Hyperlipidemias: Krempf M

Sicard D, Chanu B, Badoc G, Beucler I, Chauvenet M, Clavel J, Cocaul-André M, Denolle T, Desson J, Ducimetière P, Farnier M, Fontbonne A, Gautier J, Hoog-Labouret N, Janowski M, Krempf M, Le Goaziou M, Marechaud M, Mottier D, Ribier A, Signeyrole D, Veyssier-Belot C, Mlika-Cabanne N, Anonymous00274. · No affiliation provided · Ann Endocrinol (Paris). · Pubmed #11240408 No free full text.

This publication has no abstract.

Costet P, Krempf M, Cariou B. · INSERM, UMR915, L'Institut du Thorax, 1 Rue Gaston Veil, Nantes, France. · Trends Biochem Sci. · Pubmed #18672372 No free full text.

Abstract: Gain-of-function mutations within proprotein convertase subtilisin kexin type 9 (PCSK9) are linked to familial autosomal dominant hypercholesterolaemia, a disease characterized by elevated plasma concentrations of cholesterol associated with low-density lipoproteins (LDLs). Conversely, PCSK9 loss-of-function mutations result in low levels of LDL cholesterol (LDLC) and protect against coronary heart disease. Although compelling evidence indicates that PCSK9 impairs the LDLR pathway, its role in cholesterol metabolism remains incompletely defined. In the past two years, several new biochemical findings, including the PCSK9 crystal structure and the identification of several transcriptional repressors, were reported. Moreover, new clinical and epidemiological data have revealed the correlation between plasma PCSK9 concentrations and LDLC levels.

Krempf M. · Clinique d'Endocrinologie, Maladies Métaboliques et Nutrition, Hôtel-Dieu, 44093 Nantes Cedex 1. · Ann Med Interne (Paris). · Pubmed #11431581 No free full text.

Abstract: Diet prescription is a fundamental first-line element in the management of patients with dyslipidemia. Weight loss should be a primary goal for all overweight patients. A 5 to 10% weight loss is often sufficient to obtain a significant improvement in lipid levels. Dietary fat should not provide more than 30% of total calorie intake. Saturated fatty acids should not exceed 7% and polyunsaturated fatty acids should also be limited to 7 to 10%. For monounsaturated fatty acids the dietary allowance can be a bit wider, up to 15% of total calorie intake. Carbohydrates, particularly complex carbohydrates, should replace the fat calories. Dietary fiber (more than 20g/d) as well as soy protein or phyto-sterols can be helpful in reducing LDL-cholesterol by about 10%. Consumption of fruits and vegetables should also be encouraged because they provide antioxidants that have effects on other cardiovascular risk factors. Long-term education is needed to encourage the patient to comply with this type of diet. Psycho-behavioral strategies can be useful here.

Rabès JP, Varret M, Devillers M, Aegerter P, Villéger L, Krempf M, Junien C, Boileau C. · INSERM U383, the Hôpital Necker-Enfants Malades, Paris, France. · Arterioscler Thromb Vasc Biol. · Pubmed #11031227 links to  free full text

Abstract: Familial hypercholesterolemia and familial ligand-defective apolipoprotein B-100 (FDB) are dominantly inherited disorders leading to impaired low-density lipoprotein receptor (LDLR) and apolipoprotein B-100 (APOB) interaction, plasma LDL elevation, and hypercholesterolemia. We previously identified the first French FDB-R3531C proband, a woman with very high total cholesterol, in a group of type IIa hypercholesterolemic families. We report here the investigation of her family at large that revealed the total absence of cosegregation with hypercholesterolemia. Six of the 10 subjects heterozygous for the R3531C mutation had plasma cholesterol lower than the 97.5th percentile for their age and gender, and mean cholesterol levels were not significantly different between affected and unaffected persons. Furthermore, 2 family members with similar high LDL-cholesterol levels were not carriers of the R3531C substitution, suggesting the implication of another mutation. Segregation analysis of the LDLR gene revealed statistically significant genetic linkage with hypercholesterolemia, and analysis of the proband LDLR gene led to the identification of the 664 proline to leucine defective mutation and its detection in all 6 hypercholesterolemic-related members of this family. Therefore, our results show that the family presents with familial hypercholesterolemia and give evidence that the R3531C substitution in the APOB gene is not an allelic variant leading to FDB. Furthermore, thorough analysis of our data suggests that the APOB-R3531C mutation enhances the hypercholesterolemic effect of the LDLR-P664L defect, suggesting that it is a susceptibility mutation.

Frénais R, Maugeais C, Ouguerram K, Zaïr Y, Bard JM, Charbonnel B, Magot T, Krempf M. · Centre de Recherche en Nutrition Humaine, Groupe Métabolisme, Hôtel Dieu, Nantes, France. · Metabolism. · Pubmed #11398137 No free full text.

Abstract: In patients with heterozygous familial hypercholesterolemia (FH), both synthetic and clearance rates of high-density lipoproteins (HDL) are increased compared with control subjects. According to in vitro data on hepatocytes, the expanded pool size of low-density lipoproteins (LDL) in FH could partly explain the enhanced HDL production. Therefore, we have tested the hypothesis that a reduction of LDL pool size, achieved by LDL-apheresis, is associated with a downregulation of HDL synthesis. We studied the kinetics of HDL by infusing [5,5,5-(2)H(3)]-leucine in 7 heterozygous FH patients before and after 3 biweekly LDL-apheresis using dextran sulfate columns. Both plasma and LDL-cholesterol levels were decreased after LDL-apheresis (169 +/- 35 v 422 +/- 27 mg/dL, P <.05, and 85 +/- 19 v 327 +/- 52 mg/dL, P <.05, respectively). Plasma triglyceride level was unaffected (162 +/- 43 v 176 +/- 35 mg/dL, not significant [NS]) and HDL composition remained stable (HDL-cholesterol 29 +/- 6 v 37 +/- 7 mg/dL, NS, and HDL-triglyceride 20 +/- 6 v 19 +/- 8 mg/dL, NS). Plasma apolipoprotein AI (apo AI) was also similar (122 +/- 20 v 115 +/- 18 mg/dL, NS). Mean HDL-apo AI fractional catabolic rate (FCR) was slightly higher (0.41 +/- 0.07 v 0.36 +/- 0.14 pool/d, NS), and absolute production rate (APR) was increased (22.1 +/- 5.7 v 18.0 +/- 5.7 mg/kg/d, P <.05) after LDL-apheresis. These human kinetic data suggest that LDL do not play a major role on HDL production in heterozygous FH patients.

Krempf M, Rohmer V, Farnier M, Issa-Sayegh M, Corda C, Sirugue I, Gerlinger C, Masseyeff-Elbaz MF. · Clinique d'Endocrinologie et Nutrition, Hôtel-Dieu, 44093 Nantes Cedex 1, France. · Diabetes Metab. · Pubmed #10880891 links to  free full text

Abstract: The aim of this study was to evaluate the efficacy on LDL-cholesterol (LDL-C) of micronised fenofibrate given for three months at doses ranging from 200 to 400 mg once daily, compared with placebo. A double-blind, randomised, parallel-group, multi-centre trial was performed in four centers of France in 340 hypercholesterolemic patients (163M, 177F) aged 18-75 years. After a 2-3 month single-blind run-in period on placebo and diet, patients with LDL-C greater than or equal to 4.65 mmol/l (180 mg/dl) maintained on the same diet throughout the study were randomly allocated to placebo or to 200, 267, 340 or 400 mg micronised fenofibrate, given once daily with the evening meal for 3 months. LDL-C, total cholesterol (TC), total triglycerides (TG) and apolipoprotein B (Apo B) significantly decreased compared with placebo in all four fenofibrate groups. For all randomised patients, the decrease in the fenofibrate groups ranged from 31.6-38.8% for LDL-C, 24.5-31.9% for TC, 26.7-40.8% for TG, and 27.3-35.0% for Apo B. An increase in HDL-cholesterol of 4.1-8.2% was observed in the fenofibrate groups, but did not reach statistical significance. Lipid values in the placebo group remained unchanged. The therapeutic goal of LDL-C<3.36 mmol/l (130 mg/dl) was reached in 27% in the 200 mg group and increased to 56% in the 300 mg group. There were no major clinical or biological adverse events in the dose interval from 200 mg to 400 mg of micronised fenofibrate per day. This study showed treatment for 3 months with micronised fenofibrate at doses up to 400 mg per day is effective and can reduce LDL-cholesterol up to 30% allowing further evaluation of these doses on longer trials.

Ouguerram K, Zair Y, Billon S, Chétiveaux M, Brunet-François C, Ngohou-Bach K, Allavena C, Reliquet V, Milpied B, Magot T, Raffi F, Krempf M. · Centre de Recherche en Nutrition Humaine, INSERM U 915, Hotel Dieu, 44035 Nantes cedex 1, France. · Med Chem. · Pubmed #18991738 No free full text.

Abstract: The aim was to study the mechanisms involved in the dyslipidemia associated with lipodystrophy in HIV infected patients on antiretroviral therapy (ART). We investigated the in vivo kinetics of apolipoprotein B100 (apoB) containing lipoproteins using a 14 h primed constant infusion of [5,5,5, (2)H(3)] leucine and compartmental modelling in normolipidemic without lipodystrophy (7 patients, NLD) or dyslipidemic with lipodystrophy (7 patients, LD) treated with ART. Subjects in group LD showed higher plasma triglycerides (5.73+/-3.58 vs 1.29+/-0.54 g/L, p<0.005), total cholesterol (2.98+/-0.95 vs 1.74+/-0.26 g/L, p<0.05), apoB (1.49+/-1.11 vs 0.51+/-0.11 g/L, p<0.005) and apolipoprotein CIII in apoB containing lipoproteins (117.7+/-42.2 vs 22.6+/-23.9 g/L, p<0.005). LD subjects exhibited an insulin resistant as observed by higher HOMA (3.44+/-1.62 vs 1.60+/-0.61, p<0.05). They exhibited an increase in VLDL (1.24+/-0.33 vs 0.80+/-0.21 mg/kg/h, p<0.05), decrease in IDL (0.20+/-0.10 vs 0.48+/-0.24 mg/kg/h, p<0.05) and no difference in LDL (0.38+/-0.19 vs 0.45+/-0.25 mg/kg/h) production rate. LD subject also showed a dramatic decrease in transformation of VLDL to IDL (0.013+/-0.010 vs 0.258+/-0.206 h(-1), p<0.005) and IDL to LDL (0.088+/-0.093 vs 0.366+/-0.189 h(-1), p<0.05) and a decrease in fractional catabolic rate (FCR) of VLDL (0.199+/-0.132 vs 0.555+/-0.398 h(-1), p<0.05), IDL (0.110+/-0.08 vs 0.523+/-0.275 h(-1), p<0.05) and LDL (0.010+/-0.005 vs 0.025+/-0.014 h(-1), p<0.05). These disturbances, overproduction and an overall delayed catabolism of apoB, are similar to those observed using the same protocol in insulin resistant subjects. Our study suggests that metabolic disturbance of apoB100 observed in lipodystrophic HIV in combined antiretroviral therapy are consecutive to insulin resistance induced by the treatment.

Weidner C, Krempf M, Bard JM, Cazaubiel M, Bell D. · Cognis GmbH, Monheim, Germany. · Lipids Health Dis. · Pubmed #18837970 links to  free full text

Abstract: BACKGROUND: Plant sterols are an established non-pharmacological means to reduce total and LDL blood cholesterol concentrations and are therefore recommended for cholesterol management by worldwide-renown health care institutions. Their efficacy has been proven in many types of foods with the majority of trials conducted in spreads or dairy products. As an alternative to dairy products, soy based foods are common throughout the world. Yet, there is little evidence supporting the efficacy of plant sterols in soy-based foods. The objective of this study was to investigate the effect of a soy drink enriched with plant sterols on blood lipid profiles in moderately hypercholesterolemic subjects. METHODS: In a randomized, placebo-controlled double-blind mono-centric study, 50 subjects were assigned to 200 ml of soy drink either enriched with 2.6 g plant sterol esters (1.6 g/d free plant sterol equivalents) or without plant sterols (control) for 8 weeks. Subjects were instructed to maintain stable diet pattern and physical activity. Plasma concentrations of lipids were measured at initial visit, after 4 weeks and after 8 weeks. The primary measurement was the change in LDL cholesterol (LDL-C). Secondary measurements were changes in total cholesterol (TC), non-HDL cholesterol (non-HDL-C), HDL cholesterol (HDL-C) and triglycerides. RESULTS: Regular consumption of the soy drink enriched with plant sterols for 8 weeks significantly reduced LDL- C by 0.29 mmol/l or 7% compared to baseline (p < 0.05). TC and non-HDL-C concentrations decreased by 0.26 mmol/l and 0.31 mmol/l (each p < 0.05), respectively. Mean reductions in total, LDL and non-HDL cholesterol were significantly greater than in the placebo group (p < 0.05). HDL-C and triglycerides were not affected. Compliance was very high (>96%), and products were well tolerated. CONCLUSION: Daily consumption of a plant sterol-enriched soy drink significantly decreased total, non-HDL and LDL cholesterol and is therefore an interesting and convenient aid in managing mild to moderate hypercholesterolemia.

Kourimate S, Le May C, Langhi C, Jarnoux AL, Ouguerram K, Zaïr Y, Nguyen P, Krempf M, Cariou B, Costet P. · INSERM U915, CHU Hotel Dieu, 9 Quai Moncousu, Nantes, France. · J Biol Chem. · Pubmed #18245819 links to  free full text

Abstract: Proprotein convertase subtilisin/kexin type 9 (PCSK9) is associated with familial autosomal dominant hypercholesterolemia and is a natural inhibitor of the LDL receptor (LDLr). PCSK9 is degraded by other proprotein convertases: PC5/6A and furin. Both PCSK9 and the LDLr are up-regulated by the hypocholesterolemic statins. Thus, inhibitors or repressors of PCSK9 should amplify their beneficial effects. In the present study, we showed that PPARalpha activation counteracts PCSK9 induction by statins by repressing PCSK9 promoter activity and by increasing PC5/6A and furin expression. Quantification of mRNA and protein levels showed that various fibrates decreased PCSK9 and increased PC5/6A and furin expression. Fenofibric acid (FA) reduced PCSK9 protein content in immortalized human hepatocytes (IHH) as well as its cellular secretion. FA suppressed PCSK9 induction by statins or by the liver X receptor agonist TO901317. PCSK9 repression is occurring at the promoter level. We showed that PC5/6A and furin fibrate-mediated up-regulation is PPARalpha-dependent. As a functional test, we observed that FA increased by 30% the effect of pravastatin on the LDLr activity in vitro. In conclusion, fibrates simultaneously decreased PCSK9 expression while increasing PC5/6A and furin expression, indicating a broad action of PPARalpha activation in proprotein convertase-mediated lipid homeostasis. Moreover, this study validates the functional relevance of a combined therapy associating PCSK9 repressors and statins.

Hansel B, Nicolle C, Lalanne F, Tondu F, Lassel T, Donazzolo Y, Ferrières J, Krempf M, Schlienger JL, Verges B, Chapman MJ, Bruckert E. · Service d'Endocrinologie-Métabolisme, AP-HP, Hôpital de la Pitié, Paris, France. · Am J Clin Nutr. · Pubmed #17823447 links to  free full text

Abstract: BACKGROUND: Plant sterol (PS)-enriched foods have been shown to reduce plasma LDL-cholesterol concentrations. In most studies, however, PSs were incorporated into food products of high fat content. OBJECTIVE: We examined the effect of daily consumption of PS-supplemented low-fat fermented milk (FM) on the plasma lipid profile and on systemic oxidative stress in hypercholesterolemic subjects. DESIGN: Hypercholesterolemic subjects (LDL-cholesterol concentrations >or=130 and <or= 190 mg/dL; n = 194) consumed 2 low-fat portions of FM in the same meal daily for 6 wk. Subjects were randomly assigned to 2 groups: low-fat FM enriched with 0.8 g PS ester per portion or control FM. Plasma concentrations of lipids, oxidized LDL, beta-carotene, beta-sitosterol, campesterol, and high-sensitivity C-reactive protein were measured during the trial. RESULTS: Plasma LDL-cholesterol concentrations were reduced by 9.5% and 7.8% after 3 and 6 wk, respectively, in the 1.6-g/d PS group compared with the control group, whereas plasma triacylglycerol and HDL-cholesterol concentrations were not significantly affected. In addition, there were no significant changes in serum beta-carotene on normalization to LDL cholesterol during the study period in both groups, whereas plasma concentrations of oxidized LDL were reduced significantly in the PS group compared with the control group (-1.73 compared with 1.40 U/L, respectively; P < 0.05). Plasma sitosterol concentrations were increased by 35% (P < 0.001 compared with control); however, campesterol concentrations did not change during the study period. CONCLUSION: Daily consumption of 1.6 g PS in low-fat FM efficiently lowers LDL cholesterol in subjects with moderate hypercholesterolemia without deleterious effects on biomarkers of oxidative stress.

Lambert G, Jarnoux AL, Pineau T, Pape O, Chetiveaux M, Laboisse C, Krempf M, Costet P. · Université de Nantes, UFR de Médecine, Institut National de la Santé et de la Recherche Médicale, Unité 539, Centre Hospitalier Universitaire Hôtel Dieu, 44093 Nantes, France. · Endocrinology. · Pubmed #16794006 links to  free full text

Abstract: Several proprotein convertase subtilisin kexin type 9 (PCSK9) mutations lead to familial hypercholesterolemia by virtue of its role as a negative modulator of the low-density lipoprotein receptor (LDLr). Here, we uncover that upon dietary challenge, the down-regulation of the LDLr is also a key mechanism by which PCSK9 modulates the hepatic production of apolipoprotein-B-containing lipoproteins. Thus, adenoviral-mediated overexpression of PCSK9 in 24-h fasted mice results in massive hyperlipidemia, due to a striking increase in very-low-density lipoprotein (VLDL) triglycerides and apolipoprotein B100 hepatic output. Similar studies in LDLr (-/-) mice demonstrate that PCSK9-mediated alteration of VLDL output in the fasted state requires the LDLr. This increased production of VLDL was associated with a concomitant reduction of intrahepatic lipid stores as well as a lack of down-regulation of peroxisome proliferator-activated receptor-alpha activity and target genes expression. Finally, we show that PCSK9 hepatic expression is inhibited by the hypotriglyceridemic peroxisome proliferator-activated receptor-alpha agonist fenofibrate. In summary, the negative modulation of LDLr expression by PCSK9, which decreases plasma LDL clearance, also promotes an overproduction of nascent VLDL in vivo upon fasting.

Lambert G, Krempf M, Costet P. · University of Nantes, Medical School, INSERM U539, CHU Hôtel-Dieu, 3(e) Nord, 1 Place Alexis Ricordeau, F-44093 Nantes cedex 1, France. · Trends Endocrinol Metab. · Pubmed #16487721 No free full text.

Abstract: PCSK9 is the third gene to be implicated in autosomal dominant hypercholesterolemia. The recent discovery of mutations in PCSK9 protein associated with low plasma low-density lipoprotein in humans, the characterization of PCSK9-deficient mice hypersensitive to statins and the severely pathological phenotype of D374Y PCSK9-mutated patients shed a new light on this gene: is it a promising therapeutic target for dyslipidemias?

Allard D, Amsellem S, Abifadel M, Trillard M, Devillers M, Luc G, Krempf M, Reznik Y, Girardet JP, Fredenrich A, Junien C, Varret M, Boileau C, Benlian P, Rabès JP. · INSERM UR383, Hôpital Necker-Enfants Malades. · Hum Mutat. · Pubmed #16211558 No free full text.

Abstract: Autosomal dominant hypercholesterolemia (ADH) is a frequent (1/500) monogenic inherited disorder characterized by isolated elevation of LDL leading to premature cardiovascular disease. ADH is known to result from mutations at two main loci: LDLR (encoding the low density lipoprotein receptor), and APOB (encoding apolipoprotein B100), its natural ligand. We previously demonstrated that ADH is also caused by mutations of the PCSK9 (proprotein convertase subtilisin/kexin type 9) gene that encodes Narc-1 (neural apoptosis-regulated convertase 1). However, the role of this novel disease locus as a cause of hypercholesterolemia remains unclear. In the present study, we analysed the PCSK9 coding region and intronic junctions in 130 adult or pediatric patients with ADH, previously found as being non LDLR/non APOB mutation carriers. Four novel heterozygous missense variations were found: c.654A>T (p.R218S), c.1070G>A (p.R357H), c.1405C>T (p.R469W), and c.1327G>A (p.A443T). All mutations were absent in 340 normolipidemic controls. Except for the A443T, all mutations are nonconservative and modify a highly conserved residue. Segregation with hypercholesterolemia is incomplete in one pedigree. Type and severity of hyperlipidemia and of cardiovascular disease could vary among subjects from the same family. Finally, the proband carrying the R357H mutation exhibited very high plasma cholesterol during pregnancy, whereas the proband carrying the p.R469W mutation exhibited a severe phenotype of hypercholesterolemia in combination with a LDLR mutation resulting from a frameshift at residue F382 (1209delC). These observations suggest that variations in PCSK9 are a rare cause of non LDLR/non APOB ADH (approximately 2.3%) and that additional environmental or genetic factors may contribute to the phenotype caused by PCSK9 missense mutations in humans.

Krempf M. · Clinique d'Endocrinologie, Maladies Métaboliques et Nutrition, Hôtel Dieu, Nantes. · Ann Endocrinol (Paris). · Pubmed #15798592 No free full text.

This publication has no abstract.

Ferrières J, Lablanche JM, Pouchain D, Girerd X, Krempf M, Nguyen G, Glanddier PY. · Unité de prévention de l'athérosclérose, service de cardiologie B, CHU Rangueil, Toulouse. · Arch Mal Coeur Vaiss. · Pubmed #15724421 No free full text.

Abstract: The objective of the SPOT study (Study of Practice versus Objectives of Treatment) was the biochemical evaluation of the results of long term lipid regulating treatment in France, compared to the objectives defined by AFSSAPS (French regulatory agency for the safety of medical products) in 2000. A random sample of doctors was recruited in 21 French regions by the Regional Health Observation service. To be included in the SPOT study, the patients had to be on lipid regulating medication for at least six months and consent to biochemical evaluation following a consultation. A sample of 641 doctors examined 2,479 patients treated for 7 years on average. These middle aged patients (aged 63 +/- 11 years) were mostly taking statins (72%). They had an average total cholesterol level of 5.41 +/- 1.01 mmol/L (2.10 +/- 0.39 g/L). and LDL of 3.25 +/- 0.93 mmol/L (1.26 +/- 0.36 g/L), reflecting previous results and confirming the stability of their treatment. In primary prevention and in low risk subjects (with less than 2 associated risk factors), the AFSSAPS objectives were achieved in 95% of cases. In secondary prevention or in very high risk subjects (at least 3 associated risk factors 0), 35% of patients had LDL cholesterol greater than 3.4 mmol/L (1.30 g/L). The SPOT study, performed on subjects who had in theory been stabilised with lipid regulating medication, gave two conclusions: cardiovascular prevention with lipid regulating medication is improving in France, and the subjects at greatest risk attain the recommended objectives less often despite the expected benefit of treatment being higher.

Ouguerram K, Chetiveaux M, Zair Y, Costet P, Abifadel M, Varret M, Boileau C, Magot T, Krempf M. · INSERM U 539, Centre de Recherche en Nutrition Humaine de Nantes, France. · Arterioscler Thromb Vasc Biol. · Pubmed #15166014 links to  free full text

Abstract: OBJECTIVE: We have reported further heterogeneity in familial autosomal-dominant hypercholesterolemia (FH) related to mutation in proprotein convertase subtilisin/kexin type 9 (PCSK9) gene previously named neural apoptosis regulated convertase 1 (Narc-1). Our aim was to define the metabolic bases of this new form of hypercholesterolemia. METHODS AND RESULTS: In vivo kinetics of apolipoprotein B100-containing lipoproteins using a 14-hour primed constant infusion of [2H3] leucine was conducted in 2 subjects carrying the mutation S127R in PCSK9, controls subjects, and FH subjects with known mutations on the low-density lipoprotein (LDL) receptor gene (LDL-R). Apo B100 production, catabolism, and transfer rates were estimated from very LDL (VLDL), intermediate-density lipoprotein (IDL), and LDL tracer enrichments by compartmental analysis. PCSK9 mutation dramatically increased the production rate of apolipoprotein B100 (3-fold) compared with controls or LDL-R mutated subjects, related to direct overproduction of VLDL (3-fold), IDL (3-fold), and LDL (5-fold). The 2 subjects also showed a decrease in VLDL and IDL conversion (10% to 30% of the controls). LDL fractional catabolic rate was slightly decreased (by 30%) compared with controls but still higher than LDL-R-mutated subjects. CONCLUSIONS: These results showed that the effect of the S127R mutation of PCSK9 on plasma cholesterol homeostasis is mainly related to an overproduction of apolipoprotein B100.

Bailhache E, Ouguerram K, Gayet C, Krempf M, Siliart B, Magot T, Nguyen P. · USC INRA de Nutrition et Endocrinologie, Ecole nationale vétérinaire de Nantes, France. · J Anim Physiol Anim Nutr (Berl). · Pubmed #14511132 No free full text.

Abstract: Many studies have shown that in humans insulin resistance (IR) is associated with obesity and hypertriglyceridaemia. The aim of our study was to develop slowly dietary-induced obesity in dogs through long-term overfeeding of a high-fat diet, and to characterize this IR, hypertriglyceridaemic and normotensive model. Insulin resistance was assessed by the euglycaemic hyperinsulinaemic clamp technique. The contribution of hepatic glucose production during the clamp was evaluated using a constant stable-isotope-labelled glucose infusion. Overfeeding a high-fat diet for 7 months was associated with a 43+/-5% body weight increase. Insulin resistance was characterized by hyperinsulinaemia in the unfed state (10+/-1 vs. 24+/-1 microU/ml, in healthy and obese dogs, respectively, p<0.02) and by a reduction of the insulin-mediated glucose uptake (28+/-3 vs. 16+/-1 mg/kg/min, p<0.02). Hepatic glucose production suppression under insulin infusion allowed to conclude that this reduced glucose uptake resulted from a decrease of insulin sensitivity in obese dogs. Furthermore, animals remained normotensive and exhibited a marked hypertriglyceridaemia (0.26+/-0.04 vs. 0.76+/-0.15 mmol/l, in healthy and obese dogs, respectively, p<0.02). Because hypertriglyceridaemia is the most common lipid abnormality in insulin-resistant humans, this dog with slowly induced obesity may constitute a good model to study the consequences of IR in lipid metabolism independently of vascular changes.

Abifadel M, Varret M, Rabès JP, Allard D, Ouguerram K, Devillers M, Cruaud C, Benjannet S, Wickham L, Erlich D, Derré A, Villéger L, Farnier M, Beucler I, Bruckert E, Chambaz J, Chanu B, Lecerf JM, Luc G, Moulin P, Weissenbach J, Prat A, Krempf M, Junien C, Seidah NG, Boileau C. · INSERM U383, Hôpital Necker-Enfants Malades, AP-HP, Université Paris V, 149-161 rue de Sèvres, 75743 Paris Cedex 15, France. · Nat Genet. · Pubmed #12730697 No free full text.

Abstract: Autosomal dominant hypercholesterolemia (ADH; OMIM144400), a risk factor for coronary heart disease, is characterized by an increase in low-density lipoprotein cholesterol levels that is associated with mutations in the genes LDLR (encoding low-density lipoprotein receptor) or APOB (encoding apolipoprotein B). We mapped a third locus associated with ADH, HCHOLA3 at 1p32, and now report two mutations in the gene PCSK9 (encoding proprotein convertase subtilisin/kexin type 9) that cause ADH. PCSK9 encodes NARC-1 (neural apoptosis regulated convertase), a newly identified human subtilase that is highly expressed in the liver and contributes to cholesterol homeostasis.

Amsellem S, Briffaut D, Carrié A, Rabès JP, Girardet JP, Fredenrich A, Moulin P, Krempf M, Reznik Y, Vialettes B, de Gennes JL, Brukert E, Benlian P. · Department of Biochemistry and Molecular Biology, APHP Saint Antoine Hospital, Paris, France. · Hum Genet. · Pubmed #12436241 No free full text.

Abstract: Familial hypercholesterolemia (FH), a frequent monogenic condition complicated by premature cardiovascular disease, is characterized by high allelic heterogeneity at the low-density lipoprotein receptor ( LDLR) locus. Despite more than a decade of genetic testing, knowledge about intronic disease-causing mutations has remained limited because of lack of available genomic sequences. Based on the finding from bioinformatic analysis that Alu repeats represent 85% of LDLR intronic sequences outside exon-intron junctions, we designed a strategy to improve the exploration of genomic regions in the vicinity of exons in 110 FH subjects from an admixed population. In the first group of 42 patients of negative mutation carriers, as previously established by former screening strategies (denaturing gradient gel electrophoresis, DNA sequencing with former primers overlapping splice-sites, Southern Blotting), about half ( n=22) were found to be carriers of at least one heterozygous mutation. Among a second group of 68 newly recruited patients, 27% of mutation carriers ( n=37) had a splicing regulatory mutation. Overall, out of the 54 mutations identified, 13 were intronic, and 18 were novel, out of which nearly half were intronic. Two novel intronic mutations (IVS8-10G-->A within the polypyrimidine tract and IVS7+10G-->A downstream of donor site) might create potential aberrant splice sites according to neural-network computed estimation, contrary to 31 common single nucleotide variations also identified at exon-intron junctions. This new strategy of detecting the most likely disease-causing LDLR mutations outside of Alu-rich genomic regions reveals that intronic mutations may have a greater impact than previously reported on the molecular basis of FH.

Ferrer F, Bigot-Corbel E, N'Guyen P, Krempf M, Bard JM. · INSERM U539, Centre de Recherche en Nutrition Humaine, CHU Hôtel Dieu, 44035 Nantes, France. · Clin Chem. · Pubmed #12029004 links to  free full text

Abstract: BACKGROUND: A reliable method for plasma would be useful to investigate the role of apolipoprotein (apo) AIV when associated with apo B-containing or triglyceride-rich lipoproteins. METHOD: We used a sandwich ELISA to quantify lipoprotein B:AIV particles (Lp B:AIVf; lipoproteins containing at least apo B and apo AIV) in plasma. The method used microtiter plates coated with purified anti-apo B immunoglobulins that selectively retained apo B-containing particles. Lipoproteins containing both apo B and apo AIV were distinguished from those containing only apo B by use of a peroxidase-labeled anti-apo AIV antibody. These subspecies were revealed by ABTS reagent and further quantified by spectrophotometry. Results were expressed in mg/L apo AIV associated with apo B. This method was applied to samples with different cholesterol and triglyceride concentrations. RESULTS: The developed sandwich ELISA method identified and quantified Lp B:AIVf in plasma samples. Within- and between-run CVs were approximately 10%, and analytical recoveries were 95-107%. Results were not significantly influenced by addition of triglycerides or by storage at -20 degrees C (up to 9 months). Under these conditions, plasma Lp B:AIVf concentrations were statistically higher in hypercholesterolemic and mixed hyperlipidemic individuals (53 +/- 13 mg/L; P <0.001 and 70 +/- 18 mg/L; P <0.001, respectively) than in normolipidemic individuals (43 +/- 12 mg/L). Lp B:AIVf concentration appeared to be well correlated with total cholesterol, triglycerides, LDL-cholesterol, and apo B. These results were in contrast to total apo AIV, which was not different between dyslipidemic and normolipidemic individuals. CONCLUSIONS: The developed ELISA method for Lp B:AIVf in plasma combines specificity, reliability, and speed. The increase in Lp B:AIVf concentrations in various dyslipidemic states, together with a lack of change in total apo AIV concentrations, suggests a redistribution of apo AIV toward apo B-containing lipoproteins when these lipoproteins accumulate.

Maugeais C, Ouguerram K, Frénais R, Maugère P, Charbonnel B, Magot T, Krempf M. · Centre de Recherche en Nutrition Humaine, Hôtel Dieu, 44093 Nantes Cedex 01, France. · J Clin Endocrinol Metab. · Pubmed #11297603 links to  free full text

Abstract: The acute reduction of low-density lipoprotein (LDL) cholesterol obtained by LDL-apheresis allows the role of the high level of circulating LDL on lipoprotein metabolism in heterozygous familial hypercholesterolemia (heterozygous FH) to be addressed. We studied apolipoprotein B (apoB) kinetics in five heterozygous FH patients before and the day after an apheresis treatment using endogenous labeling with [(2)H(3)]leucine. Compared with younger control subjects, heterozygous FH patients before apheresis showed a significant decrease in the fractional catabolic rate of LDL (0.24 +/- 0.08 vs. 0.65 +/- 0.22 day(-1); P < 0.01), and LDL production was increased in heterozygous FH patients (18.9 +/- 7.0 vs. 9.9 +/- 4.2 mg/kg.day; P < 0.05). The modeling of postapheresis apoB kinetics was performed using a nonsteady state condition, taking into account the changing pool size of very low density lipoprotein (VLDL), intermediate density lipoprotein, and LDL apoB. The postapheresis kinetic parameters did not show statistical differences compared with preapheresis parameters in heterozygous FH patients; however, a trend for increases in fractional catabolic rate of LDL (0.24 +/- 0.08 vs. 0.35 +/- 0.09 day(-1); P = 0.067) and the production of VLDL (13.7 +/- 8.3 vs. 21.9 +/- 1.6 mg/kg.day; P = 0.076) was observed. These results suggested that the marked decrease in plasma LDL obtained a short time after LDL-apheresis is able to stimulate LDL receptor activity and VLDL production in heterozygous FH.

Bach-Ngohou K, Giraud F, Krempf M, Bard JM. · Laboratoire de Biochimie fondamentale et appliquée, UFR de Pharmacie, Nantes, France. · Metabolism. · Pubmed #11230778 No free full text.

Abstract: Lipoprotein(a) [Lp(a)], an atherosclerosis marker, has 2 subspecies differing in structure and composition that can easily be distinguished by the presence or absence of apolipoprotein E (apoE). The subspecies containing apo E [Lp(a):B:E] is found mainly in the very-low-density lipoprotein (VLDL) size range, while that free of apoE [Lp(a):B] is found mainly in the LDL size range. As little is known about the physiologic function of these subspecies, this study investigated Lp(a):B and Lp(a):B:E concentrations in a population of normotriglyceridemic and moderately hypertriglyceridemic subjects in fasting state and attempted to determine the parameters influencing their plasma concentrations. The subjects studied (n = 98) had a mean total Lp(a) concentration of 108 mg/dL (28 to 252, minimum to maximum), a mean Lp(a):B concentration of 92.6 mg/dL (5 to 254), and a mean Lp(a):B:E concentration of 15.6 mg/dL (0 to 137). These results indicate that Lp(a):B:E, even in normolipidemic subjects, constitutes a detectable part of total Lp(a), ie, a mean percentage of 16.2% (0% to 96%). Multiple stepwise regression analyses showed that triacylglycerol has no independent effect on the concentration of Lp(a) subspecies, and that remnant accumulation markers, such as the E/LpB:E molar ratio (number of apoE per particle containing both apoB and apoE) and apoE-LpB (mass of apoE bound to particles containing both apoB and apoE), have a strong independent effect on this concentration. A strong positive influence of E/LpB:E on Lp(a):B:E subspecies was noted, as well as a negative influence of apo E-LpB on Lp(a):B subspecies. Taken together, these results suggest that the apoE bound to LpB:E particles plays a dominant role in the concentration of Lp(a) subspecies and that a redistribution of Lp(a) subspecies occurs under the influence of the apoE content of triacylglycerol-rich lipoprotein particles.

Saint-Jore B, Varret M, Dachet C, Rabès JP, Devillers M, Erlich D, Blanchard P, Krempf M, Mathé D, Chanu B, Jacotot B, Farnier M, Bonaïti-Péllié C, Junien C, Boileau C. · INSERM U383, Université René Descartes, Paris V, Hôpital Necker-Enfants Malades, France. · Eur J Hum Genet. · Pubmed #10952765 links to  free full text

Abstract: Autosomal dominant type IIa hypercholesterolaemia (ADH) is characterised by an elevation of total plasma cholesterol associated with increased LDL particles. Numerous different molecular defects have been identified in the LDL receptor (LDLR) and few specific mutations in the apolipoprotein B (APOB) gene resulting in familial hypercholesterolaemia and familial defective apoB-100 respectively. To estimate the respective contribution of LDLR, APOB and other gene defects in this disease, we studied 33 well characterised French families diagnosed over at least three generations with ADH through the candidate gene approach. An estimation of the proportions performed with the HOMOG3R program showed that an LDLR gene defect was involved in approximately 50% of the families (P = 0.001). On the other hand, the estimated contribution of an APOB gene defect was only 15%. This low estimation of ADH due to an APOB gene defect is further strengthened by the existence of only two probands carrying the APOB (R3500Q) mutation in the sample. More importantly and surprisingly, 35% of the families in the sample were estimated to be linked to neither LDLR nor APOB genes. These data were confirmed by the exclusion of both genes through direct haplotyping in three families. Our results demonstrate that the relative contributions of LDLR and APOB gene defects to the disease are very different. Furthermore, our results also show that genetic heterogeneity is, generally, underestimated in ADH, and that at least three major groups of defects are involved. At this point, the contribution of the recently mapped FH3 gene to ADH cannot be assessed nor its importance in the group of 'non LDLR/non APOB' families.

Frénais R, Ouguerram K, Maugeais C, Marchini JS, Benlian P, Bard JM, Magot T, Krempf M. · Centre de Recherche en Nutrition Humaine, Groupe Métabolisme, Hôtel Dieu, Nantes, France. · J Lipid Res. · Pubmed #10428988 links to  free full text

Abstract: Heterozygous familial hypercholesterolemia (FH) is associated with a moderate decrease of plasma apoA-I and HDL-cholesterol levels. The aim of the study was to test the hypothesis that these abnormalities were related to an increase of HDL-apoA-I fractional catabolic rate (FCR). We performed a 14-h infusion of [5,5,5-(2)H(3)]leucine in seven control subjects and seven heterozygous FH patients (plasma total cholesterol 422 +/- 27 vs. 186 +/- 42 mg/dL, P < 0.001, respectively). Plasma apoA-I concentration was not changed in FH compared to controls (respectively 115 +/- 18 vs. 122 +/- 15 mg/dL, NS), and HDL-cholesterol level was decreased (37 +/- 7 vs. 46 +/- 19 mg/dL, NS). Kinetics of HDL metabolism were modeled as a single compartment as no differences were observed between HDL(2) and HDL(3) subclasses. Both mean apoA-I FCR and absolute production rate (APR) were increased in FH (respectively, 0.36 +/- 0.14 vs. 0.22 +/- 0.05 pool/d, P < 0.05, and 18.0 +/- 7.7 and 11.2 +/- 2.3 mg/kg/d, P < 0.05). Higher HDL-triglyceride and HDL-apoE levels were observed in patients with heterozygous FH. (Respectively 19 +/- 8 vs. 8 +/- 3 mg/dL, P < 0.05, and 5.3 +/- 0.8 vs. 3.7 +/- 0.9 mg/dL, P < 0.05). We conclude that the catabolism of HDL-apoA-I is increased in heterozygous FH patients. However, plasma apoA-I concentration was maintained because of an increased HDL-apoA-I production rate.

Varret M, Rabès JP, Saint-Jore B, Cenarro A, Marinoni JC, Civeira F, Devillers M, Krempf M, Coulon M, Thiart R, Kotze MJ, Schmidt H, Buzzi JC, Kostner GM, Bertolini S, Pocovi M, Rosa A, Farnier M, Martinez M, Junien C, Boileau C. · Hôpital Necker-Enfants Malades, Institut National de la Santé et de la Recherche Médicale, Unit 383, Université René Descartes, 75743 Paris Cedex 15, France. · Am J Hum Genet. · Pubmed #10205269 links to  free full text

Abstract: Autosomal dominant hypercholesterolemia (ADH), one of the most frequent hereditary disorders, is characterized by an isolated elevation of LDL particles that leads to premature mortality from cardiovascular complications. It is generally assumed that mutations in the LDLR and APOB genes account for ADH. We identified one large French pedigree (HC2) and 12 additional white families with ADH in which we excluded linkage to the LDLR and APOB, implicating a new locus we named "FH3." A LOD score of 3.13 at a recombination fraction of 0 was obtained at markers D1S2892 and D1S2722. We localized the FH3 locus to a 9-cM interval at 1p34.1-p32. We tested four regional markers in another set of 12 ADH families. Positive LOD scores were obtained in three pedigrees, whereas linkage was excluded in the others. Heterogeneity tests indicated linkage to FH3 in approximately 27% of these non-LDLR/non-APOB ADH families and implied a fourth locus. Radiation hybrid mapping located four candidate genes at 1p34.1-p32, outside the critical region, showing no identity with FH3. Our results show that ADH is genetically more heterogeneous than conventionally accepted.