Cannon, Barbara, and Jan Nedergaard. Brown Adipose Tissue: Function and Physiological Significance. Physiol Rev 84: 277–359, 2004; 10.1152/physrev.00015.2003.—The function of brown adipose tissue i...

Brown Adipose Tissue: Function and Physiological Significance

Thermogenic mechanisms in brown fat.

Obesity results when energy intake exceeds energy expenditure Naturally occurring genetic mutations, as well as ablative lesions, have shown that the brain regulates both aspects of energy balance and that abnormalities in energy expenditure contribute to the development of obesity Energy can be expended by performing work or producing heat (thermogenesis) Adaptive thermogenesis, or the regulated production of heat, is influenced by environmental temperature and diet Mitochondria, the organelles that convert food to carbon dioxide, water and ATP, are fundamental in mediating effects on energy dissipation Recently, there have been significant advances in understanding the molecular regulation of energy expenditure in mitochondria and the mechanisms of transcriptional control of mitochondrial genes Here we explore these developments in relation to classical physiological views of adaptive thermogenesis

Towards a molecular understanding of adaptive thermogenesis.

Leptin Differentially Regulates NPY and POMC Neurons Projecting to the Lateral Hypothalamic Area

Equations for the calculation of VO2, VCO2, and evaporative water loss were derived for use of a paramagnetic gas analyzer with a flow-through respirometry system and an open or closed mask. The magnitude of errors involved in the determination of VO2 with no CO2 absorbent are small (+/-3%) but may be greater if no H2O absorbent is used, unless an appropriate correctionis made for evaporative water loss. Data collected for hummingbirds (Selasphorus sasin) and monitor lizards (Varanus gouldii) indicate the validity ofthe technics described for the measurement of RQ and evaporative water lossand demonstrate the use of paramagnetic gas analyzers in monitoring respiratory patterns.

Measurement of VO2, VCO2, and evaporative water loss with a flow-through mask

A basic formulation of methods of obtaining oxygen consumption data from measurements of oxygen partial pressure in open and closed-circuit systems is made. For open-circuit systems used in the ste...

Use of the Pauling Oxygen Analyzer for Measurement of Oxygen Consumption of Animals in Open-Circuit Systems and in a Short-Lag, Closed-Circuit Apparatus

Shivering measured by the electromyogram was absent in cold acclimated rats at 6°C, indicating that thermogenesis apparently was almost exclusively of the chemical type. Chemical thermogenesis alon...

Cold acclimation and the electromyogram of unanesthetized rats.

Harbor seals maintained in sea water were either starved or fed graded amounts of herring of known water and total chloride contents. Total body water and exchangeable chloride in the seals were me...

Sea water drinking and water flux in starved and in fed harbor seals, Phoca vitulina.

The heat production (indirect) of 30°C acclimated ( I ) and 6°C acclimated ( II ) Sprague-Dawley adult male rats was determined with an open-circuit metabolism apparatus and with a low-lag, closed-circuit apparatus over the temperature range −36° to 30°C. Heat production of II was linearly related to temperature between −36° and 20°C and was always higher than that of I . At the lower temperatures heat production of I fell rapidly with time of exposure to the test temperature, and showed a maximal initial value (obtained between the 3rd and 20th minute of exposure) which was independent of temperature between −35° and −25°C and fully elicited at the start of the measurements. Heat balance of I and II measured at −15°C indicated that body cooling in I was a resultant of the failure to produce enough heat to balance the heat loss. These results indicate that the metabolic response of white rats to cold exposure occurs within 3 minutes of the beginning of exposure and that I reach a maximum metabolic rate at temperatures at which II can still show an increase on further lowering of the environmental temperature.

Submitted on September 14, 1956

Energy metabolism of the white rat after acclimation to warm and cold environments.

The effects of sham, unilateral, and bilateral surgical denervation of rat interscapular brown adipose tissue (IBAT) on blood flow to the two IBAT pads of cold-acclimated (CA) rats during exposure of the animals to 22 or -6 degrees C and on the noradrenaline (NA) content and total dopamine beta-hydroxylase (DBH) (EC 1.14.17.1) activity of the pads in both warm-acclimated (WA)rats and CA rats were examined. Increase in IBAT blood flow upon cold exposure was taken as an index of sympathetically medicated calorigenesis in the tissue, and decreases in tissue levels of NA and DBH served as indices of the extent of destruction of the sympathetic innervation. At 24 h postsurgery, denervated pads of CA rats, rats, whether from unilaterally or bilaterally denervated IBAT, had less than 3% of the NA, 40-44% of the DBH, and 0% of the 10-fold, cold-induced increase in blood flow measured in intact pads of CA rats with sham-operated or unilaterally denervated IBAT. IBAT bilaterally denervated for 24 h was as responsive in terms of its maximum increase in blood flow during infusion of CA rats with NA as intact IBAT. DBH in denervated pads of both WA rats and CA rats fell to 5% or less of control levels at 2 days postdenervation and remained at these low levels, as did NA, for at least 8 weeks. These results strongly support the longstanding but recently challenged hypothesis that each pad of rat IBAT is independently innervated by sympathetic fibers.

Florent Depocas

Papers

Use of the Pauling Oxygen Analyzer for Measurement of Oxygen Consumption of Animals in Open-Circuit Systems and in a Short-Lag, Closed-Circuit Apparatus

Cold acclimation and the electromyogram of unanesthetized rats.

Sea water drinking and water flux in starved and in fed harbor seals, Phoca vitulina.

Energy metabolism of the white rat after acclimation to warm and cold environments.

Unilaterality of the sympathetic innervation of each pad of rat interscapular brown adipose tissue