Metabolic and morphologic characteristics of adipose tissue associated with the growth of malignant tumors.

Changes in total body fat and the metabolic and morphologic characteristics of adipose tissue were sequentially investigated in individual rabbits implanted with VX2 tumors to elucidate the pathology of the fat reduction in animals with malignant tumors as compared with that of diet-restricted rabbits. Lipogenesis in normal, VX2-implanted, and diet-restricted rabbit groups on day 40 after the start of the experiments was 19.1 +/- 2.9, 13.3 +/- 3.5, and 41.7 +/- 6.0 x 10(5) cpm/g/h, respectively, and glycerol liberation by their adipose tissue was 199 +/- 21, 528 +/- 94, and 301 +/- 45 nmol/g/h, respectively. In addition, apoptotic cells were noted in the adipose tissue of VX2-implanted rabbits on days 20-30 after implantation, but not in diet-restricted rabbits. The results showed clear differences between the total body fat reduction profiles of VX2-implanted rabbits and diet-restricted rabbits, suggesting a characteristic lipid metabolism with enhanced lipolysis and diminished lipogenesis in VX2-implanted rabbits. The results strongly suggest that adipocyte apoptosis might be involved in these phenomena.