Overexpression of human lecithin:cholesterol acyltransferase in cholesterol-fed rabbits: LDL metabolism and HDL metabolism are affected in a gene dose-dependent manner

Lecithin:cholesterol acyltransferase (LCAT) is an enzyme well known for its involvement in the intravascular metabolism of high density lipoproteins; however, its role in the regulation of apolipoprotein (apo) B-containing lipoproteins remains elusive. The present study was designed to investigate the metabolic mechanisms responsible for the differential lipoprotein response observed between cholesterol-fed hLCAT transgenic and control rabbits. 131I-labeled HDL apoA-I and 125I-labeled LDL kinetics were assessed in age- and sex-matched groups of rabbits with high (HE), low (LE), or no hLCAT expression after 6 weeks on a 0.3% cholesterol diet. In HE, the mean total cholesterol concentration on this diet, mg/dl (230 +/- 50), was not significantly different from that of either LE (313 +/- 46) or controls (332 +/- 52) due to the elevated level of HDL-C observed in HE (127 +/- 19), as compared with both LE (100 +/- 33) and controls (31 +/- 4). In contrast, the mean nonHDL-C concentration for HE (103 +/- 33) was much lower than that for either LE (213 +/- 39) or controls (301 +/- 55). FPLC analysis of plasma confirmed that HDL was the predominant lipoprotein class in HE on the cholesterol diet, whereas cholesteryl ester-rich, apoB-containing lipoproteins characterized the plasma of LE and, most notably, of controls. In vivo kinetic experiments demonstrated that the differences in HDL levels noted between the three groups were attributable to distinctive rates of apoA-I catabolism, with the mean fractional catabolic rate (FCR, d-1) of apoA-I slowest in HE (0.282 +/- 0.03), followed by LE (0.340 +/- 0.01) and controls (0.496 +/- 0.04). A similar, but opposite, pattern was observed for nonHDL-C levels and LDL metabolism (h-1), such that HE had the lowest nonHDL-C levels with the fastest rate of clearance (0.131 +/- 0.027), followed by LE (0.057 +/- 0.009) and controls (0.031 +/- 0.001). Strong correlations were noted between LCAT activity and both apoA-I (r= -0.868, P < 0.01) and LDL (r = 0.670, P = 0.06) FCR, indicating that LCAT activity played a major role in the mediation of lipoprotein metabolism. In summary, these data are the first to show that LCAT overexpression can regulate both LDL and HDL metabolism in cholesterol-fed rabbits and provide a potential explanation for the prevention of diet-induced atherosclerosis observed in our previous study.

Interaction of diet and genes in atherogenesis. Report of an NHLBI working group

Recent advances in genetics and information emerging from the Human Genome Project make it feasible to examine the importance of dietary-genetic interactions in the development of atherosclerosis. In the opinion of the Working Group, three approaches are necessary to examine this concern. The first approach utilizes animal models to map and identify candidate genes involved in dietary responsiveness and atherogenesis. The second approach involves the evaluation of these genes in specific physiological processes involved in dietary responsiveness and atherogenesis. Finally, the third approach is to extend the studies performed in animal models to human populations using linkage or association studies.

Effects of short-term hormone replacement therapies on low-density lipoprotein metabolism in cynomologus monkeys

Estrogen replacement therapy reduces the risk of coronary heart disease in women and decreases the extent of atherosclerosis in monkeys. In our previous studies, estrogen treatment decreased arterial LDL degradation and accumulation, thus indicating one mechanism by which estrogen inhibits the progression of atherosclerosis. The influence of progestins on these processes remains nuclear. The objective of this study was to determine the effects of oral estrogen (conjugated equine estrogens) and progestin (medroxyprogesterone acetate) alone or in combination on arterial LDL metabolism after 12 weeks of atherogenic stimulus. This relatively short period of treatment was chosen to determine effects on arterial LDL metabolism before substantial subendothelial macrophage accumulation. In contrast to previous studies (16 to 18 weeks of treatment), when macrophages were present in the intima, neither estrogen nor progestin (nor their combination) had any effect on any index of arterial LDL metabolism. These results suggest that estrogen may preferentially reduce LDL metabolism in macrophages with little effect on cells of the normal artery. In contrast to arterial LDL metabolism, hepatic LDL uptake was significantly increased in animals treated with estrogen or estrogen plus progestin. Despite the increased LDL uptake by the liver, hepatic lipid content was significantly decreased by approximately 50% in both estrogen and estrogen-plus-progestin treatment compared with control and progestin-treated animals. The decrease in hepatic cholesterol content in hypothesized to be due to increased biliary secretion of cholesterol.

Analysis of protein structure-function in vivo. Adenovirus-mediated transfer of lipase lid mutants in hepatic lipase-deficient mice

Hepatic lipase (HL) and lipoprotein lipase (LPL) are key enzymes involved in the hydrolysis of triglycerides and phospholipids present in circulating plasma lipoproteins. Despite their similarities, the role that each of these two lipases play in the metabolism of triglyceride-rich lipoproteins and high density lipoproteins is distinct. In order to identify structural domains that may confer the different substrate specificities between HL and LPL, we have utilized a novel approach for performing structure-function analysis of a protein, in vivo, by using recombinant adenovirus vectors to express native and mutant enzymes in an animal model for a human genetic deficiency. HL-deficient mice (n = 19) characterized by increased plasma cholesterol and phospholipid concentrations were injected with adenovirus expressing luciferase (rLucif-AdV), native hepatic (rHL-AdV), and lipoprotein lipase (rLPL-AdV) or lipase mutants in which the lid covering the catalytic site of either enzyme was exchanged (rHL+LPL lid-AdV and rLPL+HL lid-AdV). Mice injected with rLucif-AdV had no changes in post-heparin HL and LPL activities (217 +/- 29 and 7 +/- 2 nmol/min/ml, respectively) as well as plasma lipids. Despite expression of similar levels of post-heparin plasma lipase activity on day 5 post-adenovirus infusion (9806 +/- 915 and 9677 +/- 2033 nmol/min/ml, respectively) mice injected with rHL-AdV or rHL+LPL lid-AdV demonstrated marked differences in the reduction of plasma phospholipids (70% and 32%, respectively, p < 0.005). Similarly, despite post-heparin plasma lipolytic activities of 4495 +/- 534 and 4844 +/- 1336 nmol/min/ml, injection of rLPL-AdV or rLPL+HL lid-AdV resulted in phospholipid reductions of 31% and 81% (p < 0.005). Exchange of the lipase lid did not significantly alter plasma triglyceride concentrations. Thus, preferential in vivo hydrolysis of phospholipids was demonstrated in animals expressing lipases containing the HL lid but not the LPL lid. These studies identify the lipase lid as a major structural motif responsible for conferring the different in vivo phospholipase activities between HL and LPL, a function which may modulate the distinct physiological roles of these two similar lipolytic enzymes in lipoprotein metabolism. The use of recombinant adenovirus to express mutant proteins in animal models for human genetic deficiencies represents a powerful, new approach for performing structure-function analysis of proteins in vivo.

Hepatic lipase gene therapy in hepatic lipase-deficient mice. Adenovirus-mediated replacement of a lipolytic enzyme to the vascular endothelium

Hepatic lipase (HL) is an endothelial-bound lipolytic enzyme which functions as a phospholipase as well as a triacylglycerol hydrolase and is necessary for the metabolism of IDL and HDL. To evaluate the feasibility of replacing an enzyme whose in vivo physiologic function depends on its localization on the vascular endothelium, we have infused recombinant replication-deficient adenovirus vectors expressing either human HL (HL-rAdV; n = 7) or luciferase cDNA (Lucif-rAdV; n = 4) into HL-deficient mice with pretreatment plasma cholesterol, phospholipid, and HDL cholesterol values of 176 +/- 9, 314 +/- 12, and 129 +/- 9, respectively. After infusion of HL-rAdV, HL could be detected in the postheparin plasma of HL-deficient mice by immunoblotting and postheparin plasma HL activities were 25,700 +/- 4,810 and 1,510 +/- 688 nmol/min/ml on days 5 and 15, respectively. Unlike the mouse HL, 97% of the newly synthesized human HL was heparin releasable, indicating that the human enzyme was virtually totally bound to the mouse vascular endothelium. Infusion of HL-rAdV in HL-deficient mice was associated with a 50-80% decrease in total cholesterol, triglyceride, phospholipids, cholesteryl ester, and HDL cholesterol (P < 0.001) as well as normalization of the plasma fast protein liquid chromatography lipoprotein profile by day 8. These studies demonstrate successful expression and delivery of a lipolytic enzyme to the vascular endothelium for ultimate correction of the HL gene defect in HL-deficient mice and indicate that recombinant adenovirus vectors may be useful in the replacement of endothelial-bound lipolytic enzymes in human lipolytic deficiency states.

Apolipoprotein E deficiency in mice: gene replacement and prevention of atherosclerosis using adenovirus vectors

Apolipoprotein E (apoE)-deficient mice develop marked hyperlipidemia as well as atherosclerosis and thus are an excellent animal model for evaluating the potential for gene therapy in human genetic dyslipoproteinemias. Recombinant adenovirus containing either human apoE (rAdv.apoE) or the reporter gene luciferase (rAdv.luc) were generated and infused intravenously in apoE-deficient mice with preinfusion plasma total cholesterol of 644 +/- 149 mg/dl an cholesterol rich VLDL/IDL. After a single infusion of rAdv.apoE, plasma concentrations of human apoE ranging from 1.5 to 650 mg/dl were achieved. Adenovirus-mediated apoE replacement resulted in normalization of the lipid and lipoprotein profile with markedly decreased total cholesterol (103 +/- 18mg/dl), VLDL, IDL, and LDL, as well as increased HDL. Measurement of aortic atherosclerosis 1 mo after adenoviral infusion demonstrated a marked reduction in the mean lesion area of mice infused with rAdv.apoE (58 +/- 8 x 10(3) microns2) when compared with control mice infused with rAdv.luc (161 +/- 10 x 10(3) microns2; P < 0.0001). Thus, apoE expression for 4 wk was sufficient to markedly reduce atherosclerosis, demonstrating the feasibility of gene therapy for correction of genetic hyperlipidemias resulting in atherosclerosis. The combined use of adenovirus vectors and the apoE-deficient mouse represents a new in vivo approach that will permit rapid screening of candidate genes for the prevention of atherosclerosis.

Lipases and lecithin: cholesterol acyltransferase in the control of lipoprotein metabolism

Lipoprotein lipase, hepatic lipase, and lecithin: cholesterol acyltransferase have coordinated enzymatic roles in lipoprotein metabolism. New evidence suggests that the lipases are multifunctional proteins that are able to mediate lipoprotein binding and uptake. The importance of all three enzymes in the control of lipoprotein metabolism can be explored in the future by using the newly generated transgenic animals.

A dose-response relationship between sex hormone-induced change in hepatic triglyceride lipase and high-density lipoprotein cholesterol in postmenopausal women

In previous studies, we have demonstrated a temporal relationship between the postheparin hepatic triglyceride lipase (HTGL) response to sex steroids and the high-density lipoprotein (HDL) cholesterol response. To determine if this relationship is dose-dependent, we compared the effect of three graduated doses of orally administered estradiol and norgestrel in two groups of six postmenopausal women. With estradiol administration, postheparin HTGL activity decreased from 91 +/- 46 to 50 +/- 29 nmol/min/mL, baseline to high dose (P less than .05); HDL cholesterol increased from 54 +/- 6 to 64 +/- 10 mg/dL (P less than .05); HDL2 cholesterol increased from 16 +/- 4 to 23 +/- 7 mg/dL (P less than .05); and HDL3 cholesterol concentration did not change. With norgestrel administration, HTGL activity increased from 79 +/- 19 to 109 +/- 24 nmol/min/mL (P less than .05); HDL cholesterol decreased from 64 +/- 17 to 43 +/- 7 mg/dL (P less than .05); HDL2 cholesterol decreased from 21 +/- 17 to 6 +/- 5 mg/dL (P less than .05); and HDL3 cholesterol concentration decreased from 43 +/- 8 to 38 +/- 8 mg/dL (P less than .05). The HTGL activity response was inversely correlated with estrogen dose (rs = -.733, P = .0001) and directly correlated with progestin dose (rs = .895, P = .0001). The HDL cholesterol response was directly correlated with estrogen dose (HDL: rs = .741, P = .001; HDL2: rs = .586, P = 0.003) and inversely correlated with progestin dose (HDL: rs = -.933, P = .0001; HDL2: rs = -.866, P = .0001; HDL3: rs = -.576, P = .003).(ABSTRACT TRUNCATED AT 250 WORDS)

Hirsutism: metabolic effects of two commonly used oral contraceptives and spironolactone

Fifty-one hirsute women were randomly treated for nine months with ethinyl estradiol 35 ug plus norethindrone 0.4 mg or 30 ug ethinyl estradiol plus 1.5 mg norethindrone acetate if they needed contraception or spironolactone 200 mg daily if they did not. Metabolic evaluations in response to therapy demonstrated triglyceride elevations with the two oral contraceptives but not with spironolactone. While systolic blood pressure was lower with spironolactone, fasting insulin levels were higher as opposed to either low-dose oral contraceptive preparation. Ethinyl estradiol 30 ug plus 1.5 mg norethindrone acetate lowered 3-alpha-diol glucuronide levels, yet ethinyl estradiol 35 ug plus norethindrone 0.4 mg and spironolactone were more effective in lowering Ferriman-Gallwey Scores. Treatment strategies for hirsute women need to consider metabolic consequences as well as efficacy.

Evidence of heterogeneous mechanisms in lipoprotein lipid alterations in hyperandrogenic women

Fifty-one hyperandrogenic women had their lipoprotein lipid profiles determined. Free and albumin-bound testosterone was associated with triglycerides and with high-density lipoprotein cholesterol independent of fasting insulin levels, percent ideal body weight, and waist/hip ratio. To gain insight into mechanisms of these lipid alterations, the women were subgrouped according to apparent source of androgen excess. Whereas all groups had low levels of high-density lipoprotein-2 cholesterol and high triglyceride concentrations, only in those with high luteinizing hormone-to-follicle-stimulating hormone ratios was free and albumin-bound testosterone associated with triglycerides and high-density lipoprotein cholesterol independent of fasting insulin levels. Relationships between percent ideal body weight and waist/hip ratios, free and albumin-bound testosterone, sex hormone binding globulin, fasting insulin and 2-hour insulin levels and blood pressure are not significant in all subgroups, suggesting differing endocrinological influences and differing mechanisms for lipoprotein lipid alterations.

Differential effects of oral estrone versus 17 beta-estradiol on lipoproteins in postmenopausal women

Toward the definition of optimal postmenopausal estrogen replacement we compared the effects of three graduated doses of two oral estrogens, estrone sulfate and 17 beta-estradiol, on the lipid profiles of two groups of six postmenopausal women. Because of metabolic interconversions equivalent serum concentrations of estrone and estradiol were produced with these regimens. However, differential effects were noted in lipoproteins. 17 beta-Estradiol caused an increase in total plasma cholesterol (from 5.71 +/- 0.36 to 5.99 +/- 0.57 mmol/L, baseline to high dose; P less than 0.02), high density lipoprotein (HDL) cholesterol (from 1.45 +/- 0.15 to 1.78 +/- 0.36 mmol/L; P less than 0.02), HDL2 cholesterol concentration (from 0.41 +/- 0.08 to 0.62 +/- 0.26 mmol/L; P less than 0.01), and triglyceride concentration (from 1.09 +/- 0.29 to 1.24 +/- 0.30 mmol/L; P less than 0.01) without affecting low density lipoprotein (LDL) cholesterol concentration. By contrast, estrone sulfate caused a decrease in total plasma cholesterol (from 6.51 +/- 0.85 to 5.87 +/- 0.41 mmol/L; P less than 0.05) and LDL cholesterol concentration (from 4.34 +/- 0.57 to 3.67 +/- 0.44 mmol/L; P less than 0.01) and an increase in HDL cholesterol (from 1.37 +/- 0.20 to 1.50 +/- 0.26 mmol/L; P less than 0.05) and HDL2 cholesterol concentration (from 0.34 +/- 0.18 to 0.49 +/- 0.18 mmol/L; P less than 0.01), but no change in total triglyceride concentration. We deduce that the differential effect of orally administered estrogens on lipoprotein metabolism in postmenopausal women may be attributed to a first pass effect on hepatic metabolism.

A rapid and sensitive micro-assay for the enzymatic determination of plasma and lipoprotein cholesterol

A rapid and inexpensive micro-assay for determining cholesterol in plasma and isolated lipoprotein fractions has been established which utilizes a commercially available enzymatic reagent with semi-automated instruments and microtiter plates. The assay is sensitive, precise, and easy to perform. The color development is linear from 0.4 to 20 micrograms cholesterol/well, with sample volumes of 2 to 100 microliters. Inter- and intra-assay variability yielded coefficients of variation (CV) of 2.75% (n = 51) and 1.09% (n = 32), respectively. The concentrations of total plasma and lipoprotein cholesterol (d greater than 1.006 g/ml) obtained with this method were compared with those analyzed in a lipid laboratory standardized to the Centers for Disease Control. The correlation coefficients between the two methods were 0.976 and 0.964, respectively. For total high density lipoprotein (HDL) and the HDL3 subfraction, inter-assay variability was 4.12% and 6.33% (n = 27), respectively; the intra-assay variability was 2.79% and 4.19% (n = 12).

Lipoprotein lipids in women with androgen excess: independent associations with increased insulin and androgen

Concentrations of triglycerides are increased and concentrations of high-density lipoprotein (HDL) cholesterol are low in women with hyperandrogenism. These alterations could be related to excessive androgen or estrogen, to hyperinsulinism, or to a combination of these abnormalities. We examined their independent influences on lipids in 21 women with hyperandrogenism, subgrouped according to apparent source of androgen excess. Results for lipid, androgen, and insulin did not differ among subgroups, so these data were pooled. Free plus albumin-bound testosterone (uT) was correlated with triglycerides (r = 0.69, P less than 0.01) and HDL cholesterol (r = -0.56, P less than 0.01). Both triglycerides (r = 0.66, P less than 0.01) and HDL cholesterol (r = -0.48, P less than 0.05) were also correlated with insulin measured during fasting. Partial correlation revealed that, after adjusting for insulin, lipids were associated with uT. This suggests that androgen excess is independently related to lipid excess. Insulin also was correlated with lipids when adjusted for uT. Free plus albumin-bound estradiol was not associated with any of the lipids. We conclude that altered lipids in women with hyperandrogenism result from the independent effects of androgen and insulin.

Lipoprotein lipids in women with androgen excess: independent associations with increased insulin and androgen

Concentrations of triglycerides are increased and concentrations of high-density lipoprotein (HDL) cholesterol are low in women with hyperandrogenism. These alterations could be related to excessive androgen or estrogen, to hyperinsulinism, or to a combination of these abnormalities. We examined their independent influences on lipids in 21 women with hyperandrogenism, subgrouped according to apparent source of androgen excess. Results for lipid, androgen, and insulin did not differ among subgroups, so these data were pooled. Free plus albumin-bound testosterone (uT) was correlated with triglycerides (r = 0.69, P less than 0.01) and HDL cholesterol (r = -0.56, P less than 0.01). Both triglycerides (r = 0.66, P less than 0.01) and HDL cholesterol (r = -0.48, P less than 0.05) were also correlated with insulin measured during fasting. Partial correlation revealed that, after adjusting for insulin, lipids were associated with uT. This suggests that androgen excess is independently related to lipid excess. Insulin also was correlated with lipids when adjusted for uT. Free plus albumin-bound estradiol was not associated with any of the lipids. We conclude that altered lipids in women with hyperandrogenism result from the independent effects of androgen and insulin.

Lipoprotein, apolipoprotein, and lipolytic enzyme changes following estrogen administration in postmenopausal women

To test whether estrogen can modulate the cholesterolemic response to an Occidental diet, six healthy postmenopausal women were studied for 84 days while ingesting a solid food diet of constant composition high in cholesterol content (995 mg/d). In the middle of the study, estrogen (17 alpha-ethinyl estradiol, 1 microgram/kg per day) was administered orally. Ingestion of the diet for the initial 28 days did not alter lipoprotein lipid or apolipoprotein (apo) levels. However, with just 4 days of estrogen use there were significant decreases in apoE (-36%), low density lipoprotein cholesterol (-26%), and postheparin plasma hepatic triglyceride lipase activity (HTGL) (-61%), and an increase in high density lipoprotein (HDL) triglyceride (72%). These changes persisted throughout the estrogen use. The percent change in HTGL with 4 days of estrogen correlated inversely with the percent change in HDL triglyceride (rs = -0.94). After 28 days of estrogen there were also significant increases in HDL cholesterol (21%), HDL2 cholesterol (42%), apoA-I (37%), and apoA-II (9%), and a decrease in apoB (-11%). The level of apoE at this juncture correlated inversely with the level of HDL cholesterol (rs = -0.90), and the levels of HTGL and apoA-I correlated with HDL2 cholesterol (rs = -0.89 and rs = 0.89, respectively). Thus, HTGL may play a role in both the early estrogen-related changes in HDL triglyceride and apoE and the late estrogen-related changes in HDL cholesterol, apoA-I, and apoA-II.

Improved glycemic control lowers plasma apoprotein E and triglyceride levels following ingestion of a fat load in insulin-dependent diabetic subjects

To assess the effect of glycemic control on triglyceride (TG) and apoprotein E (apo E) metabolism, plasma levels of TG and apo E were studied in nine nonobese subjects with insulin-dependent diabetes mellitus (IDDM) following acute ingestion of polyunsaturated fat. Each subject was studied twice: before and after ten days of continuous subcutaneous insulin infusion (CSII). Each subject ingested identical meals on both study days. Plasma glucose was determined in all patients before and two hours after each meal and at 3 AM, and a mean value was calculated for each patient. CSII reduced mean plasma glucose from 205 to 113 mg/dL (P less than .005, paired t test); there was no change in the total daily insulin dose. Plasma TG and apo E levels were measured before and 3.5, 5, and 7 hours after a breakfast which contained 50 g of fish oil (five subjects) or vegetable oil (four subjects). A repeated-measures ANOVA was performed to assess the effects of the following three factors on plasma TG and apoE levels: type of oil ingested (Oil, factor A), glycemic control (Glycemic control, factor B), and the response to fat ingestion over time (Times, factor C). Plasma levels of both apo E and TG increased significantly after fat ingestion (F test, ANOVA, P less than .005 and P less than .001, respectively). Glycemic control significantly reduced the rise in both apo E and TG levels (P less than .005 and P less than .05, respectively). The effect of the type of oil and the interactions tested (AB, AC, BC, ABC) were not statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)

The dyslipoproteinemia of anabolic steroid therapy: increase in hepatic triglyceride lipase precedes the decrease in high density lipoprotein2 cholesterol

Administration of the androgenic anabolic steroid, stanozolol, is associated with decreased high density lipoprotein (HDL) cholesterol (primarily due to decreased HDL2 cholesterol) and increased levels of postheparin plasma hepatic triglyceride lipase (HTGL) activity. Since HTGL appears to play a role in HDL metabolism, we examined the temporal relationship between these changes. HDL cholesterol remained stable during the first two days of stanozolol administration, but decreased 14% (P less than .01) by the third day and 39% (P less than .01) by the seventh day of stanozolol. HDL2 cholesterol paralleled the total HDL cholesterol level and remained stable for the first two days, but decreased 22% (P less than .01) after three days and 71% (P less than .01) after seven days of stanozolol. In contrast, HTGL increased 62% (P less than .001) during the first day, 161% (P less than .001) with two days, 230% (P less than .001) with three days of stanozolol administration, and remained elevated thereafter. Thus, during stanozolol administration HTGL increased dramatically and clearly before any change in HDL or HDL2 cholesterol.

Dyslipoproteinemia in systemic lupus erythematosus. Effect of corticosteroids

The increased incidence of atherosclerotic coronary artery disease in patients with systemic lupus erythematosus (SLE) may be due to a dyslipoproteinemia caused by corticosteroid administration. To determine whether lipoprotein lipid levels are abnormal in SLE and the relation of lipoprotein levels to corticosteroid use, lipid and apolipoprotein levels were measured in 46 female patients with SLE and 30 matched control subjects. The patients with SLE had higher levels of plasma triglyceride (134 versus 73 mg/dl; p less than 0.001), cholesterol (201 versus 168 mg/dl; p less than 0.001), and low-density lipoprotein cholesterol (121 versus 94 mg/dl; p less than 0.001) than control subjects. The levels of high-density lipoprotein cholesterol, high-density lipoprotein subfraction 3 cholesterol, and apolipoprotein Al were similar in the two groups, but high-density lipoprotein subfraction 2 cholesterol was lower in the patients with SLE (10.2 versus 18.2 mg/dl; p less than 0.001). When patients with SLE treated with prednisone (n = 32) were compared to patients with SLE not treated with prednisone (n = 14), the former had higher triglyceride (158 versus 87 mg/dl; p less than 0.001), cholesterol (214 versus 170 mg/dl; p less than 0.001), and low-density lipoprotein cholesterol (130 versus 103 mg/dl; p less than 0.001) levels. The patients with SLE not treated with prednisone had lipid levels similar to those in control subjects except that high-density lipoprotein cholesterol was lower (49.7 versus 59.0 mg/dl; p less than 0.05). The daily prednisone dosage in the treated patients with SLE correlated with levels of cholesterol (r = 0.38, p less than 0.02), high-density lipoprotein cholesterol (r = 0.40, p less than 0.02), and high-density lipoprotein subfraction 3 cholesterol (r = 0.47, p less than 0.01). Thus, female patients with SLE have a dyslipoproteinemia of the type that would place them at an increased risk for coronary artery disease. Corticosteroids, used in the treatment of SLE, seem to play a role in the pathogenesis of the observed lipoprotein abnormalities.

Postheparin plasma triglyceride lipases. Relationships with very low density lipoprotein triglyceride and high density lipoprotein2 cholesterol

Hepatic triglyceride (HTGL) and lipoprotein lipase (LPL) probably have major roles in the removal of triglyceride from triglyceride-rich lipoprotein and in the formation of high density lipoprotein (HDL). However, no population-based study of their activity and relationship to lipoprotein lipid levels has been reported. To determine these relationships, we recalled 33 men and 17 women of a randomly selected sample of the Lipid Research Clinics Pacific Northwest Bell Telephone Company Health Survey. The subjects were 53 +/- 7 years old (mean +/- SD) with total triglyceride levels of 120 +/- 57 mg/dl and total cholesterol levels of 224 +/- 35 mg/dl. Postheparin plasma LPL activity (127 +/- 61 nmol/min/ml) was not significantly correlated with either age, sex, or adiposity. In contrast, HTGL activity was significantly higher in men (235 +/- 84 nmol/min/ml) than women (170 +/- 91 nmol/min/ml, p less than 0.02), and was correlated with age in men and with adiposity in women. In both men and women, HTGL activity was related positively with VLDL triglyceride and inversely with HDL2 cholesterol. When the association between HTGL activity and VLDL triglyceride was examined with values from men and women pooled, the relationship was not weakened after adjustment for the linear effect of sex, adiposity, LPL, or HDL2 cholesterol.

Hepatic triglyceride lipase in diabetic dogs

Circulating triglyceride is cleared by a combination of hepatic triglyceride lipase (H-TGL) and lipoprotein lipase (LPL). Although LPL has been extensively studied in diabetes, the effect of insulinization on H-TGL activity has not been well characterized. To determine whether H-TGL activity is altered in insulin-deficient diabetes, postheparin plasma was obtained from eight beagle dogs: three normal (nondiabetic) control dogs and five pancreatectomized diabetic dogs were studied acutely in poor diabetic control (underinsulinized), and again in short-term good control (well insulinized). Plasma glucose, measured at the start of the studies, was 88 +/- 10 mg/100 mL (mean +/- SD) in the normal control dogs, 434 +/- 31 mL in pancreatectomized dogs in poor diabetic control, and 87 +/- 16 in good diabetic control. Peak (five minutes) postheparin plasma H-TGL activity was increased in dogs in poor diabetic control (212 +/- 43 nmol FFA/min/mL) v the normal control dogs (135 +/- 21 nmol FFA/min/mL, P less than 0.02). When the dogs were in good diabetic control, the peak H-TGL (202 +/- 40 nmol FFA/min/mL) was also significantly increased compared with the level in normal dogs, while the sum of five and 45 minute postheparin H-TGL levels for the dogs in good diabetic control was less than when they were in poor diabetic control (P less than 0.01). Thus, insulin-deficient diabetes in dogs increases H-TGL, and short-term improvement of glycemic control with insulin partially corrects this increase.

Epidemiological correlates of high density lipoprotein subfractions, apolipoproteins A-I, A-II, and D, and lecithin cholesterol acyltransferase. Effects of smoking, alcohol, and adiposity

Recent data suggest that the protection against ischemic heart disease afforded by high density lipoprotein (HDL) cholesterol (C) may be concentrated in the HDL2 subfraction. To examine the behavioral correlates of the HDL subfractions, we recalled 33 men and 17 women of a random sample from the Pacific Northwest Bell Telephone Company Health Survey. Adiposity and very low density lipoprotein (VLDL) triglyceride were negatively correlated with HDL2C. Smoking was not correlated with HDL2C, but was negatively correlated with HDL3C (men, rs = -0.635, p = 0.001; women, rs = -0.534, p = 0.014); this relationship was independent of alcohol consumption, adiposity, and VLDL triglyceride. Alcohol consumption was also more strongly related to HDL3C (men, rs = 0.248, p = 0.082; women, rs = 0.586, p = 0.007). Lecithin cholesterol acyltransferase (LCAT) mass was negatively related with HDL2C, but was positively correlated with HDL3C and apolipoprotein A-II. Smoking was negatively correlated with LCAT mass. Since it is believed that HDL3C is not associated with the risk of ischemic heart disease and since both smoking and alcohol consumption may mainly affect HDL3C, the current study suggests that the increase in risk of ischemic heart disease with smoking and the possible decrease with alcohol consumption may be mediated through mechanisms other than their effects on HDLC.

Chylomicron and very low-density lipoprotein apolipoprotein B metabolism: mechanism of the response to stanozolol in a patient with severe hypertriglyceridemia

Studies of simultaneous autologous 131I-chylomicron (Sf greater than 400) and 125I-very low density lipoprotein (VLDL) (Sf 20 to 400) apolipoprotein B (apo B) were performed both before (triglyceride level c 1500 mg/dL) and during treatment with stanozolol, a 17 alpha-methyl anabolic androgenic steroid (triglyceride level c 750 mg/dL) in a 74-year-old woman with a past history of recurrent chylomicronemic pancreatitis. Both before and during stanozolol treatment chylomicron apo B disappeared rapidly and directly, little appearing in VLDL and virtually none in intermediate (IDL) or low density lipoproteins (LDL). Multicompartmental analysis indicated that the great majority of chylomicron apo B was removed via an extremely rapid compartment (estimated fractional catabolic rate [FCR], 5.0/h), accounting for 66% before and 88% during stanozolol treatment. The remaining 131I-apo B decayed biphasically, with total Sf greater than 400 residence times of 8.6 hours before and 3.7 hours during stanozolol treatment. Hence, despite a moderately depressed adipose tissue lipoprotein lipase activity, the subject's hypertriglyceridemia did not appear to proceed solely from retarded chylomicron removal, nor was the dramatic decrease in triglyceride in response to stanozolol a function only of the acceleration of such removal. VLDL apo B kinetics were analyzed by a multicompartmental model featuring a rapid, stepwise delipidation chain which proceeds either rapidly to IDL and LDL or to a slowly turning over compartment within VLDL. While VLDL. apo B synthesis remained essentially constant, the major effect of stanozolol was a substantial reduction in the fraction of VLDL apo B diverted to this slowly turning over compartment, which decreased from 5.0% before to 1.2% during treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduction of lecithin-cholesterol acyltransferase, apolipoprotein D and the Lp(a) lipoprotein with the anabolic steroid stanozolol

The effects of the anabolic steroid stanozolol (17-methyl-2H-5 alpha-androst-2-eno-(3,2-c)pyrazol-17 beta-ol) on lecithin-cholesterol acyltransferase, apolipoproteins B and D and the Lp(a) lipoprotein were determined in a prospective study of ten normolipidemic women with postmenopausal osteoporosis. Lecithin-cholesterol acyltransferase was reduced approx. 30% by 6 weeks of treatment with stanozolol (off treatment 5.1 +/- 1.2, on treatment 3.4 +/- 0.8 muml; P less than 0.02). The Lp(a) lipoprotein was reduced 65 +/- 23% by the steroid treatment (off treatment 5.5 +/- 5.5, on treatment 1.4 +/- 0.7 mg/dl; P less than 0.02). Apolipoprotein D was reduced 23 +/- 9% by the treatment (off treatment 5.9 +/- 0.9, on treatment 4.5 +/- 0.7 mg/dl; P less than 0.02). In contrast, apolipoprotein B increased slightly but insignificantly on steroid therapy (off treatment 90 +/- 21, on treatment 112 +/- 24 mg/dl). By 5 weeks after the drug was discontinued, all four of these proteins were near pretreatment levels. These significant changes in lipoprotein metabolism, combined with our previous report of reductions of HDL and particularly HDL2, suggest the need for caution in the long-term use of anabolic steroids.

Preliminary report: kinetic studies on the modulation of high-density lipoprotein, apolipoprotein, and subfraction metabolism by sex steroids in a postmenopausal woman

To investigate the effects of estrogens and androgens on the metabolism of high density lipoproteins (HDL) and low density lipoproteins (LDL), a normolipidemic postmenopausal woman was studied under the following conditions: (1) during supplementation with ethinyl estradiol (0.06 mg/d); (2) without sex steroid therapy; (3) during treatment with stanozolol, an androgenic, anabolic steroid (6 mg/d). During these manipulations HDL and LDL cholesterol levels fluctuated widely but reciprocally: during estrogen supplementation HDL increased while LDL decreased; during stanozolol HDL-C decreased while LDL-C increased. Simultaneous changes in post-heparin plasma hepatic triglyceride lipase activity paralleled those of LDL (and opposed those of HDL), decreasing with estrogen and increasing with stanozolol. During all three phases, autologous 125I-HDL turnover studies disclosed similarities between HDL2 and apolipoprotein A-I metabolism and between HDL3 and apolipoprotein A-II metabolism. In the untreated state the residence times of HDL2 and apo A-I were only half those of HDL3 and apo A-II. During estrogen treatment HDL2 and apo A-I, residence times were selectively prolonged, coming to resemble those of HDL3 and apo A-II, which remained unchanged. By contrast, during stanozolol treatment HDL3 and apo A-II residence times were selectively reduced, coming to resemble those of HDL2 and apo A-I, which remained unchanged. Apo A-I levels increased on estrogen and decreased on stanozolol, while apo A-II remained stable. Hence, estrogen increased HDL primarily by retarding the catabolism of the HDL2 subfraction rich in apo A-I, whereas stanozolol decreased HDL by accelerating the catabolism of HDL3, relatively rich in apo A-II.(ABSTRACT TRUNCATED AT 250 WORDS)

Down-regulation of the low-density lipoprotein receptor by dietary cholesterol

To determine the effect of dietary cholesterol on the low-density lipoprotein (LDL) receptor of circulating mononuclear cells, nine adults (six men, three women) consumed a natural diet consisting of 45% of the calories as carbohydrate, 40% as fat, and 15% as protein, polyunsaturated/saturated fatty acid ratio 0.80 to 0.84, and either 137 +/- 25 mg cholesterol per day (low cholesterol phase) or 1034 +/- 25 mg cholesterol per day (high cholesterol phase). The study lasted 2 months with 1 month in each phase and used a cross-over design. The levels of plasma triglyceride, plasma cholesterol, very low-density and high-density lipoprotein cholesterol, and apolipoproteins B, A-I, and A-II were similar in the two diet phases. The high cholesterol diet was associated with an 11 +/- 9% increase (p less than 0.02) in LDL cholesterol level and a 41 +/- 14% decrease in LDL receptor activity (p less than 0.05, n = 6). The percentage decrease in LDL receptor activity correlated with the percentage increase in LDL cholesterol (r = -0.796, p = 0.06, n = 6). Thus, high levels of dietary cholesterol can down-regulate the LDL receptor in humans.

Plasma and lipoprotein lipid responses to four hypolipid drugs

The responses of 14 hyperlipidemic subjects to 4 hypolipidemic agents were compared by measuring cholesterol and triglyceride in whole plasma, very low density lipoproteins (VLDL), low density lipoproteins (LDL), and high density lipoproteins (HDL) monthly for 2 months before and 3 months during treatment with each of 4 drugs: clofibrate, 2 g/d; colestipol, 20 g/d; para-aminosalicylic acid-ascorbate (PAS-C), 6-8 g/d; and oxandrolone, 7.5 mg/d. Lipid responses proved to be stable by the first monthly evaluation both off and on each drug. Mean adherence was high and similar for all agents (81-92% of the prescribed dose). Clofibrate was associated with significant decreases in mean plasma cholesterol (-16%, p less than .01), plasma triglyceride (-51%, p less than .005), VLDL-cholesterol (-61%, p less than .005) and VLDL-triglyceride (-61%, P less than .005), while HDL cholesterol increased (+20%, p less than .01), and the LDL-cholesterol/HDL ratio declined (-24%, p less than .05). Colestipol was associated with decreases in mean plasma cholesterol (-15%, p less than .01) and LDL-cholesterol (-22%, p less than .05), while VLDL-triglyceride increased (+41%, p less than .05), and the LDL-cholesterol/HDL-cholesterol radio declined (-25%, p less than .05). PAS-C was associated with decreases in VLDL-cholesterol (-30%, p less than .05), and VLDL-triglyceride (-29%, p less than .05), while the LDL-cholesterol/HDL-cholesterol ratio remained unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of diet and age on lipoprotein lipase and hepatic triglyceride lipase activities in the rat

Plasma clearance of triglyceride-rich lipoproteins appears decreased in aged humans and rats and may be due to lowered activities of the lipases responsible for lipid degradation. This study was designed to examine differential effects of age and diet on lipoprotein lipase (LPL) activity of adipose and heart tissue and hepatic triglyceride lipase (HTGL) activity. LPL and HTGL activities were examined in 3- and 13-month-old Sprague-Dawley rats after they had consumed either a high-carbohydrate or a high-fat diet for 14 days. The data were analyzed for age and diet differences by two-way analysis of variance. Although animals in the two age groups consumed diets of equal caloric content, the older rats gained less weight. Rats on the high-carbohydrate diet consumed less calories and gained less weight than the fat fed rats in both age groups. Neither heart nor adipose tissue LPL activity differed when examined for age or diet. HTGL activity levels, while not affected by age, were higher in the carbohydrate fed rats (P = 0.014). Regardless of age group, fasting plasma cholesterol levels were significantly higher in the carbohydrate-fed rats than fat-fed rats (P = 0.002). Thus, the diet effect was much stronger than the age effect for HTGL and plasma cholesterol levels.

The effect of training and diet on lipoprotein cholesterol, tissue lipoprotein lipase and hepatic triglyceride lipase in rats

Treadmill training for 1 hr/day for 10 wk did not significantly affect chylomicron, very low density, low density, or high density lipoprotein cholesterol in rats fed either a high carbohydrate (glucose) or high fat (coconut oil) diet. Lipoprotein lipase activity of heart, adipose tissue, and skeletal muscle fibers was also unaffected by training. Carbohydrate feeding, however, when compared to fat feeding significantly lowered all lipoprotein cholesterol values as well as heart and fast-oxidative-glycolytic muscle fiber lipase activity and, conversely, significantly elevated hepatic triglyceride lipase activity. Thus, in the rat, an alteration in the serum lipid profile did not occur as a result of training, but dietary differences did independently influence serum lipid levels and tissue enzyme activity. It is suggested that human studies need to control for the possible independent influence of dietary differences when investigating the effects of training on lipoprotein metabolism.

Studies on the metabolic mechanism of reduced high density lipoproteins during anabolic steroid therapy

To explore the mechanism whereby stanozolol, a 17 alpha-methyl androgenic anabolic steroid, depresses high density lipoproteins (HDL), 6 subjects, aged 46-71 yr (4 postmenopausal women and 2 men), underwent paired studies of 125I-HDL turnover (including HDL2 and HDL3 and Apo A-I and A-II) and postheparin plasma (PHP) lipolytic activity (hepatic triglyceride lipase, HTGL, and lipoprotein lipase LPL) before and during treatment with stanozolol, 6 mg/day. While total cholesterol and triglyceride levels did not change during stanozolol, HDL-cholesterol decreased from 59 +/- 18 mg/dl (x +/- SD) to 29 +/- 7 mg/dl (p less than 0.01) and low density lipoprotein (LDL)-cholesterol increased from 160 +/- 36 mg/dl to 181 +/- 42 mg/dl (p less than 0.02). PHP-HTGL increased from 111 +/- 47 nmole/min/ml to 369 +/- 202 nmole/min/ml (p less than 0.04), while PHP-LPL did not change. At baseline the residence time of HDL2 (4.00 +/- 1.04 day) was shorter than that of HDL3 (6.79 +/- 1.00 day) (p less than 0.001). Residence times of both declined on stanozolol, to 3.25 +/- 0.83 day and 4.00 +/- 0.29 day, respectively (0.1 less than p less than 0.2); however, only the reduction in residence time of HDL3 was statistically significant (p less than 0.001). At baseline the residence time of apo A-I (4.93 +/- 1.32 day) was shorter than that of A-II (6.85 +/- 1.98 day) (p less than 0.025); on stanozolol these declined to 3.19 +/- 0.41 (p less than 0.02) and 5.10 +/- 1.13 (p = 0.07), respectively, still significantly different from each other (p less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Reduction in high density lipoproteins by anabolic steroid (stanozolol) therapy for postmenopausal osteoporosis

The effects of stanozolol, 17-methyl-2H-5 alpha-androst-2-eno [3,2-c] pyrazol-17 beta-ol, on lipoprotein levels were assessed in a short-term (6 wk) prospective study of 10 normolipidemic, postmenopausal, osteoporotic women. While total cholesterol and triglyceride levels remained constant, equal and offsetting responses were seen in low density lipoprotein (LDL) cholesterol (+30.9 +/- 28.1 mg/dl [mean +/- S.D.], p less than 0.01, a 21% increase) and high density lipoprotein (HDL) cholesterol (-32.5 +/- 11.9 mg/dl [mean +/- S.D.], p less than 0.001, a 53% decline). Hence the LDL/HDL ratio increased dramatically, from 2.5 +/- 0.7 to 6.8 +/- 2.5. Within HDL, stanozolol was associated with a greater decline in HDL2 (from 26.0 +/- 7.4 mg/dl to 3.8 +/- 1.9 mg/dl, p less than 0.001, an 85% decrease) than HDL3 (which diminished from 35.7 +/- 3.2 to 24.1 +/- 5.8 mg/dl. p less than 0.001, a 35% decrease). The major HLD apolipoproteins also declined (A-I by a mean of 41% and A-II by 24%, both p less than 0.001). Postheparin hepatic triglyceride lipase increased (off treatment 74 +/- 42 nmole free fatty acid min-1 mole-1, on treatment 242 +/- 110, n = 6, p = 0.06). All changes were reversed by 5 wk following termination of the drug. These lipoprotein changes suggest caution in the long term prescription of stanozolol, particularly in those without overriding clinical indications for its use.

Short-term egg yolk feeding in humans. Increase in apolipoprotein B and low density lipoprotein cholesterol

In animal studies, hypercholesterolemia induced by cholesterol feeding results in the plasma cholesterol being transported by lipoproteins of lower densities. Little information is available for humans. To determine the specific lipoprotein responses to dietary cholesterol challenge in humans, four volunteer subjects ingested a liquid formula diet containing 5000 mg of egg yolk cholesterol per day for 30 days and the changes in their lipoprotein fractions were examined. The high dietary cholesterol (above the range of normal diet) was associated with marked increases in apolipoprotein B and low density lipoprotein (LDL) cholesterol levels. An elevated cholesterol : triglyceride ratio in the LDL fraction indicated that the diet altered both LDL level and composition. High density lipoprotein cholesterol and apolipoprotein AI increased slightly. Very low and intermediate density lipoprotein cholesterol and apolipoprotein E levels did not increase during the diet. Thus, high dietary cholesterol was associated with major changes in LDL level and composition, but only minor changes in the other lipoprotein fractions and suggested only minor accumulation of remnant particles.