Ob Mouse and Fa Rat

Ob/ob mouse and Fa/Fa rat (what are they, who discovered them, when they were discovered, how was it discovered

The Ob/ob mouse (i.e. obese mouse model) was first discovered in the Jackson laboratory in Bar Harbor, ME and is popular for studying Type 2 diabetes, food intake, and obesity. A recessive mutation on a certain chromosome in the mouse results in premature termination of leptin and therefore a deficiency of leptin in the mouse.

These ob/ob mice are hypherhagic and already obese at 2 weeks old. They also show other signs indicative of diabetes such as marked hyperglycemia, mildly impaired glucose tolerance, severe hyperinsulinemia, and impaired fertility and wound healing. They are also resistant to insulin. With all the signs of diabetes, the mice become severely and fatally diabetic with pancreatic collapse resulting in death.

The Zucker fa / fa (fatty) rat was discovered in 1961 and is a popular model for studying obesity and the prediabetic state. The state of the rat has come about due to an autosomal recessive mutation of the structural gene for the leptin receptor which results in reduced expression of leptin receptivity on cell surface and decreased leptin binding as well as intracellular retention of leptin. The rats are obese and hypherhagic with a large amount of subcutaneous fat at an early age. They also demonstrate hyperglycemia, insulin resistance, hyperlipidemia, and hyperinsulinemia. Their pancreatic cell numbers diminish as the rats grow.

Leptin (what is it, how it relates to the ob/ob mouse and fa/fa rat, who discovered it, how they discovered it, when it was discovered)

Leptin is a 16 kDa peptide which is predominantly produced by adipose tissue and plays an important role in regulating appetite and energy by its activity in the hypothalamus. Plasma leptin levels correspond to levels of adipose tissue and there is, therefore, a direct correspondence between levels of leptin and obesity / body fat.

Animals (such as rats or mice) deficit in leptin have greater amounts of neuropeptide Y which increases their appetite. They also have greater amounts of cortisol which contributes to resistance of muscle insulin.

The ob/ob mouse is widely used since it lacks leptin. The fa / fa rat too is widely used in order to study the leptin receptor. Another kind of mouse that is used as model is the Zucker diabetic fatty (ZDF) rat that is extremely diabetic.

What does this have to do with food intake control?

Plasma leptin levels correspond to levels of adipose tissue and there is, therefore, a direct correspondence between levels of leptin and obesity / body fat.

Animals (such as rats or mice) deficit in leptin have greater amounts of neuropeptide Y which increases their appetite. They also have greater amounts of cortisol which contributes to resistance of muscle insulin. The ob / ob mouse and fa / fa rat, in other words, have difficulty in controlling their appetite and have a deficiency in their insulin. Obesity may be reducible to the same problems. This too is a reducible element to diabetes where problems in food intake corral may be reducible to biological reasons. These rats are therefore used in order to study whether there are ways to treat this.