Correlation between mammary tumor and blood glucose, serum insulin, and free fatty acids in mice

The blood glucose level and serum levels of insulin, glucagon, and free fatty acids were examined in 7- to 8-mo-old female SHN mice with or without spontaneous mammary tumors (MT). Blood glucose levels in the females with MT were significantly higher than in those without MT, rising in proportion to the increase in size of MT up to 30 mm in diameter. In 4-mo-old male SHN and 11-mo-old female C57BL mice bearing mammary tumor grafts (MTg), the blood glucose level was significantly higher than in mice without MTg. Serum insulin and free fatty acids in female SHN mice with MT rose to higher levels than in mice without MT, whereas serum glucagon levels were unaltered. In 50% of mice with MT, pancreatic islets contained a large number of pyknotic cells. Livers of mice with MT or MTg were significantly heavier than those of mice without MT or MTg. In both female SHN mice with spontaneous MT and male SHN and female C57BL mice with MTg, the total number of hepatocytes and the total amount of liver DNA increased significantly compared with values from corresponding controls without MT or MTg. These findings suggest that MT or MTg induce a hyperglycemic state and an enhanced production of free fatty acids and insulin, which may in turn stimulate the growth of mammary tumors and the liver.