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At least 19 recordsLinked to original sources
PubMed1976

Abnormalities in the adrenergic control and the rate of lipolysis in isolated human subcutaneous adipose tissue in diabetes mellitus.

Subcutaneous adipose tissue was obtained from 9 patients with untreated diabetes mellitus and from 13 obese nondiabetics. After incubation with isoprenaline or noradrenaline, glycerol release and tissue cyclic AMP (cAMP) were determined. Basal glycerol release was twice as rapid from the diabetic adipose tissue. With isoprenaline, the cAMP concentration and the glycerol production was significantly higher in the diabetic adipose tissue. Noradrenaline did not increase glycerol production or cAMP concentration in the diabetic adipose tissue. Subcutaneous adipose tissue was also removed from the diabetics after antidiabetic treatment. Basal lipolysis was significantly reduced and noradrenaline significantly increased both glycerol release and cAMP production. With isoprenaline, cAMP production and glycerol release were significantly less after antidiabetic treatment than in the untreated state. The data provide evidence for increased alpha- as well as beta-adrenergic receptor sensitivity in human subcutaneous adipose tissue of untreated diabetic patients.

Adipose Tissue↗
PubMed1977

Changes in ATP and cyclic nucleotide levels during sympathetic nerve stimulation in canine subcutaneous adipose tissue in situ.

Subcutaneous adipose tissue in fed, female dogs was isolated. Biopsies of the tissue (30-150 mg) were taken and rapidly frozen in liquid nitrogen before, during and after nerve stimulation (3-4 Hz). In unstimulated adipose tissue the levels of ATP1 were 74+/-7 nmol/g, of cyclic AMP 90 +/- 12 pmol/g and of cyclic PGMP 18 +/- 3 pmol/g (mean+/-S.E.). During sympathetic nerve stimulation the levels of ATP and cyclic GMP fell by 30 and 50% respectively (p less than 0.01), while the cyclic AMP content increased by 50% (p less than 0.05). After nerve stimulation there was a marked increase in glycerol release, and the levels of all three nucleotides returned to control. The fall in ATP during nerve stimulation was essentially eliminated by prior adrenergic alpha-receptor blockade. It is concluded that 1) sympathetic nerve stimulaton induces a rapid, reversible fall in tissue ATP content, which may be related to hypoxia secondary to the vasoconstriction, and 2) lipolytic responses to sympathetic nerve stimulation in vivo are preceeded by small increases in the tissue cyclic AMP level, and a 3-fold increase in the cyclic AMP/cyclic GMP ratio.

Adenosine Triphosphate↗
PubMed1976

Oxygen uptake and tissue oxygen tension during adrenergic stimulation in canine subcutaneous adipose tissue.

The effect of sympathetic nerve stimulation (NS) and injected noradenaline (NA) or isoprenaline (Iso) on PVO2, VO2 and PtO2 was studied in isolated canine subcutaneous adipose tissue. These effects were compared to those produced by mechanical blood flow reduction (clamping). Resting VO2 measured 13.0+/- 2.3 mumol X min-1 X 100 g-1. When blood flow was reduced by 20% or less there was no significant change of VO2. Reducing blood flow to 50% of control or less by NS caused a parallel reduction in VO2, while clamping reduced VO2 significantly less. NA gave effects similar to those of NS. After NS or NA there was a period of hyperemia and increased oxygen extraction which more than compensated for the decrease in VO2 during vasoconstriction. Such a net increase in VO2 was not produced by clamping. Control PtO2 averaged 29+/-2 mmHg. NA reduced it by 70% and clamping to the same blood flow level only by 14% (p less than 0.01). Thus, a mere reduction in blood flow has little effect on PtO2, while blood flow reduction combined with redistribution of blood flow and an increased oxygen deman can lead to tissue hypoxia.

Adipose Tissue↗
PubMed1978

[Absence of lipolytic action of adrenaline on a human subcutaneous adipose tissue. Role of alpha-adrenergic receptors].

Epinephrine cannot stimulate adipocytes' lipolysis of human subcutaneous adipose tissue (lateral part of the thigh) while a clear lipolytic action can be shown on the omental tissue. However, at the same concentrations, isoproterenol (a beta-agonist) exerts a strong adipokinetic effect on adipocytes of the both types of adipose tissue. An alpha-adrenolytic (phentolamine) enhances the lipolytic action of epinephrine on the omental adipose tissue and unmasks a lipolytic action of epinephrine on the subcutaneous. Epinephrine antagonizes the lipolysis induced by theophyline on the subscutaneous adipocytes, this action is increased by propranolol (a beta-adrenergic blocking agent). The unresponsiveness to epinephrine of the subcutaneous adipose tissue studied here could be linked to a strong antilipolytic alpha-adrenergic effect.

Adipose Tissue↗
PubMed1978

Comparison of beta-adrenoceptors mediating vasodilatation in canine subcutaneous adipose tissue and skeletal muscle.

Blood flow changes in response to various drugs in simulataneously autoperfused canine subcutaneous adipose tissue and gracilis muscle were compared to study the vascular beta-adrenoceptors. Compared to isoprenaline the beta 2-selective agonist salbutamol was 4--6 times more potent as a vasodilator in the muscle than in adipose tissue. Furthermore two beta 1-selective agonists (Tazolol and H80/62) caused vasodilatation in adipose tissue but not in the gracilis muscle. When given by close i.a. injection after beta-adrenoceptor blockade, adrenaline was a more potent vasoconstrictor than noradrenaline in both tissues. Before beta-blockade, however, noradrenaline was the more potent vasoconstrictor in the gracilis muscle whereas adrenaline was more potent in adipose tissue. Intravenous infusion of adrenaline in doses causing vasodilatation in the muscle caused vasoconstriction in adipose tissue whereas intravenous infusion of noradrenaline caused vasoconstriction in both tissues. The present findings suggest that the beta-adrenoceptors mediating vasodilatation in skeletal muscle are mainly ose tissue. Since adrenaline is a much more potent beta2- than beta1-agonist, these differences point to different roles of intravascular adrenaline in the two sites. In skeletal muscle circulating adrenaline is mainly a vasodilator whereas in subcutaneous adipose tissue it mainly acts as a vasoconstrictor.

Adipose Tissue↗
PubMed1978

Hexokinase isozymes of normal human subcutaneous adipose tissue.

The isozymes of hexokinase in surgical specimens of human subcutaneous adipose tissue were separated by elution from DEAE-cellulose with linear KCl gradients at ph 7.4. Two peaks of activity were found: Peak 1 eluted at 0.05M KCl, and Peak 2 at 0.19M KCl. Michaelis constants (Km) for glucose were: Peak 1, 6.5 x 10-5M; Peak 2, 1.5 x 10-4M. Peak 2 was more susceptible than Peak 1 to inactivation by trypsin, 0.1 mg/ml, and was protected by 0.1M glucose. Both peaks were protected from heat inactivation (45 degrees) by 0.1M glucose. Peak 2 comprised 66 +/- 5 percent of the total hexokinase activity. No activity with the characteristics of hexokinase III was detected in human fat. In all these characteristics, the isozymes of human adipose tissue closely resemble hexokinases I and II from rats.

Adipose Tissue↗
PubMed1979

Identification of methyl-branched fatty acids from the triacylglycerols of subcutaneous adipose tissue of lambs.

A concentrate of branched chain fatty acids (as methyl esters) was prepared from the triacylglycerols of subcutaneous adipose tissue lipids of lambs receiving a carbohydrate-rich (cereal diet). This was accomplished by procedures which allowed the removal of unsaturated components by peroxidation and straight chain saturated components by urea-adduct formation. The concentrate was analyzed by high resolution gas chromatography in combination with mass spectrometry and was shown to consist of a complex mixture of saturated methyl-substituted fatty acids. Methyl substitution occurred on even-numbered carbon atoms (relative to the carboxyl group) and the chain lengths of the acids ranged from 10 to 18 carbon atoms. Acids with one methyl substituent in the fatty acyl chain were most abundant; di-, tri- and tetramethyl-substituted acids were also present. The biosynthesis of these methyl-substituted acids is discussed briefly.

Adipose Tissue↗
PubMed1977

Exposure to methylene chloride. Content in subcutaneous adipose tissue.

The fat content of the body was calculated in 12 healthy male subjects aged 21 to 35 years by means of hydrostatic weighing and anthropometric estimation of skeletal weight. The subjects were exposed to a concentration of 2,600 mg of methylene chloride per cubic meter of inspired air (750 ppm) for 1 h while performing work at an intensity of 50 W on a bicycle ergometer. The uptake in the organism was measured continuously with the Douglas bag technique. The amount of methylene chloride absorbed correlated highly with degree of obesity and body weight. Needle biopsy specimens of subcutaneous adipose tissue were taken from the buttocks before exposure and 0, 1, 2, 3 and 4 h after exposure. The mean yield of tissue from the 72 biopsies was 25 mg. The concentration of methylene chloride in the adipose tissue was determined by gas chromatography, using a headspace method. The mean concentration was 10.2 mg/kg 1 h after exposure and 8.4 mg/kg after 4 h. There was a wide distribution around the mean values. In the six slim subjects the concentration in the adipose tissue during the 4 h after exposure was on an average twice that of the six more obese subjects. On the other hand, in spite of lower concentrations, the obese subjects had a greater calculated amount of methylene chloride in the total fat depots of the body. Two subjects were studied about 22 h after exposure, the concentration in subcutaneous adipose tissue being 1.6 and 1.7 mg/kg, respectively, at that time.

Adipose Tissue↗
PubMed1978

Vascular and metabolic responses to adrenergic stimulation in isolated canine subcutaneous adipose tissue at normal and reduced temperature.

1. The circulatory and metabolic effects of temperature reduction were studied in autoperfused canine subcutaneous adipose tissue in situ. 2. Cooling the adipose tissue sufficiently to reduce venous effluent temperature by 5--6 degrees C decreased blood flow from an average of 6.4--4.1 ml. min-1 . 100g-1. 3. Vasoconstrictor responses to sympathetic nerve stimulation (4 HZ) and injected noradrenaline (5 n-mole) were potentiated by cooling while vasodilator components of the vascular responses, such as autoregulatory escape and post-stimulatory hyperaemia, were virtually abolished by this treatment. 4. Oxygen uptake was reduced by cooling without signs of tissue hypoxia. This reduced oxygen demand may partly cause the decrease in adipose tissue blood flow. 5. Cooling inhibited glycerol mobilization from the adipose tissue during sympathetic nerve stimulation. Post-stimulatory lipolysis was, however, not inhibited. In vitro studies with 'perifused' rat fat cells suggest that this may be due to impaired inactivation of the lipolytic process, rather than to changes in transmitter removal, following stimulation at low temperature. 6. Cooling inhibited the mobilization of fatty acids more than that of glycerol, suggesting increased re-esterification of fatty acids within the tissue at low temperature. 7. It is concluded that cooling increases the sensitivity to vasoconstrictor stimuli and that inhibition of metabolic vasodilator mechanisms play a role for this effect. The stimultaneous inhibition of activating and inactivating mechanisms could explain the unchanged vascular and lipolytic responses to brief stimuli. Some possible implications of the present findings for the physiology of adipose tissue during cooling are discussed.

Adipose Tissue↗
PubMed1977

Effect of reflex stimuli on vascular resistance and glycerol release in in vivo dog subcutaneous adipose tissue.

Although direct autonomic nerve stimulation and infusion of catecholamine has been shown to result in substantial amounts of lipolysis in dog subcutaneous adipose tissue, there is no evidence to indicate that reflex autonomic stimulation will result in qualitatively and quantitatively similar changes. The present studies were performed to evaluate the effects of reflex autonomic stimulation on vascular resistance and glycerol release in isolated, innervated and blood-perfused subcutaneous fat pad. Autonomic nerve stimulation at physiological frequencies was performed and resulted in release of glycerol that was compatible with previously reported data. Reflex stimulation by moderate and severe hypoxemia did not result in a significant glycerol release, but a maximal reflex stimulus (ventricular fibrillation) did. Since the majority of these reflex stimuli resulted in large change in vascular resistance, it would appear that reflex hemodynamic changes can occur in these preparations without concomitant changes in glycerol release. Alpha blockade of the vasoconstriction resulted in the appearance of rising glycerol output suggesting that vasoconstriction prevents lipolysis.

Adipose Tissue↗
PubMed1979

Vascular responses in canine subcutaneous adipose tissue to hypothalamic stimulation.

The present studies investigated vascular responses to electrical stimulation of the posterior hypothalamus in isolated but perfused and innervated subcutaneous adipose tissue in adult dogs. Three groups of dogs were distinguished: in one, electrical stimulation elicited vasodilation; in another, vasoconstriction, and in a third, neither significant vasodilation nor vasoconstriction occurred. Histological examination revealed that electrode placements were in the medial posterior hypothalamus, the lateral posterior hypothalamus, and the medial septal region, respectively. Hypothalamic stimulation failed to alter concentrations of free fatty acids or glycerol in venous blood from subcutaneous fat. Local beta-adrenergic block (propranolol) reversed the vasodilation to vasoconstriction while local alpha-adrenergic block (dihydroergotamine) abolished the vaso constrictor response. These results suggest that selective stimulation of the posterior hypothalamus results in neurogenic activation of both alpha- and beta-adrenergic mechanisms in adipose tissue vasculature. beta-Adrenergic vasodilation appears to predominate if the electrode is located medially, and alpha-adrenergic vasoconstriction appears to predominate if the electrode is located in the lateral posterior hypothalamus.

Adipose Tissue↗
PubMed1978

Lipoprotein-lipase activity in subcutaneous, adipose tissue in healthy subjects: variation of activity in a population of 60-year-old men.

The lipoprotein-lipase activity (LPLA) in the abdominal, subcutaneous, adipose tissue was studied in a random sample (n = 69) of 60-year-old men. A new method for the quantification of LPLA was applied. The mean value was 67 mU/g when expressed per gram (wet weight) of adipose tissue. Several subjects within the lower part of the range of adipose-tissue LPLA values had low concentrations of serum-triglycerides (S-TG). There was no correlation between the LPLA and S-TG concentrations in the fasting state. Among the 69 subjects, four had newly detected diabetes mellitus and had significantly lower LPLA in the adipose tissue than the control group. The fat-cell size and the LPLA per gram of adipose tissue were not correlated. Thus, obesity without diabetes mellitus does not imply a low LPLA concentration in adipose tissue. The variation of the concentration of adipose-tissue LPLA in the fasting state in this population was explained only to a minor extent by the variation of S-insulin and blood-glucose parameters, when analysed statistically by a stepwise multiple-regression technique.

Abdominal Muscles↗
PubMed1978

Vasodilatation and modulation of vasoconstriction in canine subcutaneous adipose tissue caused by activation of beta-adrenoceptors.

The present experiments were undertaken to study the balance between vascular alpha- and beta-adrenoceptors in canine subcutaneous adipose tissue during sympathetic nerve stimulation and noradrenaline injections. Propranolol potentiated and prolonged the vasoconstrictor response to close i.a. injections of noradrenaline. The vasoconstriction induced by brief nerve stimulation (0.5 to 8 Hz) was, however, unaltered by the beta-adrenoceptor blockade. During prolonged nerve stimulation the vasoconstrictor response was well maintained at 1.5 Hz but at 4 Hz there was a gradual escape. The escape phenomenon at 4 Hz was diminished by propranolol. The beta1-selective antagonist practolol, like propranolol, potentiated and prolonged the vasoconstriction induced by noradrenaline injections and reduced the vasoconstrictor escape during prolonged nerve stimulation at 4 Hz. Furthermore, the vasodilatation induced by noradrenaline injection or nerve stimulation during alpha-adrenoceptor blockade was diminished by practolol. Practolol also blocked the lipolytic response to noradrenaline and nerve stimulation. The beta2-selective antagonist H35/25 blocked the effects of the beta2-selective agonist salbutamol but failed to alter noradrenaline as well as nerve stimulation induced vascular and lipolytic beta-adrenoceptor responses. The present results provide further support for the hypothesis that vascular beta-adrenoceptors in adipose tissue are humoral (noninnervated), preferentially activated by circulating noradrenaline. Moreover, both vascular and lipolytic beta-adrenoceptors activated by noradrenaline in adipose tissue are best classified as beta1-adrenoceptors.

Adipose Tissue↗
PubMed1976

Metabolism of mono- and diacylglycerols in subcutaneous adipose tissue of obese and normal-weight subjects.

Tissue monoacylglycerols (MG), diacylglycerols (DG), free fatty acids (FFA), and cyclic AMP (cAMP) and release of FFA and glycerol have been studied in vitro in subcutaneous adipose tissue of 6 obese and 7 normal-weight subjects. The tissue was incubated without or with 6 X 10(-5) mol/l of isoprenaline (ISNA). The DG level and the fat cell volume were strongly interrelated (r=+0.95, p less than 0.001). The concentration of DG was increased (p less than 0.05) in obesity. The changes in DG and MG were significantly interrelated (r=+0.65, p less than 0.05) during basal incubation. ISNA increased the DG concentration in a way that was correlated (r=+0.81, p less than 0.001) with the ISNA-induced glycerol release. This indicates that 1) the basal metabolic activities of MG and DG lipase are similar and 2) DG lipase is an important rate limiting factor in lipolysis. Without ISNA, tissue FFA and the release of FFA and glycerol were significantly increased in the obese patients. As a mean, MG and DG did not accumulate in the basal state in the two patient groups. The findings indicate that basal lipolysis was increased in obesity. This was probably due to increased basal metabolic activity of triacylglycerol lipase, since the basal cAMP levels were similar in the two patient groups. In the presence of ISNA, the production of FFA and the glycerol release were similar in both patient groups, as was the increase in tissue DG. Also the ISNA-induced maximal level of cAMP was similar in the two groups. With ISNA, a small increment of MG was observed in adipose tissue of the normal-weight subjects. Taking all metabolites into account, the rate of lipolysis as well as the activation of triacylglycerol lipase via cAMP in the presence of ISNA appeared to be unaltered in obesity. Separate experiments with 1-14C-glycerol provided further evidence for the existence of a MG pathway for the esterification of FFA.

Adipose Tissue↗
PubMed1979

Site differences in the fatty acid composition of subcutaneous adipose tissue of obese women.

1. Adipose tissue samples were obtained by needle biopsy from three subcutaneous sites (thigh, abdomen and upper arm) in twenty-two obese women. The fatty acid composition was determined using gas-liquid chromatography and the results presented relate to eleven component fatty acids. 2. The fatty acid composition of adipose tissue obtained from the arm and abdomen was remarkably similar, with the exception of the levels of lauric acid. 3. The analyses showed that the majority of the saturated fatty acids were present in smaller proportions whilst the majority of unsaturated fatty acids were present in larger proportions in the thigh than in the two other sites. Highly significant inter-site differences were demonstrated for six of the major fatty acids and also for both the total amounts of saturated and unsaturated fatty acids and their ratios. 4. No marked differences in the fatty acid composition of adipose tissue from obese subjects were revealed during this study when compared with previously reported results obtained from 'normal-weight' subjects.

Abdomen↗
PubMed1975

[Study of atherosclerosis in different geographical zones of the Soviet Union. 1. Comparative study of fatty acid composition of subcutaneous adipose tissue].

Gas-liquid chromatography was used for the study of the fat-acid composition of the subcutaneous tissue in males, aged 20 to 70 years, who had died in accidents. The investigation was conducted in the cities of Samarkand, Tashkent, Riga and Moscow. A significantly higher relative level of linoleic acid in the subcutaneous tissue of the native population of Central Asia than in the non-native residents of the same regions was found (19.4 and 13.7%, respectively). It is accounted for by a high consumption of cotton oil rich in linoleic acid by the native population of Uzbekistan. No significant differences in the proportion of linoleic, oleic and other fatty acids in the adipose tissue of the Russian population of Samarkand and Tashkent, as well as Riga and Moscow were found. No differences were either found in the composition of the adipose tissue of the native and non-native residents of Riga. The lower incidence of atherosclerosis among the native population of Central Asia in comparison with the non-native population of the same region and the population of the Baltic region is emphasized.

Adipose Tissue↗
PubMed1979

Distribution of m-xylene to subcutaneous adipose tissue in short-term experimental human exposure.

When volunteers were exposed in three different patterns of exposure to approximately 3.7--8.2 mumol/l (90--200 ppm, constant or time-weighted average concentration) of m-xylene for five consecutive days plus one day after the weekend, approximately 3.7--8.0% of the total body uptake was estimated to be distributed to the adipose tissue on the basis of m-xylene determinations made from subcutaneous fat. Distribution seemed to be affected by the exposure pattern; a proportionately greater distribution to subcutaneous fat occurred when the volunteers performed physical exercise part of the time, particularly when the peak xylene concentrations in the air coincided with the exercise. The median elimination half-time of m-xylene from subcutaneous fat was 58 h (range 25--128 h). A positive correlation was found between the individual elimination half-times of m-xylene in subcutaneous fat and the relative fat mass of the individuals in two exposure groups, but not in one.

Adipose Tissue↗