AJP - Regulatory, Integrative and Comparative Physiology, Vol 257, Issue 1 224-R228, Copyright © 1989 by American Physiological Society
Site of action of putative lipostatic factor: hypothalamic metabolism of parabiotic rats
T. R. Kasser, R. B. Harris and R. J. Martin
Department of Foods and Nutrition, University of Georgia, Athens 30602.
Studies were conducted to determine whether metabolic adaptation occurred
in the hypothalamus of overfed parabiotic rats and their partners to
distinguish between the adaptations caused by increased caloric intake and
those caused by the production of a "lipostatic factor." The induction of
overfed obesity in one parabiotic partner was employed to test the
hypothesis that a putative lipostatic factor produced in the obese
parabiotic elicited the hypophagic-lipid-mobilizing effect observed in the
lean parabiotic via alterations in hypothalamic fatty acid and glucose
metabolism. Fatty acid oxidation in the ventrolateral hypothalamus (VLH) of
overfed parabiotic rats and their partners was lower than in ad libitum
parabiotic rats. Net flux of glucose through the VLH gamma-aminobutyric
acid (GABA) shunt was elevated in overfed parabiotic rats compared with the
net flux observed in their partners and ad libitum parabiotic rats, the
levels being similar in these last two groups. Net flux of glucose through
the ventromedial hypothalamic (VMH) pentose shunt in overfed parabiotic
rats and their partners was elevated relative to ad libitum parabiotic
rats. The putative lipostatic factor may act to regulate energy balance
through modification of VLH fatty acid oxidation and/or glucose flux via
the VMH pentose shunt.
