Animal models for
insulin resistance and
type 2 diabetes are required for the study of the mechanism of these phenomena and for a better understanding of
diabetes complications in human populations.
Type 2 diabetes is a syndrome that affects 5-10% of the adult population. Hyperinsulinaemia, hypertriglyceridaemia, decreased
high-density lipoprotein (
HDL) cholesterol levels,
obesity and
hypertension, all form a cluster of risk factors that increase the risk of
coronary artery disease, and are known as
insulin resistance syndrome or syndrome X. The gerbil, Psammomys obesus is characterized by primary
insulin resistance and is a well-defined model for dietary induced
type 2 diabetes. Weanling Psammomys and Albino rats were held individually for several weeks on high energy (HE) and low energy (LE) diets in order to determine the development of metabolic changes leading to diabetes. Feeding Psammomys on HE diet resulted in hyperglycaemia (303 +/- 40 mg/dl), hyperinsulinaemia (194 +/- 31 microU/ml) and a moderate elevation in
body weight,
obesity and plasma
triglycerides. Albino rats on HE diet demonstrated an elevation in plasma
insulin (30 +/- 4 microU/ml), hypertriglyceridaemia (170 +/- 11 mg/dl), an elevation in
body weight and
obesity, but maintained normoglycaemia (98 +/- 6 mg/dl). Psammomys represent a model that is similar to human populations, with primary
insulin resistance expressed in young age, which leads to a high percentage of adult
type 2 diabetes. Examples for such populations are the Pima Indians, Australian Aborigines and many other Third World populations. The results indicate that the metabolism of Psammomys is well adapted towards life in a low energy environment, where Psammomys takes advantage of its capacity for a constant accumulation of adipose tissue that will serve for maintenance and breeding in periods of scarcity. This metabolism known as 'thrifty metabolism', is compromised at a high nutrient intake.