[Hyperinsulinism, heart rate variability and circadian variation of arterial pressure in obese hypertensive patients]. / Hyperinsulinisme, variabilité de la fréquence cardiaque et variation circadienne de la pression artérielle chez les sujets obèses hypertendus.

AIMS: During insulin resistance, sympathetic nerve activity is increased. However insulin resistance is a common feature of obesity and essential hypertension, it is unclear if chronic hyperinsulinemia per se contributes to sympathetic overactivation. The purpose of our study was to explore++ the relationships between chronic hyperinsulinemia and heart rate variability (HRV), a non-intensive tool to assess autonomic function, in obese and hypertensive subjects. METHODS: 24 hours Holter ECG for HRV time and frequency domain analysis was performed in 77 patients, mean age 53 +/- 10 years, 52 men and 25 women, free of diabetes, without beta-blockers, divided in four groups according to three parameters, body mass index (BMI > 27 kg/m2 in man and > 25 kg/m2 in woman defined obesity), arterial pressure and insulinemia (fasting insulinemia > 25 mUI/L defined hyperinsulinemia): 27 patients obese, hypertensive, with hyperinsulinemia; 28 patients obese, hypertensive, without hyperinsulinemia; 12 patients non obese, hypertensive, without hyperinsulinemia; 10 patients obese, normotensive, without hyperinsulinemia. RESULTS: In comparison with the three other groups, patients with hyperinsulinemia showed a significant decrease (p < 0.05) of SDNN and the power of total spectrum (0.01-1 Hz) band, which are indexes of global HRV, and a significant decrease (p < 0.005) of SD and the normalized power of the low frequency (0.04-0.15 Hz) band, both indexes reflecting sympathetic modulation of HRV. In contrast, no significant difference was observed between the four groups for indexes of HRV reflecting parasympathetic tone. These relations were independent of mean RR. Fasting insulinemia was significantly (p < 0.0001) related with HRV in time domain (SDNN; r = -0.43; SD: r = -0.49) and spectral domain (total spectrum: r = -0.49; low frequency: r = -0.52). CONCLUSION: Chronic hyperinsulinemia appears to be an important determinant of HRV, particularly for the indexes reflecting sympathetic influence, independent of obesity and hypertension.

Study of fluidity of low density lipoproteins from liver cirrhotic patients.

BACKGROUND AND AIM: Liver disease is accompanied by major quantitative and qualitative modifications in plasma lipoprotein metabolism. Alterations in plasma lipoprotein composition and a lower susceptibility to in vitro peroxidation of low density lipoprotein (LDL) and erythrocyte membranes have been observed in liver cirrhosis. The main objective of the present work was to investigate LDL chemical composition and fluidity in liver cirrhosis using the fluorescence polarization (Pf) of the 1,6-diphenyl-1,3,5-hexatriene (DPH) probe. METHODS AND RESULTS: The chemical composition of LDL was studied in 12 cirrhotic patients and 22 controls by conventional methods and its fatty acid composition by gas chromatography. LDL fluidity was determined by measuring the DPH Pf values. A decrease in molecular order was demonstrated by the significant (p < 0.05) decrease in Pf values in the cirrhotics. Modifications in LDL fluidity are correlated with its composition. A significant increase in triglyceride content (p < 0.05), and significant increases in triglyceride/protein and triglyceride/phospholipid ratios were observed in the cirrhotics. CONCLUSIONS: Our results demonstrate that the higher LDL fluidity of cirrhotic patients may be due to an increased triglyceride content.

Metabolic and anti-atherogenic effects of long-term benfluorex in dyslipidemic insulin-resistant sand rats (Psammomys obesus).

Benfluorex is a clinical lipid-lowering agent with antihyperglycemic properties. The effect of long-term oral treatment (10 mg/kg/day for 7.5 months) on carbohydrate and lipid metabolism and aortic morphology was investigated in 24 insulin-resistant sand rats receiving a standard laboratory diet supplemented with cholesterol (2%). Untreated controls (n=34) developed impaired glucose tolerance, hyperinsulinemia, hypertriglyceridemia, hypercholesterolemia and elevated plasma LDL- and VLDL-cholesterol, positively correlated with the proportion of the thoracic aorta displaying oil red O-positive atherosclerosis; ultrastructural examination showed intimal lipid deposits, foam cells, polymorph infiltrates and fibrosis. Benfluorex-treated animals showed significant decreases in glucose intolerance, hyperinsulinemia, hypertriglyceridemia, hypercholesterolemia, and plasma LDL- and VLDL-cholesterol, with no evidence of aortic atheroma. The metabolic benefits of benfluorex may protect against the long-term development of atherosclerosis in the insulin-resistant dyslipidemic syndrome.

S15261, a novel agent for the treatment of insulin resistance. Studies on Psammomys obesus.

S15261 is a novel compound that has been proposed for the treatment of insulin resistance syndrome. We have studied the effects of this drug in insulin resistant sand rats (Psammomys obesus). When sand rats are transferred from their natural desert environment and placed on a laboratory chow diet, they become overweight, develop hypertriglyceridaemia, hypercholesterolaemia, become insulin resistant, and ultimately diabetic. In the present study glucose intolerant animals, with very mild if any hyperglycaemia were used. Chronic treatment for a month with S15261 normalised plasma levels of triglycerides and cholesterol. The effects on cholesterol were the result of a decrease in LDL- and VLDL-cholesterol without any modification of HDL-cholesterol. In this study only female sand rats showed elevated plasma glucose levels, which were normalised by S15261. The compound also decreased plasma insulin levels both in male and female sand rats. An oral glucose tolerance test showed a major improvement in glucose tolerance in both male and female animals treated with S15261. These data confirm in another animal model the therapeutic benefits of S15261 in insulin resistant states.

Increased susceptibility to lipid oxidation of low-density lipoproteins and erythrocyte membranes from diabetic patients.

The aim of the present study was to determine if low-density lipoproteins (LDLs) and red blood cell (RBC) membranes from diabetic patients present an increased susceptibility to lipoperoxidation, which might be related to the increased incidence of atherosclerosis in diabetes. LDLs and RBC membranes were isolated from 11 insulin-dependent (IDDM) and 18 non-insulin-dependent diabetic (NIDDM) patients and exposed to a peroxidative stress by incubation with phenylhydrazine. The susceptibility to peroxidation was determined by measuring the production of thiobarbituric acid-reactive substances (TBARS) after the incubation. The following parameters were also evaluated: plasma glucose, triglycerides (TG), phospholipids (PL), total and high-density lipoprotein (HDL) cholesterol, apolipoprotein (apo) A-I, apo B, hemoglobin A1c (HbA1c), LDL PL and cholesterol, LDL fatty acid composition, and RBC membrane PL and cholesterol. Although they were apparently normolipidemic, diabetic patients showed an increased susceptibility to peroxidation in LDLs and erythrocyte membranes as compared with control subjects. The amount of arachidonic acid in LDLs and the PL concentration of RBC membranes from diabetic patients were significantly higher than in normal subjects. The increased lipoperoxidability of both RBC membranes and LDLs might play a central role in the pathogenesis of the vascular complications of diabetes mellitus.

Reduced Na(+)-K(+)-ATPase activity and plasma lysophosphatidylcholine concentrations in diabetic patients.

A fraction from normal human plasma inhibiting Na(+)-K(+)-ATPase has been recently identified as lysophosphatidylcholine (LPC). The aim of this study was to investigate the existence of a relationship between the activity of the cellular membrane Na(+)-K(+)-ATPase and plasma LPC in human diabetes. We studied 10 patients with insulin-dependent-diabetes mellitus (IDDM), 14 patients with non-insulin-dependent diabetes mellitus (NIDDM), and 10 sex- and age-matched control subjects. Plasma LPC concentrations were increased in both IDDM and NIDDM patients compared with control subjects. Na(+)-K(+)-ATPase activity was reduced in both groups of patients in erythrocyte and platelet membranes. There was a significant correlation between the concentrations of plasma LPC and Na(+)-K(+)-ATPase activity in both erythrocyte and platelet membranes (P < 0.01). To investigate the effect of LPC on the enzyme, Na(+)-K(+)-ATPase activity was determined in erythrocyte membranes obtained from six healthy subjects after in vitro incubation with increasing concentrations of LPC (1-10 microM). Enzymatic activity was significantly reduced by in vitro LPC at a concentration of 2.5 microM, with a further decrease at 5 microM. These data suggest that the decrease in Na(+)-K(+)-ATPase activity in diabetes might be due to increased LPC concentrations.

Susceptibility to in vitro lipid peroxidation of low density lipoproteins and erythrocyte membranes from liver cirrhotic patients.

The aim of the present study was to investigate the susceptibility of low density lipoprotein (LDL) and red blood cell membranes (RCM) from liver cirrhotic patients and control subjects, to the peroxidative stress, induced in vitro by phenylhydrazine. The susceptibility to peroxidation was determined by measuring the formation of the thiobarbituric acid reactive substances (TBARS) after incubation with phenylhydrazine. Moreover the levels of cholesterol (C) and phospholipid (PL) were evaluated in plasma and isolated LDL and RCM. A significant decrease in plasma C, LDL-C and RCM-C content (p < 0.001, p < 0.01 and p < 0.05 respectively) and RCM-PL content (p < 0.01) were found in cirrhotic patients compared to controls. The lower susceptibility to in vitro peroxidation was shown by the TBARS levels significantly lower in LDL and RCM from cirrhotic patients with respect to controls (p < 0.0001 for both of them). Moreover significant positive correlations were found between TBARS-LDL and LDL-C or LDL-PL (r = +0.72, p < 0.0001; r = +0.58, p < 0.001) and between TBARS-RCM and RCM-C (r = +0.35, p < 0.05) or RCM-PL (r = 0.37, p < 0.05) from combined patients and controls. Our data seem to ascribe the lower in vitro peroxidability to the lower levels of plasma lipids.

Effect of desialylation on low density lipoproteins: comparative study before and after oxidative stress.

Aim of our study was to investigate the effect of the desialylation induced by neuraminidase treatment on low density lipoprotein susceptibility to peroxidative stress induced by incubation with copper ions. Our results show that peroxidative stress induces the formation of aggregates that was not observed in desialylated low density lipoproteins. An increase in thiobarbituric reactive substances and a decrease in polyunsaturated fatty acids content have been shown in oxidized LDL. These modifications were less pronounced in oxidized low density lipoproteins previously treated by neuraminidase. The present data suggest a lower susceptibility to peroxidative stress in previously desialylated low density lipoproteins.

Physico-chemical properties of copper-oxidized high density lipoprotein: a fluorescence study.

The modifications of the physico-chemical properties of the high density lipoprotein (HDL) before and after in vitro induced oxidation by copper ions have been studied using the fluorescence polarization (Pf) of the phosphatidylcholine derivative of 1,6-diphenyl-1,3,5-hexatriene (DPH-PC) and of the cationic derivative (TMA-DPH). We have observed that HDL oxidation is associated with a decrease of the molecular order at the lipoprotein surface as demonstrated by the increase in Pf with respect to untreated HDL. Moreover in oxidized HDL the polarity-sensitive probe laurdan has shown a decrease of the polarity in its microenvironment. It has been suggested that a decrease in HDL fluidity would inhibit cholesterol reverse transport from peripheral tissues in form of HDL core cholesteryl esters. Peroxidation of HDL, if occurring in vivo, could contribute to the progress of atherogenesis by decreasing cholesterol efflux from peripheral tissues.

Lower susceptibility of low density lipoprotein to in vitro oxidation in diabetic patients.

The susceptibility to peroxidative stress of low density lipoprotein (LDL), induced by incubation with CuSO4, has been studied in eleven diabetic patients and eleven control subjects. Our results suggest that oxidized LDL (OX-LDL) of diabetic patients have a significant higher reactivity to 2,4,6-trinitrobenzene sulfonic acid (TNBS) than controls, that indicates a lower susceptibility of LDL to oxidative stress. Furthermore using the fluorescence polarization (Pf) of 1,6-diphenyl-1,3,5-hexatriene (DPH) and its phosphatidylcholine derivative (DPH-PC) we have shown that peroxidation induces a decrease of fluidity in OX-LDL of controls and diabetic patients, both at the lipoprotein surface, where is localized DPH-PC and at the interface between lipoprotein surface and core which is probed by DPH.

[Biological reference values in the human fetus. 106 cord blood sampling in utero]. / Valeurs biologiques de référence chez le foetus humain. A propos de 106 ponctions de cordon in utero.

The authors give biological reference figures obtained from 106 fetuses that were sampled in utero between the 20th and 34th week of amenorrhoea. These fetuses were considered to be normal because there was no clinical or ultrasound evidence of an abnormality. Furthermore the biological values sought in antenatal testing and the absence of all pathology in the first year of life, confirmed that these were normal fetuses. The result has been expressed as a global figure for all 106 fetuses; then they have been divided up according to the gestational age groups (20-23, 24-27, and 28-34 weeks of amenorrhoea). These biological reference values and their changes as the age of the fetuses advanced are discussed and compared with the figures reported in the literature.

Desialylated low density lipoproteins and atherosclerosis.

Oxidative modification of LDL is accompanied by a number of compositional and structural changes, now well known. In addition, other atherogenic modifications of LDL exist, such as desialylation. The present article summarizes the recent data related to desialylated LDL and to the presence of these LDL in blood plasma of patients with coronary atherosclerosis. In addition, this review examines the sensitivity of these LDL to peroxidative stress.

[Predictive value of plasma apolipoprotein B in myocardial infarction in young subjects. Correlations with coronarographic data]. / Valeur prédictive de l'apolipoprotéine B plasmatique dans l'infarctus du myocarde du sujet jeune. Corrélations avec les données coronarographiques.

In recent epidemiological studies, apolipoprotein-B (apo B), the main low density lipoprotein (LDL), was found to be significantly elevated in patients with early atherosclerosis. The aim of this study was to compare plasma apo B in a population of men who had suffered myocardial infarction before 45 years of age (N = 31) with a control population (N = 22). In the coronary group, there were 27 angiographies between the end of the first and third month. The plasma lipoproteins were separated by ultracentrifugation, cholesterol and triglycerides measured by enzymatic methods and apo B by Laurell's technique of immunoelectrophoresis. Our results showed significantly higher apo B in the coronary group (p less than 0.05). Serum cholesterol, triglycerides, very low density lipoprotein (VLDL) and LDL cholesterol were also significantly higher whilst high density lipoprotein (HDL) cholesterol was significantly lower. In addition, apo B levels correlated with the severity of the coronary lesions on angiography. Therefore, the plasma apo B level is a good predictive indicator of the presence of early coronary atherosclerosis and its severity.

Determination of apoprotein B in the skin.

To determine the origin of cutaneous cholesterol a method has been developed for extracting and determining by electro-immuno-assay apoprotein B in the skin as already performed by Hoff at the arterial level. This study demonstrated the presence of apoprotein B in the skin and its quantification. The easy and reliable technique employed required only conventional laboratory instruments. Repeatability and reproducibility studies give encouraging results comparable with those obtained on arterial tissue. They show that at least one part of skin cholesterol originates in low density lipoproteins.

[Cutaneous cholesterol in the young and aged coronary patient]. / Le cholestérol cutané du coronarien jeune et âgé.

Serum cholesterol (ch), its lipoprotein fractions and triglycerides were measured in three populations of proven coronary patients (less than 50 years, n = 56; between 50 and 65 years, n = 56; greater than 65 years, n = 23); the risk factor total ch/HDL ch was calculated. The level of skin cholesterol was also estimated by skin biopsy in each patient and compared to that of three control populations of the same age. The results indicated that 1) there was no significant difference in skin cholesterol of patients with myocardial infarction whatever their age, 2) there was a significant difference (p less than 0,001) with control subjects of the same age except in the over 65 population, 3) the total cholesterol was normal in all three groups, 4) the HDL cholesterol of coronary patients over 50 year old was normal and slightly reduced in younger coronary patients, 5) the ratio total ch/HDL ch was increased in coronary patients under 50, but normal after this age, 6) the triglyceride level was higher in the young coronary patients than in those over 50 years old. Four conclusions are drawn: 1) the total Ch/HDL ch ratio is a good indicator of coronary risk in patients under 50 years old but shows less sensitive variations than the level of skin cholesterol, 2) the ch/HDL ch in coronary patients between 50 and 65 years old is normal; the only laboratory finding which correlates with the coronary event is skin cholesterol; after 65 years of age the skin cholesterol stabilises to the same levels as found in control subjects; 3) from the outset, at whatever age infarction occurs, skin cholesterol is increased (about 0,45 mumol/100 ngr of fresh skin), whilst the risk factor is higher in the younger population; 4) skin cholesterol shows less variation in the three coronary groups than the other blood parameters measured. It would therefore appear to be a very discriminating index of coronary atherosclerosis.

Skin cholesterol and skin apoprotein B in atherosclerosis.

In order to quantify the accumulation of apoprotein B in skin we determined the amount of apo B in the skin of atherosclerotic patients using a modified Hoff's method with extraction and electroimmunoassay. Skin biopsies were taken from the lower limbs of nineteen male patients with arteriosclerosis obliterans during revascularization and from the thoracic region of thirty male patients with ischemic heart disease during coronary bypass graft surgery and thirty one male patients with abnormalities of cardiac valves during valvuloplasty. A significant positive correlation between skin apo B and skin cholesterol was found in three groups. Our data support the hypothesis that cholesterol deposit in the skin of patients with atherosclerosis is derived from plasma lipoprotein B and that the content of skin lipids parallels with the development of atherosclerosis in man.

Cutaneous cholesterol and plasma lipoproteins in elderly active and bedridden patients compared with young adults.

This report concerns two groups of elderly patients, one active and the other inactive with cardiovascular histories. Cutaneous and plasma cholesterol (Ch) and the lipoprotein fractions were analyzed in each group and compared with those of a young group. The cutaneous histological ageing type was studied in the three groups. No histological difference was seen to exist between the elderly populations (skin type II), the young group had normal type O skin. A significant difference was seen to exist between the levels of cutaneous Ch of the two elderly groups and that of the young group. Changes in the cutaneous Ch with respect to the ratio (total Ch/HDL Ch) were found to differ in the two elderly groups: the active elderly patients presented a positive correlation as did the young subjects but the inactive patients showed a negative correlation.

Cutaneous cholesterol and plasma lipoproteins in young subjects.

The present report concerns the biochemical and anatomo-pathological study of the skin and the plasma lipoprotein fractions in a young population (average age : 22 +/- 1.5 years). The levels of cutaneous cholesterol and the ratio HDL cholesterol/total cholesterol are closely linked even through the histological structure of the skin is still normal; the level of cutaneous cholesterol giving a good indication of the degree of vascular ageing. The observations confirm the usefulness of measuring these two parameters in the detection of early atherosclerosis.