Acute and chronic effects on cholesterol biosynthesis of LDL-apheresis with or without concomitant HMG-CoA reductase inhibitor therapy

To determine the acute and long-term effects of low density lipoprotein (LDL) reduction on cholesterol biosynthesis, we studied changes in the cholesterol precursors mevalonic acid (MVA) and lathosterol in patients with heterozygous familial hypercholesterolemia undergoing LDL-apheresis. Long-term LDL-apheresis in eight patients resulted in slight but insignificant increases in plasma MVA levels and lathosterol/cholesterol (L/C) ratios over 18 months. In short-term studies, six patients not on drugs and six patients treated with lovastatin or pravastatin had blood taken immediately before and after LDL-apheresis, and afterwards on days 1, 2, 3, 5, and 7. Plasma L/C ratios and MVA concentration did not change significantly on the first day after LDL-apheresis in those not on statin therapy (1.11 +/- 0.08 vs. 1.40 +/- 0.18, and 9.2 +/- 1.3 vs. 9.1 +/- 0.6 ng/ml, respectively) but increased in the statin-treated group (from 0.78 +/- 0.09 to 1.55 +/- 0.21, P = 0.003 and from 5.0 +/- 0.7 to 11.0 +/- 1.6 ng/ml, P = 0.008, respectively). There was no clear correlation between the changes in either of these precursors and the extent of reduction of total cholesterol by LDL-apheresis, but there was a strong inverse correlation with the post-apheresis LDL-cholesterol level (r = -0.77, P = 0.002 for L/C ratio; r = -0.75, P = 0.003 for MVA). Post-apheresis changes in L/C ratio and MVA were mutually correlated (r = 0.68. P = 0.01). We conclude that LDL-apheresis stimulates cholesterol biosynthesis transiently despite concomitant therapy with an HMG-CoA reductase inhibitor, the degree of stimulation being inversely related to the level to which the LDL-cholesterol was reduced.

Intra-amniotic methotrexate versus CO2 laser laparoscopic salpingotomy in the management of tubal ectopic pregnancy--a prospective randomized trial

Tubal pregnancy can be safely and effectively managed by MTX or CO2 laparoscopic salpingotomy techniques. Methotrexate may be superior because of its simplicity, requiring only basic laparoscopic skills, whereas laparoscopic salpingotomy necessitates operative laparoscopic input.

The effect of growth hormone replacement on serum lipids, lipoproteins, apolipoproteins and cholesterol precursors in adult growth hormone deficient patients

OBJECTIVE

Adult patients with growth hormone deficiency are thought to be at higher risk of mortality from cardiovascular disease. We therefore investigated the effect of recombinant human growth hormone (rhGH) replacement therapy on fasting serum concentrations of lipids, lipoproteins and cholesterol precursors in adult growth hormone deficient patients.

DESIGN

Double-blind placebo controlled trial. Patients were randomly allocated to placebo or rhGH replacement therapy (0.018 U/kg/day for 1 month followed by 0.036 U/kg/day for 1 month).

PATIENTS

Eighteen patients with severe growth hormone deficiency.

MEASUREMENTS

Fasting lipid, lipoprotein and cholesterol precursors (lathosterol and mevalonic acid) were measured at baseline and after 2 months.

RESULTS

In the rhGH treated group there was a significant fall in serum cholesterol (P < 0.01) (6.44 +/- 0.49 to 5.71 +/- 0.48 mmol/l), LDL cholesterol (P < 0.02) (4.29 +/- 0.49 to 3.62 +/- 0.44 mmol/l), LDL cholesterol/HDL cholesterol ratio (P < 0.02) (3.99 +/- 0.62 to 3.26 +/- 0.39), apolipoprotein B (P < 0.01 (1.30 +/- 0.11 to 1.15 +/- 0.11 g/l) and mevalonic acid (P < 0.05) (13.4 +/- 10.96 to 6.21 +/- 1.91 micrograms/l). There were no significant changes in triglycerides, HDL cholesterol, apolipoprotein A1, lipoprotein (a) or lathosterol concentrations. In the GH treated group the rise in serum insulin was inversely correlated with the fall in cholesterol (P < 0.05), LDL cholesterol (P < 0.01) and apolipoprotein B (P < 0.01). There were no significant changes in any of the measured variables in the placebo group.

CONCLUSION

We conclude that GH may be involved in the regulation of lipid and lipoprotein metabolism and that rhGH replacement therapy of adult GHD patients is associated with beneficial changes in lipid and lipoprotein profiles. The reduction in mevalonic acid is consistent with up-regulation of hepatic LDL receptors caused by GH and this may explain the fall in LDL cholesterol and apolipoprotein B concentrations.

Beta HCG levels after conservative treatment of ectopic pregnancy: is a plateau normal?

In 32 women with unruptured tubal ectopic pregnancies we undertook conservative laparoscopic treatment [local injection of 20 mg methotrexate (n = 18), laser salpingotomy (n = 14)]. The results of serial quantitative beta HCG measurement were followed until either a negative level was reached or until rising levels necessitated alternative/additional therapy. Plateaued values of beta HCG were observed in both the successful (n = 16) and the unsuccessful cases (n = 5). To test the hypothesis that daily variation in the assay could account for some or all of the observed plateaued results in successful cases, the sera were retested serially on the same 'run'. In only one case did laboratory variation account for the observed plateau. The clinical implications of the findings are discussed. We conclude that serially monitored beta HCG results after conservative treatment of ectopic pregnancy may show plateaued values without indicating failure of treatment.

Soil fertility factors in relation to oesophageal cancer risk areas in Transkei, southern Africa

Soil samples were collected during certain years for the period 1982-89 from high- and low-risk areas for oesophageal cancer in Transkei, southern Africa. These samples were taken either from cultivated soils under maize monoculture, or from uncultivated soils (1989 only) adjacent to the maize fields. Analyses of mineral elements in the soil samples were performed at two independent laboratories. Furthermore, soil and maize leaf samples, from field trials in a high- and a low-risk area for oesophageal cancer were analysed. The results from this study do not agree with those reported previously for Transkei. Cultivated soils in both high- and low-risk areas were found to be highly fertile. The levels of Mn, Ni, Mg, Ca, K and soil pH were significantly higher, and Al, Fe and organic matter significantly lower in the high-risk compared with the low-risk area. Leaf analysis, although not tested statistically, indicated higher levels of Mn K, Ca and Fe, and lower levels of P, in the high-risk area.

Management of hyperlipidaemia: guidelines of the British Hyperlipidaemia Association

There is considerable evidence to suggest that the identification and treatment of dyslipidaemia will reduce the risk of premature CHD, i.e. before the age of 65. Diagnosis of the cause of raised plasma lipid levels will enable appropriate decisions to be taken with regard to management. The cornerstone of treatment is nutritional counselling and attention to other major risk factors for CHD, particularly smoking and hypertension. For a small percentage of patients with severe hyperlipidaemia drug therapy is indicated. Appropriate drug choices need to be made based on the particular lipid abnormality to be treated. In general those patients with clinical vascular disease are treated more aggressively than those where the aim is primary prevention. More research is needed to determine individual risk more precisely and to allow proper targeting of therapy. Genetic factors, qualitative changes in lipoproteins, lipoprotein (a), fibrinogen, and other coagulation and thrombotic factors are likely to be important in individual risk assessment. There is no doubt that more information is needed from prospective studies of lipid-lowering therapy in terms of risk benefit for affected individuals. Hopefully the major studies currently underway will fill some of the gaps in our knowledge. Until then aggressive therapy with drugs should be reserved for those at highest risk where the benefit is likely to be greatest.

Lipoprotein(a) and accelerated coronary artery disease in cardiac transplant recipients

High concentrations of serum lipoprotein(a) (Lp(a)) are associated with an increased risk of atherosclerotic vascular disease in the nontransplanted population. However, its relation with accelerated coronary artery disease (CAD) in cardiac transplant recipients has not been reported. We measured serum Lp(a) in 130 cardiac transplant recipients undergoing routine follow-up, which included annual coronary angiography. The median Lp(a) concentration in 33 patients with CAD was 71 mg/dl, which was significantly higher than the corresponding value of 22 mg/dL in the 97 patients without CAD (p = 0.0006). Multivariant analysis showed the serum Lp(a) value to be a higher significant risk factor for CAD irrespective of the other factors included in the regression analysis. Thus a high concentration of serum Lp(a) is an important, independent risk factor for the development of accelerated CAD in transplant recipients.

Maxepa versus bezafibrate in hyperlipidemic cardiac transplant recipients

Accelerated coronary artery disease is the most serious obstacle to long-term survival in cardiac transplant recipients. Lipid abnormalities are found frequently in these patients, and there is growing evidence that even minimally increased levels of cholesterol and triglycerides contribute to the development of accelerated coronary artery disease. However, the optimal lipid-lowering therapy after cardiac transplantation has not been defined. In an open, randomized study, the efficacy and safety of bezafibrate (400 mg/day) and fish oil (Maxepa) (10 g/day) for 3 months were compared in 87 cardiac transplant recipients with serum total cholesterol > 6.5 or triglycerides > 2.8 mmol/liter, or both. After 1 month, bezafibrate reduced total cholesterol by 13%, low-density lipoprotein cholesterol by 20% and apolipoprotein B by 13%. It also increased apolipoprotein A1 and high-density lipoprotein cholesterol by 12 and 20%, respectively, and significantly reduced fibrinogen at 3 months. Maxepa had no significant effect on these variables, but was as effective as bezafibrate in reducing triglycerides (36 and 31%, respectively). Both drugs increased lipoprotein (a) to a similar extent, and bezafibrate significantly increased serum creatinine. These results suggest that bezafibrate has better lipid-, apolipoprotein- and hemostatic modifying properties than does Maxepa, but its potentially adverse effect on renal function needs further investigation.

Normal levels of lipoproteins including lipoprotein(a) after liver-heart transplantation in a patient with homozygous familial hypercholesterolaemia

A 33-year-old female with severe diffuse coronary artery disease and left ventricular outflow tract obstruction secondary to homozygous familial hypercholesterolaemia underwent liver and heart transplantation. During a post-operative follow-up period of 13 months, apart from one episode of cardiac rejection at 3 weeks, she has remained well and without evidence of accelerated coronary disease on angiography. By 3 months after transplantation serum total cholesterol, low density lipoprotein cholesterol, apolipoprotein B and lipoprotein(a) levels had decreased and apolipoprotein A-I and high density lipoprotein cholesterol levels had increased, all to within the normal range. These changes were accompanied by marked regression of xanthomata and were maintained at 13 months. Liver transplantation provides an effective means of correcting serum lipids in patients with homozygous familial hypercholesterolaemia and is an important adjunct to cardiac transplantation.

Phaeochromocytomas as a cause of hypotension

A patient presented with apparent septicaemic shock. Full invasive cardiovascular monitoring revealed systemic hypotension, high normal cardiac output, and a low systemic vascular resistance. Maintenance of systemic vascular resistance and blood pressure was shown to be highly dependent on noradrenaline. Subsequent investigation revealed the presence of a phaeochromocytoma producing adrenaline. The mechanisms by which phaeochromocytomas may produce hypotension are discussed.

Possible mechanism and treatment of o,p'DDD-induced hypercholesterolaemia

Ortho,para,dichlorodiphenyl dichloroethane (o,p'DDD, Mitotane (Roussell)) is used as an adrenolytic drug to reduce adrenocortical mass and circulating cortisol levels in Cushing's syndrome but has the unwanted side-effect of inducing hypercholesterolaemia. This paper examined the mechanism of that effect in 30 patients with Cushing's syndrome treated with o,p'DDD during the past 10 years. o,p'DDD increased serum cholesterol by 68 per cent, mainly by increasing LDL-cholesterol. The latter effect was not due to impaired binding of LDL to its receptor, as shown in vitro using cultured fibroblasts. Increases in plasma mevalonic acid during o,p'DDD administration were suggestive of increased cholesterol synthesis, this effect being reversed by simvastatin. These findings suggest that o,p'DDD causes hypercholesterolaemia by increasing cholesterol synthesis. It is proposed that this effect is due to the drug's known ability to block cytochrome P450-mediated reactions, thus impairing the formation of oxysterols responsible for down-regulating hepatic cholesterol synthesis. Treatment with simvastatin, an inhibitor of cholesterol synthesis, reverses the hyperlipidaemia and enables o,p'DDD therapy to be maintained without increasing cardiovascular risk.

Effective reduction of plasma LDL levels by LDL apheresis in familial defective apolipoprotein B-100

The clinical response to long-term reduction of the plasma LDL cholesterol concentration was studied in a man with severe coronary artery disease associated with familial defective apolipoprotein B-100 (FDB). Plasma exchange repeated at 2-week intervals, combined with lipid-lowering drugs, led to remission of angina and improved exercise test performance. A similar clinical response was achieved after LDL apheresis with dextran sulphate columns repeated once every 2 weeks in combination with drug treatment. The reduction in plasma LDL cholesterol level brought about by LDL apheresis was at least as marked in the FDB patient as in 5 patients with familial hypercholesterolaemia. We conclude that FDB patients with coronary artery disease may derive clinical benefit from prolonged reduction of their plasma cholesterol levels and that LDL containing apo B-100 in which arginine at position 3500 is replaced by glutamine is removed from plasma by dextran sulphate columns as efficiently as is normal LDL.

Characterization of deletions in the LDL receptor gene in patients with familial hypercholesterolemia in the United Kingdom

A sample of 200 patients with a clinical diagnosis of heterozygous (189) or homozygous (11) familial hypercholesterolemia (FH) attending lipid clinics in the London area have been screened for the presence of major gene defects in the low density lipoprotein (LDL) receptor gene by Southern blotting of genomic DNA with specific probes. This study is part of a project to determine the frequency of known mutations in the LDL receptor gene in this population. A new polymorphism for the enzyme Bgl II was identified by hybridization with a probe specific for the promoter plus exon 1 of the LDL receptor gene. The observed frequency of the rare allele, characterized by a Bgl II fragment of 13 kb compared with 10 kb for the common allele, was 0.08 in this group of FH patients. Several individuals who were heterozygous for the rare allele were also heterozygous for a mutation elsewhere in the LDL receptor gene that is known to cause FH. Eight different mutations, seven deletions and one duplication, were detected in a total of nine patients, accounting for 4.5% of the mutant alleles in this group. Three of the mutations are apparently identical to deletions that have been described previously in FH patients of British or European origin, while the remaining five have not been described. Two of these were in patients of Polish and Asian Indian origin, while the other three were in patients of apparently British ancestry.

Laboratory facilities for investigating lipid disorders in the United Kingdom: results of the British Hyperlipidaemia Association survey

AIMS

To determine the availability of facilities for the investigation of hyperlipidaemia in the United Kingdom.

METHODS

A questionnaire was sent to all health districts in the United Kingdom.

RESULTS

The response rate was 81%. All laboratories used enzymatic techniques to measure serum triglyceride and cholesterol concentrations, although there were differences in standardisation procedures. Reference ranges for serum lipids were quoted by 58% of laboratories while 50% quoted "desirable limits". Almost half specified that fasting blood samples were required. High density lipoprotein cholesterol concentrations were estimated by 75% and apolipoproteins AI and B by 14% of laboratories; there were differences in specimen type and considerable diversity in procedures used for measurement.

CONCLUSIONS

Many laboratories were unaware of current recommendations for screening for hypercholesterolaemia in the community. The present survey indicated an urgent need for the introduction of better reference methods, standardisation, and quality assurance procedures before apolipoproteins become a routine part of coronary heart disease risk assessment.

Response to cholesterol-lowering drugs in familial defective apolipoprotein B-100

The effect of cholestyramine and simvastatin, given separately or in combination, on serum lipid concentrations in 11 patients with heterozygous familial defective apolipoprotein B-100 was compared with that in 11 matched patients with heterozygous familial hypercholesterolaemia. In both groups of patients there was a substantial fall in serum lipid levels in response to treatment. There were no significant differences between the reductions in serum total or low-density lipoprotein cholesterol levels in the two groups.

Relationship of immunosuppression and serum lipids to the development of coronary arterial disease in the transplanted heart

Coronary arterial disease in the cardiac allograft has emerged as the most serious long term complication of cardiac transplantation. The influence of patient-related and other potential risk factors on the development of coronary arterial disease at 1 year subsequent to cardiac transplantation was examined in 207 recipients. The mean age of donors in patients with coronary arterial disease was 28.5 +/- 9.5 years, compared to 22.6 +/- 7.9 years in patients without coronary arterial disease (P less than 0.01). Eight of the 35 patients who received immunosuppression by means of prednisone and azathioprine developed coronary arterial disease compared to 5 of the 172 patients who were treated with cyclosporin and azathioprine without routine oral prednisone (P less than 0.01). The relationship of levels of serum lipids to the subsequent development of coronary arterial disease was investigated in 95 patients with angiographically normal coronary arteries one year after cardiac transplantation. The cumulative probability of coronary arterial disease in those with total cholesterol greater than 5.8 mmol/l was 9.3% at 2 years (n = 40), 24.4% at 4 years (n = 21) and 45% at 4 years (n = 9) compared with 4.3% at 2 years (n = 45), 7.4% at 3 years (n = 32) and 14% at 4 years (n = 14) in those with a total cholesterol less than 5.8 mmol/l (P less than 0.05). Similarly, the incidence of coronary arterial disease was increased in patients with serum triglyceride greater than 1.4 mmol/l (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitation of plasma mevalonic acid using gas chromatography-electron capture mass spectrometry

Circulating concentrations of mevalonic acid (MVA) change in parallel with, and may be used as a marker of cholesterol biosynthesis. Plasma MVA levels have been quantified using a sensitive and specific capillary gas chromatography-electron capture mass spectrometric assay. The detection limit for MVA in plasma is 100 pg/ml; the intra-assay variation is 5.11%; the inter-assay variation is 7.7%. Using this assay, the mean plasma MVA in 15 normolipidemic subjects was 2.37 +/- 1.2 ng/ml (range 0.41-5.31 ng/ml). Administration of 40 mg of simvastatin (an HMG-CoA reductase inhibitor) significantly accenutated the diurnal decrease in plasma MVA levels. This assay may be useful in investigating cholesterol synthesis rates in different dyslipidemias and individual responses of HMG-CoA reductase-inhibiting drugs.

Cholesterol flux in cholesterol ester-loaded macrophages in an in vitro perfusion system

Cholesterol ester-loaded J774 macrophages attached to microcarrier beads were perfused or incubated with lipoproteins in vitro. Cholesterol influx was reduced by decreasing LDL cholesterol, efflux was promoted by increasing HDL cholesterol or by adding apolipoprotein A-I/phosphatidylcholine complexes to the perfusate or incubation medium. Addition of sera obtained from patients after LDL apheresis or plasma exchange resulted in much smaller increments in cell cholesterol than pretreatment sera, due to decreased influx, but efflux was unchanged despite the reduction in HDL cholesterol by plasma exchange. These data suggest that extracorporeal cholesterol removal promotes mobilization of intracellular cholesterol ester mainly by reducing cholesterol influx.

Methotrexate injection of tubal ectopic pregnancy. A logical evolution?

OBJECTIVE

To test the efficacy and possible side effects of a single 20 mg dose of methotrexate injected at the time of laparoscopy, in the treatment of tubal ectopic pregnancy.

DESIGN

The study was a non-randomised non-blinded prospective clinical trial.

SETTING

The study was carried out at two tertiary referral hospitals.

PATIENTS

Eighteen patients with unruptured tubal ectopic pregnancies and in a stable haemodynamic condition were offered entry into the study and all of these agreed.

INTERVENTIONS

At diagnostic laparoscopy, 20 mg of methotrexate in 0.8 mL was injected by fine needle in or around the ectopic gestation.

MAIN OUTCOME

Patients were followed up as outpatients by serial blood tests until resolution of the ectopic pregnancy was demonstrated by a return of the level of beta-human chorionic gonadotrophin to the normal range.

RESULTS

There was one failure of treatment. The ectopic pregnancy resolved in the remaining 17 patients. There were no side effects attributable to methotrexate and tubal patency was demonstrated in the eight patients tested by hysterosalpingography.

Expression of IL-2 receptor p55 and p75 chains by human B lymphocytes: effects of activation and differentiation

Whilst B cells in human blood can be shown to express interleukin-2 receptor (IL-2R) p55 and p75 chains, using a high-sensitivity immunofluorescence procedure, fresh tonsil B cells did not show detectable levels of expression. Culture of tonsil B cells led to low levels of expression of the p55 chain of the IL-2R, an effect which was dependent on protein synthesis. The level of expression of IL-2R chains could be modulated by culturing in the presence of a number of factors which activate B cells. p55 levels were more readily modulated than p75 levels. IL-4 and combinations of IL-4 with anti-IgM, IL-2 or tumour necrosis factor-beta (TNF-beta) modulated p55 levels, but IL-5 did not. Changes in IL-2R expression were small when compared with other B-cell activation markers such as CD23. When unfractionated tonsil cells were activated with a polyclonal stimulus, the major change was the expression of p55 by T-cell blasts--p75 expression remained low in T and B cells, and p55 expression by B cells remained low.

CO2 laser laparoscopic salpingotomy for treatment of tubal ectopic pregnancies: potential limitations

Linear salpingotomy was performed on 16 patients using the CO2 laser laparoscopically directed. Median operating time was 60 minutes (range 40-100) and all patients were discharged on the first postoperative day. There were 4 patients in whom persistence of trophoblast activity was detected, 2 of whom were treated surgically and 2 by oral methotrexate therapy.

Primary hyperlipidaemia

It is estimated that over 60% of the variability in serum lipids is genetically determined, most of this variation being due to polygenic influences. Interaction between the latter and environmental factors is probably the commonest cause of hyperlipidaemia in the general population. Familial forms of hyperlipidaemia are usually more clearly defined, especially those which have a monogenic or dominant pattern of inheritance, but are less common. This type of disorder, exemplified by familial hypercholesterolaemia, is expressed independently of environmental influences. In contrast, in familial type III hyperlipoproteinaemia inheritance of the underlying gene defect is often insufficient to produce hyperlipidaemia unless additional environmental or genetic influences coexist. Rarely, hyperlipidaemia is recessively inherited, as in familial deficiency of lipoprotein lipase and of apolipoprotein CII. Primary hyperlipidaemias characterized by severe hypertriglyceridaemia predispose to acute pancreatitis whereas those disorders characterized by hypercholesterolaemia, apart from hyper alpha lipoproteinaemia, are associated with an increased risk of premature vascular disease.

CO2 laser laparoscopic salpingotomy for treatment of tubal ectopic pregnancies: potential limitations

Linear salpingotomy was performed on 16 patients using the CO2 laser laparoscopically directed. Median operating time was 60 minutes (range 40-100) and all patients were discharged on the first postoperative day. There were 4 patients in whom persistence of trophoblast activity was detected, 2 of whom were treated surgically and 2 by oral methotrexate therapy. Conservative techniques for the treatment of ectopic pregnancy have proliferated since 1953 being made possible because of the early presentation of patients and the more sensitive methods of intrauterine pregnancy detection. In the past decade laser technology has been added to the armamentarium of infertility surgeons and there have been 2 reports of its successful use in cases of ectopic pregnancy. The present study aimed to examine the application of this technique in our patient population and to investigate any associated problems.

Relation of serum lipoprotein(a) concentration and apolipoprotein(a) phenotype to coronary heart disease in patients with familial hypercholesterolemia

Familial hypercholesterolemia carries a marked increase in the risk of coronary heart disease (CHD), but there is considerable variation between individuals in susceptibility to CHD. To investigate the possible role of lipoprotein(a) as a risk factor for CHD, we studied the association between serum lipoprotein(a) levels, genetic types of apolipoprotein(a) (which influence lipoprotein(a) levels), and CHD in 115 patients with heterozygous familial hypercholesterolemia. The median lipoprotein(a) level in the 54 patients with CHD was 57 mg per deciliter, which is significantly higher than the corresponding value of 18 mg per deciliter in the 61 patients without CHD. According to discriminant-function analysis, the lipoprotein(a) level was the best discriminator between the two groups (as compared with all other lipid and lipoprotein levels, age, sex, and smoking status). Phenotyping for apolipoprotein(a) was performed in 109 patients. The frequencies of the apolipoprotein(a) phenotypes and alleles differed significantly between the patients with and those without CHD. The allele LpS2, which is associated with high lipoprotein(a) levels, was found more frequently among the patients with CHD (0.33 vs. 0.12). In contrast, the LpS4 allele, which is associated with low lipoprotein(a) levels, was more frequent among those without CHD (0.27 vs. 0.15). We conclude that an elevated level of lipoprotein(a) is a strong risk factor for CHD in patients with familial hypercholesterolemia, and the increase in risk is independent of age, sex, smoking status, and serum levels of total cholesterol, triglyceride, or high-density lipoprotein cholesterol. The higher level of lipoprotein(a) observed in the patients with CHD is the result of genetic influence.

HMG CoA reductase inhibitors as lipid-lowering agents: five years experience with lovastatin and an appraisal of simvastatin and pravastatin

The HMG CoA reductase inhibitors are the most effective drugs for treating hypercholesterolaemia currently available. They inhibit cholesterol synthesis and thus stimulate receptor-mediated uptake and degradation of low-density lipoprotein cholesterol by the liver. In 30 patients with severe hypercholesterolaemia administration of lovastatin alone or in combination with other lipid-lowering manoeuvres maintained reductions of 25 to 31 per cent in serum cholesterol over five years. The drug was easy to take and well tolerated, the only significant side effect being a reversible myopathy. Two similar compounds, simvastatin and pravastatin, exert comparable effects on serum lipids, including modest reductions in triglycerides and increases in high-density lipoprotein cholesterol. The use of these drugs seems likely to exert a beneficial effect on atherosclerosis.

Towards a new era: is coronary artery disease reversible?

There is increasing evidence that conventional lipid-lowering therapy can arrest the progression of coronary atherosclerosis. Trials are now under way to determine whether more radical reduction of low-density-lipoprotein cholesterol will reverse atherosclerosis and lead to regression of coronary lesions. The ability to effect such reductions has been markedly enhanced by the introduction into clinical practice of the 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors.

Lipid related consequences of intestinal malabsorption

The small intestine plays a key role in lipid metabolism by absorbing fat and synthesising apoproteins. Fat malabsorption secondary to intestinal disease results in abnormalities of lipoprotein concentration and composition and can lead to deficiency of essential fatty acids and fat-soluble vitamins. Malabsorption of fat can be induced by administration of neomycin and malabsorption of bile acids by administration of anion-exchange resins or by creating a partial ileal bypass. These induced forms of malabsorption are useful in the treatment of hyperlipidaemic patients liable to atherosclerosis.

Current management of hyperlipidaemia

Hyperlipidaemia is a major cause of coronary heart disease (CHD) and is especially prevalent in Britain. Prior to lipid-lowering therapy it is necessary to define the type of lipoprotein abnormality present and whether it is primary or secondary. Diet forms the initial treatment but additional drug therapy may be necessary in patients with established CHD or considered to be at high risk of developing CHD or rarely, in the case of severe hypertriglyceridaemia, acute pancreatitis.

Effect of enprostil on glucose and lipid metabolism in type 2 diabetes

Enprostil, a dehydro-prostaglandin E2 analogue, has been tested as treatment for peptic ulcer. Its effect on blood glucose and lipid metabolism in Type 2 diabetes was assessed in a randomized, double-blind trial. Fifteen patients on sulphonylurea therapy received, in addition, enprostil 35 micrograms or placebo thrice daily for two weeks, with a 2-week wash-out before crossover. Data from 12 patients were analysed. After a 530 Cal test breakfast at the end of active treatment, plasma glucose rose from a fasting concentration similar to that after the last placebo dose (10.5 +/- 0.8 (+/- SE) and 10.6 +/- 1.1 mmol l-1 respectively) to 1, 2 and 3 h concentrations which were 1.5 to 2.1 mmol l-1 lower than on placebo (2 h concentration 14.6 +/- 0.9 vs 16.4 +/- 1.3 mmol l-1, p less than 0.05). Serum fructosamine concentrations at the end of active treatment and placebo were 3.66 +/- 0.22 and 3.78 +/- 0.24 respectively (p = 0.051). No changes in fasting or post-prandial insulin concentrations were observed. After 2 weeks of enprostil, fasting serum triglyceride (1.76 +/- 0.18 mmol l-1) and total cholesterol (6.27 +/- 0.29 mmol l-1) concentrations were lower than after placebo (2.14 +/- 0.25 and 7.35 +/- 0.46 mmol l-1, p = 0.031 and p = 0.002, respectively), the latter effect being primarily due to reduced LDL-cholesterol.(ABSTRACT TRUNCATED AT 250 WORDS)

Apolipoprotein A-I gene polymorphisms: frequency in patients with coronary artery disease and healthy controls and association with serum apo A-I and HDL-cholesterol concentration

We have investigated the association between serum high density lipoprotein-cholesterol (HDL-C) and apo A-I concentration and the PstI and XmnI restriction fragment length polymorphisms of the apolipoprotein AI-CIII-AIV multigene complex. Two groups of subjects were examined. The first comprised 174 unrelated male patients under 60 years of age with angiographic evidence of coronary artery disease (CAD). Of this group 34 were non-North European. The second group consisted of 104 unrelated healthy male North European subjects aged under 60 and free from demonstrable CAD, who attended a health screening clinic in London. For the PstI polymorphism, the frequency of the rarer P2 allele was 0.12 in both the North European and non-North European patients and this was higher than in the control group (P2 frequency 0.06, P less than 0.05). Healthy individuals with the genotype P1P2 had higher levels of apo A-I but similar levels of HDL-C compared to those with the genotype P1P1. However, CAD patients with the genotype P1P2 had lower serum levels of apo A-I and significantly lower serum levels of HDL-C compared to those with the genotype P1P1 (0.85 mmol/l vs. 1.0 mmol/l, P less than 0.05). The allele frequencies of the XmnI polymorphisms were not significantly different in the control group and the group of North European patients, although within the sample of non-North European patients, the frequency of the X2 allele was significantly higher than that found in the North European controls (0.26 vs. 0.09). Patients with the genotype X1X2 had a higher mean serum concentration of HDL-C and apo A-I compared with patients with the genotype X1X1 (1.14 and 0.93 mmol/l for HDL-C, P less than 0.05; 147 and 123 mg/dl for apo A-I, P less than 0.05). Associations between HDL-C and apo A-I levels and PstI and XmnI genotype were similar in patients taking and not taking beta-blockers. The data show that genetic variation in the apo AI-CIII-AIV gene cluster is associated with coronary artery disease although only weakly, and suggest that the mechanism of this association may operate through an effect in determining the serum concentration of apo A-I and HDL-cholesterol.

Reappraisal of partial ileal bypass for the treatment of familial hypercholesterolemia

Eleven patients with heterozygous familial hypercholesterolemia (type IIa) were treated by partial ileal bypass. Postoperatively, mean total cholesterol levels fell by 26% at 1 month, and then rose steadily to 20% below preoperative levels of 20-24 months. The rise in cholesterol levels was due in part to an increase in high density lipoprotein (HDL) cholesterol with a resultant improvement in the HDL:LDL ratio (LDL, low density lipoprotein). Five patients had refractory hypercholesterolemia and were treated with lovastatin. One of them was treated with a combination of lovastatin and LDL-apheresis. All patients experienced diarrhea which improved with time, but two patients required reversal of their bypass for intractable gas bloat syndrome. Each received lovastatin to control recrudescence of hypercholesterolamia following reversal. Ten patients are alive and well, but one patient died after a myocardial infarction 55 months postoperatively. The advent of lovastatin and other HMG COA reductase inhibitors is likely to decrease the use of partial ileal bypass to treat familial hypercholesterolemia.

Restriction fragment length polymorphisms in the apo B gene in relation to coronary artery disease

We have determined the frequencies of the alleles at the EcoRI (E), XbaI (X) and PvuII (P) polymorphic restriction sites in the apo B gene in 124 white men with coronary artery disease (CAD) and in 146 white men free from CAD. The frequencies of the E- (restriction site absent) and X- alleles were both significantly higher in normocholesterolaemic men with CAD than in those without CAD, but the frequency of the P+ allele (restriction site present) was similar in the 2 groups. The frequency of the E- allele was significantly higher in CAD men with hypertriglyceridaemia than in normal men without hypertriglyceridaemia. In the normocholesterolaemic men without CAD, the mean serum cholesterol concentration was higher in those with genotype X++ than in those with genotype X--. Mean serum LDL-apo B and LDL-cholesterol concentrations did not differ significantly between men with different XbaI or EcoRI genotypes. Serum apo A-I levels differed significantly between normal men with different XbaI genotypes. Serum HDL-cholesterol levels differed significantly between CAD men with different XbaI genotypes. These results suggest that in white men the E- and X- alleles are in linkage disequilibrium with a nearby allele that is causally related to CAD. It is also possible that the amino acid substitution at position 4154 in apo B, brought about by the nucleotide change responsible for the EcoRI polymorphism, has a direct effect on the atherogenicity of LDL.

Genotypic and phenotypic variation in familial hypercholesterolemia

Familial hypercholesterolemia is characterized by an increase in low density lipoprotein (LDL) cholesterol, tendon xanthomata, and premature atherosclerosis. In homozygotes, phenotypic expression of the disorder is dominated by genotypic variation at the LDL-receptor gene locus, with other influences, like gender, exerting relatively little effect. In contrast, phenotypic variation in heterozygotes is influenced not only by the nature of the underlying gene mutation but also by gender, diet, and other forms of genetic polymorphism, including the apolipoprotein E genotype.