Imperfect Homeothermia in the Hereditary Obese-Hyperglycemic Syndrome of Mice

Abstract

The obese-hyperglycemic syndrome was previously reported to be associated with extreme sensitivity to cold, leading to death on exposure to temps. normally endured by the nonobese siblings. Thyroid and cortical failure were ruled out. An attempt to elucidate the cause of this sensitivity is presented. Nonobese siblings made obese by goldthioglucose treatment are resistant to cold. This fact, with previous observations on "fuzzy" mice, eliminates obesity per se and decreased thickness of pelage as causative factors. Shivering and pilo-erection take place in the obese animals, eliminating another possible cause for sensitivity. Decreased spontaneous exercise was likewise eliminated by comparing obese and nonobese animals kept in small chambers where movement was impossible. Resistance to high environmental temps. appears normal in obese animals. Mice with the hereditary obese -hyperglycemic syndrome are unable to raise their metabolic rate in the cold: O2 consumption, normally doubled in thin control animals under the exptl. conditions described here, is not increased in the obese animals; this leads to a drop in body temp., decreased respiratory rate and Cheyne-Stokes respiration and eventually death. Obese mice recovered from exposure to cold so long as their central temp. had not dropped below 14-16[degree]C. A discussion of this failure to resist cold in terms of the known metabolic abnormality in these obese animals is presented.