The relationship between the thermogenic response of brown adipose tissue and age during noradrenaline infusion in the young rabbit

1985 ◽  
Vol 63 (10) ◽  
pp. 1215-1220
Author(s):  
W. H. Harris ◽  
D. O. Foster ◽  
B. E. Nadeau
Keyword(s):  
Blood Flow ◽  
Oxygen Consumption ◽  
Age Groups ◽  
Brown Fat ◽  
Young Rabbit ◽  
Morphological Evidence ◽  
Response Curves ◽  
Total Blood ◽  
Noradrenaline Infusion ◽  
Brown Adipose

This work was undertaken to determine if the thermogenic activity of brown fat decreased with age in young rabbits despite the morphological evidence indicating persistence of the brown adipocytes at 4 weeks of age. Data obtained by infusing five doses of noradrenaline and measuring oxygen consumption were used to construct cumulative dose–response curves for five age groups between 3 and 32 days of age. Blood flow to brown fat and other tissues was measured by the microsphere method at 1 and 3 weeks of age. The noradrenaline-induced increase in oxygen consumption when expressed as a percentage of resting oxygen consumption in millilitres per 100 g of body weight decreased (p < 0.05) with age. However, the absolute noradrenaline-induced increase in metabolic rate (millilitres per minute) increased with age. Total blood flow to brown fat (millilitres per minute) during noradrenaline infusion was unchanged between 1 and 3 weeks of age, but when the blood flow was expressed in millilitres per minute per gram of tissue flow decreased significantly (p < 0.05) probably because of infiltration of brown fat with white fat. These data suggest that the amount of brown fat and its thermogenic capacity remain relatively constant between 1 and 3 weeks of age, but as a thermogenic organ, brown fat becomes proportionally less effective with age because of the large increase in body mass.

Evidence for a contribution by brown adipose tissue to the development of fever in the young rabbit

1985 ◽  
Vol 63 (6) ◽  
pp. 595-598 ◽  
Author(s):  
W. H. Harris ◽  
D. O. Foster ◽  
B. E. Nadeau
Keyword(s):  
Blood Flow ◽  
Adipose Tissue ◽  
Brown Adipose Tissue ◽  
Heat Production ◽  
Brown Fat ◽  
Young Rabbit ◽  
Tissue Blood Flow ◽  
Febrile Response ◽  
Arterial Blood ◽  
Brown Adipose

This study was undertaken to determine if brown adipose tissue was involved in heat production during fever produced by S. abortus equi (1 μg) in unanesthetized rabbits aged 19–26 days. The fever (0.9–1.6 °C) occurred after a delay of 20–30 min and was frequently biphasic. Radiolabelled microspheres for measuring tissue blood flow were injected intraventricularly into three groups of animals: rabbits not given pyrogen, rabbits in which the febrile response to pyrogen was developing, and rabbits in which the febrile response had peaked. Blood flow to brown fat deposits and other organs was calculated from the fractional distribution of the microspheres and the recovery of microspheres in a reference arterial blood sample. At the fever peak, blood flow to brown fat was not significantly different (p > 0.05) from the control value (0.9 ± 0.2), but during the rising phase of the fever the flow increased significantly (p < 0.01) to 2.6 ± 0.4 mL min−1 g−1. The blood flow to muscles of the forelimbs and hind limbs was also increased significantly (p < 0.05) during the rising phase of the fever. No significant change in blood flow to other organs or tissues was found during the rising phase of the fever. These results indicate that both nonshivering as well as shivering thermogenesis contribute to heat production during development of fever in the young rabbit. However, nonshivering thermogenesis was not involved in the maintenance of the elevated body temperature after the fever had peaked.

Blood flow to brown fat in lean and obese adrenalectomized Zucker rats

1986 ◽  
Vol 251 (5) ◽  
pp. R851-R858
Author(s):  
S. J. Wickler ◽  
B. A. Horwitz ◽  
J. S. Stern
Keyword(s):  
Blood Flow ◽  
Weight Gain ◽  
Brown Fat ◽  
Zucker Rats ◽  
Zucker Rat ◽  
Nonshivering Thermogenesis ◽  
Brown Adipose ◽  
Obese Rats

The Zucker obese rat is characterized by decreased capacity for diet-induced and for nonshivering thermogenesis. This decrease is due, in large part, to reduced thermogenesis in depots of brown adipose tissue, a major source of heat production in rats. Adrenalectomy retards the weight gain observed in the obese rats and also normalizes brown fat guanosine 5'-diphosphate (GDP) binding, an in vitro measure of brown fat thermogenic capacity. This study examined the effect of adrenalectomy on brown fat blood flow, an in vivo measure of the tissue's function, and on norepinephrine-induced O2 consumption (NST) of 11-wk-old obese (fa/fa) and lean (Fa/?) rats. Adrenalectomy had little effect on weight gain, NST, or norepinephrine-stimulated blood flow to brown fat in lean rats. However, adrenalectomy produced profound changes in the obese animals, preventing the weight gain normally occurring in the obese rats and normalizing both NST capacity and norepinephrine-stimulated blood flow to brown fat. These findings provide further support for the importance of brown fat thermogenesis and glucocorticoids in modulating the obesity of the Zucker rat.

Regional blood flow in rats after a single low-protein, high-carbohydrate test meal

1984 ◽  
Vol 247 (1) ◽  
pp. R160-R166 ◽  
Author(s):  
Z. Glick ◽  
S. J. Wickler ◽  
J. S. Stern ◽  
B. A. Horwitz
Keyword(s):  
Blood Flow ◽  
Test Meal ◽  
Resting State ◽  
Brown Fat ◽  
Blood Flows ◽  
High Carbohydrate ◽  
Low Protein ◽  
Brown Adipose ◽  
White Fat

It was previously observed that a single low-protein, high-carbohydrate test meal results in increased in vitro thermic activity of brown adipose tissue. In the present study, we have examined whether such a meal increases the in vivo thermic activity, estimated from measurement of the rate of blood flow. With radioactively labeled microspheres, blood flows into brown fat and several other tissues were determined in meal-deprived (n = 11) and meal-fed (n = 11) rats. The microspheres were injected into the heart of anesthetized animals about 2-2.5 h after the test meal, one injection in the resting state and one during maximal norepinephrine stimulation. In the resting state, blood flow per gram tissue more than doubled in the brown fat (P less than 0.05) and was increased more than 50% in the heart (P less than 0.01) of the fed group. Blood flows into liver and retroperitoneal white fat were reduced by 40 (P less than 0.01) and 30%, respectively, in the fed group. During norepinephrine infusion, significant meal-associated increases in blood flow were evident only in brown fat (P less than 0.05) and the soleus muscle (P less than 0.05), whereas a significant decrease was observed in the liver (P less than 0.05). No statistically significant meal-associated changes in norepinephrine-stimulated blood flow were found in the other tissues examined (i.e., heart, gastrocnemius, and diaphragm muscles, kidneys, white fat, spleen, and adrenals). Our in vivo data thus support the view that brown fat plays a role in the thermic effect of a meal.

EFFECT OF TEMPERATURE ON METABOLIC RATES OF LIVER AND BROWN FAT HOMOGENATES

1967 ◽  
Vol 45 (11) ◽  
pp. 1763-1771 ◽  
Author(s):  
Jane C. Roberts ◽  
Robert E. Smith
Keyword(s):  
Adipose Tissue ◽  
Oxygen Consumption ◽  
Brown Adipose Tissue ◽  
Brown Fat ◽  
Effect Of Temperature ◽  
Metabolic Rates ◽  
Brown Adipose ◽  
Rate Of Oxygen Consumption ◽  
Effects Of Temperature

The effects of temperature in vitro upon metabolic rates of homogenates of brown fat and liver from control and cold-acclimated rats have been examined over the range 10–37 °C. At all temperatures, brown adipose tissue exhibits a higher rate of oxygen consumption [Formula: see text] than does liver, α-ketoglutarate being used as substrate. At 10 °C, brown adipose tissue retains a larger percentage (36–38%) of its 37 °C metabolic rate than does liver (22–24%).Q10 values and energies of activation (Ea) have been determined and compared with other data reported for these tissues. At 20 °C, breaks appear in the Arrhenius plots for liver from both control and cold-acclimated rats and also for brown fat from control rats, but not for the brown fat from cold-acclimated rats. Thus brown adipose tissue from cold-acclimated rats retains relatively higher levels of respiration at temperatures below the 20 °C breaking point than does brown fat from control rats.In view of previously reported cold-induced increases in mass, vascularity, and [Formula: see text] of brown fat, this decreased temperature sensitivity in the cold-acclimated rats appears wholly consonant with the adaptive behavior of brown fat in its role as a thermogenic effector.

Oxygen requirements of the dyskinetic myocardial segment

1989 ◽  
Vol 257 (4) ◽  
pp. H1184-H1191 ◽  
Author(s):  
P. A. Gayheart ◽  
J. Vinten-Johansen ◽  
W. E. Johnston ◽  
T. O. Hester ◽  
A. R. Cordell
Keyword(s):  
Blood Flow ◽  
Oxygen Consumption ◽  
Coronary Arteries ◽  
Dose Response ◽  
Contractile Function ◽  
Myocardial Segment ◽  
Response Curves ◽  
Intracoronary Infusion ◽  
Oxygen Requirements ◽  
Measure Oxygen Consumption

Oxygen requirements of a noncontracting myocardial segment subjected to passive systolic stretch (dyskinesis) have not been well described. The purpose of this study was to measure oxygen consumption (MVO2) of a myocardial segment made dyskinetic by intracoronary infusion of lidocaine. In 12 anesthetized open-chest dogs, segmental shortening was measured sonomicrometrically in regions perfused by the left anterior descending (LAD) and circumflex (Cfx) coronary arteries. MVO2 was measured by arterial-venous oxygen content differences and transmural blood flow. Dose-response curves to intracoronary lidocaine showed that complete dyskinesis was achieved by a 0.25-mg/ml dose of lidocaine, whereas the Cfx region maintained a constant level of segmental shortening. MVO2 of the LAD segment was similar to that of the Cfx segment under control conditions. With lidocaine-induced dyskinesis, MVO2 in the arrested segment was reduced by 33% (P less than 0.05), despite the loss of contractile function. When bulging was prevented by ventricular unloading, MVO2 in the arrested segment decreased to 2.65 ml O2.min-1.100 g-1 (i.e., basal oxygen requirements). In conclusion, MVO2 in a pharmacologically arrested myocardial segment undergoing systolic bulging is paradoxically high relative to both basal requirements and MVO2 in the normally contracting segment.

The receptors responsible for heat production in brown adipose tissue in the young rabbit

1986 ◽  
Vol 64 (2) ◽  
pp. 133-137 ◽  
Author(s):  
W. H. Harris ◽  
L. A. Moore ◽  
S. Yamashiro
Keyword(s):  
Brown Fat ◽  
Young Rabbit ◽  
Low Doses ◽  
Adrenergic Agonists ◽  
Alpha Adrenoceptors ◽  
Brown Adipose ◽  
Adrenergic Antagonist ◽  
Auxiliary Role ◽  
Stimulation Of ◽  
Thermogenic Response

It is known that adrenergic agonists stimulate thermogenesis in the brown fat of the young rabbit but the receptors responsible for mediating the response have not been identified. The infusion of either noradrenaline or isoproterenol (1–2 μg∙kg−1∙min−1) produced an increase in subcutaneous temperature (0.93 ± 0.15 and 1.22 ± 0.10 °C, respectively over the interscapular brown fat. At low doses (0.4 μg∙kg−1∙min−1) only isoproterenol was effective. The thermogenic response to isoproterenol was blocked by atenolol, a beta1-adrenergic antagonist. Neither salbutamol or terbutaline, both beta2-agonists, produced a temperature increase. Collectively, these data suggest that stimulation of beta1-adrenoceptor is primarily responsible for the thermogenic activity of brown fat in the rabbit. However, it was found that 53% of the increase in temperature could be blocked by prazosin, an alpha1-antagonist. Phentolamine was not effective as a blocker. Although a maximal brown fat thermogenic response can be achieved by stimulating the beta-adernoceptors, the alpha-adrenoceptors appear to play at least an auxiliary role in the young rabbit.

Contribution of BAT and skeletal muscle to thermogenesis induced by ephedrine in man

1985 ◽  
Vol 248 (5) ◽  
pp. E507-E515 ◽  
Author(s):  
A. Astrup ◽  
J. Bulow ◽  
J. Madsen ◽  
N. J. Christensen
Keyword(s):  
Skeletal Muscle ◽  
Blood Flow ◽  
Adipose Tissue ◽  
Oxygen Consumption ◽  
Local Temperature ◽  
Whole Body ◽  
Tissue Blood Flow ◽  
Muscle Oxygen ◽  
Brown Adipose ◽  
Muscle Oxygen Consumption

This investigation was performed to examine the role of brown adipose tissue (BAT) in thermogenesis induced by ephedrine in man. Light microscopy of biopsies from necropsy cases showed BAT to occur most frequently in the perirenal fat. Perirenal BAT thermogenesis was investigated in five lean men before and during stimulation with 1 mg ephedrine orally X kg body wt-1. Perirenal BAT thermogenesis was assessed by continuous measurements of local temperature and blood flow with the 133xenon clearance method. In the same study the effect of ephedrine on skeletal muscle oxygen consumption was estimated by measurements of leg blood flow and arteriovenous oxygen difference. The perirenal adipose tissue blood flow increased approximately twofold, whereas the local temperature increased approximately 0.1 degrees C on an average. Assuming that man possesses 700 g of BAT with a similar thermogenic capacity, this tissue contributed only 10 ml X min-1 to the 40 ml X min-1 increase in oxygen consumption in the subject whose perirenal BAT showed the most pronounced response to ephedrine. The leg oxygen consumption increased on an average 60% after ephedrine. By extrapolation of this value to whole body skeletal muscle, approximately 50% of the increase in oxygen consumption induced by ephedrine may take place in skeletal muscle. It is concluded that skeletal muscle is a tissue of importance with respect to the thermogenic effect of sympathomimetics in man, whereas the results do not support a major role for perirenal BAT.

scholarly journals Relationship of brown adipose tissue perfusion and function: a study through β2-adrenoreceptor stimulation

2016 ◽  
Vol 120 (8) ◽  
pp. 825-832 ◽  
Author(s):  
Laura Ernande ◽  
Kristin I. Stanford ◽  
Robrecht Thoonen ◽  
Haihua Zhang ◽  
Maëva Clerte ◽  
...  
Keyword(s):  
Blood Flow ◽  
Adipose Tissue ◽  
Oxygen Consumption ◽  
Brown Adipose Tissue ◽  
Glucose Uptake ◽  
Direct Effect ◽  
Brown Adipocytes ◽  
Bat Activity ◽  
Brown Adipose

Brown adipose tissue (BAT) activation increases glucose and lipid consumption; as such, it is been considered as a potential therapy to decrease obesity. BAT is highly vascularized and its activation is associated with a necessary increase in blood flow. However, whether increasing BAT blood flow per se increases BAT activity is unknown. To examine this hypothesis, we investigated whether an isolated increase in BAT blood flow obtained by β2-adrenoreceptor (β2-AR) stimulation with salbutamol increased BAT activity. BAT blood flow was estimated in vivo in mice using contrast-enhanced ultrasound. The absence of direct effect of salbutamol on the function of isolated brown adipocytes was assessed by measuring oxygen consumption. The effect of salbutamol on BAT activity was investigated by measuring BAT glucose uptake in vivo. BAT blood flow increased by 2.3 ± 0.6-fold during β2-AR stimulation using salbutamol infusion in mice ( P = 0.003). β2-AR gene expression was detectable in BAT but was extremely low in isolated brown adipocytes. Oxygen consumption of isolated brown adipocytes did not change with salbutamol exposure, confirming the absence of a direct effect of β2-AR agonist on brown adipocytes. Finally, β2-AR stimulation by salbutamol increased BAT glucose uptake in vivo (991 ± 358 vs. 135 ± 49 ng glucose/mg tissue/45 min in salbutamol vs. saline injected mice, respectively, P = 0.046). In conclusion, an increase in BAT blood flow without direct stimulation of the brown adipocytes is associated with increased BAT metabolic activity. Increasing BAT blood flow might represent a new therapeutic target in obesity.

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