Effects of peripheral ghrelin on the carbohydrate and lipid metabolism of the tundra vole (Microtus oeconomus).

Ghrelin is a novel orexigenic peptide hormone. In humans and rodents, it increases food intake and its levels are reduced in obesity but increased in fasting. It is an antagonistic signal to leptin informing the central nervous system about negative energy balance. The tundra vole (Microtus oeconomus) is an interesting model to study the effects of ghrelin, as it is poorly adapted to fasting. In this study, 10 male voles were injected with intraperitoneal ghrelin at 10 microg kg(-1)day(-1) for four days, while 10 males received sham injections. Additional five males were food deprived for 4 h with five males as fed controls. Exogenous ghrelin caused an expected elevation in the plasma ghrelin concentrations. Furthermore, the plasma glucose and high density lipoprotein cholesterol concentrations increased but the kidney and muscle glycogen contents decreased. The liver lipase and kidney glycogen phosphorylase activities increased at the same time. Food deprivation caused an increase in the plasma ghrelin concentrations. In voles, ghrelin may be a mediator to recruit body energy reserves during negative energy balance that would be detrimental to voles very rapidly if foraging does not prove to be successful.