Thiazolidinediones inhibit lipoprotein lipase activity in adipocytes

The thiazolidinediones troglitazone and BRL 49653 improve insulin sensitivity in humans and animals with insulin resistance. Adipose tissue lipoprotein lipase is an insulin-sensitive enzyme. We examined the effects of thiazolidinediones on lipoprotein lipase expression in adipocytes. When added to 3T3-F442A, 3T3-L1, and rat adipocytes in culture, troglitazone and BRL 49653 inhibited lipoprotein lipase activity. This inhibition was observed at concentrations as low as 0.1 microM and within 2 h after addition of the drug. Lipoprotein lipase activity was inhibited in differentiated adipocytes as well as the differentiating cells. Despite this decrease in enzyme activity, these drugs increased mRNA levels in undifferentiated 3T3-F442A and 3T3-L1 cells and had no effect on mRNA expression or synthesis of lipoprotein lipase in differentiated cells. Western blot analysis showed that these drugs did not affect the mass of the enzyme protein. Lipoprotein lipase activity in cultured Chinese hamster ovary cells was not inhibited by troglitazone. Glucose transport, biosynthesis of lipids from glucose or the biosynthesis of proteins were unaffected by thiazolidinediones in differentiated cells, whereas glucose transport and lipid biosynthesis were increased when these drugs were added during differentiation. These results show that troglitazone and BRL 49653 have a specific, post-translational inhibitory effect on lipoprotein lipase in adipocytes, yet they promote lipid accumulation and differentiation in preadipocytes.     

Plasma lipoprotein(a) is not a predictor for restenosis after elective high-pressure coronary stenting

BACKGROUND: Preceding mucosal response to one allergen leads to the priming of the nasal mucosal response to another allergen. This study aimed to determine whether environmental allergens, especially ubiquitous animal dander, can induce nasal priming. METHODS: We investigated 26 grass-pollen-allergic subjects with additional sensitization to other aeroallergens. We performed continuous allergen challenge for 2 h with 1500 Dactylis glomerata pollen/m3 in the Vienna challenge chamber. The nasal flow at 150 Pa was examined, and subjective scores were obtained every 15 min. Statistical analysis was calculated from the area under curve of nasal flow reduction by Student's t-test and the Mann-Whitney U-test. Alpha was 0.05. RESULTS: In subjects with positive cat-dander RAST (class of > or = 3), besides grass-pollen allergy, the specific nasal allergic reaction to Dactylis challenge was significantly pronounced (P < 0.01), and an earlier onset of reaction was evident. The same results were obtained with additional sensitization to dog dander (P < 0.05). Concomitant sensitization to mugwort also led to escalating symptoms (P < 0.05). CONCLUSIONS: These results indicate that a specific nasal allergic reaction is augmented by environmental priming caused by ubiquitous animal dander and possibly is influenced by the daily use of spices.     

GH but not IGF-I or insulin increases lipoprotein lipase activity in muscle tissues of hypophysectomised rats

Changes in GH secretion are associated with changes in serum lipoproteins, utilisation of fuels and body composition. Since lipoprotein lipase (LPL) is a key enzyme in the regulation of lipid and lipoprotein metabolism, changes in LPL activity may contribute to these effects of GH. The present study was undertaken to investigate the role of GH and the GH-dependent growth factor, IGF-I, in the regulation of LPL in heart, skeletal muscle and adipose tissue. Female rats were hypophysectomised at 50 days of age. One week later, hormonal therapy was commenced. All hypophysectomised rats received l-thyroxine and cortisol. Adipose tissue, the heart, soleus and gastrocnemius muscles were excised after 1 week of hormonal therapy. The effect of insulin injections on adipose tissue and heart LPL activity was also studied. In separate experiments, LPL activity in post-heparin plasma was measured. Hypophysectomy had no effect on adipose tissue LPL activity, whereas activity was reduced in heart, soleus and gastrocnemius muscle tissues. GH treatment had no significant effect on LPL activity in adipose tissue or soleus muscle, but increased the LPL activity in heart and gastrocnemius muscle. GH treatment increased post-heparin plasma LPL activity. Recombinant human IGF-I treatment (1.25 mg/kg per day) markedly reduced LPL activity in adipose tissue, but had no effect in muscle tissues. The effect of IGF-I treatment on adipose tissue LPL was not reflected by a decrease in post-heparin plasma LPL activity. Daily injections of insulin for 7 days increased LPL activity in adipose tissue but had no effect on heart LPL activity. In adipose tissue, LPL mRNA levels tended to decrease as a result of IGF-I treatment. In the muscle tissues, no significant effects of hypophysectomy, GH or IGF-I treatment on LPL mRNA levels were observed.%It is concluded that GH increases heart and skeletal muscle tissue LPL activity, which probably contributes to an increased post-heparin plasma LPL activity. The effect of GH on muscle LPL activity is probably not mediated by IGF-I or insulin. Insulin and IGF-I have opposite effects on LPL activity in adipose tissue.     

Involvement of adenosine in vanadate-stimulated release of lipoprotein lipase activity

BACKGROUND: Optimal bottle weaning should occur between 12 and 15 months of age. We hypothesized that high-risk populations have different parental attitudes, learned behaviors, and knowledge of weaning practices. OBJECTIVE: To determine whether high-risk populations are less likely to wean their children by 15 months of age than low-risk populations. METHODS: A cross-sectional survey using a convenience sample of parents was conducted at 3 community-based pediatric clinics. Spanish- and English-speaking parents with weaned and unweaned children 12 to 36 months of age were included in the study. A self-administered questionnaire was completed at a clinic visit. The questionnaire addressed aspects of parents' sociodemographic characteristics and included feeding history; weaning practices; sources of information about weaning; and parental behaviors, attitudes, and knowledge of age at which the child should be weaned. RESULTS: One hundred eighty questionnaires were completed. Marital status was related to weaning behavior. Seventy-six percent of single mothers had weaned their children in a timely manner, whereas 48% of married mothers had done so (chi2 = 7.70; P = .008). Parental education, race, and income were not significantly related to the timeliness of weaning. When respondents rated the helpfulness of multiple sources, only the health clinic was found to be significantly more important for the timely weaning group (t = -2.13; P = .04). Parents with timely weaned children stated that the mean +/- SD optimal age for weaning is 13.6 +/- 3.2 months. Parents with unweaned and late-weaned children stated that the mean +/- SD optimal age is 19.9 +/- 6.6 months. Bedtime bottle feedings were reported in more than 87% of the unweaned group. Sixty-nine percent reported poor dental development associated with delayed weaning. CONCLUSIONS: Married parents are at risk of late weaning. Parents continue to allow their children to sleep with milk bottles in their mouths in bed at night. Parents are not aware of the medical problems associated with late weaning. Late-weaning parents are not knowledgeable about current weaning recommendations. Current approaches are not effective in altering set patterns of inappropriate weaning habits. Additional interventions and innovative parental education methods are needed to improve age-appropriate weaning practices.     

Growth hormone inhibits lipoprotein lipase activity in human adipose tissue

The in vitro effects of GH on human adipose tissue lipoprotein lipase (LPL) activity and messenger ribonucleic acid (mRNA) levels were studied using a tissue incubation technique. After preincubation for 3 days, abdominal sc adipose tissue pieces were exposed to cortisol (1000 nmol/L) for 3 days to induce LPL activity. Addition of GH (50 micrograms/L) to the cortisol-containing medium during the last 24 h (day 6) caused a decrease by 84 +/- 4% (P < 0.01) in heparin-releasable LPL activity and by 65 +/- 4% (P < 0.01) in total LPL activity. Moreover, the heparin-releasable fraction was reduced from 42% of the total LPL activity with cortisol alone to 17% when both GH and cortisol were present in the incubation medium during the last 24 h (P < 0.01). The reduction in LPL activity in response to GH was not accompanied by a decrease in the level of LPL mRNA measured by a solution hybridization ribonuclease protection assay. In adipose tissue incubated in the control medium for 6 days, the addition of GH alone during the last 24 h caused an insignificant decrease in heparin-releasable LPL activity. Low control activities limited the scope for further decrease. It is concluded that GH counteracts the potent stimulatory effect of glucocorticoids on LPL activity without affecting LPL mRNA levels. Therefore, the inhibition of LPL activity by GH probably occurs during translation and/or posttranslational processing of the enzyme, and the mechanism may involve a decreased channeling of the lipase to the cell surface.     

Linkage of low-density lipoprotein size to the lipoprotein lipase gene in heterozygous lipoprotein lipase deficiency

Small low-density lipoprotein (LDL) particles are a genetically influenced coronary disease risk factor. Lipoprotein lipase (LpL) is a rate-limiting enzyme in the formation of LDL particles. The current study examined genetic linkage of LDL particle size to the LpL gene in five families with structural mutations in the LpL gene. LDL particle size was smaller among the heterozygous subjects, compared with controls. Among heterozygous subjects, 44% were classified as affected by LDL subclass phenotype B, compared with 8% of normal family members. Plasma triglyceride levels were significantly higher, and high-density lipoprotein cholesterol (HDL-C) levels were lower, in heterozygous subjects, compared with normal subjects, after age and sex adjustment. A highly significant LOD score of 6.24 at straight theta=0 was obtained for linkage of LDL particle size to the LpL gene, after adjustment of LDL particle size for within-genotype variance resulting from triglyceride and HDL-C. Failure to adjust for this variance led to only a modest positive LOD score of 1.54 at straight theta=0. Classifying small LDL particles as a qualitative trait (LDL subclass phenotype B) provided only suggestive evidence for linkage to the LpL gene (LOD=1. 65 at straight theta=0). Thus, use of the quantitative trait adjusted for within-genotype variance, resulting from physiologic covariates, was crucial for detection of significant evidence of linkage in this study. These results indicate that heterozygous LpL deficiency may be one cause of small LDL particles and may provide a potential mechanism for the increase in coronary disease seen in heterozygous LpL deficiency. This study also demonstrates a successful strategy of genotypic specific adjustment of complex traits in mapping a quantitative trait locus.     

Variations in interleukin-2 and interleukin-6 due to surgical trauma in cancer patients

Inflammatory response after surgical trauma, which is necessary for infection control and tissue repairing, can actually produce some cytokines suppressive of the antitumoral immunity response. In this study the authors evaluate pre- and post-operative IL-2 (antitumor response activator) and IL-6 (lymphocytic response inhibitor and tumor growth factor) levels in 26 cancer patients undergoing resective surgery. Analysis of the results showed a significative IL-6 increase and a tendency to IL-2 decrease in the post-operative period. It is thus confirmed, even on the basis of the cytokines, the meaningful immunosuppressive effect of the surgical trauma on neoplastic growth control.     

Decreased release of lipoprotein lipase is associated with vascular endothelial damage in NIDDM patients with microalbuminuria

OBJECTIVE: To explore mechanisms for hypertriglyceridemia in diabetic patients with microalbuminuria, we examined an association between heparin-releasable lipoprotein lipase (LPL) and the von Willebrand factor (vWF), based on the hypothesis that LPL bound to endothelium is decreased by generalized endothelial damage. RESEARCH DESIGN AND METHODS: A total of 37 NIDDM patients with microalbuminuria and 69 patients with normoalbuminuria were studied. Plasma LPL mass in post-heparin plasma and plasma vWF antigen were quantified by sandwich-enzyme immunoassay and enzyme-linked immunosorbent assay, respectively. RESULTS: The NIDDM patients with microalbuminuria had higher plasma triglyceride (TG) and lower HDL cholesterol concentrations compared with the patients with normoalbuminuria. Heparin-releasable LPL mass was significantly lower in the microalbuminuric than in the normoalbuminuric subjects. Plasma level of vWF, a marker for endothelial damage, was significantly increased in microalbuminuric subjects compared with their normoalbuminuric counterparts. The LPL mass was inversely correlated with plasma vWF level at a high correlation coefficient value. The LPL mass was inversely related to TG and positively to HDL cholesterol concentrations. CONCLUSIONS: These results suggest that widespread endothelial damage occurred in NIDDM patients with microalbuminuria, thereby LPL moiety bound to the endothelium is decreased, which results in an impaired catabolism of TG-rich lipoproteins.     

Plasma lipoprotein(a) levels in patients with hyperthyroidism

Thyroid function and regulation were studied in 14 consecutive male outpatients with asymptomatic human immunodeficiency virus (HIV) infection (CDC II/III, n = 8) or AIDS (CDC IV, n = 6) who were free of concomitant infections and hepatic dysfunction, and in eight healthy, age- and weight-matched male controls. Blood was sampled every 10 minutes over 24 hours for measurement of thyrotropin (TSH). Thereafter, thyroid hormones and TSH responsiveness to thyrotropin-releasing hormone (TRH) were measured. Triiodothyronine (T3) and thyroxine (T4) did not differ between HIV-infected patients and controls, but HIV patients had lower thyroid hormone-binding index ([THBI] HIV patients, 1.01 +/- 0.02; controls, 1.11 +/- 0.03; P < .02), free thyroxine (FT4) index (94 +/- 3 v 110 +/- 4, P < .01), FT4 (11.8 +/- 0.4 v 14.3 +/- 0.4 pmol/L, P < .01), and reverse triiodothyronine (rT3) values (0.18 +/- 0.01 v 0.26 +/- 0.02 nmol/L, P < .001) and higher thyroxine-binding globulin ([TBG] 20 +/- 1 v 16 +/- 1 mg/L, P < .02) values. Mean 24-hour TSH levels were increased in HIV patients (2.39 +/- 0.33 v 1.44 +/- 0.16 mU/L, P < .05), associated with increased mean TSH pulse amplitude and TSH responsiveness to TRH. No differences were observed between asymptomatic HIV-seropositive and AIDS patients. In conclusion, there is a hypothyroid-like regulation of the pituitary-thyroid axis in stable HIV infection, which differs distinctly from the euthyroid sick syndrome in non-HIV-nonthyroidal illnesses.(ABSTRACT TRUNCATED AT 250 WORDS)     

The inhibition in vivo of lipoprotein lipase (clearing-factor lipase) activity by triton WR-1339

1. Lipoprotein lipase activity was measured in heart homogenates and in heparin-releasable and non-releasable fractions of isolated perfused rat hearts, after the intravenous injection of Triton WR-1339. 2. In homogenates of hearts from starved, rats, lipoprotein lipase activity was significantly inhibited (P less than 0.001) 2h after the injection of Triton. This inhibition was restricted exclusively to the heparin-releasable fraction. Maximum inhibition occurred 30 min after the injection and corresponded to about 60% of the lipoprotein lipase activity that could be released from the heart during 30 s perfusion with heparin. 3. Hearts of Triton-treated starved rats were unable to take up and utilize 14C-labelled chylomicron triacylglycerol fatty acids, even though about 40% of heparin-releasable activity remained in the hearts. 4. It is concluded that Triton selectively inhibits the functional lipoprotein lipase, i.e. the enzyme directly involved in the hydrolysis of circulating plasma triacylglycerols. 5. Lipoprotein lipase activities measured in homogenates of soleus muscle of starved rats and adipose tissue of fed rats were decreased by 25 and 39% respectively after Triton injection. It is concluded that, by analogy with the heart, these Triton-inhibitable activities correspond to the functional lipoprotein lipase.     

Proopiomelanocorticotropin (POMC) peptides and lipoprotein lipase activity in vitro

Effects of alpha-melanocyte-stimulating hormone (alpha-MSH), beta-melanocyte-stimulating hormone (beta-MSH), beta-lipotropin (beta-LPH), and beta-endorphin (beta-EPH) at concentrations from 10(-9) M up to 10(-6) M on human adipose tissue lipoprotein lipase (LPL) were studied in a cell-free system. alpha-MSH and beta-MSH did not exert any effect on LPL; no degradation of these peptides in the incubation medium could be detected by HPLC analysis. beta-LPH and beta-EPH failed to alter enzyme activity. However, HPLC analysis revealed an unspecific rapid degradation of the peptides due to the activity of tissue proteases. Therefore, the protease inhibitors amastatin, antipain, APMSF, and TPCK were tested at concentrations of 10(-5), 10(-4), and 10(-3) M for their efficacy to inhibit degradation. None of the inhibitors was able to substantially reduce proteolysis of beta-LPH, as was the case with amastatin, APMSF, and TPCK for beta-EPH. However, antipain at 10(-4) M preserved at least 20% of the initial peptide concentration from proteolysis up to 150 min. Antipain caused a decrease in lipoprotein lipase activity (LPLA), which was dependent on concentration. The adverse effect of antipain at concentrations of 10(-4) M on LPL was completely abolished by beta-EPH at a concentration of 10(-6) M.     

Lipid binding of apolipoprotein CII is required for stimulation of lipoprotein lipase activity against apolipoprotein CII-deficient chylomicrons

Human apolipoprotein CII (apo CII) consists of 79 amino acid residues. The amino-terminal two thirds of the molecule binds to lipid through the formation of amphipathic helixes, while the carboxy-terminal third is engaged in activation of lipoprotein lipase (LPL). On the basis of studies in model systems, it was previously concluded that fragments of apo CII spanning residues 51-79 were sufficient for activation, although they do not bind to lipid. In the present study, we used chylomicrons from an apo CII-deficient patient to reinvestigate this possibility, with a physiologically relevant substrate. Human LPL expressed very low activity against these chylomicrons. Addition of apo CII caused an immediate > 100-fold increase in lipase activity. The apo CII fragment 50-79 caused very little stimulation, though with some synthetic lipid substrates, this fragment was fully effective. LPL bound to the chylomicrons even in the absence of apo CII but apparently in a nonproductive manner. In accord with this finding, the main effect of apo CII was on the VMAX for the reaction, with little or no change in the apparent K(M). We conclude that the lipid-binding part of apo CII is needed for activity of LPL against chylomicrons. This idea is in accord with previous studies with lipid monolayers, which showed that the lipid-binding part is necessary for activation of the enzyme at high surface pressures.     

Bacillus Calmette-Guérin potentiates monocyte responses to lipopolysaccharide-induced tumor necrosis factor and interleukin-1, but not interleukin-6 in bladder cancer patients

During the past decade, particular attention has been focused on treatment of bladder cancer patients with the bacterial agent bacillus Calmette-Guérin (BCG). In these studies, bladder cancer patients were instilled with BCG (75 mg/50 ml) once per week for 6 weeks, 1-2 weeks following trans-urethral resection of the bladder. Cystoscopy was performed after 6 weeks and, unless tumor progression was present, monthly treatments were given for 1 year. Blood was drawn 2 h after the last instillation, and monocytes were isolated (5 x 10(6) cells/ml) and treated, or not, with lipopolysaccharide (LPS) (20 microgram/ml) for tumor necrosis factor alpha (TNF alpha), interleukin-1 alpha (IL-1 alpha) and interleukin-6 (IL-6) release. The levels of monokines were determined by a monokine-specific enzyme-linked immunosorbent assay. Our results clearly show that, after 18 h incubation, macrophages from BCG-treated bladder cancer patients produced from 2.8- to 1.9-fold and from 2.0- to 1.3-fold greater amounts of TNF alpha and IL-1 alpha respectively, compared to macrophages from healthy controls, 5-fold higher than bladder cancer patients not treated with BCG. IL-6 was not affected. In another set of experiments macrophages (5 x 10(6) cells/ml) from healthy subjects were pretreated, or not, with BCG (100 micrograms/ml) overnight and treated, or not, with LPS 20 microgram/ml alone and in combination with interleukin-1 receptor antagonist (IL-1ra) 250 ng/ml. Macrophages treated with BCG had a strong stimulatory effect on IL-1 alpha release (9.45 ng/ml) while LPS was less effective (3.59 ng/ml). The combination of BCG plus LPS produced an additive effect on IL-1 alpha release (13.71 ng/ml) compared to the effect of the compound alone. The addition of IL-1ra (250 ng/ml) to BCG was not effective, while when IL-1ra was added to BCG plus LPS only a partial inhibition of IL-1 alpha release was found (9.83 ng/ml), compared to BCG plus LPS without IL-1ra (13.71 ng/ml). These effects seem to be related to the inhibition of IL-1 alpha stimulated with LPS, but not BCG. The priming effect of BCG exerted on LPS-stimulated monocyte production of TNF alpha and IL-1 alpha from bladder cancer patients led us to study the possible modulation of fibrinogen and C-reactive protein in the serum of BCG-treated cancer patients. The plasma levels of fibrinogen and C-reactive protein were higher (approximately twice) in BCG-treated patients compared to values obtained in untreated patients or healthy controls. We conclude that the beneficial immunotherapeutic effects of BCG in bladder cancer patients are related to its capacity to prime macrophages to enhance the release of TNF alpha and IL-1 alpha, but not IL-6 in response to physiological secondary stimuli, or through the direct stimulation of BCG on IL-1 alpha or TNF alpha, which are directly involved in the killing of cancer cells.(ABSTRACT TRUNCATED AT 400 WORDS)     

Plasma cholesteryl ester transfer activity is modulated by the phase transition of the lipoprotein core

Previous studies have shown that lipid transfer protein (LTP) activity is strongly temperature dependent, demonstrating a dramatic rise in activity near 37 degrees C. We have investigated the origin of this rapid rise in LTP activity. LTP-mediated transfers of radiolabeled cholesteryl ester (CE) from LDL to HDL, HDL to LDL, LDL to biotin-LDL, HDL to biotin-HDL, and between liposomes were determined as a function of assay temperature. Only assays containing LDL demonstrated this rapid rise in CE transfer activity. In contrast, TG transfer was almost linear with assay temperature. As human LDL CE undergoes a thermal phase transition near 37 degrees C, we investigated whether the rapid rise in CE transfer was dependent on this transition. Monkey LDL were isolated from animals consuming diets containing cholesterol and enriched in saturated, monounsaturated, or polyunsaturated fatty acids. With these LDL as substrate, the CE transfer between 21 degrees and 49 degrees C could be described by two straight lines, the intersection of which defined the inflection temperature. Among eight LDL samples, the inflection temperature was highly correlated with the CE phase transition determined by differential scanning calorimetry (r2 = 0.86). Both calorimetry and CE transfer activity inflection values were correlated with the saturated + monoene/polyene ratio of the LDL cholesteryl esters (r2 = 0.733 and 0.612, respectively). For LDL with inflection temperatures below 37 degrees C, CE transfer activity at 37 degrees C increased 10-14% for each 1 degree C decrease in the inflection temperature. We conclude that LTP activity is markedly affected by the physical state of the core CE. Diets rich in saturated fatty acids may result in LDL that are poor LTP substrates, which may hinder LTP's ability to promote normal lipoprotein remodeling.     

Cardiac heparin-releasable lipoprotein lipase activity in fructose-hypertensive rats: effect of coronary vasodilation

Lipoprotein lipase (LPL) is an endothelium-bound enzyme that is rate determining for the clearance of triacylglycerol-rich lipoproteins. We assessed cardiac heparin-releasable LPL activity in an acquired model of hypertension, the fructose-hypertensive rat. Fructose feeding (10% solution in drinking water ad libitum) for 2 (short-term) or 4-6 (long-term) weeks induced hypertension, hypertriglyceridemia, and hyperinsulinemia in male Wistar rats. After short- and long-term fructose treatment, LPL activity in coronary perfusates was determined by retrogradely perfusing the hearts with heparin. Short-term fructose treatment did not alter cardiac heparin-releasable LPL activity, whereas a significant decrease in LPL activity was seen in the long-term treated group. Discontinuation of fructose treatment for 2 weeks from the long-term group normalized blood pressure and cardiac heparin-releasable LPL activity. Interestingly, acute vasodilation by in vitro perfusion of coronary vasodilators like nifedipine and CGS-21680 increased cardiac heparin-releasable LPL activity in the long-term group to control levels. These studies demonstrate that long-term fructose-induced hypertension may play a significant role in regulating cardiac LPL activity. Whether or not this altered LPL activity has a role in the regulation of fatty acid supply to the hypertensive heart has yet to be determined.     

Blood transfusion and postoperative serum interleukin-6 levels in colorectal cancer patients

BACKGROUND/AIMS: Postoperative cytokine response affects various factors. However, excessive stress responses are deleterious as increased serum concentration of cytokines may induce tissue injury and an impaired immune system. METHODOLOGY: We determined serum IL-6 levels in 35 patients who had undergone resection of colorectal carcinoma. Eleven patients had a blood transfusion before or during the operation (transfused group) but 24 patients had received no blood transfusion (control group). Serum IL-6 levels were determined before the operation, and at the end of operation,POD-1, 3, and 7. RESULTS: There was no significant difference of preoperative mean levels of IL-6 between these two groups (p=0.20). Postoperative serum IL-6 levels were significantly elevated. Mean serum levels of IL-6 were significantly higher at the end of operation in the transfused group than in the control group (131.7 pg/ml in control group and 269.8 pg/ml in transfused group; p=0.02). CONCLUSION: The present study suggested that perioperative allogeneic blood transfusion can induce an excessive cytokine response and may be deleterious.     

Reduced cholesteryl ester transfer in plasma of patients with lipoprotein lipase deficiency

The net mass transfer of cholesteryl ester (CE) from high density lipoprotein (HDL) to the apolipoprotein (apo) B-containing lipoproteins, very low density lipoprotein (VLDL) and low density lipoprotein (LDL) in plasma (cholesteryl ester transfer (CET)) from three patients lacking lipoprotein lipase (LpL) activity was significantly lower (P < 0.001) than in plasma from fasting control subjects with comparable triglyceride levels. Chylomicrons isolated from LpL-deficient fasting plasma showed the same low level of CET activity as observed in the intact plasma when combined with HDL and cholesteryl ester transfer protein (CETP)-containing d 1.063 g/ml bottom fractions from control subjects. Preincubation of chylomicrons and large triglyceride-rich lipoproteins (Sf > 400) from LpL-deficient plasma with milk LpL, however, stimulated the capacity to engage in CET 4- to 5-fold to the same level as chylomicrons and VLDL from control subjects after a fat load. Consistent with these measurements of CET activity in plasma, chylomicrons obtained from the LpL-deficient subjects after a 14-h fast had higher TG/CE ratios than chylomicrons from controls 3 h after ingesting a fat load (LpL-deficient 26.3 +/- 9.0 vs. controls 6.9 +/- 2.1; mean +/- SD). The mass of CETP did not differ in LpL-deficient and control subjects (LpL-deficient 1.03 +/- 0.22 micrograms/ml vs. controls 1.58 +/- 0.58 micrograms/ml). These studies are consistent with earlier in vitro studies showing that the actions of lipoprotein lipase and its lipolytic products are essential, for maximal cholesteryl ester transfer protein activity.