A rapid electrophoretic method for the detection of serum Lp(a) lipoprotein

The ins and outs of lipoprotein(a) assay methods

Pathophysiological, epidemiological and genetic studies convincingly showed lipoprotein(a) (Lp(a)) to be a causal mediator of atherosclerotic cardiovascular disease (ASCVD). This happens through a myriad of mechanisms including activation of innate immune cells, endothelial cells as well as platelets. Although these certainties whether or not Lp(a) is ready for prime-time clinical use remain debated. Thus, remit of the present review is to provide an overview of different methods that have been employed for the measurement of Lp(a). The methods include dynamic light scattering, multi-angle light scattering analysis, near-field imaging, sedimentation, gel filtration, and electron microscopy. The development of multiple Lp(a) detection methods is vital for improved prediction of ASCVD risk.

Hypothyroidism increases angiotensinogen gene expression associated with vascular smooth muscle cells cholesterol metabolism dysfunction and aorta remodeling in Psammomys obesus

It has been previously shown that clinical cardiovascular manifestations can be caused by mild changes in thyroid function. However, the implication of angiotensinogen (Agt) and vascular smooth muscle cells (VSMCs) dysfunction in the pathophysiology of cardiovascular manifestations in hypothyroidism have not yet been investigated. We induced experimental hypothyroidism in Psammomys obesus by administering carbimazole for five months. At the end of the experiment, the animals were sacrificed and histopathological analysis was performed using Masson's trichrome staining of the aorta and thyroid gland. The expression of the Agt gene and the genes implicated in cholesterol metabolism regulation in the liver and VSMCs was determined by qRT-PCR. Histological observations revealed profound remodeling of the aorta structure in animals with hypothyroidism. In addition, Agt gene expression in the liver was significantly increased. In vitro study, showed that VSMCs from hypothyroid animals overexpressed 3-hydroxy-3-methylglutaryl coenzyme A reductase (Hmgcr) and Acyl CoA:cholesterol acyltransferase (Acat) 1, with failure to increase the efflux pathway genes (ATP-binding cassette subfamily G member (Abcg) 1 and 4). These results suggest that hypothyroidism leads to vascular alterations, including structural remodeling, VSMCs cholesterol metabolism dysfunction, and their switch to a synthetic phenotype, together with hepatic Agt gene overexpression.

In Vivo Subacute Toxicity and Antidiabetic Effect of Aqueous Extract of Nigella sativa

Context. Nigella sativa seeds are usually used as traditional medicine for a wide range of therapeutic purposes. Objective. To investigate the subacute toxicity of NS aqueous extract and select its lowest dose to study its antidiabetic effect. Methods. 5 AqE.NS doses (2, 6.4, 21, 33, and 60 g/Kg) were daily administered to mice by gavage. Biochemical parameters measurements and histological study of the liver and the kidney were performed after 6 weeks of supplementation. Thereafter, and after inducing diabetes by alloxan, rats were treated by 2 g/Kg of AqE.NS during 8 weeks. Metabolic parameters were measured on sera. A horizontal electrophoresis of plasmatic lipoprotein was conducted. Glycogen, total lipids, and triglycerides were measured in the liver. TBARS were evaluated on adipose tissue, liver, and pancreas. Results. AqE.NS showed no variation in urea and albumin at the 5 doses, but hepatotoxicity from 21 g/Kg was confirmed by histopathological observations of the liver. In diabetic rats, AqE.NS significantly decreased glycemia, TG, T-cholesterol, LDL-c, and TBARS and showed a restored insulinemia and a significant increase in HDL-c. Results on the liver indicated a decrease in lipids and a possible glycogenogenesis. Conclusion. AqE.NS showed its safety at low doses and its evident antihyperglycemic, antihyperlipidemic, and antioxidant effect.

Plasma and Aorta Biochemistry and MMPs Activities in Female Rabbit Fed Methionine Enriched Diet and Their Offspring

This study investigated whether a high Met diet influences biochemical parameters, MMPs activities in plasma, and biochemical and histological remodeling in aorta, in both pregnant female rabbits and their offspring. Four female rabbit groups are constituted (each n = 8), nonpregnant control (NPC), pregnant control (PC) that received normal commercial chow, nonpregnant Met (NPMet), and pregnant Met (PMet) that received the same diet supplemented with 0,35% L-methionine (w/w) for 3 months (500 mg/d). All pregnant females realize 3 successive pregnancies. Plasma results showed that Met excess increased Hcy, raised CRP in NPMet and decreased it in PMet, enhanced significantly proMMP-2 and proMMP-9 activities in NPMet, and reduced them in PMet. Aorta showed a rise in collagen level, essentially in PMet, a reduction of elastin content in both PMet and NPMet, and a significant decrease in lipid content in PMet, with histological changes that are more pronounced in NPMet than PMet. Met excess enhanced proMMP-9 activities in NPMet while it decreased them in PMet. PMet newborn presented increase in uremia and CRP and significant rise of active MMP-2 and MMP-9 forms. In aorta, media and adventitia thickness increased, total lipids content decreased, proMMP-9 activity decreased, and proMMP-2 activity increased.

Myocardial Structural and Biological Anomalies Induced by High Fat Diet in Psammomys obesus Gerbils

BACKGROUND

Psammomys obesus gerbils are particularly prone to develop diabetes and obesity after brief period of abundant food intake. A hypercaloric high fat diet has been shown to affect cardiac function. Here, we sought to determine whether a short period of high fat feeding might alter myocardial structure and expression of calcium handling proteins in this particular strain of gerbils.

METHODS

Twenty Psammomys obesus gerbils were randomly assigned to receive a normal plant diet (controls) or a high fat diet. At baseline and 16-week later, body weight, plasma biochemical parameters (including lipid and carbohydrate levels) were evaluated. Myocardial samples were collected for pathobiological evaluation.

RESULTS

Sixteen-week high fat dieting resulted in body weight gain and hyperlipidemia, while levels of carbohydrates remained unchanged. At myocardial level, high fat diet induced structural disorganization, including cardiomyocyte hypertrophy, lipid accumulation, interstitial and perivascular fibrosis and increased number of infiltrating neutrophils. Myocardial expressions of pro-apoptotic Bax-to-Bcl-2 ratio, pro-inflammatory cytokines [interleukin (IL)-1β and tumor necrosis factor (TNF)-α], intercellular (ICAM1) and vascular adhesion molecules (VCAM1) increased, while gene encoding cardiac muscle protein, the alpha myosin heavy polypeptide (MYH6), was downregulated. Myocardial expressions of sarco(endo)plasmic calcium-ATPase (SERCA2) and voltage-dependent calcium channel (Cacna1c) decreased, while protein kinase A (PKA) and calcium-calmodulin-dependent protein kinase (CaMK2D) expressions increased. Myocardial expressions of ryanodine receptor, phospholamban and sodium/calcium exchanger (Slc8a1) did not change.

CONCLUSIONS

We conclude that a relative short period of high fat diet in Psammomys obesus results in severe alterations of cardiac structure, activation of inflammatory and apoptotic processes, and altered expression of calcium-cycling determinants.

Composition and electrophoretic mobility of plasma lipoproteins of dromedary camels (Camelus dromedarius)

OBJECTIVE

To determine the lipid composition and electrophoretic pattern of plasma lipoproteins in samples obtained from healthy 1-humped camels (Camelus dromedarius).

ANIMALS

34 healthy camels raised under similar farming and dietary conditions.

PROCEDURES

Plasma samples were subjected to density-gradient ultracentrifugation for separation of plasma lipoproteins, including very-low-density lipoproteins (VLDL), low-density lipoproteins (LDL), and high-density lipoproteins (HDL). Purity of the separation was assessed by use of polyacrylamide gel disk electrophoresis. Concentrations of triglycerides, cholesterol, and phospholipids were measured in each lipoprotein fraction, and lipoprotein electrophoretic patterns were determined in plasma samples.

RESULTS

Phospholipid was the major constituent of VLDL (mean +/- SD concentration, 10.62 +/- 1.2 mg/dL), LDL (24.66 +/- 3.12 mg/dL), and HDL (38.08 +/- 0.76 mg/dL). Low-density lipoprotein, VLDL, and HDL were important plasma lipoprotein carriers for cholesterol (67.94 +/- 9.51%), triglyceride (55.83 +/- 7.81%), and phospholipid (51.91 +/- 1.55%), respectively. On the basis of electrophoresis results, relative percentages of alpha- and beta-lipoproteins were 31.72 +/- 4.88% and 68.3 +/- 4.68%, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

The lipoprotein profile in 1-humped camels differed substantially from that of other ruminants. Results may be useful in the evaluation of metabolic disorders in camels.

Sphingosine 1-phosphate may be a major component of plasma lipoproteins responsible for the cytoprotective actions in human umbilical vein endothelial cells

Sphingosine 1-phosphate (S1P), a novel lipid mediator, is concentrated in the fraction of lipoproteins that include high density lipoprotein (HDL) and low density lipoprotein (LDL) in human plasma. Here, we show that oxidation of LDL resulted in a marked reduction in the S1P level in association with a marked accumulation of lysophosphatidylcholine (LPC). We therefore investigated the role of the lipoprotein-associated lipids especially S1P in the lipoprotein-induced cytoprotective or cytotoxic actions in human umbilical vein endothelial cells. The viability of the cells gradually decreased in the absence of serum or growth factors in the culture medium. The addition of oxidized LDL (ox-LDL) accelerated the decrease in the cell viability. LPC and 7-ketocholesterol mimicked ox-LDL actions. On the other hand, HDL and LDL almost completely reversed the serum deprivation- or ox-LDL-induced cytotoxicity. Exogenous S1P mimicked cytoprotective actions. Moreover, the S1P-rich fraction and chromatographically purified S1P from HDL exerted cytoprotective actions, but the rest of the fractions did not. The cytoprotective actions of HDL and S1P were associated with extracellular signal-regulated kinase (ERK) activation and were almost completely inhibited by pertussis toxin and PD98059, an ERK kinase inhibitor. The HDL-induced action was specifically desensitized in the S1P-pretreated cells. Taken together, these results indicate that the lipoprotein-associated S1P and the lipid receptor-mediated signal pathways may be responsible for the lipoprotein-induced cytoprotective actions. Furthermore, the decrease in the S1P content, in addition to the accumulation of cytotoxic substances such as LPC, may be important for the acquisition of the cytotoxic property to ox-LDL.

Predictive value of electrophoretically detected lipoprotein(a) for coronary heart disease and cerebrovascular disease in a community-based cohort of 9936 men and women

BACKGROUND

Elevated lipoprotein(a) [Lp(a)] levels have been associated with the presence of atherosclerotic disease. However, the results of prospective studies of Lp(a) and cardiovascular disease have been contradictory.

METHODS AND RESULTS

From 1968 through 1982, lipoprotein analysis was performed in 11,335 Olmsted County residents. Quantitative cholesterol and triglycerides were obtained along with semiquantitative Lp(a) levels based on electrophoretic pattern. Lp(a) bands were scored from 0 (absent) to 3 (increased). A cohort of 4967 men and 4968 women with no prior history of atherosclerotic disease who had baseline Lp(a) determinations were followed up for 14 years for development of coronary artery disease (CAD) and cerebrovascular disease (CVD). During 131,330 person-years of follow-up, there were 1848 CAD events and 841 CVD events. Age, diabetes, hypertension, cholesterol, and triglycerides were significantly and independently associated with an increased risk of CAD and CVD in men and women. There was a significant increase in the adjusted hazards ratio for CAD with increasing Lp(a) levels for men and women. For Lp(a) level 3, the hazard ratio was 1.9 (range, 1.3 to 2.9) in women and 1.6 (range, 1.0 to 2.5) in men. The adjusted hazard ratio for CVD showed an irregular association with Lp(a) levels in men and no association in women.

CONCLUSIONS

In this cohort of 9936 men and women initially free of cardiovascular disease who were followed up for 14 years, Lp(a) was a significant predictor of risk of future CAD. Lp(a) was a weak risk factor for CVD in men and was not a significant predictor of CVD risk in women.

Lipoprotein(a) is an independent risk factor for multiple cerebral infarctions

In an attempt to ascertain whether Lp(a) is a risk factor for multiple cerebral infarctions (MCI), we have studied 83 patients with proven MCI and 39 subjects without MCI by computed tomography (CT). Seventy-one patients with non-insulin-dependent diabetes mellitus (NIDDM) were included: 52 with and 19 without MCI. Serum Lp(a) levels were significantly higher in patients with MCI than in subjects without MCI. There were no differences in serum Lp(a) levels between NIDDM and non-diabetic patients with MCI. The logistic regression analysis revealed that Lp(a) and hypertension were independent risk factors for the cerebral event. The current study demonstrated that Lp(a) and hypertension are significant risk factors for multiple cerebral infarctions.

Advances in agarose gel electrophoresis of serum lipoproteins

Agarose gel electrophoresis has been extensively employed by researchers to gain a greater understanding of lipoprotein biology and its relationship to cardiovascular disease. Advances in this technique have been made in the visualization and quantitation of separated lipoproteins, in the use of agarose gel electrophoresis for detection and quantitation of apolipoproteins of the separated lipoproteins, and in the detection of lipoprotein heterogeneity. Agarose gel electrophoresis has been employed for two-dimensional electrophoretic analysis of lipoproteins as well as in several different methods which probe the immunological properties of lipoproteins. Agarose gel electrophoresis has thus become an important tool in the study of serum lipoproteins in both clinical and basic science laboratories.

A screening method for abnormally high lipoprotein(a) concentrations by agarose lipoprotein electrophoresis

A routine electrophoretic method detecting plasma lipoprotein(a) (Lp(a)) is described. Plasma lipoproteins were electrophoresed using an agarose gel film containing cations which retard migration of beta-, prebeta- and alpha-bands. When present, the Lp(a)-band was detected between prebeta- and alpha-bands. This extra-band lipoprotein has been demonstrated to be Lp(a), by an immunofixation technique using anti-Lp(a) antibodies. This original procedure allows a distinct separation of Lp(a) from prebeta even after samples have been stored at 4 degrees C for several days, or in cases of hyperlipemic samples with increased prebeta lipoproteins. The reliability of this detection test has been tested in comparison with an Lp(a) electroimmunoassay. Both these techniques have been performed on 719 randomly selected subjects. With electrophoresis, the Lp(a)-positive subjects accounted for 34.2% of the subjects and although this method does not distinguish between different levels of positivity (depending on the sample), the presence of Lp(a)-band was always perceptible at concentrations that belong to the upper 15th percentile of values as determined by electroimmunodiffusion; inversely, all Lp(a)-positive plasma was measurable. In consequence, since it is reliable and relatively inexpensive, this detection test on modified agarose gel appears very useful for revealing the presence of abnormally high values of Lp(a) in populations.

A prospective investigation of elevated lipoprotein (a) detected by electrophoresis and cardiovascular disease in women. The Framingham Heart Study

BACKGROUND

Sinking prebeta lipoprotein is a putative marker for elevated levels of lipoprotein (a). Although prospective data suggest that increased plasma lipoprotein (a) is an independent risk factor for coronary heart disease in men, no prospective studies are available in women.

METHODS AND RESULTS

From 1968 through 1975, sinking prebeta lipoprotein was determined by paper electrophoresis in 3103 women Framingham Heart Study participants who were free of prevalent cardiovascular disease. A sinking prebeta lipoprotein band was detectable in 434 of the women (14%) studied. The median follow-up interval was approximately 12 years. Incident cardiovascular disease was associated with band presence using a proportional hazards model that included age, smoking, body mass index, systolic blood pressure, glucose intolerance, low- and high-density lipoprotein cholesterol, and ECG left ventricular hypertrophy. Multivariable adjusted relative risk estimates (with 95% confidence intervals) for outcomes in the band present versus absent groups were as follows: myocardial infarction (82 events), 2.37 (1.48 to 3.81); intermittent claudication (62 events), 1.94 (1.07 to 3.50); cerebrovascular disease (83 events), 1.88 (1.12 to 3.15); total coronary heart disease (174 events), 1.61 (1.13 to 2.29); and total cardiovascular disease (305 events), 1.44 (1.09 to 1.91). A subset analysis indicated that band presence was 50.9% sensitive and 95.4% specific for detecting plasma lipoprotein (a) levels of > 30 mg/dL, the threshold value linked to increased cardiovascular disease risk in men.

CONCLUSIONS

Sinking prebeta lipoprotein was a valid surrogate for elevated lipoprotein (a) levels in Framingham Heart Study women. Band presence and, equivalently, elevated plasma lipoprotein (a), was a strong, independent predictor of myocardial infarction, intermittent claudication, and cerebrovascular disease. Confirmation of these findings in other longitudinal studies of women is needed.