Impact of the bowel-screening programme on the diagnosis of colorectal cancer in Ayrshire and Arran.

AIM: Bowel screening aims to reduce colorectal-cancer mortality by the detection and treatment of early-stage asymptomatic disease and the removal of precancerous adenomas. Bowel screening started in Ayrshire and Arran in September 2007. We report the impact of this screening on the diagnosis and stage of colorectal cancer and characterize screen-detected cancers in comparison with those diagnosed through other pathways. METHOD: Diagnoses were identified from an audit database. Referrals were grouped into screen detected, routine, urgent and emergency presentations. RESULTS: Between January 2001 and December 2010, 2289 diagnoses of colorectal cancer were made. From 2001 to 2006, the mean (range) number of new colorectal-cancer diagnoses per year was 210 (198-220). Between 2007 and 2010, the mean (range) number of diagnoses per year was 256 (239-274), a significant (P = 0.008) increase. Since September 2007, 877 colorectal cancers have been diagnosed: 17% were screen detected; 11% were detected as a result of routine GP referral; 51% were detected after urgent GP referral; and 21% were emergency presentations. TNM stage increased with urgency of referral. Approximately two-thirds (66%) of screen-detected colorectal cancers were node negative vs 25% of emergency presentations (P < 0.001). Most screen-detected cancers were distal to the splenic flexure (75%). Screened cancers had favourable pathology; lower T and N stages (both P < 0.001), less venous invasion (P < 0.001) and better differentiation (P < 0.05). Similar results were seen after stratification for TNM stage. Screening has not yet resulted in a significant shift towards early-stage disease since 2007. CONCLUSION: Screening has been associated with an increase in the numbers of both new and early-stage colorectal cancers. Screen-detected cancers are predominantly early-stage disease with favourable pathology. At present, it remains to be seen whether screening will ultimately translate into an overall reduction in advanced-stage disease.

Molecular mechanism for inhibition of 3-hydroxy-3-methylglutaryl CoA (HMG-CoA) reductase by rosuvastatin.

The statins are inhibitors of 3-hydroxy-3-methylglutaryl CoA (HMG-CoA) reductase (HMG-CoAR), and are utilized to decrease levels of atherogenic lipoproteins in patients with, or who are at high risk of, cardiovascular disease. This study describes the inhibition of a recombinant, catalytic fragment of human HMG-CoAR by a new statin, rosuvastatin (CRESTOR(R)). Binding is reversible and involves an initial complex [inhibition constant involving the enzyme-inhibitor complex (E.I), K (i), approximately 1 nM], which undergoes a slow transition ( t ((1/2)) to reach steady state is 33-360 s) to give tighter association [steady-state inhibition constant involving E.I and the second E.I complex in a two-step mechanism (E.I*), K (i)*, approximately 0.1 nM]. At steady state, rosuvastatin is at least as potent as atorvastatin, cerivastatin and simvastatin. It is more potent than fluvastatin and pravastatin. For rosuvastatin, inhibition kinetics are competitive with respect to HMG-CoA and non-competitive when NADPH is varied. At 37 degrees C, binding is linked to a large favourable enthalpy change [Delta H degrees =-69.0 kJ/mol (-16.5 kcal/mol)] and a small entropic penalty [ T Delta S degrees =-9.6 kJ/mol (-2.3 kcal/mol)]. These characteristics, and the high affinity relative to that of 3 S -HMG-CoA ( K (d) approximately 6.6 microM), are discussed in relation to the crystal structures of complexes with HMG-CoAR.

Preclinical and clinical pharmacology of Rosuvastatin, a new 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor.

Rosuvastatin (formerly ZD4522) is a new 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor (statin) with distinct pharmacologic properties. Compared with most other statins, it is relatively hydrophilic, similar in this respect to pravastatin. Rosuvastatin has been shown to be a comparatively potent inhibitor of HMG-CoA reductase activity in a purified preparation of the catalytic domain of the human enzyme, as well as in rat and human hepatic microsomes. In rat hepatocytes, rosuvastatin was found to have significantly higher potency as an inhibitor of cholesterol synthesis than 5 other statins. Rosuvastatin was approximately 1,000-fold more potent in rat hepatocytes than in rat fibroblasts. Further studies in rat hepatocytes demonstrated that rosuvastatin is taken up into these cells by a high-affinity active uptake process. Rosuvastatin was also taken up selectively into the liver after intravenous administration in rats. Potent and prolonged HMG-CoA reductase inhibitory activity has been demonstrated after oral administration to rats and dogs. Pharmacokinetic studies in humans using oral doses of 5 to 80 mg showed that maximum plasma concentrations and areas under the concentration-time curve are approximately linear with dose. The terminal half-life is approximately 20 hours. Studies with human hepatic microsomes and human hepatocytes have suggested little or no metabolism via the cytochrome P-450 3A4 isoenzyme. On the basis of these observations, it is suggested that rosuvastatin has the potential to exert a profound effect on atherogenic lipoproteins.

A novel series of 4-piperidinopyridine and 4-piperidinopyrimidine inhibitors of 2,3-oxidosqualene cyclase-lanosterol synthase.

A novel series of 4-piperidinopyridines and 4-piperidinopyrimidines showed potent and selective inhibition of rat 2,3-oxidosqualene cyclase-lanosterol synthase (OSC) (e.g. 26 IC(50) rat = 398 +/- 25 nM, human = 112 +/- 25 nM) and gave selective oral inhibition of rat cholesterol biosynthesis (26 ED(80) = 1.2 +/- 0.3 mg/kg, n = 5; HMGCoA reductase inhibitor simvastatin ED(80) = 1.2 +/- 0.3 mg/kg, n = 5). The piperidinopyrimidine OSC inhibitors have a significantly lower pK(a) than the corresponding pyridine or the previously reported quinuclidine OSC inhibitor series. This indicates that other novel OSC inhibitors may be found in analogues of this series across a broader pK(a) range (6.0-9.0). These series may yield novel hypocholesterolemic agents for the treatment of cardiovascular disease.

Quinuclidine inhibitors of 2,3-oxidosqualene cyclase-lanosterol synthase: optimization from lipid profiles.

Novel 3-substituted quinuclidine inhibitors of cholesterol biosynthesis are reported. Compounds were optimized against oxidosqualene cyclase-lanosterol synthase (OSC) inhibition in vivo, rather than by the conventional optimization of structure-activity relationship information based on in vitro OSC inhibition. Thus, examination of HPLC lipid profiles from orally dosed rats showed cholesterol biosynthetic intermediates and whether cholesterol levels were reduced. A new substituted quinuclidine pharmacophore 18a-c was rapidly found for the inhibition of OSC, and the most promising inhibitors were validated by the confirmation of potent OSC inhibition. Compound 16 gave an IC50 value of 83 +/- 11 nM for human and an IC50 value of 124 +/- 14 nM, for rat, coupled with oral and selective inhibition of cholesterol biosynthesis derived from OSC inhibition (rat, ED50 = 1.3 +/- 0.7 mg/kg, n = 5; marmoset, 15 mg/kg dose, n = 3, caused complete inhibition). These 3-substituted quinuclidines, which were derived from a quinuclidine series previously known to inhibit cholesterol biosynthesis at the squalene synthase step, may afford a novel series of hypocholesterolemic agents acting by the inhibition of OSC.

Oxidized low-density lipoproteins inhibit endothelium-dependent relaxations in isolated large and small rabbit coronary arteries.

1. Previous studies suggest that oxidatively modified low-density lipoproteins (oxLDL) contribute to the impairment of endothelium-dependent vasodilation in the large arteries of hypercholesterolaemic animals, whereas this may not be the case with regard to the impairment of coronary resistance vessels. For this reason, the effect of lipoproteins on coronary resistance arteries has been examined in this study. 2. The influence of lipoproteins on endothelium-dependent relaxation induced by acetylcholine (ACh) or sodium nitroprusside in PGF2 alpha-preconstricted rings from the large (1st order branch) and small coronary arteries (3rd order branch) and the aorta of New Zealand White rabbits, was investigated. 3. The sensitivity to ACh was greater in the large compared with the small diameter coronary arteries. 4. Endothelium-dependent relaxations were unaffected by native LDL. Oxidized LDL (0.5 and 1 mg protein mL-1) caused a reversible inhibition of relaxations in both preconstricted small and large coronary arteries which was overcome at high ACh concentrations. Similar inhibitions were found in the aorta. 5. Endothelium-independent relaxations elicited by sodium nitroprusside in the large and small coronary arteries were unaffected by the oxidized lipoproteins, indicating that soluble guanylate cyclase activity was unaltered. 6. It is concluded that inhibition of endothelium-dependent relaxation in the small diameter coronary arteries in hypercholesterolaemia may arise from products of oxidative modification of LDL present in the artery itself or released upstream from proximal lesions.

Synthesis and activity of a novel series of 3-biarylquinuclidine squalene synthase inhibitors.

Quinuclidines with a 3-biaryl substituent are a new class of potent, orally active squalene synthase (SQS) inhibitors. Variants around these rigid structures indicate key structural requirements for cationic SQS inhibitors. Thus the lower in vitro potency found for quinuclidines bearing 3-substituents, which did not overlay the biphenyl group of 3-(biphenyl-4-yl)-3-hydroxyquinuclidine (2) (IC50 = 16 nM, rat microsomal SQS), implied a directional requirement for the 3-substituent. Similarly, the lower potency of the 3-terphenyl analogue 6 (IC50 = 370 nM) indicated size constraints for this substituent. In compounds with a linking group between the quinuclidine and biphenyl ring, linking groups of lower lipophilicity were less well tolerated (e.g., 17, CH2CH2, IC50 = 5 nM vs 19, NHCO, IC50 = 1.2 microM). Replacement of the distal phenyl ring of 2 with a more polar pyridine heterocycle caused a reduction in in vitro potency. In general, good in vivo activity in the rat was restricted to 3-hydroxy analogues, with the 3-[4-(pyrid-4-yl)phenyl] derivative 39 (IC50 = 161 nM) showing the best inhibition (following oral dosing) of cholesterol biosynthesis from mevalonate (ED50 = 2.7 mg/kg).

Inhibition of squalene synthase of rat liver by novel 3' substituted quinuclidines.

Squalene synthase (SQS) is a key enzyme in the biosynthetic pathway for cholesterol and is a target for improved agents to lower plasma levels of low-density lipoprotein (LDL). A series of novel 3' substituted quinuclidines have been discovered as inhibitors of the rat liver microsomal enzyme. In this study, we demonstrate the inhibitory effects in vitro and in vivo, of two examples of the series. When microsomes were preincubated with compounds, before addition of substrate, both 3-(biphenyl-4-yl)quinuclidine (BPQ) and 3-(biphenyl-4-yl)-3-hydroxyquinuclidine (BPQ-OH) were found to cause biphasic inhibition of the enzyme with apparent inhibition constants (K'i) for the sensitive phases of 12 nM and 15 nM, respectively. The K'i values for the insensitive phases were 1.8 microM and 2.9 microM, respectively. The two examples inhibited equally both steps of the SQS-catalysed reaction, as shown by parallel inhibition of 3H+ release and labelled squalene formation from [1-3H]farnesyl pyrophosphate (FPP). BPQ and BPQ-OH were shown to be inhibitors of hepatic sterol synthesis from mevalonate with ED50 values of 10.6 and 7.1 mg/kg, respectively, after acute oral administration to the rat. BPQ-OH was chosen for further study and, to determine its selectivity of effect on the mevalonate pathway in vivo, the effect of a dose of 70 mg/kg on the pattern of labelled mevalonate incorporation into the various lipid fractions of the rat liver was examined. As expected, the incorporation into squalene and sterol products was inhibited by about 70%. An appearance of label in fractions corresponding to farnesyl and geranylgeranylpyrophosphates, as well as the corresponding alcohols, was observed in treated but not control animals. In addition, the administration of compound resulted in the appearance of peaks of mevalonate-derived radioactivity in an acidic fraction believed to represent metabolites of farnesol. Such results are consistent with inhibition of the mevalonate pathway at, and not before, SQS. In contrast, there was a significant increase in the incorporation of labelled mevalonate into ubiquinone 10, and the synthesis of dolichols was apparently unchanged. The results suggest a specific effect of BPQ-OH on rat liver SQS. The compound is, therefore, an interesting lead for further investigation of this class of compounds.

Inhibition of squalene synthase in vitro by 3-(biphenyl-4-yl)-quinuclidine.

Squalene synthase (SQS) catalyses a step following the final branch in the pathway of cholesterol biosynthesis. Inhibition of this enzyme, therefore, is an approach for the treatment of atherosclerosis with the potential for low side effects. We have characterised the inhibition of rat liver microsomal SQS by 3-(biphenyl-4-yl)quinuclidine (BPQ). BPQ follows slow binding kinetics in that the rate of accumulation of product decreases with time if the inhibitor is added when the assay is started. Preincubation of BPQ and SQS leads to a biphasic dose-response where accumulation of product is linear with time only for the sensitive phase. When the farnesyl pyrophosphate (FPP) substrate is present at 19.6 microM, approximately 77% of the SQS activity is sensitive to the inhibitor (vOs) and the remainder is insensitive (vOi). The apparent inhibition constants (K'i values) are respectively K'is = 4.5 nM and K'ii = 1300 nM. Similar biphasic behaviour is exhibited by other inhibitors and in microsomes prepared from human and marmoset liver. As the concentration of FPP is reduced below 19.6 microM, there is a decrease in the relative contribution from vOi. Conversely, the value of K'is for BPQ remains constant when the FPP concentration is changed, showing noncompetitive kinetics with respect to this substrate. Possible causes of the observed kinetics are discussed. Inhibition by BPQ is said to follow tight binding kinetics because the value of K'is is similar to the concentration of inhibitor binding sites. Thus, to avoid an artefactual variation in potency when the enzyme concentration is varied, it is necessary to allow for the effects of depletion of free inhibitor. Furthermore, estimates of potency that average activity across the two phases are influenced by the relative contributions of each phase. These contributions differ according to the FPP concentration and the species used as the source of microsomes. Thus, it is necessary to separate the phases to compare measurements made in different experiments. Our observations indicate that careful experimental design and data analysis are required to characterise the kinetics of SQS inhibitors.

Lipoprotein fractions and antithrombin III consumption during clotting.

Plasma and serum antithrombin levels were measured in functional (initial rate measurement) and immunological assays together with serum lipid levels in normal subjects and patients with coronary artery disease. Specific antithrombin activity in plasma showed a negative correlation with triglyceride levels. The consumption of antithrombin activity during blood clotting was negatively correlated with both serum total triglyceride and heparin precipitable lipoprotein and positively correlated with serum high density lipoprotein cholesterol. Different blood lipoprotein fractions may influence the activity of the antithrombin III molecule.

Relationship between plasma high-density lipoprotein concentrations and lipoprotein lipase and hepatic lipase activities in children with hyperlipidaemia.

1. Significant positive correlations were found between the lipoprotein lipase and hepatic lipase activities of post-heparin plasma samples and plasma high-density-lipoprotein (HDL) cholesterol concentrations in 21 children with hyperlipidaemia and six normal adult males. 2. A significant positive correlation was also observed between the two lipase activities and the ratio of HDL cholesterol to apoprotein AI (apo AI) concentrations. 3. These findings provide further evidence that a significant proportion of HDL and possibly the HDL, subfraction is formed during the clearance of triglyceride-rich lipoproteins.

Comparison of guinea-pig serum lipoproteins after iodination by two different methods.

1. Guinea-pig low-density lipoproteins were isolated by ultracentrifugation and iodinated either by the IC1 method or by the chloramine-T procedure. 2. The efficiency of labelling by both methods was essentially the same. 3. When the two products were compared by ultracentrifugation, gel chromatography and immunodiffusion analysis, no significant difference in their properties was detected. 4. When they were compared by gradient-gel electrophoresis, aggregates were found in the product of the IC1 method, but not in the lipoprotein iodinated by the chloramine-T process. 5. Both products were metabolized by the guinea pig with essentially the same fractional catabolic rate. 6. The fractional catabolic rate of lipoprotein iodinated by the chloramine-T method was not significantly different from that of lipoprotein biologically labelled in the protein moiety with [75Se]selenomethionine. 7. It is concluded that the products of both methods of iodination are almost equally acceptable, provided that the optimum conditions for the chloramine-T reaction are carefully established.