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At least 19 recordsLinked to original sources
PubMed1992

Alpha-2 adrenoceptors in lipolysis: alpha 2 antagonists and lipid-mobilizing strategies.

The lipid-mobilizing and thermogenic effects of several alpha 2 antagonists were explored. Studies were undertaken in humans and in the dog, which possess fat-cell alpha 2-adrenergic receptors (alpha 2-AR) and beta-adrenergic receptors (beta-AR) that are very similar. Yohimbine (alpha 2-AR antagonist) was used in humans whereas other recent alpha 2 antagonists were used in dogs. Oral yohimbine (0.2 mg/kg) promoted a lasting increment of plasma nonesterified fatty acids (NEFAs) and noradrenaline concentrations without significant action on cardiovascular parameters or insulin secretion. In dogs, a direct correlation between the variations of plasma NEFA and noradrenaline concentrations induced by alpha 2 antagonists (1.2 mmol/kg iv) was observed; a result supporting the relationship between lipolysis and the pharmacologic activation of the sympathetic nervous system. Cardiovascular effects were almost absent whereas a long-lasting thermogenic effect was observed. The lipid-mobilizing effect of alpha 2 antagonists is mainly attributable to the increase in synaptic noradrenaline. The potential interest of alpha 2 antagonists in diet therapy is discussed.

Adrenergic alpha-Antagonists↗
PubMed1992

Importance of beta-adrenoceptor function in fat cells for lipid mobilization.

The role of peripheral catecholamine sensitivity in lipid mobilization was investigated in 78 healthy non-obese subjects by comparing beta-adrenergic regulation of lipolysis in isolated adipocytes with circulating catecholamines and glycerol (lipolysis index). Small intra-individual variations (5-7%) in adipocyte lipolytic beta-adrenoceptor sensitivity (ED50) for isoprenaline were found. However, large inter-individual variations (almost 10(5)-fold) in isoprenaline ED50 were observed in abdominal or gluteal adipocytes, which correlated (r = 0.52) negatively with the resting plasma noradrenaline levels. A correlation was also observed between circulating noradrenaline and adipocyte ED50 for noradrenaline (r = -0.38). In subjects with high (ED50 less than 10(-11) mol l-1) as compared to low isoprenaline sensitivity (ED50 greater than 10(-10) mol l-1) physical exercise induced a two times greater increase in plasma glycerol (P less than 0.01), in spite of a 50% less marked increase of plasma noradrenaline (P less than 0.01). Findings with beta-adrenoceptor mRNA and with total beta-adrenoceptor number or affinity for agonist did not show any strong correlation with the resting plasma noradrenaline level (r less than 0.25). In conclusion, inter-individual variations in beta-adrenoceptor sensitivity and its relation to circulating noradrenaline can be ascribed to specific modulations of either BAR-subtypes or in the postreceptor activation of lipolysis. These variations in adipocyte beta-adrenoceptor sensitivity may participate in the regulation of peripheral nervous activity and play a putative role in lipolysis during exercise when subjects with high beta-adrenoceptor sensitivity increased their ability to mobilize lipids despite a reduced noradrenaline response.

Adipose Tissue↗
PubMed1975

Lipid mobilizing hormones of the hypothalamus and pituitary.

Lipid mobilizing substances (LMS) are present in the hypothalamus and pituitary of mammals and probably are involved in the central neural control of obesity. Most of these have direct lipolytic effects, like lipid mobilizing factor (LMF) and LH-RH from the hypothalamus as well as lipotropin (LPH), melanocyte-stimulating hormone (MSH), corticotropin (ACTH), and growth hormone (GH) from the pituitary gland. Some of the substances, like GH-release inhibiting hormone (GH-RIH), affect lipolysis by secondary actions on pancreatic hormones such as insulin and glucagon. Other hypothalamic hormones, like GH-releasing hormone (GH-RH) may influence lipolysis secondarily through the pituitary hormones (e.g. GH) whose release they control. Regardless of how lipid mobilization is affected, investigations into the problem of obesity should take these LMS into consideration.

Adipose Tissue↗
PubMed1976

Lipid mobilizing activity in the blood of obese patients during prolonged fasting.

Lipid mobilizing activity is lowered in the serum of obese patients. During short-term fasting, this activity increases in non-obese subjects. The present study was concerned with the changes in lipid mobilizing activity in the blood of obese patients during prolonged fasting, and with the behavior of esterified and free fatty acids. Serum levels of free fatty acids in the control subjects were significantly lower than in the obese women. During a 14-day period of complete fasting, levels of free fatty acids increased in all cases. In non-obese subjects this was accompanied by a significant rise in lipid mobilizing acitivity, but in obese subjects no significant change took place in this activity. The findings indicate that high levels of free fatty acids in obese persons during fasting are caused by inhibition of their esterification.

Adult↗
PubMed1991

Plasma catecholamine levels and lipid mobilization induced by yohimbine in obese and non-obese women.

Oral yohimbine administration (0.2 mg/kg) induced lipid mobilization (increase in plasma non-esterified fatty acids, NEFA) in fasting non-obese women (body mass index BMI = 20.2 +/- 0.5, age 35.5 +/- 2.7 years) without significant action on plasma glucose, insulin levels, heart rate or blood pressure during the time-course of the experiment (240 min). Plasma norpinephrine (but not epinephrine) concentrations were increased (100 percent) after oral yohimbine administration. Oral administration of propranolol (40 mg, 60 min before yohimbine) reduced the lipid-mobilizing action of yohimbine (70 percent) during the 60 min following its administration and then totally suppressed its effect until the end of the experimental period (180 min). In fasting obese women (BMI = 36.4 +/- 2.1, age 37 +/- 3.6 years), yohimbine provoked an increase in plasma NEFA levels which was not markedly different from that observed in non-obese subjects. It had no significant effect on plasma glucose, insulin levels, heart rate or blood pressure. Plasma norepinephrine increased in the same proportions. The lipid-mobilizing effect of yohimbine in women is mainly attributable to the increase in synaptic norepinephrine with a resultant increment in lipolysis by beta-adrenergic agonism. In the standard fasting conditions (12 hours) the blockade of the antilipolytic fat cell alpha 2-adrenoceptors seems to be a minor component of the lipomobilizing effect of yohimbine. Morever, when compared with non-obese women, the lipomobilizing effect of yohimbine is not enhanced in obese women.

Administration, Oral↗
PubMed1976

Studies on lipolytic system of human placenta, blood lipids and lipid mobilizing activity in pregnant women and newborns.

Lipolytic activity of human placenta and lipid mobilizing activity (LMA), free fatty acids (FFA) as well as esterified fatty acid (EFA) levels in serum of pregnant women in different periods of pregnancy and in newborn's serum were studied. Lipolytic activity of human placenta is low in the first trimester of pregnancy and increases in samples examined after delivery. The levels of FFA and EFA in blood of pregnant women are significantly increased in the second and third trimester of pregnancy. The newborn's blood lipid level is significantly lower than that in the mother's blood. Lipid mobilizing activity in serum of pregnant women increases especially in the third trimester of pregnancy and is also high in newborn's blood. This may indicate that fatty acids released from newborn's adipose tissue are metabolized as a source of energy.

Adipose Tissue↗
PubMed1992

Effects of nutritional state, insulin, and glucagon on lipid mobilization in rainbow trout, Oncorhynchus mykiss.

The effects of nutritional state, insulin, and glucagon on lipid mobilization were determined in rainbow trout, Oncorhynchus mykiss. In nutritional state experiments, fish were either fed continuously (except 24 to 36 hr prior to experimentation) with commercial trout chow or fasted for 4 weeks. Lipase activity in liver tissue isolated from fasted fish and cultured for 5 hr was greater than that in tissue isolated from fed fish and cultured. The presence of glucose (5.55 mM) in the incubation medium accentuates lipolytic activity in both liver and adipose tissue. Hormone response was assessed both in vivo and in vitro. Salmon insulin was injected into anesthetized fish (fed continuously except 24 hr prior to injections) in 10 microliters of saline/g body weight; final hormone dose was 100 ng/g body weight. Tissue and plasma were sampled 1 and 3 hr after injection. Insulin resulted in depressed plasma FA concentration and reduced hepatic triacylglycerol lipase activity. In vitro effects of hormones were evaluated by incubating liver and adipose tissue pieces in Hanks-MEM. Glucagon (bovine/porcine) directly stimulated lipid breakdown in both liver and adipose tissue. These actions were manifested by enhanced FA and glycerol released into the culture medium and by elevated triacylglycerol lipase activity. Insulin (bovine) generally appeared antilipolytic as this agent inhibited glucagon-stimulated lipase activity and glucagon-stimulated FA release. Furthermore, insulin (in the presence of glucose) reduced net lipolysis, as indicated by glycerol release, compared to control cultures. These results indicate that nutritional state and glucose are important modulators of lipid mobilization and that glucagon and insulin act directly on lipid storage sites to coordinate lipolysis in rainbow trout.

Adipose Tissue↗
PubMed1976

[Lipid-mobilizing activity of a synthetic peptide identical to 33-44 fragment of human growth hormone].

The lipid-mobilizing activity of a synthetic peptide, NH2-Phe-Glu-Glu-Ala-Tyr-Ile-Pro-Lys-Glu-Gln-Lys-Tyr-Ser-Phe-COOH, corresponding to the 31-44 amino-acid sequence of human growth hormone, was studied. The peptide stimulated lypolysis upon administration to fasted rats and during incubation with isolated epidiymal adiposed tissue of rat and perirenal adiposed tissue of rabbit. The lipid-mobilizing effect of the peptide,unlike the corresponding effect of the native growth hormone, developed fast and was markedly pronounced 15-30 min after the incubation was started. Direct dependence between the peptide dose logarithm and the effect studied was observed at concentrations of 0.01-10microng/ml during incubation with rat adipose tissue and at 0.001-0.1 microng/ml during incubation with rabbit tissue.

Adipose Tissue↗
PubMed1977

Effect of different albumin media on the lipid-mobilizing action of sympathicotropic substances in vitro.

The authors studied the effect of adrenotropic substances on lipolysis in rat epididymal adipose tissue in albumin medium in vitro. On using albumins of different origin (human, bovine), the pD2 values for catecholamines differed by more than one order, in correlation to the type of albumin used. The isopropylnorsynephrine pD2 values did not differ. The addition of ascorbic acid (100 microng/ml) raised the catecholamine pD2 values and completely equalized the pD2 values found in both media. The pD2 values for the synephrine derivative did not alter. The propranolol pA2 values were not negatively affected by the addition of ascorbic acid. Ascorbic acid also produced a mild increase in the maximum lipid-mobilizing values obtained with any of the given substances in either medium. It was concluded in the discussion that catecholamines are oxidized at different rates in different albumin media and that this oxidation can be inhibited by adding ascorbic acid. Ascorbic acid likewise mildly stimulates the maximum lipid-mobilizing effect. The authors recommend the addition of ascorbic acid to albumin medium as a regular component for the study of adrenergic lipid mobilization.

Albumins↗
PubMed1977

[Mechanism of the lipid mobilizing effect of etimizol].

The influence of ethymizol on the mobilization of free fatty acids and the role of hormones of the pituitary-adrenal system in the lipolytic effect of this drug was studied in experiments on rats. The lipomobilizing effect of ethymizol was clearly expressed in the intact, hypophysectomized and adrenalectomized rats. The effect of the drug disappears in rats with a simultaneous extirpation of the pituitary and the adrenal glands, but it again manifests itself after hydrocortisone injection to these animals. A conclusion on the presence of direct ethymizol action on the mobilization of fatty acids and on the permissive role of corticosteroids in lipid mobilization effect of ethymizol was made.

11-Hydroxycorticosteroids↗
PubMedDate not supplied

[The effect of hydrocortisone on lipid mobilization].

Acetate-1-C14 was administered to rats 18 hours before the administration of hydrocortisone for the purpose of studying the action of this hormone on lipid mobilization. Blood plasma and adipose tissue lipid content failed to change, but it decreased in the liver. Hydrocortisone accelerated the elimination of the label from lipids of the liver, did not alter the radioactivity of blood plasma lipids and stimulated accumulation of endogenous label in the lipids of adipose tissue. An acceleration of lipid catabolism in the liver and of lipid anabolism in the adipose tissue was accompanied by stimulation of gluconeogenesis in the liver from the endogenous precursors. In discussing the materials the primary role of intensification of gluconeogenesis in the liver in the mechanism of the regulating action of glucocorticoids on lipid metabolism was postulated.

Acetates↗
PubMed1991

Studies of chemotactic factor-induced polarity in human neutrophils. Lipid mobility, receptor distribution and the time-sequence of polarization.

Differences in membrane composition between the anterior and posterior poles of human blood neutrophils on exposure to chemoattractant were studied using a laser microscope, and the effects of attractant concentration and time on the ability of neutrophils to polarize were determined. The findings were as follows. (1) The fluorescein-labelled chemotactic hexapeptide fLeu-Norleu-Phe-Norleu-Tyr-Lys was asymmetrically distributed on polarized cells with the highest concentration at the anterior pole of the cell. (2) Differences in membrane lipid behaviour were studied by fluorescence recovery after photobleaching (FRAP) using the probe 5-N-(octadecanoyl)-aminofluorescein. Recovery curves suggested that the proportion of mobile lipid probe at the anterior pole of the cell was higher than at the posterior. However, no difference was found in the rate of recovery between the two poles. (3) Studies of the time-course of polarization were undertaken using neutrophils in suspension exposed to different isotropic concentrations of fMet-Leu-Phe (fMLP). At low concentrations (less than or equal to 10(-9) M), the cells polarized immediately on exposure to the attractant. At a high concentration (10(-7) M) they assumed multipolar morphologies and polarized very poorly, suggesting that ligand binding was too rapid for the cells to form a dominant pole. At the optimal concentration, 10(-8) M fMLP, the cells assumed irregular, ruffled, morphologies after 30s, but showed an increasing proportion of polarized forms over the next 30 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1975

The relation between lipid mobility and the specific hormone binding of thyroid membranes.

1. The specific binding of thyroid-stimulating hormone to isolated human thyroid membranes was examined under a variety of conditions. 2. In phosphate-saline buffer (in the presence of 0.14 M-NaCl) on increasing the temperature the binding of the hormone is increased, the plots of bound/free hormone against temperature showing a distinct break around 30 degrees C. 3. Detailed analysis showed that the increased binding is associated with an increase in the number of binding sites. 4. The motional characteristics of three membrane-bound fluorescent probes, 2-(9-anthroyl)palmitic acid, 12-(9-anthryl)stearic acid and N-1-naphthyl-N-phenylamine, were also examined as a function of temperature by measuring both fluorescence polarizations and lifetimes. 5. The results indicated that the 'fluidity' of membrane lipids also increased with temperature. The temperature-dependence of this property also shows a change at about 30 degrees C. 6. Bivalent cations decreased both membrane fluidity and hormone binding. 7. Similar correlations were found between the binding of adrenocorticotrophic hormone and the fluidity of the plasma membranes obtained from adrenal-cortical cells, with the discontinuity occurring in this case at 23 degrees C. 8. The possibility of lipid mobility being important in controlling hormone-receptor function is discussed.

Anthracenes↗
PubMed1992

Relationship between membrane lipid mobility and spectrin distribution in lymphocytes.

We have previously established that T and B lymphocytes in situ are remarkably heterogeneous with respect to the cytoskeletal protein spectrin. Since in erythrocytes spectrin is known to play an important role in the regulation of membrane fluidity, lipid organization and lateral mobility of membrane proteins, we have sought to determine if the heterogeneous patterns of spectrin distribution that we have observed are related to possible differences in membrane lipid organization in these various subsets. To this end, we have utilized a fluorescent pyrene-labelled phospholipid as a probe of the lipid lateral mobility and have examined two related T cell systems maintained in vitro, DO.11.10 cells and a spontaneously arising variant, DO.11.10V. In these (and other cloned in vitro systems) we have previously observed that the cells homogeneously express one of the kinds of spectrin distribution patterns observed in situ. Thus the uniformity of staining of these systems permits us to address whether the various patterns of spectrin distribution may be predictive of differences in membrane lipid properties. Here we show that in cells in which there is little or nor spectrin at the plasma membrane (DO.11.10) that the lipids in the plasma membrane are considerably less mobile than in its related variant in which spectrin is diffusely distributed within the cell and at the plasma membrane. From this and previous results, we conclude that differences in the distribution of the cytoskeletal protein spectrin among lymphocytes may be a useful parameter in helping to predict the status of membrane lipid organization.

Cell Line↗
PubMed1975

Role of growth hormone in lipid mobilization stimulated by prolonged muscular exercise in the rat.

The effects of prolonged muscular exercise (swim in tepid water for 60 min) on blood glucose, plasma FFA and R-GH were studied in a group of normal rats and the effect on blood glucose and plasma FFA in a group of hypophysectomized rats. The data obtained showed that, whereas in normal rats plasma FFA rose after muscular exercise, plasma R-GH fell sharply. In Hypophysectomized rats, however, muscular exercise did not increase plasma FFA levels.

Animals↗