Bilirubin and the risk of common non-hepatic diseases

Bilirubin is a potent antioxidant but can be toxic at high concentrations. This article critically reviews the reported relationships of plasma bilirubin levels to the severity and/or incidence of various common non-hepatic diseases. Plasma bilirubin levels are reportedly negatively related to the risk of atherosclerotic diseases, cancers, demyelinating neuropathies and seasonal affective disorder. By contrast, the incidence and severity of schizophrenia are increased by elevated bilirubin levels. The data strongly suggest that the level of plasma bilirubin should be considered as a risk factor for several common non-hepatic diseases. Additional studies are needed to clarify the mechanisms of this influence, which are thought to be related to unconjugated bilirubin counteracting the oxidative stress underlying these disorders.     

Enzymatic removal of bilirubin toxicity by bilirubin oxidase in vitro and excretion of degradation products in vivo

The toxic effects of the degradation products of bilirubin that were formed by reaction with bilirubin oxidase were investigated with the C 1300 mouse neuroblastoma cell line by examining the following parameters: growth inhibition, morphologic characteristics, membrane transport, DNA synthesis, and protein synthesis. The addition of bilirubin to the cells resulted in definite cytotoxic effects on all of these parameters in a dose-dependent fashion; the addition of bilirubin oxidase reversed the toxic effects on the C 1300 cells in vitro. Furthermore, we found that most of these enzymatic degradation products of bilirubin were excreted by the kidney into the urine in a few hours after intravenous injection of the degradation products; in contrast, no intact bilirubin was excreted. Thus, these findings suggest that hyperbilirubinemia in newborn infants (kernicterus) may be prevented by administering polyethylene glycol-conjugated bilirubin oxidase, with a longer plasma half-life which has been reported previously to oxidize bilirubin to its nontoxic components in the bloodstream.     

Seasonal Pattern of Phototherapy: A Study in the Sardinian Population

The relationship between season of birth and human diseases is well known and it has been suggested that such a relationship could be mediated by seasonal and environmental effects on early events of extrauterine life. In this context the physiological increase of bilirubin occurring in all infants during the neonatal period may be of paramount importance. Indeed, recent studies suggest a beneficial action of bilirubin in the early stages of extrauterine life due to its protective action against secondary oxidants. The newborn infant is particularly sensible to oxidative damage, thus seasonal variation of bilirubin level in the first few days of life could influence further development and susceptibility to pathological manifestations. In the present paper we have analysed the seasonal effect on the level of the serum bilirubin during the neonatal period by an analysis of the incidence of phototherapy in a sample of 5540 infants born consecutively in the population of Sassari during the years 1993-96. The proportion of infants undergoing phototherapy for neonatal hyperbilirubinemia is lower in those without glucose-6-phosphate-dehydrogenaser (G-6-PD) deficiency than in those with G-6-PD deficiency and in both categories the proportion is lower in females than in males. A highly significant association between the date of birth and the proportion of infants undergoing phototherapy has been observed in males without G-6-PD deficiency. The maximum incidence of phototherapy has been observed in the period May-August. A Fourier analysis carried out on these infants has shown the presence of two main components (harmonics) contributing to the seasonal cycle and corresponding respectively to a one year and to a two years period.     

Seasonal Pattern of Phototherapy: A Study in the Sardinian Population

The relationship between season of birth and human diseases is well known and it has been suggested that such a relationship could be mediated by seasonal and environmental effects on early events of extrauterine life. In this context the physiological increase of bilirubin occurring in all infants during the neonatal period may be of paramount importance. Indeed, recent studies suggest a beneficial action of bilirubin in the early stages of extrauterine life due to its protective action against secondary oxidants. The newborn infant is particularly sensible to oxidative damage, thus seasonal variation of bilirubin level in the first few days of life could influence further development and susceptibility to pathological manifestations. In the present paper we have analysed the seasonal effect on the level of the serum bilirubin during the neonatal period by an analysis of the incidence of phototherapy in a sample of 5540 infants born consecutively in the population of Sassari during the years 1993-96. The proportion of infants undergoing phototherapy for neonatal hyperbilirubinemia is lower in those without glucose-6-phosphate-dehydrogenaser (G-6-PD) deficiency than in those with G-6-PD deficiency and in both categories the proportion is lower in females than in males. A highly significant association between the date of birth and the proportion of infants undergoing phototherapy has been observed in males without G-6-PD deficiency. The maximum incidence of phototherapy has been observed in the period May-August. A Fourier analysis carried out on these infants has shown the presence of two main components (harmonics) contributing to the seasonal cycle and corresponding respectively to a one year and to a two years period.     

A new tactic for the treatment of jaundice: an injectable polymer-conjugated Bilirubin oxidase

Bilirubin oxidase (BOX) derived from Myrothecium verrucaria was modified with polyethylene glycol (PEG). When the conjugated PEG-BOX was given intravenously to rats, its plasma half-life was 20 times longer than that of native BOX. In our preliminary investigations with experimentally jaundiced rats, the plasma bilirubin level dropped to normal after only one injection, and the low bilirubin level could be maintained for 12-48 hr; native BOX had a transitory suppressive effect that lasted only a few hours. The antigenicity of PEG-BOX was greatly reduced as expected. PEG-BOX appears to have potential value for the treatment of hyperbilirubinemia observed in such diseases as fulminant hepatitis and neonatal bilirubin encephalopathy.     

Lack of therapeutic improvement of liver fibrosis in rats by dexamethasone in spite of ascites amelioration

Pathophysiology of liver fibrosis (LF) includes hepatic parenchymal cell destruction and connective tissue formation. Although dexamethasone has been used in the liver diseases, there is controversy over the beneficial effects of dexamethasone on LF. Previous studies showed that CCAAT/enhancer binding protein-beta (C/EBPbeta) activation contributes to hepatocyte regeneration and dissolution of fibrosis and that dexamethasone activates C/EBPbeta whereas C/EBPbeta-mediated gene induction by dexamethasone is antagonized by a corepressor. The present study investigated the possible therapeutic effect of dexamethasone for the treatment of LF in rats. We injected rats with multiple doses of dimethylnitrosamine (DMN) for 4 weeks and then used the LF rats to determine whether dexamethasone treatment therapeutically improved liver functions and resolved fibers accumulated in the liver. Dexamethasone (100 microg/kg, po, three times per week for 4 weeks) failed to restore the body weight gain and liver weight decreased by LF. The body weight gain reduced during LF was further decreased by dexamethasone treatment. Animals were subjected to blood biochemical, liver histopathological and immunochemical analyses. Although dexamethasone treatment significantly reduced ascites in LF rats, the plasma albumin and total protein levels decreased in fibrotic rats were not restored. Impaired liver functions during LF including elevated plasma aminotransferases and bilirubin levels along with GSTA2 repression were not recovered by dexamethasone. Dexamethasone failed to decrease the fibrosis score and to eliminate the extracellular matrix and alpha-smooth muscle actin accumulated in the fibrotic liver. The results of the present study showed that dexamethasone ameliorated ascites in LF rats but failed to improve the liver functions and fiber accumulation, and that the possible beneficial effect of dexamethasone might result from anti-inflammatory effect but not from liver improvement.     

Degradation of plasma bilirubin by a bilirubin oxidase derivative which has a relatively long half-life in the circulation

To enhance degradation of unconjugated bilirubin in hyperbilirubinemic subjects, we synthesized a bilirubin oxidase (EC 1.3.3.5) (BO) derivative (PEGBO) by covalently linking (2,4-bis[O-methoxy(polyethyleneglycol)]-6-chloro-s-triazine) (PEG) to the enzyme. Intravenously injected BO in rats disappeared from the circulation with a half-life of 2.5 min; the half-life of PEGBO was 190 min. Intravenously injected BO minimally and transiently decreased plasma bilirubin levels in jaundiced Gunn rats and in bile-duct-ligated jaundiced rats. In contrast, PEGBO rapidly and substantially decreased plasma bilirubin levels and the effect persisted for longer than 3 h. Renal dysfunction often occurs in patients with liver diseases. To study the role of bilirubin toxicity for the kidney, functions of transtubular transport for organic anions was measured in bile-duct-ligated jaundiced animals before and after treatment with PEGBO. Bile duct ligation decreased urinary excretion of phenolsulfophthalein (PSP), an organic anion used for renal function test. Treatment of the jaundiced animals with PEGBO increased the rate of PSP disappearance from the circulation and normalized its urinary excretion. Thus, PEGBO might be useful for the study of bilirubin toxicity in jaundiced animals.     

Androgen deficiency in the aging male: benefits and risks of androgen supplementation

There is now convincing evidence that in a subset of aging men, increasing with age, plasma testosterone levels fall below a critical level resulting in hypogonadism. This state of testosterone deficiency has an impact on bone, muscle and brain function and is maybe a factor in the accumulation of visceral fat which again has a significant impact on the cardiovascular risk profile. From the above it follows that androgen replacement to selected men with proven androgen deficiency will have beneficial effects. There is, however a concern that androgen administration to aging men may be harmful in view of effects on prostate disease. Benign prostate hyperplasia (BPH) and prostate cancer are typically diseases of the aging male, steeply increasing with age. But epidemiological studies provide no clues that the levels of circulating androgen are correlated with or predict prostate disease. Similarly, androgen replacement studies in men do not suggest that these men suffer in a higher degree from prostate disease than control subjects. It seems a defensible practice to treat aging men with androgens if and when they are testosterone-deficient, but long-term studies including sufficient numbers of men are needed.     

The role of interferon gamma in regulation of CD4+ T-cells and its clinical implications

Interferon gamma (IFNgamma) plays a central role in the immune response against infection and tumur immune surveillance. Its functions include not only activation of the host immune system to control microbial infections but also repression of autoimmune responses by turning on T-regulatory cells and increasing T effector cell apoptosis. Defects in IFNgamma and IFNgamma receptor genes have been associated with autoimmune diseases such as rheumatoid arthritis, type 1 diabetes and multiple sclerosis. However, treatment of autoimmune diseases by supplementing with IFNgamma has been satisfactory due to its broad biological effects. Instead, its target T-regulatory cells may be used for the clinical treatment of autoimmune diseases. Future study could also focus on promotion of the beneficial effects of IFNgamma and blocking those unwanted IFNgamma-induced activities.     

Bartter's syndrome associated with indirect hyperbilirubinemia: a possible clinical variety

This report deals with three cases of Bartter's syndrome whose symptomatology was associated with indirect hyperbilirubinemia. The bilirubin disorder was suggestive of Gilbert's syndrome, with no pathological findings being detected as far as the liver function was concerned. Furthermore, the unconjugated fraction of bilirubin increased after fasting. The therapy with indomethacin exerted beneficial effects on both electrolytes and bilirubin disorders, and the patients recovered a good healthy state. These findings suggest the possibility that Bartter's syndrome may coexist in a variety associated with indirect hyperbilirubinemia.     

Green tea and its polyphenolic catechins: medicinal uses in cancer and noncancer applications

Can drinking several cups of green tea a day keep the doctor away? This certainly seems so, given the popularity of this practice in East Asian culture and the increased interest in green tea in the Western world. Several epidemiological studies have shown beneficial effects of green tea in cancer, cardiovascular, and neurological diseases. The health benefits associated with green tea consumption have also been corroborated in animal studies of cancer chemoprevention, hypercholesterolemia, artherosclerosis, Parkinson's disease, Alzheimer's disease, and other aging-related disorders. However, the use of green tea as a cancer chemopreventive or for other health benefits has been confounded by the low oral bioavailability of its active polyphenolic catechins, particularly epigallocatechin-3-gallate (EGCG), the most active catechin. This review summarizes the purported beneficial effects of green tea and EGCG in various animal models of human diseases. Dose-related differences in the effects of EGCG in cancer versus neurodegenerative and cardiovascular diseases, as well as discrepancies between doses used in in vitro studies and achievable plasma understanding of the in vivo effects of green tea catechins in humans, before the use of green tea is widely adopted as health-promoting measure.     

The role of albumin in the hepatic transport of bilirubin: studies in mutant analbuminemic rats

Bilirubin and other cholephilic organic anions are bound to albumin in the circulation; their hepatic uptake involves a carrier-mediated process. To investigate the possible role of serum albumin in the transhepatic transport of a cholephilic ligand, plasma clearance of radioactive bilirubin and its biliary excretion as well as its interaction with plasma proteins were compared between normal and mutant analbuminemic rats (NAR). With a tracer amount of 3H-labeled bilirubin, its plasma clearance and biliary excretion were comparable in both animal groups. However, the plasma clearance of a loading dose of the ligand was significantly increased and its biliary recovery was low in NAR as compared with normal animals. In accord with these findings in vivo, gel permeation chromatographic analysis revealed that the bilirubin binding capacity of serum proteins was significantly lower in NAR than in control animals. When bilirubin was administered to NAR as a mixture with equimolar albumin, its plasma disappearance was considerably decreased and its biliary recovery was increased. Similar effects were observed when albumin was replaced by an equimolar amount of glutathione S-transferases (ligandins). These observations indicate that, although ligand-protein interaction in the circulation is important for directing bilirubin to the plasma membranes of the hepatocyte, this mechanism is not specific for albumin.     

The role of interferon γ in regulation of CD4 T-cells and its clinical implications

Interferon γ (IFNγ) plays a central role in the immune response against infection and tumur immune surveillance. Its functions include not only activation of the host immune system to control microbial infections but also repression of autoimmune responses by turning on T-regulatory cells and increasing T effector cell apoptosis. Defects in IFNγ and IFNγ receptor genes have been associated with autoimmune diseases such as rheumatoid arthritis, type 1 diabetes and multiple sclerosis. However, treatment of autoimmune diseases by supplementing with IFNγ has been satisfactory due to its broad biological effects. Instead, its target T-regulatory cells may be used for the clinical treatment of autoimmune diseases. Future study could also focus on promotion of the beneficial effects of IFNγ and blocking those unwanted IFNγ-induced activities.     

New sorbent for bilirubin removal from human plasma: Cibacron Blue F3GA-immobilized poly(EGDMA–HEMA) microbeads

Cibacron Blue F3GA-immobilized poly(EGDMA–HEMA) microbeads were investigated as a specific sorbent for bilirubin removal from human plasma. The poly(EGDMA–HEMA) microbeads were prepared by a modified suspension copolymerization technique. Cibacron Blue F3GA was covalently coupled to the poly(EGDMA–HEMA) microbeads via the nucleophilic reaction between the chloride of its triazine ring and the hydroxyl groups of the HEMA molecule, under alkaline conditions. Bilirubin adsorption was investigated from hyperbilirubinemic human plasma on the poly(EGDMA–HEMA) microbeads containing different amounts of immobilized Cibacron Blue F3GA, (between 5.0–16.5 μmol/g). The non-specific bilirubin adsorption on the unmodified poly(EGDMA–HEMA) microbeads were 0.32 mg/g from human plasma. Higher bilirubin adsorption values, up to 14.8 mg/g, were obtained with the Cibacron Blue F3GA-immobilized microbeads. Bilirubin molecules interacted with these sorbents directly. Contribution of albumin adsorption on the bilirubin adsorption was pronounced. Bilirubin adsorption increased with increasing temperature.     

Role of apolipoprotein D in the transport of bilirubin in plasma

Apolipoprotein D (apo D) is a 30-kDa glycoprotein of unknown function that is associated with high-density lipoproteins (HDL). Because unconjugated bilirubin has been shown to bind apo D with a 0. 8:1 stoichiometry, we examined the contribution of this protein to transport of bilirubin in human plasma. Density gradient centrifugation analysis using physiological concentrations of [(14)C]bilirubin reveals that 9% of unconjugated bilirubin is associated with HDL, with the remaining pigment bound primarily to serum proteins (i.e., albumin). The percentage of total plasma bilirubin bound to HDL was found to increase proportionally with bilirubin concentration. Affinity of human apo D for bilirubin was determined by steady-state fluorescence quenching, with Scatchard analysis demonstrating a single binding site for unconjugated bilirubin with an affinity constant (K(a)) of approximately 3 x 10(7) M(-1). Incorporation of apo D into phosphatidylcholine vesicles had no effect on K(a), suggesting that a lipid environment does not alter the affinity of the protein for bilirubin. Using stopped-flow techniques, the first-order rate constant for bilirubin dissociation from apo D was measured at 5.4 s(-1) (half-time = 129 ms). Our findings indicate that HDL is the principal nonalbumin carrier of bilirubin in human plasma and further support the proposition that the affinity of HDL for bilirubin is primarily the result of binding to apo D.     

Reference intervals for some clinical chemical parameters in the marmoset (Callithrix jacchus): effect of age and sex

Reference intervals for some clinical chemistry parameters in the marmoset were calculated. The effects of age (250-300 days compared with 500-550 days) and sex on the values found was investigated. Alkaline phosphatase levels decreased with age, young males having higher plasma levels than young females, but no sex differences were discernible for older animals. Levels of gamma-glutamyl transpeptidase and sorbitol dehydrogenase were higher in older males than in younger females. Higher plasma iron levels were found in the males with increasing age. Age and sex effects for protein and albumin were interactive and further interpretation was therefore difficult. No significant age or sex effects were seen for cholinesterase, acetylcholinesterase, isocitrate dehydrogenase, malate dehydrogenase, lactate dehydrogenase, glutamate dehydrogenase, aspartate amino transferase, alanine aminotransferase or bilirubin.     

The Therapeutic Effects and Mechanisms of Salidroside on Cardiovascular and Metabolic Diseases: An Updated Review

The increasing incidence of metabolic and cardiovascular diseases has severely affected global human health and life safety. In recent years, some effective drugs with remarkable curative effects and few side effects found in natural compounds have attracted attention. Salidroside (SAL), a phenylpropane glycoside, is the main active ingredient of the plateau plant Rhodiola. So far, many animal experiments proved that SAL has good biological activity against some metabolic and cardiovascular diseases. However, most of these reports are scattered. This review systematically summarizes the pharmacological progress of SAL in the treatment of several metabolic (e. g., diabetes and non-alcoholic fatty liver disease) and cardiovascular (e. g., atherosclerosis) diseases in a timely manner to promote the clinical application and basic research of SAL. Accumulating evidence proves that SAL has beneficial effects on these diseases. It can improve glucose tolerance, insulin sensitivity, and β-cell and liver functions, and inhibit adipogenesis, inflammation and oxidative stress. Overall, SAL may be a valuable and potential drug candidate for the treatment of metabolic and cardiovascular diseases. However, more studies especially clinical trials are needed to further confirm its therapeutic effects and molecular mechanisms.     

New dammarane-type glucosides as potential activators of AMP-activated protein kinase (AMPK) from Gynostemma pentaphyllum

AMP-activated protein kinase (AMPK) is a key sensor and regulator of glucose, lipid, and energy metabolism throughout the body. Activation of AMPK improves metabolic abnormalities associated with metabolic diseases including obesity and type-2 diabetes. The oriental traditional medicinal herbal plant, Gynostemma pentaphyllum, has shown a wide range of beneficial effects on glucose and lipid metabolism. In this study, we found that G. pentaphyllum contains two novel dammarane-type saponins designated as damulin A (1), 2α,3β,12β-trihydroxydammar-20(22)-E,24-diene-3-O-[β-D-glucopyranosyl-(1→2)-β-D-glucopyranoside], and damulin B (2), 2α,3β,12β-trihydroxydammar-20,24-diene-3-O-[β-D-glucopyranosyl-(1→2)-β-D-glucopyranoside], that strongly activate AMPK in cultured L6 myotube cells. Damulins A and B also increased β-oxidation and glucose uptake with increasing GluT4 translocation to the plasma membrane in L6 myotube cells. Taken together our results indicate that activation of AMPK by damulins A and B may contribute to beneficial effect of G. pentaphyllum on glucose and lipid metabolism.     

Oxidative damage of albumin in advanced liver disease

Albumin has a number of biological functions and the serum albumin level is related to prognosis in advanced liver disease. Oxidative stress is believed to play an important role in the pathogenesis of liver failure. The aim of the present study was to characterize oxidative modification of albumin in patients with various degrees of liver failure and to investigate implications for its binding function. Patients with liver cirrhosis (n=10), acute-on-chronic liver failure (n=8) and healthy controls (n=15) were included in the study. Three fractions of albumin were separated by HPLC according to the redox state of cysteine-34 and detected by fluorescence as well as UV absorption. Carbonyl groups were measured as a marker of oxidative modification in plasma proteins and, by western blotting, on albumin. Progressive oxidative modification of albumin was found with increasing severity of liver failure indicated by an increased content of carbonyl groups and oxidation of cysteine-34. Fluorescence properties of albumin were altered by oxidation and, in patients with acute-on-chronic liver failure, by high plasma levels of bilirubin. This alteration of albumin fluorescence by bilirubin provides evidence for a preferred binding of bilirubin to the fully reduced form of albumin.