Effects of combined physical exercise on plasma lipid variables, paraoxonase 1 activity, and inflammation parameters in adults with obesity: a randomized clinical trial

OBJECTIVE

We aimed to investigate whether combined physical exercise may affect plasma lipid variables, paraoxonase 1 (PON1) activity, and inflammation parameters in adults with obesity.

METHODS

Thirty-six participants were recruited to complete the study protocol. The mean age was 37 ± 1 years, and the baseline body mass index was 33.0 ± 0.4 kg/m². Participants were allocated to the control group (CG) and the exercise group (EG). The EG performed three weekly sessions of combined physical exercise for 16 weeks. Plasma lipid variables, PON1 activity, and inflammatory profile were determined before and after intervention.

RESULTS

Total cholesterol levels decreased in both groups, without intergroup difference (time p = 0.001). Non-high-density lipoprotein cholesterol (HDL-C) levels decreased in both groups (time p = 0.001); however, they were lower in the EG than in the CG (p = 0.038). The EG had increased HDL-C levels, but the CG had decreased HDL-C levels (time*group p = 0.011). PON1 activity was reduced in both groups (time, p = 0.001). The Castelli risk Index I and II reduced in the EG and increased in the CG (time*group, p = 0.008 and p = 0.011, respectively). The inflammatory markers were not modified.

CONCLUSION

Adults with obesity may benefit from regular practice of combined physical exercise training in many metabolic aspects that are related to protection against the development of cardiovascular disease.

Lipid core nanoparticles resembling low-density lipoprotein and regression of atherosclerotic lesions: effects of particle size

Particles are usually polydispersed and size is an important feature for lipid-based drug delivery systems in order to optimize cell-particle interactions as to pharmacologic action and toxicity. Lipid nanoparticles (LDE) with composition similar to that of low-density lipoprotein carrying paclitaxel were shown to markedly reduce atherosclerosis lesions induced in rabbits by cholesterol feeding. The aim of this study was to test whether two LDE fractions, one with small (20-60 nm) and the other with large (60-100 nm) particles, had different actions on the atherosclerotic lesions. The two LDE-paclitaxel fractions, prepared by microfluidization, were separated by density gradient ultracentrifugation and injected (4 mg/body weight, intravenously once a week) into two groups of rabbits previously fed cholesterol for 4 weeks. A group of cholesterol-fed animals injected with saline solution was used as control to assess lesion reduction with treatment. After the treatment period, the animals were euthanized for analysis. After treatment, both the small and large nanoparticle preparations of LDE-paclitaxel had equally strong anti-atherosclerosis action. Both reduced lesion extension in the aorta by roughly 50%, decreased the intima width by 75% and the macrophage presence in the intima by 50%. The two preparations also showed similar toxicity profile. In conclusion, within the 20-100 nm range, size is apparently not an important feature regarding the LDE nanoparticle system and perhaps other solid lipid-based systems.

Methotrexate associated to lipid core nanoparticles improves cardiac allograft vasculopathy and the inflammatory profile in a rabbit heart graft model

Coronary allograft vasculopathy is an inflammatory-proliferative process that compromises the long-term success of heart transplantation and has no effective treatment. A lipid nanoemulsion (LDE) can carry chemotherapeutic agents in the circulation and concentrates them in the heart graft. The aim of the study was to investigate the effects of methotrexate (MTX) associated to LDE. Rabbits fed a 0.5% cholesterol diet and submitted to heterotopic heart transplantation were treated with cyclosporine A (10 mg·kg^–1·day^–1 orally) and allocated to treatment with intravenous LDE-MTX (4 mg/kg, weekly, n=10) or with weekly intravenous saline solution (control group, n=10), beginning on the day of surgery. Animals were euthanized 6 weeks later. Compared to controls, grafts of LDE-MTX treated rabbits showed 20% reduction of coronary stenosis, with a four-fold increase in vessel lumen and 80% reduction of macrophage staining in grafts. Necrosis was attenuated by LDE-MTX. Native hearts of both LDE-MTX and Control groups were apparently normal. Gene expression of lipoprotein receptors was significantly greater in grafts compared to native hearts. In LDE-MTX group, gene expression of the pro-inflammatory factors tumor necrosis factor-α, monocyte chemoattractant protein-1, interleukin-18, vascular cell adhesion molecule-1, and matrix metalloproteinase-12 was strongly diminished whereas expression of anti-inflammatory interleukin-10 increased. LDE-MTX promoted improvement of the cardiac allograft vasculopathy and diminished inflammation in heart grafts.

Metabolism of triglyceride-rich lipoproteins and transfer of lipids to high-density lipoproteins (HDL) in vegan and omnivore subjects

BACKGROUND AND AIMS

Vegan diet excludes all foodstuffs of animal origin and leads to cholesterol lowering and possibly reduction of cardiovascular disease risk. The aim was to investigate whether vegan diet improves the metabolic pathway of triglyceride-rich lipoproteins, consisting in lipoprotein lipolysis and removal from circulation of the resulting remnants and to verify whether the diet alters HDL metabolism by changing lipid transfers to this lipoprotein.

METHODS AND RESULTS

21 vegan and 29 omnivores eutrophic and normolipidemic subjects were intravenously injected triglyceride-rich emulsions labeled with (14)C-cholesterol oleate and (3)H-triolein: fractional clearance rates (FCR, in min(-1)) were calculated from samples collected during 60 min for radioactive counting. Lipid transfer to HDL was assayed by incubating plasma samples with a donor nanoemulsion labeled with radioactive lipids; % lipids transferred to HDL were quantified in supernatant after chemical precipitation of non-HDL fractions and nanoemulsion. Serum LDL cholesterol was lower in vegans than in omnivores (2.1 ± 0.8, 2.7 ± 0.7 mmol/L, respectively, p < 0,05), but HDL cholesterol and triglycerides were equal. Cholesteryl ester FCR was greater in vegans than in omnivores (0.016 ± 0.012, 0.003 ± 0.003, p < 0.01), whereas triglyceride FCR was equal (0.024 ± 0.014, 0.030 ± 0.016, N.S.). Cholesteryl ester transfer to HDL was lower in vegans than in omnivores (2.7 ± 0.6, 3.5 ± 1.5%, p < 0,05). Free-cholesterol, triglyceride and phospholipid transfer were equal, as well as HDL size.

CONCLUSION

Remnant removal from circulation, estimated by cholesteryl oleate FCR was faster in vegans, but the lipolysis process, estimated by triglyceride FCR was equal. Increased removal of atherogenic remnants and diminution of cholesteryl ester transfer may favor atherosclerosis prevention by vegan diet.

Effect of neoadjuvant chemotherapy on low-density lipoprotein (LDL) receptor and LDL receptor-related protein 1 (LRP-1) receptor in locally advanced breast cancer

Low-density lipoprotein (LDL) receptors are overexpressed in most neoplastic cell lines and provide a mechanism for the internalization and concentration of drug-laden nanoemulsions that bind to these receptors. The aim of the present study was to determine whether the administration of standard chemotherapeutic schemes can alter the expression of LDL and LDL receptor-related protein 1 (LRP-1) receptors in breast carcinoma. Fragments of tumoral and normal breast tissue from 16 consecutive volunteer women with breast cancer in stage II or III were obtained from biopsies before the beginning of neoadjuvant chemotherapy and after chemotherapy, from fragments excised during mastectomy. Tissues were analyzed by immunohistochemistry for both receptors. Because complete response to treatment was achieved in 4 patients, only the tumors from 12 were analyzed. Before chemotherapy, there was overexpression of LDL receptor in the tumoral tissue compared to normal breast tissue in 8 of these patients. LRP-1 receptor overexpression was observed in tumors of 4 patients. After chemotherapy, expression of both receptors decreased in the tumors of 6 patients, increased in 4 and was unchanged in 2. Nonetheless, even when chemotherapy reduced receptors expression, the expression was still above normal. The fact that chemotherapy does not impair LDL receptors expression supports the use of drug carrier systems that target neoplastic cells by the LDL receptor endocytic pathway in patients on conventional chemotherapy.

Uptake by breast carcinoma of a lipidic nanoemulsion after intralesional injection into the patients: A new strategy for neoadjuvant chemotherapy

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Background: Previously we showed that after intravenous injection a lipidic nanoemulsion concentrates in breast carcinoma tissue and other solid tumors may carry drugs directed against neoplastic tissues. Use of the nanoemulsion decreases toxicity of the chemotherapeutic agents without decreasing the anticancer action. Currently, the hypothesis was tested whether the nanoemulsion concentrates in breast carcinoma tissue after locoregional injection. Methods: Three different techniques of injection of the nanoemulsion were tested in patients scheduled for surgical treatment: G1 (n=4) into the mammary tissue 5 cm away from the tumor; G2 (n=4) into the peritumoral mammary tissue; G3 (n=6) into the tumoral tissue. The nanoemulsion labeled with radioactive cholesteryl oleate was injected 12 hours before surgery; plasma decay of the label was determined from blood samples collected over 24 h and the tissue fragments excised during the surgery were analyzed for radioactivity uptake. Results: Among the three nanoemulsion injection techniques, G3 showed the greatest uptake (data expressed in c.p.m/g of tissue) by the tumor (44769±54749) and by the lymph node (2356±2966), as well as the greatest concentration in tumor compared to normal tissue (844±1673). In G1 and G2, uptakes were, respectively, tumor: 60±71 and 843±1526; lymph node: 263±375 and 102±74; normal tissue: 139±102 and 217±413. Conclusions: Therefore, with intralesional injection of the nanoemulsion, a great concentration effect can be achieved. This injection technique may be thus a promising approach for drug-targeting in neoadjuvant chemotherapy in breast cancer treatment.

No significant financial relationships to disclose.

Plasma kinetics of chylomicron-like emulsion in renal transplant patients receiving cyclosporin-based immunosuppression

BACKGROUND

Atherosclerotic cardiovascular disease is prevalent among renal transplant patients. Increase in serum total cholesterol, low-density lipoprotein, and very low-density lipoprotein is common in those patients. Alterations in chylomicron metabolism, however, are also related to atherogenesis and were not studied in renal transplant.

HYPOTHESIS

The aim of this study was to evaluate chylomicron metabolism in renal transplant recipients receiving cyclosporin-based immunosuppression. We determined the plasma kinetics of triglyceride-rich emulsions labeled with [3H]triolein and [14C]cholesteryl oleate that are known to mimic the chylomicron metabolism when injected into the blood stream.

METHODS

Fourteen renal transplant recipients with normal renal function (10 men, 4 women, aged 40 +/- 6.1 years) and 17 age- and gender-matched healthy controls received bolus injections of the chylomicron-like emulsion. Plasma samples were then taken at regular intervals during 60 min. Disappearance curves of the labels and the respective fractional clearance rates (FCR) were calculated in order to measure lipolysis and chylomicron remnant removal from the plasma.

RESULTS

Fasting serum lipid levels did not differ in the two groups. The difference between Median FCR of [3H]triolein emulsion in renal transplant patients and that obtained in the controls (0.07 vs. 0.11 min-1, NS) was not statistically significant. Median FCR of [14C]cholesteryl oleate also did not differ between the groups (patients: 0.044; controls: 0.046, NS).

CONCLUSION

These results indicate that neither chylomicron lipolysis nor remnant removal are affected in stable renal transplant patients treated with cyclosporin-based immunosuppression.

Lipolysis of emulsion models of triglyceride-rich lipoproteins is altered in male patients with abdominal aorta aneurysm

Disorders of the lipid metabolism may play a role in the genesis of abdominal aorta aneurysm. The present study examined the intravascular catabolism of chylomicrons, the lipoproteins that carry the dietary lipids absorbed by the intestine in the circulation in patients with abdominal aorta aneurysm. Thirteen male patients (72 +/- 5 years) with abdominal aorta aneurysm with normal plasma lipid profile and 13 healthy male control subjects (73 +/- 5 years) participated in the study. The method of chylomicron-like emulsions was used to evaluate this metabolism. The emulsion labeled with 14C-cholesteryl oleate and (3)H-triolein was injected intravenously in both groups. Blood samples were taken at regular intervals over 60 min to determine the decay curves. The fractional clearance rate (FCR) of the radioactive labels was calculated by compartmental analysis. The FCR of the emulsion with (3)H-triolein was smaller in the aortic aneurysm patients than in controls (0.025 +/- 0.017 vs 0.039 +/- 0.019 min-1; P < 0.05), but the FCR of 14C-cholesteryl oleate of both groups did not differ. In conclusion, as indicated by the triglyceride FCR, chylomicron lipolysis is diminished in male patients with aortic aneurysm, whereas the remnant removal which is traced by the cholesteryl oleate FCR is not altered. The results suggest that defects in the chylomicron metabolism may represent a risk factor for development of abdominal aortic aneurysm.

Chloroquine increases low-density lipoprotein removal from plasma in systemic lupus patients

Low-density lipoprotein (LDL) pathway in systemic lupus erythematosus (SLE) patients taking chloroquine diphosphate (CDP) was evaluated through the kinetic behavior of a radioactive cholesterol-rich nanoemulsion (LDE) that resembles the LDL lipidic structure. LDE was labeled with (14)C-cholesteryl ester ((14)C-CE), then IV injected in inactive female SLE patients: 10 taking CDP (CDP), 10 without therapy (NO THERAPY); and 10 normal subjects (CONTROL). Groups were age-matched and followed rigorous selection criteria of conditions that interfere in the lipid profile. Blood samples were collected in pre-established intervals after infusion for radioactivity measurement. Fasting lipoproteins were determined in the beginning of kinetic studies. Fractional clearance rate (FCR) of (14)C-CE was significantly different in the three groups (P = 0.03). In fact, a greater FCR of (14)C-CE was observed in CDP compared to NO THERAPY (0.076 +/- 0.037 versus 0.046 +/- 0.021 h(-1); P < 0.05) and to CONTROL (0.0516 +/- 0.0125 h(-1); P < 0.05). Accordingly, a significant lower total and LDL cholesterol were observed in CDP (156 +/- 16 and 88 +/- 16 mg/dl) compared to NO THERAPY (174 +/- 15 and 108 +/- 17 mg/dl; P < 0.05) and to CONTROL (200 +/- 24 and 118 +/- 23 mg/dl; P < 0.05). In contrast, no difference in (FCR) of (14)C-CE of NO THERAPY and CONTROL groups was observed. This is the first in vivo demonstration that LDE removal by LDL receptor from plasma is increased in SLE patients taking CDP with a consequent beneficial decrease in LDL-c levels.

Plasma kinetics, uptake by neoplastic breast tissue and preliminary toxicity data of a cholesterol-rich microemulsion (LDE) associated to a paclitaxel (PCT) derivative

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Background: Previously we described the association of PCT to a cholesterol-rich microemulsion (LDE) that binds to low-density lipoprotein (LDL) receptors and concentrates in neoplastic tissues. The association is stable, preserves the anti-proliferative activity and reduces the toxicity to animals. The present study was designed to provide preliminary toxicity data on the LDE-PCT oleate formulation, to determine its plasma kinetics compared to that of commercial PCT and to verify the complex ability to concentrate in malignant breast tissue. Methods: To determine the plasma kinetics [3H]-PCT oleate associated to LDE labeled with [14C]-Cholesteryl oleate was intravenously injected into 3 pts and [3H]-commercial PCT into 2 pts 24 h before surgery. Blood samples were collected over the 24 h to quantified radioactivity and the pharmacokinetic parameters. Tumoral and normal breast tissue were excised during the surgery. Other 3 heavily pretreated pts with breast cancer were included in this study to assess toxicity. LDE-PCT (175 mg/m2) was administered as a 1-hour infusion at 3 week interval, without pre medication. Results: Fractional clearance rate (FCR) of LDE and of the drug were similar (0.030 ± 0.026 e 0.018 ± 0.018, respectively, P = 0.5742). The uptake of both [14C]-LDE and [3H]-paclitaxel oleate by breast malignant tissue was 2 and 3 fold greater than that of the normal breast tissue. The PCT oleate T1/2 (h) was greater than the commercial PCT (T½ = 18.97 ± 7.7 and 7.34 ± 0.40) and the clearence (L/h) of PCT oleate was lesser than the commercial (CL = 1.51 ± 0.18 and 7.95 ± 4.32). No hematological or neurotoxicity was found. Nausea and anorexia grade 1 was found only in one patient. Conclusion: Most of the drug is retained in the microemulsion until its removal from the circulation. The complex is stable and has greater plasma half life and lesser clearance than those for commercial one and can be concentrated in malignant breast tissue. Furthermore, LDE-PCT showed no considerable toxicity events in the 3 patients. Although data regarding response rates were not assessed, our preliminary results suggest that LDE-PCT may be a suitable and powerful weapon to treat breast cancer patients.

No significant financial relationships to disclose.

Relationships in women between body mass index and the intravascular metabolism of chylomicron-like emulsions

OBJECTIVE

To investigate whether increasing body mass index (BMI) produces increasingly intense disturbances in the metabolism of chylomicrons, the lipoproteins that carry the dietary lipids absorbed by the intestine in the circulation.

SUBJECTS

Four groups of 10 normolipidemic nondiabetic women at the normal (BMI<25 kg/m(2)), preobese (BMI 25-30), obese (BMI 30-40) and morbid obese (BMI>40).

METHODS

Chylomicron metabolism was studied using the method of triglyceride-rich emulsions that mimic chylomicrons. The chylomicron-like emulsion doubly labeled with (3)H-triolein (TO) and (14)C-cholesteryl-oleate (CO) was intravenously injected to calculate the plasma fractional clearance rates (FCR, in min(-1)) by a compartmental analysis model. FCR-TO mirrors both the lipolysis from lipoprotein lipase that the emulsion suffers while still in the circulation, and the triglycerides portion that is not broken down and is removed from the plasma together with the remnant particles. Lipolysis index is calculated subtracting CO from TO areas under the curve.

RESULTS

FCR-TO did not differ among the four groups. The lipolysis index was positively correlated with BMI (r=0.310; P=0.05). On the other hand, FCR-CO progressively diminished from the normal to the morbid obese group (0.069+/-0.01; 0.064+/-0.01; 0.031+/-0.003; 0.029+/-0.005 min(-1), respectively, P=0.003) and there was a negative correlation between FCR-CO and BMI (r=-0.388; P=0.01).

CONCLUSION

In obesity, the capacity to break down chylomicron triglycerides by lipoprotein lipase in vivo increases, but the ability of the organism to remove the resulting chylomicron remnants particles progressively diminishes as the BMI rises. Remnant accumulation most likely predisposes to coronary artery disease development.

Plasma kinetics of a chylomicron-like emulsion in normolipidemic obese women after a short-period weight loss by energy-restricted diet

Chylomicrons carry dietary fats in the bloodstream for storage in body tissues, and thus play an important role in obesity. The 2-step chylomicron metabolism consists of lipolysis by lipoprotein lipase (LPL) on vessel walls and hepatic uptake of triglyceride-depleted remnants. A triglyceride-rich emulsion that mimics chylomicrons, labeled with [9,10-(3)H]glycerol-trioleate (TG) and [1-(14)C] cholesteryl-oleate (CE) was intravenously injected into 14 obese women with body mass index between 30 and 40 kg/m(2) (age, 30 to 40 years), before and after a 2-month energy-restricted diet and into non-obese controls for determination of radioactive lipid plasma kinetics. TG kinetics evaluates lipolysis, whereas CE kinetics evaluates remnant removal. The emulsion TG fractional clearance rate (FCR, in min(-1)) was similar in obese women and their controls (0.126 +/- 0.065; controls, 0.111 +/- 0.031), but the CE-FCR was pronouncedly reduced in the obese subjects (0.028 +/- 0.014; controls, 0.070 +/- 0.009 min(-1); P <.0001). After the energy-restricted diet, TG-FCR was reduced in the obese women (0.075 +/- 0.044 min(-1); P <.05), but CE-FCR was unchanged (0.032 +/- 0.025 min(-1)). Therefore, the lipolysis of the chylomicron-like emulsion is normal in obese women, but remnant removal from the plasma is diminished. After active weight loss by an energy-restricted diet, the remnant removal was unchanged but lipolysis was diminished, possibly due to adaptative changes in LPL activity.

Plasma kinetics of a cholesterol-rich emulsion in young, middle-aged, and elderly subjects

Low density lipoprotein (LDL) plasma concentration is increased in the elderly. In this group, the incidence of coronary artery disease (CAD) is greater and LDL remains an important risk factor for CAD development. In this study, the plasma kinetics of a cholesterol-rich emulsion that binds to LDL receptors was studied in 10-subject groups of the elderly (70 +/- 4 yr), middle-aged (42 +/- 5 yr) and young (23 +/- 2 yr). All were normolipidemic, nonobese, nondiabetic subjects who did not have CAD. The emulsion was labeled with 14C-cholesteryl oleate and injected intravenously into the subjects. Blood samples were drawn at regular intervals over 24 h to determine the plasma decay curve of the emulsion radioactive label and to estimate its plasma fractional clearance rate (FCR, in h(-1)). FCR of the emulsion label was smaller in elderly compared to young subjects (0.032 +/- 0.035 and 0.071 +/- 0.049 h(-1), respectively; mean +/- SD, P< 0.05). FCR of the middle-aged subjects (0.050 +/- 0.071 h(-1)) was intermediate between the values of the elderly and young subjects, although not statistically different from them. A negative correlation was found betweeen the emulsion FCR and subjects' age (r = -0.47, P = 0.008). We conclude that aging is accompanied by progressively diminished clearance of the emulsion cholesterol esters and, by analogy, of the native LDL.

In vitro cytotoxicity of the LDE: daunorubicin complex in acute myelogenous leukemia blast cells

Acute myelogenous leukemia (AML) blast cells show high-affinity degradation of low-density lipoprotein (LDL), suggesting an increased expression of cellular LDL receptors. LDE is a lipid microemulsion easily synthesized in vitro which is known to mimic the metabolic pathway of LDL. We used LDE as a carrier for daunorubicin and assayed the cytotoxicity of the complex using AML blast cells since RT-PCR analysis showed that AML cells express LDL receptor mRNA. The LDE:daunorubicin complex killed 46.7% of blast cells and 20.2% of normal bone marrow cells (P<0.001; Student t-test). Moreover, this complex destroyed AML blast cells as efficiently as free daunorubicin. Thus, LDE might be a suitable carrier of chemotherapeutic agents targeting these drugs to neoplastic cells and protecting normal tissues.

Triglyceride and lipoprotein (a) are markers of coronary artery disease severity among postmenopausal women

OBJECTIVE

After menopause, some women manifest coronary artery disease (CAD) with highly variable angiographic severity. For these women, postmenopausal appearing of some CAD risk factors may have differently influenced the CAD risk and severity. In this study, we attempt to unravel differences in the frequency or intensity of CAD risk factors among postmenopausal women with different angiographic severity.

METHODS

We studied 182 postmenopausal women (64+/-6 years) who underwent coronary angiography to investigate thoracic pain. Subjects with no detectable coronary lesions at angiography were recruited to the non-obstructive group and patients with CAD were grouped in one-vessel or multi-vessel groups. We compared clinical variables as the body mass index (BMI), age at menopause, age, hypertension, diabetes and cigarette smoking, and lipid measurements as plasma levels of total cholesterol, triglyceride, low-density lipoprotein cholesterol, very low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, apolipoprotein (apo) A1, apo B and lipoprotein(a) (Lp(a)).

RESULTS

Comparing to the non-obstructive group, Lp(a) was twofold higher in the one-vessel group and threefold higher in the multi-vessel group and triglycerides were 34% higher in the one-vessel group and 50% higher in the multi-vessel group. No further difference was found among the three groups. After multivariate logistic regression analysis, triglyceride (odds ratio: 1.01; P=0.0013) and Lp(a) (odds ratio: 1.006; P<0.0001) were independently indicative of the presence of obstructive CAD.

CONCLUSIONS

We found that both Lp(a) and triglycerides constitute useful markers of CAD severity among postmenopausal women.

Uptake of a cholesterol-rich emulsion by neoplastic ovarian tissues

OBJECTIVE

Previously, it was shown that a lipidic emulsion (LDE) composed of phospholipids and cholesterol esters which binds to low-density lipoprotein (LDL) receptors may concentrate in acute myeloid leukemia cells. In this study, we aimed to verify whether LDE also has the ability to concentrate in malignant ovarian cancer after being injected into the blood circulation of the patients.

METHODS

Three groups of women scheduled for surgery were included in the survey: 13 bearing malignant tumors, 9 with benign ovarian tumors, and 13 without ovarian tumor who were scheduled to undergo oophorectomy due to malignant disease of the uterine cervix or endometrium. On the day prior to surgery they were injected with LDE labeled with [(14)C]cholesteryl oleate. Specimens of tumors and normal ovaries excised during surgery were lipid extracted and analyzed for radioactivity counting. Results were expressed in radioactive count (cpm) per gram of tissue.

RESULTS

The mean of the uptakes of the emulsion radioactivity by the malignant tumors was roughly eightfold greater when compared with that of the contralateral normal ovaries (2261 +/- 1444 and 275 +/- 137 cpm/g, respectively, P < 0.012), benign tumors, and normal ovaries of the patients without ovarian tumors.

CONCLUSION

LDE has the ability to concentrate in malignant ovarian tumor tissue. Therefore, it can be used as a vehicle to direct cytotoxic drugs against malignant ovarian tumors, thus diminishing the side effects of chemotherapy.

The effects of gemfibrozil upon the metabolism of chylomicron-like emulsions in patients with endogenous hypertriglyceridemia

OBJECTIVE

To evaluate the effects of gemfibrozil upon the intravascular metabolism of chylomicron-like emulsions in endogenous hypertriglyceridemia.

METHODS

We evaluated the plasma kinetics of a chylomicron-like emulsion in 39 subjects: 27 hypertriglyceridemics, total cholesterol (TC) expressed as median (%25; %75) 7.47 (6.1; 8.19) mmol/l and plasma triglycerides (TG) 4.28 (3.6; 18.5) mmol/l and in 12 normolipidemics, TC 4.7 (3.85; 5.37) mmol/l and TG 0.91 (0.64; 1.75) mmol/l. Hypertriglyceridemics were evaluated at baseline and after a 30-day 1200-mg/day gemfibrozil (n=8) or placebo treatment (n=7). The emulsion labelled with 14C-cholesteryl oleate (14C-CO) and 3H-triolein (3H-TO) was injected intravenously after a 12-h fast. The plasma kinetics of 3H-TO and 14C-CO were determined to assess, respectively, lipolysis and clearance of chylomicron and remnants by compartmental analysis.

RESULTS

The residence times (in minutes) of 3H-TO and 14C-CO of hypertriglyceridemics were roughly twice the values of normolipidemics, i.e. 8.0 (5.5; 12.0) versus 15.0 (11.0; 24.0) and 21.5 (14.0; 33.0) versus 44.0 (32.0; 72.0), P=0.001. Gemfibrozil treatment of hypertriglyceridemic patients reduced the residence times of 3H-TO and 14C-CO, respectively, by 46% (P=0.003) and 53% (P=0.008). Effects were noted on the slow phase of emulsion plasma removal, which was reduced in hypertriglyceridemics. After treatment, the emulsion residence times determined in hypertriglyceridemics attained the values of the normolipidemic group.

CONCLUSIONS

Gemfibrozil treatment normalised the defects in chylomicron-like emulsion catabolism observed in endogenous hypertriglyceridemia patients.

Etofibrate but not controlled-release niacin decreases LDL cholesterol and lipoprotein (a) in type IIb dyslipidemic subjects

Etofibrate is a hybrid drug which combines niacin with clofibrate. After contact with plasma hydrolases, both constituents are gradually released in a controlled-release manner. In this study, we compared the effects of etofibrate and controlled-release niacin on lipid profile and plasma lipoprotein (a) (Lp(a)) levels of patients with triglyceride levels of 200 to 400 mg/dl, total cholesterol above 240 mg/dl and Lp(a) above 40 mg/dl. These patients were randomly assigned to a double-blind 16-week treatment period with etofibrate (500 mg twice daily, N = 14) or niacin (500 mg twice daily, N = 11). In both treatment groups total cholesterol, VLDL cholesterol and triglycerides were equally reduced and high-density lipoprotein cholesterol was increased. Etofibrate, but not niacin, reduced Lp(a) by 26% and low-density lipoprotein (LDL) cholesterol by 23%. The hybrid compound etofibrate produced a more effective reduction in plasma LDL cholesterol and Lp(a) levels than controlled-release niacin in type IIb dyslipidemic subjects.

Effects of etofibrate upon the metabolism of chylomicron-like emulsions in patients with coronary artery disease

Slow chylomicron intravascular catabolism has been associated with coronary artery disease and screening for drugs that can speed-up this process can be important. In this study, the effects of etofibrate upon chylomicron metabolism was tested by determination of the plasma kinetics of a chylomicron-like emulsion model in 12 patients with coronary artery disease, aged 59+/-11 years, (total cholesterol: 240+/-41 mg/dl; triglycerides: 188+/-42 mg/dl) submitted to a randomized, crossover, double-blind, placebo-controlled study with administration of 1 g per day etofibrate or placebo for 1-month. A 1-month washout period was inserted between the treatment periods. Patients were intravenously injected a chylomicron-like emulsion doubly labeled with 14C-cholesteryl oleate and 3H-triolein at baseline and after treatments. After etofibrate treatment, there was decrease of total cholesterol and triglyceride plasma levels and a trend to increase high-density lipoprotein cholesterol plasma levels. Etofibrate elicited 62% enhancement of post-heparin lipolytic activity and 100% increase of 3H-triglyceride fractional clearance rate compared with placebo treatment. 14C-cholesterol ester fractional clearance rate was 260% greater after etofibrate than after placebo. Therefore, a potent effect of etofibrate on both chylomicron lipolysis and remnant removal was achieved, indicating that this drug can be used to improve this metabolism in future prospective studies.

Levels of lipoprotein (a) in pulmonary arterial hypertension

We compared the levels of lipoprotein (a) in 48 Caucasian patients with pulmonary arterial hypertension, comprising 32 females and 16 males, aged 28.0 +/- 12.0 years, with a range from 4 through 52 years, with 48 normal Caucasian subjects matched for age and sex. Pulmonary hypertension was secondary in 41 patients with Eisenmenger's syndrome, these comprising 27 females and 14 males aged 27.0 +/- 12.0 years, with a range from 4 through 51 years, and primary in the other 7 patients, 5 females and 2 males, whose age was 30.0 +/- 14.0 years, with a range from 9 through 52 years. Lipoprotein (a) was measured using an immunoprecipitation and turbidimetric assay after a 12 hour fast. Levels of the protein, expressed as the median (% 25; % 75), were higher in those with Eisenmenger's syndrome than in normal controls (p=0.003). In addition, there was a greater prevalence of levels of lipoprotein greater than 30.0 mg/dl in those with secondary pulmonary arterial hypertension patients than in our normal population (p = 0.03). We have found no differences, however, in the levels of lipoprotein(a) in those who had primary pulmonary arterial hypertension when compared with their matched controls, albeit that the number of patients studied was small. We conclude that increased levels of lipoprotein (a) may be secondary to pulmonary arterial hypertension as a marker of tissue damage or may be genetically determined. In either way, the increase in lipoprotein (a) could be an additional factor predisposing to the vascular alterations known to occur in this disease.

Plasma kinetics of an artificial emulsion resembling chylomicrons in patients with chronic lymphocytic leukemia

Chylomicrons are the lipoproteins that transport dietary lipids in the blood. Although neoplastic diseases are often accompanied by alterations in lipid metabolism, chylomicrons are scarcely explored in cancer, despite their importance for the body's energy supply. Moreover, no data are available regarding chylomicron metabolism in chronic lymphocytic leukemia (CLL). Chylomicron metabolism in the bloodstream consists of lipolysis by lipoprotein lipase and uptake of remnants by the liver and is difficult to assess in the human body. Among the methods to evaluate this pathway, the determination of the plasma kinetics of triglyceride-rich emulsions that mimic chylomicrons is a practical and straightforward approach. A double-labeled chylomicron-resembling emulsion was injected into 10 patients with CLL and into 11 normolipidemic healthy subjects. The plasma kinetic curves of the emulsion 3H-triglyceride and 14Ccholesteryl ester were determined in plasma samples collected over 30 min. The fractional clearance rate (FCR) of triglycerides in CLL was not changed compared with controls. The FCR of cholesteryl esters was also no different from controls. These results indicate that chylomicron lipolysis and remnant removal are not affected in CLL.

Effect of pravastatin on plasma removal of a chylomicron-like emulsion in men with coronary artery disease

The speed of the plasma removal of chylomicrons, the lipoproteins that carry dietary lipids absorbed in the intestine, may influence atherogenesis. Thus, the effects of a 30-day pravastatin or placebo treatment on the plasma kinetics of chylomicron-like emulsions were evaluated in 25 patients with coronary artery disease who were not hypertriglyceridemic in a randomized, single-blinded study. Eleven patients (53 +/- 4 years, 10 men) received pravastatin 40 mg/day and 14 received placebo (52 +/- 3 years, 13 men). Emulsions labeled with triolein ((3)H-TO) and cholesteryl oleate ((14)C-CO) to assess lipolysis and clearance of chylomicron and remnants, respectively, were injected intravenously in a bolus after a 12-hour fast. Blood samples were collected during 60 minutes to determine radio isotope decaying curves and fractional catabolic rates. Subjects were studied at baseline and after the treatment period. Compared with placebo (data expressed as mean +/- SEM), pravastatin treatment increased the (14)C-CO fractional catabolic rates (70 +/- 45% vs 18 +/- 10%, p = 0.01), reduced total cholesterol (-21 +/- 3% vs -3 +/- 2% p = 0.0001), low-density lipoprotein (LDL) cholesterol (-25 +/- 5% vs 4 +/- 6%, p = 0.0001), and apolipoprotein B levels (-22 +/- 3% vs -7 +/- 3% p = 0.01). (3)H-TO fractional catabolic rates, plasma triglycerides, very-low-density lipoprotein (VLDL) cholesterol and high-density lipoprotein (HDL) cholesterol variations did not differ between the groups. The fractional catabolic rate of (14)C-CO was inversely correlated with plasma apolipoprotein B levels (r = -0.7, p = 0.04). This suggests that besides reducing LDL cholesterol, pravastatin also increases chylomicron remnant clearance, with possible antiatherogenic implications.

Chylomicron metabolism is markedly altered in systemic lupus erythematosus

OBJECTIVE

To verify the in vivo status of chylomicron metabolism in systemic lupus erythematosus (SLE) since there is a high incidence of atherosclerosis in this disease and chylomicrons may have an important role in atherogenesis.

METHODS

A chylomicron-like emulsion labeled with 14C-cholesteryl esters and 3H-triglycerides was injected intravenously into 10 female patients with inactive SLE and 10 healthy age- and sex-matched control subjects to determine the plasma kinetics of the emulsion lipids from consecutive plasma samples taken at regular intervals for 1 hour. Lipolytic activity was determined in vitro after incubation of the labeled emulsion with postheparin plasma.

RESULTS

The decay curves for the emulsion were markedly slowed in SLE. Chylomicron lipolysis, indicated by the fractional clearance rate (FCR) of emulsion 3H-triglyceride, was 2-fold smaller in SLE patients than in controls (mean +/- SD 0.023 +/- 0.011 versus 0.047 +/-0.015 minute(-1); P = 0.010). Chylomicron removal, indicated by emulsion 14C-cholesteryl ester FCR, was 3-fold smaller in SLE patients than in controls (0.007 +/-0.007 versus 0.023 +/- 0.011 minute(-1); P = 0.009). In vitro lipolysis in SLE patients was nearly half that of the controls (mean +/- SD 10,199 +/- 2,959 versus 6,598 +/-2,215; P = 0.014). Higher levels of very-low-density lipoprotein cholesterol and triglycerides and lower levels of high-density lipoprotein cholesterol and apolipoprotein A-I were also observed in the SLE patients.

CONCLUSION

SLE patients have disturbances in chylomicron metabolism that are characterized by decreased lipolysis and chylomicron remnant removal from the plasma. This finding, together with other alterations in lipid profiles that were confirmed in the present study, is largely accountable for the accelerated atherosclerotic process of the disease.

Chylomicron metabolism in patients submitted to cardiac transplantation

BACKGROUND

Development of coronary graft disease is the most important cause of late heart graft failure. Alterations in plasma lipid profile are frequent in heart transplant (HT) patients, but they seem not to be prominent. Currently, the metabolism of chylomicrons, the lipoproteins that carry dietary lipids absorbed by the intestine, was evaluated because chylomicron remnants are considered atherogenic.

METHODS

An emulsion labeled with 3H-triolein and 14C-cholesteryl oleate and known to mimic the metabolic behavior of chylomicrons was injected intravenously after a 12-hr fast into 34 HT patients, 24 patients with end-stage heart failure (ESHF), and 30 healthy normolipidemic subjects. The plasma disappearance curves of the radioisotopes were determined from blood samples collected over 1 hr. In some of the patients and in controls, in vitro postheparin lipolytic activity was measured and an oral fat load test with postprandial measurement of triglyceridemia was performed.

RESULTS

Fractional clearance rate (in m(-1), median [25%; 75%]) of both emulsion 3H-triolein and 14C-cholesteryl oleate was extremely diminished in HT patients (HT: 0.0114 [0.0114; 0.0179] and 0.2x10(-8) [0.2x10(-8); 0.0041, respectively]; ESHF: 0.0226 [0.0223; 0.0568] and 0.0160 [0.0055; 0.0189]; control subjects: 0.0270 [0.0226; 0.0392] and 0.0090 [0.0042; 0.0180], respectively, P<0.05). HT patients also had reduced postheparin lipolysis and marked elevation of postprandial triglyceridemia compared with the controls.

CONCLUSIONS

HT patients develop accumulation in the plasma of chylomicrons and their remnants. The observed alterations were so intense that they may suggest an important involvement of atherogenic chylomicron remnants in coronary graft disease.

Metabolism of an artificial emulsion resembling chylomicrons in patients with multiple myeloma

Multiple myeloma, as other neoplastic diseases, is accompanied by alterations in lipid metabolism. The metabolism of chylomicrons is unexplored in this condition, despite the importance of these lipoproteins for the energy body supply. Chylomicron metabolism in the bloodstream consists of lipolysis by lipoprotein lipase and uptake of remnants by the liver. Triglyceride-rich emulsions can mimic chylomicron metabolism in man and are a useful tool to evaluate this metabolic pathway. A double-labeled chylomicron-resembling emulsion was injected into 20 patients with multiple myeloma and 30 normolipidemic healthy subjects. The plasma kinetic curves of the emulsion 3H-triglyceride and 14C-cholesteryl ester were determined in plasma samples collected over 60 minutes. The fractional clearance rate (FCR) of triglycerides in multiple myeloma was not changed compared to controls. However, FCR of cholesteryl esters was smaller in multiple myeloma (0.025 +/- 0.003 and 0.061 +/- 0.010 min(-1), respectively). These results indicate that chylomicron lipolysis is not affected in multiple myeloma, whereas remnant removal is diminished.

Effects of apolipoprotein B-100 on the metabolism of a lipid microemulsion model in rats

In previous studies, it was shown that lipid microemulsions resembling LDL (LDE) but not containing protein, acquire apolipoprotein E when injected into the bloodstream and bind to LDL receptors (LDLR) using this protein as ligand. Aiming to evaluate the effects of apolipoprotein (apo) B-100 on the catabolism of these microemulsions, LDE with incorporated apo B-100 (LDE-apoB) and native LDL, all labeled with radioactive lipids were studied after intraarterial injection into Wistar rats. Plasma decay curves of the labels were determined in samples collected over 10 h and tissue uptake was assayed from organs excised from the animals sacrificed 24 h after injection. LDE-apo B had a fractional clearance rate (FCR) similar to native LDL (0.40 and 0.33, respectively) but both had FCR pronouncedly smaller than LDE (0.56, P<0.01). Liver was the main uptake site for LDE, LDE-apoB, and native LDL, but LDE-apoB and native LDL had lower hepatic uptake rates than LDE. Pre-treatment of the rats with 17alpha-ethinylestradiol, known to upregulate LDLR, accelerated the removal from plasma of both LDE and LDE-apoB, but the effect was greater upon LDE than LDE-apoB. These differences in metabolic behavior documented in vivo can be interpreted by the lower affinity of LDLR for apo B-100 than for apo E, demonstrated in in vitro studies. Therefore, our study shows in vivo that, in comparison with apo E, apo B is a less efficient ligand to remove lipid particles such as microemulsions or lipoproteins from the intravascular compartment.

[Comparison of hypercholesterolemic men and women at high risk for atherosclerosis. Study of risk factors and response to pravastatin treatment]

PURPOSE

To compare the prevalence of risk factors, and the response to pravastatin treatment between men and women.

METHODS

We evaluated 486 men and 386 women, of these 230 men and 187 women received 10 mg of pravastatin for three months.

RESULTS

There were differences between women and men in respectively: arterial hypertension (45.5% vs 40.8%; p = 0.0012), left ventricular hypertrophy (33.0% vs 22.0%; p = 0.0041), sedentarism (94.8% vs 87.8%; p = 0.0005), smoking (43.0% vs 61.8%; p < 0.0001), Framingham scores (20.0 +/- 7.1 vs 16.0 +/- 7.6 p < 0.0001), HDL-C (43.0 +/- 11.0 vs 38.0 +/- 9.0 mg/dL; p 0.001), triglycerides-TG (216.0 +/- 115.0 vs 271.0 +/- 172.0 mg/dL; p < 0.001) and Castelli's indexes (CI) I and II (7.7 +/- 2.6 vs 8.6 +/- 3.2; p = 0.002 and 5.0 +/- 1.5 vs 5.5 +/- 2.0; p = 0.015). In men under pravastatin treatment there was a greater reduction in TG (32.0 vs 21.0% p < 0.05) and CI I (-41.0% vs -37.0%; p < 0.05) and II (-40.0% vs -38.0%; p < 0.05).

CONCLUSION

Men and women differed in risk factors prevalence and response to treatment with pravastatin.

Plasma kinetic behavior in hyperlipidemic subjects of a lipidic microemulsion that binds to low density lipoprotein receptors

It was previously reported that a protein-free microemulsion (LDE) with structure roughly resembling that of the lipid portion of low density lipoprotein (LDL) was presumably taken up by LDL receptors when injected into the bloodstream. In contact with plasma, LDE acquires apolipoproteins (apo) including apo E that would be the ligand for receptor binding. Currently, apo were associated to LDE by incubation with high density lipoprotein (HDL). LDE-apo uptake by mononuclear cells showed a saturation kinetics, with an apparent K(m) of 13.1 ng protein/mL. LDE-apo is able to displace LDL uptake by mononuclear cells with a Ki of 11.5 ng protein/mL. LDE without apo is, however, unable to displace LDL. The uptake of 14C-HDL is not dislocated by increasing amounts of LDE-apo, indicating that HDL and LDE-apo do not bind to the same receptor sites. In human hyperlipidemias, LDE labeled with 14C-cholesteryl ester behaved kinetically as expected for native LDL. LDE plasma disappearance curve obtained from eight hypercholesterolemic patients was markedly slower than that from 10 control normolipidemic subjects [fractional clearance rate (FCR) = 0.02 +/- 0.01 and 0.12 +/- 0.04 h-1, respectively; P < 0.0001]. On the other hand, in four severely hypertriglyceridemic patients, LDE FCR was not significantly different from the controls (0.07 +/- 0.03 h-1). These results suggest that LDE can be a useful device to study lipoprotein metabolism.

Early elevation of lipoprotein(a) levels in chronic renal insufficiency

Serum lipoprotein(a) [Lp(a)] concentrations in chronic renal failure patients were investigated in relation to the degree of renal insufficiency, treatment by maintenance hemodialysis, and correction of uremia by renal transplantation with or without cyclosporin immunosuppression. Fast serum levels of Lp(a) (mg/100 mL) were determined in 34 chronic renal failure patients not in need of maintenance dialysis (16 with serum creatinine 2.0-4.0 mg/100 mL; 18 with serum creatinine higher than 4.0 mg/100 mL), 40 patients treated by hemodialysis, 55 successful renal transplant recipients (28 under cyclosporin treatment and 27 receiving no cyclosporin), and 34 healthy controls. Age and sex distributions were similar among groups. Pregnant women; non-White individuals; subjects with obesity, diabetes, nephrotic syndrome, and hepatic and thyroid diseases; and those treated with oral contraceptives or lipid-lowering drugs were excluded from the study. Compared to controls, median Lp(a) was increased in nondialyzed renal failure patients (11 vs. 47.5 p < 0.001) and this was the only lipid abnormally observed in the group. There was no significant difference in Lp(a) levels between nondialized renal failure patients with serum creatinine 2.0-4.0 and > 4.0 mg/100 mL (47 vs. 49, NS). Moreover, Pearson correlation coefficient (r = 0.01, NS) showed that Lp(a) values were not related to serum creatinine in nondialyzed patients, In hemodialysis subjects Lp(a) concentrations (median = 29) were intermediate between those observed in nondialyzed patients and controls but the differences were not significant. Lp(a) levels in renal transplant patients treated with cyclosporin (median = 6) and not receiving cyclosporin (median = 13) were similar and did not differ from controls. Serum Lp(a) increases and attains maximum levels with mild/moderate reduction in renal function, and does not seem to change through late renal failure stages or in relation to the introduction of maintenance hemodialysis treatment. Correction of uremia by successful renal transplant caused normalization of Lp(a) levels regardless of the use of cyclosporin. Increased Lp(a) levels may be the earliest and more consistent lipid alteration seen in predialysis renal failure.

Plasma kinetics of a chylomicron-like emulsion in patients with coronary artery disease

Chylomicron catabolism in the bloodstream consists of lipolysis by lipoprotein lipase and uptake of remnants by the liver. In rats, triglyceride-rich emulsions can mimic chylomicron metabolism. To further validate this model in man, the emulsion was injected intravenously into fasting and into subjects previously fed a test fatty meal. The plasma kinetic curves of the emulsion 3H-triglyceride and 14C-cholesteryl ester were determined. The fractional clearance rate (FCR) of both labels was markedly reduced in the fed subjects (triglycerides: fed = 0.018 +/- 0.007; fasting = 0.105 +/- 0.013 min-1, P < 0.001; cholesteryl ester: fed = 0.016 +/- 0.001; fasting = 0.040 +/- 0.006 min-1; P < 0.05) indicating that the emulsion and chylomicrons generated from the testinal lipid absorption compete for the same catabolic processes, confirming the validity of the method. The emulsion was injected into 11 patients with CAD and into 11 controls. All had plasma cholesterol < 240 and triglycerides < 250 mg/dl. FCR of triglycerides was 5-fold smaller in CAD compared to controls (0.028 +/- 0.004 and 0.141 +/- 0.069 min-1, respectively, P < 0.01). FCR of cholesteryl ester was 4-fold smaller in CAD than in controls (0.015 +/- 0.004 and 0.056 +/- 0.067 min-1 respectively, P < 0.05). These results indicate that both chylomicron lipolysis and remnant removal are diminished in CAD.

Malignant hypertension is accompanied by marked alterations in chylomicron metabolism

Malignant hypertension (MH) is a severe complication of untreated arterial hypertension that damages the vascular system. It is often accompanied by disturbances in lipid metabolism that could contribute to its pathophysiology. We examined chylomicron metabolism in MH patients using a triglyceride-rich emulsion known to mimic natural chylomicrons when injected into the bloodstream. The emulsion was labeled with [3H]triolein and [14C]cholesteryl oleate and injected intravenously into 15 normolipidemic MH patients aged 29 to 56 years (8 men) for comparison with 17 healthy control subjects. Consecutive plasma samples were taken at regular intervals during 1 hour for determination of the disappearance curves of the labels. The fractional clearance rate of the [3H]triolein emulsion in MH patients was twice as small as that of control subjects (0.061 +/- 0.012 and 0.141 +/- 0.074 min-1, respectively). On the other hand, [14C]cholesteryl oleate fractional clearance rate was not statistically different in MH patients and control subjects (0.032 +/- 0.004 and 0.056 +/- 0.014 min-1, respectively). These results indicate that in MH, lipolysis (measured by the fractional clearance rate of [3H]triolein) is pronounced diminished, whereas the removal of the remnant particles (measured by the fractional clearance rate of [14C]cholesteryl oleate) is not importantly affected. In conclusion, there is an alteration in the circulatory transport of dietary lipids that may be an important component in the vascular disease associated with MH.

Evaluation of oxidative stress in patients with hyperlipidemia

An antioxidant defense system consisting of enzymes and non-enzymatic compounds prevents oxidative damage of lipoproteins in the plasma. When the activity of this system decreases or the reactive oxygen species (ROS) production increases, an oxidative stress may occur. Since fatty acids and triglyceride-rich emulsions can stimulate leukocytes to produce ROS, it is conceivable that raised plasma triglyceride-rich lipoproteins such as very low density lipoprotein (VLDL) may overload the antioxidant system. To test this hypothesis, we selected 14 patients with combined hyperlipidemia (HLP), in whom low density lipoprotein (LDL) and VLDL levels are elevated, as well as 18 hypercholesterolemic patients (HCH) with increased LDL levels and 19 controls (NL) to examine the trend for an imbalance between the production of oxidative species and the antioxidant defense system as challenged by increased plasma lipids. With this goal, plasma lipoprotein lipid fractions were determined and correlated with the release of ROS by leukocytes monitored by luminol-enhanced chemiluminescence. Plasma beta-carotene, alpha-tocopherol, lycopene and the lipoprotein lipid hydroperoxides were determined by high pressure liquid chromatography with electrochemical detection. HLP had lower plasma superoxide dismutase (SOD) activity (0.04 and 0.11 U/mg protein; P < 0.05) as well as lower concentrations of lycopene (0.1 and 0.2 nmol/mg cholesterol; P < 0.05) and beta-carotene (0.8 and 2.7 nmol/mg cholesterol; P < 0.05) in the plasma, as compared with NL. Moreover, HLP showed the highest ROS production by resting mononuclear leukocytes (MN) among the three study groups. When the results of the subjects of the three groups were taken together, the plasma triglyceride concentration was positively correlated to ROS release by resting polymorphonuclear leukocytes (PMN, r = 0.38, P = 0.04) and MN (r = 0.56, P < 0.005). Moreover, ROS release by resting MN was positively correlated with VLDL (r = 0.47, P = 0.02) and LDL (r = 0.57, P = 0.01) triglycerides. There was also a positive correlation between ROS release by stimulated PMN and VLDL (r = 0.44, P = 0.03) as well as LDL (r = 0.53, P = 0.01) triglycerides. High density lipoprotein (HDL) cholesterol showed a negative correlation with ROS release by resting MN (r = -0.48, P = 0.02) and resting PMN (r = -0.49, P = 0.01). VLDL susceptibility to copper (II) oxidation was not different among the three groups. Regarding LDL, there was an increased oxidizability in HLP group.(ABSTRACT TRUNCATED AT 400 WORDS)

Sialic acid and oxidizability of low density lipoprotein subfractions of hyperlipidemic patients

OBJECTIVES

Low density lipoprotein (LDL) does not constitute an homogenous fraction and it is known that the heavy LDL subfraction is potentially more atherogenic than the light one. Because concentration of LDL subfractions tend to be different in hyperlipidemias, it was verified whether these subfractions can also differ in sialic acid and neutral sugar content, as well as their resistance to oxidation.

DESIGN AND METHODS

Two subfractions of low density lipoprotein (light LDL, density 1.019-1.034 g/mL and heavy LDL, density 1.034-1.063 g/mL) were isolated from the plasma of 17 patients with hypercholesterolemia, 11 with combined hyperlipidemia, 7 with hypertriglyceridemia, and 19 normolipidemic subjects. The content of sialic acids and neutral sugars of apo B was determined, respectively, by the periodate-thiobarbituric acid method and by reaction with phenol. The oxidation of LDL subfractions was determined by exposure to 5 microM copper (II) followed by the measurement of lipid hydroperoxides production by high performance liquid chromatography with electrochemical detection.

RESULTS

The study groups did not differ in the neutral sugar content of LDL subfractions. However, compared to normolipidemic subjects, the sialic acid concentration of both LDL subfractions was lower in patients with hypercholesterolemia and hypertriglyceridemia and higher in those with combined hyperlipidemia (p < 0.05). In the hypercholesterolemia and combined hyperlipidemia groups, the lipid hydroperoxide content (microM) of heavy LDL was higher than in normolipidemic subjects (p < 0.05).

CONCLUSIONS

The heavy LDL subfraction was more susceptible to oxidation in the patients with combined hyperlipidemia compared to controls and the other hyperlipidemic groups. The effect of sialic acids on heavy LDL oxidizability seems to vary according to the type of hyperlipidemia.

[Comparative study of gemfibrozil versus pravastatin in the treatment of patients with coronary artery disease and low HDL cholesterol levels]

PURPOSE

To evaluate the effects of gemfibrozil and pravastatin in coronary artery disease patients with HDL-cholesterol (HDL-C) < 35 mg/dl).

METHODS

Twenty-nine patients (20 males, 60 +/- 9) were divided in a gemfibrozil group (G) (1200 mg/day n = 15) and a pravastatin group (P) (10 or 20 mg n = 10 and 4, respectively). The plasma lipid profile (LP) e.g. total cholesterol (TC), fractions and triglycerides (TG) was determined at 4 and 12 weeks of treatment.

RESULTS

HDL-C was not affected in P, TC and LDL-cholesterol (LDL-C) reductions were superior to those in G (31.3% vs 13.4% and 38.7 and 11.5%, p < 0.05 and < 0.01 respectively). In G HDL-C raised by 50% (12th week p < 0.01). Gemfibrozil reduced TG levels in 44.7% while in P it varied -32.2% (12th week p < 0.01 and < 0.05 respectively).

CONCLUSION

Gemfibrozil is more effective in reducing TG and raising HDL-C than pravastatin. On the other hand, pravastatin was more potent in reducing LDL-C levels.

Lipoprotein (a) in subjects with or without coronary artery disease: relation to clinical history and risk factors

Lipoprotein (a) [Lp(a)] is an atherogenic lipoprotein resembling low-density lipoprotein (LDL) but with an additional apoprotein (apo), apo(a). To determine whether plasma Lp(a) levels can influence the clinical presentation and extent of coronary artery disease (CAD), Lp(a), plasma lipids and apolipoproteins were determined in 203 Caucasian subjects with CAD and in 66 subjects without CAD, all confirmed by cinecoronariography. CAD patients were divided into groups according to their clinical history. The extent of the disease was evaluated by a scoring system. Lp(a) was elevated in CAD patients compared to subjects without CAD. However, there was no difference between patients that had myocardial infarction as the first manifestation of the disease and those who had only angina pectoris for at least two years. Plasma Lp(a) levels were correlated with extent of the disease. Among patients with CAD, Lp(a) was higher in females. Lp(a) was also studied separately in 29 Black subjects, 12 without CAD and 17 with CAD. In Black subjects, Lp(a) was higher than in Caucasians but there was no difference between subjects with and without CAD. Among the other risk factors studied, only plasma apo B levels and smoking were correlated with CAD.

Clearance of a chylomicron-like emulsion from plasma is delayed in patients with coronary artery disease

To determine whether the metabolism of chylomicrons and their remnants is related to atherogenesis, a triglyceride-rich emulsion known to mimic chylomicron behavior in plasma and labeled with 1-14C-cholesteryl oleate was injected intravenously into 11 normolipidemic patients (triglycerides: 133 +/- 60 mg/dl; total cholesterol: 207 +/- 20 mg/dl; LDL: 143 +/- 20 mg/dl; VLDL: 27 +/- 13 mg/dl; and HDL cholesterol: 41 +/- 11 mg/dl; apo AI: 1.27 +/- 0.54 g/l and apo B: 1.42 +/- 0.31 g/l) with atherosclerotic coronary artery disease and into 11 control subjects (triglycerides: 109 +/- 32 mg/dl; total cholesterol: 190 +/- 38 mg/dl; LDL: 125 +/- 29 mg/dl; VLDL: 22 +/- 6 mg/ dl; and HDL cholesterol: 44 +/- 9 mg/dl; apo AI: 1.09 +/- 0.28 g/l and apo B: 1.09 +/- 0.28 g/l) without the disease. The emulsion (69% triolein, 23% lecithin, 6% cholesteryl oleate and 2% cholesterol) was injected intravenously at approximately 9:00 a.m., after a 12-h fast. The clearance of the emulsion label from plasma, expressed as fractional clearance rate (FCR), was lower in coronary artery disease compared to controls (0.019 +/- 0.005/min vs 0.036 +/- 0.018/min, respectively, P < 0.05). These results indicate that the rate of removal of chylomicron remnants is slower in patients with coronary artery disease.

Plasma kinetics and biodistribution of a lipid emulsion resembling low-density lipoprotein in patients with acute leukemia

Low-density lipoprotein (LDL) could be used as a carrier of chemotherapeutic agents to neoplastic cells that overexpress LDL receptors (rLDL), but LDL is difficult to obtain and handle. Recently, it was observed that a protein-free emulsion resembling the lipid portion of LDL (LDE) behave like native LDL when injected into the bloodstream. In this study, the evidence that LDE is taken up by rLDL was expanded by comparing LDL and LDE plasma decay curves in rabbits and by competition experiments with lymphocytes. To verify whether LDE could be removed from the plasma by neoplastic cells with increased rLDL, LDE labeled with 14Ccholesteryl ester was injected into 14 patients with acute myeloid leukemia (AML) and into 7 with acute lymphocytic leukemia (ALL). In AML rLDL expression is increased but in ALL it is normal. LDE plasma fractional clearance rate (FCR, in h-1) was calculated from the remaining radioactivity measured in plasma samples collected during 24 h following injection. LDE FCR was 3-fold greater in AML than in ALL patients 0.192 +/- 0.210 (SD) and 0.066 +/- 0.033 h-1, respectively, P < 0.035. When LDE injection was repeated in 9 AML patients in hematological remission, LDE FCR diminished 66% compared to the pretreatment values (from 0.192 +/- 0.210 to 0.065 +/- 0.038 h-1, P < 0.02), so that it could be estimated that nearly 66% of the emulsion was taken up by AML cells and only 34% by the normal tissues. As expected, LDE FCR was unchanged in 4 patients with ALL in hematological remission (0.069 +/- 0.044 h-1). Gamma camera images obtained 6 h after the injection of 99mTc-label LDE into one patient with ALL showed biodistribution similar to that of LDL. In one AML patient LDE was comparatively more concentrated over the areas corresponding to the bone marrow infiltrated by AML cells. Our results indicate that LDE FCR is increased in a disease known to contain malignant cells that overexpress rLDL, suggesting that LDE is taken up by malignant cells with increased rLDL.

Metabolism of a chylomicron-like emulsion in rats with Walker 256 tumor: influence of a polyunsaturated (n-6) compared with a saturated fatty acid-rich diet

OBJECTIVE

Defects in lipid metabolism secondary to development of cancer are frequently observed and, in experimental animals, manipulation of the lipid content of the diet can significantly influence tumor growth. The effects of a high polyunsaturated fat vs a high saturated fat diet upon the chylomicron metabolism of rats bearing Walker 256 tumor were examined.

METHODS

Chylomicron-like emulsions labeled with radioactive lipids were injected into rats bearing the tumor and control rats. The two groups were previously given a high polyunsaturated (n-6) (15% fat) or a high saturated fat diet (15% fat) for 6 weeks. Following injection, plasma samples were collected at 8 time intervals in 60 minutes and tissue fragments were excised after the animals were killed, for determination of the plasma fractional clearance rate (FCR, min-1) and organ uptake of radioactive lipids.

RESULTS

FCR of the emulsion triacylglycerols (TG) and cholesteryl oleate ether (CE) decreased in the tumor-bearing rats fed the polyunsaturated fat-rich diet (FCR-TG control = 0.26 +/- 0.09, tumor = 0.11 +/- 0.04; FCR-CE controls = 0.18 +/- 0.05, tumor = 0.10 +/- 0.02), as did activity of the lipoprotein and hepatic lipases (p < 0.05). This indicates that in this group, the presence of the tumor elicited defective lipolysis and delayed removal of the emulsion from the plasma. In the group fed the saturated fatty acid-rich diet, however, these alterations were not observed (FCR-TG control = 0.21 +/- 0.11, tumor = 0.20 +/- 0.08; FCR-CE control = 0.13 +/- 0.06, tumor = 0.10 +/- 0.05). The uptake by several tissues of the emulsion CE was similar in all rat groups.

CONCLUSION

The saturated fat-rich diet avoids the deficiency in chylomicron lipolysis elicited by the implanted Walker 256 tumor.

Lipoprotein(a) levels in systemic lupus erythematosus

OBJECTIVE

To determine lipoprotein(a) [Lp(a)] levels in systemic lupus erythematosus (SLE) and its possible correlation with thrombosis, disease activity, anticardiolipin antibodies (aCL) and steroid therapy.

METHODS

Serum Lp(a) levels were determined by radioimmunoassay (RIA) in 34 Caucasian patients with SLE and compared to 66 healthy subjects.

RESULTS

In patients with SLE Lp(a) levels were higher than in controls (42 +/- 35 vs 26 +/- 25 mg/dl, p = 0.01). Lp(a) levels were high (> or = 30 mg/dl) in 56% of the patients with SLE and in 30% of controls (p = 0.02) but were not correlated with the clinical and laboratory findings.

CONCLUSIONS

Lp(a) levels are significantly higher in patients with SLE and are not influenced by disease activity, thrombosis, aCL and steroid therapy.

Metabolic behavior in rats of a nonprotein microemulsion resembling low-density lipoprotein

A protein-free microemulsion (LDE) with a lipid composition resembling that of low-density lipoprotein (LDL) was used in metabolic studies in rats to compare LDE with the native lipoprotein. LDE labeled with radioactive lipids was injected into the bloodstream of male Wistar rats, and plasma kinetics of the labeled lipids were followed on plasma samples collected at regular intervals for 12 h after injection. The 24-h LDE uptake by different tissues was also measured in tissue samples excised after the animals had been sacrificed. We found that LDE plasma kinetics were similar to those described for native LDL [fractional clearance rate (FCR) of cholesteryl ester, 0.42 +/- 0.11 h-1]. The major site for LDE uptake was the liver, and the tissue distribution of the LDE injected radioactivity was as one would expect for LDL. To test whether LDE was taken up by the specific LDL receptors, the LDE emulsion was injected into rats treated with 17 alpha-ethinylestradiol, which is known to increase the activity of these receptors; as expected, removal of LDE from the bloodstream increased (FCR = 0.90 +/- 0.35 h-1). On the other hand, saturation of the receptors that remove remnants by prior infusion of massive amounts of lymph chylomicrons did not change LDE plasma kinetics. These results indicate that LDE is cleared from plasma by B,E receptors and not by the E receptors that remove remnants. Incorporation of free cholesterol into LDE increased LDE plasma clearance. Incubation studies also showed that LDE incorporates a variety of apolipoproteins, including apo E, a ligand for recognition of lipoproteins by specific receptors.(ABSTRACT TRUNCATED AT 250 WORDS)