How does Hoodia gordonii work?

In 2004, a study was published that demonstrated the effects of p57, the proposed active ingredient of Hoodia gordonii, on rat brains.  To date, this is the only study of its kind, meaning that no one else has published any research findings on p57.  Here's what researchers did, and what they found (MacLean):    

• Rats used in this study were either maintained on a "ad-lib" diet (they could eat as much as they wanted) or on a restricted diet that was deficient in calories.

• Researches took p57, which had been isolated and purified from Hoodia gordonii, and injected it directly into the brains of some of the rats; the other rats received a placebo injection.

• Over the course of several studies, researchers measured the levels of specific chemicals and ions within the hypothalamus of the rat brains, which is the center of the brain that regulates appetite.

• The results of this study indicate that p57 increases the production and/or content of ATP by 50-150% within the brain cells of the hypothalamus.

• It was also found that the brains of rats that had been on a moderately restricted diet had lower concentrations of hypothamalic ATP before p57 injection.

• Thus, this study indicates that hypothalamic ATP is involved in appetite regulation.  However, the exact relationship between ATP and appetite suppression is unknown.

• Furthermore, it is unknown as to how p57 causes ATP increase in the hypothalamic neurons. 

• In addition, researchers noted that rat food intake on the ad-lib diet was decreased by 40-60% for approximately 24 hours after the injection of p57.