Comparison of the activity and disposition of the novel cholesterol absorption inhibitor, SCH58235, and its glucuronide, SCH60663

Previous studies described the metabolism-based discovery of a potent, selective inhibitor of intestinal absorption of cholesterol, SCH58235 (Ezetimibe). Here we demonstrate that the phenolic glucuronide (SCH60663) of SCH58235, was more potent at inhibiting cholesterol absorption in rats than SCH58235, when administered by the intraduodenal route. To understand the increased potency of the glucuronide, the metabolism and distribution of SCH58235 and SCH60663 were studied in bile duct-cannulated rats. One minute after intraduodenal delivery of SCH58235, significant levels of compound were detected in portal plasma; >95% was glucuronidated, indicating that the intestine was metabolizing SCH58235 to its glucuronide. When intraduodenally delivered as SCH58235, the compound was glucuronidated, moved through the intestinal wall, into portal plasma, through the liver, and into bile. However, when delivered as SCH60663, >95% of the compound remained in the intestinal lumen and wall, which may explain its increased potency. Significant inhibition of cholesterol absorption and glucuronidation of SCH58235 occurred when SCH58235 was intravenously injected into bile duct-cannulated rats. Autoradiographic analysis demonstrated that drug related material was located throughout the intestinal villi, but concentrated in the villus tip. These data indicate that (a) SCH58235 is rapidly metabolized in the intestine to its glucuronide; (b) once glucuronidated, the dose is excreted in the bile, thereby delivering drug related material back to the site of action and (c) the glucuronide is more potent than the parent possibly because it localizes to the intestine. Taken together, these data may explain the potency of SCH58235 in the rat (ID(50) = 0.0015 mg kg(-1)) and rhesus monkey (ID(50) = 0.0005 mg kg(-1)).

Ezetimibe selectively inhibits intestinal cholesterol absorption in rodents in the presence and absence of exocrine pancreatic function

1. Ezetimibe potently inhibits the transport of cholesterol across the intestinal wall, thereby reducing plasma cholesterol in preclinical animal models of hypercholesterolemia. The effect of ezetimibe on known absorptive processes was determined in the present studies. 2. Experiments were conducted in the hamster and/or rat to determine whether ezetimibe would affect the absorption of molecules other than free cholesterol, namely cholesteryl ester, triglyceride, ethinylestradiol, progesterone, vitamins A and D, and taurocholic acid. In addition, to determine whether exocrine pancreatic function is involved in the mechanism of action of ezetimibe, a biliary anastomosis model, which eliminates exocrine pancreatic function from the intestine while maintaining bile flow, was established in the rat. 3. Ezetimibe reduced plasma cholesterol and hepatic cholesterol accumulation in cholesterol-fed hamsters with an ED(50) of 0.04 mg kg(-1). Utilizing cholesteryl esters labelled on either the cholesterol or the fatty acid moiety, we demonstrated that ezetimibe did not affect cholesteryl ester hydrolysis and the absorption of fatty acid thus generated in both hamsters and rats. The free cholesterol from this hydrolysis, however, was not absorbed (92 - 96% inhibition) in the presence of ezetimibe. Eliminating pancreatic function in rats abolished hydrolysis of cholesteryl esters, but did not affect the ability of ezetimibe to block absorption of free cholesterol (-94%). Ezetimibe did not affect the absorption of triglyceride, ethinylestradiol, progesterone, vitamins A and D, and taurocholic acid in rats. 4. Ezetimibe is a potent inhibitor of intestinal free cholesterol absorption that does not require exocrine pancreatic function for activity. Ezetimibe does not affect the absorption of triglyceride as a pancreatic lipase inhibitor (Orlistat) would, nor does it affect the absorption of vitamin A, D or taurocholate, as a bile acid sequestrant (cholestyramine) would.

Mode of action of bullatacin, a potent antitumor acetogenin: inhibition of NADH oxidase activity of HeLa and HL-60, but not liver, plasma membranes

Bullatacin, a potential antitumor substance isolated from plants of the Annonaceae, and analogs of bullatacin, known collectively as acetogenins, have been reported previously to show potent activity in the inhibition of growth of murine tumors and human tumor xenografts grown in athymic mice as well as an ability to inhibit mitochondrial electron transport. In this report, we show activity of bullatacin in inhibition of NADH oxidase activity of plasma membrane vesicles isolated from HeLa cells and HL-60 cells but not with plasma membrane vesicles isolated from rat livers which, unlike the inhibition of mitochondrial activity, correlated with the ability of the acetogenins to kill tumor cells. Additionally, bullatacin is active against HL-60 cells that are resistant to adriamycin which may suggest utility for bullatacin in management of drug-resistant cells and cell lines.

Ezetimibe, a potent cholesterol absorption inhibitor, normalizes combined dyslipidemia in obese hyperinsulinemic hamsters

Ezetimibe potently and selectively inhibits cholesterol absorption in the intestine, thereby reducing plasma cholesterol in preclinical models of hypercholesterolemia. Clinical trials have demonstrated that ezetimibe lowers LDL cholesterol and raises HDL cholesterol in humans. The effect of ezetimibe on other dyslipidemias, particularly hypertriglyceridemia, is not yet known. In the present studies, we assessed the effect of ezetimibe on combined hypercholesterolemia and hypertriglyceridemia in obese hyperinsulinemic hamsters. Hamsters were fed chow, chow with cholesterol (0.12%), or the same cholesterol diet containing different dietary triglycerides (15%) in the absence or presence of 1 mg/kg ezetimibe (in diet) for up to 84 days. Body weight, serum insulin, leptin, glucose, cholesterol, and triglyceride levels were analyzed. Cholesterol and triglyceride levels were also determined in VLDL+IDL, LDL, and HDL. Hamsters maintained on high-fat diets became obese, hyperinsulinemic, hyperleptinemic, hypercholesterolemic, and hypertriglyceridemic. Ezetimibe did not affect body weight, insulin, or leptin, but ablated the combined hypercholesterolemia and hypertriglyceridemia induced by high-fat diets. Ezetimibe normalized VLDL+IDL cholesterol and triglyceride and significantly decreased LDL cholesterol to below chow-fed levels. The ratio of HDL to LDL cholesterol increased significantly with the addition of ezetimibe. Ezetimibe completely eliminated the accumulation of cholesteryl ester and free cholesterol in liver that was induced under the various dietary conditions in the absence of drug. In conclusion, ezetimibe is very effective in correcting the combined dyslipidemia in diet-induced obese hyperinsulinemic hamsters and may be an effective therapy for ameliorating combined dyslipidemia in obese insulin-resistant and/or type 2 diabetic humans.

Transgenic overexpression of neuromedin U promotes leanness and hypophagia in mice

Recent work has shown that neuromedin U (NmU), a peptide initially identified as a smooth muscle contractor, may play a role in regulating food intake and energy homeostasis. To further evaluate this putative function, we measured food intake, body weight, energy expenditure and glucose homeostasis in transgenic mice that ubiquitously overexpress murine proNmU. NmU transgenic mice were lighter and had less somatic and liver fat, were hypophagic, and had improved insulin sensitivity as judged by an intraperitoneal insulin tolerance test. Transgenic mice had higher levels of hypothalamic NPY, POMC and MCH mRNA. There was no difference in O2 consumption between genotypes; however, NmU transgenic mice displayed a modest increase in respiratory quotient during food deprivation and refeeding. There were no behavioral disturbances in the NmU transgenic mice that could account for the results (e.g. changes in locomotor activity). When placed on a high-fat diet, transgenic mice remained lighter than wild-type mice and ate less, but gained weight at a rate similar to wild-type mice. Despite the increased weight gain with high-fat feeding, glucose tolerance was significantly improved in the transgenic mice. These findings support the hypothesized role of NmU as an endogenous anorexigenic peptide.

The effects of a 4-year program promoting bicycle helmet use among children in Quebec

OBJECTIVES

This study assessed the effectiveness of a 4-year program of bicycle helmet promotion that targeted elementary school children in one region of Quebec. The program revolved primarily around persuasive communication and community organization, combining standard educational activities and activities to facilitate helmet acquisition and use.

METHODS

Helmet use was compared between more than 8000 young cyclists in municipalities exposed or not exposed to the program. Factors influencing helmet use were controlled through the use of multivariate analyses.

RESULTS

Helmet use increased from 1.3% before program implementation to 33% in 1993. The program was clearly effective in most cycling circumstances and for various groups of children. However, the benefits of the program were unequally distributed; the program was one third as effective in poorer municipalities as in "average-rich" ones.

CONCLUSIONS

This community-based program that combined various types of activities appeared to be effective. New intervention models are needed to ensure an equitable distribution of benefits.

Efficiency of uphill locomotion in nocturnal and diurnal lizards

Nocturnal geckos can walk on level ground more economically than diurnal lizards. One hypothesis for why nocturnal geckos have a low cost of locomotion is that they can perform mechanical work during locomotion more efficiently than other lizards. To test this hypothesis, we compared the efficiency of the nocturnal gecko Coleonyx variegatus (average body mass 4.2 g) and the diurnal skink Eumeces skiltonianus (average body mass 4.8 g) when they performed vertical work during uphill locomotion. We measured the rate of oxygen consumption when each species walked on the level and up a 50 slope over a range of speeds. For Coleonyx variegatus, the energetic cost of traveling a unit distance (the minimum cost of transport, Cmin) increased from 1.5 to 2.7 ml O2 kg-1 m-1 between level and uphill locomotion. For Eumeces skiltonianus, Cmin increased from 2.5 to 4.7 ml O2 kg-1 m-1 between level and uphill locomotion. By taking the difference between Cmin for level and uphill locomotion, we found that the efficiency of performing vertical work during locomotion was 37 % for Coleonyx variegatus and 19 % for Eumeces skiltonianus. The similarity between the 1.9-fold difference in vertical efficiency and the 1.7-fold difference in the cost of transport on level ground is consistent with the hypothesis that nocturnal geckos have a lower cost of locomotion than other lizards because they can perform mechanical work during locomotion more efficiently.

Evidence for distinct systemic extravasation effects of platelet activating factor, leukotrienes B4, C4, D4 and histamine in the guinea pig

The relative potencies of platelet-activating factor (PAF), leukotrienes B4 (LTB4), C4 (LTC4), D4 (LTD4) and histamine to induce hemoconcentration (HC) were evaluated in the guinea pig. The maximal hematocrit increase (MHI) from PAF, LTD4 and histamine occurred 5-7 min after i.v. injection, whereas the MHI of LTC4 occurred 13-15 min after injection. LTB4 (2.97-5.95 nmol kg-1) did not produce HC. The magnitude of PAF-induced MHI was 2-fold that of LTC4 or LTD4, regardless of the dose of leukotrienes used. The doses (nmol kg-1) needed to produce 30% HC were: 0.14-PAF, 0.71-LTD4 and 3.37-LTC4 and 2,400 histamine. The HC effects of LTD4 were markedly reduced by prior administration of FPL-55712. However, neither LTC4 or LTD4 HC effects were significantly reduced by prior i.v. injection of CV-3988 (3.4 mg kg-1), a competitive receptor antagonist to PAF which is 98% effective in abolishing HC response to 0.14 nmol kg-1 PAF. Diphenhydramine abolished histamine-induced hemoconcentration but was without effect on PAF or LTD4. These results suggest that the responses of PAF, leukotrienes and histamine differ in their potency and may involve separate vascular recognition sites related to acute increases in vascular permeability.

Bicycle helmet campaigns and head injuries among children. Does poverty matter?

OBJECTIVES

To assess the impact of a community based bicycle helmet programme aimed at children aged 5-12 years (about 140,000) from poor and well off municipalities.

METHODS

A quasi-experimental design, including a control group, was used. Changes in the risk of bicycle related head injuries leading to hospitalisation were measured, using rates ratios.

RESULTS

Reductions in bicycle related head injuries were registered in both categories of municipalities. Compared with the pre-programme period, the protective effect of the programme during the post-programme period was as significant among children from poor municipalities (RR= 0.45 95%CI 0.26 to 0.78) as among those from richer municipalities (RR=0.55 95%CI 0.41 to 0.75).

CONCLUSION

Population based educational programmes may have a favourable impact on injury risks in poor areas despite lower adoption of protective behaviours.

Variegated micelle surfaces: correlating the microstructure of mixed surfactant micelles with bulk solution properties

Electron paramagnetic resonance, viscosity, and small-angle neutron scattering (SANS) measurements have been used to study the interaction of mixed anionic/nonionic surfactant micelles with the polyampholytic protein gelatin. Sodium dodecyl sulfate (SDS) and the nonionic surfactant dodecylmalono-bis-N-methylglucamide (C12BNMG) were chosen as "interacting" and "noninteracting" surfactants, respectively; SDS micelles bind strongly to gelatin but C12BNMG micelles do not. Further, the two surfactants interact synergistically in the absence of the gelatin. The effects of total surfactant concentration and surfactant mole fraction have been investigated. Previous work (Griffiths et al. Langmuir 2000, 16 (26), 9983-9990) has shown that above a critical solution mole fraction, mixed micelles bind to gelatin. This critical mole fraction corresponds to a micelle surface that has no displaceable water (Griffiths et al. J. Phys. Chem. B 2001, 105 (31), 7465). On binding of the mixed micelle, the bulk solution viscosity increases, with the viscosity-surfactant concentration behavior being strongly dependent on the solution surfactant mole fraction. The viscosity at a stoichiometry of approximately one micelle per gelatin molecule observed in SDS-rich mixtures scales with the surface area of the micelle occupied by the interacting surfactant, SDS. Below the critical solution mole fraction, there is no significant increase in viscosity with increasing surfactant concentration. Further, the SANS behavior of the gelatin/mixed surfactant systems below the critical micelle mole fraction can be described as a simple summation of those arising from the separate gelatin and binary mixed surfactant micelles. By contrast, for systems above the critical micelle mole fraction, the SANS data cannot be described by such a simple approach. No signature from any unperturbed gelatin could be detected in the gelatin/mixed surfactant system. The gelatin scattering is very similar in form to the surfactant scattering, confirming the widely accepted picture that the polymer "wraps" around the micelle surface. The gelatin scattering in the presence of deuterated surfactants is insensitive to the micelle composition provided the composition is above the critical value, suggesting that the viscosity enhancement observed arises from the number and strength of the micelle-polymer contact points rather than the gelatin conformation per se.

Parameterization of the shape of intracranial saccular aneurysms using Legendre polynomials

Our recent studies of the nonlinear mechanics of saccular aneurysms suggest that it is unlikely that these lesions enlarge or rupture via material (limit point) or dynamic (resonance) instabilities. Rather, there is a growing body of evidence from both vascular biology and biomechanical analyses that implicate mechanosensitive growth and remodeling processes. There is, therefore, a pressing need to quantify regional multiaxial wall stresses which, because of the membrane-like behavior of many aneurysms, necessitates better information on the applied loads and regional surface curvatures. Herein, we present and illustrate a method whereby regional curvatures can be estimated easily for sub-classes of human aneurysms based on clinically available data from magnetic resonance angiography (MRA). Whereas Legendre polynomials are used to illustrate this approach, different functions may prove useful for different sub-classes of lesions.

Exploring the Validity of Adolescent Responses to a Measure of Psychological Flexibility and Inflexibility

Validating measures of psychological flexibility (PF) and psychological inflexibility (PI) has occurred in multiple adult samples, but little research has validated PF and PI measures with adolescents. This manuscript describes two studies exploring the validity of responses to the Multidimensional Psychological Flexibility Inventory (MPFI) with two samples of adolescents. The first study used exploratory factor analyses on responses to the MPFI with a sample of 16-17-year-olds (N = 249). The results yielded a reduced and simplified measurement model that consisted of two general factors: one for PF and the other for PI. These exploratory findings were further investigated with confirmatory factor analyses in the second study, with a larger sample of 14-17-year-olds (N = 503). The results from the second study generally confirmed the factor model from the first study. Findings from both studies showed that scores derived from the reduced MPFI measurement model evidenced convergent and divergent validity with a variety of mental health criterion measures. Moreover, findings from the second study showed that PF and PI scores had differential predictive power on different concurrent mental health outcomes. This discussion highlights the implications of measuring PF and PI in adolescents, considers limitations of the present studies, and recommends next steps for research.

Predicting and reinforcing children's intentions to wear protective helmets while bicycling

The researchers undertook to identify the factors that are most likely to influence children's intentions to use bicycle helmets. To determine the most important intention influencing factors, a random sample of 797 students in grades 4 through 6 completed a self-administered questionnaire concerning their beliefs about helmet use. They were asked about their perceptions of the risk of riding bicycles unprotected, the severity of possible head injuries, and about other bicycle-safety related behaviors. Factors that best predicted the student's intentions to use bicycle helmets involved both behavioral beliefs and normative beliefs. Analysis of factors influencing those with low intentions to use helmets, compared to those with high intentions, suggests the most effective messages that health planners can provide preadolescents to influence them to use helmets. They are that helmet use is fun and attractive, helmets provide a new look and a sporting image, and friends approve of and value this behavior. Parents, and particularly mothers, can reinforce their children's intentions to use helmets and their involvement should be encouraged.

Characterisation of colistin resistance in Gram-negative microbiota of pregnant women and neonates in Nigeria

A mobile colistin resistance gene mcr was first reported in 2016 in China and has since been found with increasing prevalence across South-East Asia. Here we survey the presence of mcr genes in 4907 rectal swabs from mothers and neonates from three hospital sites across Nigeria; a country with limited availability or history of colistin use clinically. Forty mother and seven neonatal swabs carried mcr genes in a range of bacterial species: 46 Enterobacter spp. and single isolates of; Shigella, E. coli and Klebsiella quasipneumoniae. Ninety percent of the genes were mcr-10 (n = 45) we also found mcr-1 (n = 3) and mcr-9 (n = 1). While the prevalence during this collection (2015-2016) was low, the widespread diversity of mcr-gene type and range of bacterial species in this sentinel population sampling is concerning. It suggests that agricultural colistin use was likely encouraging sustainment of mcr-positive isolates in the community and implementation of medical colistin use will rapidly select and expand resistant isolates.

Evaluation of a four-year bicycle helmet promotion campaign in Quebec aimed at children ages 8 to 12: impact on attitudes, norms and behaviours

OBJECTIVE

This study evaluated a four-year bicycle helmet promotion campaign.

METHODS

Children's attitudes, social norms, intentions to wear a bicycle helmet as well as helmet ownership were measured. Evaluation was based on a pre-experimental static group comparison design repeated at two (1991) and four years (1993) after implantation, with a non-randomized control group. 3,424 students completed a self-administered questionnaire (experimental: 2,097, control: 1,327).

RESULTS

The program had a significant impact on helmet ownership (1989: 4%; 1991: 26%; 1993: 56%). The program was the principal predictor of high intention to use a bicycle helmet. Time was the principal predictor of ownership with exposure to the program being the next predictor.

CONCLUSION

This study showed that time is an important factor in bicycle helmet acquisition, and that a long-term community-based program can accelerate the process of adopting this behaviour.