The role of the cholesteryl ester transfer protein in lipoprotein metabolism

Efficacy and safety of lomitapide in familial chylomicronaemia syndrome

BACKGROUND AND AIMS

Familial chylomicronaemia syndrome (FCS) is a rare autosomal recessive disorder, resulting in elevated triglycerides (TGs), abdominal pain and pancreatitis. Treatment options are limited. Lomitapide, a microsomal triglyceride transfer protein inhibitor, is approved for the treatment of homozygous familial hypercholesterolaemia. Whether its therapeutic use may be extended to FCS remains unknown. The aim of this study was to evaluate the efficacy and safety of lomitapide in adult patients with FCS.

METHODS

The open-label, single-arm 'LOCHNES' study of lomitapide in FCS enrolled patients >18 years with genetically confirmed FCS, elevated fasting TG ≥ 750 mg/dL and history of pancreatitis. Patients were administered lomitapide to the maximum tolerated dose for 26 weeks. The primary endpoint was the percent change in TGs from baseline to Week 26.

RESULTS

Eighteen patients were enrolled with median baseline TG levels 1803.5 mg/dL (97.5% CI, 1452-2391 mg/dL). At Week 26, median fasting TGs were reduced to 305 mg/dL (97.5% CI 219-801 mg/dL; 70.5% reduction); median lomitapide dose was 35 mg/day; 13 patients achieved TGs ≤750 mg/dL. Adverse events were mild to moderate and mainly related to gastrointestinal tolerability. Liver imaging at baseline and Week 26 revealed hepatic fat increases from median 12.0%-32.5%, while median hepatic stiffness remained normal. No patient experienced acute pancreatitis or severe abdominal pain during lomitapide treatment.

CONCLUSIONS

Lomitapide is effective and well tolerated in reducing TGs in FCS patients with a history of pancreatitis. Larger studies are warranted to determine lomitapide effectiveness in FCS.

Metabolic effects of cross-sex hormone therapy in transgender individuals in Taiwan

BACKGROUND

Transgender individuals often require gender-affirming interventions, such as endogenous sex hormone inhibition or gender-affirming hormone therapy (HT), while there is discordance between their body and gender identity. However, a recent study found that the incidence of cardiovascular events is higher in transgender patients receiving cross-sex HT. The aim of this study was to investigate the metabolic effects of an altered sex hormone profile.

METHODS

This retrospective study, conducted in a referral center in Northern Taiwan, analyzed metabolic changes over time in 65 trans masculine and 45 trans feminine persons. The transgender individuals were examined at 4 time points: before the gender affirming HT, as well as 3, 6, and 12 months following treatment.

RESULTS

Compared with baseline measurements, the trans masculine patients showed significant increases in body mass index (BMI) (22.6 ± 0.3 vs 23.3 ± 0.4 kg/m2; p < 0.001; t = 3M), low-density lipoprotein cholesterol (124.3 ± 3.7 vs 131.3 ± 3.9 mg/dL; p = 0.03; t = 12M), creatinine (0.75 ± 0.01 vs 0.83 ± 0.14 mg/dL; p < 0.001; t = 12M), and hemoglobin (13.5 ± 0.7 vs 15.2 ± 0.2 g/dL; p < 0.001; t = 12M), as well as decreased high-density lipoprotein cholesterol (57 ± 2.1 vs 51 ± 2.0 mg/dL; p < 0.001; t = 12M). The trans feminine patients had reduced low-density lipoprotein cholesterol (104.2 ± 3.2 vs 100.8 ± 3.5 mg/dL; p = 0.05; t = 3M), hemoglobin (14.0 ± 0.1 vs 13.5 ± 0.1 g/dL; p = 0.008; t = 12M), and creatinine (0.82 ± 0.01 vs 0.79 ± 0.14 mg/dL; p < 0.001; t = 3M) compared with baseline data. In addition, most of these metabolic effects persisted during the follow-up period.

CONCLUSION

This observational, retrospective study revealed that gender-affirming HT increased the relative cardiovascular risk in trans masculine individuals.

Targeting inflammation in metabolic syndrome

The metabolic syndrome (MetS) is comprised of a cluster of closely related risk factors, including visceral adiposity, insulin resistance, hypertension, high triglyceride, and low high-density lipoprotein cholesterol; all of which increase the risk for the development of type 2 diabetes and cardiovascular disease. A chronic state of inflammation appears to be a central mechanism underlying the pathophysiology of insulin resistance and MetS. In this review, we summarize recent research which has provided insight into the mechanisms by which inflammation underlies the pathophysiology of the individual components of MetS including visceral adiposity, hyperglycemia and insulin resistance, dyslipidemia, and hypertension. On the basis of these mechanisms, we summarize therapeutic modalities to target inflammation in the MetS and its individual components. Current therapeutic modalities can modulate the individual components of MetS and have a direct anti-inflammatory effect. Lifestyle modifications including exercise, weight loss, and diets high in fruits, vegetables, fiber, whole grains, and low-fat dairy and low in saturated fat and glucose are recommended as a first line therapy. The Mediterranean and dietary approaches to stop hypertension diets are especially beneficial and have been shown to prevent development of MetS. Moreover, the Mediterranean diet has been associated with reductions in total and cardiovascular mortality. Omega-3 fatty acids and peroxisome proliferator-activated receptor α agonists lower high levels of triglyceride; their role in targeting inflammation is reviewed. Angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and aldosterone blockers comprise pharmacologic therapies for hypertension but also target other aspects of MetS including inflammation. Statin drugs target many of the underlying inflammatory pathways involved in MetS.

Revising the high-density lipoprotein targeting strategies - insights from human and preclinical studies

In recent years, the high-density lipoprotein (HDL) hypothesis has been challenged. Several completed randomized clinical trials continue to fall short in demonstrating HDL, or at least HDL-cholesterol (HDL-C) levels, as being a consistent target in the prevention of cardiovascular diseases. However, population studies and findings in lipid modifying trials continue to strongly support HDL-C as a superb risk predictor. It is increasingly evident that the complexity of HDL metabolism confounds the use of HDL-C concentration as a unified target. However, important insights continue to emerge from the post hoc analyses of recently completed (i) fibrate-based FIELD and ACCORD trials, including the unexpected beneficial effect of fibrates in microvascular diseases, (ii) the niacin-based AIM-HIGH and HPS2-THRIVE studies, (iii) recombinant HDL-based as well as (iv) the completed CETP inhibitor-based trials. These together with on-going mechanistic studies on novel pathways, which include the unique roles of microRNAs, post-translational remodeling of HDL and novel pathways related to HDL modulators will provide valuable insights to guide how best to refocus and redesign the conceptual framework for selecting HDL-based targets.

How do elevated triglycerides and low HDL-cholesterol affect inflammation and atherothrombosis?

This review article summarizes recent research into the mechanisms as to how elevated levels of triglyceride (TG) and low levels of high- density- lipoprotein cholesterol (HDL-C) contribute to inflammation and atherosclerosis. Evidence supports the role of TG-rich lipoproteins in signaling mechanisms via apolipoproteins C-III and free fatty acids leading to activation of NFKβ, VCAM-1 and other inflammatory mediators which lead to fatty streak formation and advanced atherosclerosis. Moreover, the cholesterol content in TG-rich lipoproteins has been shown to predict CAD risk better than LDL-C. In addition to reverse cholesterol transport, HDL has many other cardioprotective effects which include regulating immune function. The "functionality" of HDL appears more important than the level of HDL-C. Insulin resistance and central obesity underlie the pathophysiology of elevated TG and low HDL-C in metabolic syndrome and type 2 diabetes. Lifestyle recommendations including exercise and weight loss remain first line therapy in ameliorating insulin resistance and the adverse signaling processes from elevated levels of TG-rich lipoproteins and low HDL-C.

Insulin resistance and coronary heart disease in nondiabetic individuals

The goal of this review was to summarize evidence supporting the view that insulin resistance/compensatory hyperinsulinemia play an important role in the pathogenesis of coronary heart disease (CHD) in nondiabetic individuals. Results of case-control and epidemiological studies in nondiabetic individuals will be reviewed to examine the link between insulin resistance/compensatory hyperinsulinemia, associated abnormalities, and CHD. The primary focus of the review will be on the central role that dyslipidemia plays in the link between insulin resistance/compensatory hyperinsulinemia and CHD. Additional issues to be addressed include the following: (1) the relationship among obesity, insulin resistance, and CHD; (2) a listing of other abnormalities that contribute to risk of CHD in insulin-resistant individuals; and (3) discussion of the importance of differential tissue insulin sensitivity in the development of abnormalities that increase CHD risk in insulin-resistant, nondiabetic individuals. The information will reflect the author's decision as to what issues are believed to be of particular relevance or less well appreciated concerning the complex relationship between insulin resistance and CHD. Resistance to insulin-mediated glucose disposal and hyperinsulinemia is a common finding in apparently healthy individuals and is associated with a number of abnormalities that greatly increase risk of CHD.

A survey of the genetics of stomach, liver, and adipose gene expression from a morbidly obese cohort

To map the genetics of gene expression in metabolically relevant tissues and investigate the diversity of expression SNPs (eSNPs) in multiple tissues from the same individual, we collected four tissues from approximately 1000 patients undergoing Roux-en-Y gastric bypass (RYGB) and clinical traits associated with their weight loss and co-morbidities. We then performed high-throughput genotyping and gene expression profiling and carried out a genome-wide association analyses for more than 100,000 gene expression traits representing four metabolically relevant tissues: liver, omental adipose, subcutaneous adipose, and stomach. We successfully identified 24,531 eSNPs corresponding to about 10,000 distinct genes. This represents the greatest number of eSNPs identified to our knowledge by any study to date and the first study to identify eSNPs from stomach tissue. We then demonstrate how these eSNPs provide a high-quality disease map for each tissue in morbidly obese patients to not only inform genetic associations identified in this cohort, but in previously published genome-wide association studies as well. These data can aid in elucidating the key networks associated with morbid obesity, response to RYGB, and disease as a whole.

[Can bariatric surgery cure metabolic syndrome?]

OBJECTIVES

To evaluate the impact of bariatric surgery on the metabolic syndrome (MS) and what are the criteria that contribute the most for its exclusion after surgery. The progress of leucometry was also analyzed.

METHODS AND PROCEDURES

47 obese women with MS were evaluated. All patients were operated with the Roux-en-Y vertical gastric bypass technique, with the insertion of a contention ring on the gastro-jejune anastomosis (Fobi-Capella). Patients were evaluated before and on the first year post-surgery.

RESULTS

Fasting glucose presented a relevant decrease at 3 months after surgery. After 12 months, all 20 patients who had DM2 or altered fasting glucose presented normal levels of fasting glucose and glicated hemoglobin, and none of them was using any anti-diabetic drug. Triglycerides levels were reduced by 49.2%, whereas HDL-cholesterol increased by 27.2%. Systolic and diastolic blood pressures were reduced by an average of 28.7 and 20.8 mmHg, respectively. Leucocytes counting fell from 7671/microL to 6156/microL. Fasting glucose, triglycerides, DBP, SBP and HDL-cholesterol were the variables that contributed most for the reduction of MS. At the end of the first year, elimination of MS occurred in 80.9% of the patients.

DISCUSSION

Bariatric surgery reduces resistance to insulin and consequently the cardiovascular risk factors.

The metabolic syndrome: is this diagnosis necessary?

Values of insulin-mediated glucose disposal vary continuously throughout a population of apparently healthy persons, and a difference of > or = 600% exists between the most insulin-sensitive and the most insulin-resistant persons. Approximately 50% of this variability can be attributed to differences in adiposity (25%) and fitness (25%), with the remaining 50% likely of genetic origin. The more insulin-resistant a person, the more likely that he or she will develop some degree of glucose intolerance, high triacylglycerol and low HDL concentrations, essential hypertension, and procoagulant and proinflammatory states, all of which increase the risk of cardiovascular disease (CVD). To identify persons at greater CVD risk because of these abnormalities, the World Health Organization, the Adult Treatment Panel III, and the International Diabetes Federation created a new diagnostic category, the metabolic syndrome. Although the components of the 3 versions of the metabolic syndrome are similar, the specific values for those components that define an abnormality are somewhat different, and the manner in which the abnormalities are used to make a positive diagnosis varies dramatically from version to version. This review will summarize the similarities in and differences between the 3 versions of the metabolic syndrome, point out that the clustering of components that make up all 3 definitions of the metabolic syndrome is not accidental and occurs only in insulin-resistant persons, develop the argument that diagnosing the metabolic syndrome in a person has neither pedagogical nor clinical utility, and suggest that the clinical emphasis should be on treating effectively any CVD risk factor that is present.

Compensatory hyperinsulinemia and the development of an atherogenic lipoprotein profile: the price paid to maintain glucose homeostasis in insulin-resistant individuals

The ability of insulin to stimulate glucose disposal varies sixfold to eightfold among apparently healthy individuals. The only way that insulin-resistant persons can prevent the development of type 2 diabetes is by secreting the increased amount of insulin that is necessary to compensate for the resistance to insulin action. The greater the magnitude of muscle and adipose tissue insulin resistance, the more insulin must be secreted to maintain normal or near-normal glucose tolerance. Although compensatory hyperinsulinemia may prevent the development of fasting hyperglycemia in insulin-resistant individuals, the price paid is the untoward physiologic effects of increased circulating insulin concentrations on tissues that retain normal insulin sensitivity. This article focused on the interplay between insulin resistance at the level of the muscle and adipose tissue and normal hepatic insulin sensitivity; this leads to the atherogenic lipoprotein profile that is characteristic of insulin-resistant individuals. It would be inappropriate to minimize the importance of differential insulin sensitivity in the genesis of the changes in lipoprotein metabolism that increase CVD risk in insulin-resistant persons. It would be equally remiss not to emphasize that differential tissue insulin resistance also is necessary to explain why insulin-resistant/hyperinsulinemic individuals are more likely to develop the clinical syndromes (with the exception of type 2 diabetes mellitus) that are listed in Box 1.

Alterations of lipolytic enzymes and high-density lipoprotein subfractions induced by physical activity in type 2 diabetes mellitus

OBJECTIVE

This study investigates the effects of regular moderate physical activity on lipolytic enzymes and plasma lipid concentration, particularly high-density lipoprotein cholesterol (HDL-C) subfractions, in patients with type 2 diabetes mellitus.

DESIGN

Ten patients participated in a 3-month exercise programme without any changes in current medical therapy. The control group consisted of six patients who were matched with regard to sex, age, diabetes duration and diabetes therapy.

RESULTS

Mean (+/- SE) physical activity in the intervention group increased from 70 +/- 21 to 220 +/- 28 min per week, which resulted in an increase in total HDL-C from 1.04 +/- 0.07 to 1.28 +/- 0.12 (P < 0.001). The HDL3-C subfraction increased from 0.71 +/- 0.08 to 0.86 +/- 0.08 mM (P = 0.01) with no significant changes in the HDL2-C subfraction (0.33 +/- 0.04 vs. 0.42 +/- 0.05). These changes were paralleled by an 85% increase in hepatic lipase (HL) activity, from 25.7 +/- 5.1 to 47.4 +/- 4.9 micromol x mL(-1) x h(-1) (P < 0.001) and a 45% increase in lipoprotein lipase (LPL) activity, from 16.8 +/- 3.0-24.3 +/- 2.7 micromol x mL(-1) x h(-1) (P = 0.01). Lecithin-cholesterol acyl-transferase (LCAT) activity increased by 32%, from 156 +/- 26 to 206 +/- 32 nmol x mL(-1) x h(-1) (P < 0.001). In the control group there were no significant changes in any of the variables assessed.

CONCLUSIONS

Regular moderate physical activity in patients with type 2 diabetes led to an overall increase in HL, LPL, and LCAT. HL showed a more pronounced increase than LPL and LCAT. The changes in lipolytic and transferase enzyme pattern resulted in a significant increase of plasma HDL-C, mainly of the HDL3-C subfraction.

Intensive lipid-lowering strategy in patients with diabetes mellitus

AIMS

To assess the feasibility of an intensive lipid-lowering strategy in diabetic subjects pursuing target plasma lipid levels.

METHODS

Patients with diabetes mellitus (DM), Type 1 or 2, with plasma lipid levels exceeding target values (LDL-cholesterol <2.6 mmol/l, triglycerides < 1.7 mmol/l, HDL-cholesterol > 0.9 mmol/l for men and > 1.1 mmol/l for women) were eligible. After 6-12 weeks of diet and glycaemic control, lipid-lowering medication (simvastatin/gemfibrozil/acipimox) was prescribed in steps of incremental dosages and combinations for 30 weeks.

RESULTS

Of all eligible clinic patients, 25% initially responded and finally 12% were entered. Thirty-six patients with Type 1 and 59 with Type 2 DM were studied. Mean baseline lipid levels in Type 1 and Type 2 diabetic subjects were: LDL-cholesterol 3.6 and 3.7 mmol/l, triglycerides 1.7 and 2.2 mmol/l, HDL-cholesterol for men 1.1 and 1.0 mmol/l, and for women 1.4 and 1.2 mmol/l, respectively. All three target values were reached in 66% of the patients. LDL-cholesterol was reduced by 1.2 mmol/l in Type 1 and 1.3 mmol/l in Type 2 diabetic patients and triglycerides by 0.7 mmol/l and 1.1 mmol/l, respectively. HDL-cholesterol increased by 0.15 mmol/l and 0.34 mmol/l in men and women with Type 1 diabetes mellitus, respectively. The cholesterol-triglyceride ratio decreased significantly in VLDL in Type 1 diabetes and in IDL in Type 2 diabetes and increased significantly in HDL in Type 2 DM.

CONCLUSIONS

A minority of subjects eligible for intensive lipid lowering agreed to participate in a feasibility study, suggesting a potentially large compliance problem for a general lipid-lowering programme in a diabetes clinic. Nevertheless, intensive lipid lowering with drug combinations can attain the recommended target lipid levels in 66% of subjects with diabetes. With this strategy the plasma lipoprotein composition shifts towards a less atherogenic profile. Subjects with diabetes should therefore receive lipid-lowering therapy tailored to reach target levels, rather than standard dosages, in order to reduce atherogenic risk.

Insulin resistance and human disease: a short history

The notion that tissue resistance to insulin might play an important role in certain disease states is approximately 60 years old. However, recognition of its central role in this regard is a relatively recent phenomenon. In this review an effort has been made to trace a brief history of insulin resistance from its inception to its current position as the fundamental abnormality in both type 2 diabetes and Syndrome X.

R451Q mutation in the cholesteryl ester transfer protein (CETP) gene is associated with high plasma CETP activity

Cholesteryl ester transfer protein (CETP), as a candidate gene for dyslipoproteinemia and coronary heart disease, was studied in 105 men with low plasma concentrations of high density lipoprotein cholesterol (HDL-C) and established coronary heart disease as well as in 515 randomly selected men and women. A one-nucleotide substitution (G to A) in exon 15, which changes arginine (451) to glutamine in CETP protein, was detected by PCR-SSCP and direct sequencing and screened in the population sample by a simple PCR-based restriction assay. In the random population sample the allele frequency of the R451Q mutation was 1.9%. Men heterozygous for the R451Q mutation (n = 7) had 27% higher CETP activity than age-, body mass index-, smoking- and alcohol consumption-matched controls with normal genotype (n = 21; P = 0.003). Women heterozygous for the R451Q mutation (n = 7) had 16% lower total cholesterol compared to matched controls (n = 21; P = 0.07), but no such difference was detected in men. In the random population sample the correlation between plasma total cholesterol level and CETP activity was 0.19 (P = 0.044), both in men and women. When women with total cholesterol over 5.2 mmol/l were excluded from analysis, heterozygotes (n = 4) had plasma CETP activity of 113 nmol/h/ml plasma, whereas those of normal genotype (n = 12) had 103 nmol/h/ml plasma, but this difference was not statistically significant. Women heterozygous for the R451Q mutation and consuming less than 10 g alcohol a week had 23% lower HDL-C compared to women with the normal genotype (P = 0.032). In conclusion, we describe a mutation in the CETP gene associated with high plasma CETP activity in men and with low total cholesterol in women. Further studies are needed to evaluate the effect of mutation on the risk of coronary heart disease.

A polymorphic site in the 3' untranslated region of the cholesteryl ester transfer protein (CETP) gene is associated with low CETP activity

The exon 16 of the cholesteryl ester transfer protein (CETP) gene was screened for possible mutations in patients with low plasma high-density lipoprotein cholesterol (HDL-C) levels and established coronary heart disease. 115 men who had undergone coronary bypass surgery were compared with a random population sample of 515 subjects. A single G to A substitution at base pair 1696 was found in the 3' untranslated region of the CETP gene. Among the patients with low HDL-C, the plasma CETP activity was 29% lower (P = 0.002) in the subjects homozygous for the mutation than in those with other genotypes. The same effect was observed in the random population sample (P = 0.02). The mutation did not affect the plasma lipid or lipoprotein values, although the mean HDL-C tended to be slightly higher and the ratio of cholesterol content in the apo B-containing lipoproteins to HDL-C slightly lower in the homozygotes compared with the other genotypes. In conclusion, we describe a prevalent mutation at the CETP gene locus associated with low plasma CETP activity. Our results support previous findings suggesting that the genes in chromosome 16 may be important in the regulation of reverse cholesterol transport and in protection against coronary heart disease.

Cholesteryl ester transfer activity in liver disease and cholestasis, and its relation with fatty acid composition of lipoprotein lipids

Liver disease is accompanied by major qualitative and quantitative disturbances in plasma lipoprotein metabolism, the extent and intensity of which depend on the degree of parenchymal damage, cholestasis, or both. The main objective of this study was to determine the cholesteryl ester transfer CETP activity and its association with the lipoprotein neutral lipid composition in patients with either liver cirrhosis or cholestasis, as compared to normal controls. Lipoproteins were isolated by ultracentrifugation, lipids and apolipoproteins were measured by conventional methods, and the fatty acid composition was established by gas chromatography; CETP activity in lipoprotein-deficient plasma was measured by determining the transfer of [3H]cholesteryl esters from HDL to VLDL. Lipoprotein lipase and hepatic lipase activities were measured in post-heparin plasma by radiochemical methods. In patients with liver cirrhosis, low levels of VLDL, HDL, apo B, and Lp(a) were observed, as well as a change in the composition of HDL particles, with increases in the relative proportion of triglyceride and free cholesterol. Respectively, the last two changes could be attributed in part to the low hepatic lipase activity observed in this study, and to the low lecithin:cholesterol acyltransferase activity previously observed by others. In patients with cholestasis, a moderate hyperlipidemia due to the elevation of LDL was found. In contrast, HDL and apo A-I levels were very low reflecting a low number of HDL particles, which also had altered compositions with increases in the triglyceride and free cholesterol contents relative to apo A-I and esterified cholesterol, respectively. As regards the fatty acid composition of lipoprotein lipids, the two groups of patients showed, in general, a lower proportion of linoleic acid and a compensating higher proportion of oleic acid as compared to the controls, changes that were observed in both cholesteryl esters and triglycerides. In contrast, the proportions of oleic and palmitoleic acids in phospholipids were increased, whereas that of stearic acid was decreased in patients as compared to controls. In patients with liver cirrhosis, as well as in controls, no changes were observed in the fatty acid compositions of cholesteryl ester, triglycerides, or phospholipids among the different lipoproteins, which probably reflects the equilibration reached by the action of CETP. In patients with cholestasis, no differences were observed in fatty acid composition among the lipoprotein phospholipids but, interestingly, cholesteryl esters from VLDL had a significantly lower linoleic acid content than those from HDL, whereas triglycerides from VLDL had significantly higher oleic acid and lower linoleic acid contents than those from HDL. This distinct fatty acid composition of the neutral lipids between lipoproteins was associated with a significant decrease (25%) in the cholesteryl ester transfer activity in patients with cholestasis. We suggest that fat malabsorption due to the biliary defect may induce a decrease in cholesteryl ester transfer protein synthesis or section, which in turn would slow the equilibration of the neutral lipids among plasma lipoproteins.

Inhibition of lecithin: cholesterol acyltransferase activity in human blood plasma by cigarette smoke extract and reactive aldehydes

Cigarette smoking is a risk factor for atherosclerosis. It is conceivable that reactive chemical components in cigarette smoke may adversely affect reverse cholesterol transport at the level of lecithin: cholesterol acyltransferase (LCAT) and promote atherogenesis. Hence, the effect of cigarette smoke extract (CSE) on the activity of LCAT in human plasma was studied. When incubated with plasma, CSE caused both concentration- and time-dependent losses of LCAT activity. Addition of glutathione, but not ascorbate, to plasma prevented loss of LCAT activity caused by CSE. Incubation of plasma with some reactive aldehydes known to be present in cigarette smoke also inhibited LCAT activity. Among five aldehydes tested, acrolein was the strongest inhibitor of LCAT, with complete enzyme inhibition occurring at 1 mM. Acetaldehyde was the weakest inhibitor of LCAT, with 85% enzyme inhibition at 50 mM. Hexanal, formaldehyde, and malondialdehyde completely inhibited LCAT activity at 10, 50, and 50 mM, respectively. When plasma was incubated with 1 mM acrolein in the presence of 2.5 mM glutathione or dihydrolipoic acid, 100 and 57% of LCAT activity, respectively, remained after incubation. This finding suggest that reactive aldehydes may form adducts with certain free sulfhydryl groups functioning in the active site of LCAT to inhibit enzyme activity. It is concluded that reactive aldehydes are at least partially responsible for the reduction in LCAT activity in plasma treated with CSE.

Chemical synthesis of 15-ketosterols and their inhibitions of cholesteryl ester transfer protein

Described herein are the chemical syntheses of 3 beta-hydroxy-5 alpha-cholest-8(14)-en-15-one and 3 beta-hydroxy-5 alpha-cholest-8(14),16-dien-15-one from diosgenin and the examinations of their ability to inhibit the cholesteryl ester transfer protein (CETP). Clemmensen reduction of diosgenin gave cholest-5-ene-3 beta, 16 beta,26-triol. Tosylation of the latter compound gave cholest-5-ene-3 beta,16 beta,26-triol 26-tosylate which, upon reduction with LiAIH4, gave cholest-5-ene-3 beta,16 beta-diol. Hydrogenation-benzoylation of the latter to 5 alpha-cholest-3 beta,16 beta-diol 3 beta-benzoate followed by mesylation-elimination gave 5 alpha-cholest-16-ene-3 beta-ol 3 beta-benzoate. Controlled oxidation of the latter with CrO3-dimethylpyrazole gave 3 beta-hydroxy-5 alpha, 14 alpha-cholest-16-en-15-one 3 beta-benzoate. Oxidation of delta 16-15-one with SeO2 gave 3 beta-hydroxy-5 alpha-cholest-8(14),16-dien-15-one 3 beta-benzoate along with 3 beta-hydroxy-5 alpha, 14 beta-cholest-16-en-15-one 3 beta-benzoate. Selective hydrogenation of the delta 8(14),16-15-ketosteryl ester, followed by base hydrolysis gave 3 beta-hydroxy-5 alpha-cholest-8(14)-en-15-one. Hydrolysis of 3 beta-hydroxy-5 alpha-cholest-8(14),16-dien-15-one 3 beta-benzoate in basic media gave 3 beta-hydroxy-5 alpha-cholest-8(14),16-dien-15-one. The effects of the 15-ketosterols on the CETP activity were studied in vitro by incubating cholesteryl ester donor (HDL), cholesteryl ester acceptor (LDL) and human plasma as a CETP source at 37 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

Cholesteryl ester transfer protein inhibition by PD 140195

The presence of plasma cholesteryl ester transfer protein (CETP) activity may be atherogenic, and, therefore, strategies to inhibit its activity or production may result in a beneficial effect on lipoprotein profiles and the disease process. The current report describes 4-phenyl-5-tridecyl-4H-1,2,4- triazole-3-thiol (PD 140195), a novel CETP inhibitor. The concentration-dependent inhibition of CETP by PD 140195 and the inhibitory monoclonal antibody (Mab) TP2 is demonstrated in a variety of in vitro assay systems. Molecular models of PD 140195 suggest a spatial mimicry of the cholesteryl ester structure. Despite the structural similarity, kinetic studies with a fluorescent cholesteryl ester analog suggest that the inhibition of transfer is not competitive. PD 140195 also selectively inhibited cholesteryl ester but not triglyceride transfer, while the Mab TP2 blocked CETP transfer of both. Studies were carried out to determine whether CETP inhibition observed in vitro could also be demonstrated in vivo. When PD 140195 was intravenously infused to anesthetized rabbits (up to 20 mg/kg), only transient CETP inhibition was observed. In vitro reconstitution studies in the presence of bovine serum albumin resulted in marked reduction of PD 140195 inhibitory activity. Thus, the low activity of PD 140195 in whole plasma probably results from binding to other plasma proteins.