Modulation of cholesterol crystallization in bile. Implications for non-surgical treatment of cholesterol gallstone disease

The first step in cholesterol gallstone disease is precipitation of cholesterol crystals in bile. In gallbladder bile. cholesterol is normally solubilized together with bile salts and phospholipids to form mixed micellar structures. When cholesterol in bile is in excess, vesicles (i.e. phospholipid-cholesterol globular structures: liquid crystals) form which become supersaturated in cholesterol. Early aggregation and precipitation of cholesterol molecules into submicroscopic nuclei occurs from these supersaturated vesicles. This crucial step is followed by precipitation and agglomeration of cholesterol crystals which then become visible at light microscopy. Here we describe the mechanism of cholesterol crystallization and its modulation in vivo and in vitro. Recent advances on the role of ursodeoxycholate as an agent preventing the precipitation of cholesterol crystals in bile will be highligthed.     

The binary phase diagram of propranolol hydrochloride and crystallization‐based enantioseparation

Inconsistent results were reported for the solid‐state nature of the racemic species of the pharmaceutical relevant compound propranolol hydrochloride. In this work the binary phase diagram of the propranolol hydrochloride enantiomers is studied. Differential scanning calorimetry (DSC), X‐ray powder diffraction (XRPD), and high performance liquid chromatography (HPLC) were used as analytical methods. The type of the racemic species, the presence and extent of partial solid solutions and the stability regions of polymorphic forms in the system were investigated. The identified binary phase diagram is sketched. Finally, the feasibility of crystallization‐based resolution is discussed. © 2009 Wiley‐Liss, Inc. and the American Pharmacists Association J Pharm Sci 99: 1762–1773, 2010     

The genetic background of cholesterol gallstone formation: an inventory of human lithogenic genes

Family and twin studies as well as animal studies indicate that gallstone disease is, in part, genetically determined. Recently new single gene defects have been identified in specific patients with cholesterol and pigment gallstones. Examples include low phospholipid-associated cholelithiasis due to mutations of the gene encoding the hepatocanalicular phosphatidylcholine transporter, and pigment stones in association with mutations of the ileal bile salt transporter gene. Here we summarize the evidence for common genetic determinants of human gallstone disease in general and provide an inventory of human lithogenic genes. The precise understanding of such genes and their molecular mechanisms will establish new targets for rational drugdesign for this exceptionally prevalent and economically significant digestive disease.     

Mesophase formation during cholesterol gallstone dissolution in human bile: effect of bile acid composition

Duodenal bile obtained from patients with gallstones who were acutely infused with chenodeoxycholic acid, ursodeoxycholic acid, or cholic acid were examined for the propensity toward the formation of a liquid crystalline mesomorphic phase when cholesterol gallstones were incubated in these bile acids. Bile taken from patients infused with ursodeoxycholic acid was found to be enriched in ursodeoxycholic acid; mesophase formation was detected in these samples but not in bile from patients infused with chenodeoxycholic acid or cholic acid.     

Farnesoid X receptor agonism -- a new approach to the treatment of cholesterol gallstone disease

Gallstone disease is very common among native Americans and Hispanics, and approximately 20 million patients are treated for this disease annually in the US. The nuclear farnesoid X receptor (FXR) is the receptor for bile acids, and GW4064 is a synthetic agonist at the FXR. FXR(-/-) mice fed a lithogenic diet (high fat, cholesterol and cholic acid) are more susceptible to gallstone disease than wild-type mice with the same mixed background, thus establishing that the ablation of FXR is associated with this disease. The C57L mouse is susceptible to gallstone formation. When C57L mice are fed a lithogenic diet for a week, the bile contains large aggregates of cholesterol precipitates, and two of five C57L mice had macroscopic cholesterol crystals. In contrast, when C57L mice were fed the lithogenic diet and administered GW4064 100 mg/kg/day by oral gavage, there was no precipitation of cholesterol. Treatment with this agent also increased bile salt and phospholipid concentration, and prevented gallbladder epithelium damage. As FXR agonism with GW4064 has been shown to be useful in a mouse model of cholesterol gallstone disease, it should undergo further development for the treatment of this condition.     

Limits and perspective of oral therapy with statins and aspirin for the prevention of symptomatic cholesterol gallstone disease

The prevalence of gallstones disease in Western countries is 10 – 15%. Gallstones can be one of two types – cholesterol or pigment – with cholesterol gallstones representing nearly the 80% of the total. Cholesterol and pigment gallstones have different predisposing factors: cholesterol gallstones are related to supersaturated bile in cholesterol, whereas black pigment gallstones are related to hyperbilirubinbilia factors (hemolysis, etc.); these are necessary, but not sufficient, factors to produce gallstones in vivo. Gall bladder mucosa factors (gall bladder secretion of mucin, local bile stasis and production of endogenous biliary β-glucuronidase) may coexist with the aforementioned factors and facilitate gallstone nucleation and growth. The gold-standard treatment for symptomatic gallstones is laparoscopic cholecystectomy. Several studies have reported a significant reduction in the onset of symptomatic gallstones disease in patients undergoing chronic therapy with statins, which can reduce bile cholesterol saturation. Aspirin, which has been shown to reduce the local production of gall bladder mucins (mucosal or parietal factors of gallstone formation) in animal experimental models, does not appear to reduce the risk of symptomatic gallstones disease when tested alone. The new horizon of oral therapy for the prevention of symptomatic gallstone disease needs to evaluate the long-term effect of statins and chronic aspirin administration in patients with dyslipidemia and/or atherosclerosis.     

Limits and perspective of oral therapy with statins and aspirin for the prevention of symptomatic cholesterol gallstone disease

The prevalence of gallstones disease in Western countries is 10 - 15%. Gallstones can be one of two types - cholesterol or pigment - with cholesterol gallstones representing nearly the 80% of the total. Cholesterol and pigment gallstones have different predisposing factors: cholesterol gallstones are related to supersaturated bile in cholesterol, whereas black pigment gallstones are related to hyperbilirubinbilia factors (hemolysis, etc.); these are necessary, but not sufficient, factors to produce gallstones in vivo. Gall bladder mucosa factors (gall bladder secretion of mucin, local bile stasis and production of endogenous biliary β-glucuronidase) may coexist with the aforementioned factors and facilitate gallstone nucleation and growth. The gold-standard treatment for symptomatic gallstones is laparoscopic cholecystectomy. Several studies have reported a significant reduction in the onset of symptomatic gallstones disease in patients undergoing chronic therapy with statins, which can reduce bile cholesterol saturation. Aspirin, which has been shown to reduce the local production of gall bladder mucins (mucosal or parietal factors of gallstone formation) in animal experimental models, does not appear to reduce the risk of symptomatic gallstones disease when tested alone. The new horizon of oral therapy for the prevention of symptomatic gallstone disease needs to evaluate the long-term effect of statins and chronic aspirin administration in patients with dyslipidemia and/or atherosclerosis.     

Mechanism of nanoparticle formation from ternary coground phenytoin and its derivatives

The mechanism of drug nanoparticle formation of phenytoin (DPH) and its derivatives monomethylphenytoin (MDPH) and dimethylphenytoin (DMDPH) was investigated. The drug, polyvinylpyrrolidone K17 (PVP), and sodium dodecyl sulfate were coground to obtain the ground mixture (GM). The DPH GM was amorphous; however, MDPH and DMDPH GMs contained drug crystals. Spectral changes in infrared and (13)C solid-state nuclear magnetic resonance were observed in the DPH GM, partially observed in the MDPH GM, and hardly observed in the DMDPH GM. Mean particle sizes of the DPH, MDPH, and DMDPH GM nanosuspension were almost the same; however, stability after storage differed in the order of DPH > MDPH > DMDPH. The intermolecular interaction between the drug and PVP reflected not only the crystallinity of the drug in the GM but also the stability of the GM suspension. The size and stiffness of drug nanoparticles were evaluated using atomic force microscopy. Crystallization of the amorphous GM and agglomeration of the primary nanocrystals were observed in the DPH GM suspension. In contrast, primary nanocrystals were observed in the DMDPH GM suspension. The size of the drug nanocrystals formed from the different molecular states of the drug in the GM reflects the agglomerated states in water and stability.     

Substrate specificity for formation of cholesterol ester conjugates from fenvalerate analogues and for granuloma formation

1. The substrate specificity of microsomal carboxyesterase(s) responsible for the formation of cholesteryl [2R]-2-(4-chlorophenyl) isovalerate from fenvalerate was investigated by incubating mouse kidney microsomes with 14C-cholesterol and the following substrates: fenvalerate isomers, fenvalerate analogues, other pyrethroids, methoprene and cycloprate analogues. Among the four isomers of fenvalerate, only the [2R, alpha S]-isomer yielded a cholesterol ester, being identical with the result obtained in the in vivo study. Some fenvalerate analogues produced cholesterol ester conjugates, but no other pyrethroids nor methoprene produced such conjugates. Some cycloprate analogues gave the corresponding cholesterol ester, the yields of which were dependent on their carbon-chain lengths. 2. Cholesterol ester formation in vitro from these fenvalerate analogues was well correlated with granuloma formation observed when the analogues were given to mice at 3000 ppm for a month. 3. Steroids other than cholesterol were also investigated as acceptors of the acid moiety of the [2R, alpha S]-isomer by incubating solubilized carboxyesterase(s) with the [2R, alpha S]-isomer in the presence of egg lecithin and several steroids. Dehydroisoandrosterone and pregnenolone were found to give the corresponding ester conjugates.     

Partially crystalline systems in lyophilization: I. Use of ternary state diagrams to determine extent of crystallization of bulking agent

Two model ternary systems: water-glycine-raffinose and water-glycine-trehalose were investigated to determine the extent of glycine crystallization in frozen solutions. The use of such partially crystalline systems allows primary drying to be carried out substantially above the collapse temperature. Differential scanning calorimetry (DSC) and variable temperature X-ray diffractometry (XRD) were used to monitor phase transitions in frozen systems as well as to determine the T'g. Aqueous solutions containing different glycine to carbohydrate weight ratios were first cooled to -60 degrees C and then warmed to room temperature. In both raffinose and trehalose systems, when the initial glycine to sugar (raffinose pentahydrate or trehalose dihydrate) ratio was <1, glycine crystallization was not detected. When the ratio was >or=1, partial glycine crystallization was observed during warming. The presence of amorphous glycine caused the T'g to be substantially lower than that of the solution containing only the carbohydrate. To determine the extent of glycine crystallization, the solutions were annealed for 5 h just above the temperature of glycine crystallization. The T'g observed in the second warming curve was very close to that of the carbohydrate solution alone, indicating almost complete glycine crystallization. These studies enabled the construction of the water-rich sections of the raffinose-glycine-water and trehalose-glycine-water state diagrams. These diagrams consist of a kinetically stable freeze-concentrated solution and a doubly unstable glassy region, which readily crystallizes during cooling or subsequent warming. In addition, there is an intermediate region, where during the experimental timescale, there appears to be hindered glycine nucleation but unhindered crystal growth. To obtain substantially crystalline glycine in the frozen solutions, the glycine to carbohydrate ratios should be >or=1.     

Effects of leptin on biliary lipids: potential consequences for gallstone formation and therapy in obesity

Gallstone disease is exceptionally common, occurring especially in Western populations, with cholesterol gallstones predominating. Currently, it is believed that obesity is the most consistent and important risk factor for the development of cholesterol gallstones. Obesity has been shown to be associated with the supersaturation of bile with cholesterol because of increased hepatic secretion of the sterol. In accord with current information from experimental studies, leptin appears to be involved in biliary cholesterol secretion and cholesterol gallstone formation in humans. This review summarizes the current information on the role of obesity in biliary lipid secretion as well as the effect of leptin and its potential consequences for gallstone formation and therapy in the obese.     

The Complexity of Secondary Cascade Consequent to Traumatic Brain Injury: Pathobiology and Potential Treatments

According to the World Health Organization, Traumatic brain injury (TBI) is the major cause of death and disability and will surpass the other diseases by the year 2020. Patients who suffer TBI face many difficulties which negatively affect their social and personal life. TBI patients suffer from changes in mood, impulsivity, poor social judgment and memory deficits. Both open and closed head injuries have their own consequences. Open head injury associated problems are specific in nature e.g. loss of motor functions whereas closed head injuries are diffused in nature like poor memory, problems in concentration etc. Brain injury may have a detrimental effect on the biochemical processes responsible for the homeostatic and physiological disturbances in the brain. Although significant research has been done in order to decrease the overall TBI-related mortality, many individuals suffer from a life-long disability. In this article, we have discussed the causes of TBI, its consequence and the pathobiology of secondary injury. We have also tried to discuss the evidence-based strategies which are shown to decline the devastating consequences of TBI.