INS and diabetes mellitus: The complete mechanism behind this observation is unclear, but leptin infusion directly into the cerebral ventricles, at a dose and route that is believed to act locally in the brain and not outside the CNS, attenuates hyperglycaemia in rats with profound diabetes due to severe insulin deficiency; this effect was independent from leptin's effect on feeding and hepatic insulin sensitivity, but involved reduced HGP and increasing glucose uptake into brain, muscle and brown fat74.