Metabolic and morphologic changes in brown adipose tissue from non-growing mice with an isogeneic sarcoma. Evaluation with respect to development of cachexia.

Brown adipose tissue plays a thermoregulatory role influencing energy balance in experimental animals and possibly also in humans. In the present study we have reevaluated whether brown adipose tissue may contribute to the development of cancer cachexia in non-growing mice bearing an isogeneic tumor. Interscapular brown adipose tissue mass decreased by 20% in freely-fed sarcoma-bearing mice housed at room temperature. Increased mitochondrial density and increased oxidation rate of acetate at low acetate concentrations were found in brown fat from sarcoma-bearing mice, while the oxidation capacity was unchanged compared with that of freely-fed controls. Metabolic and morphologic changes in brown fat from sarcoma-bearing mice were similar to those found in weight-paired controls, which had experienced the same loss of body weight as the tumor-bearing mice. Selective and non-selective B-receptor blockade and surgical removal of interscapular brown fat before tumor implantation did not influence the nutritional state of freely-fed tumor-bearing mice. Injections of noradrenaline caused a proportionately lower increase in oxygen uptake in tumor-bearing animals than in freely-fed controls. Exposure to cold (+5 degrees C) doubled food intake and led to hypertrophy of brown fat in both sarcoma-bearing mice and control animals. Tumor growth was lower although not statistically different in animals housed at +5 degrees C compared with animals housed at +25 degrees C. It is concluded that brown adipose tissue from sarcoma-bearing mice could not account quantitatively for the host wasting in tumor-bearing mice housed at room temperature.