessed risk before (pre-PCT), during (during-PCT) and after (post-PCT) the typical period of first onset to diagnosis, treatment and remission.

RESULTS

Overall, persons with PCT had a 40% increased risk (hazard ratio [HR] = 1.4, 95% confidence interval [CI] = 1.3, 1.5) of LTSL and a 50% increased risk (HR = 1.5, CI = 1.3, 1.7) of disability pension. Risk of disability pension was increased pre-PCT (HR = 1.3, CI 1.3 (1.0, 1.6), during-PCT (HR 1.5, CI 1.0, 2.2) and post-PCT (HR = 2.0, CI 1.5, 2.6). For LTSL, risk was increased pre-PCT (HR = 1.3, CI 1.1, 1.4) and during-PCT (HR = 1.5, CI 1.1, 2.1), but not post-PCT. Risk was greatest in persons with sporadic than familial PCT. Diagnostic reasons for disability pension that were increased compared to matched controls were PCT or skin disease in 11 of 199 cases (PCT: n = 7, incident rate ratios [IRR] = 49.2, CI = 38.8, 62.4; diseases of the skin and subcutaneous tissue, n = 4, IRR = 4.2, CI = 1.6, 11.0). The vast majority of diagnostic reasons for accessing disability pension were related to comorbidities, PCT susceptibility factors and more general health issues such as: malignant neoplasms (n = 12, IRR = 2.4, CI = 1.4, 4.2), substance and alcohol dependence (n = 7, IRR = 5.0, CI = 2.5, 10.1), neurotic and mood-disorders (n = 21, IRR = 1.7, CI = 1.1, 2.6), and diseases of the musculoskeletal system and connective tissue (n = 71, IRR = 2.5, CI = 1.9, 3.2).

CONCLUSIONS

Persons with PCT have an increased risk of LTSL and disability pension indicating significant morbidity in this patient group. Appropriate long-term follow-up and monitoring for relapses and co-morbid diseases are recommended.

Efficacy and safety of givosiran for acute hepatic porphyria: 24-month interim analysis of the randomized phase 3 ENVISION study

BACKGROUND & AIMS

Upregulation of hepatic delta-aminolevulinic acid synthase 1 with accumulation of potentially toxic heme precursors delta-aminolevulinic acid and porphobilinogen is fundamental to the pathogenesis of acute hepatic porphyria.

AIMS

evaluate long-term efficacy and safety of givosiran in acute hepatic porphyria.

METHODS

Interim analysis of ongoing ENVISION study (NCT03338816), after all active patients completed their Month 24 visit. Patients with acute hepatic porphyria (≥12 years) with recurrent attacks received givosiran (2.5 mg/kg monthly) (n = 48) or placebo (n = 46) for 6 months (double-blind period); 93 received givosiran (2.5 mg or 1.25 mg/kg monthly) in the open-label extension (continuous givosiran, n = 47/48; placebo crossover, n = 46/46). Endpoints included annualized attack rate, urinary delta-aminolevulinic acid and porphobilinogen levels, hemin use, daily worst pain, quality of life, and adverse events.

RESULTS

Patients receiving continuous givosiran had sustained annualized attack rate reduction (median 1.0 in double-blind period, 0.0 in open-label extension); in placebo crossover patients, median annualized attack rate decreased from 10.7 to 1.4. Median annualized days of hemin use were 0.0 (double-blind period) and 0.0 (open-label extension) for continuous givosiran patients and reduced from 14.98 to 0.71 for placebo crossover patients. Long-term givosiran led to sustained lowering of delta-aminolevulinic acid and porphobilinogen and improvements in daily worst pain and quality of life. Safety findings were consistent with the double-blind period.

CONCLUSIONS

Long-term givosiran has an acceptable safety profile and significantly benefits acute hepatic porphyria patients with recurrent attacks by reducing attack frequency, hemin use, and severity of daily worst pain while improving quality of life.

In vitro Assessment of Solar Filters for Erythropoietic Protoporphyria in the Action Spectrum of Protoporphyrin IX

Introduction: Subjects with erythropoietic protoporphyria rely on broad-spectrum sunscreens with high sun protection factor, which is not informative on efficacy in the absorption spectrum of protoporphyrin IX, spanning visible radiation and peaking around 408 nm. Photoactivation of protoporphyrin IX is responsible for painful skin photosensitivity in erythropoietic protoporphyria. The authors assessed the protective efficacy of six sunscreens in vitro in the absorption spectrum of protoporphyrin IX. Method: Transmittance measurements were performed in the 300-850 nm wavelengths on samples of six photoprotective products applied to polymethyl methacrylate plates. Porphyrin protection factor was calculated in the 300-700 nm region to provide a measurement for the efficacy of each product based on the action spectrum of protoporphyrin IX. Results: Product A showed the highest porphyrin protection factor among tested products with a median value of 4.22. Product A is a sunscreen containing organic filters, titanium dioxide and synthetic iron oxides, pigmentary grade active ingredients that absorb visible radiation. Other products showed inefficient protection in the visible, with transmittance between 75 and 95% at 500 nm. The low porphyrin protection factor of inorganic filter product B was attributed to particle micronization, as declared by the manufacturer. Conclusion: Adding porphyrin protection factor to sunscreen labeling could help patients with erythropoietic protoporphyria and other photosensitivity disorders identify products tailored on their specific needs. The development of sunscreens providing protection from visible radiation and excellent cosmetical tolerability could improve the lifestyle of patients with erythropoietic protoporphyria.

Hypertensive Crisis in Patients with Acute Intermittent Porphyria

Introduction

Acute intermittent porphyria (AIP) is the most common and the most severe form of acute hepatic porphyria.

Case report

Patient, 39 years old, was admitted to the Emergency Department because of abdominal pain. Abdominal pain started 5 days before the admission. The diagnostic research in his hospital showed presence of a stone in the right kidney, and the patient was transported to the other Clinical Centre, where a common urine test showed: high values of delta - aminolevulinic acid and porphobilinogen. The patient was transported to our Clinical Centre.

At the admission, abdominal pain decreased, but the patient had a hypertensive crisis with a headache, tearing eyes, swelling, anxiety. Common laboratory tests were in reference range, except creatinine, CRP, arterial blood gas analysis, urine test. The hypertensive crisis was treated by beta blockers and diuretics in maximal doses, but without a positive effect, so we decided to try with Glyceryl trinitrate intravenously. Control blood pressure was 170/100mmHg….130/80mmHg.

Discussion

Porphyria can be a diagnostic problem, because one of the manifestations can be abdominal pain.

Conclusions

Comorbidities can be critical in the therapy of life threating conditions.

Paediatric porphyria and human hemin: a treatment challenge in a lower middle income country

Here, we report a case of a 15-year-old girl who presented to the emergency department with symptoms of abdominal pain, nausea, vomiting and seizures. She was diagnosed with acute intermittent porphyria. Treatment was started by removing all porphogenic drugs, providing high glucose intake (oral and intravenous), which initially resulted in good clinical outcomes. However, she deteriorated again and also developed neurological manifestation (paraplegia) for which she required mechanical ventilation because of acute respiratory failure. This time she was initiated on human hemin for four consecutive days. After 2 days of therapy, her porphobilinogen levels decreased to 50% of the initial raised value. Increased lactic acid and blood urea nitrogen were the two side effects observed after the treatment, with no apparent signs of acute kidney injury. To the best of our knowledge, in paediatric population, this is the first reported case of treatment of acute intermittent porphyria with human hemin in Pakistan.

Do We Utilize Our Knowledge of the Skin Protective Effects of Carotenoids Enough?

Due to their potential health-promoting effects, carotenoids have drawn both scientific and public attention in recent years. The primary source of carotenoids in the human skin is diet, mainly fruits, vegetables, and marine product, but they may originate from supplementation and topical application, too. In the skin, they accumulate mostly in the epidermis and act as a protective barrier to various environmental influences. Namely, the skin is exposed to numerous environmental factors, including ultraviolet radiation (UVR), air pollution, and smoking, that cause oxidative stress within the skin with consequent premature (extrinsic) aging. UVR, as the most prominent environmental factor, may cause additional detrimental skin effects, such as sunburn, DNA damage, and skin cancer. Therefore, photoprotection is the first line intervention in the prevention of premature aging and skin cancer. Numerous studies have demonstrated that carotenoids, particularly β-carotene, lycopene, lutein, and astaxanthin, have photoprotective effects, not only through direct light-absorbing properties, but also through their antioxidant effects (scavenging reactive oxygen species), as well as by regulation of UV light-induced gene expression, modulation of stress-dependent signaling, and/or suppression of cellular and tissue responses like inflammation. Interventional studies in humans with carotenoid-rich diet have shown its photoprotective effects on the skin (mostly by decreasing the sensitivity to UVR-induced erythema) and its beneficial effects in prevention and improvement of skin aging (improved skin elasticity and hydration, skin texture, wrinkles, and age spots). Furthermore, carotenoids may be helpful in the prevention and treatment of some photodermatoses, including erythropoietic protoporphyria (EPP), porphyria cutanea tarda (PCT) and polymorphous light eruption (PMLE). Although UVR is recognized as the main etiopathogenetic factor in the development of non-melanoma skin cancer (NMSC) and melanoma, and the photoprotective effects of carotenoids are certain, available studies still could not undoubtedly confirm the protective role of carotenoids in skin photocarcinogenesis.

Sugammadex and amino acid infusion can contribute to safe anesthetic management of variegate porphyria

BACKGROUND

Variegate porphyria (VP) is an inherited type of porphyria characterized by cutaneous manifestations and/or acute neurovisceral attacks. We report successful anesthetic management of VP.

CASE PRESENTATION

A 66-year-old woman with VP was scheduled to undergo distal pancreatectomy for pancreatic cancer. Medical history was unremarkable except for sudden onset of abdominal pain that occurred every few months, possibly due to VP. There was no abnormality in laboratory data except for a mild increase in creatinine levels. General anesthesia was induced and maintained with total intravenous anesthesia using propofol, remifentanil, and rocuronium. Blood glucose levels were measured every hour and glucose administered to prevent hypoglycemia. Amino acids were also infused to treat hypothermia. Upon completion of distal pancreatectomy, sugammadex was administered to reverse neuromuscular blockade. She was neurologically intact and discharged on postoperative day 15 with no acute attack.

CONCLUSIONS

Sugammadex and amino acids can be used safely in patients with VP.

Porphyria cutanea tarda associated with HFE C282Y homozygosity, iron overload, and use of a contraceptive vaginal ring

Porphyria cutanea tarda (PCT) is characterized by decreased uroporphyrinogen decarboxylase activity in hepatocytes, uroporphyrin I and heptacarboxyl porphyrin III accumulation, photosensitivity dermatitis, and increased storage iron. In women, estrogen therapy, including oral contraceptives, postmenopausal hormone replacement, and tamoxifen for breast cancer treatment, is a risk factor for PCT. We report the case of a woman who presented with PCT, HFE C282Y homozygosity, and hepatic iron overload and was using a contraceptive vaginal ring containing ethinyl estradiol, an estrogen. We discuss this case in the context of characteristics of other persons with PCT, including common HFE mutations, iron overload, and estrogen exposure.

Challenges in the successful management of a case of acute intermittent porphyria in India

Acute intermittent porphyria (AIP) is a rare metabolic disease involving a defect in haem biosynthesis resulting in the accumulation and excessive secretion of porphyrins and its precursors. Acute attacks present with episodes of severe abdominal pain, nausea, confusion and severe life-threatening seizures. A high index of suspicion is required for the initial diagnosis of AIP.

Hydroxychloroquine: a multifaceted treatment in lupus

The efficacy of antimalarials, especially hydroxychloroquine (HCQ), in preventing systemic lupus erythematosus (SLE) flares is well demonstrated. However, many studies show that the percentage of SLE patients treated with HCQ remains low. By blocking the toll-like receptor 7 and 9 in plasmacytoid dendritic cells, HCQ inhibits interferon-alpha production which plays a crucial role in SLE pathogenesis. In addition to reducing damage accrual in SLE patients, HCQ appears to protect against the occurrence of diabetes, thrombotic events, and dyslipidemia. As a consequence, some studies have suggested that HCQ, which is inexpensive, has a protective effect on survival in SLE patients. Thanks to the pharmacokinetic properties of HCQ (long half-life) and to the availability of its blood assay, very low or undetectable blood HCQ concentrations are a valuable marker of non-adherence to treatment, thus adding a new benefit to HCQ prescriptions. The main side effect of HCQ is retinal toxicity. This complication is very rare, but may be potentially severe, thus requiring regular screening. Retinal toxicity remains the only absolute contra-indication of HCQ in adult SLE patients. Other contra-indications are few and rare. During pregnancy and breast-feeding, HCQ continuation is not only allowed but recommended. In conclusion, the risk/benefit ratio of HCQ is excellent. Many now believe that all SLE patients should be offered this treatment.

High risk of primary liver cancer in a cohort of 179 patients with Acute Hepatic Porphyria

BACKGROUND/AIMS

Previous studies have indicated a high risk of hepatocellular carcinoma in acute hepatic porphyrias. In this retrospective study we present the incidence of primary liver cancer and clinical characteristics in a cohort of 179 acute porphyria patients above the age of 50 years.

METHODS

Twenty-three cases with primary liver cancer were found either by a surveillance program or due to clinical suspicion. Standardized rate ratio was used to estimate the relative risk of primary liver cancer after indirect standardization. Survival data were calculated using the Kaplan-Meier method.

RESULTS

The mean age at diagnosis was 69 years. Hepatocellular carcinoma was found in 19 patients while four patients had cholangiocarcinoma or a combination of the two. Four patients had underlying cirrhosis. Mean tumour size was 4.3 cm in the surveillance group and 10.3 cm in the non-surveillance group (p = 0.01). The overall relative risk of primary liver cancer was 86 above the age of 50: 150 for women and 37 for men. Mean survival time was 5.7 years.

CONCLUSION

Acute hepatic porphyria carries a high risk of primary liver cancer above the age of 50 which warrants ultrasound surveillance. Sex distribution and frequency of cirrhosis differs from more common aetiologies of primary liver cancer.

Cutaneous porphyrias part II: treatment strategies

The porphyrias are diverse in pathophysiology, clinical presentation, severity, and prognosis, presenting a diagnostic and therapeutic challenge. Although not easily curable, the dermatological manifestations of these diseases, photosensitivity and associated cutaneous pathology, can be effectively prevented and managed. Sun avoidance is essential, and patient education regarding the irreversibility of photocutaneous damage is a necessary corollary. Beyond preventative measures, the care of fragile, vulnerable skin, and pain management, each of the porphyrias has a limited number of unique additional therapeutic options. Many of the treatments have been published only in small case series or anecdotal reports and do not have well-understood nor proven mechanisms of action. This article presents a comprehensive review of available therapeutic options and long-term management recommendations for the cutaneous porphyrias.

Hepatitis C, porphyria cutanea tarda and liver iron: an update

Porphyria cutanea tarda (PCT) is the most common form of porphyria across the world. Unlike other forms of porphyria, which are inborn errors of metabolism, PCT is usually an acquired liver disease caused by exogenous factors, chief among which are excess alcohol intake, iron overload, chronic hepatitis C, oestrogen therapy and cigarette smoking. The pathogenesis of PCT is complex and varied, but hereditary or acquired factors that lead to hepatic iron loading and increased oxidative stress are of central importance. Iron loading is usually only mild or moderate in degree [less than that associated with full-blown haemochromatosis (HFE)] and is usually acquired and/or mutations in HFE. Among acquired factors are excessive alcohol intake and chronic hepatitis C infection, which, like mutations in HFE, decrease hepcidin production by hepatocytes. The decrease in hepcidin leads to increased iron absorption from the gut. In the liver, iron loading and increased oxidative stress leads to the formation of non-porphyrin inhibitor(s) of uroporphyrinogen decarboxylase and to oxidation of porphyrinogens to porphyrins. The treatment of choice of active PCT is iron reduction by phlebotomy and maintenance of a mildly iron-reduced state without anaemia. Low-dose antimalarials (cinchona alkaloids) are also useful as additional therapy or as alternative therapy for active PCT in those without haemochromatosis or chronic hepatitis C. In this review, we provide an update of PCT with special emphasis upon the important role often played by the hepatitis C virus.

Liver transplantation for erythropoietic protoporphyria in Europe

Liver transplantation is an established lifesaving treatment for patients with severe protoporphyric liver disease, but disease recurrence in the graft occurs for the majority of recipients. Severe burn injuries may occur when protective light filters are not used with surgical luminaires. Motor neuropathy with an unclear pathogenesis is a frequent complication. We retrospectively studied 35 transplants performed for protoporphyric liver disease in 31 European patients between 1983 and 2008. Most of the patients were male (61.3%), and the mean age at the time of primary transplantation was 39 years (range = 9-60 years). The overall patient survival rates were 77% at 1 year and 66% at 5 and 10 years. The overall rate of disease recurrence in the graft was 69%. Forty-three percent of the patients experienced recurrence within a year, but this was often a transient finding that was associated with other graft complications. Phototoxic injuries due to surgical luminaires were seen in 25.0% of the patients who were not protected by filters, but these injuries were not seen in the 9 patients who were protected by filters. Significant motor neuropathies requiring prolonged ventilation complicated the postoperative course for 5 of the 31 patients (16.1%). Hematopoietic stem cell transplantation was performed for 3 patients to prevent graft loss due to disease recurrence. Prognostic markers are needed to identify patients prone to severe protoporphyric liver disease so that curative stem cell transplantation can be offered to select patients instead of liver transplantation.

Erythropoietic protoporphyria in Sweden: demographic, clinical, biochemical and genetic characteristics

OBJECTIVE

To investigate the demographic, clinical, biochemical and genotypic features of patients with erythropoietic protoporphyria (EPP) in a Swedish cohort.

DESIGN

Cross-sectional questionnaire, biochemical and genetic study.

SETTING

Sweden.

SUBJECTS

Fifty-one Swedish individuals known in 2008 to have EPP confirmed by molecular diagnosis. There were no exclusion criteria; all patients were included in the demographic and genetic study. A total of 92% participants completed the questionnaire study and 82% the biochemical study.

RESULTS

The prevalence of EPP was 1 : 180,000. Nine novel ferrochelatase gene mutations were found. The most commonly reported age at onset of symptoms was the first year of life and the mean age at diagnosis was 22 years. Painful photosensitivity was the main symptom. Exogenous factors other than sunlight were frequently reported to cause cutaneous symptoms. One in five patients reported a positive effect of beta-carotene therapy. A marked impact of EPP on quality of life was reported. Women had a significantly lower mean erythrocyte protoporphyrin concentration than men. Of all participants, 84% had insufficient vitamin D concentrations, 44% had below normal serum ferritin or transferrin saturation levels and red cell abnormalities were common.

CONCLUSIONS

The notably delayed diagnosis suggests the need for an increased awareness of EPP. Disturbed erythropoiesis, biochemical signs of iron deficiency and low vitamin D levels are frequent findings in this disease. New and better treatments are needed as current treatment options for symptom amelioration are limited. Vitamin D supplementation should be considered.

Beta-carotene is an important vitamin A source for humans

Experts in the field of carotenoids met at the Hohenheim consensus conference in July 2009 to elucidate the current status of β-carotene research and to summarize the current knowledge with respect to the chemical properties, physiological function, and intake of β-carotene. The experts discussed 17 questions and reached an agreement formulated in a consensus answer in each case. These consensus answers are based on published valid data, which were carefully reviewed by the individual experts and are justified here by background statements. Ascertaining the impact of β-carotene on the total dietary intake of vitamin A is complicated, because the efficiency of conversion of β-carotene to retinol is not a single ratio and different conversion factors have been used in various surveys and following governmental recommendations within different countries. However, a role of β-carotene in fulfilling the recommended intake for vitamin A is apparent from a variety of studies. Thus, besides elucidating the various functions, distribution, and uptake of β-carotene, the consensus conference placed special emphasis on the provitamin A function of β-carotene and the role of β-carotene in the realization of the required/recommended total vitamin A intake in both developed and developing countries. There was consensus that β-carotene is a safe source of vitamin A and that the provitamin A function of β-carotene contributes to vitamin A intake.

Combined liver and kidney transplantation in acute intermittent porphyria

We report two patients with acute intermittent porphyria (AIP) who were successfully treated with combined liver and kidney transplantation. Both had a very poor quality of life as a result of years of frequent acute porphyria symptoms, chronic peripheral neuropathy and renal failure requiring dialysis. After transplantation, clinical and biochemical signs of porphyria disappeared. The excretion pattern of porphyrin precursors normalized within the first day and plasma porphyrins returned to normal within a week. These and other recent cases have clarified previous concerns and have helped to formulate the indications for and the timing of transplantation in AIP.

Site-directed mutagenesis and computational study of the Y366 active site in Bacillus subtilis protoporphyrinogen oxidase

Protoporphyrinogen IX oxidase (PPO), the last common enzyme of heme and chlorophyll biosynthesis, catalyses the oxidation of protoporphyrinogen IX to protoporphyrin IX, with FAD as cofactor. Among PPO, Bacillus subtilis PPO (bsPPO) is unique because of its broad substrate specificity and resistance to inhibition by diphenylethers. Identification of the activity of bsPPO would help us to understand the catalysis and resistance mechanisms. Based on the modeling and docking studies, we found that Y366 site in bsPPO was adjacent to substrate and FAD. In order to evaluate the functional role of this site, three mutants Y366A Y366E and Y366H were cloned and kinetically characterized. The efficiency of catalysis for Y366A and Y366H reduced to 10% of the wild-type enzyme's activity, while Y366E just retained 1%. Y366E shows large resistance (K (i) = 153.94 microM) to acifluorfen. Molecular docking was carried out to understand the structure and functional relationship of PPO. The experimental results from the site-directed mutagenesis are consistent with the computational studies. The residue at position 366 is seemed to be responsible for substrate binding and catalysis and involved in herbicide resistance of bsPPO.