Effects of taurodihydrofusidate, a bile salt analogue, on bile formation and biliary lipid secretion in the rhesus monkey

A "forward genomics" approach links genotype to phenotype using independent phenotypic losses among related species

Genotype-phenotype mapping is hampered by countless genomic changes between species. We introduce a computational "forward genomics" strategy that-given only an independently lost phenotype and whole genomes-matches genomic and phenotypic loss patterns to associate specific genomic regions with this phenotype. We conducted genome-wide screens for two metabolic phenotypes. First, our approach correctly matches the inactivated Gulo gene exactly with the species that lost the ability to synthesize vitamin C. Second, we attribute naturally low biliary phospholipid levels in guinea pigs and horses to the inactivated phospholipid transporter Abcb4. Human ABCB4 mutations also result in low phospholipid levels but lead to severe liver disease, suggesting compensatory mechanisms in guinea pig and horse. Our simulation studies, counts of independent changes in existing phenotype surveys, and the forthcoming availability of many new genomes all suggest that forward genomics can be applied to many phenotypes, including those relevant for human evolution and disease.

Tissue Manganese Concentrations in Young Male Rhesus Monkeys following Subchronic Manganese Sulfate Inhalation

High-dose human exposure to manganese results in manganese accumulation in the basal ganglia and dopaminergic neuropathology. Occupational manganese neurotoxicity is most frequently linked with manganese oxide inhalation; however, exposure to other forms of manganese may lead to higher body burdens. The objective of this study was to determine tissue manganese concentrations in rhesus monkeys following subchronic (6 h/day, 5 days/week) manganese sulfate (MnSO(4)) inhalation. A group of monkeys were exposed to either air or MnSO(4) (0.06, 0.3, or 1.5 mg Mn/m(3)) for 65 exposure days before tissue analysis. Additional monkeys were exposed to MnSO(4) at 1.5 mg Mn/m(3) for 15 or 33 exposure days and evaluated immediately thereafter or for 65 exposure days followed by a 45- or 90-day delay before evaluation. Tissue manganese concentrations depended upon the aerosol concentration, exposure duration, and tissue. Monkeys exposed to MnSO(4) at > or = 0.06 mg Mn/m(3) for 65 exposure days or to MnSO(4) at 1.5 mg Mn/m(3) for > or = 15 exposure days developed increased manganese concentrations in the olfactory epithelium, olfactory bulb, olfactory cortex, globus pallidus, putamen, and cerebellum. The olfactory epithelium, olfactory bulb, globus pallidus, caudate, putamen, pituitary gland, and bile developed the greatest relative increase in manganese concentration following MnSO(4) exposure. Tissue manganese concentrations returned to levels observed in the air-exposed animals by 90 days after the end of the subchronic MnSO(4) exposure. These results provide an improved understanding of MnSO(4) exposure conditions that lead to increased concentrations of manganese within the nonhuman primate brain and other tissues.

Fusidic acid-induced hyperbilirubinemia

A 72-year old man developed jaundice while on fusidic acid therapy for suspected osteomyelitis. Hyperbilirubinemia was predominantly of the conjugated variety and elevation in liver enzymes was mild and transient. Although serum bilirubin fell rapidly after fusidic acid was stopped, complete resolution of the hyperbilirubinemia took nearly a month. Other possible causes of jaundice were excluded. Light microscopy of a needle liver biopsy showed focal hepatocyte feathery degeneration, intracellular bile retention, and canalicular bile plugging, most prominent in perivenous regions. Electron microscopy revealed varying degrees of canalicular dilatation, loss of microvilli, and disruption of the canalicular membrane with vesicular bleb formation as well as canalicular bile plugs. Widening of the pericanalicular ectoplasmic zone with accumulation of cytoskeletal filaments was also noted. These findings are similar to those reported in experimental cholestasis induced by bile acids. Possible mechanisms of jaundice caused by fusidic acid are discussed.

Effects of sodium taurodihydrofusidate on nasal absorption of insulin in sheep

To investigate the utility of a novel adjuvant, sodium taurodihydrofusidate (STDHF), as an enhancer of mucosal permeation of drugs, experiments involving intranasal insulin:STDHF administration in sheep were performed. Rabbit erythrocyte lysis assays were employed to assess the relative membrane lytic activity of STDHF, as well as that of its glycine-conjugated analogue, compared with a nonionic detergent and a common bile salt. Equivalent weight concentrations of the fusidates were found to be 5- to 10-fold less lytic than the bile salt and at least 100-fold less lytic than the nonionic detergent laureth-9. Provided the concentration of STDHF was greater than its critical micellar concentration, formulations of insulin with STDHF greatly enhanced intranasal insulin absorption. Optimal nasal insulin absorption was attained at a molar ratio of STDHF to insulin of 5:1. In addition, intranasal absorption was linearly related to insulin dose. Compared with intravenous administration, the mean bioavailability of intranasal insulin was 16.4%. Interovine variability was low, with a coefficient of variation of 14% for 12 animals. It was found that intranasal absorption of sodium insulin was not significantly different from that of zinc insulin. However, formulations of both crystalline insulin preparations were absorbed more efficiently than a formulation prepared using commercially available solutions of U-500 insulin. The results taken together indicate that STDHF is an excellent enhancer of insulin absorption from the nasal mucosa.

Regulation of 3-hydroxy-3-methylglutaryl CoA reductase by analogs of cholesterol and bile acids in cultured intestinal mucosa

Sodium fusidate and its glycine conjugate, which have the same detergent properties as bile acids, significantly (p less than 0.05) stimulate HMG-CoA reductase of cultured intestine below the critical micellar concentration (CMC) without affecting brush border enzymes. Above CMC, both amphiphiles are cytotoxic. At concentrations between 1 and 5 mM, sodium fusidate decreased cholesterol contents of cultured mucosa (P less than 0.05), the increase in synthesis only partially compensating for the sterol loss. Oxygenated sterols, 7-keto- and 25-hydroxycholesterol, also depleted mucosal cholesterol at 0.5 mM, exerting their effect differently by inhibiting HMG-CoA reductase (p less than 0.01). In contrast to their marked effect on total mucosal cholesterol contents, brush border cholesterol was unaffected by both cholesterol and bile acid analogs.

Bile acid structure and biliary lipid secretion. II. A comparison of three hydroxy and two keto bile acids

The effect of five bile acids on biliary lipid secretion was studied in the pentobarbital-anesthetized cat. The dihydroxy acid, taurohyodeoxycholic acid, was indistinguishable from another dihydroxy acid, taurochenodeoxycholic acid, but secretion of both phospholipid and cholesterol was considerably reduced with two mono-keto dihydroxy acids, tauro-3alpha,12alpha-dihydroxy-7-keto-5beta-cholanoic acid and tauro-3alpha,7alpha-dihydroxy-12-keto-5beta-cholanoic acid. The effect of a trihydroxy bile acid, taurocholic acid was as previously described. The effect of the keto bile acids may be explained by the ability of these bile acids to solubilize lipid, but such an explanation is inadequate for the difference between di- and trihydroxy bile acids. An intracellular effect of bile acid is postulated.

Interaction of fusidates with bile acid uptake by isolated rat hepatocytes

The interaction of fisidic acid and two of its conjugates with carrier-mediated uptake of bile acids was investigated in isolated rat hepatocytes. All three fusidates inhibited the uptake of both cholate and taurocholate competitively suggesting a direct interaction of fusidates with bile acid carrier. The inhibition constants for all three fusidates for the inhibition of cholate uptake were significantly different from the respective inhibition constants for the inhibition of taurocholate uptake. This would indicate that both cholate and taurocholate are transported by more than one carrier into hepatocytes. The results may also indicate that taurine conjugated bile acids may be transported preferentially by one transport system while unconjugated bile acids may be preferentially transported by another transport system.