Four-day hyperinsulinemia in euglycemic conditions alters local cerebral glucose utilization in specific brain nuclei of freely moving rats.

Although insulin is a well known regulator of peripheral tissue glucose metabolism, there is little agreement over its effects on brain glucose metabolism. Several investigators report that peripheral insulin may enter the brain via several routes. The presence of insulin receptors specific to brain, coupled to diverse reports of the effect of acute insulin administration on brain glucose use, led us to carry out a 4-day hyperinsulinemic euglycemic clamp in freely moving rats with subsequent labelled 2-deoxyglucose metabolic mapping studies. It was found that after 4 days of peripheral insulin infusion, several brain regions (Anterior Hypothalamic area, Suprachiasmatic nucleus, Basolateral Amygdaloid nucleus, Supramammillary bodies, Medial Geniculate nucleus and Locus Coeruleus) had an altered local cerebral glucose utilization. Upon subsequent analysis of their anatomical and functional connections it is proposed that insulin may regulate an integrated circuit of pathways within the central nervous system.