Serum Unconjugated Bilirubin Research Articles

The inverse starving test is not a suitable provocation test for Gilbert's syndrome

BackgroundIntroductionThe aim of this study was to evaluate a simple diagnostic test for Gilbert's syndrome (GS), which avoids hospitalization and exposure to toxic test substrates. GS is the most frequent cause of isolated unconjugated hyperbilirubinemia. The nicotinic acid test and the starving test are established approaches to diagnose GS. However, these tests cause considerable side effects or require hospital admission. In single GS patients, we observed rapid serum bilirubin normalization after a standard European lunch (the "inverse starving test").FindingsAt two consecutive days, 18 profoundly characterized GS patients (7 females, 11 males, median age 34.5 years, range 21–58 years) were investigated with the nicotinic acid test and the inverse starving test. Unconjugated serum bilirubin (UCB) levels were measured before and hourly up to four hours after lunch (median 645 kcal), and after the ingestion of 170 milligrams nicotinic acid, respectively. Patients who consulted their physicians with jaundice were significantly more likely to undergo invasive diagnostic procedures than patients with an incidental finding of elevated UCB, despite UCB levels were indifferent in both groups. Two hours after nicotinic acid ingestion, relative UCB exceeded 1.7 fold the fasting levels (median, range 0.9–2.4 fold, sensitivity 83%). In the inverse starving test, UCB remained almost unchanged three hours after lunch (median 1.0; range: 0.8–1.2 fold). Molecular analysis established the genotype of the TATAA box of the UGT1A1 gene; all patients carried an UGT1A1 promotor polymorphism.ConclusionThe inverse starving test is not an appropriate provocation test for patients with suspected GS. The 100% prevalence of the UGT1A1 polymorphism in our cohort underlines that the diagnosis of GS may be substantiated with this simple molecular test in patients with an uncertain diagnosis of GS.

Unbound Bilirubin: A Better Predictor of Kernicterus?

The peroxidase method described in this paper measures non–protein-bound bilirubin by oxidation of the free fraction. The oxidation rate is slow compared with rapid dissociation of albumin-bound bilirubin. Thus, the unbound bilirubin can be estimated from the initial rate of decline in total bilirubin concentration. In the 1970s, severe neonatal hyperbilirubinemia and kernicterus were major clinical problems. Kernicterus could usually be prevented by administering an exchange transfusion to infants whose serum unconjugated bilirubin concentration reached 341 μmol/L (20 mg/dL), but the diagnostic specificity of 341 μmol/L (20 mg/dL) was quite poor. Premature infants sometimes developed encephalopathy at very low bilirubin concentrations, especially when receiving sulfonamides. While engaged in a fellowship in neonatal medicine, I was stimulated by Gerald Odell’s 1959 paper, in which he used pharmacological arguments to explain how these drugs produced kernicterus by …

OATP1B1 POLYMORPHISM IS A MAJOR DETERMINANT OF SERUM BILIRUBIN LEVEL BUT NOT ASSOCIATED WITH RIFAMPICIN‐MEDIATED BILIRUBIN ELEVATION

1. Elevated serum bilirubin levels are caused mainly by liver diseases, haematolysis, genetic defects and drug intake. Unconjugated bilirubin (UCB) is taken up into hepatocytes by human organic anion transporting polypeptide 1B1 (OATP1B1; encoded for by the SLCO1B1 gene). The present study was performed to determine the association between SLCO1B1 gene polymorphisms and serum bilirubin levels in vivo. Moreover, the effects of administration of low-dose rifampicin on serum bilirubin levels in different SLCO1B1 genotypes was examined. 2. Serum bilirubin levels were examined in 42 healthy volunteers who had been analysed for SLCO1B1 genotype (seven, 13, 14 and eight with SLCO1B1 genotypes *1a/*1a, *1b/*1b, *1b/*15 and *15/*15, respectively). Among them, 24 subjects (seven, seven, eight and two with SLCO1B1 genotypes *1a/*1a, *1b/*1b, *1b/*15 and *15/*15, respectively) were selected to participate in an open-label, two-phase clinical trial. Each was given 450 mg rifampicin orally once daily at 2000 hours for 5 consecutive days. Serum bilirubin concentrations at 0800 hours on the 1st and 6th days were compared between the different SLCO1B1 genotypes. 3. In the 42 volunteers, the mean (+/-SD) serum UCB in both SLCO1B1*1b/*15 and *15/*15 groups was significantly higher than that in the SLCO1B1*1b/*1b group (11.07 +/- 2.31, 13.01 +/- 3.87 and 8.21 +/- 2.68 micromol/L, respectively; P = 0.009 and P < 0.001). Total bilirum (T.BIL) in both the SLCO1B1*1b/*15 and *15/*15 groups was significantly higher than that in the SLCO1B1*1b/*1b group (16.69 +/- 4.09, 20.71 +/- 5.12 and 13.06 +/- 5.12 micromol/L, respectively; P = 0.029 and P < 0.001). The direct bilirubin (D.BIL) in the SLCO1B1*15/*15 group was significantly higher than that in the SLCO1B1*1b/*1b group (7.69 +/- 1.81 vs 4.85 +/- 1.81 micromol/L, respectively; P = 0.001). Rifampicin significantly increased UCB, T.BIL and D.BIL concentrations in 24 healthy volunteers (17.68 +/- 5.96 vs 13.95 +/- 4.44 micromol/L (P = 0.040), 5.72 +/- 2.01 vs 4.35 +/- 1.50 micromol/L (P = 0.028) and 12.00 +/- 4.26 vs 9.61 +/- 3.15 micromol/L (P = 0.035), respectively). However, the extent of the increase in serum bilirubin caused by 450 mg rifampicin for 5 days was not affected by SLCO1B1 genotype. 4. Genetic polymorphism in SLCO1B1 is a major determinant of interindividual variability in the serum bilirubin level. SLCO1B1*15 carriers had higher baseline serum UCB, T.BIL and D.BIL levels compared with subjects with the SLCO1B1*1a/*1a and SLCO1B1*1b/*1b genotypes. SLCO1B1*15/*15 homozygotes are more susceptible to hyperbilirubinaemia. Serum bilirubin levels could be increased by low-dose rifampicin administration, but the extent of the increase was not associated with SLCO1B1 genotype.

Preventing kernicterus: a wake-up call

Preventing kernicterus: a wake-up call

Atazanavir/Ritonavir: A Valuable Once-Daily HIV Protease Inhibitor with Little Impact on Lipid Profile

Atazanavir is the first once-daily azapeptide HIV protease inhibitor that may offer simpler and safer protease inhibitor-based highly active antiretroviral therapy, as it has been associated with less hyperlipemia and diarrhea compared with the other drugs of the same class. The typical side effect of atazanavir is an asymptomatic increase in serum unconjugated bilirubin. Ritonavir-boosted atazanavir has proved to be effective in treatment-naive HIV-infected individuals, and there is no evidence that it leads to the selection of mutations conferring cross-resistance to other protease inhibitors. Its efficacy in patients harboring drug-resistant variants is not statistically different from that of the reference protease inhibitor, lopinavir/ritonavir. It has been approved by the US FDA for use in drug-experienced HIV-infected patients, although atazanavir/ritonavir-based regimens have now been included among those recommended by the International AIDS Society – USA Panel and the Department of Health and Human Services Panel as initial treatment. The aim of this article is to describe the pharmacological characteristics of atazanavir/ritonavir, and the results of the main clinical trials investigating the safety and efficacy of this antiretroviral combination.

Gamma Glutamyl Transferase Activity in Gilbert's Disease

Gilbert's disease (GD), an isolated non-haemolytic unconjugated hyperbilirubinaemia occuring in 8% of the population, is diagnosed by estimating serum unconjugated bilirubin level. GD is under diagnosed leading to inappropriate expensive and invasive Investigation. A patient with congenital hyperbilirubinaemia was noted to have low gamma glutamyl transferase (gGT) activity. A prospective study has been undertaken to determine if low gGT is a marker for unconjugated hyperbilirubinaemia. The gGT and bilirubin results of random blood samples sent for liver function tests to the Clinical Biochemistry Department were abstracted and entered into a database.

Prospective surveillance study of severe hyperbilirubinaemia in the newborn in the UK and Ireland

Objectives:To determine the incidence of severe hyperbilirubinaemia in the newborn, and to identify associated clinical and demographic variables, and short-term outcomes.Design:Prospective, population-based study.Setting:UK and Republic of Ireland, between 1 May...

Relationship between hyperbilirubinaemia and UDP-glucuronosyltransferase 1A1 (UGT1A1) polymorphism in adult HIV-infected Thai patients treated with indinavir

To investigate the association between the UGT1A1*6 (G71R) and UGT1A1*28 (promoter (TA)7-repeat) genotypes and hyperbilirubinaemia in Thai patients treated with indinavir, and characterize the inhibition of human UGTs by indinavir in vitro. Ninety-six Thai HIV patients receiving indinavir, 800 mg t.i.d. or 800 mg b.i.d. "boosted" with ritonavir (100 mg b.i.d.), had serum bilirubin levels measured to 24 weeks post-treatment and were genotyped for UGT1A1*6 and UGT1A1*28. The inhibition selectivity and kinetics of indinavir were determined using a panel of recombinant human UGTs. UGT1A1*6 and UGT1A1*28 frequencies in the Thai patients were 10.4% and 15.6%, respectively. Total, conjugated (direct) and unconjugated (indirect) serum bilirubin concentrations increased significantly at 24 weeks of indinavir treatment for all four genotypes, with a trend towards higher levels depending on the number of UGT1A1 mutant alleles; *6/*28 > *6 > *28 > reference. The hazards ratio (HR) for serious hyperbilirubinaemia (total bilirubin > 2.5 mg/dl) at week 24 was statistically significant only in those patients carrying the UGT1A1*6 (HR 2.87) and UGT1A1*6/*28 (HR 11.42) genotypes. The Ki values for indinavir inhibition of UGT1A1 and UGT1A1*6 were 4.1 and 10.7 mumol/l respectively. However, indinavir was also shown to inhibit other human UGTs, notably UGT1A3 and UGT1A7. In contrast to Caucasian HIV-infected patients treated with indinavir, the promoter polymorphism (UGT1A1*28) is of less significance than the coding region (UGT1A1*6) mutation as a risk factor for hyperbilirubinaemia. The Ki values determined for indinavir inhibition of UGT1A1 are consistent with an interaction in vivo, with an additive effect in patients with already impaired bilirubin glucuronidation activity.

Hyperbilirubinemia Is Not a Major Contributing Factor to Altered Bone Mineral Density in Patients With Chronic Liver Disease

Reduced bone density is commonly encountered in patients with chronic liver disease. Prior studies have shown that unconjugated bilirubin inhibits osteoblast activity and function in vitro and in animal models of bone mineralization. To determine whether hyperbilirubinemia promotes the development of hepatic osteodystrophy, bone mineral density (BMD) was measured by dual energy X-ray absorptiometry in a cohort of 86 consecutive patients with chronic liver disease referred for liver transplant evaluation. The mean age of the study population was 52 years (range, 22-73), in which 52% were female and 90% were white. Average bone density values were significantly lower than expected for age, race, and sex, with Z-scores for the femoral neck and spine of -0.50 (95% confidence interval [CI] -0.63 to -0.37; p=0.0003) and -0.69 (95% CI -0.85 to -0.52; p=0.0001), respectively. Sixty-one subjects (71%) exhibited reduced BMD (T-score of femoral neck or spine<or=-1 standard deviation [SD] below the young-adult mean), and 18 subjects (21%) met criteria for osteoporosis (T-score<-2.5 SD). Stepwise logistic regression analyses identified significant associations between BMD and serum creatinine, alkaline phosphatase, age, and gender. On the other hand, neither unconjugated, nor conjugated, nor total serum bilirubin levels were found to predict diminished BMD. The lack of association between serum unconjugated bilirubin levels and bone mineralization was validated in hyperbilirubinemic Gunn rats, in which BMD and serum osteocalcin levels were no different than in wild-type rodents. In conclusion, the finding that serum bilirubin levels do not correlate with reduced BMD in patients with end-stage liver disease, and that chronic unconjugated hyperbilirubinemia does not lead to alterations in bone mineralization in Gunn rats, suggests that bilirubin is not a major contributing factor to hepatic osteodystrophy.

Association of maximum voluntary dietary intake of freeze-dried garlic with Heinz body anemia in horses

To characterize hematologic and clinical consequences of chronic dietary consumption of freeze-dried garlic at maximum voluntary intake in horses. 4 healthy sex- and age-matched horses. An initial garlic dose (0.05 g/kg, twice daily) was fed to 2 horses in a molasses carrier as part of their normal ration and was gradually increased to maximum voluntary intake (0.25 g/kg, twice daily) over 41 days. Dietary supplementation then continued for a total of 71 days. Two control horses were fed molasses with no garlic with their ration. Blood samples were collected weekly and analyzed for hematologic and biochemical changes, including the presence of Heinz bodies. Recovery of affected blood values was followed for 5 weeks after termination of dietary supplementation with garlic. At a daily dose of > 0.2 g/kg, horses fed garlic developed hematologic and biochemical indications of Heinz body anemia, as characterized by increases in Heinz body score (HBS), mean corpuscular volume (MCV), mean corpuscular hemoglobin, platelet count, and serum unconjugated and total bilirubin concentrations and decreases in RBC count, blood hemoglobin concentration, mean corpuscular hemoglobin concentration, and serum haptoglobin concentration. Recovery from anemia was largely complete within 5 weeks after termination of dietary supplementation with garlic. Heinz body score and MCV remained high at the end of the 5-week recovery period. Horses will voluntarily consume sufficient quantities of garlic to cause Heinz body anemia. The potential for garlic toxicosis exists when horses are chronically fed garlic. Further study is required to determine the safe dietary dose of garlic in horses.

Types of anaemic crises in paediatric patients with sickle cell anaemia seen in Enugu, Nigeria

Background: Anaemic crises in paediatric patients with sickle cell anaemia are major causes of morbidity and mortality. Some children admitted to hospitals’ emergency rooms or paediatric wards of the hospitals...

Liver Function Status in some Nigerian Children with Protein Energy Malnutrition

Objective: To ascertain functional status of the liver in Nigeria Children with Protein energy malnutrition Materials and Methods: Liver function tests were performed on a total of 88 children with protein energy malnutrition (PEM). These were compared with 22 apparently well-nourished children who served as controls. High performance enzymatic colorimetric commercial kits (RANDOX Laboratories Ltd. UK) were used for the assay. Anthropometry, haematocrit, liver enzymes and bilirubin levels of the patients and controls were measured. Results: Serum total proteins and albumin fraction were significantly reduced (p < 0.05) in all the types of PEM compared with the controls. There was marked hypoproteinaemia and hypoalbuminaemia in kwashiorkor. Haemoglobin (Hb), packed cell volume (PCV) and alkaline phosphatase (ALP) levels were reduced (p < 0.05) while aspartate transaminase (AST), and alanine transaminase (ALT) were significantly elevated (p < 0.05). Although serum unconjugated bilirubin was reduced in the PEM cases, its value did not differ significantly in marasmic patients. Conclusion: These findings suggest that abnormalities in serum levels of these parameters occur in any form of PEM and are related to the severity of the condition. Key Words: Liver Function status in PEM; Nigeria Orient Journal of Medicine Vol.15(1&2) 2003: 58-63

Modulation of organic anion transporting polypeptide 1 and multidrug resistance protein 3 expression in the liver and kidney of Gunn rats.

Background: Gunn rat is an animal model of Crigler-Najjar syndrome (CNS) type I that develops jaundice due to defect of bilirubin conjugation. Bilirubin UDP-glucuronosyltransferase (UGT1A1), which plays a critical role in bilirubin glucuronidation, has been reported to be deficient in CNS type 1. On the other hand, little is known about the expression of organic anion transporters in Gunn rats. In the present study, we evaluated expressions of organic anion transporting polypeptide (oatp) 1 and 2, multidrug resistance-associated protein (mrp) 2 and mrp3 in the liver and kidney of Gunn rats. Methods: Serum samples, liver and kidney tissues were obtained from Gunn rats and normal SD rats ( [Formula: see text], in each group). Semi-quantitative mRNA expression of oatp1, oatp2, mrp2, and mrp3 mRNA was evaluated by constructed reverse transcription-polymerase chain reaction (RT-PCR). Protein expressions were determined by Western blotting and by immunohistochemistry. Results: Marked elevation of serum unconjugated bilirubin concentration ( [Formula: see text] micromol/l) was observed in Gunn rats. Hepatic expression of oatp1 and oatp2 mRNA was 44% ( [Formula: see text] ) and 35% ( [Formula: see text] ) lower in Gunn rats than in SD rats, respectively. Hepatic oatp1 protein expression was 37% ( [Formula: see text] ) lower in Gunn rats than in SD rats. In contrast to oatp1, hepatic expression of mrp3 mRNA and protein was 76% ( [Formula: see text] ) and 557% ( [Formula: see text] ) higher in Gunn rats than in SD rats, respectively. Hepatic expression of oatp2 and mrp2 protein was not significantly different between Gunn rats and SD rats. Like the Western blot analysis, immunohistochemical staining disclosed decrease of oatp1 and increase of mrp3 protein expressions in the liver of Gunn rats. Decrease of oatp1 and increase of mrp3 expressions were also observed in the kidney of Gunn rats. Conclusion: Decreased expression of oatp1 and increased expression of mrp3 were observed in the liver and kidney of Gunn rats. Deficient UGT1A1 activity-associated retention of unconjugated bilirubin in the hepatocytes may modulate the expressions of these transporters in Gunn rats.

Upregulation in the expression of multidrug resistance protein Mrp1 mRNA and protein by increased bilirubin production in rat

Earlier studies suggest that Mrp1 may mediate ATP-dependent cellular extrusion of unconjugated bilirubin (UCB). We studied the serial responses of expression of Mrp1 mRNA and protein in rats with increased bilirubin production due to hemolysis induced by phenylhydrazine (PHZ) treatment. Mrp1 mRNA was analyzed by quantitative PCR and protein by Western blot. Hepatic expression of Mrp1 mRNA and protein peaked at day 3 of PHZ treatment. Splenic expression of Mrp1 mRNA peaked within 24 h and returned to baseline at day 5 whereas Mrp1 protein expression peaked at day 3. Pretreatment with heme-oxygenase inhibitor, tin mesoporphyrin, blunted the increase in serum UCB and erased the overexpression of Mrp1 both in liver and spleen. Thus, the upregulation of Mrp1 in hemolysis is mediated by UCB and/or other products of heme oxygenase, further supporting a role of Mrp1 in UCB transport and protection from its cellular toxicity.

Analysis of the A(TA) nTAA configuration in the promoter region of the UGT1 A1 gene in Greek patients with thalassemia intermedia and sickle cell disease

Gilbert’s syndrome is characterized by mild unconjugated hyperbilirubinemia. The molecular basis of this syndrome usually concerns an additional dinucleotide insertion (TA) in the A(TA) n TAA configuration residing in the promoter region of the UGT1 A1 gene. This configuration may vary in length; the “ n” represents the different number of TA repeats. The homozygosity A(TA) 7TAA/A(TA) 7TAA is involved in Gilbert’s syndrome. In many cases of patients with thalassemia intermedia and sickle cell disease considerable variation in bilirubin levels is observed. In this study we investigated the contribution of the A(TA) 7TAA/A(TA) 7TAA genotype in the variable unconjugated serum bilirubin levels in 31 Greek patients with thalassemia intermedia and 27 Greek compound heterozygotes for β thalassemia and sickle cell anemia. Analysis of the A(TA) n TAA configuration in the promoter region of the latter patients showed that those who were carrying the homozygosity A(TA) 7TAA/A(TA) 7TAA had higher levels of unconjugated bilirubin. These findings suggest that the coexistence of Gilbert’s syndrome in patients with thalassemia intermedia and sickle cell disease may be the cause of the elevated values of unconjugated bilirubin, reducing the possibility of excessive hemolysis in these patients.

Mild hemolysis in a girl with G6PD Sumaré (class I variant) associated with G6PD A−

In the present study we describe the clinical and laboratory features of a female child, a compound heterozygote for glucose-6-phosphate dehydrogenase (G6PD) Sumaré (1292T→G) and African variants (202G→A). G6PD Sumaré is a variant causing chronic nonspherocytic hemolytic anemia. The child had neonatal jaundice 2 days after birth and needed phototherapy for 8 days. Since then, she has not had episodes of dark urine or new episodes of jaundice. She has not had hemolytic crises in spite of five respiratory infections and antibiotics administration. Laboratory data showed a reticulocytosis (5.6%) without anemia and serum unconjugated bilirubin at the upper limit of the normalcy. No hemoglobin and hemosiderin in the urine were detected. G6PD activity at 37°C was 1.15 UI/g Hb and G6PD cellulose acetate electrophoresis at pH 9.0 revealed two bands, in equal amounts, with normal and faster migration, respectively. She was homozygous for the normal (TA)6(TA)6 repeat in the UGT1A1 promoter. We conclude that the association of G6PD Sumaré and G6PD A− gave rise to a very mild chronic hemolysis, and the red cell population containing G6PD A− is probably enough to protect against severe chronic hemolysis.

Severe autoimmune cytopenias in treatment-naive hepatitis C virus infection: clinical description of 35 cases.

To determine the clinical characteristics and outcome of patients with chronic hepatitis C virus (HCV) infection presenting severe autoimmune cytopenia unrelated to interferon alpha therapy, we analyzed characteristics and outcomes of 35 patients with HCV (16 from our departments and 19 from the literature). We considered active autoimmune hemolytic anemia (AHA) as a decrease of at least 2 g/dL in hemoglobin levels, an increase of at least 0.6 mg/dL in the serum unconjugated bilirubin level, a reticulocyte count >5%, and a positive direct Coombs test. Severe neutropenia was defined as a neutrophil count <0.5 x 10(9)/L, and severe thrombocytopenia as a platelet count <30 x 10(9)/L. We identified the following cytopenias: AHA (17 cases), severe thrombocytopenia (16 cases), aplastic anemia (2 cases), severe neutropenia (1 case), refractory sideroblastic anemia (1 case), and pure red cell aplasia (1 case). Three patients simultaneously presented 2 types of severe cytopenias. Twenty-seven patients (77%) were female and 8 (23%) male, with a mean age at diagnosis of cytopenia of 51.7 years (range, 18-84 yr). Immunologic markers were detected in 19 (68%) of 28 patients, the most frequent being hypocomplementemia in 16 (57%), cryoglobulins in 15 (54%), antinuclear antibodies in 12 (43%), and rheumatoid factor in 5 (18%). Other associated processes were autoimmune diseases in 14 (50%) of 28 and human immunodeficiency virus (HIV) coinfection in 3 (9%) of 32. We found clinical and immunologic differences between HCV patients with AHA and those with severe thrombocytopenia. Patients with HCV-related AHA showed a higher prevalence of associated autoimmune diseases (71%), cryoglobulins (67%), and cirrhosis (59%). All had a good response to corticosteroids, but a poor prognosis (47% mortality). In contrast, patients with HCV-related severe thrombocytopenia had a lower prevalence of associated autoimmune diseases (11%), a poorer response to corticosteroids (55%), and lower mortality (6%), with HIV/HBV coinfections in some patients. The 35 cases presented demonstrate that different types of immune-mediated cytopenias may be severe and clinically significant in patients with HCV infection. Hemolytic anemia and severe thrombocytopenia were the most frequent cytopenias observed. Most patients responded well to corticosteroids, although a higher rate of mortality was observed in those with liver cirrhosis.

Breastfeeding and jaundice.

In the breastfed infant, prolongation of unconjugated hyperbilirubinemia into the third and later weeks of life in the healthy newborn is a normal and regularly occurring extension of physiologic jaundice. This is known as breastmilk jaundice. A factor in human milk increases the enterohepatic circulation of bilirubin. Insufficient caloric intake resulting from maternal and/or infant breastfeeding difficulties may also increase serum unconjugated bilirubin concentrations. This is the infantile equivalent of adult starvation jaundice. It is known as breastfeeding jaundice or "breast-nonfeeding jaundice." This increase in severity of physiologic jaundice of the newborn also results from increased enterohepatic circulation of bilirubin, but not because of a factor in human milk. In extreme cases, it may place the infant at risk for development of bilirubin encephalopathy. Optimal breastfeeding practices, which result in minimal initial weight loss and early onset of weight gain, are associated with both reduced breastfeeding jaundice and minimization of the intensity of breastmilk jaundice.

Mechanism of indinavir-induced hyperbilirubinemia.

Indinavir is a viral protease inhibitor used for the treatment of HIV infection. Unconjugated hyperbilirubinemia develops in up to 25% of patients receiving indinavir, prompting drug discontinuation and further clinical evaluation in some instances. We postulated that this side-effect is due to indinavir-mediated impairment of bilirubin UDP-glucuronosyltransferase (UGT) activity and would be most pronounced in individuals with reduced hepatic enzyme levels, as occurs in approximately 10% of the population manifesting Gilbert's syndrome. This hypothesis was tested in vitro, in the Gunn rat model of UGT deficiency, and in HIV-infected patients with and without the Gilbert's polymorphism. Indinavir was found to competitively inhibit UGT enzymatic activity (K(I) = 183 microM) while concomitantly inducing hepatic bilirubin UGT mRNA and protein expression. Although oral indinavir increased plasma bilirubin levels in wild-type and heterozygous Gunn rats, the mean rise was significantly greater in the latter group of animals. Similarly, serum bilirubin increased by a mean of 0.34 mg/dl in indinavir-treated HIV patients lacking the Gilbert's polymorphism versus 1.45 mg/dl in those who were either heterozygous or homozygous for the mutant allele. Whereas saquinavir also competitively inhibits UGT activity, this drug has not been associated with hyperbilirubinemia, most likely because of the higher K(I) (360 microM) and substantially lower therapeutic levels as compared with indinavir. Taken together, these findings indicate that elevations in serum-unconjugated bilirubin associated with indinavir treatment result from direct inhibition of bilirubin-conjugating activity.

Impairment of erythrocyte viscoelasticity is correlated with levels of glycosylated haemoglobin in diabetic patients.

Erythrocytes from diabetic patients exhibit impaired viscoelastic properties when estimated by various methods. We determined erythrocyte filterability through 5-microm pores, in 51 patients with non-insulin-dependent diabetes mellitus, 18 healthy controls, 15 patients with homozygous beta-thalassemia and 15 with beta-thalassemia traits. The filtration measurements were made with a Hemorheometer, which uses the "initial flow rate" principle. To determine the Index of Rigidity (IR) of the red blood cells, we measured the passage time of white blood cell-free erythrocyte suspensions, 8% per volume, through the filter. Diabetic patients had significantly increased IR in comparison to healthy controls and to patients with beta-thalassemia trait, but not at the level found in patients with homozygous beta-thalassemia. In diabetic patients, a strong correlation between IR and the percentage of glycosylated haemoglobin was found (r=0.737, P < 0.0001), and a weaker one with serum unconjugated bilirubin (r=0.363, P=0.0097) and serum total lipids (r=0.321, P=0.0286). Patients with severe retinopathy also had significantly increased IR, in comparison to those with or without mild retinopathy. Anaemic diabetic patients, especially those with the anaemia of chronic disease, also had significantly increased IR in comparison to non-anaemic diabetics. No correlation between IR, MCV, MCH, MCHC, RDW, RBC morphology, serum LDH or the presence of erythrocyte inclusions after incubation with nitrous sodium solution was found. Our findings suggest that glycosylation of skeletal proteins probably contributes significantly to the increased membrane rigidity of diabetic erythrocytes.