The Natural Course of Defibrination Syndrome Caused by Echis Colorata Venom in Man

The natural course of defibrination syndrome caused by Echis colorata venom (ECV) in five patients is reported. All patients developed afibrinogenemia within six hours after the bite. Concomitantly a depression in factor V was recorded. Factor VIII and thrombocyte count in blood were normal in most patients. In the light of the known effects of ECV on blood coagulation in vivo and in vitro it is concluded that the afibrinogenemia is due to intravascular clotting.

Four patients had transient renal damage, manifested by oliguria, azotemia, albuminuria and cylindruria, ascribed to microthrombi in the renal glomeruli.

After the bite, the natural course was benign, no major bleeding was observed, and all signs of coagulopathy reverted to normal within 7 days. Therefore we recommend no specific treatment for this condition. In the case of heavily bleeding patients, administration of antiserum against ECV and/or heparin should be considered.

Dietary enrichment with alpha-linolenic acid during pregnancy attenuates insulin resistance in adult offspring in mice

OBJECTIVE

Our objective was to test the contribution of dietary enrichment in essential or saturated fatty acids, in normocaloric diets, on the lipid accumulation and insulin resistance in the adult offspring in a C57Bl6/J mice model.

METHODS

Pregnant mothers were fed normocaloric diets containing 6% fat enriched in essential fatty acids (EFA): alpha-linolenic (ALA-18:3, n-3), linoleic (LA-18:2, n-6), or saturated fatty acids (SFA). After a washing-out period with regular diet, the offspring received a high-fat diet before euthanization.

RESULTS

Adult mice fed maternal ALA showed lower body weight gain and lower liver fat accumulation, lower HOMA index and lower stearoyl-CoA desaturase (SCD1) activity than those fed maternal SFA.

CONCLUSION

The results observed using this novel model suggest that ALA in maternal diet may have the potential to inhibit insulin resistance in adult offspring.

Weight gain and insulin resistance during nicotine replacement therapy

BACKGROUND

Although the cessation of smoking reduces the increased risk for ischemic heart disease, it is associated with marked weight gain and presumably insulin resistance, both of which heighten the risk of coronary heart disease.

HYPOTHESIS

We investigated the isolated effect of nicotine on body weight and insulin resistance during smoking cessation.

METHODS

Eleven healthy, middle-aged heavy smokers were studied. Insulin sensitivity was assessed by an insulin-enhanced, frequently sampled intravenous glucose tolerance test with minimal model analysis. The subjects were studied at baseline (last day of smoking) (phase 1), at the end of the 6-week nicotine replacement program (phase 2), and after 8 weeks without smoking or nicotine replacement (phase 3).

RESULTS

The subjects started to gain weight during nicotine replacement (phase 2) (0.3 +/- 0.2 kg/week, mean +/- standard deviation) and continued to do so at a steady rate after nicotine replacement was stopped (0.2 +/- 0.2 kg/week) (p = 0.3). Insulin sensitivity decreased by 14 +/- 2.6% during nicotine replacement but increased by 16 +/- 5.1% (compared with phase 2) during phase 3, even though the weight gain continued (p = 0.047; 95% confidence interval: 0.05-5.73).

CONCLUSIONS

Smoking cessation is associated with weight gain and improvement in insulin resistance. Nicotine is the main ingredient in cigarette smoke causing insulin resistance, but the withdrawal of another, unknown ingredient in cigarette smoke is responsible for the weight gain associated with smoking cessation.

Acute myocardial infarction is associated with increased susceptibility of serum lipids to copper-induced peroxidation in vitro

BACKGROUND

Low-density lipoprotein (LDL) oxidation in the arterial intima plays a pivotal role in atherogenesis. Under physiologic conditions, several mechanisms protect LDL against oxidation, including hydrolysis of oxidation products by high-density lipoprotein (HDL)-associated enzymes. Some of these protective mechanisms are less effective under acute phase conditions.

HYPOTHESIS

Conditions of acute phase response, including acute myocardial infarction (MI), may be expected to result in increased susceptibility of serum lipids to oxidation. The present study was undertaken to test this possibility.

METHODS

Using our previously developed spectroscopic method, we have monitored prospectively the kinetics of copper-induced oxidation of serum lipids obtained from 15 men during and after acute MI. This was tested within 6 h from the onset of chest pain, on Days 1, 3, and 7 of infarction and 1 year after recovery.

RESULTS

The lag phase preceding oxidation of serum lipids was much shorter during the first week after MI when compared with values obtained after recovery (52-59 vs. 107 min, respectively, p <0.001). During the first week after MI, we observed no significant correlations between kinetic parameters and serum lipid composition, in contrast both to the correlations previously reported for hyperlipidemic patients and to the similar correlations observed in the present study after recovery.

CONCLUSIONS

Acute MI is associated with an increased susceptibility of serum lipids to oxidation in vitro. This propensity for oxidation may reflect enhanced in vivo formation of free radicals and/or reduced efficiency of defense mechanisms. Both these possibilities may carry detrimental effects on the course, complications, and prognosis of the patients after acute MI.

Kinetics of lipid peroxidation in mixtures of HDL and LDL, mutual effects

In view of the proposed central role of LDL oxidation in atherogenesis and the established role of HDL in reducing the risk of atherosclerosis, several studies were undertaken to investigate the possible effect of HDL on LDL peroxidation. Since these investigations yielded contradictory results, we have conducted systematic kinetic studies on the oxidation in mixtures of HDL and LDL induced by different concentrations of copper, 2, 2'-azo bis (2-amidinopropane) hydrochloride (AAPH) and myeloperoxidase (MPO). These studies revealed that oxidation of LDL induced either by AAPH or MPO is inhibited by HDL under all the studied conditions, whereas copper-induced oxidation of LDL is inhibited by HDL at low copper/lipoprotein ratio but accelerated by HDL at high copper/lipoprotein ratio. The antioxidative effects of HDL are only partially due to HDL-associated enzymes, as indicated by the finding that reconstituted HDL, containing no such enzymes, inhibits peroxidation induced by low copper concentration. Reduction of the binding of copper to LDL by competitive binding to the HDL also contributes to the antioxidative effect of HDL. The acceleration of copper-induced oxidation of LDL by HDL may be attributed to the hydroperoxides formed in the "more oxidizable" HDL, which migrate to the "less oxidizable" LDL and enhance the oxidation of the LDL lipids induced by bound copper. This hypothesis is supported by the results of experiments in which native LDL was added to oxidizing lipoprotein at different time points. When the native LDL was added prior to decomposition of the hydroperoxides in the oxidizing lipoprotein, the lag preceding oxidation of the LDL was much shorter than the lag observed when the native LDL was added at latter stages, after the level of hydroperoxides became reduced due to their copper-catalyzed decomposition. The observed dependence of the interrelationship between the oxidation of HDL and LDL on the oxidative stress should be considered in future investigations regarding the oxidation of lipoprotein mixtures.

Insulin resistance in obesity: body-weight or energy balance?

Weight reduction is recommended for the treatment of subjects with insulin resistance (IR) syndrome; however, the relative importance of the decrease in body fat or the negative energy balance achieved during a hypo-energetic diet in the improvement of this metabolic syndrome is still debated. Therefore, we undertook to study their relative impact on amelioration of the metabolic abnormalities associated with IR in obese subjects. Twelve obese subjects (six males and six females, mean+/-s.d. body mass index 36.1+/-4.7 kg/m(2)) aged 38-57 years were investigated. During the first phase they were fed a hypo-energetic diet for 6 weeks (week 0-6). During the second phase, lasting 4 weeks (week 6-10) they consumed an iso-energetic diet. During the third phase (week 10-16) the subjects were put again on a hypo-energetic diet. Insulin sensitivity (SI) was assessed by an insulin-enhanced, frequently sampled i.v. glucose tolerance test with minimal model analysis. All subjects reduced weight during both hypo-energetic periods: 5.49+/-0.75 and 2.32+/-0.37%, means+/-s.e.m., P<0.005, week 0-6 and 10-16 respectively. One-third of this loss was achieved within the first week of each period. SI increased by 353+/-121 and 147+/-38% (P<0.005), means+/-s.e.m., at the end of both hypo-energetic periods (week 6 vs 0 and 16 vs 10 respectively). Two-thirds of this improvement were observed within the first week of each period (week 1 vs 0 and 11 vs 10 respectively). During the iso-energetic weight-maintaining period (week 10 vs 6), SI decreased by 43.5+/-7.9% (P<0.002). Serum levels of leptin and triglyceride followed a similar pattern, but to a lesser extent. It may be concluded that negative energy balance is more effective when compared with maintaining a stable lower weight in achieving an improvement in the metabolic parameters of the IR syndrome.

Insulin resistance is increased by transdermal estrogen therapy in postmenopausal women with cardiac syndrome X

Estrogen has been reported to have both short- and long-term effects on the cardiovascular system. However, it remains to be examined how short-term transdermal estrogen therapy (TET) affects insulin sensitivity (SI) in patients with cardiac syndrome X (CSX), who are characterized by elevated insulin resistance. SI was assessed in a randomized, double-blind, placebo-controlled crossover study by minimal model analysis in seven postmenopausal women with CSX treated by TET. SI decreased by 32 +/- 8.3%, from 5.94 +/- 1.14 at baseline to 3.61 +/- 0.40 [(10(-4) x min(-1))/(microU/ml)] during TET (p = 0.03). Time to the onset of symptoms increased from 414.2 +/- 51.0 s at baseline to 450.0 +/- 53.2 s (p = 0.04). We conclude that TET increases SI in postmenopausal women with CSX. This effect is unrelated to the beneficial anti-ischemic effects on exercise duration.

Basal and post-methionine serum homocysteine and lipoprotein abnormalities in patients with chronic liver disease

BACKGROUND

Lipoprotein abnormalities are commonly found in chronic liver diseases (CLDs), particularly hypercholesterolemia in primary biliary cirrhosis (PBC). However, affected patients may not be at increased risk of coronary heart disease. Cirrhotic patients display impaired methionine clearance, and an increased level of homocysteine, a methionine metabolite, is an independent risk factor for coronary heart disease. Thus, we hypothesized that the low risk of coronary heart disease in patients with CLD may be related to low serum levels of homocysteine. The aim of this study was to test this hypothesis after methionine load and to describe the serum lipoprotein profile in patients with PBC and in patients with hepatocellular liver disease.

METHODS

Fifteen female patients (mean age, 58.2 +/- 11.7 years) with PBC, 15 female patients (mean age, 54.5 +/- 9.6 years) with other causes of CLD, and 15 healthy sex- and age-matched controls were given L-methionine (50 mg/kg of ideal body weight). Basal fasting serum homocysteine level and 2, 4, and 6 hours of post-methionine load were determined using high-performance liquid chromatography with a fluorometric detector. Levels of fasting serum cholesterol, triglycerides, high-density lipoprotein (HDL), low-density lipoprotein (LDL), lipoprotein (a) (Lp(a)), and apoprotein B were also determined.

RESULTS

Results showed that mean basal and post-methionine load (6 hours) serum homocysteine levels were statistically significantly higher in the patients with PBC and with CLD than in the control group (P=0.04) and that levels of serum cholesterol, LDL, HDL, and apoprotein B were significantly higher in the PBC patients than in the other two groups (P < or = 0.05). There was no correlation between any of these parameters and the severity of liver disease. Serum HDL was significantly lower in the CLD group (P < or = 0.05) and correlated with severity of liver disease. There was no significant difference in serum cholesterol, LDL, or apoprotein B between the CLD group and the controls. Serum triglyceride and Lp(a) levels were similar for all three groups.

CONCLUSIONS

In contrast to previous reports, the site of the methionine metabolic impairment was found to be below the homocysteine synthesis level. For most patients with CLD, factors other than serum homocysteine or Lp(a) are responsible for the reduction in the risk of coronary heart disease. Further studies with larger samples are needed.

The effect of neck dissection on human fat transport

This study examines the effect of neck dissection and thoracic duct ligation on lipid metabolism. Included were 23 patients undergoing neck dissection with thoracic duct ligation. The results showed a temporary reduction in lipid metabolism in approximately half the patients who had a left neck dissection. This effect subsided within 6 months, possibly because of the development of alternative lymph channels. The reduction in fat metabolism in selected cases may have therapeutic effects on patients with morbid hypertriglyceridemia or those who receive chemopreventive regimens. To the best of our knowledge, no similar studies have been reported heretofore in humans.

Secondary prevention with antioxidants of cardiovascular disease in endstage renal disease (SPACE): randomised placebo-controlled trial

BACKGROUND

Excess cardiovascular mortality has been documented in chronic haemodialysis patients. Oxidative stress is greater in haemodialysis patients with prevalent cardiovascular disease than in those without, suggesting a role for oxidative stress in excess cardiovascular disease in haemodialysis. We investigated the effect of high-dose vitamin E supplementation on cardiovascular disease outcomes in haemodialysis patients with pre-existing cardiovascular disease.

METHODS

Haemodialysis patients with pre-existing cardiovascular disease (n=196) aged 40-75 years at baseline from six dialysis centres were enrolled and randomised to receive 800 IU/day vitamin E or matching placebo. Patients were followed for a median 519 days. The primary endpoint was a composite variable consisting of: myocardial infarction (fatal and non-fatal), ischaemic stroke, peripheral vascular disease (excluding the arteriovenous fistula), and unstable angina. Secondary outcomes included each of the component outcomes, total mortality, and cardiovascular-disease mortality.

FINDINGS

A total of 15 (16%) of the 97 patients assigned to vitamin E and 33 (33%) of the 99 patients assigned to placebo had a primary endpoint (relative risk 0.46 [95% CI 0.27-0.78], p=0.014). Five (5.1%) patients assigned to vitamin E and 17 (17.2%) patients assigned to placebo had myocardial infarction (0.3 [0.11-0.78], p=0.016). No significant differences in other secondary endpoints, cardiovascular disease, or total mortality were detected.

INTERPRETATION

In haemodialysis patients with prevalent cardiovascular disease, supplementation with 800 IU/day vitamin E reduces composite cardiovascular disease endpoints and myocardial infarction.

Kinetic analysis of copper-induced peroxidation of HDL, autoaccelerated and tocopherol-mediated peroxidation

Comparison of the kinetic profiles of copper-induced peroxidation of HDL and LDL at different copper concentrations reveals that under all the studied experimental conditions HDL is more susceptible to oxidation than LDL. The mechanism responsible for HDL oxidation is a complex function of the copper/HDL ratio and of the tocopherol content of the HDL. At high copper concentrations, the kinetic profiles were similar to those observed for LDL oxidation, namely, relatively rapid accumulation of oxidation products, via an autoaccelerated, noninhibited mechanism, was preceded by an initial "lag phase." Under these conditions, the maximal peroxidation rate (V(max)) of HDL and LDL depended similarly on the molar ratio of bound copper/lipoprotein. Analysis of this dependency in terms of the binding characteristics of copper to lipoprotein, yielded similar dissociation constant (K = 10(-6) M) but different maximal binding capacities for the two lipoproteins (8 Cu(+2)/HDL as compared to 17 Cu(+2)/LDL). Given the size difference between HDL and LDL, these results imply that the maximal surface density of bound copper is at least 2-fold higher for HDL than for LDL. This difference may be responsible for the higher susceptibility of HDL to copper-induced oxidation in the presence of high copper concentrations. At relatively low copper concentrations, the kinetic profile of HDL oxidation was biphasic, similar to but more pronounced than the biphasic kinetics observed for the oxidation of LDL lipids at the same concentration of copper. Our results are consistent with the hypothesis that the first phase of rapid oxidation occurs via a tocopherol-mediated-peroxidation (TMP) mechanism. Accordingly, enrichment of HDL with tocopherol resulted in enhanced accumulation of hydroperoxides during the first phase of copper-induced oxidation. Notably, the maximal accumulation during the first phase decreased upon increasing the ratio of bound copper/HDL. This behavior can be predicted theoretically for peroxidation via a TMP mechanism, in opposition to autoaccelerated peroxidation. The possible pathophysiological significance of these findings is discussed.

Effect of prolonged fasting on plasma lipids, lipoproteins and apolipoprotein B in 12 physicians participating in a hunger strike: an observational study

BACKGROUND

Dyslipidemia and obesity serve as risk factors for the development of atherosclerotic cardiovascular disease. Fasting is sometimes recommended for treating these conditions. This study was undertaken to try to resolve conflicting results reported in the literature.

OBJECTIVES

To study the effect of fasting (0 calories, with free intake of fluids) for 3-5 days on plasma concentration of triglyceride, cholesterol and apolipoprotein B.

METHODS

Physicians, about to begin a hunger strike, were divided into four groups: normolipidemic non-obese men (group 1), two moderately obese men and two men with type IV hyperlipidemia (group 2), healthy non-obese women (group 3), and healthy non-obese women on oral contraceptives (group 4). Adherence to fasting was monitored daily by detailed interviews, loss of weight, drop in plasma glucose, presence of ketonuria, progressive rise in serum creatinine and uric acid, and decrease in plasma pH. We monitored their serum glucose, electrolytes, liver function, lipids, lipoproteins and apolipoprotein B on days 0, 3, and 5.

RESULTS

Physicians who adhered to complete fasting lost more than 1.5% of their body weight after 3 days of fasting (n = 12), and more than 3.2% at 5 days (n = 5). All non-obese normolipidemic males and females (groups 1 and 3) showed an increase in plasma triglyceride (by 28-162%) and very low density lipoprotein cholesterol (by 22-316%) after 3 days of fasting. The obese and hyperlipidemic men (group 2) showed a decrease of 17-63% in their VLDL cholesterol, and the women on oral contraceptives (group 4) showed a 20% decrease in their plasma triglyceride on day 3. Low density lipoprotein cholesterol increased by 13% in group 2, decreased by 7.3% in group 4, and remained unchanged in group 1 and 3. Apolipoprotein B level correlated well with LDL cholesterol in all groups. High density lipoprotein cholesterol changes were inconsistent.

CONCLUSIONS

These results help to explain and reconcile previous published reports. The metabolic background of the individual together with the amount of energy consumed affect the behavior of plasma lipids and lipoproteins levels during fasting.

A model for educating humanistic physicians in the 21st century: the new medicine, patient, and society course at Tel Aviv University

BACKGROUND

The impact of the social and behavioral sciences on medical education has often been limited due to a variety of organizational, curricular and professional barriers. The new "Medicine, Patient, and Society (MPS)" program in Tel Aviv attempts to rectify this educational shortcoming by exploring new ways to help students acquire the knowledge, attitudes and skills needed for becoming humanistic physicians and for helping patients (and themselves) adopt healthy behaviors. To work toward this goal, this program integrates the biomedical and psychosocial aspects of health care, providing developmentally appropriate learning experiences according to levels of training, together with a variety of educational methods, including learner-centered approaches.

OBJECTIVES

To implement and evaluate the MPS pilot program.

METHODS

The MPS program uses a "seamless" model of behavioral science education. This integrated curriculum interweaves several elements: behavioral science topics (presented through multiple approaches), clinical experiences, practical medical skills, and an independent project. During the program's first year there is a strong focus on "health" rather than "disease," with activities designed to encourage healthy behaviors, including smoking cessation, stress management, birth control, AIDS education, life cycle and preventive health services. Assessment of the pilot for first-year students included standardized questionnaires, student focus groups, participant observation of educational activities, and committee feedback.

RESULTS

Students' quantitative evaluations indicated high levels of satisfaction with the MPS program, but their qualitative evaluations revealed some concerns. Participant observations and focus groups added unexpected insights. Student concerns included performance fears, difficulties with "learner-centered" education, and incompatibilities between more traditional first-year courses and the MPS program. Long-term follow-up will be needed to determine the impact of this emphasis on health during the first year. We assume it serves as a helpful foundation for students before they focus on disease and its sequelae in their later years.

Impact of treatment for childhood obesity on parental risk factors for cardiovascular disease

BACKGROUND

Family-based approaches using the parents as agents of change to treat childhood obesity are superior to programs targeting only children in achieving weight reduction and have a lower dropout rate.

OBJECTIVE

The aim of this study was to compare the impact of two behavioral approaches (parents only vs children only) for the treatment of childhood obesity on parental weight, eating, and activity habits as well as cardiovascular risk factors.

DESIGN

A randomized 1-year clinical intervention study was performed.

METHODS

Sixty obese children (>/=20% over ideal weight for age, height, and sex), ages 6-11 years, were randomly allocated to the experimental (parents as sole agents of change) or conventional groups (children as sole agents of change). Fourteen (1-h-long) support/educational sessions were conducted by a clinical dietitian for the parents in the experimental group and 30 sessions for children in the conventional group. Anthropometric and biochemical measurements were determined at the start and end of the program.

RESULTS

The experimental approach, when compared to the conventional intervention, was found to be superior in the reduction of fathers overweight (P < 0.05). The former approach resulted also in improved profile of risk factors for cardiovascular disease in both parents. These changes could be ascribed to a greater improvement in eating and activity behaviors observed in parents belonging to the experimental intervention group who participated in a family-based intervention to treat their children's obesity.

CONCLUSIONS

Treatment of childhood obesity targeting the parents as the sole agent of change, which is more effective for the treatment of childhood obesity when compared to a children-oriented program, may in addition award parents with the benefit of changing their own eating and activity patterns, thus making this program ideal for treatment of obesity in children and their overweight parents.

Serum malondialdehyde and prevalent cardiovascular disease in hemodialysis

BACKGROUND

Oxidative stress has been proposed as a mechanism by which the accelerated rate of cardiovascular disease (CVD) observed in maintenance hemodialysis (HD) patients may be explained. This study examined the effects of HD and CVD on serum malondialdehyde (MDA) levels as a marker of oxidative stress in HD patients with and without prevalent CVD. Serum MDA levels and CVD prevalence in HD were modeled.

METHODS

Serum MDA was determined using spectrophotometry in HD patients (N = 76, 53 men and 23 women, mean age 63.8 years) immediately prior to and at the conclusion of one midweek HD treatment. Traditional CVD risk factors, including serum lipids, lipoproteins, apolipoproteins, and fibrinogen, were also measured, as were serum chemistry and dialysis adequacy.

RESULTS

Mean serum MDA levels were significantly elevated in HD patients with prevalent CVD compared with those without, whereas serum lipoprotein and plasma fibrinogen levels did not differ between the two groups. Patients in the highest compared with the lowest tertile of postdialysis MDA were nearly four times as likely to have prevalent CVD, and serum MDA was the single strongest predictor of prevalent CVD in this patient population.

CONCLUSIONS

These findings indicate the presence of oxidative stress in HD patients, and are consistent with the theory of oxidative stress as a factor in accelerated CVD in this population.

Comparison of hemostatic factors and serum malondialdehyde as predictive factors for cardiovascular disease in hemodialysis patients

Hemodialysis (HD) patients have accelerated cardiovascular morbidity and mortality rates compared with the general population. Identifying the factors that predict major coronary events in this population can direct the focus on prevention. This cross-sectional study compares known and suspected cardiovascular risk factors in HD patients with and without prevalent cardiovascular disease (CVD). In 76 HD patients (prevalent CVD, 44 of 76 patients), serum lipid, lipoprotein, apolipoprotein (Apo), plasma fibrinogen, tissue plasminogen activator (TPA), plasminogen activator inhibitor (PAI-1), and factor VII levels were measured using standard kits. Serum malondialdehyde (MDA; a marker of oxidative stress) was measured using spectrophotometry. Predictor variables were compared using analysis of variance and chi-squared tests, as appropriate. CVD prevalence was modeled using multiple logistic regression analysis, and odds ratios (OR) were calculated. Serum lipid, lipoprotein, Apo, plasma TPA, PAI-1, and factor VII values did not differ significantly from laboratory norms or discriminate for prevalent CVD in HD patients. Plasma fibrinogen levels were significantly elevated in HD patients compared with laboratory norms (369.4 +/- 130.02 v 276.7 +/- 77.7 mg/dL; P < 0.0001) but were not significantly different in HD patients with and without prevalent CVD. Serum MDA levels, both before and after the midweek HD treatment, were significantly elevated in all HD patients compared with laboratory norms (pretreatment, 2.6 +/- 0.8 nmol/mL; posttreatment, 2.1 +/- 0.3 v 0.91 +/- 0.09 nmol/mL; P < 0.01) and were significantly elevated in HD patients with prevalent CVD versus those without (pretreatment, 2.8 +/- 0.6 v 2.4 +/- 0.4 nmol/mL; P < 0.01; posttreatment, 2.3 +/- 0.4 v 1.94 +/- 0.2 nmol/mL; P < 0.01). Only serum MDA levels, both before and after the midweek treatment, contributed to the explanation of variation in CVD prevalence. OR for CVD in the highest versus lowest tertile of pretreatment MDA level was 2.71 (95% confidence interval [CI], 1.42 to 5.19). ORs for CVD in the highest versus lowest tertile of posttreatment MDA level was 3.65 (95% CI, 1.6 to 8.32).

Susceptibility of serum lipids to copper-induced peroxidation correlates with the level of high density lipoprotein cholesterol

As a first step in evaluating the significance of our recently developed method of monitoring the kinetics of copper-induced oxidation in unfractionated serum, we recorded the kinetics of lipid oxidation in the sera of 62 hyperlipidemic patients and analyzed the correlation between oxidation and lipid composition of the sera [high density lipoprotein (HDL) cholesterol, low density lipoprotein (LDL) cholesterol, and triglycerides]. We used six factors to characterize the kinetics of oxidation, namely, the maximal absorbance of oxidation products (ODmax), the maximal rate of their production (Vmax), and the time at which the rate was maximal (t(max)) at two wavelengths (245 nm, where 7-ketocholesterol and conjugated dienic hydroperoxides absorb intensely, and 268 nm, where the absorbance is mostly due to dienals). The major conclusions of our analyses are that: (i) Both ODmax and Vmax correlate positively with the sum of concentrations of the major oxidizable lipids, cholesterol, and cholesteryl esters. (ii). The value of t(max), which is a measure of the lag preceding oxidation and therefore reflects the resistance of the serum lipids to copper-induced oxidation, exhibits a negative correlation with HDL cholesterol. Although this finding accords with the observation of shorter lags for HDL than for LDL, it is apparently inconsistent with the role of HDL as an antirisk factor in coronary heart diseases.

Role of behaviour modification in the treatment of childhood obesity with the parents as the exclusive agents of change

OBJECTIVE

This study examined the reduction in overweight and changes in eating-related behaviours in obese children treated with a family-based approach, in which the parents were the exclusive agents of change. Results were compared to the conventional approach in which children are responsible for their own weight loss.

DESIGN

A one-year longitudinal prospective design was used. Participants were randomly allocated for the experimental (parents as the agents of change) or the conventional (children as the agents of change) intervention.

METHODS

Sixty obese children (20% over ideal weight for age, height and gender) aged 6-11 y (mean+/-s.d. 9.2+/-1.0 y) were included in the study. Anthropometric measurements and biochemical tests were performed on the children and their parents before and after the programme, and both parents completed a sociodemographic and a family eating and activity habits questionnaire. Hour-long support/educational sessions were conducted by a clinical dietitian-14 sessions for the parents in the experimental intervention and 30 for the children in the conventional intervention. Individual sessions were held for members of both groups, when necessary.

RESULTS

Significant differences were found between the two groups in the reduction of exposure to food stimuli and changes in eating habits (eating while standing, watching TV, reading or doing homework, eating following stress and eating between meals). Mean weight reduction (by percentile) was significantly greater in the experimental intervention group (parent-only treatment) in comparison to the conventional intervention group (child-only treatment).

CONCLUSIONS

Treatment of childhood obesity with the parents as the exclusive agents of change, induces more behavioural changes as well as greater weight loss, than the conventional approach.

Parents as the exclusive agents of change in the treatment of childhood obesity

BACKGROUND

Excessive weight in childhood is a serious public health concern because of its costly health consequences and its increasing prevalence.

OBJECTIVE

Our objective was to compare the efficacy of a family-based approach for the treatment of childhood obesity, in which the parents served as the exclusive agents of change, with that of the conventional approach, in which the children served as the agents of change.

DESIGN

This study had a randomized, longitudinal prospective design and lasted 1 y. Sixty obese children aged 6-11 y were randomly allocated to the experimental (parents as agents of change) or control (children as agents of change) group. Anthropometric and biochemical measurements were determined at the start and end of the study. A sociodemographic questionnaire and a family eating and activity habits questionnaire were completed by both parents. Hour-long support and educational sessions were conducted by a clinical dietitian: 14 sessions for the parents in the experimental group and 30 sessions for the children in the control group.

RESULTS

The dropout rate was nine times greater in the control group (n = 9) than in the experimental group (n = 1). Mean percentile weight reduction was significantly (P < 0.03) higher in children in the experimental group (14.6%) than in the control group (8.1%).

CONCLUSIONS

Treatment of childhood obesity with parents as the exclusive agents of change was superior to the conventional approach, as indicated by the dropout rate and the percentage weight loss of the children during the 1-y intervention.

LDL-associated phospholipase A does not protect LDL against lipid peroxidation in vitro

The irreversible proteinase inhibitor Pefabloc (4-[2-aminoethyl] benzenesulfonyl fluoride) inactivates LDL-catalyzed hydrolysis of the short-chain fluorescent phospholipid C6-NBD-PC (1-acyl-2-(N-4-nitrobenzo-2-oxa-1,3-diazole)-aminocaproyl phosphatidylcholine). The dose-dependence of this inactivation is similar to that obtained previously for the inhibitory effect of Pefabloc on the hydrolysis of platelet activating factor (PAF) by the LDL-associated PAF acetylhydrolase (PAF-AH), in agreement with the notion that the hydrolysis of C6-NBD-PC and PAF is catalyzed by the same enzyme (LDL-associated phospholipase A; LDL-PLA). This conclusion is also supported by the finding that hydrolysis of C6-NBD-PC by LDL becomes inactivated by LDL oxidation only at late stages of the oxidation, similar to the effect of oxidation on the hydrolysis of PAF by the LDL-associated PAF-AH. Under conditions of complete inactivation of this enzyme towards C6-NBD-PC, the kinetics of lipid peroxidation, induced either by copper ions or by the free radical generator AAPH at varying doses of the prooxidant, was similar to that observed when the PLA was active (i.e., in the absence of Pefabloc). Hence, LDL-associated PLA (PAF-AH) does not protect LDL lipids from peroxidation. Similar results were obtained with fractionated LDL in albumin-containing buffer and for non-fractionated serum, in which copper-induced peroxidation was also not influenced by inactivation of the enzyme responsible for hydrolysis of C6-NBD-PC. Phospholipolysis of short chain phospholipids by LDL-PLA may still play a protective role against the toxic effects of oxidized phospholipids by reducing their internalization into cells (Schmitt et al. 1995).

Lipid oxidation in unfractionated serum and plasma

In an attempt to develop an assay for the susceptibility of plasma lipids to oxidation, we have studied the kinetics of copper-induced oxidation in diluted serum and plasma prepared with different anticoagulants (heparin, citrate and EDTA) by monitoring the absorbance of oxidation-products at several wavelengths. These studies revealed the complex and interrelated effects of the water-soluble antioxidant ascorbic acid, citrate and chloride ions on the kinetics of copper-induced oxidation of plasma lipids. Specifically, the onset of oxidation induced by copper-citrate chelates is only slightly affected by chloride ions and is accelerated upon increasing the copper concentration. By contrast, in the absence of citrate, the lag preceding oxidation in diluted serum or plasma (but not the maximal rate of oxidation) depends markedly on the chloride concentration in the diluting medium. In the absence of Cl-, the lag preceding oxidation is a decreasing saturable function of copper concentration, whereas in a normal phosphate-buffered saline solution (PBS), the lag shows a biphasic dependence on copper concentration such that at copper concentrations above 10-30 microM (depending on the extent of plasma dilution), increasing the concentration of copper results in prolongation of the lag. This dependence of copper-induced oxidation on the concentration of copper is not observed for dialyzed serum unless ascorbic acid is added. Our interpretation of these results is that water-soluble reductants and chloride ions act synergistically to stabilize Cu+, on the expense of Cu2+. Quenching of free radicals by Cu+ may be responsible for the prolongation of the lag at high copper concentrations, with no reduction of the maximal rate of oxidation. In spite of the complex dependencies described above, spectrophotometric monitoring of the kinetics of oxidation of plasma lipids, under 'optimized conditions' (50-fold diluted serum, in PBS containing 720 microM sodium citrate and 100 microM copper), agrees with independent measurements of the consumption of polyunsaturated fatty acids. Hence, the spectroscopic method may become useful for evaluation of the susceptibility of plasma lipids to oxidation. This possibility, however, has yet to be elucidated through investigations of the correlation between the susceptibility of serum lipids to copper-induced oxidation in vitro and clinical factors of significance.

The effect of albumin on copper-induced LDL oxidation

In an attempt to gain deeper understanding of the mechanism or mechanisms responsible for the protective effect of serum albumin against Cu(2+)-induced peroxidation of low density lipoprotein (LDL), we have examined the influence of the concentrations of bovine serum albumin (BSA), Cu2+ and LDL on the kinetics of peroxidation. Since the common method of monitoring the oxidation by continuous recording of the absorbance of conjugated dienes at 234 nm cannot be used at high BSA-concentrations because of the intensive absorption of BSA, we have monitored the time-dependent increase of absorbance at 245 nm. At this wavelength, conjugated dienes absorb intensely, whereas the background absorbance of BSA is low. Using this method, as well as the TBARS assay for determination of malondialdehyde, over a large range of BSA concentrations, we show that in many cases the influence of BSA on the kinetics of oxidation can be compensated for by increasing the concentration of copper. This reconciles the apparent contradiction between previously published data. Detailed studies of the kinetic profiles obtained under different conditions indicate that binding of Cu2+ to albumin plays the major role in its protective effect while other mechanisms contribute much less than copper binding. This conclusion is consistent with the less pronounced effect of BSA on the oxidation induced by the free radical generator AAPH. It is also shown that the copper-albumin complex is capable of inducing LDL oxidation, although the kinetics of the latter process is very different from that of copper-induced oxidation. Nevertheless, when compared to copper induced oxidation at similar concentration of the oxidation-promotor, the kinetics of oxidation induced by copper-albumin complex is very different and is consistent with a tocopherol mediated peroxidation, characteristic under low radical flux. Similar kinetics was observed for copper-induced oxidation only at much lower copper concentrations.

Diurnal heterogeneity in structure and function of low density lipoproteins of normolipidemic males

Structural changes in low density lipoproteins (LDL) have been shown to alter their metabolism and atherogenic potential. We investigated the diurnal changes in size and composition of LDL in seven healthy, non-obese, normolipidemic male volunteers consuming a standard diet (14.5% protein, 31.9% fat, 53.6% carbohydrate and 383 mg cholesterol/day) and continuing their daily routine. The food was divided into three meals and three snacks, and blood samples were obtained at 7 AM (after 12 h fasting), noon, 8 PM, midnight and 3 AM. LDL were isolated by both sequential and density gradient ultracentrifugation (d = 1.019 - 1.050 g/ml), and analyzed for lipids, apolipoproteins, size, and affinity to LDL receptors. Diurnal LDL preparations differ from fasting LDL in both chemical and physical parameters. The former get richer in triglyceride (TG/cholesterol weight ratio 0.23 vs. 0.16), larger in diameter (21.2 +/- 0.2 vs. 22.4 +/- 0.1 nm), and enriched in a more buoyant fraction (74.0 +/- 4.6 vs. 41.9 +/- 3.8% of LDL cholesterol in d = 1.019 - 1.035 g/ml). These structural changes in LDL were associated with enhanced affinity to LDL receptors in both human skin fibroblasts and HepG2 cells, as demonstrated by competition experiments with fasting human 125I-LDL. The observed diurnal heterogeneity in both the structure and the function of LDL may be attributed to the absorptive state as it did not occur during prolonged fasting. These diurnal changes may be important for better understanding LDL metabolism in vivo and for the elucidation of the atherogenic process.

Copper-induced lipid oxidation in unfractionated plasma: the lag preceding oxidation as a measure of oxidation-resistance

In spite of the pathological significance of oxidation of plasma lipids, no method is currently available for the evaluation of the susceptibility of these lipids to oxidation in unfractionated plasma. Here we demonstrate that copper-induced oxidation of diluted plasma, in the presence of citrate can be monitored continuously by recording the absorbance at 245 nm. The kinetics of accumulation of oxidation products in unfractionated plasma is a sum of lipid oxidation products obtained in low and high density lipoproteins isolated from the same plasma. The kinetic profiles are reproducible and can be performed with plasma samples even after prolonged storage at 4 degrees C (up to two months) or after freezing and thawing of the plasma. Being simple and reproducible, yet correlating with the oxidizability of low and high density lipoproteins, this method can be used to evaluate the "oxidation resistance" of plasma lipids and thus serve as a standard index of the susceptibility of the plasma lipids of patients to oxidation-inflicted pathologies, including atherosclerosis.

[International postgraduate training program in medicine: survey of 13 training courses, 1988-1994]

In 1988 an International Postgraduate Training Program in Medicine was established as a joint venture of the Tel Aviv University School of Continuing Medical Education and the Ministry for Foreign Affairs, Division of International Cooperation. During 1988-1994, 359 physicians participated. A survey of 271 graduates was carried out within 1-5 years following the completion of training, and 57% responded to our questionnaire. The program fulfilled the academic expectations of 78% of the trainees, and the practical clinical expectations of 80%. 95% graded the program as good-to-excellent from the sociocultural aspect. 75% and 67.5% of the trainees graded the program as good-to-excellent with regard to improvement in their theoretical and practical skills, respectively. Regretfully, only 45% have continued their ties with the host departments and only 11% have carried out joint research projects. These results imply that further attention should be paid to the trainees' real-time input, in order to increase satisfaction. Personal tutors should be nominated in each department, and should be adequately compensated. More emphasis should be given to initiation of bilateral research projects and maintenance of professional ties between the trainees and their host departments.

Oxidation of low density lipoprotein upon sequential exposure to copper ions

Copper-induced LDL oxidation is characterized by an 'induction phase' (lag phase) during which the endogenous antioxidants are consumed, followed by a 'propagation phase' in which the LDL-associated polyunsaturated fatty acids are oxidized. Oxidation products may play an important role in the propagation of the oxidative process in the arterial intima as they increase the permeability of the damaged endothelium to various plasma components, including LDL. We therefore found it of interest to investigate the kinetics of LDL oxidation in vitro under conditions where LDL is sequentially exposed to Cu(2+)-induced oxidation. The results of our studies demonstrate that when native LDL is exposed to copper oxidation in a medium containing oxidized LDL, oxidation of the added LDL may be almost instantaneous. Furthermore, even when native LDL is added to 'oxidizing LDL' towards the end of the lag phase or during the propagation phase it becomes oxidized after a very short lag. This oxidation process, occurring in spite of the possible protective effect of the antioxidants present in the newly added LDL, indicates that although antioxidants prolong the latency period by preventing the formation of active free radicals, when such radicals are present in the system, oxidation propagates. These results lend strong support to the generally accepted paradigm regarding the mechanism of propagation of lipid oxidation. In view of the effect of oxidation products on the permeability of the endothelium, the observed shortening of the lag period may result in a vicious cycle, independent of the LDL-associated antioxidants, leading to continuing oxidation and foam cell formation.

The effect of lovastatin on early restenosis

The effect of lovastatin given before percutaneous coronary angioplasty (PTCA) on early restenosis was investigated in men with mild to moderate hypercholesterolemia. Thirty-four hypercholesterolemic patients (serum LDL cholesterol 130-200 mg/dL) undergoing their first PTCA completed a 6-month prospective, double-blind, placebo-controlled trial. Eighteen received lovastatin 20 mg/day (Lo group) and 16 placebo (P1 group), beginning 10 to 21 days before PTCA. All underwent a thallium-201 quantitative exercise test 5 to 7 days after PTCA. Endpoints for restenosis were either 50% narrowing of the dilated artery on coronary angiography, performed in symptomatic patients or, in asymptomatic patients, the appearance of newly developed reversible filling defects in the vascular territory of the dilated artery on a second thallium scan done 6 months after PTCA. The hypocholesterolemic change observed in the Lo group was not accompanied by a reduction in early restenosis risk. The authors conclude that effective hypocholesterolemic therapy before PTCA does not affect early restenosis rate in men with mild to moderate hypercholesterolemia.

Diurnal changes in plasma lipoproteins of free-living healthy men consuming a standard diet

Although it is well established that plasma lipoproteins are involved in atherogenesis, most patients with coronary heart disease have normal or nearly normal fasting plasma lipid and lipoprotein levels. As most of the human life is spent in the fed state we elected to investigate the changes occurring in plasma lipids and lipoproteins during normal daily activities. We studied 12 healthy, normolipidemic and non-obese subjects on a standard diet divided into three meals and three snacks. This method was found to be accurate and reproducible in four subjects who underwent repeated studies. The major diurnal changes were observed in plasma triglyceride level and in the composition of plasma lipoproteins. The degree and pattern of these changes differed among subjects but was specific and constant for each individual. The extent of these diurnal changes, which correlated positively with fasting plasma triglyceride and inversely with plasma HDL2 levels, may play an important role in the pathogenesis of atherosclerosis.

Efficacy and safety of pravastatin once daily in primary moderate hypercholesterolemia: the Israeli experience

Seventy-seven hypercholesterolemic patients participated in a 26-week, multicenter, randomized, double-blind, placebo-controlled study that investigated the efficacy and safety of pravastatin therapy. All patients had primary moderate hypercholesterolemia (total cholesterol 200-300 mg/dl, at the end of a 6-week dietary run-in period) and two additional coronary risk factors. Pravastatin, 20-40 mg/day given at bedtime, reduced total cholesterol by 19-22%, LDL-cholesterol by 24-30%, triglycerides by 10-30% and increased HDL-cholesterol by 9-13%. The drug caused mild elevation in alanine aminotransferase and aspartate aminotransferase. Almost all these elevations were within normal limits and no patient was clinically symptomatic. No other significant differences were observed between the pravastatin and the placebo-treated groups with regard to other adverse effects and to patient compliance and withdrawal. It is concluded that pravastatin has a beneficial effect on the lipid profile and that the drug is safe and well tolerated.

Heterogeneity in peritoneal transport during continuous ambulatory peritoneal dialysis and its impact on ultrafiltration, loss of macromolecules and plasma level of proteins, lipids and lipoproteins

We investigated the effect of heterogeneity in the peritoneal transport of plasma proteins on dialysis efficiency and plasma levels of proteins, lipids and lipoproteins in 32 patients undergoing long-term continuous ambulatory peritoneal dialysis (CAPD; 9 females and 23 males, 18-76 years old). Eleven patients were studied on several occasions (at 0-42 months) and the remainder at 6-60 months on CAPD (n = 49). We have divided our patients arbitrarily into two equal groups according to their protein concentration in the peritoneal effluent at the end of an 8-hour cycle. Patients with a high peritoneal protein concentration (> or = 2 g/l/1.73 m2) have lower ultrafiltration capacity, higher glucose absorption rate and increased loss of most plasma proteins [including albumin, immunoglobulins (Ig), complement components and high-density lipoproteins (HDL)] compared to patients with a low peritoneal protein concentration (< 2 g/l/1.73 m2). Consequently, plasma levels of albumin, IgM and HDL were lower in patients with a high peritoneal protein concentration. The latter had also increased levels of plasma triglycerides and very-low-density lipoproteins. The difference observed in peritoneal transport between the groups could be ascribed only in part to the duration of CAPD treatment, and hence to the number of peritonitis episodes but not to medications. Therefore, we suggest that inherent constitutional factors may be responsible for some of the observed heterogeneity in the peritoneal transport of these patients which is already evident at the start of CAPD treatment. Patients with high peritoneal transport are exposed to an augmented atherogenic plasma lipid profile in addition to a reduction in dialysis efficiency (ultrafiltration failure). These patients may become prone also to nutritional and immunological disturbances. Therefore, we suggest taking these effects into consideration before choosing the appropriate dialysis modality in patients with increased peritoneal transport for plasma proteins.

Regulation of lipoprotein lipase secretion in murine macrophages during foam cell formation in vitro. Effect of triglyceride-rich lipoproteins

Triglyceride rich-lipoproteins induce triglyceride accumulation in macrophages, leading to foam cell formation. The correlation between cell triglyceride accumulation and lipoprotein lipase (LPL) secretion in murine macrophages and the role that LPL plays in the accumulation process were examined. LPL secretion is defined as the extracellular LPL activity that accumulates during a 4-hour incubation of treated and untreated cells in a bovine serum albumin-containing RPMI-1640 medium. LPL secretion was suppressed (up to 70%) in a dose- and time-dependent manner when J774.1 cells were incubated with chylomicrons, very low density lipoproteins, and intermediate density lipoproteins but not with low or high density lipoproteins from normolipidemic and hypertriglyceridemic subjects. Oleic acid both suppressed LPL secretion and invoked triglyceride accumulation. Suppression of LPL secretion preceded gross triglyceride accumulation, was reversible, and was not the result of a reduction in LPL mRNA. P388D1 cells neither secreted LPL nor accumulated triglyceride. Inhibition of LPL secretion by tunicamycin in both peritoneal macrophages and J774.1 cells prevented a hypertriglyceridemic very low density lipoprotein-induced triglyceride accumulation, an effect that was counteracted by addition of exogenous LPL. The results suggest that 1) extracellular hydrolysis of lipoprotein triglyceride is a major factor in inducing foam cell formation and 2) LPL secretion may be regulated by cell energy needs, and when these needs are exceeded, LPL secretion is suppressed.

Fish apolipoprotein-A-I has heparin binding activity: implication for nerve regeneration

This study provides evidence that apolipoprotein-A-I (apo-A-I), derived from fish plasma and nerve, has heparin binding activity. We have shown previously that injury in a regenerative CNS, such as that of fish optic nerves, leads to increased levels of apo-A-I in media conditioned by these nerves, as compared with media conditioned by noninjured nerves. In the present study, we have purified and characterized apo-A-I from both fish plasma and optic nerves. Sequence analysis of the 15 N-terminal amino acids revealed that at least 14 amino acids are identical in these two purified apo-A-I samples. The purified apo-A-I derived from both fish plasma and optic nerves binds to heparin. Binding measurements using [3H]heparin followed by Scatchard analysis revealed that apo-A-I binds to heparin with relatively low affinity (KD = 2.8 x 10(-6) M). Results are discussed with respect to the possibility that accumulation of apo-A-I in the extracellular matrix of fish optic nerves is made possible via heparin binding, like that to apolipoprotein-E in mammals.

Kinetics of peritoneal protein loss during CAPD: I. Different characteristics for low and high molecular weight proteins

We studied the peritoneal protein loss in 13 patients during CAPD using 2 liters of 1.5% dextrose dialysis solutions. We compared the kinetic characteristics of the peritoneal mass transfer and clearance of proteins over a wide range of molecular size, to those of small molecular weight solutes. The peritoneal clearance of all studied proteins and solutes correlated strongly and negatively with their molecular mass. No changes were observed in these clearances during 58 months of dialysis. Unlike the peritoneal mass transfer and clearance of small molecular weight solutes (less than 200) which revealed a remarkable progressive drop after the first hour of an eight-hour dialysis cycle, the mass transfer and clearance of proteins of large molecular weight (greater than 68,000) was continuous throughout the eight hours. The clearance of proteins of small molecular weight (less than 15,000) showed similar kinetics to small solutes (less than 200). These results indicate that long dwell times (6 or 8 hr) of peritoneal dialysis are detrimental for the loss of large molecular weight proteins (such as albumin and immunoglobulins) in view of the negligible dialysance of both small solutes (creatinine and potassium) and "intermediate molecules" (represented by the small molecular weight proteins) during the latter hours of long dwell cycles. Thus we suggest that substituting CAPD (3 x 8 hr or 4 x 6 hr) with CCPD (6 x 1 hr) may limit protein loss in these patients.

Kinetics of peritoneal protein loss during CAPD: II. Lipoprotein leakage and its impact on plasma lipid levels

We quantified the plasma levels and peritoneal loss of lipids and lipoproteins, and studied the composition of plasma and effluent lipoproteins in 16 patients on CAPD (5 females and 11 males, 18 to 76 years old). Five patients were studied prospectively (at 0, 1, 3 and 6 months) and 11 patients at 6 to 58 months on CAPD (N = 30). Elevated levels of plasma VLDL and reduced levels of plasma HDL were maintained in these patients throughout 58 months of CAPD, whereas the initially increased LDL levels showed a tendency towards normalization. All plasma lipoproteins (VLDL, IDL, LDL and HDL) were present in the peritoneal effluent. The lipoproteins isolated from plasma and peritoneal fluid shared a similar lipid and apolipoprotein composition. The peritoneal transport characteristics of plasma lipoproteins were similar to other plasma macromolecules. Their clearance correlated with their molecular mass, plasma concentration and dwell time, but was not affected by duration of CAPD treatment. The plasma lipid and lipoprotein levels were unaffected by the rate of glucose absorption. The peritoneal protein clearance correlated positively with plasma levels of triglyceride and LDL, and negatively with plasma HDL. An inverse correlation was observed also between plasma levels of HDL and its peritoneal clearance (r = -0.393, P less than 0.025, N = 30). The continuous peritoneal loss of HDL and the hypertriglyceridemia were found to contribute most to the persistent low plasma levels of HDL in CAPD patients, and thus may lead to the accelerated atherosclerosis observed in these patients.

Chylomicron-chylomicron remnant clearance by liver and bone marrow in rabbits. Factors that modify tissue-specific uptake

The metabolism of [14C]cholesterol- and [3H]retinol-labeled chylomicrons obtained from canine thoracic duct or rabbit mesenteric lymph was investigated in normal fasted rabbits. Typically, 70-80% of the chylomicrons injected into the rabbits were cleared from the plasma in 20 min, and their uptake was accounted for principally by the liver and the bone marrow. Surprisingly, the bone marrow was a major site of uptake; the uptake ranged from about half that of the liver to a nearly equal amount. The importance and specificity of chylomicron-chylomicron remnant uptake by the bone marrow were established by demonstrating that (a) bone marrow throughout the body accumulated these lipoproteins, (b) the level of uptake was consistent regardless of how the values were calculated or how the chylomicrons were prepared, (c) the uptake represented specific binding, and (d) radiolabeled intestinal lipoproteins induced in vivo delivered cholesterol and retinol to the marrow. Electron microscopic examination of the rabbit bone marrow established that perisinusoidal macrophages uniquely accounted for the uptake of the chylomicrons. Whereas liver cleared a variety of both triglyceride-rich lipoproteins (chylomicrons, chylomicron remnants, and very low density lipoproteins) and cholesterol-rich lipoproteins (beta-very low density lipoproteins and high density lipoproteins containing apolipoprotein E), bone marrow uptake appeared to be restricted to the triglyceride-rich lipoproteins. More chylomicron remnants (generated in a hepatectomized rabbit) were cleared by the liver than by the bone marrow, and the addition of excess apolipoprotein E to chylomicrons resulted in their preferential uptake by the liver. The role of chylomicron-chylomicron remnant delivery of lipids or lipid-soluble vitamins to rabbit bone marrow is open to speculation, and whether triglyceride-rich lipoprotein uptake occurs to a significant extent in the bone marrow of humans remains to be determined.

Optic nerve regeneration in adult fish and apolipoprotein A-I

Fish optic nerves, unlike mammalian optic nerves, are endowed with a high capacity to regenerate. Injury to fish optic nerves causes pronounced changes in the composition of pulse-labeled substances derived from the surrounding non-neuronal cells. The most prominent of these injury-induced changes is in a 28-kilodalton (kDa) polypeptide whose level increases after injury, as revealed by one-dimensional gel electrophoresis and autoradiography. The present study identified as apolipoprotein A-I (apo-A-I) a polypeptide of 28 kDa in media conditioned by regenerating fish optic nerves. The level of this polypeptide increased after injury by approximately 35%. Apo-A-I was isolated by gel-permeation chromatography from delipidated high-density lipoproteins (HDL) that had been obtained from carp plasma by sequential ultracentrifugation. Further identification of the purified protein as apo-A-I was based on its molecular mass (28 kDa) as determined by gel electrophoresis, amino acid composition, and microheterogeneity studies. The isolated protein was further analyzed by immunoblots of two-dimensional gels and was found to contain six isoforms. Western blot analysis using antibodies directed against the isolated plasma protein showed that the 28-kDa polypeptide in the preparation of soluble substances derived from the fish optic nerves (conditioned media, CM) cross-reacted immunologically with the isolated fish plasma apo-A-I. Immunoblots of two-dimensional gels revealed the presence of three apo-A-I isoforms in the CM of regenerating fish optic nerves (pIs: 6.49, 6.64, and 6.73). At least some of the apo-A-I found in the CM is derived from the nerve, as was shown by pulse labeling with [35S]methionine, followed by immunoprecipitation. The apo-A-I immunoactive polypeptides in the CM of the fish optic nerve were found in high molecular-weight, putative HDL-like particles. Immunocytochemical staining revealed that apo-A-I immunoreactive sites were present in the fish optic nerves. Higher labeling was found in injured nerves (between the site of injury and the brain) than in non-injured nerves. The accumulation of apo-A-I in nerves that are capable of regenerating may be similar to that of apo-E in sciatic nerves of mammals (a regenerative system); in contrast, although its synthesis is increased, apo-A-I does not accumulate in avian optic nerves nor does apo-E in rat optic nerves (two nonregenerative systems).

Hypolipidemic effect of beta, beta'-methyl-substituted hexadecanedioic acid (MEDICA 16) in normal and nephrotic rats

Treatment of normal or puromycin aminonucleoside-nephrotic rats, kept on a balanced Purina chow diet, with beta, beta'-tetramethyl-substituted hexadecanedioic acid (MEDICA 16) (Bar-Tana, J., G. Rose-Kahn, and M. Srebnik. 1985. J. Biol. Chem. 260: 8404-8410) resulted in an acute reversible inhibition of liver lipogenesis and cholesterogenesis with a concomitant hypolipidemic effect which was sustained as long as the drug was administered. The hypolipidemic effect in normal and nephrotic rats consisted of 70-80% and 40-60% reduction in plasma VLDL-triacylglycerols and cholesterol, respectively, with a respective increase in the HDL-cholesterol/(VLDL + LDL)-cholesterol ratio. The observed hypolipidemic effect was accompanied by a 10-fold decrease in VLDL-apoC-III content with a concomitant enrichment of the VLDL fraction by VLDL remnants having an increased apoB-100/apoB-48 ratio. The pharmacological reduction of VLDL by MEDICA 16 may offer a treatment mode of choice for selected hyperlipidemic states.

Metabolism of canine beta-very low density lipoproteins in normal and cholesterol-fed dogs

Cholesteryl ester-rich beta-very low density lipoproteins (beta-VLDL) are beta-migrating lipoproteins that accumulate in the plasma of cholesterol-fed animals and of patients with type III hyperlipoproteinemia. There are two distinct fractions: fraction I beta-VLDL are chylomicron remnants of intestinal origin, and fraction II beta-VLDL are cholesterol-rich VLDL of hepatic origin. The liver rapidly clears fraction I beta-VLDL from the plasma of both normal and cholesterol-fed dogs. The liver also clears fraction II beta-VLDL rapidly and efficiently from the plasma of normal dogs by receptor-mediated uptake. In cholesterol-fed dogs the clearance is biphasic: an initial rapid die-away of about 30% to 40% of the injected dose within 5 minutes, followed by a slow clearance of plasma radioactivity (a half-life of more than 20 hours). The rapid, initial phase of fraction II beta-VLDL clearance appears to be related to sequestration of the lipoproteins presumably on endothelial cells and is apparently associated with lipolytic processing. Treatment of the fraction II beta-VLDL with lipoprotein lipase abolishes this rapid phase. In the cholesterol-fed dog, the slow, late phase of clearance corresponds to the conversion of fraction II beta-VLDL to the smaller, denser intermediate and low density lipoproteins (IDL and LDL), which are slowly cleared from the plasma. It is concluded that fraction II beta-VLDL are catabolized in the normal dog by rapid uptake mediated at least in part by the apo B,E(LDL) receptor of hepatic parenchymal cells. In cholesterol-fed dogs, in which these receptors are markedly down-regulated, fraction II beta-VLDL are apparently initially bound to endothelial cells and converted to IDL and LDL by lipolytic processing.

Interactions between human and carp (Cyprimus carpio) low density lipoproteins (LDL) and LDL receptors

1. We have compared the concentration and chemical composition of carp and human plasma lipoproteins and studied their interaction with human fibroblast LDL receptors. 2. The main lipoproteins in carp are of high density (HDL) in contrast to low density lipoproteins (LDL) in human. 3. Carp lipoproteins are devoid of apolipoprotein (apo) E, a major ligand for interaction with LDL receptors in mammals. 4. Carp very low density lipoproteins (VLDL) and LDL but not HDL nor apoA-I cross react with human LDL in their interaction with LDL receptors on human cultured fibroblasts. 5. Carp liver membranes possess high affinity receptors that are saturable and have calcium dependent ligand specificity (apoB and apoE) similar to human LDL receptor. Carp VLDL and LDL but not HDL nor its major apolipoprotein complexed to L-alpha-phosphatidylcholine dimyristoyl (apoA-I-DMPC) competed with the specific binding of human LDL to this receptor.

Effect of moderate isocaloric modification of dietary carbohydrate on high-density lipoprotein composition and apolipoprotein A-1 turnover in humans

Plasma lipid and apolipoprotein (apo) levels were determined in five normolipidemic subjects and five patients with Type IV hypertriglyceridemia (HTG) who were fed for greater than or equal to 6 weeks on two isocaloric diets. The first diet contained carbohydrates (CHO) as 55% of total calories, 29% as fat and 16% as protein. The second diet contained 40% CHO, 45% fat and 15% protein in normolipidemic subjects and 40% CHO, 41% fat and 19% protein in patients with HTG. All diets had a cholesterol content of approximately 400 mg/day and a polyunsaturated/saturated fatty acid ratio of approximately 1:0. Apo A-1 kinetics were measured during the last 2 weeks of each dietary period. The composition and distribution of high-density lipoproteins (HDL), subclasses HDL2 and HDL3, were determined at the end of each dietary term. In the HTG patients, administration of a 40% compared with 55% CHO diet caused a significant decrease of plasma triglyceride levels and an increase of HDL-cholesterol; low-density lipoprotein (LDL) levels increased and very low-density lipoprotein (VLDL) levels decreased (P less than 0.01 and less than 0.07, respectively). Similar quantitative changes of VLDL and HDL levels were found in the normolipidemic subjects. No significant change in plasma levels of apo A-I, A-II and E occurred. Apo A-I kinetic studies revealed decreased synthetic rates and fractional catabolic rates on the low CHO diet. Separation of HDL subfractions by zonal ultracentrifugation in both groups revealed an increase in HDL3-cholesterol ester and protein, and a decrease in HDL2 protein, phospholipid and cholesterol. Our findings indicate that moderate changes in dietary CHO and fat content affect HDL levels, composition and apo A-I metabolism.

Change in very low-, low-, and high-density lipoproteins during lipid lowering (bezafibrate) therapy: studies in type IIA and type IIb hyperlipoproteinaemia

The effects of lipid lowering therapy (bezafibrate) on plasma lipoproteins was investigated in twelve patients with familial hypercholesterolaemia (type IIA) and eight with familial combined hyperlipidaemia (type IIB). Bezafibrate caused a decrease of plasma cholesterol, plasma triglycerides, plasma apolipoprotein B, VLDL cholesterol and LDL cholesterol and an increase of HDL cholesterol. Post-heparin plasma lipoprotein and hepatic lipase activities increased in both groups (significant only in type IIB). Lipoprotein composition showed the following changes: Increased protein and phospholipids and decreased triglycerides and cholesteryl esters in VLDL. Decreased protein and triglycerides and increased free and esterified cholesterol in LDL. Decreased triglycerides and increased phospholipids in HDL. Cholesteryl ester to protein ratios decreased in VLDL and increased in LDL. The hydrated density of LDL (both groups) and of HDL3 (type IIB) decreased following bezafibrate therapy. These changes were in general similar to those observed in hypertriglyceridaemic patients and could be ascribed, at least in part, to the increase of plasma lipase activities and the decrease of lipid transfer reactions. Comparing the present data with that previously reported, it was found that bezafibrate caused decreased LDL cholesterol in types IIA and IIB but increased levels in type IV. This change was correlated with the initial plasma triglycerides (r = 0.74, P less than 0.0001) and initial plasma LDL cholesterol (r = 0.66, P less than 0.001). It is concluded that varied response of LDL to therapy reflects a complex interaction of metabolic events, including changing rates of VLDL conversion to LDL, lipoprotein compositional changes and effects of therapy on LDL degradation rates.