Effect of alcohol on delta-aminolevulinic acid dehydratase and porphyrin metabolism in man

Understanding Coproporphyrins and their Disposition: Coproporphyrinuria is Common, of Diverse Cause, and Rarely Indicates Porphyria

Coproporphyrins [CPs] are often mildly increased in plasma and urine, which leads to erroneous over-diagnosis of porphyrias. Herein we provide an overview of normal CP metabolism and factors that influence its disposition. We reviewed extant literature and here summarize and put into context current knowledge of CP metabolism and its disposition. CPs are formed as byproducts of normal heme synthesis. Normally they are removed chiefly by hepatocytes into bile and then stool. Organic anion transporting peptides [OATPs] and multidrug resistance-associated proteins [MRPs] facilitate the uptake of CPs into epithelial cells and removal. Xenobiotics inhibit the activities of MRPs and/or OATPs and affect the metabolism and disposition of CPs. CP concentrations are used as endogenous probes for assessing altered functions of OATPs. Diverse liver diseases and disorders lead to decreased secretion of CPs into bile and thus to increased concentrations of CPs in plasma and urine. Usually, mild to moderate increases in urinary CPs are due to alcohol, heavy metals, drug effects on transporters, or non-porphyric liver diseases not to porphyrias or to other inherited syndromes.

Causes and Pathophysiology of Acquired Sideroblastic Anemia

The sideroblastic anemias are a heterogeneous group of inherited and acquired disorders characterized by anemia and the presence of ring sideroblasts in the bone marrow. Ring sideroblasts are abnormal erythroblasts with iron-loaded mitochondria that are visualized by Prussian blue staining as a perinuclear ring of green-blue granules. The mechanisms that lead to the ring sideroblast formation are heterogeneous, but in all of them, there is an abnormal deposition of iron in the mitochondria of erythroblasts. Congenital sideroblastic anemias include nonsyndromic and syndromic disorders. Acquired sideroblastic anemias include conditions that range from clonal disorders (myeloid neoplasms as myelodysplastic syndromes and myelodysplastic/myeloproliferative neoplasms with ring sideroblasts) to toxic or metabolic reversible sideroblastic anemia. In the last 30 years, due to the advances in genomic techniques, a deep knowledge of the pathophysiological mechanisms has been accomplished and the bases for possible targeted treatments have been established. The distinction between the different forms of sideroblastic anemia is based on the study of the characteristics of the anemia, age of diagnosis, clinical manifestations, and the performance of laboratory analysis involving genetic testing in many cases. This review focuses on the differential diagnosis of acquired disorders associated with ring sideroblasts.

Candidate genes, pathways and mechanisms for alcoholism: an expanded convergent functional genomics approach

We describe a comprehensive translational approach for identifying candidate genes for alcoholism. The approach relies on the cross-matching of animal model brain gene expression data with human genetic linkage data, as well as human tissue data and biological roles data, an approach termed convergent functional genomics. An analysis of three animal model paradigms, based on inbred alcohol-preferring (iP) and alcohol-non-preferring (iNP) rats, and their response to treatments with alcohol, was used. A comprehensive analysis of microarray gene expression data from five key brain regions (frontal cortex, amygdala, caudate-putamen, nucleus accumbens and hippocampus) was carried out. The Bayesian-like integration of multiple independent lines of evidence, each by itself lacking sufficient discriminatory power, led to the identification of high probability candidate genes, pathways and mechanisms for alcoholism. These data reveal that alcohol has pleiotropic effects on multiple systems, which may explain the diverse neuropsychiatric and medical pathology in alcoholism. Some of the pathways identified suggest avenues for pharmacotherapy of alcoholism with existing agents, such as angiotensin-converting enzyme (ACE) inhibitors. Experiments we carried out in alcohol-preferring rats with an ACE inhibitor show a marked modulation of alcohol intake. Other pathways are new potential targets for drug development. The emergent overall picture is that physical and physiological robustness may permit alcohol-preferring individuals to withstand the aversive effects of alcohol. In conjunction with a higher reactivity to its rewarding effects, they may able to ingest enough of this nonspecific drug for a strong hedonic and addictive effect to occur.

Effects of ethanol and diphenyl diselenide exposure on the activity of δ-aminolevulinate dehydratase from mouse liver and brain

Ethanol toxicity is affected by both environmental and inherited features. Since oxidative stress is an important molecular mechanism for ethanol-induced cellular damage, the concomitant exposure to ethanol and pro-oxidative or antioxidant compounds can alter its toxicity. Here, we investigate the effects of exposure to ethanol and/or diphenyl diselenide, an organochalcogen with antioxidant properties, on parameters related to oxidative stress (thiobarbituric acid reactive species-TBARS-and delta-aminolevulinate dehydratase-delta-ALA-D activity) in mouse liver and brain. In addition, the in vitro effects of ethanol and acetaldehyde on the activity of delta-ALA-D from human erythrocytes were also investigated. Both ethanol and diphenyl diselenide decreased hepatic delta-ALA-D activity and DL-dithiothreitol (DTT) reactivated this enzyme only after ethanol-induced inhibition. Moreover, ethanol increased liver TBARS levels, independently of the presence of diphenyl diselenide treatment. Brain delta-ALA-D activity and TBARS levels were not changed by ethanol or diphenyl diselenide exposure. Under in vitro conditions, acetaldehyde was a more potent inhibitor of delta-ALA-D from human erythrocytes when compared to ethanol, demonstrating a dose-dependent effect. This study indicates that (1) hepatic delta-ALA-D is a molecular target for the damaging effect of ethanol under in vivo conditions; (2) diphenyl diselenide and ethanol seem to inhibit delta-ALA-D by different mechanisms; (3) acetaldehyde, a metabolite of ethanol, is probably the main molecule responsible for the inhibitory effects of the parent compound on delta-ALA-D.

[Hepatic porphyrias and alcohol]

Alcohol has an porphyrinogenic action and can cause a disturbance of porphyrin metabolism in healthy people as well as lead to a biochemical and clinical manifestation of acute and chronic hepatic porphyrias, especially acute intermittent porphyria and porphyria cutanea tarda. After excessive consumption of alcohol a temporary, clinically asymptomatic secondary hepatic coproporphyrinuria in man can be observed, which can become persistent in cases of alcohol-induced liver damage. Nowadays alcohol-liver-porphyrinuria syndrome is the first to be mentioned in secondary hepatic disturbances of porphyrin metabolism. In people with a genetic lack of uroporphyrinogen-decarboxylase alcohol is able to transform an asymptomatic coproporphyrinuria into a chronic hepatic porphyria or porphyria cutanea tarda. From experimental and clinical studies the conclusion can be drawn that alcohol inhibits the enzymes delta-aminolevulinic-acid-dehydratase (synonym: porphobilinogen-synthase), uroporphyrinogen-decarboxylase and coproporphyrinogen-oxidase and induces delta-aminolevulinic-acid-synthase in the liver. Abstinence of alcohol is a therapeutically and prophylactically important measurement in all types of hepatic porphyrias. For clinical experience follows that in cases with chronic consumption of alcohol, fatty liver, alcohol induced hepatitis and liver cirrhosis porphyrin studies in urine should be made to notice a hepatic porphyria in the latent phase very early. When dealing with abdominal and cutaneous symptoms in clinical context with consumption of alcohol one has to exclude hepatic porphyria differential diagnostically.

Environmental lead exposure and activity of delta-aminolevulinic acid dehydratase (ALA-D) in maternal and cord blood

The hypothesis that environmental lead exposure measured from blood (Pb-B) inhibits delta-aminolevulinic acid dehydratase activity (ALA-D) from whole blood was tested in 241 urban mothers and their newborns. Geometric means and (5th and 95th Percentiles) for maternal and cord Pb-B were 6.4 microg dl(-1) (3.4-11.9) and 4.6 microg dl(-1) (2.8-9.2). Spearman correlations between mother and cord Pb-B and ALA-D were all negative but statistically significant only for cord Pb-B and mother ALA-D. A potential lead threshold, was identified between 3.2 and 4.8 microg dl(-1), above which ALA-D may be inhibited by lead, and below which ALA-D may be insensitive or even activated. In conclusion, low environmental exposure to lead is responsible for a demonstrable biochemical effect. This potential ALA-D inhibition may lead to neurotoxic effects, especially in newborns who have high level of neurogenesis.

Nonsynergic effect of ethanol and lead on heme metabolism in rats

The heme biosynthetic pathway is a metabolic target of alcohol and lead poisoning. To analyze the interdependence of both xenobiotics on porphyrin metabolism, male Wistar rats (n=47) were divided into four groups and were fed Lieber-DeCarli semiliquid control or alcoholic diets containing or not containing lead acetate (160 mg/liter) for 8 weeks. After this period, hematocrit values and porphyrin concentration in liver and urine were similar in all groups, indicating that the goal of inducing only mild chronic intoxication was achieved. Compared with the control group, rats poisoned only with lead exhibited high levels of this metal in blood and liver, increased erythrocytic protoporphyrin, and hypoactivity of aminolevulinate dehydrase (ALA-D) in both blood and liver. Rats intoxicated only with alcohol exhibited mild hypoactivity of both hepatic and erythrocytic ALA-D, although such decreased enzymatic values did not achieve statistical significance. Rats receiving ethanol and lead simultaneously demonstrated abnormalities in heme biosynthesis similar to those in rats exposed to lead, although zinc hepatic levels decreased significantly only in animals exposed to both xenobiotics. Hepatic GSH and urinary ALA and porphyrin levels were maintained in a similar range in all groups.

5-Aminolevulinic acid dehydratase deficiency porphyria: a twenty-year clinical and biochemical follow-up

5-Aminolevulinic acid dehydratase (ALAD) activity in two patients with compound heterozygous 5-aminolevulinic acid dehydratase deficiency porphyria was studied over the last 20 years. The patients’ enzyme activity was <10% from 1977 to 1997. An acute crisis in each patient was successfully treated by infusion of glucose and heme arginate. After this therapy both urinary 5-aminolevulinic acid (ALA) and total porphyrins were diminished to 65% in patient B. In patient H, ALA was decreased to 80%, and total porphyrins were reduced to 15% after treatment with heme arginate and glucose. The patients remained free of symptoms after this therapy. Family studies of patient B showed cross-reactive immunological material (CRIM), in which the maternal mutation is CRIM(+), whereas the paternal mutation is CRIM(−). Incubation of erythrocyte lysates with ALA decreased porphyrin formation, whereas incubation with porphobilinogen produced porphyrin concentrations within reference values in both patients, confirming that ALAD activity is rate-limiting in these cells.

Hepatic uroporphyrinogen decarboxylase activity in porphyria cutanea tarda patients: the influence of virus C infection

Porphyria cutanea tarda (PCT) is caused by a decreased activity of the hepatic enzyme uroporphyrinogen decarboxylase (URO-D). This deficiency causes overproduction, hepatic deposition, and increased excretion of uroporphyrin. Iron overload and hepatic viral infections are considered aggravating factors of the disease. Two forms of PCT have been described, as follows: a familial one with an inherited decrease of URO-D activity in all tissues and a sporadic one with a decreased activity of URO-D restricted to the liver. To assess whether the hepatic URO-D returns to normal during a remission of the disease, this activity was measured in liver biopsy samples in 24 sporadic PCT patients. The hepatic and urinary porphyrin concentrations were also measured. Viral status and histopathological findings were analyzed to assess their involvement in PCT. Six patients treated by phlebotomy to reduce hepatic iron and who were considered to be in clinical remission, characterized by a disappearance of cutaneous lesions, showed higher hepatic URO-D activities and lower hepatic porphyrin concentrations than did patients with overt PCT. The medians of these variables, however, did not achieve normal values. The hepatic URO-D activity showed a significant inverse relationship with both hepatic porphyrins and urinary uroporphyrin excretion. Hepatic URO-D activity was not reduced by hepatitis C virus (HCV) infection and liver damage. We conclude that the achievement of remission in PCT largely depends on the transient normalization of hepatic URO-D activity. A small increase in hepatic coproporphyrin in nonporphyric patients could reflect hepatic injury/iron/alcohol-induced oxidative stress oxidizing the accumulated heme precursors rather than a direct effect on hepatic URO-D enzyme.

Effect of beryllium chloride on porphyrin metabolism in pregnant mice administered by subcutaneous injection

The effect of beryllium (Be) compounds on porphyrins was investigated in pregnant mice. The blood protoporphyrin (Proto) and zinc protoporphyrin (Zn Proto) concentrations were increased in pregnancy. Regardless of pregnancy or nonpregnancy, the Proto concentration was decreased after Be injection. Delta-aminolevulinic acid dehydratase (ALA-D) and porphobilinogen deaminase (PBG-D) activities in blood were significantly elevated in the pregnant untreated (Con-pregnant) group, compared to the nonpregnant mice untreated (Con-nonpregnant) and nonpregnant mice treated with Be (Be-nonpregnant) groups. The blood ALA-D activity of the pregnant mice treated with Be (Be-pregnant group) tended to decrease, compared to Con-pregnant group. The blood PBG-D activity in the Be-pregnant group was significantly lower compared with that of the Con-pregnant group. The ALA-D and PBG-D activities in the spleen were also significantly elevated in the Con-pregnant group, compared to nonpregnant groups. However, it was noted that these values in the Be-pregnant group were almost the same as that of the Con-nonpregnant group and were significantly lower than that in the Con-pregnant group. The elevation of ALA-D and PBG-D activities in the blood and spleen, which play a role in the hematopoietic function of mice, was observed in the Con-pregnant mice compared to the nonpregnant mice. However, the phenomenon was not observed in the Be-pregnant mice, it suggesting that Be suppressed the pregnancy-induced increase in hematopoietic function.

How useful is aminolevulinic acid dehydratase as a marker of recent alcohol intake?

Erythroycte delta aminolevulinic acid dehydratase (ALAD) has been suggested as a marker for detecting recent alcohol intake. Unlike other markers, ALAD activity decreases after alcohol intake. Review of the literature suggests that the main interest in this marker is because it increases rapidly after withdrawal. The present study investigated the changes in erythrocyte ALAD and serum gamma-glutamyltransferase activities after alcohol withdrawal in 120 alcoholics. Our data showed that ALAD is less sensitive than GGT as an indicator of recent alcohol intake (56% and 84% abnormal, respectively). The increase in ALAD activity was greater between day 12 and 18 after withdrawal (11%) than between day 1 and 12 after withdrawal (5%). There were as many patients returning to normal values 12 and 18 days after withdrawal, for GGT as for ALAD. Thus, our results contradict the claim that ALAD rises rapidly after withdrawal. ALAD shows no advantage over GGT as a marker of recent alcohol intake.

Coexistence of deficiencies of uroporphyrinogen III synthase and decarboxylase in a patient with congenital erythropoietic porphyria and in his family

A hitherto undescribed dual deficiency of uroporphyrinogen III synthase and uroporphyrinogen decarboxylase was observed in the erythrocytes in a 14 year-old patient who had presented with congenital erythropoietic porphyria since early childhood. Whereas congenital erythropoietic porphyria was metabolically and clinically overt, a hereditary deficiency of uroporphyrinogen decarboxylase was confirmed by family study. The uroporphyrinogen III synthase activity of the propositus was decreased to 26% of the control while his asymptomatic family members had activities between 53-65% of the control. Additionally, the uroporphyrinogen decarboxylase activity was 55-66% of the control in the patient and his family. Family investigations have shown that the two disorders do not consistently segregate together. Although urinary porphyrin excretions of relatives were in the physiological range, the proportion of coproporphyrin isomer I showed a relative increase, which can serve as a biochemical indicator for heterozygous uroporphyrinogen III synthase gene carriers.

Alcohol-induced changes in urinary aminolevulinic acid and porphyrins: unrelated to liver disease

Urinary porphyrins and their metabolites aminolevulinic acid (ALA) and porphobilinogen (PBG) were determined in 15 normal volunteers and in 45 alcoholics, subdivided into three groups according to their liver function tests and histology: alcoholics exhibiting no evidence of hepatocellular damage; alcoholics with fatty liver and impaired function of liver enzymes; and alcoholics with proven liver cirrhosis. The dominant trend observed in those alcoholics devoid of any evidence of liver disease was increased ALA, PBG, and uroporphyrin. Coproporphyrinuria was shared by the patients exhibiting liver damage. The data shown enabled us to differentiate between the direct, primary effect of alcohol on the heme biosynthetic pathway and the secondary indirect effect, which is probably related to liver damage that follows alcohol consumption. Evaluation of the results led to the suggestion that urinary ALA could possibly serve as a marker of alcoholism. The specificity and sensitivity of the test were found to be 87% and 80%, respectively.

Influence of protein calorie malnutrition and fasting on the activities of delta-aminolevulinic acid dehydratase and porphobilinogen deaminase in rats

Rats were fed a restricted standard diet (6-8 g daily) for 4 weeks. The erythrocyte activity of delta-aminolevulinic acid dehydratase showed a very expressed decrease (7.9 times) and its hepatic activity diminished more than twice. Porphobilinogen deaminase activity was reduced by 40% and 17% respectively. After a 3-day total food deprivation delta-aminolevulinic acid dehydratase activity remained unchanged in red blood cells, but an increase by 52% was found in the liver. The erythrocyte activity of porphobilinogen deaminase was reduced by 42% and its hepatic activity--by 16%.

Variable phenotypic expression of genotypic abnormalities in the porphyrias

The inherited porphyrias are the consequence of inherited deficiencies of enzymes in the heme synthesis pathway; they exhibit classical Mendelian inheritance patterns. The acute porphyrias (acute intermittent, porphyria variegata, hereditary coproporphyria) result from 50% (approx.) deficiencies of specific enzymes, which demonstrate autosomal dominant inheritance. However, only approx. 10% of subjects who inherit a porphyrin enzyme deficiency develop the corresponding acute porphyria and in most instances there is no obvious reason why one patient with an enzyme deficiency is symptomatic whereas another is not. Control of heme synthesis is achieved by the repressor effect of heme on the enzyme ALA synthase. Acute attacks of porphyria can be precipitated in susceptible persons by drugs, ethanol, starvation, hormones, stress and infection. The mechanism is usually by induction of ALA synthase activity. The molecular biology of porphyria variegata and hereditary coproporphyria is large unexplored. Acute intermittent porphyria is due to a partial deficiency of the enzyme porphobilinogen deaminase in the liver. The location of the gene for this enzyme has been identified on the long arm of chromosome 11. Acute intermittent porphyria is a genetically heterogenous disease with the abnormality frequently being a point mutation affecting synthesis of the enzyme.