Rapamycin Increases Mortality in db/db Mice, a Mouse Model of Type 2 Diabetes

We examined the effect of rapamycin on the life span of a mouse model of type 2 diabetes, db/db mice. At 4 months of age, male and female C57BLKSJ-lepr (db/db) mice (db/db) were placed on either a control diet, lacking rapamycin or a diet containing rapamycin and maintained on these diets over their life span. Rapamycin was found to reduce the life span of the db/db mice. The median survival of male db/db mice fed the control and rapamycin diets was 349 and 302 days, respectively, and the median survival of female db/db mice fed the control and rapamycin diets was 487 and 411 days, respectively. Adjusting for gender differences, rapamycin increased the mortality risk 1.7-fold in both male and female db/db mice. End-of-life pathological data showed that suppurative inflammation was the main cause of death in the db/db mice, which is enhanced slightly by rapamycin treatment.

Rapamycin selectively alters serum chemistry in diabetic mice

The study was undertaken to explore the effect of rapamycin, an anti-inflammatory agent, on the metabolic profile of type 2 diabetic mice. Seven-month-old diabetic db/db mice and their lean littermate non-diabetic controls (db/m) were randomized to receive control chow or chow mixed with rapamycin (2.24 mg/kg/day) (each group n =20, males and females) for 4 months and sacrificed. Serum samples were analyzed for the measurement of glucose, creatinine, blood urea nitrogen (BUN), alkaline phosphatase (ALP), alanine aminotransferase (ALT), total cholesterol, total triglyceride, and total protein, using the automated dry chemistry analysis. Rapamycin elevated serum glucose in female diabetic mice. Serum creatinine tended to be higher in diabetic mice but was not affected by rapamycin; there was no difference in BUN levels among the groups. Serum ALP was elevated in diabetic mice and rapamycin lowered it only in female diabetic mice; serum ALT levels were increased in female diabetic mice, unaffected by rapamycin. Serum total protein was elevated in diabetic mice of both genders but was not affected by rapamycin. Diabetic mice from both genders had elevated serum cholesterol and triglycerides; rapamycin did not affect serum cholesterol but decreased serum total triglycerides in male diabetic mice. We conclude that rapamycin elicits complex metabolic responses in aging diabetic mice, worsening hyperglycemia in females but improving ALP in female diabetic and total triglycerides in male diabetic mice, respectively. The metabolic effects of rapamycin should be considered while performing studies with rapamycin in mice.