Usefulness of lipids, lipoprotein(a) and fibrinogen measurements in identifying subjects at risk of occlusive complications following vascular and endovascular surgery.

The study was designed to establish the usefulness of measuring lipoprotein(a) [Lp(a)], total cholesterol, triglycerides, low-density lipoprotein [LDL]-cholesterol, high-density lipoprotein [HDL]-cholesterol, total-to-HDL-cholesterol ratio and fibrinogen in identifying subjects at risk of occlusive complications following vascular and endovascular surgery, including primary successful ileofemoral percutaneous transluminal angioplasty, infrainguinal and aortic bypass graft and carotid endarterectomy. A total of 68 volunteers subjected to vascular and endovascular surgery were recruited to the study. Six months after successful interventions, no occlusive complications verified by angiography were observed in 45 patients (66%; No-restenosis group), whereas significant restenosis or reocclusion occurred in 23 patients (34%; Restenosis group). Significant lower concentrations of Lp(a) (p=0.032), total cholesterol (p<0.0001), LDL-cholesterol (p=0.001) and total-to-HDL-cholesterol ratio (p<0.0001) and higher concentrations of HDL-cholesterol (p=0.048) were observed in the No-restenosis group compared to the Restenosis group. The concentrations of triglycerides (p=0.080) and fibrinogen (p=0.510) did not differ significantly between groups. In multivariate discriminant analysis, the best predictors of restenosis or reocclusion were in decreasing order: LDL-cholesterol, Lp(a), total-to-HDL-cholesterol ratio, HDL-cholesterol and total cholesterol. A statistical difference of particular interest was observed in the overall distribution of Lp(a) concentrations between groups (p<0.0001), occlusive complications being unlikely to occur in patients with Lp(a) concentrations below 50 mg L(-1). The potential interference from a concurrent acute phase response, the most common source of elevation of Lp(a) in humans, was less likely in view of the absence of differences in erythrocyte sedimentation rate between the No-restenosis and Restenosis groups (p=0.463). In conclusion, the results of the present investigation point to a definite role of the combined measurements LDL-cholesterol, Lp(a), total-to-HDL-cholesterol ratio, HDL-cholesterol and total cholesterol in the identification of subjects at risk of occlusive events following vascular and endovascular surgical procedures.

Evaluation of the analytical performances of a new fully automated commercial immunonephelometric assay for lipoprotein(a).

Several commercial methods have been proposed for lipoprotein(a) (Lp(a)) measurements over the past decades. However, only a few of them appear completely suitable in terms of analytical performance, costs and practicability. We evaluated the analytical performance of a new commercial fully automated immunonephelometric assay for Lp(a) measurements on the IMMAGE Immunochemistry System. Mean within- and between-run coefficients of variation were 2.7% (range 1.2-4.7%) and 3.8% (range 1.8-7.9%), respectively. The linearity of the assay was confirmed up to 102 mg/dl and the deviation from the expected values did not exceed 4% (mean deviation: 1.9%). Moreover, the relative non-linearity was acceptable, ranging from 1.4% to 1.6% and hence constantly lower than the 2.5% upper limit. Since there is no reference method for Lp(a) measurements, 100 routine random serum samples measured by the IMMAGE Immunochemistry System immunonephelometric assay were further compared with two other commercial immunonephelometric assays (Array LPA immunonephelometric assay and BNA Latex-Enhanced Lp(a) nephelometric assay). Non-parametric regression and relative Spearman's correlation coefficients were satisfactory, (y=1.009x - 1.38; r=0.998 IMMAGE Immunochemistry System vs. Array LPA and y=0.922x - 0.40; r=0.989 IMMAGE Immunochemistry System vs. Behring Nephelometer Analyzer (BNA) Latex Lp(a) assay). On the basis of the results of the present evaluation we conclude that the analytical performance and the main technical features of the IMMAGE Immunochemistry System immunonephelometric assay make it a suitable method for Lp(a) measurement in clinical laboratories.

Effects of nandrolone decanoate (Decadurabolin) on serum Lp(a), lipids and lipoproteins in women with postmenopausal osteoporosis.

Although lipoprotein(a) (Lp(a)) concentrations are mainly regulated genetically, it has been reported that variations in sex hormone concentrations may have effects on serum Lp(a). We evaluated the effect of nandrolone decanoate, a testosterone-derived synthetic anabolic steroid, on serum Lp(a), lipids and lipoproteins in 19 postmenopausal women who were given parenteral nandrolone decanoate (Decadurabolin) once a week for 3 weeks. At the 4th week, a significant decrease was observed for total cholesterol (p = 0.003), Lp(a) (p = 0.0003), apolipoprotein A-I (apo A-I) (p < 0.0001), and high density lipoprotein-cholesterol (HDL-C) (p < 0.0001). Moreover, a significant decrease in serum albumin concentration (p = 0.002) was concomitantly observed. We conclude that the administration of nandrolone decanoate significantly affects the lipid profile of postmenopausal women, showing controversial effects in terms of cardiovascular risk.

Evaluation of five new liquid stable applications on the Roche Cobas Integra.

In the present study the analytical performances of five new liquid applications on the Roche Cobas Integra were evaluated: urea and high density lipoprotein (HDL) cholesterol in serum and glucose, creatinine and inorganic phosphorus in urine. The analytical evaluation consisted of imprecision, linearity and method comparison performed against either the actual Cobas Integra granulate applications or the corresponding methods on a Hitachi 704, according to the National Committee for Clinical Laboratory Standards protocols. Over 3700 results were obtained within 3 months. Average values of within-run and between-day coefficients of variation (CVs) were 1.15% and 1.48%, respectively, holding to a mean total CV of 2.17%. The linearity was excellent for all the five applications evaluated as the relative non-linearity was always within 1.53%, thus completely fulfilling the 2.5% upper limit. A strict correlation was observed by comparing results of 120 samples with either the corresponding granulate applications on Cobas Integra or the Hitachi reagents. Linear regression analysis of the results yielded correlation coefficients always above 0.987 and the slopes of the Passing & Bablok regression lines did not deviate by more than 7% from unity. No drift was observed over 4 hours of operations. In conclusion, the performance of these new Cobas Integra liquid applications, as demonstrated by the present study, proved them to be highly suitable for routine use in clinical laboratories.

Significant reduction of the bias among commercial immunoassays for lipoprotein(a) after use of a uniform calibrator.

Despite the increasing interest in the measurements of lipoprotein(a) (Lp(a) in serum or plasma, at present there is no effective standardization for Lp(a) assays; the main problems to solve are represented either by the lack of a suitable primary standard or by the absence of a reliable and widely available reference method. A first step is hence the uniformity of calibration of different immunoassays. We calibrated three commercial immunoassays for Lp(a) (enzyme linked immunosorbent assay (ELISA), latex-enhanced immunonephelometric assay (LINA), and immunonephelometric assay (INA) with either proprietary standards or purified Lp(a) material obtained with a rapid and simple procedure. Final results of purified Lp(a) calibration were reported in terms of protein Lp(a) mass whereas we were able to quantify the exact protein concentration of our purified lipoprotein. The uniformity of the calibration of the different assays led to a significant improvement of regression slopes (from 1.88 to 0.90 ELISA vs. LINA, from 1.45 to 0.95 ELISA vs. INA and from 1.27 to 0.96 INA vs. LINA) and correlation coefficients (from 0.990 to 0.994 ELISA vs. LINA, from 0.987 to 0.990 ELISA vs. INA and from 0.985 to 0.987 INA vs. LINA). Furthermore, the significant differences among Lp(a) values obtained after calibration with proprietary standards were minimized, becoming non-significant in two out of three cases. In conclusion, we demonstrated that a better agreement of Lp(a) values obtained with different commercial assays could be simply reached by uniformity of calibration and by employing standards with values accurately measured.

Simple and rapid procedure for the purification of lipoprotein(a).

Lipoprotein(a) [Lp(a)] is a low-density lipoprotein-like particle displaying strong athero-thrombotic properties. Highly purified Lp(a) is increasingly requested for standardization of Lp(a) measurements and for biological studies. Several procedures have been described for Lp(a) separation and purification but none of them appear completely suitable. We present here a procedure for Lp(a) purification based on sequential elutions after lysine-Sepharose affinity chromatography. We were able to identify four distinct subspecies of Lp(a) showing different affinity to epsilon-amino groups of lysine-Sepharose, simply by modifying molarity and pH of the eluents; the fraction obtained in highly purified state represented the major form and could be eluted with 0.5 M sodium phosphate buffer (pH 4.4). Advantages of this procedure are represented by simplicity, rapidity and final yield.

Gastric emptying of solids is markedly delayed when meals are fried.

We studied the effect of heat-treated fats on gastric emptying. Eight healthy asymptomatic volunteers (five males; age 28-41 years) ate on different days and in random order two meals identical in contents (pasta, tomato, beef, olive oil, carrots, orange, water; 870 kcal males, 700 kcal females; 47% of calories from carbohydrate, 36% from fat, 17% from protein), but cooked differently (fats fried or not). Ultrasound measurement of antral diameters was used to calculate basal antral section, its maximal dilation after the meal, the time necessary for total emptying, and the percent retention at hourly intervals. No difference was found in basal and maximal antral diameters after the two meals. On the contrary, total gastric emptying was significantly delayed after the fried meal [317.1 (24.12) vs 226.7 (18.4) min, mean (1 SEM); P < 0.002]. A significantly greater percentage of maximal antral distension was still present between 120 and 240 min after the fried meal. The glycemic response and hunger feeling were the same after the two meals, whereas there was a longer persistence of satiety and epigastric fullness after the fried meal. In conclusion, gastric emptying can be influenced not only by the meal content, but also by the way it is cooked.

Use of purified dermatan sulfate for heparin cofactor II (HC II) assay.

HC II functional assays are generally preferred with respect to immunochemical assays. Nevertheless functional assays can be biased by the antithrombin III (AT III)-heparin complex activity; in fact trace amounts of heparin generally contaminate dermatan sulfate (DS) commercial preparations used as HC II reaction activators. We have employed a purified DS preparation showing these features: DS concentration 94.4%, chondroitin sulfate 5.6%, M.W. 21.4 kDa. The absence of any interference due to AT III-heparin complexes was verified in a kinetic HC II assay of some human plasma pools. The immunological inhibition of AT III by anti-AT III caused a minimal decrease (6-8%) of the reaction slope, attributable to AT III activity. Progressive increase of heparin concentration in the assay was effective only starting from 30 U/ml (the assay was carried out in the presence of polybrene to prevent any AT III activation). The reference interval (mean +/- SD) obtained from 157 normal subjects was 100.8 +/- 20.2%; there was a good correlation with immunoreactive HC II. The purified DS we have used seems suitable for routinary assays of HC II where a minimal interference due to AT III-heparin is required.

Selenium supplementation increases renal glomerular filtration rate.

Selenium (Se) is a trace element variously distributed in the human body and especially concentrated in certain organs, such as the renal cortex. We report results obtained during a ten weeks' oral Se supplementation. Experiments were devised to evaluate previous preliminary observations which suggested a possible effect of Se addition on the renal glomerular filtration rate. Eleven healthy volunteers have given increasing oral Se (as a sodium selenite solution) as follows: on the first week they have given 100 micrograms Se per day; this was progressively increased 100 micrograms per day for each of the following 6 weeks; the last dose (700 micrograms per day) was maintained for three further weeks. Serum and 24-hour urine were collected weekly for creatinine determination by kinetic Jaffé reaction and Se measurement by proton-induced X ray emission (PIXE). The final mean serum creatinine concentration was 13% lower than the initial mean value (p less than 0.01). Mean creatinine clearance increased significantly (p less than 0.05) and showed a direct correlation with mean Se clearance (r = 0.79; p less than 0.001). As the increase of creatinine clearance was concomitant with a reduction of serum creatinine levels, we excluded the possibility of toxic effects. Our results seem to suggest a positive influence of Se supplementation on the rate of glomerular filtration and we hypothesize that Se might be involved in the vascular regulatory mechanism of the kidney.

Membrane polyunsaturated fatty acids and lithium-sodium countertransport in human erythrocytes.

Two groups of individuals, 26 normotensive normolipemic and 37 normotensive hyperlipemic, all without family history of hypertension have been selected in attempt to demonstrate whether Li-Na countertransport of erythrocytes is influenced by plasma and membrane lipid composition. The maximal rate of Li-Na countertransport was elevated in hyperlipemics (0.344 +/- 0.168 vs 0.220 +/- 0.074 mmol/l erythrocytes/h). This difference is highly significant. Hyperlipemics had different composition of membrane lipids than normals. The most important variations were: increase of palmitic, palmitoleic and total saturated fatty acids (SFA) as well as increase of cholesterol/phospholipids ratio (C/PL); in contrast, hyperlipemics had a reduced amount of linoleic acid and total unsaturated fatty acids (UFA) as well as total polyunsaturated fatty acids (PUFA). Consequently, UFA/SFA and PUFA/SFA ratios were lower than in normals. Li-Na countertransport was negatively correlated with the amount of PUFA (P less than 0.02), whereas it was positively correlated with the following parameters: oleic/linoleic ratio (p less than 0.02), monounsaturated fatty acids/polyunsaturated fatty acids ratio (p less than 0.03) as well as with the SFA + monounsaturated fatty acid/PUFA ratio (p less than 0.03). These findings suggest that the V max of Li-Na countertransport in erythrocytes is influenced by the lipid composition of the membrane.

Elevation of red cell sodium-lithium countertransport in hyperlipidemias.

Red cell Na-Li countertransport was measured in 78 normal subjects, 64 patients with essential hypertension, and 67 patients with hyperlipidemias. Both hypertensive and hyperlipidemic patients had elevated Na-Li countertransport compared to normal controls (p less than 0.001). Subjects with hyperlipidemia and hypertension had higher countertransport (p less than 0.02) than patients with only hyperlipidemia. Normotensive hyperlipidemic subjects had higher countertransport than normotensive and normolipidemic controls (p less than 0.02). This suggest that hypertension and high plasma lipids can influence independently the Na-Li countertransport. In another group of 52 normotensive subjects, Na-Li countertransport was positively correlated with serum total and free (unesterified) cholesterol, phospholipids and triglycerides. No correlations were found with HDL-cholesterol or HDL-phospholipids. A very high positive correlation was found between Na-Li countertransport and plasma acetylcholinesterase (p less than 0.005). These findings suggest that plasma lipids, probably through membrane lipids, can affect the maximal rate of the Na-Li exchange in red cells. The relationship between plasma or membrane lipids and cation transport should be further studied in erythrocytes and other cells.