AJP - Endocrinology and Metabolism, Vol 239, Issue 5 340-E345, Copyright © 1980 by American Physiological Society
Reevaluation of the sand rat as a model for diabetes mellitus
M. G. Rice and R. P. Robertson
The North African sand rat, Psammomys obesus, has been claimed to be a
valuable model for investigating diabetes. It has been reported that, in
the laboratory with free access to food, sand rats overeat, become obese,
and develop hyperglycemia and ketoacidosis. We have observed that, although
sand rats from our colony become obese and hyperinsulinemic, hyperglycemia
is rare and ketoacidosis is virtually nonexistent. Because age, obesity,
and dietary sucrose have been reported to be risk factors for diabetes, we
have attempted to cause diabetes in a large group of sand rats by inducing
obesity through sucrose feeding over an extended period of time. Animals
fed sucrose-rich diets were compared to controls fed normal carbohydrate
(starch) diets. No group of animals studied over 18 mo developed
hyperglycemia and virtually all groups maintained small but significant
glucose-induced acute insulin responses. Hyperinsulinemia and insulin
resistance accompanied obesity, but there were no differences between
dietary groups. Lean sand rats fed sucrose had higher circulating levels of
triglyceride (TG) and accelerated TG secretion rates (TGSR) compared to
lean controls. After a longer period of observation, all sand rats had
elevated plasma TG levels, however, TGSR were normal, indicating that TG
removal may have become defective. Although this animal is an excellent
model in which to examine spontaneous obesity, Psammomys obesus is a poor
model for the study of human diabetes mellitus.
