SHORT REPORT Effect of food deprivation on rat plasma estrone fatty acid esters R. Vila Á, C. Ada Ân, M. M. Grasa, R. M. Masane Âs, M. Esteve, C. Cabot, J. A. Ferna Ândez-Lo Âpez, X. Remesar and M. Alemany* Departament de BioquõÂmica i Biologia Molecular, Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain Summary The present study was devised to determine whether the circulating levels of estrone fatty esters aremodi®edby6±48hstarvationintherat,inparalleltochangesinfatreserves,asatesttocheck theplausibilityofitsfunctionasaponderostatsignalinthemammal.Fooddeprivationresultedin adecreaseinglucoseandtriacylglycerols,rapiddisappearanceofliverglycogenandincreasesin fatty acids and, especially, 3-hydroxybutyrate. Insulin and leptin decreased, corticosterone and free estrone increased from 6h onwards and total estrone levels were maintained. Starvation reduced the lipid content of the rat by 25.6%. Plasma esteri®ed estrone levels decreased more slowly,by13%in48h,butitscirculatingmassdecreasedinthesameproportionasthetotallipid content of the rat. The small change in circulating estrone fatty esters is consistent with the postulated role of oleoyl-estrone as a medium-term ponderostat signal. Keywords: estrone, oleoyl-estrone, leptin, body weight, starvation Received 4 March 1999; revised version accepted 13 May 1999 Introduction Short-term±i.e. physiological±starvation is character- ized by the fast mobilization of glycogen and amino acids to maintain blood glucose levels [1]. When food deprivation continues, there is a shift towards the preferential utilization of fat reserves, sparing body protein and massively increasing ketone body metabo- lism. Starvation strongly decreases the thermogenic activity of brown adipose tissue. Fooddeprivationreducestheexpressionoftheobgene in white adipose tissue, thus lowering the circulating leptinlevels[2].Leptinhasbeenpostulatedasapondero- statsignal,buttherapidchangesshownbyplasmaleptin even under short-term starvation [2] are not consistent with a role as a signal of adipose tissue mass. Oleoyl- estrone has also been postulated as a ponderostat signal, since its administration in liposomes elicits the loss of bodyfatinlean,geneticallyobeseandcafeteria-dietobese rats [3,4]. Oleoyl-estrone has been found in plasma lipoproteins [3], and its levels have been related to fat massinhumans[5],asisthecasewithleptin[6]. The present study was devised to determine whether the circulating levels of estrone fatty esters are modi®ed by starvation in the rat, as a further test to check the plausibility of its function as a ponderostat signal in the mammal. Materials and Methods Fifteen-week-old female Zucker lean (Fa/?) rats from Charles River (France), weighing 200 6 6g were used. Author and Correspondence: Prof.Dr Maria Á Alemany, Departament de BioquõÂmica i Biologia Molecular, Facultat de Biologia, Universitat de Barcelona, Av. Diagonal, 645, 08028 Barcelona, SPAIN, Tel:+34 934021521; Fax:+34 934021559, E-mail: alemany@porthos.bio.ub.es | SR ã 1999 Blackwell Science Ltd Diabetes, Obesity and Metabolism, 1, 1999, 353±356 | 353