Thomas P. Bersot

An International Atherosclerosis Society Position Paper: Global recommendations for the management of dyslipidemia

An international panel of the International Atherosclerosis Society has developed a new set of recommendations for management of dyslipidemia. The panel identifies non-high density lipoprotein cholesterol (non-HDL-C) as the major atherogenic lipoprotein. Primary and secondary prevention are considered separately. Optimal levels for atherogenic lipoproteins are derived for the two forms of prevention. For primary prevention, the recommendations emphasize lifestyle therapies to reduce atherogenic lipoproteins; drug therapy is reserved for higher risk subjects. Risk assessment is based on estimation of lifetime risk according to differences in baseline population risk in different nations or regions. Secondary prevention emphasizes use of cholesterol-lowering drugs to attain optimal levels of atherogenic lipoproteins.

A-Imilano apoprotein. Isolation and characterization of a cysteine-containing variant of the A-I apoprotein from human high density lipoproteins.

A recently discovered familial lipoprotein disorder is characterized by reduced plasma levels of high density lipoproteins (HDL) and elevated triglyceride levels. The clinical aspects of this disorder are presented in an accompanying article (Franceschini et al. 1980. J. Clin. Invest. 66: 892-900). The apoprotein content of the HDL isolated from these patients differed markedly from that of normal HDL in that three apoprotein bands not previously described in man were present as major protein components. As determined by sodium dodecyl sulfate (SDS) gel electrophoresis, the relative molecular weights (Mr) of these new apoprotein bands were 55,000, 35,000, and 28,000. Although the Mr 28,000 apoprotein coelectrophoresed with authentic A-I on SDS polyacrylamide gels and showed immunochemical identity with the A-I apoprotein when tested with monospecific apo-A-I antiserum, it contained two amino acid residues, cysteine and isoleucine, which were not present in the amino acid sequence of normal human apo-A-I. This variant form of the A-I apoprotein was designated the A-IMilano apoprotein and denoted A-Icys. By virtue of the presence of cysteine (2 mol/mol A-Icys), the A-Icys apoprotein was capable of forming intermolecular disulfide bonds, and dimer formation of A-Icys produced the Mr 55,000 apoprotein. The Mr 35,000 apoprotein was composed of two different subunits, A-Icys and A-II. By analogy to the apo(E--A-II) complex, which also occurs in human HDL, this mixed disulfide complex was designated as the apo(A-Icys--A-II) complex. The A-IMilano (A-Icys) is the first example of a variation in the primary sequence of a protein of plasma lipoproteins.

Genome-wide linkage and association analyses to identify genes influencing adiponectin levels: the GEMS Study.

Adiponectin has a variety of metabolic effects on obesity, insulin sensitivity, and atherosclerosis. To identify genes influencing variation in plasma adiponectin levels, we performed genome‐wide linkage and association scans of adiponectin in two cohorts of subjects recruited in the Genetic Epidemiology of Metabolic Syndrome Study. The genome‐wide linkage scan was conducted in families of Turkish and southern European (TSE, n = 789) and Northern and Western European (NWE, N = 2,280) origin. A whole genome association (WGA) analysis (500K Affymetrix platform) was carried out in a set of unrelated NWE subjects consisting of approximately 1,000 subjects with dyslipidemia and 1,000 overweight subjects with normal lipids. Peak evidence for linkage occurred at chromosome 8p23 in NWE subjects (lod = 3.10) and at chromosome 3q28 near ADIPOQ, the adiponectin structural gene, in TSE subjects (lod = 1.70). In the WGA analysis, the single‐nucleotide polymorphisms (SNPs) most strongly associated with adiponectin were rs3774261 and rs6773957 (P < 10−7). These two SNPs were in high linkage disequilibrium (r2 = 0.98) and located within ADIPOQ. Interestingly, our fourth strongest region of association (P < 2 × 10−5) was to an SNP within CDH13, whose protein product is a newly identified receptor for high‐molecular‐weight species of adiponectin. Through WGA analysis, we confirmed previous studies showing SNPs within ADIPOQ to be strongly associated with variation in adiponectin levels and further observed these to have the strongest effects on adiponectin levels throughout the genome. We additionally identified a second gene (CDH13) possibly influencing variation in adiponectin levels. The impact of these SNPs on health and disease has yet to be determined.

Fat feeding in humans induces lipoproteins of density less than 1.006 that are enriched in apolipoprotein [a] and that cause lipid accumulation in macrophages.

Formula diets containing lard or lard and egg yolks were fed to six normolipidemic volunteers to investigate subsequent changes in the composition of lipoproteins of d less than 1.006 g/ml and in their ability to bind and be taken up by receptors on mouse macrophages. Both formulas induced the formation of d less than 1.006 lipoproteins that were approximately 3.5-fold more active than fasting very low density lipoproteins (VLDL) in binding to the receptor for beta-VLDL on macrophages. Subfractionation of postprandial d less than 1.006 lipoproteins by agarose chromatography yielded two subfractions, fraction I (chylomicron remnants) and fraction II (hepatic VLDL remnants), which bound to receptors on macrophages. However, fraction I lipoproteins induced a 4.6-fold greater increase in macrophage triglyceride content than fraction II lipoproteins or fasting VLDL. Fraction I lipoproteins were enriched in apolipoproteins (apo) B48, E, and [a]. Fraction II lipoproteins lacked apo[a] but possessed apo B100 and apo E. The apo[a] was absent in normal fasting VLDL, but was present in the d less than 1.006 lipoproteins (beta-VLDL) of fasting individuals with type III hyperlipoproteinemia. The apo[a] from postprandial d less than 1.006 lipoproteins was larger than either of two apo[a] subspecies obtained from lipoprotein (a) [Lp(a)] isolated at d = 1.05-1.09. However, all three apo[a] subspecies were immunochemically identical and had similar amino acid compositions: all were enriched in proline and contained relatively little lysine, phenylalanine, isoleucine, or leucine. The association of apo[a] with dietary fat-induced fraction I lipoproteins suggests that the previously observed correlation between plasma Lp(a) concentrations and premature atherosclerosis may be mediated, in part, by the effect of apo[a] on chylomicron remnant metabolism.

Identification of a new structural variant of human apolipoprotein E, E2(Lys146 leads to Gln), in a type III hyperlipoproteinemic subject with the E3/2 phenotype.

A type III hyperlipoproteinemic subject having the apolipoprotein E (apo E) phenotype E3/2 was identified. From isoelectric focusing experiments in conjunction with cysteamine treatment (a method that measures cysteine content in apo E), the E2 isoform of this subject was determined to have only one cysteine residue, in contrast to all previously studied E2 apoproteins, which had two cysteines. This single cysteine was shown to be at residue 112, the same site at which it occurs in apo E3. From amino acid and sequence analyses, it was determined that this apo E2 differed from apo E3 by the occurrence of glutamine rather than lysine at residue 146. When phospholipid X protein recombinants of the subjects isolated E3 and E2 isoforms were tested for their ability to bind to the human fibroblast apo-B,E receptor, it was found that the E3 bound normally (compared with an apo E3 control) but that the E2 had defective binding (approximately 40% of normal). Although they contained E3 as well as E2, the beta-very low density lipoproteins (beta-VLDL) from this subject were very similar in character to the beta-VLDL from an E2/2 type III hyperlipoproteinemic subject; similar subfractions could be obtained from each subject and were shown to have a similar ability to stimulate cholesteryl ester accumulation in mouse peritoneal macrophages. The new apo E2 variant has also been detected in a second type III hyperlipoproteinemic subject.

Type III hyperlipoproteinemia associated with apolipoprotein E phenotype E3/3. Structure and genetics of an apolipoprotein E3 variant.

A family has been described in which type III hyperlipoproteinemia is associated with apo E phenotype E3/3 (Havel, R. J., L. Kotite, J. P. Kane, P. Tun, and T. Bersot. 1983. J. Clin. Invest. 72:379-387). In the current study, the structure of apo E from the propositus of this family was determined using both protein and DNA analyses. The propositus is heterozygous for two different apo E alleles, one coding for normal apo E3 and one for a previously undescribed variant apo E3 in which arginine replaces cysteine at residue 112 and cysteine replaces arginine at residue 142. Apo E gene analysis of nine other family members spanning four generations indicated that only those five members having type III hyperlipoproteinemia possess the variant apo E3. Like the propositus, all five are heterozygous for this variant, suggesting that the disorder in this family is transmitted in a dominant fashion. The variant apo E3 was defective in its ability to bind to lipoprotein receptors, and this functional defect probably contributes to the expression of type III hyperlipoproteinemia in this family.

Atypical familial dysbetalipoproteinemia associated with apolipoprotein phenotype E3/3.

Familial dysbetalipoproteinemia has been reported to be associated uniquely with an apolipoprotein E phenotype (E2/2) that occurs in approximately 1% of all persons. We have observed the typical clinical and biochemical characteristics of this disorder in five members of a family, in all of whom the apolipoprotein E phenotype, as determined by isoelectric focusing electrophoresis, is E3/3. The disorder is present in three generations of the family: the proband, her mother, and three of the probands five children. The probands husband, father of all five children, also has apolipoprotein E phenotype E3/3, as do his two unaffected children. As in normal persons with phenotype E3/3, the apolipoprotein E of affected members appears to have a single residue of cysteine. When incorporated with egg lecithin into discoidal complexes, the apolipoprotein E from affected members was taken up normally into perfused livers of estradiol-treated rats, in which a high level of LDL receptors is expressed. When isoelectric focusing electrophoresis was carried out over a narrow range of pH (5-7), each of the apolipoprotein E isoforms of affected members was observed as a doublet, even after reduction of dimers of the protein with 2-mercaptoethanol and treatment with neuraminidase to minimize the content of sialylated forms of the protein. Doublets were also observed in the apolipoprotein E-2 of patients with classical dysbetalipoproteinemia, but only in the affected members of the family with atypical dysbetalipoproteinemia were the components of the doublets equally prominent. As in classical dysbetalipoproteinemia, both apolipoprotein B-100 and B-48 were present in the very low density lipoprotein fraction of plasma obtained in the postabsorptive state, indicating that remnantlike lipoproteins of both hepatic and intestinal origin accumulate. This observation, together with available evidence on the structural and functional heterogeneity of human apolipoprotein E, lead us to suggest that the disorder in this family is caused by one or two structurally abnormal forms of apolipoprotein E that contain a single residue of cysteine.

Effect of a High-Fructose Weight-Maintaining Diet on Lipogenesis and Liver Fat

CONTEXT Consumption of high-fructose diets promotes hepatic fatty acid synthesis (de novo lipogenesis [DNL]) and an atherogenic lipid profile. It is unclear whether these effects occur independent of positive energy balance and weight gain. OBJECTIVES We compared the effects of a high-fructose, (25% of energy content) weight-maintaining diet to those of an isocaloric diet with the same macronutrient distribution but in which complex carbohydrate (CCHO) was substituted for fructose. DESIGN, SETTING, AND PARTICIPANTS Eight healthy men were studied as inpatients for consecutive 9-day periods. Stable isotope tracers were used to measure fractional hepatic DNL and endogenous glucose production (EGP) and its suppression during a euglycemic-hyperinsulinemic clamp. Liver fat was measured by magnetic resonance spectroscopy. RESULTS Weight remained stable. Regardless of the order in which the diets were fed, the high-fructose diet was associated with both higher DNL (average, 18.6 ± 1.4% vs 11.0 ± 1.4% for CCHO; P = .001) and higher liver fat (median, +137% of CCHO; P = .016) in all participants. Fasting EGP and insulin-mediated glucose disposal did not differ significantly, but EGP during hyperinsulinemia was greater (0.60 ± 0.07 vs 0.46 ± 0.06 mg/kg/min; P = .013) with the high-fructose diet, suggesting blunted suppression of EGP. CONCLUSION Short-term high-fructose intake was associated with increased DNL and liver fat in healthy men fed weight-maintaining diets.

Anthropometric indices and their relationship with cardiometabolic risk factors in a sample of Turkish adults.

OBJECTIVE To identify the best anthropometric index that predicts cardiometabolic risk factors.Design and settingCross-sectional study in Turkey, in 2003. SUBJECTS Turkish men and women aged 18 years and over (n 1692) were examined. Body weight, height, waist and hip circumferences, blood pressure, total cholesterol, HDL cholesterol, TAG, glucose and insulin were measured. Metabolic syndrome score was calculated as the sum of modified National Cholesterol Education Program Adult Treatment Panel III criteria, excluding waist circumference. Insulin resistance was estimated by homeostasis model assessment (HOMA-IR). RESULTS BMI, waist:hip ratio (WHpR), waist:height ratio (WHtR), waist circumference (WC) and hip circumference (HC) were significantly correlated with each other. Partial correlation coefficients between systolic blood pressure, HDL cholesterol, TAG levels or HOMA-IR and BMI, WC or WHtR were similar and higher than correlation coefficients of WHpR and HC. The association of anthropometric indices with metabolic syndrome score and Framingham risk score was highest for WHtR. Areas under the receiver-operating characteristic curves showed that WHtR was the best anthropometric index that discriminated between the presence and absence of hypertension, diabetes and metabolic syndrome, whereas WHpR was better for dyslipidaemia. CONCLUSIONS WHtR was the best anthropometric index for predicting most cardiometabolic risk factors. WC and BMI ranked second for their predictive capability of cardiometabolic risk, followed by WHpR and HC.

Analysis of agreement among definitions of metabolic syndrome in nondiabetic Turkish adults: a methodological study

BackgroundWe aimed to explore the agreement among World Health Organization (WHO), European Group for the Study of Insulin Resistance (EGIR), National Cholesterol Education Program (NCEP), American College of Endocrinology (ACE), and International Diabetes Federation (IDF) definitions of the metabolic syndrome.Methods1568 subjects (532 men, 1036 women, mean age 45 and standard deviation (SD) 13 years) were evaluated in this cross-sectional, methodological study. Cardiometabolic risk factors were determined. Insulin sensitivity was calculated by HOMA-IR. Agreement among definitions was determined by the kappa statistic. ANOVA and post hoc Tukeys test were used to compare multiple groups.ResultsThe agreement between WHO and EGIR definitions was very good (kappa: 0.83). The agreement between NCEP, ACE, and IDF definitions was substantial to very good (kappa: 0.77–0.84). The agreement between NCEP or ACE or IDF and WHO or EGIR definitions was fair (kappa: 0.32–0.37). The age and sex adjusted prevalence of metabolic syndrome was 38% by NCEP, 42% by ACE and IDF, 20% by EGIR and 19% by WHO definition. The evaluated definitions were dichotomized after analysis of design, agreement and prevalence: insulin measurement requiring definitions (WHO and EGIR) and definitions not requiring insulin measurement (NCEP, ACE, IDF). One definition was selected from each set for comparison. WHO-defined subjects were more insulin resistant than subjects without the metabolic syndrome (mean and SD for log HOMA-IR, 0.53 ± 0.14 vs. 0.07 ± 0.23, respectively, p < 0.05) and had higher Framingham risk scores (mean and SD, 2.99 ± 4.64% vs. 1.10 ± 1.87%, respectively, p < 0.05). The additional subjects identified by IDF definition, but not by WHO definition also had more insulin resistance and higher Framingham risk scores than subjects without the metabolic syndrome (mean and SD, log HOMA-IR 0.18 ± 0.18 vs. 0.07 ± 0.23, p < 0.05 and Framingham risk score 2.93 ± 4.54% vs. 1.10 ± 1.87%, p < 0.05). The IDF-identified additional subjects had similar Framingham risk scores as WHO-identified subjects (p > 0.05), but lower log HOMA-IR values (p < 0.05).ConclusionThe metabolic syndrome definitions that do not require measurement of insulin levels (NCEP, ACE and IDF) identify twice more patients with insulin resistance and increased Framingham risk scores and are more useful than the definitions that require measurement of insulin levels (WHO and EGIR).