Archives Internationales de Physiologie, de Biochimie et de Biophysique, 1992, 100, 207-21 1
207
Requ Le 17 juin 1991.
Effect of food deprivation and refeeding on rat organ temperatures. BY
D. CLOSA, M. ALEMANY and X. REMESAR
Archives of Physiology and Biochemistry Downloaded from informahealthcare.com by University of Newcastle on 12/30/14 For personal use only.
(Departament de Bioquimica i Fisiologia, Universitat de Barcelona, 08071 Barcelona, Spain)
(2 figures)
Small thermocouple sensors were surgically implanted in the liver, kidney, kind leg muscle, interscapular brown adipose tissue, small and large intestines, dorso-lumbar internal side of the skin, periovaric adipose tissue and the lower aorta of Wistar rats. The aortic temperature was taken as core temperature. The sensors allowed continuous long-term monitoring of the temperatures of these organs. A period of 18 hours of food deprivation resulted in an overall decrease of mean core and organ temperature, brown adipose tissue temperature dropping to values lower than those of the aorta in the fed state. Liver, kidney and small intestine maintained higher temperatures than the aorta both in fed and starved states. Refeeding overshot the core temperature with increases in most organs versus both the fed and food-deprived situations. The results are concordant with an active role of brown adipose tissue in dietary induced thermogenesis. Three days of food deprivation did not alter the basic circadian rhythm of core temperatures in the rat kept at 22"C, whereas it did modulate both nightly maximum and diurnal minimum temperatures to much lower settings than either in the fed or refed situations. The rat adapts to starvation by decreasing core and organ temperatures and widening the amplitude of the daily temperature cycle.
Introduction
During food deprivation, the mammal adapts its energy needs to a lower setting (WESTERTERP, 1977) and calls upon its metabolic reserves, essentially glycogen in short-term situations and fats for more prolonged periods (PALOU et al., 1981). Food deprivation is a situation under which diet-induced thermogenesis cannot be expected to operate. In mammals, however, the body temperature, or at least the core temperature (BLIGH& JOHNSON,1973), must be maintained at the expense of thermogenic processes, despite the lack of external energy sources. In part, the energy budget is balanced by limiting expenditure (HIMMS-HAGEN, 1986), as well as by slight reduction of the temperature in eurytherms. The rat is considered an euthermic animal (HIMMS-HAGEN, 1986). The combined effects of cold exposure and food deprivation result in very severe et al., 1983). drainage of the resources (VALLERAND Brown adipose tissue has been considered a main site of mammalian thermogenesis (SMITH& HORWITZ, 1969; JANSKY, 1973; ROTHWELL& STOCK, 1979; FOSTER,1984; SHRAGO& STRIELEMAN,1987). This tissue is characterized by a distribution around the core organs (SMITH,1964), intense and controlled irrigation 1978; NNODIM& LEVER,1988) (FOSTER& FRYDMAN, and sympathetic innervation (SEYDOUX& GIRARDIER,
1978), as well as by the uniqueness of its uncoupling system (NICHOLLS& LOCKE, 1984). Brown adipose tissue thermogenesis is activated by the effect of cold (HIMMS-HAGEN, 1986), which provokes a hyperplasic response (BUCKOWIECKI et al., 1984) as well as a shift from the partial utilization of glucose to a massive oxet al., idation of blood-carried fats (LOPEZ-SORLANO 1988). Overfeeding also results in marked hyperplasia & STOCK, of brown adipose tissue masses (ROTHWELL 1986; MONFARet al., 1987), as well as in higher ther& STOCK, mogenic oxidation of substrates (ROTHWELL 1979; 1986). Food deprivation induces a loss of activity of the tissue as well as depletion of its lipid content et al., 1984; DESAUTELS et al., 1986), with (ROTHWELL et al., 1989). very low fluxes of blood (LOPEZ-SORIANO In the present study we have attempted to determine the extent of changes in internal organ remperature as part of the adaptations to lower or nil external input of nutrients. Materials and Methods
Subjects. Female virgin Wistar rats aged 9 weeks and weighing 180-190 g were used. All animals were maintained in individual cages with standard food pellets (type A02 from Panlab, Barcelona) and tap water ad libitum. The rats were housed in a temperature
208
D. CLOSA, M. ALEMANY AND X. REMESAR
Archives of Physiology and Biochemistry Downloaded from informahealthcare.com by University of Newcastle on 12/30/14 For personal use only.
liaht/darkness cycle
FIG.1. Temperature differences between interscapular brown adipose tissue and aortic core temperature of rats subjected to 18 hours of food deprivation. The vertical axis indicates the temperature differences in "C versus the aortic measurements : higher (positive values) or lower (negative values). The time scale is expressed in clock hours. The marks on the horizontal axis (days) correspond to midnight (24 hours). The periods of light and dark are represented by a top horizontal bar; black areas indicate darkness periods. The vertical dotted lines delimitate the light cycle days. The dashed bar placed on top indicates when food was available. The graph represents the data of a single representative rat. The horizontal dashed lines represent the mean temperatures for the fed/food-deprivedhefered periods (0.35 0.03 "C,-0.09 k 0.03 "C and 0.18 k 0.02 "C, respectively); the means correspond to the whole duration of every period presented in the figure. The means were statistically different (PO.O5; Temperaturedifferences versus controls : * = P
207
Requ Le 17 juin 1991.
Effect of food deprivation and refeeding on rat organ temperatures. BY
D. CLOSA, M. ALEMANY and X. REMESAR
Archives of Physiology and Biochemistry Downloaded from informahealthcare.com by University of Newcastle on 12/30/14 For personal use only.
(Departament de Bioquimica i Fisiologia, Universitat de Barcelona, 08071 Barcelona, Spain)
(2 figures)
Small thermocouple sensors were surgically implanted in the liver, kidney, kind leg muscle, interscapular brown adipose tissue, small and large intestines, dorso-lumbar internal side of the skin, periovaric adipose tissue and the lower aorta of Wistar rats. The aortic temperature was taken as core temperature. The sensors allowed continuous long-term monitoring of the temperatures of these organs. A period of 18 hours of food deprivation resulted in an overall decrease of mean core and organ temperature, brown adipose tissue temperature dropping to values lower than those of the aorta in the fed state. Liver, kidney and small intestine maintained higher temperatures than the aorta both in fed and starved states. Refeeding overshot the core temperature with increases in most organs versus both the fed and food-deprived situations. The results are concordant with an active role of brown adipose tissue in dietary induced thermogenesis. Three days of food deprivation did not alter the basic circadian rhythm of core temperatures in the rat kept at 22"C, whereas it did modulate both nightly maximum and diurnal minimum temperatures to much lower settings than either in the fed or refed situations. The rat adapts to starvation by decreasing core and organ temperatures and widening the amplitude of the daily temperature cycle.
Introduction
During food deprivation, the mammal adapts its energy needs to a lower setting (WESTERTERP, 1977) and calls upon its metabolic reserves, essentially glycogen in short-term situations and fats for more prolonged periods (PALOU et al., 1981). Food deprivation is a situation under which diet-induced thermogenesis cannot be expected to operate. In mammals, however, the body temperature, or at least the core temperature (BLIGH& JOHNSON,1973), must be maintained at the expense of thermogenic processes, despite the lack of external energy sources. In part, the energy budget is balanced by limiting expenditure (HIMMS-HAGEN, 1986), as well as by slight reduction of the temperature in eurytherms. The rat is considered an euthermic animal (HIMMS-HAGEN, 1986). The combined effects of cold exposure and food deprivation result in very severe et al., 1983). drainage of the resources (VALLERAND Brown adipose tissue has been considered a main site of mammalian thermogenesis (SMITH& HORWITZ, 1969; JANSKY, 1973; ROTHWELL& STOCK, 1979; FOSTER,1984; SHRAGO& STRIELEMAN,1987). This tissue is characterized by a distribution around the core organs (SMITH,1964), intense and controlled irrigation 1978; NNODIM& LEVER,1988) (FOSTER& FRYDMAN, and sympathetic innervation (SEYDOUX& GIRARDIER,
1978), as well as by the uniqueness of its uncoupling system (NICHOLLS& LOCKE, 1984). Brown adipose tissue thermogenesis is activated by the effect of cold (HIMMS-HAGEN, 1986), which provokes a hyperplasic response (BUCKOWIECKI et al., 1984) as well as a shift from the partial utilization of glucose to a massive oxet al., idation of blood-carried fats (LOPEZ-SORLANO 1988). Overfeeding also results in marked hyperplasia & STOCK, of brown adipose tissue masses (ROTHWELL 1986; MONFARet al., 1987), as well as in higher ther& STOCK, mogenic oxidation of substrates (ROTHWELL 1979; 1986). Food deprivation induces a loss of activity of the tissue as well as depletion of its lipid content et al., 1984; DESAUTELS et al., 1986), with (ROTHWELL et al., 1989). very low fluxes of blood (LOPEZ-SORIANO In the present study we have attempted to determine the extent of changes in internal organ remperature as part of the adaptations to lower or nil external input of nutrients. Materials and Methods
Subjects. Female virgin Wistar rats aged 9 weeks and weighing 180-190 g were used. All animals were maintained in individual cages with standard food pellets (type A02 from Panlab, Barcelona) and tap water ad libitum. The rats were housed in a temperature
208
D. CLOSA, M. ALEMANY AND X. REMESAR
Archives of Physiology and Biochemistry Downloaded from informahealthcare.com by University of Newcastle on 12/30/14 For personal use only.
liaht/darkness cycle
FIG.1. Temperature differences between interscapular brown adipose tissue and aortic core temperature of rats subjected to 18 hours of food deprivation. The vertical axis indicates the temperature differences in "C versus the aortic measurements : higher (positive values) or lower (negative values). The time scale is expressed in clock hours. The marks on the horizontal axis (days) correspond to midnight (24 hours). The periods of light and dark are represented by a top horizontal bar; black areas indicate darkness periods. The vertical dotted lines delimitate the light cycle days. The dashed bar placed on top indicates when food was available. The graph represents the data of a single representative rat. The horizontal dashed lines represent the mean temperatures for the fed/food-deprivedhefered periods (0.35 0.03 "C,-0.09 k 0.03 "C and 0.18 k 0.02 "C, respectively); the means correspond to the whole duration of every period presented in the figure. The means were statistically different (PO.O5; Temperaturedifferences versus controls : * = P
