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.

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.

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.

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.

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).

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.

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.

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.

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).