Effect of oestradiol on catecholamine-stimulated lipolysis

The authors studied the effect of a single in vivo dose of oestradiol (OE) on adrenergic lipolysis in the epididymal adipose tissue of adult and juvenile male rats, and the effect of OE on plasma free fatty acids (FFA), cholesterol and beta-lipoprotein levels at various intervals after its administration. It was found that OE injected 24 h beforehand in vivo (s.c.), in doses of 100 and 200 micrograms X kg-1 body weight, significantly potentiated the lipid-mobilizing action of the catecholamines noradrenaline (NOR) and isoprenaline (ISO) in adult rats (the action of ISO was potentiated more intensively); in addition, the adipose tissue became more sensitive to the action of NOR, but not of ISO. Raising the dose of OE to 400 micrograms X kg-1 did not enhance the potentiation of the lipolytic action of the catecholamines any further; on the contrary, the lipid mobilizing effect of the catecholamines was potentiated less than after half this dose. Following the s.c. injection of an oily OE solution, the lipolytic effect was potentiated after more than 7 h; the potentiation was strongest after 12 h, but only as far as the maximum attainable degree of lipolysis was concerned. Potentiation of adrenergic lipolysis was found only in adult male rats. In male rats weighing 130-150 g the lipolytic effect of catecholamines (in mumol/g adipose tissue) was significantly greater than in adult animals and the pre-administration of OE did not potentiate adrenergic lipolysis any further. Determination of plasma FFA, cholesterol and beta-lipoprotein levels 1, 2, 4 and 6 hours after the s.c. injection of OE showed only nonsignificant changes (an increase in FFA and a decrease in cholesterol). The authors consider it important to distinguish between the effect of OE on catecholamine-stimulated lipolysis in depot adipose tissue and its effect on lipid metabolism. In their opinion, the dose-dependent effect of OE on muscular and metabolic adrenergic reactions could be one of the factors co-reversible for certain side reactions to steroid contraceptives.     

Effect of nitric oxide donors on isoprenaline-induced lipolysis in rat epididymal adipose tissue: studies in isolated adipose tissues and immobilized perfused adipocytes

The present investigation was directed to study the effect of in vitro or ex vivo NO donors, sodium nitroprusside and molsidomine, using isolated sliced adipose tissue or in the form of immobilized and perfused adipocytes on the basal and isoprenaline-stimulated lipolysis. The results demonstrated that 1) in vitro application of sodium nitroprusside to perfused adipocytes or molsidomine to sliced adipose tissues affects isoprenaline-induced lipolysis in two ways, an increase in lipolysis at low isoprenaline concentrations (which means the sensitization of adipose tissues to adrenergic effect by NO) and decreased adrenergic agonist-stimulated lipolysis at higher concentration of isoprenaline (a decrease in the maximum lipolytic effect of isoprenaline), 2) low concentrations of molsidomine alone induced lipolysis from adipose tissue which attained more than 60% of that by isoprenaline (pD2 value for molsidomine = 11.2, while pD2 for isoprenaline = 8.17) while sodium nitroprusside did not affect the basal lipolysis significantly, 3) in vivo administration of molsidomine for 2 days reduced the maximum lipolytic effect of isoprenaline and (only non-significantly) increased the sensitivity to low doses of isoprenaline. In conclusion the present data demonstrate that NO plays an important role in adrenergic lipolysis in adipose tissues and further investigations are needed to unravel the exact role of NO in lipolysis.     

Effect of hypothermia on lipolytic processes in blood and adipose tissue of rat

Short-lasting hypothermia raises the FFA level in the blood and this rise is associated with increased lipid-mobilizing activity and higher lipolytic activity of the serum. Raised FFA level and increased lipid-mobilizing activity of the serum persist even when the degree of general anaesthesia is sufficient for preventing thermogenesis signs (shivering and piloerection) caused by falling body temperature. Beta-adrenergic blockade fails to abolish the effect of lipolysis activation caused by hypothermia. These observations suggest that during hypothermia in the blood of the animals appear factors stimulating lipolysis in the adipose tissue. One of these factors may stimulate tissue lipolysis independently of beta-adrenergic receptors. Insulin blocks significantly lipolytic processes in the adipose tissue of hypothermic animals, but its administration is connected with the danger of hypoglycaemia development.     

Regional adipose tissue metabolism in postmenopausal women after treatment with exogenous sex steroids

In order to evaluate the effect of exogenous sex steroids on adipose tissue metabolism, two groups of postmenopausal women were studied. In one of the groups, the effect of 50 micrograms ethinyl estradiol (EE) was investigated given orally alone and in combination with 10 mg norethisterone acetate (NET). This combination is reminiscent of an old high dose oral contraceptive. In the other group, the effect of 3 mg 17 beta-estradiol was evaluated when administered percutaneously alone and in combination with 300 mg micronized progesterone given orally. These substances and doses were chosen to provide a "physiological" hormonal influence. In the femoral region 50 micrograms EE induced an increase in LPL activity. This elevated LPL value was reversed with the addition of 10 mg NET. Moreover, during treatment with 50 micrograms EE, a decrease in norepinephrine stimulated lipolysis was seen in the abdominal region. The percutaneous administration of 17 beta-estradiol with or without micronized progesterone, however, was inert as regards subcutaneous adipose tissue metabolism. Our findings indicate, therefore, that EE in doses used in oral contraception might promote lipid accumulation in the femoral adipose tissue depot.     

Biogenic Amine-Stimulated Cyclic Adenosine-3'',5''-Monophosphate Formation in the Rat Carotid Body

The subcutaneous injection of isoprenaline, salbutamol, histamine, and adrenaline to rats, which were subsequently killed by microwave irradiation, resulted in a rapid increase in the cyclic AMP content of the carotid body. On the other hand, noradrenaline, dopamine, adenosine, and 5-hydroxytryptamine, at doses at least 100 times greater than that of isoprenaline, did not significantly alter the cyclic nucleotide content in vivo. The response to isoprenaline was dose related, with an ED50 of 15 micrograms X kg-1, and reached a peak level 1-1.5 min after injection. Incubation of intact carotid bodies with isoprenaline (10(-5) M) in vitro also resulted in a 10-fold increase in cyclic AMP content. The in vivo response to isoprenaline could be blocked stereo-selectively by propranolol, and ICI 118.551, a beta 2-selective antagonist, blocks the isoprenaline-elicited increase in cyclic AMP completely at a dose of 30 micrograms X kg-1; whereas betaxolol, a beta 1-selective antagonist, was ineffective, even at a dose of 300 micrograms X kg-1. Hypoxia (5% oxygen in 95% N2) did not result in a significant increase in the cyclic AMP content, nor did it significantly alter the isoprenaline-stimulated increase in the cyclic AMP content of the rat carotid body. These results suggest that some catecholamines may stimulate cyclic AMP formation by interacting with a beta 2-adrenoceptor in the rat carotid body.     

Glucocorticoids suppress and oestrogens enhance the lipopolysaccharide-induced increase in putrescine and N1-acetylspermidine in mouse liver

Previously we reported that administration of lipopolysaccharide (LPS) to mice increased the hepatic levels of putrescine (PUT) and N¹-acetylspermidine (N¹-acetyl-SPD). In the current study, we examined the in vivo effects of some steroid hormones on the LPS-induced increase in PUT and N¹-acetyl-SPD. Corticosterone, hydrocortisone and dexamethasone suppressed the LPS-induced increase in PUT and N¹-acetyl-SPD in mouse liver in a dose-dependent manner, dexamethasone being the most effective among them. On the other hand, oesterone and oestradiol-17β enhanced the LPS-induced increase in PUT and N¹-acetyl-SPD in a dose-dependent manner. Oestradiol-17 and 16β-ethyl-oestradiol, as an inactive oestradiol isomer and an antioestrogen, respectively, likewise enhanced the increase in PUT and N¹-acetyl-SPD concentrations induced by LPS. 16-hydroxy-oestradiol (oestriol), 16-hydroxyestrone, 2-hydroxyoestradiol, 2-hydroxyoestrone, progesterone, testosterone, diethylstilboestrol and nonsteroidal antioestrogen such as tamoxifen and nafoxidine had no effect on the increase. Oestradiol-17β enhanced and corticosterone had little on the carbon tetrachloride-induced increase in PUT and N¹-acetyl-SPD. These results suggest that glucocorticoids suppress the increase by preventing the immunological injury by Kupffer cells on hepatocytes and that the stimulatory effect of oestrogens may not be associated with their oestrogenic activities mediated by the oestrogen receptor system.     

In vitro lipolytic effect of bovine pituitary diabetogenic protein

Bovine diabetogenic protein has been further purified by gel filtration yielding a fraction (M_r 25 000–28 000) having increased diabetogenic and in vitro lipolytic activity. Using rat epididymal fat pads, this fraction was shown to be lipolytic at concentrations as low as 1–10 μg/ml. The in vitro lipolytic effect was unaffected by the nutritional state of the animals, was not potentiated by dexamethasone, could be demonstrated in the presence and absence of glucose and was not mediated by α- and β-adrenergic receptors. A lag phase of > 1 h was observed before diabetogenic protein induced lipolysis occurred, suggesting that protein synthesis might be involved. Cycloheximide (10 μg/ml), added initially, prevented the diabetogenic protein-induced lipolysis. This direct effect of the purified protein on adipose tissue helps explain the elevation of free fatty acids seen when bovine diabetogenic hormone is administered in vivo and suggests that this anterior pituitary protein may be a new lipid-mobilizing hormone.     

Lipolytic activity of purified pituitary and bacterially derived growth hormone on chicken adipose tissue in vitro

The ability of growth hormone (GH) to stimulate lipolysis was examined using chicken abdominal adipose tissue explants incubated in vitro and purified pituitary and bacterially derived chicken and bovine GH. Consistently in the fourth hour of incubation, lipolysis (as determined by glycerol release) was increased by the presence of GH (1 micrograms/ml), irrespective of pituitary or bacterial derivation or of chicken or bovine origins. This effect of GH was observed with adipose tissue originating from young (6-8 weeks old) intact and hypophysectomized chicks and adult (6-9 months old) male chickens. Glycerol release was also enhanced by lower doses of GH (10 ng/ml with tissue from young and 100 ng/ml with tissue from adult chickens).     

Nuclear oestrogen receptors in rat liver. Development of assay conditions, characterization and the translocation of oestrogens in vivo.

A method for the determination of specific oestrogen-receptor binding sites in rat liver nuclei is described. Nuclear receptors showed a high affinity for oestradiol (Kd approximately 3 x 10(-9)M), a low capacity, and a distinct specificity for substances with known oestrogenic and anti-oestrogenic activity. No sex differences were seen in the concentrations of nuclear receptors from either vehicle- or ethynyloestradiol-pretreated rats. Only a limited number of binding sites could be extracted with 0.4 M-KCl. The remaining sites, which were solubilized by sonication and treatment with deoxyribonuclease I, sedimented at 3-4 S. Of four oestrogens tested (oestradiol, ethynyloestradiol, diethylstilboestrol, tri-p-anisylchloroethylene), ethynyloestradiol was the most effective translocation agent in vivo, nuclear uptake occurring at doses below 1 microgram/rat; changes in salt extractability of nuclear receptors occurred at doses lower than those required to achieve absolute increases in nuclear receptor concentrations.     

Reduction of adrenaline-dependent lipolysis in the adipose tissue of adrenalectomized dogs by an alpha adrenergic effect]

In dog, surrenalectomy reduces isoprenalino-depending lipolysis but still more adrenalino-depending lipolysis. Phentolamine potentializes the response to adrenaline but does not that observed with isoprenaline. Surrenalectomy unmasks an alpha adrenergical effect of adrenaline on adipocytes of dog adipose tissue.     

Mannose, glucosamine and inositol monophosphate inhibit the effects of insulin on lipogenesis. Further evidence for a role for inositol phosphate-oligosaccharides in insulin action.

The mechanism of insulin signalling is not yet understood in detail. Recently, a role for inositol phosphate (IP)-oligosaccharides as second messengers transmitting the insulin signal at the post-kinase level was proposed. To evaluate this hypothesis further, we studied whether IP-oligosaccharides isolated from 'haemodialysate' have insulin-like activity. We found that these compounds mimic, in a dose-dependent fashion, the following effects of insulin in adipocytes. (1) Lipogenesis. Incorporation of [3H]glucose into lipids (expressed in nmol/min per 10(6) cells): basal, 0.74 +/- 0.05; insulin (1 mu unit/ml), 4.43 +/- 0.21; IP-oligosaccharide (2 micrograms/ml), 4.07 +/- 0.19. (2) Inhibition of isoprenaline (isoproterenol) (1 microM)-stimulated cyclic AMP levels and lipolysis. Cyclic AMP (pmol/10(5) cells): basal 0.84 +/- 0.05; isoprenaline, 4.03 +/- 0.19; isoprenaline + insulin (200 mu units/ml), 2.06 +/- 0.7; isoprenaline + IP-oligosaccharides (2 micrograms/ml), 2.4 +/- 0.29. Inhibition of lipolysis (mumol of glycerol/mg of protein): isoprenaline (1 microM), 166 +/- 11; isoprenaline+insulin (150 mu units/ml), 53 +/- 3.5; isoprenaline+IP-oligosaccharides (2 micrograms/ml), 58 +/- 5. (3) Stimulation of 3-O-methylglucose transport; basal, 9 +/- 3%; insulin (1 mu unit/ml), 67 +/- 4%, IP-oligosaccharides (2 micrograms/ml), 54 +/- 2%. To identify the active molecules of the IP-oligosaccharide fraction, competition experiments were performed. IP-oligosaccharide effects on lipogenesis were blocked by inositol monophosphate, glucosamine and mannose. In contrast, these compounds did not inhibit IP-oligosaccharide effects on membrane-mediated functions (3-O-methylglucose transport, cyclic AMP levels, lipolysis). We also found that the effect of insulin on lipogenesis was blocked by mannose, glucosamine and inositol monophosphate, whereas the insulin effects on 3-O-methylglucose, cyclic AMP and lipolysis were unaffected. The following conclusions were reached. (1) IP-oligosaccharides mimic the major metabolic effects of insulin in adipocytes. This is consistent with the proposed role of IP-oligosaccharides as second messengers of certain insulin effects. (2) Mannose and glucosamine are functionally important sugar residues for the effect of IP-oligosaccharide on lipogenesis. (3) The observation that mannose, inositol monophosphate and glucosamine block the action of insulin of on lipogenesis supports a role of mannose- and glucosamine-containing IP-oligosaccharides as second messengers for this insulin effect.     

Monohydroxytamoxifen: an antioestrogen with high affinity for the chick oviduct oestrogen receptor

The monohydroxylated derivative of tamoxifen (a non-steroidal triaryl ethylene antioestrogen) shows an apparent affinity (Ki = 0.2 nM) for the chick oviduct oestrogen receptor which is higher than that of oestradiol itself, and ～ 10 times higher than that of tamoxifen. Administered $\text{in}\text{vivo}$ with oestradiol benzoate, it inhibited the increase of tissue growth, progesterone receptor content, ornithine decarboxylase activity (ODC), and ovalbumin and conalbumin synthesis, and also inhibited the oestradiol induced increase of ODC $\text{in}\text{vitro}$. It did not display any oestrogenic effect by itself. We conclude that antioestrogenic action may be exhibited by a molecule with higher affinity binding to the oestrogen receptor than oestradiol itself. Metabolic studies demonstrated that the antioestrogenic action of tamoxifen is not due to its prior conversion to monohydroxytamoxifen.     

Antioestrogenic action of the aldosterone antagonist canrenoate K in the rat (adenohypophysis, ceruloplasmin).

In a dose of 7,k mg/rat/day in food, the aldosterone antagonist canrenoate K inhibited the adenohypophyseal reaction (growth, raised thyroxine-binding capacity of the adenohypophyseal proteins in vitro) and the ceruloplasmin reaction (elevation of the serum ceruloplasmin level) to three weeks' intramuscular administration of long-acting oestradiol benzoate in doses of 1 mg twice a week. The effect was similar to that of the antioestrogen clomiphen in a dose of 1.25 mg/rat/day in food. In combined administration of clomiphen and canrenoate K, no summation of their effect was observed. Neither canrenoate nor clomiphen affected the post-oestradiol drop in body weight, but they both potentiated the oestradiol-induced decrease in testicular weight and canrenoate potentiated the effect of oestradiol on uterine weight. It was therefore concluded that the effect of canrenoate is not of a catatoxic nature, i.e. that it is not determined by increased metabolic degradation of oestradiol.     

The effect of oxidized isoprenaline on the chick embryonic heart

Intra-amnial administration of isoprenaline (IPRO) to chick embryos induces a number of myocardial lesions. The purpose of the present study was to investigate whether similar changes may also be induced after injection of spontaneously oxidized isoprenaline and commercially obtained adrenochrome. Cardiotoxicity of these substances has been demonstrated in adult animals. IPRO, oxidized IPRO, or adrenochrome were administered intra-amnially to 10-day-old chick embryos at doses of 0.1, 1.0, 10.0, and 100.0 mg X kg-1. Parallel experimental groups received propranolol at a dose of 1 mg X kg-1, 15 s before injection of IPRO or oxidized IPRO. The cAMP level in the heart was determined by radioimmunoassay 2 and 30 min after administration of IPRO, oxidized IPRO, or adrenochrome at a single dose of 10.0 mg X kg-1. It has been found that in embryos the effect of IPRO and oxidized IPRO is dose dependent. The rise in mortality and development of cardiomegaly together with increased hydration and disturbances of the development of coronary vascularization were highly significant starting from the dose of 10 mg X kg-1. Furthermore, both drugs significantly increased cAMP levels in the embryonic heart. On the other hand, the administration of adrenochrome was without any effect. The changes induced by IPRO were prevented by the administration of the beta-blocking agent propranolol; the lesions induced by spontaneously oxidized IPRO were, however, prevented only partially.     

Effect of substance P on ethanol consumption in subchronically alcoholized rats in the limited scheduled access paradigm

The effect of substance P on alcohol intake was studied in rats using a limited scheduled access paradigm. Ascending doses of substance P (100 and 200 micrograms/kg) were administered intraperitoneally to rats approximately 30 minute prior to their 1-hour-per-day access to alcohol. Each dose was administered for 3 successive days, and the effect of substance P was compared to that of saline solution control. Substance P at the dose of 100 micrograms/kg had no effect on alcohol consumption but significantly decreased the alcohol intake at the dose of 200 micrograms/kg. Thus, substance P reduces the alcohol motivation of rats in a limited scheduled access paradigm.     

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.     

Glucocorticoids suppress and oestrogens enhance the lipopolysaccharide-induced increase in putrescine and N-acetylspermidine in mouse liver

Previously we reported that administration of lipopolysaccharide (LPS) to mice increased the hepatic levels of putrescine (PUT) and N¹-acetylspermidine (N¹-acetyl-SPD). In the current study, we examined the in vivo effects of some steroid hormones on the LPS-induced increase in PUT and N¹-acetyl-SPD. Corticosterone, hydrocortisone and dexamethasone suppressed the LPS-induced increase in PUT and N¹-acetyl-SPD in mouse liver in a dose-dependent manner, dexamethasone being the most effective among them. On the other hand, oesterone and oestradiol-17β enhanced the LPS-induced increase in PUT and N¹-acetyl-SPD in a dose-dependent manner. Oestradiol-17α and 16β-ethyl-oestradiol, as an inactive oestradiol isomer and an antioestrogen, respectively, likewise enhanced the increase in PUT and N¹-acetyl-SPD concentrations induced by LPS. 16α-hydroxy-oestradiol (oestriol), 16α-hydroxyestrone, 2-hydroxyoestradiol, 2-hydroxyoestrone, progesterone, testosterone, diethylstilboestrol and nonsteroidal antioestrogen such as tamoxifen and nafoxidine had no effect on the increase. Oestradiol-17β enhanced and corticosterone had little on the carbon tetrachloride-induced increase in PUT and N¹-acetyl-SPD. These results suggest that glucocorticoids suppress the increase by preventing the immunological injury by Kupffer cells on hepatocytes and that the stimulatory effect of oestrogens may not be associated with their oestrogenic activities mediated by the oestrogen receptor system.     

Induction of lipolysis in vitro and loss of body fat in vivo by zinc-alpha2-glycoprotein

Loss of adipose tissue in cancer cachexia has been associated with tumour production of a lipid-mobilizing factor (LMF) which has been shown to be homologous with the plasma protein zinc-alpha(2)-glycoprotein (ZAG). The aim of this study was to compare the ability of human ZAG with LMF to stimulate lipolysis in vitro and induce loss of body fat in vivo, and to determine the mechanisms involved. ZAG was purified from human plasma using a combination of Q Sepharose and Superdex 75 chromatography, and was shown to stimulate glycerol release from isolated murine epididymal adipocytes in a dose-dependent manner. The effect was enhanced by the cyclic AMP phosphodiesterase inhibitor Ro20-1724, and attenuated by freeze/thawing and the specific beta3-adrenoreceptor antagonist SR59230A. In vivo ZAG caused highly significant, time-dependent, decreases in body weight without a reduction in food and water intake. Body composition analysis showed that loss of body weight could be attributed entirely to the loss of body fat. Loss of adipose tissue may have been due to the lipolytic effect of ZAG coupled with an increase in energy expenditure, since there was a dose-dependent increase in expression of uncoupling protein-1 (UCP-1) in brown adipose tissue. These results suggest that ZAG may be effective in the treatment of obesity.     

Triglyceride Storage Disease: A Disorder of Lipolysis in Adipose Tissue in Two Patients

An obese patient was studied whose adipose tissue showed a significant reduction in release of glycerol (P < 0·05) when stimulated by isoprenaline despite normal rises in tissue levels of cyclic-AMP. However, lipolysis was stimulated by a fast of 14 days as judged by weight loss and a rise in plasma fatty acids from 0·4 to 1·2 mM. The defect in this patient may be familial since her obese daughter also showed diminished release of glycerol from adipose tissue on three occasions when stimulated by isoprenaline, despite normal rises in levels of cyclic-AMP.     

The development of beta-adrenergic mediated inhibition of growth hormone secretion in the ovine fetus

The ontogeny of the suppressive effect of the beta-adrenergic agonist, isoprenaline, on fetal growth hormone (GH) release was examined in 14 chronically-catheterized ovine fetuses. Isoprenaline was administered as an intravenous infusion over 1 h (200 micrograms/kg). In seven fetuses between 72 and 99 days of gestation, isoprenaline had no effect on fetal plasma GH concentrations. In seven older fetuses between 114 and 140 days of gestation, isoprenaline infusion suppressed (P less than 0.02) fetal GH release. No effect was observed in five saline-treated control fetuses (119-131 days). Propranolol (250 micrograms/kg i.v.) administered 5 min prior to the isoprenaline infusion to four fetuses (117-136 days) delayed (P less than 0.05) the onset of the suppressive effect of isoprenaline demonstrating that the action of isoprenaline was mediated by the beta-adrenergic receptor. Propranolol alone (n = 6) had no effect. These observations demonstrate that the potential for beta-adrenergic inhibition of fetal GH release differentiates after 100 days of gestation. Comparison with previous studies of the ontogenesis of the control of GH secretion suggests that the hypothalamic beta-adrenergic control of GH release differentiates with an intermediate time course compared to other potential neuroendocrine controls.