Israel Medical Association Journal

Background: In lipid oxidation kinetics studies, prevalent cardiovascular disease has been associated with shortened lag phase, the length of time preceding the onset of oxidation.

Objectives: To examine, in vitro, copper-induced lipid oxidation kinetics in unfractionated serum from hemodialysis patients and to determine differences in kinetic parameters between patients with and without a history of CVD[1].

Methods: Of the 76 patients enrolled in a study of oxidative stress in hemodialysis (44/76 with prevalent CVD, 53/76 males), 9 males with a history of myocardial infarction were selected and matched for age, diabetes and smoking status with 9 males from the non-CVD group. The kinetics of lipid oxidation was studied. Blood chemistry determinations including serum lipids, lipoproteins, hemostatic factors and serum malondialdehyde were obtained. Variables were compared using the t-test for independent samples with history of MI[2] entered as the categorical variable.

Results: Tmax, the oxidation kinetic parameter defined as the time at which the rate of absorbing product accumulation was maximal, was significantly shorter in dialysis patients with a history of MI than in those without (115.2 ± 38.5 vs. 162.7 ± 48.9 minutes, P = 0.04). Further, Tmax and MDA[3] were negatively correlated to one another (r = -0.47, P = 0.04). Odds ratios indicate that each 1 minute increase in Tmax was associated with a 3% decrease in odds that a subject had a history of MI.

Conclusions: These findings indicate the presence of increased oxidative stress in hemodialysis patients with a history of MI.

Background: Decreased elasticity of the aorta is associated with aging and several risk factors of atherosclerosis. The data regarding this phenomenon in patients with familial hypercholesterolemia are rather sparse.

Objectives: To evaluate non-invasively the elasticity of the proximal ascending aorta of 51 heterozygous FH[1] patients compared to 42 normal age and gender-matched controls.

Methods: Aortic elasticity was estimated by transthoracic echocardiography using the “pressure-strain” elastic modulus and aortic strain formulas.

Results: The elastic modulus score was higher in the FH group than in the controls (1.12 ± 0.91 10⁶ dynes/cm² vs. 0.65 ± 0.46 10⁶ dynes/cm² respectively, P = 0.01). This was consistent in both the pediatric (0.5 ± 0.2 10⁶ dynes/cm² vs. 0.4 ± 0.1 10⁶ dynes/cm² respectively, P = 0.009) and adult subgroups (1.3 ± 1.0 10⁶ dynes/cm² vs. 0.8 ± 0.5 10⁶ dynes/cm² respectively, P = 0.0004). Aortic strain was significantly lower in patients with FH than in controls (6 ± 4% vs. 9 ± 5% respectively, P = 0.0002). These findings reflected decreased elasticity of the proximal ascending aorta in the FH patients. In multivariate analysis, age, serum cholesterol level and serum triglycerides level were the independent predictors of the elastic modulus score, whereas age was the predictor of aortic strain.

Conclusions: The elasticity of the proximal ascending aorta is decreased in heterozygous FH patients.

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.

____________________________________

VLDL= very low density lipoprotein

LDL= low density lipoprotein