Intracerebroventricular administration of cobalt protoporphyrin elicits prolonged weight reduction in rats

Intracerebroventricular administration of the synthetic heme analogue cobalt protoporphyrin (CoPP) results in a dose-dependent decrease in body weight in rats. Among several other metalloporphyrins tested, this effect was found to be specific to cobalt chelated in native or minimally modified protoporphyrin rings. Metabolic balance studies showed that the initial effect of intracerebroventricular treatment with CoPP (0.4 mumol/kg body wt) was a transient reduction in food intake. However, following resumption of normal food intake and growth rate, absolute body weights remained reduced for prolonged periods of time (200-300 days) in both male and female rats. Heme oxygenase activity was induced and cytochrome P-450 activities were reduced in both brain and hypothalamus following intracerebroventricular administration of CoPP. The proximate mechanism of action of this synthetic heme analogue is not known at present, but it appears to act in the central nervous system, probably in the vicinity of the hypothalamus, to reduce the body weight set point of treated animals.