The effect of endurance exercise training on plasma lipoprotein AI and lipoprotein AI:AII concentrations in sedentary adults.

The effect of 6 months of endurance exercise training on plasma concentrations of lipoprotein (Lp)AI and LpAI:AII was determined in 39 sedentary subjects (17 men, 22 women, average age, 57 years) with abnormal cholesterol concentrations (total cholesterol [TC] > 200 mg/dL, or high-density lipoprotein-cholesterol [HDL-C] < 35 mg/dL). Following exercise training, plasma LpAI concentrations increased (+5.9 +/- 1.2 mg/dL; P <.001), but there was no change in total apolipoprotein (apo) A-I or LpAI:AII concentrations. The change in plasma LpAI concentration was positively correlated to changes in total HDL-C (r =.495, P =.001), the sum of HDL4-C(nmr) + HDL5-C(nmr) (r =.417, P =.008), and average HDL particle size (r =.415, P =.009), but not to changes in body composition or Vo2max. In the 8 subjects with the greatest change in LpAI concentration following training, the size distribution of LpAI and LpAI:AII particles in plasma also was measured before and after training. In these subjects, the size distribution of LpAI:AII particles did not change with training, but there was a significant increase (0.1 nm; P =.048) in the peak size of the "medium" (7.8 to 9.8 nm) LpAI particles after training. In 7 subjects who served as age- and weight-matched sedentary controls, plasma concentrations of total apo A-I, the LpAI and LpAI:AII subfractions, and plasma lipoprotein-lipids did not differ significantly between baseline and final testing. These data indicate that endurance exercise training increases the average size and plasma concentrations of LpAI, but not LpAI:AII, particles, which may represent possible enhancements of reverse cholesterol transport and may provide insight into the role that exercise plays in reducing cardiovascular disease risk.

Value of HDL cholesterol, apolipoprotein A-I, lipoprotein A-I, and lipoprotein A-I/A-II in prediction of coronary heart disease: the PRIME Study. Prospective Epidemiological Study of Myocardial Infarction.

OBJECTIVE: We have examined the association between the incidence of coronary heart disease (CHD) and plasma high density lipoprotein (HDL) cholesterol, apolipoprotein A-I (apoA-I), and 2 HDL fractions, lipoprotein A-I and lipoprotein A-I:A-II. METHODS AND RESULTS: These parameters were measured in subjects recruited in France and in Northern Ireland in the Prospective Epidemiological Study of Myocardial Infarction (PRIME) Study, a prospective cohort study. Among the subjects free of CHD on entry, 176 in France and 113 in Northern Ireland suffered an ischemic attack (CHD patients) during the 5-year follow-up, whereas 6612 French and 2172 Northern Irish men showed no CHD symptoms (CHD-free subjects). All 4 HDL parameter levels were lower in CHD patients than in CHD-free subjects. After the cohort was divided into quintiles based on the distribution of HDL parameter levels, a significant (P<0.0001) linear increase in relative risk was observed for each HDL parameter level. However, regression logistic analyses showed that apoA-I was the strongest predictor (more powerful than HDL cholesterol) and that lipoprotein A-I and lipoprotein A-I:A-II did not supplement apoA-I in predicting CHD. CONCLUSIONS: Among the parameters related to HDL, apoA-I appears to be the strongest independent risk factor.

LpAI in HDL subfractions: serum levels in men and women with coronary heart disease and changes under hypolipemic therapy.

BACKGROUND: It is generally accepted that different HDL subpopulations may vary in their antiatherogenic potential, and the identification and differentiation of individual HDL subclasses may be useful in documentation and understanding of metabolic changes of different HDL particle groups. METHODS: In the present study, LpAI particles concentrations in HDL(2) and HDL(3) subfractions were determined in serum of 54 CHD patients (33 men and 21 women) and 46 control subjects (19 men and 27 women) with similar total cholesterol and HDL-cholesterol levels. RESULTS: In CHD patients, both men and women, as compared to control subjects lower levels of LpAI subpopulations were found, however, the difference was much more predominant for LpAI-HDL(2) than for LpAI-HDL(3). The effect of hypolipidemic treatment on the distribution of LpAI subpopulations between HDL subfractions was investigated in 44 hyperlipidemic patients assigned to fenofibrate therapy and 43 patients assigned to simvastatin therapy. Fenofibrate did not change LpAI level but had an effect on LpAI particle distribution among HDL(2) and HDL(3) increasing LpAI concentration in HDL(2) and slightly decreasing LpAI concentration in HDL(3). Simvastatin led to an increase in LpAI-HDL(3) and did not change significantly LpAI-HDL(2) particle concentration. CONCLUSION: Further studies are needed to evaluate the significance of different HDL subpopulations.

[Clinical significance of serum LpA-I levels measured by immunoturbidimetric assay in type 2 diabetes mellitus patients].

Previously, we developed an immunoturbidimetric assay method for lipoprotein A-I(LpA-I) on sera pre-absorbed with anti-apolipoprotein A-II. In the present study, correlations between serum lipoprotein A-I and other serum parameters levels were examined and LpA-I levels were studied in patients with type 2 diabetes mellitus. The serum levels of LpA-I did not correlate with those of diabetic markers such as fasted blood glucose, glycohemoglobin(HbA1c) and fructosamine, but correlated well with the levels of total cholesterol and HDL cholesterol, phospholipids, apolipoprotein A-I and seemed to correlate inversely with arteriosclerosis index. In patients with type 2 diabetes mellitus, LpA-I levels were significantly lower than those in normal subjects. Especially, LpA-I levels of patients with diabetic complications were significantly lower than those in normal subjects and non-complicated diabetic patients. Then, the measurement of LpA-I levels in patients with type 2 diabetes mellitus was considered to be useful for prevention and management of arteriosclerosis.

Effect of acylglyceride content on the structure and function of reconstituted high density lipoprotein particles.

The effects of different acylglycerides on the conformation and charge of apolipoprotein A-I (apoA-I) have been investigated in reconstituted high density lipoproteins (LpA-I). Various amounts of diacylglycerol (DG) and triacylglycerol (TG) were incorporated into sonicated spherical LpA-I particles containing 2 molecules of apoA-I and 80 molecules of phospholipid. Inclusion of 30 molecules of TG into the LpA-I particle increases the net negative charge of apoA-I (-8.5 to -9.3 mV), but has little effect on the amount and thermodynamic stability of the alpha helices in apoA-I. Incorporation of 30 molecules of DG into the lipoprotein complex promotes a small increase in the alpha-helix content and stability, but greatly increases the net negative charge of apoA-I (-8.5 to -11.2 mV). Inclusion of DG increases the immunoreactivity of two epitopes in the N terminus of apoA-I, but decreases the exposure of a domain closer to the C terminus (residues 148;-186) of the apoprotein. In contrast, TG increases the exposure of epitopes over the entire apoA-I molecule; TG increases the immunoreactivity of epitopes for 13 different monoclonal antibodies to apoA-I. Incubations with purified lecithin:cholesterol acyltransferase show that cholesterol esterification is stimulated by DG, but inhibited by TG. The data show that TG and DG have different effects on apoA-I structure and function and this suggests that the TG-to-DG ratio in HDL may directly affect the metabolism of this lipoprotein class. - Braschi, S., C. R. Coffill, T. A-M. Neville, D. M. Hutt, and D. L. Sparks. Effect of acylglyceride content on the structure and function of reconstituted high density lipoprotein particles. J. Lipid Res. 2001. 42: 79;-87.

[Central hemodynamic status in young patients with myocardial ischemia]. / Stan tsentral'noï gemodynamiky u khvorykh na ishemichnu khvorobu sertsia molodogo viku.

Results are submitted of investigations designed to study central hemodynamics and intracardiac kinetics in young patients with ischemic heart disease (IHD). In young coronary patients the course of the disease has been shown to be more often accompanied by the development of cardiac aneurism than in the elder ones in spite of the presence in the latter of more significant changes in their echocardiograms. Concomitant with aggravation of clinical manifestations of IHD (higher functional class of stable angina) there is an increase in the size of the left ventricle and decrease in the ejection fraction. It has been shown that hemodynamic parameters are closely related to both veloergometry indices and levels of cholesterol of high density lipoproteins APO-A-I.

The relationship between apolipoprotein AI-containing lipoprotein fractions and environmental factors: the prospective epidemiological study of myocardial infarction (PRIME study).

Apolipoprotein (apo) AI is distributed within high-density lipoproteins (HDL) between different types of particles, one containing both apoAI and apoAII (LpAI:AII), the other containing no apoAII (LpAI). We investigated the associations between LpAI and LpAI:AII with several factors such as body mass index (BMI), waist to hip ratio (WHR), alcohol intake, cigarette consumption and physical activity, in three French and one Northern Irish male populations included in a prospective study (PRIME study). LpAI and LpAI:AII were associated with variations in all environmental factors, except LpAI:AII, which was not associated with WHR. These relationships were unchanged after adjustment for other environmental factors, but slightly modified after adjustment for triglyceride levels. LpAI decreased when BMI, WHR and cigarette smoking increased, and increased with alcohol consumption and physical activity. LpAI:AII had a similar variation except for the absence of LpAI:AII modification associated with WHR variation. The associations between LpAI and BMI, alcohol consumption and cigarette smoking were largely dependent on HDL-cholesterol as indicated by the lack of any significance when the adjustment for HDL-cholesterol was made. Conversely, after adjustment for HDL-cholesterol, the significant association between LpAI:AII and BMI disappeared, while the associations between LpAI:AII and alcohol consumption, cigarette smoking and physical activity remained significant. These results suggest that the mechanisms of LpAI and LpAI:AII modulations differ according to each environmental factor, some dependent on the lipid content of lipoproteins and others not, but LpAI and LpAI:AII levels seem independent of triglyceride concentration.

Probucol promotes reverse cholesterol transport in heterozygous familial hypercholesterolemia. Effects on apolipoprotein AI-containing lipoprotein particles.

In order to investigate the effect of Probucol therapy on reverse cholesterol transport, apo AI-containing lipoprotein particles were isolated and characterized, and their cholesterol effluxing capacity and LCAT activity were assayed in four familial hypercholesterolemia patients before and after 12 weeks of Probucol therapy. Four major subpopulations of apo A-containing lipoprotein particles are separated before and after drug treatment; LpAI, LpAI:AII, LpAIV, LpAI:AIV:AII. Probucol reduces both total plasma and LDL-cholesterol (-17 and -14%, respectively). Apo B decreases slightly (-7.6%). Plasma HDL-cholesterol and apo AI decrease by 36.6 and 34.7%. LpA-I showed a marked decrease (-46%). Moreover, plasma LCAT and CETP activities were markedly increased under Probucol treatment. Analysis of lipoprotein particles showed that Probucol induces a decrease of protein content and an increase of cholesterol and triglycerides contents. Interestingly, Probucol induces an enhancement of LCAT activity in LpAI (4.5-fold). This drug induces a trend toward greater cholesterol efflux from cholesterol-preloaded adipose cells promoted by Lp AI and Lp AIV but not by Lp AI:AII. This study confirms the hypothesis, in addition to the lowering LDL-cholesterol levels and antioxidant effects of Probucol, that HDL reduction was not an atherogenic change in HDL system but may cause an antiatherogenic action by accelerating cholesterol transport through HDL system, promoting reverse cholesterol transport from peripheral tissues.

In vivo metabolism of HDL, apo A-I, and lp A-I, and function of HDL--a clinical perspective.

Serum levels of high density lipoprotein cholesterol (HDL-C) are inversely correlated with coronary heart disease (CHD). Kinetic studies indicate that the mechanism for the variation in HDL levels associated with various pathophysiologic states includes changes in the fractional catabolic rate (FCR) and/or the synthesis rate of HDL and its major proteins apolipoprotein (apo) A-I and apo A-II. The antiatherogenic effects of HDL are thought to be mainly due to its role in reverse cholesterol transport. HDL is an assembly of heterogeneous particles. HDL enlarges when it takes up cellular cholesterol, and shrinks when HDL cholesterol ester (CE) is transfered to low density lipoprotein (LDL) and very low density lipoprotein (VLDL) particles. The functional ability of HDL (to remove cellular cholesterol) has drawn considerable attention. The fractional esterification rate of cholesterol in HDL (FER(HDL)) has been established as a functional assay of HDL, and reflects the size of HDL particles. We investigated the clinical significance of FER(HDL) and its relationship to the quantity of HDL. FER(HDL) values were inversely correlated with levels of HDL-C and large lipoprotein containing apo A-I (LpA-I). The association between FER(HDL) and CHD changed with serum HDL-C levels: increased FER(HDL) values significantly increased the risk of CHD when serum HDL-C levels were low, while there was no such relationship when HDL-C levels were high. We concluded that the combination of HDL-C levels and FER(HDL) is a stronger indicator of CHD than either the HDL-C level (quantitative measure of HDL) or FER(HDL) (functional measure of HDL) alone.

[Development of a serum lipoprotein A-I immunoassay method].

We developed an immunoturbidimetric assay method for lipoprotein A-I by treating sera with an anti-apo lipoprotein A-II and A-I antibody sequentially. The assay is sensitive to detect lipoprotein A-I as little as 155 mg/l with good precision. There was a good correlation in the level of serum lipoprotein A-I between the present assay and a conventional differential electroimmunoassay on ready-to-use plates (r = 0.947; p < 0.001). Reference intervals in normal healthy adults (n = 109) ranged from 284 to 736 mg/l. The values were significantly lower in patients with coronary artery disease than in normal subjects (p < 0.001). The present assay can be useful to analyze patho-physiologic events in various lipid disorders.

Moderate red wine consumption in healthy volunteers reduced plasma clearance of apolipoprotein AII.

BACKGROUND: The mechanisms of the positive relationship between alcohol intake and plasma concentration of high-density lipoprotein (HDL) are still unclear. The present study shows the metabolism modifications of apolipoprotein (apo) AI and apoAII in normolipidaemic healthy volunteers after a period of moderate red wine consumption. DESIGN: Five non-smoking male subjects were studied at the end of two consecutive 4-week periods, one without alcohol and the other with an intake of 50 g per day of alcohol, in random order. The metabolic parameters of apoAI and apoAII in HDL were determined after endogenous labelling using amino acid labelled with stable isotope. Cholesterol, triacylglycerols, HDL-cholesterol, apoAI, apoAII, LpAI, LpAI:AII were determined in plasma at the end of the two study periods. RESULTS: Cholesterol and triacylglycerols did not vary significantly during the two periods, whereas HDL-cholesterol increased from 43.8 to 50.0 mg dL-1 (P < 0.05). ApoAI and apoAII increased significantly (20% and 60% respectively) after the diet was supplemented with alcohol. LpAI:AII increased from 73.8 to 101.6 mg dL-1 (+32%) (P < 0.05), whereas alcohol had no effect on the concentration of LpAI. The alcohol treatment did not significantly alter the metabolism of apoAI. Conversely, the fractional catabolic rate of apoAII decreased significantly by 21% (P < 0.05) with alcohol, whereas the production rate of apoAII tended to increase by 18% (P = 0.08). CONCLUSION: The decrease in the fractional catabolic rate of apoAII could lead to an accumulation of apoAII-containing lipoproteins in plasma and account for the dramatic increase in LpAI:AII observed in the plasma of subjects consuming alcohol.

The structure of human lipoprotein A-I. Evidence for the "belt" model.

The two main competing models for the structure of discoidal lipoprotein A-I complexes both presume that the protein component is helical and situated around the perimeter of a lipid bilayer disc. However, the more popular "picket fence" model orients the protein helices perpendicular to the surface of the lipid bilayer, while the alternative "belt" model orients them parallel to the bilayer surface. To distinguish between these models, we have investigated the structure of human lipoprotein A-I using a novel form of polarized internal reflection infrared spectroscopy that can characterize the relative orientation of protein and lipid components in the lipoprotein complexes under native conditions. Our results verify lipid bilayer structure in the complexes and point unambiguously to the belt model.

Abnormal capacity to induce cholesterol efflux and a new LpA-I pre-beta particle in type 2 diabetic patients.

In this study, we first characterized the lipoprotein components of serum samples obtained from a group of well-controlled diabetic patients and from healthy subjects in fasting and postprandial states. We then explored some aspects of reverse cholesterol transport in the same population. Patients showed high levels of fasting triglycerides, postprandial triglyceride responses and LpC-III levels (3.18+/-0.86 vs 2.17+/-0.54 mg/dl, P < 0.001). There were also positive correlations between LpC-III and fasting triglycerides (r = 0.82, P < 0.001), total triglyceride area (r = 0.75, P < 0.001) and incremental triglyceride area (r = 0.54, P < 0.001). HDL-C and apo A-I were significantly decreased in diabetic patients due to a selective reduction in LpA-I subfraction, whose antiatherogenic role is generally accepted (37.4+/-8.0 vs 49.2+/-12.5 mg/dl, P < 0.001). In addition, HDL from patients proved to be triglyceride enriched and cholesteryl ester depleted, alterations which were further amplified in the postprandial state. The molar ratio HDL-C/apo A-I + apo A-II, already defined as a predictor of apo A-I fractional catabolic rate, was significantly diminished in the patient group (15.1+/-2.2 vs 20.8+/-3.3, P < 0.001), thus suggesting an accelerated catabolism of apo A-I. For the first time, we describe here the presence of a small apo A-I-containing particle, isolated by two-dimensional electrophoresis and characterized by immunoblotting, only in samples from diabetic patients. This particle that we named pre-beta0, has an apparent molecular weight of 40 kDa. As regards the capacity of serum samples to promote cholesterol efflux from [3H]cholesterol-labeled Fu5AH rat hepatoma cells, patient samples were found to induce significantly lower cholesterol efflux than controls only in the postprandial state (21.2+/-3.3 vs 23.8+/-1.8%, P = 0.012). The presence of pre-beta0 in samples from diabetic patients might therefore be associated to an altered capacity of these serum samples to promote cellular cholesterol efflux. Overall, these abnormalities may contribute to a delay in the reverse cholesterol transport pathway in type 2 diabetic patients.

Apolipoprotein A-I charge and conformation regulate the clearance of reconstituted high density lipoprotein in vivo.

While low apolipoprotein A-I (apoA-I) levels are primarily associated with increased high density lipoprotein (HDL) fractional catabolic rate (FCR), the factors that regulate the clearance of HDL from the plasma are unclear. In this study, the effect of lipid composition of reconstituted HDL particles (LpA-I) on their rate of clearance from rabbit plasma has been investigated. Sonicated LpA-I containing 1 to 2 molecules of purified human apoA-I and 5 to 120 molecules of palmitoyl-oleoyl phosphatidylcholine (POPC) exhibit similar charge and plasma FCR to that for lipid free apoA-I, 2.8 pools/day. Inclusion of 1 molecule of apoA-II to an LpA-I complex increases the FCR to 3.5 pools/day, a value similar to that observed for exchanged-labeled HDL3. In contrast, addition of 40 molecules of triglyceride, diglyceride, or cholesteryl ester to a sonicated LpA-I containing 120 moles of POPC and 2 molecules of apoA-I increases the negative charge of the particle and reduces the FCR to 1.8 pools/day. Discoidal LpA-I are the most positively charged lipoprotein particles and also have the fastest clearance rates, 4.5 pools/day. Immunochemical characterization of the different LpA-I particles shows that the exposure of an epitope at residues 98 to 121 of the apoA-I molecule is associated with an increased negative particle charge and a slower clearance from the plasma. We conclude that the charge and conformation of apoA-I are sensitive to the lipid composition of LpA-I and play a central role in regulating the clearance of these lipoproteins from plasma. conformation regulate the clearance of reconstituted high density lipoprotein in vivo.

Importance of central alpha-helices of human apolipoprotein A-I in the maturation of high-density lipoproteins.

We have studied the role of amphipathic alpha-helices in the ability of apoA-I to promote cholesterol efflux from human skin fibroblasts and activate lecithin:cholesterol acyltransferase (LCAT). Three apoA-I mutants were designed, each by deletion of a pair of predicted adjacent central alpha-helices [Delta(100-143), Delta(122-165), Delta(144-186)], and expressed in Escherichia coli. This strategy was used to minimize disruption of the predicted secondary structure of the resulting protein. These three central deletion mutants have been previously shown to be expressed as stable folded proteins but to exhibit altered phospholipid-binding properties. When recombined with phospholipids to form homogeneous LpA-I containing equivalent amounts of POPC and tested for their ability to promote diffusional cholesterol efflux from normal [3H]cholesterol-labeled fibroblasts, each mutant and the wild-type recombinant protein (Rec.-apoA-I) promoted cholesterol efflux with very similar rates at all the concentrations tested. These experiments showed that all LpA-I could acquire cellular cholesterol with similar affinity and binding capacity. However, when the cell-incubated LpA-I were incubated with purified LCAT, two mutants, Delta(122-165) and Delta(144-186), appeared incapable of activating the enzyme. To directly determine their ability to activate LCAT, each mutant and the control were recombined with equivalent amounts of cholesterol and phospholipid and incubated with the purified enzyme. The results show that whereas deletion of residues 100-143 has little effect on LCAT activation, deletion of residues 122-165 or 144-186 results in an inability of the mutants to promote cholesterol esterification. In conclusion, our results show that no specific sequence in the central domain of apoA-I is required for efficient diffusional cholesterol efflux from normal fibroblasts; however, residues 144-186 appear critical for optimum LCAT activation and cholesteryl ester accumulation. Since deletion of residues 144-186 also perturbs phospholipid association and prevents the formation of large LpA-I particles [Frank, P. G., Bergeron, J., Emmanuel, F., Lavigne, J. P., Sparks, D. L., Denèfle, P., Rassart, E., and Marcel, Y. L. (1997) Biochemistry 36, 1798-1806], the data show that this pair of alpha-helices plays an important role in the maturation of HDL. Sequence analysis of these apoA-I helices further identifies specific residues that appear essential to this activity.

Beneficial effect on serum apo AI, apo B and Lp AI levels of Ramadan fasting.

In order to investigate for the first time in Morocco the effect of fasting in Ramadan, the ninth lunar month of the muslim year, on lipoprotein metabolism, we determined the levels of serum apolipoproteins; apolipoprotein AI (apo AI), apo B, apo AIV and those of lipoprotein particles; apo AI-containing lipoprotein particles (Lp AI) and also apo AI and apo AII containing lipoprotein particles (Lp AI:AII) in a group of 32 healthy, volunteer adult males. Determination of all these parameters was carried out on each week of the month of Ramadan and the results are compared with the pre-fasting and the post-fasting values. Ramadan fasting reduces significantly serum apo B (P < 0.05), while serum apo AI is significantly increased (P < 0.05) compared with the pre-fasting period. The increase of apo AI occurred on day 29 of Ramadan by 11.8%. Serum apo AIV was unchanged during the fasting period indicating that food intake during Ramadan is not based on lipid diet. The observed diet pattern during Ramadan showed an increase of total energy intake based on carbohydrates (+1.4% of total energy), proteins (+0.4% of total energy) but not on fat (-0.7% of total energy), compared with a usual diet used in the rest of the year. The fat diet is high in monounsaturated (P < 0.05) and polyunsaturated fatty acid in contrast to saturated fatty acid which decreased (P < 0.05) during Ramadan. On the other hand, analysis of serum Lp AI and Lp AI:AII showed that the levels of Lp AI:AII were unchanged but those of Lp AI were significantly increased (P < 0.01) at the end of Ramadan. These findings show that feeding behaviour that occurs during Ramadan beneficially affects serum apolipoprotein metabolism and may contribute to prevention of cardiovascular diseases.

Distribution and correlates of serum high-density lipoprotein subclasses (LpA-I and LpA-I:A-II) in children from a biracial community. The Bogalusa Heart Study.

High-density lipoprotein (HDL) subclasses are considered to differ in terms of antiatherogenic potential. Therefore, the distribution and correlates of serum lipoprotein A-I (LpA-I) and LpA-I:A-II were examined in a random community-based subsample of black (n = 1,021) and white (n = 1,087) children aged 5 to 17 years. Black children had significantly higher LpA-I levels than white children. With respect to LpA-I:A-II, prepubertal (age 5 to 10 years) black males and pubertal (age 11 to 17 years) white children showed significantly higher values than their counterparts. With the exception of the LpA-I:A-II difference among prepubertal males, the observed black-white difference was independent of the racial differential in serum triglycerides, a metabolic correlate of HDL. A significant sex differential (males > females) was noted among blacks and whites for both HDL subclasses, with the exception of LpA-I levels at the pubertal age. Among the pubertal age group, a male-female crossover trend (females > males) in LpA-I levels was apparent after age 14. Sexual maturation and age were the major factors (negative) contributing to the variability in the levels of HDL subclasses among race-sex groups; adiposity (negative), insulin (negative), alcohol intake (positive), and oral contraceptive use (positive) emerged as minor but significant predictor variables. In terms of a relation to other lipoprotein variables, LpA-I compared with LpA-I:A-II correlated much more strongly with HDL cholesterol. Unlike LpA-I, LpA-I:A-II was associated significantly (positively) with low-density lipoprotein (LDL) cholesterol. These findings are indicative of intrinsic metabolic differences among the race-sex groups early in life, resulting in variability in the HDL subclass pattern and attendant antiatherogenic potential.

Chimpanzee lipoprotein(A): Relationship between apolipoprotein(A) isoform size and the density profile of lipoprotein(A) in animals with different heterozygous apo(A) phenotypes.

In a previous study [C. Doucet et al., J. Lipid Res 35:263-270, 1994], we have shown that plasma lipoprotein (a) [Lp(a)] levels were significantly elevated in a population of unrelated chimpanzees as compared to those in normolipidemic human subjects. Nonetheless, the inverse correlation between Lp(a) levels and apolipoprotein (a) [apo(a)] isoforms typical of man was maintained in the chimpanzee. In the present study, we describe the density profiles of apo B- and apo A1-containing lipoproteins and of Lp(a) in chimpanzee plasmas heterozygous for apo(a) isoforms after fractionation by single spin ultracentrifugation in an isopycnic gradient. The distribution of apo(a) isoforms in the density gradient was also examined by SDS-agarose gel electrophoresis and immunoblotting using chemiluminescence detection. In all double-band phenotypes examined, the smallest isoform was present along the entire length of the density gradient. The density distribution of the second isoform varied according to the size difference between the respective isoforms. Two isoforms close in size (difference in apparent molecular mass = 60 kDa) were present together in every gradient subfraction. On the contrary, when the two isoforms displayed distinct molecular mass (maximal difference in apparent molecular mass = 340 kDa), then the largest was principally present in the densest fractions of the gradient (d > 1.1 mg/ml). These observations suggest that Lp(a) particles with small apo(a) isoforms are more susceptible to interact with other lipoproteins than are Lp(a) particles with large isoforms.

In vivo glucosylated LpA-I subfraction. Evidence for structural and functional alterations.

This study compared the structural and functional properties of glucosylated and non-glucosylated LpA-I particle subfractions (GLpA-I and NGLpA-I, respectively) isolated from patients with poorly controlled type 1 (insulin-dependent) diabetes. Compared with NGLpA-I, GLpA-I showed an enrichment in triglycerides (P < .05) and a depletion in phospholipid (P < .05) content. Moreover, the triglycerides-to-cholesteryl esters ratio was increased (P < .05), suggesting an increased cholesteryl ester transfer protein activity and a possible transport defect that accelerates atherogenesis. The surface-to-core constituents ratio, an indirect estimate of particles size, is lower in GLpA-I (P < .01) than in NGLpA-I, correlating well with a larger median size (P < .05) as seen by electron microscopy. The apolipoprotein (apo) A-I conformation was evaluated through determination of the immunological accessibility of three different domains defining specific epitopes for anti-apo A-I monoclonal antibodies. We observed a marked decreased accessibility for two of these regions, which interestingly have already been implicated in the interaction with cells. Cell culture data suggest that nonenzymatic glycosylation occurring on apo A-I can modify lipoprotein function, since it results in a decreased binding of GLpA-I to HeLa cells and impaired cholesterol efflux from Fu5AH rat hepatoma cells.

Apolipoprotein L, a new human high density lipoprotein apolipoprotein expressed by the pancreas. Identification, cloning, characterization, and plasma distribution of apolipoprotein L.

In this study, we have identified and characterized a new protein present in human high density lipoprotein that we have designated apolipoprotein L. Using a combination of liquid-phase isoelectrophoresis and high resolution two-dimensional gel electrophoresis, apolipoprotein L was identified and partially sequenced from immunoisolated high density lipoprotein (Lp(A-I)). Expression was only detected in the pancreas. The cDNA sequence encoding the full-length protein was cloned using reverse transcription-polymerase chain reaction. The deduced amino acid sequence contains 383 residues, including a typical signal peptide of 12 amino acids. No significant homology was found with known sequences. The plasma protein is a single chain polypeptide with an apparent molecular mass of 42 kDa. Antibodies raised against this protein detected a truncated form with a molecular mass of 39 kDa. Both forms were predominantly associated with immunoaffinity-isolated apoA-I-containing lipoproteins and detected mainly in the density range 1.123 < d < 1.21 g/ml. Free apoL was not detected in plasma. Anti-apoL immunoaffinity chromatography was used to purify apoL-containing lipoproteins (Lp(L)) directly from plasma. Nondenaturing gel electrophoresis of Lp(L) showed two major molecular species with apparent diameters of 12.2-17 and 10.4-12.2 nm. Moreover, Lp(L) exhibited both pre-beta and alpha electromobility. Apolipoproteins A-I, A-II, A-IV, and C-III were also detected in the apoL-containing lipoprotein particles.