Brain insulin response to feeding in the rat is both macronutrient and area specific (vol 65, pg 271, 1998)

Using microdialysis, we showed recently that hypothalamic immune-reactive i nsulin (IRI) levels increased after a meal of chow and decreased in respons e to a fat meal. In the present study, we have compared extracellular hypot halamic and extrahypothalamic basal IRI levels and investigated the effect of meals composed exclusively of either carbohydrates (85% starch, 15% sucr ose) or casein on both plasma and medial hypothalamic (PVN-VMH) insulin. Th e response of IRI to a carbohydrate meal was also investigated in the cereb ellum. Basal hypothalamic IRI was twofold higher in the hypothalamus as com pared to the cerebellum (33 +/- 4 and 15 +/- 2 pg/mL, respectively). Hypoth alamic IRI increased twofold in response to the carbohydrate meal (72 +/- 1 5 pg/mL) but remained unchanged during the casein meal. No IRI change was f ound in the cerebellum after a meal of carbohydrates (16 +/- 2 pg/mL). Insu linemia was increased by both the carbohydrate and the casein meal. However , the protein-induced increase was less pronounced (maximum + 359% compared to 1650% for carbohydrates). The present data show a dual specificity of b rain insulin response to feeding; in addition to the macronutrient specific variations, a regional specificity was also observed. Taken together with previous observations, the present data are in favor of an involvement of P VN-VMH insulin in the control of feeding and macronutrient-specific appetit es. (C) 1998 Elsevier Science Inc.