Animal models of diabetes and obesity, including the PBB/Ld mouse

Diabetes mellitus occurs in many animal species. However, only a few have been utilized in systematic studies designed to answer unsolved problems associated with the disorder in man such as this molecular basis, the pathogenesis of the vascular and neural lesions, and the roles of diet, exercise and obesity. Among the animal models available, rodents have been studied most thoroughly for a number of reasons: short generation time (sexually mature at about 3 mth of age, gestation time 21 days) and life span approximately 3 yr; hyperglycemia and/or obesity is known to be inherited in several species; environmental factors can be controlled easily in the laboratory because of small size; and economic considerations. The better known rodent diabetes/obesity syndromes may be categorized as follows; hyperglycemia with ketoacidosis, nonobese (Chinese hamster, South African hamster); hyperglycemia with insulin hypersecretion, moderate obesity and may develop ketoacidosis (diabetic mouse (db/db), spiny mouse, sand rat); and less pronounced hyperglycemia with hyperinsulinemia, insulin 'resistance' and marked obesity; obese (ob/ob), yellow (A(Y)) and New Zealand obese (NZO) mice, and the Zucker 'fatty' rat. The PBB/Ld mouse, described here in detail for the first time, is a new strain of mouse that also fits into the latter category. Members of this strain following maturity develop an obesity that is characterized by increasing cellularity of adipose tissue, increased serum immunoreactive insulin, reduced glucose tolerance, fatty liver and hyperlipidemia. Therefore, this strain of mouse represents another model for study of adult onset obesity.