Gene or size: metabolic rate and body temperature in obese growth hormone-deficient dwarf mice.
OBJECTIVE
SMA1 mice carry a missense mutation in the growth hormone gene that leads to semidominant dwarfism and obesity. In this study, the basic thermal and metabolic properties of SMA1 mice were examined to detect metabolic alterations that can support the accretion of excess fat.


METHODS
Basal and resting metabolic rates (RMRs) in wild-type and SMA1 (sma1/+ and sma1/sma1) mice were determined by indirect calorimetry. Body temperature (T(b)) was recorded using intraperitoneally implanted temperature-sensitive transmitters, and body composition was determined by DXA.


RESULTS
SMA1 mice have proportionally lower basal and resting metabolic rates, higher body mass (BM)-specific RMRs, and a higher lower critical temperature, and display a decrease in T(b) by 0.4 degrees C in sma1/+ and 0.9 degrees C in sma1/sma1.


CONCLUSIONS
The analysis of gene effects on BM and energy expenditure in mouse mutants must consider the appropriate allometric relationship between BM and metabolic rate. With the exception of T(b), all metabolic alterations observed in SMA1 reflect reduced size.
Animal Physiology, Department of Biology, Karl-von-Frisch Strasse 8, Philipps University Marburg, D-35043 Marburg, Germany. meyerc@staff.uni-marburg.de.
Carola W E
CW
Meyer
Martin
M
Klingenspor
Jan
J
Rozman
Gerhard
G
Heldmaier
D000818:Animals; D001481:Basal Metabolism / Q000235:genetics*; D001823:Body Composition; D049628:Body Size; D001831:Body Temperature; D002153:Calorimetry, Indirect; D004393:Dwarfism, Pituitary / Q000150:complications / Q000235:genetics* / Q000503:physiopathology*; D004734:Energy Metabolism / Q000235:genetics; D051379:Mice; D008809:Mice, Inbred C3H; D009765:Obesity / Q000150:complications*; D010101:Oxygen Consumption; D012146:Rest