Insulin Resistance of Parabiotic Obese-Hyperglycemic Mice (obob)

Abstract

Obese-hyperglycemic mice (obob) were parabiosed with lean littermates and body weight, blood glucose, serum insulin and triglycerides as well as insulin-sensitivity of diaphragm muscle and epididymal fat were determined on the 50th postoperative day. Single (non-parabiosed) mice and lean/lean, obob/obob parabiosed pairs served as controls.

The mortality rate was highest among lean/obob and lowest among lean/lean pairs. The gain in body weight was also least among both partners of lean/obob pairs. Parabiosis had a small (lowering) effect on the blood glucose and serum insulin level of lean mice but it improved markedly the hyperglycemia of parabiotic obob in both obob/obob and obob/lean pairs; in the latter the serum insulin was also significantly decreased suggesting an improvement of the animal's sensitivity to insulin.

In vitro studies involving incubation of diaphragm muscle and epididymal fat tissue in the absence and presence of insulin (1 mU/ml) revealed that while parabiosis had no effect on the tissue-sensitivity to insulin in lean mice, it increased that of obob joined with either obese or lean mice. These changes are attributed to the decrease in body weight of the obese parabiotic mice, probably as a result of a reduced caloric intake. Thus, limiting the caloric intake of the obob and lean mice for 5 days brought about changes similar to those caused by parabiosis.

Key words

Parabiosis - Insulin Resistance - Obese-Hyperglycemic Mice - Hyperglycemia - Obesity - Caloric Restriction